2 * SPDX-License-Identifier: BSD-3-Clause
4 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
5 * The Regents of the University of California. All rights reserved.
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the University nor the names of its contributors
16 * may be used to endorse or promote products derived from this software
17 * without specific prior written permission.
19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95
34 #include <sys/cdefs.h>
35 __FBSDID("$FreeBSD$");
38 #include "opt_inet6.h"
39 #include "opt_ipsec.h"
40 #include "opt_kern_tls.h"
41 #include "opt_tcpdebug.h"
43 #include <sys/param.h>
44 #include <sys/systm.h>
46 #include <sys/domain.h>
48 #include <sys/hhook.h>
50 #include <sys/kernel.h>
56 #include <sys/mutex.h>
57 #include <sys/protosw.h>
58 #include <sys/qmath.h>
60 #include <sys/socket.h>
61 #include <sys/socketvar.h>
62 #include <sys/sysctl.h>
63 #include <sys/stats.h>
66 #include <net/route.h>
67 #include <net/route/nhop.h>
70 #include <netinet/in.h>
71 #include <netinet/in_kdtrace.h>
72 #include <netinet/in_systm.h>
73 #include <netinet/ip.h>
74 #include <netinet/in_pcb.h>
75 #include <netinet/ip_var.h>
76 #include <netinet/ip_options.h>
78 #include <netinet6/in6_pcb.h>
79 #include <netinet/ip6.h>
80 #include <netinet6/ip6_var.h>
82 #include <netinet/tcp.h>
84 #include <netinet/tcp_fsm.h>
85 #include <netinet/tcp_log_buf.h>
86 #include <netinet/tcp_seq.h>
87 #include <netinet/tcp_var.h>
88 #include <netinet/tcp_syncache.h>
89 #include <netinet/tcp_timer.h>
90 #include <netinet/tcpip.h>
91 #include <netinet/cc/cc.h>
92 #include <netinet/tcp_fastopen.h>
94 #include <netinet/tcp_pcap.h>
97 #include <netinet/tcp_debug.h>
100 #include <netinet/tcp_offload.h>
102 #include <netinet/tcp_ecn.h>
104 #include <netipsec/ipsec_support.h>
106 #include <netinet/udp.h>
107 #include <netinet/udp_var.h>
108 #include <machine/in_cksum.h>
110 #include <security/mac/mac_framework.h>
112 VNET_DEFINE(int, path_mtu_discovery) = 1;
113 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_VNET | CTLFLAG_RW,
114 &VNET_NAME(path_mtu_discovery), 1,
115 "Enable Path MTU Discovery");
117 VNET_DEFINE(int, tcp_do_tso) = 1;
118 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_VNET | CTLFLAG_RW,
119 &VNET_NAME(tcp_do_tso), 0,
120 "Enable TCP Segmentation Offload");
122 VNET_DEFINE(int, tcp_sendspace) = 1024*32;
123 #define V_tcp_sendspace VNET(tcp_sendspace)
124 SYSCTL_INT(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, CTLFLAG_VNET | CTLFLAG_RW,
125 &VNET_NAME(tcp_sendspace), 0, "Initial send socket buffer size");
127 VNET_DEFINE(int, tcp_do_autosndbuf) = 1;
128 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_VNET | CTLFLAG_RW,
129 &VNET_NAME(tcp_do_autosndbuf), 0,
130 "Enable automatic send buffer sizing");
132 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024;
133 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_VNET | CTLFLAG_RW,
134 &VNET_NAME(tcp_autosndbuf_inc), 0,
135 "Incrementor step size of automatic send buffer");
137 VNET_DEFINE(int, tcp_autosndbuf_max) = 2*1024*1024;
138 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_VNET | CTLFLAG_RW,
139 &VNET_NAME(tcp_autosndbuf_max), 0,
140 "Max size of automatic send buffer");
142 VNET_DEFINE(int, tcp_sendbuf_auto_lowat) = 0;
143 #define V_tcp_sendbuf_auto_lowat VNET(tcp_sendbuf_auto_lowat)
144 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto_lowat, CTLFLAG_VNET | CTLFLAG_RW,
145 &VNET_NAME(tcp_sendbuf_auto_lowat), 0,
146 "Modify threshold for auto send buffer growth to account for SO_SNDLOWAT");
149 * Make sure that either retransmit or persist timer is set for SYN, FIN and
152 #define TCP_XMIT_TIMER_ASSERT(tp, len, th_flags) \
153 KASSERT(((len) == 0 && ((th_flags) & (TH_SYN | TH_FIN)) == 0) ||\
154 tcp_timer_active((tp), TT_REXMT) || \
155 tcp_timer_active((tp), TT_PERSIST), \
156 ("neither rexmt nor persist timer is set"))
158 static void inline cc_after_idle(struct tcpcb *tp);
162 * Wrapper for the TCP established output helper hook.
165 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th,
166 struct tcpopt *to, uint32_t len, int tso)
168 struct tcp_hhook_data hhook_data;
170 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) {
174 hhook_data.len = len;
175 hhook_data.tso = tso;
177 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data,
184 * CC wrapper hook functions
187 cc_after_idle(struct tcpcb *tp)
189 INP_WLOCK_ASSERT(tp->t_inpcb);
191 if (CC_ALGO(tp)->after_idle != NULL)
192 CC_ALGO(tp)->after_idle(tp->ccv);
196 * Tcp output routine: figure out what should be sent and send it.
199 tcp_default_output(struct tcpcb *tp)
201 struct socket *so = tp->t_inpcb->inp_socket;
203 uint32_t recwin, sendwin;
205 int off, error = 0; /* Keep compiler happy */
206 u_int if_hw_tsomaxsegcount = 0;
207 u_int if_hw_tsomaxsegsize = 0;
209 struct ip *ip = NULL;
211 struct ipovly *ipov = NULL;
214 u_char opt[TCP_MAXOLEN];
215 unsigned ipoptlen, optlen, hdrlen, ulen;
216 #if defined(IPSEC) || defined(IPSEC_SUPPORT)
217 unsigned ipsec_optlen = 0;
219 int idle, sendalot, curticks;
220 int sack_rxmit, sack_bytes_rxmt;
224 struct udphdr *udp = NULL;
225 unsigned int wanted_cookie = 0;
226 unsigned int dont_sendalot = 0;
228 int maxburst = TCP_MAXBURST;
231 struct ip6_hdr *ip6 = NULL;
234 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0;
237 const bool hw_tls = (so->so_snd.sb_flags & SB_TLS_IFNET) != 0;
239 const bool hw_tls = false;
243 INP_WLOCK_ASSERT(tp->t_inpcb);
246 if (tp->t_flags & TF_TOE)
247 return (tcp_offload_output(tp));
251 * For TFO connections in SYN_SENT or SYN_RECEIVED,
252 * only allow the initial SYN or SYN|ACK and those sent
253 * by the retransmit timer.
255 if (IS_FASTOPEN(tp->t_flags) &&
256 ((tp->t_state == TCPS_SYN_SENT) ||
257 (tp->t_state == TCPS_SYN_RECEIVED)) &&
258 SEQ_GT(tp->snd_max, tp->snd_una) && /* initial SYN or SYN|ACK sent */
259 (tp->snd_nxt != tp->snd_una)) /* not a retransmit */
263 * Determine length of data that should be transmitted,
264 * and flags that will be used.
265 * If there is some data or critical controls (SYN, RST)
266 * to send, then transmit; otherwise, investigate further.
268 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una);
269 if (idle && (((ticks - tp->t_rcvtime) >= tp->t_rxtcur) ||
270 (tp->t_sndtime && ((ticks - tp->t_sndtime) >= tp->t_rxtcur))))
272 tp->t_flags &= ~TF_LASTIDLE;
274 if (tp->t_flags & TF_MORETOCOME) {
275 tp->t_flags |= TF_LASTIDLE;
281 * If we've recently taken a timeout, snd_max will be greater than
282 * snd_nxt. There may be SACK information that allows us to avoid
283 * resending already delivered data. Adjust snd_nxt accordingly.
285 if ((tp->t_flags & TF_SACK_PERMIT) &&
286 SEQ_LT(tp->snd_nxt, tp->snd_max))
291 off = tp->snd_nxt - tp->snd_una;
292 sendwin = min(tp->snd_wnd, tp->snd_cwnd);
294 flags = tcp_outflags[tp->t_state];
296 * Send any SACK-generated retransmissions. If we're explicitly trying
297 * to send out new data (when sendalot is 1), bypass this function.
298 * If we retransmit in fast recovery mode, decrement snd_cwnd, since
299 * we're replacing a (future) new transmission with a retransmission
300 * now, and we previously incremented snd_cwnd in tcp_input().
303 * Still in sack recovery , reset rxmit flag to zero.
309 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) &&
310 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) {
314 imax(min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt, 0);
315 /* Do not retransmit SACK segments beyond snd_recover */
316 if (SEQ_GT(p->end, tp->snd_recover)) {
318 * (At least) part of sack hole extends beyond
319 * snd_recover. Check to see if we can rexmit data
322 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) {
324 * Can't rexmit any more data for this hole.
325 * That data will be rexmitted in the next
326 * sack recovery episode, when snd_recover
327 * moves past p->rxmit.
330 goto after_sack_rexmit;
332 /* Can rexmit part of the current hole */
333 len = ((int32_t)ulmin(cwin,
334 tp->snd_recover - p->rxmit));
336 len = ((int32_t)ulmin(cwin, p->end - p->rxmit));
337 off = p->rxmit - tp->snd_una;
338 KASSERT(off >= 0,("%s: sack block to the left of una : %d",
343 TCPSTAT_INC(tcps_sack_rexmits);
344 TCPSTAT_ADD(tcps_sack_rexmit_bytes,
345 min(len, tcp_maxseg(tp)));
350 * Get standard flags, and add SYN or FIN if requested by 'hidden'
353 if (tp->t_flags & TF_NEEDFIN)
355 if (tp->t_flags & TF_NEEDSYN)
358 SOCKBUF_LOCK(&so->so_snd);
360 * If in persist timeout with window of 0, send 1 byte.
361 * Otherwise, if window is small but nonzero
362 * and timer expired, we will send what we can
363 * and go to transmit state.
365 if (tp->t_flags & TF_FORCEDATA) {
368 * If we still have some data to send, then
369 * clear the FIN bit. Usually this would
370 * happen below when it realizes that we
371 * aren't sending all the data. However,
372 * if we have exactly 1 byte of unsent data,
373 * then it won't clear the FIN bit below,
374 * and if we are in persist state, we wind
375 * up sending the packet without recording
376 * that we sent the FIN bit.
378 * We can't just blindly clear the FIN bit,
379 * because if we don't have any more data
380 * to send then the probe will be the FIN
383 if (off < sbused(&so->so_snd))
387 tcp_timer_activate(tp, TT_PERSIST, 0);
393 * If snd_nxt == snd_max and we have transmitted a FIN, the
394 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in
395 * a negative length. This can also occur when TCP opens up
396 * its congestion window while receiving additional duplicate
397 * acks after fast-retransmit because TCP will reset snd_nxt
398 * to snd_max after the fast-retransmit.
400 * In the normal retransmit-FIN-only case, however, snd_nxt will
401 * be set to snd_una, the offset will be 0, and the length may
404 * If sack_rxmit is true we are retransmitting from the scoreboard
405 * in which case len is already set.
407 if (sack_rxmit == 0) {
408 if (sack_bytes_rxmt == 0)
409 len = ((int32_t)min(sbavail(&so->so_snd), sendwin) -
415 * We are inside of a SACK recovery episode and are
416 * sending new data, having retransmitted all the
417 * data possible in the scoreboard.
419 len = ((int32_t)min(sbavail(&so->so_snd), tp->snd_wnd) -
422 * Don't remove this (len > 0) check !
423 * We explicitly check for len > 0 here (although it
424 * isn't really necessary), to work around a gcc
425 * optimization issue - to force gcc to compute
426 * len above. Without this check, the computation
427 * of len is bungled by the optimizer.
430 cwin = tp->snd_cwnd -
431 (tp->snd_nxt - tp->snd_recover) -
435 len = imin(len, cwin);
441 * Lop off SYN bit if it has already been sent. However, if this
442 * is SYN-SENT state and if segment contains data and if we don't
443 * know that foreign host supports TAO, suppress sending segment.
445 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) {
446 if (tp->t_state != TCPS_SYN_RECEIVED)
449 * When sending additional segments following a TFO SYN|ACK,
450 * do not include the SYN bit.
452 if (IS_FASTOPEN(tp->t_flags) &&
453 (tp->t_state == TCPS_SYN_RECEIVED))
459 * Be careful not to send data and/or FIN on SYN segments.
460 * This measure is needed to prevent interoperability problems
461 * with not fully conformant TCP implementations.
463 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) {
469 * On TFO sockets, ensure no data is sent in the following cases:
471 * - When retransmitting SYN|ACK on a passively-created socket
473 * - When retransmitting SYN on an actively created socket
475 * - When sending a zero-length cookie (cookie request) on an
476 * actively created socket
478 * - When the socket is in the CLOSED state (RST is being sent)
480 if (IS_FASTOPEN(tp->t_flags) &&
481 (((flags & TH_SYN) && (tp->t_rxtshift > 0)) ||
482 ((tp->t_state == TCPS_SYN_SENT) &&
483 (tp->t_tfo_client_cookie_len == 0)) ||
488 * If FIN has been sent but not acked,
489 * but we haven't been called to retransmit,
490 * len will be < 0. Otherwise, window shrank
491 * after we sent into it. If window shrank to 0,
492 * cancel pending retransmit, pull snd_nxt back
493 * to (closed) window, and set the persist timer
494 * if it isn't already going. If the window didn't
495 * close completely, just wait for an ACK.
497 * We also do a general check here to ensure that
498 * we will set the persist timer when we have data
499 * to send, but a 0-byte window. This makes sure
500 * the persist timer is set even if the packet
501 * hits one of the "goto send" lines below.
504 if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) &&
505 (off < (int) sbavail(&so->so_snd))) {
506 tcp_timer_activate(tp, TT_REXMT, 0);
508 tp->snd_nxt = tp->snd_una;
509 if (!tcp_timer_active(tp, TT_PERSIST))
514 /* len will be >= 0 after this point. */
515 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__));
517 tcp_sndbuf_autoscale(tp, so, sendwin);
520 * Decide if we can use TCP Segmentation Offloading (if supported by
523 * TSO may only be used if we are in a pure bulk sending state. The
524 * presence of TCP-MD5, SACK retransmits, SACK advertizements and
525 * IP options prevent using TSO. With TSO the TCP header is the same
526 * (except for the sequence number) for all generated packets. This
527 * makes it impossible to transmit any options which vary per generated
530 * IPv4 handling has a clear separation of ip options and ip header
531 * flags while IPv6 combines both in in6p_outputopts. ip6_optlen() does
532 * the right thing below to provide length of just ip options and thus
533 * checking for ipoptlen is enough to decide if ip options are present.
535 #if defined(IPSEC) || defined(IPSEC_SUPPORT)
537 * Pre-calculate here as we save another lookup into the darknesses
538 * of IPsec that way and can actually decide if TSO is ok.
541 if (isipv6 && IPSEC_ENABLED(ipv6))
542 ipsec_optlen = IPSEC_HDRSIZE(ipv6, tp->t_inpcb);
548 if (IPSEC_ENABLED(ipv4))
549 ipsec_optlen = IPSEC_HDRSIZE(ipv4, tp->t_inpcb);
554 ipoptlen = ip6_optlen(tp->t_inpcb);
557 if (tp->t_inpcb->inp_options)
558 ipoptlen = tp->t_inpcb->inp_options->m_len -
559 offsetof(struct ipoption, ipopt_list);
562 #if defined(IPSEC) || defined(IPSEC_SUPPORT)
563 ipoptlen += ipsec_optlen;
566 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg &&
568 ((tp->t_flags & TF_SIGNATURE) == 0) &&
569 tp->rcv_numsacks == 0 && sack_rxmit == 0 &&
570 ipoptlen == 0 && !(flags & TH_SYN))
574 if (SEQ_LT(p->rxmit + len, tp->snd_una + sbused(&so->so_snd)))
577 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una +
578 sbused(&so->so_snd)))
582 recwin = lmin(lmax(sbspace(&so->so_rcv), 0),
583 (long)TCP_MAXWIN << tp->rcv_scale);
586 * Sender silly window avoidance. We transmit under the following
587 * conditions when len is non-zero:
589 * - We have a full segment (or more with TSO)
590 * - This is the last buffer in a write()/send() and we are
591 * either idle or running NODELAY
592 * - we've timed out (e.g. persist timer)
593 * - we have more then 1/2 the maximum send window's worth of
594 * data (receiver may be limited the window size)
595 * - we need to retransmit
598 if (len >= tp->t_maxseg)
601 * As the TCP header options are now
602 * considered when setting up the initial
603 * window, we would not send the last segment
604 * if we skip considering the option length here.
605 * Note: this may not work when tcp headers change
606 * very dynamically in the future.
608 if ((((tp->t_flags & TF_SIGNATURE) ?
609 PADTCPOLEN(TCPOLEN_SIGNATURE) : 0) +
610 ((tp->t_flags & TF_RCVD_TSTMP) ?
611 PADTCPOLEN(TCPOLEN_TIMESTAMP) : 0) +
612 len) >= tp->t_maxseg)
615 * NOTE! on localhost connections an 'ack' from the remote
616 * end may occur synchronously with the output and cause
617 * us to flush a buffer queued with moretocome. XXX
619 * note: the len + off check is almost certainly unnecessary.
621 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */
622 (idle || (tp->t_flags & TF_NODELAY)) &&
623 (uint32_t)len + (uint32_t)off >= sbavail(&so->so_snd) &&
624 (tp->t_flags & TF_NOPUSH) == 0) {
627 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */
629 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0)
631 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */
638 * Sending of standalone window updates.
640 * Window updates are important when we close our window due to a
641 * full socket buffer and are opening it again after the application
642 * reads data from it. Once the window has opened again and the
643 * remote end starts to send again the ACK clock takes over and
644 * provides the most current window information.
646 * We must avoid the silly window syndrome whereas every read
647 * from the receive buffer, no matter how small, causes a window
648 * update to be sent. We also should avoid sending a flurry of
649 * window updates when the socket buffer had queued a lot of data
650 * and the application is doing small reads.
652 * Prevent a flurry of pointless window updates by only sending
653 * an update when we can increase the advertized window by more
654 * than 1/4th of the socket buffer capacity. When the buffer is
655 * getting full or is very small be more aggressive and send an
656 * update whenever we can increase by two mss sized segments.
657 * In all other situations the ACK's to new incoming data will
658 * carry further window increases.
660 * Don't send an independent window update if a delayed
661 * ACK is pending (it will get piggy-backed on it) or the
662 * remote side already has done a half-close and won't send
663 * more data. Skip this if the connection is in T/TCP
666 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) &&
667 !(tp->t_flags & TF_DELACK) &&
668 !TCPS_HAVERCVDFIN(tp->t_state)) {
670 * "adv" is the amount we could increase the window,
671 * taking into account that we are limited by
672 * TCP_MAXWIN << tp->rcv_scale.
678 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) {
679 oldwin = (tp->rcv_adv - tp->rcv_nxt);
688 * If the new window size ends up being the same as or less
689 * than the old size when it is scaled, then don't force
692 if (oldwin >> tp->rcv_scale >= (adv + oldwin) >> tp->rcv_scale)
695 if (adv >= (int32_t)(2 * tp->t_maxseg) &&
696 (adv >= (int32_t)(so->so_rcv.sb_hiwat / 4) ||
697 recwin <= (so->so_rcv.sb_hiwat / 8) ||
698 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg ||
699 adv >= TCP_MAXWIN << tp->rcv_scale))
701 if (2 * adv >= (int32_t)so->so_rcv.sb_hiwat)
707 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW
708 * is also a catch-all for the retransmit timer timeout case.
710 if (tp->t_flags & TF_ACKNOW)
712 if ((flags & TH_RST) ||
713 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0))
715 if (SEQ_GT(tp->snd_up, tp->snd_una))
718 * If our state indicates that FIN should be sent
719 * and we have not yet done so, then we need to send.
721 if (flags & TH_FIN &&
722 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una))
725 * In SACK, it is possible for tcp_output to fail to send a segment
726 * after the retransmission timer has been turned off. Make sure
727 * that the retransmission timer is set.
729 if ((tp->t_flags & TF_SACK_PERMIT) &&
730 SEQ_GT(tp->snd_max, tp->snd_una) &&
731 !tcp_timer_active(tp, TT_REXMT) &&
732 !tcp_timer_active(tp, TT_PERSIST)) {
733 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
737 * TCP window updates are not reliable, rather a polling protocol
738 * using ``persist'' packets is used to insure receipt of window
739 * updates. The three ``states'' for the output side are:
740 * idle not doing retransmits or persists
741 * persisting to move a small or zero window
742 * (re)transmitting and thereby not persisting
744 * tcp_timer_active(tp, TT_PERSIST)
745 * is true when we are in persist state.
746 * (tp->t_flags & TF_FORCEDATA)
747 * is set when we are called to send a persist packet.
748 * tcp_timer_active(tp, TT_REXMT)
749 * is set when we are retransmitting
750 * The output side is idle when both timers are zero.
752 * If send window is too small, there is data to transmit, and no
753 * retransmit or persist is pending, then go to persist state.
754 * If nothing happens soon, send when timer expires:
755 * if window is nonzero, transmit what we can,
756 * otherwise force out a byte.
758 if (sbavail(&so->so_snd) && !tcp_timer_active(tp, TT_REXMT) &&
759 !tcp_timer_active(tp, TT_PERSIST)) {
765 * No reason to send a segment, just return.
768 SOCKBUF_UNLOCK(&so->so_snd);
772 SOCKBUF_LOCK_ASSERT(&so->so_snd);
774 if (len >= tp->t_maxseg)
775 tp->t_flags2 |= TF2_PLPMTU_MAXSEGSNT;
777 tp->t_flags2 &= ~TF2_PLPMTU_MAXSEGSNT;
780 * Before ESTABLISHED, force sending of initial options
781 * unless TCP set not to do any options.
782 * NOTE: we assume that the IP/TCP header plus TCP options
783 * always fit in a single mbuf, leaving room for a maximum
785 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES
790 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr);
793 hdrlen = sizeof (struct tcpiphdr);
795 if (flags & TH_SYN) {
796 tp->snd_nxt = tp->iss;
800 * Compute options for segment.
801 * We only have to care about SYN and established connection
802 * segments. Options for SYN-ACK segments are handled in TCP
806 if ((tp->t_flags & TF_NOOPT) == 0) {
807 /* Maximum segment size. */
808 if (flags & TH_SYN) {
809 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc);
811 to.to_mss -= V_tcp_udp_tunneling_overhead;
812 to.to_flags |= TOF_MSS;
815 * On SYN or SYN|ACK transmits on TFO connections,
816 * only include the TFO option if it is not a
817 * retransmit, as the presence of the TFO option may
818 * have caused the original SYN or SYN|ACK to have
819 * been dropped by a middlebox.
821 if (IS_FASTOPEN(tp->t_flags) &&
822 (tp->t_rxtshift == 0)) {
823 if (tp->t_state == TCPS_SYN_RECEIVED) {
824 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN;
826 (u_int8_t *)&tp->t_tfo_cookie.server;
827 to.to_flags |= TOF_FASTOPEN;
829 } else if (tp->t_state == TCPS_SYN_SENT) {
831 tp->t_tfo_client_cookie_len;
833 tp->t_tfo_cookie.client;
834 to.to_flags |= TOF_FASTOPEN;
837 * If we wind up having more data to
838 * send with the SYN than can fit in
839 * one segment, don't send any more
840 * until the SYN|ACK comes back from
847 /* Window scaling. */
848 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) {
849 to.to_wscale = tp->request_r_scale;
850 to.to_flags |= TOF_SCALE;
853 if ((tp->t_flags & TF_RCVD_TSTMP) ||
854 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) {
855 curticks = tcp_ts_getticks();
856 to.to_tsval = curticks + tp->ts_offset;
857 to.to_tsecr = tp->ts_recent;
858 to.to_flags |= TOF_TS;
859 if (tp->t_rxtshift == 1)
860 tp->t_badrxtwin = curticks;
863 /* Set receive buffer autosizing timestamp. */
864 if (tp->rfbuf_ts == 0 &&
865 (so->so_rcv.sb_flags & SB_AUTOSIZE))
866 tp->rfbuf_ts = tcp_ts_getticks();
868 /* Selective ACK's. */
869 if (tp->t_flags & TF_SACK_PERMIT) {
871 to.to_flags |= TOF_SACKPERM;
872 else if (TCPS_HAVEESTABLISHED(tp->t_state) &&
873 tp->rcv_numsacks > 0) {
874 to.to_flags |= TOF_SACK;
875 to.to_nsacks = tp->rcv_numsacks;
876 to.to_sacks = (u_char *)tp->sackblks;
879 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
880 /* TCP-MD5 (RFC2385). */
882 * Check that TCP_MD5SIG is enabled in tcpcb to
883 * account the size needed to set this TCP option.
885 if (tp->t_flags & TF_SIGNATURE)
886 to.to_flags |= TOF_SIGNATURE;
887 #endif /* TCP_SIGNATURE */
889 /* Processing the options. */
890 hdrlen += optlen = tcp_addoptions(&to, opt);
892 * If we wanted a TFO option to be added, but it was unable
893 * to fit, ensure no data is sent.
895 if (IS_FASTOPEN(tp->t_flags) && wanted_cookie &&
896 !(to.to_flags & TOF_FASTOPEN))
900 if (V_tcp_udp_tunneling_port == 0) {
901 /* The port was removed?? */
902 SOCKBUF_UNLOCK(&so->so_snd);
903 return (EHOSTUNREACH);
905 hdrlen += sizeof(struct udphdr);
908 * Adjust data length if insertion of options will
909 * bump the packet length beyond the t_maxseg length.
910 * Clear the FIN bit because we cut off the tail of
913 if (len + optlen + ipoptlen > tp->t_maxseg) {
921 /* extract TSO information */
922 if_hw_tsomax = tp->t_tsomax;
923 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount;
924 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize;
927 * Limit a TSO burst to prevent it from
928 * overflowing or exceeding the maximum length
929 * allowed by the network interface:
931 KASSERT(ipoptlen == 0,
932 ("%s: TSO can't do IP options", __func__));
935 * Check if we should limit by maximum payload
938 if (if_hw_tsomax != 0) {
939 /* compute maximum TSO length */
940 max_len = (if_hw_tsomax - hdrlen -
944 } else if (len > max_len) {
951 * Prevent the last segment from being
952 * fractional unless the send sockbuf can be
955 max_len = (tp->t_maxseg - optlen);
956 if (((uint32_t)off + (uint32_t)len) <
957 sbavail(&so->so_snd)) {
958 moff = len % max_len;
966 * In case there are too many small fragments
969 if (len <= max_len) {
976 * Send the FIN in a separate segment
977 * after the bulk sending is done.
978 * We don't trust the TSO implementations
979 * to clear the FIN flag on all but the
982 if (tp->t_flags & TF_NEEDFIN)
985 if (optlen + ipoptlen >= tp->t_maxseg) {
987 * Since we don't have enough space to put
988 * the IP header chain and the TCP header in
989 * one packet as required by RFC 7112, don't
990 * send it. Also ensure that at least one
991 * byte of the payload can be put into the
994 SOCKBUF_UNLOCK(&so->so_snd);
999 len = tp->t_maxseg - optlen - ipoptlen;
1007 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET,
1008 ("%s: len > IP_MAXPACKET", __func__));
1010 /*#ifdef DIAGNOSTIC*/
1012 if (max_linkhdr + hdrlen > MCLBYTES)
1014 if (max_linkhdr + hdrlen > MHLEN)
1016 panic("tcphdr too big");
1020 * This KASSERT is here to catch edge cases at a well defined place.
1021 * Before, those had triggered (random) panic conditions further down.
1023 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__));
1026 * Grab a header mbuf, attaching a copy of data to
1027 * be transmitted, and initialize the header from
1028 * the template for sends on this connection.
1032 struct sockbuf *msb;
1035 if ((tp->t_flags & TF_FORCEDATA) && len == 1) {
1036 TCPSTAT_INC(tcps_sndprobe);
1038 if (SEQ_LT(tp->snd_nxt, tp->snd_max))
1039 stats_voi_update_abs_u32(tp->t_stats,
1040 VOI_TCP_RETXPB, len);
1042 stats_voi_update_abs_u64(tp->t_stats,
1045 } else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) {
1046 tp->t_sndrexmitpack++;
1047 TCPSTAT_INC(tcps_sndrexmitpack);
1048 TCPSTAT_ADD(tcps_sndrexmitbyte, len);
1050 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_RETXPB,
1054 TCPSTAT_INC(tcps_sndpack);
1055 TCPSTAT_ADD(tcps_sndbyte, len);
1057 stats_voi_update_abs_u64(tp->t_stats, VOI_TCP_TXPB,
1062 if (MHLEN < hdrlen + max_linkhdr)
1063 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR);
1066 m = m_gethdr(M_NOWAIT, MT_DATA);
1069 SOCKBUF_UNLOCK(&so->so_snd);
1075 m->m_data += max_linkhdr;
1079 * Start the m_copy functions from the closest mbuf
1080 * to the offset in the socket buffer chain.
1082 mb = sbsndptr_noadv(&so->so_snd, off, &moff);
1083 if (len <= MHLEN - hdrlen - max_linkhdr && !hw_tls) {
1084 m_copydata(mb, moff, len,
1085 mtod(m, caddr_t) + hdrlen);
1086 if (SEQ_LT(tp->snd_nxt, tp->snd_max))
1087 sbsndptr_adv(&so->so_snd, mb, len);
1090 if (SEQ_LT(tp->snd_nxt, tp->snd_max))
1094 m->m_next = tcp_m_copym(mb, moff,
1095 &len, if_hw_tsomaxsegcount,
1096 if_hw_tsomaxsegsize, msb, hw_tls);
1097 if (len <= (tp->t_maxseg - optlen)) {
1099 * Must have ran out of mbufs for the copy
1100 * shorten it to no longer need tso. Lets
1101 * not put on sendalot since we are low on
1106 if (m->m_next == NULL) {
1107 SOCKBUF_UNLOCK(&so->so_snd);
1116 * If we're sending everything we've got, set PUSH.
1117 * (This will keep happy those implementations which only
1118 * give data to the user when a buffer fills or
1121 if (((uint32_t)off + (uint32_t)len == sbused(&so->so_snd)) &&
1124 SOCKBUF_UNLOCK(&so->so_snd);
1126 SOCKBUF_UNLOCK(&so->so_snd);
1127 if (tp->t_flags & TF_ACKNOW)
1128 TCPSTAT_INC(tcps_sndacks);
1129 else if (flags & (TH_SYN|TH_FIN|TH_RST))
1130 TCPSTAT_INC(tcps_sndctrl);
1131 else if (SEQ_GT(tp->snd_up, tp->snd_una))
1132 TCPSTAT_INC(tcps_sndurg);
1134 TCPSTAT_INC(tcps_sndwinup);
1136 m = m_gethdr(M_NOWAIT, MT_DATA);
1143 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) &&
1148 m->m_data += max_linkhdr;
1151 SOCKBUF_UNLOCK_ASSERT(&so->so_snd);
1152 m->m_pkthdr.rcvif = (struct ifnet *)0;
1154 mac_inpcb_create_mbuf(tp->t_inpcb, m);
1158 ip6 = mtod(m, struct ip6_hdr *);
1160 udp = (struct udphdr *)((caddr_t)ip6 + sizeof(struct ip6_hdr));
1161 udp->uh_sport = htons(V_tcp_udp_tunneling_port);
1162 udp->uh_dport = tp->t_port;
1163 ulen = hdrlen + len - sizeof(struct ip6_hdr);
1164 udp->uh_ulen = htons(ulen);
1165 th = (struct tcphdr *)(udp + 1);
1167 th = (struct tcphdr *)(ip6 + 1);
1169 tcpip_fillheaders(tp->t_inpcb, tp->t_port, ip6, th);
1173 ip = mtod(m, struct ip *);
1175 ipov = (struct ipovly *)ip;
1178 udp = (struct udphdr *)((caddr_t)ip + sizeof(struct ip));
1179 udp->uh_sport = htons(V_tcp_udp_tunneling_port);
1180 udp->uh_dport = tp->t_port;
1181 ulen = hdrlen + len - sizeof(struct ip);
1182 udp->uh_ulen = htons(ulen);
1183 th = (struct tcphdr *)(udp + 1);
1185 th = (struct tcphdr *)(ip + 1);
1186 tcpip_fillheaders(tp->t_inpcb, tp->t_port, ip, th);
1190 * Fill in fields, remembering maximum advertised
1191 * window for use in delaying messages about window sizes.
1192 * If resending a FIN, be sure not to use a new sequence number.
1194 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN &&
1195 tp->snd_nxt == tp->snd_max)
1198 * If we are starting a connection, send ECN setup
1199 * SYN packet. If we are on a retransmit, we may
1200 * resend those bits a number of times as per
1203 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) {
1204 flags |= tcp_ecn_output_syn_sent(tp);
1206 /* Also handle parallel SYN for ECN */
1207 if ((TCPS_HAVERCVDSYN(tp->t_state)) &&
1208 (tp->t_flags2 & TF2_ECN_PERMIT)) {
1209 int ect = tcp_ecn_output_established(tp, &flags, len, sack_rxmit);
1210 if ((tp->t_state == TCPS_SYN_RECEIVED) &&
1211 (tp->t_flags2 & TF2_ECN_SND_ECE))
1212 tp->t_flags2 &= ~TF2_ECN_SND_ECE;
1215 ip6->ip6_flow &= ~htonl(IPTOS_ECN_MASK << 20);
1216 ip6->ip6_flow |= htonl(ect << 20);
1221 ip->ip_tos &= ~IPTOS_ECN_MASK;
1227 * If we are doing retransmissions, then snd_nxt will
1228 * not reflect the first unsent octet. For ACK only
1229 * packets, we do not want the sequence number of the
1230 * retransmitted packet, we want the sequence number
1231 * of the next unsent octet. So, if there is no data
1232 * (and no SYN or FIN), use snd_max instead of snd_nxt
1233 * when filling in ti_seq. But if we are in persist
1234 * state, snd_max might reflect one byte beyond the
1235 * right edge of the window, so use snd_nxt in that
1236 * case, since we know we aren't doing a retransmission.
1237 * (retransmit and persist are mutually exclusive...)
1239 if (sack_rxmit == 0) {
1240 if (len || (flags & (TH_SYN|TH_FIN)) ||
1241 tcp_timer_active(tp, TT_PERSIST))
1242 th->th_seq = htonl(tp->snd_nxt);
1244 th->th_seq = htonl(tp->snd_max);
1246 th->th_seq = htonl(p->rxmit);
1249 * Lost Retransmission Detection
1250 * trigger resending of a (then
1251 * still existing) hole, when
1252 * fack acks recoverypoint.
1254 if ((tp->t_flags & TF_LRD) && SEQ_GEQ(p->rxmit, p->end))
1255 p->rxmit = tp->snd_recover;
1256 tp->sackhint.sack_bytes_rexmit += len;
1258 if (IN_RECOVERY(tp->t_flags)) {
1260 * Account all bytes transmitted while
1261 * IN_RECOVERY, simplifying PRR and
1262 * Lost Retransmit Detection
1264 tp->sackhint.prr_out += len;
1266 th->th_ack = htonl(tp->rcv_nxt);
1268 bcopy(opt, th + 1, optlen);
1269 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2;
1271 tcp_set_flags(th, flags);
1273 * Calculate receive window. Don't shrink window,
1274 * but avoid silly window syndrome.
1275 * If a RST segment is sent, advertise a window of zero.
1277 if (flags & TH_RST) {
1280 if (recwin < (so->so_rcv.sb_hiwat / 4) &&
1281 recwin < tp->t_maxseg)
1283 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) &&
1284 recwin < (tp->rcv_adv - tp->rcv_nxt))
1285 recwin = (tp->rcv_adv - tp->rcv_nxt);
1288 * According to RFC1323 the window field in a SYN (i.e., a <SYN>
1289 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK>
1290 * case is handled in syncache.
1293 th->th_win = htons((u_short)
1294 (min(sbspace(&so->so_rcv), TCP_MAXWIN)));
1296 /* Avoid shrinking window with window scaling. */
1297 recwin = roundup2(recwin, 1 << tp->rcv_scale);
1298 th->th_win = htons((u_short)(recwin >> tp->rcv_scale));
1302 * Adjust the RXWIN0SENT flag - indicate that we have advertised
1303 * a 0 window. This may cause the remote transmitter to stall. This
1304 * flag tells soreceive() to disable delayed acknowledgements when
1305 * draining the buffer. This can occur if the receiver is attempting
1306 * to read more data than can be buffered prior to transmitting on
1309 if (th->th_win == 0) {
1311 tp->t_flags |= TF_RXWIN0SENT;
1313 tp->t_flags &= ~TF_RXWIN0SENT;
1314 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) {
1315 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt));
1316 th->th_flags |= TH_URG;
1319 * If no urgent pointer to send, then we pull
1320 * the urgent pointer to the left edge of the send window
1321 * so that it doesn't drift into the send window on sequence
1322 * number wraparound.
1324 tp->snd_up = tp->snd_una; /* drag it along */
1327 * Put TCP length in extended header, and then
1328 * checksum extended header and data.
1330 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */
1332 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1333 if (to.to_flags & TOF_SIGNATURE) {
1335 * Calculate MD5 signature and put it into the place
1336 * determined before.
1337 * NOTE: since TCP options buffer doesn't point into
1338 * mbuf's data, calculate offset and use it.
1340 if (!TCPMD5_ENABLED() || (error = TCPMD5_OUTPUT(m, th,
1341 (u_char *)(th + 1) + (to.to_signature - opt))) != 0) {
1343 * Do not send segment if the calculation of MD5
1344 * digest has failed.
1354 * There is no need to fill in ip6_plen right now.
1355 * It will be filled later by ip6_output.
1358 m->m_pkthdr.csum_flags = CSUM_UDP_IPV6;
1359 m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum);
1360 udp->uh_sum = in6_cksum_pseudo(ip6, ulen, IPPROTO_UDP, 0);
1361 th->th_sum = htons(0);
1362 UDPSTAT_INC(udps_opackets);
1364 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
1365 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1366 th->th_sum = in6_cksum_pseudo(ip6,
1367 sizeof(struct tcphdr) + optlen + len, IPPROTO_TCP,
1372 #if defined(INET6) && defined(INET)
1378 m->m_pkthdr.csum_flags = CSUM_UDP;
1379 m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum);
1380 udp->uh_sum = in_pseudo(ip->ip_src.s_addr,
1381 ip->ip_dst.s_addr, htons(ulen + IPPROTO_UDP));
1382 th->th_sum = htons(0);
1383 UDPSTAT_INC(udps_opackets);
1385 m->m_pkthdr.csum_flags = CSUM_TCP;
1386 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1387 th->th_sum = in_pseudo(ip->ip_src.s_addr,
1388 ip->ip_dst.s_addr, htons(sizeof(struct tcphdr) +
1389 IPPROTO_TCP + len + optlen));
1392 /* IP version must be set here for ipv4/ipv6 checking later */
1393 KASSERT(ip->ip_v == IPVERSION,
1394 ("%s: IP version incorrect: %d", __func__, ip->ip_v));
1399 * Enable TSO and specify the size of the segments.
1400 * The TCP pseudo header checksum is always provided.
1403 KASSERT(len > tp->t_maxseg - optlen,
1404 ("%s: len <= tso_segsz", __func__));
1405 m->m_pkthdr.csum_flags |= CSUM_TSO;
1406 m->m_pkthdr.tso_segsz = tp->t_maxseg - optlen;
1409 KASSERT(len + hdrlen == m_length(m, NULL),
1410 ("%s: mbuf chain shorter than expected: %d + %u != %u",
1411 __func__, len, hdrlen, m_length(m, NULL)));
1414 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */
1415 hhook_run_tcp_est_out(tp, th, &to, len, tso);
1422 if (so->so_options & SO_DEBUG) {
1428 save = ipov->ih_len;
1429 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */);
1431 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0);
1435 ipov->ih_len = save;
1437 #endif /* TCPDEBUG */
1438 TCP_PROBE3(debug__output, tp, th, m);
1440 /* We're getting ready to send; log now. */
1441 TCP_LOG_EVENT(tp, th, &so->so_rcv, &so->so_snd, TCP_LOG_OUT, ERRNO_UNK,
1445 * Fill in IP length and desired time to live and
1446 * send to IP level. There should be a better way
1447 * to handle ttl and tos; we could keep them in
1448 * the template, but need a way to checksum without them.
1451 * m->m_pkthdr.len should have been set before checksum calculation,
1452 * because in6_cksum() need it.
1457 * we separately set hoplimit for every segment, since the
1458 * user might want to change the value via setsockopt.
1459 * Also, desired default hop limit might be changed via
1460 * Neighbor Discovery.
1462 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL);
1465 * Set the packet size here for the benefit of DTrace probes.
1466 * ip6_output() will set it properly; it's supposed to include
1467 * the option header lengths as well.
1469 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6));
1471 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss)
1472 tp->t_flags2 |= TF2_PLPMTU_PMTUD;
1474 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
1476 if (tp->t_state == TCPS_SYN_SENT)
1477 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th);
1479 TCP_PROBE5(send, NULL, tp, ip6, tp, th);
1482 /* Save packet, if requested. */
1483 tcp_pcap_add(th, m, &(tp->t_outpkts));
1486 /* TODO: IPv6 IP6TOS_ECT bit on */
1487 error = ip6_output(m, tp->t_inpcb->in6p_outputopts,
1488 &tp->t_inpcb->inp_route6,
1489 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0),
1490 NULL, NULL, tp->t_inpcb);
1492 if (error == EMSGSIZE && tp->t_inpcb->inp_route6.ro_nh != NULL)
1493 mtu = tp->t_inpcb->inp_route6.ro_nh->nh_mtu;
1496 #if defined(INET) && defined(INET6)
1501 ip->ip_len = htons(m->m_pkthdr.len);
1503 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO)
1504 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL);
1507 * If we do path MTU discovery, then we set DF on every packet.
1508 * This might not be the best thing to do according to RFC3390
1509 * Section 2. However the tcp hostcache migitates the problem
1510 * so it affects only the first tcp connection with a host.
1512 * NB: Don't set DF on small MTU/MSS to have a safe fallback.
1514 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) {
1515 tp->t_flags2 |= TF2_PLPMTU_PMTUD;
1516 if (tp->t_port == 0 || len < V_tcp_minmss) {
1517 ip->ip_off |= htons(IP_DF);
1520 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
1523 if (tp->t_state == TCPS_SYN_SENT)
1524 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th);
1526 TCP_PROBE5(send, NULL, tp, ip, tp, th);
1529 /* Save packet, if requested. */
1530 tcp_pcap_add(th, m, &(tp->t_outpkts));
1533 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route,
1534 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0,
1537 if (error == EMSGSIZE && tp->t_inpcb->inp_route.ro_nh != NULL)
1538 mtu = tp->t_inpcb->inp_route.ro_nh->nh_mtu;
1544 tcp_account_for_send(tp, len, (tp->snd_nxt != tp->snd_max), 0, hw_tls);
1546 * In transmit state, time the transmission and arrange for
1547 * the retransmit. In persist state, just set snd_max.
1549 if ((tp->t_flags & TF_FORCEDATA) == 0 ||
1550 !tcp_timer_active(tp, TT_PERSIST)) {
1551 tcp_seq startseq = tp->snd_nxt;
1554 * Advance snd_nxt over sequence space of this segment.
1556 if (flags & (TH_SYN|TH_FIN)) {
1559 if (flags & TH_FIN) {
1561 tp->t_flags |= TF_SENTFIN;
1567 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) {
1568 tp->snd_max = tp->snd_nxt;
1570 * Time this transmission if not a retransmission and
1571 * not currently timing anything.
1573 tp->t_sndtime = ticks;
1574 if (tp->t_rtttime == 0) {
1575 tp->t_rtttime = ticks;
1576 tp->t_rtseq = startseq;
1577 TCPSTAT_INC(tcps_segstimed);
1580 if (!(tp->t_flags & TF_GPUTINPROG) && len) {
1581 tp->t_flags |= TF_GPUTINPROG;
1582 tp->gput_seq = startseq;
1583 tp->gput_ack = startseq +
1584 ulmin(sbavail(&so->so_snd) - off, sendwin);
1585 tp->gput_ts = tcp_ts_getticks();
1591 * Set retransmit timer if not currently set,
1592 * and not doing a pure ack or a keep-alive probe.
1593 * Initial value for retransmit timer is smoothed
1594 * round-trip time + 2 * round-trip time variance.
1595 * Initialize shift counter which is used for backoff
1596 * of retransmit time.
1599 if (!tcp_timer_active(tp, TT_REXMT) &&
1600 ((sack_rxmit && tp->snd_nxt != tp->snd_max) ||
1601 (tp->snd_nxt != tp->snd_una))) {
1602 if (tcp_timer_active(tp, TT_PERSIST)) {
1603 tcp_timer_activate(tp, TT_PERSIST, 0);
1606 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
1607 } else if (len == 0 && sbavail(&so->so_snd) &&
1608 !tcp_timer_active(tp, TT_REXMT) &&
1609 !tcp_timer_active(tp, TT_PERSIST)) {
1611 * Avoid a situation where we do not set persist timer
1612 * after a zero window condition. For example:
1613 * 1) A -> B: packet with enough data to fill the window
1614 * 2) B -> A: ACK for #1 + new data (0 window
1616 * 3) A -> B: ACK for #2, 0 len packet
1618 * In this case, A will not activate the persist timer,
1619 * because it chose to send a packet. Unless tcp_output
1620 * is called for some other reason (delayed ack timer,
1621 * another input packet from B, socket syscall), A will
1622 * not send zero window probes.
1624 * So, if you send a 0-length packet, but there is data
1625 * in the socket buffer, and neither the rexmt or
1626 * persist timer is already set, then activate the
1634 * Persist case, update snd_max but since we are in
1635 * persist mode (no window) we do not update snd_nxt.
1640 if (flags & TH_FIN) {
1642 tp->t_flags |= TF_SENTFIN;
1644 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max))
1645 tp->snd_max = tp->snd_nxt + xlen;
1648 (TCPS_HAVEESTABLISHED(tp->t_state) &&
1649 (tp->t_flags & TF_SACK_PERMIT) &&
1650 tp->rcv_numsacks > 0)) {
1651 /* Clean up any DSACK's sent */
1652 tcp_clean_dsack_blocks(tp);
1655 /* Record the error. */
1656 TCP_LOG_EVENT(tp, NULL, &so->so_rcv, &so->so_snd, TCP_LOG_OUT,
1657 error, 0, NULL, false);
1660 * We know that the packet was lost, so back out the
1661 * sequence number advance, if any.
1663 * If the error is EPERM the packet got blocked by the
1664 * local firewall. Normally we should terminate the
1665 * connection but the blocking may have been spurious
1666 * due to a firewall reconfiguration cycle. So we treat
1667 * it like a packet loss and let the retransmit timer and
1668 * timeouts do their work over time.
1669 * XXX: It is a POLA question whether calling tcp_drop right
1670 * away would be the really correct behavior instead.
1672 if (((tp->t_flags & TF_FORCEDATA) == 0 ||
1673 !tcp_timer_active(tp, TT_PERSIST)) &&
1674 ((flags & TH_SYN) == 0) &&
1678 tp->sackhint.sack_bytes_rexmit -= len;
1679 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0,
1680 ("sackhint bytes rtx >= 0"));
1684 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */
1688 tp->t_softerror = error;
1691 TCP_XMIT_TIMER_ASSERT(tp, len, flags);
1692 tp->snd_cwnd = tp->t_maxseg;
1696 * For some reason the interface we used initially
1697 * to send segments changed to another or lowered
1699 * If TSO was active we either got an interface
1700 * without TSO capabilits or TSO was turned off.
1701 * If we obtained mtu from ip_output() then update
1705 tp->t_flags &= ~TF_TSO;
1707 tcp_mss_update(tp, -1, mtu, NULL, NULL);
1715 if (TCPS_HAVERCVDSYN(tp->t_state)) {
1716 tp->t_softerror = error;
1724 TCPSTAT_INC(tcps_sndtotal);
1727 * Data sent (as far as we can tell).
1728 * If this advertises a larger window than any other segment,
1729 * then remember the size of the advertised window.
1730 * Any pending ACK has now been sent.
1732 if (SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv))
1733 tp->rcv_adv = tp->rcv_nxt + recwin;
1734 tp->last_ack_sent = tp->rcv_nxt;
1735 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK);
1736 if (tcp_timer_active(tp, TT_DELACK))
1737 tcp_timer_activate(tp, TT_DELACK, 0);
1740 * This completely breaks TCP if newreno is turned on. What happens
1741 * is that if delayed-acks are turned on on the receiver, this code
1742 * on the transmitter effectively destroys the TCP window, forcing
1743 * it to four packets (1.5Kx4 = 6K window).
1745 if (sendalot && --maxburst)
1754 tcp_setpersist(struct tcpcb *tp)
1756 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1;
1759 tp->t_flags &= ~TF_PREVVALID;
1760 if (tcp_timer_active(tp, TT_REXMT))
1761 panic("tcp_setpersist: retransmit pending");
1763 * Start/restart persistence timer.
1765 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift],
1766 tcp_persmin, tcp_persmax);
1767 tcp_timer_activate(tp, TT_PERSIST, tt);
1768 if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
1773 * Insert TCP options according to the supplied parameters to the place
1774 * optp in a consistent way. Can handle unaligned destinations.
1776 * The order of the option processing is crucial for optimal packing and
1777 * alignment for the scarce option space.
1779 * The optimal order for a SYN/SYN-ACK segment is:
1780 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) +
1781 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40.
1783 * The SACK options should be last. SACK blocks consume 8*n+2 bytes.
1784 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks).
1785 * At minimum we need 10 bytes (to generate 1 SACK block). If both
1786 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present,
1787 * we only have 10 bytes for SACK options (40 - (12 + 18)).
1790 tcp_addoptions(struct tcpopt *to, u_char *optp)
1792 u_int32_t mask, optlen = 0;
1794 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) {
1795 if ((to->to_flags & mask) != mask)
1797 if (optlen == TCP_MAXOLEN)
1799 switch (to->to_flags & mask) {
1801 while (optlen % 4) {
1802 optlen += TCPOLEN_NOP;
1803 *optp++ = TCPOPT_NOP;
1805 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG)
1807 optlen += TCPOLEN_MAXSEG;
1808 *optp++ = TCPOPT_MAXSEG;
1809 *optp++ = TCPOLEN_MAXSEG;
1810 to->to_mss = htons(to->to_mss);
1811 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss));
1812 optp += sizeof(to->to_mss);
1815 while (!optlen || optlen % 2 != 1) {
1816 optlen += TCPOLEN_NOP;
1817 *optp++ = TCPOPT_NOP;
1819 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW)
1821 optlen += TCPOLEN_WINDOW;
1822 *optp++ = TCPOPT_WINDOW;
1823 *optp++ = TCPOLEN_WINDOW;
1824 *optp++ = to->to_wscale;
1827 while (optlen % 2) {
1828 optlen += TCPOLEN_NOP;
1829 *optp++ = TCPOPT_NOP;
1831 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED)
1833 optlen += TCPOLEN_SACK_PERMITTED;
1834 *optp++ = TCPOPT_SACK_PERMITTED;
1835 *optp++ = TCPOLEN_SACK_PERMITTED;
1838 while (!optlen || optlen % 4 != 2) {
1839 optlen += TCPOLEN_NOP;
1840 *optp++ = TCPOPT_NOP;
1842 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP)
1844 optlen += TCPOLEN_TIMESTAMP;
1845 *optp++ = TCPOPT_TIMESTAMP;
1846 *optp++ = TCPOLEN_TIMESTAMP;
1847 to->to_tsval = htonl(to->to_tsval);
1848 to->to_tsecr = htonl(to->to_tsecr);
1849 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval));
1850 optp += sizeof(to->to_tsval);
1851 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr));
1852 optp += sizeof(to->to_tsecr);
1856 int siglen = TCPOLEN_SIGNATURE - 2;
1858 while (!optlen || optlen % 4 != 2) {
1859 optlen += TCPOLEN_NOP;
1860 *optp++ = TCPOPT_NOP;
1862 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) {
1863 to->to_flags &= ~TOF_SIGNATURE;
1866 optlen += TCPOLEN_SIGNATURE;
1867 *optp++ = TCPOPT_SIGNATURE;
1868 *optp++ = TCPOLEN_SIGNATURE;
1869 to->to_signature = optp;
1877 struct sackblk *sack = (struct sackblk *)to->to_sacks;
1880 while (!optlen || optlen % 4 != 2) {
1881 optlen += TCPOLEN_NOP;
1882 *optp++ = TCPOPT_NOP;
1884 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK)
1886 optlen += TCPOLEN_SACKHDR;
1887 *optp++ = TCPOPT_SACK;
1888 sackblks = min(to->to_nsacks,
1889 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK);
1890 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK;
1891 while (sackblks--) {
1892 sack_seq = htonl(sack->start);
1893 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq));
1894 optp += sizeof(sack_seq);
1895 sack_seq = htonl(sack->end);
1896 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq));
1897 optp += sizeof(sack_seq);
1898 optlen += TCPOLEN_SACK;
1901 TCPSTAT_INC(tcps_sack_send_blocks);
1908 /* XXX is there any point to aligning this option? */
1909 total_len = TCPOLEN_FAST_OPEN_EMPTY + to->to_tfo_len;
1910 if (TCP_MAXOLEN - optlen < total_len) {
1911 to->to_flags &= ~TOF_FASTOPEN;
1914 *optp++ = TCPOPT_FAST_OPEN;
1915 *optp++ = total_len;
1916 if (to->to_tfo_len > 0) {
1917 bcopy(to->to_tfo_cookie, optp, to->to_tfo_len);
1918 optp += to->to_tfo_len;
1920 optlen += total_len;
1924 panic("%s: unknown TCP option type", __func__);
1929 /* Terminate and pad TCP options to a 4 byte boundary. */
1931 optlen += TCPOLEN_EOL;
1932 *optp++ = TCPOPT_EOL;
1935 * According to RFC 793 (STD0007):
1936 * "The content of the header beyond the End-of-Option option
1937 * must be header padding (i.e., zero)."
1938 * and later: "The padding is composed of zeros."
1940 while (optlen % 4) {
1941 optlen += TCPOLEN_PAD;
1942 *optp++ = TCPOPT_PAD;
1945 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__));
1950 * This is a copy of m_copym(), taking the TSO segment size/limit
1951 * constraints into account, and advancing the sndptr as it goes.
1954 tcp_m_copym(struct mbuf *m, int32_t off0, int32_t *plen,
1955 int32_t seglimit, int32_t segsize, struct sockbuf *sb, bool hw_tls)
1958 struct ktls_session *tls, *ntls;
1961 struct mbuf *n, **np;
1964 int32_t len = *plen;
1968 uint32_t mlen, frags;
1971 KASSERT(off >= 0, ("tcp_m_copym, negative off %d", off));
1972 KASSERT(len >= 0, ("tcp_m_copym, negative len %d", len));
1973 if (off == 0 && m->m_flags & M_PKTHDR)
1978 KASSERT(m != NULL, ("tcp_m_copym, offset > size of mbuf chain"));
1982 if ((sb) && (m == sb->sb_sndptr)) {
1983 sb->sb_sndptroff += m->m_len;
1984 sb->sb_sndptr = m->m_next;
1992 if (hw_tls && (m->m_flags & M_EXTPG))
2000 KASSERT(len == M_COPYALL,
2001 ("tcp_m_copym, length > size of mbuf chain"));
2003 if (pkthdrlen != NULL)
2004 *pkthdrlen = len_cp;
2009 if (m->m_flags & M_EXTPG)
2010 ntls = m->m_epg_tls;
2015 * Avoid mixing TLS records with handshake
2016 * data or TLS records from different
2022 if (pkthdrlen != NULL)
2023 *pkthdrlen = len_cp;
2028 mlen = min(len, m->m_len - off);
2031 * For M_EXTPG mbufs, add 3 segments
2032 * + 1 in case we are crossing page boundaries
2033 * + 2 in case the TLS hdr/trailer are used
2034 * It is cheaper to just add the segments
2035 * than it is to take the cache miss to look
2036 * at the mbuf ext_pgs state in detail.
2038 if (m->m_flags & M_EXTPG) {
2039 fragsize = min(segsize, PAGE_SIZE);
2046 /* Break if we really can't fit anymore. */
2047 if ((frags + 1) >= seglimit) {
2049 if (pkthdrlen != NULL)
2050 *pkthdrlen = len_cp;
2055 * Reduce size if you can't copy the whole
2056 * mbuf. If we can't copy the whole mbuf, also
2057 * adjust len so the loop will end after this
2060 if ((frags + howmany(mlen, fragsize)) >= seglimit) {
2061 mlen = (seglimit - frags - 1) * fragsize;
2063 *plen = len_cp + len;
2064 if (pkthdrlen != NULL)
2067 frags += howmany(mlen, fragsize);
2071 KASSERT(seglimit > 0,
2072 ("%s: seglimit went too low", __func__));
2075 n = m_gethdr(M_NOWAIT, m->m_type);
2077 n = m_get(M_NOWAIT, m->m_type);
2082 if (!m_dup_pkthdr(n, m, M_NOWAIT))
2084 if (len == M_COPYALL)
2085 n->m_pkthdr.len -= off0;
2087 n->m_pkthdr.len = len;
2088 pkthdrlen = &n->m_pkthdr.len;
2093 if (m->m_flags & (M_EXT|M_EXTPG)) {
2094 n->m_data = m->m_data + off;
2097 bcopy(mtod(m, caddr_t)+off, mtod(n, caddr_t),
2100 if (sb && (sb->sb_sndptr == m) &&
2101 ((n->m_len + off) >= m->m_len) && m->m_next) {
2102 sb->sb_sndptroff += m->m_len;
2103 sb->sb_sndptr = m->m_next;
2106 if (len != M_COPYALL) {
2119 tcp_sndbuf_autoscale(struct tcpcb *tp, struct socket *so, uint32_t sendwin)
2123 * Automatic sizing of send socket buffer. Often the send buffer
2124 * size is not optimally adjusted to the actual network conditions
2125 * at hand (delay bandwidth product). Setting the buffer size too
2126 * small limits throughput on links with high bandwidth and high
2127 * delay (eg. trans-continental/oceanic links). Setting the
2128 * buffer size too big consumes too much real kernel memory,
2129 * especially with many connections on busy servers.
2131 * The criteria to step up the send buffer one notch are:
2132 * 1. receive window of remote host is larger than send buffer
2133 * (with a fudge factor of 5/4th);
2134 * 2. send buffer is filled to 7/8th with data (so we actually
2135 * have data to make use of it);
2136 * 3. send buffer fill has not hit maximal automatic size;
2137 * 4. our send window (slow start and cogestion controlled) is
2138 * larger than sent but unacknowledged data in send buffer.
2140 * The remote host receive window scaling factor may limit the
2141 * growing of the send buffer before it reaches its allowed
2144 * It scales directly with slow start or congestion window
2145 * and does at most one step per received ACK. This fast
2146 * scaling has the drawback of growing the send buffer beyond
2147 * what is strictly necessary to make full use of a given
2148 * delay*bandwidth product. However testing has shown this not
2149 * to be much of an problem. At worst we are trading wasting
2150 * of available bandwidth (the non-use of it) for wasting some
2151 * socket buffer memory.
2153 * TODO: Shrink send buffer during idle periods together
2154 * with congestion window. Requires another timer. Has to
2155 * wait for upcoming tcp timer rewrite.
2157 * XXXGL: should there be used sbused() or sbavail()?
2159 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) {
2162 lowat = V_tcp_sendbuf_auto_lowat ? so->so_snd.sb_lowat : 0;
2163 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat - lowat &&
2164 sbused(&so->so_snd) >=
2165 (so->so_snd.sb_hiwat / 8 * 7) - lowat &&
2166 sbused(&so->so_snd) < V_tcp_autosndbuf_max &&
2167 sendwin >= (sbused(&so->so_snd) -
2168 (tp->snd_nxt - tp->snd_una))) {
2169 if (!sbreserve_locked(&so->so_snd,
2170 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc,
2171 V_tcp_autosndbuf_max), so, curthread))
2172 so->so_snd.sb_flags &= ~SB_AUTOSIZE;
projects / FreeBSD / FreeBSD.git / blob