sys/netinet/tcp_output.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-3-Clause
   3  *
   4  * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. Neither the name of the University nor the names of its contributors
  16  *    may be used to endorse or promote products derived from this software
  17  *    without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  *
  31  *      @(#)tcp_output.c        8.4 (Berkeley) 5/24/95
  32  */
  33
  34 #include <sys/cdefs.h>
  35 __FBSDID("$FreeBSD$");
  36
  37 #include "opt_inet.h"
  38 #include "opt_inet6.h"
  39 #include "opt_ipsec.h"
  40 #include "opt_kern_tls.h"
  41 #include "opt_tcpdebug.h"
  42
  43 #include <sys/param.h>
  44 #include <sys/systm.h>
  45 #include <sys/arb.h>
  46 #include <sys/domain.h>
  47 #ifdef TCP_HHOOK
  48 #include <sys/hhook.h>
  49 #endif
  50 #include <sys/kernel.h>
  51 #ifdef KERN_TLS
  52 #include <sys/ktls.h>
  53 #endif
  54 #include <sys/lock.h>
  55 #include <sys/mbuf.h>
  56 #include <sys/mutex.h>
  57 #include <sys/protosw.h>
  58 #include <sys/qmath.h>
  59 #include <sys/sdt.h>
  60 #include <sys/socket.h>
  61 #include <sys/socketvar.h>
  62 #include <sys/sysctl.h>
  63 #include <sys/stats.h>
  64
  65 #include <net/if.h>
  66 #include <net/route.h>
  67 #include <net/route/nhop.h>
  68 #include <net/vnet.h>
  69
  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>
  77 #ifdef INET6
  78 #include <netinet6/in6_pcb.h>
  79 #include <netinet/ip6.h>
  80 #include <netinet6/ip6_var.h>
  81 #endif
  82 #include <netinet/tcp.h>
  83 #define TCPOUTFLAGS
  84 #include <netinet/tcp_fsm.h>
  85 #include <netinet/tcp_log_buf.h>
  86 #include <netinet/tcp_seq.h>
  87 #include <netinet/tcp_var.h>
  88 #include <netinet/tcp_syncache.h>
  89 #include <netinet/tcp_timer.h>
  90 #include <netinet/tcpip.h>
  91 #include <netinet/cc/cc.h>
  92 #include <netinet/tcp_fastopen.h>
  93 #ifdef TCPPCAP
  94 #include <netinet/tcp_pcap.h>
  95 #endif
  96 #ifdef TCPDEBUG
  97 #include <netinet/tcp_debug.h>
  98 #endif
  99 #ifdef TCP_OFFLOAD
 100 #include <netinet/tcp_offload.h>
 101 #endif
 102 #include <netinet/tcp_ecn.h>
 103
 104 #include <netipsec/ipsec_support.h>
 105
 106 #include <netinet/udp.h>
 107 #include <netinet/udp_var.h>
 108 #include <machine/in_cksum.h>
 109
 110 #include <security/mac/mac_framework.h>
 111
 112 VNET_DEFINE(int, path_mtu_discovery) = 1;
 113 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_VNET | CTLFLAG_RW,
 114         &VNET_NAME(path_mtu_discovery), 1,
 115         "Enable Path MTU Discovery");
 116
 117 VNET_DEFINE(int, tcp_do_tso) = 1;
 118 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_VNET | CTLFLAG_RW,
 119         &VNET_NAME(tcp_do_tso), 0,
 120         "Enable TCP Segmentation Offload");
 121
 122 VNET_DEFINE(int, tcp_sendspace) = 1024*32;
 123 #define V_tcp_sendspace VNET(tcp_sendspace)
 124 SYSCTL_INT(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, CTLFLAG_VNET | CTLFLAG_RW,
 125         &VNET_NAME(tcp_sendspace), 0, "Initial send socket buffer size");
 126
 127 VNET_DEFINE(int, tcp_do_autosndbuf) = 1;
 128 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_VNET | CTLFLAG_RW,
 129         &VNET_NAME(tcp_do_autosndbuf), 0,
 130         "Enable automatic send buffer sizing");
 131
 132 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024;
 133 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_VNET | CTLFLAG_RW,
 134         &VNET_NAME(tcp_autosndbuf_inc), 0,
 135         "Incrementor step size of automatic send buffer");
 136
 137 VNET_DEFINE(int, tcp_autosndbuf_max) = 2*1024*1024;
 138 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_VNET | CTLFLAG_RW,
 139         &VNET_NAME(tcp_autosndbuf_max), 0,
 140         "Max size of automatic send buffer");
 141
 142 VNET_DEFINE(int, tcp_sendbuf_auto_lowat) = 0;
 143 #define V_tcp_sendbuf_auto_lowat        VNET(tcp_sendbuf_auto_lowat)
 144 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto_lowat, CTLFLAG_VNET | CTLFLAG_RW,
 145         &VNET_NAME(tcp_sendbuf_auto_lowat), 0,
 146         "Modify threshold for auto send buffer growth to account for SO_SNDLOWAT");
 147
 148 /*
 149  * Make sure that either retransmit or persist timer is set for SYN, FIN and
 150  * non-ACK.
 151  */
 152 #define TCP_XMIT_TIMER_ASSERT(tp, len, th_flags)                        \
 153         KASSERT(((len) == 0 && ((th_flags) & (TH_SYN | TH_FIN)) == 0) ||\
 154             tcp_timer_active((tp), TT_REXMT) ||                         \
 155             tcp_timer_active((tp), TT_PERSIST),                         \
 156             ("neither rexmt nor persist timer is set"))
 157
 158 #ifdef TCP_HHOOK
 159 /*
 160  * Wrapper for the TCP established output helper hook.
 161  */
 162 void
 163 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th,
 164     struct tcpopt *to, uint32_t len, int tso)
 165 {
 166         struct tcp_hhook_data hhook_data;
 167
 168         if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) {
 169                 hhook_data.tp = tp;
 170                 hhook_data.th = th;
 171                 hhook_data.to = to;
 172                 hhook_data.len = len;
 173                 hhook_data.tso = tso;
 174
 175                 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data,
 176                     tp->osd);
 177         }
 178 }
 179 #endif
 180
 181 /*
 182  * CC wrapper hook functions
 183  */
 184 void
 185 cc_after_idle(struct tcpcb *tp)
 186 {
 187         INP_WLOCK_ASSERT(tptoinpcb(tp));
 188
 189         if (CC_ALGO(tp)->after_idle != NULL)
 190                 CC_ALGO(tp)->after_idle(tp->ccv);
 191 }
 192
 193 /*
 194  * Tcp output routine: figure out what should be sent and send it.
 195  */
 196 int
 197 tcp_default_output(struct tcpcb *tp)
 198 {
 199         struct socket *so = tptosocket(tp);
 200         struct inpcb *inp = tptoinpcb(tp);
 201         int32_t len;
 202         uint32_t recwin, sendwin;
 203         uint16_t flags;
 204         int off, error = 0;     /* Keep compiler happy */
 205         u_int if_hw_tsomaxsegcount = 0;
 206         u_int if_hw_tsomaxsegsize = 0;
 207         struct mbuf *m;
 208         struct ip *ip = NULL;
 209 #ifdef TCPDEBUG
 210         struct ipovly *ipov = NULL;
 211 #endif
 212         struct tcphdr *th;
 213         u_char opt[TCP_MAXOLEN];
 214         unsigned ipoptlen, optlen, hdrlen, ulen;
 215 #if defined(IPSEC) || defined(IPSEC_SUPPORT)
 216         unsigned ipsec_optlen = 0;
 217 #endif
 218         int idle, sendalot, curticks;
 219         int sack_rxmit, sack_bytes_rxmt;
 220         struct sackhole *p;
 221         int tso, mtu;
 222         struct tcpopt to;
 223         struct udphdr *udp = NULL;
 224         struct tcp_log_buffer *lgb;
 225         unsigned int wanted_cookie = 0;
 226         unsigned int dont_sendalot = 0;
 227 #if 0
 228         int maxburst = TCP_MAXBURST;
 229 #endif
 230 #ifdef INET6
 231         struct ip6_hdr *ip6 = NULL;
 232         int isipv6;
 233
 234         isipv6 = (inp->inp_vflag & INP_IPV6) != 0;
 235 #endif
 236 #ifdef KERN_TLS
 237         const bool hw_tls = (so->so_snd.sb_flags & SB_TLS_IFNET) != 0;
 238 #else
 239         const bool hw_tls = false;
 240 #endif
 241
 242         NET_EPOCH_ASSERT();
 243         INP_WLOCK_ASSERT(inp);
 244
 245 #ifdef TCP_OFFLOAD
 246         if (tp->t_flags & TF_TOE)
 247                 return (tcp_offload_output(tp));
 248 #endif
 249
 250         /*
 251          * For TFO connections in SYN_SENT or SYN_RECEIVED,
 252          * only allow the initial SYN or SYN|ACK and those sent
 253          * by the retransmit timer.
 254          */
 255         if (IS_FASTOPEN(tp->t_flags) &&
 256             ((tp->t_state == TCPS_SYN_SENT) ||
 257              (tp->t_state == TCPS_SYN_RECEIVED)) &&
 258             SEQ_GT(tp->snd_max, tp->snd_una) && /* initial SYN or SYN|ACK sent */
 259             (tp->snd_nxt != tp->snd_una))       /* not a retransmit */
 260                 return (0);
 261
 262         /*
 263          * Determine length of data that should be transmitted,
 264          * and flags that will be used.
 265          * If there is some data or critical controls (SYN, RST)
 266          * to send, then transmit; otherwise, investigate further.
 267          */
 268         idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una);
 269         if (idle && (((ticks - tp->t_rcvtime) >= tp->t_rxtcur) ||
 270             (tp->t_sndtime && ((ticks - tp->t_sndtime) >= tp->t_rxtcur))))
 271                 cc_after_idle(tp);
 272         tp->t_flags &= ~TF_LASTIDLE;
 273         if (idle) {
 274                 if (tp->t_flags & TF_MORETOCOME) {
 275                         tp->t_flags |= TF_LASTIDLE;
 276                         idle = 0;
 277                 }
 278         }
 279 again:
 280         /*
 281          * If we've recently taken a timeout, snd_max will be greater than
 282          * snd_nxt.  There may be SACK information that allows us to avoid
 283          * resending already delivered data.  Adjust snd_nxt accordingly.
 284          */
 285         if ((tp->t_flags & TF_SACK_PERMIT) &&
 286             SEQ_LT(tp->snd_nxt, tp->snd_max))
 287                 tcp_sack_adjust(tp);
 288         sendalot = 0;
 289         tso = 0;
 290         mtu = 0;
 291         off = tp->snd_nxt - tp->snd_una;
 292         sendwin = min(tp->snd_wnd, tp->snd_cwnd);
 293
 294         flags = tcp_outflags[tp->t_state];
 295         /*
 296          * Send any SACK-generated retransmissions.  If we're explicitly trying
 297          * to send out new data (when sendalot is 1), bypass this function.
 298          * If we retransmit in fast recovery mode, decrement snd_cwnd, since
 299          * we're replacing a (future) new transmission with a retransmission
 300          * now, and we previously incremented snd_cwnd in tcp_input().
 301          */
 302         /*
 303          * Still in sack recovery , reset rxmit flag to zero.
 304          */
 305         sack_rxmit = 0;
 306         sack_bytes_rxmt = 0;
 307         len = 0;
 308         p = NULL;
 309         if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) &&
 310             (p = tcp_sack_output(tp, &sack_bytes_rxmt))) {
 311                 uint32_t cwin;
 312
 313                 cwin =
 314                     imax(min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt, 0);
 315                 /* Do not retransmit SACK segments beyond snd_recover */
 316                 if (SEQ_GT(p->end, tp->snd_recover)) {
 317                         /*
 318                          * (At least) part of sack hole extends beyond
 319                          * snd_recover. Check to see if we can rexmit data
 320                          * for this hole.
 321                          */
 322                         if (SEQ_GEQ(p->rxmit, tp->snd_recover)) {
 323                                 /*
 324                                  * Can't rexmit any more data for this hole.
 325                                  * That data will be rexmitted in the next
 326                                  * sack recovery episode, when snd_recover
 327                                  * moves past p->rxmit.
 328                                  */
 329                                 p = NULL;
 330                                 goto after_sack_rexmit;
 331                         } else {
 332                                 /* Can rexmit part of the current hole */
 333                                 len = ((int32_t)ulmin(cwin,
 334                                     SEQ_SUB(tp->snd_recover, p->rxmit)));
 335                         }
 336                 } else {
 337                         len = ((int32_t)ulmin(cwin,
 338                             SEQ_SUB(p->end, p->rxmit)));
 339                 }
 340                 if (len > 0) {
 341                         off = SEQ_SUB(p->rxmit, tp->snd_una);
 342                         KASSERT(off >= 0,("%s: sack block to the left of una : %d",
 343                             __func__, off));
 344                         sack_rxmit = 1;
 345                         sendalot = 1;
 346                         TCPSTAT_INC(tcps_sack_rexmits);
 347                         TCPSTAT_ADD(tcps_sack_rexmit_bytes,
 348                             min(len, tcp_maxseg(tp)));
 349                 }
 350         }
 351 after_sack_rexmit:
 352         /*
 353          * Get standard flags, and add SYN or FIN if requested by 'hidden'
 354          * state flags.
 355          */
 356         if (tp->t_flags & TF_NEEDFIN)
 357                 flags |= TH_FIN;
 358         if (tp->t_flags & TF_NEEDSYN)
 359                 flags |= TH_SYN;
 360
 361         SOCKBUF_LOCK(&so->so_snd);
 362         /*
 363          * If in persist timeout with window of 0, send 1 byte.
 364          * Otherwise, if window is small but nonzero
 365          * and timer expired, we will send what we can
 366          * and go to transmit state.
 367          */
 368         if (tp->t_flags & TF_FORCEDATA) {
 369                 if (sendwin == 0) {
 370                         /*
 371                          * If we still have some data to send, then
 372                          * clear the FIN bit.  Usually this would
 373                          * happen below when it realizes that we
 374                          * aren't sending all the data.  However,
 375                          * if we have exactly 1 byte of unsent data,
 376                          * then it won't clear the FIN bit below,
 377                          * and if we are in persist state, we wind
 378                          * up sending the packet without recording
 379                          * that we sent the FIN bit.
 380                          *
 381                          * We can't just blindly clear the FIN bit,
 382                          * because if we don't have any more data
 383                          * to send then the probe will be the FIN
 384                          * itself.
 385                          */
 386                         if (off < sbused(&so->so_snd))
 387                                 flags &= ~TH_FIN;
 388                         sendwin = 1;
 389                 } else {
 390                         tcp_timer_activate(tp, TT_PERSIST, 0);
 391                         tp->t_rxtshift = 0;
 392                 }
 393         }
 394
 395         /*
 396          * If snd_nxt == snd_max and we have transmitted a FIN, the
 397          * offset will be > 0 even if so_snd.sb_cc is 0, resulting in
 398          * a negative length.  This can also occur when TCP opens up
 399          * its congestion window while receiving additional duplicate
 400          * acks after fast-retransmit because TCP will reset snd_nxt
 401          * to snd_max after the fast-retransmit.
 402          *
 403          * In the normal retransmit-FIN-only case, however, snd_nxt will
 404          * be set to snd_una, the offset will be 0, and the length may
 405          * wind up 0.
 406          *
 407          * If sack_rxmit is true we are retransmitting from the scoreboard
 408          * in which case len is already set.
 409          */
 410         if (sack_rxmit == 0) {
 411                 if (sack_bytes_rxmt == 0)
 412                         len = ((int32_t)min(sbavail(&so->so_snd), sendwin) -
 413                             off);
 414                 else {
 415                         int32_t cwin;
 416
 417                         /*
 418                          * We are inside of a SACK recovery episode and are
 419                          * sending new data, having retransmitted all the
 420                          * data possible in the scoreboard.
 421                          */
 422                         len = ((int32_t)min(sbavail(&so->so_snd), tp->snd_wnd) -
 423                             off);
 424                         /*
 425                          * Don't remove this (len > 0) check !
 426                          * We explicitly check for len > 0 here (although it
 427                          * isn't really necessary), to work around a gcc
 428                          * optimization issue - to force gcc to compute
 429                          * len above. Without this check, the computation
 430                          * of len is bungled by the optimizer.
 431                          */
 432                         if (len > 0) {
 433                                 cwin = tp->snd_cwnd - imax(0, (int32_t)
 434                                         (tp->snd_nxt - tp->snd_recover)) -
 435                                         sack_bytes_rxmt;
 436                                 if (cwin < 0)
 437                                         cwin = 0;
 438                                 len = imin(len, cwin);
 439                         }
 440                 }
 441         }
 442
 443         /*
 444          * Lop off SYN bit if it has already been sent.  However, if this
 445          * is SYN-SENT state and if segment contains data and if we don't
 446          * know that foreign host supports TAO, suppress sending segment.
 447          */
 448         if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) {
 449                 if (tp->t_state != TCPS_SYN_RECEIVED)
 450                         flags &= ~TH_SYN;
 451                 /*
 452                  * When sending additional segments following a TFO SYN|ACK,
 453                  * do not include the SYN bit.
 454                  */
 455                 if (IS_FASTOPEN(tp->t_flags) &&
 456                     (tp->t_state == TCPS_SYN_RECEIVED))
 457                         flags &= ~TH_SYN;
 458                 off--, len++;
 459         }
 460
 461         /*
 462          * Be careful not to send data and/or FIN on SYN segments.
 463          * This measure is needed to prevent interoperability problems
 464          * with not fully conformant TCP implementations.
 465          */
 466         if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) {
 467                 len = 0;
 468                 flags &= ~TH_FIN;
 469         }
 470
 471         /*
 472          * On TFO sockets, ensure no data is sent in the following cases:
 473          *
 474          *  - When retransmitting SYN|ACK on a passively-created socket
 475          *
 476          *  - When retransmitting SYN on an actively created socket
 477          *
 478          *  - When sending a zero-length cookie (cookie request) on an
 479          *    actively created socket
 480          *
 481          *  - When the socket is in the CLOSED state (RST is being sent)
 482          */
 483         if (IS_FASTOPEN(tp->t_flags) &&
 484             (((flags & TH_SYN) && (tp->t_rxtshift > 0)) ||
 485              ((tp->t_state == TCPS_SYN_SENT) &&
 486               (tp->t_tfo_client_cookie_len == 0)) ||
 487              (flags & TH_RST)))
 488                 len = 0;
 489         if (len <= 0) {
 490                 /*
 491                  * If FIN has been sent but not acked,
 492                  * but we haven't been called to retransmit,
 493                  * len will be < 0.  Otherwise, window shrank
 494                  * after we sent into it.  If window shrank to 0,
 495                  * cancel pending retransmit, pull snd_nxt back
 496                  * to (closed) window, and set the persist timer
 497                  * if it isn't already going.  If the window didn't
 498                  * close completely, just wait for an ACK.
 499                  *
 500                  * We also do a general check here to ensure that
 501                  * we will set the persist timer when we have data
 502                  * to send, but a 0-byte window. This makes sure
 503                  * the persist timer is set even if the packet
 504                  * hits one of the "goto send" lines below.
 505                  */
 506                 len = 0;
 507                 if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) &&
 508                     (off < (int) sbavail(&so->so_snd)) &&
 509                     !tcp_timer_active(tp, TT_PERSIST)) {
 510                         tcp_timer_activate(tp, TT_REXMT, 0);
 511                         tp->t_rxtshift = 0;
 512                         tp->snd_nxt = tp->snd_una;
 513                         if (!tcp_timer_active(tp, TT_PERSIST))
 514                                 tcp_setpersist(tp);
 515                 }
 516         }
 517
 518         /* len will be >= 0 after this point. */
 519         KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__));
 520
 521         tcp_sndbuf_autoscale(tp, so, sendwin);
 522
 523         /*
 524          * Decide if we can use TCP Segmentation Offloading (if supported by
 525          * hardware).
 526          *
 527          * TSO may only be used if we are in a pure bulk sending state.  The
 528          * presence of TCP-MD5, SACK retransmits, SACK advertizements and
 529          * IP options prevent using TSO.  With TSO the TCP header is the same
 530          * (except for the sequence number) for all generated packets.  This
 531          * makes it impossible to transmit any options which vary per generated
 532          * segment or packet.
 533          *
 534          * IPv4 handling has a clear separation of ip options and ip header
 535          * flags while IPv6 combines both in in6p_outputopts. ip6_optlen() does
 536          * the right thing below to provide length of just ip options and thus
 537          * checking for ipoptlen is enough to decide if ip options are present.
 538          */
 539 #if defined(IPSEC) || defined(IPSEC_SUPPORT)
 540         /*
 541          * Pre-calculate here as we save another lookup into the darknesses
 542          * of IPsec that way and can actually decide if TSO is ok.
 543          */
 544 #ifdef INET6
 545         if (isipv6 && IPSEC_ENABLED(ipv6))
 546                 ipsec_optlen = IPSEC_HDRSIZE(ipv6, inp);
 547 #ifdef INET
 548         else
 549 #endif
 550 #endif /* INET6 */
 551 #ifdef INET
 552         if (IPSEC_ENABLED(ipv4))
 553                 ipsec_optlen = IPSEC_HDRSIZE(ipv4, inp);
 554 #endif /* INET */
 555 #endif /* IPSEC */
 556 #ifdef INET6
 557         if (isipv6)
 558                 ipoptlen = ip6_optlen(inp);
 559         else
 560 #endif
 561         if (inp->inp_options)
 562                 ipoptlen = inp->inp_options->m_len -
 563                                 offsetof(struct ipoption, ipopt_list);
 564         else
 565                 ipoptlen = 0;
 566 #if defined(IPSEC) || defined(IPSEC_SUPPORT)
 567         ipoptlen += ipsec_optlen;
 568 #endif
 569
 570         if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg &&
 571             (tp->t_port == 0) &&
 572             ((tp->t_flags & TF_SIGNATURE) == 0) &&
 573             tp->rcv_numsacks == 0 && sack_rxmit == 0 &&
 574             ipoptlen == 0 && !(flags & TH_SYN))
 575                 tso = 1;
 576
 577         if (sack_rxmit) {
 578                 if (SEQ_LT(p->rxmit + len, tp->snd_una + sbused(&so->so_snd)))
 579                         flags &= ~TH_FIN;
 580         } else {
 581                 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una +
 582                     sbused(&so->so_snd)))
 583                         flags &= ~TH_FIN;
 584         }
 585
 586         recwin = lmin(lmax(sbspace(&so->so_rcv), 0),
 587             (long)TCP_MAXWIN << tp->rcv_scale);
 588
 589         /*
 590          * Sender silly window avoidance.   We transmit under the following
 591          * conditions when len is non-zero:
 592          *
 593          *      - We have a full segment (or more with TSO)
 594          *      - This is the last buffer in a write()/send() and we are
 595          *        either idle or running NODELAY
 596          *      - we've timed out (e.g. persist timer)
 597          *      - we have more then 1/2 the maximum send window's worth of
 598          *        data (receiver may be limited the window size)
 599          *      - we need to retransmit
 600          */
 601         if (len) {
 602                 if (len >= tp->t_maxseg)
 603                         goto send;
 604                 /*
 605                  * As the TCP header options are now
 606                  * considered when setting up the initial
 607                  * window, we would not send the last segment
 608                  * if we skip considering the option length here.
 609                  * Note: this may not work when tcp headers change
 610                  * very dynamically in the future.
 611                  */
 612                 if ((((tp->t_flags & TF_SIGNATURE) ?
 613                         PADTCPOLEN(TCPOLEN_SIGNATURE) : 0) +
 614                     ((tp->t_flags & TF_RCVD_TSTMP) ?
 615                         PADTCPOLEN(TCPOLEN_TIMESTAMP) : 0) +
 616                     len) >= tp->t_maxseg)
 617                         goto send;
 618                 /*
 619                  * NOTE! on localhost connections an 'ack' from the remote
 620                  * end may occur synchronously with the output and cause
 621                  * us to flush a buffer queued with moretocome.  XXX
 622                  *
 623                  * note: the len + off check is almost certainly unnecessary.
 624                  */
 625                 if (!(tp->t_flags & TF_MORETOCOME) &&   /* normal case */
 626                     (idle || (tp->t_flags & TF_NODELAY)) &&
 627                     (uint32_t)len + (uint32_t)off >= sbavail(&so->so_snd) &&
 628                     (tp->t_flags & TF_NOPUSH) == 0) {
 629                         goto send;
 630                 }
 631                 if (tp->t_flags & TF_FORCEDATA)         /* typ. timeout case */
 632                         goto send;
 633                 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0)
 634                         goto send;
 635                 if (SEQ_LT(tp->snd_nxt, tp->snd_max))   /* retransmit case */
 636                         goto send;
 637                 if (sack_rxmit)
 638                         goto send;
 639         }
 640
 641         /*
 642          * Sending of standalone window updates.
 643          *
 644          * Window updates are important when we close our window due to a
 645          * full socket buffer and are opening it again after the application
 646          * reads data from it.  Once the window has opened again and the
 647          * remote end starts to send again the ACK clock takes over and
 648          * provides the most current window information.
 649          *
 650          * We must avoid the silly window syndrome whereas every read
 651          * from the receive buffer, no matter how small, causes a window
 652          * update to be sent.  We also should avoid sending a flurry of
 653          * window updates when the socket buffer had queued a lot of data
 654          * and the application is doing small reads.
 655          *
 656          * Prevent a flurry of pointless window updates by only sending
 657          * an update when we can increase the advertized window by more
 658          * than 1/4th of the socket buffer capacity.  When the buffer is
 659          * getting full or is very small be more aggressive and send an
 660          * update whenever we can increase by two mss sized segments.
 661          * In all other situations the ACK's to new incoming data will
 662          * carry further window increases.
 663          *
 664          * Don't send an independent window update if a delayed
 665          * ACK is pending (it will get piggy-backed on it) or the
 666          * remote side already has done a half-close and won't send
 667          * more data.  Skip this if the connection is in T/TCP
 668          * half-open state.
 669          */
 670         if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) &&
 671             !(tp->t_flags & TF_DELACK) &&
 672             !TCPS_HAVERCVDFIN(tp->t_state)) {
 673                 /*
 674                  * "adv" is the amount we could increase the window,
 675                  * taking into account that we are limited by
 676                  * TCP_MAXWIN << tp->rcv_scale.
 677                  */
 678                 int32_t adv;
 679                 int oldwin;
 680
 681                 adv = recwin;
 682                 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) {
 683                         oldwin = (tp->rcv_adv - tp->rcv_nxt);
 684                         if (adv > oldwin)
 685                                 adv -= oldwin;
 686                         else
 687                                 adv = 0;
 688                 } else
 689                         oldwin = 0;
 690
 691                 /*
 692                  * If the new window size ends up being the same as or less
 693                  * than the old size when it is scaled, then don't force
 694                  * a window update.
 695                  */
 696                 if (oldwin >> tp->rcv_scale >= (adv + oldwin) >> tp->rcv_scale)
 697                         goto dontupdate;
 698
 699                 if (adv >= (int32_t)(2 * tp->t_maxseg) &&
 700                     (adv >= (int32_t)(so->so_rcv.sb_hiwat / 4) ||
 701                      recwin <= (so->so_rcv.sb_hiwat / 8) ||
 702                      so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg ||
 703                      adv >= TCP_MAXWIN << tp->rcv_scale))
 704                         goto send;
 705                 if (2 * adv >= (int32_t)so->so_rcv.sb_hiwat)
 706                         goto send;
 707         }
 708 dontupdate:
 709
 710         /*
 711          * Send if we owe the peer an ACK, RST, SYN, or urgent data.  ACKNOW
 712          * is also a catch-all for the retransmit timer timeout case.
 713          */
 714         if (tp->t_flags & TF_ACKNOW)
 715                 goto send;
 716         if ((flags & TH_RST) ||
 717             ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0))
 718                 goto send;
 719         if (SEQ_GT(tp->snd_up, tp->snd_una))
 720                 goto send;
 721         /*
 722          * If our state indicates that FIN should be sent
 723          * and we have not yet done so, then we need to send.
 724          */
 725         if (flags & TH_FIN &&
 726             ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una))
 727                 goto send;
 728         /*
 729          * In SACK, it is possible for tcp_output to fail to send a segment
 730          * after the retransmission timer has been turned off.  Make sure
 731          * that the retransmission timer is set.
 732          */
 733         if ((tp->t_flags & TF_SACK_PERMIT) &&
 734             SEQ_GT(tp->snd_max, tp->snd_una) &&
 735             !tcp_timer_active(tp, TT_REXMT) &&
 736             !tcp_timer_active(tp, TT_PERSIST)) {
 737                 tcp_timer_activate(tp, TT_REXMT, TP_RXTCUR(tp));
 738                 goto just_return;
 739         }
 740         /*
 741          * TCP window updates are not reliable, rather a polling protocol
 742          * using ``persist'' packets is used to insure receipt of window
 743          * updates.  The three ``states'' for the output side are:
 744          *      idle                    not doing retransmits or persists
 745          *      persisting              to move a small or zero window
 746          *      (re)transmitting        and thereby not persisting
 747          *
 748          * tcp_timer_active(tp, TT_PERSIST)
 749          *      is true when we are in persist state.
 750          * (tp->t_flags & TF_FORCEDATA)
 751          *      is set when we are called to send a persist packet.
 752          * tcp_timer_active(tp, TT_REXMT)
 753          *      is set when we are retransmitting
 754          * The output side is idle when both timers are zero.
 755          *
 756          * If send window is too small, there is data to transmit, and no
 757          * retransmit or persist is pending, then go to persist state.
 758          * If nothing happens soon, send when timer expires:
 759          * if window is nonzero, transmit what we can,
 760          * otherwise force out a byte.
 761          */
 762         if (sbavail(&so->so_snd) && !tcp_timer_active(tp, TT_REXMT) &&
 763             !tcp_timer_active(tp, TT_PERSIST)) {
 764                 tp->t_rxtshift = 0;
 765                 tcp_setpersist(tp);
 766         }
 767
 768         /*
 769          * No reason to send a segment, just return.
 770          */
 771 just_return:
 772         SOCKBUF_UNLOCK(&so->so_snd);
 773         return (0);
 774
 775 send:
 776         SOCKBUF_LOCK_ASSERT(&so->so_snd);
 777         if (len > 0) {
 778                 if (len >= tp->t_maxseg)
 779                         tp->t_flags2 |= TF2_PLPMTU_MAXSEGSNT;
 780                 else
 781                         tp->t_flags2 &= ~TF2_PLPMTU_MAXSEGSNT;
 782         }
 783         /*
 784          * Before ESTABLISHED, force sending of initial options
 785          * unless TCP set not to do any options.
 786          * NOTE: we assume that the IP/TCP header plus TCP options
 787          * always fit in a single mbuf, leaving room for a maximum
 788          * link header, i.e.
 789          *      max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES
 790          */
 791         optlen = 0;
 792 #ifdef INET6
 793         if (isipv6)
 794                 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr);
 795         else
 796 #endif
 797                 hdrlen = sizeof (struct tcpiphdr);
 798
 799         if (flags & TH_SYN) {
 800                 tp->snd_nxt = tp->iss;
 801         }
 802
 803         /*
 804          * Compute options for segment.
 805          * We only have to care about SYN and established connection
 806          * segments.  Options for SYN-ACK segments are handled in TCP
 807          * syncache.
 808          */
 809         to.to_flags = 0;
 810         if ((tp->t_flags & TF_NOOPT) == 0) {
 811                 /* Maximum segment size. */
 812                 if (flags & TH_SYN) {
 813                         to.to_mss = tcp_mssopt(&inp->inp_inc);
 814                         if (tp->t_port)
 815                                 to.to_mss -= V_tcp_udp_tunneling_overhead;
 816                         to.to_flags |= TOF_MSS;
 817
 818                         /*
 819                          * On SYN or SYN|ACK transmits on TFO connections,
 820                          * only include the TFO option if it is not a
 821                          * retransmit, as the presence of the TFO option may
 822                          * have caused the original SYN or SYN|ACK to have
 823                          * been dropped by a middlebox.
 824                          */
 825                         if (IS_FASTOPEN(tp->t_flags) &&
 826                             (tp->t_rxtshift == 0)) {
 827                                 if (tp->t_state == TCPS_SYN_RECEIVED) {
 828                                         to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN;
 829                                         to.to_tfo_cookie =
 830                                             (u_int8_t *)&tp->t_tfo_cookie.server;
 831                                         to.to_flags |= TOF_FASTOPEN;
 832                                         wanted_cookie = 1;
 833                                 } else if (tp->t_state == TCPS_SYN_SENT) {
 834                                         to.to_tfo_len =
 835                                             tp->t_tfo_client_cookie_len;
 836                                         to.to_tfo_cookie =
 837                                             tp->t_tfo_cookie.client;
 838                                         to.to_flags |= TOF_FASTOPEN;
 839                                         wanted_cookie = 1;
 840                                         /*
 841                                          * If we wind up having more data to
 842                                          * send with the SYN than can fit in
 843                                          * one segment, don't send any more
 844                                          * until the SYN|ACK comes back from
 845                                          * the other end.
 846                                          */
 847                                         dont_sendalot = 1;
 848                                 }
 849                         }
 850                 }
 851                 /* Window scaling. */
 852                 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) {
 853                         to.to_wscale = tp->request_r_scale;
 854                         to.to_flags |= TOF_SCALE;
 855                 }
 856                 /* Timestamps. */
 857                 if ((tp->t_flags & TF_RCVD_TSTMP) ||
 858                     ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) {
 859                         curticks = tcp_ts_getticks();
 860                         to.to_tsval = curticks + tp->ts_offset;
 861                         to.to_tsecr = tp->ts_recent;
 862                         to.to_flags |= TOF_TS;
 863                         if (tp->t_rxtshift == 1)
 864                                 tp->t_badrxtwin = curticks;
 865                 }
 866
 867                 /* Set receive buffer autosizing timestamp. */
 868                 if (tp->rfbuf_ts == 0 &&
 869                     (so->so_rcv.sb_flags & SB_AUTOSIZE))
 870                         tp->rfbuf_ts = tcp_ts_getticks();
 871
 872                 /* Selective ACK's. */
 873                 if (tp->t_flags & TF_SACK_PERMIT) {
 874                         if (flags & TH_SYN)
 875                                 to.to_flags |= TOF_SACKPERM;
 876                         else if (TCPS_HAVEESTABLISHED(tp->t_state) &&
 877                             tp->rcv_numsacks > 0) {
 878                                 to.to_flags |= TOF_SACK;
 879                                 to.to_nsacks = tp->rcv_numsacks;
 880                                 to.to_sacks = (u_char *)tp->sackblks;
 881                         }
 882                 }
 883 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
 884                 /* TCP-MD5 (RFC2385). */
 885                 /*
 886                  * Check that TCP_MD5SIG is enabled in tcpcb to
 887                  * account the size needed to set this TCP option.
 888                  */
 889                 if (tp->t_flags & TF_SIGNATURE)
 890                         to.to_flags |= TOF_SIGNATURE;
 891 #endif /* TCP_SIGNATURE */
 892
 893                 /* Processing the options. */
 894                 hdrlen += optlen = tcp_addoptions(&to, opt);
 895                 /*
 896                  * If we wanted a TFO option to be added, but it was unable
 897                  * to fit, ensure no data is sent.
 898                  */
 899                 if (IS_FASTOPEN(tp->t_flags) && wanted_cookie &&
 900                     !(to.to_flags & TOF_FASTOPEN))
 901                         len = 0;
 902         }
 903         if (tp->t_port) {
 904                 if (V_tcp_udp_tunneling_port == 0) {
 905                         /* The port was removed?? */
 906                         SOCKBUF_UNLOCK(&so->so_snd);
 907                         return (EHOSTUNREACH);
 908                 }
 909                 hdrlen += sizeof(struct udphdr);
 910         }
 911         /*
 912          * Adjust data length if insertion of options will
 913          * bump the packet length beyond the t_maxseg length.
 914          * Clear the FIN bit because we cut off the tail of
 915          * the segment.
 916          */
 917         if (len + optlen + ipoptlen > tp->t_maxseg) {
 918                 flags &= ~TH_FIN;
 919
 920                 if (tso) {
 921                         u_int if_hw_tsomax;
 922                         u_int moff;
 923                         int max_len;
 924
 925                         /* extract TSO information */
 926                         if_hw_tsomax = tp->t_tsomax;
 927                         if_hw_tsomaxsegcount = tp->t_tsomaxsegcount;
 928                         if_hw_tsomaxsegsize = tp->t_tsomaxsegsize;
 929
 930                         /*
 931                          * Limit a TSO burst to prevent it from
 932                          * overflowing or exceeding the maximum length
 933                          * allowed by the network interface:
 934                          */
 935                         KASSERT(ipoptlen == 0,
 936                             ("%s: TSO can't do IP options", __func__));
 937
 938                         /*
 939                          * Check if we should limit by maximum payload
 940                          * length:
 941                          */
 942                         if (if_hw_tsomax != 0) {
 943                                 /* compute maximum TSO length */
 944                                 max_len = (if_hw_tsomax - hdrlen -
 945                                     max_linkhdr);
 946                                 if (max_len <= 0) {
 947                                         len = 0;
 948                                 } else if (len > max_len) {
 949                                         sendalot = 1;
 950                                         len = max_len;
 951                                 }
 952                         }
 953
 954                         /*
 955                          * Prevent the last segment from being
 956                          * fractional unless the send sockbuf can be
 957                          * emptied:
 958                          */
 959                         max_len = (tp->t_maxseg - optlen);
 960                         if (((uint32_t)off + (uint32_t)len) <
 961                             sbavail(&so->so_snd)) {
 962                                 moff = len % max_len;
 963                                 if (moff != 0) {
 964                                         len -= moff;
 965                                         sendalot = 1;
 966                                 }
 967                         }
 968
 969                         /*
 970                          * In case there are too many small fragments
 971                          * don't use TSO:
 972                          */
 973                         if (len <= max_len) {
 974                                 len = max_len;
 975                                 sendalot = 1;
 976                                 tso = 0;
 977                         }
 978
 979                         /*
 980                          * Send the FIN in a separate segment
 981                          * after the bulk sending is done.
 982                          * We don't trust the TSO implementations
 983                          * to clear the FIN flag on all but the
 984                          * last segment.
 985                          */
 986                         if (tp->t_flags & TF_NEEDFIN)
 987                                 sendalot = 1;
 988                 } else {
 989                         if (optlen + ipoptlen >= tp->t_maxseg) {
 990                                 /*
 991                                  * Since we don't have enough space to put
 992                                  * the IP header chain and the TCP header in
 993                                  * one packet as required by RFC 7112, don't
 994                                  * send it. Also ensure that at least one
 995                                  * byte of the payload can be put into the
 996                                  * TCP segment.
 997                                  */
 998                                 SOCKBUF_UNLOCK(&so->so_snd);
 999                                 error = EMSGSIZE;
1000                                 sack_rxmit = 0;
1001                                 goto out;
1002                         }
1003                         len = tp->t_maxseg - optlen - ipoptlen;
1004                         sendalot = 1;
1005                         if (dont_sendalot)
1006                                 sendalot = 0;
1007                 }
1008         } else
1009                 tso = 0;
1010
1011         KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET,
1012             ("%s: len > IP_MAXPACKET", __func__));
1013
1014 /*#ifdef DIAGNOSTIC*/
1015 #ifdef INET6
1016         if (max_linkhdr + hdrlen > MCLBYTES)
1017 #else
1018         if (max_linkhdr + hdrlen > MHLEN)
1019 #endif
1020                 panic("tcphdr too big");
1021 /*#endif*/
1022
1023         /*
1024          * This KASSERT is here to catch edge cases at a well defined place.
1025          * Before, those had triggered (random) panic conditions further down.
1026          */
1027         KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__));
1028
1029         /*
1030          * Grab a header mbuf, attaching a copy of data to
1031          * be transmitted, and initialize the header from
1032          * the template for sends on this connection.
1033          */
1034         if (len) {
1035                 struct mbuf *mb;
1036                 struct sockbuf *msb;
1037                 u_int moff;
1038
1039                 if ((tp->t_flags & TF_FORCEDATA) && len == 1) {
1040                         TCPSTAT_INC(tcps_sndprobe);
1041 #ifdef STATS
1042                         if (SEQ_LT(tp->snd_nxt, tp->snd_max))
1043                                 stats_voi_update_abs_u32(tp->t_stats,
1044                                 VOI_TCP_RETXPB, len);
1045                         else
1046                                 stats_voi_update_abs_u64(tp->t_stats,
1047                                     VOI_TCP_TXPB, len);
1048 #endif /* STATS */
1049                 } else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) {
1050                         tp->t_sndrexmitpack++;
1051                         TCPSTAT_INC(tcps_sndrexmitpack);
1052                         TCPSTAT_ADD(tcps_sndrexmitbyte, len);
1053 #ifdef STATS
1054                         stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_RETXPB,
1055                             len);
1056 #endif /* STATS */
1057                 } else {
1058                         TCPSTAT_INC(tcps_sndpack);
1059                         TCPSTAT_ADD(tcps_sndbyte, len);
1060 #ifdef STATS
1061                         stats_voi_update_abs_u64(tp->t_stats, VOI_TCP_TXPB,
1062                             len);
1063 #endif /* STATS */
1064                 }
1065 #ifdef INET6
1066                 if (MHLEN < hdrlen + max_linkhdr)
1067                         m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR);
1068                 else
1069 #endif
1070                         m = m_gethdr(M_NOWAIT, MT_DATA);
1071
1072                 if (m == NULL) {
1073                         SOCKBUF_UNLOCK(&so->so_snd);
1074                         error = ENOBUFS;
1075                         sack_rxmit = 0;
1076                         goto out;
1077                 }
1078
1079                 m->m_data += max_linkhdr;
1080                 m->m_len = hdrlen;
1081
1082                 /*
1083                  * Start the m_copy functions from the closest mbuf
1084                  * to the offset in the socket buffer chain.
1085                  */
1086                 mb = sbsndptr_noadv(&so->so_snd, off, &moff);
1087                 if (len <= MHLEN - hdrlen - max_linkhdr && !hw_tls) {
1088                         m_copydata(mb, moff, len,
1089                             mtod(m, caddr_t) + hdrlen);
1090                         if (SEQ_LT(tp->snd_nxt, tp->snd_max))
1091                                 sbsndptr_adv(&so->so_snd, mb, len);
1092                         m->m_len += len;
1093                 } else {
1094                         if (SEQ_LT(tp->snd_nxt, tp->snd_max))
1095                                 msb = NULL;
1096                         else
1097                                 msb = &so->so_snd;
1098                         m->m_next = tcp_m_copym(mb, moff,
1099                             &len, if_hw_tsomaxsegcount,
1100                             if_hw_tsomaxsegsize, msb, hw_tls);
1101                         if (len <= (tp->t_maxseg - optlen)) {
1102                                 /*
1103                                  * Must have ran out of mbufs for the copy
1104                                  * shorten it to no longer need tso. Lets
1105                                  * not put on sendalot since we are low on
1106                                  * mbufs.
1107                                  */
1108                                 tso = 0;
1109                         }
1110                         if (m->m_next == NULL) {
1111                                 SOCKBUF_UNLOCK(&so->so_snd);
1112                                 (void) m_free(m);
1113                                 error = ENOBUFS;
1114                                 sack_rxmit = 0;
1115                                 goto out;
1116                         }
1117                 }
1118
1119                 /*
1120                  * If we're sending everything we've got, set PUSH.
1121                  * (This will keep happy those implementations which only
1122                  * give data to the user when a buffer fills or
1123                  * a PUSH comes in.)
1124                  */
1125                 if (((uint32_t)off + (uint32_t)len == sbused(&so->so_snd)) &&
1126                     !(flags & TH_SYN))
1127                         flags |= TH_PUSH;
1128                 SOCKBUF_UNLOCK(&so->so_snd);
1129         } else {
1130                 SOCKBUF_UNLOCK(&so->so_snd);
1131                 if (tp->t_flags & TF_ACKNOW)
1132                         TCPSTAT_INC(tcps_sndacks);
1133                 else if (flags & (TH_SYN|TH_FIN|TH_RST))
1134                         TCPSTAT_INC(tcps_sndctrl);
1135                 else if (SEQ_GT(tp->snd_up, tp->snd_una))
1136                         TCPSTAT_INC(tcps_sndurg);
1137                 else
1138                         TCPSTAT_INC(tcps_sndwinup);
1139
1140                 m = m_gethdr(M_NOWAIT, MT_DATA);
1141                 if (m == NULL) {
1142                         error = ENOBUFS;
1143                         sack_rxmit = 0;
1144                         goto out;
1145                 }
1146 #ifdef INET6
1147                 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) &&
1148                     MHLEN >= hdrlen) {
1149                         M_ALIGN(m, hdrlen);
1150                 } else
1151 #endif
1152                 m->m_data += max_linkhdr;
1153                 m->m_len = hdrlen;
1154         }
1155         SOCKBUF_UNLOCK_ASSERT(&so->so_snd);
1156         m->m_pkthdr.rcvif = (struct ifnet *)0;
1157 #ifdef MAC
1158         mac_inpcb_create_mbuf(inp, m);
1159 #endif
1160 #ifdef INET6
1161         if (isipv6) {
1162                 ip6 = mtod(m, struct ip6_hdr *);
1163                 if (tp->t_port) {
1164                         udp = (struct udphdr *)((caddr_t)ip6 + sizeof(struct ip6_hdr));
1165                         udp->uh_sport = htons(V_tcp_udp_tunneling_port);
1166                         udp->uh_dport = tp->t_port;
1167                         ulen = hdrlen + len - sizeof(struct ip6_hdr);
1168                         udp->uh_ulen = htons(ulen);
1169                         th = (struct tcphdr *)(udp + 1);
1170                 } else {
1171                         th = (struct tcphdr *)(ip6 + 1);
1172                 }
1173                 tcpip_fillheaders(inp, tp->t_port, ip6, th);
1174         } else
1175 #endif /* INET6 */
1176         {
1177                 ip = mtod(m, struct ip *);
1178 #ifdef TCPDEBUG
1179                 ipov = (struct ipovly *)ip;
1180 #endif
1181                 if (tp->t_port) {
1182                         udp = (struct udphdr *)((caddr_t)ip + sizeof(struct ip));
1183                         udp->uh_sport = htons(V_tcp_udp_tunneling_port);
1184                         udp->uh_dport = tp->t_port;
1185                         ulen = hdrlen + len - sizeof(struct ip);
1186                         udp->uh_ulen = htons(ulen);
1187                         th = (struct tcphdr *)(udp + 1);
1188                 } else
1189                         th = (struct tcphdr *)(ip + 1);
1190                 tcpip_fillheaders(inp, tp->t_port, ip, th);
1191         }
1192
1193         /*
1194          * Fill in fields, remembering maximum advertised
1195          * window for use in delaying messages about window sizes.
1196          * If resending a FIN, be sure not to use a new sequence number.
1197          */
1198         if (flags & TH_FIN && tp->t_flags & TF_SENTFIN &&
1199             tp->snd_nxt == tp->snd_max)
1200                 tp->snd_nxt--;
1201         /*
1202          * If we are starting a connection, send ECN setup
1203          * SYN packet. If we are on a retransmit, we may
1204          * resend those bits a number of times as per
1205          * RFC 3168.
1206          */
1207         if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) {
1208                 flags |= tcp_ecn_output_syn_sent(tp);
1209         }
1210         /* Also handle parallel SYN for ECN */
1211         if ((TCPS_HAVERCVDSYN(tp->t_state)) &&
1212             (tp->t_flags2 & (TF2_ECN_PERMIT | TF2_ACE_PERMIT))) {
1213                 int ect = tcp_ecn_output_established(tp, &flags, len, sack_rxmit);
1214                 if ((tp->t_state == TCPS_SYN_RECEIVED) &&
1215                     (tp->t_flags2 & TF2_ECN_SND_ECE))
1216                         tp->t_flags2 &= ~TF2_ECN_SND_ECE;
1217 #ifdef INET6
1218                 if (isipv6) {
1219                         ip6->ip6_flow &= ~htonl(IPTOS_ECN_MASK << 20);
1220                         ip6->ip6_flow |= htonl(ect << 20);
1221                 }
1222                 else
1223 #endif
1224                 {
1225                         ip->ip_tos &= ~IPTOS_ECN_MASK;
1226                         ip->ip_tos |= ect;
1227                 }
1228         }
1229
1230         /*
1231          * If we are doing retransmissions, then snd_nxt will
1232          * not reflect the first unsent octet.  For ACK only
1233          * packets, we do not want the sequence number of the
1234          * retransmitted packet, we want the sequence number
1235          * of the next unsent octet.  So, if there is no data
1236          * (and no SYN or FIN), use snd_max instead of snd_nxt
1237          * when filling in ti_seq.  But if we are in persist
1238          * state, snd_max might reflect one byte beyond the
1239          * right edge of the window, so use snd_nxt in that
1240          * case, since we know we aren't doing a retransmission.
1241          * (retransmit and persist are mutually exclusive...)
1242          */
1243         if (sack_rxmit == 0) {
1244                 if (len || (flags & (TH_SYN|TH_FIN)) ||
1245                     tcp_timer_active(tp, TT_PERSIST))
1246                         th->th_seq = htonl(tp->snd_nxt);
1247                 else
1248                         th->th_seq = htonl(tp->snd_max);
1249         } else {
1250                 th->th_seq = htonl(p->rxmit);
1251                 p->rxmit += len;
1252                 /*
1253                  * Lost Retransmission Detection
1254                  * trigger resending of a (then
1255                  * still existing) hole, when
1256                  * fack acks recoverypoint.
1257                  */
1258                 if ((tp->t_flags & TF_LRD) && SEQ_GEQ(p->rxmit, p->end))
1259                         p->rxmit = tp->snd_recover;
1260                 tp->sackhint.sack_bytes_rexmit += len;
1261         }
1262         if (IN_RECOVERY(tp->t_flags)) {
1263                 /*
1264                  * Account all bytes transmitted while
1265                  * IN_RECOVERY, simplifying PRR and
1266                  * Lost Retransmit Detection
1267                  */
1268                 tp->sackhint.prr_out += len;
1269         }
1270         th->th_ack = htonl(tp->rcv_nxt);
1271         if (optlen) {
1272                 bcopy(opt, th + 1, optlen);
1273                 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2;
1274         }
1275         tcp_set_flags(th, flags);
1276         /*
1277          * Calculate receive window.  Don't shrink window,
1278          * but avoid silly window syndrome.
1279          * If a RST segment is sent, advertise a window of zero.
1280          */
1281         if (flags & TH_RST) {
1282                 recwin = 0;
1283         } else {
1284                 if (recwin < (so->so_rcv.sb_hiwat / 4) &&
1285                     recwin < tp->t_maxseg)
1286                         recwin = 0;
1287                 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) &&
1288                     recwin < (tp->rcv_adv - tp->rcv_nxt))
1289                         recwin = (tp->rcv_adv - tp->rcv_nxt);
1290         }
1291         /*
1292          * According to RFC1323 the window field in a SYN (i.e., a <SYN>
1293          * or <SYN,ACK>) segment itself is never scaled.  The <SYN,ACK>
1294          * case is handled in syncache.
1295          */
1296         if (flags & TH_SYN)
1297                 th->th_win = htons((u_short)
1298                                 (min(sbspace(&so->so_rcv), TCP_MAXWIN)));
1299         else {
1300                 /* Avoid shrinking window with window scaling. */
1301                 recwin = roundup2(recwin, 1 << tp->rcv_scale);
1302                 th->th_win = htons((u_short)(recwin >> tp->rcv_scale));
1303         }
1304
1305         /*
1306          * Adjust the RXWIN0SENT flag - indicate that we have advertised
1307          * a 0 window.  This may cause the remote transmitter to stall.  This
1308          * flag tells soreceive() to disable delayed acknowledgements when
1309          * draining the buffer.  This can occur if the receiver is attempting
1310          * to read more data than can be buffered prior to transmitting on
1311          * the connection.
1312          */
1313         if (th->th_win == 0) {
1314                 tp->t_sndzerowin++;
1315                 tp->t_flags |= TF_RXWIN0SENT;
1316         } else
1317                 tp->t_flags &= ~TF_RXWIN0SENT;
1318         if (SEQ_GT(tp->snd_up, tp->snd_nxt)) {
1319                 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt));
1320                 th->th_flags |= TH_URG;
1321         } else
1322                 /*
1323                  * If no urgent pointer to send, then we pull
1324                  * the urgent pointer to the left edge of the send window
1325                  * so that it doesn't drift into the send window on sequence
1326                  * number wraparound.
1327                  */
1328                 tp->snd_up = tp->snd_una;               /* drag it along */
1329
1330         /*
1331          * Put TCP length in extended header, and then
1332          * checksum extended header and data.
1333          */
1334         m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */
1335
1336 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1337         if (to.to_flags & TOF_SIGNATURE) {
1338                 /*
1339                  * Calculate MD5 signature and put it into the place
1340                  * determined before.
1341                  * NOTE: since TCP options buffer doesn't point into
1342                  * mbuf's data, calculate offset and use it.
1343                  */
1344                 if (!TCPMD5_ENABLED() || (error = TCPMD5_OUTPUT(m, th,
1345                     (u_char *)(th + 1) + (to.to_signature - opt))) != 0) {
1346                         /*
1347                          * Do not send segment if the calculation of MD5
1348                          * digest has failed.
1349                          */
1350                         m_freem(m);
1351                         goto out;
1352                 }
1353         }
1354 #endif
1355 #ifdef INET6
1356         if (isipv6) {
1357                 /*
1358                  * There is no need to fill in ip6_plen right now.
1359                  * It will be filled later by ip6_output.
1360                  */
1361                 if (tp->t_port) {
1362                         m->m_pkthdr.csum_flags = CSUM_UDP_IPV6;
1363                         m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum);
1364                         udp->uh_sum = in6_cksum_pseudo(ip6, ulen, IPPROTO_UDP, 0);
1365                         th->th_sum = htons(0);
1366                         UDPSTAT_INC(udps_opackets);
1367                 } else {
1368                         m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
1369                         m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1370                         th->th_sum = in6_cksum_pseudo(ip6,
1371                             sizeof(struct tcphdr) + optlen + len, IPPROTO_TCP,
1372                             0);
1373                 }
1374         }
1375 #endif
1376 #if defined(INET6) && defined(INET)
1377         else
1378 #endif
1379 #ifdef INET
1380         {
1381                 if (tp->t_port) {
1382                         m->m_pkthdr.csum_flags = CSUM_UDP;
1383                         m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum);
1384                         udp->uh_sum = in_pseudo(ip->ip_src.s_addr,
1385                            ip->ip_dst.s_addr, htons(ulen + IPPROTO_UDP));
1386                         th->th_sum = htons(0);
1387                         UDPSTAT_INC(udps_opackets);
1388                 } else {
1389                         m->m_pkthdr.csum_flags = CSUM_TCP;
1390                         m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1391                         th->th_sum = in_pseudo(ip->ip_src.s_addr,
1392                             ip->ip_dst.s_addr, htons(sizeof(struct tcphdr) +
1393                             IPPROTO_TCP + len + optlen));
1394                 }
1395
1396                 /* IP version must be set here for ipv4/ipv6 checking later */
1397                 KASSERT(ip->ip_v == IPVERSION,
1398                     ("%s: IP version incorrect: %d", __func__, ip->ip_v));
1399         }
1400 #endif
1401
1402         /*
1403          * Enable TSO and specify the size of the segments.
1404          * The TCP pseudo header checksum is always provided.
1405          */
1406         if (tso) {
1407                 KASSERT(len > tp->t_maxseg - optlen,
1408                     ("%s: len <= tso_segsz", __func__));
1409                 m->m_pkthdr.csum_flags |= CSUM_TSO;
1410                 m->m_pkthdr.tso_segsz = tp->t_maxseg - optlen;
1411         }
1412
1413         KASSERT(len + hdrlen == m_length(m, NULL),
1414             ("%s: mbuf chain shorter than expected: %d + %u != %u",
1415             __func__, len, hdrlen, m_length(m, NULL)));
1416
1417 #ifdef TCP_HHOOK
1418         /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */
1419         hhook_run_tcp_est_out(tp, th, &to, len, tso);
1420 #endif
1421
1422 #ifdef TCPDEBUG
1423         /*
1424          * Trace.
1425          */
1426         if (so->so_options & SO_DEBUG) {
1427                 u_short save = 0;
1428 #ifdef INET6
1429                 if (!isipv6)
1430 #endif
1431                 {
1432                         save = ipov->ih_len;
1433                         ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */);
1434                 }
1435                 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0);
1436 #ifdef INET6
1437                 if (!isipv6)
1438 #endif
1439                 ipov->ih_len = save;
1440         }
1441 #endif /* TCPDEBUG */
1442         TCP_PROBE3(debug__output, tp, th, m);
1443
1444         /* We're getting ready to send; log now. */
1445         /* XXXMT: We are not honoring verbose logging. */
1446         if (tp->t_logstate != TCP_LOG_STATE_OFF)
1447                 lgb = tcp_log_event_(tp, th, &so->so_rcv, &so->so_snd,
1448                     TCP_LOG_OUT, ERRNO_UNK, len, NULL, false, NULL, NULL, 0,
1449                     NULL);
1450         else
1451                 lgb = NULL;
1452
1453         /*
1454          * Fill in IP length and desired time to live and
1455          * send to IP level.  There should be a better way
1456          * to handle ttl and tos; we could keep them in
1457          * the template, but need a way to checksum without them.
1458          */
1459         /*
1460          * m->m_pkthdr.len should have been set before checksum calculation,
1461          * because in6_cksum() need it.
1462          */
1463 #ifdef INET6
1464         if (isipv6) {
1465                 /*
1466                  * we separately set hoplimit for every segment, since the
1467                  * user might want to change the value via setsockopt.
1468                  * Also, desired default hop limit might be changed via
1469                  * Neighbor Discovery.
1470                  */
1471                 ip6->ip6_hlim = in6_selecthlim(inp, NULL);
1472
1473                 /*
1474                  * Set the packet size here for the benefit of DTrace probes.
1475                  * ip6_output() will set it properly; it's supposed to include
1476                  * the option header lengths as well.
1477                  */
1478                 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6));
1479
1480                 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss)
1481                         tp->t_flags2 |= TF2_PLPMTU_PMTUD;
1482                 else
1483                         tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
1484
1485                 if (tp->t_state == TCPS_SYN_SENT)
1486                         TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th);
1487
1488                 TCP_PROBE5(send, NULL, tp, ip6, tp, th);
1489
1490 #ifdef TCPPCAP
1491                 /* Save packet, if requested. */
1492                 tcp_pcap_add(th, m, &(tp->t_outpkts));
1493 #endif
1494
1495                 /* TODO: IPv6 IP6TOS_ECT bit on */
1496                 error = ip6_output(m, inp->in6p_outputopts, &inp->inp_route6,
1497                     ((so->so_options & SO_DONTROUTE) ?  IP_ROUTETOIF : 0),
1498                     NULL, NULL, inp);
1499
1500                 if (error == EMSGSIZE && inp->inp_route6.ro_nh != NULL)
1501                         mtu = inp->inp_route6.ro_nh->nh_mtu;
1502         }
1503 #endif /* INET6 */
1504 #if defined(INET) && defined(INET6)
1505         else
1506 #endif
1507 #ifdef INET
1508     {
1509         ip->ip_len = htons(m->m_pkthdr.len);
1510 #ifdef INET6
1511         if (inp->inp_vflag & INP_IPV6PROTO)
1512                 ip->ip_ttl = in6_selecthlim(inp, NULL);
1513 #endif /* INET6 */
1514         /*
1515          * If we do path MTU discovery, then we set DF on every packet.
1516          * This might not be the best thing to do according to RFC3390
1517          * Section 2. However the tcp hostcache migitates the problem
1518          * so it affects only the first tcp connection with a host.
1519          *
1520          * NB: Don't set DF on small MTU/MSS to have a safe fallback.
1521          */
1522         if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) {
1523                 tp->t_flags2 |= TF2_PLPMTU_PMTUD;
1524                 if (tp->t_port == 0 || len < V_tcp_minmss) {
1525                         ip->ip_off |= htons(IP_DF);
1526                 }
1527         } else {
1528                 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
1529         }
1530
1531         if (tp->t_state == TCPS_SYN_SENT)
1532                 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th);
1533
1534         TCP_PROBE5(send, NULL, tp, ip, tp, th);
1535
1536 #ifdef TCPPCAP
1537         /* Save packet, if requested. */
1538         tcp_pcap_add(th, m, &(tp->t_outpkts));
1539 #endif
1540
1541         error = ip_output(m, inp->inp_options, &inp->inp_route,
1542             ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, inp);
1543
1544         if (error == EMSGSIZE && inp->inp_route.ro_nh != NULL)
1545                 mtu = inp->inp_route.ro_nh->nh_mtu;
1546     }
1547 #endif /* INET */
1548
1549         if (lgb != NULL) {
1550                 lgb->tlb_errno = error;
1551                 lgb = NULL;
1552         }
1553 out:
1554         if (error == 0)
1555                 tcp_account_for_send(tp, len, (tp->snd_nxt != tp->snd_max), 0, hw_tls);
1556         /*
1557          * In transmit state, time the transmission and arrange for
1558          * the retransmit.  In persist state, just set snd_max.
1559          */
1560         if ((tp->t_flags & TF_FORCEDATA) == 0 ||
1561             !tcp_timer_active(tp, TT_PERSIST)) {
1562                 tcp_seq startseq = tp->snd_nxt;
1563
1564                 /*
1565                  * Advance snd_nxt over sequence space of this segment.
1566                  */
1567                 if (flags & (TH_SYN|TH_FIN)) {
1568                         if (flags & TH_SYN)
1569                                 tp->snd_nxt++;
1570                         if (flags & TH_FIN) {
1571                                 tp->snd_nxt++;
1572                                 tp->t_flags |= TF_SENTFIN;
1573                         }
1574                 }
1575                 if (sack_rxmit)
1576                         goto timer;
1577                 tp->snd_nxt += len;
1578                 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) {
1579                         /*
1580                          * Update "made progress" indication if we just
1581                          * added new data to an empty socket buffer.
1582                          */
1583                         if (tp->snd_una == tp->snd_max)
1584                                 tp->t_acktime = ticks;
1585                         tp->snd_max = tp->snd_nxt;
1586                         /*
1587                          * Time this transmission if not a retransmission and
1588                          * not currently timing anything.
1589                          */
1590                         tp->t_sndtime = ticks;
1591                         if (tp->t_rtttime == 0) {
1592                                 tp->t_rtttime = ticks;
1593                                 tp->t_rtseq = startseq;
1594                                 TCPSTAT_INC(tcps_segstimed);
1595                         }
1596 #ifdef STATS
1597                         if (!(tp->t_flags & TF_GPUTINPROG) && len) {
1598                                 tp->t_flags |= TF_GPUTINPROG;
1599                                 tp->gput_seq = startseq;
1600                                 tp->gput_ack = startseq +
1601                                     ulmin(sbavail(&so->so_snd) - off, sendwin);
1602                                 tp->gput_ts = tcp_ts_getticks();
1603                         }
1604 #endif /* STATS */
1605                 }
1606
1607                 /*
1608                  * Set retransmit timer if not currently set,
1609                  * and not doing a pure ack or a keep-alive probe.
1610                  * Initial value for retransmit timer is smoothed
1611                  * round-trip time + 2 * round-trip time variance.
1612                  * Initialize shift counter which is used for backoff
1613                  * of retransmit time.
1614                  */
1615 timer:
1616                 if (!tcp_timer_active(tp, TT_REXMT) &&
1617                     ((sack_rxmit && tp->snd_nxt != tp->snd_max) ||
1618                      (tp->snd_nxt != tp->snd_una))) {
1619                         if (tcp_timer_active(tp, TT_PERSIST)) {
1620                                 tcp_timer_activate(tp, TT_PERSIST, 0);
1621                                 tp->t_rxtshift = 0;
1622                         }
1623                         tcp_timer_activate(tp, TT_REXMT, TP_RXTCUR(tp));
1624                 } else if (len == 0 && sbavail(&so->so_snd) &&
1625                     !tcp_timer_active(tp, TT_REXMT) &&
1626                     !tcp_timer_active(tp, TT_PERSIST)) {
1627                         /*
1628                          * Avoid a situation where we do not set persist timer
1629                          * after a zero window condition. For example:
1630                          * 1) A -> B: packet with enough data to fill the window
1631                          * 2) B -> A: ACK for #1 + new data (0 window
1632                          *    advertisement)
1633                          * 3) A -> B: ACK for #2, 0 len packet
1634                          *
1635                          * In this case, A will not activate the persist timer,
1636                          * because it chose to send a packet. Unless tcp_output
1637                          * is called for some other reason (delayed ack timer,
1638                          * another input packet from B, socket syscall), A will
1639                          * not send zero window probes.
1640                          *
1641                          * So, if you send a 0-length packet, but there is data
1642                          * in the socket buffer, and neither the rexmt or
1643                          * persist timer is already set, then activate the
1644                          * persist timer.
1645                          */
1646                         tp->t_rxtshift = 0;
1647                         tcp_setpersist(tp);
1648                 }
1649         } else {
1650                 /*
1651                  * Persist case, update snd_max but since we are in
1652                  * persist mode (no window) we do not update snd_nxt.
1653                  */
1654                 int xlen = len;
1655                 if (flags & TH_SYN)
1656                         ++xlen;
1657                 if (flags & TH_FIN) {
1658                         ++xlen;
1659                         tp->t_flags |= TF_SENTFIN;
1660                 }
1661                 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max))
1662                         tp->snd_max = tp->snd_nxt + xlen;
1663         }
1664         if ((error == 0) &&
1665             (TCPS_HAVEESTABLISHED(tp->t_state) &&
1666              (tp->t_flags & TF_SACK_PERMIT) &&
1667              tp->rcv_numsacks > 0)) {
1668                     /* Clean up any DSACK's sent */
1669                     tcp_clean_dsack_blocks(tp);
1670         }
1671         if (error) {
1672                 /*
1673                  * We know that the packet was lost, so back out the
1674                  * sequence number advance, if any.
1675                  *
1676                  * If the error is EPERM the packet got blocked by the
1677                  * local firewall.  Normally we should terminate the
1678                  * connection but the blocking may have been spurious
1679                  * due to a firewall reconfiguration cycle.  So we treat
1680                  * it like a packet loss and let the retransmit timer and
1681                  * timeouts do their work over time.
1682                  * XXX: It is a POLA question whether calling tcp_drop right
1683                  * away would be the really correct behavior instead.
1684                  */
1685                 if (((tp->t_flags & TF_FORCEDATA) == 0 ||
1686                     !tcp_timer_active(tp, TT_PERSIST)) &&
1687                     ((flags & TH_SYN) == 0) &&
1688                     (error != EPERM)) {
1689                         if (sack_rxmit) {
1690                                 p->rxmit -= len;
1691                                 tp->sackhint.sack_bytes_rexmit -= len;
1692                                 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0,
1693                                     ("sackhint bytes rtx >= 0"));
1694                                 KASSERT((flags & TH_FIN) == 0,
1695                                     ("error while FIN with SACK rxmit"));
1696                         } else {
1697                                 tp->snd_nxt -= len;
1698                                 if (flags & TH_FIN)
1699                                         tp->snd_nxt--;
1700                         }
1701                 }
1702                 SOCKBUF_UNLOCK_ASSERT(&so->so_snd);     /* Check gotos. */
1703                 switch (error) {
1704                 case EACCES:
1705                 case EPERM:
1706                         tp->t_softerror = error;
1707                         return (error);
1708                 case ENOBUFS:
1709                         TCP_XMIT_TIMER_ASSERT(tp, len, flags);
1710                         tp->snd_cwnd = tp->t_maxseg;
1711                         return (0);
1712                 case EMSGSIZE:
1713                         /*
1714                          * For some reason the interface we used initially
1715                          * to send segments changed to another or lowered
1716                          * its MTU.
1717                          * If TSO was active we either got an interface
1718                          * without TSO capabilits or TSO was turned off.
1719                          * If we obtained mtu from ip_output() then update
1720                          * it and try again.
1721                          */
1722                         if (tso)
1723                                 tp->t_flags &= ~TF_TSO;
1724                         if (mtu != 0) {
1725                                 tcp_mss_update(tp, -1, mtu, NULL, NULL);
1726                                 goto again;
1727                         }
1728                         return (error);
1729                 case EHOSTDOWN:
1730                 case EHOSTUNREACH:
1731                 case ENETDOWN:
1732                 case ENETUNREACH:
1733                         if (TCPS_HAVERCVDSYN(tp->t_state)) {
1734                                 tp->t_softerror = error;
1735                                 return (0);
1736                         }
1737                         /* FALLTHROUGH */
1738                 default:
1739                         return (error);
1740                 }
1741         }
1742         TCPSTAT_INC(tcps_sndtotal);
1743
1744         /*
1745          * Data sent (as far as we can tell).
1746          * If this advertises a larger window than any other segment,
1747          * then remember the size of the advertised window.
1748          * Any pending ACK has now been sent.
1749          */
1750         if (SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv))
1751                 tp->rcv_adv = tp->rcv_nxt + recwin;
1752         tp->last_ack_sent = tp->rcv_nxt;
1753         tp->t_flags &= ~(TF_ACKNOW | TF_DELACK);
1754         if (tcp_timer_active(tp, TT_DELACK))
1755                 tcp_timer_activate(tp, TT_DELACK, 0);
1756 #if 0
1757         /*
1758          * This completely breaks TCP if newreno is turned on.  What happens
1759          * is that if delayed-acks are turned on on the receiver, this code
1760          * on the transmitter effectively destroys the TCP window, forcing
1761          * it to four packets (1.5Kx4 = 6K window).
1762          */
1763         if (sendalot && --maxburst)
1764                 goto again;
1765 #endif
1766         if (sendalot)
1767                 goto again;
1768         return (0);
1769 }
1770
1771 void
1772 tcp_setpersist(struct tcpcb *tp)
1773 {
1774         int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1;
1775         int tt;
1776         int maxunacktime;
1777
1778         tp->t_flags &= ~TF_PREVVALID;
1779         if (tcp_timer_active(tp, TT_REXMT))
1780                 panic("tcp_setpersist: retransmit pending");
1781         /*
1782          * If the state is already closed, don't bother.
1783          */
1784         if (tp->t_state == TCPS_CLOSED)
1785                 return;
1786
1787         /*
1788          * Start/restart persistence timer.
1789          */
1790         TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift],
1791                       tcp_persmin, tcp_persmax);
1792         if (TP_MAXUNACKTIME(tp) && tp->t_acktime) {
1793                 maxunacktime = tp->t_acktime + TP_MAXUNACKTIME(tp) - ticks;
1794                 if (maxunacktime < 1)
1795                         maxunacktime = 1;
1796                 if (maxunacktime < tt)
1797                         tt = maxunacktime;
1798         }
1799         tcp_timer_activate(tp, TT_PERSIST, tt);
1800         if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
1801                 tp->t_rxtshift++;
1802 }
1803
1804 /*
1805  * Insert TCP options according to the supplied parameters to the place
1806  * optp in a consistent way.  Can handle unaligned destinations.
1807  *
1808  * The order of the option processing is crucial for optimal packing and
1809  * alignment for the scarce option space.
1810  *
1811  * The optimal order for a SYN/SYN-ACK segment is:
1812  *   MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) +
1813  *   Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40.
1814  *
1815  * The SACK options should be last.  SACK blocks consume 8*n+2 bytes.
1816  * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks).
1817  * At minimum we need 10 bytes (to generate 1 SACK block).  If both
1818  * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present,
1819  * we only have 10 bytes for SACK options (40 - (12 + 18)).
1820  */
1821 int
1822 tcp_addoptions(struct tcpopt *to, u_char *optp)
1823 {
1824         u_int32_t mask, optlen = 0;
1825
1826         for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) {
1827                 if ((to->to_flags & mask) != mask)
1828                         continue;
1829                 if (optlen == TCP_MAXOLEN)
1830                         break;
1831                 switch (to->to_flags & mask) {
1832                 case TOF_MSS:
1833                         while (optlen % 4) {
1834                                 optlen += TCPOLEN_NOP;
1835                                 *optp++ = TCPOPT_NOP;
1836                         }
1837                         if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG)
1838                                 continue;
1839                         optlen += TCPOLEN_MAXSEG;
1840                         *optp++ = TCPOPT_MAXSEG;
1841                         *optp++ = TCPOLEN_MAXSEG;
1842                         to->to_mss = htons(to->to_mss);
1843                         bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss));
1844                         optp += sizeof(to->to_mss);
1845                         break;
1846                 case TOF_SCALE:
1847                         while (!optlen || optlen % 2 != 1) {
1848                                 optlen += TCPOLEN_NOP;
1849                                 *optp++ = TCPOPT_NOP;
1850                         }
1851                         if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW)
1852                                 continue;
1853                         optlen += TCPOLEN_WINDOW;
1854                         *optp++ = TCPOPT_WINDOW;
1855                         *optp++ = TCPOLEN_WINDOW;
1856                         *optp++ = to->to_wscale;
1857                         break;
1858                 case TOF_SACKPERM:
1859                         while (optlen % 2) {
1860                                 optlen += TCPOLEN_NOP;
1861                                 *optp++ = TCPOPT_NOP;
1862                         }
1863                         if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED)
1864                                 continue;
1865                         optlen += TCPOLEN_SACK_PERMITTED;
1866                         *optp++ = TCPOPT_SACK_PERMITTED;
1867                         *optp++ = TCPOLEN_SACK_PERMITTED;
1868                         break;
1869                 case TOF_TS:
1870                         while (!optlen || optlen % 4 != 2) {
1871                                 optlen += TCPOLEN_NOP;
1872                                 *optp++ = TCPOPT_NOP;
1873                         }
1874                         if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP)
1875                                 continue;
1876                         optlen += TCPOLEN_TIMESTAMP;
1877                         *optp++ = TCPOPT_TIMESTAMP;
1878                         *optp++ = TCPOLEN_TIMESTAMP;
1879                         to->to_tsval = htonl(to->to_tsval);
1880                         to->to_tsecr = htonl(to->to_tsecr);
1881                         bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval));
1882                         optp += sizeof(to->to_tsval);
1883                         bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr));
1884                         optp += sizeof(to->to_tsecr);
1885                         break;
1886                 case TOF_SIGNATURE:
1887                         {
1888                         int siglen = TCPOLEN_SIGNATURE - 2;
1889
1890                         while (!optlen || optlen % 4 != 2) {
1891                                 optlen += TCPOLEN_NOP;
1892                                 *optp++ = TCPOPT_NOP;
1893                         }
1894                         if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) {
1895                                 to->to_flags &= ~TOF_SIGNATURE;
1896                                 continue;
1897                         }
1898                         optlen += TCPOLEN_SIGNATURE;
1899                         *optp++ = TCPOPT_SIGNATURE;
1900                         *optp++ = TCPOLEN_SIGNATURE;
1901                         to->to_signature = optp;
1902                         while (siglen--)
1903                                  *optp++ = 0;
1904                         break;
1905                         }
1906                 case TOF_SACK:
1907                         {
1908                         int sackblks = 0;
1909                         struct sackblk *sack = (struct sackblk *)to->to_sacks;
1910                         tcp_seq sack_seq;
1911
1912                         while (!optlen || optlen % 4 != 2) {
1913                                 optlen += TCPOLEN_NOP;
1914                                 *optp++ = TCPOPT_NOP;
1915                         }
1916                         if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK)
1917                                 continue;
1918                         optlen += TCPOLEN_SACKHDR;
1919                         *optp++ = TCPOPT_SACK;
1920                         sackblks = min(to->to_nsacks,
1921                                         (TCP_MAXOLEN - optlen) / TCPOLEN_SACK);
1922                         *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK;
1923                         while (sackblks--) {
1924                                 sack_seq = htonl(sack->start);
1925                                 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq));
1926                                 optp += sizeof(sack_seq);
1927                                 sack_seq = htonl(sack->end);
1928                                 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq));
1929                                 optp += sizeof(sack_seq);
1930                                 optlen += TCPOLEN_SACK;
1931                                 sack++;
1932                         }
1933                         TCPSTAT_INC(tcps_sack_send_blocks);
1934                         break;
1935                         }
1936                 case TOF_FASTOPEN:
1937                         {
1938                         int total_len;
1939
1940                         /* XXX is there any point to aligning this option? */
1941                         total_len = TCPOLEN_FAST_OPEN_EMPTY + to->to_tfo_len;
1942                         if (TCP_MAXOLEN - optlen < total_len) {
1943                                 to->to_flags &= ~TOF_FASTOPEN;
1944                                 continue;
1945                         }
1946                         *optp++ = TCPOPT_FAST_OPEN;
1947                         *optp++ = total_len;
1948                         if (to->to_tfo_len > 0) {
1949                                 bcopy(to->to_tfo_cookie, optp, to->to_tfo_len);
1950                                 optp += to->to_tfo_len;
1951                         }
1952                         optlen += total_len;
1953                         break;
1954                         }
1955                 default:
1956                         panic("%s: unknown TCP option type", __func__);
1957                         break;
1958                 }
1959         }
1960
1961         /* Terminate and pad TCP options to a 4 byte boundary. */
1962         if (optlen % 4) {
1963                 optlen += TCPOLEN_EOL;
1964                 *optp++ = TCPOPT_EOL;
1965         }
1966         /*
1967          * According to RFC 793 (STD0007):
1968          *   "The content of the header beyond the End-of-Option option
1969          *    must be header padding (i.e., zero)."
1970          *   and later: "The padding is composed of zeros."
1971          */
1972         while (optlen % 4) {
1973                 optlen += TCPOLEN_PAD;
1974                 *optp++ = TCPOPT_PAD;
1975         }
1976
1977         KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__));
1978         return (optlen);
1979 }
1980
1981 /*
1982  * This is a copy of m_copym(), taking the TSO segment size/limit
1983  * constraints into account, and advancing the sndptr as it goes.
1984  */
1985 struct mbuf *
1986 tcp_m_copym(struct mbuf *m, int32_t off0, int32_t *plen,
1987     int32_t seglimit, int32_t segsize, struct sockbuf *sb, bool hw_tls)
1988 {
1989 #ifdef KERN_TLS
1990         struct ktls_session *tls, *ntls;
1991         struct mbuf *start __diagused;
1992 #endif
1993         struct mbuf *n, **np;
1994         struct mbuf *top;
1995         int32_t off = off0;
1996         int32_t len = *plen;
1997         int32_t fragsize;
1998         int32_t len_cp = 0;
1999         int32_t *pkthdrlen;
2000         uint32_t mlen, frags;
2001         bool copyhdr;
2002
2003         KASSERT(off >= 0, ("tcp_m_copym, negative off %d", off));
2004         KASSERT(len >= 0, ("tcp_m_copym, negative len %d", len));
2005         if (off == 0 && m->m_flags & M_PKTHDR)
2006                 copyhdr = true;
2007         else
2008                 copyhdr = false;
2009         while (off > 0) {
2010                 KASSERT(m != NULL, ("tcp_m_copym, offset > size of mbuf chain"));
2011                 if (off < m->m_len)
2012                         break;
2013                 off -= m->m_len;
2014                 if ((sb) && (m == sb->sb_sndptr)) {
2015                         sb->sb_sndptroff += m->m_len;
2016                         sb->sb_sndptr = m->m_next;
2017                 }
2018                 m = m->m_next;
2019         }
2020         np = &top;
2021         top = NULL;
2022         pkthdrlen = NULL;
2023 #ifdef KERN_TLS
2024         if (hw_tls && (m->m_flags & M_EXTPG))
2025                 tls = m->m_epg_tls;
2026         else
2027                 tls = NULL;
2028         start = m;
2029 #endif
2030         while (len > 0) {
2031                 if (m == NULL) {
2032                         KASSERT(len == M_COPYALL,
2033                             ("tcp_m_copym, length > size of mbuf chain"));
2034                         *plen = len_cp;
2035                         if (pkthdrlen != NULL)
2036                                 *pkthdrlen = len_cp;
2037                         break;
2038                 }
2039 #ifdef KERN_TLS
2040                 if (hw_tls) {
2041                         if (m->m_flags & M_EXTPG)
2042                                 ntls = m->m_epg_tls;
2043                         else
2044                                 ntls = NULL;
2045
2046                         /*
2047                          * Avoid mixing TLS records with handshake
2048                          * data or TLS records from different
2049                          * sessions.
2050                          */
2051                         if (tls != ntls) {
2052                                 MPASS(m != start);
2053                                 *plen = len_cp;
2054                                 if (pkthdrlen != NULL)
2055                                         *pkthdrlen = len_cp;
2056                                 break;
2057                         }
2058                 }
2059 #endif
2060                 mlen = min(len, m->m_len - off);
2061                 if (seglimit) {
2062                         /*
2063                          * For M_EXTPG mbufs, add 3 segments
2064                          * + 1 in case we are crossing page boundaries
2065                          * + 2 in case the TLS hdr/trailer are used
2066                          * It is cheaper to just add the segments
2067                          * than it is to take the cache miss to look
2068                          * at the mbuf ext_pgs state in detail.
2069                          */
2070                         if (m->m_flags & M_EXTPG) {
2071                                 fragsize = min(segsize, PAGE_SIZE);
2072                                 frags = 3;
2073                         } else {
2074                                 fragsize = segsize;
2075                                 frags = 0;
2076                         }
2077
2078                         /* Break if we really can't fit anymore. */
2079                         if ((frags + 1) >= seglimit) {
2080                                 *plen = len_cp;
2081                                 if (pkthdrlen != NULL)
2082                                         *pkthdrlen = len_cp;
2083                                 break;
2084                         }
2085
2086                         /*
2087                          * Reduce size if you can't copy the whole
2088                          * mbuf. If we can't copy the whole mbuf, also
2089                          * adjust len so the loop will end after this
2090                          * mbuf.
2091                          */
2092                         if ((frags + howmany(mlen, fragsize)) >= seglimit) {
2093                                 mlen = (seglimit - frags - 1) * fragsize;
2094                                 len = mlen;
2095                                 *plen = len_cp + len;
2096                                 if (pkthdrlen != NULL)
2097                                         *pkthdrlen = *plen;
2098                         }
2099                         frags += howmany(mlen, fragsize);
2100                         if (frags == 0)
2101                                 frags++;
2102                         seglimit -= frags;
2103                         KASSERT(seglimit > 0,
2104                             ("%s: seglimit went too low", __func__));
2105                 }
2106                 if (copyhdr)
2107                         n = m_gethdr(M_NOWAIT, m->m_type);
2108                 else
2109                         n = m_get(M_NOWAIT, m->m_type);
2110                 *np = n;
2111                 if (n == NULL)
2112                         goto nospace;
2113                 if (copyhdr) {
2114                         if (!m_dup_pkthdr(n, m, M_NOWAIT))
2115                                 goto nospace;
2116                         if (len == M_COPYALL)
2117                                 n->m_pkthdr.len -= off0;
2118                         else
2119                                 n->m_pkthdr.len = len;
2120                         pkthdrlen = &n->m_pkthdr.len;
2121                         copyhdr = false;
2122                 }
2123                 n->m_len = mlen;
2124                 len_cp += n->m_len;
2125                 if (m->m_flags & (M_EXT|M_EXTPG)) {
2126                         n->m_data = m->m_data + off;
2127                         mb_dupcl(n, m);
2128                 } else
2129                         bcopy(mtod(m, caddr_t)+off, mtod(n, caddr_t),
2130                             (u_int)n->m_len);
2131
2132                 if (sb && (sb->sb_sndptr == m) &&
2133                     ((n->m_len + off) >= m->m_len) && m->m_next) {
2134                         sb->sb_sndptroff += m->m_len;
2135                         sb->sb_sndptr = m->m_next;
2136                 }
2137                 off = 0;
2138                 if (len != M_COPYALL) {
2139                         len -= n->m_len;
2140                 }
2141                 m = m->m_next;
2142                 np = &n->m_next;
2143         }
2144         return (top);
2145 nospace:
2146         m_freem(top);
2147         return (NULL);
2148 }
2149
2150 void
2151 tcp_sndbuf_autoscale(struct tcpcb *tp, struct socket *so, uint32_t sendwin)
2152 {
2153
2154         /*
2155          * Automatic sizing of send socket buffer.  Often the send buffer
2156          * size is not optimally adjusted to the actual network conditions
2157          * at hand (delay bandwidth product).  Setting the buffer size too
2158          * small limits throughput on links with high bandwidth and high
2159          * delay (eg. trans-continental/oceanic links).  Setting the
2160          * buffer size too big consumes too much real kernel memory,
2161          * especially with many connections on busy servers.
2162          *
2163          * The criteria to step up the send buffer one notch are:
2164          *  1. receive window of remote host is larger than send buffer
2165          *     (with a fudge factor of 5/4th);
2166          *  2. send buffer is filled to 7/8th with data (so we actually
2167          *     have data to make use of it);
2168          *  3. send buffer fill has not hit maximal automatic size;
2169          *  4. our send window (slow start and cogestion controlled) is
2170          *     larger than sent but unacknowledged data in send buffer.
2171          *
2172          * The remote host receive window scaling factor may limit the
2173          * growing of the send buffer before it reaches its allowed
2174          * maximum.
2175          *
2176          * It scales directly with slow start or congestion window
2177          * and does at most one step per received ACK.  This fast
2178          * scaling has the drawback of growing the send buffer beyond
2179          * what is strictly necessary to make full use of a given
2180          * delay*bandwidth product.  However testing has shown this not
2181          * to be much of an problem.  At worst we are trading wasting
2182          * of available bandwidth (the non-use of it) for wasting some
2183          * socket buffer memory.
2184          *
2185          * TODO: Shrink send buffer during idle periods together
2186          * with congestion window.  Requires another timer.  Has to
2187          * wait for upcoming tcp timer rewrite.
2188          *
2189          * XXXGL: should there be used sbused() or sbavail()?
2190          */
2191         if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) {
2192                 int lowat;
2193
2194                 lowat = V_tcp_sendbuf_auto_lowat ? so->so_snd.sb_lowat : 0;
2195                 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat - lowat &&
2196                     sbused(&so->so_snd) >=
2197                     (so->so_snd.sb_hiwat / 8 * 7) - lowat &&
2198                     sbused(&so->so_snd) < V_tcp_autosndbuf_max &&
2199                     sendwin >= (sbused(&so->so_snd) -
2200                     (tp->snd_nxt - tp->snd_una))) {
2201                         if (!sbreserve_locked(so, SO_SND,
2202                             min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc,
2203                              V_tcp_autosndbuf_max), curthread))
2204                                 so->so_snd.sb_flags &= ~SB_AUTOSIZE;
2205                 }
2206         }
2207 }