2 * SPDX-License-Identifier: BSD-3-Clause
4 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
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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 SEQ_SUB(tp->snd_recover, p->rxmit)));
337 len = ((int32_t)ulmin(cwin,
338 SEQ_SUB(p->end, p->rxmit)));
340 off = SEQ_SUB(p->rxmit, tp->snd_una);
341 KASSERT(off >= 0,("%s: sack block to the left of una : %d",
346 TCPSTAT_INC(tcps_sack_rexmits);
347 TCPSTAT_ADD(tcps_sack_rexmit_bytes,
348 min(len, tcp_maxseg(tp)));
353 * Get standard flags, and add SYN or FIN if requested by 'hidden'
356 if (tp->t_flags & TF_NEEDFIN)
358 if (tp->t_flags & TF_NEEDSYN)
361 SOCKBUF_LOCK(&so->so_snd);
363 * If in persist timeout with window of 0, send 1 byte.
364 * Otherwise, if window is small but nonzero
365 * and timer expired, we will send what we can
366 * and go to transmit state.
368 if (tp->t_flags & TF_FORCEDATA) {
371 * If we still have some data to send, then
372 * clear the FIN bit. Usually this would
373 * happen below when it realizes that we
374 * aren't sending all the data. However,
375 * if we have exactly 1 byte of unsent data,
376 * then it won't clear the FIN bit below,
377 * and if we are in persist state, we wind
378 * up sending the packet without recording
379 * that we sent the FIN bit.
381 * We can't just blindly clear the FIN bit,
382 * because if we don't have any more data
383 * to send then the probe will be the FIN
386 if (off < sbused(&so->so_snd))
390 tcp_timer_activate(tp, TT_PERSIST, 0);
396 * If snd_nxt == snd_max and we have transmitted a FIN, the
397 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in
398 * a negative length. This can also occur when TCP opens up
399 * its congestion window while receiving additional duplicate
400 * acks after fast-retransmit because TCP will reset snd_nxt
401 * to snd_max after the fast-retransmit.
403 * In the normal retransmit-FIN-only case, however, snd_nxt will
404 * be set to snd_una, the offset will be 0, and the length may
407 * If sack_rxmit is true we are retransmitting from the scoreboard
408 * in which case len is already set.
410 if (sack_rxmit == 0) {
411 if (sack_bytes_rxmt == 0)
412 len = ((int32_t)min(sbavail(&so->so_snd), sendwin) -
418 * We are inside of a SACK recovery episode and are
419 * sending new data, having retransmitted all the
420 * data possible in the scoreboard.
422 len = ((int32_t)min(sbavail(&so->so_snd), tp->snd_wnd) -
425 * Don't remove this (len > 0) check !
426 * We explicitly check for len > 0 here (although it
427 * isn't really necessary), to work around a gcc
428 * optimization issue - to force gcc to compute
429 * len above. Without this check, the computation
430 * of len is bungled by the optimizer.
433 cwin = tp->snd_cwnd -
434 (tp->snd_nxt - tp->snd_recover) -
438 len = imin(len, cwin);
444 * Lop off SYN bit if it has already been sent. However, if this
445 * is SYN-SENT state and if segment contains data and if we don't
446 * know that foreign host supports TAO, suppress sending segment.
448 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) {
449 if (tp->t_state != TCPS_SYN_RECEIVED)
452 * When sending additional segments following a TFO SYN|ACK,
453 * do not include the SYN bit.
455 if (IS_FASTOPEN(tp->t_flags) &&
456 (tp->t_state == TCPS_SYN_RECEIVED))
462 * Be careful not to send data and/or FIN on SYN segments.
463 * This measure is needed to prevent interoperability problems
464 * with not fully conformant TCP implementations.
466 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) {
472 * On TFO sockets, ensure no data is sent in the following cases:
474 * - When retransmitting SYN|ACK on a passively-created socket
476 * - When retransmitting SYN on an actively created socket
478 * - When sending a zero-length cookie (cookie request) on an
479 * actively created socket
481 * - When the socket is in the CLOSED state (RST is being sent)
483 if (IS_FASTOPEN(tp->t_flags) &&
484 (((flags & TH_SYN) && (tp->t_rxtshift > 0)) ||
485 ((tp->t_state == TCPS_SYN_SENT) &&
486 (tp->t_tfo_client_cookie_len == 0)) ||
491 * If FIN has been sent but not acked,
492 * but we haven't been called to retransmit,
493 * len will be < 0. Otherwise, window shrank
494 * after we sent into it. If window shrank to 0,
495 * cancel pending retransmit, pull snd_nxt back
496 * to (closed) window, and set the persist timer
497 * if it isn't already going. If the window didn't
498 * close completely, just wait for an ACK.
500 * We also do a general check here to ensure that
501 * we will set the persist timer when we have data
502 * to send, but a 0-byte window. This makes sure
503 * the persist timer is set even if the packet
504 * hits one of the "goto send" lines below.
507 if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) &&
508 (off < (int) sbavail(&so->so_snd))) {
509 tcp_timer_activate(tp, TT_REXMT, 0);
511 tp->snd_nxt = tp->snd_una;
512 if (!tcp_timer_active(tp, TT_PERSIST))
517 /* len will be >= 0 after this point. */
518 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__));
520 tcp_sndbuf_autoscale(tp, so, sendwin);
523 * Decide if we can use TCP Segmentation Offloading (if supported by
526 * TSO may only be used if we are in a pure bulk sending state. The
527 * presence of TCP-MD5, SACK retransmits, SACK advertizements and
528 * IP options prevent using TSO. With TSO the TCP header is the same
529 * (except for the sequence number) for all generated packets. This
530 * makes it impossible to transmit any options which vary per generated
533 * IPv4 handling has a clear separation of ip options and ip header
534 * flags while IPv6 combines both in in6p_outputopts. ip6_optlen() does
535 * the right thing below to provide length of just ip options and thus
536 * checking for ipoptlen is enough to decide if ip options are present.
538 #if defined(IPSEC) || defined(IPSEC_SUPPORT)
540 * Pre-calculate here as we save another lookup into the darknesses
541 * of IPsec that way and can actually decide if TSO is ok.
544 if (isipv6 && IPSEC_ENABLED(ipv6))
545 ipsec_optlen = IPSEC_HDRSIZE(ipv6, tp->t_inpcb);
551 if (IPSEC_ENABLED(ipv4))
552 ipsec_optlen = IPSEC_HDRSIZE(ipv4, tp->t_inpcb);
557 ipoptlen = ip6_optlen(tp->t_inpcb);
560 if (tp->t_inpcb->inp_options)
561 ipoptlen = tp->t_inpcb->inp_options->m_len -
562 offsetof(struct ipoption, ipopt_list);
565 #if defined(IPSEC) || defined(IPSEC_SUPPORT)
566 ipoptlen += ipsec_optlen;
569 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg &&
571 ((tp->t_flags & TF_SIGNATURE) == 0) &&
572 tp->rcv_numsacks == 0 && sack_rxmit == 0 &&
573 ipoptlen == 0 && !(flags & TH_SYN))
577 if (SEQ_LT(p->rxmit + len, tp->snd_una + sbused(&so->so_snd)))
580 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una +
581 sbused(&so->so_snd)))
585 recwin = lmin(lmax(sbspace(&so->so_rcv), 0),
586 (long)TCP_MAXWIN << tp->rcv_scale);
589 * Sender silly window avoidance. We transmit under the following
590 * conditions when len is non-zero:
592 * - We have a full segment (or more with TSO)
593 * - This is the last buffer in a write()/send() and we are
594 * either idle or running NODELAY
595 * - we've timed out (e.g. persist timer)
596 * - we have more then 1/2 the maximum send window's worth of
597 * data (receiver may be limited the window size)
598 * - we need to retransmit
601 if (len >= tp->t_maxseg)
604 * As the TCP header options are now
605 * considered when setting up the initial
606 * window, we would not send the last segment
607 * if we skip considering the option length here.
608 * Note: this may not work when tcp headers change
609 * very dynamically in the future.
611 if ((((tp->t_flags & TF_SIGNATURE) ?
612 PADTCPOLEN(TCPOLEN_SIGNATURE) : 0) +
613 ((tp->t_flags & TF_RCVD_TSTMP) ?
614 PADTCPOLEN(TCPOLEN_TIMESTAMP) : 0) +
615 len) >= tp->t_maxseg)
618 * NOTE! on localhost connections an 'ack' from the remote
619 * end may occur synchronously with the output and cause
620 * us to flush a buffer queued with moretocome. XXX
622 * note: the len + off check is almost certainly unnecessary.
624 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */
625 (idle || (tp->t_flags & TF_NODELAY)) &&
626 (uint32_t)len + (uint32_t)off >= sbavail(&so->so_snd) &&
627 (tp->t_flags & TF_NOPUSH) == 0) {
630 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */
632 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0)
634 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */
641 * Sending of standalone window updates.
643 * Window updates are important when we close our window due to a
644 * full socket buffer and are opening it again after the application
645 * reads data from it. Once the window has opened again and the
646 * remote end starts to send again the ACK clock takes over and
647 * provides the most current window information.
649 * We must avoid the silly window syndrome whereas every read
650 * from the receive buffer, no matter how small, causes a window
651 * update to be sent. We also should avoid sending a flurry of
652 * window updates when the socket buffer had queued a lot of data
653 * and the application is doing small reads.
655 * Prevent a flurry of pointless window updates by only sending
656 * an update when we can increase the advertized window by more
657 * than 1/4th of the socket buffer capacity. When the buffer is
658 * getting full or is very small be more aggressive and send an
659 * update whenever we can increase by two mss sized segments.
660 * In all other situations the ACK's to new incoming data will
661 * carry further window increases.
663 * Don't send an independent window update if a delayed
664 * ACK is pending (it will get piggy-backed on it) or the
665 * remote side already has done a half-close and won't send
666 * more data. Skip this if the connection is in T/TCP
669 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) &&
670 !(tp->t_flags & TF_DELACK) &&
671 !TCPS_HAVERCVDFIN(tp->t_state)) {
673 * "adv" is the amount we could increase the window,
674 * taking into account that we are limited by
675 * TCP_MAXWIN << tp->rcv_scale.
681 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) {
682 oldwin = (tp->rcv_adv - tp->rcv_nxt);
691 * If the new window size ends up being the same as or less
692 * than the old size when it is scaled, then don't force
695 if (oldwin >> tp->rcv_scale >= (adv + oldwin) >> tp->rcv_scale)
698 if (adv >= (int32_t)(2 * tp->t_maxseg) &&
699 (adv >= (int32_t)(so->so_rcv.sb_hiwat / 4) ||
700 recwin <= (so->so_rcv.sb_hiwat / 8) ||
701 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg ||
702 adv >= TCP_MAXWIN << tp->rcv_scale))
704 if (2 * adv >= (int32_t)so->so_rcv.sb_hiwat)
710 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW
711 * is also a catch-all for the retransmit timer timeout case.
713 if (tp->t_flags & TF_ACKNOW)
715 if ((flags & TH_RST) ||
716 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0))
718 if (SEQ_GT(tp->snd_up, tp->snd_una))
721 * If our state indicates that FIN should be sent
722 * and we have not yet done so, then we need to send.
724 if (flags & TH_FIN &&
725 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una))
728 * In SACK, it is possible for tcp_output to fail to send a segment
729 * after the retransmission timer has been turned off. Make sure
730 * that the retransmission timer is set.
732 if ((tp->t_flags & TF_SACK_PERMIT) &&
733 SEQ_GT(tp->snd_max, tp->snd_una) &&
734 !tcp_timer_active(tp, TT_REXMT) &&
735 !tcp_timer_active(tp, TT_PERSIST)) {
736 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
740 * TCP window updates are not reliable, rather a polling protocol
741 * using ``persist'' packets is used to insure receipt of window
742 * updates. The three ``states'' for the output side are:
743 * idle not doing retransmits or persists
744 * persisting to move a small or zero window
745 * (re)transmitting and thereby not persisting
747 * tcp_timer_active(tp, TT_PERSIST)
748 * is true when we are in persist state.
749 * (tp->t_flags & TF_FORCEDATA)
750 * is set when we are called to send a persist packet.
751 * tcp_timer_active(tp, TT_REXMT)
752 * is set when we are retransmitting
753 * The output side is idle when both timers are zero.
755 * If send window is too small, there is data to transmit, and no
756 * retransmit or persist is pending, then go to persist state.
757 * If nothing happens soon, send when timer expires:
758 * if window is nonzero, transmit what we can,
759 * otherwise force out a byte.
761 if (sbavail(&so->so_snd) && !tcp_timer_active(tp, TT_REXMT) &&
762 !tcp_timer_active(tp, TT_PERSIST)) {
768 * No reason to send a segment, just return.
771 SOCKBUF_UNLOCK(&so->so_snd);
775 SOCKBUF_LOCK_ASSERT(&so->so_snd);
777 if (len >= tp->t_maxseg)
778 tp->t_flags2 |= TF2_PLPMTU_MAXSEGSNT;
780 tp->t_flags2 &= ~TF2_PLPMTU_MAXSEGSNT;
783 * Before ESTABLISHED, force sending of initial options
784 * unless TCP set not to do any options.
785 * NOTE: we assume that the IP/TCP header plus TCP options
786 * always fit in a single mbuf, leaving room for a maximum
788 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES
793 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr);
796 hdrlen = sizeof (struct tcpiphdr);
798 if (flags & TH_SYN) {
799 tp->snd_nxt = tp->iss;
803 * Compute options for segment.
804 * We only have to care about SYN and established connection
805 * segments. Options for SYN-ACK segments are handled in TCP
809 if ((tp->t_flags & TF_NOOPT) == 0) {
810 /* Maximum segment size. */
811 if (flags & TH_SYN) {
812 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc);
814 to.to_mss -= V_tcp_udp_tunneling_overhead;
815 to.to_flags |= TOF_MSS;
818 * On SYN or SYN|ACK transmits on TFO connections,
819 * only include the TFO option if it is not a
820 * retransmit, as the presence of the TFO option may
821 * have caused the original SYN or SYN|ACK to have
822 * been dropped by a middlebox.
824 if (IS_FASTOPEN(tp->t_flags) &&
825 (tp->t_rxtshift == 0)) {
826 if (tp->t_state == TCPS_SYN_RECEIVED) {
827 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN;
829 (u_int8_t *)&tp->t_tfo_cookie.server;
830 to.to_flags |= TOF_FASTOPEN;
832 } else if (tp->t_state == TCPS_SYN_SENT) {
834 tp->t_tfo_client_cookie_len;
836 tp->t_tfo_cookie.client;
837 to.to_flags |= TOF_FASTOPEN;
840 * If we wind up having more data to
841 * send with the SYN than can fit in
842 * one segment, don't send any more
843 * until the SYN|ACK comes back from
850 /* Window scaling. */
851 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) {
852 to.to_wscale = tp->request_r_scale;
853 to.to_flags |= TOF_SCALE;
856 if ((tp->t_flags & TF_RCVD_TSTMP) ||
857 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) {
858 curticks = tcp_ts_getticks();
859 to.to_tsval = curticks + tp->ts_offset;
860 to.to_tsecr = tp->ts_recent;
861 to.to_flags |= TOF_TS;
862 if (tp->t_rxtshift == 1)
863 tp->t_badrxtwin = curticks;
866 /* Set receive buffer autosizing timestamp. */
867 if (tp->rfbuf_ts == 0 &&
868 (so->so_rcv.sb_flags & SB_AUTOSIZE))
869 tp->rfbuf_ts = tcp_ts_getticks();
871 /* Selective ACK's. */
872 if (tp->t_flags & TF_SACK_PERMIT) {
874 to.to_flags |= TOF_SACKPERM;
875 else if (TCPS_HAVEESTABLISHED(tp->t_state) &&
876 tp->rcv_numsacks > 0) {
877 to.to_flags |= TOF_SACK;
878 to.to_nsacks = tp->rcv_numsacks;
879 to.to_sacks = (u_char *)tp->sackblks;
882 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
883 /* TCP-MD5 (RFC2385). */
885 * Check that TCP_MD5SIG is enabled in tcpcb to
886 * account the size needed to set this TCP option.
888 if (tp->t_flags & TF_SIGNATURE)
889 to.to_flags |= TOF_SIGNATURE;
890 #endif /* TCP_SIGNATURE */
892 /* Processing the options. */
893 hdrlen += optlen = tcp_addoptions(&to, opt);
895 * If we wanted a TFO option to be added, but it was unable
896 * to fit, ensure no data is sent.
898 if (IS_FASTOPEN(tp->t_flags) && wanted_cookie &&
899 !(to.to_flags & TOF_FASTOPEN))
903 if (V_tcp_udp_tunneling_port == 0) {
904 /* The port was removed?? */
905 SOCKBUF_UNLOCK(&so->so_snd);
906 return (EHOSTUNREACH);
908 hdrlen += sizeof(struct udphdr);
911 * Adjust data length if insertion of options will
912 * bump the packet length beyond the t_maxseg length.
913 * Clear the FIN bit because we cut off the tail of
916 if (len + optlen + ipoptlen > tp->t_maxseg) {
924 /* extract TSO information */
925 if_hw_tsomax = tp->t_tsomax;
926 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount;
927 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize;
930 * Limit a TSO burst to prevent it from
931 * overflowing or exceeding the maximum length
932 * allowed by the network interface:
934 KASSERT(ipoptlen == 0,
935 ("%s: TSO can't do IP options", __func__));
938 * Check if we should limit by maximum payload
941 if (if_hw_tsomax != 0) {
942 /* compute maximum TSO length */
943 max_len = (if_hw_tsomax - hdrlen -
947 } else if (len > max_len) {
954 * Prevent the last segment from being
955 * fractional unless the send sockbuf can be
958 max_len = (tp->t_maxseg - optlen);
959 if (((uint32_t)off + (uint32_t)len) <
960 sbavail(&so->so_snd)) {
961 moff = len % max_len;
969 * In case there are too many small fragments
972 if (len <= max_len) {
979 * Send the FIN in a separate segment
980 * after the bulk sending is done.
981 * We don't trust the TSO implementations
982 * to clear the FIN flag on all but the
985 if (tp->t_flags & TF_NEEDFIN)
988 if (optlen + ipoptlen >= tp->t_maxseg) {
990 * Since we don't have enough space to put
991 * the IP header chain and the TCP header in
992 * one packet as required by RFC 7112, don't
993 * send it. Also ensure that at least one
994 * byte of the payload can be put into the
997 SOCKBUF_UNLOCK(&so->so_snd);
1002 len = tp->t_maxseg - optlen - ipoptlen;
1010 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET,
1011 ("%s: len > IP_MAXPACKET", __func__));
1013 /*#ifdef DIAGNOSTIC*/
1015 if (max_linkhdr + hdrlen > MCLBYTES)
1017 if (max_linkhdr + hdrlen > MHLEN)
1019 panic("tcphdr too big");
1023 * This KASSERT is here to catch edge cases at a well defined place.
1024 * Before, those had triggered (random) panic conditions further down.
1026 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__));
1029 * Grab a header mbuf, attaching a copy of data to
1030 * be transmitted, and initialize the header from
1031 * the template for sends on this connection.
1035 struct sockbuf *msb;
1038 if ((tp->t_flags & TF_FORCEDATA) && len == 1) {
1039 TCPSTAT_INC(tcps_sndprobe);
1041 if (SEQ_LT(tp->snd_nxt, tp->snd_max))
1042 stats_voi_update_abs_u32(tp->t_stats,
1043 VOI_TCP_RETXPB, len);
1045 stats_voi_update_abs_u64(tp->t_stats,
1048 } else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) {
1049 tp->t_sndrexmitpack++;
1050 TCPSTAT_INC(tcps_sndrexmitpack);
1051 TCPSTAT_ADD(tcps_sndrexmitbyte, len);
1053 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_RETXPB,
1057 TCPSTAT_INC(tcps_sndpack);
1058 TCPSTAT_ADD(tcps_sndbyte, len);
1060 stats_voi_update_abs_u64(tp->t_stats, VOI_TCP_TXPB,
1065 if (MHLEN < hdrlen + max_linkhdr)
1066 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR);
1069 m = m_gethdr(M_NOWAIT, MT_DATA);
1072 SOCKBUF_UNLOCK(&so->so_snd);
1078 m->m_data += max_linkhdr;
1082 * Start the m_copy functions from the closest mbuf
1083 * to the offset in the socket buffer chain.
1085 mb = sbsndptr_noadv(&so->so_snd, off, &moff);
1086 if (len <= MHLEN - hdrlen - max_linkhdr && !hw_tls) {
1087 m_copydata(mb, moff, len,
1088 mtod(m, caddr_t) + hdrlen);
1089 if (SEQ_LT(tp->snd_nxt, tp->snd_max))
1090 sbsndptr_adv(&so->so_snd, mb, len);
1093 if (SEQ_LT(tp->snd_nxt, tp->snd_max))
1097 m->m_next = tcp_m_copym(mb, moff,
1098 &len, if_hw_tsomaxsegcount,
1099 if_hw_tsomaxsegsize, msb, hw_tls);
1100 if (len <= (tp->t_maxseg - optlen)) {
1102 * Must have ran out of mbufs for the copy
1103 * shorten it to no longer need tso. Lets
1104 * not put on sendalot since we are low on
1109 if (m->m_next == NULL) {
1110 SOCKBUF_UNLOCK(&so->so_snd);
1119 * If we're sending everything we've got, set PUSH.
1120 * (This will keep happy those implementations which only
1121 * give data to the user when a buffer fills or
1124 if (((uint32_t)off + (uint32_t)len == sbused(&so->so_snd)) &&
1127 SOCKBUF_UNLOCK(&so->so_snd);
1129 SOCKBUF_UNLOCK(&so->so_snd);
1130 if (tp->t_flags & TF_ACKNOW)
1131 TCPSTAT_INC(tcps_sndacks);
1132 else if (flags & (TH_SYN|TH_FIN|TH_RST))
1133 TCPSTAT_INC(tcps_sndctrl);
1134 else if (SEQ_GT(tp->snd_up, tp->snd_una))
1135 TCPSTAT_INC(tcps_sndurg);
1137 TCPSTAT_INC(tcps_sndwinup);
1139 m = m_gethdr(M_NOWAIT, MT_DATA);
1146 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) &&
1151 m->m_data += max_linkhdr;
1154 SOCKBUF_UNLOCK_ASSERT(&so->so_snd);
1155 m->m_pkthdr.rcvif = (struct ifnet *)0;
1157 mac_inpcb_create_mbuf(tp->t_inpcb, m);
1161 ip6 = mtod(m, struct ip6_hdr *);
1163 udp = (struct udphdr *)((caddr_t)ip6 + sizeof(struct ip6_hdr));
1164 udp->uh_sport = htons(V_tcp_udp_tunneling_port);
1165 udp->uh_dport = tp->t_port;
1166 ulen = hdrlen + len - sizeof(struct ip6_hdr);
1167 udp->uh_ulen = htons(ulen);
1168 th = (struct tcphdr *)(udp + 1);
1170 th = (struct tcphdr *)(ip6 + 1);
1172 tcpip_fillheaders(tp->t_inpcb, tp->t_port, ip6, th);
1176 ip = mtod(m, struct ip *);
1178 ipov = (struct ipovly *)ip;
1181 udp = (struct udphdr *)((caddr_t)ip + sizeof(struct ip));
1182 udp->uh_sport = htons(V_tcp_udp_tunneling_port);
1183 udp->uh_dport = tp->t_port;
1184 ulen = hdrlen + len - sizeof(struct ip);
1185 udp->uh_ulen = htons(ulen);
1186 th = (struct tcphdr *)(udp + 1);
1188 th = (struct tcphdr *)(ip + 1);
1189 tcpip_fillheaders(tp->t_inpcb, tp->t_port, ip, th);
1193 * Fill in fields, remembering maximum advertised
1194 * window for use in delaying messages about window sizes.
1195 * If resending a FIN, be sure not to use a new sequence number.
1197 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN &&
1198 tp->snd_nxt == tp->snd_max)
1201 * If we are starting a connection, send ECN setup
1202 * SYN packet. If we are on a retransmit, we may
1203 * resend those bits a number of times as per
1206 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) {
1207 flags |= tcp_ecn_output_syn_sent(tp);
1209 /* Also handle parallel SYN for ECN */
1210 if ((TCPS_HAVERCVDSYN(tp->t_state)) &&
1211 (tp->t_flags2 & TF2_ECN_PERMIT)) {
1212 int ect = tcp_ecn_output_established(tp, &flags, len, sack_rxmit);
1213 if ((tp->t_state == TCPS_SYN_RECEIVED) &&
1214 (tp->t_flags2 & TF2_ECN_SND_ECE))
1215 tp->t_flags2 &= ~TF2_ECN_SND_ECE;
1218 ip6->ip6_flow &= ~htonl(IPTOS_ECN_MASK << 20);
1219 ip6->ip6_flow |= htonl(ect << 20);
1224 ip->ip_tos &= ~IPTOS_ECN_MASK;
1230 * If we are doing retransmissions, then snd_nxt will
1231 * not reflect the first unsent octet. For ACK only
1232 * packets, we do not want the sequence number of the
1233 * retransmitted packet, we want the sequence number
1234 * of the next unsent octet. So, if there is no data
1235 * (and no SYN or FIN), use snd_max instead of snd_nxt
1236 * when filling in ti_seq. But if we are in persist
1237 * state, snd_max might reflect one byte beyond the
1238 * right edge of the window, so use snd_nxt in that
1239 * case, since we know we aren't doing a retransmission.
1240 * (retransmit and persist are mutually exclusive...)
1242 if (sack_rxmit == 0) {
1243 if (len || (flags & (TH_SYN|TH_FIN)) ||
1244 tcp_timer_active(tp, TT_PERSIST))
1245 th->th_seq = htonl(tp->snd_nxt);
1247 th->th_seq = htonl(tp->snd_max);
1249 th->th_seq = htonl(p->rxmit);
1252 * Lost Retransmission Detection
1253 * trigger resending of a (then
1254 * still existing) hole, when
1255 * fack acks recoverypoint.
1257 if ((tp->t_flags & TF_LRD) && SEQ_GEQ(p->rxmit, p->end))
1258 p->rxmit = tp->snd_recover;
1259 tp->sackhint.sack_bytes_rexmit += len;
1261 if (IN_RECOVERY(tp->t_flags)) {
1263 * Account all bytes transmitted while
1264 * IN_RECOVERY, simplifying PRR and
1265 * Lost Retransmit Detection
1267 tp->sackhint.prr_out += len;
1269 th->th_ack = htonl(tp->rcv_nxt);
1271 bcopy(opt, th + 1, optlen);
1272 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2;
1274 tcp_set_flags(th, flags);
1276 * Calculate receive window. Don't shrink window,
1277 * but avoid silly window syndrome.
1278 * If a RST segment is sent, advertise a window of zero.
1280 if (flags & TH_RST) {
1283 if (recwin < (so->so_rcv.sb_hiwat / 4) &&
1284 recwin < tp->t_maxseg)
1286 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) &&
1287 recwin < (tp->rcv_adv - tp->rcv_nxt))
1288 recwin = (tp->rcv_adv - tp->rcv_nxt);
1291 * According to RFC1323 the window field in a SYN (i.e., a <SYN>
1292 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK>
1293 * case is handled in syncache.
1296 th->th_win = htons((u_short)
1297 (min(sbspace(&so->so_rcv), TCP_MAXWIN)));
1299 /* Avoid shrinking window with window scaling. */
1300 recwin = roundup2(recwin, 1 << tp->rcv_scale);
1301 th->th_win = htons((u_short)(recwin >> tp->rcv_scale));
1305 * Adjust the RXWIN0SENT flag - indicate that we have advertised
1306 * a 0 window. This may cause the remote transmitter to stall. This
1307 * flag tells soreceive() to disable delayed acknowledgements when
1308 * draining the buffer. This can occur if the receiver is attempting
1309 * to read more data than can be buffered prior to transmitting on
1312 if (th->th_win == 0) {
1314 tp->t_flags |= TF_RXWIN0SENT;
1316 tp->t_flags &= ~TF_RXWIN0SENT;
1317 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) {
1318 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt));
1319 th->th_flags |= TH_URG;
1322 * If no urgent pointer to send, then we pull
1323 * the urgent pointer to the left edge of the send window
1324 * so that it doesn't drift into the send window on sequence
1325 * number wraparound.
1327 tp->snd_up = tp->snd_una; /* drag it along */
1330 * Put TCP length in extended header, and then
1331 * checksum extended header and data.
1333 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */
1335 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1336 if (to.to_flags & TOF_SIGNATURE) {
1338 * Calculate MD5 signature and put it into the place
1339 * determined before.
1340 * NOTE: since TCP options buffer doesn't point into
1341 * mbuf's data, calculate offset and use it.
1343 if (!TCPMD5_ENABLED() || (error = TCPMD5_OUTPUT(m, th,
1344 (u_char *)(th + 1) + (to.to_signature - opt))) != 0) {
1346 * Do not send segment if the calculation of MD5
1347 * digest has failed.
1357 * There is no need to fill in ip6_plen right now.
1358 * It will be filled later by ip6_output.
1361 m->m_pkthdr.csum_flags = CSUM_UDP_IPV6;
1362 m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum);
1363 udp->uh_sum = in6_cksum_pseudo(ip6, ulen, IPPROTO_UDP, 0);
1364 th->th_sum = htons(0);
1365 UDPSTAT_INC(udps_opackets);
1367 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
1368 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1369 th->th_sum = in6_cksum_pseudo(ip6,
1370 sizeof(struct tcphdr) + optlen + len, IPPROTO_TCP,
1375 #if defined(INET6) && defined(INET)
1381 m->m_pkthdr.csum_flags = CSUM_UDP;
1382 m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum);
1383 udp->uh_sum = in_pseudo(ip->ip_src.s_addr,
1384 ip->ip_dst.s_addr, htons(ulen + IPPROTO_UDP));
1385 th->th_sum = htons(0);
1386 UDPSTAT_INC(udps_opackets);
1388 m->m_pkthdr.csum_flags = CSUM_TCP;
1389 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1390 th->th_sum = in_pseudo(ip->ip_src.s_addr,
1391 ip->ip_dst.s_addr, htons(sizeof(struct tcphdr) +
1392 IPPROTO_TCP + len + optlen));
1395 /* IP version must be set here for ipv4/ipv6 checking later */
1396 KASSERT(ip->ip_v == IPVERSION,
1397 ("%s: IP version incorrect: %d", __func__, ip->ip_v));
1402 * Enable TSO and specify the size of the segments.
1403 * The TCP pseudo header checksum is always provided.
1406 KASSERT(len > tp->t_maxseg - optlen,
1407 ("%s: len <= tso_segsz", __func__));
1408 m->m_pkthdr.csum_flags |= CSUM_TSO;
1409 m->m_pkthdr.tso_segsz = tp->t_maxseg - optlen;
1412 KASSERT(len + hdrlen == m_length(m, NULL),
1413 ("%s: mbuf chain shorter than expected: %d + %u != %u",
1414 __func__, len, hdrlen, m_length(m, NULL)));
1417 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */
1418 hhook_run_tcp_est_out(tp, th, &to, len, tso);
1425 if (so->so_options & SO_DEBUG) {
1431 save = ipov->ih_len;
1432 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */);
1434 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0);
1438 ipov->ih_len = save;
1440 #endif /* TCPDEBUG */
1441 TCP_PROBE3(debug__output, tp, th, m);
1443 /* We're getting ready to send; log now. */
1444 TCP_LOG_EVENT(tp, th, &so->so_rcv, &so->so_snd, TCP_LOG_OUT, ERRNO_UNK,
1448 * Fill in IP length and desired time to live and
1449 * send to IP level. There should be a better way
1450 * to handle ttl and tos; we could keep them in
1451 * the template, but need a way to checksum without them.
1454 * m->m_pkthdr.len should have been set before checksum calculation,
1455 * because in6_cksum() need it.
1460 * we separately set hoplimit for every segment, since the
1461 * user might want to change the value via setsockopt.
1462 * Also, desired default hop limit might be changed via
1463 * Neighbor Discovery.
1465 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL);
1468 * Set the packet size here for the benefit of DTrace probes.
1469 * ip6_output() will set it properly; it's supposed to include
1470 * the option header lengths as well.
1472 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6));
1474 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss)
1475 tp->t_flags2 |= TF2_PLPMTU_PMTUD;
1477 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
1479 if (tp->t_state == TCPS_SYN_SENT)
1480 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th);
1482 TCP_PROBE5(send, NULL, tp, ip6, tp, th);
1485 /* Save packet, if requested. */
1486 tcp_pcap_add(th, m, &(tp->t_outpkts));
1489 /* TODO: IPv6 IP6TOS_ECT bit on */
1490 error = ip6_output(m, tp->t_inpcb->in6p_outputopts,
1491 &tp->t_inpcb->inp_route6,
1492 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0),
1493 NULL, NULL, tp->t_inpcb);
1495 if (error == EMSGSIZE && tp->t_inpcb->inp_route6.ro_nh != NULL)
1496 mtu = tp->t_inpcb->inp_route6.ro_nh->nh_mtu;
1499 #if defined(INET) && defined(INET6)
1504 ip->ip_len = htons(m->m_pkthdr.len);
1506 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO)
1507 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL);
1510 * If we do path MTU discovery, then we set DF on every packet.
1511 * This might not be the best thing to do according to RFC3390
1512 * Section 2. However the tcp hostcache migitates the problem
1513 * so it affects only the first tcp connection with a host.
1515 * NB: Don't set DF on small MTU/MSS to have a safe fallback.
1517 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) {
1518 tp->t_flags2 |= TF2_PLPMTU_PMTUD;
1519 if (tp->t_port == 0 || len < V_tcp_minmss) {
1520 ip->ip_off |= htons(IP_DF);
1523 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
1526 if (tp->t_state == TCPS_SYN_SENT)
1527 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th);
1529 TCP_PROBE5(send, NULL, tp, ip, tp, th);
1532 /* Save packet, if requested. */
1533 tcp_pcap_add(th, m, &(tp->t_outpkts));
1536 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route,
1537 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0,
1540 if (error == EMSGSIZE && tp->t_inpcb->inp_route.ro_nh != NULL)
1541 mtu = tp->t_inpcb->inp_route.ro_nh->nh_mtu;
1547 tcp_account_for_send(tp, len, (tp->snd_nxt != tp->snd_max), 0, hw_tls);
1549 * In transmit state, time the transmission and arrange for
1550 * the retransmit. In persist state, just set snd_max.
1552 if ((tp->t_flags & TF_FORCEDATA) == 0 ||
1553 !tcp_timer_active(tp, TT_PERSIST)) {
1554 tcp_seq startseq = tp->snd_nxt;
1557 * Advance snd_nxt over sequence space of this segment.
1559 if (flags & (TH_SYN|TH_FIN)) {
1562 if (flags & TH_FIN) {
1564 tp->t_flags |= TF_SENTFIN;
1570 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) {
1571 tp->snd_max = tp->snd_nxt;
1573 * Time this transmission if not a retransmission and
1574 * not currently timing anything.
1576 tp->t_sndtime = ticks;
1577 if (tp->t_rtttime == 0) {
1578 tp->t_rtttime = ticks;
1579 tp->t_rtseq = startseq;
1580 TCPSTAT_INC(tcps_segstimed);
1583 if (!(tp->t_flags & TF_GPUTINPROG) && len) {
1584 tp->t_flags |= TF_GPUTINPROG;
1585 tp->gput_seq = startseq;
1586 tp->gput_ack = startseq +
1587 ulmin(sbavail(&so->so_snd) - off, sendwin);
1588 tp->gput_ts = tcp_ts_getticks();
1594 * Set retransmit timer if not currently set,
1595 * and not doing a pure ack or a keep-alive probe.
1596 * Initial value for retransmit timer is smoothed
1597 * round-trip time + 2 * round-trip time variance.
1598 * Initialize shift counter which is used for backoff
1599 * of retransmit time.
1602 if (!tcp_timer_active(tp, TT_REXMT) &&
1603 ((sack_rxmit && tp->snd_nxt != tp->snd_max) ||
1604 (tp->snd_nxt != tp->snd_una))) {
1605 if (tcp_timer_active(tp, TT_PERSIST)) {
1606 tcp_timer_activate(tp, TT_PERSIST, 0);
1609 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
1610 } else if (len == 0 && sbavail(&so->so_snd) &&
1611 !tcp_timer_active(tp, TT_REXMT) &&
1612 !tcp_timer_active(tp, TT_PERSIST)) {
1614 * Avoid a situation where we do not set persist timer
1615 * after a zero window condition. For example:
1616 * 1) A -> B: packet with enough data to fill the window
1617 * 2) B -> A: ACK for #1 + new data (0 window
1619 * 3) A -> B: ACK for #2, 0 len packet
1621 * In this case, A will not activate the persist timer,
1622 * because it chose to send a packet. Unless tcp_output
1623 * is called for some other reason (delayed ack timer,
1624 * another input packet from B, socket syscall), A will
1625 * not send zero window probes.
1627 * So, if you send a 0-length packet, but there is data
1628 * in the socket buffer, and neither the rexmt or
1629 * persist timer is already set, then activate the
1637 * Persist case, update snd_max but since we are in
1638 * persist mode (no window) we do not update snd_nxt.
1643 if (flags & TH_FIN) {
1645 tp->t_flags |= TF_SENTFIN;
1647 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max))
1648 tp->snd_max = tp->snd_nxt + xlen;
1651 (TCPS_HAVEESTABLISHED(tp->t_state) &&
1652 (tp->t_flags & TF_SACK_PERMIT) &&
1653 tp->rcv_numsacks > 0)) {
1654 /* Clean up any DSACK's sent */
1655 tcp_clean_dsack_blocks(tp);
1658 /* Record the error. */
1659 TCP_LOG_EVENT(tp, NULL, &so->so_rcv, &so->so_snd, TCP_LOG_OUT,
1660 error, 0, NULL, false);
1663 * We know that the packet was lost, so back out the
1664 * sequence number advance, if any.
1666 * If the error is EPERM the packet got blocked by the
1667 * local firewall. Normally we should terminate the
1668 * connection but the blocking may have been spurious
1669 * due to a firewall reconfiguration cycle. So we treat
1670 * it like a packet loss and let the retransmit timer and
1671 * timeouts do their work over time.
1672 * XXX: It is a POLA question whether calling tcp_drop right
1673 * away would be the really correct behavior instead.
1675 if (((tp->t_flags & TF_FORCEDATA) == 0 ||
1676 !tcp_timer_active(tp, TT_PERSIST)) &&
1677 ((flags & TH_SYN) == 0) &&
1681 tp->sackhint.sack_bytes_rexmit -= len;
1682 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0,
1683 ("sackhint bytes rtx >= 0"));
1687 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */
1691 tp->t_softerror = error;
1694 TCP_XMIT_TIMER_ASSERT(tp, len, flags);
1695 tp->snd_cwnd = tp->t_maxseg;
1699 * For some reason the interface we used initially
1700 * to send segments changed to another or lowered
1702 * If TSO was active we either got an interface
1703 * without TSO capabilits or TSO was turned off.
1704 * If we obtained mtu from ip_output() then update
1708 tp->t_flags &= ~TF_TSO;
1710 tcp_mss_update(tp, -1, mtu, NULL, NULL);
1718 if (TCPS_HAVERCVDSYN(tp->t_state)) {
1719 tp->t_softerror = error;
1727 TCPSTAT_INC(tcps_sndtotal);
1730 * Data sent (as far as we can tell).
1731 * If this advertises a larger window than any other segment,
1732 * then remember the size of the advertised window.
1733 * Any pending ACK has now been sent.
1735 if (SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv))
1736 tp->rcv_adv = tp->rcv_nxt + recwin;
1737 tp->last_ack_sent = tp->rcv_nxt;
1738 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK);
1739 if (tcp_timer_active(tp, TT_DELACK))
1740 tcp_timer_activate(tp, TT_DELACK, 0);
1743 * This completely breaks TCP if newreno is turned on. What happens
1744 * is that if delayed-acks are turned on on the receiver, this code
1745 * on the transmitter effectively destroys the TCP window, forcing
1746 * it to four packets (1.5Kx4 = 6K window).
1748 if (sendalot && --maxburst)
1757 tcp_setpersist(struct tcpcb *tp)
1759 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1;
1762 tp->t_flags &= ~TF_PREVVALID;
1763 if (tcp_timer_active(tp, TT_REXMT))
1764 panic("tcp_setpersist: retransmit pending");
1766 * Start/restart persistence timer.
1768 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift],
1769 tcp_persmin, tcp_persmax);
1770 tcp_timer_activate(tp, TT_PERSIST, tt);
1771 if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
1776 * Insert TCP options according to the supplied parameters to the place
1777 * optp in a consistent way. Can handle unaligned destinations.
1779 * The order of the option processing is crucial for optimal packing and
1780 * alignment for the scarce option space.
1782 * The optimal order for a SYN/SYN-ACK segment is:
1783 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) +
1784 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40.
1786 * The SACK options should be last. SACK blocks consume 8*n+2 bytes.
1787 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks).
1788 * At minimum we need 10 bytes (to generate 1 SACK block). If both
1789 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present,
1790 * we only have 10 bytes for SACK options (40 - (12 + 18)).
1793 tcp_addoptions(struct tcpopt *to, u_char *optp)
1795 u_int32_t mask, optlen = 0;
1797 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) {
1798 if ((to->to_flags & mask) != mask)
1800 if (optlen == TCP_MAXOLEN)
1802 switch (to->to_flags & mask) {
1804 while (optlen % 4) {
1805 optlen += TCPOLEN_NOP;
1806 *optp++ = TCPOPT_NOP;
1808 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG)
1810 optlen += TCPOLEN_MAXSEG;
1811 *optp++ = TCPOPT_MAXSEG;
1812 *optp++ = TCPOLEN_MAXSEG;
1813 to->to_mss = htons(to->to_mss);
1814 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss));
1815 optp += sizeof(to->to_mss);
1818 while (!optlen || optlen % 2 != 1) {
1819 optlen += TCPOLEN_NOP;
1820 *optp++ = TCPOPT_NOP;
1822 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW)
1824 optlen += TCPOLEN_WINDOW;
1825 *optp++ = TCPOPT_WINDOW;
1826 *optp++ = TCPOLEN_WINDOW;
1827 *optp++ = to->to_wscale;
1830 while (optlen % 2) {
1831 optlen += TCPOLEN_NOP;
1832 *optp++ = TCPOPT_NOP;
1834 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED)
1836 optlen += TCPOLEN_SACK_PERMITTED;
1837 *optp++ = TCPOPT_SACK_PERMITTED;
1838 *optp++ = TCPOLEN_SACK_PERMITTED;
1841 while (!optlen || optlen % 4 != 2) {
1842 optlen += TCPOLEN_NOP;
1843 *optp++ = TCPOPT_NOP;
1845 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP)
1847 optlen += TCPOLEN_TIMESTAMP;
1848 *optp++ = TCPOPT_TIMESTAMP;
1849 *optp++ = TCPOLEN_TIMESTAMP;
1850 to->to_tsval = htonl(to->to_tsval);
1851 to->to_tsecr = htonl(to->to_tsecr);
1852 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval));
1853 optp += sizeof(to->to_tsval);
1854 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr));
1855 optp += sizeof(to->to_tsecr);
1859 int siglen = TCPOLEN_SIGNATURE - 2;
1861 while (!optlen || optlen % 4 != 2) {
1862 optlen += TCPOLEN_NOP;
1863 *optp++ = TCPOPT_NOP;
1865 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) {
1866 to->to_flags &= ~TOF_SIGNATURE;
1869 optlen += TCPOLEN_SIGNATURE;
1870 *optp++ = TCPOPT_SIGNATURE;
1871 *optp++ = TCPOLEN_SIGNATURE;
1872 to->to_signature = optp;
1880 struct sackblk *sack = (struct sackblk *)to->to_sacks;
1883 while (!optlen || optlen % 4 != 2) {
1884 optlen += TCPOLEN_NOP;
1885 *optp++ = TCPOPT_NOP;
1887 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK)
1889 optlen += TCPOLEN_SACKHDR;
1890 *optp++ = TCPOPT_SACK;
1891 sackblks = min(to->to_nsacks,
1892 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK);
1893 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK;
1894 while (sackblks--) {
1895 sack_seq = htonl(sack->start);
1896 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq));
1897 optp += sizeof(sack_seq);
1898 sack_seq = htonl(sack->end);
1899 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq));
1900 optp += sizeof(sack_seq);
1901 optlen += TCPOLEN_SACK;
1904 TCPSTAT_INC(tcps_sack_send_blocks);
1911 /* XXX is there any point to aligning this option? */
1912 total_len = TCPOLEN_FAST_OPEN_EMPTY + to->to_tfo_len;
1913 if (TCP_MAXOLEN - optlen < total_len) {
1914 to->to_flags &= ~TOF_FASTOPEN;
1917 *optp++ = TCPOPT_FAST_OPEN;
1918 *optp++ = total_len;
1919 if (to->to_tfo_len > 0) {
1920 bcopy(to->to_tfo_cookie, optp, to->to_tfo_len);
1921 optp += to->to_tfo_len;
1923 optlen += total_len;
1927 panic("%s: unknown TCP option type", __func__);
1932 /* Terminate and pad TCP options to a 4 byte boundary. */
1934 optlen += TCPOLEN_EOL;
1935 *optp++ = TCPOPT_EOL;
1938 * According to RFC 793 (STD0007):
1939 * "The content of the header beyond the End-of-Option option
1940 * must be header padding (i.e., zero)."
1941 * and later: "The padding is composed of zeros."
1943 while (optlen % 4) {
1944 optlen += TCPOLEN_PAD;
1945 *optp++ = TCPOPT_PAD;
1948 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__));
1953 * This is a copy of m_copym(), taking the TSO segment size/limit
1954 * constraints into account, and advancing the sndptr as it goes.
1957 tcp_m_copym(struct mbuf *m, int32_t off0, int32_t *plen,
1958 int32_t seglimit, int32_t segsize, struct sockbuf *sb, bool hw_tls)
1961 struct ktls_session *tls, *ntls;
1962 struct mbuf *start __diagused;
1964 struct mbuf *n, **np;
1967 int32_t len = *plen;
1971 uint32_t mlen, frags;
1974 KASSERT(off >= 0, ("tcp_m_copym, negative off %d", off));
1975 KASSERT(len >= 0, ("tcp_m_copym, negative len %d", len));
1976 if (off == 0 && m->m_flags & M_PKTHDR)
1981 KASSERT(m != NULL, ("tcp_m_copym, offset > size of mbuf chain"));
1985 if ((sb) && (m == sb->sb_sndptr)) {
1986 sb->sb_sndptroff += m->m_len;
1987 sb->sb_sndptr = m->m_next;
1995 if (hw_tls && (m->m_flags & M_EXTPG))
2003 KASSERT(len == M_COPYALL,
2004 ("tcp_m_copym, length > size of mbuf chain"));
2006 if (pkthdrlen != NULL)
2007 *pkthdrlen = len_cp;
2012 if (m->m_flags & M_EXTPG)
2013 ntls = m->m_epg_tls;
2018 * Avoid mixing TLS records with handshake
2019 * data or TLS records from different
2025 if (pkthdrlen != NULL)
2026 *pkthdrlen = len_cp;
2031 mlen = min(len, m->m_len - off);
2034 * For M_EXTPG mbufs, add 3 segments
2035 * + 1 in case we are crossing page boundaries
2036 * + 2 in case the TLS hdr/trailer are used
2037 * It is cheaper to just add the segments
2038 * than it is to take the cache miss to look
2039 * at the mbuf ext_pgs state in detail.
2041 if (m->m_flags & M_EXTPG) {
2042 fragsize = min(segsize, PAGE_SIZE);
2049 /* Break if we really can't fit anymore. */
2050 if ((frags + 1) >= seglimit) {
2052 if (pkthdrlen != NULL)
2053 *pkthdrlen = len_cp;
2058 * Reduce size if you can't copy the whole
2059 * mbuf. If we can't copy the whole mbuf, also
2060 * adjust len so the loop will end after this
2063 if ((frags + howmany(mlen, fragsize)) >= seglimit) {
2064 mlen = (seglimit - frags - 1) * fragsize;
2066 *plen = len_cp + len;
2067 if (pkthdrlen != NULL)
2070 frags += howmany(mlen, fragsize);
2074 KASSERT(seglimit > 0,
2075 ("%s: seglimit went too low", __func__));
2078 n = m_gethdr(M_NOWAIT, m->m_type);
2080 n = m_get(M_NOWAIT, m->m_type);
2085 if (!m_dup_pkthdr(n, m, M_NOWAIT))
2087 if (len == M_COPYALL)
2088 n->m_pkthdr.len -= off0;
2090 n->m_pkthdr.len = len;
2091 pkthdrlen = &n->m_pkthdr.len;
2096 if (m->m_flags & (M_EXT|M_EXTPG)) {
2097 n->m_data = m->m_data + off;
2100 bcopy(mtod(m, caddr_t)+off, mtod(n, caddr_t),
2103 if (sb && (sb->sb_sndptr == m) &&
2104 ((n->m_len + off) >= m->m_len) && m->m_next) {
2105 sb->sb_sndptroff += m->m_len;
2106 sb->sb_sndptr = m->m_next;
2109 if (len != M_COPYALL) {
2122 tcp_sndbuf_autoscale(struct tcpcb *tp, struct socket *so, uint32_t sendwin)
2126 * Automatic sizing of send socket buffer. Often the send buffer
2127 * size is not optimally adjusted to the actual network conditions
2128 * at hand (delay bandwidth product). Setting the buffer size too
2129 * small limits throughput on links with high bandwidth and high
2130 * delay (eg. trans-continental/oceanic links). Setting the
2131 * buffer size too big consumes too much real kernel memory,
2132 * especially with many connections on busy servers.
2134 * The criteria to step up the send buffer one notch are:
2135 * 1. receive window of remote host is larger than send buffer
2136 * (with a fudge factor of 5/4th);
2137 * 2. send buffer is filled to 7/8th with data (so we actually
2138 * have data to make use of it);
2139 * 3. send buffer fill has not hit maximal automatic size;
2140 * 4. our send window (slow start and cogestion controlled) is
2141 * larger than sent but unacknowledged data in send buffer.
2143 * The remote host receive window scaling factor may limit the
2144 * growing of the send buffer before it reaches its allowed
2147 * It scales directly with slow start or congestion window
2148 * and does at most one step per received ACK. This fast
2149 * scaling has the drawback of growing the send buffer beyond
2150 * what is strictly necessary to make full use of a given
2151 * delay*bandwidth product. However testing has shown this not
2152 * to be much of an problem. At worst we are trading wasting
2153 * of available bandwidth (the non-use of it) for wasting some
2154 * socket buffer memory.
2156 * TODO: Shrink send buffer during idle periods together
2157 * with congestion window. Requires another timer. Has to
2158 * wait for upcoming tcp timer rewrite.
2160 * XXXGL: should there be used sbused() or sbavail()?
2162 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) {
2165 lowat = V_tcp_sendbuf_auto_lowat ? so->so_snd.sb_lowat : 0;
2166 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat - lowat &&
2167 sbused(&so->so_snd) >=
2168 (so->so_snd.sb_hiwat / 8 * 7) - lowat &&
2169 sbused(&so->so_snd) < V_tcp_autosndbuf_max &&
2170 sendwin >= (sbused(&so->so_snd) -
2171 (tp->snd_nxt - tp->snd_una))) {
2172 if (!sbreserve_locked(so, SO_SND,
2173 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc,
2174 V_tcp_autosndbuf_max), curthread))
2175 so->so_snd.sb_flags &= ~SB_AUTOSIZE;
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