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
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of The DragonFly Project nor the names of its
17 * contributors may be used to endorse or promote products derived
18 * from this software without specific, prior written permission.
20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
23 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
24 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
25 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
26 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
27 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
28 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
29 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
30 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
35 * Copyright (c) 2002, 2003, 2004 Jeffrey M. Hsu. All rights reserved.
37 * License terms: all terms for the DragonFly license above plus the following:
39 * 4. All advertising materials mentioning features or use of this software
40 * must display the following acknowledgement:
42 * This product includes software developed by Jeffrey M. Hsu
43 * for the DragonFly Project.
45 * This requirement may be waived with permission from Jeffrey Hsu.
46 * This requirement will sunset and may be removed on July 8 2005,
47 * after which the standard DragonFly license (as shown above) will
52 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995
53 * The Regents of the University of California. All rights reserved.
55 * Redistribution and use in source and binary forms, with or without
56 * modification, are permitted provided that the following conditions
58 * 1. Redistributions of source code must retain the above copyright
59 * notice, this list of conditions and the following disclaimer.
60 * 2. Redistributions in binary form must reproduce the above copyright
61 * notice, this list of conditions and the following disclaimer in the
62 * documentation and/or other materials provided with the distribution.
63 * 3. All advertising materials mentioning features or use of this software
64 * must display the following acknowledgement:
65 * This product includes software developed by the University of
66 * California, Berkeley and its contributors.
67 * 4. Neither the name of the University nor the names of its contributors
68 * may be used to endorse or promote products derived from this software
69 * without specific prior written permission.
71 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
72 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
73 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
74 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
75 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
76 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
77 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
78 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
79 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
80 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
83 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95
84 * $FreeBSD: src/sys/netinet/tcp_input.c,v 1.107.2.38 2003/05/21 04:46:41 cjc Exp $
85 * $DragonFly: src/sys/netinet/tcp_input.c,v 1.43 2004/12/04 10:14:27 hsu Exp $
88 #include "opt_ipfw.h" /* for ipfw_fwd */
89 #include "opt_inet6.h"
90 #include "opt_ipsec.h"
91 #include "opt_tcpdebug.h"
92 #include "opt_tcp_input.h"
94 #include <sys/param.h>
95 #include <sys/systm.h>
96 #include <sys/kernel.h>
97 #include <sys/sysctl.h>
98 #include <sys/malloc.h>
100 #include <sys/proc.h> /* for proc0 declaration */
101 #include <sys/protosw.h>
102 #include <sys/socket.h>
103 #include <sys/socketvar.h>
104 #include <sys/syslog.h>
105 #include <sys/in_cksum.h>
107 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */
108 #include <machine/stdarg.h>
111 #include <net/route.h>
113 #include <netinet/in.h>
114 #include <netinet/in_systm.h>
115 #include <netinet/ip.h>
116 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */
117 #include <netinet/in_var.h>
118 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */
119 #include <netinet/in_pcb.h>
120 #include <netinet/ip_var.h>
121 #include <netinet/ip6.h>
122 #include <netinet/icmp6.h>
123 #include <netinet6/nd6.h>
124 #include <netinet6/ip6_var.h>
125 #include <netinet6/in6_pcb.h>
126 #include <netinet/tcp.h>
127 #include <netinet/tcp_fsm.h>
128 #include <netinet/tcp_seq.h>
129 #include <netinet/tcp_timer.h>
130 #include <netinet/tcp_var.h>
131 #include <netinet6/tcp6_var.h>
132 #include <netinet/tcpip.h>
135 #include <netinet/tcp_debug.h>
137 u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */
138 struct tcphdr tcp_savetcp;
142 #include <netproto/ipsec/ipsec.h>
143 #include <netproto/ipsec/ipsec6.h>
147 #include <netinet6/ipsec.h>
148 #include <netinet6/ipsec6.h>
149 #include <netproto/key/key.h>
152 MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry");
155 static int log_in_vain = 0;
156 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW,
157 &log_in_vain, 0, "Log all incoming TCP connections");
159 static int blackhole = 0;
160 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW,
161 &blackhole, 0, "Do not send RST when dropping refused connections");
163 int tcp_delack_enabled = 1;
164 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW,
165 &tcp_delack_enabled, 0,
166 "Delay ACK to try and piggyback it onto a data packet");
168 #ifdef TCP_DROP_SYNFIN
169 static int drop_synfin = 0;
170 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW,
171 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set");
174 static int tcp_do_limitedtransmit = 1;
175 SYSCTL_INT(_net_inet_tcp, OID_AUTO, limitedtransmit, CTLFLAG_RW,
176 &tcp_do_limitedtransmit, 0, "Enable RFC 3042 (Limited Transmit)");
178 static int tcp_do_early_retransmit = 1;
179 SYSCTL_INT(_net_inet_tcp, OID_AUTO, earlyretransmit, CTLFLAG_RW,
180 &tcp_do_early_retransmit, 0, "Early retransmit");
182 static int tcp_do_rfc3390 = 1;
183 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW,
185 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)");
187 static int tcp_do_eifel_detect = 1;
188 SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW,
189 &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)");
192 * Define as tunable for easy testing with SACK on and off.
193 * Warning: do not change setting in the middle of an existing active TCP flow,
194 * else strange things might happen to that flow.
197 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW,
198 &tcp_do_sack, 0, "Enable SACK Algorithms");
200 int tcp_do_smartsack = 1;
201 SYSCTL_INT(_net_inet_tcp, OID_AUTO, smartsack, CTLFLAG_RW,
202 &tcp_do_smartsack, 0, "Enable Smart SACK Algorithms");
204 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0,
205 "TCP Segment Reassembly Queue");
207 int tcp_reass_maxseg = 0;
208 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD,
209 &tcp_reass_maxseg, 0,
210 "Global maximum number of TCP Segments in Reassembly Queue");
212 int tcp_reass_qsize = 0;
213 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD,
215 "Global number of TCP Segments currently in Reassembly Queue");
217 static int tcp_reass_overflows = 0;
218 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD,
219 &tcp_reass_overflows, 0,
220 "Global number of TCP Segment Reassembly Queue Overflows");
222 static void tcp_dooptions(struct tcpopt *, u_char *, int, boolean_t);
223 static void tcp_pulloutofband(struct socket *,
224 struct tcphdr *, struct mbuf *, int);
225 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *,
227 static void tcp_xmit_timer(struct tcpcb *, int);
228 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *, int);
229 static void tcp_sack_rexmt(struct tcpcb *, struct tcphdr *);
231 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */
233 #define ND6_HINT(tp) \
235 if ((tp) && (tp)->t_inpcb && \
236 ((tp)->t_inpcb->inp_vflag & INP_IPV6) && \
237 (tp)->t_inpcb->in6p_route.ro_rt) \
238 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \
245 * Indicate whether this ack should be delayed. We can delay the ack if
246 * - delayed acks are enabled and
247 * - there is no delayed ack timer in progress and
248 * - our last ack wasn't a 0-sized window. We never want to delay
249 * the ack that opens up a 0-sized window.
251 #define DELAY_ACK(tp) \
252 (tcp_delack_enabled && !callout_pending(tp->tt_delack) && \
253 !(tp->t_flags & TF_RXWIN0SENT))
255 #define acceptable_window_update(tp, th, tiwin) \
256 (SEQ_LT(tp->snd_wl1, th->th_seq) || \
257 (tp->snd_wl1 == th->th_seq && \
258 (SEQ_LT(tp->snd_wl2, th->th_ack) || \
259 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))
262 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m)
265 struct tseg_qent *p = NULL;
266 struct tseg_qent *te;
267 struct socket *so = tp->t_inpcb->inp_socket;
271 * Call with th == NULL after become established to
272 * force pre-ESTABLISHED data up to user socket.
278 * Limit the number of segments in the reassembly queue to prevent
279 * holding on to too many segments (and thus running out of mbufs).
280 * Make sure to let the missing segment through which caused this
281 * queue. Always keep one global queue entry spare to be able to
282 * process the missing segment.
284 if (th->th_seq != tp->rcv_nxt &&
285 tcp_reass_qsize + 1 >= tcp_reass_maxseg) {
286 tcp_reass_overflows++;
287 tcpstat.tcps_rcvmemdrop++;
289 /* no SACK block to report */
290 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
294 /* Allocate a new queue entry. */
295 MALLOC(te, struct tseg_qent *, sizeof(struct tseg_qent), M_TSEGQ,
296 M_INTWAIT | M_NULLOK);
298 tcpstat.tcps_rcvmemdrop++;
300 /* no SACK block to report */
301 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
307 * Find a segment which begins after this one does.
309 LIST_FOREACH(q, &tp->t_segq, tqe_q) {
310 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
316 * If there is a preceding segment, it may provide some of
317 * our data already. If so, drop the data from the incoming
318 * segment. If it provides all of our data, drop us.
323 /* conversion to int (in i) handles seq wraparound */
324 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
325 if (i > 0) { /* overlaps preceding segment */
326 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG);
327 /* enclosing block starts w/ preceding segment */
328 tp->encloseblk.rblk_start = p->tqe_th->th_seq;
330 /* preceding encloses incoming segment */
331 tp->encloseblk.rblk_end = p->tqe_th->th_seq +
333 tcpstat.tcps_rcvduppack++;
334 tcpstat.tcps_rcvdupbyte += *tlenp;
339 * Try to present any queued data
340 * at the left window edge to the user.
341 * This is needed after the 3-WHS
344 goto present; /* ??? */
349 /* incoming segment end is enclosing block end */
350 tp->encloseblk.rblk_end = th->th_seq + *tlenp +
351 ((th->th_flags & TH_FIN) != 0);
352 /* trim end of reported D-SACK block */
353 tp->reportblk.rblk_end = th->th_seq;
356 tcpstat.tcps_rcvoopack++;
357 tcpstat.tcps_rcvoobyte += *tlenp;
360 * While we overlap succeeding segments trim them or,
361 * if they are completely covered, dequeue them.
364 int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
365 tcp_seq qend = q->tqe_th->th_seq + q->tqe_len;
366 struct tseg_qent *nq;
370 if (!(tp->t_flags & TF_DUPSEG)) { /* first time through */
371 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG);
372 tp->encloseblk = tp->reportblk;
373 /* report trailing duplicate D-SACK segment */
374 tp->reportblk.rblk_start = q->tqe_th->th_seq;
376 if ((tp->t_flags & TF_ENCLOSESEG) &&
377 SEQ_GT(qend, tp->encloseblk.rblk_end)) {
378 /* extend enclosing block if one exists */
379 tp->encloseblk.rblk_end = qend;
381 if (i < q->tqe_len) {
382 q->tqe_th->th_seq += i;
388 nq = LIST_NEXT(q, tqe_q);
389 LIST_REMOVE(q, tqe_q);
396 /* Insert the new segment queue entry into place. */
399 te->tqe_len = *tlenp;
401 /* check if can coalesce with following segment */
402 if (q != NULL && (th->th_seq + *tlenp == q->tqe_th->th_seq)) {
403 tcp_seq tend = te->tqe_th->th_seq + te->tqe_len;
405 te->tqe_len += q->tqe_len;
406 if (q->tqe_th->th_flags & TH_FIN)
407 te->tqe_th->th_flags |= TH_FIN;
408 m_cat(te->tqe_m, q->tqe_m);
409 tp->encloseblk.rblk_end = tend;
411 * When not reporting a duplicate segment, use
412 * the larger enclosing block as the SACK block.
414 if (!(tp->t_flags & TF_DUPSEG))
415 tp->reportblk.rblk_end = tend;
416 LIST_REMOVE(q, tqe_q);
422 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q);
424 /* check if can coalesce with preceding segment */
425 if (p->tqe_th->th_seq + p->tqe_len == th->th_seq) {
426 p->tqe_len += te->tqe_len;
427 m_cat(p->tqe_m, te->tqe_m);
428 tp->encloseblk.rblk_start = p->tqe_th->th_seq;
430 * When not reporting a duplicate segment, use
431 * the larger enclosing block as the SACK block.
433 if (!(tp->t_flags & TF_DUPSEG))
434 tp->reportblk.rblk_start = p->tqe_th->th_seq;
438 LIST_INSERT_AFTER(p, te, tqe_q);
443 * Present data to user, advancing rcv_nxt through
444 * completed sequence space.
446 if (!TCPS_HAVEESTABLISHED(tp->t_state))
448 q = LIST_FIRST(&tp->t_segq);
449 if (q == NULL || q->tqe_th->th_seq != tp->rcv_nxt)
451 tp->rcv_nxt += q->tqe_len;
452 if (!(tp->t_flags & TF_DUPSEG)) {
453 /* no SACK block to report since ACK advanced */
454 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
456 /* no enclosing block to report since ACK advanced */
457 tp->t_flags &= ~TF_ENCLOSESEG;
458 flags = q->tqe_th->th_flags & TH_FIN;
459 LIST_REMOVE(q, tqe_q);
460 KASSERT(LIST_EMPTY(&tp->t_segq) ||
461 LIST_FIRST(&tp->t_segq)->tqe_th->th_seq != tp->rcv_nxt,
462 ("segment not coalesced"));
463 if (so->so_state & SS_CANTRCVMORE)
466 sbappend(&so->so_rcv, q->tqe_m);
475 * TCP input routine, follows pages 65-76 of the
476 * protocol specification dated September, 1981 very closely.
480 tcp6_input(struct mbuf **mp, int *offp, int proto)
482 struct mbuf *m = *mp;
483 struct in6_ifaddr *ia6;
485 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE);
488 * draft-itojun-ipv6-tcp-to-anycast
489 * better place to put this in?
491 ia6 = ip6_getdstifaddr(m);
492 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) {
495 ip6 = mtod(m, struct ip6_hdr *);
496 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
497 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6);
498 return (IPPROTO_DONE);
501 tcp_input(m, *offp, proto);
502 return (IPPROTO_DONE);
507 tcp_input(struct mbuf *m, ...)
512 struct ip *ip = NULL;
514 struct inpcb *inp = NULL;
519 struct tcpcb *tp = NULL;
521 struct socket *so = 0;
523 boolean_t ourfinisacked, needoutput = FALSE;
526 struct tcpopt to; /* options in this segment */
527 struct rmxp_tao *taop; /* pointer to our TAO cache entry */
528 struct rmxp_tao tao_noncached; /* in case there's no cached entry */
529 struct sockaddr_in *next_hop = NULL;
530 int rstreason; /* For badport_bandlim accounting purposes */
532 struct ip6_hdr *ip6 = NULL;
536 const boolean_t isipv6 = FALSE;
543 off0 = __va_arg(ap, int);
544 proto = __va_arg(ap, int);
547 tcpstat.tcps_rcvtotal++;
549 /* Grab info from and strip MT_TAG mbufs prepended to the chain. */
550 while (m->m_type == MT_TAG) {
551 if (m->_m_tag_id == PACKET_TAG_IPFORWARD)
552 next_hop = (struct sockaddr_in *)m->m_hdr.mh_data;
557 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE;
561 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */
562 ip6 = mtod(m, struct ip6_hdr *);
563 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0;
564 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) {
565 tcpstat.tcps_rcvbadsum++;
568 th = (struct tcphdr *)((caddr_t)ip6 + off0);
571 * Be proactive about unspecified IPv6 address in source.
572 * As we use all-zero to indicate unbounded/unconnected pcb,
573 * unspecified IPv6 address can be used to confuse us.
575 * Note that packets with unspecified IPv6 destination is
576 * already dropped in ip6_input.
578 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
584 * Get IP and TCP header together in first mbuf.
585 * Note: IP leaves IP header in first mbuf.
587 if (off0 > sizeof(struct ip)) {
589 off0 = sizeof(struct ip);
591 /* already checked and pulled up in ip_demux() */
592 KASSERT(m->m_len >= sizeof(struct tcpiphdr),
593 ("TCP header not in one mbuf: m->m_len %d", m->m_len));
594 ip = mtod(m, struct ip *);
595 ipov = (struct ipovly *)ip;
596 th = (struct tcphdr *)((caddr_t)ip + off0);
599 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
600 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
601 th->th_sum = m->m_pkthdr.csum_data;
603 th->th_sum = in_pseudo(ip->ip_src.s_addr,
605 htonl(m->m_pkthdr.csum_data +
608 th->th_sum ^= 0xffff;
611 * Checksum extended TCP header and data.
613 len = sizeof(struct ip) + tlen;
614 bzero(ipov->ih_x1, sizeof(ipov->ih_x1));
615 ipov->ih_len = (u_short)tlen;
616 ipov->ih_len = htons(ipov->ih_len);
617 th->th_sum = in_cksum(m, len);
620 tcpstat.tcps_rcvbadsum++;
624 /* Re-initialization for later version check */
625 ip->ip_v = IPVERSION;
630 * Check that TCP offset makes sense,
631 * pull out TCP options and adjust length. XXX
633 off = th->th_off << 2;
634 /* already checked and pulled up in ip_demux() */
635 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen,
636 ("bad TCP data offset %d (tlen %d)", off, tlen));
637 tlen -= off; /* tlen is used instead of ti->ti_len */
638 if (off > sizeof(struct tcphdr)) {
640 IP6_EXTHDR_CHECK(m, off0, off, );
641 ip6 = mtod(m, struct ip6_hdr *);
642 th = (struct tcphdr *)((caddr_t)ip6 + off0);
644 /* already pulled up in ip_demux() */
645 KASSERT(m->m_len >= sizeof(struct ip) + off,
646 ("TCP header and options not in one mbuf: "
647 "m_len %d, off %d", m->m_len, off));
649 optlen = off - sizeof(struct tcphdr);
650 optp = (u_char *)(th + 1);
652 thflags = th->th_flags;
654 #ifdef TCP_DROP_SYNFIN
656 * If the drop_synfin option is enabled, drop all packets with
657 * both the SYN and FIN bits set. This prevents e.g. nmap from
658 * identifying the TCP/IP stack.
660 * This is a violation of the TCP specification.
662 if (drop_synfin && (thflags & (TH_SYN | TH_FIN)) == (TH_SYN | TH_FIN))
667 * Convert TCP protocol specific fields to host format.
669 th->th_seq = ntohl(th->th_seq);
670 th->th_ack = ntohl(th->th_ack);
671 th->th_win = ntohs(th->th_win);
672 th->th_urp = ntohs(th->th_urp);
675 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options,
676 * until after ip6_savecontrol() is called and before other functions
677 * which don't want those proto headers.
678 * Because ip6_savecontrol() is going to parse the mbuf to
679 * search for data to be passed up to user-land, it wants mbuf
680 * parameters to be unchanged.
681 * XXX: the call of ip6_savecontrol() has been obsoleted based on
682 * latest version of the advanced API (20020110).
684 drop_hdrlen = off0 + off;
687 * Locate pcb for segment.
690 /* IPFIREWALL_FORWARD section */
691 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */
693 * Transparently forwarded. Pretend to be the destination.
694 * already got one like this?
696 cpu = mycpu->gd_cpuid;
697 inp = in_pcblookup_hash(&tcbinfo[cpu],
698 ip->ip_src, th->th_sport,
699 ip->ip_dst, th->th_dport,
700 0, m->m_pkthdr.rcvif);
703 * It's new. Try to find the ambushing socket.
707 * The rest of the ipfw code stores the port in
709 * (The IP address is still in network order.)
711 in_port_t dport = next_hop->sin_port ?
712 htons(next_hop->sin_port) :
715 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport,
716 next_hop->sin_addr.s_addr, dport);
717 inp = in_pcblookup_hash(&tcbinfo[cpu],
718 ip->ip_src, th->th_sport,
719 next_hop->sin_addr, dport,
720 1, m->m_pkthdr.rcvif);
724 inp = in6_pcblookup_hash(&tcbinfo[0],
725 &ip6->ip6_src, th->th_sport,
726 &ip6->ip6_dst, th->th_dport,
727 1, m->m_pkthdr.rcvif);
729 cpu = mycpu->gd_cpuid;
730 inp = in_pcblookup_hash(&tcbinfo[cpu],
731 ip->ip_src, th->th_sport,
732 ip->ip_dst, th->th_dport,
733 1, m->m_pkthdr.rcvif);
738 * If the state is CLOSED (i.e., TCB does not exist) then
739 * all data in the incoming segment is discarded.
740 * If the TCB exists but is in CLOSED state, it is embryonic,
741 * but should either do a listen or a connect soon.
746 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2];
748 char dbuf[4 * sizeof "123"], sbuf[4 * sizeof "123"];
752 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst));
755 strcat(sbuf, ip6_sprintf(&ip6->ip6_src));
758 strcpy(dbuf, inet_ntoa(ip->ip_dst));
759 strcpy(sbuf, inet_ntoa(ip->ip_src));
761 switch (log_in_vain) {
763 if (!(thflags & TH_SYN))
767 "Connection attempt to TCP %s:%d "
768 "from %s:%d flags:0x%02x\n",
769 dbuf, ntohs(th->th_dport), sbuf,
770 ntohs(th->th_sport), thflags);
779 if (thflags & TH_SYN)
788 rstreason = BANDLIM_RST_CLOSEDPORT;
794 if (ipsec6_in_reject_so(m, inp->inp_socket)) {
795 ipsec6stat.in_polvio++;
799 if (ipsec4_in_reject_so(m, inp->inp_socket)) {
800 ipsecstat.in_polvio++;
807 if (ipsec6_in_reject(m, inp))
810 if (ipsec4_in_reject(m, inp))
817 rstreason = BANDLIM_RST_CLOSEDPORT;
820 if (tp->t_state <= TCPS_CLOSED)
823 /* Unscale the window into a 32-bit value. */
824 if (!(thflags & TH_SYN))
825 tiwin = th->th_win << tp->snd_scale;
829 so = inp->inp_socket;
832 if (so->so_options & SO_DEBUG) {
833 ostate = tp->t_state;
835 bcopy(ip6, tcp_saveipgen, sizeof(*ip6));
837 bcopy(ip, tcp_saveipgen, sizeof(*ip));
842 bzero(&to, sizeof(to));
844 if (so->so_options & SO_ACCEPTCONN) {
845 struct in_conninfo inc;
848 inc.inc_isipv6 = (isipv6 == TRUE);
851 inc.inc6_faddr = ip6->ip6_src;
852 inc.inc6_laddr = ip6->ip6_dst;
853 inc.inc6_route.ro_rt = NULL; /* XXX */
855 inc.inc_faddr = ip->ip_src;
856 inc.inc_laddr = ip->ip_dst;
857 inc.inc_route.ro_rt = NULL; /* XXX */
859 inc.inc_fport = th->th_sport;
860 inc.inc_lport = th->th_dport;
863 * If the state is LISTEN then ignore segment if it contains
864 * a RST. If the segment contains an ACK then it is bad and
865 * send a RST. If it does not contain a SYN then it is not
866 * interesting; drop it.
868 * If the state is SYN_RECEIVED (syncache) and seg contains
869 * an ACK, but not for our SYN/ACK, send a RST. If the seg
870 * contains a RST, check the sequence number to see if it
871 * is a valid reset segment.
873 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) != TH_SYN) {
874 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) == TH_ACK) {
875 if (!syncache_expand(&inc, th, &so, m)) {
877 * No syncache entry, or ACK was not
878 * for our SYN/ACK. Send a RST.
880 tcpstat.tcps_badsyn++;
881 rstreason = BANDLIM_RST_OPENPORT;
886 * Could not complete 3-way handshake,
887 * connection is being closed down, and
888 * syncache will free mbuf.
892 * Socket is created in state SYN_RECEIVED.
893 * Continue processing segment.
898 * This is what would have happened in
899 * tcp_output() when the SYN,ACK was sent.
901 tp->snd_up = tp->snd_una;
902 tp->snd_max = tp->snd_nxt = tp->iss + 1;
903 tp->last_ack_sent = tp->rcv_nxt;
905 * XXX possible bug - it doesn't appear that tp->snd_wnd is unscaled
906 * until the _second_ ACK is received:
907 * rcv SYN (set wscale opts) --> send SYN/ACK, set snd_wnd = window.
908 * rcv ACK, calculate tiwin --> process SYN_RECEIVED, determine wscale,
909 * move to ESTAB, set snd_wnd to tiwin.
911 tp->snd_wnd = tiwin; /* unscaled */
914 if (thflags & TH_RST) {
915 syncache_chkrst(&inc, th);
918 if (thflags & TH_ACK) {
919 syncache_badack(&inc);
920 tcpstat.tcps_badsyn++;
921 rstreason = BANDLIM_RST_OPENPORT;
928 * Segment's flags are (SYN) or (SYN | FIN).
932 * If deprecated address is forbidden,
933 * we do not accept SYN to deprecated interface
934 * address to prevent any new inbound connection from
935 * getting established.
936 * When we do not accept SYN, we send a TCP RST,
937 * with deprecated source address (instead of dropping
938 * it). We compromise it as it is much better for peer
939 * to send a RST, and RST will be the final packet
942 * If we do not forbid deprecated addresses, we accept
943 * the SYN packet. RFC2462 does not suggest dropping
945 * If we decipher RFC2462 5.5.4, it says like this:
946 * 1. use of deprecated addr with existing
947 * communication is okay - "SHOULD continue to be
949 * 2. use of it with new communication:
950 * (2a) "SHOULD NOT be used if alternate address
951 * with sufficient scope is available"
952 * (2b) nothing mentioned otherwise.
953 * Here we fall into (2b) case as we have no choice in
954 * our source address selection - we must obey the peer.
956 * The wording in RFC2462 is confusing, and there are
957 * multiple description text for deprecated address
958 * handling - worse, they are not exactly the same.
959 * I believe 5.5.4 is the best one, so we follow 5.5.4.
961 if (isipv6 && !ip6_use_deprecated) {
962 struct in6_ifaddr *ia6;
964 if ((ia6 = ip6_getdstifaddr(m)) &&
965 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
967 rstreason = BANDLIM_RST_OPENPORT;
973 * If it is from this socket, drop it, it must be forged.
974 * Don't bother responding if the destination was a broadcast.
976 if (th->th_dport == th->th_sport) {
978 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst,
982 if (ip->ip_dst.s_addr == ip->ip_src.s_addr)
987 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN
989 * Note that it is quite possible to receive unicast
990 * link-layer packets with a broadcast IP address. Use
991 * in_broadcast() to find them.
993 if (m->m_flags & (M_BCAST | M_MCAST))
996 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
997 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
1000 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
1001 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
1002 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
1003 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
1007 * SYN appears to be valid; create compressed TCP state
1008 * for syncache, or perform t/tcp connection.
1010 if (so->so_qlen <= so->so_qlimit) {
1011 tcp_dooptions(&to, optp, optlen, TRUE);
1012 if (!syncache_add(&inc, &to, th, &so, m))
1016 * Entry added to syncache, mbuf used to
1017 * send SYN,ACK packet.
1021 * Segment passed TAO tests.
1023 inp = sotoinpcb(so);
1024 tp = intotcpcb(inp);
1025 tp->snd_wnd = tiwin;
1026 tp->t_starttime = ticks;
1027 tp->t_state = TCPS_ESTABLISHED;
1030 * If there is a FIN, or if there is data and the
1031 * connection is local, then delay SYN,ACK(SYN) in
1032 * the hope of piggy-backing it on a response
1033 * segment. Otherwise must send ACK now in case
1034 * the other side is slow starting.
1036 if (DELAY_ACK(tp) &&
1037 ((thflags & TH_FIN) ||
1039 ((isipv6 && in6_localaddr(&inp->in6p_faddr)) ||
1040 (!isipv6 && in_localaddr(inp->inp_faddr)))))) {
1041 callout_reset(tp->tt_delack, tcp_delacktime,
1042 tcp_timer_delack, tp);
1043 tp->t_flags |= TF_NEEDSYN;
1045 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN);
1047 tcpstat.tcps_connects++;
1055 /* should not happen - syncache should pick up these connections */
1056 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN state"));
1059 * Segment received on connection.
1060 * Reset idle time and keep-alive timer.
1062 tp->t_rcvtime = ticks;
1063 if (TCPS_HAVEESTABLISHED(tp->t_state))
1064 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp);
1068 * XXX this is tradtitional behavior, may need to be cleaned up.
1070 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0);
1071 if (thflags & TH_SYN) {
1072 if (to.to_flags & TOF_SCALE) {
1073 tp->t_flags |= TF_RCVD_SCALE;
1074 tp->requested_s_scale = to.to_requested_s_scale;
1076 if (to.to_flags & TOF_TS) {
1077 tp->t_flags |= TF_RCVD_TSTMP;
1078 tp->ts_recent = to.to_tsval;
1079 tp->ts_recent_age = ticks;
1081 if (to.to_flags & (TOF_CC | TOF_CCNEW))
1082 tp->t_flags |= TF_RCVD_CC;
1083 if (to.to_flags & TOF_MSS)
1084 tcp_mss(tp, to.to_mss);
1086 * Only set the TF_SACK_PERMITTED per-connection flag
1087 * if we got a SACK_PERMITTED option from the other side
1088 * and the global tcp_do_sack variable is true.
1090 if (tcp_do_sack && (to.to_flags & TOF_SACK_PERMITTED))
1091 tp->t_flags |= TF_SACK_PERMITTED;
1095 * Header prediction: check for the two common cases
1096 * of a uni-directional data xfer. If the packet has
1097 * no control flags, is in-sequence, the window didn't
1098 * change and we're not retransmitting, it's a
1099 * candidate. If the length is zero and the ack moved
1100 * forward, we're the sender side of the xfer. Just
1101 * free the data acked & wake any higher level process
1102 * that was blocked waiting for space. If the length
1103 * is non-zero and the ack didn't move, we're the
1104 * receiver side. If we're getting packets in-order
1105 * (the reassembly queue is empty), add the data to
1106 * the socket buffer and note that we need a delayed ack.
1107 * Make sure that the hidden state-flags are also off.
1108 * Since we check for TCPS_ESTABLISHED above, it can only
1111 if (tp->t_state == TCPS_ESTABLISHED &&
1112 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
1113 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) &&
1114 (!(to.to_flags & TOF_TS) ||
1115 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) &&
1117 * Using the CC option is compulsory if once started:
1118 * the segment is OK if no T/TCP was negotiated or
1119 * if the segment has a CC option equal to CCrecv
1121 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) ||
1122 ((to.to_flags & TOF_CC) && to.to_cc == tp->cc_recv)) &&
1123 th->th_seq == tp->rcv_nxt &&
1124 tp->snd_nxt == tp->snd_max) {
1127 * If last ACK falls within this segment's sequence numbers,
1128 * record the timestamp.
1129 * NOTE that the test is modified according to the latest
1130 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1132 if ((to.to_flags & TOF_TS) &&
1133 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
1134 tp->ts_recent_age = ticks;
1135 tp->ts_recent = to.to_tsval;
1139 if (SEQ_GT(th->th_ack, tp->snd_una) &&
1140 SEQ_LEQ(th->th_ack, tp->snd_max) &&
1141 tp->snd_cwnd >= tp->snd_wnd &&
1142 !IN_FASTRECOVERY(tp)) {
1144 * this is a pure ack for outstanding data.
1146 ++tcpstat.tcps_predack;
1148 * "bad retransmit" recovery
1150 * If Eifel detection applies, then
1151 * it is deterministic, so use it
1152 * unconditionally over the old heuristic.
1153 * Otherwise, fall back to the old heuristic.
1155 if (tcp_do_eifel_detect &&
1156 (to.to_flags & TOF_TS) && to.to_tsecr &&
1157 (tp->t_flags & TF_FIRSTACCACK)) {
1158 /* Eifel detection applicable. */
1159 if (to.to_tsecr < tp->t_rexmtTS) {
1160 tcp_revert_congestion_state(tp);
1161 ++tcpstat.tcps_eifeldetected;
1163 } else if (tp->t_rxtshift == 1 &&
1164 ticks < tp->t_badrxtwin) {
1165 tcp_revert_congestion_state(tp);
1166 ++tcpstat.tcps_rttdetected;
1168 tp->t_flags &= ~(TF_FIRSTACCACK |
1169 TF_FASTREXMT | TF_EARLYREXMT);
1171 * Recalculate the retransmit timer / rtt.
1173 * Some machines (certain windows boxes)
1174 * send broken timestamp replies during the
1175 * SYN+ACK phase, ignore timestamps of 0.
1177 if ((to.to_flags & TOF_TS) && to.to_tsecr) {
1179 ticks - to.to_tsecr + 1);
1180 } else if (tp->t_rtttime &&
1181 SEQ_GT(th->th_ack, tp->t_rtseq)) {
1183 ticks - tp->t_rtttime);
1185 tcp_xmit_bandwidth_limit(tp, th->th_ack);
1186 acked = th->th_ack - tp->snd_una;
1187 tcpstat.tcps_rcvackpack++;
1188 tcpstat.tcps_rcvackbyte += acked;
1189 sbdrop(&so->so_snd, acked);
1190 tp->snd_recover = th->th_ack - 1;
1191 tp->snd_una = th->th_ack;
1194 * Update window information.
1196 if (tiwin != tp->snd_wnd &&
1197 acceptable_window_update(tp, th, tiwin)) {
1198 /* keep track of pure window updates */
1199 if (tp->snd_wl2 == th->th_ack &&
1200 tiwin > tp->snd_wnd)
1201 tcpstat.tcps_rcvwinupd++;
1202 tp->snd_wnd = tiwin;
1203 tp->snd_wl1 = th->th_seq;
1204 tp->snd_wl2 = th->th_ack;
1205 if (tp->snd_wnd > tp->max_sndwnd)
1206 tp->max_sndwnd = tp->snd_wnd;
1209 ND6_HINT(tp); /* some progress has been done */
1211 * If all outstanding data are acked, stop
1212 * retransmit timer, otherwise restart timer
1213 * using current (possibly backed-off) value.
1214 * If process is waiting for space,
1215 * wakeup/selwakeup/signal. If data
1216 * are ready to send, let tcp_output
1217 * decide between more output or persist.
1219 if (tp->snd_una == tp->snd_max)
1220 callout_stop(tp->tt_rexmt);
1221 else if (!callout_active(tp->tt_persist))
1222 callout_reset(tp->tt_rexmt,
1224 tcp_timer_rexmt, tp);
1227 if (so->so_snd.sb_cc)
1228 (void) tcp_output(tp);
1231 } else if (tiwin == tp->snd_wnd &&
1232 th->th_ack == tp->snd_una &&
1233 LIST_EMPTY(&tp->t_segq) &&
1234 tlen <= sbspace(&so->so_rcv)) {
1236 * this is a pure, in-sequence data packet
1237 * with nothing on the reassembly queue and
1238 * we have enough buffer space to take it.
1240 ++tcpstat.tcps_preddat;
1241 tp->rcv_nxt += tlen;
1242 tcpstat.tcps_rcvpack++;
1243 tcpstat.tcps_rcvbyte += tlen;
1244 ND6_HINT(tp); /* some progress has been done */
1246 * Add data to socket buffer.
1248 if (so->so_state & SS_CANTRCVMORE) {
1251 m_adj(m, drop_hdrlen); /* delayed header drop */
1252 sbappend(&so->so_rcv, m);
1257 * This code is responsible for most of the ACKs
1258 * the TCP stack sends back after receiving a data
1259 * packet. Note that the DELAY_ACK check fails if
1260 * the delack timer is already running, which results
1261 * in an ack being sent every other packet (which is
1264 if (DELAY_ACK(tp)) {
1265 callout_reset(tp->tt_delack, tcp_delacktime,
1266 tcp_timer_delack, tp);
1268 tp->t_flags |= TF_ACKNOW;
1269 if (!(tp->t_flags & TF_ONOUTPUTQ)) {
1270 tp->t_flags |= TF_ONOUTPUTQ;
1271 tp->tt_cpu = mycpu->gd_cpuid;
1273 &tcpcbackq[tp->tt_cpu],
1282 * Calculate amount of space in receive window,
1283 * and then do TCP input processing.
1284 * Receive window is amount of space in rcv queue,
1285 * but not less than advertised window.
1287 recvwin = sbspace(&so->so_rcv);
1290 tp->rcv_wnd = imax(recvwin, (int)(tp->rcv_adv - tp->rcv_nxt));
1292 switch (tp->t_state) {
1294 * If the state is SYN_RECEIVED:
1295 * if seg contains an ACK, but not for our SYN/ACK, send a RST.
1297 case TCPS_SYN_RECEIVED:
1298 if ((thflags & TH_ACK) &&
1299 (SEQ_LEQ(th->th_ack, tp->snd_una) ||
1300 SEQ_GT(th->th_ack, tp->snd_max))) {
1301 rstreason = BANDLIM_RST_OPENPORT;
1307 * If the state is SYN_SENT:
1308 * if seg contains an ACK, but not for our SYN, drop the input.
1309 * if seg contains a RST, then drop the connection.
1310 * if seg does not contain SYN, then drop it.
1311 * Otherwise this is an acceptable SYN segment
1312 * initialize tp->rcv_nxt and tp->irs
1313 * if seg contains ack then advance tp->snd_una
1314 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state
1315 * arrange for segment to be acked (eventually)
1316 * continue processing rest of data/controls, beginning with URG
1319 if ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL) {
1320 taop = &tao_noncached;
1321 bzero(taop, sizeof(*taop));
1324 if ((thflags & TH_ACK) &&
1325 (SEQ_LEQ(th->th_ack, tp->iss) ||
1326 SEQ_GT(th->th_ack, tp->snd_max))) {
1328 * If we have a cached CCsent for the remote host,
1329 * hence we haven't just crashed and restarted,
1330 * do not send a RST. This may be a retransmission
1331 * from the other side after our earlier ACK was lost.
1332 * Our new SYN, when it arrives, will serve as the
1335 if (taop->tao_ccsent != 0)
1338 rstreason = BANDLIM_UNLIMITED;
1342 if (thflags & TH_RST) {
1343 if (thflags & TH_ACK)
1344 tp = tcp_drop(tp, ECONNREFUSED);
1347 if (!(thflags & TH_SYN))
1349 tp->snd_wnd = th->th_win; /* initial send window */
1350 tp->cc_recv = to.to_cc; /* foreign CC */
1352 tp->irs = th->th_seq;
1354 if (thflags & TH_ACK) {
1356 * Our SYN was acked. If segment contains CC.ECHO
1357 * option, check it to make sure this segment really
1358 * matches our SYN. If not, just drop it as old
1359 * duplicate, but send an RST if we're still playing
1360 * by the old rules. If no CC.ECHO option, make sure
1361 * we don't get fooled into using T/TCP.
1363 if (to.to_flags & TOF_CCECHO) {
1364 if (tp->cc_send != to.to_ccecho) {
1365 if (taop->tao_ccsent != 0)
1368 rstreason = BANDLIM_UNLIMITED;
1373 tp->t_flags &= ~TF_RCVD_CC;
1374 tcpstat.tcps_connects++;
1376 /* Do window scaling on this connection? */
1377 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) ==
1378 (TF_RCVD_SCALE | TF_REQ_SCALE)) {
1379 tp->snd_scale = tp->requested_s_scale;
1380 tp->rcv_scale = tp->request_r_scale;
1382 /* Segment is acceptable, update cache if undefined. */
1383 if (taop->tao_ccsent == 0)
1384 taop->tao_ccsent = to.to_ccecho;
1386 tp->rcv_adv += tp->rcv_wnd;
1387 tp->snd_una++; /* SYN is acked */
1388 callout_stop(tp->tt_rexmt);
1390 * If there's data, delay ACK; if there's also a FIN
1391 * ACKNOW will be turned on later.
1393 if (DELAY_ACK(tp) && tlen != 0)
1394 callout_reset(tp->tt_delack, tcp_delacktime,
1395 tcp_timer_delack, tp);
1397 tp->t_flags |= TF_ACKNOW;
1399 * Received <SYN,ACK> in SYN_SENT[*] state.
1401 * SYN_SENT --> ESTABLISHED
1402 * SYN_SENT* --> FIN_WAIT_1
1404 tp->t_starttime = ticks;
1405 if (tp->t_flags & TF_NEEDFIN) {
1406 tp->t_state = TCPS_FIN_WAIT_1;
1407 tp->t_flags &= ~TF_NEEDFIN;
1410 tp->t_state = TCPS_ESTABLISHED;
1411 callout_reset(tp->tt_keep, tcp_keepidle,
1412 tcp_timer_keep, tp);
1416 * Received initial SYN in SYN-SENT[*] state =>
1417 * simultaneous open. If segment contains CC option
1418 * and there is a cached CC, apply TAO test.
1419 * If it succeeds, connection is * half-synchronized.
1420 * Otherwise, do 3-way handshake:
1421 * SYN-SENT -> SYN-RECEIVED
1422 * SYN-SENT* -> SYN-RECEIVED*
1423 * If there was no CC option, clear cached CC value.
1425 tp->t_flags |= TF_ACKNOW;
1426 callout_stop(tp->tt_rexmt);
1427 if (to.to_flags & TOF_CC) {
1428 if (taop->tao_cc != 0 &&
1429 CC_GT(to.to_cc, taop->tao_cc)) {
1431 * update cache and make transition:
1432 * SYN-SENT -> ESTABLISHED*
1433 * SYN-SENT* -> FIN-WAIT-1*
1435 taop->tao_cc = to.to_cc;
1436 tp->t_starttime = ticks;
1437 if (tp->t_flags & TF_NEEDFIN) {
1438 tp->t_state = TCPS_FIN_WAIT_1;
1439 tp->t_flags &= ~TF_NEEDFIN;
1441 tp->t_state = TCPS_ESTABLISHED;
1442 callout_reset(tp->tt_keep,
1447 tp->t_flags |= TF_NEEDSYN;
1449 tp->t_state = TCPS_SYN_RECEIVED;
1451 /* CC.NEW or no option => invalidate cache */
1453 tp->t_state = TCPS_SYN_RECEIVED;
1459 * Advance th->th_seq to correspond to first data byte.
1460 * If data, trim to stay within window,
1461 * dropping FIN if necessary.
1464 if (tlen > tp->rcv_wnd) {
1465 todrop = tlen - tp->rcv_wnd;
1469 tcpstat.tcps_rcvpackafterwin++;
1470 tcpstat.tcps_rcvbyteafterwin += todrop;
1472 tp->snd_wl1 = th->th_seq - 1;
1473 tp->rcv_up = th->th_seq;
1475 * Client side of transaction: already sent SYN and data.
1476 * If the remote host used T/TCP to validate the SYN,
1477 * our data will be ACK'd; if so, enter normal data segment
1478 * processing in the middle of step 5, ack processing.
1479 * Otherwise, goto step 6.
1481 if (thflags & TH_ACK)
1487 * If the state is LAST_ACK or CLOSING or TIME_WAIT:
1488 * if segment contains a SYN and CC [not CC.NEW] option:
1489 * if state == TIME_WAIT and connection duration > MSL,
1490 * drop packet and send RST;
1492 * if SEG.CC > CCrecv then is new SYN, and can implicitly
1493 * ack the FIN (and data) in retransmission queue.
1494 * Complete close and delete TCPCB. Then reprocess
1495 * segment, hoping to find new TCPCB in LISTEN state;
1497 * else must be old SYN; drop it.
1498 * else do normal processing.
1502 case TCPS_TIME_WAIT:
1503 if ((thflags & TH_SYN) &&
1504 (to.to_flags & TOF_CC) && tp->cc_recv != 0) {
1505 if (tp->t_state == TCPS_TIME_WAIT &&
1506 (ticks - tp->t_starttime) > tcp_msl) {
1507 rstreason = BANDLIM_UNLIMITED;
1510 if (CC_GT(to.to_cc, tp->cc_recv)) {
1517 break; /* continue normal processing */
1521 * States other than LISTEN or SYN_SENT.
1522 * First check the RST flag and sequence number since reset segments
1523 * are exempt from the timestamp and connection count tests. This
1524 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix
1525 * below which allowed reset segments in half the sequence space
1526 * to fall though and be processed (which gives forged reset
1527 * segments with a random sequence number a 50 percent chance of
1528 * killing a connection).
1529 * Then check timestamp, if present.
1530 * Then check the connection count, if present.
1531 * Then check that at least some bytes of segment are within
1532 * receive window. If segment begins before rcv_nxt,
1533 * drop leading data (and SYN); if nothing left, just ack.
1536 * If the RST bit is set, check the sequence number to see
1537 * if this is a valid reset segment.
1539 * In all states except SYN-SENT, all reset (RST) segments
1540 * are validated by checking their SEQ-fields. A reset is
1541 * valid if its sequence number is in the window.
1542 * Note: this does not take into account delayed ACKs, so
1543 * we should test against last_ack_sent instead of rcv_nxt.
1544 * The sequence number in the reset segment is normally an
1545 * echo of our outgoing acknowledgement numbers, but some hosts
1546 * send a reset with the sequence number at the rightmost edge
1547 * of our receive window, and we have to handle this case.
1548 * If we have multiple segments in flight, the intial reset
1549 * segment sequence numbers will be to the left of last_ack_sent,
1550 * but they will eventually catch up.
1551 * In any case, it never made sense to trim reset segments to
1552 * fit the receive window since RFC 1122 says:
1553 * 4.2.2.12 RST Segment: RFC-793 Section 3.4
1555 * A TCP SHOULD allow a received RST segment to include data.
1558 * It has been suggested that a RST segment could contain
1559 * ASCII text that encoded and explained the cause of the
1560 * RST. No standard has yet been established for such
1563 * If the reset segment passes the sequence number test examine
1565 * SYN_RECEIVED STATE:
1566 * If passive open, return to LISTEN state.
1567 * If active open, inform user that connection was refused.
1568 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES:
1569 * Inform user that connection was reset, and close tcb.
1570 * CLOSING, LAST_ACK STATES:
1573 * Drop the segment - see Stevens, vol. 2, p. 964 and
1576 if (thflags & TH_RST) {
1577 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
1578 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) {
1579 switch (tp->t_state) {
1581 case TCPS_SYN_RECEIVED:
1582 so->so_error = ECONNREFUSED;
1585 case TCPS_ESTABLISHED:
1586 case TCPS_FIN_WAIT_1:
1587 case TCPS_FIN_WAIT_2:
1588 case TCPS_CLOSE_WAIT:
1589 so->so_error = ECONNRESET;
1591 tp->t_state = TCPS_CLOSED;
1592 tcpstat.tcps_drops++;
1601 case TCPS_TIME_WAIT:
1609 * RFC 1323 PAWS: If we have a timestamp reply on this segment
1610 * and it's less than ts_recent, drop it.
1612 if ((to.to_flags & TOF_TS) && tp->ts_recent != 0 &&
1613 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
1615 /* Check to see if ts_recent is over 24 days old. */
1616 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) {
1618 * Invalidate ts_recent. If this segment updates
1619 * ts_recent, the age will be reset later and ts_recent
1620 * will get a valid value. If it does not, setting
1621 * ts_recent to zero will at least satisfy the
1622 * requirement that zero be placed in the timestamp
1623 * echo reply when ts_recent isn't valid. The
1624 * age isn't reset until we get a valid ts_recent
1625 * because we don't want out-of-order segments to be
1626 * dropped when ts_recent is old.
1630 tcpstat.tcps_rcvduppack++;
1631 tcpstat.tcps_rcvdupbyte += tlen;
1632 tcpstat.tcps_pawsdrop++;
1641 * If T/TCP was negotiated and the segment doesn't have CC,
1642 * or if its CC is wrong then drop the segment.
1643 * RST segments do not have to comply with this.
1645 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) &&
1646 (!(to.to_flags & TOF_CC) || tp->cc_recv != to.to_cc))
1650 * In the SYN-RECEIVED state, validate that the packet belongs to
1651 * this connection before trimming the data to fit the receive
1652 * window. Check the sequence number versus IRS since we know
1653 * the sequence numbers haven't wrapped. This is a partial fix
1654 * for the "LAND" DoS attack.
1656 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) {
1657 rstreason = BANDLIM_RST_OPENPORT;
1661 todrop = tp->rcv_nxt - th->th_seq;
1663 if (TCP_DO_SACK(tp)) {
1664 /* Report duplicate segment at head of packet. */
1665 tp->reportblk.rblk_start = th->th_seq;
1666 tp->reportblk.rblk_end = th->th_seq + tlen;
1667 if (thflags & TH_FIN)
1668 ++tp->reportblk.rblk_end;
1669 if (SEQ_GT(tp->reportblk.rblk_end, tp->rcv_nxt))
1670 tp->reportblk.rblk_end = tp->rcv_nxt;
1671 tp->t_flags |= (TF_DUPSEG | TF_SACKLEFT | TF_ACKNOW);
1673 if (thflags & TH_SYN) {
1683 * Following if statement from Stevens, vol. 2, p. 960.
1685 if (todrop > tlen ||
1686 (todrop == tlen && !(thflags & TH_FIN))) {
1688 * Any valid FIN must be to the left of the window.
1689 * At this point the FIN must be a duplicate or out
1690 * of sequence; drop it.
1695 * Send an ACK to resynchronize and drop any data.
1696 * But keep on processing for RST or ACK.
1698 tp->t_flags |= TF_ACKNOW;
1700 tcpstat.tcps_rcvduppack++;
1701 tcpstat.tcps_rcvdupbyte += todrop;
1703 tcpstat.tcps_rcvpartduppack++;
1704 tcpstat.tcps_rcvpartdupbyte += todrop;
1706 drop_hdrlen += todrop; /* drop from the top afterwards */
1707 th->th_seq += todrop;
1709 if (th->th_urp > todrop)
1710 th->th_urp -= todrop;
1718 * If new data are received on a connection after the
1719 * user processes are gone, then RST the other end.
1721 if ((so->so_state & SS_NOFDREF) &&
1722 tp->t_state > TCPS_CLOSE_WAIT && tlen) {
1724 tcpstat.tcps_rcvafterclose++;
1725 rstreason = BANDLIM_UNLIMITED;
1730 * If segment ends after window, drop trailing data
1731 * (and PUSH and FIN); if nothing left, just ACK.
1733 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd);
1735 tcpstat.tcps_rcvpackafterwin++;
1736 if (todrop >= tlen) {
1737 tcpstat.tcps_rcvbyteafterwin += tlen;
1739 * If a new connection request is received
1740 * while in TIME_WAIT, drop the old connection
1741 * and start over if the sequence numbers
1742 * are above the previous ones.
1744 if (thflags & TH_SYN &&
1745 tp->t_state == TCPS_TIME_WAIT &&
1746 SEQ_GT(th->th_seq, tp->rcv_nxt)) {
1751 * If window is closed can only take segments at
1752 * window edge, and have to drop data and PUSH from
1753 * incoming segments. Continue processing, but
1754 * remember to ack. Otherwise, drop segment
1757 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
1758 tp->t_flags |= TF_ACKNOW;
1759 tcpstat.tcps_rcvwinprobe++;
1763 tcpstat.tcps_rcvbyteafterwin += todrop;
1766 thflags &= ~(TH_PUSH | TH_FIN);
1770 * If last ACK falls within this segment's sequence numbers,
1771 * record its timestamp.
1772 * NOTE that the test is modified according to the latest
1773 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1775 if ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
1776 tp->ts_recent_age = ticks;
1777 tp->ts_recent = to.to_tsval;
1781 * If a SYN is in the window, then this is an
1782 * error and we send an RST and drop the connection.
1784 if (thflags & TH_SYN) {
1785 tp = tcp_drop(tp, ECONNRESET);
1786 rstreason = BANDLIM_UNLIMITED;
1791 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN
1792 * flag is on (half-synchronized state), then queue data for
1793 * later processing; else drop segment and return.
1795 if (!(thflags & TH_ACK)) {
1796 if (tp->t_state == TCPS_SYN_RECEIVED ||
1797 (tp->t_flags & TF_NEEDSYN))
1806 switch (tp->t_state) {
1808 * In SYN_RECEIVED state, the ACK acknowledges our SYN, so enter
1809 * ESTABLISHED state and continue processing.
1810 * The ACK was checked above.
1812 case TCPS_SYN_RECEIVED:
1814 tcpstat.tcps_connects++;
1816 /* Do window scaling? */
1817 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) ==
1818 (TF_RCVD_SCALE | TF_REQ_SCALE)) {
1819 tp->snd_scale = tp->requested_s_scale;
1820 tp->rcv_scale = tp->request_r_scale;
1823 * Upon successful completion of 3-way handshake,
1824 * update cache.CC if it was undefined, pass any queued
1825 * data to the user, and advance state appropriately.
1827 if ((taop = tcp_gettaocache(&inp->inp_inc)) != NULL &&
1829 taop->tao_cc = tp->cc_recv;
1833 * SYN-RECEIVED -> ESTABLISHED
1834 * SYN-RECEIVED* -> FIN-WAIT-1
1836 tp->t_starttime = ticks;
1837 if (tp->t_flags & TF_NEEDFIN) {
1838 tp->t_state = TCPS_FIN_WAIT_1;
1839 tp->t_flags &= ~TF_NEEDFIN;
1841 tp->t_state = TCPS_ESTABLISHED;
1842 callout_reset(tp->tt_keep, tcp_keepidle,
1843 tcp_timer_keep, tp);
1846 * If segment contains data or ACK, will call tcp_reass()
1847 * later; if not, do so now to pass queued data to user.
1849 if (tlen == 0 && !(thflags & TH_FIN))
1850 (void) tcp_reass(tp, NULL, NULL, NULL);
1854 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
1855 * ACKs. If the ack is in the range
1856 * tp->snd_una < th->th_ack <= tp->snd_max
1857 * then advance tp->snd_una to th->th_ack and drop
1858 * data from the retransmission queue. If this ACK reflects
1859 * more up to date window information we update our window information.
1861 case TCPS_ESTABLISHED:
1862 case TCPS_FIN_WAIT_1:
1863 case TCPS_FIN_WAIT_2:
1864 case TCPS_CLOSE_WAIT:
1867 case TCPS_TIME_WAIT:
1869 if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
1870 if (TCP_DO_SACK(tp))
1871 tcp_sack_update_scoreboard(tp, &to);
1872 if (tlen != 0 || tiwin != tp->snd_wnd) {
1876 tcpstat.tcps_rcvdupack++;
1877 if (!callout_active(tp->tt_rexmt) ||
1878 th->th_ack != tp->snd_una) {
1883 * We have outstanding data (other than
1884 * a window probe), this is a completely
1885 * duplicate ack (ie, window info didn't
1886 * change), the ack is the biggest we've
1887 * seen and we've seen exactly our rexmt
1888 * threshhold of them, so assume a packet
1889 * has been dropped and retransmit it.
1890 * Kludge snd_nxt & the congestion
1891 * window so we send only this one
1894 if (IN_FASTRECOVERY(tp)) {
1895 if (TCP_DO_SACK(tp)) {
1896 /* No artifical cwnd inflation. */
1897 tcp_sack_rexmt(tp, th);
1900 * Dup acks mean that packets
1901 * have left the network
1902 * (they're now cached at the
1903 * receiver) so bump cwnd by
1904 * the amount in the receiver
1905 * to keep a constant cwnd
1906 * packets in the network.
1908 tp->snd_cwnd += tp->t_maxseg;
1909 (void) tcp_output(tp);
1911 } else if (SEQ_LT(th->th_ack, tp->snd_recover)) {
1914 } else if (++tp->t_dupacks == tcprexmtthresh) {
1915 tcp_seq old_snd_nxt;
1919 if (tcp_do_eifel_detect &&
1920 (tp->t_flags & TF_RCVD_TSTMP)) {
1921 tcp_save_congestion_state(tp);
1922 tp->t_flags |= TF_FASTREXMT;
1925 * We know we're losing at the current
1926 * window size, so do congestion avoidance:
1927 * set ssthresh to half the current window
1928 * and pull our congestion window back to the
1931 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 /
1935 tp->snd_ssthresh = win * tp->t_maxseg;
1936 ENTER_FASTRECOVERY(tp);
1937 tp->snd_recover = tp->snd_max;
1938 callout_stop(tp->tt_rexmt);
1940 old_snd_nxt = tp->snd_nxt;
1941 tp->snd_nxt = th->th_ack;
1942 tp->snd_cwnd = tp->t_maxseg;
1943 (void) tcp_output(tp);
1944 ++tcpstat.tcps_sndfastrexmit;
1945 tp->snd_cwnd = tp->snd_ssthresh;
1946 tp->rexmt_high = tp->snd_nxt;
1947 if (SEQ_GT(old_snd_nxt, tp->snd_nxt))
1948 tp->snd_nxt = old_snd_nxt;
1949 KASSERT(tp->snd_limited <= 2,
1950 ("tp->snd_limited too big"));
1951 if (TCP_DO_SACK(tp))
1952 tcp_sack_rexmt(tp, th);
1954 tp->snd_cwnd += tp->t_maxseg *
1955 (tp->t_dupacks - tp->snd_limited);
1956 } else if (tcp_do_limitedtransmit) {
1957 u_long oldcwnd = tp->snd_cwnd;
1958 tcp_seq oldsndmax = tp->snd_max;
1959 /* outstanding data */
1960 uint32_t ownd = tp->snd_max - tp->snd_una;
1963 #define iceildiv(n, d) (((n)+(d)-1) / (d))
1965 KASSERT(tp->t_dupacks == 1 ||
1967 ("dupacks not 1 or 2"));
1968 if (tp->t_dupacks == 1)
1969 tp->snd_limited = 0;
1970 tp->snd_cwnd = ownd +
1971 (tp->t_dupacks - tp->snd_limited) *
1973 (void) tcp_output(tp);
1974 tp->snd_cwnd = oldcwnd;
1975 sent = tp->snd_max - oldsndmax;
1976 if (sent > tp->t_maxseg) {
1977 KASSERT((tp->t_dupacks == 2 &&
1978 tp->snd_limited == 0) ||
1979 (sent == tp->t_maxseg + 1 &&
1980 tp->t_flags & TF_SENTFIN),
1982 KASSERT(sent <= tp->t_maxseg * 2,
1983 ("sent too many segments"));
1984 tp->snd_limited = 2;
1985 tcpstat.tcps_sndlimited += 2;
1986 } else if (sent > 0) {
1988 ++tcpstat.tcps_sndlimited;
1989 } else if (tcp_do_early_retransmit &&
1990 (tcp_do_eifel_detect &&
1991 (tp->t_flags & TF_RCVD_TSTMP)) &&
1992 ownd < 4 * tp->t_maxseg &&
1993 tp->t_dupacks + 1 >=
1994 iceildiv(ownd, tp->t_maxseg) &&
1995 (!TCP_DO_SACK(tp) ||
1996 ownd <= tp->t_maxseg ||
1997 tcp_sack_has_sacked(&tp->scb,
1998 ownd - tp->t_maxseg))) {
1999 ++tcpstat.tcps_sndearlyrexmit;
2000 tp->t_flags |= TF_EARLYREXMT;
2001 goto fastretransmit;
2007 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una"));
2009 if (SEQ_GT(th->th_ack, tp->snd_max)) {
2011 * Detected optimistic ACK attack.
2012 * Force slow-start to de-synchronize attack.
2014 tp->snd_cwnd = tp->t_maxseg;
2016 tcpstat.tcps_rcvacktoomuch++;
2020 * If we reach this point, ACK is not a duplicate,
2021 * i.e., it ACKs something we sent.
2023 if (tp->t_flags & TF_NEEDSYN) {
2025 * T/TCP: Connection was half-synchronized, and our
2026 * SYN has been ACK'd (so connection is now fully
2027 * synchronized). Go to non-starred state,
2028 * increment snd_una for ACK of SYN, and check if
2029 * we can do window scaling.
2031 tp->t_flags &= ~TF_NEEDSYN;
2033 /* Do window scaling? */
2034 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) ==
2035 (TF_RCVD_SCALE | TF_REQ_SCALE)) {
2036 tp->snd_scale = tp->requested_s_scale;
2037 tp->rcv_scale = tp->request_r_scale;
2042 acked = th->th_ack - tp->snd_una;
2043 tcpstat.tcps_rcvackpack++;
2044 tcpstat.tcps_rcvackbyte += acked;
2046 if (tcp_do_eifel_detect && acked > 0 &&
2047 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) &&
2048 (tp->t_flags & TF_FIRSTACCACK)) {
2049 /* Eifel detection applicable. */
2050 if (to.to_tsecr < tp->t_rexmtTS) {
2051 ++tcpstat.tcps_eifeldetected;
2052 tcp_revert_congestion_state(tp);
2053 if (tp->t_rxtshift == 1 &&
2054 ticks >= tp->t_badrxtwin)
2055 ++tcpstat.tcps_rttcantdetect;
2057 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) {
2059 * If we just performed our first retransmit,
2060 * and the ACK arrives within our recovery window,
2061 * then it was a mistake to do the retransmit
2062 * in the first place. Recover our original cwnd
2063 * and ssthresh, and proceed to transmit where we
2066 tcp_revert_congestion_state(tp);
2067 ++tcpstat.tcps_rttdetected;
2071 * If we have a timestamp reply, update smoothed
2072 * round trip time. If no timestamp is present but
2073 * transmit timer is running and timed sequence
2074 * number was acked, update smoothed round trip time.
2075 * Since we now have an rtt measurement, cancel the
2076 * timer backoff (cf., Phil Karn's retransmit alg.).
2077 * Recompute the initial retransmit timer.
2079 * Some machines (certain windows boxes) send broken
2080 * timestamp replies during the SYN+ACK phase, ignore
2083 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0))
2084 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1);
2085 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq))
2086 tcp_xmit_timer(tp, ticks - tp->t_rtttime);
2087 tcp_xmit_bandwidth_limit(tp, th->th_ack);
2090 * If no data (only SYN) was ACK'd,
2091 * skip rest of ACK processing.
2096 /* Stop looking for an acceptable ACK since one was received. */
2097 tp->t_flags &= ~(TF_FIRSTACCACK | TF_FASTREXMT | TF_EARLYREXMT);
2099 if (acked > so->so_snd.sb_cc) {
2100 tp->snd_wnd -= so->so_snd.sb_cc;
2101 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc);
2102 ourfinisacked = TRUE;
2104 sbdrop(&so->so_snd, acked);
2105 tp->snd_wnd -= acked;
2106 ourfinisacked = FALSE;
2111 * Update window information.
2112 * Don't look at window if no ACK:
2113 * TAC's send garbage on first SYN.
2115 if (SEQ_LT(tp->snd_wl1, th->th_seq) ||
2116 (tp->snd_wl1 == th->th_seq &&
2117 (SEQ_LT(tp->snd_wl2, th->th_ack) ||
2118 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) {
2119 /* keep track of pure window updates */
2120 if (tlen == 0 && tp->snd_wl2 == th->th_ack &&
2121 tiwin > tp->snd_wnd)
2122 tcpstat.tcps_rcvwinupd++;
2123 tp->snd_wnd = tiwin;
2124 tp->snd_wl1 = th->th_seq;
2125 tp->snd_wl2 = th->th_ack;
2126 if (tp->snd_wnd > tp->max_sndwnd)
2127 tp->max_sndwnd = tp->snd_wnd;
2131 tp->snd_una = th->th_ack;
2132 if (TCP_DO_SACK(tp))
2133 tcp_sack_update_scoreboard(tp, &to);
2134 if (IN_FASTRECOVERY(tp)) {
2135 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) {
2136 EXIT_FASTRECOVERY(tp);
2139 * If the congestion window was inflated
2140 * to account for the other side's
2141 * cached packets, retract it.
2143 * Window inflation should have left us
2144 * with approximately snd_ssthresh outstanding
2145 * data. But, in case we would be inclined
2146 * to send a burst, better do it using
2149 if (!TCP_DO_SACK(tp))
2150 tp->snd_cwnd = tp->snd_ssthresh;
2152 if (SEQ_GT(th->th_ack + tp->snd_cwnd,
2153 tp->snd_max + 2 * tp->t_maxseg))
2155 (tp->snd_max - tp->snd_una) +
2158 if (TCP_DO_SACK(tp)) {
2159 tp->snd_max_rexmt = tp->snd_max;
2160 tcp_sack_rexmt(tp, th);
2162 tcp_newreno_partial_ack(tp, th, acked);
2168 * When new data is acked, open the congestion window.
2169 * If the window gives us less than ssthresh packets
2170 * in flight, open exponentially (maxseg per packet).
2171 * Otherwise open linearly: maxseg per window
2172 * (maxseg^2 / cwnd per packet).
2174 u_int cw = tp->snd_cwnd;
2177 if (cw > tp->snd_ssthresh)
2178 incr = tp->t_maxseg * tp->t_maxseg / cw;
2180 incr = tp->t_maxseg;
2181 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale);
2182 tp->snd_recover = th->th_ack - 1;
2184 if (SEQ_LT(tp->snd_nxt, tp->snd_una))
2185 tp->snd_nxt = tp->snd_una;
2188 * If all outstanding data is acked, stop retransmit
2189 * timer and remember to restart (more output or persist).
2190 * If there is more data to be acked, restart retransmit
2191 * timer, using current (possibly backed-off) value.
2193 if (th->th_ack == tp->snd_max) {
2194 callout_stop(tp->tt_rexmt);
2196 } else if (!callout_active(tp->tt_persist))
2197 callout_reset(tp->tt_rexmt, tp->t_rxtcur,
2198 tcp_timer_rexmt, tp);
2200 switch (tp->t_state) {
2202 * In FIN_WAIT_1 STATE in addition to the processing
2203 * for the ESTABLISHED state if our FIN is now acknowledged
2204 * then enter FIN_WAIT_2.
2206 case TCPS_FIN_WAIT_1:
2207 if (ourfinisacked) {
2209 * If we can't receive any more
2210 * data, then closing user can proceed.
2211 * Starting the timer is contrary to the
2212 * specification, but if we don't get a FIN
2213 * we'll hang forever.
2215 if (so->so_state & SS_CANTRCVMORE) {
2216 soisdisconnected(so);
2217 callout_reset(tp->tt_2msl, tcp_maxidle,
2218 tcp_timer_2msl, tp);
2220 tp->t_state = TCPS_FIN_WAIT_2;
2225 * In CLOSING STATE in addition to the processing for
2226 * the ESTABLISHED state if the ACK acknowledges our FIN
2227 * then enter the TIME-WAIT state, otherwise ignore
2231 if (ourfinisacked) {
2232 tp->t_state = TCPS_TIME_WAIT;
2233 tcp_canceltimers(tp);
2234 /* Shorten TIME_WAIT [RFC-1644, p.28] */
2235 if (tp->cc_recv != 0 &&
2236 (ticks - tp->t_starttime) < tcp_msl)
2237 callout_reset(tp->tt_2msl,
2238 tp->t_rxtcur * TCPTV_TWTRUNC,
2239 tcp_timer_2msl, tp);
2241 callout_reset(tp->tt_2msl, 2 * tcp_msl,
2242 tcp_timer_2msl, tp);
2243 soisdisconnected(so);
2248 * In LAST_ACK, we may still be waiting for data to drain
2249 * and/or to be acked, as well as for the ack of our FIN.
2250 * If our FIN is now acknowledged, delete the TCB,
2251 * enter the closed state and return.
2254 if (ourfinisacked) {
2261 * In TIME_WAIT state the only thing that should arrive
2262 * is a retransmission of the remote FIN. Acknowledge
2263 * it and restart the finack timer.
2265 case TCPS_TIME_WAIT:
2266 callout_reset(tp->tt_2msl, 2 * tcp_msl,
2267 tcp_timer_2msl, tp);
2274 * Update window information.
2275 * Don't look at window if no ACK: TAC's send garbage on first SYN.
2277 if ((thflags & TH_ACK) &&
2278 acceptable_window_update(tp, th, tiwin)) {
2279 /* keep track of pure window updates */
2280 if (tlen == 0 && tp->snd_wl2 == th->th_ack &&
2281 tiwin > tp->snd_wnd)
2282 tcpstat.tcps_rcvwinupd++;
2283 tp->snd_wnd = tiwin;
2284 tp->snd_wl1 = th->th_seq;
2285 tp->snd_wl2 = th->th_ack;
2286 if (tp->snd_wnd > tp->max_sndwnd)
2287 tp->max_sndwnd = tp->snd_wnd;
2292 * Process segments with URG.
2294 if ((thflags & TH_URG) && th->th_urp &&
2295 !TCPS_HAVERCVDFIN(tp->t_state)) {
2297 * This is a kludge, but if we receive and accept
2298 * random urgent pointers, we'll crash in
2299 * soreceive. It's hard to imagine someone
2300 * actually wanting to send this much urgent data.
2302 if (th->th_urp + so->so_rcv.sb_cc > sb_max) {
2303 th->th_urp = 0; /* XXX */
2304 thflags &= ~TH_URG; /* XXX */
2305 goto dodata; /* XXX */
2308 * If this segment advances the known urgent pointer,
2309 * then mark the data stream. This should not happen
2310 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
2311 * a FIN has been received from the remote side.
2312 * In these states we ignore the URG.
2314 * According to RFC961 (Assigned Protocols),
2315 * the urgent pointer points to the last octet
2316 * of urgent data. We continue, however,
2317 * to consider it to indicate the first octet
2318 * of data past the urgent section as the original
2319 * spec states (in one of two places).
2321 if (SEQ_GT(th->th_seq + th->th_urp, tp->rcv_up)) {
2322 tp->rcv_up = th->th_seq + th->th_urp;
2323 so->so_oobmark = so->so_rcv.sb_cc +
2324 (tp->rcv_up - tp->rcv_nxt) - 1;
2325 if (so->so_oobmark == 0)
2326 so->so_state |= SS_RCVATMARK;
2328 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
2331 * Remove out of band data so doesn't get presented to user.
2332 * This can happen independent of advancing the URG pointer,
2333 * but if two URG's are pending at once, some out-of-band
2334 * data may creep in... ick.
2336 if (th->th_urp <= (u_long)tlen &&
2337 !(so->so_options & SO_OOBINLINE)) {
2338 /* hdr drop is delayed */
2339 tcp_pulloutofband(so, th, m, drop_hdrlen);
2343 * If no out of band data is expected,
2344 * pull receive urgent pointer along
2345 * with the receive window.
2347 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
2348 tp->rcv_up = tp->rcv_nxt;
2353 * Process the segment text, merging it into the TCP sequencing queue,
2354 * and arranging for acknowledgment of receipt if necessary.
2355 * This process logically involves adjusting tp->rcv_wnd as data
2356 * is presented to the user (this happens in tcp_usrreq.c,
2357 * case PRU_RCVD). If a FIN has already been received on this
2358 * connection then we just ignore the text.
2360 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) {
2361 m_adj(m, drop_hdrlen); /* delayed header drop */
2363 * Insert segment which includes th into TCP reassembly queue
2364 * with control block tp. Set thflags to whether reassembly now
2365 * includes a segment with FIN. This handles the common case
2366 * inline (segment is the next to be received on an established
2367 * connection, and the queue is empty), avoiding linkage into
2368 * and removal from the queue and repetition of various
2370 * Set DELACK for segments received in order, but ack
2371 * immediately when segments are out of order (so
2372 * fast retransmit can work).
2374 if (th->th_seq == tp->rcv_nxt &&
2375 LIST_EMPTY(&tp->t_segq) &&
2376 TCPS_HAVEESTABLISHED(tp->t_state)) {
2378 callout_reset(tp->tt_delack, tcp_delacktime,
2379 tcp_timer_delack, tp);
2381 tp->t_flags |= TF_ACKNOW;
2382 tp->rcv_nxt += tlen;
2383 thflags = th->th_flags & TH_FIN;
2384 tcpstat.tcps_rcvpack++;
2385 tcpstat.tcps_rcvbyte += tlen;
2387 if (so->so_state & SS_CANTRCVMORE)
2390 sbappend(&so->so_rcv, m);
2393 if (!(tp->t_flags & TF_DUPSEG)) {
2394 /* Initialize SACK report block. */
2395 tp->reportblk.rblk_start = th->th_seq;
2396 tp->reportblk.rblk_end = th->th_seq + tlen +
2397 ((thflags & TH_FIN) != 0);
2399 thflags = tcp_reass(tp, th, &tlen, m);
2400 tp->t_flags |= TF_ACKNOW;
2404 * Note the amount of data that peer has sent into
2405 * our window, in order to estimate the sender's
2408 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
2415 * If FIN is received ACK the FIN and let the user know
2416 * that the connection is closing.
2418 if (thflags & TH_FIN) {
2419 if (!TCPS_HAVERCVDFIN(tp->t_state)) {
2422 * If connection is half-synchronized
2423 * (ie NEEDSYN flag on) then delay ACK,
2424 * so it may be piggybacked when SYN is sent.
2425 * Otherwise, since we received a FIN then no
2426 * more input can be expected, send ACK now.
2428 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN))
2429 callout_reset(tp->tt_delack, tcp_delacktime,
2430 tcp_timer_delack, tp);
2432 tp->t_flags |= TF_ACKNOW;
2436 switch (tp->t_state) {
2438 * In SYN_RECEIVED and ESTABLISHED STATES
2439 * enter the CLOSE_WAIT state.
2441 case TCPS_SYN_RECEIVED:
2442 tp->t_starttime = ticks;
2444 case TCPS_ESTABLISHED:
2445 tp->t_state = TCPS_CLOSE_WAIT;
2449 * If still in FIN_WAIT_1 STATE FIN has not been acked so
2450 * enter the CLOSING state.
2452 case TCPS_FIN_WAIT_1:
2453 tp->t_state = TCPS_CLOSING;
2457 * In FIN_WAIT_2 state enter the TIME_WAIT state,
2458 * starting the time-wait timer, turning off the other
2461 case TCPS_FIN_WAIT_2:
2462 tp->t_state = TCPS_TIME_WAIT;
2463 tcp_canceltimers(tp);
2464 /* Shorten TIME_WAIT [RFC-1644, p.28] */
2465 if (tp->cc_recv != 0 &&
2466 (ticks - tp->t_starttime) < tcp_msl) {
2467 callout_reset(tp->tt_2msl,
2468 tp->t_rxtcur * TCPTV_TWTRUNC,
2469 tcp_timer_2msl, tp);
2470 /* For transaction client, force ACK now. */
2471 tp->t_flags |= TF_ACKNOW;
2474 callout_reset(tp->tt_2msl, 2 * tcp_msl,
2475 tcp_timer_2msl, tp);
2476 soisdisconnected(so);
2480 * In TIME_WAIT state restart the 2 MSL time_wait timer.
2482 case TCPS_TIME_WAIT:
2483 callout_reset(tp->tt_2msl, 2 * tcp_msl,
2484 tcp_timer_2msl, tp);
2490 if (so->so_options & SO_DEBUG)
2491 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen,
2496 * Return any desired output.
2498 if (needoutput || (tp->t_flags & TF_ACKNOW))
2499 (void) tcp_output(tp);
2504 * Generate an ACK dropping incoming segment if it occupies
2505 * sequence space, where the ACK reflects our state.
2507 * We can now skip the test for the RST flag since all
2508 * paths to this code happen after packets containing
2509 * RST have been dropped.
2511 * In the SYN-RECEIVED state, don't send an ACK unless the
2512 * segment we received passes the SYN-RECEIVED ACK test.
2513 * If it fails send a RST. This breaks the loop in the
2514 * "LAND" DoS attack, and also prevents an ACK storm
2515 * between two listening ports that have been sent forged
2516 * SYN segments, each with the source address of the other.
2518 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
2519 (SEQ_GT(tp->snd_una, th->th_ack) ||
2520 SEQ_GT(th->th_ack, tp->snd_max)) ) {
2521 rstreason = BANDLIM_RST_OPENPORT;
2525 if (so->so_options & SO_DEBUG)
2526 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
2530 tp->t_flags |= TF_ACKNOW;
2531 (void) tcp_output(tp);
2536 * Generate a RST, dropping incoming segment.
2537 * Make ACK acceptable to originator of segment.
2538 * Don't bother to respond if destination was broadcast/multicast.
2540 if ((thflags & TH_RST) || m->m_flags & (M_BCAST | M_MCAST))
2543 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
2544 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
2547 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
2548 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
2549 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
2550 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
2553 /* IPv6 anycast check is done at tcp6_input() */
2556 * Perform bandwidth limiting.
2559 if (badport_bandlim(rstreason) < 0)
2564 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
2565 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
2568 if (thflags & TH_ACK)
2569 /* mtod() below is safe as long as hdr dropping is delayed */
2570 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack,
2573 if (thflags & TH_SYN)
2575 /* mtod() below is safe as long as hdr dropping is delayed */
2576 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen,
2577 (tcp_seq)0, TH_RST | TH_ACK);
2583 * Drop space held by incoming segment and return.
2586 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
2587 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
2595 * Parse TCP options and place in tcpopt.
2598 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn)
2603 for (; cnt > 0; cnt -= optlen, cp += optlen) {
2605 if (opt == TCPOPT_EOL)
2607 if (opt == TCPOPT_NOP)
2613 if (optlen < 2 || optlen > cnt)
2618 if (optlen != TCPOLEN_MAXSEG)
2622 to->to_flags |= TOF_MSS;
2623 bcopy(cp + 2, &to->to_mss, sizeof(to->to_mss));
2624 to->to_mss = ntohs(to->to_mss);
2627 if (optlen != TCPOLEN_WINDOW)
2631 to->to_flags |= TOF_SCALE;
2632 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT);
2634 case TCPOPT_TIMESTAMP:
2635 if (optlen != TCPOLEN_TIMESTAMP)
2637 to->to_flags |= TOF_TS;
2638 bcopy(cp + 2, &to->to_tsval, sizeof(to->to_tsval));
2639 to->to_tsval = ntohl(to->to_tsval);
2640 bcopy(cp + 6, &to->to_tsecr, sizeof(to->to_tsecr));
2641 to->to_tsecr = ntohl(to->to_tsecr);
2644 if (optlen != TCPOLEN_CC)
2646 to->to_flags |= TOF_CC;
2647 bcopy(cp + 2, &to->to_cc, sizeof(to->to_cc));
2648 to->to_cc = ntohl(to->to_cc);
2651 if (optlen != TCPOLEN_CC)
2655 to->to_flags |= TOF_CCNEW;
2656 bcopy(cp + 2, &to->to_cc, sizeof(to->to_cc));
2657 to->to_cc = ntohl(to->to_cc);
2660 if (optlen != TCPOLEN_CC)
2664 to->to_flags |= TOF_CCECHO;
2665 bcopy(cp + 2, &to->to_ccecho, sizeof(to->to_ccecho));
2666 to->to_ccecho = ntohl(to->to_ccecho);
2668 case TCPOPT_SACK_PERMITTED:
2669 if (optlen != TCPOLEN_SACK_PERMITTED)
2673 to->to_flags |= TOF_SACK_PERMITTED;
2676 if ((optlen - 2) & 0x07) /* not multiple of 8 */
2678 to->to_nsackblocks = (optlen - 2) / 8;
2679 to->to_sackblocks = (struct raw_sackblock *) (cp + 2);
2680 to->to_flags |= TOF_SACK;
2681 for (i = 0; i < to->to_nsackblocks; i++) {
2682 struct raw_sackblock *r = &to->to_sackblocks[i];
2684 r->rblk_start = ntohl(r->rblk_start);
2685 r->rblk_end = ntohl(r->rblk_end);
2695 * Pull out of band byte out of a segment so
2696 * it doesn't appear in the user's data queue.
2697 * It is still reflected in the segment length for
2698 * sequencing purposes.
2699 * "off" is the delayed to be dropped hdrlen.
2702 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off)
2704 int cnt = off + th->th_urp - 1;
2707 if (m->m_len > cnt) {
2708 char *cp = mtod(m, caddr_t) + cnt;
2709 struct tcpcb *tp = sototcpcb(so);
2712 tp->t_oobflags |= TCPOOB_HAVEDATA;
2713 bcopy(cp + 1, cp, m->m_len - cnt - 1);
2715 if (m->m_flags & M_PKTHDR)
2724 panic("tcp_pulloutofband");
2728 * Collect new round-trip time estimate
2729 * and update averages and current timeout.
2732 tcp_xmit_timer(struct tcpcb *tp, int rtt)
2736 tcpstat.tcps_rttupdated++;
2738 if (tp->t_srtt != 0) {
2740 * srtt is stored as fixed point with 5 bits after the
2741 * binary point (i.e., scaled by 8). The following magic
2742 * is equivalent to the smoothing algorithm in rfc793 with
2743 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
2744 * point). Adjust rtt to origin 0.
2746 delta = ((rtt - 1) << TCP_DELTA_SHIFT)
2747 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
2749 if ((tp->t_srtt += delta) <= 0)
2753 * We accumulate a smoothed rtt variance (actually, a
2754 * smoothed mean difference), then set the retransmit
2755 * timer to smoothed rtt + 4 times the smoothed variance.
2756 * rttvar is stored as fixed point with 4 bits after the
2757 * binary point (scaled by 16). The following is
2758 * equivalent to rfc793 smoothing with an alpha of .75
2759 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces
2760 * rfc793's wired-in beta.
2764 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
2765 if ((tp->t_rttvar += delta) <= 0)
2767 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
2768 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2771 * No rtt measurement yet - use the unsmoothed rtt.
2772 * Set the variance to half the rtt (so our first
2773 * retransmit happens at 3*rtt).
2775 tp->t_srtt = rtt << TCP_RTT_SHIFT;
2776 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
2777 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2783 * the retransmit should happen at rtt + 4 * rttvar.
2784 * Because of the way we do the smoothing, srtt and rttvar
2785 * will each average +1/2 tick of bias. When we compute
2786 * the retransmit timer, we want 1/2 tick of rounding and
2787 * 1 extra tick because of +-1/2 tick uncertainty in the
2788 * firing of the timer. The bias will give us exactly the
2789 * 1.5 tick we need. But, because the bias is
2790 * statistical, we have to test that we don't drop below
2791 * the minimum feasible timer (which is 2 ticks).
2793 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
2794 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);
2797 * We received an ack for a packet that wasn't retransmitted;
2798 * it is probably safe to discard any error indications we've
2799 * received recently. This isn't quite right, but close enough
2800 * for now (a route might have failed after we sent a segment,
2801 * and the return path might not be symmetrical).
2803 tp->t_softerror = 0;
2807 * Determine a reasonable value for maxseg size.
2808 * If the route is known, check route for mtu.
2809 * If none, use an mss that can be handled on the outgoing
2810 * interface without forcing IP to fragment; if bigger than
2811 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES
2812 * to utilize large mbufs. If no route is found, route has no mtu,
2813 * or the destination isn't local, use a default, hopefully conservative
2814 * size (usually 512 or the default IP max size, but no more than the mtu
2815 * of the interface), as we can't discover anything about intervening
2816 * gateways or networks. We also initialize the congestion/slow start
2817 * window to be a single segment if the destination isn't local.
2818 * While looking at the routing entry, we also initialize other path-dependent
2819 * parameters from pre-set or cached values in the routing entry.
2821 * Also take into account the space needed for options that we
2822 * send regularly. Make maxseg shorter by that amount to assure
2823 * that we can send maxseg amount of data even when the options
2824 * are present. Store the upper limit of the length of options plus
2827 * NOTE that this routine is only called when we process an incoming
2828 * segment, for outgoing segments only tcp_mssopt is called.
2830 * In case of T/TCP, we call this routine during implicit connection
2831 * setup as well (offer = -1), to initialize maxseg from the cached
2835 tcp_mss(struct tcpcb *tp, int offer)
2841 struct inpcb *inp = tp->t_inpcb;
2843 struct rmxp_tao *taop;
2844 int origoffer = offer;
2846 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE);
2847 size_t min_protoh = isipv6 ?
2848 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) :
2849 sizeof(struct tcpiphdr);
2851 const boolean_t isipv6 = FALSE;
2852 const size_t min_protoh = sizeof(struct tcpiphdr);
2856 rt = tcp_rtlookup6(&inp->inp_inc);
2858 rt = tcp_rtlookup(&inp->inp_inc);
2860 tp->t_maxopd = tp->t_maxseg =
2861 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt);
2865 so = inp->inp_socket;
2867 taop = rmx_taop(rt->rt_rmx);
2869 * Offer == -1 means that we didn't receive SYN yet,
2870 * use cached value in that case;
2873 offer = taop->tao_mssopt;
2875 * Offer == 0 means that there was no MSS on the SYN segment,
2876 * in this case we use tcp_mssdflt.
2879 offer = (isipv6 ? tcp_v6mssdflt : tcp_mssdflt);
2882 * Sanity check: make sure that maxopd will be large
2883 * enough to allow some data on segments even is the
2884 * all the option space is used (40bytes). Otherwise
2885 * funny things may happen in tcp_output.
2887 offer = max(offer, 64);
2888 taop->tao_mssopt = offer;
2891 * While we're here, check if there's an initial rtt
2892 * or rttvar. Convert from the route-table units
2893 * to scaled multiples of the slow timeout timer.
2895 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) {
2897 * XXX the lock bit for RTT indicates that the value
2898 * is also a minimum value; this is subject to time.
2900 if (rt->rt_rmx.rmx_locks & RTV_RTT)
2901 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz);
2902 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE));
2903 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE;
2904 tcpstat.tcps_usedrtt++;
2905 if (rt->rt_rmx.rmx_rttvar) {
2906 tp->t_rttvar = rt->rt_rmx.rmx_rttvar /
2907 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE));
2908 tcpstat.tcps_usedrttvar++;
2910 /* default variation is +- 1 rtt */
2912 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
2914 TCPT_RANGESET(tp->t_rxtcur,
2915 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
2916 tp->t_rttmin, TCPTV_REXMTMAX);
2919 * if there's an mtu associated with the route, use it
2920 * else, use the link mtu.
2922 if (rt->rt_rmx.rmx_mtu)
2923 mss = rt->rt_rmx.rmx_mtu - min_protoh;
2926 mss = nd_ifinfo[rt->rt_ifp->if_index].linkmtu -
2928 if (!in6_localaddr(&inp->in6p_faddr))
2929 mss = min(mss, tcp_v6mssdflt);
2931 mss = ifp->if_mtu - min_protoh;
2932 if (!in_localaddr(inp->inp_faddr))
2933 mss = min(mss, tcp_mssdflt);
2936 mss = min(mss, offer);
2938 * maxopd stores the maximum length of data AND options
2939 * in a segment; maxseg is the amount of data in a normal
2940 * segment. We need to store this value (maxopd) apart
2941 * from maxseg, because now every segment carries options
2942 * and thus we normally have somewhat less data in segments.
2947 * In case of T/TCP, origoffer==-1 indicates, that no segments
2948 * were received yet. In this case we just guess, otherwise
2949 * we do the same as before T/TCP.
2951 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP &&
2953 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP))
2954 mss -= TCPOLEN_TSTAMP_APPA;
2955 if ((tp->t_flags & (TF_REQ_CC | TF_NOOPT)) == TF_REQ_CC &&
2957 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC))
2958 mss -= TCPOLEN_CC_APPA;
2960 #if (MCLBYTES & (MCLBYTES - 1)) == 0
2962 mss &= ~(MCLBYTES-1);
2965 mss = mss / MCLBYTES * MCLBYTES;
2968 * If there's a pipesize, change the socket buffer
2969 * to that size. Make the socket buffers an integral
2970 * number of mss units; if the mss is larger than
2971 * the socket buffer, decrease the mss.
2974 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0)
2976 bufsize = so->so_snd.sb_hiwat;
2980 bufsize = roundup(bufsize, mss);
2981 if (bufsize > sb_max)
2983 if (bufsize > so->so_snd.sb_hiwat)
2984 (void)sbreserve(&so->so_snd, bufsize, so, NULL);
2989 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0)
2991 bufsize = so->so_rcv.sb_hiwat;
2992 if (bufsize > mss) {
2993 bufsize = roundup(bufsize, mss);
2994 if (bufsize > sb_max)
2996 if (bufsize > so->so_rcv.sb_hiwat)
2997 (void)sbreserve(&so->so_rcv, bufsize, so, NULL);
3001 * Set the slow-start flight size depending on whether this
3002 * is a local network or not.
3005 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380));
3006 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) ||
3007 (!isipv6 && in_localaddr(inp->inp_faddr)))
3008 tp->snd_cwnd = mss * ss_fltsz_local;
3010 tp->snd_cwnd = mss * ss_fltsz;
3012 if (rt->rt_rmx.rmx_ssthresh) {
3014 * There's some sort of gateway or interface
3015 * buffer limit on the path. Use this to set
3016 * the slow start threshhold, but set the
3017 * threshold to no less than 2*mss.
3019 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh);
3020 tcpstat.tcps_usedssthresh++;
3025 * Determine the MSS option to send on an outgoing SYN.
3028 tcp_mssopt(struct tcpcb *tp)
3033 ((tp->t_inpcb->inp_vflag & INP_IPV6) ? TRUE : FALSE);
3034 int min_protoh = isipv6 ?
3035 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) :
3036 sizeof(struct tcpiphdr);
3038 const boolean_t isipv6 = FALSE;
3039 const size_t min_protoh = sizeof(struct tcpiphdr);
3043 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc);
3045 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc);
3047 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt);
3049 return (rt->rt_ifp->if_mtu - min_protoh);
3053 * When a partial ack arrives, force the retransmission of the
3054 * next unacknowledged segment. Do not exit Fast Recovery.
3056 * Implement the Slow-but-Steady variant of NewReno by restarting the
3057 * the retransmission timer. Turn it off here so it can be restarted
3058 * later in tcp_output().
3061 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th, int acked)
3063 tcp_seq old_snd_nxt = tp->snd_nxt;
3064 u_long ocwnd = tp->snd_cwnd;
3066 callout_stop(tp->tt_rexmt);
3068 tp->snd_nxt = th->th_ack;
3069 /* Set snd_cwnd to one segment beyond acknowledged offset. */
3070 tp->snd_cwnd = tp->t_maxseg;
3071 tp->t_flags |= TF_ACKNOW;
3072 (void) tcp_output(tp);
3073 if (SEQ_GT(old_snd_nxt, tp->snd_nxt))
3074 tp->snd_nxt = old_snd_nxt;
3075 /* partial window deflation */
3076 tp->snd_cwnd = ocwnd - acked + tp->t_maxseg;
3080 * In contrast to the Slow-but-Steady NewReno variant,
3081 * we do not reset the retransmission timer for SACK retransmissions,
3082 * except when retransmitting snd_una.
3085 tcp_sack_rexmt(struct tcpcb *tp, struct tcphdr *th)
3087 uint32_t pipe, seglen;
3090 tcp_seq old_snd_nxt = tp->snd_nxt;
3091 u_long ocwnd = tp->snd_cwnd;
3092 int nseg = 0; /* consecutive new segments */
3093 #define MAXBURST 4 /* limit burst of new packets on partial ack */
3096 pipe = tcp_sack_compute_pipe(tp);
3097 while ((tcp_seq_diff_t)(ocwnd - pipe) >= (tcp_seq_diff_t)tp->t_maxseg &&
3098 (!tcp_do_smartsack || nseg < MAXBURST) &&
3099 tcp_sack_nextseg(tp, &nextrexmt, &seglen, &lostdup)) {
3101 tcp_seq old_snd_max;
3104 if (nextrexmt == tp->snd_max) ++nseg;
3105 tp->snd_nxt = nextrexmt;
3106 tp->snd_cwnd = nextrexmt - tp->snd_una + seglen;
3107 old_snd_max = tp->snd_max;
3108 if (nextrexmt == tp->snd_una)
3109 callout_stop(tp->tt_rexmt);
3110 error = tcp_output(tp);
3113 sent = tp->snd_nxt - nextrexmt;
3118 tcpstat.tcps_sndsackpack++;
3119 tcpstat.tcps_sndsackbyte += sent;
3120 if (SEQ_LT(nextrexmt, old_snd_max) &&
3121 SEQ_LT(tp->rexmt_high, tp->snd_nxt))
3122 tp->rexmt_high = seq_min(tp->snd_nxt, old_snd_max);
3124 if (SEQ_GT(old_snd_nxt, tp->snd_nxt))
3125 tp->snd_nxt = old_snd_nxt;
3126 tp->snd_cwnd = ocwnd;
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