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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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 */
73 #include "opt_inet6.h"
74 #include "opt_ipsec.h"
75 #include "opt_tcpdebug.h"
76 #include "opt_tcp_input.h"
78 #include <sys/param.h>
79 #include <sys/systm.h>
80 #include <sys/kernel.h>
81 #include <sys/sysctl.h>
82 #include <sys/malloc.h>
84 #include <sys/proc.h> /* for proc0 declaration */
85 #include <sys/protosw.h>
86 #include <sys/socket.h>
87 #include <sys/socketvar.h>
88 #include <sys/syslog.h>
89 #include <sys/in_cksum.h>
91 #include <sys/socketvar2.h>
93 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */
94 #include <machine/stdarg.h>
97 #include <net/route.h>
99 #include <netinet/in.h>
100 #include <netinet/in_systm.h>
101 #include <netinet/ip.h>
102 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */
103 #include <netinet/in_var.h>
104 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */
105 #include <netinet/in_pcb.h>
106 #include <netinet/ip_var.h>
107 #include <netinet/ip6.h>
108 #include <netinet/icmp6.h>
109 #include <netinet6/nd6.h>
110 #include <netinet6/ip6_var.h>
111 #include <netinet6/in6_pcb.h>
112 #include <netinet/tcp.h>
113 #include <netinet/tcp_fsm.h>
114 #include <netinet/tcp_seq.h>
115 #include <netinet/tcp_timer.h>
116 #include <netinet/tcp_timer2.h>
117 #include <netinet/tcp_var.h>
118 #include <netinet6/tcp6_var.h>
119 #include <netinet/tcpip.h>
122 #include <netinet/tcp_debug.h>
124 u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */
125 struct tcphdr tcp_savetcp;
129 #include <netproto/ipsec/ipsec.h>
130 #include <netproto/ipsec/ipsec6.h>
134 #include <netinet6/ipsec.h>
135 #include <netinet6/ipsec6.h>
136 #include <netproto/key/key.h>
139 MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry");
141 static int log_in_vain = 0;
142 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW,
143 &log_in_vain, 0, "Log all incoming TCP connections");
145 static int blackhole = 0;
146 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW,
147 &blackhole, 0, "Do not send RST when dropping refused connections");
149 int tcp_delack_enabled = 1;
150 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW,
151 &tcp_delack_enabled, 0,
152 "Delay ACK to try and piggyback it onto a data packet");
154 #ifdef TCP_DROP_SYNFIN
155 static int drop_synfin = 0;
156 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW,
157 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set");
160 static int tcp_do_limitedtransmit = 1;
161 SYSCTL_INT(_net_inet_tcp, OID_AUTO, limitedtransmit, CTLFLAG_RW,
162 &tcp_do_limitedtransmit, 0, "Enable RFC 3042 (Limited Transmit)");
164 static int tcp_do_early_retransmit = 1;
165 SYSCTL_INT(_net_inet_tcp, OID_AUTO, earlyretransmit, CTLFLAG_RW,
166 &tcp_do_early_retransmit, 0, "Early retransmit");
168 int tcp_aggregate_acks = 1;
169 SYSCTL_INT(_net_inet_tcp, OID_AUTO, aggregate_acks, CTLFLAG_RW,
170 &tcp_aggregate_acks, 0, "Aggregate built-up acks into one ack");
172 int tcp_do_rfc3390 = 1;
173 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW,
175 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)");
177 static int tcp_do_eifel_detect = 1;
178 SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW,
179 &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)");
181 static int tcp_do_abc = 1;
182 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc, CTLFLAG_RW,
184 "TCP Appropriate Byte Counting (RFC 3465)");
187 * Define as tunable for easy testing with SACK on and off.
188 * Warning: do not change setting in the middle of an existing active TCP flow,
189 * else strange things might happen to that flow.
192 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW,
193 &tcp_do_sack, 0, "Enable SACK Algorithms");
195 int tcp_do_smartsack = 1;
196 SYSCTL_INT(_net_inet_tcp, OID_AUTO, smartsack, CTLFLAG_RW,
197 &tcp_do_smartsack, 0, "Enable Smart SACK Algorithms");
199 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0,
200 "TCP Segment Reassembly Queue");
202 int tcp_reass_maxseg = 0;
203 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD,
204 &tcp_reass_maxseg, 0,
205 "Global maximum number of TCP Segments in Reassembly Queue");
207 int tcp_reass_qsize = 0;
208 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD,
210 "Global number of TCP Segments currently in Reassembly Queue");
212 static int tcp_reass_overflows = 0;
213 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD,
214 &tcp_reass_overflows, 0,
215 "Global number of TCP Segment Reassembly Queue Overflows");
217 int tcp_do_autorcvbuf = 1;
218 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW,
219 &tcp_do_autorcvbuf, 0, "Enable automatic receive buffer sizing");
221 int tcp_autorcvbuf_inc = 16*1024;
222 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW,
223 &tcp_autorcvbuf_inc, 0,
224 "Incrementor step size of automatic receive buffer");
226 int tcp_autorcvbuf_max = 2*1024*1024;
227 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW,
228 &tcp_autorcvbuf_max, 0, "Max size of automatic receive buffer");
230 int tcp_sosnd_agglim = 2;
231 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosnd_agglim, CTLFLAG_RW,
232 &tcp_sosnd_agglim, 0, "TCP sosend mbuf aggregation limit");
234 int tcp_sosnd_async = 0;
235 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosnd_async, CTLFLAG_RW,
236 &tcp_sosnd_async, 0, "TCP asynchronized pru_send");
238 static void tcp_dooptions(struct tcpopt *, u_char *, int, boolean_t);
239 static void tcp_pulloutofband(struct socket *,
240 struct tcphdr *, struct mbuf *, int);
241 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *,
243 static void tcp_xmit_timer(struct tcpcb *, int);
244 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *, int);
245 static void tcp_sack_rexmt(struct tcpcb *, struct tcphdr *);
247 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */
249 #define ND6_HINT(tp) \
251 if ((tp) && (tp)->t_inpcb && \
252 ((tp)->t_inpcb->inp_vflag & INP_IPV6) && \
253 (tp)->t_inpcb->in6p_route.ro_rt) \
254 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \
261 * Indicate whether this ack should be delayed. We can delay the ack if
262 * - delayed acks are enabled and
263 * - there is no delayed ack timer in progress and
264 * - our last ack wasn't a 0-sized window. We never want to delay
265 * the ack that opens up a 0-sized window.
267 #define DELAY_ACK(tp) \
268 (tcp_delack_enabled && !tcp_callout_pending(tp, tp->tt_delack) && \
269 !(tp->t_flags & TF_RXWIN0SENT))
271 #define acceptable_window_update(tp, th, tiwin) \
272 (SEQ_LT(tp->snd_wl1, th->th_seq) || \
273 (tp->snd_wl1 == th->th_seq && \
274 (SEQ_LT(tp->snd_wl2, th->th_ack) || \
275 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))
278 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m)
281 struct tseg_qent *p = NULL;
282 struct tseg_qent *te;
283 struct socket *so = tp->t_inpcb->inp_socket;
287 * Call with th == NULL after become established to
288 * force pre-ESTABLISHED data up to user socket.
294 * Limit the number of segments in the reassembly queue to prevent
295 * holding on to too many segments (and thus running out of mbufs).
296 * Make sure to let the missing segment through which caused this
297 * queue. Always keep one global queue entry spare to be able to
298 * process the missing segment.
300 if (th->th_seq != tp->rcv_nxt &&
301 tcp_reass_qsize + 1 >= tcp_reass_maxseg) {
302 tcp_reass_overflows++;
303 tcpstat.tcps_rcvmemdrop++;
305 /* no SACK block to report */
306 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
310 /* Allocate a new queue entry. */
311 MALLOC(te, struct tseg_qent *, sizeof(struct tseg_qent), M_TSEGQ,
312 M_INTWAIT | M_NULLOK);
314 tcpstat.tcps_rcvmemdrop++;
316 /* no SACK block to report */
317 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
320 atomic_add_int(&tcp_reass_qsize, 1);
323 * Find a segment which begins after this one does.
325 LIST_FOREACH(q, &tp->t_segq, tqe_q) {
326 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
332 * If there is a preceding segment, it may provide some of
333 * our data already. If so, drop the data from the incoming
334 * segment. If it provides all of our data, drop us.
339 /* conversion to int (in i) handles seq wraparound */
340 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
341 if (i > 0) { /* overlaps preceding segment */
342 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG);
343 /* enclosing block starts w/ preceding segment */
344 tp->encloseblk.rblk_start = p->tqe_th->th_seq;
346 /* preceding encloses incoming segment */
347 tp->encloseblk.rblk_end = p->tqe_th->th_seq +
349 tcpstat.tcps_rcvduppack++;
350 tcpstat.tcps_rcvdupbyte += *tlenp;
353 atomic_add_int(&tcp_reass_qsize, -1);
355 * Try to present any queued data
356 * at the left window edge to the user.
357 * This is needed after the 3-WHS
360 goto present; /* ??? */
365 /* incoming segment end is enclosing block end */
366 tp->encloseblk.rblk_end = th->th_seq + *tlenp +
367 ((th->th_flags & TH_FIN) != 0);
368 /* trim end of reported D-SACK block */
369 tp->reportblk.rblk_end = th->th_seq;
372 tcpstat.tcps_rcvoopack++;
373 tcpstat.tcps_rcvoobyte += *tlenp;
376 * While we overlap succeeding segments trim them or,
377 * if they are completely covered, dequeue them.
380 tcp_seq_diff_t i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
381 tcp_seq qend = q->tqe_th->th_seq + q->tqe_len;
382 struct tseg_qent *nq;
386 if (!(tp->t_flags & TF_DUPSEG)) { /* first time through */
387 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG);
388 tp->encloseblk = tp->reportblk;
389 /* report trailing duplicate D-SACK segment */
390 tp->reportblk.rblk_start = q->tqe_th->th_seq;
392 if ((tp->t_flags & TF_ENCLOSESEG) &&
393 SEQ_GT(qend, tp->encloseblk.rblk_end)) {
394 /* extend enclosing block if one exists */
395 tp->encloseblk.rblk_end = qend;
397 if (i < q->tqe_len) {
398 q->tqe_th->th_seq += i;
404 nq = LIST_NEXT(q, tqe_q);
405 LIST_REMOVE(q, tqe_q);
408 atomic_add_int(&tcp_reass_qsize, -1);
412 /* Insert the new segment queue entry into place. */
415 te->tqe_len = *tlenp;
417 /* check if can coalesce with following segment */
418 if (q != NULL && (th->th_seq + *tlenp == q->tqe_th->th_seq)) {
419 tcp_seq tend = te->tqe_th->th_seq + te->tqe_len;
421 te->tqe_len += q->tqe_len;
422 if (q->tqe_th->th_flags & TH_FIN)
423 te->tqe_th->th_flags |= TH_FIN;
424 m_cat(te->tqe_m, q->tqe_m);
425 tp->encloseblk.rblk_end = tend;
427 * When not reporting a duplicate segment, use
428 * the larger enclosing block as the SACK block.
430 if (!(tp->t_flags & TF_DUPSEG))
431 tp->reportblk.rblk_end = tend;
432 LIST_REMOVE(q, tqe_q);
434 atomic_add_int(&tcp_reass_qsize, -1);
438 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q);
440 /* check if can coalesce with preceding segment */
441 if (p->tqe_th->th_seq + p->tqe_len == th->th_seq) {
442 p->tqe_len += te->tqe_len;
443 m_cat(p->tqe_m, te->tqe_m);
444 tp->encloseblk.rblk_start = p->tqe_th->th_seq;
446 * When not reporting a duplicate segment, use
447 * the larger enclosing block as the SACK block.
449 if (!(tp->t_flags & TF_DUPSEG))
450 tp->reportblk.rblk_start = p->tqe_th->th_seq;
452 atomic_add_int(&tcp_reass_qsize, -1);
454 LIST_INSERT_AFTER(p, te, tqe_q);
460 * Present data to user, advancing rcv_nxt through
461 * completed sequence space.
463 if (!TCPS_HAVEESTABLISHED(tp->t_state))
465 q = LIST_FIRST(&tp->t_segq);
466 if (q == NULL || q->tqe_th->th_seq != tp->rcv_nxt)
468 tp->rcv_nxt += q->tqe_len;
469 if (!(tp->t_flags & TF_DUPSEG)) {
470 /* no SACK block to report since ACK advanced */
471 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
473 /* no enclosing block to report since ACK advanced */
474 tp->t_flags &= ~TF_ENCLOSESEG;
475 flags = q->tqe_th->th_flags & TH_FIN;
476 LIST_REMOVE(q, tqe_q);
477 KASSERT(LIST_EMPTY(&tp->t_segq) ||
478 LIST_FIRST(&tp->t_segq)->tqe_th->th_seq != tp->rcv_nxt,
479 ("segment not coalesced"));
480 if (so->so_state & SS_CANTRCVMORE) {
483 lwkt_gettoken(&so->so_rcv.ssb_token);
484 ssb_appendstream(&so->so_rcv, q->tqe_m);
485 lwkt_reltoken(&so->so_rcv.ssb_token);
488 atomic_add_int(&tcp_reass_qsize, -1);
495 * TCP input routine, follows pages 65-76 of the
496 * protocol specification dated September, 1981 very closely.
500 tcp6_input(struct mbuf **mp, int *offp, int proto)
502 struct mbuf *m = *mp;
503 struct in6_ifaddr *ia6;
505 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE);
508 * draft-itojun-ipv6-tcp-to-anycast
509 * better place to put this in?
511 ia6 = ip6_getdstifaddr(m);
512 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) {
515 ip6 = mtod(m, struct ip6_hdr *);
516 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
517 offsetof(struct ip6_hdr, ip6_dst));
518 return (IPPROTO_DONE);
521 tcp_input(mp, offp, proto);
522 return (IPPROTO_DONE);
527 tcp_input(struct mbuf **mp, int *offp, int proto)
531 struct ip *ip = NULL;
533 struct inpcb *inp = NULL;
539 struct tcpcb *tp = NULL;
541 struct socket *so = 0;
543 boolean_t ourfinisacked, needoutput = FALSE;
546 struct tcpopt to; /* options in this segment */
547 struct sockaddr_in *next_hop = NULL;
548 int rstreason; /* For badport_bandlim accounting purposes */
550 struct ip6_hdr *ip6 = NULL;
555 const boolean_t isipv6 = FALSE;
565 tcpstat.tcps_rcvtotal++;
567 if (m->m_pkthdr.fw_flags & IPFORWARD_MBUF_TAGGED) {
570 mtag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL);
571 KKASSERT(mtag != NULL);
572 next_hop = m_tag_data(mtag);
576 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE;
580 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */
581 ip6 = mtod(m, struct ip6_hdr *);
582 tlen = (sizeof *ip6) + ntohs(ip6->ip6_plen) - off0;
583 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) {
584 tcpstat.tcps_rcvbadsum++;
587 th = (struct tcphdr *)((caddr_t)ip6 + off0);
590 * Be proactive about unspecified IPv6 address in source.
591 * As we use all-zero to indicate unbounded/unconnected pcb,
592 * unspecified IPv6 address can be used to confuse us.
594 * Note that packets with unspecified IPv6 destination is
595 * already dropped in ip6_input.
597 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
603 * Get IP and TCP header together in first mbuf.
604 * Note: IP leaves IP header in first mbuf.
606 if (off0 > sizeof(struct ip)) {
608 off0 = sizeof(struct ip);
610 /* already checked and pulled up in ip_demux() */
611 KASSERT(m->m_len >= sizeof(struct tcpiphdr),
612 ("TCP header not in one mbuf: m->m_len %d", m->m_len));
613 ip = mtod(m, struct ip *);
614 ipov = (struct ipovly *)ip;
615 th = (struct tcphdr *)((caddr_t)ip + off0);
618 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
619 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
620 th->th_sum = m->m_pkthdr.csum_data;
622 th->th_sum = in_pseudo(ip->ip_src.s_addr,
624 htonl(m->m_pkthdr.csum_data +
627 th->th_sum ^= 0xffff;
630 * Checksum extended TCP header and data.
632 len = sizeof(struct ip) + tlen;
633 bzero(ipov->ih_x1, sizeof ipov->ih_x1);
634 ipov->ih_len = (u_short)tlen;
635 ipov->ih_len = htons(ipov->ih_len);
636 th->th_sum = in_cksum(m, len);
639 tcpstat.tcps_rcvbadsum++;
643 /* Re-initialization for later version check */
644 ip->ip_v = IPVERSION;
649 * Check that TCP offset makes sense,
650 * pull out TCP options and adjust length. XXX
652 off = th->th_off << 2;
653 /* already checked and pulled up in ip_demux() */
654 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen,
655 ("bad TCP data offset %d (tlen %d)", off, tlen));
656 tlen -= off; /* tlen is used instead of ti->ti_len */
657 if (off > sizeof(struct tcphdr)) {
659 IP6_EXTHDR_CHECK(m, off0, off, IPPROTO_DONE);
660 ip6 = mtod(m, struct ip6_hdr *);
661 th = (struct tcphdr *)((caddr_t)ip6 + off0);
663 /* already pulled up in ip_demux() */
664 KASSERT(m->m_len >= sizeof(struct ip) + off,
665 ("TCP header and options not in one mbuf: "
666 "m_len %d, off %d", m->m_len, off));
668 optlen = off - sizeof(struct tcphdr);
669 optp = (u_char *)(th + 1);
671 thflags = th->th_flags;
673 #ifdef TCP_DROP_SYNFIN
675 * If the drop_synfin option is enabled, drop all packets with
676 * both the SYN and FIN bits set. This prevents e.g. nmap from
677 * identifying the TCP/IP stack.
679 * This is a violation of the TCP specification.
681 if (drop_synfin && (thflags & (TH_SYN | TH_FIN)) == (TH_SYN | TH_FIN))
686 * Convert TCP protocol specific fields to host format.
688 th->th_seq = ntohl(th->th_seq);
689 th->th_ack = ntohl(th->th_ack);
690 th->th_win = ntohs(th->th_win);
691 th->th_urp = ntohs(th->th_urp);
694 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options,
695 * until after ip6_savecontrol() is called and before other functions
696 * which don't want those proto headers.
697 * Because ip6_savecontrol() is going to parse the mbuf to
698 * search for data to be passed up to user-land, it wants mbuf
699 * parameters to be unchanged.
700 * XXX: the call of ip6_savecontrol() has been obsoleted based on
701 * latest version of the advanced API (20020110).
703 drop_hdrlen = off0 + off;
706 * Locate pcb for segment.
709 /* IPFIREWALL_FORWARD section */
710 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */
712 * Transparently forwarded. Pretend to be the destination.
713 * already got one like this?
715 cpu = mycpu->gd_cpuid;
716 inp = in_pcblookup_hash(&tcbinfo[cpu],
717 ip->ip_src, th->th_sport,
718 ip->ip_dst, th->th_dport,
719 0, m->m_pkthdr.rcvif);
722 * It's new. Try to find the ambushing socket.
726 * The rest of the ipfw code stores the port in
728 * (The IP address is still in network order.)
730 in_port_t dport = next_hop->sin_port ?
731 htons(next_hop->sin_port) :
734 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport,
735 next_hop->sin_addr.s_addr, dport);
736 inp = in_pcblookup_hash(&tcbinfo[cpu],
737 ip->ip_src, th->th_sport,
738 next_hop->sin_addr, dport,
739 1, m->m_pkthdr.rcvif);
743 inp = in6_pcblookup_hash(&tcbinfo[0],
744 &ip6->ip6_src, th->th_sport,
745 &ip6->ip6_dst, th->th_dport,
746 1, m->m_pkthdr.rcvif);
748 cpu = mycpu->gd_cpuid;
749 inp = in_pcblookup_hash(&tcbinfo[cpu],
750 ip->ip_src, th->th_sport,
751 ip->ip_dst, th->th_dport,
752 1, m->m_pkthdr.rcvif);
757 * If the state is CLOSED (i.e., TCB does not exist) then
758 * all data in the incoming segment is discarded.
759 * If the TCB exists but is in CLOSED state, it is embryonic,
760 * but should either do a listen or a connect soon.
765 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2];
767 char dbuf[sizeof "aaa.bbb.ccc.ddd"];
768 char sbuf[sizeof "aaa.bbb.ccc.ddd"];
772 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst));
775 strcat(sbuf, ip6_sprintf(&ip6->ip6_src));
778 strcpy(dbuf, inet_ntoa(ip->ip_dst));
779 strcpy(sbuf, inet_ntoa(ip->ip_src));
781 switch (log_in_vain) {
783 if (!(thflags & TH_SYN))
787 "Connection attempt to TCP %s:%d "
788 "from %s:%d flags:0x%02x\n",
789 dbuf, ntohs(th->th_dport), sbuf,
790 ntohs(th->th_sport), thflags);
799 if (thflags & TH_SYN)
808 rstreason = BANDLIM_RST_CLOSEDPORT;
814 if (ipsec6_in_reject_so(m, inp->inp_socket)) {
815 ipsec6stat.in_polvio++;
819 if (ipsec4_in_reject_so(m, inp->inp_socket)) {
820 ipsecstat.in_polvio++;
827 if (ipsec6_in_reject(m, inp))
830 if (ipsec4_in_reject(m, inp))
834 /* Check the minimum TTL for socket. */
836 if ((isipv6 ? ip6->ip6_hlim : ip->ip_ttl) < inp->inp_ip_minttl)
842 rstreason = BANDLIM_RST_CLOSEDPORT;
845 if (tp->t_state <= TCPS_CLOSED)
848 /* Unscale the window into a 32-bit value. */
849 if (!(thflags & TH_SYN))
850 tiwin = th->th_win << tp->snd_scale;
854 so = inp->inp_socket;
857 if (so->so_options & SO_DEBUG) {
858 ostate = tp->t_state;
860 bcopy(ip6, tcp_saveipgen, sizeof(*ip6));
862 bcopy(ip, tcp_saveipgen, sizeof(*ip));
867 bzero(&to, sizeof to);
869 if (so->so_options & SO_ACCEPTCONN) {
870 struct in_conninfo inc;
873 inc.inc_isipv6 = (isipv6 == TRUE);
876 inc.inc6_faddr = ip6->ip6_src;
877 inc.inc6_laddr = ip6->ip6_dst;
878 inc.inc6_route.ro_rt = NULL; /* XXX */
880 inc.inc_faddr = ip->ip_src;
881 inc.inc_laddr = ip->ip_dst;
882 inc.inc_route.ro_rt = NULL; /* XXX */
884 inc.inc_fport = th->th_sport;
885 inc.inc_lport = th->th_dport;
888 * If the state is LISTEN then ignore segment if it contains
889 * a RST. If the segment contains an ACK then it is bad and
890 * send a RST. If it does not contain a SYN then it is not
891 * interesting; drop it.
893 * If the state is SYN_RECEIVED (syncache) and seg contains
894 * an ACK, but not for our SYN/ACK, send a RST. If the seg
895 * contains a RST, check the sequence number to see if it
896 * is a valid reset segment.
898 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) != TH_SYN) {
899 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) == TH_ACK) {
900 if (!syncache_expand(&inc, th, &so, m)) {
902 * No syncache entry, or ACK was not
903 * for our SYN/ACK. Send a RST.
905 tcpstat.tcps_badsyn++;
906 rstreason = BANDLIM_RST_OPENPORT;
911 * Could not complete 3-way handshake,
912 * connection is being closed down, and
913 * syncache will free mbuf.
916 return(IPPROTO_DONE);
919 * We must be in the correct protocol thread
920 * for this connection.
922 KKASSERT(so->so_port == &curthread->td_msgport);
925 * Socket is created in state SYN_RECEIVED.
926 * Continue processing segment.
931 * This is what would have happened in
932 * tcp_output() when the SYN,ACK was sent.
934 tp->snd_up = tp->snd_una;
935 tp->snd_max = tp->snd_nxt = tp->iss + 1;
936 tp->last_ack_sent = tp->rcv_nxt;
938 * XXX possible bug - it doesn't appear that tp->snd_wnd is unscaled
939 * until the _second_ ACK is received:
940 * rcv SYN (set wscale opts) --> send SYN/ACK, set snd_wnd = window.
941 * rcv ACK, calculate tiwin --> process SYN_RECEIVED, determine wscale,
942 * move to ESTAB, set snd_wnd to tiwin.
944 tp->snd_wnd = tiwin; /* unscaled */
947 if (thflags & TH_RST) {
948 syncache_chkrst(&inc, th);
951 if (thflags & TH_ACK) {
952 syncache_badack(&inc);
953 tcpstat.tcps_badsyn++;
954 rstreason = BANDLIM_RST_OPENPORT;
961 * Segment's flags are (SYN) or (SYN | FIN).
965 * If deprecated address is forbidden,
966 * we do not accept SYN to deprecated interface
967 * address to prevent any new inbound connection from
968 * getting established.
969 * When we do not accept SYN, we send a TCP RST,
970 * with deprecated source address (instead of dropping
971 * it). We compromise it as it is much better for peer
972 * to send a RST, and RST will be the final packet
975 * If we do not forbid deprecated addresses, we accept
976 * the SYN packet. RFC2462 does not suggest dropping
978 * If we decipher RFC2462 5.5.4, it says like this:
979 * 1. use of deprecated addr with existing
980 * communication is okay - "SHOULD continue to be
982 * 2. use of it with new communication:
983 * (2a) "SHOULD NOT be used if alternate address
984 * with sufficient scope is available"
985 * (2b) nothing mentioned otherwise.
986 * Here we fall into (2b) case as we have no choice in
987 * our source address selection - we must obey the peer.
989 * The wording in RFC2462 is confusing, and there are
990 * multiple description text for deprecated address
991 * handling - worse, they are not exactly the same.
992 * I believe 5.5.4 is the best one, so we follow 5.5.4.
994 if (isipv6 && !ip6_use_deprecated) {
995 struct in6_ifaddr *ia6;
997 if ((ia6 = ip6_getdstifaddr(m)) &&
998 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
1000 rstreason = BANDLIM_RST_OPENPORT;
1006 * If it is from this socket, drop it, it must be forged.
1007 * Don't bother responding if the destination was a broadcast.
1009 if (th->th_dport == th->th_sport) {
1011 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst,
1015 if (ip->ip_dst.s_addr == ip->ip_src.s_addr)
1020 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN
1022 * Note that it is quite possible to receive unicast
1023 * link-layer packets with a broadcast IP address. Use
1024 * in_broadcast() to find them.
1026 if (m->m_flags & (M_BCAST | M_MCAST))
1029 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
1030 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
1033 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
1034 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
1035 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
1036 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
1040 * SYN appears to be valid; create compressed TCP state
1041 * for syncache, or perform t/tcp connection.
1043 if (so->so_qlen <= so->so_qlimit) {
1044 tcp_dooptions(&to, optp, optlen, TRUE);
1045 if (!syncache_add(&inc, &to, th, &so, m))
1049 * Entry added to syncache, mbuf used to
1050 * send SYN,ACK packet.
1053 return(IPPROTO_DONE);
1056 * We must be in the correct protocol thread for
1059 KKASSERT(so->so_port == &curthread->td_msgport);
1062 tp = intotcpcb(inp);
1063 tp->snd_wnd = tiwin;
1064 tp->t_starttime = ticks;
1065 tp->t_state = TCPS_ESTABLISHED;
1068 * If there is a FIN, or if there is data and the
1069 * connection is local, then delay SYN,ACK(SYN) in
1070 * the hope of piggy-backing it on a response
1071 * segment. Otherwise must send ACK now in case
1072 * the other side is slow starting.
1074 if (DELAY_ACK(tp) &&
1075 ((thflags & TH_FIN) ||
1077 ((isipv6 && in6_localaddr(&inp->in6p_faddr)) ||
1078 (!isipv6 && in_localaddr(inp->inp_faddr)))))) {
1079 tcp_callout_reset(tp, tp->tt_delack,
1080 tcp_delacktime, tcp_timer_delack);
1081 tp->t_flags |= TF_NEEDSYN;
1083 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN);
1086 tcpstat.tcps_connects++;
1095 * Should not happen - syncache should pick up these connections.
1097 * Once we are past handling listen sockets we must be in the
1098 * correct protocol processing thread.
1100 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN state"));
1101 KKASSERT(so->so_port == &curthread->td_msgport);
1104 * This is the second part of the MSS DoS prevention code (after
1105 * minmss on the sending side) and it deals with too many too small
1106 * tcp packets in a too short timeframe (1 second).
1108 * XXX Removed. This code was crap. It does not scale to network
1109 * speed, and default values break NFS. Gone.
1114 * Segment received on connection.
1116 * Reset idle time and keep-alive timer. Don't waste time if less
1117 * then a second has elapsed.
1119 if ((int)(ticks - tp->t_rcvtime) > hz)
1120 tcp_timer_keep_activity(tp, thflags);
1124 * XXX this is tradtitional behavior, may need to be cleaned up.
1126 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0);
1127 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) {
1128 if (to.to_flags & TOF_SCALE) {
1129 tp->t_flags |= TF_RCVD_SCALE;
1130 tp->requested_s_scale = to.to_requested_s_scale;
1132 if (to.to_flags & TOF_TS) {
1133 tp->t_flags |= TF_RCVD_TSTMP;
1134 tp->ts_recent = to.to_tsval;
1135 tp->ts_recent_age = ticks;
1137 if (to.to_flags & TOF_MSS)
1138 tcp_mss(tp, to.to_mss);
1140 * Only set the TF_SACK_PERMITTED per-connection flag
1141 * if we got a SACK_PERMITTED option from the other side
1142 * and the global tcp_do_sack variable is true.
1144 if (tcp_do_sack && (to.to_flags & TOF_SACK_PERMITTED))
1145 tp->t_flags |= TF_SACK_PERMITTED;
1149 * Header prediction: check for the two common cases
1150 * of a uni-directional data xfer. If the packet has
1151 * no control flags, is in-sequence, the window didn't
1152 * change and we're not retransmitting, it's a
1153 * candidate. If the length is zero and the ack moved
1154 * forward, we're the sender side of the xfer. Just
1155 * free the data acked & wake any higher level process
1156 * that was blocked waiting for space. If the length
1157 * is non-zero and the ack didn't move, we're the
1158 * receiver side. If we're getting packets in-order
1159 * (the reassembly queue is empty), add the data to
1160 * the socket buffer and note that we need a delayed ack.
1161 * Make sure that the hidden state-flags are also off.
1162 * Since we check for TCPS_ESTABLISHED above, it can only
1165 if (tp->t_state == TCPS_ESTABLISHED &&
1166 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
1167 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) &&
1168 (!(to.to_flags & TOF_TS) ||
1169 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) &&
1170 th->th_seq == tp->rcv_nxt &&
1171 tp->snd_nxt == tp->snd_max) {
1174 * If last ACK falls within this segment's sequence numbers,
1175 * record the timestamp.
1176 * NOTE that the test is modified according to the latest
1177 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1179 if ((to.to_flags & TOF_TS) &&
1180 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
1181 tp->ts_recent_age = ticks;
1182 tp->ts_recent = to.to_tsval;
1186 if (SEQ_GT(th->th_ack, tp->snd_una) &&
1187 SEQ_LEQ(th->th_ack, tp->snd_max) &&
1188 tp->snd_cwnd >= tp->snd_wnd &&
1189 !IN_FASTRECOVERY(tp)) {
1191 * This is a pure ack for outstanding data.
1193 ++tcpstat.tcps_predack;
1195 * "bad retransmit" recovery
1197 * If Eifel detection applies, then
1198 * it is deterministic, so use it
1199 * unconditionally over the old heuristic.
1200 * Otherwise, fall back to the old heuristic.
1202 if (tcp_do_eifel_detect &&
1203 (to.to_flags & TOF_TS) && to.to_tsecr &&
1204 (tp->t_flags & TF_FIRSTACCACK)) {
1205 /* Eifel detection applicable. */
1206 if (to.to_tsecr < tp->t_rexmtTS) {
1207 tcp_revert_congestion_state(tp);
1208 ++tcpstat.tcps_eifeldetected;
1210 } else if (tp->t_rxtshift == 1 &&
1211 ticks < tp->t_badrxtwin) {
1212 tcp_revert_congestion_state(tp);
1213 ++tcpstat.tcps_rttdetected;
1215 tp->t_flags &= ~(TF_FIRSTACCACK |
1216 TF_FASTREXMT | TF_EARLYREXMT);
1218 * Recalculate the retransmit timer / rtt.
1220 * Some machines (certain windows boxes)
1221 * send broken timestamp replies during the
1222 * SYN+ACK phase, ignore timestamps of 0.
1224 if ((to.to_flags & TOF_TS) && to.to_tsecr) {
1226 ticks - to.to_tsecr + 1);
1227 } else if (tp->t_rtttime &&
1228 SEQ_GT(th->th_ack, tp->t_rtseq)) {
1230 ticks - tp->t_rtttime);
1232 tcp_xmit_bandwidth_limit(tp, th->th_ack);
1233 acked = th->th_ack - tp->snd_una;
1234 tcpstat.tcps_rcvackpack++;
1235 tcpstat.tcps_rcvackbyte += acked;
1236 sbdrop(&so->so_snd.sb, acked);
1237 tp->snd_recover = th->th_ack - 1;
1238 tp->snd_una = th->th_ack;
1241 * Update window information.
1243 if (tiwin != tp->snd_wnd &&
1244 acceptable_window_update(tp, th, tiwin)) {
1245 /* keep track of pure window updates */
1246 if (tp->snd_wl2 == th->th_ack &&
1247 tiwin > tp->snd_wnd)
1248 tcpstat.tcps_rcvwinupd++;
1249 tp->snd_wnd = tiwin;
1250 tp->snd_wl1 = th->th_seq;
1251 tp->snd_wl2 = th->th_ack;
1252 if (tp->snd_wnd > tp->max_sndwnd)
1253 tp->max_sndwnd = tp->snd_wnd;
1256 ND6_HINT(tp); /* some progress has been done */
1258 * If all outstanding data are acked, stop
1259 * retransmit timer, otherwise restart timer
1260 * using current (possibly backed-off) value.
1261 * If process is waiting for space,
1262 * wakeup/selwakeup/signal. If data
1263 * are ready to send, let tcp_output
1264 * decide between more output or persist.
1266 if (tp->snd_una == tp->snd_max) {
1267 tcp_callout_stop(tp, tp->tt_rexmt);
1268 } else if (!tcp_callout_active(tp,
1270 tcp_callout_reset(tp, tp->tt_rexmt,
1271 tp->t_rxtcur, tcp_timer_rexmt);
1274 if (so->so_snd.ssb_cc > 0)
1276 return(IPPROTO_DONE);
1278 } else if (tiwin == tp->snd_wnd &&
1279 th->th_ack == tp->snd_una &&
1280 LIST_EMPTY(&tp->t_segq) &&
1281 tlen <= ssb_space(&so->so_rcv)) {
1282 u_long newsize = 0; /* automatic sockbuf scaling */
1284 * This is a pure, in-sequence data packet
1285 * with nothing on the reassembly queue and
1286 * we have enough buffer space to take it.
1288 ++tcpstat.tcps_preddat;
1289 tp->rcv_nxt += tlen;
1290 tcpstat.tcps_rcvpack++;
1291 tcpstat.tcps_rcvbyte += tlen;
1292 ND6_HINT(tp); /* some progress has been done */
1294 * Automatic sizing of receive socket buffer. Often the send
1295 * buffer size is not optimally adjusted to the actual network
1296 * conditions at hand (delay bandwidth product). Setting the
1297 * buffer size too small limits throughput on links with high
1298 * bandwidth and high delay (eg. trans-continental/oceanic links).
1300 * On the receive side the socket buffer memory is only rarely
1301 * used to any significant extent. This allows us to be much
1302 * more aggressive in scaling the receive socket buffer. For
1303 * the case that the buffer space is actually used to a large
1304 * extent and we run out of kernel memory we can simply drop
1305 * the new segments; TCP on the sender will just retransmit it
1306 * later. Setting the buffer size too big may only consume too
1307 * much kernel memory if the application doesn't read() from
1308 * the socket or packet loss or reordering makes use of the
1311 * The criteria to step up the receive buffer one notch are:
1312 * 1. the number of bytes received during the time it takes
1313 * one timestamp to be reflected back to us (the RTT);
1314 * 2. received bytes per RTT is within seven eighth of the
1315 * current socket buffer size;
1316 * 3. receive buffer size has not hit maximal automatic size;
1318 * This algorithm does one step per RTT at most and only if
1319 * we receive a bulk stream w/o packet losses or reorderings.
1320 * Shrinking the buffer during idle times is not necessary as
1321 * it doesn't consume any memory when idle.
1323 * TODO: Only step up if the application is actually serving
1324 * the buffer to better manage the socket buffer resources.
1326 if (tcp_do_autorcvbuf &&
1328 (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) {
1329 if (to.to_tsecr > tp->rfbuf_ts &&
1330 to.to_tsecr - tp->rfbuf_ts < hz) {
1332 (so->so_rcv.ssb_hiwat / 8 * 7) &&
1333 so->so_rcv.ssb_hiwat <
1334 tcp_autorcvbuf_max) {
1336 ulmin(so->so_rcv.ssb_hiwat +
1338 tcp_autorcvbuf_max);
1340 /* Start over with next RTT. */
1344 tp->rfbuf_cnt += tlen; /* add up */
1347 * Add data to socket buffer.
1349 if (so->so_state & SS_CANTRCVMORE) {
1353 * Set new socket buffer size, give up when
1356 * Adjusting the size can mess up ACK
1357 * sequencing when pure window updates are
1358 * being avoided (which is the default),
1361 lwkt_gettoken(&so->so_rcv.ssb_token);
1363 tp->t_flags |= TF_RXRESIZED;
1364 if (!ssb_reserve(&so->so_rcv, newsize,
1366 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE);
1369 (TCP_MAXWIN << tp->rcv_scale)) {
1370 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE);
1373 m_adj(m, drop_hdrlen); /* delayed header drop */
1374 ssb_appendstream(&so->so_rcv, m);
1375 lwkt_reltoken(&so->so_rcv.ssb_token);
1379 * This code is responsible for most of the ACKs
1380 * the TCP stack sends back after receiving a data
1381 * packet. Note that the DELAY_ACK check fails if
1382 * the delack timer is already running, which results
1383 * in an ack being sent every other packet (which is
1386 * We then further aggregate acks by not actually
1387 * sending one until the protocol thread has completed
1388 * processing the current backlog of packets. This
1389 * does not delay the ack any further, but allows us
1390 * to take advantage of the packet aggregation that
1391 * high speed NICs do (usually blocks of 8-10 packets)
1392 * to send a single ack rather then four or five acks,
1393 * greatly reducing the ack rate, the return channel
1394 * bandwidth, and the protocol overhead on both ends.
1396 * Since this also has the effect of slowing down
1397 * the exponential slow-start ramp-up, systems with
1398 * very large bandwidth-delay products might want
1399 * to turn the feature off.
1401 if (DELAY_ACK(tp)) {
1402 tcp_callout_reset(tp, tp->tt_delack,
1403 tcp_delacktime, tcp_timer_delack);
1404 } else if (tcp_aggregate_acks) {
1405 tp->t_flags |= TF_ACKNOW;
1406 if (!(tp->t_flags & TF_ONOUTPUTQ)) {
1407 tp->t_flags |= TF_ONOUTPUTQ;
1408 tp->tt_cpu = mycpu->gd_cpuid;
1410 &tcpcbackq[tp->tt_cpu],
1414 tp->t_flags |= TF_ACKNOW;
1417 return(IPPROTO_DONE);
1422 * Calculate amount of space in receive window,
1423 * and then do TCP input processing.
1424 * Receive window is amount of space in rcv queue,
1425 * but not less than advertised window.
1427 recvwin = ssb_space(&so->so_rcv);
1430 tp->rcv_wnd = imax(recvwin, (int)(tp->rcv_adv - tp->rcv_nxt));
1432 /* Reset receive buffer auto scaling when not in bulk receive mode. */
1436 switch (tp->t_state) {
1438 * If the state is SYN_RECEIVED:
1439 * if seg contains an ACK, but not for our SYN/ACK, send a RST.
1441 case TCPS_SYN_RECEIVED:
1442 if ((thflags & TH_ACK) &&
1443 (SEQ_LEQ(th->th_ack, tp->snd_una) ||
1444 SEQ_GT(th->th_ack, tp->snd_max))) {
1445 rstreason = BANDLIM_RST_OPENPORT;
1451 * If the state is SYN_SENT:
1452 * if seg contains an ACK, but not for our SYN, drop the input.
1453 * if seg contains a RST, then drop the connection.
1454 * if seg does not contain SYN, then drop it.
1455 * Otherwise this is an acceptable SYN segment
1456 * initialize tp->rcv_nxt and tp->irs
1457 * if seg contains ack then advance tp->snd_una
1458 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state
1459 * arrange for segment to be acked (eventually)
1460 * continue processing rest of data/controls, beginning with URG
1463 if ((thflags & TH_ACK) &&
1464 (SEQ_LEQ(th->th_ack, tp->iss) ||
1465 SEQ_GT(th->th_ack, tp->snd_max))) {
1466 rstreason = BANDLIM_UNLIMITED;
1469 if (thflags & TH_RST) {
1470 if (thflags & TH_ACK)
1471 tp = tcp_drop(tp, ECONNREFUSED);
1474 if (!(thflags & TH_SYN))
1476 tp->snd_wnd = th->th_win; /* initial send window */
1478 tp->irs = th->th_seq;
1480 if (thflags & TH_ACK) {
1481 /* Our SYN was acked. */
1482 tcpstat.tcps_connects++;
1484 /* Do window scaling on this connection? */
1485 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) ==
1486 (TF_RCVD_SCALE | TF_REQ_SCALE)) {
1487 tp->snd_scale = tp->requested_s_scale;
1488 tp->rcv_scale = tp->request_r_scale;
1490 tp->rcv_adv += tp->rcv_wnd;
1491 tp->snd_una++; /* SYN is acked */
1492 tcp_callout_stop(tp, tp->tt_rexmt);
1494 * If there's data, delay ACK; if there's also a FIN
1495 * ACKNOW will be turned on later.
1497 if (DELAY_ACK(tp) && tlen != 0) {
1498 tcp_callout_reset(tp, tp->tt_delack,
1499 tcp_delacktime, tcp_timer_delack);
1501 tp->t_flags |= TF_ACKNOW;
1504 * Received <SYN,ACK> in SYN_SENT[*] state.
1506 * SYN_SENT --> ESTABLISHED
1507 * SYN_SENT* --> FIN_WAIT_1
1509 tp->t_starttime = ticks;
1510 if (tp->t_flags & TF_NEEDFIN) {
1511 tp->t_state = TCPS_FIN_WAIT_1;
1512 tp->t_flags &= ~TF_NEEDFIN;
1515 tp->t_state = TCPS_ESTABLISHED;
1516 tcp_callout_reset(tp, tp->tt_keep,
1517 tcp_getkeepidle(tp),
1522 * Received initial SYN in SYN-SENT[*] state =>
1523 * simultaneous open.
1524 * Do 3-way handshake:
1525 * SYN-SENT -> SYN-RECEIVED
1526 * SYN-SENT* -> SYN-RECEIVED*
1528 tp->t_flags |= TF_ACKNOW;
1529 tcp_callout_stop(tp, tp->tt_rexmt);
1530 tp->t_state = TCPS_SYN_RECEIVED;
1535 * Advance th->th_seq to correspond to first data byte.
1536 * If data, trim to stay within window,
1537 * dropping FIN if necessary.
1540 if (tlen > tp->rcv_wnd) {
1541 todrop = tlen - tp->rcv_wnd;
1545 tcpstat.tcps_rcvpackafterwin++;
1546 tcpstat.tcps_rcvbyteafterwin += todrop;
1548 tp->snd_wl1 = th->th_seq - 1;
1549 tp->rcv_up = th->th_seq;
1551 * Client side of transaction: already sent SYN and data.
1552 * If the remote host used T/TCP to validate the SYN,
1553 * our data will be ACK'd; if so, enter normal data segment
1554 * processing in the middle of step 5, ack processing.
1555 * Otherwise, goto step 6.
1557 if (thflags & TH_ACK)
1563 * If the state is LAST_ACK or CLOSING or TIME_WAIT:
1564 * do normal processing (we no longer bother with T/TCP).
1568 case TCPS_TIME_WAIT:
1569 break; /* continue normal processing */
1573 * States other than LISTEN or SYN_SENT.
1574 * First check the RST flag and sequence number since reset segments
1575 * are exempt from the timestamp and connection count tests. This
1576 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix
1577 * below which allowed reset segments in half the sequence space
1578 * to fall though and be processed (which gives forged reset
1579 * segments with a random sequence number a 50 percent chance of
1580 * killing a connection).
1581 * Then check timestamp, if present.
1582 * Then check the connection count, if present.
1583 * Then check that at least some bytes of segment are within
1584 * receive window. If segment begins before rcv_nxt,
1585 * drop leading data (and SYN); if nothing left, just ack.
1588 * If the RST bit is set, check the sequence number to see
1589 * if this is a valid reset segment.
1591 * In all states except SYN-SENT, all reset (RST) segments
1592 * are validated by checking their SEQ-fields. A reset is
1593 * valid if its sequence number is in the window.
1594 * Note: this does not take into account delayed ACKs, so
1595 * we should test against last_ack_sent instead of rcv_nxt.
1596 * The sequence number in the reset segment is normally an
1597 * echo of our outgoing acknowledgement numbers, but some hosts
1598 * send a reset with the sequence number at the rightmost edge
1599 * of our receive window, and we have to handle this case.
1600 * If we have multiple segments in flight, the intial reset
1601 * segment sequence numbers will be to the left of last_ack_sent,
1602 * but they will eventually catch up.
1603 * In any case, it never made sense to trim reset segments to
1604 * fit the receive window since RFC 1122 says:
1605 * 4.2.2.12 RST Segment: RFC-793 Section 3.4
1607 * A TCP SHOULD allow a received RST segment to include data.
1610 * It has been suggested that a RST segment could contain
1611 * ASCII text that encoded and explained the cause of the
1612 * RST. No standard has yet been established for such
1615 * If the reset segment passes the sequence number test examine
1617 * SYN_RECEIVED STATE:
1618 * If passive open, return to LISTEN state.
1619 * If active open, inform user that connection was refused.
1620 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES:
1621 * Inform user that connection was reset, and close tcb.
1622 * CLOSING, LAST_ACK STATES:
1625 * Drop the segment - see Stevens, vol. 2, p. 964 and
1628 if (thflags & TH_RST) {
1629 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
1630 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) {
1631 switch (tp->t_state) {
1633 case TCPS_SYN_RECEIVED:
1634 so->so_error = ECONNREFUSED;
1637 case TCPS_ESTABLISHED:
1638 case TCPS_FIN_WAIT_1:
1639 case TCPS_FIN_WAIT_2:
1640 case TCPS_CLOSE_WAIT:
1641 so->so_error = ECONNRESET;
1643 tp->t_state = TCPS_CLOSED;
1644 tcpstat.tcps_drops++;
1653 case TCPS_TIME_WAIT:
1661 * RFC 1323 PAWS: If we have a timestamp reply on this segment
1662 * and it's less than ts_recent, drop it.
1664 if ((to.to_flags & TOF_TS) && tp->ts_recent != 0 &&
1665 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
1667 /* Check to see if ts_recent is over 24 days old. */
1668 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) {
1670 * Invalidate ts_recent. If this segment updates
1671 * ts_recent, the age will be reset later and ts_recent
1672 * will get a valid value. If it does not, setting
1673 * ts_recent to zero will at least satisfy the
1674 * requirement that zero be placed in the timestamp
1675 * echo reply when ts_recent isn't valid. The
1676 * age isn't reset until we get a valid ts_recent
1677 * because we don't want out-of-order segments to be
1678 * dropped when ts_recent is old.
1682 tcpstat.tcps_rcvduppack++;
1683 tcpstat.tcps_rcvdupbyte += tlen;
1684 tcpstat.tcps_pawsdrop++;
1692 * In the SYN-RECEIVED state, validate that the packet belongs to
1693 * this connection before trimming the data to fit the receive
1694 * window. Check the sequence number versus IRS since we know
1695 * the sequence numbers haven't wrapped. This is a partial fix
1696 * for the "LAND" DoS attack.
1698 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) {
1699 rstreason = BANDLIM_RST_OPENPORT;
1703 todrop = tp->rcv_nxt - th->th_seq;
1705 if (TCP_DO_SACK(tp)) {
1706 /* Report duplicate segment at head of packet. */
1707 tp->reportblk.rblk_start = th->th_seq;
1708 tp->reportblk.rblk_end = th->th_seq + tlen;
1709 if (thflags & TH_FIN)
1710 ++tp->reportblk.rblk_end;
1711 if (SEQ_GT(tp->reportblk.rblk_end, tp->rcv_nxt))
1712 tp->reportblk.rblk_end = tp->rcv_nxt;
1713 tp->t_flags |= (TF_DUPSEG | TF_SACKLEFT | TF_ACKNOW);
1715 if (thflags & TH_SYN) {
1725 * Following if statement from Stevens, vol. 2, p. 960.
1727 if (todrop > tlen ||
1728 (todrop == tlen && !(thflags & TH_FIN))) {
1730 * Any valid FIN must be to the left of the window.
1731 * At this point the FIN must be a duplicate or out
1732 * of sequence; drop it.
1737 * Send an ACK to resynchronize and drop any data.
1738 * But keep on processing for RST or ACK.
1740 tp->t_flags |= TF_ACKNOW;
1742 tcpstat.tcps_rcvduppack++;
1743 tcpstat.tcps_rcvdupbyte += todrop;
1745 tcpstat.tcps_rcvpartduppack++;
1746 tcpstat.tcps_rcvpartdupbyte += todrop;
1748 drop_hdrlen += todrop; /* drop from the top afterwards */
1749 th->th_seq += todrop;
1751 if (th->th_urp > todrop)
1752 th->th_urp -= todrop;
1760 * If new data are received on a connection after the
1761 * user processes are gone, then RST the other end.
1763 if ((so->so_state & SS_NOFDREF) &&
1764 tp->t_state > TCPS_CLOSE_WAIT && tlen) {
1766 tcpstat.tcps_rcvafterclose++;
1767 rstreason = BANDLIM_UNLIMITED;
1772 * If segment ends after window, drop trailing data
1773 * (and PUSH and FIN); if nothing left, just ACK.
1775 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd);
1777 tcpstat.tcps_rcvpackafterwin++;
1778 if (todrop >= tlen) {
1779 tcpstat.tcps_rcvbyteafterwin += tlen;
1781 * If a new connection request is received
1782 * while in TIME_WAIT, drop the old connection
1783 * and start over if the sequence numbers
1784 * are above the previous ones.
1786 if (thflags & TH_SYN &&
1787 tp->t_state == TCPS_TIME_WAIT &&
1788 SEQ_GT(th->th_seq, tp->rcv_nxt)) {
1793 * If window is closed can only take segments at
1794 * window edge, and have to drop data and PUSH from
1795 * incoming segments. Continue processing, but
1796 * remember to ack. Otherwise, drop segment
1799 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
1800 tp->t_flags |= TF_ACKNOW;
1801 tcpstat.tcps_rcvwinprobe++;
1805 tcpstat.tcps_rcvbyteafterwin += todrop;
1808 thflags &= ~(TH_PUSH | TH_FIN);
1812 * If last ACK falls within this segment's sequence numbers,
1813 * record its timestamp.
1815 * 1) That the test incorporates suggestions from the latest
1816 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1817 * 2) That updating only on newer timestamps interferes with
1818 * our earlier PAWS tests, so this check should be solely
1819 * predicated on the sequence space of this segment.
1820 * 3) That we modify the segment boundary check to be
1821 * Last.ACK.Sent <= SEG.SEQ + SEG.LEN
1822 * instead of RFC1323's
1823 * Last.ACK.Sent < SEG.SEQ + SEG.LEN,
1824 * This modified check allows us to overcome RFC1323's
1825 * limitations as described in Stevens TCP/IP Illustrated
1826 * Vol. 2 p.869. In such cases, we can still calculate the
1827 * RTT correctly when RCV.NXT == Last.ACK.Sent.
1829 if ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent) &&
1830 SEQ_LEQ(tp->last_ack_sent, (th->th_seq + tlen
1831 + ((thflags & TH_SYN) != 0)
1832 + ((thflags & TH_FIN) != 0)))) {
1833 tp->ts_recent_age = ticks;
1834 tp->ts_recent = to.to_tsval;
1838 * If a SYN is in the window, then this is an
1839 * error and we send an RST and drop the connection.
1841 if (thflags & TH_SYN) {
1842 tp = tcp_drop(tp, ECONNRESET);
1843 rstreason = BANDLIM_UNLIMITED;
1848 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN
1849 * flag is on (half-synchronized state), then queue data for
1850 * later processing; else drop segment and return.
1852 if (!(thflags & TH_ACK)) {
1853 if (tp->t_state == TCPS_SYN_RECEIVED ||
1854 (tp->t_flags & TF_NEEDSYN))
1863 switch (tp->t_state) {
1865 * In SYN_RECEIVED state, the ACK acknowledges our SYN, so enter
1866 * ESTABLISHED state and continue processing.
1867 * The ACK was checked above.
1869 case TCPS_SYN_RECEIVED:
1871 tcpstat.tcps_connects++;
1873 /* Do window scaling? */
1874 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) ==
1875 (TF_RCVD_SCALE | TF_REQ_SCALE)) {
1876 tp->snd_scale = tp->requested_s_scale;
1877 tp->rcv_scale = tp->request_r_scale;
1881 * SYN-RECEIVED -> ESTABLISHED
1882 * SYN-RECEIVED* -> FIN-WAIT-1
1884 tp->t_starttime = ticks;
1885 if (tp->t_flags & TF_NEEDFIN) {
1886 tp->t_state = TCPS_FIN_WAIT_1;
1887 tp->t_flags &= ~TF_NEEDFIN;
1889 tp->t_state = TCPS_ESTABLISHED;
1890 tcp_callout_reset(tp, tp->tt_keep,
1891 tcp_getkeepidle(tp),
1895 * If segment contains data or ACK, will call tcp_reass()
1896 * later; if not, do so now to pass queued data to user.
1898 if (tlen == 0 && !(thflags & TH_FIN))
1899 tcp_reass(tp, NULL, NULL, NULL);
1903 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
1904 * ACKs. If the ack is in the range
1905 * tp->snd_una < th->th_ack <= tp->snd_max
1906 * then advance tp->snd_una to th->th_ack and drop
1907 * data from the retransmission queue. If this ACK reflects
1908 * more up to date window information we update our window information.
1910 case TCPS_ESTABLISHED:
1911 case TCPS_FIN_WAIT_1:
1912 case TCPS_FIN_WAIT_2:
1913 case TCPS_CLOSE_WAIT:
1916 case TCPS_TIME_WAIT:
1918 if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
1919 if (TCP_DO_SACK(tp))
1920 tcp_sack_update_scoreboard(tp, &to);
1921 if (tlen != 0 || tiwin != tp->snd_wnd) {
1925 tcpstat.tcps_rcvdupack++;
1926 if (!tcp_callout_active(tp, tp->tt_rexmt) ||
1927 th->th_ack != tp->snd_una) {
1932 * We have outstanding data (other than
1933 * a window probe), this is a completely
1934 * duplicate ack (ie, window info didn't
1935 * change), the ack is the biggest we've
1936 * seen and we've seen exactly our rexmt
1937 * threshhold of them, so assume a packet
1938 * has been dropped and retransmit it.
1939 * Kludge snd_nxt & the congestion
1940 * window so we send only this one
1943 if (IN_FASTRECOVERY(tp)) {
1944 if (TCP_DO_SACK(tp)) {
1945 /* No artifical cwnd inflation. */
1946 tcp_sack_rexmt(tp, th);
1949 * Dup acks mean that packets
1950 * have left the network
1951 * (they're now cached at the
1952 * receiver) so bump cwnd by
1953 * the amount in the receiver
1954 * to keep a constant cwnd
1955 * packets in the network.
1957 tp->snd_cwnd += tp->t_maxseg;
1960 } else if (SEQ_LT(th->th_ack, tp->snd_recover)) {
1963 } else if (++tp->t_dupacks == tcprexmtthresh) {
1964 tcp_seq old_snd_nxt;
1968 if (tcp_do_eifel_detect &&
1969 (tp->t_flags & TF_RCVD_TSTMP)) {
1970 tcp_save_congestion_state(tp);
1971 tp->t_flags |= TF_FASTREXMT;
1974 * We know we're losing at the current
1975 * window size, so do congestion avoidance:
1976 * set ssthresh to half the current window
1977 * and pull our congestion window back to the
1980 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 /
1984 tp->snd_ssthresh = win * tp->t_maxseg;
1985 ENTER_FASTRECOVERY(tp);
1986 tp->snd_recover = tp->snd_max;
1987 tcp_callout_stop(tp, tp->tt_rexmt);
1989 old_snd_nxt = tp->snd_nxt;
1990 tp->snd_nxt = th->th_ack;
1991 tp->snd_cwnd = tp->t_maxseg;
1993 ++tcpstat.tcps_sndfastrexmit;
1994 tp->snd_cwnd = tp->snd_ssthresh;
1995 tp->rexmt_high = tp->snd_nxt;
1996 if (SEQ_GT(old_snd_nxt, tp->snd_nxt))
1997 tp->snd_nxt = old_snd_nxt;
1998 KASSERT(tp->snd_limited <= 2,
1999 ("tp->snd_limited too big"));
2000 if (TCP_DO_SACK(tp))
2001 tcp_sack_rexmt(tp, th);
2003 tp->snd_cwnd += tp->t_maxseg *
2004 (tp->t_dupacks - tp->snd_limited);
2005 } else if (tcp_do_limitedtransmit) {
2006 u_long oldcwnd = tp->snd_cwnd;
2007 tcp_seq oldsndmax = tp->snd_max;
2008 tcp_seq oldsndnxt = tp->snd_nxt;
2009 /* outstanding data */
2010 uint32_t ownd = tp->snd_max - tp->snd_una;
2013 #define iceildiv(n, d) (((n)+(d)-1) / (d))
2015 KASSERT(tp->t_dupacks == 1 ||
2017 ("dupacks not 1 or 2"));
2018 if (tp->t_dupacks == 1)
2019 tp->snd_limited = 0;
2020 tp->snd_nxt = tp->snd_max;
2021 tp->snd_cwnd = ownd +
2022 (tp->t_dupacks - tp->snd_limited) *
2027 * Other acks may have been processed,
2028 * snd_nxt cannot be reset to a value less
2031 if (SEQ_LT(oldsndnxt, oldsndmax)) {
2032 if (SEQ_GT(oldsndnxt, tp->snd_una))
2033 tp->snd_nxt = oldsndnxt;
2035 tp->snd_nxt = tp->snd_una;
2037 tp->snd_cwnd = oldcwnd;
2038 sent = tp->snd_max - oldsndmax;
2039 if (sent > tp->t_maxseg) {
2040 KASSERT((tp->t_dupacks == 2 &&
2041 tp->snd_limited == 0) ||
2042 (sent == tp->t_maxseg + 1 &&
2043 tp->t_flags & TF_SENTFIN),
2045 KASSERT(sent <= tp->t_maxseg * 2,
2046 ("sent too many segments"));
2047 tp->snd_limited = 2;
2048 tcpstat.tcps_sndlimited += 2;
2049 } else if (sent > 0) {
2051 ++tcpstat.tcps_sndlimited;
2052 } else if (tcp_do_early_retransmit &&
2053 (tcp_do_eifel_detect &&
2054 (tp->t_flags & TF_RCVD_TSTMP)) &&
2055 ownd < 4 * tp->t_maxseg &&
2056 tp->t_dupacks + 1 >=
2057 iceildiv(ownd, tp->t_maxseg) &&
2058 (!TCP_DO_SACK(tp) ||
2059 ownd <= tp->t_maxseg ||
2060 tcp_sack_has_sacked(&tp->scb,
2061 ownd - tp->t_maxseg))) {
2062 ++tcpstat.tcps_sndearlyrexmit;
2063 tp->t_flags |= TF_EARLYREXMT;
2064 goto fastretransmit;
2070 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una"));
2072 if (SEQ_GT(th->th_ack, tp->snd_max)) {
2074 * Detected optimistic ACK attack.
2075 * Force slow-start to de-synchronize attack.
2077 tp->snd_cwnd = tp->t_maxseg;
2080 tcpstat.tcps_rcvacktoomuch++;
2084 * If we reach this point, ACK is not a duplicate,
2085 * i.e., it ACKs something we sent.
2087 if (tp->t_flags & TF_NEEDSYN) {
2089 * T/TCP: Connection was half-synchronized, and our
2090 * SYN has been ACK'd (so connection is now fully
2091 * synchronized). Go to non-starred state,
2092 * increment snd_una for ACK of SYN, and check if
2093 * we can do window scaling.
2095 tp->t_flags &= ~TF_NEEDSYN;
2097 /* Do window scaling? */
2098 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) ==
2099 (TF_RCVD_SCALE | TF_REQ_SCALE)) {
2100 tp->snd_scale = tp->requested_s_scale;
2101 tp->rcv_scale = tp->request_r_scale;
2106 acked = th->th_ack - tp->snd_una;
2107 tcpstat.tcps_rcvackpack++;
2108 tcpstat.tcps_rcvackbyte += acked;
2110 if (tcp_do_eifel_detect && acked > 0 &&
2111 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) &&
2112 (tp->t_flags & TF_FIRSTACCACK)) {
2113 /* Eifel detection applicable. */
2114 if (to.to_tsecr < tp->t_rexmtTS) {
2115 ++tcpstat.tcps_eifeldetected;
2116 tcp_revert_congestion_state(tp);
2117 if (tp->t_rxtshift == 1 &&
2118 ticks >= tp->t_badrxtwin)
2119 ++tcpstat.tcps_rttcantdetect;
2121 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) {
2123 * If we just performed our first retransmit,
2124 * and the ACK arrives within our recovery window,
2125 * then it was a mistake to do the retransmit
2126 * in the first place. Recover our original cwnd
2127 * and ssthresh, and proceed to transmit where we
2130 tcp_revert_congestion_state(tp);
2131 ++tcpstat.tcps_rttdetected;
2135 * If we have a timestamp reply, update smoothed
2136 * round trip time. If no timestamp is present but
2137 * transmit timer is running and timed sequence
2138 * number was acked, update smoothed round trip time.
2139 * Since we now have an rtt measurement, cancel the
2140 * timer backoff (cf., Phil Karn's retransmit alg.).
2141 * Recompute the initial retransmit timer.
2143 * Some machines (certain windows boxes) send broken
2144 * timestamp replies during the SYN+ACK phase, ignore
2147 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0))
2148 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1);
2149 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq))
2150 tcp_xmit_timer(tp, ticks - tp->t_rtttime);
2151 tcp_xmit_bandwidth_limit(tp, th->th_ack);
2154 * If no data (only SYN) was ACK'd,
2155 * skip rest of ACK processing.
2160 /* Stop looking for an acceptable ACK since one was received. */
2161 tp->t_flags &= ~(TF_FIRSTACCACK | TF_FASTREXMT | TF_EARLYREXMT);
2163 if (acked > so->so_snd.ssb_cc) {
2164 tp->snd_wnd -= so->so_snd.ssb_cc;
2165 sbdrop(&so->so_snd.sb, (int)so->so_snd.ssb_cc);
2166 ourfinisacked = TRUE;
2168 sbdrop(&so->so_snd.sb, acked);
2169 tp->snd_wnd -= acked;
2170 ourfinisacked = FALSE;
2175 * Update window information.
2176 * Don't look at window if no ACK:
2177 * TAC's send garbage on first SYN.
2179 if (SEQ_LT(tp->snd_wl1, th->th_seq) ||
2180 (tp->snd_wl1 == th->th_seq &&
2181 (SEQ_LT(tp->snd_wl2, th->th_ack) ||
2182 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) {
2183 /* keep track of pure window updates */
2184 if (tlen == 0 && tp->snd_wl2 == th->th_ack &&
2185 tiwin > tp->snd_wnd)
2186 tcpstat.tcps_rcvwinupd++;
2187 tp->snd_wnd = tiwin;
2188 tp->snd_wl1 = th->th_seq;
2189 tp->snd_wl2 = th->th_ack;
2190 if (tp->snd_wnd > tp->max_sndwnd)
2191 tp->max_sndwnd = tp->snd_wnd;
2195 tp->snd_una = th->th_ack;
2196 if (TCP_DO_SACK(tp))
2197 tcp_sack_update_scoreboard(tp, &to);
2198 if (IN_FASTRECOVERY(tp)) {
2199 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) {
2200 EXIT_FASTRECOVERY(tp);
2203 * If the congestion window was inflated
2204 * to account for the other side's
2205 * cached packets, retract it.
2207 if (!TCP_DO_SACK(tp))
2208 tp->snd_cwnd = tp->snd_ssthresh;
2211 * Window inflation should have left us
2212 * with approximately snd_ssthresh outstanding
2213 * data. But, in case we would be inclined
2214 * to send a burst, better do it using
2217 if (SEQ_GT(th->th_ack + tp->snd_cwnd,
2218 tp->snd_max + 2 * tp->t_maxseg))
2220 (tp->snd_max - tp->snd_una) +
2225 if (TCP_DO_SACK(tp)) {
2226 tp->snd_max_rexmt = tp->snd_max;
2227 tcp_sack_rexmt(tp, th);
2229 tcp_newreno_partial_ack(tp, th, acked);
2235 * Open the congestion window. When in slow-start,
2236 * open exponentially: maxseg per packet. Otherwise,
2237 * open linearly: maxseg per window.
2239 if (tp->snd_cwnd <= tp->snd_ssthresh) {
2241 (SEQ_LT(tp->snd_nxt, tp->snd_max) ?
2242 tp->t_maxseg : 2 * tp->t_maxseg);
2245 tp->snd_cwnd += tcp_do_abc ?
2246 min(acked, abc_sslimit) : tp->t_maxseg;
2248 /* linear increase */
2249 tp->snd_wacked += tcp_do_abc ? acked :
2251 if (tp->snd_wacked >= tp->snd_cwnd) {
2252 tp->snd_wacked -= tp->snd_cwnd;
2253 tp->snd_cwnd += tp->t_maxseg;
2256 tp->snd_cwnd = min(tp->snd_cwnd,
2257 TCP_MAXWIN << tp->snd_scale);
2258 tp->snd_recover = th->th_ack - 1;
2260 if (SEQ_LT(tp->snd_nxt, tp->snd_una))
2261 tp->snd_nxt = tp->snd_una;
2264 * If all outstanding data is acked, stop retransmit
2265 * timer and remember to restart (more output or persist).
2266 * If there is more data to be acked, restart retransmit
2267 * timer, using current (possibly backed-off) value.
2269 if (th->th_ack == tp->snd_max) {
2270 tcp_callout_stop(tp, tp->tt_rexmt);
2272 } else if (!tcp_callout_active(tp, tp->tt_persist)) {
2273 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur,
2277 switch (tp->t_state) {
2279 * In FIN_WAIT_1 STATE in addition to the processing
2280 * for the ESTABLISHED state if our FIN is now acknowledged
2281 * then enter FIN_WAIT_2.
2283 case TCPS_FIN_WAIT_1:
2284 if (ourfinisacked) {
2286 * If we can't receive any more
2287 * data, then closing user can proceed.
2288 * Starting the timer is contrary to the
2289 * specification, but if we don't get a FIN
2290 * we'll hang forever.
2292 if (so->so_state & SS_CANTRCVMORE) {
2293 soisdisconnected(so);
2294 tcp_callout_reset(tp, tp->tt_2msl,
2295 tp->t_maxidle, tcp_timer_2msl);
2297 tp->t_state = TCPS_FIN_WAIT_2;
2302 * In CLOSING STATE in addition to the processing for
2303 * the ESTABLISHED state if the ACK acknowledges our FIN
2304 * then enter the TIME-WAIT state, otherwise ignore
2308 if (ourfinisacked) {
2309 tp->t_state = TCPS_TIME_WAIT;
2310 tcp_canceltimers(tp);
2311 tcp_callout_reset(tp, tp->tt_2msl,
2312 2 * tcp_msl, tcp_timer_2msl);
2313 soisdisconnected(so);
2318 * In LAST_ACK, we may still be waiting for data to drain
2319 * and/or to be acked, as well as for the ack of our FIN.
2320 * If our FIN is now acknowledged, delete the TCB,
2321 * enter the closed state and return.
2324 if (ourfinisacked) {
2331 * In TIME_WAIT state the only thing that should arrive
2332 * is a retransmission of the remote FIN. Acknowledge
2333 * it and restart the finack timer.
2335 case TCPS_TIME_WAIT:
2336 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_msl,
2344 * Update window information.
2345 * Don't look at window if no ACK: TAC's send garbage on first SYN.
2347 if ((thflags & TH_ACK) &&
2348 acceptable_window_update(tp, th, tiwin)) {
2349 /* keep track of pure window updates */
2350 if (tlen == 0 && tp->snd_wl2 == th->th_ack &&
2351 tiwin > tp->snd_wnd)
2352 tcpstat.tcps_rcvwinupd++;
2353 tp->snd_wnd = tiwin;
2354 tp->snd_wl1 = th->th_seq;
2355 tp->snd_wl2 = th->th_ack;
2356 if (tp->snd_wnd > tp->max_sndwnd)
2357 tp->max_sndwnd = tp->snd_wnd;
2362 * Process segments with URG.
2364 if ((thflags & TH_URG) && th->th_urp &&
2365 !TCPS_HAVERCVDFIN(tp->t_state)) {
2367 * This is a kludge, but if we receive and accept
2368 * random urgent pointers, we'll crash in
2369 * soreceive. It's hard to imagine someone
2370 * actually wanting to send this much urgent data.
2372 if (th->th_urp + so->so_rcv.ssb_cc > sb_max) {
2373 th->th_urp = 0; /* XXX */
2374 thflags &= ~TH_URG; /* XXX */
2375 goto dodata; /* XXX */
2378 * If this segment advances the known urgent pointer,
2379 * then mark the data stream. This should not happen
2380 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
2381 * a FIN has been received from the remote side.
2382 * In these states we ignore the URG.
2384 * According to RFC961 (Assigned Protocols),
2385 * the urgent pointer points to the last octet
2386 * of urgent data. We continue, however,
2387 * to consider it to indicate the first octet
2388 * of data past the urgent section as the original
2389 * spec states (in one of two places).
2391 if (SEQ_GT(th->th_seq + th->th_urp, tp->rcv_up)) {
2392 tp->rcv_up = th->th_seq + th->th_urp;
2393 so->so_oobmark = so->so_rcv.ssb_cc +
2394 (tp->rcv_up - tp->rcv_nxt) - 1;
2395 if (so->so_oobmark == 0)
2396 sosetstate(so, SS_RCVATMARK);
2398 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
2401 * Remove out of band data so doesn't get presented to user.
2402 * This can happen independent of advancing the URG pointer,
2403 * but if two URG's are pending at once, some out-of-band
2404 * data may creep in... ick.
2406 if (th->th_urp <= (u_long)tlen &&
2407 !(so->so_options & SO_OOBINLINE)) {
2408 /* hdr drop is delayed */
2409 tcp_pulloutofband(so, th, m, drop_hdrlen);
2413 * If no out of band data is expected,
2414 * pull receive urgent pointer along
2415 * with the receive window.
2417 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
2418 tp->rcv_up = tp->rcv_nxt;
2423 * Process the segment text, merging it into the TCP sequencing queue,
2424 * and arranging for acknowledgment of receipt if necessary.
2425 * This process logically involves adjusting tp->rcv_wnd as data
2426 * is presented to the user (this happens in tcp_usrreq.c,
2427 * case PRU_RCVD). If a FIN has already been received on this
2428 * connection then we just ignore the text.
2430 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) {
2431 m_adj(m, drop_hdrlen); /* delayed header drop */
2433 * Insert segment which includes th into TCP reassembly queue
2434 * with control block tp. Set thflags to whether reassembly now
2435 * includes a segment with FIN. This handles the common case
2436 * inline (segment is the next to be received on an established
2437 * connection, and the queue is empty), avoiding linkage into
2438 * and removal from the queue and repetition of various
2440 * Set DELACK for segments received in order, but ack
2441 * immediately when segments are out of order (so
2442 * fast retransmit can work).
2444 if (th->th_seq == tp->rcv_nxt &&
2445 LIST_EMPTY(&tp->t_segq) &&
2446 TCPS_HAVEESTABLISHED(tp->t_state)) {
2447 if (DELAY_ACK(tp)) {
2448 tcp_callout_reset(tp, tp->tt_delack,
2449 tcp_delacktime, tcp_timer_delack);
2451 tp->t_flags |= TF_ACKNOW;
2453 tp->rcv_nxt += tlen;
2454 thflags = th->th_flags & TH_FIN;
2455 tcpstat.tcps_rcvpack++;
2456 tcpstat.tcps_rcvbyte += tlen;
2458 if (so->so_state & SS_CANTRCVMORE) {
2461 lwkt_gettoken(&so->so_rcv.ssb_token);
2462 ssb_appendstream(&so->so_rcv, m);
2463 lwkt_reltoken(&so->so_rcv.ssb_token);
2467 if (!(tp->t_flags & TF_DUPSEG)) {
2468 /* Initialize SACK report block. */
2469 tp->reportblk.rblk_start = th->th_seq;
2470 tp->reportblk.rblk_end = th->th_seq + tlen +
2471 ((thflags & TH_FIN) != 0);
2473 thflags = tcp_reass(tp, th, &tlen, m);
2474 tp->t_flags |= TF_ACKNOW;
2478 * Note the amount of data that peer has sent into
2479 * our window, in order to estimate the sender's
2482 len = so->so_rcv.ssb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
2489 * If FIN is received ACK the FIN and let the user know
2490 * that the connection is closing.
2492 if (thflags & TH_FIN) {
2493 if (!TCPS_HAVERCVDFIN(tp->t_state)) {
2496 * If connection is half-synchronized
2497 * (ie NEEDSYN flag on) then delay ACK,
2498 * so it may be piggybacked when SYN is sent.
2499 * Otherwise, since we received a FIN then no
2500 * more input can be expected, send ACK now.
2502 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) {
2503 tcp_callout_reset(tp, tp->tt_delack,
2504 tcp_delacktime, tcp_timer_delack);
2506 tp->t_flags |= TF_ACKNOW;
2511 switch (tp->t_state) {
2513 * In SYN_RECEIVED and ESTABLISHED STATES
2514 * enter the CLOSE_WAIT state.
2516 case TCPS_SYN_RECEIVED:
2517 tp->t_starttime = ticks;
2519 case TCPS_ESTABLISHED:
2520 tp->t_state = TCPS_CLOSE_WAIT;
2524 * If still in FIN_WAIT_1 STATE FIN has not been acked so
2525 * enter the CLOSING state.
2527 case TCPS_FIN_WAIT_1:
2528 tp->t_state = TCPS_CLOSING;
2532 * In FIN_WAIT_2 state enter the TIME_WAIT state,
2533 * starting the time-wait timer, turning off the other
2536 case TCPS_FIN_WAIT_2:
2537 tp->t_state = TCPS_TIME_WAIT;
2538 tcp_canceltimers(tp);
2539 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_msl,
2541 soisdisconnected(so);
2545 * In TIME_WAIT state restart the 2 MSL time_wait timer.
2547 case TCPS_TIME_WAIT:
2548 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_msl,
2555 if (so->so_options & SO_DEBUG)
2556 tcp_trace(TA_INPUT, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
2560 * Return any desired output.
2562 if (needoutput || (tp->t_flags & TF_ACKNOW))
2564 return(IPPROTO_DONE);
2568 * Generate an ACK dropping incoming segment if it occupies
2569 * sequence space, where the ACK reflects our state.
2571 * We can now skip the test for the RST flag since all
2572 * paths to this code happen after packets containing
2573 * RST have been dropped.
2575 * In the SYN-RECEIVED state, don't send an ACK unless the
2576 * segment we received passes the SYN-RECEIVED ACK test.
2577 * If it fails send a RST. This breaks the loop in the
2578 * "LAND" DoS attack, and also prevents an ACK storm
2579 * between two listening ports that have been sent forged
2580 * SYN segments, each with the source address of the other.
2582 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
2583 (SEQ_GT(tp->snd_una, th->th_ack) ||
2584 SEQ_GT(th->th_ack, tp->snd_max)) ) {
2585 rstreason = BANDLIM_RST_OPENPORT;
2589 if (so->so_options & SO_DEBUG)
2590 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
2593 tp->t_flags |= TF_ACKNOW;
2595 return(IPPROTO_DONE);
2599 * Generate a RST, dropping incoming segment.
2600 * Make ACK acceptable to originator of segment.
2601 * Don't bother to respond if destination was broadcast/multicast.
2603 if ((thflags & TH_RST) || m->m_flags & (M_BCAST | M_MCAST))
2606 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
2607 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
2610 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
2611 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
2612 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
2613 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
2616 /* IPv6 anycast check is done at tcp6_input() */
2619 * Perform bandwidth limiting.
2622 if (badport_bandlim(rstreason) < 0)
2627 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
2628 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
2630 if (thflags & TH_ACK)
2631 /* mtod() below is safe as long as hdr dropping is delayed */
2632 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack,
2635 if (thflags & TH_SYN)
2637 /* mtod() below is safe as long as hdr dropping is delayed */
2638 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen,
2639 (tcp_seq)0, TH_RST | TH_ACK);
2641 return(IPPROTO_DONE);
2645 * Drop space held by incoming segment and return.
2648 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
2649 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
2652 return(IPPROTO_DONE);
2656 * Parse TCP options and place in tcpopt.
2659 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn)
2664 for (; cnt > 0; cnt -= optlen, cp += optlen) {
2666 if (opt == TCPOPT_EOL)
2668 if (opt == TCPOPT_NOP)
2674 if (optlen < 2 || optlen > cnt)
2679 if (optlen != TCPOLEN_MAXSEG)
2683 to->to_flags |= TOF_MSS;
2684 bcopy(cp + 2, &to->to_mss, sizeof to->to_mss);
2685 to->to_mss = ntohs(to->to_mss);
2688 if (optlen != TCPOLEN_WINDOW)
2692 to->to_flags |= TOF_SCALE;
2693 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT);
2695 case TCPOPT_TIMESTAMP:
2696 if (optlen != TCPOLEN_TIMESTAMP)
2698 to->to_flags |= TOF_TS;
2699 bcopy(cp + 2, &to->to_tsval, sizeof to->to_tsval);
2700 to->to_tsval = ntohl(to->to_tsval);
2701 bcopy(cp + 6, &to->to_tsecr, sizeof to->to_tsecr);
2702 to->to_tsecr = ntohl(to->to_tsecr);
2704 * If echoed timestamp is later than the current time,
2705 * fall back to non RFC1323 RTT calculation.
2707 if (to->to_tsecr != 0 && TSTMP_GT(to->to_tsecr, ticks))
2710 case TCPOPT_SACK_PERMITTED:
2711 if (optlen != TCPOLEN_SACK_PERMITTED)
2715 to->to_flags |= TOF_SACK_PERMITTED;
2718 if ((optlen - 2) & 0x07) /* not multiple of 8 */
2720 to->to_nsackblocks = (optlen - 2) / 8;
2721 to->to_sackblocks = (struct raw_sackblock *) (cp + 2);
2722 to->to_flags |= TOF_SACK;
2723 for (i = 0; i < to->to_nsackblocks; i++) {
2724 struct raw_sackblock *r = &to->to_sackblocks[i];
2726 r->rblk_start = ntohl(r->rblk_start);
2727 r->rblk_end = ntohl(r->rblk_end);
2730 #ifdef TCP_SIGNATURE
2732 * XXX In order to reply to a host which has set the
2733 * TCP_SIGNATURE option in its initial SYN, we have to
2734 * record the fact that the option was observed here
2735 * for the syncache code to perform the correct response.
2737 case TCPOPT_SIGNATURE:
2738 if (optlen != TCPOLEN_SIGNATURE)
2740 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN);
2742 #endif /* TCP_SIGNATURE */
2750 * Pull out of band byte out of a segment so
2751 * it doesn't appear in the user's data queue.
2752 * It is still reflected in the segment length for
2753 * sequencing purposes.
2754 * "off" is the delayed to be dropped hdrlen.
2757 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off)
2759 int cnt = off + th->th_urp - 1;
2762 if (m->m_len > cnt) {
2763 char *cp = mtod(m, caddr_t) + cnt;
2764 struct tcpcb *tp = sototcpcb(so);
2767 tp->t_oobflags |= TCPOOB_HAVEDATA;
2768 bcopy(cp + 1, cp, m->m_len - cnt - 1);
2770 if (m->m_flags & M_PKTHDR)
2779 panic("tcp_pulloutofband");
2783 * Collect new round-trip time estimate
2784 * and update averages and current timeout.
2787 tcp_xmit_timer(struct tcpcb *tp, int rtt)
2791 tcpstat.tcps_rttupdated++;
2793 if (tp->t_srtt != 0) {
2795 * srtt is stored as fixed point with 5 bits after the
2796 * binary point (i.e., scaled by 8). The following magic
2797 * is equivalent to the smoothing algorithm in rfc793 with
2798 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
2799 * point). Adjust rtt to origin 0.
2801 delta = ((rtt - 1) << TCP_DELTA_SHIFT)
2802 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
2804 if ((tp->t_srtt += delta) <= 0)
2808 * We accumulate a smoothed rtt variance (actually, a
2809 * smoothed mean difference), then set the retransmit
2810 * timer to smoothed rtt + 4 times the smoothed variance.
2811 * rttvar is stored as fixed point with 4 bits after the
2812 * binary point (scaled by 16). The following is
2813 * equivalent to rfc793 smoothing with an alpha of .75
2814 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces
2815 * rfc793's wired-in beta.
2819 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
2820 if ((tp->t_rttvar += delta) <= 0)
2822 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
2823 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2826 * No rtt measurement yet - use the unsmoothed rtt.
2827 * Set the variance to half the rtt (so our first
2828 * retransmit happens at 3*rtt).
2830 tp->t_srtt = rtt << TCP_RTT_SHIFT;
2831 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
2832 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2838 * the retransmit should happen at rtt + 4 * rttvar.
2839 * Because of the way we do the smoothing, srtt and rttvar
2840 * will each average +1/2 tick of bias. When we compute
2841 * the retransmit timer, we want 1/2 tick of rounding and
2842 * 1 extra tick because of +-1/2 tick uncertainty in the
2843 * firing of the timer. The bias will give us exactly the
2844 * 1.5 tick we need. But, because the bias is
2845 * statistical, we have to test that we don't drop below
2846 * the minimum feasible timer (which is 2 ticks).
2848 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
2849 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);
2852 * We received an ack for a packet that wasn't retransmitted;
2853 * it is probably safe to discard any error indications we've
2854 * received recently. This isn't quite right, but close enough
2855 * for now (a route might have failed after we sent a segment,
2856 * and the return path might not be symmetrical).
2858 tp->t_softerror = 0;
2862 * Determine a reasonable value for maxseg size.
2863 * If the route is known, check route for mtu.
2864 * If none, use an mss that can be handled on the outgoing
2865 * interface without forcing IP to fragment; if bigger than
2866 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES
2867 * to utilize large mbufs. If no route is found, route has no mtu,
2868 * or the destination isn't local, use a default, hopefully conservative
2869 * size (usually 512 or the default IP max size, but no more than the mtu
2870 * of the interface), as we can't discover anything about intervening
2871 * gateways or networks. We also initialize the congestion/slow start
2872 * window to be a single segment if the destination isn't local.
2873 * While looking at the routing entry, we also initialize other path-dependent
2874 * parameters from pre-set or cached values in the routing entry.
2876 * Also take into account the space needed for options that we
2877 * send regularly. Make maxseg shorter by that amount to assure
2878 * that we can send maxseg amount of data even when the options
2879 * are present. Store the upper limit of the length of options plus
2882 * NOTE that this routine is only called when we process an incoming
2883 * segment, for outgoing segments only tcp_mssopt is called.
2886 tcp_mss(struct tcpcb *tp, int offer)
2892 struct inpcb *inp = tp->t_inpcb;
2895 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE);
2896 size_t min_protoh = isipv6 ?
2897 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) :
2898 sizeof(struct tcpiphdr);
2900 const boolean_t isipv6 = FALSE;
2901 const size_t min_protoh = sizeof(struct tcpiphdr);
2905 rt = tcp_rtlookup6(&inp->inp_inc);
2907 rt = tcp_rtlookup(&inp->inp_inc);
2909 tp->t_maxopd = tp->t_maxseg =
2910 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt);
2914 so = inp->inp_socket;
2917 * Offer == 0 means that there was no MSS on the SYN segment,
2918 * in this case we use either the interface mtu or tcp_mssdflt.
2920 * An offer which is too large will be cut down later.
2924 if (in6_localaddr(&inp->in6p_faddr)) {
2925 offer = ND_IFINFO(rt->rt_ifp)->linkmtu -
2928 offer = tcp_v6mssdflt;
2931 if (in_localaddr(inp->inp_faddr))
2932 offer = ifp->if_mtu - min_protoh;
2934 offer = tcp_mssdflt;
2939 * Prevent DoS attack with too small MSS. Round up
2940 * to at least minmss.
2942 * Sanity check: make sure that maxopd will be large
2943 * enough to allow some data on segments even is the
2944 * all the option space is used (40bytes). Otherwise
2945 * funny things may happen in tcp_output.
2947 offer = max(offer, tcp_minmss);
2948 offer = max(offer, 64);
2950 rt->rt_rmx.rmx_mssopt = offer;
2953 * While we're here, check if there's an initial rtt
2954 * or rttvar. Convert from the route-table units
2955 * to scaled multiples of the slow timeout timer.
2957 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) {
2959 * XXX the lock bit for RTT indicates that the value
2960 * is also a minimum value; this is subject to time.
2962 if (rt->rt_rmx.rmx_locks & RTV_RTT)
2963 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz);
2964 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE));
2965 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE;
2966 tcpstat.tcps_usedrtt++;
2967 if (rt->rt_rmx.rmx_rttvar) {
2968 tp->t_rttvar = rt->rt_rmx.rmx_rttvar /
2969 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE));
2970 tcpstat.tcps_usedrttvar++;
2972 /* default variation is +- 1 rtt */
2974 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
2976 TCPT_RANGESET(tp->t_rxtcur,
2977 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
2978 tp->t_rttmin, TCPTV_REXMTMAX);
2982 * if there's an mtu associated with the route, use it
2983 * else, use the link mtu. Take the smaller of mss or offer
2986 if (rt->rt_rmx.rmx_mtu) {
2987 mss = rt->rt_rmx.rmx_mtu - min_protoh;
2990 mss = ND_IFINFO(rt->rt_ifp)->linkmtu - min_protoh;
2992 mss = ifp->if_mtu - min_protoh;
2994 mss = min(mss, offer);
2997 * maxopd stores the maximum length of data AND options
2998 * in a segment; maxseg is the amount of data in a normal
2999 * segment. We need to store this value (maxopd) apart
3000 * from maxseg, because now every segment carries options
3001 * and thus we normally have somewhat less data in segments.
3005 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP &&
3006 ((tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP))
3007 mss -= TCPOLEN_TSTAMP_APPA;
3009 #if (MCLBYTES & (MCLBYTES - 1)) == 0
3011 mss &= ~(MCLBYTES-1);
3014 mss = mss / MCLBYTES * MCLBYTES;
3017 * If there's a pipesize, change the socket buffer
3018 * to that size. Make the socket buffers an integral
3019 * number of mss units; if the mss is larger than
3020 * the socket buffer, decrease the mss.
3023 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0)
3025 bufsize = so->so_snd.ssb_hiwat;
3029 bufsize = roundup(bufsize, mss);
3030 if (bufsize > sb_max)
3032 if (bufsize > so->so_snd.ssb_hiwat)
3033 ssb_reserve(&so->so_snd, bufsize, so, NULL);
3038 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0)
3040 bufsize = so->so_rcv.ssb_hiwat;
3041 if (bufsize > mss) {
3042 bufsize = roundup(bufsize, mss);
3043 if (bufsize > sb_max)
3045 if (bufsize > so->so_rcv.ssb_hiwat) {
3046 lwkt_gettoken(&so->so_rcv.ssb_token);
3047 ssb_reserve(&so->so_rcv, bufsize, so, NULL);
3048 lwkt_reltoken(&so->so_rcv.ssb_token);
3053 * Set the slow-start flight size depending on whether this
3054 * is a local network or not.
3057 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380));
3061 if (rt->rt_rmx.rmx_ssthresh) {
3063 * There's some sort of gateway or interface
3064 * buffer limit on the path. Use this to set
3065 * the slow start threshhold, but set the
3066 * threshold to no less than 2*mss.
3068 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh);
3069 tcpstat.tcps_usedssthresh++;
3074 * Determine the MSS option to send on an outgoing SYN.
3077 tcp_mssopt(struct tcpcb *tp)
3082 ((tp->t_inpcb->inp_vflag & INP_IPV6) ? TRUE : FALSE);
3083 int min_protoh = isipv6 ?
3084 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) :
3085 sizeof(struct tcpiphdr);
3087 const boolean_t isipv6 = FALSE;
3088 const size_t min_protoh = sizeof(struct tcpiphdr);
3092 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc);
3094 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc);
3096 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt);
3098 return (rt->rt_ifp->if_mtu - min_protoh);
3102 * When a partial ack arrives, force the retransmission of the
3103 * next unacknowledged segment. Do not exit Fast Recovery.
3105 * Implement the Slow-but-Steady variant of NewReno by restarting the
3106 * the retransmission timer. Turn it off here so it can be restarted
3107 * later in tcp_output().
3110 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th, int acked)
3112 tcp_seq old_snd_nxt = tp->snd_nxt;
3113 u_long ocwnd = tp->snd_cwnd;
3115 tcp_callout_stop(tp, tp->tt_rexmt);
3117 tp->snd_nxt = th->th_ack;
3118 /* Set snd_cwnd to one segment beyond acknowledged offset. */
3119 tp->snd_cwnd = tp->t_maxseg;
3120 tp->t_flags |= TF_ACKNOW;
3122 if (SEQ_GT(old_snd_nxt, tp->snd_nxt))
3123 tp->snd_nxt = old_snd_nxt;
3124 /* partial window deflation */
3126 tp->snd_cwnd = ocwnd - acked + tp->t_maxseg;
3128 tp->snd_cwnd = tp->t_maxseg;
3132 * In contrast to the Slow-but-Steady NewReno variant,
3133 * we do not reset the retransmission timer for SACK retransmissions,
3134 * except when retransmitting snd_una.
3137 tcp_sack_rexmt(struct tcpcb *tp, struct tcphdr *th)
3139 uint32_t pipe, seglen;
3142 tcp_seq old_snd_nxt = tp->snd_nxt;
3143 u_long ocwnd = tp->snd_cwnd;
3144 int nseg = 0; /* consecutive new segments */
3145 #define MAXBURST 4 /* limit burst of new packets on partial ack */
3148 pipe = tcp_sack_compute_pipe(tp);
3149 while ((tcp_seq_diff_t)(ocwnd - pipe) >= (tcp_seq_diff_t)tp->t_maxseg &&
3150 (!tcp_do_smartsack || nseg < MAXBURST) &&
3151 tcp_sack_nextseg(tp, &nextrexmt, &seglen, &lostdup)) {
3153 tcp_seq old_snd_max;
3156 if (nextrexmt == tp->snd_max)
3158 tp->snd_nxt = nextrexmt;
3159 tp->snd_cwnd = nextrexmt - tp->snd_una + seglen;
3160 old_snd_max = tp->snd_max;
3161 if (nextrexmt == tp->snd_una)
3162 tcp_callout_stop(tp, tp->tt_rexmt);
3163 error = tcp_output(tp);
3166 sent = tp->snd_nxt - nextrexmt;
3171 tcpstat.tcps_sndsackpack++;
3172 tcpstat.tcps_sndsackbyte += sent;
3173 if (SEQ_LT(nextrexmt, old_snd_max) &&
3174 SEQ_LT(tp->rexmt_high, tp->snd_nxt))
3175 tp->rexmt_high = seq_min(tp->snd_nxt, old_snd_max);
3177 if (SEQ_GT(old_snd_nxt, tp->snd_nxt))
3178 tp->snd_nxt = old_snd_nxt;
3179 tp->snd_cwnd = ocwnd;
3183 * Reset idle time and keep-alive timer, typically called when a valid
3184 * tcp packet is received but may also be called when FASTKEEP is set
3185 * to prevent the previous long-timeout from calculating to a drop.
3187 * Only update t_rcvtime for non-SYN packets.
3189 * Handle the case where one side thinks the connection is established
3190 * but the other side has, say, rebooted without cleaning out the
3191 * connection. The SYNs could be construed as an attack and wind
3192 * up ignored, but in case it isn't an attack we can validate the
3193 * connection by forcing a keepalive.
3196 tcp_timer_keep_activity(struct tcpcb *tp, int thflags)
3198 if (TCPS_HAVEESTABLISHED(tp->t_state)) {
3199 if ((thflags & (TH_SYN | TH_ACK)) == TH_SYN) {
3200 tp->t_flags |= TF_KEEPALIVE;
3201 tcp_callout_reset(tp, tp->tt_keep, hz / 2,
3204 tp->t_rcvtime = ticks;
3205 tp->t_flags &= ~TF_KEEPALIVE;
3206 tcp_callout_reset(tp, tp->tt_keep,
3207 tcp_getkeepidle(tp),
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