KNF/style and warnings clean up. ANSI style prototype for printb(), and
[dragonfly.git] / sys / netinet / tcp_input.c
CommitLineData
984263bc 1/*
66d6c637
JH
2 * Copyright (c) 2002, 2003, 2004 Jeffrey M. Hsu. All rights reserved.
3 * Copyright (c) 2002, 2003, 2004 The DragonFly Project. All rights reserved.
95b22adf 4 *
66d6c637
JH
5 * This code is derived from software contributed to The DragonFly Project
6 * by Jeffrey M. Hsu.
95b22adf 7 *
66d6c637
JH
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of The DragonFly Project nor the names of its
17 * contributors may be used to endorse or promote products derived
18 * from this software without specific, prior written permission.
95b22adf 19 *
66d6c637
JH
20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
23 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
24 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
25 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
26 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
27 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
28 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
29 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
30 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34/*
35 * Copyright (c) 2002, 2003, 2004 Jeffrey M. Hsu. All rights reserved.
36 *
37 * License terms: all terms for the DragonFly license above plus the following:
38 *
39 * 4. All advertising materials mentioning features or use of this software
40 * must display the following acknowledgement:
41 *
42 * This product includes software developed by Jeffrey M. Hsu
43 * for the DragonFly Project.
44 *
45 * This requirement may be waived with permission from Jeffrey Hsu.
46 * This requirement will sunset and may be removed on July 8 2005,
47 * after which the standard DragonFly license (as shown above) will
48 * apply.
49 */
50
51/*
984263bc
MD
52 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995
53 * The Regents of the University of California. All rights reserved.
54 *
55 * Redistribution and use in source and binary forms, with or without
56 * modification, are permitted provided that the following conditions
57 * are met:
58 * 1. Redistributions of source code must retain the above copyright
59 * notice, this list of conditions and the following disclaimer.
60 * 2. Redistributions in binary form must reproduce the above copyright
61 * notice, this list of conditions and the following disclaimer in the
62 * documentation and/or other materials provided with the distribution.
63 * 3. All advertising materials mentioning features or use of this software
64 * must display the following acknowledgement:
65 * This product includes software developed by the University of
66 * California, Berkeley and its contributors.
67 * 4. Neither the name of the University nor the names of its contributors
68 * may be used to endorse or promote products derived from this software
69 * without specific prior written permission.
70 *
71 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
72 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
73 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
74 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
75 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
76 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
77 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
78 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
79 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
80 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
81 * SUCH DAMAGE.
82 *
83 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95
84 * $FreeBSD: src/sys/netinet/tcp_input.c,v 1.107.2.38 2003/05/21 04:46:41 cjc Exp $
95b22adf 85 * $DragonFly: src/sys/netinet/tcp_input.c,v 1.31 2004/07/17 20:31:31 hsu Exp $
984263bc
MD
86 */
87
88#include "opt_ipfw.h" /* for ipfw_fwd */
89#include "opt_inet6.h"
90#include "opt_ipsec.h"
91#include "opt_tcpdebug.h"
92#include "opt_tcp_input.h"
93
94#include <sys/param.h>
95#include <sys/systm.h>
96#include <sys/kernel.h>
97#include <sys/sysctl.h>
98#include <sys/malloc.h>
99#include <sys/mbuf.h>
100#include <sys/proc.h> /* for proc0 declaration */
101#include <sys/protosw.h>
102#include <sys/socket.h>
103#include <sys/socketvar.h>
104#include <sys/syslog.h>
3f9db7f8 105#include <sys/in_cksum.h>
984263bc
MD
106
107#include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */
a00138cb 108#include <machine/stdarg.h>
984263bc
MD
109
110#include <net/if.h>
111#include <net/route.h>
112
113#include <netinet/in.h>
114#include <netinet/in_systm.h>
115#include <netinet/ip.h>
95b22adf 116#include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */
984263bc 117#include <netinet/in_var.h>
95b22adf 118#include <netinet/icmp_var.h> /* for ICMP_BANDLIM */
984263bc
MD
119#include <netinet/in_pcb.h>
120#include <netinet/ip_var.h>
121#include <netinet/ip6.h>
122#include <netinet/icmp6.h>
123#include <netinet6/nd6.h>
124#include <netinet6/ip6_var.h>
125#include <netinet6/in6_pcb.h>
126#include <netinet/tcp.h>
127#include <netinet/tcp_fsm.h>
128#include <netinet/tcp_seq.h>
129#include <netinet/tcp_timer.h>
130#include <netinet/tcp_var.h>
131#include <netinet6/tcp6_var.h>
132#include <netinet/tcpip.h>
95b22adf 133
984263bc
MD
134#ifdef TCPDEBUG
135#include <netinet/tcp_debug.h>
136
95b22adf 137u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */
984263bc 138struct tcphdr tcp_savetcp;
95b22adf 139#endif
984263bc
MD
140
141#ifdef FAST_IPSEC
142#include <netipsec/ipsec.h>
143#include <netipsec/ipsec6.h>
144#endif
145
146#ifdef IPSEC
147#include <netinet6/ipsec.h>
148#include <netinet6/ipsec6.h>
d2438d69 149#include <netproto/key/key.h>
95b22adf 150#endif
984263bc 151
984263bc
MD
152MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry");
153
154static const int tcprexmtthresh = 3;
155tcp_cc tcp_ccgen;
984263bc 156static int log_in_vain = 0;
d24ce1dc 157SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW,
984263bc
MD
158 &log_in_vain, 0, "Log all incoming TCP connections");
159
160static int blackhole = 0;
161SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW,
162 &blackhole, 0, "Do not send RST when dropping refused connections");
163
164int tcp_delack_enabled = 1;
d24ce1dc
JH
165SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW,
166 &tcp_delack_enabled, 0,
984263bc
MD
167 "Delay ACK to try and piggyback it onto a data packet");
168
169#ifdef TCP_DROP_SYNFIN
170static int drop_synfin = 0;
171SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW,
172 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set");
173#endif
174
33abdd1c
MD
175static int tcp_do_limitedtransmit = 1;
176SYSCTL_INT(_net_inet_tcp, OID_AUTO, limitedtransmit, CTLFLAG_RW,
177 &tcp_do_limitedtransmit, 0, "Enable RFC 3042 (Limited Transmit)");
178
8819433a
JH
179static int tcp_do_early_retransmit = 0;
180SYSCTL_INT(_net_inet_tcp, OID_AUTO, earlyretransmit, CTLFLAG_RW,
181 &tcp_do_early_retransmit, 0, "Early retransmit");
182
4b52d5ee
JH
183static int tcp_do_rfc3390 = 1;
184SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW,
185 &tcp_do_rfc3390, 0,
186 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)");
187
efd4b327
JH
188static int tcp_do_eifel_detect = 1;
189SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW,
190 &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)");
191
3edf7c37
RG
192SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0,
193 "TCP Segment Reassembly Queue");
194
195int tcp_reass_maxseg = 0;
196SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD,
197 &tcp_reass_maxseg, 0,
198 "Global maximum number of TCP Segments in Reassembly Queue");
199
200int tcp_reass_qsize = 0;
201SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD,
202 &tcp_reass_qsize, 0,
203 "Global number of TCP Segments currently in Reassembly Queue");
204
205static int tcp_reass_overflows = 0;
206SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD,
207 &tcp_reass_overflows, 0,
208 "Global number of TCP Segment Reassembly Queue Overflows");
209
d371a63a 210struct inpcbinfo tcbinfo[MAXCPU];
984263bc 211
95b22adf 212static void tcp_dooptions(struct tcpopt *, u_char *, int, boolean_t);
984263bc
MD
213static void tcp_pulloutofband(struct socket *,
214 struct tcphdr *, struct mbuf *, int);
215static int tcp_reass(struct tcpcb *, struct tcphdr *, int *,
216 struct mbuf *);
217static void tcp_xmit_timer(struct tcpcb *, int);
218static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *);
219
220/* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */
221#ifdef INET6
222#define ND6_HINT(tp) \
223do { \
224 if ((tp) && (tp)->t_inpcb && \
225 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0 && \
226 (tp)->t_inpcb->in6p_route.ro_rt) \
227 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \
228} while (0)
229#else
230#define ND6_HINT(tp)
231#endif
232
233/*
234 * Indicate whether this ack should be delayed. We can delay the ack if
235 * - delayed acks are enabled and
236 * - there is no delayed ack timer in progress and
237 * - our last ack wasn't a 0-sized window. We never want to delay
238 * the ack that opens up a 0-sized window.
239 */
240#define DELAY_ACK(tp) \
241 (tcp_delack_enabled && !callout_pending(tp->tt_delack) && \
242 (tp->t_flags & TF_RXWIN0SENT) == 0)
243
244static int
95b22adf 245tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m)
984263bc
MD
246{
247 struct tseg_qent *q;
248 struct tseg_qent *p = NULL;
249 struct tseg_qent *nq;
250 struct tseg_qent *te;
251 struct socket *so = tp->t_inpcb->inp_socket;
252 int flags;
253
254 /*
255 * Call with th==0 after become established to
256 * force pre-ESTABLISHED data up to user socket.
257 */
258 if (th == 0)
259 goto present;
260
3edf7c37
RG
261 /*
262 * Limit the number of segments in the reassembly queue to prevent
263 * holding on to too many segments (and thus running out of mbufs).
264 * Make sure to let the missing segment through which caused this
265 * queue. Always keep one global queue entry spare to be able to
266 * process the missing segment.
267 */
268 if (th->th_seq != tp->rcv_nxt &&
269 tcp_reass_qsize + 1 >= tcp_reass_maxseg) {
270 tcp_reass_overflows++;
271 tcpstat.tcps_rcvmemdrop++;
272 m_freem(m);
273 return (0);
274 }
275
ba4e3dbe 276 /* Allocate a new queue entry. */
984263bc 277 MALLOC(te, struct tseg_qent *, sizeof(struct tseg_qent), M_TSEGQ,
ba4e3dbe 278 M_INTWAIT | M_NULLOK);
984263bc
MD
279 if (te == NULL) {
280 tcpstat.tcps_rcvmemdrop++;
281 m_freem(m);
282 return (0);
283 }
3edf7c37 284 tcp_reass_qsize++;
984263bc
MD
285
286 /*
287 * Find a segment which begins after this one does.
288 */
289 LIST_FOREACH(q, &tp->t_segq, tqe_q) {
290 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
291 break;
292 p = q;
293 }
294
295 /*
296 * If there is a preceding segment, it may provide some of
297 * our data already. If so, drop the data from the incoming
298 * segment. If it provides all of our data, drop us.
299 */
300 if (p != NULL) {
2256ba69 301 int i;
984263bc
MD
302 /* conversion to int (in i) handles seq wraparound */
303 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
304 if (i > 0) {
305 if (i >= *tlenp) {
306 tcpstat.tcps_rcvduppack++;
307 tcpstat.tcps_rcvdupbyte += *tlenp;
308 m_freem(m);
309 free(te, M_TSEGQ);
3edf7c37 310 tcp_reass_qsize--;
984263bc
MD
311 /*
312 * Try to present any queued data
313 * at the left window edge to the user.
314 * This is needed after the 3-WHS
315 * completes.
316 */
317 goto present; /* ??? */
318 }
319 m_adj(m, i);
320 *tlenp -= i;
321 th->th_seq += i;
322 }
323 }
324 tcpstat.tcps_rcvoopack++;
325 tcpstat.tcps_rcvoobyte += *tlenp;
326
327 /*
328 * While we overlap succeeding segments trim them or,
329 * if they are completely covered, dequeue them.
330 */
331 while (q) {
2256ba69 332 int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
984263bc
MD
333 if (i <= 0)
334 break;
335 if (i < q->tqe_len) {
336 q->tqe_th->th_seq += i;
337 q->tqe_len -= i;
338 m_adj(q->tqe_m, i);
339 break;
340 }
341
342 nq = LIST_NEXT(q, tqe_q);
343 LIST_REMOVE(q, tqe_q);
344 m_freem(q->tqe_m);
345 free(q, M_TSEGQ);
3edf7c37 346 tcp_reass_qsize--;
984263bc
MD
347 q = nq;
348 }
349
350 /* Insert the new segment queue entry into place. */
351 te->tqe_m = m;
352 te->tqe_th = th;
353 te->tqe_len = *tlenp;
354
355 if (p == NULL) {
356 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q);
357 } else {
358 LIST_INSERT_AFTER(p, te, tqe_q);
359 }
360
361present:
362 /*
363 * Present data to user, advancing rcv_nxt through
364 * completed sequence space.
365 */
366 if (!TCPS_HAVEESTABLISHED(tp->t_state))
367 return (0);
368 q = LIST_FIRST(&tp->t_segq);
369 if (!q || q->tqe_th->th_seq != tp->rcv_nxt)
370 return (0);
371 do {
372 tp->rcv_nxt += q->tqe_len;
373 flags = q->tqe_th->th_flags & TH_FIN;
374 nq = LIST_NEXT(q, tqe_q);
375 LIST_REMOVE(q, tqe_q);
376 if (so->so_state & SS_CANTRCVMORE)
377 m_freem(q->tqe_m);
378 else
379 sbappend(&so->so_rcv, q->tqe_m);
380 free(q, M_TSEGQ);
3edf7c37 381 tcp_reass_qsize--;
984263bc
MD
382 q = nq;
383 } while (q && q->tqe_th->th_seq == tp->rcv_nxt);
384 ND6_HINT(tp);
385 sorwakeup(so);
386 return (flags);
387}
388
389/*
390 * TCP input routine, follows pages 65-76 of the
391 * protocol specification dated September, 1981 very closely.
392 */
393#ifdef INET6
394int
95b22adf 395tcp6_input(struct mbuf **mp, int *offp, int proto)
984263bc 396{
2256ba69 397 struct mbuf *m = *mp;
984263bc
MD
398 struct in6_ifaddr *ia6;
399
400 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE);
401
402 /*
403 * draft-itojun-ipv6-tcp-to-anycast
404 * better place to put this in?
405 */
406 ia6 = ip6_getdstifaddr(m);
d24ce1dc 407 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) {
984263bc
MD
408 struct ip6_hdr *ip6;
409
410 ip6 = mtod(m, struct ip6_hdr *);
411 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
412 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6);
d24ce1dc 413 return (IPPROTO_DONE);
984263bc
MD
414 }
415
416 tcp_input(m, *offp, proto);
d24ce1dc 417 return (IPPROTO_DONE);
984263bc
MD
418}
419#endif
420
421void
a00138cb 422tcp_input(struct mbuf *m, ...)
984263bc 423{
a00138cb
JS
424 __va_list ap;
425 int off0, proto;
2256ba69
RG
426 struct tcphdr *th;
427 struct ip *ip = NULL;
428 struct ipovly *ipov;
429 struct inpcb *inp = NULL;
984263bc
MD
430 u_char *optp = NULL;
431 int optlen = 0;
432 int len, tlen, off;
433 int drop_hdrlen;
2256ba69
RG
434 struct tcpcb *tp = NULL;
435 int thflags;
984263bc
MD
436 struct socket *so = 0;
437 int todrop, acked, ourfinisacked, needoutput = 0;
438 u_long tiwin;
439 struct tcpopt to; /* options in this segment */
440 struct rmxp_tao *taop; /* pointer to our TAO cache entry */
441 struct rmxp_tao tao_noncached; /* in case there's no cached entry */
442 struct sockaddr_in *next_hop = NULL;
443 int rstreason; /* For badport_bandlim accounting purposes */
d371a63a 444 int cpu;
984263bc
MD
445 struct ip6_hdr *ip6 = NULL;
446#ifdef INET6
d24ce1dc 447 boolean_t isipv6;
984263bc 448#else
d24ce1dc 449 const boolean_t isipv6 = FALSE;
984263bc
MD
450#endif
451#ifdef TCPDEBUG
452 short ostate = 0;
453#endif
454
a00138cb
JS
455 __va_start(ap, m);
456 off0 = __va_arg(ap, int);
457 proto = __va_arg(ap, int);
458 __va_end(ap);
459
d24ce1dc
JH
460 tcpstat.tcps_rcvtotal++;
461
462 /* Grab info from and strip MT_TAG mbufs prepended to the chain. */
463 while (m->m_type == MT_TAG) {
984263bc
MD
464 if (m->_m_tag_id == PACKET_TAG_IPFORWARD)
465 next_hop = (struct sockaddr_in *)m->m_hdr.mh_data;
d24ce1dc 466 m = m->m_next;
984263bc 467 }
d24ce1dc 468
984263bc 469#ifdef INET6
d24ce1dc 470 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE;
984263bc 471#endif
984263bc
MD
472
473 if (isipv6) {
474 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */
475 ip6 = mtod(m, struct ip6_hdr *);
476 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0;
477 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) {
478 tcpstat.tcps_rcvbadsum++;
479 goto drop;
480 }
481 th = (struct tcphdr *)((caddr_t)ip6 + off0);
482
483 /*
484 * Be proactive about unspecified IPv6 address in source.
485 * As we use all-zero to indicate unbounded/unconnected pcb,
486 * unspecified IPv6 address can be used to confuse us.
487 *
488 * Note that packets with unspecified IPv6 destination is
489 * already dropped in ip6_input.
490 */
491 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
492 /* XXX stat */
493 goto drop;
494 }
495 } else {
496 /*
497 * Get IP and TCP header together in first mbuf.
498 * Note: IP leaves IP header in first mbuf.
499 */
500 if (off0 > sizeof(struct ip)) {
bddf0751 501 ip_stripoptions(m);
984263bc
MD
502 off0 = sizeof(struct ip);
503 }
55d829f8
JH
504 /* already checked and pulled up in ip_demux() */
505 KASSERT(m->m_len >= sizeof(struct tcpiphdr),
506 ("TCP header not in one mbuf"));
984263bc
MD
507 ip = mtod(m, struct ip *);
508 ipov = (struct ipovly *)ip;
509 th = (struct tcphdr *)((caddr_t)ip + off0);
510 tlen = ip->ip_len;
511
512 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
513 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
514 th->th_sum = m->m_pkthdr.csum_data;
515 else
516 th->th_sum = in_pseudo(ip->ip_src.s_addr,
517 ip->ip_dst.s_addr,
518 htonl(m->m_pkthdr.csum_data +
519 ip->ip_len +
520 IPPROTO_TCP));
521 th->th_sum ^= 0xffff;
522 } else {
523 /*
524 * Checksum extended TCP header and data.
525 */
526 len = sizeof(struct ip) + tlen;
527 bzero(ipov->ih_x1, sizeof(ipov->ih_x1));
528 ipov->ih_len = (u_short)tlen;
529 ipov->ih_len = htons(ipov->ih_len);
530 th->th_sum = in_cksum(m, len);
531 }
532 if (th->th_sum) {
533 tcpstat.tcps_rcvbadsum++;
534 goto drop;
535 }
536#ifdef INET6
537 /* Re-initialization for later version check */
538 ip->ip_v = IPVERSION;
539#endif
540 }
541
542 /*
543 * Check that TCP offset makes sense,
544 * pull out TCP options and adjust length. XXX
545 */
546 off = th->th_off << 2;
55d829f8
JH
547 /* already checked and pulled up in ip_demux() */
548 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen,
549 ("bad TCP data offset"));
984263bc
MD
550 tlen -= off; /* tlen is used instead of ti->ti_len */
551 if (off > sizeof(struct tcphdr)) {
552 if (isipv6) {
553 IP6_EXTHDR_CHECK(m, off0, off, );
554 ip6 = mtod(m, struct ip6_hdr *);
555 th = (struct tcphdr *)((caddr_t)ip6 + off0);
556 } else {
55d829f8
JH
557 /* already pulled up in ip_demux() */
558 KASSERT(m->m_len >= sizeof(struct ip) + off,
559 ("TCP header and options not in one mbuf"));
984263bc
MD
560 }
561 optlen = off - sizeof(struct tcphdr);
562 optp = (u_char *)(th + 1);
563 }
564 thflags = th->th_flags;
565
566#ifdef TCP_DROP_SYNFIN
567 /*
568 * If the drop_synfin option is enabled, drop all packets with
569 * both the SYN and FIN bits set. This prevents e.g. nmap from
570 * identifying the TCP/IP stack.
571 *
572 * This is a violation of the TCP specification.
573 */
574 if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN))
575 goto drop;
576#endif
577
578 /*
579 * Convert TCP protocol specific fields to host format.
580 */
581 th->th_seq = ntohl(th->th_seq);
582 th->th_ack = ntohl(th->th_ack);
583 th->th_win = ntohs(th->th_win);
584 th->th_urp = ntohs(th->th_urp);
585
586 /*
d24ce1dc 587 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options,
984263bc
MD
588 * until after ip6_savecontrol() is called and before other functions
589 * which don't want those proto headers.
590 * Because ip6_savecontrol() is going to parse the mbuf to
591 * search for data to be passed up to user-land, it wants mbuf
592 * parameters to be unchanged.
593 * XXX: the call of ip6_savecontrol() has been obsoleted based on
594 * latest version of the advanced API (20020110).
595 */
596 drop_hdrlen = off0 + off;
597
598 /*
599 * Locate pcb for segment.
600 */
601findpcb:
602 /* IPFIREWALL_FORWARD section */
d24ce1dc 603 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */
984263bc
MD
604 /*
605 * Transparently forwarded. Pretend to be the destination.
d24ce1dc 606 * already got one like this?
984263bc 607 */
6ca1a1cd 608 cpu = mycpu->gd_cpuid;
6ca1a1cd 609 inp = in_pcblookup_hash(&tcbinfo[cpu],
d371a63a 610 ip->ip_src, th->th_sport,
984263bc
MD
611 ip->ip_dst, th->th_dport,
612 0, m->m_pkthdr.rcvif);
613 if (!inp) {
83be63fe
JH
614 /*
615 * It's new. Try to find the ambushing socket.
616 */
617
618 /*
619 * The rest of the ipfw code stores the port in
620 * host order. XXX
621 * (The IP address is still in network order.)
622 */
623 in_port_t dport = next_hop->sin_port ?
624 htons(next_hop->sin_port) :
625 th->th_dport;
626
d371a63a 627 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport,
83be63fe 628 next_hop->sin_addr.s_addr, dport);
d371a63a 629 inp = in_pcblookup_hash(&tcbinfo[cpu],
984263bc 630 ip->ip_src, th->th_sport,
83be63fe 631 next_hop->sin_addr, dport,
984263bc
MD
632 1, m->m_pkthdr.rcvif);
633 }
634 } else {
6ca1a1cd 635 if (isipv6) {
d371a63a 636 inp = in6_pcblookup_hash(&tcbinfo[0],
984263bc
MD
637 &ip6->ip6_src, th->th_sport,
638 &ip6->ip6_dst, th->th_dport,
639 1, m->m_pkthdr.rcvif);
6ca1a1cd 640 } else {
6ca1a1cd 641 cpu = mycpu->gd_cpuid;
6ca1a1cd 642 inp = in_pcblookup_hash(&tcbinfo[cpu],
984263bc
MD
643 ip->ip_src, th->th_sport,
644 ip->ip_dst, th->th_dport,
645 1, m->m_pkthdr.rcvif);
6ca1a1cd 646 }
984263bc
MD
647 }
648
649#ifdef IPSEC
650 if (isipv6) {
651 if (inp != NULL && ipsec6_in_reject_so(m, inp->inp_socket)) {
652 ipsec6stat.in_polvio++;
653 goto drop;
654 }
655 } else {
656 if (inp != NULL && ipsec4_in_reject_so(m, inp->inp_socket)) {
657 ipsecstat.in_polvio++;
658 goto drop;
659 }
660 }
661#endif
662#ifdef FAST_IPSEC
663 if (isipv6) {
664 if (inp != NULL && ipsec6_in_reject(m, inp)) {
665 goto drop;
666 }
667 } else {
668 if (inp != NULL && ipsec4_in_reject(m, inp)) {
669 goto drop;
670 }
671 }
672#endif
673
674 /*
675 * If the state is CLOSED (i.e., TCB does not exist) then
676 * all data in the incoming segment is discarded.
677 * If the TCB exists but is in CLOSED state, it is embryonic,
678 * but should either do a listen or a connect soon.
679 */
680 if (inp == NULL) {
681 if (log_in_vain) {
682#ifdef INET6
683 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2];
684#else
d24ce1dc 685 char dbuf[4 * sizeof "123"], sbuf[4 * sizeof "123"];
984263bc
MD
686#endif
687 if (isipv6) {
688 strcpy(dbuf, "[");
984263bc 689 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst));
984263bc 690 strcat(dbuf, "]");
95b22adf
JH
691 strcpy(sbuf, "[");
692 strcat(sbuf, ip6_sprintf(&ip6->ip6_src));
984263bc
MD
693 strcat(sbuf, "]");
694 } else {
695 strcpy(dbuf, inet_ntoa(ip->ip_dst));
696 strcpy(sbuf, inet_ntoa(ip->ip_src));
697 }
698 switch (log_in_vain) {
699 case 1:
700 if ((thflags & TH_SYN) == 0)
701 break;
702 case 2:
703 log(LOG_INFO,
704 "Connection attempt to TCP %s:%d "
705 "from %s:%d flags:0x%02x\n",
706 dbuf, ntohs(th->th_dport), sbuf,
707 ntohs(th->th_sport), thflags);
708 break;
709 default:
710 break;
711 }
712 }
d24ce1dc 713 if (blackhole) {
984263bc
MD
714 switch (blackhole) {
715 case 1:
716 if (thflags & TH_SYN)
717 goto drop;
718 break;
719 case 2:
720 goto drop;
721 default:
722 goto drop;
723 }
724 }
725 rstreason = BANDLIM_RST_CLOSEDPORT;
726 goto dropwithreset;
727 }
728 tp = intotcpcb(inp);
729 if (tp == NULL) {
730 rstreason = BANDLIM_RST_CLOSEDPORT;
731 goto dropwithreset;
732 }
733 if (tp->t_state == TCPS_CLOSED)
734 goto drop;
735
736 /* Unscale the window into a 32-bit value. */
95b22adf 737 if (!(thflags & TH_SYN))
984263bc
MD
738 tiwin = th->th_win << tp->snd_scale;
739 else
740 tiwin = th->th_win;
741
742 so = inp->inp_socket;
47654766 743
984263bc 744#ifdef TCPDEBUG
47654766
JH
745 if (so->so_options & SO_DEBUG) {
746 ostate = tp->t_state;
747 if (isipv6)
95b22adf 748 bcopy(ip6, tcp_saveipgen, sizeof(*ip6));
47654766 749 else
95b22adf 750 bcopy(ip, tcp_saveipgen, sizeof(*ip));
47654766
JH
751 tcp_savetcp = *th;
752 }
984263bc 753#endif
47654766 754
95b22adf 755 bzero(&to, sizeof(to));
d24ce1dc 756
47654766
JH
757 if (so->so_options & SO_ACCEPTCONN) {
758 struct in_conninfo inc;
759
984263bc 760#ifdef INET6
d24ce1dc 761 inc.inc_isipv6 = (isipv6 == TRUE);
984263bc
MD
762#endif
763 if (isipv6) {
764 inc.inc6_faddr = ip6->ip6_src;
765 inc.inc6_laddr = ip6->ip6_dst;
766 inc.inc6_route.ro_rt = NULL; /* XXX */
767 } else {
768 inc.inc_faddr = ip->ip_src;
769 inc.inc_laddr = ip->ip_dst;
770 inc.inc_route.ro_rt = NULL; /* XXX */
771 }
772 inc.inc_fport = th->th_sport;
773 inc.inc_lport = th->th_dport;
774
775 /*
776 * If the state is LISTEN then ignore segment if it contains
777 * a RST. If the segment contains an ACK then it is bad and
778 * send a RST. If it does not contain a SYN then it is not
779 * interesting; drop it.
780 *
781 * If the state is SYN_RECEIVED (syncache) and seg contains
782 * an ACK, but not for our SYN/ACK, send a RST. If the seg
783 * contains a RST, check the sequence number to see if it
784 * is a valid reset segment.
785 */
786 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) {
787 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) {
788 if (!syncache_expand(&inc, th, &so, m)) {
789 /*
790 * No syncache entry, or ACK was not
791 * for our SYN/ACK. Send a RST.
792 */
793 tcpstat.tcps_badsyn++;
794 rstreason = BANDLIM_RST_OPENPORT;
795 goto dropwithreset;
796 }
797 if (so == NULL)
798 /*
799 * Could not complete 3-way handshake,
800 * connection is being closed down, and
801 * syncache will free mbuf.
802 */
803 return;
804 /*
805 * Socket is created in state SYN_RECEIVED.
806 * Continue processing segment.
807 */
808 inp = sotoinpcb(so);
809 tp = intotcpcb(inp);
810 /*
811 * This is what would have happened in
812 * tcp_output() when the SYN,ACK was sent.
813 */
814 tp->snd_up = tp->snd_una;
815 tp->snd_max = tp->snd_nxt = tp->iss + 1;
816 tp->last_ack_sent = tp->rcv_nxt;
817/*
818 * XXX possible bug - it doesn't appear that tp->snd_wnd is unscaled
819 * until the _second_ ACK is received:
820 * rcv SYN (set wscale opts) --> send SYN/ACK, set snd_wnd = window.
821 * rcv ACK, calculate tiwin --> process SYN_RECEIVED, determine wscale,
822 * move to ESTAB, set snd_wnd to tiwin.
d24ce1dc 823 */
984263bc
MD
824 tp->snd_wnd = tiwin; /* unscaled */
825 goto after_listen;
826 }
827 if (thflags & TH_RST) {
828 syncache_chkrst(&inc, th);
829 goto drop;
830 }
831 if (thflags & TH_ACK) {
832 syncache_badack(&inc);
833 tcpstat.tcps_badsyn++;
834 rstreason = BANDLIM_RST_OPENPORT;
835 goto dropwithreset;
836 }
837 goto drop;
838 }
839
840 /*
841 * Segment's flags are (SYN) or (SYN|FIN).
842 */
843#ifdef INET6
844 /*
845 * If deprecated address is forbidden,
846 * we do not accept SYN to deprecated interface
847 * address to prevent any new inbound connection from
848 * getting established.
849 * When we do not accept SYN, we send a TCP RST,
850 * with deprecated source address (instead of dropping
851 * it). We compromise it as it is much better for peer
852 * to send a RST, and RST will be the final packet
853 * for the exchange.
854 *
855 * If we do not forbid deprecated addresses, we accept
856 * the SYN packet. RFC2462 does not suggest dropping
857 * SYN in this case.
858 * If we decipher RFC2462 5.5.4, it says like this:
859 * 1. use of deprecated addr with existing
860 * communication is okay - "SHOULD continue to be
861 * used"
862 * 2. use of it with new communication:
863 * (2a) "SHOULD NOT be used if alternate address
864 * with sufficient scope is available"
865 * (2b) nothing mentioned otherwise.
866 * Here we fall into (2b) case as we have no choice in
867 * our source address selection - we must obey the peer.
868 *
869 * The wording in RFC2462 is confusing, and there are
870 * multiple description text for deprecated address
871 * handling - worse, they are not exactly the same.
872 * I believe 5.5.4 is the best one, so we follow 5.5.4.
873 */
874 if (isipv6 && !ip6_use_deprecated) {
875 struct in6_ifaddr *ia6;
876
877 if ((ia6 = ip6_getdstifaddr(m)) &&
878 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
879 tp = NULL;
880 rstreason = BANDLIM_RST_OPENPORT;
881 goto dropwithreset;
882 }
883 }
884#endif
885 /*
886 * If it is from this socket, drop it, it must be forged.
887 * Don't bother responding if the destination was a broadcast.
888 */
889 if (th->th_dport == th->th_sport) {
890 if (isipv6) {
891 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst,
892 &ip6->ip6_src))
893 goto drop;
894 } else {
895 if (ip->ip_dst.s_addr == ip->ip_src.s_addr)
896 goto drop;
897 }
898 }
899 /*
900 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN
901 *
902 * Note that it is quite possible to receive unicast
903 * link-layer packets with a broadcast IP address. Use
904 * in_broadcast() to find them.
905 */
906 if (m->m_flags & (M_BCAST|M_MCAST))
907 goto drop;
908 if (isipv6) {
909 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
910 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
911 goto drop;
912 } else {
913 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
914 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
915 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
916 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
917 goto drop;
918 }
919 /*
920 * SYN appears to be valid; create compressed TCP state
921 * for syncache, or perform t/tcp connection.
922 */
923 if (so->so_qlen <= so->so_qlimit) {
95b22adf 924 tcp_dooptions(&to, optp, optlen, TRUE);
984263bc
MD
925 if (!syncache_add(&inc, &to, th, &so, m))
926 goto drop;
927 if (so == NULL)
928 /*
929 * Entry added to syncache, mbuf used to
930 * send SYN,ACK packet.
931 */
932 return;
933 /*
934 * Segment passed TAO tests.
935 */
936 inp = sotoinpcb(so);
937 tp = intotcpcb(inp);
938 tp->snd_wnd = tiwin;
939 tp->t_starttime = ticks;
940 tp->t_state = TCPS_ESTABLISHED;
941
942 /*
943 * If there is a FIN, or if there is data and the
944 * connection is local, then delay SYN,ACK(SYN) in
945 * the hope of piggy-backing it on a response
946 * segment. Otherwise must send ACK now in case
947 * the other side is slow starting.
948 */
949 if (DELAY_ACK(tp) &&
950 ((thflags & TH_FIN) ||
951 (tlen != 0 &&
952 ((isipv6 && in6_localaddr(&inp->in6p_faddr)) ||
953 (!isipv6 && in_localaddr(inp->inp_faddr)))))) {
d24ce1dc
JH
954 callout_reset(tp->tt_delack, tcp_delacktime,
955 tcp_timer_delack, tp);
984263bc 956 tp->t_flags |= TF_NEEDSYN;
d24ce1dc 957 } else
984263bc
MD
958 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN);
959
960 tcpstat.tcps_connects++;
961 soisconnected(so);
962 goto trimthenstep6;
963 }
964 goto drop;
965 }
966after_listen:
967
968/* XXX temp debugging */
969 /* should not happen - syncache should pick up these connections */
970 if (tp->t_state == TCPS_LISTEN)
971 panic("tcp_input: TCPS_LISTEN");
972
973 /*
974 * Segment received on connection.
975 * Reset idle time and keep-alive timer.
976 */
977 tp->t_rcvtime = ticks;
978 if (TCPS_HAVEESTABLISHED(tp->t_state))
979 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp);
980
981 /*
982 * Process options.
983 * XXX this is tradtitional behavior, may need to be cleaned up.
984 */
95b22adf 985 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0);
984263bc
MD
986 if (thflags & TH_SYN) {
987 if (to.to_flags & TOF_SCALE) {
988 tp->t_flags |= TF_RCVD_SCALE;
989 tp->requested_s_scale = to.to_requested_s_scale;
990 }
991 if (to.to_flags & TOF_TS) {
992 tp->t_flags |= TF_RCVD_TSTMP;
993 tp->ts_recent = to.to_tsval;
994 tp->ts_recent_age = ticks;
995 }
996 if (to.to_flags & (TOF_CC|TOF_CCNEW))
997 tp->t_flags |= TF_RCVD_CC;
998 if (to.to_flags & TOF_MSS)
999 tcp_mss(tp, to.to_mss);
1000 }
1001
1002 /*
1003 * Header prediction: check for the two common cases
1004 * of a uni-directional data xfer. If the packet has
1005 * no control flags, is in-sequence, the window didn't
1006 * change and we're not retransmitting, it's a
1007 * candidate. If the length is zero and the ack moved
1008 * forward, we're the sender side of the xfer. Just
1009 * free the data acked & wake any higher level process
1010 * that was blocked waiting for space. If the length
1011 * is non-zero and the ack didn't move, we're the
1012 * receiver side. If we're getting packets in-order
1013 * (the reassembly queue is empty), add the data to
1014 * the socket buffer and note that we need a delayed ack.
1015 * Make sure that the hidden state-flags are also off.
1016 * Since we check for TCPS_ESTABLISHED above, it can only
1017 * be TH_NEEDSYN.
1018 */
1019 if (tp->t_state == TCPS_ESTABLISHED &&
1020 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
1021 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) &&
1022 ((to.to_flags & TOF_TS) == 0 ||
1023 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) &&
1024 /*
1025 * Using the CC option is compulsory if once started:
1026 * the segment is OK if no T/TCP was negotiated or
1027 * if the segment has a CC option equal to CCrecv
1028 */
1029 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) ||
1030 ((to.to_flags & TOF_CC) != 0 && to.to_cc == tp->cc_recv)) &&
1031 th->th_seq == tp->rcv_nxt &&
1032 tiwin && tiwin == tp->snd_wnd &&
1033 tp->snd_nxt == tp->snd_max) {
1034
1035 /*
1036 * If last ACK falls within this segment's sequence numbers,
1037 * record the timestamp.
1038 * NOTE that the test is modified according to the latest
1039 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1040 */
1041 if ((to.to_flags & TOF_TS) != 0 &&
1042 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
1043 tp->ts_recent_age = ticks;
1044 tp->ts_recent = to.to_tsval;
1045 }
1046
1047 if (tlen == 0) {
1048 if (SEQ_GT(th->th_ack, tp->snd_una) &&
1049 SEQ_LEQ(th->th_ack, tp->snd_max) &&
1050 tp->snd_cwnd >= tp->snd_wnd &&
95b22adf 1051 !IN_FASTRECOVERY(tp)) {
984263bc
MD
1052 /*
1053 * this is a pure ack for outstanding data.
1054 */
1055 ++tcpstat.tcps_predack;
1056 /*
1057 * "bad retransmit" recovery
bfdb979e
JH
1058 *
1059 * If Eifel detection applies, then
1060 * it is deterministic, so use it
1061 * unconditionally over the old heuristic.
1062 * Otherwise, fall back to the old heuristic.
984263bc 1063 */
bfdb979e
JH
1064 if (tcp_do_eifel_detect &&
1065 (to.to_flags & TOF_TS) && to.to_tsecr &&
1066 (tp->t_flags & TF_FIRSTACCACK)) {
1067 /* Eifel detection applicable. */
1068 if (to.to_tsecr < tp->t_rexmtTS) {
1069 tcp_revert_congestion_state(tp);
1070 ++tcpstat.tcps_eifeldetected;
1071 }
1072 } else if (tp->t_rxtshift == 1 &&
1073 ticks < tp->t_badrxtwin) {
1074 tcp_revert_congestion_state(tp);
1075 ++tcpstat.tcps_rttdetected;
984263bc 1076 }
8819433a
JH
1077 tp->t_flags &= ~(TF_FIRSTACCACK |
1078 TF_FASTREXMT | TF_EARLYREXMT);
984263bc
MD
1079 /*
1080 * Recalculate the retransmit timer / rtt.
1081 *
d24ce1dc 1082 * Some machines (certain windows boxes)
984263bc
MD
1083 * send broken timestamp replies during the
1084 * SYN+ACK phase, ignore timestamps of 0.
1085 */
95b22adf 1086 if ((to.to_flags & TOF_TS) && to.to_tsecr) {
984263bc 1087 tcp_xmit_timer(tp,
95b22adf 1088 ticks - to.to_tsecr + 1);
984263bc 1089 } else if (tp->t_rtttime &&
95b22adf 1090 SEQ_GT(th->th_ack, tp->t_rtseq)) {
984263bc
MD
1091 tcp_xmit_timer(tp,
1092 ticks - tp->t_rtttime);
1093 }
1094 tcp_xmit_bandwidth_limit(tp, th->th_ack);
1095 acked = th->th_ack - tp->snd_una;
1096 tcpstat.tcps_rcvackpack++;
1097 tcpstat.tcps_rcvackbyte += acked;
1098 sbdrop(&so->so_snd, acked);
cfb3f3f4 1099 tp->snd_recover = th->th_ack - 1;
9845754e 1100 tp->snd_una = th->th_ack;
984263bc
MD
1101 tp->t_dupacks = 0;
1102 m_freem(m);
1103 ND6_HINT(tp); /* some progress has been done */
1104
1105 /*
1106 * If all outstanding data are acked, stop
1107 * retransmit timer, otherwise restart timer
1108 * using current (possibly backed-off) value.
1109 * If process is waiting for space,
1110 * wakeup/selwakeup/signal. If data
1111 * are ready to send, let tcp_output
1112 * decide between more output or persist.
1113 */
1114 if (tp->snd_una == tp->snd_max)
1115 callout_stop(tp->tt_rexmt);
1116 else if (!callout_active(tp->tt_persist))
d24ce1dc 1117 callout_reset(tp->tt_rexmt,
984263bc
MD
1118 tp->t_rxtcur,
1119 tcp_timer_rexmt, tp);
1120
1121 sowwakeup(so);
1122 if (so->so_snd.sb_cc)
1123 (void) tcp_output(tp);
1124 return;
1125 }
1126 } else if (th->th_ack == tp->snd_una &&
1127 LIST_EMPTY(&tp->t_segq) &&
1128 tlen <= sbspace(&so->so_rcv)) {
1129 /*
1130 * this is a pure, in-sequence data packet
1131 * with nothing on the reassembly queue and
1132 * we have enough buffer space to take it.
1133 */
1134 ++tcpstat.tcps_preddat;
1135 tp->rcv_nxt += tlen;
1136 tcpstat.tcps_rcvpack++;
1137 tcpstat.tcps_rcvbyte += tlen;
1138 ND6_HINT(tp); /* some progress has been done */
1139 /*
1140 * Add data to socket buffer.
1141 */
1142 if (so->so_state & SS_CANTRCVMORE) {
1143 m_freem(m);
1144 } else {
1145 m_adj(m, drop_hdrlen); /* delayed header drop */
1146 sbappend(&so->so_rcv, m);
1147 }
1148 sorwakeup(so);
1149 if (DELAY_ACK(tp)) {
1150 callout_reset(tp->tt_delack, tcp_delacktime,
1151 tcp_timer_delack, tp);
1152 } else {
1153 tp->t_flags |= TF_ACKNOW;
1154 tcp_output(tp);
1155 }
1156 return;
1157 }
1158 }
1159
1160 /*
1161 * Calculate amount of space in receive window,
1162 * and then do TCP input processing.
1163 * Receive window is amount of space in rcv queue,
1164 * but not less than advertised window.
1165 */
1166 { int win;
1167
1168 win = sbspace(&so->so_rcv);
1169 if (win < 0)
1170 win = 0;
1171 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt));
1172 }
1173
1174 switch (tp->t_state) {
1175
1176 /*
1177 * If the state is SYN_RECEIVED:
1178 * if seg contains an ACK, but not for our SYN/ACK, send a RST.
1179 */
1180 case TCPS_SYN_RECEIVED:
1181 if ((thflags & TH_ACK) &&
1182 (SEQ_LEQ(th->th_ack, tp->snd_una) ||
1183 SEQ_GT(th->th_ack, tp->snd_max))) {
1184 rstreason = BANDLIM_RST_OPENPORT;
1185 goto dropwithreset;
1186 }
1187 break;
1188
1189 /*
1190 * If the state is SYN_SENT:
1191 * if seg contains an ACK, but not for our SYN, drop the input.
1192 * if seg contains a RST, then drop the connection.
1193 * if seg does not contain SYN, then drop it.
1194 * Otherwise this is an acceptable SYN segment
1195 * initialize tp->rcv_nxt and tp->irs
1196 * if seg contains ack then advance tp->snd_una
1197 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state
1198 * arrange for segment to be acked (eventually)
1199 * continue processing rest of data/controls, beginning with URG
1200 */
1201 case TCPS_SYN_SENT:
1202 if ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL) {
1203 taop = &tao_noncached;
1204 bzero(taop, sizeof(*taop));
1205 }
1206
1207 if ((thflags & TH_ACK) &&
1208 (SEQ_LEQ(th->th_ack, tp->iss) ||
1209 SEQ_GT(th->th_ack, tp->snd_max))) {
1210 /*
1211 * If we have a cached CCsent for the remote host,
1212 * hence we haven't just crashed and restarted,
1213 * do not send a RST. This may be a retransmission
1214 * from the other side after our earlier ACK was lost.
1215 * Our new SYN, when it arrives, will serve as the
1216 * needed ACK.
1217 */
1218 if (taop->tao_ccsent != 0)
1219 goto drop;
1220 else {
1221 rstreason = BANDLIM_UNLIMITED;
1222 goto dropwithreset;
1223 }
1224 }
1225 if (thflags & TH_RST) {
1226 if (thflags & TH_ACK)
1227 tp = tcp_drop(tp, ECONNREFUSED);
1228 goto drop;
1229 }
1230 if ((thflags & TH_SYN) == 0)
1231 goto drop;
1232 tp->snd_wnd = th->th_win; /* initial send window */
1233 tp->cc_recv = to.to_cc; /* foreign CC */
1234
1235 tp->irs = th->th_seq;
1236 tcp_rcvseqinit(tp);
1237 if (thflags & TH_ACK) {
1238 /*
1239 * Our SYN was acked. If segment contains CC.ECHO
1240 * option, check it to make sure this segment really
1241 * matches our SYN. If not, just drop it as old
1242 * duplicate, but send an RST if we're still playing
1243 * by the old rules. If no CC.ECHO option, make sure
1244 * we don't get fooled into using T/TCP.
1245 */
1246 if (to.to_flags & TOF_CCECHO) {
1247 if (tp->cc_send != to.to_ccecho) {
1248 if (taop->tao_ccsent != 0)
1249 goto drop;
1250 else {
1251 rstreason = BANDLIM_UNLIMITED;
1252 goto dropwithreset;
1253 }
1254 }
1255 } else
1256 tp->t_flags &= ~TF_RCVD_CC;
1257 tcpstat.tcps_connects++;
1258 soisconnected(so);
1259 /* Do window scaling on this connection? */
1260 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
1261 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
1262 tp->snd_scale = tp->requested_s_scale;
1263 tp->rcv_scale = tp->request_r_scale;
1264 }
1265 /* Segment is acceptable, update cache if undefined. */
1266 if (taop->tao_ccsent == 0)
1267 taop->tao_ccsent = to.to_ccecho;
1268
1269 tp->rcv_adv += tp->rcv_wnd;
1270 tp->snd_una++; /* SYN is acked */
1271 /*
1272 * If there's data, delay ACK; if there's also a FIN
1273 * ACKNOW will be turned on later.
1274 */
1275 if (DELAY_ACK(tp) && tlen != 0)
d24ce1dc
JH
1276 callout_reset(tp->tt_delack, tcp_delacktime,
1277 tcp_timer_delack, tp);
984263bc
MD
1278 else
1279 tp->t_flags |= TF_ACKNOW;
1280 /*
1281 * Received <SYN,ACK> in SYN_SENT[*] state.
1282 * Transitions:
1283 * SYN_SENT --> ESTABLISHED
1284 * SYN_SENT* --> FIN_WAIT_1
1285 */
1286 tp->t_starttime = ticks;
1287 if (tp->t_flags & TF_NEEDFIN) {
1288 tp->t_state = TCPS_FIN_WAIT_1;
1289 tp->t_flags &= ~TF_NEEDFIN;
1290 thflags &= ~TH_SYN;
1291 } else {
1292 tp->t_state = TCPS_ESTABLISHED;
1293 callout_reset(tp->tt_keep, tcp_keepidle,
1294 tcp_timer_keep, tp);
1295 }
1296 } else {
1297 /*
95b22adf
JH
1298 * Received initial SYN in SYN-SENT[*] state =>
1299 * simultaneous open. If segment contains CC option
1300 * and there is a cached CC, apply TAO test.
1301 * If it succeeds, connection is * half-synchronized.
1302 * Otherwise, do 3-way handshake:
1303 * SYN-SENT -> SYN-RECEIVED
1304 * SYN-SENT* -> SYN-RECEIVED*
1305 * If there was no CC option, clear cached CC value.
1306 */
984263bc
MD
1307 tp->t_flags |= TF_ACKNOW;
1308 callout_stop(tp->tt_rexmt);
1309 if (to.to_flags & TOF_CC) {
1310 if (taop->tao_cc != 0 &&
1311 CC_GT(to.to_cc, taop->tao_cc)) {
1312 /*
1313 * update cache and make transition:
1314 * SYN-SENT -> ESTABLISHED*
1315 * SYN-SENT* -> FIN-WAIT-1*
1316 */
1317 taop->tao_cc = to.to_cc;
1318 tp->t_starttime = ticks;
1319 if (tp->t_flags & TF_NEEDFIN) {
1320 tp->t_state = TCPS_FIN_WAIT_1;
1321 tp->t_flags &= ~TF_NEEDFIN;
1322 } else {
1323 tp->t_state = TCPS_ESTABLISHED;
1324 callout_reset(tp->tt_keep,
1325 tcp_keepidle,
1326 tcp_timer_keep,
1327 tp);
1328 }
1329 tp->t_flags |= TF_NEEDSYN;
1330 } else
1331 tp->t_state = TCPS_SYN_RECEIVED;
1332 } else {
1333 /* CC.NEW or no option => invalidate cache */
1334 taop->tao_cc = 0;
1335 tp->t_state = TCPS_SYN_RECEIVED;
1336 }
1337 }
1338
1339trimthenstep6:
1340 /*
1341 * Advance th->th_seq to correspond to first data byte.
1342 * If data, trim to stay within window,
1343 * dropping FIN if necessary.
1344 */
1345 th->th_seq++;
1346 if (tlen > tp->rcv_wnd) {
1347 todrop = tlen - tp->rcv_wnd;
1348 m_adj(m, -todrop);
1349 tlen = tp->rcv_wnd;
1350 thflags &= ~TH_FIN;
1351 tcpstat.tcps_rcvpackafterwin++;
1352 tcpstat.tcps_rcvbyteafterwin += todrop;
1353 }
1354 tp->snd_wl1 = th->th_seq - 1;
1355 tp->rcv_up = th->th_seq;
1356 /*
1357 * Client side of transaction: already sent SYN and data.
1358 * If the remote host used T/TCP to validate the SYN,
1359 * our data will be ACK'd; if so, enter normal data segment
1360 * processing in the middle of step 5, ack processing.
1361 * Otherwise, goto step 6.
1362 */
95b22adf 1363 if (thflags & TH_ACK)
984263bc
MD
1364 goto process_ACK;
1365
1366 goto step6;
1367
1368 /*
1369 * If the state is LAST_ACK or CLOSING or TIME_WAIT:
1370 * if segment contains a SYN and CC [not CC.NEW] option:
1371 * if state == TIME_WAIT and connection duration > MSL,
1372 * drop packet and send RST;
1373 *
1374 * if SEG.CC > CCrecv then is new SYN, and can implicitly
1375 * ack the FIN (and data) in retransmission queue.
1376 * Complete close and delete TCPCB. Then reprocess
1377 * segment, hoping to find new TCPCB in LISTEN state;
1378 *
1379 * else must be old SYN; drop it.
1380 * else do normal processing.
1381 */
1382 case TCPS_LAST_ACK:
1383 case TCPS_CLOSING:
1384 case TCPS_TIME_WAIT:
1385 if ((thflags & TH_SYN) &&
1386 (to.to_flags & TOF_CC) && tp->cc_recv != 0) {
1387 if (tp->t_state == TCPS_TIME_WAIT &&
1388 (ticks - tp->t_starttime) > tcp_msl) {
1389 rstreason = BANDLIM_UNLIMITED;
1390 goto dropwithreset;
1391 }
1392 if (CC_GT(to.to_cc, tp->cc_recv)) {
1393 tp = tcp_close(tp);
1394 goto findpcb;
1395 }
1396 else
1397 goto drop;
1398 }
95b22adf 1399 break; /* continue normal processing */
984263bc
MD
1400 }
1401
1402 /*
1403 * States other than LISTEN or SYN_SENT.
1404 * First check the RST flag and sequence number since reset segments
1405 * are exempt from the timestamp and connection count tests. This
1406 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix
1407 * below which allowed reset segments in half the sequence space
1408 * to fall though and be processed (which gives forged reset
1409 * segments with a random sequence number a 50 percent chance of
1410 * killing a connection).
1411 * Then check timestamp, if present.
1412 * Then check the connection count, if present.
1413 * Then check that at least some bytes of segment are within
1414 * receive window. If segment begins before rcv_nxt,
1415 * drop leading data (and SYN); if nothing left, just ack.
1416 *
1417 *
1418 * If the RST bit is set, check the sequence number to see
1419 * if this is a valid reset segment.
1420 * RFC 793 page 37:
1421 * In all states except SYN-SENT, all reset (RST) segments
1422 * are validated by checking their SEQ-fields. A reset is
1423 * valid if its sequence number is in the window.
1424 * Note: this does not take into account delayed ACKs, so
1425 * we should test against last_ack_sent instead of rcv_nxt.
1426 * The sequence number in the reset segment is normally an
1427 * echo of our outgoing acknowlegement numbers, but some hosts
1428 * send a reset with the sequence number at the rightmost edge
1429 * of our receive window, and we have to handle this case.
1430 * If we have multiple segments in flight, the intial reset
1431 * segment sequence numbers will be to the left of last_ack_sent,
1432 * but they will eventually catch up.
1433 * In any case, it never made sense to trim reset segments to
1434 * fit the receive window since RFC 1122 says:
1435 * 4.2.2.12 RST Segment: RFC-793 Section 3.4
1436 *
1437 * A TCP SHOULD allow a received RST segment to include data.
1438 *
1439 * DISCUSSION
1440 * It has been suggested that a RST segment could contain
1441 * ASCII text that encoded and explained the cause of the
1442 * RST. No standard has yet been established for such
1443 * data.
1444 *
1445 * If the reset segment passes the sequence number test examine
1446 * the state:
1447 * SYN_RECEIVED STATE:
1448 * If passive open, return to LISTEN state.
1449 * If active open, inform user that connection was refused.
1450 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES:
1451 * Inform user that connection was reset, and close tcb.
1452 * CLOSING, LAST_ACK STATES:
1453 * Close the tcb.
1454 * TIME_WAIT STATE:
1455 * Drop the segment - see Stevens, vol. 2, p. 964 and
1456 * RFC 1337.
1457 */
1458 if (thflags & TH_RST) {
1459 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
1460 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) {
1461 switch (tp->t_state) {
1462
1463 case TCPS_SYN_RECEIVED:
1464 so->so_error = ECONNREFUSED;
1465 goto close;
1466
1467 case TCPS_ESTABLISHED:
1468 case TCPS_FIN_WAIT_1:
1469 case TCPS_FIN_WAIT_2:
1470 case TCPS_CLOSE_WAIT:
1471 so->so_error = ECONNRESET;
1472 close:
1473 tp->t_state = TCPS_CLOSED;
1474 tcpstat.tcps_drops++;
1475 tp = tcp_close(tp);
1476 break;
1477
1478 case TCPS_CLOSING:
1479 case TCPS_LAST_ACK:
1480 tp = tcp_close(tp);
1481 break;
1482
1483 case TCPS_TIME_WAIT:
1484 break;
1485 }
1486 }
1487 goto drop;
1488 }
1489
1490 /*
1491 * RFC 1323 PAWS: If we have a timestamp reply on this segment
1492 * and it's less than ts_recent, drop it.
1493 */
1494 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
1495 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
1496
1497 /* Check to see if ts_recent is over 24 days old. */
1498 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) {
1499 /*
1500 * Invalidate ts_recent. If this segment updates
1501 * ts_recent, the age will be reset later and ts_recent
1502 * will get a valid value. If it does not, setting
1503 * ts_recent to zero will at least satisfy the
1504 * requirement that zero be placed in the timestamp
1505 * echo reply when ts_recent isn't valid. The
1506 * age isn't reset until we get a valid ts_recent
1507 * because we don't want out-of-order segments to be
1508 * dropped when ts_recent is old.
1509 */
1510 tp->ts_recent = 0;
1511 } else {
1512 tcpstat.tcps_rcvduppack++;
1513 tcpstat.tcps_rcvdupbyte += tlen;
1514 tcpstat.tcps_pawsdrop++;
1515 if (tlen)
1516 goto dropafterack;
1517 goto drop;
1518 }
1519 }
1520
1521 /*
1522 * T/TCP mechanism
1523 * If T/TCP was negotiated and the segment doesn't have CC,
1524 * or if its CC is wrong then drop the segment.
1525 * RST segments do not have to comply with this.
1526 */
1527 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) &&
1528 ((to.to_flags & TOF_CC) == 0 || tp->cc_recv != to.to_cc))
95b22adf 1529 goto dropafterack;
984263bc
MD
1530
1531 /*
1532 * In the SYN-RECEIVED state, validate that the packet belongs to
1533 * this connection before trimming the data to fit the receive
1534 * window. Check the sequence number versus IRS since we know
1535 * the sequence numbers haven't wrapped. This is a partial fix
1536 * for the "LAND" DoS attack.
1537 */
1538 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) {
1539 rstreason = BANDLIM_RST_OPENPORT;
1540 goto dropwithreset;
1541 }
1542
1543 todrop = tp->rcv_nxt - th->th_seq;
1544 if (todrop > 0) {
1545 if (thflags & TH_SYN) {
1546 thflags &= ~TH_SYN;
1547 th->th_seq++;
1548 if (th->th_urp > 1)
1549 th->th_urp--;
1550 else
1551 thflags &= ~TH_URG;
1552 todrop--;
1553 }
1554 /*
1555 * Following if statement from Stevens, vol. 2, p. 960.
1556 */
1557 if (todrop > tlen
1558 || (todrop == tlen && (thflags & TH_FIN) == 0)) {
1559 /*
1560 * Any valid FIN must be to the left of the window.
1561 * At this point the FIN must be a duplicate or out
1562 * of sequence; drop it.
1563 */
1564 thflags &= ~TH_FIN;
1565
1566 /*
1567 * Send an ACK to resynchronize and drop any data.
1568 * But keep on processing for RST or ACK.
1569 */
1570 tp->t_flags |= TF_ACKNOW;
1571 todrop = tlen;
1572 tcpstat.tcps_rcvduppack++;
1573 tcpstat.tcps_rcvdupbyte += todrop;
1574 } else {
1575 tcpstat.tcps_rcvpartduppack++;
1576 tcpstat.tcps_rcvpartdupbyte += todrop;
1577 }
1578 drop_hdrlen += todrop; /* drop from the top afterwards */
1579 th->th_seq += todrop;
1580 tlen -= todrop;
1581 if (th->th_urp > todrop)
1582 th->th_urp -= todrop;
1583 else {
1584 thflags &= ~TH_URG;
1585 th->th_urp = 0;
1586 }
1587 }
1588
1589 /*
1590 * If new data are received on a connection after the
1591 * user processes are gone, then RST the other end.
1592 */
1593 if ((so->so_state & SS_NOFDREF) &&
1594 tp->t_state > TCPS_CLOSE_WAIT && tlen) {
1595 tp = tcp_close(tp);
1596 tcpstat.tcps_rcvafterclose++;
1597 rstreason = BANDLIM_UNLIMITED;
1598 goto dropwithreset;
1599 }
1600
1601 /*
1602 * If segment ends after window, drop trailing data
1603 * (and PUSH and FIN); if nothing left, just ACK.
1604 */
1605 todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd);
1606 if (todrop > 0) {
1607 tcpstat.tcps_rcvpackafterwin++;
1608 if (todrop >= tlen) {
1609 tcpstat.tcps_rcvbyteafterwin += tlen;
1610 /*
1611 * If a new connection request is received
1612 * while in TIME_WAIT, drop the old connection
1613 * and start over if the sequence numbers
1614 * are above the previous ones.
1615 */
1616 if (thflags & TH_SYN &&
1617 tp->t_state == TCPS_TIME_WAIT &&
1618 SEQ_GT(th->th_seq, tp->rcv_nxt)) {
1619 tp = tcp_close(tp);
1620 goto findpcb;
1621 }
1622 /*
1623 * If window is closed can only take segments at
1624 * window edge, and have to drop data and PUSH from
1625 * incoming segments. Continue processing, but
1626 * remember to ack. Otherwise, drop segment
1627 * and ack.
1628 */
1629 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
1630 tp->t_flags |= TF_ACKNOW;
1631 tcpstat.tcps_rcvwinprobe++;
1632 } else
1633 goto dropafterack;
1634 } else
1635 tcpstat.tcps_rcvbyteafterwin += todrop;
1636 m_adj(m, -todrop);
1637 tlen -= todrop;
1638 thflags &= ~(TH_PUSH|TH_FIN);
1639 }
1640
1641 /*
1642 * If last ACK falls within this segment's sequence numbers,
1643 * record its timestamp.
1644 * NOTE that the test is modified according to the latest
1645 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1646 */
1647 if ((to.to_flags & TOF_TS) != 0 &&
1648 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
1649 tp->ts_recent_age = ticks;
1650 tp->ts_recent = to.to_tsval;
1651 }
1652
1653 /*
1654 * If a SYN is in the window, then this is an
1655 * error and we send an RST and drop the connection.
1656 */
1657 if (thflags & TH_SYN) {
1658 tp = tcp_drop(tp, ECONNRESET);
1659 rstreason = BANDLIM_UNLIMITED;
1660 goto dropwithreset;
1661 }
1662
1663 /*
1664 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN
1665 * flag is on (half-synchronized state), then queue data for
1666 * later processing; else drop segment and return.
1667 */
1668 if ((thflags & TH_ACK) == 0) {
1669 if (tp->t_state == TCPS_SYN_RECEIVED ||
1670 (tp->t_flags & TF_NEEDSYN))
1671 goto step6;
1672 else
1673 goto drop;
1674 }
1675
1676 /*
1677 * Ack processing.
1678 */
1679 switch (tp->t_state) {
1680
1681 /*
1682 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter
1683 * ESTABLISHED state and continue processing.
1684 * The ACK was checked above.
1685 */
1686 case TCPS_SYN_RECEIVED:
1687
1688 tcpstat.tcps_connects++;
1689 soisconnected(so);
1690 /* Do window scaling? */
1691 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
1692 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
1693 tp->snd_scale = tp->requested_s_scale;
1694 tp->rcv_scale = tp->request_r_scale;
1695 }
1696 /*
1697 * Upon successful completion of 3-way handshake,
1698 * update cache.CC if it was undefined, pass any queued
1699 * data to the user, and advance state appropriately.
1700 */
1701 if ((taop = tcp_gettaocache(&inp->inp_inc)) != NULL &&
1702 taop->tao_cc == 0)
1703 taop->tao_cc = tp->cc_recv;
1704
1705 /*
1706 * Make transitions:
1707 * SYN-RECEIVED -> ESTABLISHED
1708 * SYN-RECEIVED* -> FIN-WAIT-1
1709 */
1710 tp->t_starttime = ticks;
1711 if (tp->t_flags & TF_NEEDFIN) {
1712 tp->t_state = TCPS_FIN_WAIT_1;
1713 tp->t_flags &= ~TF_NEEDFIN;
1714 } else {
1715 tp->t_state = TCPS_ESTABLISHED;
d24ce1dc 1716 callout_reset(tp->tt_keep, tcp_keepidle,
984263bc
MD
1717 tcp_timer_keep, tp);
1718 }
1719 /*
1720 * If segment contains data or ACK, will call tcp_reass()
1721 * later; if not, do so now to pass queued data to user.
1722 */
1723 if (tlen == 0 && (thflags & TH_FIN) == 0)
1724 (void) tcp_reass(tp, (struct tcphdr *)0, 0,
1725 (struct mbuf *)0);
1726 tp->snd_wl1 = th->th_seq - 1;
1727 /* fall into ... */
1728
1729 /*
1730 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
1731 * ACKs. If the ack is in the range
1732 * tp->snd_una < th->th_ack <= tp->snd_max
1733 * then advance tp->snd_una to th->th_ack and drop
1734 * data from the retransmission queue. If this ACK reflects
1735 * more up to date window information we update our window information.
1736 */
1737 case TCPS_ESTABLISHED:
1738 case TCPS_FIN_WAIT_1:
1739 case TCPS_FIN_WAIT_2:
1740 case TCPS_CLOSE_WAIT:
1741 case TCPS_CLOSING:
1742 case TCPS_LAST_ACK:
1743 case TCPS_TIME_WAIT:
1744
1745 if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
95b22adf
JH
1746 if (tlen != 0 || tiwin != tp->snd_wnd) {
1747 tp->t_dupacks = 0;
1748 break;
1749 }
1750 tcpstat.tcps_rcvdupack++;
1751 /*
1752 * If we have outstanding data (other than
1753 * a window probe), this is a completely
1754 * duplicate ack (ie, window info didn't
1755 * change), the ack is the biggest we've
1756 * seen and we've seen exactly our rexmt
1757 * threshhold of them, assume a packet
1758 * has been dropped and retransmit it.
1759 * Kludge snd_nxt & the congestion
1760 * window so we send only this one
1761 * packet.
1762 *
1763 * We know we're losing at the current
1764 * window size so do congestion avoidance
1765 * (set ssthresh to half the current window
1766 * and pull our congestion window back to
1767 * the new ssthresh).
1768 *
1769 * Dup acks mean that packets have left the
1770 * network (they're now cached at the receiver)
1771 * so bump cwnd by the amount in the receiver
1772 * to keep a constant cwnd packets in the
1773 * network.
1774 */
1775 if (!callout_active(tp->tt_rexmt) ||
1776 th->th_ack != tp->snd_una) {
1777 tp->t_dupacks = 0;
1778 break;
1779 }
1780 if (IN_FASTRECOVERY(tp)) {
1781 tp->snd_cwnd += tp->t_maxseg;
1782 (void) tcp_output(tp);
1783 } else if (++tp->t_dupacks == tcprexmtthresh) {
1784 tcp_seq onxt;
1785 u_int win;
1786
1787 if (SEQ_LEQ(th->th_ack, tp->snd_recover)) {
984263bc 1788 tp->t_dupacks = 0;
95b22adf
JH
1789 break;
1790 }
8819433a 1791fastretransmit:
95b22adf
JH
1792 if (tcp_do_eifel_detect &&
1793 (tp->t_flags & TF_RCVD_TSTMP)) {
1794 tcp_save_congestion_state(tp);
1795 tp->t_flags |= TF_FASTREXMT;
1796 }
1797 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 /
1798 tp->t_maxseg;
1799 if (win < 2)
1800 win = 2;
1801 tp->snd_ssthresh = win * tp->t_maxseg;
1802 ENTER_FASTRECOVERY(tp);
1803 tp->snd_recover = tp->snd_max;
1804 callout_stop(tp->tt_rexmt);
1805 tp->t_rtttime = 0;
1806 onxt = tp->snd_nxt;
1807 tp->snd_nxt = th->th_ack;
1808 tp->snd_cwnd = tp->t_maxseg;
1809 (void) tcp_output(tp);
1810 ++tcpstat.tcps_sndfastrexmit;
1811 KASSERT(tp->snd_limited <= 2,
1812 ("tp->snd_limited too big"));
1813 tp->snd_cwnd = tp->snd_ssthresh +
1814 (tp->t_maxseg *
1815 (tp->t_dupacks - tp->snd_limited));
1816 if (SEQ_GT(onxt, tp->snd_nxt))
1817 tp->snd_nxt = onxt;
1818 } else if (tcp_do_limitedtransmit) {
1819 u_long oldcwnd = tp->snd_cwnd;
1820 tcp_seq oldsndmax = tp->snd_max;
1821 /* outstanding data */
1822 uint32_t ownd = tp->snd_max - tp->snd_una;
1823 u_int sent;
ca94b4a6 1824
8819433a
JH
1825#define iceildiv(n, d) (((n)+(d)-1) / (d))
1826
95b22adf
JH
1827 KASSERT(tp->t_dupacks == 1 ||
1828 tp->t_dupacks == 2,
1829 ("dupacks not 1 or 2"));
1830 if (tp->t_dupacks == 1)
1831 tp->snd_limited = 0;
1832 tp->snd_cwnd = ownd +
1833 (tp->t_dupacks - tp->snd_limited) *
1834 tp->t_maxseg;
1835 (void) tcp_output(tp);
1836 tp->snd_cwnd = oldcwnd;
1837 sent = tp->snd_max - oldsndmax;
1838 if (sent > tp->t_maxseg) {
1839 KASSERT((tp->t_dupacks == 2 &&
1840 tp->snd_limited == 0) ||
1841 (sent == tp->t_maxseg + 1 &&
1842 tp->t_flags & TF_SENTFIN),
1843 ("sent too much"));
1844 KASSERT(sent <= tp->t_maxseg * 2,
1845 ("sent too many segments"));
1846 tp->snd_limited = 2;
1847 tcpstat.tcps_sndlimited += 2;
1848 } else if (sent > 0) {
1849 ++tp->snd_limited;
1850 ++tcpstat.tcps_sndlimited;
1851 } else if (tcp_do_early_retransmit &&
1852 (tcp_do_eifel_detect &&
1853 (tp->t_flags & TF_RCVD_TSTMP)) &&
1854 tp->t_dupacks + 1 >=
1855 iceildiv(ownd, tp->t_maxseg)) {
1856 ++tcpstat.tcps_sndearlyrexmit;
1857 tp->t_flags |= TF_EARLYREXMT;
1858 goto fastretransmit;
984263bc 1859 }
95b22adf
JH
1860 }
1861 goto drop;
984263bc
MD
1862 }
1863
1864 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una"));
1865
1866 /*
1867 * If the congestion window was inflated to account
1868 * for the other side's cached packets, retract it.
1869 */
95b22adf
JH
1870 if (IN_FASTRECOVERY(tp)) {
1871 if (SEQ_LT(th->th_ack, tp->snd_recover)) {
1872 tcp_newreno_partial_ack(tp, th);
1873 } else {
1874 /*
1875 * Window inflation should have left us
1876 * with approximately snd_ssthresh
1877 * outstanding data.
1878 * But in case we would be inclined to
1879 * send a burst, better to do it via
1880 * the slow start mechanism.
1881 */
1882 if (SEQ_GT(th->th_ack + tp->snd_ssthresh,
1883 tp->snd_max))
1884 tp->snd_cwnd = tp->snd_max -
1885 th->th_ack + tp->t_maxseg;
1886 else
1887 tp->snd_cwnd = tp->snd_ssthresh;
984263bc 1888 }
95b22adf 1889 }
984263bc
MD
1890 tp->t_dupacks = 0;
1891 if (SEQ_GT(th->th_ack, tp->snd_max)) {
5a274421
JH
1892 /*
1893 * Detected optimistic ACK attack.
1894 * Force slow-start to de-synchronize attack.
1895 */
1896 tp->snd_cwnd = tp->t_maxseg;
1897
984263bc
MD
1898 tcpstat.tcps_rcvacktoomuch++;
1899 goto dropafterack;
1900 }
1901 /*
1902 * If we reach this point, ACK is not a duplicate,
1903 * i.e., it ACKs something we sent.
1904 */
1905 if (tp->t_flags & TF_NEEDSYN) {
1906 /*
1907 * T/TCP: Connection was half-synchronized, and our
1908 * SYN has been ACK'd (so connection is now fully
1909 * synchronized). Go to non-starred state,
1910 * increment snd_una for ACK of SYN, and check if
1911 * we can do window scaling.
1912 */
1913 tp->t_flags &= ~TF_NEEDSYN;
1914 tp->snd_una++;
1915 /* Do window scaling? */
1916 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
95b22adf 1917 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
984263bc
MD
1918 tp->snd_scale = tp->requested_s_scale;
1919 tp->rcv_scale = tp->request_r_scale;
1920 }
1921 }
1922
1923process_ACK:
1924 acked = th->th_ack - tp->snd_una;
1925 tcpstat.tcps_rcvackpack++;
1926 tcpstat.tcps_rcvackbyte += acked;
1927
1928 /*
1929 * If we just performed our first retransmit, and the ACK
1930 * arrives within our recovery window, then it was a mistake
1931 * to do the retransmit in the first place. Recover our
1932 * original cwnd and ssthresh, and proceed to transmit where
1933 * we left off.
1934 */
bfdb979e 1935 if (tcp_do_eifel_detect && acked &&
95b22adf 1936 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) &&
bfdb979e
JH
1937 (tp->t_flags & TF_FIRSTACCACK)) {
1938 /* Eifel detection applicable. */
1939 if (to.to_tsecr < tp->t_rexmtTS) {
bfdb979e 1940 ++tcpstat.tcps_eifeldetected;
8819433a
JH
1941 tcp_revert_congestion_state(tp);
1942 if (tp->t_rxtshift == 1 &&
1943 ticks >= tp->t_badrxtwin)
1944 ++tcpstat.tcps_rttcantdetect;
bfdb979e
JH
1945 }
1946 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) {
1947 tcp_revert_congestion_state(tp);
1948 ++tcpstat.tcps_rttdetected;
984263bc
MD
1949 }
1950
1951 /*
1952 * If we have a timestamp reply, update smoothed
1953 * round trip time. If no timestamp is present but
1954 * transmit timer is running and timed sequence
1955 * number was acked, update smoothed round trip time.
1956 * Since we now have an rtt measurement, cancel the
1957 * timer backoff (cf., Phil Karn's retransmit alg.).
1958 * Recompute the initial retransmit timer.
1959 *
1960 * Some machines (certain windows boxes) send broken
d24ce1dc 1961 * timestamp replies during the SYN+ACK phase, ignore
984263bc
MD
1962 * timestamps of 0.
1963 */
95b22adf 1964 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0))
984263bc 1965 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1);
95b22adf 1966 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq))
984263bc 1967 tcp_xmit_timer(tp, ticks - tp->t_rtttime);
984263bc
MD
1968 tcp_xmit_bandwidth_limit(tp, th->th_ack);
1969
1970 /*
1971 * If all outstanding data is acked, stop retransmit
1972 * timer and remember to restart (more output or persist).
1973 * If there is more data to be acked, restart retransmit
1974 * timer, using current (possibly backed-off) value.
1975 */
1976 if (th->th_ack == tp->snd_max) {
1977 callout_stop(tp->tt_rexmt);
1978 needoutput = 1;
1979 } else if (!callout_active(tp->tt_persist))
1980 callout_reset(tp->tt_rexmt, tp->t_rxtcur,
1981 tcp_timer_rexmt, tp);
1982
1983 /*
1984 * If no data (only SYN) was ACK'd,
1985 * skip rest of ACK processing.
1986 */
1987 if (acked == 0)
1988 goto step6;
1989
efd4b327 1990 /* Stop looking for an acceptable ACK since one was received. */
8819433a 1991 tp->t_flags &= ~(TF_FIRSTACCACK | TF_FASTREXMT | TF_EARLYREXMT);
efd4b327 1992
984263bc
MD
1993 /*
1994 * When new data is acked, open the congestion window.
1995 * If the window gives us less than ssthresh packets
1996 * in flight, open exponentially (maxseg per packet).
1997 * Otherwise open linearly: maxseg per window
1998 * (maxseg^2 / cwnd per packet).
1999 */
95b22adf 2000 if (!IN_FASTRECOVERY(tp)) {
2256ba69
RG
2001 u_int cw = tp->snd_cwnd;
2002 u_int incr = tp->t_maxseg;
95b22adf 2003
984263bc
MD
2004 if (cw > tp->snd_ssthresh)
2005 incr = incr * incr / cw;
2006 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale);
2007 }
2008 if (acked > so->so_snd.sb_cc) {
2009 tp->snd_wnd -= so->so_snd.sb_cc;
2010 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc);
2011 ourfinisacked = 1;
2012 } else {
2013 sbdrop(&so->so_snd, acked);
2014 tp->snd_wnd -= acked;
2015 ourfinisacked = 0;
2016 }
2017 sowwakeup(so);
95b22adf
JH
2018 if (IN_FASTRECOVERY(tp)) {
2019 if (SEQ_GEQ(th->th_ack, tp->snd_recover))
2020 EXIT_FASTRECOVERY(tp);
2021 } else {
2022 tp->snd_recover = th->th_ack - 1;
cfb3f3f4 2023 }
984263bc
MD
2024 tp->snd_una = th->th_ack;
2025 if (SEQ_LT(tp->snd_nxt, tp->snd_una))
2026 tp->snd_nxt = tp->snd_una;
2027
2028 switch (tp->t_state) {
2029
2030 /*
2031 * In FIN_WAIT_1 STATE in addition to the processing
2032 * for the ESTABLISHED state if our FIN is now acknowledged
2033 * then enter FIN_WAIT_2.
2034 */
2035 case TCPS_FIN_WAIT_1:
2036 if (ourfinisacked) {
2037 /*
2038 * If we can't receive any more
2039 * data, then closing user can proceed.
2040 * Starting the timer is contrary to the
2041 * specification, but if we don't get a FIN
2042 * we'll hang forever.
2043 */
2044 if (so->so_state & SS_CANTRCVMORE) {
2045 soisdisconnected(so);
2046 callout_reset(tp->tt_2msl, tcp_maxidle,
2047 tcp_timer_2msl, tp);
2048 }
2049 tp->t_state = TCPS_FIN_WAIT_2;
2050 }
2051 break;
2052
95b22adf 2053 /*
984263bc
MD
2054 * In CLOSING STATE in addition to the processing for
2055 * the ESTABLISHED state if the ACK acknowledges our FIN
2056 * then enter the TIME-WAIT state, otherwise ignore
2057 * the segment.
2058 */
2059 case TCPS_CLOSING:
2060 if (ourfinisacked) {
2061 tp->t_state = TCPS_TIME_WAIT;
2062 tcp_canceltimers(tp);
2063 /* Shorten TIME_WAIT [RFC-1644, p.28] */
2064 if (tp->cc_recv != 0 &&
2065 (ticks - tp->t_starttime) < tcp_msl)
2066 callout_reset(tp->tt_2msl,
2067 tp->t_rxtcur *
2068 TCPTV_TWTRUNC,
2069 tcp_timer_2msl, tp);
2070 else
2071 callout_reset(tp->tt_2msl, 2 * tcp_msl,
2072 tcp_timer_2msl, tp);
2073 soisdisconnected(so);
2074 }
2075 break;
2076
2077 /*
2078 * In LAST_ACK, we may still be waiting for data to drain
2079 * and/or to be acked, as well as for the ack of our FIN.
2080 * If our FIN is now acknowledged, delete the TCB,
2081 * enter the closed state and return.
2082 */
2083 case TCPS_LAST_ACK:
2084 if (ourfinisacked) {
2085 tp = tcp_close(tp);
2086 goto drop;
2087 }
2088 break;
2089
2090 /*
2091 * In TIME_WAIT state the only thing that should arrive
2092 * is a retransmission of the remote FIN. Acknowledge
2093 * it and restart the finack timer.
2094 */
2095 case TCPS_TIME_WAIT:
2096 callout_reset(tp->tt_2msl, 2 * tcp_msl,
2097 tcp_timer_2msl, tp);
2098 goto dropafterack;
2099 }
2100 }
2101
2102step6:
2103 /*
2104 * Update window information.
2105 * Don't look at window if no ACK: TAC's send garbage on first SYN.
2106 */
2107 if ((thflags & TH_ACK) &&
2108 (SEQ_LT(tp->snd_wl1, th->th_seq) ||
2109 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) ||
2110 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) {
2111 /* keep track of pure window updates */
2112 if (tlen == 0 &&
2113 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)
2114 tcpstat.tcps_rcvwinupd++;
2115 tp->snd_wnd = tiwin;
2116 tp->snd_wl1 = th->th_seq;
2117 tp->snd_wl2 = th->th_ack;
2118 if (tp->snd_wnd > tp->max_sndwnd)
2119 tp->max_sndwnd = tp->snd_wnd;
2120 needoutput = 1;
2121 }
2122
2123 /*
2124 * Process segments with URG.
2125 */
2126 if ((thflags & TH_URG) && th->th_urp &&
95b22adf 2127 !TCPS_HAVERCVDFIN(tp->t_state)) {
984263bc
MD
2128 /*
2129 * This is a kludge, but if we receive and accept
2130 * random urgent pointers, we'll crash in
2131 * soreceive. It's hard to imagine someone
2132 * actually wanting to send this much urgent data.
2133 */
2134 if (th->th_urp + so->so_rcv.sb_cc > sb_max) {
2135 th->th_urp = 0; /* XXX */
2136 thflags &= ~TH_URG; /* XXX */
2137 goto dodata; /* XXX */
2138 }
2139 /*
2140 * If this segment advances the known urgent pointer,
2141 * then mark the data stream. This should not happen
2142 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
2143 * a FIN has been received from the remote side.
2144 * In these states we ignore the URG.
2145 *
2146 * According to RFC961 (Assigned Protocols),
2147 * the urgent pointer points to the last octet
2148 * of urgent data. We continue, however,
2149 * to consider it to indicate the first octet
2150 * of data past the urgent section as the original
2151 * spec states (in one of two places).
2152 */
2153 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) {
2154 tp->rcv_up = th->th_seq + th->th_urp;
2155 so->so_oobmark = so->so_rcv.sb_cc +
2156 (tp->rcv_up - tp->rcv_nxt) - 1;
2157 if (so->so_oobmark == 0)
2158 so->so_state |= SS_RCVATMARK;
2159 sohasoutofband(so);
2160 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
2161 }
2162 /*
2163 * Remove out of band data so doesn't get presented to user.
2164 * This can happen independent of advancing the URG pointer,
2165 * but if two URG's are pending at once, some out-of-band
2166 * data may creep in... ick.
2167 */
2168 if (th->th_urp <= (u_long)tlen
2169#ifdef SO_OOBINLINE
2170 && (so->so_options & SO_OOBINLINE) == 0
2171#endif
2172 )
2173 tcp_pulloutofband(so, th, m,
2174 drop_hdrlen); /* hdr drop is delayed */
2175 } else {
2176 /*
2177 * If no out of band data is expected,
2178 * pull receive urgent pointer along
2179 * with the receive window.
2180 */
2181 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
2182 tp->rcv_up = tp->rcv_nxt;
2183 }
2184dodata: /* XXX */
2185
2186 /*
2187 * Process the segment text, merging it into the TCP sequencing queue,
2188 * and arranging for acknowledgment of receipt if necessary.
2189 * This process logically involves adjusting tp->rcv_wnd as data
2190 * is presented to the user (this happens in tcp_usrreq.c,
2191 * case PRU_RCVD). If a FIN has already been received on this
2192 * connection then we just ignore the text.
2193 */
95b22adf 2194 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) {
984263bc
MD
2195 m_adj(m, drop_hdrlen); /* delayed header drop */
2196 /*
2197 * Insert segment which includes th into TCP reassembly queue
2198 * with control block tp. Set thflags to whether reassembly now
2199 * includes a segment with FIN. This handles the common case
2200 * inline (segment is the next to be received on an established
2201 * connection, and the queue is empty), avoiding linkage into
2202 * and removal from the queue and repetition of various
2203 * conversions.
2204 * Set DELACK for segments received in order, but ack
2205 * immediately when segments are out of order (so
2206 * fast retransmit can work).
2207 */
2208 if (th->th_seq == tp->rcv_nxt &&
2209 LIST_EMPTY(&tp->t_segq) &&
2210 TCPS_HAVEESTABLISHED(tp->t_state)) {
2211 if (DELAY_ACK(tp))
2212 callout_reset(tp->tt_delack, tcp_delacktime,
2213 tcp_timer_delack, tp);
2214 else
2215 tp->t_flags |= TF_ACKNOW;
2216 tp->rcv_nxt += tlen;
2217 thflags = th->th_flags & TH_FIN;
2218 tcpstat.tcps_rcvpack++;
2219 tcpstat.tcps_rcvbyte += tlen;
2220 ND6_HINT(tp);
2221 if (so->so_state & SS_CANTRCVMORE)
2222 m_freem(m);
2223 else
2224 sbappend(&so->so_rcv, m);
2225 sorwakeup(so);
2226 } else {
2227 thflags = tcp_reass(tp, th, &tlen, m);
2228 tp->t_flags |= TF_ACKNOW;
2229 }
2230
2231 /*
2232 * Note the amount of data that peer has sent into
2233 * our window, in order to estimate the sender's
2234 * buffer size.
2235 */
2236 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
2237 } else {
2238 m_freem(m);
2239 thflags &= ~TH_FIN;
2240 }
2241
2242 /*
2243 * If FIN is received ACK the FIN and let the user know
2244 * that the connection is closing.
2245 */
2246 if (thflags & TH_FIN) {
95b22adf 2247 if (!TCPS_HAVERCVDFIN(tp->t_state)) {
984263bc
MD
2248 socantrcvmore(so);
2249 /*
2250 * If connection is half-synchronized
2251 * (ie NEEDSYN flag on) then delay ACK,
2252 * so it may be piggybacked when SYN is sent.
2253 * Otherwise, since we received a FIN then no
2254 * more input can be expected, send ACK now.
2255 */
2256 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN))
d24ce1dc
JH
2257 callout_reset(tp->tt_delack, tcp_delacktime,
2258 tcp_timer_delack, tp);
984263bc
MD
2259 else
2260 tp->t_flags |= TF_ACKNOW;
2261 tp->rcv_nxt++;
2262 }
2263 switch (tp->t_state) {
2264
95b22adf 2265 /*
984263bc
MD
2266 * In SYN_RECEIVED and ESTABLISHED STATES
2267 * enter the CLOSE_WAIT state.
2268 */
2269 case TCPS_SYN_RECEIVED:
2270 tp->t_starttime = ticks;
2271 /*FALLTHROUGH*/
2272 case TCPS_ESTABLISHED:
2273 tp->t_state = TCPS_CLOSE_WAIT;
2274 break;
2275
95b22adf 2276 /*
984263bc
MD
2277 * If still in FIN_WAIT_1 STATE FIN has not been acked so
2278 * enter the CLOSING state.
2279 */
2280 case TCPS_FIN_WAIT_1:
2281 tp->t_state = TCPS_CLOSING;
2282 break;
2283
95b22adf 2284 /*
984263bc
MD
2285 * In FIN_WAIT_2 state enter the TIME_WAIT state,
2286 * starting the time-wait timer, turning off the other
2287 * standard timers.
2288 */
2289 case TCPS_FIN_WAIT_2:
2290 tp->t_state = TCPS_TIME_WAIT;
2291 tcp_canceltimers(tp);
2292 /* Shorten TIME_WAIT [RFC-1644, p.28] */
2293 if (tp->cc_recv != 0 &&
2294 (ticks - tp->t_starttime) < tcp_msl) {
2295 callout_reset(tp->tt_2msl,
2296 tp->t_rxtcur * TCPTV_TWTRUNC,
2297 tcp_timer_2msl, tp);
2298 /* For transaction client, force ACK now. */
2299 tp->t_flags |= TF_ACKNOW;
2300 }
2301 else
2302 callout_reset(tp->tt_2msl, 2 * tcp_msl,
2303 tcp_timer_2msl, tp);
2304 soisdisconnected(so);
2305 break;
2306
2307 /*
2308 * In TIME_WAIT state restart the 2 MSL time_wait timer.
2309 */
2310 case TCPS_TIME_WAIT:
2311 callout_reset(tp->tt_2msl, 2 * tcp_msl,
2312 tcp_timer_2msl, tp);
2313 break;
2314 }
2315 }
2316#ifdef TCPDEBUG
2317 if (so->so_options & SO_DEBUG)
2318 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen,
2319 &tcp_savetcp, 0);
2320#endif
2321
2322 /*
2323 * Return any desired output.
2324 */
2325 if (needoutput || (tp->t_flags & TF_ACKNOW))
2326 (void) tcp_output(tp);
2327 return;
2328
2329dropafterack:
2330 /*
2331 * Generate an ACK dropping incoming segment if it occupies
2332 * sequence space, where the ACK reflects our state.
2333 *
2334 * We can now skip the test for the RST flag since all
2335 * paths to this code happen after packets containing
2336 * RST have been dropped.
2337 *
2338 * In the SYN-RECEIVED state, don't send an ACK unless the
2339 * segment we received passes the SYN-RECEIVED ACK test.
2340 * If it fails send a RST. This breaks the loop in the
2341 * "LAND" DoS attack, and also prevents an ACK storm
2342 * between two listening ports that have been sent forged
2343 * SYN segments, each with the source address of the other.
2344 */
2345 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
2346 (SEQ_GT(tp->snd_una, th->th_ack) ||
2347 SEQ_GT(th->th_ack, tp->snd_max)) ) {
2348 rstreason = BANDLIM_RST_OPENPORT;
2349 goto dropwithreset;
2350 }
2351#ifdef TCPDEBUG
2352 if (so->so_options & SO_DEBUG)
2353 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
2354 &tcp_savetcp, 0);
2355#endif
2356 m_freem(m);
2357 tp->t_flags |= TF_ACKNOW;
2358 (void) tcp_output(tp);
2359 return;
2360
2361dropwithreset:
2362 /*
2363 * Generate a RST, dropping incoming segment.
2364 * Make ACK acceptable to originator of segment.
2365 * Don't bother to respond if destination was broadcast/multicast.
2366 */
2367 if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST))
2368 goto drop;
2369 if (isipv6) {
2370 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
2371 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
2372 goto drop;
2373 } else {
2374 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
2375 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
95b22adf
JH
2376 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
2377 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
984263bc
MD
2378 goto drop;
2379 }
2380 /* IPv6 anycast check is done at tcp6_input() */
2381
2382 /*
2383 * Perform bandwidth limiting.
2384 */
2385#ifdef ICMP_BANDLIM
2386 if (badport_bandlim(rstreason) < 0)
2387 goto drop;
2388#endif
2389
2390#ifdef TCPDEBUG
2391 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
2392 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
2393 &tcp_savetcp, 0);
2394#endif
2395 if (thflags & TH_ACK)
2396 /* mtod() below is safe as long as hdr dropping is delayed */
2397 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack,
2398 TH_RST);
2399 else {
2400 if (thflags & TH_SYN)
2401 tlen++;
2402 /* mtod() below is safe as long as hdr dropping is delayed */
2403 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen,
2404 (tcp_seq)0, TH_RST|TH_ACK);
2405 }
2406 return;
2407
2408drop:
2409 /*
2410 * Drop space held by incoming segment and return.
2411 */
2412#ifdef TCPDEBUG
2413 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
2414 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
2415 &tcp_savetcp, 0);
2416#endif
2417 m_freem(m);
2418 return;
2419}
2420
2421/*
2422 * Parse TCP options and place in tcpopt.
2423 */
2424static void
95b22adf 2425tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn)
984263bc
MD
2426{
2427 int opt, optlen;
2428
2429 to->to_flags = 0;
2430 for (; cnt > 0; cnt -= optlen, cp += optlen) {
2431 opt = cp[0];
2432 if (opt == TCPOPT_EOL)
2433 break;
2434 if (opt == TCPOPT_NOP)
2435 optlen = 1;
2436 else {
2437 if (cnt < 2)
2438 break;
2439 optlen = cp[1];
2440 if (optlen < 2 || optlen > cnt)
2441 break;
2442 }
2443 switch (opt) {
2444 case TCPOPT_MAXSEG:
2445 if (optlen != TCPOLEN_MAXSEG)
2446 continue;
2447 if (!is_syn)
2448 continue;
2449 to->to_flags |= TOF_MSS;
95b22adf 2450 bcopy(cp + 2, &to->to_mss, sizeof(to->to_mss));
984263bc
MD
2451 to->to_mss = ntohs(to->to_mss);
2452 break;
2453 case TCPOPT_WINDOW:
2454 if (optlen != TCPOLEN_WINDOW)
2455 continue;
95b22adf 2456 if (!is_syn)
984263bc
MD
2457 continue;
2458 to->to_flags |= TOF_SCALE;
2459 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT);
2460 break;
2461 case TCPOPT_TIMESTAMP:
2462 if (optlen != TCPOLEN_TIMESTAMP)
2463 continue;
2464 to->to_flags |= TOF_TS;
95b22adf 2465 bcopy(cp + 2, &to->to_tsval, sizeof(to->to_tsval));
984263bc 2466 to->to_tsval = ntohl(to->to_tsval);
95b22adf 2467 bcopy(cp + 6, &to->to_tsecr, sizeof(to->to_tsecr));
984263bc
MD
2468 to->to_tsecr = ntohl(to->to_tsecr);
2469 break;
2470 case TCPOPT_CC:
2471 if (optlen != TCPOLEN_CC)
2472 continue;
2473 to->to_flags |= TOF_CC;
95b22adf 2474 bcopy(cp + 2, &to->to_cc, sizeof(to->to_cc));
984263bc
MD
2475 to->to_cc = ntohl(to->to_cc);
2476 break;
2477 case TCPOPT_CCNEW:
2478 if (optlen != TCPOLEN_CC)
2479 continue;
2480 if (!is_syn)
2481 continue;
2482 to->to_flags |= TOF_CCNEW;
95b22adf 2483 bcopy(cp + 2, &to->to_cc, sizeof(to->to_cc));
984263bc
MD
2484 to->to_cc = ntohl(to->to_cc);
2485 break;
2486 case TCPOPT_CCECHO:
2487 if (optlen != TCPOLEN_CC)
2488 continue;
2489 if (!is_syn)
2490 continue;
2491 to->to_flags |= TOF_CCECHO;
95b22adf 2492 bcopy(cp + 2, &to->to_ccecho, sizeof(to->to_ccecho));
984263bc
MD
2493 to->to_ccecho = ntohl(to->to_ccecho);
2494 break;
2495 default:
2496 continue;
2497 }
2498 }
2499}
2500
2501/*
2502 * Pull out of band byte out of a segment so
2503 * it doesn't appear in the user's data queue.
2504 * It is still reflected in the segment length for
2505 * sequencing purposes.
95b22adf 2506 * "off" is the delayed to be dropped hdrlen.
984263bc
MD
2507 */
2508static void
95b22adf 2509tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off)
984263bc
MD
2510{
2511 int cnt = off + th->th_urp - 1;
2512
2513 while (cnt >= 0) {
2514 if (m->m_len > cnt) {
2515 char *cp = mtod(m, caddr_t) + cnt;
2516 struct tcpcb *tp = sototcpcb(so);
2517
2518 tp->t_iobc = *cp;
2519 tp->t_oobflags |= TCPOOB_HAVEDATA;
95b22adf 2520 bcopy(cp + 1, cp, m->m_len - cnt - 1);
984263bc
MD
2521 m->m_len--;
2522 if (m->m_flags & M_PKTHDR)
2523 m->m_pkthdr.len--;
2524 return;
2525 }
2526 cnt -= m->m_len;
2527 m = m->m_next;
2528 if (m == 0)
2529 break;
2530 }
2531 panic("tcp_pulloutofband");
2532}
2533
2534/*
2535 * Collect new round-trip time estimate
2536 * and update averages and current timeout.
2537 */
2538static void
95b22adf 2539tcp_xmit_timer(struct tcpcb *tp, int rtt)
984263bc 2540{
2256ba69 2541 int delta;
984263bc
MD
2542
2543 tcpstat.tcps_rttupdated++;
2544 tp->t_rttupdated++;
2545 if (tp->t_srtt != 0) {
2546 /*
2547 * srtt is stored as fixed point with 5 bits after the
2548 * binary point (i.e., scaled by 8). The following magic
2549 * is equivalent to the smoothing algorithm in rfc793 with
2550 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
2551 * point). Adjust rtt to origin 0.
2552 */
2553 delta = ((rtt - 1) << TCP_DELTA_SHIFT)
2554 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
2555
2556 if ((tp->t_srtt += delta) <= 0)
2557 tp->t_srtt = 1;
2558
2559 /*
2560 * We accumulate a smoothed rtt variance (actually, a
2561 * smoothed mean difference), then set the retransmit
2562 * timer to smoothed rtt + 4 times the smoothed variance.
2563 * rttvar is stored as fixed point with 4 bits after the
2564 * binary point (scaled by 16). The following is
2565 * equivalent to rfc793 smoothing with an alpha of .75
2566 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces
2567 * rfc793's wired-in beta.
2568 */
2569 if (delta < 0)
2570 delta = -delta;
2571 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
2572 if ((tp->t_rttvar += delta) <= 0)
2573 tp->t_rttvar = 1;
2574 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
2575 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2576 } else {
2577 /*
2578 * No rtt measurement yet - use the unsmoothed rtt.
2579 * Set the variance to half the rtt (so our first
2580 * retransmit happens at 3*rtt).
2581 */
2582 tp->t_srtt = rtt << TCP_RTT_SHIFT;
2583 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
2584 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2585 }
2586 tp->t_rtttime = 0;
2587 tp->t_rxtshift = 0;
2588
2589 /*
2590 * the retransmit should happen at rtt + 4 * rttvar.
2591 * Because of the way we do the smoothing, srtt and rttvar
2592 * will each average +1/2 tick of bias. When we compute
2593 * the retransmit timer, we want 1/2 tick of rounding and
2594 * 1 extra tick because of +-1/2 tick uncertainty in the
2595 * firing of the timer. The bias will give us exactly the
2596 * 1.5 tick we need. But, because the bias is
2597 * statistical, we have to test that we don't drop below
2598 * the minimum feasible timer (which is 2 ticks).
2599 */
2600 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
2601 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);
2602
2603 /*
2604 * We received an ack for a packet that wasn't retransmitted;
2605 * it is probably safe to discard any error indications we've
2606 * received recently. This isn't quite right, but close enough
2607 * for now (a route might have failed after we sent a segment,
2608 * and the return path might not be symmetrical).
2609 */
2610 tp->t_softerror = 0;
2611}
2612
2613/*
2614 * Determine a reasonable value for maxseg size.
2615 * If the route is known, check route for mtu.
2616 * If none, use an mss that can be handled on the outgoing
2617 * interface without forcing IP to fragment; if bigger than
2618 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES
2619 * to utilize large mbufs. If no route is found, route has no mtu,
2620 * or the destination isn't local, use a default, hopefully conservative
2621 * size (usually 512 or the default IP max size, but no more than the mtu
2622 * of the interface), as we can't discover anything about intervening
2623 * gateways or networks. We also initialize the congestion/slow start
2624 * window to be a single segment if the destination isn't local.
2625 * While looking at the routing entry, we also initialize other path-dependent
2626 * parameters from pre-set or cached values in the routing entry.
2627 *
2628 * Also take into account the space needed for options that we
2629 * send regularly. Make maxseg shorter by that amount to assure
2630 * that we can send maxseg amount of data even when the options
2631 * are present. Store the upper limit of the length of options plus
2632 * data in maxopd.
2633 *
2634 * NOTE that this routine is only called when we process an incoming
2635 * segment, for outgoing segments only tcp_mssopt is called.
2636 *
2637 * In case of T/TCP, we call this routine during implicit connection
2638 * setup as well (offer = -1), to initialize maxseg from the cached
2639 * MSS of our peer.
2640 */
2641void
95b22adf 2642tcp_mss(struct tcpcb *tp, int offer)
984263bc 2643{
2256ba69 2644 struct rtentry *rt;
984263bc 2645 struct ifnet *ifp;
2256ba69 2646 int rtt, mss;
984263bc
MD
2647 u_long bufsize;
2648 struct inpcb *inp = tp->t_inpcb;
2649 struct socket *so;
2650 struct rmxp_tao *taop;
2651 int origoffer = offer;
2652#ifdef INET6
d24ce1dc 2653 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE);
984263bc
MD
2654 size_t min_protoh = isipv6 ?
2655 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) :
2656 sizeof(struct tcpiphdr);
2657#else
d24ce1dc 2658 const boolean_t isipv6 = FALSE;
984263bc
MD
2659 const size_t min_protoh = sizeof(struct tcpiphdr);
2660#endif
2661
2662 if (isipv6)
2663 rt = tcp_rtlookup6(&inp->inp_inc);
2664 else
2665 rt = tcp_rtlookup(&inp->inp_inc);
2666 if (rt == NULL) {
2667 tp->t_maxopd = tp->t_maxseg =
d24ce1dc 2668 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt);
984263bc
MD
2669 return;
2670 }
2671 ifp = rt->rt_ifp;
2672 so = inp->inp_socket;
2673
2674 taop = rmx_taop(rt->rt_rmx);
2675 /*
2676 * Offer == -1 means that we didn't receive SYN yet,
2677 * use cached value in that case;
2678 */
2679 if (offer == -1)
2680 offer = taop->tao_mssopt;
2681 /*
2682 * Offer == 0 means that there was no MSS on the SYN segment,
2683 * in this case we use tcp_mssdflt.
2684 */
2685 if (offer == 0)
d24ce1dc 2686 offer = (isipv6 ? tcp_v6mssdflt : tcp_mssdflt);
984263bc
MD
2687 else
2688 /*
2689 * Sanity check: make sure that maxopd will be large
2690 * enough to allow some data on segments even is the
2691 * all the option space is used (40bytes). Otherwise
2692 * funny things may happen in tcp_output.
2693 */
2694 offer = max(offer, 64);
2695 taop->tao_mssopt = offer;
2696
2697 /*
2698 * While we're here, check if there's an initial rtt
2699 * or rttvar. Convert from the route-table units
2700 * to scaled multiples of the slow timeout timer.
2701 */
2702 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) {
2703 /*
2704 * XXX the lock bit for RTT indicates that the value
2705 * is also a minimum value; this is subject to time.
2706 */
2707 if (rt->rt_rmx.rmx_locks & RTV_RTT)
2708 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz);
2709 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE));
2710 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE;
2711 tcpstat.tcps_usedrtt++;
2712 if (rt->rt_rmx.rmx_rttvar) {
2713 tp->t_rttvar = rt->rt_rmx.rmx_rttvar /
2714 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE));
2715 tcpstat.tcps_usedrttvar++;
2716 } else {
2717 /* default variation is +- 1 rtt */
2718 tp->t_rttvar =
2719 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
2720 }
2721 TCPT_RANGESET(tp->t_rxtcur,
2722 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
2723 tp->t_rttmin, TCPTV_REXMTMAX);
2724 }
2725 /*
2726 * if there's an mtu associated with the route, use it
2727 * else, use the link mtu.
2728 */
2729 if (rt->rt_rmx.rmx_mtu)
2730 mss = rt->rt_rmx.rmx_mtu - min_protoh;
2731 else {
2732 if (isipv6) {
2733 mss = nd_ifinfo[rt->rt_ifp->if_index].linkmtu -
2734 min_protoh;
2735 if (!in6_localaddr(&inp->in6p_faddr))
2736 mss = min(mss, tcp_v6mssdflt);
2737 } else {
2738 mss = ifp->if_mtu - min_protoh;
2739 if (!in_localaddr(inp->inp_faddr))
2740 mss = min(mss, tcp_mssdflt);
2741 }
2742 }
2743 mss = min(mss, offer);
2744 /*
2745 * maxopd stores the maximum length of data AND options
2746 * in a segment; maxseg is the amount of data in a normal
2747 * segment. We need to store this value (maxopd) apart
2748 * from maxseg, because now every segment carries options
2749 * and thus we normally have somewhat less data in segments.
2750 */
2751 tp->t_maxopd = mss;
2752
2753 /*
2754 * In case of T/TCP, origoffer==-1 indicates, that no segments
2755 * were received yet. In this case we just guess, otherwise
2756 * we do the same as before T/TCP.
2757 */
95b22adf 2758 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
984263bc
MD
2759 (origoffer == -1 ||
2760 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP))
2761 mss -= TCPOLEN_TSTAMP_APPA;
95b22adf 2762 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC &&
984263bc
MD
2763 (origoffer == -1 ||
2764 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC))
2765 mss -= TCPOLEN_CC_APPA;
2766
2767#if (MCLBYTES & (MCLBYTES - 1)) == 0
2768 if (mss > MCLBYTES)
2769 mss &= ~(MCLBYTES-1);
2770#else
2771 if (mss > MCLBYTES)
2772 mss = mss / MCLBYTES * MCLBYTES;
2773#endif
2774 /*
2775 * If there's a pipesize, change the socket buffer
2776 * to that size. Make the socket buffers an integral
2777 * number of mss units; if the mss is larger than
2778 * the socket buffer, decrease the mss.
2779 */
2780#ifdef RTV_SPIPE
2781 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0)
2782#endif
2783 bufsize = so->so_snd.sb_hiwat;
2784 if (bufsize < mss)
2785 mss = bufsize;
2786 else {
2787 bufsize = roundup(bufsize, mss);
2788 if (bufsize > sb_max)
2789 bufsize = sb_max;
2790 if (bufsize > so->so_snd.sb_hiwat)
2791 (void)sbreserve(&so->so_snd, bufsize, so, NULL);
2792 }
2793 tp->t_maxseg = mss;
2794
2795#ifdef RTV_RPIPE
2796 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0)
2797#endif
2798 bufsize = so->so_rcv.sb_hiwat;
2799 if (bufsize > mss) {
2800 bufsize = roundup(bufsize, mss);
2801 if (bufsize > sb_max)
2802 bufsize = sb_max;
2803 if (bufsize > so->so_rcv.sb_hiwat)
2804 (void)sbreserve(&so->so_rcv, bufsize, so, NULL);
2805 }
2806
2807 /*
2808 * Set the slow-start flight size depending on whether this
2809 * is a local network or not.
2810 */
4b52d5ee
JH
2811 if (tcp_do_rfc3390)
2812 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380));
2813 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) ||
2814 (!isipv6 && in_localaddr(inp->inp_faddr)))
984263bc 2815 tp->snd_cwnd = mss * ss_fltsz_local;
4b52d5ee 2816 else
984263bc
MD
2817 tp->snd_cwnd = mss * ss_fltsz;
2818
2819 if (rt->rt_rmx.rmx_ssthresh) {
2820 /*
2821 * There's some sort of gateway or interface
2822 * buffer limit on the path. Use this to set
2823 * the slow start threshhold, but set the
2824 * threshold to no less than 2*mss.
2825 */
2826 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh);
2827 tcpstat.tcps_usedssthresh++;
2828 }
2829}
2830
2831/*
2832 * Determine the MSS option to send on an outgoing SYN.
2833 */
2834int
95b22adf 2835tcp_mssopt(struct tcpcb *tp)
984263bc
MD
2836{
2837 struct rtentry *rt;
2838#ifdef INET6
d24ce1dc
JH
2839 boolean_t isipv6 =
2840 ((tp->t_inpcb->inp_vflag & INP_IPV6) ? TRUE : FALSE);
984263bc
MD
2841 int min_protoh = isipv6 ?
2842 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) :
2843 sizeof(struct tcpiphdr);
2844#else
d24ce1dc 2845 const boolean_t isipv6 = FALSE;
984263bc
MD
2846 const size_t min_protoh = sizeof(struct tcpiphdr);
2847#endif
2848
2849 if (isipv6)
2850 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc);
2851 else
2852 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc);
2853 if (rt == NULL)
2854 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt);
2855
2856 return (rt->rt_ifp->if_mtu - min_protoh);
2857}
2858
2859
2860/*
2861 * When a partial ack arrives, force the retransmission of the
2862 * next unacknowledged segment. Do not clear tp->t_dupacks.
2863 * By setting snd_nxt to ti_ack, this forces retransmission timer to
2864 * be started again.
2865 */
2866static void
95b22adf 2867tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th)
984263bc
MD
2868{
2869 tcp_seq onxt = tp->snd_nxt;
2870 u_long ocwnd = tp->snd_cwnd;
2871
2872 callout_stop(tp->tt_rexmt);
2873 tp->t_rtttime = 0;
2874 tp->snd_nxt = th->th_ack;
2875 /*
2876 * Set snd_cwnd to one segment beyond acknowledged offset
2877 * (tp->snd_una has not yet been updated when this function is called.)
2878 */
2879 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una);
2880 tp->t_flags |= TF_ACKNOW;
2881 (void) tcp_output(tp);
2882 tp->snd_cwnd = ocwnd;
2883 if (SEQ_GT(onxt, tp->snd_nxt))
2884 tp->snd_nxt = onxt;
2885 /*
2886 * Partial window deflation. Relies on fact that tp->snd_una
2887 * not updated yet.
2888 */
2889 tp->snd_cwnd -= (th->th_ack - tp->snd_una - tp->t_maxseg);
2890}