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 #define V_tcp_do_tso VNET(tcp_do_tso) 106 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_VNET | CTLFLAG_RW, 107 &VNET_NAME(tcp_do_tso), 0, 108 "Enable TCP Segmentation Offload"); 109 110 VNET_DEFINE(int, tcp_sendspace) = 1024*32; 111 #define V_tcp_sendspace VNET(tcp_sendspace) 112 SYSCTL_INT(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, CTLFLAG_VNET | CTLFLAG_RW, 113 &VNET_NAME(tcp_sendspace), 0, "Initial send socket buffer size"); 114 115 VNET_DEFINE(int, tcp_do_autosndbuf) = 1; 116 #define V_tcp_do_autosndbuf VNET(tcp_do_autosndbuf) 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 #define V_tcp_autosndbuf_inc VNET(tcp_autosndbuf_inc) 123 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_VNET | CTLFLAG_RW, 124 &VNET_NAME(tcp_autosndbuf_inc), 0, 125 "Incrementor step size of automatic send buffer"); 126 127 VNET_DEFINE(int, tcp_autosndbuf_max) = 2*1024*1024; 128 #define V_tcp_autosndbuf_max VNET(tcp_autosndbuf_max) 129 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_VNET | CTLFLAG_RW, 130 &VNET_NAME(tcp_autosndbuf_max), 0, 131 "Max size of automatic send buffer"); 132 133 /* 134 * Make sure that either retransmit or persist timer is set for SYN, FIN and 135 * non-ACK. 136 */ 137 #define TCP_XMIT_TIMER_ASSERT(tp, len, th_flags) \ 138 KASSERT(((len) == 0 && ((th_flags) & (TH_SYN | TH_FIN)) == 0) ||\ 139 tcp_timer_active((tp), TT_REXMT) || \ 140 tcp_timer_active((tp), TT_PERSIST), \ 141 ("neither rexmt nor persist timer is set")) 142 143 #ifdef TCP_HHOOK 144 static void inline hhook_run_tcp_est_out(struct tcpcb *tp, 145 struct tcphdr *th, struct tcpopt *to, 146 uint32_t len, int tso); 147 #endif 148 static void inline cc_after_idle(struct tcpcb *tp); 149 150 #ifdef TCP_HHOOK 151 /* 152 * Wrapper for the TCP established output helper hook. 153 */ 154 static void inline 155 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th, 156 struct tcpopt *to, uint32_t len, int tso) 157 { 158 struct tcp_hhook_data hhook_data; 159 160 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) { 161 hhook_data.tp = tp; 162 hhook_data.th = th; 163 hhook_data.to = to; 164 hhook_data.len = len; 165 hhook_data.tso = tso; 166 167 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data, 168 tp->osd); 169 } 170 } 171 #endif 172 173 /* 174 * CC wrapper hook functions 175 */ 176 static void inline 177 cc_after_idle(struct tcpcb *tp) 178 { 179 INP_WLOCK_ASSERT(tp->t_inpcb); 180 181 if (CC_ALGO(tp)->after_idle != NULL) 182 CC_ALGO(tp)->after_idle(tp->ccv); 183 } 184 185 /* 186 * Tcp output routine: figure out what should be sent and send it. 187 */ 188 int 189 tcp_output(struct tcpcb *tp) 190 { 191 struct socket *so = tp->t_inpcb->inp_socket; 192 int32_t len; 193 uint32_t recwin, sendwin; 194 int off, flags, error = 0; /* Keep compiler happy */ 195 struct mbuf *m; 196 struct ip *ip = NULL; 197 struct ipovly *ipov = NULL; 198 struct tcphdr *th; 199 u_char opt[TCP_MAXOLEN]; 200 unsigned ipoptlen, optlen, hdrlen; 201 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 202 unsigned ipsec_optlen = 0; 203 #endif 204 int idle, sendalot; 205 int sack_rxmit, sack_bytes_rxmt; 206 struct sackhole *p; 207 int tso, mtu; 208 struct tcpopt to; 209 #if 0 210 int maxburst = TCP_MAXBURST; 211 #endif 212 #ifdef INET6 213 struct ip6_hdr *ip6 = NULL; 214 int isipv6; 215 216 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 217 #endif 218 219 INP_WLOCK_ASSERT(tp->t_inpcb); 220 221 #ifdef TCP_OFFLOAD 222 if (tp->t_flags & TF_TOE) 223 return (tcp_offload_output(tp)); 224 #endif 225 226 #ifdef TCP_RFC7413 227 /* 228 * For TFO connections in SYN_RECEIVED, only allow the initial 229 * SYN|ACK and those sent by the retransmit timer. 230 */ 231 if (IS_FASTOPEN(tp->t_flags) && 232 (tp->t_state == TCPS_SYN_RECEIVED) && 233 SEQ_GT(tp->snd_max, tp->snd_una) && /* initial SYN|ACK sent */ 234 (tp->snd_nxt != tp->snd_una)) /* not a retransmit */ 235 return (0); 236 #endif 237 /* 238 * Determine length of data that should be transmitted, 239 * and flags that will be used. 240 * If there is some data or critical controls (SYN, RST) 241 * to send, then transmit; otherwise, investigate further. 242 */ 243 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 244 if (idle && ticks - tp->t_rcvtime >= tp->t_rxtcur) 245 cc_after_idle(tp); 246 tp->t_flags &= ~TF_LASTIDLE; 247 if (idle) { 248 if (tp->t_flags & TF_MORETOCOME) { 249 tp->t_flags |= TF_LASTIDLE; 250 idle = 0; 251 } 252 } 253 again: 254 /* 255 * If we've recently taken a timeout, snd_max will be greater than 256 * snd_nxt. There may be SACK information that allows us to avoid 257 * resending already delivered data. Adjust snd_nxt accordingly. 258 */ 259 if ((tp->t_flags & TF_SACK_PERMIT) && 260 SEQ_LT(tp->snd_nxt, tp->snd_max)) 261 tcp_sack_adjust(tp); 262 sendalot = 0; 263 tso = 0; 264 mtu = 0; 265 off = tp->snd_nxt - tp->snd_una; 266 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 267 268 flags = tcp_outflags[tp->t_state]; 269 /* 270 * Send any SACK-generated retransmissions. If we're explicitly trying 271 * to send out new data (when sendalot is 1), bypass this function. 272 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 273 * we're replacing a (future) new transmission with a retransmission 274 * now, and we previously incremented snd_cwnd in tcp_input(). 275 */ 276 /* 277 * Still in sack recovery , reset rxmit flag to zero. 278 */ 279 sack_rxmit = 0; 280 sack_bytes_rxmt = 0; 281 len = 0; 282 p = NULL; 283 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) && 284 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 285 uint32_t cwin; 286 287 cwin = 288 imax(min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt, 0); 289 /* Do not retransmit SACK segments beyond snd_recover */ 290 if (SEQ_GT(p->end, tp->snd_recover)) { 291 /* 292 * (At least) part of sack hole extends beyond 293 * snd_recover. Check to see if we can rexmit data 294 * for this hole. 295 */ 296 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 297 /* 298 * Can't rexmit any more data for this hole. 299 * That data will be rexmitted in the next 300 * sack recovery episode, when snd_recover 301 * moves past p->rxmit. 302 */ 303 p = NULL; 304 goto after_sack_rexmit; 305 } else 306 /* Can rexmit part of the current hole */ 307 len = ((int32_t)ulmin(cwin, 308 tp->snd_recover - p->rxmit)); 309 } else 310 len = ((int32_t)ulmin(cwin, p->end - p->rxmit)); 311 off = p->rxmit - tp->snd_una; 312 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 313 __func__, off)); 314 if (len > 0) { 315 sack_rxmit = 1; 316 sendalot = 1; 317 TCPSTAT_INC(tcps_sack_rexmits); 318 TCPSTAT_ADD(tcps_sack_rexmit_bytes, 319 min(len, tp->t_maxseg)); 320 } 321 } 322 after_sack_rexmit: 323 /* 324 * Get standard flags, and add SYN or FIN if requested by 'hidden' 325 * state flags. 326 */ 327 if (tp->t_flags & TF_NEEDFIN) 328 flags |= TH_FIN; 329 if (tp->t_flags & TF_NEEDSYN) 330 flags |= TH_SYN; 331 332 SOCKBUF_LOCK(&so->so_snd); 333 /* 334 * If in persist timeout with window of 0, send 1 byte. 335 * Otherwise, if window is small but nonzero 336 * and timer expired, we will send what we can 337 * and go to transmit state. 338 */ 339 if (tp->t_flags & TF_FORCEDATA) { 340 if (sendwin == 0) { 341 /* 342 * If we still have some data to send, then 343 * clear the FIN bit. Usually this would 344 * happen below when it realizes that we 345 * aren't sending all the data. However, 346 * if we have exactly 1 byte of unsent data, 347 * then it won't clear the FIN bit below, 348 * and if we are in persist state, we wind 349 * up sending the packet without recording 350 * that we sent the FIN bit. 351 * 352 * We can't just blindly clear the FIN bit, 353 * because if we don't have any more data 354 * to send then the probe will be the FIN 355 * itself. 356 */ 357 if (off < sbused(&so->so_snd)) 358 flags &= ~TH_FIN; 359 sendwin = 1; 360 } else { 361 tcp_timer_activate(tp, TT_PERSIST, 0); 362 tp->t_rxtshift = 0; 363 } 364 } 365 366 /* 367 * If snd_nxt == snd_max and we have transmitted a FIN, the 368 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 369 * a negative length. This can also occur when TCP opens up 370 * its congestion window while receiving additional duplicate 371 * acks after fast-retransmit because TCP will reset snd_nxt 372 * to snd_max after the fast-retransmit. 373 * 374 * In the normal retransmit-FIN-only case, however, snd_nxt will 375 * be set to snd_una, the offset will be 0, and the length may 376 * wind up 0. 377 * 378 * If sack_rxmit is true we are retransmitting from the scoreboard 379 * in which case len is already set. 380 */ 381 if (sack_rxmit == 0) { 382 if (sack_bytes_rxmt == 0) 383 len = ((int32_t)ulmin(sbavail(&so->so_snd), sendwin) - 384 off); 385 else { 386 int32_t cwin; 387 388 /* 389 * We are inside of a SACK recovery episode and are 390 * sending new data, having retransmitted all the 391 * data possible in the scoreboard. 392 */ 393 len = ((int32_t)min(sbavail(&so->so_snd), tp->snd_wnd) - 394 off); 395 /* 396 * Don't remove this (len > 0) check ! 397 * We explicitly check for len > 0 here (although it 398 * isn't really necessary), to work around a gcc 399 * optimization issue - to force gcc to compute 400 * len above. Without this check, the computation 401 * of len is bungled by the optimizer. 402 */ 403 if (len > 0) { 404 cwin = tp->snd_cwnd - 405 (tp->snd_nxt - tp->sack_newdata) - 406 sack_bytes_rxmt; 407 if (cwin < 0) 408 cwin = 0; 409 len = imin(len, cwin); 410 } 411 } 412 } 413 414 /* 415 * Lop off SYN bit if it has already been sent. However, if this 416 * is SYN-SENT state and if segment contains data and if we don't 417 * know that foreign host supports TAO, suppress sending segment. 418 */ 419 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 420 if (tp->t_state != TCPS_SYN_RECEIVED) 421 flags &= ~TH_SYN; 422 #ifdef TCP_RFC7413 423 /* 424 * When sending additional segments following a TFO SYN|ACK, 425 * do not include the SYN bit. 426 */ 427 if (IS_FASTOPEN(tp->t_flags) && 428 (tp->t_state == TCPS_SYN_RECEIVED)) 429 flags &= ~TH_SYN; 430 #endif 431 off--, len++; 432 } 433 434 /* 435 * Be careful not to send data and/or FIN on SYN segments. 436 * This measure is needed to prevent interoperability problems 437 * with not fully conformant TCP implementations. 438 */ 439 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 440 len = 0; 441 flags &= ~TH_FIN; 442 } 443 444 #ifdef TCP_RFC7413 445 /* 446 * When retransmitting SYN|ACK on a passively-created TFO socket, 447 * don't include data, as the presence of data may have caused the 448 * original SYN|ACK to have been dropped by a middlebox. 449 */ 450 if (IS_FASTOPEN(tp->t_flags) && 451 (((tp->t_state == TCPS_SYN_RECEIVED) && (tp->t_rxtshift > 0)) || 452 (flags & TH_RST))) 453 len = 0; 454 #endif 455 if (len <= 0) { 456 /* 457 * If FIN has been sent but not acked, 458 * but we haven't been called to retransmit, 459 * len will be < 0. Otherwise, window shrank 460 * after we sent into it. If window shrank to 0, 461 * cancel pending retransmit, pull snd_nxt back 462 * to (closed) window, and set the persist timer 463 * if it isn't already going. If the window didn't 464 * close completely, just wait for an ACK. 465 * 466 * We also do a general check here to ensure that 467 * we will set the persist timer when we have data 468 * to send, but a 0-byte window. This makes sure 469 * the persist timer is set even if the packet 470 * hits one of the "goto send" lines below. 471 */ 472 len = 0; 473 if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) && 474 (off < (int) sbavail(&so->so_snd))) { 475 tcp_timer_activate(tp, TT_REXMT, 0); 476 tp->t_rxtshift = 0; 477 tp->snd_nxt = tp->snd_una; 478 if (!tcp_timer_active(tp, TT_PERSIST)) 479 tcp_setpersist(tp); 480 } 481 } 482 483 /* len will be >= 0 after this point. */ 484 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 485 486 /* 487 * Automatic sizing of send socket buffer. Often the send buffer 488 * size is not optimally adjusted to the actual network conditions 489 * at hand (delay bandwidth product). Setting the buffer size too 490 * small limits throughput on links with high bandwidth and high 491 * delay (eg. trans-continental/oceanic links). Setting the 492 * buffer size too big consumes too much real kernel memory, 493 * especially with many connections on busy servers. 494 * 495 * The criteria to step up the send buffer one notch are: 496 * 1. receive window of remote host is larger than send buffer 497 * (with a fudge factor of 5/4th); 498 * 2. send buffer is filled to 7/8th with data (so we actually 499 * have data to make use of it); 500 * 3. send buffer fill has not hit maximal automatic size; 501 * 4. our send window (slow start and cogestion controlled) is 502 * larger than sent but unacknowledged data in send buffer. 503 * 504 * The remote host receive window scaling factor may limit the 505 * growing of the send buffer before it reaches its allowed 506 * maximum. 507 * 508 * It scales directly with slow start or congestion window 509 * and does at most one step per received ACK. This fast 510 * scaling has the drawback of growing the send buffer beyond 511 * what is strictly necessary to make full use of a given 512 * delay*bandwidth product. However testing has shown this not 513 * to be much of an problem. At worst we are trading wasting 514 * of available bandwidth (the non-use of it) for wasting some 515 * socket buffer memory. 516 * 517 * TODO: Shrink send buffer during idle periods together 518 * with congestion window. Requires another timer. Has to 519 * wait for upcoming tcp timer rewrite. 520 * 521 * XXXGL: should there be used sbused() or sbavail()? 522 */ 523 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 524 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat && 525 sbused(&so->so_snd) >= (so->so_snd.sb_hiwat / 8 * 7) && 526 sbused(&so->so_snd) < V_tcp_autosndbuf_max && 527 sendwin >= (sbused(&so->so_snd) - 528 (tp->snd_nxt - tp->snd_una))) { 529 if (!sbreserve_locked(&so->so_snd, 530 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 531 V_tcp_autosndbuf_max), so, curthread)) 532 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 533 } 534 } 535 536 /* 537 * Decide if we can use TCP Segmentation Offloading (if supported by 538 * hardware). 539 * 540 * TSO may only be used if we are in a pure bulk sending state. The 541 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 542 * IP options prevent using TSO. With TSO the TCP header is the same 543 * (except for the sequence number) for all generated packets. This 544 * makes it impossible to transmit any options which vary per generated 545 * segment or packet. 546 * 547 * IPv4 handling has a clear separation of ip options and ip header 548 * flags while IPv6 combines both in in6p_outputopts. ip6_optlen() does 549 * the right thing below to provide length of just ip options and thus 550 * checking for ipoptlen is enough to decide if ip options are present. 551 */ 552 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 553 /* 554 * Pre-calculate here as we save another lookup into the darknesses 555 * of IPsec that way and can actually decide if TSO is ok. 556 */ 557 #ifdef INET6 558 if (isipv6 && IPSEC_ENABLED(ipv6)) 559 ipsec_optlen = IPSEC_HDRSIZE(ipv6, tp->t_inpcb); 560 #ifdef INET 561 else 562 #endif 563 #endif /* INET6 */ 564 #ifdef INET 565 if (IPSEC_ENABLED(ipv4)) 566 ipsec_optlen = IPSEC_HDRSIZE(ipv4, tp->t_inpcb); 567 #endif /* INET */ 568 #endif /* IPSEC */ 569 #ifdef INET6 570 if (isipv6) 571 ipoptlen = ip6_optlen(tp->t_inpcb); 572 else 573 #endif 574 if (tp->t_inpcb->inp_options) 575 ipoptlen = tp->t_inpcb->inp_options->m_len - 576 offsetof(struct ipoption, ipopt_list); 577 else 578 ipoptlen = 0; 579 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 580 ipoptlen += ipsec_optlen; 581 #endif 582 583 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg && 584 ((tp->t_flags & TF_SIGNATURE) == 0) && 585 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 586 ipoptlen == 0) 587 tso = 1; 588 589 if (sack_rxmit) { 590 if (SEQ_LT(p->rxmit + len, tp->snd_una + sbused(&so->so_snd))) 591 flags &= ~TH_FIN; 592 } else { 593 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + 594 sbused(&so->so_snd))) 595 flags &= ~TH_FIN; 596 } 597 598 recwin = lmin(lmax(sbspace(&so->so_rcv), 0), 599 (long)TCP_MAXWIN << tp->rcv_scale); 600 601 /* 602 * Sender silly window avoidance. We transmit under the following 603 * conditions when len is non-zero: 604 * 605 * - We have a full segment (or more with TSO) 606 * - This is the last buffer in a write()/send() and we are 607 * either idle or running NODELAY 608 * - we've timed out (e.g. persist timer) 609 * - we have more then 1/2 the maximum send window's worth of 610 * data (receiver may be limited the window size) 611 * - we need to retransmit 612 */ 613 if (len) { 614 if (len >= tp->t_maxseg) 615 goto send; 616 /* 617 * NOTE! on localhost connections an 'ack' from the remote 618 * end may occur synchronously with the output and cause 619 * us to flush a buffer queued with moretocome. XXX 620 * 621 * note: the len + off check is almost certainly unnecessary. 622 */ 623 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 624 (idle || (tp->t_flags & TF_NODELAY)) && 625 (uint32_t)len + (uint32_t)off >= sbavail(&so->so_snd) && 626 (tp->t_flags & TF_NOPUSH) == 0) { 627 goto send; 628 } 629 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 630 goto send; 631 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 632 goto send; 633 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 634 goto send; 635 if (sack_rxmit) 636 goto send; 637 } 638 639 /* 640 * Sending of standalone window updates. 641 * 642 * Window updates are important when we close our window due to a 643 * full socket buffer and are opening it again after the application 644 * reads data from it. Once the window has opened again and the 645 * remote end starts to send again the ACK clock takes over and 646 * provides the most current window information. 647 * 648 * We must avoid the silly window syndrome whereas every read 649 * from the receive buffer, no matter how small, causes a window 650 * update to be sent. We also should avoid sending a flurry of 651 * window updates when the socket buffer had queued a lot of data 652 * and the application is doing small reads. 653 * 654 * Prevent a flurry of pointless window updates by only sending 655 * an update when we can increase the advertized window by more 656 * than 1/4th of the socket buffer capacity. When the buffer is 657 * getting full or is very small be more aggressive and send an 658 * update whenever we can increase by two mss sized segments. 659 * In all other situations the ACK's to new incoming data will 660 * carry further window increases. 661 * 662 * Don't send an independent window update if a delayed 663 * ACK is pending (it will get piggy-backed on it) or the 664 * remote side already has done a half-close and won't send 665 * more data. Skip this if the connection is in T/TCP 666 * half-open state. 667 */ 668 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 669 !(tp->t_flags & TF_DELACK) && 670 !TCPS_HAVERCVDFIN(tp->t_state)) { 671 /* 672 * "adv" is the amount we could increase the window, 673 * taking into account that we are limited by 674 * TCP_MAXWIN << tp->rcv_scale. 675 */ 676 int32_t adv; 677 int oldwin; 678 679 adv = recwin; 680 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { 681 oldwin = (tp->rcv_adv - tp->rcv_nxt); 682 adv -= oldwin; 683 } else 684 oldwin = 0; 685 686 /* 687 * If the new window size ends up being the same as or less 688 * than the old size when it is scaled, then don't force 689 * a window update. 690 */ 691 if (oldwin >> tp->rcv_scale >= (adv + oldwin) >> tp->rcv_scale) 692 goto dontupdate; 693 694 if (adv >= (int32_t)(2 * tp->t_maxseg) && 695 (adv >= (int32_t)(so->so_rcv.sb_hiwat / 4) || 696 recwin <= (so->so_rcv.sb_hiwat / 8) || 697 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg)) 698 goto send; 699 if (2 * adv >= (int32_t)so->so_rcv.sb_hiwat) 700 goto send; 701 } 702 dontupdate: 703 704 /* 705 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 706 * is also a catch-all for the retransmit timer timeout case. 707 */ 708 if (tp->t_flags & TF_ACKNOW) 709 goto send; 710 if ((flags & TH_RST) || 711 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 712 goto send; 713 if (SEQ_GT(tp->snd_up, tp->snd_una)) 714 goto send; 715 /* 716 * If our state indicates that FIN should be sent 717 * and we have not yet done so, then we need to send. 718 */ 719 if (flags & TH_FIN && 720 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 721 goto send; 722 /* 723 * In SACK, it is possible for tcp_output to fail to send a segment 724 * after the retransmission timer has been turned off. Make sure 725 * that the retransmission timer is set. 726 */ 727 if ((tp->t_flags & TF_SACK_PERMIT) && 728 SEQ_GT(tp->snd_max, tp->snd_una) && 729 !tcp_timer_active(tp, TT_REXMT) && 730 !tcp_timer_active(tp, TT_PERSIST)) { 731 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 732 goto just_return; 733 } 734 /* 735 * TCP window updates are not reliable, rather a polling protocol 736 * using ``persist'' packets is used to insure receipt of window 737 * updates. The three ``states'' for the output side are: 738 * idle not doing retransmits or persists 739 * persisting to move a small or zero window 740 * (re)transmitting and thereby not persisting 741 * 742 * tcp_timer_active(tp, TT_PERSIST) 743 * is true when we are in persist state. 744 * (tp->t_flags & TF_FORCEDATA) 745 * is set when we are called to send a persist packet. 746 * tcp_timer_active(tp, TT_REXMT) 747 * is set when we are retransmitting 748 * The output side is idle when both timers are zero. 749 * 750 * If send window is too small, there is data to transmit, and no 751 * retransmit or persist is pending, then go to persist state. 752 * If nothing happens soon, send when timer expires: 753 * if window is nonzero, transmit what we can, 754 * otherwise force out a byte. 755 */ 756 if (sbavail(&so->so_snd) && !tcp_timer_active(tp, TT_REXMT) && 757 !tcp_timer_active(tp, TT_PERSIST)) { 758 tp->t_rxtshift = 0; 759 tcp_setpersist(tp); 760 } 761 762 /* 763 * No reason to send a segment, just return. 764 */ 765 just_return: 766 SOCKBUF_UNLOCK(&so->so_snd); 767 return (0); 768 769 send: 770 SOCKBUF_LOCK_ASSERT(&so->so_snd); 771 if (len > 0) { 772 if (len >= tp->t_maxseg) 773 tp->t_flags2 |= TF2_PLPMTU_MAXSEGSNT; 774 else 775 tp->t_flags2 &= ~TF2_PLPMTU_MAXSEGSNT; 776 } 777 /* 778 * Before ESTABLISHED, force sending of initial options 779 * unless TCP set not to do any options. 780 * NOTE: we assume that the IP/TCP header plus TCP options 781 * always fit in a single mbuf, leaving room for a maximum 782 * link header, i.e. 783 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 784 */ 785 optlen = 0; 786 #ifdef INET6 787 if (isipv6) 788 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 789 else 790 #endif 791 hdrlen = sizeof (struct tcpiphdr); 792 793 /* 794 * Compute options for segment. 795 * We only have to care about SYN and established connection 796 * segments. Options for SYN-ACK segments are handled in TCP 797 * syncache. 798 */ 799 to.to_flags = 0; 800 if ((tp->t_flags & TF_NOOPT) == 0) { 801 /* Maximum segment size. */ 802 if (flags & TH_SYN) { 803 tp->snd_nxt = tp->iss; 804 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 805 to.to_flags |= TOF_MSS; 806 #ifdef TCP_RFC7413 807 /* 808 * Only include the TFO option on the first 809 * transmission of the SYN|ACK on a 810 * passively-created TFO socket, as the presence of 811 * the TFO option may have caused the original 812 * SYN|ACK to have been dropped by a middlebox. 813 */ 814 if (IS_FASTOPEN(tp->t_flags) && 815 (tp->t_state == TCPS_SYN_RECEIVED) && 816 (tp->t_rxtshift == 0)) { 817 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN; 818 to.to_tfo_cookie = (u_char *)&tp->t_tfo_cookie; 819 to.to_flags |= TOF_FASTOPEN; 820 } 821 #endif 822 } 823 /* Window scaling. */ 824 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 825 to.to_wscale = tp->request_r_scale; 826 to.to_flags |= TOF_SCALE; 827 } 828 /* Timestamps. */ 829 if ((tp->t_flags & TF_RCVD_TSTMP) || 830 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 831 to.to_tsval = tcp_ts_getticks() + tp->ts_offset; 832 to.to_tsecr = tp->ts_recent; 833 to.to_flags |= TOF_TS; 834 /* Set receive buffer autosizing timestamp. */ 835 if (tp->rfbuf_ts == 0 && 836 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 837 tp->rfbuf_ts = tcp_ts_getticks(); 838 } 839 /* Selective ACK's. */ 840 if (tp->t_flags & TF_SACK_PERMIT) { 841 if (flags & TH_SYN) 842 to.to_flags |= TOF_SACKPERM; 843 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 844 (tp->t_flags & TF_SACK_PERMIT) && 845 tp->rcv_numsacks > 0) { 846 to.to_flags |= TOF_SACK; 847 to.to_nsacks = tp->rcv_numsacks; 848 to.to_sacks = (u_char *)tp->sackblks; 849 } 850 } 851 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 852 /* TCP-MD5 (RFC2385). */ 853 /* 854 * Check that TCP_MD5SIG is enabled in tcpcb to 855 * account the size needed to set this TCP option. 856 */ 857 if (tp->t_flags & TF_SIGNATURE) 858 to.to_flags |= TOF_SIGNATURE; 859 #endif /* TCP_SIGNATURE */ 860 861 /* Processing the options. */ 862 hdrlen += optlen = tcp_addoptions(&to, opt); 863 } 864 865 /* 866 * Adjust data length if insertion of options will 867 * bump the packet length beyond the t_maxseg length. 868 * Clear the FIN bit because we cut off the tail of 869 * the segment. 870 */ 871 if (len + optlen + ipoptlen > tp->t_maxseg) { 872 flags &= ~TH_FIN; 873 874 if (tso) { 875 u_int if_hw_tsomax; 876 u_int if_hw_tsomaxsegcount; 877 u_int if_hw_tsomaxsegsize; 878 struct mbuf *mb; 879 u_int moff; 880 int max_len; 881 882 /* extract TSO information */ 883 if_hw_tsomax = tp->t_tsomax; 884 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount; 885 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize; 886 887 /* 888 * Limit a TSO burst to prevent it from 889 * overflowing or exceeding the maximum length 890 * allowed by the network interface: 891 */ 892 KASSERT(ipoptlen == 0, 893 ("%s: TSO can't do IP options", __func__)); 894 895 /* 896 * Check if we should limit by maximum payload 897 * length: 898 */ 899 if (if_hw_tsomax != 0) { 900 /* compute maximum TSO length */ 901 max_len = (if_hw_tsomax - hdrlen - 902 max_linkhdr); 903 if (max_len <= 0) { 904 len = 0; 905 } else if (len > max_len) { 906 sendalot = 1; 907 len = max_len; 908 } 909 } 910 911 /* 912 * Check if we should limit by maximum segment 913 * size and count: 914 */ 915 if (if_hw_tsomaxsegcount != 0 && 916 if_hw_tsomaxsegsize != 0) { 917 /* 918 * Subtract one segment for the LINK 919 * and TCP/IP headers mbuf that will 920 * be prepended to this mbuf chain 921 * after the code in this section 922 * limits the number of mbufs in the 923 * chain to if_hw_tsomaxsegcount. 924 */ 925 if_hw_tsomaxsegcount -= 1; 926 max_len = 0; 927 mb = sbsndmbuf(&so->so_snd, off, &moff); 928 929 while (mb != NULL && max_len < len) { 930 u_int mlen; 931 u_int frags; 932 933 /* 934 * Get length of mbuf fragment 935 * and how many hardware frags, 936 * rounded up, it would use: 937 */ 938 mlen = (mb->m_len - moff); 939 frags = howmany(mlen, 940 if_hw_tsomaxsegsize); 941 942 /* Handle special case: Zero Length Mbuf */ 943 if (frags == 0) 944 frags = 1; 945 946 /* 947 * Check if the fragment limit 948 * will be reached or exceeded: 949 */ 950 if (frags >= if_hw_tsomaxsegcount) { 951 max_len += min(mlen, 952 if_hw_tsomaxsegcount * 953 if_hw_tsomaxsegsize); 954 break; 955 } 956 max_len += mlen; 957 if_hw_tsomaxsegcount -= frags; 958 moff = 0; 959 mb = mb->m_next; 960 } 961 if (max_len <= 0) { 962 len = 0; 963 } else if (len > max_len) { 964 sendalot = 1; 965 len = max_len; 966 } 967 } 968 969 /* 970 * Prevent the last segment from being 971 * fractional unless the send sockbuf can be 972 * emptied: 973 */ 974 max_len = (tp->t_maxseg - optlen); 975 if (((uint32_t)off + (uint32_t)len) < 976 sbavail(&so->so_snd)) { 977 moff = len % max_len; 978 if (moff != 0) { 979 len -= moff; 980 sendalot = 1; 981 } 982 } 983 984 /* 985 * In case there are too many small fragments 986 * don't use TSO: 987 */ 988 if (len <= max_len) { 989 len = max_len; 990 sendalot = 1; 991 tso = 0; 992 } 993 994 /* 995 * Send the FIN in a separate segment 996 * after the bulk sending is done. 997 * We don't trust the TSO implementations 998 * to clear the FIN flag on all but the 999 * last segment. 1000 */ 1001 if (tp->t_flags & TF_NEEDFIN) 1002 sendalot = 1; 1003 1004 } else { 1005 len = tp->t_maxseg - optlen - ipoptlen; 1006 sendalot = 1; 1007 } 1008 } else 1009 tso = 0; 1010 1011 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 1012 ("%s: len > IP_MAXPACKET", __func__)); 1013 1014 /*#ifdef DIAGNOSTIC*/ 1015 #ifdef INET6 1016 if (max_linkhdr + hdrlen > MCLBYTES) 1017 #else 1018 if (max_linkhdr + hdrlen > MHLEN) 1019 #endif 1020 panic("tcphdr too big"); 1021 /*#endif*/ 1022 1023 /* 1024 * This KASSERT is here to catch edge cases at a well defined place. 1025 * Before, those had triggered (random) panic conditions further down. 1026 */ 1027 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 1028 1029 /* 1030 * Grab a header mbuf, attaching a copy of data to 1031 * be transmitted, and initialize the header from 1032 * the template for sends on this connection. 1033 */ 1034 if (len) { 1035 struct mbuf *mb; 1036 u_int moff; 1037 1038 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 1039 TCPSTAT_INC(tcps_sndprobe); 1040 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 1041 tp->t_sndrexmitpack++; 1042 TCPSTAT_INC(tcps_sndrexmitpack); 1043 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 1044 } else { 1045 TCPSTAT_INC(tcps_sndpack); 1046 TCPSTAT_ADD(tcps_sndbyte, len); 1047 } 1048 #ifdef INET6 1049 if (MHLEN < hdrlen + max_linkhdr) 1050 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR); 1051 else 1052 #endif 1053 m = m_gethdr(M_NOWAIT, MT_DATA); 1054 1055 if (m == NULL) { 1056 SOCKBUF_UNLOCK(&so->so_snd); 1057 error = ENOBUFS; 1058 sack_rxmit = 0; 1059 goto out; 1060 } 1061 1062 m->m_data += max_linkhdr; 1063 m->m_len = hdrlen; 1064 1065 /* 1066 * Start the m_copy functions from the closest mbuf 1067 * to the offset in the socket buffer chain. 1068 */ 1069 mb = sbsndptr(&so->so_snd, off, len, &moff); 1070 1071 if (len <= MHLEN - hdrlen - max_linkhdr) { 1072 m_copydata(mb, moff, len, 1073 mtod(m, caddr_t) + hdrlen); 1074 m->m_len += len; 1075 } else { 1076 m->m_next = m_copym(mb, moff, len, M_NOWAIT); 1077 if (m->m_next == NULL) { 1078 SOCKBUF_UNLOCK(&so->so_snd); 1079 (void) m_free(m); 1080 error = ENOBUFS; 1081 sack_rxmit = 0; 1082 goto out; 1083 } 1084 } 1085 1086 /* 1087 * If we're sending everything we've got, set PUSH. 1088 * (This will keep happy those implementations which only 1089 * give data to the user when a buffer fills or 1090 * a PUSH comes in.) 1091 */ 1092 if (((uint32_t)off + (uint32_t)len == sbused(&so->so_snd)) && 1093 !(flags & TH_SYN)) 1094 flags |= TH_PUSH; 1095 SOCKBUF_UNLOCK(&so->so_snd); 1096 } else { 1097 SOCKBUF_UNLOCK(&so->so_snd); 1098 if (tp->t_flags & TF_ACKNOW) 1099 TCPSTAT_INC(tcps_sndacks); 1100 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 1101 TCPSTAT_INC(tcps_sndctrl); 1102 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 1103 TCPSTAT_INC(tcps_sndurg); 1104 else 1105 TCPSTAT_INC(tcps_sndwinup); 1106 1107 m = m_gethdr(M_NOWAIT, MT_DATA); 1108 if (m == NULL) { 1109 error = ENOBUFS; 1110 sack_rxmit = 0; 1111 goto out; 1112 } 1113 #ifdef INET6 1114 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 1115 MHLEN >= hdrlen) { 1116 M_ALIGN(m, hdrlen); 1117 } else 1118 #endif 1119 m->m_data += max_linkhdr; 1120 m->m_len = hdrlen; 1121 } 1122 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 1123 m->m_pkthdr.rcvif = (struct ifnet *)0; 1124 #ifdef MAC 1125 mac_inpcb_create_mbuf(tp->t_inpcb, m); 1126 #endif 1127 #ifdef INET6 1128 if (isipv6) { 1129 ip6 = mtod(m, struct ip6_hdr *); 1130 th = (struct tcphdr *)(ip6 + 1); 1131 tcpip_fillheaders(tp->t_inpcb, ip6, th); 1132 } else 1133 #endif /* INET6 */ 1134 { 1135 ip = mtod(m, struct ip *); 1136 ipov = (struct ipovly *)ip; 1137 th = (struct tcphdr *)(ip + 1); 1138 tcpip_fillheaders(tp->t_inpcb, ip, th); 1139 } 1140 1141 /* 1142 * Fill in fields, remembering maximum advertised 1143 * window for use in delaying messages about window sizes. 1144 * If resending a FIN, be sure not to use a new sequence number. 1145 */ 1146 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 1147 tp->snd_nxt == tp->snd_max) 1148 tp->snd_nxt--; 1149 /* 1150 * If we are starting a connection, send ECN setup 1151 * SYN packet. If we are on a retransmit, we may 1152 * resend those bits a number of times as per 1153 * RFC 3168. 1154 */ 1155 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn == 1) { 1156 if (tp->t_rxtshift >= 1) { 1157 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 1158 flags |= TH_ECE|TH_CWR; 1159 } else 1160 flags |= TH_ECE|TH_CWR; 1161 } 1162 1163 if (tp->t_state == TCPS_ESTABLISHED && 1164 (tp->t_flags & TF_ECN_PERMIT)) { 1165 /* 1166 * If the peer has ECN, mark data packets with 1167 * ECN capable transmission (ECT). 1168 * Ignore pure ack packets, retransmissions and window probes. 1169 */ 1170 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 1171 !((tp->t_flags & TF_FORCEDATA) && len == 1)) { 1172 #ifdef INET6 1173 if (isipv6) 1174 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 1175 else 1176 #endif 1177 ip->ip_tos |= IPTOS_ECN_ECT0; 1178 TCPSTAT_INC(tcps_ecn_ect0); 1179 } 1180 1181 /* 1182 * Reply with proper ECN notifications. 1183 */ 1184 if (tp->t_flags & TF_ECN_SND_CWR) { 1185 flags |= TH_CWR; 1186 tp->t_flags &= ~TF_ECN_SND_CWR; 1187 } 1188 if (tp->t_flags & TF_ECN_SND_ECE) 1189 flags |= TH_ECE; 1190 } 1191 1192 /* 1193 * If we are doing retransmissions, then snd_nxt will 1194 * not reflect the first unsent octet. For ACK only 1195 * packets, we do not want the sequence number of the 1196 * retransmitted packet, we want the sequence number 1197 * of the next unsent octet. So, if there is no data 1198 * (and no SYN or FIN), use snd_max instead of snd_nxt 1199 * when filling in ti_seq. But if we are in persist 1200 * state, snd_max might reflect one byte beyond the 1201 * right edge of the window, so use snd_nxt in that 1202 * case, since we know we aren't doing a retransmission. 1203 * (retransmit and persist are mutually exclusive...) 1204 */ 1205 if (sack_rxmit == 0) { 1206 if (len || (flags & (TH_SYN|TH_FIN)) || 1207 tcp_timer_active(tp, TT_PERSIST)) 1208 th->th_seq = htonl(tp->snd_nxt); 1209 else 1210 th->th_seq = htonl(tp->snd_max); 1211 } else { 1212 th->th_seq = htonl(p->rxmit); 1213 p->rxmit += len; 1214 tp->sackhint.sack_bytes_rexmit += len; 1215 } 1216 th->th_ack = htonl(tp->rcv_nxt); 1217 if (optlen) { 1218 bcopy(opt, th + 1, optlen); 1219 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1220 } 1221 th->th_flags = flags; 1222 /* 1223 * Calculate receive window. Don't shrink window, 1224 * but avoid silly window syndrome. 1225 */ 1226 if (recwin < (so->so_rcv.sb_hiwat / 4) && 1227 recwin < tp->t_maxseg) 1228 recwin = 0; 1229 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1230 recwin < (tp->rcv_adv - tp->rcv_nxt)) 1231 recwin = (tp->rcv_adv - tp->rcv_nxt); 1232 1233 /* 1234 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1235 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1236 * case is handled in syncache. 1237 */ 1238 if (flags & TH_SYN) 1239 th->th_win = htons((u_short) 1240 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1241 else 1242 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1243 1244 /* 1245 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1246 * a 0 window. This may cause the remote transmitter to stall. This 1247 * flag tells soreceive() to disable delayed acknowledgements when 1248 * draining the buffer. This can occur if the receiver is attempting 1249 * to read more data than can be buffered prior to transmitting on 1250 * the connection. 1251 */ 1252 if (th->th_win == 0) { 1253 tp->t_sndzerowin++; 1254 tp->t_flags |= TF_RXWIN0SENT; 1255 } else 1256 tp->t_flags &= ~TF_RXWIN0SENT; 1257 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1258 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1259 th->th_flags |= TH_URG; 1260 } else 1261 /* 1262 * If no urgent pointer to send, then we pull 1263 * the urgent pointer to the left edge of the send window 1264 * so that it doesn't drift into the send window on sequence 1265 * number wraparound. 1266 */ 1267 tp->snd_up = tp->snd_una; /* drag it along */ 1268 1269 /* 1270 * Put TCP length in extended header, and then 1271 * checksum extended header and data. 1272 */ 1273 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1274 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1275 1276 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1277 if (to.to_flags & TOF_SIGNATURE) { 1278 /* 1279 * Calculate MD5 signature and put it into the place 1280 * determined before. 1281 * NOTE: since TCP options buffer doesn't point into 1282 * mbuf's data, calculate offset and use it. 1283 */ 1284 if (!TCPMD5_ENABLED() || TCPMD5_OUTPUT(m, th, 1285 (u_char *)(th + 1) + (to.to_signature - opt)) != 0) { 1286 /* 1287 * Do not send segment if the calculation of MD5 1288 * digest has failed. 1289 */ 1290 goto out; 1291 } 1292 } 1293 #endif 1294 #ifdef INET6 1295 if (isipv6) { 1296 /* 1297 * There is no need to fill in ip6_plen right now. 1298 * It will be filled later by ip6_output. 1299 */ 1300 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1301 th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) + 1302 optlen + len, IPPROTO_TCP, 0); 1303 } 1304 #endif 1305 #if defined(INET6) && defined(INET) 1306 else 1307 #endif 1308 #ifdef INET 1309 { 1310 m->m_pkthdr.csum_flags = CSUM_TCP; 1311 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1312 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1313 1314 /* IP version must be set here for ipv4/ipv6 checking later */ 1315 KASSERT(ip->ip_v == IPVERSION, 1316 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1317 } 1318 #endif 1319 1320 /* 1321 * Enable TSO and specify the size of the segments. 1322 * The TCP pseudo header checksum is always provided. 1323 */ 1324 if (tso) { 1325 KASSERT(len > tp->t_maxseg - optlen, 1326 ("%s: len <= tso_segsz", __func__)); 1327 m->m_pkthdr.csum_flags |= CSUM_TSO; 1328 m->m_pkthdr.tso_segsz = tp->t_maxseg - optlen; 1329 } 1330 1331 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 1332 KASSERT(len + hdrlen + ipoptlen - ipsec_optlen == m_length(m, NULL), 1333 ("%s: mbuf chain shorter than expected: %d + %u + %u - %u != %u", 1334 __func__, len, hdrlen, ipoptlen, ipsec_optlen, m_length(m, NULL))); 1335 #else 1336 KASSERT(len + hdrlen + ipoptlen == m_length(m, NULL), 1337 ("%s: mbuf chain shorter than expected: %d + %u + %u != %u", 1338 __func__, len, hdrlen, ipoptlen, m_length(m, NULL))); 1339 #endif 1340 1341 #ifdef TCP_HHOOK 1342 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1343 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1344 #endif 1345 1346 #ifdef TCPDEBUG 1347 /* 1348 * Trace. 1349 */ 1350 if (so->so_options & SO_DEBUG) { 1351 u_short save = 0; 1352 #ifdef INET6 1353 if (!isipv6) 1354 #endif 1355 { 1356 save = ipov->ih_len; 1357 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1358 } 1359 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1360 #ifdef INET6 1361 if (!isipv6) 1362 #endif 1363 ipov->ih_len = save; 1364 } 1365 #endif /* TCPDEBUG */ 1366 TCP_PROBE3(debug__output, tp, th, m); 1367 1368 /* 1369 * Fill in IP length and desired time to live and 1370 * send to IP level. There should be a better way 1371 * to handle ttl and tos; we could keep them in 1372 * the template, but need a way to checksum without them. 1373 */ 1374 /* 1375 * m->m_pkthdr.len should have been set before checksum calculation, 1376 * because in6_cksum() need it. 1377 */ 1378 #ifdef INET6 1379 if (isipv6) { 1380 struct route_in6 ro; 1381 1382 bzero(&ro, sizeof(ro)); 1383 /* 1384 * we separately set hoplimit for every segment, since the 1385 * user might want to change the value via setsockopt. 1386 * Also, desired default hop limit might be changed via 1387 * Neighbor Discovery. 1388 */ 1389 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1390 1391 /* 1392 * Set the packet size here for the benefit of DTrace probes. 1393 * ip6_output() will set it properly; it's supposed to include 1394 * the option header lengths as well. 1395 */ 1396 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6)); 1397 1398 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) 1399 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1400 else 1401 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1402 1403 if (tp->t_state == TCPS_SYN_SENT) 1404 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th); 1405 1406 TCP_PROBE5(send, NULL, tp, ip6, tp, th); 1407 1408 #ifdef TCPPCAP 1409 /* Save packet, if requested. */ 1410 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1411 #endif 1412 1413 /* TODO: IPv6 IP6TOS_ECT bit on */ 1414 error = ip6_output(m, tp->t_inpcb->in6p_outputopts, &ro, 1415 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 1416 NULL, NULL, tp->t_inpcb); 1417 1418 if (error == EMSGSIZE && ro.ro_rt != NULL) 1419 mtu = ro.ro_rt->rt_mtu; 1420 RO_RTFREE(&ro); 1421 } 1422 #endif /* INET6 */ 1423 #if defined(INET) && defined(INET6) 1424 else 1425 #endif 1426 #ifdef INET 1427 { 1428 ip->ip_len = htons(m->m_pkthdr.len); 1429 #ifdef INET6 1430 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1431 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1432 #endif /* INET6 */ 1433 /* 1434 * If we do path MTU discovery, then we set DF on every packet. 1435 * This might not be the best thing to do according to RFC3390 1436 * Section 2. However the tcp hostcache migitates the problem 1437 * so it affects only the first tcp connection with a host. 1438 * 1439 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1440 */ 1441 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) { 1442 ip->ip_off |= htons(IP_DF); 1443 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1444 } else { 1445 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1446 } 1447 1448 if (tp->t_state == TCPS_SYN_SENT) 1449 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th); 1450 1451 TCP_PROBE5(send, NULL, tp, ip, tp, th); 1452 1453 #ifdef TCPPCAP 1454 /* Save packet, if requested. */ 1455 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1456 #endif 1457 1458 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, 1459 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1460 tp->t_inpcb); 1461 1462 if (error == EMSGSIZE && tp->t_inpcb->inp_route.ro_rt != NULL) 1463 mtu = tp->t_inpcb->inp_route.ro_rt->rt_mtu; 1464 } 1465 #endif /* INET */ 1466 1467 out: 1468 /* 1469 * In transmit state, time the transmission and arrange for 1470 * the retransmit. In persist state, just set snd_max. 1471 */ 1472 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1473 !tcp_timer_active(tp, TT_PERSIST)) { 1474 tcp_seq startseq = tp->snd_nxt; 1475 1476 /* 1477 * Advance snd_nxt over sequence space of this segment. 1478 */ 1479 if (flags & (TH_SYN|TH_FIN)) { 1480 if (flags & TH_SYN) 1481 tp->snd_nxt++; 1482 if (flags & TH_FIN) { 1483 tp->snd_nxt++; 1484 tp->t_flags |= TF_SENTFIN; 1485 } 1486 } 1487 if (sack_rxmit) 1488 goto timer; 1489 tp->snd_nxt += len; 1490 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1491 tp->snd_max = tp->snd_nxt; 1492 /* 1493 * Time this transmission if not a retransmission and 1494 * not currently timing anything. 1495 */ 1496 if (tp->t_rtttime == 0) { 1497 tp->t_rtttime = ticks; 1498 tp->t_rtseq = startseq; 1499 TCPSTAT_INC(tcps_segstimed); 1500 } 1501 } 1502 1503 /* 1504 * Set retransmit timer if not currently set, 1505 * and not doing a pure ack or a keep-alive probe. 1506 * Initial value for retransmit timer is smoothed 1507 * round-trip time + 2 * round-trip time variance. 1508 * Initialize shift counter which is used for backoff 1509 * of retransmit time. 1510 */ 1511 timer: 1512 if (!tcp_timer_active(tp, TT_REXMT) && 1513 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1514 (tp->snd_nxt != tp->snd_una))) { 1515 if (tcp_timer_active(tp, TT_PERSIST)) { 1516 tcp_timer_activate(tp, TT_PERSIST, 0); 1517 tp->t_rxtshift = 0; 1518 } 1519 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1520 } else if (len == 0 && sbavail(&so->so_snd) && 1521 !tcp_timer_active(tp, TT_REXMT) && 1522 !tcp_timer_active(tp, TT_PERSIST)) { 1523 /* 1524 * Avoid a situation where we do not set persist timer 1525 * after a zero window condition. For example: 1526 * 1) A -> B: packet with enough data to fill the window 1527 * 2) B -> A: ACK for #1 + new data (0 window 1528 * advertisement) 1529 * 3) A -> B: ACK for #2, 0 len packet 1530 * 1531 * In this case, A will not activate the persist timer, 1532 * because it chose to send a packet. Unless tcp_output 1533 * is called for some other reason (delayed ack timer, 1534 * another input packet from B, socket syscall), A will 1535 * not send zero window probes. 1536 * 1537 * So, if you send a 0-length packet, but there is data 1538 * in the socket buffer, and neither the rexmt or 1539 * persist timer is already set, then activate the 1540 * persist timer. 1541 */ 1542 tp->t_rxtshift = 0; 1543 tcp_setpersist(tp); 1544 } 1545 } else { 1546 /* 1547 * Persist case, update snd_max but since we are in 1548 * persist mode (no window) we do not update snd_nxt. 1549 */ 1550 int xlen = len; 1551 if (flags & TH_SYN) 1552 ++xlen; 1553 if (flags & TH_FIN) { 1554 ++xlen; 1555 tp->t_flags |= TF_SENTFIN; 1556 } 1557 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1558 tp->snd_max = tp->snd_nxt + xlen; 1559 } 1560 1561 if (error) { 1562 1563 /* 1564 * We know that the packet was lost, so back out the 1565 * sequence number advance, if any. 1566 * 1567 * If the error is EPERM the packet got blocked by the 1568 * local firewall. Normally we should terminate the 1569 * connection but the blocking may have been spurious 1570 * due to a firewall reconfiguration cycle. So we treat 1571 * it like a packet loss and let the retransmit timer and 1572 * timeouts do their work over time. 1573 * XXX: It is a POLA question whether calling tcp_drop right 1574 * away would be the really correct behavior instead. 1575 */ 1576 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1577 !tcp_timer_active(tp, TT_PERSIST)) && 1578 ((flags & TH_SYN) == 0) && 1579 (error != EPERM)) { 1580 if (sack_rxmit) { 1581 p->rxmit -= len; 1582 tp->sackhint.sack_bytes_rexmit -= len; 1583 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1584 ("sackhint bytes rtx >= 0")); 1585 } else 1586 tp->snd_nxt -= len; 1587 } 1588 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1589 switch (error) { 1590 case EACCES: 1591 tp->t_softerror = error; 1592 return (0); 1593 case EPERM: 1594 tp->t_softerror = error; 1595 return (error); 1596 case ENOBUFS: 1597 TCP_XMIT_TIMER_ASSERT(tp, len, flags); 1598 tp->snd_cwnd = tp->t_maxseg; 1599 return (0); 1600 case EMSGSIZE: 1601 /* 1602 * For some reason the interface we used initially 1603 * to send segments changed to another or lowered 1604 * its MTU. 1605 * If TSO was active we either got an interface 1606 * without TSO capabilits or TSO was turned off. 1607 * If we obtained mtu from ip_output() then update 1608 * it and try again. 1609 */ 1610 if (tso) 1611 tp->t_flags &= ~TF_TSO; 1612 if (mtu != 0) { 1613 tcp_mss_update(tp, -1, mtu, NULL, NULL); 1614 goto again; 1615 } 1616 return (error); 1617 case EHOSTDOWN: 1618 case EHOSTUNREACH: 1619 case ENETDOWN: 1620 case ENETUNREACH: 1621 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1622 tp->t_softerror = error; 1623 return (0); 1624 } 1625 /* FALLTHROUGH */ 1626 default: 1627 return (error); 1628 } 1629 } 1630 TCPSTAT_INC(tcps_sndtotal); 1631 1632 /* 1633 * Data sent (as far as we can tell). 1634 * If this advertises a larger window than any other segment, 1635 * then remember the size of the advertised window. 1636 * Any pending ACK has now been sent. 1637 */ 1638 if (SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1639 tp->rcv_adv = tp->rcv_nxt + recwin; 1640 tp->last_ack_sent = tp->rcv_nxt; 1641 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1642 if (tcp_timer_active(tp, TT_DELACK)) 1643 tcp_timer_activate(tp, TT_DELACK, 0); 1644 #if 0 1645 /* 1646 * This completely breaks TCP if newreno is turned on. What happens 1647 * is that if delayed-acks are turned on on the receiver, this code 1648 * on the transmitter effectively destroys the TCP window, forcing 1649 * it to four packets (1.5Kx4 = 6K window). 1650 */ 1651 if (sendalot && --maxburst) 1652 goto again; 1653 #endif 1654 if (sendalot) 1655 goto again; 1656 return (0); 1657 } 1658 1659 void 1660 tcp_setpersist(struct tcpcb *tp) 1661 { 1662 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1663 int tt; 1664 1665 tp->t_flags &= ~TF_PREVVALID; 1666 if (tcp_timer_active(tp, TT_REXMT)) 1667 panic("tcp_setpersist: retransmit pending"); 1668 /* 1669 * Start/restart persistence timer. 1670 */ 1671 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1672 tcp_persmin, tcp_persmax); 1673 tcp_timer_activate(tp, TT_PERSIST, tt); 1674 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1675 tp->t_rxtshift++; 1676 } 1677 1678 /* 1679 * Insert TCP options according to the supplied parameters to the place 1680 * optp in a consistent way. Can handle unaligned destinations. 1681 * 1682 * The order of the option processing is crucial for optimal packing and 1683 * alignment for the scarce option space. 1684 * 1685 * The optimal order for a SYN/SYN-ACK segment is: 1686 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1687 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1688 * 1689 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1690 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1691 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1692 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1693 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1694 */ 1695 int 1696 tcp_addoptions(struct tcpopt *to, u_char *optp) 1697 { 1698 u_int32_t mask, optlen = 0; 1699 1700 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1701 if ((to->to_flags & mask) != mask) 1702 continue; 1703 if (optlen == TCP_MAXOLEN) 1704 break; 1705 switch (to->to_flags & mask) { 1706 case TOF_MSS: 1707 while (optlen % 4) { 1708 optlen += TCPOLEN_NOP; 1709 *optp++ = TCPOPT_NOP; 1710 } 1711 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1712 continue; 1713 optlen += TCPOLEN_MAXSEG; 1714 *optp++ = TCPOPT_MAXSEG; 1715 *optp++ = TCPOLEN_MAXSEG; 1716 to->to_mss = htons(to->to_mss); 1717 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1718 optp += sizeof(to->to_mss); 1719 break; 1720 case TOF_SCALE: 1721 while (!optlen || optlen % 2 != 1) { 1722 optlen += TCPOLEN_NOP; 1723 *optp++ = TCPOPT_NOP; 1724 } 1725 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1726 continue; 1727 optlen += TCPOLEN_WINDOW; 1728 *optp++ = TCPOPT_WINDOW; 1729 *optp++ = TCPOLEN_WINDOW; 1730 *optp++ = to->to_wscale; 1731 break; 1732 case TOF_SACKPERM: 1733 while (optlen % 2) { 1734 optlen += TCPOLEN_NOP; 1735 *optp++ = TCPOPT_NOP; 1736 } 1737 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1738 continue; 1739 optlen += TCPOLEN_SACK_PERMITTED; 1740 *optp++ = TCPOPT_SACK_PERMITTED; 1741 *optp++ = TCPOLEN_SACK_PERMITTED; 1742 break; 1743 case TOF_TS: 1744 while (!optlen || optlen % 4 != 2) { 1745 optlen += TCPOLEN_NOP; 1746 *optp++ = TCPOPT_NOP; 1747 } 1748 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1749 continue; 1750 optlen += TCPOLEN_TIMESTAMP; 1751 *optp++ = TCPOPT_TIMESTAMP; 1752 *optp++ = TCPOLEN_TIMESTAMP; 1753 to->to_tsval = htonl(to->to_tsval); 1754 to->to_tsecr = htonl(to->to_tsecr); 1755 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1756 optp += sizeof(to->to_tsval); 1757 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1758 optp += sizeof(to->to_tsecr); 1759 break; 1760 case TOF_SIGNATURE: 1761 { 1762 int siglen = TCPOLEN_SIGNATURE - 2; 1763 1764 while (!optlen || optlen % 4 != 2) { 1765 optlen += TCPOLEN_NOP; 1766 *optp++ = TCPOPT_NOP; 1767 } 1768 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) { 1769 to->to_flags &= ~TOF_SIGNATURE; 1770 continue; 1771 } 1772 optlen += TCPOLEN_SIGNATURE; 1773 *optp++ = TCPOPT_SIGNATURE; 1774 *optp++ = TCPOLEN_SIGNATURE; 1775 to->to_signature = optp; 1776 while (siglen--) 1777 *optp++ = 0; 1778 break; 1779 } 1780 case TOF_SACK: 1781 { 1782 int sackblks = 0; 1783 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1784 tcp_seq sack_seq; 1785 1786 while (!optlen || optlen % 4 != 2) { 1787 optlen += TCPOLEN_NOP; 1788 *optp++ = TCPOPT_NOP; 1789 } 1790 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1791 continue; 1792 optlen += TCPOLEN_SACKHDR; 1793 *optp++ = TCPOPT_SACK; 1794 sackblks = min(to->to_nsacks, 1795 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1796 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1797 while (sackblks--) { 1798 sack_seq = htonl(sack->start); 1799 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1800 optp += sizeof(sack_seq); 1801 sack_seq = htonl(sack->end); 1802 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1803 optp += sizeof(sack_seq); 1804 optlen += TCPOLEN_SACK; 1805 sack++; 1806 } 1807 TCPSTAT_INC(tcps_sack_send_blocks); 1808 break; 1809 } 1810 #ifdef TCP_RFC7413 1811 case TOF_FASTOPEN: 1812 { 1813 int total_len; 1814 1815 /* XXX is there any point to aligning this option? */ 1816 total_len = TCPOLEN_FAST_OPEN_EMPTY + to->to_tfo_len; 1817 if (TCP_MAXOLEN - optlen < total_len) 1818 continue; 1819 *optp++ = TCPOPT_FAST_OPEN; 1820 *optp++ = total_len; 1821 if (to->to_tfo_len > 0) { 1822 bcopy(to->to_tfo_cookie, optp, to->to_tfo_len); 1823 optp += to->to_tfo_len; 1824 } 1825 optlen += total_len; 1826 break; 1827 } 1828 #endif 1829 default: 1830 panic("%s: unknown TCP option type", __func__); 1831 break; 1832 } 1833 } 1834 1835 /* Terminate and pad TCP options to a 4 byte boundary. */ 1836 if (optlen % 4) { 1837 optlen += TCPOLEN_EOL; 1838 *optp++ = TCPOPT_EOL; 1839 } 1840 /* 1841 * According to RFC 793 (STD0007): 1842 * "The content of the header beyond the End-of-Option option 1843 * must be header padding (i.e., zero)." 1844 * and later: "The padding is composed of zeros." 1845 */ 1846 while (optlen % 4) { 1847 optlen += TCPOLEN_PAD; 1848 *optp++ = TCPOPT_PAD; 1849 } 1850 1851 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1852 return (optlen); 1853 } 1854