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
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18 * from this software without specific, prior written permission.
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66 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95
67 * $FreeBSD: src/sys/netinet/tcp_input.c,v 1.107.2.38 2003/05/21 04:46:41 cjc Exp $
68 * $DragonFly: src/sys/netinet/tcp_input.c,v 1.68 2008/08/22 09:14:17 sephe Exp $
71 #include "opt_ipfw.h" /* for ipfw_fwd */
72 #include "opt_inet6.h"
73 #include "opt_ipsec.h"
74 #include "opt_tcpdebug.h"
75 #include "opt_tcp_input.h"
77 #include <sys/param.h>
78 #include <sys/systm.h>
79 #include <sys/kernel.h>
80 #include <sys/sysctl.h>
81 #include <sys/malloc.h>
83 #include <sys/proc.h> /* for proc0 declaration */
84 #include <sys/protosw.h>
85 #include <sys/socket.h>
86 #include <sys/socketvar.h>
87 #include <sys/syslog.h>
88 #include <sys/in_cksum.h>
90 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */
91 #include <machine/stdarg.h>
94 #include <net/route.h>
96 #include <netinet/in.h>
97 #include <netinet/in_systm.h>
98 #include <netinet/ip.h>
99 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */
100 #include <netinet/in_var.h>
101 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */
102 #include <netinet/in_pcb.h>
103 #include <netinet/ip_var.h>
104 #include <netinet/ip6.h>
105 #include <netinet/icmp6.h>
106 #include <netinet6/nd6.h>
107 #include <netinet6/ip6_var.h>
108 #include <netinet6/in6_pcb.h>
109 #include <netinet/tcp.h>
110 #include <netinet/tcp_fsm.h>
111 #include <netinet/tcp_seq.h>
112 #include <netinet/tcp_timer.h>
113 #include <netinet/tcp_timer2.h>
114 #include <netinet/tcp_var.h>
115 #include <netinet6/tcp6_var.h>
116 #include <netinet/tcpip.h>
119 #include <netinet/tcp_debug.h>
121 u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */
122 struct tcphdr tcp_savetcp;
126 #include <netproto/ipsec/ipsec.h>
127 #include <netproto/ipsec/ipsec6.h>
131 #include <netinet6/ipsec.h>
132 #include <netinet6/ipsec6.h>
133 #include <netproto/key/key.h>
136 MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry");
139 static int log_in_vain = 0;
140 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW,
141 &log_in_vain, 0, "Log all incoming TCP connections");
143 static int blackhole = 0;
144 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW,
145 &blackhole, 0, "Do not send RST when dropping refused connections");
147 int tcp_delack_enabled = 1;
148 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW,
149 &tcp_delack_enabled, 0,
150 "Delay ACK to try and piggyback it onto a data packet");
152 #ifdef TCP_DROP_SYNFIN
153 static int drop_synfin = 0;
154 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW,
155 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set");
158 static int tcp_do_limitedtransmit = 1;
159 SYSCTL_INT(_net_inet_tcp, OID_AUTO, limitedtransmit, CTLFLAG_RW,
160 &tcp_do_limitedtransmit, 0, "Enable RFC 3042 (Limited Transmit)");
162 static int tcp_do_early_retransmit = 1;
163 SYSCTL_INT(_net_inet_tcp, OID_AUTO, earlyretransmit, CTLFLAG_RW,
164 &tcp_do_early_retransmit, 0, "Early retransmit");
166 int tcp_aggregate_acks = 1;
167 SYSCTL_INT(_net_inet_tcp, OID_AUTO, aggregate_acks, CTLFLAG_RW,
168 &tcp_aggregate_acks, 0, "Aggregate built-up acks into one ack");
170 int tcp_do_rfc3390 = 1;
171 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW,
173 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)");
175 static int tcp_do_eifel_detect = 1;
176 SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW,
177 &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)");
179 static int tcp_do_abc = 1;
180 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc, CTLFLAG_RW,
182 "TCP Appropriate Byte Counting (RFC 3465)");
185 * Define as tunable for easy testing with SACK on and off.
186 * Warning: do not change setting in the middle of an existing active TCP flow,
187 * else strange things might happen to that flow.
190 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW,
191 &tcp_do_sack, 0, "Enable SACK Algorithms");
193 int tcp_do_smartsack = 1;
194 SYSCTL_INT(_net_inet_tcp, OID_AUTO, smartsack, CTLFLAG_RW,
195 &tcp_do_smartsack, 0, "Enable Smart SACK Algorithms");
197 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0,
198 "TCP Segment Reassembly Queue");
200 int tcp_reass_maxseg = 0;
201 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD,
202 &tcp_reass_maxseg, 0,
203 "Global maximum number of TCP Segments in Reassembly Queue");
205 int tcp_reass_qsize = 0;
206 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD,
208 "Global number of TCP Segments currently in Reassembly Queue");
210 static int tcp_reass_overflows = 0;
211 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD,
212 &tcp_reass_overflows, 0,
213 "Global number of TCP Segment Reassembly Queue Overflows");
215 int tcp_do_autorcvbuf = 1;
216 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW,
217 &tcp_do_autorcvbuf, 0, "Enable automatic receive buffer sizing");
219 int tcp_autorcvbuf_inc = 16*1024;
220 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW,
221 &tcp_autorcvbuf_inc, 0,
222 "Incrementor step size of automatic receive buffer");
224 int tcp_autorcvbuf_max = 16*1024*1024;
225 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW,
226 &tcp_autorcvbuf_max, 0, "Max size of automatic receive buffer");
229 static void tcp_dooptions(struct tcpopt *, u_char *, int, boolean_t);
230 static void tcp_pulloutofband(struct socket *,
231 struct tcphdr *, struct mbuf *, int);
232 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *,
234 static void tcp_xmit_timer(struct tcpcb *, int);
235 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *, int);
236 static void tcp_sack_rexmt(struct tcpcb *, struct tcphdr *);
238 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */
240 #define ND6_HINT(tp) \
242 if ((tp) && (tp)->t_inpcb && \
243 ((tp)->t_inpcb->inp_vflag & INP_IPV6) && \
244 (tp)->t_inpcb->in6p_route.ro_rt) \
245 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \
252 * Indicate whether this ack should be delayed. We can delay the ack if
253 * - delayed acks are enabled and
254 * - there is no delayed ack timer in progress and
255 * - our last ack wasn't a 0-sized window. We never want to delay
256 * the ack that opens up a 0-sized window.
258 #define DELAY_ACK(tp) \
259 (tcp_delack_enabled && !tcp_callout_pending(tp, tp->tt_delack) && \
260 !(tp->t_flags & TF_RXWIN0SENT))
262 #define acceptable_window_update(tp, th, tiwin) \
263 (SEQ_LT(tp->snd_wl1, th->th_seq) || \
264 (tp->snd_wl1 == th->th_seq && \
265 (SEQ_LT(tp->snd_wl2, th->th_ack) || \
266 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))
269 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m)
272 struct tseg_qent *p = NULL;
273 struct tseg_qent *te;
274 struct socket *so = tp->t_inpcb->inp_socket;
278 * Call with th == NULL after become established to
279 * force pre-ESTABLISHED data up to user socket.
285 * Limit the number of segments in the reassembly queue to prevent
286 * holding on to too many segments (and thus running out of mbufs).
287 * Make sure to let the missing segment through which caused this
288 * queue. Always keep one global queue entry spare to be able to
289 * process the missing segment.
291 if (th->th_seq != tp->rcv_nxt &&
292 tcp_reass_qsize + 1 >= tcp_reass_maxseg) {
293 tcp_reass_overflows++;
294 tcpstat.tcps_rcvmemdrop++;
296 /* no SACK block to report */
297 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
301 /* Allocate a new queue entry. */
302 MALLOC(te, struct tseg_qent *, sizeof(struct tseg_qent), M_TSEGQ,
303 M_INTWAIT | M_NULLOK);
305 tcpstat.tcps_rcvmemdrop++;
307 /* no SACK block to report */
308 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
314 * Find a segment which begins after this one does.
316 LIST_FOREACH(q, &tp->t_segq, tqe_q) {
317 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
323 * If there is a preceding segment, it may provide some of
324 * our data already. If so, drop the data from the incoming
325 * segment. If it provides all of our data, drop us.
330 /* conversion to int (in i) handles seq wraparound */
331 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
332 if (i > 0) { /* overlaps preceding segment */
333 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG);
334 /* enclosing block starts w/ preceding segment */
335 tp->encloseblk.rblk_start = p->tqe_th->th_seq;
337 /* preceding encloses incoming segment */
338 tp->encloseblk.rblk_end = p->tqe_th->th_seq +
340 tcpstat.tcps_rcvduppack++;
341 tcpstat.tcps_rcvdupbyte += *tlenp;
346 * Try to present any queued data
347 * at the left window edge to the user.
348 * This is needed after the 3-WHS
351 goto present; /* ??? */
356 /* incoming segment end is enclosing block end */
357 tp->encloseblk.rblk_end = th->th_seq + *tlenp +
358 ((th->th_flags & TH_FIN) != 0);
359 /* trim end of reported D-SACK block */
360 tp->reportblk.rblk_end = th->th_seq;
363 tcpstat.tcps_rcvoopack++;
364 tcpstat.tcps_rcvoobyte += *tlenp;
367 * While we overlap succeeding segments trim them or,
368 * if they are completely covered, dequeue them.
371 tcp_seq_diff_t i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
372 tcp_seq qend = q->tqe_th->th_seq + q->tqe_len;
373 struct tseg_qent *nq;
377 if (!(tp->t_flags & TF_DUPSEG)) { /* first time through */
378 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG);
379 tp->encloseblk = tp->reportblk;
380 /* report trailing duplicate D-SACK segment */
381 tp->reportblk.rblk_start = q->tqe_th->th_seq;
383 if ((tp->t_flags & TF_ENCLOSESEG) &&
384 SEQ_GT(qend, tp->encloseblk.rblk_end)) {
385 /* extend enclosing block if one exists */
386 tp->encloseblk.rblk_end = qend;
388 if (i < q->tqe_len) {
389 q->tqe_th->th_seq += i;
395 nq = LIST_NEXT(q, tqe_q);
396 LIST_REMOVE(q, tqe_q);
403 /* Insert the new segment queue entry into place. */
406 te->tqe_len = *tlenp;
408 /* check if can coalesce with following segment */
409 if (q != NULL && (th->th_seq + *tlenp == q->tqe_th->th_seq)) {
410 tcp_seq tend = te->tqe_th->th_seq + te->tqe_len;
412 te->tqe_len += q->tqe_len;
413 if (q->tqe_th->th_flags & TH_FIN)
414 te->tqe_th->th_flags |= TH_FIN;
415 m_cat(te->tqe_m, q->tqe_m);
416 tp->encloseblk.rblk_end = tend;
418 * When not reporting a duplicate segment, use
419 * the larger enclosing block as the SACK block.
421 if (!(tp->t_flags & TF_DUPSEG))
422 tp->reportblk.rblk_end = tend;
423 LIST_REMOVE(q, tqe_q);
429 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q);
431 /* check if can coalesce with preceding segment */
432 if (p->tqe_th->th_seq + p->tqe_len == th->th_seq) {
433 p->tqe_len += te->tqe_len;
434 m_cat(p->tqe_m, te->tqe_m);
435 tp->encloseblk.rblk_start = p->tqe_th->th_seq;
437 * When not reporting a duplicate segment, use
438 * the larger enclosing block as the SACK block.
440 if (!(tp->t_flags & TF_DUPSEG))
441 tp->reportblk.rblk_start = p->tqe_th->th_seq;
445 LIST_INSERT_AFTER(p, te, tqe_q);
450 * Present data to user, advancing rcv_nxt through
451 * completed sequence space.
453 if (!TCPS_HAVEESTABLISHED(tp->t_state))
455 q = LIST_FIRST(&tp->t_segq);
456 if (q == NULL || q->tqe_th->th_seq != tp->rcv_nxt)
458 tp->rcv_nxt += q->tqe_len;
459 if (!(tp->t_flags & TF_DUPSEG)) {
460 /* no SACK block to report since ACK advanced */
461 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
463 /* no enclosing block to report since ACK advanced */
464 tp->t_flags &= ~TF_ENCLOSESEG;
465 flags = q->tqe_th->th_flags & TH_FIN;
466 LIST_REMOVE(q, tqe_q);
467 KASSERT(LIST_EMPTY(&tp->t_segq) ||
468 LIST_FIRST(&tp->t_segq)->tqe_th->th_seq != tp->rcv_nxt,
469 ("segment not coalesced"));
470 if (so->so_state & SS_CANTRCVMORE)
473 ssb_appendstream(&so->so_rcv, q->tqe_m);
482 * TCP input routine, follows pages 65-76 of the
483 * protocol specification dated September, 1981 very closely.
487 tcp6_input(struct mbuf **mp, int *offp, int proto)
489 struct mbuf *m = *mp;
490 struct in6_ifaddr *ia6;
492 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE);
495 * draft-itojun-ipv6-tcp-to-anycast
496 * better place to put this in?
498 ia6 = ip6_getdstifaddr(m);
499 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) {
502 ip6 = mtod(m, struct ip6_hdr *);
503 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
504 offsetof(struct ip6_hdr, ip6_dst));
505 return (IPPROTO_DONE);
508 tcp_input(m, *offp, proto);
509 return (IPPROTO_DONE);
514 tcp_input(struct mbuf *m, ...)
519 struct ip *ip = NULL;
521 struct inpcb *inp = NULL;
526 struct tcpcb *tp = NULL;
528 struct socket *so = 0;
530 boolean_t ourfinisacked, needoutput = FALSE;
533 struct tcpopt to; /* options in this segment */
534 struct rmxp_tao *taop; /* pointer to our TAO cache entry */
535 struct rmxp_tao tao_noncached; /* in case there's no cached entry */
536 struct sockaddr_in *next_hop = NULL;
537 int rstreason; /* For badport_bandlim accounting purposes */
539 struct ip6_hdr *ip6 = NULL;
543 const boolean_t isipv6 = FALSE;
550 off0 = __va_arg(ap, int);
551 proto = __va_arg(ap, int);
554 tcpstat.tcps_rcvtotal++;
556 if (m->m_pkthdr.fw_flags & IPFORWARD_MBUF_TAGGED) {
559 mtag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL);
560 KKASSERT(mtag != NULL);
561 next_hop = m_tag_data(mtag);
565 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE;
569 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */
570 ip6 = mtod(m, struct ip6_hdr *);
571 tlen = (sizeof *ip6) + ntohs(ip6->ip6_plen) - off0;
572 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) {
573 tcpstat.tcps_rcvbadsum++;
576 th = (struct tcphdr *)((caddr_t)ip6 + off0);
579 * Be proactive about unspecified IPv6 address in source.
580 * As we use all-zero to indicate unbounded/unconnected pcb,
581 * unspecified IPv6 address can be used to confuse us.
583 * Note that packets with unspecified IPv6 destination is
584 * already dropped in ip6_input.
586 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
592 * Get IP and TCP header together in first mbuf.
593 * Note: IP leaves IP header in first mbuf.
595 if (off0 > sizeof(struct ip)) {
597 off0 = sizeof(struct ip);
599 /* already checked and pulled up in ip_demux() */
600 KASSERT(m->m_len >= sizeof(struct tcpiphdr),
601 ("TCP header not in one mbuf: m->m_len %d", m->m_len));
602 ip = mtod(m, struct ip *);
603 ipov = (struct ipovly *)ip;
604 th = (struct tcphdr *)((caddr_t)ip + off0);
607 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
608 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
609 th->th_sum = m->m_pkthdr.csum_data;
611 th->th_sum = in_pseudo(ip->ip_src.s_addr,
613 htonl(m->m_pkthdr.csum_data +
616 th->th_sum ^= 0xffff;
619 * Checksum extended TCP header and data.
621 len = sizeof(struct ip) + tlen;
622 bzero(ipov->ih_x1, sizeof ipov->ih_x1);
623 ipov->ih_len = (u_short)tlen;
624 ipov->ih_len = htons(ipov->ih_len);
625 th->th_sum = in_cksum(m, len);
628 tcpstat.tcps_rcvbadsum++;
632 /* Re-initialization for later version check */
633 ip->ip_v = IPVERSION;
638 * Check that TCP offset makes sense,
639 * pull out TCP options and adjust length. XXX
641 off = th->th_off << 2;
642 /* already checked and pulled up in ip_demux() */
643 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen,
644 ("bad TCP data offset %d (tlen %d)", off, tlen));
645 tlen -= off; /* tlen is used instead of ti->ti_len */
646 if (off > sizeof(struct tcphdr)) {
648 IP6_EXTHDR_CHECK(m, off0, off, );
649 ip6 = mtod(m, struct ip6_hdr *);
650 th = (struct tcphdr *)((caddr_t)ip6 + off0);
652 /* already pulled up in ip_demux() */
653 KASSERT(m->m_len >= sizeof(struct ip) + off,
654 ("TCP header and options not in one mbuf: "
655 "m_len %d, off %d", m->m_len, off));
657 optlen = off - sizeof(struct tcphdr);
658 optp = (u_char *)(th + 1);
660 thflags = th->th_flags;
662 #ifdef TCP_DROP_SYNFIN
664 * If the drop_synfin option is enabled, drop all packets with
665 * both the SYN and FIN bits set. This prevents e.g. nmap from
666 * identifying the TCP/IP stack.
668 * This is a violation of the TCP specification.
670 if (drop_synfin && (thflags & (TH_SYN | TH_FIN)) == (TH_SYN | TH_FIN))
675 * Convert TCP protocol specific fields to host format.
677 th->th_seq = ntohl(th->th_seq);
678 th->th_ack = ntohl(th->th_ack);
679 th->th_win = ntohs(th->th_win);
680 th->th_urp = ntohs(th->th_urp);
683 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options,
684 * until after ip6_savecontrol() is called and before other functions
685 * which don't want those proto headers.
686 * Because ip6_savecontrol() is going to parse the mbuf to
687 * search for data to be passed up to user-land, it wants mbuf
688 * parameters to be unchanged.
689 * XXX: the call of ip6_savecontrol() has been obsoleted based on
690 * latest version of the advanced API (20020110).
692 drop_hdrlen = off0 + off;
695 * Locate pcb for segment.
698 /* IPFIREWALL_FORWARD section */
699 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */
701 * Transparently forwarded. Pretend to be the destination.
702 * already got one like this?
704 cpu = mycpu->gd_cpuid;
705 inp = in_pcblookup_hash(&tcbinfo[cpu],
706 ip->ip_src, th->th_sport,
707 ip->ip_dst, th->th_dport,
708 0, m->m_pkthdr.rcvif);
711 * It's new. Try to find the ambushing socket.
715 * The rest of the ipfw code stores the port in
717 * (The IP address is still in network order.)
719 in_port_t dport = next_hop->sin_port ?
720 htons(next_hop->sin_port) :
723 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport,
724 next_hop->sin_addr.s_addr, dport);
725 inp = in_pcblookup_hash(&tcbinfo[cpu],
726 ip->ip_src, th->th_sport,
727 next_hop->sin_addr, dport,
728 1, m->m_pkthdr.rcvif);
732 inp = in6_pcblookup_hash(&tcbinfo[0],
733 &ip6->ip6_src, th->th_sport,
734 &ip6->ip6_dst, th->th_dport,
735 1, m->m_pkthdr.rcvif);
737 cpu = mycpu->gd_cpuid;
738 inp = in_pcblookup_hash(&tcbinfo[cpu],
739 ip->ip_src, th->th_sport,
740 ip->ip_dst, th->th_dport,
741 1, m->m_pkthdr.rcvif);
746 * If the state is CLOSED (i.e., TCB does not exist) then
747 * all data in the incoming segment is discarded.
748 * If the TCB exists but is in CLOSED state, it is embryonic,
749 * but should either do a listen or a connect soon.
754 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2];
756 char dbuf[sizeof "aaa.bbb.ccc.ddd"];
757 char sbuf[sizeof "aaa.bbb.ccc.ddd"];
761 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst));
764 strcat(sbuf, ip6_sprintf(&ip6->ip6_src));
767 strcpy(dbuf, inet_ntoa(ip->ip_dst));
768 strcpy(sbuf, inet_ntoa(ip->ip_src));
770 switch (log_in_vain) {
772 if (!(thflags & TH_SYN))
776 "Connection attempt to TCP %s:%d "
777 "from %s:%d flags:0x%02x\n",
778 dbuf, ntohs(th->th_dport), sbuf,
779 ntohs(th->th_sport), thflags);
788 if (thflags & TH_SYN)
797 rstreason = BANDLIM_RST_CLOSEDPORT;
803 if (ipsec6_in_reject_so(m, inp->inp_socket)) {
804 ipsec6stat.in_polvio++;
808 if (ipsec4_in_reject_so(m, inp->inp_socket)) {
809 ipsecstat.in_polvio++;
816 if (ipsec6_in_reject(m, inp))
819 if (ipsec4_in_reject(m, inp))
823 /* Check the minimum TTL for socket. */
825 if ((isipv6 ? ip6->ip6_hlim : ip->ip_ttl) < inp->inp_ip_minttl)
831 rstreason = BANDLIM_RST_CLOSEDPORT;
834 if (tp->t_state <= TCPS_CLOSED)
837 /* Unscale the window into a 32-bit value. */
838 if (!(thflags & TH_SYN))
839 tiwin = th->th_win << tp->snd_scale;
843 so = inp->inp_socket;
846 if (so->so_options & SO_DEBUG) {
847 ostate = tp->t_state;
849 bcopy(ip6, tcp_saveipgen, sizeof(*ip6));
851 bcopy(ip, tcp_saveipgen, sizeof(*ip));
856 bzero(&to, sizeof to);
858 if (so->so_options & SO_ACCEPTCONN) {
859 struct in_conninfo inc;
862 inc.inc_isipv6 = (isipv6 == TRUE);
865 inc.inc6_faddr = ip6->ip6_src;
866 inc.inc6_laddr = ip6->ip6_dst;
867 inc.inc6_route.ro_rt = NULL; /* XXX */
869 inc.inc_faddr = ip->ip_src;
870 inc.inc_laddr = ip->ip_dst;
871 inc.inc_route.ro_rt = NULL; /* XXX */
873 inc.inc_fport = th->th_sport;
874 inc.inc_lport = th->th_dport;
877 * If the state is LISTEN then ignore segment if it contains
878 * a RST. If the segment contains an ACK then it is bad and
879 * send a RST. If it does not contain a SYN then it is not
880 * interesting; drop it.
882 * If the state is SYN_RECEIVED (syncache) and seg contains
883 * an ACK, but not for our SYN/ACK, send a RST. If the seg
884 * contains a RST, check the sequence number to see if it
885 * is a valid reset segment.
887 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) != TH_SYN) {
888 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) == TH_ACK) {
889 if (!syncache_expand(&inc, th, &so, m)) {
891 * No syncache entry, or ACK was not
892 * for our SYN/ACK. Send a RST.
894 tcpstat.tcps_badsyn++;
895 rstreason = BANDLIM_RST_OPENPORT;
900 * Could not complete 3-way handshake,
901 * connection is being closed down, and
902 * syncache will free mbuf.
906 * Socket is created in state SYN_RECEIVED.
907 * Continue processing segment.
912 * This is what would have happened in
913 * tcp_output() when the SYN,ACK was sent.
915 tp->snd_up = tp->snd_una;
916 tp->snd_max = tp->snd_nxt = tp->iss + 1;
917 tp->last_ack_sent = tp->rcv_nxt;
919 * XXX possible bug - it doesn't appear that tp->snd_wnd is unscaled
920 * until the _second_ ACK is received:
921 * rcv SYN (set wscale opts) --> send SYN/ACK, set snd_wnd = window.
922 * rcv ACK, calculate tiwin --> process SYN_RECEIVED, determine wscale,
923 * move to ESTAB, set snd_wnd to tiwin.
925 tp->snd_wnd = tiwin; /* unscaled */
928 if (thflags & TH_RST) {
929 syncache_chkrst(&inc, th);
932 if (thflags & TH_ACK) {
933 syncache_badack(&inc);
934 tcpstat.tcps_badsyn++;
935 rstreason = BANDLIM_RST_OPENPORT;
942 * Segment's flags are (SYN) or (SYN | FIN).
946 * If deprecated address is forbidden,
947 * we do not accept SYN to deprecated interface
948 * address to prevent any new inbound connection from
949 * getting established.
950 * When we do not accept SYN, we send a TCP RST,
951 * with deprecated source address (instead of dropping
952 * it). We compromise it as it is much better for peer
953 * to send a RST, and RST will be the final packet
956 * If we do not forbid deprecated addresses, we accept
957 * the SYN packet. RFC2462 does not suggest dropping
959 * If we decipher RFC2462 5.5.4, it says like this:
960 * 1. use of deprecated addr with existing
961 * communication is okay - "SHOULD continue to be
963 * 2. use of it with new communication:
964 * (2a) "SHOULD NOT be used if alternate address
965 * with sufficient scope is available"
966 * (2b) nothing mentioned otherwise.
967 * Here we fall into (2b) case as we have no choice in
968 * our source address selection - we must obey the peer.
970 * The wording in RFC2462 is confusing, and there are
971 * multiple description text for deprecated address
972 * handling - worse, they are not exactly the same.
973 * I believe 5.5.4 is the best one, so we follow 5.5.4.
975 if (isipv6 && !ip6_use_deprecated) {
976 struct in6_ifaddr *ia6;
978 if ((ia6 = ip6_getdstifaddr(m)) &&
979 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
981 rstreason = BANDLIM_RST_OPENPORT;
987 * If it is from this socket, drop it, it must be forged.
988 * Don't bother responding if the destination was a broadcast.
990 if (th->th_dport == th->th_sport) {
992 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst,
996 if (ip->ip_dst.s_addr == ip->ip_src.s_addr)
1001 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN
1003 * Note that it is quite possible to receive unicast
1004 * link-layer packets with a broadcast IP address. Use
1005 * in_broadcast() to find them.
1007 if (m->m_flags & (M_BCAST | M_MCAST))
1010 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
1011 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
1014 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
1015 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
1016 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
1017 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
1021 * SYN appears to be valid; create compressed TCP state
1022 * for syncache, or perform t/tcp connection.
1024 if (so->so_qlen <= so->so_qlimit) {
1025 tcp_dooptions(&to, optp, optlen, TRUE);
1026 if (!syncache_add(&inc, &to, th, &so, m))
1030 * Entry added to syncache, mbuf used to
1031 * send SYN,ACK packet.
1035 * Segment passed TAO tests.
1038 tp = intotcpcb(inp);
1039 tp->snd_wnd = tiwin;
1040 tp->t_starttime = ticks;
1041 tp->t_state = TCPS_ESTABLISHED;
1044 * If there is a FIN, or if there is data and the
1045 * connection is local, then delay SYN,ACK(SYN) in
1046 * the hope of piggy-backing it on a response
1047 * segment. Otherwise must send ACK now in case
1048 * the other side is slow starting.
1050 if (DELAY_ACK(tp) &&
1051 ((thflags & TH_FIN) ||
1053 ((isipv6 && in6_localaddr(&inp->in6p_faddr)) ||
1054 (!isipv6 && in_localaddr(inp->inp_faddr)))))) {
1055 tcp_callout_reset(tp, tp->tt_delack,
1056 tcp_delacktime, tcp_timer_delack);
1057 tp->t_flags |= TF_NEEDSYN;
1059 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN);
1062 tcpstat.tcps_connects++;
1070 /* should not happen - syncache should pick up these connections */
1071 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN state"));
1074 * This is the second part of the MSS DoS prevention code (after
1075 * minmss on the sending side) and it deals with too many too small
1076 * tcp packets in a too short timeframe (1 second).
1078 * XXX Removed. This code was crap. It does not scale to network
1079 * speed, and default values break NFS. Gone.
1084 * Segment received on connection.
1085 * Reset idle time and keep-alive timer.
1087 tp->t_rcvtime = ticks;
1088 if (TCPS_HAVEESTABLISHED(tp->t_state)) {
1089 tcp_callout_reset(tp, tp->tt_keep, tcp_keepidle,
1095 * XXX this is tradtitional behavior, may need to be cleaned up.
1097 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0);
1098 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) {
1099 if (to.to_flags & TOF_SCALE) {
1100 tp->t_flags |= TF_RCVD_SCALE;
1101 tp->requested_s_scale = to.to_requested_s_scale;
1103 if (to.to_flags & TOF_TS) {
1104 tp->t_flags |= TF_RCVD_TSTMP;
1105 tp->ts_recent = to.to_tsval;
1106 tp->ts_recent_age = ticks;
1108 if (to.to_flags & (TOF_CC | TOF_CCNEW))
1109 tp->t_flags |= TF_RCVD_CC;
1110 if (to.to_flags & TOF_MSS)
1111 tcp_mss(tp, to.to_mss);
1113 * Only set the TF_SACK_PERMITTED per-connection flag
1114 * if we got a SACK_PERMITTED option from the other side
1115 * and the global tcp_do_sack variable is true.
1117 if (tcp_do_sack && (to.to_flags & TOF_SACK_PERMITTED))
1118 tp->t_flags |= TF_SACK_PERMITTED;
1122 * Header prediction: check for the two common cases
1123 * of a uni-directional data xfer. If the packet has
1124 * no control flags, is in-sequence, the window didn't
1125 * change and we're not retransmitting, it's a
1126 * candidate. If the length is zero and the ack moved
1127 * forward, we're the sender side of the xfer. Just
1128 * free the data acked & wake any higher level process
1129 * that was blocked waiting for space. If the length
1130 * is non-zero and the ack didn't move, we're the
1131 * receiver side. If we're getting packets in-order
1132 * (the reassembly queue is empty), add the data to
1133 * the socket buffer and note that we need a delayed ack.
1134 * Make sure that the hidden state-flags are also off.
1135 * Since we check for TCPS_ESTABLISHED above, it can only
1138 if (tp->t_state == TCPS_ESTABLISHED &&
1139 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
1140 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) &&
1141 (!(to.to_flags & TOF_TS) ||
1142 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) &&
1144 * Using the CC option is compulsory if once started:
1145 * the segment is OK if no T/TCP was negotiated or
1146 * if the segment has a CC option equal to CCrecv
1148 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) ||
1149 ((to.to_flags & TOF_CC) && to.to_cc == tp->cc_recv)) &&
1150 th->th_seq == tp->rcv_nxt &&
1151 tp->snd_nxt == tp->snd_max) {
1154 * If last ACK falls within this segment's sequence numbers,
1155 * record the timestamp.
1156 * NOTE that the test is modified according to the latest
1157 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1159 if ((to.to_flags & TOF_TS) &&
1160 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
1161 tp->ts_recent_age = ticks;
1162 tp->ts_recent = to.to_tsval;
1166 if (SEQ_GT(th->th_ack, tp->snd_una) &&
1167 SEQ_LEQ(th->th_ack, tp->snd_max) &&
1168 tp->snd_cwnd >= tp->snd_wnd &&
1169 !IN_FASTRECOVERY(tp)) {
1171 * This is a pure ack for outstanding data.
1173 ++tcpstat.tcps_predack;
1175 * "bad retransmit" recovery
1177 * If Eifel detection applies, then
1178 * it is deterministic, so use it
1179 * unconditionally over the old heuristic.
1180 * Otherwise, fall back to the old heuristic.
1182 if (tcp_do_eifel_detect &&
1183 (to.to_flags & TOF_TS) && to.to_tsecr &&
1184 (tp->t_flags & TF_FIRSTACCACK)) {
1185 /* Eifel detection applicable. */
1186 if (to.to_tsecr < tp->t_rexmtTS) {
1187 tcp_revert_congestion_state(tp);
1188 ++tcpstat.tcps_eifeldetected;
1190 } else if (tp->t_rxtshift == 1 &&
1191 ticks < tp->t_badrxtwin) {
1192 tcp_revert_congestion_state(tp);
1193 ++tcpstat.tcps_rttdetected;
1195 tp->t_flags &= ~(TF_FIRSTACCACK |
1196 TF_FASTREXMT | TF_EARLYREXMT);
1198 * Recalculate the retransmit timer / rtt.
1200 * Some machines (certain windows boxes)
1201 * send broken timestamp replies during the
1202 * SYN+ACK phase, ignore timestamps of 0.
1204 if ((to.to_flags & TOF_TS) && to.to_tsecr) {
1206 ticks - to.to_tsecr + 1);
1207 } else if (tp->t_rtttime &&
1208 SEQ_GT(th->th_ack, tp->t_rtseq)) {
1210 ticks - tp->t_rtttime);
1212 tcp_xmit_bandwidth_limit(tp, th->th_ack);
1213 acked = th->th_ack - tp->snd_una;
1214 tcpstat.tcps_rcvackpack++;
1215 tcpstat.tcps_rcvackbyte += acked;
1216 sbdrop(&so->so_snd.sb, acked);
1217 tp->snd_recover = th->th_ack - 1;
1218 tp->snd_una = th->th_ack;
1221 * Update window information.
1223 if (tiwin != tp->snd_wnd &&
1224 acceptable_window_update(tp, th, tiwin)) {
1225 /* keep track of pure window updates */
1226 if (tp->snd_wl2 == th->th_ack &&
1227 tiwin > tp->snd_wnd)
1228 tcpstat.tcps_rcvwinupd++;
1229 tp->snd_wnd = tiwin;
1230 tp->snd_wl1 = th->th_seq;
1231 tp->snd_wl2 = th->th_ack;
1232 if (tp->snd_wnd > tp->max_sndwnd)
1233 tp->max_sndwnd = tp->snd_wnd;
1236 ND6_HINT(tp); /* some progress has been done */
1238 * If all outstanding data are acked, stop
1239 * retransmit timer, otherwise restart timer
1240 * using current (possibly backed-off) value.
1241 * If process is waiting for space,
1242 * wakeup/selwakeup/signal. If data
1243 * are ready to send, let tcp_output
1244 * decide between more output or persist.
1246 if (tp->snd_una == tp->snd_max) {
1247 tcp_callout_stop(tp, tp->tt_rexmt);
1248 } else if (!tcp_callout_active(tp,
1250 tcp_callout_reset(tp, tp->tt_rexmt,
1251 tp->t_rxtcur, tcp_timer_rexmt);
1254 if (so->so_snd.ssb_cc > 0)
1258 } else if (tiwin == tp->snd_wnd &&
1259 th->th_ack == tp->snd_una &&
1260 LIST_EMPTY(&tp->t_segq) &&
1261 tlen <= ssb_space(&so->so_rcv)) {
1262 int newsize = 0; /* automatic sockbuf scaling */
1264 * This is a pure, in-sequence data packet
1265 * with nothing on the reassembly queue and
1266 * we have enough buffer space to take it.
1268 ++tcpstat.tcps_preddat;
1269 tp->rcv_nxt += tlen;
1270 tcpstat.tcps_rcvpack++;
1271 tcpstat.tcps_rcvbyte += tlen;
1272 ND6_HINT(tp); /* some progress has been done */
1274 * Automatic sizing of receive socket buffer. Often the send
1275 * buffer size is not optimally adjusted to the actual network
1276 * conditions at hand (delay bandwidth product). Setting the
1277 * buffer size too small limits throughput on links with high
1278 * bandwidth and high delay (eg. trans-continental/oceanic links).
1280 * On the receive side the socket buffer memory is only rarely
1281 * used to any significant extent. This allows us to be much
1282 * more aggressive in scaling the receive socket buffer. For
1283 * the case that the buffer space is actually used to a large
1284 * extent and we run out of kernel memory we can simply drop
1285 * the new segments; TCP on the sender will just retransmit it
1286 * later. Setting the buffer size too big may only consume too
1287 * much kernel memory if the application doesn't read() from
1288 * the socket or packet loss or reordering makes use of the
1291 * The criteria to step up the receive buffer one notch are:
1292 * 1. the number of bytes received during the time it takes
1293 * one timestamp to be reflected back to us (the RTT);
1294 * 2. received bytes per RTT is within seven eighth of the
1295 * current socket buffer size;
1296 * 3. receive buffer size has not hit maximal automatic size;
1298 * This algorithm does one step per RTT at most and only if
1299 * we receive a bulk stream w/o packet losses or reorderings.
1300 * Shrinking the buffer during idle times is not necessary as
1301 * it doesn't consume any memory when idle.
1303 * TODO: Only step up if the application is actually serving
1304 * the buffer to better manage the socket buffer resources.
1306 if (tcp_do_autorcvbuf &&
1308 (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) {
1309 if (to.to_tsecr > tp->rfbuf_ts &&
1310 to.to_tsecr - tp->rfbuf_ts < hz) {
1312 (so->so_rcv.ssb_hiwat / 8 * 7) &&
1313 so->so_rcv.ssb_hiwat <
1314 tcp_autorcvbuf_max) {
1316 min(so->so_rcv.ssb_hiwat +
1318 tcp_autorcvbuf_max);
1320 /* Start over with next RTT. */
1324 tp->rfbuf_cnt += tlen; /* add up */
1327 * Add data to socket buffer.
1329 if (so->so_state & SS_CANTRCVMORE) {
1333 * Set new socket buffer size.
1334 * Give up when limit is reached.
1337 if (!ssb_reserve(&so->so_rcv, newsize,
1339 so->so_rcv.ssb_flags &= ~SSB_AUTOSIZE;
1340 m_adj(m, drop_hdrlen); /* delayed header drop */
1341 ssb_appendstream(&so->so_rcv, m);
1345 * This code is responsible for most of the ACKs
1346 * the TCP stack sends back after receiving a data
1347 * packet. Note that the DELAY_ACK check fails if
1348 * the delack timer is already running, which results
1349 * in an ack being sent every other packet (which is
1352 * We then further aggregate acks by not actually
1353 * sending one until the protocol thread has completed
1354 * processing the current backlog of packets. This
1355 * does not delay the ack any further, but allows us
1356 * to take advantage of the packet aggregation that
1357 * high speed NICs do (usually blocks of 8-10 packets)
1358 * to send a single ack rather then four or five acks,
1359 * greatly reducing the ack rate, the return channel
1360 * bandwidth, and the protocol overhead on both ends.
1362 * Since this also has the effect of slowing down
1363 * the exponential slow-start ramp-up, systems with
1364 * very large bandwidth-delay products might want
1365 * to turn the feature off.
1367 if (DELAY_ACK(tp)) {
1368 tcp_callout_reset(tp, tp->tt_delack,
1369 tcp_delacktime, tcp_timer_delack);
1370 } else if (tcp_aggregate_acks) {
1371 tp->t_flags |= TF_ACKNOW;
1372 if (!(tp->t_flags & TF_ONOUTPUTQ)) {
1373 tp->t_flags |= TF_ONOUTPUTQ;
1374 tp->tt_cpu = mycpu->gd_cpuid;
1376 &tcpcbackq[tp->tt_cpu],
1380 tp->t_flags |= TF_ACKNOW;
1388 * Calculate amount of space in receive window,
1389 * and then do TCP input processing.
1390 * Receive window is amount of space in rcv queue,
1391 * but not less than advertised window.
1393 recvwin = ssb_space(&so->so_rcv);
1396 tp->rcv_wnd = imax(recvwin, (int)(tp->rcv_adv - tp->rcv_nxt));
1398 /* Reset receive buffer auto scaling when not in bulk receive mode. */
1402 switch (tp->t_state) {
1404 * If the state is SYN_RECEIVED:
1405 * if seg contains an ACK, but not for our SYN/ACK, send a RST.
1407 case TCPS_SYN_RECEIVED:
1408 if ((thflags & TH_ACK) &&
1409 (SEQ_LEQ(th->th_ack, tp->snd_una) ||
1410 SEQ_GT(th->th_ack, tp->snd_max))) {
1411 rstreason = BANDLIM_RST_OPENPORT;
1417 * If the state is SYN_SENT:
1418 * if seg contains an ACK, but not for our SYN, drop the input.
1419 * if seg contains a RST, then drop the connection.
1420 * if seg does not contain SYN, then drop it.
1421 * Otherwise this is an acceptable SYN segment
1422 * initialize tp->rcv_nxt and tp->irs
1423 * if seg contains ack then advance tp->snd_una
1424 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state
1425 * arrange for segment to be acked (eventually)
1426 * continue processing rest of data/controls, beginning with URG
1429 if ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL) {
1430 taop = &tao_noncached;
1431 bzero(taop, sizeof *taop);
1434 if ((thflags & TH_ACK) &&
1435 (SEQ_LEQ(th->th_ack, tp->iss) ||
1436 SEQ_GT(th->th_ack, tp->snd_max))) {
1438 * If we have a cached CCsent for the remote host,
1439 * hence we haven't just crashed and restarted,
1440 * do not send a RST. This may be a retransmission
1441 * from the other side after our earlier ACK was lost.
1442 * Our new SYN, when it arrives, will serve as the
1445 if (taop->tao_ccsent != 0)
1448 rstreason = BANDLIM_UNLIMITED;
1452 if (thflags & TH_RST) {
1453 if (thflags & TH_ACK)
1454 tp = tcp_drop(tp, ECONNREFUSED);
1457 if (!(thflags & TH_SYN))
1459 tp->snd_wnd = th->th_win; /* initial send window */
1460 tp->cc_recv = to.to_cc; /* foreign CC */
1462 tp->irs = th->th_seq;
1464 if (thflags & TH_ACK) {
1466 * Our SYN was acked. If segment contains CC.ECHO
1467 * option, check it to make sure this segment really
1468 * matches our SYN. If not, just drop it as old
1469 * duplicate, but send an RST if we're still playing
1470 * by the old rules. If no CC.ECHO option, make sure
1471 * we don't get fooled into using T/TCP.
1473 if (to.to_flags & TOF_CCECHO) {
1474 if (tp->cc_send != to.to_ccecho) {
1475 if (taop->tao_ccsent != 0)
1478 rstreason = BANDLIM_UNLIMITED;
1483 tp->t_flags &= ~TF_RCVD_CC;
1484 tcpstat.tcps_connects++;
1486 /* Do window scaling on this connection? */
1487 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) ==
1488 (TF_RCVD_SCALE | TF_REQ_SCALE)) {
1489 tp->snd_scale = tp->requested_s_scale;
1490 tp->rcv_scale = tp->request_r_scale;
1492 /* Segment is acceptable, update cache if undefined. */
1493 if (taop->tao_ccsent == 0)
1494 taop->tao_ccsent = to.to_ccecho;
1496 tp->rcv_adv += tp->rcv_wnd;
1497 tp->snd_una++; /* SYN is acked */
1498 tcp_callout_stop(tp, tp->tt_rexmt);
1500 * If there's data, delay ACK; if there's also a FIN
1501 * ACKNOW will be turned on later.
1503 if (DELAY_ACK(tp) && tlen != 0) {
1504 tcp_callout_reset(tp, tp->tt_delack,
1505 tcp_delacktime, tcp_timer_delack);
1507 tp->t_flags |= TF_ACKNOW;
1510 * Received <SYN,ACK> in SYN_SENT[*] state.
1512 * SYN_SENT --> ESTABLISHED
1513 * SYN_SENT* --> FIN_WAIT_1
1515 tp->t_starttime = ticks;
1516 if (tp->t_flags & TF_NEEDFIN) {
1517 tp->t_state = TCPS_FIN_WAIT_1;
1518 tp->t_flags &= ~TF_NEEDFIN;
1521 tp->t_state = TCPS_ESTABLISHED;
1522 tcp_callout_reset(tp, tp->tt_keep, tcp_keepidle,
1527 * Received initial SYN in SYN-SENT[*] state =>
1528 * simultaneous open. If segment contains CC option
1529 * and there is a cached CC, apply TAO test.
1530 * If it succeeds, connection is * half-synchronized.
1531 * Otherwise, do 3-way handshake:
1532 * SYN-SENT -> SYN-RECEIVED
1533 * SYN-SENT* -> SYN-RECEIVED*
1534 * If there was no CC option, clear cached CC value.
1536 tp->t_flags |= TF_ACKNOW;
1537 tcp_callout_stop(tp, tp->tt_rexmt);
1538 if (to.to_flags & TOF_CC) {
1539 if (taop->tao_cc != 0 &&
1540 CC_GT(to.to_cc, taop->tao_cc)) {
1542 * update cache and make transition:
1543 * SYN-SENT -> ESTABLISHED*
1544 * SYN-SENT* -> FIN-WAIT-1*
1546 taop->tao_cc = to.to_cc;
1547 tp->t_starttime = ticks;
1548 if (tp->t_flags & TF_NEEDFIN) {
1549 tp->t_state = TCPS_FIN_WAIT_1;
1550 tp->t_flags &= ~TF_NEEDFIN;
1552 tp->t_state = TCPS_ESTABLISHED;
1553 tcp_callout_reset(tp,
1554 tp->tt_keep, tcp_keepidle,
1557 tp->t_flags |= TF_NEEDSYN;
1559 tp->t_state = TCPS_SYN_RECEIVED;
1561 /* CC.NEW or no option => invalidate cache */
1563 tp->t_state = TCPS_SYN_RECEIVED;
1569 * Advance th->th_seq to correspond to first data byte.
1570 * If data, trim to stay within window,
1571 * dropping FIN if necessary.
1574 if (tlen > tp->rcv_wnd) {
1575 todrop = tlen - tp->rcv_wnd;
1579 tcpstat.tcps_rcvpackafterwin++;
1580 tcpstat.tcps_rcvbyteafterwin += todrop;
1582 tp->snd_wl1 = th->th_seq - 1;
1583 tp->rcv_up = th->th_seq;
1585 * Client side of transaction: already sent SYN and data.
1586 * If the remote host used T/TCP to validate the SYN,
1587 * our data will be ACK'd; if so, enter normal data segment
1588 * processing in the middle of step 5, ack processing.
1589 * Otherwise, goto step 6.
1591 if (thflags & TH_ACK)
1597 * If the state is LAST_ACK or CLOSING or TIME_WAIT:
1598 * if segment contains a SYN and CC [not CC.NEW] option:
1599 * if state == TIME_WAIT and connection duration > MSL,
1600 * drop packet and send RST;
1602 * if SEG.CC > CCrecv then is new SYN, and can implicitly
1603 * ack the FIN (and data) in retransmission queue.
1604 * Complete close and delete TCPCB. Then reprocess
1605 * segment, hoping to find new TCPCB in LISTEN state;
1607 * else must be old SYN; drop it.
1608 * else do normal processing.
1612 case TCPS_TIME_WAIT:
1613 if ((thflags & TH_SYN) &&
1614 (to.to_flags & TOF_CC) && tp->cc_recv != 0) {
1615 if (tp->t_state == TCPS_TIME_WAIT &&
1616 (ticks - tp->t_starttime) > tcp_msl) {
1617 rstreason = BANDLIM_UNLIMITED;
1620 if (CC_GT(to.to_cc, tp->cc_recv)) {
1627 break; /* continue normal processing */
1631 * States other than LISTEN or SYN_SENT.
1632 * First check the RST flag and sequence number since reset segments
1633 * are exempt from the timestamp and connection count tests. This
1634 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix
1635 * below which allowed reset segments in half the sequence space
1636 * to fall though and be processed (which gives forged reset
1637 * segments with a random sequence number a 50 percent chance of
1638 * killing a connection).
1639 * Then check timestamp, if present.
1640 * Then check the connection count, if present.
1641 * Then check that at least some bytes of segment are within
1642 * receive window. If segment begins before rcv_nxt,
1643 * drop leading data (and SYN); if nothing left, just ack.
1646 * If the RST bit is set, check the sequence number to see
1647 * if this is a valid reset segment.
1649 * In all states except SYN-SENT, all reset (RST) segments
1650 * are validated by checking their SEQ-fields. A reset is
1651 * valid if its sequence number is in the window.
1652 * Note: this does not take into account delayed ACKs, so
1653 * we should test against last_ack_sent instead of rcv_nxt.
1654 * The sequence number in the reset segment is normally an
1655 * echo of our outgoing acknowledgement numbers, but some hosts
1656 * send a reset with the sequence number at the rightmost edge
1657 * of our receive window, and we have to handle this case.
1658 * If we have multiple segments in flight, the intial reset
1659 * segment sequence numbers will be to the left of last_ack_sent,
1660 * but they will eventually catch up.
1661 * In any case, it never made sense to trim reset segments to
1662 * fit the receive window since RFC 1122 says:
1663 * 4.2.2.12 RST Segment: RFC-793 Section 3.4
1665 * A TCP SHOULD allow a received RST segment to include data.
1668 * It has been suggested that a RST segment could contain
1669 * ASCII text that encoded and explained the cause of the
1670 * RST. No standard has yet been established for such
1673 * If the reset segment passes the sequence number test examine
1675 * SYN_RECEIVED STATE:
1676 * If passive open, return to LISTEN state.
1677 * If active open, inform user that connection was refused.
1678 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES:
1679 * Inform user that connection was reset, and close tcb.
1680 * CLOSING, LAST_ACK STATES:
1683 * Drop the segment - see Stevens, vol. 2, p. 964 and
1686 if (thflags & TH_RST) {
1687 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
1688 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) {
1689 switch (tp->t_state) {
1691 case TCPS_SYN_RECEIVED:
1692 so->so_error = ECONNREFUSED;
1695 case TCPS_ESTABLISHED:
1696 case TCPS_FIN_WAIT_1:
1697 case TCPS_FIN_WAIT_2:
1698 case TCPS_CLOSE_WAIT:
1699 so->so_error = ECONNRESET;
1701 tp->t_state = TCPS_CLOSED;
1702 tcpstat.tcps_drops++;
1711 case TCPS_TIME_WAIT:
1719 * RFC 1323 PAWS: If we have a timestamp reply on this segment
1720 * and it's less than ts_recent, drop it.
1722 if ((to.to_flags & TOF_TS) && tp->ts_recent != 0 &&
1723 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
1725 /* Check to see if ts_recent is over 24 days old. */
1726 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) {
1728 * Invalidate ts_recent. If this segment updates
1729 * ts_recent, the age will be reset later and ts_recent
1730 * will get a valid value. If it does not, setting
1731 * ts_recent to zero will at least satisfy the
1732 * requirement that zero be placed in the timestamp
1733 * echo reply when ts_recent isn't valid. The
1734 * age isn't reset until we get a valid ts_recent
1735 * because we don't want out-of-order segments to be
1736 * dropped when ts_recent is old.
1740 tcpstat.tcps_rcvduppack++;
1741 tcpstat.tcps_rcvdupbyte += tlen;
1742 tcpstat.tcps_pawsdrop++;
1751 * If T/TCP was negotiated and the segment doesn't have CC,
1752 * or if its CC is wrong then drop the segment.
1753 * RST segments do not have to comply with this.
1755 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) &&
1756 (!(to.to_flags & TOF_CC) || tp->cc_recv != to.to_cc))
1760 * In the SYN-RECEIVED state, validate that the packet belongs to
1761 * this connection before trimming the data to fit the receive
1762 * window. Check the sequence number versus IRS since we know
1763 * the sequence numbers haven't wrapped. This is a partial fix
1764 * for the "LAND" DoS attack.
1766 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) {
1767 rstreason = BANDLIM_RST_OPENPORT;
1771 todrop = tp->rcv_nxt - th->th_seq;
1773 if (TCP_DO_SACK(tp)) {
1774 /* Report duplicate segment at head of packet. */
1775 tp->reportblk.rblk_start = th->th_seq;
1776 tp->reportblk.rblk_end = th->th_seq + tlen;
1777 if (thflags & TH_FIN)
1778 ++tp->reportblk.rblk_end;
1779 if (SEQ_GT(tp->reportblk.rblk_end, tp->rcv_nxt))
1780 tp->reportblk.rblk_end = tp->rcv_nxt;
1781 tp->t_flags |= (TF_DUPSEG | TF_SACKLEFT | TF_ACKNOW);
1783 if (thflags & TH_SYN) {
1793 * Following if statement from Stevens, vol. 2, p. 960.
1795 if (todrop > tlen ||
1796 (todrop == tlen && !(thflags & TH_FIN))) {
1798 * Any valid FIN must be to the left of the window.
1799 * At this point the FIN must be a duplicate or out
1800 * of sequence; drop it.
1805 * Send an ACK to resynchronize and drop any data.
1806 * But keep on processing for RST or ACK.
1808 tp->t_flags |= TF_ACKNOW;
1810 tcpstat.tcps_rcvduppack++;
1811 tcpstat.tcps_rcvdupbyte += todrop;
1813 tcpstat.tcps_rcvpartduppack++;
1814 tcpstat.tcps_rcvpartdupbyte += todrop;
1816 drop_hdrlen += todrop; /* drop from the top afterwards */
1817 th->th_seq += todrop;
1819 if (th->th_urp > todrop)
1820 th->th_urp -= todrop;
1828 * If new data are received on a connection after the
1829 * user processes are gone, then RST the other end.
1831 if ((so->so_state & SS_NOFDREF) &&
1832 tp->t_state > TCPS_CLOSE_WAIT && tlen) {
1834 tcpstat.tcps_rcvafterclose++;
1835 rstreason = BANDLIM_UNLIMITED;
1840 * If segment ends after window, drop trailing data
1841 * (and PUSH and FIN); if nothing left, just ACK.
1843 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd);
1845 tcpstat.tcps_rcvpackafterwin++;
1846 if (todrop >= tlen) {
1847 tcpstat.tcps_rcvbyteafterwin += tlen;
1849 * If a new connection request is received
1850 * while in TIME_WAIT, drop the old connection
1851 * and start over if the sequence numbers
1852 * are above the previous ones.
1854 if (thflags & TH_SYN &&
1855 tp->t_state == TCPS_TIME_WAIT &&
1856 SEQ_GT(th->th_seq, tp->rcv_nxt)) {
1861 * If window is closed can only take segments at
1862 * window edge, and have to drop data and PUSH from
1863 * incoming segments. Continue processing, but
1864 * remember to ack. Otherwise, drop segment
1867 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
1868 tp->t_flags |= TF_ACKNOW;
1869 tcpstat.tcps_rcvwinprobe++;
1873 tcpstat.tcps_rcvbyteafterwin += todrop;
1876 thflags &= ~(TH_PUSH | TH_FIN);
1880 * If last ACK falls within this segment's sequence numbers,
1881 * record its timestamp.
1883 * 1) That the test incorporates suggestions from the latest
1884 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1885 * 2) That updating only on newer timestamps interferes with
1886 * our earlier PAWS tests, so this check should be solely
1887 * predicated on the sequence space of this segment.
1888 * 3) That we modify the segment boundary check to be
1889 * Last.ACK.Sent <= SEG.SEQ + SEG.LEN
1890 * instead of RFC1323's
1891 * Last.ACK.Sent < SEG.SEQ + SEG.LEN,
1892 * This modified check allows us to overcome RFC1323's
1893 * limitations as described in Stevens TCP/IP Illustrated
1894 * Vol. 2 p.869. In such cases, we can still calculate the
1895 * RTT correctly when RCV.NXT == Last.ACK.Sent.
1897 if ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent) &&
1898 SEQ_LEQ(tp->last_ack_sent, (th->th_seq + tlen
1899 + ((thflags & TH_SYN) != 0)
1900 + ((thflags & TH_FIN) != 0)))) {
1901 tp->ts_recent_age = ticks;
1902 tp->ts_recent = to.to_tsval;
1906 * If a SYN is in the window, then this is an
1907 * error and we send an RST and drop the connection.
1909 if (thflags & TH_SYN) {
1910 tp = tcp_drop(tp, ECONNRESET);
1911 rstreason = BANDLIM_UNLIMITED;
1916 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN
1917 * flag is on (half-synchronized state), then queue data for
1918 * later processing; else drop segment and return.
1920 if (!(thflags & TH_ACK)) {
1921 if (tp->t_state == TCPS_SYN_RECEIVED ||
1922 (tp->t_flags & TF_NEEDSYN))
1931 switch (tp->t_state) {
1933 * In SYN_RECEIVED state, the ACK acknowledges our SYN, so enter
1934 * ESTABLISHED state and continue processing.
1935 * The ACK was checked above.
1937 case TCPS_SYN_RECEIVED:
1939 tcpstat.tcps_connects++;
1941 /* Do window scaling? */
1942 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) ==
1943 (TF_RCVD_SCALE | TF_REQ_SCALE)) {
1944 tp->snd_scale = tp->requested_s_scale;
1945 tp->rcv_scale = tp->request_r_scale;
1948 * Upon successful completion of 3-way handshake,
1949 * update cache.CC if it was undefined, pass any queued
1950 * data to the user, and advance state appropriately.
1952 if ((taop = tcp_gettaocache(&inp->inp_inc)) != NULL &&
1954 taop->tao_cc = tp->cc_recv;
1958 * SYN-RECEIVED -> ESTABLISHED
1959 * SYN-RECEIVED* -> FIN-WAIT-1
1961 tp->t_starttime = ticks;
1962 if (tp->t_flags & TF_NEEDFIN) {
1963 tp->t_state = TCPS_FIN_WAIT_1;
1964 tp->t_flags &= ~TF_NEEDFIN;
1966 tp->t_state = TCPS_ESTABLISHED;
1967 tcp_callout_reset(tp, tp->tt_keep, tcp_keepidle,
1971 * If segment contains data or ACK, will call tcp_reass()
1972 * later; if not, do so now to pass queued data to user.
1974 if (tlen == 0 && !(thflags & TH_FIN))
1975 tcp_reass(tp, NULL, NULL, NULL);
1979 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
1980 * ACKs. If the ack is in the range
1981 * tp->snd_una < th->th_ack <= tp->snd_max
1982 * then advance tp->snd_una to th->th_ack and drop
1983 * data from the retransmission queue. If this ACK reflects
1984 * more up to date window information we update our window information.
1986 case TCPS_ESTABLISHED:
1987 case TCPS_FIN_WAIT_1:
1988 case TCPS_FIN_WAIT_2:
1989 case TCPS_CLOSE_WAIT:
1992 case TCPS_TIME_WAIT:
1994 if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
1995 if (TCP_DO_SACK(tp))
1996 tcp_sack_update_scoreboard(tp, &to);
1997 if (tlen != 0 || tiwin != tp->snd_wnd) {
2001 tcpstat.tcps_rcvdupack++;
2002 if (!tcp_callout_active(tp, tp->tt_rexmt) ||
2003 th->th_ack != tp->snd_una) {
2008 * We have outstanding data (other than
2009 * a window probe), this is a completely
2010 * duplicate ack (ie, window info didn't
2011 * change), the ack is the biggest we've
2012 * seen and we've seen exactly our rexmt
2013 * threshhold of them, so assume a packet
2014 * has been dropped and retransmit it.
2015 * Kludge snd_nxt & the congestion
2016 * window so we send only this one
2019 if (IN_FASTRECOVERY(tp)) {
2020 if (TCP_DO_SACK(tp)) {
2021 /* No artifical cwnd inflation. */
2022 tcp_sack_rexmt(tp, th);
2025 * Dup acks mean that packets
2026 * have left the network
2027 * (they're now cached at the
2028 * receiver) so bump cwnd by
2029 * the amount in the receiver
2030 * to keep a constant cwnd
2031 * packets in the network.
2033 tp->snd_cwnd += tp->t_maxseg;
2036 } else if (SEQ_LT(th->th_ack, tp->snd_recover)) {
2039 } else if (++tp->t_dupacks == tcprexmtthresh) {
2040 tcp_seq old_snd_nxt;
2044 if (tcp_do_eifel_detect &&
2045 (tp->t_flags & TF_RCVD_TSTMP)) {
2046 tcp_save_congestion_state(tp);
2047 tp->t_flags |= TF_FASTREXMT;
2050 * We know we're losing at the current
2051 * window size, so do congestion avoidance:
2052 * set ssthresh to half the current window
2053 * and pull our congestion window back to the
2056 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 /
2060 tp->snd_ssthresh = win * tp->t_maxseg;
2061 ENTER_FASTRECOVERY(tp);
2062 tp->snd_recover = tp->snd_max;
2063 tcp_callout_stop(tp, tp->tt_rexmt);
2065 old_snd_nxt = tp->snd_nxt;
2066 tp->snd_nxt = th->th_ack;
2067 tp->snd_cwnd = tp->t_maxseg;
2069 ++tcpstat.tcps_sndfastrexmit;
2070 tp->snd_cwnd = tp->snd_ssthresh;
2071 tp->rexmt_high = tp->snd_nxt;
2072 if (SEQ_GT(old_snd_nxt, tp->snd_nxt))
2073 tp->snd_nxt = old_snd_nxt;
2074 KASSERT(tp->snd_limited <= 2,
2075 ("tp->snd_limited too big"));
2076 if (TCP_DO_SACK(tp))
2077 tcp_sack_rexmt(tp, th);
2079 tp->snd_cwnd += tp->t_maxseg *
2080 (tp->t_dupacks - tp->snd_limited);
2081 } else if (tcp_do_limitedtransmit) {
2082 u_long oldcwnd = tp->snd_cwnd;
2083 tcp_seq oldsndmax = tp->snd_max;
2084 tcp_seq oldsndnxt = tp->snd_nxt;
2085 /* outstanding data */
2086 uint32_t ownd = tp->snd_max - tp->snd_una;
2089 #define iceildiv(n, d) (((n)+(d)-1) / (d))
2091 KASSERT(tp->t_dupacks == 1 ||
2093 ("dupacks not 1 or 2"));
2094 if (tp->t_dupacks == 1)
2095 tp->snd_limited = 0;
2096 tp->snd_nxt = tp->snd_max;
2097 tp->snd_cwnd = ownd +
2098 (tp->t_dupacks - tp->snd_limited) *
2103 * Other acks may have been processed,
2104 * snd_nxt cannot be reset to a value less
2107 if (SEQ_LT(oldsndnxt, oldsndmax)) {
2108 if (SEQ_GT(oldsndnxt, tp->snd_una))
2109 tp->snd_nxt = oldsndnxt;
2111 tp->snd_nxt = tp->snd_una;
2113 tp->snd_cwnd = oldcwnd;
2114 sent = tp->snd_max - oldsndmax;
2115 if (sent > tp->t_maxseg) {
2116 KASSERT((tp->t_dupacks == 2 &&
2117 tp->snd_limited == 0) ||
2118 (sent == tp->t_maxseg + 1 &&
2119 tp->t_flags & TF_SENTFIN),
2121 KASSERT(sent <= tp->t_maxseg * 2,
2122 ("sent too many segments"));
2123 tp->snd_limited = 2;
2124 tcpstat.tcps_sndlimited += 2;
2125 } else if (sent > 0) {
2127 ++tcpstat.tcps_sndlimited;
2128 } else if (tcp_do_early_retransmit &&
2129 (tcp_do_eifel_detect &&
2130 (tp->t_flags & TF_RCVD_TSTMP)) &&
2131 ownd < 4 * tp->t_maxseg &&
2132 tp->t_dupacks + 1 >=
2133 iceildiv(ownd, tp->t_maxseg) &&
2134 (!TCP_DO_SACK(tp) ||
2135 ownd <= tp->t_maxseg ||
2136 tcp_sack_has_sacked(&tp->scb,
2137 ownd - tp->t_maxseg))) {
2138 ++tcpstat.tcps_sndearlyrexmit;
2139 tp->t_flags |= TF_EARLYREXMT;
2140 goto fastretransmit;
2146 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una"));
2148 if (SEQ_GT(th->th_ack, tp->snd_max)) {
2150 * Detected optimistic ACK attack.
2151 * Force slow-start to de-synchronize attack.
2153 tp->snd_cwnd = tp->t_maxseg;
2156 tcpstat.tcps_rcvacktoomuch++;
2160 * If we reach this point, ACK is not a duplicate,
2161 * i.e., it ACKs something we sent.
2163 if (tp->t_flags & TF_NEEDSYN) {
2165 * T/TCP: Connection was half-synchronized, and our
2166 * SYN has been ACK'd (so connection is now fully
2167 * synchronized). Go to non-starred state,
2168 * increment snd_una for ACK of SYN, and check if
2169 * we can do window scaling.
2171 tp->t_flags &= ~TF_NEEDSYN;
2173 /* Do window scaling? */
2174 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) ==
2175 (TF_RCVD_SCALE | TF_REQ_SCALE)) {
2176 tp->snd_scale = tp->requested_s_scale;
2177 tp->rcv_scale = tp->request_r_scale;
2182 acked = th->th_ack - tp->snd_una;
2183 tcpstat.tcps_rcvackpack++;
2184 tcpstat.tcps_rcvackbyte += acked;
2186 if (tcp_do_eifel_detect && acked > 0 &&
2187 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) &&
2188 (tp->t_flags & TF_FIRSTACCACK)) {
2189 /* Eifel detection applicable. */
2190 if (to.to_tsecr < tp->t_rexmtTS) {
2191 ++tcpstat.tcps_eifeldetected;
2192 tcp_revert_congestion_state(tp);
2193 if (tp->t_rxtshift == 1 &&
2194 ticks >= tp->t_badrxtwin)
2195 ++tcpstat.tcps_rttcantdetect;
2197 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) {
2199 * If we just performed our first retransmit,
2200 * and the ACK arrives within our recovery window,
2201 * then it was a mistake to do the retransmit
2202 * in the first place. Recover our original cwnd
2203 * and ssthresh, and proceed to transmit where we
2206 tcp_revert_congestion_state(tp);
2207 ++tcpstat.tcps_rttdetected;
2211 * If we have a timestamp reply, update smoothed
2212 * round trip time. If no timestamp is present but
2213 * transmit timer is running and timed sequence
2214 * number was acked, update smoothed round trip time.
2215 * Since we now have an rtt measurement, cancel the
2216 * timer backoff (cf., Phil Karn's retransmit alg.).
2217 * Recompute the initial retransmit timer.
2219 * Some machines (certain windows boxes) send broken
2220 * timestamp replies during the SYN+ACK phase, ignore
2223 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0))
2224 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1);
2225 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq))
2226 tcp_xmit_timer(tp, ticks - tp->t_rtttime);
2227 tcp_xmit_bandwidth_limit(tp, th->th_ack);
2230 * If no data (only SYN) was ACK'd,
2231 * skip rest of ACK processing.
2236 /* Stop looking for an acceptable ACK since one was received. */
2237 tp->t_flags &= ~(TF_FIRSTACCACK | TF_FASTREXMT | TF_EARLYREXMT);
2239 if (acked > so->so_snd.ssb_cc) {
2240 tp->snd_wnd -= so->so_snd.ssb_cc;
2241 sbdrop(&so->so_snd.sb, (int)so->so_snd.ssb_cc);
2242 ourfinisacked = TRUE;
2244 sbdrop(&so->so_snd.sb, acked);
2245 tp->snd_wnd -= acked;
2246 ourfinisacked = FALSE;
2251 * Update window information.
2252 * Don't look at window if no ACK:
2253 * TAC's send garbage on first SYN.
2255 if (SEQ_LT(tp->snd_wl1, th->th_seq) ||
2256 (tp->snd_wl1 == th->th_seq &&
2257 (SEQ_LT(tp->snd_wl2, th->th_ack) ||
2258 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) {
2259 /* keep track of pure window updates */
2260 if (tlen == 0 && tp->snd_wl2 == th->th_ack &&
2261 tiwin > tp->snd_wnd)
2262 tcpstat.tcps_rcvwinupd++;
2263 tp->snd_wnd = tiwin;
2264 tp->snd_wl1 = th->th_seq;
2265 tp->snd_wl2 = th->th_ack;
2266 if (tp->snd_wnd > tp->max_sndwnd)
2267 tp->max_sndwnd = tp->snd_wnd;
2271 tp->snd_una = th->th_ack;
2272 if (TCP_DO_SACK(tp))
2273 tcp_sack_update_scoreboard(tp, &to);
2274 if (IN_FASTRECOVERY(tp)) {
2275 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) {
2276 EXIT_FASTRECOVERY(tp);
2279 * If the congestion window was inflated
2280 * to account for the other side's
2281 * cached packets, retract it.
2283 if (!TCP_DO_SACK(tp))
2284 tp->snd_cwnd = tp->snd_ssthresh;
2287 * Window inflation should have left us
2288 * with approximately snd_ssthresh outstanding
2289 * data. But, in case we would be inclined
2290 * to send a burst, better do it using
2293 if (SEQ_GT(th->th_ack + tp->snd_cwnd,
2294 tp->snd_max + 2 * tp->t_maxseg))
2296 (tp->snd_max - tp->snd_una) +
2301 if (TCP_DO_SACK(tp)) {
2302 tp->snd_max_rexmt = tp->snd_max;
2303 tcp_sack_rexmt(tp, th);
2305 tcp_newreno_partial_ack(tp, th, acked);
2311 * Open the congestion window. When in slow-start,
2312 * open exponentially: maxseg per packet. Otherwise,
2313 * open linearly: maxseg per window.
2315 if (tp->snd_cwnd <= tp->snd_ssthresh) {
2317 (SEQ_LT(tp->snd_nxt, tp->snd_max) ?
2318 tp->t_maxseg : 2 * tp->t_maxseg);
2321 tp->snd_cwnd += tcp_do_abc ?
2322 min(acked, abc_sslimit) : tp->t_maxseg;
2324 /* linear increase */
2325 tp->snd_wacked += tcp_do_abc ? acked :
2327 if (tp->snd_wacked >= tp->snd_cwnd) {
2328 tp->snd_wacked -= tp->snd_cwnd;
2329 tp->snd_cwnd += tp->t_maxseg;
2332 tp->snd_cwnd = min(tp->snd_cwnd,
2333 TCP_MAXWIN << tp->snd_scale);
2334 tp->snd_recover = th->th_ack - 1;
2336 if (SEQ_LT(tp->snd_nxt, tp->snd_una))
2337 tp->snd_nxt = tp->snd_una;
2340 * If all outstanding data is acked, stop retransmit
2341 * timer and remember to restart (more output or persist).
2342 * If there is more data to be acked, restart retransmit
2343 * timer, using current (possibly backed-off) value.
2345 if (th->th_ack == tp->snd_max) {
2346 tcp_callout_stop(tp, tp->tt_rexmt);
2348 } else if (!tcp_callout_active(tp, tp->tt_persist)) {
2349 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur,
2353 switch (tp->t_state) {
2355 * In FIN_WAIT_1 STATE in addition to the processing
2356 * for the ESTABLISHED state if our FIN is now acknowledged
2357 * then enter FIN_WAIT_2.
2359 case TCPS_FIN_WAIT_1:
2360 if (ourfinisacked) {
2362 * If we can't receive any more
2363 * data, then closing user can proceed.
2364 * Starting the timer is contrary to the
2365 * specification, but if we don't get a FIN
2366 * we'll hang forever.
2368 if (so->so_state & SS_CANTRCVMORE) {
2369 soisdisconnected(so);
2370 tcp_callout_reset(tp, tp->tt_2msl,
2371 tcp_maxidle, tcp_timer_2msl);
2373 tp->t_state = TCPS_FIN_WAIT_2;
2378 * In CLOSING STATE in addition to the processing for
2379 * the ESTABLISHED state if the ACK acknowledges our FIN
2380 * then enter the TIME-WAIT state, otherwise ignore
2384 if (ourfinisacked) {
2385 tp->t_state = TCPS_TIME_WAIT;
2386 tcp_canceltimers(tp);
2387 /* Shorten TIME_WAIT [RFC-1644, p.28] */
2388 if (tp->cc_recv != 0 &&
2389 (ticks - tp->t_starttime) < tcp_msl) {
2390 tcp_callout_reset(tp, tp->tt_2msl,
2391 tp->t_rxtcur * TCPTV_TWTRUNC,
2394 tcp_callout_reset(tp, tp->tt_2msl,
2395 2 * tcp_msl, tcp_timer_2msl);
2397 soisdisconnected(so);
2402 * In LAST_ACK, we may still be waiting for data to drain
2403 * and/or to be acked, as well as for the ack of our FIN.
2404 * If our FIN is now acknowledged, delete the TCB,
2405 * enter the closed state and return.
2408 if (ourfinisacked) {
2415 * In TIME_WAIT state the only thing that should arrive
2416 * is a retransmission of the remote FIN. Acknowledge
2417 * it and restart the finack timer.
2419 case TCPS_TIME_WAIT:
2420 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_msl,
2428 * Update window information.
2429 * Don't look at window if no ACK: TAC's send garbage on first SYN.
2431 if ((thflags & TH_ACK) &&
2432 acceptable_window_update(tp, th, tiwin)) {
2433 /* keep track of pure window updates */
2434 if (tlen == 0 && tp->snd_wl2 == th->th_ack &&
2435 tiwin > tp->snd_wnd)
2436 tcpstat.tcps_rcvwinupd++;
2437 tp->snd_wnd = tiwin;
2438 tp->snd_wl1 = th->th_seq;
2439 tp->snd_wl2 = th->th_ack;
2440 if (tp->snd_wnd > tp->max_sndwnd)
2441 tp->max_sndwnd = tp->snd_wnd;
2446 * Process segments with URG.
2448 if ((thflags & TH_URG) && th->th_urp &&
2449 !TCPS_HAVERCVDFIN(tp->t_state)) {
2451 * This is a kludge, but if we receive and accept
2452 * random urgent pointers, we'll crash in
2453 * soreceive. It's hard to imagine someone
2454 * actually wanting to send this much urgent data.
2456 if (th->th_urp + so->so_rcv.ssb_cc > sb_max) {
2457 th->th_urp = 0; /* XXX */
2458 thflags &= ~TH_URG; /* XXX */
2459 goto dodata; /* XXX */
2462 * If this segment advances the known urgent pointer,
2463 * then mark the data stream. This should not happen
2464 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
2465 * a FIN has been received from the remote side.
2466 * In these states we ignore the URG.
2468 * According to RFC961 (Assigned Protocols),
2469 * the urgent pointer points to the last octet
2470 * of urgent data. We continue, however,
2471 * to consider it to indicate the first octet
2472 * of data past the urgent section as the original
2473 * spec states (in one of two places).
2475 if (SEQ_GT(th->th_seq + th->th_urp, tp->rcv_up)) {
2476 tp->rcv_up = th->th_seq + th->th_urp;
2477 so->so_oobmark = so->so_rcv.ssb_cc +
2478 (tp->rcv_up - tp->rcv_nxt) - 1;
2479 if (so->so_oobmark == 0)
2480 so->so_state |= SS_RCVATMARK;
2482 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
2485 * Remove out of band data so doesn't get presented to user.
2486 * This can happen independent of advancing the URG pointer,
2487 * but if two URG's are pending at once, some out-of-band
2488 * data may creep in... ick.
2490 if (th->th_urp <= (u_long)tlen &&
2491 !(so->so_options & SO_OOBINLINE)) {
2492 /* hdr drop is delayed */
2493 tcp_pulloutofband(so, th, m, drop_hdrlen);
2497 * If no out of band data is expected,
2498 * pull receive urgent pointer along
2499 * with the receive window.
2501 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
2502 tp->rcv_up = tp->rcv_nxt;
2507 * Process the segment text, merging it into the TCP sequencing queue,
2508 * and arranging for acknowledgment of receipt if necessary.
2509 * This process logically involves adjusting tp->rcv_wnd as data
2510 * is presented to the user (this happens in tcp_usrreq.c,
2511 * case PRU_RCVD). If a FIN has already been received on this
2512 * connection then we just ignore the text.
2514 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) {
2515 m_adj(m, drop_hdrlen); /* delayed header drop */
2517 * Insert segment which includes th into TCP reassembly queue
2518 * with control block tp. Set thflags to whether reassembly now
2519 * includes a segment with FIN. This handles the common case
2520 * inline (segment is the next to be received on an established
2521 * connection, and the queue is empty), avoiding linkage into
2522 * and removal from the queue and repetition of various
2524 * Set DELACK for segments received in order, but ack
2525 * immediately when segments are out of order (so
2526 * fast retransmit can work).
2528 if (th->th_seq == tp->rcv_nxt &&
2529 LIST_EMPTY(&tp->t_segq) &&
2530 TCPS_HAVEESTABLISHED(tp->t_state)) {
2531 if (DELAY_ACK(tp)) {
2532 tcp_callout_reset(tp, tp->tt_delack,
2533 tcp_delacktime, tcp_timer_delack);
2535 tp->t_flags |= TF_ACKNOW;
2537 tp->rcv_nxt += tlen;
2538 thflags = th->th_flags & TH_FIN;
2539 tcpstat.tcps_rcvpack++;
2540 tcpstat.tcps_rcvbyte += tlen;
2542 if (so->so_state & SS_CANTRCVMORE)
2545 ssb_appendstream(&so->so_rcv, m);
2548 if (!(tp->t_flags & TF_DUPSEG)) {
2549 /* Initialize SACK report block. */
2550 tp->reportblk.rblk_start = th->th_seq;
2551 tp->reportblk.rblk_end = th->th_seq + tlen +
2552 ((thflags & TH_FIN) != 0);
2554 thflags = tcp_reass(tp, th, &tlen, m);
2555 tp->t_flags |= TF_ACKNOW;
2559 * Note the amount of data that peer has sent into
2560 * our window, in order to estimate the sender's
2563 len = so->so_rcv.ssb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
2570 * If FIN is received ACK the FIN and let the user know
2571 * that the connection is closing.
2573 if (thflags & TH_FIN) {
2574 if (!TCPS_HAVERCVDFIN(tp->t_state)) {
2577 * If connection is half-synchronized
2578 * (ie NEEDSYN flag on) then delay ACK,
2579 * so it may be piggybacked when SYN is sent.
2580 * Otherwise, since we received a FIN then no
2581 * more input can be expected, send ACK now.
2583 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) {
2584 tcp_callout_reset(tp, tp->tt_delack,
2585 tcp_delacktime, tcp_timer_delack);
2587 tp->t_flags |= TF_ACKNOW;
2592 switch (tp->t_state) {
2594 * In SYN_RECEIVED and ESTABLISHED STATES
2595 * enter the CLOSE_WAIT state.
2597 case TCPS_SYN_RECEIVED:
2598 tp->t_starttime = ticks;
2600 case TCPS_ESTABLISHED:
2601 tp->t_state = TCPS_CLOSE_WAIT;
2605 * If still in FIN_WAIT_1 STATE FIN has not been acked so
2606 * enter the CLOSING state.
2608 case TCPS_FIN_WAIT_1:
2609 tp->t_state = TCPS_CLOSING;
2613 * In FIN_WAIT_2 state enter the TIME_WAIT state,
2614 * starting the time-wait timer, turning off the other
2617 case TCPS_FIN_WAIT_2:
2618 tp->t_state = TCPS_TIME_WAIT;
2619 tcp_canceltimers(tp);
2620 /* Shorten TIME_WAIT [RFC-1644, p.28] */
2621 if (tp->cc_recv != 0 &&
2622 (ticks - tp->t_starttime) < tcp_msl) {
2623 tcp_callout_reset(tp, tp->tt_2msl,
2624 tp->t_rxtcur * TCPTV_TWTRUNC,
2626 /* For transaction client, force ACK now. */
2627 tp->t_flags |= TF_ACKNOW;
2629 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_msl,
2632 soisdisconnected(so);
2636 * In TIME_WAIT state restart the 2 MSL time_wait timer.
2638 case TCPS_TIME_WAIT:
2639 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_msl,
2646 if (so->so_options & SO_DEBUG)
2647 tcp_trace(TA_INPUT, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
2651 * Return any desired output.
2653 if (needoutput || (tp->t_flags & TF_ACKNOW))
2659 * Generate an ACK dropping incoming segment if it occupies
2660 * sequence space, where the ACK reflects our state.
2662 * We can now skip the test for the RST flag since all
2663 * paths to this code happen after packets containing
2664 * RST have been dropped.
2666 * In the SYN-RECEIVED state, don't send an ACK unless the
2667 * segment we received passes the SYN-RECEIVED ACK test.
2668 * If it fails send a RST. This breaks the loop in the
2669 * "LAND" DoS attack, and also prevents an ACK storm
2670 * between two listening ports that have been sent forged
2671 * SYN segments, each with the source address of the other.
2673 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
2674 (SEQ_GT(tp->snd_una, th->th_ack) ||
2675 SEQ_GT(th->th_ack, tp->snd_max)) ) {
2676 rstreason = BANDLIM_RST_OPENPORT;
2680 if (so->so_options & SO_DEBUG)
2681 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
2684 tp->t_flags |= TF_ACKNOW;
2690 * Generate a RST, dropping incoming segment.
2691 * Make ACK acceptable to originator of segment.
2692 * Don't bother to respond if destination was broadcast/multicast.
2694 if ((thflags & TH_RST) || m->m_flags & (M_BCAST | M_MCAST))
2697 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
2698 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
2701 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
2702 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
2703 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
2704 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
2707 /* IPv6 anycast check is done at tcp6_input() */
2710 * Perform bandwidth limiting.
2713 if (badport_bandlim(rstreason) < 0)
2718 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
2719 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
2721 if (thflags & TH_ACK)
2722 /* mtod() below is safe as long as hdr dropping is delayed */
2723 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack,
2726 if (thflags & TH_SYN)
2728 /* mtod() below is safe as long as hdr dropping is delayed */
2729 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen,
2730 (tcp_seq)0, TH_RST | TH_ACK);
2736 * Drop space held by incoming segment and return.
2739 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
2740 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
2747 * Parse TCP options and place in tcpopt.
2750 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn)
2755 for (; cnt > 0; cnt -= optlen, cp += optlen) {
2757 if (opt == TCPOPT_EOL)
2759 if (opt == TCPOPT_NOP)
2765 if (optlen < 2 || optlen > cnt)
2770 if (optlen != TCPOLEN_MAXSEG)
2774 to->to_flags |= TOF_MSS;
2775 bcopy(cp + 2, &to->to_mss, sizeof to->to_mss);
2776 to->to_mss = ntohs(to->to_mss);
2779 if (optlen != TCPOLEN_WINDOW)
2783 to->to_flags |= TOF_SCALE;
2784 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT);
2786 case TCPOPT_TIMESTAMP:
2787 if (optlen != TCPOLEN_TIMESTAMP)
2789 to->to_flags |= TOF_TS;
2790 bcopy(cp + 2, &to->to_tsval, sizeof to->to_tsval);
2791 to->to_tsval = ntohl(to->to_tsval);
2792 bcopy(cp + 6, &to->to_tsecr, sizeof to->to_tsecr);
2793 to->to_tsecr = ntohl(to->to_tsecr);
2795 * If echoed timestamp is later than the current time,
2796 * fall back to non RFC1323 RTT calculation.
2798 if (to->to_tsecr != 0 && TSTMP_GT(to->to_tsecr, ticks))
2802 if (optlen != TCPOLEN_CC)
2804 to->to_flags |= TOF_CC;
2805 bcopy(cp + 2, &to->to_cc, sizeof to->to_cc);
2806 to->to_cc = ntohl(to->to_cc);
2809 if (optlen != TCPOLEN_CC)
2813 to->to_flags |= TOF_CCNEW;
2814 bcopy(cp + 2, &to->to_cc, sizeof to->to_cc);
2815 to->to_cc = ntohl(to->to_cc);
2818 if (optlen != TCPOLEN_CC)
2822 to->to_flags |= TOF_CCECHO;
2823 bcopy(cp + 2, &to->to_ccecho, sizeof to->to_ccecho);
2824 to->to_ccecho = ntohl(to->to_ccecho);
2826 case TCPOPT_SACK_PERMITTED:
2827 if (optlen != TCPOLEN_SACK_PERMITTED)
2831 to->to_flags |= TOF_SACK_PERMITTED;
2834 if ((optlen - 2) & 0x07) /* not multiple of 8 */
2836 to->to_nsackblocks = (optlen - 2) / 8;
2837 to->to_sackblocks = (struct raw_sackblock *) (cp + 2);
2838 to->to_flags |= TOF_SACK;
2839 for (i = 0; i < to->to_nsackblocks; i++) {
2840 struct raw_sackblock *r = &to->to_sackblocks[i];
2842 r->rblk_start = ntohl(r->rblk_start);
2843 r->rblk_end = ntohl(r->rblk_end);
2853 * Pull out of band byte out of a segment so
2854 * it doesn't appear in the user's data queue.
2855 * It is still reflected in the segment length for
2856 * sequencing purposes.
2857 * "off" is the delayed to be dropped hdrlen.
2860 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off)
2862 int cnt = off + th->th_urp - 1;
2865 if (m->m_len > cnt) {
2866 char *cp = mtod(m, caddr_t) + cnt;
2867 struct tcpcb *tp = sototcpcb(so);
2870 tp->t_oobflags |= TCPOOB_HAVEDATA;
2871 bcopy(cp + 1, cp, m->m_len - cnt - 1);
2873 if (m->m_flags & M_PKTHDR)
2882 panic("tcp_pulloutofband");
2886 * Collect new round-trip time estimate
2887 * and update averages and current timeout.
2890 tcp_xmit_timer(struct tcpcb *tp, int rtt)
2894 tcpstat.tcps_rttupdated++;
2896 if (tp->t_srtt != 0) {
2898 * srtt is stored as fixed point with 5 bits after the
2899 * binary point (i.e., scaled by 8). The following magic
2900 * is equivalent to the smoothing algorithm in rfc793 with
2901 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
2902 * point). Adjust rtt to origin 0.
2904 delta = ((rtt - 1) << TCP_DELTA_SHIFT)
2905 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
2907 if ((tp->t_srtt += delta) <= 0)
2911 * We accumulate a smoothed rtt variance (actually, a
2912 * smoothed mean difference), then set the retransmit
2913 * timer to smoothed rtt + 4 times the smoothed variance.
2914 * rttvar is stored as fixed point with 4 bits after the
2915 * binary point (scaled by 16). The following is
2916 * equivalent to rfc793 smoothing with an alpha of .75
2917 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces
2918 * rfc793's wired-in beta.
2922 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
2923 if ((tp->t_rttvar += delta) <= 0)
2925 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
2926 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2929 * No rtt measurement yet - use the unsmoothed rtt.
2930 * Set the variance to half the rtt (so our first
2931 * retransmit happens at 3*rtt).
2933 tp->t_srtt = rtt << TCP_RTT_SHIFT;
2934 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
2935 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2941 * the retransmit should happen at rtt + 4 * rttvar.
2942 * Because of the way we do the smoothing, srtt and rttvar
2943 * will each average +1/2 tick of bias. When we compute
2944 * the retransmit timer, we want 1/2 tick of rounding and
2945 * 1 extra tick because of +-1/2 tick uncertainty in the
2946 * firing of the timer. The bias will give us exactly the
2947 * 1.5 tick we need. But, because the bias is
2948 * statistical, we have to test that we don't drop below
2949 * the minimum feasible timer (which is 2 ticks).
2951 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
2952 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);
2955 * We received an ack for a packet that wasn't retransmitted;
2956 * it is probably safe to discard any error indications we've
2957 * received recently. This isn't quite right, but close enough
2958 * for now (a route might have failed after we sent a segment,
2959 * and the return path might not be symmetrical).
2961 tp->t_softerror = 0;
2965 * Determine a reasonable value for maxseg size.
2966 * If the route is known, check route for mtu.
2967 * If none, use an mss that can be handled on the outgoing
2968 * interface without forcing IP to fragment; if bigger than
2969 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES
2970 * to utilize large mbufs. If no route is found, route has no mtu,
2971 * or the destination isn't local, use a default, hopefully conservative
2972 * size (usually 512 or the default IP max size, but no more than the mtu
2973 * of the interface), as we can't discover anything about intervening
2974 * gateways or networks. We also initialize the congestion/slow start
2975 * window to be a single segment if the destination isn't local.
2976 * While looking at the routing entry, we also initialize other path-dependent
2977 * parameters from pre-set or cached values in the routing entry.
2979 * Also take into account the space needed for options that we
2980 * send regularly. Make maxseg shorter by that amount to assure
2981 * that we can send maxseg amount of data even when the options
2982 * are present. Store the upper limit of the length of options plus
2985 * NOTE that this routine is only called when we process an incoming
2986 * segment, for outgoing segments only tcp_mssopt is called.
2988 * In case of T/TCP, we call this routine during implicit connection
2989 * setup as well (offer = -1), to initialize maxseg from the cached
2993 tcp_mss(struct tcpcb *tp, int offer)
2999 struct inpcb *inp = tp->t_inpcb;
3001 struct rmxp_tao *taop;
3002 int origoffer = offer;
3004 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE);
3005 size_t min_protoh = isipv6 ?
3006 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) :
3007 sizeof(struct tcpiphdr);
3009 const boolean_t isipv6 = FALSE;
3010 const size_t min_protoh = sizeof(struct tcpiphdr);
3014 rt = tcp_rtlookup6(&inp->inp_inc);
3016 rt = tcp_rtlookup(&inp->inp_inc);
3018 tp->t_maxopd = tp->t_maxseg =
3019 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt);
3023 so = inp->inp_socket;
3025 taop = rmx_taop(rt->rt_rmx);
3027 * Offer == -1 means that we didn't receive SYN yet,
3028 * use cached value in that case;
3031 offer = taop->tao_mssopt;
3033 * Offer == 0 means that there was no MSS on the SYN segment,
3034 * in this case we use tcp_mssdflt.
3037 offer = (isipv6 ? tcp_v6mssdflt : tcp_mssdflt);
3040 * Prevent DoS attack with too small MSS. Round up
3041 * to at least minmss.
3043 offer = max(offer, tcp_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, 64);
3052 taop->tao_mssopt = offer;
3055 * While we're here, check if there's an initial rtt
3056 * or rttvar. Convert from the route-table units
3057 * to scaled multiples of the slow timeout timer.
3059 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) {
3061 * XXX the lock bit for RTT indicates that the value
3062 * is also a minimum value; this is subject to time.
3064 if (rt->rt_rmx.rmx_locks & RTV_RTT)
3065 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz);
3066 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE));
3067 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE;
3068 tcpstat.tcps_usedrtt++;
3069 if (rt->rt_rmx.rmx_rttvar) {
3070 tp->t_rttvar = rt->rt_rmx.rmx_rttvar /
3071 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE));
3072 tcpstat.tcps_usedrttvar++;
3074 /* default variation is +- 1 rtt */
3076 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
3078 TCPT_RANGESET(tp->t_rxtcur,
3079 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
3080 tp->t_rttmin, TCPTV_REXMTMAX);
3083 * if there's an mtu associated with the route, use it
3084 * else, use the link mtu.
3086 if (rt->rt_rmx.rmx_mtu)
3087 mss = rt->rt_rmx.rmx_mtu - min_protoh;
3090 mss = ND_IFINFO(rt->rt_ifp)->linkmtu - min_protoh;
3091 if (!in6_localaddr(&inp->in6p_faddr))
3092 mss = min(mss, tcp_v6mssdflt);
3094 mss = ifp->if_mtu - min_protoh;
3095 if (!in_localaddr(inp->inp_faddr))
3096 mss = min(mss, tcp_mssdflt);
3099 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.
3110 * In case of T/TCP, origoffer==-1 indicates, that no segments
3111 * were received yet. In this case we just guess, otherwise
3112 * we do the same as before T/TCP.
3114 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP &&
3116 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP))
3117 mss -= TCPOLEN_TSTAMP_APPA;
3118 if ((tp->t_flags & (TF_REQ_CC | TF_NOOPT)) == TF_REQ_CC &&
3120 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC))
3121 mss -= TCPOLEN_CC_APPA;
3123 #if (MCLBYTES & (MCLBYTES - 1)) == 0
3125 mss &= ~(MCLBYTES-1);
3128 mss = mss / MCLBYTES * MCLBYTES;
3131 * If there's a pipesize, change the socket buffer
3132 * to that size. Make the socket buffers an integral
3133 * number of mss units; if the mss is larger than
3134 * the socket buffer, decrease the mss.
3137 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0)
3139 bufsize = so->so_snd.ssb_hiwat;
3143 bufsize = roundup(bufsize, mss);
3144 if (bufsize > sb_max)
3146 if (bufsize > so->so_snd.ssb_hiwat)
3147 ssb_reserve(&so->so_snd, bufsize, so, NULL);
3152 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0)
3154 bufsize = so->so_rcv.ssb_hiwat;
3155 if (bufsize > mss) {
3156 bufsize = roundup(bufsize, mss);
3157 if (bufsize > sb_max)
3159 if (bufsize > so->so_rcv.ssb_hiwat)
3160 ssb_reserve(&so->so_rcv, bufsize, so, NULL);
3164 * Set the slow-start flight size depending on whether this
3165 * is a local network or not.
3168 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380));
3172 if (rt->rt_rmx.rmx_ssthresh) {
3174 * There's some sort of gateway or interface
3175 * buffer limit on the path. Use this to set
3176 * the slow start threshhold, but set the
3177 * threshold to no less than 2*mss.
3179 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh);
3180 tcpstat.tcps_usedssthresh++;
3185 * Determine the MSS option to send on an outgoing SYN.
3188 tcp_mssopt(struct tcpcb *tp)
3193 ((tp->t_inpcb->inp_vflag & INP_IPV6) ? TRUE : FALSE);
3194 int min_protoh = isipv6 ?
3195 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) :
3196 sizeof(struct tcpiphdr);
3198 const boolean_t isipv6 = FALSE;
3199 const size_t min_protoh = sizeof(struct tcpiphdr);
3203 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc);
3205 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc);
3207 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt);
3209 return (rt->rt_ifp->if_mtu - min_protoh);
3213 * When a partial ack arrives, force the retransmission of the
3214 * next unacknowledged segment. Do not exit Fast Recovery.
3216 * Implement the Slow-but-Steady variant of NewReno by restarting the
3217 * the retransmission timer. Turn it off here so it can be restarted
3218 * later in tcp_output().
3221 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th, int acked)
3223 tcp_seq old_snd_nxt = tp->snd_nxt;
3224 u_long ocwnd = tp->snd_cwnd;
3226 tcp_callout_stop(tp, tp->tt_rexmt);
3228 tp->snd_nxt = th->th_ack;
3229 /* Set snd_cwnd to one segment beyond acknowledged offset. */
3230 tp->snd_cwnd = tp->t_maxseg;
3231 tp->t_flags |= TF_ACKNOW;
3233 if (SEQ_GT(old_snd_nxt, tp->snd_nxt))
3234 tp->snd_nxt = old_snd_nxt;
3235 /* partial window deflation */
3237 tp->snd_cwnd = ocwnd - acked + tp->t_maxseg;
3239 tp->snd_cwnd = tp->t_maxseg;
3243 * In contrast to the Slow-but-Steady NewReno variant,
3244 * we do not reset the retransmission timer for SACK retransmissions,
3245 * except when retransmitting snd_una.
3248 tcp_sack_rexmt(struct tcpcb *tp, struct tcphdr *th)
3250 uint32_t pipe, seglen;
3253 tcp_seq old_snd_nxt = tp->snd_nxt;
3254 u_long ocwnd = tp->snd_cwnd;
3255 int nseg = 0; /* consecutive new segments */
3256 #define MAXBURST 4 /* limit burst of new packets on partial ack */
3259 pipe = tcp_sack_compute_pipe(tp);
3260 while ((tcp_seq_diff_t)(ocwnd - pipe) >= (tcp_seq_diff_t)tp->t_maxseg &&
3261 (!tcp_do_smartsack || nseg < MAXBURST) &&
3262 tcp_sack_nextseg(tp, &nextrexmt, &seglen, &lostdup)) {
3264 tcp_seq old_snd_max;
3267 if (nextrexmt == tp->snd_max)
3269 tp->snd_nxt = nextrexmt;
3270 tp->snd_cwnd = nextrexmt - tp->snd_una + seglen;
3271 old_snd_max = tp->snd_max;
3272 if (nextrexmt == tp->snd_una)
3273 tcp_callout_stop(tp, tp->tt_rexmt);
3274 error = tcp_output(tp);
3277 sent = tp->snd_nxt - nextrexmt;
3282 tcpstat.tcps_sndsackpack++;
3283 tcpstat.tcps_sndsackbyte += sent;
3284 if (SEQ_LT(nextrexmt, old_snd_max) &&
3285 SEQ_LT(tp->rexmt_high, tp->snd_nxt))
3286 tp->rexmt_high = seq_min(tp->snd_nxt, old_snd_max);
3288 if (SEQ_GT(old_snd_nxt, tp->snd_nxt))
3289 tp->snd_nxt = old_snd_nxt;
3290 tp->snd_cwnd = ocwnd;
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