2 * Copyright (c) 2004 Jeffrey M. Hsu. All rights reserved.
3 * Copyright (c) 2004 The DragonFly Project. All rights reserved.
5 * This code is derived from software contributed to The DragonFly Project
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of The DragonFly Project nor the names of its
17 * contributors may be used to endorse or promote products derived
18 * from this software without specific, prior written permission.
20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
23 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
24 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
25 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
26 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
27 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
28 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
29 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
30 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
35 * Copyright (c) 2004 Jeffrey M. Hsu. All rights reserved.
37 * License terms: all terms for the DragonFly license above plus the following:
39 * 4. All advertising materials mentioning features or use of this software
40 * must display the following acknowledgement:
42 * This product includes software developed by Jeffrey M. Hsu
43 * for the DragonFly Project.
45 * This requirement may be waived with permission from Jeffrey Hsu.
46 * This requirement will sunset and may be removed on July 8 2005,
47 * after which the standard DragonFly license (as shown above) will
52 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
53 * The Regents of the University of California. All rights reserved.
55 * Redistribution and use in source and binary forms, with or without
56 * modification, are permitted provided that the following conditions
58 * 1. Redistributions of source code must retain the above copyright
59 * notice, this list of conditions and the following disclaimer.
60 * 2. Redistributions in binary form must reproduce the above copyright
61 * notice, this list of conditions and the following disclaimer in the
62 * documentation and/or other materials provided with the distribution.
63 * 3. All advertising materials mentioning features or use of this software
64 * must display the following acknowledgement:
65 * This product includes software developed by the University of
66 * California, Berkeley and its contributors.
67 * 4. Neither the name of the University nor the names of its contributors
68 * may be used to endorse or promote products derived from this software
69 * without specific prior written permission.
71 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
72 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
73 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
74 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
75 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
76 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
77 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
78 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
79 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
80 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
83 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95
84 * $FreeBSD: src/sys/netinet/tcp_output.c,v 1.39.2.20 2003/01/29 22:45:36 hsu Exp $
85 * $DragonFly: src/sys/netinet/tcp_output.c,v 1.21 2004/12/21 02:54:15 hsu Exp $
88 #include "opt_inet6.h"
89 #include "opt_ipsec.h"
90 #include "opt_tcpdebug.h"
92 #include <sys/param.h>
93 #include <sys/systm.h>
94 #include <sys/kernel.h>
95 #include <sys/sysctl.h>
97 #include <sys/domain.h>
98 #include <sys/protosw.h>
99 #include <sys/socket.h>
100 #include <sys/socketvar.h>
101 #include <sys/in_cksum.h>
102 #include <sys/thread.h>
103 #include <sys/globaldata.h>
105 #include <net/route.h>
107 #include <netinet/in.h>
108 #include <netinet/in_systm.h>
109 #include <netinet/ip.h>
110 #include <netinet/in_pcb.h>
111 #include <netinet/ip_var.h>
112 #include <netinet6/in6_pcb.h>
113 #include <netinet/ip6.h>
114 #include <netinet6/ip6_var.h>
115 #include <netinet/tcp.h>
117 #include <netinet/tcp_fsm.h>
118 #include <netinet/tcp_seq.h>
119 #include <netinet/tcp_timer.h>
120 #include <netinet/tcp_var.h>
121 #include <netinet/tcpip.h>
123 #include <netinet/tcp_debug.h>
127 #include <netinet6/ipsec.h>
131 #include <netproto/ipsec/ipsec.h>
133 #endif /*FAST_IPSEC*/
136 extern struct mbuf *m_copypack();
139 int path_mtu_discovery = 1;
140 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW,
141 &path_mtu_discovery, 1, "Enable Path MTU Discovery");
144 SYSCTL_INT(_net_inet_tcp, OID_AUTO, slowstart_flightsize, CTLFLAG_RW,
145 &ss_fltsz, 1, "Slow start flight size");
147 int ss_fltsz_local = 4;
148 SYSCTL_INT(_net_inet_tcp, OID_AUTO, local_slowstart_flightsize, CTLFLAG_RW,
149 &ss_fltsz_local, 1, "Slow start flight size for local networks");
151 static int avoid_pure_win_update = 1;
152 SYSCTL_INT(_net_inet_tcp, OID_AUTO, avoid_pure_win_update, CTLFLAG_RW,
153 &avoid_pure_win_update, 1, "Avoid pure window updates when possible");
156 * Tcp output routine: figure out what should be sent and send it.
162 struct inpcb * const inp = tp->t_inpcb;
163 struct socket *so = inp->inp_socket;
164 long len, recvwin, sendwin;
165 int off, flags, error;
167 struct ip *ip = NULL;
168 struct ipovly *ipov = NULL;
170 u_char opt[TCP_MAXOLEN];
171 unsigned int ipoptlen, optlen, hdrlen;
174 struct ip6_hdr *ip6 = NULL;
176 const boolean_t isipv6 = (inp->inp_vflag & INP_IPV6) != 0;
178 const boolean_t isipv6 = FALSE;
180 struct rmxp_tao *taop;
183 * Determine length of data that should be transmitted,
184 * and flags that will be used.
185 * If there is some data or critical controls (SYN, RST)
186 * to send, then transmit; otherwise, investigate further.
188 if ((tp->snd_max == tp->snd_una) &&
189 (ticks - tp->t_rcvtime) >= tp->t_rxtcur) {
191 * We have been idle for "a while" and no acks are
192 * expected to clock out any data we send --
193 * slow start to get ack "clock" running again.
195 * Set the slow-start flight size depending on whether
196 * this is a local network or not.
198 if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) ||
199 (!isipv6 && in_localaddr(inp->inp_faddr)))
200 tp->snd_cwnd = tp->t_maxseg * ss_fltsz_local;
202 tp->snd_cwnd = tp->t_maxseg * ss_fltsz;
204 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una);
205 if (idle && (tp->t_flags & TF_MORETOCOME))
206 tp->t_flags |= TF_LASTIDLE;
208 tp->t_flags &= ~TF_LASTIDLE;
211 /* Make use of SACK information when slow-starting after a RTO. */
212 if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max &&
213 !IN_FASTRECOVERY(tp))
214 tcp_sack_skip_sacked(&tp->scb, &tp->snd_nxt);
217 off = tp->snd_nxt - tp->snd_una;
218 sendwin = min(tp->snd_wnd, tp->snd_cwnd);
219 sendwin = min(sendwin, tp->snd_bwnd);
221 flags = tcp_outflags[tp->t_state];
223 * Get standard flags, and add SYN or FIN if requested by 'hidden'
226 if (tp->t_flags & TF_NEEDFIN)
228 if (tp->t_flags & TF_NEEDSYN)
232 * If in persist timeout with window of 0, send 1 byte.
233 * Otherwise, if window is small but nonzero
234 * and timer expired, we will send what we can
235 * and go to transmit state.
237 if (tp->t_flags & TF_FORCE) {
240 * If we still have some data to send, then
241 * clear the FIN bit. Usually this would
242 * happen below when it realizes that we
243 * aren't sending all the data. However,
244 * if we have exactly 1 byte of unsent data,
245 * then it won't clear the FIN bit below,
246 * and if we are in persist state, we wind
247 * up sending the packet without recording
248 * that we sent the FIN bit.
250 * We can't just blindly clear the FIN bit,
251 * because if we don't have any more data
252 * to send then the probe will be the FIN
255 if (off < so->so_snd.sb_cc)
259 callout_stop(tp->tt_persist);
265 * If snd_nxt == snd_max and we have transmitted a FIN, the
266 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in
267 * a negative length. This can also occur when TCP opens up
268 * its congestion window while receiving additional duplicate
269 * acks after fast-retransmit because TCP will reset snd_nxt
270 * to snd_max after the fast-retransmit.
272 * In the normal retransmit-FIN-only case, however, snd_nxt will
273 * be set to snd_una, the offset will be 0, and the length may
276 len = (long)ulmin(so->so_snd.sb_cc, sendwin) - off;
279 * Lop off SYN bit if it has already been sent. However, if this
280 * is SYN-SENT state and if segment contains data and if we don't
281 * know that foreign host supports TAO, suppress sending segment.
283 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) {
286 if (len > 0 && tp->t_state == TCPS_SYN_SENT &&
287 ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL ||
288 taop->tao_ccsent == 0))
293 * Be careful not to send data and/or FIN on SYN segments
294 * in cases when no CC option will be sent.
295 * This measure is needed to prevent interoperability problems
296 * with not fully conformant TCP implementations.
298 if ((flags & TH_SYN) &&
299 ((tp->t_flags & TF_NOOPT) || !(tp->t_flags & TF_REQ_CC) ||
300 ((flags & TH_ACK) && !(tp->t_flags & TF_RCVD_CC)))) {
307 * If FIN has been sent but not acked,
308 * but we haven't been called to retransmit,
309 * len will be < 0. Otherwise, window shrank
310 * after we sent into it. If window shrank to 0,
311 * cancel pending retransmit, pull snd_nxt back
312 * to (closed) window, and set the persist timer
313 * if it isn't already going. If the window didn't
314 * close completely, just wait for an ACK.
318 callout_stop(tp->tt_rexmt);
320 tp->snd_nxt = tp->snd_una;
321 if (!callout_active(tp->tt_persist))
327 * len will be >= 0 after this point. Truncate to the maximum
328 * segment length and ensure that FIN is removed if the length
329 * no longer contains the last data byte.
331 if (len > tp->t_maxseg) {
335 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc))
338 recvwin = sbspace(&so->so_rcv);
341 * Sender silly window avoidance. We transmit under the following
342 * conditions when len is non-zero:
344 * - We have a full segment
345 * - This is the last buffer in a write()/send() and we are
346 * either idle or running NODELAY
347 * - we've timed out (e.g. persist timer)
348 * - we have more then 1/2 the maximum send window's worth of
349 * data (receiver may be limited the window size)
350 * - we need to retransmit
353 if (len == tp->t_maxseg)
356 * NOTE! on localhost connections an 'ack' from the remote
357 * end may occur synchronously with the output and cause
358 * us to flush a buffer queued with moretocome. XXX
360 * note: the len + off check is almost certainly unnecessary.
362 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */
363 (idle || (tp->t_flags & TF_NODELAY)) &&
364 len + off >= so->so_snd.sb_cc &&
365 !(tp->t_flags & TF_NOPUSH)) {
368 if (tp->t_flags & TF_FORCE) /* typ. timeout case */
370 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0)
372 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */
377 * Compare available window to amount of window
378 * known to peer (as advertised window less
379 * next expected input). If the difference is at least two
380 * max size segments, or at least 50% of the maximum possible
381 * window, then want to send a window update to peer.
385 * "adv" is the amount we can increase the window,
386 * taking into account that we are limited by
387 * TCP_MAXWIN << tp->rcv_scale.
389 long adv = min(recvwin, (long)TCP_MAXWIN << tp->rcv_scale) -
390 (tp->rcv_adv - tp->rcv_nxt);
393 * This ack case typically occurs when the user has drained
394 * the TCP socket buffer sufficiently to warrent an ack
395 * containing a 'pure window update'... that is, an ack that
396 * ONLY updates the tcp window.
398 * It is unclear why we would need to do a pure window update
399 * past 2 segments if we are going to do one at 1/2 the high
400 * water mark anyway, especially since under normal conditions
401 * the user program will drain the socket buffer quickly.
402 * The 2-segment pure window update will often add a large
403 * number of extra, unnecessary acks to the stream.
405 * avoid_pure_win_update now defaults to 1.
407 if (avoid_pure_win_update == 0) {
408 if (adv >= (long) (2 * tp->t_maxseg))
411 if (2 * adv >= (long) so->so_rcv.sb_hiwat)
416 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW
417 * is also a catch-all for the retransmit timer timeout case.
419 if (tp->t_flags & TF_ACKNOW)
421 if ((flags & TH_RST) ||
422 ((flags & TH_SYN) && !(tp->t_flags & TF_NEEDSYN)))
424 if (SEQ_GT(tp->snd_up, tp->snd_una))
427 * If our state indicates that FIN should be sent
428 * and we have not yet done so, then we need to send.
430 if (flags & TH_FIN &&
431 (!(tp->t_flags & TF_SENTFIN) || tp->snd_nxt == tp->snd_una))
435 * TCP window updates are not reliable, rather a polling protocol
436 * using ``persist'' packets is used to insure receipt of window
437 * updates. The three ``states'' for the output side are:
438 * idle not doing retransmits or persists
439 * persisting to move a small or zero window
440 * (re)transmitting and thereby not persisting
442 * callout_active(tp->tt_persist)
443 * is true when we are in persist state.
444 * The TF_FORCE flag in tp->t_flags
445 * is set when we are called to send a persist packet.
446 * callout_active(tp->tt_rexmt)
447 * is set when we are retransmitting
448 * The output side is idle when both timers are zero.
450 * If send window is too small, there is data to transmit, and no
451 * retransmit or persist is pending, then go to persist state.
452 * If nothing happens soon, send when timer expires:
453 * if window is nonzero, transmit what we can,
454 * otherwise force out a byte.
456 if (so->so_snd.sb_cc > 0 &&
457 !callout_active(tp->tt_rexmt) && !callout_active(tp->tt_persist)) {
463 * No reason to send a segment, just return.
469 * Before ESTABLISHED, force sending of initial options
470 * unless TCP set not to do any options.
471 * NOTE: we assume that the IP/TCP header plus TCP options
472 * always fit in a single mbuf, leaving room for a maximum
474 * max_linkhdr + sizeof(struct tcpiphdr) + optlen <= MCLBYTES
478 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
480 hdrlen = sizeof(struct tcpiphdr);
481 if (flags & TH_SYN) {
482 tp->snd_nxt = tp->iss;
483 if (!(tp->t_flags & TF_NOOPT)) {
486 opt[0] = TCPOPT_MAXSEG;
487 opt[1] = TCPOLEN_MAXSEG;
488 mss = htons((u_short) tcp_mssopt(tp));
489 memcpy(opt + 2, &mss, sizeof mss);
490 optlen = TCPOLEN_MAXSEG;
492 if ((tp->t_flags & TF_REQ_SCALE) &&
493 (!(flags & TH_ACK) ||
494 (tp->t_flags & TF_RCVD_SCALE))) {
495 *((u_int32_t *)(opt + optlen)) = htonl(
497 TCPOPT_WINDOW << 16 |
498 TCPOLEN_WINDOW << 8 |
499 tp->request_r_scale);
503 if ((tcp_do_sack && !(flags & TH_ACK)) ||
504 tp->t_flags & TF_SACK_PERMITTED) {
505 uint32_t *lp = (uint32_t *)(opt + optlen);
507 *lp = htonl(TCPOPT_SACK_PERMITTED_ALIGNED);
508 optlen += TCPOLEN_SACK_PERMITTED_ALIGNED;
514 * Send a timestamp and echo-reply if this is a SYN and our side
515 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side
516 * and our peer have sent timestamps in our SYN's.
518 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP &&
520 (!(flags & TH_ACK) || (tp->t_flags & TF_RCVD_TSTMP))) {
521 u_int32_t *lp = (u_int32_t *)(opt + optlen);
523 /* Form timestamp option as shown in appendix A of RFC 1323. */
524 *lp++ = htonl(TCPOPT_TSTAMP_HDR);
525 *lp++ = htonl(ticks);
526 *lp = htonl(tp->ts_recent);
527 optlen += TCPOLEN_TSTAMP_APPA;
531 * Send `CC-family' options if our side wants to use them (TF_REQ_CC),
532 * options are allowed (!TF_NOOPT) and it's not a RST.
534 if ((tp->t_flags & (TF_REQ_CC | TF_NOOPT)) == TF_REQ_CC &&
536 switch (flags & (TH_SYN | TH_ACK)) {
538 * This is a normal ACK, send CC if we received CC before
542 if (!(tp->t_flags & TF_RCVD_CC))
547 * We can only get here in T/TCP's SYN_SENT* state, when
548 * we're a sending a non-SYN segment without waiting for
549 * the ACK of our SYN. A check above assures that we only
550 * do this if our peer understands T/TCP.
553 opt[optlen++] = TCPOPT_NOP;
554 opt[optlen++] = TCPOPT_NOP;
555 opt[optlen++] = TCPOPT_CC;
556 opt[optlen++] = TCPOLEN_CC;
557 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send);
562 * This is our initial SYN, check whether we have to use
566 opt[optlen++] = TCPOPT_NOP;
567 opt[optlen++] = TCPOPT_NOP;
568 opt[optlen++] = tp->t_flags & TF_SENDCCNEW ?
569 TCPOPT_CCNEW : TCPOPT_CC;
570 opt[optlen++] = TCPOLEN_CC;
571 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send);
576 * This is a SYN,ACK; send CC and CC.echo if we received
579 case (TH_SYN | TH_ACK):
580 if (tp->t_flags & TF_RCVD_CC) {
581 opt[optlen++] = TCPOPT_NOP;
582 opt[optlen++] = TCPOPT_NOP;
583 opt[optlen++] = TCPOPT_CC;
584 opt[optlen++] = TCPOLEN_CC;
585 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send);
587 opt[optlen++] = TCPOPT_NOP;
588 opt[optlen++] = TCPOPT_NOP;
589 opt[optlen++] = TCPOPT_CCECHO;
590 opt[optlen++] = TCPOLEN_CC;
591 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_recv);
599 * If this is a SACK connection and we have a block to report,
600 * fill in the SACK blocks in the TCP options.
602 if ((tp->t_flags & (TF_SACK_PERMITTED | TF_NOOPT)) ==
604 (!LIST_EMPTY(&tp->t_segq) ||
605 tp->reportblk.rblk_start != tp->reportblk.rblk_end))
606 tcp_sack_fill_report(tp, opt, &optlen);
608 KASSERT(optlen <= TCP_MAXOLEN, ("too many TCP options"));
612 ipoptlen = ip6_optlen(inp);
614 if (inp->inp_options) {
615 ipoptlen = inp->inp_options->m_len -
616 offsetof(struct ipoption, ipopt_list);
622 ipoptlen += ipsec_hdrsiz_tcp(tp);
626 * Adjust data length if insertion of options will
627 * bump the packet length beyond the t_maxopd length.
628 * Clear the FIN bit because we cut off the tail of
631 if (len + optlen + ipoptlen > tp->t_maxopd) {
633 * If there is still more to send, don't close the connection.
636 len = tp->t_maxopd - optlen - ipoptlen;
641 KASSERT(max_linkhdr + hdrlen <= MCLBYTES, ("tcphdr too big"));
643 KASSERT(max_linkhdr + hdrlen <= MHLEN, ("tcphdr too big"));
647 * Grab a header mbuf, attaching a copy of data to
648 * be transmitted, and initialize the header from
649 * the template for sends on this connection.
652 if ((tp->t_flags & TF_FORCE) && len == 1)
653 tcpstat.tcps_sndprobe++;
654 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) {
655 if (tp->snd_nxt == tp->snd_una)
656 tp->snd_max_rexmt = tp->snd_max;
657 tcpstat.tcps_sndrexmitpack++;
658 tcpstat.tcps_sndrexmitbyte += len;
660 tcpstat.tcps_sndpack++;
661 tcpstat.tcps_sndbyte += len;
664 if ((m = m_copypack(so->so_snd.sb_mb, off, (int)len,
665 max_linkhdr + hdrlen)) == NULL) {
670 * m_copypack left space for our hdr; use it.
675 MGETHDR(m, MB_DONTWAIT, MT_HEADER);
681 if (MHLEN < hdrlen + max_linkhdr) {
682 MCLGET(m, MB_DONTWAIT);
683 if (!(m->m_flags & M_EXT)) {
690 m->m_data += max_linkhdr;
692 if (len <= MHLEN - hdrlen - max_linkhdr) {
693 m_copydata(so->so_snd.sb_mb, off, (int) len,
694 mtod(m, caddr_t) + hdrlen);
697 m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len);
698 if (m->m_next == NULL) {
706 * If we're sending everything we've got, set PUSH.
707 * (This will keep happy those implementations which only
708 * give data to the user when a buffer fills or
711 if (off + len == so->so_snd.sb_cc)
714 if (tp->t_flags & TF_ACKNOW)
715 tcpstat.tcps_sndacks++;
716 else if (flags & (TH_SYN | TH_FIN | TH_RST))
717 tcpstat.tcps_sndctrl++;
718 else if (SEQ_GT(tp->snd_up, tp->snd_una))
719 tcpstat.tcps_sndurg++;
721 tcpstat.tcps_sndwinup++;
723 MGETHDR(m, MB_DONTWAIT, MT_HEADER);
729 (hdrlen + max_linkhdr > MHLEN) && hdrlen <= MHLEN)
732 m->m_data += max_linkhdr;
735 m->m_pkthdr.rcvif = (struct ifnet *)0;
737 ip6 = mtod(m, struct ip6_hdr *);
738 th = (struct tcphdr *)(ip6 + 1);
739 tcp_fillheaders(tp, ip6, th);
741 ip = mtod(m, struct ip *);
742 ipov = (struct ipovly *)ip;
743 th = (struct tcphdr *)(ip + 1);
744 /* this picks up the pseudo header (w/o the length) */
745 tcp_fillheaders(tp, ip, th);
749 * Fill in fields, remembering maximum advertised
750 * window for use in delaying messages about window sizes.
751 * If resending a FIN, be sure not to use a new sequence number.
753 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN &&
754 tp->snd_nxt == tp->snd_max)
757 * If we are doing retransmissions, then snd_nxt will
758 * not reflect the first unsent octet. For ACK only
759 * packets, we do not want the sequence number of the
760 * retransmitted packet, we want the sequence number
761 * of the next unsent octet. So, if there is no data
762 * (and no SYN or FIN), use snd_max instead of snd_nxt
763 * when filling in ti_seq. But if we are in persist
764 * state, snd_max might reflect one byte beyond the
765 * right edge of the window, so use snd_nxt in that
766 * case, since we know we aren't doing a retransmission.
767 * (retransmit and persist are mutually exclusive...)
769 if (len || (flags & (TH_SYN|TH_FIN)) || callout_active(tp->tt_persist))
770 th->th_seq = htonl(tp->snd_nxt);
772 th->th_seq = htonl(tp->snd_max);
773 th->th_ack = htonl(tp->rcv_nxt);
775 bcopy(opt, th + 1, optlen);
776 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
778 th->th_flags = flags;
780 * Calculate receive window. Don't shrink window,
781 * but avoid silly window syndrome.
783 if (recvwin < (long)(so->so_rcv.sb_hiwat / 4) &&
784 recvwin < (long)tp->t_maxseg)
786 if (recvwin < (long)(tp->rcv_adv - tp->rcv_nxt))
787 recvwin = (long)(tp->rcv_adv - tp->rcv_nxt);
788 if (recvwin > (long)TCP_MAXWIN << tp->rcv_scale)
789 recvwin = (long)TCP_MAXWIN << tp->rcv_scale;
790 th->th_win = htons((u_short) (recvwin>>tp->rcv_scale));
793 * Adjust the RXWIN0SENT flag - indicate that we have advertised
794 * a 0 window. This may cause the remote transmitter to stall. This
795 * flag tells soreceive() to disable delayed acknowledgements when
796 * draining the buffer. This can occur if the receiver is attempting
797 * to read more data then can be buffered prior to transmitting on
801 tp->t_flags |= TF_RXWIN0SENT;
803 tp->t_flags &= ~TF_RXWIN0SENT;
805 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) {
806 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt));
807 th->th_flags |= TH_URG;
810 * If no urgent pointer to send, then we pull
811 * the urgent pointer to the left edge of the send window
812 * so that it doesn't drift into the send window on sequence
815 tp->snd_up = tp->snd_una; /* drag it along */
819 * Put TCP length in extended header, and then
820 * checksum extended header and data.
822 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */
825 * ip6_plen is not need to be filled now, and will be filled
828 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr),
829 sizeof(struct tcphdr) + optlen + len);
831 m->m_pkthdr.csum_flags = CSUM_TCP;
832 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
834 th->th_sum = in_addword(th->th_sum,
835 htons((u_short)(optlen + len)));
837 /* IP version must be set here for ipv4/ipv6 checking later */
838 KASSERT(ip->ip_v == IPVERSION,
839 ("%s: IP version incorrect: %d", __func__, ip->ip_v));
843 * In transmit state, time the transmission and arrange for
844 * the retransmit. In persist state, just set snd_max.
846 if (!(tp->t_flags & TF_FORCE) || !callout_active(tp->tt_persist)) {
847 tcp_seq startseq = tp->snd_nxt;
850 * Advance snd_nxt over sequence space of this segment.
852 if (flags & (TH_SYN | TH_FIN)) {
855 if (flags & TH_FIN) {
857 tp->t_flags |= TF_SENTFIN;
861 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) {
862 tp->snd_max = tp->snd_nxt;
864 * Time this transmission if not a retransmission and
865 * not currently timing anything.
867 if (tp->t_rtttime == 0) {
868 tp->t_rtttime = ticks;
869 tp->t_rtseq = startseq;
870 tcpstat.tcps_segstimed++;
875 * Set retransmit timer if not currently set,
876 * and not doing a pure ack or a keep-alive probe.
877 * Initial value for retransmit timer is smoothed
878 * round-trip time + 2 * round-trip time variance.
879 * Initialize shift counter which is used for backoff
880 * of retransmit time.
882 if (!callout_active(tp->tt_rexmt) &&
883 tp->snd_nxt != tp->snd_una) {
884 if (callout_active(tp->tt_persist)) {
885 callout_stop(tp->tt_persist);
888 callout_reset(tp->tt_rexmt, tp->t_rxtcur,
889 tcp_timer_rexmt, tp);
893 * Persist case, update snd_max but since we are in
894 * persist mode (no window) we do not update snd_nxt.
899 if (flags & TH_FIN) {
901 tp->t_flags |= TF_SENTFIN;
903 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max))
904 tp->snd_max = tp->snd_nxt + xlen;
911 if (so->so_options & SO_DEBUG)
912 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0);
916 * Fill in IP length and desired time to live and
917 * send to IP level. There should be a better way
918 * to handle ttl and tos; we could keep them in
919 * the template, but need a way to checksum without them.
922 * m->m_pkthdr.len should have been set before cksum calcuration,
923 * because in6_cksum() need it.
927 * we separately set hoplimit for every segment, since the
928 * user might want to change the value via setsockopt.
929 * Also, desired default hop limit might be changed via
930 * Neighbor Discovery.
932 ip6->ip6_hlim = in6_selecthlim(inp,
933 (inp->in6p_route.ro_rt ?
934 inp->in6p_route.ro_rt->rt_ifp : NULL));
936 /* TODO: IPv6 IP6TOS_ECT bit on */
937 error = ip6_output(m, inp->in6p_outputopts, &inp->in6p_route,
938 (so->so_options & SO_DONTROUTE), NULL, NULL, inp);
941 ip->ip_len = m->m_pkthdr.len;
943 if (INP_CHECK_SOCKAF(so, AF_INET6))
944 ip->ip_ttl = in6_selecthlim(inp,
945 (inp->in6p_route.ro_rt ?
946 inp->in6p_route.ro_rt->rt_ifp : NULL));
949 ip->ip_ttl = inp->inp_ip_ttl; /* XXX */
951 ip->ip_tos = inp->inp_ip_tos; /* XXX */
953 * See if we should do MTU discovery.
954 * We do it only if the following are true:
955 * 1) we have a valid route to the destination
956 * 2) the MTU is not locked (if it is,
957 * then discovery has been disabled)
959 if (path_mtu_discovery &&
960 (rt = inp->inp_route.ro_rt) && (rt->rt_flags & RTF_UP) &&
961 !(rt->rt_rmx.rmx_locks & RTV_MTU))
964 error = ip_output(m, inp->inp_options, &inp->inp_route,
965 (so->so_options & SO_DONTROUTE), NULL, inp);
970 * We know that the packet was lost, so back out the
971 * sequence number advance, if any.
973 if (!(tp->t_flags & TF_FORCE) ||
974 !callout_active(tp->tt_persist)) {
976 * No need to check for TH_FIN here because
977 * the TF_SENTFIN flag handles that case.
979 if (!(flags & TH_SYN))
984 if (error == ENOBUFS) {
986 * If we can't send, make sure there is something
987 * to get us going again later. Persist state
988 * is not necessarily right, but it is close enough.
990 if (!callout_active(tp->tt_rexmt) &&
991 !callout_active(tp->tt_persist)) {
998 if (error == EMSGSIZE) {
1000 * ip_output() will have already fixed the route
1001 * for us. tcp_mtudisc() will, as its last action,
1002 * initiate retransmission, so it is important to
1005 tcp_mtudisc(inp, 0);
1008 if ((error == EHOSTUNREACH || error == ENETDOWN) &&
1009 TCPS_HAVERCVDSYN(tp->t_state)) {
1010 tp->t_softerror = error;
1015 tcpstat.tcps_sndtotal++;
1018 * Data sent (as far as we can tell).
1019 * If this advertises a larger window than any other segment,
1020 * then remember the size of the advertised window.
1021 * Any pending ACK has now been sent.
1023 if (recvwin > 0 && SEQ_GT(tp->rcv_nxt + recvwin, tp->rcv_adv))
1024 tp->rcv_adv = tp->rcv_nxt + recvwin;
1025 tp->last_ack_sent = tp->rcv_nxt;
1026 tp->t_flags &= ~TF_ACKNOW;
1027 if (tcp_delack_enabled)
1028 callout_stop(tp->tt_delack);
1038 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1;
1041 if (callout_active(tp->tt_rexmt))
1042 panic("tcp_setpersist: retransmit pending");
1044 * Start/restart persistance timer.
1046 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift],
1047 TCPTV_PERSMIN, TCPTV_PERSMAX);
1048 callout_reset(tp->tt_persist, tt, tcp_timer_persist, tp);
1049 if (tp->t_rxtshift < TCP_MAXRXTSHIFT)