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 } 835 836 /* Set receive buffer autosizing timestamp. */ 837 if (tp->rfbuf_ts == 0 && 838 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 839 tp->rfbuf_ts = tcp_ts_getticks(); 840 841 /* Selective ACK's. */ 842 if (tp->t_flags & TF_SACK_PERMIT) { 843 if (flags & TH_SYN) 844 to.to_flags |= TOF_SACKPERM; 845 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 846 (tp->t_flags & TF_SACK_PERMIT) && 847 tp->rcv_numsacks > 0) { 848 to.to_flags |= TOF_SACK; 849 to.to_nsacks = tp->rcv_numsacks; 850 to.to_sacks = (u_char *)tp->sackblks; 851 } 852 } 853 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 854 /* TCP-MD5 (RFC2385). */ 855 /* 856 * Check that TCP_MD5SIG is enabled in tcpcb to 857 * account the size needed to set this TCP option. 858 */ 859 if (tp->t_flags & TF_SIGNATURE) 860 to.to_flags |= TOF_SIGNATURE; 861 #endif /* TCP_SIGNATURE */ 862 863 /* Processing the options. */ 864 hdrlen += optlen = tcp_addoptions(&to, opt); 865 } 866 867 /* 868 * Adjust data length if insertion of options will 869 * bump the packet length beyond the t_maxseg length. 870 * Clear the FIN bit because we cut off the tail of 871 * the segment. 872 */ 873 if (len + optlen + ipoptlen > tp->t_maxseg) { 874 flags &= ~TH_FIN; 875 876 if (tso) { 877 u_int if_hw_tsomax; 878 u_int if_hw_tsomaxsegcount; 879 u_int if_hw_tsomaxsegsize; 880 struct mbuf *mb; 881 u_int moff; 882 int max_len; 883 884 /* extract TSO information */ 885 if_hw_tsomax = tp->t_tsomax; 886 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount; 887 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize; 888 889 /* 890 * Limit a TSO burst to prevent it from 891 * overflowing or exceeding the maximum length 892 * allowed by the network interface: 893 */ 894 KASSERT(ipoptlen == 0, 895 ("%s: TSO can't do IP options", __func__)); 896 897 /* 898 * Check if we should limit by maximum payload 899 * length: 900 */ 901 if (if_hw_tsomax != 0) { 902 /* compute maximum TSO length */ 903 max_len = (if_hw_tsomax - hdrlen - 904 max_linkhdr); 905 if (max_len <= 0) { 906 len = 0; 907 } else if (len > max_len) { 908 sendalot = 1; 909 len = max_len; 910 } 911 } 912 913 /* 914 * Check if we should limit by maximum segment 915 * size and count: 916 */ 917 if (if_hw_tsomaxsegcount != 0 && 918 if_hw_tsomaxsegsize != 0) { 919 /* 920 * Subtract one segment for the LINK 921 * and TCP/IP headers mbuf that will 922 * be prepended to this mbuf chain 923 * after the code in this section 924 * limits the number of mbufs in the 925 * chain to if_hw_tsomaxsegcount. 926 */ 927 if_hw_tsomaxsegcount -= 1; 928 max_len = 0; 929 mb = sbsndmbuf(&so->so_snd, off, &moff); 930 931 while (mb != NULL && max_len < len) { 932 u_int mlen; 933 u_int frags; 934 935 /* 936 * Get length of mbuf fragment 937 * and how many hardware frags, 938 * rounded up, it would use: 939 */ 940 mlen = (mb->m_len - moff); 941 frags = howmany(mlen, 942 if_hw_tsomaxsegsize); 943 944 /* Handle special case: Zero Length Mbuf */ 945 if (frags == 0) 946 frags = 1; 947 948 /* 949 * Check if the fragment limit 950 * will be reached or exceeded: 951 */ 952 if (frags >= if_hw_tsomaxsegcount) { 953 max_len += min(mlen, 954 if_hw_tsomaxsegcount * 955 if_hw_tsomaxsegsize); 956 break; 957 } 958 max_len += mlen; 959 if_hw_tsomaxsegcount -= frags; 960 moff = 0; 961 mb = mb->m_next; 962 } 963 if (max_len <= 0) { 964 len = 0; 965 } else if (len > max_len) { 966 sendalot = 1; 967 len = max_len; 968 } 969 } 970 971 /* 972 * Prevent the last segment from being 973 * fractional unless the send sockbuf can be 974 * emptied: 975 */ 976 max_len = (tp->t_maxseg - optlen); 977 if (((uint32_t)off + (uint32_t)len) < 978 sbavail(&so->so_snd)) { 979 moff = len % max_len; 980 if (moff != 0) { 981 len -= moff; 982 sendalot = 1; 983 } 984 } 985 986 /* 987 * In case there are too many small fragments 988 * don't use TSO: 989 */ 990 if (len <= max_len) { 991 len = max_len; 992 sendalot = 1; 993 tso = 0; 994 } 995 996 /* 997 * Send the FIN in a separate segment 998 * after the bulk sending is done. 999 * We don't trust the TSO implementations 1000 * to clear the FIN flag on all but the 1001 * last segment. 1002 */ 1003 if (tp->t_flags & TF_NEEDFIN) 1004 sendalot = 1; 1005 1006 } else { 1007 len = tp->t_maxseg - optlen - ipoptlen; 1008 sendalot = 1; 1009 } 1010 } else 1011 tso = 0; 1012 1013 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 1014 ("%s: len > IP_MAXPACKET", __func__)); 1015 1016 /*#ifdef DIAGNOSTIC*/ 1017 #ifdef INET6 1018 if (max_linkhdr + hdrlen > MCLBYTES) 1019 #else 1020 if (max_linkhdr + hdrlen > MHLEN) 1021 #endif 1022 panic("tcphdr too big"); 1023 /*#endif*/ 1024 1025 /* 1026 * This KASSERT is here to catch edge cases at a well defined place. 1027 * Before, those had triggered (random) panic conditions further down. 1028 */ 1029 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 1030 1031 /* 1032 * Grab a header mbuf, attaching a copy of data to 1033 * be transmitted, and initialize the header from 1034 * the template for sends on this connection. 1035 */ 1036 if (len) { 1037 struct mbuf *mb; 1038 u_int moff; 1039 1040 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 1041 TCPSTAT_INC(tcps_sndprobe); 1042 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 1043 tp->t_sndrexmitpack++; 1044 TCPSTAT_INC(tcps_sndrexmitpack); 1045 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 1046 } else { 1047 TCPSTAT_INC(tcps_sndpack); 1048 TCPSTAT_ADD(tcps_sndbyte, len); 1049 } 1050 #ifdef INET6 1051 if (MHLEN < hdrlen + max_linkhdr) 1052 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR); 1053 else 1054 #endif 1055 m = m_gethdr(M_NOWAIT, MT_DATA); 1056 1057 if (m == NULL) { 1058 SOCKBUF_UNLOCK(&so->so_snd); 1059 error = ENOBUFS; 1060 sack_rxmit = 0; 1061 goto out; 1062 } 1063 1064 m->m_data += max_linkhdr; 1065 m->m_len = hdrlen; 1066 1067 /* 1068 * Start the m_copy functions from the closest mbuf 1069 * to the offset in the socket buffer chain. 1070 */ 1071 mb = sbsndptr(&so->so_snd, off, len, &moff); 1072 1073 if (len <= MHLEN - hdrlen - max_linkhdr) { 1074 m_copydata(mb, moff, len, 1075 mtod(m, caddr_t) + hdrlen); 1076 m->m_len += len; 1077 } else { 1078 m->m_next = m_copym(mb, moff, len, M_NOWAIT); 1079 if (m->m_next == NULL) { 1080 SOCKBUF_UNLOCK(&so->so_snd); 1081 (void) m_free(m); 1082 error = ENOBUFS; 1083 sack_rxmit = 0; 1084 goto out; 1085 } 1086 } 1087 1088 /* 1089 * If we're sending everything we've got, set PUSH. 1090 * (This will keep happy those implementations which only 1091 * give data to the user when a buffer fills or 1092 * a PUSH comes in.) 1093 */ 1094 if (((uint32_t)off + (uint32_t)len == sbused(&so->so_snd)) && 1095 !(flags & TH_SYN)) 1096 flags |= TH_PUSH; 1097 SOCKBUF_UNLOCK(&so->so_snd); 1098 } else { 1099 SOCKBUF_UNLOCK(&so->so_snd); 1100 if (tp->t_flags & TF_ACKNOW) 1101 TCPSTAT_INC(tcps_sndacks); 1102 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 1103 TCPSTAT_INC(tcps_sndctrl); 1104 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 1105 TCPSTAT_INC(tcps_sndurg); 1106 else 1107 TCPSTAT_INC(tcps_sndwinup); 1108 1109 m = m_gethdr(M_NOWAIT, MT_DATA); 1110 if (m == NULL) { 1111 error = ENOBUFS; 1112 sack_rxmit = 0; 1113 goto out; 1114 } 1115 #ifdef INET6 1116 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 1117 MHLEN >= hdrlen) { 1118 M_ALIGN(m, hdrlen); 1119 } else 1120 #endif 1121 m->m_data += max_linkhdr; 1122 m->m_len = hdrlen; 1123 } 1124 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 1125 m->m_pkthdr.rcvif = (struct ifnet *)0; 1126 #ifdef MAC 1127 mac_inpcb_create_mbuf(tp->t_inpcb, m); 1128 #endif 1129 #ifdef INET6 1130 if (isipv6) { 1131 ip6 = mtod(m, struct ip6_hdr *); 1132 th = (struct tcphdr *)(ip6 + 1); 1133 tcpip_fillheaders(tp->t_inpcb, ip6, th); 1134 } else 1135 #endif /* INET6 */ 1136 { 1137 ip = mtod(m, struct ip *); 1138 ipov = (struct ipovly *)ip; 1139 th = (struct tcphdr *)(ip + 1); 1140 tcpip_fillheaders(tp->t_inpcb, ip, th); 1141 } 1142 1143 /* 1144 * Fill in fields, remembering maximum advertised 1145 * window for use in delaying messages about window sizes. 1146 * If resending a FIN, be sure not to use a new sequence number. 1147 */ 1148 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 1149 tp->snd_nxt == tp->snd_max) 1150 tp->snd_nxt--; 1151 /* 1152 * If we are starting a connection, send ECN setup 1153 * SYN packet. If we are on a retransmit, we may 1154 * resend those bits a number of times as per 1155 * RFC 3168. 1156 */ 1157 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn == 1) { 1158 if (tp->t_rxtshift >= 1) { 1159 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 1160 flags |= TH_ECE|TH_CWR; 1161 } else 1162 flags |= TH_ECE|TH_CWR; 1163 } 1164 1165 if (tp->t_state == TCPS_ESTABLISHED && 1166 (tp->t_flags & TF_ECN_PERMIT)) { 1167 /* 1168 * If the peer has ECN, mark data packets with 1169 * ECN capable transmission (ECT). 1170 * Ignore pure ack packets, retransmissions and window probes. 1171 */ 1172 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 1173 !((tp->t_flags & TF_FORCEDATA) && len == 1)) { 1174 #ifdef INET6 1175 if (isipv6) 1176 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 1177 else 1178 #endif 1179 ip->ip_tos |= IPTOS_ECN_ECT0; 1180 TCPSTAT_INC(tcps_ecn_ect0); 1181 } 1182 1183 /* 1184 * Reply with proper ECN notifications. 1185 */ 1186 if (tp->t_flags & TF_ECN_SND_CWR) { 1187 flags |= TH_CWR; 1188 tp->t_flags &= ~TF_ECN_SND_CWR; 1189 } 1190 if (tp->t_flags & TF_ECN_SND_ECE) 1191 flags |= TH_ECE; 1192 } 1193 1194 /* 1195 * If we are doing retransmissions, then snd_nxt will 1196 * not reflect the first unsent octet. For ACK only 1197 * packets, we do not want the sequence number of the 1198 * retransmitted packet, we want the sequence number 1199 * of the next unsent octet. So, if there is no data 1200 * (and no SYN or FIN), use snd_max instead of snd_nxt 1201 * when filling in ti_seq. But if we are in persist 1202 * state, snd_max might reflect one byte beyond the 1203 * right edge of the window, so use snd_nxt in that 1204 * case, since we know we aren't doing a retransmission. 1205 * (retransmit and persist are mutually exclusive...) 1206 */ 1207 if (sack_rxmit == 0) { 1208 if (len || (flags & (TH_SYN|TH_FIN)) || 1209 tcp_timer_active(tp, TT_PERSIST)) 1210 th->th_seq = htonl(tp->snd_nxt); 1211 else 1212 th->th_seq = htonl(tp->snd_max); 1213 } else { 1214 th->th_seq = htonl(p->rxmit); 1215 p->rxmit += len; 1216 tp->sackhint.sack_bytes_rexmit += len; 1217 } 1218 th->th_ack = htonl(tp->rcv_nxt); 1219 if (optlen) { 1220 bcopy(opt, th + 1, optlen); 1221 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1222 } 1223 th->th_flags = flags; 1224 /* 1225 * Calculate receive window. Don't shrink window, 1226 * but avoid silly window syndrome. 1227 */ 1228 if (recwin < (so->so_rcv.sb_hiwat / 4) && 1229 recwin < tp->t_maxseg) 1230 recwin = 0; 1231 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1232 recwin < (tp->rcv_adv - tp->rcv_nxt)) 1233 recwin = (tp->rcv_adv - tp->rcv_nxt); 1234 1235 /* 1236 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1237 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1238 * case is handled in syncache. 1239 */ 1240 if (flags & TH_SYN) 1241 th->th_win = htons((u_short) 1242 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1243 else 1244 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1245 1246 /* 1247 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1248 * a 0 window. This may cause the remote transmitter to stall. This 1249 * flag tells soreceive() to disable delayed acknowledgements when 1250 * draining the buffer. This can occur if the receiver is attempting 1251 * to read more data than can be buffered prior to transmitting on 1252 * the connection. 1253 */ 1254 if (th->th_win == 0) { 1255 tp->t_sndzerowin++; 1256 tp->t_flags |= TF_RXWIN0SENT; 1257 } else 1258 tp->t_flags &= ~TF_RXWIN0SENT; 1259 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1260 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1261 th->th_flags |= TH_URG; 1262 } else 1263 /* 1264 * If no urgent pointer to send, then we pull 1265 * the urgent pointer to the left edge of the send window 1266 * so that it doesn't drift into the send window on sequence 1267 * number wraparound. 1268 */ 1269 tp->snd_up = tp->snd_una; /* drag it along */ 1270 1271 /* 1272 * Put TCP length in extended header, and then 1273 * checksum extended header and data. 1274 */ 1275 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1276 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1277 1278 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1279 if (to.to_flags & TOF_SIGNATURE) { 1280 /* 1281 * Calculate MD5 signature and put it into the place 1282 * determined before. 1283 * NOTE: since TCP options buffer doesn't point into 1284 * mbuf's data, calculate offset and use it. 1285 */ 1286 if (!TCPMD5_ENABLED() || TCPMD5_OUTPUT(m, th, 1287 (u_char *)(th + 1) + (to.to_signature - opt)) != 0) { 1288 /* 1289 * Do not send segment if the calculation of MD5 1290 * digest has failed. 1291 */ 1292 goto out; 1293 } 1294 } 1295 #endif 1296 #ifdef INET6 1297 if (isipv6) { 1298 /* 1299 * There is no need to fill in ip6_plen right now. 1300 * It will be filled later by ip6_output. 1301 */ 1302 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1303 th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) + 1304 optlen + len, IPPROTO_TCP, 0); 1305 } 1306 #endif 1307 #if defined(INET6) && defined(INET) 1308 else 1309 #endif 1310 #ifdef INET 1311 { 1312 m->m_pkthdr.csum_flags = CSUM_TCP; 1313 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1314 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1315 1316 /* IP version must be set here for ipv4/ipv6 checking later */ 1317 KASSERT(ip->ip_v == IPVERSION, 1318 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1319 } 1320 #endif 1321 1322 /* 1323 * Enable TSO and specify the size of the segments. 1324 * The TCP pseudo header checksum is always provided. 1325 */ 1326 if (tso) { 1327 KASSERT(len > tp->t_maxseg - optlen, 1328 ("%s: len <= tso_segsz", __func__)); 1329 m->m_pkthdr.csum_flags |= CSUM_TSO; 1330 m->m_pkthdr.tso_segsz = tp->t_maxseg - optlen; 1331 } 1332 1333 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 1334 KASSERT(len + hdrlen + ipoptlen - ipsec_optlen == m_length(m, NULL), 1335 ("%s: mbuf chain shorter than expected: %d + %u + %u - %u != %u", 1336 __func__, len, hdrlen, ipoptlen, ipsec_optlen, m_length(m, NULL))); 1337 #else 1338 KASSERT(len + hdrlen + ipoptlen == m_length(m, NULL), 1339 ("%s: mbuf chain shorter than expected: %d + %u + %u != %u", 1340 __func__, len, hdrlen, ipoptlen, m_length(m, NULL))); 1341 #endif 1342 1343 #ifdef TCP_HHOOK 1344 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1345 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1346 #endif 1347 1348 #ifdef TCPDEBUG 1349 /* 1350 * Trace. 1351 */ 1352 if (so->so_options & SO_DEBUG) { 1353 u_short save = 0; 1354 #ifdef INET6 1355 if (!isipv6) 1356 #endif 1357 { 1358 save = ipov->ih_len; 1359 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1360 } 1361 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1362 #ifdef INET6 1363 if (!isipv6) 1364 #endif 1365 ipov->ih_len = save; 1366 } 1367 #endif /* TCPDEBUG */ 1368 TCP_PROBE3(debug__output, tp, th, m); 1369 1370 /* 1371 * Fill in IP length and desired time to live and 1372 * send to IP level. There should be a better way 1373 * to handle ttl and tos; we could keep them in 1374 * the template, but need a way to checksum without them. 1375 */ 1376 /* 1377 * m->m_pkthdr.len should have been set before checksum calculation, 1378 * because in6_cksum() need it. 1379 */ 1380 #ifdef INET6 1381 if (isipv6) { 1382 /* 1383 * we separately set hoplimit for every segment, since the 1384 * user might want to change the value via setsockopt. 1385 * Also, desired default hop limit might be changed via 1386 * Neighbor Discovery. 1387 */ 1388 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1389 1390 /* 1391 * Set the packet size here for the benefit of DTrace probes. 1392 * ip6_output() will set it properly; it's supposed to include 1393 * the option header lengths as well. 1394 */ 1395 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6)); 1396 1397 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) 1398 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1399 else 1400 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1401 1402 if (tp->t_state == TCPS_SYN_SENT) 1403 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th); 1404 1405 TCP_PROBE5(send, NULL, tp, ip6, tp, th); 1406 1407 #ifdef TCPPCAP 1408 /* Save packet, if requested. */ 1409 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1410 #endif 1411 1412 /* TODO: IPv6 IP6TOS_ECT bit on */ 1413 error = ip6_output(m, tp->t_inpcb->in6p_outputopts, 1414 &tp->t_inpcb->inp_route6, 1415 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 1416 NULL, NULL, tp->t_inpcb); 1417 1418 if (error == EMSGSIZE && tp->t_inpcb->inp_route6.ro_rt != NULL) 1419 mtu = tp->t_inpcb->inp_route6.ro_rt->rt_mtu; 1420 } 1421 #endif /* INET6 */ 1422 #if defined(INET) && defined(INET6) 1423 else 1424 #endif 1425 #ifdef INET 1426 { 1427 ip->ip_len = htons(m->m_pkthdr.len); 1428 #ifdef INET6 1429 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1430 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1431 #endif /* INET6 */ 1432 /* 1433 * If we do path MTU discovery, then we set DF on every packet. 1434 * This might not be the best thing to do according to RFC3390 1435 * Section 2. However the tcp hostcache migitates the problem 1436 * so it affects only the first tcp connection with a host. 1437 * 1438 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1439 */ 1440 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) { 1441 ip->ip_off |= htons(IP_DF); 1442 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1443 } else { 1444 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1445 } 1446 1447 if (tp->t_state == TCPS_SYN_SENT) 1448 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th); 1449 1450 TCP_PROBE5(send, NULL, tp, ip, tp, th); 1451 1452 #ifdef TCPPCAP 1453 /* Save packet, if requested. */ 1454 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1455 #endif 1456 1457 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, 1458 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1459 tp->t_inpcb); 1460 1461 if (error == EMSGSIZE && tp->t_inpcb->inp_route.ro_rt != NULL) 1462 mtu = tp->t_inpcb->inp_route.ro_rt->rt_mtu; 1463 } 1464 #endif /* INET */ 1465 1466 out: 1467 /* 1468 * In transmit state, time the transmission and arrange for 1469 * the retransmit. In persist state, just set snd_max. 1470 */ 1471 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1472 !tcp_timer_active(tp, TT_PERSIST)) { 1473 tcp_seq startseq = tp->snd_nxt; 1474 1475 /* 1476 * Advance snd_nxt over sequence space of this segment. 1477 */ 1478 if (flags & (TH_SYN|TH_FIN)) { 1479 if (flags & TH_SYN) 1480 tp->snd_nxt++; 1481 if (flags & TH_FIN) { 1482 tp->snd_nxt++; 1483 tp->t_flags |= TF_SENTFIN; 1484 } 1485 } 1486 if (sack_rxmit) 1487 goto timer; 1488 tp->snd_nxt += len; 1489 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1490 tp->snd_max = tp->snd_nxt; 1491 /* 1492 * Time this transmission if not a retransmission and 1493 * not currently timing anything. 1494 */ 1495 if (tp->t_rtttime == 0) { 1496 tp->t_rtttime = ticks; 1497 tp->t_rtseq = startseq; 1498 TCPSTAT_INC(tcps_segstimed); 1499 } 1500 } 1501 1502 /* 1503 * Set retransmit timer if not currently set, 1504 * and not doing a pure ack or a keep-alive probe. 1505 * Initial value for retransmit timer is smoothed 1506 * round-trip time + 2 * round-trip time variance. 1507 * Initialize shift counter which is used for backoff 1508 * of retransmit time. 1509 */ 1510 timer: 1511 if (!tcp_timer_active(tp, TT_REXMT) && 1512 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1513 (tp->snd_nxt != tp->snd_una))) { 1514 if (tcp_timer_active(tp, TT_PERSIST)) { 1515 tcp_timer_activate(tp, TT_PERSIST, 0); 1516 tp->t_rxtshift = 0; 1517 } 1518 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1519 } else if (len == 0 && sbavail(&so->so_snd) && 1520 !tcp_timer_active(tp, TT_REXMT) && 1521 !tcp_timer_active(tp, TT_PERSIST)) { 1522 /* 1523 * Avoid a situation where we do not set persist timer 1524 * after a zero window condition. For example: 1525 * 1) A -> B: packet with enough data to fill the window 1526 * 2) B -> A: ACK for #1 + new data (0 window 1527 * advertisement) 1528 * 3) A -> B: ACK for #2, 0 len packet 1529 * 1530 * In this case, A will not activate the persist timer, 1531 * because it chose to send a packet. Unless tcp_output 1532 * is called for some other reason (delayed ack timer, 1533 * another input packet from B, socket syscall), A will 1534 * not send zero window probes. 1535 * 1536 * So, if you send a 0-length packet, but there is data 1537 * in the socket buffer, and neither the rexmt or 1538 * persist timer is already set, then activate the 1539 * persist timer. 1540 */ 1541 tp->t_rxtshift = 0; 1542 tcp_setpersist(tp); 1543 } 1544 } else { 1545 /* 1546 * Persist case, update snd_max but since we are in 1547 * persist mode (no window) we do not update snd_nxt. 1548 */ 1549 int xlen = len; 1550 if (flags & TH_SYN) 1551 ++xlen; 1552 if (flags & TH_FIN) { 1553 ++xlen; 1554 tp->t_flags |= TF_SENTFIN; 1555 } 1556 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1557 tp->snd_max = tp->snd_nxt + xlen; 1558 } 1559 1560 if (error) { 1561 1562 /* 1563 * We know that the packet was lost, so back out the 1564 * sequence number advance, if any. 1565 * 1566 * If the error is EPERM the packet got blocked by the 1567 * local firewall. Normally we should terminate the 1568 * connection but the blocking may have been spurious 1569 * due to a firewall reconfiguration cycle. So we treat 1570 * it like a packet loss and let the retransmit timer and 1571 * timeouts do their work over time. 1572 * XXX: It is a POLA question whether calling tcp_drop right 1573 * away would be the really correct behavior instead. 1574 */ 1575 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1576 !tcp_timer_active(tp, TT_PERSIST)) && 1577 ((flags & TH_SYN) == 0) && 1578 (error != EPERM)) { 1579 if (sack_rxmit) { 1580 p->rxmit -= len; 1581 tp->sackhint.sack_bytes_rexmit -= len; 1582 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1583 ("sackhint bytes rtx >= 0")); 1584 } else 1585 tp->snd_nxt -= len; 1586 } 1587 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1588 switch (error) { 1589 case EACCES: 1590 tp->t_softerror = error; 1591 return (0); 1592 case EPERM: 1593 tp->t_softerror = error; 1594 return (error); 1595 case ENOBUFS: 1596 TCP_XMIT_TIMER_ASSERT(tp, len, flags); 1597 tp->snd_cwnd = tp->t_maxseg; 1598 return (0); 1599 case EMSGSIZE: 1600 /* 1601 * For some reason the interface we used initially 1602 * to send segments changed to another or lowered 1603 * its MTU. 1604 * If TSO was active we either got an interface 1605 * without TSO capabilits or TSO was turned off. 1606 * If we obtained mtu from ip_output() then update 1607 * it and try again. 1608 */ 1609 if (tso) 1610 tp->t_flags &= ~TF_TSO; 1611 if (mtu != 0) { 1612 tcp_mss_update(tp, -1, mtu, NULL, NULL); 1613 goto again; 1614 } 1615 return (error); 1616 case EHOSTDOWN: 1617 case EHOSTUNREACH: 1618 case ENETDOWN: 1619 case ENETUNREACH: 1620 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1621 tp->t_softerror = error; 1622 return (0); 1623 } 1624 /* FALLTHROUGH */ 1625 default: 1626 return (error); 1627 } 1628 } 1629 TCPSTAT_INC(tcps_sndtotal); 1630 1631 /* 1632 * Data sent (as far as we can tell). 1633 * If this advertises a larger window than any other segment, 1634 * then remember the size of the advertised window. 1635 * Any pending ACK has now been sent. 1636 */ 1637 if (SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1638 tp->rcv_adv = tp->rcv_nxt + recwin; 1639 tp->last_ack_sent = tp->rcv_nxt; 1640 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1641 if (tcp_timer_active(tp, TT_DELACK)) 1642 tcp_timer_activate(tp, TT_DELACK, 0); 1643 #if 0 1644 /* 1645 * This completely breaks TCP if newreno is turned on. What happens 1646 * is that if delayed-acks are turned on on the receiver, this code 1647 * on the transmitter effectively destroys the TCP window, forcing 1648 * it to four packets (1.5Kx4 = 6K window). 1649 */ 1650 if (sendalot && --maxburst) 1651 goto again; 1652 #endif 1653 if (sendalot) 1654 goto again; 1655 return (0); 1656 } 1657 1658 void 1659 tcp_setpersist(struct tcpcb *tp) 1660 { 1661 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1662 int tt; 1663 1664 tp->t_flags &= ~TF_PREVVALID; 1665 if (tcp_timer_active(tp, TT_REXMT)) 1666 panic("tcp_setpersist: retransmit pending"); 1667 /* 1668 * Start/restart persistence timer. 1669 */ 1670 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1671 tcp_persmin, tcp_persmax); 1672 tcp_timer_activate(tp, TT_PERSIST, tt); 1673 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1674 tp->t_rxtshift++; 1675 } 1676 1677 /* 1678 * Insert TCP options according to the supplied parameters to the place 1679 * optp in a consistent way. Can handle unaligned destinations. 1680 * 1681 * The order of the option processing is crucial for optimal packing and 1682 * alignment for the scarce option space. 1683 * 1684 * The optimal order for a SYN/SYN-ACK segment is: 1685 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1686 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1687 * 1688 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1689 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1690 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1691 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1692 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1693 */ 1694 int 1695 tcp_addoptions(struct tcpopt *to, u_char *optp) 1696 { 1697 u_int32_t mask, optlen = 0; 1698 1699 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1700 if ((to->to_flags & mask) != mask) 1701 continue; 1702 if (optlen == TCP_MAXOLEN) 1703 break; 1704 switch (to->to_flags & mask) { 1705 case TOF_MSS: 1706 while (optlen % 4) { 1707 optlen += TCPOLEN_NOP; 1708 *optp++ = TCPOPT_NOP; 1709 } 1710 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1711 continue; 1712 optlen += TCPOLEN_MAXSEG; 1713 *optp++ = TCPOPT_MAXSEG; 1714 *optp++ = TCPOLEN_MAXSEG; 1715 to->to_mss = htons(to->to_mss); 1716 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1717 optp += sizeof(to->to_mss); 1718 break; 1719 case TOF_SCALE: 1720 while (!optlen || optlen % 2 != 1) { 1721 optlen += TCPOLEN_NOP; 1722 *optp++ = TCPOPT_NOP; 1723 } 1724 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1725 continue; 1726 optlen += TCPOLEN_WINDOW; 1727 *optp++ = TCPOPT_WINDOW; 1728 *optp++ = TCPOLEN_WINDOW; 1729 *optp++ = to->to_wscale; 1730 break; 1731 case TOF_SACKPERM: 1732 while (optlen % 2) { 1733 optlen += TCPOLEN_NOP; 1734 *optp++ = TCPOPT_NOP; 1735 } 1736 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1737 continue; 1738 optlen += TCPOLEN_SACK_PERMITTED; 1739 *optp++ = TCPOPT_SACK_PERMITTED; 1740 *optp++ = TCPOLEN_SACK_PERMITTED; 1741 break; 1742 case TOF_TS: 1743 while (!optlen || optlen % 4 != 2) { 1744 optlen += TCPOLEN_NOP; 1745 *optp++ = TCPOPT_NOP; 1746 } 1747 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1748 continue; 1749 optlen += TCPOLEN_TIMESTAMP; 1750 *optp++ = TCPOPT_TIMESTAMP; 1751 *optp++ = TCPOLEN_TIMESTAMP; 1752 to->to_tsval = htonl(to->to_tsval); 1753 to->to_tsecr = htonl(to->to_tsecr); 1754 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1755 optp += sizeof(to->to_tsval); 1756 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1757 optp += sizeof(to->to_tsecr); 1758 break; 1759 case TOF_SIGNATURE: 1760 { 1761 int siglen = TCPOLEN_SIGNATURE - 2; 1762 1763 while (!optlen || optlen % 4 != 2) { 1764 optlen += TCPOLEN_NOP; 1765 *optp++ = TCPOPT_NOP; 1766 } 1767 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) { 1768 to->to_flags &= ~TOF_SIGNATURE; 1769 continue; 1770 } 1771 optlen += TCPOLEN_SIGNATURE; 1772 *optp++ = TCPOPT_SIGNATURE; 1773 *optp++ = TCPOLEN_SIGNATURE; 1774 to->to_signature = optp; 1775 while (siglen--) 1776 *optp++ = 0; 1777 break; 1778 } 1779 case TOF_SACK: 1780 { 1781 int sackblks = 0; 1782 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1783 tcp_seq sack_seq; 1784 1785 while (!optlen || optlen % 4 != 2) { 1786 optlen += TCPOLEN_NOP; 1787 *optp++ = TCPOPT_NOP; 1788 } 1789 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1790 continue; 1791 optlen += TCPOLEN_SACKHDR; 1792 *optp++ = TCPOPT_SACK; 1793 sackblks = min(to->to_nsacks, 1794 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1795 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1796 while (sackblks--) { 1797 sack_seq = htonl(sack->start); 1798 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1799 optp += sizeof(sack_seq); 1800 sack_seq = htonl(sack->end); 1801 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1802 optp += sizeof(sack_seq); 1803 optlen += TCPOLEN_SACK; 1804 sack++; 1805 } 1806 TCPSTAT_INC(tcps_sack_send_blocks); 1807 break; 1808 } 1809 #ifdef TCP_RFC7413 1810 case TOF_FASTOPEN: 1811 { 1812 int total_len; 1813 1814 /* XXX is there any point to aligning this option? */ 1815 total_len = TCPOLEN_FAST_OPEN_EMPTY + to->to_tfo_len; 1816 if (TCP_MAXOLEN - optlen < total_len) 1817 continue; 1818 *optp++ = TCPOPT_FAST_OPEN; 1819 *optp++ = total_len; 1820 if (to->to_tfo_len > 0) { 1821 bcopy(to->to_tfo_cookie, optp, to->to_tfo_len); 1822 optp += to->to_tfo_len; 1823 } 1824 optlen += total_len; 1825 break; 1826 } 1827 #endif 1828 default: 1829 panic("%s: unknown TCP option type", __func__); 1830 break; 1831 } 1832 } 1833 1834 /* Terminate and pad TCP options to a 4 byte boundary. */ 1835 if (optlen % 4) { 1836 optlen += TCPOLEN_EOL; 1837 *optp++ = TCPOPT_EOL; 1838 } 1839 /* 1840 * According to RFC 793 (STD0007): 1841 * "The content of the header beyond the End-of-Option option 1842 * must be header padding (i.e., zero)." 1843 * and later: "The padding is composed of zeros." 1844 */ 1845 while (optlen % 4) { 1846 optlen += TCPOLEN_PAD; 1847 *optp++ = TCPOPT_PAD; 1848 } 1849 1850 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1851 return (optlen); 1852 } 1853