2 * Copyright (c) 2002, 2003, 2004 Jeffrey M. Hsu. All rights reserved.
3 * Copyright (c) 2002, 2003, 2004 The DragonFly Project. All rights reserved.
5 * This code is derived from software contributed to The DragonFly Project
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
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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.
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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
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35 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995
36 * The Regents of the University of California. All rights reserved.
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39 * modification, are permitted provided that the following conditions
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51 * may be used to endorse or promote products derived from this software
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56 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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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
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 $
71 #include "opt_inet6.h"
72 #include "opt_ipsec.h"
73 #include "opt_tcpdebug.h"
74 #include "opt_tcp_input.h"
76 #include <sys/param.h>
77 #include <sys/systm.h>
78 #include <sys/kernel.h>
79 #include <sys/sysctl.h>
80 #include <sys/malloc.h>
82 #include <sys/proc.h> /* for proc0 declaration */
83 #include <sys/protosw.h>
84 #include <sys/socket.h>
85 #include <sys/socketvar.h>
86 #include <sys/syslog.h>
87 #include <sys/in_cksum.h>
89 #include <sys/socketvar2.h>
91 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */
92 #include <machine/stdarg.h>
95 #include <net/route.h>
97 #include <netinet/in.h>
98 #include <netinet/in_systm.h>
99 #include <netinet/ip.h>
100 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */
101 #include <netinet/in_var.h>
102 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */
103 #include <netinet/in_pcb.h>
104 #include <netinet/ip_var.h>
105 #include <netinet/ip6.h>
106 #include <netinet/icmp6.h>
107 #include <netinet6/nd6.h>
108 #include <netinet6/ip6_var.h>
109 #include <netinet6/in6_pcb.h>
110 #include <netinet/tcp.h>
111 #include <netinet/tcp_fsm.h>
112 #include <netinet/tcp_seq.h>
113 #include <netinet/tcp_timer.h>
114 #include <netinet/tcp_timer2.h>
115 #include <netinet/tcp_var.h>
116 #include <netinet6/tcp6_var.h>
117 #include <netinet/tcpip.h>
120 #include <netinet/tcp_debug.h>
122 u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */
123 struct tcphdr tcp_savetcp;
127 #include <netproto/ipsec/ipsec.h>
128 #include <netproto/ipsec/ipsec6.h>
132 #include <netinet6/ipsec.h>
133 #include <netinet6/ipsec6.h>
134 #include <netproto/key/key.h>
137 MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry");
139 static int log_in_vain = 0;
140 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW,
141 &log_in_vain, 0, "Log all incoming TCP connections");
143 static int blackhole = 0;
144 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW,
145 &blackhole, 0, "Do not send RST when dropping refused connections");
147 int tcp_delack_enabled = 1;
148 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW,
149 &tcp_delack_enabled, 0,
150 "Delay ACK to try and piggyback it onto a data packet");
152 #ifdef TCP_DROP_SYNFIN
153 static int drop_synfin = 0;
154 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW,
155 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set");
158 static int tcp_do_limitedtransmit = 1;
159 SYSCTL_INT(_net_inet_tcp, OID_AUTO, limitedtransmit, CTLFLAG_RW,
160 &tcp_do_limitedtransmit, 0, "Enable RFC 3042 (Limited Transmit)");
162 static int tcp_do_early_retransmit = 1;
163 SYSCTL_INT(_net_inet_tcp, OID_AUTO, earlyretransmit, CTLFLAG_RW,
164 &tcp_do_early_retransmit, 0, "Early retransmit");
166 int tcp_aggregate_acks = 1;
167 SYSCTL_INT(_net_inet_tcp, OID_AUTO, aggregate_acks, CTLFLAG_RW,
168 &tcp_aggregate_acks, 0, "Aggregate built-up acks into one ack");
170 static int tcp_do_eifel_detect = 1;
171 SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW,
172 &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)");
174 static int tcp_do_abc = 1;
175 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc, CTLFLAG_RW,
177 "TCP Appropriate Byte Counting (RFC 3465)");
180 * The following value actually takes range [25ms, 250ms],
181 * given that most modern systems use 1ms ~ 10ms as the unit
182 * of timestamp option.
184 static u_int tcp_paws_tolerance = 25;
185 SYSCTL_UINT(_net_inet_tcp, OID_AUTO, paws_tolerance, CTLFLAG_RW,
186 &tcp_paws_tolerance, 0, "RFC1323 PAWS tolerance");
189 * Define as tunable for easy testing with SACK on and off.
190 * Warning: do not change setting in the middle of an existing active TCP flow,
191 * else strange things might happen to that flow.
194 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW,
195 &tcp_do_sack, 0, "Enable SACK Algorithms");
197 int tcp_do_smartsack = 1;
198 SYSCTL_INT(_net_inet_tcp, OID_AUTO, smartsack, CTLFLAG_RW,
199 &tcp_do_smartsack, 0, "Enable Smart SACK Algorithms");
201 int tcp_do_rescuesack = 1;
202 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rescuesack, CTLFLAG_RW,
203 &tcp_do_rescuesack, 0, "Rescue retransmission for SACK");
205 int tcp_aggressive_rescuesack = 0;
206 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rescuesack_agg, CTLFLAG_RW,
207 &tcp_aggressive_rescuesack, 0, "Aggressive rescue retransmission for SACK");
209 static int tcp_force_sackrxt = 1;
210 SYSCTL_INT(_net_inet_tcp, OID_AUTO, force_sackrxt, CTLFLAG_RW,
211 &tcp_force_sackrxt, 0, "Allowed forced SACK retransmit burst");
213 int tcp_do_rfc6675 = 1;
214 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc6675, CTLFLAG_RW,
215 &tcp_do_rfc6675, 0, "Enable RFC6675");
217 int tcp_rfc6675_rxt = 0;
218 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc6675_rxt, CTLFLAG_RW,
219 &tcp_rfc6675_rxt, 0, "Enable RFC6675 retransmit");
221 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0,
222 "TCP Segment Reassembly Queue");
224 int tcp_reass_maxseg = 0;
225 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD,
226 &tcp_reass_maxseg, 0,
227 "Global maximum number of TCP Segments in Reassembly Queue");
229 int tcp_reass_qsize = 0;
230 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD,
232 "Global number of TCP Segments currently in Reassembly Queue");
234 static int tcp_reass_overflows = 0;
235 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD,
236 &tcp_reass_overflows, 0,
237 "Global number of TCP Segment Reassembly Queue Overflows");
239 int tcp_do_autorcvbuf = 1;
240 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW,
241 &tcp_do_autorcvbuf, 0, "Enable automatic receive buffer sizing");
243 int tcp_autorcvbuf_inc = 16*1024;
244 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW,
245 &tcp_autorcvbuf_inc, 0,
246 "Incrementor step size of automatic receive buffer");
248 int tcp_autorcvbuf_max = 2*1024*1024;
249 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW,
250 &tcp_autorcvbuf_max, 0, "Max size of automatic receive buffer");
252 int tcp_sosend_agglim = 3;
253 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosend_agglim, CTLFLAG_RW,
254 &tcp_sosend_agglim, 0, "TCP sosend mbuf aggregation limit");
256 int tcp_sosend_async = 1;
257 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosend_async, CTLFLAG_RW,
258 &tcp_sosend_async, 0, "TCP asynchronized pru_send");
260 static int tcp_ignore_redun_dsack = 1;
261 SYSCTL_INT(_net_inet_tcp, OID_AUTO, ignore_redun_dsack, CTLFLAG_RW,
262 &tcp_ignore_redun_dsack, 0, "Ignore redundant DSACK");
264 static void tcp_dooptions(struct tcpopt *, u_char *, int, boolean_t,
266 static void tcp_pulloutofband(struct socket *,
267 struct tcphdr *, struct mbuf *, int);
268 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *,
270 static void tcp_xmit_timer(struct tcpcb *, int, tcp_seq);
271 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *, int);
272 static void tcp_sack_rexmt(struct tcpcb *, boolean_t);
273 static boolean_t tcp_sack_limitedxmit(struct tcpcb *);
274 static int tcp_rmx_msl(const struct tcpcb *);
275 static void tcp_established(struct tcpcb *);
276 static boolean_t tcp_recv_dupack(struct tcpcb *, tcp_seq, u_int);
278 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */
280 #define ND6_HINT(tp) \
282 if ((tp) && (tp)->t_inpcb && \
283 ((tp)->t_inpcb->inp_vflag & INP_IPV6) && \
284 (tp)->t_inpcb->in6p_route.ro_rt) \
285 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \
292 * Indicate whether this ack should be delayed. We can delay the ack if
293 * - delayed acks are enabled and
294 * - there is no delayed ack timer in progress and
295 * - our last ack wasn't a 0-sized window. We never want to delay
296 * the ack that opens up a 0-sized window.
298 #define DELAY_ACK(tp) \
299 (tcp_delack_enabled && !tcp_callout_pending(tp, tp->tt_delack) && \
300 !(tp->t_flags & TF_RXWIN0SENT))
302 #define acceptable_window_update(tp, th, tiwin) \
303 (SEQ_LT(tp->snd_wl1, th->th_seq) || \
304 (tp->snd_wl1 == th->th_seq && \
305 (SEQ_LT(tp->snd_wl2, th->th_ack) || \
306 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))
308 #define iceildiv(n, d) (((n)+(d)-1) / (d))
309 #define need_early_retransmit(tp, ownd) \
310 (tcp_do_early_retransmit && \
311 (tcp_do_eifel_detect && (tp->t_flags & TF_RCVD_TSTMP)) && \
312 ownd < ((tp->t_rxtthresh + 1) * tp->t_maxseg) && \
313 tp->t_dupacks + 1 >= iceildiv(ownd, tp->t_maxseg) && \
314 (!TCP_DO_SACK(tp) || ownd <= tp->t_maxseg || \
315 tcp_sack_has_sacked(&tp->scb, ownd - tp->t_maxseg)))
318 * Returns TRUE, if this segment can be merged with the last
319 * pending segment in the reassemble queue and this segment
320 * does not overlap with the pending segment immediately
321 * preceeding the last pending segment.
323 static __inline boolean_t
324 tcp_paws_canreasslast(const struct tcpcb *tp, const struct tcphdr *th, int tlen)
326 const struct tseg_qent *last, *prev;
328 last = TAILQ_LAST(&tp->t_segq, tsegqe_head);
332 /* This segment comes immediately after the last pending segment */
333 if (last->tqe_th->th_seq + last->tqe_len == th->th_seq) {
334 if (last->tqe_th->th_flags & TH_FIN) {
335 /* No segments should follow segment w/ FIN */
341 if (th->th_seq + tlen != last->tqe_th->th_seq)
343 /* This segment comes immediately before the last pending segment */
345 prev = TAILQ_PREV(last, tsegqe_head, tqe_q);
348 * No pending preceeding segment, we assume this segment
349 * could be reassembled.
354 /* This segment does not overlap with the preceeding segment */
355 if (SEQ_GEQ(th->th_seq, prev->tqe_th->th_seq + prev->tqe_len))
362 tcp_ncr_update_rxtthresh(struct tcpcb *tp)
364 int old_rxtthresh = tp->t_rxtthresh;
365 uint32_t ownd = tp->snd_max - tp->snd_una;
367 tp->t_rxtthresh = max(tcprexmtthresh, ((ownd / tp->t_maxseg) >> 1));
368 if (tp->t_rxtthresh != old_rxtthresh) {
369 tcp_sack_update_lostseq(&tp->scb, tp->snd_una,
370 tp->t_maxseg, tp->t_rxtthresh);
375 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m)
378 struct tseg_qent *p = NULL;
379 struct tseg_qent *te;
380 struct socket *so = tp->t_inpcb->inp_socket;
384 * Call with th == NULL after become established to
385 * force pre-ESTABLISHED data up to user socket.
391 * Limit the number of segments in the reassembly queue to prevent
392 * holding on to too many segments (and thus running out of mbufs).
393 * Make sure to let the missing segment through which caused this
394 * queue. Always keep one global queue entry spare to be able to
395 * process the missing segment.
397 if (th->th_seq != tp->rcv_nxt &&
398 tcp_reass_qsize + 1 >= tcp_reass_maxseg) {
399 tcp_reass_overflows++;
400 tcpstat.tcps_rcvmemdrop++;
402 /* no SACK block to report */
403 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
407 /* Allocate a new queue entry. */
408 te = kmalloc(sizeof(struct tseg_qent), M_TSEGQ, M_INTWAIT | M_NULLOK);
410 tcpstat.tcps_rcvmemdrop++;
412 /* no SACK block to report */
413 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
416 atomic_add_int(&tcp_reass_qsize, 1);
418 if (th->th_flags & TH_FIN)
419 tp->t_flags |= TF_QUEDFIN;
422 * Find a segment which begins after this one does.
424 TAILQ_FOREACH(q, &tp->t_segq, tqe_q) {
425 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
431 * If there is a preceding segment, it may provide some of
432 * our data already. If so, drop the data from the incoming
433 * segment. If it provides all of our data, drop us.
438 /* conversion to int (in i) handles seq wraparound */
439 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
440 if (i > 0) { /* overlaps preceding segment */
442 (TSACK_F_DUPSEG | TSACK_F_ENCLOSESEG);
443 /* enclosing block starts w/ preceding segment */
444 tp->encloseblk.rblk_start = p->tqe_th->th_seq;
446 if (th->th_flags & TH_FIN)
447 p->tqe_th->th_flags |= TH_FIN;
449 /* preceding encloses incoming segment */
450 tp->encloseblk.rblk_end = TCP_SACK_BLKEND(
451 p->tqe_th->th_seq + p->tqe_len,
452 p->tqe_th->th_flags);
453 tcpstat.tcps_rcvduppack++;
454 tcpstat.tcps_rcvdupbyte += *tlenp;
457 atomic_add_int(&tcp_reass_qsize, -1);
459 * Try to present any queued data
460 * at the left window edge to the user.
461 * This is needed after the 3-WHS
464 goto present; /* ??? */
469 /* incoming segment end is enclosing block end */
470 tp->encloseblk.rblk_end = TCP_SACK_BLKEND(
471 th->th_seq + *tlenp, th->th_flags);
472 /* trim end of reported D-SACK block */
473 tp->reportblk.rblk_end = th->th_seq;
476 tcpstat.tcps_rcvoopack++;
477 tcpstat.tcps_rcvoobyte += *tlenp;
480 * While we overlap succeeding segments trim them or,
481 * if they are completely covered, dequeue them.
484 tcp_seq_diff_t i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
485 tcp_seq qend = q->tqe_th->th_seq + q->tqe_len;
486 tcp_seq qend_sack = TCP_SACK_BLKEND(qend, q->tqe_th->th_flags);
487 struct tseg_qent *nq;
491 if (!(tp->sack_flags & TSACK_F_DUPSEG)) {
492 /* first time through */
493 tp->sack_flags |= (TSACK_F_DUPSEG | TSACK_F_ENCLOSESEG);
494 tp->encloseblk = tp->reportblk;
495 /* report trailing duplicate D-SACK segment */
496 tp->reportblk.rblk_start = q->tqe_th->th_seq;
498 if ((tp->sack_flags & TSACK_F_ENCLOSESEG) &&
499 SEQ_GT(qend_sack, tp->encloseblk.rblk_end)) {
500 /* extend enclosing block if one exists */
501 tp->encloseblk.rblk_end = qend_sack;
503 if (i < q->tqe_len) {
504 q->tqe_th->th_seq += i;
510 if (q->tqe_th->th_flags & TH_FIN)
511 th->th_flags |= TH_FIN;
513 nq = TAILQ_NEXT(q, tqe_q);
514 TAILQ_REMOVE(&tp->t_segq, q, tqe_q);
517 atomic_add_int(&tcp_reass_qsize, -1);
521 /* Insert the new segment queue entry into place. */
524 te->tqe_len = *tlenp;
526 /* check if can coalesce with following segment */
527 if (q != NULL && (th->th_seq + *tlenp == q->tqe_th->th_seq)) {
530 te->tqe_len += q->tqe_len;
531 if (q->tqe_th->th_flags & TH_FIN)
532 te->tqe_th->th_flags |= TH_FIN;
533 tend_sack = TCP_SACK_BLKEND(te->tqe_th->th_seq + te->tqe_len,
534 te->tqe_th->th_flags);
536 m_cat(te->tqe_m, q->tqe_m);
537 tp->encloseblk.rblk_end = tend_sack;
539 * When not reporting a duplicate segment, use
540 * the larger enclosing block as the SACK block.
542 if (!(tp->sack_flags & TSACK_F_DUPSEG))
543 tp->reportblk.rblk_end = tend_sack;
544 TAILQ_REMOVE(&tp->t_segq, q, tqe_q);
546 atomic_add_int(&tcp_reass_qsize, -1);
550 TAILQ_INSERT_HEAD(&tp->t_segq, te, tqe_q);
552 /* check if can coalesce with preceding segment */
553 if (p->tqe_th->th_seq + p->tqe_len == th->th_seq) {
554 if (te->tqe_th->th_flags & TH_FIN)
555 p->tqe_th->th_flags |= TH_FIN;
556 p->tqe_len += te->tqe_len;
557 m_cat(p->tqe_m, te->tqe_m);
558 tp->encloseblk.rblk_start = p->tqe_th->th_seq;
560 * When not reporting a duplicate segment, use
561 * the larger enclosing block as the SACK block.
563 if (!(tp->sack_flags & TSACK_F_DUPSEG))
564 tp->reportblk.rblk_start = p->tqe_th->th_seq;
566 atomic_add_int(&tcp_reass_qsize, -1);
568 TAILQ_INSERT_AFTER(&tp->t_segq, p, te, tqe_q);
574 * Present data to user, advancing rcv_nxt through
575 * completed sequence space.
577 if (!TCPS_HAVEESTABLISHED(tp->t_state))
579 q = TAILQ_FIRST(&tp->t_segq);
580 if (q == NULL || q->tqe_th->th_seq != tp->rcv_nxt)
582 tp->rcv_nxt += q->tqe_len;
583 if (!(tp->sack_flags & TSACK_F_DUPSEG)) {
584 /* no SACK block to report since ACK advanced */
585 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
587 /* no enclosing block to report since ACK advanced */
588 tp->sack_flags &= ~TSACK_F_ENCLOSESEG;
589 flags = q->tqe_th->th_flags & TH_FIN;
590 TAILQ_REMOVE(&tp->t_segq, q, tqe_q);
591 KASSERT(TAILQ_EMPTY(&tp->t_segq) ||
592 TAILQ_FIRST(&tp->t_segq)->tqe_th->th_seq != tp->rcv_nxt,
593 ("segment not coalesced"));
594 if (so->so_state & SS_CANTRCVMORE) {
597 lwkt_gettoken(&so->so_rcv.ssb_token);
598 ssb_appendstream(&so->so_rcv, q->tqe_m);
599 lwkt_reltoken(&so->so_rcv.ssb_token);
602 atomic_add_int(&tcp_reass_qsize, -1);
609 * TCP input routine, follows pages 65-76 of the
610 * protocol specification dated September, 1981 very closely.
614 tcp6_input(struct mbuf **mp, int *offp, int proto)
616 struct mbuf *m = *mp;
617 struct in6_ifaddr *ia6;
619 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE);
622 * draft-itojun-ipv6-tcp-to-anycast
623 * better place to put this in?
625 ia6 = ip6_getdstifaddr(m);
626 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) {
629 ip6 = mtod(m, struct ip6_hdr *);
630 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
631 offsetof(struct ip6_hdr, ip6_dst));
632 return (IPPROTO_DONE);
635 tcp_input(mp, offp, proto);
636 return (IPPROTO_DONE);
641 tcp_input(struct mbuf **mp, int *offp, int proto)
645 struct ip *ip = NULL;
647 struct inpcb *inp = NULL;
653 struct tcpcb *tp = NULL;
655 struct socket *so = NULL;
657 boolean_t ourfinisacked, needoutput = FALSE, delayed_dupack = FALSE;
658 tcp_seq th_dupack = 0; /* XXX gcc warning */
659 u_int to_flags = 0; /* XXX gcc warning */
662 struct tcpopt to; /* options in this segment */
663 struct sockaddr_in *next_hop = NULL;
664 int rstreason; /* For badport_bandlim accounting purposes */
666 struct ip6_hdr *ip6 = NULL;
671 const boolean_t isipv6 = FALSE;
681 tcpstat.tcps_rcvtotal++;
683 if (m->m_pkthdr.fw_flags & IPFORWARD_MBUF_TAGGED) {
686 mtag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL);
687 KKASSERT(mtag != NULL);
688 next_hop = m_tag_data(mtag);
692 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE;
696 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */
697 ip6 = mtod(m, struct ip6_hdr *);
698 tlen = (sizeof *ip6) + ntohs(ip6->ip6_plen) - off0;
699 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) {
700 tcpstat.tcps_rcvbadsum++;
703 th = (struct tcphdr *)((caddr_t)ip6 + off0);
706 * Be proactive about unspecified IPv6 address in source.
707 * As we use all-zero to indicate unbounded/unconnected pcb,
708 * unspecified IPv6 address can be used to confuse us.
710 * Note that packets with unspecified IPv6 destination is
711 * already dropped in ip6_input.
713 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
719 * Get IP and TCP header together in first mbuf.
720 * Note: IP leaves IP header in first mbuf.
722 if (off0 > sizeof(struct ip)) {
724 off0 = sizeof(struct ip);
726 /* already checked and pulled up in ip_demux() */
727 KASSERT(m->m_len >= sizeof(struct tcpiphdr),
728 ("TCP header not in one mbuf: m->m_len %d", m->m_len));
729 ip = mtod(m, struct ip *);
730 ipov = (struct ipovly *)ip;
731 th = (struct tcphdr *)((caddr_t)ip + off0);
734 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
735 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
736 th->th_sum = m->m_pkthdr.csum_data;
738 th->th_sum = in_pseudo(ip->ip_src.s_addr,
740 htonl(m->m_pkthdr.csum_data +
743 th->th_sum ^= 0xffff;
746 * Checksum extended TCP header and data.
748 len = sizeof(struct ip) + tlen;
749 bzero(ipov->ih_x1, sizeof ipov->ih_x1);
750 ipov->ih_len = (u_short)tlen;
751 ipov->ih_len = htons(ipov->ih_len);
752 th->th_sum = in_cksum(m, len);
755 tcpstat.tcps_rcvbadsum++;
759 /* Re-initialization for later version check */
760 ip->ip_v = IPVERSION;
765 * Check that TCP offset makes sense,
766 * pull out TCP options and adjust length. XXX
768 off = th->th_off << 2;
769 /* already checked and pulled up in ip_demux() */
770 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen,
771 ("bad TCP data offset %d (tlen %d)", off, tlen));
772 tlen -= off; /* tlen is used instead of ti->ti_len */
773 if (off > sizeof(struct tcphdr)) {
775 IP6_EXTHDR_CHECK(m, off0, off, IPPROTO_DONE);
776 ip6 = mtod(m, struct ip6_hdr *);
777 th = (struct tcphdr *)((caddr_t)ip6 + off0);
779 /* already pulled up in ip_demux() */
780 KASSERT(m->m_len >= sizeof(struct ip) + off,
781 ("TCP header and options not in one mbuf: "
782 "m_len %d, off %d", m->m_len, off));
784 optlen = off - sizeof(struct tcphdr);
785 optp = (u_char *)(th + 1);
787 thflags = th->th_flags;
789 #ifdef TCP_DROP_SYNFIN
791 * If the drop_synfin option is enabled, drop all packets with
792 * both the SYN and FIN bits set. This prevents e.g. nmap from
793 * identifying the TCP/IP stack.
795 * This is a violation of the TCP specification.
797 if (drop_synfin && (thflags & (TH_SYN | TH_FIN)) == (TH_SYN | TH_FIN))
802 * Convert TCP protocol specific fields to host format.
804 th->th_seq = ntohl(th->th_seq);
805 th->th_ack = ntohl(th->th_ack);
806 th->th_win = ntohs(th->th_win);
807 th->th_urp = ntohs(th->th_urp);
810 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options,
811 * until after ip6_savecontrol() is called and before other functions
812 * which don't want those proto headers.
813 * Because ip6_savecontrol() is going to parse the mbuf to
814 * search for data to be passed up to user-land, it wants mbuf
815 * parameters to be unchanged.
816 * XXX: the call of ip6_savecontrol() has been obsoleted based on
817 * latest version of the advanced API (20020110).
819 drop_hdrlen = off0 + off;
822 * Locate pcb for segment.
825 /* IPFIREWALL_FORWARD section */
826 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */
828 * Transparently forwarded. Pretend to be the destination.
829 * already got one like this?
831 cpu = mycpu->gd_cpuid;
832 inp = in_pcblookup_hash(&tcbinfo[cpu],
833 ip->ip_src, th->th_sport,
834 ip->ip_dst, th->th_dport,
835 0, m->m_pkthdr.rcvif);
838 * It's new. Try to find the ambushing socket.
842 * The rest of the ipfw code stores the port in
844 * (The IP address is still in network order.)
846 in_port_t dport = next_hop->sin_port ?
847 htons(next_hop->sin_port) :
850 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport,
851 next_hop->sin_addr.s_addr, dport);
852 inp = in_pcblookup_hash(&tcbinfo[cpu],
853 ip->ip_src, th->th_sport,
854 next_hop->sin_addr, dport,
855 1, m->m_pkthdr.rcvif);
859 inp = in6_pcblookup_hash(&tcbinfo[0],
860 &ip6->ip6_src, th->th_sport,
861 &ip6->ip6_dst, th->th_dport,
862 1, m->m_pkthdr.rcvif);
864 cpu = mycpu->gd_cpuid;
865 inp = in_pcblookup_hash(&tcbinfo[cpu],
866 ip->ip_src, th->th_sport,
867 ip->ip_dst, th->th_dport,
868 1, m->m_pkthdr.rcvif);
873 * If the state is CLOSED (i.e., TCB does not exist) then
874 * all data in the incoming segment is discarded.
875 * If the TCB exists but is in CLOSED state, it is embryonic,
876 * but should either do a listen or a connect soon.
881 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2];
883 char dbuf[sizeof "aaa.bbb.ccc.ddd"];
884 char sbuf[sizeof "aaa.bbb.ccc.ddd"];
888 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst));
891 strcat(sbuf, ip6_sprintf(&ip6->ip6_src));
894 strcpy(dbuf, inet_ntoa(ip->ip_dst));
895 strcpy(sbuf, inet_ntoa(ip->ip_src));
897 switch (log_in_vain) {
899 if (!(thflags & TH_SYN))
903 "Connection attempt to TCP %s:%d "
904 "from %s:%d flags:0x%02x\n",
905 dbuf, ntohs(th->th_dport), sbuf,
906 ntohs(th->th_sport), thflags);
915 if (thflags & TH_SYN)
924 rstreason = BANDLIM_RST_CLOSEDPORT;
930 if (ipsec6_in_reject_so(m, inp->inp_socket)) {
931 ipsec6stat.in_polvio++;
935 if (ipsec4_in_reject_so(m, inp->inp_socket)) {
936 ipsecstat.in_polvio++;
943 if (ipsec6_in_reject(m, inp))
946 if (ipsec4_in_reject(m, inp))
950 /* Check the minimum TTL for socket. */
952 if ((isipv6 ? ip6->ip6_hlim : ip->ip_ttl) < inp->inp_ip_minttl)
958 rstreason = BANDLIM_RST_CLOSEDPORT;
961 if (tp->t_state <= TCPS_CLOSED)
964 so = inp->inp_socket;
967 if (so->so_options & SO_DEBUG) {
968 ostate = tp->t_state;
970 bcopy(ip6, tcp_saveipgen, sizeof(*ip6));
972 bcopy(ip, tcp_saveipgen, sizeof(*ip));
977 bzero(&to, sizeof to);
979 if (so->so_options & SO_ACCEPTCONN) {
980 struct in_conninfo inc;
983 inc.inc_isipv6 = (isipv6 == TRUE);
986 inc.inc6_faddr = ip6->ip6_src;
987 inc.inc6_laddr = ip6->ip6_dst;
988 inc.inc6_route.ro_rt = NULL; /* XXX */
990 inc.inc_faddr = ip->ip_src;
991 inc.inc_laddr = ip->ip_dst;
992 inc.inc_route.ro_rt = NULL; /* XXX */
994 inc.inc_fport = th->th_sport;
995 inc.inc_lport = th->th_dport;
998 * If the state is LISTEN then ignore segment if it contains
999 * a RST. If the segment contains an ACK then it is bad and
1000 * send a RST. If it does not contain a SYN then it is not
1001 * interesting; drop it.
1003 * If the state is SYN_RECEIVED (syncache) and seg contains
1004 * an ACK, but not for our SYN/ACK, send a RST. If the seg
1005 * contains a RST, check the sequence number to see if it
1006 * is a valid reset segment.
1008 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) != TH_SYN) {
1009 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) == TH_ACK) {
1010 if (!syncache_expand(&inc, th, &so, m)) {
1012 * No syncache entry, or ACK was not
1013 * for our SYN/ACK. Send a RST.
1015 tcpstat.tcps_badsyn++;
1016 rstreason = BANDLIM_RST_OPENPORT;
1021 * Could not complete 3-way handshake,
1022 * connection is being closed down, and
1023 * syncache will free mbuf.
1026 return(IPPROTO_DONE);
1029 * We must be in the correct protocol thread
1030 * for this connection.
1032 KKASSERT(so->so_port == &curthread->td_msgport);
1035 * Socket is created in state SYN_RECEIVED.
1036 * Continue processing segment.
1039 tp = intotcpcb(inp);
1041 * This is what would have happened in
1042 * tcp_output() when the SYN,ACK was sent.
1044 tp->snd_up = tp->snd_una;
1045 tp->snd_max = tp->snd_nxt = tp->iss + 1;
1046 tp->last_ack_sent = tp->rcv_nxt;
1050 if (thflags & TH_RST) {
1051 syncache_chkrst(&inc, th);
1054 if (thflags & TH_ACK) {
1055 syncache_badack(&inc);
1056 tcpstat.tcps_badsyn++;
1057 rstreason = BANDLIM_RST_OPENPORT;
1064 * Segment's flags are (SYN) or (SYN | FIN).
1068 * If deprecated address is forbidden,
1069 * we do not accept SYN to deprecated interface
1070 * address to prevent any new inbound connection from
1071 * getting established.
1072 * When we do not accept SYN, we send a TCP RST,
1073 * with deprecated source address (instead of dropping
1074 * it). We compromise it as it is much better for peer
1075 * to send a RST, and RST will be the final packet
1078 * If we do not forbid deprecated addresses, we accept
1079 * the SYN packet. RFC2462 does not suggest dropping
1081 * If we decipher RFC2462 5.5.4, it says like this:
1082 * 1. use of deprecated addr with existing
1083 * communication is okay - "SHOULD continue to be
1085 * 2. use of it with new communication:
1086 * (2a) "SHOULD NOT be used if alternate address
1087 * with sufficient scope is available"
1088 * (2b) nothing mentioned otherwise.
1089 * Here we fall into (2b) case as we have no choice in
1090 * our source address selection - we must obey the peer.
1092 * The wording in RFC2462 is confusing, and there are
1093 * multiple description text for deprecated address
1094 * handling - worse, they are not exactly the same.
1095 * I believe 5.5.4 is the best one, so we follow 5.5.4.
1097 if (isipv6 && !ip6_use_deprecated) {
1098 struct in6_ifaddr *ia6;
1100 if ((ia6 = ip6_getdstifaddr(m)) &&
1101 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
1103 rstreason = BANDLIM_RST_OPENPORT;
1109 * If it is from this socket, drop it, it must be forged.
1110 * Don't bother responding if the destination was a broadcast.
1112 if (th->th_dport == th->th_sport) {
1114 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst,
1118 if (ip->ip_dst.s_addr == ip->ip_src.s_addr)
1123 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN
1125 * Note that it is quite possible to receive unicast
1126 * link-layer packets with a broadcast IP address. Use
1127 * in_broadcast() to find them.
1129 if (m->m_flags & (M_BCAST | M_MCAST))
1132 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
1133 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
1136 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
1137 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
1138 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
1139 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
1143 * SYN appears to be valid; create compressed TCP state
1144 * for syncache, or perform t/tcp connection.
1146 if (so->so_qlen <= so->so_qlimit) {
1147 tcp_dooptions(&to, optp, optlen, TRUE, th->th_ack);
1148 if (!syncache_add(&inc, &to, th, so, m))
1152 * Entry added to syncache, mbuf used to
1153 * send SYN,ACK packet.
1155 return(IPPROTO_DONE);
1162 * Should not happen - syncache should pick up these connections.
1164 * Once we are past handling listen sockets we must be in the
1165 * correct protocol processing thread.
1167 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN state"));
1168 KKASSERT(so->so_port == &curthread->td_msgport);
1170 /* Unscale the window into a 32-bit value. */
1171 if (!(thflags & TH_SYN))
1172 tiwin = th->th_win << tp->snd_scale;
1177 * This is the second part of the MSS DoS prevention code (after
1178 * minmss on the sending side) and it deals with too many too small
1179 * tcp packets in a too short timeframe (1 second).
1181 * XXX Removed. This code was crap. It does not scale to network
1182 * speed, and default values break NFS. Gone.
1187 * Segment received on connection.
1189 * Reset idle time and keep-alive timer. Don't waste time if less
1190 * then a second has elapsed.
1192 if ((int)(ticks - tp->t_rcvtime) > hz)
1193 tcp_timer_keep_activity(tp, thflags);
1197 * XXX this is tradtitional behavior, may need to be cleaned up.
1199 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0, th->th_ack);
1200 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) {
1201 if ((to.to_flags & TOF_SCALE) && (tp->t_flags & TF_REQ_SCALE)) {
1202 tp->t_flags |= TF_RCVD_SCALE;
1203 tp->snd_scale = to.to_requested_s_scale;
1207 * Initial send window; will be updated upon next ACK
1209 tp->snd_wnd = th->th_win;
1211 if (to.to_flags & TOF_TS) {
1212 tp->t_flags |= TF_RCVD_TSTMP;
1213 tp->ts_recent = to.to_tsval;
1214 tp->ts_recent_age = ticks;
1216 if (!(to.to_flags & TOF_MSS))
1218 tcp_mss(tp, to.to_mss);
1220 * Only set the TF_SACK_PERMITTED per-connection flag
1221 * if we got a SACK_PERMITTED option from the other side
1222 * and the global tcp_do_sack variable is true.
1224 if (tcp_do_sack && (to.to_flags & TOF_SACK_PERMITTED))
1225 tp->t_flags |= TF_SACK_PERMITTED;
1229 * Header prediction: check for the two common cases
1230 * of a uni-directional data xfer. If the packet has
1231 * no control flags, is in-sequence, the window didn't
1232 * change and we're not retransmitting, it's a
1233 * candidate. If the length is zero and the ack moved
1234 * forward, we're the sender side of the xfer. Just
1235 * free the data acked & wake any higher level process
1236 * that was blocked waiting for space. If the length
1237 * is non-zero and the ack didn't move, we're the
1238 * receiver side. If we're getting packets in-order
1239 * (the reassembly queue is empty), add the data to
1240 * the socket buffer and note that we need a delayed ack.
1241 * Make sure that the hidden state-flags are also off.
1242 * Since we check for TCPS_ESTABLISHED above, it can only
1245 if (tp->t_state == TCPS_ESTABLISHED &&
1246 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
1247 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) &&
1248 (!(to.to_flags & TOF_TS) ||
1249 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) &&
1250 th->th_seq == tp->rcv_nxt &&
1251 tp->snd_nxt == tp->snd_max) {
1254 * If last ACK falls within this segment's sequence numbers,
1255 * record the timestamp.
1256 * NOTE that the test is modified according to the latest
1257 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1259 if ((to.to_flags & TOF_TS) &&
1260 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
1261 tp->ts_recent_age = ticks;
1262 tp->ts_recent = to.to_tsval;
1266 if (SEQ_GT(th->th_ack, tp->snd_una) &&
1267 SEQ_LEQ(th->th_ack, tp->snd_max) &&
1268 tp->snd_cwnd >= tp->snd_wnd &&
1269 !IN_FASTRECOVERY(tp)) {
1271 * This is a pure ack for outstanding data.
1273 ++tcpstat.tcps_predack;
1275 * "bad retransmit" recovery
1277 * If Eifel detection applies, then
1278 * it is deterministic, so use it
1279 * unconditionally over the old heuristic.
1280 * Otherwise, fall back to the old heuristic.
1282 if (tcp_do_eifel_detect &&
1283 (to.to_flags & TOF_TS) && to.to_tsecr &&
1284 (tp->rxt_flags & TRXT_F_FIRSTACCACK)) {
1285 /* Eifel detection applicable. */
1286 if (to.to_tsecr < tp->t_rexmtTS) {
1287 tcp_revert_congestion_state(tp);
1288 ++tcpstat.tcps_eifeldetected;
1289 if (tp->t_rxtshift != 1 ||
1290 ticks >= tp->t_badrxtwin)
1291 ++tcpstat.tcps_rttcantdetect;
1293 } else if (tp->t_rxtshift == 1 &&
1294 ticks < tp->t_badrxtwin) {
1295 tcp_revert_congestion_state(tp);
1296 ++tcpstat.tcps_rttdetected;
1298 tp->rxt_flags &= ~(TRXT_F_FIRSTACCACK |
1299 TRXT_F_FASTREXMT | TRXT_F_EARLYREXMT);
1301 * Recalculate the retransmit timer / rtt.
1303 * Some machines (certain windows boxes)
1304 * send broken timestamp replies during the
1305 * SYN+ACK phase, ignore timestamps of 0.
1307 if ((to.to_flags & TOF_TS) && to.to_tsecr) {
1309 ticks - to.to_tsecr + 1,
1311 } else if (tp->t_rtttime &&
1312 SEQ_GT(th->th_ack, tp->t_rtseq)) {
1314 ticks - tp->t_rtttime,
1317 tcp_xmit_bandwidth_limit(tp, th->th_ack);
1318 acked = th->th_ack - tp->snd_una;
1319 tcpstat.tcps_rcvackpack++;
1320 tcpstat.tcps_rcvackbyte += acked;
1321 sbdrop(&so->so_snd.sb, acked);
1322 tp->snd_recover = th->th_ack - 1;
1323 tp->snd_una = th->th_ack;
1326 * Update window information.
1328 if (tiwin != tp->snd_wnd &&
1329 acceptable_window_update(tp, th, tiwin)) {
1330 /* keep track of pure window updates */
1331 if (tp->snd_wl2 == th->th_ack &&
1332 tiwin > tp->snd_wnd)
1333 tcpstat.tcps_rcvwinupd++;
1334 tp->snd_wnd = tiwin;
1335 tp->snd_wl1 = th->th_seq;
1336 tp->snd_wl2 = th->th_ack;
1337 if (tp->snd_wnd > tp->max_sndwnd)
1338 tp->max_sndwnd = tp->snd_wnd;
1341 ND6_HINT(tp); /* some progress has been done */
1343 * If all outstanding data are acked, stop
1344 * retransmit timer, otherwise restart timer
1345 * using current (possibly backed-off) value.
1346 * If process is waiting for space,
1347 * wakeup/selwakeup/signal. If data
1348 * are ready to send, let tcp_output
1349 * decide between more output or persist.
1351 if (tp->snd_una == tp->snd_max) {
1352 tcp_callout_stop(tp, tp->tt_rexmt);
1353 } else if (!tcp_callout_active(tp,
1355 tcp_callout_reset(tp, tp->tt_rexmt,
1356 tp->t_rxtcur, tcp_timer_rexmt);
1359 if (so->so_snd.ssb_cc > 0)
1361 return(IPPROTO_DONE);
1363 } else if (tiwin == tp->snd_wnd &&
1364 th->th_ack == tp->snd_una &&
1365 TAILQ_EMPTY(&tp->t_segq) &&
1366 tlen <= ssb_space(&so->so_rcv)) {
1367 u_long newsize = 0; /* automatic sockbuf scaling */
1369 * This is a pure, in-sequence data packet
1370 * with nothing on the reassembly queue and
1371 * we have enough buffer space to take it.
1373 ++tcpstat.tcps_preddat;
1374 tp->rcv_nxt += tlen;
1375 tcpstat.tcps_rcvpack++;
1376 tcpstat.tcps_rcvbyte += tlen;
1377 ND6_HINT(tp); /* some progress has been done */
1379 * Automatic sizing of receive socket buffer. Often the send
1380 * buffer size is not optimally adjusted to the actual network
1381 * conditions at hand (delay bandwidth product). Setting the
1382 * buffer size too small limits throughput on links with high
1383 * bandwidth and high delay (eg. trans-continental/oceanic links).
1385 * On the receive side the socket buffer memory is only rarely
1386 * used to any significant extent. This allows us to be much
1387 * more aggressive in scaling the receive socket buffer. For
1388 * the case that the buffer space is actually used to a large
1389 * extent and we run out of kernel memory we can simply drop
1390 * the new segments; TCP on the sender will just retransmit it
1391 * later. Setting the buffer size too big may only consume too
1392 * much kernel memory if the application doesn't read() from
1393 * the socket or packet loss or reordering makes use of the
1396 * The criteria to step up the receive buffer one notch are:
1397 * 1. the number of bytes received during the time it takes
1398 * one timestamp to be reflected back to us (the RTT);
1399 * 2. received bytes per RTT is within seven eighth of the
1400 * current socket buffer size;
1401 * 3. receive buffer size has not hit maximal automatic size;
1403 * This algorithm does one step per RTT at most and only if
1404 * we receive a bulk stream w/o packet losses or reorderings.
1405 * Shrinking the buffer during idle times is not necessary as
1406 * it doesn't consume any memory when idle.
1408 * TODO: Only step up if the application is actually serving
1409 * the buffer to better manage the socket buffer resources.
1411 if (tcp_do_autorcvbuf &&
1413 (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) {
1414 if (to.to_tsecr > tp->rfbuf_ts &&
1415 to.to_tsecr - tp->rfbuf_ts < hz) {
1417 (so->so_rcv.ssb_hiwat / 8 * 7) &&
1418 so->so_rcv.ssb_hiwat <
1419 tcp_autorcvbuf_max) {
1421 ulmin(so->so_rcv.ssb_hiwat +
1423 tcp_autorcvbuf_max);
1425 /* Start over with next RTT. */
1429 tp->rfbuf_cnt += tlen; /* add up */
1432 * Add data to socket buffer.
1434 if (so->so_state & SS_CANTRCVMORE) {
1438 * Set new socket buffer size, give up when
1441 * Adjusting the size can mess up ACK
1442 * sequencing when pure window updates are
1443 * being avoided (which is the default),
1446 lwkt_gettoken(&so->so_rcv.ssb_token);
1448 tp->t_flags |= TF_RXRESIZED;
1449 if (!ssb_reserve(&so->so_rcv, newsize,
1451 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE);
1454 (TCP_MAXWIN << tp->rcv_scale)) {
1455 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE);
1458 m_adj(m, drop_hdrlen); /* delayed header drop */
1459 ssb_appendstream(&so->so_rcv, m);
1460 lwkt_reltoken(&so->so_rcv.ssb_token);
1464 * This code is responsible for most of the ACKs
1465 * the TCP stack sends back after receiving a data
1466 * packet. Note that the DELAY_ACK check fails if
1467 * the delack timer is already running, which results
1468 * in an ack being sent every other packet (which is
1471 * We then further aggregate acks by not actually
1472 * sending one until the protocol thread has completed
1473 * processing the current backlog of packets. This
1474 * does not delay the ack any further, but allows us
1475 * to take advantage of the packet aggregation that
1476 * high speed NICs do (usually blocks of 8-10 packets)
1477 * to send a single ack rather then four or five acks,
1478 * greatly reducing the ack rate, the return channel
1479 * bandwidth, and the protocol overhead on both ends.
1481 * Since this also has the effect of slowing down
1482 * the exponential slow-start ramp-up, systems with
1483 * very large bandwidth-delay products might want
1484 * to turn the feature off.
1486 if (DELAY_ACK(tp)) {
1487 tcp_callout_reset(tp, tp->tt_delack,
1488 tcp_delacktime, tcp_timer_delack);
1489 } else if (tcp_aggregate_acks) {
1490 tp->t_flags |= TF_ACKNOW;
1491 if (!(tp->t_flags & TF_ONOUTPUTQ)) {
1492 tp->t_flags |= TF_ONOUTPUTQ;
1493 tp->tt_cpu = mycpu->gd_cpuid;
1495 &tcpcbackq[tp->tt_cpu],
1499 tp->t_flags |= TF_ACKNOW;
1502 return(IPPROTO_DONE);
1507 * Calculate amount of space in receive window,
1508 * and then do TCP input processing.
1509 * Receive window is amount of space in rcv queue,
1510 * but not less than advertised window.
1512 recvwin = ssb_space(&so->so_rcv);
1515 tp->rcv_wnd = imax(recvwin, (int)(tp->rcv_adv - tp->rcv_nxt));
1517 /* Reset receive buffer auto scaling when not in bulk receive mode. */
1521 switch (tp->t_state) {
1523 * If the state is SYN_RECEIVED:
1524 * if seg contains an ACK, but not for our SYN/ACK, send a RST.
1526 case TCPS_SYN_RECEIVED:
1527 if ((thflags & TH_ACK) &&
1528 (SEQ_LEQ(th->th_ack, tp->snd_una) ||
1529 SEQ_GT(th->th_ack, tp->snd_max))) {
1530 rstreason = BANDLIM_RST_OPENPORT;
1536 * If the state is SYN_SENT:
1537 * if seg contains an ACK, but not for our SYN, drop the input.
1538 * if seg contains a RST, then drop the connection.
1539 * if seg does not contain SYN, then drop it.
1540 * Otherwise this is an acceptable SYN segment
1541 * initialize tp->rcv_nxt and tp->irs
1542 * if seg contains ack then advance tp->snd_una
1543 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state
1544 * arrange for segment to be acked (eventually)
1545 * continue processing rest of data/controls, beginning with URG
1548 if ((thflags & TH_ACK) &&
1549 (SEQ_LEQ(th->th_ack, tp->iss) ||
1550 SEQ_GT(th->th_ack, tp->snd_max))) {
1551 rstreason = BANDLIM_UNLIMITED;
1554 if (thflags & TH_RST) {
1555 if (thflags & TH_ACK)
1556 tp = tcp_drop(tp, ECONNREFUSED);
1559 if (!(thflags & TH_SYN))
1562 tp->irs = th->th_seq;
1564 if (thflags & TH_ACK) {
1565 /* Our SYN was acked. */
1566 tcpstat.tcps_connects++;
1568 /* Do window scaling on this connection? */
1569 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) ==
1570 (TF_RCVD_SCALE | TF_REQ_SCALE))
1571 tp->rcv_scale = tp->request_r_scale;
1572 tp->rcv_adv += tp->rcv_wnd;
1573 tp->snd_una++; /* SYN is acked */
1574 tcp_callout_stop(tp, tp->tt_rexmt);
1576 * If there's data, delay ACK; if there's also a FIN
1577 * ACKNOW will be turned on later.
1579 if (DELAY_ACK(tp) && tlen != 0) {
1580 tcp_callout_reset(tp, tp->tt_delack,
1581 tcp_delacktime, tcp_timer_delack);
1583 tp->t_flags |= TF_ACKNOW;
1586 * Received <SYN,ACK> in SYN_SENT[*] state.
1588 * SYN_SENT --> ESTABLISHED
1589 * SYN_SENT* --> FIN_WAIT_1
1591 tp->t_starttime = ticks;
1592 if (tp->t_flags & TF_NEEDFIN) {
1593 tp->t_state = TCPS_FIN_WAIT_1;
1594 tp->t_flags &= ~TF_NEEDFIN;
1597 tcp_established(tp);
1601 * Received initial SYN in SYN-SENT[*] state =>
1602 * simultaneous open.
1603 * Do 3-way handshake:
1604 * SYN-SENT -> SYN-RECEIVED
1605 * SYN-SENT* -> SYN-RECEIVED*
1607 tp->t_flags |= TF_ACKNOW;
1608 tcp_callout_stop(tp, tp->tt_rexmt);
1609 tp->t_state = TCPS_SYN_RECEIVED;
1613 * Advance th->th_seq to correspond to first data byte.
1614 * If data, trim to stay within window,
1615 * dropping FIN if necessary.
1618 if (tlen > tp->rcv_wnd) {
1619 todrop = tlen - tp->rcv_wnd;
1623 tcpstat.tcps_rcvpackafterwin++;
1624 tcpstat.tcps_rcvbyteafterwin += todrop;
1626 tp->snd_wl1 = th->th_seq - 1;
1627 tp->rcv_up = th->th_seq;
1629 * Client side of transaction: already sent SYN and data.
1630 * If the remote host used T/TCP to validate the SYN,
1631 * our data will be ACK'd; if so, enter normal data segment
1632 * processing in the middle of step 5, ack processing.
1633 * Otherwise, goto step 6.
1635 if (thflags & TH_ACK)
1641 * If the state is LAST_ACK or CLOSING or TIME_WAIT:
1642 * do normal processing (we no longer bother with T/TCP).
1646 case TCPS_TIME_WAIT:
1647 break; /* continue normal processing */
1651 * States other than LISTEN or SYN_SENT.
1652 * First check the RST flag and sequence number since reset segments
1653 * are exempt from the timestamp and connection count tests. This
1654 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix
1655 * below which allowed reset segments in half the sequence space
1656 * to fall though and be processed (which gives forged reset
1657 * segments with a random sequence number a 50 percent chance of
1658 * killing a connection).
1659 * Then check timestamp, if present.
1660 * Then check the connection count, if present.
1661 * Then check that at least some bytes of segment are within
1662 * receive window. If segment begins before rcv_nxt,
1663 * drop leading data (and SYN); if nothing left, just ack.
1666 * If the RST bit is set, check the sequence number to see
1667 * if this is a valid reset segment.
1669 * In all states except SYN-SENT, all reset (RST) segments
1670 * are validated by checking their SEQ-fields. A reset is
1671 * valid if its sequence number is in the window.
1672 * Note: this does not take into account delayed ACKs, so
1673 * we should test against last_ack_sent instead of rcv_nxt.
1674 * The sequence number in the reset segment is normally an
1675 * echo of our outgoing acknowledgement numbers, but some hosts
1676 * send a reset with the sequence number at the rightmost edge
1677 * of our receive window, and we have to handle this case.
1678 * If we have multiple segments in flight, the intial reset
1679 * segment sequence numbers will be to the left of last_ack_sent,
1680 * but they will eventually catch up.
1681 * In any case, it never made sense to trim reset segments to
1682 * fit the receive window since RFC 1122 says:
1683 * 4.2.2.12 RST Segment: RFC-793 Section 3.4
1685 * A TCP SHOULD allow a received RST segment to include data.
1688 * It has been suggested that a RST segment could contain
1689 * ASCII text that encoded and explained the cause of the
1690 * RST. No standard has yet been established for such
1693 * If the reset segment passes the sequence number test examine
1695 * SYN_RECEIVED STATE:
1696 * If passive open, return to LISTEN state.
1697 * If active open, inform user that connection was refused.
1698 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES:
1699 * Inform user that connection was reset, and close tcb.
1700 * CLOSING, LAST_ACK STATES:
1703 * Drop the segment - see Stevens, vol. 2, p. 964 and
1706 if (thflags & TH_RST) {
1707 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
1708 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) {
1709 switch (tp->t_state) {
1711 case TCPS_SYN_RECEIVED:
1712 so->so_error = ECONNREFUSED;
1715 case TCPS_ESTABLISHED:
1716 case TCPS_FIN_WAIT_1:
1717 case TCPS_FIN_WAIT_2:
1718 case TCPS_CLOSE_WAIT:
1719 so->so_error = ECONNRESET;
1721 tp->t_state = TCPS_CLOSED;
1722 tcpstat.tcps_drops++;
1731 case TCPS_TIME_WAIT:
1739 * RFC 1323 PAWS: If we have a timestamp reply on this segment
1740 * and it's less than ts_recent, drop it.
1742 if ((to.to_flags & TOF_TS) && tp->ts_recent != 0 &&
1743 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
1744 /* Check to see if ts_recent is over 24 days old. */
1745 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) {
1747 * Invalidate ts_recent. If this segment updates
1748 * ts_recent, the age will be reset later and ts_recent
1749 * will get a valid value. If it does not, setting
1750 * ts_recent to zero will at least satisfy the
1751 * requirement that zero be placed in the timestamp
1752 * echo reply when ts_recent isn't valid. The
1753 * age isn't reset until we get a valid ts_recent
1754 * because we don't want out-of-order segments to be
1755 * dropped when ts_recent is old.
1758 } else if (tcp_paws_tolerance && tlen != 0 &&
1759 tp->t_state == TCPS_ESTABLISHED &&
1760 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK&&
1761 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) &&
1762 th->th_ack == tp->snd_una &&
1763 tiwin == tp->snd_wnd &&
1764 TSTMP_GEQ(to.to_tsval + tcp_paws_tolerance, tp->ts_recent)&&
1765 (th->th_seq == tp->rcv_nxt ||
1766 (SEQ_GT(th->th_seq, tp->rcv_nxt) &&
1767 tcp_paws_canreasslast(tp, th, tlen)))) {
1769 * This tends to prevent valid new segments from being
1770 * dropped by the reordered segments sent by the fast
1771 * retransmission algorithm on the sending side, i.e.
1772 * the fast retransmitted segment w/ larger timestamp
1773 * arrives earlier than the previously sent new segments
1774 * w/ smaller timestamp.
1776 * If following conditions are met, the segment is
1778 * - The segment contains data
1779 * - The connection is established
1780 * - The header does not contain important flags
1781 * - SYN or FIN is not needed
1782 * - It does not acknowledge new data
1783 * - Receive window is not changed
1784 * - The timestamp is within "acceptable" range
1785 * - The new segment is what we are expecting or
1786 * the new segment could be merged w/ the last
1787 * pending segment on the reassemble queue
1789 tcpstat.tcps_pawsaccept++;
1790 tcpstat.tcps_pawsdrop++;
1792 tcpstat.tcps_rcvduppack++;
1793 tcpstat.tcps_rcvdupbyte += tlen;
1794 tcpstat.tcps_pawsdrop++;
1802 * In the SYN-RECEIVED state, validate that the packet belongs to
1803 * this connection before trimming the data to fit the receive
1804 * window. Check the sequence number versus IRS since we know
1805 * the sequence numbers haven't wrapped. This is a partial fix
1806 * for the "LAND" DoS attack.
1808 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) {
1809 rstreason = BANDLIM_RST_OPENPORT;
1813 todrop = tp->rcv_nxt - th->th_seq;
1815 if (TCP_DO_SACK(tp)) {
1816 /* Report duplicate segment at head of packet. */
1817 tp->reportblk.rblk_start = th->th_seq;
1818 tp->reportblk.rblk_end = TCP_SACK_BLKEND(
1819 th->th_seq + tlen, thflags);
1820 if (SEQ_GT(tp->reportblk.rblk_end, tp->rcv_nxt))
1821 tp->reportblk.rblk_end = tp->rcv_nxt;
1822 tp->sack_flags |= (TSACK_F_DUPSEG | TSACK_F_SACKLEFT);
1823 tp->t_flags |= TF_ACKNOW;
1825 if (thflags & TH_SYN) {
1835 * Following if statement from Stevens, vol. 2, p. 960.
1837 if (todrop > tlen ||
1838 (todrop == tlen && !(thflags & TH_FIN))) {
1840 * Any valid FIN must be to the left of the window.
1841 * At this point the FIN must be a duplicate or out
1842 * of sequence; drop it.
1847 * Send an ACK to resynchronize and drop any data.
1848 * But keep on processing for RST or ACK.
1850 tp->t_flags |= TF_ACKNOW;
1852 tcpstat.tcps_rcvduppack++;
1853 tcpstat.tcps_rcvdupbyte += todrop;
1855 tcpstat.tcps_rcvpartduppack++;
1856 tcpstat.tcps_rcvpartdupbyte += todrop;
1858 drop_hdrlen += todrop; /* drop from the top afterwards */
1859 th->th_seq += todrop;
1861 if (th->th_urp > todrop)
1862 th->th_urp -= todrop;
1870 * If new data are received on a connection after the
1871 * user processes are gone, then RST the other end.
1873 if ((so->so_state & SS_NOFDREF) &&
1874 tp->t_state > TCPS_CLOSE_WAIT && tlen) {
1876 tcpstat.tcps_rcvafterclose++;
1877 rstreason = BANDLIM_UNLIMITED;
1882 * If segment ends after window, drop trailing data
1883 * (and PUSH and FIN); if nothing left, just ACK.
1885 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd);
1887 tcpstat.tcps_rcvpackafterwin++;
1888 if (todrop >= tlen) {
1889 tcpstat.tcps_rcvbyteafterwin += tlen;
1891 * If a new connection request is received
1892 * while in TIME_WAIT, drop the old connection
1893 * and start over if the sequence numbers
1894 * are above the previous ones.
1896 if (thflags & TH_SYN &&
1897 tp->t_state == TCPS_TIME_WAIT &&
1898 SEQ_GT(th->th_seq, tp->rcv_nxt)) {
1903 * If window is closed can only take segments at
1904 * window edge, and have to drop data and PUSH from
1905 * incoming segments. Continue processing, but
1906 * remember to ack. Otherwise, drop segment
1909 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
1910 tp->t_flags |= TF_ACKNOW;
1911 tcpstat.tcps_rcvwinprobe++;
1915 tcpstat.tcps_rcvbyteafterwin += todrop;
1918 thflags &= ~(TH_PUSH | TH_FIN);
1922 * If last ACK falls within this segment's sequence numbers,
1923 * record its timestamp.
1925 * 1) That the test incorporates suggestions from the latest
1926 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1927 * 2) That updating only on newer timestamps interferes with
1928 * our earlier PAWS tests, so this check should be solely
1929 * predicated on the sequence space of this segment.
1930 * 3) That we modify the segment boundary check to be
1931 * Last.ACK.Sent <= SEG.SEQ + SEG.LEN
1932 * instead of RFC1323's
1933 * Last.ACK.Sent < SEG.SEQ + SEG.LEN,
1934 * This modified check allows us to overcome RFC1323's
1935 * limitations as described in Stevens TCP/IP Illustrated
1936 * Vol. 2 p.869. In such cases, we can still calculate the
1937 * RTT correctly when RCV.NXT == Last.ACK.Sent.
1939 if ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent) &&
1940 SEQ_LEQ(tp->last_ack_sent, (th->th_seq + tlen
1941 + ((thflags & TH_SYN) != 0)
1942 + ((thflags & TH_FIN) != 0)))) {
1943 tp->ts_recent_age = ticks;
1944 tp->ts_recent = to.to_tsval;
1948 * If a SYN is in the window, then this is an
1949 * error and we send an RST and drop the connection.
1951 if (thflags & TH_SYN) {
1952 tp = tcp_drop(tp, ECONNRESET);
1953 rstreason = BANDLIM_UNLIMITED;
1958 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN
1959 * flag is on (half-synchronized state), then queue data for
1960 * later processing; else drop segment and return.
1962 if (!(thflags & TH_ACK)) {
1963 if (tp->t_state == TCPS_SYN_RECEIVED ||
1964 (tp->t_flags & TF_NEEDSYN))
1973 switch (tp->t_state) {
1975 * In SYN_RECEIVED state, the ACK acknowledges our SYN, so enter
1976 * ESTABLISHED state and continue processing.
1977 * The ACK was checked above.
1979 case TCPS_SYN_RECEIVED:
1981 tcpstat.tcps_connects++;
1983 /* Do window scaling? */
1984 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) ==
1985 (TF_RCVD_SCALE | TF_REQ_SCALE))
1986 tp->rcv_scale = tp->request_r_scale;
1989 * SYN-RECEIVED -> ESTABLISHED
1990 * SYN-RECEIVED* -> FIN-WAIT-1
1992 tp->t_starttime = ticks;
1993 if (tp->t_flags & TF_NEEDFIN) {
1994 tp->t_state = TCPS_FIN_WAIT_1;
1995 tp->t_flags &= ~TF_NEEDFIN;
1997 tcp_established(tp);
2000 * If segment contains data or ACK, will call tcp_reass()
2001 * later; if not, do so now to pass queued data to user.
2003 if (tlen == 0 && !(thflags & TH_FIN))
2004 tcp_reass(tp, NULL, NULL, NULL);
2008 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
2009 * ACKs. If the ack is in the range
2010 * tp->snd_una < th->th_ack <= tp->snd_max
2011 * then advance tp->snd_una to th->th_ack and drop
2012 * data from the retransmission queue. If this ACK reflects
2013 * more up to date window information we update our window information.
2015 case TCPS_ESTABLISHED:
2016 case TCPS_FIN_WAIT_1:
2017 case TCPS_FIN_WAIT_2:
2018 case TCPS_CLOSE_WAIT:
2021 case TCPS_TIME_WAIT:
2023 if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
2024 boolean_t maynotdup = FALSE;
2026 if (TCP_DO_SACK(tp))
2027 tcp_sack_update_scoreboard(tp, &to);
2029 if (tlen != 0 || tiwin != tp->snd_wnd ||
2030 ((thflags & TH_FIN) && !(tp->t_flags & TF_SAWFIN)))
2033 if (!tcp_callout_active(tp, tp->tt_rexmt) ||
2034 th->th_ack != tp->snd_una) {
2036 tcpstat.tcps_rcvdupack++;
2041 #define DELAY_DUPACK \
2043 delayed_dupack = TRUE; \
2044 th_dupack = th->th_ack; \
2045 to_flags = to.to_flags; \
2048 if (!tcp_do_rfc6675 ||
2051 (TOF_SACK | TOF_SACK_REDUNDANT))
2059 if ((thflags & TH_FIN) && !(tp->t_flags & TF_QUEDFIN)) {
2061 * This could happen, if the reassemable
2062 * queue overflew or was drained. Don't
2063 * drop this FIN here; defer the duplicated
2064 * ACK processing until this FIN gets queued.
2071 if (tcp_recv_dupack(tp, th->th_ack, to.to_flags))
2077 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una"));
2079 if (SEQ_GT(th->th_ack, tp->snd_max)) {
2081 * Detected optimistic ACK attack.
2082 * Force slow-start to de-synchronize attack.
2084 tp->snd_cwnd = tp->t_maxseg;
2087 tcpstat.tcps_rcvacktoomuch++;
2091 * If we reach this point, ACK is not a duplicate,
2092 * i.e., it ACKs something we sent.
2094 if (tp->t_flags & TF_NEEDSYN) {
2096 * T/TCP: Connection was half-synchronized, and our
2097 * SYN has been ACK'd (so connection is now fully
2098 * synchronized). Go to non-starred state,
2099 * increment snd_una for ACK of SYN, and check if
2100 * we can do window scaling.
2102 tp->t_flags &= ~TF_NEEDSYN;
2104 /* Do window scaling? */
2105 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) ==
2106 (TF_RCVD_SCALE | TF_REQ_SCALE))
2107 tp->rcv_scale = tp->request_r_scale;
2111 acked = th->th_ack - tp->snd_una;
2112 tcpstat.tcps_rcvackpack++;
2113 tcpstat.tcps_rcvackbyte += acked;
2115 if (tcp_do_eifel_detect && acked > 0 &&
2116 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) &&
2117 (tp->rxt_flags & TRXT_F_FIRSTACCACK)) {
2118 /* Eifel detection applicable. */
2119 if (to.to_tsecr < tp->t_rexmtTS) {
2120 ++tcpstat.tcps_eifeldetected;
2121 tcp_revert_congestion_state(tp);
2122 if (tp->t_rxtshift != 1 ||
2123 ticks >= tp->t_badrxtwin)
2124 ++tcpstat.tcps_rttcantdetect;
2126 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) {
2128 * If we just performed our first retransmit,
2129 * and the ACK arrives within our recovery window,
2130 * then it was a mistake to do the retransmit
2131 * in the first place. Recover our original cwnd
2132 * and ssthresh, and proceed to transmit where we
2135 tcp_revert_congestion_state(tp);
2136 ++tcpstat.tcps_rttdetected;
2140 * If we have a timestamp reply, update smoothed
2141 * round trip time. If no timestamp is present but
2142 * transmit timer is running and timed sequence
2143 * number was acked, update smoothed round trip time.
2144 * Since we now have an rtt measurement, cancel the
2145 * timer backoff (cf., Phil Karn's retransmit alg.).
2146 * Recompute the initial retransmit timer.
2148 * Some machines (certain windows boxes) send broken
2149 * timestamp replies during the SYN+ACK phase, ignore
2152 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0))
2153 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1, th->th_ack);
2154 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq))
2155 tcp_xmit_timer(tp, ticks - tp->t_rtttime, th->th_ack);
2156 tcp_xmit_bandwidth_limit(tp, th->th_ack);
2159 * If no data (only SYN) was ACK'd,
2160 * skip rest of ACK processing.
2165 /* Stop looking for an acceptable ACK since one was received. */
2166 tp->rxt_flags &= ~(TRXT_F_FIRSTACCACK |
2167 TRXT_F_FASTREXMT | TRXT_F_EARLYREXMT);
2169 if (acked > so->so_snd.ssb_cc) {
2170 tp->snd_wnd -= so->so_snd.ssb_cc;
2171 sbdrop(&so->so_snd.sb, (int)so->so_snd.ssb_cc);
2172 ourfinisacked = TRUE;
2174 sbdrop(&so->so_snd.sb, acked);
2175 tp->snd_wnd -= acked;
2176 ourfinisacked = FALSE;
2181 * Update window information.
2183 if (acceptable_window_update(tp, th, tiwin)) {
2184 /* keep track of pure window updates */
2185 if (tlen == 0 && tp->snd_wl2 == th->th_ack &&
2186 tiwin > tp->snd_wnd)
2187 tcpstat.tcps_rcvwinupd++;
2188 tp->snd_wnd = tiwin;
2189 tp->snd_wl1 = th->th_seq;
2190 tp->snd_wl2 = th->th_ack;
2191 if (tp->snd_wnd > tp->max_sndwnd)
2192 tp->max_sndwnd = tp->snd_wnd;
2196 tp->snd_una = th->th_ack;
2197 if (TCP_DO_SACK(tp))
2198 tcp_sack_update_scoreboard(tp, &to);
2199 if (IN_FASTRECOVERY(tp)) {
2200 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) {
2201 EXIT_FASTRECOVERY(tp);
2204 * If the congestion window was inflated
2205 * to account for the other side's
2206 * cached packets, retract it.
2208 if (!TCP_DO_SACK(tp))
2209 tp->snd_cwnd = tp->snd_ssthresh;
2212 * Window inflation should have left us
2213 * with approximately snd_ssthresh outstanding
2214 * data. But, in case we would be inclined
2215 * to send a burst, better do it using
2218 if (SEQ_GT(th->th_ack + tp->snd_cwnd,
2219 tp->snd_max + 2 * tp->t_maxseg))
2221 (tp->snd_max - tp->snd_una) +
2226 if (TCP_DO_SACK(tp)) {
2227 tp->snd_max_rexmt = tp->snd_max;
2229 tp->snd_una == tp->rexmt_high);
2231 tcp_newreno_partial_ack(tp, th, acked);
2237 * Open the congestion window. When in slow-start,
2238 * open exponentially: maxseg per packet. Otherwise,
2239 * open linearly: maxseg per window.
2241 if (tp->snd_cwnd <= tp->snd_ssthresh) {
2243 (SEQ_LT(tp->snd_nxt, tp->snd_max) ?
2244 tp->t_maxseg : 2 * tp->t_maxseg);
2247 tp->snd_cwnd += tcp_do_abc ?
2248 min(acked, abc_sslimit) : tp->t_maxseg;
2250 /* linear increase */
2251 tp->snd_wacked += tcp_do_abc ? acked :
2253 if (tp->snd_wacked >= tp->snd_cwnd) {
2254 tp->snd_wacked -= tp->snd_cwnd;
2255 tp->snd_cwnd += tp->t_maxseg;
2258 tp->snd_cwnd = min(tp->snd_cwnd,
2259 TCP_MAXWIN << tp->snd_scale);
2260 tp->snd_recover = th->th_ack - 1;
2262 if (SEQ_LT(tp->snd_nxt, tp->snd_una))
2263 tp->snd_nxt = tp->snd_una;
2266 * If all outstanding data is acked, stop retransmit
2267 * timer and remember to restart (more output or persist).
2268 * If there is more data to be acked, restart retransmit
2269 * timer, using current (possibly backed-off) value.
2271 if (th->th_ack == tp->snd_max) {
2272 tcp_callout_stop(tp, tp->tt_rexmt);
2274 } else if (!tcp_callout_active(tp, tp->tt_persist)) {
2275 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur,
2279 switch (tp->t_state) {
2281 * In FIN_WAIT_1 STATE in addition to the processing
2282 * for the ESTABLISHED state if our FIN is now acknowledged
2283 * then enter FIN_WAIT_2.
2285 case TCPS_FIN_WAIT_1:
2286 if (ourfinisacked) {
2288 * If we can't receive any more
2289 * data, then closing user can proceed.
2290 * Starting the timer is contrary to the
2291 * specification, but if we don't get a FIN
2292 * we'll hang forever.
2294 if (so->so_state & SS_CANTRCVMORE) {
2295 soisdisconnected(so);
2296 tcp_callout_reset(tp, tp->tt_2msl,
2297 tp->t_maxidle, tcp_timer_2msl);
2299 tp->t_state = TCPS_FIN_WAIT_2;
2304 * In CLOSING STATE in addition to the processing for
2305 * the ESTABLISHED state if the ACK acknowledges our FIN
2306 * then enter the TIME-WAIT state, otherwise ignore
2310 if (ourfinisacked) {
2311 tp->t_state = TCPS_TIME_WAIT;
2312 tcp_canceltimers(tp);
2313 tcp_callout_reset(tp, tp->tt_2msl,
2314 2 * tcp_rmx_msl(tp),
2316 soisdisconnected(so);
2321 * In LAST_ACK, we may still be waiting for data to drain
2322 * and/or to be acked, as well as for the ack of our FIN.
2323 * If our FIN is now acknowledged, delete the TCB,
2324 * enter the closed state and return.
2327 if (ourfinisacked) {
2334 * In TIME_WAIT state the only thing that should arrive
2335 * is a retransmission of the remote FIN. Acknowledge
2336 * it and restart the finack timer.
2338 case TCPS_TIME_WAIT:
2339 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp),
2347 * Update window information.
2348 * Don't look at window if no ACK: TAC's send garbage on first SYN.
2350 if ((thflags & TH_ACK) &&
2351 acceptable_window_update(tp, th, tiwin)) {
2352 /* keep track of pure window updates */
2353 if (tlen == 0 && tp->snd_wl2 == th->th_ack &&
2354 tiwin > tp->snd_wnd)
2355 tcpstat.tcps_rcvwinupd++;
2356 tp->snd_wnd = tiwin;
2357 tp->snd_wl1 = th->th_seq;
2358 tp->snd_wl2 = th->th_ack;
2359 if (tp->snd_wnd > tp->max_sndwnd)
2360 tp->max_sndwnd = tp->snd_wnd;
2365 * Process segments with URG.
2367 if ((thflags & TH_URG) && th->th_urp &&
2368 !TCPS_HAVERCVDFIN(tp->t_state)) {
2370 * This is a kludge, but if we receive and accept
2371 * random urgent pointers, we'll crash in
2372 * soreceive. It's hard to imagine someone
2373 * actually wanting to send this much urgent data.
2375 if (th->th_urp + so->so_rcv.ssb_cc > sb_max) {
2376 th->th_urp = 0; /* XXX */
2377 thflags &= ~TH_URG; /* XXX */
2378 goto dodata; /* XXX */
2381 * If this segment advances the known urgent pointer,
2382 * then mark the data stream. This should not happen
2383 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
2384 * a FIN has been received from the remote side.
2385 * In these states we ignore the URG.
2387 * According to RFC961 (Assigned Protocols),
2388 * the urgent pointer points to the last octet
2389 * of urgent data. We continue, however,
2390 * to consider it to indicate the first octet
2391 * of data past the urgent section as the original
2392 * spec states (in one of two places).
2394 if (SEQ_GT(th->th_seq + th->th_urp, tp->rcv_up)) {
2395 tp->rcv_up = th->th_seq + th->th_urp;
2396 so->so_oobmark = so->so_rcv.ssb_cc +
2397 (tp->rcv_up - tp->rcv_nxt) - 1;
2398 if (so->so_oobmark == 0)
2399 sosetstate(so, SS_RCVATMARK);
2401 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
2404 * Remove out of band data so doesn't get presented to user.
2405 * This can happen independent of advancing the URG pointer,
2406 * but if two URG's are pending at once, some out-of-band
2407 * data may creep in... ick.
2409 if (th->th_urp <= (u_long)tlen &&
2410 !(so->so_options & SO_OOBINLINE)) {
2411 /* hdr drop is delayed */
2412 tcp_pulloutofband(so, th, m, drop_hdrlen);
2416 * If no out of band data is expected,
2417 * pull receive urgent pointer along
2418 * with the receive window.
2420 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
2421 tp->rcv_up = tp->rcv_nxt;
2426 * Process the segment text, merging it into the TCP sequencing queue,
2427 * and arranging for acknowledgment of receipt if necessary.
2428 * This process logically involves adjusting tp->rcv_wnd as data
2429 * is presented to the user (this happens in tcp_usrreq.c,
2430 * case PRU_RCVD). If a FIN has already been received on this
2431 * connection then we just ignore the text.
2433 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) {
2434 if (thflags & TH_FIN)
2435 tp->t_flags |= TF_SAWFIN;
2436 m_adj(m, drop_hdrlen); /* delayed header drop */
2438 * Insert segment which includes th into TCP reassembly queue
2439 * with control block tp. Set thflags to whether reassembly now
2440 * includes a segment with FIN. This handles the common case
2441 * inline (segment is the next to be received on an established
2442 * connection, and the queue is empty), avoiding linkage into
2443 * and removal from the queue and repetition of various
2445 * Set DELACK for segments received in order, but ack
2446 * immediately when segments are out of order (so
2447 * fast retransmit can work).
2449 if (th->th_seq == tp->rcv_nxt &&
2450 TAILQ_EMPTY(&tp->t_segq) &&
2451 TCPS_HAVEESTABLISHED(tp->t_state)) {
2452 if (thflags & TH_FIN)
2453 tp->t_flags |= TF_QUEDFIN;
2454 if (DELAY_ACK(tp)) {
2455 tcp_callout_reset(tp, tp->tt_delack,
2456 tcp_delacktime, tcp_timer_delack);
2458 tp->t_flags |= TF_ACKNOW;
2460 tp->rcv_nxt += tlen;
2461 thflags = th->th_flags & TH_FIN;
2462 tcpstat.tcps_rcvpack++;
2463 tcpstat.tcps_rcvbyte += tlen;
2465 if (so->so_state & SS_CANTRCVMORE) {
2468 lwkt_gettoken(&so->so_rcv.ssb_token);
2469 ssb_appendstream(&so->so_rcv, m);
2470 lwkt_reltoken(&so->so_rcv.ssb_token);
2474 if (!(tp->sack_flags & TSACK_F_DUPSEG)) {
2475 /* Initialize SACK report block. */
2476 tp->reportblk.rblk_start = th->th_seq;
2477 tp->reportblk.rblk_end = TCP_SACK_BLKEND(
2478 th->th_seq + tlen, thflags);
2480 thflags = tcp_reass(tp, th, &tlen, m);
2481 tp->t_flags |= TF_ACKNOW;
2485 * Note the amount of data that peer has sent into
2486 * our window, in order to estimate the sender's
2489 len = so->so_rcv.ssb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
2496 * If FIN is received ACK the FIN and let the user know
2497 * that the connection is closing.
2499 if (thflags & TH_FIN) {
2500 if (!TCPS_HAVERCVDFIN(tp->t_state)) {
2503 * If connection is half-synchronized
2504 * (ie NEEDSYN flag on) then delay ACK,
2505 * so it may be piggybacked when SYN is sent.
2506 * Otherwise, since we received a FIN then no
2507 * more input can be expected, send ACK now.
2509 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) {
2510 tcp_callout_reset(tp, tp->tt_delack,
2511 tcp_delacktime, tcp_timer_delack);
2513 tp->t_flags |= TF_ACKNOW;
2518 switch (tp->t_state) {
2520 * In SYN_RECEIVED and ESTABLISHED STATES
2521 * enter the CLOSE_WAIT state.
2523 case TCPS_SYN_RECEIVED:
2524 tp->t_starttime = ticks;
2526 case TCPS_ESTABLISHED:
2527 tp->t_state = TCPS_CLOSE_WAIT;
2531 * If still in FIN_WAIT_1 STATE FIN has not been acked so
2532 * enter the CLOSING state.
2534 case TCPS_FIN_WAIT_1:
2535 tp->t_state = TCPS_CLOSING;
2539 * In FIN_WAIT_2 state enter the TIME_WAIT state,
2540 * starting the time-wait timer, turning off the other
2543 case TCPS_FIN_WAIT_2:
2544 tp->t_state = TCPS_TIME_WAIT;
2545 tcp_canceltimers(tp);
2546 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp),
2548 soisdisconnected(so);
2552 * In TIME_WAIT state restart the 2 MSL time_wait timer.
2554 case TCPS_TIME_WAIT:
2555 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp),
2562 if (so->so_options & SO_DEBUG)
2563 tcp_trace(TA_INPUT, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
2567 * Delayed duplicated ACK processing
2569 if (delayed_dupack && tcp_recv_dupack(tp, th_dupack, to_flags))
2573 * Return any desired output.
2575 if (needoutput || (tp->t_flags & TF_ACKNOW))
2577 tcp_sack_report_cleanup(tp);
2578 return(IPPROTO_DONE);
2582 * Generate an ACK dropping incoming segment if it occupies
2583 * sequence space, where the ACK reflects our state.
2585 * We can now skip the test for the RST flag since all
2586 * paths to this code happen after packets containing
2587 * RST have been dropped.
2589 * In the SYN-RECEIVED state, don't send an ACK unless the
2590 * segment we received passes the SYN-RECEIVED ACK test.
2591 * If it fails send a RST. This breaks the loop in the
2592 * "LAND" DoS attack, and also prevents an ACK storm
2593 * between two listening ports that have been sent forged
2594 * SYN segments, each with the source address of the other.
2596 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
2597 (SEQ_GT(tp->snd_una, th->th_ack) ||
2598 SEQ_GT(th->th_ack, tp->snd_max)) ) {
2599 rstreason = BANDLIM_RST_OPENPORT;
2603 if (so->so_options & SO_DEBUG)
2604 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
2607 tp->t_flags |= TF_ACKNOW;
2609 tcp_sack_report_cleanup(tp);
2610 return(IPPROTO_DONE);
2614 * Generate a RST, dropping incoming segment.
2615 * Make ACK acceptable to originator of segment.
2616 * Don't bother to respond if destination was broadcast/multicast.
2618 if ((thflags & TH_RST) || m->m_flags & (M_BCAST | M_MCAST))
2621 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
2622 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
2625 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
2626 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
2627 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
2628 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
2631 /* IPv6 anycast check is done at tcp6_input() */
2634 * Perform bandwidth limiting.
2637 if (badport_bandlim(rstreason) < 0)
2642 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
2643 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
2645 if (thflags & TH_ACK)
2646 /* mtod() below is safe as long as hdr dropping is delayed */
2647 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack,
2650 if (thflags & TH_SYN)
2652 /* mtod() below is safe as long as hdr dropping is delayed */
2653 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen,
2654 (tcp_seq)0, TH_RST | TH_ACK);
2657 tcp_sack_report_cleanup(tp);
2658 return(IPPROTO_DONE);
2662 * Drop space held by incoming segment and return.
2665 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
2666 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
2670 tcp_sack_report_cleanup(tp);
2671 return(IPPROTO_DONE);
2675 * Parse TCP options and place in tcpopt.
2678 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn,
2684 for (; cnt > 0; cnt -= optlen, cp += optlen) {
2686 if (opt == TCPOPT_EOL)
2688 if (opt == TCPOPT_NOP)
2694 if (optlen < 2 || optlen > cnt)
2699 if (optlen != TCPOLEN_MAXSEG)
2703 to->to_flags |= TOF_MSS;
2704 bcopy(cp + 2, &to->to_mss, sizeof to->to_mss);
2705 to->to_mss = ntohs(to->to_mss);
2708 if (optlen != TCPOLEN_WINDOW)
2712 to->to_flags |= TOF_SCALE;
2713 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT);
2715 case TCPOPT_TIMESTAMP:
2716 if (optlen != TCPOLEN_TIMESTAMP)
2718 to->to_flags |= TOF_TS;
2719 bcopy(cp + 2, &to->to_tsval, sizeof to->to_tsval);
2720 to->to_tsval = ntohl(to->to_tsval);
2721 bcopy(cp + 6, &to->to_tsecr, sizeof to->to_tsecr);
2722 to->to_tsecr = ntohl(to->to_tsecr);
2724 * If echoed timestamp is later than the current time,
2725 * fall back to non RFC1323 RTT calculation.
2727 if (to->to_tsecr != 0 && TSTMP_GT(to->to_tsecr, ticks))
2730 case TCPOPT_SACK_PERMITTED:
2731 if (optlen != TCPOLEN_SACK_PERMITTED)
2735 to->to_flags |= TOF_SACK_PERMITTED;
2738 if ((optlen - 2) & 0x07) /* not multiple of 8 */
2740 to->to_nsackblocks = (optlen - 2) / 8;
2741 to->to_sackblocks = (struct raw_sackblock *) (cp + 2);
2742 to->to_flags |= TOF_SACK;
2743 for (i = 0; i < to->to_nsackblocks; i++) {
2744 struct raw_sackblock *r = &to->to_sackblocks[i];
2746 r->rblk_start = ntohl(r->rblk_start);
2747 r->rblk_end = ntohl(r->rblk_end);
2749 if (SEQ_LEQ(r->rblk_end, r->rblk_start)) {
2751 * Invalid SACK block; discard all
2754 tcpstat.tcps_rcvbadsackopt++;
2755 to->to_nsackblocks = 0;
2756 to->to_sackblocks = NULL;
2757 to->to_flags &= ~TOF_SACK;
2761 if ((to->to_flags & TOF_SACK) &&
2762 tcp_sack_ndsack_blocks(to->to_sackblocks,
2763 to->to_nsackblocks, ack))
2764 to->to_flags |= TOF_DSACK;
2766 #ifdef TCP_SIGNATURE
2768 * XXX In order to reply to a host which has set the
2769 * TCP_SIGNATURE option in its initial SYN, we have to
2770 * record the fact that the option was observed here
2771 * for the syncache code to perform the correct response.
2773 case TCPOPT_SIGNATURE:
2774 if (optlen != TCPOLEN_SIGNATURE)
2776 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN);
2778 #endif /* TCP_SIGNATURE */
2786 * Pull out of band byte out of a segment so
2787 * it doesn't appear in the user's data queue.
2788 * It is still reflected in the segment length for
2789 * sequencing purposes.
2790 * "off" is the delayed to be dropped hdrlen.
2793 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off)
2795 int cnt = off + th->th_urp - 1;
2798 if (m->m_len > cnt) {
2799 char *cp = mtod(m, caddr_t) + cnt;
2800 struct tcpcb *tp = sototcpcb(so);
2803 tp->t_oobflags |= TCPOOB_HAVEDATA;
2804 bcopy(cp + 1, cp, m->m_len - cnt - 1);
2806 if (m->m_flags & M_PKTHDR)
2815 panic("tcp_pulloutofband");
2819 * Collect new round-trip time estimate
2820 * and update averages and current timeout.
2823 tcp_xmit_timer(struct tcpcb *tp, int rtt, tcp_seq ack)
2827 tcpstat.tcps_rttupdated++;
2829 if ((tp->rxt_flags & TRXT_F_REBASERTO) &&
2830 SEQ_GT(ack, tp->snd_max_prev)) {
2831 #ifdef DEBUG_EIFEL_RESPONSE
2832 kprintf("srtt/rttvar, prev %d/%d, cur %d/%d, ",
2833 tp->t_srtt_prev, tp->t_rttvar_prev,
2834 tp->t_srtt, tp->t_rttvar);
2837 tcpstat.tcps_eifelresponse++;
2839 tp->rxt_flags &= ~TRXT_F_REBASERTO;
2840 tp->t_srtt = max(tp->t_srtt_prev, (rtt << TCP_RTT_SHIFT));
2841 tp->t_rttvar = max(tp->t_rttvar_prev,
2842 (rtt << (TCP_RTTVAR_SHIFT - 1)));
2843 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
2844 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2846 #ifdef DEBUG_EIFEL_RESPONSE
2847 kprintf("new %d/%d ", tp->t_srtt, tp->t_rttvar);
2849 } else if (tp->t_srtt != 0) {
2853 * srtt is stored as fixed point with 5 bits after the
2854 * binary point (i.e., scaled by 8). The following magic
2855 * is equivalent to the smoothing algorithm in rfc793 with
2856 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
2857 * point). Adjust rtt to origin 0.
2859 delta = ((rtt - 1) << TCP_DELTA_SHIFT)
2860 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
2862 if ((tp->t_srtt += delta) <= 0)
2866 * We accumulate a smoothed rtt variance (actually, a
2867 * smoothed mean difference), then set the retransmit
2868 * timer to smoothed rtt + 4 times the smoothed variance.
2869 * rttvar is stored as fixed point with 4 bits after the
2870 * binary point (scaled by 16). The following is
2871 * equivalent to rfc793 smoothing with an alpha of .75
2872 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces
2873 * rfc793's wired-in beta.
2877 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
2878 if ((tp->t_rttvar += delta) <= 0)
2880 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
2881 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2884 * No rtt measurement yet - use the unsmoothed rtt.
2885 * Set the variance to half the rtt (so our first
2886 * retransmit happens at 3*rtt).
2888 tp->t_srtt = rtt << TCP_RTT_SHIFT;
2889 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
2890 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2895 #ifdef DEBUG_EIFEL_RESPONSE
2897 kprintf("| rxtcur prev %d, old %d, ",
2898 tp->t_rxtcur_prev, tp->t_rxtcur);
2903 * the retransmit should happen at rtt + 4 * rttvar.
2904 * Because of the way we do the smoothing, srtt and rttvar
2905 * will each average +1/2 tick of bias. When we compute
2906 * the retransmit timer, we want 1/2 tick of rounding and
2907 * 1 extra tick because of +-1/2 tick uncertainty in the
2908 * firing of the timer. The bias will give us exactly the
2909 * 1.5 tick we need. But, because the bias is
2910 * statistical, we have to test that we don't drop below
2911 * the minimum feasible timer (which is 2 ticks).
2913 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
2914 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);
2917 if (tp->t_rxtcur < tp->t_rxtcur_prev + tcp_eifel_rtoinc) {
2919 * RFC4015 requires that the new RTO is at least
2920 * 2*G (tcp_eifel_rtoinc) greater then the RTO
2921 * (t_rxtcur_prev) when the spurious retransmit
2924 * The above condition could be true, if the SRTT
2925 * and RTTVAR used to calculate t_rxtcur_prev
2926 * resulted in a value less than t_rttmin. So
2927 * simply increasing SRTT by tcp_eifel_rtoinc when
2928 * preparing for the Eifel response could not ensure
2929 * that the new RTO will be tcp_eifel_rtoinc greater
2932 tp->t_rxtcur = tp->t_rxtcur_prev + tcp_eifel_rtoinc;
2934 #ifdef DEBUG_EIFEL_RESPONSE
2935 kprintf("new %d\n", tp->t_rxtcur);
2940 * We received an ack for a packet that wasn't retransmitted;
2941 * it is probably safe to discard any error indications we've
2942 * received recently. This isn't quite right, but close enough
2943 * for now (a route might have failed after we sent a segment,
2944 * and the return path might not be symmetrical).
2946 tp->t_softerror = 0;
2950 * Determine a reasonable value for maxseg size.
2951 * If the route is known, check route for mtu.
2952 * If none, use an mss that can be handled on the outgoing
2953 * interface without forcing IP to fragment; if bigger than
2954 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES
2955 * to utilize large mbufs. If no route is found, route has no mtu,
2956 * or the destination isn't local, use a default, hopefully conservative
2957 * size (usually 512 or the default IP max size, but no more than the mtu
2958 * of the interface), as we can't discover anything about intervening
2959 * gateways or networks. We also initialize the congestion/slow start
2960 * window to be a single segment if the destination isn't local.
2961 * While looking at the routing entry, we also initialize other path-dependent
2962 * parameters from pre-set or cached values in the routing entry.
2964 * Also take into account the space needed for options that we
2965 * send regularly. Make maxseg shorter by that amount to assure
2966 * that we can send maxseg amount of data even when the options
2967 * are present. Store the upper limit of the length of options plus
2970 * NOTE that this routine is only called when we process an incoming
2971 * segment, for outgoing segments only tcp_mssopt is called.
2974 tcp_mss(struct tcpcb *tp, int offer)
2980 struct inpcb *inp = tp->t_inpcb;
2983 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE);
2984 size_t min_protoh = isipv6 ?
2985 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) :
2986 sizeof(struct tcpiphdr);
2988 const boolean_t isipv6 = FALSE;
2989 const size_t min_protoh = sizeof(struct tcpiphdr);
2993 rt = tcp_rtlookup6(&inp->inp_inc);
2995 rt = tcp_rtlookup(&inp->inp_inc);
2997 tp->t_maxopd = tp->t_maxseg =
2998 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt);
3002 so = inp->inp_socket;
3005 * Offer == 0 means that there was no MSS on the SYN segment,
3006 * in this case we use either the interface mtu or tcp_mssdflt.
3008 * An offer which is too large will be cut down later.
3012 if (in6_localaddr(&inp->in6p_faddr)) {
3013 offer = ND_IFINFO(rt->rt_ifp)->linkmtu -
3016 offer = tcp_v6mssdflt;
3019 if (in_localaddr(inp->inp_faddr))
3020 offer = ifp->if_mtu - min_protoh;
3022 offer = tcp_mssdflt;
3027 * Prevent DoS attack with too small MSS. Round up
3028 * to at least minmss.
3030 * Sanity check: make sure that maxopd will be large
3031 * enough to allow some data on segments even is the
3032 * all the option space is used (40bytes). Otherwise
3033 * funny things may happen in tcp_output.
3035 offer = max(offer, tcp_minmss);
3036 offer = max(offer, 64);
3038 rt->rt_rmx.rmx_mssopt = offer;
3041 * While we're here, check if there's an initial rtt
3042 * or rttvar. Convert from the route-table units
3043 * to scaled multiples of the slow timeout timer.
3045 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) {
3047 * XXX the lock bit for RTT indicates that the value
3048 * is also a minimum value; this is subject to time.
3050 if (rt->rt_rmx.rmx_locks & RTV_RTT)
3051 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz);
3052 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE));
3053 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE;
3054 tcpstat.tcps_usedrtt++;
3055 if (rt->rt_rmx.rmx_rttvar) {
3056 tp->t_rttvar = rt->rt_rmx.rmx_rttvar /
3057 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE));
3058 tcpstat.tcps_usedrttvar++;
3060 /* default variation is +- 1 rtt */
3062 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
3064 TCPT_RANGESET(tp->t_rxtcur,
3065 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
3066 tp->t_rttmin, TCPTV_REXMTMAX);
3070 * if there's an mtu associated with the route, use it
3071 * else, use the link mtu. Take the smaller of mss or offer
3074 if (rt->rt_rmx.rmx_mtu) {
3075 mss = rt->rt_rmx.rmx_mtu - min_protoh;
3078 mss = ND_IFINFO(rt->rt_ifp)->linkmtu - min_protoh;
3080 mss = ifp->if_mtu - min_protoh;
3082 mss = min(mss, offer);
3085 * maxopd stores the maximum length of data AND options
3086 * in a segment; maxseg is the amount of data in a normal
3087 * segment. We need to store this value (maxopd) apart
3088 * from maxseg, because now every segment carries options
3089 * and thus we normally have somewhat less data in segments.
3093 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP &&
3094 ((tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP))
3095 mss -= TCPOLEN_TSTAMP_APPA;
3097 #if (MCLBYTES & (MCLBYTES - 1)) == 0
3099 mss &= ~(MCLBYTES-1);
3102 mss = mss / MCLBYTES * MCLBYTES;
3105 * If there's a pipesize, change the socket buffer
3106 * to that size. Make the socket buffers an integral
3107 * number of mss units; if the mss is larger than
3108 * the socket buffer, decrease the mss.
3111 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0)
3113 bufsize = so->so_snd.ssb_hiwat;
3117 bufsize = roundup(bufsize, mss);
3118 if (bufsize > sb_max)
3120 if (bufsize > so->so_snd.ssb_hiwat)
3121 ssb_reserve(&so->so_snd, bufsize, so, NULL);
3126 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0)
3128 bufsize = so->so_rcv.ssb_hiwat;
3129 if (bufsize > mss) {
3130 bufsize = roundup(bufsize, mss);
3131 if (bufsize > sb_max)
3133 if (bufsize > so->so_rcv.ssb_hiwat) {
3134 lwkt_gettoken(&so->so_rcv.ssb_token);
3135 ssb_reserve(&so->so_rcv, bufsize, so, NULL);
3136 lwkt_reltoken(&so->so_rcv.ssb_token);
3141 * Set the slow-start flight size
3143 * NOTE: t_maxseg must have been configured!
3145 tp->snd_cwnd = tcp_initial_window(tp);
3147 if (rt->rt_rmx.rmx_ssthresh) {
3149 * There's some sort of gateway or interface
3150 * buffer limit on the path. Use this to set
3151 * the slow start threshhold, but set the
3152 * threshold to no less than 2*mss.
3154 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh);
3155 tcpstat.tcps_usedssthresh++;
3160 * Determine the MSS option to send on an outgoing SYN.
3163 tcp_mssopt(struct tcpcb *tp)
3168 ((tp->t_inpcb->inp_vflag & INP_IPV6) ? TRUE : FALSE);
3169 int min_protoh = isipv6 ?
3170 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) :
3171 sizeof(struct tcpiphdr);
3173 const boolean_t isipv6 = FALSE;
3174 const size_t min_protoh = sizeof(struct tcpiphdr);
3178 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc);
3180 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc);
3182 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt);
3184 return (rt->rt_ifp->if_mtu - min_protoh);
3188 * When a partial ack arrives, force the retransmission of the
3189 * next unacknowledged segment. Do not exit Fast Recovery.
3191 * Implement the Slow-but-Steady variant of NewReno by restarting the
3192 * the retransmission timer. Turn it off here so it can be restarted
3193 * later in tcp_output().
3196 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th, int acked)
3198 tcp_seq old_snd_nxt = tp->snd_nxt;
3199 u_long ocwnd = tp->snd_cwnd;
3201 tcp_callout_stop(tp, tp->tt_rexmt);
3203 tp->snd_nxt = th->th_ack;
3204 /* Set snd_cwnd to one segment beyond acknowledged offset. */
3205 tp->snd_cwnd = tp->t_maxseg;
3206 tp->t_flags |= TF_ACKNOW;
3208 if (SEQ_GT(old_snd_nxt, tp->snd_nxt))
3209 tp->snd_nxt = old_snd_nxt;
3210 /* partial window deflation */
3212 tp->snd_cwnd = ocwnd - acked + tp->t_maxseg;
3214 tp->snd_cwnd = tp->t_maxseg;
3218 * In contrast to the Slow-but-Steady NewReno variant,
3219 * we do not reset the retransmission timer for SACK retransmissions,
3220 * except when retransmitting snd_una.
3223 tcp_sack_rexmt(struct tcpcb *tp, boolean_t force)
3225 tcp_seq old_snd_nxt = tp->snd_nxt;
3226 u_long ocwnd = tp->snd_cwnd;
3228 int nseg = 0; /* consecutive new segments */
3229 int nseg_rexmt = 0; /* retransmitted segments */
3231 #define MAXBURST 4 /* limit burst of new packets on partial ack */
3234 uint32_t unsacked = tcp_sack_first_unsacked_len(tp);
3237 * Try to fill the first hole in the receiver's
3240 maxrexmt = howmany(unsacked, tp->t_maxseg);
3241 if (maxrexmt > tcp_force_sackrxt)
3242 maxrexmt = tcp_force_sackrxt;
3246 pipe = tcp_sack_compute_pipe(tp);
3247 while (((tcp_seq_diff_t)(ocwnd - pipe) >= (tcp_seq_diff_t)tp->t_maxseg
3248 || (force && nseg_rexmt < maxrexmt && nseg == 0)) &&
3249 (!tcp_do_smartsack || nseg < MAXBURST)) {
3250 tcp_seq old_snd_max, old_rexmt_high, nextrexmt;
3251 uint32_t sent, seglen;
3255 old_rexmt_high = tp->rexmt_high;
3256 if (!tcp_sack_nextseg(tp, &nextrexmt, &seglen, &rescue)) {
3257 tp->rexmt_high = old_rexmt_high;
3262 * If the next tranmission is a rescue retranmission,
3263 * we check whether we have already sent some data
3264 * (either new segments or retransmitted segments)
3265 * into the the network or not. Since the idea of rescue
3266 * retransmission is to sustain ACK clock, as long as
3267 * some segments are in the network, ACK clock will be
3270 if (rescue && (nseg_rexmt > 0 || nseg > 0)) {
3271 tp->rexmt_high = old_rexmt_high;
3275 if (nextrexmt == tp->snd_max)
3279 tp->snd_nxt = nextrexmt;
3280 tp->snd_cwnd = nextrexmt - tp->snd_una + seglen;
3281 old_snd_max = tp->snd_max;
3282 if (nextrexmt == tp->snd_una)
3283 tcp_callout_stop(tp, tp->tt_rexmt);
3284 tp->t_flags |= TF_XMITNOW;
3285 error = tcp_output(tp);
3287 tp->rexmt_high = old_rexmt_high;
3290 sent = tp->snd_nxt - nextrexmt;
3292 tp->rexmt_high = old_rexmt_high;
3296 tcpstat.tcps_sndsackpack++;
3297 tcpstat.tcps_sndsackbyte += sent;
3300 tcpstat.tcps_sackrescue++;
3301 tp->rexmt_rescue = tp->snd_nxt;
3302 tp->sack_flags |= TSACK_F_SACKRESCUED;
3305 if (SEQ_LT(nextrexmt, old_snd_max) &&
3306 SEQ_LT(tp->rexmt_high, tp->snd_nxt)) {
3307 tp->rexmt_high = seq_min(tp->snd_nxt, old_snd_max);
3308 if (tcp_aggressive_rescuesack &&
3309 (tp->sack_flags & TSACK_F_SACKRESCUED) &&
3310 SEQ_LT(tp->rexmt_rescue, tp->rexmt_high)) {
3311 /* Drag RescueRxt along with HighRxt */
3312 tp->rexmt_rescue = tp->rexmt_high;
3316 if (SEQ_GT(old_snd_nxt, tp->snd_nxt))
3317 tp->snd_nxt = old_snd_nxt;
3318 tp->snd_cwnd = ocwnd;
3322 * Return TRUE, if some new segments are sent
3325 tcp_sack_limitedxmit(struct tcpcb *tp)
3327 tcp_seq oldsndnxt = tp->snd_nxt;
3328 tcp_seq oldsndmax = tp->snd_max;
3329 u_long ocwnd = tp->snd_cwnd;
3330 uint32_t pipe, sent;
3331 boolean_t ret = FALSE;
3332 tcp_seq_diff_t cwnd_left;
3335 tp->rexmt_high = tp->snd_una - 1;
3336 pipe = tcp_sack_compute_pipe(tp);
3337 cwnd_left = (tcp_seq_diff_t)(ocwnd - pipe);
3338 if (cwnd_left < (tcp_seq_diff_t)tp->t_maxseg)
3341 next = tp->snd_nxt = tp->snd_max;
3342 tp->snd_cwnd = tp->snd_nxt - tp->snd_una +
3343 rounddown(cwnd_left, tp->t_maxseg);
3345 tp->t_flags |= TF_XMITNOW;
3348 sent = tp->snd_nxt - next;
3350 tcpstat.tcps_sndlimited += howmany(sent, tp->t_maxseg);
3354 if (SEQ_LT(oldsndnxt, oldsndmax)) {
3355 KASSERT(SEQ_GEQ(oldsndnxt, tp->snd_una),
3356 ("snd_una moved in other threads"));
3357 tp->snd_nxt = oldsndnxt;
3359 tp->snd_cwnd = ocwnd;
3361 if (ret && TCP_DO_NCR(tp))
3362 tcp_ncr_update_rxtthresh(tp);
3368 * Reset idle time and keep-alive timer, typically called when a valid
3369 * tcp packet is received but may also be called when FASTKEEP is set
3370 * to prevent the previous long-timeout from calculating to a drop.
3372 * Only update t_rcvtime for non-SYN packets.
3374 * Handle the case where one side thinks the connection is established
3375 * but the other side has, say, rebooted without cleaning out the
3376 * connection. The SYNs could be construed as an attack and wind
3377 * up ignored, but in case it isn't an attack we can validate the
3378 * connection by forcing a keepalive.
3381 tcp_timer_keep_activity(struct tcpcb *tp, int thflags)
3383 if (TCPS_HAVEESTABLISHED(tp->t_state)) {
3384 if ((thflags & (TH_SYN | TH_ACK)) == TH_SYN) {
3385 tp->t_flags |= TF_KEEPALIVE;
3386 tcp_callout_reset(tp, tp->tt_keep, hz / 2,
3389 tp->t_rcvtime = ticks;
3390 tp->t_flags &= ~TF_KEEPALIVE;
3391 tcp_callout_reset(tp, tp->tt_keep,
3399 tcp_rmx_msl(const struct tcpcb *tp)
3402 struct inpcb *inp = tp->t_inpcb;
3405 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE);
3407 const boolean_t isipv6 = FALSE;
3411 rt = tcp_rtlookup6(&inp->inp_inc);
3413 rt = tcp_rtlookup(&inp->inp_inc);
3414 if (rt == NULL || rt->rt_rmx.rmx_msl == 0)
3417 msl = (rt->rt_rmx.rmx_msl * hz) / 1000;
3425 tcp_established(struct tcpcb *tp)
3427 tp->t_state = TCPS_ESTABLISHED;
3428 tcp_callout_reset(tp, tp->tt_keep, tp->t_keepidle, tcp_timer_keep);
3430 if (tp->t_rxtsyn > 0) {
3433 * "If the timer expires awaiting the ACK of a SYN segment
3434 * and the TCP implementation is using an RTO less than 3
3435 * seconds, the RTO MUST be re-initialized to 3 seconds
3436 * when data transmission begins"
3438 if (tp->t_rxtcur < TCPTV_RTOBASE3)
3439 tp->t_rxtcur = TCPTV_RTOBASE3;
3444 * Returns TRUE, if the ACK should be dropped
3447 tcp_recv_dupack(struct tcpcb *tp, tcp_seq th_ack, u_int to_flags)
3449 boolean_t fast_sack_rexmt = TRUE;
3451 tcpstat.tcps_rcvdupack++;
3454 * We have outstanding data (other than a window probe),
3455 * this is a completely duplicate ack (ie, window info
3456 * didn't change), the ack is the biggest we've seen and
3457 * we've seen exactly our rexmt threshhold of them, so
3458 * assume a packet has been dropped and retransmit it.
3459 * Kludge snd_nxt & the congestion window so we send only
3462 if (IN_FASTRECOVERY(tp)) {
3463 if (TCP_DO_SACK(tp)) {
3464 boolean_t force = FALSE;
3466 if (tp->snd_una == tp->rexmt_high &&
3467 (to_flags & (TOF_SACK | TOF_SACK_REDUNDANT)) ==
3470 * New segments got SACKed and
3471 * no retransmit yet.
3476 /* No artifical cwnd inflation. */
3477 tcp_sack_rexmt(tp, force);
3480 * Dup acks mean that packets have left
3481 * the network (they're now cached at the
3482 * receiver) so bump cwnd by the amount in
3483 * the receiver to keep a constant cwnd
3484 * packets in the network.
3486 tp->snd_cwnd += tp->t_maxseg;
3490 } else if (SEQ_LT(th_ack, tp->snd_recover)) {
3493 } else if (tcp_ignore_redun_dsack && TCP_DO_SACK(tp) &&
3494 (to_flags & (TOF_DSACK | TOF_SACK_REDUNDANT)) ==
3495 (TOF_DSACK | TOF_SACK_REDUNDANT)) {
3497 * If the ACK carries DSACK and other SACK blocks
3498 * carry information that we have already known,
3499 * don't count this ACK as duplicate ACK. This
3500 * prevents spurious early retransmit and fast
3501 * retransmit. This also meets the requirement of
3502 * RFC3042 that new segments should not be sent if
3503 * the SACK blocks do not contain new information
3504 * (XXX we actually loosen the requirment that only
3505 * DSACK is checked here).
3507 * This kind of ACKs are usually sent after spurious
3510 /* Do nothing; don't change t_dupacks */
3512 } else if (tp->t_dupacks == 0 && TCP_DO_NCR(tp)) {
3513 tcp_ncr_update_rxtthresh(tp);
3516 if (++tp->t_dupacks == tp->t_rxtthresh) {
3517 tcp_seq old_snd_nxt;
3521 if (tcp_do_eifel_detect && (tp->t_flags & TF_RCVD_TSTMP)) {
3522 tcp_save_congestion_state(tp);
3523 tp->rxt_flags |= TRXT_F_FASTREXMT;
3526 * We know we're losing at the current window size,
3527 * so do congestion avoidance: set ssthresh to half
3528 * the current window and pull our congestion window
3529 * back to the new ssthresh.
3531 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
3534 tp->snd_ssthresh = win * tp->t_maxseg;
3535 ENTER_FASTRECOVERY(tp);
3536 tp->snd_recover = tp->snd_max;
3537 tcp_callout_stop(tp, tp->tt_rexmt);
3539 old_snd_nxt = tp->snd_nxt;
3540 tp->snd_nxt = th_ack;
3541 if (TCP_DO_SACK(tp)) {
3544 rxtlen = tcp_sack_first_unsacked_len(tp);
3545 if (rxtlen > tp->t_maxseg)
3546 rxtlen = tp->t_maxseg;
3547 tp->snd_cwnd = rxtlen;
3549 tp->snd_cwnd = tp->t_maxseg;
3552 ++tcpstat.tcps_sndfastrexmit;
3553 tp->snd_cwnd = tp->snd_ssthresh;
3554 tp->rexmt_high = tp->snd_nxt;
3555 tp->sack_flags &= ~TSACK_F_SACKRESCUED;
3556 if (SEQ_GT(old_snd_nxt, tp->snd_nxt))
3557 tp->snd_nxt = old_snd_nxt;
3558 KASSERT(tp->snd_limited <= 2, ("tp->snd_limited too big"));
3559 if (TCP_DO_SACK(tp)) {
3560 if (fast_sack_rexmt)
3561 tcp_sack_rexmt(tp, FALSE);
3563 tp->snd_cwnd += tp->t_maxseg *
3564 (tp->t_dupacks - tp->snd_limited);
3566 } else if ((tcp_do_rfc6675 && TCP_DO_SACK(tp)) || TCP_DO_NCR(tp)) {
3568 * The RFC6675 recommends to reduce the byte threshold,
3569 * and enter fast retransmit if IsLost(snd_una). However,
3570 * if we use IsLost(snd_una) based fast retransmit here,
3571 * segments reordering will cause spurious retransmit. So
3572 * we defer the IsLost(snd_una) based fast retransmit until
3573 * the extended limited transmit can't send any segments and
3574 * early retransmit can't be done.
3576 if (tcp_rfc6675_rxt && tcp_do_rfc6675 &&
3577 tcp_sack_islost(&tp->scb, tp->snd_una))
3578 goto fastretransmit;
3580 if (tcp_do_limitedtransmit || TCP_DO_NCR(tp)) {
3581 if (!tcp_sack_limitedxmit(tp)) {
3582 /* outstanding data */
3583 uint32_t ownd = tp->snd_max - tp->snd_una;
3585 if (need_early_retransmit(tp, ownd)) {
3586 ++tcpstat.tcps_sndearlyrexmit;
3587 tp->rxt_flags |= TRXT_F_EARLYREXMT;
3588 goto fastretransmit;
3589 } else if (tcp_do_rfc6675 &&
3590 tcp_sack_islost(&tp->scb, tp->snd_una)) {
3591 fast_sack_rexmt = FALSE;
3592 goto fastretransmit;
3596 } else if (tcp_do_limitedtransmit) {
3597 u_long oldcwnd = tp->snd_cwnd;
3598 tcp_seq oldsndmax = tp->snd_max;
3599 tcp_seq oldsndnxt = tp->snd_nxt;
3600 /* outstanding data */
3601 uint32_t ownd = tp->snd_max - tp->snd_una;
3604 KASSERT(tp->t_dupacks == 1 || tp->t_dupacks == 2,
3605 ("dupacks not 1 or 2"));
3606 if (tp->t_dupacks == 1)
3607 tp->snd_limited = 0;
3608 tp->snd_nxt = tp->snd_max;
3609 tp->snd_cwnd = ownd +
3610 (tp->t_dupacks - tp->snd_limited) * tp->t_maxseg;
3611 tp->t_flags |= TF_XMITNOW;
3614 if (SEQ_LT(oldsndnxt, oldsndmax)) {
3615 KASSERT(SEQ_GEQ(oldsndnxt, tp->snd_una),
3616 ("snd_una moved in other threads"));
3617 tp->snd_nxt = oldsndnxt;
3619 tp->snd_cwnd = oldcwnd;
3620 sent = tp->snd_max - oldsndmax;
3621 if (sent > tp->t_maxseg) {
3622 KASSERT((tp->t_dupacks == 2 && tp->snd_limited == 0) ||
3623 (sent == tp->t_maxseg + 1 &&
3624 (tp->t_flags & TF_SENTFIN)),
3626 KASSERT(sent <= tp->t_maxseg * 2,
3627 ("sent too many segments"));
3628 tp->snd_limited = 2;
3629 tcpstat.tcps_sndlimited += 2;
3630 } else if (sent > 0) {
3632 ++tcpstat.tcps_sndlimited;
3633 } else if (need_early_retransmit(tp, ownd)) {
3634 ++tcpstat.tcps_sndearlyrexmit;
3635 tp->rxt_flags |= TRXT_F_EARLYREXMT;
3636 goto fastretransmit;
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