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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12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
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15 * documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of The DragonFly Project nor the names of its
17 * contributors may be used to endorse or promote products derived
18 * from this software without specific, prior written permission.
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21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
23 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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36 * The Regents of the University of California. All rights reserved.
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39 * modification, are permitted provided that the following conditions
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51 * may be used to endorse or promote products derived from this software
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56 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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61 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
62 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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 $
71 #include "opt_inet6.h"
72 #include "opt_ipsec.h"
73 #include "opt_tcpdebug.h"
74 #include "opt_tcp_input.h"
76 #include <sys/param.h>
77 #include <sys/systm.h>
78 #include <sys/kernel.h>
79 #include <sys/sysctl.h>
80 #include <sys/malloc.h>
82 #include <sys/proc.h> /* for proc0 declaration */
83 #include <sys/protosw.h>
84 #include <sys/socket.h>
85 #include <sys/socketvar.h>
86 #include <sys/syslog.h>
87 #include <sys/in_cksum.h>
89 #include <sys/socketvar2.h>
91 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */
92 #include <machine/stdarg.h>
95 #include <net/route.h>
97 #include <netinet/in.h>
98 #include <netinet/in_systm.h>
99 #include <netinet/ip.h>
100 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */
101 #include <netinet/in_var.h>
102 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */
103 #include <netinet/in_pcb.h>
104 #include <netinet/ip_var.h>
105 #include <netinet/ip6.h>
106 #include <netinet/icmp6.h>
107 #include <netinet6/nd6.h>
108 #include <netinet6/ip6_var.h>
109 #include <netinet6/in6_pcb.h>
110 #include <netinet/tcp.h>
111 #include <netinet/tcp_fsm.h>
112 #include <netinet/tcp_seq.h>
113 #include <netinet/tcp_timer.h>
114 #include <netinet/tcp_timer2.h>
115 #include <netinet/tcp_var.h>
116 #include <netinet6/tcp6_var.h>
117 #include <netinet/tcpip.h>
120 #include <netinet/tcp_debug.h>
122 u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */
123 struct tcphdr tcp_savetcp;
127 #include <netproto/ipsec/ipsec.h>
128 #include <netproto/ipsec/ipsec6.h>
132 #include <netinet6/ipsec.h>
133 #include <netinet6/ipsec6.h>
134 #include <netproto/key/key.h>
137 MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry");
139 static int log_in_vain = 0;
140 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW,
141 &log_in_vain, 0, "Log all incoming TCP connections");
143 static int blackhole = 0;
144 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW,
145 &blackhole, 0, "Do not send RST when dropping refused connections");
147 int tcp_delack_enabled = 1;
148 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW,
149 &tcp_delack_enabled, 0,
150 "Delay ACK to try and piggyback it onto a data packet");
152 #ifdef TCP_DROP_SYNFIN
153 static int drop_synfin = 0;
154 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW,
155 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set");
158 static int tcp_do_limitedtransmit = 1;
159 SYSCTL_INT(_net_inet_tcp, OID_AUTO, limitedtransmit, CTLFLAG_RW,
160 &tcp_do_limitedtransmit, 0, "Enable RFC 3042 (Limited Transmit)");
162 static int tcp_do_early_retransmit = 1;
163 SYSCTL_INT(_net_inet_tcp, OID_AUTO, earlyretransmit, CTLFLAG_RW,
164 &tcp_do_early_retransmit, 0, "Early retransmit");
166 int tcp_aggregate_acks = 1;
167 SYSCTL_INT(_net_inet_tcp, OID_AUTO, aggregate_acks, CTLFLAG_RW,
168 &tcp_aggregate_acks, 0, "Aggregate built-up acks into one ack");
170 static int tcp_do_eifel_detect = 1;
171 SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW,
172 &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)");
174 static int tcp_do_abc = 1;
175 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc, CTLFLAG_RW,
177 "TCP Appropriate Byte Counting (RFC 3465)");
180 * The following value actually takes range [25ms, 250ms],
181 * given that most modern systems use 1ms ~ 10ms as the unit
182 * of timestamp option.
184 static u_int tcp_paws_tolerance = 25;
185 SYSCTL_UINT(_net_inet_tcp, OID_AUTO, paws_tolerance, CTLFLAG_RW,
186 &tcp_paws_tolerance, 0, "RFC1323 PAWS tolerance");
189 * Define as tunable for easy testing with SACK on and off.
190 * Warning: do not change setting in the middle of an existing active TCP flow,
191 * else strange things might happen to that flow.
194 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW,
195 &tcp_do_sack, 0, "Enable SACK Algorithms");
197 int tcp_do_smartsack = 1;
198 SYSCTL_INT(_net_inet_tcp, OID_AUTO, smartsack, CTLFLAG_RW,
199 &tcp_do_smartsack, 0, "Enable Smart SACK Algorithms");
201 int tcp_do_rescuesack = 1;
202 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rescuesack, CTLFLAG_RW,
203 &tcp_do_rescuesack, 0, "Rescue retransmission for SACK");
205 int tcp_aggressive_rescuesack = 0;
206 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rescuesack_agg, CTLFLAG_RW,
207 &tcp_aggressive_rescuesack, 0, "Aggressive rescue retransmission for SACK");
209 int tcp_do_rfc3517bis = 0;
210 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3517bis, CTLFLAG_RW,
211 &tcp_do_rfc3517bis, 0, "Enable RFC3517 update");
213 int tcp_rfc3517bis_rxt = 0;
214 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3517bis_rxt, CTLFLAG_RW,
215 &tcp_rfc3517bis_rxt, 0, "Enable RFC3517 retransmit update");
217 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0,
218 "TCP Segment Reassembly Queue");
220 int tcp_reass_maxseg = 0;
221 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD,
222 &tcp_reass_maxseg, 0,
223 "Global maximum number of TCP Segments in Reassembly Queue");
225 int tcp_reass_qsize = 0;
226 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD,
228 "Global number of TCP Segments currently in Reassembly Queue");
230 static int tcp_reass_overflows = 0;
231 SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD,
232 &tcp_reass_overflows, 0,
233 "Global number of TCP Segment Reassembly Queue Overflows");
235 int tcp_do_autorcvbuf = 1;
236 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW,
237 &tcp_do_autorcvbuf, 0, "Enable automatic receive buffer sizing");
239 int tcp_autorcvbuf_inc = 16*1024;
240 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW,
241 &tcp_autorcvbuf_inc, 0,
242 "Incrementor step size of automatic receive buffer");
244 int tcp_autorcvbuf_max = 2*1024*1024;
245 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW,
246 &tcp_autorcvbuf_max, 0, "Max size of automatic receive buffer");
248 int tcp_sosend_agglim = 2;
249 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosend_agglim, CTLFLAG_RW,
250 &tcp_sosend_agglim, 0, "TCP sosend mbuf aggregation limit");
252 int tcp_sosend_async = 1;
253 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosend_async, CTLFLAG_RW,
254 &tcp_sosend_async, 0, "TCP asynchronized pru_send");
256 static int tcp_ignore_redun_dsack = 1;
257 SYSCTL_INT(_net_inet_tcp, OID_AUTO, ignore_redun_dsack, CTLFLAG_RW,
258 &tcp_ignore_redun_dsack, 0, "Ignore redundant DSACK");
260 static void tcp_dooptions(struct tcpopt *, u_char *, int, boolean_t,
262 static void tcp_pulloutofband(struct socket *,
263 struct tcphdr *, struct mbuf *, int);
264 static int tcp_reass(struct tcpcb *, struct tcphdr *, int *,
266 static void tcp_xmit_timer(struct tcpcb *, int, tcp_seq);
267 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *, int);
268 static void tcp_sack_rexmt(struct tcpcb *);
269 static boolean_t tcp_sack_limitedxmit(struct tcpcb *);
270 static int tcp_rmx_msl(const struct tcpcb *);
271 static void tcp_established(struct tcpcb *);
272 static boolean_t tcp_fast_recovery(struct tcpcb *, tcp_seq,
273 const struct tcpopt *);
275 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */
277 #define ND6_HINT(tp) \
279 if ((tp) && (tp)->t_inpcb && \
280 ((tp)->t_inpcb->inp_vflag & INP_IPV6) && \
281 (tp)->t_inpcb->in6p_route.ro_rt) \
282 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \
289 * Indicate whether this ack should be delayed. We can delay the ack if
290 * - delayed acks are enabled and
291 * - there is no delayed ack timer in progress and
292 * - our last ack wasn't a 0-sized window. We never want to delay
293 * the ack that opens up a 0-sized window.
295 #define DELAY_ACK(tp) \
296 (tcp_delack_enabled && !tcp_callout_pending(tp, tp->tt_delack) && \
297 !(tp->t_flags & TF_RXWIN0SENT))
299 #define acceptable_window_update(tp, th, tiwin) \
300 (SEQ_LT(tp->snd_wl1, th->th_seq) || \
301 (tp->snd_wl1 == th->th_seq && \
302 (SEQ_LT(tp->snd_wl2, th->th_ack) || \
303 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))
305 #define iceildiv(n, d) (((n)+(d)-1) / (d))
306 #define need_early_retransmit(tp, ownd) \
307 (tcp_do_early_retransmit && \
308 (tcp_do_eifel_detect && (tp->t_flags & TF_RCVD_TSTMP)) && \
309 ownd < ((tp->t_rxtthresh + 1) * tp->t_maxseg) && \
310 tp->t_dupacks + 1 >= iceildiv(ownd, tp->t_maxseg) && \
311 (!TCP_DO_SACK(tp) || ownd <= tp->t_maxseg || \
312 tcp_sack_has_sacked(&tp->scb, ownd - tp->t_maxseg)))
315 * Returns TRUE, if this segment can be merged with the last
316 * pending segment in the reassemble queue and this segment
317 * does not overlap with the pending segment immediately
318 * preceeding the last pending segment.
320 static __inline boolean_t
321 tcp_paws_canreasslast(const struct tcpcb *tp, const struct tcphdr *th, int tlen)
323 const struct tseg_qent *last, *prev;
325 last = TAILQ_LAST(&tp->t_segq, tsegqe_head);
329 /* This segment comes immediately after the last pending segment */
330 if (last->tqe_th->th_seq + last->tqe_len == th->th_seq)
333 if (th->th_seq + tlen != last->tqe_th->th_seq)
335 /* This segment comes immediately before the last pending segment */
337 prev = TAILQ_PREV(last, tsegqe_head, tqe_q);
340 * No pending preceeding segment, we assume this segment
341 * could be reassembled.
346 /* This segment does not overlap with the preceeding segment */
347 if (SEQ_GEQ(th->th_seq, prev->tqe_th->th_seq + prev->tqe_len))
354 tcp_ncr_update_rxtthresh(struct tcpcb *tp)
356 int old_rxtthresh = tp->t_rxtthresh;
357 uint32_t ownd = tp->snd_max - tp->snd_una;
359 tp->t_rxtthresh = max(3, ((ownd / tp->t_maxseg) >> 1));
360 if (tp->t_rxtthresh != old_rxtthresh) {
361 tcp_sack_update_lostseq(&tp->scb, tp->snd_una,
362 tp->t_maxseg, tp->t_rxtthresh);
367 tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m)
370 struct tseg_qent *p = NULL;
371 struct tseg_qent *te;
372 struct socket *so = tp->t_inpcb->inp_socket;
376 * Call with th == NULL after become established to
377 * force pre-ESTABLISHED data up to user socket.
383 * Limit the number of segments in the reassembly queue to prevent
384 * holding on to too many segments (and thus running out of mbufs).
385 * Make sure to let the missing segment through which caused this
386 * queue. Always keep one global queue entry spare to be able to
387 * process the missing segment.
389 if (th->th_seq != tp->rcv_nxt &&
390 tcp_reass_qsize + 1 >= tcp_reass_maxseg) {
391 tcp_reass_overflows++;
392 tcpstat.tcps_rcvmemdrop++;
394 /* no SACK block to report */
395 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
399 /* Allocate a new queue entry. */
400 te = kmalloc(sizeof(struct tseg_qent), M_TSEGQ, M_INTWAIT | M_NULLOK);
402 tcpstat.tcps_rcvmemdrop++;
404 /* no SACK block to report */
405 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
408 atomic_add_int(&tcp_reass_qsize, 1);
411 * Find a segment which begins after this one does.
413 TAILQ_FOREACH(q, &tp->t_segq, tqe_q) {
414 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
420 * If there is a preceding segment, it may provide some of
421 * our data already. If so, drop the data from the incoming
422 * segment. If it provides all of our data, drop us.
427 /* conversion to int (in i) handles seq wraparound */
428 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
429 if (i > 0) { /* overlaps preceding segment */
431 (TSACK_F_DUPSEG | TSACK_F_ENCLOSESEG);
432 /* enclosing block starts w/ preceding segment */
433 tp->encloseblk.rblk_start = p->tqe_th->th_seq;
435 /* preceding encloses incoming segment */
436 tp->encloseblk.rblk_end = TCP_SACK_BLKEND(
437 p->tqe_th->th_seq + p->tqe_len,
438 p->tqe_th->th_flags);
439 tcpstat.tcps_rcvduppack++;
440 tcpstat.tcps_rcvdupbyte += *tlenp;
443 atomic_add_int(&tcp_reass_qsize, -1);
445 * Try to present any queued data
446 * at the left window edge to the user.
447 * This is needed after the 3-WHS
450 goto present; /* ??? */
455 /* incoming segment end is enclosing block end */
456 tp->encloseblk.rblk_end = TCP_SACK_BLKEND(
457 th->th_seq + *tlenp, th->th_flags);
458 /* trim end of reported D-SACK block */
459 tp->reportblk.rblk_end = th->th_seq;
462 tcpstat.tcps_rcvoopack++;
463 tcpstat.tcps_rcvoobyte += *tlenp;
466 * While we overlap succeeding segments trim them or,
467 * if they are completely covered, dequeue them.
470 tcp_seq_diff_t i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
471 tcp_seq qend = q->tqe_th->th_seq + q->tqe_len;
472 tcp_seq qend_sack = TCP_SACK_BLKEND(qend, q->tqe_th->th_flags);
473 struct tseg_qent *nq;
477 if (!(tp->sack_flags & TSACK_F_DUPSEG)) {
478 /* first time through */
479 tp->sack_flags |= (TSACK_F_DUPSEG | TSACK_F_ENCLOSESEG);
480 tp->encloseblk = tp->reportblk;
481 /* report trailing duplicate D-SACK segment */
482 tp->reportblk.rblk_start = q->tqe_th->th_seq;
484 if ((tp->sack_flags & TSACK_F_ENCLOSESEG) &&
485 SEQ_GT(qend_sack, tp->encloseblk.rblk_end)) {
486 /* extend enclosing block if one exists */
487 tp->encloseblk.rblk_end = qend_sack;
489 if (i < q->tqe_len) {
490 q->tqe_th->th_seq += i;
496 nq = TAILQ_NEXT(q, tqe_q);
497 TAILQ_REMOVE(&tp->t_segq, q, tqe_q);
500 atomic_add_int(&tcp_reass_qsize, -1);
504 /* Insert the new segment queue entry into place. */
507 te->tqe_len = *tlenp;
509 /* check if can coalesce with following segment */
510 if (q != NULL && (th->th_seq + *tlenp == q->tqe_th->th_seq)) {
511 tcp_seq tend = te->tqe_th->th_seq + te->tqe_len;
512 tcp_seq tend_sack = TCP_SACK_BLKEND(tend, te->tqe_th->th_flags);
514 te->tqe_len += q->tqe_len;
515 if (q->tqe_th->th_flags & TH_FIN)
516 te->tqe_th->th_flags |= TH_FIN;
517 m_cat(te->tqe_m, q->tqe_m);
518 tp->encloseblk.rblk_end = tend_sack;
520 * When not reporting a duplicate segment, use
521 * the larger enclosing block as the SACK block.
523 if (!(tp->sack_flags & TSACK_F_DUPSEG))
524 tp->reportblk.rblk_end = tend_sack;
525 TAILQ_REMOVE(&tp->t_segq, q, tqe_q);
527 atomic_add_int(&tcp_reass_qsize, -1);
531 TAILQ_INSERT_HEAD(&tp->t_segq, te, tqe_q);
533 /* check if can coalesce with preceding segment */
534 if (p->tqe_th->th_seq + p->tqe_len == th->th_seq) {
535 p->tqe_len += te->tqe_len;
536 m_cat(p->tqe_m, te->tqe_m);
537 tp->encloseblk.rblk_start = p->tqe_th->th_seq;
539 * When not reporting a duplicate segment, use
540 * the larger enclosing block as the SACK block.
542 if (!(tp->sack_flags & TSACK_F_DUPSEG))
543 tp->reportblk.rblk_start = p->tqe_th->th_seq;
545 atomic_add_int(&tcp_reass_qsize, -1);
547 TAILQ_INSERT_AFTER(&tp->t_segq, p, te, tqe_q);
553 * Present data to user, advancing rcv_nxt through
554 * completed sequence space.
556 if (!TCPS_HAVEESTABLISHED(tp->t_state))
558 q = TAILQ_FIRST(&tp->t_segq);
559 if (q == NULL || q->tqe_th->th_seq != tp->rcv_nxt)
561 tp->rcv_nxt += q->tqe_len;
562 if (!(tp->sack_flags & TSACK_F_DUPSEG)) {
563 /* no SACK block to report since ACK advanced */
564 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
566 /* no enclosing block to report since ACK advanced */
567 tp->sack_flags &= ~TSACK_F_ENCLOSESEG;
568 flags = q->tqe_th->th_flags & TH_FIN;
569 TAILQ_REMOVE(&tp->t_segq, q, tqe_q);
570 KASSERT(TAILQ_EMPTY(&tp->t_segq) ||
571 TAILQ_FIRST(&tp->t_segq)->tqe_th->th_seq != tp->rcv_nxt,
572 ("segment not coalesced"));
573 if (so->so_state & SS_CANTRCVMORE) {
576 lwkt_gettoken(&so->so_rcv.ssb_token);
577 ssb_appendstream(&so->so_rcv, q->tqe_m);
578 lwkt_reltoken(&so->so_rcv.ssb_token);
581 atomic_add_int(&tcp_reass_qsize, -1);
588 * TCP input routine, follows pages 65-76 of the
589 * protocol specification dated September, 1981 very closely.
593 tcp6_input(struct mbuf **mp, int *offp, int proto)
595 struct mbuf *m = *mp;
596 struct in6_ifaddr *ia6;
598 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE);
601 * draft-itojun-ipv6-tcp-to-anycast
602 * better place to put this in?
604 ia6 = ip6_getdstifaddr(m);
605 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) {
608 ip6 = mtod(m, struct ip6_hdr *);
609 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
610 offsetof(struct ip6_hdr, ip6_dst));
611 return (IPPROTO_DONE);
614 tcp_input(mp, offp, proto);
615 return (IPPROTO_DONE);
620 tcp_input(struct mbuf **mp, int *offp, int proto)
624 struct ip *ip = NULL;
626 struct inpcb *inp = NULL;
632 struct tcpcb *tp = NULL;
634 struct socket *so = NULL;
636 boolean_t ourfinisacked, needoutput = FALSE, delayed_dupack = FALSE;
637 tcp_seq th_dupack = 0; /* XXX gcc warning */
640 struct tcpopt to; /* options in this segment */
641 struct sockaddr_in *next_hop = NULL;
642 int rstreason; /* For badport_bandlim accounting purposes */
644 struct ip6_hdr *ip6 = NULL;
649 const boolean_t isipv6 = FALSE;
659 tcpstat.tcps_rcvtotal++;
661 if (m->m_pkthdr.fw_flags & IPFORWARD_MBUF_TAGGED) {
664 mtag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL);
665 KKASSERT(mtag != NULL);
666 next_hop = m_tag_data(mtag);
670 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE;
674 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */
675 ip6 = mtod(m, struct ip6_hdr *);
676 tlen = (sizeof *ip6) + ntohs(ip6->ip6_plen) - off0;
677 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) {
678 tcpstat.tcps_rcvbadsum++;
681 th = (struct tcphdr *)((caddr_t)ip6 + off0);
684 * Be proactive about unspecified IPv6 address in source.
685 * As we use all-zero to indicate unbounded/unconnected pcb,
686 * unspecified IPv6 address can be used to confuse us.
688 * Note that packets with unspecified IPv6 destination is
689 * already dropped in ip6_input.
691 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
697 * Get IP and TCP header together in first mbuf.
698 * Note: IP leaves IP header in first mbuf.
700 if (off0 > sizeof(struct ip)) {
702 off0 = sizeof(struct ip);
704 /* already checked and pulled up in ip_demux() */
705 KASSERT(m->m_len >= sizeof(struct tcpiphdr),
706 ("TCP header not in one mbuf: m->m_len %d", m->m_len));
707 ip = mtod(m, struct ip *);
708 ipov = (struct ipovly *)ip;
709 th = (struct tcphdr *)((caddr_t)ip + off0);
712 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
713 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
714 th->th_sum = m->m_pkthdr.csum_data;
716 th->th_sum = in_pseudo(ip->ip_src.s_addr,
718 htonl(m->m_pkthdr.csum_data +
721 th->th_sum ^= 0xffff;
724 * Checksum extended TCP header and data.
726 len = sizeof(struct ip) + tlen;
727 bzero(ipov->ih_x1, sizeof ipov->ih_x1);
728 ipov->ih_len = (u_short)tlen;
729 ipov->ih_len = htons(ipov->ih_len);
730 th->th_sum = in_cksum(m, len);
733 tcpstat.tcps_rcvbadsum++;
737 /* Re-initialization for later version check */
738 ip->ip_v = IPVERSION;
743 * Check that TCP offset makes sense,
744 * pull out TCP options and adjust length. XXX
746 off = th->th_off << 2;
747 /* already checked and pulled up in ip_demux() */
748 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen,
749 ("bad TCP data offset %d (tlen %d)", off, tlen));
750 tlen -= off; /* tlen is used instead of ti->ti_len */
751 if (off > sizeof(struct tcphdr)) {
753 IP6_EXTHDR_CHECK(m, off0, off, IPPROTO_DONE);
754 ip6 = mtod(m, struct ip6_hdr *);
755 th = (struct tcphdr *)((caddr_t)ip6 + off0);
757 /* already pulled up in ip_demux() */
758 KASSERT(m->m_len >= sizeof(struct ip) + off,
759 ("TCP header and options not in one mbuf: "
760 "m_len %d, off %d", m->m_len, off));
762 optlen = off - sizeof(struct tcphdr);
763 optp = (u_char *)(th + 1);
765 thflags = th->th_flags;
767 #ifdef TCP_DROP_SYNFIN
769 * If the drop_synfin option is enabled, drop all packets with
770 * both the SYN and FIN bits set. This prevents e.g. nmap from
771 * identifying the TCP/IP stack.
773 * This is a violation of the TCP specification.
775 if (drop_synfin && (thflags & (TH_SYN | TH_FIN)) == (TH_SYN | TH_FIN))
780 * Convert TCP protocol specific fields to host format.
782 th->th_seq = ntohl(th->th_seq);
783 th->th_ack = ntohl(th->th_ack);
784 th->th_win = ntohs(th->th_win);
785 th->th_urp = ntohs(th->th_urp);
788 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options,
789 * until after ip6_savecontrol() is called and before other functions
790 * which don't want those proto headers.
791 * Because ip6_savecontrol() is going to parse the mbuf to
792 * search for data to be passed up to user-land, it wants mbuf
793 * parameters to be unchanged.
794 * XXX: the call of ip6_savecontrol() has been obsoleted based on
795 * latest version of the advanced API (20020110).
797 drop_hdrlen = off0 + off;
800 * Locate pcb for segment.
803 /* IPFIREWALL_FORWARD section */
804 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */
806 * Transparently forwarded. Pretend to be the destination.
807 * already got one like this?
809 cpu = mycpu->gd_cpuid;
810 inp = in_pcblookup_hash(&tcbinfo[cpu],
811 ip->ip_src, th->th_sport,
812 ip->ip_dst, th->th_dport,
813 0, m->m_pkthdr.rcvif);
816 * It's new. Try to find the ambushing socket.
820 * The rest of the ipfw code stores the port in
822 * (The IP address is still in network order.)
824 in_port_t dport = next_hop->sin_port ?
825 htons(next_hop->sin_port) :
828 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport,
829 next_hop->sin_addr.s_addr, dport);
830 inp = in_pcblookup_hash(&tcbinfo[cpu],
831 ip->ip_src, th->th_sport,
832 next_hop->sin_addr, dport,
833 1, m->m_pkthdr.rcvif);
837 inp = in6_pcblookup_hash(&tcbinfo[0],
838 &ip6->ip6_src, th->th_sport,
839 &ip6->ip6_dst, th->th_dport,
840 1, m->m_pkthdr.rcvif);
842 cpu = mycpu->gd_cpuid;
843 inp = in_pcblookup_hash(&tcbinfo[cpu],
844 ip->ip_src, th->th_sport,
845 ip->ip_dst, th->th_dport,
846 1, m->m_pkthdr.rcvif);
851 * If the state is CLOSED (i.e., TCB does not exist) then
852 * all data in the incoming segment is discarded.
853 * If the TCB exists but is in CLOSED state, it is embryonic,
854 * but should either do a listen or a connect soon.
859 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2];
861 char dbuf[sizeof "aaa.bbb.ccc.ddd"];
862 char sbuf[sizeof "aaa.bbb.ccc.ddd"];
866 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst));
869 strcat(sbuf, ip6_sprintf(&ip6->ip6_src));
872 strcpy(dbuf, inet_ntoa(ip->ip_dst));
873 strcpy(sbuf, inet_ntoa(ip->ip_src));
875 switch (log_in_vain) {
877 if (!(thflags & TH_SYN))
881 "Connection attempt to TCP %s:%d "
882 "from %s:%d flags:0x%02x\n",
883 dbuf, ntohs(th->th_dport), sbuf,
884 ntohs(th->th_sport), thflags);
893 if (thflags & TH_SYN)
902 rstreason = BANDLIM_RST_CLOSEDPORT;
908 if (ipsec6_in_reject_so(m, inp->inp_socket)) {
909 ipsec6stat.in_polvio++;
913 if (ipsec4_in_reject_so(m, inp->inp_socket)) {
914 ipsecstat.in_polvio++;
921 if (ipsec6_in_reject(m, inp))
924 if (ipsec4_in_reject(m, inp))
928 /* Check the minimum TTL for socket. */
930 if ((isipv6 ? ip6->ip6_hlim : ip->ip_ttl) < inp->inp_ip_minttl)
936 rstreason = BANDLIM_RST_CLOSEDPORT;
939 if (tp->t_state <= TCPS_CLOSED)
942 so = inp->inp_socket;
945 if (so->so_options & SO_DEBUG) {
946 ostate = tp->t_state;
948 bcopy(ip6, tcp_saveipgen, sizeof(*ip6));
950 bcopy(ip, tcp_saveipgen, sizeof(*ip));
955 bzero(&to, sizeof to);
957 if (so->so_options & SO_ACCEPTCONN) {
958 struct in_conninfo inc;
961 inc.inc_isipv6 = (isipv6 == TRUE);
964 inc.inc6_faddr = ip6->ip6_src;
965 inc.inc6_laddr = ip6->ip6_dst;
966 inc.inc6_route.ro_rt = NULL; /* XXX */
968 inc.inc_faddr = ip->ip_src;
969 inc.inc_laddr = ip->ip_dst;
970 inc.inc_route.ro_rt = NULL; /* XXX */
972 inc.inc_fport = th->th_sport;
973 inc.inc_lport = th->th_dport;
976 * If the state is LISTEN then ignore segment if it contains
977 * a RST. If the segment contains an ACK then it is bad and
978 * send a RST. If it does not contain a SYN then it is not
979 * interesting; drop it.
981 * If the state is SYN_RECEIVED (syncache) and seg contains
982 * an ACK, but not for our SYN/ACK, send a RST. If the seg
983 * contains a RST, check the sequence number to see if it
984 * is a valid reset segment.
986 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) != TH_SYN) {
987 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) == TH_ACK) {
988 if (!syncache_expand(&inc, th, &so, m)) {
990 * No syncache entry, or ACK was not
991 * for our SYN/ACK. Send a RST.
993 tcpstat.tcps_badsyn++;
994 rstreason = BANDLIM_RST_OPENPORT;
999 * Could not complete 3-way handshake,
1000 * connection is being closed down, and
1001 * syncache will free mbuf.
1004 return(IPPROTO_DONE);
1007 * We must be in the correct protocol thread
1008 * for this connection.
1010 KKASSERT(so->so_port == &curthread->td_msgport);
1013 * Socket is created in state SYN_RECEIVED.
1014 * Continue processing segment.
1017 tp = intotcpcb(inp);
1019 * This is what would have happened in
1020 * tcp_output() when the SYN,ACK was sent.
1022 tp->snd_up = tp->snd_una;
1023 tp->snd_max = tp->snd_nxt = tp->iss + 1;
1024 tp->last_ack_sent = tp->rcv_nxt;
1028 if (thflags & TH_RST) {
1029 syncache_chkrst(&inc, th);
1032 if (thflags & TH_ACK) {
1033 syncache_badack(&inc);
1034 tcpstat.tcps_badsyn++;
1035 rstreason = BANDLIM_RST_OPENPORT;
1042 * Segment's flags are (SYN) or (SYN | FIN).
1046 * If deprecated address is forbidden,
1047 * we do not accept SYN to deprecated interface
1048 * address to prevent any new inbound connection from
1049 * getting established.
1050 * When we do not accept SYN, we send a TCP RST,
1051 * with deprecated source address (instead of dropping
1052 * it). We compromise it as it is much better for peer
1053 * to send a RST, and RST will be the final packet
1056 * If we do not forbid deprecated addresses, we accept
1057 * the SYN packet. RFC2462 does not suggest dropping
1059 * If we decipher RFC2462 5.5.4, it says like this:
1060 * 1. use of deprecated addr with existing
1061 * communication is okay - "SHOULD continue to be
1063 * 2. use of it with new communication:
1064 * (2a) "SHOULD NOT be used if alternate address
1065 * with sufficient scope is available"
1066 * (2b) nothing mentioned otherwise.
1067 * Here we fall into (2b) case as we have no choice in
1068 * our source address selection - we must obey the peer.
1070 * The wording in RFC2462 is confusing, and there are
1071 * multiple description text for deprecated address
1072 * handling - worse, they are not exactly the same.
1073 * I believe 5.5.4 is the best one, so we follow 5.5.4.
1075 if (isipv6 && !ip6_use_deprecated) {
1076 struct in6_ifaddr *ia6;
1078 if ((ia6 = ip6_getdstifaddr(m)) &&
1079 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
1081 rstreason = BANDLIM_RST_OPENPORT;
1087 * If it is from this socket, drop it, it must be forged.
1088 * Don't bother responding if the destination was a broadcast.
1090 if (th->th_dport == th->th_sport) {
1092 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst,
1096 if (ip->ip_dst.s_addr == ip->ip_src.s_addr)
1101 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN
1103 * Note that it is quite possible to receive unicast
1104 * link-layer packets with a broadcast IP address. Use
1105 * in_broadcast() to find them.
1107 if (m->m_flags & (M_BCAST | M_MCAST))
1110 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
1111 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
1114 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
1115 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
1116 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
1117 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
1121 * SYN appears to be valid; create compressed TCP state
1122 * for syncache, or perform t/tcp connection.
1124 if (so->so_qlen <= so->so_qlimit) {
1125 tcp_dooptions(&to, optp, optlen, TRUE, th->th_ack);
1126 if (!syncache_add(&inc, &to, th, so, m))
1130 * Entry added to syncache, mbuf used to
1131 * send SYN,ACK packet.
1133 return(IPPROTO_DONE);
1140 * Should not happen - syncache should pick up these connections.
1142 * Once we are past handling listen sockets we must be in the
1143 * correct protocol processing thread.
1145 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN state"));
1146 KKASSERT(so->so_port == &curthread->td_msgport);
1148 /* Unscale the window into a 32-bit value. */
1149 if (!(thflags & TH_SYN))
1150 tiwin = th->th_win << tp->snd_scale;
1155 * This is the second part of the MSS DoS prevention code (after
1156 * minmss on the sending side) and it deals with too many too small
1157 * tcp packets in a too short timeframe (1 second).
1159 * XXX Removed. This code was crap. It does not scale to network
1160 * speed, and default values break NFS. Gone.
1165 * Segment received on connection.
1167 * Reset idle time and keep-alive timer. Don't waste time if less
1168 * then a second has elapsed.
1170 if ((int)(ticks - tp->t_rcvtime) > hz)
1171 tcp_timer_keep_activity(tp, thflags);
1175 * XXX this is tradtitional behavior, may need to be cleaned up.
1177 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0, th->th_ack);
1178 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) {
1179 if ((to.to_flags & TOF_SCALE) && (tp->t_flags & TF_REQ_SCALE)) {
1180 tp->t_flags |= TF_RCVD_SCALE;
1181 tp->snd_scale = to.to_requested_s_scale;
1185 * Initial send window; will be updated upon next ACK
1187 tp->snd_wnd = th->th_win;
1189 if (to.to_flags & TOF_TS) {
1190 tp->t_flags |= TF_RCVD_TSTMP;
1191 tp->ts_recent = to.to_tsval;
1192 tp->ts_recent_age = ticks;
1194 if (!(to.to_flags & TOF_MSS))
1196 tcp_mss(tp, to.to_mss);
1198 * Only set the TF_SACK_PERMITTED per-connection flag
1199 * if we got a SACK_PERMITTED option from the other side
1200 * and the global tcp_do_sack variable is true.
1202 if (tcp_do_sack && (to.to_flags & TOF_SACK_PERMITTED))
1203 tp->t_flags |= TF_SACK_PERMITTED;
1207 * Header prediction: check for the two common cases
1208 * of a uni-directional data xfer. If the packet has
1209 * no control flags, is in-sequence, the window didn't
1210 * change and we're not retransmitting, it's a
1211 * candidate. If the length is zero and the ack moved
1212 * forward, we're the sender side of the xfer. Just
1213 * free the data acked & wake any higher level process
1214 * that was blocked waiting for space. If the length
1215 * is non-zero and the ack didn't move, we're the
1216 * receiver side. If we're getting packets in-order
1217 * (the reassembly queue is empty), add the data to
1218 * the socket buffer and note that we need a delayed ack.
1219 * Make sure that the hidden state-flags are also off.
1220 * Since we check for TCPS_ESTABLISHED above, it can only
1223 if (tp->t_state == TCPS_ESTABLISHED &&
1224 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
1225 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) &&
1226 (!(to.to_flags & TOF_TS) ||
1227 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) &&
1228 th->th_seq == tp->rcv_nxt &&
1229 tp->snd_nxt == tp->snd_max) {
1232 * If last ACK falls within this segment's sequence numbers,
1233 * record the timestamp.
1234 * NOTE that the test is modified according to the latest
1235 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1237 if ((to.to_flags & TOF_TS) &&
1238 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
1239 tp->ts_recent_age = ticks;
1240 tp->ts_recent = to.to_tsval;
1244 if (SEQ_GT(th->th_ack, tp->snd_una) &&
1245 SEQ_LEQ(th->th_ack, tp->snd_max) &&
1246 tp->snd_cwnd >= tp->snd_wnd &&
1247 !IN_FASTRECOVERY(tp)) {
1249 * This is a pure ack for outstanding data.
1251 ++tcpstat.tcps_predack;
1253 * "bad retransmit" recovery
1255 * If Eifel detection applies, then
1256 * it is deterministic, so use it
1257 * unconditionally over the old heuristic.
1258 * Otherwise, fall back to the old heuristic.
1260 if (tcp_do_eifel_detect &&
1261 (to.to_flags & TOF_TS) && to.to_tsecr &&
1262 (tp->rxt_flags & TRXT_F_FIRSTACCACK)) {
1263 /* Eifel detection applicable. */
1264 if (to.to_tsecr < tp->t_rexmtTS) {
1265 tcp_revert_congestion_state(tp);
1266 ++tcpstat.tcps_eifeldetected;
1267 if (tp->t_rxtshift != 1 ||
1268 ticks >= tp->t_badrxtwin)
1269 ++tcpstat.tcps_rttcantdetect;
1271 } else if (tp->t_rxtshift == 1 &&
1272 ticks < tp->t_badrxtwin) {
1273 tcp_revert_congestion_state(tp);
1274 ++tcpstat.tcps_rttdetected;
1276 tp->rxt_flags &= ~(TRXT_F_FIRSTACCACK |
1277 TRXT_F_FASTREXMT | TRXT_F_EARLYREXMT);
1279 * Recalculate the retransmit timer / rtt.
1281 * Some machines (certain windows boxes)
1282 * send broken timestamp replies during the
1283 * SYN+ACK phase, ignore timestamps of 0.
1285 if ((to.to_flags & TOF_TS) && to.to_tsecr) {
1287 ticks - to.to_tsecr + 1,
1289 } else if (tp->t_rtttime &&
1290 SEQ_GT(th->th_ack, tp->t_rtseq)) {
1292 ticks - tp->t_rtttime,
1295 tcp_xmit_bandwidth_limit(tp, th->th_ack);
1296 acked = th->th_ack - tp->snd_una;
1297 tcpstat.tcps_rcvackpack++;
1298 tcpstat.tcps_rcvackbyte += acked;
1299 sbdrop(&so->so_snd.sb, acked);
1300 tp->snd_recover = th->th_ack - 1;
1301 tp->snd_una = th->th_ack;
1304 * Update window information.
1306 if (tiwin != tp->snd_wnd &&
1307 acceptable_window_update(tp, th, tiwin)) {
1308 /* keep track of pure window updates */
1309 if (tp->snd_wl2 == th->th_ack &&
1310 tiwin > tp->snd_wnd)
1311 tcpstat.tcps_rcvwinupd++;
1312 tp->snd_wnd = tiwin;
1313 tp->snd_wl1 = th->th_seq;
1314 tp->snd_wl2 = th->th_ack;
1315 if (tp->snd_wnd > tp->max_sndwnd)
1316 tp->max_sndwnd = tp->snd_wnd;
1319 ND6_HINT(tp); /* some progress has been done */
1321 * If all outstanding data are acked, stop
1322 * retransmit timer, otherwise restart timer
1323 * using current (possibly backed-off) value.
1324 * If process is waiting for space,
1325 * wakeup/selwakeup/signal. If data
1326 * are ready to send, let tcp_output
1327 * decide between more output or persist.
1329 if (tp->snd_una == tp->snd_max) {
1330 tcp_callout_stop(tp, tp->tt_rexmt);
1331 } else if (!tcp_callout_active(tp,
1333 tcp_callout_reset(tp, tp->tt_rexmt,
1334 tp->t_rxtcur, tcp_timer_rexmt);
1337 if (so->so_snd.ssb_cc > 0)
1339 return(IPPROTO_DONE);
1341 } else if (tiwin == tp->snd_wnd &&
1342 th->th_ack == tp->snd_una &&
1343 TAILQ_EMPTY(&tp->t_segq) &&
1344 tlen <= ssb_space(&so->so_rcv)) {
1345 u_long newsize = 0; /* automatic sockbuf scaling */
1347 * This is a pure, in-sequence data packet
1348 * with nothing on the reassembly queue and
1349 * we have enough buffer space to take it.
1351 ++tcpstat.tcps_preddat;
1352 tp->rcv_nxt += tlen;
1353 tcpstat.tcps_rcvpack++;
1354 tcpstat.tcps_rcvbyte += tlen;
1355 ND6_HINT(tp); /* some progress has been done */
1357 * Automatic sizing of receive socket buffer. Often the send
1358 * buffer size is not optimally adjusted to the actual network
1359 * conditions at hand (delay bandwidth product). Setting the
1360 * buffer size too small limits throughput on links with high
1361 * bandwidth and high delay (eg. trans-continental/oceanic links).
1363 * On the receive side the socket buffer memory is only rarely
1364 * used to any significant extent. This allows us to be much
1365 * more aggressive in scaling the receive socket buffer. For
1366 * the case that the buffer space is actually used to a large
1367 * extent and we run out of kernel memory we can simply drop
1368 * the new segments; TCP on the sender will just retransmit it
1369 * later. Setting the buffer size too big may only consume too
1370 * much kernel memory if the application doesn't read() from
1371 * the socket or packet loss or reordering makes use of the
1374 * The criteria to step up the receive buffer one notch are:
1375 * 1. the number of bytes received during the time it takes
1376 * one timestamp to be reflected back to us (the RTT);
1377 * 2. received bytes per RTT is within seven eighth of the
1378 * current socket buffer size;
1379 * 3. receive buffer size has not hit maximal automatic size;
1381 * This algorithm does one step per RTT at most and only if
1382 * we receive a bulk stream w/o packet losses or reorderings.
1383 * Shrinking the buffer during idle times is not necessary as
1384 * it doesn't consume any memory when idle.
1386 * TODO: Only step up if the application is actually serving
1387 * the buffer to better manage the socket buffer resources.
1389 if (tcp_do_autorcvbuf &&
1391 (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) {
1392 if (to.to_tsecr > tp->rfbuf_ts &&
1393 to.to_tsecr - tp->rfbuf_ts < hz) {
1395 (so->so_rcv.ssb_hiwat / 8 * 7) &&
1396 so->so_rcv.ssb_hiwat <
1397 tcp_autorcvbuf_max) {
1399 ulmin(so->so_rcv.ssb_hiwat +
1401 tcp_autorcvbuf_max);
1403 /* Start over with next RTT. */
1407 tp->rfbuf_cnt += tlen; /* add up */
1410 * Add data to socket buffer.
1412 if (so->so_state & SS_CANTRCVMORE) {
1416 * Set new socket buffer size, give up when
1419 * Adjusting the size can mess up ACK
1420 * sequencing when pure window updates are
1421 * being avoided (which is the default),
1424 lwkt_gettoken(&so->so_rcv.ssb_token);
1426 tp->t_flags |= TF_RXRESIZED;
1427 if (!ssb_reserve(&so->so_rcv, newsize,
1429 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE);
1432 (TCP_MAXWIN << tp->rcv_scale)) {
1433 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE);
1436 m_adj(m, drop_hdrlen); /* delayed header drop */
1437 ssb_appendstream(&so->so_rcv, m);
1438 lwkt_reltoken(&so->so_rcv.ssb_token);
1442 * This code is responsible for most of the ACKs
1443 * the TCP stack sends back after receiving a data
1444 * packet. Note that the DELAY_ACK check fails if
1445 * the delack timer is already running, which results
1446 * in an ack being sent every other packet (which is
1449 * We then further aggregate acks by not actually
1450 * sending one until the protocol thread has completed
1451 * processing the current backlog of packets. This
1452 * does not delay the ack any further, but allows us
1453 * to take advantage of the packet aggregation that
1454 * high speed NICs do (usually blocks of 8-10 packets)
1455 * to send a single ack rather then four or five acks,
1456 * greatly reducing the ack rate, the return channel
1457 * bandwidth, and the protocol overhead on both ends.
1459 * Since this also has the effect of slowing down
1460 * the exponential slow-start ramp-up, systems with
1461 * very large bandwidth-delay products might want
1462 * to turn the feature off.
1464 if (DELAY_ACK(tp)) {
1465 tcp_callout_reset(tp, tp->tt_delack,
1466 tcp_delacktime, tcp_timer_delack);
1467 } else if (tcp_aggregate_acks) {
1468 tp->t_flags |= TF_ACKNOW;
1469 if (!(tp->t_flags & TF_ONOUTPUTQ)) {
1470 tp->t_flags |= TF_ONOUTPUTQ;
1471 tp->tt_cpu = mycpu->gd_cpuid;
1473 &tcpcbackq[tp->tt_cpu],
1477 tp->t_flags |= TF_ACKNOW;
1480 return(IPPROTO_DONE);
1485 * Calculate amount of space in receive window,
1486 * and then do TCP input processing.
1487 * Receive window is amount of space in rcv queue,
1488 * but not less than advertised window.
1490 recvwin = ssb_space(&so->so_rcv);
1493 tp->rcv_wnd = imax(recvwin, (int)(tp->rcv_adv - tp->rcv_nxt));
1495 /* Reset receive buffer auto scaling when not in bulk receive mode. */
1499 switch (tp->t_state) {
1501 * If the state is SYN_RECEIVED:
1502 * if seg contains an ACK, but not for our SYN/ACK, send a RST.
1504 case TCPS_SYN_RECEIVED:
1505 if ((thflags & TH_ACK) &&
1506 (SEQ_LEQ(th->th_ack, tp->snd_una) ||
1507 SEQ_GT(th->th_ack, tp->snd_max))) {
1508 rstreason = BANDLIM_RST_OPENPORT;
1514 * If the state is SYN_SENT:
1515 * if seg contains an ACK, but not for our SYN, drop the input.
1516 * if seg contains a RST, then drop the connection.
1517 * if seg does not contain SYN, then drop it.
1518 * Otherwise this is an acceptable SYN segment
1519 * initialize tp->rcv_nxt and tp->irs
1520 * if seg contains ack then advance tp->snd_una
1521 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state
1522 * arrange for segment to be acked (eventually)
1523 * continue processing rest of data/controls, beginning with URG
1526 if ((thflags & TH_ACK) &&
1527 (SEQ_LEQ(th->th_ack, tp->iss) ||
1528 SEQ_GT(th->th_ack, tp->snd_max))) {
1529 rstreason = BANDLIM_UNLIMITED;
1532 if (thflags & TH_RST) {
1533 if (thflags & TH_ACK)
1534 tp = tcp_drop(tp, ECONNREFUSED);
1537 if (!(thflags & TH_SYN))
1540 tp->irs = th->th_seq;
1542 if (thflags & TH_ACK) {
1543 /* Our SYN was acked. */
1544 tcpstat.tcps_connects++;
1546 /* Do window scaling on this connection? */
1547 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) ==
1548 (TF_RCVD_SCALE | TF_REQ_SCALE))
1549 tp->rcv_scale = tp->request_r_scale;
1550 tp->rcv_adv += tp->rcv_wnd;
1551 tp->snd_una++; /* SYN is acked */
1552 tcp_callout_stop(tp, tp->tt_rexmt);
1554 * If there's data, delay ACK; if there's also a FIN
1555 * ACKNOW will be turned on later.
1557 if (DELAY_ACK(tp) && tlen != 0) {
1558 tcp_callout_reset(tp, tp->tt_delack,
1559 tcp_delacktime, tcp_timer_delack);
1561 tp->t_flags |= TF_ACKNOW;
1564 * Received <SYN,ACK> in SYN_SENT[*] state.
1566 * SYN_SENT --> ESTABLISHED
1567 * SYN_SENT* --> FIN_WAIT_1
1569 tp->t_starttime = ticks;
1570 if (tp->t_flags & TF_NEEDFIN) {
1571 tp->t_state = TCPS_FIN_WAIT_1;
1572 tp->t_flags &= ~TF_NEEDFIN;
1575 tcp_established(tp);
1579 * Received initial SYN in SYN-SENT[*] state =>
1580 * simultaneous open.
1581 * Do 3-way handshake:
1582 * SYN-SENT -> SYN-RECEIVED
1583 * SYN-SENT* -> SYN-RECEIVED*
1585 tp->t_flags |= TF_ACKNOW;
1586 tcp_callout_stop(tp, tp->tt_rexmt);
1587 tp->t_state = TCPS_SYN_RECEIVED;
1591 * Advance th->th_seq to correspond to first data byte.
1592 * If data, trim to stay within window,
1593 * dropping FIN if necessary.
1596 if (tlen > tp->rcv_wnd) {
1597 todrop = tlen - tp->rcv_wnd;
1601 tcpstat.tcps_rcvpackafterwin++;
1602 tcpstat.tcps_rcvbyteafterwin += todrop;
1604 tp->snd_wl1 = th->th_seq - 1;
1605 tp->rcv_up = th->th_seq;
1607 * Client side of transaction: already sent SYN and data.
1608 * If the remote host used T/TCP to validate the SYN,
1609 * our data will be ACK'd; if so, enter normal data segment
1610 * processing in the middle of step 5, ack processing.
1611 * Otherwise, goto step 6.
1613 if (thflags & TH_ACK)
1619 * If the state is LAST_ACK or CLOSING or TIME_WAIT:
1620 * do normal processing (we no longer bother with T/TCP).
1624 case TCPS_TIME_WAIT:
1625 break; /* continue normal processing */
1629 * States other than LISTEN or SYN_SENT.
1630 * First check the RST flag and sequence number since reset segments
1631 * are exempt from the timestamp and connection count tests. This
1632 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix
1633 * below which allowed reset segments in half the sequence space
1634 * to fall though and be processed (which gives forged reset
1635 * segments with a random sequence number a 50 percent chance of
1636 * killing a connection).
1637 * Then check timestamp, if present.
1638 * Then check the connection count, if present.
1639 * Then check that at least some bytes of segment are within
1640 * receive window. If segment begins before rcv_nxt,
1641 * drop leading data (and SYN); if nothing left, just ack.
1644 * If the RST bit is set, check the sequence number to see
1645 * if this is a valid reset segment.
1647 * In all states except SYN-SENT, all reset (RST) segments
1648 * are validated by checking their SEQ-fields. A reset is
1649 * valid if its sequence number is in the window.
1650 * Note: this does not take into account delayed ACKs, so
1651 * we should test against last_ack_sent instead of rcv_nxt.
1652 * The sequence number in the reset segment is normally an
1653 * echo of our outgoing acknowledgement numbers, but some hosts
1654 * send a reset with the sequence number at the rightmost edge
1655 * of our receive window, and we have to handle this case.
1656 * If we have multiple segments in flight, the intial reset
1657 * segment sequence numbers will be to the left of last_ack_sent,
1658 * but they will eventually catch up.
1659 * In any case, it never made sense to trim reset segments to
1660 * fit the receive window since RFC 1122 says:
1661 * 4.2.2.12 RST Segment: RFC-793 Section 3.4
1663 * A TCP SHOULD allow a received RST segment to include data.
1666 * It has been suggested that a RST segment could contain
1667 * ASCII text that encoded and explained the cause of the
1668 * RST. No standard has yet been established for such
1671 * If the reset segment passes the sequence number test examine
1673 * SYN_RECEIVED STATE:
1674 * If passive open, return to LISTEN state.
1675 * If active open, inform user that connection was refused.
1676 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES:
1677 * Inform user that connection was reset, and close tcb.
1678 * CLOSING, LAST_ACK STATES:
1681 * Drop the segment - see Stevens, vol. 2, p. 964 and
1684 if (thflags & TH_RST) {
1685 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
1686 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) {
1687 switch (tp->t_state) {
1689 case TCPS_SYN_RECEIVED:
1690 so->so_error = ECONNREFUSED;
1693 case TCPS_ESTABLISHED:
1694 case TCPS_FIN_WAIT_1:
1695 case TCPS_FIN_WAIT_2:
1696 case TCPS_CLOSE_WAIT:
1697 so->so_error = ECONNRESET;
1699 tp->t_state = TCPS_CLOSED;
1700 tcpstat.tcps_drops++;
1709 case TCPS_TIME_WAIT:
1717 * RFC 1323 PAWS: If we have a timestamp reply on this segment
1718 * and it's less than ts_recent, drop it.
1720 if ((to.to_flags & TOF_TS) && tp->ts_recent != 0 &&
1721 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
1722 /* Check to see if ts_recent is over 24 days old. */
1723 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) {
1725 * Invalidate ts_recent. If this segment updates
1726 * ts_recent, the age will be reset later and ts_recent
1727 * will get a valid value. If it does not, setting
1728 * ts_recent to zero will at least satisfy the
1729 * requirement that zero be placed in the timestamp
1730 * echo reply when ts_recent isn't valid. The
1731 * age isn't reset until we get a valid ts_recent
1732 * because we don't want out-of-order segments to be
1733 * dropped when ts_recent is old.
1736 } else if (tcp_paws_tolerance && tlen != 0 &&
1737 tp->t_state == TCPS_ESTABLISHED &&
1738 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK&&
1739 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) &&
1740 th->th_ack == tp->snd_una &&
1741 tiwin == tp->snd_wnd &&
1742 TSTMP_GEQ(to.to_tsval + tcp_paws_tolerance, tp->ts_recent)&&
1743 (th->th_seq == tp->rcv_nxt ||
1744 (SEQ_GT(th->th_seq, tp->rcv_nxt) &&
1745 tcp_paws_canreasslast(tp, th, tlen)))) {
1747 * This tends to prevent valid new segments from being
1748 * dropped by the reordered segments sent by the fast
1749 * retransmission algorithm on the sending side, i.e.
1750 * the fast retransmitted segment w/ larger timestamp
1751 * arrives earlier than the previously sent new segments
1752 * w/ smaller timestamp.
1754 * If following conditions are met, the segment is
1756 * - The segment contains data
1757 * - The connection is established
1758 * - The header does not contain important flags
1759 * - SYN or FIN is not needed
1760 * - It does not acknowledge new data
1761 * - Receive window is not changed
1762 * - The timestamp is within "acceptable" range
1763 * - The new segment is what we are expecting or
1764 * the new segment could be merged w/ the last
1765 * pending segment on the reassemble queue
1767 tcpstat.tcps_pawsaccept++;
1768 tcpstat.tcps_pawsdrop++;
1770 tcpstat.tcps_rcvduppack++;
1771 tcpstat.tcps_rcvdupbyte += tlen;
1772 tcpstat.tcps_pawsdrop++;
1780 * In the SYN-RECEIVED state, validate that the packet belongs to
1781 * this connection before trimming the data to fit the receive
1782 * window. Check the sequence number versus IRS since we know
1783 * the sequence numbers haven't wrapped. This is a partial fix
1784 * for the "LAND" DoS attack.
1786 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) {
1787 rstreason = BANDLIM_RST_OPENPORT;
1791 todrop = tp->rcv_nxt - th->th_seq;
1793 if (TCP_DO_SACK(tp)) {
1794 /* Report duplicate segment at head of packet. */
1795 tp->reportblk.rblk_start = th->th_seq;
1796 tp->reportblk.rblk_end = TCP_SACK_BLKEND(
1797 th->th_seq + tlen, thflags);
1798 if (SEQ_GT(tp->reportblk.rblk_end, tp->rcv_nxt))
1799 tp->reportblk.rblk_end = tp->rcv_nxt;
1800 tp->sack_flags |= (TSACK_F_DUPSEG | TSACK_F_SACKLEFT);
1801 tp->t_flags |= TF_ACKNOW;
1803 if (thflags & TH_SYN) {
1813 * Following if statement from Stevens, vol. 2, p. 960.
1815 if (todrop > tlen ||
1816 (todrop == tlen && !(thflags & TH_FIN))) {
1818 * Any valid FIN must be to the left of the window.
1819 * At this point the FIN must be a duplicate or out
1820 * of sequence; drop it.
1825 * Send an ACK to resynchronize and drop any data.
1826 * But keep on processing for RST or ACK.
1828 tp->t_flags |= TF_ACKNOW;
1830 tcpstat.tcps_rcvduppack++;
1831 tcpstat.tcps_rcvdupbyte += todrop;
1833 tcpstat.tcps_rcvpartduppack++;
1834 tcpstat.tcps_rcvpartdupbyte += todrop;
1836 drop_hdrlen += todrop; /* drop from the top afterwards */
1837 th->th_seq += todrop;
1839 if (th->th_urp > todrop)
1840 th->th_urp -= todrop;
1848 * If new data are received on a connection after the
1849 * user processes are gone, then RST the other end.
1851 if ((so->so_state & SS_NOFDREF) &&
1852 tp->t_state > TCPS_CLOSE_WAIT && tlen) {
1854 tcpstat.tcps_rcvafterclose++;
1855 rstreason = BANDLIM_UNLIMITED;
1860 * If segment ends after window, drop trailing data
1861 * (and PUSH and FIN); if nothing left, just ACK.
1863 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd);
1865 tcpstat.tcps_rcvpackafterwin++;
1866 if (todrop >= tlen) {
1867 tcpstat.tcps_rcvbyteafterwin += tlen;
1869 * If a new connection request is received
1870 * while in TIME_WAIT, drop the old connection
1871 * and start over if the sequence numbers
1872 * are above the previous ones.
1874 if (thflags & TH_SYN &&
1875 tp->t_state == TCPS_TIME_WAIT &&
1876 SEQ_GT(th->th_seq, tp->rcv_nxt)) {
1881 * If window is closed can only take segments at
1882 * window edge, and have to drop data and PUSH from
1883 * incoming segments. Continue processing, but
1884 * remember to ack. Otherwise, drop segment
1887 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
1888 tp->t_flags |= TF_ACKNOW;
1889 tcpstat.tcps_rcvwinprobe++;
1893 tcpstat.tcps_rcvbyteafterwin += todrop;
1896 thflags &= ~(TH_PUSH | TH_FIN);
1900 * If last ACK falls within this segment's sequence numbers,
1901 * record its timestamp.
1903 * 1) That the test incorporates suggestions from the latest
1904 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1905 * 2) That updating only on newer timestamps interferes with
1906 * our earlier PAWS tests, so this check should be solely
1907 * predicated on the sequence space of this segment.
1908 * 3) That we modify the segment boundary check to be
1909 * Last.ACK.Sent <= SEG.SEQ + SEG.LEN
1910 * instead of RFC1323's
1911 * Last.ACK.Sent < SEG.SEQ + SEG.LEN,
1912 * This modified check allows us to overcome RFC1323's
1913 * limitations as described in Stevens TCP/IP Illustrated
1914 * Vol. 2 p.869. In such cases, we can still calculate the
1915 * RTT correctly when RCV.NXT == Last.ACK.Sent.
1917 if ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent) &&
1918 SEQ_LEQ(tp->last_ack_sent, (th->th_seq + tlen
1919 + ((thflags & TH_SYN) != 0)
1920 + ((thflags & TH_FIN) != 0)))) {
1921 tp->ts_recent_age = ticks;
1922 tp->ts_recent = to.to_tsval;
1926 * If a SYN is in the window, then this is an
1927 * error and we send an RST and drop the connection.
1929 if (thflags & TH_SYN) {
1930 tp = tcp_drop(tp, ECONNRESET);
1931 rstreason = BANDLIM_UNLIMITED;
1936 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN
1937 * flag is on (half-synchronized state), then queue data for
1938 * later processing; else drop segment and return.
1940 if (!(thflags & TH_ACK)) {
1941 if (tp->t_state == TCPS_SYN_RECEIVED ||
1942 (tp->t_flags & TF_NEEDSYN))
1951 switch (tp->t_state) {
1953 * In SYN_RECEIVED state, the ACK acknowledges our SYN, so enter
1954 * ESTABLISHED state and continue processing.
1955 * The ACK was checked above.
1957 case TCPS_SYN_RECEIVED:
1959 tcpstat.tcps_connects++;
1961 /* Do window scaling? */
1962 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) ==
1963 (TF_RCVD_SCALE | TF_REQ_SCALE))
1964 tp->rcv_scale = tp->request_r_scale;
1967 * SYN-RECEIVED -> ESTABLISHED
1968 * SYN-RECEIVED* -> FIN-WAIT-1
1970 tp->t_starttime = ticks;
1971 if (tp->t_flags & TF_NEEDFIN) {
1972 tp->t_state = TCPS_FIN_WAIT_1;
1973 tp->t_flags &= ~TF_NEEDFIN;
1975 tcp_established(tp);
1978 * If segment contains data or ACK, will call tcp_reass()
1979 * later; if not, do so now to pass queued data to user.
1981 if (tlen == 0 && !(thflags & TH_FIN))
1982 tcp_reass(tp, NULL, NULL, NULL);
1986 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
1987 * ACKs. If the ack is in the range
1988 * tp->snd_una < th->th_ack <= tp->snd_max
1989 * then advance tp->snd_una to th->th_ack and drop
1990 * data from the retransmission queue. If this ACK reflects
1991 * more up to date window information we update our window information.
1993 case TCPS_ESTABLISHED:
1994 case TCPS_FIN_WAIT_1:
1995 case TCPS_FIN_WAIT_2:
1996 case TCPS_CLOSE_WAIT:
1999 case TCPS_TIME_WAIT:
2001 if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
2002 if (TCP_DO_SACK(tp))
2003 tcp_sack_update_scoreboard(tp, &to);
2004 if (!tcp_callout_active(tp, tp->tt_rexmt) ||
2005 th->th_ack != tp->snd_una) {
2006 if (tlen == 0 && tiwin == tp->snd_wnd)
2007 tcpstat.tcps_rcvdupack++;
2011 if (tlen != 0 || tiwin != tp->snd_wnd) {
2012 if (!tcp_do_rfc3517bis ||
2015 (TOF_SACK | TOF_SACK_REDUNDANT))
2019 delayed_dupack = TRUE;
2020 th_dupack = th->th_ack;
2024 if (tcp_fast_recovery(tp, th->th_ack, &to))
2030 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una"));
2032 if (SEQ_GT(th->th_ack, tp->snd_max)) {
2034 * Detected optimistic ACK attack.
2035 * Force slow-start to de-synchronize attack.
2037 tp->snd_cwnd = tp->t_maxseg;
2040 tcpstat.tcps_rcvacktoomuch++;
2044 * If we reach this point, ACK is not a duplicate,
2045 * i.e., it ACKs something we sent.
2047 if (tp->t_flags & TF_NEEDSYN) {
2049 * T/TCP: Connection was half-synchronized, and our
2050 * SYN has been ACK'd (so connection is now fully
2051 * synchronized). Go to non-starred state,
2052 * increment snd_una for ACK of SYN, and check if
2053 * we can do window scaling.
2055 tp->t_flags &= ~TF_NEEDSYN;
2057 /* Do window scaling? */
2058 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) ==
2059 (TF_RCVD_SCALE | TF_REQ_SCALE))
2060 tp->rcv_scale = tp->request_r_scale;
2064 acked = th->th_ack - tp->snd_una;
2065 tcpstat.tcps_rcvackpack++;
2066 tcpstat.tcps_rcvackbyte += acked;
2068 if (tcp_do_eifel_detect && acked > 0 &&
2069 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) &&
2070 (tp->rxt_flags & TRXT_F_FIRSTACCACK)) {
2071 /* Eifel detection applicable. */
2072 if (to.to_tsecr < tp->t_rexmtTS) {
2073 ++tcpstat.tcps_eifeldetected;
2074 tcp_revert_congestion_state(tp);
2075 if (tp->t_rxtshift != 1 ||
2076 ticks >= tp->t_badrxtwin)
2077 ++tcpstat.tcps_rttcantdetect;
2079 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) {
2081 * If we just performed our first retransmit,
2082 * and the ACK arrives within our recovery window,
2083 * then it was a mistake to do the retransmit
2084 * in the first place. Recover our original cwnd
2085 * and ssthresh, and proceed to transmit where we
2088 tcp_revert_congestion_state(tp);
2089 ++tcpstat.tcps_rttdetected;
2093 * If we have a timestamp reply, update smoothed
2094 * round trip time. If no timestamp is present but
2095 * transmit timer is running and timed sequence
2096 * number was acked, update smoothed round trip time.
2097 * Since we now have an rtt measurement, cancel the
2098 * timer backoff (cf., Phil Karn's retransmit alg.).
2099 * Recompute the initial retransmit timer.
2101 * Some machines (certain windows boxes) send broken
2102 * timestamp replies during the SYN+ACK phase, ignore
2105 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0))
2106 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1, th->th_ack);
2107 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq))
2108 tcp_xmit_timer(tp, ticks - tp->t_rtttime, th->th_ack);
2109 tcp_xmit_bandwidth_limit(tp, th->th_ack);
2112 * If no data (only SYN) was ACK'd,
2113 * skip rest of ACK processing.
2118 /* Stop looking for an acceptable ACK since one was received. */
2119 tp->rxt_flags &= ~(TRXT_F_FIRSTACCACK |
2120 TRXT_F_FASTREXMT | TRXT_F_EARLYREXMT);
2122 if (acked > so->so_snd.ssb_cc) {
2123 tp->snd_wnd -= so->so_snd.ssb_cc;
2124 sbdrop(&so->so_snd.sb, (int)so->so_snd.ssb_cc);
2125 ourfinisacked = TRUE;
2127 sbdrop(&so->so_snd.sb, acked);
2128 tp->snd_wnd -= acked;
2129 ourfinisacked = FALSE;
2134 * Update window information.
2136 if (acceptable_window_update(tp, th, tiwin)) {
2137 /* keep track of pure window updates */
2138 if (tlen == 0 && tp->snd_wl2 == th->th_ack &&
2139 tiwin > tp->snd_wnd)
2140 tcpstat.tcps_rcvwinupd++;
2141 tp->snd_wnd = tiwin;
2142 tp->snd_wl1 = th->th_seq;
2143 tp->snd_wl2 = th->th_ack;
2144 if (tp->snd_wnd > tp->max_sndwnd)
2145 tp->max_sndwnd = tp->snd_wnd;
2149 tp->snd_una = th->th_ack;
2150 if (TCP_DO_SACK(tp))
2151 tcp_sack_update_scoreboard(tp, &to);
2152 if (IN_FASTRECOVERY(tp)) {
2153 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) {
2154 EXIT_FASTRECOVERY(tp);
2157 * If the congestion window was inflated
2158 * to account for the other side's
2159 * cached packets, retract it.
2161 if (!TCP_DO_SACK(tp))
2162 tp->snd_cwnd = tp->snd_ssthresh;
2165 * Window inflation should have left us
2166 * with approximately snd_ssthresh outstanding
2167 * data. But, in case we would be inclined
2168 * to send a burst, better do it using
2171 if (SEQ_GT(th->th_ack + tp->snd_cwnd,
2172 tp->snd_max + 2 * tp->t_maxseg))
2174 (tp->snd_max - tp->snd_una) +
2179 if (TCP_DO_SACK(tp)) {
2180 tp->snd_max_rexmt = tp->snd_max;
2183 tcp_newreno_partial_ack(tp, th, acked);
2189 * Open the congestion window. When in slow-start,
2190 * open exponentially: maxseg per packet. Otherwise,
2191 * open linearly: maxseg per window.
2193 if (tp->snd_cwnd <= tp->snd_ssthresh) {
2195 (SEQ_LT(tp->snd_nxt, tp->snd_max) ?
2196 tp->t_maxseg : 2 * tp->t_maxseg);
2199 tp->snd_cwnd += tcp_do_abc ?
2200 min(acked, abc_sslimit) : tp->t_maxseg;
2202 /* linear increase */
2203 tp->snd_wacked += tcp_do_abc ? acked :
2205 if (tp->snd_wacked >= tp->snd_cwnd) {
2206 tp->snd_wacked -= tp->snd_cwnd;
2207 tp->snd_cwnd += tp->t_maxseg;
2210 tp->snd_cwnd = min(tp->snd_cwnd,
2211 TCP_MAXWIN << tp->snd_scale);
2212 tp->snd_recover = th->th_ack - 1;
2214 if (SEQ_LT(tp->snd_nxt, tp->snd_una))
2215 tp->snd_nxt = tp->snd_una;
2218 * If all outstanding data is acked, stop retransmit
2219 * timer and remember to restart (more output or persist).
2220 * If there is more data to be acked, restart retransmit
2221 * timer, using current (possibly backed-off) value.
2223 if (th->th_ack == tp->snd_max) {
2224 tcp_callout_stop(tp, tp->tt_rexmt);
2226 } else if (!tcp_callout_active(tp, tp->tt_persist)) {
2227 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur,
2231 switch (tp->t_state) {
2233 * In FIN_WAIT_1 STATE in addition to the processing
2234 * for the ESTABLISHED state if our FIN is now acknowledged
2235 * then enter FIN_WAIT_2.
2237 case TCPS_FIN_WAIT_1:
2238 if (ourfinisacked) {
2240 * If we can't receive any more
2241 * data, then closing user can proceed.
2242 * Starting the timer is contrary to the
2243 * specification, but if we don't get a FIN
2244 * we'll hang forever.
2246 if (so->so_state & SS_CANTRCVMORE) {
2247 soisdisconnected(so);
2248 tcp_callout_reset(tp, tp->tt_2msl,
2249 tp->t_maxidle, tcp_timer_2msl);
2251 tp->t_state = TCPS_FIN_WAIT_2;
2256 * In CLOSING STATE in addition to the processing for
2257 * the ESTABLISHED state if the ACK acknowledges our FIN
2258 * then enter the TIME-WAIT state, otherwise ignore
2262 if (ourfinisacked) {
2263 tp->t_state = TCPS_TIME_WAIT;
2264 tcp_canceltimers(tp);
2265 tcp_callout_reset(tp, tp->tt_2msl,
2266 2 * tcp_rmx_msl(tp),
2268 soisdisconnected(so);
2273 * In LAST_ACK, we may still be waiting for data to drain
2274 * and/or to be acked, as well as for the ack of our FIN.
2275 * If our FIN is now acknowledged, delete the TCB,
2276 * enter the closed state and return.
2279 if (ourfinisacked) {
2286 * In TIME_WAIT state the only thing that should arrive
2287 * is a retransmission of the remote FIN. Acknowledge
2288 * it and restart the finack timer.
2290 case TCPS_TIME_WAIT:
2291 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp),
2299 * Update window information.
2300 * Don't look at window if no ACK: TAC's send garbage on first SYN.
2302 if ((thflags & TH_ACK) &&
2303 acceptable_window_update(tp, th, tiwin)) {
2304 /* keep track of pure window updates */
2305 if (tlen == 0 && tp->snd_wl2 == th->th_ack &&
2306 tiwin > tp->snd_wnd)
2307 tcpstat.tcps_rcvwinupd++;
2308 tp->snd_wnd = tiwin;
2309 tp->snd_wl1 = th->th_seq;
2310 tp->snd_wl2 = th->th_ack;
2311 if (tp->snd_wnd > tp->max_sndwnd)
2312 tp->max_sndwnd = tp->snd_wnd;
2317 * Process segments with URG.
2319 if ((thflags & TH_URG) && th->th_urp &&
2320 !TCPS_HAVERCVDFIN(tp->t_state)) {
2322 * This is a kludge, but if we receive and accept
2323 * random urgent pointers, we'll crash in
2324 * soreceive. It's hard to imagine someone
2325 * actually wanting to send this much urgent data.
2327 if (th->th_urp + so->so_rcv.ssb_cc > sb_max) {
2328 th->th_urp = 0; /* XXX */
2329 thflags &= ~TH_URG; /* XXX */
2330 goto dodata; /* XXX */
2333 * If this segment advances the known urgent pointer,
2334 * then mark the data stream. This should not happen
2335 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
2336 * a FIN has been received from the remote side.
2337 * In these states we ignore the URG.
2339 * According to RFC961 (Assigned Protocols),
2340 * the urgent pointer points to the last octet
2341 * of urgent data. We continue, however,
2342 * to consider it to indicate the first octet
2343 * of data past the urgent section as the original
2344 * spec states (in one of two places).
2346 if (SEQ_GT(th->th_seq + th->th_urp, tp->rcv_up)) {
2347 tp->rcv_up = th->th_seq + th->th_urp;
2348 so->so_oobmark = so->so_rcv.ssb_cc +
2349 (tp->rcv_up - tp->rcv_nxt) - 1;
2350 if (so->so_oobmark == 0)
2351 sosetstate(so, SS_RCVATMARK);
2353 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
2356 * Remove out of band data so doesn't get presented to user.
2357 * This can happen independent of advancing the URG pointer,
2358 * but if two URG's are pending at once, some out-of-band
2359 * data may creep in... ick.
2361 if (th->th_urp <= (u_long)tlen &&
2362 !(so->so_options & SO_OOBINLINE)) {
2363 /* hdr drop is delayed */
2364 tcp_pulloutofband(so, th, m, drop_hdrlen);
2368 * If no out of band data is expected,
2369 * pull receive urgent pointer along
2370 * with the receive window.
2372 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
2373 tp->rcv_up = tp->rcv_nxt;
2378 * Process the segment text, merging it into the TCP sequencing queue,
2379 * and arranging for acknowledgment of receipt if necessary.
2380 * This process logically involves adjusting tp->rcv_wnd as data
2381 * is presented to the user (this happens in tcp_usrreq.c,
2382 * case PRU_RCVD). If a FIN has already been received on this
2383 * connection then we just ignore the text.
2385 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) {
2386 m_adj(m, drop_hdrlen); /* delayed header drop */
2388 * Insert segment which includes th into TCP reassembly queue
2389 * with control block tp. Set thflags to whether reassembly now
2390 * includes a segment with FIN. This handles the common case
2391 * inline (segment is the next to be received on an established
2392 * connection, and the queue is empty), avoiding linkage into
2393 * and removal from the queue and repetition of various
2395 * Set DELACK for segments received in order, but ack
2396 * immediately when segments are out of order (so
2397 * fast retransmit can work).
2399 if (th->th_seq == tp->rcv_nxt &&
2400 TAILQ_EMPTY(&tp->t_segq) &&
2401 TCPS_HAVEESTABLISHED(tp->t_state)) {
2402 if (DELAY_ACK(tp)) {
2403 tcp_callout_reset(tp, tp->tt_delack,
2404 tcp_delacktime, tcp_timer_delack);
2406 tp->t_flags |= TF_ACKNOW;
2408 tp->rcv_nxt += tlen;
2409 thflags = th->th_flags & TH_FIN;
2410 tcpstat.tcps_rcvpack++;
2411 tcpstat.tcps_rcvbyte += tlen;
2413 if (so->so_state & SS_CANTRCVMORE) {
2416 lwkt_gettoken(&so->so_rcv.ssb_token);
2417 ssb_appendstream(&so->so_rcv, m);
2418 lwkt_reltoken(&so->so_rcv.ssb_token);
2422 if (!(tp->sack_flags & TSACK_F_DUPSEG)) {
2423 /* Initialize SACK report block. */
2424 tp->reportblk.rblk_start = th->th_seq;
2425 tp->reportblk.rblk_end = TCP_SACK_BLKEND(
2426 th->th_seq + tlen, thflags);
2428 thflags = tcp_reass(tp, th, &tlen, m);
2429 tp->t_flags |= TF_ACKNOW;
2433 * Note the amount of data that peer has sent into
2434 * our window, in order to estimate the sender's
2437 len = so->so_rcv.ssb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
2444 * If FIN is received ACK the FIN and let the user know
2445 * that the connection is closing.
2447 if (thflags & TH_FIN) {
2448 if (!TCPS_HAVERCVDFIN(tp->t_state)) {
2451 * If connection is half-synchronized
2452 * (ie NEEDSYN flag on) then delay ACK,
2453 * so it may be piggybacked when SYN is sent.
2454 * Otherwise, since we received a FIN then no
2455 * more input can be expected, send ACK now.
2457 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) {
2458 tcp_callout_reset(tp, tp->tt_delack,
2459 tcp_delacktime, tcp_timer_delack);
2461 tp->t_flags |= TF_ACKNOW;
2466 switch (tp->t_state) {
2468 * In SYN_RECEIVED and ESTABLISHED STATES
2469 * enter the CLOSE_WAIT state.
2471 case TCPS_SYN_RECEIVED:
2472 tp->t_starttime = ticks;
2474 case TCPS_ESTABLISHED:
2475 tp->t_state = TCPS_CLOSE_WAIT;
2479 * If still in FIN_WAIT_1 STATE FIN has not been acked so
2480 * enter the CLOSING state.
2482 case TCPS_FIN_WAIT_1:
2483 tp->t_state = TCPS_CLOSING;
2487 * In FIN_WAIT_2 state enter the TIME_WAIT state,
2488 * starting the time-wait timer, turning off the other
2491 case TCPS_FIN_WAIT_2:
2492 tp->t_state = TCPS_TIME_WAIT;
2493 tcp_canceltimers(tp);
2494 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp),
2496 soisdisconnected(so);
2500 * In TIME_WAIT state restart the 2 MSL time_wait timer.
2502 case TCPS_TIME_WAIT:
2503 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp),
2510 if (so->so_options & SO_DEBUG)
2511 tcp_trace(TA_INPUT, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
2515 * Delayed duplicated ACK processing
2517 if (delayed_dupack && tcp_fast_recovery(tp, th_dupack, &to))
2521 * Return any desired output.
2523 if (needoutput || (tp->t_flags & TF_ACKNOW))
2525 tcp_sack_report_cleanup(tp);
2526 return(IPPROTO_DONE);
2530 * Generate an ACK dropping incoming segment if it occupies
2531 * sequence space, where the ACK reflects our state.
2533 * We can now skip the test for the RST flag since all
2534 * paths to this code happen after packets containing
2535 * RST have been dropped.
2537 * In the SYN-RECEIVED state, don't send an ACK unless the
2538 * segment we received passes the SYN-RECEIVED ACK test.
2539 * If it fails send a RST. This breaks the loop in the
2540 * "LAND" DoS attack, and also prevents an ACK storm
2541 * between two listening ports that have been sent forged
2542 * SYN segments, each with the source address of the other.
2544 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
2545 (SEQ_GT(tp->snd_una, th->th_ack) ||
2546 SEQ_GT(th->th_ack, tp->snd_max)) ) {
2547 rstreason = BANDLIM_RST_OPENPORT;
2551 if (so->so_options & SO_DEBUG)
2552 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
2555 tp->t_flags |= TF_ACKNOW;
2557 tcp_sack_report_cleanup(tp);
2558 return(IPPROTO_DONE);
2562 * Generate a RST, dropping incoming segment.
2563 * Make ACK acceptable to originator of segment.
2564 * Don't bother to respond if destination was broadcast/multicast.
2566 if ((thflags & TH_RST) || m->m_flags & (M_BCAST | M_MCAST))
2569 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
2570 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
2573 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
2574 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
2575 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
2576 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
2579 /* IPv6 anycast check is done at tcp6_input() */
2582 * Perform bandwidth limiting.
2585 if (badport_bandlim(rstreason) < 0)
2590 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
2591 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
2593 if (thflags & TH_ACK)
2594 /* mtod() below is safe as long as hdr dropping is delayed */
2595 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack,
2598 if (thflags & TH_SYN)
2600 /* mtod() below is safe as long as hdr dropping is delayed */
2601 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen,
2602 (tcp_seq)0, TH_RST | TH_ACK);
2605 tcp_sack_report_cleanup(tp);
2606 return(IPPROTO_DONE);
2610 * Drop space held by incoming segment and return.
2613 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
2614 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
2618 tcp_sack_report_cleanup(tp);
2619 return(IPPROTO_DONE);
2623 * Parse TCP options and place in tcpopt.
2626 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn,
2632 for (; cnt > 0; cnt -= optlen, cp += optlen) {
2634 if (opt == TCPOPT_EOL)
2636 if (opt == TCPOPT_NOP)
2642 if (optlen < 2 || optlen > cnt)
2647 if (optlen != TCPOLEN_MAXSEG)
2651 to->to_flags |= TOF_MSS;
2652 bcopy(cp + 2, &to->to_mss, sizeof to->to_mss);
2653 to->to_mss = ntohs(to->to_mss);
2656 if (optlen != TCPOLEN_WINDOW)
2660 to->to_flags |= TOF_SCALE;
2661 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT);
2663 case TCPOPT_TIMESTAMP:
2664 if (optlen != TCPOLEN_TIMESTAMP)
2666 to->to_flags |= TOF_TS;
2667 bcopy(cp + 2, &to->to_tsval, sizeof to->to_tsval);
2668 to->to_tsval = ntohl(to->to_tsval);
2669 bcopy(cp + 6, &to->to_tsecr, sizeof to->to_tsecr);
2670 to->to_tsecr = ntohl(to->to_tsecr);
2672 * If echoed timestamp is later than the current time,
2673 * fall back to non RFC1323 RTT calculation.
2675 if (to->to_tsecr != 0 && TSTMP_GT(to->to_tsecr, ticks))
2678 case TCPOPT_SACK_PERMITTED:
2679 if (optlen != TCPOLEN_SACK_PERMITTED)
2683 to->to_flags |= TOF_SACK_PERMITTED;
2686 if ((optlen - 2) & 0x07) /* not multiple of 8 */
2688 to->to_nsackblocks = (optlen - 2) / 8;
2689 to->to_sackblocks = (struct raw_sackblock *) (cp + 2);
2690 to->to_flags |= TOF_SACK;
2691 for (i = 0; i < to->to_nsackblocks; i++) {
2692 struct raw_sackblock *r = &to->to_sackblocks[i];
2694 r->rblk_start = ntohl(r->rblk_start);
2695 r->rblk_end = ntohl(r->rblk_end);
2697 if (SEQ_LEQ(r->rblk_end, r->rblk_start)) {
2699 * Invalid SACK block; discard all
2702 tcpstat.tcps_rcvbadsackopt++;
2703 to->to_nsackblocks = 0;
2704 to->to_sackblocks = NULL;
2705 to->to_flags &= ~TOF_SACK;
2709 if ((to->to_flags & TOF_SACK) &&
2710 tcp_sack_ndsack_blocks(to->to_sackblocks,
2711 to->to_nsackblocks, ack))
2712 to->to_flags |= TOF_DSACK;
2714 #ifdef TCP_SIGNATURE
2716 * XXX In order to reply to a host which has set the
2717 * TCP_SIGNATURE option in its initial SYN, we have to
2718 * record the fact that the option was observed here
2719 * for the syncache code to perform the correct response.
2721 case TCPOPT_SIGNATURE:
2722 if (optlen != TCPOLEN_SIGNATURE)
2724 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN);
2726 #endif /* TCP_SIGNATURE */
2734 * Pull out of band byte out of a segment so
2735 * it doesn't appear in the user's data queue.
2736 * It is still reflected in the segment length for
2737 * sequencing purposes.
2738 * "off" is the delayed to be dropped hdrlen.
2741 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off)
2743 int cnt = off + th->th_urp - 1;
2746 if (m->m_len > cnt) {
2747 char *cp = mtod(m, caddr_t) + cnt;
2748 struct tcpcb *tp = sototcpcb(so);
2751 tp->t_oobflags |= TCPOOB_HAVEDATA;
2752 bcopy(cp + 1, cp, m->m_len - cnt - 1);
2754 if (m->m_flags & M_PKTHDR)
2763 panic("tcp_pulloutofband");
2767 * Collect new round-trip time estimate
2768 * and update averages and current timeout.
2771 tcp_xmit_timer(struct tcpcb *tp, int rtt, tcp_seq ack)
2775 tcpstat.tcps_rttupdated++;
2777 if ((tp->rxt_flags & TRXT_F_REBASERTO) &&
2778 SEQ_GT(ack, tp->snd_max_prev)) {
2779 #ifdef DEBUG_EIFEL_RESPONSE
2780 kprintf("srtt/rttvar, prev %d/%d, cur %d/%d, ",
2781 tp->t_srtt_prev, tp->t_rttvar_prev,
2782 tp->t_srtt, tp->t_rttvar);
2785 tcpstat.tcps_eifelresponse++;
2787 tp->rxt_flags &= ~TRXT_F_REBASERTO;
2788 tp->t_srtt = max(tp->t_srtt_prev, (rtt << TCP_RTT_SHIFT));
2789 tp->t_rttvar = max(tp->t_rttvar_prev,
2790 (rtt << (TCP_RTTVAR_SHIFT - 1)));
2791 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
2792 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2794 #ifdef DEBUG_EIFEL_RESPONSE
2795 kprintf("new %d/%d ", tp->t_srtt, tp->t_rttvar);
2797 } else if (tp->t_srtt != 0) {
2801 * srtt is stored as fixed point with 5 bits after the
2802 * binary point (i.e., scaled by 8). The following magic
2803 * is equivalent to the smoothing algorithm in rfc793 with
2804 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
2805 * point). Adjust rtt to origin 0.
2807 delta = ((rtt - 1) << TCP_DELTA_SHIFT)
2808 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
2810 if ((tp->t_srtt += delta) <= 0)
2814 * We accumulate a smoothed rtt variance (actually, a
2815 * smoothed mean difference), then set the retransmit
2816 * timer to smoothed rtt + 4 times the smoothed variance.
2817 * rttvar is stored as fixed point with 4 bits after the
2818 * binary point (scaled by 16). The following is
2819 * equivalent to rfc793 smoothing with an alpha of .75
2820 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces
2821 * rfc793's wired-in beta.
2825 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
2826 if ((tp->t_rttvar += delta) <= 0)
2828 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
2829 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2832 * No rtt measurement yet - use the unsmoothed rtt.
2833 * Set the variance to half the rtt (so our first
2834 * retransmit happens at 3*rtt).
2836 tp->t_srtt = rtt << TCP_RTT_SHIFT;
2837 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
2838 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2843 #ifdef DEBUG_EIFEL_RESPONSE
2845 kprintf("| rxtcur prev %d, old %d, ",
2846 tp->t_rxtcur_prev, tp->t_rxtcur);
2851 * the retransmit should happen at rtt + 4 * rttvar.
2852 * Because of the way we do the smoothing, srtt and rttvar
2853 * will each average +1/2 tick of bias. When we compute
2854 * the retransmit timer, we want 1/2 tick of rounding and
2855 * 1 extra tick because of +-1/2 tick uncertainty in the
2856 * firing of the timer. The bias will give us exactly the
2857 * 1.5 tick we need. But, because the bias is
2858 * statistical, we have to test that we don't drop below
2859 * the minimum feasible timer (which is 2 ticks).
2861 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
2862 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);
2865 if (tp->t_rxtcur < tp->t_rxtcur_prev + tcp_eifel_rtoinc) {
2867 * RFC4015 requires that the new RTO is at least
2868 * 2*G (tcp_eifel_rtoinc) greater then the RTO
2869 * (t_rxtcur_prev) when the spurious retransmit
2872 * The above condition could be true, if the SRTT
2873 * and RTTVAR used to calculate t_rxtcur_prev
2874 * resulted in a value less than t_rttmin. So
2875 * simply increasing SRTT by tcp_eifel_rtoinc when
2876 * preparing for the Eifel response in
2877 * tcp_save_congestion_state() could not ensure
2878 * that the new RTO will be tcp_eifel_rtoinc greater
2881 tp->t_rxtcur = tp->t_rxtcur_prev + tcp_eifel_rtoinc;
2883 #ifdef DEBUG_EIFEL_RESPONSE
2884 kprintf("new %d\n", tp->t_rxtcur);
2889 * We received an ack for a packet that wasn't retransmitted;
2890 * it is probably safe to discard any error indications we've
2891 * received recently. This isn't quite right, but close enough
2892 * for now (a route might have failed after we sent a segment,
2893 * and the return path might not be symmetrical).
2895 tp->t_softerror = 0;
2899 * Determine a reasonable value for maxseg size.
2900 * If the route is known, check route for mtu.
2901 * If none, use an mss that can be handled on the outgoing
2902 * interface without forcing IP to fragment; if bigger than
2903 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES
2904 * to utilize large mbufs. If no route is found, route has no mtu,
2905 * or the destination isn't local, use a default, hopefully conservative
2906 * size (usually 512 or the default IP max size, but no more than the mtu
2907 * of the interface), as we can't discover anything about intervening
2908 * gateways or networks. We also initialize the congestion/slow start
2909 * window to be a single segment if the destination isn't local.
2910 * While looking at the routing entry, we also initialize other path-dependent
2911 * parameters from pre-set or cached values in the routing entry.
2913 * Also take into account the space needed for options that we
2914 * send regularly. Make maxseg shorter by that amount to assure
2915 * that we can send maxseg amount of data even when the options
2916 * are present. Store the upper limit of the length of options plus
2919 * NOTE that this routine is only called when we process an incoming
2920 * segment, for outgoing segments only tcp_mssopt is called.
2923 tcp_mss(struct tcpcb *tp, int offer)
2929 struct inpcb *inp = tp->t_inpcb;
2932 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE);
2933 size_t min_protoh = isipv6 ?
2934 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) :
2935 sizeof(struct tcpiphdr);
2937 const boolean_t isipv6 = FALSE;
2938 const size_t min_protoh = sizeof(struct tcpiphdr);
2942 rt = tcp_rtlookup6(&inp->inp_inc);
2944 rt = tcp_rtlookup(&inp->inp_inc);
2946 tp->t_maxopd = tp->t_maxseg =
2947 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt);
2951 so = inp->inp_socket;
2954 * Offer == 0 means that there was no MSS on the SYN segment,
2955 * in this case we use either the interface mtu or tcp_mssdflt.
2957 * An offer which is too large will be cut down later.
2961 if (in6_localaddr(&inp->in6p_faddr)) {
2962 offer = ND_IFINFO(rt->rt_ifp)->linkmtu -
2965 offer = tcp_v6mssdflt;
2968 if (in_localaddr(inp->inp_faddr))
2969 offer = ifp->if_mtu - min_protoh;
2971 offer = tcp_mssdflt;
2976 * Prevent DoS attack with too small MSS. Round up
2977 * to at least minmss.
2979 * Sanity check: make sure that maxopd will be large
2980 * enough to allow some data on segments even is the
2981 * all the option space is used (40bytes). Otherwise
2982 * funny things may happen in tcp_output.
2984 offer = max(offer, tcp_minmss);
2985 offer = max(offer, 64);
2987 rt->rt_rmx.rmx_mssopt = offer;
2990 * While we're here, check if there's an initial rtt
2991 * or rttvar. Convert from the route-table units
2992 * to scaled multiples of the slow timeout timer.
2994 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) {
2996 * XXX the lock bit for RTT indicates that the value
2997 * is also a minimum value; this is subject to time.
2999 if (rt->rt_rmx.rmx_locks & RTV_RTT)
3000 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz);
3001 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE));
3002 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE;
3003 tcpstat.tcps_usedrtt++;
3004 if (rt->rt_rmx.rmx_rttvar) {
3005 tp->t_rttvar = rt->rt_rmx.rmx_rttvar /
3006 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE));
3007 tcpstat.tcps_usedrttvar++;
3009 /* default variation is +- 1 rtt */
3011 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
3013 TCPT_RANGESET(tp->t_rxtcur,
3014 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
3015 tp->t_rttmin, TCPTV_REXMTMAX);
3019 * if there's an mtu associated with the route, use it
3020 * else, use the link mtu. Take the smaller of mss or offer
3023 if (rt->rt_rmx.rmx_mtu) {
3024 mss = rt->rt_rmx.rmx_mtu - min_protoh;
3027 mss = ND_IFINFO(rt->rt_ifp)->linkmtu - min_protoh;
3029 mss = ifp->if_mtu - min_protoh;
3031 mss = min(mss, offer);
3034 * maxopd stores the maximum length of data AND options
3035 * in a segment; maxseg is the amount of data in a normal
3036 * segment. We need to store this value (maxopd) apart
3037 * from maxseg, because now every segment carries options
3038 * and thus we normally have somewhat less data in segments.
3042 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP &&
3043 ((tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP))
3044 mss -= TCPOLEN_TSTAMP_APPA;
3046 #if (MCLBYTES & (MCLBYTES - 1)) == 0
3048 mss &= ~(MCLBYTES-1);
3051 mss = mss / MCLBYTES * MCLBYTES;
3054 * If there's a pipesize, change the socket buffer
3055 * to that size. Make the socket buffers an integral
3056 * number of mss units; if the mss is larger than
3057 * the socket buffer, decrease the mss.
3060 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0)
3062 bufsize = so->so_snd.ssb_hiwat;
3066 bufsize = roundup(bufsize, mss);
3067 if (bufsize > sb_max)
3069 if (bufsize > so->so_snd.ssb_hiwat)
3070 ssb_reserve(&so->so_snd, bufsize, so, NULL);
3075 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0)
3077 bufsize = so->so_rcv.ssb_hiwat;
3078 if (bufsize > mss) {
3079 bufsize = roundup(bufsize, mss);
3080 if (bufsize > sb_max)
3082 if (bufsize > so->so_rcv.ssb_hiwat) {
3083 lwkt_gettoken(&so->so_rcv.ssb_token);
3084 ssb_reserve(&so->so_rcv, bufsize, so, NULL);
3085 lwkt_reltoken(&so->so_rcv.ssb_token);
3090 * Set the slow-start flight size
3092 * NOTE: t_maxseg must have been configured!
3094 tp->snd_cwnd = tcp_initial_window(tp);
3096 if (rt->rt_rmx.rmx_ssthresh) {
3098 * There's some sort of gateway or interface
3099 * buffer limit on the path. Use this to set
3100 * the slow start threshhold, but set the
3101 * threshold to no less than 2*mss.
3103 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh);
3104 tcpstat.tcps_usedssthresh++;
3109 * Determine the MSS option to send on an outgoing SYN.
3112 tcp_mssopt(struct tcpcb *tp)
3117 ((tp->t_inpcb->inp_vflag & INP_IPV6) ? TRUE : FALSE);
3118 int min_protoh = isipv6 ?
3119 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) :
3120 sizeof(struct tcpiphdr);
3122 const boolean_t isipv6 = FALSE;
3123 const size_t min_protoh = sizeof(struct tcpiphdr);
3127 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc);
3129 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc);
3131 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt);
3133 return (rt->rt_ifp->if_mtu - min_protoh);
3137 * When a partial ack arrives, force the retransmission of the
3138 * next unacknowledged segment. Do not exit Fast Recovery.
3140 * Implement the Slow-but-Steady variant of NewReno by restarting the
3141 * the retransmission timer. Turn it off here so it can be restarted
3142 * later in tcp_output().
3145 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th, int acked)
3147 tcp_seq old_snd_nxt = tp->snd_nxt;
3148 u_long ocwnd = tp->snd_cwnd;
3150 tcp_callout_stop(tp, tp->tt_rexmt);
3152 tp->snd_nxt = th->th_ack;
3153 /* Set snd_cwnd to one segment beyond acknowledged offset. */
3154 tp->snd_cwnd = tp->t_maxseg;
3155 tp->t_flags |= TF_ACKNOW;
3157 if (SEQ_GT(old_snd_nxt, tp->snd_nxt))
3158 tp->snd_nxt = old_snd_nxt;
3159 /* partial window deflation */
3161 tp->snd_cwnd = ocwnd - acked + tp->t_maxseg;
3163 tp->snd_cwnd = tp->t_maxseg;
3167 * In contrast to the Slow-but-Steady NewReno variant,
3168 * we do not reset the retransmission timer for SACK retransmissions,
3169 * except when retransmitting snd_una.
3172 tcp_sack_rexmt(struct tcpcb *tp)
3174 tcp_seq old_snd_nxt = tp->snd_nxt;
3175 u_long ocwnd = tp->snd_cwnd;
3177 int nseg = 0; /* consecutive new segments */
3178 int nseg_rexmt = 0; /* retransmitted segments */
3179 #define MAXBURST 4 /* limit burst of new packets on partial ack */
3182 pipe = tcp_sack_compute_pipe(tp);
3183 while ((tcp_seq_diff_t)(ocwnd - pipe) >= (tcp_seq_diff_t)tp->t_maxseg &&
3184 (!tcp_do_smartsack || nseg < MAXBURST)) {
3185 tcp_seq old_snd_max, old_rexmt_high, nextrexmt;
3186 uint32_t sent, seglen;
3190 old_rexmt_high = tp->rexmt_high;
3191 if (!tcp_sack_nextseg(tp, &nextrexmt, &seglen, &rescue)) {
3192 tp->rexmt_high = old_rexmt_high;
3197 * If the next tranmission is a rescue retranmission,
3198 * we check whether we have already sent some data
3199 * (either new segments or retransmitted segments)
3200 * into the the network or not. Since the idea of rescue
3201 * retransmission is to sustain ACK clock, as long as
3202 * some segments are in the network, ACK clock will be
3205 if (rescue && (nseg_rexmt > 0 || nseg > 0)) {
3206 tp->rexmt_high = old_rexmt_high;
3210 if (nextrexmt == tp->snd_max)
3214 tp->snd_nxt = nextrexmt;
3215 tp->snd_cwnd = nextrexmt - tp->snd_una + seglen;
3216 old_snd_max = tp->snd_max;
3217 if (nextrexmt == tp->snd_una)
3218 tcp_callout_stop(tp, tp->tt_rexmt);
3219 error = tcp_output(tp);
3221 tp->rexmt_high = old_rexmt_high;
3224 sent = tp->snd_nxt - nextrexmt;
3226 tp->rexmt_high = old_rexmt_high;
3230 tcpstat.tcps_sndsackpack++;
3231 tcpstat.tcps_sndsackbyte += sent;
3234 tcpstat.tcps_sackrescue++;
3235 tp->rexmt_rescue = tp->snd_nxt;
3236 tp->sack_flags |= TSACK_F_SACKRESCUED;
3239 if (SEQ_LT(nextrexmt, old_snd_max) &&
3240 SEQ_LT(tp->rexmt_high, tp->snd_nxt)) {
3241 tp->rexmt_high = seq_min(tp->snd_nxt, old_snd_max);
3242 if (tcp_aggressive_rescuesack &&
3243 (tp->sack_flags & TSACK_F_SACKRESCUED) &&
3244 SEQ_LT(tp->rexmt_rescue, tp->rexmt_high)) {
3245 /* Drag RescueRxt along with HighRxt */
3246 tp->rexmt_rescue = tp->rexmt_high;
3250 if (SEQ_GT(old_snd_nxt, tp->snd_nxt))
3251 tp->snd_nxt = old_snd_nxt;
3252 tp->snd_cwnd = ocwnd;
3256 * Return TRUE, if some new segments are sent
3259 tcp_sack_limitedxmit(struct tcpcb *tp)
3261 tcp_seq oldsndnxt = tp->snd_nxt;
3262 tcp_seq oldsndmax = tp->snd_max;
3263 u_long ocwnd = tp->snd_cwnd;
3264 uint32_t pipe, sent;
3265 boolean_t ret = FALSE;
3266 tcp_seq_diff_t cwnd_left;
3269 tp->rexmt_high = tp->snd_una - 1;
3270 pipe = tcp_sack_compute_pipe(tp);
3271 cwnd_left = (tcp_seq_diff_t)(ocwnd - pipe);
3272 if (cwnd_left < (tcp_seq_diff_t)tp->t_maxseg)
3275 next = tp->snd_nxt = tp->snd_max;
3276 tp->snd_cwnd = tp->snd_nxt - tp->snd_una +
3277 rounddown(cwnd_left, tp->t_maxseg);
3281 sent = tp->snd_nxt - next;
3283 tcpstat.tcps_sndlimited += howmany(sent, tp->t_maxseg);
3287 if (SEQ_LT(oldsndnxt, oldsndmax)) {
3288 KASSERT(SEQ_GEQ(oldsndnxt, tp->snd_una),
3289 ("snd_una moved in other threads"));
3290 tp->snd_nxt = oldsndnxt;
3292 tp->snd_cwnd = ocwnd;
3294 if (ret && TCP_DO_NCR(tp))
3295 tcp_ncr_update_rxtthresh(tp);
3301 * Reset idle time and keep-alive timer, typically called when a valid
3302 * tcp packet is received but may also be called when FASTKEEP is set
3303 * to prevent the previous long-timeout from calculating to a drop.
3305 * Only update t_rcvtime for non-SYN packets.
3307 * Handle the case where one side thinks the connection is established
3308 * but the other side has, say, rebooted without cleaning out the
3309 * connection. The SYNs could be construed as an attack and wind
3310 * up ignored, but in case it isn't an attack we can validate the
3311 * connection by forcing a keepalive.
3314 tcp_timer_keep_activity(struct tcpcb *tp, int thflags)
3316 if (TCPS_HAVEESTABLISHED(tp->t_state)) {
3317 if ((thflags & (TH_SYN | TH_ACK)) == TH_SYN) {
3318 tp->t_flags |= TF_KEEPALIVE;
3319 tcp_callout_reset(tp, tp->tt_keep, hz / 2,
3322 tp->t_rcvtime = ticks;
3323 tp->t_flags &= ~TF_KEEPALIVE;
3324 tcp_callout_reset(tp, tp->tt_keep,
3332 tcp_rmx_msl(const struct tcpcb *tp)
3335 struct inpcb *inp = tp->t_inpcb;
3338 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE);
3340 const boolean_t isipv6 = FALSE;
3344 rt = tcp_rtlookup6(&inp->inp_inc);
3346 rt = tcp_rtlookup(&inp->inp_inc);
3347 if (rt == NULL || rt->rt_rmx.rmx_msl == 0)
3350 msl = (rt->rt_rmx.rmx_msl * hz) / 1000;
3358 tcp_established(struct tcpcb *tp)
3360 tp->t_state = TCPS_ESTABLISHED;
3361 tcp_callout_reset(tp, tp->tt_keep, tp->t_keepidle, tcp_timer_keep);
3363 if (tp->t_rxtsyn > 0) {
3366 * "If the timer expires awaiting the ACK of a SYN segment
3367 * and the TCP implementation is using an RTO less than 3
3368 * seconds, the RTO MUST be re-initialized to 3 seconds
3369 * when data transmission begins"
3371 if (tp->t_rxtcur < TCPTV_RTOBASE3)
3372 tp->t_rxtcur = TCPTV_RTOBASE3;
3377 * Returns TRUE, if the ACK should be dropped
3380 tcp_fast_recovery(struct tcpcb *tp, tcp_seq th_ack, const struct tcpopt *to)
3382 tcpstat.tcps_rcvdupack++;
3385 * We have outstanding data (other than a window probe),
3386 * this is a completely duplicate ack (ie, window info
3387 * didn't change), the ack is the biggest we've seen and
3388 * we've seen exactly our rexmt threshhold of them, so
3389 * assume a packet has been dropped and retransmit it.
3390 * Kludge snd_nxt & the congestion window so we send only
3393 if (IN_FASTRECOVERY(tp)) {
3394 if (TCP_DO_SACK(tp)) {
3395 /* No artifical cwnd inflation. */
3399 * Dup acks mean that packets have left
3400 * the network (they're now cached at the
3401 * receiver) so bump cwnd by the amount in
3402 * the receiver to keep a constant cwnd
3403 * packets in the network.
3405 tp->snd_cwnd += tp->t_maxseg;
3409 } else if (SEQ_LT(th_ack, tp->snd_recover)) {
3412 } else if (tcp_ignore_redun_dsack && TCP_DO_SACK(tp) &&
3413 (to->to_flags & (TOF_DSACK | TOF_SACK_REDUNDANT)) ==
3414 (TOF_DSACK | TOF_SACK_REDUNDANT)) {
3416 * If the ACK carries DSACK and other SACK blocks
3417 * carry information that we have already known,
3418 * don't count this ACK as duplicate ACK. This
3419 * prevents spurious early retransmit and fast
3420 * retransmit. This also meets the requirement of
3421 * RFC3042 that new segments should not be sent if
3422 * the SACK blocks do not contain new information
3423 * (XXX we actually loosen the requirment that only
3424 * DSACK is checked here).
3426 * This kind of ACKs are usually sent after spurious
3429 /* Do nothing; don't change t_dupacks */
3431 } else if (tp->t_dupacks == 0 && TCP_DO_NCR(tp)) {
3432 tcp_ncr_update_rxtthresh(tp);
3435 if (++tp->t_dupacks == tp->t_rxtthresh) {
3436 tcp_seq old_snd_nxt;
3440 if (tcp_do_eifel_detect && (tp->t_flags & TF_RCVD_TSTMP)) {
3441 tcp_save_congestion_state(tp);
3442 tp->rxt_flags |= TRXT_F_FASTREXMT;
3445 * We know we're losing at the current window size,
3446 * so do congestion avoidance: set ssthresh to half
3447 * the current window and pull our congestion window
3448 * back to the new ssthresh.
3450 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
3453 tp->snd_ssthresh = win * tp->t_maxseg;
3454 ENTER_FASTRECOVERY(tp);
3455 tp->snd_recover = tp->snd_max;
3456 tcp_callout_stop(tp, tp->tt_rexmt);
3458 old_snd_nxt = tp->snd_nxt;
3459 tp->snd_nxt = th_ack;
3460 tp->snd_cwnd = tp->t_maxseg;
3462 ++tcpstat.tcps_sndfastrexmit;
3463 tp->snd_cwnd = tp->snd_ssthresh;
3464 tp->rexmt_high = tp->snd_nxt;
3465 tp->sack_flags &= ~TSACK_F_SACKRESCUED;
3466 if (SEQ_GT(old_snd_nxt, tp->snd_nxt))
3467 tp->snd_nxt = old_snd_nxt;
3468 KASSERT(tp->snd_limited <= 2, ("tp->snd_limited too big"));
3469 if (TCP_DO_SACK(tp)) {
3472 tp->snd_cwnd += tp->t_maxseg *
3473 (tp->t_dupacks - tp->snd_limited);
3475 } else if ((tcp_do_rfc3517bis && TCP_DO_SACK(tp)) || TCP_DO_NCR(tp)) {
3476 if (tcp_rfc3517bis_rxt && tcp_do_rfc3517bis &&
3477 tcp_sack_islost(&tp->scb, tp->snd_una))
3478 goto fastretransmit;
3479 if (tcp_do_limitedtransmit || TCP_DO_NCR(tp)) {
3480 /* outstanding data */
3481 uint32_t ownd = tp->snd_max - tp->snd_una;
3483 if (!tcp_sack_limitedxmit(tp) &&
3484 need_early_retransmit(tp, ownd)) {
3485 ++tcpstat.tcps_sndearlyrexmit;
3486 tp->rxt_flags |= TRXT_F_EARLYREXMT;
3487 goto fastretransmit;
3490 } else if (tcp_do_limitedtransmit) {
3491 u_long oldcwnd = tp->snd_cwnd;
3492 tcp_seq oldsndmax = tp->snd_max;
3493 tcp_seq oldsndnxt = tp->snd_nxt;
3494 /* outstanding data */
3495 uint32_t ownd = tp->snd_max - tp->snd_una;
3498 KASSERT(tp->t_dupacks == 1 || tp->t_dupacks == 2,
3499 ("dupacks not 1 or 2"));
3500 if (tp->t_dupacks == 1)
3501 tp->snd_limited = 0;
3502 tp->snd_nxt = tp->snd_max;
3503 tp->snd_cwnd = ownd +
3504 (tp->t_dupacks - tp->snd_limited) * tp->t_maxseg;
3507 if (SEQ_LT(oldsndnxt, oldsndmax)) {
3508 KASSERT(SEQ_GEQ(oldsndnxt, tp->snd_una),
3509 ("snd_una moved in other threads"));
3510 tp->snd_nxt = oldsndnxt;
3512 tp->snd_cwnd = oldcwnd;
3513 sent = tp->snd_max - oldsndmax;
3514 if (sent > tp->t_maxseg) {
3515 KASSERT((tp->t_dupacks == 2 && tp->snd_limited == 0) ||
3516 (sent == tp->t_maxseg + 1 &&
3517 (tp->t_flags & TF_SENTFIN)),
3519 KASSERT(sent <= tp->t_maxseg * 2,
3520 ("sent too many segments"));
3521 tp->snd_limited = 2;
3522 tcpstat.tcps_sndlimited += 2;
3523 } else if (sent > 0) {
3525 ++tcpstat.tcps_sndlimited;
3526 } else if (need_early_retransmit(tp, ownd)) {
3527 ++tcpstat.tcps_sndearlyrexmit;
3528 tp->rxt_flags |= TRXT_F_EARLYREXMT;
3529 goto fastretransmit;
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