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_tcpdebug.h" 41 42 #include <sys/param.h> 43 #include <sys/systm.h> 44 #include <sys/domain.h> 45 #ifdef TCP_HHOOK 46 #include <sys/hhook.h> 47 #endif 48 #include <sys/kernel.h> 49 #include <sys/lock.h> 50 #include <sys/mbuf.h> 51 #include <sys/mutex.h> 52 #include <sys/protosw.h> 53 #include <sys/sdt.h> 54 #include <sys/socket.h> 55 #include <sys/socketvar.h> 56 #include <sys/sysctl.h> 57 58 #include <net/if.h> 59 #include <net/route.h> 60 #include <net/vnet.h> 61 62 #include <netinet/in.h> 63 #include <netinet/in_kdtrace.h> 64 #include <netinet/in_systm.h> 65 #include <netinet/ip.h> 66 #include <netinet/in_pcb.h> 67 #include <netinet/ip_var.h> 68 #include <netinet/ip_options.h> 69 #ifdef INET6 70 #include <netinet6/in6_pcb.h> 71 #include <netinet/ip6.h> 72 #include <netinet6/ip6_var.h> 73 #endif 74 #ifdef TCP_RFC7413 75 #include <netinet/tcp_fastopen.h> 76 #endif 77 #include <netinet/tcp.h> 78 #define TCPOUTFLAGS 79 #include <netinet/tcp_fsm.h> 80 #include <netinet/tcp_seq.h> 81 #include <netinet/tcp_timer.h> 82 #include <netinet/tcp_var.h> 83 #include <netinet/tcpip.h> 84 #include <netinet/cc/cc.h> 85 #ifdef TCPPCAP 86 #include <netinet/tcp_pcap.h> 87 #endif 88 #ifdef TCPDEBUG 89 #include <netinet/tcp_debug.h> 90 #endif 91 #ifdef TCP_OFFLOAD 92 #include <netinet/tcp_offload.h> 93 #endif 94 95 #include <netipsec/ipsec_support.h> 96 97 #include <machine/in_cksum.h> 98 99 #include <security/mac/mac_framework.h> 100 101 VNET_DEFINE(int, path_mtu_discovery) = 1; 102 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_VNET | CTLFLAG_RW, 103 &VNET_NAME(path_mtu_discovery), 1, 104 "Enable Path MTU Discovery"); 105 106 VNET_DEFINE(int, tcp_do_tso) = 1; 107 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_VNET | CTLFLAG_RW, 108 &VNET_NAME(tcp_do_tso), 0, 109 "Enable TCP Segmentation Offload"); 110 111 VNET_DEFINE(int, tcp_sendspace) = 1024*32; 112 #define V_tcp_sendspace VNET(tcp_sendspace) 113 SYSCTL_INT(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, CTLFLAG_VNET | CTLFLAG_RW, 114 &VNET_NAME(tcp_sendspace), 0, "Initial send socket buffer size"); 115 116 VNET_DEFINE(int, tcp_do_autosndbuf) = 1; 117 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_VNET | CTLFLAG_RW, 118 &VNET_NAME(tcp_do_autosndbuf), 0, 119 "Enable automatic send buffer sizing"); 120 121 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024; 122 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_VNET | CTLFLAG_RW, 123 &VNET_NAME(tcp_autosndbuf_inc), 0, 124 "Incrementor step size of automatic send buffer"); 125 126 VNET_DEFINE(int, tcp_autosndbuf_max) = 2*1024*1024; 127 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_VNET | CTLFLAG_RW, 128 &VNET_NAME(tcp_autosndbuf_max), 0, 129 "Max size of automatic send buffer"); 130 131 VNET_DEFINE(int, tcp_sendbuf_auto_lowat) = 0; 132 #define V_tcp_sendbuf_auto_lowat VNET(tcp_sendbuf_auto_lowat) 133 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto_lowat, CTLFLAG_VNET | CTLFLAG_RW, 134 &VNET_NAME(tcp_sendbuf_auto_lowat), 0, 135 "Modify threshold for auto send buffer growth to account for SO_SNDLOWAT"); 136 137 /* 138 * Make sure that either retransmit or persist timer is set for SYN, FIN and 139 * non-ACK. 140 */ 141 #define TCP_XMIT_TIMER_ASSERT(tp, len, th_flags) \ 142 KASSERT(((len) == 0 && ((th_flags) & (TH_SYN | TH_FIN)) == 0) ||\ 143 tcp_timer_active((tp), TT_REXMT) || \ 144 tcp_timer_active((tp), TT_PERSIST), \ 145 ("neither rexmt nor persist timer is set")) 146 147 #ifdef TCP_HHOOK 148 static void inline hhook_run_tcp_est_out(struct tcpcb *tp, 149 struct tcphdr *th, struct tcpopt *to, 150 uint32_t len, int tso); 151 #endif 152 static void inline cc_after_idle(struct tcpcb *tp); 153 154 #ifdef TCP_HHOOK 155 /* 156 * Wrapper for the TCP established output helper hook. 157 */ 158 static void inline 159 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th, 160 struct tcpopt *to, uint32_t len, int tso) 161 { 162 struct tcp_hhook_data hhook_data; 163 164 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) { 165 hhook_data.tp = tp; 166 hhook_data.th = th; 167 hhook_data.to = to; 168 hhook_data.len = len; 169 hhook_data.tso = tso; 170 171 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data, 172 tp->osd); 173 } 174 } 175 #endif 176 177 /* 178 * CC wrapper hook functions 179 */ 180 static void inline 181 cc_after_idle(struct tcpcb *tp) 182 { 183 INP_WLOCK_ASSERT(tp->t_inpcb); 184 185 if (CC_ALGO(tp)->after_idle != NULL) 186 CC_ALGO(tp)->after_idle(tp->ccv); 187 } 188 189 /* 190 * Tcp output routine: figure out what should be sent and send it. 191 */ 192 int 193 tcp_output(struct tcpcb *tp) 194 { 195 struct socket *so = tp->t_inpcb->inp_socket; 196 int32_t len; 197 uint32_t recwin, sendwin; 198 int off, flags, error = 0; /* Keep compiler happy */ 199 struct mbuf *m; 200 struct ip *ip = NULL; 201 struct ipovly *ipov = NULL; 202 struct tcphdr *th; 203 u_char opt[TCP_MAXOLEN]; 204 unsigned ipoptlen, optlen, hdrlen; 205 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 206 unsigned ipsec_optlen = 0; 207 #endif 208 int idle, sendalot; 209 int sack_rxmit, sack_bytes_rxmt; 210 struct sackhole *p; 211 int tso, mtu; 212 struct tcpopt to; 213 #if 0 214 int maxburst = TCP_MAXBURST; 215 #endif 216 #ifdef INET6 217 struct ip6_hdr *ip6 = NULL; 218 int isipv6; 219 220 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 221 #endif 222 223 INP_WLOCK_ASSERT(tp->t_inpcb); 224 225 #ifdef TCP_OFFLOAD 226 if (tp->t_flags & TF_TOE) 227 return (tcp_offload_output(tp)); 228 #endif 229 230 #ifdef TCP_RFC7413 231 /* 232 * For TFO connections in SYN_RECEIVED, only allow the initial 233 * SYN|ACK and those sent by the retransmit timer. 234 */ 235 if (IS_FASTOPEN(tp->t_flags) && 236 (tp->t_state == TCPS_SYN_RECEIVED) && 237 SEQ_GT(tp->snd_max, tp->snd_una) && /* initial SYN|ACK sent */ 238 (tp->snd_nxt != tp->snd_una)) /* not a retransmit */ 239 return (0); 240 #endif 241 /* 242 * Determine length of data that should be transmitted, 243 * and flags that will be used. 244 * If there is some data or critical controls (SYN, RST) 245 * to send, then transmit; otherwise, investigate further. 246 */ 247 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 248 if (idle && ticks - tp->t_rcvtime >= tp->t_rxtcur) 249 cc_after_idle(tp); 250 tp->t_flags &= ~TF_LASTIDLE; 251 if (idle) { 252 if (tp->t_flags & TF_MORETOCOME) { 253 tp->t_flags |= TF_LASTIDLE; 254 idle = 0; 255 } 256 } 257 again: 258 /* 259 * If we've recently taken a timeout, snd_max will be greater than 260 * snd_nxt. There may be SACK information that allows us to avoid 261 * resending already delivered data. Adjust snd_nxt accordingly. 262 */ 263 if ((tp->t_flags & TF_SACK_PERMIT) && 264 SEQ_LT(tp->snd_nxt, tp->snd_max)) 265 tcp_sack_adjust(tp); 266 sendalot = 0; 267 tso = 0; 268 mtu = 0; 269 off = tp->snd_nxt - tp->snd_una; 270 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 271 272 flags = tcp_outflags[tp->t_state]; 273 /* 274 * Send any SACK-generated retransmissions. If we're explicitly trying 275 * to send out new data (when sendalot is 1), bypass this function. 276 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 277 * we're replacing a (future) new transmission with a retransmission 278 * now, and we previously incremented snd_cwnd in tcp_input(). 279 */ 280 /* 281 * Still in sack recovery , reset rxmit flag to zero. 282 */ 283 sack_rxmit = 0; 284 sack_bytes_rxmt = 0; 285 len = 0; 286 p = NULL; 287 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) && 288 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 289 uint32_t cwin; 290 291 cwin = 292 imax(min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt, 0); 293 /* Do not retransmit SACK segments beyond snd_recover */ 294 if (SEQ_GT(p->end, tp->snd_recover)) { 295 /* 296 * (At least) part of sack hole extends beyond 297 * snd_recover. Check to see if we can rexmit data 298 * for this hole. 299 */ 300 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 301 /* 302 * Can't rexmit any more data for this hole. 303 * That data will be rexmitted in the next 304 * sack recovery episode, when snd_recover 305 * moves past p->rxmit. 306 */ 307 p = NULL; 308 goto after_sack_rexmit; 309 } else 310 /* Can rexmit part of the current hole */ 311 len = ((int32_t)ulmin(cwin, 312 tp->snd_recover - p->rxmit)); 313 } else 314 len = ((int32_t)ulmin(cwin, p->end - p->rxmit)); 315 off = p->rxmit - tp->snd_una; 316 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 317 __func__, off)); 318 if (len > 0) { 319 sack_rxmit = 1; 320 sendalot = 1; 321 TCPSTAT_INC(tcps_sack_rexmits); 322 TCPSTAT_ADD(tcps_sack_rexmit_bytes, 323 min(len, tp->t_maxseg)); 324 } 325 } 326 after_sack_rexmit: 327 /* 328 * Get standard flags, and add SYN or FIN if requested by 'hidden' 329 * state flags. 330 */ 331 if (tp->t_flags & TF_NEEDFIN) 332 flags |= TH_FIN; 333 if (tp->t_flags & TF_NEEDSYN) 334 flags |= TH_SYN; 335 336 SOCKBUF_LOCK(&so->so_snd); 337 /* 338 * If in persist timeout with window of 0, send 1 byte. 339 * Otherwise, if window is small but nonzero 340 * and timer expired, we will send what we can 341 * and go to transmit state. 342 */ 343 if (tp->t_flags & TF_FORCEDATA) { 344 if (sendwin == 0) { 345 /* 346 * If we still have some data to send, then 347 * clear the FIN bit. Usually this would 348 * happen below when it realizes that we 349 * aren't sending all the data. However, 350 * if we have exactly 1 byte of unsent data, 351 * then it won't clear the FIN bit below, 352 * and if we are in persist state, we wind 353 * up sending the packet without recording 354 * that we sent the FIN bit. 355 * 356 * We can't just blindly clear the FIN bit, 357 * because if we don't have any more data 358 * to send then the probe will be the FIN 359 * itself. 360 */ 361 if (off < sbused(&so->so_snd)) 362 flags &= ~TH_FIN; 363 sendwin = 1; 364 } else { 365 tcp_timer_activate(tp, TT_PERSIST, 0); 366 tp->t_rxtshift = 0; 367 } 368 } 369 370 /* 371 * If snd_nxt == snd_max and we have transmitted a FIN, the 372 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 373 * a negative length. This can also occur when TCP opens up 374 * its congestion window while receiving additional duplicate 375 * acks after fast-retransmit because TCP will reset snd_nxt 376 * to snd_max after the fast-retransmit. 377 * 378 * In the normal retransmit-FIN-only case, however, snd_nxt will 379 * be set to snd_una, the offset will be 0, and the length may 380 * wind up 0. 381 * 382 * If sack_rxmit is true we are retransmitting from the scoreboard 383 * in which case len is already set. 384 */ 385 if (sack_rxmit == 0) { 386 if (sack_bytes_rxmt == 0) 387 len = ((int32_t)min(sbavail(&so->so_snd), sendwin) - 388 off); 389 else { 390 int32_t cwin; 391 392 /* 393 * We are inside of a SACK recovery episode and are 394 * sending new data, having retransmitted all the 395 * data possible in the scoreboard. 396 */ 397 len = ((int32_t)min(sbavail(&so->so_snd), tp->snd_wnd) - 398 off); 399 /* 400 * Don't remove this (len > 0) check ! 401 * We explicitly check for len > 0 here (although it 402 * isn't really necessary), to work around a gcc 403 * optimization issue - to force gcc to compute 404 * len above. Without this check, the computation 405 * of len is bungled by the optimizer. 406 */ 407 if (len > 0) { 408 cwin = tp->snd_cwnd - 409 (tp->snd_nxt - tp->sack_newdata) - 410 sack_bytes_rxmt; 411 if (cwin < 0) 412 cwin = 0; 413 len = imin(len, cwin); 414 } 415 } 416 } 417 418 /* 419 * Lop off SYN bit if it has already been sent. However, if this 420 * is SYN-SENT state and if segment contains data and if we don't 421 * know that foreign host supports TAO, suppress sending segment. 422 */ 423 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 424 if (tp->t_state != TCPS_SYN_RECEIVED) 425 flags &= ~TH_SYN; 426 #ifdef TCP_RFC7413 427 /* 428 * When sending additional segments following a TFO SYN|ACK, 429 * do not include the SYN bit. 430 */ 431 if (IS_FASTOPEN(tp->t_flags) && 432 (tp->t_state == TCPS_SYN_RECEIVED)) 433 flags &= ~TH_SYN; 434 #endif 435 off--, len++; 436 } 437 438 /* 439 * Be careful not to send data and/or FIN on SYN segments. 440 * This measure is needed to prevent interoperability problems 441 * with not fully conformant TCP implementations. 442 */ 443 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 444 len = 0; 445 flags &= ~TH_FIN; 446 } 447 448 #ifdef TCP_RFC7413 449 /* 450 * When retransmitting SYN|ACK on a passively-created TFO socket, 451 * don't include data, as the presence of data may have caused the 452 * original SYN|ACK to have been dropped by a middlebox. 453 */ 454 if (IS_FASTOPEN(tp->t_flags) && 455 (((tp->t_state == TCPS_SYN_RECEIVED) && (tp->t_rxtshift > 0)) || 456 (flags & TH_RST))) 457 len = 0; 458 #endif 459 if (len <= 0) { 460 /* 461 * If FIN has been sent but not acked, 462 * but we haven't been called to retransmit, 463 * len will be < 0. Otherwise, window shrank 464 * after we sent into it. If window shrank to 0, 465 * cancel pending retransmit, pull snd_nxt back 466 * to (closed) window, and set the persist timer 467 * if it isn't already going. If the window didn't 468 * close completely, just wait for an ACK. 469 * 470 * We also do a general check here to ensure that 471 * we will set the persist timer when we have data 472 * to send, but a 0-byte window. This makes sure 473 * the persist timer is set even if the packet 474 * hits one of the "goto send" lines below. 475 */ 476 len = 0; 477 if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) && 478 (off < (int) sbavail(&so->so_snd))) { 479 tcp_timer_activate(tp, TT_REXMT, 0); 480 tp->t_rxtshift = 0; 481 tp->snd_nxt = tp->snd_una; 482 if (!tcp_timer_active(tp, TT_PERSIST)) 483 tcp_setpersist(tp); 484 } 485 } 486 487 /* len will be >= 0 after this point. */ 488 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 489 490 /* 491 * Automatic sizing of send socket buffer. Often the send buffer 492 * size is not optimally adjusted to the actual network conditions 493 * at hand (delay bandwidth product). Setting the buffer size too 494 * small limits throughput on links with high bandwidth and high 495 * delay (eg. trans-continental/oceanic links). Setting the 496 * buffer size too big consumes too much real kernel memory, 497 * especially with many connections on busy servers. 498 * 499 * The criteria to step up the send buffer one notch are: 500 * 1. receive window of remote host is larger than send buffer 501 * (with a fudge factor of 5/4th); 502 * 2. send buffer is filled to 7/8th with data (so we actually 503 * have data to make use of it); 504 * 3. send buffer fill has not hit maximal automatic size; 505 * 4. our send window (slow start and cogestion controlled) is 506 * larger than sent but unacknowledged data in send buffer. 507 * 508 * The remote host receive window scaling factor may limit the 509 * growing of the send buffer before it reaches its allowed 510 * maximum. 511 * 512 * It scales directly with slow start or congestion window 513 * and does at most one step per received ACK. This fast 514 * scaling has the drawback of growing the send buffer beyond 515 * what is strictly necessary to make full use of a given 516 * delay*bandwidth product. However testing has shown this not 517 * to be much of an problem. At worst we are trading wasting 518 * of available bandwidth (the non-use of it) for wasting some 519 * socket buffer memory. 520 * 521 * TODO: Shrink send buffer during idle periods together 522 * with congestion window. Requires another timer. Has to 523 * wait for upcoming tcp timer rewrite. 524 * 525 * XXXGL: should there be used sbused() or sbavail()? 526 */ 527 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 528 int lowat; 529 530 lowat = V_tcp_sendbuf_auto_lowat ? so->so_snd.sb_lowat : 0; 531 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat - lowat && 532 sbused(&so->so_snd) >= 533 (so->so_snd.sb_hiwat / 8 * 7) - lowat && 534 sbused(&so->so_snd) < V_tcp_autosndbuf_max && 535 sendwin >= (sbused(&so->so_snd) - 536 (tp->snd_nxt - tp->snd_una))) { 537 if (!sbreserve_locked(&so->so_snd, 538 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 539 V_tcp_autosndbuf_max), so, curthread)) 540 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 541 } 542 } 543 544 /* 545 * Decide if we can use TCP Segmentation Offloading (if supported by 546 * hardware). 547 * 548 * TSO may only be used if we are in a pure bulk sending state. The 549 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 550 * IP options prevent using TSO. With TSO the TCP header is the same 551 * (except for the sequence number) for all generated packets. This 552 * makes it impossible to transmit any options which vary per generated 553 * segment or packet. 554 * 555 * IPv4 handling has a clear separation of ip options and ip header 556 * flags while IPv6 combines both in in6p_outputopts. ip6_optlen() does 557 * the right thing below to provide length of just ip options and thus 558 * checking for ipoptlen is enough to decide if ip options are present. 559 */ 560 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 561 /* 562 * Pre-calculate here as we save another lookup into the darknesses 563 * of IPsec that way and can actually decide if TSO is ok. 564 */ 565 #ifdef INET6 566 if (isipv6 && IPSEC_ENABLED(ipv6)) 567 ipsec_optlen = IPSEC_HDRSIZE(ipv6, tp->t_inpcb); 568 #ifdef INET 569 else 570 #endif 571 #endif /* INET6 */ 572 #ifdef INET 573 if (IPSEC_ENABLED(ipv4)) 574 ipsec_optlen = IPSEC_HDRSIZE(ipv4, tp->t_inpcb); 575 #endif /* INET */ 576 #endif /* IPSEC */ 577 #ifdef INET6 578 if (isipv6) 579 ipoptlen = ip6_optlen(tp->t_inpcb); 580 else 581 #endif 582 if (tp->t_inpcb->inp_options) 583 ipoptlen = tp->t_inpcb->inp_options->m_len - 584 offsetof(struct ipoption, ipopt_list); 585 else 586 ipoptlen = 0; 587 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 588 ipoptlen += ipsec_optlen; 589 #endif 590 591 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg && 592 ((tp->t_flags & TF_SIGNATURE) == 0) && 593 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 594 ipoptlen == 0) 595 tso = 1; 596 597 if (sack_rxmit) { 598 if (SEQ_LT(p->rxmit + len, tp->snd_una + sbused(&so->so_snd))) 599 flags &= ~TH_FIN; 600 } else { 601 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + 602 sbused(&so->so_snd))) 603 flags &= ~TH_FIN; 604 } 605 606 recwin = lmin(lmax(sbspace(&so->so_rcv), 0), 607 (long)TCP_MAXWIN << tp->rcv_scale); 608 609 /* 610 * Sender silly window avoidance. We transmit under the following 611 * conditions when len is non-zero: 612 * 613 * - We have a full segment (or more with TSO) 614 * - This is the last buffer in a write()/send() and we are 615 * either idle or running NODELAY 616 * - we've timed out (e.g. persist timer) 617 * - we have more then 1/2 the maximum send window's worth of 618 * data (receiver may be limited the window size) 619 * - we need to retransmit 620 */ 621 if (len) { 622 if (len >= tp->t_maxseg) 623 goto send; 624 /* 625 * NOTE! on localhost connections an 'ack' from the remote 626 * end may occur synchronously with the output and cause 627 * us to flush a buffer queued with moretocome. XXX 628 * 629 * note: the len + off check is almost certainly unnecessary. 630 */ 631 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 632 (idle || (tp->t_flags & TF_NODELAY)) && 633 (uint32_t)len + (uint32_t)off >= sbavail(&so->so_snd) && 634 (tp->t_flags & TF_NOPUSH) == 0) { 635 goto send; 636 } 637 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 638 goto send; 639 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 640 goto send; 641 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 642 goto send; 643 if (sack_rxmit) 644 goto send; 645 } 646 647 /* 648 * Sending of standalone window updates. 649 * 650 * Window updates are important when we close our window due to a 651 * full socket buffer and are opening it again after the application 652 * reads data from it. Once the window has opened again and the 653 * remote end starts to send again the ACK clock takes over and 654 * provides the most current window information. 655 * 656 * We must avoid the silly window syndrome whereas every read 657 * from the receive buffer, no matter how small, causes a window 658 * update to be sent. We also should avoid sending a flurry of 659 * window updates when the socket buffer had queued a lot of data 660 * and the application is doing small reads. 661 * 662 * Prevent a flurry of pointless window updates by only sending 663 * an update when we can increase the advertized window by more 664 * than 1/4th of the socket buffer capacity. When the buffer is 665 * getting full or is very small be more aggressive and send an 666 * update whenever we can increase by two mss sized segments. 667 * In all other situations the ACK's to new incoming data will 668 * carry further window increases. 669 * 670 * Don't send an independent window update if a delayed 671 * ACK is pending (it will get piggy-backed on it) or the 672 * remote side already has done a half-close and won't send 673 * more data. Skip this if the connection is in T/TCP 674 * half-open state. 675 */ 676 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 677 !(tp->t_flags & TF_DELACK) && 678 !TCPS_HAVERCVDFIN(tp->t_state)) { 679 /* 680 * "adv" is the amount we could increase the window, 681 * taking into account that we are limited by 682 * TCP_MAXWIN << tp->rcv_scale. 683 */ 684 int32_t adv; 685 int oldwin; 686 687 adv = recwin; 688 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { 689 oldwin = (tp->rcv_adv - tp->rcv_nxt); 690 adv -= oldwin; 691 } else 692 oldwin = 0; 693 694 /* 695 * If the new window size ends up being the same as or less 696 * than the old size when it is scaled, then don't force 697 * a window update. 698 */ 699 if (oldwin >> tp->rcv_scale >= (adv + oldwin) >> tp->rcv_scale) 700 goto dontupdate; 701 702 if (adv >= (int32_t)(2 * tp->t_maxseg) && 703 (adv >= (int32_t)(so->so_rcv.sb_hiwat / 4) || 704 recwin <= (so->so_rcv.sb_hiwat / 8) || 705 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg)) 706 goto send; 707 if (2 * adv >= (int32_t)so->so_rcv.sb_hiwat) 708 goto send; 709 } 710 dontupdate: 711 712 /* 713 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 714 * is also a catch-all for the retransmit timer timeout case. 715 */ 716 if (tp->t_flags & TF_ACKNOW) 717 goto send; 718 if ((flags & TH_RST) || 719 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 720 goto send; 721 if (SEQ_GT(tp->snd_up, tp->snd_una)) 722 goto send; 723 /* 724 * If our state indicates that FIN should be sent 725 * and we have not yet done so, then we need to send. 726 */ 727 if (flags & TH_FIN && 728 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 729 goto send; 730 /* 731 * In SACK, it is possible for tcp_output to fail to send a segment 732 * after the retransmission timer has been turned off. Make sure 733 * that the retransmission timer is set. 734 */ 735 if ((tp->t_flags & TF_SACK_PERMIT) && 736 SEQ_GT(tp->snd_max, tp->snd_una) && 737 !tcp_timer_active(tp, TT_REXMT) && 738 !tcp_timer_active(tp, TT_PERSIST)) { 739 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 740 goto just_return; 741 } 742 /* 743 * TCP window updates are not reliable, rather a polling protocol 744 * using ``persist'' packets is used to insure receipt of window 745 * updates. The three ``states'' for the output side are: 746 * idle not doing retransmits or persists 747 * persisting to move a small or zero window 748 * (re)transmitting and thereby not persisting 749 * 750 * tcp_timer_active(tp, TT_PERSIST) 751 * is true when we are in persist state. 752 * (tp->t_flags & TF_FORCEDATA) 753 * is set when we are called to send a persist packet. 754 * tcp_timer_active(tp, TT_REXMT) 755 * is set when we are retransmitting 756 * The output side is idle when both timers are zero. 757 * 758 * If send window is too small, there is data to transmit, and no 759 * retransmit or persist is pending, then go to persist state. 760 * If nothing happens soon, send when timer expires: 761 * if window is nonzero, transmit what we can, 762 * otherwise force out a byte. 763 */ 764 if (sbavail(&so->so_snd) && !tcp_timer_active(tp, TT_REXMT) && 765 !tcp_timer_active(tp, TT_PERSIST)) { 766 tp->t_rxtshift = 0; 767 tcp_setpersist(tp); 768 } 769 770 /* 771 * No reason to send a segment, just return. 772 */ 773 just_return: 774 SOCKBUF_UNLOCK(&so->so_snd); 775 return (0); 776 777 send: 778 SOCKBUF_LOCK_ASSERT(&so->so_snd); 779 if (len > 0) { 780 if (len >= tp->t_maxseg) 781 tp->t_flags2 |= TF2_PLPMTU_MAXSEGSNT; 782 else 783 tp->t_flags2 &= ~TF2_PLPMTU_MAXSEGSNT; 784 } 785 /* 786 * Before ESTABLISHED, force sending of initial options 787 * unless TCP set not to do any options. 788 * NOTE: we assume that the IP/TCP header plus TCP options 789 * always fit in a single mbuf, leaving room for a maximum 790 * link header, i.e. 791 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 792 */ 793 optlen = 0; 794 #ifdef INET6 795 if (isipv6) 796 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 797 else 798 #endif 799 hdrlen = sizeof (struct tcpiphdr); 800 801 /* 802 * Compute options for segment. 803 * We only have to care about SYN and established connection 804 * segments. Options for SYN-ACK segments are handled in TCP 805 * syncache. 806 */ 807 to.to_flags = 0; 808 if ((tp->t_flags & TF_NOOPT) == 0) { 809 /* Maximum segment size. */ 810 if (flags & TH_SYN) { 811 tp->snd_nxt = tp->iss; 812 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 813 to.to_flags |= TOF_MSS; 814 #ifdef TCP_RFC7413 815 /* 816 * Only include the TFO option on the first 817 * transmission of the SYN|ACK on a 818 * passively-created TFO socket, as the presence of 819 * the TFO option may have caused the original 820 * SYN|ACK to have been dropped by a middlebox. 821 */ 822 if (IS_FASTOPEN(tp->t_flags) && 823 (tp->t_state == TCPS_SYN_RECEIVED) && 824 (tp->t_rxtshift == 0)) { 825 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN; 826 to.to_tfo_cookie = (u_char *)&tp->t_tfo_cookie; 827 to.to_flags |= TOF_FASTOPEN; 828 } 829 #endif 830 } 831 /* Window scaling. */ 832 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 833 to.to_wscale = tp->request_r_scale; 834 to.to_flags |= TOF_SCALE; 835 } 836 /* Timestamps. */ 837 if ((tp->t_flags & TF_RCVD_TSTMP) || 838 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 839 to.to_tsval = tcp_ts_getticks() + tp->ts_offset; 840 to.to_tsecr = tp->ts_recent; 841 to.to_flags |= TOF_TS; 842 } 843 844 /* Set receive buffer autosizing timestamp. */ 845 if (tp->rfbuf_ts == 0 && 846 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 847 tp->rfbuf_ts = tcp_ts_getticks(); 848 849 /* Selective ACK's. */ 850 if (tp->t_flags & TF_SACK_PERMIT) { 851 if (flags & TH_SYN) 852 to.to_flags |= TOF_SACKPERM; 853 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 854 (tp->t_flags & TF_SACK_PERMIT) && 855 tp->rcv_numsacks > 0) { 856 to.to_flags |= TOF_SACK; 857 to.to_nsacks = tp->rcv_numsacks; 858 to.to_sacks = (u_char *)tp->sackblks; 859 } 860 } 861 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 862 /* TCP-MD5 (RFC2385). */ 863 /* 864 * Check that TCP_MD5SIG is enabled in tcpcb to 865 * account the size needed to set this TCP option. 866 */ 867 if (tp->t_flags & TF_SIGNATURE) 868 to.to_flags |= TOF_SIGNATURE; 869 #endif /* TCP_SIGNATURE */ 870 871 /* Processing the options. */ 872 hdrlen += optlen = tcp_addoptions(&to, opt); 873 } 874 875 /* 876 * Adjust data length if insertion of options will 877 * bump the packet length beyond the t_maxseg length. 878 * Clear the FIN bit because we cut off the tail of 879 * the segment. 880 */ 881 if (len + optlen + ipoptlen > tp->t_maxseg) { 882 flags &= ~TH_FIN; 883 884 if (tso) { 885 u_int if_hw_tsomax; 886 u_int if_hw_tsomaxsegcount; 887 u_int if_hw_tsomaxsegsize; 888 struct mbuf *mb; 889 u_int moff; 890 int max_len; 891 892 /* extract TSO information */ 893 if_hw_tsomax = tp->t_tsomax; 894 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount; 895 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize; 896 897 /* 898 * Limit a TSO burst to prevent it from 899 * overflowing or exceeding the maximum length 900 * allowed by the network interface: 901 */ 902 KASSERT(ipoptlen == 0, 903 ("%s: TSO can't do IP options", __func__)); 904 905 /* 906 * Check if we should limit by maximum payload 907 * length: 908 */ 909 if (if_hw_tsomax != 0) { 910 /* compute maximum TSO length */ 911 max_len = (if_hw_tsomax - hdrlen - 912 max_linkhdr); 913 if (max_len <= 0) { 914 len = 0; 915 } else if (len > max_len) { 916 sendalot = 1; 917 len = max_len; 918 } 919 } 920 921 /* 922 * Check if we should limit by maximum segment 923 * size and count: 924 */ 925 if (if_hw_tsomaxsegcount != 0 && 926 if_hw_tsomaxsegsize != 0) { 927 /* 928 * Subtract one segment for the LINK 929 * and TCP/IP headers mbuf that will 930 * be prepended to this mbuf chain 931 * after the code in this section 932 * limits the number of mbufs in the 933 * chain to if_hw_tsomaxsegcount. 934 */ 935 if_hw_tsomaxsegcount -= 1; 936 max_len = 0; 937 mb = sbsndmbuf(&so->so_snd, off, &moff); 938 939 while (mb != NULL && max_len < len) { 940 u_int mlen; 941 u_int frags; 942 943 /* 944 * Get length of mbuf fragment 945 * and how many hardware frags, 946 * rounded up, it would use: 947 */ 948 mlen = (mb->m_len - moff); 949 frags = howmany(mlen, 950 if_hw_tsomaxsegsize); 951 952 /* Handle special case: Zero Length Mbuf */ 953 if (frags == 0) 954 frags = 1; 955 956 /* 957 * Check if the fragment limit 958 * will be reached or exceeded: 959 */ 960 if (frags >= if_hw_tsomaxsegcount) { 961 max_len += min(mlen, 962 if_hw_tsomaxsegcount * 963 if_hw_tsomaxsegsize); 964 break; 965 } 966 max_len += mlen; 967 if_hw_tsomaxsegcount -= frags; 968 moff = 0; 969 mb = mb->m_next; 970 } 971 if (max_len <= 0) { 972 len = 0; 973 } else if (len > max_len) { 974 sendalot = 1; 975 len = max_len; 976 } 977 } 978 979 /* 980 * Prevent the last segment from being 981 * fractional unless the send sockbuf can be 982 * emptied: 983 */ 984 max_len = (tp->t_maxseg - optlen); 985 if (((uint32_t)off + (uint32_t)len) < 986 sbavail(&so->so_snd)) { 987 moff = len % max_len; 988 if (moff != 0) { 989 len -= moff; 990 sendalot = 1; 991 } 992 } 993 994 /* 995 * In case there are too many small fragments 996 * don't use TSO: 997 */ 998 if (len <= max_len) { 999 len = max_len; 1000 sendalot = 1; 1001 tso = 0; 1002 } 1003 1004 /* 1005 * Send the FIN in a separate segment 1006 * after the bulk sending is done. 1007 * We don't trust the TSO implementations 1008 * to clear the FIN flag on all but the 1009 * last segment. 1010 */ 1011 if (tp->t_flags & TF_NEEDFIN) 1012 sendalot = 1; 1013 1014 } else { 1015 len = tp->t_maxseg - optlen - ipoptlen; 1016 sendalot = 1; 1017 } 1018 } else 1019 tso = 0; 1020 1021 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 1022 ("%s: len > IP_MAXPACKET", __func__)); 1023 1024 /*#ifdef DIAGNOSTIC*/ 1025 #ifdef INET6 1026 if (max_linkhdr + hdrlen > MCLBYTES) 1027 #else 1028 if (max_linkhdr + hdrlen > MHLEN) 1029 #endif 1030 panic("tcphdr too big"); 1031 /*#endif*/ 1032 1033 /* 1034 * This KASSERT is here to catch edge cases at a well defined place. 1035 * Before, those had triggered (random) panic conditions further down. 1036 */ 1037 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 1038 1039 /* 1040 * Grab a header mbuf, attaching a copy of data to 1041 * be transmitted, and initialize the header from 1042 * the template for sends on this connection. 1043 */ 1044 if (len) { 1045 struct mbuf *mb; 1046 u_int moff; 1047 1048 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 1049 TCPSTAT_INC(tcps_sndprobe); 1050 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 1051 tp->t_sndrexmitpack++; 1052 TCPSTAT_INC(tcps_sndrexmitpack); 1053 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 1054 } else { 1055 TCPSTAT_INC(tcps_sndpack); 1056 TCPSTAT_ADD(tcps_sndbyte, len); 1057 } 1058 #ifdef INET6 1059 if (MHLEN < hdrlen + max_linkhdr) 1060 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR); 1061 else 1062 #endif 1063 m = m_gethdr(M_NOWAIT, MT_DATA); 1064 1065 if (m == NULL) { 1066 SOCKBUF_UNLOCK(&so->so_snd); 1067 error = ENOBUFS; 1068 sack_rxmit = 0; 1069 goto out; 1070 } 1071 1072 m->m_data += max_linkhdr; 1073 m->m_len = hdrlen; 1074 1075 /* 1076 * Start the m_copy functions from the closest mbuf 1077 * to the offset in the socket buffer chain. 1078 */ 1079 mb = sbsndptr(&so->so_snd, off, len, &moff); 1080 1081 if (len <= MHLEN - hdrlen - max_linkhdr) { 1082 m_copydata(mb, moff, len, 1083 mtod(m, caddr_t) + hdrlen); 1084 m->m_len += len; 1085 } else { 1086 m->m_next = m_copym(mb, moff, len, M_NOWAIT); 1087 if (m->m_next == NULL) { 1088 SOCKBUF_UNLOCK(&so->so_snd); 1089 (void) m_free(m); 1090 error = ENOBUFS; 1091 sack_rxmit = 0; 1092 goto out; 1093 } 1094 } 1095 1096 /* 1097 * If we're sending everything we've got, set PUSH. 1098 * (This will keep happy those implementations which only 1099 * give data to the user when a buffer fills or 1100 * a PUSH comes in.) 1101 */ 1102 if (((uint32_t)off + (uint32_t)len == sbused(&so->so_snd)) && 1103 !(flags & TH_SYN)) 1104 flags |= TH_PUSH; 1105 SOCKBUF_UNLOCK(&so->so_snd); 1106 } else { 1107 SOCKBUF_UNLOCK(&so->so_snd); 1108 if (tp->t_flags & TF_ACKNOW) 1109 TCPSTAT_INC(tcps_sndacks); 1110 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 1111 TCPSTAT_INC(tcps_sndctrl); 1112 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 1113 TCPSTAT_INC(tcps_sndurg); 1114 else 1115 TCPSTAT_INC(tcps_sndwinup); 1116 1117 m = m_gethdr(M_NOWAIT, MT_DATA); 1118 if (m == NULL) { 1119 error = ENOBUFS; 1120 sack_rxmit = 0; 1121 goto out; 1122 } 1123 #ifdef INET6 1124 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 1125 MHLEN >= hdrlen) { 1126 M_ALIGN(m, hdrlen); 1127 } else 1128 #endif 1129 m->m_data += max_linkhdr; 1130 m->m_len = hdrlen; 1131 } 1132 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 1133 m->m_pkthdr.rcvif = (struct ifnet *)0; 1134 #ifdef MAC 1135 mac_inpcb_create_mbuf(tp->t_inpcb, m); 1136 #endif 1137 #ifdef INET6 1138 if (isipv6) { 1139 ip6 = mtod(m, struct ip6_hdr *); 1140 th = (struct tcphdr *)(ip6 + 1); 1141 tcpip_fillheaders(tp->t_inpcb, ip6, th); 1142 } else 1143 #endif /* INET6 */ 1144 { 1145 ip = mtod(m, struct ip *); 1146 ipov = (struct ipovly *)ip; 1147 th = (struct tcphdr *)(ip + 1); 1148 tcpip_fillheaders(tp->t_inpcb, ip, th); 1149 } 1150 1151 /* 1152 * Fill in fields, remembering maximum advertised 1153 * window for use in delaying messages about window sizes. 1154 * If resending a FIN, be sure not to use a new sequence number. 1155 */ 1156 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 1157 tp->snd_nxt == tp->snd_max) 1158 tp->snd_nxt--; 1159 /* 1160 * If we are starting a connection, send ECN setup 1161 * SYN packet. If we are on a retransmit, we may 1162 * resend those bits a number of times as per 1163 * RFC 3168. 1164 */ 1165 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn == 1) { 1166 if (tp->t_rxtshift >= 1) { 1167 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 1168 flags |= TH_ECE|TH_CWR; 1169 } else 1170 flags |= TH_ECE|TH_CWR; 1171 } 1172 1173 if (tp->t_state == TCPS_ESTABLISHED && 1174 (tp->t_flags & TF_ECN_PERMIT)) { 1175 /* 1176 * If the peer has ECN, mark data packets with 1177 * ECN capable transmission (ECT). 1178 * Ignore pure ack packets, retransmissions and window probes. 1179 */ 1180 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 1181 !((tp->t_flags & TF_FORCEDATA) && len == 1)) { 1182 #ifdef INET6 1183 if (isipv6) 1184 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 1185 else 1186 #endif 1187 ip->ip_tos |= IPTOS_ECN_ECT0; 1188 TCPSTAT_INC(tcps_ecn_ect0); 1189 } 1190 1191 /* 1192 * Reply with proper ECN notifications. 1193 */ 1194 if (tp->t_flags & TF_ECN_SND_CWR) { 1195 flags |= TH_CWR; 1196 tp->t_flags &= ~TF_ECN_SND_CWR; 1197 } 1198 if (tp->t_flags & TF_ECN_SND_ECE) 1199 flags |= TH_ECE; 1200 } 1201 1202 /* 1203 * If we are doing retransmissions, then snd_nxt will 1204 * not reflect the first unsent octet. For ACK only 1205 * packets, we do not want the sequence number of the 1206 * retransmitted packet, we want the sequence number 1207 * of the next unsent octet. So, if there is no data 1208 * (and no SYN or FIN), use snd_max instead of snd_nxt 1209 * when filling in ti_seq. But if we are in persist 1210 * state, snd_max might reflect one byte beyond the 1211 * right edge of the window, so use snd_nxt in that 1212 * case, since we know we aren't doing a retransmission. 1213 * (retransmit and persist are mutually exclusive...) 1214 */ 1215 if (sack_rxmit == 0) { 1216 if (len || (flags & (TH_SYN|TH_FIN)) || 1217 tcp_timer_active(tp, TT_PERSIST)) 1218 th->th_seq = htonl(tp->snd_nxt); 1219 else 1220 th->th_seq = htonl(tp->snd_max); 1221 } else { 1222 th->th_seq = htonl(p->rxmit); 1223 p->rxmit += len; 1224 tp->sackhint.sack_bytes_rexmit += len; 1225 } 1226 th->th_ack = htonl(tp->rcv_nxt); 1227 if (optlen) { 1228 bcopy(opt, th + 1, optlen); 1229 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1230 } 1231 th->th_flags = flags; 1232 /* 1233 * Calculate receive window. Don't shrink window, 1234 * but avoid silly window syndrome. 1235 */ 1236 if (recwin < (so->so_rcv.sb_hiwat / 4) && 1237 recwin < tp->t_maxseg) 1238 recwin = 0; 1239 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1240 recwin < (tp->rcv_adv - tp->rcv_nxt)) 1241 recwin = (tp->rcv_adv - tp->rcv_nxt); 1242 1243 /* 1244 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1245 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1246 * case is handled in syncache. 1247 */ 1248 if (flags & TH_SYN) 1249 th->th_win = htons((u_short) 1250 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1251 else 1252 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1253 1254 /* 1255 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1256 * a 0 window. This may cause the remote transmitter to stall. This 1257 * flag tells soreceive() to disable delayed acknowledgements when 1258 * draining the buffer. This can occur if the receiver is attempting 1259 * to read more data than can be buffered prior to transmitting on 1260 * the connection. 1261 */ 1262 if (th->th_win == 0) { 1263 tp->t_sndzerowin++; 1264 tp->t_flags |= TF_RXWIN0SENT; 1265 } else 1266 tp->t_flags &= ~TF_RXWIN0SENT; 1267 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1268 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1269 th->th_flags |= TH_URG; 1270 } else 1271 /* 1272 * If no urgent pointer to send, then we pull 1273 * the urgent pointer to the left edge of the send window 1274 * so that it doesn't drift into the send window on sequence 1275 * number wraparound. 1276 */ 1277 tp->snd_up = tp->snd_una; /* drag it along */ 1278 1279 /* 1280 * Put TCP length in extended header, and then 1281 * checksum extended header and data. 1282 */ 1283 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1284 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1285 1286 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1287 if (to.to_flags & TOF_SIGNATURE) { 1288 /* 1289 * Calculate MD5 signature and put it into the place 1290 * determined before. 1291 * NOTE: since TCP options buffer doesn't point into 1292 * mbuf's data, calculate offset and use it. 1293 */ 1294 if (!TCPMD5_ENABLED() || TCPMD5_OUTPUT(m, th, 1295 (u_char *)(th + 1) + (to.to_signature - opt)) != 0) { 1296 /* 1297 * Do not send segment if the calculation of MD5 1298 * digest has failed. 1299 */ 1300 goto out; 1301 } 1302 } 1303 #endif 1304 #ifdef INET6 1305 if (isipv6) { 1306 /* 1307 * There is no need to fill in ip6_plen right now. 1308 * It will be filled later by ip6_output. 1309 */ 1310 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1311 th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) + 1312 optlen + len, IPPROTO_TCP, 0); 1313 } 1314 #endif 1315 #if defined(INET6) && defined(INET) 1316 else 1317 #endif 1318 #ifdef INET 1319 { 1320 m->m_pkthdr.csum_flags = CSUM_TCP; 1321 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1322 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1323 1324 /* IP version must be set here for ipv4/ipv6 checking later */ 1325 KASSERT(ip->ip_v == IPVERSION, 1326 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1327 } 1328 #endif 1329 1330 /* 1331 * Enable TSO and specify the size of the segments. 1332 * The TCP pseudo header checksum is always provided. 1333 */ 1334 if (tso) { 1335 KASSERT(len > tp->t_maxseg - optlen, 1336 ("%s: len <= tso_segsz", __func__)); 1337 m->m_pkthdr.csum_flags |= CSUM_TSO; 1338 m->m_pkthdr.tso_segsz = tp->t_maxseg - optlen; 1339 } 1340 1341 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 1342 KASSERT(len + hdrlen + ipoptlen - ipsec_optlen == m_length(m, NULL), 1343 ("%s: mbuf chain shorter than expected: %d + %u + %u - %u != %u", 1344 __func__, len, hdrlen, ipoptlen, ipsec_optlen, m_length(m, NULL))); 1345 #else 1346 KASSERT(len + hdrlen + ipoptlen == m_length(m, NULL), 1347 ("%s: mbuf chain shorter than expected: %d + %u + %u != %u", 1348 __func__, len, hdrlen, ipoptlen, m_length(m, NULL))); 1349 #endif 1350 1351 #ifdef TCP_HHOOK 1352 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1353 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1354 #endif 1355 1356 #ifdef TCPDEBUG 1357 /* 1358 * Trace. 1359 */ 1360 if (so->so_options & SO_DEBUG) { 1361 u_short save = 0; 1362 #ifdef INET6 1363 if (!isipv6) 1364 #endif 1365 { 1366 save = ipov->ih_len; 1367 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1368 } 1369 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1370 #ifdef INET6 1371 if (!isipv6) 1372 #endif 1373 ipov->ih_len = save; 1374 } 1375 #endif /* TCPDEBUG */ 1376 TCP_PROBE3(debug__output, tp, th, m); 1377 1378 /* 1379 * Fill in IP length and desired time to live and 1380 * send to IP level. There should be a better way 1381 * to handle ttl and tos; we could keep them in 1382 * the template, but need a way to checksum without them. 1383 */ 1384 /* 1385 * m->m_pkthdr.len should have been set before checksum calculation, 1386 * because in6_cksum() need it. 1387 */ 1388 #ifdef INET6 1389 if (isipv6) { 1390 /* 1391 * we separately set hoplimit for every segment, since the 1392 * user might want to change the value via setsockopt. 1393 * Also, desired default hop limit might be changed via 1394 * Neighbor Discovery. 1395 */ 1396 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1397 1398 /* 1399 * Set the packet size here for the benefit of DTrace probes. 1400 * ip6_output() will set it properly; it's supposed to include 1401 * the option header lengths as well. 1402 */ 1403 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6)); 1404 1405 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) 1406 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1407 else 1408 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1409 1410 if (tp->t_state == TCPS_SYN_SENT) 1411 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th); 1412 1413 TCP_PROBE5(send, NULL, tp, ip6, tp, th); 1414 1415 #ifdef TCPPCAP 1416 /* Save packet, if requested. */ 1417 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1418 #endif 1419 1420 /* TODO: IPv6 IP6TOS_ECT bit on */ 1421 error = ip6_output(m, tp->t_inpcb->in6p_outputopts, 1422 &tp->t_inpcb->inp_route6, 1423 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 1424 NULL, NULL, tp->t_inpcb); 1425 1426 if (error == EMSGSIZE && tp->t_inpcb->inp_route6.ro_rt != NULL) 1427 mtu = tp->t_inpcb->inp_route6.ro_rt->rt_mtu; 1428 } 1429 #endif /* INET6 */ 1430 #if defined(INET) && defined(INET6) 1431 else 1432 #endif 1433 #ifdef INET 1434 { 1435 ip->ip_len = htons(m->m_pkthdr.len); 1436 #ifdef INET6 1437 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1438 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1439 #endif /* INET6 */ 1440 /* 1441 * If we do path MTU discovery, then we set DF on every packet. 1442 * This might not be the best thing to do according to RFC3390 1443 * Section 2. However the tcp hostcache migitates the problem 1444 * so it affects only the first tcp connection with a host. 1445 * 1446 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1447 */ 1448 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) { 1449 ip->ip_off |= htons(IP_DF); 1450 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1451 } else { 1452 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1453 } 1454 1455 if (tp->t_state == TCPS_SYN_SENT) 1456 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th); 1457 1458 TCP_PROBE5(send, NULL, tp, ip, tp, th); 1459 1460 #ifdef TCPPCAP 1461 /* Save packet, if requested. */ 1462 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1463 #endif 1464 1465 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, 1466 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1467 tp->t_inpcb); 1468 1469 if (error == EMSGSIZE && tp->t_inpcb->inp_route.ro_rt != NULL) 1470 mtu = tp->t_inpcb->inp_route.ro_rt->rt_mtu; 1471 } 1472 #endif /* INET */ 1473 1474 out: 1475 /* 1476 * In transmit state, time the transmission and arrange for 1477 * the retransmit. In persist state, just set snd_max. 1478 */ 1479 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1480 !tcp_timer_active(tp, TT_PERSIST)) { 1481 tcp_seq startseq = tp->snd_nxt; 1482 1483 /* 1484 * Advance snd_nxt over sequence space of this segment. 1485 */ 1486 if (flags & (TH_SYN|TH_FIN)) { 1487 if (flags & TH_SYN) 1488 tp->snd_nxt++; 1489 if (flags & TH_FIN) { 1490 tp->snd_nxt++; 1491 tp->t_flags |= TF_SENTFIN; 1492 } 1493 } 1494 if (sack_rxmit) 1495 goto timer; 1496 tp->snd_nxt += len; 1497 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1498 tp->snd_max = tp->snd_nxt; 1499 /* 1500 * Time this transmission if not a retransmission and 1501 * not currently timing anything. 1502 */ 1503 if (tp->t_rtttime == 0) { 1504 tp->t_rtttime = ticks; 1505 tp->t_rtseq = startseq; 1506 TCPSTAT_INC(tcps_segstimed); 1507 } 1508 } 1509 1510 /* 1511 * Set retransmit timer if not currently set, 1512 * and not doing a pure ack or a keep-alive probe. 1513 * Initial value for retransmit timer is smoothed 1514 * round-trip time + 2 * round-trip time variance. 1515 * Initialize shift counter which is used for backoff 1516 * of retransmit time. 1517 */ 1518 timer: 1519 if (!tcp_timer_active(tp, TT_REXMT) && 1520 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1521 (tp->snd_nxt != tp->snd_una))) { 1522 if (tcp_timer_active(tp, TT_PERSIST)) { 1523 tcp_timer_activate(tp, TT_PERSIST, 0); 1524 tp->t_rxtshift = 0; 1525 } 1526 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1527 } else if (len == 0 && sbavail(&so->so_snd) && 1528 !tcp_timer_active(tp, TT_REXMT) && 1529 !tcp_timer_active(tp, TT_PERSIST)) { 1530 /* 1531 * Avoid a situation where we do not set persist timer 1532 * after a zero window condition. For example: 1533 * 1) A -> B: packet with enough data to fill the window 1534 * 2) B -> A: ACK for #1 + new data (0 window 1535 * advertisement) 1536 * 3) A -> B: ACK for #2, 0 len packet 1537 * 1538 * In this case, A will not activate the persist timer, 1539 * because it chose to send a packet. Unless tcp_output 1540 * is called for some other reason (delayed ack timer, 1541 * another input packet from B, socket syscall), A will 1542 * not send zero window probes. 1543 * 1544 * So, if you send a 0-length packet, but there is data 1545 * in the socket buffer, and neither the rexmt or 1546 * persist timer is already set, then activate the 1547 * persist timer. 1548 */ 1549 tp->t_rxtshift = 0; 1550 tcp_setpersist(tp); 1551 } 1552 } else { 1553 /* 1554 * Persist case, update snd_max but since we are in 1555 * persist mode (no window) we do not update snd_nxt. 1556 */ 1557 int xlen = len; 1558 if (flags & TH_SYN) 1559 ++xlen; 1560 if (flags & TH_FIN) { 1561 ++xlen; 1562 tp->t_flags |= TF_SENTFIN; 1563 } 1564 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1565 tp->snd_max = tp->snd_nxt + xlen; 1566 } 1567 1568 if (error) { 1569 1570 /* 1571 * We know that the packet was lost, so back out the 1572 * sequence number advance, if any. 1573 * 1574 * If the error is EPERM the packet got blocked by the 1575 * local firewall. Normally we should terminate the 1576 * connection but the blocking may have been spurious 1577 * due to a firewall reconfiguration cycle. So we treat 1578 * it like a packet loss and let the retransmit timer and 1579 * timeouts do their work over time. 1580 * XXX: It is a POLA question whether calling tcp_drop right 1581 * away would be the really correct behavior instead. 1582 */ 1583 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1584 !tcp_timer_active(tp, TT_PERSIST)) && 1585 ((flags & TH_SYN) == 0) && 1586 (error != EPERM)) { 1587 if (sack_rxmit) { 1588 p->rxmit -= len; 1589 tp->sackhint.sack_bytes_rexmit -= len; 1590 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1591 ("sackhint bytes rtx >= 0")); 1592 } else 1593 tp->snd_nxt -= len; 1594 } 1595 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1596 switch (error) { 1597 case EACCES: 1598 tp->t_softerror = error; 1599 return (0); 1600 case EPERM: 1601 tp->t_softerror = error; 1602 return (error); 1603 case ENOBUFS: 1604 TCP_XMIT_TIMER_ASSERT(tp, len, flags); 1605 tp->snd_cwnd = tp->t_maxseg; 1606 return (0); 1607 case EMSGSIZE: 1608 /* 1609 * For some reason the interface we used initially 1610 * to send segments changed to another or lowered 1611 * its MTU. 1612 * If TSO was active we either got an interface 1613 * without TSO capabilits or TSO was turned off. 1614 * If we obtained mtu from ip_output() then update 1615 * it and try again. 1616 */ 1617 if (tso) 1618 tp->t_flags &= ~TF_TSO; 1619 if (mtu != 0) { 1620 tcp_mss_update(tp, -1, mtu, NULL, NULL); 1621 goto again; 1622 } 1623 return (error); 1624 case EHOSTDOWN: 1625 case EHOSTUNREACH: 1626 case ENETDOWN: 1627 case ENETUNREACH: 1628 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1629 tp->t_softerror = error; 1630 return (0); 1631 } 1632 /* FALLTHROUGH */ 1633 default: 1634 return (error); 1635 } 1636 } 1637 TCPSTAT_INC(tcps_sndtotal); 1638 1639 /* 1640 * Data sent (as far as we can tell). 1641 * If this advertises a larger window than any other segment, 1642 * then remember the size of the advertised window. 1643 * Any pending ACK has now been sent. 1644 */ 1645 if (SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1646 tp->rcv_adv = tp->rcv_nxt + recwin; 1647 tp->last_ack_sent = tp->rcv_nxt; 1648 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1649 if (tcp_timer_active(tp, TT_DELACK)) 1650 tcp_timer_activate(tp, TT_DELACK, 0); 1651 #if 0 1652 /* 1653 * This completely breaks TCP if newreno is turned on. What happens 1654 * is that if delayed-acks are turned on on the receiver, this code 1655 * on the transmitter effectively destroys the TCP window, forcing 1656 * it to four packets (1.5Kx4 = 6K window). 1657 */ 1658 if (sendalot && --maxburst) 1659 goto again; 1660 #endif 1661 if (sendalot) 1662 goto again; 1663 return (0); 1664 } 1665 1666 void 1667 tcp_setpersist(struct tcpcb *tp) 1668 { 1669 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1670 int tt; 1671 1672 tp->t_flags &= ~TF_PREVVALID; 1673 if (tcp_timer_active(tp, TT_REXMT)) 1674 panic("tcp_setpersist: retransmit pending"); 1675 /* 1676 * Start/restart persistence timer. 1677 */ 1678 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1679 tcp_persmin, tcp_persmax); 1680 tcp_timer_activate(tp, TT_PERSIST, tt); 1681 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1682 tp->t_rxtshift++; 1683 } 1684 1685 /* 1686 * Insert TCP options according to the supplied parameters to the place 1687 * optp in a consistent way. Can handle unaligned destinations. 1688 * 1689 * The order of the option processing is crucial for optimal packing and 1690 * alignment for the scarce option space. 1691 * 1692 * The optimal order for a SYN/SYN-ACK segment is: 1693 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1694 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1695 * 1696 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1697 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1698 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1699 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1700 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1701 */ 1702 int 1703 tcp_addoptions(struct tcpopt *to, u_char *optp) 1704 { 1705 u_int32_t mask, optlen = 0; 1706 1707 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1708 if ((to->to_flags & mask) != mask) 1709 continue; 1710 if (optlen == TCP_MAXOLEN) 1711 break; 1712 switch (to->to_flags & mask) { 1713 case TOF_MSS: 1714 while (optlen % 4) { 1715 optlen += TCPOLEN_NOP; 1716 *optp++ = TCPOPT_NOP; 1717 } 1718 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1719 continue; 1720 optlen += TCPOLEN_MAXSEG; 1721 *optp++ = TCPOPT_MAXSEG; 1722 *optp++ = TCPOLEN_MAXSEG; 1723 to->to_mss = htons(to->to_mss); 1724 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1725 optp += sizeof(to->to_mss); 1726 break; 1727 case TOF_SCALE: 1728 while (!optlen || optlen % 2 != 1) { 1729 optlen += TCPOLEN_NOP; 1730 *optp++ = TCPOPT_NOP; 1731 } 1732 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1733 continue; 1734 optlen += TCPOLEN_WINDOW; 1735 *optp++ = TCPOPT_WINDOW; 1736 *optp++ = TCPOLEN_WINDOW; 1737 *optp++ = to->to_wscale; 1738 break; 1739 case TOF_SACKPERM: 1740 while (optlen % 2) { 1741 optlen += TCPOLEN_NOP; 1742 *optp++ = TCPOPT_NOP; 1743 } 1744 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1745 continue; 1746 optlen += TCPOLEN_SACK_PERMITTED; 1747 *optp++ = TCPOPT_SACK_PERMITTED; 1748 *optp++ = TCPOLEN_SACK_PERMITTED; 1749 break; 1750 case TOF_TS: 1751 while (!optlen || optlen % 4 != 2) { 1752 optlen += TCPOLEN_NOP; 1753 *optp++ = TCPOPT_NOP; 1754 } 1755 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1756 continue; 1757 optlen += TCPOLEN_TIMESTAMP; 1758 *optp++ = TCPOPT_TIMESTAMP; 1759 *optp++ = TCPOLEN_TIMESTAMP; 1760 to->to_tsval = htonl(to->to_tsval); 1761 to->to_tsecr = htonl(to->to_tsecr); 1762 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1763 optp += sizeof(to->to_tsval); 1764 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1765 optp += sizeof(to->to_tsecr); 1766 break; 1767 case TOF_SIGNATURE: 1768 { 1769 int siglen = TCPOLEN_SIGNATURE - 2; 1770 1771 while (!optlen || optlen % 4 != 2) { 1772 optlen += TCPOLEN_NOP; 1773 *optp++ = TCPOPT_NOP; 1774 } 1775 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) { 1776 to->to_flags &= ~TOF_SIGNATURE; 1777 continue; 1778 } 1779 optlen += TCPOLEN_SIGNATURE; 1780 *optp++ = TCPOPT_SIGNATURE; 1781 *optp++ = TCPOLEN_SIGNATURE; 1782 to->to_signature = optp; 1783 while (siglen--) 1784 *optp++ = 0; 1785 break; 1786 } 1787 case TOF_SACK: 1788 { 1789 int sackblks = 0; 1790 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1791 tcp_seq sack_seq; 1792 1793 while (!optlen || optlen % 4 != 2) { 1794 optlen += TCPOLEN_NOP; 1795 *optp++ = TCPOPT_NOP; 1796 } 1797 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1798 continue; 1799 optlen += TCPOLEN_SACKHDR; 1800 *optp++ = TCPOPT_SACK; 1801 sackblks = min(to->to_nsacks, 1802 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1803 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1804 while (sackblks--) { 1805 sack_seq = htonl(sack->start); 1806 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1807 optp += sizeof(sack_seq); 1808 sack_seq = htonl(sack->end); 1809 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1810 optp += sizeof(sack_seq); 1811 optlen += TCPOLEN_SACK; 1812 sack++; 1813 } 1814 TCPSTAT_INC(tcps_sack_send_blocks); 1815 break; 1816 } 1817 #ifdef TCP_RFC7413 1818 case TOF_FASTOPEN: 1819 { 1820 int total_len; 1821 1822 /* XXX is there any point to aligning this option? */ 1823 total_len = TCPOLEN_FAST_OPEN_EMPTY + to->to_tfo_len; 1824 if (TCP_MAXOLEN - optlen < total_len) 1825 continue; 1826 *optp++ = TCPOPT_FAST_OPEN; 1827 *optp++ = total_len; 1828 if (to->to_tfo_len > 0) { 1829 bcopy(to->to_tfo_cookie, optp, to->to_tfo_len); 1830 optp += to->to_tfo_len; 1831 } 1832 optlen += total_len; 1833 break; 1834 } 1835 #endif 1836 default: 1837 panic("%s: unknown TCP option type", __func__); 1838 break; 1839 } 1840 } 1841 1842 /* Terminate and pad TCP options to a 4 byte boundary. */ 1843 if (optlen % 4) { 1844 optlen += TCPOLEN_EOL; 1845 *optp++ = TCPOPT_EOL; 1846 } 1847 /* 1848 * According to RFC 793 (STD0007): 1849 * "The content of the header beyond the End-of-Option option 1850 * must be header padding (i.e., zero)." 1851 * and later: "The padding is composed of zeros." 1852 */ 1853 while (optlen % 4) { 1854 optlen += TCPOLEN_PAD; 1855 *optp++ = TCPOPT_PAD; 1856 } 1857 1858 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1859 return (optlen); 1860 } 1861