kernel - Fix TCP MSS calculation
[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 $
5de23090 68 * $DragonFly: src/sys/netinet/tcp_input.c,v 1.68 2008/08/22 09:14:17 sephe Exp $
984263bc
MD
69 */
70
71#include "opt_ipfw.h" /* for ipfw_fwd */
72#include "opt_inet6.h"
73#include "opt_ipsec.h"
74#include "opt_tcpdebug.h"
75#include "opt_tcp_input.h"
76
77#include <sys/param.h>
78#include <sys/systm.h>
79#include <sys/kernel.h>
80#include <sys/sysctl.h>
81#include <sys/malloc.h>
82#include <sys/mbuf.h>
83#include <sys/proc.h> /* for proc0 declaration */
84#include <sys/protosw.h>
85#include <sys/socket.h>
86#include <sys/socketvar.h>
87#include <sys/syslog.h>
3f9db7f8 88#include <sys/in_cksum.h>
984263bc
MD
89
90#include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */
a00138cb 91#include <machine/stdarg.h>
984263bc
MD
92
93#include <net/if.h>
94#include <net/route.h>
95
96#include <netinet/in.h>
97#include <netinet/in_systm.h>
98#include <netinet/ip.h>
95b22adf 99#include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */
984263bc 100#include <netinet/in_var.h>
95b22adf 101#include <netinet/icmp_var.h> /* for ICMP_BANDLIM */
984263bc
MD
102#include <netinet/in_pcb.h>
103#include <netinet/ip_var.h>
104#include <netinet/ip6.h>
105#include <netinet/icmp6.h>
106#include <netinet6/nd6.h>
107#include <netinet6/ip6_var.h>
108#include <netinet6/in6_pcb.h>
109#include <netinet/tcp.h>
110#include <netinet/tcp_fsm.h>
111#include <netinet/tcp_seq.h>
112#include <netinet/tcp_timer.h>
a48c5dd5 113#include <netinet/tcp_timer2.h>
984263bc
MD
114#include <netinet/tcp_var.h>
115#include <netinet6/tcp6_var.h>
116#include <netinet/tcpip.h>
95b22adf 117
984263bc
MD
118#ifdef TCPDEBUG
119#include <netinet/tcp_debug.h>
120
95b22adf 121u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */
984263bc 122struct tcphdr tcp_savetcp;
95b22adf 123#endif
984263bc
MD
124
125#ifdef FAST_IPSEC
bf844ffa
JH
126#include <netproto/ipsec/ipsec.h>
127#include <netproto/ipsec/ipsec6.h>
984263bc
MD
128#endif
129
130#ifdef IPSEC
131#include <netinet6/ipsec.h>
132#include <netinet6/ipsec6.h>
d2438d69 133#include <netproto/key/key.h>
95b22adf 134#endif
984263bc 135
984263bc
MD
136MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry");
137
984263bc 138tcp_cc tcp_ccgen;
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
8d573eef 170int tcp_do_rfc3390 = 1;
4b52d5ee
JH
171SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW,
172 &tcp_do_rfc3390, 0,
173 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)");
174
efd4b327
JH
175static int tcp_do_eifel_detect = 1;
176SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW,
177 &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)");
178
8acdb67c
JH
179static int tcp_do_abc = 1;
180SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc, CTLFLAG_RW,
181 &tcp_do_abc, 0,
182 "TCP Appropriate Byte Counting (RFC 3465)");
183
91489f6b
JH
184/*
185 * Define as tunable for easy testing with SACK on and off.
186 * Warning: do not change setting in the middle of an existing active TCP flow,
187 * else strange things might happen to that flow.
188 */
6e5bbdda 189int tcp_do_sack = 1;
91489f6b
JH
190SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW,
191 &tcp_do_sack, 0, "Enable SACK Algorithms");
192
193int tcp_do_smartsack = 1;
194SYSCTL_INT(_net_inet_tcp, OID_AUTO, smartsack, CTLFLAG_RW,
195 &tcp_do_smartsack, 0, "Enable Smart SACK Algorithms");
196
3edf7c37
RG
197SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0,
198 "TCP Segment Reassembly Queue");
199
200int tcp_reass_maxseg = 0;
201SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD,
202 &tcp_reass_maxseg, 0,
203 "Global maximum number of TCP Segments in Reassembly Queue");
204
205int tcp_reass_qsize = 0;
206SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD,
207 &tcp_reass_qsize, 0,
208 "Global number of TCP Segments currently in Reassembly Queue");
209
210static int tcp_reass_overflows = 0;
211SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD,
212 &tcp_reass_overflows, 0,
213 "Global number of TCP Segment Reassembly Queue Overflows");
214
5b0b9fa5
PA
215int tcp_do_autorcvbuf = 1;
216SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW,
217 &tcp_do_autorcvbuf, 0, "Enable automatic receive buffer sizing");
218
219int tcp_autorcvbuf_inc = 16*1024;
220SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW,
221 &tcp_autorcvbuf_inc, 0,
222 "Incrementor step size of automatic receive buffer");
223
46e92930 224int tcp_autorcvbuf_max = 2*1024*1024;
5b0b9fa5
PA
225SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW,
226 &tcp_autorcvbuf_max, 0, "Max size of automatic receive buffer");
227
228
95b22adf 229static void tcp_dooptions(struct tcpopt *, u_char *, int, boolean_t);
984263bc
MD
230static void tcp_pulloutofband(struct socket *,
231 struct tcphdr *, struct mbuf *, int);
232static int tcp_reass(struct tcpcb *, struct tcphdr *, int *,
233 struct mbuf *);
234static void tcp_xmit_timer(struct tcpcb *, int);
91489f6b
JH
235static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *, int);
236static void tcp_sack_rexmt(struct tcpcb *, struct tcphdr *);
984263bc
MD
237
238/* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */
239#ifdef INET6
240#define ND6_HINT(tp) \
241do { \
242 if ((tp) && (tp)->t_inpcb && \
61896e3c 243 ((tp)->t_inpcb->inp_vflag & INP_IPV6) && \
984263bc
MD
244 (tp)->t_inpcb->in6p_route.ro_rt) \
245 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \
246} while (0)
247#else
248#define ND6_HINT(tp)
249#endif
250
251/*
252 * Indicate whether this ack should be delayed. We can delay the ack if
253 * - delayed acks are enabled and
254 * - there is no delayed ack timer in progress and
255 * - our last ack wasn't a 0-sized window. We never want to delay
256 * the ack that opens up a 0-sized window.
257 */
258#define DELAY_ACK(tp) \
a48c5dd5 259 (tcp_delack_enabled && !tcp_callout_pending(tp, tp->tt_delack) && \
61896e3c 260 !(tp->t_flags & TF_RXWIN0SENT))
984263bc 261
df9d7670
JH
262#define acceptable_window_update(tp, th, tiwin) \
263 (SEQ_LT(tp->snd_wl1, th->th_seq) || \
264 (tp->snd_wl1 == th->th_seq && \
265 (SEQ_LT(tp->snd_wl2, th->th_ack) || \
266 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))
267
984263bc 268static int
95b22adf 269tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m)
984263bc
MD
270{
271 struct tseg_qent *q;
272 struct tseg_qent *p = NULL;
984263bc
MD
273 struct tseg_qent *te;
274 struct socket *so = tp->t_inpcb->inp_socket;
275 int flags;
276
277 /*
61896e3c 278 * Call with th == NULL after become established to
984263bc
MD
279 * force pre-ESTABLISHED data up to user socket.
280 */
61896e3c 281 if (th == NULL)
984263bc
MD
282 goto present;
283
3edf7c37
RG
284 /*
285 * Limit the number of segments in the reassembly queue to prevent
286 * holding on to too many segments (and thus running out of mbufs).
287 * Make sure to let the missing segment through which caused this
288 * queue. Always keep one global queue entry spare to be able to
289 * process the missing segment.
290 */
291 if (th->th_seq != tp->rcv_nxt &&
292 tcp_reass_qsize + 1 >= tcp_reass_maxseg) {
293 tcp_reass_overflows++;
294 tcpstat.tcps_rcvmemdrop++;
295 m_freem(m);
91489f6b
JH
296 /* no SACK block to report */
297 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
3edf7c37
RG
298 return (0);
299 }
300
ba4e3dbe 301 /* Allocate a new queue entry. */
984263bc 302 MALLOC(te, struct tseg_qent *, sizeof(struct tseg_qent), M_TSEGQ,
ba4e3dbe 303 M_INTWAIT | M_NULLOK);
984263bc
MD
304 if (te == NULL) {
305 tcpstat.tcps_rcvmemdrop++;
306 m_freem(m);
91489f6b
JH
307 /* no SACK block to report */
308 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
984263bc
MD
309 return (0);
310 }
3edf7c37 311 tcp_reass_qsize++;
984263bc
MD
312
313 /*
314 * Find a segment which begins after this one does.
315 */
316 LIST_FOREACH(q, &tp->t_segq, tqe_q) {
317 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
318 break;
319 p = q;
320 }
321
322 /*
323 * If there is a preceding segment, it may provide some of
324 * our data already. If so, drop the data from the incoming
325 * segment. If it provides all of our data, drop us.
326 */
327 if (p != NULL) {
76cf5e41 328 tcp_seq_diff_t i;
91489f6b 329
984263bc
MD
330 /* conversion to int (in i) handles seq wraparound */
331 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
91489f6b
JH
332 if (i > 0) { /* overlaps preceding segment */
333 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG);
334 /* enclosing block starts w/ preceding segment */
335 tp->encloseblk.rblk_start = p->tqe_th->th_seq;
984263bc 336 if (i >= *tlenp) {
91489f6b
JH
337 /* preceding encloses incoming segment */
338 tp->encloseblk.rblk_end = p->tqe_th->th_seq +
339 p->tqe_len;
984263bc
MD
340 tcpstat.tcps_rcvduppack++;
341 tcpstat.tcps_rcvdupbyte += *tlenp;
342 m_freem(m);
efda3bd0 343 kfree(te, M_TSEGQ);
3edf7c37 344 tcp_reass_qsize--;
984263bc
MD
345 /*
346 * Try to present any queued data
347 * at the left window edge to the user.
348 * This is needed after the 3-WHS
349 * completes.
350 */
351 goto present; /* ??? */
352 }
353 m_adj(m, i);
354 *tlenp -= i;
355 th->th_seq += i;
91489f6b
JH
356 /* incoming segment end is enclosing block end */
357 tp->encloseblk.rblk_end = th->th_seq + *tlenp +
358 ((th->th_flags & TH_FIN) != 0);
359 /* trim end of reported D-SACK block */
360 tp->reportblk.rblk_end = th->th_seq;
984263bc
MD
361 }
362 }
363 tcpstat.tcps_rcvoopack++;
364 tcpstat.tcps_rcvoobyte += *tlenp;
365
366 /*
367 * While we overlap succeeding segments trim them or,
368 * if they are completely covered, dequeue them.
369 */
370 while (q) {
76cf5e41 371 tcp_seq_diff_t i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
91489f6b
JH
372 tcp_seq qend = q->tqe_th->th_seq + q->tqe_len;
373 struct tseg_qent *nq;
374
984263bc
MD
375 if (i <= 0)
376 break;
91489f6b
JH
377 if (!(tp->t_flags & TF_DUPSEG)) { /* first time through */
378 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG);
379 tp->encloseblk = tp->reportblk;
380 /* report trailing duplicate D-SACK segment */
381 tp->reportblk.rblk_start = q->tqe_th->th_seq;
382 }
383 if ((tp->t_flags & TF_ENCLOSESEG) &&
384 SEQ_GT(qend, tp->encloseblk.rblk_end)) {
385 /* extend enclosing block if one exists */
386 tp->encloseblk.rblk_end = qend;
387 }
984263bc
MD
388 if (i < q->tqe_len) {
389 q->tqe_th->th_seq += i;
390 q->tqe_len -= i;
391 m_adj(q->tqe_m, i);
392 break;
393 }
394
395 nq = LIST_NEXT(q, tqe_q);
396 LIST_REMOVE(q, tqe_q);
397 m_freem(q->tqe_m);
efda3bd0 398 kfree(q, M_TSEGQ);
3edf7c37 399 tcp_reass_qsize--;
984263bc
MD
400 q = nq;
401 }
402
403 /* Insert the new segment queue entry into place. */
404 te->tqe_m = m;
405 te->tqe_th = th;
406 te->tqe_len = *tlenp;
407
91489f6b
JH
408 /* check if can coalesce with following segment */
409 if (q != NULL && (th->th_seq + *tlenp == q->tqe_th->th_seq)) {
410 tcp_seq tend = te->tqe_th->th_seq + te->tqe_len;
411
412 te->tqe_len += q->tqe_len;
a174690a 413 if (q->tqe_th->th_flags & TH_FIN)
f16f8cc3 414 te->tqe_th->th_flags |= TH_FIN;
91489f6b
JH
415 m_cat(te->tqe_m, q->tqe_m);
416 tp->encloseblk.rblk_end = tend;
417 /*
418 * When not reporting a duplicate segment, use
419 * the larger enclosing block as the SACK block.
420 */
421 if (!(tp->t_flags & TF_DUPSEG))
422 tp->reportblk.rblk_end = tend;
423 LIST_REMOVE(q, tqe_q);
efda3bd0 424 kfree(q, M_TSEGQ);
91489f6b
JH
425 tcp_reass_qsize--;
426 }
427
984263bc
MD
428 if (p == NULL) {
429 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q);
430 } else {
91489f6b
JH
431 /* check if can coalesce with preceding segment */
432 if (p->tqe_th->th_seq + p->tqe_len == th->th_seq) {
a174690a
JH
433 p->tqe_len += te->tqe_len;
434 m_cat(p->tqe_m, te->tqe_m);
91489f6b
JH
435 tp->encloseblk.rblk_start = p->tqe_th->th_seq;
436 /*
437 * When not reporting a duplicate segment, use
438 * the larger enclosing block as the SACK block.
439 */
440 if (!(tp->t_flags & TF_DUPSEG))
441 tp->reportblk.rblk_start = p->tqe_th->th_seq;
efda3bd0 442 kfree(te, M_TSEGQ);
a174690a 443 tcp_reass_qsize--;
91489f6b
JH
444 } else
445 LIST_INSERT_AFTER(p, te, tqe_q);
984263bc
MD
446 }
447
448present:
449 /*
450 * Present data to user, advancing rcv_nxt through
451 * completed sequence space.
452 */
453 if (!TCPS_HAVEESTABLISHED(tp->t_state))
454 return (0);
455 q = LIST_FIRST(&tp->t_segq);
61896e3c 456 if (q == NULL || q->tqe_th->th_seq != tp->rcv_nxt)
984263bc 457 return (0);
91489f6b
JH
458 tp->rcv_nxt += q->tqe_len;
459 if (!(tp->t_flags & TF_DUPSEG)) {
460 /* no SACK block to report since ACK advanced */
461 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
462 }
463 /* no enclosing block to report since ACK advanced */
464 tp->t_flags &= ~TF_ENCLOSESEG;
465 flags = q->tqe_th->th_flags & TH_FIN;
466 LIST_REMOVE(q, tqe_q);
467 KASSERT(LIST_EMPTY(&tp->t_segq) ||
468 LIST_FIRST(&tp->t_segq)->tqe_th->th_seq != tp->rcv_nxt,
469 ("segment not coalesced"));
470 if (so->so_state & SS_CANTRCVMORE)
471 m_freem(q->tqe_m);
472 else
6d49aa6f 473 ssb_appendstream(&so->so_rcv, q->tqe_m);
efda3bd0 474 kfree(q, M_TSEGQ);
91489f6b 475 tcp_reass_qsize--;
984263bc
MD
476 ND6_HINT(tp);
477 sorwakeup(so);
478 return (flags);
479}
480
481/*
482 * TCP input routine, follows pages 65-76 of the
483 * protocol specification dated September, 1981 very closely.
484 */
485#ifdef INET6
486int
95b22adf 487tcp6_input(struct mbuf **mp, int *offp, int proto)
984263bc 488{
2256ba69 489 struct mbuf *m = *mp;
984263bc
MD
490 struct in6_ifaddr *ia6;
491
492 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE);
493
494 /*
495 * draft-itojun-ipv6-tcp-to-anycast
496 * better place to put this in?
497 */
498 ia6 = ip6_getdstifaddr(m);
d24ce1dc 499 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) {
984263bc
MD
500 struct ip6_hdr *ip6;
501
502 ip6 = mtod(m, struct ip6_hdr *);
503 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
f23061d4 504 offsetof(struct ip6_hdr, ip6_dst));
d24ce1dc 505 return (IPPROTO_DONE);
984263bc
MD
506 }
507
508 tcp_input(m, *offp, proto);
d24ce1dc 509 return (IPPROTO_DONE);
984263bc
MD
510}
511#endif
512
513void
a00138cb 514tcp_input(struct mbuf *m, ...)
984263bc 515{
a00138cb
JS
516 __va_list ap;
517 int off0, proto;
2256ba69
RG
518 struct tcphdr *th;
519 struct ip *ip = NULL;
520 struct ipovly *ipov;
521 struct inpcb *inp = NULL;
984263bc
MD
522 u_char *optp = NULL;
523 int optlen = 0;
524 int len, tlen, off;
525 int drop_hdrlen;
2256ba69
RG
526 struct tcpcb *tp = NULL;
527 int thflags;
984263bc 528 struct socket *so = 0;
61896e3c
JH
529 int todrop, acked;
530 boolean_t ourfinisacked, needoutput = FALSE;
984263bc 531 u_long tiwin;
61896e3c 532 int recvwin;
984263bc
MD
533 struct tcpopt to; /* options in this segment */
534 struct rmxp_tao *taop; /* pointer to our TAO cache entry */
535 struct rmxp_tao tao_noncached; /* in case there's no cached entry */
536 struct sockaddr_in *next_hop = NULL;
537 int rstreason; /* For badport_bandlim accounting purposes */
d371a63a 538 int cpu;
984263bc
MD
539 struct ip6_hdr *ip6 = NULL;
540#ifdef INET6
d24ce1dc 541 boolean_t isipv6;
984263bc 542#else
d24ce1dc 543 const boolean_t isipv6 = FALSE;
984263bc
MD
544#endif
545#ifdef TCPDEBUG
546 short ostate = 0;
547#endif
548
a00138cb
JS
549 __va_start(ap, m);
550 off0 = __va_arg(ap, int);
551 proto = __va_arg(ap, int);
552 __va_end(ap);
553
d24ce1dc
JH
554 tcpstat.tcps_rcvtotal++;
555
5de23090
SZ
556 if (m->m_pkthdr.fw_flags & IPFORWARD_MBUF_TAGGED) {
557 struct m_tag *mtag;
558
559 mtag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL);
560 KKASSERT(mtag != NULL);
561 next_hop = m_tag_data(mtag);
984263bc 562 }
d24ce1dc 563
984263bc 564#ifdef INET6
d24ce1dc 565 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE;
984263bc 566#endif
984263bc
MD
567
568 if (isipv6) {
569 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */
570 ip6 = mtod(m, struct ip6_hdr *);
407e896e 571 tlen = (sizeof *ip6) + ntohs(ip6->ip6_plen) - off0;
984263bc
MD
572 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) {
573 tcpstat.tcps_rcvbadsum++;
574 goto drop;
575 }
576 th = (struct tcphdr *)((caddr_t)ip6 + off0);
577
578 /*
579 * Be proactive about unspecified IPv6 address in source.
580 * As we use all-zero to indicate unbounded/unconnected pcb,
581 * unspecified IPv6 address can be used to confuse us.
582 *
583 * Note that packets with unspecified IPv6 destination is
584 * already dropped in ip6_input.
585 */
586 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
587 /* XXX stat */
588 goto drop;
589 }
590 } else {
591 /*
592 * Get IP and TCP header together in first mbuf.
593 * Note: IP leaves IP header in first mbuf.
594 */
595 if (off0 > sizeof(struct ip)) {
bddf0751 596 ip_stripoptions(m);
984263bc
MD
597 off0 = sizeof(struct ip);
598 }
55d829f8
JH
599 /* already checked and pulled up in ip_demux() */
600 KASSERT(m->m_len >= sizeof(struct tcpiphdr),
61896e3c 601 ("TCP header not in one mbuf: m->m_len %d", m->m_len));
984263bc
MD
602 ip = mtod(m, struct ip *);
603 ipov = (struct ipovly *)ip;
604 th = (struct tcphdr *)((caddr_t)ip + off0);
605 tlen = ip->ip_len;
606
607 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
608 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
609 th->th_sum = m->m_pkthdr.csum_data;
610 else
611 th->th_sum = in_pseudo(ip->ip_src.s_addr,
612 ip->ip_dst.s_addr,
613 htonl(m->m_pkthdr.csum_data +
614 ip->ip_len +
615 IPPROTO_TCP));
616 th->th_sum ^= 0xffff;
617 } else {
618 /*
619 * Checksum extended TCP header and data.
620 */
621 len = sizeof(struct ip) + tlen;
407e896e 622 bzero(ipov->ih_x1, sizeof ipov->ih_x1);
984263bc
MD
623 ipov->ih_len = (u_short)tlen;
624 ipov->ih_len = htons(ipov->ih_len);
625 th->th_sum = in_cksum(m, len);
626 }
627 if (th->th_sum) {
628 tcpstat.tcps_rcvbadsum++;
629 goto drop;
630 }
631#ifdef INET6
632 /* Re-initialization for later version check */
633 ip->ip_v = IPVERSION;
634#endif
635 }
636
637 /*
638 * Check that TCP offset makes sense,
639 * pull out TCP options and adjust length. XXX
640 */
641 off = th->th_off << 2;
55d829f8
JH
642 /* already checked and pulled up in ip_demux() */
643 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen,
61896e3c 644 ("bad TCP data offset %d (tlen %d)", off, tlen));
984263bc
MD
645 tlen -= off; /* tlen is used instead of ti->ti_len */
646 if (off > sizeof(struct tcphdr)) {
647 if (isipv6) {
648 IP6_EXTHDR_CHECK(m, off0, off, );
649 ip6 = mtod(m, struct ip6_hdr *);
650 th = (struct tcphdr *)((caddr_t)ip6 + off0);
651 } else {
55d829f8
JH
652 /* already pulled up in ip_demux() */
653 KASSERT(m->m_len >= sizeof(struct ip) + off,
61896e3c
JH
654 ("TCP header and options not in one mbuf: "
655 "m_len %d, off %d", m->m_len, off));
984263bc
MD
656 }
657 optlen = off - sizeof(struct tcphdr);
658 optp = (u_char *)(th + 1);
659 }
660 thflags = th->th_flags;
661
662#ifdef TCP_DROP_SYNFIN
663 /*
664 * If the drop_synfin option is enabled, drop all packets with
665 * both the SYN and FIN bits set. This prevents e.g. nmap from
666 * identifying the TCP/IP stack.
667 *
668 * This is a violation of the TCP specification.
669 */
61896e3c 670 if (drop_synfin && (thflags & (TH_SYN | TH_FIN)) == (TH_SYN | TH_FIN))
984263bc
MD
671 goto drop;
672#endif
673
674 /*
675 * Convert TCP protocol specific fields to host format.
676 */
677 th->th_seq = ntohl(th->th_seq);
678 th->th_ack = ntohl(th->th_ack);
679 th->th_win = ntohs(th->th_win);
680 th->th_urp = ntohs(th->th_urp);
681
682 /*
d24ce1dc 683 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options,
984263bc
MD
684 * until after ip6_savecontrol() is called and before other functions
685 * which don't want those proto headers.
686 * Because ip6_savecontrol() is going to parse the mbuf to
687 * search for data to be passed up to user-land, it wants mbuf
688 * parameters to be unchanged.
689 * XXX: the call of ip6_savecontrol() has been obsoleted based on
690 * latest version of the advanced API (20020110).
691 */
692 drop_hdrlen = off0 + off;
693
694 /*
695 * Locate pcb for segment.
696 */
697findpcb:
698 /* IPFIREWALL_FORWARD section */
d24ce1dc 699 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */
984263bc
MD
700 /*
701 * Transparently forwarded. Pretend to be the destination.
d24ce1dc 702 * already got one like this?
984263bc 703 */
6ca1a1cd 704 cpu = mycpu->gd_cpuid;
6ca1a1cd 705 inp = in_pcblookup_hash(&tcbinfo[cpu],
d371a63a 706 ip->ip_src, th->th_sport,
984263bc
MD
707 ip->ip_dst, th->th_dport,
708 0, m->m_pkthdr.rcvif);
709 if (!inp) {
83be63fe
JH
710 /*
711 * It's new. Try to find the ambushing socket.
712 */
713
714 /*
715 * The rest of the ipfw code stores the port in
716 * host order. XXX
717 * (The IP address is still in network order.)
718 */
719 in_port_t dport = next_hop->sin_port ?
720 htons(next_hop->sin_port) :
721 th->th_dport;
722
d371a63a 723 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport,
83be63fe 724 next_hop->sin_addr.s_addr, dport);
d371a63a 725 inp = in_pcblookup_hash(&tcbinfo[cpu],
984263bc 726 ip->ip_src, th->th_sport,
83be63fe 727 next_hop->sin_addr, dport,
984263bc
MD
728 1, m->m_pkthdr.rcvif);
729 }
730 } else {
6ca1a1cd 731 if (isipv6) {
d371a63a 732 inp = in6_pcblookup_hash(&tcbinfo[0],
984263bc
MD
733 &ip6->ip6_src, th->th_sport,
734 &ip6->ip6_dst, th->th_dport,
735 1, m->m_pkthdr.rcvif);
6ca1a1cd 736 } else {
6ca1a1cd 737 cpu = mycpu->gd_cpuid;
6ca1a1cd 738 inp = in_pcblookup_hash(&tcbinfo[cpu],
984263bc
MD
739 ip->ip_src, th->th_sport,
740 ip->ip_dst, th->th_dport,
741 1, m->m_pkthdr.rcvif);
6ca1a1cd 742 }
984263bc 743 }
984263bc
MD
744
745 /*
746 * If the state is CLOSED (i.e., TCB does not exist) then
747 * all data in the incoming segment is discarded.
748 * If the TCB exists but is in CLOSED state, it is embryonic,
749 * but should either do a listen or a connect soon.
750 */
751 if (inp == NULL) {
752 if (log_in_vain) {
753#ifdef INET6
754 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2];
755#else
1141eb20
JH
756 char dbuf[sizeof "aaa.bbb.ccc.ddd"];
757 char sbuf[sizeof "aaa.bbb.ccc.ddd"];
984263bc
MD
758#endif
759 if (isipv6) {
760 strcpy(dbuf, "[");
984263bc 761 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst));
984263bc 762 strcat(dbuf, "]");
95b22adf
JH
763 strcpy(sbuf, "[");
764 strcat(sbuf, ip6_sprintf(&ip6->ip6_src));
984263bc
MD
765 strcat(sbuf, "]");
766 } else {
767 strcpy(dbuf, inet_ntoa(ip->ip_dst));
768 strcpy(sbuf, inet_ntoa(ip->ip_src));
769 }
770 switch (log_in_vain) {
771 case 1:
61896e3c 772 if (!(thflags & TH_SYN))
984263bc
MD
773 break;
774 case 2:
775 log(LOG_INFO,
776 "Connection attempt to TCP %s:%d "
777 "from %s:%d flags:0x%02x\n",
778 dbuf, ntohs(th->th_dport), sbuf,
779 ntohs(th->th_sport), thflags);
780 break;
781 default:
782 break;
783 }
784 }
d24ce1dc 785 if (blackhole) {
984263bc
MD
786 switch (blackhole) {
787 case 1:
788 if (thflags & TH_SYN)
789 goto drop;
790 break;
791 case 2:
792 goto drop;
793 default:
794 goto drop;
795 }
796 }
797 rstreason = BANDLIM_RST_CLOSEDPORT;
798 goto dropwithreset;
799 }
61896e3c
JH
800
801#ifdef IPSEC
802 if (isipv6) {
803 if (ipsec6_in_reject_so(m, inp->inp_socket)) {
804 ipsec6stat.in_polvio++;
805 goto drop;
806 }
807 } else {
808 if (ipsec4_in_reject_so(m, inp->inp_socket)) {
809 ipsecstat.in_polvio++;
810 goto drop;
811 }
812 }
813#endif
814#ifdef FAST_IPSEC
815 if (isipv6) {
816 if (ipsec6_in_reject(m, inp))
817 goto drop;
818 } else {
819 if (ipsec4_in_reject(m, inp))
820 goto drop;
821 }
822#endif
95926362
MD
823 /* Check the minimum TTL for socket. */
824#ifdef INET6
825 if ((isipv6 ? ip6->ip6_hlim : ip->ip_ttl) < inp->inp_ip_minttl)
826 goto drop;
827#endif
61896e3c 828
984263bc
MD
829 tp = intotcpcb(inp);
830 if (tp == NULL) {
831 rstreason = BANDLIM_RST_CLOSEDPORT;
832 goto dropwithreset;
833 }
eb594563 834 if (tp->t_state <= TCPS_CLOSED)
984263bc
MD
835 goto drop;
836
837 /* Unscale the window into a 32-bit value. */
95b22adf 838 if (!(thflags & TH_SYN))
984263bc
MD
839 tiwin = th->th_win << tp->snd_scale;
840 else
841 tiwin = th->th_win;
842
843 so = inp->inp_socket;
47654766 844
984263bc 845#ifdef TCPDEBUG
47654766
JH
846 if (so->so_options & SO_DEBUG) {
847 ostate = tp->t_state;
848 if (isipv6)
95b22adf 849 bcopy(ip6, tcp_saveipgen, sizeof(*ip6));
47654766 850 else
95b22adf 851 bcopy(ip, tcp_saveipgen, sizeof(*ip));
47654766
JH
852 tcp_savetcp = *th;
853 }
984263bc 854#endif
47654766 855
407e896e 856 bzero(&to, sizeof to);
d24ce1dc 857
47654766
JH
858 if (so->so_options & SO_ACCEPTCONN) {
859 struct in_conninfo inc;
860
984263bc 861#ifdef INET6
d24ce1dc 862 inc.inc_isipv6 = (isipv6 == TRUE);
984263bc
MD
863#endif
864 if (isipv6) {
865 inc.inc6_faddr = ip6->ip6_src;
866 inc.inc6_laddr = ip6->ip6_dst;
867 inc.inc6_route.ro_rt = NULL; /* XXX */
868 } else {
869 inc.inc_faddr = ip->ip_src;
870 inc.inc_laddr = ip->ip_dst;
871 inc.inc_route.ro_rt = NULL; /* XXX */
872 }
873 inc.inc_fport = th->th_sport;
874 inc.inc_lport = th->th_dport;
875
61896e3c
JH
876 /*
877 * If the state is LISTEN then ignore segment if it contains
984263bc
MD
878 * a RST. If the segment contains an ACK then it is bad and
879 * send a RST. If it does not contain a SYN then it is not
880 * interesting; drop it.
881 *
882 * If the state is SYN_RECEIVED (syncache) and seg contains
883 * an ACK, but not for our SYN/ACK, send a RST. If the seg
884 * contains a RST, check the sequence number to see if it
885 * is a valid reset segment.
886 */
61896e3c
JH
887 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) != TH_SYN) {
888 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) == TH_ACK) {
984263bc
MD
889 if (!syncache_expand(&inc, th, &so, m)) {
890 /*
891 * No syncache entry, or ACK was not
892 * for our SYN/ACK. Send a RST.
893 */
894 tcpstat.tcps_badsyn++;
895 rstreason = BANDLIM_RST_OPENPORT;
896 goto dropwithreset;
897 }
898 if (so == NULL)
899 /*
900 * Could not complete 3-way handshake,
901 * connection is being closed down, and
902 * syncache will free mbuf.
903 */
904 return;
905 /*
906 * Socket is created in state SYN_RECEIVED.
907 * Continue processing segment.
908 */
ed894f8c 909 inp = so->so_pcb;
984263bc
MD
910 tp = intotcpcb(inp);
911 /*
912 * This is what would have happened in
913 * tcp_output() when the SYN,ACK was sent.
914 */
915 tp->snd_up = tp->snd_una;
916 tp->snd_max = tp->snd_nxt = tp->iss + 1;
917 tp->last_ack_sent = tp->rcv_nxt;
918/*
919 * XXX possible bug - it doesn't appear that tp->snd_wnd is unscaled
920 * until the _second_ ACK is received:
921 * rcv SYN (set wscale opts) --> send SYN/ACK, set snd_wnd = window.
922 * rcv ACK, calculate tiwin --> process SYN_RECEIVED, determine wscale,
61896e3c 923 * move to ESTAB, set snd_wnd to tiwin.
d24ce1dc 924 */
984263bc
MD
925 tp->snd_wnd = tiwin; /* unscaled */
926 goto after_listen;
927 }
928 if (thflags & TH_RST) {
929 syncache_chkrst(&inc, th);
930 goto drop;
931 }
932 if (thflags & TH_ACK) {
933 syncache_badack(&inc);
934 tcpstat.tcps_badsyn++;
935 rstreason = BANDLIM_RST_OPENPORT;
936 goto dropwithreset;
937 }
938 goto drop;
939 }
940
941 /*
61896e3c 942 * Segment's flags are (SYN) or (SYN | FIN).
984263bc
MD
943 */
944#ifdef INET6
945 /*
946 * If deprecated address is forbidden,
947 * we do not accept SYN to deprecated interface
948 * address to prevent any new inbound connection from
949 * getting established.
950 * When we do not accept SYN, we send a TCP RST,
951 * with deprecated source address (instead of dropping
952 * it). We compromise it as it is much better for peer
953 * to send a RST, and RST will be the final packet
954 * for the exchange.
955 *
956 * If we do not forbid deprecated addresses, we accept
957 * the SYN packet. RFC2462 does not suggest dropping
958 * SYN in this case.
959 * If we decipher RFC2462 5.5.4, it says like this:
960 * 1. use of deprecated addr with existing
961 * communication is okay - "SHOULD continue to be
962 * used"
963 * 2. use of it with new communication:
964 * (2a) "SHOULD NOT be used if alternate address
61896e3c 965 * with sufficient scope is available"
984263bc
MD
966 * (2b) nothing mentioned otherwise.
967 * Here we fall into (2b) case as we have no choice in
968 * our source address selection - we must obey the peer.
969 *
970 * The wording in RFC2462 is confusing, and there are
971 * multiple description text for deprecated address
972 * handling - worse, they are not exactly the same.
973 * I believe 5.5.4 is the best one, so we follow 5.5.4.
974 */
975 if (isipv6 && !ip6_use_deprecated) {
976 struct in6_ifaddr *ia6;
977
978 if ((ia6 = ip6_getdstifaddr(m)) &&
979 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
980 tp = NULL;
981 rstreason = BANDLIM_RST_OPENPORT;
982 goto dropwithreset;
983 }
984 }
985#endif
986 /*
987 * If it is from this socket, drop it, it must be forged.
988 * Don't bother responding if the destination was a broadcast.
989 */
990 if (th->th_dport == th->th_sport) {
991 if (isipv6) {
992 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst,
993 &ip6->ip6_src))
994 goto drop;
995 } else {
996 if (ip->ip_dst.s_addr == ip->ip_src.s_addr)
997 goto drop;
998 }
999 }
1000 /*
1001 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN
1002 *
1003 * Note that it is quite possible to receive unicast
1004 * link-layer packets with a broadcast IP address. Use
1005 * in_broadcast() to find them.
1006 */
61896e3c 1007 if (m->m_flags & (M_BCAST | M_MCAST))
984263bc
MD
1008 goto drop;
1009 if (isipv6) {
1010 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
1011 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
1012 goto drop;
1013 } else {
1014 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
1015 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
1016 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
1017 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
1018 goto drop;
1019 }
1020 /*
1021 * SYN appears to be valid; create compressed TCP state
1022 * for syncache, or perform t/tcp connection.
1023 */
1024 if (so->so_qlen <= so->so_qlimit) {
95b22adf 1025 tcp_dooptions(&to, optp, optlen, TRUE);
984263bc
MD
1026 if (!syncache_add(&inc, &to, th, &so, m))
1027 goto drop;
1028 if (so == NULL)
1029 /*
1030 * Entry added to syncache, mbuf used to
1031 * send SYN,ACK packet.
1032 */
1033 return;
1034 /*
1035 * Segment passed TAO tests.
1036 */
ed894f8c 1037 inp = so->so_pcb;
984263bc
MD
1038 tp = intotcpcb(inp);
1039 tp->snd_wnd = tiwin;
1040 tp->t_starttime = ticks;
1041 tp->t_state = TCPS_ESTABLISHED;
1042
1043 /*
1044 * If there is a FIN, or if there is data and the
1045 * connection is local, then delay SYN,ACK(SYN) in
1046 * the hope of piggy-backing it on a response
1047 * segment. Otherwise must send ACK now in case
1048 * the other side is slow starting.
1049 */
1050 if (DELAY_ACK(tp) &&
1051 ((thflags & TH_FIN) ||
1052 (tlen != 0 &&
1053 ((isipv6 && in6_localaddr(&inp->in6p_faddr)) ||
1054 (!isipv6 && in_localaddr(inp->inp_faddr)))))) {
a48c5dd5
SZ
1055 tcp_callout_reset(tp, tp->tt_delack,
1056 tcp_delacktime, tcp_timer_delack);
984263bc 1057 tp->t_flags |= TF_NEEDSYN;
a48c5dd5 1058 } else {
984263bc 1059 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN);
a48c5dd5 1060 }
984263bc
MD
1061
1062 tcpstat.tcps_connects++;
1063 soisconnected(so);
1064 goto trimthenstep6;
1065 }
1066 goto drop;
1067 }
1068after_listen:
1069
984263bc 1070 /* should not happen - syncache should pick up these connections */
61896e3c 1071 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN state"));
984263bc
MD
1072
1073 /*
5b0b9fa5
PA
1074 * This is the second part of the MSS DoS prevention code (after
1075 * minmss on the sending side) and it deals with too many too small
1076 * tcp packets in a too short timeframe (1 second).
1077 *
153d34ac
MD
1078 * XXX Removed. This code was crap. It does not scale to network
1079 * speed, and default values break NFS. Gone.
5b0b9fa5 1080 */
153d34ac 1081 /* REMOVED */
5b0b9fa5
PA
1082
1083 /*
984263bc 1084 * Segment received on connection.
efca2b8e
MD
1085 *
1086 * Reset idle time and keep-alive timer. Don't waste time if less
1087 * then a second has elapsed. Only update t_rcvtime for non-SYN
1088 * packets.
1089 *
1090 * Handle the case where one side thinks the connection is established
1091 * but the other side has, say, rebooted without cleaning out the
1092 * connection. The SYNs could be construed as an attack and wind
1093 * up ignored, but in case it isn't an attack we can validate the
1094 * connection by forcing a keepalive.
984263bc 1095 */
efca2b8e
MD
1096 if (TCPS_HAVEESTABLISHED(tp->t_state) && (ticks - tp->t_rcvtime) > hz) {
1097 if ((thflags & (TH_SYN | TH_ACK)) == TH_SYN) {
1098 tp->t_flags |= TF_KEEPALIVE;
1099 tcp_callout_reset(tp, tp->tt_keep, hz / 2,
1100 tcp_timer_keep);
1101 } else {
1102 tp->t_rcvtime = ticks;
1103 tp->t_flags &= ~TF_KEEPALIVE;
1104 tcp_callout_reset(tp, tp->tt_keep, tcp_keepidle,
1105 tcp_timer_keep);
1106 }
a48c5dd5 1107 }
984263bc
MD
1108
1109 /*
1110 * Process options.
1111 * XXX this is tradtitional behavior, may need to be cleaned up.
1112 */
95b22adf 1113 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0);
ad0af98b 1114 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) {
984263bc
MD
1115 if (to.to_flags & TOF_SCALE) {
1116 tp->t_flags |= TF_RCVD_SCALE;
1117 tp->requested_s_scale = to.to_requested_s_scale;
1118 }
1119 if (to.to_flags & TOF_TS) {
1120 tp->t_flags |= TF_RCVD_TSTMP;
1121 tp->ts_recent = to.to_tsval;
1122 tp->ts_recent_age = ticks;
1123 }
61896e3c 1124 if (to.to_flags & (TOF_CC | TOF_CCNEW))
984263bc
MD
1125 tp->t_flags |= TF_RCVD_CC;
1126 if (to.to_flags & TOF_MSS)
1127 tcp_mss(tp, to.to_mss);
91489f6b
JH
1128 /*
1129 * Only set the TF_SACK_PERMITTED per-connection flag
1130 * if we got a SACK_PERMITTED option from the other side
1131 * and the global tcp_do_sack variable is true.
1132 */
1133 if (tcp_do_sack && (to.to_flags & TOF_SACK_PERMITTED))
1134 tp->t_flags |= TF_SACK_PERMITTED;
984263bc
MD
1135 }
1136
1137 /*
1138 * Header prediction: check for the two common cases
1139 * of a uni-directional data xfer. If the packet has
1140 * no control flags, is in-sequence, the window didn't
1141 * change and we're not retransmitting, it's a
1142 * candidate. If the length is zero and the ack moved
1143 * forward, we're the sender side of the xfer. Just
1144 * free the data acked & wake any higher level process
1145 * that was blocked waiting for space. If the length
1146 * is non-zero and the ack didn't move, we're the
1147 * receiver side. If we're getting packets in-order
1148 * (the reassembly queue is empty), add the data to
1149 * the socket buffer and note that we need a delayed ack.
1150 * Make sure that the hidden state-flags are also off.
1151 * Since we check for TCPS_ESTABLISHED above, it can only
1152 * be TH_NEEDSYN.
1153 */
1154 if (tp->t_state == TCPS_ESTABLISHED &&
1155 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
61896e3c
JH
1156 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) &&
1157 (!(to.to_flags & TOF_TS) ||
984263bc
MD
1158 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) &&
1159 /*
1160 * Using the CC option is compulsory if once started:
1161 * the segment is OK if no T/TCP was negotiated or
1162 * if the segment has a CC option equal to CCrecv
1163 */
1164 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) ||
61896e3c 1165 ((to.to_flags & TOF_CC) && to.to_cc == tp->cc_recv)) &&
984263bc 1166 th->th_seq == tp->rcv_nxt &&
984263bc
MD
1167 tp->snd_nxt == tp->snd_max) {
1168
1169 /*
1170 * If last ACK falls within this segment's sequence numbers,
1171 * record the timestamp.
1172 * NOTE that the test is modified according to the latest
1173 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1174 */
61896e3c 1175 if ((to.to_flags & TOF_TS) &&
984263bc
MD
1176 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
1177 tp->ts_recent_age = ticks;
1178 tp->ts_recent = to.to_tsval;
1179 }
1180
1181 if (tlen == 0) {
1182 if (SEQ_GT(th->th_ack, tp->snd_una) &&
1183 SEQ_LEQ(th->th_ack, tp->snd_max) &&
1184 tp->snd_cwnd >= tp->snd_wnd &&
95b22adf 1185 !IN_FASTRECOVERY(tp)) {
984263bc 1186 /*
be23faf1 1187 * This is a pure ack for outstanding data.
984263bc
MD
1188 */
1189 ++tcpstat.tcps_predack;
1190 /*
1191 * "bad retransmit" recovery
bfdb979e
JH
1192 *
1193 * If Eifel detection applies, then
1194 * it is deterministic, so use it
1195 * unconditionally over the old heuristic.
1196 * Otherwise, fall back to the old heuristic.
984263bc 1197 */
bfdb979e
JH
1198 if (tcp_do_eifel_detect &&
1199 (to.to_flags & TOF_TS) && to.to_tsecr &&
1200 (tp->t_flags & TF_FIRSTACCACK)) {
1201 /* Eifel detection applicable. */
1202 if (to.to_tsecr < tp->t_rexmtTS) {
1203 tcp_revert_congestion_state(tp);
1204 ++tcpstat.tcps_eifeldetected;
1205 }
1206 } else if (tp->t_rxtshift == 1 &&
1207 ticks < tp->t_badrxtwin) {
1208 tcp_revert_congestion_state(tp);
1209 ++tcpstat.tcps_rttdetected;
984263bc 1210 }
8819433a
JH
1211 tp->t_flags &= ~(TF_FIRSTACCACK |
1212 TF_FASTREXMT | TF_EARLYREXMT);
984263bc
MD
1213 /*
1214 * Recalculate the retransmit timer / rtt.
1215 *
d24ce1dc 1216 * Some machines (certain windows boxes)
984263bc
MD
1217 * send broken timestamp replies during the
1218 * SYN+ACK phase, ignore timestamps of 0.
1219 */
95b22adf 1220 if ((to.to_flags & TOF_TS) && to.to_tsecr) {
984263bc 1221 tcp_xmit_timer(tp,
95b22adf 1222 ticks - to.to_tsecr + 1);
984263bc 1223 } else if (tp->t_rtttime &&
95b22adf 1224 SEQ_GT(th->th_ack, tp->t_rtseq)) {
984263bc
MD
1225 tcp_xmit_timer(tp,
1226 ticks - tp->t_rtttime);
1227 }
1228 tcp_xmit_bandwidth_limit(tp, th->th_ack);
1229 acked = th->th_ack - tp->snd_una;
1230 tcpstat.tcps_rcvackpack++;
1231 tcpstat.tcps_rcvackbyte += acked;
6d49aa6f 1232 sbdrop(&so->so_snd.sb, acked);
cfb3f3f4 1233 tp->snd_recover = th->th_ack - 1;
9845754e 1234 tp->snd_una = th->th_ack;
984263bc 1235 tp->t_dupacks = 0;
df9d7670
JH
1236 /*
1237 * Update window information.
1238 */
1239 if (tiwin != tp->snd_wnd &&
1240 acceptable_window_update(tp, th, tiwin)) {
1241 /* keep track of pure window updates */
1242 if (tp->snd_wl2 == th->th_ack &&
1243 tiwin > tp->snd_wnd)
1244 tcpstat.tcps_rcvwinupd++;
1245 tp->snd_wnd = tiwin;
1246 tp->snd_wl1 = th->th_seq;
1247 tp->snd_wl2 = th->th_ack;
1248 if (tp->snd_wnd > tp->max_sndwnd)
1249 tp->max_sndwnd = tp->snd_wnd;
1250 }
984263bc
MD
1251 m_freem(m);
1252 ND6_HINT(tp); /* some progress has been done */
984263bc
MD
1253 /*
1254 * If all outstanding data are acked, stop
1255 * retransmit timer, otherwise restart timer
1256 * using current (possibly backed-off) value.
1257 * If process is waiting for space,
1258 * wakeup/selwakeup/signal. If data
1259 * are ready to send, let tcp_output
1260 * decide between more output or persist.
1261 */
a48c5dd5
SZ
1262 if (tp->snd_una == tp->snd_max) {
1263 tcp_callout_stop(tp, tp->tt_rexmt);
1264 } else if (!tcp_callout_active(tp,
1265 tp->tt_persist)) {
1266 tcp_callout_reset(tp, tp->tt_rexmt,
1267 tp->t_rxtcur, tcp_timer_rexmt);
1268 }
984263bc 1269 sowwakeup(so);
6d49aa6f 1270 if (so->so_snd.ssb_cc > 0)
f23061d4 1271 tcp_output(tp);
984263bc
MD
1272 return;
1273 }
df9d7670
JH
1274 } else if (tiwin == tp->snd_wnd &&
1275 th->th_ack == tp->snd_una &&
984263bc 1276 LIST_EMPTY(&tp->t_segq) &&
6d49aa6f 1277 tlen <= ssb_space(&so->so_rcv)) {
46e92930 1278 u_long newsize = 0; /* automatic sockbuf scaling */
984263bc 1279 /*
be23faf1 1280 * This is a pure, in-sequence data packet
984263bc
MD
1281 * with nothing on the reassembly queue and
1282 * we have enough buffer space to take it.
1283 */
1284 ++tcpstat.tcps_preddat;
1285 tp->rcv_nxt += tlen;
1286 tcpstat.tcps_rcvpack++;
1287 tcpstat.tcps_rcvbyte += tlen;
1288 ND6_HINT(tp); /* some progress has been done */
5b0b9fa5
PA
1289 /*
1290 * Automatic sizing of receive socket buffer. Often the send
1291 * buffer size is not optimally adjusted to the actual network
1292 * conditions at hand (delay bandwidth product). Setting the
1293 * buffer size too small limits throughput on links with high
1294 * bandwidth and high delay (eg. trans-continental/oceanic links).
1295 *
1296 * On the receive side the socket buffer memory is only rarely
1297 * used to any significant extent. This allows us to be much
1298 * more aggressive in scaling the receive socket buffer. For
1299 * the case that the buffer space is actually used to a large
1300 * extent and we run out of kernel memory we can simply drop
1301 * the new segments; TCP on the sender will just retransmit it
1302 * later. Setting the buffer size too big may only consume too
1303 * much kernel memory if the application doesn't read() from
1304 * the socket or packet loss or reordering makes use of the
1305 * reassembly queue.
1306 *
1307 * The criteria to step up the receive buffer one notch are:
1308 * 1. the number of bytes received during the time it takes
1309 * one timestamp to be reflected back to us (the RTT);
1310 * 2. received bytes per RTT is within seven eighth of the
1311 * current socket buffer size;
1312 * 3. receive buffer size has not hit maximal automatic size;
1313 *
1314 * This algorithm does one step per RTT at most and only if
1315 * we receive a bulk stream w/o packet losses or reorderings.
1316 * Shrinking the buffer during idle times is not necessary as
1317 * it doesn't consume any memory when idle.
1318 *
1319 * TODO: Only step up if the application is actually serving
1320 * the buffer to better manage the socket buffer resources.
1321 */
1322 if (tcp_do_autorcvbuf &&
1323 to.to_tsecr &&
1324 (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) {
1325 if (to.to_tsecr > tp->rfbuf_ts &&
1326 to.to_tsecr - tp->rfbuf_ts < hz) {
1327 if (tp->rfbuf_cnt >
1328 (so->so_rcv.ssb_hiwat / 8 * 7) &&
1329 so->so_rcv.ssb_hiwat <
1330 tcp_autorcvbuf_max) {
1331 newsize =
46e92930
MD
1332 ulmin(so->so_rcv.ssb_hiwat +
1333 tcp_autorcvbuf_inc,
1334 tcp_autorcvbuf_max);
5b0b9fa5
PA
1335 }
1336 /* Start over with next RTT. */
1337 tp->rfbuf_ts = 0;
1338 tp->rfbuf_cnt = 0;
1339 } else
1340 tp->rfbuf_cnt += tlen; /* add up */
1341 }
984263bc
MD
1342 /*
1343 * Add data to socket buffer.
1344 */
1345 if (so->so_state & SS_CANTRCVMORE) {
1346 m_freem(m);
1347 } else {
5b0b9fa5 1348 /*
46e92930
MD
1349 * Set new socket buffer size, give up when
1350 * limit is reached.
1351 *
1352 * Adjusting the size can mess up ACK
1353 * sequencing when pure window updates are
1354 * being avoided (which is the default),
1355 * so force an ack.
5b0b9fa5 1356 */
46e92930
MD
1357 if (newsize) {
1358 tp->t_flags |= TF_RXRESIZED;
5b0b9fa5 1359 if (!ssb_reserve(&so->so_rcv, newsize,
46e92930
MD
1360 so, NULL)) {
1361 so->so_rcv.ssb_flags &= ~SSB_AUTOSIZE;
1362 }
1363 if (newsize >=
1364 (TCP_MAXWIN << tp->rcv_scale)) {
5b0b9fa5 1365 so->so_rcv.ssb_flags &= ~SSB_AUTOSIZE;
46e92930
MD
1366 }
1367 }
09cf73e0 1368 m_adj(m, drop_hdrlen); /* delayed header drop */
6d49aa6f 1369 ssb_appendstream(&so->so_rcv, m);
984263bc
MD
1370 }
1371 sorwakeup(so);
2b1ce38a
MD
1372 /*
1373 * This code is responsible for most of the ACKs
1374 * the TCP stack sends back after receiving a data
1375 * packet. Note that the DELAY_ACK check fails if
1376 * the delack timer is already running, which results
1377 * in an ack being sent every other packet (which is
1378 * what we want).
72b37eeb
MD
1379 *
1380 * We then further aggregate acks by not actually
1381 * sending one until the protocol thread has completed
1382 * processing the current backlog of packets. This
1383 * does not delay the ack any further, but allows us
1384 * to take advantage of the packet aggregation that
1385 * high speed NICs do (usually blocks of 8-10 packets)
1386 * to send a single ack rather then four or five acks,
1387 * greatly reducing the ack rate, the return channel
1388 * bandwidth, and the protocol overhead on both ends.
1389 *
1390 * Since this also has the effect of slowing down
1391 * the exponential slow-start ramp-up, systems with
1392 * very large bandwidth-delay products might want
1393 * to turn the feature off.
2b1ce38a 1394 */
984263bc 1395 if (DELAY_ACK(tp)) {
a48c5dd5
SZ
1396 tcp_callout_reset(tp, tp->tt_delack,
1397 tcp_delacktime, tcp_timer_delack);
72b37eeb 1398 } else if (tcp_aggregate_acks) {
984263bc 1399 tp->t_flags |= TF_ACKNOW;
61896e3c 1400 if (!(tp->t_flags & TF_ONOUTPUTQ)) {
2b1ce38a
MD
1401 tp->t_flags |= TF_ONOUTPUTQ;
1402 tp->tt_cpu = mycpu->gd_cpuid;
1403 TAILQ_INSERT_TAIL(
1404 &tcpcbackq[tp->tt_cpu],
1405 tp, t_outputq);
1406 }
72b37eeb
MD
1407 } else {
1408 tp->t_flags |= TF_ACKNOW;
1409 tcp_output(tp);
984263bc
MD
1410 }
1411 return;
1412 }
1413 }
1414
1415 /*
1416 * Calculate amount of space in receive window,
1417 * and then do TCP input processing.
1418 * Receive window is amount of space in rcv queue,
1419 * but not less than advertised window.
1420 */
6d49aa6f 1421 recvwin = ssb_space(&so->so_rcv);
61896e3c
JH
1422 if (recvwin < 0)
1423 recvwin = 0;
1424 tp->rcv_wnd = imax(recvwin, (int)(tp->rcv_adv - tp->rcv_nxt));
984263bc 1425
5b0b9fa5
PA
1426 /* Reset receive buffer auto scaling when not in bulk receive mode. */
1427 tp->rfbuf_ts = 0;
1428 tp->rfbuf_cnt = 0;
1429
984263bc 1430 switch (tp->t_state) {
984263bc
MD
1431 /*
1432 * If the state is SYN_RECEIVED:
1433 * if seg contains an ACK, but not for our SYN/ACK, send a RST.
1434 */
1435 case TCPS_SYN_RECEIVED:
1436 if ((thflags & TH_ACK) &&
1437 (SEQ_LEQ(th->th_ack, tp->snd_una) ||
1438 SEQ_GT(th->th_ack, tp->snd_max))) {
1439 rstreason = BANDLIM_RST_OPENPORT;
1440 goto dropwithreset;
1441 }
1442 break;
1443
1444 /*
1445 * If the state is SYN_SENT:
1446 * if seg contains an ACK, but not for our SYN, drop the input.
1447 * if seg contains a RST, then drop the connection.
1448 * if seg does not contain SYN, then drop it.
1449 * Otherwise this is an acceptable SYN segment
1450 * initialize tp->rcv_nxt and tp->irs
1451 * if seg contains ack then advance tp->snd_una
1452 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state
1453 * arrange for segment to be acked (eventually)
1454 * continue processing rest of data/controls, beginning with URG
1455 */
1456 case TCPS_SYN_SENT:
1457 if ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL) {
1458 taop = &tao_noncached;
407e896e 1459 bzero(taop, sizeof *taop);
984263bc
MD
1460 }
1461
1462 if ((thflags & TH_ACK) &&
1463 (SEQ_LEQ(th->th_ack, tp->iss) ||
1464 SEQ_GT(th->th_ack, tp->snd_max))) {
1465 /*
1466 * If we have a cached CCsent for the remote host,
1467 * hence we haven't just crashed and restarted,
1468 * do not send a RST. This may be a retransmission
1469 * from the other side after our earlier ACK was lost.
1470 * Our new SYN, when it arrives, will serve as the
1471 * needed ACK.
1472 */
1473 if (taop->tao_ccsent != 0)
1474 goto drop;
1475 else {
1476 rstreason = BANDLIM_UNLIMITED;
1477 goto dropwithreset;
1478 }
1479 }
1480 if (thflags & TH_RST) {
1481 if (thflags & TH_ACK)
1482 tp = tcp_drop(tp, ECONNREFUSED);
1483 goto drop;
1484 }
61896e3c 1485 if (!(thflags & TH_SYN))
984263bc
MD
1486 goto drop;
1487 tp->snd_wnd = th->th_win; /* initial send window */
1488 tp->cc_recv = to.to_cc; /* foreign CC */
1489
1490 tp->irs = th->th_seq;
1491 tcp_rcvseqinit(tp);
1492 if (thflags & TH_ACK) {
1493 /*
1494 * Our SYN was acked. If segment contains CC.ECHO
1495 * option, check it to make sure this segment really
1496 * matches our SYN. If not, just drop it as old
1497 * duplicate, but send an RST if we're still playing
1498 * by the old rules. If no CC.ECHO option, make sure
1499 * we don't get fooled into using T/TCP.
1500 */
1501 if (to.to_flags & TOF_CCECHO) {
1502 if (tp->cc_send != to.to_ccecho) {
1503 if (taop->tao_ccsent != 0)
1504 goto drop;
1505 else {
1506 rstreason = BANDLIM_UNLIMITED;
1507 goto dropwithreset;
1508 }
1509 }
1510 } else
1511 tp->t_flags &= ~TF_RCVD_CC;
1512 tcpstat.tcps_connects++;
1513 soisconnected(so);
1514 /* Do window scaling on this connection? */
61896e3c 1515 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) ==
b5572302 1516 (TF_RCVD_SCALE | TF_REQ_SCALE)) {
984263bc
MD
1517 tp->snd_scale = tp->requested_s_scale;
1518 tp->rcv_scale = tp->request_r_scale;
1519 }
1520 /* Segment is acceptable, update cache if undefined. */
1521 if (taop->tao_ccsent == 0)
1522 taop->tao_ccsent = to.to_ccecho;
1523
1524 tp->rcv_adv += tp->rcv_wnd;
1525 tp->snd_una++; /* SYN is acked */
a48c5dd5 1526 tcp_callout_stop(tp, tp->tt_rexmt);
984263bc
MD
1527 /*
1528 * If there's data, delay ACK; if there's also a FIN
1529 * ACKNOW will be turned on later.
1530 */
a48c5dd5
SZ
1531 if (DELAY_ACK(tp) && tlen != 0) {
1532 tcp_callout_reset(tp, tp->tt_delack,
1533 tcp_delacktime, tcp_timer_delack);
1534 } else {
984263bc 1535 tp->t_flags |= TF_ACKNOW;
a48c5dd5 1536 }
984263bc
MD
1537 /*
1538 * Received <SYN,ACK> in SYN_SENT[*] state.
1539 * Transitions:
1540 * SYN_SENT --> ESTABLISHED
1541 * SYN_SENT* --> FIN_WAIT_1
1542 */
1543 tp->t_starttime = ticks;
1544 if (tp->t_flags & TF_NEEDFIN) {
1545 tp->t_state = TCPS_FIN_WAIT_1;
1546 tp->t_flags &= ~TF_NEEDFIN;
1547 thflags &= ~TH_SYN;
1548 } else {
1549 tp->t_state = TCPS_ESTABLISHED;
a48c5dd5
SZ
1550 tcp_callout_reset(tp, tp->tt_keep, tcp_keepidle,
1551 tcp_timer_keep);
984263bc
MD
1552 }
1553 } else {
1554 /*
95b22adf
JH
1555 * Received initial SYN in SYN-SENT[*] state =>
1556 * simultaneous open. If segment contains CC option
1557 * and there is a cached CC, apply TAO test.
1558 * If it succeeds, connection is * half-synchronized.
1559 * Otherwise, do 3-way handshake:
61896e3c
JH
1560 * SYN-SENT -> SYN-RECEIVED
1561 * SYN-SENT* -> SYN-RECEIVED*
95b22adf
JH
1562 * If there was no CC option, clear cached CC value.
1563 */
984263bc 1564 tp->t_flags |= TF_ACKNOW;
a48c5dd5 1565 tcp_callout_stop(tp, tp->tt_rexmt);
984263bc
MD
1566 if (to.to_flags & TOF_CC) {
1567 if (taop->tao_cc != 0 &&
1568 CC_GT(to.to_cc, taop->tao_cc)) {
1569 /*
1570 * update cache and make transition:
61896e3c
JH
1571 * SYN-SENT -> ESTABLISHED*
1572 * SYN-SENT* -> FIN-WAIT-1*
984263bc
MD
1573 */
1574 taop->tao_cc = to.to_cc;
1575 tp->t_starttime = ticks;
1576 if (tp->t_flags & TF_NEEDFIN) {
1577 tp->t_state = TCPS_FIN_WAIT_1;
1578 tp->t_flags &= ~TF_NEEDFIN;
1579 } else {
1580 tp->t_state = TCPS_ESTABLISHED;
a48c5dd5
SZ
1581 tcp_callout_reset(tp,
1582 tp->tt_keep, tcp_keepidle,
1583 tcp_timer_keep);
984263bc
MD
1584 }
1585 tp->t_flags |= TF_NEEDSYN;
1586 } else
1587 tp->t_state = TCPS_SYN_RECEIVED;
1588 } else {
1589 /* CC.NEW or no option => invalidate cache */
1590 taop->tao_cc = 0;
1591 tp->t_state = TCPS_SYN_RECEIVED;
1592 }
1593 }
1594
1595trimthenstep6:
1596 /*
1597 * Advance th->th_seq to correspond to first data byte.
1598 * If data, trim to stay within window,
1599 * dropping FIN if necessary.
1600 */
1601 th->th_seq++;
1602 if (tlen > tp->rcv_wnd) {
1603 todrop = tlen - tp->rcv_wnd;
1604 m_adj(m, -todrop);
1605 tlen = tp->rcv_wnd;
1606 thflags &= ~TH_FIN;
1607 tcpstat.tcps_rcvpackafterwin++;
1608 tcpstat.tcps_rcvbyteafterwin += todrop;
1609 }
1610 tp->snd_wl1 = th->th_seq - 1;
1611 tp->rcv_up = th->th_seq;
1612 /*
1613 * Client side of transaction: already sent SYN and data.
1614 * If the remote host used T/TCP to validate the SYN,
1615 * our data will be ACK'd; if so, enter normal data segment
1616 * processing in the middle of step 5, ack processing.
1617 * Otherwise, goto step 6.
1618 */
95b22adf 1619 if (thflags & TH_ACK)
984263bc
MD
1620 goto process_ACK;
1621
1622 goto step6;
1623
1624 /*
1625 * If the state is LAST_ACK or CLOSING or TIME_WAIT:
1626 * if segment contains a SYN and CC [not CC.NEW] option:
61896e3c
JH
1627 * if state == TIME_WAIT and connection duration > MSL,
1628 * drop packet and send RST;
984263bc
MD
1629 *
1630 * if SEG.CC > CCrecv then is new SYN, and can implicitly
1631 * ack the FIN (and data) in retransmission queue.
61896e3c
JH
1632 * Complete close and delete TCPCB. Then reprocess
1633 * segment, hoping to find new TCPCB in LISTEN state;
984263bc
MD
1634 *
1635 * else must be old SYN; drop it.
61896e3c 1636 * else do normal processing.
984263bc
MD
1637 */
1638 case TCPS_LAST_ACK:
1639 case TCPS_CLOSING:
1640 case TCPS_TIME_WAIT:
1641 if ((thflags & TH_SYN) &&
1642 (to.to_flags & TOF_CC) && tp->cc_recv != 0) {
1643 if (tp->t_state == TCPS_TIME_WAIT &&
1644 (ticks - tp->t_starttime) > tcp_msl) {
1645 rstreason = BANDLIM_UNLIMITED;
1646 goto dropwithreset;
1647 }
1648 if (CC_GT(to.to_cc, tp->cc_recv)) {
1649 tp = tcp_close(tp);
1650 goto findpcb;
1651 }
1652 else
1653 goto drop;
1654 }
95b22adf 1655 break; /* continue normal processing */
984263bc
MD
1656 }
1657
1658 /*
1659 * States other than LISTEN or SYN_SENT.
1660 * First check the RST flag and sequence number since reset segments
1661 * are exempt from the timestamp and connection count tests. This
1662 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix
1663 * below which allowed reset segments in half the sequence space
1664 * to fall though and be processed (which gives forged reset
1665 * segments with a random sequence number a 50 percent chance of
1666 * killing a connection).
1667 * Then check timestamp, if present.
1668 * Then check the connection count, if present.
1669 * Then check that at least some bytes of segment are within
1670 * receive window. If segment begins before rcv_nxt,
1671 * drop leading data (and SYN); if nothing left, just ack.
1672 *
1673 *
1674 * If the RST bit is set, check the sequence number to see
1675 * if this is a valid reset segment.
1676 * RFC 793 page 37:
1677 * In all states except SYN-SENT, all reset (RST) segments
1678 * are validated by checking their SEQ-fields. A reset is
1679 * valid if its sequence number is in the window.
1680 * Note: this does not take into account delayed ACKs, so
1681 * we should test against last_ack_sent instead of rcv_nxt.
1682 * The sequence number in the reset segment is normally an
91489f6b 1683 * echo of our outgoing acknowledgement numbers, but some hosts
984263bc
MD
1684 * send a reset with the sequence number at the rightmost edge
1685 * of our receive window, and we have to handle this case.
1686 * If we have multiple segments in flight, the intial reset
1687 * segment sequence numbers will be to the left of last_ack_sent,
1688 * but they will eventually catch up.
1689 * In any case, it never made sense to trim reset segments to
1690 * fit the receive window since RFC 1122 says:
1691 * 4.2.2.12 RST Segment: RFC-793 Section 3.4
1692 *
1693 * A TCP SHOULD allow a received RST segment to include data.
1694 *
1695 * DISCUSSION
61896e3c
JH
1696 * It has been suggested that a RST segment could contain
1697 * ASCII text that encoded and explained the cause of the
91489f6b 1698 * RST. No standard has yet been established for such
61896e3c 1699 * data.
984263bc
MD
1700 *
1701 * If the reset segment passes the sequence number test examine
1702 * the state:
1703 * SYN_RECEIVED STATE:
1704 * If passive open, return to LISTEN state.
1705 * If active open, inform user that connection was refused.
1706 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES:
1707 * Inform user that connection was reset, and close tcb.
1708 * CLOSING, LAST_ACK STATES:
1709 * Close the tcb.
1710 * TIME_WAIT STATE:
1711 * Drop the segment - see Stevens, vol. 2, p. 964 and
61896e3c 1712 * RFC 1337.
984263bc
MD
1713 */
1714 if (thflags & TH_RST) {
1715 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
d4dbb5be 1716 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) {
984263bc
MD
1717 switch (tp->t_state) {
1718
1719 case TCPS_SYN_RECEIVED:
1720 so->so_error = ECONNREFUSED;
1721 goto close;
1722
1723 case TCPS_ESTABLISHED:
1724 case TCPS_FIN_WAIT_1:
1725 case TCPS_FIN_WAIT_2:
1726 case TCPS_CLOSE_WAIT:
1727 so->so_error = ECONNRESET;
1728 close:
1729 tp->t_state = TCPS_CLOSED;
1730 tcpstat.tcps_drops++;
1731 tp = tcp_close(tp);
1732 break;
1733
1734 case TCPS_CLOSING:
1735 case TCPS_LAST_ACK:
1736 tp = tcp_close(tp);
1737 break;
1738
1739 case TCPS_TIME_WAIT:
1740 break;
1741 }
1742 }
1743 goto drop;
1744 }
1745
1746 /*
1747 * RFC 1323 PAWS: If we have a timestamp reply on this segment
1748 * and it's less than ts_recent, drop it.
1749 */
61896e3c 1750 if ((to.to_flags & TOF_TS) && tp->ts_recent != 0 &&
984263bc
MD
1751 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
1752
1753 /* Check to see if ts_recent is over 24 days old. */
1754 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) {
1755 /*
1756 * Invalidate ts_recent. If this segment updates
1757 * ts_recent, the age will be reset later and ts_recent
1758 * will get a valid value. If it does not, setting
1759 * ts_recent to zero will at least satisfy the
1760 * requirement that zero be placed in the timestamp
1761 * echo reply when ts_recent isn't valid. The
1762 * age isn't reset until we get a valid ts_recent
1763 * because we don't want out-of-order segments to be
1764 * dropped when ts_recent is old.
1765 */
1766 tp->ts_recent = 0;
1767 } else {
1768 tcpstat.tcps_rcvduppack++;
1769 tcpstat.tcps_rcvdupbyte += tlen;
1770 tcpstat.tcps_pawsdrop++;
1771 if (tlen)
1772 goto dropafterack;
1773 goto drop;
1774 }
1775 }
1776
1777 /*
1778 * T/TCP mechanism
1779 * If T/TCP was negotiated and the segment doesn't have CC,
1780 * or if its CC is wrong then drop the segment.
1781 * RST segments do not have to comply with this.
1782 */
1783 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) &&
61896e3c 1784 (!(to.to_flags & TOF_CC) || tp->cc_recv != to.to_cc))
95b22adf 1785 goto dropafterack;
984263bc
MD
1786
1787 /*
1788 * In the SYN-RECEIVED state, validate that the packet belongs to
1789 * this connection before trimming the data to fit the receive
1790 * window. Check the sequence number versus IRS since we know
1791 * the sequence numbers haven't wrapped. This is a partial fix
1792 * for the "LAND" DoS attack.
1793 */
1794 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) {
1795 rstreason = BANDLIM_RST_OPENPORT;
1796 goto dropwithreset;
1797 }
1798
1799 todrop = tp->rcv_nxt - th->th_seq;
1800 if (todrop > 0) {
91489f6b
JH
1801 if (TCP_DO_SACK(tp)) {
1802 /* Report duplicate segment at head of packet. */
1803 tp->reportblk.rblk_start = th->th_seq;
1804 tp->reportblk.rblk_end = th->th_seq + tlen;
1805 if (thflags & TH_FIN)
1806 ++tp->reportblk.rblk_end;
1807 if (SEQ_GT(tp->reportblk.rblk_end, tp->rcv_nxt))
1808 tp->reportblk.rblk_end = tp->rcv_nxt;
1809 tp->t_flags |= (TF_DUPSEG | TF_SACKLEFT | TF_ACKNOW);
1810 }
984263bc
MD
1811 if (thflags & TH_SYN) {
1812 thflags &= ~TH_SYN;
1813 th->th_seq++;
1814 if (th->th_urp > 1)
1815 th->th_urp--;
1816 else
1817 thflags &= ~TH_URG;
1818 todrop--;
1819 }
1820 /*
1821 * Following if statement from Stevens, vol. 2, p. 960.
1822 */
61896e3c
JH
1823 if (todrop > tlen ||
1824 (todrop == tlen && !(thflags & TH_FIN))) {
984263bc
MD
1825 /*
1826 * Any valid FIN must be to the left of the window.
1827 * At this point the FIN must be a duplicate or out
1828 * of sequence; drop it.
1829 */
1830 thflags &= ~TH_FIN;
1831
1832 /*
1833 * Send an ACK to resynchronize and drop any data.
1834 * But keep on processing for RST or ACK.
1835 */
1836 tp->t_flags |= TF_ACKNOW;
1837 todrop = tlen;
1838 tcpstat.tcps_rcvduppack++;
1839 tcpstat.tcps_rcvdupbyte += todrop;
1840 } else {
1841 tcpstat.tcps_rcvpartduppack++;
1842 tcpstat.tcps_rcvpartdupbyte += todrop;
1843 }
1844 drop_hdrlen += todrop; /* drop from the top afterwards */
1845 th->th_seq += todrop;
1846 tlen -= todrop;
1847 if (th->th_urp > todrop)
1848 th->th_urp -= todrop;
1849 else {
1850 thflags &= ~TH_URG;
1851 th->th_urp = 0;
1852 }
1853 }
1854
1855 /*
1856 * If new data are received on a connection after the
1857 * user processes are gone, then RST the other end.
1858 */
1859 if ((so->so_state & SS_NOFDREF) &&
1860 tp->t_state > TCPS_CLOSE_WAIT && tlen) {
1861 tp = tcp_close(tp);
1862 tcpstat.tcps_rcvafterclose++;
1863 rstreason = BANDLIM_UNLIMITED;
1864 goto dropwithreset;
1865 }
1866
1867 /*
1868 * If segment ends after window, drop trailing data
1869 * (and PUSH and FIN); if nothing left, just ACK.
1870 */
61896e3c 1871 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd);
984263bc
MD
1872 if (todrop > 0) {
1873 tcpstat.tcps_rcvpackafterwin++;
1874 if (todrop >= tlen) {
1875 tcpstat.tcps_rcvbyteafterwin += tlen;
1876 /*
1877 * If a new connection request is received
1878 * while in TIME_WAIT, drop the old connection
1879 * and start over if the sequence numbers
1880 * are above the previous ones.
1881 */
1882 if (thflags & TH_SYN &&
1883 tp->t_state == TCPS_TIME_WAIT &&
1884 SEQ_GT(th->th_seq, tp->rcv_nxt)) {
1885 tp = tcp_close(tp);
1886 goto findpcb;
1887 }
1888 /*
1889 * If window is closed can only take segments at
1890 * window edge, and have to drop data and PUSH from
1891 * incoming segments. Continue processing, but
1892 * remember to ack. Otherwise, drop segment
1893 * and ack.
1894 */
1895 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
1896 tp->t_flags |= TF_ACKNOW;
1897 tcpstat.tcps_rcvwinprobe++;
1898 } else
1899 goto dropafterack;
1900 } else
1901 tcpstat.tcps_rcvbyteafterwin += todrop;
1902 m_adj(m, -todrop);
1903 tlen -= todrop;
61896e3c 1904 thflags &= ~(TH_PUSH | TH_FIN);
984263bc
MD
1905 }
1906
1907 /*
1908 * If last ACK falls within this segment's sequence numbers,
1909 * record its timestamp.
ad0af98b
ND
1910 * NOTE:
1911 * 1) That the test incorporates suggestions from the latest
1912 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1913 * 2) That updating only on newer timestamps interferes with
1914 * our earlier PAWS tests, so this check should be solely
1915 * predicated on the sequence space of this segment.
1916 * 3) That we modify the segment boundary check to be
1917 * Last.ACK.Sent <= SEG.SEQ + SEG.LEN
1918 * instead of RFC1323's
1919 * Last.ACK.Sent < SEG.SEQ + SEG.LEN,
1920 * This modified check allows us to overcome RFC1323's
1921 * limitations as described in Stevens TCP/IP Illustrated
1922 * Vol. 2 p.869. In such cases, we can still calculate the
1923 * RTT correctly when RCV.NXT == Last.ACK.Sent.
984263bc 1924 */
ad0af98b
ND
1925 if ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent) &&
1926 SEQ_LEQ(tp->last_ack_sent, (th->th_seq + tlen
1927 + ((thflags & TH_SYN) != 0)
1928 + ((thflags & TH_FIN) != 0)))) {
984263bc
MD
1929 tp->ts_recent_age = ticks;
1930 tp->ts_recent = to.to_tsval;
1931 }
1932
1933 /*
1934 * If a SYN is in the window, then this is an
1935 * error and we send an RST and drop the connection.
1936 */
1937 if (thflags & TH_SYN) {
1938 tp = tcp_drop(tp, ECONNRESET);
1939 rstreason = BANDLIM_UNLIMITED;
1940 goto dropwithreset;
1941 }
1942
1943 /*
1944 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN
1945 * flag is on (half-synchronized state), then queue data for
1946 * later processing; else drop segment and return.
1947 */
61896e3c 1948 if (!(thflags & TH_ACK)) {
984263bc
MD
1949 if (tp->t_state == TCPS_SYN_RECEIVED ||
1950 (tp->t_flags & TF_NEEDSYN))
1951 goto step6;
1952 else
1953 goto drop;
1954 }
1955
1956 /*
1957 * Ack processing.
1958 */
1959 switch (tp->t_state) {
984263bc 1960 /*
91489f6b 1961 * In SYN_RECEIVED state, the ACK acknowledges our SYN, so enter
984263bc
MD
1962 * ESTABLISHED state and continue processing.
1963 * The ACK was checked above.
1964 */
1965 case TCPS_SYN_RECEIVED:
1966
1967 tcpstat.tcps_connects++;
1968 soisconnected(so);
1969 /* Do window scaling? */
61896e3c 1970 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) ==
b5572302 1971 (TF_RCVD_SCALE | TF_REQ_SCALE)) {
984263bc
MD
1972 tp->snd_scale = tp->requested_s_scale;
1973 tp->rcv_scale = tp->request_r_scale;
1974 }
1975 /*
1976 * Upon successful completion of 3-way handshake,
1977 * update cache.CC if it was undefined, pass any queued
1978 * data to the user, and advance state appropriately.
1979 */
1980 if ((taop = tcp_gettaocache(&inp->inp_inc)) != NULL &&
1981 taop->tao_cc == 0)
1982 taop->tao_cc = tp->cc_recv;
1983
1984 /*
1985 * Make transitions:
1986 * SYN-RECEIVED -> ESTABLISHED
1987 * SYN-RECEIVED* -> FIN-WAIT-1
1988 */
1989 tp->t_starttime = ticks;
1990 if (tp->t_flags & TF_NEEDFIN) {
1991 tp->t_state = TCPS_FIN_WAIT_1;
1992 tp->t_flags &= ~TF_NEEDFIN;
1993 } else {
1994 tp->t_state = TCPS_ESTABLISHED;
a48c5dd5
SZ
1995 tcp_callout_reset(tp, tp->tt_keep, tcp_keepidle,
1996 tcp_timer_keep);
984263bc
MD
1997 }
1998 /*
1999 * If segment contains data or ACK, will call tcp_reass()
2000 * later; if not, do so now to pass queued data to user.
2001 */
61896e3c 2002 if (tlen == 0 && !(thflags & TH_FIN))
f23061d4 2003 tcp_reass(tp, NULL, NULL, NULL);
984263bc
MD
2004 /* fall into ... */
2005
2006 /*
2007 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
2008 * ACKs. If the ack is in the range
2009 * tp->snd_una < th->th_ack <= tp->snd_max
2010 * then advance tp->snd_una to th->th_ack and drop
2011 * data from the retransmission queue. If this ACK reflects
2012 * more up to date window information we update our window information.
2013 */
2014 case TCPS_ESTABLISHED:
2015 case TCPS_FIN_WAIT_1:
2016 case TCPS_FIN_WAIT_2:
2017 case TCPS_CLOSE_WAIT:
2018 case TCPS_CLOSING:
2019 case TCPS_LAST_ACK:
2020 case TCPS_TIME_WAIT:
2021
2022 if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
91489f6b
JH
2023 if (TCP_DO_SACK(tp))
2024 tcp_sack_update_scoreboard(tp, &to);
95b22adf
JH
2025 if (tlen != 0 || tiwin != tp->snd_wnd) {
2026 tp->t_dupacks = 0;
2027 break;
2028 }
2029 tcpstat.tcps_rcvdupack++;
a48c5dd5 2030 if (!tcp_callout_active(tp, tp->tt_rexmt) ||
91489f6b
JH
2031 th->th_ack != tp->snd_una) {
2032 tp->t_dupacks = 0;
2033 break;
2034 }
95b22adf 2035 /*
91489f6b 2036 * We have outstanding data (other than
95b22adf
JH
2037 * a window probe), this is a completely
2038 * duplicate ack (ie, window info didn't
2039 * change), the ack is the biggest we've
2040 * seen and we've seen exactly our rexmt
91489f6b 2041 * threshhold of them, so assume a packet
95b22adf
JH
2042 * has been dropped and retransmit it.
2043 * Kludge snd_nxt & the congestion
2044 * window so we send only this one
2045 * packet.
95b22adf 2046 */
91489f6b
JH
2047 if (IN_FASTRECOVERY(tp)) {
2048 if (TCP_DO_SACK(tp)) {
2049 /* No artifical cwnd inflation. */
2050 tcp_sack_rexmt(tp, th);
2051 } else {
2052 /*
2053 * Dup acks mean that packets
2054 * have left the network
2055 * (they're now cached at the
2056 * receiver) so bump cwnd by
2057 * the amount in the receiver
2058 * to keep a constant cwnd
2059 * packets in the network.
2060 */
2061 tp->snd_cwnd += tp->t_maxseg;
f23061d4 2062 tcp_output(tp);
91489f6b
JH
2063 }
2064 } else if (SEQ_LT(th->th_ack, tp->snd_recover)) {
95b22adf
JH
2065 tp->t_dupacks = 0;
2066 break;
95b22adf 2067 } else if (++tp->t_dupacks == tcprexmtthresh) {
91489f6b 2068 tcp_seq old_snd_nxt;
95b22adf
JH
2069 u_int win;
2070
8819433a 2071fastretransmit:
95b22adf
JH
2072 if (tcp_do_eifel_detect &&
2073 (tp->t_flags & TF_RCVD_TSTMP)) {
2074 tcp_save_congestion_state(tp);
2075 tp->t_flags |= TF_FASTREXMT;
2076 }
91489f6b
JH
2077 /*
2078 * We know we're losing at the current
2079 * window size, so do congestion avoidance:
2080 * set ssthresh to half the current window
2081 * and pull our congestion window back to the
2082 * new ssthresh.
2083 */
95b22adf
JH
2084 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 /
2085 tp->t_maxseg;
2086 if (win < 2)
2087 win = 2;
2088 tp->snd_ssthresh = win * tp->t_maxseg;
2089 ENTER_FASTRECOVERY(tp);
2090 tp->snd_recover = tp->snd_max;
a48c5dd5 2091 tcp_callout_stop(tp, tp->tt_rexmt);
95b22adf 2092 tp->t_rtttime = 0;
91489f6b 2093 old_snd_nxt = tp->snd_nxt;
95b22adf
JH
2094 tp->snd_nxt = th->th_ack;
2095 tp->snd_cwnd = tp->t_maxseg;
f23061d4 2096 tcp_output(tp);
95b22adf 2097 ++tcpstat.tcps_sndfastrexmit;
91489f6b
JH
2098 tp->snd_cwnd = tp->snd_ssthresh;
2099 tp->rexmt_high = tp->snd_nxt;
2100 if (SEQ_GT(old_snd_nxt, tp->snd_nxt))
2101 tp->snd_nxt = old_snd_nxt;
95b22adf
JH
2102 KASSERT(tp->snd_limited <= 2,
2103 ("tp->snd_limited too big"));
91489f6b
JH
2104 if (TCP_DO_SACK(tp))
2105 tcp_sack_rexmt(tp, th);
2106 else
2107 tp->snd_cwnd += tp->t_maxseg *
2108 (tp->t_dupacks - tp->snd_limited);
95b22adf
JH
2109 } else if (tcp_do_limitedtransmit) {
2110 u_long oldcwnd = tp->snd_cwnd;
2111 tcp_seq oldsndmax = tp->snd_max;
9e707f76 2112 tcp_seq oldsndnxt = tp->snd_nxt;
95b22adf
JH
2113 /* outstanding data */
2114 uint32_t ownd = tp->snd_max - tp->snd_una;
2115 u_int sent;
ca94b4a6 2116
8819433a
JH
2117#define iceildiv(n, d) (((n)+(d)-1) / (d))
2118
95b22adf
JH
2119 KASSERT(tp->t_dupacks == 1 ||
2120 tp->t_dupacks == 2,
2121 ("dupacks not 1 or 2"));
2122 if (tp->t_dupacks == 1)
2123 tp->snd_limited = 0;
9e707f76 2124 tp->snd_nxt = tp->snd_max;
95b22adf
JH
2125 tp->snd_cwnd = ownd +
2126 (tp->t_dupacks - tp->snd_limited) *
2127 tp->t_maxseg;
f23061d4 2128 tcp_output(tp);
98cb2337
MD
2129
2130 /*
2131 * Other acks may have been processed,
2132 * snd_nxt cannot be reset to a value less
2133 * then snd_una.
2134 */
2135 if (SEQ_LT(oldsndnxt, oldsndmax)) {
2136 if (SEQ_GT(oldsndnxt, tp->snd_una))
6d08465d 2137 tp->snd_nxt = oldsndnxt;
98cb2337
MD
2138 else
2139 tp->snd_nxt = tp->snd_una;
2140 }
95b22adf
JH
2141 tp->snd_cwnd = oldcwnd;
2142 sent = tp->snd_max - oldsndmax;
2143 if (sent > tp->t_maxseg) {
2144 KASSERT((tp->t_dupacks == 2 &&
2145 tp->snd_limited == 0) ||
2146 (sent == tp->t_maxseg + 1 &&
2147 tp->t_flags & TF_SENTFIN),
2148 ("sent too much"));
2149 KASSERT(sent <= tp->t_maxseg * 2,
2150 ("sent too many segments"));
2151 tp->snd_limited = 2;
2152 tcpstat.tcps_sndlimited += 2;
2153 } else if (sent > 0) {
2154 ++tp->snd_limited;
2155 ++tcpstat.tcps_sndlimited;
2156 } else if (tcp_do_early_retransmit &&
2157 (tcp_do_eifel_detect &&
2158 (tp->t_flags & TF_RCVD_TSTMP)) &&
91489f6b 2159 ownd < 4 * tp->t_maxseg &&
95b22adf 2160 tp->t_dupacks + 1 >=
91489f6b
JH
2161 iceildiv(ownd, tp->t_maxseg) &&
2162 (!TCP_DO_SACK(tp) ||
f23061d4 2163 ownd <= tp->t_maxseg ||
91489f6b 2164 tcp_sack_has_sacked(&tp->scb,
f23061d4 2165 ownd - tp->t_maxseg))) {
95b22adf
JH
2166 ++tcpstat.tcps_sndearlyrexmit;
2167 tp->t_flags |= TF_EARLYREXMT;
2168 goto fastretransmit;
984263bc 2169 }
95b22adf
JH
2170 }
2171 goto drop;
984263bc
MD
2172 }
2173
2174 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una"));
984263bc
MD
2175 tp->t_dupacks = 0;
2176 if (SEQ_GT(th->th_ack, tp->snd_max)) {
5a274421
JH
2177 /*
2178 * Detected optimistic ACK attack.
2179 * Force slow-start to de-synchronize attack.
2180 */
2181 tp->snd_cwnd = tp->t_maxseg;
8acdb67c 2182 tp->snd_wacked = 0;
5a274421 2183
984263bc
MD
2184 tcpstat.tcps_rcvacktoomuch++;
2185 goto dropafterack;
2186 }
2187 /*
2188 * If we reach this point, ACK is not a duplicate,
2189 * i.e., it ACKs something we sent.
2190 */
2191 if (tp->t_flags & TF_NEEDSYN) {
2192 /*
2193 * T/TCP: Connection was half-synchronized, and our
2194 * SYN has been ACK'd (so connection is now fully
2195 * synchronized). Go to non-starred state,
2196 * increment snd_una for ACK of SYN, and check if
2197 * we can do window scaling.
2198 */
2199 tp->t_flags &= ~TF_NEEDSYN;
2200 tp->snd_una++;
2201 /* Do window scaling? */
61896e3c
JH
2202 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) ==
2203 (TF_RCVD_SCALE | TF_REQ_SCALE)) {
984263bc
MD
2204 tp->snd_scale = tp->requested_s_scale;
2205 tp->rcv_scale = tp->request_r_scale;
2206 }
2207 }
2208
2209process_ACK:
2210 acked = th->th_ack - tp->snd_una;
2211 tcpstat.tcps_rcvackpack++;
2212 tcpstat.tcps_rcvackbyte += acked;
2213
b5572302 2214 if (tcp_do_eifel_detect && acked > 0 &&
95b22adf 2215 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) &&
bfdb979e
JH
2216 (tp->t_flags & TF_FIRSTACCACK)) {
2217 /* Eifel detection applicable. */
2218 if (to.to_tsecr < tp->t_rexmtTS) {
bfdb979e 2219 ++tcpstat.tcps_eifeldetected;
8819433a
JH
2220 tcp_revert_congestion_state(tp);
2221 if (tp->t_rxtshift == 1 &&
2222 ticks >= tp->t_badrxtwin)
2223 ++tcpstat.tcps_rttcantdetect;
bfdb979e
JH
2224 }
2225 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) {
b5572302
JH
2226 /*
2227 * If we just performed our first retransmit,
2228 * and the ACK arrives within our recovery window,
2229 * then it was a mistake to do the retransmit
91489f6b 2230 * in the first place. Recover our original cwnd
b5572302
JH
2231 * and ssthresh, and proceed to transmit where we
2232 * left off.
2233 */
bfdb979e
JH
2234 tcp_revert_congestion_state(tp);
2235 ++tcpstat.tcps_rttdetected;
984263bc
MD
2236 }
2237
2238 /*
2239 * If we have a timestamp reply, update smoothed
2240 * round trip time. If no timestamp is present but
2241 * transmit timer is running and timed sequence
2242 * number was acked, update smoothed round trip time.
2243 * Since we now have an rtt measurement, cancel the
2244 * timer backoff (cf., Phil Karn's retransmit alg.).
2245 * Recompute the initial retransmit timer.
2246 *
2247 * Some machines (certain windows boxes) send broken
d24ce1dc 2248 * timestamp replies during the SYN+ACK phase, ignore
984263bc
MD
2249 * timestamps of 0.
2250 */
95b22adf 2251 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0))
984263bc 2252 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1);
95b22adf 2253 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq))
984263bc 2254 tcp_xmit_timer(tp, ticks - tp->t_rtttime);
984263bc
MD
2255 tcp_xmit_bandwidth_limit(tp, th->th_ack);
2256
2257 /*
984263bc
MD
2258 * If no data (only SYN) was ACK'd,
2259 * skip rest of ACK processing.
2260 */
2261 if (acked == 0)
2262 goto step6;
2263
efd4b327 2264 /* Stop looking for an acceptable ACK since one was received. */
8819433a 2265 tp->t_flags &= ~(TF_FIRSTACCACK | TF_FASTREXMT | TF_EARLYREXMT);
efd4b327 2266
6d49aa6f
MD
2267 if (acked > so->so_snd.ssb_cc) {
2268 tp->snd_wnd -= so->so_snd.ssb_cc;
2269 sbdrop(&so->so_snd.sb, (int)so->so_snd.ssb_cc);
61896e3c 2270 ourfinisacked = TRUE;
984263bc 2271 } else {
6d49aa6f 2272 sbdrop(&so->so_snd.sb, acked);
984263bc 2273 tp->snd_wnd -= acked;
61896e3c 2274 ourfinisacked = FALSE;
984263bc
MD
2275 }
2276 sowwakeup(so);
91489f6b
JH
2277
2278 /*
2279 * Update window information.
2280 * Don't look at window if no ACK:
2281 * TAC's send garbage on first SYN.
2282 */
2283 if (SEQ_LT(tp->snd_wl1, th->th_seq) ||
2284 (tp->snd_wl1 == th->th_seq &&
2285 (SEQ_LT(tp->snd_wl2, th->th_ack) ||
2286 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) {
2287 /* keep track of pure window updates */
2288 if (tlen == 0 && tp->snd_wl2 == th->th_ack &&
2289 tiwin > tp->snd_wnd)
2290 tcpstat.tcps_rcvwinupd++;
2291 tp->snd_wnd = tiwin;
2292 tp->snd_wl1 = th->th_seq;
2293 tp->snd_wl2 = th->th_ack;
2294 if (tp->snd_wnd > tp->max_sndwnd)
2295 tp->max_sndwnd = tp->snd_wnd;
2296 needoutput = TRUE;
2297 }
2298
2299 tp->snd_una = th->th_ack;
2300 if (TCP_DO_SACK(tp))
2301 tcp_sack_update_scoreboard(tp, &to);
95b22adf 2302 if (IN_FASTRECOVERY(tp)) {
91489f6b 2303 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) {
95b22adf 2304 EXIT_FASTRECOVERY(tp);
91489f6b
JH
2305 needoutput = TRUE;
2306 /*
2307 * If the congestion window was inflated
2308 * to account for the other side's
2309 * cached packets, retract it.
8acdb67c
JH
2310 */
2311 if (!TCP_DO_SACK(tp))
2312 tp->snd_cwnd = tp->snd_ssthresh;
2313
2314 /*
91489f6b
JH
2315 * Window inflation should have left us
2316 * with approximately snd_ssthresh outstanding
2317 * data. But, in case we would be inclined
2318 * to send a burst, better do it using
2319 * slow start.
2320 */
91489f6b
JH
2321 if (SEQ_GT(th->th_ack + tp->snd_cwnd,
2322 tp->snd_max + 2 * tp->t_maxseg))
2323 tp->snd_cwnd =
2324 (tp->snd_max - tp->snd_una) +
2325 2 * tp->t_maxseg;
8acdb67c
JH
2326
2327 tp->snd_wacked = 0;
91489f6b
JH
2328 } else {
2329 if (TCP_DO_SACK(tp)) {
2330 tp->snd_max_rexmt = tp->snd_max;
2331 tcp_sack_rexmt(tp, th);
2332 } else {
2333 tcp_newreno_partial_ack(tp, th, acked);
2334 }
2335 needoutput = FALSE;
2336 }
95b22adf 2337 } else {
91489f6b 2338 /*
8acdb67c
JH
2339 * Open the congestion window. When in slow-start,
2340 * open exponentially: maxseg per packet. Otherwise,
2341 * open linearly: maxseg per window.
91489f6b 2342 */
8acdb67c
JH
2343 if (tp->snd_cwnd <= tp->snd_ssthresh) {
2344 u_int abc_sslimit =
2345 (SEQ_LT(tp->snd_nxt, tp->snd_max) ?
2346 tp->t_maxseg : 2 * tp->t_maxseg);
2347
2348 /* slow-start */
2349 tp->snd_cwnd += tcp_do_abc ?
2350 min(acked, abc_sslimit) : tp->t_maxseg;
2351 } else {
2352 /* linear increase */
2353 tp->snd_wacked += tcp_do_abc ? acked :
2354 tp->t_maxseg;
2355 if (tp->snd_wacked >= tp->snd_cwnd) {
2356 tp->snd_wacked -= tp->snd_cwnd;
2357 tp->snd_cwnd += tp->t_maxseg;
2358 }
2359 }
2360 tp->snd_cwnd = min(tp->snd_cwnd,
2361 TCP_MAXWIN << tp->snd_scale);
95b22adf 2362 tp->snd_recover = th->th_ack - 1;
cfb3f3f4 2363 }
984263bc
MD
2364 if (SEQ_LT(tp->snd_nxt, tp->snd_una))
2365 tp->snd_nxt = tp->snd_una;
2366
91489f6b
JH
2367 /*
2368 * If all outstanding data is acked, stop retransmit
2369 * timer and remember to restart (more output or persist).
2370 * If there is more data to be acked, restart retransmit
2371 * timer, using current (possibly backed-off) value.
2372 */
2373 if (th->th_ack == tp->snd_max) {
a48c5dd5 2374 tcp_callout_stop(tp, tp->tt_rexmt);
91489f6b 2375 needoutput = TRUE;
a48c5dd5
SZ
2376 } else if (!tcp_callout_active(tp, tp->tt_persist)) {
2377 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur,
2378 tcp_timer_rexmt);
2379 }
91489f6b 2380
984263bc 2381 switch (tp->t_state) {
984263bc
MD
2382 /*
2383 * In FIN_WAIT_1 STATE in addition to the processing
2384 * for the ESTABLISHED state if our FIN is now acknowledged
2385 * then enter FIN_WAIT_2.
2386 */
2387 case TCPS_FIN_WAIT_1:
2388 if (ourfinisacked) {
2389 /*
2390 * If we can't receive any more
2391 * data, then closing user can proceed.
2392 * Starting the timer is contrary to the
2393 * specification, but if we don't get a FIN
2394 * we'll hang forever.
2395 */
2396 if (so->so_state & SS_CANTRCVMORE) {
2397 soisdisconnected(so);
a48c5dd5
SZ
2398 tcp_callout_reset(tp, tp->tt_2msl,
2399 tcp_maxidle, tcp_timer_2msl);
984263bc
MD
2400 }
2401 tp->t_state = TCPS_FIN_WAIT_2;
2402 }
2403 break;
2404
95b22adf 2405 /*
984263bc
MD
2406 * In CLOSING STATE in addition to the processing for
2407 * the ESTABLISHED state if the ACK acknowledges our FIN
2408 * then enter the TIME-WAIT state, otherwise ignore
2409 * the segment.
2410 */
2411 case TCPS_CLOSING:
2412 if (ourfinisacked) {
2413 tp->t_state = TCPS_TIME_WAIT;
2414 tcp_canceltimers(tp);
2415 /* Shorten TIME_WAIT [RFC-1644, p.28] */
2416 if (tp->cc_recv != 0 &&
a48c5dd5
SZ
2417 (ticks - tp->t_starttime) < tcp_msl) {
2418 tcp_callout_reset(tp, tp->tt_2msl,
b5572302 2419 tp->t_rxtcur * TCPTV_TWTRUNC,
a48c5dd5
SZ
2420 tcp_timer_2msl);
2421 } else {
2422 tcp_callout_reset(tp, tp->tt_2msl,
2423 2 * tcp_msl, tcp_timer_2msl);
2424 }
984263bc
MD
2425 soisdisconnected(so);
2426 }
2427 break;
2428
2429 /*
2430 * In LAST_ACK, we may still be waiting for data to drain
2431 * and/or to be acked, as well as for the ack of our FIN.
2432 * If our FIN is now acknowledged, delete the TCB,
2433 * enter the closed state and return.
2434 */
2435 case TCPS_LAST_ACK:
2436 if (ourfinisacked) {
2437 tp = tcp_close(tp);
2438 goto drop;
2439 }
2440 break;
2441
2442 /*
2443 * In TIME_WAIT state the only thing that should arrive
2444 * is a retransmission of the remote FIN. Acknowledge
2445 * it and restart the finack timer.
2446 */
2447 case TCPS_TIME_WAIT:
a48c5dd5
SZ
2448 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_msl,
2449 tcp_timer_2msl);
984263bc
MD
2450 goto dropafterack;
2451 }
2452 }
2453
2454step6:
2455 /*
2456 * Update window information.
2457 * Don't look at window if no ACK: TAC's send garbage on first SYN.
2458 */
2459 if ((thflags & TH_ACK) &&
df9d7670 2460 acceptable_window_update(tp, th, tiwin)) {
984263bc 2461 /* keep track of pure window updates */
b5572302
JH
2462 if (tlen == 0 && tp->snd_wl2 == th->th_ack &&
2463 tiwin > tp->snd_wnd)
984263bc
MD
2464 tcpstat.tcps_rcvwinupd++;
2465 tp->snd_wnd = tiwin;
2466 tp->snd_wl1 = th->th_seq;
2467 tp->snd_wl2 = th->th_ack;
2468 if (tp->snd_wnd > tp->max_sndwnd)
2469 tp->max_sndwnd = tp->snd_wnd;
61896e3c 2470 needoutput = TRUE;
984263bc
MD
2471 }
2472
2473 /*
2474 * Process segments with URG.
2475 */
2476 if ((thflags & TH_URG) && th->th_urp &&
95b22adf 2477 !TCPS_HAVERCVDFIN(tp->t_state)) {
984263bc
MD
2478 /*
2479 * This is a kludge, but if we receive and accept
2480 * random urgent pointers, we'll crash in
2481 * soreceive. It's hard to imagine someone
2482 * actually wanting to send this much urgent data.
2483 */
6d49aa6f 2484 if (th->th_urp + so->so_rcv.ssb_cc > sb_max) {
984263bc
MD
2485 th->th_urp = 0; /* XXX */
2486 thflags &= ~TH_URG; /* XXX */
2487 goto dodata; /* XXX */
2488 }
2489 /*
2490 * If this segment advances the known urgent pointer,
2491 * then mark the data stream. This should not happen
2492 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
2493 * a FIN has been received from the remote side.
2494 * In these states we ignore the URG.
2495 *
2496 * According to RFC961 (Assigned Protocols),
2497 * the urgent pointer points to the last octet
2498 * of urgent data. We continue, however,
2499 * to consider it to indicate the first octet
2500 * of data past the urgent section as the original
2501 * spec states (in one of two places).
2502 */
61896e3c 2503 if (SEQ_GT(th->th_seq + th->th_urp, tp->rcv_up)) {
984263bc 2504 tp->rcv_up = th->th_seq + th->th_urp;
6d49aa6f 2505 so->so_oobmark = so->so_rcv.ssb_cc +
984263bc
MD
2506 (tp->rcv_up - tp->rcv_nxt) - 1;
2507 if (so->so_oobmark == 0)
2508 so->so_state |= SS_RCVATMARK;
2509 sohasoutofband(so);
2510 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
2511 }
2512 /*
2513 * Remove out of band data so doesn't get presented to user.
2514 * This can happen independent of advancing the URG pointer,
2515 * but if two URG's are pending at once, some out-of-band
2516 * data may creep in... ick.
2517 */
61896e3c
JH
2518 if (th->th_urp <= (u_long)tlen &&
2519 !(so->so_options & SO_OOBINLINE)) {
2520 /* hdr drop is delayed */
2521 tcp_pulloutofband(so, th, m, drop_hdrlen);
2522 }
984263bc
MD
2523 } else {
2524 /*
2525 * If no out of band data is expected,
2526 * pull receive urgent pointer along
2527 * with the receive window.
2528 */
2529 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
2530 tp->rcv_up = tp->rcv_nxt;
2531 }
984263bc 2532
61896e3c 2533dodata: /* XXX */
984263bc
MD
2534 /*
2535 * Process the segment text, merging it into the TCP sequencing queue,
2536 * and arranging for acknowledgment of receipt if necessary.
2537 * This process logically involves adjusting tp->rcv_wnd as data
2538 * is presented to the user (this happens in tcp_usrreq.c,
2539 * case PRU_RCVD). If a FIN has already been received on this
2540 * connection then we just ignore the text.
2541 */
95b22adf 2542 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) {
984263bc
MD
2543 m_adj(m, drop_hdrlen); /* delayed header drop */
2544 /*
2545 * Insert segment which includes th into TCP reassembly queue
2546 * with control block tp. Set thflags to whether reassembly now
2547 * includes a segment with FIN. This handles the common case
2548 * inline (segment is the next to be received on an established
2549 * connection, and the queue is empty), avoiding linkage into
2550 * and removal from the queue and repetition of various
2551 * conversions.
2552 * Set DELACK for segments received in order, but ack
2553 * immediately when segments are out of order (so
2554 * fast retransmit can work).
2555 */
2556 if (th->th_seq == tp->rcv_nxt &&
2557 LIST_EMPTY(&tp->t_segq) &&
2558 TCPS_HAVEESTABLISHED(tp->t_state)) {
a48c5dd5
SZ
2559 if (DELAY_ACK(tp)) {
2560 tcp_callout_reset(tp, tp->tt_delack,
2561 tcp_delacktime, tcp_timer_delack);
2562 } else {
984263bc 2563 tp->t_flags |= TF_ACKNOW;
a48c5dd5 2564 }
984263bc
MD
2565 tp->rcv_nxt += tlen;
2566 thflags = th->th_flags & TH_FIN;
2567 tcpstat.tcps_rcvpack++;
2568 tcpstat.tcps_rcvbyte += tlen;
2569 ND6_HINT(tp);
2570 if (so->so_state & SS_CANTRCVMORE)
2571 m_freem(m);
2572 else
6d49aa6f 2573 ssb_appendstream(&so->so_rcv, m);
984263bc
MD
2574 sorwakeup(so);
2575 } else {
91489f6b
JH
2576 if (!(tp->t_flags & TF_DUPSEG)) {
2577 /* Initialize SACK report block. */
2578 tp->reportblk.rblk_start = th->th_seq;
2579 tp->reportblk.rblk_end = th->th_seq + tlen +
2580 ((thflags & TH_FIN) != 0);
2581 }
984263bc
MD
2582 thflags = tcp_reass(tp, th, &tlen, m);
2583 tp->t_flags |= TF_ACKNOW;
2584 }
2585
2586 /*
2587 * Note the amount of data that peer has sent into
2588 * our window, in order to estimate the sender's
2589 * buffer size.
2590 */
6d49aa6f 2591 len = so->so_rcv.ssb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
984263bc
MD
2592 } else {
2593 m_freem(m);
2594 thflags &= ~TH_FIN;
2595 }
2596
2597 /*
2598 * If FIN is received ACK the FIN and let the user know
2599 * that the connection is closing.
2600 */
2601 if (thflags & TH_FIN) {
95b22adf 2602 if (!TCPS_HAVERCVDFIN(tp->t_state)) {
984263bc
MD
2603 socantrcvmore(so);
2604 /*
2605 * If connection is half-synchronized
2606 * (ie NEEDSYN flag on) then delay ACK,
2607 * so it may be piggybacked when SYN is sent.
2608 * Otherwise, since we received a FIN then no
2609 * more input can be expected, send ACK now.
2610 */
a48c5dd5
SZ
2611 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) {
2612 tcp_callout_reset(tp, tp->tt_delack,
2613 tcp_delacktime, tcp_timer_delack);
2614 } else {
984263bc 2615 tp->t_flags |= TF_ACKNOW;
a48c5dd5 2616 }
984263bc
MD
2617 tp->rcv_nxt++;
2618 }
984263bc 2619
61896e3c 2620 switch (tp->t_state) {
95b22adf 2621 /*
984263bc
MD
2622 * In SYN_RECEIVED and ESTABLISHED STATES
2623 * enter the CLOSE_WAIT state.
2624 */
2625 case TCPS_SYN_RECEIVED:
2626 tp->t_starttime = ticks;
2627 /*FALLTHROUGH*/
2628 case TCPS_ESTABLISHED:
2629 tp->t_state = TCPS_CLOSE_WAIT;
2630 break;
2631
95b22adf 2632 /*
984263bc
MD
2633 * If still in FIN_WAIT_1 STATE FIN has not been acked so
2634 * enter the CLOSING state.
2635 */
2636 case TCPS_FIN_WAIT_1:
2637 tp->t_state = TCPS_CLOSING;
2638 break;
2639
95b22adf 2640 /*
984263bc
MD
2641 * In FIN_WAIT_2 state enter the TIME_WAIT state,
2642 * starting the time-wait timer, turning off the other
2643 * standard timers.
2644 */
2645 case TCPS_FIN_WAIT_2:
2646 tp->t_state = TCPS_TIME_WAIT;
2647 tcp_canceltimers(tp);
2648 /* Shorten TIME_WAIT [RFC-1644, p.28] */
2649 if (tp->cc_recv != 0 &&
2650 (ticks - tp->t_starttime) < tcp_msl) {
a48c5dd5
SZ
2651 tcp_callout_reset(tp, tp->tt_2msl,
2652 tp->t_rxtcur * TCPTV_TWTRUNC,
2653 tcp_timer_2msl);
984263bc
MD
2654 /* For transaction client, force ACK now. */
2655 tp->t_flags |= TF_ACKNOW;
a48c5dd5
SZ
2656 } else {
2657 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_msl,
2658 tcp_timer_2msl);
984263bc 2659 }
984263bc
MD
2660 soisdisconnected(so);
2661 break;
2662
2663 /*
2664 * In TIME_WAIT state restart the 2 MSL time_wait timer.
2665 */
2666 case TCPS_TIME_WAIT:
a48c5dd5
SZ
2667 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_msl,
2668 tcp_timer_2msl);
984263bc
MD
2669 break;
2670 }
2671 }
61896e3c 2672
984263bc
MD
2673#ifdef TCPDEBUG
2674 if (so->so_options & SO_DEBUG)
f23061d4 2675 tcp_trace(TA_INPUT, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
984263bc
MD
2676#endif
2677
2678 /*
2679 * Return any desired output.
2680 */
2681 if (needoutput || (tp->t_flags & TF_ACKNOW))
f23061d4 2682 tcp_output(tp);
984263bc
MD
2683 return;
2684
2685dropafterack:
2686 /*
2687 * Generate an ACK dropping incoming segment if it occupies
2688 * sequence space, where the ACK reflects our state.
2689 *
2690 * We can now skip the test for the RST flag since all
2691 * paths to this code happen after packets containing
2692 * RST have been dropped.
2693 *
2694 * In the SYN-RECEIVED state, don't send an ACK unless the
2695 * segment we received passes the SYN-RECEIVED ACK test.
2696 * If it fails send a RST. This breaks the loop in the
2697 * "LAND" DoS attack, and also prevents an ACK storm
2698 * between two listening ports that have been sent forged
2699 * SYN segments, each with the source address of the other.
2700 */
2701 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
2702 (SEQ_GT(tp->snd_una, th->th_ack) ||
2703 SEQ_GT(th->th_ack, tp->snd_max)) ) {
2704 rstreason = BANDLIM_RST_OPENPORT;
2705 goto dropwithreset;
2706 }
2707#ifdef TCPDEBUG
2708 if (so->so_options & SO_DEBUG)
f23061d4 2709 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
984263bc
MD
2710#endif
2711 m_freem(m);
2712 tp->t_flags |= TF_ACKNOW;
f23061d4 2713 tcp_output(tp);
984263bc
MD
2714 return;
2715
2716dropwithreset:
2717 /*
2718 * Generate a RST, dropping incoming segment.
2719 * Make ACK acceptable to originator of segment.
2720 * Don't bother to respond if destination was broadcast/multicast.
2721 */
61896e3c 2722 if ((thflags & TH_RST) || m->m_flags & (M_BCAST | M_MCAST))
984263bc
MD
2723 goto drop;
2724 if (isipv6) {
2725 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
2726 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
2727 goto drop;
2728 } else {
2729 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
2730 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
95b22adf
JH
2731 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
2732 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
984263bc
MD
2733 goto drop;
2734 }
2735 /* IPv6 anycast check is done at tcp6_input() */
2736
2737 /*
2738 * Perform bandwidth limiting.
2739 */
2740#ifdef ICMP_BANDLIM
2741 if (badport_bandlim(rstreason) < 0)
2742 goto drop;
2743#endif
2744
2745#ifdef TCPDEBUG
2746 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
f23061d4 2747 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
984263bc
MD
2748#endif
2749 if (thflags & TH_ACK)
2750 /* mtod() below is safe as long as hdr dropping is delayed */
2751 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack,
2752 TH_RST);
2753 else {
2754 if (thflags & TH_SYN)
2755 tlen++;
2756 /* mtod() below is safe as long as hdr dropping is delayed */
61896e3c
JH
2757 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen,
2758 (tcp_seq)0, TH_RST | TH_ACK);
984263bc
MD
2759 }
2760 return;
2761
2762drop:
2763 /*
2764 * Drop space held by incoming segment and return.
2765 */
2766#ifdef TCPDEBUG
2767 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
f23061d4 2768 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
984263bc
MD
2769#endif
2770 m_freem(m);
2771 return;
2772}
2773
2774/*
2775 * Parse TCP options and place in tcpopt.
2776 */
2777static void
95b22adf 2778tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn)
984263bc 2779{
91489f6b 2780 int opt, optlen, i;
984263bc
MD
2781
2782 to->to_flags = 0;
2783 for (; cnt > 0; cnt -= optlen, cp += optlen) {
2784 opt = cp[0];
2785 if (opt == TCPOPT_EOL)
2786 break;
2787 if (opt == TCPOPT_NOP)
2788 optlen = 1;
2789 else {
2790 if (cnt < 2)
2791 break;
2792 optlen = cp[1];
2793 if (optlen < 2 || optlen > cnt)
2794 break;
2795 }
2796 switch (opt) {
2797 case TCPOPT_MAXSEG:
2798 if (optlen != TCPOLEN_MAXSEG)
2799 continue;
2800 if (!is_syn)
2801 continue;
2802 to->to_flags |= TOF_MSS;
407e896e 2803 bcopy(cp + 2, &to->to_mss, sizeof to->to_mss);
984263bc
MD
2804 to->to_mss = ntohs(to->to_mss);
2805 break;
2806 case TCPOPT_WINDOW:
2807 if (optlen != TCPOLEN_WINDOW)
2808 continue;
95b22adf 2809 if (!is_syn)
984263bc
MD
2810 continue;
2811 to->to_flags |= TOF_SCALE;
2812 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT);
2813 break;
2814 case TCPOPT_TIMESTAMP:
2815 if (optlen != TCPOLEN_TIMESTAMP)
2816 continue;
2817 to->to_flags |= TOF_TS;
407e896e 2818 bcopy(cp + 2, &to->to_tsval, sizeof to->to_tsval);
984263bc 2819 to->to_tsval = ntohl(to->to_tsval);
407e896e 2820 bcopy(cp + 6, &to->to_tsecr, sizeof to->to_tsecr);
984263bc 2821 to->to_tsecr = ntohl(to->to_tsecr);
ad0af98b
ND
2822 /*
2823 * If echoed timestamp is later than the current time,
2824 * fall back to non RFC1323 RTT calculation.
2825 */
2826 if (to->to_tsecr != 0 && TSTMP_GT(to->to_tsecr, ticks))
2827 to->to_tsecr = 0;
984263bc
MD
2828 break;
2829 case TCPOPT_CC:
2830 if (optlen != TCPOLEN_CC)
2831 continue;
2832 to->to_flags |= TOF_CC;
407e896e 2833 bcopy(cp + 2, &to->to_cc, sizeof to->to_cc);
984263bc
MD
2834 to->to_cc = ntohl(to->to_cc);
2835 break;
2836 case TCPOPT_CCNEW:
2837 if (optlen != TCPOLEN_CC)
2838 continue;
2839 if (!is_syn)
2840 continue;
2841 to->to_flags |= TOF_CCNEW;
d08de609 2842 bcopy(cp + 2, &to->to_cc, sizeof to->to_cc);
984263bc
MD
2843 to->to_cc = ntohl(to->to_cc);
2844 break;
2845 case TCPOPT_CCECHO:
2846 if (optlen != TCPOLEN_CC)
2847 continue;
2848 if (!is_syn)
2849 continue;
2850 to->to_flags |= TOF_CCECHO;
407e896e 2851 bcopy(cp + 2, &to->to_ccecho, sizeof to->to_ccecho);
984263bc
MD
2852 to->to_ccecho = ntohl(to->to_ccecho);
2853 break;
91489f6b
JH
2854 case TCPOPT_SACK_PERMITTED:
2855 if (optlen != TCPOLEN_SACK_PERMITTED)
2856 continue;
2857 if (!is_syn)
2858 continue;
2859 to->to_flags |= TOF_SACK_PERMITTED;
2860 break;
2861 case TCPOPT_SACK:
2862 if ((optlen - 2) & 0x07) /* not multiple of 8 */
2863 continue;
2864 to->to_nsackblocks = (optlen - 2) / 8;
2865 to->to_sackblocks = (struct raw_sackblock *) (cp + 2);
2866 to->to_flags |= TOF_SACK;
2867 for (i = 0; i < to->to_nsackblocks; i++) {
2868 struct raw_sackblock *r = &to->to_sackblocks[i];
2869
2870 r->rblk_start = ntohl(r->rblk_start);
2871 r->rblk_end = ntohl(r->rblk_end);
2872 }
2873 break;
984263bc
MD
2874 default:
2875 continue;
2876 }
2877 }
2878}
2879
2880/*
2881 * Pull out of band byte out of a segment so
2882 * it doesn't appear in the user's data queue.
2883 * It is still reflected in the segment length for
2884 * sequencing purposes.
95b22adf 2885 * "off" is the delayed to be dropped hdrlen.
984263bc
MD
2886 */
2887static void
95b22adf 2888tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off)
984263bc
MD
2889{
2890 int cnt = off + th->th_urp - 1;
2891
2892 while (cnt >= 0) {
2893 if (m->m_len > cnt) {
2894 char *cp = mtod(m, caddr_t) + cnt;
2895 struct tcpcb *tp = sototcpcb(so);
2896
2897 tp->t_iobc = *cp;
2898 tp->t_oobflags |= TCPOOB_HAVEDATA;
95b22adf 2899 bcopy(cp + 1, cp, m->m_len - cnt - 1);
984263bc
MD
2900 m->m_len--;
2901 if (m->m_flags & M_PKTHDR)
2902 m->m_pkthdr.len--;
2903 return;
2904 }
2905 cnt -= m->m_len;
2906 m = m->m_next;
2907 if (m == 0)
2908 break;
2909 }
2910 panic("tcp_pulloutofband");
2911}
2912
2913/*
2914 * Collect new round-trip time estimate
2915 * and update averages and current timeout.
2916 */
2917static void
95b22adf 2918tcp_xmit_timer(struct tcpcb *tp, int rtt)
984263bc 2919{
2256ba69 2920 int delta;
984263bc
MD
2921
2922 tcpstat.tcps_rttupdated++;
2923 tp->t_rttupdated++;
2924 if (tp->t_srtt != 0) {
2925 /*
2926 * srtt is stored as fixed point with 5 bits after the
2927 * binary point (i.e., scaled by 8). The following magic
2928 * is equivalent to the smoothing algorithm in rfc793 with
2929 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
2930 * point). Adjust rtt to origin 0.
2931 */
2932 delta = ((rtt - 1) << TCP_DELTA_SHIFT)
2933 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
2934
2935 if ((tp->t_srtt += delta) <= 0)
2936 tp->t_srtt = 1;
2937
2938 /*
2939 * We accumulate a smoothed rtt variance (actually, a
2940 * smoothed mean difference), then set the retransmit
2941 * timer to smoothed rtt + 4 times the smoothed variance.
2942 * rttvar is stored as fixed point with 4 bits after the
2943 * binary point (scaled by 16). The following is
2944 * equivalent to rfc793 smoothing with an alpha of .75
2945 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces
2946 * rfc793's wired-in beta.
2947 */
2948 if (delta < 0)
2949 delta = -delta;
2950 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
2951 if ((tp->t_rttvar += delta) <= 0)
2952 tp->t_rttvar = 1;
2953 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
2954 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2955 } else {
2956 /*
2957 * No rtt measurement yet - use the unsmoothed rtt.
2958 * Set the variance to half the rtt (so our first
2959 * retransmit happens at 3*rtt).
2960 */
2961 tp->t_srtt = rtt << TCP_RTT_SHIFT;
2962 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
2963 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2964 }
2965 tp->t_rtttime = 0;
2966 tp->t_rxtshift = 0;
2967
2968 /*
2969 * the retransmit should happen at rtt + 4 * rttvar.
2970 * Because of the way we do the smoothing, srtt and rttvar
2971 * will each average +1/2 tick of bias. When we compute
2972 * the retransmit timer, we want 1/2 tick of rounding and
2973 * 1 extra tick because of +-1/2 tick uncertainty in the
2974 * firing of the timer. The bias will give us exactly the
2975 * 1.5 tick we need. But, because the bias is
2976 * statistical, we have to test that we don't drop below
2977 * the minimum feasible timer (which is 2 ticks).
2978 */
2979 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
2980 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);
2981
2982 /*
2983 * We received an ack for a packet that wasn't retransmitted;
2984 * it is probably safe to discard any error indications we've
2985 * received recently. This isn't quite right, but close enough
2986 * for now (a route might have failed after we sent a segment,
2987 * and the return path might not be symmetrical).
2988 */
2989 tp->t_softerror = 0;
2990}
2991
2992/*
2993 * Determine a reasonable value for maxseg size.
2994 * If the route is known, check route for mtu.
2995 * If none, use an mss that can be handled on the outgoing
2996 * interface without forcing IP to fragment; if bigger than
2997 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES
2998 * to utilize large mbufs. If no route is found, route has no mtu,
2999 * or the destination isn't local, use a default, hopefully conservative
3000 * size (usually 512 or the default IP max size, but no more than the mtu
3001 * of the interface), as we can't discover anything about intervening
3002 * gateways or networks. We also initialize the congestion/slow start
3003 * window to be a single segment if the destination isn't local.
3004 * While looking at the routing entry, we also initialize other path-dependent
3005 * parameters from pre-set or cached values in the routing entry.
3006 *
3007 * Also take into account the space needed for options that we
3008 * send regularly. Make maxseg shorter by that amount to assure
3009 * that we can send maxseg amount of data even when the options
3010 * are present. Store the upper limit of the length of options plus
3011 * data in maxopd.
3012 *
3013 * NOTE that this routine is only called when we process an incoming
3014 * segment, for outgoing segments only tcp_mssopt is called.
3015 *
3016 * In case of T/TCP, we call this routine during implicit connection
3017 * setup as well (offer = -1), to initialize maxseg from the cached
3018 * MSS of our peer.
3019 */
3020void
95b22adf 3021tcp_mss(struct tcpcb *tp, int offer)
984263bc 3022{
2256ba69 3023 struct rtentry *rt;
984263bc 3024 struct ifnet *ifp;
2256ba69 3025 int rtt, mss;
984263bc
MD
3026 u_long bufsize;
3027 struct inpcb *inp = tp->t_inpcb;
3028 struct socket *so;
3029 struct rmxp_tao *taop;
3030 int origoffer = offer;
3031#ifdef INET6
d24ce1dc 3032 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE);
984263bc
MD
3033 size_t min_protoh = isipv6 ?
3034 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) :
3035 sizeof(struct tcpiphdr);
3036#else
d24ce1dc 3037 const boolean_t isipv6 = FALSE;
984263bc
MD
3038 const size_t min_protoh = sizeof(struct tcpiphdr);
3039#endif
3040
3041 if (isipv6)
3042 rt = tcp_rtlookup6(&inp->inp_inc);
3043 else
3044 rt = tcp_rtlookup(&inp->inp_inc);
3045 if (rt == NULL) {
3046 tp->t_maxopd = tp->t_maxseg =
d24ce1dc 3047 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt);
984263bc
MD
3048 return;
3049 }
3050 ifp = rt->rt_ifp;
3051 so = inp->inp_socket;
3052
3053 taop = rmx_taop(rt->rt_rmx);
b235ad6d 3054
984263bc
MD
3055 /*
3056 * Offer == -1 means that we didn't receive SYN yet,
3057 * use cached value in that case;
3058 */
3059 if (offer == -1)
3060 offer = taop->tao_mssopt;
b235ad6d 3061
984263bc
MD
3062 /*
3063 * Offer == 0 means that there was no MSS on the SYN segment,
b235ad6d
MD
3064 * in this case we use either the interface mtu or tcp_mssdflt.
3065 *
3066 * An offer which is too large will be cut down later.
984263bc 3067 */
5b0b9fa5 3068 if (offer == 0) {
b235ad6d
MD
3069 if (isipv6) {
3070 if (in6_localaddr(&inp->in6p_faddr)) {
3071 offer = ND_IFINFO(rt->rt_ifp)->linkmtu -
3072 min_protoh;
3073 } else {
3074 offer = tcp_v6mssdflt;
3075 }
3076 } else {
3077 if (in_localaddr(inp->inp_faddr))
3078 offer = ifp->if_mtu - min_protoh;
3079 else
3080 offer = tcp_mssdflt;
3081 }
5b0b9fa5 3082 }
b235ad6d
MD
3083
3084 /*
3085 * Prevent DoS attack with too small MSS. Round up
3086 * to at least minmss.
3087 *
3088 * Sanity check: make sure that maxopd will be large
3089 * enough to allow some data on segments even is the
3090 * all the option space is used (40bytes). Otherwise
3091 * funny things may happen in tcp_output.
3092 */
3093 offer = max(offer, tcp_minmss);
3094 offer = max(offer, 64);
3095
984263bc
MD
3096 taop->tao_mssopt = offer;
3097
3098 /*
3099 * While we're here, check if there's an initial rtt
3100 * or rttvar. Convert from the route-table units
3101 * to scaled multiples of the slow timeout timer.
3102 */
3103 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) {
3104 /*
3105 * XXX the lock bit for RTT indicates that the value
3106 * is also a minimum value; this is subject to time.
3107 */
3108 if (rt->rt_rmx.rmx_locks & RTV_RTT)
3109 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz);
3110 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE));
3111 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE;
3112 tcpstat.tcps_usedrtt++;
3113 if (rt->rt_rmx.rmx_rttvar) {
3114 tp->t_rttvar = rt->rt_rmx.rmx_rttvar /
3115 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE));
3116 tcpstat.tcps_usedrttvar++;
3117 } else {
3118 /* default variation is +- 1 rtt */
3119 tp->t_rttvar =
3120 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
3121 }
3122 TCPT_RANGESET(tp->t_rxtcur,
3123 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
3124 tp->t_rttmin, TCPTV_REXMTMAX);
3125 }
b235ad6d 3126
984263bc
MD
3127 /*
3128 * if there's an mtu associated with the route, use it
b235ad6d
MD
3129 * else, use the link mtu. Take the smaller of mss or offer
3130 * as our final mss.
984263bc 3131 */
b235ad6d 3132 if (rt->rt_rmx.rmx_mtu) {
984263bc 3133 mss = rt->rt_rmx.rmx_mtu - min_protoh;
b235ad6d
MD
3134 } else {
3135 if (isipv6)
698ac46c 3136 mss = ND_IFINFO(rt->rt_ifp)->linkmtu - min_protoh;
b235ad6d 3137 else
984263bc 3138 mss = ifp->if_mtu - min_protoh;
984263bc
MD
3139 }
3140 mss = min(mss, offer);
b235ad6d 3141
984263bc
MD
3142 /*
3143 * maxopd stores the maximum length of data AND options
3144 * in a segment; maxseg is the amount of data in a normal
3145 * segment. We need to store this value (maxopd) apart
3146 * from maxseg, because now every segment carries options
3147 * and thus we normally have somewhat less data in segments.
3148 */
3149 tp->t_maxopd = mss;
3150
3151 /*
3152 * In case of T/TCP, origoffer==-1 indicates, that no segments
3153 * were received yet. In this case we just guess, otherwise
3154 * we do the same as before T/TCP.
3155 */
61896e3c 3156 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP &&
984263bc
MD
3157 (origoffer == -1 ||
3158 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP))
3159 mss -= TCPOLEN_TSTAMP_APPA;
61896e3c 3160 if ((tp->t_flags & (TF_REQ_CC | TF_NOOPT)) == TF_REQ_CC &&
984263bc
MD
3161 (origoffer == -1 ||
3162 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC))
3163 mss -= TCPOLEN_CC_APPA;
3164
3165#if (MCLBYTES & (MCLBYTES - 1)) == 0
3166 if (mss > MCLBYTES)
3167 mss &= ~(MCLBYTES-1);
3168#else
3169 if (mss > MCLBYTES)
3170 mss = mss / MCLBYTES * MCLBYTES;
3171#endif
3172 /*
3173 * If there's a pipesize, change the socket buffer
3174 * to that size. Make the socket buffers an integral
3175 * number of mss units; if the mss is larger than
3176 * the socket buffer, decrease the mss.
3177 */
3178#ifdef RTV_SPIPE
3179 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0)
3180#endif
6d49aa6f 3181 bufsize = so->so_snd.ssb_hiwat;
984263bc
MD
3182 if (bufsize < mss)
3183 mss = bufsize;
3184 else {
3185 bufsize = roundup(bufsize, mss);
3186 if (bufsize > sb_max)
3187 bufsize = sb_max;
6d49aa6f
MD
3188 if (bufsize > so->so_snd.ssb_hiwat)
3189 ssb_reserve(&so->so_snd, bufsize, so, NULL);
984263bc
MD
3190 }
3191 tp->t_maxseg = mss;
3192
3193#ifdef RTV_RPIPE
3194 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0)
3195#endif
6d49aa6f 3196 bufsize = so->so_rcv.ssb_hiwat;
984263bc
MD
3197 if (bufsize > mss) {
3198 bufsize = roundup(bufsize, mss);
3199 if (bufsize > sb_max)
3200 bufsize = sb_max;
6d49aa6f
MD
3201 if (bufsize > so->so_rcv.ssb_hiwat)
3202 ssb_reserve(&so->so_rcv, bufsize, so, NULL);
984263bc
MD
3203 }
3204
3205 /*
3206 * Set the slow-start flight size depending on whether this
3207 * is a local network or not.
3208 */
4b52d5ee
JH
3209 if (tcp_do_rfc3390)
3210 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380));
4b52d5ee 3211 else
cd149066 3212 tp->snd_cwnd = mss;
984263bc
MD
3213
3214 if (rt->rt_rmx.rmx_ssthresh) {
3215 /*
3216 * There's some sort of gateway or interface
3217 * buffer limit on the path. Use this to set
3218 * the slow start threshhold, but set the
3219 * threshold to no less than 2*mss.
3220 */
3221 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh);
3222 tcpstat.tcps_usedssthresh++;
3223 }
3224}
3225
3226/*
3227 * Determine the MSS option to send on an outgoing SYN.
3228 */
3229int
95b22adf 3230tcp_mssopt(struct tcpcb *tp)
984263bc
MD
3231{
3232 struct rtentry *rt;
3233#ifdef INET6
d24ce1dc
JH
3234 boolean_t isipv6 =
3235 ((tp->t_inpcb->inp_vflag & INP_IPV6) ? TRUE : FALSE);
984263bc
MD
3236 int min_protoh = isipv6 ?
3237 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) :
3238 sizeof(struct tcpiphdr);
3239#else
d24ce1dc 3240 const boolean_t isipv6 = FALSE;
984263bc
MD
3241 const size_t min_protoh = sizeof(struct tcpiphdr);
3242#endif
3243
3244 if (isipv6)
3245 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc);
3246 else
3247 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc);
3248 if (rt == NULL)
3249 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt);
3250
3251 return (rt->rt_ifp->if_mtu - min_protoh);
3252}
3253
984263bc
MD
3254/*
3255 * When a partial ack arrives, force the retransmission of the
91489f6b
JH
3256 * next unacknowledged segment. Do not exit Fast Recovery.
3257 *
3258 * Implement the Slow-but-Steady variant of NewReno by restarting the
3259 * the retransmission timer. Turn it off here so it can be restarted
3260 * later in tcp_output().
984263bc
MD
3261 */
3262static void
91489f6b 3263tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th, int acked)
984263bc 3264{
91489f6b
JH
3265 tcp_seq old_snd_nxt = tp->snd_nxt;
3266 u_long ocwnd = tp->snd_cwnd;
984263bc 3267
a48c5dd5 3268 tcp_callout_stop(tp, tp->tt_rexmt);
984263bc
MD
3269 tp->t_rtttime = 0;
3270 tp->snd_nxt = th->th_ack;
91489f6b
JH
3271 /* Set snd_cwnd to one segment beyond acknowledged offset. */
3272 tp->snd_cwnd = tp->t_maxseg;
984263bc 3273 tp->t_flags |= TF_ACKNOW;
f23061d4 3274 tcp_output(tp);
91489f6b
JH
3275 if (SEQ_GT(old_snd_nxt, tp->snd_nxt))
3276 tp->snd_nxt = old_snd_nxt;
3277 /* partial window deflation */
68947d12
ND
3278 if (ocwnd > acked)
3279 tp->snd_cwnd = ocwnd - acked + tp->t_maxseg;
3280 else
3281 tp->snd_cwnd = tp->t_maxseg;
91489f6b
JH
3282}
3283
3284/*
3285 * In contrast to the Slow-but-Steady NewReno variant,
3286 * we do not reset the retransmission timer for SACK retransmissions,
3287 * except when retransmitting snd_una.
3288 */
3289static void
3290tcp_sack_rexmt(struct tcpcb *tp, struct tcphdr *th)
3291{
3292 uint32_t pipe, seglen;
3293 tcp_seq nextrexmt;
3294 boolean_t lostdup;
3295 tcp_seq old_snd_nxt = tp->snd_nxt;
3296 u_long ocwnd = tp->snd_cwnd;
3297 int nseg = 0; /* consecutive new segments */
3298#define MAXBURST 4 /* limit burst of new packets on partial ack */
3299
3300 tp->t_rtttime = 0;
3301 pipe = tcp_sack_compute_pipe(tp);
3302 while ((tcp_seq_diff_t)(ocwnd - pipe) >= (tcp_seq_diff_t)tp->t_maxseg &&
3303 (!tcp_do_smartsack || nseg < MAXBURST) &&
3304 tcp_sack_nextseg(tp, &nextrexmt, &seglen, &lostdup)) {
3305 uint32_t sent;
3306 tcp_seq old_snd_max;
3307 int error;
3308
98cb2337
MD
3309 if (nextrexmt == tp->snd_max)
3310 ++nseg;
91489f6b
JH
3311 tp->snd_nxt = nextrexmt;
3312 tp->snd_cwnd = nextrexmt - tp->snd_una + seglen;
3313 old_snd_max = tp->snd_max;
3314 if (nextrexmt == tp->snd_una)
a48c5dd5 3315 tcp_callout_stop(tp, tp->tt_rexmt);
91489f6b
JH
3316 error = tcp_output(tp);
3317 if (error != 0)
3318 break;
3319 sent = tp->snd_nxt - nextrexmt;
3320 if (sent <= 0)
3321 break;
3322 if (!lostdup)
3323 pipe += sent;
3324 tcpstat.tcps_sndsackpack++;
3325 tcpstat.tcps_sndsackbyte += sent;
3326 if (SEQ_LT(nextrexmt, old_snd_max) &&
3327 SEQ_LT(tp->rexmt_high, tp->snd_nxt))
3328 tp->rexmt_high = seq_min(tp->snd_nxt, old_snd_max);
3329 }
3330 if (SEQ_GT(old_snd_nxt, tp->snd_nxt))
3331 tp->snd_nxt = old_snd_nxt;
984263bc 3332 tp->snd_cwnd = ocwnd;
984263bc 3333}