1 /*- 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95 30 */ 31 32 #include <sys/cdefs.h> 33 __FBSDID("$FreeBSD$"); 34 35 #include "opt_inet.h" 36 #include "opt_inet6.h" 37 #include "opt_ipsec.h" 38 #include "opt_tcpdebug.h" 39 40 #include <sys/param.h> 41 #include <sys/systm.h> 42 #include <sys/domain.h> 43 #ifdef TCP_HHOOK 44 #include <sys/hhook.h> 45 #endif 46 #include <sys/kernel.h> 47 #include <sys/lock.h> 48 #include <sys/mbuf.h> 49 #include <sys/mutex.h> 50 #include <sys/protosw.h> 51 #include <sys/sdt.h> 52 #include <sys/socket.h> 53 #include <sys/socketvar.h> 54 #include <sys/sysctl.h> 55 56 #include <net/if.h> 57 #include <net/route.h> 58 #include <net/vnet.h> 59 60 #include <netinet/in.h> 61 #include <netinet/in_kdtrace.h> 62 #include <netinet/in_systm.h> 63 #include <netinet/ip.h> 64 #include <netinet/in_pcb.h> 65 #include <netinet/ip_var.h> 66 #include <netinet/ip_options.h> 67 #ifdef INET6 68 #include <netinet6/in6_pcb.h> 69 #include <netinet/ip6.h> 70 #include <netinet6/ip6_var.h> 71 #endif 72 #ifdef TCP_RFC7413 73 #include <netinet/tcp_fastopen.h> 74 #endif 75 #include <netinet/tcp.h> 76 #define TCPOUTFLAGS 77 #include <netinet/tcp_fsm.h> 78 #include <netinet/tcp_seq.h> 79 #include <netinet/tcp_timer.h> 80 #include <netinet/tcp_var.h> 81 #include <netinet/tcpip.h> 82 #include <netinet/cc/cc.h> 83 #ifdef TCPPCAP 84 #include <netinet/tcp_pcap.h> 85 #endif 86 #ifdef TCPDEBUG 87 #include <netinet/tcp_debug.h> 88 #endif 89 #ifdef TCP_OFFLOAD 90 #include <netinet/tcp_offload.h> 91 #endif 92 93 #include <netipsec/ipsec_support.h> 94 95 #include <machine/in_cksum.h> 96 97 #include <security/mac/mac_framework.h> 98 99 VNET_DEFINE(int, path_mtu_discovery) = 1; 100 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_VNET | CTLFLAG_RW, 101 &VNET_NAME(path_mtu_discovery), 1, 102 "Enable Path MTU Discovery"); 103 104 VNET_DEFINE(int, tcp_do_tso) = 1; 105 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_VNET | CTLFLAG_RW, 106 &VNET_NAME(tcp_do_tso), 0, 107 "Enable TCP Segmentation Offload"); 108 109 VNET_DEFINE(int, tcp_sendspace) = 1024*32; 110 #define V_tcp_sendspace VNET(tcp_sendspace) 111 SYSCTL_INT(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, CTLFLAG_VNET | CTLFLAG_RW, 112 &VNET_NAME(tcp_sendspace), 0, "Initial send socket buffer size"); 113 114 VNET_DEFINE(int, tcp_do_autosndbuf) = 1; 115 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_VNET | CTLFLAG_RW, 116 &VNET_NAME(tcp_do_autosndbuf), 0, 117 "Enable automatic send buffer sizing"); 118 119 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024; 120 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_VNET | CTLFLAG_RW, 121 &VNET_NAME(tcp_autosndbuf_inc), 0, 122 "Incrementor step size of automatic send buffer"); 123 124 VNET_DEFINE(int, tcp_autosndbuf_max) = 2*1024*1024; 125 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_VNET | CTLFLAG_RW, 126 &VNET_NAME(tcp_autosndbuf_max), 0, 127 "Max size of automatic send buffer"); 128 129 VNET_DEFINE(int, tcp_sendbuf_auto_lowat) = 0; 130 #define V_tcp_sendbuf_auto_lowat VNET(tcp_sendbuf_auto_lowat) 131 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto_lowat, CTLFLAG_VNET | CTLFLAG_RW, 132 &VNET_NAME(tcp_sendbuf_auto_lowat), 0, 133 "Modify threshold for auto send buffer growth to account for SO_SNDLOWAT"); 134 135 /* 136 * Make sure that either retransmit or persist timer is set for SYN, FIN and 137 * non-ACK. 138 */ 139 #define TCP_XMIT_TIMER_ASSERT(tp, len, th_flags) \ 140 KASSERT(((len) == 0 && ((th_flags) & (TH_SYN | TH_FIN)) == 0) ||\ 141 tcp_timer_active((tp), TT_REXMT) || \ 142 tcp_timer_active((tp), TT_PERSIST), \ 143 ("neither rexmt nor persist timer is set")) 144 145 #ifdef TCP_HHOOK 146 static void inline hhook_run_tcp_est_out(struct tcpcb *tp, 147 struct tcphdr *th, struct tcpopt *to, 148 uint32_t len, int tso); 149 #endif 150 static void inline cc_after_idle(struct tcpcb *tp); 151 152 #ifdef TCP_HHOOK 153 /* 154 * Wrapper for the TCP established output helper hook. 155 */ 156 static void inline 157 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th, 158 struct tcpopt *to, uint32_t len, int tso) 159 { 160 struct tcp_hhook_data hhook_data; 161 162 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) { 163 hhook_data.tp = tp; 164 hhook_data.th = th; 165 hhook_data.to = to; 166 hhook_data.len = len; 167 hhook_data.tso = tso; 168 169 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data, 170 tp->osd); 171 } 172 } 173 #endif 174 175 /* 176 * CC wrapper hook functions 177 */ 178 static void inline 179 cc_after_idle(struct tcpcb *tp) 180 { 181 INP_WLOCK_ASSERT(tp->t_inpcb); 182 183 if (CC_ALGO(tp)->after_idle != NULL) 184 CC_ALGO(tp)->after_idle(tp->ccv); 185 } 186 187 /* 188 * Tcp output routine: figure out what should be sent and send it. 189 */ 190 int 191 tcp_output(struct tcpcb *tp) 192 { 193 struct socket *so = tp->t_inpcb->inp_socket; 194 int32_t len; 195 uint32_t recwin, sendwin; 196 int off, flags, error = 0; /* Keep compiler happy */ 197 struct mbuf *m; 198 struct ip *ip = NULL; 199 struct ipovly *ipov = NULL; 200 struct tcphdr *th; 201 u_char opt[TCP_MAXOLEN]; 202 unsigned ipoptlen, optlen, hdrlen; 203 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 204 unsigned ipsec_optlen = 0; 205 #endif 206 int idle, sendalot; 207 int sack_rxmit, sack_bytes_rxmt; 208 struct sackhole *p; 209 int tso, mtu; 210 struct tcpopt to; 211 #if 0 212 int maxburst = TCP_MAXBURST; 213 #endif 214 #ifdef INET6 215 struct ip6_hdr *ip6 = NULL; 216 int isipv6; 217 218 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 219 #endif 220 221 INP_WLOCK_ASSERT(tp->t_inpcb); 222 223 #ifdef TCP_OFFLOAD 224 if (tp->t_flags & TF_TOE) 225 return (tcp_offload_output(tp)); 226 #endif 227 228 #ifdef TCP_RFC7413 229 /* 230 * For TFO connections in SYN_RECEIVED, only allow the initial 231 * SYN|ACK and those sent by the retransmit timer. 232 */ 233 if (IS_FASTOPEN(tp->t_flags) && 234 (tp->t_state == TCPS_SYN_RECEIVED) && 235 SEQ_GT(tp->snd_max, tp->snd_una) && /* initial SYN|ACK sent */ 236 (tp->snd_nxt != tp->snd_una)) /* not a retransmit */ 237 return (0); 238 #endif 239 /* 240 * Determine length of data that should be transmitted, 241 * and flags that will be used. 242 * If there is some data or critical controls (SYN, RST) 243 * to send, then transmit; otherwise, investigate further. 244 */ 245 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 246 if (idle && ticks - tp->t_rcvtime >= tp->t_rxtcur) 247 cc_after_idle(tp); 248 tp->t_flags &= ~TF_LASTIDLE; 249 if (idle) { 250 if (tp->t_flags & TF_MORETOCOME) { 251 tp->t_flags |= TF_LASTIDLE; 252 idle = 0; 253 } 254 } 255 again: 256 /* 257 * If we've recently taken a timeout, snd_max will be greater than 258 * snd_nxt. There may be SACK information that allows us to avoid 259 * resending already delivered data. Adjust snd_nxt accordingly. 260 */ 261 if ((tp->t_flags & TF_SACK_PERMIT) && 262 SEQ_LT(tp->snd_nxt, tp->snd_max)) 263 tcp_sack_adjust(tp); 264 sendalot = 0; 265 tso = 0; 266 mtu = 0; 267 off = tp->snd_nxt - tp->snd_una; 268 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 269 270 flags = tcp_outflags[tp->t_state]; 271 /* 272 * Send any SACK-generated retransmissions. If we're explicitly trying 273 * to send out new data (when sendalot is 1), bypass this function. 274 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 275 * we're replacing a (future) new transmission with a retransmission 276 * now, and we previously incremented snd_cwnd in tcp_input(). 277 */ 278 /* 279 * Still in sack recovery , reset rxmit flag to zero. 280 */ 281 sack_rxmit = 0; 282 sack_bytes_rxmt = 0; 283 len = 0; 284 p = NULL; 285 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) && 286 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 287 uint32_t cwin; 288 289 cwin = 290 imax(min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt, 0); 291 /* Do not retransmit SACK segments beyond snd_recover */ 292 if (SEQ_GT(p->end, tp->snd_recover)) { 293 /* 294 * (At least) part of sack hole extends beyond 295 * snd_recover. Check to see if we can rexmit data 296 * for this hole. 297 */ 298 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 299 /* 300 * Can't rexmit any more data for this hole. 301 * That data will be rexmitted in the next 302 * sack recovery episode, when snd_recover 303 * moves past p->rxmit. 304 */ 305 p = NULL; 306 goto after_sack_rexmit; 307 } else 308 /* Can rexmit part of the current hole */ 309 len = ((int32_t)ulmin(cwin, 310 tp->snd_recover - p->rxmit)); 311 } else 312 len = ((int32_t)ulmin(cwin, p->end - p->rxmit)); 313 off = p->rxmit - tp->snd_una; 314 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 315 __func__, off)); 316 if (len > 0) { 317 sack_rxmit = 1; 318 sendalot = 1; 319 TCPSTAT_INC(tcps_sack_rexmits); 320 TCPSTAT_ADD(tcps_sack_rexmit_bytes, 321 min(len, tp->t_maxseg)); 322 } 323 } 324 after_sack_rexmit: 325 /* 326 * Get standard flags, and add SYN or FIN if requested by 'hidden' 327 * state flags. 328 */ 329 if (tp->t_flags & TF_NEEDFIN) 330 flags |= TH_FIN; 331 if (tp->t_flags & TF_NEEDSYN) 332 flags |= TH_SYN; 333 334 SOCKBUF_LOCK(&so->so_snd); 335 /* 336 * If in persist timeout with window of 0, send 1 byte. 337 * Otherwise, if window is small but nonzero 338 * and timer expired, we will send what we can 339 * and go to transmit state. 340 */ 341 if (tp->t_flags & TF_FORCEDATA) { 342 if (sendwin == 0) { 343 /* 344 * If we still have some data to send, then 345 * clear the FIN bit. Usually this would 346 * happen below when it realizes that we 347 * aren't sending all the data. However, 348 * if we have exactly 1 byte of unsent data, 349 * then it won't clear the FIN bit below, 350 * and if we are in persist state, we wind 351 * up sending the packet without recording 352 * that we sent the FIN bit. 353 * 354 * We can't just blindly clear the FIN bit, 355 * because if we don't have any more data 356 * to send then the probe will be the FIN 357 * itself. 358 */ 359 if (off < sbused(&so->so_snd)) 360 flags &= ~TH_FIN; 361 sendwin = 1; 362 } else { 363 tcp_timer_activate(tp, TT_PERSIST, 0); 364 tp->t_rxtshift = 0; 365 } 366 } 367 368 /* 369 * If snd_nxt == snd_max and we have transmitted a FIN, the 370 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 371 * a negative length. This can also occur when TCP opens up 372 * its congestion window while receiving additional duplicate 373 * acks after fast-retransmit because TCP will reset snd_nxt 374 * to snd_max after the fast-retransmit. 375 * 376 * In the normal retransmit-FIN-only case, however, snd_nxt will 377 * be set to snd_una, the offset will be 0, and the length may 378 * wind up 0. 379 * 380 * If sack_rxmit is true we are retransmitting from the scoreboard 381 * in which case len is already set. 382 */ 383 if (sack_rxmit == 0) { 384 if (sack_bytes_rxmt == 0) 385 len = ((int32_t)min(sbavail(&so->so_snd), sendwin) - 386 off); 387 else { 388 int32_t cwin; 389 390 /* 391 * We are inside of a SACK recovery episode and are 392 * sending new data, having retransmitted all the 393 * data possible in the scoreboard. 394 */ 395 len = ((int32_t)min(sbavail(&so->so_snd), tp->snd_wnd) - 396 off); 397 /* 398 * Don't remove this (len > 0) check ! 399 * We explicitly check for len > 0 here (although it 400 * isn't really necessary), to work around a gcc 401 * optimization issue - to force gcc to compute 402 * len above. Without this check, the computation 403 * of len is bungled by the optimizer. 404 */ 405 if (len > 0) { 406 cwin = tp->snd_cwnd - 407 (tp->snd_nxt - tp->sack_newdata) - 408 sack_bytes_rxmt; 409 if (cwin < 0) 410 cwin = 0; 411 len = imin(len, cwin); 412 } 413 } 414 } 415 416 /* 417 * Lop off SYN bit if it has already been sent. However, if this 418 * is SYN-SENT state and if segment contains data and if we don't 419 * know that foreign host supports TAO, suppress sending segment. 420 */ 421 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 422 if (tp->t_state != TCPS_SYN_RECEIVED) 423 flags &= ~TH_SYN; 424 #ifdef TCP_RFC7413 425 /* 426 * When sending additional segments following a TFO SYN|ACK, 427 * do not include the SYN bit. 428 */ 429 if (IS_FASTOPEN(tp->t_flags) && 430 (tp->t_state == TCPS_SYN_RECEIVED)) 431 flags &= ~TH_SYN; 432 #endif 433 off--, len++; 434 } 435 436 /* 437 * Be careful not to send data and/or FIN on SYN segments. 438 * This measure is needed to prevent interoperability problems 439 * with not fully conformant TCP implementations. 440 */ 441 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 442 len = 0; 443 flags &= ~TH_FIN; 444 } 445 446 #ifdef TCP_RFC7413 447 /* 448 * When retransmitting SYN|ACK on a passively-created TFO socket, 449 * don't include data, as the presence of data may have caused the 450 * original SYN|ACK to have been dropped by a middlebox. 451 */ 452 if (IS_FASTOPEN(tp->t_flags) && 453 (((tp->t_state == TCPS_SYN_RECEIVED) && (tp->t_rxtshift > 0)) || 454 (flags & TH_RST))) 455 len = 0; 456 #endif 457 if (len <= 0) { 458 /* 459 * If FIN has been sent but not acked, 460 * but we haven't been called to retransmit, 461 * len will be < 0. Otherwise, window shrank 462 * after we sent into it. If window shrank to 0, 463 * cancel pending retransmit, pull snd_nxt back 464 * to (closed) window, and set the persist timer 465 * if it isn't already going. If the window didn't 466 * close completely, just wait for an ACK. 467 * 468 * We also do a general check here to ensure that 469 * we will set the persist timer when we have data 470 * to send, but a 0-byte window. This makes sure 471 * the persist timer is set even if the packet 472 * hits one of the "goto send" lines below. 473 */ 474 len = 0; 475 if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) && 476 (off < (int) sbavail(&so->so_snd))) { 477 tcp_timer_activate(tp, TT_REXMT, 0); 478 tp->t_rxtshift = 0; 479 tp->snd_nxt = tp->snd_una; 480 if (!tcp_timer_active(tp, TT_PERSIST)) 481 tcp_setpersist(tp); 482 } 483 } 484 485 /* len will be >= 0 after this point. */ 486 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 487 488 /* 489 * Automatic sizing of send socket buffer. Often the send buffer 490 * size is not optimally adjusted to the actual network conditions 491 * at hand (delay bandwidth product). Setting the buffer size too 492 * small limits throughput on links with high bandwidth and high 493 * delay (eg. trans-continental/oceanic links). Setting the 494 * buffer size too big consumes too much real kernel memory, 495 * especially with many connections on busy servers. 496 * 497 * The criteria to step up the send buffer one notch are: 498 * 1. receive window of remote host is larger than send buffer 499 * (with a fudge factor of 5/4th); 500 * 2. send buffer is filled to 7/8th with data (so we actually 501 * have data to make use of it); 502 * 3. send buffer fill has not hit maximal automatic size; 503 * 4. our send window (slow start and cogestion controlled) is 504 * larger than sent but unacknowledged data in send buffer. 505 * 506 * The remote host receive window scaling factor may limit the 507 * growing of the send buffer before it reaches its allowed 508 * maximum. 509 * 510 * It scales directly with slow start or congestion window 511 * and does at most one step per received ACK. This fast 512 * scaling has the drawback of growing the send buffer beyond 513 * what is strictly necessary to make full use of a given 514 * delay*bandwidth product. However testing has shown this not 515 * to be much of an problem. At worst we are trading wasting 516 * of available bandwidth (the non-use of it) for wasting some 517 * socket buffer memory. 518 * 519 * TODO: Shrink send buffer during idle periods together 520 * with congestion window. Requires another timer. Has to 521 * wait for upcoming tcp timer rewrite. 522 * 523 * XXXGL: should there be used sbused() or sbavail()? 524 */ 525 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 526 int autosndbuf_mod = 0; 527 if (V_tcp_sendbuf_auto_lowat) 528 autosndbuf_mod = so->so_snd.sb_lowat; 529 530 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat - autosndbuf_mod && 531 sbused(&so->so_snd) >= (so->so_snd.sb_hiwat / 8 * 7) - autosndbuf_mod && 532 sbused(&so->so_snd) < V_tcp_autosndbuf_max && 533 sendwin >= (sbused(&so->so_snd) - 534 (tp->snd_nxt - tp->snd_una))) { 535 if (!sbreserve_locked(&so->so_snd, 536 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 537 V_tcp_autosndbuf_max), so, curthread)) 538 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 539 } 540 } 541 542 /* 543 * Decide if we can use TCP Segmentation Offloading (if supported by 544 * hardware). 545 * 546 * TSO may only be used if we are in a pure bulk sending state. The 547 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 548 * IP options prevent using TSO. With TSO the TCP header is the same 549 * (except for the sequence number) for all generated packets. This 550 * makes it impossible to transmit any options which vary per generated 551 * segment or packet. 552 * 553 * IPv4 handling has a clear separation of ip options and ip header 554 * flags while IPv6 combines both in in6p_outputopts. ip6_optlen() does 555 * the right thing below to provide length of just ip options and thus 556 * checking for ipoptlen is enough to decide if ip options are present. 557 */ 558 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 559 /* 560 * Pre-calculate here as we save another lookup into the darknesses 561 * of IPsec that way and can actually decide if TSO is ok. 562 */ 563 #ifdef INET6 564 if (isipv6 && IPSEC_ENABLED(ipv6)) 565 ipsec_optlen = IPSEC_HDRSIZE(ipv6, tp->t_inpcb); 566 #ifdef INET 567 else 568 #endif 569 #endif /* INET6 */ 570 #ifdef INET 571 if (IPSEC_ENABLED(ipv4)) 572 ipsec_optlen = IPSEC_HDRSIZE(ipv4, tp->t_inpcb); 573 #endif /* INET */ 574 #endif /* IPSEC */ 575 #ifdef INET6 576 if (isipv6) 577 ipoptlen = ip6_optlen(tp->t_inpcb); 578 else 579 #endif 580 if (tp->t_inpcb->inp_options) 581 ipoptlen = tp->t_inpcb->inp_options->m_len - 582 offsetof(struct ipoption, ipopt_list); 583 else 584 ipoptlen = 0; 585 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 586 ipoptlen += ipsec_optlen; 587 #endif 588 589 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg && 590 ((tp->t_flags & TF_SIGNATURE) == 0) && 591 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 592 ipoptlen == 0) 593 tso = 1; 594 595 if (sack_rxmit) { 596 if (SEQ_LT(p->rxmit + len, tp->snd_una + sbused(&so->so_snd))) 597 flags &= ~TH_FIN; 598 } else { 599 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + 600 sbused(&so->so_snd))) 601 flags &= ~TH_FIN; 602 } 603 604 recwin = lmin(lmax(sbspace(&so->so_rcv), 0), 605 (long)TCP_MAXWIN << tp->rcv_scale); 606 607 /* 608 * Sender silly window avoidance. We transmit under the following 609 * conditions when len is non-zero: 610 * 611 * - We have a full segment (or more with TSO) 612 * - This is the last buffer in a write()/send() and we are 613 * either idle or running NODELAY 614 * - we've timed out (e.g. persist timer) 615 * - we have more then 1/2 the maximum send window's worth of 616 * data (receiver may be limited the window size) 617 * - we need to retransmit 618 */ 619 if (len) { 620 if (len >= tp->t_maxseg) 621 goto send; 622 /* 623 * NOTE! on localhost connections an 'ack' from the remote 624 * end may occur synchronously with the output and cause 625 * us to flush a buffer queued with moretocome. XXX 626 * 627 * note: the len + off check is almost certainly unnecessary. 628 */ 629 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 630 (idle || (tp->t_flags & TF_NODELAY)) && 631 (uint32_t)len + (uint32_t)off >= sbavail(&so->so_snd) && 632 (tp->t_flags & TF_NOPUSH) == 0) { 633 goto send; 634 } 635 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 636 goto send; 637 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 638 goto send; 639 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 640 goto send; 641 if (sack_rxmit) 642 goto send; 643 } 644 645 /* 646 * Sending of standalone window updates. 647 * 648 * Window updates are important when we close our window due to a 649 * full socket buffer and are opening it again after the application 650 * reads data from it. Once the window has opened again and the 651 * remote end starts to send again the ACK clock takes over and 652 * provides the most current window information. 653 * 654 * We must avoid the silly window syndrome whereas every read 655 * from the receive buffer, no matter how small, causes a window 656 * update to be sent. We also should avoid sending a flurry of 657 * window updates when the socket buffer had queued a lot of data 658 * and the application is doing small reads. 659 * 660 * Prevent a flurry of pointless window updates by only sending 661 * an update when we can increase the advertized window by more 662 * than 1/4th of the socket buffer capacity. When the buffer is 663 * getting full or is very small be more aggressive and send an 664 * update whenever we can increase by two mss sized segments. 665 * In all other situations the ACK's to new incoming data will 666 * carry further window increases. 667 * 668 * Don't send an independent window update if a delayed 669 * ACK is pending (it will get piggy-backed on it) or the 670 * remote side already has done a half-close and won't send 671 * more data. Skip this if the connection is in T/TCP 672 * half-open state. 673 */ 674 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 675 !(tp->t_flags & TF_DELACK) && 676 !TCPS_HAVERCVDFIN(tp->t_state)) { 677 /* 678 * "adv" is the amount we could increase the window, 679 * taking into account that we are limited by 680 * TCP_MAXWIN << tp->rcv_scale. 681 */ 682 int32_t adv; 683 int oldwin; 684 685 adv = recwin; 686 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { 687 oldwin = (tp->rcv_adv - tp->rcv_nxt); 688 adv -= oldwin; 689 } else 690 oldwin = 0; 691 692 /* 693 * If the new window size ends up being the same as or less 694 * than the old size when it is scaled, then don't force 695 * a window update. 696 */ 697 if (oldwin >> tp->rcv_scale >= (adv + oldwin) >> tp->rcv_scale) 698 goto dontupdate; 699 700 if (adv >= (int32_t)(2 * tp->t_maxseg) && 701 (adv >= (int32_t)(so->so_rcv.sb_hiwat / 4) || 702 recwin <= (so->so_rcv.sb_hiwat / 8) || 703 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg)) 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->t_rxtcur); 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 /* 800 * Compute options for segment. 801 * We only have to care about SYN and established connection 802 * segments. Options for SYN-ACK segments are handled in TCP 803 * syncache. 804 */ 805 to.to_flags = 0; 806 if ((tp->t_flags & TF_NOOPT) == 0) { 807 /* Maximum segment size. */ 808 if (flags & TH_SYN) { 809 tp->snd_nxt = tp->iss; 810 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 811 to.to_flags |= TOF_MSS; 812 #ifdef TCP_RFC7413 813 /* 814 * Only include the TFO option on the first 815 * transmission of the SYN|ACK on a 816 * passively-created TFO socket, as the presence of 817 * the TFO option may have caused the original 818 * SYN|ACK to have been dropped by a middlebox. 819 */ 820 if (IS_FASTOPEN(tp->t_flags) && 821 (tp->t_state == TCPS_SYN_RECEIVED) && 822 (tp->t_rxtshift == 0)) { 823 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN; 824 to.to_tfo_cookie = (u_char *)&tp->t_tfo_cookie; 825 to.to_flags |= TOF_FASTOPEN; 826 } 827 #endif 828 } 829 /* Window scaling. */ 830 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 831 to.to_wscale = tp->request_r_scale; 832 to.to_flags |= TOF_SCALE; 833 } 834 /* Timestamps. */ 835 if ((tp->t_flags & TF_RCVD_TSTMP) || 836 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 837 to.to_tsval = tcp_ts_getticks() + tp->ts_offset; 838 to.to_tsecr = tp->ts_recent; 839 to.to_flags |= TOF_TS; 840 } 841 842 /* Set receive buffer autosizing timestamp. */ 843 if (tp->rfbuf_ts == 0 && 844 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 845 tp->rfbuf_ts = tcp_ts_getticks(); 846 847 /* Selective ACK's. */ 848 if (tp->t_flags & TF_SACK_PERMIT) { 849 if (flags & TH_SYN) 850 to.to_flags |= TOF_SACKPERM; 851 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 852 (tp->t_flags & TF_SACK_PERMIT) && 853 tp->rcv_numsacks > 0) { 854 to.to_flags |= TOF_SACK; 855 to.to_nsacks = tp->rcv_numsacks; 856 to.to_sacks = (u_char *)tp->sackblks; 857 } 858 } 859 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 860 /* TCP-MD5 (RFC2385). */ 861 /* 862 * Check that TCP_MD5SIG is enabled in tcpcb to 863 * account the size needed to set this TCP option. 864 */ 865 if (tp->t_flags & TF_SIGNATURE) 866 to.to_flags |= TOF_SIGNATURE; 867 #endif /* TCP_SIGNATURE */ 868 869 /* Processing the options. */ 870 hdrlen += optlen = tcp_addoptions(&to, opt); 871 } 872 873 /* 874 * Adjust data length if insertion of options will 875 * bump the packet length beyond the t_maxseg length. 876 * Clear the FIN bit because we cut off the tail of 877 * the segment. 878 */ 879 if (len + optlen + ipoptlen > tp->t_maxseg) { 880 flags &= ~TH_FIN; 881 882 if (tso) { 883 u_int if_hw_tsomax; 884 u_int if_hw_tsomaxsegcount; 885 u_int if_hw_tsomaxsegsize; 886 struct mbuf *mb; 887 u_int moff; 888 int max_len; 889 890 /* extract TSO information */ 891 if_hw_tsomax = tp->t_tsomax; 892 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount; 893 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize; 894 895 /* 896 * Limit a TSO burst to prevent it from 897 * overflowing or exceeding the maximum length 898 * allowed by the network interface: 899 */ 900 KASSERT(ipoptlen == 0, 901 ("%s: TSO can't do IP options", __func__)); 902 903 /* 904 * Check if we should limit by maximum payload 905 * length: 906 */ 907 if (if_hw_tsomax != 0) { 908 /* compute maximum TSO length */ 909 max_len = (if_hw_tsomax - hdrlen - 910 max_linkhdr); 911 if (max_len <= 0) { 912 len = 0; 913 } else if (len > max_len) { 914 sendalot = 1; 915 len = max_len; 916 } 917 } 918 919 /* 920 * Check if we should limit by maximum segment 921 * size and count: 922 */ 923 if (if_hw_tsomaxsegcount != 0 && 924 if_hw_tsomaxsegsize != 0) { 925 /* 926 * Subtract one segment for the LINK 927 * and TCP/IP headers mbuf that will 928 * be prepended to this mbuf chain 929 * after the code in this section 930 * limits the number of mbufs in the 931 * chain to if_hw_tsomaxsegcount. 932 */ 933 if_hw_tsomaxsegcount -= 1; 934 max_len = 0; 935 mb = sbsndmbuf(&so->so_snd, off, &moff); 936 937 while (mb != NULL && max_len < len) { 938 u_int mlen; 939 u_int frags; 940 941 /* 942 * Get length of mbuf fragment 943 * and how many hardware frags, 944 * rounded up, it would use: 945 */ 946 mlen = (mb->m_len - moff); 947 frags = howmany(mlen, 948 if_hw_tsomaxsegsize); 949 950 /* Handle special case: Zero Length Mbuf */ 951 if (frags == 0) 952 frags = 1; 953 954 /* 955 * Check if the fragment limit 956 * will be reached or exceeded: 957 */ 958 if (frags >= if_hw_tsomaxsegcount) { 959 max_len += min(mlen, 960 if_hw_tsomaxsegcount * 961 if_hw_tsomaxsegsize); 962 break; 963 } 964 max_len += mlen; 965 if_hw_tsomaxsegcount -= frags; 966 moff = 0; 967 mb = mb->m_next; 968 } 969 if (max_len <= 0) { 970 len = 0; 971 } else if (len > max_len) { 972 sendalot = 1; 973 len = max_len; 974 } 975 } 976 977 /* 978 * Prevent the last segment from being 979 * fractional unless the send sockbuf can be 980 * emptied: 981 */ 982 max_len = (tp->t_maxseg - optlen); 983 if (((uint32_t)off + (uint32_t)len) < 984 sbavail(&so->so_snd)) { 985 moff = len % max_len; 986 if (moff != 0) { 987 len -= moff; 988 sendalot = 1; 989 } 990 } 991 992 /* 993 * In case there are too many small fragments 994 * don't use TSO: 995 */ 996 if (len <= max_len) { 997 len = max_len; 998 sendalot = 1; 999 tso = 0; 1000 } 1001 1002 /* 1003 * Send the FIN in a separate segment 1004 * after the bulk sending is done. 1005 * We don't trust the TSO implementations 1006 * to clear the FIN flag on all but the 1007 * last segment. 1008 */ 1009 if (tp->t_flags & TF_NEEDFIN) 1010 sendalot = 1; 1011 1012 } else { 1013 len = tp->t_maxseg - optlen - ipoptlen; 1014 sendalot = 1; 1015 } 1016 } else 1017 tso = 0; 1018 1019 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 1020 ("%s: len > IP_MAXPACKET", __func__)); 1021 1022 /*#ifdef DIAGNOSTIC*/ 1023 #ifdef INET6 1024 if (max_linkhdr + hdrlen > MCLBYTES) 1025 #else 1026 if (max_linkhdr + hdrlen > MHLEN) 1027 #endif 1028 panic("tcphdr too big"); 1029 /*#endif*/ 1030 1031 /* 1032 * This KASSERT is here to catch edge cases at a well defined place. 1033 * Before, those had triggered (random) panic conditions further down. 1034 */ 1035 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 1036 1037 /* 1038 * Grab a header mbuf, attaching a copy of data to 1039 * be transmitted, and initialize the header from 1040 * the template for sends on this connection. 1041 */ 1042 if (len) { 1043 struct mbuf *mb; 1044 u_int moff; 1045 1046 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 1047 TCPSTAT_INC(tcps_sndprobe); 1048 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 1049 tp->t_sndrexmitpack++; 1050 TCPSTAT_INC(tcps_sndrexmitpack); 1051 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 1052 } else { 1053 TCPSTAT_INC(tcps_sndpack); 1054 TCPSTAT_ADD(tcps_sndbyte, len); 1055 } 1056 #ifdef INET6 1057 if (MHLEN < hdrlen + max_linkhdr) 1058 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR); 1059 else 1060 #endif 1061 m = m_gethdr(M_NOWAIT, MT_DATA); 1062 1063 if (m == NULL) { 1064 SOCKBUF_UNLOCK(&so->so_snd); 1065 error = ENOBUFS; 1066 sack_rxmit = 0; 1067 goto out; 1068 } 1069 1070 m->m_data += max_linkhdr; 1071 m->m_len = hdrlen; 1072 1073 /* 1074 * Start the m_copy functions from the closest mbuf 1075 * to the offset in the socket buffer chain. 1076 */ 1077 mb = sbsndptr(&so->so_snd, off, len, &moff); 1078 1079 if (len <= MHLEN - hdrlen - max_linkhdr) { 1080 m_copydata(mb, moff, len, 1081 mtod(m, caddr_t) + hdrlen); 1082 m->m_len += len; 1083 } else { 1084 m->m_next = m_copym(mb, moff, len, M_NOWAIT); 1085 if (m->m_next == NULL) { 1086 SOCKBUF_UNLOCK(&so->so_snd); 1087 (void) m_free(m); 1088 error = ENOBUFS; 1089 sack_rxmit = 0; 1090 goto out; 1091 } 1092 } 1093 1094 /* 1095 * If we're sending everything we've got, set PUSH. 1096 * (This will keep happy those implementations which only 1097 * give data to the user when a buffer fills or 1098 * a PUSH comes in.) 1099 */ 1100 if (((uint32_t)off + (uint32_t)len == sbused(&so->so_snd)) && 1101 !(flags & TH_SYN)) 1102 flags |= TH_PUSH; 1103 SOCKBUF_UNLOCK(&so->so_snd); 1104 } else { 1105 SOCKBUF_UNLOCK(&so->so_snd); 1106 if (tp->t_flags & TF_ACKNOW) 1107 TCPSTAT_INC(tcps_sndacks); 1108 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 1109 TCPSTAT_INC(tcps_sndctrl); 1110 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 1111 TCPSTAT_INC(tcps_sndurg); 1112 else 1113 TCPSTAT_INC(tcps_sndwinup); 1114 1115 m = m_gethdr(M_NOWAIT, MT_DATA); 1116 if (m == NULL) { 1117 error = ENOBUFS; 1118 sack_rxmit = 0; 1119 goto out; 1120 } 1121 #ifdef INET6 1122 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 1123 MHLEN >= hdrlen) { 1124 M_ALIGN(m, hdrlen); 1125 } else 1126 #endif 1127 m->m_data += max_linkhdr; 1128 m->m_len = hdrlen; 1129 } 1130 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 1131 m->m_pkthdr.rcvif = (struct ifnet *)0; 1132 #ifdef MAC 1133 mac_inpcb_create_mbuf(tp->t_inpcb, m); 1134 #endif 1135 #ifdef INET6 1136 if (isipv6) { 1137 ip6 = mtod(m, struct ip6_hdr *); 1138 th = (struct tcphdr *)(ip6 + 1); 1139 tcpip_fillheaders(tp->t_inpcb, ip6, th); 1140 } else 1141 #endif /* INET6 */ 1142 { 1143 ip = mtod(m, struct ip *); 1144 ipov = (struct ipovly *)ip; 1145 th = (struct tcphdr *)(ip + 1); 1146 tcpip_fillheaders(tp->t_inpcb, ip, th); 1147 } 1148 1149 /* 1150 * Fill in fields, remembering maximum advertised 1151 * window for use in delaying messages about window sizes. 1152 * If resending a FIN, be sure not to use a new sequence number. 1153 */ 1154 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 1155 tp->snd_nxt == tp->snd_max) 1156 tp->snd_nxt--; 1157 /* 1158 * If we are starting a connection, send ECN setup 1159 * SYN packet. If we are on a retransmit, we may 1160 * resend those bits a number of times as per 1161 * RFC 3168. 1162 */ 1163 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn == 1) { 1164 if (tp->t_rxtshift >= 1) { 1165 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 1166 flags |= TH_ECE|TH_CWR; 1167 } else 1168 flags |= TH_ECE|TH_CWR; 1169 } 1170 1171 if (tp->t_state == TCPS_ESTABLISHED && 1172 (tp->t_flags & TF_ECN_PERMIT)) { 1173 /* 1174 * If the peer has ECN, mark data packets with 1175 * ECN capable transmission (ECT). 1176 * Ignore pure ack packets, retransmissions and window probes. 1177 */ 1178 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 1179 !((tp->t_flags & TF_FORCEDATA) && len == 1)) { 1180 #ifdef INET6 1181 if (isipv6) 1182 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 1183 else 1184 #endif 1185 ip->ip_tos |= IPTOS_ECN_ECT0; 1186 TCPSTAT_INC(tcps_ecn_ect0); 1187 } 1188 1189 /* 1190 * Reply with proper ECN notifications. 1191 */ 1192 if (tp->t_flags & TF_ECN_SND_CWR) { 1193 flags |= TH_CWR; 1194 tp->t_flags &= ~TF_ECN_SND_CWR; 1195 } 1196 if (tp->t_flags & TF_ECN_SND_ECE) 1197 flags |= TH_ECE; 1198 } 1199 1200 /* 1201 * If we are doing retransmissions, then snd_nxt will 1202 * not reflect the first unsent octet. For ACK only 1203 * packets, we do not want the sequence number of the 1204 * retransmitted packet, we want the sequence number 1205 * of the next unsent octet. So, if there is no data 1206 * (and no SYN or FIN), use snd_max instead of snd_nxt 1207 * when filling in ti_seq. But if we are in persist 1208 * state, snd_max might reflect one byte beyond the 1209 * right edge of the window, so use snd_nxt in that 1210 * case, since we know we aren't doing a retransmission. 1211 * (retransmit and persist are mutually exclusive...) 1212 */ 1213 if (sack_rxmit == 0) { 1214 if (len || (flags & (TH_SYN|TH_FIN)) || 1215 tcp_timer_active(tp, TT_PERSIST)) 1216 th->th_seq = htonl(tp->snd_nxt); 1217 else 1218 th->th_seq = htonl(tp->snd_max); 1219 } else { 1220 th->th_seq = htonl(p->rxmit); 1221 p->rxmit += len; 1222 tp->sackhint.sack_bytes_rexmit += len; 1223 } 1224 th->th_ack = htonl(tp->rcv_nxt); 1225 if (optlen) { 1226 bcopy(opt, th + 1, optlen); 1227 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1228 } 1229 th->th_flags = flags; 1230 /* 1231 * Calculate receive window. Don't shrink window, 1232 * but avoid silly window syndrome. 1233 */ 1234 if (recwin < (so->so_rcv.sb_hiwat / 4) && 1235 recwin < tp->t_maxseg) 1236 recwin = 0; 1237 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1238 recwin < (tp->rcv_adv - tp->rcv_nxt)) 1239 recwin = (tp->rcv_adv - tp->rcv_nxt); 1240 1241 /* 1242 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1243 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1244 * case is handled in syncache. 1245 */ 1246 if (flags & TH_SYN) 1247 th->th_win = htons((u_short) 1248 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1249 else 1250 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1251 1252 /* 1253 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1254 * a 0 window. This may cause the remote transmitter to stall. This 1255 * flag tells soreceive() to disable delayed acknowledgements when 1256 * draining the buffer. This can occur if the receiver is attempting 1257 * to read more data than can be buffered prior to transmitting on 1258 * the connection. 1259 */ 1260 if (th->th_win == 0) { 1261 tp->t_sndzerowin++; 1262 tp->t_flags |= TF_RXWIN0SENT; 1263 } else 1264 tp->t_flags &= ~TF_RXWIN0SENT; 1265 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1266 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1267 th->th_flags |= TH_URG; 1268 } else 1269 /* 1270 * If no urgent pointer to send, then we pull 1271 * the urgent pointer to the left edge of the send window 1272 * so that it doesn't drift into the send window on sequence 1273 * number wraparound. 1274 */ 1275 tp->snd_up = tp->snd_una; /* drag it along */ 1276 1277 /* 1278 * Put TCP length in extended header, and then 1279 * checksum extended header and data. 1280 */ 1281 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1282 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1283 1284 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1285 if (to.to_flags & TOF_SIGNATURE) { 1286 /* 1287 * Calculate MD5 signature and put it into the place 1288 * determined before. 1289 * NOTE: since TCP options buffer doesn't point into 1290 * mbuf's data, calculate offset and use it. 1291 */ 1292 if (!TCPMD5_ENABLED() || TCPMD5_OUTPUT(m, th, 1293 (u_char *)(th + 1) + (to.to_signature - opt)) != 0) { 1294 /* 1295 * Do not send segment if the calculation of MD5 1296 * digest has failed. 1297 */ 1298 goto out; 1299 } 1300 } 1301 #endif 1302 #ifdef INET6 1303 if (isipv6) { 1304 /* 1305 * There is no need to fill in ip6_plen right now. 1306 * It will be filled later by ip6_output. 1307 */ 1308 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1309 th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) + 1310 optlen + len, IPPROTO_TCP, 0); 1311 } 1312 #endif 1313 #if defined(INET6) && defined(INET) 1314 else 1315 #endif 1316 #ifdef INET 1317 { 1318 m->m_pkthdr.csum_flags = CSUM_TCP; 1319 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1320 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1321 1322 /* IP version must be set here for ipv4/ipv6 checking later */ 1323 KASSERT(ip->ip_v == IPVERSION, 1324 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1325 } 1326 #endif 1327 1328 /* 1329 * Enable TSO and specify the size of the segments. 1330 * The TCP pseudo header checksum is always provided. 1331 */ 1332 if (tso) { 1333 KASSERT(len > tp->t_maxseg - optlen, 1334 ("%s: len <= tso_segsz", __func__)); 1335 m->m_pkthdr.csum_flags |= CSUM_TSO; 1336 m->m_pkthdr.tso_segsz = tp->t_maxseg - optlen; 1337 } 1338 1339 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 1340 KASSERT(len + hdrlen + ipoptlen - ipsec_optlen == m_length(m, NULL), 1341 ("%s: mbuf chain shorter than expected: %d + %u + %u - %u != %u", 1342 __func__, len, hdrlen, ipoptlen, ipsec_optlen, m_length(m, NULL))); 1343 #else 1344 KASSERT(len + hdrlen + ipoptlen == m_length(m, NULL), 1345 ("%s: mbuf chain shorter than expected: %d + %u + %u != %u", 1346 __func__, len, hdrlen, ipoptlen, m_length(m, NULL))); 1347 #endif 1348 1349 #ifdef TCP_HHOOK 1350 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1351 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1352 #endif 1353 1354 #ifdef TCPDEBUG 1355 /* 1356 * Trace. 1357 */ 1358 if (so->so_options & SO_DEBUG) { 1359 u_short save = 0; 1360 #ifdef INET6 1361 if (!isipv6) 1362 #endif 1363 { 1364 save = ipov->ih_len; 1365 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1366 } 1367 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1368 #ifdef INET6 1369 if (!isipv6) 1370 #endif 1371 ipov->ih_len = save; 1372 } 1373 #endif /* TCPDEBUG */ 1374 TCP_PROBE3(debug__output, tp, th, m); 1375 1376 /* 1377 * Fill in IP length and desired time to live and 1378 * send to IP level. There should be a better way 1379 * to handle ttl and tos; we could keep them in 1380 * the template, but need a way to checksum without them. 1381 */ 1382 /* 1383 * m->m_pkthdr.len should have been set before checksum calculation, 1384 * because in6_cksum() need it. 1385 */ 1386 #ifdef INET6 1387 if (isipv6) { 1388 /* 1389 * we separately set hoplimit for every segment, since the 1390 * user might want to change the value via setsockopt. 1391 * Also, desired default hop limit might be changed via 1392 * Neighbor Discovery. 1393 */ 1394 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1395 1396 /* 1397 * Set the packet size here for the benefit of DTrace probes. 1398 * ip6_output() will set it properly; it's supposed to include 1399 * the option header lengths as well. 1400 */ 1401 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6)); 1402 1403 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) 1404 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1405 else 1406 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1407 1408 if (tp->t_state == TCPS_SYN_SENT) 1409 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th); 1410 1411 TCP_PROBE5(send, NULL, tp, ip6, tp, th); 1412 1413 #ifdef TCPPCAP 1414 /* Save packet, if requested. */ 1415 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1416 #endif 1417 1418 /* TODO: IPv6 IP6TOS_ECT bit on */ 1419 error = ip6_output(m, tp->t_inpcb->in6p_outputopts, 1420 &tp->t_inpcb->inp_route6, 1421 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 1422 NULL, NULL, tp->t_inpcb); 1423 1424 if (error == EMSGSIZE && tp->t_inpcb->inp_route6.ro_rt != NULL) 1425 mtu = tp->t_inpcb->inp_route6.ro_rt->rt_mtu; 1426 } 1427 #endif /* INET6 */ 1428 #if defined(INET) && defined(INET6) 1429 else 1430 #endif 1431 #ifdef INET 1432 { 1433 ip->ip_len = htons(m->m_pkthdr.len); 1434 #ifdef INET6 1435 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1436 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1437 #endif /* INET6 */ 1438 /* 1439 * If we do path MTU discovery, then we set DF on every packet. 1440 * This might not be the best thing to do according to RFC3390 1441 * Section 2. However the tcp hostcache migitates the problem 1442 * so it affects only the first tcp connection with a host. 1443 * 1444 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1445 */ 1446 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) { 1447 ip->ip_off |= htons(IP_DF); 1448 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1449 } else { 1450 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1451 } 1452 1453 if (tp->t_state == TCPS_SYN_SENT) 1454 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th); 1455 1456 TCP_PROBE5(send, NULL, tp, ip, tp, th); 1457 1458 #ifdef TCPPCAP 1459 /* Save packet, if requested. */ 1460 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1461 #endif 1462 1463 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, 1464 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1465 tp->t_inpcb); 1466 1467 if (error == EMSGSIZE && tp->t_inpcb->inp_route.ro_rt != NULL) 1468 mtu = tp->t_inpcb->inp_route.ro_rt->rt_mtu; 1469 } 1470 #endif /* INET */ 1471 1472 out: 1473 /* 1474 * In transmit state, time the transmission and arrange for 1475 * the retransmit. In persist state, just set snd_max. 1476 */ 1477 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1478 !tcp_timer_active(tp, TT_PERSIST)) { 1479 tcp_seq startseq = tp->snd_nxt; 1480 1481 /* 1482 * Advance snd_nxt over sequence space of this segment. 1483 */ 1484 if (flags & (TH_SYN|TH_FIN)) { 1485 if (flags & TH_SYN) 1486 tp->snd_nxt++; 1487 if (flags & TH_FIN) { 1488 tp->snd_nxt++; 1489 tp->t_flags |= TF_SENTFIN; 1490 } 1491 } 1492 if (sack_rxmit) 1493 goto timer; 1494 tp->snd_nxt += len; 1495 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1496 tp->snd_max = tp->snd_nxt; 1497 /* 1498 * Time this transmission if not a retransmission and 1499 * not currently timing anything. 1500 */ 1501 if (tp->t_rtttime == 0) { 1502 tp->t_rtttime = ticks; 1503 tp->t_rtseq = startseq; 1504 TCPSTAT_INC(tcps_segstimed); 1505 } 1506 } 1507 1508 /* 1509 * Set retransmit timer if not currently set, 1510 * and not doing a pure ack or a keep-alive probe. 1511 * Initial value for retransmit timer is smoothed 1512 * round-trip time + 2 * round-trip time variance. 1513 * Initialize shift counter which is used for backoff 1514 * of retransmit time. 1515 */ 1516 timer: 1517 if (!tcp_timer_active(tp, TT_REXMT) && 1518 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1519 (tp->snd_nxt != tp->snd_una))) { 1520 if (tcp_timer_active(tp, TT_PERSIST)) { 1521 tcp_timer_activate(tp, TT_PERSIST, 0); 1522 tp->t_rxtshift = 0; 1523 } 1524 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1525 } else if (len == 0 && sbavail(&so->so_snd) && 1526 !tcp_timer_active(tp, TT_REXMT) && 1527 !tcp_timer_active(tp, TT_PERSIST)) { 1528 /* 1529 * Avoid a situation where we do not set persist timer 1530 * after a zero window condition. For example: 1531 * 1) A -> B: packet with enough data to fill the window 1532 * 2) B -> A: ACK for #1 + new data (0 window 1533 * advertisement) 1534 * 3) A -> B: ACK for #2, 0 len packet 1535 * 1536 * In this case, A will not activate the persist timer, 1537 * because it chose to send a packet. Unless tcp_output 1538 * is called for some other reason (delayed ack timer, 1539 * another input packet from B, socket syscall), A will 1540 * not send zero window probes. 1541 * 1542 * So, if you send a 0-length packet, but there is data 1543 * in the socket buffer, and neither the rexmt or 1544 * persist timer is already set, then activate the 1545 * persist timer. 1546 */ 1547 tp->t_rxtshift = 0; 1548 tcp_setpersist(tp); 1549 } 1550 } else { 1551 /* 1552 * Persist case, update snd_max but since we are in 1553 * persist mode (no window) we do not update snd_nxt. 1554 */ 1555 int xlen = len; 1556 if (flags & TH_SYN) 1557 ++xlen; 1558 if (flags & TH_FIN) { 1559 ++xlen; 1560 tp->t_flags |= TF_SENTFIN; 1561 } 1562 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1563 tp->snd_max = tp->snd_nxt + xlen; 1564 } 1565 1566 if (error) { 1567 1568 /* 1569 * We know that the packet was lost, so back out the 1570 * sequence number advance, if any. 1571 * 1572 * If the error is EPERM the packet got blocked by the 1573 * local firewall. Normally we should terminate the 1574 * connection but the blocking may have been spurious 1575 * due to a firewall reconfiguration cycle. So we treat 1576 * it like a packet loss and let the retransmit timer and 1577 * timeouts do their work over time. 1578 * XXX: It is a POLA question whether calling tcp_drop right 1579 * away would be the really correct behavior instead. 1580 */ 1581 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1582 !tcp_timer_active(tp, TT_PERSIST)) && 1583 ((flags & TH_SYN) == 0) && 1584 (error != EPERM)) { 1585 if (sack_rxmit) { 1586 p->rxmit -= len; 1587 tp->sackhint.sack_bytes_rexmit -= len; 1588 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1589 ("sackhint bytes rtx >= 0")); 1590 } else 1591 tp->snd_nxt -= len; 1592 } 1593 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1594 switch (error) { 1595 case EACCES: 1596 tp->t_softerror = error; 1597 return (0); 1598 case EPERM: 1599 tp->t_softerror = error; 1600 return (error); 1601 case ENOBUFS: 1602 TCP_XMIT_TIMER_ASSERT(tp, len, flags); 1603 tp->snd_cwnd = tp->t_maxseg; 1604 return (0); 1605 case EMSGSIZE: 1606 /* 1607 * For some reason the interface we used initially 1608 * to send segments changed to another or lowered 1609 * its MTU. 1610 * If TSO was active we either got an interface 1611 * without TSO capabilits or TSO was turned off. 1612 * If we obtained mtu from ip_output() then update 1613 * it and try again. 1614 */ 1615 if (tso) 1616 tp->t_flags &= ~TF_TSO; 1617 if (mtu != 0) { 1618 tcp_mss_update(tp, -1, mtu, NULL, NULL); 1619 goto again; 1620 } 1621 return (error); 1622 case EHOSTDOWN: 1623 case EHOSTUNREACH: 1624 case ENETDOWN: 1625 case ENETUNREACH: 1626 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1627 tp->t_softerror = error; 1628 return (0); 1629 } 1630 /* FALLTHROUGH */ 1631 default: 1632 return (error); 1633 } 1634 } 1635 TCPSTAT_INC(tcps_sndtotal); 1636 1637 /* 1638 * Data sent (as far as we can tell). 1639 * If this advertises a larger window than any other segment, 1640 * then remember the size of the advertised window. 1641 * Any pending ACK has now been sent. 1642 */ 1643 if (SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1644 tp->rcv_adv = tp->rcv_nxt + recwin; 1645 tp->last_ack_sent = tp->rcv_nxt; 1646 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1647 if (tcp_timer_active(tp, TT_DELACK)) 1648 tcp_timer_activate(tp, TT_DELACK, 0); 1649 #if 0 1650 /* 1651 * This completely breaks TCP if newreno is turned on. What happens 1652 * is that if delayed-acks are turned on on the receiver, this code 1653 * on the transmitter effectively destroys the TCP window, forcing 1654 * it to four packets (1.5Kx4 = 6K window). 1655 */ 1656 if (sendalot && --maxburst) 1657 goto again; 1658 #endif 1659 if (sendalot) 1660 goto again; 1661 return (0); 1662 } 1663 1664 void 1665 tcp_setpersist(struct tcpcb *tp) 1666 { 1667 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1668 int tt; 1669 1670 tp->t_flags &= ~TF_PREVVALID; 1671 if (tcp_timer_active(tp, TT_REXMT)) 1672 panic("tcp_setpersist: retransmit pending"); 1673 /* 1674 * Start/restart persistence timer. 1675 */ 1676 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1677 tcp_persmin, tcp_persmax); 1678 tcp_timer_activate(tp, TT_PERSIST, tt); 1679 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1680 tp->t_rxtshift++; 1681 } 1682 1683 /* 1684 * Insert TCP options according to the supplied parameters to the place 1685 * optp in a consistent way. Can handle unaligned destinations. 1686 * 1687 * The order of the option processing is crucial for optimal packing and 1688 * alignment for the scarce option space. 1689 * 1690 * The optimal order for a SYN/SYN-ACK segment is: 1691 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1692 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1693 * 1694 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1695 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1696 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1697 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1698 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1699 */ 1700 int 1701 tcp_addoptions(struct tcpopt *to, u_char *optp) 1702 { 1703 u_int32_t mask, optlen = 0; 1704 1705 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1706 if ((to->to_flags & mask) != mask) 1707 continue; 1708 if (optlen == TCP_MAXOLEN) 1709 break; 1710 switch (to->to_flags & mask) { 1711 case TOF_MSS: 1712 while (optlen % 4) { 1713 optlen += TCPOLEN_NOP; 1714 *optp++ = TCPOPT_NOP; 1715 } 1716 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1717 continue; 1718 optlen += TCPOLEN_MAXSEG; 1719 *optp++ = TCPOPT_MAXSEG; 1720 *optp++ = TCPOLEN_MAXSEG; 1721 to->to_mss = htons(to->to_mss); 1722 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1723 optp += sizeof(to->to_mss); 1724 break; 1725 case TOF_SCALE: 1726 while (!optlen || optlen % 2 != 1) { 1727 optlen += TCPOLEN_NOP; 1728 *optp++ = TCPOPT_NOP; 1729 } 1730 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1731 continue; 1732 optlen += TCPOLEN_WINDOW; 1733 *optp++ = TCPOPT_WINDOW; 1734 *optp++ = TCPOLEN_WINDOW; 1735 *optp++ = to->to_wscale; 1736 break; 1737 case TOF_SACKPERM: 1738 while (optlen % 2) { 1739 optlen += TCPOLEN_NOP; 1740 *optp++ = TCPOPT_NOP; 1741 } 1742 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1743 continue; 1744 optlen += TCPOLEN_SACK_PERMITTED; 1745 *optp++ = TCPOPT_SACK_PERMITTED; 1746 *optp++ = TCPOLEN_SACK_PERMITTED; 1747 break; 1748 case TOF_TS: 1749 while (!optlen || optlen % 4 != 2) { 1750 optlen += TCPOLEN_NOP; 1751 *optp++ = TCPOPT_NOP; 1752 } 1753 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1754 continue; 1755 optlen += TCPOLEN_TIMESTAMP; 1756 *optp++ = TCPOPT_TIMESTAMP; 1757 *optp++ = TCPOLEN_TIMESTAMP; 1758 to->to_tsval = htonl(to->to_tsval); 1759 to->to_tsecr = htonl(to->to_tsecr); 1760 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1761 optp += sizeof(to->to_tsval); 1762 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1763 optp += sizeof(to->to_tsecr); 1764 break; 1765 case TOF_SIGNATURE: 1766 { 1767 int siglen = TCPOLEN_SIGNATURE - 2; 1768 1769 while (!optlen || optlen % 4 != 2) { 1770 optlen += TCPOLEN_NOP; 1771 *optp++ = TCPOPT_NOP; 1772 } 1773 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) { 1774 to->to_flags &= ~TOF_SIGNATURE; 1775 continue; 1776 } 1777 optlen += TCPOLEN_SIGNATURE; 1778 *optp++ = TCPOPT_SIGNATURE; 1779 *optp++ = TCPOLEN_SIGNATURE; 1780 to->to_signature = optp; 1781 while (siglen--) 1782 *optp++ = 0; 1783 break; 1784 } 1785 case TOF_SACK: 1786 { 1787 int sackblks = 0; 1788 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1789 tcp_seq sack_seq; 1790 1791 while (!optlen || optlen % 4 != 2) { 1792 optlen += TCPOLEN_NOP; 1793 *optp++ = TCPOPT_NOP; 1794 } 1795 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1796 continue; 1797 optlen += TCPOLEN_SACKHDR; 1798 *optp++ = TCPOPT_SACK; 1799 sackblks = min(to->to_nsacks, 1800 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1801 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1802 while (sackblks--) { 1803 sack_seq = htonl(sack->start); 1804 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1805 optp += sizeof(sack_seq); 1806 sack_seq = htonl(sack->end); 1807 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1808 optp += sizeof(sack_seq); 1809 optlen += TCPOLEN_SACK; 1810 sack++; 1811 } 1812 TCPSTAT_INC(tcps_sack_send_blocks); 1813 break; 1814 } 1815 #ifdef TCP_RFC7413 1816 case TOF_FASTOPEN: 1817 { 1818 int total_len; 1819 1820 /* XXX is there any point to aligning this option? */ 1821 total_len = TCPOLEN_FAST_OPEN_EMPTY + to->to_tfo_len; 1822 if (TCP_MAXOLEN - optlen < total_len) 1823 continue; 1824 *optp++ = TCPOPT_FAST_OPEN; 1825 *optp++ = total_len; 1826 if (to->to_tfo_len > 0) { 1827 bcopy(to->to_tfo_cookie, optp, to->to_tfo_len); 1828 optp += to->to_tfo_len; 1829 } 1830 optlen += total_len; 1831 break; 1832 } 1833 #endif 1834 default: 1835 panic("%s: unknown TCP option type", __func__); 1836 break; 1837 } 1838 } 1839 1840 /* Terminate and pad TCP options to a 4 byte boundary. */ 1841 if (optlen % 4) { 1842 optlen += TCPOLEN_EOL; 1843 *optp++ = TCPOPT_EOL; 1844 } 1845 /* 1846 * According to RFC 793 (STD0007): 1847 * "The content of the header beyond the End-of-Option option 1848 * must be header padding (i.e., zero)." 1849 * and later: "The padding is composed of zeros." 1850 */ 1851 while (optlen % 4) { 1852 optlen += TCPOLEN_PAD; 1853 *optp++ = TCPOPT_PAD; 1854 } 1855 1856 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1857 return (optlen); 1858 } 1859