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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17 * contributors may be used to endorse or promote products derived
18 * from this software without specific, prior written permission.
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62 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95
63 * $FreeBSD: src/sys/netinet/tcp_input.c,v 1.107.2.38 2003/05/21 04:46:41 cjc Exp $
67 #include "opt_inet6.h"
68 #include "opt_ipsec.h"
69 #include "opt_tcpdebug.h"
70 #include "opt_tcp_input.h"
72 #include <sys/param.h>
73 #include <sys/systm.h>
74 #include <sys/kernel.h>
75 #include <sys/sysctl.h>
76 #include <sys/malloc.h>
78 #include <sys/proc.h> /* for proc0 declaration */
79 #include <sys/protosw.h>
80 #include <sys/socket.h>
81 #include <sys/socketvar.h>
82 #include <sys/syslog.h>
83 #include <sys/in_cksum.h>
85 #include <sys/socketvar2.h>
87 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */
88 #include <machine/stdarg.h>
91 #include <net/route.h>
93 #include <netinet/in.h>
94 #include <netinet/in_systm.h>
95 #include <netinet/ip.h>
96 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */
97 #include <netinet/in_var.h>
98 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */
99 #include <netinet/in_pcb.h>
100 #include <netinet/ip_var.h>
101 #include <netinet/ip6.h>
102 #include <netinet/icmp6.h>
103 #include <netinet6/nd6.h>
104 #include <netinet6/ip6_var.h>
105 #include <netinet6/in6_pcb.h>
106 #include <netinet/tcp.h>
107 #include <netinet/tcp_fsm.h>
108 #include <netinet/tcp_seq.h>
109 #include <netinet/tcp_timer.h>
110 #include <netinet/tcp_timer2.h>
111 #include <netinet/tcp_var.h>
112 #include <netinet6/tcp6_var.h>
113 #include <netinet/tcpip.h>
116 #include <netinet/tcp_debug.h>
118 u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */
119 struct tcphdr tcp_savetcp;
123 #include <netproto/ipsec/ipsec.h>
124 #include <netproto/ipsec/ipsec6.h>
128 #include <netinet6/ipsec.h>
129 #include <netinet6/ipsec6.h>
130 #include <netproto/key/key.h>
134 * Limit burst of new packets during SACK based fast recovery
135 * or extended limited transmit.
137 #define TCP_SACK_MAXBURST 4
139 MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry");
141 static int log_in_vain = 0;
142 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW,
143 &log_in_vain, 0, "Log all incoming TCP connections");
145 static int blackhole = 0;
146 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW,
147 &blackhole, 0, "Do not send RST when dropping refused connections");
149 int tcp_delack_enabled = 1;
150 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW,
151 &tcp_delack_enabled, 0,
152 "Delay ACK to try and piggyback it onto a data packet");
154 #ifdef TCP_DROP_SYNFIN
155 static int drop_synfin = 0;
156 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW,
157 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set");
160 static int tcp_do_limitedtransmit = 1;
161 SYSCTL_INT(_net_inet_tcp, OID_AUTO, limitedtransmit, CTLFLAG_RW,
162 &tcp_do_limitedtransmit, 0, "Enable RFC 3042 (Limited Transmit)");
164 static int tcp_do_early_retransmit = 1;
165 SYSCTL_INT(_net_inet_tcp, OID_AUTO, earlyretransmit, CTLFLAG_RW,
166 &tcp_do_early_retransmit, 0, "Early retransmit");
168 int tcp_aggregate_acks = 1;
169 SYSCTL_INT(_net_inet_tcp, OID_AUTO, aggregate_acks, CTLFLAG_RW,
170 &tcp_aggregate_acks, 0, "Aggregate built-up acks into one ack");
172 static int tcp_do_eifel_detect = 1;
173 SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW,
174 &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)");
176 static int tcp_do_abc = 1;
177 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc, CTLFLAG_RW,
179 "TCP Appropriate Byte Counting (RFC 3465)");
182 * The following value actually takes range [25ms, 250ms],
183 * given that most modern systems use 1ms ~ 10ms as the unit
184 * of timestamp option.
186 static u_int tcp_paws_tolerance = 25;
187 SYSCTL_UINT(_net_inet_tcp, OID_AUTO, paws_tolerance, CTLFLAG_RW,
188 &tcp_paws_tolerance, 0, "RFC1323 PAWS tolerance");
191 * Define as tunable for easy testing with SACK on and off.
192 * Warning: do not change setting in the middle of an existing active TCP flow,
193 * else strange things might happen to that flow.
196 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW,
197 &tcp_do_sack, 0, "Enable SACK Algorithms");
199 int tcp_do_smartsack = 1;
200 SYSCTL_INT(_net_inet_tcp, OID_AUTO, smartsack, CTLFLAG_RW,
201 &tcp_do_smartsack, 0, "Enable Smart SACK Algorithms");
203 int tcp_do_rescuesack = 1;
204 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rescuesack, CTLFLAG_RW,
205 &tcp_do_rescuesack, 0, "Rescue retransmission for SACK");
207 int tcp_aggressive_rescuesack = 0;
208 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rescuesack_agg, CTLFLAG_RW,
209 &tcp_aggressive_rescuesack, 0, "Aggressive rescue retransmission for SACK");
211 static int tcp_force_sackrxt = 1;
212 SYSCTL_INT(_net_inet_tcp, OID_AUTO, force_sackrxt, CTLFLAG_RW,
213 &tcp_force_sackrxt, 0, "Allowed forced SACK retransmit burst");
215 int tcp_do_rfc6675 = 1;
216 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc6675, CTLFLAG_RW,
217 &tcp_do_rfc6675, 0, "Enable RFC6675");
219 int tcp_rfc6675_rxt = 0;
220 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc6675_rxt, CTLFLAG_RW,
221 &tcp_rfc6675_rxt, 0, "Enable RFC6675 retransmit");
223 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0,
224 "TCP Segment Reassembly Queue");
226 int tcp_reass_maxseg = 0;
227 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD,
228 &tcp_reass_maxseg, 0,
229 "Global maximum number of TCP Segments in Reassembly Queue");
231 int tcp_reass_qsize = 0;
232 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD,
234 "Global number of TCP Segments currently in Reassembly Queue");
236 static int tcp_reass_overflows = 0;
237 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD,
238 &tcp_reass_overflows, 0,
239 "Global number of TCP Segment Reassembly Queue Overflows");
241 int tcp_do_autorcvbuf = 1;
242 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW,
243 &tcp_do_autorcvbuf, 0, "Enable automatic receive buffer sizing");
245 int tcp_autorcvbuf_inc = 16*1024;
246 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW,
247 &tcp_autorcvbuf_inc, 0,
248 "Incrementor step size of automatic receive buffer");
250 int tcp_autorcvbuf_max = 2*1024*1024;
251 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW,
252 &tcp_autorcvbuf_max, 0, "Max size of automatic receive buffer");
254 int tcp_sosend_agglim = 2;
255 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosend_agglim, CTLFLAG_RW,
256 &tcp_sosend_agglim, 0, "TCP sosend mbuf aggregation limit");
258 int tcp_sosend_async = 1;
259 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosend_async, CTLFLAG_RW,
260 &tcp_sosend_async, 0, "TCP asynchronized pru_send");
262 int tcp_sosend_jcluster = 1;
263 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosend_jcluster, CTLFLAG_RW,
264 &tcp_sosend_jcluster, 0, "TCP output uses jcluster");
266 static int tcp_ignore_redun_dsack = 1;
267 SYSCTL_INT(_net_inet_tcp, OID_AUTO, ignore_redun_dsack, CTLFLAG_RW,
268 &tcp_ignore_redun_dsack, 0, "Ignore redundant DSACK");
270 static int tcp_reuseport_ext = 1;
271 SYSCTL_INT(_net_inet_tcp, OID_AUTO, reuseport_ext, CTLFLAG_RW,
272 &tcp_reuseport_ext, 0, "SO_REUSEPORT extension");
274 static void tcp_dooptions(struct tcpopt *, u_char *, int, boolean_t,
276 static void tcp_pulloutofband(struct socket *,
277 struct tcphdr *, struct mbuf *, int);
278 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *,
280 static void tcp_xmit_timer(struct tcpcb *, int, tcp_seq);
281 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *, int);
282 static void tcp_sack_rexmt(struct tcpcb *, boolean_t);
283 static boolean_t tcp_sack_limitedxmit(struct tcpcb *);
284 static int tcp_rmx_msl(const struct tcpcb *);
285 static void tcp_established(struct tcpcb *);
286 static boolean_t tcp_recv_dupack(struct tcpcb *, tcp_seq, u_int);
288 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */
290 #define ND6_HINT(tp) \
292 if ((tp) && (tp)->t_inpcb && \
293 INP_ISIPV6((tp)->t_inpcb) && \
294 (tp)->t_inpcb->in6p_route.ro_rt) \
295 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \
302 * Indicate whether this ack should be delayed. We can delay the ack if
303 * - delayed acks are enabled and
304 * - there is no delayed ack timer in progress and
305 * - our last ack wasn't a 0-sized window. We never want to delay
306 * the ack that opens up a 0-sized window.
308 #define DELAY_ACK(tp) \
309 (tcp_delack_enabled && !tcp_callout_pending(tp, tp->tt_delack) && \
310 !(tp->t_flags & TF_RXWIN0SENT))
312 #define acceptable_window_update(tp, th, tiwin) \
313 (SEQ_LT(tp->snd_wl1, th->th_seq) || \
314 (tp->snd_wl1 == th->th_seq && \
315 (SEQ_LT(tp->snd_wl2, th->th_ack) || \
316 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))
318 #define iceildiv(n, d) (((n)+(d)-1) / (d))
319 #define need_early_retransmit(tp, ownd) \
320 (tcp_do_early_retransmit && \
321 (tcp_do_eifel_detect && (tp->t_flags & TF_RCVD_TSTMP)) && \
322 ownd < ((tp->t_rxtthresh + 1) * tp->t_maxseg) && \
323 tp->t_dupacks + 1 >= iceildiv(ownd, tp->t_maxseg) && \
324 (!TCP_DO_SACK(tp) || ownd <= tp->t_maxseg || \
325 tcp_sack_has_sacked(&tp->scb, ownd - tp->t_maxseg)))
328 * Returns TRUE, if this segment can be merged with the last
329 * pending segment in the reassemble queue and this segment
330 * does not overlap with the pending segment immediately
331 * preceeding the last pending segment.
333 static __inline boolean_t
334 tcp_paws_canreasslast(const struct tcpcb *tp, const struct tcphdr *th, int tlen)
336 const struct tseg_qent *last, *prev;
338 last = TAILQ_LAST(&tp->t_segq, tsegqe_head);
342 /* This segment comes immediately after the last pending segment */
343 if (last->tqe_th->th_seq + last->tqe_len == th->th_seq) {
344 if (last->tqe_th->th_flags & TH_FIN) {
345 /* No segments should follow segment w/ FIN */
351 if (th->th_seq + tlen != last->tqe_th->th_seq)
353 /* This segment comes immediately before the last pending segment */
355 prev = TAILQ_PREV(last, tsegqe_head, tqe_q);
358 * No pending preceeding segment, we assume this segment
359 * could be reassembled.
364 /* This segment does not overlap with the preceeding segment */
365 if (SEQ_GEQ(th->th_seq, prev->tqe_th->th_seq + prev->tqe_len))
372 tcp_ncr_update_rxtthresh(struct tcpcb *tp)
374 int old_rxtthresh = tp->t_rxtthresh;
375 uint32_t ownd = tp->snd_max - tp->snd_una;
377 tp->t_rxtthresh = min(tcp_ncr_rxtthresh_max,
378 max(tcprexmtthresh, ((ownd / tp->t_maxseg) >> 1)));
379 if (tp->t_rxtthresh != old_rxtthresh) {
380 tcp_sack_update_lostseq(&tp->scb, tp->snd_una,
381 tp->t_maxseg, tp->t_rxtthresh);
386 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m)
389 struct tseg_qent *p = NULL;
390 struct tseg_qent *te;
391 struct socket *so = tp->t_inpcb->inp_socket;
395 * Call with th == NULL after become established to
396 * force pre-ESTABLISHED data up to user socket.
402 * Limit the number of segments in the reassembly queue to prevent
403 * holding on to too many segments (and thus running out of mbufs).
404 * Make sure to let the missing segment through which caused this
405 * queue. Always keep one global queue entry spare to be able to
406 * process the missing segment.
408 if (th->th_seq != tp->rcv_nxt &&
409 tcp_reass_qsize + 1 >= tcp_reass_maxseg) {
410 tcp_reass_overflows++;
411 tcpstat.tcps_rcvmemdrop++;
413 /* no SACK block to report */
414 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
418 /* Allocate a new queue entry. */
419 te = kmalloc(sizeof(struct tseg_qent), M_TSEGQ, M_INTWAIT | M_NULLOK);
421 tcpstat.tcps_rcvmemdrop++;
423 /* no SACK block to report */
424 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
427 atomic_add_int(&tcp_reass_qsize, 1);
429 if (th->th_flags & TH_FIN)
430 tp->t_flags |= TF_QUEDFIN;
433 * Find a segment which begins after this one does.
435 TAILQ_FOREACH(q, &tp->t_segq, tqe_q) {
436 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
442 * If there is a preceding segment, it may provide some of
443 * our data already. If so, drop the data from the incoming
444 * segment. If it provides all of our data, drop us.
449 /* conversion to int (in i) handles seq wraparound */
450 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
451 if (i > 0) { /* overlaps preceding segment */
453 (TSACK_F_DUPSEG | TSACK_F_ENCLOSESEG);
454 /* enclosing block starts w/ preceding segment */
455 tp->encloseblk.rblk_start = p->tqe_th->th_seq;
457 if (th->th_flags & TH_FIN)
458 p->tqe_th->th_flags |= TH_FIN;
460 /* preceding encloses incoming segment */
461 tp->encloseblk.rblk_end = TCP_SACK_BLKEND(
462 p->tqe_th->th_seq + p->tqe_len,
463 p->tqe_th->th_flags);
464 tcpstat.tcps_rcvduppack++;
465 tcpstat.tcps_rcvdupbyte += *tlenp;
468 atomic_add_int(&tcp_reass_qsize, -1);
470 * Try to present any queued data
471 * at the left window edge to the user.
472 * This is needed after the 3-WHS
475 goto present; /* ??? */
480 /* incoming segment end is enclosing block end */
481 tp->encloseblk.rblk_end = TCP_SACK_BLKEND(
482 th->th_seq + *tlenp, th->th_flags);
483 /* trim end of reported D-SACK block */
484 tp->reportblk.rblk_end = th->th_seq;
487 tcpstat.tcps_rcvoopack++;
488 tcpstat.tcps_rcvoobyte += *tlenp;
491 * While we overlap succeeding segments trim them or,
492 * if they are completely covered, dequeue them.
495 tcp_seq_diff_t i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
496 tcp_seq qend = q->tqe_th->th_seq + q->tqe_len;
497 tcp_seq qend_sack = TCP_SACK_BLKEND(qend, q->tqe_th->th_flags);
498 struct tseg_qent *nq;
502 if (!(tp->sack_flags & TSACK_F_DUPSEG)) {
503 /* first time through */
504 tp->sack_flags |= (TSACK_F_DUPSEG | TSACK_F_ENCLOSESEG);
505 tp->encloseblk = tp->reportblk;
506 /* report trailing duplicate D-SACK segment */
507 tp->reportblk.rblk_start = q->tqe_th->th_seq;
509 if ((tp->sack_flags & TSACK_F_ENCLOSESEG) &&
510 SEQ_GT(qend_sack, tp->encloseblk.rblk_end)) {
511 /* extend enclosing block if one exists */
512 tp->encloseblk.rblk_end = qend_sack;
514 if (i < q->tqe_len) {
515 q->tqe_th->th_seq += i;
521 if (q->tqe_th->th_flags & TH_FIN)
522 th->th_flags |= TH_FIN;
524 nq = TAILQ_NEXT(q, tqe_q);
525 TAILQ_REMOVE(&tp->t_segq, q, tqe_q);
528 atomic_add_int(&tcp_reass_qsize, -1);
532 /* Insert the new segment queue entry into place. */
535 te->tqe_len = *tlenp;
537 /* check if can coalesce with following segment */
538 if (q != NULL && (th->th_seq + *tlenp == q->tqe_th->th_seq)) {
541 te->tqe_len += q->tqe_len;
542 if (q->tqe_th->th_flags & TH_FIN)
543 te->tqe_th->th_flags |= TH_FIN;
544 tend_sack = TCP_SACK_BLKEND(te->tqe_th->th_seq + te->tqe_len,
545 te->tqe_th->th_flags);
547 m_cat(te->tqe_m, q->tqe_m);
548 tp->encloseblk.rblk_end = tend_sack;
550 * When not reporting a duplicate segment, use
551 * the larger enclosing block as the SACK block.
553 if (!(tp->sack_flags & TSACK_F_DUPSEG))
554 tp->reportblk.rblk_end = tend_sack;
555 TAILQ_REMOVE(&tp->t_segq, q, tqe_q);
557 atomic_add_int(&tcp_reass_qsize, -1);
561 TAILQ_INSERT_HEAD(&tp->t_segq, te, tqe_q);
563 /* check if can coalesce with preceding segment */
564 if (p->tqe_th->th_seq + p->tqe_len == th->th_seq) {
565 if (te->tqe_th->th_flags & TH_FIN)
566 p->tqe_th->th_flags |= TH_FIN;
567 p->tqe_len += te->tqe_len;
568 m_cat(p->tqe_m, te->tqe_m);
569 tp->encloseblk.rblk_start = p->tqe_th->th_seq;
571 * When not reporting a duplicate segment, use
572 * the larger enclosing block as the SACK block.
574 if (!(tp->sack_flags & TSACK_F_DUPSEG))
575 tp->reportblk.rblk_start = p->tqe_th->th_seq;
577 atomic_add_int(&tcp_reass_qsize, -1);
579 TAILQ_INSERT_AFTER(&tp->t_segq, p, te, tqe_q);
585 * Present data to user, advancing rcv_nxt through
586 * completed sequence space.
588 if (!TCPS_HAVEESTABLISHED(tp->t_state))
590 q = TAILQ_FIRST(&tp->t_segq);
591 if (q == NULL || q->tqe_th->th_seq != tp->rcv_nxt)
593 tp->rcv_nxt += q->tqe_len;
594 if (!(tp->sack_flags & TSACK_F_DUPSEG)) {
595 /* no SACK block to report since ACK advanced */
596 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
598 /* no enclosing block to report since ACK advanced */
599 tp->sack_flags &= ~TSACK_F_ENCLOSESEG;
600 flags = q->tqe_th->th_flags & TH_FIN;
601 TAILQ_REMOVE(&tp->t_segq, q, tqe_q);
602 KASSERT(TAILQ_EMPTY(&tp->t_segq) ||
603 TAILQ_FIRST(&tp->t_segq)->tqe_th->th_seq != tp->rcv_nxt,
604 ("segment not coalesced"));
605 if (so->so_state & SS_CANTRCVMORE) {
608 lwkt_gettoken(&so->so_rcv.ssb_token);
609 ssb_appendstream(&so->so_rcv, q->tqe_m);
610 lwkt_reltoken(&so->so_rcv.ssb_token);
613 atomic_add_int(&tcp_reass_qsize, -1);
620 * TCP input routine, follows pages 65-76 of the
621 * protocol specification dated September, 1981 very closely.
625 tcp6_input(struct mbuf **mp, int *offp, int proto)
627 struct mbuf *m = *mp;
628 struct in6_ifaddr *ia6;
630 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE);
633 * draft-itojun-ipv6-tcp-to-anycast
634 * better place to put this in?
636 ia6 = ip6_getdstifaddr(m);
637 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) {
638 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
639 offsetof(struct ip6_hdr, ip6_dst));
640 return (IPPROTO_DONE);
643 tcp_input(mp, offp, proto);
644 return (IPPROTO_DONE);
649 tcp_input(struct mbuf **mp, int *offp, int proto)
653 struct ip *ip = NULL;
655 struct inpcb *inp = NULL;
661 struct tcpcb *tp = NULL;
663 struct socket *so = NULL;
665 boolean_t ourfinisacked, needoutput = FALSE, delayed_dupack = FALSE;
666 tcp_seq th_dupack = 0; /* XXX gcc warning */
667 u_int to_flags = 0; /* XXX gcc warning */
670 struct tcpopt to; /* options in this segment */
671 struct sockaddr_in *next_hop = NULL;
672 int rstreason; /* For badport_bandlim accounting purposes */
674 struct ip6_hdr *ip6 = NULL;
679 const boolean_t isipv6 = FALSE;
689 tcpstat.tcps_rcvtotal++;
691 if (m->m_pkthdr.fw_flags & IPFORWARD_MBUF_TAGGED) {
694 mtag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL);
695 KKASSERT(mtag != NULL);
696 next_hop = m_tag_data(mtag);
700 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE;
704 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */
705 ip6 = mtod(m, struct ip6_hdr *);
706 tlen = (sizeof *ip6) + ntohs(ip6->ip6_plen) - off0;
707 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) {
708 tcpstat.tcps_rcvbadsum++;
711 th = (struct tcphdr *)((caddr_t)ip6 + off0);
714 * Be proactive about unspecified IPv6 address in source.
715 * As we use all-zero to indicate unbounded/unconnected pcb,
716 * unspecified IPv6 address can be used to confuse us.
718 * Note that packets with unspecified IPv6 destination is
719 * already dropped in ip6_input.
721 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
727 * Get IP and TCP header together in first mbuf.
728 * Note: IP leaves IP header in first mbuf.
730 if (off0 > sizeof(struct ip)) {
732 off0 = sizeof(struct ip);
734 /* already checked and pulled up in ip_demux() */
735 KASSERT(m->m_len >= sizeof(struct tcpiphdr),
736 ("TCP header not in one mbuf: m->m_len %d", m->m_len));
737 ip = mtod(m, struct ip *);
738 ipov = (struct ipovly *)ip;
739 th = (struct tcphdr *)((caddr_t)ip + off0);
742 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
743 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
744 th->th_sum = m->m_pkthdr.csum_data;
746 th->th_sum = in_pseudo(ip->ip_src.s_addr,
748 htonl(m->m_pkthdr.csum_data +
751 th->th_sum ^= 0xffff;
754 * Checksum extended TCP header and data.
756 len = sizeof(struct ip) + tlen;
757 bzero(ipov->ih_x1, sizeof ipov->ih_x1);
758 ipov->ih_len = (u_short)tlen;
759 ipov->ih_len = htons(ipov->ih_len);
760 th->th_sum = in_cksum(m, len);
763 tcpstat.tcps_rcvbadsum++;
767 /* Re-initialization for later version check */
768 ip->ip_v = IPVERSION;
773 * Check that TCP offset makes sense,
774 * pull out TCP options and adjust length. XXX
776 off = th->th_off << 2;
777 /* already checked and pulled up in ip_demux() */
778 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen,
779 ("bad TCP data offset %d (tlen %d)", off, tlen));
780 tlen -= off; /* tlen is used instead of ti->ti_len */
781 if (off > sizeof(struct tcphdr)) {
783 IP6_EXTHDR_CHECK(m, off0, off, IPPROTO_DONE);
784 ip6 = mtod(m, struct ip6_hdr *);
785 th = (struct tcphdr *)((caddr_t)ip6 + off0);
787 /* already pulled up in ip_demux() */
788 KASSERT(m->m_len >= sizeof(struct ip) + off,
789 ("TCP header and options not in one mbuf: "
790 "m_len %d, off %d", m->m_len, off));
792 optlen = off - sizeof(struct tcphdr);
793 optp = (u_char *)(th + 1);
795 thflags = th->th_flags;
797 #ifdef TCP_DROP_SYNFIN
799 * If the drop_synfin option is enabled, drop all packets with
800 * both the SYN and FIN bits set. This prevents e.g. nmap from
801 * identifying the TCP/IP stack.
803 * This is a violation of the TCP specification.
805 if (drop_synfin && (thflags & (TH_SYN | TH_FIN)) == (TH_SYN | TH_FIN))
810 * Convert TCP protocol specific fields to host format.
812 th->th_seq = ntohl(th->th_seq);
813 th->th_ack = ntohl(th->th_ack);
814 th->th_win = ntohs(th->th_win);
815 th->th_urp = ntohs(th->th_urp);
818 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options,
819 * until after ip6_savecontrol() is called and before other functions
820 * which don't want those proto headers.
821 * Because ip6_savecontrol() is going to parse the mbuf to
822 * search for data to be passed up to user-land, it wants mbuf
823 * parameters to be unchanged.
824 * XXX: the call of ip6_savecontrol() has been obsoleted based on
825 * latest version of the advanced API (20020110).
827 drop_hdrlen = off0 + off;
830 * Locate pcb for segment.
833 /* IPFIREWALL_FORWARD section */
834 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */
836 * Transparently forwarded. Pretend to be the destination.
837 * already got one like this?
839 cpu = mycpu->gd_cpuid;
840 inp = in_pcblookup_hash(&tcbinfo[cpu],
841 ip->ip_src, th->th_sport,
842 ip->ip_dst, th->th_dport,
843 0, m->m_pkthdr.rcvif);
846 * It's new. Try to find the ambushing socket.
850 * The rest of the ipfw code stores the port in
852 * (The IP address is still in network order.)
854 in_port_t dport = next_hop->sin_port ?
855 htons(next_hop->sin_port) :
858 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport,
859 next_hop->sin_addr.s_addr, dport);
860 inp = in_pcblookup_hash(&tcbinfo[cpu],
861 ip->ip_src, th->th_sport,
862 next_hop->sin_addr, dport,
863 1, m->m_pkthdr.rcvif);
867 inp = in6_pcblookup_hash(&tcbinfo[0],
868 &ip6->ip6_src, th->th_sport,
869 &ip6->ip6_dst, th->th_dport,
870 1, m->m_pkthdr.rcvif);
872 cpu = mycpu->gd_cpuid;
873 inp = in_pcblookup_pkthash(&tcbinfo[cpu],
874 ip->ip_src, th->th_sport,
875 ip->ip_dst, th->th_dport,
876 1, m->m_pkthdr.rcvif,
877 tcp_reuseport_ext ? m : NULL);
882 * If the state is CLOSED (i.e., TCB does not exist) then
883 * all data in the incoming segment is discarded.
884 * If the TCB exists but is in CLOSED state, it is embryonic,
885 * but should either do a listen or a connect soon.
890 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2];
892 char dbuf[sizeof "aaa.bbb.ccc.ddd"];
893 char sbuf[sizeof "aaa.bbb.ccc.ddd"];
897 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst));
900 strcat(sbuf, ip6_sprintf(&ip6->ip6_src));
903 strcpy(dbuf, inet_ntoa(ip->ip_dst));
904 strcpy(sbuf, inet_ntoa(ip->ip_src));
906 switch (log_in_vain) {
908 if (!(thflags & TH_SYN))
912 "Connection attempt to TCP %s:%d "
913 "from %s:%d flags:0x%02x\n",
914 dbuf, ntohs(th->th_dport), sbuf,
915 ntohs(th->th_sport), thflags);
924 if (thflags & TH_SYN)
933 rstreason = BANDLIM_RST_CLOSEDPORT;
939 if (ipsec6_in_reject_so(m, inp->inp_socket)) {
940 ipsec6stat.in_polvio++;
944 if (ipsec4_in_reject_so(m, inp->inp_socket)) {
945 ipsecstat.in_polvio++;
952 if (ipsec6_in_reject(m, inp))
955 if (ipsec4_in_reject(m, inp))
959 /* Check the minimum TTL for socket. */
961 if ((isipv6 ? ip6->ip6_hlim : ip->ip_ttl) < inp->inp_ip_minttl)
967 rstreason = BANDLIM_RST_CLOSEDPORT;
970 if (tp->t_state <= TCPS_CLOSED)
973 so = inp->inp_socket;
976 if (so->so_options & SO_DEBUG) {
977 ostate = tp->t_state;
979 bcopy(ip6, tcp_saveipgen, sizeof(*ip6));
981 bcopy(ip, tcp_saveipgen, sizeof(*ip));
986 bzero(&to, sizeof to);
988 if (so->so_options & SO_ACCEPTCONN) {
989 struct in_conninfo inc;
992 inc.inc_isipv6 = (isipv6 == TRUE);
995 inc.inc6_faddr = ip6->ip6_src;
996 inc.inc6_laddr = ip6->ip6_dst;
997 inc.inc6_route.ro_rt = NULL; /* XXX */
999 inc.inc_faddr = ip->ip_src;
1000 inc.inc_laddr = ip->ip_dst;
1001 inc.inc_route.ro_rt = NULL; /* XXX */
1003 inc.inc_fport = th->th_sport;
1004 inc.inc_lport = th->th_dport;
1007 * If the state is LISTEN then ignore segment if it contains
1008 * a RST. If the segment contains an ACK then it is bad and
1009 * send a RST. If it does not contain a SYN then it is not
1010 * interesting; drop it.
1012 * If the state is SYN_RECEIVED (syncache) and seg contains
1013 * an ACK, but not for our SYN/ACK, send a RST. If the seg
1014 * contains a RST, check the sequence number to see if it
1015 * is a valid reset segment.
1017 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) != TH_SYN) {
1018 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) == TH_ACK) {
1019 if (!syncache_expand(&inc, th, &so, m)) {
1021 * No syncache entry, or ACK was not
1022 * for our SYN/ACK. Send a RST.
1024 tcpstat.tcps_badsyn++;
1025 rstreason = BANDLIM_RST_OPENPORT;
1030 * Could not complete 3-way handshake,
1031 * connection is being closed down, and
1032 * syncache will free mbuf.
1035 return(IPPROTO_DONE);
1038 * We must be in the correct protocol thread
1039 * for this connection.
1041 KKASSERT(so->so_port == &curthread->td_msgport);
1044 * Socket is created in state SYN_RECEIVED.
1045 * Continue processing segment.
1048 tp = intotcpcb(inp);
1050 * This is what would have happened in
1051 * tcp_output() when the SYN,ACK was sent.
1053 tp->snd_up = tp->snd_una;
1054 tp->snd_max = tp->snd_nxt = tp->iss + 1;
1055 tp->last_ack_sent = tp->rcv_nxt;
1059 if (thflags & TH_RST) {
1060 syncache_chkrst(&inc, th);
1063 if (thflags & TH_ACK) {
1064 syncache_badack(&inc);
1065 tcpstat.tcps_badsyn++;
1066 rstreason = BANDLIM_RST_OPENPORT;
1073 * Segment's flags are (SYN) or (SYN | FIN).
1077 * If deprecated address is forbidden,
1078 * we do not accept SYN to deprecated interface
1079 * address to prevent any new inbound connection from
1080 * getting established.
1081 * When we do not accept SYN, we send a TCP RST,
1082 * with deprecated source address (instead of dropping
1083 * it). We compromise it as it is much better for peer
1084 * to send a RST, and RST will be the final packet
1087 * If we do not forbid deprecated addresses, we accept
1088 * the SYN packet. RFC2462 does not suggest dropping
1090 * If we decipher RFC2462 5.5.4, it says like this:
1091 * 1. use of deprecated addr with existing
1092 * communication is okay - "SHOULD continue to be
1094 * 2. use of it with new communication:
1095 * (2a) "SHOULD NOT be used if alternate address
1096 * with sufficient scope is available"
1097 * (2b) nothing mentioned otherwise.
1098 * Here we fall into (2b) case as we have no choice in
1099 * our source address selection - we must obey the peer.
1101 * The wording in RFC2462 is confusing, and there are
1102 * multiple description text for deprecated address
1103 * handling - worse, they are not exactly the same.
1104 * I believe 5.5.4 is the best one, so we follow 5.5.4.
1106 if (isipv6 && !ip6_use_deprecated) {
1107 struct in6_ifaddr *ia6;
1109 if ((ia6 = ip6_getdstifaddr(m)) &&
1110 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
1112 rstreason = BANDLIM_RST_OPENPORT;
1118 * If it is from this socket, drop it, it must be forged.
1119 * Don't bother responding if the destination was a broadcast.
1121 if (th->th_dport == th->th_sport) {
1123 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst,
1127 if (ip->ip_dst.s_addr == ip->ip_src.s_addr)
1132 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN
1134 * Note that it is quite possible to receive unicast
1135 * link-layer packets with a broadcast IP address. Use
1136 * in_broadcast() to find them.
1138 if (m->m_flags & (M_BCAST | M_MCAST))
1141 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
1142 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
1145 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
1146 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
1147 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
1148 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
1152 * SYN appears to be valid; create compressed TCP state
1153 * for syncache, or perform t/tcp connection.
1155 if (so->so_qlen <= so->so_qlimit) {
1156 tcp_dooptions(&to, optp, optlen, TRUE, th->th_ack);
1157 if (!syncache_add(&inc, &to, th, so, m))
1161 * Entry added to syncache, mbuf used to
1162 * send SYN,ACK packet.
1164 return(IPPROTO_DONE);
1171 * Should not happen - syncache should pick up these connections.
1173 * Once we are past handling listen sockets we must be in the
1174 * correct protocol processing thread.
1176 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN state"));
1177 KKASSERT(so->so_port == &curthread->td_msgport);
1179 /* Unscale the window into a 32-bit value. */
1180 if (!(thflags & TH_SYN))
1181 tiwin = th->th_win << tp->snd_scale;
1186 * This is the second part of the MSS DoS prevention code (after
1187 * minmss on the sending side) and it deals with too many too small
1188 * tcp packets in a too short timeframe (1 second).
1190 * XXX Removed. This code was crap. It does not scale to network
1191 * speed, and default values break NFS. Gone.
1196 * Segment received on connection.
1198 * Reset idle time and keep-alive timer. Don't waste time if less
1199 * then a second has elapsed.
1201 if ((int)(ticks - tp->t_rcvtime) > hz)
1202 tcp_timer_keep_activity(tp, thflags);
1206 * XXX this is tradtitional behavior, may need to be cleaned up.
1208 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0, th->th_ack);
1209 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) {
1210 if ((to.to_flags & TOF_SCALE) && (tp->t_flags & TF_REQ_SCALE)) {
1211 tp->t_flags |= TF_RCVD_SCALE;
1212 tp->snd_scale = to.to_requested_s_scale;
1216 * Initial send window; will be updated upon next ACK
1218 tp->snd_wnd = th->th_win;
1220 if (to.to_flags & TOF_TS) {
1221 tp->t_flags |= TF_RCVD_TSTMP;
1222 tp->ts_recent = to.to_tsval;
1223 tp->ts_recent_age = ticks;
1225 if (!(to.to_flags & TOF_MSS))
1227 tcp_mss(tp, to.to_mss);
1229 * Only set the TF_SACK_PERMITTED per-connection flag
1230 * if we got a SACK_PERMITTED option from the other side
1231 * and the global tcp_do_sack variable is true.
1233 if (tcp_do_sack && (to.to_flags & TOF_SACK_PERMITTED))
1234 tp->t_flags |= TF_SACK_PERMITTED;
1238 * Header prediction: check for the two common cases
1239 * of a uni-directional data xfer. If the packet has
1240 * no control flags, is in-sequence, the window didn't
1241 * change and we're not retransmitting, it's a
1242 * candidate. If the length is zero and the ack moved
1243 * forward, we're the sender side of the xfer. Just
1244 * free the data acked & wake any higher level process
1245 * that was blocked waiting for space. If the length
1246 * is non-zero and the ack didn't move, we're the
1247 * receiver side. If we're getting packets in-order
1248 * (the reassembly queue is empty), add the data to
1249 * the socket buffer and note that we need a delayed ack.
1250 * Make sure that the hidden state-flags are also off.
1251 * Since we check for TCPS_ESTABLISHED above, it can only
1254 if (tp->t_state == TCPS_ESTABLISHED &&
1255 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
1256 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) &&
1257 (!(to.to_flags & TOF_TS) ||
1258 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) &&
1259 th->th_seq == tp->rcv_nxt &&
1260 tp->snd_nxt == tp->snd_max) {
1263 * If last ACK falls within this segment's sequence numbers,
1264 * record the timestamp.
1265 * NOTE that the test is modified according to the latest
1266 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1268 if ((to.to_flags & TOF_TS) &&
1269 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
1270 tp->ts_recent_age = ticks;
1271 tp->ts_recent = to.to_tsval;
1275 if (SEQ_GT(th->th_ack, tp->snd_una) &&
1276 SEQ_LEQ(th->th_ack, tp->snd_max) &&
1277 tp->snd_cwnd >= tp->snd_wnd &&
1278 !IN_FASTRECOVERY(tp)) {
1280 * This is a pure ack for outstanding data.
1282 ++tcpstat.tcps_predack;
1284 * "bad retransmit" recovery
1286 * If Eifel detection applies, then
1287 * it is deterministic, so use it
1288 * unconditionally over the old heuristic.
1289 * Otherwise, fall back to the old heuristic.
1291 if (tcp_do_eifel_detect &&
1292 (to.to_flags & TOF_TS) && to.to_tsecr &&
1293 (tp->rxt_flags & TRXT_F_FIRSTACCACK)) {
1294 /* Eifel detection applicable. */
1295 if (to.to_tsecr < tp->t_rexmtTS) {
1296 tcp_revert_congestion_state(tp);
1297 ++tcpstat.tcps_eifeldetected;
1298 if (tp->t_rxtshift != 1 ||
1299 ticks >= tp->t_badrxtwin)
1300 ++tcpstat.tcps_rttcantdetect;
1302 } else if (tp->t_rxtshift == 1 &&
1303 ticks < tp->t_badrxtwin) {
1304 tcp_revert_congestion_state(tp);
1305 ++tcpstat.tcps_rttdetected;
1307 tp->rxt_flags &= ~(TRXT_F_FIRSTACCACK |
1308 TRXT_F_FASTREXMT | TRXT_F_EARLYREXMT);
1310 * Recalculate the retransmit timer / rtt.
1312 * Some machines (certain windows boxes)
1313 * send broken timestamp replies during the
1314 * SYN+ACK phase, ignore timestamps of 0.
1316 if ((to.to_flags & TOF_TS) && to.to_tsecr) {
1318 ticks - to.to_tsecr + 1,
1320 } else if (tp->t_rtttime &&
1321 SEQ_GT(th->th_ack, tp->t_rtseq)) {
1323 ticks - tp->t_rtttime + 1,
1326 tcp_xmit_bandwidth_limit(tp, th->th_ack);
1327 acked = th->th_ack - tp->snd_una;
1328 tcpstat.tcps_rcvackpack++;
1329 tcpstat.tcps_rcvackbyte += acked;
1330 sbdrop(&so->so_snd.sb, acked);
1331 tp->snd_recover = th->th_ack - 1;
1332 tp->snd_una = th->th_ack;
1335 * Update window information.
1337 if (tiwin != tp->snd_wnd &&
1338 acceptable_window_update(tp, th, tiwin)) {
1339 /* keep track of pure window updates */
1340 if (tp->snd_wl2 == th->th_ack &&
1341 tiwin > tp->snd_wnd)
1342 tcpstat.tcps_rcvwinupd++;
1343 tp->snd_wnd = tiwin;
1344 tp->snd_wl1 = th->th_seq;
1345 tp->snd_wl2 = th->th_ack;
1346 if (tp->snd_wnd > tp->max_sndwnd)
1347 tp->max_sndwnd = tp->snd_wnd;
1350 ND6_HINT(tp); /* some progress has been done */
1352 * If all outstanding data are acked, stop
1353 * retransmit timer, otherwise restart timer
1354 * using current (possibly backed-off) value.
1355 * If process is waiting for space,
1356 * wakeup/selwakeup/signal. If data
1357 * are ready to send, let tcp_output
1358 * decide between more output or persist.
1360 if (tp->snd_una == tp->snd_max) {
1361 tcp_callout_stop(tp, tp->tt_rexmt);
1362 } else if (!tcp_callout_active(tp,
1364 tcp_callout_reset(tp, tp->tt_rexmt,
1365 tp->t_rxtcur, tcp_timer_rexmt);
1368 if (so->so_snd.ssb_cc > 0 &&
1369 !tcp_output_pending(tp))
1370 tcp_output_fair(tp);
1371 return(IPPROTO_DONE);
1373 } else if (tiwin == tp->snd_wnd &&
1374 th->th_ack == tp->snd_una &&
1375 TAILQ_EMPTY(&tp->t_segq) &&
1376 tlen <= ssb_space(&so->so_rcv)) {
1377 u_long newsize = 0; /* automatic sockbuf scaling */
1379 * This is a pure, in-sequence data packet
1380 * with nothing on the reassembly queue and
1381 * we have enough buffer space to take it.
1383 ++tcpstat.tcps_preddat;
1384 tp->rcv_nxt += tlen;
1385 tcpstat.tcps_rcvpack++;
1386 tcpstat.tcps_rcvbyte += tlen;
1387 ND6_HINT(tp); /* some progress has been done */
1389 * Automatic sizing of receive socket buffer. Often the send
1390 * buffer size is not optimally adjusted to the actual network
1391 * conditions at hand (delay bandwidth product). Setting the
1392 * buffer size too small limits throughput on links with high
1393 * bandwidth and high delay (eg. trans-continental/oceanic links).
1395 * On the receive side the socket buffer memory is only rarely
1396 * used to any significant extent. This allows us to be much
1397 * more aggressive in scaling the receive socket buffer. For
1398 * the case that the buffer space is actually used to a large
1399 * extent and we run out of kernel memory we can simply drop
1400 * the new segments; TCP on the sender will just retransmit it
1401 * later. Setting the buffer size too big may only consume too
1402 * much kernel memory if the application doesn't read() from
1403 * the socket or packet loss or reordering makes use of the
1406 * The criteria to step up the receive buffer one notch are:
1407 * 1. the number of bytes received during the time it takes
1408 * one timestamp to be reflected back to us (the RTT);
1409 * 2. received bytes per RTT is within seven eighth of the
1410 * current socket buffer size;
1411 * 3. receive buffer size has not hit maximal automatic size;
1413 * This algorithm does one step per RTT at most and only if
1414 * we receive a bulk stream w/o packet losses or reorderings.
1415 * Shrinking the buffer during idle times is not necessary as
1416 * it doesn't consume any memory when idle.
1418 * TODO: Only step up if the application is actually serving
1419 * the buffer to better manage the socket buffer resources.
1421 if (tcp_do_autorcvbuf &&
1423 (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) {
1424 if (to.to_tsecr > tp->rfbuf_ts &&
1425 to.to_tsecr - tp->rfbuf_ts < hz) {
1427 (so->so_rcv.ssb_hiwat / 8 * 7) &&
1428 so->so_rcv.ssb_hiwat <
1429 tcp_autorcvbuf_max) {
1431 ulmin(so->so_rcv.ssb_hiwat +
1433 tcp_autorcvbuf_max);
1435 /* Start over with next RTT. */
1439 tp->rfbuf_cnt += tlen; /* add up */
1442 * Add data to socket buffer.
1444 if (so->so_state & SS_CANTRCVMORE) {
1448 * Set new socket buffer size, give up when
1451 * Adjusting the size can mess up ACK
1452 * sequencing when pure window updates are
1453 * being avoided (which is the default),
1456 lwkt_gettoken(&so->so_rcv.ssb_token);
1458 tp->t_flags |= TF_RXRESIZED;
1459 if (!ssb_reserve(&so->so_rcv, newsize,
1461 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE);
1464 (TCP_MAXWIN << tp->rcv_scale)) {
1465 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE);
1468 m_adj(m, drop_hdrlen); /* delayed header drop */
1469 ssb_appendstream(&so->so_rcv, m);
1470 lwkt_reltoken(&so->so_rcv.ssb_token);
1474 * This code is responsible for most of the ACKs
1475 * the TCP stack sends back after receiving a data
1476 * packet. Note that the DELAY_ACK check fails if
1477 * the delack timer is already running, which results
1478 * in an ack being sent every other packet (which is
1481 * We then further aggregate acks by not actually
1482 * sending one until the protocol thread has completed
1483 * processing the current backlog of packets. This
1484 * does not delay the ack any further, but allows us
1485 * to take advantage of the packet aggregation that
1486 * high speed NICs do (usually blocks of 8-10 packets)
1487 * to send a single ack rather then four or five acks,
1488 * greatly reducing the ack rate, the return channel
1489 * bandwidth, and the protocol overhead on both ends.
1491 * Since this also has the effect of slowing down
1492 * the exponential slow-start ramp-up, systems with
1493 * very large bandwidth-delay products might want
1494 * to turn the feature off.
1496 if (DELAY_ACK(tp)) {
1497 tcp_callout_reset(tp, tp->tt_delack,
1498 tcp_delacktime, tcp_timer_delack);
1499 } else if (tcp_aggregate_acks) {
1500 tp->t_flags |= TF_ACKNOW;
1501 if (!(tp->t_flags & TF_ONOUTPUTQ)) {
1502 tp->t_flags |= TF_ONOUTPUTQ;
1503 tp->tt_cpu = mycpu->gd_cpuid;
1505 &tcpcbackq[tp->tt_cpu],
1509 tp->t_flags |= TF_ACKNOW;
1512 return(IPPROTO_DONE);
1517 * Calculate amount of space in receive window,
1518 * and then do TCP input processing.
1519 * Receive window is amount of space in rcv queue,
1520 * but not less than advertised window.
1522 recvwin = ssb_space(&so->so_rcv);
1525 tp->rcv_wnd = imax(recvwin, (int)(tp->rcv_adv - tp->rcv_nxt));
1527 /* Reset receive buffer auto scaling when not in bulk receive mode. */
1531 switch (tp->t_state) {
1533 * If the state is SYN_RECEIVED:
1534 * if seg contains an ACK, but not for our SYN/ACK, send a RST.
1536 case TCPS_SYN_RECEIVED:
1537 if ((thflags & TH_ACK) &&
1538 (SEQ_LEQ(th->th_ack, tp->snd_una) ||
1539 SEQ_GT(th->th_ack, tp->snd_max))) {
1540 rstreason = BANDLIM_RST_OPENPORT;
1546 * If the state is SYN_SENT:
1547 * if seg contains an ACK, but not for our SYN, drop the input.
1548 * if seg contains a RST, then drop the connection.
1549 * if seg does not contain SYN, then drop it.
1550 * Otherwise this is an acceptable SYN segment
1551 * initialize tp->rcv_nxt and tp->irs
1552 * if seg contains ack then advance tp->snd_una
1553 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state
1554 * arrange for segment to be acked (eventually)
1555 * continue processing rest of data/controls, beginning with URG
1558 if ((thflags & TH_ACK) &&
1559 (SEQ_LEQ(th->th_ack, tp->iss) ||
1560 SEQ_GT(th->th_ack, tp->snd_max))) {
1561 rstreason = BANDLIM_UNLIMITED;
1564 if (thflags & TH_RST) {
1565 if (thflags & TH_ACK)
1566 tp = tcp_drop(tp, ECONNREFUSED);
1569 if (!(thflags & TH_SYN))
1572 tp->irs = th->th_seq;
1574 if (thflags & TH_ACK) {
1575 /* Our SYN was acked. */
1576 tcpstat.tcps_connects++;
1578 /* Do window scaling on this connection? */
1579 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) ==
1580 (TF_RCVD_SCALE | TF_REQ_SCALE))
1581 tp->rcv_scale = tp->request_r_scale;
1582 tp->rcv_adv += tp->rcv_wnd;
1583 tp->snd_una++; /* SYN is acked */
1584 tcp_callout_stop(tp, tp->tt_rexmt);
1586 * If there's data, delay ACK; if there's also a FIN
1587 * ACKNOW will be turned on later.
1589 if (DELAY_ACK(tp) && tlen != 0) {
1590 tcp_callout_reset(tp, tp->tt_delack,
1591 tcp_delacktime, tcp_timer_delack);
1593 tp->t_flags |= TF_ACKNOW;
1596 * Received <SYN,ACK> in SYN_SENT[*] state.
1598 * SYN_SENT --> ESTABLISHED
1599 * SYN_SENT* --> FIN_WAIT_1
1601 tp->t_starttime = ticks;
1602 if (tp->t_flags & TF_NEEDFIN) {
1603 tp->t_state = TCPS_FIN_WAIT_1;
1604 tp->t_flags &= ~TF_NEEDFIN;
1607 tcp_established(tp);
1611 * Received initial SYN in SYN-SENT[*] state =>
1612 * simultaneous open.
1613 * Do 3-way handshake:
1614 * SYN-SENT -> SYN-RECEIVED
1615 * SYN-SENT* -> SYN-RECEIVED*
1617 tp->t_flags |= TF_ACKNOW;
1618 tcp_callout_stop(tp, tp->tt_rexmt);
1619 tp->t_state = TCPS_SYN_RECEIVED;
1623 * Advance th->th_seq to correspond to first data byte.
1624 * If data, trim to stay within window,
1625 * dropping FIN if necessary.
1628 if (tlen > tp->rcv_wnd) {
1629 todrop = tlen - tp->rcv_wnd;
1633 tcpstat.tcps_rcvpackafterwin++;
1634 tcpstat.tcps_rcvbyteafterwin += todrop;
1636 tp->snd_wl1 = th->th_seq - 1;
1637 tp->rcv_up = th->th_seq;
1639 * Client side of transaction: already sent SYN and data.
1640 * If the remote host used T/TCP to validate the SYN,
1641 * our data will be ACK'd; if so, enter normal data segment
1642 * processing in the middle of step 5, ack processing.
1643 * Otherwise, goto step 6.
1645 if (thflags & TH_ACK)
1651 * If the state is LAST_ACK or CLOSING or TIME_WAIT:
1652 * do normal processing (we no longer bother with T/TCP).
1656 case TCPS_TIME_WAIT:
1657 break; /* continue normal processing */
1661 * States other than LISTEN or SYN_SENT.
1662 * First check the RST flag and sequence number since reset segments
1663 * are exempt from the timestamp and connection count tests. This
1664 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix
1665 * below which allowed reset segments in half the sequence space
1666 * to fall though and be processed (which gives forged reset
1667 * segments with a random sequence number a 50 percent chance of
1668 * killing a connection).
1669 * Then check timestamp, if present.
1670 * Then check the connection count, if present.
1671 * Then check that at least some bytes of segment are within
1672 * receive window. If segment begins before rcv_nxt,
1673 * drop leading data (and SYN); if nothing left, just ack.
1676 * If the RST bit is set, check the sequence number to see
1677 * if this is a valid reset segment.
1679 * In all states except SYN-SENT, all reset (RST) segments
1680 * are validated by checking their SEQ-fields. A reset is
1681 * valid if its sequence number is in the window.
1682 * Note: this does not take into account delayed ACKs, so
1683 * we should test against last_ack_sent instead of rcv_nxt.
1684 * The sequence number in the reset segment is normally an
1685 * echo of our outgoing acknowledgement numbers, but some hosts
1686 * send a reset with the sequence number at the rightmost edge
1687 * of our receive window, and we have to handle this case.
1688 * If we have multiple segments in flight, the intial reset
1689 * segment sequence numbers will be to the left of last_ack_sent,
1690 * but they will eventually catch up.
1691 * In any case, it never made sense to trim reset segments to
1692 * fit the receive window since RFC 1122 says:
1693 * 4.2.2.12 RST Segment: RFC-793 Section 3.4
1695 * A TCP SHOULD allow a received RST segment to include data.
1698 * It has been suggested that a RST segment could contain
1699 * ASCII text that encoded and explained the cause of the
1700 * RST. No standard has yet been established for such
1703 * If the reset segment passes the sequence number test examine
1705 * SYN_RECEIVED STATE:
1706 * If passive open, return to LISTEN state.
1707 * If active open, inform user that connection was refused.
1708 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES:
1709 * Inform user that connection was reset, and close tcb.
1710 * CLOSING, LAST_ACK STATES:
1713 * Drop the segment - see Stevens, vol. 2, p. 964 and
1716 if (thflags & TH_RST) {
1717 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
1718 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) {
1719 switch (tp->t_state) {
1721 case TCPS_SYN_RECEIVED:
1722 so->so_error = ECONNREFUSED;
1725 case TCPS_ESTABLISHED:
1726 case TCPS_FIN_WAIT_1:
1727 case TCPS_FIN_WAIT_2:
1728 case TCPS_CLOSE_WAIT:
1729 so->so_error = ECONNRESET;
1731 tp->t_state = TCPS_CLOSED;
1732 tcpstat.tcps_drops++;
1741 case TCPS_TIME_WAIT:
1749 * RFC 1323 PAWS: If we have a timestamp reply on this segment
1750 * and it's less than ts_recent, drop it.
1752 if ((to.to_flags & TOF_TS) && tp->ts_recent != 0 &&
1753 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
1754 /* Check to see if ts_recent is over 24 days old. */
1755 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) {
1757 * Invalidate ts_recent. If this segment updates
1758 * ts_recent, the age will be reset later and ts_recent
1759 * will get a valid value. If it does not, setting
1760 * ts_recent to zero will at least satisfy the
1761 * requirement that zero be placed in the timestamp
1762 * echo reply when ts_recent isn't valid. The
1763 * age isn't reset until we get a valid ts_recent
1764 * because we don't want out-of-order segments to be
1765 * dropped when ts_recent is old.
1768 } else if (tcp_paws_tolerance && tlen != 0 &&
1769 tp->t_state == TCPS_ESTABLISHED &&
1770 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK&&
1771 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) &&
1772 th->th_ack == tp->snd_una &&
1773 tiwin == tp->snd_wnd &&
1774 TSTMP_GEQ(to.to_tsval + tcp_paws_tolerance, tp->ts_recent)&&
1775 (th->th_seq == tp->rcv_nxt ||
1776 (SEQ_GT(th->th_seq, tp->rcv_nxt) &&
1777 tcp_paws_canreasslast(tp, th, tlen)))) {
1779 * This tends to prevent valid new segments from being
1780 * dropped by the reordered segments sent by the fast
1781 * retransmission algorithm on the sending side, i.e.
1782 * the fast retransmitted segment w/ larger timestamp
1783 * arrives earlier than the previously sent new segments
1784 * w/ smaller timestamp.
1786 * If following conditions are met, the segment is
1788 * - The segment contains data
1789 * - The connection is established
1790 * - The header does not contain important flags
1791 * - SYN or FIN is not needed
1792 * - It does not acknowledge new data
1793 * - Receive window is not changed
1794 * - The timestamp is within "acceptable" range
1795 * - The new segment is what we are expecting or
1796 * the new segment could be merged w/ the last
1797 * pending segment on the reassemble queue
1799 tcpstat.tcps_pawsaccept++;
1800 tcpstat.tcps_pawsdrop++;
1802 tcpstat.tcps_rcvduppack++;
1803 tcpstat.tcps_rcvdupbyte += tlen;
1804 tcpstat.tcps_pawsdrop++;
1812 * In the SYN-RECEIVED state, validate that the packet belongs to
1813 * this connection before trimming the data to fit the receive
1814 * window. Check the sequence number versus IRS since we know
1815 * the sequence numbers haven't wrapped. This is a partial fix
1816 * for the "LAND" DoS attack.
1818 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) {
1819 rstreason = BANDLIM_RST_OPENPORT;
1823 todrop = tp->rcv_nxt - th->th_seq;
1825 if (TCP_DO_SACK(tp)) {
1826 /* Report duplicate segment at head of packet. */
1827 tp->reportblk.rblk_start = th->th_seq;
1828 tp->reportblk.rblk_end = TCP_SACK_BLKEND(
1829 th->th_seq + tlen, thflags);
1830 if (SEQ_GT(tp->reportblk.rblk_end, tp->rcv_nxt))
1831 tp->reportblk.rblk_end = tp->rcv_nxt;
1832 tp->sack_flags |= (TSACK_F_DUPSEG | TSACK_F_SACKLEFT);
1833 tp->t_flags |= TF_ACKNOW;
1835 if (thflags & TH_SYN) {
1845 * Following if statement from Stevens, vol. 2, p. 960.
1847 if (todrop > tlen ||
1848 (todrop == tlen && !(thflags & TH_FIN))) {
1850 * Any valid FIN must be to the left of the window.
1851 * At this point the FIN must be a duplicate or out
1852 * of sequence; drop it.
1857 * Send an ACK to resynchronize and drop any data.
1858 * But keep on processing for RST or ACK.
1860 tp->t_flags |= TF_ACKNOW;
1862 tcpstat.tcps_rcvduppack++;
1863 tcpstat.tcps_rcvdupbyte += todrop;
1865 tcpstat.tcps_rcvpartduppack++;
1866 tcpstat.tcps_rcvpartdupbyte += todrop;
1868 drop_hdrlen += todrop; /* drop from the top afterwards */
1869 th->th_seq += todrop;
1871 if (th->th_urp > todrop)
1872 th->th_urp -= todrop;
1880 * If new data are received on a connection after the
1881 * user processes are gone, then RST the other end.
1883 if ((so->so_state & SS_NOFDREF) &&
1884 tp->t_state > TCPS_CLOSE_WAIT && tlen) {
1886 tcpstat.tcps_rcvafterclose++;
1887 rstreason = BANDLIM_UNLIMITED;
1892 * If segment ends after window, drop trailing data
1893 * (and PUSH and FIN); if nothing left, just ACK.
1895 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd);
1897 tcpstat.tcps_rcvpackafterwin++;
1898 if (todrop >= tlen) {
1899 tcpstat.tcps_rcvbyteafterwin += tlen;
1901 * If a new connection request is received
1902 * while in TIME_WAIT, drop the old connection
1903 * and start over if the sequence numbers
1904 * are above the previous ones.
1906 if (thflags & TH_SYN &&
1907 tp->t_state == TCPS_TIME_WAIT &&
1908 SEQ_GT(th->th_seq, tp->rcv_nxt)) {
1913 * If window is closed can only take segments at
1914 * window edge, and have to drop data and PUSH from
1915 * incoming segments. Continue processing, but
1916 * remember to ack. Otherwise, drop segment
1919 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
1920 tp->t_flags |= TF_ACKNOW;
1921 tcpstat.tcps_rcvwinprobe++;
1925 tcpstat.tcps_rcvbyteafterwin += todrop;
1928 thflags &= ~(TH_PUSH | TH_FIN);
1932 * If last ACK falls within this segment's sequence numbers,
1933 * record its timestamp.
1935 * 1) That the test incorporates suggestions from the latest
1936 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1937 * 2) That updating only on newer timestamps interferes with
1938 * our earlier PAWS tests, so this check should be solely
1939 * predicated on the sequence space of this segment.
1940 * 3) That we modify the segment boundary check to be
1941 * Last.ACK.Sent <= SEG.SEQ + SEG.LEN
1942 * instead of RFC1323's
1943 * Last.ACK.Sent < SEG.SEQ + SEG.LEN,
1944 * This modified check allows us to overcome RFC1323's
1945 * limitations as described in Stevens TCP/IP Illustrated
1946 * Vol. 2 p.869. In such cases, we can still calculate the
1947 * RTT correctly when RCV.NXT == Last.ACK.Sent.
1949 if ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent) &&
1950 SEQ_LEQ(tp->last_ack_sent, (th->th_seq + tlen
1951 + ((thflags & TH_SYN) != 0)
1952 + ((thflags & TH_FIN) != 0)))) {
1953 tp->ts_recent_age = ticks;
1954 tp->ts_recent = to.to_tsval;
1958 * If a SYN is in the window, then this is an
1959 * error and we send an RST and drop the connection.
1961 if (thflags & TH_SYN) {
1962 tp = tcp_drop(tp, ECONNRESET);
1963 rstreason = BANDLIM_UNLIMITED;
1968 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN
1969 * flag is on (half-synchronized state), then queue data for
1970 * later processing; else drop segment and return.
1972 if (!(thflags & TH_ACK)) {
1973 if (tp->t_state == TCPS_SYN_RECEIVED ||
1974 (tp->t_flags & TF_NEEDSYN))
1983 switch (tp->t_state) {
1985 * In SYN_RECEIVED state, the ACK acknowledges our SYN, so enter
1986 * ESTABLISHED state and continue processing.
1987 * The ACK was checked above.
1989 case TCPS_SYN_RECEIVED:
1991 tcpstat.tcps_connects++;
1993 /* Do window scaling? */
1994 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) ==
1995 (TF_RCVD_SCALE | TF_REQ_SCALE))
1996 tp->rcv_scale = tp->request_r_scale;
1999 * SYN-RECEIVED -> ESTABLISHED
2000 * SYN-RECEIVED* -> FIN-WAIT-1
2002 tp->t_starttime = ticks;
2003 if (tp->t_flags & TF_NEEDFIN) {
2004 tp->t_state = TCPS_FIN_WAIT_1;
2005 tp->t_flags &= ~TF_NEEDFIN;
2007 tcp_established(tp);
2010 * If segment contains data or ACK, will call tcp_reass()
2011 * later; if not, do so now to pass queued data to user.
2013 if (tlen == 0 && !(thflags & TH_FIN))
2014 tcp_reass(tp, NULL, NULL, NULL);
2018 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
2019 * ACKs. If the ack is in the range
2020 * tp->snd_una < th->th_ack <= tp->snd_max
2021 * then advance tp->snd_una to th->th_ack and drop
2022 * data from the retransmission queue. If this ACK reflects
2023 * more up to date window information we update our window information.
2025 case TCPS_ESTABLISHED:
2026 case TCPS_FIN_WAIT_1:
2027 case TCPS_FIN_WAIT_2:
2028 case TCPS_CLOSE_WAIT:
2031 case TCPS_TIME_WAIT:
2033 if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
2034 boolean_t maynotdup = FALSE;
2036 if (TCP_DO_SACK(tp))
2037 tcp_sack_update_scoreboard(tp, &to);
2039 if (tlen != 0 || tiwin != tp->snd_wnd ||
2040 ((thflags & TH_FIN) && !(tp->t_flags & TF_SAWFIN)))
2043 if (!tcp_callout_active(tp, tp->tt_rexmt) ||
2044 th->th_ack != tp->snd_una) {
2046 tcpstat.tcps_rcvdupack++;
2051 #define DELAY_DUPACK \
2053 delayed_dupack = TRUE; \
2054 th_dupack = th->th_ack; \
2055 to_flags = to.to_flags; \
2058 if (!tcp_do_rfc6675 ||
2061 (TOF_SACK | TOF_SACK_REDUNDANT))
2069 if ((thflags & TH_FIN) && !(tp->t_flags & TF_QUEDFIN)) {
2071 * This could happen, if the reassemable
2072 * queue overflew or was drained. Don't
2073 * drop this FIN here; defer the duplicated
2074 * ACK processing until this FIN gets queued.
2081 if (tcp_recv_dupack(tp, th->th_ack, to.to_flags))
2087 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una"));
2089 if (SEQ_GT(th->th_ack, tp->snd_max)) {
2091 * Detected optimistic ACK attack.
2092 * Force slow-start to de-synchronize attack.
2094 tp->snd_cwnd = tp->t_maxseg;
2097 tcpstat.tcps_rcvacktoomuch++;
2101 * If we reach this point, ACK is not a duplicate,
2102 * i.e., it ACKs something we sent.
2104 if (tp->t_flags & TF_NEEDSYN) {
2106 * T/TCP: Connection was half-synchronized, and our
2107 * SYN has been ACK'd (so connection is now fully
2108 * synchronized). Go to non-starred state,
2109 * increment snd_una for ACK of SYN, and check if
2110 * we can do window scaling.
2112 tp->t_flags &= ~TF_NEEDSYN;
2114 /* Do window scaling? */
2115 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) ==
2116 (TF_RCVD_SCALE | TF_REQ_SCALE))
2117 tp->rcv_scale = tp->request_r_scale;
2121 acked = th->th_ack - tp->snd_una;
2122 tcpstat.tcps_rcvackpack++;
2123 tcpstat.tcps_rcvackbyte += acked;
2125 if (tcp_do_eifel_detect && acked > 0 &&
2126 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) &&
2127 (tp->rxt_flags & TRXT_F_FIRSTACCACK)) {
2128 /* Eifel detection applicable. */
2129 if (to.to_tsecr < tp->t_rexmtTS) {
2130 ++tcpstat.tcps_eifeldetected;
2131 tcp_revert_congestion_state(tp);
2132 if (tp->t_rxtshift != 1 ||
2133 ticks >= tp->t_badrxtwin)
2134 ++tcpstat.tcps_rttcantdetect;
2136 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) {
2138 * If we just performed our first retransmit,
2139 * and the ACK arrives within our recovery window,
2140 * then it was a mistake to do the retransmit
2141 * in the first place. Recover our original cwnd
2142 * and ssthresh, and proceed to transmit where we
2145 tcp_revert_congestion_state(tp);
2146 ++tcpstat.tcps_rttdetected;
2150 * If we have a timestamp reply, update smoothed
2151 * round trip time. If no timestamp is present but
2152 * transmit timer is running and timed sequence
2153 * number was acked, update smoothed round trip time.
2154 * Since we now have an rtt measurement, cancel the
2155 * timer backoff (cf., Phil Karn's retransmit alg.).
2156 * Recompute the initial retransmit timer.
2158 * Some machines (certain windows boxes) send broken
2159 * timestamp replies during the SYN+ACK phase, ignore
2162 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0))
2163 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1,
2165 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq))
2166 tcp_xmit_timer(tp, ticks - tp->t_rtttime + 1,
2168 tcp_xmit_bandwidth_limit(tp, th->th_ack);
2171 * If no data (only SYN) was ACK'd,
2172 * skip rest of ACK processing.
2177 /* Stop looking for an acceptable ACK since one was received. */
2178 tp->rxt_flags &= ~(TRXT_F_FIRSTACCACK |
2179 TRXT_F_FASTREXMT | TRXT_F_EARLYREXMT);
2181 if (acked > so->so_snd.ssb_cc) {
2182 tp->snd_wnd -= so->so_snd.ssb_cc;
2183 sbdrop(&so->so_snd.sb, (int)so->so_snd.ssb_cc);
2184 ourfinisacked = TRUE;
2186 sbdrop(&so->so_snd.sb, acked);
2187 tp->snd_wnd -= acked;
2188 ourfinisacked = FALSE;
2193 * Update window information.
2195 if (acceptable_window_update(tp, th, tiwin)) {
2196 /* keep track of pure window updates */
2197 if (tlen == 0 && tp->snd_wl2 == th->th_ack &&
2198 tiwin > tp->snd_wnd)
2199 tcpstat.tcps_rcvwinupd++;
2200 tp->snd_wnd = tiwin;
2201 tp->snd_wl1 = th->th_seq;
2202 tp->snd_wl2 = th->th_ack;
2203 if (tp->snd_wnd > tp->max_sndwnd)
2204 tp->max_sndwnd = tp->snd_wnd;
2208 tp->snd_una = th->th_ack;
2209 if (TCP_DO_SACK(tp))
2210 tcp_sack_update_scoreboard(tp, &to);
2211 if (IN_FASTRECOVERY(tp)) {
2212 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) {
2213 EXIT_FASTRECOVERY(tp);
2216 * If the congestion window was inflated
2217 * to account for the other side's
2218 * cached packets, retract it.
2220 if (!TCP_DO_SACK(tp))
2221 tp->snd_cwnd = tp->snd_ssthresh;
2224 * Window inflation should have left us
2225 * with approximately snd_ssthresh outstanding
2226 * data. But, in case we would be inclined
2227 * to send a burst, better do it using
2230 if (SEQ_GT(th->th_ack + tp->snd_cwnd,
2231 tp->snd_max + 2 * tp->t_maxseg))
2233 (tp->snd_max - tp->snd_una) +
2238 if (TCP_DO_SACK(tp)) {
2239 tp->snd_max_rexmt = tp->snd_max;
2241 tp->snd_una == tp->rexmt_high);
2243 tcp_newreno_partial_ack(tp, th, acked);
2249 * Open the congestion window. When in slow-start,
2250 * open exponentially: maxseg per packet. Otherwise,
2251 * open linearly: maxseg per window.
2253 if (tp->snd_cwnd <= tp->snd_ssthresh) {
2255 (SEQ_LT(tp->snd_nxt, tp->snd_max) ?
2256 tp->t_maxseg : 2 * tp->t_maxseg);
2259 tp->snd_cwnd += tcp_do_abc ?
2260 min(acked, abc_sslimit) : tp->t_maxseg;
2262 /* linear increase */
2263 tp->snd_wacked += tcp_do_abc ? acked :
2265 if (tp->snd_wacked >= tp->snd_cwnd) {
2266 tp->snd_wacked -= tp->snd_cwnd;
2267 tp->snd_cwnd += tp->t_maxseg;
2270 tp->snd_cwnd = min(tp->snd_cwnd,
2271 TCP_MAXWIN << tp->snd_scale);
2272 tp->snd_recover = th->th_ack - 1;
2274 if (SEQ_LT(tp->snd_nxt, tp->snd_una))
2275 tp->snd_nxt = tp->snd_una;
2278 * If all outstanding data is acked, stop retransmit
2279 * timer and remember to restart (more output or persist).
2280 * If there is more data to be acked, restart retransmit
2281 * timer, using current (possibly backed-off) value.
2283 if (th->th_ack == tp->snd_max) {
2284 tcp_callout_stop(tp, tp->tt_rexmt);
2286 } else if (!tcp_callout_active(tp, tp->tt_persist)) {
2287 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur,
2291 switch (tp->t_state) {
2293 * In FIN_WAIT_1 STATE in addition to the processing
2294 * for the ESTABLISHED state if our FIN is now acknowledged
2295 * then enter FIN_WAIT_2.
2297 case TCPS_FIN_WAIT_1:
2298 if (ourfinisacked) {
2300 * If we can't receive any more
2301 * data, then closing user can proceed.
2302 * Starting the timer is contrary to the
2303 * specification, but if we don't get a FIN
2304 * we'll hang forever.
2306 if (so->so_state & SS_CANTRCVMORE) {
2307 soisdisconnected(so);
2308 tcp_callout_reset(tp, tp->tt_2msl,
2309 tp->t_maxidle, tcp_timer_2msl);
2311 tp->t_state = TCPS_FIN_WAIT_2;
2316 * In CLOSING STATE in addition to the processing for
2317 * the ESTABLISHED state if the ACK acknowledges our FIN
2318 * then enter the TIME-WAIT state, otherwise ignore
2322 if (ourfinisacked) {
2323 tp->t_state = TCPS_TIME_WAIT;
2324 tcp_canceltimers(tp);
2325 tcp_callout_reset(tp, tp->tt_2msl,
2326 2 * tcp_rmx_msl(tp),
2328 soisdisconnected(so);
2333 * In LAST_ACK, we may still be waiting for data to drain
2334 * and/or to be acked, as well as for the ack of our FIN.
2335 * If our FIN is now acknowledged, delete the TCB,
2336 * enter the closed state and return.
2339 if (ourfinisacked) {
2346 * In TIME_WAIT state the only thing that should arrive
2347 * is a retransmission of the remote FIN. Acknowledge
2348 * it and restart the finack timer.
2350 case TCPS_TIME_WAIT:
2351 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp),
2359 * Update window information.
2360 * Don't look at window if no ACK: TAC's send garbage on first SYN.
2362 if ((thflags & TH_ACK) &&
2363 acceptable_window_update(tp, th, tiwin)) {
2364 /* keep track of pure window updates */
2365 if (tlen == 0 && tp->snd_wl2 == th->th_ack &&
2366 tiwin > tp->snd_wnd)
2367 tcpstat.tcps_rcvwinupd++;
2368 tp->snd_wnd = tiwin;
2369 tp->snd_wl1 = th->th_seq;
2370 tp->snd_wl2 = th->th_ack;
2371 if (tp->snd_wnd > tp->max_sndwnd)
2372 tp->max_sndwnd = tp->snd_wnd;
2377 * Process segments with URG.
2379 if ((thflags & TH_URG) && th->th_urp &&
2380 !TCPS_HAVERCVDFIN(tp->t_state)) {
2382 * This is a kludge, but if we receive and accept
2383 * random urgent pointers, we'll crash in
2384 * soreceive. It's hard to imagine someone
2385 * actually wanting to send this much urgent data.
2387 if (th->th_urp + so->so_rcv.ssb_cc > sb_max) {
2388 th->th_urp = 0; /* XXX */
2389 thflags &= ~TH_URG; /* XXX */
2390 goto dodata; /* XXX */
2393 * If this segment advances the known urgent pointer,
2394 * then mark the data stream. This should not happen
2395 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
2396 * a FIN has been received from the remote side.
2397 * In these states we ignore the URG.
2399 * According to RFC961 (Assigned Protocols),
2400 * the urgent pointer points to the last octet
2401 * of urgent data. We continue, however,
2402 * to consider it to indicate the first octet
2403 * of data past the urgent section as the original
2404 * spec states (in one of two places).
2406 if (SEQ_GT(th->th_seq + th->th_urp, tp->rcv_up)) {
2407 tp->rcv_up = th->th_seq + th->th_urp;
2408 so->so_oobmark = so->so_rcv.ssb_cc +
2409 (tp->rcv_up - tp->rcv_nxt) - 1;
2410 if (so->so_oobmark == 0)
2411 sosetstate(so, SS_RCVATMARK);
2413 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
2416 * Remove out of band data so doesn't get presented to user.
2417 * This can happen independent of advancing the URG pointer,
2418 * but if two URG's are pending at once, some out-of-band
2419 * data may creep in... ick.
2421 if (th->th_urp <= (u_long)tlen &&
2422 !(so->so_options & SO_OOBINLINE)) {
2423 /* hdr drop is delayed */
2424 tcp_pulloutofband(so, th, m, drop_hdrlen);
2428 * If no out of band data is expected,
2429 * pull receive urgent pointer along
2430 * with the receive window.
2432 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
2433 tp->rcv_up = tp->rcv_nxt;
2438 * Process the segment text, merging it into the TCP sequencing queue,
2439 * and arranging for acknowledgment of receipt if necessary.
2440 * This process logically involves adjusting tp->rcv_wnd as data
2441 * is presented to the user (this happens in tcp_usrreq.c,
2442 * case PRU_RCVD). If a FIN has already been received on this
2443 * connection then we just ignore the text.
2445 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) {
2446 if (thflags & TH_FIN)
2447 tp->t_flags |= TF_SAWFIN;
2448 m_adj(m, drop_hdrlen); /* delayed header drop */
2450 * Insert segment which includes th into TCP reassembly queue
2451 * with control block tp. Set thflags to whether reassembly now
2452 * includes a segment with FIN. This handles the common case
2453 * inline (segment is the next to be received on an established
2454 * connection, and the queue is empty), avoiding linkage into
2455 * and removal from the queue and repetition of various
2457 * Set DELACK for segments received in order, but ack
2458 * immediately when segments are out of order (so
2459 * fast retransmit can work).
2461 if (th->th_seq == tp->rcv_nxt &&
2462 TAILQ_EMPTY(&tp->t_segq) &&
2463 TCPS_HAVEESTABLISHED(tp->t_state)) {
2464 if (thflags & TH_FIN)
2465 tp->t_flags |= TF_QUEDFIN;
2466 if (DELAY_ACK(tp)) {
2467 tcp_callout_reset(tp, tp->tt_delack,
2468 tcp_delacktime, tcp_timer_delack);
2470 tp->t_flags |= TF_ACKNOW;
2472 tp->rcv_nxt += tlen;
2473 thflags = th->th_flags & TH_FIN;
2474 tcpstat.tcps_rcvpack++;
2475 tcpstat.tcps_rcvbyte += tlen;
2477 if (so->so_state & SS_CANTRCVMORE) {
2480 lwkt_gettoken(&so->so_rcv.ssb_token);
2481 ssb_appendstream(&so->so_rcv, m);
2482 lwkt_reltoken(&so->so_rcv.ssb_token);
2486 if (!(tp->sack_flags & TSACK_F_DUPSEG)) {
2487 /* Initialize SACK report block. */
2488 tp->reportblk.rblk_start = th->th_seq;
2489 tp->reportblk.rblk_end = TCP_SACK_BLKEND(
2490 th->th_seq + tlen, thflags);
2492 thflags = tcp_reass(tp, th, &tlen, m);
2493 tp->t_flags |= TF_ACKNOW;
2497 * Note the amount of data that peer has sent into
2498 * our window, in order to estimate the sender's
2501 len = so->so_rcv.ssb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
2508 * If FIN is received ACK the FIN and let the user know
2509 * that the connection is closing.
2511 if (thflags & TH_FIN) {
2512 if (!TCPS_HAVERCVDFIN(tp->t_state)) {
2515 * If connection is half-synchronized
2516 * (ie NEEDSYN flag on) then delay ACK,
2517 * so it may be piggybacked when SYN is sent.
2518 * Otherwise, since we received a FIN then no
2519 * more input can be expected, send ACK now.
2521 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) {
2522 tcp_callout_reset(tp, tp->tt_delack,
2523 tcp_delacktime, tcp_timer_delack);
2525 tp->t_flags |= TF_ACKNOW;
2530 switch (tp->t_state) {
2532 * In SYN_RECEIVED and ESTABLISHED STATES
2533 * enter the CLOSE_WAIT state.
2535 case TCPS_SYN_RECEIVED:
2536 tp->t_starttime = ticks;
2538 case TCPS_ESTABLISHED:
2539 tp->t_state = TCPS_CLOSE_WAIT;
2543 * If still in FIN_WAIT_1 STATE FIN has not been acked so
2544 * enter the CLOSING state.
2546 case TCPS_FIN_WAIT_1:
2547 tp->t_state = TCPS_CLOSING;
2551 * In FIN_WAIT_2 state enter the TIME_WAIT state,
2552 * starting the time-wait timer, turning off the other
2555 case TCPS_FIN_WAIT_2:
2556 tp->t_state = TCPS_TIME_WAIT;
2557 tcp_canceltimers(tp);
2558 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp),
2560 soisdisconnected(so);
2564 * In TIME_WAIT state restart the 2 MSL time_wait timer.
2566 case TCPS_TIME_WAIT:
2567 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp),
2574 if (so->so_options & SO_DEBUG)
2575 tcp_trace(TA_INPUT, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
2579 * Delayed duplicated ACK processing
2581 if (delayed_dupack && tcp_recv_dupack(tp, th_dupack, to_flags))
2585 * Return any desired output.
2587 if ((tp->t_flags & TF_ACKNOW) ||
2588 (needoutput && tcp_sack_report_needed(tp))) {
2589 tcp_output_cancel(tp);
2590 tcp_output_fair(tp);
2591 } else if (needoutput && !tcp_output_pending(tp)) {
2592 tcp_output_fair(tp);
2594 tcp_sack_report_cleanup(tp);
2595 return(IPPROTO_DONE);
2599 * Generate an ACK dropping incoming segment if it occupies
2600 * sequence space, where the ACK reflects our state.
2602 * We can now skip the test for the RST flag since all
2603 * paths to this code happen after packets containing
2604 * RST have been dropped.
2606 * In the SYN-RECEIVED state, don't send an ACK unless the
2607 * segment we received passes the SYN-RECEIVED ACK test.
2608 * If it fails send a RST. This breaks the loop in the
2609 * "LAND" DoS attack, and also prevents an ACK storm
2610 * between two listening ports that have been sent forged
2611 * SYN segments, each with the source address of the other.
2613 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
2614 (SEQ_GT(tp->snd_una, th->th_ack) ||
2615 SEQ_GT(th->th_ack, tp->snd_max)) ) {
2616 rstreason = BANDLIM_RST_OPENPORT;
2620 if (so->so_options & SO_DEBUG)
2621 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
2624 tp->t_flags |= TF_ACKNOW;
2626 tcp_sack_report_cleanup(tp);
2627 return(IPPROTO_DONE);
2631 * Generate a RST, dropping incoming segment.
2632 * Make ACK acceptable to originator of segment.
2633 * Don't bother to respond if destination was broadcast/multicast.
2635 if ((thflags & TH_RST) || m->m_flags & (M_BCAST | M_MCAST))
2638 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
2639 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
2642 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
2643 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
2644 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
2645 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
2648 /* IPv6 anycast check is done at tcp6_input() */
2651 * Perform bandwidth limiting.
2654 if (badport_bandlim(rstreason) < 0)
2659 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
2660 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
2662 if (thflags & TH_ACK)
2663 /* mtod() below is safe as long as hdr dropping is delayed */
2664 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack,
2667 if (thflags & TH_SYN)
2669 /* mtod() below is safe as long as hdr dropping is delayed */
2670 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen,
2671 (tcp_seq)0, TH_RST | TH_ACK);
2674 tcp_sack_report_cleanup(tp);
2675 return(IPPROTO_DONE);
2679 * Drop space held by incoming segment and return.
2682 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
2683 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
2687 tcp_sack_report_cleanup(tp);
2688 return(IPPROTO_DONE);
2692 * Parse TCP options and place in tcpopt.
2695 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn,
2701 for (; cnt > 0; cnt -= optlen, cp += optlen) {
2703 if (opt == TCPOPT_EOL)
2705 if (opt == TCPOPT_NOP)
2711 if (optlen < 2 || optlen > cnt)
2716 if (optlen != TCPOLEN_MAXSEG)
2720 to->to_flags |= TOF_MSS;
2721 bcopy(cp + 2, &to->to_mss, sizeof to->to_mss);
2722 to->to_mss = ntohs(to->to_mss);
2725 if (optlen != TCPOLEN_WINDOW)
2729 to->to_flags |= TOF_SCALE;
2730 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT);
2732 case TCPOPT_TIMESTAMP:
2733 if (optlen != TCPOLEN_TIMESTAMP)
2735 to->to_flags |= TOF_TS;
2736 bcopy(cp + 2, &to->to_tsval, sizeof to->to_tsval);
2737 to->to_tsval = ntohl(to->to_tsval);
2738 bcopy(cp + 6, &to->to_tsecr, sizeof to->to_tsecr);
2739 to->to_tsecr = ntohl(to->to_tsecr);
2741 * If echoed timestamp is later than the current time,
2742 * fall back to non RFC1323 RTT calculation.
2744 if (to->to_tsecr != 0 && TSTMP_GT(to->to_tsecr, ticks))
2747 case TCPOPT_SACK_PERMITTED:
2748 if (optlen != TCPOLEN_SACK_PERMITTED)
2752 to->to_flags |= TOF_SACK_PERMITTED;
2755 if ((optlen - 2) & 0x07) /* not multiple of 8 */
2757 to->to_nsackblocks = (optlen - 2) / 8;
2758 to->to_sackblocks = (struct raw_sackblock *) (cp + 2);
2759 to->to_flags |= TOF_SACK;
2760 for (i = 0; i < to->to_nsackblocks; i++) {
2761 struct raw_sackblock *r = &to->to_sackblocks[i];
2763 r->rblk_start = ntohl(r->rblk_start);
2764 r->rblk_end = ntohl(r->rblk_end);
2766 if (SEQ_LEQ(r->rblk_end, r->rblk_start)) {
2768 * Invalid SACK block; discard all
2771 tcpstat.tcps_rcvbadsackopt++;
2772 to->to_nsackblocks = 0;
2773 to->to_sackblocks = NULL;
2774 to->to_flags &= ~TOF_SACK;
2778 if ((to->to_flags & TOF_SACK) &&
2779 tcp_sack_ndsack_blocks(to->to_sackblocks,
2780 to->to_nsackblocks, ack))
2781 to->to_flags |= TOF_DSACK;
2783 #ifdef TCP_SIGNATURE
2785 * XXX In order to reply to a host which has set the
2786 * TCP_SIGNATURE option in its initial SYN, we have to
2787 * record the fact that the option was observed here
2788 * for the syncache code to perform the correct response.
2790 case TCPOPT_SIGNATURE:
2791 if (optlen != TCPOLEN_SIGNATURE)
2793 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN);
2795 #endif /* TCP_SIGNATURE */
2803 * Pull out of band byte out of a segment so
2804 * it doesn't appear in the user's data queue.
2805 * It is still reflected in the segment length for
2806 * sequencing purposes.
2807 * "off" is the delayed to be dropped hdrlen.
2810 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off)
2812 int cnt = off + th->th_urp - 1;
2815 if (m->m_len > cnt) {
2816 char *cp = mtod(m, caddr_t) + cnt;
2817 struct tcpcb *tp = sototcpcb(so);
2820 tp->t_oobflags |= TCPOOB_HAVEDATA;
2821 bcopy(cp + 1, cp, m->m_len - cnt - 1);
2823 if (m->m_flags & M_PKTHDR)
2832 panic("tcp_pulloutofband");
2836 * Collect new round-trip time estimate and update averages and current
2840 tcp_xmit_timer(struct tcpcb *tp, int rtt, tcp_seq ack)
2844 tcpstat.tcps_rttupdated++;
2846 if ((tp->rxt_flags & TRXT_F_REBASERTO) &&
2847 SEQ_GT(ack, tp->snd_max_prev)) {
2848 #ifdef DEBUG_EIFEL_RESPONSE
2849 kprintf("srtt/rttvar, prev %d/%d, cur %d/%d, ",
2850 tp->t_srtt_prev, tp->t_rttvar_prev,
2851 tp->t_srtt, tp->t_rttvar);
2854 tcpstat.tcps_eifelresponse++;
2856 tp->rxt_flags &= ~TRXT_F_REBASERTO;
2857 tp->t_srtt = max(tp->t_srtt_prev, (rtt << TCP_RTT_SHIFT));
2858 tp->t_rttvar = max(tp->t_rttvar_prev,
2859 (rtt << (TCP_RTTVAR_SHIFT - 1)));
2860 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
2861 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2863 #ifdef DEBUG_EIFEL_RESPONSE
2864 kprintf("new %d/%d ", tp->t_srtt, tp->t_rttvar);
2866 } else if (tp->t_srtt != 0) {
2870 * srtt is stored as fixed point with 5 bits after the
2871 * binary point (i.e., scaled by 32). The following magic
2872 * is equivalent to the smoothing algorithm in rfc793 with
2873 * an alpha of .875 (srtt = rtt/32 + srtt*31/32 in fixed
2874 * point). Adjust rtt to origin 0.
2876 delta = ((rtt - 1) << TCP_DELTA_SHIFT)
2877 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
2879 if ((tp->t_srtt += delta) <= 0)
2883 * We accumulate a smoothed rtt variance (actually, a
2884 * smoothed mean difference), then set the retransmit
2885 * timer to smoothed rtt + 4 times the smoothed variance.
2886 * rttvar is stored as fixed point with 4 bits after the
2887 * binary point (scaled by 16). The following is
2888 * equivalent to rfc793 smoothing with an alpha of .75
2889 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces
2890 * rfc793's wired-in beta.
2894 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
2895 if ((tp->t_rttvar += delta) <= 0)
2897 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
2898 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2901 * No rtt measurement yet - use the unsmoothed rtt.
2902 * Set the variance to half the rtt (so our first
2903 * retransmit happens at 3*rtt).
2905 tp->t_srtt = rtt << TCP_RTT_SHIFT;
2906 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
2907 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2912 #ifdef DEBUG_EIFEL_RESPONSE
2914 kprintf("| rxtcur prev %d, old %d, ",
2915 tp->t_rxtcur_prev, tp->t_rxtcur);
2920 * the retransmit should happen at rtt + 4 * rttvar.
2921 * Because of the way we do the smoothing, srtt and rttvar
2922 * will each average +1/2 tick of bias. When we compute
2923 * the retransmit timer, we want 1/2 tick of rounding and
2924 * 1 extra tick because of +-1/2 tick uncertainty in the
2925 * firing of the timer. The bias will give us exactly the
2926 * 1.5 tick we need. But, because the bias is
2927 * statistical, we have to test that we don't drop below
2928 * the minimum feasible timer (which is 2 ticks).
2930 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
2931 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);
2934 if (tp->t_rxtcur < tp->t_rxtcur_prev + tcp_eifel_rtoinc) {
2936 * RFC4015 requires that the new RTO is at least
2937 * 2*G (tcp_eifel_rtoinc) greater then the RTO
2938 * (t_rxtcur_prev) when the spurious retransmit
2941 * The above condition could be true, if the SRTT
2942 * and RTTVAR used to calculate t_rxtcur_prev
2943 * resulted in a value less than t_rttmin. So
2944 * simply increasing SRTT by tcp_eifel_rtoinc when
2945 * preparing for the Eifel response could not ensure
2946 * that the new RTO will be tcp_eifel_rtoinc greater
2949 tp->t_rxtcur = tp->t_rxtcur_prev + tcp_eifel_rtoinc;
2951 #ifdef DEBUG_EIFEL_RESPONSE
2952 kprintf("new %d\n", tp->t_rxtcur);
2957 * We received an ack for a packet that wasn't retransmitted;
2958 * it is probably safe to discard any error indications we've
2959 * received recently. This isn't quite right, but close enough
2960 * for now (a route might have failed after we sent a segment,
2961 * and the return path might not be symmetrical).
2963 tp->t_softerror = 0;
2967 * Determine a reasonable value for maxseg size.
2968 * If the route is known, check route for mtu.
2969 * If none, use an mss that can be handled on the outgoing
2970 * interface without forcing IP to fragment; if bigger than
2971 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES
2972 * to utilize large mbufs. If no route is found, route has no mtu,
2973 * or the destination isn't local, use a default, hopefully conservative
2974 * size (usually 512 or the default IP max size, but no more than the mtu
2975 * of the interface), as we can't discover anything about intervening
2976 * gateways or networks. We also initialize the congestion/slow start
2977 * window to be a single segment if the destination isn't local.
2978 * While looking at the routing entry, we also initialize other path-dependent
2979 * parameters from pre-set or cached values in the routing entry.
2981 * Also take into account the space needed for options that we
2982 * send regularly. Make maxseg shorter by that amount to assure
2983 * that we can send maxseg amount of data even when the options
2984 * are present. Store the upper limit of the length of options plus
2987 * NOTE that this routine is only called when we process an incoming
2988 * segment, for outgoing segments only tcp_mssopt is called.
2991 tcp_mss(struct tcpcb *tp, int offer)
2997 struct inpcb *inp = tp->t_inpcb;
3000 boolean_t isipv6 = INP_ISIPV6(inp);
3001 size_t min_protoh = isipv6 ?
3002 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) :
3003 sizeof(struct tcpiphdr);
3005 const boolean_t isipv6 = FALSE;
3006 const size_t min_protoh = sizeof(struct tcpiphdr);
3010 rt = tcp_rtlookup6(&inp->inp_inc);
3012 rt = tcp_rtlookup(&inp->inp_inc);
3014 tp->t_maxopd = tp->t_maxseg =
3015 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt);
3019 so = inp->inp_socket;
3022 * Offer == 0 means that there was no MSS on the SYN segment,
3023 * in this case we use either the interface mtu or tcp_mssdflt.
3025 * An offer which is too large will be cut down later.
3029 if (in6_localaddr(&inp->in6p_faddr))
3030 offer = IN6_LINKMTU(rt->rt_ifp) - min_protoh;
3032 offer = tcp_v6mssdflt;
3034 if (in_localaddr(inp->inp_faddr))
3035 offer = ifp->if_mtu - min_protoh;
3037 offer = tcp_mssdflt;
3042 * Prevent DoS attack with too small MSS. Round up
3043 * to at least minmss.
3045 * Sanity check: make sure that maxopd will be large
3046 * enough to allow some data on segments even is the
3047 * all the option space is used (40bytes). Otherwise
3048 * funny things may happen in tcp_output.
3050 offer = max(offer, tcp_minmss);
3051 offer = max(offer, 64);
3053 rt->rt_rmx.rmx_mssopt = offer;
3056 * While we're here, check if there's an initial rtt
3057 * or rttvar. Convert from the route-table units
3058 * to scaled multiples of the slow timeout timer.
3060 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) {
3062 * XXX the lock bit for RTT indicates that the value
3063 * is also a minimum value; this is subject to time.
3065 if (rt->rt_rmx.rmx_locks & RTV_RTT)
3066 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz);
3067 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE));
3068 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE;
3069 tcpstat.tcps_usedrtt++;
3070 if (rt->rt_rmx.rmx_rttvar) {
3071 tp->t_rttvar = rt->rt_rmx.rmx_rttvar /
3072 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE));
3073 tcpstat.tcps_usedrttvar++;
3075 /* default variation is +- 1 rtt */
3077 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
3079 TCPT_RANGESET(tp->t_rxtcur,
3080 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
3081 tp->t_rttmin, TCPTV_REXMTMAX);
3085 * if there's an mtu associated with the route, use it
3086 * else, use the link mtu. Take the smaller of mss or offer
3089 if (rt->rt_rmx.rmx_mtu) {
3090 mss = rt->rt_rmx.rmx_mtu;
3093 mss = IN6_LINKMTU(rt->rt_ifp);
3098 mss = min(mss, offer);
3101 * maxopd stores the maximum length of data AND options
3102 * in a segment; maxseg is the amount of data in a normal
3103 * segment. We need to store this value (maxopd) apart
3104 * from maxseg, because now every segment carries options
3105 * and thus we normally have somewhat less data in segments.
3109 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP &&
3110 ((tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP))
3111 mss -= TCPOLEN_TSTAMP_APPA;
3113 #if (MCLBYTES & (MCLBYTES - 1)) == 0
3115 mss &= ~(MCLBYTES-1);
3118 mss = mss / MCLBYTES * MCLBYTES;
3121 * If there's a pipesize, change the socket buffer
3122 * to that size. Make the socket buffers an integral
3123 * number of mss units; if the mss is larger than
3124 * the socket buffer, decrease the mss.
3127 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0)
3129 bufsize = so->so_snd.ssb_hiwat;
3133 bufsize = roundup(bufsize, mss);
3134 if (bufsize > sb_max)
3136 if (bufsize > so->so_snd.ssb_hiwat)
3137 ssb_reserve(&so->so_snd, bufsize, so, NULL);
3142 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0)
3144 bufsize = so->so_rcv.ssb_hiwat;
3145 if (bufsize > mss) {
3146 bufsize = roundup(bufsize, mss);
3147 if (bufsize > sb_max)
3149 if (bufsize > so->so_rcv.ssb_hiwat) {
3150 lwkt_gettoken(&so->so_rcv.ssb_token);
3151 ssb_reserve(&so->so_rcv, bufsize, so, NULL);
3152 lwkt_reltoken(&so->so_rcv.ssb_token);
3157 * Set the slow-start flight size
3159 * NOTE: t_maxseg must have been configured!
3161 tp->snd_cwnd = tcp_initial_window(tp);
3163 if (rt->rt_rmx.rmx_ssthresh) {
3165 * There's some sort of gateway or interface
3166 * buffer limit on the path. Use this to set
3167 * the slow start threshhold, but set the
3168 * threshold to no less than 2*mss.
3170 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh);
3171 tcpstat.tcps_usedssthresh++;
3176 * Determine the MSS option to send on an outgoing SYN.
3179 tcp_mssopt(struct tcpcb *tp)
3183 boolean_t isipv6 = INP_ISIPV6(tp->t_inpcb);
3184 int min_protoh = isipv6 ?
3185 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) :
3186 sizeof(struct tcpiphdr);
3188 const boolean_t isipv6 = FALSE;
3189 const size_t min_protoh = sizeof(struct tcpiphdr);
3193 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc);
3195 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc);
3197 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt);
3200 return ((isipv6 ? IN6_LINKMTU(rt->rt_ifp) : rt->rt_ifp->if_mtu) -
3203 return (rt->rt_ifp->if_mtu - min_protoh);
3208 * When a partial ack arrives, force the retransmission of the
3209 * next unacknowledged segment. Do not exit Fast Recovery.
3211 * Implement the Slow-but-Steady variant of NewReno by restarting the
3212 * the retransmission timer. Turn it off here so it can be restarted
3213 * later in tcp_output().
3216 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th, int acked)
3218 tcp_seq old_snd_nxt = tp->snd_nxt;
3219 u_long ocwnd = tp->snd_cwnd;
3221 tcp_callout_stop(tp, tp->tt_rexmt);
3223 tp->snd_nxt = th->th_ack;
3224 /* Set snd_cwnd to one segment beyond acknowledged offset. */
3225 tp->snd_cwnd = tp->t_maxseg;
3226 tp->t_flags |= TF_ACKNOW;
3228 if (SEQ_GT(old_snd_nxt, tp->snd_nxt))
3229 tp->snd_nxt = old_snd_nxt;
3230 /* partial window deflation */
3232 tp->snd_cwnd = ocwnd - acked + tp->t_maxseg;
3234 tp->snd_cwnd = tp->t_maxseg;
3238 * In contrast to the Slow-but-Steady NewReno variant,
3239 * we do not reset the retransmission timer for SACK retransmissions,
3240 * except when retransmitting snd_una.
3243 tcp_sack_rexmt(struct tcpcb *tp, boolean_t force)
3245 tcp_seq old_snd_nxt = tp->snd_nxt;
3246 u_long ocwnd = tp->snd_cwnd;
3248 int nseg = 0; /* consecutive new segments */
3249 int nseg_rexmt = 0; /* retransmitted segments */
3253 uint32_t unsacked = tcp_sack_first_unsacked_len(tp);
3256 * Try to fill the first hole in the receiver's
3259 maxrexmt = howmany(unsacked, tp->t_maxseg);
3260 if (maxrexmt > tcp_force_sackrxt)
3261 maxrexmt = tcp_force_sackrxt;
3265 pipe = tcp_sack_compute_pipe(tp);
3266 while (((tcp_seq_diff_t)(ocwnd - pipe) >= (tcp_seq_diff_t)tp->t_maxseg
3267 || (force && nseg_rexmt < maxrexmt && nseg == 0)) &&
3268 (!tcp_do_smartsack || nseg < TCP_SACK_MAXBURST)) {
3269 tcp_seq old_snd_max, old_rexmt_high, nextrexmt;
3270 uint32_t sent, seglen;
3274 old_rexmt_high = tp->rexmt_high;
3275 if (!tcp_sack_nextseg(tp, &nextrexmt, &seglen, &rescue)) {
3276 tp->rexmt_high = old_rexmt_high;
3281 * If the next tranmission is a rescue retranmission,
3282 * we check whether we have already sent some data
3283 * (either new segments or retransmitted segments)
3284 * into the the network or not. Since the idea of rescue
3285 * retransmission is to sustain ACK clock, as long as
3286 * some segments are in the network, ACK clock will be
3289 if (rescue && (nseg_rexmt > 0 || nseg > 0)) {
3290 tp->rexmt_high = old_rexmt_high;
3294 if (nextrexmt == tp->snd_max)
3298 tp->snd_nxt = nextrexmt;
3299 tp->snd_cwnd = nextrexmt - tp->snd_una + seglen;
3300 old_snd_max = tp->snd_max;
3301 if (nextrexmt == tp->snd_una)
3302 tcp_callout_stop(tp, tp->tt_rexmt);
3303 tp->t_flags |= TF_XMITNOW;
3304 error = tcp_output(tp);
3306 tp->rexmt_high = old_rexmt_high;
3309 sent = tp->snd_nxt - nextrexmt;
3311 tp->rexmt_high = old_rexmt_high;
3315 tcpstat.tcps_sndsackpack++;
3316 tcpstat.tcps_sndsackbyte += sent;
3319 tcpstat.tcps_sackrescue++;
3320 tp->rexmt_rescue = tp->snd_nxt;
3321 tp->sack_flags |= TSACK_F_SACKRESCUED;
3324 if (SEQ_LT(nextrexmt, old_snd_max) &&
3325 SEQ_LT(tp->rexmt_high, tp->snd_nxt)) {
3326 tp->rexmt_high = seq_min(tp->snd_nxt, old_snd_max);
3327 if (tcp_aggressive_rescuesack &&
3328 (tp->sack_flags & TSACK_F_SACKRESCUED) &&
3329 SEQ_LT(tp->rexmt_rescue, tp->rexmt_high)) {
3330 /* Drag RescueRxt along with HighRxt */
3331 tp->rexmt_rescue = tp->rexmt_high;
3335 if (SEQ_GT(old_snd_nxt, tp->snd_nxt))
3336 tp->snd_nxt = old_snd_nxt;
3337 tp->snd_cwnd = ocwnd;
3341 * Return TRUE, if some new segments are sent
3344 tcp_sack_limitedxmit(struct tcpcb *tp)
3346 tcp_seq oldsndnxt = tp->snd_nxt;
3347 tcp_seq oldsndmax = tp->snd_max;
3348 u_long ocwnd = tp->snd_cwnd;
3349 uint32_t pipe, sent;
3350 boolean_t ret = FALSE;
3351 tcp_seq_diff_t cwnd_left;
3354 tp->rexmt_high = tp->snd_una - 1;
3355 pipe = tcp_sack_compute_pipe(tp);
3356 cwnd_left = (tcp_seq_diff_t)(ocwnd - pipe);
3357 if (cwnd_left < (tcp_seq_diff_t)tp->t_maxseg)
3360 if (tcp_do_smartsack)
3361 cwnd_left = ulmin(cwnd_left, tp->t_maxseg * TCP_SACK_MAXBURST);
3363 next = tp->snd_nxt = tp->snd_max;
3364 tp->snd_cwnd = tp->snd_nxt - tp->snd_una +
3365 rounddown(cwnd_left, tp->t_maxseg);
3367 tp->t_flags |= TF_XMITNOW;
3370 sent = tp->snd_nxt - next;
3372 tcpstat.tcps_sndlimited += howmany(sent, tp->t_maxseg);
3376 if (SEQ_LT(oldsndnxt, oldsndmax)) {
3377 KASSERT(SEQ_GEQ(oldsndnxt, tp->snd_una),
3378 ("snd_una moved in other threads"));
3379 tp->snd_nxt = oldsndnxt;
3381 tp->snd_cwnd = ocwnd;
3383 if (ret && TCP_DO_NCR(tp))
3384 tcp_ncr_update_rxtthresh(tp);
3390 * Reset idle time and keep-alive timer, typically called when a valid
3391 * tcp packet is received but may also be called when FASTKEEP is set
3392 * to prevent the previous long-timeout from calculating to a drop.
3394 * Only update t_rcvtime for non-SYN packets.
3396 * Handle the case where one side thinks the connection is established
3397 * but the other side has, say, rebooted without cleaning out the
3398 * connection. The SYNs could be construed as an attack and wind
3399 * up ignored, but in case it isn't an attack we can validate the
3400 * connection by forcing a keepalive.
3403 tcp_timer_keep_activity(struct tcpcb *tp, int thflags)
3405 if (TCPS_HAVEESTABLISHED(tp->t_state)) {
3406 if ((thflags & (TH_SYN | TH_ACK)) == TH_SYN) {
3407 tp->t_flags |= TF_KEEPALIVE;
3408 tcp_callout_reset(tp, tp->tt_keep, hz / 2,
3411 tp->t_rcvtime = ticks;
3412 tp->t_flags &= ~TF_KEEPALIVE;
3413 tcp_callout_reset(tp, tp->tt_keep,
3421 tcp_rmx_msl(const struct tcpcb *tp)
3424 struct inpcb *inp = tp->t_inpcb;
3427 boolean_t isipv6 = INP_ISIPV6(inp);
3429 const boolean_t isipv6 = FALSE;
3433 rt = tcp_rtlookup6(&inp->inp_inc);
3435 rt = tcp_rtlookup(&inp->inp_inc);
3436 if (rt == NULL || rt->rt_rmx.rmx_msl == 0)
3439 msl = (rt->rt_rmx.rmx_msl * hz) / 1000;
3447 tcp_established(struct tcpcb *tp)
3449 tp->t_state = TCPS_ESTABLISHED;
3450 tcp_callout_reset(tp, tp->tt_keep, tp->t_keepidle, tcp_timer_keep);
3452 if (tp->t_rxtsyn > 0) {
3455 * "If the timer expires awaiting the ACK of a SYN segment
3456 * and the TCP implementation is using an RTO less than 3
3457 * seconds, the RTO MUST be re-initialized to 3 seconds
3458 * when data transmission begins"
3460 if (tp->t_rxtcur < TCPTV_RTOBASE3)
3461 tp->t_rxtcur = TCPTV_RTOBASE3;
3466 * Returns TRUE, if the ACK should be dropped
3469 tcp_recv_dupack(struct tcpcb *tp, tcp_seq th_ack, u_int to_flags)
3471 boolean_t fast_sack_rexmt = TRUE;
3473 tcpstat.tcps_rcvdupack++;
3476 * We have outstanding data (other than a window probe),
3477 * this is a completely duplicate ack (ie, window info
3478 * didn't change), the ack is the biggest we've seen and
3479 * we've seen exactly our rexmt threshhold of them, so
3480 * assume a packet has been dropped and retransmit it.
3481 * Kludge snd_nxt & the congestion window so we send only
3484 if (IN_FASTRECOVERY(tp)) {
3485 if (TCP_DO_SACK(tp)) {
3486 boolean_t force = FALSE;
3488 if (tp->snd_una == tp->rexmt_high &&
3489 (to_flags & (TOF_SACK | TOF_SACK_REDUNDANT)) ==
3492 * New segments got SACKed and
3493 * no retransmit yet.
3498 /* No artifical cwnd inflation. */
3499 tcp_sack_rexmt(tp, force);
3502 * Dup acks mean that packets have left
3503 * the network (they're now cached at the
3504 * receiver) so bump cwnd by the amount in
3505 * the receiver to keep a constant cwnd
3506 * packets in the network.
3508 tp->snd_cwnd += tp->t_maxseg;
3512 } else if (SEQ_LT(th_ack, tp->snd_recover)) {
3515 } else if (tcp_ignore_redun_dsack && TCP_DO_SACK(tp) &&
3516 (to_flags & (TOF_DSACK | TOF_SACK_REDUNDANT)) ==
3517 (TOF_DSACK | TOF_SACK_REDUNDANT)) {
3519 * If the ACK carries DSACK and other SACK blocks
3520 * carry information that we have already known,
3521 * don't count this ACK as duplicate ACK. This
3522 * prevents spurious early retransmit and fast
3523 * retransmit. This also meets the requirement of
3524 * RFC3042 that new segments should not be sent if
3525 * the SACK blocks do not contain new information
3526 * (XXX we actually loosen the requirment that only
3527 * DSACK is checked here).
3529 * This kind of ACKs are usually sent after spurious
3532 /* Do nothing; don't change t_dupacks */
3534 } else if (tp->t_dupacks == 0 && TCP_DO_NCR(tp)) {
3535 tcp_ncr_update_rxtthresh(tp);
3538 if (++tp->t_dupacks == tp->t_rxtthresh) {
3539 tcp_seq old_snd_nxt;
3543 if (tcp_do_eifel_detect && (tp->t_flags & TF_RCVD_TSTMP)) {
3544 tcp_save_congestion_state(tp);
3545 tp->rxt_flags |= TRXT_F_FASTREXMT;
3548 * We know we're losing at the current window size,
3549 * so do congestion avoidance: set ssthresh to half
3550 * the current window and pull our congestion window
3551 * back to the new ssthresh.
3553 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
3556 tp->snd_ssthresh = win * tp->t_maxseg;
3557 ENTER_FASTRECOVERY(tp);
3558 tp->snd_recover = tp->snd_max;
3559 tcp_callout_stop(tp, tp->tt_rexmt);
3561 old_snd_nxt = tp->snd_nxt;
3562 tp->snd_nxt = th_ack;
3563 if (TCP_DO_SACK(tp)) {
3566 rxtlen = tcp_sack_first_unsacked_len(tp);
3567 if (rxtlen > tp->t_maxseg)
3568 rxtlen = tp->t_maxseg;
3569 tp->snd_cwnd = rxtlen;
3571 tp->snd_cwnd = tp->t_maxseg;
3574 ++tcpstat.tcps_sndfastrexmit;
3575 tp->snd_cwnd = tp->snd_ssthresh;
3576 tp->rexmt_high = tp->snd_nxt;
3577 tp->sack_flags &= ~TSACK_F_SACKRESCUED;
3578 if (SEQ_GT(old_snd_nxt, tp->snd_nxt))
3579 tp->snd_nxt = old_snd_nxt;
3580 KASSERT(tp->snd_limited <= 2, ("tp->snd_limited too big"));
3581 if (TCP_DO_SACK(tp)) {
3582 if (fast_sack_rexmt)
3583 tcp_sack_rexmt(tp, FALSE);
3585 tp->snd_cwnd += tp->t_maxseg *
3586 (tp->t_dupacks - tp->snd_limited);
3588 } else if ((tcp_do_rfc6675 && TCP_DO_SACK(tp)) || TCP_DO_NCR(tp)) {
3590 * The RFC6675 recommends to reduce the byte threshold,
3591 * and enter fast retransmit if IsLost(snd_una). However,
3592 * if we use IsLost(snd_una) based fast retransmit here,
3593 * segments reordering will cause spurious retransmit. So
3594 * we defer the IsLost(snd_una) based fast retransmit until
3595 * the extended limited transmit can't send any segments and
3596 * early retransmit can't be done.
3598 if (tcp_rfc6675_rxt && tcp_do_rfc6675 &&
3599 tcp_sack_islost(&tp->scb, tp->snd_una))
3600 goto fastretransmit;
3602 if (tcp_do_limitedtransmit || TCP_DO_NCR(tp)) {
3603 if (!tcp_sack_limitedxmit(tp)) {
3604 /* outstanding data */
3605 uint32_t ownd = tp->snd_max - tp->snd_una;
3607 if (need_early_retransmit(tp, ownd)) {
3608 ++tcpstat.tcps_sndearlyrexmit;
3609 tp->rxt_flags |= TRXT_F_EARLYREXMT;
3610 goto fastretransmit;
3611 } else if (tcp_do_rfc6675 &&
3612 tcp_sack_islost(&tp->scb, tp->snd_una)) {
3613 fast_sack_rexmt = FALSE;
3614 goto fastretransmit;
3618 } else if (tcp_do_limitedtransmit) {
3619 u_long oldcwnd = tp->snd_cwnd;
3620 tcp_seq oldsndmax = tp->snd_max;
3621 tcp_seq oldsndnxt = tp->snd_nxt;
3622 /* outstanding data */
3623 uint32_t ownd = tp->snd_max - tp->snd_una;
3626 KASSERT(tp->t_dupacks == 1 || tp->t_dupacks == 2,
3627 ("dupacks not 1 or 2"));
3628 if (tp->t_dupacks == 1)
3629 tp->snd_limited = 0;
3630 tp->snd_nxt = tp->snd_max;
3631 tp->snd_cwnd = ownd +
3632 (tp->t_dupacks - tp->snd_limited) * tp->t_maxseg;
3633 tp->t_flags |= TF_XMITNOW;
3636 if (SEQ_LT(oldsndnxt, oldsndmax)) {
3637 KASSERT(SEQ_GEQ(oldsndnxt, tp->snd_una),
3638 ("snd_una moved in other threads"));
3639 tp->snd_nxt = oldsndnxt;
3641 tp->snd_cwnd = oldcwnd;
3642 sent = tp->snd_max - oldsndmax;
3643 if (sent > tp->t_maxseg) {
3644 KASSERT((tp->t_dupacks == 2 && tp->snd_limited == 0) ||
3645 (sent == tp->t_maxseg + 1 &&
3646 (tp->t_flags & TF_SENTFIN)),
3648 KASSERT(sent <= tp->t_maxseg * 2,
3649 ("sent too many segments"));
3650 tp->snd_limited = 2;
3651 tcpstat.tcps_sndlimited += 2;
3652 } else if (sent > 0) {
3654 ++tcpstat.tcps_sndlimited;
3655 } else if (need_early_retransmit(tp, ownd)) {
3656 ++tcpstat.tcps_sndearlyrexmit;
3657 tp->rxt_flags |= TRXT_F_EARLYREXMT;
3658 goto fastretransmit;
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