2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
3 * The Regents of the University of California. All rights reserved.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 4. Neither the name of the University nor the names of its contributors
14 * may be used to endorse or promote products derived from this software
15 * without specific prior written permission.
17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95
32 #include <sys/cdefs.h>
33 __FBSDID("$FreeBSD$");
36 #include "opt_inet6.h"
37 #include "opt_ipsec.h"
38 #include "opt_tcpdebug.h"
40 #include <sys/param.h>
41 #include <sys/systm.h>
42 #include <sys/domain.h>
43 #include <sys/hhook.h>
44 #include <sys/kernel.h>
47 #include <sys/mutex.h>
48 #include <sys/protosw.h>
50 #include <sys/socket.h>
51 #include <sys/socketvar.h>
52 #include <sys/sysctl.h>
55 #include <net/route.h>
58 #include <netinet/cc.h>
59 #include <netinet/in.h>
60 #include <netinet/in_kdtrace.h>
61 #include <netinet/in_systm.h>
62 #include <netinet/ip.h>
63 #include <netinet/in_pcb.h>
64 #include <netinet/ip_var.h>
65 #include <netinet/ip_options.h>
67 #include <netinet6/in6_pcb.h>
68 #include <netinet/ip6.h>
69 #include <netinet6/ip6_var.h>
72 #include <netinet/tcp_fastopen.h>
75 #include <netinet/tcp_fsm.h>
76 #include <netinet/tcp_seq.h>
77 #include <netinet/tcp_timer.h>
78 #include <netinet/tcp_var.h>
79 #include <netinet/tcpip.h>
81 #include <netinet/tcp_pcap.h>
84 #include <netinet/tcp_debug.h>
87 #include <netinet/tcp_offload.h>
91 #include <netipsec/ipsec.h>
94 #include <machine/in_cksum.h>
96 #include <security/mac/mac_framework.h>
98 VNET_DEFINE(int, path_mtu_discovery) = 1;
99 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_VNET | CTLFLAG_RW,
100 &VNET_NAME(path_mtu_discovery), 1,
101 "Enable Path MTU Discovery");
103 VNET_DEFINE(int, tcp_do_tso) = 1;
104 #define V_tcp_do_tso VNET(tcp_do_tso)
105 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_VNET | CTLFLAG_RW,
106 &VNET_NAME(tcp_do_tso), 0,
107 "Enable TCP Segmentation Offload");
109 VNET_DEFINE(int, tcp_sendspace) = 1024*32;
110 #define V_tcp_sendspace VNET(tcp_sendspace)
111 SYSCTL_INT(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, CTLFLAG_VNET | CTLFLAG_RW,
112 &VNET_NAME(tcp_sendspace), 0, "Initial send socket buffer size");
114 VNET_DEFINE(int, tcp_do_autosndbuf) = 1;
115 #define V_tcp_do_autosndbuf VNET(tcp_do_autosndbuf)
116 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_VNET | CTLFLAG_RW,
117 &VNET_NAME(tcp_do_autosndbuf), 0,
118 "Enable automatic send buffer sizing");
120 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024;
121 #define V_tcp_autosndbuf_inc VNET(tcp_autosndbuf_inc)
122 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_VNET | CTLFLAG_RW,
123 &VNET_NAME(tcp_autosndbuf_inc), 0,
124 "Incrementor step size of automatic send buffer");
126 VNET_DEFINE(int, tcp_autosndbuf_max) = 2*1024*1024;
127 #define V_tcp_autosndbuf_max VNET(tcp_autosndbuf_max)
128 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_VNET | CTLFLAG_RW,
129 &VNET_NAME(tcp_autosndbuf_max), 0,
130 "Max size of automatic send buffer");
132 static void inline hhook_run_tcp_est_out(struct tcpcb *tp,
133 struct tcphdr *th, struct tcpopt *to,
135 static void inline cc_after_idle(struct tcpcb *tp);
138 * Wrapper for the TCP established output helper hook.
141 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th,
142 struct tcpopt *to, long len, int tso)
144 struct tcp_hhook_data hhook_data;
146 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) {
150 hhook_data.len = len;
151 hhook_data.tso = tso;
153 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data,
159 * CC wrapper hook functions
162 cc_after_idle(struct tcpcb *tp)
164 INP_WLOCK_ASSERT(tp->t_inpcb);
166 if (CC_ALGO(tp)->after_idle != NULL)
167 CC_ALGO(tp)->after_idle(tp->ccv);
171 * Tcp output routine: figure out what should be sent and send it.
174 tcp_output(struct tcpcb *tp)
176 struct socket *so = tp->t_inpcb->inp_socket;
177 long len, recwin, sendwin;
178 int off, flags, error = 0; /* Keep compiler happy */
180 struct ip *ip = NULL;
181 struct ipovly *ipov = NULL;
183 u_char opt[TCP_MAXOLEN];
184 unsigned ipoptlen, optlen, hdrlen;
186 unsigned ipsec_optlen = 0;
189 int sack_rxmit, sack_bytes_rxmt;
194 int maxburst = TCP_MAXBURST;
197 struct ip6_hdr *ip6 = NULL;
200 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0;
203 INP_WLOCK_ASSERT(tp->t_inpcb);
206 if (tp->t_flags & TF_TOE)
207 return (tcp_offload_output(tp));
212 * For TFO connections in SYN_RECEIVED, only allow the initial
213 * SYN|ACK and those sent by the retransmit timer.
215 if ((tp->t_flags & TF_FASTOPEN) &&
216 (tp->t_state == TCPS_SYN_RECEIVED) &&
217 SEQ_GT(tp->snd_max, tp->snd_una) && /* inital SYN|ACK sent */
218 (tp->snd_nxt != tp->snd_una)) /* not a retransmit */
222 * Determine length of data that should be transmitted,
223 * and flags that will be used.
224 * If there is some data or critical controls (SYN, RST)
225 * to send, then transmit; otherwise, investigate further.
227 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una);
228 if (idle && ticks - tp->t_rcvtime >= tp->t_rxtcur)
230 tp->t_flags &= ~TF_LASTIDLE;
232 if (tp->t_flags & TF_MORETOCOME) {
233 tp->t_flags |= TF_LASTIDLE;
239 * If we've recently taken a timeout, snd_max will be greater than
240 * snd_nxt. There may be SACK information that allows us to avoid
241 * resending already delivered data. Adjust snd_nxt accordingly.
243 if ((tp->t_flags & TF_SACK_PERMIT) &&
244 SEQ_LT(tp->snd_nxt, tp->snd_max))
249 off = tp->snd_nxt - tp->snd_una;
250 sendwin = min(tp->snd_wnd, tp->snd_cwnd);
252 flags = tcp_outflags[tp->t_state];
254 * Send any SACK-generated retransmissions. If we're explicitly trying
255 * to send out new data (when sendalot is 1), bypass this function.
256 * If we retransmit in fast recovery mode, decrement snd_cwnd, since
257 * we're replacing a (future) new transmission with a retransmission
258 * now, and we previously incremented snd_cwnd in tcp_input().
261 * Still in sack recovery , reset rxmit flag to zero.
267 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) &&
268 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) {
271 cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt;
274 /* Do not retransmit SACK segments beyond snd_recover */
275 if (SEQ_GT(p->end, tp->snd_recover)) {
277 * (At least) part of sack hole extends beyond
278 * snd_recover. Check to see if we can rexmit data
281 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) {
283 * Can't rexmit any more data for this hole.
284 * That data will be rexmitted in the next
285 * sack recovery episode, when snd_recover
286 * moves past p->rxmit.
289 goto after_sack_rexmit;
291 /* Can rexmit part of the current hole */
292 len = ((long)ulmin(cwin,
293 tp->snd_recover - p->rxmit));
295 len = ((long)ulmin(cwin, p->end - p->rxmit));
296 off = p->rxmit - tp->snd_una;
297 KASSERT(off >= 0,("%s: sack block to the left of una : %d",
302 TCPSTAT_INC(tcps_sack_rexmits);
303 TCPSTAT_ADD(tcps_sack_rexmit_bytes,
304 min(len, tp->t_maxseg));
309 * Get standard flags, and add SYN or FIN if requested by 'hidden'
312 if (tp->t_flags & TF_NEEDFIN)
314 if (tp->t_flags & TF_NEEDSYN)
317 SOCKBUF_LOCK(&so->so_snd);
319 * If in persist timeout with window of 0, send 1 byte.
320 * Otherwise, if window is small but nonzero
321 * and timer expired, we will send what we can
322 * and go to transmit state.
324 if (tp->t_flags & TF_FORCEDATA) {
327 * If we still have some data to send, then
328 * clear the FIN bit. Usually this would
329 * happen below when it realizes that we
330 * aren't sending all the data. However,
331 * if we have exactly 1 byte of unsent data,
332 * then it won't clear the FIN bit below,
333 * and if we are in persist state, we wind
334 * up sending the packet without recording
335 * that we sent the FIN bit.
337 * We can't just blindly clear the FIN bit,
338 * because if we don't have any more data
339 * to send then the probe will be the FIN
342 if (off < sbused(&so->so_snd))
346 tcp_timer_activate(tp, TT_PERSIST, 0);
352 * If snd_nxt == snd_max and we have transmitted a FIN, the
353 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in
354 * a negative length. This can also occur when TCP opens up
355 * its congestion window while receiving additional duplicate
356 * acks after fast-retransmit because TCP will reset snd_nxt
357 * to snd_max after the fast-retransmit.
359 * In the normal retransmit-FIN-only case, however, snd_nxt will
360 * be set to snd_una, the offset will be 0, and the length may
363 * If sack_rxmit is true we are retransmitting from the scoreboard
364 * in which case len is already set.
366 if (sack_rxmit == 0) {
367 if (sack_bytes_rxmt == 0)
368 len = ((long)ulmin(sbavail(&so->so_snd), sendwin) -
374 * We are inside of a SACK recovery episode and are
375 * sending new data, having retransmitted all the
376 * data possible in the scoreboard.
378 len = ((long)ulmin(sbavail(&so->so_snd), tp->snd_wnd) -
381 * Don't remove this (len > 0) check !
382 * We explicitly check for len > 0 here (although it
383 * isn't really necessary), to work around a gcc
384 * optimization issue - to force gcc to compute
385 * len above. Without this check, the computation
386 * of len is bungled by the optimizer.
389 cwin = tp->snd_cwnd -
390 (tp->snd_nxt - tp->sack_newdata) -
394 len = lmin(len, cwin);
400 * Lop off SYN bit if it has already been sent. However, if this
401 * is SYN-SENT state and if segment contains data and if we don't
402 * know that foreign host supports TAO, suppress sending segment.
404 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) {
405 if (tp->t_state != TCPS_SYN_RECEIVED)
409 * When sending additional segments following a TFO SYN|ACK,
410 * do not include the SYN bit.
412 if ((tp->t_flags & TF_FASTOPEN) &&
413 (tp->t_state == TCPS_SYN_RECEIVED))
420 * Be careful not to send data and/or FIN on SYN segments.
421 * This measure is needed to prevent interoperability problems
422 * with not fully conformant TCP implementations.
424 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) {
431 * When retransmitting SYN|ACK on a passively-created TFO socket,
432 * don't include data, as the presence of data may have caused the
433 * original SYN|ACK to have been dropped by a middlebox.
435 if ((tp->t_flags & TF_FASTOPEN) &&
436 (((tp->t_state == TCPS_SYN_RECEIVED) && (tp->t_rxtshift > 0)) ||
442 * If FIN has been sent but not acked,
443 * but we haven't been called to retransmit,
444 * len will be < 0. Otherwise, window shrank
445 * after we sent into it. If window shrank to 0,
446 * cancel pending retransmit, pull snd_nxt back
447 * to (closed) window, and set the persist timer
448 * if it isn't already going. If the window didn't
449 * close completely, just wait for an ACK.
451 * We also do a general check here to ensure that
452 * we will set the persist timer when we have data
453 * to send, but a 0-byte window. This makes sure
454 * the persist timer is set even if the packet
455 * hits one of the "goto send" lines below.
458 if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) &&
459 (off < (int) sbavail(&so->so_snd))) {
460 tcp_timer_activate(tp, TT_REXMT, 0);
462 tp->snd_nxt = tp->snd_una;
463 if (!tcp_timer_active(tp, TT_PERSIST))
468 /* len will be >= 0 after this point. */
469 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__));
472 * Automatic sizing of send socket buffer. Often the send buffer
473 * size is not optimally adjusted to the actual network conditions
474 * at hand (delay bandwidth product). Setting the buffer size too
475 * small limits throughput on links with high bandwidth and high
476 * delay (eg. trans-continental/oceanic links). Setting the
477 * buffer size too big consumes too much real kernel memory,
478 * especially with many connections on busy servers.
480 * The criteria to step up the send buffer one notch are:
481 * 1. receive window of remote host is larger than send buffer
482 * (with a fudge factor of 5/4th);
483 * 2. send buffer is filled to 7/8th with data (so we actually
484 * have data to make use of it);
485 * 3. send buffer fill has not hit maximal automatic size;
486 * 4. our send window (slow start and cogestion controlled) is
487 * larger than sent but unacknowledged data in send buffer.
489 * The remote host receive window scaling factor may limit the
490 * growing of the send buffer before it reaches its allowed
493 * It scales directly with slow start or congestion window
494 * and does at most one step per received ACK. This fast
495 * scaling has the drawback of growing the send buffer beyond
496 * what is strictly necessary to make full use of a given
497 * delay*bandwith product. However testing has shown this not
498 * to be much of an problem. At worst we are trading wasting
499 * of available bandwith (the non-use of it) for wasting some
500 * socket buffer memory.
502 * TODO: Shrink send buffer during idle periods together
503 * with congestion window. Requires another timer. Has to
504 * wait for upcoming tcp timer rewrite.
506 * XXXGL: should there be used sbused() or sbavail()?
508 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) {
509 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat &&
510 sbused(&so->so_snd) >= (so->so_snd.sb_hiwat / 8 * 7) &&
511 sbused(&so->so_snd) < V_tcp_autosndbuf_max &&
512 sendwin >= (sbused(&so->so_snd) -
513 (tp->snd_nxt - tp->snd_una))) {
514 if (!sbreserve_locked(&so->so_snd,
515 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc,
516 V_tcp_autosndbuf_max), so, curthread))
517 so->so_snd.sb_flags &= ~SB_AUTOSIZE;
522 * Decide if we can use TCP Segmentation Offloading (if supported by
525 * TSO may only be used if we are in a pure bulk sending state. The
526 * presence of TCP-MD5, SACK retransmits, SACK advertizements and
527 * IP options prevent using TSO. With TSO the TCP header is the same
528 * (except for the sequence number) for all generated packets. This
529 * makes it impossible to transmit any options which vary per generated
534 * Pre-calculate here as we save another lookup into the darknesses
535 * of IPsec that way and can actually decide if TSO is ok.
537 ipsec_optlen = ipsec_hdrsiz_tcp(tp);
539 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg &&
540 ((tp->t_flags & TF_SIGNATURE) == 0) &&
541 tp->rcv_numsacks == 0 && sack_rxmit == 0 &&
545 tp->t_inpcb->inp_options == NULL &&
546 tp->t_inpcb->in6p_options == NULL)
550 if (SEQ_LT(p->rxmit + len, tp->snd_una + sbused(&so->so_snd)))
553 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una +
554 sbused(&so->so_snd)))
558 recwin = sbspace(&so->so_rcv);
561 * Sender silly window avoidance. We transmit under the following
562 * conditions when len is non-zero:
564 * - We have a full segment (or more with TSO)
565 * - This is the last buffer in a write()/send() and we are
566 * either idle or running NODELAY
567 * - we've timed out (e.g. persist timer)
568 * - we have more then 1/2 the maximum send window's worth of
569 * data (receiver may be limited the window size)
570 * - we need to retransmit
573 if (len >= tp->t_maxseg)
576 * NOTE! on localhost connections an 'ack' from the remote
577 * end may occur synchronously with the output and cause
578 * us to flush a buffer queued with moretocome. XXX
580 * note: the len + off check is almost certainly unnecessary.
582 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */
583 (idle || (tp->t_flags & TF_NODELAY)) &&
584 len + off >= sbavail(&so->so_snd) &&
585 (tp->t_flags & TF_NOPUSH) == 0) {
588 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */
590 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0)
592 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */
599 * Sending of standalone window updates.
601 * Window updates are important when we close our window due to a
602 * full socket buffer and are opening it again after the application
603 * reads data from it. Once the window has opened again and the
604 * remote end starts to send again the ACK clock takes over and
605 * provides the most current window information.
607 * We must avoid the silly window syndrome whereas every read
608 * from the receive buffer, no matter how small, causes a window
609 * update to be sent. We also should avoid sending a flurry of
610 * window updates when the socket buffer had queued a lot of data
611 * and the application is doing small reads.
613 * Prevent a flurry of pointless window updates by only sending
614 * an update when we can increase the advertized window by more
615 * than 1/4th of the socket buffer capacity. When the buffer is
616 * getting full or is very small be more aggressive and send an
617 * update whenever we can increase by two mss sized segments.
618 * In all other situations the ACK's to new incoming data will
619 * carry further window increases.
621 * Don't send an independent window update if a delayed
622 * ACK is pending (it will get piggy-backed on it) or the
623 * remote side already has done a half-close and won't send
624 * more data. Skip this if the connection is in T/TCP
627 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) &&
628 !(tp->t_flags & TF_DELACK) &&
629 !TCPS_HAVERCVDFIN(tp->t_state)) {
631 * "adv" is the amount we could increase the window,
632 * taking into account that we are limited by
633 * TCP_MAXWIN << tp->rcv_scale.
638 adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale);
639 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) {
640 oldwin = (tp->rcv_adv - tp->rcv_nxt);
646 * If the new window size ends up being the same as the old
647 * size when it is scaled, then don't force a window update.
649 if (oldwin >> tp->rcv_scale == (adv + oldwin) >> tp->rcv_scale)
652 if (adv >= (long)(2 * tp->t_maxseg) &&
653 (adv >= (long)(so->so_rcv.sb_hiwat / 4) ||
654 recwin <= (long)(so->so_rcv.sb_hiwat / 8) ||
655 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg))
661 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW
662 * is also a catch-all for the retransmit timer timeout case.
664 if (tp->t_flags & TF_ACKNOW)
666 if ((flags & TH_RST) ||
667 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0))
669 if (SEQ_GT(tp->snd_up, tp->snd_una))
672 * If our state indicates that FIN should be sent
673 * and we have not yet done so, then we need to send.
675 if (flags & TH_FIN &&
676 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una))
679 * In SACK, it is possible for tcp_output to fail to send a segment
680 * after the retransmission timer has been turned off. Make sure
681 * that the retransmission timer is set.
683 if ((tp->t_flags & TF_SACK_PERMIT) &&
684 SEQ_GT(tp->snd_max, tp->snd_una) &&
685 !tcp_timer_active(tp, TT_REXMT) &&
686 !tcp_timer_active(tp, TT_PERSIST)) {
687 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
691 * TCP window updates are not reliable, rather a polling protocol
692 * using ``persist'' packets is used to insure receipt of window
693 * updates. The three ``states'' for the output side are:
694 * idle not doing retransmits or persists
695 * persisting to move a small or zero window
696 * (re)transmitting and thereby not persisting
698 * tcp_timer_active(tp, TT_PERSIST)
699 * is true when we are in persist state.
700 * (tp->t_flags & TF_FORCEDATA)
701 * is set when we are called to send a persist packet.
702 * tcp_timer_active(tp, TT_REXMT)
703 * is set when we are retransmitting
704 * The output side is idle when both timers are zero.
706 * If send window is too small, there is data to transmit, and no
707 * retransmit or persist is pending, then go to persist state.
708 * If nothing happens soon, send when timer expires:
709 * if window is nonzero, transmit what we can,
710 * otherwise force out a byte.
712 if (sbavail(&so->so_snd) && !tcp_timer_active(tp, TT_REXMT) &&
713 !tcp_timer_active(tp, TT_PERSIST)) {
719 * No reason to send a segment, just return.
722 SOCKBUF_UNLOCK(&so->so_snd);
726 SOCKBUF_LOCK_ASSERT(&so->so_snd);
728 if (len >= tp->t_maxseg)
729 tp->t_flags2 |= TF2_PLPMTU_MAXSEGSNT;
731 tp->t_flags2 &= ~TF2_PLPMTU_MAXSEGSNT;
734 * Before ESTABLISHED, force sending of initial options
735 * unless TCP set not to do any options.
736 * NOTE: we assume that the IP/TCP header plus TCP options
737 * always fit in a single mbuf, leaving room for a maximum
739 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES
744 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr);
747 hdrlen = sizeof (struct tcpiphdr);
750 * Compute options for segment.
751 * We only have to care about SYN and established connection
752 * segments. Options for SYN-ACK segments are handled in TCP
756 if ((tp->t_flags & TF_NOOPT) == 0) {
757 /* Maximum segment size. */
758 if (flags & TH_SYN) {
759 tp->snd_nxt = tp->iss;
760 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc);
761 to.to_flags |= TOF_MSS;
764 * Only include the TFO option on the first
765 * transmission of the SYN|ACK on a
766 * passively-created TFO socket, as the presence of
767 * the TFO option may have caused the original
768 * SYN|ACK to have been dropped by a middlebox.
770 if ((tp->t_flags & TF_FASTOPEN) &&
771 (tp->t_state == TCPS_SYN_RECEIVED) &&
772 (tp->t_rxtshift == 0)) {
773 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN;
774 to.to_tfo_cookie = (u_char *)&tp->t_tfo_cookie;
775 to.to_flags |= TOF_FASTOPEN;
779 /* Window scaling. */
780 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) {
781 to.to_wscale = tp->request_r_scale;
782 to.to_flags |= TOF_SCALE;
785 if ((tp->t_flags & TF_RCVD_TSTMP) ||
786 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) {
787 to.to_tsval = tcp_ts_getticks() + tp->ts_offset;
788 to.to_tsecr = tp->ts_recent;
789 to.to_flags |= TOF_TS;
790 /* Set receive buffer autosizing timestamp. */
791 if (tp->rfbuf_ts == 0 &&
792 (so->so_rcv.sb_flags & SB_AUTOSIZE))
793 tp->rfbuf_ts = tcp_ts_getticks();
795 /* Selective ACK's. */
796 if (tp->t_flags & TF_SACK_PERMIT) {
798 to.to_flags |= TOF_SACKPERM;
799 else if (TCPS_HAVEESTABLISHED(tp->t_state) &&
800 (tp->t_flags & TF_SACK_PERMIT) &&
801 tp->rcv_numsacks > 0) {
802 to.to_flags |= TOF_SACK;
803 to.to_nsacks = tp->rcv_numsacks;
804 to.to_sacks = (u_char *)tp->sackblks;
808 /* TCP-MD5 (RFC2385). */
809 if (tp->t_flags & TF_SIGNATURE)
810 to.to_flags |= TOF_SIGNATURE;
811 #endif /* TCP_SIGNATURE */
813 /* Processing the options. */
814 hdrlen += optlen = tcp_addoptions(&to, opt);
819 ipoptlen = ip6_optlen(tp->t_inpcb);
822 if (tp->t_inpcb->inp_options)
823 ipoptlen = tp->t_inpcb->inp_options->m_len -
824 offsetof(struct ipoption, ipopt_list);
828 ipoptlen += ipsec_optlen;
832 * Adjust data length if insertion of options will
833 * bump the packet length beyond the t_maxseg length.
834 * Clear the FIN bit because we cut off the tail of
837 if (len + optlen + ipoptlen > tp->t_maxseg) {
842 u_int if_hw_tsomaxsegcount;
843 u_int if_hw_tsomaxsegsize;
848 /* extract TSO information */
849 if_hw_tsomax = tp->t_tsomax;
850 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount;
851 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize;
854 * Limit a TSO burst to prevent it from
855 * overflowing or exceeding the maximum length
856 * allowed by the network interface:
858 KASSERT(ipoptlen == 0,
859 ("%s: TSO can't do IP options", __func__));
862 * Check if we should limit by maximum payload
865 if (if_hw_tsomax != 0) {
866 /* compute maximum TSO length */
867 max_len = (if_hw_tsomax - hdrlen -
871 } else if (len > max_len) {
878 * Check if we should limit by maximum segment
881 if (if_hw_tsomaxsegcount != 0 &&
882 if_hw_tsomaxsegsize != 0) {
884 * Subtract one segment for the LINK
885 * and TCP/IP headers mbuf that will
886 * be prepended to this mbuf chain
887 * after the code in this section
888 * limits the number of mbufs in the
889 * chain to if_hw_tsomaxsegcount.
891 if_hw_tsomaxsegcount -= 1;
893 mb = sbsndmbuf(&so->so_snd, off, &moff);
895 while (mb != NULL && max_len < len) {
900 * Get length of mbuf fragment
901 * and how many hardware frags,
902 * rounded up, it would use:
904 mlen = (mb->m_len - moff);
905 frags = howmany(mlen,
906 if_hw_tsomaxsegsize);
908 /* Handle special case: Zero Length Mbuf */
913 * Check if the fragment limit
914 * will be reached or exceeded:
916 if (frags >= if_hw_tsomaxsegcount) {
918 if_hw_tsomaxsegcount *
919 if_hw_tsomaxsegsize);
923 if_hw_tsomaxsegcount -= frags;
929 } else if (len > max_len) {
936 * Prevent the last segment from being
937 * fractional unless the send sockbuf can be
940 max_len = (tp->t_maxseg - optlen);
941 if ((off + len) < sbavail(&so->so_snd)) {
942 moff = len % max_len;
950 * In case there are too many small fragments
953 if (len <= max_len) {
960 * Send the FIN in a separate segment
961 * after the bulk sending is done.
962 * We don't trust the TSO implementations
963 * to clear the FIN flag on all but the
966 if (tp->t_flags & TF_NEEDFIN)
970 len = tp->t_maxseg - optlen - ipoptlen;
976 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET,
977 ("%s: len > IP_MAXPACKET", __func__));
979 /*#ifdef DIAGNOSTIC*/
981 if (max_linkhdr + hdrlen > MCLBYTES)
983 if (max_linkhdr + hdrlen > MHLEN)
985 panic("tcphdr too big");
989 * This KASSERT is here to catch edge cases at a well defined place.
990 * Before, those had triggered (random) panic conditions further down.
992 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__));
995 * Grab a header mbuf, attaching a copy of data to
996 * be transmitted, and initialize the header from
997 * the template for sends on this connection.
1003 if ((tp->t_flags & TF_FORCEDATA) && len == 1)
1004 TCPSTAT_INC(tcps_sndprobe);
1005 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) {
1006 tp->t_sndrexmitpack++;
1007 TCPSTAT_INC(tcps_sndrexmitpack);
1008 TCPSTAT_ADD(tcps_sndrexmitbyte, len);
1010 TCPSTAT_INC(tcps_sndpack);
1011 TCPSTAT_ADD(tcps_sndbyte, len);
1014 if (MHLEN < hdrlen + max_linkhdr)
1015 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR);
1018 m = m_gethdr(M_NOWAIT, MT_DATA);
1021 SOCKBUF_UNLOCK(&so->so_snd);
1027 m->m_data += max_linkhdr;
1031 * Start the m_copy functions from the closest mbuf
1032 * to the offset in the socket buffer chain.
1034 mb = sbsndptr(&so->so_snd, off, len, &moff);
1036 if (len <= MHLEN - hdrlen - max_linkhdr) {
1037 m_copydata(mb, moff, (int)len,
1038 mtod(m, caddr_t) + hdrlen);
1041 m->m_next = m_copy(mb, moff, (int)len);
1042 if (m->m_next == NULL) {
1043 SOCKBUF_UNLOCK(&so->so_snd);
1052 * If we're sending everything we've got, set PUSH.
1053 * (This will keep happy those implementations which only
1054 * give data to the user when a buffer fills or
1057 if ((off + len == sbused(&so->so_snd)) && !(flags & TH_SYN))
1059 SOCKBUF_UNLOCK(&so->so_snd);
1061 SOCKBUF_UNLOCK(&so->so_snd);
1062 if (tp->t_flags & TF_ACKNOW)
1063 TCPSTAT_INC(tcps_sndacks);
1064 else if (flags & (TH_SYN|TH_FIN|TH_RST))
1065 TCPSTAT_INC(tcps_sndctrl);
1066 else if (SEQ_GT(tp->snd_up, tp->snd_una))
1067 TCPSTAT_INC(tcps_sndurg);
1069 TCPSTAT_INC(tcps_sndwinup);
1071 m = m_gethdr(M_NOWAIT, MT_DATA);
1078 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) &&
1083 m->m_data += max_linkhdr;
1086 SOCKBUF_UNLOCK_ASSERT(&so->so_snd);
1087 m->m_pkthdr.rcvif = (struct ifnet *)0;
1089 mac_inpcb_create_mbuf(tp->t_inpcb, m);
1093 ip6 = mtod(m, struct ip6_hdr *);
1094 th = (struct tcphdr *)(ip6 + 1);
1095 tcpip_fillheaders(tp->t_inpcb, ip6, th);
1099 ip = mtod(m, struct ip *);
1100 ipov = (struct ipovly *)ip;
1101 th = (struct tcphdr *)(ip + 1);
1102 tcpip_fillheaders(tp->t_inpcb, ip, th);
1106 * Fill in fields, remembering maximum advertised
1107 * window for use in delaying messages about window sizes.
1108 * If resending a FIN, be sure not to use a new sequence number.
1110 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN &&
1111 tp->snd_nxt == tp->snd_max)
1114 * If we are starting a connection, send ECN setup
1115 * SYN packet. If we are on a retransmit, we may
1116 * resend those bits a number of times as per
1119 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) {
1120 if (tp->t_rxtshift >= 1) {
1121 if (tp->t_rxtshift <= V_tcp_ecn_maxretries)
1122 flags |= TH_ECE|TH_CWR;
1124 flags |= TH_ECE|TH_CWR;
1127 if (tp->t_state == TCPS_ESTABLISHED &&
1128 (tp->t_flags & TF_ECN_PERMIT)) {
1130 * If the peer has ECN, mark data packets with
1131 * ECN capable transmission (ECT).
1132 * Ignore pure ack packets, retransmissions and window probes.
1134 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) &&
1135 !((tp->t_flags & TF_FORCEDATA) && len == 1)) {
1138 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20);
1141 ip->ip_tos |= IPTOS_ECN_ECT0;
1142 TCPSTAT_INC(tcps_ecn_ect0);
1146 * Reply with proper ECN notifications.
1148 if (tp->t_flags & TF_ECN_SND_CWR) {
1150 tp->t_flags &= ~TF_ECN_SND_CWR;
1152 if (tp->t_flags & TF_ECN_SND_ECE)
1157 * If we are doing retransmissions, then snd_nxt will
1158 * not reflect the first unsent octet. For ACK only
1159 * packets, we do not want the sequence number of the
1160 * retransmitted packet, we want the sequence number
1161 * of the next unsent octet. So, if there is no data
1162 * (and no SYN or FIN), use snd_max instead of snd_nxt
1163 * when filling in ti_seq. But if we are in persist
1164 * state, snd_max might reflect one byte beyond the
1165 * right edge of the window, so use snd_nxt in that
1166 * case, since we know we aren't doing a retransmission.
1167 * (retransmit and persist are mutually exclusive...)
1169 if (sack_rxmit == 0) {
1170 if (len || (flags & (TH_SYN|TH_FIN)) ||
1171 tcp_timer_active(tp, TT_PERSIST))
1172 th->th_seq = htonl(tp->snd_nxt);
1174 th->th_seq = htonl(tp->snd_max);
1176 th->th_seq = htonl(p->rxmit);
1178 tp->sackhint.sack_bytes_rexmit += len;
1180 th->th_ack = htonl(tp->rcv_nxt);
1182 bcopy(opt, th + 1, optlen);
1183 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2;
1185 th->th_flags = flags;
1187 * Calculate receive window. Don't shrink window,
1188 * but avoid silly window syndrome.
1190 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) &&
1191 recwin < (long)tp->t_maxseg)
1193 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) &&
1194 recwin < (long)(tp->rcv_adv - tp->rcv_nxt))
1195 recwin = (long)(tp->rcv_adv - tp->rcv_nxt);
1196 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale)
1197 recwin = (long)TCP_MAXWIN << tp->rcv_scale;
1200 * According to RFC1323 the window field in a SYN (i.e., a <SYN>
1201 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK>
1202 * case is handled in syncache.
1205 th->th_win = htons((u_short)
1206 (min(sbspace(&so->so_rcv), TCP_MAXWIN)));
1208 th->th_win = htons((u_short)(recwin >> tp->rcv_scale));
1211 * Adjust the RXWIN0SENT flag - indicate that we have advertised
1212 * a 0 window. This may cause the remote transmitter to stall. This
1213 * flag tells soreceive() to disable delayed acknowledgements when
1214 * draining the buffer. This can occur if the receiver is attempting
1215 * to read more data than can be buffered prior to transmitting on
1218 if (th->th_win == 0) {
1220 tp->t_flags |= TF_RXWIN0SENT;
1222 tp->t_flags &= ~TF_RXWIN0SENT;
1223 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) {
1224 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt));
1225 th->th_flags |= TH_URG;
1228 * If no urgent pointer to send, then we pull
1229 * the urgent pointer to the left edge of the send window
1230 * so that it doesn't drift into the send window on sequence
1231 * number wraparound.
1233 tp->snd_up = tp->snd_una; /* drag it along */
1235 #ifdef TCP_SIGNATURE
1236 if (to.to_flags & TOF_SIGNATURE) {
1237 int sigoff = to.to_signature - opt;
1238 tcp_signature_compute(m, 0, len, optlen,
1239 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND);
1244 * Put TCP length in extended header, and then
1245 * checksum extended header and data.
1247 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */
1248 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1252 * ip6_plen is not need to be filled now, and will be filled
1255 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
1256 th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) +
1257 optlen + len, IPPROTO_TCP, 0);
1260 #if defined(INET6) && defined(INET)
1265 m->m_pkthdr.csum_flags = CSUM_TCP;
1266 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
1267 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen));
1269 /* IP version must be set here for ipv4/ipv6 checking later */
1270 KASSERT(ip->ip_v == IPVERSION,
1271 ("%s: IP version incorrect: %d", __func__, ip->ip_v));
1276 * Enable TSO and specify the size of the segments.
1277 * The TCP pseudo header checksum is always provided.
1280 KASSERT(len > tp->t_maxseg - optlen,
1281 ("%s: len <= tso_segsz", __func__));
1282 m->m_pkthdr.csum_flags |= CSUM_TSO;
1283 m->m_pkthdr.tso_segsz = tp->t_maxseg - optlen;
1287 KASSERT(len + hdrlen + ipoptlen - ipsec_optlen == m_length(m, NULL),
1288 ("%s: mbuf chain shorter than expected: %ld + %u + %u - %u != %u",
1289 __func__, len, hdrlen, ipoptlen, ipsec_optlen, m_length(m, NULL)));
1291 KASSERT(len + hdrlen + ipoptlen == m_length(m, NULL),
1292 ("%s: mbuf chain shorter than expected: %ld + %u + %u != %u",
1293 __func__, len, hdrlen, ipoptlen, m_length(m, NULL)));
1296 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */
1297 hhook_run_tcp_est_out(tp, th, &to, len, tso);
1303 if (so->so_options & SO_DEBUG) {
1309 save = ipov->ih_len;
1310 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */);
1312 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0);
1316 ipov->ih_len = save;
1318 #endif /* TCPDEBUG */
1319 TCP_PROBE3(debug__input, tp, th, mtod(m, const char *));
1322 * Fill in IP length and desired time to live and
1323 * send to IP level. There should be a better way
1324 * to handle ttl and tos; we could keep them in
1325 * the template, but need a way to checksum without them.
1328 * m->m_pkthdr.len should have been set before checksum calculation,
1329 * because in6_cksum() need it.
1333 struct route_in6 ro;
1335 bzero(&ro, sizeof(ro));
1337 * we separately set hoplimit for every segment, since the
1338 * user might want to change the value via setsockopt.
1339 * Also, desired default hop limit might be changed via
1340 * Neighbor Discovery.
1342 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL);
1345 * Set the packet size here for the benefit of DTrace probes.
1346 * ip6_output() will set it properly; it's supposed to include
1347 * the option header lengths as well.
1349 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6));
1351 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss)
1352 tp->t_flags2 |= TF2_PLPMTU_PMTUD;
1354 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
1356 if (tp->t_state == TCPS_SYN_SENT)
1357 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th);
1359 TCP_PROBE5(send, NULL, tp, ip6, tp, th);
1362 /* Save packet, if requested. */
1363 tcp_pcap_add(th, m, &(tp->t_outpkts));
1366 /* TODO: IPv6 IP6TOS_ECT bit on */
1367 error = ip6_output(m, tp->t_inpcb->in6p_outputopts, &ro,
1368 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0),
1369 NULL, NULL, tp->t_inpcb);
1371 if (error == EMSGSIZE && ro.ro_rt != NULL)
1372 mtu = ro.ro_rt->rt_mtu;
1376 #if defined(INET) && defined(INET6)
1383 bzero(&ro, sizeof(ro));
1384 ip->ip_len = htons(m->m_pkthdr.len);
1386 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO)
1387 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL);
1390 * If we do path MTU discovery, then we set DF on every packet.
1391 * This might not be the best thing to do according to RFC3390
1392 * Section 2. However the tcp hostcache migitates the problem
1393 * so it affects only the first tcp connection with a host.
1395 * NB: Don't set DF on small MTU/MSS to have a safe fallback.
1397 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) {
1398 ip->ip_off |= htons(IP_DF);
1399 tp->t_flags2 |= TF2_PLPMTU_PMTUD;
1401 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
1404 if (tp->t_state == TCPS_SYN_SENT)
1405 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th);
1407 TCP_PROBE5(send, NULL, tp, ip, tp, th);
1410 /* Save packet, if requested. */
1411 tcp_pcap_add(th, m, &(tp->t_outpkts));
1414 error = ip_output(m, tp->t_inpcb->inp_options, &ro,
1415 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0,
1418 if (error == EMSGSIZE && ro.ro_rt != NULL)
1419 mtu = ro.ro_rt->rt_mtu;
1426 * In transmit state, time the transmission and arrange for
1427 * the retransmit. In persist state, just set snd_max.
1429 if ((tp->t_flags & TF_FORCEDATA) == 0 ||
1430 !tcp_timer_active(tp, TT_PERSIST)) {
1431 tcp_seq startseq = tp->snd_nxt;
1434 * Advance snd_nxt over sequence space of this segment.
1436 if (flags & (TH_SYN|TH_FIN)) {
1439 if (flags & TH_FIN) {
1441 tp->t_flags |= TF_SENTFIN;
1447 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) {
1448 tp->snd_max = tp->snd_nxt;
1450 * Time this transmission if not a retransmission and
1451 * not currently timing anything.
1453 if (tp->t_rtttime == 0) {
1454 tp->t_rtttime = ticks;
1455 tp->t_rtseq = startseq;
1456 TCPSTAT_INC(tcps_segstimed);
1461 * Set retransmit timer if not currently set,
1462 * and not doing a pure ack or a keep-alive probe.
1463 * Initial value for retransmit timer is smoothed
1464 * round-trip time + 2 * round-trip time variance.
1465 * Initialize shift counter which is used for backoff
1466 * of retransmit time.
1469 if (!tcp_timer_active(tp, TT_REXMT) &&
1470 ((sack_rxmit && tp->snd_nxt != tp->snd_max) ||
1471 (tp->snd_nxt != tp->snd_una))) {
1472 if (tcp_timer_active(tp, TT_PERSIST)) {
1473 tcp_timer_activate(tp, TT_PERSIST, 0);
1476 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
1477 } else if (len == 0 && sbavail(&so->so_snd) &&
1478 !tcp_timer_active(tp, TT_REXMT) &&
1479 !tcp_timer_active(tp, TT_PERSIST)) {
1481 * Avoid a situation where we do not set persist timer
1482 * after a zero window condition. For example:
1483 * 1) A -> B: packet with enough data to fill the window
1484 * 2) B -> A: ACK for #1 + new data (0 window
1486 * 3) A -> B: ACK for #2, 0 len packet
1488 * In this case, A will not activate the persist timer,
1489 * because it chose to send a packet. Unless tcp_output
1490 * is called for some other reason (delayed ack timer,
1491 * another input packet from B, socket syscall), A will
1492 * not send zero window probes.
1494 * So, if you send a 0-length packet, but there is data
1495 * in the socket buffer, and neither the rexmt or
1496 * persist timer is already set, then activate the
1504 * Persist case, update snd_max but since we are in
1505 * persist mode (no window) we do not update snd_nxt.
1510 if (flags & TH_FIN) {
1512 tp->t_flags |= TF_SENTFIN;
1514 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max))
1515 tp->snd_max = tp->snd_nxt + len;
1521 * We know that the packet was lost, so back out the
1522 * sequence number advance, if any.
1524 * If the error is EPERM the packet got blocked by the
1525 * local firewall. Normally we should terminate the
1526 * connection but the blocking may have been spurious
1527 * due to a firewall reconfiguration cycle. So we treat
1528 * it like a packet loss and let the retransmit timer and
1529 * timeouts do their work over time.
1530 * XXX: It is a POLA question whether calling tcp_drop right
1531 * away would be the really correct behavior instead.
1533 if (((tp->t_flags & TF_FORCEDATA) == 0 ||
1534 !tcp_timer_active(tp, TT_PERSIST)) &&
1535 ((flags & TH_SYN) == 0) &&
1539 tp->sackhint.sack_bytes_rexmit -= len;
1540 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0,
1541 ("sackhint bytes rtx >= 0"));
1545 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */
1548 tp->t_softerror = error;
1551 if (!tcp_timer_active(tp, TT_REXMT) &&
1552 !tcp_timer_active(tp, TT_PERSIST))
1553 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
1554 tp->snd_cwnd = tp->t_maxseg;
1558 * For some reason the interface we used initially
1559 * to send segments changed to another or lowered
1561 * If TSO was active we either got an interface
1562 * without TSO capabilits or TSO was turned off.
1563 * If we obtained mtu from ip_output() then update
1567 tp->t_flags &= ~TF_TSO;
1569 tcp_mss_update(tp, -1, mtu, NULL, NULL);
1577 if (TCPS_HAVERCVDSYN(tp->t_state)) {
1578 tp->t_softerror = error;
1586 TCPSTAT_INC(tcps_sndtotal);
1589 * Data sent (as far as we can tell).
1590 * If this advertises a larger window than any other segment,
1591 * then remember the size of the advertised window.
1592 * Any pending ACK has now been sent.
1594 if (recwin >= 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv))
1595 tp->rcv_adv = tp->rcv_nxt + recwin;
1596 tp->last_ack_sent = tp->rcv_nxt;
1597 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK);
1598 if (tcp_timer_active(tp, TT_DELACK))
1599 tcp_timer_activate(tp, TT_DELACK, 0);
1602 * This completely breaks TCP if newreno is turned on. What happens
1603 * is that if delayed-acks are turned on on the receiver, this code
1604 * on the transmitter effectively destroys the TCP window, forcing
1605 * it to four packets (1.5Kx4 = 6K window).
1607 if (sendalot && --maxburst)
1616 tcp_setpersist(struct tcpcb *tp)
1618 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1;
1621 tp->t_flags &= ~TF_PREVVALID;
1622 if (tcp_timer_active(tp, TT_REXMT))
1623 panic("tcp_setpersist: retransmit pending");
1625 * Start/restart persistance timer.
1627 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift],
1628 TCPTV_PERSMIN, TCPTV_PERSMAX);
1629 tcp_timer_activate(tp, TT_PERSIST, tt);
1630 if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
1635 * Insert TCP options according to the supplied parameters to the place
1636 * optp in a consistent way. Can handle unaligned destinations.
1638 * The order of the option processing is crucial for optimal packing and
1639 * alignment for the scarce option space.
1641 * The optimal order for a SYN/SYN-ACK segment is:
1642 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) +
1643 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40.
1645 * The SACK options should be last. SACK blocks consume 8*n+2 bytes.
1646 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks).
1647 * At minimum we need 10 bytes (to generate 1 SACK block). If both
1648 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present,
1649 * we only have 10 bytes for SACK options (40 - (12 + 18)).
1652 tcp_addoptions(struct tcpopt *to, u_char *optp)
1654 u_int mask, optlen = 0;
1656 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) {
1657 if ((to->to_flags & mask) != mask)
1659 if (optlen == TCP_MAXOLEN)
1661 switch (to->to_flags & mask) {
1663 while (optlen % 4) {
1664 optlen += TCPOLEN_NOP;
1665 *optp++ = TCPOPT_NOP;
1667 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG)
1669 optlen += TCPOLEN_MAXSEG;
1670 *optp++ = TCPOPT_MAXSEG;
1671 *optp++ = TCPOLEN_MAXSEG;
1672 to->to_mss = htons(to->to_mss);
1673 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss));
1674 optp += sizeof(to->to_mss);
1677 while (!optlen || optlen % 2 != 1) {
1678 optlen += TCPOLEN_NOP;
1679 *optp++ = TCPOPT_NOP;
1681 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW)
1683 optlen += TCPOLEN_WINDOW;
1684 *optp++ = TCPOPT_WINDOW;
1685 *optp++ = TCPOLEN_WINDOW;
1686 *optp++ = to->to_wscale;
1689 while (optlen % 2) {
1690 optlen += TCPOLEN_NOP;
1691 *optp++ = TCPOPT_NOP;
1693 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED)
1695 optlen += TCPOLEN_SACK_PERMITTED;
1696 *optp++ = TCPOPT_SACK_PERMITTED;
1697 *optp++ = TCPOLEN_SACK_PERMITTED;
1700 while (!optlen || optlen % 4 != 2) {
1701 optlen += TCPOLEN_NOP;
1702 *optp++ = TCPOPT_NOP;
1704 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP)
1706 optlen += TCPOLEN_TIMESTAMP;
1707 *optp++ = TCPOPT_TIMESTAMP;
1708 *optp++ = TCPOLEN_TIMESTAMP;
1709 to->to_tsval = htonl(to->to_tsval);
1710 to->to_tsecr = htonl(to->to_tsecr);
1711 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval));
1712 optp += sizeof(to->to_tsval);
1713 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr));
1714 optp += sizeof(to->to_tsecr);
1716 #ifdef TCP_SIGNATURE
1719 int siglen = TCPOLEN_SIGNATURE - 2;
1721 while (!optlen || optlen % 4 != 2) {
1722 optlen += TCPOLEN_NOP;
1723 *optp++ = TCPOPT_NOP;
1725 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE)
1727 optlen += TCPOLEN_SIGNATURE;
1728 *optp++ = TCPOPT_SIGNATURE;
1729 *optp++ = TCPOLEN_SIGNATURE;
1730 to->to_signature = optp;
1739 struct sackblk *sack = (struct sackblk *)to->to_sacks;
1742 while (!optlen || optlen % 4 != 2) {
1743 optlen += TCPOLEN_NOP;
1744 *optp++ = TCPOPT_NOP;
1746 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK)
1748 optlen += TCPOLEN_SACKHDR;
1749 *optp++ = TCPOPT_SACK;
1750 sackblks = min(to->to_nsacks,
1751 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK);
1752 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK;
1753 while (sackblks--) {
1754 sack_seq = htonl(sack->start);
1755 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq));
1756 optp += sizeof(sack_seq);
1757 sack_seq = htonl(sack->end);
1758 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq));
1759 optp += sizeof(sack_seq);
1760 optlen += TCPOLEN_SACK;
1763 TCPSTAT_INC(tcps_sack_send_blocks);
1771 /* XXX is there any point to aligning this option? */
1772 total_len = TCPOLEN_FAST_OPEN_EMPTY + to->to_tfo_len;
1773 if (TCP_MAXOLEN - optlen < total_len)
1775 *optp++ = TCPOPT_FAST_OPEN;
1776 *optp++ = total_len;
1777 if (to->to_tfo_len > 0) {
1778 bcopy(to->to_tfo_cookie, optp, to->to_tfo_len);
1779 optp += to->to_tfo_len;
1781 optlen += total_len;
1786 panic("%s: unknown TCP option type", __func__);
1791 /* Terminate and pad TCP options to a 4 byte boundary. */
1793 optlen += TCPOLEN_EOL;
1794 *optp++ = TCPOPT_EOL;
1797 * According to RFC 793 (STD0007):
1798 * "The content of the header beyond the End-of-Option option
1799 * must be header padding (i.e., zero)."
1800 * and later: "The padding is composed of zeros."
1802 while (optlen % 4) {
1803 optlen += TCPOLEN_PAD;
1804 *optp++ = TCPOPT_PAD;
1807 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__));