2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
3 * The Regents of the University of California. All rights reserved.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 4. Neither the name of the University nor the names of its contributors
14 * may be used to endorse or promote products derived from this software
15 * without specific prior written permission.
17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95
32 #include <sys/cdefs.h>
33 __FBSDID("$FreeBSD$");
36 #include "opt_inet6.h"
37 #include "opt_ipsec.h"
38 #include "opt_kdtrace.h"
39 #include "opt_tcpdebug.h"
41 #include <sys/param.h>
42 #include <sys/systm.h>
43 #include <sys/domain.h>
44 #include <sys/hhook.h>
45 #include <sys/kernel.h>
48 #include <sys/mutex.h>
49 #include <sys/protosw.h>
51 #include <sys/socket.h>
52 #include <sys/socketvar.h>
53 #include <sys/sysctl.h>
56 #include <net/route.h>
59 #include <netinet/cc.h>
60 #include <netinet/in.h>
61 #include <netinet/in_kdtrace.h>
62 #include <netinet/in_systm.h>
63 #include <netinet/ip.h>
64 #include <netinet/in_pcb.h>
65 #include <netinet/ip_var.h>
66 #include <netinet/ip_options.h>
68 #include <netinet6/in6_pcb.h>
69 #include <netinet/ip6.h>
70 #include <netinet6/ip6_var.h>
73 #include <netinet/tcp_fastopen.h>
76 #include <netinet/tcp_fsm.h>
77 #include <netinet/tcp_seq.h>
78 #include <netinet/tcp_timer.h>
79 #include <netinet/tcp_var.h>
80 #include <netinet/tcpip.h>
82 #include <netinet/tcp_debug.h>
85 #include <netinet/tcp_offload.h>
89 #include <netipsec/ipsec.h>
92 #include <machine/in_cksum.h>
94 #include <security/mac/mac_framework.h>
96 VNET_DEFINE(int, path_mtu_discovery) = 1;
97 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW,
98 &VNET_NAME(path_mtu_discovery), 1,
99 "Enable Path MTU Discovery");
101 VNET_DEFINE(int, tcp_do_tso) = 1;
102 #define V_tcp_do_tso VNET(tcp_do_tso)
103 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_RW,
104 &VNET_NAME(tcp_do_tso), 0,
105 "Enable TCP Segmentation Offload");
107 VNET_DEFINE(int, tcp_sendspace) = 1024*32;
108 #define V_tcp_sendspace VNET(tcp_sendspace)
109 SYSCTL_VNET_INT(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, CTLFLAG_RW,
110 &VNET_NAME(tcp_sendspace), 0, "Initial send socket buffer size");
112 VNET_DEFINE(int, tcp_do_autosndbuf) = 1;
113 #define V_tcp_do_autosndbuf VNET(tcp_do_autosndbuf)
114 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_RW,
115 &VNET_NAME(tcp_do_autosndbuf), 0,
116 "Enable automatic send buffer sizing");
118 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024;
119 #define V_tcp_autosndbuf_inc VNET(tcp_autosndbuf_inc)
120 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_RW,
121 &VNET_NAME(tcp_autosndbuf_inc), 0,
122 "Incrementor step size of automatic send buffer");
124 VNET_DEFINE(int, tcp_autosndbuf_max) = 2*1024*1024;
125 #define V_tcp_autosndbuf_max VNET(tcp_autosndbuf_max)
126 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_RW,
127 &VNET_NAME(tcp_autosndbuf_max), 0,
128 "Max size of automatic send buffer");
130 static void inline hhook_run_tcp_est_out(struct tcpcb *tp,
131 struct tcphdr *th, struct tcpopt *to,
133 static void inline cc_after_idle(struct tcpcb *tp);
136 * Wrapper for the TCP established output helper hook.
139 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th,
140 struct tcpopt *to, long len, int tso)
142 struct tcp_hhook_data hhook_data;
144 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) {
148 hhook_data.len = len;
149 hhook_data.tso = tso;
151 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data,
157 * CC wrapper hook functions
160 cc_after_idle(struct tcpcb *tp)
162 INP_WLOCK_ASSERT(tp->t_inpcb);
164 if (CC_ALGO(tp)->after_idle != NULL)
165 CC_ALGO(tp)->after_idle(tp->ccv);
169 * Tcp output routine: figure out what should be sent and send it.
172 tcp_output(struct tcpcb *tp)
174 struct socket *so = tp->t_inpcb->inp_socket;
175 long len, recwin, sendwin;
176 int off, flags, error = 0; /* Keep compiler happy */
178 struct ip *ip = NULL;
179 struct ipovly *ipov = NULL;
181 u_char opt[TCP_MAXOLEN];
182 unsigned ipoptlen, optlen, hdrlen;
184 unsigned ipsec_optlen = 0;
187 int sack_rxmit, sack_bytes_rxmt;
192 int maxburst = TCP_MAXBURST;
195 struct ip6_hdr *ip6 = NULL;
198 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0;
201 INP_WLOCK_ASSERT(tp->t_inpcb);
204 if (tp->t_flags & TF_TOE)
205 return (tcp_offload_output(tp));
210 * For TFO connections in SYN_RECEIVED, only allow the initial
211 * SYN|ACK and those sent by the retransmit timer.
213 if ((tp->t_flags & TF_FASTOPEN) &&
214 (tp->t_state == TCPS_SYN_RECEIVED) &&
215 SEQ_GT(tp->snd_max, tp->snd_una) && /* inital SYN|ACK sent */
216 (tp->snd_nxt != tp->snd_una)) /* not a retransmit */
220 * Determine length of data that should be transmitted,
221 * and flags that will be used.
222 * If there is some data or critical controls (SYN, RST)
223 * to send, then transmit; otherwise, investigate further.
225 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una);
226 if (idle && ticks - tp->t_rcvtime >= tp->t_rxtcur)
228 tp->t_flags &= ~TF_LASTIDLE;
230 if (tp->t_flags & TF_MORETOCOME) {
231 tp->t_flags |= TF_LASTIDLE;
237 * If we've recently taken a timeout, snd_max will be greater than
238 * snd_nxt. There may be SACK information that allows us to avoid
239 * resending already delivered data. Adjust snd_nxt accordingly.
241 if ((tp->t_flags & TF_SACK_PERMIT) &&
242 SEQ_LT(tp->snd_nxt, tp->snd_max))
247 off = tp->snd_nxt - tp->snd_una;
248 sendwin = min(tp->snd_wnd, tp->snd_cwnd);
250 flags = tcp_outflags[tp->t_state];
252 * Send any SACK-generated retransmissions. If we're explicitly trying
253 * to send out new data (when sendalot is 1), bypass this function.
254 * If we retransmit in fast recovery mode, decrement snd_cwnd, since
255 * we're replacing a (future) new transmission with a retransmission
256 * now, and we previously incremented snd_cwnd in tcp_input().
259 * Still in sack recovery , reset rxmit flag to zero.
265 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) &&
266 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) {
269 cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt;
272 /* Do not retransmit SACK segments beyond snd_recover */
273 if (SEQ_GT(p->end, tp->snd_recover)) {
275 * (At least) part of sack hole extends beyond
276 * snd_recover. Check to see if we can rexmit data
279 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) {
281 * Can't rexmit any more data for this hole.
282 * That data will be rexmitted in the next
283 * sack recovery episode, when snd_recover
284 * moves past p->rxmit.
287 goto after_sack_rexmit;
289 /* Can rexmit part of the current hole */
290 len = ((long)ulmin(cwin,
291 tp->snd_recover - p->rxmit));
293 len = ((long)ulmin(cwin, p->end - p->rxmit));
294 off = p->rxmit - tp->snd_una;
295 KASSERT(off >= 0,("%s: sack block to the left of una : %d",
300 TCPSTAT_INC(tcps_sack_rexmits);
301 TCPSTAT_ADD(tcps_sack_rexmit_bytes,
302 min(len, tp->t_maxseg));
307 * Get standard flags, and add SYN or FIN if requested by 'hidden'
310 if (tp->t_flags & TF_NEEDFIN)
312 if (tp->t_flags & TF_NEEDSYN)
315 SOCKBUF_LOCK(&so->so_snd);
317 * If in persist timeout with window of 0, send 1 byte.
318 * Otherwise, if window is small but nonzero
319 * and timer expired, we will send what we can
320 * and go to transmit state.
322 if (tp->t_flags & TF_FORCEDATA) {
325 * If we still have some data to send, then
326 * clear the FIN bit. Usually this would
327 * happen below when it realizes that we
328 * aren't sending all the data. However,
329 * if we have exactly 1 byte of unsent data,
330 * then it won't clear the FIN bit below,
331 * and if we are in persist state, we wind
332 * up sending the packet without recording
333 * that we sent the FIN bit.
335 * We can't just blindly clear the FIN bit,
336 * because if we don't have any more data
337 * to send then the probe will be the FIN
340 if (off < so->so_snd.sb_cc)
344 tcp_timer_activate(tp, TT_PERSIST, 0);
350 * If snd_nxt == snd_max and we have transmitted a FIN, the
351 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in
352 * a negative length. This can also occur when TCP opens up
353 * its congestion window while receiving additional duplicate
354 * acks after fast-retransmit because TCP will reset snd_nxt
355 * to snd_max after the fast-retransmit.
357 * In the normal retransmit-FIN-only case, however, snd_nxt will
358 * be set to snd_una, the offset will be 0, and the length may
361 * If sack_rxmit is true we are retransmitting from the scoreboard
362 * in which case len is already set.
364 if (sack_rxmit == 0) {
365 if (sack_bytes_rxmt == 0)
366 len = ((long)ulmin(so->so_snd.sb_cc, sendwin) - off);
371 * We are inside of a SACK recovery episode and are
372 * sending new data, having retransmitted all the
373 * data possible in the scoreboard.
375 len = ((long)ulmin(so->so_snd.sb_cc, tp->snd_wnd)
378 * Don't remove this (len > 0) check !
379 * We explicitly check for len > 0 here (although it
380 * isn't really necessary), to work around a gcc
381 * optimization issue - to force gcc to compute
382 * len above. Without this check, the computation
383 * of len is bungled by the optimizer.
386 cwin = tp->snd_cwnd -
387 (tp->snd_nxt - tp->sack_newdata) -
391 len = lmin(len, cwin);
397 * Lop off SYN bit if it has already been sent. However, if this
398 * is SYN-SENT state and if segment contains data and if we don't
399 * know that foreign host supports TAO, suppress sending segment.
401 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) {
402 if (tp->t_state != TCPS_SYN_RECEIVED)
406 * When sending additional segments following a TFO SYN|ACK,
407 * do not include the SYN bit.
409 if ((tp->t_flags & TF_FASTOPEN) &&
410 (tp->t_state == TCPS_SYN_RECEIVED))
417 * Be careful not to send data and/or FIN on SYN segments.
418 * This measure is needed to prevent interoperability problems
419 * with not fully conformant TCP implementations.
421 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) {
428 * When retransmitting SYN|ACK on a passively-created TFO socket,
429 * don't include data, as the presence of data may have caused the
430 * original SYN|ACK to have been dropped by a middlebox.
432 if ((tp->t_flags & TF_FASTOPEN) &&
433 (((tp->t_state == TCPS_SYN_RECEIVED) && (tp->t_rxtshift > 0)) ||
439 * If FIN has been sent but not acked,
440 * but we haven't been called to retransmit,
441 * len will be < 0. Otherwise, window shrank
442 * after we sent into it. If window shrank to 0,
443 * cancel pending retransmit, pull snd_nxt back
444 * to (closed) window, and set the persist timer
445 * if it isn't already going. If the window didn't
446 * close completely, just wait for an ACK.
448 * We also do a general check here to ensure that
449 * we will set the persist timer when we have data
450 * to send, but a 0-byte window. This makes sure
451 * the persist timer is set even if the packet
452 * hits one of the "goto send" lines below.
455 if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) &&
456 (off < (int) so->so_snd.sb_cc)) {
457 tcp_timer_activate(tp, TT_REXMT, 0);
459 tp->snd_nxt = tp->snd_una;
460 if (!tcp_timer_active(tp, TT_PERSIST))
465 /* len will be >= 0 after this point. */
466 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__));
469 * Automatic sizing of send socket buffer. Often the send buffer
470 * size is not optimally adjusted to the actual network conditions
471 * at hand (delay bandwidth product). Setting the buffer size too
472 * small limits throughput on links with high bandwidth and high
473 * delay (eg. trans-continental/oceanic links). Setting the
474 * buffer size too big consumes too much real kernel memory,
475 * especially with many connections on busy servers.
477 * The criteria to step up the send buffer one notch are:
478 * 1. receive window of remote host is larger than send buffer
479 * (with a fudge factor of 5/4th);
480 * 2. send buffer is filled to 7/8th with data (so we actually
481 * have data to make use of it);
482 * 3. send buffer fill has not hit maximal automatic size;
483 * 4. our send window (slow start and cogestion controlled) is
484 * larger than sent but unacknowledged data in send buffer.
486 * The remote host receive window scaling factor may limit the
487 * growing of the send buffer before it reaches its allowed
490 * It scales directly with slow start or congestion window
491 * and does at most one step per received ACK. This fast
492 * scaling has the drawback of growing the send buffer beyond
493 * what is strictly necessary to make full use of a given
494 * delay*bandwith product. However testing has shown this not
495 * to be much of an problem. At worst we are trading wasting
496 * of available bandwith (the non-use of it) for wasting some
497 * socket buffer memory.
499 * TODO: Shrink send buffer during idle periods together
500 * with congestion window. Requires another timer. Has to
501 * wait for upcoming tcp timer rewrite.
503 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) {
504 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat &&
505 so->so_snd.sb_cc >= (so->so_snd.sb_hiwat / 8 * 7) &&
506 so->so_snd.sb_cc < V_tcp_autosndbuf_max &&
507 sendwin >= (so->so_snd.sb_cc - (tp->snd_nxt - tp->snd_una))) {
508 if (!sbreserve_locked(&so->so_snd,
509 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc,
510 V_tcp_autosndbuf_max), so, curthread))
511 so->so_snd.sb_flags &= ~SB_AUTOSIZE;
516 * Decide if we can use TCP Segmentation Offloading (if supported by
519 * TSO may only be used if we are in a pure bulk sending state. The
520 * presence of TCP-MD5, SACK retransmits, SACK advertizements and
521 * IP options prevent using TSO. With TSO the TCP header is the same
522 * (except for the sequence number) for all generated packets. This
523 * makes it impossible to transmit any options which vary per generated
528 * Pre-calculate here as we save another lookup into the darknesses
529 * of IPsec that way and can actually decide if TSO is ok.
531 ipsec_optlen = ipsec_hdrsiz_tcp(tp);
533 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg &&
534 ((tp->t_flags & TF_SIGNATURE) == 0) &&
535 tp->rcv_numsacks == 0 && sack_rxmit == 0 &&
539 tp->t_inpcb->inp_options == NULL &&
540 tp->t_inpcb->in6p_options == NULL)
544 if (SEQ_LT(p->rxmit + len, tp->snd_una + so->so_snd.sb_cc))
547 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc))
551 recwin = sbspace(&so->so_rcv);
554 * Sender silly window avoidance. We transmit under the following
555 * conditions when len is non-zero:
557 * - We have a full segment (or more with TSO)
558 * - This is the last buffer in a write()/send() and we are
559 * either idle or running NODELAY
560 * - we've timed out (e.g. persist timer)
561 * - we have more then 1/2 the maximum send window's worth of
562 * data (receiver may be limited the window size)
563 * - we need to retransmit
566 if (len >= tp->t_maxseg)
569 * NOTE! on localhost connections an 'ack' from the remote
570 * end may occur synchronously with the output and cause
571 * us to flush a buffer queued with moretocome. XXX
573 * note: the len + off check is almost certainly unnecessary.
575 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */
576 (idle || (tp->t_flags & TF_NODELAY)) &&
577 len + off >= so->so_snd.sb_cc &&
578 (tp->t_flags & TF_NOPUSH) == 0) {
581 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */
583 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0)
585 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */
592 * Sending of standalone window updates.
594 * Window updates are important when we close our window due to a
595 * full socket buffer and are opening it again after the application
596 * reads data from it. Once the window has opened again and the
597 * remote end starts to send again the ACK clock takes over and
598 * provides the most current window information.
600 * We must avoid the silly window syndrome whereas every read
601 * from the receive buffer, no matter how small, causes a window
602 * update to be sent. We also should avoid sending a flurry of
603 * window updates when the socket buffer had queued a lot of data
604 * and the application is doing small reads.
606 * Prevent a flurry of pointless window updates by only sending
607 * an update when we can increase the advertized window by more
608 * than 1/4th of the socket buffer capacity. When the buffer is
609 * getting full or is very small be more aggressive and send an
610 * update whenever we can increase by two mss sized segments.
611 * In all other situations the ACK's to new incoming data will
612 * carry further window increases.
614 * Don't send an independent window update if a delayed
615 * ACK is pending (it will get piggy-backed on it) or the
616 * remote side already has done a half-close and won't send
617 * more data. Skip this if the connection is in T/TCP
620 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) &&
621 !(tp->t_flags & TF_DELACK) &&
622 !TCPS_HAVERCVDFIN(tp->t_state)) {
624 * "adv" is the amount we could increase the window,
625 * taking into account that we are limited by
626 * TCP_MAXWIN << tp->rcv_scale.
631 adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale);
632 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) {
633 oldwin = (tp->rcv_adv - tp->rcv_nxt);
639 * If the new window size ends up being the same as the old
640 * size when it is scaled, then don't force a window update.
642 if (oldwin >> tp->rcv_scale == (adv + oldwin) >> tp->rcv_scale)
645 if (adv >= (long)(2 * tp->t_maxseg) &&
646 (adv >= (long)(so->so_rcv.sb_hiwat / 4) ||
647 recwin <= (long)(so->so_rcv.sb_hiwat / 8) ||
648 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg))
654 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW
655 * is also a catch-all for the retransmit timer timeout case.
657 if (tp->t_flags & TF_ACKNOW)
659 if ((flags & TH_RST) ||
660 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0))
662 if (SEQ_GT(tp->snd_up, tp->snd_una))
665 * If our state indicates that FIN should be sent
666 * and we have not yet done so, then we need to send.
668 if (flags & TH_FIN &&
669 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una))
672 * In SACK, it is possible for tcp_output to fail to send a segment
673 * after the retransmission timer has been turned off. Make sure
674 * that the retransmission timer is set.
676 if ((tp->t_flags & TF_SACK_PERMIT) &&
677 SEQ_GT(tp->snd_max, tp->snd_una) &&
678 !tcp_timer_active(tp, TT_REXMT) &&
679 !tcp_timer_active(tp, TT_PERSIST)) {
680 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
684 * TCP window updates are not reliable, rather a polling protocol
685 * using ``persist'' packets is used to insure receipt of window
686 * updates. The three ``states'' for the output side are:
687 * idle not doing retransmits or persists
688 * persisting to move a small or zero window
689 * (re)transmitting and thereby not persisting
691 * tcp_timer_active(tp, TT_PERSIST)
692 * is true when we are in persist state.
693 * (tp->t_flags & TF_FORCEDATA)
694 * is set when we are called to send a persist packet.
695 * tcp_timer_active(tp, TT_REXMT)
696 * is set when we are retransmitting
697 * The output side is idle when both timers are zero.
699 * If send window is too small, there is data to transmit, and no
700 * retransmit or persist is pending, then go to persist state.
701 * If nothing happens soon, send when timer expires:
702 * if window is nonzero, transmit what we can,
703 * otherwise force out a byte.
705 if (so->so_snd.sb_cc && !tcp_timer_active(tp, TT_REXMT) &&
706 !tcp_timer_active(tp, TT_PERSIST)) {
712 * No reason to send a segment, just return.
715 SOCKBUF_UNLOCK(&so->so_snd);
719 SOCKBUF_LOCK_ASSERT(&so->so_snd);
721 if (len >= tp->t_maxseg)
722 tp->t_flags2 |= TF2_PLPMTU_MAXSEGSNT;
724 tp->t_flags2 &= ~TF2_PLPMTU_MAXSEGSNT;
727 * Before ESTABLISHED, force sending of initial options
728 * unless TCP set not to do any options.
729 * NOTE: we assume that the IP/TCP header plus TCP options
730 * always fit in a single mbuf, leaving room for a maximum
732 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES
737 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr);
740 hdrlen = sizeof (struct tcpiphdr);
743 * Compute options for segment.
744 * We only have to care about SYN and established connection
745 * segments. Options for SYN-ACK segments are handled in TCP
749 if ((tp->t_flags & TF_NOOPT) == 0) {
750 /* Maximum segment size. */
751 if (flags & TH_SYN) {
752 tp->snd_nxt = tp->iss;
753 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc);
754 to.to_flags |= TOF_MSS;
757 * Only include the TFO option on the first
758 * transmission of the SYN|ACK on a
759 * passively-created TFO socket, as the presence of
760 * the TFO option may have caused the original
761 * SYN|ACK to have been dropped by a middlebox.
763 if ((tp->t_flags & TF_FASTOPEN) &&
764 (tp->t_state == TCPS_SYN_RECEIVED) &&
765 (tp->t_rxtshift == 0)) {
766 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN;
767 to.to_tfo_cookie = (u_char *)&tp->t_tfo_cookie;
768 to.to_flags |= TOF_FASTOPEN;
772 /* Window scaling. */
773 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) {
774 to.to_wscale = tp->request_r_scale;
775 to.to_flags |= TOF_SCALE;
778 if ((tp->t_flags & TF_RCVD_TSTMP) ||
779 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) {
780 to.to_tsval = tcp_ts_getticks() + tp->ts_offset;
781 to.to_tsecr = tp->ts_recent;
782 to.to_flags |= TOF_TS;
783 /* Set receive buffer autosizing timestamp. */
784 if (tp->rfbuf_ts == 0 &&
785 (so->so_rcv.sb_flags & SB_AUTOSIZE))
786 tp->rfbuf_ts = tcp_ts_getticks();
788 /* Selective ACK's. */
789 if (tp->t_flags & TF_SACK_PERMIT) {
791 to.to_flags |= TOF_SACKPERM;
792 else if (TCPS_HAVEESTABLISHED(tp->t_state) &&
793 (tp->t_flags & TF_SACK_PERMIT) &&
794 tp->rcv_numsacks > 0) {
795 to.to_flags |= TOF_SACK;
796 to.to_nsacks = tp->rcv_numsacks;
797 to.to_sacks = (u_char *)tp->sackblks;
801 /* TCP-MD5 (RFC2385). */
802 if (tp->t_flags & TF_SIGNATURE)
803 to.to_flags |= TOF_SIGNATURE;
804 #endif /* TCP_SIGNATURE */
806 /* Processing the options. */
807 hdrlen += optlen = tcp_addoptions(&to, opt);
812 ipoptlen = ip6_optlen(tp->t_inpcb);
815 if (tp->t_inpcb->inp_options)
816 ipoptlen = tp->t_inpcb->inp_options->m_len -
817 offsetof(struct ipoption, ipopt_list);
821 ipoptlen += ipsec_optlen;
825 * Adjust data length if insertion of options will
826 * bump the packet length beyond the t_maxopd length.
827 * Clear the FIN bit because we cut off the tail of
830 if (len + optlen + ipoptlen > tp->t_maxopd) {
835 u_int if_hw_tsomaxsegcount;
836 u_int if_hw_tsomaxsegsize;
841 /* extract TSO information */
842 if_hw_tsomax = tp->t_tsomax;
843 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount;
844 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize;
847 * Limit a TSO burst to prevent it from
848 * overflowing or exceeding the maximum length
849 * allowed by the network interface:
851 KASSERT(ipoptlen == 0,
852 ("%s: TSO can't do IP options", __func__));
855 * Check if we should limit by maximum payload
858 if (if_hw_tsomax != 0) {
859 /* compute maximum TSO length */
860 max_len = (if_hw_tsomax - hdrlen -
864 } else if (len > max_len) {
871 * Check if we should limit by maximum segment
874 if (if_hw_tsomaxsegcount != 0 &&
875 if_hw_tsomaxsegsize != 0) {
877 * Subtract one segment for the LINK
878 * and TCP/IP headers mbuf that will
879 * be prepended to this mbuf chain
880 * after the code in this section
881 * limits the number of mbufs in the
882 * chain to if_hw_tsomaxsegcount.
884 if_hw_tsomaxsegcount -= 1;
886 mb = sbsndmbuf(&so->so_snd, off, &moff);
888 while (mb != NULL && max_len < len) {
893 * Get length of mbuf fragment
894 * and how many hardware frags,
895 * rounded up, it would use:
897 mlen = (mb->m_len - moff);
898 frags = howmany(mlen,
899 if_hw_tsomaxsegsize);
901 /* Handle special case: Zero Length Mbuf */
906 * Check if the fragment limit
907 * will be reached or exceeded:
909 if (frags >= if_hw_tsomaxsegcount) {
911 if_hw_tsomaxsegcount *
912 if_hw_tsomaxsegsize);
916 if_hw_tsomaxsegcount -= frags;
922 } else if (len > max_len) {
929 * Prevent the last segment from being
930 * fractional unless the send sockbuf can be
933 max_len = (tp->t_maxopd - optlen);
934 if ((off + len) < so->so_snd.sb_cc) {
935 moff = len % max_len;
943 * In case there are too many small fragments
946 if (len <= max_len) {
953 * Send the FIN in a separate segment
954 * after the bulk sending is done.
955 * We don't trust the TSO implementations
956 * to clear the FIN flag on all but the
959 if (tp->t_flags & TF_NEEDFIN)
963 len = tp->t_maxopd - optlen - ipoptlen;
969 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET,
970 ("%s: len > IP_MAXPACKET", __func__));
972 /*#ifdef DIAGNOSTIC*/
974 if (max_linkhdr + hdrlen > MCLBYTES)
976 if (max_linkhdr + hdrlen > MHLEN)
978 panic("tcphdr too big");
982 * This KASSERT is here to catch edge cases at a well defined place.
983 * Before, those had triggered (random) panic conditions further down.
985 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__));
988 * Grab a header mbuf, attaching a copy of data to
989 * be transmitted, and initialize the header from
990 * the template for sends on this connection.
996 if ((tp->t_flags & TF_FORCEDATA) && len == 1)
997 TCPSTAT_INC(tcps_sndprobe);
998 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) {
999 tp->t_sndrexmitpack++;
1000 TCPSTAT_INC(tcps_sndrexmitpack);
1001 TCPSTAT_ADD(tcps_sndrexmitbyte, len);
1003 TCPSTAT_INC(tcps_sndpack);
1004 TCPSTAT_ADD(tcps_sndbyte, len);
1007 if (MHLEN < hdrlen + max_linkhdr)
1008 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR);
1011 m = m_gethdr(M_NOWAIT, MT_DATA);
1014 SOCKBUF_UNLOCK(&so->so_snd);
1020 m->m_data += max_linkhdr;
1024 * Start the m_copy functions from the closest mbuf
1025 * to the offset in the socket buffer chain.
1027 mb = sbsndptr(&so->so_snd, off, len, &moff);
1029 if (len <= MHLEN - hdrlen - max_linkhdr) {
1030 m_copydata(mb, moff, (int)len,
1031 mtod(m, caddr_t) + hdrlen);
1034 m->m_next = m_copy(mb, moff, (int)len);
1035 if (m->m_next == NULL) {
1036 SOCKBUF_UNLOCK(&so->so_snd);
1045 * If we're sending everything we've got, set PUSH.
1046 * (This will keep happy those implementations which only
1047 * give data to the user when a buffer fills or
1050 if ((off + len == so->so_snd.sb_cc) && !(flags & TH_SYN))
1052 SOCKBUF_UNLOCK(&so->so_snd);
1054 SOCKBUF_UNLOCK(&so->so_snd);
1055 if (tp->t_flags & TF_ACKNOW)
1056 TCPSTAT_INC(tcps_sndacks);
1057 else if (flags & (TH_SYN|TH_FIN|TH_RST))
1058 TCPSTAT_INC(tcps_sndctrl);
1059 else if (SEQ_GT(tp->snd_up, tp->snd_una))
1060 TCPSTAT_INC(tcps_sndurg);
1062 TCPSTAT_INC(tcps_sndwinup);
1064 m = m_gethdr(M_NOWAIT, MT_DATA);
1071 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) &&
1073 MH_ALIGN(m, hdrlen);
1076 m->m_data += max_linkhdr;
1079 SOCKBUF_UNLOCK_ASSERT(&so->so_snd);
1080 m->m_pkthdr.rcvif = (struct ifnet *)0;
1082 mac_inpcb_create_mbuf(tp->t_inpcb, m);
1086 ip6 = mtod(m, struct ip6_hdr *);
1087 th = (struct tcphdr *)(ip6 + 1);
1088 tcpip_fillheaders(tp->t_inpcb, ip6, th);
1092 ip = mtod(m, struct ip *);
1093 ipov = (struct ipovly *)ip;
1094 th = (struct tcphdr *)(ip + 1);
1095 tcpip_fillheaders(tp->t_inpcb, ip, th);
1099 * Fill in fields, remembering maximum advertised
1100 * window for use in delaying messages about window sizes.
1101 * If resending a FIN, be sure not to use a new sequence number.
1103 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN &&
1104 tp->snd_nxt == tp->snd_max)
1107 * If we are starting a connection, send ECN setup
1108 * SYN packet. If we are on a retransmit, we may
1109 * resend those bits a number of times as per
1112 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) {
1113 if (tp->t_rxtshift >= 1) {
1114 if (tp->t_rxtshift <= V_tcp_ecn_maxretries)
1115 flags |= TH_ECE|TH_CWR;
1117 flags |= TH_ECE|TH_CWR;
1120 if (tp->t_state == TCPS_ESTABLISHED &&
1121 (tp->t_flags & TF_ECN_PERMIT)) {
1123 * If the peer has ECN, mark data packets with
1124 * ECN capable transmission (ECT).
1125 * Ignore pure ack packets, retransmissions and window probes.
1127 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) &&
1128 !((tp->t_flags & TF_FORCEDATA) && len == 1)) {
1131 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20);
1134 ip->ip_tos |= IPTOS_ECN_ECT0;
1135 TCPSTAT_INC(tcps_ecn_ect0);
1139 * Reply with proper ECN notifications.
1141 if (tp->t_flags & TF_ECN_SND_CWR) {
1143 tp->t_flags &= ~TF_ECN_SND_CWR;
1145 if (tp->t_flags & TF_ECN_SND_ECE)
1150 * If we are doing retransmissions, then snd_nxt will
1151 * not reflect the first unsent octet. For ACK only
1152 * packets, we do not want the sequence number of the
1153 * retransmitted packet, we want the sequence number
1154 * of the next unsent octet. So, if there is no data
1155 * (and no SYN or FIN), use snd_max instead of snd_nxt
1156 * when filling in ti_seq. But if we are in persist
1157 * state, snd_max might reflect one byte beyond the
1158 * right edge of the window, so use snd_nxt in that
1159 * case, since we know we aren't doing a retransmission.
1160 * (retransmit and persist are mutually exclusive...)
1162 if (sack_rxmit == 0) {
1163 if (len || (flags & (TH_SYN|TH_FIN)) ||
1164 tcp_timer_active(tp, TT_PERSIST))
1165 th->th_seq = htonl(tp->snd_nxt);
1167 th->th_seq = htonl(tp->snd_max);
1169 th->th_seq = htonl(p->rxmit);
1171 tp->sackhint.sack_bytes_rexmit += len;
1173 th->th_ack = htonl(tp->rcv_nxt);
1175 bcopy(opt, th + 1, optlen);
1176 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2;
1178 th->th_flags = flags;
1180 * Calculate receive window. Don't shrink window,
1181 * but avoid silly window syndrome.
1183 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) &&
1184 recwin < (long)tp->t_maxseg)
1186 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) &&
1187 recwin < (long)(tp->rcv_adv - tp->rcv_nxt))
1188 recwin = (long)(tp->rcv_adv - tp->rcv_nxt);
1189 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale)
1190 recwin = (long)TCP_MAXWIN << tp->rcv_scale;
1193 * According to RFC1323 the window field in a SYN (i.e., a <SYN>
1194 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK>
1195 * case is handled in syncache.
1198 th->th_win = htons((u_short)
1199 (min(sbspace(&so->so_rcv), TCP_MAXWIN)));
1201 th->th_win = htons((u_short)(recwin >> tp->rcv_scale));
1204 * Adjust the RXWIN0SENT flag - indicate that we have advertised
1205 * a 0 window. This may cause the remote transmitter to stall. This
1206 * flag tells soreceive() to disable delayed acknowledgements when
1207 * draining the buffer. This can occur if the receiver is attempting
1208 * to read more data than can be buffered prior to transmitting on
1211 if (th->th_win == 0) {
1213 tp->t_flags |= TF_RXWIN0SENT;
1215 tp->t_flags &= ~TF_RXWIN0SENT;
1216 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) {
1217 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt));
1218 th->th_flags |= TH_URG;
1221 * If no urgent pointer to send, then we pull
1222 * the urgent pointer to the left edge of the send window
1223 * so that it doesn't drift into the send window on sequence
1224 * number wraparound.
1226 tp->snd_up = tp->snd_una; /* drag it along */
1228 #ifdef TCP_SIGNATURE
1229 if (to.to_flags & TOF_SIGNATURE) {
1230 int sigoff = to.to_signature - opt;
1231 tcp_signature_compute(m, 0, len, optlen,
1232 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND);
1237 * Put TCP length in extended header, and then
1238 * checksum extended header and data.
1240 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */
1241 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1245 * ip6_plen is not need to be filled now, and will be filled
1248 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
1249 th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) +
1250 optlen + len, IPPROTO_TCP, 0);
1253 #if defined(INET6) && defined(INET)
1258 m->m_pkthdr.csum_flags = CSUM_TCP;
1259 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
1260 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen));
1262 /* IP version must be set here for ipv4/ipv6 checking later */
1263 KASSERT(ip->ip_v == IPVERSION,
1264 ("%s: IP version incorrect: %d", __func__, ip->ip_v));
1269 * Enable TSO and specify the size of the segments.
1270 * The TCP pseudo header checksum is always provided.
1271 * XXX: Fixme: This is currently not the case for IPv6.
1274 KASSERT(len > tp->t_maxopd - optlen,
1275 ("%s: len <= tso_segsz", __func__));
1276 m->m_pkthdr.csum_flags |= CSUM_TSO;
1277 m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen;
1281 KASSERT(len + hdrlen + ipoptlen - ipsec_optlen == m_length(m, NULL),
1282 ("%s: mbuf chain shorter than expected: %ld + %u + %u - %u != %u",
1283 __func__, len, hdrlen, ipoptlen, ipsec_optlen, m_length(m, NULL)));
1285 KASSERT(len + hdrlen + ipoptlen == m_length(m, NULL),
1286 ("%s: mbuf chain shorter than expected: %ld + %u + %u != %u",
1287 __func__, len, hdrlen, ipoptlen, m_length(m, NULL)));
1290 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */
1291 hhook_run_tcp_est_out(tp, th, &to, len, tso);
1297 if (so->so_options & SO_DEBUG) {
1303 save = ipov->ih_len;
1304 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */);
1306 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0);
1310 ipov->ih_len = save;
1312 #endif /* TCPDEBUG */
1315 * Fill in IP length and desired time to live and
1316 * send to IP level. There should be a better way
1317 * to handle ttl and tos; we could keep them in
1318 * the template, but need a way to checksum without them.
1321 * m->m_pkthdr.len should have been set before cksum calcuration,
1322 * because in6_cksum() need it.
1326 struct route_in6 ro;
1328 bzero(&ro, sizeof(ro));
1330 * we separately set hoplimit for every segment, since the
1331 * user might want to change the value via setsockopt.
1332 * Also, desired default hop limit might be changed via
1333 * Neighbor Discovery.
1335 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL);
1338 * Set the packet size here for the benefit of DTrace probes.
1339 * ip6_output() will set it properly; it's supposed to include
1340 * the option header lengths as well.
1342 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6));
1344 if (V_path_mtu_discovery && tp->t_maxopd > V_tcp_minmss)
1345 tp->t_flags2 |= TF2_PLPMTU_PMTUD;
1347 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
1349 if (tp->t_state == TCPS_SYN_SENT)
1350 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th);
1352 TCP_PROBE5(send, NULL, tp, ip6, tp, th);
1354 /* TODO: IPv6 IP6TOS_ECT bit on */
1355 error = ip6_output(m, tp->t_inpcb->in6p_outputopts, &ro,
1356 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0),
1357 NULL, NULL, tp->t_inpcb);
1359 if (error == EMSGSIZE && ro.ro_rt != NULL)
1360 mtu = ro.ro_rt->rt_mtu;
1364 #if defined(INET) && defined(INET6)
1371 bzero(&ro, sizeof(ro));
1372 ip->ip_len = htons(m->m_pkthdr.len);
1374 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO)
1375 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL);
1378 * If we do path MTU discovery, then we set DF on every packet.
1379 * This might not be the best thing to do according to RFC3390
1380 * Section 2. However the tcp hostcache migitates the problem
1381 * so it affects only the first tcp connection with a host.
1383 * NB: Don't set DF on small MTU/MSS to have a safe fallback.
1385 if (V_path_mtu_discovery && tp->t_maxopd > V_tcp_minmss) {
1386 ip->ip_off |= htons(IP_DF);
1387 tp->t_flags2 |= TF2_PLPMTU_PMTUD;
1389 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
1392 if (tp->t_state == TCPS_SYN_SENT)
1393 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th);
1395 TCP_PROBE5(send, NULL, tp, ip, tp, th);
1397 error = ip_output(m, tp->t_inpcb->inp_options, &ro,
1398 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0,
1401 if (error == EMSGSIZE && ro.ro_rt != NULL)
1402 mtu = ro.ro_rt->rt_mtu;
1409 * In transmit state, time the transmission and arrange for
1410 * the retransmit. In persist state, just set snd_max.
1412 if ((tp->t_flags & TF_FORCEDATA) == 0 ||
1413 !tcp_timer_active(tp, TT_PERSIST)) {
1414 tcp_seq startseq = tp->snd_nxt;
1417 * Advance snd_nxt over sequence space of this segment.
1419 if (flags & (TH_SYN|TH_FIN)) {
1422 if (flags & TH_FIN) {
1424 tp->t_flags |= TF_SENTFIN;
1430 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) {
1431 tp->snd_max = tp->snd_nxt;
1433 * Time this transmission if not a retransmission and
1434 * not currently timing anything.
1436 if (tp->t_rtttime == 0) {
1437 tp->t_rtttime = ticks;
1438 tp->t_rtseq = startseq;
1439 TCPSTAT_INC(tcps_segstimed);
1444 * Set retransmit timer if not currently set,
1445 * and not doing a pure ack or a keep-alive probe.
1446 * Initial value for retransmit timer is smoothed
1447 * round-trip time + 2 * round-trip time variance.
1448 * Initialize shift counter which is used for backoff
1449 * of retransmit time.
1452 if (!tcp_timer_active(tp, TT_REXMT) &&
1453 ((sack_rxmit && tp->snd_nxt != tp->snd_max) ||
1454 (tp->snd_nxt != tp->snd_una))) {
1455 if (tcp_timer_active(tp, TT_PERSIST)) {
1456 tcp_timer_activate(tp, TT_PERSIST, 0);
1459 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
1460 } else if (len == 0 && so->so_snd.sb_cc &&
1461 !tcp_timer_active(tp, TT_REXMT) &&
1462 !tcp_timer_active(tp, TT_PERSIST)) {
1464 * Avoid a situation where we do not set persist timer
1465 * after a zero window condition. For example:
1466 * 1) A -> B: packet with enough data to fill the window
1467 * 2) B -> A: ACK for #1 + new data (0 window
1469 * 3) A -> B: ACK for #2, 0 len packet
1471 * In this case, A will not activate the persist timer,
1472 * because it chose to send a packet. Unless tcp_output
1473 * is called for some other reason (delayed ack timer,
1474 * another input packet from B, socket syscall), A will
1475 * not send zero window probes.
1477 * So, if you send a 0-length packet, but there is data
1478 * in the socket buffer, and neither the rexmt or
1479 * persist timer is already set, then activate the
1487 * Persist case, update snd_max but since we are in
1488 * persist mode (no window) we do not update snd_nxt.
1493 if (flags & TH_FIN) {
1495 tp->t_flags |= TF_SENTFIN;
1497 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max))
1498 tp->snd_max = tp->snd_nxt + len;
1504 * We know that the packet was lost, so back out the
1505 * sequence number advance, if any.
1507 * If the error is EPERM the packet got blocked by the
1508 * local firewall. Normally we should terminate the
1509 * connection but the blocking may have been spurious
1510 * due to a firewall reconfiguration cycle. So we treat
1511 * it like a packet loss and let the retransmit timer and
1512 * timeouts do their work over time.
1513 * XXX: It is a POLA question whether calling tcp_drop right
1514 * away would be the really correct behavior instead.
1516 if (((tp->t_flags & TF_FORCEDATA) == 0 ||
1517 !tcp_timer_active(tp, TT_PERSIST)) &&
1518 ((flags & TH_SYN) == 0) &&
1522 tp->sackhint.sack_bytes_rexmit -= len;
1523 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0,
1524 ("sackhint bytes rtx >= 0"));
1528 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */
1531 tp->t_softerror = error;
1534 if (!tcp_timer_active(tp, TT_REXMT) &&
1535 !tcp_timer_active(tp, TT_PERSIST))
1536 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
1537 tp->snd_cwnd = tp->t_maxseg;
1541 * For some reason the interface we used initially
1542 * to send segments changed to another or lowered
1544 * If TSO was active we either got an interface
1545 * without TSO capabilits or TSO was turned off.
1546 * If we obtained mtu from ip_output() then update
1550 tp->t_flags &= ~TF_TSO;
1552 tcp_mss_update(tp, -1, mtu, NULL, NULL);
1560 if (TCPS_HAVERCVDSYN(tp->t_state)) {
1561 tp->t_softerror = error;
1569 TCPSTAT_INC(tcps_sndtotal);
1572 * Data sent (as far as we can tell).
1573 * If this advertises a larger window than any other segment,
1574 * then remember the size of the advertised window.
1575 * Any pending ACK has now been sent.
1577 if (recwin >= 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv))
1578 tp->rcv_adv = tp->rcv_nxt + recwin;
1579 tp->last_ack_sent = tp->rcv_nxt;
1580 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK);
1581 if (tcp_timer_active(tp, TT_DELACK))
1582 tcp_timer_activate(tp, TT_DELACK, 0);
1585 * This completely breaks TCP if newreno is turned on. What happens
1586 * is that if delayed-acks are turned on on the receiver, this code
1587 * on the transmitter effectively destroys the TCP window, forcing
1588 * it to four packets (1.5Kx4 = 6K window).
1590 if (sendalot && --maxburst)
1599 tcp_setpersist(struct tcpcb *tp)
1601 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1;
1604 tp->t_flags &= ~TF_PREVVALID;
1605 if (tcp_timer_active(tp, TT_REXMT))
1606 panic("tcp_setpersist: retransmit pending");
1608 * Start/restart persistance timer.
1610 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift],
1611 tcp_persmin, tcp_persmax);
1612 tcp_timer_activate(tp, TT_PERSIST, tt);
1613 if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
1618 * Insert TCP options according to the supplied parameters to the place
1619 * optp in a consistent way. Can handle unaligned destinations.
1621 * The order of the option processing is crucial for optimal packing and
1622 * alignment for the scarce option space.
1624 * The optimal order for a SYN/SYN-ACK segment is:
1625 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) +
1626 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40.
1628 * The SACK options should be last. SACK blocks consume 8*n+2 bytes.
1629 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks).
1630 * At minimum we need 10 bytes (to generate 1 SACK block). If both
1631 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present,
1632 * we only have 10 bytes for SACK options (40 - (12 + 18)).
1635 tcp_addoptions(struct tcpopt *to, u_char *optp)
1637 u_int mask, optlen = 0;
1639 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) {
1640 if ((to->to_flags & mask) != mask)
1642 if (optlen == TCP_MAXOLEN)
1644 switch (to->to_flags & mask) {
1646 while (optlen % 4) {
1647 optlen += TCPOLEN_NOP;
1648 *optp++ = TCPOPT_NOP;
1650 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG)
1652 optlen += TCPOLEN_MAXSEG;
1653 *optp++ = TCPOPT_MAXSEG;
1654 *optp++ = TCPOLEN_MAXSEG;
1655 to->to_mss = htons(to->to_mss);
1656 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss));
1657 optp += sizeof(to->to_mss);
1660 while (!optlen || optlen % 2 != 1) {
1661 optlen += TCPOLEN_NOP;
1662 *optp++ = TCPOPT_NOP;
1664 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW)
1666 optlen += TCPOLEN_WINDOW;
1667 *optp++ = TCPOPT_WINDOW;
1668 *optp++ = TCPOLEN_WINDOW;
1669 *optp++ = to->to_wscale;
1672 while (optlen % 2) {
1673 optlen += TCPOLEN_NOP;
1674 *optp++ = TCPOPT_NOP;
1676 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED)
1678 optlen += TCPOLEN_SACK_PERMITTED;
1679 *optp++ = TCPOPT_SACK_PERMITTED;
1680 *optp++ = TCPOLEN_SACK_PERMITTED;
1683 while (!optlen || optlen % 4 != 2) {
1684 optlen += TCPOLEN_NOP;
1685 *optp++ = TCPOPT_NOP;
1687 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP)
1689 optlen += TCPOLEN_TIMESTAMP;
1690 *optp++ = TCPOPT_TIMESTAMP;
1691 *optp++ = TCPOLEN_TIMESTAMP;
1692 to->to_tsval = htonl(to->to_tsval);
1693 to->to_tsecr = htonl(to->to_tsecr);
1694 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval));
1695 optp += sizeof(to->to_tsval);
1696 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr));
1697 optp += sizeof(to->to_tsecr);
1699 #ifdef TCP_SIGNATURE
1702 int siglen = TCPOLEN_SIGNATURE - 2;
1704 while (!optlen || optlen % 4 != 2) {
1705 optlen += TCPOLEN_NOP;
1706 *optp++ = TCPOPT_NOP;
1708 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE)
1710 optlen += TCPOLEN_SIGNATURE;
1711 *optp++ = TCPOPT_SIGNATURE;
1712 *optp++ = TCPOLEN_SIGNATURE;
1713 to->to_signature = optp;
1722 struct sackblk *sack = (struct sackblk *)to->to_sacks;
1725 while (!optlen || optlen % 4 != 2) {
1726 optlen += TCPOLEN_NOP;
1727 *optp++ = TCPOPT_NOP;
1729 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK)
1731 optlen += TCPOLEN_SACKHDR;
1732 *optp++ = TCPOPT_SACK;
1733 sackblks = min(to->to_nsacks,
1734 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK);
1735 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK;
1736 while (sackblks--) {
1737 sack_seq = htonl(sack->start);
1738 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq));
1739 optp += sizeof(sack_seq);
1740 sack_seq = htonl(sack->end);
1741 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq));
1742 optp += sizeof(sack_seq);
1743 optlen += TCPOLEN_SACK;
1746 TCPSTAT_INC(tcps_sack_send_blocks);
1754 /* XXX is there any point to aligning this option? */
1755 total_len = TCPOLEN_FAST_OPEN_EMPTY + to->to_tfo_len;
1756 if (TCP_MAXOLEN - optlen < total_len)
1758 *optp++ = TCPOPT_FAST_OPEN;
1759 *optp++ = total_len;
1760 if (to->to_tfo_len > 0) {
1761 bcopy(to->to_tfo_cookie, optp, to->to_tfo_len);
1762 optp += to->to_tfo_len;
1764 optlen += total_len;
1769 panic("%s: unknown TCP option type", __func__);
1774 /* Terminate and pad TCP options to a 4 byte boundary. */
1776 optlen += TCPOLEN_EOL;
1777 *optp++ = TCPOPT_EOL;
1780 * According to RFC 793 (STD0007):
1781 * "The content of the header beyond the End-of-Option option
1782 * must be header padding (i.e., zero)."
1783 * and later: "The padding is composed of zeros."
1785 while (optlen % 4) {
1786 optlen += TCPOLEN_PAD;
1787 *optp++ = TCPOPT_PAD;
1790 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__));