tcp: Reimplement TCP_FASTKEEP socket option using per-pcb keepidle
[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/*
984263bc
MD
35 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995
36 * The Regents of the University of California. All rights reserved.
37 *
38 * Redistribution and use in source and binary forms, with or without
39 * modification, are permitted provided that the following conditions
40 * are met:
41 * 1. Redistributions of source code must retain the above copyright
42 * notice, this list of conditions and the following disclaimer.
43 * 2. Redistributions in binary form must reproduce the above copyright
44 * notice, this list of conditions and the following disclaimer in the
45 * documentation and/or other materials provided with the distribution.
46 * 3. All advertising materials mentioning features or use of this software
47 * must display the following acknowledgement:
48 * This product includes software developed by the University of
49 * California, Berkeley and its contributors.
50 * 4. Neither the name of the University nor the names of its contributors
51 * may be used to endorse or promote products derived from this software
52 * without specific prior written permission.
53 *
54 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
55 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
56 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
57 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
58 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
59 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
60 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
61 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
62 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
63 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
64 * SUCH DAMAGE.
65 *
66 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95
67 * $FreeBSD: src/sys/netinet/tcp_input.c,v 1.107.2.38 2003/05/21 04:46:41 cjc Exp $
68 */
69
b1992928 70#include "opt_inet.h"
984263bc
MD
71#include "opt_inet6.h"
72#include "opt_ipsec.h"
73#include "opt_tcpdebug.h"
74#include "opt_tcp_input.h"
75
76#include <sys/param.h>
77#include <sys/systm.h>
78#include <sys/kernel.h>
79#include <sys/sysctl.h>
80#include <sys/malloc.h>
81#include <sys/mbuf.h>
82#include <sys/proc.h> /* for proc0 declaration */
83#include <sys/protosw.h>
84#include <sys/socket.h>
85#include <sys/socketvar.h>
86#include <sys/syslog.h>
3f9db7f8 87#include <sys/in_cksum.h>
984263bc 88
6cef7136
MD
89#include <sys/socketvar2.h>
90
984263bc 91#include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */
a00138cb 92#include <machine/stdarg.h>
984263bc
MD
93
94#include <net/if.h>
95#include <net/route.h>
96
97#include <netinet/in.h>
98#include <netinet/in_systm.h>
99#include <netinet/ip.h>
95b22adf 100#include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */
984263bc 101#include <netinet/in_var.h>
95b22adf 102#include <netinet/icmp_var.h> /* for ICMP_BANDLIM */
984263bc
MD
103#include <netinet/in_pcb.h>
104#include <netinet/ip_var.h>
105#include <netinet/ip6.h>
106#include <netinet/icmp6.h>
107#include <netinet6/nd6.h>
108#include <netinet6/ip6_var.h>
109#include <netinet6/in6_pcb.h>
110#include <netinet/tcp.h>
111#include <netinet/tcp_fsm.h>
112#include <netinet/tcp_seq.h>
113#include <netinet/tcp_timer.h>
a48c5dd5 114#include <netinet/tcp_timer2.h>
984263bc
MD
115#include <netinet/tcp_var.h>
116#include <netinet6/tcp6_var.h>
117#include <netinet/tcpip.h>
95b22adf 118
984263bc
MD
119#ifdef TCPDEBUG
120#include <netinet/tcp_debug.h>
121
95b22adf 122u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */
984263bc 123struct tcphdr tcp_savetcp;
95b22adf 124#endif
984263bc
MD
125
126#ifdef FAST_IPSEC
bf844ffa
JH
127#include <netproto/ipsec/ipsec.h>
128#include <netproto/ipsec/ipsec6.h>
984263bc
MD
129#endif
130
131#ifdef IPSEC
132#include <netinet6/ipsec.h>
133#include <netinet6/ipsec6.h>
d2438d69 134#include <netproto/key/key.h>
95b22adf 135#endif
984263bc 136
984263bc
MD
137MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry");
138
984263bc 139static int log_in_vain = 0;
d24ce1dc 140SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW,
984263bc
MD
141 &log_in_vain, 0, "Log all incoming TCP connections");
142
143static int blackhole = 0;
144SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW,
145 &blackhole, 0, "Do not send RST when dropping refused connections");
146
147int tcp_delack_enabled = 1;
d24ce1dc
JH
148SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW,
149 &tcp_delack_enabled, 0,
984263bc
MD
150 "Delay ACK to try and piggyback it onto a data packet");
151
152#ifdef TCP_DROP_SYNFIN
153static int drop_synfin = 0;
154SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW,
155 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set");
156#endif
157
33abdd1c
MD
158static int tcp_do_limitedtransmit = 1;
159SYSCTL_INT(_net_inet_tcp, OID_AUTO, limitedtransmit, CTLFLAG_RW,
160 &tcp_do_limitedtransmit, 0, "Enable RFC 3042 (Limited Transmit)");
161
91489f6b 162static int tcp_do_early_retransmit = 1;
8819433a
JH
163SYSCTL_INT(_net_inet_tcp, OID_AUTO, earlyretransmit, CTLFLAG_RW,
164 &tcp_do_early_retransmit, 0, "Early retransmit");
165
8acdb67c 166int tcp_aggregate_acks = 1;
72b37eeb
MD
167SYSCTL_INT(_net_inet_tcp, OID_AUTO, aggregate_acks, CTLFLAG_RW,
168 &tcp_aggregate_acks, 0, "Aggregate built-up acks into one ack");
169
efd4b327
JH
170static int tcp_do_eifel_detect = 1;
171SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW,
172 &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)");
173
8acdb67c
JH
174static int tcp_do_abc = 1;
175SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc, CTLFLAG_RW,
176 &tcp_do_abc, 0,
177 "TCP Appropriate Byte Counting (RFC 3465)");
178
91489f6b
JH
179/*
180 * Define as tunable for easy testing with SACK on and off.
181 * Warning: do not change setting in the middle of an existing active TCP flow,
182 * else strange things might happen to that flow.
183 */
6e5bbdda 184int tcp_do_sack = 1;
91489f6b
JH
185SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW,
186 &tcp_do_sack, 0, "Enable SACK Algorithms");
187
188int tcp_do_smartsack = 1;
189SYSCTL_INT(_net_inet_tcp, OID_AUTO, smartsack, CTLFLAG_RW,
190 &tcp_do_smartsack, 0, "Enable Smart SACK Algorithms");
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
5b0b9fa5
PA
210int tcp_do_autorcvbuf = 1;
211SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW,
212 &tcp_do_autorcvbuf, 0, "Enable automatic receive buffer sizing");
213
214int tcp_autorcvbuf_inc = 16*1024;
215SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW,
216 &tcp_autorcvbuf_inc, 0,
217 "Incrementor step size of automatic receive buffer");
218
46e92930 219int tcp_autorcvbuf_max = 2*1024*1024;
5b0b9fa5
PA
220SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW,
221 &tcp_autorcvbuf_max, 0, "Max size of automatic receive buffer");
222
0df7608b
SZ
223int tcp_sosend_agglim = 2;
224SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosend_agglim, CTLFLAG_RW,
225 &tcp_sosend_agglim, 0, "TCP sosend mbuf aggregation limit");
5b0b9fa5 226
0df7608b
SZ
227int tcp_sosend_async = 1;
228SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosend_async, CTLFLAG_RW,
229 &tcp_sosend_async, 0, "TCP asynchronized pru_send");
f2a3782e 230
95b22adf 231static void tcp_dooptions(struct tcpopt *, u_char *, int, boolean_t);
984263bc
MD
232static void tcp_pulloutofband(struct socket *,
233 struct tcphdr *, struct mbuf *, int);
234static int tcp_reass(struct tcpcb *, struct tcphdr *, int *,
235 struct mbuf *);
236static void tcp_xmit_timer(struct tcpcb *, int);
91489f6b
JH
237static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *, int);
238static void tcp_sack_rexmt(struct tcpcb *, struct tcphdr *);
01d3427a 239static int tcp_rmx_msl(const struct tcpcb *);
8651f7f8 240static void tcp_established(struct tcpcb *);
984263bc
MD
241
242/* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */
243#ifdef INET6
244#define ND6_HINT(tp) \
245do { \
246 if ((tp) && (tp)->t_inpcb && \
61896e3c 247 ((tp)->t_inpcb->inp_vflag & INP_IPV6) && \
984263bc
MD
248 (tp)->t_inpcb->in6p_route.ro_rt) \
249 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \
250} while (0)
251#else
252#define ND6_HINT(tp)
253#endif
254
255/*
256 * Indicate whether this ack should be delayed. We can delay the ack if
257 * - delayed acks are enabled and
258 * - there is no delayed ack timer in progress and
259 * - our last ack wasn't a 0-sized window. We never want to delay
260 * the ack that opens up a 0-sized window.
261 */
262#define DELAY_ACK(tp) \
a48c5dd5 263 (tcp_delack_enabled && !tcp_callout_pending(tp, tp->tt_delack) && \
61896e3c 264 !(tp->t_flags & TF_RXWIN0SENT))
984263bc 265
df9d7670
JH
266#define acceptable_window_update(tp, th, tiwin) \
267 (SEQ_LT(tp->snd_wl1, th->th_seq) || \
268 (tp->snd_wl1 == th->th_seq && \
269 (SEQ_LT(tp->snd_wl2, th->th_ack) || \
270 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))
271
984263bc 272static int
95b22adf 273tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m)
984263bc
MD
274{
275 struct tseg_qent *q;
276 struct tseg_qent *p = NULL;
984263bc
MD
277 struct tseg_qent *te;
278 struct socket *so = tp->t_inpcb->inp_socket;
279 int flags;
280
281 /*
61896e3c 282 * Call with th == NULL after become established to
984263bc
MD
283 * force pre-ESTABLISHED data up to user socket.
284 */
61896e3c 285 if (th == NULL)
984263bc
MD
286 goto present;
287
3edf7c37
RG
288 /*
289 * Limit the number of segments in the reassembly queue to prevent
290 * holding on to too many segments (and thus running out of mbufs).
291 * Make sure to let the missing segment through which caused this
292 * queue. Always keep one global queue entry spare to be able to
293 * process the missing segment.
294 */
295 if (th->th_seq != tp->rcv_nxt &&
296 tcp_reass_qsize + 1 >= tcp_reass_maxseg) {
297 tcp_reass_overflows++;
298 tcpstat.tcps_rcvmemdrop++;
299 m_freem(m);
91489f6b
JH
300 /* no SACK block to report */
301 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
3edf7c37
RG
302 return (0);
303 }
304
ba4e3dbe 305 /* Allocate a new queue entry. */
884717e1 306 te = kmalloc(sizeof(struct tseg_qent), M_TSEGQ, M_INTWAIT | M_NULLOK);
984263bc
MD
307 if (te == NULL) {
308 tcpstat.tcps_rcvmemdrop++;
309 m_freem(m);
91489f6b
JH
310 /* no SACK block to report */
311 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
984263bc
MD
312 return (0);
313 }
2d23a8be 314 atomic_add_int(&tcp_reass_qsize, 1);
984263bc
MD
315
316 /*
317 * Find a segment which begins after this one does.
318 */
319 LIST_FOREACH(q, &tp->t_segq, tqe_q) {
320 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
321 break;
322 p = q;
323 }
324
325 /*
326 * If there is a preceding segment, it may provide some of
327 * our data already. If so, drop the data from the incoming
328 * segment. If it provides all of our data, drop us.
329 */
330 if (p != NULL) {
76cf5e41 331 tcp_seq_diff_t i;
91489f6b 332
984263bc
MD
333 /* conversion to int (in i) handles seq wraparound */
334 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
91489f6b
JH
335 if (i > 0) { /* overlaps preceding segment */
336 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG);
337 /* enclosing block starts w/ preceding segment */
338 tp->encloseblk.rblk_start = p->tqe_th->th_seq;
984263bc 339 if (i >= *tlenp) {
91489f6b 340 /* preceding encloses incoming segment */
3a5d999b
SZ
341 tp->encloseblk.rblk_end = TCP_SACK_BLKEND(
342 p->tqe_th->th_seq + p->tqe_len,
343 p->tqe_th->th_flags);
984263bc
MD
344 tcpstat.tcps_rcvduppack++;
345 tcpstat.tcps_rcvdupbyte += *tlenp;
346 m_freem(m);
efda3bd0 347 kfree(te, M_TSEGQ);
2d23a8be 348 atomic_add_int(&tcp_reass_qsize, -1);
984263bc
MD
349 /*
350 * Try to present any queued data
351 * at the left window edge to the user.
352 * This is needed after the 3-WHS
353 * completes.
354 */
355 goto present; /* ??? */
356 }
357 m_adj(m, i);
358 *tlenp -= i;
359 th->th_seq += i;
91489f6b 360 /* incoming segment end is enclosing block end */
3a5d999b
SZ
361 tp->encloseblk.rblk_end = TCP_SACK_BLKEND(
362 th->th_seq + *tlenp, th->th_flags);
91489f6b
JH
363 /* trim end of reported D-SACK block */
364 tp->reportblk.rblk_end = th->th_seq;
984263bc
MD
365 }
366 }
367 tcpstat.tcps_rcvoopack++;
368 tcpstat.tcps_rcvoobyte += *tlenp;
369
370 /*
371 * While we overlap succeeding segments trim them or,
372 * if they are completely covered, dequeue them.
373 */
374 while (q) {
76cf5e41 375 tcp_seq_diff_t i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
91489f6b 376 tcp_seq qend = q->tqe_th->th_seq + q->tqe_len;
3a5d999b 377 tcp_seq qend_sack = TCP_SACK_BLKEND(qend, q->tqe_th->th_flags);
91489f6b
JH
378 struct tseg_qent *nq;
379
984263bc
MD
380 if (i <= 0)
381 break;
91489f6b
JH
382 if (!(tp->t_flags & TF_DUPSEG)) { /* first time through */
383 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG);
384 tp->encloseblk = tp->reportblk;
385 /* report trailing duplicate D-SACK segment */
386 tp->reportblk.rblk_start = q->tqe_th->th_seq;
387 }
388 if ((tp->t_flags & TF_ENCLOSESEG) &&
3a5d999b 389 SEQ_GT(qend_sack, tp->encloseblk.rblk_end)) {
91489f6b 390 /* extend enclosing block if one exists */
3a5d999b 391 tp->encloseblk.rblk_end = qend_sack;
91489f6b 392 }
984263bc
MD
393 if (i < q->tqe_len) {
394 q->tqe_th->th_seq += i;
395 q->tqe_len -= i;
396 m_adj(q->tqe_m, i);
397 break;
398 }
399
400 nq = LIST_NEXT(q, tqe_q);
401 LIST_REMOVE(q, tqe_q);
402 m_freem(q->tqe_m);
efda3bd0 403 kfree(q, M_TSEGQ);
2d23a8be 404 atomic_add_int(&tcp_reass_qsize, -1);
984263bc
MD
405 q = nq;
406 }
407
408 /* Insert the new segment queue entry into place. */
409 te->tqe_m = m;
410 te->tqe_th = th;
411 te->tqe_len = *tlenp;
412
91489f6b
JH
413 /* check if can coalesce with following segment */
414 if (q != NULL && (th->th_seq + *tlenp == q->tqe_th->th_seq)) {
415 tcp_seq tend = te->tqe_th->th_seq + te->tqe_len;
3a5d999b 416 tcp_seq tend_sack = TCP_SACK_BLKEND(tend, te->tqe_th->th_flags);
91489f6b
JH
417
418 te->tqe_len += q->tqe_len;
a174690a 419 if (q->tqe_th->th_flags & TH_FIN)
f16f8cc3 420 te->tqe_th->th_flags |= TH_FIN;
91489f6b 421 m_cat(te->tqe_m, q->tqe_m);
3a5d999b 422 tp->encloseblk.rblk_end = tend_sack;
91489f6b
JH
423 /*
424 * When not reporting a duplicate segment, use
425 * the larger enclosing block as the SACK block.
426 */
427 if (!(tp->t_flags & TF_DUPSEG))
3a5d999b 428 tp->reportblk.rblk_end = tend_sack;
91489f6b 429 LIST_REMOVE(q, tqe_q);
efda3bd0 430 kfree(q, M_TSEGQ);
2d23a8be 431 atomic_add_int(&tcp_reass_qsize, -1);
91489f6b
JH
432 }
433
984263bc
MD
434 if (p == NULL) {
435 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q);
436 } else {
91489f6b
JH
437 /* check if can coalesce with preceding segment */
438 if (p->tqe_th->th_seq + p->tqe_len == th->th_seq) {
a174690a
JH
439 p->tqe_len += te->tqe_len;
440 m_cat(p->tqe_m, te->tqe_m);
91489f6b
JH
441 tp->encloseblk.rblk_start = p->tqe_th->th_seq;
442 /*
443 * When not reporting a duplicate segment, use
444 * the larger enclosing block as the SACK block.
445 */
446 if (!(tp->t_flags & TF_DUPSEG))
447 tp->reportblk.rblk_start = p->tqe_th->th_seq;
efda3bd0 448 kfree(te, M_TSEGQ);
2d23a8be
MD
449 atomic_add_int(&tcp_reass_qsize, -1);
450 } else {
91489f6b 451 LIST_INSERT_AFTER(p, te, tqe_q);
2d23a8be 452 }
984263bc
MD
453 }
454
455present:
456 /*
457 * Present data to user, advancing rcv_nxt through
458 * completed sequence space.
459 */
460 if (!TCPS_HAVEESTABLISHED(tp->t_state))
461 return (0);
462 q = LIST_FIRST(&tp->t_segq);
61896e3c 463 if (q == NULL || q->tqe_th->th_seq != tp->rcv_nxt)
984263bc 464 return (0);
91489f6b
JH
465 tp->rcv_nxt += q->tqe_len;
466 if (!(tp->t_flags & TF_DUPSEG)) {
467 /* no SACK block to report since ACK advanced */
468 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
469 }
470 /* no enclosing block to report since ACK advanced */
471 tp->t_flags &= ~TF_ENCLOSESEG;
472 flags = q->tqe_th->th_flags & TH_FIN;
473 LIST_REMOVE(q, tqe_q);
474 KASSERT(LIST_EMPTY(&tp->t_segq) ||
475 LIST_FIRST(&tp->t_segq)->tqe_th->th_seq != tp->rcv_nxt,
476 ("segment not coalesced"));
6cef7136 477 if (so->so_state & SS_CANTRCVMORE) {
91489f6b 478 m_freem(q->tqe_m);
6cef7136
MD
479 } else {
480 lwkt_gettoken(&so->so_rcv.ssb_token);
6d49aa6f 481 ssb_appendstream(&so->so_rcv, q->tqe_m);
6cef7136
MD
482 lwkt_reltoken(&so->so_rcv.ssb_token);
483 }
efda3bd0 484 kfree(q, M_TSEGQ);
2d23a8be 485 atomic_add_int(&tcp_reass_qsize, -1);
984263bc
MD
486 ND6_HINT(tp);
487 sorwakeup(so);
488 return (flags);
489}
490
491/*
492 * TCP input routine, follows pages 65-76 of the
493 * protocol specification dated September, 1981 very closely.
494 */
495#ifdef INET6
496int
95b22adf 497tcp6_input(struct mbuf **mp, int *offp, int proto)
984263bc 498{
2256ba69 499 struct mbuf *m = *mp;
984263bc
MD
500 struct in6_ifaddr *ia6;
501
502 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE);
503
504 /*
505 * draft-itojun-ipv6-tcp-to-anycast
506 * better place to put this in?
507 */
508 ia6 = ip6_getdstifaddr(m);
d24ce1dc 509 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) {
984263bc
MD
510 struct ip6_hdr *ip6;
511
512 ip6 = mtod(m, struct ip6_hdr *);
513 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
f23061d4 514 offsetof(struct ip6_hdr, ip6_dst));
d24ce1dc 515 return (IPPROTO_DONE);
984263bc
MD
516 }
517
002c1265 518 tcp_input(mp, offp, proto);
d24ce1dc 519 return (IPPROTO_DONE);
984263bc
MD
520}
521#endif
522
002c1265
MD
523int
524tcp_input(struct mbuf **mp, int *offp, int proto)
984263bc 525{
002c1265 526 int off0;
2256ba69
RG
527 struct tcphdr *th;
528 struct ip *ip = NULL;
529 struct ipovly *ipov;
530 struct inpcb *inp = NULL;
984263bc
MD
531 u_char *optp = NULL;
532 int optlen = 0;
b1992928
MD
533 int tlen, off;
534 int len = 0;
984263bc 535 int drop_hdrlen;
2256ba69
RG
536 struct tcpcb *tp = NULL;
537 int thflags;
4090d6ff 538 struct socket *so = NULL;
61896e3c
JH
539 int todrop, acked;
540 boolean_t ourfinisacked, needoutput = FALSE;
984263bc 541 u_long tiwin;
61896e3c 542 int recvwin;
984263bc 543 struct tcpopt to; /* options in this segment */
984263bc
MD
544 struct sockaddr_in *next_hop = NULL;
545 int rstreason; /* For badport_bandlim accounting purposes */
d371a63a 546 int cpu;
984263bc 547 struct ip6_hdr *ip6 = NULL;
002c1265 548 struct mbuf *m;
984263bc 549#ifdef INET6
d24ce1dc 550 boolean_t isipv6;
984263bc 551#else
d24ce1dc 552 const boolean_t isipv6 = FALSE;
984263bc
MD
553#endif
554#ifdef TCPDEBUG
555 short ostate = 0;
556#endif
557
002c1265
MD
558 off0 = *offp;
559 m = *mp;
560 *mp = NULL;
a00138cb 561
d24ce1dc
JH
562 tcpstat.tcps_rcvtotal++;
563
5de23090
SZ
564 if (m->m_pkthdr.fw_flags & IPFORWARD_MBUF_TAGGED) {
565 struct m_tag *mtag;
566
567 mtag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL);
568 KKASSERT(mtag != NULL);
569 next_hop = m_tag_data(mtag);
984263bc 570 }
d24ce1dc 571
984263bc 572#ifdef INET6
d24ce1dc 573 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE;
984263bc 574#endif
984263bc
MD
575
576 if (isipv6) {
577 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */
578 ip6 = mtod(m, struct ip6_hdr *);
407e896e 579 tlen = (sizeof *ip6) + ntohs(ip6->ip6_plen) - off0;
984263bc
MD
580 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) {
581 tcpstat.tcps_rcvbadsum++;
582 goto drop;
583 }
584 th = (struct tcphdr *)((caddr_t)ip6 + off0);
585
586 /*
587 * Be proactive about unspecified IPv6 address in source.
588 * As we use all-zero to indicate unbounded/unconnected pcb,
589 * unspecified IPv6 address can be used to confuse us.
590 *
591 * Note that packets with unspecified IPv6 destination is
592 * already dropped in ip6_input.
593 */
594 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
595 /* XXX stat */
596 goto drop;
597 }
598 } else {
599 /*
600 * Get IP and TCP header together in first mbuf.
601 * Note: IP leaves IP header in first mbuf.
602 */
603 if (off0 > sizeof(struct ip)) {
bddf0751 604 ip_stripoptions(m);
984263bc
MD
605 off0 = sizeof(struct ip);
606 }
55d829f8
JH
607 /* already checked and pulled up in ip_demux() */
608 KASSERT(m->m_len >= sizeof(struct tcpiphdr),
61896e3c 609 ("TCP header not in one mbuf: m->m_len %d", m->m_len));
984263bc
MD
610 ip = mtod(m, struct ip *);
611 ipov = (struct ipovly *)ip;
612 th = (struct tcphdr *)((caddr_t)ip + off0);
613 tlen = ip->ip_len;
614
615 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
616 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
617 th->th_sum = m->m_pkthdr.csum_data;
618 else
619 th->th_sum = in_pseudo(ip->ip_src.s_addr,
620 ip->ip_dst.s_addr,
621 htonl(m->m_pkthdr.csum_data +
622 ip->ip_len +
623 IPPROTO_TCP));
624 th->th_sum ^= 0xffff;
625 } else {
626 /*
627 * Checksum extended TCP header and data.
628 */
629 len = sizeof(struct ip) + tlen;
407e896e 630 bzero(ipov->ih_x1, sizeof ipov->ih_x1);
984263bc
MD
631 ipov->ih_len = (u_short)tlen;
632 ipov->ih_len = htons(ipov->ih_len);
633 th->th_sum = in_cksum(m, len);
634 }
635 if (th->th_sum) {
636 tcpstat.tcps_rcvbadsum++;
637 goto drop;
638 }
639#ifdef INET6
640 /* Re-initialization for later version check */
641 ip->ip_v = IPVERSION;
642#endif
643 }
644
645 /*
646 * Check that TCP offset makes sense,
647 * pull out TCP options and adjust length. XXX
648 */
649 off = th->th_off << 2;
55d829f8
JH
650 /* already checked and pulled up in ip_demux() */
651 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen,
61896e3c 652 ("bad TCP data offset %d (tlen %d)", off, tlen));
984263bc
MD
653 tlen -= off; /* tlen is used instead of ti->ti_len */
654 if (off > sizeof(struct tcphdr)) {
655 if (isipv6) {
002c1265 656 IP6_EXTHDR_CHECK(m, off0, off, IPPROTO_DONE);
984263bc
MD
657 ip6 = mtod(m, struct ip6_hdr *);
658 th = (struct tcphdr *)((caddr_t)ip6 + off0);
659 } else {
55d829f8
JH
660 /* already pulled up in ip_demux() */
661 KASSERT(m->m_len >= sizeof(struct ip) + off,
61896e3c
JH
662 ("TCP header and options not in one mbuf: "
663 "m_len %d, off %d", m->m_len, off));
984263bc
MD
664 }
665 optlen = off - sizeof(struct tcphdr);
666 optp = (u_char *)(th + 1);
667 }
668 thflags = th->th_flags;
669
670#ifdef TCP_DROP_SYNFIN
671 /*
672 * If the drop_synfin option is enabled, drop all packets with
673 * both the SYN and FIN bits set. This prevents e.g. nmap from
674 * identifying the TCP/IP stack.
675 *
676 * This is a violation of the TCP specification.
677 */
61896e3c 678 if (drop_synfin && (thflags & (TH_SYN | TH_FIN)) == (TH_SYN | TH_FIN))
984263bc
MD
679 goto drop;
680#endif
681
682 /*
683 * Convert TCP protocol specific fields to host format.
684 */
685 th->th_seq = ntohl(th->th_seq);
686 th->th_ack = ntohl(th->th_ack);
687 th->th_win = ntohs(th->th_win);
688 th->th_urp = ntohs(th->th_urp);
689
690 /*
d24ce1dc 691 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options,
984263bc
MD
692 * until after ip6_savecontrol() is called and before other functions
693 * which don't want those proto headers.
694 * Because ip6_savecontrol() is going to parse the mbuf to
695 * search for data to be passed up to user-land, it wants mbuf
696 * parameters to be unchanged.
697 * XXX: the call of ip6_savecontrol() has been obsoleted based on
698 * latest version of the advanced API (20020110).
699 */
700 drop_hdrlen = off0 + off;
701
702 /*
703 * Locate pcb for segment.
704 */
705findpcb:
706 /* IPFIREWALL_FORWARD section */
d24ce1dc 707 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */
984263bc
MD
708 /*
709 * Transparently forwarded. Pretend to be the destination.
d24ce1dc 710 * already got one like this?
984263bc 711 */
6ca1a1cd 712 cpu = mycpu->gd_cpuid;
6ca1a1cd 713 inp = in_pcblookup_hash(&tcbinfo[cpu],
d371a63a 714 ip->ip_src, th->th_sport,
984263bc
MD
715 ip->ip_dst, th->th_dport,
716 0, m->m_pkthdr.rcvif);
717 if (!inp) {
83be63fe
JH
718 /*
719 * It's new. Try to find the ambushing socket.
720 */
721
722 /*
723 * The rest of the ipfw code stores the port in
724 * host order. XXX
725 * (The IP address is still in network order.)
726 */
727 in_port_t dport = next_hop->sin_port ?
728 htons(next_hop->sin_port) :
729 th->th_dport;
730
d371a63a 731 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport,
83be63fe 732 next_hop->sin_addr.s_addr, dport);
d371a63a 733 inp = in_pcblookup_hash(&tcbinfo[cpu],
984263bc 734 ip->ip_src, th->th_sport,
83be63fe 735 next_hop->sin_addr, dport,
984263bc
MD
736 1, m->m_pkthdr.rcvif);
737 }
738 } else {
6ca1a1cd 739 if (isipv6) {
d371a63a 740 inp = in6_pcblookup_hash(&tcbinfo[0],
984263bc
MD
741 &ip6->ip6_src, th->th_sport,
742 &ip6->ip6_dst, th->th_dport,
743 1, m->m_pkthdr.rcvif);
6ca1a1cd 744 } else {
6ca1a1cd 745 cpu = mycpu->gd_cpuid;
6ca1a1cd 746 inp = in_pcblookup_hash(&tcbinfo[cpu],
984263bc
MD
747 ip->ip_src, th->th_sport,
748 ip->ip_dst, th->th_dport,
749 1, m->m_pkthdr.rcvif);
6ca1a1cd 750 }
984263bc 751 }
984263bc
MD
752
753 /*
754 * If the state is CLOSED (i.e., TCB does not exist) then
755 * all data in the incoming segment is discarded.
756 * If the TCB exists but is in CLOSED state, it is embryonic,
757 * but should either do a listen or a connect soon.
758 */
759 if (inp == NULL) {
760 if (log_in_vain) {
761#ifdef INET6
762 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2];
763#else
1141eb20
JH
764 char dbuf[sizeof "aaa.bbb.ccc.ddd"];
765 char sbuf[sizeof "aaa.bbb.ccc.ddd"];
984263bc
MD
766#endif
767 if (isipv6) {
768 strcpy(dbuf, "[");
984263bc 769 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst));
984263bc 770 strcat(dbuf, "]");
95b22adf
JH
771 strcpy(sbuf, "[");
772 strcat(sbuf, ip6_sprintf(&ip6->ip6_src));
984263bc
MD
773 strcat(sbuf, "]");
774 } else {
775 strcpy(dbuf, inet_ntoa(ip->ip_dst));
776 strcpy(sbuf, inet_ntoa(ip->ip_src));
777 }
778 switch (log_in_vain) {
779 case 1:
61896e3c 780 if (!(thflags & TH_SYN))
984263bc
MD
781 break;
782 case 2:
783 log(LOG_INFO,
784 "Connection attempt to TCP %s:%d "
785 "from %s:%d flags:0x%02x\n",
786 dbuf, ntohs(th->th_dport), sbuf,
787 ntohs(th->th_sport), thflags);
788 break;
789 default:
790 break;
791 }
792 }
d24ce1dc 793 if (blackhole) {
984263bc
MD
794 switch (blackhole) {
795 case 1:
796 if (thflags & TH_SYN)
797 goto drop;
798 break;
799 case 2:
800 goto drop;
801 default:
802 goto drop;
803 }
804 }
805 rstreason = BANDLIM_RST_CLOSEDPORT;
806 goto dropwithreset;
807 }
61896e3c
JH
808
809#ifdef IPSEC
810 if (isipv6) {
811 if (ipsec6_in_reject_so(m, inp->inp_socket)) {
812 ipsec6stat.in_polvio++;
813 goto drop;
814 }
815 } else {
816 if (ipsec4_in_reject_so(m, inp->inp_socket)) {
817 ipsecstat.in_polvio++;
818 goto drop;
819 }
820 }
821#endif
822#ifdef FAST_IPSEC
823 if (isipv6) {
824 if (ipsec6_in_reject(m, inp))
825 goto drop;
826 } else {
827 if (ipsec4_in_reject(m, inp))
828 goto drop;
829 }
830#endif
95926362
MD
831 /* Check the minimum TTL for socket. */
832#ifdef INET6
833 if ((isipv6 ? ip6->ip6_hlim : ip->ip_ttl) < inp->inp_ip_minttl)
834 goto drop;
835#endif
61896e3c 836
984263bc
MD
837 tp = intotcpcb(inp);
838 if (tp == NULL) {
839 rstreason = BANDLIM_RST_CLOSEDPORT;
840 goto dropwithreset;
841 }
eb594563 842 if (tp->t_state <= TCPS_CLOSED)
984263bc
MD
843 goto drop;
844
845 /* Unscale the window into a 32-bit value. */
95b22adf 846 if (!(thflags & TH_SYN))
984263bc
MD
847 tiwin = th->th_win << tp->snd_scale;
848 else
849 tiwin = th->th_win;
850
851 so = inp->inp_socket;
47654766 852
984263bc 853#ifdef TCPDEBUG
47654766
JH
854 if (so->so_options & SO_DEBUG) {
855 ostate = tp->t_state;
856 if (isipv6)
95b22adf 857 bcopy(ip6, tcp_saveipgen, sizeof(*ip6));
47654766 858 else
95b22adf 859 bcopy(ip, tcp_saveipgen, sizeof(*ip));
47654766
JH
860 tcp_savetcp = *th;
861 }
984263bc 862#endif
47654766 863
407e896e 864 bzero(&to, sizeof to);
d24ce1dc 865
47654766
JH
866 if (so->so_options & SO_ACCEPTCONN) {
867 struct in_conninfo inc;
868
984263bc 869#ifdef INET6
d24ce1dc 870 inc.inc_isipv6 = (isipv6 == TRUE);
984263bc
MD
871#endif
872 if (isipv6) {
873 inc.inc6_faddr = ip6->ip6_src;
874 inc.inc6_laddr = ip6->ip6_dst;
875 inc.inc6_route.ro_rt = NULL; /* XXX */
876 } else {
877 inc.inc_faddr = ip->ip_src;
878 inc.inc_laddr = ip->ip_dst;
879 inc.inc_route.ro_rt = NULL; /* XXX */
880 }
881 inc.inc_fport = th->th_sport;
882 inc.inc_lport = th->th_dport;
883
61896e3c
JH
884 /*
885 * If the state is LISTEN then ignore segment if it contains
984263bc
MD
886 * a RST. If the segment contains an ACK then it is bad and
887 * send a RST. If it does not contain a SYN then it is not
888 * interesting; drop it.
889 *
890 * If the state is SYN_RECEIVED (syncache) and seg contains
891 * an ACK, but not for our SYN/ACK, send a RST. If the seg
892 * contains a RST, check the sequence number to see if it
893 * is a valid reset segment.
894 */
61896e3c
JH
895 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) != TH_SYN) {
896 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) == TH_ACK) {
984263bc
MD
897 if (!syncache_expand(&inc, th, &so, m)) {
898 /*
899 * No syncache entry, or ACK was not
900 * for our SYN/ACK. Send a RST.
901 */
902 tcpstat.tcps_badsyn++;
903 rstreason = BANDLIM_RST_OPENPORT;
904 goto dropwithreset;
905 }
2d23a8be
MD
906
907 /*
908 * Could not complete 3-way handshake,
909 * connection is being closed down, and
910 * syncache will free mbuf.
911 */
984263bc 912 if (so == NULL)
002c1265 913 return(IPPROTO_DONE);
2d23a8be
MD
914
915 /*
916 * We must be in the correct protocol thread
917 * for this connection.
918 */
919 KKASSERT(so->so_port == &curthread->td_msgport);
920
984263bc
MD
921 /*
922 * Socket is created in state SYN_RECEIVED.
923 * Continue processing segment.
924 */
ed894f8c 925 inp = so->so_pcb;
984263bc
MD
926 tp = intotcpcb(inp);
927 /*
928 * This is what would have happened in
929 * tcp_output() when the SYN,ACK was sent.
930 */
931 tp->snd_up = tp->snd_una;
932 tp->snd_max = tp->snd_nxt = tp->iss + 1;
933 tp->last_ack_sent = tp->rcv_nxt;
934/*
935 * XXX possible bug - it doesn't appear that tp->snd_wnd is unscaled
936 * until the _second_ ACK is received:
937 * rcv SYN (set wscale opts) --> send SYN/ACK, set snd_wnd = window.
938 * rcv ACK, calculate tiwin --> process SYN_RECEIVED, determine wscale,
61896e3c 939 * move to ESTAB, set snd_wnd to tiwin.
d24ce1dc 940 */
984263bc
MD
941 tp->snd_wnd = tiwin; /* unscaled */
942 goto after_listen;
943 }
944 if (thflags & TH_RST) {
945 syncache_chkrst(&inc, th);
946 goto drop;
947 }
948 if (thflags & TH_ACK) {
949 syncache_badack(&inc);
950 tcpstat.tcps_badsyn++;
951 rstreason = BANDLIM_RST_OPENPORT;
952 goto dropwithreset;
953 }
954 goto drop;
955 }
956
957 /*
61896e3c 958 * Segment's flags are (SYN) or (SYN | FIN).
984263bc
MD
959 */
960#ifdef INET6
961 /*
962 * If deprecated address is forbidden,
963 * we do not accept SYN to deprecated interface
964 * address to prevent any new inbound connection from
965 * getting established.
966 * When we do not accept SYN, we send a TCP RST,
967 * with deprecated source address (instead of dropping
968 * it). We compromise it as it is much better for peer
969 * to send a RST, and RST will be the final packet
970 * for the exchange.
971 *
972 * If we do not forbid deprecated addresses, we accept
973 * the SYN packet. RFC2462 does not suggest dropping
974 * SYN in this case.
975 * If we decipher RFC2462 5.5.4, it says like this:
976 * 1. use of deprecated addr with existing
977 * communication is okay - "SHOULD continue to be
978 * used"
979 * 2. use of it with new communication:
980 * (2a) "SHOULD NOT be used if alternate address
61896e3c 981 * with sufficient scope is available"
984263bc
MD
982 * (2b) nothing mentioned otherwise.
983 * Here we fall into (2b) case as we have no choice in
984 * our source address selection - we must obey the peer.
985 *
986 * The wording in RFC2462 is confusing, and there are
987 * multiple description text for deprecated address
988 * handling - worse, they are not exactly the same.
989 * I believe 5.5.4 is the best one, so we follow 5.5.4.
990 */
991 if (isipv6 && !ip6_use_deprecated) {
992 struct in6_ifaddr *ia6;
993
994 if ((ia6 = ip6_getdstifaddr(m)) &&
995 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
996 tp = NULL;
997 rstreason = BANDLIM_RST_OPENPORT;
998 goto dropwithreset;
999 }
1000 }
1001#endif
1002 /*
1003 * If it is from this socket, drop it, it must be forged.
1004 * Don't bother responding if the destination was a broadcast.
1005 */
1006 if (th->th_dport == th->th_sport) {
1007 if (isipv6) {
1008 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst,
1009 &ip6->ip6_src))
1010 goto drop;
1011 } else {
1012 if (ip->ip_dst.s_addr == ip->ip_src.s_addr)
1013 goto drop;
1014 }
1015 }
1016 /*
1017 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN
1018 *
1019 * Note that it is quite possible to receive unicast
1020 * link-layer packets with a broadcast IP address. Use
1021 * in_broadcast() to find them.
1022 */
61896e3c 1023 if (m->m_flags & (M_BCAST | M_MCAST))
984263bc
MD
1024 goto drop;
1025 if (isipv6) {
1026 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
1027 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
1028 goto drop;
1029 } else {
1030 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
1031 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
1032 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
1033 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
1034 goto drop;
1035 }
1036 /*
1037 * SYN appears to be valid; create compressed TCP state
1038 * for syncache, or perform t/tcp connection.
1039 */
1040 if (so->so_qlen <= so->so_qlimit) {
95b22adf 1041 tcp_dooptions(&to, optp, optlen, TRUE);
b09567cc 1042 if (!syncache_add(&inc, &to, th, so, m))
984263bc 1043 goto drop;
2d23a8be
MD
1044
1045 /*
1046 * Entry added to syncache, mbuf used to
1047 * send SYN,ACK packet.
1048 */
b09567cc 1049 return(IPPROTO_DONE);
984263bc
MD
1050 }
1051 goto drop;
1052 }
984263bc 1053
2d23a8be
MD
1054after_listen:
1055 /*
1056 * Should not happen - syncache should pick up these connections.
1057 *
1058 * Once we are past handling listen sockets we must be in the
1059 * correct protocol processing thread.
1060 */
61896e3c 1061 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN state"));
2d23a8be 1062 KKASSERT(so->so_port == &curthread->td_msgport);
984263bc
MD
1063
1064 /*
5b0b9fa5
PA
1065 * This is the second part of the MSS DoS prevention code (after
1066 * minmss on the sending side) and it deals with too many too small
1067 * tcp packets in a too short timeframe (1 second).
1068 *
153d34ac
MD
1069 * XXX Removed. This code was crap. It does not scale to network
1070 * speed, and default values break NFS. Gone.
5b0b9fa5 1071 */
153d34ac 1072 /* REMOVED */
5b0b9fa5
PA
1073
1074 /*
984263bc 1075 * Segment received on connection.
efca2b8e
MD
1076 *
1077 * Reset idle time and keep-alive timer. Don't waste time if less
0ecd93f9 1078 * then a second has elapsed.
984263bc 1079 */
0ecd93f9
MD
1080 if ((int)(ticks - tp->t_rcvtime) > hz)
1081 tcp_timer_keep_activity(tp, thflags);
984263bc
MD
1082
1083 /*
1084 * Process options.
1085 * XXX this is tradtitional behavior, may need to be cleaned up.
1086 */
95b22adf 1087 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0);
ad0af98b 1088 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) {
984263bc
MD
1089 if (to.to_flags & TOF_SCALE) {
1090 tp->t_flags |= TF_RCVD_SCALE;
1091 tp->requested_s_scale = to.to_requested_s_scale;
1092 }
1093 if (to.to_flags & TOF_TS) {
1094 tp->t_flags |= TF_RCVD_TSTMP;
1095 tp->ts_recent = to.to_tsval;
1096 tp->ts_recent_age = ticks;
1097 }
f34fd0f2
SZ
1098 if (!(to.to_flags & TOF_MSS))
1099 to.to_mss = 0;
1100 tcp_mss(tp, to.to_mss);
91489f6b
JH
1101 /*
1102 * Only set the TF_SACK_PERMITTED per-connection flag
1103 * if we got a SACK_PERMITTED option from the other side
1104 * and the global tcp_do_sack variable is true.
1105 */
1106 if (tcp_do_sack && (to.to_flags & TOF_SACK_PERMITTED))
1107 tp->t_flags |= TF_SACK_PERMITTED;
984263bc
MD
1108 }
1109
1110 /*
1111 * Header prediction: check for the two common cases
1112 * of a uni-directional data xfer. If the packet has
1113 * no control flags, is in-sequence, the window didn't
1114 * change and we're not retransmitting, it's a
1115 * candidate. If the length is zero and the ack moved
1116 * forward, we're the sender side of the xfer. Just
1117 * free the data acked & wake any higher level process
1118 * that was blocked waiting for space. If the length
1119 * is non-zero and the ack didn't move, we're the
1120 * receiver side. If we're getting packets in-order
1121 * (the reassembly queue is empty), add the data to
1122 * the socket buffer and note that we need a delayed ack.
1123 * Make sure that the hidden state-flags are also off.
1124 * Since we check for TCPS_ESTABLISHED above, it can only
1125 * be TH_NEEDSYN.
1126 */
1127 if (tp->t_state == TCPS_ESTABLISHED &&
1128 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
61896e3c
JH
1129 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) &&
1130 (!(to.to_flags & TOF_TS) ||
984263bc 1131 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) &&
984263bc 1132 th->th_seq == tp->rcv_nxt &&
984263bc
MD
1133 tp->snd_nxt == tp->snd_max) {
1134
1135 /*
1136 * If last ACK falls within this segment's sequence numbers,
1137 * record the timestamp.
1138 * NOTE that the test is modified according to the latest
1139 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1140 */
61896e3c 1141 if ((to.to_flags & TOF_TS) &&
984263bc
MD
1142 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
1143 tp->ts_recent_age = ticks;
1144 tp->ts_recent = to.to_tsval;
1145 }
1146
1147 if (tlen == 0) {
1148 if (SEQ_GT(th->th_ack, tp->snd_una) &&
1149 SEQ_LEQ(th->th_ack, tp->snd_max) &&
1150 tp->snd_cwnd >= tp->snd_wnd &&
95b22adf 1151 !IN_FASTRECOVERY(tp)) {
984263bc 1152 /*
be23faf1 1153 * This is a pure ack for outstanding data.
984263bc
MD
1154 */
1155 ++tcpstat.tcps_predack;
1156 /*
1157 * "bad retransmit" recovery
bfdb979e
JH
1158 *
1159 * If Eifel detection applies, then
1160 * it is deterministic, so use it
1161 * unconditionally over the old heuristic.
1162 * Otherwise, fall back to the old heuristic.
984263bc 1163 */
bfdb979e
JH
1164 if (tcp_do_eifel_detect &&
1165 (to.to_flags & TOF_TS) && to.to_tsecr &&
1166 (tp->t_flags & TF_FIRSTACCACK)) {
1167 /* Eifel detection applicable. */
1168 if (to.to_tsecr < tp->t_rexmtTS) {
1169 tcp_revert_congestion_state(tp);
1170 ++tcpstat.tcps_eifeldetected;
928c3291
SZ
1171 if (tp->t_rxtshift != 1 ||
1172 ticks >= tp->t_badrxtwin)
1173 ++tcpstat.tcps_rttcantdetect;
bfdb979e
JH
1174 }
1175 } else if (tp->t_rxtshift == 1 &&
1176 ticks < tp->t_badrxtwin) {
1177 tcp_revert_congestion_state(tp);
1178 ++tcpstat.tcps_rttdetected;
984263bc 1179 }
8819433a
JH
1180 tp->t_flags &= ~(TF_FIRSTACCACK |
1181 TF_FASTREXMT | TF_EARLYREXMT);
984263bc
MD
1182 /*
1183 * Recalculate the retransmit timer / rtt.
1184 *
d24ce1dc 1185 * Some machines (certain windows boxes)
984263bc
MD
1186 * send broken timestamp replies during the
1187 * SYN+ACK phase, ignore timestamps of 0.
1188 */
95b22adf 1189 if ((to.to_flags & TOF_TS) && to.to_tsecr) {
984263bc 1190 tcp_xmit_timer(tp,
95b22adf 1191 ticks - to.to_tsecr + 1);
984263bc 1192 } else if (tp->t_rtttime &&
95b22adf 1193 SEQ_GT(th->th_ack, tp->t_rtseq)) {
984263bc
MD
1194 tcp_xmit_timer(tp,
1195 ticks - tp->t_rtttime);
1196 }
1197 tcp_xmit_bandwidth_limit(tp, th->th_ack);
1198 acked = th->th_ack - tp->snd_una;
1199 tcpstat.tcps_rcvackpack++;
1200 tcpstat.tcps_rcvackbyte += acked;
6d49aa6f 1201 sbdrop(&so->so_snd.sb, acked);
cfb3f3f4 1202 tp->snd_recover = th->th_ack - 1;
9845754e 1203 tp->snd_una = th->th_ack;
984263bc 1204 tp->t_dupacks = 0;
df9d7670
JH
1205 /*
1206 * Update window information.
1207 */
1208 if (tiwin != tp->snd_wnd &&
1209 acceptable_window_update(tp, th, tiwin)) {
1210 /* keep track of pure window updates */
1211 if (tp->snd_wl2 == th->th_ack &&
1212 tiwin > tp->snd_wnd)
1213 tcpstat.tcps_rcvwinupd++;
1214 tp->snd_wnd = tiwin;
1215 tp->snd_wl1 = th->th_seq;
1216 tp->snd_wl2 = th->th_ack;
1217 if (tp->snd_wnd > tp->max_sndwnd)
1218 tp->max_sndwnd = tp->snd_wnd;
1219 }
984263bc
MD
1220 m_freem(m);
1221 ND6_HINT(tp); /* some progress has been done */
984263bc
MD
1222 /*
1223 * If all outstanding data are acked, stop
1224 * retransmit timer, otherwise restart timer
1225 * using current (possibly backed-off) value.
1226 * If process is waiting for space,
1227 * wakeup/selwakeup/signal. If data
1228 * are ready to send, let tcp_output
1229 * decide between more output or persist.
1230 */
a48c5dd5
SZ
1231 if (tp->snd_una == tp->snd_max) {
1232 tcp_callout_stop(tp, tp->tt_rexmt);
1233 } else if (!tcp_callout_active(tp,
1234 tp->tt_persist)) {
1235 tcp_callout_reset(tp, tp->tt_rexmt,
1236 tp->t_rxtcur, tcp_timer_rexmt);
1237 }
984263bc 1238 sowwakeup(so);
6d49aa6f 1239 if (so->so_snd.ssb_cc > 0)
f23061d4 1240 tcp_output(tp);
002c1265 1241 return(IPPROTO_DONE);
984263bc 1242 }
df9d7670
JH
1243 } else if (tiwin == tp->snd_wnd &&
1244 th->th_ack == tp->snd_una &&
984263bc 1245 LIST_EMPTY(&tp->t_segq) &&
6d49aa6f 1246 tlen <= ssb_space(&so->so_rcv)) {
46e92930 1247 u_long newsize = 0; /* automatic sockbuf scaling */
984263bc 1248 /*
be23faf1 1249 * This is a pure, in-sequence data packet
984263bc
MD
1250 * with nothing on the reassembly queue and
1251 * we have enough buffer space to take it.
1252 */
1253 ++tcpstat.tcps_preddat;
1254 tp->rcv_nxt += tlen;
1255 tcpstat.tcps_rcvpack++;
1256 tcpstat.tcps_rcvbyte += tlen;
1257 ND6_HINT(tp); /* some progress has been done */
5b0b9fa5
PA
1258 /*
1259 * Automatic sizing of receive socket buffer. Often the send
1260 * buffer size is not optimally adjusted to the actual network
1261 * conditions at hand (delay bandwidth product). Setting the
1262 * buffer size too small limits throughput on links with high
1263 * bandwidth and high delay (eg. trans-continental/oceanic links).
1264 *
1265 * On the receive side the socket buffer memory is only rarely
1266 * used to any significant extent. This allows us to be much
1267 * more aggressive in scaling the receive socket buffer. For
1268 * the case that the buffer space is actually used to a large
1269 * extent and we run out of kernel memory we can simply drop
1270 * the new segments; TCP on the sender will just retransmit it
1271 * later. Setting the buffer size too big may only consume too
1272 * much kernel memory if the application doesn't read() from
1273 * the socket or packet loss or reordering makes use of the
1274 * reassembly queue.
1275 *
1276 * The criteria to step up the receive buffer one notch are:
1277 * 1. the number of bytes received during the time it takes
1278 * one timestamp to be reflected back to us (the RTT);
1279 * 2. received bytes per RTT is within seven eighth of the
1280 * current socket buffer size;
1281 * 3. receive buffer size has not hit maximal automatic size;
1282 *
1283 * This algorithm does one step per RTT at most and only if
1284 * we receive a bulk stream w/o packet losses or reorderings.
1285 * Shrinking the buffer during idle times is not necessary as
1286 * it doesn't consume any memory when idle.
1287 *
1288 * TODO: Only step up if the application is actually serving
1289 * the buffer to better manage the socket buffer resources.
1290 */
1291 if (tcp_do_autorcvbuf &&
1292 to.to_tsecr &&
1293 (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) {
1294 if (to.to_tsecr > tp->rfbuf_ts &&
1295 to.to_tsecr - tp->rfbuf_ts < hz) {
1296 if (tp->rfbuf_cnt >
1297 (so->so_rcv.ssb_hiwat / 8 * 7) &&
1298 so->so_rcv.ssb_hiwat <
1299 tcp_autorcvbuf_max) {
1300 newsize =
46e92930
MD
1301 ulmin(so->so_rcv.ssb_hiwat +
1302 tcp_autorcvbuf_inc,
1303 tcp_autorcvbuf_max);
5b0b9fa5
PA
1304 }
1305 /* Start over with next RTT. */
1306 tp->rfbuf_ts = 0;
1307 tp->rfbuf_cnt = 0;
1308 } else
1309 tp->rfbuf_cnt += tlen; /* add up */
1310 }
984263bc
MD
1311 /*
1312 * Add data to socket buffer.
1313 */
1314 if (so->so_state & SS_CANTRCVMORE) {
1315 m_freem(m);
1316 } else {
5b0b9fa5 1317 /*
46e92930
MD
1318 * Set new socket buffer size, give up when
1319 * limit is reached.
1320 *
1321 * Adjusting the size can mess up ACK
1322 * sequencing when pure window updates are
1323 * being avoided (which is the default),
1324 * so force an ack.
5b0b9fa5 1325 */
6cef7136 1326 lwkt_gettoken(&so->so_rcv.ssb_token);
46e92930
MD
1327 if (newsize) {
1328 tp->t_flags |= TF_RXRESIZED;
5b0b9fa5 1329 if (!ssb_reserve(&so->so_rcv, newsize,
46e92930 1330 so, NULL)) {
14343ad3 1331 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE);
46e92930
MD
1332 }
1333 if (newsize >=
1334 (TCP_MAXWIN << tp->rcv_scale)) {
14343ad3 1335 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE);
46e92930
MD
1336 }
1337 }
09cf73e0 1338 m_adj(m, drop_hdrlen); /* delayed header drop */
6d49aa6f 1339 ssb_appendstream(&so->so_rcv, m);
6cef7136 1340 lwkt_reltoken(&so->so_rcv.ssb_token);
984263bc
MD
1341 }
1342 sorwakeup(so);
2b1ce38a
MD
1343 /*
1344 * This code is responsible for most of the ACKs
1345 * the TCP stack sends back after receiving a data
1346 * packet. Note that the DELAY_ACK check fails if
1347 * the delack timer is already running, which results
1348 * in an ack being sent every other packet (which is
1349 * what we want).
72b37eeb
MD
1350 *
1351 * We then further aggregate acks by not actually
1352 * sending one until the protocol thread has completed
1353 * processing the current backlog of packets. This
1354 * does not delay the ack any further, but allows us
1355 * to take advantage of the packet aggregation that
1356 * high speed NICs do (usually blocks of 8-10 packets)
1357 * to send a single ack rather then four or five acks,
1358 * greatly reducing the ack rate, the return channel
1359 * bandwidth, and the protocol overhead on both ends.
1360 *
1361 * Since this also has the effect of slowing down
1362 * the exponential slow-start ramp-up, systems with
1363 * very large bandwidth-delay products might want
1364 * to turn the feature off.
2b1ce38a 1365 */
984263bc 1366 if (DELAY_ACK(tp)) {
a48c5dd5
SZ
1367 tcp_callout_reset(tp, tp->tt_delack,
1368 tcp_delacktime, tcp_timer_delack);
72b37eeb 1369 } else if (tcp_aggregate_acks) {
984263bc 1370 tp->t_flags |= TF_ACKNOW;
61896e3c 1371 if (!(tp->t_flags & TF_ONOUTPUTQ)) {
2b1ce38a
MD
1372 tp->t_flags |= TF_ONOUTPUTQ;
1373 tp->tt_cpu = mycpu->gd_cpuid;
1374 TAILQ_INSERT_TAIL(
1375 &tcpcbackq[tp->tt_cpu],
1376 tp, t_outputq);
1377 }
72b37eeb
MD
1378 } else {
1379 tp->t_flags |= TF_ACKNOW;
1380 tcp_output(tp);
984263bc 1381 }
002c1265 1382 return(IPPROTO_DONE);
984263bc
MD
1383 }
1384 }
1385
1386 /*
1387 * Calculate amount of space in receive window,
1388 * and then do TCP input processing.
1389 * Receive window is amount of space in rcv queue,
1390 * but not less than advertised window.
1391 */
6d49aa6f 1392 recvwin = ssb_space(&so->so_rcv);
61896e3c
JH
1393 if (recvwin < 0)
1394 recvwin = 0;
1395 tp->rcv_wnd = imax(recvwin, (int)(tp->rcv_adv - tp->rcv_nxt));
984263bc 1396
5b0b9fa5
PA
1397 /* Reset receive buffer auto scaling when not in bulk receive mode. */
1398 tp->rfbuf_ts = 0;
1399 tp->rfbuf_cnt = 0;
1400
984263bc 1401 switch (tp->t_state) {
984263bc
MD
1402 /*
1403 * If the state is SYN_RECEIVED:
1404 * if seg contains an ACK, but not for our SYN/ACK, send a RST.
1405 */
1406 case TCPS_SYN_RECEIVED:
1407 if ((thflags & TH_ACK) &&
1408 (SEQ_LEQ(th->th_ack, tp->snd_una) ||
1409 SEQ_GT(th->th_ack, tp->snd_max))) {
1410 rstreason = BANDLIM_RST_OPENPORT;
1411 goto dropwithreset;
1412 }
1413 break;
1414
1415 /*
1416 * If the state is SYN_SENT:
1417 * if seg contains an ACK, but not for our SYN, drop the input.
1418 * if seg contains a RST, then drop the connection.
1419 * if seg does not contain SYN, then drop it.
1420 * Otherwise this is an acceptable SYN segment
1421 * initialize tp->rcv_nxt and tp->irs
1422 * if seg contains ack then advance tp->snd_una
1423 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state
1424 * arrange for segment to be acked (eventually)
1425 * continue processing rest of data/controls, beginning with URG
1426 */
1427 case TCPS_SYN_SENT:
984263bc
MD
1428 if ((thflags & TH_ACK) &&
1429 (SEQ_LEQ(th->th_ack, tp->iss) ||
1430 SEQ_GT(th->th_ack, tp->snd_max))) {
27b8aee3
AE
1431 rstreason = BANDLIM_UNLIMITED;
1432 goto dropwithreset;
984263bc
MD
1433 }
1434 if (thflags & TH_RST) {
1435 if (thflags & TH_ACK)
1436 tp = tcp_drop(tp, ECONNREFUSED);
1437 goto drop;
1438 }
61896e3c 1439 if (!(thflags & TH_SYN))
984263bc
MD
1440 goto drop;
1441 tp->snd_wnd = th->th_win; /* initial send window */
984263bc
MD
1442
1443 tp->irs = th->th_seq;
1444 tcp_rcvseqinit(tp);
1445 if (thflags & TH_ACK) {
27b8aee3 1446 /* Our SYN was acked. */
984263bc
MD
1447 tcpstat.tcps_connects++;
1448 soisconnected(so);
1449 /* Do window scaling on this connection? */
61896e3c 1450 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) ==
b5572302 1451 (TF_RCVD_SCALE | TF_REQ_SCALE)) {
984263bc
MD
1452 tp->snd_scale = tp->requested_s_scale;
1453 tp->rcv_scale = tp->request_r_scale;
1454 }
984263bc
MD
1455 tp->rcv_adv += tp->rcv_wnd;
1456 tp->snd_una++; /* SYN is acked */
a48c5dd5 1457 tcp_callout_stop(tp, tp->tt_rexmt);
984263bc
MD
1458 /*
1459 * If there's data, delay ACK; if there's also a FIN
1460 * ACKNOW will be turned on later.
1461 */
a48c5dd5
SZ
1462 if (DELAY_ACK(tp) && tlen != 0) {
1463 tcp_callout_reset(tp, tp->tt_delack,
1464 tcp_delacktime, tcp_timer_delack);
1465 } else {
984263bc 1466 tp->t_flags |= TF_ACKNOW;
a48c5dd5 1467 }
984263bc
MD
1468 /*
1469 * Received <SYN,ACK> in SYN_SENT[*] state.
1470 * Transitions:
1471 * SYN_SENT --> ESTABLISHED
1472 * SYN_SENT* --> FIN_WAIT_1
1473 */
1474 tp->t_starttime = ticks;
1475 if (tp->t_flags & TF_NEEDFIN) {
1476 tp->t_state = TCPS_FIN_WAIT_1;
1477 tp->t_flags &= ~TF_NEEDFIN;
1478 thflags &= ~TH_SYN;
1479 } else {
8651f7f8 1480 tcp_established(tp);
984263bc
MD
1481 }
1482 } else {
1483 /*
95b22adf 1484 * Received initial SYN in SYN-SENT[*] state =>
27b8aee3
AE
1485 * simultaneous open.
1486 * Do 3-way handshake:
61896e3c
JH
1487 * SYN-SENT -> SYN-RECEIVED
1488 * SYN-SENT* -> SYN-RECEIVED*
95b22adf 1489 */
984263bc 1490 tp->t_flags |= TF_ACKNOW;
a48c5dd5 1491 tcp_callout_stop(tp, tp->tt_rexmt);
27b8aee3 1492 tp->t_state = TCPS_SYN_RECEIVED;
984263bc
MD
1493 }
1494
984263bc
MD
1495 /*
1496 * Advance th->th_seq to correspond to first data byte.
1497 * If data, trim to stay within window,
1498 * dropping FIN if necessary.
1499 */
1500 th->th_seq++;
1501 if (tlen > tp->rcv_wnd) {
1502 todrop = tlen - tp->rcv_wnd;
1503 m_adj(m, -todrop);
1504 tlen = tp->rcv_wnd;
1505 thflags &= ~TH_FIN;
1506 tcpstat.tcps_rcvpackafterwin++;
1507 tcpstat.tcps_rcvbyteafterwin += todrop;
1508 }
1509 tp->snd_wl1 = th->th_seq - 1;
1510 tp->rcv_up = th->th_seq;
1511 /*
1512 * Client side of transaction: already sent SYN and data.
1513 * If the remote host used T/TCP to validate the SYN,
1514 * our data will be ACK'd; if so, enter normal data segment
1515 * processing in the middle of step 5, ack processing.
1516 * Otherwise, goto step 6.
1517 */
95b22adf 1518 if (thflags & TH_ACK)
984263bc
MD
1519 goto process_ACK;
1520
1521 goto step6;
1522
1523 /*
1524 * If the state is LAST_ACK or CLOSING or TIME_WAIT:
27b8aee3 1525 * do normal processing (we no longer bother with T/TCP).
984263bc
MD
1526 */
1527 case TCPS_LAST_ACK:
1528 case TCPS_CLOSING:
1529 case TCPS_TIME_WAIT:
95b22adf 1530 break; /* continue normal processing */
984263bc
MD
1531 }
1532
1533 /*
1534 * States other than LISTEN or SYN_SENT.
1535 * First check the RST flag and sequence number since reset segments
1536 * are exempt from the timestamp and connection count tests. This
1537 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix
1538 * below which allowed reset segments in half the sequence space
1539 * to fall though and be processed (which gives forged reset
1540 * segments with a random sequence number a 50 percent chance of
1541 * killing a connection).
1542 * Then check timestamp, if present.
1543 * Then check the connection count, if present.
1544 * Then check that at least some bytes of segment are within
1545 * receive window. If segment begins before rcv_nxt,
1546 * drop leading data (and SYN); if nothing left, just ack.
1547 *
1548 *
1549 * If the RST bit is set, check the sequence number to see
1550 * if this is a valid reset segment.
1551 * RFC 793 page 37:
1552 * In all states except SYN-SENT, all reset (RST) segments
1553 * are validated by checking their SEQ-fields. A reset is
1554 * valid if its sequence number is in the window.
1555 * Note: this does not take into account delayed ACKs, so
1556 * we should test against last_ack_sent instead of rcv_nxt.
1557 * The sequence number in the reset segment is normally an
91489f6b 1558 * echo of our outgoing acknowledgement numbers, but some hosts
984263bc
MD
1559 * send a reset with the sequence number at the rightmost edge
1560 * of our receive window, and we have to handle this case.
1561 * If we have multiple segments in flight, the intial reset
1562 * segment sequence numbers will be to the left of last_ack_sent,
1563 * but they will eventually catch up.
1564 * In any case, it never made sense to trim reset segments to
1565 * fit the receive window since RFC 1122 says:
1566 * 4.2.2.12 RST Segment: RFC-793 Section 3.4
1567 *
1568 * A TCP SHOULD allow a received RST segment to include data.
1569 *
1570 * DISCUSSION
61896e3c
JH
1571 * It has been suggested that a RST segment could contain
1572 * ASCII text that encoded and explained the cause of the
91489f6b 1573 * RST. No standard has yet been established for such
61896e3c 1574 * data.
984263bc
MD
1575 *
1576 * If the reset segment passes the sequence number test examine
1577 * the state:
1578 * SYN_RECEIVED STATE:
1579 * If passive open, return to LISTEN state.
1580 * If active open, inform user that connection was refused.
1581 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES:
1582 * Inform user that connection was reset, and close tcb.
1583 * CLOSING, LAST_ACK STATES:
1584 * Close the tcb.
1585 * TIME_WAIT STATE:
1586 * Drop the segment - see Stevens, vol. 2, p. 964 and
61896e3c 1587 * RFC 1337.
984263bc
MD
1588 */
1589 if (thflags & TH_RST) {
1590 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
d4dbb5be 1591 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) {
984263bc
MD
1592 switch (tp->t_state) {
1593
1594 case TCPS_SYN_RECEIVED:
1595 so->so_error = ECONNREFUSED;
1596 goto close;
1597
1598 case TCPS_ESTABLISHED:
1599 case TCPS_FIN_WAIT_1:
1600 case TCPS_FIN_WAIT_2:
1601 case TCPS_CLOSE_WAIT:
1602 so->so_error = ECONNRESET;
1603 close:
1604 tp->t_state = TCPS_CLOSED;
1605 tcpstat.tcps_drops++;
1606 tp = tcp_close(tp);
1607 break;
1608
1609 case TCPS_CLOSING:
1610 case TCPS_LAST_ACK:
1611 tp = tcp_close(tp);
1612 break;
1613
1614 case TCPS_TIME_WAIT:
1615 break;
1616 }
1617 }
1618 goto drop;
1619 }
1620
1621 /*
1622 * RFC 1323 PAWS: If we have a timestamp reply on this segment
1623 * and it's less than ts_recent, drop it.
1624 */
61896e3c 1625 if ((to.to_flags & TOF_TS) && tp->ts_recent != 0 &&
984263bc
MD
1626 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
1627
1628 /* Check to see if ts_recent is over 24 days old. */
1629 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) {
1630 /*
1631 * Invalidate ts_recent. If this segment updates
1632 * ts_recent, the age will be reset later and ts_recent
1633 * will get a valid value. If it does not, setting
1634 * ts_recent to zero will at least satisfy the
1635 * requirement that zero be placed in the timestamp
1636 * echo reply when ts_recent isn't valid. The
1637 * age isn't reset until we get a valid ts_recent
1638 * because we don't want out-of-order segments to be
1639 * dropped when ts_recent is old.
1640 */
1641 tp->ts_recent = 0;
1642 } else {
1643 tcpstat.tcps_rcvduppack++;
1644 tcpstat.tcps_rcvdupbyte += tlen;
1645 tcpstat.tcps_pawsdrop++;
1646 if (tlen)
1647 goto dropafterack;
1648 goto drop;
1649 }
1650 }
1651
1652 /*
984263bc
MD
1653 * In the SYN-RECEIVED state, validate that the packet belongs to
1654 * this connection before trimming the data to fit the receive
1655 * window. Check the sequence number versus IRS since we know
1656 * the sequence numbers haven't wrapped. This is a partial fix
1657 * for the "LAND" DoS attack.
1658 */
1659 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) {
1660 rstreason = BANDLIM_RST_OPENPORT;
1661 goto dropwithreset;
1662 }
1663
1664 todrop = tp->rcv_nxt - th->th_seq;
1665 if (todrop > 0) {
91489f6b
JH
1666 if (TCP_DO_SACK(tp)) {
1667 /* Report duplicate segment at head of packet. */
1668 tp->reportblk.rblk_start = th->th_seq;
3a5d999b
SZ
1669 tp->reportblk.rblk_end = TCP_SACK_BLKEND(
1670 th->th_seq + tlen, thflags);
91489f6b
JH
1671 if (SEQ_GT(tp->reportblk.rblk_end, tp->rcv_nxt))
1672 tp->reportblk.rblk_end = tp->rcv_nxt;
1673 tp->t_flags |= (TF_DUPSEG | TF_SACKLEFT | TF_ACKNOW);
1674 }
984263bc
MD
1675 if (thflags & TH_SYN) {
1676 thflags &= ~TH_SYN;
1677 th->th_seq++;
1678 if (th->th_urp > 1)
1679 th->th_urp--;
1680 else
1681 thflags &= ~TH_URG;
1682 todrop--;
1683 }
1684 /*
1685 * Following if statement from Stevens, vol. 2, p. 960.
1686 */
61896e3c
JH
1687 if (todrop > tlen ||
1688 (todrop == tlen && !(thflags & TH_FIN))) {
984263bc
MD
1689 /*
1690 * Any valid FIN must be to the left of the window.
1691 * At this point the FIN must be a duplicate or out
1692 * of sequence; drop it.
1693 */
1694 thflags &= ~TH_FIN;
1695
1696 /*
1697 * Send an ACK to resynchronize and drop any data.
1698 * But keep on processing for RST or ACK.
1699 */
1700 tp->t_flags |= TF_ACKNOW;
1701 todrop = tlen;
1702 tcpstat.tcps_rcvduppack++;
1703 tcpstat.tcps_rcvdupbyte += todrop;
1704 } else {
1705 tcpstat.tcps_rcvpartduppack++;
1706 tcpstat.tcps_rcvpartdupbyte += todrop;
1707 }
1708 drop_hdrlen += todrop; /* drop from the top afterwards */
1709 th->th_seq += todrop;
1710 tlen -= todrop;
1711 if (th->th_urp > todrop)
1712 th->th_urp -= todrop;
1713 else {
1714 thflags &= ~TH_URG;
1715 th->th_urp = 0;
1716 }
1717 }
1718
1719 /*
1720 * If new data are received on a connection after the
1721 * user processes are gone, then RST the other end.
1722 */
1723 if ((so->so_state & SS_NOFDREF) &&
1724 tp->t_state > TCPS_CLOSE_WAIT && tlen) {
1725 tp = tcp_close(tp);
1726 tcpstat.tcps_rcvafterclose++;
1727 rstreason = BANDLIM_UNLIMITED;
1728 goto dropwithreset;
1729 }
1730
1731 /*
1732 * If segment ends after window, drop trailing data
1733 * (and PUSH and FIN); if nothing left, just ACK.
1734 */
61896e3c 1735 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd);
984263bc
MD
1736 if (todrop > 0) {
1737 tcpstat.tcps_rcvpackafterwin++;
1738 if (todrop >= tlen) {
1739 tcpstat.tcps_rcvbyteafterwin += tlen;
1740 /*
1741 * If a new connection request is received
1742 * while in TIME_WAIT, drop the old connection
1743 * and start over if the sequence numbers
1744 * are above the previous ones.
1745 */
1746 if (thflags & TH_SYN &&
1747 tp->t_state == TCPS_TIME_WAIT &&
1748 SEQ_GT(th->th_seq, tp->rcv_nxt)) {
1749 tp = tcp_close(tp);
1750 goto findpcb;
1751 }
1752 /*
1753 * If window is closed can only take segments at
1754 * window edge, and have to drop data and PUSH from
1755 * incoming segments. Continue processing, but
1756 * remember to ack. Otherwise, drop segment
1757 * and ack.
1758 */
1759 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
1760 tp->t_flags |= TF_ACKNOW;
1761 tcpstat.tcps_rcvwinprobe++;
1762 } else
1763 goto dropafterack;
1764 } else
1765 tcpstat.tcps_rcvbyteafterwin += todrop;
1766 m_adj(m, -todrop);
1767 tlen -= todrop;
61896e3c 1768 thflags &= ~(TH_PUSH | TH_FIN);
984263bc
MD
1769 }
1770
1771 /*
1772 * If last ACK falls within this segment's sequence numbers,
1773 * record its timestamp.
ad0af98b
ND
1774 * NOTE:
1775 * 1) That the test incorporates suggestions from the latest
1776 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1777 * 2) That updating only on newer timestamps interferes with
1778 * our earlier PAWS tests, so this check should be solely
1779 * predicated on the sequence space of this segment.
1780 * 3) That we modify the segment boundary check to be
1781 * Last.ACK.Sent <= SEG.SEQ + SEG.LEN
1782 * instead of RFC1323's
1783 * Last.ACK.Sent < SEG.SEQ + SEG.LEN,
1784 * This modified check allows us to overcome RFC1323's
1785 * limitations as described in Stevens TCP/IP Illustrated
1786 * Vol. 2 p.869. In such cases, we can still calculate the
1787 * RTT correctly when RCV.NXT == Last.ACK.Sent.
984263bc 1788 */
ad0af98b
ND
1789 if ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent) &&
1790 SEQ_LEQ(tp->last_ack_sent, (th->th_seq + tlen
1791 + ((thflags & TH_SYN) != 0)
1792 + ((thflags & TH_FIN) != 0)))) {
984263bc
MD
1793 tp->ts_recent_age = ticks;
1794 tp->ts_recent = to.to_tsval;
1795 }
1796
1797 /*
1798 * If a SYN is in the window, then this is an
1799 * error and we send an RST and drop the connection.
1800 */
1801 if (thflags & TH_SYN) {
1802 tp = tcp_drop(tp, ECONNRESET);
1803 rstreason = BANDLIM_UNLIMITED;
1804 goto dropwithreset;
1805 }
1806
1807 /*
1808 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN
1809 * flag is on (half-synchronized state), then queue data for
1810 * later processing; else drop segment and return.
1811 */
61896e3c 1812 if (!(thflags & TH_ACK)) {
984263bc
MD
1813 if (tp->t_state == TCPS_SYN_RECEIVED ||
1814 (tp->t_flags & TF_NEEDSYN))
1815 goto step6;
1816 else
1817 goto drop;
1818 }
1819
1820 /*
1821 * Ack processing.
1822 */
1823 switch (tp->t_state) {
984263bc 1824 /*
91489f6b 1825 * In SYN_RECEIVED state, the ACK acknowledges our SYN, so enter
984263bc
MD
1826 * ESTABLISHED state and continue processing.
1827 * The ACK was checked above.
1828 */
1829 case TCPS_SYN_RECEIVED:
1830
1831 tcpstat.tcps_connects++;
1832 soisconnected(so);
1833 /* Do window scaling? */
61896e3c 1834 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) ==
b5572302 1835 (TF_RCVD_SCALE | TF_REQ_SCALE)) {
984263bc
MD
1836 tp->snd_scale = tp->requested_s_scale;
1837 tp->rcv_scale = tp->request_r_scale;
1838 }
1839 /*
984263bc
MD
1840 * Make transitions:
1841 * SYN-RECEIVED -> ESTABLISHED
1842 * SYN-RECEIVED* -> FIN-WAIT-1
1843 */
1844 tp->t_starttime = ticks;
1845 if (tp->t_flags & TF_NEEDFIN) {
1846 tp->t_state = TCPS_FIN_WAIT_1;
1847 tp->t_flags &= ~TF_NEEDFIN;
1848 } else {
8651f7f8 1849 tcp_established(tp);
984263bc
MD
1850 }
1851 /*
1852 * If segment contains data or ACK, will call tcp_reass()
1853 * later; if not, do so now to pass queued data to user.
1854 */
61896e3c 1855 if (tlen == 0 && !(thflags & TH_FIN))
f23061d4 1856 tcp_reass(tp, NULL, NULL, NULL);
984263bc
MD
1857 /* fall into ... */
1858
1859 /*
1860 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
1861 * ACKs. If the ack is in the range
1862 * tp->snd_una < th->th_ack <= tp->snd_max
1863 * then advance tp->snd_una to th->th_ack and drop
1864 * data from the retransmission queue. If this ACK reflects
1865 * more up to date window information we update our window information.
1866 */
1867 case TCPS_ESTABLISHED:
1868 case TCPS_FIN_WAIT_1:
1869 case TCPS_FIN_WAIT_2:
1870 case TCPS_CLOSE_WAIT:
1871 case TCPS_CLOSING:
1872 case TCPS_LAST_ACK:
1873 case TCPS_TIME_WAIT:
1874
1875 if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
91489f6b
JH
1876 if (TCP_DO_SACK(tp))
1877 tcp_sack_update_scoreboard(tp, &to);
95b22adf
JH
1878 if (tlen != 0 || tiwin != tp->snd_wnd) {
1879 tp->t_dupacks = 0;
1880 break;
1881 }
1882 tcpstat.tcps_rcvdupack++;
a48c5dd5 1883 if (!tcp_callout_active(tp, tp->tt_rexmt) ||
91489f6b
JH
1884 th->th_ack != tp->snd_una) {
1885 tp->t_dupacks = 0;
1886 break;
1887 }
95b22adf 1888 /*
91489f6b 1889 * We have outstanding data (other than
95b22adf
JH
1890 * a window probe), this is a completely
1891 * duplicate ack (ie, window info didn't
1892 * change), the ack is the biggest we've
1893 * seen and we've seen exactly our rexmt
91489f6b 1894 * threshhold of them, so assume a packet
95b22adf
JH
1895 * has been dropped and retransmit it.
1896 * Kludge snd_nxt & the congestion
1897 * window so we send only this one
1898 * packet.
95b22adf 1899 */
91489f6b
JH
1900 if (IN_FASTRECOVERY(tp)) {
1901 if (TCP_DO_SACK(tp)) {
1902 /* No artifical cwnd inflation. */
1903 tcp_sack_rexmt(tp, th);
1904 } else {
1905 /*
1906 * Dup acks mean that packets
1907 * have left the network
1908 * (they're now cached at the
1909 * receiver) so bump cwnd by
1910 * the amount in the receiver
1911 * to keep a constant cwnd
1912 * packets in the network.
1913 */
1914 tp->snd_cwnd += tp->t_maxseg;
f23061d4 1915 tcp_output(tp);
91489f6b
JH
1916 }
1917 } else if (SEQ_LT(th->th_ack, tp->snd_recover)) {
95b22adf
JH
1918 tp->t_dupacks = 0;
1919 break;
95b22adf 1920 } else if (++tp->t_dupacks == tcprexmtthresh) {
91489f6b 1921 tcp_seq old_snd_nxt;
95b22adf
JH
1922 u_int win;
1923
8819433a 1924fastretransmit:
95b22adf
JH
1925 if (tcp_do_eifel_detect &&
1926 (tp->t_flags & TF_RCVD_TSTMP)) {
1927 tcp_save_congestion_state(tp);
1928 tp->t_flags |= TF_FASTREXMT;
1929 }
91489f6b
JH
1930 /*
1931 * We know we're losing at the current
1932 * window size, so do congestion avoidance:
1933 * set ssthresh to half the current window
1934 * and pull our congestion window back to the
1935 * new ssthresh.
1936 */
95b22adf
JH
1937 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 /
1938 tp->t_maxseg;
1939 if (win < 2)
1940 win = 2;
1941 tp->snd_ssthresh = win * tp->t_maxseg;
1942 ENTER_FASTRECOVERY(tp);
1943 tp->snd_recover = tp->snd_max;
a48c5dd5 1944 tcp_callout_stop(tp, tp->tt_rexmt);
95b22adf 1945 tp->t_rtttime = 0;
91489f6b 1946 old_snd_nxt = tp->snd_nxt;
95b22adf
JH
1947 tp->snd_nxt = th->th_ack;
1948 tp->snd_cwnd = tp->t_maxseg;
f23061d4 1949 tcp_output(tp);
95b22adf 1950 ++tcpstat.tcps_sndfastrexmit;
91489f6b
JH
1951 tp->snd_cwnd = tp->snd_ssthresh;
1952 tp->rexmt_high = tp->snd_nxt;
1953 if (SEQ_GT(old_snd_nxt, tp->snd_nxt))
1954 tp->snd_nxt = old_snd_nxt;
95b22adf
JH
1955 KASSERT(tp->snd_limited <= 2,
1956 ("tp->snd_limited too big"));
91489f6b
JH
1957 if (TCP_DO_SACK(tp))
1958 tcp_sack_rexmt(tp, th);
1959 else
1960 tp->snd_cwnd += tp->t_maxseg *
1961 (tp->t_dupacks - tp->snd_limited);
95b22adf
JH
1962 } else if (tcp_do_limitedtransmit) {
1963 u_long oldcwnd = tp->snd_cwnd;
1964 tcp_seq oldsndmax = tp->snd_max;
9e707f76 1965 tcp_seq oldsndnxt = tp->snd_nxt;
95b22adf
JH
1966 /* outstanding data */
1967 uint32_t ownd = tp->snd_max - tp->snd_una;
1968 u_int sent;
ca94b4a6 1969
8819433a
JH
1970#define iceildiv(n, d) (((n)+(d)-1) / (d))
1971
95b22adf
JH
1972 KASSERT(tp->t_dupacks == 1 ||
1973 tp->t_dupacks == 2,
1974 ("dupacks not 1 or 2"));
1975 if (tp->t_dupacks == 1)
1976 tp->snd_limited = 0;
9e707f76 1977 tp->snd_nxt = tp->snd_max;
95b22adf
JH
1978 tp->snd_cwnd = ownd +
1979 (tp->t_dupacks - tp->snd_limited) *
1980 tp->t_maxseg;
f23061d4 1981 tcp_output(tp);
98cb2337 1982
98cb2337 1983 if (SEQ_LT(oldsndnxt, oldsndmax)) {
31ea9b1e
SZ
1984 KASSERT(SEQ_GEQ(oldsndnxt, tp->snd_una),
1985 ("snd_una moved in other threads"));
6d08465d 1986 tp->snd_nxt = oldsndnxt;
98cb2337 1987 }
95b22adf
JH
1988 tp->snd_cwnd = oldcwnd;
1989 sent = tp->snd_max - oldsndmax;
1990 if (sent > tp->t_maxseg) {
1991 KASSERT((tp->t_dupacks == 2 &&
1992 tp->snd_limited == 0) ||
1993 (sent == tp->t_maxseg + 1 &&
1994 tp->t_flags & TF_SENTFIN),
1995 ("sent too much"));
1996 KASSERT(sent <= tp->t_maxseg * 2,
1997 ("sent too many segments"));
1998 tp->snd_limited = 2;
1999 tcpstat.tcps_sndlimited += 2;
2000 } else if (sent > 0) {
2001 ++tp->snd_limited;
2002 ++tcpstat.tcps_sndlimited;
2003 } else if (tcp_do_early_retransmit &&
2004 (tcp_do_eifel_detect &&
2005 (tp->t_flags & TF_RCVD_TSTMP)) &&
91489f6b 2006 ownd < 4 * tp->t_maxseg &&
95b22adf 2007 tp->t_dupacks + 1 >=
91489f6b
JH
2008 iceildiv(ownd, tp->t_maxseg) &&
2009 (!TCP_DO_SACK(tp) ||
f23061d4 2010 ownd <= tp->t_maxseg ||
91489f6b 2011 tcp_sack_has_sacked(&tp->scb,
f23061d4 2012 ownd - tp->t_maxseg))) {
95b22adf
JH
2013 ++tcpstat.tcps_sndearlyrexmit;
2014 tp->t_flags |= TF_EARLYREXMT;
2015 goto fastretransmit;
984263bc 2016 }
95b22adf
JH
2017 }
2018 goto drop;
984263bc
MD
2019 }
2020
2021 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una"));
984263bc
MD
2022 tp->t_dupacks = 0;
2023 if (SEQ_GT(th->th_ack, tp->snd_max)) {
5a274421
JH
2024 /*
2025 * Detected optimistic ACK attack.
2026 * Force slow-start to de-synchronize attack.
2027 */
2028 tp->snd_cwnd = tp->t_maxseg;
8acdb67c 2029 tp->snd_wacked = 0;
5a274421 2030
984263bc
MD
2031 tcpstat.tcps_rcvacktoomuch++;
2032 goto dropafterack;
2033 }
2034 /*
2035 * If we reach this point, ACK is not a duplicate,
2036 * i.e., it ACKs something we sent.
2037 */
2038 if (tp->t_flags & TF_NEEDSYN) {
2039 /*
2040 * T/TCP: Connection was half-synchronized, and our
2041 * SYN has been ACK'd (so connection is now fully
2042 * synchronized). Go to non-starred state,
2043 * increment snd_una for ACK of SYN, and check if
2044 * we can do window scaling.
2045 */
2046 tp->t_flags &= ~TF_NEEDSYN;
2047 tp->snd_una++;
2048 /* Do window scaling? */
61896e3c
JH
2049 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) ==
2050 (TF_RCVD_SCALE | TF_REQ_SCALE)) {
984263bc
MD
2051 tp->snd_scale = tp->requested_s_scale;
2052 tp->rcv_scale = tp->request_r_scale;
2053 }
2054 }
2055
2056process_ACK:
2057 acked = th->th_ack - tp->snd_una;
2058 tcpstat.tcps_rcvackpack++;
2059 tcpstat.tcps_rcvackbyte += acked;
2060
b5572302 2061 if (tcp_do_eifel_detect && acked > 0 &&
95b22adf 2062 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) &&
bfdb979e
JH
2063 (tp->t_flags & TF_FIRSTACCACK)) {
2064 /* Eifel detection applicable. */
2065 if (to.to_tsecr < tp->t_rexmtTS) {
bfdb979e 2066 ++tcpstat.tcps_eifeldetected;
8819433a 2067 tcp_revert_congestion_state(tp);
928c3291 2068 if (tp->t_rxtshift != 1 ||
8819433a
JH
2069 ticks >= tp->t_badrxtwin)
2070 ++tcpstat.tcps_rttcantdetect;
bfdb979e
JH
2071 }
2072 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) {
b5572302
JH
2073 /*
2074 * If we just performed our first retransmit,
2075 * and the ACK arrives within our recovery window,
2076 * then it was a mistake to do the retransmit
91489f6b 2077 * in the first place. Recover our original cwnd
b5572302
JH
2078 * and ssthresh, and proceed to transmit where we
2079 * left off.
2080 */
bfdb979e
JH
2081 tcp_revert_congestion_state(tp);
2082 ++tcpstat.tcps_rttdetected;
984263bc
MD
2083 }
2084
2085 /*
2086 * If we have a timestamp reply, update smoothed
2087 * round trip time. If no timestamp is present but
2088 * transmit timer is running and timed sequence
2089 * number was acked, update smoothed round trip time.
2090 * Since we now have an rtt measurement, cancel the
2091 * timer backoff (cf., Phil Karn's retransmit alg.).
2092 * Recompute the initial retransmit timer.
2093 *
2094 * Some machines (certain windows boxes) send broken
d24ce1dc 2095 * timestamp replies during the SYN+ACK phase, ignore
984263bc
MD
2096 * timestamps of 0.
2097 */
95b22adf 2098 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0))
984263bc 2099 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1);
95b22adf 2100 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq))
984263bc 2101 tcp_xmit_timer(tp, ticks - tp->t_rtttime);
984263bc
MD
2102 tcp_xmit_bandwidth_limit(tp, th->th_ack);
2103
2104 /*
984263bc
MD
2105 * If no data (only SYN) was ACK'd,
2106 * skip rest of ACK processing.
2107 */
2108 if (acked == 0)
2109 goto step6;
2110
efd4b327 2111 /* Stop looking for an acceptable ACK since one was received. */
8819433a 2112 tp->t_flags &= ~(TF_FIRSTACCACK | TF_FASTREXMT | TF_EARLYREXMT);
efd4b327 2113
6d49aa6f
MD
2114 if (acked > so->so_snd.ssb_cc) {
2115 tp->snd_wnd -= so->so_snd.ssb_cc;
2116 sbdrop(&so->so_snd.sb, (int)so->so_snd.ssb_cc);
61896e3c 2117 ourfinisacked = TRUE;
984263bc 2118 } else {
6d49aa6f 2119 sbdrop(&so->so_snd.sb, acked);
984263bc 2120 tp->snd_wnd -= acked;
61896e3c 2121 ourfinisacked = FALSE;
984263bc
MD
2122 }
2123 sowwakeup(so);
91489f6b
JH
2124
2125 /*
2126 * Update window information.
91489f6b 2127 */
e126661b 2128 if (acceptable_window_update(tp, th, tiwin)) {
91489f6b
JH
2129 /* keep track of pure window updates */
2130 if (tlen == 0 && tp->snd_wl2 == th->th_ack &&
2131 tiwin > tp->snd_wnd)
2132 tcpstat.tcps_rcvwinupd++;
2133 tp->snd_wnd = tiwin;
2134 tp->snd_wl1 = th->th_seq;
2135 tp->snd_wl2 = th->th_ack;
2136 if (tp->snd_wnd > tp->max_sndwnd)
2137 tp->max_sndwnd = tp->snd_wnd;
2138 needoutput = TRUE;
2139 }
2140
2141 tp->snd_una = th->th_ack;
2142 if (TCP_DO_SACK(tp))
2143 tcp_sack_update_scoreboard(tp, &to);
95b22adf 2144 if (IN_FASTRECOVERY(tp)) {
91489f6b 2145 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) {
95b22adf 2146 EXIT_FASTRECOVERY(tp);
91489f6b
JH
2147 needoutput = TRUE;
2148 /*
2149 * If the congestion window was inflated
2150 * to account for the other side's
2151 * cached packets, retract it.
8acdb67c
JH
2152 */
2153 if (!TCP_DO_SACK(tp))
2154 tp->snd_cwnd = tp->snd_ssthresh;
2155
2156 /*
91489f6b
JH
2157 * Window inflation should have left us
2158 * with approximately snd_ssthresh outstanding
2159 * data. But, in case we would be inclined
2160 * to send a burst, better do it using
2161 * slow start.
2162 */
91489f6b
JH
2163 if (SEQ_GT(th->th_ack + tp->snd_cwnd,
2164 tp->snd_max + 2 * tp->t_maxseg))
2165 tp->snd_cwnd =
2166 (tp->snd_max - tp->snd_una) +
2167 2 * tp->t_maxseg;
8acdb67c
JH
2168
2169 tp->snd_wacked = 0;
91489f6b
JH
2170 } else {
2171 if (TCP_DO_SACK(tp)) {
2172 tp->snd_max_rexmt = tp->snd_max;
2173 tcp_sack_rexmt(tp, th);
2174 } else {
2175 tcp_newreno_partial_ack(tp, th, acked);
2176 }
2177 needoutput = FALSE;
2178 }
95b22adf 2179 } else {
91489f6b 2180 /*
8acdb67c
JH
2181 * Open the congestion window. When in slow-start,
2182 * open exponentially: maxseg per packet. Otherwise,
2183 * open linearly: maxseg per window.
91489f6b 2184 */
8acdb67c
JH
2185 if (tp->snd_cwnd <= tp->snd_ssthresh) {
2186 u_int abc_sslimit =
2187 (SEQ_LT(tp->snd_nxt, tp->snd_max) ?
2188 tp->t_maxseg : 2 * tp->t_maxseg);
2189
2190 /* slow-start */
2191 tp->snd_cwnd += tcp_do_abc ?
2192 min(acked, abc_sslimit) : tp->t_maxseg;
2193 } else {
2194 /* linear increase */
2195 tp->snd_wacked += tcp_do_abc ? acked :
2196 tp->t_maxseg;
2197 if (tp->snd_wacked >= tp->snd_cwnd) {
2198 tp->snd_wacked -= tp->snd_cwnd;
2199 tp->snd_cwnd += tp->t_maxseg;
2200 }
2201 }
2202 tp->snd_cwnd = min(tp->snd_cwnd,
2203 TCP_MAXWIN << tp->snd_scale);
95b22adf 2204 tp->snd_recover = th->th_ack - 1;
cfb3f3f4 2205 }
984263bc
MD
2206 if (SEQ_LT(tp->snd_nxt, tp->snd_una))
2207 tp->snd_nxt = tp->snd_una;
2208
91489f6b
JH
2209 /*
2210 * If all outstanding data is acked, stop retransmit
2211 * timer and remember to restart (more output or persist).
2212 * If there is more data to be acked, restart retransmit
2213 * timer, using current (possibly backed-off) value.
2214 */
2215 if (th->th_ack == tp->snd_max) {
a48c5dd5 2216 tcp_callout_stop(tp, tp->tt_rexmt);
91489f6b 2217 needoutput = TRUE;
a48c5dd5
SZ
2218 } else if (!tcp_callout_active(tp, tp->tt_persist)) {
2219 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur,
2220 tcp_timer_rexmt);
2221 }
91489f6b 2222
984263bc 2223 switch (tp->t_state) {
984263bc
MD
2224 /*
2225 * In FIN_WAIT_1 STATE in addition to the processing
2226 * for the ESTABLISHED state if our FIN is now acknowledged
2227 * then enter FIN_WAIT_2.
2228 */
2229 case TCPS_FIN_WAIT_1:
2230 if (ourfinisacked) {
2231 /*
2232 * If we can't receive any more
2233 * data, then closing user can proceed.
2234 * Starting the timer is contrary to the
2235 * specification, but if we don't get a FIN
2236 * we'll hang forever.
2237 */
2238 if (so->so_state & SS_CANTRCVMORE) {
2239 soisdisconnected(so);
a48c5dd5 2240 tcp_callout_reset(tp, tp->tt_2msl,
5d61ded3 2241 tp->t_maxidle, tcp_timer_2msl);
984263bc
MD
2242 }
2243 tp->t_state = TCPS_FIN_WAIT_2;
2244 }
2245 break;
2246
95b22adf 2247 /*
984263bc
MD
2248 * In CLOSING STATE in addition to the processing for
2249 * the ESTABLISHED state if the ACK acknowledges our FIN
2250 * then enter the TIME-WAIT state, otherwise ignore
2251 * the segment.
2252 */
2253 case TCPS_CLOSING:
2254 if (ourfinisacked) {
2255 tp->t_state = TCPS_TIME_WAIT;
2256 tcp_canceltimers(tp);
27b8aee3 2257 tcp_callout_reset(tp, tp->tt_2msl,
01d3427a
SZ
2258 2 * tcp_rmx_msl(tp),
2259 tcp_timer_2msl);
984263bc
MD
2260 soisdisconnected(so);
2261 }
2262 break;
2263
2264 /*
2265 * In LAST_ACK, we may still be waiting for data to drain
2266 * and/or to be acked, as well as for the ack of our FIN.
2267 * If our FIN is now acknowledged, delete the TCB,
2268 * enter the closed state and return.
2269 */
2270 case TCPS_LAST_ACK:
2271 if (ourfinisacked) {
2272 tp = tcp_close(tp);
2273 goto drop;
2274 }
2275 break;
2276
2277 /*
2278 * In TIME_WAIT state the only thing that should arrive
2279 * is a retransmission of the remote FIN. Acknowledge
2280 * it and restart the finack timer.
2281 */
2282 case TCPS_TIME_WAIT:
01d3427a 2283 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp),
a48c5dd5 2284 tcp_timer_2msl);
984263bc
MD
2285 goto dropafterack;
2286 }
2287 }
2288
2289step6:
2290 /*
2291 * Update window information.
2292 * Don't look at window if no ACK: TAC's send garbage on first SYN.
2293 */
2294 if ((thflags & TH_ACK) &&
df9d7670 2295 acceptable_window_update(tp, th, tiwin)) {
984263bc 2296 /* keep track of pure window updates */
b5572302
JH
2297 if (tlen == 0 && tp->snd_wl2 == th->th_ack &&
2298 tiwin > tp->snd_wnd)
984263bc
MD
2299 tcpstat.tcps_rcvwinupd++;
2300 tp->snd_wnd = tiwin;
2301 tp->snd_wl1 = th->th_seq;
2302 tp->snd_wl2 = th->th_ack;
2303 if (tp->snd_wnd > tp->max_sndwnd)
2304 tp->max_sndwnd = tp->snd_wnd;
61896e3c 2305 needoutput = TRUE;
984263bc
MD
2306 }
2307
2308 /*
2309 * Process segments with URG.
2310 */
2311 if ((thflags & TH_URG) && th->th_urp &&
95b22adf 2312 !TCPS_HAVERCVDFIN(tp->t_state)) {
984263bc
MD
2313 /*
2314 * This is a kludge, but if we receive and accept
2315 * random urgent pointers, we'll crash in
2316 * soreceive. It's hard to imagine someone
2317 * actually wanting to send this much urgent data.
2318 */
6d49aa6f 2319 if (th->th_urp + so->so_rcv.ssb_cc > sb_max) {
984263bc
MD
2320 th->th_urp = 0; /* XXX */
2321 thflags &= ~TH_URG; /* XXX */
2322 goto dodata; /* XXX */
2323 }
2324 /*
2325 * If this segment advances the known urgent pointer,
2326 * then mark the data stream. This should not happen
2327 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
2328 * a FIN has been received from the remote side.
2329 * In these states we ignore the URG.
2330 *
2331 * According to RFC961 (Assigned Protocols),
2332 * the urgent pointer points to the last octet
2333 * of urgent data. We continue, however,
2334 * to consider it to indicate the first octet
2335 * of data past the urgent section as the original
2336 * spec states (in one of two places).
2337 */
61896e3c 2338 if (SEQ_GT(th->th_seq + th->th_urp, tp->rcv_up)) {
984263bc 2339 tp->rcv_up = th->th_seq + th->th_urp;
6d49aa6f 2340 so->so_oobmark = so->so_rcv.ssb_cc +
984263bc
MD
2341 (tp->rcv_up - tp->rcv_nxt) - 1;
2342 if (so->so_oobmark == 0)
6cef7136 2343 sosetstate(so, SS_RCVATMARK);
984263bc
MD
2344 sohasoutofband(so);
2345 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
2346 }
2347 /*
2348 * Remove out of band data so doesn't get presented to user.
2349 * This can happen independent of advancing the URG pointer,
2350 * but if two URG's are pending at once, some out-of-band
2351 * data may creep in... ick.
2352 */
61896e3c
JH
2353 if (th->th_urp <= (u_long)tlen &&
2354 !(so->so_options & SO_OOBINLINE)) {
2355 /* hdr drop is delayed */
2356 tcp_pulloutofband(so, th, m, drop_hdrlen);
2357 }
984263bc
MD
2358 } else {
2359 /*
2360 * If no out of band data is expected,
2361 * pull receive urgent pointer along
2362 * with the receive window.
2363 */
2364 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
2365 tp->rcv_up = tp->rcv_nxt;
2366 }
984263bc 2367
61896e3c 2368dodata: /* XXX */
984263bc
MD
2369 /*
2370 * Process the segment text, merging it into the TCP sequencing queue,
2371 * and arranging for acknowledgment of receipt if necessary.
2372 * This process logically involves adjusting tp->rcv_wnd as data
2373 * is presented to the user (this happens in tcp_usrreq.c,
2374 * case PRU_RCVD). If a FIN has already been received on this
2375 * connection then we just ignore the text.
2376 */
95b22adf 2377 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) {
984263bc
MD
2378 m_adj(m, drop_hdrlen); /* delayed header drop */
2379 /*
2380 * Insert segment which includes th into TCP reassembly queue
2381 * with control block tp. Set thflags to whether reassembly now
2382 * includes a segment with FIN. This handles the common case
2383 * inline (segment is the next to be received on an established
2384 * connection, and the queue is empty), avoiding linkage into
2385 * and removal from the queue and repetition of various
2386 * conversions.
2387 * Set DELACK for segments received in order, but ack
2388 * immediately when segments are out of order (so
2389 * fast retransmit can work).
2390 */
2391 if (th->th_seq == tp->rcv_nxt &&
2392 LIST_EMPTY(&tp->t_segq) &&
2393 TCPS_HAVEESTABLISHED(tp->t_state)) {
a48c5dd5
SZ
2394 if (DELAY_ACK(tp)) {
2395 tcp_callout_reset(tp, tp->tt_delack,
2396 tcp_delacktime, tcp_timer_delack);
2397 } else {
984263bc 2398 tp->t_flags |= TF_ACKNOW;
a48c5dd5 2399 }
984263bc
MD
2400 tp->rcv_nxt += tlen;
2401 thflags = th->th_flags & TH_FIN;
2402 tcpstat.tcps_rcvpack++;
2403 tcpstat.tcps_rcvbyte += tlen;
2404 ND6_HINT(tp);
6cef7136 2405 if (so->so_state & SS_CANTRCVMORE) {
984263bc 2406 m_freem(m);
6cef7136
MD
2407 } else {
2408 lwkt_gettoken(&so->so_rcv.ssb_token);
6d49aa6f 2409 ssb_appendstream(&so->so_rcv, m);
6cef7136
MD
2410 lwkt_reltoken(&so->so_rcv.ssb_token);
2411 }
984263bc
MD
2412 sorwakeup(so);
2413 } else {
91489f6b
JH
2414 if (!(tp->t_flags & TF_DUPSEG)) {
2415 /* Initialize SACK report block. */
2416 tp->reportblk.rblk_start = th->th_seq;
3a5d999b
SZ
2417 tp->reportblk.rblk_end = TCP_SACK_BLKEND(
2418 th->th_seq + tlen, thflags);
91489f6b 2419 }
984263bc
MD
2420 thflags = tcp_reass(tp, th, &tlen, m);
2421 tp->t_flags |= TF_ACKNOW;
2422 }
2423
2424 /*
2425 * Note the amount of data that peer has sent into
2426 * our window, in order to estimate the sender's
2427 * buffer size.
2428 */
6d49aa6f 2429 len = so->so_rcv.ssb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
984263bc
MD
2430 } else {
2431 m_freem(m);
2432 thflags &= ~TH_FIN;
2433 }
2434
2435 /*
2436 * If FIN is received ACK the FIN and let the user know
2437 * that the connection is closing.
2438 */
2439 if (thflags & TH_FIN) {
95b22adf 2440 if (!TCPS_HAVERCVDFIN(tp->t_state)) {
984263bc
MD
2441 socantrcvmore(so);
2442 /*
2443 * If connection is half-synchronized
2444 * (ie NEEDSYN flag on) then delay ACK,
2445 * so it may be piggybacked when SYN is sent.
2446 * Otherwise, since we received a FIN then no
2447 * more input can be expected, send ACK now.
2448 */
a48c5dd5
SZ
2449 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) {
2450 tcp_callout_reset(tp, tp->tt_delack,
2451 tcp_delacktime, tcp_timer_delack);
2452 } else {
984263bc 2453 tp->t_flags |= TF_ACKNOW;
a48c5dd5 2454 }
984263bc
MD
2455 tp->rcv_nxt++;
2456 }
984263bc 2457
61896e3c 2458 switch (tp->t_state) {
95b22adf 2459 /*
984263bc
MD
2460 * In SYN_RECEIVED and ESTABLISHED STATES
2461 * enter the CLOSE_WAIT state.
2462 */
2463 case TCPS_SYN_RECEIVED:
2464 tp->t_starttime = ticks;
2465 /*FALLTHROUGH*/
2466 case TCPS_ESTABLISHED:
2467 tp->t_state = TCPS_CLOSE_WAIT;
2468 break;
2469
95b22adf 2470 /*
984263bc
MD
2471 * If still in FIN_WAIT_1 STATE FIN has not been acked so
2472 * enter the CLOSING state.
2473 */
2474 case TCPS_FIN_WAIT_1:
2475 tp->t_state = TCPS_CLOSING;
2476 break;
2477
95b22adf 2478 /*
984263bc
MD
2479 * In FIN_WAIT_2 state enter the TIME_WAIT state,
2480 * starting the time-wait timer, turning off the other
2481 * standard timers.
2482 */
2483 case TCPS_FIN_WAIT_2:
2484 tp->t_state = TCPS_TIME_WAIT;
2485 tcp_canceltimers(tp);
01d3427a 2486 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp),
a48c5dd5 2487 tcp_timer_2msl);
984263bc
MD
2488 soisdisconnected(so);
2489 break;
2490
2491 /*
2492 * In TIME_WAIT state restart the 2 MSL time_wait timer.
2493 */
2494 case TCPS_TIME_WAIT:
01d3427a 2495 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp),
a48c5dd5 2496 tcp_timer_2msl);
984263bc
MD
2497 break;
2498 }
2499 }
61896e3c 2500
984263bc
MD
2501#ifdef TCPDEBUG
2502 if (so->so_options & SO_DEBUG)
f23061d4 2503 tcp_trace(TA_INPUT, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
984263bc
MD
2504#endif
2505
2506 /*
2507 * Return any desired output.
2508 */
2509 if (needoutput || (tp->t_flags & TF_ACKNOW))
f23061d4 2510 tcp_output(tp);
d58ca578 2511 tcp_sack_report_cleanup(tp);
002c1265 2512 return(IPPROTO_DONE);
984263bc
MD
2513
2514dropafterack:
2515 /*
2516 * Generate an ACK dropping incoming segment if it occupies
2517 * sequence space, where the ACK reflects our state.
2518 *
2519 * We can now skip the test for the RST flag since all
2520 * paths to this code happen after packets containing
2521 * RST have been dropped.
2522 *
2523 * In the SYN-RECEIVED state, don't send an ACK unless the
2524 * segment we received passes the SYN-RECEIVED ACK test.
2525 * If it fails send a RST. This breaks the loop in the
2526 * "LAND" DoS attack, and also prevents an ACK storm
2527 * between two listening ports that have been sent forged
2528 * SYN segments, each with the source address of the other.
2529 */
2530 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
2531 (SEQ_GT(tp->snd_una, th->th_ack) ||
2532 SEQ_GT(th->th_ack, tp->snd_max)) ) {
2533 rstreason = BANDLIM_RST_OPENPORT;
2534 goto dropwithreset;
2535 }
2536#ifdef TCPDEBUG
2537 if (so->so_options & SO_DEBUG)
f23061d4 2538 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
984263bc
MD
2539#endif
2540 m_freem(m);
2541 tp->t_flags |= TF_ACKNOW;
f23061d4 2542 tcp_output(tp);
d58ca578 2543 tcp_sack_report_cleanup(tp);
002c1265 2544 return(IPPROTO_DONE);
984263bc
MD
2545
2546dropwithreset:
2547 /*
2548 * Generate a RST, dropping incoming segment.
2549 * Make ACK acceptable to originator of segment.
2550 * Don't bother to respond if destination was broadcast/multicast.
2551 */
61896e3c 2552 if ((thflags & TH_RST) || m->m_flags & (M_BCAST | M_MCAST))
984263bc
MD
2553 goto drop;
2554 if (isipv6) {
2555 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
2556 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
2557 goto drop;
2558 } else {
2559 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
2560 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
95b22adf
JH
2561 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
2562 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
984263bc
MD
2563 goto drop;
2564 }
2565 /* IPv6 anycast check is done at tcp6_input() */
2566
2567 /*
2568 * Perform bandwidth limiting.
2569 */
2570#ifdef ICMP_BANDLIM
2571 if (badport_bandlim(rstreason) < 0)
2572 goto drop;
2573#endif
2574
2575#ifdef TCPDEBUG
2576 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
f23061d4 2577 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
984263bc
MD
2578#endif
2579 if (thflags & TH_ACK)
2580 /* mtod() below is safe as long as hdr dropping is delayed */
2581 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack,
2582 TH_RST);
2583 else {
2584 if (thflags & TH_SYN)
2585 tlen++;
2586 /* mtod() below is safe as long as hdr dropping is delayed */
61896e3c
JH
2587 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen,
2588 (tcp_seq)0, TH_RST | TH_ACK);
984263bc 2589 }
d58ca578
SZ
2590 if (tp != NULL)
2591 tcp_sack_report_cleanup(tp);
002c1265 2592 return(IPPROTO_DONE);
984263bc
MD
2593
2594drop:
2595 /*
2596 * Drop space held by incoming segment and return.
2597 */
2598#ifdef TCPDEBUG
2599 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
f23061d4 2600 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
984263bc
MD
2601#endif
2602 m_freem(m);
d58ca578
SZ
2603 if (tp != NULL)
2604 tcp_sack_report_cleanup(tp);
002c1265 2605 return(IPPROTO_DONE);
984263bc
MD
2606}
2607
2608/*
2609 * Parse TCP options and place in tcpopt.
2610 */
2611static void
95b22adf 2612tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn)
984263bc 2613{
91489f6b 2614 int opt, optlen, i;
984263bc
MD
2615
2616 to->to_flags = 0;
2617 for (; cnt > 0; cnt -= optlen, cp += optlen) {
2618 opt = cp[0];
2619 if (opt == TCPOPT_EOL)
2620 break;
2621 if (opt == TCPOPT_NOP)
2622 optlen = 1;
2623 else {
2624 if (cnt < 2)
2625 break;
2626 optlen = cp[1];
2627 if (optlen < 2 || optlen > cnt)
2628 break;
2629 }
2630 switch (opt) {
2631 case TCPOPT_MAXSEG:
2632 if (optlen != TCPOLEN_MAXSEG)
2633 continue;
2634 if (!is_syn)
2635 continue;
2636 to->to_flags |= TOF_MSS;
407e896e 2637 bcopy(cp + 2, &to->to_mss, sizeof to->to_mss);
984263bc
MD
2638 to->to_mss = ntohs(to->to_mss);
2639 break;
2640 case TCPOPT_WINDOW:
2641 if (optlen != TCPOLEN_WINDOW)
2642 continue;
95b22adf 2643 if (!is_syn)
984263bc
MD
2644 continue;
2645 to->to_flags |= TOF_SCALE;
2646 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT);
2647 break;
2648 case TCPOPT_TIMESTAMP:
2649 if (optlen != TCPOLEN_TIMESTAMP)
2650 continue;
2651 to->to_flags |= TOF_TS;
407e896e 2652 bcopy(cp + 2, &to->to_tsval, sizeof to->to_tsval);
984263bc 2653 to->to_tsval = ntohl(to->to_tsval);
407e896e 2654 bcopy(cp + 6, &to->to_tsecr, sizeof to->to_tsecr);
984263bc 2655 to->to_tsecr = ntohl(to->to_tsecr);
ad0af98b
ND
2656 /*
2657 * If echoed timestamp is later than the current time,
2658 * fall back to non RFC1323 RTT calculation.
2659 */
2660 if (to->to_tsecr != 0 && TSTMP_GT(to->to_tsecr, ticks))
2661 to->to_tsecr = 0;
984263bc 2662 break;
91489f6b
JH
2663 case TCPOPT_SACK_PERMITTED:
2664 if (optlen != TCPOLEN_SACK_PERMITTED)
2665 continue;
2666 if (!is_syn)
2667 continue;
2668 to->to_flags |= TOF_SACK_PERMITTED;
2669 break;
2670 case TCPOPT_SACK:
2671 if ((optlen - 2) & 0x07) /* not multiple of 8 */
2672 continue;
2673 to->to_nsackblocks = (optlen - 2) / 8;
2674 to->to_sackblocks = (struct raw_sackblock *) (cp + 2);
2675 to->to_flags |= TOF_SACK;
2676 for (i = 0; i < to->to_nsackblocks; i++) {
2677 struct raw_sackblock *r = &to->to_sackblocks[i];
2678
2679 r->rblk_start = ntohl(r->rblk_start);
2680 r->rblk_end = ntohl(r->rblk_end);
865b0477
SZ
2681
2682 if (SEQ_LEQ(r->rblk_end, r->rblk_start)) {
2683 /*
2684 * Invalid SACK block; discard all
2685 * SACK blocks
2686 */
02cc2f35 2687 tcpstat.tcps_rcvbadsackopt++;
865b0477
SZ
2688 to->to_nsackblocks = 0;
2689 to->to_sackblocks = NULL;
2690 to->to_flags &= ~TOF_SACK;
2691 break;
2692 }
91489f6b
JH
2693 }
2694 break;
b1992928
MD
2695#ifdef TCP_SIGNATURE
2696 /*
2697 * XXX In order to reply to a host which has set the
2698 * TCP_SIGNATURE option in its initial SYN, we have to
2699 * record the fact that the option was observed here
2700 * for the syncache code to perform the correct response.
2701 */
2702 case TCPOPT_SIGNATURE:
2703 if (optlen != TCPOLEN_SIGNATURE)
2704 continue;
2705 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN);
2706 break;
2707#endif /* TCP_SIGNATURE */
984263bc
MD
2708 default:
2709 continue;
2710 }
2711 }
2712}
2713
2714/*
2715 * Pull out of band byte out of a segment so
2716 * it doesn't appear in the user's data queue.
2717 * It is still reflected in the segment length for
2718 * sequencing purposes.
95b22adf 2719 * "off" is the delayed to be dropped hdrlen.
984263bc
MD
2720 */
2721static void
95b22adf 2722tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off)
984263bc
MD
2723{
2724 int cnt = off + th->th_urp - 1;
2725
2726 while (cnt >= 0) {
2727 if (m->m_len > cnt) {
2728 char *cp = mtod(m, caddr_t) + cnt;
2729 struct tcpcb *tp = sototcpcb(so);
2730
2731 tp->t_iobc = *cp;
2732 tp->t_oobflags |= TCPOOB_HAVEDATA;
95b22adf 2733 bcopy(cp + 1, cp, m->m_len - cnt - 1);
984263bc
MD
2734 m->m_len--;
2735 if (m->m_flags & M_PKTHDR)
2736 m->m_pkthdr.len--;
2737 return;
2738 }
2739 cnt -= m->m_len;
2740 m = m->m_next;
4090d6ff 2741 if (m == NULL)
984263bc
MD
2742 break;
2743 }
2744 panic("tcp_pulloutofband");
2745}
2746
2747/*
2748 * Collect new round-trip time estimate
2749 * and update averages and current timeout.
2750 */
2751static void
95b22adf 2752tcp_xmit_timer(struct tcpcb *tp, int rtt)
984263bc 2753{
2256ba69 2754 int delta;
984263bc
MD
2755
2756 tcpstat.tcps_rttupdated++;
2757 tp->t_rttupdated++;
2758 if (tp->t_srtt != 0) {
2759 /*
2760 * srtt is stored as fixed point with 5 bits after the
2761 * binary point (i.e., scaled by 8). The following magic
2762 * is equivalent to the smoothing algorithm in rfc793 with
2763 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
2764 * point). Adjust rtt to origin 0.
2765 */
2766 delta = ((rtt - 1) << TCP_DELTA_SHIFT)
2767 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
2768
2769 if ((tp->t_srtt += delta) <= 0)
2770 tp->t_srtt = 1;
2771
2772 /*
2773 * We accumulate a smoothed rtt variance (actually, a
2774 * smoothed mean difference), then set the retransmit
2775 * timer to smoothed rtt + 4 times the smoothed variance.
2776 * rttvar is stored as fixed point with 4 bits after the
2777 * binary point (scaled by 16). The following is
2778 * equivalent to rfc793 smoothing with an alpha of .75
2779 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces
2780 * rfc793's wired-in beta.
2781 */
2782 if (delta < 0)
2783 delta = -delta;
2784 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
2785 if ((tp->t_rttvar += delta) <= 0)
2786 tp->t_rttvar = 1;
2787 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
2788 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2789 } else {
2790 /*
2791 * No rtt measurement yet - use the unsmoothed rtt.
2792 * Set the variance to half the rtt (so our first
2793 * retransmit happens at 3*rtt).
2794 */
2795 tp->t_srtt = rtt << TCP_RTT_SHIFT;
2796 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
2797 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2798 }
2799 tp->t_rtttime = 0;
2800 tp->t_rxtshift = 0;
2801
2802 /*
2803 * the retransmit should happen at rtt + 4 * rttvar.
2804 * Because of the way we do the smoothing, srtt and rttvar
2805 * will each average +1/2 tick of bias. When we compute
2806 * the retransmit timer, we want 1/2 tick of rounding and
2807 * 1 extra tick because of +-1/2 tick uncertainty in the
2808 * firing of the timer. The bias will give us exactly the
2809 * 1.5 tick we need. But, because the bias is
2810 * statistical, we have to test that we don't drop below
2811 * the minimum feasible timer (which is 2 ticks).
2812 */
2813 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
2814 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);
2815
2816 /*
2817 * We received an ack for a packet that wasn't retransmitted;
2818 * it is probably safe to discard any error indications we've
2819 * received recently. This isn't quite right, but close enough
2820 * for now (a route might have failed after we sent a segment,
2821 * and the return path might not be symmetrical).
2822 */
2823 tp->t_softerror = 0;
2824}
2825
2826/*
2827 * Determine a reasonable value for maxseg size.
2828 * If the route is known, check route for mtu.
2829 * If none, use an mss that can be handled on the outgoing
2830 * interface without forcing IP to fragment; if bigger than
2831 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES
2832 * to utilize large mbufs. If no route is found, route has no mtu,
2833 * or the destination isn't local, use a default, hopefully conservative
2834 * size (usually 512 or the default IP max size, but no more than the mtu
2835 * of the interface), as we can't discover anything about intervening
2836 * gateways or networks. We also initialize the congestion/slow start
2837 * window to be a single segment if the destination isn't local.
2838 * While looking at the routing entry, we also initialize other path-dependent
2839 * parameters from pre-set or cached values in the routing entry.
2840 *
2841 * Also take into account the space needed for options that we
2842 * send regularly. Make maxseg shorter by that amount to assure
2843 * that we can send maxseg amount of data even when the options
2844 * are present. Store the upper limit of the length of options plus
2845 * data in maxopd.
2846 *
2847 * NOTE that this routine is only called when we process an incoming
2848 * segment, for outgoing segments only tcp_mssopt is called.
984263bc
MD
2849 */
2850void
95b22adf 2851tcp_mss(struct tcpcb *tp, int offer)
984263bc 2852{
2256ba69 2853 struct rtentry *rt;
984263bc 2854 struct ifnet *ifp;
2256ba69 2855 int rtt, mss;
984263bc
MD
2856 u_long bufsize;
2857 struct inpcb *inp = tp->t_inpcb;
2858 struct socket *so;
984263bc 2859#ifdef INET6
d24ce1dc 2860 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE);
984263bc
MD
2861 size_t min_protoh = isipv6 ?
2862 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) :
2863 sizeof(struct tcpiphdr);
2864#else
d24ce1dc 2865 const boolean_t isipv6 = FALSE;
984263bc
MD
2866 const size_t min_protoh = sizeof(struct tcpiphdr);
2867#endif
2868
2869 if (isipv6)
2870 rt = tcp_rtlookup6(&inp->inp_inc);
2871 else
2872 rt = tcp_rtlookup(&inp->inp_inc);
2873 if (rt == NULL) {
2874 tp->t_maxopd = tp->t_maxseg =
d24ce1dc 2875 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt);
984263bc
MD
2876 return;
2877 }
2878 ifp = rt->rt_ifp;
2879 so = inp->inp_socket;
2880
984263bc
MD
2881 /*
2882 * Offer == 0 means that there was no MSS on the SYN segment,
b235ad6d
MD
2883 * in this case we use either the interface mtu or tcp_mssdflt.
2884 *
2885 * An offer which is too large will be cut down later.
984263bc 2886 */
5b0b9fa5 2887 if (offer == 0) {
b235ad6d
MD
2888 if (isipv6) {
2889 if (in6_localaddr(&inp->in6p_faddr)) {
2890 offer = ND_IFINFO(rt->rt_ifp)->linkmtu -
2891 min_protoh;
2892 } else {
2893 offer = tcp_v6mssdflt;
2894 }
2895 } else {
2896 if (in_localaddr(inp->inp_faddr))
2897 offer = ifp->if_mtu - min_protoh;
2898 else
2899 offer = tcp_mssdflt;
2900 }
5b0b9fa5 2901 }
b235ad6d
MD
2902
2903 /*
2904 * Prevent DoS attack with too small MSS. Round up
2905 * to at least minmss.
2906 *
2907 * Sanity check: make sure that maxopd will be large
2908 * enough to allow some data on segments even is the
2909 * all the option space is used (40bytes). Otherwise
2910 * funny things may happen in tcp_output.
2911 */
2912 offer = max(offer, tcp_minmss);
2913 offer = max(offer, 64);
2914
27b8aee3 2915 rt->rt_rmx.rmx_mssopt = offer;
984263bc
MD
2916
2917 /*
2918 * While we're here, check if there's an initial rtt
2919 * or rttvar. Convert from the route-table units
2920 * to scaled multiples of the slow timeout timer.
2921 */
2922 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) {
2923 /*
2924 * XXX the lock bit for RTT indicates that the value
2925 * is also a minimum value; this is subject to time.
2926 */
2927 if (rt->rt_rmx.rmx_locks & RTV_RTT)
2928 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz);
2929 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE));
2930 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE;
2931 tcpstat.tcps_usedrtt++;
2932 if (rt->rt_rmx.rmx_rttvar) {
2933 tp->t_rttvar = rt->rt_rmx.rmx_rttvar /
2934 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE));
2935 tcpstat.tcps_usedrttvar++;
2936 } else {
2937 /* default variation is +- 1 rtt */
2938 tp->t_rttvar =
2939 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
2940 }
2941 TCPT_RANGESET(tp->t_rxtcur,
2942 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
2943 tp->t_rttmin, TCPTV_REXMTMAX);
2944 }
b235ad6d 2945
984263bc
MD
2946 /*
2947 * if there's an mtu associated with the route, use it
b235ad6d
MD
2948 * else, use the link mtu. Take the smaller of mss or offer
2949 * as our final mss.
984263bc 2950 */
b235ad6d 2951 if (rt->rt_rmx.rmx_mtu) {
984263bc 2952 mss = rt->rt_rmx.rmx_mtu - min_protoh;
b235ad6d
MD
2953 } else {
2954 if (isipv6)
698ac46c 2955 mss = ND_IFINFO(rt->rt_ifp)->linkmtu - min_protoh;
b235ad6d 2956 else
984263bc 2957 mss = ifp->if_mtu - min_protoh;
984263bc
MD
2958 }
2959 mss = min(mss, offer);
b235ad6d 2960
984263bc
MD
2961 /*
2962 * maxopd stores the maximum length of data AND options
2963 * in a segment; maxseg is the amount of data in a normal
2964 * segment. We need to store this value (maxopd) apart
2965 * from maxseg, because now every segment carries options
2966 * and thus we normally have somewhat less data in segments.
2967 */
2968 tp->t_maxopd = mss;
2969
61896e3c 2970 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP &&
27b8aee3 2971 ((tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP))
984263bc 2972 mss -= TCPOLEN_TSTAMP_APPA;
984263bc
MD
2973
2974#if (MCLBYTES & (MCLBYTES - 1)) == 0
2975 if (mss > MCLBYTES)
2976 mss &= ~(MCLBYTES-1);
2977#else
2978 if (mss > MCLBYTES)
2979 mss = mss / MCLBYTES * MCLBYTES;
2980#endif
2981 /*
2982 * If there's a pipesize, change the socket buffer
2983 * to that size. Make the socket buffers an integral
2984 * number of mss units; if the mss is larger than
2985 * the socket buffer, decrease the mss.
2986 */
2987#ifdef RTV_SPIPE
2988 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0)
2989#endif
6d49aa6f 2990 bufsize = so->so_snd.ssb_hiwat;
984263bc
MD
2991 if (bufsize < mss)
2992 mss = bufsize;
2993 else {
2994 bufsize = roundup(bufsize, mss);
2995 if (bufsize > sb_max)
2996 bufsize = sb_max;
6d49aa6f
MD
2997 if (bufsize > so->so_snd.ssb_hiwat)
2998 ssb_reserve(&so->so_snd, bufsize, so, NULL);
984263bc
MD
2999 }
3000 tp->t_maxseg = mss;
3001
3002#ifdef RTV_RPIPE
3003 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0)
3004#endif
6d49aa6f 3005 bufsize = so->so_rcv.ssb_hiwat;
984263bc
MD
3006 if (bufsize > mss) {
3007 bufsize = roundup(bufsize, mss);
3008 if (bufsize > sb_max)
3009 bufsize = sb_max;
6cef7136
MD
3010 if (bufsize > so->so_rcv.ssb_hiwat) {
3011 lwkt_gettoken(&so->so_rcv.ssb_token);
6d49aa6f 3012 ssb_reserve(&so->so_rcv, bufsize, so, NULL);
6cef7136
MD
3013 lwkt_reltoken(&so->so_rcv.ssb_token);
3014 }
984263bc
MD
3015 }
3016
3017 /*
697020f5
SZ
3018 * Set the slow-start flight size
3019 *
3020 * NOTE: t_maxseg must have been configured!
984263bc 3021 */
697020f5 3022 tp->snd_cwnd = tcp_initial_window(tp);
984263bc
MD
3023
3024 if (rt->rt_rmx.rmx_ssthresh) {
3025 /*
3026 * There's some sort of gateway or interface
3027 * buffer limit on the path. Use this to set
3028 * the slow start threshhold, but set the
3029 * threshold to no less than 2*mss.
3030 */
3031 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh);
3032 tcpstat.tcps_usedssthresh++;
3033 }
3034}
3035
3036/*
3037 * Determine the MSS option to send on an outgoing SYN.
3038 */
3039int
95b22adf 3040tcp_mssopt(struct tcpcb *tp)
984263bc
MD
3041{
3042 struct rtentry *rt;
3043#ifdef INET6
d24ce1dc
JH
3044 boolean_t isipv6 =
3045 ((tp->t_inpcb->inp_vflag & INP_IPV6) ? TRUE : FALSE);
984263bc
MD
3046 int min_protoh = isipv6 ?
3047 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) :
3048 sizeof(struct tcpiphdr);
3049#else
d24ce1dc 3050 const boolean_t isipv6 = FALSE;
984263bc
MD
3051 const size_t min_protoh = sizeof(struct tcpiphdr);
3052#endif
3053
3054 if (isipv6)
3055 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc);
3056 else
3057 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc);
3058 if (rt == NULL)
3059 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt);
3060
3061 return (rt->rt_ifp->if_mtu - min_protoh);
3062}
3063
984263bc
MD
3064/*
3065 * When a partial ack arrives, force the retransmission of the
91489f6b
JH
3066 * next unacknowledged segment. Do not exit Fast Recovery.
3067 *
3068 * Implement the Slow-but-Steady variant of NewReno by restarting the
3069 * the retransmission timer. Turn it off here so it can be restarted
3070 * later in tcp_output().
984263bc
MD
3071 */
3072static void
91489f6b 3073tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th, int acked)
984263bc 3074{
91489f6b
JH
3075 tcp_seq old_snd_nxt = tp->snd_nxt;
3076 u_long ocwnd = tp->snd_cwnd;
984263bc 3077
a48c5dd5 3078 tcp_callout_stop(tp, tp->tt_rexmt);
984263bc
MD
3079 tp->t_rtttime = 0;
3080 tp->snd_nxt = th->th_ack;
91489f6b
JH
3081 /* Set snd_cwnd to one segment beyond acknowledged offset. */
3082 tp->snd_cwnd = tp->t_maxseg;
984263bc 3083 tp->t_flags |= TF_ACKNOW;
f23061d4 3084 tcp_output(tp);
91489f6b
JH
3085 if (SEQ_GT(old_snd_nxt, tp->snd_nxt))
3086 tp->snd_nxt = old_snd_nxt;
3087 /* partial window deflation */
68947d12
ND
3088 if (ocwnd > acked)
3089 tp->snd_cwnd = ocwnd - acked + tp->t_maxseg;
3090 else
3091 tp->snd_cwnd = tp->t_maxseg;
91489f6b
JH
3092}
3093
3094/*
3095 * In contrast to the Slow-but-Steady NewReno variant,
3096 * we do not reset the retransmission timer for SACK retransmissions,
3097 * except when retransmitting snd_una.
3098 */
3099static void
3100tcp_sack_rexmt(struct tcpcb *tp, struct tcphdr *th)
3101{
3102 uint32_t pipe, seglen;
3103 tcp_seq nextrexmt;
3104 boolean_t lostdup;
3105 tcp_seq old_snd_nxt = tp->snd_nxt;
3106 u_long ocwnd = tp->snd_cwnd;
3107 int nseg = 0; /* consecutive new segments */
3108#define MAXBURST 4 /* limit burst of new packets on partial ack */
3109
3110 tp->t_rtttime = 0;
3111 pipe = tcp_sack_compute_pipe(tp);
3112 while ((tcp_seq_diff_t)(ocwnd - pipe) >= (tcp_seq_diff_t)tp->t_maxseg &&
3113 (!tcp_do_smartsack || nseg < MAXBURST) &&
3114 tcp_sack_nextseg(tp, &nextrexmt, &seglen, &lostdup)) {
3115 uint32_t sent;
3116 tcp_seq old_snd_max;
3117 int error;
3118
98cb2337
MD
3119 if (nextrexmt == tp->snd_max)
3120 ++nseg;
91489f6b
JH
3121 tp->snd_nxt = nextrexmt;
3122 tp->snd_cwnd = nextrexmt - tp->snd_una + seglen;
3123 old_snd_max = tp->snd_max;
3124 if (nextrexmt == tp->snd_una)
a48c5dd5 3125 tcp_callout_stop(tp, tp->tt_rexmt);
91489f6b
JH
3126 error = tcp_output(tp);
3127 if (error != 0)
3128 break;
3129 sent = tp->snd_nxt - nextrexmt;
3130 if (sent <= 0)
3131 break;
3132 if (!lostdup)
3133 pipe += sent;
3134 tcpstat.tcps_sndsackpack++;
3135 tcpstat.tcps_sndsackbyte += sent;
3136 if (SEQ_LT(nextrexmt, old_snd_max) &&
3137 SEQ_LT(tp->rexmt_high, tp->snd_nxt))
3138 tp->rexmt_high = seq_min(tp->snd_nxt, old_snd_max);
3139 }
3140 if (SEQ_GT(old_snd_nxt, tp->snd_nxt))
3141 tp->snd_nxt = old_snd_nxt;
984263bc 3142 tp->snd_cwnd = ocwnd;
984263bc 3143}
0ecd93f9
MD
3144
3145/*
3146 * Reset idle time and keep-alive timer, typically called when a valid
3147 * tcp packet is received but may also be called when FASTKEEP is set
3148 * to prevent the previous long-timeout from calculating to a drop.
3149 *
3150 * Only update t_rcvtime for non-SYN packets.
3151 *
3152 * Handle the case where one side thinks the connection is established
3153 * but the other side has, say, rebooted without cleaning out the
3154 * connection. The SYNs could be construed as an attack and wind
3155 * up ignored, but in case it isn't an attack we can validate the
3156 * connection by forcing a keepalive.
3157 */
3158void
3159tcp_timer_keep_activity(struct tcpcb *tp, int thflags)
3160{
3161 if (TCPS_HAVEESTABLISHED(tp->t_state)) {
3162 if ((thflags & (TH_SYN | TH_ACK)) == TH_SYN) {
3163 tp->t_flags |= TF_KEEPALIVE;
3164 tcp_callout_reset(tp, tp->tt_keep, hz / 2,
3165 tcp_timer_keep);
3166 } else {
3167 tp->t_rcvtime = ticks;
3168 tp->t_flags &= ~TF_KEEPALIVE;
3169 tcp_callout_reset(tp, tp->tt_keep,
fb8d5c6d 3170 tp->t_keepidle,
0ecd93f9
MD
3171 tcp_timer_keep);
3172 }
3173 }
3174}
01d3427a
SZ
3175
3176static int
3177tcp_rmx_msl(const struct tcpcb *tp)
3178{
3179 struct rtentry *rt;
3180 struct inpcb *inp = tp->t_inpcb;
9855a4ef 3181 int msl;
01d3427a
SZ
3182#ifdef INET6
3183 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE);
3184#else
3185 const boolean_t isipv6 = FALSE;
3186#endif
3187
3188 if (isipv6)
3189 rt = tcp_rtlookup6(&inp->inp_inc);
3190 else
3191 rt = tcp_rtlookup(&inp->inp_inc);
3192 if (rt == NULL || rt->rt_rmx.rmx_msl == 0)
3193 return tcp_msl;
3194
9855a4ef
SZ
3195 msl = (rt->rt_rmx.rmx_msl * hz) / 1000;
3196 if (msl == 0)
3197 msl = 1;
3198
3199 return msl;
01d3427a 3200}
8651f7f8
SZ
3201
3202static void
3203tcp_established(struct tcpcb *tp)
3204{
3205 tp->t_state = TCPS_ESTABLISHED;
fb8d5c6d 3206 tcp_callout_reset(tp, tp->tt_keep, tp->t_keepidle, tcp_timer_keep);
be34e534 3207
d5082e3d 3208 if (tp->t_rxtsyn > 0) {
48a4676d
SZ
3209 /*
3210 * RFC6298:
3211 * "If the timer expires awaiting the ACK of a SYN segment
3212 * and the TCP implementation is using an RTO less than 3
3213 * seconds, the RTO MUST be re-initialized to 3 seconds
3214 * when data transmission begins"
3215 */
3216 if (tp->t_rxtcur < TCPTV_RTOBASE3)
3217 tp->t_rxtcur = TCPTV_RTOBASE3;
be34e534 3218 }
8651f7f8 3219}