2 * Copyright (c) 2002, 2003, 2004 Jeffrey M. Hsu. All rights reserved.
3 * Copyright (c) 2002, 2003, 2004 The DragonFly Project. All rights reserved.
5 * This code is derived from software contributed to The DragonFly Project
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
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15 * documentation and/or other materials provided with the distribution.
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17 * contributors may be used to endorse or promote products derived
18 * from this software without specific, prior written permission.
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63 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
66 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95
67 * $FreeBSD: src/sys/netinet/tcp_input.c,v 1.107.2.38 2003/05/21 04:46:41 cjc Exp $
68 * $DragonFly: src/sys/netinet/tcp_input.c,v 1.67 2007/04/22 01:13:14 dillon 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_var.h>
114 #include <netinet6/tcp6_var.h>
115 #include <netinet/tcpip.h>
118 #include <netinet/tcp_debug.h>
120 u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */
121 struct tcphdr tcp_savetcp;
125 #include <netproto/ipsec/ipsec.h>
126 #include <netproto/ipsec/ipsec6.h>
130 #include <netinet6/ipsec.h>
131 #include <netinet6/ipsec6.h>
132 #include <netproto/key/key.h>
135 MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry");
138 static int log_in_vain = 0;
139 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW,
140 &log_in_vain, 0, "Log all incoming TCP connections");
142 static int blackhole = 0;
143 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW,
144 &blackhole, 0, "Do not send RST when dropping refused connections");
146 int tcp_delack_enabled = 1;
147 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW,
148 &tcp_delack_enabled, 0,
149 "Delay ACK to try and piggyback it onto a data packet");
151 #ifdef TCP_DROP_SYNFIN
152 static int drop_synfin = 0;
153 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW,
154 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set");
157 static int tcp_do_limitedtransmit = 1;
158 SYSCTL_INT(_net_inet_tcp, OID_AUTO, limitedtransmit, CTLFLAG_RW,
159 &tcp_do_limitedtransmit, 0, "Enable RFC 3042 (Limited Transmit)");
161 static int tcp_do_early_retransmit = 1;
162 SYSCTL_INT(_net_inet_tcp, OID_AUTO, earlyretransmit, CTLFLAG_RW,
163 &tcp_do_early_retransmit, 0, "Early retransmit");
165 int tcp_aggregate_acks = 1;
166 SYSCTL_INT(_net_inet_tcp, OID_AUTO, aggregate_acks, CTLFLAG_RW,
167 &tcp_aggregate_acks, 0, "Aggregate built-up acks into one ack");
169 int tcp_do_rfc3390 = 1;
170 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW,
172 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)");
174 static int tcp_do_eifel_detect = 1;
175 SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW,
176 &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)");
178 static int tcp_do_abc = 1;
179 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc, CTLFLAG_RW,
181 "TCP Appropriate Byte Counting (RFC 3465)");
184 * Define as tunable for easy testing with SACK on and off.
185 * Warning: do not change setting in the middle of an existing active TCP flow,
186 * else strange things might happen to that flow.
189 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW,
190 &tcp_do_sack, 0, "Enable SACK Algorithms");
192 int tcp_do_smartsack = 1;
193 SYSCTL_INT(_net_inet_tcp, OID_AUTO, smartsack, CTLFLAG_RW,
194 &tcp_do_smartsack, 0, "Enable Smart SACK Algorithms");
196 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0,
197 "TCP Segment Reassembly Queue");
199 int tcp_reass_maxseg = 0;
200 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD,
201 &tcp_reass_maxseg, 0,
202 "Global maximum number of TCP Segments in Reassembly Queue");
204 int tcp_reass_qsize = 0;
205 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD,
207 "Global number of TCP Segments currently in Reassembly Queue");
209 static int tcp_reass_overflows = 0;
210 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD,
211 &tcp_reass_overflows, 0,
212 "Global number of TCP Segment Reassembly Queue Overflows");
214 static void tcp_dooptions(struct tcpopt *, u_char *, int, boolean_t);
215 static void tcp_pulloutofband(struct socket *,
216 struct tcphdr *, struct mbuf *, int);
217 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *,
219 static void tcp_xmit_timer(struct tcpcb *, int);
220 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *, int);
221 static void tcp_sack_rexmt(struct tcpcb *, struct tcphdr *);
223 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */
225 #define ND6_HINT(tp) \
227 if ((tp) && (tp)->t_inpcb && \
228 ((tp)->t_inpcb->inp_vflag & INP_IPV6) && \
229 (tp)->t_inpcb->in6p_route.ro_rt) \
230 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \
237 * Indicate whether this ack should be delayed. We can delay the ack if
238 * - delayed acks are enabled and
239 * - there is no delayed ack timer in progress and
240 * - our last ack wasn't a 0-sized window. We never want to delay
241 * the ack that opens up a 0-sized window.
243 #define DELAY_ACK(tp) \
244 (tcp_delack_enabled && !callout_pending(tp->tt_delack) && \
245 !(tp->t_flags & TF_RXWIN0SENT))
247 #define acceptable_window_update(tp, th, tiwin) \
248 (SEQ_LT(tp->snd_wl1, th->th_seq) || \
249 (tp->snd_wl1 == th->th_seq && \
250 (SEQ_LT(tp->snd_wl2, th->th_ack) || \
251 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))
254 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m)
257 struct tseg_qent *p = NULL;
258 struct tseg_qent *te;
259 struct socket *so = tp->t_inpcb->inp_socket;
263 * Call with th == NULL after become established to
264 * force pre-ESTABLISHED data up to user socket.
270 * Limit the number of segments in the reassembly queue to prevent
271 * holding on to too many segments (and thus running out of mbufs).
272 * Make sure to let the missing segment through which caused this
273 * queue. Always keep one global queue entry spare to be able to
274 * process the missing segment.
276 if (th->th_seq != tp->rcv_nxt &&
277 tcp_reass_qsize + 1 >= tcp_reass_maxseg) {
278 tcp_reass_overflows++;
279 tcpstat.tcps_rcvmemdrop++;
281 /* no SACK block to report */
282 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
286 /* Allocate a new queue entry. */
287 MALLOC(te, struct tseg_qent *, sizeof(struct tseg_qent), M_TSEGQ,
288 M_INTWAIT | M_NULLOK);
290 tcpstat.tcps_rcvmemdrop++;
292 /* no SACK block to report */
293 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
299 * Find a segment which begins after this one does.
301 LIST_FOREACH(q, &tp->t_segq, tqe_q) {
302 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
308 * If there is a preceding segment, it may provide some of
309 * our data already. If so, drop the data from the incoming
310 * segment. If it provides all of our data, drop us.
315 /* conversion to int (in i) handles seq wraparound */
316 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
317 if (i > 0) { /* overlaps preceding segment */
318 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG);
319 /* enclosing block starts w/ preceding segment */
320 tp->encloseblk.rblk_start = p->tqe_th->th_seq;
322 /* preceding encloses incoming segment */
323 tp->encloseblk.rblk_end = p->tqe_th->th_seq +
325 tcpstat.tcps_rcvduppack++;
326 tcpstat.tcps_rcvdupbyte += *tlenp;
331 * Try to present any queued data
332 * at the left window edge to the user.
333 * This is needed after the 3-WHS
336 goto present; /* ??? */
341 /* incoming segment end is enclosing block end */
342 tp->encloseblk.rblk_end = th->th_seq + *tlenp +
343 ((th->th_flags & TH_FIN) != 0);
344 /* trim end of reported D-SACK block */
345 tp->reportblk.rblk_end = th->th_seq;
348 tcpstat.tcps_rcvoopack++;
349 tcpstat.tcps_rcvoobyte += *tlenp;
352 * While we overlap succeeding segments trim them or,
353 * if they are completely covered, dequeue them.
356 tcp_seq_diff_t i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
357 tcp_seq qend = q->tqe_th->th_seq + q->tqe_len;
358 struct tseg_qent *nq;
362 if (!(tp->t_flags & TF_DUPSEG)) { /* first time through */
363 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG);
364 tp->encloseblk = tp->reportblk;
365 /* report trailing duplicate D-SACK segment */
366 tp->reportblk.rblk_start = q->tqe_th->th_seq;
368 if ((tp->t_flags & TF_ENCLOSESEG) &&
369 SEQ_GT(qend, tp->encloseblk.rblk_end)) {
370 /* extend enclosing block if one exists */
371 tp->encloseblk.rblk_end = qend;
373 if (i < q->tqe_len) {
374 q->tqe_th->th_seq += i;
380 nq = LIST_NEXT(q, tqe_q);
381 LIST_REMOVE(q, tqe_q);
388 /* Insert the new segment queue entry into place. */
391 te->tqe_len = *tlenp;
393 /* check if can coalesce with following segment */
394 if (q != NULL && (th->th_seq + *tlenp == q->tqe_th->th_seq)) {
395 tcp_seq tend = te->tqe_th->th_seq + te->tqe_len;
397 te->tqe_len += q->tqe_len;
398 if (q->tqe_th->th_flags & TH_FIN)
399 te->tqe_th->th_flags |= TH_FIN;
400 m_cat(te->tqe_m, q->tqe_m);
401 tp->encloseblk.rblk_end = tend;
403 * When not reporting a duplicate segment, use
404 * the larger enclosing block as the SACK block.
406 if (!(tp->t_flags & TF_DUPSEG))
407 tp->reportblk.rblk_end = tend;
408 LIST_REMOVE(q, tqe_q);
414 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q);
416 /* check if can coalesce with preceding segment */
417 if (p->tqe_th->th_seq + p->tqe_len == th->th_seq) {
418 p->tqe_len += te->tqe_len;
419 m_cat(p->tqe_m, te->tqe_m);
420 tp->encloseblk.rblk_start = p->tqe_th->th_seq;
422 * When not reporting a duplicate segment, use
423 * the larger enclosing block as the SACK block.
425 if (!(tp->t_flags & TF_DUPSEG))
426 tp->reportblk.rblk_start = p->tqe_th->th_seq;
430 LIST_INSERT_AFTER(p, te, tqe_q);
435 * Present data to user, advancing rcv_nxt through
436 * completed sequence space.
438 if (!TCPS_HAVEESTABLISHED(tp->t_state))
440 q = LIST_FIRST(&tp->t_segq);
441 if (q == NULL || q->tqe_th->th_seq != tp->rcv_nxt)
443 tp->rcv_nxt += q->tqe_len;
444 if (!(tp->t_flags & TF_DUPSEG)) {
445 /* no SACK block to report since ACK advanced */
446 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
448 /* no enclosing block to report since ACK advanced */
449 tp->t_flags &= ~TF_ENCLOSESEG;
450 flags = q->tqe_th->th_flags & TH_FIN;
451 LIST_REMOVE(q, tqe_q);
452 KASSERT(LIST_EMPTY(&tp->t_segq) ||
453 LIST_FIRST(&tp->t_segq)->tqe_th->th_seq != tp->rcv_nxt,
454 ("segment not coalesced"));
455 if (so->so_state & SS_CANTRCVMORE)
458 ssb_appendstream(&so->so_rcv, q->tqe_m);
467 * TCP input routine, follows pages 65-76 of the
468 * protocol specification dated September, 1981 very closely.
472 tcp6_input(struct mbuf **mp, int *offp, int proto)
474 struct mbuf *m = *mp;
475 struct in6_ifaddr *ia6;
477 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE);
480 * draft-itojun-ipv6-tcp-to-anycast
481 * better place to put this in?
483 ia6 = ip6_getdstifaddr(m);
484 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) {
487 ip6 = mtod(m, struct ip6_hdr *);
488 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
489 offsetof(struct ip6_hdr, ip6_dst));
490 return (IPPROTO_DONE);
493 tcp_input(m, *offp, proto);
494 return (IPPROTO_DONE);
499 tcp_input(struct mbuf *m, ...)
504 struct ip *ip = NULL;
506 struct inpcb *inp = NULL;
511 struct tcpcb *tp = NULL;
513 struct socket *so = 0;
515 boolean_t ourfinisacked, needoutput = FALSE;
518 struct tcpopt to; /* options in this segment */
519 struct rmxp_tao *taop; /* pointer to our TAO cache entry */
520 struct rmxp_tao tao_noncached; /* in case there's no cached entry */
521 struct sockaddr_in *next_hop = NULL;
522 int rstreason; /* For badport_bandlim accounting purposes */
524 struct ip6_hdr *ip6 = NULL;
528 const boolean_t isipv6 = FALSE;
535 off0 = __va_arg(ap, int);
536 proto = __va_arg(ap, int);
539 tcpstat.tcps_rcvtotal++;
541 /* Grab info from and strip MT_TAG mbufs prepended to the chain. */
542 while (m->m_type == MT_TAG) {
543 if (m->_m_tag_id == PACKET_TAG_IPFORWARD)
544 next_hop = (struct sockaddr_in *)m->m_hdr.mh_data;
549 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE;
553 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */
554 ip6 = mtod(m, struct ip6_hdr *);
555 tlen = (sizeof *ip6) + ntohs(ip6->ip6_plen) - off0;
556 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) {
557 tcpstat.tcps_rcvbadsum++;
560 th = (struct tcphdr *)((caddr_t)ip6 + off0);
563 * Be proactive about unspecified IPv6 address in source.
564 * As we use all-zero to indicate unbounded/unconnected pcb,
565 * unspecified IPv6 address can be used to confuse us.
567 * Note that packets with unspecified IPv6 destination is
568 * already dropped in ip6_input.
570 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
576 * Get IP and TCP header together in first mbuf.
577 * Note: IP leaves IP header in first mbuf.
579 if (off0 > sizeof(struct ip)) {
581 off0 = sizeof(struct ip);
583 /* already checked and pulled up in ip_demux() */
584 KASSERT(m->m_len >= sizeof(struct tcpiphdr),
585 ("TCP header not in one mbuf: m->m_len %d", m->m_len));
586 ip = mtod(m, struct ip *);
587 ipov = (struct ipovly *)ip;
588 th = (struct tcphdr *)((caddr_t)ip + off0);
591 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
592 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
593 th->th_sum = m->m_pkthdr.csum_data;
595 th->th_sum = in_pseudo(ip->ip_src.s_addr,
597 htonl(m->m_pkthdr.csum_data +
600 th->th_sum ^= 0xffff;
603 * Checksum extended TCP header and data.
605 len = sizeof(struct ip) + tlen;
606 bzero(ipov->ih_x1, sizeof ipov->ih_x1);
607 ipov->ih_len = (u_short)tlen;
608 ipov->ih_len = htons(ipov->ih_len);
609 th->th_sum = in_cksum(m, len);
612 tcpstat.tcps_rcvbadsum++;
616 /* Re-initialization for later version check */
617 ip->ip_v = IPVERSION;
622 * Check that TCP offset makes sense,
623 * pull out TCP options and adjust length. XXX
625 off = th->th_off << 2;
626 /* already checked and pulled up in ip_demux() */
627 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen,
628 ("bad TCP data offset %d (tlen %d)", off, tlen));
629 tlen -= off; /* tlen is used instead of ti->ti_len */
630 if (off > sizeof(struct tcphdr)) {
632 IP6_EXTHDR_CHECK(m, off0, off, );
633 ip6 = mtod(m, struct ip6_hdr *);
634 th = (struct tcphdr *)((caddr_t)ip6 + off0);
636 /* already pulled up in ip_demux() */
637 KASSERT(m->m_len >= sizeof(struct ip) + off,
638 ("TCP header and options not in one mbuf: "
639 "m_len %d, off %d", m->m_len, off));
641 optlen = off - sizeof(struct tcphdr);
642 optp = (u_char *)(th + 1);
644 thflags = th->th_flags;
646 #ifdef TCP_DROP_SYNFIN
648 * If the drop_synfin option is enabled, drop all packets with
649 * both the SYN and FIN bits set. This prevents e.g. nmap from
650 * identifying the TCP/IP stack.
652 * This is a violation of the TCP specification.
654 if (drop_synfin && (thflags & (TH_SYN | TH_FIN)) == (TH_SYN | TH_FIN))
659 * Convert TCP protocol specific fields to host format.
661 th->th_seq = ntohl(th->th_seq);
662 th->th_ack = ntohl(th->th_ack);
663 th->th_win = ntohs(th->th_win);
664 th->th_urp = ntohs(th->th_urp);
667 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options,
668 * until after ip6_savecontrol() is called and before other functions
669 * which don't want those proto headers.
670 * Because ip6_savecontrol() is going to parse the mbuf to
671 * search for data to be passed up to user-land, it wants mbuf
672 * parameters to be unchanged.
673 * XXX: the call of ip6_savecontrol() has been obsoleted based on
674 * latest version of the advanced API (20020110).
676 drop_hdrlen = off0 + off;
679 * Locate pcb for segment.
682 /* IPFIREWALL_FORWARD section */
683 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */
685 * Transparently forwarded. Pretend to be the destination.
686 * already got one like this?
688 cpu = mycpu->gd_cpuid;
689 inp = in_pcblookup_hash(&tcbinfo[cpu],
690 ip->ip_src, th->th_sport,
691 ip->ip_dst, th->th_dport,
692 0, m->m_pkthdr.rcvif);
695 * It's new. Try to find the ambushing socket.
699 * The rest of the ipfw code stores the port in
701 * (The IP address is still in network order.)
703 in_port_t dport = next_hop->sin_port ?
704 htons(next_hop->sin_port) :
707 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport,
708 next_hop->sin_addr.s_addr, dport);
709 inp = in_pcblookup_hash(&tcbinfo[cpu],
710 ip->ip_src, th->th_sport,
711 next_hop->sin_addr, dport,
712 1, m->m_pkthdr.rcvif);
716 inp = in6_pcblookup_hash(&tcbinfo[0],
717 &ip6->ip6_src, th->th_sport,
718 &ip6->ip6_dst, th->th_dport,
719 1, m->m_pkthdr.rcvif);
721 cpu = mycpu->gd_cpuid;
722 inp = in_pcblookup_hash(&tcbinfo[cpu],
723 ip->ip_src, th->th_sport,
724 ip->ip_dst, th->th_dport,
725 1, m->m_pkthdr.rcvif);
730 * If the state is CLOSED (i.e., TCB does not exist) then
731 * all data in the incoming segment is discarded.
732 * If the TCB exists but is in CLOSED state, it is embryonic,
733 * but should either do a listen or a connect soon.
738 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2];
740 char dbuf[sizeof "aaa.bbb.ccc.ddd"];
741 char sbuf[sizeof "aaa.bbb.ccc.ddd"];
745 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst));
748 strcat(sbuf, ip6_sprintf(&ip6->ip6_src));
751 strcpy(dbuf, inet_ntoa(ip->ip_dst));
752 strcpy(sbuf, inet_ntoa(ip->ip_src));
754 switch (log_in_vain) {
756 if (!(thflags & TH_SYN))
760 "Connection attempt to TCP %s:%d "
761 "from %s:%d flags:0x%02x\n",
762 dbuf, ntohs(th->th_dport), sbuf,
763 ntohs(th->th_sport), thflags);
772 if (thflags & TH_SYN)
781 rstreason = BANDLIM_RST_CLOSEDPORT;
787 if (ipsec6_in_reject_so(m, inp->inp_socket)) {
788 ipsec6stat.in_polvio++;
792 if (ipsec4_in_reject_so(m, inp->inp_socket)) {
793 ipsecstat.in_polvio++;
800 if (ipsec6_in_reject(m, inp))
803 if (ipsec4_in_reject(m, inp))
807 /* Check the minimum TTL for socket. */
809 if ((isipv6 ? ip6->ip6_hlim : ip->ip_ttl) < inp->inp_ip_minttl)
815 rstreason = BANDLIM_RST_CLOSEDPORT;
818 if (tp->t_state <= TCPS_CLOSED)
821 /* Unscale the window into a 32-bit value. */
822 if (!(thflags & TH_SYN))
823 tiwin = th->th_win << tp->snd_scale;
827 so = inp->inp_socket;
830 if (so->so_options & SO_DEBUG) {
831 ostate = tp->t_state;
833 bcopy(ip6, tcp_saveipgen, sizeof(*ip6));
835 bcopy(ip, tcp_saveipgen, sizeof(*ip));
840 bzero(&to, sizeof to);
842 if (so->so_options & SO_ACCEPTCONN) {
843 struct in_conninfo inc;
846 inc.inc_isipv6 = (isipv6 == TRUE);
849 inc.inc6_faddr = ip6->ip6_src;
850 inc.inc6_laddr = ip6->ip6_dst;
851 inc.inc6_route.ro_rt = NULL; /* XXX */
853 inc.inc_faddr = ip->ip_src;
854 inc.inc_laddr = ip->ip_dst;
855 inc.inc_route.ro_rt = NULL; /* XXX */
857 inc.inc_fport = th->th_sport;
858 inc.inc_lport = th->th_dport;
861 * If the state is LISTEN then ignore segment if it contains
862 * a RST. If the segment contains an ACK then it is bad and
863 * send a RST. If it does not contain a SYN then it is not
864 * interesting; drop it.
866 * If the state is SYN_RECEIVED (syncache) and seg contains
867 * an ACK, but not for our SYN/ACK, send a RST. If the seg
868 * contains a RST, check the sequence number to see if it
869 * is a valid reset segment.
871 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) != TH_SYN) {
872 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) == TH_ACK) {
873 if (!syncache_expand(&inc, th, &so, m)) {
875 * No syncache entry, or ACK was not
876 * for our SYN/ACK. Send a RST.
878 tcpstat.tcps_badsyn++;
879 rstreason = BANDLIM_RST_OPENPORT;
884 * Could not complete 3-way handshake,
885 * connection is being closed down, and
886 * syncache will free mbuf.
890 * Socket is created in state SYN_RECEIVED.
891 * Continue processing segment.
896 * This is what would have happened in
897 * tcp_output() when the SYN,ACK was sent.
899 tp->snd_up = tp->snd_una;
900 tp->snd_max = tp->snd_nxt = tp->iss + 1;
901 tp->last_ack_sent = tp->rcv_nxt;
903 * XXX possible bug - it doesn't appear that tp->snd_wnd is unscaled
904 * until the _second_ ACK is received:
905 * rcv SYN (set wscale opts) --> send SYN/ACK, set snd_wnd = window.
906 * rcv ACK, calculate tiwin --> process SYN_RECEIVED, determine wscale,
907 * move to ESTAB, set snd_wnd to tiwin.
909 tp->snd_wnd = tiwin; /* unscaled */
912 if (thflags & TH_RST) {
913 syncache_chkrst(&inc, th);
916 if (thflags & TH_ACK) {
917 syncache_badack(&inc);
918 tcpstat.tcps_badsyn++;
919 rstreason = BANDLIM_RST_OPENPORT;
926 * Segment's flags are (SYN) or (SYN | FIN).
930 * If deprecated address is forbidden,
931 * we do not accept SYN to deprecated interface
932 * address to prevent any new inbound connection from
933 * getting established.
934 * When we do not accept SYN, we send a TCP RST,
935 * with deprecated source address (instead of dropping
936 * it). We compromise it as it is much better for peer
937 * to send a RST, and RST will be the final packet
940 * If we do not forbid deprecated addresses, we accept
941 * the SYN packet. RFC2462 does not suggest dropping
943 * If we decipher RFC2462 5.5.4, it says like this:
944 * 1. use of deprecated addr with existing
945 * communication is okay - "SHOULD continue to be
947 * 2. use of it with new communication:
948 * (2a) "SHOULD NOT be used if alternate address
949 * with sufficient scope is available"
950 * (2b) nothing mentioned otherwise.
951 * Here we fall into (2b) case as we have no choice in
952 * our source address selection - we must obey the peer.
954 * The wording in RFC2462 is confusing, and there are
955 * multiple description text for deprecated address
956 * handling - worse, they are not exactly the same.
957 * I believe 5.5.4 is the best one, so we follow 5.5.4.
959 if (isipv6 && !ip6_use_deprecated) {
960 struct in6_ifaddr *ia6;
962 if ((ia6 = ip6_getdstifaddr(m)) &&
963 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
965 rstreason = BANDLIM_RST_OPENPORT;
971 * If it is from this socket, drop it, it must be forged.
972 * Don't bother responding if the destination was a broadcast.
974 if (th->th_dport == th->th_sport) {
976 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst,
980 if (ip->ip_dst.s_addr == ip->ip_src.s_addr)
985 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN
987 * Note that it is quite possible to receive unicast
988 * link-layer packets with a broadcast IP address. Use
989 * in_broadcast() to find them.
991 if (m->m_flags & (M_BCAST | M_MCAST))
994 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
995 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
998 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
999 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
1000 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
1001 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
1005 * SYN appears to be valid; create compressed TCP state
1006 * for syncache, or perform t/tcp connection.
1008 if (so->so_qlen <= so->so_qlimit) {
1009 tcp_dooptions(&to, optp, optlen, TRUE);
1010 if (!syncache_add(&inc, &to, th, &so, m))
1014 * Entry added to syncache, mbuf used to
1015 * send SYN,ACK packet.
1019 * Segment passed TAO tests.
1022 tp = intotcpcb(inp);
1023 tp->snd_wnd = tiwin;
1024 tp->t_starttime = ticks;
1025 tp->t_state = TCPS_ESTABLISHED;
1028 * If there is a FIN, or if there is data and the
1029 * connection is local, then delay SYN,ACK(SYN) in
1030 * the hope of piggy-backing it on a response
1031 * segment. Otherwise must send ACK now in case
1032 * the other side is slow starting.
1034 if (DELAY_ACK(tp) &&
1035 ((thflags & TH_FIN) ||
1037 ((isipv6 && in6_localaddr(&inp->in6p_faddr)) ||
1038 (!isipv6 && in_localaddr(inp->inp_faddr)))))) {
1039 callout_reset(tp->tt_delack, tcp_delacktime,
1040 tcp_timer_delack, tp);
1041 tp->t_flags |= TF_NEEDSYN;
1043 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN);
1045 tcpstat.tcps_connects++;
1053 /* should not happen - syncache should pick up these connections */
1054 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN state"));
1057 * Segment received on connection.
1058 * Reset idle time and keep-alive timer.
1060 tp->t_rcvtime = ticks;
1061 if (TCPS_HAVEESTABLISHED(tp->t_state))
1062 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp);
1066 * XXX this is tradtitional behavior, may need to be cleaned up.
1068 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0);
1069 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) {
1070 if (to.to_flags & TOF_SCALE) {
1071 tp->t_flags |= TF_RCVD_SCALE;
1072 tp->requested_s_scale = to.to_requested_s_scale;
1074 if (to.to_flags & TOF_TS) {
1075 tp->t_flags |= TF_RCVD_TSTMP;
1076 tp->ts_recent = to.to_tsval;
1077 tp->ts_recent_age = ticks;
1079 if (to.to_flags & (TOF_CC | TOF_CCNEW))
1080 tp->t_flags |= TF_RCVD_CC;
1081 if (to.to_flags & TOF_MSS)
1082 tcp_mss(tp, to.to_mss);
1084 * Only set the TF_SACK_PERMITTED per-connection flag
1085 * if we got a SACK_PERMITTED option from the other side
1086 * and the global tcp_do_sack variable is true.
1088 if (tcp_do_sack && (to.to_flags & TOF_SACK_PERMITTED))
1089 tp->t_flags |= TF_SACK_PERMITTED;
1093 * Header prediction: check for the two common cases
1094 * of a uni-directional data xfer. If the packet has
1095 * no control flags, is in-sequence, the window didn't
1096 * change and we're not retransmitting, it's a
1097 * candidate. If the length is zero and the ack moved
1098 * forward, we're the sender side of the xfer. Just
1099 * free the data acked & wake any higher level process
1100 * that was blocked waiting for space. If the length
1101 * is non-zero and the ack didn't move, we're the
1102 * receiver side. If we're getting packets in-order
1103 * (the reassembly queue is empty), add the data to
1104 * the socket buffer and note that we need a delayed ack.
1105 * Make sure that the hidden state-flags are also off.
1106 * Since we check for TCPS_ESTABLISHED above, it can only
1109 if (tp->t_state == TCPS_ESTABLISHED &&
1110 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
1111 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) &&
1112 (!(to.to_flags & TOF_TS) ||
1113 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) &&
1115 * Using the CC option is compulsory if once started:
1116 * the segment is OK if no T/TCP was negotiated or
1117 * if the segment has a CC option equal to CCrecv
1119 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) ||
1120 ((to.to_flags & TOF_CC) && to.to_cc == tp->cc_recv)) &&
1121 th->th_seq == tp->rcv_nxt &&
1122 tp->snd_nxt == tp->snd_max) {
1125 * If last ACK falls within this segment's sequence numbers,
1126 * record the timestamp.
1127 * NOTE that the test is modified according to the latest
1128 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1130 if ((to.to_flags & TOF_TS) &&
1131 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
1132 tp->ts_recent_age = ticks;
1133 tp->ts_recent = to.to_tsval;
1137 if (SEQ_GT(th->th_ack, tp->snd_una) &&
1138 SEQ_LEQ(th->th_ack, tp->snd_max) &&
1139 tp->snd_cwnd >= tp->snd_wnd &&
1140 !IN_FASTRECOVERY(tp)) {
1142 * This is a pure ack for outstanding data.
1144 ++tcpstat.tcps_predack;
1146 * "bad retransmit" recovery
1148 * If Eifel detection applies, then
1149 * it is deterministic, so use it
1150 * unconditionally over the old heuristic.
1151 * Otherwise, fall back to the old heuristic.
1153 if (tcp_do_eifel_detect &&
1154 (to.to_flags & TOF_TS) && to.to_tsecr &&
1155 (tp->t_flags & TF_FIRSTACCACK)) {
1156 /* Eifel detection applicable. */
1157 if (to.to_tsecr < tp->t_rexmtTS) {
1158 tcp_revert_congestion_state(tp);
1159 ++tcpstat.tcps_eifeldetected;
1161 } else if (tp->t_rxtshift == 1 &&
1162 ticks < tp->t_badrxtwin) {
1163 tcp_revert_congestion_state(tp);
1164 ++tcpstat.tcps_rttdetected;
1166 tp->t_flags &= ~(TF_FIRSTACCACK |
1167 TF_FASTREXMT | TF_EARLYREXMT);
1169 * Recalculate the retransmit timer / rtt.
1171 * Some machines (certain windows boxes)
1172 * send broken timestamp replies during the
1173 * SYN+ACK phase, ignore timestamps of 0.
1175 if ((to.to_flags & TOF_TS) && to.to_tsecr) {
1177 ticks - to.to_tsecr + 1);
1178 } else if (tp->t_rtttime &&
1179 SEQ_GT(th->th_ack, tp->t_rtseq)) {
1181 ticks - tp->t_rtttime);
1183 tcp_xmit_bandwidth_limit(tp, th->th_ack);
1184 acked = th->th_ack - tp->snd_una;
1185 tcpstat.tcps_rcvackpack++;
1186 tcpstat.tcps_rcvackbyte += acked;
1187 sbdrop(&so->so_snd.sb, acked);
1188 tp->snd_recover = th->th_ack - 1;
1189 tp->snd_una = th->th_ack;
1192 * Update window information.
1194 if (tiwin != tp->snd_wnd &&
1195 acceptable_window_update(tp, th, tiwin)) {
1196 /* keep track of pure window updates */
1197 if (tp->snd_wl2 == th->th_ack &&
1198 tiwin > tp->snd_wnd)
1199 tcpstat.tcps_rcvwinupd++;
1200 tp->snd_wnd = tiwin;
1201 tp->snd_wl1 = th->th_seq;
1202 tp->snd_wl2 = th->th_ack;
1203 if (tp->snd_wnd > tp->max_sndwnd)
1204 tp->max_sndwnd = tp->snd_wnd;
1207 ND6_HINT(tp); /* some progress has been done */
1209 * If all outstanding data are acked, stop
1210 * retransmit timer, otherwise restart timer
1211 * using current (possibly backed-off) value.
1212 * If process is waiting for space,
1213 * wakeup/selwakeup/signal. If data
1214 * are ready to send, let tcp_output
1215 * decide between more output or persist.
1217 if (tp->snd_una == tp->snd_max)
1218 callout_stop(tp->tt_rexmt);
1219 else if (!callout_active(tp->tt_persist))
1220 callout_reset(tp->tt_rexmt,
1222 tcp_timer_rexmt, tp);
1224 if (so->so_snd.ssb_cc > 0)
1228 } else if (tiwin == tp->snd_wnd &&
1229 th->th_ack == tp->snd_una &&
1230 LIST_EMPTY(&tp->t_segq) &&
1231 tlen <= ssb_space(&so->so_rcv)) {
1233 * This is a pure, in-sequence data packet
1234 * with nothing on the reassembly queue and
1235 * we have enough buffer space to take it.
1237 ++tcpstat.tcps_preddat;
1238 tp->rcv_nxt += tlen;
1239 tcpstat.tcps_rcvpack++;
1240 tcpstat.tcps_rcvbyte += tlen;
1241 ND6_HINT(tp); /* some progress has been done */
1243 * Add data to socket buffer.
1245 if (so->so_state & SS_CANTRCVMORE) {
1248 m_adj(m, drop_hdrlen); /* delayed header drop */
1249 ssb_appendstream(&so->so_rcv, m);
1253 * This code is responsible for most of the ACKs
1254 * the TCP stack sends back after receiving a data
1255 * packet. Note that the DELAY_ACK check fails if
1256 * the delack timer is already running, which results
1257 * in an ack being sent every other packet (which is
1260 * We then further aggregate acks by not actually
1261 * sending one until the protocol thread has completed
1262 * processing the current backlog of packets. This
1263 * does not delay the ack any further, but allows us
1264 * to take advantage of the packet aggregation that
1265 * high speed NICs do (usually blocks of 8-10 packets)
1266 * to send a single ack rather then four or five acks,
1267 * greatly reducing the ack rate, the return channel
1268 * bandwidth, and the protocol overhead on both ends.
1270 * Since this also has the effect of slowing down
1271 * the exponential slow-start ramp-up, systems with
1272 * very large bandwidth-delay products might want
1273 * to turn the feature off.
1275 if (DELAY_ACK(tp)) {
1276 callout_reset(tp->tt_delack, tcp_delacktime,
1277 tcp_timer_delack, tp);
1278 } else if (tcp_aggregate_acks) {
1279 tp->t_flags |= TF_ACKNOW;
1280 if (!(tp->t_flags & TF_ONOUTPUTQ)) {
1281 tp->t_flags |= TF_ONOUTPUTQ;
1282 tp->tt_cpu = mycpu->gd_cpuid;
1284 &tcpcbackq[tp->tt_cpu],
1288 tp->t_flags |= TF_ACKNOW;
1296 * Calculate amount of space in receive window,
1297 * and then do TCP input processing.
1298 * Receive window is amount of space in rcv queue,
1299 * but not less than advertised window.
1301 recvwin = ssb_space(&so->so_rcv);
1304 tp->rcv_wnd = imax(recvwin, (int)(tp->rcv_adv - tp->rcv_nxt));
1306 switch (tp->t_state) {
1308 * If the state is SYN_RECEIVED:
1309 * if seg contains an ACK, but not for our SYN/ACK, send a RST.
1311 case TCPS_SYN_RECEIVED:
1312 if ((thflags & TH_ACK) &&
1313 (SEQ_LEQ(th->th_ack, tp->snd_una) ||
1314 SEQ_GT(th->th_ack, tp->snd_max))) {
1315 rstreason = BANDLIM_RST_OPENPORT;
1321 * If the state is SYN_SENT:
1322 * if seg contains an ACK, but not for our SYN, drop the input.
1323 * if seg contains a RST, then drop the connection.
1324 * if seg does not contain SYN, then drop it.
1325 * Otherwise this is an acceptable SYN segment
1326 * initialize tp->rcv_nxt and tp->irs
1327 * if seg contains ack then advance tp->snd_una
1328 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state
1329 * arrange for segment to be acked (eventually)
1330 * continue processing rest of data/controls, beginning with URG
1333 if ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL) {
1334 taop = &tao_noncached;
1335 bzero(taop, sizeof *taop);
1338 if ((thflags & TH_ACK) &&
1339 (SEQ_LEQ(th->th_ack, tp->iss) ||
1340 SEQ_GT(th->th_ack, tp->snd_max))) {
1342 * If we have a cached CCsent for the remote host,
1343 * hence we haven't just crashed and restarted,
1344 * do not send a RST. This may be a retransmission
1345 * from the other side after our earlier ACK was lost.
1346 * Our new SYN, when it arrives, will serve as the
1349 if (taop->tao_ccsent != 0)
1352 rstreason = BANDLIM_UNLIMITED;
1356 if (thflags & TH_RST) {
1357 if (thflags & TH_ACK)
1358 tp = tcp_drop(tp, ECONNREFUSED);
1361 if (!(thflags & TH_SYN))
1363 tp->snd_wnd = th->th_win; /* initial send window */
1364 tp->cc_recv = to.to_cc; /* foreign CC */
1366 tp->irs = th->th_seq;
1368 if (thflags & TH_ACK) {
1370 * Our SYN was acked. If segment contains CC.ECHO
1371 * option, check it to make sure this segment really
1372 * matches our SYN. If not, just drop it as old
1373 * duplicate, but send an RST if we're still playing
1374 * by the old rules. If no CC.ECHO option, make sure
1375 * we don't get fooled into using T/TCP.
1377 if (to.to_flags & TOF_CCECHO) {
1378 if (tp->cc_send != to.to_ccecho) {
1379 if (taop->tao_ccsent != 0)
1382 rstreason = BANDLIM_UNLIMITED;
1387 tp->t_flags &= ~TF_RCVD_CC;
1388 tcpstat.tcps_connects++;
1390 /* Do window scaling on this connection? */
1391 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) ==
1392 (TF_RCVD_SCALE | TF_REQ_SCALE)) {
1393 tp->snd_scale = tp->requested_s_scale;
1394 tp->rcv_scale = tp->request_r_scale;
1396 /* Segment is acceptable, update cache if undefined. */
1397 if (taop->tao_ccsent == 0)
1398 taop->tao_ccsent = to.to_ccecho;
1400 tp->rcv_adv += tp->rcv_wnd;
1401 tp->snd_una++; /* SYN is acked */
1402 callout_stop(tp->tt_rexmt);
1404 * If there's data, delay ACK; if there's also a FIN
1405 * ACKNOW will be turned on later.
1407 if (DELAY_ACK(tp) && tlen != 0)
1408 callout_reset(tp->tt_delack, tcp_delacktime,
1409 tcp_timer_delack, tp);
1411 tp->t_flags |= TF_ACKNOW;
1413 * Received <SYN,ACK> in SYN_SENT[*] state.
1415 * SYN_SENT --> ESTABLISHED
1416 * SYN_SENT* --> FIN_WAIT_1
1418 tp->t_starttime = ticks;
1419 if (tp->t_flags & TF_NEEDFIN) {
1420 tp->t_state = TCPS_FIN_WAIT_1;
1421 tp->t_flags &= ~TF_NEEDFIN;
1424 tp->t_state = TCPS_ESTABLISHED;
1425 callout_reset(tp->tt_keep, tcp_keepidle,
1426 tcp_timer_keep, tp);
1430 * Received initial SYN in SYN-SENT[*] state =>
1431 * simultaneous open. If segment contains CC option
1432 * and there is a cached CC, apply TAO test.
1433 * If it succeeds, connection is * half-synchronized.
1434 * Otherwise, do 3-way handshake:
1435 * SYN-SENT -> SYN-RECEIVED
1436 * SYN-SENT* -> SYN-RECEIVED*
1437 * If there was no CC option, clear cached CC value.
1439 tp->t_flags |= TF_ACKNOW;
1440 callout_stop(tp->tt_rexmt);
1441 if (to.to_flags & TOF_CC) {
1442 if (taop->tao_cc != 0 &&
1443 CC_GT(to.to_cc, taop->tao_cc)) {
1445 * update cache and make transition:
1446 * SYN-SENT -> ESTABLISHED*
1447 * SYN-SENT* -> FIN-WAIT-1*
1449 taop->tao_cc = to.to_cc;
1450 tp->t_starttime = ticks;
1451 if (tp->t_flags & TF_NEEDFIN) {
1452 tp->t_state = TCPS_FIN_WAIT_1;
1453 tp->t_flags &= ~TF_NEEDFIN;
1455 tp->t_state = TCPS_ESTABLISHED;
1456 callout_reset(tp->tt_keep,
1461 tp->t_flags |= TF_NEEDSYN;
1463 tp->t_state = TCPS_SYN_RECEIVED;
1465 /* CC.NEW or no option => invalidate cache */
1467 tp->t_state = TCPS_SYN_RECEIVED;
1473 * Advance th->th_seq to correspond to first data byte.
1474 * If data, trim to stay within window,
1475 * dropping FIN if necessary.
1478 if (tlen > tp->rcv_wnd) {
1479 todrop = tlen - tp->rcv_wnd;
1483 tcpstat.tcps_rcvpackafterwin++;
1484 tcpstat.tcps_rcvbyteafterwin += todrop;
1486 tp->snd_wl1 = th->th_seq - 1;
1487 tp->rcv_up = th->th_seq;
1489 * Client side of transaction: already sent SYN and data.
1490 * If the remote host used T/TCP to validate the SYN,
1491 * our data will be ACK'd; if so, enter normal data segment
1492 * processing in the middle of step 5, ack processing.
1493 * Otherwise, goto step 6.
1495 if (thflags & TH_ACK)
1501 * If the state is LAST_ACK or CLOSING or TIME_WAIT:
1502 * if segment contains a SYN and CC [not CC.NEW] option:
1503 * if state == TIME_WAIT and connection duration > MSL,
1504 * drop packet and send RST;
1506 * if SEG.CC > CCrecv then is new SYN, and can implicitly
1507 * ack the FIN (and data) in retransmission queue.
1508 * Complete close and delete TCPCB. Then reprocess
1509 * segment, hoping to find new TCPCB in LISTEN state;
1511 * else must be old SYN; drop it.
1512 * else do normal processing.
1516 case TCPS_TIME_WAIT:
1517 if ((thflags & TH_SYN) &&
1518 (to.to_flags & TOF_CC) && tp->cc_recv != 0) {
1519 if (tp->t_state == TCPS_TIME_WAIT &&
1520 (ticks - tp->t_starttime) > tcp_msl) {
1521 rstreason = BANDLIM_UNLIMITED;
1524 if (CC_GT(to.to_cc, tp->cc_recv)) {
1531 break; /* continue normal processing */
1535 * States other than LISTEN or SYN_SENT.
1536 * First check the RST flag and sequence number since reset segments
1537 * are exempt from the timestamp and connection count tests. This
1538 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix
1539 * below which allowed reset segments in half the sequence space
1540 * to fall though and be processed (which gives forged reset
1541 * segments with a random sequence number a 50 percent chance of
1542 * killing a connection).
1543 * Then check timestamp, if present.
1544 * Then check the connection count, if present.
1545 * Then check that at least some bytes of segment are within
1546 * receive window. If segment begins before rcv_nxt,
1547 * drop leading data (and SYN); if nothing left, just ack.
1550 * If the RST bit is set, check the sequence number to see
1551 * if this is a valid reset segment.
1553 * In all states except SYN-SENT, all reset (RST) segments
1554 * are validated by checking their SEQ-fields. A reset is
1555 * valid if its sequence number is in the window.
1556 * Note: this does not take into account delayed ACKs, so
1557 * we should test against last_ack_sent instead of rcv_nxt.
1558 * The sequence number in the reset segment is normally an
1559 * echo of our outgoing acknowledgement numbers, but some hosts
1560 * send a reset with the sequence number at the rightmost edge
1561 * of our receive window, and we have to handle this case.
1562 * If we have multiple segments in flight, the intial reset
1563 * segment sequence numbers will be to the left of last_ack_sent,
1564 * but they will eventually catch up.
1565 * In any case, it never made sense to trim reset segments to
1566 * fit the receive window since RFC 1122 says:
1567 * 4.2.2.12 RST Segment: RFC-793 Section 3.4
1569 * A TCP SHOULD allow a received RST segment to include data.
1572 * It has been suggested that a RST segment could contain
1573 * ASCII text that encoded and explained the cause of the
1574 * RST. No standard has yet been established for such
1577 * If the reset segment passes the sequence number test examine
1579 * SYN_RECEIVED STATE:
1580 * If passive open, return to LISTEN state.
1581 * If active open, inform user that connection was refused.
1582 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES:
1583 * Inform user that connection was reset, and close tcb.
1584 * CLOSING, LAST_ACK STATES:
1587 * Drop the segment - see Stevens, vol. 2, p. 964 and
1590 if (thflags & TH_RST) {
1591 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
1592 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) {
1593 switch (tp->t_state) {
1595 case TCPS_SYN_RECEIVED:
1596 so->so_error = ECONNREFUSED;
1599 case TCPS_ESTABLISHED:
1600 case TCPS_FIN_WAIT_1:
1601 case TCPS_FIN_WAIT_2:
1602 case TCPS_CLOSE_WAIT:
1603 so->so_error = ECONNRESET;
1605 tp->t_state = TCPS_CLOSED;
1606 tcpstat.tcps_drops++;
1615 case TCPS_TIME_WAIT:
1623 * RFC 1323 PAWS: If we have a timestamp reply on this segment
1624 * and it's less than ts_recent, drop it.
1626 if ((to.to_flags & TOF_TS) && tp->ts_recent != 0 &&
1627 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
1629 /* Check to see if ts_recent is over 24 days old. */
1630 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) {
1632 * Invalidate ts_recent. If this segment updates
1633 * ts_recent, the age will be reset later and ts_recent
1634 * will get a valid value. If it does not, setting
1635 * ts_recent to zero will at least satisfy the
1636 * requirement that zero be placed in the timestamp
1637 * echo reply when ts_recent isn't valid. The
1638 * age isn't reset until we get a valid ts_recent
1639 * because we don't want out-of-order segments to be
1640 * dropped when ts_recent is old.
1644 tcpstat.tcps_rcvduppack++;
1645 tcpstat.tcps_rcvdupbyte += tlen;
1646 tcpstat.tcps_pawsdrop++;
1655 * If T/TCP was negotiated and the segment doesn't have CC,
1656 * or if its CC is wrong then drop the segment.
1657 * RST segments do not have to comply with this.
1659 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) &&
1660 (!(to.to_flags & TOF_CC) || tp->cc_recv != to.to_cc))
1664 * In the SYN-RECEIVED state, validate that the packet belongs to
1665 * this connection before trimming the data to fit the receive
1666 * window. Check the sequence number versus IRS since we know
1667 * the sequence numbers haven't wrapped. This is a partial fix
1668 * for the "LAND" DoS attack.
1670 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) {
1671 rstreason = BANDLIM_RST_OPENPORT;
1675 todrop = tp->rcv_nxt - th->th_seq;
1677 if (TCP_DO_SACK(tp)) {
1678 /* Report duplicate segment at head of packet. */
1679 tp->reportblk.rblk_start = th->th_seq;
1680 tp->reportblk.rblk_end = th->th_seq + tlen;
1681 if (thflags & TH_FIN)
1682 ++tp->reportblk.rblk_end;
1683 if (SEQ_GT(tp->reportblk.rblk_end, tp->rcv_nxt))
1684 tp->reportblk.rblk_end = tp->rcv_nxt;
1685 tp->t_flags |= (TF_DUPSEG | TF_SACKLEFT | TF_ACKNOW);
1687 if (thflags & TH_SYN) {
1697 * Following if statement from Stevens, vol. 2, p. 960.
1699 if (todrop > tlen ||
1700 (todrop == tlen && !(thflags & TH_FIN))) {
1702 * Any valid FIN must be to the left of the window.
1703 * At this point the FIN must be a duplicate or out
1704 * of sequence; drop it.
1709 * Send an ACK to resynchronize and drop any data.
1710 * But keep on processing for RST or ACK.
1712 tp->t_flags |= TF_ACKNOW;
1714 tcpstat.tcps_rcvduppack++;
1715 tcpstat.tcps_rcvdupbyte += todrop;
1717 tcpstat.tcps_rcvpartduppack++;
1718 tcpstat.tcps_rcvpartdupbyte += todrop;
1720 drop_hdrlen += todrop; /* drop from the top afterwards */
1721 th->th_seq += todrop;
1723 if (th->th_urp > todrop)
1724 th->th_urp -= todrop;
1732 * If new data are received on a connection after the
1733 * user processes are gone, then RST the other end.
1735 if ((so->so_state & SS_NOFDREF) &&
1736 tp->t_state > TCPS_CLOSE_WAIT && tlen) {
1738 tcpstat.tcps_rcvafterclose++;
1739 rstreason = BANDLIM_UNLIMITED;
1744 * If segment ends after window, drop trailing data
1745 * (and PUSH and FIN); if nothing left, just ACK.
1747 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd);
1749 tcpstat.tcps_rcvpackafterwin++;
1750 if (todrop >= tlen) {
1751 tcpstat.tcps_rcvbyteafterwin += tlen;
1753 * If a new connection request is received
1754 * while in TIME_WAIT, drop the old connection
1755 * and start over if the sequence numbers
1756 * are above the previous ones.
1758 if (thflags & TH_SYN &&
1759 tp->t_state == TCPS_TIME_WAIT &&
1760 SEQ_GT(th->th_seq, tp->rcv_nxt)) {
1765 * If window is closed can only take segments at
1766 * window edge, and have to drop data and PUSH from
1767 * incoming segments. Continue processing, but
1768 * remember to ack. Otherwise, drop segment
1771 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
1772 tp->t_flags |= TF_ACKNOW;
1773 tcpstat.tcps_rcvwinprobe++;
1777 tcpstat.tcps_rcvbyteafterwin += todrop;
1780 thflags &= ~(TH_PUSH | TH_FIN);
1784 * If last ACK falls within this segment's sequence numbers,
1785 * record its timestamp.
1787 * 1) That the test incorporates suggestions from the latest
1788 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1789 * 2) That updating only on newer timestamps interferes with
1790 * our earlier PAWS tests, so this check should be solely
1791 * predicated on the sequence space of this segment.
1792 * 3) That we modify the segment boundary check to be
1793 * Last.ACK.Sent <= SEG.SEQ + SEG.LEN
1794 * instead of RFC1323's
1795 * Last.ACK.Sent < SEG.SEQ + SEG.LEN,
1796 * This modified check allows us to overcome RFC1323's
1797 * limitations as described in Stevens TCP/IP Illustrated
1798 * Vol. 2 p.869. In such cases, we can still calculate the
1799 * RTT correctly when RCV.NXT == Last.ACK.Sent.
1801 if ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent) &&
1802 SEQ_LEQ(tp->last_ack_sent, (th->th_seq + tlen
1803 + ((thflags & TH_SYN) != 0)
1804 + ((thflags & TH_FIN) != 0)))) {
1805 tp->ts_recent_age = ticks;
1806 tp->ts_recent = to.to_tsval;
1810 * If a SYN is in the window, then this is an
1811 * error and we send an RST and drop the connection.
1813 if (thflags & TH_SYN) {
1814 tp = tcp_drop(tp, ECONNRESET);
1815 rstreason = BANDLIM_UNLIMITED;
1820 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN
1821 * flag is on (half-synchronized state), then queue data for
1822 * later processing; else drop segment and return.
1824 if (!(thflags & TH_ACK)) {
1825 if (tp->t_state == TCPS_SYN_RECEIVED ||
1826 (tp->t_flags & TF_NEEDSYN))
1835 switch (tp->t_state) {
1837 * In SYN_RECEIVED state, the ACK acknowledges our SYN, so enter
1838 * ESTABLISHED state and continue processing.
1839 * The ACK was checked above.
1841 case TCPS_SYN_RECEIVED:
1843 tcpstat.tcps_connects++;
1845 /* Do window scaling? */
1846 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) ==
1847 (TF_RCVD_SCALE | TF_REQ_SCALE)) {
1848 tp->snd_scale = tp->requested_s_scale;
1849 tp->rcv_scale = tp->request_r_scale;
1852 * Upon successful completion of 3-way handshake,
1853 * update cache.CC if it was undefined, pass any queued
1854 * data to the user, and advance state appropriately.
1856 if ((taop = tcp_gettaocache(&inp->inp_inc)) != NULL &&
1858 taop->tao_cc = tp->cc_recv;
1862 * SYN-RECEIVED -> ESTABLISHED
1863 * SYN-RECEIVED* -> FIN-WAIT-1
1865 tp->t_starttime = ticks;
1866 if (tp->t_flags & TF_NEEDFIN) {
1867 tp->t_state = TCPS_FIN_WAIT_1;
1868 tp->t_flags &= ~TF_NEEDFIN;
1870 tp->t_state = TCPS_ESTABLISHED;
1871 callout_reset(tp->tt_keep, tcp_keepidle,
1872 tcp_timer_keep, tp);
1875 * If segment contains data or ACK, will call tcp_reass()
1876 * later; if not, do so now to pass queued data to user.
1878 if (tlen == 0 && !(thflags & TH_FIN))
1879 tcp_reass(tp, NULL, NULL, NULL);
1883 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
1884 * ACKs. If the ack is in the range
1885 * tp->snd_una < th->th_ack <= tp->snd_max
1886 * then advance tp->snd_una to th->th_ack and drop
1887 * data from the retransmission queue. If this ACK reflects
1888 * more up to date window information we update our window information.
1890 case TCPS_ESTABLISHED:
1891 case TCPS_FIN_WAIT_1:
1892 case TCPS_FIN_WAIT_2:
1893 case TCPS_CLOSE_WAIT:
1896 case TCPS_TIME_WAIT:
1898 if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
1899 if (TCP_DO_SACK(tp))
1900 tcp_sack_update_scoreboard(tp, &to);
1901 if (tlen != 0 || tiwin != tp->snd_wnd) {
1905 tcpstat.tcps_rcvdupack++;
1906 if (!callout_active(tp->tt_rexmt) ||
1907 th->th_ack != tp->snd_una) {
1912 * We have outstanding data (other than
1913 * a window probe), this is a completely
1914 * duplicate ack (ie, window info didn't
1915 * change), the ack is the biggest we've
1916 * seen and we've seen exactly our rexmt
1917 * threshhold of them, so assume a packet
1918 * has been dropped and retransmit it.
1919 * Kludge snd_nxt & the congestion
1920 * window so we send only this one
1923 if (IN_FASTRECOVERY(tp)) {
1924 if (TCP_DO_SACK(tp)) {
1925 /* No artifical cwnd inflation. */
1926 tcp_sack_rexmt(tp, th);
1929 * Dup acks mean that packets
1930 * have left the network
1931 * (they're now cached at the
1932 * receiver) so bump cwnd by
1933 * the amount in the receiver
1934 * to keep a constant cwnd
1935 * packets in the network.
1937 tp->snd_cwnd += tp->t_maxseg;
1940 } else if (SEQ_LT(th->th_ack, tp->snd_recover)) {
1943 } else if (++tp->t_dupacks == tcprexmtthresh) {
1944 tcp_seq old_snd_nxt;
1948 if (tcp_do_eifel_detect &&
1949 (tp->t_flags & TF_RCVD_TSTMP)) {
1950 tcp_save_congestion_state(tp);
1951 tp->t_flags |= TF_FASTREXMT;
1954 * We know we're losing at the current
1955 * window size, so do congestion avoidance:
1956 * set ssthresh to half the current window
1957 * and pull our congestion window back to the
1960 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 /
1964 tp->snd_ssthresh = win * tp->t_maxseg;
1965 ENTER_FASTRECOVERY(tp);
1966 tp->snd_recover = tp->snd_max;
1967 callout_stop(tp->tt_rexmt);
1969 old_snd_nxt = tp->snd_nxt;
1970 tp->snd_nxt = th->th_ack;
1971 tp->snd_cwnd = tp->t_maxseg;
1973 ++tcpstat.tcps_sndfastrexmit;
1974 tp->snd_cwnd = tp->snd_ssthresh;
1975 tp->rexmt_high = tp->snd_nxt;
1976 if (SEQ_GT(old_snd_nxt, tp->snd_nxt))
1977 tp->snd_nxt = old_snd_nxt;
1978 KASSERT(tp->snd_limited <= 2,
1979 ("tp->snd_limited too big"));
1980 if (TCP_DO_SACK(tp))
1981 tcp_sack_rexmt(tp, th);
1983 tp->snd_cwnd += tp->t_maxseg *
1984 (tp->t_dupacks - tp->snd_limited);
1985 } else if (tcp_do_limitedtransmit) {
1986 u_long oldcwnd = tp->snd_cwnd;
1987 tcp_seq oldsndmax = tp->snd_max;
1988 tcp_seq oldsndnxt = tp->snd_nxt;
1989 /* outstanding data */
1990 uint32_t ownd = tp->snd_max - tp->snd_una;
1993 #define iceildiv(n, d) (((n)+(d)-1) / (d))
1995 KASSERT(tp->t_dupacks == 1 ||
1997 ("dupacks not 1 or 2"));
1998 if (tp->t_dupacks == 1)
1999 tp->snd_limited = 0;
2000 tp->snd_nxt = tp->snd_max;
2001 tp->snd_cwnd = ownd +
2002 (tp->t_dupacks - tp->snd_limited) *
2007 * Other acks may have been processed,
2008 * snd_nxt cannot be reset to a value less
2011 if (SEQ_LT(oldsndnxt, oldsndmax)) {
2012 if (SEQ_GT(oldsndnxt, tp->snd_una))
2013 tp->snd_nxt = oldsndnxt;
2015 tp->snd_nxt = tp->snd_una;
2017 tp->snd_cwnd = oldcwnd;
2018 sent = tp->snd_max - oldsndmax;
2019 if (sent > tp->t_maxseg) {
2020 KASSERT((tp->t_dupacks == 2 &&
2021 tp->snd_limited == 0) ||
2022 (sent == tp->t_maxseg + 1 &&
2023 tp->t_flags & TF_SENTFIN),
2025 KASSERT(sent <= tp->t_maxseg * 2,
2026 ("sent too many segments"));
2027 tp->snd_limited = 2;
2028 tcpstat.tcps_sndlimited += 2;
2029 } else if (sent > 0) {
2031 ++tcpstat.tcps_sndlimited;
2032 } else if (tcp_do_early_retransmit &&
2033 (tcp_do_eifel_detect &&
2034 (tp->t_flags & TF_RCVD_TSTMP)) &&
2035 ownd < 4 * tp->t_maxseg &&
2036 tp->t_dupacks + 1 >=
2037 iceildiv(ownd, tp->t_maxseg) &&
2038 (!TCP_DO_SACK(tp) ||
2039 ownd <= tp->t_maxseg ||
2040 tcp_sack_has_sacked(&tp->scb,
2041 ownd - tp->t_maxseg))) {
2042 ++tcpstat.tcps_sndearlyrexmit;
2043 tp->t_flags |= TF_EARLYREXMT;
2044 goto fastretransmit;
2050 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una"));
2052 if (SEQ_GT(th->th_ack, tp->snd_max)) {
2054 * Detected optimistic ACK attack.
2055 * Force slow-start to de-synchronize attack.
2057 tp->snd_cwnd = tp->t_maxseg;
2060 tcpstat.tcps_rcvacktoomuch++;
2064 * If we reach this point, ACK is not a duplicate,
2065 * i.e., it ACKs something we sent.
2067 if (tp->t_flags & TF_NEEDSYN) {
2069 * T/TCP: Connection was half-synchronized, and our
2070 * SYN has been ACK'd (so connection is now fully
2071 * synchronized). Go to non-starred state,
2072 * increment snd_una for ACK of SYN, and check if
2073 * we can do window scaling.
2075 tp->t_flags &= ~TF_NEEDSYN;
2077 /* Do window scaling? */
2078 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) ==
2079 (TF_RCVD_SCALE | TF_REQ_SCALE)) {
2080 tp->snd_scale = tp->requested_s_scale;
2081 tp->rcv_scale = tp->request_r_scale;
2086 acked = th->th_ack - tp->snd_una;
2087 tcpstat.tcps_rcvackpack++;
2088 tcpstat.tcps_rcvackbyte += acked;
2090 if (tcp_do_eifel_detect && acked > 0 &&
2091 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) &&
2092 (tp->t_flags & TF_FIRSTACCACK)) {
2093 /* Eifel detection applicable. */
2094 if (to.to_tsecr < tp->t_rexmtTS) {
2095 ++tcpstat.tcps_eifeldetected;
2096 tcp_revert_congestion_state(tp);
2097 if (tp->t_rxtshift == 1 &&
2098 ticks >= tp->t_badrxtwin)
2099 ++tcpstat.tcps_rttcantdetect;
2101 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) {
2103 * If we just performed our first retransmit,
2104 * and the ACK arrives within our recovery window,
2105 * then it was a mistake to do the retransmit
2106 * in the first place. Recover our original cwnd
2107 * and ssthresh, and proceed to transmit where we
2110 tcp_revert_congestion_state(tp);
2111 ++tcpstat.tcps_rttdetected;
2115 * If we have a timestamp reply, update smoothed
2116 * round trip time. If no timestamp is present but
2117 * transmit timer is running and timed sequence
2118 * number was acked, update smoothed round trip time.
2119 * Since we now have an rtt measurement, cancel the
2120 * timer backoff (cf., Phil Karn's retransmit alg.).
2121 * Recompute the initial retransmit timer.
2123 * Some machines (certain windows boxes) send broken
2124 * timestamp replies during the SYN+ACK phase, ignore
2127 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0))
2128 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1);
2129 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq))
2130 tcp_xmit_timer(tp, ticks - tp->t_rtttime);
2131 tcp_xmit_bandwidth_limit(tp, th->th_ack);
2134 * If no data (only SYN) was ACK'd,
2135 * skip rest of ACK processing.
2140 /* Stop looking for an acceptable ACK since one was received. */
2141 tp->t_flags &= ~(TF_FIRSTACCACK | TF_FASTREXMT | TF_EARLYREXMT);
2143 if (acked > so->so_snd.ssb_cc) {
2144 tp->snd_wnd -= so->so_snd.ssb_cc;
2145 sbdrop(&so->so_snd.sb, (int)so->so_snd.ssb_cc);
2146 ourfinisacked = TRUE;
2148 sbdrop(&so->so_snd.sb, acked);
2149 tp->snd_wnd -= acked;
2150 ourfinisacked = FALSE;
2155 * Update window information.
2156 * Don't look at window if no ACK:
2157 * TAC's send garbage on first SYN.
2159 if (SEQ_LT(tp->snd_wl1, th->th_seq) ||
2160 (tp->snd_wl1 == th->th_seq &&
2161 (SEQ_LT(tp->snd_wl2, th->th_ack) ||
2162 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) {
2163 /* keep track of pure window updates */
2164 if (tlen == 0 && tp->snd_wl2 == th->th_ack &&
2165 tiwin > tp->snd_wnd)
2166 tcpstat.tcps_rcvwinupd++;
2167 tp->snd_wnd = tiwin;
2168 tp->snd_wl1 = th->th_seq;
2169 tp->snd_wl2 = th->th_ack;
2170 if (tp->snd_wnd > tp->max_sndwnd)
2171 tp->max_sndwnd = tp->snd_wnd;
2175 tp->snd_una = th->th_ack;
2176 if (TCP_DO_SACK(tp))
2177 tcp_sack_update_scoreboard(tp, &to);
2178 if (IN_FASTRECOVERY(tp)) {
2179 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) {
2180 EXIT_FASTRECOVERY(tp);
2183 * If the congestion window was inflated
2184 * to account for the other side's
2185 * cached packets, retract it.
2187 if (!TCP_DO_SACK(tp))
2188 tp->snd_cwnd = tp->snd_ssthresh;
2191 * Window inflation should have left us
2192 * with approximately snd_ssthresh outstanding
2193 * data. But, in case we would be inclined
2194 * to send a burst, better do it using
2197 if (SEQ_GT(th->th_ack + tp->snd_cwnd,
2198 tp->snd_max + 2 * tp->t_maxseg))
2200 (tp->snd_max - tp->snd_una) +
2205 if (TCP_DO_SACK(tp)) {
2206 tp->snd_max_rexmt = tp->snd_max;
2207 tcp_sack_rexmt(tp, th);
2209 tcp_newreno_partial_ack(tp, th, acked);
2215 * Open the congestion window. When in slow-start,
2216 * open exponentially: maxseg per packet. Otherwise,
2217 * open linearly: maxseg per window.
2219 if (tp->snd_cwnd <= tp->snd_ssthresh) {
2221 (SEQ_LT(tp->snd_nxt, tp->snd_max) ?
2222 tp->t_maxseg : 2 * tp->t_maxseg);
2225 tp->snd_cwnd += tcp_do_abc ?
2226 min(acked, abc_sslimit) : tp->t_maxseg;
2228 /* linear increase */
2229 tp->snd_wacked += tcp_do_abc ? acked :
2231 if (tp->snd_wacked >= tp->snd_cwnd) {
2232 tp->snd_wacked -= tp->snd_cwnd;
2233 tp->snd_cwnd += tp->t_maxseg;
2236 tp->snd_cwnd = min(tp->snd_cwnd,
2237 TCP_MAXWIN << tp->snd_scale);
2238 tp->snd_recover = th->th_ack - 1;
2240 if (SEQ_LT(tp->snd_nxt, tp->snd_una))
2241 tp->snd_nxt = tp->snd_una;
2244 * If all outstanding data is acked, stop retransmit
2245 * timer and remember to restart (more output or persist).
2246 * If there is more data to be acked, restart retransmit
2247 * timer, using current (possibly backed-off) value.
2249 if (th->th_ack == tp->snd_max) {
2250 callout_stop(tp->tt_rexmt);
2252 } else if (!callout_active(tp->tt_persist))
2253 callout_reset(tp->tt_rexmt, tp->t_rxtcur,
2254 tcp_timer_rexmt, tp);
2256 switch (tp->t_state) {
2258 * In FIN_WAIT_1 STATE in addition to the processing
2259 * for the ESTABLISHED state if our FIN is now acknowledged
2260 * then enter FIN_WAIT_2.
2262 case TCPS_FIN_WAIT_1:
2263 if (ourfinisacked) {
2265 * If we can't receive any more
2266 * data, then closing user can proceed.
2267 * Starting the timer is contrary to the
2268 * specification, but if we don't get a FIN
2269 * we'll hang forever.
2271 if (so->so_state & SS_CANTRCVMORE) {
2272 soisdisconnected(so);
2273 callout_reset(tp->tt_2msl, tcp_maxidle,
2274 tcp_timer_2msl, tp);
2276 tp->t_state = TCPS_FIN_WAIT_2;
2281 * In CLOSING STATE in addition to the processing for
2282 * the ESTABLISHED state if the ACK acknowledges our FIN
2283 * then enter the TIME-WAIT state, otherwise ignore
2287 if (ourfinisacked) {
2288 tp->t_state = TCPS_TIME_WAIT;
2289 tcp_canceltimers(tp);
2290 /* Shorten TIME_WAIT [RFC-1644, p.28] */
2291 if (tp->cc_recv != 0 &&
2292 (ticks - tp->t_starttime) < tcp_msl)
2293 callout_reset(tp->tt_2msl,
2294 tp->t_rxtcur * TCPTV_TWTRUNC,
2295 tcp_timer_2msl, tp);
2297 callout_reset(tp->tt_2msl, 2 * tcp_msl,
2298 tcp_timer_2msl, tp);
2299 soisdisconnected(so);
2304 * In LAST_ACK, we may still be waiting for data to drain
2305 * and/or to be acked, as well as for the ack of our FIN.
2306 * If our FIN is now acknowledged, delete the TCB,
2307 * enter the closed state and return.
2310 if (ourfinisacked) {
2317 * In TIME_WAIT state the only thing that should arrive
2318 * is a retransmission of the remote FIN. Acknowledge
2319 * it and restart the finack timer.
2321 case TCPS_TIME_WAIT:
2322 callout_reset(tp->tt_2msl, 2 * tcp_msl,
2323 tcp_timer_2msl, tp);
2330 * Update window information.
2331 * Don't look at window if no ACK: TAC's send garbage on first SYN.
2333 if ((thflags & TH_ACK) &&
2334 acceptable_window_update(tp, th, tiwin)) {
2335 /* keep track of pure window updates */
2336 if (tlen == 0 && tp->snd_wl2 == th->th_ack &&
2337 tiwin > tp->snd_wnd)
2338 tcpstat.tcps_rcvwinupd++;
2339 tp->snd_wnd = tiwin;
2340 tp->snd_wl1 = th->th_seq;
2341 tp->snd_wl2 = th->th_ack;
2342 if (tp->snd_wnd > tp->max_sndwnd)
2343 tp->max_sndwnd = tp->snd_wnd;
2348 * Process segments with URG.
2350 if ((thflags & TH_URG) && th->th_urp &&
2351 !TCPS_HAVERCVDFIN(tp->t_state)) {
2353 * This is a kludge, but if we receive and accept
2354 * random urgent pointers, we'll crash in
2355 * soreceive. It's hard to imagine someone
2356 * actually wanting to send this much urgent data.
2358 if (th->th_urp + so->so_rcv.ssb_cc > sb_max) {
2359 th->th_urp = 0; /* XXX */
2360 thflags &= ~TH_URG; /* XXX */
2361 goto dodata; /* XXX */
2364 * If this segment advances the known urgent pointer,
2365 * then mark the data stream. This should not happen
2366 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
2367 * a FIN has been received from the remote side.
2368 * In these states we ignore the URG.
2370 * According to RFC961 (Assigned Protocols),
2371 * the urgent pointer points to the last octet
2372 * of urgent data. We continue, however,
2373 * to consider it to indicate the first octet
2374 * of data past the urgent section as the original
2375 * spec states (in one of two places).
2377 if (SEQ_GT(th->th_seq + th->th_urp, tp->rcv_up)) {
2378 tp->rcv_up = th->th_seq + th->th_urp;
2379 so->so_oobmark = so->so_rcv.ssb_cc +
2380 (tp->rcv_up - tp->rcv_nxt) - 1;
2381 if (so->so_oobmark == 0)
2382 so->so_state |= SS_RCVATMARK;
2384 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
2387 * Remove out of band data so doesn't get presented to user.
2388 * This can happen independent of advancing the URG pointer,
2389 * but if two URG's are pending at once, some out-of-band
2390 * data may creep in... ick.
2392 if (th->th_urp <= (u_long)tlen &&
2393 !(so->so_options & SO_OOBINLINE)) {
2394 /* hdr drop is delayed */
2395 tcp_pulloutofband(so, th, m, drop_hdrlen);
2399 * If no out of band data is expected,
2400 * pull receive urgent pointer along
2401 * with the receive window.
2403 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
2404 tp->rcv_up = tp->rcv_nxt;
2409 * Process the segment text, merging it into the TCP sequencing queue,
2410 * and arranging for acknowledgment of receipt if necessary.
2411 * This process logically involves adjusting tp->rcv_wnd as data
2412 * is presented to the user (this happens in tcp_usrreq.c,
2413 * case PRU_RCVD). If a FIN has already been received on this
2414 * connection then we just ignore the text.
2416 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) {
2417 m_adj(m, drop_hdrlen); /* delayed header drop */
2419 * Insert segment which includes th into TCP reassembly queue
2420 * with control block tp. Set thflags to whether reassembly now
2421 * includes a segment with FIN. This handles the common case
2422 * inline (segment is the next to be received on an established
2423 * connection, and the queue is empty), avoiding linkage into
2424 * and removal from the queue and repetition of various
2426 * Set DELACK for segments received in order, but ack
2427 * immediately when segments are out of order (so
2428 * fast retransmit can work).
2430 if (th->th_seq == tp->rcv_nxt &&
2431 LIST_EMPTY(&tp->t_segq) &&
2432 TCPS_HAVEESTABLISHED(tp->t_state)) {
2434 callout_reset(tp->tt_delack, tcp_delacktime,
2435 tcp_timer_delack, tp);
2437 tp->t_flags |= TF_ACKNOW;
2438 tp->rcv_nxt += tlen;
2439 thflags = th->th_flags & TH_FIN;
2440 tcpstat.tcps_rcvpack++;
2441 tcpstat.tcps_rcvbyte += tlen;
2443 if (so->so_state & SS_CANTRCVMORE)
2446 ssb_appendstream(&so->so_rcv, m);
2449 if (!(tp->t_flags & TF_DUPSEG)) {
2450 /* Initialize SACK report block. */
2451 tp->reportblk.rblk_start = th->th_seq;
2452 tp->reportblk.rblk_end = th->th_seq + tlen +
2453 ((thflags & TH_FIN) != 0);
2455 thflags = tcp_reass(tp, th, &tlen, m);
2456 tp->t_flags |= TF_ACKNOW;
2460 * Note the amount of data that peer has sent into
2461 * our window, in order to estimate the sender's
2464 len = so->so_rcv.ssb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
2471 * If FIN is received ACK the FIN and let the user know
2472 * that the connection is closing.
2474 if (thflags & TH_FIN) {
2475 if (!TCPS_HAVERCVDFIN(tp->t_state)) {
2478 * If connection is half-synchronized
2479 * (ie NEEDSYN flag on) then delay ACK,
2480 * so it may be piggybacked when SYN is sent.
2481 * Otherwise, since we received a FIN then no
2482 * more input can be expected, send ACK now.
2484 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN))
2485 callout_reset(tp->tt_delack, tcp_delacktime,
2486 tcp_timer_delack, tp);
2488 tp->t_flags |= TF_ACKNOW;
2492 switch (tp->t_state) {
2494 * In SYN_RECEIVED and ESTABLISHED STATES
2495 * enter the CLOSE_WAIT state.
2497 case TCPS_SYN_RECEIVED:
2498 tp->t_starttime = ticks;
2500 case TCPS_ESTABLISHED:
2501 tp->t_state = TCPS_CLOSE_WAIT;
2505 * If still in FIN_WAIT_1 STATE FIN has not been acked so
2506 * enter the CLOSING state.
2508 case TCPS_FIN_WAIT_1:
2509 tp->t_state = TCPS_CLOSING;
2513 * In FIN_WAIT_2 state enter the TIME_WAIT state,
2514 * starting the time-wait timer, turning off the other
2517 case TCPS_FIN_WAIT_2:
2518 tp->t_state = TCPS_TIME_WAIT;
2519 tcp_canceltimers(tp);
2520 /* Shorten TIME_WAIT [RFC-1644, p.28] */
2521 if (tp->cc_recv != 0 &&
2522 (ticks - tp->t_starttime) < tcp_msl) {
2523 callout_reset(tp->tt_2msl,
2524 tp->t_rxtcur * TCPTV_TWTRUNC,
2525 tcp_timer_2msl, tp);
2526 /* For transaction client, force ACK now. */
2527 tp->t_flags |= TF_ACKNOW;
2530 callout_reset(tp->tt_2msl, 2 * tcp_msl,
2531 tcp_timer_2msl, tp);
2532 soisdisconnected(so);
2536 * In TIME_WAIT state restart the 2 MSL time_wait timer.
2538 case TCPS_TIME_WAIT:
2539 callout_reset(tp->tt_2msl, 2 * tcp_msl,
2540 tcp_timer_2msl, tp);
2546 if (so->so_options & SO_DEBUG)
2547 tcp_trace(TA_INPUT, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
2551 * Return any desired output.
2553 if (needoutput || (tp->t_flags & TF_ACKNOW))
2559 * Generate an ACK dropping incoming segment if it occupies
2560 * sequence space, where the ACK reflects our state.
2562 * We can now skip the test for the RST flag since all
2563 * paths to this code happen after packets containing
2564 * RST have been dropped.
2566 * In the SYN-RECEIVED state, don't send an ACK unless the
2567 * segment we received passes the SYN-RECEIVED ACK test.
2568 * If it fails send a RST. This breaks the loop in the
2569 * "LAND" DoS attack, and also prevents an ACK storm
2570 * between two listening ports that have been sent forged
2571 * SYN segments, each with the source address of the other.
2573 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
2574 (SEQ_GT(tp->snd_una, th->th_ack) ||
2575 SEQ_GT(th->th_ack, tp->snd_max)) ) {
2576 rstreason = BANDLIM_RST_OPENPORT;
2580 if (so->so_options & SO_DEBUG)
2581 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
2584 tp->t_flags |= TF_ACKNOW;
2590 * Generate a RST, dropping incoming segment.
2591 * Make ACK acceptable to originator of segment.
2592 * Don't bother to respond if destination was broadcast/multicast.
2594 if ((thflags & TH_RST) || m->m_flags & (M_BCAST | M_MCAST))
2597 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
2598 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
2601 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
2602 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
2603 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
2604 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
2607 /* IPv6 anycast check is done at tcp6_input() */
2610 * Perform bandwidth limiting.
2613 if (badport_bandlim(rstreason) < 0)
2618 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
2619 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
2621 if (thflags & TH_ACK)
2622 /* mtod() below is safe as long as hdr dropping is delayed */
2623 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack,
2626 if (thflags & TH_SYN)
2628 /* mtod() below is safe as long as hdr dropping is delayed */
2629 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen,
2630 (tcp_seq)0, TH_RST | TH_ACK);
2636 * Drop space held by incoming segment and return.
2639 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
2640 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
2647 * Parse TCP options and place in tcpopt.
2650 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn)
2655 for (; cnt > 0; cnt -= optlen, cp += optlen) {
2657 if (opt == TCPOPT_EOL)
2659 if (opt == TCPOPT_NOP)
2665 if (optlen < 2 || optlen > cnt)
2670 if (optlen != TCPOLEN_MAXSEG)
2674 to->to_flags |= TOF_MSS;
2675 bcopy(cp + 2, &to->to_mss, sizeof to->to_mss);
2676 to->to_mss = ntohs(to->to_mss);
2679 if (optlen != TCPOLEN_WINDOW)
2683 to->to_flags |= TOF_SCALE;
2684 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT);
2686 case TCPOPT_TIMESTAMP:
2687 if (optlen != TCPOLEN_TIMESTAMP)
2689 to->to_flags |= TOF_TS;
2690 bcopy(cp + 2, &to->to_tsval, sizeof to->to_tsval);
2691 to->to_tsval = ntohl(to->to_tsval);
2692 bcopy(cp + 6, &to->to_tsecr, sizeof to->to_tsecr);
2693 to->to_tsecr = ntohl(to->to_tsecr);
2695 * If echoed timestamp is later than the current time,
2696 * fall back to non RFC1323 RTT calculation.
2698 if (to->to_tsecr != 0 && TSTMP_GT(to->to_tsecr, ticks))
2702 if (optlen != TCPOLEN_CC)
2704 to->to_flags |= TOF_CC;
2705 bcopy(cp + 2, &to->to_cc, sizeof to->to_cc);
2706 to->to_cc = ntohl(to->to_cc);
2709 if (optlen != TCPOLEN_CC)
2713 to->to_flags |= TOF_CCNEW;
2714 bcopy(cp + 2, &to->to_cc, sizeof to->to_cc);
2715 to->to_cc = ntohl(to->to_cc);
2718 if (optlen != TCPOLEN_CC)
2722 to->to_flags |= TOF_CCECHO;
2723 bcopy(cp + 2, &to->to_ccecho, sizeof to->to_ccecho);
2724 to->to_ccecho = ntohl(to->to_ccecho);
2726 case TCPOPT_SACK_PERMITTED:
2727 if (optlen != TCPOLEN_SACK_PERMITTED)
2731 to->to_flags |= TOF_SACK_PERMITTED;
2734 if ((optlen - 2) & 0x07) /* not multiple of 8 */
2736 to->to_nsackblocks = (optlen - 2) / 8;
2737 to->to_sackblocks = (struct raw_sackblock *) (cp + 2);
2738 to->to_flags |= TOF_SACK;
2739 for (i = 0; i < to->to_nsackblocks; i++) {
2740 struct raw_sackblock *r = &to->to_sackblocks[i];
2742 r->rblk_start = ntohl(r->rblk_start);
2743 r->rblk_end = ntohl(r->rblk_end);
2753 * Pull out of band byte out of a segment so
2754 * it doesn't appear in the user's data queue.
2755 * It is still reflected in the segment length for
2756 * sequencing purposes.
2757 * "off" is the delayed to be dropped hdrlen.
2760 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off)
2762 int cnt = off + th->th_urp - 1;
2765 if (m->m_len > cnt) {
2766 char *cp = mtod(m, caddr_t) + cnt;
2767 struct tcpcb *tp = sototcpcb(so);
2770 tp->t_oobflags |= TCPOOB_HAVEDATA;
2771 bcopy(cp + 1, cp, m->m_len - cnt - 1);
2773 if (m->m_flags & M_PKTHDR)
2782 panic("tcp_pulloutofband");
2786 * Collect new round-trip time estimate
2787 * and update averages and current timeout.
2790 tcp_xmit_timer(struct tcpcb *tp, int rtt)
2794 tcpstat.tcps_rttupdated++;
2796 if (tp->t_srtt != 0) {
2798 * srtt is stored as fixed point with 5 bits after the
2799 * binary point (i.e., scaled by 8). The following magic
2800 * is equivalent to the smoothing algorithm in rfc793 with
2801 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
2802 * point). Adjust rtt to origin 0.
2804 delta = ((rtt - 1) << TCP_DELTA_SHIFT)
2805 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
2807 if ((tp->t_srtt += delta) <= 0)
2811 * We accumulate a smoothed rtt variance (actually, a
2812 * smoothed mean difference), then set the retransmit
2813 * timer to smoothed rtt + 4 times the smoothed variance.
2814 * rttvar is stored as fixed point with 4 bits after the
2815 * binary point (scaled by 16). The following is
2816 * equivalent to rfc793 smoothing with an alpha of .75
2817 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces
2818 * rfc793's wired-in beta.
2822 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
2823 if ((tp->t_rttvar += delta) <= 0)
2825 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
2826 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2829 * No rtt measurement yet - use the unsmoothed rtt.
2830 * Set the variance to half the rtt (so our first
2831 * retransmit happens at 3*rtt).
2833 tp->t_srtt = rtt << TCP_RTT_SHIFT;
2834 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
2835 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2841 * the retransmit should happen at rtt + 4 * rttvar.
2842 * Because of the way we do the smoothing, srtt and rttvar
2843 * will each average +1/2 tick of bias. When we compute
2844 * the retransmit timer, we want 1/2 tick of rounding and
2845 * 1 extra tick because of +-1/2 tick uncertainty in the
2846 * firing of the timer. The bias will give us exactly the
2847 * 1.5 tick we need. But, because the bias is
2848 * statistical, we have to test that we don't drop below
2849 * the minimum feasible timer (which is 2 ticks).
2851 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
2852 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);
2855 * We received an ack for a packet that wasn't retransmitted;
2856 * it is probably safe to discard any error indications we've
2857 * received recently. This isn't quite right, but close enough
2858 * for now (a route might have failed after we sent a segment,
2859 * and the return path might not be symmetrical).
2861 tp->t_softerror = 0;
2865 * Determine a reasonable value for maxseg size.
2866 * If the route is known, check route for mtu.
2867 * If none, use an mss that can be handled on the outgoing
2868 * interface without forcing IP to fragment; if bigger than
2869 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES
2870 * to utilize large mbufs. If no route is found, route has no mtu,
2871 * or the destination isn't local, use a default, hopefully conservative
2872 * size (usually 512 or the default IP max size, but no more than the mtu
2873 * of the interface), as we can't discover anything about intervening
2874 * gateways or networks. We also initialize the congestion/slow start
2875 * window to be a single segment if the destination isn't local.
2876 * While looking at the routing entry, we also initialize other path-dependent
2877 * parameters from pre-set or cached values in the routing entry.
2879 * Also take into account the space needed for options that we
2880 * send regularly. Make maxseg shorter by that amount to assure
2881 * that we can send maxseg amount of data even when the options
2882 * are present. Store the upper limit of the length of options plus
2885 * NOTE that this routine is only called when we process an incoming
2886 * segment, for outgoing segments only tcp_mssopt is called.
2888 * In case of T/TCP, we call this routine during implicit connection
2889 * setup as well (offer = -1), to initialize maxseg from the cached
2893 tcp_mss(struct tcpcb *tp, int offer)
2899 struct inpcb *inp = tp->t_inpcb;
2901 struct rmxp_tao *taop;
2902 int origoffer = offer;
2904 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE);
2905 size_t min_protoh = isipv6 ?
2906 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) :
2907 sizeof(struct tcpiphdr);
2909 const boolean_t isipv6 = FALSE;
2910 const size_t min_protoh = sizeof(struct tcpiphdr);
2914 rt = tcp_rtlookup6(&inp->inp_inc);
2916 rt = tcp_rtlookup(&inp->inp_inc);
2918 tp->t_maxopd = tp->t_maxseg =
2919 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt);
2923 so = inp->inp_socket;
2925 taop = rmx_taop(rt->rt_rmx);
2927 * Offer == -1 means that we didn't receive SYN yet,
2928 * use cached value in that case;
2931 offer = taop->tao_mssopt;
2933 * Offer == 0 means that there was no MSS on the SYN segment,
2934 * in this case we use tcp_mssdflt.
2937 offer = (isipv6 ? tcp_v6mssdflt : tcp_mssdflt);
2940 * Sanity check: make sure that maxopd will be large
2941 * enough to allow some data on segments even is the
2942 * all the option space is used (40bytes). Otherwise
2943 * funny things may happen in tcp_output.
2945 offer = max(offer, 64);
2946 taop->tao_mssopt = offer;
2949 * While we're here, check if there's an initial rtt
2950 * or rttvar. Convert from the route-table units
2951 * to scaled multiples of the slow timeout timer.
2953 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) {
2955 * XXX the lock bit for RTT indicates that the value
2956 * is also a minimum value; this is subject to time.
2958 if (rt->rt_rmx.rmx_locks & RTV_RTT)
2959 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz);
2960 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE));
2961 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE;
2962 tcpstat.tcps_usedrtt++;
2963 if (rt->rt_rmx.rmx_rttvar) {
2964 tp->t_rttvar = rt->rt_rmx.rmx_rttvar /
2965 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE));
2966 tcpstat.tcps_usedrttvar++;
2968 /* default variation is +- 1 rtt */
2970 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
2972 TCPT_RANGESET(tp->t_rxtcur,
2973 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
2974 tp->t_rttmin, TCPTV_REXMTMAX);
2977 * if there's an mtu associated with the route, use it
2978 * else, use the link mtu.
2980 if (rt->rt_rmx.rmx_mtu)
2981 mss = rt->rt_rmx.rmx_mtu - min_protoh;
2984 mss = ND_IFINFO(rt->rt_ifp)->linkmtu - min_protoh;
2985 if (!in6_localaddr(&inp->in6p_faddr))
2986 mss = min(mss, tcp_v6mssdflt);
2988 mss = ifp->if_mtu - min_protoh;
2989 if (!in_localaddr(inp->inp_faddr))
2990 mss = min(mss, tcp_mssdflt);
2993 mss = min(mss, offer);
2995 * maxopd stores the maximum length of data AND options
2996 * in a segment; maxseg is the amount of data in a normal
2997 * segment. We need to store this value (maxopd) apart
2998 * from maxseg, because now every segment carries options
2999 * and thus we normally have somewhat less data in segments.
3004 * In case of T/TCP, origoffer==-1 indicates, that no segments
3005 * were received yet. In this case we just guess, otherwise
3006 * we do the same as before T/TCP.
3008 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP &&
3010 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP))
3011 mss -= TCPOLEN_TSTAMP_APPA;
3012 if ((tp->t_flags & (TF_REQ_CC | TF_NOOPT)) == TF_REQ_CC &&
3014 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC))
3015 mss -= TCPOLEN_CC_APPA;
3017 #if (MCLBYTES & (MCLBYTES - 1)) == 0
3019 mss &= ~(MCLBYTES-1);
3022 mss = mss / MCLBYTES * MCLBYTES;
3025 * If there's a pipesize, change the socket buffer
3026 * to that size. Make the socket buffers an integral
3027 * number of mss units; if the mss is larger than
3028 * the socket buffer, decrease the mss.
3031 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0)
3033 bufsize = so->so_snd.ssb_hiwat;
3037 bufsize = roundup(bufsize, mss);
3038 if (bufsize > sb_max)
3040 if (bufsize > so->so_snd.ssb_hiwat)
3041 ssb_reserve(&so->so_snd, bufsize, so, NULL);
3046 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0)
3048 bufsize = so->so_rcv.ssb_hiwat;
3049 if (bufsize > mss) {
3050 bufsize = roundup(bufsize, mss);
3051 if (bufsize > sb_max)
3053 if (bufsize > so->so_rcv.ssb_hiwat)
3054 ssb_reserve(&so->so_rcv, bufsize, so, NULL);
3058 * Set the slow-start flight size depending on whether this
3059 * is a local network or not.
3062 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380));
3066 if (rt->rt_rmx.rmx_ssthresh) {
3068 * There's some sort of gateway or interface
3069 * buffer limit on the path. Use this to set
3070 * the slow start threshhold, but set the
3071 * threshold to no less than 2*mss.
3073 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh);
3074 tcpstat.tcps_usedssthresh++;
3079 * Determine the MSS option to send on an outgoing SYN.
3082 tcp_mssopt(struct tcpcb *tp)
3087 ((tp->t_inpcb->inp_vflag & INP_IPV6) ? TRUE : FALSE);
3088 int min_protoh = isipv6 ?
3089 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) :
3090 sizeof(struct tcpiphdr);
3092 const boolean_t isipv6 = FALSE;
3093 const size_t min_protoh = sizeof(struct tcpiphdr);
3097 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc);
3099 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc);
3101 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt);
3103 return (rt->rt_ifp->if_mtu - min_protoh);
3107 * When a partial ack arrives, force the retransmission of the
3108 * next unacknowledged segment. Do not exit Fast Recovery.
3110 * Implement the Slow-but-Steady variant of NewReno by restarting the
3111 * the retransmission timer. Turn it off here so it can be restarted
3112 * later in tcp_output().
3115 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th, int acked)
3117 tcp_seq old_snd_nxt = tp->snd_nxt;
3118 u_long ocwnd = tp->snd_cwnd;
3120 callout_stop(tp->tt_rexmt);
3122 tp->snd_nxt = th->th_ack;
3123 /* Set snd_cwnd to one segment beyond acknowledged offset. */
3124 tp->snd_cwnd = tp->t_maxseg;
3125 tp->t_flags |= TF_ACKNOW;
3127 if (SEQ_GT(old_snd_nxt, tp->snd_nxt))
3128 tp->snd_nxt = old_snd_nxt;
3129 /* partial window deflation */
3131 tp->snd_cwnd = ocwnd - acked + tp->t_maxseg;
3133 tp->snd_cwnd = tp->t_maxseg;
3137 * In contrast to the Slow-but-Steady NewReno variant,
3138 * we do not reset the retransmission timer for SACK retransmissions,
3139 * except when retransmitting snd_una.
3142 tcp_sack_rexmt(struct tcpcb *tp, struct tcphdr *th)
3144 uint32_t pipe, seglen;
3147 tcp_seq old_snd_nxt = tp->snd_nxt;
3148 u_long ocwnd = tp->snd_cwnd;
3149 int nseg = 0; /* consecutive new segments */
3150 #define MAXBURST 4 /* limit burst of new packets on partial ack */
3153 pipe = tcp_sack_compute_pipe(tp);
3154 while ((tcp_seq_diff_t)(ocwnd - pipe) >= (tcp_seq_diff_t)tp->t_maxseg &&
3155 (!tcp_do_smartsack || nseg < MAXBURST) &&
3156 tcp_sack_nextseg(tp, &nextrexmt, &seglen, &lostdup)) {
3158 tcp_seq old_snd_max;
3161 if (nextrexmt == tp->snd_max)
3163 tp->snd_nxt = nextrexmt;
3164 tp->snd_cwnd = nextrexmt - tp->snd_una + seglen;
3165 old_snd_max = tp->snd_max;
3166 if (nextrexmt == tp->snd_una)
3167 callout_stop(tp->tt_rexmt);
3168 error = tcp_output(tp);
3171 sent = tp->snd_nxt - nextrexmt;
3176 tcpstat.tcps_sndsackpack++;
3177 tcpstat.tcps_sndsackbyte += sent;
3178 if (SEQ_LT(nextrexmt, old_snd_max) &&
3179 SEQ_LT(tp->rexmt_high, tp->snd_nxt))
3180 tp->rexmt_high = seq_min(tp->snd_nxt, old_snd_max);
3182 if (SEQ_GT(old_snd_nxt, tp->snd_nxt))
3183 tp->snd_nxt = old_snd_nxt;
3184 tp->snd_cwnd = ocwnd;
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