105MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry");
106
107static int tcprexmtthresh = 3;
108tcp_seq tcp_iss;
109tcp_cc tcp_ccgen;
110
111struct tcpstat tcpstat;
112SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RD,
113 &tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)");
114
115static int log_in_vain = 0;
116SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW,
117 &log_in_vain, 0, "Log all incoming TCP connections");
118
119static int blackhole = 0;
120SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW,
121 &blackhole, 0, "Do not send RST when dropping refused connections");
122
123int tcp_delack_enabled = 1;
124SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW,
125 &tcp_delack_enabled, 0,
126 "Delay ACK to try and piggyback it onto a data packet");
127
128#ifdef TCP_DROP_SYNFIN
129static int drop_synfin = 0;
130SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW,
131 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set");
132#endif
133
134#ifdef TCP_RESTRICT_RST
135static int restrict_rst = 0;
136SYSCTL_INT(_net_inet_tcp, OID_AUTO, restrict_rst, CTLFLAG_RW,
137 &restrict_rst, 0, "Restrict RST emission");
138#endif
139
140struct inpcbhead tcb;
141#define tcb6 tcb /* for KAME src sync over BSD*'s */
142struct inpcbinfo tcbinfo;
143
144static void tcp_dooptions __P((struct tcpcb *,
145 u_char *, int, struct tcphdr *, struct tcpopt *));
146static void tcp_pulloutofband __P((struct socket *,
147 struct tcphdr *, struct mbuf *, int));
148static int tcp_reass __P((struct tcpcb *, struct tcphdr *, int *,
149 struct mbuf *));
150static void tcp_xmit_timer __P((struct tcpcb *, int));
151
152/* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */
153#ifdef INET6
154#define ND6_HINT(tp) \
155do { \
156 if ((tp) && (tp)->t_inpcb && \
157 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0 && \
158 (tp)->t_inpcb->in6p_route.ro_rt) \
159 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL); \
160} while (0)
161#else
162#define ND6_HINT(tp)
163#endif
164
165/*
166 * Insert segment which inludes th into reassembly queue of tcp with
167 * control block tp. Return TH_FIN if reassembly now includes
168 * a segment with FIN. The macro form does the common case inline
169 * (segment is the next to be received on an established connection,
170 * and the queue is empty), avoiding linkage into and removal
171 * from the queue and repetition of various conversions.
172 * Set DELACK for segments received in order, but ack immediately
173 * when segments are out of order (so fast retransmit can work).
174 */
175#define TCP_REASS(tp, th, tlenp, m, so, flags) { \
176 if ((th)->th_seq == (tp)->rcv_nxt && \
177 LIST_EMPTY(&(tp)->t_segq) && \
178 (tp)->t_state == TCPS_ESTABLISHED) { \
179 if (tcp_delack_enabled) \
180 callout_reset(tp->tt_delack, tcp_delacktime, \
181 tcp_timer_delack, tp); \
182 else \
183 tp->t_flags |= TF_ACKNOW; \
184 (tp)->rcv_nxt += *(tlenp); \
185 flags = (th)->th_flags & TH_FIN; \
186 tcpstat.tcps_rcvpack++;\
187 tcpstat.tcps_rcvbyte += *(tlenp);\
188 ND6_HINT(tp); \
189 sbappend(&(so)->so_rcv, (m)); \
190 sorwakeup(so); \
191 } else { \
192 (flags) = tcp_reass((tp), (th), (tlenp), (m)); \
193 tp->t_flags |= TF_ACKNOW; \
194 } \
195}
196
197static int
198tcp_reass(tp, th, tlenp, m)
199 register struct tcpcb *tp;
200 register struct tcphdr *th;
201 int *tlenp;
202 struct mbuf *m;
203{
204 struct tseg_qent *q;
205 struct tseg_qent *p = NULL;
206 struct tseg_qent *nq;
207 struct tseg_qent *te;
208 struct socket *so = tp->t_inpcb->inp_socket;
209 int flags;
210
211 /*
212 * Call with th==0 after become established to
213 * force pre-ESTABLISHED data up to user socket.
214 */
215 if (th == 0)
216 goto present;
217
218 /* Allocate a new queue entry. If we can't, just drop the pkt. XXX */
219 MALLOC(te, struct tseg_qent *, sizeof (struct tseg_qent), M_TSEGQ,
220 M_NOWAIT);
221 if (te == NULL) {
222 tcpstat.tcps_rcvmemdrop++;
223 m_freem(m);
224 return (0);
225 }
226
227 /*
228 * Find a segment which begins after this one does.
229 */
230 LIST_FOREACH(q, &tp->t_segq, tqe_q) {
231 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
232 break;
233 p = q;
234 }
235
236 /*
237 * If there is a preceding segment, it may provide some of
238 * our data already. If so, drop the data from the incoming
239 * segment. If it provides all of our data, drop us.
240 */
241 if (p != NULL) {
242 register int i;
243 /* conversion to int (in i) handles seq wraparound */
244 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
245 if (i > 0) {
246 if (i >= *tlenp) {
247 tcpstat.tcps_rcvduppack++;
248 tcpstat.tcps_rcvdupbyte += *tlenp;
249 m_freem(m);
250 FREE(te, M_TSEGQ);
251 /*
252 * Try to present any queued data
253 * at the left window edge to the user.
254 * This is needed after the 3-WHS
255 * completes.
256 */
257 goto present; /* ??? */
258 }
259 m_adj(m, i);
260 *tlenp -= i;
261 th->th_seq += i;
262 }
263 }
264 tcpstat.tcps_rcvoopack++;
265 tcpstat.tcps_rcvoobyte += *tlenp;
266
267 /*
268 * While we overlap succeeding segments trim them or,
269 * if they are completely covered, dequeue them.
270 */
271 while (q) {
272 register int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
273 if (i <= 0)
274 break;
275 if (i < q->tqe_len) {
276 q->tqe_th->th_seq += i;
277 q->tqe_len -= i;
278 m_adj(q->tqe_m, i);
279 break;
280 }
281
282 nq = LIST_NEXT(q, tqe_q);
283 LIST_REMOVE(q, tqe_q);
284 m_freem(q->tqe_m);
285 FREE(q, M_TSEGQ);
286 q = nq;
287 }
288
289 /* Insert the new segment queue entry into place. */
290 te->tqe_m = m;
291 te->tqe_th = th;
292 te->tqe_len = *tlenp;
293
294 if (p == NULL) {
295 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q);
296 } else {
297 LIST_INSERT_AFTER(p, te, tqe_q);
298 }
299
300present:
301 /*
302 * Present data to user, advancing rcv_nxt through
303 * completed sequence space.
304 */
305 if (!TCPS_HAVEESTABLISHED(tp->t_state))
306 return (0);
307 q = LIST_FIRST(&tp->t_segq);
308 if (!q || q->tqe_th->th_seq != tp->rcv_nxt)
309 return (0);
310 do {
311 tp->rcv_nxt += q->tqe_len;
312 flags = q->tqe_th->th_flags & TH_FIN;
313 nq = LIST_NEXT(q, tqe_q);
314 LIST_REMOVE(q, tqe_q);
315 if (so->so_state & SS_CANTRCVMORE)
316 m_freem(q->tqe_m);
317 else
318 sbappend(&so->so_rcv, q->tqe_m);
319 FREE(q, M_TSEGQ);
320 q = nq;
321 } while (q && q->tqe_th->th_seq == tp->rcv_nxt);
322 ND6_HINT(tp);
323 sorwakeup(so);
324 return (flags);
325}
326
327/*
328 * TCP input routine, follows pages 65-76 of the
329 * protocol specification dated September, 1981 very closely.
330 */
331#ifdef INET6
332int
333tcp6_input(mp, offp, proto)
334 struct mbuf **mp;
335 int *offp, proto;
336{
337 register struct mbuf *m = *mp;
338
339 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE);
340
341 /*
342 * draft-itojun-ipv6-tcp-to-anycast
343 * better place to put this in?
344 */
345 if (m->m_flags & M_ANYCAST6) {
346 struct ip6_hdr *ip6;
347
348 ip6 = mtod(m, struct ip6_hdr *);
349 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
350 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6);
351 return IPPROTO_DONE;
352 }
353
354 tcp_input(m, *offp, proto);
355 return IPPROTO_DONE;
356}
357#endif
358
359void
360tcp_input(m, off0, proto)
361 register struct mbuf *m;
362 int off0, proto;
363{
364 register struct tcphdr *th;
365 register struct ip *ip = NULL;
366 register struct ipovly *ipov;
367 register struct inpcb *inp;
368 u_char *optp = NULL;
369 int optlen = 0;
370 int len, tlen, off;
371 int drop_hdrlen;
372 register struct tcpcb *tp = 0;
373 register int thflags;
374 struct socket *so = 0;
375 int todrop, acked, ourfinisacked, needoutput = 0;
376 struct in_addr laddr;
377#ifdef INET6
378 struct in6_addr laddr6;
379#endif
380 int dropsocket = 0;
381 int iss = 0;
382 u_long tiwin;
383 struct tcpopt to; /* options in this segment */
384 struct rmxp_tao *taop; /* pointer to our TAO cache entry */
385 struct rmxp_tao tao_noncached; /* in case there's no cached entry */
386#ifdef TCPDEBUG
387 short ostate = 0;
388#endif
389#ifdef INET6
390 struct ip6_hdr *ip6 = NULL;
391 int isipv6;
392#endif /* INET6 */
393
394#ifdef INET6
395 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0;
396#endif
397 bzero((char *)&to, sizeof(to));
398
399 tcpstat.tcps_rcvtotal++;
400
401#ifdef INET6
402 if (isipv6) {
403 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */
404 ip6 = mtod(m, struct ip6_hdr *);
405 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0;
406 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) {
407 tcpstat.tcps_rcvbadsum++;
408 goto drop;
409 }
410 th = (struct tcphdr *)((caddr_t)ip6 + off0);
411 } else
412#endif /* INET6 */
413 {
414 /*
415 * Get IP and TCP header together in first mbuf.
416 * Note: IP leaves IP header in first mbuf.
417 */
418 if (off0 > sizeof (struct ip)) {
419 ip_stripoptions(m, (struct mbuf *)0);
420 off0 = sizeof(struct ip);
421 }
422 if (m->m_len < sizeof (struct tcpiphdr)) {
423 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) {
424 tcpstat.tcps_rcvshort++;
425 return;
426 }
427 }
428 ip = mtod(m, struct ip *);
429 ipov = (struct ipovly *)ip;
|
451 if (th->th_sum) {
452 tcpstat.tcps_rcvbadsum++;
453 goto drop;
454 }
455#ifdef INET6
456 /* Re-initialization for later version check */
457 ip->ip_v = IPVERSION;
458#endif
459 }
460
461 /*
462 * Check that TCP offset makes sense,
463 * pull out TCP options and adjust length. XXX
464 */
465 off = th->th_off << 2;
466 if (off < sizeof (struct tcphdr) || off > tlen) {
467 tcpstat.tcps_rcvbadoff++;
468 goto drop;
469 }
470 tlen -= off; /* tlen is used instead of ti->ti_len */
471 if (off > sizeof (struct tcphdr)) {
472#ifdef INET6
473 if (isipv6) {
474 IP6_EXTHDR_CHECK(m, off0, off, );
475 ip6 = mtod(m, struct ip6_hdr *);
476 th = (struct tcphdr *)((caddr_t)ip6 + off0);
477 } else
478#endif /* INET6 */
479 {
480 if (m->m_len < sizeof(struct ip) + off) {
481 if ((m = m_pullup(m, sizeof (struct ip) + off)) == 0) {
482 tcpstat.tcps_rcvshort++;
483 return;
484 }
485 ip = mtod(m, struct ip *);
486 ipov = (struct ipovly *)ip;
487 th = (struct tcphdr *)((caddr_t)ip + off0);
488 }
489 }
490 optlen = off - sizeof (struct tcphdr);
491 optp = (u_char *)(th + 1);
492 }
493 thflags = th->th_flags;
494
495#ifdef TCP_DROP_SYNFIN
496 /*
497 * If the drop_synfin option is enabled, drop all packets with
498 * both the SYN and FIN bits set. This prevents e.g. nmap from
499 * identifying the TCP/IP stack.
500 *
501 * This is incompatible with RFC1644 extensions (T/TCP).
502 */
503 if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN))
504 goto drop;
505#endif
506
507 /*
508 * Convert TCP protocol specific fields to host format.
509 */
510 NTOHL(th->th_seq);
511 NTOHL(th->th_ack);
512 NTOHS(th->th_win);
513 NTOHS(th->th_urp);
514
515 /*
516 * Delay droping TCP, IP headers, IPv6 ext headers, and TCP options,
517 * until after ip6_savecontrol() is called and before other functions
518 * which don't want those proto headers.
519 * Because ip6_savecontrol() is going to parse the mbuf to
520 * search for data to be passed up to user-land, it wants mbuf
521 * parameters to be unchanged.
522 */
523 drop_hdrlen = off0 + off;
524
525 /*
526 * Locate pcb for segment.
527 */
528findpcb:
529#ifdef IPFIREWALL_FORWARD
530 if (ip_fw_fwd_addr != NULL
531#ifdef INET6
532 && isipv6 == NULL /* IPv6 support is not yet */
533#endif /* INET6 */
534 ) {
535 /*
536 * Diverted. Pretend to be the destination.
537 * already got one like this?
538 */
539 inp = in_pcblookup_hash(&tcbinfo, ip->ip_src, th->th_sport,
540 ip->ip_dst, th->th_dport, 0, m->m_pkthdr.rcvif);
541 if (!inp) {
542 /*
543 * No, then it's new. Try find the ambushing socket
544 */
545 if (!ip_fw_fwd_addr->sin_port) {
546 inp = in_pcblookup_hash(&tcbinfo, ip->ip_src,
547 th->th_sport, ip_fw_fwd_addr->sin_addr,
548 th->th_dport, 1, m->m_pkthdr.rcvif);
549 } else {
550 inp = in_pcblookup_hash(&tcbinfo,
551 ip->ip_src, th->th_sport,
552 ip_fw_fwd_addr->sin_addr,
553 ntohs(ip_fw_fwd_addr->sin_port), 1,
554 m->m_pkthdr.rcvif);
555 }
556 }
557 ip_fw_fwd_addr = NULL;
558 } else
559#endif /* IPFIREWALL_FORWARD */
560 {
561#ifdef INET6
562 if (isipv6)
563 inp = in6_pcblookup_hash(&tcbinfo, &ip6->ip6_src, th->th_sport,
564 &ip6->ip6_dst, th->th_dport, 1,
565 m->m_pkthdr.rcvif);
566 else
567#endif /* INET6 */
568 inp = in_pcblookup_hash(&tcbinfo, ip->ip_src, th->th_sport,
569 ip->ip_dst, th->th_dport, 1, m->m_pkthdr.rcvif);
570 }
571
572#ifdef IPSEC
573#ifdef INET6
574 if (isipv6) {
575 if (inp != NULL && ipsec6_in_reject_so(m, inp->inp_socket)) {
576 ipsec6stat.in_polvio++;
577 goto drop;
578 }
579 } else
580#endif /* INET6 */
581 if (inp != NULL && ipsec4_in_reject_so(m, inp->inp_socket)) {
582 ipsecstat.in_polvio++;
583 goto drop;
584 }
585#endif /*IPSEC*/
586
587 /*
588 * If the state is CLOSED (i.e., TCB does not exist) then
589 * all data in the incoming segment is discarded.
590 * If the TCB exists but is in CLOSED state, it is embryonic,
591 * but should either do a listen or a connect soon.
592 */
593 if (inp == NULL) {
594 if (log_in_vain) {
595#ifdef INET6
596 char dbuf[INET6_ADDRSTRLEN], sbuf[INET6_ADDRSTRLEN];
597#else /* INET6 */
598 char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"];
599#endif /* INET6 */
600
601#ifdef INET6
602 if (isipv6) {
603 strcpy(dbuf, ip6_sprintf(&ip6->ip6_dst));
604 strcpy(sbuf, ip6_sprintf(&ip6->ip6_src));
605 } else
606#endif
607 {
608 strcpy(dbuf, inet_ntoa(ip->ip_dst));
609 strcpy(sbuf, inet_ntoa(ip->ip_src));
610 }
611 switch (log_in_vain) {
612 case 1:
613 if(thflags & TH_SYN)
614 log(LOG_INFO,
615 "Connection attempt to TCP %s:%d from %s:%d\n",
616 dbuf, ntohs(th->th_dport),
617 sbuf,
618 ntohs(th->th_sport));
619 break;
620 case 2:
621 log(LOG_INFO,
622 "Connection attempt to TCP %s:%d from %s:%d flags:0x%x\n",
623 dbuf, ntohs(th->th_dport), sbuf,
624 ntohs(th->th_sport), thflags);
625 break;
626 default:
627 break;
628 }
629 }
630 if (blackhole) {
631 switch (blackhole) {
632 case 1:
633 if (thflags & TH_SYN)
634 goto drop;
635 break;
636 case 2:
637 goto drop;
638 default:
639 goto drop;
640 }
641 }
642 goto maybedropwithreset;
643 }
644 tp = intotcpcb(inp);
645 if (tp == 0)
646 goto maybedropwithreset;
647 if (tp->t_state == TCPS_CLOSED)
648 goto drop;
649
650 /* Unscale the window into a 32-bit value. */
651 if ((thflags & TH_SYN) == 0)
652 tiwin = th->th_win << tp->snd_scale;
653 else
654 tiwin = th->th_win;
655
656#ifdef INET6
657 /* save packet options if user wanted */
658 if (isipv6 && inp->in6p_flags & INP_CONTROLOPTS) {
659 if (inp->in6p_options) {
660 m_freem(inp->in6p_options);
661 inp->in6p_options = 0;
662 }
663 ip6_savecontrol(inp, &inp->in6p_options, ip6, m);
664 }
665 /* else, should also do ip_srcroute() here? */
666#endif /* INET6 */
667
668 so = inp->inp_socket;
669 if (so->so_options & (SO_DEBUG|SO_ACCEPTCONN)) {
670#ifdef TCPDEBUG
671 if (so->so_options & SO_DEBUG) {
672 ostate = tp->t_state;
673#ifdef INET6
674 if (isipv6)
675 bcopy((char *)ip6, (char *)tcp_saveipgen,
676 sizeof(*ip6));
677 else
678#endif /* INET6 */
679 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip));
680 tcp_savetcp = *th;
681 }
682#endif
683 if (so->so_options & SO_ACCEPTCONN) {
684 register struct tcpcb *tp0 = tp;
685 struct socket *so2;
686#ifdef IPSEC
687 struct socket *oso;
688#endif
689#ifdef INET6
690 struct inpcb *oinp = sotoinpcb(so);
691#endif /* INET6 */
692
693#ifndef IPSEC
694 /*
695 * Current IPsec implementation makes incorrect IPsec
696 * cache if this check is done here.
697 * So delay this until duplicated socket is created.
698 */
699 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) {
700 /*
701 * Note: dropwithreset makes sure we don't
702 * send a RST in response to a RST.
703 */
704 if (thflags & TH_ACK) {
705 tcpstat.tcps_badsyn++;
706 goto maybedropwithreset;
707 }
708 goto drop;
709 }
710#endif
711 so2 = sonewconn(so, 0);
712 if (so2 == 0) {
713 tcpstat.tcps_listendrop++;
714 so2 = sodropablereq(so);
715 if (so2) {
716 tcp_drop(sototcpcb(so2), ETIMEDOUT);
717 so2 = sonewconn(so, 0);
718 }
719 if (!so2)
720 goto drop;
721 }
722#ifdef IPSEC
723 oso = so;
724#endif
725 so = so2;
726 /*
727 * This is ugly, but ....
728 *
729 * Mark socket as temporary until we're
730 * committed to keeping it. The code at
731 * ``drop'' and ``dropwithreset'' check the
732 * flag dropsocket to see if the temporary
733 * socket created here should be discarded.
734 * We mark the socket as discardable until
735 * we're committed to it below in TCPS_LISTEN.
736 */
737 dropsocket++;
738 inp = (struct inpcb *)so->so_pcb;
739#ifdef INET6
740 if (isipv6)
741 inp->in6p_laddr = ip6->ip6_dst;
742 else {
743 if (ip6_mapped_addr_on) {
744 inp->inp_vflag &= ~INP_IPV6;
745 inp->inp_vflag |= INP_IPV4;
746 }
747#endif /* INET6 */
748 inp->inp_laddr = ip->ip_dst;
749#ifdef INET6
750 }
751#endif /* INET6 */
752 inp->inp_lport = th->th_dport;
753 if (in_pcbinshash(inp) != 0) {
754 /*
755 * Undo the assignments above if we failed to
756 * put the PCB on the hash lists.
757 */
758#ifdef INET6
759 if (isipv6)
760 inp->in6p_laddr = in6addr_any;
761 else
762#endif /* INET6 */
763 inp->inp_laddr.s_addr = INADDR_ANY;
764 inp->inp_lport = 0;
765 goto drop;
766 }
767#ifdef IPSEC
768 /*
769 * To avoid creating incorrectly cached IPsec
770 * association, this is need to be done here.
771 *
772 * Subject: (KAME-snap 748)
773 * From: Wayne Knowles <w.knowles@niwa.cri.nz>
774 * ftp://ftp.kame.net/pub/mail-list/snap-users/748
775 */
776 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) {
777 /*
778 * Note: dropwithreset makes sure we don't
779 * send a RST in response to a RST.
780 */
781 if (thflags & TH_ACK) {
782 tcpstat.tcps_badsyn++;
783 goto maybedropwithreset;
784 }
785 goto drop;
786 }
787#endif
788#ifdef INET6
789 if (isipv6) {
790 /*
791 * inherit socket options from the listening
792 * socket.
793 */
794 inp->inp_flags |=
795 oinp->inp_flags & INP_CONTROLOPTS;
796 if (inp->inp_flags & INP_CONTROLOPTS) {
797 if (inp->in6p_options) {
798 m_freem(inp->in6p_options);
799 inp->in6p_options = 0;
800 }
801 ip6_savecontrol(inp,
802 &inp->in6p_options,
803 ip6, m);
804 }
805 } else
806#endif /* INET6 */
807 inp->inp_options = ip_srcroute();
808#ifdef IPSEC
809 /* copy old policy into new socket's */
810 if (ipsec_copy_policy(sotoinpcb(oso)->inp_sp,
811 inp->inp_sp))
812 printf("tcp_input: could not copy policy\n");
813#endif
814 tp = intotcpcb(inp);
815 tp->t_state = TCPS_LISTEN;
816 tp->t_flags |= tp0->t_flags & (TF_NOPUSH|TF_NOOPT);
817
818 /* Compute proper scaling value from buffer space */
819 while (tp->request_r_scale < TCP_MAX_WINSHIFT &&
820 TCP_MAXWIN << tp->request_r_scale <
821 so->so_rcv.sb_hiwat)
822 tp->request_r_scale++;
823 }
824 }
825
826 /*
827 * Segment received on connection.
828 * Reset idle time and keep-alive timer.
829 */
830 tp->t_rcvtime = ticks;
831 if (TCPS_HAVEESTABLISHED(tp->t_state))
832 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp);
833
834 /*
835 * Process options if not in LISTEN state,
836 * else do it below (after getting remote address).
837 */
838 if (tp->t_state != TCPS_LISTEN)
839 tcp_dooptions(tp, optp, optlen, th, &to);
840
841 /*
842 * Header prediction: check for the two common cases
843 * of a uni-directional data xfer. If the packet has
844 * no control flags, is in-sequence, the window didn't
845 * change and we're not retransmitting, it's a
846 * candidate. If the length is zero and the ack moved
847 * forward, we're the sender side of the xfer. Just
848 * free the data acked & wake any higher level process
849 * that was blocked waiting for space. If the length
850 * is non-zero and the ack didn't move, we're the
851 * receiver side. If we're getting packets in-order
852 * (the reassembly queue is empty), add the data to
853 * the socket buffer and note that we need a delayed ack.
854 * Make sure that the hidden state-flags are also off.
855 * Since we check for TCPS_ESTABLISHED above, it can only
856 * be TH_NEEDSYN.
857 */
858 if (tp->t_state == TCPS_ESTABLISHED &&
859 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
860 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) &&
861 ((to.to_flag & TOF_TS) == 0 ||
862 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) &&
863 /*
864 * Using the CC option is compulsory if once started:
865 * the segment is OK if no T/TCP was negotiated or
866 * if the segment has a CC option equal to CCrecv
867 */
868 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) ||
869 ((to.to_flag & TOF_CC) != 0 && to.to_cc == tp->cc_recv)) &&
870 th->th_seq == tp->rcv_nxt &&
871 tiwin && tiwin == tp->snd_wnd &&
872 tp->snd_nxt == tp->snd_max) {
873
874 /*
875 * If last ACK falls within this segment's sequence numbers,
876 * record the timestamp.
877 * NOTE that the test is modified according to the latest
878 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
879 */
880 if ((to.to_flag & TOF_TS) != 0 &&
881 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
882 tp->ts_recent_age = ticks;
883 tp->ts_recent = to.to_tsval;
884 }
885
886 if (tlen == 0) {
887 if (SEQ_GT(th->th_ack, tp->snd_una) &&
888 SEQ_LEQ(th->th_ack, tp->snd_max) &&
889 tp->snd_cwnd >= tp->snd_wnd &&
890 tp->t_dupacks < tcprexmtthresh) {
891 /*
892 * this is a pure ack for outstanding data.
893 */
894 ++tcpstat.tcps_predack;
895 /*
896 * "bad retransmit" recovery
897 */
898 if (tp->t_rxtshift == 1 &&
899 ticks < tp->t_badrxtwin) {
900 tp->snd_cwnd = tp->snd_cwnd_prev;
901 tp->snd_ssthresh =
902 tp->snd_ssthresh_prev;
903 tp->snd_nxt = tp->snd_max;
904 tp->t_badrxtwin = 0;
905 }
906 if ((to.to_flag & TOF_TS) != 0)
907 tcp_xmit_timer(tp,
908 ticks - to.to_tsecr + 1);
909 else if (tp->t_rtttime &&
910 SEQ_GT(th->th_ack, tp->t_rtseq))
911 tcp_xmit_timer(tp, ticks - tp->t_rtttime);
912 acked = th->th_ack - tp->snd_una;
913 tcpstat.tcps_rcvackpack++;
914 tcpstat.tcps_rcvackbyte += acked;
915 sbdrop(&so->so_snd, acked);
916 tp->snd_una = th->th_ack;
917 m_freem(m);
918 ND6_HINT(tp); /* some progress has been done */
919
920 /*
921 * If all outstanding data are acked, stop
922 * retransmit timer, otherwise restart timer
923 * using current (possibly backed-off) value.
924 * If process is waiting for space,
925 * wakeup/selwakeup/signal. If data
926 * are ready to send, let tcp_output
927 * decide between more output or persist.
928 */
929 if (tp->snd_una == tp->snd_max)
930 callout_stop(tp->tt_rexmt);
931 else if (!callout_active(tp->tt_persist))
932 callout_reset(tp->tt_rexmt,
933 tp->t_rxtcur,
934 tcp_timer_rexmt, tp);
935
936 sowwakeup(so);
937 if (so->so_snd.sb_cc)
938 (void) tcp_output(tp);
939 return;
940 }
941 } else if (th->th_ack == tp->snd_una &&
942 LIST_EMPTY(&tp->t_segq) &&
943 tlen <= sbspace(&so->so_rcv)) {
944 /*
945 * this is a pure, in-sequence data packet
946 * with nothing on the reassembly queue and
947 * we have enough buffer space to take it.
948 */
949 ++tcpstat.tcps_preddat;
950 tp->rcv_nxt += tlen;
951 tcpstat.tcps_rcvpack++;
952 tcpstat.tcps_rcvbyte += tlen;
953 ND6_HINT(tp); /* some progress has been done */
954 /*
955 * Add data to socket buffer.
956 */
957 m_adj(m, drop_hdrlen); /* delayed header drop */
958 sbappend(&so->so_rcv, m);
959 sorwakeup(so);
960 if (tcp_delack_enabled) {
961 callout_reset(tp->tt_delack, tcp_delacktime,
962 tcp_timer_delack, tp);
963 } else {
964 tp->t_flags |= TF_ACKNOW;
965 tcp_output(tp);
966 }
967 return;
968 }
969 }
970
971 /*
972 * Calculate amount of space in receive window,
973 * and then do TCP input processing.
974 * Receive window is amount of space in rcv queue,
975 * but not less than advertised window.
976 */
977 { int win;
978
979 win = sbspace(&so->so_rcv);
980 if (win < 0)
981 win = 0;
982 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt));
983 }
984
985 switch (tp->t_state) {
986
987 /*
988 * If the state is LISTEN then ignore segment if it contains an RST.
989 * If the segment contains an ACK then it is bad and send a RST.
990 * If it does not contain a SYN then it is not interesting; drop it.
991 * If it is from this socket, drop it, it must be forged.
992 * Don't bother responding if the destination was a broadcast.
993 * Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial
994 * tp->iss, and send a segment:
995 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
996 * Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss.
997 * Fill in remote peer address fields if not previously specified.
998 * Enter SYN_RECEIVED state, and process any other fields of this
999 * segment in this state.
1000 */
1001 case TCPS_LISTEN: {
1002 register struct sockaddr_in *sin;
1003#ifdef INET6
1004 register struct sockaddr_in6 *sin6;
1005#endif
1006
1007 if (thflags & TH_RST)
1008 goto drop;
1009 if (thflags & TH_ACK)
1010 goto maybedropwithreset;
1011 if ((thflags & TH_SYN) == 0)
1012 goto drop;
1013 if (th->th_dport == th->th_sport) {
1014#ifdef INET6
1015 if (isipv6) {
1016 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst,
1017 &ip6->ip6_src))
1018 goto drop;
1019 } else
1020#endif /* INET6 */
1021 if (ip->ip_dst.s_addr == ip->ip_src.s_addr)
1022 goto drop;
1023 }
1024 /*
1025 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN
1026 * in_broadcast() should never return true on a received
1027 * packet with M_BCAST not set.
1028 *
1029 * Packets with a multicast source address should also
1030 * be discarded.
1031 */
1032 if (m->m_flags & (M_BCAST|M_MCAST))
1033 goto drop;
1034#ifdef INET6
1035 if (isipv6) {
1036 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
1037 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
1038 goto drop;
1039 } else
1040#endif
1041 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
1042 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
1043 ip->ip_src.s_addr == htonl(INADDR_BROADCAST))
1044 goto drop;
1045#ifdef INET6
1046 if (isipv6) {
1047 MALLOC(sin6, struct sockaddr_in6 *, sizeof *sin6,
1048 M_SONAME, M_NOWAIT);
1049 if (sin6 == NULL)
1050 goto drop;
1051 bzero(sin6, sizeof(*sin6));
1052 sin6->sin6_family = AF_INET6;
1053 sin6->sin6_len = sizeof(*sin6);
1054 sin6->sin6_addr = ip6->ip6_src;
1055 sin6->sin6_port = th->th_sport;
1056 laddr6 = inp->in6p_laddr;
1057 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr))
1058 inp->in6p_laddr = ip6->ip6_dst;
1059 if (in6_pcbconnect(inp, (struct sockaddr *)sin6,
1060 &proc0)) {
1061 inp->in6p_laddr = laddr6;
1062 FREE(sin6, M_SONAME);
1063 goto drop;
1064 }
1065 FREE(sin6, M_SONAME);
1066 } else
1067#endif
1068 {
1069 MALLOC(sin, struct sockaddr_in *, sizeof *sin, M_SONAME,
1070 M_NOWAIT);
1071 if (sin == NULL)
1072 goto drop;
1073 sin->sin_family = AF_INET;
1074 sin->sin_len = sizeof(*sin);
1075 sin->sin_addr = ip->ip_src;
1076 sin->sin_port = th->th_sport;
1077 bzero((caddr_t)sin->sin_zero, sizeof(sin->sin_zero));
1078 laddr = inp->inp_laddr;
1079 if (inp->inp_laddr.s_addr == INADDR_ANY)
1080 inp->inp_laddr = ip->ip_dst;
1081 if (in_pcbconnect(inp, (struct sockaddr *)sin, &proc0)) {
1082 inp->inp_laddr = laddr;
1083 FREE(sin, M_SONAME);
1084 goto drop;
1085 }
1086 FREE(sin, M_SONAME);
1087 }
1088 tp->t_template = tcp_template(tp);
1089 if (tp->t_template == 0) {
1090 tp = tcp_drop(tp, ENOBUFS);
1091 dropsocket = 0; /* socket is already gone */
1092 goto drop;
1093 }
1094 if ((taop = tcp_gettaocache(inp)) == NULL) {
1095 taop = &tao_noncached;
1096 bzero(taop, sizeof(*taop));
1097 }
1098 tcp_dooptions(tp, optp, optlen, th, &to);
1099 if (iss)
1100 tp->iss = iss;
1101 else
1102 tp->iss = tcp_iss;
1103 tcp_iss += TCP_ISSINCR/4;
1104 tp->irs = th->th_seq;
1105 tcp_sendseqinit(tp);
1106 tcp_rcvseqinit(tp);
1107 /*
1108 * Initialization of the tcpcb for transaction;
1109 * set SND.WND = SEG.WND,
1110 * initialize CCsend and CCrecv.
1111 */
1112 tp->snd_wnd = tiwin; /* initial send-window */
1113 tp->cc_send = CC_INC(tcp_ccgen);
1114 tp->cc_recv = to.to_cc;
1115 /*
1116 * Perform TAO test on incoming CC (SEG.CC) option, if any.
1117 * - compare SEG.CC against cached CC from the same host,
1118 * if any.
1119 * - if SEG.CC > chached value, SYN must be new and is accepted
1120 * immediately: save new CC in the cache, mark the socket
1121 * connected, enter ESTABLISHED state, turn on flag to
1122 * send a SYN in the next segment.
1123 * A virtual advertised window is set in rcv_adv to
1124 * initialize SWS prevention. Then enter normal segment
1125 * processing: drop SYN, process data and FIN.
1126 * - otherwise do a normal 3-way handshake.
1127 */
1128 if ((to.to_flag & TOF_CC) != 0) {
1129 if (((tp->t_flags & TF_NOPUSH) != 0) &&
1130 taop->tao_cc != 0 && CC_GT(to.to_cc, taop->tao_cc)) {
1131
1132 taop->tao_cc = to.to_cc;
1133 tp->t_starttime = ticks;
1134 tp->t_state = TCPS_ESTABLISHED;
1135
1136 /*
1137 * If there is a FIN, or if there is data and the
1138 * connection is local, then delay SYN,ACK(SYN) in
1139 * the hope of piggy-backing it on a response
1140 * segment. Otherwise must send ACK now in case
1141 * the other side is slow starting.
1142 */
1143 if (tcp_delack_enabled && ((thflags & TH_FIN) ||
1144 (tlen != 0 &&
1145#ifdef INET6
1146 ((isipv6 && in6_localaddr(&inp->in6p_faddr))
1147 ||
1148 (!isipv6 &&
1149#endif
1150 in_localaddr(inp->inp_faddr)
1151#ifdef INET6
1152 ))
1153#endif
1154 ))) {
1155 callout_reset(tp->tt_delack, tcp_delacktime,
1156 tcp_timer_delack, tp);
1157 tp->t_flags |= TF_NEEDSYN;
1158 } else
1159 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN);
1160
1161 /*
1162 * Limit the `virtual advertised window' to TCP_MAXWIN
1163 * here. Even if we requested window scaling, it will
1164 * become effective only later when our SYN is acked.
1165 */
1166 tp->rcv_adv += min(tp->rcv_wnd, TCP_MAXWIN);
1167 tcpstat.tcps_connects++;
1168 soisconnected(so);
1169 callout_reset(tp->tt_keep, tcp_keepinit,
1170 tcp_timer_keep, tp);
1171 dropsocket = 0; /* committed to socket */
1172 tcpstat.tcps_accepts++;
1173 goto trimthenstep6;
1174 }
1175 /* else do standard 3-way handshake */
1176 } else {
1177 /*
1178 * No CC option, but maybe CC.NEW:
1179 * invalidate cached value.
1180 */
1181 taop->tao_cc = 0;
1182 }
1183 /*
1184 * TAO test failed or there was no CC option,
1185 * do a standard 3-way handshake.
1186 */
1187 tp->t_flags |= TF_ACKNOW;
1188 tp->t_state = TCPS_SYN_RECEIVED;
1189 callout_reset(tp->tt_keep, tcp_keepinit, tcp_timer_keep, tp);
1190 dropsocket = 0; /* committed to socket */
1191 tcpstat.tcps_accepts++;
1192 ND6_HINT((struct tcpcb *)inp->inp_ppcb);
1193 goto trimthenstep6;
1194 }
1195
1196 /*
1197 * If the state is SYN_RECEIVED:
1198 * if seg contains an ACK, but not for our SYN/ACK, send a RST.
1199 */
1200 case TCPS_SYN_RECEIVED:
1201 if ((thflags & TH_ACK) &&
1202 (SEQ_LEQ(th->th_ack, tp->snd_una) ||
1203 SEQ_GT(th->th_ack, tp->snd_max)))
1204 goto maybedropwithreset;
1205 break;
1206
1207 /*
1208 * If the state is SYN_SENT:
1209 * if seg contains an ACK, but not for our SYN, drop the input.
1210 * if seg contains a RST, then drop the connection.
1211 * if seg does not contain SYN, then drop it.
1212 * Otherwise this is an acceptable SYN segment
1213 * initialize tp->rcv_nxt and tp->irs
1214 * if seg contains ack then advance tp->snd_una
1215 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state
1216 * arrange for segment to be acked (eventually)
1217 * continue processing rest of data/controls, beginning with URG
1218 */
1219 case TCPS_SYN_SENT:
1220 if ((taop = tcp_gettaocache(inp)) == NULL) {
1221 taop = &tao_noncached;
1222 bzero(taop, sizeof(*taop));
1223 }
1224
1225 if ((thflags & TH_ACK) &&
1226 (SEQ_LEQ(th->th_ack, tp->iss) ||
1227 SEQ_GT(th->th_ack, tp->snd_max))) {
1228 /*
1229 * If we have a cached CCsent for the remote host,
1230 * hence we haven't just crashed and restarted,
1231 * do not send a RST. This may be a retransmission
1232 * from the other side after our earlier ACK was lost.
1233 * Our new SYN, when it arrives, will serve as the
1234 * needed ACK.
1235 */
1236 if (taop->tao_ccsent != 0)
1237 goto drop;
1238 else
1239 goto dropwithreset;
1240 }
1241 if (thflags & TH_RST) {
1242 if (thflags & TH_ACK)
1243 tp = tcp_drop(tp, ECONNREFUSED);
1244 goto drop;
1245 }
1246 if ((thflags & TH_SYN) == 0)
1247 goto drop;
1248 tp->snd_wnd = th->th_win; /* initial send window */
1249 tp->cc_recv = to.to_cc; /* foreign CC */
1250
1251 tp->irs = th->th_seq;
1252 tcp_rcvseqinit(tp);
1253 if (thflags & TH_ACK) {
1254 /*
1255 * Our SYN was acked. If segment contains CC.ECHO
1256 * option, check it to make sure this segment really
1257 * matches our SYN. If not, just drop it as old
1258 * duplicate, but send an RST if we're still playing
1259 * by the old rules. If no CC.ECHO option, make sure
1260 * we don't get fooled into using T/TCP.
1261 */
1262 if (to.to_flag & TOF_CCECHO) {
1263 if (tp->cc_send != to.to_ccecho) {
1264 if (taop->tao_ccsent != 0)
1265 goto drop;
1266 else
1267 goto dropwithreset;
1268 }
1269 } else
1270 tp->t_flags &= ~TF_RCVD_CC;
1271 tcpstat.tcps_connects++;
1272 soisconnected(so);
1273 /* Do window scaling on this connection? */
1274 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
1275 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
1276 tp->snd_scale = tp->requested_s_scale;
1277 tp->rcv_scale = tp->request_r_scale;
1278 }
1279 /* Segment is acceptable, update cache if undefined. */
1280 if (taop->tao_ccsent == 0)
1281 taop->tao_ccsent = to.to_ccecho;
1282
1283 tp->rcv_adv += tp->rcv_wnd;
1284 tp->snd_una++; /* SYN is acked */
1285 /*
1286 * If there's data, delay ACK; if there's also a FIN
1287 * ACKNOW will be turned on later.
1288 */
1289 if (tcp_delack_enabled && tlen != 0)
1290 callout_reset(tp->tt_delack, tcp_delacktime,
1291 tcp_timer_delack, tp);
1292 else
1293 tp->t_flags |= TF_ACKNOW;
1294 /*
1295 * Received <SYN,ACK> in SYN_SENT[*] state.
1296 * Transitions:
1297 * SYN_SENT --> ESTABLISHED
1298 * SYN_SENT* --> FIN_WAIT_1
1299 */
1300 tp->t_starttime = ticks;
1301 if (tp->t_flags & TF_NEEDFIN) {
1302 tp->t_state = TCPS_FIN_WAIT_1;
1303 tp->t_flags &= ~TF_NEEDFIN;
1304 thflags &= ~TH_SYN;
1305 } else {
1306 tp->t_state = TCPS_ESTABLISHED;
1307 callout_reset(tp->tt_keep, tcp_keepidle,
1308 tcp_timer_keep, tp);
1309 }
1310 } else {
1311 /*
1312 * Received initial SYN in SYN-SENT[*] state => simul-
1313 * taneous open. If segment contains CC option and there is
1314 * a cached CC, apply TAO test; if it succeeds, connection is
1315 * half-synchronized. Otherwise, do 3-way handshake:
1316 * SYN-SENT -> SYN-RECEIVED
1317 * SYN-SENT* -> SYN-RECEIVED*
1318 * If there was no CC option, clear cached CC value.
1319 */
1320 tp->t_flags |= TF_ACKNOW;
1321 callout_stop(tp->tt_rexmt);
1322 if (to.to_flag & TOF_CC) {
1323 if (taop->tao_cc != 0 &&
1324 CC_GT(to.to_cc, taop->tao_cc)) {
1325 /*
1326 * update cache and make transition:
1327 * SYN-SENT -> ESTABLISHED*
1328 * SYN-SENT* -> FIN-WAIT-1*
1329 */
1330 taop->tao_cc = to.to_cc;
1331 tp->t_starttime = ticks;
1332 if (tp->t_flags & TF_NEEDFIN) {
1333 tp->t_state = TCPS_FIN_WAIT_1;
1334 tp->t_flags &= ~TF_NEEDFIN;
1335 } else {
1336 tp->t_state = TCPS_ESTABLISHED;
1337 callout_reset(tp->tt_keep,
1338 tcp_keepidle,
1339 tcp_timer_keep,
1340 tp);
1341 }
1342 tp->t_flags |= TF_NEEDSYN;
1343 } else
1344 tp->t_state = TCPS_SYN_RECEIVED;
1345 } else {
1346 /* CC.NEW or no option => invalidate cache */
1347 taop->tao_cc = 0;
1348 tp->t_state = TCPS_SYN_RECEIVED;
1349 }
1350 }
1351
1352trimthenstep6:
1353 /*
1354 * Advance th->th_seq to correspond to first data byte.
1355 * If data, trim to stay within window,
1356 * dropping FIN if necessary.
1357 */
1358 th->th_seq++;
1359 if (tlen > tp->rcv_wnd) {
1360 todrop = tlen - tp->rcv_wnd;
1361 m_adj(m, -todrop);
1362 tlen = tp->rcv_wnd;
1363 thflags &= ~TH_FIN;
1364 tcpstat.tcps_rcvpackafterwin++;
1365 tcpstat.tcps_rcvbyteafterwin += todrop;
1366 }
1367 tp->snd_wl1 = th->th_seq - 1;
1368 tp->rcv_up = th->th_seq;
1369 /*
1370 * Client side of transaction: already sent SYN and data.
1371 * If the remote host used T/TCP to validate the SYN,
1372 * our data will be ACK'd; if so, enter normal data segment
1373 * processing in the middle of step 5, ack processing.
1374 * Otherwise, goto step 6.
1375 */
1376 if (thflags & TH_ACK)
1377 goto process_ACK;
1378 goto step6;
1379 /*
1380 * If the state is LAST_ACK or CLOSING or TIME_WAIT:
1381 * if segment contains a SYN and CC [not CC.NEW] option:
1382 * if state == TIME_WAIT and connection duration > MSL,
1383 * drop packet and send RST;
1384 *
1385 * if SEG.CC > CCrecv then is new SYN, and can implicitly
1386 * ack the FIN (and data) in retransmission queue.
1387 * Complete close and delete TCPCB. Then reprocess
1388 * segment, hoping to find new TCPCB in LISTEN state;
1389 *
1390 * else must be old SYN; drop it.
1391 * else do normal processing.
1392 */
1393 case TCPS_LAST_ACK:
1394 case TCPS_CLOSING:
1395 case TCPS_TIME_WAIT:
1396 if ((thflags & TH_SYN) &&
1397 (to.to_flag & TOF_CC) && tp->cc_recv != 0) {
1398 if (tp->t_state == TCPS_TIME_WAIT &&
1399 (ticks - tp->t_starttime) > tcp_msl)
1400 goto dropwithreset;
1401 if (CC_GT(to.to_cc, tp->cc_recv)) {
1402 tp = tcp_close(tp);
1403 goto findpcb;
1404 }
1405 else
1406 goto drop;
1407 }
1408 break; /* continue normal processing */
1409 }
1410
1411 /*
1412 * States other than LISTEN or SYN_SENT.
1413 * First check the RST flag and sequence number since reset segments
1414 * are exempt from the timestamp and connection count tests. This
1415 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix
1416 * below which allowed reset segments in half the sequence space
1417 * to fall though and be processed (which gives forged reset
1418 * segments with a random sequence number a 50 percent chance of
1419 * killing a connection).
1420 * Then check timestamp, if present.
1421 * Then check the connection count, if present.
1422 * Then check that at least some bytes of segment are within
1423 * receive window. If segment begins before rcv_nxt,
1424 * drop leading data (and SYN); if nothing left, just ack.
1425 *
1426 *
1427 * If the RST bit is set, check the sequence number to see
1428 * if this is a valid reset segment.
1429 * RFC 793 page 37:
1430 * In all states except SYN-SENT, all reset (RST) segments
1431 * are validated by checking their SEQ-fields. A reset is
1432 * valid if its sequence number is in the window.
1433 * Note: this does not take into account delayed ACKs, so
1434 * we should test against last_ack_sent instead of rcv_nxt.
1435 * The sequence number in the reset segment is normally an
1436 * echo of our outgoing acknowlegement numbers, but some hosts
1437 * send a reset with the sequence number at the rightmost edge
1438 * of our receive window, and we have to handle this case.
1439 * If we have multiple segments in flight, the intial reset
1440 * segment sequence numbers will be to the left of last_ack_sent,
1441 * but they will eventually catch up.
1442 * In any case, it never made sense to trim reset segments to
1443 * fit the receive window since RFC 1122 says:
1444 * 4.2.2.12 RST Segment: RFC-793 Section 3.4
1445 *
1446 * A TCP SHOULD allow a received RST segment to include data.
1447 *
1448 * DISCUSSION
1449 * It has been suggested that a RST segment could contain
1450 * ASCII text that encoded and explained the cause of the
1451 * RST. No standard has yet been established for such
1452 * data.
1453 *
1454 * If the reset segment passes the sequence number test examine
1455 * the state:
1456 * SYN_RECEIVED STATE:
1457 * If passive open, return to LISTEN state.
1458 * If active open, inform user that connection was refused.
1459 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES:
1460 * Inform user that connection was reset, and close tcb.
1461 * CLOSING, LAST_ACK STATES:
1462 * Close the tcb.
1463 * TIME_WAIT STATE:
1464 * Drop the segment - see Stevens, vol. 2, p. 964 and
1465 * RFC 1337.
1466 */
1467 if (thflags & TH_RST) {
1468 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
1469 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) {
1470 switch (tp->t_state) {
1471
1472 case TCPS_SYN_RECEIVED:
1473 so->so_error = ECONNREFUSED;
1474 goto close;
1475
1476 case TCPS_ESTABLISHED:
1477 case TCPS_FIN_WAIT_1:
1478 case TCPS_FIN_WAIT_2:
1479 case TCPS_CLOSE_WAIT:
1480 so->so_error = ECONNRESET;
1481 close:
1482 tp->t_state = TCPS_CLOSED;
1483 tcpstat.tcps_drops++;
1484 tp = tcp_close(tp);
1485 break;
1486
1487 case TCPS_CLOSING:
1488 case TCPS_LAST_ACK:
1489 tp = tcp_close(tp);
1490 break;
1491
1492 case TCPS_TIME_WAIT:
1493 break;
1494 }
1495 }
1496 goto drop;
1497 }
1498
1499 /*
1500 * RFC 1323 PAWS: If we have a timestamp reply on this segment
1501 * and it's less than ts_recent, drop it.
1502 */
1503 if ((to.to_flag & TOF_TS) != 0 && tp->ts_recent &&
1504 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
1505
1506 /* Check to see if ts_recent is over 24 days old. */
1507 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) {
1508 /*
1509 * Invalidate ts_recent. If this segment updates
1510 * ts_recent, the age will be reset later and ts_recent
1511 * will get a valid value. If it does not, setting
1512 * ts_recent to zero will at least satisfy the
1513 * requirement that zero be placed in the timestamp
1514 * echo reply when ts_recent isn't valid. The
1515 * age isn't reset until we get a valid ts_recent
1516 * because we don't want out-of-order segments to be
1517 * dropped when ts_recent is old.
1518 */
1519 tp->ts_recent = 0;
1520 } else {
1521 tcpstat.tcps_rcvduppack++;
1522 tcpstat.tcps_rcvdupbyte += tlen;
1523 tcpstat.tcps_pawsdrop++;
1524 goto dropafterack;
1525 }
1526 }
1527
1528 /*
1529 * T/TCP mechanism
1530 * If T/TCP was negotiated and the segment doesn't have CC,
1531 * or if its CC is wrong then drop the segment.
1532 * RST segments do not have to comply with this.
1533 */
1534 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) &&
1535 ((to.to_flag & TOF_CC) == 0 || tp->cc_recv != to.to_cc))
1536 goto dropafterack;
1537
1538 /*
1539 * In the SYN-RECEIVED state, validate that the packet belongs to
1540 * this connection before trimming the data to fit the receive
1541 * window. Check the sequence number versus IRS since we know
1542 * the sequence numbers haven't wrapped. This is a partial fix
1543 * for the "LAND" DoS attack.
1544 */
1545 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs))
1546 goto maybedropwithreset;
1547
1548 todrop = tp->rcv_nxt - th->th_seq;
1549 if (todrop > 0) {
1550 if (thflags & TH_SYN) {
1551 thflags &= ~TH_SYN;
1552 th->th_seq++;
1553 if (th->th_urp > 1)
1554 th->th_urp--;
1555 else
1556 thflags &= ~TH_URG;
1557 todrop--;
1558 }
1559 /*
1560 * Following if statement from Stevens, vol. 2, p. 960.
1561 */
1562 if (todrop > tlen
1563 || (todrop == tlen && (thflags & TH_FIN) == 0)) {
1564 /*
1565 * Any valid FIN must be to the left of the window.
1566 * At this point the FIN must be a duplicate or out
1567 * of sequence; drop it.
1568 */
1569 thflags &= ~TH_FIN;
1570
1571 /*
1572 * Send an ACK to resynchronize and drop any data.
1573 * But keep on processing for RST or ACK.
1574 */
1575 tp->t_flags |= TF_ACKNOW;
1576 todrop = tlen;
1577 tcpstat.tcps_rcvduppack++;
1578 tcpstat.tcps_rcvdupbyte += todrop;
1579 } else {
1580 tcpstat.tcps_rcvpartduppack++;
1581 tcpstat.tcps_rcvpartdupbyte += todrop;
1582 }
1583 drop_hdrlen += todrop; /* drop from the top afterwards */
1584 th->th_seq += todrop;
1585 tlen -= todrop;
1586 if (th->th_urp > todrop)
1587 th->th_urp -= todrop;
1588 else {
1589 thflags &= ~TH_URG;
1590 th->th_urp = 0;
1591 }
1592 }
1593
1594 /*
1595 * If new data are received on a connection after the
1596 * user processes are gone, then RST the other end.
1597 */
1598 if ((so->so_state & SS_NOFDREF) &&
1599 tp->t_state > TCPS_CLOSE_WAIT && tlen) {
1600 tp = tcp_close(tp);
1601 tcpstat.tcps_rcvafterclose++;
1602 goto dropwithreset;
1603 }
1604
1605 /*
1606 * If segment ends after window, drop trailing data
1607 * (and PUSH and FIN); if nothing left, just ACK.
1608 */
1609 todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd);
1610 if (todrop > 0) {
1611 tcpstat.tcps_rcvpackafterwin++;
1612 if (todrop >= tlen) {
1613 tcpstat.tcps_rcvbyteafterwin += tlen;
1614 /*
1615 * If a new connection request is received
1616 * while in TIME_WAIT, drop the old connection
1617 * and start over if the sequence numbers
1618 * are above the previous ones.
1619 */
1620 if (thflags & TH_SYN &&
1621 tp->t_state == TCPS_TIME_WAIT &&
1622 SEQ_GT(th->th_seq, tp->rcv_nxt)) {
1623 iss = tp->snd_nxt + TCP_ISSINCR;
1624 tp = tcp_close(tp);
1625 goto findpcb;
1626 }
1627 /*
1628 * If window is closed can only take segments at
1629 * window edge, and have to drop data and PUSH from
1630 * incoming segments. Continue processing, but
1631 * remember to ack. Otherwise, drop segment
1632 * and ack.
1633 */
1634 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
1635 tp->t_flags |= TF_ACKNOW;
1636 tcpstat.tcps_rcvwinprobe++;
1637 } else
1638 goto dropafterack;
1639 } else
1640 tcpstat.tcps_rcvbyteafterwin += todrop;
1641 m_adj(m, -todrop);
1642 tlen -= todrop;
1643 thflags &= ~(TH_PUSH|TH_FIN);
1644 }
1645
1646 /*
1647 * If last ACK falls within this segment's sequence numbers,
1648 * record its timestamp.
1649 * NOTE that the test is modified according to the latest
1650 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1651 */
1652 if ((to.to_flag & TOF_TS) != 0 &&
1653 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
1654 tp->ts_recent_age = ticks;
1655 tp->ts_recent = to.to_tsval;
1656 }
1657
1658 /*
1659 * If a SYN is in the window, then this is an
1660 * error and we send an RST and drop the connection.
1661 */
1662 if (thflags & TH_SYN) {
1663 tp = tcp_drop(tp, ECONNRESET);
1664 goto dropwithreset;
1665 }
1666
1667 /*
1668 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN
1669 * flag is on (half-synchronized state), then queue data for
1670 * later processing; else drop segment and return.
1671 */
1672 if ((thflags & TH_ACK) == 0) {
1673 if (tp->t_state == TCPS_SYN_RECEIVED ||
1674 (tp->t_flags & TF_NEEDSYN))
1675 goto step6;
1676 else
1677 goto drop;
1678 }
1679
1680 /*
1681 * Ack processing.
1682 */
1683 switch (tp->t_state) {
1684
1685 /*
1686 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter
1687 * ESTABLISHED state and continue processing.
1688 * The ACK was checked above.
1689 */
1690 case TCPS_SYN_RECEIVED:
1691
1692 tcpstat.tcps_connects++;
1693 soisconnected(so);
1694 /* Do window scaling? */
1695 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
1696 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
1697 tp->snd_scale = tp->requested_s_scale;
1698 tp->rcv_scale = tp->request_r_scale;
1699 }
1700 /*
1701 * Upon successful completion of 3-way handshake,
1702 * update cache.CC if it was undefined, pass any queued
1703 * data to the user, and advance state appropriately.
1704 */
1705 if ((taop = tcp_gettaocache(inp)) != NULL &&
1706 taop->tao_cc == 0)
1707 taop->tao_cc = tp->cc_recv;
1708
1709 /*
1710 * Make transitions:
1711 * SYN-RECEIVED -> ESTABLISHED
1712 * SYN-RECEIVED* -> FIN-WAIT-1
1713 */
1714 tp->t_starttime = ticks;
1715 if (tp->t_flags & TF_NEEDFIN) {
1716 tp->t_state = TCPS_FIN_WAIT_1;
1717 tp->t_flags &= ~TF_NEEDFIN;
1718 } else {
1719 tp->t_state = TCPS_ESTABLISHED;
1720 callout_reset(tp->tt_keep, tcp_keepidle,
1721 tcp_timer_keep, tp);
1722 }
1723 /*
1724 * If segment contains data or ACK, will call tcp_reass()
1725 * later; if not, do so now to pass queued data to user.
1726 */
1727 if (tlen == 0 && (thflags & TH_FIN) == 0)
1728 (void) tcp_reass(tp, (struct tcphdr *)0, 0,
1729 (struct mbuf *)0);
1730 tp->snd_wl1 = th->th_seq - 1;
1731 /* fall into ... */
1732
1733 /*
1734 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
1735 * ACKs. If the ack is in the range
1736 * tp->snd_una < th->th_ack <= tp->snd_max
1737 * then advance tp->snd_una to th->th_ack and drop
1738 * data from the retransmission queue. If this ACK reflects
1739 * more up to date window information we update our window information.
1740 */
1741 case TCPS_ESTABLISHED:
1742 case TCPS_FIN_WAIT_1:
1743 case TCPS_FIN_WAIT_2:
1744 case TCPS_CLOSE_WAIT:
1745 case TCPS_CLOSING:
1746 case TCPS_LAST_ACK:
1747 case TCPS_TIME_WAIT:
1748
1749 if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
1750 if (tlen == 0 && tiwin == tp->snd_wnd) {
1751 tcpstat.tcps_rcvdupack++;
1752 /*
1753 * If we have outstanding data (other than
1754 * a window probe), this is a completely
1755 * duplicate ack (ie, window info didn't
1756 * change), the ack is the biggest we've
1757 * seen and we've seen exactly our rexmt
1758 * threshhold of them, assume a packet
1759 * has been dropped and retransmit it.
1760 * Kludge snd_nxt & the congestion
1761 * window so we send only this one
1762 * packet.
1763 *
1764 * We know we're losing at the current
1765 * window size so do congestion avoidance
1766 * (set ssthresh to half the current window
1767 * and pull our congestion window back to
1768 * the new ssthresh).
1769 *
1770 * Dup acks mean that packets have left the
1771 * network (they're now cached at the receiver)
1772 * so bump cwnd by the amount in the receiver
1773 * to keep a constant cwnd packets in the
1774 * network.
1775 */
1776 if (!callout_active(tp->tt_rexmt) ||
1777 th->th_ack != tp->snd_una)
1778 tp->t_dupacks = 0;
1779 else if (++tp->t_dupacks == tcprexmtthresh) {
1780 tcp_seq onxt = tp->snd_nxt;
1781 u_int win =
1782 min(tp->snd_wnd, tp->snd_cwnd) / 2 /
1783 tp->t_maxseg;
1784
1785 if (win < 2)
1786 win = 2;
1787 tp->snd_ssthresh = win * tp->t_maxseg;
1788 callout_stop(tp->tt_rexmt);
1789 tp->t_rtttime = 0;
1790 tp->snd_nxt = th->th_ack;
1791 tp->snd_cwnd = tp->t_maxseg;
1792 (void) tcp_output(tp);
1793 tp->snd_cwnd = tp->snd_ssthresh +
1794 tp->t_maxseg * tp->t_dupacks;
1795 if (SEQ_GT(onxt, tp->snd_nxt))
1796 tp->snd_nxt = onxt;
1797 goto drop;
1798 } else if (tp->t_dupacks > tcprexmtthresh) {
1799 tp->snd_cwnd += tp->t_maxseg;
1800 (void) tcp_output(tp);
1801 goto drop;
1802 }
1803 } else
1804 tp->t_dupacks = 0;
1805 break;
1806 }
1807 /*
1808 * If the congestion window was inflated to account
1809 * for the other side's cached packets, retract it.
1810 */
1811 if (tp->t_dupacks >= tcprexmtthresh &&
1812 tp->snd_cwnd > tp->snd_ssthresh)
1813 tp->snd_cwnd = tp->snd_ssthresh;
1814 tp->t_dupacks = 0;
1815 if (SEQ_GT(th->th_ack, tp->snd_max)) {
1816 tcpstat.tcps_rcvacktoomuch++;
1817 goto dropafterack;
1818 }
1819 /*
1820 * If we reach this point, ACK is not a duplicate,
1821 * i.e., it ACKs something we sent.
1822 */
1823 if (tp->t_flags & TF_NEEDSYN) {
1824 /*
1825 * T/TCP: Connection was half-synchronized, and our
1826 * SYN has been ACK'd (so connection is now fully
1827 * synchronized). Go to non-starred state,
1828 * increment snd_una for ACK of SYN, and check if
1829 * we can do window scaling.
1830 */
1831 tp->t_flags &= ~TF_NEEDSYN;
1832 tp->snd_una++;
1833 /* Do window scaling? */
1834 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
1835 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
1836 tp->snd_scale = tp->requested_s_scale;
1837 tp->rcv_scale = tp->request_r_scale;
1838 }
1839 }
1840
1841process_ACK:
1842 acked = th->th_ack - tp->snd_una;
1843 tcpstat.tcps_rcvackpack++;
1844 tcpstat.tcps_rcvackbyte += acked;
1845
1846 /*
1847 * If we just performed our first retransmit, and the ACK
1848 * arrives within our recovery window, then it was a mistake
1849 * to do the retransmit in the first place. Recover our
1850 * original cwnd and ssthresh, and proceed to transmit where
1851 * we left off.
1852 */
1853 if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) {
1854 tp->snd_cwnd = tp->snd_cwnd_prev;
1855 tp->snd_ssthresh = tp->snd_ssthresh_prev;
1856 tp->snd_nxt = tp->snd_max;
1857 tp->t_badrxtwin = 0; /* XXX probably not required */
1858 }
1859
1860 /*
1861 * If we have a timestamp reply, update smoothed
1862 * round trip time. If no timestamp is present but
1863 * transmit timer is running and timed sequence
1864 * number was acked, update smoothed round trip time.
1865 * Since we now have an rtt measurement, cancel the
1866 * timer backoff (cf., Phil Karn's retransmit alg.).
1867 * Recompute the initial retransmit timer.
1868 */
1869 if (to.to_flag & TOF_TS)
1870 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1);
1871 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq))
1872 tcp_xmit_timer(tp, ticks - tp->t_rtttime);
1873
1874 /*
1875 * If all outstanding data is acked, stop retransmit
1876 * timer and remember to restart (more output or persist).
1877 * If there is more data to be acked, restart retransmit
1878 * timer, using current (possibly backed-off) value.
1879 */
1880 if (th->th_ack == tp->snd_max) {
1881 callout_stop(tp->tt_rexmt);
1882 needoutput = 1;
1883 } else if (!callout_active(tp->tt_persist))
1884 callout_reset(tp->tt_rexmt, tp->t_rxtcur,
1885 tcp_timer_rexmt, tp);
1886
1887 /*
1888 * If no data (only SYN) was ACK'd,
1889 * skip rest of ACK processing.
1890 */
1891 if (acked == 0)
1892 goto step6;
1893
1894 /*
1895 * When new data is acked, open the congestion window.
1896 * If the window gives us less than ssthresh packets
1897 * in flight, open exponentially (maxseg per packet).
1898 * Otherwise open linearly: maxseg per window
1899 * (maxseg^2 / cwnd per packet).
1900 */
1901 {
1902 register u_int cw = tp->snd_cwnd;
1903 register u_int incr = tp->t_maxseg;
1904
1905 if (cw > tp->snd_ssthresh)
1906 incr = incr * incr / cw;
1907 tp->snd_cwnd = min(cw + incr, TCP_MAXWIN << tp->snd_scale);
1908 }
1909 if (acked > so->so_snd.sb_cc) {
1910 tp->snd_wnd -= so->so_snd.sb_cc;
1911 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc);
1912 ourfinisacked = 1;
1913 } else {
1914 sbdrop(&so->so_snd, acked);
1915 tp->snd_wnd -= acked;
1916 ourfinisacked = 0;
1917 }
1918 sowwakeup(so);
1919 tp->snd_una = th->th_ack;
1920 if (SEQ_LT(tp->snd_nxt, tp->snd_una))
1921 tp->snd_nxt = tp->snd_una;
1922
1923 switch (tp->t_state) {
1924
1925 /*
1926 * In FIN_WAIT_1 STATE in addition to the processing
1927 * for the ESTABLISHED state if our FIN is now acknowledged
1928 * then enter FIN_WAIT_2.
1929 */
1930 case TCPS_FIN_WAIT_1:
1931 if (ourfinisacked) {
1932 /*
1933 * If we can't receive any more
1934 * data, then closing user can proceed.
1935 * Starting the timer is contrary to the
1936 * specification, but if we don't get a FIN
1937 * we'll hang forever.
1938 */
1939 if (so->so_state & SS_CANTRCVMORE) {
1940 soisdisconnected(so);
1941 callout_reset(tp->tt_2msl, tcp_maxidle,
1942 tcp_timer_2msl, tp);
1943 }
1944 tp->t_state = TCPS_FIN_WAIT_2;
1945 }
1946 break;
1947
1948 /*
1949 * In CLOSING STATE in addition to the processing for
1950 * the ESTABLISHED state if the ACK acknowledges our FIN
1951 * then enter the TIME-WAIT state, otherwise ignore
1952 * the segment.
1953 */
1954 case TCPS_CLOSING:
1955 if (ourfinisacked) {
1956 tp->t_state = TCPS_TIME_WAIT;
1957 tcp_canceltimers(tp);
1958 /* Shorten TIME_WAIT [RFC-1644, p.28] */
1959 if (tp->cc_recv != 0 &&
1960 (ticks - tp->t_starttime) < tcp_msl)
1961 callout_reset(tp->tt_2msl,
1962 tp->t_rxtcur *
1963 TCPTV_TWTRUNC,
1964 tcp_timer_2msl, tp);
1965 else
1966 callout_reset(tp->tt_2msl, 2 * tcp_msl,
1967 tcp_timer_2msl, tp);
1968 soisdisconnected(so);
1969 }
1970 break;
1971
1972 /*
1973 * In LAST_ACK, we may still be waiting for data to drain
1974 * and/or to be acked, as well as for the ack of our FIN.
1975 * If our FIN is now acknowledged, delete the TCB,
1976 * enter the closed state and return.
1977 */
1978 case TCPS_LAST_ACK:
1979 if (ourfinisacked) {
1980 tp = tcp_close(tp);
1981 goto drop;
1982 }
1983 break;
1984
1985 /*
1986 * In TIME_WAIT state the only thing that should arrive
1987 * is a retransmission of the remote FIN. Acknowledge
1988 * it and restart the finack timer.
1989 */
1990 case TCPS_TIME_WAIT:
1991 callout_reset(tp->tt_2msl, 2 * tcp_msl,
1992 tcp_timer_2msl, tp);
1993 goto dropafterack;
1994 }
1995 }
1996
1997step6:
1998 /*
1999 * Update window information.
2000 * Don't look at window if no ACK: TAC's send garbage on first SYN.
2001 */
2002 if ((thflags & TH_ACK) &&
2003 (SEQ_LT(tp->snd_wl1, th->th_seq) ||
2004 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) ||
2005 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) {
2006 /* keep track of pure window updates */
2007 if (tlen == 0 &&
2008 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)
2009 tcpstat.tcps_rcvwinupd++;
2010 tp->snd_wnd = tiwin;
2011 tp->snd_wl1 = th->th_seq;
2012 tp->snd_wl2 = th->th_ack;
2013 if (tp->snd_wnd > tp->max_sndwnd)
2014 tp->max_sndwnd = tp->snd_wnd;
2015 needoutput = 1;
2016 }
2017
2018 /*
2019 * Process segments with URG.
2020 */
2021 if ((thflags & TH_URG) && th->th_urp &&
2022 TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2023 /*
2024 * This is a kludge, but if we receive and accept
2025 * random urgent pointers, we'll crash in
2026 * soreceive. It's hard to imagine someone
2027 * actually wanting to send this much urgent data.
2028 */
2029 if (th->th_urp + so->so_rcv.sb_cc > sb_max) {
2030 th->th_urp = 0; /* XXX */
2031 thflags &= ~TH_URG; /* XXX */
2032 goto dodata; /* XXX */
2033 }
2034 /*
2035 * If this segment advances the known urgent pointer,
2036 * then mark the data stream. This should not happen
2037 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
2038 * a FIN has been received from the remote side.
2039 * In these states we ignore the URG.
2040 *
2041 * According to RFC961 (Assigned Protocols),
2042 * the urgent pointer points to the last octet
2043 * of urgent data. We continue, however,
2044 * to consider it to indicate the first octet
2045 * of data past the urgent section as the original
2046 * spec states (in one of two places).
2047 */
2048 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) {
2049 tp->rcv_up = th->th_seq + th->th_urp;
2050 so->so_oobmark = so->so_rcv.sb_cc +
2051 (tp->rcv_up - tp->rcv_nxt) - 1;
2052 if (so->so_oobmark == 0)
2053 so->so_state |= SS_RCVATMARK;
2054 sohasoutofband(so);
2055 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
2056 }
2057 /*
2058 * Remove out of band data so doesn't get presented to user.
2059 * This can happen independent of advancing the URG pointer,
2060 * but if two URG's are pending at once, some out-of-band
2061 * data may creep in... ick.
2062 */
2063 if (th->th_urp <= (u_long)tlen
2064#ifdef SO_OOBINLINE
2065 && (so->so_options & SO_OOBINLINE) == 0
2066#endif
2067 )
2068 tcp_pulloutofband(so, th, m,
2069 drop_hdrlen); /* hdr drop is delayed */
2070 } else
2071 /*
2072 * If no out of band data is expected,
2073 * pull receive urgent pointer along
2074 * with the receive window.
2075 */
2076 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
2077 tp->rcv_up = tp->rcv_nxt;
2078dodata: /* XXX */
2079
2080 /*
2081 * Process the segment text, merging it into the TCP sequencing queue,
2082 * and arranging for acknowledgment of receipt if necessary.
2083 * This process logically involves adjusting tp->rcv_wnd as data
2084 * is presented to the user (this happens in tcp_usrreq.c,
2085 * case PRU_RCVD). If a FIN has already been received on this
2086 * connection then we just ignore the text.
2087 */
2088 if ((tlen || (thflags&TH_FIN)) &&
2089 TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2090 m_adj(m, drop_hdrlen); /* delayed header drop */
2091 TCP_REASS(tp, th, &tlen, m, so, thflags);
2092 /*
2093 * Note the amount of data that peer has sent into
2094 * our window, in order to estimate the sender's
2095 * buffer size.
2096 */
2097 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
2098 } else {
2099 m_freem(m);
2100 thflags &= ~TH_FIN;
2101 }
2102
2103 /*
2104 * If FIN is received ACK the FIN and let the user know
2105 * that the connection is closing.
2106 */
2107 if (thflags & TH_FIN) {
2108 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2109 socantrcvmore(so);
2110 /*
2111 * If connection is half-synchronized
2112 * (ie NEEDSYN flag on) then delay ACK,
2113 * so it may be piggybacked when SYN is sent.
2114 * Otherwise, since we received a FIN then no
2115 * more input can be expected, send ACK now.
2116 */
2117 if (tcp_delack_enabled && (tp->t_flags & TF_NEEDSYN))
2118 callout_reset(tp->tt_delack, tcp_delacktime,
2119 tcp_timer_delack, tp);
2120 else
2121 tp->t_flags |= TF_ACKNOW;
2122 tp->rcv_nxt++;
2123 }
2124 switch (tp->t_state) {
2125
2126 /*
2127 * In SYN_RECEIVED and ESTABLISHED STATES
2128 * enter the CLOSE_WAIT state.
2129 */
2130 case TCPS_SYN_RECEIVED:
2131 tp->t_starttime = ticks;
2132 /*FALLTHROUGH*/
2133 case TCPS_ESTABLISHED:
2134 tp->t_state = TCPS_CLOSE_WAIT;
2135 break;
2136
2137 /*
2138 * If still in FIN_WAIT_1 STATE FIN has not been acked so
2139 * enter the CLOSING state.
2140 */
2141 case TCPS_FIN_WAIT_1:
2142 tp->t_state = TCPS_CLOSING;
2143 break;
2144
2145 /*
2146 * In FIN_WAIT_2 state enter the TIME_WAIT state,
2147 * starting the time-wait timer, turning off the other
2148 * standard timers.
2149 */
2150 case TCPS_FIN_WAIT_2:
2151 tp->t_state = TCPS_TIME_WAIT;
2152 tcp_canceltimers(tp);
2153 /* Shorten TIME_WAIT [RFC-1644, p.28] */
2154 if (tp->cc_recv != 0 &&
2155 (ticks - tp->t_starttime) < tcp_msl) {
2156 callout_reset(tp->tt_2msl,
2157 tp->t_rxtcur * TCPTV_TWTRUNC,
2158 tcp_timer_2msl, tp);
2159 /* For transaction client, force ACK now. */
2160 tp->t_flags |= TF_ACKNOW;
2161 }
2162 else
2163 callout_reset(tp->tt_2msl, 2 * tcp_msl,
2164 tcp_timer_2msl, tp);
2165 soisdisconnected(so);
2166 break;
2167
2168 /*
2169 * In TIME_WAIT state restart the 2 MSL time_wait timer.
2170 */
2171 case TCPS_TIME_WAIT:
2172 callout_reset(tp->tt_2msl, 2 * tcp_msl,
2173 tcp_timer_2msl, tp);
2174 break;
2175 }
2176 }
2177#ifdef TCPDEBUG
2178 if (so->so_options & SO_DEBUG)
2179 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen,
2180 &tcp_savetcp, 0);
2181#endif
2182
2183 /*
2184 * Return any desired output.
2185 */
2186 if (needoutput || (tp->t_flags & TF_ACKNOW))
2187 (void) tcp_output(tp);
2188 return;
2189
2190dropafterack:
2191 /*
2192 * Generate an ACK dropping incoming segment if it occupies
2193 * sequence space, where the ACK reflects our state.
2194 *
2195 * We can now skip the test for the RST flag since all
2196 * paths to this code happen after packets containing
2197 * RST have been dropped.
2198 *
2199 * In the SYN-RECEIVED state, don't send an ACK unless the
2200 * segment we received passes the SYN-RECEIVED ACK test.
2201 * If it fails send a RST. This breaks the loop in the
2202 * "LAND" DoS attack, and also prevents an ACK storm
2203 * between two listening ports that have been sent forged
2204 * SYN segments, each with the source address of the other.
2205 */
2206 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
2207 (SEQ_GT(tp->snd_una, th->th_ack) ||
2208 SEQ_GT(th->th_ack, tp->snd_max)) )
2209 goto maybedropwithreset;
2210#ifdef TCPDEBUG
2211 if (so->so_options & SO_DEBUG)
2212 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
2213 &tcp_savetcp, 0);
2214#endif
2215 m_freem(m);
2216 tp->t_flags |= TF_ACKNOW;
2217 (void) tcp_output(tp);
2218 return;
2219
2220
2221 /*
2222 * Conditionally drop with reset or just drop depending on whether
2223 * we think we are under attack or not.
2224 */
2225maybedropwithreset:
2226#ifdef ICMP_BANDLIM
2227 if (badport_bandlim(1) < 0)
2228 goto drop;
2229#endif
2230 /* fall through */
2231dropwithreset:
2232#ifdef TCP_RESTRICT_RST
2233 if (restrict_rst)
2234 goto drop;
2235#endif
2236 /*
2237 * Generate a RST, dropping incoming segment.
2238 * Make ACK acceptable to originator of segment.
2239 * Don't bother to respond if destination was broadcast/multicast.
2240 */
2241 if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST))
2242 goto drop;
2243#ifdef INET6
2244 if (isipv6) {
2245 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
2246 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
2247 goto drop;
2248 } else
2249#endif /* INET6 */
2250 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
2251 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
2252 ip->ip_src.s_addr == htonl(INADDR_BROADCAST))
2253 goto drop;
2254 /* IPv6 anycast check is done at tcp6_input() */
2255#ifdef TCPDEBUG
2256 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
2257 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
2258 &tcp_savetcp, 0);
2259#endif
2260 if (thflags & TH_ACK)
2261 /* mtod() below is safe as long as hdr dropping is delayed */
2262 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack,
2263 TH_RST);
2264 else {
2265 if (thflags & TH_SYN)
2266 tlen++;
2267 /* mtod() below is safe as long as hdr dropping is delayed */
2268 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen,
2269 (tcp_seq)0, TH_RST|TH_ACK);
2270 }
2271 /* destroy temporarily created socket */
2272 if (dropsocket)
2273 (void) soabort(so);
2274 return;
2275
2276drop:
2277 /*
2278 * Drop space held by incoming segment and return.
2279 */
2280#ifdef TCPDEBUG
2281 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
2282 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
2283 &tcp_savetcp, 0);
2284#endif
2285 m_freem(m);
2286 /* destroy temporarily created socket */
2287 if (dropsocket)
2288 (void) soabort(so);
2289 return;
2290}
2291
2292static void
2293tcp_dooptions(tp, cp, cnt, th, to)
2294 struct tcpcb *tp;
2295 u_char *cp;
2296 int cnt;
2297 struct tcphdr *th;
2298 struct tcpopt *to;
2299{
2300 u_short mss = 0;
2301 int opt, optlen;
2302
2303 for (; cnt > 0; cnt -= optlen, cp += optlen) {
2304 opt = cp[0];
2305 if (opt == TCPOPT_EOL)
2306 break;
2307 if (opt == TCPOPT_NOP)
2308 optlen = 1;
2309 else {
2310 optlen = cp[1];
2311 if (optlen <= 0)
2312 break;
2313 }
2314 switch (opt) {
2315
2316 default:
2317 continue;
2318
2319 case TCPOPT_MAXSEG:
2320 if (optlen != TCPOLEN_MAXSEG)
2321 continue;
2322 if (!(th->th_flags & TH_SYN))
2323 continue;
2324 bcopy((char *) cp + 2, (char *) &mss, sizeof(mss));
2325 NTOHS(mss);
2326 break;
2327
2328 case TCPOPT_WINDOW:
2329 if (optlen != TCPOLEN_WINDOW)
2330 continue;
2331 if (!(th->th_flags & TH_SYN))
2332 continue;
2333 tp->t_flags |= TF_RCVD_SCALE;
2334 tp->requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT);
2335 break;
2336
2337 case TCPOPT_TIMESTAMP:
2338 if (optlen != TCPOLEN_TIMESTAMP)
2339 continue;
2340 to->to_flag |= TOF_TS;
2341 bcopy((char *)cp + 2,
2342 (char *)&to->to_tsval, sizeof(to->to_tsval));
2343 NTOHL(to->to_tsval);
2344 bcopy((char *)cp + 6,
2345 (char *)&to->to_tsecr, sizeof(to->to_tsecr));
2346 NTOHL(to->to_tsecr);
2347
2348 /*
2349 * A timestamp received in a SYN makes
2350 * it ok to send timestamp requests and replies.
2351 */
2352 if (th->th_flags & TH_SYN) {
2353 tp->t_flags |= TF_RCVD_TSTMP;
2354 tp->ts_recent = to->to_tsval;
2355 tp->ts_recent_age = ticks;
2356 }
2357 break;
2358 case TCPOPT_CC:
2359 if (optlen != TCPOLEN_CC)
2360 continue;
2361 to->to_flag |= TOF_CC;
2362 bcopy((char *)cp + 2,
2363 (char *)&to->to_cc, sizeof(to->to_cc));
2364 NTOHL(to->to_cc);
2365 /*
2366 * A CC or CC.new option received in a SYN makes
2367 * it ok to send CC in subsequent segments.
2368 */
2369 if (th->th_flags & TH_SYN)
2370 tp->t_flags |= TF_RCVD_CC;
2371 break;
2372 case TCPOPT_CCNEW:
2373 if (optlen != TCPOLEN_CC)
2374 continue;
2375 if (!(th->th_flags & TH_SYN))
2376 continue;
2377 to->to_flag |= TOF_CCNEW;
2378 bcopy((char *)cp + 2,
2379 (char *)&to->to_cc, sizeof(to->to_cc));
2380 NTOHL(to->to_cc);
2381 /*
2382 * A CC or CC.new option received in a SYN makes
2383 * it ok to send CC in subsequent segments.
2384 */
2385 tp->t_flags |= TF_RCVD_CC;
2386 break;
2387 case TCPOPT_CCECHO:
2388 if (optlen != TCPOLEN_CC)
2389 continue;
2390 if (!(th->th_flags & TH_SYN))
2391 continue;
2392 to->to_flag |= TOF_CCECHO;
2393 bcopy((char *)cp + 2,
2394 (char *)&to->to_ccecho, sizeof(to->to_ccecho));
2395 NTOHL(to->to_ccecho);
2396 break;
2397 }
2398 }
2399 if (th->th_flags & TH_SYN)
2400 tcp_mss(tp, mss); /* sets t_maxseg */
2401}
2402
2403/*
2404 * Pull out of band byte out of a segment so
2405 * it doesn't appear in the user's data queue.
2406 * It is still reflected in the segment length for
2407 * sequencing purposes.
2408 */
2409static void
2410tcp_pulloutofband(so, th, m, off)
2411 struct socket *so;
2412 struct tcphdr *th;
2413 register struct mbuf *m;
2414 int off; /* delayed to be droped hdrlen */
2415{
2416 int cnt = off + th->th_urp - 1;
2417
2418 while (cnt >= 0) {
2419 if (m->m_len > cnt) {
2420 char *cp = mtod(m, caddr_t) + cnt;
2421 struct tcpcb *tp = sototcpcb(so);
2422
2423 tp->t_iobc = *cp;
2424 tp->t_oobflags |= TCPOOB_HAVEDATA;
2425 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1));
2426 m->m_len--;
2427 if (m->m_flags & M_PKTHDR)
2428 m->m_pkthdr.len--;
2429 return;
2430 }
2431 cnt -= m->m_len;
2432 m = m->m_next;
2433 if (m == 0)
2434 break;
2435 }
2436 panic("tcp_pulloutofband");
2437}
2438
2439/*
2440 * Collect new round-trip time estimate
2441 * and update averages and current timeout.
2442 */
2443static void
2444tcp_xmit_timer(tp, rtt)
2445 register struct tcpcb *tp;
2446 int rtt;
2447{
2448 register int delta;
2449
2450 tcpstat.tcps_rttupdated++;
2451 tp->t_rttupdated++;
2452 if (tp->t_srtt != 0) {
2453 /*
2454 * srtt is stored as fixed point with 5 bits after the
2455 * binary point (i.e., scaled by 8). The following magic
2456 * is equivalent to the smoothing algorithm in rfc793 with
2457 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
2458 * point). Adjust rtt to origin 0.
2459 */
2460 delta = ((rtt - 1) << TCP_DELTA_SHIFT)
2461 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
2462
2463 if ((tp->t_srtt += delta) <= 0)
2464 tp->t_srtt = 1;
2465
2466 /*
2467 * We accumulate a smoothed rtt variance (actually, a
2468 * smoothed mean difference), then set the retransmit
2469 * timer to smoothed rtt + 4 times the smoothed variance.
2470 * rttvar is stored as fixed point with 4 bits after the
2471 * binary point (scaled by 16). The following is
2472 * equivalent to rfc793 smoothing with an alpha of .75
2473 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces
2474 * rfc793's wired-in beta.
2475 */
2476 if (delta < 0)
2477 delta = -delta;
2478 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
2479 if ((tp->t_rttvar += delta) <= 0)
2480 tp->t_rttvar = 1;
2481 } else {
2482 /*
2483 * No rtt measurement yet - use the unsmoothed rtt.
2484 * Set the variance to half the rtt (so our first
2485 * retransmit happens at 3*rtt).
2486 */
2487 tp->t_srtt = rtt << TCP_RTT_SHIFT;
2488 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
2489 }
2490 tp->t_rtttime = 0;
2491 tp->t_rxtshift = 0;
2492
2493 /*
2494 * the retransmit should happen at rtt + 4 * rttvar.
2495 * Because of the way we do the smoothing, srtt and rttvar
2496 * will each average +1/2 tick of bias. When we compute
2497 * the retransmit timer, we want 1/2 tick of rounding and
2498 * 1 extra tick because of +-1/2 tick uncertainty in the
2499 * firing of the timer. The bias will give us exactly the
2500 * 1.5 tick we need. But, because the bias is
2501 * statistical, we have to test that we don't drop below
2502 * the minimum feasible timer (which is 2 ticks).
2503 */
2504 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
2505 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);
2506
2507 /*
2508 * We received an ack for a packet that wasn't retransmitted;
2509 * it is probably safe to discard any error indications we've
2510 * received recently. This isn't quite right, but close enough
2511 * for now (a route might have failed after we sent a segment,
2512 * and the return path might not be symmetrical).
2513 */
2514 tp->t_softerror = 0;
2515}
2516
2517/*
2518 * Determine a reasonable value for maxseg size.
2519 * If the route is known, check route for mtu.
2520 * If none, use an mss that can be handled on the outgoing
2521 * interface without forcing IP to fragment; if bigger than
2522 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES
2523 * to utilize large mbufs. If no route is found, route has no mtu,
2524 * or the destination isn't local, use a default, hopefully conservative
2525 * size (usually 512 or the default IP max size, but no more than the mtu
2526 * of the interface), as we can't discover anything about intervening
2527 * gateways or networks. We also initialize the congestion/slow start
2528 * window to be a single segment if the destination isn't local.
2529 * While looking at the routing entry, we also initialize other path-dependent
2530 * parameters from pre-set or cached values in the routing entry.
2531 *
2532 * Also take into account the space needed for options that we
2533 * send regularly. Make maxseg shorter by that amount to assure
2534 * that we can send maxseg amount of data even when the options
2535 * are present. Store the upper limit of the length of options plus
2536 * data in maxopd.
2537 *
2538 * NOTE that this routine is only called when we process an incoming
2539 * segment, for outgoing segments only tcp_mssopt is called.
2540 *
2541 * In case of T/TCP, we call this routine during implicit connection
2542 * setup as well (offer = -1), to initialize maxseg from the cached
2543 * MSS of our peer.
2544 */
2545void
2546tcp_mss(tp, offer)
2547 struct tcpcb *tp;
2548 int offer;
2549{
2550 register struct rtentry *rt;
2551 struct ifnet *ifp;
2552 register int rtt, mss;
2553 u_long bufsize;
2554 struct inpcb *inp;
2555 struct socket *so;
2556 struct rmxp_tao *taop;
2557 int origoffer = offer;
2558#ifdef INET6
2559 int isipv6;
2560 int min_protoh;
2561#endif
2562
2563 inp = tp->t_inpcb;
2564#ifdef INET6
2565 isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0;
2566 min_protoh = isipv6 ? sizeof (struct ip6_hdr) + sizeof (struct tcphdr)
2567 : sizeof (struct tcpiphdr);
2568#else
2569#define min_protoh (sizeof (struct tcpiphdr))
2570#endif
2571#ifdef INET6
2572 if (isipv6)
2573 rt = tcp_rtlookup6(inp);
2574 else
2575#endif
2576 rt = tcp_rtlookup(inp);
2577 if (rt == NULL) {
2578 tp->t_maxopd = tp->t_maxseg =
2579#ifdef INET6
2580 isipv6 ? tcp_v6mssdflt :
2581#endif /* INET6 */
2582 tcp_mssdflt;
2583 return;
2584 }
2585 ifp = rt->rt_ifp;
2586 so = inp->inp_socket;
2587
2588 taop = rmx_taop(rt->rt_rmx);
2589 /*
2590 * Offer == -1 means that we didn't receive SYN yet,
2591 * use cached value in that case;
2592 */
2593 if (offer == -1)
2594 offer = taop->tao_mssopt;
2595 /*
2596 * Offer == 0 means that there was no MSS on the SYN segment,
2597 * in this case we use tcp_mssdflt.
2598 */
2599 if (offer == 0)
2600 offer =
2601#ifdef INET6
2602 isipv6 ? tcp_v6mssdflt :
2603#endif /* INET6 */
2604 tcp_mssdflt;
2605 else
2606 /*
2607 * Sanity check: make sure that maxopd will be large
2608 * enough to allow some data on segments even is the
2609 * all the option space is used (40bytes). Otherwise
2610 * funny things may happen in tcp_output.
2611 */
2612 offer = max(offer, 64);
2613 taop->tao_mssopt = offer;
2614
2615 /*
2616 * While we're here, check if there's an initial rtt
2617 * or rttvar. Convert from the route-table units
2618 * to scaled multiples of the slow timeout timer.
2619 */
2620 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) {
2621 /*
2622 * XXX the lock bit for RTT indicates that the value
2623 * is also a minimum value; this is subject to time.
2624 */
2625 if (rt->rt_rmx.rmx_locks & RTV_RTT)
2626 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz);
2627 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE));
2628 tcpstat.tcps_usedrtt++;
2629 if (rt->rt_rmx.rmx_rttvar) {
2630 tp->t_rttvar = rt->rt_rmx.rmx_rttvar /
2631 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE));
2632 tcpstat.tcps_usedrttvar++;
2633 } else {
2634 /* default variation is +- 1 rtt */
2635 tp->t_rttvar =
2636 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
2637 }
2638 TCPT_RANGESET(tp->t_rxtcur,
2639 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
2640 tp->t_rttmin, TCPTV_REXMTMAX);
2641 }
2642 /*
2643 * if there's an mtu associated with the route, use it
2644 * else, use the link mtu.
2645 */
2646 if (rt->rt_rmx.rmx_mtu)
2647 mss = rt->rt_rmx.rmx_mtu - min_protoh;
2648 else
2649 {
2650 mss =
2651#ifdef INET6
2652 (isipv6 ? nd_ifinfo[rt->rt_ifp->if_index].linkmtu :
2653#endif
2654 ifp->if_mtu
2655#ifdef INET6
2656 )
2657#endif
2658 - min_protoh;
2659#ifdef INET6
2660 if (isipv6) {
2661 if (!in6_localaddr(&inp->in6p_faddr))
2662 mss = min(mss, tcp_v6mssdflt);
2663 } else
2664#endif
2665 if (!in_localaddr(inp->inp_faddr))
2666 mss = min(mss, tcp_mssdflt);
2667 }
2668 mss = min(mss, offer);
2669 /*
2670 * maxopd stores the maximum length of data AND options
2671 * in a segment; maxseg is the amount of data in a normal
2672 * segment. We need to store this value (maxopd) apart
2673 * from maxseg, because now every segment carries options
2674 * and thus we normally have somewhat less data in segments.
2675 */
2676 tp->t_maxopd = mss;
2677
2678 /*
2679 * In case of T/TCP, origoffer==-1 indicates, that no segments
2680 * were received yet. In this case we just guess, otherwise
2681 * we do the same as before T/TCP.
2682 */
2683 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
2684 (origoffer == -1 ||
2685 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP))
2686 mss -= TCPOLEN_TSTAMP_APPA;
2687 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC &&
2688 (origoffer == -1 ||
2689 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC))
2690 mss -= TCPOLEN_CC_APPA;
2691
2692#if (MCLBYTES & (MCLBYTES - 1)) == 0
2693 if (mss > MCLBYTES)
2694 mss &= ~(MCLBYTES-1);
2695#else
2696 if (mss > MCLBYTES)
2697 mss = mss / MCLBYTES * MCLBYTES;
2698#endif
2699 /*
2700 * If there's a pipesize, change the socket buffer
2701 * to that size. Make the socket buffers an integral
2702 * number of mss units; if the mss is larger than
2703 * the socket buffer, decrease the mss.
2704 */
2705#ifdef RTV_SPIPE
2706 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0)
2707#endif
2708 bufsize = so->so_snd.sb_hiwat;
2709 if (bufsize < mss)
2710 mss = bufsize;
2711 else {
2712 bufsize = roundup(bufsize, mss);
2713 if (bufsize > sb_max)
2714 bufsize = sb_max;
2715 (void)sbreserve(&so->so_snd, bufsize, so, NULL);
2716 }
2717 tp->t_maxseg = mss;
2718
2719#ifdef RTV_RPIPE
2720 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0)
2721#endif
2722 bufsize = so->so_rcv.sb_hiwat;
2723 if (bufsize > mss) {
2724 bufsize = roundup(bufsize, mss);
2725 if (bufsize > sb_max)
2726 bufsize = sb_max;
2727 (void)sbreserve(&so->so_rcv, bufsize, so, NULL);
2728 }
2729
2730 /*
2731 * Set the slow-start flight size depending on whether this
2732 * is a local network or not.
2733 */
2734 if (
2735#ifdef INET6
2736 (isipv6 && in6_localaddr(&inp->in6p_faddr)) ||
2737 (!isipv6 &&
2738#endif
2739 in_localaddr(inp->inp_faddr)
2740#ifdef INET6
2741 )
2742#endif
2743 )
2744 tp->snd_cwnd = mss * ss_fltsz_local;
2745 else
2746 tp->snd_cwnd = mss * ss_fltsz;
2747
2748 if (rt->rt_rmx.rmx_ssthresh) {
2749 /*
2750 * There's some sort of gateway or interface
2751 * buffer limit on the path. Use this to set
2752 * the slow start threshhold, but set the
2753 * threshold to no less than 2*mss.
2754 */
2755 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh);
2756 tcpstat.tcps_usedssthresh++;
2757 }
2758}
2759
2760/*
2761 * Determine the MSS option to send on an outgoing SYN.
2762 */
2763int
2764tcp_mssopt(tp)
2765 struct tcpcb *tp;
2766{
2767 struct rtentry *rt;
2768#ifdef INET6
2769 int isipv6;
2770 int min_protoh;
2771#endif
2772
2773#ifdef INET6
2774 isipv6 = ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) ? 1 : 0;
2775 min_protoh = isipv6 ? sizeof (struct ip6_hdr) + sizeof (struct tcphdr)
2776 : sizeof (struct tcpiphdr);
2777#else
2778#define min_protoh (sizeof (struct tcpiphdr))
2779#endif
2780#ifdef INET6
2781 if (isipv6)
2782 rt = tcp_rtlookup6(tp->t_inpcb);
2783 else
2784#endif /* INET6 */
2785 rt = tcp_rtlookup(tp->t_inpcb);
2786 if (rt == NULL)
2787 return
2788#ifdef INET6
2789 isipv6 ? tcp_v6mssdflt :
2790#endif /* INET6 */
2791 tcp_mssdflt;
2792
2793 return rt->rt_ifp->if_mtu - min_protoh;
2794}
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