1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 5 * The Regents of the University of California. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. Neither the name of the University nor the names of its contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 * 31 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95 32 */ 33 34 #include <sys/cdefs.h> 35 __FBSDID("$FreeBSD$"); 36 37 #include "opt_inet.h" 38 #include "opt_inet6.h" 39 #include "opt_ipsec.h" 40 #include "opt_tcpdebug.h" 41 42 #include <sys/param.h> 43 #include <sys/systm.h> 44 #include <sys/domain.h> 45 #ifdef TCP_HHOOK 46 #include <sys/hhook.h> 47 #endif 48 #include <sys/kernel.h> 49 #include <sys/lock.h> 50 #include <sys/mbuf.h> 51 #include <sys/mutex.h> 52 #include <sys/protosw.h> 53 #include <sys/sdt.h> 54 #include <sys/socket.h> 55 #include <sys/socketvar.h> 56 #include <sys/sysctl.h> 57 58 #include <net/if.h> 59 #include <net/route.h> 60 #include <net/vnet.h> 61 62 #include <netinet/in.h> 63 #include <netinet/in_kdtrace.h> 64 #include <netinet/in_systm.h> 65 #include <netinet/ip.h> 66 #include <netinet/in_pcb.h> 67 #include <netinet/ip_var.h> 68 #include <netinet/ip_options.h> 69 #ifdef INET6 70 #include <netinet6/in6_pcb.h> 71 #include <netinet/ip6.h> 72 #include <netinet6/ip6_var.h> 73 #endif 74 #include <netinet/tcp.h> 75 #define TCPOUTFLAGS 76 #include <netinet/tcp_fsm.h> 77 #include <netinet/tcp_log_buf.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 #include <netinet/tcp_fastopen.h> 84 #ifdef TCPPCAP 85 #include <netinet/tcp_pcap.h> 86 #endif 87 #ifdef TCPDEBUG 88 #include <netinet/tcp_debug.h> 89 #endif 90 #ifdef TCP_OFFLOAD 91 #include <netinet/tcp_offload.h> 92 #endif 93 94 #include <netipsec/ipsec_support.h> 95 96 #include <machine/in_cksum.h> 97 98 #include <security/mac/mac_framework.h> 99 100 VNET_DEFINE(int, path_mtu_discovery) = 1; 101 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_VNET | CTLFLAG_RW, 102 &VNET_NAME(path_mtu_discovery), 1, 103 "Enable Path MTU Discovery"); 104 105 VNET_DEFINE(int, tcp_do_tso) = 1; 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 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_VNET | CTLFLAG_RW, 117 &VNET_NAME(tcp_do_autosndbuf), 0, 118 "Enable automatic send buffer sizing"); 119 120 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024; 121 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_VNET | CTLFLAG_RW, 122 &VNET_NAME(tcp_autosndbuf_inc), 0, 123 "Incrementor step size of automatic send buffer"); 124 125 VNET_DEFINE(int, tcp_autosndbuf_max) = 2*1024*1024; 126 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_VNET | CTLFLAG_RW, 127 &VNET_NAME(tcp_autosndbuf_max), 0, 128 "Max size of automatic send buffer"); 129 130 VNET_DEFINE(int, tcp_sendbuf_auto_lowat) = 0; 131 #define V_tcp_sendbuf_auto_lowat VNET(tcp_sendbuf_auto_lowat) 132 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto_lowat, CTLFLAG_VNET | CTLFLAG_RW, 133 &VNET_NAME(tcp_sendbuf_auto_lowat), 0, 134 "Modify threshold for auto send buffer growth to account for SO_SNDLOWAT"); 135 136 /* 137 * Make sure that either retransmit or persist timer is set for SYN, FIN and 138 * non-ACK. 139 */ 140 #define TCP_XMIT_TIMER_ASSERT(tp, len, th_flags) \ 141 KASSERT(((len) == 0 && ((th_flags) & (TH_SYN | TH_FIN)) == 0) ||\ 142 tcp_timer_active((tp), TT_REXMT) || \ 143 tcp_timer_active((tp), TT_PERSIST), \ 144 ("neither rexmt nor persist timer is set")) 145 146 #ifdef TCP_HHOOK 147 static void inline hhook_run_tcp_est_out(struct tcpcb *tp, 148 struct tcphdr *th, struct tcpopt *to, 149 uint32_t len, int tso); 150 #endif 151 static void inline cc_after_idle(struct tcpcb *tp); 152 153 #ifdef TCP_HHOOK 154 /* 155 * Wrapper for the TCP established output helper hook. 156 */ 157 static void inline 158 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th, 159 struct tcpopt *to, uint32_t len, int tso) 160 { 161 struct tcp_hhook_data hhook_data; 162 163 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) { 164 hhook_data.tp = tp; 165 hhook_data.th = th; 166 hhook_data.to = to; 167 hhook_data.len = len; 168 hhook_data.tso = tso; 169 170 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data, 171 tp->osd); 172 } 173 } 174 #endif 175 176 /* 177 * CC wrapper hook functions 178 */ 179 static void inline 180 cc_after_idle(struct tcpcb *tp) 181 { 182 INP_WLOCK_ASSERT(tp->t_inpcb); 183 184 if (CC_ALGO(tp)->after_idle != NULL) 185 CC_ALGO(tp)->after_idle(tp->ccv); 186 } 187 188 /* 189 * Tcp output routine: figure out what should be sent and send it. 190 */ 191 int 192 tcp_output(struct tcpcb *tp) 193 { 194 struct socket *so = tp->t_inpcb->inp_socket; 195 int32_t len; 196 uint32_t recwin, sendwin; 197 int off, flags, error = 0; /* Keep compiler happy */ 198 struct mbuf *m; 199 struct ip *ip = NULL; 200 #ifdef TCPDEBUG 201 struct ipovly *ipov = NULL; 202 #endif 203 struct tcphdr *th; 204 u_char opt[TCP_MAXOLEN]; 205 unsigned ipoptlen, optlen, hdrlen; 206 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 207 unsigned ipsec_optlen = 0; 208 #endif 209 int idle, sendalot; 210 int sack_rxmit, sack_bytes_rxmt; 211 struct sackhole *p; 212 int tso, mtu; 213 struct tcpopt to; 214 unsigned int wanted_cookie = 0; 215 unsigned int dont_sendalot = 0; 216 #if 0 217 int maxburst = TCP_MAXBURST; 218 #endif 219 #ifdef INET6 220 struct ip6_hdr *ip6 = NULL; 221 int isipv6; 222 223 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 224 #endif 225 226 INP_WLOCK_ASSERT(tp->t_inpcb); 227 228 #ifdef TCP_OFFLOAD 229 if (tp->t_flags & TF_TOE) 230 return (tcp_offload_output(tp)); 231 #endif 232 233 /* 234 * For TFO connections in SYN_RECEIVED, only allow the initial 235 * SYN|ACK and those sent by the retransmit timer. 236 */ 237 if (IS_FASTOPEN(tp->t_flags) && 238 (tp->t_state == TCPS_SYN_RECEIVED) && 239 SEQ_GT(tp->snd_max, tp->snd_una) && /* initial SYN|ACK sent */ 240 (tp->snd_nxt != tp->snd_una)) /* not a retransmit */ 241 return (0); 242 243 /* 244 * Determine length of data that should be transmitted, 245 * and flags that will be used. 246 * If there is some data or critical controls (SYN, RST) 247 * to send, then transmit; otherwise, investigate further. 248 */ 249 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 250 if (idle && ticks - tp->t_rcvtime >= tp->t_rxtcur) 251 cc_after_idle(tp); 252 tp->t_flags &= ~TF_LASTIDLE; 253 if (idle) { 254 if (tp->t_flags & TF_MORETOCOME) { 255 tp->t_flags |= TF_LASTIDLE; 256 idle = 0; 257 } 258 } 259 again: 260 /* 261 * If we've recently taken a timeout, snd_max will be greater than 262 * snd_nxt. There may be SACK information that allows us to avoid 263 * resending already delivered data. Adjust snd_nxt accordingly. 264 */ 265 if ((tp->t_flags & TF_SACK_PERMIT) && 266 SEQ_LT(tp->snd_nxt, tp->snd_max)) 267 tcp_sack_adjust(tp); 268 sendalot = 0; 269 tso = 0; 270 mtu = 0; 271 off = tp->snd_nxt - tp->snd_una; 272 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 273 274 flags = tcp_outflags[tp->t_state]; 275 /* 276 * Send any SACK-generated retransmissions. If we're explicitly trying 277 * to send out new data (when sendalot is 1), bypass this function. 278 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 279 * we're replacing a (future) new transmission with a retransmission 280 * now, and we previously incremented snd_cwnd in tcp_input(). 281 */ 282 /* 283 * Still in sack recovery , reset rxmit flag to zero. 284 */ 285 sack_rxmit = 0; 286 sack_bytes_rxmt = 0; 287 len = 0; 288 p = NULL; 289 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) && 290 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 291 uint32_t cwin; 292 293 cwin = 294 imax(min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt, 0); 295 /* Do not retransmit SACK segments beyond snd_recover */ 296 if (SEQ_GT(p->end, tp->snd_recover)) { 297 /* 298 * (At least) part of sack hole extends beyond 299 * snd_recover. Check to see if we can rexmit data 300 * for this hole. 301 */ 302 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 303 /* 304 * Can't rexmit any more data for this hole. 305 * That data will be rexmitted in the next 306 * sack recovery episode, when snd_recover 307 * moves past p->rxmit. 308 */ 309 p = NULL; 310 goto after_sack_rexmit; 311 } else 312 /* Can rexmit part of the current hole */ 313 len = ((int32_t)ulmin(cwin, 314 tp->snd_recover - p->rxmit)); 315 } else 316 len = ((int32_t)ulmin(cwin, p->end - p->rxmit)); 317 off = p->rxmit - tp->snd_una; 318 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 319 __func__, off)); 320 if (len > 0) { 321 sack_rxmit = 1; 322 sendalot = 1; 323 TCPSTAT_INC(tcps_sack_rexmits); 324 TCPSTAT_ADD(tcps_sack_rexmit_bytes, 325 min(len, tp->t_maxseg)); 326 } 327 } 328 after_sack_rexmit: 329 /* 330 * Get standard flags, and add SYN or FIN if requested by 'hidden' 331 * state flags. 332 */ 333 if (tp->t_flags & TF_NEEDFIN) 334 flags |= TH_FIN; 335 if (tp->t_flags & TF_NEEDSYN) 336 flags |= TH_SYN; 337 338 SOCKBUF_LOCK(&so->so_snd); 339 /* 340 * If in persist timeout with window of 0, send 1 byte. 341 * Otherwise, if window is small but nonzero 342 * and timer expired, we will send what we can 343 * and go to transmit state. 344 */ 345 if (tp->t_flags & TF_FORCEDATA) { 346 if (sendwin == 0) { 347 /* 348 * If we still have some data to send, then 349 * clear the FIN bit. Usually this would 350 * happen below when it realizes that we 351 * aren't sending all the data. However, 352 * if we have exactly 1 byte of unsent data, 353 * then it won't clear the FIN bit below, 354 * and if we are in persist state, we wind 355 * up sending the packet without recording 356 * that we sent the FIN bit. 357 * 358 * We can't just blindly clear the FIN bit, 359 * because if we don't have any more data 360 * to send then the probe will be the FIN 361 * itself. 362 */ 363 if (off < sbused(&so->so_snd)) 364 flags &= ~TH_FIN; 365 sendwin = 1; 366 } else { 367 tcp_timer_activate(tp, TT_PERSIST, 0); 368 tp->t_rxtshift = 0; 369 } 370 } 371 372 /* 373 * If snd_nxt == snd_max and we have transmitted a FIN, the 374 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 375 * a negative length. This can also occur when TCP opens up 376 * its congestion window while receiving additional duplicate 377 * acks after fast-retransmit because TCP will reset snd_nxt 378 * to snd_max after the fast-retransmit. 379 * 380 * In the normal retransmit-FIN-only case, however, snd_nxt will 381 * be set to snd_una, the offset will be 0, and the length may 382 * wind up 0. 383 * 384 * If sack_rxmit is true we are retransmitting from the scoreboard 385 * in which case len is already set. 386 */ 387 if (sack_rxmit == 0) { 388 if (sack_bytes_rxmt == 0) 389 len = ((int32_t)min(sbavail(&so->so_snd), sendwin) - 390 off); 391 else { 392 int32_t cwin; 393 394 /* 395 * We are inside of a SACK recovery episode and are 396 * sending new data, having retransmitted all the 397 * data possible in the scoreboard. 398 */ 399 len = ((int32_t)min(sbavail(&so->so_snd), tp->snd_wnd) - 400 off); 401 /* 402 * Don't remove this (len > 0) check ! 403 * We explicitly check for len > 0 here (although it 404 * isn't really necessary), to work around a gcc 405 * optimization issue - to force gcc to compute 406 * len above. Without this check, the computation 407 * of len is bungled by the optimizer. 408 */ 409 if (len > 0) { 410 cwin = tp->snd_cwnd - 411 (tp->snd_nxt - tp->sack_newdata) - 412 sack_bytes_rxmt; 413 if (cwin < 0) 414 cwin = 0; 415 len = imin(len, cwin); 416 } 417 } 418 } 419 420 /* 421 * Lop off SYN bit if it has already been sent. However, if this 422 * is SYN-SENT state and if segment contains data and if we don't 423 * know that foreign host supports TAO, suppress sending segment. 424 */ 425 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 426 if (tp->t_state != TCPS_SYN_RECEIVED) 427 flags &= ~TH_SYN; 428 /* 429 * When sending additional segments following a TFO SYN|ACK, 430 * do not include the SYN bit. 431 */ 432 if (IS_FASTOPEN(tp->t_flags) && 433 (tp->t_state == TCPS_SYN_RECEIVED)) 434 flags &= ~TH_SYN; 435 off--, len++; 436 } 437 438 /* 439 * Be careful not to send data and/or FIN on SYN segments. 440 * This measure is needed to prevent interoperability problems 441 * with not fully conformant TCP implementations. 442 */ 443 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 444 len = 0; 445 flags &= ~TH_FIN; 446 } 447 448 /* 449 * On TFO sockets, ensure no data is sent in the following cases: 450 * 451 * - When retransmitting SYN|ACK on a passively-created socket 452 * 453 * - When retransmitting SYN on an actively created socket 454 * 455 * - When sending a zero-length cookie (cookie request) on an 456 * actively created socket 457 * 458 * - When the socket is in the CLOSED state (RST is being sent) 459 */ 460 if (IS_FASTOPEN(tp->t_flags) && 461 (((flags & TH_SYN) && (tp->t_rxtshift > 0)) || 462 ((tp->t_state == TCPS_SYN_SENT) && 463 (tp->t_tfo_client_cookie_len == 0)) || 464 (flags & TH_RST))) 465 len = 0; 466 if (len <= 0) { 467 /* 468 * If FIN has been sent but not acked, 469 * but we haven't been called to retransmit, 470 * len will be < 0. Otherwise, window shrank 471 * after we sent into it. If window shrank to 0, 472 * cancel pending retransmit, pull snd_nxt back 473 * to (closed) window, and set the persist timer 474 * if it isn't already going. If the window didn't 475 * close completely, just wait for an ACK. 476 * 477 * We also do a general check here to ensure that 478 * we will set the persist timer when we have data 479 * to send, but a 0-byte window. This makes sure 480 * the persist timer is set even if the packet 481 * hits one of the "goto send" lines below. 482 */ 483 len = 0; 484 if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) && 485 (off < (int) sbavail(&so->so_snd))) { 486 tcp_timer_activate(tp, TT_REXMT, 0); 487 tp->t_rxtshift = 0; 488 tp->snd_nxt = tp->snd_una; 489 if (!tcp_timer_active(tp, TT_PERSIST)) 490 tcp_setpersist(tp); 491 } 492 } 493 494 /* len will be >= 0 after this point. */ 495 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 496 497 tcp_sndbuf_autoscale(tp, so, sendwin); 498 499 /* 500 * Decide if we can use TCP Segmentation Offloading (if supported by 501 * hardware). 502 * 503 * TSO may only be used if we are in a pure bulk sending state. The 504 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 505 * IP options prevent using TSO. With TSO the TCP header is the same 506 * (except for the sequence number) for all generated packets. This 507 * makes it impossible to transmit any options which vary per generated 508 * segment or packet. 509 * 510 * IPv4 handling has a clear separation of ip options and ip header 511 * flags while IPv6 combines both in in6p_outputopts. ip6_optlen() does 512 * the right thing below to provide length of just ip options and thus 513 * checking for ipoptlen is enough to decide if ip options are present. 514 */ 515 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 516 /* 517 * Pre-calculate here as we save another lookup into the darknesses 518 * of IPsec that way and can actually decide if TSO is ok. 519 */ 520 #ifdef INET6 521 if (isipv6 && IPSEC_ENABLED(ipv6)) 522 ipsec_optlen = IPSEC_HDRSIZE(ipv6, tp->t_inpcb); 523 #ifdef INET 524 else 525 #endif 526 #endif /* INET6 */ 527 #ifdef INET 528 if (IPSEC_ENABLED(ipv4)) 529 ipsec_optlen = IPSEC_HDRSIZE(ipv4, tp->t_inpcb); 530 #endif /* INET */ 531 #endif /* IPSEC */ 532 #ifdef INET6 533 if (isipv6) 534 ipoptlen = ip6_optlen(tp->t_inpcb); 535 else 536 #endif 537 if (tp->t_inpcb->inp_options) 538 ipoptlen = tp->t_inpcb->inp_options->m_len - 539 offsetof(struct ipoption, ipopt_list); 540 else 541 ipoptlen = 0; 542 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 543 ipoptlen += ipsec_optlen; 544 #endif 545 546 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg && 547 ((tp->t_flags & TF_SIGNATURE) == 0) && 548 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 549 ipoptlen == 0 && !(flags & TH_SYN)) 550 tso = 1; 551 552 if (sack_rxmit) { 553 if (SEQ_LT(p->rxmit + len, tp->snd_una + sbused(&so->so_snd))) 554 flags &= ~TH_FIN; 555 } else { 556 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + 557 sbused(&so->so_snd))) 558 flags &= ~TH_FIN; 559 } 560 561 recwin = lmin(lmax(sbspace(&so->so_rcv), 0), 562 (long)TCP_MAXWIN << tp->rcv_scale); 563 564 /* 565 * Sender silly window avoidance. We transmit under the following 566 * conditions when len is non-zero: 567 * 568 * - We have a full segment (or more with TSO) 569 * - This is the last buffer in a write()/send() and we are 570 * either idle or running NODELAY 571 * - we've timed out (e.g. persist timer) 572 * - we have more then 1/2 the maximum send window's worth of 573 * data (receiver may be limited the window size) 574 * - we need to retransmit 575 */ 576 if (len) { 577 if (len >= tp->t_maxseg) 578 goto send; 579 /* 580 * NOTE! on localhost connections an 'ack' from the remote 581 * end may occur synchronously with the output and cause 582 * us to flush a buffer queued with moretocome. XXX 583 * 584 * note: the len + off check is almost certainly unnecessary. 585 */ 586 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 587 (idle || (tp->t_flags & TF_NODELAY)) && 588 (uint32_t)len + (uint32_t)off >= sbavail(&so->so_snd) && 589 (tp->t_flags & TF_NOPUSH) == 0) { 590 goto send; 591 } 592 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 593 goto send; 594 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 595 goto send; 596 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 597 goto send; 598 if (sack_rxmit) 599 goto send; 600 } 601 602 /* 603 * Sending of standalone window updates. 604 * 605 * Window updates are important when we close our window due to a 606 * full socket buffer and are opening it again after the application 607 * reads data from it. Once the window has opened again and the 608 * remote end starts to send again the ACK clock takes over and 609 * provides the most current window information. 610 * 611 * We must avoid the silly window syndrome whereas every read 612 * from the receive buffer, no matter how small, causes a window 613 * update to be sent. We also should avoid sending a flurry of 614 * window updates when the socket buffer had queued a lot of data 615 * and the application is doing small reads. 616 * 617 * Prevent a flurry of pointless window updates by only sending 618 * an update when we can increase the advertized window by more 619 * than 1/4th of the socket buffer capacity. When the buffer is 620 * getting full or is very small be more aggressive and send an 621 * update whenever we can increase by two mss sized segments. 622 * In all other situations the ACK's to new incoming data will 623 * carry further window increases. 624 * 625 * Don't send an independent window update if a delayed 626 * ACK is pending (it will get piggy-backed on it) or the 627 * remote side already has done a half-close and won't send 628 * more data. Skip this if the connection is in T/TCP 629 * half-open state. 630 */ 631 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 632 !(tp->t_flags & TF_DELACK) && 633 !TCPS_HAVERCVDFIN(tp->t_state)) { 634 /* 635 * "adv" is the amount we could increase the window, 636 * taking into account that we are limited by 637 * TCP_MAXWIN << tp->rcv_scale. 638 */ 639 int32_t adv; 640 int oldwin; 641 642 adv = recwin; 643 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { 644 oldwin = (tp->rcv_adv - tp->rcv_nxt); 645 adv -= oldwin; 646 } else 647 oldwin = 0; 648 649 /* 650 * If the new window size ends up being the same as or less 651 * than the old size when it is scaled, then don't force 652 * a window update. 653 */ 654 if (oldwin >> tp->rcv_scale >= (adv + oldwin) >> tp->rcv_scale) 655 goto dontupdate; 656 657 if (adv >= (int32_t)(2 * tp->t_maxseg) && 658 (adv >= (int32_t)(so->so_rcv.sb_hiwat / 4) || 659 recwin <= (so->so_rcv.sb_hiwat / 8) || 660 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg)) 661 goto send; 662 if (2 * adv >= (int32_t)so->so_rcv.sb_hiwat) 663 goto send; 664 } 665 dontupdate: 666 667 /* 668 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 669 * is also a catch-all for the retransmit timer timeout case. 670 */ 671 if (tp->t_flags & TF_ACKNOW) 672 goto send; 673 if ((flags & TH_RST) || 674 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 675 goto send; 676 if (SEQ_GT(tp->snd_up, tp->snd_una)) 677 goto send; 678 /* 679 * If our state indicates that FIN should be sent 680 * and we have not yet done so, then we need to send. 681 */ 682 if (flags & TH_FIN && 683 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 684 goto send; 685 /* 686 * In SACK, it is possible for tcp_output to fail to send a segment 687 * after the retransmission timer has been turned off. Make sure 688 * that the retransmission timer is set. 689 */ 690 if ((tp->t_flags & TF_SACK_PERMIT) && 691 SEQ_GT(tp->snd_max, tp->snd_una) && 692 !tcp_timer_active(tp, TT_REXMT) && 693 !tcp_timer_active(tp, TT_PERSIST)) { 694 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 695 goto just_return; 696 } 697 /* 698 * TCP window updates are not reliable, rather a polling protocol 699 * using ``persist'' packets is used to insure receipt of window 700 * updates. The three ``states'' for the output side are: 701 * idle not doing retransmits or persists 702 * persisting to move a small or zero window 703 * (re)transmitting and thereby not persisting 704 * 705 * tcp_timer_active(tp, TT_PERSIST) 706 * is true when we are in persist state. 707 * (tp->t_flags & TF_FORCEDATA) 708 * is set when we are called to send a persist packet. 709 * tcp_timer_active(tp, TT_REXMT) 710 * is set when we are retransmitting 711 * The output side is idle when both timers are zero. 712 * 713 * If send window is too small, there is data to transmit, and no 714 * retransmit or persist is pending, then go to persist state. 715 * If nothing happens soon, send when timer expires: 716 * if window is nonzero, transmit what we can, 717 * otherwise force out a byte. 718 */ 719 if (sbavail(&so->so_snd) && !tcp_timer_active(tp, TT_REXMT) && 720 !tcp_timer_active(tp, TT_PERSIST)) { 721 tp->t_rxtshift = 0; 722 tcp_setpersist(tp); 723 } 724 725 /* 726 * No reason to send a segment, just return. 727 */ 728 just_return: 729 SOCKBUF_UNLOCK(&so->so_snd); 730 return (0); 731 732 send: 733 SOCKBUF_LOCK_ASSERT(&so->so_snd); 734 if (len > 0) { 735 if (len >= tp->t_maxseg) 736 tp->t_flags2 |= TF2_PLPMTU_MAXSEGSNT; 737 else 738 tp->t_flags2 &= ~TF2_PLPMTU_MAXSEGSNT; 739 } 740 /* 741 * Before ESTABLISHED, force sending of initial options 742 * unless TCP set not to do any options. 743 * NOTE: we assume that the IP/TCP header plus TCP options 744 * always fit in a single mbuf, leaving room for a maximum 745 * link header, i.e. 746 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 747 */ 748 optlen = 0; 749 #ifdef INET6 750 if (isipv6) 751 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 752 else 753 #endif 754 hdrlen = sizeof (struct tcpiphdr); 755 756 /* 757 * Compute options for segment. 758 * We only have to care about SYN and established connection 759 * segments. Options for SYN-ACK segments are handled in TCP 760 * syncache. 761 */ 762 to.to_flags = 0; 763 if ((tp->t_flags & TF_NOOPT) == 0) { 764 /* Maximum segment size. */ 765 if (flags & TH_SYN) { 766 tp->snd_nxt = tp->iss; 767 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 768 to.to_flags |= TOF_MSS; 769 770 /* 771 * On SYN or SYN|ACK transmits on TFO connections, 772 * only include the TFO option if it is not a 773 * retransmit, as the presence of the TFO option may 774 * have caused the original SYN or SYN|ACK to have 775 * been dropped by a middlebox. 776 */ 777 if (IS_FASTOPEN(tp->t_flags) && 778 (tp->t_rxtshift == 0)) { 779 if (tp->t_state == TCPS_SYN_RECEIVED) { 780 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN; 781 to.to_tfo_cookie = 782 (u_int8_t *)&tp->t_tfo_cookie.server; 783 to.to_flags |= TOF_FASTOPEN; 784 wanted_cookie = 1; 785 } else if (tp->t_state == TCPS_SYN_SENT) { 786 to.to_tfo_len = 787 tp->t_tfo_client_cookie_len; 788 to.to_tfo_cookie = 789 tp->t_tfo_cookie.client; 790 to.to_flags |= TOF_FASTOPEN; 791 wanted_cookie = 1; 792 /* 793 * If we wind up having more data to 794 * send with the SYN than can fit in 795 * one segment, don't send any more 796 * until the SYN|ACK comes back from 797 * the other end. 798 */ 799 dont_sendalot = 1; 800 } 801 } 802 } 803 /* Window scaling. */ 804 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 805 to.to_wscale = tp->request_r_scale; 806 to.to_flags |= TOF_SCALE; 807 } 808 /* Timestamps. */ 809 if ((tp->t_flags & TF_RCVD_TSTMP) || 810 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 811 to.to_tsval = tcp_ts_getticks() + tp->ts_offset; 812 to.to_tsecr = tp->ts_recent; 813 to.to_flags |= TOF_TS; 814 } 815 816 /* Set receive buffer autosizing timestamp. */ 817 if (tp->rfbuf_ts == 0 && 818 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 819 tp->rfbuf_ts = tcp_ts_getticks(); 820 821 /* Selective ACK's. */ 822 if (tp->t_flags & TF_SACK_PERMIT) { 823 if (flags & TH_SYN) 824 to.to_flags |= TOF_SACKPERM; 825 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 826 (tp->t_flags & TF_SACK_PERMIT) && 827 tp->rcv_numsacks > 0) { 828 to.to_flags |= TOF_SACK; 829 to.to_nsacks = tp->rcv_numsacks; 830 to.to_sacks = (u_char *)tp->sackblks; 831 } 832 } 833 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 834 /* TCP-MD5 (RFC2385). */ 835 /* 836 * Check that TCP_MD5SIG is enabled in tcpcb to 837 * account the size needed to set this TCP option. 838 */ 839 if (tp->t_flags & TF_SIGNATURE) 840 to.to_flags |= TOF_SIGNATURE; 841 #endif /* TCP_SIGNATURE */ 842 843 /* Processing the options. */ 844 hdrlen += optlen = tcp_addoptions(&to, opt); 845 /* 846 * If we wanted a TFO option to be added, but it was unable 847 * to fit, ensure no data is sent. 848 */ 849 if (IS_FASTOPEN(tp->t_flags) && wanted_cookie && 850 !(to.to_flags & TOF_FASTOPEN)) 851 len = 0; 852 } 853 854 /* 855 * Adjust data length if insertion of options will 856 * bump the packet length beyond the t_maxseg length. 857 * Clear the FIN bit because we cut off the tail of 858 * the segment. 859 */ 860 if (len + optlen + ipoptlen > tp->t_maxseg) { 861 flags &= ~TH_FIN; 862 863 if (tso) { 864 u_int if_hw_tsomax; 865 u_int if_hw_tsomaxsegcount; 866 u_int if_hw_tsomaxsegsize; 867 struct mbuf *mb; 868 u_int moff; 869 int max_len; 870 871 /* extract TSO information */ 872 if_hw_tsomax = tp->t_tsomax; 873 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount; 874 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize; 875 876 /* 877 * Limit a TSO burst to prevent it from 878 * overflowing or exceeding the maximum length 879 * allowed by the network interface: 880 */ 881 KASSERT(ipoptlen == 0, 882 ("%s: TSO can't do IP options", __func__)); 883 884 /* 885 * Check if we should limit by maximum payload 886 * length: 887 */ 888 if (if_hw_tsomax != 0) { 889 /* compute maximum TSO length */ 890 max_len = (if_hw_tsomax - hdrlen - 891 max_linkhdr); 892 if (max_len <= 0) { 893 len = 0; 894 } else if (len > max_len) { 895 sendalot = 1; 896 len = max_len; 897 } 898 } 899 900 /* 901 * Check if we should limit by maximum segment 902 * size and count: 903 */ 904 if (if_hw_tsomaxsegcount != 0 && 905 if_hw_tsomaxsegsize != 0) { 906 /* 907 * Subtract one segment for the LINK 908 * and TCP/IP headers mbuf that will 909 * be prepended to this mbuf chain 910 * after the code in this section 911 * limits the number of mbufs in the 912 * chain to if_hw_tsomaxsegcount. 913 */ 914 if_hw_tsomaxsegcount -= 1; 915 max_len = 0; 916 mb = sbsndmbuf(&so->so_snd, off, &moff); 917 918 while (mb != NULL && max_len < len) { 919 u_int mlen; 920 u_int frags; 921 922 /* 923 * Get length of mbuf fragment 924 * and how many hardware frags, 925 * rounded up, it would use: 926 */ 927 mlen = (mb->m_len - moff); 928 frags = howmany(mlen, 929 if_hw_tsomaxsegsize); 930 931 /* Handle special case: Zero Length Mbuf */ 932 if (frags == 0) 933 frags = 1; 934 935 /* 936 * Check if the fragment limit 937 * will be reached or exceeded: 938 */ 939 if (frags >= if_hw_tsomaxsegcount) { 940 max_len += min(mlen, 941 if_hw_tsomaxsegcount * 942 if_hw_tsomaxsegsize); 943 break; 944 } 945 max_len += mlen; 946 if_hw_tsomaxsegcount -= frags; 947 moff = 0; 948 mb = mb->m_next; 949 } 950 if (max_len <= 0) { 951 len = 0; 952 } else if (len > max_len) { 953 sendalot = 1; 954 len = max_len; 955 } 956 } 957 958 /* 959 * Prevent the last segment from being 960 * fractional unless the send sockbuf can be 961 * emptied: 962 */ 963 max_len = (tp->t_maxseg - optlen); 964 if (((uint32_t)off + (uint32_t)len) < 965 sbavail(&so->so_snd)) { 966 moff = len % max_len; 967 if (moff != 0) { 968 len -= moff; 969 sendalot = 1; 970 } 971 } 972 973 /* 974 * In case there are too many small fragments 975 * don't use TSO: 976 */ 977 if (len <= max_len) { 978 len = max_len; 979 sendalot = 1; 980 tso = 0; 981 } 982 983 /* 984 * Send the FIN in a separate segment 985 * after the bulk sending is done. 986 * We don't trust the TSO implementations 987 * to clear the FIN flag on all but the 988 * last segment. 989 */ 990 if (tp->t_flags & TF_NEEDFIN) 991 sendalot = 1; 992 993 } else { 994 len = tp->t_maxseg - optlen - ipoptlen; 995 sendalot = 1; 996 if (dont_sendalot) 997 sendalot = 0; 998 } 999 } else 1000 tso = 0; 1001 1002 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 1003 ("%s: len > IP_MAXPACKET", __func__)); 1004 1005 /*#ifdef DIAGNOSTIC*/ 1006 #ifdef INET6 1007 if (max_linkhdr + hdrlen > MCLBYTES) 1008 #else 1009 if (max_linkhdr + hdrlen > MHLEN) 1010 #endif 1011 panic("tcphdr too big"); 1012 /*#endif*/ 1013 1014 /* 1015 * This KASSERT is here to catch edge cases at a well defined place. 1016 * Before, those had triggered (random) panic conditions further down. 1017 */ 1018 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 1019 1020 /* 1021 * Grab a header mbuf, attaching a copy of data to 1022 * be transmitted, and initialize the header from 1023 * the template for sends on this connection. 1024 */ 1025 if (len) { 1026 struct mbuf *mb; 1027 u_int moff; 1028 1029 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 1030 TCPSTAT_INC(tcps_sndprobe); 1031 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 1032 tp->t_sndrexmitpack++; 1033 TCPSTAT_INC(tcps_sndrexmitpack); 1034 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 1035 } else { 1036 TCPSTAT_INC(tcps_sndpack); 1037 TCPSTAT_ADD(tcps_sndbyte, len); 1038 } 1039 #ifdef INET6 1040 if (MHLEN < hdrlen + max_linkhdr) 1041 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR); 1042 else 1043 #endif 1044 m = m_gethdr(M_NOWAIT, MT_DATA); 1045 1046 if (m == NULL) { 1047 SOCKBUF_UNLOCK(&so->so_snd); 1048 error = ENOBUFS; 1049 sack_rxmit = 0; 1050 goto out; 1051 } 1052 1053 m->m_data += max_linkhdr; 1054 m->m_len = hdrlen; 1055 1056 /* 1057 * Start the m_copy functions from the closest mbuf 1058 * to the offset in the socket buffer chain. 1059 */ 1060 mb = sbsndptr(&so->so_snd, off, len, &moff); 1061 1062 if (len <= MHLEN - hdrlen - max_linkhdr) { 1063 m_copydata(mb, moff, len, 1064 mtod(m, caddr_t) + hdrlen); 1065 m->m_len += len; 1066 } else { 1067 m->m_next = m_copym(mb, moff, len, M_NOWAIT); 1068 if (m->m_next == NULL) { 1069 SOCKBUF_UNLOCK(&so->so_snd); 1070 (void) m_free(m); 1071 error = ENOBUFS; 1072 sack_rxmit = 0; 1073 goto out; 1074 } 1075 } 1076 1077 /* 1078 * If we're sending everything we've got, set PUSH. 1079 * (This will keep happy those implementations which only 1080 * give data to the user when a buffer fills or 1081 * a PUSH comes in.) 1082 */ 1083 if (((uint32_t)off + (uint32_t)len == sbused(&so->so_snd)) && 1084 !(flags & TH_SYN)) 1085 flags |= TH_PUSH; 1086 SOCKBUF_UNLOCK(&so->so_snd); 1087 } else { 1088 SOCKBUF_UNLOCK(&so->so_snd); 1089 if (tp->t_flags & TF_ACKNOW) 1090 TCPSTAT_INC(tcps_sndacks); 1091 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 1092 TCPSTAT_INC(tcps_sndctrl); 1093 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 1094 TCPSTAT_INC(tcps_sndurg); 1095 else 1096 TCPSTAT_INC(tcps_sndwinup); 1097 1098 m = m_gethdr(M_NOWAIT, MT_DATA); 1099 if (m == NULL) { 1100 error = ENOBUFS; 1101 sack_rxmit = 0; 1102 goto out; 1103 } 1104 #ifdef INET6 1105 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 1106 MHLEN >= hdrlen) { 1107 M_ALIGN(m, hdrlen); 1108 } else 1109 #endif 1110 m->m_data += max_linkhdr; 1111 m->m_len = hdrlen; 1112 } 1113 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 1114 m->m_pkthdr.rcvif = (struct ifnet *)0; 1115 #ifdef MAC 1116 mac_inpcb_create_mbuf(tp->t_inpcb, m); 1117 #endif 1118 #ifdef INET6 1119 if (isipv6) { 1120 ip6 = mtod(m, struct ip6_hdr *); 1121 th = (struct tcphdr *)(ip6 + 1); 1122 tcpip_fillheaders(tp->t_inpcb, ip6, th); 1123 } else 1124 #endif /* INET6 */ 1125 { 1126 ip = mtod(m, struct ip *); 1127 #ifdef TCPDEBUG 1128 ipov = (struct ipovly *)ip; 1129 #endif 1130 th = (struct tcphdr *)(ip + 1); 1131 tcpip_fillheaders(tp->t_inpcb, ip, th); 1132 } 1133 1134 /* 1135 * Fill in fields, remembering maximum advertised 1136 * window for use in delaying messages about window sizes. 1137 * If resending a FIN, be sure not to use a new sequence number. 1138 */ 1139 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 1140 tp->snd_nxt == tp->snd_max) 1141 tp->snd_nxt--; 1142 /* 1143 * If we are starting a connection, send ECN setup 1144 * SYN packet. If we are on a retransmit, we may 1145 * resend those bits a number of times as per 1146 * RFC 3168. 1147 */ 1148 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn == 1) { 1149 if (tp->t_rxtshift >= 1) { 1150 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 1151 flags |= TH_ECE|TH_CWR; 1152 } else 1153 flags |= TH_ECE|TH_CWR; 1154 } 1155 1156 if (tp->t_state == TCPS_ESTABLISHED && 1157 (tp->t_flags & TF_ECN_PERMIT)) { 1158 /* 1159 * If the peer has ECN, mark data packets with 1160 * ECN capable transmission (ECT). 1161 * Ignore pure ack packets, retransmissions and window probes. 1162 */ 1163 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 1164 !((tp->t_flags & TF_FORCEDATA) && len == 1)) { 1165 #ifdef INET6 1166 if (isipv6) 1167 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 1168 else 1169 #endif 1170 ip->ip_tos |= IPTOS_ECN_ECT0; 1171 TCPSTAT_INC(tcps_ecn_ect0); 1172 } 1173 1174 /* 1175 * Reply with proper ECN notifications. 1176 */ 1177 if (tp->t_flags & TF_ECN_SND_CWR) { 1178 flags |= TH_CWR; 1179 tp->t_flags &= ~TF_ECN_SND_CWR; 1180 } 1181 if (tp->t_flags & TF_ECN_SND_ECE) 1182 flags |= TH_ECE; 1183 } 1184 1185 /* 1186 * If we are doing retransmissions, then snd_nxt will 1187 * not reflect the first unsent octet. For ACK only 1188 * packets, we do not want the sequence number of the 1189 * retransmitted packet, we want the sequence number 1190 * of the next unsent octet. So, if there is no data 1191 * (and no SYN or FIN), use snd_max instead of snd_nxt 1192 * when filling in ti_seq. But if we are in persist 1193 * state, snd_max might reflect one byte beyond the 1194 * right edge of the window, so use snd_nxt in that 1195 * case, since we know we aren't doing a retransmission. 1196 * (retransmit and persist are mutually exclusive...) 1197 */ 1198 if (sack_rxmit == 0) { 1199 if (len || (flags & (TH_SYN|TH_FIN)) || 1200 tcp_timer_active(tp, TT_PERSIST)) 1201 th->th_seq = htonl(tp->snd_nxt); 1202 else 1203 th->th_seq = htonl(tp->snd_max); 1204 } else { 1205 th->th_seq = htonl(p->rxmit); 1206 p->rxmit += len; 1207 tp->sackhint.sack_bytes_rexmit += len; 1208 } 1209 th->th_ack = htonl(tp->rcv_nxt); 1210 if (optlen) { 1211 bcopy(opt, th + 1, optlen); 1212 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1213 } 1214 th->th_flags = flags; 1215 /* 1216 * Calculate receive window. Don't shrink window, 1217 * but avoid silly window syndrome. 1218 */ 1219 if (recwin < (so->so_rcv.sb_hiwat / 4) && 1220 recwin < tp->t_maxseg) 1221 recwin = 0; 1222 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1223 recwin < (tp->rcv_adv - tp->rcv_nxt)) 1224 recwin = (tp->rcv_adv - tp->rcv_nxt); 1225 1226 /* 1227 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1228 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1229 * case is handled in syncache. 1230 */ 1231 if (flags & TH_SYN) 1232 th->th_win = htons((u_short) 1233 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1234 else 1235 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1236 1237 /* 1238 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1239 * a 0 window. This may cause the remote transmitter to stall. This 1240 * flag tells soreceive() to disable delayed acknowledgements when 1241 * draining the buffer. This can occur if the receiver is attempting 1242 * to read more data than can be buffered prior to transmitting on 1243 * the connection. 1244 */ 1245 if (th->th_win == 0) { 1246 tp->t_sndzerowin++; 1247 tp->t_flags |= TF_RXWIN0SENT; 1248 } else 1249 tp->t_flags &= ~TF_RXWIN0SENT; 1250 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1251 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1252 th->th_flags |= TH_URG; 1253 } else 1254 /* 1255 * If no urgent pointer to send, then we pull 1256 * the urgent pointer to the left edge of the send window 1257 * so that it doesn't drift into the send window on sequence 1258 * number wraparound. 1259 */ 1260 tp->snd_up = tp->snd_una; /* drag it along */ 1261 1262 /* 1263 * Put TCP length in extended header, and then 1264 * checksum extended header and data. 1265 */ 1266 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1267 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1268 1269 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1270 if (to.to_flags & TOF_SIGNATURE) { 1271 /* 1272 * Calculate MD5 signature and put it into the place 1273 * determined before. 1274 * NOTE: since TCP options buffer doesn't point into 1275 * mbuf's data, calculate offset and use it. 1276 */ 1277 if (!TCPMD5_ENABLED() || (error = TCPMD5_OUTPUT(m, th, 1278 (u_char *)(th + 1) + (to.to_signature - opt))) != 0) { 1279 /* 1280 * Do not send segment if the calculation of MD5 1281 * digest has failed. 1282 */ 1283 m_freem(m); 1284 goto out; 1285 } 1286 } 1287 #endif 1288 #ifdef INET6 1289 if (isipv6) { 1290 /* 1291 * There is no need to fill in ip6_plen right now. 1292 * It will be filled later by ip6_output. 1293 */ 1294 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1295 th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) + 1296 optlen + len, IPPROTO_TCP, 0); 1297 } 1298 #endif 1299 #if defined(INET6) && defined(INET) 1300 else 1301 #endif 1302 #ifdef INET 1303 { 1304 m->m_pkthdr.csum_flags = CSUM_TCP; 1305 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1306 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1307 1308 /* IP version must be set here for ipv4/ipv6 checking later */ 1309 KASSERT(ip->ip_v == IPVERSION, 1310 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1311 } 1312 #endif 1313 1314 /* 1315 * Enable TSO and specify the size of the segments. 1316 * The TCP pseudo header checksum is always provided. 1317 */ 1318 if (tso) { 1319 KASSERT(len > tp->t_maxseg - optlen, 1320 ("%s: len <= tso_segsz", __func__)); 1321 m->m_pkthdr.csum_flags |= CSUM_TSO; 1322 m->m_pkthdr.tso_segsz = tp->t_maxseg - optlen; 1323 } 1324 1325 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 1326 KASSERT(len + hdrlen + ipoptlen - ipsec_optlen == m_length(m, NULL), 1327 ("%s: mbuf chain shorter than expected: %d + %u + %u - %u != %u", 1328 __func__, len, hdrlen, ipoptlen, ipsec_optlen, m_length(m, NULL))); 1329 #else 1330 KASSERT(len + hdrlen + ipoptlen == m_length(m, NULL), 1331 ("%s: mbuf chain shorter than expected: %d + %u + %u != %u", 1332 __func__, len, hdrlen, ipoptlen, m_length(m, NULL))); 1333 #endif 1334 1335 #ifdef TCP_HHOOK 1336 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1337 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1338 #endif 1339 1340 #ifdef TCPDEBUG 1341 /* 1342 * Trace. 1343 */ 1344 if (so->so_options & SO_DEBUG) { 1345 u_short save = 0; 1346 #ifdef INET6 1347 if (!isipv6) 1348 #endif 1349 { 1350 save = ipov->ih_len; 1351 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1352 } 1353 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1354 #ifdef INET6 1355 if (!isipv6) 1356 #endif 1357 ipov->ih_len = save; 1358 } 1359 #endif /* TCPDEBUG */ 1360 TCP_PROBE3(debug__output, tp, th, m); 1361 1362 /* We're getting ready to send; log now. */ 1363 TCP_LOG_EVENT(tp, th, &so->so_rcv, &so->so_snd, TCP_LOG_OUT, ERRNO_UNK, 1364 len, NULL, false); 1365 1366 /* 1367 * Fill in IP length and desired time to live and 1368 * send to IP level. There should be a better way 1369 * to handle ttl and tos; we could keep them in 1370 * the template, but need a way to checksum without them. 1371 */ 1372 /* 1373 * m->m_pkthdr.len should have been set before checksum calculation, 1374 * because in6_cksum() need it. 1375 */ 1376 #ifdef INET6 1377 if (isipv6) { 1378 /* 1379 * we separately set hoplimit for every segment, since the 1380 * user might want to change the value via setsockopt. 1381 * Also, desired default hop limit might be changed via 1382 * Neighbor Discovery. 1383 */ 1384 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1385 1386 /* 1387 * Set the packet size here for the benefit of DTrace probes. 1388 * ip6_output() will set it properly; it's supposed to include 1389 * the option header lengths as well. 1390 */ 1391 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6)); 1392 1393 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) 1394 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1395 else 1396 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1397 1398 if (tp->t_state == TCPS_SYN_SENT) 1399 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th); 1400 1401 TCP_PROBE5(send, NULL, tp, ip6, tp, th); 1402 1403 #ifdef TCPPCAP 1404 /* Save packet, if requested. */ 1405 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1406 #endif 1407 1408 /* TODO: IPv6 IP6TOS_ECT bit on */ 1409 error = ip6_output(m, tp->t_inpcb->in6p_outputopts, 1410 &tp->t_inpcb->inp_route6, 1411 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 1412 NULL, NULL, tp->t_inpcb); 1413 1414 if (error == EMSGSIZE && tp->t_inpcb->inp_route6.ro_rt != NULL) 1415 mtu = tp->t_inpcb->inp_route6.ro_rt->rt_mtu; 1416 } 1417 #endif /* INET6 */ 1418 #if defined(INET) && defined(INET6) 1419 else 1420 #endif 1421 #ifdef INET 1422 { 1423 ip->ip_len = htons(m->m_pkthdr.len); 1424 #ifdef INET6 1425 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1426 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1427 #endif /* INET6 */ 1428 /* 1429 * If we do path MTU discovery, then we set DF on every packet. 1430 * This might not be the best thing to do according to RFC3390 1431 * Section 2. However the tcp hostcache migitates the problem 1432 * so it affects only the first tcp connection with a host. 1433 * 1434 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1435 */ 1436 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) { 1437 ip->ip_off |= htons(IP_DF); 1438 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1439 } else { 1440 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1441 } 1442 1443 if (tp->t_state == TCPS_SYN_SENT) 1444 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th); 1445 1446 TCP_PROBE5(send, NULL, tp, ip, tp, th); 1447 1448 #ifdef TCPPCAP 1449 /* Save packet, if requested. */ 1450 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1451 #endif 1452 1453 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, 1454 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1455 tp->t_inpcb); 1456 1457 if (error == EMSGSIZE && tp->t_inpcb->inp_route.ro_rt != NULL) 1458 mtu = tp->t_inpcb->inp_route.ro_rt->rt_mtu; 1459 } 1460 #endif /* INET */ 1461 1462 out: 1463 /* 1464 * In transmit state, time the transmission and arrange for 1465 * the retransmit. In persist state, just set snd_max. 1466 */ 1467 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1468 !tcp_timer_active(tp, TT_PERSIST)) { 1469 tcp_seq startseq = tp->snd_nxt; 1470 1471 /* 1472 * Advance snd_nxt over sequence space of this segment. 1473 */ 1474 if (flags & (TH_SYN|TH_FIN)) { 1475 if (flags & TH_SYN) 1476 tp->snd_nxt++; 1477 if (flags & TH_FIN) { 1478 tp->snd_nxt++; 1479 tp->t_flags |= TF_SENTFIN; 1480 } 1481 } 1482 if (sack_rxmit) 1483 goto timer; 1484 tp->snd_nxt += len; 1485 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1486 tp->snd_max = tp->snd_nxt; 1487 /* 1488 * Time this transmission if not a retransmission and 1489 * not currently timing anything. 1490 */ 1491 if (tp->t_rtttime == 0) { 1492 tp->t_rtttime = ticks; 1493 tp->t_rtseq = startseq; 1494 TCPSTAT_INC(tcps_segstimed); 1495 } 1496 } 1497 1498 /* 1499 * Set retransmit timer if not currently set, 1500 * and not doing a pure ack or a keep-alive probe. 1501 * Initial value for retransmit timer is smoothed 1502 * round-trip time + 2 * round-trip time variance. 1503 * Initialize shift counter which is used for backoff 1504 * of retransmit time. 1505 */ 1506 timer: 1507 if (!tcp_timer_active(tp, TT_REXMT) && 1508 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1509 (tp->snd_nxt != tp->snd_una))) { 1510 if (tcp_timer_active(tp, TT_PERSIST)) { 1511 tcp_timer_activate(tp, TT_PERSIST, 0); 1512 tp->t_rxtshift = 0; 1513 } 1514 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1515 } else if (len == 0 && sbavail(&so->so_snd) && 1516 !tcp_timer_active(tp, TT_REXMT) && 1517 !tcp_timer_active(tp, TT_PERSIST)) { 1518 /* 1519 * Avoid a situation where we do not set persist timer 1520 * after a zero window condition. For example: 1521 * 1) A -> B: packet with enough data to fill the window 1522 * 2) B -> A: ACK for #1 + new data (0 window 1523 * advertisement) 1524 * 3) A -> B: ACK for #2, 0 len packet 1525 * 1526 * In this case, A will not activate the persist timer, 1527 * because it chose to send a packet. Unless tcp_output 1528 * is called for some other reason (delayed ack timer, 1529 * another input packet from B, socket syscall), A will 1530 * not send zero window probes. 1531 * 1532 * So, if you send a 0-length packet, but there is data 1533 * in the socket buffer, and neither the rexmt or 1534 * persist timer is already set, then activate the 1535 * persist timer. 1536 */ 1537 tp->t_rxtshift = 0; 1538 tcp_setpersist(tp); 1539 } 1540 } else { 1541 /* 1542 * Persist case, update snd_max but since we are in 1543 * persist mode (no window) we do not update snd_nxt. 1544 */ 1545 int xlen = len; 1546 if (flags & TH_SYN) 1547 ++xlen; 1548 if (flags & TH_FIN) { 1549 ++xlen; 1550 tp->t_flags |= TF_SENTFIN; 1551 } 1552 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1553 tp->snd_max = tp->snd_nxt + xlen; 1554 } 1555 1556 if (error) { 1557 /* Record the error. */ 1558 TCP_LOG_EVENT(tp, NULL, &so->so_rcv, &so->so_snd, TCP_LOG_OUT, 1559 error, 0, NULL, false); 1560 1561 /* 1562 * We know that the packet was lost, so back out the 1563 * sequence number advance, if any. 1564 * 1565 * If the error is EPERM the packet got blocked by the 1566 * local firewall. Normally we should terminate the 1567 * connection but the blocking may have been spurious 1568 * due to a firewall reconfiguration cycle. So we treat 1569 * it like a packet loss and let the retransmit timer and 1570 * timeouts do their work over time. 1571 * XXX: It is a POLA question whether calling tcp_drop right 1572 * away would be the really correct behavior instead. 1573 */ 1574 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1575 !tcp_timer_active(tp, TT_PERSIST)) && 1576 ((flags & TH_SYN) == 0) && 1577 (error != EPERM)) { 1578 if (sack_rxmit) { 1579 p->rxmit -= len; 1580 tp->sackhint.sack_bytes_rexmit -= len; 1581 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1582 ("sackhint bytes rtx >= 0")); 1583 } else 1584 tp->snd_nxt -= len; 1585 } 1586 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1587 switch (error) { 1588 case EACCES: 1589 tp->t_softerror = error; 1590 return (0); 1591 case EPERM: 1592 tp->t_softerror = error; 1593 return (error); 1594 case ENOBUFS: 1595 TCP_XMIT_TIMER_ASSERT(tp, len, flags); 1596 tp->snd_cwnd = tp->t_maxseg; 1597 return (0); 1598 case EMSGSIZE: 1599 /* 1600 * For some reason the interface we used initially 1601 * to send segments changed to another or lowered 1602 * its MTU. 1603 * If TSO was active we either got an interface 1604 * without TSO capabilits or TSO was turned off. 1605 * If we obtained mtu from ip_output() then update 1606 * it and try again. 1607 */ 1608 if (tso) 1609 tp->t_flags &= ~TF_TSO; 1610 if (mtu != 0) { 1611 tcp_mss_update(tp, -1, mtu, NULL, NULL); 1612 goto again; 1613 } 1614 return (error); 1615 case EHOSTDOWN: 1616 case EHOSTUNREACH: 1617 case ENETDOWN: 1618 case ENETUNREACH: 1619 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1620 tp->t_softerror = error; 1621 return (0); 1622 } 1623 /* FALLTHROUGH */ 1624 default: 1625 return (error); 1626 } 1627 } 1628 TCPSTAT_INC(tcps_sndtotal); 1629 1630 /* 1631 * Data sent (as far as we can tell). 1632 * If this advertises a larger window than any other segment, 1633 * then remember the size of the advertised window. 1634 * Any pending ACK has now been sent. 1635 */ 1636 if (SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1637 tp->rcv_adv = tp->rcv_nxt + recwin; 1638 tp->last_ack_sent = tp->rcv_nxt; 1639 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1640 if (tcp_timer_active(tp, TT_DELACK)) 1641 tcp_timer_activate(tp, TT_DELACK, 0); 1642 #if 0 1643 /* 1644 * This completely breaks TCP if newreno is turned on. What happens 1645 * is that if delayed-acks are turned on on the receiver, this code 1646 * on the transmitter effectively destroys the TCP window, forcing 1647 * it to four packets (1.5Kx4 = 6K window). 1648 */ 1649 if (sendalot && --maxburst) 1650 goto again; 1651 #endif 1652 if (sendalot) 1653 goto again; 1654 return (0); 1655 } 1656 1657 void 1658 tcp_setpersist(struct tcpcb *tp) 1659 { 1660 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1661 int tt; 1662 1663 tp->t_flags &= ~TF_PREVVALID; 1664 if (tcp_timer_active(tp, TT_REXMT)) 1665 panic("tcp_setpersist: retransmit pending"); 1666 /* 1667 * Start/restart persistence timer. 1668 */ 1669 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1670 tcp_persmin, tcp_persmax); 1671 tcp_timer_activate(tp, TT_PERSIST, tt); 1672 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1673 tp->t_rxtshift++; 1674 } 1675 1676 /* 1677 * Insert TCP options according to the supplied parameters to the place 1678 * optp in a consistent way. Can handle unaligned destinations. 1679 * 1680 * The order of the option processing is crucial for optimal packing and 1681 * alignment for the scarce option space. 1682 * 1683 * The optimal order for a SYN/SYN-ACK segment is: 1684 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1685 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1686 * 1687 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1688 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1689 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1690 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1691 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1692 */ 1693 int 1694 tcp_addoptions(struct tcpopt *to, u_char *optp) 1695 { 1696 u_int32_t mask, optlen = 0; 1697 1698 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1699 if ((to->to_flags & mask) != mask) 1700 continue; 1701 if (optlen == TCP_MAXOLEN) 1702 break; 1703 switch (to->to_flags & mask) { 1704 case TOF_MSS: 1705 while (optlen % 4) { 1706 optlen += TCPOLEN_NOP; 1707 *optp++ = TCPOPT_NOP; 1708 } 1709 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1710 continue; 1711 optlen += TCPOLEN_MAXSEG; 1712 *optp++ = TCPOPT_MAXSEG; 1713 *optp++ = TCPOLEN_MAXSEG; 1714 to->to_mss = htons(to->to_mss); 1715 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1716 optp += sizeof(to->to_mss); 1717 break; 1718 case TOF_SCALE: 1719 while (!optlen || optlen % 2 != 1) { 1720 optlen += TCPOLEN_NOP; 1721 *optp++ = TCPOPT_NOP; 1722 } 1723 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1724 continue; 1725 optlen += TCPOLEN_WINDOW; 1726 *optp++ = TCPOPT_WINDOW; 1727 *optp++ = TCPOLEN_WINDOW; 1728 *optp++ = to->to_wscale; 1729 break; 1730 case TOF_SACKPERM: 1731 while (optlen % 2) { 1732 optlen += TCPOLEN_NOP; 1733 *optp++ = TCPOPT_NOP; 1734 } 1735 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1736 continue; 1737 optlen += TCPOLEN_SACK_PERMITTED; 1738 *optp++ = TCPOPT_SACK_PERMITTED; 1739 *optp++ = TCPOLEN_SACK_PERMITTED; 1740 break; 1741 case TOF_TS: 1742 while (!optlen || optlen % 4 != 2) { 1743 optlen += TCPOLEN_NOP; 1744 *optp++ = TCPOPT_NOP; 1745 } 1746 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1747 continue; 1748 optlen += TCPOLEN_TIMESTAMP; 1749 *optp++ = TCPOPT_TIMESTAMP; 1750 *optp++ = TCPOLEN_TIMESTAMP; 1751 to->to_tsval = htonl(to->to_tsval); 1752 to->to_tsecr = htonl(to->to_tsecr); 1753 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1754 optp += sizeof(to->to_tsval); 1755 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1756 optp += sizeof(to->to_tsecr); 1757 break; 1758 case TOF_SIGNATURE: 1759 { 1760 int siglen = TCPOLEN_SIGNATURE - 2; 1761 1762 while (!optlen || optlen % 4 != 2) { 1763 optlen += TCPOLEN_NOP; 1764 *optp++ = TCPOPT_NOP; 1765 } 1766 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) { 1767 to->to_flags &= ~TOF_SIGNATURE; 1768 continue; 1769 } 1770 optlen += TCPOLEN_SIGNATURE; 1771 *optp++ = TCPOPT_SIGNATURE; 1772 *optp++ = TCPOLEN_SIGNATURE; 1773 to->to_signature = optp; 1774 while (siglen--) 1775 *optp++ = 0; 1776 break; 1777 } 1778 case TOF_SACK: 1779 { 1780 int sackblks = 0; 1781 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1782 tcp_seq sack_seq; 1783 1784 while (!optlen || optlen % 4 != 2) { 1785 optlen += TCPOLEN_NOP; 1786 *optp++ = TCPOPT_NOP; 1787 } 1788 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1789 continue; 1790 optlen += TCPOLEN_SACKHDR; 1791 *optp++ = TCPOPT_SACK; 1792 sackblks = min(to->to_nsacks, 1793 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1794 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1795 while (sackblks--) { 1796 sack_seq = htonl(sack->start); 1797 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1798 optp += sizeof(sack_seq); 1799 sack_seq = htonl(sack->end); 1800 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1801 optp += sizeof(sack_seq); 1802 optlen += TCPOLEN_SACK; 1803 sack++; 1804 } 1805 TCPSTAT_INC(tcps_sack_send_blocks); 1806 break; 1807 } 1808 case TOF_FASTOPEN: 1809 { 1810 int total_len; 1811 1812 /* XXX is there any point to aligning this option? */ 1813 total_len = TCPOLEN_FAST_OPEN_EMPTY + to->to_tfo_len; 1814 if (TCP_MAXOLEN - optlen < total_len) { 1815 to->to_flags &= ~TOF_FASTOPEN; 1816 continue; 1817 } 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 default: 1828 panic("%s: unknown TCP option type", __func__); 1829 break; 1830 } 1831 } 1832 1833 /* Terminate and pad TCP options to a 4 byte boundary. */ 1834 if (optlen % 4) { 1835 optlen += TCPOLEN_EOL; 1836 *optp++ = TCPOPT_EOL; 1837 } 1838 /* 1839 * According to RFC 793 (STD0007): 1840 * "The content of the header beyond the End-of-Option option 1841 * must be header padding (i.e., zero)." 1842 * and later: "The padding is composed of zeros." 1843 */ 1844 while (optlen % 4) { 1845 optlen += TCPOLEN_PAD; 1846 *optp++ = TCPOPT_PAD; 1847 } 1848 1849 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1850 return (optlen); 1851 } 1852 1853 void 1854 tcp_sndbuf_autoscale(struct tcpcb *tp, struct socket *so, uint32_t sendwin) 1855 { 1856 1857 /* 1858 * Automatic sizing of send socket buffer. Often the send buffer 1859 * size is not optimally adjusted to the actual network conditions 1860 * at hand (delay bandwidth product). Setting the buffer size too 1861 * small limits throughput on links with high bandwidth and high 1862 * delay (eg. trans-continental/oceanic links). Setting the 1863 * buffer size too big consumes too much real kernel memory, 1864 * especially with many connections on busy servers. 1865 * 1866 * The criteria to step up the send buffer one notch are: 1867 * 1. receive window of remote host is larger than send buffer 1868 * (with a fudge factor of 5/4th); 1869 * 2. send buffer is filled to 7/8th with data (so we actually 1870 * have data to make use of it); 1871 * 3. send buffer fill has not hit maximal automatic size; 1872 * 4. our send window (slow start and cogestion controlled) is 1873 * larger than sent but unacknowledged data in send buffer. 1874 * 1875 * The remote host receive window scaling factor may limit the 1876 * growing of the send buffer before it reaches its allowed 1877 * maximum. 1878 * 1879 * It scales directly with slow start or congestion window 1880 * and does at most one step per received ACK. This fast 1881 * scaling has the drawback of growing the send buffer beyond 1882 * what is strictly necessary to make full use of a given 1883 * delay*bandwidth product. However testing has shown this not 1884 * to be much of an problem. At worst we are trading wasting 1885 * of available bandwidth (the non-use of it) for wasting some 1886 * socket buffer memory. 1887 * 1888 * TODO: Shrink send buffer during idle periods together 1889 * with congestion window. Requires another timer. Has to 1890 * wait for upcoming tcp timer rewrite. 1891 * 1892 * XXXGL: should there be used sbused() or sbavail()? 1893 */ 1894 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 1895 int lowat; 1896 1897 lowat = V_tcp_sendbuf_auto_lowat ? so->so_snd.sb_lowat : 0; 1898 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat - lowat && 1899 sbused(&so->so_snd) >= 1900 (so->so_snd.sb_hiwat / 8 * 7) - lowat && 1901 sbused(&so->so_snd) < V_tcp_autosndbuf_max && 1902 sendwin >= (sbused(&so->so_snd) - 1903 (tp->snd_nxt - tp->snd_una))) { 1904 if (!sbreserve_locked(&so->so_snd, 1905 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 1906 V_tcp_autosndbuf_max), so, curthread)) 1907 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 1908 } 1909 } 1910 } 1911