31 */
32
33#include "opt_ipfw.h" /* for ipfw_fwd */
34#include "opt_inet.h"
35#include "opt_inet6.h"
36#include "opt_ipsec.h"
37#include "opt_mac.h"
38#include "opt_tcpdebug.h"
39#include "opt_tcp_input.h"
40#include "opt_tcp_sack.h"
41
42#include <sys/param.h>
43#include <sys/kernel.h>
44#include <sys/mac.h>
45#include <sys/malloc.h>
46#include <sys/mbuf.h>
47#include <sys/proc.h> /* for proc0 declaration */
48#include <sys/protosw.h>
49#include <sys/signalvar.h>
50#include <sys/socket.h>
51#include <sys/socketvar.h>
52#include <sys/sysctl.h>
53#include <sys/syslog.h>
54#include <sys/systm.h>
55
56#include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */
57
58#include <vm/uma.h>
59
60#include <net/if.h>
61#include <net/route.h>
62
63#include <netinet/in.h>
64#include <netinet/in_pcb.h>
65#include <netinet/in_systm.h>
66#include <netinet/in_var.h>
67#include <netinet/ip.h>
68#include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */
69#include <netinet/icmp_var.h> /* for ICMP_BANDLIM */
70#include <netinet/ip_var.h>
71#include <netinet/ip6.h>
72#include <netinet/icmp6.h>
73#include <netinet6/in6_pcb.h>
74#include <netinet6/ip6_var.h>
75#include <netinet6/nd6.h>
76#include <netinet/tcp.h>
77#include <netinet/tcp_fsm.h>
78#include <netinet/tcp_seq.h>
79#include <netinet/tcp_timer.h>
80#include <netinet/tcp_var.h>
81#include <netinet6/tcp6_var.h>
82#include <netinet/tcpip.h>
83#ifdef TCPDEBUG
84#include <netinet/tcp_debug.h>
85#endif /* TCPDEBUG */
86
87#ifdef FAST_IPSEC
88#include <netipsec/ipsec.h>
89#include <netipsec/ipsec6.h>
90#endif /*FAST_IPSEC*/
91
92#ifdef IPSEC
93#include <netinet6/ipsec.h>
94#include <netinet6/ipsec6.h>
95#include <netkey/key.h>
96#endif /*IPSEC*/
97
98#include <machine/in_cksum.h>
99
100static const int tcprexmtthresh = 3;
101
102struct tcpstat tcpstat;
103SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW,
104 &tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)");
105
106static int log_in_vain = 0;
107SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW,
108 &log_in_vain, 0, "Log all incoming TCP connections");
109
110static int blackhole = 0;
111SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW,
112 &blackhole, 0, "Do not send RST when dropping refused connections");
113
114int tcp_delack_enabled = 1;
115SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW,
116 &tcp_delack_enabled, 0,
117 "Delay ACK to try and piggyback it onto a data packet");
118
119#ifdef TCP_DROP_SYNFIN
120static int drop_synfin = 0;
121SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW,
122 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set");
123#endif
124
125static int tcp_do_rfc3042 = 1;
126SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW,
127 &tcp_do_rfc3042, 0, "Enable RFC 3042 (Limited Transmit)");
128
129static int tcp_do_rfc3390 = 1;
130SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW,
131 &tcp_do_rfc3390, 0,
132 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)");
133
134static int tcp_insecure_rst = 0;
135SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_RW,
136 &tcp_insecure_rst, 0,
137 "Follow the old (insecure) criteria for accepting RST packets.");
138
139SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0,
140 "TCP Segment Reassembly Queue");
141
142static int tcp_reass_maxseg = 0;
143SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN,
144 &tcp_reass_maxseg, 0,
145 "Global maximum number of TCP Segments in Reassembly Queue");
146
147int tcp_reass_qsize = 0;
148SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD,
149 &tcp_reass_qsize, 0,
150 "Global number of TCP Segments currently in Reassembly Queue");
151
152static int tcp_reass_maxqlen = 48;
153SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxqlen, CTLFLAG_RW,
154 &tcp_reass_maxqlen, 0,
155 "Maximum number of TCP Segments per individual Reassembly Queue");
156
157static int tcp_reass_overflows = 0;
158SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD,
159 &tcp_reass_overflows, 0,
160 "Global number of TCP Segment Reassembly Queue Overflows");
161
162struct inpcbhead tcb;
163#define tcb6 tcb /* for KAME src sync over BSD*'s */
164struct inpcbinfo tcbinfo;
165struct mtx *tcbinfo_mtx;
166
167static void tcp_dooptions(struct tcpopt *, u_char *, int, int);
168
169static void tcp_pulloutofband(struct socket *,
170 struct tcphdr *, struct mbuf *, int);
171static int tcp_reass(struct tcpcb *, struct tcphdr *, int *,
172 struct mbuf *);
173static void tcp_xmit_timer(struct tcpcb *, int);
174static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *);
175static int tcp_timewait(struct tcptw *, struct tcpopt *,
176 struct tcphdr *, struct mbuf *, int);
177
178/* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */
179#ifdef INET6
180#define ND6_HINT(tp) \
181do { \
182 if ((tp) && (tp)->t_inpcb && \
183 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \
184 nd6_nud_hint(NULL, NULL, 0); \
185} while (0)
186#else
187#define ND6_HINT(tp)
188#endif
189
190/*
191 * Indicate whether this ack should be delayed. We can delay the ack if
192 * - there is no delayed ack timer in progress and
193 * - our last ack wasn't a 0-sized window. We never want to delay
194 * the ack that opens up a 0-sized window and
195 * - delayed acks are enabled or
196 * - this is a half-synchronized T/TCP connection.
197 */
198#define DELAY_ACK(tp) \
199 ((!callout_active(tp->tt_delack) && \
200 (tp->t_flags & TF_RXWIN0SENT) == 0) && \
201 (tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN)))
202
203/* Initialize TCP reassembly queue */
204uma_zone_t tcp_reass_zone;
205void
206tcp_reass_init()
207{
208 tcp_reass_maxseg = nmbclusters / 16;
209 TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments",
210 &tcp_reass_maxseg);
211 tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent),
212 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
213 uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg);
214}
215
216static int
217tcp_reass(tp, th, tlenp, m)
218 register struct tcpcb *tp;
219 register struct tcphdr *th;
220 int *tlenp;
221 struct mbuf *m;
222{
223 struct tseg_qent *q;
224 struct tseg_qent *p = NULL;
225 struct tseg_qent *nq;
226 struct tseg_qent *te = NULL;
227 struct socket *so = tp->t_inpcb->inp_socket;
228 int flags;
229
230 INP_LOCK_ASSERT(tp->t_inpcb);
231
232 /*
233 * XXX: tcp_reass() is rather inefficient with its data structures
234 * and should be rewritten (see NetBSD for optimizations). While
235 * doing that it should move to its own file tcp_reass.c.
236 */
237
238 /*
239 * Call with th==NULL after become established to
240 * force pre-ESTABLISHED data up to user socket.
241 */
242 if (th == NULL)
243 goto present;
244
245 /*
246 * Limit the number of segments in the reassembly queue to prevent
247 * holding on to too many segments (and thus running out of mbufs).
248 * Make sure to let the missing segment through which caused this
249 * queue. Always keep one global queue entry spare to be able to
250 * process the missing segment.
251 */
252 if (th->th_seq != tp->rcv_nxt &&
253 (tcp_reass_qsize + 1 >= tcp_reass_maxseg ||
254 tp->t_segqlen >= tcp_reass_maxqlen)) {
255 tcp_reass_overflows++;
256 tcpstat.tcps_rcvmemdrop++;
257 m_freem(m);
258 *tlenp = 0;
259 return (0);
260 }
261
262 /*
263 * Allocate a new queue entry. If we can't, or hit the zone limit
264 * just drop the pkt.
265 */
266 te = uma_zalloc(tcp_reass_zone, M_NOWAIT);
267 if (te == NULL) {
268 tcpstat.tcps_rcvmemdrop++;
269 m_freem(m);
270 *tlenp = 0;
271 return (0);
272 }
273 tp->t_segqlen++;
274 tcp_reass_qsize++;
275
276 /*
277 * Find a segment which begins after this one does.
278 */
279 LIST_FOREACH(q, &tp->t_segq, tqe_q) {
280 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
281 break;
282 p = q;
283 }
284
285 /*
286 * If there is a preceding segment, it may provide some of
287 * our data already. If so, drop the data from the incoming
288 * segment. If it provides all of our data, drop us.
289 */
290 if (p != NULL) {
291 register int i;
292 /* conversion to int (in i) handles seq wraparound */
293 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
294 if (i > 0) {
295 if (i >= *tlenp) {
296 tcpstat.tcps_rcvduppack++;
297 tcpstat.tcps_rcvdupbyte += *tlenp;
298 m_freem(m);
299 uma_zfree(tcp_reass_zone, te);
300 tp->t_segqlen--;
301 tcp_reass_qsize--;
302 /*
303 * Try to present any queued data
304 * at the left window edge to the user.
305 * This is needed after the 3-WHS
306 * completes.
307 */
308 goto present; /* ??? */
309 }
310 m_adj(m, i);
311 *tlenp -= i;
312 th->th_seq += i;
313 }
314 }
315 tcpstat.tcps_rcvoopack++;
316 tcpstat.tcps_rcvoobyte += *tlenp;
317
318 /*
319 * While we overlap succeeding segments trim them or,
320 * if they are completely covered, dequeue them.
321 */
322 while (q) {
323 register int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
324 if (i <= 0)
325 break;
326 if (i < q->tqe_len) {
327 q->tqe_th->th_seq += i;
328 q->tqe_len -= i;
329 m_adj(q->tqe_m, i);
330 break;
331 }
332
333 nq = LIST_NEXT(q, tqe_q);
334 LIST_REMOVE(q, tqe_q);
335 m_freem(q->tqe_m);
336 uma_zfree(tcp_reass_zone, q);
337 tp->t_segqlen--;
338 tcp_reass_qsize--;
339 q = nq;
340 }
341
342 /* Insert the new segment queue entry into place. */
343 te->tqe_m = m;
344 te->tqe_th = th;
345 te->tqe_len = *tlenp;
346
347 if (p == NULL) {
348 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q);
349 } else {
350 LIST_INSERT_AFTER(p, te, tqe_q);
351 }
352
353present:
354 /*
355 * Present data to user, advancing rcv_nxt through
356 * completed sequence space.
357 */
358 if (!TCPS_HAVEESTABLISHED(tp->t_state))
359 return (0);
360 q = LIST_FIRST(&tp->t_segq);
361 if (!q || q->tqe_th->th_seq != tp->rcv_nxt)
362 return (0);
363 SOCKBUF_LOCK(&so->so_rcv);
364 do {
365 tp->rcv_nxt += q->tqe_len;
366 flags = q->tqe_th->th_flags & TH_FIN;
367 nq = LIST_NEXT(q, tqe_q);
368 LIST_REMOVE(q, tqe_q);
369 if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
370 m_freem(q->tqe_m);
371 else
372 sbappendstream_locked(&so->so_rcv, q->tqe_m);
373 uma_zfree(tcp_reass_zone, q);
374 tp->t_segqlen--;
375 tcp_reass_qsize--;
376 q = nq;
377 } while (q && q->tqe_th->th_seq == tp->rcv_nxt);
378 ND6_HINT(tp);
379 sorwakeup_locked(so);
380 return (flags);
381}
382
383/*
384 * TCP input routine, follows pages 65-76 of the
385 * protocol specification dated September, 1981 very closely.
386 */
387#ifdef INET6
388int
389tcp6_input(mp, offp, proto)
390 struct mbuf **mp;
391 int *offp, proto;
392{
393 register struct mbuf *m = *mp;
394 struct in6_ifaddr *ia6;
395
396 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE);
397
398 /*
399 * draft-itojun-ipv6-tcp-to-anycast
400 * better place to put this in?
401 */
402 ia6 = ip6_getdstifaddr(m);
403 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) {
404 struct ip6_hdr *ip6;
405
406 ip6 = mtod(m, struct ip6_hdr *);
407 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
408 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6);
409 return IPPROTO_DONE;
410 }
411
412 tcp_input(m, *offp);
413 return IPPROTO_DONE;
414}
415#endif
416
417void
418tcp_input(m, off0)
419 register struct mbuf *m;
420 int off0;
421{
422 register struct tcphdr *th;
423 register struct ip *ip = NULL;
424 register struct ipovly *ipov;
425 register struct inpcb *inp = NULL;
426 u_char *optp = NULL;
427 int optlen = 0;
428 int len, tlen, off;
429 int drop_hdrlen;
430 register struct tcpcb *tp = 0;
431 register int thflags;
432 struct socket *so = 0;
433 int todrop, acked, ourfinisacked, needoutput = 0;
434 u_long tiwin;
435 struct tcpopt to; /* options in this segment */
436 int headlocked = 0;
437#ifdef IPFIREWALL_FORWARD
438 struct m_tag *fwd_tag;
439#endif
440 int rstreason; /* For badport_bandlim accounting purposes */
441
442 struct ip6_hdr *ip6 = NULL;
443#ifdef INET6
444 int isipv6;
445#else
446 const int isipv6 = 0;
447#endif
448
449#ifdef TCPDEBUG
450 /*
451 * The size of tcp_saveipgen must be the size of the max ip header,
452 * now IPv6.
453 */
454 u_char tcp_saveipgen[40];
455 struct tcphdr tcp_savetcp;
456 short ostate = 0;
457#endif
458
459#ifdef INET6
460 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0;
461#endif
462 bzero((char *)&to, sizeof(to));
463
464 tcpstat.tcps_rcvtotal++;
465
466 if (isipv6) {
467#ifdef INET6
468 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */
469 ip6 = mtod(m, struct ip6_hdr *);
470 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0;
471 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) {
472 tcpstat.tcps_rcvbadsum++;
473 goto drop;
474 }
475 th = (struct tcphdr *)((caddr_t)ip6 + off0);
476
477 /*
478 * Be proactive about unspecified IPv6 address in source.
479 * As we use all-zero to indicate unbounded/unconnected pcb,
480 * unspecified IPv6 address can be used to confuse us.
481 *
482 * Note that packets with unspecified IPv6 destination is
483 * already dropped in ip6_input.
484 */
485 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
486 /* XXX stat */
487 goto drop;
488 }
489#else
490 th = NULL; /* XXX: avoid compiler warning */
491#endif
492 } else {
493 /*
494 * Get IP and TCP header together in first mbuf.
495 * Note: IP leaves IP header in first mbuf.
496 */
497 if (off0 > sizeof (struct ip)) {
498 ip_stripoptions(m, (struct mbuf *)0);
499 off0 = sizeof(struct ip);
500 }
501 if (m->m_len < sizeof (struct tcpiphdr)) {
502 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) {
503 tcpstat.tcps_rcvshort++;
504 return;
505 }
506 }
507 ip = mtod(m, struct ip *);
508 ipov = (struct ipovly *)ip;
509 th = (struct tcphdr *)((caddr_t)ip + off0);
510 tlen = ip->ip_len;
511
512 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
513 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
514 th->th_sum = m->m_pkthdr.csum_data;
515 else
516 th->th_sum = in_pseudo(ip->ip_src.s_addr,
517 ip->ip_dst.s_addr,
518 htonl(m->m_pkthdr.csum_data +
519 ip->ip_len +
520 IPPROTO_TCP));
521 th->th_sum ^= 0xffff;
522#ifdef TCPDEBUG
523 ipov->ih_len = (u_short)tlen;
524 ipov->ih_len = htons(ipov->ih_len);
525#endif
526 } else {
527 /*
528 * Checksum extended TCP header and data.
529 */
530 len = sizeof (struct ip) + tlen;
531 bzero(ipov->ih_x1, sizeof(ipov->ih_x1));
532 ipov->ih_len = (u_short)tlen;
533 ipov->ih_len = htons(ipov->ih_len);
534 th->th_sum = in_cksum(m, len);
535 }
536 if (th->th_sum) {
537 tcpstat.tcps_rcvbadsum++;
538 goto drop;
539 }
540#ifdef INET6
541 /* Re-initialization for later version check */
542 ip->ip_v = IPVERSION;
543#endif
544 }
545
546 /*
547 * Check that TCP offset makes sense,
548 * pull out TCP options and adjust length. XXX
549 */
550 off = th->th_off << 2;
551 if (off < sizeof (struct tcphdr) || off > tlen) {
552 tcpstat.tcps_rcvbadoff++;
553 goto drop;
554 }
555 tlen -= off; /* tlen is used instead of ti->ti_len */
556 if (off > sizeof (struct tcphdr)) {
557 if (isipv6) {
558#ifdef INET6
559 IP6_EXTHDR_CHECK(m, off0, off, );
560 ip6 = mtod(m, struct ip6_hdr *);
561 th = (struct tcphdr *)((caddr_t)ip6 + off0);
562#endif
563 } else {
564 if (m->m_len < sizeof(struct ip) + off) {
565 if ((m = m_pullup(m, sizeof (struct ip) + off))
566 == 0) {
567 tcpstat.tcps_rcvshort++;
568 return;
569 }
570 ip = mtod(m, struct ip *);
571 ipov = (struct ipovly *)ip;
572 th = (struct tcphdr *)((caddr_t)ip + off0);
573 }
574 }
575 optlen = off - sizeof (struct tcphdr);
576 optp = (u_char *)(th + 1);
577 }
578 thflags = th->th_flags;
579
580#ifdef TCP_DROP_SYNFIN
581 /*
582 * If the drop_synfin option is enabled, drop all packets with
583 * both the SYN and FIN bits set. This prevents e.g. nmap from
584 * identifying the TCP/IP stack.
585 *
586 * This is a violation of the TCP specification.
587 */
588 if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN))
589 goto drop;
590#endif
591
592 /*
593 * Convert TCP protocol specific fields to host format.
594 */
595 th->th_seq = ntohl(th->th_seq);
596 th->th_ack = ntohl(th->th_ack);
597 th->th_win = ntohs(th->th_win);
598 th->th_urp = ntohs(th->th_urp);
599
600 /*
601 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options,
602 * until after ip6_savecontrol() is called and before other functions
603 * which don't want those proto headers.
604 * Because ip6_savecontrol() is going to parse the mbuf to
605 * search for data to be passed up to user-land, it wants mbuf
606 * parameters to be unchanged.
607 * XXX: the call of ip6_savecontrol() has been obsoleted based on
608 * latest version of the advanced API (20020110).
609 */
610 drop_hdrlen = off0 + off;
611
612 /*
613 * Locate pcb for segment.
614 */
615 INP_INFO_WLOCK(&tcbinfo);
616 headlocked = 1;
617findpcb:
618 KASSERT(headlocked, ("tcp_input: findpcb: head not locked"));
619#ifdef IPFIREWALL_FORWARD
620 /* Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. */
621 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL);
622
623 if (fwd_tag != NULL && isipv6 == 0) { /* IPv6 support is not yet */
624 struct sockaddr_in *next_hop;
625
626 next_hop = (struct sockaddr_in *)(fwd_tag+1);
627 /*
628 * Transparently forwarded. Pretend to be the destination.
629 * already got one like this?
630 */
631 inp = in_pcblookup_hash(&tcbinfo,
632 ip->ip_src, th->th_sport,
633 ip->ip_dst, th->th_dport,
634 0, m->m_pkthdr.rcvif);
635 if (!inp) {
636 /* It's new. Try to find the ambushing socket. */
637 inp = in_pcblookup_hash(&tcbinfo,
638 ip->ip_src, th->th_sport,
639 next_hop->sin_addr,
640 next_hop->sin_port ?
641 ntohs(next_hop->sin_port) :
642 th->th_dport,
643 1, m->m_pkthdr.rcvif);
644 }
645 /* Remove the tag from the packet. We don't need it anymore. */
646 m_tag_delete(m, fwd_tag);
647 } else {
648#endif /* IPFIREWALL_FORWARD */
649 if (isipv6) {
650#ifdef INET6
651 inp = in6_pcblookup_hash(&tcbinfo,
652 &ip6->ip6_src, th->th_sport,
653 &ip6->ip6_dst, th->th_dport,
654 1, m->m_pkthdr.rcvif);
655#endif
656 } else
657 inp = in_pcblookup_hash(&tcbinfo,
658 ip->ip_src, th->th_sport,
659 ip->ip_dst, th->th_dport,
660 1, m->m_pkthdr.rcvif);
661#ifdef IPFIREWALL_FORWARD
662 }
663#endif /* IPFIREWALL_FORWARD */
664
665#if defined(IPSEC) || defined(FAST_IPSEC)
666#ifdef INET6
667 if (isipv6) {
668 if (inp != NULL && ipsec6_in_reject(m, inp)) {
669#ifdef IPSEC
670 ipsec6stat.in_polvio++;
671#endif
672 goto drop;
673 }
674 } else
675#endif /* INET6 */
676 if (inp != NULL && ipsec4_in_reject(m, inp)) {
677#ifdef IPSEC
678 ipsecstat.in_polvio++;
679#endif
680 goto drop;
681 }
682#endif /*IPSEC || FAST_IPSEC*/
683
684 /*
685 * If the state is CLOSED (i.e., TCB does not exist) then
686 * all data in the incoming segment is discarded.
687 * If the TCB exists but is in CLOSED state, it is embryonic,
688 * but should either do a listen or a connect soon.
689 */
690 if (inp == NULL) {
691 if (log_in_vain) {
692#ifdef INET6
693 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2];
694#else
695 char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"];
696#endif
697
698 if (isipv6) {
699#ifdef INET6
700 strcpy(dbuf, "[");
701 strcpy(sbuf, "[");
702 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst));
703 strcat(sbuf, ip6_sprintf(&ip6->ip6_src));
704 strcat(dbuf, "]");
705 strcat(sbuf, "]");
706#endif
707 } else {
708 strcpy(dbuf, inet_ntoa(ip->ip_dst));
709 strcpy(sbuf, inet_ntoa(ip->ip_src));
710 }
711 switch (log_in_vain) {
712 case 1:
713 if ((thflags & TH_SYN) == 0)
714 break;
715 /* FALLTHROUGH */
716 case 2:
717 log(LOG_INFO,
718 "Connection attempt to TCP %s:%d "
719 "from %s:%d flags:0x%02x\n",
720 dbuf, ntohs(th->th_dport), sbuf,
721 ntohs(th->th_sport), thflags);
722 break;
723 default:
724 break;
725 }
726 }
727 if (blackhole) {
728 switch (blackhole) {
729 case 1:
730 if (thflags & TH_SYN)
731 goto drop;
732 break;
733 case 2:
734 goto drop;
735 default:
736 goto drop;
737 }
738 }
739 rstreason = BANDLIM_RST_CLOSEDPORT;
740 goto dropwithreset;
741 }
742 INP_LOCK(inp);
743 if (inp->inp_vflag & INP_TIMEWAIT) {
744 /*
745 * The only option of relevance is TOF_CC, and only if
746 * present in a SYN segment. See tcp_timewait().
747 */
748 if (thflags & TH_SYN)
749 tcp_dooptions(&to, optp, optlen, 1);
750 if (tcp_timewait((struct tcptw *)inp->inp_ppcb,
751 &to, th, m, tlen))
752 goto findpcb;
753 /*
754 * tcp_timewait unlocks inp.
755 */
756 INP_INFO_WUNLOCK(&tcbinfo);
757 return;
758 }
759 tp = intotcpcb(inp);
760 if (tp == 0) {
761 INP_UNLOCK(inp);
762 rstreason = BANDLIM_RST_CLOSEDPORT;
763 goto dropwithreset;
764 }
765 if (tp->t_state == TCPS_CLOSED)
766 goto drop;
767
768 /* Unscale the window into a 32-bit value. */
769 if ((thflags & TH_SYN) == 0)
770 tiwin = th->th_win << tp->snd_scale;
771 else
772 tiwin = th->th_win;
773
774#ifdef MAC
775 INP_LOCK_ASSERT(inp);
776 if (mac_check_inpcb_deliver(inp, m))
777 goto drop;
778#endif
779 so = inp->inp_socket;
780#ifdef TCPDEBUG
781 if (so->so_options & SO_DEBUG) {
782 ostate = tp->t_state;
783 if (isipv6)
784 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6));
785 else
786 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip));
787 tcp_savetcp = *th;
788 }
789#endif
790 if (so->so_options & SO_ACCEPTCONN) {
791 struct in_conninfo inc;
792
793#ifdef INET6
794 inc.inc_isipv6 = isipv6;
795#endif
796 if (isipv6) {
797 inc.inc6_faddr = ip6->ip6_src;
798 inc.inc6_laddr = ip6->ip6_dst;
799 } else {
800 inc.inc_faddr = ip->ip_src;
801 inc.inc_laddr = ip->ip_dst;
802 }
803 inc.inc_fport = th->th_sport;
804 inc.inc_lport = th->th_dport;
805
806 /*
807 * If the state is LISTEN then ignore segment if it contains
808 * a RST. If the segment contains an ACK then it is bad and
809 * send a RST. If it does not contain a SYN then it is not
810 * interesting; drop it.
811 *
812 * If the state is SYN_RECEIVED (syncache) and seg contains
813 * an ACK, but not for our SYN/ACK, send a RST. If the seg
814 * contains a RST, check the sequence number to see if it
815 * is a valid reset segment.
816 */
817 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) {
818 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) {
819 if (!syncache_expand(&inc, th, &so, m)) {
820 /*
821 * No syncache entry, or ACK was not
822 * for our SYN/ACK. Send a RST.
823 */
824 tcpstat.tcps_badsyn++;
825 rstreason = BANDLIM_RST_OPENPORT;
826 goto dropwithreset;
827 }
828 if (so == NULL) {
829 /*
830 * Could not complete 3-way handshake,
831 * connection is being closed down, and
832 * syncache will free mbuf.
833 */
834 INP_UNLOCK(inp);
835 INP_INFO_WUNLOCK(&tcbinfo);
836 return;
837 }
838 /*
839 * Socket is created in state SYN_RECEIVED.
840 * Continue processing segment.
841 */
842 INP_UNLOCK(inp);
843 inp = sotoinpcb(so);
844 INP_LOCK(inp);
845 tp = intotcpcb(inp);
846 /*
847 * This is what would have happened in
848 * tcp_output() when the SYN,ACK was sent.
849 */
850 tp->snd_up = tp->snd_una;
851 tp->snd_max = tp->snd_nxt = tp->iss + 1;
852 tp->last_ack_sent = tp->rcv_nxt;
853 /*
854 * RFC1323: The window in SYN & SYN/ACK
855 * segments is never scaled.
856 */
857 tp->snd_wnd = tiwin; /* unscaled */
858 goto after_listen;
859 }
860 if (thflags & TH_RST) {
861 syncache_chkrst(&inc, th);
862 goto drop;
863 }
864 if (thflags & TH_ACK) {
865 syncache_badack(&inc);
866 tcpstat.tcps_badsyn++;
867 rstreason = BANDLIM_RST_OPENPORT;
868 goto dropwithreset;
869 }
870 goto drop;
871 }
872
873 /*
874 * Segment's flags are (SYN) or (SYN|FIN).
875 */
876#ifdef INET6
877 /*
878 * If deprecated address is forbidden,
879 * we do not accept SYN to deprecated interface
880 * address to prevent any new inbound connection from
881 * getting established.
882 * When we do not accept SYN, we send a TCP RST,
883 * with deprecated source address (instead of dropping
884 * it). We compromise it as it is much better for peer
885 * to send a RST, and RST will be the final packet
886 * for the exchange.
887 *
888 * If we do not forbid deprecated addresses, we accept
889 * the SYN packet. RFC2462 does not suggest dropping
890 * SYN in this case.
891 * If we decipher RFC2462 5.5.4, it says like this:
892 * 1. use of deprecated addr with existing
893 * communication is okay - "SHOULD continue to be
894 * used"
895 * 2. use of it with new communication:
896 * (2a) "SHOULD NOT be used if alternate address
897 * with sufficient scope is available"
898 * (2b) nothing mentioned otherwise.
899 * Here we fall into (2b) case as we have no choice in
900 * our source address selection - we must obey the peer.
901 *
902 * The wording in RFC2462 is confusing, and there are
903 * multiple description text for deprecated address
904 * handling - worse, they are not exactly the same.
905 * I believe 5.5.4 is the best one, so we follow 5.5.4.
906 */
907 if (isipv6 && !ip6_use_deprecated) {
908 struct in6_ifaddr *ia6;
909
910 if ((ia6 = ip6_getdstifaddr(m)) &&
911 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
912 INP_UNLOCK(inp);
913 tp = NULL;
914 rstreason = BANDLIM_RST_OPENPORT;
915 goto dropwithreset;
916 }
917 }
918#endif
919 /*
920 * If it is from this socket, drop it, it must be forged.
921 * Don't bother responding if the destination was a broadcast.
922 */
923 if (th->th_dport == th->th_sport) {
924 if (isipv6) {
925 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst,
926 &ip6->ip6_src))
927 goto drop;
928 } else {
929 if (ip->ip_dst.s_addr == ip->ip_src.s_addr)
930 goto drop;
931 }
932 }
933 /*
934 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN
935 *
936 * Note that it is quite possible to receive unicast
937 * link-layer packets with a broadcast IP address. Use
938 * in_broadcast() to find them.
939 */
940 if (m->m_flags & (M_BCAST|M_MCAST))
941 goto drop;
942 if (isipv6) {
943 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
944 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
945 goto drop;
946 } else {
947 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
948 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
949 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
950 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
951 goto drop;
952 }
953 /*
954 * SYN appears to be valid; create compressed TCP state
955 * for syncache, or perform t/tcp connection.
956 */
957 if (so->so_qlen <= so->so_qlimit) {
958#ifdef TCPDEBUG
959 if (so->so_options & SO_DEBUG)
960 tcp_trace(TA_INPUT, ostate, tp,
961 (void *)tcp_saveipgen, &tcp_savetcp, 0);
962#endif
963 tcp_dooptions(&to, optp, optlen, 1);
964 if (!syncache_add(&inc, &to, th, &so, m))
965 goto drop;
966 if (so == NULL) {
967 /*
968 * Entry added to syncache, mbuf used to
969 * send SYN,ACK packet.
970 */
971 KASSERT(headlocked, ("headlocked"));
972 INP_UNLOCK(inp);
973 INP_INFO_WUNLOCK(&tcbinfo);
974 return;
975 }
976 /*
977 * Segment passed TAO tests.
978 */
979 INP_UNLOCK(inp);
980 inp = sotoinpcb(so);
981 INP_LOCK(inp);
982 tp = intotcpcb(inp);
983 tp->snd_wnd = tiwin;
984 tp->t_starttime = ticks;
985 tp->t_state = TCPS_ESTABLISHED;
986
987 /*
988 * T/TCP logic:
989 * If there is a FIN or if there is data, then
990 * delay SYN,ACK(SYN) in the hope of piggy-backing
991 * it on a response segment. Otherwise must send
992 * ACK now in case the other side is slow starting.
993 */
994 if (thflags & TH_FIN || tlen != 0)
995 tp->t_flags |= (TF_DELACK | TF_NEEDSYN);
996 else
997 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN);
998 tcpstat.tcps_connects++;
999 soisconnected(so);
1000 goto trimthenstep6;
1001 }
1002 goto drop;
1003 }
1004after_listen:
1005 KASSERT(headlocked, ("tcp_input: after_listen: head not locked"));
1006 INP_LOCK_ASSERT(inp);
1007
1008 /* XXX temp debugging */
1009 /* should not happen - syncache should pick up these connections */
1010 if (tp->t_state == TCPS_LISTEN)
1011 panic("tcp_input: TCPS_LISTEN");
1012
1013 /*
1014 * This is the second part of the MSS DoS prevention code (after
1015 * minmss on the sending side) and it deals with too many too small
1016 * tcp packets in a too short timeframe (1 second).
1017 *
1018 * For every full second we count the number of received packets
1019 * and bytes. If we get a lot of packets per second for this connection
1020 * (tcp_minmssoverload) we take a closer look at it and compute the
1021 * average packet size for the past second. If that is less than
1022 * tcp_minmss we get too many packets with very small payload which
1023 * is not good and burdens our system (and every packet generates
1024 * a wakeup to the process connected to our socket). We can reasonable
1025 * expect this to be small packet DoS attack to exhaust our CPU
1026 * cycles.
1027 *
1028 * Care has to be taken for the minimum packet overload value. This
1029 * value defines the minimum number of packets per second before we
1030 * start to worry. This must not be too low to avoid killing for
1031 * example interactive connections with many small packets like
1032 * telnet or SSH.
1033 *
1034 * Setting either tcp_minmssoverload or tcp_minmss to "0" disables
1035 * this check.
1036 *
1037 * Account for packet if payload packet, skip over ACK, etc.
1038 */
1039 if (tcp_minmss && tcp_minmssoverload &&
1040 tp->t_state == TCPS_ESTABLISHED && tlen > 0) {
1041 if ((unsigned int)(tp->rcv_second - ticks) < hz) {
1042 tp->rcv_pps++;
1043 tp->rcv_byps += tlen + off;
1044 if (tp->rcv_pps > tcp_minmssoverload) {
1045 if ((tp->rcv_byps / tp->rcv_pps) < tcp_minmss) {
1046 printf("too many small tcp packets from "
1047 "%s:%u, av. %lubyte/packet, "
1048 "dropping connection\n",
1049#ifdef INET6
1050 isipv6 ?
1051 ip6_sprintf(&inp->inp_inc.inc6_faddr) :
1052#endif
1053 inet_ntoa(inp->inp_inc.inc_faddr),
1054 inp->inp_inc.inc_fport,
1055 tp->rcv_byps / tp->rcv_pps);
1056 KASSERT(headlocked, ("tcp_input: "
1057 "after_listen: tcp_drop: head "
1058 "not locked"));
1059 tp = tcp_drop(tp, ECONNRESET);
1060 tcpstat.tcps_minmssdrops++;
1061 goto drop;
1062 }
1063 }
1064 } else {
1065 tp->rcv_second = ticks + hz;
1066 tp->rcv_pps = 1;
1067 tp->rcv_byps = tlen + off;
1068 }
1069 }
1070
1071 /*
1072 * Segment received on connection.
1073 * Reset idle time and keep-alive timer.
1074 */
1075 tp->t_rcvtime = ticks;
1076 if (TCPS_HAVEESTABLISHED(tp->t_state))
1077 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp);
1078
1079 /*
1080 * Process options only when we get SYN/ACK back. The SYN case
1081 * for incoming connections is handled in tcp_syncache.
1082 * XXX this is traditional behavior, may need to be cleaned up.
1083 */
1084 tcp_dooptions(&to, optp, optlen, thflags & TH_SYN);
| 31 */
32
33#include "opt_ipfw.h" /* for ipfw_fwd */
34#include "opt_inet.h"
35#include "opt_inet6.h"
36#include "opt_ipsec.h"
37#include "opt_mac.h"
38#include "opt_tcpdebug.h"
39#include "opt_tcp_input.h"
40#include "opt_tcp_sack.h"
41
42#include <sys/param.h>
43#include <sys/kernel.h>
44#include <sys/mac.h>
45#include <sys/malloc.h>
46#include <sys/mbuf.h>
47#include <sys/proc.h> /* for proc0 declaration */
48#include <sys/protosw.h>
49#include <sys/signalvar.h>
50#include <sys/socket.h>
51#include <sys/socketvar.h>
52#include <sys/sysctl.h>
53#include <sys/syslog.h>
54#include <sys/systm.h>
55
56#include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */
57
58#include <vm/uma.h>
59
60#include <net/if.h>
61#include <net/route.h>
62
63#include <netinet/in.h>
64#include <netinet/in_pcb.h>
65#include <netinet/in_systm.h>
66#include <netinet/in_var.h>
67#include <netinet/ip.h>
68#include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */
69#include <netinet/icmp_var.h> /* for ICMP_BANDLIM */
70#include <netinet/ip_var.h>
71#include <netinet/ip6.h>
72#include <netinet/icmp6.h>
73#include <netinet6/in6_pcb.h>
74#include <netinet6/ip6_var.h>
75#include <netinet6/nd6.h>
76#include <netinet/tcp.h>
77#include <netinet/tcp_fsm.h>
78#include <netinet/tcp_seq.h>
79#include <netinet/tcp_timer.h>
80#include <netinet/tcp_var.h>
81#include <netinet6/tcp6_var.h>
82#include <netinet/tcpip.h>
83#ifdef TCPDEBUG
84#include <netinet/tcp_debug.h>
85#endif /* TCPDEBUG */
86
87#ifdef FAST_IPSEC
88#include <netipsec/ipsec.h>
89#include <netipsec/ipsec6.h>
90#endif /*FAST_IPSEC*/
91
92#ifdef IPSEC
93#include <netinet6/ipsec.h>
94#include <netinet6/ipsec6.h>
95#include <netkey/key.h>
96#endif /*IPSEC*/
97
98#include <machine/in_cksum.h>
99
100static const int tcprexmtthresh = 3;
101
102struct tcpstat tcpstat;
103SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW,
104 &tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)");
105
106static int log_in_vain = 0;
107SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW,
108 &log_in_vain, 0, "Log all incoming TCP connections");
109
110static int blackhole = 0;
111SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW,
112 &blackhole, 0, "Do not send RST when dropping refused connections");
113
114int tcp_delack_enabled = 1;
115SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW,
116 &tcp_delack_enabled, 0,
117 "Delay ACK to try and piggyback it onto a data packet");
118
119#ifdef TCP_DROP_SYNFIN
120static int drop_synfin = 0;
121SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW,
122 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set");
123#endif
124
125static int tcp_do_rfc3042 = 1;
126SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW,
127 &tcp_do_rfc3042, 0, "Enable RFC 3042 (Limited Transmit)");
128
129static int tcp_do_rfc3390 = 1;
130SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW,
131 &tcp_do_rfc3390, 0,
132 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)");
133
134static int tcp_insecure_rst = 0;
135SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_RW,
136 &tcp_insecure_rst, 0,
137 "Follow the old (insecure) criteria for accepting RST packets.");
138
139SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0,
140 "TCP Segment Reassembly Queue");
141
142static int tcp_reass_maxseg = 0;
143SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN,
144 &tcp_reass_maxseg, 0,
145 "Global maximum number of TCP Segments in Reassembly Queue");
146
147int tcp_reass_qsize = 0;
148SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD,
149 &tcp_reass_qsize, 0,
150 "Global number of TCP Segments currently in Reassembly Queue");
151
152static int tcp_reass_maxqlen = 48;
153SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxqlen, CTLFLAG_RW,
154 &tcp_reass_maxqlen, 0,
155 "Maximum number of TCP Segments per individual Reassembly Queue");
156
157static int tcp_reass_overflows = 0;
158SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD,
159 &tcp_reass_overflows, 0,
160 "Global number of TCP Segment Reassembly Queue Overflows");
161
162struct inpcbhead tcb;
163#define tcb6 tcb /* for KAME src sync over BSD*'s */
164struct inpcbinfo tcbinfo;
165struct mtx *tcbinfo_mtx;
166
167static void tcp_dooptions(struct tcpopt *, u_char *, int, int);
168
169static void tcp_pulloutofband(struct socket *,
170 struct tcphdr *, struct mbuf *, int);
171static int tcp_reass(struct tcpcb *, struct tcphdr *, int *,
172 struct mbuf *);
173static void tcp_xmit_timer(struct tcpcb *, int);
174static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *);
175static int tcp_timewait(struct tcptw *, struct tcpopt *,
176 struct tcphdr *, struct mbuf *, int);
177
178/* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */
179#ifdef INET6
180#define ND6_HINT(tp) \
181do { \
182 if ((tp) && (tp)->t_inpcb && \
183 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \
184 nd6_nud_hint(NULL, NULL, 0); \
185} while (0)
186#else
187#define ND6_HINT(tp)
188#endif
189
190/*
191 * Indicate whether this ack should be delayed. We can delay the ack if
192 * - there is no delayed ack timer in progress and
193 * - our last ack wasn't a 0-sized window. We never want to delay
194 * the ack that opens up a 0-sized window and
195 * - delayed acks are enabled or
196 * - this is a half-synchronized T/TCP connection.
197 */
198#define DELAY_ACK(tp) \
199 ((!callout_active(tp->tt_delack) && \
200 (tp->t_flags & TF_RXWIN0SENT) == 0) && \
201 (tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN)))
202
203/* Initialize TCP reassembly queue */
204uma_zone_t tcp_reass_zone;
205void
206tcp_reass_init()
207{
208 tcp_reass_maxseg = nmbclusters / 16;
209 TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments",
210 &tcp_reass_maxseg);
211 tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent),
212 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
213 uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg);
214}
215
216static int
217tcp_reass(tp, th, tlenp, m)
218 register struct tcpcb *tp;
219 register struct tcphdr *th;
220 int *tlenp;
221 struct mbuf *m;
222{
223 struct tseg_qent *q;
224 struct tseg_qent *p = NULL;
225 struct tseg_qent *nq;
226 struct tseg_qent *te = NULL;
227 struct socket *so = tp->t_inpcb->inp_socket;
228 int flags;
229
230 INP_LOCK_ASSERT(tp->t_inpcb);
231
232 /*
233 * XXX: tcp_reass() is rather inefficient with its data structures
234 * and should be rewritten (see NetBSD for optimizations). While
235 * doing that it should move to its own file tcp_reass.c.
236 */
237
238 /*
239 * Call with th==NULL after become established to
240 * force pre-ESTABLISHED data up to user socket.
241 */
242 if (th == NULL)
243 goto present;
244
245 /*
246 * Limit the number of segments in the reassembly queue to prevent
247 * holding on to too many segments (and thus running out of mbufs).
248 * Make sure to let the missing segment through which caused this
249 * queue. Always keep one global queue entry spare to be able to
250 * process the missing segment.
251 */
252 if (th->th_seq != tp->rcv_nxt &&
253 (tcp_reass_qsize + 1 >= tcp_reass_maxseg ||
254 tp->t_segqlen >= tcp_reass_maxqlen)) {
255 tcp_reass_overflows++;
256 tcpstat.tcps_rcvmemdrop++;
257 m_freem(m);
258 *tlenp = 0;
259 return (0);
260 }
261
262 /*
263 * Allocate a new queue entry. If we can't, or hit the zone limit
264 * just drop the pkt.
265 */
266 te = uma_zalloc(tcp_reass_zone, M_NOWAIT);
267 if (te == NULL) {
268 tcpstat.tcps_rcvmemdrop++;
269 m_freem(m);
270 *tlenp = 0;
271 return (0);
272 }
273 tp->t_segqlen++;
274 tcp_reass_qsize++;
275
276 /*
277 * Find a segment which begins after this one does.
278 */
279 LIST_FOREACH(q, &tp->t_segq, tqe_q) {
280 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
281 break;
282 p = q;
283 }
284
285 /*
286 * If there is a preceding segment, it may provide some of
287 * our data already. If so, drop the data from the incoming
288 * segment. If it provides all of our data, drop us.
289 */
290 if (p != NULL) {
291 register int i;
292 /* conversion to int (in i) handles seq wraparound */
293 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
294 if (i > 0) {
295 if (i >= *tlenp) {
296 tcpstat.tcps_rcvduppack++;
297 tcpstat.tcps_rcvdupbyte += *tlenp;
298 m_freem(m);
299 uma_zfree(tcp_reass_zone, te);
300 tp->t_segqlen--;
301 tcp_reass_qsize--;
302 /*
303 * Try to present any queued data
304 * at the left window edge to the user.
305 * This is needed after the 3-WHS
306 * completes.
307 */
308 goto present; /* ??? */
309 }
310 m_adj(m, i);
311 *tlenp -= i;
312 th->th_seq += i;
313 }
314 }
315 tcpstat.tcps_rcvoopack++;
316 tcpstat.tcps_rcvoobyte += *tlenp;
317
318 /*
319 * While we overlap succeeding segments trim them or,
320 * if they are completely covered, dequeue them.
321 */
322 while (q) {
323 register int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
324 if (i <= 0)
325 break;
326 if (i < q->tqe_len) {
327 q->tqe_th->th_seq += i;
328 q->tqe_len -= i;
329 m_adj(q->tqe_m, i);
330 break;
331 }
332
333 nq = LIST_NEXT(q, tqe_q);
334 LIST_REMOVE(q, tqe_q);
335 m_freem(q->tqe_m);
336 uma_zfree(tcp_reass_zone, q);
337 tp->t_segqlen--;
338 tcp_reass_qsize--;
339 q = nq;
340 }
341
342 /* Insert the new segment queue entry into place. */
343 te->tqe_m = m;
344 te->tqe_th = th;
345 te->tqe_len = *tlenp;
346
347 if (p == NULL) {
348 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q);
349 } else {
350 LIST_INSERT_AFTER(p, te, tqe_q);
351 }
352
353present:
354 /*
355 * Present data to user, advancing rcv_nxt through
356 * completed sequence space.
357 */
358 if (!TCPS_HAVEESTABLISHED(tp->t_state))
359 return (0);
360 q = LIST_FIRST(&tp->t_segq);
361 if (!q || q->tqe_th->th_seq != tp->rcv_nxt)
362 return (0);
363 SOCKBUF_LOCK(&so->so_rcv);
364 do {
365 tp->rcv_nxt += q->tqe_len;
366 flags = q->tqe_th->th_flags & TH_FIN;
367 nq = LIST_NEXT(q, tqe_q);
368 LIST_REMOVE(q, tqe_q);
369 if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
370 m_freem(q->tqe_m);
371 else
372 sbappendstream_locked(&so->so_rcv, q->tqe_m);
373 uma_zfree(tcp_reass_zone, q);
374 tp->t_segqlen--;
375 tcp_reass_qsize--;
376 q = nq;
377 } while (q && q->tqe_th->th_seq == tp->rcv_nxt);
378 ND6_HINT(tp);
379 sorwakeup_locked(so);
380 return (flags);
381}
382
383/*
384 * TCP input routine, follows pages 65-76 of the
385 * protocol specification dated September, 1981 very closely.
386 */
387#ifdef INET6
388int
389tcp6_input(mp, offp, proto)
390 struct mbuf **mp;
391 int *offp, proto;
392{
393 register struct mbuf *m = *mp;
394 struct in6_ifaddr *ia6;
395
396 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE);
397
398 /*
399 * draft-itojun-ipv6-tcp-to-anycast
400 * better place to put this in?
401 */
402 ia6 = ip6_getdstifaddr(m);
403 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) {
404 struct ip6_hdr *ip6;
405
406 ip6 = mtod(m, struct ip6_hdr *);
407 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
408 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6);
409 return IPPROTO_DONE;
410 }
411
412 tcp_input(m, *offp);
413 return IPPROTO_DONE;
414}
415#endif
416
417void
418tcp_input(m, off0)
419 register struct mbuf *m;
420 int off0;
421{
422 register struct tcphdr *th;
423 register struct ip *ip = NULL;
424 register struct ipovly *ipov;
425 register struct inpcb *inp = NULL;
426 u_char *optp = NULL;
427 int optlen = 0;
428 int len, tlen, off;
429 int drop_hdrlen;
430 register struct tcpcb *tp = 0;
431 register int thflags;
432 struct socket *so = 0;
433 int todrop, acked, ourfinisacked, needoutput = 0;
434 u_long tiwin;
435 struct tcpopt to; /* options in this segment */
436 int headlocked = 0;
437#ifdef IPFIREWALL_FORWARD
438 struct m_tag *fwd_tag;
439#endif
440 int rstreason; /* For badport_bandlim accounting purposes */
441
442 struct ip6_hdr *ip6 = NULL;
443#ifdef INET6
444 int isipv6;
445#else
446 const int isipv6 = 0;
447#endif
448
449#ifdef TCPDEBUG
450 /*
451 * The size of tcp_saveipgen must be the size of the max ip header,
452 * now IPv6.
453 */
454 u_char tcp_saveipgen[40];
455 struct tcphdr tcp_savetcp;
456 short ostate = 0;
457#endif
458
459#ifdef INET6
460 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0;
461#endif
462 bzero((char *)&to, sizeof(to));
463
464 tcpstat.tcps_rcvtotal++;
465
466 if (isipv6) {
467#ifdef INET6
468 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */
469 ip6 = mtod(m, struct ip6_hdr *);
470 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0;
471 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) {
472 tcpstat.tcps_rcvbadsum++;
473 goto drop;
474 }
475 th = (struct tcphdr *)((caddr_t)ip6 + off0);
476
477 /*
478 * Be proactive about unspecified IPv6 address in source.
479 * As we use all-zero to indicate unbounded/unconnected pcb,
480 * unspecified IPv6 address can be used to confuse us.
481 *
482 * Note that packets with unspecified IPv6 destination is
483 * already dropped in ip6_input.
484 */
485 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
486 /* XXX stat */
487 goto drop;
488 }
489#else
490 th = NULL; /* XXX: avoid compiler warning */
491#endif
492 } else {
493 /*
494 * Get IP and TCP header together in first mbuf.
495 * Note: IP leaves IP header in first mbuf.
496 */
497 if (off0 > sizeof (struct ip)) {
498 ip_stripoptions(m, (struct mbuf *)0);
499 off0 = sizeof(struct ip);
500 }
501 if (m->m_len < sizeof (struct tcpiphdr)) {
502 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) {
503 tcpstat.tcps_rcvshort++;
504 return;
505 }
506 }
507 ip = mtod(m, struct ip *);
508 ipov = (struct ipovly *)ip;
509 th = (struct tcphdr *)((caddr_t)ip + off0);
510 tlen = ip->ip_len;
511
512 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
513 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
514 th->th_sum = m->m_pkthdr.csum_data;
515 else
516 th->th_sum = in_pseudo(ip->ip_src.s_addr,
517 ip->ip_dst.s_addr,
518 htonl(m->m_pkthdr.csum_data +
519 ip->ip_len +
520 IPPROTO_TCP));
521 th->th_sum ^= 0xffff;
522#ifdef TCPDEBUG
523 ipov->ih_len = (u_short)tlen;
524 ipov->ih_len = htons(ipov->ih_len);
525#endif
526 } else {
527 /*
528 * Checksum extended TCP header and data.
529 */
530 len = sizeof (struct ip) + tlen;
531 bzero(ipov->ih_x1, sizeof(ipov->ih_x1));
532 ipov->ih_len = (u_short)tlen;
533 ipov->ih_len = htons(ipov->ih_len);
534 th->th_sum = in_cksum(m, len);
535 }
536 if (th->th_sum) {
537 tcpstat.tcps_rcvbadsum++;
538 goto drop;
539 }
540#ifdef INET6
541 /* Re-initialization for later version check */
542 ip->ip_v = IPVERSION;
543#endif
544 }
545
546 /*
547 * Check that TCP offset makes sense,
548 * pull out TCP options and adjust length. XXX
549 */
550 off = th->th_off << 2;
551 if (off < sizeof (struct tcphdr) || off > tlen) {
552 tcpstat.tcps_rcvbadoff++;
553 goto drop;
554 }
555 tlen -= off; /* tlen is used instead of ti->ti_len */
556 if (off > sizeof (struct tcphdr)) {
557 if (isipv6) {
558#ifdef INET6
559 IP6_EXTHDR_CHECK(m, off0, off, );
560 ip6 = mtod(m, struct ip6_hdr *);
561 th = (struct tcphdr *)((caddr_t)ip6 + off0);
562#endif
563 } else {
564 if (m->m_len < sizeof(struct ip) + off) {
565 if ((m = m_pullup(m, sizeof (struct ip) + off))
566 == 0) {
567 tcpstat.tcps_rcvshort++;
568 return;
569 }
570 ip = mtod(m, struct ip *);
571 ipov = (struct ipovly *)ip;
572 th = (struct tcphdr *)((caddr_t)ip + off0);
573 }
574 }
575 optlen = off - sizeof (struct tcphdr);
576 optp = (u_char *)(th + 1);
577 }
578 thflags = th->th_flags;
579
580#ifdef TCP_DROP_SYNFIN
581 /*
582 * If the drop_synfin option is enabled, drop all packets with
583 * both the SYN and FIN bits set. This prevents e.g. nmap from
584 * identifying the TCP/IP stack.
585 *
586 * This is a violation of the TCP specification.
587 */
588 if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN))
589 goto drop;
590#endif
591
592 /*
593 * Convert TCP protocol specific fields to host format.
594 */
595 th->th_seq = ntohl(th->th_seq);
596 th->th_ack = ntohl(th->th_ack);
597 th->th_win = ntohs(th->th_win);
598 th->th_urp = ntohs(th->th_urp);
599
600 /*
601 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options,
602 * until after ip6_savecontrol() is called and before other functions
603 * which don't want those proto headers.
604 * Because ip6_savecontrol() is going to parse the mbuf to
605 * search for data to be passed up to user-land, it wants mbuf
606 * parameters to be unchanged.
607 * XXX: the call of ip6_savecontrol() has been obsoleted based on
608 * latest version of the advanced API (20020110).
609 */
610 drop_hdrlen = off0 + off;
611
612 /*
613 * Locate pcb for segment.
614 */
615 INP_INFO_WLOCK(&tcbinfo);
616 headlocked = 1;
617findpcb:
618 KASSERT(headlocked, ("tcp_input: findpcb: head not locked"));
619#ifdef IPFIREWALL_FORWARD
620 /* Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. */
621 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL);
622
623 if (fwd_tag != NULL && isipv6 == 0) { /* IPv6 support is not yet */
624 struct sockaddr_in *next_hop;
625
626 next_hop = (struct sockaddr_in *)(fwd_tag+1);
627 /*
628 * Transparently forwarded. Pretend to be the destination.
629 * already got one like this?
630 */
631 inp = in_pcblookup_hash(&tcbinfo,
632 ip->ip_src, th->th_sport,
633 ip->ip_dst, th->th_dport,
634 0, m->m_pkthdr.rcvif);
635 if (!inp) {
636 /* It's new. Try to find the ambushing socket. */
637 inp = in_pcblookup_hash(&tcbinfo,
638 ip->ip_src, th->th_sport,
639 next_hop->sin_addr,
640 next_hop->sin_port ?
641 ntohs(next_hop->sin_port) :
642 th->th_dport,
643 1, m->m_pkthdr.rcvif);
644 }
645 /* Remove the tag from the packet. We don't need it anymore. */
646 m_tag_delete(m, fwd_tag);
647 } else {
648#endif /* IPFIREWALL_FORWARD */
649 if (isipv6) {
650#ifdef INET6
651 inp = in6_pcblookup_hash(&tcbinfo,
652 &ip6->ip6_src, th->th_sport,
653 &ip6->ip6_dst, th->th_dport,
654 1, m->m_pkthdr.rcvif);
655#endif
656 } else
657 inp = in_pcblookup_hash(&tcbinfo,
658 ip->ip_src, th->th_sport,
659 ip->ip_dst, th->th_dport,
660 1, m->m_pkthdr.rcvif);
661#ifdef IPFIREWALL_FORWARD
662 }
663#endif /* IPFIREWALL_FORWARD */
664
665#if defined(IPSEC) || defined(FAST_IPSEC)
666#ifdef INET6
667 if (isipv6) {
668 if (inp != NULL && ipsec6_in_reject(m, inp)) {
669#ifdef IPSEC
670 ipsec6stat.in_polvio++;
671#endif
672 goto drop;
673 }
674 } else
675#endif /* INET6 */
676 if (inp != NULL && ipsec4_in_reject(m, inp)) {
677#ifdef IPSEC
678 ipsecstat.in_polvio++;
679#endif
680 goto drop;
681 }
682#endif /*IPSEC || FAST_IPSEC*/
683
684 /*
685 * If the state is CLOSED (i.e., TCB does not exist) then
686 * all data in the incoming segment is discarded.
687 * If the TCB exists but is in CLOSED state, it is embryonic,
688 * but should either do a listen or a connect soon.
689 */
690 if (inp == NULL) {
691 if (log_in_vain) {
692#ifdef INET6
693 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2];
694#else
695 char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"];
696#endif
697
698 if (isipv6) {
699#ifdef INET6
700 strcpy(dbuf, "[");
701 strcpy(sbuf, "[");
702 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst));
703 strcat(sbuf, ip6_sprintf(&ip6->ip6_src));
704 strcat(dbuf, "]");
705 strcat(sbuf, "]");
706#endif
707 } else {
708 strcpy(dbuf, inet_ntoa(ip->ip_dst));
709 strcpy(sbuf, inet_ntoa(ip->ip_src));
710 }
711 switch (log_in_vain) {
712 case 1:
713 if ((thflags & TH_SYN) == 0)
714 break;
715 /* FALLTHROUGH */
716 case 2:
717 log(LOG_INFO,
718 "Connection attempt to TCP %s:%d "
719 "from %s:%d flags:0x%02x\n",
720 dbuf, ntohs(th->th_dport), sbuf,
721 ntohs(th->th_sport), thflags);
722 break;
723 default:
724 break;
725 }
726 }
727 if (blackhole) {
728 switch (blackhole) {
729 case 1:
730 if (thflags & TH_SYN)
731 goto drop;
732 break;
733 case 2:
734 goto drop;
735 default:
736 goto drop;
737 }
738 }
739 rstreason = BANDLIM_RST_CLOSEDPORT;
740 goto dropwithreset;
741 }
742 INP_LOCK(inp);
743 if (inp->inp_vflag & INP_TIMEWAIT) {
744 /*
745 * The only option of relevance is TOF_CC, and only if
746 * present in a SYN segment. See tcp_timewait().
747 */
748 if (thflags & TH_SYN)
749 tcp_dooptions(&to, optp, optlen, 1);
750 if (tcp_timewait((struct tcptw *)inp->inp_ppcb,
751 &to, th, m, tlen))
752 goto findpcb;
753 /*
754 * tcp_timewait unlocks inp.
755 */
756 INP_INFO_WUNLOCK(&tcbinfo);
757 return;
758 }
759 tp = intotcpcb(inp);
760 if (tp == 0) {
761 INP_UNLOCK(inp);
762 rstreason = BANDLIM_RST_CLOSEDPORT;
763 goto dropwithreset;
764 }
765 if (tp->t_state == TCPS_CLOSED)
766 goto drop;
767
768 /* Unscale the window into a 32-bit value. */
769 if ((thflags & TH_SYN) == 0)
770 tiwin = th->th_win << tp->snd_scale;
771 else
772 tiwin = th->th_win;
773
774#ifdef MAC
775 INP_LOCK_ASSERT(inp);
776 if (mac_check_inpcb_deliver(inp, m))
777 goto drop;
778#endif
779 so = inp->inp_socket;
780#ifdef TCPDEBUG
781 if (so->so_options & SO_DEBUG) {
782 ostate = tp->t_state;
783 if (isipv6)
784 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6));
785 else
786 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip));
787 tcp_savetcp = *th;
788 }
789#endif
790 if (so->so_options & SO_ACCEPTCONN) {
791 struct in_conninfo inc;
792
793#ifdef INET6
794 inc.inc_isipv6 = isipv6;
795#endif
796 if (isipv6) {
797 inc.inc6_faddr = ip6->ip6_src;
798 inc.inc6_laddr = ip6->ip6_dst;
799 } else {
800 inc.inc_faddr = ip->ip_src;
801 inc.inc_laddr = ip->ip_dst;
802 }
803 inc.inc_fport = th->th_sport;
804 inc.inc_lport = th->th_dport;
805
806 /*
807 * If the state is LISTEN then ignore segment if it contains
808 * a RST. If the segment contains an ACK then it is bad and
809 * send a RST. If it does not contain a SYN then it is not
810 * interesting; drop it.
811 *
812 * If the state is SYN_RECEIVED (syncache) and seg contains
813 * an ACK, but not for our SYN/ACK, send a RST. If the seg
814 * contains a RST, check the sequence number to see if it
815 * is a valid reset segment.
816 */
817 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) {
818 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) {
819 if (!syncache_expand(&inc, th, &so, m)) {
820 /*
821 * No syncache entry, or ACK was not
822 * for our SYN/ACK. Send a RST.
823 */
824 tcpstat.tcps_badsyn++;
825 rstreason = BANDLIM_RST_OPENPORT;
826 goto dropwithreset;
827 }
828 if (so == NULL) {
829 /*
830 * Could not complete 3-way handshake,
831 * connection is being closed down, and
832 * syncache will free mbuf.
833 */
834 INP_UNLOCK(inp);
835 INP_INFO_WUNLOCK(&tcbinfo);
836 return;
837 }
838 /*
839 * Socket is created in state SYN_RECEIVED.
840 * Continue processing segment.
841 */
842 INP_UNLOCK(inp);
843 inp = sotoinpcb(so);
844 INP_LOCK(inp);
845 tp = intotcpcb(inp);
846 /*
847 * This is what would have happened in
848 * tcp_output() when the SYN,ACK was sent.
849 */
850 tp->snd_up = tp->snd_una;
851 tp->snd_max = tp->snd_nxt = tp->iss + 1;
852 tp->last_ack_sent = tp->rcv_nxt;
853 /*
854 * RFC1323: The window in SYN & SYN/ACK
855 * segments is never scaled.
856 */
857 tp->snd_wnd = tiwin; /* unscaled */
858 goto after_listen;
859 }
860 if (thflags & TH_RST) {
861 syncache_chkrst(&inc, th);
862 goto drop;
863 }
864 if (thflags & TH_ACK) {
865 syncache_badack(&inc);
866 tcpstat.tcps_badsyn++;
867 rstreason = BANDLIM_RST_OPENPORT;
868 goto dropwithreset;
869 }
870 goto drop;
871 }
872
873 /*
874 * Segment's flags are (SYN) or (SYN|FIN).
875 */
876#ifdef INET6
877 /*
878 * If deprecated address is forbidden,
879 * we do not accept SYN to deprecated interface
880 * address to prevent any new inbound connection from
881 * getting established.
882 * When we do not accept SYN, we send a TCP RST,
883 * with deprecated source address (instead of dropping
884 * it). We compromise it as it is much better for peer
885 * to send a RST, and RST will be the final packet
886 * for the exchange.
887 *
888 * If we do not forbid deprecated addresses, we accept
889 * the SYN packet. RFC2462 does not suggest dropping
890 * SYN in this case.
891 * If we decipher RFC2462 5.5.4, it says like this:
892 * 1. use of deprecated addr with existing
893 * communication is okay - "SHOULD continue to be
894 * used"
895 * 2. use of it with new communication:
896 * (2a) "SHOULD NOT be used if alternate address
897 * with sufficient scope is available"
898 * (2b) nothing mentioned otherwise.
899 * Here we fall into (2b) case as we have no choice in
900 * our source address selection - we must obey the peer.
901 *
902 * The wording in RFC2462 is confusing, and there are
903 * multiple description text for deprecated address
904 * handling - worse, they are not exactly the same.
905 * I believe 5.5.4 is the best one, so we follow 5.5.4.
906 */
907 if (isipv6 && !ip6_use_deprecated) {
908 struct in6_ifaddr *ia6;
909
910 if ((ia6 = ip6_getdstifaddr(m)) &&
911 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
912 INP_UNLOCK(inp);
913 tp = NULL;
914 rstreason = BANDLIM_RST_OPENPORT;
915 goto dropwithreset;
916 }
917 }
918#endif
919 /*
920 * If it is from this socket, drop it, it must be forged.
921 * Don't bother responding if the destination was a broadcast.
922 */
923 if (th->th_dport == th->th_sport) {
924 if (isipv6) {
925 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst,
926 &ip6->ip6_src))
927 goto drop;
928 } else {
929 if (ip->ip_dst.s_addr == ip->ip_src.s_addr)
930 goto drop;
931 }
932 }
933 /*
934 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN
935 *
936 * Note that it is quite possible to receive unicast
937 * link-layer packets with a broadcast IP address. Use
938 * in_broadcast() to find them.
939 */
940 if (m->m_flags & (M_BCAST|M_MCAST))
941 goto drop;
942 if (isipv6) {
943 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
944 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
945 goto drop;
946 } else {
947 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
948 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
949 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
950 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
951 goto drop;
952 }
953 /*
954 * SYN appears to be valid; create compressed TCP state
955 * for syncache, or perform t/tcp connection.
956 */
957 if (so->so_qlen <= so->so_qlimit) {
958#ifdef TCPDEBUG
959 if (so->so_options & SO_DEBUG)
960 tcp_trace(TA_INPUT, ostate, tp,
961 (void *)tcp_saveipgen, &tcp_savetcp, 0);
962#endif
963 tcp_dooptions(&to, optp, optlen, 1);
964 if (!syncache_add(&inc, &to, th, &so, m))
965 goto drop;
966 if (so == NULL) {
967 /*
968 * Entry added to syncache, mbuf used to
969 * send SYN,ACK packet.
970 */
971 KASSERT(headlocked, ("headlocked"));
972 INP_UNLOCK(inp);
973 INP_INFO_WUNLOCK(&tcbinfo);
974 return;
975 }
976 /*
977 * Segment passed TAO tests.
978 */
979 INP_UNLOCK(inp);
980 inp = sotoinpcb(so);
981 INP_LOCK(inp);
982 tp = intotcpcb(inp);
983 tp->snd_wnd = tiwin;
984 tp->t_starttime = ticks;
985 tp->t_state = TCPS_ESTABLISHED;
986
987 /*
988 * T/TCP logic:
989 * If there is a FIN or if there is data, then
990 * delay SYN,ACK(SYN) in the hope of piggy-backing
991 * it on a response segment. Otherwise must send
992 * ACK now in case the other side is slow starting.
993 */
994 if (thflags & TH_FIN || tlen != 0)
995 tp->t_flags |= (TF_DELACK | TF_NEEDSYN);
996 else
997 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN);
998 tcpstat.tcps_connects++;
999 soisconnected(so);
1000 goto trimthenstep6;
1001 }
1002 goto drop;
1003 }
1004after_listen:
1005 KASSERT(headlocked, ("tcp_input: after_listen: head not locked"));
1006 INP_LOCK_ASSERT(inp);
1007
1008 /* XXX temp debugging */
1009 /* should not happen - syncache should pick up these connections */
1010 if (tp->t_state == TCPS_LISTEN)
1011 panic("tcp_input: TCPS_LISTEN");
1012
1013 /*
1014 * This is the second part of the MSS DoS prevention code (after
1015 * minmss on the sending side) and it deals with too many too small
1016 * tcp packets in a too short timeframe (1 second).
1017 *
1018 * For every full second we count the number of received packets
1019 * and bytes. If we get a lot of packets per second for this connection
1020 * (tcp_minmssoverload) we take a closer look at it and compute the
1021 * average packet size for the past second. If that is less than
1022 * tcp_minmss we get too many packets with very small payload which
1023 * is not good and burdens our system (and every packet generates
1024 * a wakeup to the process connected to our socket). We can reasonable
1025 * expect this to be small packet DoS attack to exhaust our CPU
1026 * cycles.
1027 *
1028 * Care has to be taken for the minimum packet overload value. This
1029 * value defines the minimum number of packets per second before we
1030 * start to worry. This must not be too low to avoid killing for
1031 * example interactive connections with many small packets like
1032 * telnet or SSH.
1033 *
1034 * Setting either tcp_minmssoverload or tcp_minmss to "0" disables
1035 * this check.
1036 *
1037 * Account for packet if payload packet, skip over ACK, etc.
1038 */
1039 if (tcp_minmss && tcp_minmssoverload &&
1040 tp->t_state == TCPS_ESTABLISHED && tlen > 0) {
1041 if ((unsigned int)(tp->rcv_second - ticks) < hz) {
1042 tp->rcv_pps++;
1043 tp->rcv_byps += tlen + off;
1044 if (tp->rcv_pps > tcp_minmssoverload) {
1045 if ((tp->rcv_byps / tp->rcv_pps) < tcp_minmss) {
1046 printf("too many small tcp packets from "
1047 "%s:%u, av. %lubyte/packet, "
1048 "dropping connection\n",
1049#ifdef INET6
1050 isipv6 ?
1051 ip6_sprintf(&inp->inp_inc.inc6_faddr) :
1052#endif
1053 inet_ntoa(inp->inp_inc.inc_faddr),
1054 inp->inp_inc.inc_fport,
1055 tp->rcv_byps / tp->rcv_pps);
1056 KASSERT(headlocked, ("tcp_input: "
1057 "after_listen: tcp_drop: head "
1058 "not locked"));
1059 tp = tcp_drop(tp, ECONNRESET);
1060 tcpstat.tcps_minmssdrops++;
1061 goto drop;
1062 }
1063 }
1064 } else {
1065 tp->rcv_second = ticks + hz;
1066 tp->rcv_pps = 1;
1067 tp->rcv_byps = tlen + off;
1068 }
1069 }
1070
1071 /*
1072 * Segment received on connection.
1073 * Reset idle time and keep-alive timer.
1074 */
1075 tp->t_rcvtime = ticks;
1076 if (TCPS_HAVEESTABLISHED(tp->t_state))
1077 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp);
1078
1079 /*
1080 * Process options only when we get SYN/ACK back. The SYN case
1081 * for incoming connections is handled in tcp_syncache.
1082 * XXX this is traditional behavior, may need to be cleaned up.
1083 */
1084 tcp_dooptions(&to, optp, optlen, thflags & TH_SYN);
|
1086 if (to.to_flags & TOF_SCALE) {
1087 tp->t_flags |= TF_RCVD_SCALE;
1088 tp->requested_s_scale = to.to_requested_s_scale;
1089 }
1090 if (to.to_flags & TOF_TS) {
1091 tp->t_flags |= TF_RCVD_TSTMP;
1092 tp->ts_recent = to.to_tsval;
1093 tp->ts_recent_age = ticks;
1094 }
1095 if (to.to_flags & TOF_MSS)
1096 tcp_mss(tp, to.to_mss);
1097 if (tp->sack_enable) {
1098 if (!(to.to_flags & TOF_SACK))
1099 tp->sack_enable = 0;
1100 else
1101 tp->t_flags |= TF_SACK_PERMIT;
1102 }
1103
1104 }
1105
1106 /*
1107 * Header prediction: check for the two common cases
1108 * of a uni-directional data xfer. If the packet has
1109 * no control flags, is in-sequence, the window didn't
1110 * change and we're not retransmitting, it's a
1111 * candidate. If the length is zero and the ack moved
1112 * forward, we're the sender side of the xfer. Just
1113 * free the data acked & wake any higher level process
1114 * that was blocked waiting for space. If the length
1115 * is non-zero and the ack didn't move, we're the
1116 * receiver side. If we're getting packets in-order
1117 * (the reassembly queue is empty), add the data to
1118 * the socket buffer and note that we need a delayed ack.
1119 * Make sure that the hidden state-flags are also off.
1120 * Since we check for TCPS_ESTABLISHED above, it can only
1121 * be TH_NEEDSYN.
1122 */
1123 if (tp->t_state == TCPS_ESTABLISHED &&
1124 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
1125 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) &&
1126 ((to.to_flags & TOF_TS) == 0 ||
1127 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) &&
1128 th->th_seq == tp->rcv_nxt && tiwin && tiwin == tp->snd_wnd &&
1129 tp->snd_nxt == tp->snd_max) {
1130
1131 /*
1132 * If last ACK falls within this segment's sequence numbers,
1133 * record the timestamp.
1134 * NOTE that the test is modified according to the latest
1135 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1136 */
1137 if ((to.to_flags & TOF_TS) != 0 &&
1138 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
1139 tp->ts_recent_age = ticks;
1140 tp->ts_recent = to.to_tsval;
1141 }
1142
1143 if (tlen == 0) {
1144 if (SEQ_GT(th->th_ack, tp->snd_una) &&
1145 SEQ_LEQ(th->th_ack, tp->snd_max) &&
1146 tp->snd_cwnd >= tp->snd_wnd &&
1147 ((!tcp_do_newreno && !tp->sack_enable &&
1148 tp->t_dupacks < tcprexmtthresh) ||
1149 ((tcp_do_newreno || tp->sack_enable) &&
1150 !IN_FASTRECOVERY(tp) && to.to_nsacks == 0))) {
1151 KASSERT(headlocked, ("headlocked"));
1152 INP_INFO_WUNLOCK(&tcbinfo);
1153 headlocked = 0;
1154 /*
1155 * this is a pure ack for outstanding data.
1156 */
1157 ++tcpstat.tcps_predack;
1158 /*
1159 * "bad retransmit" recovery
1160 */
1161 if (tp->t_rxtshift == 1 &&
1162 ticks < tp->t_badrxtwin) {
1163 ++tcpstat.tcps_sndrexmitbad;
1164 tp->snd_cwnd = tp->snd_cwnd_prev;
1165 tp->snd_ssthresh =
1166 tp->snd_ssthresh_prev;
1167 tp->snd_recover = tp->snd_recover_prev;
1168 if (tp->t_flags & TF_WASFRECOVERY)
1169 ENTER_FASTRECOVERY(tp);
1170 tp->snd_nxt = tp->snd_max;
1171 tp->t_badrxtwin = 0;
1172 }
1173
1174 /*
1175 * Recalculate the transmit timer / rtt.
1176 *
1177 * Some boxes send broken timestamp replies
1178 * during the SYN+ACK phase, ignore
1179 * timestamps of 0 or we could calculate a
1180 * huge RTT and blow up the retransmit timer.
1181 */
1182 if ((to.to_flags & TOF_TS) != 0 &&
1183 to.to_tsecr) {
1184 tcp_xmit_timer(tp,
1185 ticks - to.to_tsecr + 1);
1186 } else if (tp->t_rtttime &&
1187 SEQ_GT(th->th_ack, tp->t_rtseq)) {
1188 tcp_xmit_timer(tp,
1189 ticks - tp->t_rtttime);
1190 }
1191 tcp_xmit_bandwidth_limit(tp, th->th_ack);
1192 acked = th->th_ack - tp->snd_una;
1193 tcpstat.tcps_rcvackpack++;
1194 tcpstat.tcps_rcvackbyte += acked;
1195 sbdrop(&so->so_snd, acked);
1196 if (SEQ_GT(tp->snd_una, tp->snd_recover) &&
1197 SEQ_LEQ(th->th_ack, tp->snd_recover))
1198 tp->snd_recover = th->th_ack - 1;
1199 tp->snd_una = th->th_ack;
1200 /*
1201 * pull snd_wl2 up to prevent seq wrap relative
1202 * to th_ack.
1203 */
1204 tp->snd_wl2 = th->th_ack;
1205 tp->t_dupacks = 0;
1206 m_freem(m);
1207 ND6_HINT(tp); /* some progress has been done */
1208
1209 /*
1210 * If all outstanding data are acked, stop
1211 * retransmit timer, otherwise restart timer
1212 * using current (possibly backed-off) value.
1213 * If process is waiting for space,
1214 * wakeup/selwakeup/signal. If data
1215 * are ready to send, let tcp_output
1216 * decide between more output or persist.
1217
1218#ifdef TCPDEBUG
1219 if (so->so_options & SO_DEBUG)
1220 tcp_trace(TA_INPUT, ostate, tp,
1221 (void *)tcp_saveipgen,
1222 &tcp_savetcp, 0);
1223#endif
1224 */
1225 if (tp->snd_una == tp->snd_max)
1226 callout_stop(tp->tt_rexmt);
1227 else if (!callout_active(tp->tt_persist))
1228 callout_reset(tp->tt_rexmt,
1229 tp->t_rxtcur,
1230 tcp_timer_rexmt, tp);
1231
1232 sowwakeup(so);
1233 if (so->so_snd.sb_cc)
1234 (void) tcp_output(tp);
1235 goto check_delack;
1236 }
1237 } else if (th->th_ack == tp->snd_una &&
1238 LIST_EMPTY(&tp->t_segq) &&
1239 tlen <= sbspace(&so->so_rcv)) {
1240 KASSERT(headlocked, ("headlocked"));
1241 INP_INFO_WUNLOCK(&tcbinfo);
1242 headlocked = 0;
1243 /*
1244 * this is a pure, in-sequence data packet
1245 * with nothing on the reassembly queue and
1246 * we have enough buffer space to take it.
1247 */
1248 /* Clean receiver SACK report if present */
1249 if (tp->sack_enable && tp->rcv_numsacks)
1250 tcp_clean_sackreport(tp);
1251 ++tcpstat.tcps_preddat;
1252 tp->rcv_nxt += tlen;
1253 /*
1254 * Pull snd_wl1 up to prevent seq wrap relative to
1255 * th_seq.
1256 */
1257 tp->snd_wl1 = th->th_seq;
1258 /*
1259 * Pull rcv_up up to prevent seq wrap relative to
1260 * rcv_nxt.
1261 */
1262 tp->rcv_up = tp->rcv_nxt;
1263 tcpstat.tcps_rcvpack++;
1264 tcpstat.tcps_rcvbyte += tlen;
1265 ND6_HINT(tp); /* some progress has been done */
1266 /*
1267#ifdef TCPDEBUG
1268 if (so->so_options & SO_DEBUG)
1269 tcp_trace(TA_INPUT, ostate, tp,
1270 (void *)tcp_saveipgen, &tcp_savetcp, 0);
1271#endif
1272 * Add data to socket buffer.
1273 */
1274 SOCKBUF_LOCK(&so->so_rcv);
1275 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
1276 m_freem(m);
1277 } else {
1278 m_adj(m, drop_hdrlen); /* delayed header drop */
1279 sbappendstream_locked(&so->so_rcv, m);
1280 }
1281 sorwakeup_locked(so);
1282 if (DELAY_ACK(tp)) {
1283 tp->t_flags |= TF_DELACK;
1284 } else {
1285 tp->t_flags |= TF_ACKNOW;
1286 tcp_output(tp);
1287 }
1288 goto check_delack;
1289 }
1290 }
1291
1292 /*
1293 * Calculate amount of space in receive window,
1294 * and then do TCP input processing.
1295 * Receive window is amount of space in rcv queue,
1296 * but not less than advertised window.
1297 */
1298 { int win;
1299
1300 win = sbspace(&so->so_rcv);
1301 if (win < 0)
1302 win = 0;
1303 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt));
1304 }
1305
1306 switch (tp->t_state) {
1307
1308 /*
1309 * If the state is SYN_RECEIVED:
1310 * if seg contains an ACK, but not for our SYN/ACK, send a RST.
1311 */
1312 case TCPS_SYN_RECEIVED:
1313 if ((thflags & TH_ACK) &&
1314 (SEQ_LEQ(th->th_ack, tp->snd_una) ||
1315 SEQ_GT(th->th_ack, tp->snd_max))) {
1316 rstreason = BANDLIM_RST_OPENPORT;
1317 goto dropwithreset;
1318 }
1319 break;
1320
1321 /*
1322 * If the state is SYN_SENT:
1323 * if seg contains an ACK, but not for our SYN, drop the input.
1324 * if seg contains a RST, then drop the connection.
1325 * if seg does not contain SYN, then drop it.
1326 * Otherwise this is an acceptable SYN segment
1327 * initialize tp->rcv_nxt and tp->irs
1328 * if seg contains ack then advance tp->snd_una
1329 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state
1330 * arrange for segment to be acked (eventually)
1331 * continue processing rest of data/controls, beginning with URG
1332 */
1333 case TCPS_SYN_SENT:
1334 if ((thflags & TH_ACK) &&
1335 (SEQ_LEQ(th->th_ack, tp->iss) ||
1336 SEQ_GT(th->th_ack, tp->snd_max))) {
1337 rstreason = BANDLIM_UNLIMITED;
1338 goto dropwithreset;
1339 }
1340 if (thflags & TH_RST) {
1341 if (thflags & TH_ACK) {
1342 KASSERT(headlocked, ("tcp_input: after_listen"
1343 ": tcp_drop.2: head not locked"));
1344 tp = tcp_drop(tp, ECONNREFUSED);
1345 }
1346 goto drop;
1347 }
1348 if ((thflags & TH_SYN) == 0)
1349 goto drop;
1350 tp->snd_wnd = th->th_win; /* initial send window */
1351
1352 tp->irs = th->th_seq;
1353 tcp_rcvseqinit(tp);
1354 if (thflags & TH_ACK) {
1355 tcpstat.tcps_connects++;
1356 soisconnected(so);
1357#ifdef MAC
1358 SOCK_LOCK(so);
1359 mac_set_socket_peer_from_mbuf(m, so);
1360 SOCK_UNLOCK(so);
1361#endif
1362 /* Do window scaling on this connection? */
1363 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
1364 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
1365 tp->snd_scale = tp->requested_s_scale;
1366 tp->rcv_scale = tp->request_r_scale;
1367 }
1368 tp->rcv_adv += tp->rcv_wnd;
1369 tp->snd_una++; /* SYN is acked */
1370 /*
1371 * If there's data, delay ACK; if there's also a FIN
1372 * ACKNOW will be turned on later.
1373 */
1374 if (DELAY_ACK(tp) && tlen != 0)
1375 callout_reset(tp->tt_delack, tcp_delacktime,
1376 tcp_timer_delack, tp);
1377 else
1378 tp->t_flags |= TF_ACKNOW;
1379 /*
1380 * Received <SYN,ACK> in SYN_SENT[*] state.
1381 * Transitions:
1382 * SYN_SENT --> ESTABLISHED
1383 * SYN_SENT* --> FIN_WAIT_1
1384 */
1385 tp->t_starttime = ticks;
1386 if (tp->t_flags & TF_NEEDFIN) {
1387 tp->t_state = TCPS_FIN_WAIT_1;
1388 tp->t_flags &= ~TF_NEEDFIN;
1389 thflags &= ~TH_SYN;
1390 } else {
1391 tp->t_state = TCPS_ESTABLISHED;
1392 callout_reset(tp->tt_keep, tcp_keepidle,
1393 tcp_timer_keep, tp);
1394 }
1395 } else {
1396 /*
1397 * Received initial SYN in SYN-SENT[*] state =>
1398 * simultaneous open. If segment contains CC option
1399 * and there is a cached CC, apply TAO test.
1400 * If it succeeds, connection is * half-synchronized.
1401 * Otherwise, do 3-way handshake:
1402 * SYN-SENT -> SYN-RECEIVED
1403 * SYN-SENT* -> SYN-RECEIVED*
1404 * If there was no CC option, clear cached CC value.
1405 */
1406 tp->t_flags |= TF_ACKNOW;
1407 callout_stop(tp->tt_rexmt);
1408 tp->t_state = TCPS_SYN_RECEIVED;
1409 }
1410
1411trimthenstep6:
1412 KASSERT(headlocked, ("tcp_input: trimthenstep6: head not "
1413 "locked"));
1414 INP_LOCK_ASSERT(inp);
1415
1416 /*
1417 * Advance th->th_seq to correspond to first data byte.
1418 * If data, trim to stay within window,
1419 * dropping FIN if necessary.
1420 */
1421 th->th_seq++;
1422 if (tlen > tp->rcv_wnd) {
1423 todrop = tlen - tp->rcv_wnd;
1424 m_adj(m, -todrop);
1425 tlen = tp->rcv_wnd;
1426 thflags &= ~TH_FIN;
1427 tcpstat.tcps_rcvpackafterwin++;
1428 tcpstat.tcps_rcvbyteafterwin += todrop;
1429 }
1430 tp->snd_wl1 = th->th_seq - 1;
1431 tp->rcv_up = th->th_seq;
1432 /*
1433 * Client side of transaction: already sent SYN and data.
1434 * If the remote host used T/TCP to validate the SYN,
1435 * our data will be ACK'd; if so, enter normal data segment
1436 * processing in the middle of step 5, ack processing.
1437 * Otherwise, goto step 6.
1438 */
1439 if (thflags & TH_ACK)
1440 goto process_ACK;
1441
1442 goto step6;
1443
1444 /*
1445 * If the state is LAST_ACK or CLOSING or TIME_WAIT:
1446 * do normal processing.
1447 *
1448 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later.
1449 */
1450 case TCPS_LAST_ACK:
1451 case TCPS_CLOSING:
1452 case TCPS_TIME_WAIT:
1453 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
1454 break; /* continue normal processing */
1455 }
1456
1457 /*
1458 * States other than LISTEN or SYN_SENT.
1459 * First check the RST flag and sequence number since reset segments
1460 * are exempt from the timestamp and connection count tests. This
1461 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix
1462 * below which allowed reset segments in half the sequence space
1463 * to fall though and be processed (which gives forged reset
1464 * segments with a random sequence number a 50 percent chance of
1465 * killing a connection).
1466 * Then check timestamp, if present.
1467 * Then check the connection count, if present.
1468 * Then check that at least some bytes of segment are within
1469 * receive window. If segment begins before rcv_nxt,
1470 * drop leading data (and SYN); if nothing left, just ack.
1471 *
1472 *
1473 * If the RST bit is set, check the sequence number to see
1474 * if this is a valid reset segment.
1475 * RFC 793 page 37:
1476 * In all states except SYN-SENT, all reset (RST) segments
1477 * are validated by checking their SEQ-fields. A reset is
1478 * valid if its sequence number is in the window.
1479 * Note: this does not take into account delayed ACKs, so
1480 * we should test against last_ack_sent instead of rcv_nxt.
1481 * The sequence number in the reset segment is normally an
1482 * echo of our outgoing acknowlegement numbers, but some hosts
1483 * send a reset with the sequence number at the rightmost edge
1484 * of our receive window, and we have to handle this case.
1485 * Note 2: Paul Watson's paper "Slipping in the Window" has shown
1486 * that brute force RST attacks are possible. To combat this,
1487 * we use a much stricter check while in the ESTABLISHED state,
1488 * only accepting RSTs where the sequence number is equal to
1489 * last_ack_sent. In all other states (the states in which a
1490 * RST is more likely), the more permissive check is used.
1491 * If we have multiple segments in flight, the intial reset
1492 * segment sequence numbers will be to the left of last_ack_sent,
1493 * but they will eventually catch up.
1494 * In any case, it never made sense to trim reset segments to
1495 * fit the receive window since RFC 1122 says:
1496 * 4.2.2.12 RST Segment: RFC-793 Section 3.4
1497 *
1498 * A TCP SHOULD allow a received RST segment to include data.
1499 *
1500 * DISCUSSION
1501 * It has been suggested that a RST segment could contain
1502 * ASCII text that encoded and explained the cause of the
1503 * RST. No standard has yet been established for such
1504 * data.
1505 *
1506 * If the reset segment passes the sequence number test examine
1507 * the state:
1508 * SYN_RECEIVED STATE:
1509 * If passive open, return to LISTEN state.
1510 * If active open, inform user that connection was refused.
1511 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES:
1512 * Inform user that connection was reset, and close tcb.
1513 * CLOSING, LAST_ACK STATES:
1514 * Close the tcb.
1515 * TIME_WAIT STATE:
1516 * Drop the segment - see Stevens, vol. 2, p. 964 and
1517 * RFC 1337.
1518 */
1519 if (thflags & TH_RST) {
1520 if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
1521 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) ||
1522 (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) {
1523 switch (tp->t_state) {
1524
1525 case TCPS_SYN_RECEIVED:
1526 so->so_error = ECONNREFUSED;
1527 goto close;
1528
1529 case TCPS_ESTABLISHED:
1530 if (tp->last_ack_sent != th->th_seq &&
1531 tcp_insecure_rst == 0) {
1532 tcpstat.tcps_badrst++;
1533 goto drop;
1534 }
1535 case TCPS_FIN_WAIT_1:
1536 case TCPS_FIN_WAIT_2:
1537 case TCPS_CLOSE_WAIT:
1538 so->so_error = ECONNRESET;
1539 close:
1540 tp->t_state = TCPS_CLOSED;
1541 tcpstat.tcps_drops++;
1542 KASSERT(headlocked, ("tcp_input: "
1543 "trimthenstep6: tcp_close: head not "
1544 "locked"));
1545 tp = tcp_close(tp);
1546 break;
1547
1548 case TCPS_CLOSING:
1549 case TCPS_LAST_ACK:
1550 KASSERT(headlocked, ("trimthenstep6: "
1551 "tcp_close.2: head not locked"));
1552 tp = tcp_close(tp);
1553 break;
1554
1555 case TCPS_TIME_WAIT:
1556 KASSERT(tp->t_state != TCPS_TIME_WAIT,
1557 ("timewait"));
1558 break;
1559 }
1560 }
1561 goto drop;
1562 }
1563
1564 /*
1565 * RFC 1323 PAWS: If we have a timestamp reply on this segment
1566 * and it's less than ts_recent, drop it.
1567 */
1568 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
1569 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
1570
1571 /* Check to see if ts_recent is over 24 days old. */
1572 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) {
1573 /*
1574 * Invalidate ts_recent. If this segment updates
1575 * ts_recent, the age will be reset later and ts_recent
1576 * will get a valid value. If it does not, setting
1577 * ts_recent to zero will at least satisfy the
1578 * requirement that zero be placed in the timestamp
1579 * echo reply when ts_recent isn't valid. The
1580 * age isn't reset until we get a valid ts_recent
1581 * because we don't want out-of-order segments to be
1582 * dropped when ts_recent is old.
1583 */
1584 tp->ts_recent = 0;
1585 } else {
1586 tcpstat.tcps_rcvduppack++;
1587 tcpstat.tcps_rcvdupbyte += tlen;
1588 tcpstat.tcps_pawsdrop++;
1589 if (tlen)
1590 goto dropafterack;
1591 goto drop;
1592 }
1593 }
1594
1595 /*
1596 * In the SYN-RECEIVED state, validate that the packet belongs to
1597 * this connection before trimming the data to fit the receive
1598 * window. Check the sequence number versus IRS since we know
1599 * the sequence numbers haven't wrapped. This is a partial fix
1600 * for the "LAND" DoS attack.
1601 */
1602 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) {
1603 rstreason = BANDLIM_RST_OPENPORT;
1604 goto dropwithreset;
1605 }
1606
1607 todrop = tp->rcv_nxt - th->th_seq;
1608 if (todrop > 0) {
1609 if (thflags & TH_SYN) {
1610 thflags &= ~TH_SYN;
1611 th->th_seq++;
1612 if (th->th_urp > 1)
1613 th->th_urp--;
1614 else
1615 thflags &= ~TH_URG;
1616 todrop--;
1617 }
1618 /*
1619 * Following if statement from Stevens, vol. 2, p. 960.
1620 */
1621 if (todrop > tlen
1622 || (todrop == tlen && (thflags & TH_FIN) == 0)) {
1623 /*
1624 * Any valid FIN must be to the left of the window.
1625 * At this point the FIN must be a duplicate or out
1626 * of sequence; drop it.
1627 */
1628 thflags &= ~TH_FIN;
1629
1630 /*
1631 * Send an ACK to resynchronize and drop any data.
1632 * But keep on processing for RST or ACK.
1633 */
1634 tp->t_flags |= TF_ACKNOW;
1635 todrop = tlen;
1636 tcpstat.tcps_rcvduppack++;
1637 tcpstat.tcps_rcvdupbyte += todrop;
1638 } else {
1639 tcpstat.tcps_rcvpartduppack++;
1640 tcpstat.tcps_rcvpartdupbyte += todrop;
1641 }
1642 drop_hdrlen += todrop; /* drop from the top afterwards */
1643 th->th_seq += todrop;
1644 tlen -= todrop;
1645 if (th->th_urp > todrop)
1646 th->th_urp -= todrop;
1647 else {
1648 thflags &= ~TH_URG;
1649 th->th_urp = 0;
1650 }
1651 }
1652
1653 /*
1654 * If new data are received on a connection after the
1655 * user processes are gone, then RST the other end.
1656 */
1657 if ((so->so_state & SS_NOFDREF) &&
1658 tp->t_state > TCPS_CLOSE_WAIT && tlen) {
1659 KASSERT(headlocked, ("trimthenstep6: tcp_close.3: head not "
1660 "locked"));
1661 tp = tcp_close(tp);
1662 tcpstat.tcps_rcvafterclose++;
1663 rstreason = BANDLIM_UNLIMITED;
1664 goto dropwithreset;
1665 }
1666
1667 /*
1668 * If segment ends after window, drop trailing data
1669 * (and PUSH and FIN); if nothing left, just ACK.
1670 */
1671 todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd);
1672 if (todrop > 0) {
1673 tcpstat.tcps_rcvpackafterwin++;
1674 if (todrop >= tlen) {
1675 tcpstat.tcps_rcvbyteafterwin += tlen;
1676 /*
1677 * If a new connection request is received
1678 * while in TIME_WAIT, drop the old connection
1679 * and start over if the sequence numbers
1680 * are above the previous ones.
1681 */
1682 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
1683 if (thflags & TH_SYN &&
1684 tp->t_state == TCPS_TIME_WAIT &&
1685 SEQ_GT(th->th_seq, tp->rcv_nxt)) {
1686 KASSERT(headlocked, ("trimthenstep6: "
1687 "tcp_close.4: head not locked"));
1688 tp = tcp_close(tp);
1689 goto findpcb;
1690 }
1691 /*
1692 * If window is closed can only take segments at
1693 * window edge, and have to drop data and PUSH from
1694 * incoming segments. Continue processing, but
1695 * remember to ack. Otherwise, drop segment
1696 * and ack.
1697 */
1698 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
1699 tp->t_flags |= TF_ACKNOW;
1700 tcpstat.tcps_rcvwinprobe++;
1701 } else
1702 goto dropafterack;
1703 } else
1704 tcpstat.tcps_rcvbyteafterwin += todrop;
1705 m_adj(m, -todrop);
1706 tlen -= todrop;
1707 thflags &= ~(TH_PUSH|TH_FIN);
1708 }
1709
1710 /*
1711 * If last ACK falls within this segment's sequence numbers,
1712 * record its timestamp.
1713 * NOTE:
1714 * 1) That the test incorporates suggestions from the latest
1715 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1716 * 2) That updating only on newer timestamps interferes with
1717 * our earlier PAWS tests, so this check should be solely
1718 * predicated on the sequence space of this segment.
1719 * 3) That we modify the segment boundary check to be
1720 * Last.ACK.Sent <= SEG.SEQ + SEG.Len
1721 * instead of RFC1323's
1722 * Last.ACK.Sent < SEG.SEQ + SEG.Len,
1723 * This modified check allows us to overcome RFC1323's
1724 * limitations as described in Stevens TCP/IP Illustrated
1725 * Vol. 2 p.869. In such cases, we can still calculate the
1726 * RTT correctly when RCV.NXT == Last.ACK.Sent.
1727 */
1728 if ((to.to_flags & TOF_TS) != 0 &&
1729 SEQ_LEQ(th->th_seq, tp->last_ack_sent) &&
1730 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen +
1731 ((thflags & (TH_SYN|TH_FIN)) != 0))) {
1732 tp->ts_recent_age = ticks;
1733 tp->ts_recent = to.to_tsval;
1734 }
1735
1736 /*
1737 * If a SYN is in the window, then this is an
1738 * error and we send an RST and drop the connection.
1739 */
1740 if (thflags & TH_SYN) {
1741 KASSERT(headlocked, ("tcp_input: tcp_drop: trimthenstep6: "
1742 "head not locked"));
1743 tp = tcp_drop(tp, ECONNRESET);
1744 rstreason = BANDLIM_UNLIMITED;
1745 goto drop;
1746 }
1747
1748 /*
1749 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN
1750 * flag is on (half-synchronized state), then queue data for
1751 * later processing; else drop segment and return.
1752 */
1753 if ((thflags & TH_ACK) == 0) {
1754 if (tp->t_state == TCPS_SYN_RECEIVED ||
1755 (tp->t_flags & TF_NEEDSYN))
1756 goto step6;
1757 else
1758 goto drop;
1759 }
1760
1761 /*
1762 * Ack processing.
1763 */
1764 switch (tp->t_state) {
1765
1766 /*
1767 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter
1768 * ESTABLISHED state and continue processing.
1769 * The ACK was checked above.
1770 */
1771 case TCPS_SYN_RECEIVED:
1772
1773 tcpstat.tcps_connects++;
1774 soisconnected(so);
1775 /* Do window scaling? */
1776 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
1777 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
1778 tp->snd_scale = tp->requested_s_scale;
1779 tp->rcv_scale = tp->request_r_scale;
1780 }
1781 /*
1782 * Make transitions:
1783 * SYN-RECEIVED -> ESTABLISHED
1784 * SYN-RECEIVED* -> FIN-WAIT-1
1785 */
1786 tp->t_starttime = ticks;
1787 if (tp->t_flags & TF_NEEDFIN) {
1788 tp->t_state = TCPS_FIN_WAIT_1;
1789 tp->t_flags &= ~TF_NEEDFIN;
1790 } else {
1791 tp->t_state = TCPS_ESTABLISHED;
1792 callout_reset(tp->tt_keep, tcp_keepidle,
1793 tcp_timer_keep, tp);
1794 }
1795 /*
1796 * If segment contains data or ACK, will call tcp_reass()
1797 * later; if not, do so now to pass queued data to user.
1798 */
1799 if (tlen == 0 && (thflags & TH_FIN) == 0)
1800 (void) tcp_reass(tp, (struct tcphdr *)0, 0,
1801 (struct mbuf *)0);
1802 tp->snd_wl1 = th->th_seq - 1;
1803 /* FALLTHROUGH */
1804
1805 /*
1806 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
1807 * ACKs. If the ack is in the range
1808 * tp->snd_una < th->th_ack <= tp->snd_max
1809 * then advance tp->snd_una to th->th_ack and drop
1810 * data from the retransmission queue. If this ACK reflects
1811 * more up to date window information we update our window information.
1812 */
1813 case TCPS_ESTABLISHED:
1814 case TCPS_FIN_WAIT_1:
1815 case TCPS_FIN_WAIT_2:
1816 case TCPS_CLOSE_WAIT:
1817 case TCPS_CLOSING:
1818 case TCPS_LAST_ACK:
1819 case TCPS_TIME_WAIT:
1820 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
1821 if (SEQ_GT(th->th_ack, tp->snd_max)) {
1822 tcpstat.tcps_rcvacktoomuch++;
1823 goto dropafterack;
1824 }
1825 if (tp->sack_enable)
1826 tcp_sack_doack(tp, &to, th->th_ack);
1827 if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
1828 if (tlen == 0 && tiwin == tp->snd_wnd) {
1829 tcpstat.tcps_rcvdupack++;
1830 /*
1831 * If we have outstanding data (other than
1832 * a window probe), this is a completely
1833 * duplicate ack (ie, window info didn't
1834 * change), the ack is the biggest we've
1835 * seen and we've seen exactly our rexmt
1836 * threshhold of them, assume a packet
1837 * has been dropped and retransmit it.
1838 * Kludge snd_nxt & the congestion
1839 * window so we send only this one
1840 * packet.
1841 *
1842 * We know we're losing at the current
1843 * window size so do congestion avoidance
1844 * (set ssthresh to half the current window
1845 * and pull our congestion window back to
1846 * the new ssthresh).
1847 *
1848 * Dup acks mean that packets have left the
1849 * network (they're now cached at the receiver)
1850 * so bump cwnd by the amount in the receiver
1851 * to keep a constant cwnd packets in the
1852 * network.
1853 */
1854 if (!callout_active(tp->tt_rexmt) ||
1855 th->th_ack != tp->snd_una)
1856 tp->t_dupacks = 0;
1857 else if (++tp->t_dupacks > tcprexmtthresh ||
1858 ((tcp_do_newreno || tp->sack_enable) &&
1859 IN_FASTRECOVERY(tp))) {
1860 if (tp->sack_enable && IN_FASTRECOVERY(tp)) {
1861 int awnd;
1862
1863 /*
1864 * Compute the amount of data in flight first.
1865 * We can inject new data into the pipe iff
1866 * we have less than 1/2 the original window's
1867 * worth of data in flight.
1868 */
1869 awnd = (tp->snd_nxt - tp->snd_fack) +
1870 tp->sackhint.sack_bytes_rexmit;
1871 if (awnd < tp->snd_ssthresh) {
1872 tp->snd_cwnd += tp->t_maxseg;
1873 if (tp->snd_cwnd > tp->snd_ssthresh)
1874 tp->snd_cwnd = tp->snd_ssthresh;
1875 }
1876 } else
1877 tp->snd_cwnd += tp->t_maxseg;
1878 (void) tcp_output(tp);
1879 goto drop;
1880 } else if (tp->t_dupacks == tcprexmtthresh) {
1881 tcp_seq onxt = tp->snd_nxt;
1882 u_int win;
1883
1884 /*
1885 * If we're doing sack, check to
1886 * see if we're already in sack
1887 * recovery. If we're not doing sack,
1888 * check to see if we're in newreno
1889 * recovery.
1890 */
1891 if (tp->sack_enable) {
1892 if (IN_FASTRECOVERY(tp)) {
1893 tp->t_dupacks = 0;
1894 break;
1895 }
1896 } else if (tcp_do_newreno) {
1897 if (SEQ_LEQ(th->th_ack,
1898 tp->snd_recover)) {
1899 tp->t_dupacks = 0;
1900 break;
1901 }
1902 }
1903 win = min(tp->snd_wnd, tp->snd_cwnd) /
1904 2 / tp->t_maxseg;
1905 if (win < 2)
1906 win = 2;
1907 tp->snd_ssthresh = win * tp->t_maxseg;
1908 ENTER_FASTRECOVERY(tp);
1909 tp->snd_recover = tp->snd_max;
1910 callout_stop(tp->tt_rexmt);
1911 tp->t_rtttime = 0;
1912 if (tp->sack_enable) {
1913 KASSERT(tp->sackhint.
1914 sack_bytes_rexmit == 0,
1915 ("sackhint rexmit == 0"));
1916 tcpstat.tcps_sack_recovery_episode++;
1917 tp->sack_newdata = tp->snd_nxt;
1918 tp->snd_cwnd = tp->t_maxseg;
1919 (void) tcp_output(tp);
1920 goto drop;
1921 }
1922 tp->snd_nxt = th->th_ack;
1923 tp->snd_cwnd = tp->t_maxseg;
1924 (void) tcp_output(tp);
1925 KASSERT(tp->snd_limited <= 2,
1926 ("tp->snd_limited too big"));
1927 tp->snd_cwnd = tp->snd_ssthresh +
1928 tp->t_maxseg *
1929 (tp->t_dupacks - tp->snd_limited);
1930 if (SEQ_GT(onxt, tp->snd_nxt))
1931 tp->snd_nxt = onxt;
1932 goto drop;
1933 } else if (tcp_do_rfc3042) {
1934 u_long oldcwnd = tp->snd_cwnd;
1935 tcp_seq oldsndmax = tp->snd_max;
1936 u_int sent;
1937
1938 KASSERT(tp->t_dupacks == 1 ||
1939 tp->t_dupacks == 2,
1940 ("dupacks not 1 or 2"));
1941 if (tp->t_dupacks == 1)
1942 tp->snd_limited = 0;
1943 tp->snd_cwnd =
1944 (tp->snd_nxt - tp->snd_una) +
1945 (tp->t_dupacks - tp->snd_limited) *
1946 tp->t_maxseg;
1947 (void) tcp_output(tp);
1948 sent = tp->snd_max - oldsndmax;
1949 if (sent > tp->t_maxseg) {
1950 KASSERT((tp->t_dupacks == 2 &&
1951 tp->snd_limited == 0) ||
1952 (sent == tp->t_maxseg + 1 &&
1953 tp->t_flags & TF_SENTFIN),
1954 ("sent too much"));
1955 tp->snd_limited = 2;
1956 } else if (sent > 0)
1957 ++tp->snd_limited;
1958 tp->snd_cwnd = oldcwnd;
1959 goto drop;
1960 }
1961 } else
1962 tp->t_dupacks = 0;
1963 break;
1964 }
1965
1966 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una"));
1967
1968 /*
1969 * If the congestion window was inflated to account
1970 * for the other side's cached packets, retract it.
1971 */
1972 if (tcp_do_newreno || tp->sack_enable) {
1973 if (IN_FASTRECOVERY(tp)) {
1974 if (SEQ_LT(th->th_ack, tp->snd_recover)) {
1975 if (tp->sack_enable)
1976 tcp_sack_partialack(tp, th);
1977 else
1978 tcp_newreno_partial_ack(tp, th);
1979 } else {
1980 /*
1981 * Out of fast recovery.
1982 * Window inflation should have left us
1983 * with approximately snd_ssthresh
1984 * outstanding data.
1985 * But in case we would be inclined to
1986 * send a burst, better to do it via
1987 * the slow start mechanism.
1988 */
1989 if (SEQ_GT(th->th_ack +
1990 tp->snd_ssthresh,
1991 tp->snd_max))
1992 tp->snd_cwnd = tp->snd_max -
1993 th->th_ack +
1994 tp->t_maxseg;
1995 else
1996 tp->snd_cwnd = tp->snd_ssthresh;
1997 }
1998 }
1999 } else {
2000 if (tp->t_dupacks >= tcprexmtthresh &&
2001 tp->snd_cwnd > tp->snd_ssthresh)
2002 tp->snd_cwnd = tp->snd_ssthresh;
2003 }
2004 tp->t_dupacks = 0;
2005 /*
2006 * If we reach this point, ACK is not a duplicate,
2007 * i.e., it ACKs something we sent.
2008 */
2009 if (tp->t_flags & TF_NEEDSYN) {
2010 /*
2011 * T/TCP: Connection was half-synchronized, and our
2012 * SYN has been ACK'd (so connection is now fully
2013 * synchronized). Go to non-starred state,
2014 * increment snd_una for ACK of SYN, and check if
2015 * we can do window scaling.
2016 */
2017 tp->t_flags &= ~TF_NEEDSYN;
2018 tp->snd_una++;
2019 /* Do window scaling? */
2020 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
2021 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
2022 tp->snd_scale = tp->requested_s_scale;
2023 tp->rcv_scale = tp->request_r_scale;
2024 }
2025 }
2026
2027process_ACK:
2028 KASSERT(headlocked, ("tcp_input: process_ACK: head not "
2029 "locked"));
2030 INP_LOCK_ASSERT(inp);
2031
2032 acked = th->th_ack - tp->snd_una;
2033 tcpstat.tcps_rcvackpack++;
2034 tcpstat.tcps_rcvackbyte += acked;
2035
2036 /*
2037 * If we just performed our first retransmit, and the ACK
2038 * arrives within our recovery window, then it was a mistake
2039 * to do the retransmit in the first place. Recover our
2040 * original cwnd and ssthresh, and proceed to transmit where
2041 * we left off.
2042 */
2043 if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) {
2044 ++tcpstat.tcps_sndrexmitbad;
2045 tp->snd_cwnd = tp->snd_cwnd_prev;
2046 tp->snd_ssthresh = tp->snd_ssthresh_prev;
2047 tp->snd_recover = tp->snd_recover_prev;
2048 if (tp->t_flags & TF_WASFRECOVERY)
2049 ENTER_FASTRECOVERY(tp);
2050 tp->snd_nxt = tp->snd_max;
2051 tp->t_badrxtwin = 0; /* XXX probably not required */
2052 }
2053
2054 /*
2055 * If we have a timestamp reply, update smoothed
2056 * round trip time. If no timestamp is present but
2057 * transmit timer is running and timed sequence
2058 * number was acked, update smoothed round trip time.
2059 * Since we now have an rtt measurement, cancel the
2060 * timer backoff (cf., Phil Karn's retransmit alg.).
2061 * Recompute the initial retransmit timer.
2062 *
2063 * Some boxes send broken timestamp replies
2064 * during the SYN+ACK phase, ignore
2065 * timestamps of 0 or we could calculate a
2066 * huge RTT and blow up the retransmit timer.
2067 */
2068 if ((to.to_flags & TOF_TS) != 0 &&
2069 to.to_tsecr) {
2070 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1);
2071 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) {
2072 tcp_xmit_timer(tp, ticks - tp->t_rtttime);
2073 }
2074 tcp_xmit_bandwidth_limit(tp, th->th_ack);
2075
2076 /*
2077 * If all outstanding data is acked, stop retransmit
2078 * timer and remember to restart (more output or persist).
2079 * If there is more data to be acked, restart retransmit
2080 * timer, using current (possibly backed-off) value.
2081 */
2082 if (th->th_ack == tp->snd_max) {
2083 callout_stop(tp->tt_rexmt);
2084 needoutput = 1;
2085 } else if (!callout_active(tp->tt_persist))
2086 callout_reset(tp->tt_rexmt, tp->t_rxtcur,
2087 tcp_timer_rexmt, tp);
2088
2089 /*
2090 * If no data (only SYN) was ACK'd,
2091 * skip rest of ACK processing.
2092 */
2093 if (acked == 0)
2094 goto step6;
2095
2096 /*
2097 * When new data is acked, open the congestion window.
2098 * If the window gives us less than ssthresh packets
2099 * in flight, open exponentially (maxseg per packet).
2100 * Otherwise open linearly: maxseg per window
2101 * (maxseg^2 / cwnd per packet).
2102 */
2103 if ((!tcp_do_newreno && !tp->sack_enable) ||
2104 !IN_FASTRECOVERY(tp)) {
2105 register u_int cw = tp->snd_cwnd;
2106 register u_int incr = tp->t_maxseg;
2107 if (cw > tp->snd_ssthresh)
2108 incr = incr * incr / cw;
2109 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale);
2110 }
2111 SOCKBUF_LOCK(&so->so_snd);
2112 if (acked > so->so_snd.sb_cc) {
2113 tp->snd_wnd -= so->so_snd.sb_cc;
2114 sbdrop_locked(&so->so_snd, (int)so->so_snd.sb_cc);
2115 ourfinisacked = 1;
2116 } else {
2117 sbdrop_locked(&so->so_snd, acked);
2118 tp->snd_wnd -= acked;
2119 ourfinisacked = 0;
2120 }
2121 sowwakeup_locked(so);
2122 /* detect una wraparound */
2123 if ((tcp_do_newreno || tp->sack_enable) &&
2124 !IN_FASTRECOVERY(tp) &&
2125 SEQ_GT(tp->snd_una, tp->snd_recover) &&
2126 SEQ_LEQ(th->th_ack, tp->snd_recover))
2127 tp->snd_recover = th->th_ack - 1;
2128 if ((tcp_do_newreno || tp->sack_enable) &&
2129 IN_FASTRECOVERY(tp) &&
2130 SEQ_GEQ(th->th_ack, tp->snd_recover))
2131 EXIT_FASTRECOVERY(tp);
2132 tp->snd_una = th->th_ack;
2133 if (tp->sack_enable) {
2134 if (SEQ_GT(tp->snd_una, tp->snd_recover))
2135 tp->snd_recover = tp->snd_una;
2136 }
2137 if (SEQ_LT(tp->snd_nxt, tp->snd_una))
2138 tp->snd_nxt = tp->snd_una;
2139
2140 switch (tp->t_state) {
2141
2142 /*
2143 * In FIN_WAIT_1 STATE in addition to the processing
2144 * for the ESTABLISHED state if our FIN is now acknowledged
2145 * then enter FIN_WAIT_2.
2146 */
2147 case TCPS_FIN_WAIT_1:
2148 if (ourfinisacked) {
2149 /*
2150 * If we can't receive any more
2151 * data, then closing user can proceed.
2152 * Starting the timer is contrary to the
2153 * specification, but if we don't get a FIN
2154 * we'll hang forever.
2155 */
2156 /* XXXjl
2157 * we should release the tp also, and use a
2158 * compressed state.
2159 */
2160 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
2161 soisdisconnected(so);
2162 callout_reset(tp->tt_2msl, tcp_maxidle,
2163 tcp_timer_2msl, tp);
2164 }
2165 tp->t_state = TCPS_FIN_WAIT_2;
2166 }
2167 break;
2168
2169 /*
2170 * In CLOSING STATE in addition to the processing for
2171 * the ESTABLISHED state if the ACK acknowledges our FIN
2172 * then enter the TIME-WAIT state, otherwise ignore
2173 * the segment.
2174 */
2175 case TCPS_CLOSING:
2176 if (ourfinisacked) {
2177 KASSERT(headlocked, ("tcp_input: process_ACK: "
2178 "head not locked"));
2179 tcp_twstart(tp);
2180 INP_INFO_WUNLOCK(&tcbinfo);
2181 m_freem(m);
2182 return;
2183 }
2184 break;
2185
2186 /*
2187 * In LAST_ACK, we may still be waiting for data to drain
2188 * and/or to be acked, as well as for the ack of our FIN.
2189 * If our FIN is now acknowledged, delete the TCB,
2190 * enter the closed state and return.
2191 */
2192 case TCPS_LAST_ACK:
2193 if (ourfinisacked) {
2194 KASSERT(headlocked, ("tcp_input: process_ACK:"
2195 " tcp_close: head not locked"));
2196 tp = tcp_close(tp);
2197 goto drop;
2198 }
2199 break;
2200
2201 /*
2202 * In TIME_WAIT state the only thing that should arrive
2203 * is a retransmission of the remote FIN. Acknowledge
2204 * it and restart the finack timer.
2205 */
2206 case TCPS_TIME_WAIT:
2207 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
2208 callout_reset(tp->tt_2msl, 2 * tcp_msl,
2209 tcp_timer_2msl, tp);
2210 goto dropafterack;
2211 }
2212 }
2213
2214step6:
2215 KASSERT(headlocked, ("tcp_input: step6: head not locked"));
2216 INP_LOCK_ASSERT(inp);
2217
2218 /*
2219 * Update window information.
2220 * Don't look at window if no ACK: TAC's send garbage on first SYN.
2221 */
2222 if ((thflags & TH_ACK) &&
2223 (SEQ_LT(tp->snd_wl1, th->th_seq) ||
2224 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) ||
2225 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) {
2226 /* keep track of pure window updates */
2227 if (tlen == 0 &&
2228 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)
2229 tcpstat.tcps_rcvwinupd++;
2230 tp->snd_wnd = tiwin;
2231 tp->snd_wl1 = th->th_seq;
2232 tp->snd_wl2 = th->th_ack;
2233 if (tp->snd_wnd > tp->max_sndwnd)
2234 tp->max_sndwnd = tp->snd_wnd;
2235 needoutput = 1;
2236 }
2237
2238 /*
2239 * Process segments with URG.
2240 */
2241 if ((thflags & TH_URG) && th->th_urp &&
2242 TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2243 /*
2244 * This is a kludge, but if we receive and accept
2245 * random urgent pointers, we'll crash in
2246 * soreceive. It's hard to imagine someone
2247 * actually wanting to send this much urgent data.
2248 */
2249 SOCKBUF_LOCK(&so->so_rcv);
2250 if (th->th_urp + so->so_rcv.sb_cc > sb_max) {
2251 th->th_urp = 0; /* XXX */
2252 thflags &= ~TH_URG; /* XXX */
2253 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */
2254 goto dodata; /* XXX */
2255 }
2256 /*
2257 * If this segment advances the known urgent pointer,
2258 * then mark the data stream. This should not happen
2259 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
2260 * a FIN has been received from the remote side.
2261 * In these states we ignore the URG.
2262 *
2263 * According to RFC961 (Assigned Protocols),
2264 * the urgent pointer points to the last octet
2265 * of urgent data. We continue, however,
2266 * to consider it to indicate the first octet
2267 * of data past the urgent section as the original
2268 * spec states (in one of two places).
2269 */
2270 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) {
2271 tp->rcv_up = th->th_seq + th->th_urp;
2272 so->so_oobmark = so->so_rcv.sb_cc +
2273 (tp->rcv_up - tp->rcv_nxt) - 1;
2274 if (so->so_oobmark == 0)
2275 so->so_rcv.sb_state |= SBS_RCVATMARK;
2276 sohasoutofband(so);
2277 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
2278 }
2279 SOCKBUF_UNLOCK(&so->so_rcv);
2280 /*
2281 * Remove out of band data so doesn't get presented to user.
2282 * This can happen independent of advancing the URG pointer,
2283 * but if two URG's are pending at once, some out-of-band
2284 * data may creep in... ick.
2285 */
2286 if (th->th_urp <= (u_long)tlen &&
2287 !(so->so_options & SO_OOBINLINE)) {
2288 /* hdr drop is delayed */
2289 tcp_pulloutofband(so, th, m, drop_hdrlen);
2290 }
2291 } else {
2292 /*
2293 * If no out of band data is expected,
2294 * pull receive urgent pointer along
2295 * with the receive window.
2296 */
2297 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
2298 tp->rcv_up = tp->rcv_nxt;
2299 }
2300dodata: /* XXX */
2301 KASSERT(headlocked, ("tcp_input: dodata: head not locked"));
2302 INP_LOCK_ASSERT(inp);
2303
2304 /*
2305 * Process the segment text, merging it into the TCP sequencing queue,
2306 * and arranging for acknowledgment of receipt if necessary.
2307 * This process logically involves adjusting tp->rcv_wnd as data
2308 * is presented to the user (this happens in tcp_usrreq.c,
2309 * case PRU_RCVD). If a FIN has already been received on this
2310 * connection then we just ignore the text.
2311 */
2312 if ((tlen || (thflags & TH_FIN)) &&
2313 TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2314 m_adj(m, drop_hdrlen); /* delayed header drop */
2315 /*
2316 * Insert segment which includes th into TCP reassembly queue
2317 * with control block tp. Set thflags to whether reassembly now
2318 * includes a segment with FIN. This handles the common case
2319 * inline (segment is the next to be received on an established
2320 * connection, and the queue is empty), avoiding linkage into
2321 * and removal from the queue and repetition of various
2322 * conversions.
2323 * Set DELACK for segments received in order, but ack
2324 * immediately when segments are out of order (so
2325 * fast retransmit can work).
2326 */
2327 if (th->th_seq == tp->rcv_nxt &&
2328 LIST_EMPTY(&tp->t_segq) &&
2329 TCPS_HAVEESTABLISHED(tp->t_state)) {
2330 if (DELAY_ACK(tp))
2331 tp->t_flags |= TF_DELACK;
2332 else
2333 tp->t_flags |= TF_ACKNOW;
2334 tp->rcv_nxt += tlen;
2335 thflags = th->th_flags & TH_FIN;
2336 tcpstat.tcps_rcvpack++;
2337 tcpstat.tcps_rcvbyte += tlen;
2338 ND6_HINT(tp);
2339 SOCKBUF_LOCK(&so->so_rcv);
2340 if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
2341 m_freem(m);
2342 else
2343 sbappendstream_locked(&so->so_rcv, m);
2344 sorwakeup_locked(so);
2345 } else {
2346 thflags = tcp_reass(tp, th, &tlen, m);
2347 tp->t_flags |= TF_ACKNOW;
2348 }
2349 if (tlen > 0 && tp->sack_enable)
2350 tcp_update_sack_list(tp, th->th_seq, th->th_seq + tlen);
2351 /*
2352 * Note the amount of data that peer has sent into
2353 * our window, in order to estimate the sender's
2354 * buffer size.
2355 */
2356 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
2357 } else {
2358 m_freem(m);
2359 thflags &= ~TH_FIN;
2360 }
2361
2362 /*
2363 * If FIN is received ACK the FIN and let the user know
2364 * that the connection is closing.
2365 */
2366 if (thflags & TH_FIN) {
2367 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2368 socantrcvmore(so);
2369 /*
2370 * If connection is half-synchronized
2371 * (ie NEEDSYN flag on) then delay ACK,
2372 * so it may be piggybacked when SYN is sent.
2373 * Otherwise, since we received a FIN then no
2374 * more input can be expected, send ACK now.
2375 */
2376 if (tp->t_flags & TF_NEEDSYN)
2377 tp->t_flags |= TF_DELACK;
2378 else
2379 tp->t_flags |= TF_ACKNOW;
2380 tp->rcv_nxt++;
2381 }
2382 switch (tp->t_state) {
2383
2384 /*
2385 * In SYN_RECEIVED and ESTABLISHED STATES
2386 * enter the CLOSE_WAIT state.
2387 */
2388 case TCPS_SYN_RECEIVED:
2389 tp->t_starttime = ticks;
2390 /*FALLTHROUGH*/
2391 case TCPS_ESTABLISHED:
2392 tp->t_state = TCPS_CLOSE_WAIT;
2393 break;
2394
2395 /*
2396 * If still in FIN_WAIT_1 STATE FIN has not been acked so
2397 * enter the CLOSING state.
2398 */
2399 case TCPS_FIN_WAIT_1:
2400 tp->t_state = TCPS_CLOSING;
2401 break;
2402
2403 /*
2404 * In FIN_WAIT_2 state enter the TIME_WAIT state,
2405 * starting the time-wait timer, turning off the other
2406 * standard timers.
2407 */
2408 case TCPS_FIN_WAIT_2:
2409 KASSERT(headlocked == 1, ("tcp_input: dodata: "
2410 "TCP_FIN_WAIT_2: head not locked"));
2411 tcp_twstart(tp);
2412 INP_INFO_WUNLOCK(&tcbinfo);
2413 return;
2414
2415 /*
2416 * In TIME_WAIT state restart the 2 MSL time_wait timer.
2417 */
2418 case TCPS_TIME_WAIT:
2419 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
2420 callout_reset(tp->tt_2msl, 2 * tcp_msl,
2421 tcp_timer_2msl, tp);
2422 break;
2423 }
2424 }
2425 INP_INFO_WUNLOCK(&tcbinfo);
2426 headlocked = 0;
2427#ifdef TCPDEBUG
2428 if (so->so_options & SO_DEBUG)
2429 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen,
2430 &tcp_savetcp, 0);
2431#endif
2432
2433 /*
2434 * Return any desired output.
2435 */
2436 if (needoutput || (tp->t_flags & TF_ACKNOW))
2437 (void) tcp_output(tp);
2438
2439check_delack:
2440 KASSERT(headlocked == 0, ("tcp_input: check_delack: head locked"));
2441 INP_LOCK_ASSERT(inp);
2442 if (tp->t_flags & TF_DELACK) {
2443 tp->t_flags &= ~TF_DELACK;
2444 callout_reset(tp->tt_delack, tcp_delacktime,
2445 tcp_timer_delack, tp);
2446 }
2447 INP_UNLOCK(inp);
2448 return;
2449
2450dropafterack:
2451 KASSERT(headlocked, ("tcp_input: dropafterack: head not locked"));
2452 /*
2453 * Generate an ACK dropping incoming segment if it occupies
2454 * sequence space, where the ACK reflects our state.
2455 *
2456 * We can now skip the test for the RST flag since all
2457 * paths to this code happen after packets containing
2458 * RST have been dropped.
2459 *
2460 * In the SYN-RECEIVED state, don't send an ACK unless the
2461 * segment we received passes the SYN-RECEIVED ACK test.
2462 * If it fails send a RST. This breaks the loop in the
2463 * "LAND" DoS attack, and also prevents an ACK storm
2464 * between two listening ports that have been sent forged
2465 * SYN segments, each with the source address of the other.
2466 */
2467 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
2468 (SEQ_GT(tp->snd_una, th->th_ack) ||
2469 SEQ_GT(th->th_ack, tp->snd_max)) ) {
2470 rstreason = BANDLIM_RST_OPENPORT;
2471 goto dropwithreset;
2472 }
2473#ifdef TCPDEBUG
2474 if (so->so_options & SO_DEBUG)
2475 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
2476 &tcp_savetcp, 0);
2477#endif
2478 KASSERT(headlocked, ("headlocked should be 1"));
2479 INP_INFO_WUNLOCK(&tcbinfo);
2480 tp->t_flags |= TF_ACKNOW;
2481 (void) tcp_output(tp);
2482 INP_UNLOCK(inp);
2483 m_freem(m);
2484 return;
2485
2486dropwithreset:
2487 KASSERT(headlocked, ("tcp_input: dropwithreset: head not locked"));
2488 /*
2489 * Generate a RST, dropping incoming segment.
2490 * Make ACK acceptable to originator of segment.
2491 * Don't bother to respond if destination was broadcast/multicast.
2492 */
2493 if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST))
2494 goto drop;
2495 if (isipv6) {
2496 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
2497 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
2498 goto drop;
2499 } else {
2500 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
2501 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
2502 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
2503 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
2504 goto drop;
2505 }
2506 /* IPv6 anycast check is done at tcp6_input() */
2507
2508 /*
2509 * Perform bandwidth limiting.
2510 */
2511 if (badport_bandlim(rstreason) < 0)
2512 goto drop;
2513
2514#ifdef TCPDEBUG
2515 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
2516 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
2517 &tcp_savetcp, 0);
2518#endif
2519
2520 if (thflags & TH_ACK)
2521 /* mtod() below is safe as long as hdr dropping is delayed */
2522 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack,
2523 TH_RST);
2524 else {
2525 if (thflags & TH_SYN)
2526 tlen++;
2527 /* mtod() below is safe as long as hdr dropping is delayed */
2528 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen,
2529 (tcp_seq)0, TH_RST|TH_ACK);
2530 }
2531
2532 if (tp)
2533 INP_UNLOCK(inp);
2534 if (headlocked)
2535 INP_INFO_WUNLOCK(&tcbinfo);
2536 return;
2537
2538drop:
2539 /*
2540 * Drop space held by incoming segment and return.
2541 */
2542#ifdef TCPDEBUG
2543 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
2544 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
2545 &tcp_savetcp, 0);
2546#endif
2547 if (tp)
2548 INP_UNLOCK(inp);
2549 if (headlocked)
2550 INP_INFO_WUNLOCK(&tcbinfo);
2551 m_freem(m);
2552 return;
2553}
2554
2555/*
2556 * Parse TCP options and place in tcpopt.
2557 */
2558static void
2559tcp_dooptions(to, cp, cnt, is_syn)
2560 struct tcpopt *to;
2561 u_char *cp;
2562 int cnt;
2563 int is_syn;
2564{
2565 int opt, optlen;
2566
2567 to->to_flags = 0;
2568 for (; cnt > 0; cnt -= optlen, cp += optlen) {
2569 opt = cp[0];
2570 if (opt == TCPOPT_EOL)
2571 break;
2572 if (opt == TCPOPT_NOP)
2573 optlen = 1;
2574 else {
2575 if (cnt < 2)
2576 break;
2577 optlen = cp[1];
2578 if (optlen < 2 || optlen > cnt)
2579 break;
2580 }
2581 switch (opt) {
2582 case TCPOPT_MAXSEG:
2583 if (optlen != TCPOLEN_MAXSEG)
2584 continue;
2585 if (!is_syn)
2586 continue;
2587 to->to_flags |= TOF_MSS;
2588 bcopy((char *)cp + 2,
2589 (char *)&to->to_mss, sizeof(to->to_mss));
2590 to->to_mss = ntohs(to->to_mss);
2591 break;
2592 case TCPOPT_WINDOW:
2593 if (optlen != TCPOLEN_WINDOW)
2594 continue;
2595 if (! is_syn)
2596 continue;
2597 to->to_flags |= TOF_SCALE;
2598 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT);
2599 break;
2600 case TCPOPT_TIMESTAMP:
2601 if (optlen != TCPOLEN_TIMESTAMP)
2602 continue;
2603 to->to_flags |= TOF_TS;
2604 bcopy((char *)cp + 2,
2605 (char *)&to->to_tsval, sizeof(to->to_tsval));
2606 to->to_tsval = ntohl(to->to_tsval);
2607 bcopy((char *)cp + 6,
2608 (char *)&to->to_tsecr, sizeof(to->to_tsecr));
2609 to->to_tsecr = ntohl(to->to_tsecr);
2610 /*
2611 * If echoed timestamp is later than the current time,
2612 * fall back to non RFC1323 RTT calculation.
2613 */
2614 if ((to->to_tsecr != 0) && TSTMP_GT(to->to_tsecr, ticks))
2615 to->to_tsecr = 0;
2616 break;
2617#ifdef TCP_SIGNATURE
2618 /*
2619 * XXX In order to reply to a host which has set the
2620 * TCP_SIGNATURE option in its initial SYN, we have to
2621 * record the fact that the option was observed here
2622 * for the syncache code to perform the correct response.
2623 */
2624 case TCPOPT_SIGNATURE:
2625 if (optlen != TCPOLEN_SIGNATURE)
2626 continue;
2627 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN);
2628 break;
2629#endif
2630 case TCPOPT_SACK_PERMITTED:
2631 if (!tcp_do_sack ||
2632 optlen != TCPOLEN_SACK_PERMITTED)
2633 continue;
2634 if (is_syn) {
2635 /* MUST only be set on SYN */
2636 to->to_flags |= TOF_SACK;
2637 }
2638 break;
2639 case TCPOPT_SACK:
2640 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0)
2641 continue;
2642 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK;
2643 to->to_sacks = cp + 2;
2644 tcpstat.tcps_sack_rcv_blocks++;
2645 break;
2646 default:
2647 continue;
2648 }
2649 }
2650}
2651
2652/*
2653 * Pull out of band byte out of a segment so
2654 * it doesn't appear in the user's data queue.
2655 * It is still reflected in the segment length for
2656 * sequencing purposes.
2657 */
2658static void
2659tcp_pulloutofband(so, th, m, off)
2660 struct socket *so;
2661 struct tcphdr *th;
2662 register struct mbuf *m;
2663 int off; /* delayed to be droped hdrlen */
2664{
2665 int cnt = off + th->th_urp - 1;
2666
2667 while (cnt >= 0) {
2668 if (m->m_len > cnt) {
2669 char *cp = mtod(m, caddr_t) + cnt;
2670 struct tcpcb *tp = sototcpcb(so);
2671
2672 tp->t_iobc = *cp;
2673 tp->t_oobflags |= TCPOOB_HAVEDATA;
2674 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1));
2675 m->m_len--;
2676 if (m->m_flags & M_PKTHDR)
2677 m->m_pkthdr.len--;
2678 return;
2679 }
2680 cnt -= m->m_len;
2681 m = m->m_next;
2682 if (m == 0)
2683 break;
2684 }
2685 panic("tcp_pulloutofband");
2686}
2687
2688/*
2689 * Collect new round-trip time estimate
2690 * and update averages and current timeout.
2691 */
2692static void
2693tcp_xmit_timer(tp, rtt)
2694 register struct tcpcb *tp;
2695 int rtt;
2696{
2697 register int delta;
2698
2699 INP_LOCK_ASSERT(tp->t_inpcb);
2700
2701 tcpstat.tcps_rttupdated++;
2702 tp->t_rttupdated++;
2703 if (tp->t_srtt != 0) {
2704 /*
2705 * srtt is stored as fixed point with 5 bits after the
2706 * binary point (i.e., scaled by 8). The following magic
2707 * is equivalent to the smoothing algorithm in rfc793 with
2708 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
2709 * point). Adjust rtt to origin 0.
2710 */
2711 delta = ((rtt - 1) << TCP_DELTA_SHIFT)
2712 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
2713
2714 if ((tp->t_srtt += delta) <= 0)
2715 tp->t_srtt = 1;
2716
2717 /*
2718 * We accumulate a smoothed rtt variance (actually, a
2719 * smoothed mean difference), then set the retransmit
2720 * timer to smoothed rtt + 4 times the smoothed variance.
2721 * rttvar is stored as fixed point with 4 bits after the
2722 * binary point (scaled by 16). The following is
2723 * equivalent to rfc793 smoothing with an alpha of .75
2724 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces
2725 * rfc793's wired-in beta.
2726 */
2727 if (delta < 0)
2728 delta = -delta;
2729 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
2730 if ((tp->t_rttvar += delta) <= 0)
2731 tp->t_rttvar = 1;
2732 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
2733 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2734 } else {
2735 /*
2736 * No rtt measurement yet - use the unsmoothed rtt.
2737 * Set the variance to half the rtt (so our first
2738 * retransmit happens at 3*rtt).
2739 */
2740 tp->t_srtt = rtt << TCP_RTT_SHIFT;
2741 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
2742 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2743 }
2744 tp->t_rtttime = 0;
2745 tp->t_rxtshift = 0;
2746
2747 /*
2748 * the retransmit should happen at rtt + 4 * rttvar.
2749 * Because of the way we do the smoothing, srtt and rttvar
2750 * will each average +1/2 tick of bias. When we compute
2751 * the retransmit timer, we want 1/2 tick of rounding and
2752 * 1 extra tick because of +-1/2 tick uncertainty in the
2753 * firing of the timer. The bias will give us exactly the
2754 * 1.5 tick we need. But, because the bias is
2755 * statistical, we have to test that we don't drop below
2756 * the minimum feasible timer (which is 2 ticks).
2757 */
2758 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
2759 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);
2760
2761 /*
2762 * We received an ack for a packet that wasn't retransmitted;
2763 * it is probably safe to discard any error indications we've
2764 * received recently. This isn't quite right, but close enough
2765 * for now (a route might have failed after we sent a segment,
2766 * and the return path might not be symmetrical).
2767 */
2768 tp->t_softerror = 0;
2769}
2770
2771/*
2772 * Determine a reasonable value for maxseg size.
2773 * If the route is known, check route for mtu.
2774 * If none, use an mss that can be handled on the outgoing
2775 * interface without forcing IP to fragment; if bigger than
2776 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES
2777 * to utilize large mbufs. If no route is found, route has no mtu,
2778 * or the destination isn't local, use a default, hopefully conservative
2779 * size (usually 512 or the default IP max size, but no more than the mtu
2780 * of the interface), as we can't discover anything about intervening
2781 * gateways or networks. We also initialize the congestion/slow start
2782 * window to be a single segment if the destination isn't local.
2783 * While looking at the routing entry, we also initialize other path-dependent
2784 * parameters from pre-set or cached values in the routing entry.
2785 *
2786 * Also take into account the space needed for options that we
2787 * send regularly. Make maxseg shorter by that amount to assure
2788 * that we can send maxseg amount of data even when the options
2789 * are present. Store the upper limit of the length of options plus
2790 * data in maxopd.
2791 *
2792 *
2793 * In case of T/TCP, we call this routine during implicit connection
2794 * setup as well (offer = -1), to initialize maxseg from the cached
2795 * MSS of our peer.
2796 *
2797 * NOTE that this routine is only called when we process an incoming
2798 * segment. Outgoing SYN/ACK MSS settings are handled in tcp_mssopt().
2799 */
2800void
2801tcp_mss(tp, offer)
2802 struct tcpcb *tp;
2803 int offer;
2804{
2805 int rtt, mss;
2806 u_long bufsize;
2807 u_long maxmtu;
2808 struct inpcb *inp = tp->t_inpcb;
2809 struct socket *so;
2810 struct hc_metrics_lite metrics;
2811 int origoffer = offer;
2812#ifdef INET6
2813 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0;
2814 size_t min_protoh = isipv6 ?
2815 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) :
2816 sizeof (struct tcpiphdr);
2817#else
2818 const size_t min_protoh = sizeof(struct tcpiphdr);
2819#endif
2820
2821 /* initialize */
2822#ifdef INET6
2823 if (isipv6) {
2824 maxmtu = tcp_maxmtu6(&inp->inp_inc);
2825 tp->t_maxopd = tp->t_maxseg = tcp_v6mssdflt;
2826 } else
2827#endif
2828 {
2829 maxmtu = tcp_maxmtu(&inp->inp_inc);
2830 tp->t_maxopd = tp->t_maxseg = tcp_mssdflt;
2831 }
2832 so = inp->inp_socket;
2833
2834 /*
2835 * no route to sender, stay with default mss and return
2836 */
2837 if (maxmtu == 0)
2838 return;
2839
2840 /* what have we got? */
2841 switch (offer) {
2842 case 0:
2843 /*
2844 * Offer == 0 means that there was no MSS on the SYN
2845 * segment, in this case we use tcp_mssdflt.
2846 */
2847 offer =
2848#ifdef INET6
2849 isipv6 ? tcp_v6mssdflt :
2850#endif
2851 tcp_mssdflt;
2852 break;
2853
2854 case -1:
2855 /*
2856 * Offer == -1 means that we didn't receive SYN yet.
2857 */
2858 /* FALLTHROUGH */
2859
2860 default:
2861 /*
2862 * Prevent DoS attack with too small MSS. Round up
2863 * to at least minmss.
2864 */
2865 offer = max(offer, tcp_minmss);
2866 /*
2867 * Sanity check: make sure that maxopd will be large
2868 * enough to allow some data on segments even if the
2869 * all the option space is used (40bytes). Otherwise
2870 * funny things may happen in tcp_output.
2871 */
2872 offer = max(offer, 64);
2873 }
2874
2875 /*
2876 * rmx information is now retrieved from tcp_hostcache
2877 */
2878 tcp_hc_get(&inp->inp_inc, &metrics);
2879
2880 /*
2881 * if there's a discovered mtu int tcp hostcache, use it
2882 * else, use the link mtu.
2883 */
2884 if (metrics.rmx_mtu)
2885 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh;
2886 else {
2887#ifdef INET6
2888 if (isipv6) {
2889 mss = maxmtu - min_protoh;
2890 if (!path_mtu_discovery &&
2891 !in6_localaddr(&inp->in6p_faddr))
2892 mss = min(mss, tcp_v6mssdflt);
2893 } else
2894#endif
2895 {
2896 mss = maxmtu - min_protoh;
2897 if (!path_mtu_discovery &&
2898 !in_localaddr(inp->inp_faddr))
2899 mss = min(mss, tcp_mssdflt);
2900 }
2901 }
2902 mss = min(mss, offer);
2903
2904 /*
2905 * maxopd stores the maximum length of data AND options
2906 * in a segment; maxseg is the amount of data in a normal
2907 * segment. We need to store this value (maxopd) apart
2908 * from maxseg, because now every segment carries options
2909 * and thus we normally have somewhat less data in segments.
2910 */
2911 tp->t_maxopd = mss;
2912
2913 /*
2914 * origoffer==-1 indicates, that no segments were received yet.
2915 * In this case we just guess.
2916 */
2917 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
2918 (origoffer == -1 ||
2919 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP))
2920 mss -= TCPOLEN_TSTAMP_APPA;
2921 tp->t_maxseg = mss;
2922
2923#if (MCLBYTES & (MCLBYTES - 1)) == 0
2924 if (mss > MCLBYTES)
2925 mss &= ~(MCLBYTES-1);
2926#else
2927 if (mss > MCLBYTES)
2928 mss = mss / MCLBYTES * MCLBYTES;
2929#endif
2930 tp->t_maxseg = mss;
2931
2932 /*
2933 * If there's a pipesize, change the socket buffer to that size,
2934 * don't change if sb_hiwat is different than default (then it
2935 * has been changed on purpose with setsockopt).
2936 * Make the socket buffers an integral number of mss units;
2937 * if the mss is larger than the socket buffer, decrease the mss.
2938 */
2939 SOCKBUF_LOCK(&so->so_snd);
2940 if ((so->so_snd.sb_hiwat == tcp_sendspace) && metrics.rmx_sendpipe)
2941 bufsize = metrics.rmx_sendpipe;
2942 else
2943 bufsize = so->so_snd.sb_hiwat;
2944 if (bufsize < mss)
2945 mss = bufsize;
2946 else {
2947 bufsize = roundup(bufsize, mss);
2948 if (bufsize > sb_max)
2949 bufsize = sb_max;
2950 if (bufsize > so->so_snd.sb_hiwat)
2951 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL);
2952 }
2953 SOCKBUF_UNLOCK(&so->so_snd);
2954 tp->t_maxseg = mss;
2955
2956 SOCKBUF_LOCK(&so->so_rcv);
2957 if ((so->so_rcv.sb_hiwat == tcp_recvspace) && metrics.rmx_recvpipe)
2958 bufsize = metrics.rmx_recvpipe;
2959 else
2960 bufsize = so->so_rcv.sb_hiwat;
2961 if (bufsize > mss) {
2962 bufsize = roundup(bufsize, mss);
2963 if (bufsize > sb_max)
2964 bufsize = sb_max;
2965 if (bufsize > so->so_rcv.sb_hiwat)
2966 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL);
2967 }
2968 SOCKBUF_UNLOCK(&so->so_rcv);
2969 /*
2970 * While we're here, check the others too
2971 */
2972 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) {
2973 tp->t_srtt = rtt;
2974 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE;
2975 tcpstat.tcps_usedrtt++;
2976 if (metrics.rmx_rttvar) {
2977 tp->t_rttvar = metrics.rmx_rttvar;
2978 tcpstat.tcps_usedrttvar++;
2979 } else {
2980 /* default variation is +- 1 rtt */
2981 tp->t_rttvar =
2982 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
2983 }
2984 TCPT_RANGESET(tp->t_rxtcur,
2985 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
2986 tp->t_rttmin, TCPTV_REXMTMAX);
2987 }
2988 if (metrics.rmx_ssthresh) {
2989 /*
2990 * There's some sort of gateway or interface
2991 * buffer limit on the path. Use this to set
2992 * the slow start threshhold, but set the
2993 * threshold to no less than 2*mss.
2994 */
2995 tp->snd_ssthresh = max(2 * mss, metrics.rmx_ssthresh);
2996 tcpstat.tcps_usedssthresh++;
2997 }
2998 if (metrics.rmx_bandwidth)
2999 tp->snd_bandwidth = metrics.rmx_bandwidth;
3000
3001 /*
3002 * Set the slow-start flight size depending on whether this
3003 * is a local network or not.
3004 *
3005 * Extend this so we cache the cwnd too and retrieve it here.
3006 * Make cwnd even bigger than RFC3390 suggests but only if we
3007 * have previous experience with the remote host. Be careful
3008 * not make cwnd bigger than remote receive window or our own
3009 * send socket buffer. Maybe put some additional upper bound
3010 * on the retrieved cwnd. Should do incremental updates to
3011 * hostcache when cwnd collapses so next connection doesn't
3012 * overloads the path again.
3013 *
3014 * RFC3390 says only do this if SYN or SYN/ACK didn't got lost.
3015 * We currently check only in syncache_socket for that.
3016 */
3017#define TCP_METRICS_CWND
3018#ifdef TCP_METRICS_CWND
3019 if (metrics.rmx_cwnd)
3020 tp->snd_cwnd = max(mss,
3021 min(metrics.rmx_cwnd / 2,
3022 min(tp->snd_wnd, so->so_snd.sb_hiwat)));
3023 else
3024#endif
3025 if (tcp_do_rfc3390)
3026 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380));
3027#ifdef INET6
3028 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) ||
3029 (!isipv6 && in_localaddr(inp->inp_faddr)))
3030#else
3031 else if (in_localaddr(inp->inp_faddr))
3032#endif
3033 tp->snd_cwnd = mss * ss_fltsz_local;
3034 else
3035 tp->snd_cwnd = mss * ss_fltsz;
3036}
3037
3038/*
3039 * Determine the MSS option to send on an outgoing SYN.
3040 */
3041int
3042tcp_mssopt(inc)
3043 struct in_conninfo *inc;
3044{
3045 int mss = 0;
3046 u_long maxmtu = 0;
3047 u_long thcmtu = 0;
3048 size_t min_protoh;
3049#ifdef INET6
3050 int isipv6 = inc->inc_isipv6 ? 1 : 0;
3051#endif
3052
3053 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer"));
3054
3055#ifdef INET6
3056 if (isipv6) {
3057 mss = tcp_v6mssdflt;
3058 maxmtu = tcp_maxmtu6(inc);
3059 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */
3060 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
3061 } else
3062#endif
3063 {
3064 mss = tcp_mssdflt;
3065 maxmtu = tcp_maxmtu(inc);
3066 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */
3067 min_protoh = sizeof(struct tcpiphdr);
3068 }
3069 if (maxmtu && thcmtu)
3070 mss = min(maxmtu, thcmtu) - min_protoh;
3071 else if (maxmtu || thcmtu)
3072 mss = max(maxmtu, thcmtu) - min_protoh;
3073
3074 return (mss);
3075}
3076
3077
3078/*
3079 * On a partial ack arrives, force the retransmission of the
3080 * next unacknowledged segment. Do not clear tp->t_dupacks.
3081 * By setting snd_nxt to ti_ack, this forces retransmission timer to
3082 * be started again.
3083 */
3084static void
3085tcp_newreno_partial_ack(tp, th)
3086 struct tcpcb *tp;
3087 struct tcphdr *th;
3088{
3089 tcp_seq onxt = tp->snd_nxt;
3090 u_long ocwnd = tp->snd_cwnd;
3091
3092 callout_stop(tp->tt_rexmt);
3093 tp->t_rtttime = 0;
3094 tp->snd_nxt = th->th_ack;
3095 /*
3096 * Set snd_cwnd to one segment beyond acknowledged offset.
3097 * (tp->snd_una has not yet been updated when this function is called.)
3098 */
3099 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una);
3100 tp->t_flags |= TF_ACKNOW;
3101 (void) tcp_output(tp);
3102 tp->snd_cwnd = ocwnd;
3103 if (SEQ_GT(onxt, tp->snd_nxt))
3104 tp->snd_nxt = onxt;
3105 /*
3106 * Partial window deflation. Relies on fact that tp->snd_una
3107 * not updated yet.
3108 */
3109 tp->snd_cwnd -= (th->th_ack - tp->snd_una - tp->t_maxseg);
3110}
3111
3112/*
3113 * Returns 1 if the TIME_WAIT state was killed and we should start over,
3114 * looking for a pcb in the listen state. Returns 0 otherwise.
3115 */
3116static int
3117tcp_timewait(tw, to, th, m, tlen)
3118 struct tcptw *tw;
3119 struct tcpopt *to;
3120 struct tcphdr *th;
3121 struct mbuf *m;
3122 int tlen;
3123{
3124 int thflags;
3125 tcp_seq seq;
3126#ifdef INET6
3127 int isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0;
3128#else
3129 const int isipv6 = 0;
3130#endif
3131
3132 /* tcbinfo lock required for tcp_twclose(), tcp_2msl_reset. */
3133 INP_INFO_WLOCK_ASSERT(&tcbinfo);
3134 INP_LOCK_ASSERT(tw->tw_inpcb);
3135
3136 thflags = th->th_flags;
3137
3138 /*
3139 * NOTE: for FIN_WAIT_2 (to be added later),
3140 * must validate sequence number before accepting RST
3141 */
3142
3143 /*
3144 * If the segment contains RST:
3145 * Drop the segment - see Stevens, vol. 2, p. 964 and
3146 * RFC 1337.
3147 */
3148 if (thflags & TH_RST)
3149 goto drop;
3150
3151#if 0
3152/* PAWS not needed at the moment */
3153 /*
3154 * RFC 1323 PAWS: If we have a timestamp reply on this segment
3155 * and it's less than ts_recent, drop it.
3156 */
3157 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
3158 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
3159 if ((thflags & TH_ACK) == 0)
3160 goto drop;
3161 goto ack;
3162 }
3163 /*
3164 * ts_recent is never updated because we never accept new segments.
3165 */
3166#endif
3167
3168 /*
3169 * If a new connection request is received
3170 * while in TIME_WAIT, drop the old connection
3171 * and start over if the sequence numbers
3172 * are above the previous ones.
3173 */
3174 if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) {
3175 (void) tcp_twclose(tw, 0);
3176 return (1);
3177 }
3178
3179 /*
3180 * Drop the the segment if it does not contain an ACK.
3181 */
3182 if ((thflags & TH_ACK) == 0)
3183 goto drop;
3184
3185 /*
3186 * Reset the 2MSL timer if this is a duplicate FIN.
3187 */
3188 if (thflags & TH_FIN) {
3189 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0);
3190 if (seq + 1 == tw->rcv_nxt)
3191 tcp_timer_2msl_reset(tw, 2 * tcp_msl);
3192 }
3193
3194 /*
3195 * Acknowledge the segment if it has data or is not a duplicate ACK.
3196 */
3197 if (thflags != TH_ACK || tlen != 0 ||
3198 th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt)
3199 tcp_twrespond(tw, TH_ACK);
3200 goto drop;
3201
3202 /*
3203 * Generate a RST, dropping incoming segment.
3204 * Make ACK acceptable to originator of segment.
3205 * Don't bother to respond if destination was broadcast/multicast.
3206 */
3207 if (m->m_flags & (M_BCAST|M_MCAST))
3208 goto drop;
3209 if (isipv6) {
3210 struct ip6_hdr *ip6;
3211
3212 /* IPv6 anycast check is done at tcp6_input() */
3213 ip6 = mtod(m, struct ip6_hdr *);
3214 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
3215 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
3216 goto drop;
3217 } else {
3218 struct ip *ip;
3219
3220 ip = mtod(m, struct ip *);
3221 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
3222 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
3223 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
3224 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
3225 goto drop;
3226 }
3227 if (thflags & TH_ACK) {
3228 tcp_respond(NULL,
3229 mtod(m, void *), th, m, 0, th->th_ack, TH_RST);
3230 } else {
3231 seq = th->th_seq + (thflags & TH_SYN ? 1 : 0);
3232 tcp_respond(NULL,
3233 mtod(m, void *), th, m, seq, 0, TH_RST|TH_ACK);
3234 }
3235 INP_UNLOCK(tw->tw_inpcb);
3236 return (0);
3237
3238drop:
3239 INP_UNLOCK(tw->tw_inpcb);
3240 m_freem(m);
3241 return (0);
3242}
| 1086 if (to.to_flags & TOF_SCALE) {
1087 tp->t_flags |= TF_RCVD_SCALE;
1088 tp->requested_s_scale = to.to_requested_s_scale;
1089 }
1090 if (to.to_flags & TOF_TS) {
1091 tp->t_flags |= TF_RCVD_TSTMP;
1092 tp->ts_recent = to.to_tsval;
1093 tp->ts_recent_age = ticks;
1094 }
1095 if (to.to_flags & TOF_MSS)
1096 tcp_mss(tp, to.to_mss);
1097 if (tp->sack_enable) {
1098 if (!(to.to_flags & TOF_SACK))
1099 tp->sack_enable = 0;
1100 else
1101 tp->t_flags |= TF_SACK_PERMIT;
1102 }
1103
1104 }
1105
1106 /*
1107 * Header prediction: check for the two common cases
1108 * of a uni-directional data xfer. If the packet has
1109 * no control flags, is in-sequence, the window didn't
1110 * change and we're not retransmitting, it's a
1111 * candidate. If the length is zero and the ack moved
1112 * forward, we're the sender side of the xfer. Just
1113 * free the data acked & wake any higher level process
1114 * that was blocked waiting for space. If the length
1115 * is non-zero and the ack didn't move, we're the
1116 * receiver side. If we're getting packets in-order
1117 * (the reassembly queue is empty), add the data to
1118 * the socket buffer and note that we need a delayed ack.
1119 * Make sure that the hidden state-flags are also off.
1120 * Since we check for TCPS_ESTABLISHED above, it can only
1121 * be TH_NEEDSYN.
1122 */
1123 if (tp->t_state == TCPS_ESTABLISHED &&
1124 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
1125 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) &&
1126 ((to.to_flags & TOF_TS) == 0 ||
1127 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) &&
1128 th->th_seq == tp->rcv_nxt && tiwin && tiwin == tp->snd_wnd &&
1129 tp->snd_nxt == tp->snd_max) {
1130
1131 /*
1132 * If last ACK falls within this segment's sequence numbers,
1133 * record the timestamp.
1134 * NOTE that the test is modified according to the latest
1135 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1136 */
1137 if ((to.to_flags & TOF_TS) != 0 &&
1138 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
1139 tp->ts_recent_age = ticks;
1140 tp->ts_recent = to.to_tsval;
1141 }
1142
1143 if (tlen == 0) {
1144 if (SEQ_GT(th->th_ack, tp->snd_una) &&
1145 SEQ_LEQ(th->th_ack, tp->snd_max) &&
1146 tp->snd_cwnd >= tp->snd_wnd &&
1147 ((!tcp_do_newreno && !tp->sack_enable &&
1148 tp->t_dupacks < tcprexmtthresh) ||
1149 ((tcp_do_newreno || tp->sack_enable) &&
1150 !IN_FASTRECOVERY(tp) && to.to_nsacks == 0))) {
1151 KASSERT(headlocked, ("headlocked"));
1152 INP_INFO_WUNLOCK(&tcbinfo);
1153 headlocked = 0;
1154 /*
1155 * this is a pure ack for outstanding data.
1156 */
1157 ++tcpstat.tcps_predack;
1158 /*
1159 * "bad retransmit" recovery
1160 */
1161 if (tp->t_rxtshift == 1 &&
1162 ticks < tp->t_badrxtwin) {
1163 ++tcpstat.tcps_sndrexmitbad;
1164 tp->snd_cwnd = tp->snd_cwnd_prev;
1165 tp->snd_ssthresh =
1166 tp->snd_ssthresh_prev;
1167 tp->snd_recover = tp->snd_recover_prev;
1168 if (tp->t_flags & TF_WASFRECOVERY)
1169 ENTER_FASTRECOVERY(tp);
1170 tp->snd_nxt = tp->snd_max;
1171 tp->t_badrxtwin = 0;
1172 }
1173
1174 /*
1175 * Recalculate the transmit timer / rtt.
1176 *
1177 * Some boxes send broken timestamp replies
1178 * during the SYN+ACK phase, ignore
1179 * timestamps of 0 or we could calculate a
1180 * huge RTT and blow up the retransmit timer.
1181 */
1182 if ((to.to_flags & TOF_TS) != 0 &&
1183 to.to_tsecr) {
1184 tcp_xmit_timer(tp,
1185 ticks - to.to_tsecr + 1);
1186 } else if (tp->t_rtttime &&
1187 SEQ_GT(th->th_ack, tp->t_rtseq)) {
1188 tcp_xmit_timer(tp,
1189 ticks - tp->t_rtttime);
1190 }
1191 tcp_xmit_bandwidth_limit(tp, th->th_ack);
1192 acked = th->th_ack - tp->snd_una;
1193 tcpstat.tcps_rcvackpack++;
1194 tcpstat.tcps_rcvackbyte += acked;
1195 sbdrop(&so->so_snd, acked);
1196 if (SEQ_GT(tp->snd_una, tp->snd_recover) &&
1197 SEQ_LEQ(th->th_ack, tp->snd_recover))
1198 tp->snd_recover = th->th_ack - 1;
1199 tp->snd_una = th->th_ack;
1200 /*
1201 * pull snd_wl2 up to prevent seq wrap relative
1202 * to th_ack.
1203 */
1204 tp->snd_wl2 = th->th_ack;
1205 tp->t_dupacks = 0;
1206 m_freem(m);
1207 ND6_HINT(tp); /* some progress has been done */
1208
1209 /*
1210 * If all outstanding data are acked, stop
1211 * retransmit timer, otherwise restart timer
1212 * using current (possibly backed-off) value.
1213 * If process is waiting for space,
1214 * wakeup/selwakeup/signal. If data
1215 * are ready to send, let tcp_output
1216 * decide between more output or persist.
1217
1218#ifdef TCPDEBUG
1219 if (so->so_options & SO_DEBUG)
1220 tcp_trace(TA_INPUT, ostate, tp,
1221 (void *)tcp_saveipgen,
1222 &tcp_savetcp, 0);
1223#endif
1224 */
1225 if (tp->snd_una == tp->snd_max)
1226 callout_stop(tp->tt_rexmt);
1227 else if (!callout_active(tp->tt_persist))
1228 callout_reset(tp->tt_rexmt,
1229 tp->t_rxtcur,
1230 tcp_timer_rexmt, tp);
1231
1232 sowwakeup(so);
1233 if (so->so_snd.sb_cc)
1234 (void) tcp_output(tp);
1235 goto check_delack;
1236 }
1237 } else if (th->th_ack == tp->snd_una &&
1238 LIST_EMPTY(&tp->t_segq) &&
1239 tlen <= sbspace(&so->so_rcv)) {
1240 KASSERT(headlocked, ("headlocked"));
1241 INP_INFO_WUNLOCK(&tcbinfo);
1242 headlocked = 0;
1243 /*
1244 * this is a pure, in-sequence data packet
1245 * with nothing on the reassembly queue and
1246 * we have enough buffer space to take it.
1247 */
1248 /* Clean receiver SACK report if present */
1249 if (tp->sack_enable && tp->rcv_numsacks)
1250 tcp_clean_sackreport(tp);
1251 ++tcpstat.tcps_preddat;
1252 tp->rcv_nxt += tlen;
1253 /*
1254 * Pull snd_wl1 up to prevent seq wrap relative to
1255 * th_seq.
1256 */
1257 tp->snd_wl1 = th->th_seq;
1258 /*
1259 * Pull rcv_up up to prevent seq wrap relative to
1260 * rcv_nxt.
1261 */
1262 tp->rcv_up = tp->rcv_nxt;
1263 tcpstat.tcps_rcvpack++;
1264 tcpstat.tcps_rcvbyte += tlen;
1265 ND6_HINT(tp); /* some progress has been done */
1266 /*
1267#ifdef TCPDEBUG
1268 if (so->so_options & SO_DEBUG)
1269 tcp_trace(TA_INPUT, ostate, tp,
1270 (void *)tcp_saveipgen, &tcp_savetcp, 0);
1271#endif
1272 * Add data to socket buffer.
1273 */
1274 SOCKBUF_LOCK(&so->so_rcv);
1275 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
1276 m_freem(m);
1277 } else {
1278 m_adj(m, drop_hdrlen); /* delayed header drop */
1279 sbappendstream_locked(&so->so_rcv, m);
1280 }
1281 sorwakeup_locked(so);
1282 if (DELAY_ACK(tp)) {
1283 tp->t_flags |= TF_DELACK;
1284 } else {
1285 tp->t_flags |= TF_ACKNOW;
1286 tcp_output(tp);
1287 }
1288 goto check_delack;
1289 }
1290 }
1291
1292 /*
1293 * Calculate amount of space in receive window,
1294 * and then do TCP input processing.
1295 * Receive window is amount of space in rcv queue,
1296 * but not less than advertised window.
1297 */
1298 { int win;
1299
1300 win = sbspace(&so->so_rcv);
1301 if (win < 0)
1302 win = 0;
1303 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt));
1304 }
1305
1306 switch (tp->t_state) {
1307
1308 /*
1309 * If the state is SYN_RECEIVED:
1310 * if seg contains an ACK, but not for our SYN/ACK, send a RST.
1311 */
1312 case TCPS_SYN_RECEIVED:
1313 if ((thflags & TH_ACK) &&
1314 (SEQ_LEQ(th->th_ack, tp->snd_una) ||
1315 SEQ_GT(th->th_ack, tp->snd_max))) {
1316 rstreason = BANDLIM_RST_OPENPORT;
1317 goto dropwithreset;
1318 }
1319 break;
1320
1321 /*
1322 * If the state is SYN_SENT:
1323 * if seg contains an ACK, but not for our SYN, drop the input.
1324 * if seg contains a RST, then drop the connection.
1325 * if seg does not contain SYN, then drop it.
1326 * Otherwise this is an acceptable SYN segment
1327 * initialize tp->rcv_nxt and tp->irs
1328 * if seg contains ack then advance tp->snd_una
1329 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state
1330 * arrange for segment to be acked (eventually)
1331 * continue processing rest of data/controls, beginning with URG
1332 */
1333 case TCPS_SYN_SENT:
1334 if ((thflags & TH_ACK) &&
1335 (SEQ_LEQ(th->th_ack, tp->iss) ||
1336 SEQ_GT(th->th_ack, tp->snd_max))) {
1337 rstreason = BANDLIM_UNLIMITED;
1338 goto dropwithreset;
1339 }
1340 if (thflags & TH_RST) {
1341 if (thflags & TH_ACK) {
1342 KASSERT(headlocked, ("tcp_input: after_listen"
1343 ": tcp_drop.2: head not locked"));
1344 tp = tcp_drop(tp, ECONNREFUSED);
1345 }
1346 goto drop;
1347 }
1348 if ((thflags & TH_SYN) == 0)
1349 goto drop;
1350 tp->snd_wnd = th->th_win; /* initial send window */
1351
1352 tp->irs = th->th_seq;
1353 tcp_rcvseqinit(tp);
1354 if (thflags & TH_ACK) {
1355 tcpstat.tcps_connects++;
1356 soisconnected(so);
1357#ifdef MAC
1358 SOCK_LOCK(so);
1359 mac_set_socket_peer_from_mbuf(m, so);
1360 SOCK_UNLOCK(so);
1361#endif
1362 /* Do window scaling on this connection? */
1363 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
1364 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
1365 tp->snd_scale = tp->requested_s_scale;
1366 tp->rcv_scale = tp->request_r_scale;
1367 }
1368 tp->rcv_adv += tp->rcv_wnd;
1369 tp->snd_una++; /* SYN is acked */
1370 /*
1371 * If there's data, delay ACK; if there's also a FIN
1372 * ACKNOW will be turned on later.
1373 */
1374 if (DELAY_ACK(tp) && tlen != 0)
1375 callout_reset(tp->tt_delack, tcp_delacktime,
1376 tcp_timer_delack, tp);
1377 else
1378 tp->t_flags |= TF_ACKNOW;
1379 /*
1380 * Received <SYN,ACK> in SYN_SENT[*] state.
1381 * Transitions:
1382 * SYN_SENT --> ESTABLISHED
1383 * SYN_SENT* --> FIN_WAIT_1
1384 */
1385 tp->t_starttime = ticks;
1386 if (tp->t_flags & TF_NEEDFIN) {
1387 tp->t_state = TCPS_FIN_WAIT_1;
1388 tp->t_flags &= ~TF_NEEDFIN;
1389 thflags &= ~TH_SYN;
1390 } else {
1391 tp->t_state = TCPS_ESTABLISHED;
1392 callout_reset(tp->tt_keep, tcp_keepidle,
1393 tcp_timer_keep, tp);
1394 }
1395 } else {
1396 /*
1397 * Received initial SYN in SYN-SENT[*] state =>
1398 * simultaneous open. If segment contains CC option
1399 * and there is a cached CC, apply TAO test.
1400 * If it succeeds, connection is * half-synchronized.
1401 * Otherwise, do 3-way handshake:
1402 * SYN-SENT -> SYN-RECEIVED
1403 * SYN-SENT* -> SYN-RECEIVED*
1404 * If there was no CC option, clear cached CC value.
1405 */
1406 tp->t_flags |= TF_ACKNOW;
1407 callout_stop(tp->tt_rexmt);
1408 tp->t_state = TCPS_SYN_RECEIVED;
1409 }
1410
1411trimthenstep6:
1412 KASSERT(headlocked, ("tcp_input: trimthenstep6: head not "
1413 "locked"));
1414 INP_LOCK_ASSERT(inp);
1415
1416 /*
1417 * Advance th->th_seq to correspond to first data byte.
1418 * If data, trim to stay within window,
1419 * dropping FIN if necessary.
1420 */
1421 th->th_seq++;
1422 if (tlen > tp->rcv_wnd) {
1423 todrop = tlen - tp->rcv_wnd;
1424 m_adj(m, -todrop);
1425 tlen = tp->rcv_wnd;
1426 thflags &= ~TH_FIN;
1427 tcpstat.tcps_rcvpackafterwin++;
1428 tcpstat.tcps_rcvbyteafterwin += todrop;
1429 }
1430 tp->snd_wl1 = th->th_seq - 1;
1431 tp->rcv_up = th->th_seq;
1432 /*
1433 * Client side of transaction: already sent SYN and data.
1434 * If the remote host used T/TCP to validate the SYN,
1435 * our data will be ACK'd; if so, enter normal data segment
1436 * processing in the middle of step 5, ack processing.
1437 * Otherwise, goto step 6.
1438 */
1439 if (thflags & TH_ACK)
1440 goto process_ACK;
1441
1442 goto step6;
1443
1444 /*
1445 * If the state is LAST_ACK or CLOSING or TIME_WAIT:
1446 * do normal processing.
1447 *
1448 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later.
1449 */
1450 case TCPS_LAST_ACK:
1451 case TCPS_CLOSING:
1452 case TCPS_TIME_WAIT:
1453 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
1454 break; /* continue normal processing */
1455 }
1456
1457 /*
1458 * States other than LISTEN or SYN_SENT.
1459 * First check the RST flag and sequence number since reset segments
1460 * are exempt from the timestamp and connection count tests. This
1461 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix
1462 * below which allowed reset segments in half the sequence space
1463 * to fall though and be processed (which gives forged reset
1464 * segments with a random sequence number a 50 percent chance of
1465 * killing a connection).
1466 * Then check timestamp, if present.
1467 * Then check the connection count, if present.
1468 * Then check that at least some bytes of segment are within
1469 * receive window. If segment begins before rcv_nxt,
1470 * drop leading data (and SYN); if nothing left, just ack.
1471 *
1472 *
1473 * If the RST bit is set, check the sequence number to see
1474 * if this is a valid reset segment.
1475 * RFC 793 page 37:
1476 * In all states except SYN-SENT, all reset (RST) segments
1477 * are validated by checking their SEQ-fields. A reset is
1478 * valid if its sequence number is in the window.
1479 * Note: this does not take into account delayed ACKs, so
1480 * we should test against last_ack_sent instead of rcv_nxt.
1481 * The sequence number in the reset segment is normally an
1482 * echo of our outgoing acknowlegement numbers, but some hosts
1483 * send a reset with the sequence number at the rightmost edge
1484 * of our receive window, and we have to handle this case.
1485 * Note 2: Paul Watson's paper "Slipping in the Window" has shown
1486 * that brute force RST attacks are possible. To combat this,
1487 * we use a much stricter check while in the ESTABLISHED state,
1488 * only accepting RSTs where the sequence number is equal to
1489 * last_ack_sent. In all other states (the states in which a
1490 * RST is more likely), the more permissive check is used.
1491 * If we have multiple segments in flight, the intial reset
1492 * segment sequence numbers will be to the left of last_ack_sent,
1493 * but they will eventually catch up.
1494 * In any case, it never made sense to trim reset segments to
1495 * fit the receive window since RFC 1122 says:
1496 * 4.2.2.12 RST Segment: RFC-793 Section 3.4
1497 *
1498 * A TCP SHOULD allow a received RST segment to include data.
1499 *
1500 * DISCUSSION
1501 * It has been suggested that a RST segment could contain
1502 * ASCII text that encoded and explained the cause of the
1503 * RST. No standard has yet been established for such
1504 * data.
1505 *
1506 * If the reset segment passes the sequence number test examine
1507 * the state:
1508 * SYN_RECEIVED STATE:
1509 * If passive open, return to LISTEN state.
1510 * If active open, inform user that connection was refused.
1511 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES:
1512 * Inform user that connection was reset, and close tcb.
1513 * CLOSING, LAST_ACK STATES:
1514 * Close the tcb.
1515 * TIME_WAIT STATE:
1516 * Drop the segment - see Stevens, vol. 2, p. 964 and
1517 * RFC 1337.
1518 */
1519 if (thflags & TH_RST) {
1520 if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
1521 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) ||
1522 (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) {
1523 switch (tp->t_state) {
1524
1525 case TCPS_SYN_RECEIVED:
1526 so->so_error = ECONNREFUSED;
1527 goto close;
1528
1529 case TCPS_ESTABLISHED:
1530 if (tp->last_ack_sent != th->th_seq &&
1531 tcp_insecure_rst == 0) {
1532 tcpstat.tcps_badrst++;
1533 goto drop;
1534 }
1535 case TCPS_FIN_WAIT_1:
1536 case TCPS_FIN_WAIT_2:
1537 case TCPS_CLOSE_WAIT:
1538 so->so_error = ECONNRESET;
1539 close:
1540 tp->t_state = TCPS_CLOSED;
1541 tcpstat.tcps_drops++;
1542 KASSERT(headlocked, ("tcp_input: "
1543 "trimthenstep6: tcp_close: head not "
1544 "locked"));
1545 tp = tcp_close(tp);
1546 break;
1547
1548 case TCPS_CLOSING:
1549 case TCPS_LAST_ACK:
1550 KASSERT(headlocked, ("trimthenstep6: "
1551 "tcp_close.2: head not locked"));
1552 tp = tcp_close(tp);
1553 break;
1554
1555 case TCPS_TIME_WAIT:
1556 KASSERT(tp->t_state != TCPS_TIME_WAIT,
1557 ("timewait"));
1558 break;
1559 }
1560 }
1561 goto drop;
1562 }
1563
1564 /*
1565 * RFC 1323 PAWS: If we have a timestamp reply on this segment
1566 * and it's less than ts_recent, drop it.
1567 */
1568 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
1569 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
1570
1571 /* Check to see if ts_recent is over 24 days old. */
1572 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) {
1573 /*
1574 * Invalidate ts_recent. If this segment updates
1575 * ts_recent, the age will be reset later and ts_recent
1576 * will get a valid value. If it does not, setting
1577 * ts_recent to zero will at least satisfy the
1578 * requirement that zero be placed in the timestamp
1579 * echo reply when ts_recent isn't valid. The
1580 * age isn't reset until we get a valid ts_recent
1581 * because we don't want out-of-order segments to be
1582 * dropped when ts_recent is old.
1583 */
1584 tp->ts_recent = 0;
1585 } else {
1586 tcpstat.tcps_rcvduppack++;
1587 tcpstat.tcps_rcvdupbyte += tlen;
1588 tcpstat.tcps_pawsdrop++;
1589 if (tlen)
1590 goto dropafterack;
1591 goto drop;
1592 }
1593 }
1594
1595 /*
1596 * In the SYN-RECEIVED state, validate that the packet belongs to
1597 * this connection before trimming the data to fit the receive
1598 * window. Check the sequence number versus IRS since we know
1599 * the sequence numbers haven't wrapped. This is a partial fix
1600 * for the "LAND" DoS attack.
1601 */
1602 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) {
1603 rstreason = BANDLIM_RST_OPENPORT;
1604 goto dropwithreset;
1605 }
1606
1607 todrop = tp->rcv_nxt - th->th_seq;
1608 if (todrop > 0) {
1609 if (thflags & TH_SYN) {
1610 thflags &= ~TH_SYN;
1611 th->th_seq++;
1612 if (th->th_urp > 1)
1613 th->th_urp--;
1614 else
1615 thflags &= ~TH_URG;
1616 todrop--;
1617 }
1618 /*
1619 * Following if statement from Stevens, vol. 2, p. 960.
1620 */
1621 if (todrop > tlen
1622 || (todrop == tlen && (thflags & TH_FIN) == 0)) {
1623 /*
1624 * Any valid FIN must be to the left of the window.
1625 * At this point the FIN must be a duplicate or out
1626 * of sequence; drop it.
1627 */
1628 thflags &= ~TH_FIN;
1629
1630 /*
1631 * Send an ACK to resynchronize and drop any data.
1632 * But keep on processing for RST or ACK.
1633 */
1634 tp->t_flags |= TF_ACKNOW;
1635 todrop = tlen;
1636 tcpstat.tcps_rcvduppack++;
1637 tcpstat.tcps_rcvdupbyte += todrop;
1638 } else {
1639 tcpstat.tcps_rcvpartduppack++;
1640 tcpstat.tcps_rcvpartdupbyte += todrop;
1641 }
1642 drop_hdrlen += todrop; /* drop from the top afterwards */
1643 th->th_seq += todrop;
1644 tlen -= todrop;
1645 if (th->th_urp > todrop)
1646 th->th_urp -= todrop;
1647 else {
1648 thflags &= ~TH_URG;
1649 th->th_urp = 0;
1650 }
1651 }
1652
1653 /*
1654 * If new data are received on a connection after the
1655 * user processes are gone, then RST the other end.
1656 */
1657 if ((so->so_state & SS_NOFDREF) &&
1658 tp->t_state > TCPS_CLOSE_WAIT && tlen) {
1659 KASSERT(headlocked, ("trimthenstep6: tcp_close.3: head not "
1660 "locked"));
1661 tp = tcp_close(tp);
1662 tcpstat.tcps_rcvafterclose++;
1663 rstreason = BANDLIM_UNLIMITED;
1664 goto dropwithreset;
1665 }
1666
1667 /*
1668 * If segment ends after window, drop trailing data
1669 * (and PUSH and FIN); if nothing left, just ACK.
1670 */
1671 todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd);
1672 if (todrop > 0) {
1673 tcpstat.tcps_rcvpackafterwin++;
1674 if (todrop >= tlen) {
1675 tcpstat.tcps_rcvbyteafterwin += tlen;
1676 /*
1677 * If a new connection request is received
1678 * while in TIME_WAIT, drop the old connection
1679 * and start over if the sequence numbers
1680 * are above the previous ones.
1681 */
1682 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
1683 if (thflags & TH_SYN &&
1684 tp->t_state == TCPS_TIME_WAIT &&
1685 SEQ_GT(th->th_seq, tp->rcv_nxt)) {
1686 KASSERT(headlocked, ("trimthenstep6: "
1687 "tcp_close.4: head not locked"));
1688 tp = tcp_close(tp);
1689 goto findpcb;
1690 }
1691 /*
1692 * If window is closed can only take segments at
1693 * window edge, and have to drop data and PUSH from
1694 * incoming segments. Continue processing, but
1695 * remember to ack. Otherwise, drop segment
1696 * and ack.
1697 */
1698 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
1699 tp->t_flags |= TF_ACKNOW;
1700 tcpstat.tcps_rcvwinprobe++;
1701 } else
1702 goto dropafterack;
1703 } else
1704 tcpstat.tcps_rcvbyteafterwin += todrop;
1705 m_adj(m, -todrop);
1706 tlen -= todrop;
1707 thflags &= ~(TH_PUSH|TH_FIN);
1708 }
1709
1710 /*
1711 * If last ACK falls within this segment's sequence numbers,
1712 * record its timestamp.
1713 * NOTE:
1714 * 1) That the test incorporates suggestions from the latest
1715 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1716 * 2) That updating only on newer timestamps interferes with
1717 * our earlier PAWS tests, so this check should be solely
1718 * predicated on the sequence space of this segment.
1719 * 3) That we modify the segment boundary check to be
1720 * Last.ACK.Sent <= SEG.SEQ + SEG.Len
1721 * instead of RFC1323's
1722 * Last.ACK.Sent < SEG.SEQ + SEG.Len,
1723 * This modified check allows us to overcome RFC1323's
1724 * limitations as described in Stevens TCP/IP Illustrated
1725 * Vol. 2 p.869. In such cases, we can still calculate the
1726 * RTT correctly when RCV.NXT == Last.ACK.Sent.
1727 */
1728 if ((to.to_flags & TOF_TS) != 0 &&
1729 SEQ_LEQ(th->th_seq, tp->last_ack_sent) &&
1730 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen +
1731 ((thflags & (TH_SYN|TH_FIN)) != 0))) {
1732 tp->ts_recent_age = ticks;
1733 tp->ts_recent = to.to_tsval;
1734 }
1735
1736 /*
1737 * If a SYN is in the window, then this is an
1738 * error and we send an RST and drop the connection.
1739 */
1740 if (thflags & TH_SYN) {
1741 KASSERT(headlocked, ("tcp_input: tcp_drop: trimthenstep6: "
1742 "head not locked"));
1743 tp = tcp_drop(tp, ECONNRESET);
1744 rstreason = BANDLIM_UNLIMITED;
1745 goto drop;
1746 }
1747
1748 /*
1749 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN
1750 * flag is on (half-synchronized state), then queue data for
1751 * later processing; else drop segment and return.
1752 */
1753 if ((thflags & TH_ACK) == 0) {
1754 if (tp->t_state == TCPS_SYN_RECEIVED ||
1755 (tp->t_flags & TF_NEEDSYN))
1756 goto step6;
1757 else
1758 goto drop;
1759 }
1760
1761 /*
1762 * Ack processing.
1763 */
1764 switch (tp->t_state) {
1765
1766 /*
1767 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter
1768 * ESTABLISHED state and continue processing.
1769 * The ACK was checked above.
1770 */
1771 case TCPS_SYN_RECEIVED:
1772
1773 tcpstat.tcps_connects++;
1774 soisconnected(so);
1775 /* Do window scaling? */
1776 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
1777 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
1778 tp->snd_scale = tp->requested_s_scale;
1779 tp->rcv_scale = tp->request_r_scale;
1780 }
1781 /*
1782 * Make transitions:
1783 * SYN-RECEIVED -> ESTABLISHED
1784 * SYN-RECEIVED* -> FIN-WAIT-1
1785 */
1786 tp->t_starttime = ticks;
1787 if (tp->t_flags & TF_NEEDFIN) {
1788 tp->t_state = TCPS_FIN_WAIT_1;
1789 tp->t_flags &= ~TF_NEEDFIN;
1790 } else {
1791 tp->t_state = TCPS_ESTABLISHED;
1792 callout_reset(tp->tt_keep, tcp_keepidle,
1793 tcp_timer_keep, tp);
1794 }
1795 /*
1796 * If segment contains data or ACK, will call tcp_reass()
1797 * later; if not, do so now to pass queued data to user.
1798 */
1799 if (tlen == 0 && (thflags & TH_FIN) == 0)
1800 (void) tcp_reass(tp, (struct tcphdr *)0, 0,
1801 (struct mbuf *)0);
1802 tp->snd_wl1 = th->th_seq - 1;
1803 /* FALLTHROUGH */
1804
1805 /*
1806 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
1807 * ACKs. If the ack is in the range
1808 * tp->snd_una < th->th_ack <= tp->snd_max
1809 * then advance tp->snd_una to th->th_ack and drop
1810 * data from the retransmission queue. If this ACK reflects
1811 * more up to date window information we update our window information.
1812 */
1813 case TCPS_ESTABLISHED:
1814 case TCPS_FIN_WAIT_1:
1815 case TCPS_FIN_WAIT_2:
1816 case TCPS_CLOSE_WAIT:
1817 case TCPS_CLOSING:
1818 case TCPS_LAST_ACK:
1819 case TCPS_TIME_WAIT:
1820 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
1821 if (SEQ_GT(th->th_ack, tp->snd_max)) {
1822 tcpstat.tcps_rcvacktoomuch++;
1823 goto dropafterack;
1824 }
1825 if (tp->sack_enable)
1826 tcp_sack_doack(tp, &to, th->th_ack);
1827 if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
1828 if (tlen == 0 && tiwin == tp->snd_wnd) {
1829 tcpstat.tcps_rcvdupack++;
1830 /*
1831 * If we have outstanding data (other than
1832 * a window probe), this is a completely
1833 * duplicate ack (ie, window info didn't
1834 * change), the ack is the biggest we've
1835 * seen and we've seen exactly our rexmt
1836 * threshhold of them, assume a packet
1837 * has been dropped and retransmit it.
1838 * Kludge snd_nxt & the congestion
1839 * window so we send only this one
1840 * packet.
1841 *
1842 * We know we're losing at the current
1843 * window size so do congestion avoidance
1844 * (set ssthresh to half the current window
1845 * and pull our congestion window back to
1846 * the new ssthresh).
1847 *
1848 * Dup acks mean that packets have left the
1849 * network (they're now cached at the receiver)
1850 * so bump cwnd by the amount in the receiver
1851 * to keep a constant cwnd packets in the
1852 * network.
1853 */
1854 if (!callout_active(tp->tt_rexmt) ||
1855 th->th_ack != tp->snd_una)
1856 tp->t_dupacks = 0;
1857 else if (++tp->t_dupacks > tcprexmtthresh ||
1858 ((tcp_do_newreno || tp->sack_enable) &&
1859 IN_FASTRECOVERY(tp))) {
1860 if (tp->sack_enable && IN_FASTRECOVERY(tp)) {
1861 int awnd;
1862
1863 /*
1864 * Compute the amount of data in flight first.
1865 * We can inject new data into the pipe iff
1866 * we have less than 1/2 the original window's
1867 * worth of data in flight.
1868 */
1869 awnd = (tp->snd_nxt - tp->snd_fack) +
1870 tp->sackhint.sack_bytes_rexmit;
1871 if (awnd < tp->snd_ssthresh) {
1872 tp->snd_cwnd += tp->t_maxseg;
1873 if (tp->snd_cwnd > tp->snd_ssthresh)
1874 tp->snd_cwnd = tp->snd_ssthresh;
1875 }
1876 } else
1877 tp->snd_cwnd += tp->t_maxseg;
1878 (void) tcp_output(tp);
1879 goto drop;
1880 } else if (tp->t_dupacks == tcprexmtthresh) {
1881 tcp_seq onxt = tp->snd_nxt;
1882 u_int win;
1883
1884 /*
1885 * If we're doing sack, check to
1886 * see if we're already in sack
1887 * recovery. If we're not doing sack,
1888 * check to see if we're in newreno
1889 * recovery.
1890 */
1891 if (tp->sack_enable) {
1892 if (IN_FASTRECOVERY(tp)) {
1893 tp->t_dupacks = 0;
1894 break;
1895 }
1896 } else if (tcp_do_newreno) {
1897 if (SEQ_LEQ(th->th_ack,
1898 tp->snd_recover)) {
1899 tp->t_dupacks = 0;
1900 break;
1901 }
1902 }
1903 win = min(tp->snd_wnd, tp->snd_cwnd) /
1904 2 / tp->t_maxseg;
1905 if (win < 2)
1906 win = 2;
1907 tp->snd_ssthresh = win * tp->t_maxseg;
1908 ENTER_FASTRECOVERY(tp);
1909 tp->snd_recover = tp->snd_max;
1910 callout_stop(tp->tt_rexmt);
1911 tp->t_rtttime = 0;
1912 if (tp->sack_enable) {
1913 KASSERT(tp->sackhint.
1914 sack_bytes_rexmit == 0,
1915 ("sackhint rexmit == 0"));
1916 tcpstat.tcps_sack_recovery_episode++;
1917 tp->sack_newdata = tp->snd_nxt;
1918 tp->snd_cwnd = tp->t_maxseg;
1919 (void) tcp_output(tp);
1920 goto drop;
1921 }
1922 tp->snd_nxt = th->th_ack;
1923 tp->snd_cwnd = tp->t_maxseg;
1924 (void) tcp_output(tp);
1925 KASSERT(tp->snd_limited <= 2,
1926 ("tp->snd_limited too big"));
1927 tp->snd_cwnd = tp->snd_ssthresh +
1928 tp->t_maxseg *
1929 (tp->t_dupacks - tp->snd_limited);
1930 if (SEQ_GT(onxt, tp->snd_nxt))
1931 tp->snd_nxt = onxt;
1932 goto drop;
1933 } else if (tcp_do_rfc3042) {
1934 u_long oldcwnd = tp->snd_cwnd;
1935 tcp_seq oldsndmax = tp->snd_max;
1936 u_int sent;
1937
1938 KASSERT(tp->t_dupacks == 1 ||
1939 tp->t_dupacks == 2,
1940 ("dupacks not 1 or 2"));
1941 if (tp->t_dupacks == 1)
1942 tp->snd_limited = 0;
1943 tp->snd_cwnd =
1944 (tp->snd_nxt - tp->snd_una) +
1945 (tp->t_dupacks - tp->snd_limited) *
1946 tp->t_maxseg;
1947 (void) tcp_output(tp);
1948 sent = tp->snd_max - oldsndmax;
1949 if (sent > tp->t_maxseg) {
1950 KASSERT((tp->t_dupacks == 2 &&
1951 tp->snd_limited == 0) ||
1952 (sent == tp->t_maxseg + 1 &&
1953 tp->t_flags & TF_SENTFIN),
1954 ("sent too much"));
1955 tp->snd_limited = 2;
1956 } else if (sent > 0)
1957 ++tp->snd_limited;
1958 tp->snd_cwnd = oldcwnd;
1959 goto drop;
1960 }
1961 } else
1962 tp->t_dupacks = 0;
1963 break;
1964 }
1965
1966 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una"));
1967
1968 /*
1969 * If the congestion window was inflated to account
1970 * for the other side's cached packets, retract it.
1971 */
1972 if (tcp_do_newreno || tp->sack_enable) {
1973 if (IN_FASTRECOVERY(tp)) {
1974 if (SEQ_LT(th->th_ack, tp->snd_recover)) {
1975 if (tp->sack_enable)
1976 tcp_sack_partialack(tp, th);
1977 else
1978 tcp_newreno_partial_ack(tp, th);
1979 } else {
1980 /*
1981 * Out of fast recovery.
1982 * Window inflation should have left us
1983 * with approximately snd_ssthresh
1984 * outstanding data.
1985 * But in case we would be inclined to
1986 * send a burst, better to do it via
1987 * the slow start mechanism.
1988 */
1989 if (SEQ_GT(th->th_ack +
1990 tp->snd_ssthresh,
1991 tp->snd_max))
1992 tp->snd_cwnd = tp->snd_max -
1993 th->th_ack +
1994 tp->t_maxseg;
1995 else
1996 tp->snd_cwnd = tp->snd_ssthresh;
1997 }
1998 }
1999 } else {
2000 if (tp->t_dupacks >= tcprexmtthresh &&
2001 tp->snd_cwnd > tp->snd_ssthresh)
2002 tp->snd_cwnd = tp->snd_ssthresh;
2003 }
2004 tp->t_dupacks = 0;
2005 /*
2006 * If we reach this point, ACK is not a duplicate,
2007 * i.e., it ACKs something we sent.
2008 */
2009 if (tp->t_flags & TF_NEEDSYN) {
2010 /*
2011 * T/TCP: Connection was half-synchronized, and our
2012 * SYN has been ACK'd (so connection is now fully
2013 * synchronized). Go to non-starred state,
2014 * increment snd_una for ACK of SYN, and check if
2015 * we can do window scaling.
2016 */
2017 tp->t_flags &= ~TF_NEEDSYN;
2018 tp->snd_una++;
2019 /* Do window scaling? */
2020 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
2021 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
2022 tp->snd_scale = tp->requested_s_scale;
2023 tp->rcv_scale = tp->request_r_scale;
2024 }
2025 }
2026
2027process_ACK:
2028 KASSERT(headlocked, ("tcp_input: process_ACK: head not "
2029 "locked"));
2030 INP_LOCK_ASSERT(inp);
2031
2032 acked = th->th_ack - tp->snd_una;
2033 tcpstat.tcps_rcvackpack++;
2034 tcpstat.tcps_rcvackbyte += acked;
2035
2036 /*
2037 * If we just performed our first retransmit, and the ACK
2038 * arrives within our recovery window, then it was a mistake
2039 * to do the retransmit in the first place. Recover our
2040 * original cwnd and ssthresh, and proceed to transmit where
2041 * we left off.
2042 */
2043 if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) {
2044 ++tcpstat.tcps_sndrexmitbad;
2045 tp->snd_cwnd = tp->snd_cwnd_prev;
2046 tp->snd_ssthresh = tp->snd_ssthresh_prev;
2047 tp->snd_recover = tp->snd_recover_prev;
2048 if (tp->t_flags & TF_WASFRECOVERY)
2049 ENTER_FASTRECOVERY(tp);
2050 tp->snd_nxt = tp->snd_max;
2051 tp->t_badrxtwin = 0; /* XXX probably not required */
2052 }
2053
2054 /*
2055 * If we have a timestamp reply, update smoothed
2056 * round trip time. If no timestamp is present but
2057 * transmit timer is running and timed sequence
2058 * number was acked, update smoothed round trip time.
2059 * Since we now have an rtt measurement, cancel the
2060 * timer backoff (cf., Phil Karn's retransmit alg.).
2061 * Recompute the initial retransmit timer.
2062 *
2063 * Some boxes send broken timestamp replies
2064 * during the SYN+ACK phase, ignore
2065 * timestamps of 0 or we could calculate a
2066 * huge RTT and blow up the retransmit timer.
2067 */
2068 if ((to.to_flags & TOF_TS) != 0 &&
2069 to.to_tsecr) {
2070 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1);
2071 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) {
2072 tcp_xmit_timer(tp, ticks - tp->t_rtttime);
2073 }
2074 tcp_xmit_bandwidth_limit(tp, th->th_ack);
2075
2076 /*
2077 * If all outstanding data is acked, stop retransmit
2078 * timer and remember to restart (more output or persist).
2079 * If there is more data to be acked, restart retransmit
2080 * timer, using current (possibly backed-off) value.
2081 */
2082 if (th->th_ack == tp->snd_max) {
2083 callout_stop(tp->tt_rexmt);
2084 needoutput = 1;
2085 } else if (!callout_active(tp->tt_persist))
2086 callout_reset(tp->tt_rexmt, tp->t_rxtcur,
2087 tcp_timer_rexmt, tp);
2088
2089 /*
2090 * If no data (only SYN) was ACK'd,
2091 * skip rest of ACK processing.
2092 */
2093 if (acked == 0)
2094 goto step6;
2095
2096 /*
2097 * When new data is acked, open the congestion window.
2098 * If the window gives us less than ssthresh packets
2099 * in flight, open exponentially (maxseg per packet).
2100 * Otherwise open linearly: maxseg per window
2101 * (maxseg^2 / cwnd per packet).
2102 */
2103 if ((!tcp_do_newreno && !tp->sack_enable) ||
2104 !IN_FASTRECOVERY(tp)) {
2105 register u_int cw = tp->snd_cwnd;
2106 register u_int incr = tp->t_maxseg;
2107 if (cw > tp->snd_ssthresh)
2108 incr = incr * incr / cw;
2109 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale);
2110 }
2111 SOCKBUF_LOCK(&so->so_snd);
2112 if (acked > so->so_snd.sb_cc) {
2113 tp->snd_wnd -= so->so_snd.sb_cc;
2114 sbdrop_locked(&so->so_snd, (int)so->so_snd.sb_cc);
2115 ourfinisacked = 1;
2116 } else {
2117 sbdrop_locked(&so->so_snd, acked);
2118 tp->snd_wnd -= acked;
2119 ourfinisacked = 0;
2120 }
2121 sowwakeup_locked(so);
2122 /* detect una wraparound */
2123 if ((tcp_do_newreno || tp->sack_enable) &&
2124 !IN_FASTRECOVERY(tp) &&
2125 SEQ_GT(tp->snd_una, tp->snd_recover) &&
2126 SEQ_LEQ(th->th_ack, tp->snd_recover))
2127 tp->snd_recover = th->th_ack - 1;
2128 if ((tcp_do_newreno || tp->sack_enable) &&
2129 IN_FASTRECOVERY(tp) &&
2130 SEQ_GEQ(th->th_ack, tp->snd_recover))
2131 EXIT_FASTRECOVERY(tp);
2132 tp->snd_una = th->th_ack;
2133 if (tp->sack_enable) {
2134 if (SEQ_GT(tp->snd_una, tp->snd_recover))
2135 tp->snd_recover = tp->snd_una;
2136 }
2137 if (SEQ_LT(tp->snd_nxt, tp->snd_una))
2138 tp->snd_nxt = tp->snd_una;
2139
2140 switch (tp->t_state) {
2141
2142 /*
2143 * In FIN_WAIT_1 STATE in addition to the processing
2144 * for the ESTABLISHED state if our FIN is now acknowledged
2145 * then enter FIN_WAIT_2.
2146 */
2147 case TCPS_FIN_WAIT_1:
2148 if (ourfinisacked) {
2149 /*
2150 * If we can't receive any more
2151 * data, then closing user can proceed.
2152 * Starting the timer is contrary to the
2153 * specification, but if we don't get a FIN
2154 * we'll hang forever.
2155 */
2156 /* XXXjl
2157 * we should release the tp also, and use a
2158 * compressed state.
2159 */
2160 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
2161 soisdisconnected(so);
2162 callout_reset(tp->tt_2msl, tcp_maxidle,
2163 tcp_timer_2msl, tp);
2164 }
2165 tp->t_state = TCPS_FIN_WAIT_2;
2166 }
2167 break;
2168
2169 /*
2170 * In CLOSING STATE in addition to the processing for
2171 * the ESTABLISHED state if the ACK acknowledges our FIN
2172 * then enter the TIME-WAIT state, otherwise ignore
2173 * the segment.
2174 */
2175 case TCPS_CLOSING:
2176 if (ourfinisacked) {
2177 KASSERT(headlocked, ("tcp_input: process_ACK: "
2178 "head not locked"));
2179 tcp_twstart(tp);
2180 INP_INFO_WUNLOCK(&tcbinfo);
2181 m_freem(m);
2182 return;
2183 }
2184 break;
2185
2186 /*
2187 * In LAST_ACK, we may still be waiting for data to drain
2188 * and/or to be acked, as well as for the ack of our FIN.
2189 * If our FIN is now acknowledged, delete the TCB,
2190 * enter the closed state and return.
2191 */
2192 case TCPS_LAST_ACK:
2193 if (ourfinisacked) {
2194 KASSERT(headlocked, ("tcp_input: process_ACK:"
2195 " tcp_close: head not locked"));
2196 tp = tcp_close(tp);
2197 goto drop;
2198 }
2199 break;
2200
2201 /*
2202 * In TIME_WAIT state the only thing that should arrive
2203 * is a retransmission of the remote FIN. Acknowledge
2204 * it and restart the finack timer.
2205 */
2206 case TCPS_TIME_WAIT:
2207 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
2208 callout_reset(tp->tt_2msl, 2 * tcp_msl,
2209 tcp_timer_2msl, tp);
2210 goto dropafterack;
2211 }
2212 }
2213
2214step6:
2215 KASSERT(headlocked, ("tcp_input: step6: head not locked"));
2216 INP_LOCK_ASSERT(inp);
2217
2218 /*
2219 * Update window information.
2220 * Don't look at window if no ACK: TAC's send garbage on first SYN.
2221 */
2222 if ((thflags & TH_ACK) &&
2223 (SEQ_LT(tp->snd_wl1, th->th_seq) ||
2224 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) ||
2225 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) {
2226 /* keep track of pure window updates */
2227 if (tlen == 0 &&
2228 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)
2229 tcpstat.tcps_rcvwinupd++;
2230 tp->snd_wnd = tiwin;
2231 tp->snd_wl1 = th->th_seq;
2232 tp->snd_wl2 = th->th_ack;
2233 if (tp->snd_wnd > tp->max_sndwnd)
2234 tp->max_sndwnd = tp->snd_wnd;
2235 needoutput = 1;
2236 }
2237
2238 /*
2239 * Process segments with URG.
2240 */
2241 if ((thflags & TH_URG) && th->th_urp &&
2242 TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2243 /*
2244 * This is a kludge, but if we receive and accept
2245 * random urgent pointers, we'll crash in
2246 * soreceive. It's hard to imagine someone
2247 * actually wanting to send this much urgent data.
2248 */
2249 SOCKBUF_LOCK(&so->so_rcv);
2250 if (th->th_urp + so->so_rcv.sb_cc > sb_max) {
2251 th->th_urp = 0; /* XXX */
2252 thflags &= ~TH_URG; /* XXX */
2253 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */
2254 goto dodata; /* XXX */
2255 }
2256 /*
2257 * If this segment advances the known urgent pointer,
2258 * then mark the data stream. This should not happen
2259 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
2260 * a FIN has been received from the remote side.
2261 * In these states we ignore the URG.
2262 *
2263 * According to RFC961 (Assigned Protocols),
2264 * the urgent pointer points to the last octet
2265 * of urgent data. We continue, however,
2266 * to consider it to indicate the first octet
2267 * of data past the urgent section as the original
2268 * spec states (in one of two places).
2269 */
2270 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) {
2271 tp->rcv_up = th->th_seq + th->th_urp;
2272 so->so_oobmark = so->so_rcv.sb_cc +
2273 (tp->rcv_up - tp->rcv_nxt) - 1;
2274 if (so->so_oobmark == 0)
2275 so->so_rcv.sb_state |= SBS_RCVATMARK;
2276 sohasoutofband(so);
2277 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
2278 }
2279 SOCKBUF_UNLOCK(&so->so_rcv);
2280 /*
2281 * Remove out of band data so doesn't get presented to user.
2282 * This can happen independent of advancing the URG pointer,
2283 * but if two URG's are pending at once, some out-of-band
2284 * data may creep in... ick.
2285 */
2286 if (th->th_urp <= (u_long)tlen &&
2287 !(so->so_options & SO_OOBINLINE)) {
2288 /* hdr drop is delayed */
2289 tcp_pulloutofband(so, th, m, drop_hdrlen);
2290 }
2291 } else {
2292 /*
2293 * If no out of band data is expected,
2294 * pull receive urgent pointer along
2295 * with the receive window.
2296 */
2297 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
2298 tp->rcv_up = tp->rcv_nxt;
2299 }
2300dodata: /* XXX */
2301 KASSERT(headlocked, ("tcp_input: dodata: head not locked"));
2302 INP_LOCK_ASSERT(inp);
2303
2304 /*
2305 * Process the segment text, merging it into the TCP sequencing queue,
2306 * and arranging for acknowledgment of receipt if necessary.
2307 * This process logically involves adjusting tp->rcv_wnd as data
2308 * is presented to the user (this happens in tcp_usrreq.c,
2309 * case PRU_RCVD). If a FIN has already been received on this
2310 * connection then we just ignore the text.
2311 */
2312 if ((tlen || (thflags & TH_FIN)) &&
2313 TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2314 m_adj(m, drop_hdrlen); /* delayed header drop */
2315 /*
2316 * Insert segment which includes th into TCP reassembly queue
2317 * with control block tp. Set thflags to whether reassembly now
2318 * includes a segment with FIN. This handles the common case
2319 * inline (segment is the next to be received on an established
2320 * connection, and the queue is empty), avoiding linkage into
2321 * and removal from the queue and repetition of various
2322 * conversions.
2323 * Set DELACK for segments received in order, but ack
2324 * immediately when segments are out of order (so
2325 * fast retransmit can work).
2326 */
2327 if (th->th_seq == tp->rcv_nxt &&
2328 LIST_EMPTY(&tp->t_segq) &&
2329 TCPS_HAVEESTABLISHED(tp->t_state)) {
2330 if (DELAY_ACK(tp))
2331 tp->t_flags |= TF_DELACK;
2332 else
2333 tp->t_flags |= TF_ACKNOW;
2334 tp->rcv_nxt += tlen;
2335 thflags = th->th_flags & TH_FIN;
2336 tcpstat.tcps_rcvpack++;
2337 tcpstat.tcps_rcvbyte += tlen;
2338 ND6_HINT(tp);
2339 SOCKBUF_LOCK(&so->so_rcv);
2340 if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
2341 m_freem(m);
2342 else
2343 sbappendstream_locked(&so->so_rcv, m);
2344 sorwakeup_locked(so);
2345 } else {
2346 thflags = tcp_reass(tp, th, &tlen, m);
2347 tp->t_flags |= TF_ACKNOW;
2348 }
2349 if (tlen > 0 && tp->sack_enable)
2350 tcp_update_sack_list(tp, th->th_seq, th->th_seq + tlen);
2351 /*
2352 * Note the amount of data that peer has sent into
2353 * our window, in order to estimate the sender's
2354 * buffer size.
2355 */
2356 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
2357 } else {
2358 m_freem(m);
2359 thflags &= ~TH_FIN;
2360 }
2361
2362 /*
2363 * If FIN is received ACK the FIN and let the user know
2364 * that the connection is closing.
2365 */
2366 if (thflags & TH_FIN) {
2367 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2368 socantrcvmore(so);
2369 /*
2370 * If connection is half-synchronized
2371 * (ie NEEDSYN flag on) then delay ACK,
2372 * so it may be piggybacked when SYN is sent.
2373 * Otherwise, since we received a FIN then no
2374 * more input can be expected, send ACK now.
2375 */
2376 if (tp->t_flags & TF_NEEDSYN)
2377 tp->t_flags |= TF_DELACK;
2378 else
2379 tp->t_flags |= TF_ACKNOW;
2380 tp->rcv_nxt++;
2381 }
2382 switch (tp->t_state) {
2383
2384 /*
2385 * In SYN_RECEIVED and ESTABLISHED STATES
2386 * enter the CLOSE_WAIT state.
2387 */
2388 case TCPS_SYN_RECEIVED:
2389 tp->t_starttime = ticks;
2390 /*FALLTHROUGH*/
2391 case TCPS_ESTABLISHED:
2392 tp->t_state = TCPS_CLOSE_WAIT;
2393 break;
2394
2395 /*
2396 * If still in FIN_WAIT_1 STATE FIN has not been acked so
2397 * enter the CLOSING state.
2398 */
2399 case TCPS_FIN_WAIT_1:
2400 tp->t_state = TCPS_CLOSING;
2401 break;
2402
2403 /*
2404 * In FIN_WAIT_2 state enter the TIME_WAIT state,
2405 * starting the time-wait timer, turning off the other
2406 * standard timers.
2407 */
2408 case TCPS_FIN_WAIT_2:
2409 KASSERT(headlocked == 1, ("tcp_input: dodata: "
2410 "TCP_FIN_WAIT_2: head not locked"));
2411 tcp_twstart(tp);
2412 INP_INFO_WUNLOCK(&tcbinfo);
2413 return;
2414
2415 /*
2416 * In TIME_WAIT state restart the 2 MSL time_wait timer.
2417 */
2418 case TCPS_TIME_WAIT:
2419 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
2420 callout_reset(tp->tt_2msl, 2 * tcp_msl,
2421 tcp_timer_2msl, tp);
2422 break;
2423 }
2424 }
2425 INP_INFO_WUNLOCK(&tcbinfo);
2426 headlocked = 0;
2427#ifdef TCPDEBUG
2428 if (so->so_options & SO_DEBUG)
2429 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen,
2430 &tcp_savetcp, 0);
2431#endif
2432
2433 /*
2434 * Return any desired output.
2435 */
2436 if (needoutput || (tp->t_flags & TF_ACKNOW))
2437 (void) tcp_output(tp);
2438
2439check_delack:
2440 KASSERT(headlocked == 0, ("tcp_input: check_delack: head locked"));
2441 INP_LOCK_ASSERT(inp);
2442 if (tp->t_flags & TF_DELACK) {
2443 tp->t_flags &= ~TF_DELACK;
2444 callout_reset(tp->tt_delack, tcp_delacktime,
2445 tcp_timer_delack, tp);
2446 }
2447 INP_UNLOCK(inp);
2448 return;
2449
2450dropafterack:
2451 KASSERT(headlocked, ("tcp_input: dropafterack: head not locked"));
2452 /*
2453 * Generate an ACK dropping incoming segment if it occupies
2454 * sequence space, where the ACK reflects our state.
2455 *
2456 * We can now skip the test for the RST flag since all
2457 * paths to this code happen after packets containing
2458 * RST have been dropped.
2459 *
2460 * In the SYN-RECEIVED state, don't send an ACK unless the
2461 * segment we received passes the SYN-RECEIVED ACK test.
2462 * If it fails send a RST. This breaks the loop in the
2463 * "LAND" DoS attack, and also prevents an ACK storm
2464 * between two listening ports that have been sent forged
2465 * SYN segments, each with the source address of the other.
2466 */
2467 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
2468 (SEQ_GT(tp->snd_una, th->th_ack) ||
2469 SEQ_GT(th->th_ack, tp->snd_max)) ) {
2470 rstreason = BANDLIM_RST_OPENPORT;
2471 goto dropwithreset;
2472 }
2473#ifdef TCPDEBUG
2474 if (so->so_options & SO_DEBUG)
2475 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
2476 &tcp_savetcp, 0);
2477#endif
2478 KASSERT(headlocked, ("headlocked should be 1"));
2479 INP_INFO_WUNLOCK(&tcbinfo);
2480 tp->t_flags |= TF_ACKNOW;
2481 (void) tcp_output(tp);
2482 INP_UNLOCK(inp);
2483 m_freem(m);
2484 return;
2485
2486dropwithreset:
2487 KASSERT(headlocked, ("tcp_input: dropwithreset: head not locked"));
2488 /*
2489 * Generate a RST, dropping incoming segment.
2490 * Make ACK acceptable to originator of segment.
2491 * Don't bother to respond if destination was broadcast/multicast.
2492 */
2493 if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST))
2494 goto drop;
2495 if (isipv6) {
2496 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
2497 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
2498 goto drop;
2499 } else {
2500 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
2501 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
2502 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
2503 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
2504 goto drop;
2505 }
2506 /* IPv6 anycast check is done at tcp6_input() */
2507
2508 /*
2509 * Perform bandwidth limiting.
2510 */
2511 if (badport_bandlim(rstreason) < 0)
2512 goto drop;
2513
2514#ifdef TCPDEBUG
2515 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
2516 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
2517 &tcp_savetcp, 0);
2518#endif
2519
2520 if (thflags & TH_ACK)
2521 /* mtod() below is safe as long as hdr dropping is delayed */
2522 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack,
2523 TH_RST);
2524 else {
2525 if (thflags & TH_SYN)
2526 tlen++;
2527 /* mtod() below is safe as long as hdr dropping is delayed */
2528 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen,
2529 (tcp_seq)0, TH_RST|TH_ACK);
2530 }
2531
2532 if (tp)
2533 INP_UNLOCK(inp);
2534 if (headlocked)
2535 INP_INFO_WUNLOCK(&tcbinfo);
2536 return;
2537
2538drop:
2539 /*
2540 * Drop space held by incoming segment and return.
2541 */
2542#ifdef TCPDEBUG
2543 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
2544 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
2545 &tcp_savetcp, 0);
2546#endif
2547 if (tp)
2548 INP_UNLOCK(inp);
2549 if (headlocked)
2550 INP_INFO_WUNLOCK(&tcbinfo);
2551 m_freem(m);
2552 return;
2553}
2554
2555/*
2556 * Parse TCP options and place in tcpopt.
2557 */
2558static void
2559tcp_dooptions(to, cp, cnt, is_syn)
2560 struct tcpopt *to;
2561 u_char *cp;
2562 int cnt;
2563 int is_syn;
2564{
2565 int opt, optlen;
2566
2567 to->to_flags = 0;
2568 for (; cnt > 0; cnt -= optlen, cp += optlen) {
2569 opt = cp[0];
2570 if (opt == TCPOPT_EOL)
2571 break;
2572 if (opt == TCPOPT_NOP)
2573 optlen = 1;
2574 else {
2575 if (cnt < 2)
2576 break;
2577 optlen = cp[1];
2578 if (optlen < 2 || optlen > cnt)
2579 break;
2580 }
2581 switch (opt) {
2582 case TCPOPT_MAXSEG:
2583 if (optlen != TCPOLEN_MAXSEG)
2584 continue;
2585 if (!is_syn)
2586 continue;
2587 to->to_flags |= TOF_MSS;
2588 bcopy((char *)cp + 2,
2589 (char *)&to->to_mss, sizeof(to->to_mss));
2590 to->to_mss = ntohs(to->to_mss);
2591 break;
2592 case TCPOPT_WINDOW:
2593 if (optlen != TCPOLEN_WINDOW)
2594 continue;
2595 if (! is_syn)
2596 continue;
2597 to->to_flags |= TOF_SCALE;
2598 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT);
2599 break;
2600 case TCPOPT_TIMESTAMP:
2601 if (optlen != TCPOLEN_TIMESTAMP)
2602 continue;
2603 to->to_flags |= TOF_TS;
2604 bcopy((char *)cp + 2,
2605 (char *)&to->to_tsval, sizeof(to->to_tsval));
2606 to->to_tsval = ntohl(to->to_tsval);
2607 bcopy((char *)cp + 6,
2608 (char *)&to->to_tsecr, sizeof(to->to_tsecr));
2609 to->to_tsecr = ntohl(to->to_tsecr);
2610 /*
2611 * If echoed timestamp is later than the current time,
2612 * fall back to non RFC1323 RTT calculation.
2613 */
2614 if ((to->to_tsecr != 0) && TSTMP_GT(to->to_tsecr, ticks))
2615 to->to_tsecr = 0;
2616 break;
2617#ifdef TCP_SIGNATURE
2618 /*
2619 * XXX In order to reply to a host which has set the
2620 * TCP_SIGNATURE option in its initial SYN, we have to
2621 * record the fact that the option was observed here
2622 * for the syncache code to perform the correct response.
2623 */
2624 case TCPOPT_SIGNATURE:
2625 if (optlen != TCPOLEN_SIGNATURE)
2626 continue;
2627 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN);
2628 break;
2629#endif
2630 case TCPOPT_SACK_PERMITTED:
2631 if (!tcp_do_sack ||
2632 optlen != TCPOLEN_SACK_PERMITTED)
2633 continue;
2634 if (is_syn) {
2635 /* MUST only be set on SYN */
2636 to->to_flags |= TOF_SACK;
2637 }
2638 break;
2639 case TCPOPT_SACK:
2640 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0)
2641 continue;
2642 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK;
2643 to->to_sacks = cp + 2;
2644 tcpstat.tcps_sack_rcv_blocks++;
2645 break;
2646 default:
2647 continue;
2648 }
2649 }
2650}
2651
2652/*
2653 * Pull out of band byte out of a segment so
2654 * it doesn't appear in the user's data queue.
2655 * It is still reflected in the segment length for
2656 * sequencing purposes.
2657 */
2658static void
2659tcp_pulloutofband(so, th, m, off)
2660 struct socket *so;
2661 struct tcphdr *th;
2662 register struct mbuf *m;
2663 int off; /* delayed to be droped hdrlen */
2664{
2665 int cnt = off + th->th_urp - 1;
2666
2667 while (cnt >= 0) {
2668 if (m->m_len > cnt) {
2669 char *cp = mtod(m, caddr_t) + cnt;
2670 struct tcpcb *tp = sototcpcb(so);
2671
2672 tp->t_iobc = *cp;
2673 tp->t_oobflags |= TCPOOB_HAVEDATA;
2674 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1));
2675 m->m_len--;
2676 if (m->m_flags & M_PKTHDR)
2677 m->m_pkthdr.len--;
2678 return;
2679 }
2680 cnt -= m->m_len;
2681 m = m->m_next;
2682 if (m == 0)
2683 break;
2684 }
2685 panic("tcp_pulloutofband");
2686}
2687
2688/*
2689 * Collect new round-trip time estimate
2690 * and update averages and current timeout.
2691 */
2692static void
2693tcp_xmit_timer(tp, rtt)
2694 register struct tcpcb *tp;
2695 int rtt;
2696{
2697 register int delta;
2698
2699 INP_LOCK_ASSERT(tp->t_inpcb);
2700
2701 tcpstat.tcps_rttupdated++;
2702 tp->t_rttupdated++;
2703 if (tp->t_srtt != 0) {
2704 /*
2705 * srtt is stored as fixed point with 5 bits after the
2706 * binary point (i.e., scaled by 8). The following magic
2707 * is equivalent to the smoothing algorithm in rfc793 with
2708 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
2709 * point). Adjust rtt to origin 0.
2710 */
2711 delta = ((rtt - 1) << TCP_DELTA_SHIFT)
2712 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
2713
2714 if ((tp->t_srtt += delta) <= 0)
2715 tp->t_srtt = 1;
2716
2717 /*
2718 * We accumulate a smoothed rtt variance (actually, a
2719 * smoothed mean difference), then set the retransmit
2720 * timer to smoothed rtt + 4 times the smoothed variance.
2721 * rttvar is stored as fixed point with 4 bits after the
2722 * binary point (scaled by 16). The following is
2723 * equivalent to rfc793 smoothing with an alpha of .75
2724 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces
2725 * rfc793's wired-in beta.
2726 */
2727 if (delta < 0)
2728 delta = -delta;
2729 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
2730 if ((tp->t_rttvar += delta) <= 0)
2731 tp->t_rttvar = 1;
2732 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
2733 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2734 } else {
2735 /*
2736 * No rtt measurement yet - use the unsmoothed rtt.
2737 * Set the variance to half the rtt (so our first
2738 * retransmit happens at 3*rtt).
2739 */
2740 tp->t_srtt = rtt << TCP_RTT_SHIFT;
2741 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
2742 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2743 }
2744 tp->t_rtttime = 0;
2745 tp->t_rxtshift = 0;
2746
2747 /*
2748 * the retransmit should happen at rtt + 4 * rttvar.
2749 * Because of the way we do the smoothing, srtt and rttvar
2750 * will each average +1/2 tick of bias. When we compute
2751 * the retransmit timer, we want 1/2 tick of rounding and
2752 * 1 extra tick because of +-1/2 tick uncertainty in the
2753 * firing of the timer. The bias will give us exactly the
2754 * 1.5 tick we need. But, because the bias is
2755 * statistical, we have to test that we don't drop below
2756 * the minimum feasible timer (which is 2 ticks).
2757 */
2758 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
2759 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);
2760
2761 /*
2762 * We received an ack for a packet that wasn't retransmitted;
2763 * it is probably safe to discard any error indications we've
2764 * received recently. This isn't quite right, but close enough
2765 * for now (a route might have failed after we sent a segment,
2766 * and the return path might not be symmetrical).
2767 */
2768 tp->t_softerror = 0;
2769}
2770
2771/*
2772 * Determine a reasonable value for maxseg size.
2773 * If the route is known, check route for mtu.
2774 * If none, use an mss that can be handled on the outgoing
2775 * interface without forcing IP to fragment; if bigger than
2776 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES
2777 * to utilize large mbufs. If no route is found, route has no mtu,
2778 * or the destination isn't local, use a default, hopefully conservative
2779 * size (usually 512 or the default IP max size, but no more than the mtu
2780 * of the interface), as we can't discover anything about intervening
2781 * gateways or networks. We also initialize the congestion/slow start
2782 * window to be a single segment if the destination isn't local.
2783 * While looking at the routing entry, we also initialize other path-dependent
2784 * parameters from pre-set or cached values in the routing entry.
2785 *
2786 * Also take into account the space needed for options that we
2787 * send regularly. Make maxseg shorter by that amount to assure
2788 * that we can send maxseg amount of data even when the options
2789 * are present. Store the upper limit of the length of options plus
2790 * data in maxopd.
2791 *
2792 *
2793 * In case of T/TCP, we call this routine during implicit connection
2794 * setup as well (offer = -1), to initialize maxseg from the cached
2795 * MSS of our peer.
2796 *
2797 * NOTE that this routine is only called when we process an incoming
2798 * segment. Outgoing SYN/ACK MSS settings are handled in tcp_mssopt().
2799 */
2800void
2801tcp_mss(tp, offer)
2802 struct tcpcb *tp;
2803 int offer;
2804{
2805 int rtt, mss;
2806 u_long bufsize;
2807 u_long maxmtu;
2808 struct inpcb *inp = tp->t_inpcb;
2809 struct socket *so;
2810 struct hc_metrics_lite metrics;
2811 int origoffer = offer;
2812#ifdef INET6
2813 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0;
2814 size_t min_protoh = isipv6 ?
2815 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) :
2816 sizeof (struct tcpiphdr);
2817#else
2818 const size_t min_protoh = sizeof(struct tcpiphdr);
2819#endif
2820
2821 /* initialize */
2822#ifdef INET6
2823 if (isipv6) {
2824 maxmtu = tcp_maxmtu6(&inp->inp_inc);
2825 tp->t_maxopd = tp->t_maxseg = tcp_v6mssdflt;
2826 } else
2827#endif
2828 {
2829 maxmtu = tcp_maxmtu(&inp->inp_inc);
2830 tp->t_maxopd = tp->t_maxseg = tcp_mssdflt;
2831 }
2832 so = inp->inp_socket;
2833
2834 /*
2835 * no route to sender, stay with default mss and return
2836 */
2837 if (maxmtu == 0)
2838 return;
2839
2840 /* what have we got? */
2841 switch (offer) {
2842 case 0:
2843 /*
2844 * Offer == 0 means that there was no MSS on the SYN
2845 * segment, in this case we use tcp_mssdflt.
2846 */
2847 offer =
2848#ifdef INET6
2849 isipv6 ? tcp_v6mssdflt :
2850#endif
2851 tcp_mssdflt;
2852 break;
2853
2854 case -1:
2855 /*
2856 * Offer == -1 means that we didn't receive SYN yet.
2857 */
2858 /* FALLTHROUGH */
2859
2860 default:
2861 /*
2862 * Prevent DoS attack with too small MSS. Round up
2863 * to at least minmss.
2864 */
2865 offer = max(offer, tcp_minmss);
2866 /*
2867 * Sanity check: make sure that maxopd will be large
2868 * enough to allow some data on segments even if the
2869 * all the option space is used (40bytes). Otherwise
2870 * funny things may happen in tcp_output.
2871 */
2872 offer = max(offer, 64);
2873 }
2874
2875 /*
2876 * rmx information is now retrieved from tcp_hostcache
2877 */
2878 tcp_hc_get(&inp->inp_inc, &metrics);
2879
2880 /*
2881 * if there's a discovered mtu int tcp hostcache, use it
2882 * else, use the link mtu.
2883 */
2884 if (metrics.rmx_mtu)
2885 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh;
2886 else {
2887#ifdef INET6
2888 if (isipv6) {
2889 mss = maxmtu - min_protoh;
2890 if (!path_mtu_discovery &&
2891 !in6_localaddr(&inp->in6p_faddr))
2892 mss = min(mss, tcp_v6mssdflt);
2893 } else
2894#endif
2895 {
2896 mss = maxmtu - min_protoh;
2897 if (!path_mtu_discovery &&
2898 !in_localaddr(inp->inp_faddr))
2899 mss = min(mss, tcp_mssdflt);
2900 }
2901 }
2902 mss = min(mss, offer);
2903
2904 /*
2905 * maxopd stores the maximum length of data AND options
2906 * in a segment; maxseg is the amount of data in a normal
2907 * segment. We need to store this value (maxopd) apart
2908 * from maxseg, because now every segment carries options
2909 * and thus we normally have somewhat less data in segments.
2910 */
2911 tp->t_maxopd = mss;
2912
2913 /*
2914 * origoffer==-1 indicates, that no segments were received yet.
2915 * In this case we just guess.
2916 */
2917 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
2918 (origoffer == -1 ||
2919 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP))
2920 mss -= TCPOLEN_TSTAMP_APPA;
2921 tp->t_maxseg = mss;
2922
2923#if (MCLBYTES & (MCLBYTES - 1)) == 0
2924 if (mss > MCLBYTES)
2925 mss &= ~(MCLBYTES-1);
2926#else
2927 if (mss > MCLBYTES)
2928 mss = mss / MCLBYTES * MCLBYTES;
2929#endif
2930 tp->t_maxseg = mss;
2931
2932 /*
2933 * If there's a pipesize, change the socket buffer to that size,
2934 * don't change if sb_hiwat is different than default (then it
2935 * has been changed on purpose with setsockopt).
2936 * Make the socket buffers an integral number of mss units;
2937 * if the mss is larger than the socket buffer, decrease the mss.
2938 */
2939 SOCKBUF_LOCK(&so->so_snd);
2940 if ((so->so_snd.sb_hiwat == tcp_sendspace) && metrics.rmx_sendpipe)
2941 bufsize = metrics.rmx_sendpipe;
2942 else
2943 bufsize = so->so_snd.sb_hiwat;
2944 if (bufsize < mss)
2945 mss = bufsize;
2946 else {
2947 bufsize = roundup(bufsize, mss);
2948 if (bufsize > sb_max)
2949 bufsize = sb_max;
2950 if (bufsize > so->so_snd.sb_hiwat)
2951 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL);
2952 }
2953 SOCKBUF_UNLOCK(&so->so_snd);
2954 tp->t_maxseg = mss;
2955
2956 SOCKBUF_LOCK(&so->so_rcv);
2957 if ((so->so_rcv.sb_hiwat == tcp_recvspace) && metrics.rmx_recvpipe)
2958 bufsize = metrics.rmx_recvpipe;
2959 else
2960 bufsize = so->so_rcv.sb_hiwat;
2961 if (bufsize > mss) {
2962 bufsize = roundup(bufsize, mss);
2963 if (bufsize > sb_max)
2964 bufsize = sb_max;
2965 if (bufsize > so->so_rcv.sb_hiwat)
2966 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL);
2967 }
2968 SOCKBUF_UNLOCK(&so->so_rcv);
2969 /*
2970 * While we're here, check the others too
2971 */
2972 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) {
2973 tp->t_srtt = rtt;
2974 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE;
2975 tcpstat.tcps_usedrtt++;
2976 if (metrics.rmx_rttvar) {
2977 tp->t_rttvar = metrics.rmx_rttvar;
2978 tcpstat.tcps_usedrttvar++;
2979 } else {
2980 /* default variation is +- 1 rtt */
2981 tp->t_rttvar =
2982 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
2983 }
2984 TCPT_RANGESET(tp->t_rxtcur,
2985 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
2986 tp->t_rttmin, TCPTV_REXMTMAX);
2987 }
2988 if (metrics.rmx_ssthresh) {
2989 /*
2990 * There's some sort of gateway or interface
2991 * buffer limit on the path. Use this to set
2992 * the slow start threshhold, but set the
2993 * threshold to no less than 2*mss.
2994 */
2995 tp->snd_ssthresh = max(2 * mss, metrics.rmx_ssthresh);
2996 tcpstat.tcps_usedssthresh++;
2997 }
2998 if (metrics.rmx_bandwidth)
2999 tp->snd_bandwidth = metrics.rmx_bandwidth;
3000
3001 /*
3002 * Set the slow-start flight size depending on whether this
3003 * is a local network or not.
3004 *
3005 * Extend this so we cache the cwnd too and retrieve it here.
3006 * Make cwnd even bigger than RFC3390 suggests but only if we
3007 * have previous experience with the remote host. Be careful
3008 * not make cwnd bigger than remote receive window or our own
3009 * send socket buffer. Maybe put some additional upper bound
3010 * on the retrieved cwnd. Should do incremental updates to
3011 * hostcache when cwnd collapses so next connection doesn't
3012 * overloads the path again.
3013 *
3014 * RFC3390 says only do this if SYN or SYN/ACK didn't got lost.
3015 * We currently check only in syncache_socket for that.
3016 */
3017#define TCP_METRICS_CWND
3018#ifdef TCP_METRICS_CWND
3019 if (metrics.rmx_cwnd)
3020 tp->snd_cwnd = max(mss,
3021 min(metrics.rmx_cwnd / 2,
3022 min(tp->snd_wnd, so->so_snd.sb_hiwat)));
3023 else
3024#endif
3025 if (tcp_do_rfc3390)
3026 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380));
3027#ifdef INET6
3028 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) ||
3029 (!isipv6 && in_localaddr(inp->inp_faddr)))
3030#else
3031 else if (in_localaddr(inp->inp_faddr))
3032#endif
3033 tp->snd_cwnd = mss * ss_fltsz_local;
3034 else
3035 tp->snd_cwnd = mss * ss_fltsz;
3036}
3037
3038/*
3039 * Determine the MSS option to send on an outgoing SYN.
3040 */
3041int
3042tcp_mssopt(inc)
3043 struct in_conninfo *inc;
3044{
3045 int mss = 0;
3046 u_long maxmtu = 0;
3047 u_long thcmtu = 0;
3048 size_t min_protoh;
3049#ifdef INET6
3050 int isipv6 = inc->inc_isipv6 ? 1 : 0;
3051#endif
3052
3053 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer"));
3054
3055#ifdef INET6
3056 if (isipv6) {
3057 mss = tcp_v6mssdflt;
3058 maxmtu = tcp_maxmtu6(inc);
3059 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */
3060 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
3061 } else
3062#endif
3063 {
3064 mss = tcp_mssdflt;
3065 maxmtu = tcp_maxmtu(inc);
3066 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */
3067 min_protoh = sizeof(struct tcpiphdr);
3068 }
3069 if (maxmtu && thcmtu)
3070 mss = min(maxmtu, thcmtu) - min_protoh;
3071 else if (maxmtu || thcmtu)
3072 mss = max(maxmtu, thcmtu) - min_protoh;
3073
3074 return (mss);
3075}
3076
3077
3078/*
3079 * On a partial ack arrives, force the retransmission of the
3080 * next unacknowledged segment. Do not clear tp->t_dupacks.
3081 * By setting snd_nxt to ti_ack, this forces retransmission timer to
3082 * be started again.
3083 */
3084static void
3085tcp_newreno_partial_ack(tp, th)
3086 struct tcpcb *tp;
3087 struct tcphdr *th;
3088{
3089 tcp_seq onxt = tp->snd_nxt;
3090 u_long ocwnd = tp->snd_cwnd;
3091
3092 callout_stop(tp->tt_rexmt);
3093 tp->t_rtttime = 0;
3094 tp->snd_nxt = th->th_ack;
3095 /*
3096 * Set snd_cwnd to one segment beyond acknowledged offset.
3097 * (tp->snd_una has not yet been updated when this function is called.)
3098 */
3099 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una);
3100 tp->t_flags |= TF_ACKNOW;
3101 (void) tcp_output(tp);
3102 tp->snd_cwnd = ocwnd;
3103 if (SEQ_GT(onxt, tp->snd_nxt))
3104 tp->snd_nxt = onxt;
3105 /*
3106 * Partial window deflation. Relies on fact that tp->snd_una
3107 * not updated yet.
3108 */
3109 tp->snd_cwnd -= (th->th_ack - tp->snd_una - tp->t_maxseg);
3110}
3111
3112/*
3113 * Returns 1 if the TIME_WAIT state was killed and we should start over,
3114 * looking for a pcb in the listen state. Returns 0 otherwise.
3115 */
3116static int
3117tcp_timewait(tw, to, th, m, tlen)
3118 struct tcptw *tw;
3119 struct tcpopt *to;
3120 struct tcphdr *th;
3121 struct mbuf *m;
3122 int tlen;
3123{
3124 int thflags;
3125 tcp_seq seq;
3126#ifdef INET6
3127 int isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0;
3128#else
3129 const int isipv6 = 0;
3130#endif
3131
3132 /* tcbinfo lock required for tcp_twclose(), tcp_2msl_reset. */
3133 INP_INFO_WLOCK_ASSERT(&tcbinfo);
3134 INP_LOCK_ASSERT(tw->tw_inpcb);
3135
3136 thflags = th->th_flags;
3137
3138 /*
3139 * NOTE: for FIN_WAIT_2 (to be added later),
3140 * must validate sequence number before accepting RST
3141 */
3142
3143 /*
3144 * If the segment contains RST:
3145 * Drop the segment - see Stevens, vol. 2, p. 964 and
3146 * RFC 1337.
3147 */
3148 if (thflags & TH_RST)
3149 goto drop;
3150
3151#if 0
3152/* PAWS not needed at the moment */
3153 /*
3154 * RFC 1323 PAWS: If we have a timestamp reply on this segment
3155 * and it's less than ts_recent, drop it.
3156 */
3157 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
3158 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
3159 if ((thflags & TH_ACK) == 0)
3160 goto drop;
3161 goto ack;
3162 }
3163 /*
3164 * ts_recent is never updated because we never accept new segments.
3165 */
3166#endif
3167
3168 /*
3169 * If a new connection request is received
3170 * while in TIME_WAIT, drop the old connection
3171 * and start over if the sequence numbers
3172 * are above the previous ones.
3173 */
3174 if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) {
3175 (void) tcp_twclose(tw, 0);
3176 return (1);
3177 }
3178
3179 /*
3180 * Drop the the segment if it does not contain an ACK.
3181 */
3182 if ((thflags & TH_ACK) == 0)
3183 goto drop;
3184
3185 /*
3186 * Reset the 2MSL timer if this is a duplicate FIN.
3187 */
3188 if (thflags & TH_FIN) {
3189 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0);
3190 if (seq + 1 == tw->rcv_nxt)
3191 tcp_timer_2msl_reset(tw, 2 * tcp_msl);
3192 }
3193
3194 /*
3195 * Acknowledge the segment if it has data or is not a duplicate ACK.
3196 */
3197 if (thflags != TH_ACK || tlen != 0 ||
3198 th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt)
3199 tcp_twrespond(tw, TH_ACK);
3200 goto drop;
3201
3202 /*
3203 * Generate a RST, dropping incoming segment.
3204 * Make ACK acceptable to originator of segment.
3205 * Don't bother to respond if destination was broadcast/multicast.
3206 */
3207 if (m->m_flags & (M_BCAST|M_MCAST))
3208 goto drop;
3209 if (isipv6) {
3210 struct ip6_hdr *ip6;
3211
3212 /* IPv6 anycast check is done at tcp6_input() */
3213 ip6 = mtod(m, struct ip6_hdr *);
3214 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
3215 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
3216 goto drop;
3217 } else {
3218 struct ip *ip;
3219
3220 ip = mtod(m, struct ip *);
3221 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
3222 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
3223 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
3224 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
3225 goto drop;
3226 }
3227 if (thflags & TH_ACK) {
3228 tcp_respond(NULL,
3229 mtod(m, void *), th, m, 0, th->th_ack, TH_RST);
3230 } else {
3231 seq = th->th_seq + (thflags & TH_SYN ? 1 : 0);
3232 tcp_respond(NULL,
3233 mtod(m, void *), th, m, seq, 0, TH_RST|TH_ACK);
3234 }
3235 INP_UNLOCK(tw->tw_inpcb);
3236 return (0);
3237
3238drop:
3239 INP_UNLOCK(tw->tw_inpcb);
3240 m_freem(m);
3241 return (0);
3242}
|