103MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry");
104
105static int tcprexmtthresh = 3;
106tcp_seq tcp_iss;
107tcp_cc tcp_ccgen;
108
109struct tcpstat tcpstat;
110SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RD,
111 &tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)");
112
113static int log_in_vain = 0;
114SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW,
115 &log_in_vain, 0, "Log all incoming TCP connections");
116
117static int blackhole = 0;
118SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW,
119 &blackhole, 0, "Do not send RST when dropping refused connections");
120
121int tcp_delack_enabled = 1;
122SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW,
123 &tcp_delack_enabled, 0,
124 "Delay ACK to try and piggyback it onto a data packet");
125
126#ifdef TCP_DROP_SYNFIN
127static int drop_synfin = 0;
128SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW,
129 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set");
130#endif
131
132#ifdef TCP_RESTRICT_RST
133static int restrict_rst = 0;
134SYSCTL_INT(_net_inet_tcp, OID_AUTO, restrict_rst, CTLFLAG_RW,
135 &restrict_rst, 0, "Restrict RST emission");
136#endif
137
138struct inpcbhead tcb;
139#define tcb6 tcb /* for KAME src sync over BSD*'s */
140struct inpcbinfo tcbinfo;
141
142static void tcp_dooptions __P((struct tcpcb *,
143 u_char *, int, struct tcphdr *, struct tcpopt *));
144static void tcp_pulloutofband __P((struct socket *,
145 struct tcphdr *, struct mbuf *, int));
146static int tcp_reass __P((struct tcpcb *, struct tcphdr *, int *,
147 struct mbuf *));
148static void tcp_xmit_timer __P((struct tcpcb *, int));
149
150/* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */
151#ifdef INET6
152#define ND6_HINT(tp) \
153do { \
154 if ((tp) && (tp)->t_inpcb && \
155 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0 && \
156 (tp)->t_inpcb->in6p_route.ro_rt) \
157 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL); \
158} while (0)
159#else
160#define ND6_HINT(tp)
161#endif
162
163/*
164 * Insert segment which inludes th into reassembly queue of tcp with
165 * control block tp. Return TH_FIN if reassembly now includes
166 * a segment with FIN. The macro form does the common case inline
167 * (segment is the next to be received on an established connection,
168 * and the queue is empty), avoiding linkage into and removal
169 * from the queue and repetition of various conversions.
170 * Set DELACK for segments received in order, but ack immediately
171 * when segments are out of order (so fast retransmit can work).
172 */
173#define TCP_REASS(tp, th, tlenp, m, so, flags) { \
174 if ((th)->th_seq == (tp)->rcv_nxt && \
175 LIST_EMPTY(&(tp)->t_segq) && \
176 (tp)->t_state == TCPS_ESTABLISHED) { \
177 if (tcp_delack_enabled) \
178 callout_reset(tp->tt_delack, tcp_delacktime, \
179 tcp_timer_delack, tp); \
180 else \
181 tp->t_flags |= TF_ACKNOW; \
182 (tp)->rcv_nxt += *(tlenp); \
183 flags = (th)->th_flags & TH_FIN; \
184 tcpstat.tcps_rcvpack++;\
185 tcpstat.tcps_rcvbyte += *(tlenp);\
186 ND6_HINT(tp); \
187 sbappend(&(so)->so_rcv, (m)); \
188 sorwakeup(so); \
189 } else { \
190 (flags) = tcp_reass((tp), (th), (tlenp), (m)); \
191 tp->t_flags |= TF_ACKNOW; \
192 } \
193}
194
195static int
196tcp_reass(tp, th, tlenp, m)
197 register struct tcpcb *tp;
198 register struct tcphdr *th;
199 int *tlenp;
200 struct mbuf *m;
201{
202 struct tseg_qent *q;
203 struct tseg_qent *p = NULL;
204 struct tseg_qent *nq;
205 struct tseg_qent *te;
206 struct socket *so = tp->t_inpcb->inp_socket;
207 int flags;
208
209 /*
210 * Call with th==0 after become established to
211 * force pre-ESTABLISHED data up to user socket.
212 */
213 if (th == 0)
214 goto present;
215
216 /* Allocate a new queue entry. If we can't, just drop the pkt. XXX */
217 MALLOC(te, struct tseg_qent *, sizeof (struct tseg_qent), M_TSEGQ,
218 M_NOWAIT);
219 if (te == NULL) {
220 tcpstat.tcps_rcvmemdrop++;
221 m_freem(m);
222 return (0);
223 }
224
225 /*
226 * Find a segment which begins after this one does.
227 */
228 LIST_FOREACH(q, &tp->t_segq, tqe_q) {
229 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
230 break;
231 p = q;
232 }
233
234 /*
235 * If there is a preceding segment, it may provide some of
236 * our data already. If so, drop the data from the incoming
237 * segment. If it provides all of our data, drop us.
238 */
239 if (p != NULL) {
240 register int i;
241 /* conversion to int (in i) handles seq wraparound */
242 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
243 if (i > 0) {
244 if (i >= *tlenp) {
245 tcpstat.tcps_rcvduppack++;
246 tcpstat.tcps_rcvdupbyte += *tlenp;
247 m_freem(m);
248 FREE(te, M_TSEGQ);
249 /*
250 * Try to present any queued data
251 * at the left window edge to the user.
252 * This is needed after the 3-WHS
253 * completes.
254 */
255 goto present; /* ??? */
256 }
257 m_adj(m, i);
258 *tlenp -= i;
259 th->th_seq += i;
260 }
261 }
262 tcpstat.tcps_rcvoopack++;
263 tcpstat.tcps_rcvoobyte += *tlenp;
264
265 /*
266 * While we overlap succeeding segments trim them or,
267 * if they are completely covered, dequeue them.
268 */
269 while (q) {
270 register int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
271 if (i <= 0)
272 break;
273 if (i < q->tqe_len) {
274 q->tqe_th->th_seq += i;
275 q->tqe_len -= i;
276 m_adj(q->tqe_m, i);
277 break;
278 }
279
280 nq = LIST_NEXT(q, tqe_q);
281 LIST_REMOVE(q, tqe_q);
282 m_freem(q->tqe_m);
283 FREE(q, M_TSEGQ);
284 q = nq;
285 }
286
287 /* Insert the new segment queue entry into place. */
288 te->tqe_m = m;
289 te->tqe_th = th;
290 te->tqe_len = *tlenp;
291
292 if (p == NULL) {
293 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q);
294 } else {
295 LIST_INSERT_AFTER(p, te, tqe_q);
296 }
297
298present:
299 /*
300 * Present data to user, advancing rcv_nxt through
301 * completed sequence space.
302 */
303 if (!TCPS_HAVEESTABLISHED(tp->t_state))
304 return (0);
305 q = LIST_FIRST(&tp->t_segq);
306 if (!q || q->tqe_th->th_seq != tp->rcv_nxt)
307 return (0);
308 do {
309 tp->rcv_nxt += q->tqe_len;
310 flags = q->tqe_th->th_flags & TH_FIN;
311 nq = LIST_NEXT(q, tqe_q);
312 LIST_REMOVE(q, tqe_q);
313 if (so->so_state & SS_CANTRCVMORE)
314 m_freem(q->tqe_m);
315 else
316 sbappend(&so->so_rcv, q->tqe_m);
317 FREE(q, M_TSEGQ);
318 q = nq;
319 } while (q && q->tqe_th->th_seq == tp->rcv_nxt);
320 ND6_HINT(tp);
321 sorwakeup(so);
322 return (flags);
323}
324
325/*
326 * TCP input routine, follows pages 65-76 of the
327 * protocol specification dated September, 1981 very closely.
328 */
329#ifdef INET6
330int
331tcp6_input(mp, offp, proto)
332 struct mbuf **mp;
333 int *offp, proto;
334{
335 register struct mbuf *m = *mp;
336
337 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE);
338
339 /*
340 * draft-itojun-ipv6-tcp-to-anycast
341 * better place to put this in?
342 */
343 if (m->m_flags & M_ANYCAST6) {
344 struct ip6_hdr *ip6;
345
346 ip6 = mtod(m, struct ip6_hdr *);
347 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
348 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6);
349 return IPPROTO_DONE;
350 }
351
352 tcp_input(m, *offp, proto);
353 return IPPROTO_DONE;
354}
355#endif
356
357void
358tcp_input(m, off0, proto)
359 register struct mbuf *m;
360 int off0, proto;
361{
362 register struct tcphdr *th;
363 register struct ip *ip = NULL;
364 register struct ipovly *ipov;
365 register struct inpcb *inp;
366 u_char *optp = NULL;
367 int optlen = 0;
368 int len, tlen, off;
369 int drop_hdrlen;
370 register struct tcpcb *tp = 0;
371 register int thflags;
372 struct socket *so = 0;
373 int todrop, acked, ourfinisacked, needoutput = 0;
374 struct in_addr laddr;
375#ifdef INET6
376 struct in6_addr laddr6;
377#endif
378 int dropsocket = 0;
379 int iss = 0;
380 u_long tiwin;
381 struct tcpopt to; /* options in this segment */
382 struct rmxp_tao *taop; /* pointer to our TAO cache entry */
383 struct rmxp_tao tao_noncached; /* in case there's no cached entry */
384#ifdef TCPDEBUG
385 short ostate = 0;
386#endif
387#ifdef INET6
388 struct ip6_hdr *ip6 = NULL;
389 int isipv6;
390#endif /* INET6 */
391
392#ifdef INET6
393 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0;
394#endif
395 bzero((char *)&to, sizeof(to));
396
397 tcpstat.tcps_rcvtotal++;
398
399#ifdef INET6
400 if (isipv6) {
401 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */
402 ip6 = mtod(m, struct ip6_hdr *);
403 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0;
404 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) {
405 tcpstat.tcps_rcvbadsum++;
406 goto drop;
407 }
408 th = (struct tcphdr *)((caddr_t)ip6 + off0);
409 } else
410#endif /* INET6 */
411 {
412 /*
413 * Get IP and TCP header together in first mbuf.
414 * Note: IP leaves IP header in first mbuf.
415 */
416 if (off0 > sizeof (struct ip)) {
417 ip_stripoptions(m, (struct mbuf *)0);
418 off0 = sizeof(struct ip);
419 }
420 if (m->m_len < sizeof (struct tcpiphdr)) {
421 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) {
422 tcpstat.tcps_rcvshort++;
423 return;
424 }
425 }
426 ip = mtod(m, struct ip *);
427 ipov = (struct ipovly *)ip;
| 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;
|
439 if (th->th_sum) {
440 tcpstat.tcps_rcvbadsum++;
441 goto drop;
442 }
443#ifdef INET6
444 /* Re-initialization for later version check */
445 ip->ip_v = IPVERSION;
446#endif
447 }
448
449 /*
450 * Check that TCP offset makes sense,
451 * pull out TCP options and adjust length. XXX
452 */
453 off = th->th_off << 2;
454 if (off < sizeof (struct tcphdr) || off > tlen) {
455 tcpstat.tcps_rcvbadoff++;
456 goto drop;
457 }
458 tlen -= off; /* tlen is used instead of ti->ti_len */
459 if (off > sizeof (struct tcphdr)) {
460#ifdef INET6
461 if (isipv6) {
462 IP6_EXTHDR_CHECK(m, off0, off, );
463 ip6 = mtod(m, struct ip6_hdr *);
464 th = (struct tcphdr *)((caddr_t)ip6 + off0);
465 } else
466#endif /* INET6 */
467 {
468 if (m->m_len < sizeof(struct ip) + off) {
469 if ((m = m_pullup(m, sizeof (struct ip) + off)) == 0) {
470 tcpstat.tcps_rcvshort++;
471 return;
472 }
473 ip = mtod(m, struct ip *);
474 ipov = (struct ipovly *)ip;
475 th = (struct tcphdr *)((caddr_t)ip + off0);
476 }
477 }
478 optlen = off - sizeof (struct tcphdr);
479 optp = (u_char *)(th + 1);
480 }
481 thflags = th->th_flags;
482
483#ifdef TCP_DROP_SYNFIN
484 /*
485 * If the drop_synfin option is enabled, drop all packets with
486 * both the SYN and FIN bits set. This prevents e.g. nmap from
487 * identifying the TCP/IP stack.
488 *
489 * This is incompatible with RFC1644 extensions (T/TCP).
490 */
491 if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN))
492 goto drop;
493#endif
494
495 /*
496 * Convert TCP protocol specific fields to host format.
497 */
498 NTOHL(th->th_seq);
499 NTOHL(th->th_ack);
500 NTOHS(th->th_win);
501 NTOHS(th->th_urp);
502
503 /*
504 * Delay droping TCP, IP headers, IPv6 ext headers, and TCP options,
505 * until after ip6_savecontrol() is called and before other functions
506 * which don't want those proto headers.
507 * Because ip6_savecontrol() is going to parse the mbuf to
508 * search for data to be passed up to user-land, it wants mbuf
509 * parameters to be unchanged.
510 */
511 drop_hdrlen = off0 + off;
512
513 /*
514 * Locate pcb for segment.
515 */
516findpcb:
517#ifdef IPFIREWALL_FORWARD
518 if (ip_fw_fwd_addr != NULL
519#ifdef INET6
520 && isipv6 == NULL /* IPv6 support is not yet */
521#endif /* INET6 */
522 ) {
523 /*
524 * Diverted. Pretend to be the destination.
525 * already got one like this?
526 */
527 inp = in_pcblookup_hash(&tcbinfo, ip->ip_src, th->th_sport,
528 ip->ip_dst, th->th_dport, 0, m->m_pkthdr.rcvif);
529 if (!inp) {
530 /*
531 * No, then it's new. Try find the ambushing socket
532 */
533 if (!ip_fw_fwd_addr->sin_port) {
534 inp = in_pcblookup_hash(&tcbinfo, ip->ip_src,
535 th->th_sport, ip_fw_fwd_addr->sin_addr,
536 th->th_dport, 1, m->m_pkthdr.rcvif);
537 } else {
538 inp = in_pcblookup_hash(&tcbinfo,
539 ip->ip_src, th->th_sport,
540 ip_fw_fwd_addr->sin_addr,
541 ntohs(ip_fw_fwd_addr->sin_port), 1,
542 m->m_pkthdr.rcvif);
543 }
544 }
545 ip_fw_fwd_addr = NULL;
546 } else
547#endif /* IPFIREWALL_FORWARD */
548 {
549#ifdef INET6
550 if (isipv6)
551 inp = in6_pcblookup_hash(&tcbinfo, &ip6->ip6_src, th->th_sport,
552 &ip6->ip6_dst, th->th_dport, 1,
553 m->m_pkthdr.rcvif);
554 else
555#endif /* INET6 */
556 inp = in_pcblookup_hash(&tcbinfo, ip->ip_src, th->th_sport,
557 ip->ip_dst, th->th_dport, 1, m->m_pkthdr.rcvif);
558 }
559
560#ifdef IPSEC
561#ifdef INET6
562 if (isipv6) {
563 if (inp != NULL && ipsec6_in_reject_so(m, inp->inp_socket)) {
564 ipsec6stat.in_polvio++;
565 goto drop;
566 }
567 } else
568#endif /* INET6 */
569 if (inp != NULL && ipsec4_in_reject_so(m, inp->inp_socket)) {
570 ipsecstat.in_polvio++;
571 goto drop;
572 }
573#endif /*IPSEC*/
574
575 /*
576 * If the state is CLOSED (i.e., TCB does not exist) then
577 * all data in the incoming segment is discarded.
578 * If the TCB exists but is in CLOSED state, it is embryonic,
579 * but should either do a listen or a connect soon.
580 */
581 if (inp == NULL) {
582 if (log_in_vain) {
583#ifdef INET6
584 char dbuf[INET6_ADDRSTRLEN], sbuf[INET6_ADDRSTRLEN];
585#else /* INET6 */
586 char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"];
587#endif /* INET6 */
588
589#ifdef INET6
590 if (isipv6) {
591 strcpy(dbuf, ip6_sprintf(&ip6->ip6_dst));
592 strcpy(sbuf, ip6_sprintf(&ip6->ip6_src));
593 } else
594#endif
595 {
596 strcpy(dbuf, inet_ntoa(ip->ip_dst));
597 strcpy(sbuf, inet_ntoa(ip->ip_src));
598 }
599 switch (log_in_vain) {
600 case 1:
601 if(thflags & TH_SYN)
602 log(LOG_INFO,
603 "Connection attempt to TCP %s:%d from %s:%d\n",
604 dbuf, ntohs(th->th_dport),
605 sbuf,
606 ntohs(th->th_sport));
607 break;
608 case 2:
609 log(LOG_INFO,
610 "Connection attempt to TCP %s:%d from %s:%d flags:0x%x\n",
611 dbuf, ntohs(th->th_dport), sbuf,
612 ntohs(th->th_sport), thflags);
613 break;
614 default:
615 break;
616 }
617 }
618 if (blackhole) {
619 switch (blackhole) {
620 case 1:
621 if (thflags & TH_SYN)
622 goto drop;
623 break;
624 case 2:
625 goto drop;
626 default:
627 goto drop;
628 }
629 }
630 goto maybedropwithreset;
631 }
632 tp = intotcpcb(inp);
633 if (tp == 0)
634 goto maybedropwithreset;
635 if (tp->t_state == TCPS_CLOSED)
636 goto drop;
637
638 /* Unscale the window into a 32-bit value. */
639 if ((thflags & TH_SYN) == 0)
640 tiwin = th->th_win << tp->snd_scale;
641 else
642 tiwin = th->th_win;
643
644#ifdef INET6
645 /* save packet options if user wanted */
646 if (isipv6 && inp->in6p_flags & INP_CONTROLOPTS) {
647 if (inp->in6p_options) {
648 m_freem(inp->in6p_options);
649 inp->in6p_options = 0;
650 }
651 ip6_savecontrol(inp, &inp->in6p_options, ip6, m);
652 }
653 /* else, should also do ip_srcroute() here? */
654#endif /* INET6 */
655
656 so = inp->inp_socket;
657 if (so->so_options & (SO_DEBUG|SO_ACCEPTCONN)) {
658#ifdef TCPDEBUG
659 if (so->so_options & SO_DEBUG) {
660 ostate = tp->t_state;
661#ifdef INET6
662 if (isipv6)
663 bcopy((char *)ip6, (char *)tcp_saveipgen,
664 sizeof(*ip6));
665 else
666#endif /* INET6 */
667 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip));
668 tcp_savetcp = *th;
669 }
670#endif
671 if (so->so_options & SO_ACCEPTCONN) {
672 register struct tcpcb *tp0 = tp;
673 struct socket *so2;
674#ifdef IPSEC
675 struct socket *oso;
676#endif
677#ifdef INET6
678 struct inpcb *oinp = sotoinpcb(so);
679#endif /* INET6 */
680
681#ifndef IPSEC
682 /*
683 * Current IPsec implementation makes incorrect IPsec
684 * cache if this check is done here.
685 * So delay this until duplicated socket is created.
686 */
687 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) {
688 /*
689 * Note: dropwithreset makes sure we don't
690 * send a RST in response to a RST.
691 */
692 if (thflags & TH_ACK) {
693 tcpstat.tcps_badsyn++;
694 goto maybedropwithreset;
695 }
696 goto drop;
697 }
698#endif
699 so2 = sonewconn(so, 0);
700 if (so2 == 0) {
701 tcpstat.tcps_listendrop++;
702 so2 = sodropablereq(so);
703 if (so2) {
704 tcp_drop(sototcpcb(so2), ETIMEDOUT);
705 so2 = sonewconn(so, 0);
706 }
707 if (!so2)
708 goto drop;
709 }
710#ifdef IPSEC
711 oso = so;
712#endif
713 so = so2;
714 /*
715 * This is ugly, but ....
716 *
717 * Mark socket as temporary until we're
718 * committed to keeping it. The code at
719 * ``drop'' and ``dropwithreset'' check the
720 * flag dropsocket to see if the temporary
721 * socket created here should be discarded.
722 * We mark the socket as discardable until
723 * we're committed to it below in TCPS_LISTEN.
724 */
725 dropsocket++;
726 inp = (struct inpcb *)so->so_pcb;
727#ifdef INET6
728 if (isipv6)
729 inp->in6p_laddr = ip6->ip6_dst;
730 else {
731 if (ip6_mapped_addr_on) {
732 inp->inp_vflag &= ~INP_IPV6;
733 inp->inp_vflag |= INP_IPV4;
734 }
735#endif /* INET6 */
736 inp->inp_laddr = ip->ip_dst;
737#ifdef INET6
738 }
739#endif /* INET6 */
740 inp->inp_lport = th->th_dport;
741 if (in_pcbinshash(inp) != 0) {
742 /*
743 * Undo the assignments above if we failed to
744 * put the PCB on the hash lists.
745 */
746#ifdef INET6
747 if (isipv6)
748 inp->in6p_laddr = in6addr_any;
749 else
750#endif /* INET6 */
751 inp->inp_laddr.s_addr = INADDR_ANY;
752 inp->inp_lport = 0;
753 goto drop;
754 }
755#ifdef IPSEC
756 /*
757 * To avoid creating incorrectly cached IPsec
758 * association, this is need to be done here.
759 *
760 * Subject: (KAME-snap 748)
761 * From: Wayne Knowles <w.knowles@niwa.cri.nz>
762 * ftp://ftp.kame.net/pub/mail-list/snap-users/748
763 */
764 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) {
765 /*
766 * Note: dropwithreset makes sure we don't
767 * send a RST in response to a RST.
768 */
769 if (thflags & TH_ACK) {
770 tcpstat.tcps_badsyn++;
771 goto maybedropwithreset;
772 }
773 goto drop;
774 }
775#endif
776#ifdef INET6
777 if (isipv6) {
778 /*
779 * inherit socket options from the listening
780 * socket.
781 */
782 inp->inp_flags |=
783 oinp->inp_flags & INP_CONTROLOPTS;
784 if (inp->inp_flags & INP_CONTROLOPTS) {
785 if (inp->in6p_options) {
786 m_freem(inp->in6p_options);
787 inp->in6p_options = 0;
788 }
789 ip6_savecontrol(inp,
790 &inp->in6p_options,
791 ip6, m);
792 }
793 } else
794#endif /* INET6 */
795 inp->inp_options = ip_srcroute();
796#ifdef IPSEC
797 /* copy old policy into new socket's */
798 if (ipsec_copy_policy(sotoinpcb(oso)->inp_sp,
799 inp->inp_sp))
800 printf("tcp_input: could not copy policy\n");
801#endif
802 tp = intotcpcb(inp);
803 tp->t_state = TCPS_LISTEN;
804 tp->t_flags |= tp0->t_flags & (TF_NOPUSH|TF_NOOPT);
805
806 /* Compute proper scaling value from buffer space */
807 while (tp->request_r_scale < TCP_MAX_WINSHIFT &&
808 TCP_MAXWIN << tp->request_r_scale <
809 so->so_rcv.sb_hiwat)
810 tp->request_r_scale++;
811 }
812 }
813
814 /*
815 * Segment received on connection.
816 * Reset idle time and keep-alive timer.
817 */
818 tp->t_rcvtime = ticks;
819 if (TCPS_HAVEESTABLISHED(tp->t_state))
820 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp);
821
822 /*
823 * Process options if not in LISTEN state,
824 * else do it below (after getting remote address).
825 */
826 if (tp->t_state != TCPS_LISTEN)
827 tcp_dooptions(tp, optp, optlen, th, &to);
828
829 /*
830 * Header prediction: check for the two common cases
831 * of a uni-directional data xfer. If the packet has
832 * no control flags, is in-sequence, the window didn't
833 * change and we're not retransmitting, it's a
834 * candidate. If the length is zero and the ack moved
835 * forward, we're the sender side of the xfer. Just
836 * free the data acked & wake any higher level process
837 * that was blocked waiting for space. If the length
838 * is non-zero and the ack didn't move, we're the
839 * receiver side. If we're getting packets in-order
840 * (the reassembly queue is empty), add the data to
841 * the socket buffer and note that we need a delayed ack.
842 * Make sure that the hidden state-flags are also off.
843 * Since we check for TCPS_ESTABLISHED above, it can only
844 * be TH_NEEDSYN.
845 */
846 if (tp->t_state == TCPS_ESTABLISHED &&
847 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
848 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) &&
849 ((to.to_flag & TOF_TS) == 0 ||
850 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) &&
851 /*
852 * Using the CC option is compulsory if once started:
853 * the segment is OK if no T/TCP was negotiated or
854 * if the segment has a CC option equal to CCrecv
855 */
856 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) ||
857 ((to.to_flag & TOF_CC) != 0 && to.to_cc == tp->cc_recv)) &&
858 th->th_seq == tp->rcv_nxt &&
859 tiwin && tiwin == tp->snd_wnd &&
860 tp->snd_nxt == tp->snd_max) {
861
862 /*
863 * If last ACK falls within this segment's sequence numbers,
864 * record the timestamp.
865 * NOTE that the test is modified according to the latest
866 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
867 */
868 if ((to.to_flag & TOF_TS) != 0 &&
869 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
870 tp->ts_recent_age = ticks;
871 tp->ts_recent = to.to_tsval;
872 }
873
874 if (tlen == 0) {
875 if (SEQ_GT(th->th_ack, tp->snd_una) &&
876 SEQ_LEQ(th->th_ack, tp->snd_max) &&
877 tp->snd_cwnd >= tp->snd_wnd &&
878 tp->t_dupacks < tcprexmtthresh) {
879 /*
880 * this is a pure ack for outstanding data.
881 */
882 ++tcpstat.tcps_predack;
883 /*
884 * "bad retransmit" recovery
885 */
886 if (tp->t_rxtshift == 1 &&
887 ticks < tp->t_badrxtwin) {
888 tp->snd_cwnd = tp->snd_cwnd_prev;
889 tp->snd_ssthresh =
890 tp->snd_ssthresh_prev;
891 tp->snd_nxt = tp->snd_max;
892 tp->t_badrxtwin = 0;
893 }
894 if ((to.to_flag & TOF_TS) != 0)
895 tcp_xmit_timer(tp,
896 ticks - to.to_tsecr + 1);
897 else if (tp->t_rtttime &&
898 SEQ_GT(th->th_ack, tp->t_rtseq))
899 tcp_xmit_timer(tp, ticks - tp->t_rtttime);
900 acked = th->th_ack - tp->snd_una;
901 tcpstat.tcps_rcvackpack++;
902 tcpstat.tcps_rcvackbyte += acked;
903 sbdrop(&so->so_snd, acked);
904 tp->snd_una = th->th_ack;
905 m_freem(m);
906 ND6_HINT(tp); /* some progress has been done */
907
908 /*
909 * If all outstanding data are acked, stop
910 * retransmit timer, otherwise restart timer
911 * using current (possibly backed-off) value.
912 * If process is waiting for space,
913 * wakeup/selwakeup/signal. If data
914 * are ready to send, let tcp_output
915 * decide between more output or persist.
916 */
917 if (tp->snd_una == tp->snd_max)
918 callout_stop(tp->tt_rexmt);
919 else if (!callout_active(tp->tt_persist))
920 callout_reset(tp->tt_rexmt,
921 tp->t_rxtcur,
922 tcp_timer_rexmt, tp);
923
924 sowwakeup(so);
925 if (so->so_snd.sb_cc)
926 (void) tcp_output(tp);
927 return;
928 }
929 } else if (th->th_ack == tp->snd_una &&
930 LIST_EMPTY(&tp->t_segq) &&
931 tlen <= sbspace(&so->so_rcv)) {
932 /*
933 * this is a pure, in-sequence data packet
934 * with nothing on the reassembly queue and
935 * we have enough buffer space to take it.
936 */
937 ++tcpstat.tcps_preddat;
938 tp->rcv_nxt += tlen;
939 tcpstat.tcps_rcvpack++;
940 tcpstat.tcps_rcvbyte += tlen;
941 ND6_HINT(tp); /* some progress has been done */
942 /*
943 * Add data to socket buffer.
944 */
945 m_adj(m, drop_hdrlen); /* delayed header drop */
946 sbappend(&so->so_rcv, m);
947 sorwakeup(so);
948 if (tcp_delack_enabled) {
949 callout_reset(tp->tt_delack, tcp_delacktime,
950 tcp_timer_delack, tp);
951 } else {
952 tp->t_flags |= TF_ACKNOW;
953 tcp_output(tp);
954 }
955 return;
956 }
957 }
958
959 /*
960 * Calculate amount of space in receive window,
961 * and then do TCP input processing.
962 * Receive window is amount of space in rcv queue,
963 * but not less than advertised window.
964 */
965 { int win;
966
967 win = sbspace(&so->so_rcv);
968 if (win < 0)
969 win = 0;
970 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt));
971 }
972
973 switch (tp->t_state) {
974
975 /*
976 * If the state is LISTEN then ignore segment if it contains an RST.
977 * If the segment contains an ACK then it is bad and send a RST.
978 * If it does not contain a SYN then it is not interesting; drop it.
979 * If it is from this socket, drop it, it must be forged.
980 * Don't bother responding if the destination was a broadcast.
981 * Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial
982 * tp->iss, and send a segment:
983 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
984 * Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss.
985 * Fill in remote peer address fields if not previously specified.
986 * Enter SYN_RECEIVED state, and process any other fields of this
987 * segment in this state.
988 */
989 case TCPS_LISTEN: {
990 register struct sockaddr_in *sin;
991#ifdef INET6
992 register struct sockaddr_in6 *sin6;
993#endif
994
995 if (thflags & TH_RST)
996 goto drop;
997 if (thflags & TH_ACK)
998 goto maybedropwithreset;
999 if ((thflags & TH_SYN) == 0)
1000 goto drop;
1001 if (th->th_dport == th->th_sport) {
1002#ifdef INET6
1003 if (isipv6) {
1004 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst,
1005 &ip6->ip6_src))
1006 goto drop;
1007 } else
1008#endif /* INET6 */
1009 if (ip->ip_dst.s_addr == ip->ip_src.s_addr)
1010 goto drop;
1011 }
1012 /*
1013 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN
1014 * in_broadcast() should never return true on a received
1015 * packet with M_BCAST not set.
1016 *
1017 * Packets with a multicast source address should also
1018 * be discarded.
1019 */
1020 if (m->m_flags & (M_BCAST|M_MCAST))
1021 goto drop;
1022#ifdef INET6
1023 if (isipv6) {
1024 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
1025 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
1026 goto drop;
1027 } else
1028#endif
1029 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
1030 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
1031 ip->ip_src.s_addr == htonl(INADDR_BROADCAST))
1032 goto drop;
1033#ifdef INET6
1034 if (isipv6) {
1035 MALLOC(sin6, struct sockaddr_in6 *, sizeof *sin6,
1036 M_SONAME, M_NOWAIT);
1037 if (sin6 == NULL)
1038 goto drop;
1039 bzero(sin6, sizeof(*sin6));
1040 sin6->sin6_family = AF_INET6;
1041 sin6->sin6_len = sizeof(*sin6);
1042 sin6->sin6_addr = ip6->ip6_src;
1043 sin6->sin6_port = th->th_sport;
1044 laddr6 = inp->in6p_laddr;
1045 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr))
1046 inp->in6p_laddr = ip6->ip6_dst;
1047 if (in6_pcbconnect(inp, (struct sockaddr *)sin6,
1048 &proc0)) {
1049 inp->in6p_laddr = laddr6;
1050 FREE(sin6, M_SONAME);
1051 goto drop;
1052 }
1053 FREE(sin6, M_SONAME);
1054 } else
1055#endif
1056 {
1057 MALLOC(sin, struct sockaddr_in *, sizeof *sin, M_SONAME,
1058 M_NOWAIT);
1059 if (sin == NULL)
1060 goto drop;
1061 sin->sin_family = AF_INET;
1062 sin->sin_len = sizeof(*sin);
1063 sin->sin_addr = ip->ip_src;
1064 sin->sin_port = th->th_sport;
1065 bzero((caddr_t)sin->sin_zero, sizeof(sin->sin_zero));
1066 laddr = inp->inp_laddr;
1067 if (inp->inp_laddr.s_addr == INADDR_ANY)
1068 inp->inp_laddr = ip->ip_dst;
1069 if (in_pcbconnect(inp, (struct sockaddr *)sin, &proc0)) {
1070 inp->inp_laddr = laddr;
1071 FREE(sin, M_SONAME);
1072 goto drop;
1073 }
1074 FREE(sin, M_SONAME);
1075 }
1076 tp->t_template = tcp_template(tp);
1077 if (tp->t_template == 0) {
1078 tp = tcp_drop(tp, ENOBUFS);
1079 dropsocket = 0; /* socket is already gone */
1080 goto drop;
1081 }
1082 if ((taop = tcp_gettaocache(inp)) == NULL) {
1083 taop = &tao_noncached;
1084 bzero(taop, sizeof(*taop));
1085 }
1086 tcp_dooptions(tp, optp, optlen, th, &to);
1087 if (iss)
1088 tp->iss = iss;
1089 else
1090 tp->iss = tcp_iss;
1091 tcp_iss += TCP_ISSINCR/4;
1092 tp->irs = th->th_seq;
1093 tcp_sendseqinit(tp);
1094 tcp_rcvseqinit(tp);
1095 /*
1096 * Initialization of the tcpcb for transaction;
1097 * set SND.WND = SEG.WND,
1098 * initialize CCsend and CCrecv.
1099 */
1100 tp->snd_wnd = tiwin; /* initial send-window */
1101 tp->cc_send = CC_INC(tcp_ccgen);
1102 tp->cc_recv = to.to_cc;
1103 /*
1104 * Perform TAO test on incoming CC (SEG.CC) option, if any.
1105 * - compare SEG.CC against cached CC from the same host,
1106 * if any.
1107 * - if SEG.CC > chached value, SYN must be new and is accepted
1108 * immediately: save new CC in the cache, mark the socket
1109 * connected, enter ESTABLISHED state, turn on flag to
1110 * send a SYN in the next segment.
1111 * A virtual advertised window is set in rcv_adv to
1112 * initialize SWS prevention. Then enter normal segment
1113 * processing: drop SYN, process data and FIN.
1114 * - otherwise do a normal 3-way handshake.
1115 */
1116 if ((to.to_flag & TOF_CC) != 0) {
1117 if (((tp->t_flags & TF_NOPUSH) != 0) &&
1118 taop->tao_cc != 0 && CC_GT(to.to_cc, taop->tao_cc)) {
1119
1120 taop->tao_cc = to.to_cc;
1121 tp->t_starttime = ticks;
1122 tp->t_state = TCPS_ESTABLISHED;
1123
1124 /*
1125 * If there is a FIN, or if there is data and the
1126 * connection is local, then delay SYN,ACK(SYN) in
1127 * the hope of piggy-backing it on a response
1128 * segment. Otherwise must send ACK now in case
1129 * the other side is slow starting.
1130 */
1131 if (tcp_delack_enabled && ((thflags & TH_FIN) ||
1132 (tlen != 0 &&
1133#ifdef INET6
1134 ((isipv6 && in6_localaddr(&inp->in6p_faddr))
1135 ||
1136 (!isipv6 &&
1137#endif
1138 in_localaddr(inp->inp_faddr)
1139#ifdef INET6
1140 ))
1141#endif
1142 ))) {
1143 callout_reset(tp->tt_delack, tcp_delacktime,
1144 tcp_timer_delack, tp);
1145 tp->t_flags |= TF_NEEDSYN;
1146 } else
1147 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN);
1148
1149 /*
1150 * Limit the `virtual advertised window' to TCP_MAXWIN
1151 * here. Even if we requested window scaling, it will
1152 * become effective only later when our SYN is acked.
1153 */
1154 tp->rcv_adv += min(tp->rcv_wnd, TCP_MAXWIN);
1155 tcpstat.tcps_connects++;
1156 soisconnected(so);
1157 callout_reset(tp->tt_keep, tcp_keepinit,
1158 tcp_timer_keep, tp);
1159 dropsocket = 0; /* committed to socket */
1160 tcpstat.tcps_accepts++;
1161 goto trimthenstep6;
1162 }
1163 /* else do standard 3-way handshake */
1164 } else {
1165 /*
1166 * No CC option, but maybe CC.NEW:
1167 * invalidate cached value.
1168 */
1169 taop->tao_cc = 0;
1170 }
1171 /*
1172 * TAO test failed or there was no CC option,
1173 * do a standard 3-way handshake.
1174 */
1175 tp->t_flags |= TF_ACKNOW;
1176 tp->t_state = TCPS_SYN_RECEIVED;
1177 callout_reset(tp->tt_keep, tcp_keepinit, tcp_timer_keep, tp);
1178 dropsocket = 0; /* committed to socket */
1179 tcpstat.tcps_accepts++;
1180 ND6_HINT((struct tcpcb *)inp->inp_ppcb);
1181 goto trimthenstep6;
1182 }
1183
1184 /*
1185 * If the state is SYN_RECEIVED:
1186 * if seg contains an ACK, but not for our SYN/ACK, send a RST.
1187 */
1188 case TCPS_SYN_RECEIVED:
1189 if ((thflags & TH_ACK) &&
1190 (SEQ_LEQ(th->th_ack, tp->snd_una) ||
1191 SEQ_GT(th->th_ack, tp->snd_max)))
1192 goto maybedropwithreset;
1193 break;
1194
1195 /*
1196 * If the state is SYN_SENT:
1197 * if seg contains an ACK, but not for our SYN, drop the input.
1198 * if seg contains a RST, then drop the connection.
1199 * if seg does not contain SYN, then drop it.
1200 * Otherwise this is an acceptable SYN segment
1201 * initialize tp->rcv_nxt and tp->irs
1202 * if seg contains ack then advance tp->snd_una
1203 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state
1204 * arrange for segment to be acked (eventually)
1205 * continue processing rest of data/controls, beginning with URG
1206 */
1207 case TCPS_SYN_SENT:
1208 if ((taop = tcp_gettaocache(inp)) == NULL) {
1209 taop = &tao_noncached;
1210 bzero(taop, sizeof(*taop));
1211 }
1212
1213 if ((thflags & TH_ACK) &&
1214 (SEQ_LEQ(th->th_ack, tp->iss) ||
1215 SEQ_GT(th->th_ack, tp->snd_max))) {
1216 /*
1217 * If we have a cached CCsent for the remote host,
1218 * hence we haven't just crashed and restarted,
1219 * do not send a RST. This may be a retransmission
1220 * from the other side after our earlier ACK was lost.
1221 * Our new SYN, when it arrives, will serve as the
1222 * needed ACK.
1223 */
1224 if (taop->tao_ccsent != 0)
1225 goto drop;
1226 else
1227 goto dropwithreset;
1228 }
1229 if (thflags & TH_RST) {
1230 if (thflags & TH_ACK)
1231 tp = tcp_drop(tp, ECONNREFUSED);
1232 goto drop;
1233 }
1234 if ((thflags & TH_SYN) == 0)
1235 goto drop;
1236 tp->snd_wnd = th->th_win; /* initial send window */
1237 tp->cc_recv = to.to_cc; /* foreign CC */
1238
1239 tp->irs = th->th_seq;
1240 tcp_rcvseqinit(tp);
1241 if (thflags & TH_ACK) {
1242 /*
1243 * Our SYN was acked. If segment contains CC.ECHO
1244 * option, check it to make sure this segment really
1245 * matches our SYN. If not, just drop it as old
1246 * duplicate, but send an RST if we're still playing
1247 * by the old rules. If no CC.ECHO option, make sure
1248 * we don't get fooled into using T/TCP.
1249 */
1250 if (to.to_flag & TOF_CCECHO) {
1251 if (tp->cc_send != to.to_ccecho) {
1252 if (taop->tao_ccsent != 0)
1253 goto drop;
1254 else
1255 goto dropwithreset;
1256 }
1257 } else
1258 tp->t_flags &= ~TF_RCVD_CC;
1259 tcpstat.tcps_connects++;
1260 soisconnected(so);
1261 /* Do window scaling on this connection? */
1262 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
1263 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
1264 tp->snd_scale = tp->requested_s_scale;
1265 tp->rcv_scale = tp->request_r_scale;
1266 }
1267 /* Segment is acceptable, update cache if undefined. */
1268 if (taop->tao_ccsent == 0)
1269 taop->tao_ccsent = to.to_ccecho;
1270
1271 tp->rcv_adv += tp->rcv_wnd;
1272 tp->snd_una++; /* SYN is acked */
1273 /*
1274 * If there's data, delay ACK; if there's also a FIN
1275 * ACKNOW will be turned on later.
1276 */
1277 if (tcp_delack_enabled && tlen != 0)
1278 callout_reset(tp->tt_delack, tcp_delacktime,
1279 tcp_timer_delack, tp);
1280 else
1281 tp->t_flags |= TF_ACKNOW;
1282 /*
1283 * Received <SYN,ACK> in SYN_SENT[*] state.
1284 * Transitions:
1285 * SYN_SENT --> ESTABLISHED
1286 * SYN_SENT* --> FIN_WAIT_1
1287 */
1288 tp->t_starttime = ticks;
1289 if (tp->t_flags & TF_NEEDFIN) {
1290 tp->t_state = TCPS_FIN_WAIT_1;
1291 tp->t_flags &= ~TF_NEEDFIN;
1292 thflags &= ~TH_SYN;
1293 } else {
1294 tp->t_state = TCPS_ESTABLISHED;
1295 callout_reset(tp->tt_keep, tcp_keepidle,
1296 tcp_timer_keep, tp);
1297 }
1298 } else {
1299 /*
1300 * Received initial SYN in SYN-SENT[*] state => simul-
1301 * taneous open. If segment contains CC option and there is
1302 * a cached CC, apply TAO test; if it succeeds, connection is
1303 * half-synchronized. Otherwise, do 3-way handshake:
1304 * SYN-SENT -> SYN-RECEIVED
1305 * SYN-SENT* -> SYN-RECEIVED*
1306 * If there was no CC option, clear cached CC value.
1307 */
1308 tp->t_flags |= TF_ACKNOW;
1309 callout_stop(tp->tt_rexmt);
1310 if (to.to_flag & TOF_CC) {
1311 if (taop->tao_cc != 0 &&
1312 CC_GT(to.to_cc, taop->tao_cc)) {
1313 /*
1314 * update cache and make transition:
1315 * SYN-SENT -> ESTABLISHED*
1316 * SYN-SENT* -> FIN-WAIT-1*
1317 */
1318 taop->tao_cc = to.to_cc;
1319 tp->t_starttime = ticks;
1320 if (tp->t_flags & TF_NEEDFIN) {
1321 tp->t_state = TCPS_FIN_WAIT_1;
1322 tp->t_flags &= ~TF_NEEDFIN;
1323 } else {
1324 tp->t_state = TCPS_ESTABLISHED;
1325 callout_reset(tp->tt_keep,
1326 tcp_keepidle,
1327 tcp_timer_keep,
1328 tp);
1329 }
1330 tp->t_flags |= TF_NEEDSYN;
1331 } else
1332 tp->t_state = TCPS_SYN_RECEIVED;
1333 } else {
1334 /* CC.NEW or no option => invalidate cache */
1335 taop->tao_cc = 0;
1336 tp->t_state = TCPS_SYN_RECEIVED;
1337 }
1338 }
1339
1340trimthenstep6:
1341 /*
1342 * Advance th->th_seq to correspond to first data byte.
1343 * If data, trim to stay within window,
1344 * dropping FIN if necessary.
1345 */
1346 th->th_seq++;
1347 if (tlen > tp->rcv_wnd) {
1348 todrop = tlen - tp->rcv_wnd;
1349 m_adj(m, -todrop);
1350 tlen = tp->rcv_wnd;
1351 thflags &= ~TH_FIN;
1352 tcpstat.tcps_rcvpackafterwin++;
1353 tcpstat.tcps_rcvbyteafterwin += todrop;
1354 }
1355 tp->snd_wl1 = th->th_seq - 1;
1356 tp->rcv_up = th->th_seq;
1357 /*
1358 * Client side of transaction: already sent SYN and data.
1359 * If the remote host used T/TCP to validate the SYN,
1360 * our data will be ACK'd; if so, enter normal data segment
1361 * processing in the middle of step 5, ack processing.
1362 * Otherwise, goto step 6.
1363 */
1364 if (thflags & TH_ACK)
1365 goto process_ACK;
1366 goto step6;
1367 /*
1368 * If the state is LAST_ACK or CLOSING or TIME_WAIT:
1369 * if segment contains a SYN and CC [not CC.NEW] option:
1370 * if state == TIME_WAIT and connection duration > MSL,
1371 * drop packet and send RST;
1372 *
1373 * if SEG.CC > CCrecv then is new SYN, and can implicitly
1374 * ack the FIN (and data) in retransmission queue.
1375 * Complete close and delete TCPCB. Then reprocess
1376 * segment, hoping to find new TCPCB in LISTEN state;
1377 *
1378 * else must be old SYN; drop it.
1379 * else do normal processing.
1380 */
1381 case TCPS_LAST_ACK:
1382 case TCPS_CLOSING:
1383 case TCPS_TIME_WAIT:
1384 if ((thflags & TH_SYN) &&
1385 (to.to_flag & TOF_CC) && tp->cc_recv != 0) {
1386 if (tp->t_state == TCPS_TIME_WAIT &&
1387 (ticks - tp->t_starttime) > tcp_msl)
1388 goto dropwithreset;
1389 if (CC_GT(to.to_cc, tp->cc_recv)) {
1390 tp = tcp_close(tp);
1391 goto findpcb;
1392 }
1393 else
1394 goto drop;
1395 }
1396 break; /* continue normal processing */
1397 }
1398
1399 /*
1400 * States other than LISTEN or SYN_SENT.
1401 * First check the RST flag and sequence number since reset segments
1402 * are exempt from the timestamp and connection count tests. This
1403 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix
1404 * below which allowed reset segments in half the sequence space
1405 * to fall though and be processed (which gives forged reset
1406 * segments with a random sequence number a 50 percent chance of
1407 * killing a connection).
1408 * Then check timestamp, if present.
1409 * Then check the connection count, if present.
1410 * Then check that at least some bytes of segment are within
1411 * receive window. If segment begins before rcv_nxt,
1412 * drop leading data (and SYN); if nothing left, just ack.
1413 *
1414 *
1415 * If the RST bit is set, check the sequence number to see
1416 * if this is a valid reset segment.
1417 * RFC 793 page 37:
1418 * In all states except SYN-SENT, all reset (RST) segments
1419 * are validated by checking their SEQ-fields. A reset is
1420 * valid if its sequence number is in the window.
1421 * Note: this does not take into account delayed ACKs, so
1422 * we should test against last_ack_sent instead of rcv_nxt.
1423 * The sequence number in the reset segment is normally an
1424 * echo of our outgoing acknowlegement numbers, but some hosts
1425 * send a reset with the sequence number at the rightmost edge
1426 * of our receive window, and we have to handle this case.
1427 * If we have multiple segments in flight, the intial reset
1428 * segment sequence numbers will be to the left of last_ack_sent,
1429 * but they will eventually catch up.
1430 * In any case, it never made sense to trim reset segments to
1431 * fit the receive window since RFC 1122 says:
1432 * 4.2.2.12 RST Segment: RFC-793 Section 3.4
1433 *
1434 * A TCP SHOULD allow a received RST segment to include data.
1435 *
1436 * DISCUSSION
1437 * It has been suggested that a RST segment could contain
1438 * ASCII text that encoded and explained the cause of the
1439 * RST. No standard has yet been established for such
1440 * data.
1441 *
1442 * If the reset segment passes the sequence number test examine
1443 * the state:
1444 * SYN_RECEIVED STATE:
1445 * If passive open, return to LISTEN state.
1446 * If active open, inform user that connection was refused.
1447 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES:
1448 * Inform user that connection was reset, and close tcb.
1449 * CLOSING, LAST_ACK STATES:
1450 * Close the tcb.
1451 * TIME_WAIT STATE:
1452 * Drop the segment - see Stevens, vol. 2, p. 964 and
1453 * RFC 1337.
1454 */
1455 if (thflags & TH_RST) {
1456 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
1457 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) {
1458 switch (tp->t_state) {
1459
1460 case TCPS_SYN_RECEIVED:
1461 so->so_error = ECONNREFUSED;
1462 goto close;
1463
1464 case TCPS_ESTABLISHED:
1465 case TCPS_FIN_WAIT_1:
1466 case TCPS_FIN_WAIT_2:
1467 case TCPS_CLOSE_WAIT:
1468 so->so_error = ECONNRESET;
1469 close:
1470 tp->t_state = TCPS_CLOSED;
1471 tcpstat.tcps_drops++;
1472 tp = tcp_close(tp);
1473 break;
1474
1475 case TCPS_CLOSING:
1476 case TCPS_LAST_ACK:
1477 tp = tcp_close(tp);
1478 break;
1479
1480 case TCPS_TIME_WAIT:
1481 break;
1482 }
1483 }
1484 goto drop;
1485 }
1486
1487 /*
1488 * RFC 1323 PAWS: If we have a timestamp reply on this segment
1489 * and it's less than ts_recent, drop it.
1490 */
1491 if ((to.to_flag & TOF_TS) != 0 && tp->ts_recent &&
1492 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
1493
1494 /* Check to see if ts_recent is over 24 days old. */
1495 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) {
1496 /*
1497 * Invalidate ts_recent. If this segment updates
1498 * ts_recent, the age will be reset later and ts_recent
1499 * will get a valid value. If it does not, setting
1500 * ts_recent to zero will at least satisfy the
1501 * requirement that zero be placed in the timestamp
1502 * echo reply when ts_recent isn't valid. The
1503 * age isn't reset until we get a valid ts_recent
1504 * because we don't want out-of-order segments to be
1505 * dropped when ts_recent is old.
1506 */
1507 tp->ts_recent = 0;
1508 } else {
1509 tcpstat.tcps_rcvduppack++;
1510 tcpstat.tcps_rcvdupbyte += tlen;
1511 tcpstat.tcps_pawsdrop++;
1512 goto dropafterack;
1513 }
1514 }
1515
1516 /*
1517 * T/TCP mechanism
1518 * If T/TCP was negotiated and the segment doesn't have CC,
1519 * or if its CC is wrong then drop the segment.
1520 * RST segments do not have to comply with this.
1521 */
1522 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) &&
1523 ((to.to_flag & TOF_CC) == 0 || tp->cc_recv != to.to_cc))
1524 goto dropafterack;
1525
1526 /*
1527 * In the SYN-RECEIVED state, validate that the packet belongs to
1528 * this connection before trimming the data to fit the receive
1529 * window. Check the sequence number versus IRS since we know
1530 * the sequence numbers haven't wrapped. This is a partial fix
1531 * for the "LAND" DoS attack.
1532 */
1533 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs))
1534 goto maybedropwithreset;
1535
1536 todrop = tp->rcv_nxt - th->th_seq;
1537 if (todrop > 0) {
1538 if (thflags & TH_SYN) {
1539 thflags &= ~TH_SYN;
1540 th->th_seq++;
1541 if (th->th_urp > 1)
1542 th->th_urp--;
1543 else
1544 thflags &= ~TH_URG;
1545 todrop--;
1546 }
1547 /*
1548 * Following if statement from Stevens, vol. 2, p. 960.
1549 */
1550 if (todrop > tlen
1551 || (todrop == tlen && (thflags & TH_FIN) == 0)) {
1552 /*
1553 * Any valid FIN must be to the left of the window.
1554 * At this point the FIN must be a duplicate or out
1555 * of sequence; drop it.
1556 */
1557 thflags &= ~TH_FIN;
1558
1559 /*
1560 * Send an ACK to resynchronize and drop any data.
1561 * But keep on processing for RST or ACK.
1562 */
1563 tp->t_flags |= TF_ACKNOW;
1564 todrop = tlen;
1565 tcpstat.tcps_rcvduppack++;
1566 tcpstat.tcps_rcvdupbyte += todrop;
1567 } else {
1568 tcpstat.tcps_rcvpartduppack++;
1569 tcpstat.tcps_rcvpartdupbyte += todrop;
1570 }
1571 drop_hdrlen += todrop; /* drop from the top afterwards */
1572 th->th_seq += todrop;
1573 tlen -= todrop;
1574 if (th->th_urp > todrop)
1575 th->th_urp -= todrop;
1576 else {
1577 thflags &= ~TH_URG;
1578 th->th_urp = 0;
1579 }
1580 }
1581
1582 /*
1583 * If new data are received on a connection after the
1584 * user processes are gone, then RST the other end.
1585 */
1586 if ((so->so_state & SS_NOFDREF) &&
1587 tp->t_state > TCPS_CLOSE_WAIT && tlen) {
1588 tp = tcp_close(tp);
1589 tcpstat.tcps_rcvafterclose++;
1590 goto dropwithreset;
1591 }
1592
1593 /*
1594 * If segment ends after window, drop trailing data
1595 * (and PUSH and FIN); if nothing left, just ACK.
1596 */
1597 todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd);
1598 if (todrop > 0) {
1599 tcpstat.tcps_rcvpackafterwin++;
1600 if (todrop >= tlen) {
1601 tcpstat.tcps_rcvbyteafterwin += tlen;
1602 /*
1603 * If a new connection request is received
1604 * while in TIME_WAIT, drop the old connection
1605 * and start over if the sequence numbers
1606 * are above the previous ones.
1607 */
1608 if (thflags & TH_SYN &&
1609 tp->t_state == TCPS_TIME_WAIT &&
1610 SEQ_GT(th->th_seq, tp->rcv_nxt)) {
1611 iss = tp->snd_nxt + TCP_ISSINCR;
1612 tp = tcp_close(tp);
1613 goto findpcb;
1614 }
1615 /*
1616 * If window is closed can only take segments at
1617 * window edge, and have to drop data and PUSH from
1618 * incoming segments. Continue processing, but
1619 * remember to ack. Otherwise, drop segment
1620 * and ack.
1621 */
1622 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
1623 tp->t_flags |= TF_ACKNOW;
1624 tcpstat.tcps_rcvwinprobe++;
1625 } else
1626 goto dropafterack;
1627 } else
1628 tcpstat.tcps_rcvbyteafterwin += todrop;
1629 m_adj(m, -todrop);
1630 tlen -= todrop;
1631 thflags &= ~(TH_PUSH|TH_FIN);
1632 }
1633
1634 /*
1635 * If last ACK falls within this segment's sequence numbers,
1636 * record its timestamp.
1637 * NOTE that the test is modified according to the latest
1638 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1639 */
1640 if ((to.to_flag & TOF_TS) != 0 &&
1641 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
1642 tp->ts_recent_age = ticks;
1643 tp->ts_recent = to.to_tsval;
1644 }
1645
1646 /*
1647 * If a SYN is in the window, then this is an
1648 * error and we send an RST and drop the connection.
1649 */
1650 if (thflags & TH_SYN) {
1651 tp = tcp_drop(tp, ECONNRESET);
1652 goto dropwithreset;
1653 }
1654
1655 /*
1656 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN
1657 * flag is on (half-synchronized state), then queue data for
1658 * later processing; else drop segment and return.
1659 */
1660 if ((thflags & TH_ACK) == 0) {
1661 if (tp->t_state == TCPS_SYN_RECEIVED ||
1662 (tp->t_flags & TF_NEEDSYN))
1663 goto step6;
1664 else
1665 goto drop;
1666 }
1667
1668 /*
1669 * Ack processing.
1670 */
1671 switch (tp->t_state) {
1672
1673 /*
1674 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter
1675 * ESTABLISHED state and continue processing.
1676 * The ACK was checked above.
1677 */
1678 case TCPS_SYN_RECEIVED:
1679
1680 tcpstat.tcps_connects++;
1681 soisconnected(so);
1682 /* Do window scaling? */
1683 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
1684 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
1685 tp->snd_scale = tp->requested_s_scale;
1686 tp->rcv_scale = tp->request_r_scale;
1687 }
1688 /*
1689 * Upon successful completion of 3-way handshake,
1690 * update cache.CC if it was undefined, pass any queued
1691 * data to the user, and advance state appropriately.
1692 */
1693 if ((taop = tcp_gettaocache(inp)) != NULL &&
1694 taop->tao_cc == 0)
1695 taop->tao_cc = tp->cc_recv;
1696
1697 /*
1698 * Make transitions:
1699 * SYN-RECEIVED -> ESTABLISHED
1700 * SYN-RECEIVED* -> FIN-WAIT-1
1701 */
1702 tp->t_starttime = ticks;
1703 if (tp->t_flags & TF_NEEDFIN) {
1704 tp->t_state = TCPS_FIN_WAIT_1;
1705 tp->t_flags &= ~TF_NEEDFIN;
1706 } else {
1707 tp->t_state = TCPS_ESTABLISHED;
1708 callout_reset(tp->tt_keep, tcp_keepidle,
1709 tcp_timer_keep, tp);
1710 }
1711 /*
1712 * If segment contains data or ACK, will call tcp_reass()
1713 * later; if not, do so now to pass queued data to user.
1714 */
1715 if (tlen == 0 && (thflags & TH_FIN) == 0)
1716 (void) tcp_reass(tp, (struct tcphdr *)0, 0,
1717 (struct mbuf *)0);
1718 tp->snd_wl1 = th->th_seq - 1;
1719 /* fall into ... */
1720
1721 /*
1722 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
1723 * ACKs. If the ack is in the range
1724 * tp->snd_una < th->th_ack <= tp->snd_max
1725 * then advance tp->snd_una to th->th_ack and drop
1726 * data from the retransmission queue. If this ACK reflects
1727 * more up to date window information we update our window information.
1728 */
1729 case TCPS_ESTABLISHED:
1730 case TCPS_FIN_WAIT_1:
1731 case TCPS_FIN_WAIT_2:
1732 case TCPS_CLOSE_WAIT:
1733 case TCPS_CLOSING:
1734 case TCPS_LAST_ACK:
1735 case TCPS_TIME_WAIT:
1736
1737 if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
1738 if (tlen == 0 && tiwin == tp->snd_wnd) {
1739 tcpstat.tcps_rcvdupack++;
1740 /*
1741 * If we have outstanding data (other than
1742 * a window probe), this is a completely
1743 * duplicate ack (ie, window info didn't
1744 * change), the ack is the biggest we've
1745 * seen and we've seen exactly our rexmt
1746 * threshhold of them, assume a packet
1747 * has been dropped and retransmit it.
1748 * Kludge snd_nxt & the congestion
1749 * window so we send only this one
1750 * packet.
1751 *
1752 * We know we're losing at the current
1753 * window size so do congestion avoidance
1754 * (set ssthresh to half the current window
1755 * and pull our congestion window back to
1756 * the new ssthresh).
1757 *
1758 * Dup acks mean that packets have left the
1759 * network (they're now cached at the receiver)
1760 * so bump cwnd by the amount in the receiver
1761 * to keep a constant cwnd packets in the
1762 * network.
1763 */
1764 if (!callout_active(tp->tt_rexmt) ||
1765 th->th_ack != tp->snd_una)
1766 tp->t_dupacks = 0;
1767 else if (++tp->t_dupacks == tcprexmtthresh) {
1768 tcp_seq onxt = tp->snd_nxt;
1769 u_int win =
1770 min(tp->snd_wnd, tp->snd_cwnd) / 2 /
1771 tp->t_maxseg;
1772
1773 if (win < 2)
1774 win = 2;
1775 tp->snd_ssthresh = win * tp->t_maxseg;
1776 callout_stop(tp->tt_rexmt);
1777 tp->t_rtttime = 0;
1778 tp->snd_nxt = th->th_ack;
1779 tp->snd_cwnd = tp->t_maxseg;
1780 (void) tcp_output(tp);
1781 tp->snd_cwnd = tp->snd_ssthresh +
1782 tp->t_maxseg * tp->t_dupacks;
1783 if (SEQ_GT(onxt, tp->snd_nxt))
1784 tp->snd_nxt = onxt;
1785 goto drop;
1786 } else if (tp->t_dupacks > tcprexmtthresh) {
1787 tp->snd_cwnd += tp->t_maxseg;
1788 (void) tcp_output(tp);
1789 goto drop;
1790 }
1791 } else
1792 tp->t_dupacks = 0;
1793 break;
1794 }
1795 /*
1796 * If the congestion window was inflated to account
1797 * for the other side's cached packets, retract it.
1798 */
1799 if (tp->t_dupacks >= tcprexmtthresh &&
1800 tp->snd_cwnd > tp->snd_ssthresh)
1801 tp->snd_cwnd = tp->snd_ssthresh;
1802 tp->t_dupacks = 0;
1803 if (SEQ_GT(th->th_ack, tp->snd_max)) {
1804 tcpstat.tcps_rcvacktoomuch++;
1805 goto dropafterack;
1806 }
1807 /*
1808 * If we reach this point, ACK is not a duplicate,
1809 * i.e., it ACKs something we sent.
1810 */
1811 if (tp->t_flags & TF_NEEDSYN) {
1812 /*
1813 * T/TCP: Connection was half-synchronized, and our
1814 * SYN has been ACK'd (so connection is now fully
1815 * synchronized). Go to non-starred state,
1816 * increment snd_una for ACK of SYN, and check if
1817 * we can do window scaling.
1818 */
1819 tp->t_flags &= ~TF_NEEDSYN;
1820 tp->snd_una++;
1821 /* Do window scaling? */
1822 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
1823 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
1824 tp->snd_scale = tp->requested_s_scale;
1825 tp->rcv_scale = tp->request_r_scale;
1826 }
1827 }
1828
1829process_ACK:
1830 acked = th->th_ack - tp->snd_una;
1831 tcpstat.tcps_rcvackpack++;
1832 tcpstat.tcps_rcvackbyte += acked;
1833
1834 /*
1835 * If we just performed our first retransmit, and the ACK
1836 * arrives within our recovery window, then it was a mistake
1837 * to do the retransmit in the first place. Recover our
1838 * original cwnd and ssthresh, and proceed to transmit where
1839 * we left off.
1840 */
1841 if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) {
1842 tp->snd_cwnd = tp->snd_cwnd_prev;
1843 tp->snd_ssthresh = tp->snd_ssthresh_prev;
1844 tp->snd_nxt = tp->snd_max;
1845 tp->t_badrxtwin = 0; /* XXX probably not required */
1846 }
1847
1848 /*
1849 * If we have a timestamp reply, update smoothed
1850 * round trip time. If no timestamp is present but
1851 * transmit timer is running and timed sequence
1852 * number was acked, update smoothed round trip time.
1853 * Since we now have an rtt measurement, cancel the
1854 * timer backoff (cf., Phil Karn's retransmit alg.).
1855 * Recompute the initial retransmit timer.
1856 */
1857 if (to.to_flag & TOF_TS)
1858 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1);
1859 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq))
1860 tcp_xmit_timer(tp, ticks - tp->t_rtttime);
1861
1862 /*
1863 * If all outstanding data is acked, stop retransmit
1864 * timer and remember to restart (more output or persist).
1865 * If there is more data to be acked, restart retransmit
1866 * timer, using current (possibly backed-off) value.
1867 */
1868 if (th->th_ack == tp->snd_max) {
1869 callout_stop(tp->tt_rexmt);
1870 needoutput = 1;
1871 } else if (!callout_active(tp->tt_persist))
1872 callout_reset(tp->tt_rexmt, tp->t_rxtcur,
1873 tcp_timer_rexmt, tp);
1874
1875 /*
1876 * If no data (only SYN) was ACK'd,
1877 * skip rest of ACK processing.
1878 */
1879 if (acked == 0)
1880 goto step6;
1881
1882 /*
1883 * When new data is acked, open the congestion window.
1884 * If the window gives us less than ssthresh packets
1885 * in flight, open exponentially (maxseg per packet).
1886 * Otherwise open linearly: maxseg per window
1887 * (maxseg^2 / cwnd per packet).
1888 */
1889 {
1890 register u_int cw = tp->snd_cwnd;
1891 register u_int incr = tp->t_maxseg;
1892
1893 if (cw > tp->snd_ssthresh)
1894 incr = incr * incr / cw;
1895 tp->snd_cwnd = min(cw + incr, TCP_MAXWIN << tp->snd_scale);
1896 }
1897 if (acked > so->so_snd.sb_cc) {
1898 tp->snd_wnd -= so->so_snd.sb_cc;
1899 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc);
1900 ourfinisacked = 1;
1901 } else {
1902 sbdrop(&so->so_snd, acked);
1903 tp->snd_wnd -= acked;
1904 ourfinisacked = 0;
1905 }
1906 sowwakeup(so);
1907 tp->snd_una = th->th_ack;
1908 if (SEQ_LT(tp->snd_nxt, tp->snd_una))
1909 tp->snd_nxt = tp->snd_una;
1910
1911 switch (tp->t_state) {
1912
1913 /*
1914 * In FIN_WAIT_1 STATE in addition to the processing
1915 * for the ESTABLISHED state if our FIN is now acknowledged
1916 * then enter FIN_WAIT_2.
1917 */
1918 case TCPS_FIN_WAIT_1:
1919 if (ourfinisacked) {
1920 /*
1921 * If we can't receive any more
1922 * data, then closing user can proceed.
1923 * Starting the timer is contrary to the
1924 * specification, but if we don't get a FIN
1925 * we'll hang forever.
1926 */
1927 if (so->so_state & SS_CANTRCVMORE) {
1928 soisdisconnected(so);
1929 callout_reset(tp->tt_2msl, tcp_maxidle,
1930 tcp_timer_2msl, tp);
1931 }
1932 tp->t_state = TCPS_FIN_WAIT_2;
1933 }
1934 break;
1935
1936 /*
1937 * In CLOSING STATE in addition to the processing for
1938 * the ESTABLISHED state if the ACK acknowledges our FIN
1939 * then enter the TIME-WAIT state, otherwise ignore
1940 * the segment.
1941 */
1942 case TCPS_CLOSING:
1943 if (ourfinisacked) {
1944 tp->t_state = TCPS_TIME_WAIT;
1945 tcp_canceltimers(tp);
1946 /* Shorten TIME_WAIT [RFC-1644, p.28] */
1947 if (tp->cc_recv != 0 &&
1948 (ticks - tp->t_starttime) < tcp_msl)
1949 callout_reset(tp->tt_2msl,
1950 tp->t_rxtcur *
1951 TCPTV_TWTRUNC,
1952 tcp_timer_2msl, tp);
1953 else
1954 callout_reset(tp->tt_2msl, 2 * tcp_msl,
1955 tcp_timer_2msl, tp);
1956 soisdisconnected(so);
1957 }
1958 break;
1959
1960 /*
1961 * In LAST_ACK, we may still be waiting for data to drain
1962 * and/or to be acked, as well as for the ack of our FIN.
1963 * If our FIN is now acknowledged, delete the TCB,
1964 * enter the closed state and return.
1965 */
1966 case TCPS_LAST_ACK:
1967 if (ourfinisacked) {
1968 tp = tcp_close(tp);
1969 goto drop;
1970 }
1971 break;
1972
1973 /*
1974 * In TIME_WAIT state the only thing that should arrive
1975 * is a retransmission of the remote FIN. Acknowledge
1976 * it and restart the finack timer.
1977 */
1978 case TCPS_TIME_WAIT:
1979 callout_reset(tp->tt_2msl, 2 * tcp_msl,
1980 tcp_timer_2msl, tp);
1981 goto dropafterack;
1982 }
1983 }
1984
1985step6:
1986 /*
1987 * Update window information.
1988 * Don't look at window if no ACK: TAC's send garbage on first SYN.
1989 */
1990 if ((thflags & TH_ACK) &&
1991 (SEQ_LT(tp->snd_wl1, th->th_seq) ||
1992 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) ||
1993 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) {
1994 /* keep track of pure window updates */
1995 if (tlen == 0 &&
1996 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)
1997 tcpstat.tcps_rcvwinupd++;
1998 tp->snd_wnd = tiwin;
1999 tp->snd_wl1 = th->th_seq;
2000 tp->snd_wl2 = th->th_ack;
2001 if (tp->snd_wnd > tp->max_sndwnd)
2002 tp->max_sndwnd = tp->snd_wnd;
2003 needoutput = 1;
2004 }
2005
2006 /*
2007 * Process segments with URG.
2008 */
2009 if ((thflags & TH_URG) && th->th_urp &&
2010 TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2011 /*
2012 * This is a kludge, but if we receive and accept
2013 * random urgent pointers, we'll crash in
2014 * soreceive. It's hard to imagine someone
2015 * actually wanting to send this much urgent data.
2016 */
2017 if (th->th_urp + so->so_rcv.sb_cc > sb_max) {
2018 th->th_urp = 0; /* XXX */
2019 thflags &= ~TH_URG; /* XXX */
2020 goto dodata; /* XXX */
2021 }
2022 /*
2023 * If this segment advances the known urgent pointer,
2024 * then mark the data stream. This should not happen
2025 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
2026 * a FIN has been received from the remote side.
2027 * In these states we ignore the URG.
2028 *
2029 * According to RFC961 (Assigned Protocols),
2030 * the urgent pointer points to the last octet
2031 * of urgent data. We continue, however,
2032 * to consider it to indicate the first octet
2033 * of data past the urgent section as the original
2034 * spec states (in one of two places).
2035 */
2036 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) {
2037 tp->rcv_up = th->th_seq + th->th_urp;
2038 so->so_oobmark = so->so_rcv.sb_cc +
2039 (tp->rcv_up - tp->rcv_nxt) - 1;
2040 if (so->so_oobmark == 0)
2041 so->so_state |= SS_RCVATMARK;
2042 sohasoutofband(so);
2043 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
2044 }
2045 /*
2046 * Remove out of band data so doesn't get presented to user.
2047 * This can happen independent of advancing the URG pointer,
2048 * but if two URG's are pending at once, some out-of-band
2049 * data may creep in... ick.
2050 */
2051 if (th->th_urp <= (u_long)tlen
2052#ifdef SO_OOBINLINE
2053 && (so->so_options & SO_OOBINLINE) == 0
2054#endif
2055 )
2056 tcp_pulloutofband(so, th, m,
2057 drop_hdrlen); /* hdr drop is delayed */
2058 } else
2059 /*
2060 * If no out of band data is expected,
2061 * pull receive urgent pointer along
2062 * with the receive window.
2063 */
2064 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
2065 tp->rcv_up = tp->rcv_nxt;
2066dodata: /* XXX */
2067
2068 /*
2069 * Process the segment text, merging it into the TCP sequencing queue,
2070 * and arranging for acknowledgment of receipt if necessary.
2071 * This process logically involves adjusting tp->rcv_wnd as data
2072 * is presented to the user (this happens in tcp_usrreq.c,
2073 * case PRU_RCVD). If a FIN has already been received on this
2074 * connection then we just ignore the text.
2075 */
2076 if ((tlen || (thflags&TH_FIN)) &&
2077 TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2078 m_adj(m, drop_hdrlen); /* delayed header drop */
2079 TCP_REASS(tp, th, &tlen, m, so, thflags);
2080 /*
2081 * Note the amount of data that peer has sent into
2082 * our window, in order to estimate the sender's
2083 * buffer size.
2084 */
2085 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
2086 } else {
2087 m_freem(m);
2088 thflags &= ~TH_FIN;
2089 }
2090
2091 /*
2092 * If FIN is received ACK the FIN and let the user know
2093 * that the connection is closing.
2094 */
2095 if (thflags & TH_FIN) {
2096 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2097 socantrcvmore(so);
2098 /*
2099 * If connection is half-synchronized
2100 * (ie NEEDSYN flag on) then delay ACK,
2101 * so it may be piggybacked when SYN is sent.
2102 * Otherwise, since we received a FIN then no
2103 * more input can be expected, send ACK now.
2104 */
2105 if (tcp_delack_enabled && (tp->t_flags & TF_NEEDSYN))
2106 callout_reset(tp->tt_delack, tcp_delacktime,
2107 tcp_timer_delack, tp);
2108 else
2109 tp->t_flags |= TF_ACKNOW;
2110 tp->rcv_nxt++;
2111 }
2112 switch (tp->t_state) {
2113
2114 /*
2115 * In SYN_RECEIVED and ESTABLISHED STATES
2116 * enter the CLOSE_WAIT state.
2117 */
2118 case TCPS_SYN_RECEIVED:
2119 tp->t_starttime = ticks;
2120 /*FALLTHROUGH*/
2121 case TCPS_ESTABLISHED:
2122 tp->t_state = TCPS_CLOSE_WAIT;
2123 break;
2124
2125 /*
2126 * If still in FIN_WAIT_1 STATE FIN has not been acked so
2127 * enter the CLOSING state.
2128 */
2129 case TCPS_FIN_WAIT_1:
2130 tp->t_state = TCPS_CLOSING;
2131 break;
2132
2133 /*
2134 * In FIN_WAIT_2 state enter the TIME_WAIT state,
2135 * starting the time-wait timer, turning off the other
2136 * standard timers.
2137 */
2138 case TCPS_FIN_WAIT_2:
2139 tp->t_state = TCPS_TIME_WAIT;
2140 tcp_canceltimers(tp);
2141 /* Shorten TIME_WAIT [RFC-1644, p.28] */
2142 if (tp->cc_recv != 0 &&
2143 (ticks - tp->t_starttime) < tcp_msl) {
2144 callout_reset(tp->tt_2msl,
2145 tp->t_rxtcur * TCPTV_TWTRUNC,
2146 tcp_timer_2msl, tp);
2147 /* For transaction client, force ACK now. */
2148 tp->t_flags |= TF_ACKNOW;
2149 }
2150 else
2151 callout_reset(tp->tt_2msl, 2 * tcp_msl,
2152 tcp_timer_2msl, tp);
2153 soisdisconnected(so);
2154 break;
2155
2156 /*
2157 * In TIME_WAIT state restart the 2 MSL time_wait timer.
2158 */
2159 case TCPS_TIME_WAIT:
2160 callout_reset(tp->tt_2msl, 2 * tcp_msl,
2161 tcp_timer_2msl, tp);
2162 break;
2163 }
2164 }
2165#ifdef TCPDEBUG
2166 if (so->so_options & SO_DEBUG)
2167 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen,
2168 &tcp_savetcp, 0);
2169#endif
2170
2171 /*
2172 * Return any desired output.
2173 */
2174 if (needoutput || (tp->t_flags & TF_ACKNOW))
2175 (void) tcp_output(tp);
2176 return;
2177
2178dropafterack:
2179 /*
2180 * Generate an ACK dropping incoming segment if it occupies
2181 * sequence space, where the ACK reflects our state.
2182 *
2183 * We can now skip the test for the RST flag since all
2184 * paths to this code happen after packets containing
2185 * RST have been dropped.
2186 *
2187 * In the SYN-RECEIVED state, don't send an ACK unless the
2188 * segment we received passes the SYN-RECEIVED ACK test.
2189 * If it fails send a RST. This breaks the loop in the
2190 * "LAND" DoS attack, and also prevents an ACK storm
2191 * between two listening ports that have been sent forged
2192 * SYN segments, each with the source address of the other.
2193 */
2194 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
2195 (SEQ_GT(tp->snd_una, th->th_ack) ||
2196 SEQ_GT(th->th_ack, tp->snd_max)) )
2197 goto maybedropwithreset;
2198#ifdef TCPDEBUG
2199 if (so->so_options & SO_DEBUG)
2200 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
2201 &tcp_savetcp, 0);
2202#endif
2203 m_freem(m);
2204 tp->t_flags |= TF_ACKNOW;
2205 (void) tcp_output(tp);
2206 return;
2207
2208
2209 /*
2210 * Conditionally drop with reset or just drop depending on whether
2211 * we think we are under attack or not.
2212 */
2213maybedropwithreset:
2214#ifdef ICMP_BANDLIM
2215 if (badport_bandlim(1) < 0)
2216 goto drop;
2217#endif
2218 /* fall through */
2219dropwithreset:
2220#ifdef TCP_RESTRICT_RST
2221 if (restrict_rst)
2222 goto drop;
2223#endif
2224 /*
2225 * Generate a RST, dropping incoming segment.
2226 * Make ACK acceptable to originator of segment.
2227 * Don't bother to respond if destination was broadcast/multicast.
2228 */
2229 if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST))
2230 goto drop;
2231#ifdef INET6
2232 if (isipv6) {
2233 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
2234 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
2235 goto drop;
2236 } else
2237#endif /* INET6 */
2238 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
2239 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
2240 ip->ip_src.s_addr == htonl(INADDR_BROADCAST))
2241 goto drop;
2242 /* IPv6 anycast check is done at tcp6_input() */
2243#ifdef TCPDEBUG
2244 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
2245 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
2246 &tcp_savetcp, 0);
2247#endif
2248 if (thflags & TH_ACK)
2249 /* mtod() below is safe as long as hdr dropping is delayed */
2250 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack,
2251 TH_RST);
2252 else {
2253 if (thflags & TH_SYN)
2254 tlen++;
2255 /* mtod() below is safe as long as hdr dropping is delayed */
2256 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen,
2257 (tcp_seq)0, TH_RST|TH_ACK);
2258 }
2259 /* destroy temporarily created socket */
2260 if (dropsocket)
2261 (void) soabort(so);
2262 return;
2263
2264drop:
2265 /*
2266 * Drop space held by incoming segment and return.
2267 */
2268#ifdef TCPDEBUG
2269 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
2270 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
2271 &tcp_savetcp, 0);
2272#endif
2273 m_freem(m);
2274 /* destroy temporarily created socket */
2275 if (dropsocket)
2276 (void) soabort(so);
2277 return;
2278}
2279
2280static void
2281tcp_dooptions(tp, cp, cnt, th, to)
2282 struct tcpcb *tp;
2283 u_char *cp;
2284 int cnt;
2285 struct tcphdr *th;
2286 struct tcpopt *to;
2287{
2288 u_short mss = 0;
2289 int opt, optlen;
2290
2291 for (; cnt > 0; cnt -= optlen, cp += optlen) {
2292 opt = cp[0];
2293 if (opt == TCPOPT_EOL)
2294 break;
2295 if (opt == TCPOPT_NOP)
2296 optlen = 1;
2297 else {
2298 optlen = cp[1];
2299 if (optlen <= 0)
2300 break;
2301 }
2302 switch (opt) {
2303
2304 default:
2305 continue;
2306
2307 case TCPOPT_MAXSEG:
2308 if (optlen != TCPOLEN_MAXSEG)
2309 continue;
2310 if (!(th->th_flags & TH_SYN))
2311 continue;
2312 bcopy((char *) cp + 2, (char *) &mss, sizeof(mss));
2313 NTOHS(mss);
2314 break;
2315
2316 case TCPOPT_WINDOW:
2317 if (optlen != TCPOLEN_WINDOW)
2318 continue;
2319 if (!(th->th_flags & TH_SYN))
2320 continue;
2321 tp->t_flags |= TF_RCVD_SCALE;
2322 tp->requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT);
2323 break;
2324
2325 case TCPOPT_TIMESTAMP:
2326 if (optlen != TCPOLEN_TIMESTAMP)
2327 continue;
2328 to->to_flag |= TOF_TS;
2329 bcopy((char *)cp + 2,
2330 (char *)&to->to_tsval, sizeof(to->to_tsval));
2331 NTOHL(to->to_tsval);
2332 bcopy((char *)cp + 6,
2333 (char *)&to->to_tsecr, sizeof(to->to_tsecr));
2334 NTOHL(to->to_tsecr);
2335
2336 /*
2337 * A timestamp received in a SYN makes
2338 * it ok to send timestamp requests and replies.
2339 */
2340 if (th->th_flags & TH_SYN) {
2341 tp->t_flags |= TF_RCVD_TSTMP;
2342 tp->ts_recent = to->to_tsval;
2343 tp->ts_recent_age = ticks;
2344 }
2345 break;
2346 case TCPOPT_CC:
2347 if (optlen != TCPOLEN_CC)
2348 continue;
2349 to->to_flag |= TOF_CC;
2350 bcopy((char *)cp + 2,
2351 (char *)&to->to_cc, sizeof(to->to_cc));
2352 NTOHL(to->to_cc);
2353 /*
2354 * A CC or CC.new option received in a SYN makes
2355 * it ok to send CC in subsequent segments.
2356 */
2357 if (th->th_flags & TH_SYN)
2358 tp->t_flags |= TF_RCVD_CC;
2359 break;
2360 case TCPOPT_CCNEW:
2361 if (optlen != TCPOLEN_CC)
2362 continue;
2363 if (!(th->th_flags & TH_SYN))
2364 continue;
2365 to->to_flag |= TOF_CCNEW;
2366 bcopy((char *)cp + 2,
2367 (char *)&to->to_cc, sizeof(to->to_cc));
2368 NTOHL(to->to_cc);
2369 /*
2370 * A CC or CC.new option received in a SYN makes
2371 * it ok to send CC in subsequent segments.
2372 */
2373 tp->t_flags |= TF_RCVD_CC;
2374 break;
2375 case TCPOPT_CCECHO:
2376 if (optlen != TCPOLEN_CC)
2377 continue;
2378 if (!(th->th_flags & TH_SYN))
2379 continue;
2380 to->to_flag |= TOF_CCECHO;
2381 bcopy((char *)cp + 2,
2382 (char *)&to->to_ccecho, sizeof(to->to_ccecho));
2383 NTOHL(to->to_ccecho);
2384 break;
2385 }
2386 }
2387 if (th->th_flags & TH_SYN)
2388 tcp_mss(tp, mss); /* sets t_maxseg */
2389}
2390
2391/*
2392 * Pull out of band byte out of a segment so
2393 * it doesn't appear in the user's data queue.
2394 * It is still reflected in the segment length for
2395 * sequencing purposes.
2396 */
2397static void
2398tcp_pulloutofband(so, th, m, off)
2399 struct socket *so;
2400 struct tcphdr *th;
2401 register struct mbuf *m;
2402 int off; /* delayed to be droped hdrlen */
2403{
2404 int cnt = off + th->th_urp - 1;
2405
2406 while (cnt >= 0) {
2407 if (m->m_len > cnt) {
2408 char *cp = mtod(m, caddr_t) + cnt;
2409 struct tcpcb *tp = sototcpcb(so);
2410
2411 tp->t_iobc = *cp;
2412 tp->t_oobflags |= TCPOOB_HAVEDATA;
2413 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1));
2414 m->m_len--;
2415 if (m->m_flags & M_PKTHDR)
2416 m->m_pkthdr.len--;
2417 return;
2418 }
2419 cnt -= m->m_len;
2420 m = m->m_next;
2421 if (m == 0)
2422 break;
2423 }
2424 panic("tcp_pulloutofband");
2425}
2426
2427/*
2428 * Collect new round-trip time estimate
2429 * and update averages and current timeout.
2430 */
2431static void
2432tcp_xmit_timer(tp, rtt)
2433 register struct tcpcb *tp;
2434 int rtt;
2435{
2436 register int delta;
2437
2438 tcpstat.tcps_rttupdated++;
2439 tp->t_rttupdated++;
2440 if (tp->t_srtt != 0) {
2441 /*
2442 * srtt is stored as fixed point with 5 bits after the
2443 * binary point (i.e., scaled by 8). The following magic
2444 * is equivalent to the smoothing algorithm in rfc793 with
2445 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
2446 * point). Adjust rtt to origin 0.
2447 */
2448 delta = ((rtt - 1) << TCP_DELTA_SHIFT)
2449 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
2450
2451 if ((tp->t_srtt += delta) <= 0)
2452 tp->t_srtt = 1;
2453
2454 /*
2455 * We accumulate a smoothed rtt variance (actually, a
2456 * smoothed mean difference), then set the retransmit
2457 * timer to smoothed rtt + 4 times the smoothed variance.
2458 * rttvar is stored as fixed point with 4 bits after the
2459 * binary point (scaled by 16). The following is
2460 * equivalent to rfc793 smoothing with an alpha of .75
2461 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces
2462 * rfc793's wired-in beta.
2463 */
2464 if (delta < 0)
2465 delta = -delta;
2466 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
2467 if ((tp->t_rttvar += delta) <= 0)
2468 tp->t_rttvar = 1;
2469 } else {
2470 /*
2471 * No rtt measurement yet - use the unsmoothed rtt.
2472 * Set the variance to half the rtt (so our first
2473 * retransmit happens at 3*rtt).
2474 */
2475 tp->t_srtt = rtt << TCP_RTT_SHIFT;
2476 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
2477 }
2478 tp->t_rtttime = 0;
2479 tp->t_rxtshift = 0;
2480
2481 /*
2482 * the retransmit should happen at rtt + 4 * rttvar.
2483 * Because of the way we do the smoothing, srtt and rttvar
2484 * will each average +1/2 tick of bias. When we compute
2485 * the retransmit timer, we want 1/2 tick of rounding and
2486 * 1 extra tick because of +-1/2 tick uncertainty in the
2487 * firing of the timer. The bias will give us exactly the
2488 * 1.5 tick we need. But, because the bias is
2489 * statistical, we have to test that we don't drop below
2490 * the minimum feasible timer (which is 2 ticks).
2491 */
2492 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
2493 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);
2494
2495 /*
2496 * We received an ack for a packet that wasn't retransmitted;
2497 * it is probably safe to discard any error indications we've
2498 * received recently. This isn't quite right, but close enough
2499 * for now (a route might have failed after we sent a segment,
2500 * and the return path might not be symmetrical).
2501 */
2502 tp->t_softerror = 0;
2503}
2504
2505/*
2506 * Determine a reasonable value for maxseg size.
2507 * If the route is known, check route for mtu.
2508 * If none, use an mss that can be handled on the outgoing
2509 * interface without forcing IP to fragment; if bigger than
2510 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES
2511 * to utilize large mbufs. If no route is found, route has no mtu,
2512 * or the destination isn't local, use a default, hopefully conservative
2513 * size (usually 512 or the default IP max size, but no more than the mtu
2514 * of the interface), as we can't discover anything about intervening
2515 * gateways or networks. We also initialize the congestion/slow start
2516 * window to be a single segment if the destination isn't local.
2517 * While looking at the routing entry, we also initialize other path-dependent
2518 * parameters from pre-set or cached values in the routing entry.
2519 *
2520 * Also take into account the space needed for options that we
2521 * send regularly. Make maxseg shorter by that amount to assure
2522 * that we can send maxseg amount of data even when the options
2523 * are present. Store the upper limit of the length of options plus
2524 * data in maxopd.
2525 *
2526 * NOTE that this routine is only called when we process an incoming
2527 * segment, for outgoing segments only tcp_mssopt is called.
2528 *
2529 * In case of T/TCP, we call this routine during implicit connection
2530 * setup as well (offer = -1), to initialize maxseg from the cached
2531 * MSS of our peer.
2532 */
2533void
2534tcp_mss(tp, offer)
2535 struct tcpcb *tp;
2536 int offer;
2537{
2538 register struct rtentry *rt;
2539 struct ifnet *ifp;
2540 register int rtt, mss;
2541 u_long bufsize;
2542 struct inpcb *inp;
2543 struct socket *so;
2544 struct rmxp_tao *taop;
2545 int origoffer = offer;
2546#ifdef INET6
2547 int isipv6;
2548 int min_protoh;
2549#endif
2550
2551 inp = tp->t_inpcb;
2552#ifdef INET6
2553 isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0;
2554 min_protoh = isipv6 ? sizeof (struct ip6_hdr) + sizeof (struct tcphdr)
2555 : sizeof (struct tcpiphdr);
2556#else
2557#define min_protoh (sizeof (struct tcpiphdr))
2558#endif
2559#ifdef INET6
2560 if (isipv6)
2561 rt = tcp_rtlookup6(inp);
2562 else
2563#endif
2564 rt = tcp_rtlookup(inp);
2565 if (rt == NULL) {
2566 tp->t_maxopd = tp->t_maxseg =
2567#ifdef INET6
2568 isipv6 ? tcp_v6mssdflt :
2569#endif /* INET6 */
2570 tcp_mssdflt;
2571 return;
2572 }
2573 ifp = rt->rt_ifp;
2574 so = inp->inp_socket;
2575
2576 taop = rmx_taop(rt->rt_rmx);
2577 /*
2578 * Offer == -1 means that we didn't receive SYN yet,
2579 * use cached value in that case;
2580 */
2581 if (offer == -1)
2582 offer = taop->tao_mssopt;
2583 /*
2584 * Offer == 0 means that there was no MSS on the SYN segment,
2585 * in this case we use tcp_mssdflt.
2586 */
2587 if (offer == 0)
2588 offer =
2589#ifdef INET6
2590 isipv6 ? tcp_v6mssdflt :
2591#endif /* INET6 */
2592 tcp_mssdflt;
2593 else
2594 /*
2595 * Sanity check: make sure that maxopd will be large
2596 * enough to allow some data on segments even is the
2597 * all the option space is used (40bytes). Otherwise
2598 * funny things may happen in tcp_output.
2599 */
2600 offer = max(offer, 64);
2601 taop->tao_mssopt = offer;
2602
2603 /*
2604 * While we're here, check if there's an initial rtt
2605 * or rttvar. Convert from the route-table units
2606 * to scaled multiples of the slow timeout timer.
2607 */
2608 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) {
2609 /*
2610 * XXX the lock bit for RTT indicates that the value
2611 * is also a minimum value; this is subject to time.
2612 */
2613 if (rt->rt_rmx.rmx_locks & RTV_RTT)
2614 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz);
2615 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE));
2616 tcpstat.tcps_usedrtt++;
2617 if (rt->rt_rmx.rmx_rttvar) {
2618 tp->t_rttvar = rt->rt_rmx.rmx_rttvar /
2619 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE));
2620 tcpstat.tcps_usedrttvar++;
2621 } else {
2622 /* default variation is +- 1 rtt */
2623 tp->t_rttvar =
2624 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
2625 }
2626 TCPT_RANGESET(tp->t_rxtcur,
2627 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
2628 tp->t_rttmin, TCPTV_REXMTMAX);
2629 }
2630 /*
2631 * if there's an mtu associated with the route, use it
2632 * else, use the link mtu.
2633 */
2634 if (rt->rt_rmx.rmx_mtu)
2635 mss = rt->rt_rmx.rmx_mtu - min_protoh;
2636 else
2637 {
2638 mss =
2639#ifdef INET6
2640 (isipv6 ? nd_ifinfo[rt->rt_ifp->if_index].linkmtu :
2641#endif
2642 ifp->if_mtu
2643#ifdef INET6
2644 )
2645#endif
2646 - min_protoh;
2647#ifdef INET6
2648 if (isipv6) {
2649 if (!in6_localaddr(&inp->in6p_faddr))
2650 mss = min(mss, tcp_v6mssdflt);
2651 } else
2652#endif
2653 if (!in_localaddr(inp->inp_faddr))
2654 mss = min(mss, tcp_mssdflt);
2655 }
2656 mss = min(mss, offer);
2657 /*
2658 * maxopd stores the maximum length of data AND options
2659 * in a segment; maxseg is the amount of data in a normal
2660 * segment. We need to store this value (maxopd) apart
2661 * from maxseg, because now every segment carries options
2662 * and thus we normally have somewhat less data in segments.
2663 */
2664 tp->t_maxopd = mss;
2665
2666 /*
2667 * In case of T/TCP, origoffer==-1 indicates, that no segments
2668 * were received yet. In this case we just guess, otherwise
2669 * we do the same as before T/TCP.
2670 */
2671 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
2672 (origoffer == -1 ||
2673 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP))
2674 mss -= TCPOLEN_TSTAMP_APPA;
2675 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC &&
2676 (origoffer == -1 ||
2677 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC))
2678 mss -= TCPOLEN_CC_APPA;
2679
2680#if (MCLBYTES & (MCLBYTES - 1)) == 0
2681 if (mss > MCLBYTES)
2682 mss &= ~(MCLBYTES-1);
2683#else
2684 if (mss > MCLBYTES)
2685 mss = mss / MCLBYTES * MCLBYTES;
2686#endif
2687 /*
2688 * If there's a pipesize, change the socket buffer
2689 * to that size. Make the socket buffers an integral
2690 * number of mss units; if the mss is larger than
2691 * the socket buffer, decrease the mss.
2692 */
2693#ifdef RTV_SPIPE
2694 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0)
2695#endif
2696 bufsize = so->so_snd.sb_hiwat;
2697 if (bufsize < mss)
2698 mss = bufsize;
2699 else {
2700 bufsize = roundup(bufsize, mss);
2701 if (bufsize > sb_max)
2702 bufsize = sb_max;
2703 (void)sbreserve(&so->so_snd, bufsize, so, NULL);
2704 }
2705 tp->t_maxseg = mss;
2706
2707#ifdef RTV_RPIPE
2708 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0)
2709#endif
2710 bufsize = so->so_rcv.sb_hiwat;
2711 if (bufsize > mss) {
2712 bufsize = roundup(bufsize, mss);
2713 if (bufsize > sb_max)
2714 bufsize = sb_max;
2715 (void)sbreserve(&so->so_rcv, bufsize, so, NULL);
2716 }
2717
2718 /*
2719 * Set the slow-start flight size depending on whether this
2720 * is a local network or not.
2721 */
2722 if (
2723#ifdef INET6
2724 (isipv6 && in6_localaddr(&inp->in6p_faddr)) ||
2725 (!isipv6 &&
2726#endif
2727 in_localaddr(inp->inp_faddr)
2728#ifdef INET6
2729 )
2730#endif
2731 )
2732 tp->snd_cwnd = mss * ss_fltsz_local;
2733 else
2734 tp->snd_cwnd = mss * ss_fltsz;
2735
2736 if (rt->rt_rmx.rmx_ssthresh) {
2737 /*
2738 * There's some sort of gateway or interface
2739 * buffer limit on the path. Use this to set
2740 * the slow start threshhold, but set the
2741 * threshold to no less than 2*mss.
2742 */
2743 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh);
2744 tcpstat.tcps_usedssthresh++;
2745 }
2746}
2747
2748/*
2749 * Determine the MSS option to send on an outgoing SYN.
2750 */
2751int
2752tcp_mssopt(tp)
2753 struct tcpcb *tp;
2754{
2755 struct rtentry *rt;
2756#ifdef INET6
2757 int isipv6;
2758 int min_protoh;
2759#endif
2760
2761#ifdef INET6
2762 isipv6 = ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) ? 1 : 0;
2763 min_protoh = isipv6 ? sizeof (struct ip6_hdr) + sizeof (struct tcphdr)
2764 : sizeof (struct tcpiphdr);
2765#else
2766#define min_protoh (sizeof (struct tcpiphdr))
2767#endif
2768#ifdef INET6
2769 if (isipv6)
2770 rt = tcp_rtlookup6(tp->t_inpcb);
2771 else
2772#endif /* INET6 */
2773 rt = tcp_rtlookup(tp->t_inpcb);
2774 if (rt == NULL)
2775 return
2776#ifdef INET6
2777 isipv6 ? tcp_v6mssdflt :
2778#endif /* INET6 */
2779 tcp_mssdflt;
2780
2781 return rt->rt_ifp->if_mtu - min_protoh;
2782}
| 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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