2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
3 * The Regents of the University of California. All rights reserved.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 4. Neither the name of the University nor the names of its contributors
14 * may be used to endorse or promote products derived from this software
15 * without specific prior written permission.
17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95
32 #include <sys/cdefs.h>
33 __FBSDID("$FreeBSD$");
36 #include "opt_inet6.h"
37 #include "opt_ipsec.h"
38 #include "opt_kdtrace.h"
39 #include "opt_tcpdebug.h"
41 #include <sys/param.h>
42 #include <sys/systm.h>
43 #include <sys/domain.h>
44 #include <sys/hhook.h>
45 #include <sys/kernel.h>
48 #include <sys/mutex.h>
49 #include <sys/protosw.h>
51 #include <sys/socket.h>
52 #include <sys/socketvar.h>
53 #include <sys/sysctl.h>
56 #include <net/route.h>
59 #include <netinet/cc.h>
60 #include <netinet/in.h>
61 #include <netinet/in_kdtrace.h>
62 #include <netinet/in_systm.h>
63 #include <netinet/ip.h>
64 #include <netinet/in_pcb.h>
65 #include <netinet/ip_var.h>
66 #include <netinet/ip_options.h>
68 #include <netinet6/in6_pcb.h>
69 #include <netinet/ip6.h>
70 #include <netinet6/ip6_var.h>
73 #include <netinet/tcp_fsm.h>
74 #include <netinet/tcp_seq.h>
75 #include <netinet/tcp_timer.h>
76 #include <netinet/tcp_var.h>
77 #include <netinet/tcpip.h>
79 #include <netinet/tcp_debug.h>
82 #include <netinet/tcp_offload.h>
86 #include <netipsec/ipsec.h>
89 #include <machine/in_cksum.h>
91 #include <security/mac/mac_framework.h>
93 VNET_DEFINE(int, path_mtu_discovery) = 1;
94 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW,
95 &VNET_NAME(path_mtu_discovery), 1,
96 "Enable Path MTU Discovery");
98 VNET_DEFINE(int, tcp_do_tso) = 1;
99 #define V_tcp_do_tso VNET(tcp_do_tso)
100 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_RW,
101 &VNET_NAME(tcp_do_tso), 0,
102 "Enable TCP Segmentation Offload");
104 VNET_DEFINE(int, tcp_sendspace) = 1024*32;
105 #define V_tcp_sendspace VNET(tcp_sendspace)
106 SYSCTL_VNET_INT(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, CTLFLAG_RW,
107 &VNET_NAME(tcp_sendspace), 0, "Initial send socket buffer size");
109 VNET_DEFINE(int, tcp_do_autosndbuf) = 1;
110 #define V_tcp_do_autosndbuf VNET(tcp_do_autosndbuf)
111 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_RW,
112 &VNET_NAME(tcp_do_autosndbuf), 0,
113 "Enable automatic send buffer sizing");
115 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024;
116 #define V_tcp_autosndbuf_inc VNET(tcp_autosndbuf_inc)
117 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_RW,
118 &VNET_NAME(tcp_autosndbuf_inc), 0,
119 "Incrementor step size of automatic send buffer");
121 VNET_DEFINE(int, tcp_autosndbuf_max) = 2*1024*1024;
122 #define V_tcp_autosndbuf_max VNET(tcp_autosndbuf_max)
123 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_RW,
124 &VNET_NAME(tcp_autosndbuf_max), 0,
125 "Max size of automatic send buffer");
127 static void inline hhook_run_tcp_est_out(struct tcpcb *tp,
128 struct tcphdr *th, struct tcpopt *to,
130 static void inline cc_after_idle(struct tcpcb *tp);
133 * Wrapper for the TCP established output helper hook.
136 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th,
137 struct tcpopt *to, long len, int tso)
139 struct tcp_hhook_data hhook_data;
141 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) {
145 hhook_data.len = len;
146 hhook_data.tso = tso;
148 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data,
154 * CC wrapper hook functions
157 cc_after_idle(struct tcpcb *tp)
159 INP_WLOCK_ASSERT(tp->t_inpcb);
161 if (CC_ALGO(tp)->after_idle != NULL)
162 CC_ALGO(tp)->after_idle(tp->ccv);
166 * Tcp output routine: figure out what should be sent and send it.
169 tcp_output(struct tcpcb *tp)
171 struct socket *so = tp->t_inpcb->inp_socket;
172 long len, recwin, sendwin;
173 int off, flags, error = 0; /* Keep compiler happy */
175 struct ip *ip = NULL;
176 struct ipovly *ipov = NULL;
178 u_char opt[TCP_MAXOLEN];
179 unsigned ipoptlen, optlen, hdrlen;
181 unsigned ipsec_optlen = 0;
184 int sack_rxmit, sack_bytes_rxmt;
189 int maxburst = TCP_MAXBURST;
192 struct ip6_hdr *ip6 = NULL;
195 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0;
198 INP_WLOCK_ASSERT(tp->t_inpcb);
201 if (tp->t_flags & TF_TOE)
202 return (tcp_offload_output(tp));
206 * Determine length of data that should be transmitted,
207 * and flags that will be used.
208 * If there is some data or critical controls (SYN, RST)
209 * to send, then transmit; otherwise, investigate further.
211 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una);
212 if (idle && ticks - tp->t_rcvtime >= tp->t_rxtcur)
214 tp->t_flags &= ~TF_LASTIDLE;
216 if (tp->t_flags & TF_MORETOCOME) {
217 tp->t_flags |= TF_LASTIDLE;
223 * If we've recently taken a timeout, snd_max will be greater than
224 * snd_nxt. There may be SACK information that allows us to avoid
225 * resending already delivered data. Adjust snd_nxt accordingly.
227 if ((tp->t_flags & TF_SACK_PERMIT) &&
228 SEQ_LT(tp->snd_nxt, tp->snd_max))
233 off = tp->snd_nxt - tp->snd_una;
234 sendwin = min(tp->snd_wnd, tp->snd_cwnd);
236 flags = tcp_outflags[tp->t_state];
238 * Send any SACK-generated retransmissions. If we're explicitly trying
239 * to send out new data (when sendalot is 1), bypass this function.
240 * If we retransmit in fast recovery mode, decrement snd_cwnd, since
241 * we're replacing a (future) new transmission with a retransmission
242 * now, and we previously incremented snd_cwnd in tcp_input().
245 * Still in sack recovery , reset rxmit flag to zero.
251 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) &&
252 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) {
255 cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt;
258 /* Do not retransmit SACK segments beyond snd_recover */
259 if (SEQ_GT(p->end, tp->snd_recover)) {
261 * (At least) part of sack hole extends beyond
262 * snd_recover. Check to see if we can rexmit data
265 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) {
267 * Can't rexmit any more data for this hole.
268 * That data will be rexmitted in the next
269 * sack recovery episode, when snd_recover
270 * moves past p->rxmit.
273 goto after_sack_rexmit;
275 /* Can rexmit part of the current hole */
276 len = ((long)ulmin(cwin,
277 tp->snd_recover - p->rxmit));
279 len = ((long)ulmin(cwin, p->end - p->rxmit));
280 off = p->rxmit - tp->snd_una;
281 KASSERT(off >= 0,("%s: sack block to the left of una : %d",
286 TCPSTAT_INC(tcps_sack_rexmits);
287 TCPSTAT_ADD(tcps_sack_rexmit_bytes,
288 min(len, tp->t_maxseg));
293 * Get standard flags, and add SYN or FIN if requested by 'hidden'
296 if (tp->t_flags & TF_NEEDFIN)
298 if (tp->t_flags & TF_NEEDSYN)
301 SOCKBUF_LOCK(&so->so_snd);
303 * If in persist timeout with window of 0, send 1 byte.
304 * Otherwise, if window is small but nonzero
305 * and timer expired, we will send what we can
306 * and go to transmit state.
308 if (tp->t_flags & TF_FORCEDATA) {
311 * If we still have some data to send, then
312 * clear the FIN bit. Usually this would
313 * happen below when it realizes that we
314 * aren't sending all the data. However,
315 * if we have exactly 1 byte of unsent data,
316 * then it won't clear the FIN bit below,
317 * and if we are in persist state, we wind
318 * up sending the packet without recording
319 * that we sent the FIN bit.
321 * We can't just blindly clear the FIN bit,
322 * because if we don't have any more data
323 * to send then the probe will be the FIN
326 if (off < so->so_snd.sb_cc)
330 tcp_timer_activate(tp, TT_PERSIST, 0);
336 * If snd_nxt == snd_max and we have transmitted a FIN, the
337 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in
338 * a negative length. This can also occur when TCP opens up
339 * its congestion window while receiving additional duplicate
340 * acks after fast-retransmit because TCP will reset snd_nxt
341 * to snd_max after the fast-retransmit.
343 * In the normal retransmit-FIN-only case, however, snd_nxt will
344 * be set to snd_una, the offset will be 0, and the length may
347 * If sack_rxmit is true we are retransmitting from the scoreboard
348 * in which case len is already set.
350 if (sack_rxmit == 0) {
351 if (sack_bytes_rxmt == 0)
352 len = ((long)ulmin(so->so_snd.sb_cc, sendwin) - off);
357 * We are inside of a SACK recovery episode and are
358 * sending new data, having retransmitted all the
359 * data possible in the scoreboard.
361 len = ((long)ulmin(so->so_snd.sb_cc, tp->snd_wnd)
364 * Don't remove this (len > 0) check !
365 * We explicitly check for len > 0 here (although it
366 * isn't really necessary), to work around a gcc
367 * optimization issue - to force gcc to compute
368 * len above. Without this check, the computation
369 * of len is bungled by the optimizer.
372 cwin = tp->snd_cwnd -
373 (tp->snd_nxt - tp->sack_newdata) -
377 len = lmin(len, cwin);
383 * Lop off SYN bit if it has already been sent. However, if this
384 * is SYN-SENT state and if segment contains data and if we don't
385 * know that foreign host supports TAO, suppress sending segment.
387 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) {
388 if (tp->t_state != TCPS_SYN_RECEIVED)
394 * Be careful not to send data and/or FIN on SYN segments.
395 * This measure is needed to prevent interoperability problems
396 * with not fully conformant TCP implementations.
398 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) {
405 * If FIN has been sent but not acked,
406 * but we haven't been called to retransmit,
407 * len will be < 0. Otherwise, window shrank
408 * after we sent into it. If window shrank to 0,
409 * cancel pending retransmit, pull snd_nxt back
410 * to (closed) window, and set the persist timer
411 * if it isn't already going. If the window didn't
412 * close completely, just wait for an ACK.
416 tcp_timer_activate(tp, TT_REXMT, 0);
418 tp->snd_nxt = tp->snd_una;
419 if (!tcp_timer_active(tp, TT_PERSIST))
424 /* len will be >= 0 after this point. */
425 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__));
428 * Automatic sizing of send socket buffer. Often the send buffer
429 * size is not optimally adjusted to the actual network conditions
430 * at hand (delay bandwidth product). Setting the buffer size too
431 * small limits throughput on links with high bandwidth and high
432 * delay (eg. trans-continental/oceanic links). Setting the
433 * buffer size too big consumes too much real kernel memory,
434 * especially with many connections on busy servers.
436 * The criteria to step up the send buffer one notch are:
437 * 1. receive window of remote host is larger than send buffer
438 * (with a fudge factor of 5/4th);
439 * 2. send buffer is filled to 7/8th with data (so we actually
440 * have data to make use of it);
441 * 3. send buffer fill has not hit maximal automatic size;
442 * 4. our send window (slow start and cogestion controlled) is
443 * larger than sent but unacknowledged data in send buffer.
445 * The remote host receive window scaling factor may limit the
446 * growing of the send buffer before it reaches its allowed
449 * It scales directly with slow start or congestion window
450 * and does at most one step per received ACK. This fast
451 * scaling has the drawback of growing the send buffer beyond
452 * what is strictly necessary to make full use of a given
453 * delay*bandwith product. However testing has shown this not
454 * to be much of an problem. At worst we are trading wasting
455 * of available bandwith (the non-use of it) for wasting some
456 * socket buffer memory.
458 * TODO: Shrink send buffer during idle periods together
459 * with congestion window. Requires another timer. Has to
460 * wait for upcoming tcp timer rewrite.
462 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) {
463 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat &&
464 so->so_snd.sb_cc >= (so->so_snd.sb_hiwat / 8 * 7) &&
465 so->so_snd.sb_cc < V_tcp_autosndbuf_max &&
466 sendwin >= (so->so_snd.sb_cc - (tp->snd_nxt - tp->snd_una))) {
467 if (!sbreserve_locked(&so->so_snd,
468 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc,
469 V_tcp_autosndbuf_max), so, curthread))
470 so->so_snd.sb_flags &= ~SB_AUTOSIZE;
475 * Decide if we can use TCP Segmentation Offloading (if supported by
478 * TSO may only be used if we are in a pure bulk sending state. The
479 * presence of TCP-MD5, SACK retransmits, SACK advertizements and
480 * IP options prevent using TSO. With TSO the TCP header is the same
481 * (except for the sequence number) for all generated packets. This
482 * makes it impossible to transmit any options which vary per generated
487 * Pre-calculate here as we save another lookup into the darknesses
488 * of IPsec that way and can actually decide if TSO is ok.
490 ipsec_optlen = ipsec_hdrsiz_tcp(tp);
492 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg &&
493 ((tp->t_flags & TF_SIGNATURE) == 0) &&
494 tp->rcv_numsacks == 0 && sack_rxmit == 0 &&
498 tp->t_inpcb->inp_options == NULL &&
499 tp->t_inpcb->in6p_options == NULL)
503 if (SEQ_LT(p->rxmit + len, tp->snd_una + so->so_snd.sb_cc))
506 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc))
510 recwin = sbspace(&so->so_rcv);
513 * Sender silly window avoidance. We transmit under the following
514 * conditions when len is non-zero:
516 * - We have a full segment (or more with TSO)
517 * - This is the last buffer in a write()/send() and we are
518 * either idle or running NODELAY
519 * - we've timed out (e.g. persist timer)
520 * - we have more then 1/2 the maximum send window's worth of
521 * data (receiver may be limited the window size)
522 * - we need to retransmit
525 if (len >= tp->t_maxseg)
528 * NOTE! on localhost connections an 'ack' from the remote
529 * end may occur synchronously with the output and cause
530 * us to flush a buffer queued with moretocome. XXX
532 * note: the len + off check is almost certainly unnecessary.
534 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */
535 (idle || (tp->t_flags & TF_NODELAY)) &&
536 len + off >= so->so_snd.sb_cc &&
537 (tp->t_flags & TF_NOPUSH) == 0) {
540 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */
542 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0)
544 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */
551 * Sending of standalone window updates.
553 * Window updates are important when we close our window due to a
554 * full socket buffer and are opening it again after the application
555 * reads data from it. Once the window has opened again and the
556 * remote end starts to send again the ACK clock takes over and
557 * provides the most current window information.
559 * We must avoid the silly window syndrome whereas every read
560 * from the receive buffer, no matter how small, causes a window
561 * update to be sent. We also should avoid sending a flurry of
562 * window updates when the socket buffer had queued a lot of data
563 * and the application is doing small reads.
565 * Prevent a flurry of pointless window updates by only sending
566 * an update when we can increase the advertized window by more
567 * than 1/4th of the socket buffer capacity. When the buffer is
568 * getting full or is very small be more aggressive and send an
569 * update whenever we can increase by two mss sized segments.
570 * In all other situations the ACK's to new incoming data will
571 * carry further window increases.
573 * Don't send an independent window update if a delayed
574 * ACK is pending (it will get piggy-backed on it) or the
575 * remote side already has done a half-close and won't send
576 * more data. Skip this if the connection is in T/TCP
579 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) &&
580 !(tp->t_flags & TF_DELACK) &&
581 !TCPS_HAVERCVDFIN(tp->t_state)) {
583 * "adv" is the amount we could increase the window,
584 * taking into account that we are limited by
585 * TCP_MAXWIN << tp->rcv_scale.
590 adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale);
591 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) {
592 oldwin = (tp->rcv_adv - tp->rcv_nxt);
598 * If the new window size ends up being the same as the old
599 * size when it is scaled, then don't force a window update.
601 if (oldwin >> tp->rcv_scale == (adv + oldwin) >> tp->rcv_scale)
604 if (adv >= (long)(2 * tp->t_maxseg) &&
605 (adv >= (long)(so->so_rcv.sb_hiwat / 4) ||
606 recwin <= (long)(so->so_rcv.sb_hiwat / 8) ||
607 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg))
613 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW
614 * is also a catch-all for the retransmit timer timeout case.
616 if (tp->t_flags & TF_ACKNOW)
618 if ((flags & TH_RST) ||
619 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0))
621 if (SEQ_GT(tp->snd_up, tp->snd_una))
624 * If our state indicates that FIN should be sent
625 * and we have not yet done so, then we need to send.
627 if (flags & TH_FIN &&
628 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una))
631 * In SACK, it is possible for tcp_output to fail to send a segment
632 * after the retransmission timer has been turned off. Make sure
633 * that the retransmission timer is set.
635 if ((tp->t_flags & TF_SACK_PERMIT) &&
636 SEQ_GT(tp->snd_max, tp->snd_una) &&
637 !tcp_timer_active(tp, TT_REXMT) &&
638 !tcp_timer_active(tp, TT_PERSIST)) {
639 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
643 * TCP window updates are not reliable, rather a polling protocol
644 * using ``persist'' packets is used to insure receipt of window
645 * updates. The three ``states'' for the output side are:
646 * idle not doing retransmits or persists
647 * persisting to move a small or zero window
648 * (re)transmitting and thereby not persisting
650 * tcp_timer_active(tp, TT_PERSIST)
651 * is true when we are in persist state.
652 * (tp->t_flags & TF_FORCEDATA)
653 * is set when we are called to send a persist packet.
654 * tcp_timer_active(tp, TT_REXMT)
655 * is set when we are retransmitting
656 * The output side is idle when both timers are zero.
658 * If send window is too small, there is data to transmit, and no
659 * retransmit or persist is pending, then go to persist state.
660 * If nothing happens soon, send when timer expires:
661 * if window is nonzero, transmit what we can,
662 * otherwise force out a byte.
664 if (so->so_snd.sb_cc && !tcp_timer_active(tp, TT_REXMT) &&
665 !tcp_timer_active(tp, TT_PERSIST)) {
671 * No reason to send a segment, just return.
674 SOCKBUF_UNLOCK(&so->so_snd);
678 SOCKBUF_LOCK_ASSERT(&so->so_snd);
680 if (len >= tp->t_maxseg)
681 tp->t_flags2 |= TF2_PLPMTU_MAXSEGSNT;
683 tp->t_flags2 &= ~TF2_PLPMTU_MAXSEGSNT;
686 * Before ESTABLISHED, force sending of initial options
687 * unless TCP set not to do any options.
688 * NOTE: we assume that the IP/TCP header plus TCP options
689 * always fit in a single mbuf, leaving room for a maximum
691 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES
696 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr);
699 hdrlen = sizeof (struct tcpiphdr);
702 * Compute options for segment.
703 * We only have to care about SYN and established connection
704 * segments. Options for SYN-ACK segments are handled in TCP
707 if ((tp->t_flags & TF_NOOPT) == 0) {
709 /* Maximum segment size. */
710 if (flags & TH_SYN) {
711 tp->snd_nxt = tp->iss;
712 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc);
713 to.to_flags |= TOF_MSS;
715 /* Window scaling. */
716 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) {
717 to.to_wscale = tp->request_r_scale;
718 to.to_flags |= TOF_SCALE;
721 if ((tp->t_flags & TF_RCVD_TSTMP) ||
722 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) {
723 to.to_tsval = tcp_ts_getticks() + tp->ts_offset;
724 to.to_tsecr = tp->ts_recent;
725 to.to_flags |= TOF_TS;
726 /* Set receive buffer autosizing timestamp. */
727 if (tp->rfbuf_ts == 0 &&
728 (so->so_rcv.sb_flags & SB_AUTOSIZE))
729 tp->rfbuf_ts = tcp_ts_getticks();
731 /* Selective ACK's. */
732 if (tp->t_flags & TF_SACK_PERMIT) {
734 to.to_flags |= TOF_SACKPERM;
735 else if (TCPS_HAVEESTABLISHED(tp->t_state) &&
736 (tp->t_flags & TF_SACK_PERMIT) &&
737 tp->rcv_numsacks > 0) {
738 to.to_flags |= TOF_SACK;
739 to.to_nsacks = tp->rcv_numsacks;
740 to.to_sacks = (u_char *)tp->sackblks;
744 /* TCP-MD5 (RFC2385). */
745 if (tp->t_flags & TF_SIGNATURE)
746 to.to_flags |= TOF_SIGNATURE;
747 #endif /* TCP_SIGNATURE */
749 /* Processing the options. */
750 hdrlen += optlen = tcp_addoptions(&to, opt);
755 ipoptlen = ip6_optlen(tp->t_inpcb);
758 if (tp->t_inpcb->inp_options)
759 ipoptlen = tp->t_inpcb->inp_options->m_len -
760 offsetof(struct ipoption, ipopt_list);
764 ipoptlen += ipsec_optlen;
768 * Adjust data length if insertion of options will
769 * bump the packet length beyond the t_maxopd length.
770 * Clear the FIN bit because we cut off the tail of
773 if (len + optlen + ipoptlen > tp->t_maxopd) {
777 KASSERT(ipoptlen == 0,
778 ("%s: TSO can't do IP options", __func__));
781 * Limit a burst to t_tsomax minus IP,
782 * TCP and options length to keep ip->ip_len
783 * from overflowing or exceeding the maximum
784 * length allowed by the network interface.
786 if (len > tp->t_tsomax - hdrlen) {
787 len = tp->t_tsomax - hdrlen;
792 * Prevent the last segment from being
793 * fractional unless the send sockbuf can
796 if (sendalot && off + len < so->so_snd.sb_cc) {
797 len -= len % (tp->t_maxopd - optlen);
802 * Send the FIN in a separate segment
803 * after the bulk sending is done.
804 * We don't trust the TSO implementations
805 * to clear the FIN flag on all but the
808 if (tp->t_flags & TF_NEEDFIN)
812 len = tp->t_maxopd - optlen - ipoptlen;
818 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET,
819 ("%s: len > IP_MAXPACKET", __func__));
821 /*#ifdef DIAGNOSTIC*/
823 if (max_linkhdr + hdrlen > MCLBYTES)
825 if (max_linkhdr + hdrlen > MHLEN)
827 panic("tcphdr too big");
831 * This KASSERT is here to catch edge cases at a well defined place.
832 * Before, those had triggered (random) panic conditions further down.
834 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__));
837 * Grab a header mbuf, attaching a copy of data to
838 * be transmitted, and initialize the header from
839 * the template for sends on this connection.
845 if ((tp->t_flags & TF_FORCEDATA) && len == 1)
846 TCPSTAT_INC(tcps_sndprobe);
847 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) {
848 tp->t_sndrexmitpack++;
849 TCPSTAT_INC(tcps_sndrexmitpack);
850 TCPSTAT_ADD(tcps_sndrexmitbyte, len);
852 TCPSTAT_INC(tcps_sndpack);
853 TCPSTAT_ADD(tcps_sndbyte, len);
856 if (MHLEN < hdrlen + max_linkhdr)
857 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR);
860 m = m_gethdr(M_NOWAIT, MT_DATA);
863 SOCKBUF_UNLOCK(&so->so_snd);
869 m->m_data += max_linkhdr;
873 * Start the m_copy functions from the closest mbuf
874 * to the offset in the socket buffer chain.
876 mb = sbsndptr(&so->so_snd, off, len, &moff);
878 if (len <= MHLEN - hdrlen - max_linkhdr) {
879 m_copydata(mb, moff, (int)len,
880 mtod(m, caddr_t) + hdrlen);
883 m->m_next = m_copy(mb, moff, (int)len);
884 if (m->m_next == NULL) {
885 SOCKBUF_UNLOCK(&so->so_snd);
894 * If we're sending everything we've got, set PUSH.
895 * (This will keep happy those implementations which only
896 * give data to the user when a buffer fills or
899 if (off + len == so->so_snd.sb_cc)
901 SOCKBUF_UNLOCK(&so->so_snd);
903 SOCKBUF_UNLOCK(&so->so_snd);
904 if (tp->t_flags & TF_ACKNOW)
905 TCPSTAT_INC(tcps_sndacks);
906 else if (flags & (TH_SYN|TH_FIN|TH_RST))
907 TCPSTAT_INC(tcps_sndctrl);
908 else if (SEQ_GT(tp->snd_up, tp->snd_una))
909 TCPSTAT_INC(tcps_sndurg);
911 TCPSTAT_INC(tcps_sndwinup);
913 m = m_gethdr(M_NOWAIT, MT_DATA);
920 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) &&
925 m->m_data += max_linkhdr;
928 SOCKBUF_UNLOCK_ASSERT(&so->so_snd);
929 m->m_pkthdr.rcvif = (struct ifnet *)0;
931 mac_inpcb_create_mbuf(tp->t_inpcb, m);
935 ip6 = mtod(m, struct ip6_hdr *);
936 th = (struct tcphdr *)(ip6 + 1);
937 tcpip_fillheaders(tp->t_inpcb, ip6, th);
941 ip = mtod(m, struct ip *);
942 ipov = (struct ipovly *)ip;
943 th = (struct tcphdr *)(ip + 1);
944 tcpip_fillheaders(tp->t_inpcb, ip, th);
948 * Fill in fields, remembering maximum advertised
949 * window for use in delaying messages about window sizes.
950 * If resending a FIN, be sure not to use a new sequence number.
952 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN &&
953 tp->snd_nxt == tp->snd_max)
956 * If we are starting a connection, send ECN setup
957 * SYN packet. If we are on a retransmit, we may
958 * resend those bits a number of times as per
961 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) {
962 if (tp->t_rxtshift >= 1) {
963 if (tp->t_rxtshift <= V_tcp_ecn_maxretries)
964 flags |= TH_ECE|TH_CWR;
966 flags |= TH_ECE|TH_CWR;
969 if (tp->t_state == TCPS_ESTABLISHED &&
970 (tp->t_flags & TF_ECN_PERMIT)) {
972 * If the peer has ECN, mark data packets with
973 * ECN capable transmission (ECT).
974 * Ignore pure ack packets, retransmissions and window probes.
976 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) &&
977 !((tp->t_flags & TF_FORCEDATA) && len == 1)) {
980 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20);
983 ip->ip_tos |= IPTOS_ECN_ECT0;
984 TCPSTAT_INC(tcps_ecn_ect0);
988 * Reply with proper ECN notifications.
990 if (tp->t_flags & TF_ECN_SND_CWR) {
992 tp->t_flags &= ~TF_ECN_SND_CWR;
994 if (tp->t_flags & TF_ECN_SND_ECE)
999 * If we are doing retransmissions, then snd_nxt will
1000 * not reflect the first unsent octet. For ACK only
1001 * packets, we do not want the sequence number of the
1002 * retransmitted packet, we want the sequence number
1003 * of the next unsent octet. So, if there is no data
1004 * (and no SYN or FIN), use snd_max instead of snd_nxt
1005 * when filling in ti_seq. But if we are in persist
1006 * state, snd_max might reflect one byte beyond the
1007 * right edge of the window, so use snd_nxt in that
1008 * case, since we know we aren't doing a retransmission.
1009 * (retransmit and persist are mutually exclusive...)
1011 if (sack_rxmit == 0) {
1012 if (len || (flags & (TH_SYN|TH_FIN)) ||
1013 tcp_timer_active(tp, TT_PERSIST))
1014 th->th_seq = htonl(tp->snd_nxt);
1016 th->th_seq = htonl(tp->snd_max);
1018 th->th_seq = htonl(p->rxmit);
1020 tp->sackhint.sack_bytes_rexmit += len;
1022 th->th_ack = htonl(tp->rcv_nxt);
1024 bcopy(opt, th + 1, optlen);
1025 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2;
1027 th->th_flags = flags;
1029 * Calculate receive window. Don't shrink window,
1030 * but avoid silly window syndrome.
1032 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) &&
1033 recwin < (long)tp->t_maxseg)
1035 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) &&
1036 recwin < (long)(tp->rcv_adv - tp->rcv_nxt))
1037 recwin = (long)(tp->rcv_adv - tp->rcv_nxt);
1038 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale)
1039 recwin = (long)TCP_MAXWIN << tp->rcv_scale;
1042 * According to RFC1323 the window field in a SYN (i.e., a <SYN>
1043 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK>
1044 * case is handled in syncache.
1047 th->th_win = htons((u_short)
1048 (min(sbspace(&so->so_rcv), TCP_MAXWIN)));
1050 th->th_win = htons((u_short)(recwin >> tp->rcv_scale));
1053 * Adjust the RXWIN0SENT flag - indicate that we have advertised
1054 * a 0 window. This may cause the remote transmitter to stall. This
1055 * flag tells soreceive() to disable delayed acknowledgements when
1056 * draining the buffer. This can occur if the receiver is attempting
1057 * to read more data than can be buffered prior to transmitting on
1060 if (th->th_win == 0) {
1062 tp->t_flags |= TF_RXWIN0SENT;
1064 tp->t_flags &= ~TF_RXWIN0SENT;
1065 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) {
1066 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt));
1067 th->th_flags |= TH_URG;
1070 * If no urgent pointer to send, then we pull
1071 * the urgent pointer to the left edge of the send window
1072 * so that it doesn't drift into the send window on sequence
1073 * number wraparound.
1075 tp->snd_up = tp->snd_una; /* drag it along */
1077 #ifdef TCP_SIGNATURE
1078 if (tp->t_flags & TF_SIGNATURE) {
1079 int sigoff = to.to_signature - opt;
1080 tcp_signature_compute(m, 0, len, optlen,
1081 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND);
1086 * Put TCP length in extended header, and then
1087 * checksum extended header and data.
1089 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */
1090 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1094 * ip6_plen is not need to be filled now, and will be filled
1097 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
1098 th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) +
1099 optlen + len, IPPROTO_TCP, 0);
1102 #if defined(INET6) && defined(INET)
1107 m->m_pkthdr.csum_flags = CSUM_TCP;
1108 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
1109 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen));
1111 /* IP version must be set here for ipv4/ipv6 checking later */
1112 KASSERT(ip->ip_v == IPVERSION,
1113 ("%s: IP version incorrect: %d", __func__, ip->ip_v));
1118 * Enable TSO and specify the size of the segments.
1119 * The TCP pseudo header checksum is always provided.
1120 * XXX: Fixme: This is currently not the case for IPv6.
1123 KASSERT(len > tp->t_maxopd - optlen,
1124 ("%s: len <= tso_segsz", __func__));
1125 m->m_pkthdr.csum_flags |= CSUM_TSO;
1126 m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen;
1130 KASSERT(len + hdrlen + ipoptlen - ipsec_optlen == m_length(m, NULL),
1131 ("%s: mbuf chain shorter than expected: %ld + %u + %u - %u != %u",
1132 __func__, len, hdrlen, ipoptlen, ipsec_optlen, m_length(m, NULL)));
1134 KASSERT(len + hdrlen + ipoptlen == m_length(m, NULL),
1135 ("%s: mbuf chain shorter than expected: %ld + %u + %u != %u",
1136 __func__, len, hdrlen, ipoptlen, m_length(m, NULL)));
1139 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */
1140 hhook_run_tcp_est_out(tp, th, &to, len, tso);
1146 if (so->so_options & SO_DEBUG) {
1152 save = ipov->ih_len;
1153 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */);
1155 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0);
1159 ipov->ih_len = save;
1161 #endif /* TCPDEBUG */
1164 * Fill in IP length and desired time to live and
1165 * send to IP level. There should be a better way
1166 * to handle ttl and tos; we could keep them in
1167 * the template, but need a way to checksum without them.
1170 * m->m_pkthdr.len should have been set before cksum calcuration,
1171 * because in6_cksum() need it.
1175 struct route_in6 ro;
1177 bzero(&ro, sizeof(ro));
1179 * we separately set hoplimit for every segment, since the
1180 * user might want to change the value via setsockopt.
1181 * Also, desired default hop limit might be changed via
1182 * Neighbor Discovery.
1184 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL);
1187 * Set the packet size here for the benefit of DTrace probes.
1188 * ip6_output() will set it properly; it's supposed to include
1189 * the option header lengths as well.
1191 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6));
1193 if (V_path_mtu_discovery && tp->t_maxopd > V_tcp_minmss)
1194 tp->t_flags2 |= TF2_PLPMTU_PMTUD;
1196 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
1198 if (tp->t_state == TCPS_SYN_SENT)
1199 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th);
1201 TCP_PROBE5(send, NULL, tp, ip6, tp, th);
1203 /* TODO: IPv6 IP6TOS_ECT bit on */
1204 error = ip6_output(m, tp->t_inpcb->in6p_outputopts, &ro,
1205 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0),
1206 NULL, NULL, tp->t_inpcb);
1208 if (error == EMSGSIZE && ro.ro_rt != NULL)
1209 mtu = ro.ro_rt->rt_mtu;
1213 #if defined(INET) && defined(INET6)
1220 bzero(&ro, sizeof(ro));
1221 ip->ip_len = htons(m->m_pkthdr.len);
1223 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO)
1224 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL);
1227 * If we do path MTU discovery, then we set DF on every packet.
1228 * This might not be the best thing to do according to RFC3390
1229 * Section 2. However the tcp hostcache migitates the problem
1230 * so it affects only the first tcp connection with a host.
1232 * NB: Don't set DF on small MTU/MSS to have a safe fallback.
1234 if (V_path_mtu_discovery && tp->t_maxopd > V_tcp_minmss) {
1235 ip->ip_off |= htons(IP_DF);
1236 tp->t_flags2 |= TF2_PLPMTU_PMTUD;
1238 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
1241 if (tp->t_state == TCPS_SYN_SENT)
1242 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th);
1244 TCP_PROBE5(send, NULL, tp, ip, tp, th);
1246 error = ip_output(m, tp->t_inpcb->inp_options, &ro,
1247 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0,
1250 if (error == EMSGSIZE && ro.ro_rt != NULL)
1251 mtu = ro.ro_rt->rt_mtu;
1258 * In transmit state, time the transmission and arrange for
1259 * the retransmit. In persist state, just set snd_max.
1261 if ((tp->t_flags & TF_FORCEDATA) == 0 ||
1262 !tcp_timer_active(tp, TT_PERSIST)) {
1263 tcp_seq startseq = tp->snd_nxt;
1266 * Advance snd_nxt over sequence space of this segment.
1268 if (flags & (TH_SYN|TH_FIN)) {
1271 if (flags & TH_FIN) {
1273 tp->t_flags |= TF_SENTFIN;
1279 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) {
1280 tp->snd_max = tp->snd_nxt;
1282 * Time this transmission if not a retransmission and
1283 * not currently timing anything.
1285 if (tp->t_rtttime == 0) {
1286 tp->t_rtttime = ticks;
1287 tp->t_rtseq = startseq;
1288 TCPSTAT_INC(tcps_segstimed);
1293 * Set retransmit timer if not currently set,
1294 * and not doing a pure ack or a keep-alive probe.
1295 * Initial value for retransmit timer is smoothed
1296 * round-trip time + 2 * round-trip time variance.
1297 * Initialize shift counter which is used for backoff
1298 * of retransmit time.
1301 if (!tcp_timer_active(tp, TT_REXMT) &&
1302 ((sack_rxmit && tp->snd_nxt != tp->snd_max) ||
1303 (tp->snd_nxt != tp->snd_una))) {
1304 if (tcp_timer_active(tp, TT_PERSIST)) {
1305 tcp_timer_activate(tp, TT_PERSIST, 0);
1308 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
1312 * Persist case, update snd_max but since we are in
1313 * persist mode (no window) we do not update snd_nxt.
1318 if (flags & TH_FIN) {
1320 tp->t_flags |= TF_SENTFIN;
1322 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max))
1323 tp->snd_max = tp->snd_nxt + len;
1329 * We know that the packet was lost, so back out the
1330 * sequence number advance, if any.
1332 * If the error is EPERM the packet got blocked by the
1333 * local firewall. Normally we should terminate the
1334 * connection but the blocking may have been spurious
1335 * due to a firewall reconfiguration cycle. So we treat
1336 * it like a packet loss and let the retransmit timer and
1337 * timeouts do their work over time.
1338 * XXX: It is a POLA question whether calling tcp_drop right
1339 * away would be the really correct behavior instead.
1341 if (((tp->t_flags & TF_FORCEDATA) == 0 ||
1342 !tcp_timer_active(tp, TT_PERSIST)) &&
1343 ((flags & TH_SYN) == 0) &&
1347 tp->sackhint.sack_bytes_rexmit -= len;
1348 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0,
1349 ("sackhint bytes rtx >= 0"));
1353 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */
1356 tp->t_softerror = error;
1359 if (!tcp_timer_active(tp, TT_REXMT) &&
1360 !tcp_timer_active(tp, TT_PERSIST))
1361 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
1362 tp->snd_cwnd = tp->t_maxseg;
1366 * For some reason the interface we used initially
1367 * to send segments changed to another or lowered
1369 * If TSO was active we either got an interface
1370 * without TSO capabilits or TSO was turned off.
1371 * If we obtained mtu from ip_output() then update
1375 tp->t_flags &= ~TF_TSO;
1377 tcp_mss_update(tp, -1, mtu, NULL, NULL);
1385 if (TCPS_HAVERCVDSYN(tp->t_state)) {
1386 tp->t_softerror = error;
1394 TCPSTAT_INC(tcps_sndtotal);
1397 * Data sent (as far as we can tell).
1398 * If this advertises a larger window than any other segment,
1399 * then remember the size of the advertised window.
1400 * Any pending ACK has now been sent.
1402 if (recwin >= 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv))
1403 tp->rcv_adv = tp->rcv_nxt + recwin;
1404 tp->last_ack_sent = tp->rcv_nxt;
1405 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK);
1406 if (tcp_timer_active(tp, TT_DELACK))
1407 tcp_timer_activate(tp, TT_DELACK, 0);
1410 * This completely breaks TCP if newreno is turned on. What happens
1411 * is that if delayed-acks are turned on on the receiver, this code
1412 * on the transmitter effectively destroys the TCP window, forcing
1413 * it to four packets (1.5Kx4 = 6K window).
1415 if (sendalot && --maxburst)
1424 tcp_setpersist(struct tcpcb *tp)
1426 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1;
1429 tp->t_flags &= ~TF_PREVVALID;
1430 if (tcp_timer_active(tp, TT_REXMT))
1431 panic("tcp_setpersist: retransmit pending");
1433 * Start/restart persistance timer.
1435 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift],
1436 TCPTV_PERSMIN, TCPTV_PERSMAX);
1437 tcp_timer_activate(tp, TT_PERSIST, tt);
1438 if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
1443 * Insert TCP options according to the supplied parameters to the place
1444 * optp in a consistent way. Can handle unaligned destinations.
1446 * The order of the option processing is crucial for optimal packing and
1447 * alignment for the scarce option space.
1449 * The optimal order for a SYN/SYN-ACK segment is:
1450 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) +
1451 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40.
1453 * The SACK options should be last. SACK blocks consume 8*n+2 bytes.
1454 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks).
1455 * At minimum we need 10 bytes (to generate 1 SACK block). If both
1456 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present,
1457 * we only have 10 bytes for SACK options (40 - (12 + 18)).
1460 tcp_addoptions(struct tcpopt *to, u_char *optp)
1462 u_int mask, optlen = 0;
1464 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) {
1465 if ((to->to_flags & mask) != mask)
1467 if (optlen == TCP_MAXOLEN)
1469 switch (to->to_flags & mask) {
1471 while (optlen % 4) {
1472 optlen += TCPOLEN_NOP;
1473 *optp++ = TCPOPT_NOP;
1475 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG)
1477 optlen += TCPOLEN_MAXSEG;
1478 *optp++ = TCPOPT_MAXSEG;
1479 *optp++ = TCPOLEN_MAXSEG;
1480 to->to_mss = htons(to->to_mss);
1481 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss));
1482 optp += sizeof(to->to_mss);
1485 while (!optlen || optlen % 2 != 1) {
1486 optlen += TCPOLEN_NOP;
1487 *optp++ = TCPOPT_NOP;
1489 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW)
1491 optlen += TCPOLEN_WINDOW;
1492 *optp++ = TCPOPT_WINDOW;
1493 *optp++ = TCPOLEN_WINDOW;
1494 *optp++ = to->to_wscale;
1497 while (optlen % 2) {
1498 optlen += TCPOLEN_NOP;
1499 *optp++ = TCPOPT_NOP;
1501 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED)
1503 optlen += TCPOLEN_SACK_PERMITTED;
1504 *optp++ = TCPOPT_SACK_PERMITTED;
1505 *optp++ = TCPOLEN_SACK_PERMITTED;
1508 while (!optlen || optlen % 4 != 2) {
1509 optlen += TCPOLEN_NOP;
1510 *optp++ = TCPOPT_NOP;
1512 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP)
1514 optlen += TCPOLEN_TIMESTAMP;
1515 *optp++ = TCPOPT_TIMESTAMP;
1516 *optp++ = TCPOLEN_TIMESTAMP;
1517 to->to_tsval = htonl(to->to_tsval);
1518 to->to_tsecr = htonl(to->to_tsecr);
1519 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval));
1520 optp += sizeof(to->to_tsval);
1521 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr));
1522 optp += sizeof(to->to_tsecr);
1526 int siglen = TCPOLEN_SIGNATURE - 2;
1528 while (!optlen || optlen % 4 != 2) {
1529 optlen += TCPOLEN_NOP;
1530 *optp++ = TCPOPT_NOP;
1532 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE)
1534 optlen += TCPOLEN_SIGNATURE;
1535 *optp++ = TCPOPT_SIGNATURE;
1536 *optp++ = TCPOLEN_SIGNATURE;
1537 to->to_signature = optp;
1545 struct sackblk *sack = (struct sackblk *)to->to_sacks;
1548 while (!optlen || optlen % 4 != 2) {
1549 optlen += TCPOLEN_NOP;
1550 *optp++ = TCPOPT_NOP;
1552 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK)
1554 optlen += TCPOLEN_SACKHDR;
1555 *optp++ = TCPOPT_SACK;
1556 sackblks = min(to->to_nsacks,
1557 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK);
1558 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK;
1559 while (sackblks--) {
1560 sack_seq = htonl(sack->start);
1561 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq));
1562 optp += sizeof(sack_seq);
1563 sack_seq = htonl(sack->end);
1564 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq));
1565 optp += sizeof(sack_seq);
1566 optlen += TCPOLEN_SACK;
1569 TCPSTAT_INC(tcps_sack_send_blocks);
1573 panic("%s: unknown TCP option type", __func__);
1578 /* Terminate and pad TCP options to a 4 byte boundary. */
1580 optlen += TCPOLEN_EOL;
1581 *optp++ = TCPOPT_EOL;
1584 * According to RFC 793 (STD0007):
1585 * "The content of the header beyond the End-of-Option option
1586 * must be header padding (i.e., zero)."
1587 * and later: "The padding is composed of zeros."
1589 while (optlen % 4) {
1590 optlen += TCPOLEN_PAD;
1591 *optp++ = TCPOPT_PAD;
1594 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__));