2 * SPDX-License-Identifier: BSD-3-Clause
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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_timer.h>
88 #include <netinet/tcp_var.h>
89 #include <netinet/tcpip.h>
90 #include <netinet/cc/cc.h>
91 #include <netinet/tcp_fastopen.h>
93 #include <netinet/tcp_pcap.h>
96 #include <netinet/tcp_debug.h>
99 #include <netinet/tcp_offload.h>
102 #include <netipsec/ipsec_support.h>
104 #include <machine/in_cksum.h>
106 #include <security/mac/mac_framework.h>
108 VNET_DEFINE(int, path_mtu_discovery) = 1;
109 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_VNET | CTLFLAG_RW,
110 &VNET_NAME(path_mtu_discovery), 1,
111 "Enable Path MTU Discovery");
113 VNET_DEFINE(int, tcp_do_tso) = 1;
114 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_VNET | CTLFLAG_RW,
115 &VNET_NAME(tcp_do_tso), 0,
116 "Enable TCP Segmentation Offload");
118 VNET_DEFINE(int, tcp_sendspace) = 1024*32;
119 #define V_tcp_sendspace VNET(tcp_sendspace)
120 SYSCTL_INT(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, CTLFLAG_VNET | CTLFLAG_RW,
121 &VNET_NAME(tcp_sendspace), 0, "Initial send socket buffer size");
123 VNET_DEFINE(int, tcp_do_autosndbuf) = 1;
124 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_VNET | CTLFLAG_RW,
125 &VNET_NAME(tcp_do_autosndbuf), 0,
126 "Enable automatic send buffer sizing");
128 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024;
129 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_VNET | CTLFLAG_RW,
130 &VNET_NAME(tcp_autosndbuf_inc), 0,
131 "Incrementor step size of automatic send buffer");
133 VNET_DEFINE(int, tcp_autosndbuf_max) = 2*1024*1024;
134 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_VNET | CTLFLAG_RW,
135 &VNET_NAME(tcp_autosndbuf_max), 0,
136 "Max size of automatic send buffer");
138 VNET_DEFINE(int, tcp_sendbuf_auto_lowat) = 0;
139 #define V_tcp_sendbuf_auto_lowat VNET(tcp_sendbuf_auto_lowat)
140 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto_lowat, CTLFLAG_VNET | CTLFLAG_RW,
141 &VNET_NAME(tcp_sendbuf_auto_lowat), 0,
142 "Modify threshold for auto send buffer growth to account for SO_SNDLOWAT");
145 * Make sure that either retransmit or persist timer is set for SYN, FIN and
148 #define TCP_XMIT_TIMER_ASSERT(tp, len, th_flags) \
149 KASSERT(((len) == 0 && ((th_flags) & (TH_SYN | TH_FIN)) == 0) ||\
150 tcp_timer_active((tp), TT_REXMT) || \
151 tcp_timer_active((tp), TT_PERSIST), \
152 ("neither rexmt nor persist timer is set"))
154 static void inline cc_after_idle(struct tcpcb *tp);
158 * Wrapper for the TCP established output helper hook.
161 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th,
162 struct tcpopt *to, uint32_t len, int tso)
164 struct tcp_hhook_data hhook_data;
166 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) {
170 hhook_data.len = len;
171 hhook_data.tso = tso;
173 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data,
180 * CC wrapper hook functions
183 cc_after_idle(struct tcpcb *tp)
185 INP_WLOCK_ASSERT(tp->t_inpcb);
187 if (CC_ALGO(tp)->after_idle != NULL)
188 CC_ALGO(tp)->after_idle(tp->ccv);
192 * Tcp output routine: figure out what should be sent and send it.
195 tcp_output(struct tcpcb *tp)
197 struct socket *so = tp->t_inpcb->inp_socket;
199 uint32_t recwin, sendwin;
200 int off, flags, error = 0; /* Keep compiler happy */
201 u_int if_hw_tsomaxsegcount = 0;
202 u_int if_hw_tsomaxsegsize = 0;
204 struct ip *ip = NULL;
206 struct ipovly *ipov = NULL;
209 u_char opt[TCP_MAXOLEN];
210 unsigned ipoptlen, optlen, hdrlen;
211 #if defined(IPSEC) || defined(IPSEC_SUPPORT)
212 unsigned ipsec_optlen = 0;
214 int idle, sendalot, curticks;
215 int sack_rxmit, sack_bytes_rxmt;
219 unsigned int wanted_cookie = 0;
220 unsigned int dont_sendalot = 0;
222 int maxburst = TCP_MAXBURST;
225 struct ip6_hdr *ip6 = NULL;
228 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0;
231 const bool hw_tls = (so->so_snd.sb_flags & SB_TLS_IFNET) != 0;
233 const bool hw_tls = false;
237 INP_WLOCK_ASSERT(tp->t_inpcb);
240 if (tp->t_flags & TF_TOE)
241 return (tcp_offload_output(tp));
245 * For TFO connections in SYN_SENT or SYN_RECEIVED,
246 * only allow the initial SYN or SYN|ACK and those sent
247 * by the retransmit timer.
249 if (IS_FASTOPEN(tp->t_flags) &&
250 ((tp->t_state == TCPS_SYN_SENT) ||
251 (tp->t_state == TCPS_SYN_RECEIVED)) &&
252 SEQ_GT(tp->snd_max, tp->snd_una) && /* initial SYN or SYN|ACK sent */
253 (tp->snd_nxt != tp->snd_una)) /* not a retransmit */
257 * Determine length of data that should be transmitted,
258 * and flags that will be used.
259 * If there is some data or critical controls (SYN, RST)
260 * to send, then transmit; otherwise, investigate further.
262 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una);
263 if (idle && (((ticks - tp->t_rcvtime) >= tp->t_rxtcur) ||
264 (tp->t_sndtime && ((ticks - tp->t_sndtime) >= tp->t_rxtcur))))
266 tp->t_flags &= ~TF_LASTIDLE;
268 if (tp->t_flags & TF_MORETOCOME) {
269 tp->t_flags |= TF_LASTIDLE;
275 * If we've recently taken a timeout, snd_max will be greater than
276 * snd_nxt. There may be SACK information that allows us to avoid
277 * resending already delivered data. Adjust snd_nxt accordingly.
279 if ((tp->t_flags & TF_SACK_PERMIT) &&
280 SEQ_LT(tp->snd_nxt, tp->snd_max))
285 off = tp->snd_nxt - tp->snd_una;
286 sendwin = min(tp->snd_wnd, tp->snd_cwnd);
288 flags = tcp_outflags[tp->t_state];
290 * Send any SACK-generated retransmissions. If we're explicitly trying
291 * to send out new data (when sendalot is 1), bypass this function.
292 * If we retransmit in fast recovery mode, decrement snd_cwnd, since
293 * we're replacing a (future) new transmission with a retransmission
294 * now, and we previously incremented snd_cwnd in tcp_input().
297 * Still in sack recovery , reset rxmit flag to zero.
303 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) &&
304 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) {
308 imax(min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt, 0);
309 /* Do not retransmit SACK segments beyond snd_recover */
310 if (SEQ_GT(p->end, tp->snd_recover)) {
312 * (At least) part of sack hole extends beyond
313 * snd_recover. Check to see if we can rexmit data
316 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) {
318 * Can't rexmit any more data for this hole.
319 * That data will be rexmitted in the next
320 * sack recovery episode, when snd_recover
321 * moves past p->rxmit.
324 goto after_sack_rexmit;
326 /* Can rexmit part of the current hole */
327 len = ((int32_t)ulmin(cwin,
328 tp->snd_recover - p->rxmit));
330 len = ((int32_t)ulmin(cwin, p->end - p->rxmit));
331 off = p->rxmit - tp->snd_una;
332 KASSERT(off >= 0,("%s: sack block to the left of una : %d",
337 TCPSTAT_INC(tcps_sack_rexmits);
338 TCPSTAT_ADD(tcps_sack_rexmit_bytes,
339 min(len, tp->t_maxseg));
344 * Get standard flags, and add SYN or FIN if requested by 'hidden'
347 if (tp->t_flags & TF_NEEDFIN)
349 if (tp->t_flags & TF_NEEDSYN)
352 SOCKBUF_LOCK(&so->so_snd);
354 * If in persist timeout with window of 0, send 1 byte.
355 * Otherwise, if window is small but nonzero
356 * and timer expired, we will send what we can
357 * and go to transmit state.
359 if (tp->t_flags & TF_FORCEDATA) {
362 * If we still have some data to send, then
363 * clear the FIN bit. Usually this would
364 * happen below when it realizes that we
365 * aren't sending all the data. However,
366 * if we have exactly 1 byte of unsent data,
367 * then it won't clear the FIN bit below,
368 * and if we are in persist state, we wind
369 * up sending the packet without recording
370 * that we sent the FIN bit.
372 * We can't just blindly clear the FIN bit,
373 * because if we don't have any more data
374 * to send then the probe will be the FIN
377 if (off < sbused(&so->so_snd))
381 tcp_timer_activate(tp, TT_PERSIST, 0);
387 * If snd_nxt == snd_max and we have transmitted a FIN, the
388 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in
389 * a negative length. This can also occur when TCP opens up
390 * its congestion window while receiving additional duplicate
391 * acks after fast-retransmit because TCP will reset snd_nxt
392 * to snd_max after the fast-retransmit.
394 * In the normal retransmit-FIN-only case, however, snd_nxt will
395 * be set to snd_una, the offset will be 0, and the length may
398 * If sack_rxmit is true we are retransmitting from the scoreboard
399 * in which case len is already set.
401 if (sack_rxmit == 0) {
402 if (sack_bytes_rxmt == 0)
403 len = ((int32_t)min(sbavail(&so->so_snd), sendwin) -
409 * We are inside of a SACK recovery episode and are
410 * sending new data, having retransmitted all the
411 * data possible in the scoreboard.
413 len = ((int32_t)min(sbavail(&so->so_snd), tp->snd_wnd) -
416 * Don't remove this (len > 0) check !
417 * We explicitly check for len > 0 here (although it
418 * isn't really necessary), to work around a gcc
419 * optimization issue - to force gcc to compute
420 * len above. Without this check, the computation
421 * of len is bungled by the optimizer.
424 cwin = tp->snd_cwnd -
425 (tp->snd_nxt - tp->snd_recover) -
429 len = imin(len, cwin);
435 * Lop off SYN bit if it has already been sent. However, if this
436 * is SYN-SENT state and if segment contains data and if we don't
437 * know that foreign host supports TAO, suppress sending segment.
439 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) {
440 if (tp->t_state != TCPS_SYN_RECEIVED)
443 * When sending additional segments following a TFO SYN|ACK,
444 * do not include the SYN bit.
446 if (IS_FASTOPEN(tp->t_flags) &&
447 (tp->t_state == TCPS_SYN_RECEIVED))
453 * Be careful not to send data and/or FIN on SYN segments.
454 * This measure is needed to prevent interoperability problems
455 * with not fully conformant TCP implementations.
457 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) {
463 * On TFO sockets, ensure no data is sent in the following cases:
465 * - When retransmitting SYN|ACK on a passively-created socket
467 * - When retransmitting SYN on an actively created socket
469 * - When sending a zero-length cookie (cookie request) on an
470 * actively created socket
472 * - When the socket is in the CLOSED state (RST is being sent)
474 if (IS_FASTOPEN(tp->t_flags) &&
475 (((flags & TH_SYN) && (tp->t_rxtshift > 0)) ||
476 ((tp->t_state == TCPS_SYN_SENT) &&
477 (tp->t_tfo_client_cookie_len == 0)) ||
482 * If FIN has been sent but not acked,
483 * but we haven't been called to retransmit,
484 * len will be < 0. Otherwise, window shrank
485 * after we sent into it. If window shrank to 0,
486 * cancel pending retransmit, pull snd_nxt back
487 * to (closed) window, and set the persist timer
488 * if it isn't already going. If the window didn't
489 * close completely, just wait for an ACK.
491 * We also do a general check here to ensure that
492 * we will set the persist timer when we have data
493 * to send, but a 0-byte window. This makes sure
494 * the persist timer is set even if the packet
495 * hits one of the "goto send" lines below.
498 if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) &&
499 (off < (int) sbavail(&so->so_snd))) {
500 tcp_timer_activate(tp, TT_REXMT, 0);
502 tp->snd_nxt = tp->snd_una;
503 if (!tcp_timer_active(tp, TT_PERSIST))
508 /* len will be >= 0 after this point. */
509 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__));
511 tcp_sndbuf_autoscale(tp, so, sendwin);
514 * Decide if we can use TCP Segmentation Offloading (if supported by
517 * TSO may only be used if we are in a pure bulk sending state. The
518 * presence of TCP-MD5, SACK retransmits, SACK advertizements and
519 * IP options prevent using TSO. With TSO the TCP header is the same
520 * (except for the sequence number) for all generated packets. This
521 * makes it impossible to transmit any options which vary per generated
524 * IPv4 handling has a clear separation of ip options and ip header
525 * flags while IPv6 combines both in in6p_outputopts. ip6_optlen() does
526 * the right thing below to provide length of just ip options and thus
527 * checking for ipoptlen is enough to decide if ip options are present.
529 #if defined(IPSEC) || defined(IPSEC_SUPPORT)
531 * Pre-calculate here as we save another lookup into the darknesses
532 * of IPsec that way and can actually decide if TSO is ok.
535 if (isipv6 && IPSEC_ENABLED(ipv6))
536 ipsec_optlen = IPSEC_HDRSIZE(ipv6, tp->t_inpcb);
542 if (IPSEC_ENABLED(ipv4))
543 ipsec_optlen = IPSEC_HDRSIZE(ipv4, tp->t_inpcb);
548 ipoptlen = ip6_optlen(tp->t_inpcb);
551 if (tp->t_inpcb->inp_options)
552 ipoptlen = tp->t_inpcb->inp_options->m_len -
553 offsetof(struct ipoption, ipopt_list);
556 #if defined(IPSEC) || defined(IPSEC_SUPPORT)
557 ipoptlen += ipsec_optlen;
560 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg &&
561 ((tp->t_flags & TF_SIGNATURE) == 0) &&
562 tp->rcv_numsacks == 0 && sack_rxmit == 0 &&
563 ipoptlen == 0 && !(flags & TH_SYN))
567 if (SEQ_LT(p->rxmit + len, tp->snd_una + sbused(&so->so_snd)))
570 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una +
571 sbused(&so->so_snd)))
575 recwin = lmin(lmax(sbspace(&so->so_rcv), 0),
576 (long)TCP_MAXWIN << tp->rcv_scale);
579 * Sender silly window avoidance. We transmit under the following
580 * conditions when len is non-zero:
582 * - We have a full segment (or more with TSO)
583 * - This is the last buffer in a write()/send() and we are
584 * either idle or running NODELAY
585 * - we've timed out (e.g. persist timer)
586 * - we have more then 1/2 the maximum send window's worth of
587 * data (receiver may be limited the window size)
588 * - we need to retransmit
591 if (len >= tp->t_maxseg)
594 * As the TCP header options are now
595 * considered when setting up the initial
596 * window, we would not send the last segment
597 * if we skip considering the option length here.
598 * Note: this may not work when tcp headers change
599 * very dynamically in the future.
601 if ((((tp->t_flags & TF_SIGNATURE) ?
602 PADTCPOLEN(TCPOLEN_SIGNATURE) : 0) +
603 ((tp->t_flags & TF_RCVD_TSTMP) ?
604 PADTCPOLEN(TCPOLEN_TIMESTAMP) : 0) +
605 len) >= tp->t_maxseg)
608 * NOTE! on localhost connections an 'ack' from the remote
609 * end may occur synchronously with the output and cause
610 * us to flush a buffer queued with moretocome. XXX
612 * note: the len + off check is almost certainly unnecessary.
614 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */
615 (idle || (tp->t_flags & TF_NODELAY)) &&
616 (uint32_t)len + (uint32_t)off >= sbavail(&so->so_snd) &&
617 (tp->t_flags & TF_NOPUSH) == 0) {
620 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */
622 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0)
624 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */
631 * Sending of standalone window updates.
633 * Window updates are important when we close our window due to a
634 * full socket buffer and are opening it again after the application
635 * reads data from it. Once the window has opened again and the
636 * remote end starts to send again the ACK clock takes over and
637 * provides the most current window information.
639 * We must avoid the silly window syndrome whereas every read
640 * from the receive buffer, no matter how small, causes a window
641 * update to be sent. We also should avoid sending a flurry of
642 * window updates when the socket buffer had queued a lot of data
643 * and the application is doing small reads.
645 * Prevent a flurry of pointless window updates by only sending
646 * an update when we can increase the advertized window by more
647 * than 1/4th of the socket buffer capacity. When the buffer is
648 * getting full or is very small be more aggressive and send an
649 * update whenever we can increase by two mss sized segments.
650 * In all other situations the ACK's to new incoming data will
651 * carry further window increases.
653 * Don't send an independent window update if a delayed
654 * ACK is pending (it will get piggy-backed on it) or the
655 * remote side already has done a half-close and won't send
656 * more data. Skip this if the connection is in T/TCP
659 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) &&
660 !(tp->t_flags & TF_DELACK) &&
661 !TCPS_HAVERCVDFIN(tp->t_state)) {
663 * "adv" is the amount we could increase the window,
664 * taking into account that we are limited by
665 * TCP_MAXWIN << tp->rcv_scale.
671 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) {
672 oldwin = (tp->rcv_adv - tp->rcv_nxt);
681 * If the new window size ends up being the same as or less
682 * than the old size when it is scaled, then don't force
685 if (oldwin >> tp->rcv_scale >= (adv + oldwin) >> tp->rcv_scale)
688 if (adv >= (int32_t)(2 * tp->t_maxseg) &&
689 (adv >= (int32_t)(so->so_rcv.sb_hiwat / 4) ||
690 recwin <= (so->so_rcv.sb_hiwat / 8) ||
691 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg ||
692 adv >= TCP_MAXWIN << tp->rcv_scale))
694 if (2 * adv >= (int32_t)so->so_rcv.sb_hiwat)
700 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW
701 * is also a catch-all for the retransmit timer timeout case.
703 if (tp->t_flags & TF_ACKNOW)
705 if ((flags & TH_RST) ||
706 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0))
708 if (SEQ_GT(tp->snd_up, tp->snd_una))
711 * If our state indicates that FIN should be sent
712 * and we have not yet done so, then we need to send.
714 if (flags & TH_FIN &&
715 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una))
718 * In SACK, it is possible for tcp_output to fail to send a segment
719 * after the retransmission timer has been turned off. Make sure
720 * that the retransmission timer is set.
722 if ((tp->t_flags & TF_SACK_PERMIT) &&
723 SEQ_GT(tp->snd_max, tp->snd_una) &&
724 !tcp_timer_active(tp, TT_REXMT) &&
725 !tcp_timer_active(tp, TT_PERSIST)) {
726 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
730 * TCP window updates are not reliable, rather a polling protocol
731 * using ``persist'' packets is used to insure receipt of window
732 * updates. The three ``states'' for the output side are:
733 * idle not doing retransmits or persists
734 * persisting to move a small or zero window
735 * (re)transmitting and thereby not persisting
737 * tcp_timer_active(tp, TT_PERSIST)
738 * is true when we are in persist state.
739 * (tp->t_flags & TF_FORCEDATA)
740 * is set when we are called to send a persist packet.
741 * tcp_timer_active(tp, TT_REXMT)
742 * is set when we are retransmitting
743 * The output side is idle when both timers are zero.
745 * If send window is too small, there is data to transmit, and no
746 * retransmit or persist is pending, then go to persist state.
747 * If nothing happens soon, send when timer expires:
748 * if window is nonzero, transmit what we can,
749 * otherwise force out a byte.
751 if (sbavail(&so->so_snd) && !tcp_timer_active(tp, TT_REXMT) &&
752 !tcp_timer_active(tp, TT_PERSIST)) {
758 * No reason to send a segment, just return.
761 SOCKBUF_UNLOCK(&so->so_snd);
765 SOCKBUF_LOCK_ASSERT(&so->so_snd);
767 if (len >= tp->t_maxseg)
768 tp->t_flags2 |= TF2_PLPMTU_MAXSEGSNT;
770 tp->t_flags2 &= ~TF2_PLPMTU_MAXSEGSNT;
773 * Before ESTABLISHED, force sending of initial options
774 * unless TCP set not to do any options.
775 * NOTE: we assume that the IP/TCP header plus TCP options
776 * always fit in a single mbuf, leaving room for a maximum
778 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES
783 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr);
786 hdrlen = sizeof (struct tcpiphdr);
789 * Compute options for segment.
790 * We only have to care about SYN and established connection
791 * segments. Options for SYN-ACK segments are handled in TCP
795 if ((tp->t_flags & TF_NOOPT) == 0) {
796 /* Maximum segment size. */
797 if (flags & TH_SYN) {
798 tp->snd_nxt = tp->iss;
799 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc);
800 to.to_flags |= TOF_MSS;
803 * On SYN or SYN|ACK transmits on TFO connections,
804 * only include the TFO option if it is not a
805 * retransmit, as the presence of the TFO option may
806 * have caused the original SYN or SYN|ACK to have
807 * been dropped by a middlebox.
809 if (IS_FASTOPEN(tp->t_flags) &&
810 (tp->t_rxtshift == 0)) {
811 if (tp->t_state == TCPS_SYN_RECEIVED) {
812 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN;
814 (u_int8_t *)&tp->t_tfo_cookie.server;
815 to.to_flags |= TOF_FASTOPEN;
817 } else if (tp->t_state == TCPS_SYN_SENT) {
819 tp->t_tfo_client_cookie_len;
821 tp->t_tfo_cookie.client;
822 to.to_flags |= TOF_FASTOPEN;
825 * If we wind up having more data to
826 * send with the SYN than can fit in
827 * one segment, don't send any more
828 * until the SYN|ACK comes back from
835 /* Window scaling. */
836 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) {
837 to.to_wscale = tp->request_r_scale;
838 to.to_flags |= TOF_SCALE;
841 if ((tp->t_flags & TF_RCVD_TSTMP) ||
842 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) {
843 curticks = tcp_ts_getticks();
844 to.to_tsval = curticks + tp->ts_offset;
845 to.to_tsecr = tp->ts_recent;
846 to.to_flags |= TOF_TS;
847 if (tp->t_rxtshift == 1)
848 tp->t_badrxtwin = curticks;
851 /* Set receive buffer autosizing timestamp. */
852 if (tp->rfbuf_ts == 0 &&
853 (so->so_rcv.sb_flags & SB_AUTOSIZE))
854 tp->rfbuf_ts = tcp_ts_getticks();
856 /* Selective ACK's. */
857 if (tp->t_flags & TF_SACK_PERMIT) {
859 to.to_flags |= TOF_SACKPERM;
860 else if (TCPS_HAVEESTABLISHED(tp->t_state) &&
861 (tp->t_flags & TF_SACK_PERMIT) &&
862 tp->rcv_numsacks > 0) {
863 to.to_flags |= TOF_SACK;
864 to.to_nsacks = tp->rcv_numsacks;
865 to.to_sacks = (u_char *)tp->sackblks;
868 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
869 /* TCP-MD5 (RFC2385). */
871 * Check that TCP_MD5SIG is enabled in tcpcb to
872 * account the size needed to set this TCP option.
874 if (tp->t_flags & TF_SIGNATURE)
875 to.to_flags |= TOF_SIGNATURE;
876 #endif /* TCP_SIGNATURE */
878 /* Processing the options. */
879 hdrlen += optlen = tcp_addoptions(&to, opt);
881 * If we wanted a TFO option to be added, but it was unable
882 * to fit, ensure no data is sent.
884 if (IS_FASTOPEN(tp->t_flags) && wanted_cookie &&
885 !(to.to_flags & TOF_FASTOPEN))
890 * Adjust data length if insertion of options will
891 * bump the packet length beyond the t_maxseg length.
892 * Clear the FIN bit because we cut off the tail of
895 if (len + optlen + ipoptlen > tp->t_maxseg) {
903 /* extract TSO information */
904 if_hw_tsomax = tp->t_tsomax;
905 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount;
906 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize;
909 * Limit a TSO burst to prevent it from
910 * overflowing or exceeding the maximum length
911 * allowed by the network interface:
913 KASSERT(ipoptlen == 0,
914 ("%s: TSO can't do IP options", __func__));
917 * Check if we should limit by maximum payload
920 if (if_hw_tsomax != 0) {
921 /* compute maximum TSO length */
922 max_len = (if_hw_tsomax - hdrlen -
926 } else if (len > max_len) {
933 * Prevent the last segment from being
934 * fractional unless the send sockbuf can be
937 max_len = (tp->t_maxseg - optlen);
938 if (((uint32_t)off + (uint32_t)len) <
939 sbavail(&so->so_snd)) {
940 moff = len % max_len;
948 * In case there are too many small fragments
951 if (len <= max_len) {
958 * Send the FIN in a separate segment
959 * after the bulk sending is done.
960 * We don't trust the TSO implementations
961 * to clear the FIN flag on all but the
964 if (tp->t_flags & TF_NEEDFIN)
967 if (optlen + ipoptlen >= tp->t_maxseg) {
969 * Since we don't have enough space to put
970 * the IP header chain and the TCP header in
971 * one packet as required by RFC 7112, don't
972 * send it. Also ensure that at least one
973 * byte of the payload can be put into the
976 SOCKBUF_UNLOCK(&so->so_snd);
981 len = tp->t_maxseg - optlen - ipoptlen;
989 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET,
990 ("%s: len > IP_MAXPACKET", __func__));
992 /*#ifdef DIAGNOSTIC*/
994 if (max_linkhdr + hdrlen > MCLBYTES)
996 if (max_linkhdr + hdrlen > MHLEN)
998 panic("tcphdr too big");
1002 * This KASSERT is here to catch edge cases at a well defined place.
1003 * Before, those had triggered (random) panic conditions further down.
1005 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__));
1008 * Grab a header mbuf, attaching a copy of data to
1009 * be transmitted, and initialize the header from
1010 * the template for sends on this connection.
1014 struct sockbuf *msb;
1017 if ((tp->t_flags & TF_FORCEDATA) && len == 1) {
1018 TCPSTAT_INC(tcps_sndprobe);
1020 if (SEQ_LT(tp->snd_nxt, tp->snd_max))
1021 stats_voi_update_abs_u32(tp->t_stats,
1022 VOI_TCP_RETXPB, len);
1024 stats_voi_update_abs_u64(tp->t_stats,
1027 } else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) {
1028 tp->t_sndrexmitpack++;
1029 TCPSTAT_INC(tcps_sndrexmitpack);
1030 TCPSTAT_ADD(tcps_sndrexmitbyte, len);
1032 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_RETXPB,
1036 TCPSTAT_INC(tcps_sndpack);
1037 TCPSTAT_ADD(tcps_sndbyte, len);
1039 stats_voi_update_abs_u64(tp->t_stats, VOI_TCP_TXPB,
1044 if (MHLEN < hdrlen + max_linkhdr)
1045 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR);
1048 m = m_gethdr(M_NOWAIT, MT_DATA);
1051 SOCKBUF_UNLOCK(&so->so_snd);
1057 m->m_data += max_linkhdr;
1061 * Start the m_copy functions from the closest mbuf
1062 * to the offset in the socket buffer chain.
1064 mb = sbsndptr_noadv(&so->so_snd, off, &moff);
1065 if (len <= MHLEN - hdrlen - max_linkhdr && !hw_tls) {
1066 m_copydata(mb, moff, len,
1067 mtod(m, caddr_t) + hdrlen);
1068 if (SEQ_LT(tp->snd_nxt, tp->snd_max))
1069 sbsndptr_adv(&so->so_snd, mb, len);
1072 if (SEQ_LT(tp->snd_nxt, tp->snd_max))
1076 m->m_next = tcp_m_copym(mb, moff,
1077 &len, if_hw_tsomaxsegcount,
1078 if_hw_tsomaxsegsize, msb, hw_tls);
1079 if (len <= (tp->t_maxseg - optlen)) {
1081 * Must have ran out of mbufs for the copy
1082 * shorten it to no longer need tso. Lets
1083 * not put on sendalot since we are low on
1088 if (m->m_next == NULL) {
1089 SOCKBUF_UNLOCK(&so->so_snd);
1098 * If we're sending everything we've got, set PUSH.
1099 * (This will keep happy those implementations which only
1100 * give data to the user when a buffer fills or
1103 if (((uint32_t)off + (uint32_t)len == sbused(&so->so_snd)) &&
1106 SOCKBUF_UNLOCK(&so->so_snd);
1108 SOCKBUF_UNLOCK(&so->so_snd);
1109 if (tp->t_flags & TF_ACKNOW)
1110 TCPSTAT_INC(tcps_sndacks);
1111 else if (flags & (TH_SYN|TH_FIN|TH_RST))
1112 TCPSTAT_INC(tcps_sndctrl);
1113 else if (SEQ_GT(tp->snd_up, tp->snd_una))
1114 TCPSTAT_INC(tcps_sndurg);
1116 TCPSTAT_INC(tcps_sndwinup);
1118 m = m_gethdr(M_NOWAIT, MT_DATA);
1125 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) &&
1130 m->m_data += max_linkhdr;
1133 SOCKBUF_UNLOCK_ASSERT(&so->so_snd);
1134 m->m_pkthdr.rcvif = (struct ifnet *)0;
1136 mac_inpcb_create_mbuf(tp->t_inpcb, m);
1140 ip6 = mtod(m, struct ip6_hdr *);
1141 th = (struct tcphdr *)(ip6 + 1);
1142 tcpip_fillheaders(tp->t_inpcb, ip6, th);
1146 ip = mtod(m, struct ip *);
1148 ipov = (struct ipovly *)ip;
1150 th = (struct tcphdr *)(ip + 1);
1151 tcpip_fillheaders(tp->t_inpcb, ip, th);
1155 * Fill in fields, remembering maximum advertised
1156 * window for use in delaying messages about window sizes.
1157 * If resending a FIN, be sure not to use a new sequence number.
1159 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN &&
1160 tp->snd_nxt == tp->snd_max)
1163 * If we are starting a connection, send ECN setup
1164 * SYN packet. If we are on a retransmit, we may
1165 * resend those bits a number of times as per
1168 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn == 1) {
1169 if (tp->t_rxtshift >= 1) {
1170 if (tp->t_rxtshift <= V_tcp_ecn_maxretries)
1171 flags |= TH_ECE|TH_CWR;
1173 flags |= TH_ECE|TH_CWR;
1175 /* Handle parallel SYN for ECN */
1176 if ((tp->t_state == TCPS_SYN_RECEIVED) &&
1177 (tp->t_flags2 & TF2_ECN_SND_ECE)) {
1179 tp->t_flags2 &= ~TF2_ECN_SND_ECE;
1182 if (tp->t_state == TCPS_ESTABLISHED &&
1183 (tp->t_flags2 & TF2_ECN_PERMIT)) {
1185 * If the peer has ECN, mark data packets with
1186 * ECN capable transmission (ECT).
1187 * Ignore pure ack packets, retransmissions and window probes.
1189 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) &&
1190 (sack_rxmit == 0) &&
1191 !((tp->t_flags & TF_FORCEDATA) && len == 1 &&
1192 SEQ_LT(tp->snd_una, tp->snd_max))) {
1195 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20);
1198 ip->ip_tos |= IPTOS_ECN_ECT0;
1199 TCPSTAT_INC(tcps_ecn_ect0);
1201 * Reply with proper ECN notifications.
1202 * Only set CWR on new data segments.
1204 if (tp->t_flags2 & TF2_ECN_SND_CWR) {
1206 tp->t_flags2 &= ~TF2_ECN_SND_CWR;
1209 if (tp->t_flags2 & TF2_ECN_SND_ECE)
1214 * If we are doing retransmissions, then snd_nxt will
1215 * not reflect the first unsent octet. For ACK only
1216 * packets, we do not want the sequence number of the
1217 * retransmitted packet, we want the sequence number
1218 * of the next unsent octet. So, if there is no data
1219 * (and no SYN or FIN), use snd_max instead of snd_nxt
1220 * when filling in ti_seq. But if we are in persist
1221 * state, snd_max might reflect one byte beyond the
1222 * right edge of the window, so use snd_nxt in that
1223 * case, since we know we aren't doing a retransmission.
1224 * (retransmit and persist are mutually exclusive...)
1226 if (sack_rxmit == 0) {
1227 if (len || (flags & (TH_SYN|TH_FIN)) ||
1228 tcp_timer_active(tp, TT_PERSIST))
1229 th->th_seq = htonl(tp->snd_nxt);
1231 th->th_seq = htonl(tp->snd_max);
1233 th->th_seq = htonl(p->rxmit);
1235 tp->sackhint.sack_bytes_rexmit += len;
1237 th->th_ack = htonl(tp->rcv_nxt);
1239 bcopy(opt, th + 1, optlen);
1240 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2;
1242 th->th_flags = flags;
1244 * Calculate receive window. Don't shrink window,
1245 * but avoid silly window syndrome.
1246 * If a RST segment is sent, advertise a window of zero.
1248 if (flags & TH_RST) {
1251 if (recwin < (so->so_rcv.sb_hiwat / 4) &&
1252 recwin < tp->t_maxseg)
1254 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) &&
1255 recwin < (tp->rcv_adv - tp->rcv_nxt))
1256 recwin = (tp->rcv_adv - tp->rcv_nxt);
1259 * According to RFC1323 the window field in a SYN (i.e., a <SYN>
1260 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK>
1261 * case is handled in syncache.
1264 th->th_win = htons((u_short)
1265 (min(sbspace(&so->so_rcv), TCP_MAXWIN)));
1267 /* Avoid shrinking window with window scaling. */
1268 recwin = roundup2(recwin, 1 << tp->rcv_scale);
1269 th->th_win = htons((u_short)(recwin >> tp->rcv_scale));
1273 * Adjust the RXWIN0SENT flag - indicate that we have advertised
1274 * a 0 window. This may cause the remote transmitter to stall. This
1275 * flag tells soreceive() to disable delayed acknowledgements when
1276 * draining the buffer. This can occur if the receiver is attempting
1277 * to read more data than can be buffered prior to transmitting on
1280 if (th->th_win == 0) {
1282 tp->t_flags |= TF_RXWIN0SENT;
1284 tp->t_flags &= ~TF_RXWIN0SENT;
1285 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) {
1286 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt));
1287 th->th_flags |= TH_URG;
1290 * If no urgent pointer to send, then we pull
1291 * the urgent pointer to the left edge of the send window
1292 * so that it doesn't drift into the send window on sequence
1293 * number wraparound.
1295 tp->snd_up = tp->snd_una; /* drag it along */
1298 * Put TCP length in extended header, and then
1299 * checksum extended header and data.
1301 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */
1302 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1304 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1305 if (to.to_flags & TOF_SIGNATURE) {
1307 * Calculate MD5 signature and put it into the place
1308 * determined before.
1309 * NOTE: since TCP options buffer doesn't point into
1310 * mbuf's data, calculate offset and use it.
1312 if (!TCPMD5_ENABLED() || (error = TCPMD5_OUTPUT(m, th,
1313 (u_char *)(th + 1) + (to.to_signature - opt))) != 0) {
1315 * Do not send segment if the calculation of MD5
1316 * digest has failed.
1326 * There is no need to fill in ip6_plen right now.
1327 * It will be filled later by ip6_output.
1329 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
1330 th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) +
1331 optlen + len, IPPROTO_TCP, 0);
1334 #if defined(INET6) && defined(INET)
1339 m->m_pkthdr.csum_flags = CSUM_TCP;
1340 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
1341 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen));
1343 /* IP version must be set here for ipv4/ipv6 checking later */
1344 KASSERT(ip->ip_v == IPVERSION,
1345 ("%s: IP version incorrect: %d", __func__, ip->ip_v));
1350 * Enable TSO and specify the size of the segments.
1351 * The TCP pseudo header checksum is always provided.
1354 KASSERT(len > tp->t_maxseg - optlen,
1355 ("%s: len <= tso_segsz", __func__));
1356 m->m_pkthdr.csum_flags |= CSUM_TSO;
1357 m->m_pkthdr.tso_segsz = tp->t_maxseg - optlen;
1360 KASSERT(len + hdrlen == m_length(m, NULL),
1361 ("%s: mbuf chain shorter than expected: %d + %u != %u",
1362 __func__, len, hdrlen, m_length(m, NULL)));
1365 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */
1366 hhook_run_tcp_est_out(tp, th, &to, len, tso);
1373 if (so->so_options & SO_DEBUG) {
1379 save = ipov->ih_len;
1380 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */);
1382 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0);
1386 ipov->ih_len = save;
1388 #endif /* TCPDEBUG */
1389 TCP_PROBE3(debug__output, tp, th, m);
1391 /* We're getting ready to send; log now. */
1392 TCP_LOG_EVENT(tp, th, &so->so_rcv, &so->so_snd, TCP_LOG_OUT, ERRNO_UNK,
1396 * Fill in IP length and desired time to live and
1397 * send to IP level. There should be a better way
1398 * to handle ttl and tos; we could keep them in
1399 * the template, but need a way to checksum without them.
1402 * m->m_pkthdr.len should have been set before checksum calculation,
1403 * because in6_cksum() need it.
1408 * we separately set hoplimit for every segment, since the
1409 * user might want to change the value via setsockopt.
1410 * Also, desired default hop limit might be changed via
1411 * Neighbor Discovery.
1413 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL);
1416 * Set the packet size here for the benefit of DTrace probes.
1417 * ip6_output() will set it properly; it's supposed to include
1418 * the option header lengths as well.
1420 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6));
1422 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss)
1423 tp->t_flags2 |= TF2_PLPMTU_PMTUD;
1425 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
1427 if (tp->t_state == TCPS_SYN_SENT)
1428 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th);
1430 TCP_PROBE5(send, NULL, tp, ip6, tp, th);
1433 /* Save packet, if requested. */
1434 tcp_pcap_add(th, m, &(tp->t_outpkts));
1437 /* TODO: IPv6 IP6TOS_ECT bit on */
1438 error = ip6_output(m, tp->t_inpcb->in6p_outputopts,
1439 &tp->t_inpcb->inp_route6,
1440 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0),
1441 NULL, NULL, tp->t_inpcb);
1443 if (error == EMSGSIZE && tp->t_inpcb->inp_route6.ro_nh != NULL)
1444 mtu = tp->t_inpcb->inp_route6.ro_nh->nh_mtu;
1447 #if defined(INET) && defined(INET6)
1452 ip->ip_len = htons(m->m_pkthdr.len);
1454 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO)
1455 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL);
1458 * If we do path MTU discovery, then we set DF on every packet.
1459 * This might not be the best thing to do according to RFC3390
1460 * Section 2. However the tcp hostcache migitates the problem
1461 * so it affects only the first tcp connection with a host.
1463 * NB: Don't set DF on small MTU/MSS to have a safe fallback.
1465 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) {
1466 ip->ip_off |= htons(IP_DF);
1467 tp->t_flags2 |= TF2_PLPMTU_PMTUD;
1469 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
1472 if (tp->t_state == TCPS_SYN_SENT)
1473 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th);
1475 TCP_PROBE5(send, NULL, tp, ip, tp, th);
1478 /* Save packet, if requested. */
1479 tcp_pcap_add(th, m, &(tp->t_outpkts));
1482 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route,
1483 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0,
1486 if (error == EMSGSIZE && tp->t_inpcb->inp_route.ro_nh != NULL)
1487 mtu = tp->t_inpcb->inp_route.ro_nh->nh_mtu;
1493 * In transmit state, time the transmission and arrange for
1494 * the retransmit. In persist state, just set snd_max.
1496 if ((tp->t_flags & TF_FORCEDATA) == 0 ||
1497 !tcp_timer_active(tp, TT_PERSIST)) {
1498 tcp_seq startseq = tp->snd_nxt;
1501 * Advance snd_nxt over sequence space of this segment.
1503 if (flags & (TH_SYN|TH_FIN)) {
1506 if (flags & TH_FIN) {
1508 tp->t_flags |= TF_SENTFIN;
1514 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) {
1515 tp->snd_max = tp->snd_nxt;
1517 * Time this transmission if not a retransmission and
1518 * not currently timing anything.
1520 tp->t_sndtime = ticks;
1521 if (tp->t_rtttime == 0) {
1522 tp->t_rtttime = ticks;
1523 tp->t_rtseq = startseq;
1524 TCPSTAT_INC(tcps_segstimed);
1527 if (!(tp->t_flags & TF_GPUTINPROG) && len) {
1528 tp->t_flags |= TF_GPUTINPROG;
1529 tp->gput_seq = startseq;
1530 tp->gput_ack = startseq +
1531 ulmin(sbavail(&so->so_snd) - off, sendwin);
1532 tp->gput_ts = tcp_ts_getticks();
1538 * Set retransmit timer if not currently set,
1539 * and not doing a pure ack or a keep-alive probe.
1540 * Initial value for retransmit timer is smoothed
1541 * round-trip time + 2 * round-trip time variance.
1542 * Initialize shift counter which is used for backoff
1543 * of retransmit time.
1546 if (!tcp_timer_active(tp, TT_REXMT) &&
1547 ((sack_rxmit && tp->snd_nxt != tp->snd_max) ||
1548 (tp->snd_nxt != tp->snd_una))) {
1549 if (tcp_timer_active(tp, TT_PERSIST)) {
1550 tcp_timer_activate(tp, TT_PERSIST, 0);
1553 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
1554 } else if (len == 0 && sbavail(&so->so_snd) &&
1555 !tcp_timer_active(tp, TT_REXMT) &&
1556 !tcp_timer_active(tp, TT_PERSIST)) {
1558 * Avoid a situation where we do not set persist timer
1559 * after a zero window condition. For example:
1560 * 1) A -> B: packet with enough data to fill the window
1561 * 2) B -> A: ACK for #1 + new data (0 window
1563 * 3) A -> B: ACK for #2, 0 len packet
1565 * In this case, A will not activate the persist timer,
1566 * because it chose to send a packet. Unless tcp_output
1567 * is called for some other reason (delayed ack timer,
1568 * another input packet from B, socket syscall), A will
1569 * not send zero window probes.
1571 * So, if you send a 0-length packet, but there is data
1572 * in the socket buffer, and neither the rexmt or
1573 * persist timer is already set, then activate the
1581 * Persist case, update snd_max but since we are in
1582 * persist mode (no window) we do not update snd_nxt.
1587 if (flags & TH_FIN) {
1589 tp->t_flags |= TF_SENTFIN;
1591 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max))
1592 tp->snd_max = tp->snd_nxt + xlen;
1595 (TCPS_HAVEESTABLISHED(tp->t_state) &&
1596 (tp->t_flags & TF_SACK_PERMIT) &&
1597 tp->rcv_numsacks > 0)) {
1598 /* Clean up any DSACK's sent */
1599 tcp_clean_dsack_blocks(tp);
1602 /* Record the error. */
1603 TCP_LOG_EVENT(tp, NULL, &so->so_rcv, &so->so_snd, TCP_LOG_OUT,
1604 error, 0, NULL, false);
1607 * We know that the packet was lost, so back out the
1608 * sequence number advance, if any.
1610 * If the error is EPERM the packet got blocked by the
1611 * local firewall. Normally we should terminate the
1612 * connection but the blocking may have been spurious
1613 * due to a firewall reconfiguration cycle. So we treat
1614 * it like a packet loss and let the retransmit timer and
1615 * timeouts do their work over time.
1616 * XXX: It is a POLA question whether calling tcp_drop right
1617 * away would be the really correct behavior instead.
1619 if (((tp->t_flags & TF_FORCEDATA) == 0 ||
1620 !tcp_timer_active(tp, TT_PERSIST)) &&
1621 ((flags & TH_SYN) == 0) &&
1625 tp->sackhint.sack_bytes_rexmit -= len;
1626 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0,
1627 ("sackhint bytes rtx >= 0"));
1631 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */
1635 tp->t_softerror = error;
1638 TCP_XMIT_TIMER_ASSERT(tp, len, flags);
1639 tp->snd_cwnd = tp->t_maxseg;
1643 * For some reason the interface we used initially
1644 * to send segments changed to another or lowered
1646 * If TSO was active we either got an interface
1647 * without TSO capabilits or TSO was turned off.
1648 * If we obtained mtu from ip_output() then update
1652 tp->t_flags &= ~TF_TSO;
1654 tcp_mss_update(tp, -1, mtu, NULL, NULL);
1662 if (TCPS_HAVERCVDSYN(tp->t_state)) {
1663 tp->t_softerror = error;
1671 TCPSTAT_INC(tcps_sndtotal);
1674 * Data sent (as far as we can tell).
1675 * If this advertises a larger window than any other segment,
1676 * then remember the size of the advertised window.
1677 * Any pending ACK has now been sent.
1679 if (SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv))
1680 tp->rcv_adv = tp->rcv_nxt + recwin;
1681 tp->last_ack_sent = tp->rcv_nxt;
1682 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK);
1683 if (tcp_timer_active(tp, TT_DELACK))
1684 tcp_timer_activate(tp, TT_DELACK, 0);
1687 * This completely breaks TCP if newreno is turned on. What happens
1688 * is that if delayed-acks are turned on on the receiver, this code
1689 * on the transmitter effectively destroys the TCP window, forcing
1690 * it to four packets (1.5Kx4 = 6K window).
1692 if (sendalot && --maxburst)
1701 tcp_setpersist(struct tcpcb *tp)
1703 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1;
1706 tp->t_flags &= ~TF_PREVVALID;
1707 if (tcp_timer_active(tp, TT_REXMT))
1708 panic("tcp_setpersist: retransmit pending");
1710 * Start/restart persistence timer.
1712 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift],
1713 tcp_persmin, tcp_persmax);
1714 tcp_timer_activate(tp, TT_PERSIST, tt);
1715 if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
1720 * Insert TCP options according to the supplied parameters to the place
1721 * optp in a consistent way. Can handle unaligned destinations.
1723 * The order of the option processing is crucial for optimal packing and
1724 * alignment for the scarce option space.
1726 * The optimal order for a SYN/SYN-ACK segment is:
1727 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) +
1728 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40.
1730 * The SACK options should be last. SACK blocks consume 8*n+2 bytes.
1731 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks).
1732 * At minimum we need 10 bytes (to generate 1 SACK block). If both
1733 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present,
1734 * we only have 10 bytes for SACK options (40 - (12 + 18)).
1737 tcp_addoptions(struct tcpopt *to, u_char *optp)
1739 u_int32_t mask, optlen = 0;
1741 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) {
1742 if ((to->to_flags & mask) != mask)
1744 if (optlen == TCP_MAXOLEN)
1746 switch (to->to_flags & mask) {
1748 while (optlen % 4) {
1749 optlen += TCPOLEN_NOP;
1750 *optp++ = TCPOPT_NOP;
1752 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG)
1754 optlen += TCPOLEN_MAXSEG;
1755 *optp++ = TCPOPT_MAXSEG;
1756 *optp++ = TCPOLEN_MAXSEG;
1757 to->to_mss = htons(to->to_mss);
1758 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss));
1759 optp += sizeof(to->to_mss);
1762 while (!optlen || optlen % 2 != 1) {
1763 optlen += TCPOLEN_NOP;
1764 *optp++ = TCPOPT_NOP;
1766 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW)
1768 optlen += TCPOLEN_WINDOW;
1769 *optp++ = TCPOPT_WINDOW;
1770 *optp++ = TCPOLEN_WINDOW;
1771 *optp++ = to->to_wscale;
1774 while (optlen % 2) {
1775 optlen += TCPOLEN_NOP;
1776 *optp++ = TCPOPT_NOP;
1778 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED)
1780 optlen += TCPOLEN_SACK_PERMITTED;
1781 *optp++ = TCPOPT_SACK_PERMITTED;
1782 *optp++ = TCPOLEN_SACK_PERMITTED;
1785 while (!optlen || optlen % 4 != 2) {
1786 optlen += TCPOLEN_NOP;
1787 *optp++ = TCPOPT_NOP;
1789 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP)
1791 optlen += TCPOLEN_TIMESTAMP;
1792 *optp++ = TCPOPT_TIMESTAMP;
1793 *optp++ = TCPOLEN_TIMESTAMP;
1794 to->to_tsval = htonl(to->to_tsval);
1795 to->to_tsecr = htonl(to->to_tsecr);
1796 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval));
1797 optp += sizeof(to->to_tsval);
1798 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr));
1799 optp += sizeof(to->to_tsecr);
1803 int siglen = TCPOLEN_SIGNATURE - 2;
1805 while (!optlen || optlen % 4 != 2) {
1806 optlen += TCPOLEN_NOP;
1807 *optp++ = TCPOPT_NOP;
1809 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) {
1810 to->to_flags &= ~TOF_SIGNATURE;
1813 optlen += TCPOLEN_SIGNATURE;
1814 *optp++ = TCPOPT_SIGNATURE;
1815 *optp++ = TCPOLEN_SIGNATURE;
1816 to->to_signature = optp;
1824 struct sackblk *sack = (struct sackblk *)to->to_sacks;
1827 while (!optlen || optlen % 4 != 2) {
1828 optlen += TCPOLEN_NOP;
1829 *optp++ = TCPOPT_NOP;
1831 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK)
1833 optlen += TCPOLEN_SACKHDR;
1834 *optp++ = TCPOPT_SACK;
1835 sackblks = min(to->to_nsacks,
1836 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK);
1837 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK;
1838 while (sackblks--) {
1839 sack_seq = htonl(sack->start);
1840 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq));
1841 optp += sizeof(sack_seq);
1842 sack_seq = htonl(sack->end);
1843 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq));
1844 optp += sizeof(sack_seq);
1845 optlen += TCPOLEN_SACK;
1848 TCPSTAT_INC(tcps_sack_send_blocks);
1855 /* XXX is there any point to aligning this option? */
1856 total_len = TCPOLEN_FAST_OPEN_EMPTY + to->to_tfo_len;
1857 if (TCP_MAXOLEN - optlen < total_len) {
1858 to->to_flags &= ~TOF_FASTOPEN;
1861 *optp++ = TCPOPT_FAST_OPEN;
1862 *optp++ = total_len;
1863 if (to->to_tfo_len > 0) {
1864 bcopy(to->to_tfo_cookie, optp, to->to_tfo_len);
1865 optp += to->to_tfo_len;
1867 optlen += total_len;
1871 panic("%s: unknown TCP option type", __func__);
1876 /* Terminate and pad TCP options to a 4 byte boundary. */
1878 optlen += TCPOLEN_EOL;
1879 *optp++ = TCPOPT_EOL;
1882 * According to RFC 793 (STD0007):
1883 * "The content of the header beyond the End-of-Option option
1884 * must be header padding (i.e., zero)."
1885 * and later: "The padding is composed of zeros."
1887 while (optlen % 4) {
1888 optlen += TCPOLEN_PAD;
1889 *optp++ = TCPOPT_PAD;
1892 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__));
1897 * This is a copy of m_copym(), taking the TSO segment size/limit
1898 * constraints into account, and advancing the sndptr as it goes.
1901 tcp_m_copym(struct mbuf *m, int32_t off0, int32_t *plen,
1902 int32_t seglimit, int32_t segsize, struct sockbuf *sb, bool hw_tls)
1905 struct ktls_session *tls, *ntls;
1908 struct mbuf *n, **np;
1911 int32_t len = *plen;
1915 uint32_t mlen, frags;
1918 KASSERT(off >= 0, ("tcp_m_copym, negative off %d", off));
1919 KASSERT(len >= 0, ("tcp_m_copym, negative len %d", len));
1920 if (off == 0 && m->m_flags & M_PKTHDR)
1925 KASSERT(m != NULL, ("tcp_m_copym, offset > size of mbuf chain"));
1929 if ((sb) && (m == sb->sb_sndptr)) {
1930 sb->sb_sndptroff += m->m_len;
1931 sb->sb_sndptr = m->m_next;
1939 if (hw_tls && (m->m_flags & M_EXTPG))
1947 KASSERT(len == M_COPYALL,
1948 ("tcp_m_copym, length > size of mbuf chain"));
1950 if (pkthdrlen != NULL)
1951 *pkthdrlen = len_cp;
1956 if (m->m_flags & M_EXTPG)
1957 ntls = m->m_epg_tls;
1962 * Avoid mixing TLS records with handshake
1963 * data or TLS records from different
1969 if (pkthdrlen != NULL)
1970 *pkthdrlen = len_cp;
1975 mlen = min(len, m->m_len - off);
1978 * For M_EXTPG mbufs, add 3 segments
1979 * + 1 in case we are crossing page boundaries
1980 * + 2 in case the TLS hdr/trailer are used
1981 * It is cheaper to just add the segments
1982 * than it is to take the cache miss to look
1983 * at the mbuf ext_pgs state in detail.
1985 if (m->m_flags & M_EXTPG) {
1986 fragsize = min(segsize, PAGE_SIZE);
1993 /* Break if we really can't fit anymore. */
1994 if ((frags + 1) >= seglimit) {
1996 if (pkthdrlen != NULL)
1997 *pkthdrlen = len_cp;
2002 * Reduce size if you can't copy the whole
2003 * mbuf. If we can't copy the whole mbuf, also
2004 * adjust len so the loop will end after this
2007 if ((frags + howmany(mlen, fragsize)) >= seglimit) {
2008 mlen = (seglimit - frags - 1) * fragsize;
2010 *plen = len_cp + len;
2011 if (pkthdrlen != NULL)
2014 frags += howmany(mlen, fragsize);
2018 KASSERT(seglimit > 0,
2019 ("%s: seglimit went too low", __func__));
2022 n = m_gethdr(M_NOWAIT, m->m_type);
2024 n = m_get(M_NOWAIT, m->m_type);
2029 if (!m_dup_pkthdr(n, m, M_NOWAIT))
2031 if (len == M_COPYALL)
2032 n->m_pkthdr.len -= off0;
2034 n->m_pkthdr.len = len;
2035 pkthdrlen = &n->m_pkthdr.len;
2040 if (m->m_flags & (M_EXT|M_EXTPG)) {
2041 n->m_data = m->m_data + off;
2044 bcopy(mtod(m, caddr_t)+off, mtod(n, caddr_t),
2047 if (sb && (sb->sb_sndptr == m) &&
2048 ((n->m_len + off) >= m->m_len) && m->m_next) {
2049 sb->sb_sndptroff += m->m_len;
2050 sb->sb_sndptr = m->m_next;
2053 if (len != M_COPYALL) {
2066 tcp_sndbuf_autoscale(struct tcpcb *tp, struct socket *so, uint32_t sendwin)
2070 * Automatic sizing of send socket buffer. Often the send buffer
2071 * size is not optimally adjusted to the actual network conditions
2072 * at hand (delay bandwidth product). Setting the buffer size too
2073 * small limits throughput on links with high bandwidth and high
2074 * delay (eg. trans-continental/oceanic links). Setting the
2075 * buffer size too big consumes too much real kernel memory,
2076 * especially with many connections on busy servers.
2078 * The criteria to step up the send buffer one notch are:
2079 * 1. receive window of remote host is larger than send buffer
2080 * (with a fudge factor of 5/4th);
2081 * 2. send buffer is filled to 7/8th with data (so we actually
2082 * have data to make use of it);
2083 * 3. send buffer fill has not hit maximal automatic size;
2084 * 4. our send window (slow start and cogestion controlled) is
2085 * larger than sent but unacknowledged data in send buffer.
2087 * The remote host receive window scaling factor may limit the
2088 * growing of the send buffer before it reaches its allowed
2091 * It scales directly with slow start or congestion window
2092 * and does at most one step per received ACK. This fast
2093 * scaling has the drawback of growing the send buffer beyond
2094 * what is strictly necessary to make full use of a given
2095 * delay*bandwidth product. However testing has shown this not
2096 * to be much of an problem. At worst we are trading wasting
2097 * of available bandwidth (the non-use of it) for wasting some
2098 * socket buffer memory.
2100 * TODO: Shrink send buffer during idle periods together
2101 * with congestion window. Requires another timer. Has to
2102 * wait for upcoming tcp timer rewrite.
2104 * XXXGL: should there be used sbused() or sbavail()?
2106 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) {
2109 lowat = V_tcp_sendbuf_auto_lowat ? so->so_snd.sb_lowat : 0;
2110 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat - lowat &&
2111 sbused(&so->so_snd) >=
2112 (so->so_snd.sb_hiwat / 8 * 7) - lowat &&
2113 sbused(&so->so_snd) < V_tcp_autosndbuf_max &&
2114 sendwin >= (sbused(&so->so_snd) -
2115 (tp->snd_nxt - tp->snd_una))) {
2116 if (!sbreserve_locked(&so->so_snd,
2117 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc,
2118 V_tcp_autosndbuf_max), so, curthread))
2119 so->so_snd.sb_flags &= ~SB_AUTOSIZE;