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, curticks; 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 curticks = tcp_ts_getticks(); 812 to.to_tsval = curticks + tp->ts_offset; 813 to.to_tsecr = tp->ts_recent; 814 to.to_flags |= TOF_TS; 815 if (tp->t_rxtshift == 1) 816 tp->t_badrxtwin = curticks; 817 } 818 819 /* Set receive buffer autosizing timestamp. */ 820 if (tp->rfbuf_ts == 0 && 821 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 822 tp->rfbuf_ts = tcp_ts_getticks(); 823 824 /* Selective ACK's. */ 825 if (tp->t_flags & TF_SACK_PERMIT) { 826 if (flags & TH_SYN) 827 to.to_flags |= TOF_SACKPERM; 828 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 829 (tp->t_flags & TF_SACK_PERMIT) && 830 tp->rcv_numsacks > 0) { 831 to.to_flags |= TOF_SACK; 832 to.to_nsacks = tp->rcv_numsacks; 833 to.to_sacks = (u_char *)tp->sackblks; 834 } 835 } 836 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 837 /* TCP-MD5 (RFC2385). */ 838 /* 839 * Check that TCP_MD5SIG is enabled in tcpcb to 840 * account the size needed to set this TCP option. 841 */ 842 if (tp->t_flags & TF_SIGNATURE) 843 to.to_flags |= TOF_SIGNATURE; 844 #endif /* TCP_SIGNATURE */ 845 846 /* Processing the options. */ 847 hdrlen += optlen = tcp_addoptions(&to, opt); 848 /* 849 * If we wanted a TFO option to be added, but it was unable 850 * to fit, ensure no data is sent. 851 */ 852 if (IS_FASTOPEN(tp->t_flags) && wanted_cookie && 853 !(to.to_flags & TOF_FASTOPEN)) 854 len = 0; 855 } 856 857 /* 858 * Adjust data length if insertion of options will 859 * bump the packet length beyond the t_maxseg length. 860 * Clear the FIN bit because we cut off the tail of 861 * the segment. 862 */ 863 if (len + optlen + ipoptlen > tp->t_maxseg) { 864 flags &= ~TH_FIN; 865 866 if (tso) { 867 u_int if_hw_tsomax; 868 u_int if_hw_tsomaxsegcount; 869 u_int if_hw_tsomaxsegsize; 870 struct mbuf *mb; 871 u_int moff; 872 int max_len; 873 874 /* extract TSO information */ 875 if_hw_tsomax = tp->t_tsomax; 876 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount; 877 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize; 878 879 /* 880 * Limit a TSO burst to prevent it from 881 * overflowing or exceeding the maximum length 882 * allowed by the network interface: 883 */ 884 KASSERT(ipoptlen == 0, 885 ("%s: TSO can't do IP options", __func__)); 886 887 /* 888 * Check if we should limit by maximum payload 889 * length: 890 */ 891 if (if_hw_tsomax != 0) { 892 /* compute maximum TSO length */ 893 max_len = (if_hw_tsomax - hdrlen - 894 max_linkhdr); 895 if (max_len <= 0) { 896 len = 0; 897 } else if (len > max_len) { 898 sendalot = 1; 899 len = max_len; 900 } 901 } 902 903 /* 904 * Check if we should limit by maximum segment 905 * size and count: 906 */ 907 if (if_hw_tsomaxsegcount != 0 && 908 if_hw_tsomaxsegsize != 0) { 909 /* 910 * Subtract one segment for the LINK 911 * and TCP/IP headers mbuf that will 912 * be prepended to this mbuf chain 913 * after the code in this section 914 * limits the number of mbufs in the 915 * chain to if_hw_tsomaxsegcount. 916 */ 917 if_hw_tsomaxsegcount -= 1; 918 max_len = 0; 919 mb = sbsndmbuf(&so->so_snd, off, &moff); 920 921 while (mb != NULL && max_len < len) { 922 u_int mlen; 923 u_int frags; 924 925 /* 926 * Get length of mbuf fragment 927 * and how many hardware frags, 928 * rounded up, it would use: 929 */ 930 mlen = (mb->m_len - moff); 931 frags = howmany(mlen, 932 if_hw_tsomaxsegsize); 933 934 /* Handle special case: Zero Length Mbuf */ 935 if (frags == 0) 936 frags = 1; 937 938 /* 939 * Check if the fragment limit 940 * will be reached or exceeded: 941 */ 942 if (frags >= if_hw_tsomaxsegcount) { 943 max_len += min(mlen, 944 if_hw_tsomaxsegcount * 945 if_hw_tsomaxsegsize); 946 break; 947 } 948 max_len += mlen; 949 if_hw_tsomaxsegcount -= frags; 950 moff = 0; 951 mb = mb->m_next; 952 } 953 if (max_len <= 0) { 954 len = 0; 955 } else if (len > max_len) { 956 sendalot = 1; 957 len = max_len; 958 } 959 } 960 961 /* 962 * Prevent the last segment from being 963 * fractional unless the send sockbuf can be 964 * emptied: 965 */ 966 max_len = (tp->t_maxseg - optlen); 967 if (((uint32_t)off + (uint32_t)len) < 968 sbavail(&so->so_snd)) { 969 moff = len % max_len; 970 if (moff != 0) { 971 len -= moff; 972 sendalot = 1; 973 } 974 } 975 976 /* 977 * In case there are too many small fragments 978 * don't use TSO: 979 */ 980 if (len <= max_len) { 981 len = max_len; 982 sendalot = 1; 983 tso = 0; 984 } 985 986 /* 987 * Send the FIN in a separate segment 988 * after the bulk sending is done. 989 * We don't trust the TSO implementations 990 * to clear the FIN flag on all but the 991 * last segment. 992 */ 993 if (tp->t_flags & TF_NEEDFIN) 994 sendalot = 1; 995 996 } else { 997 len = tp->t_maxseg - optlen - ipoptlen; 998 sendalot = 1; 999 if (dont_sendalot) 1000 sendalot = 0; 1001 } 1002 } else 1003 tso = 0; 1004 1005 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 1006 ("%s: len > IP_MAXPACKET", __func__)); 1007 1008 /*#ifdef DIAGNOSTIC*/ 1009 #ifdef INET6 1010 if (max_linkhdr + hdrlen > MCLBYTES) 1011 #else 1012 if (max_linkhdr + hdrlen > MHLEN) 1013 #endif 1014 panic("tcphdr too big"); 1015 /*#endif*/ 1016 1017 /* 1018 * This KASSERT is here to catch edge cases at a well defined place. 1019 * Before, those had triggered (random) panic conditions further down. 1020 */ 1021 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 1022 1023 /* 1024 * Grab a header mbuf, attaching a copy of data to 1025 * be transmitted, and initialize the header from 1026 * the template for sends on this connection. 1027 */ 1028 if (len) { 1029 struct mbuf *mb; 1030 u_int moff; 1031 1032 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 1033 TCPSTAT_INC(tcps_sndprobe); 1034 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 1035 tp->t_sndrexmitpack++; 1036 TCPSTAT_INC(tcps_sndrexmitpack); 1037 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 1038 } else { 1039 TCPSTAT_INC(tcps_sndpack); 1040 TCPSTAT_ADD(tcps_sndbyte, len); 1041 } 1042 #ifdef INET6 1043 if (MHLEN < hdrlen + max_linkhdr) 1044 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR); 1045 else 1046 #endif 1047 m = m_gethdr(M_NOWAIT, MT_DATA); 1048 1049 if (m == NULL) { 1050 SOCKBUF_UNLOCK(&so->so_snd); 1051 error = ENOBUFS; 1052 sack_rxmit = 0; 1053 goto out; 1054 } 1055 1056 m->m_data += max_linkhdr; 1057 m->m_len = hdrlen; 1058 1059 /* 1060 * Start the m_copy functions from the closest mbuf 1061 * to the offset in the socket buffer chain. 1062 */ 1063 mb = sbsndptr(&so->so_snd, off, len, &moff); 1064 1065 if (len <= MHLEN - hdrlen - max_linkhdr) { 1066 m_copydata(mb, moff, len, 1067 mtod(m, caddr_t) + hdrlen); 1068 m->m_len += len; 1069 } else { 1070 m->m_next = m_copym(mb, moff, len, M_NOWAIT); 1071 if (m->m_next == NULL) { 1072 SOCKBUF_UNLOCK(&so->so_snd); 1073 (void) m_free(m); 1074 error = ENOBUFS; 1075 sack_rxmit = 0; 1076 goto out; 1077 } 1078 } 1079 1080 /* 1081 * If we're sending everything we've got, set PUSH. 1082 * (This will keep happy those implementations which only 1083 * give data to the user when a buffer fills or 1084 * a PUSH comes in.) 1085 */ 1086 if (((uint32_t)off + (uint32_t)len == sbused(&so->so_snd)) && 1087 !(flags & TH_SYN)) 1088 flags |= TH_PUSH; 1089 SOCKBUF_UNLOCK(&so->so_snd); 1090 } else { 1091 SOCKBUF_UNLOCK(&so->so_snd); 1092 if (tp->t_flags & TF_ACKNOW) 1093 TCPSTAT_INC(tcps_sndacks); 1094 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 1095 TCPSTAT_INC(tcps_sndctrl); 1096 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 1097 TCPSTAT_INC(tcps_sndurg); 1098 else 1099 TCPSTAT_INC(tcps_sndwinup); 1100 1101 m = m_gethdr(M_NOWAIT, MT_DATA); 1102 if (m == NULL) { 1103 error = ENOBUFS; 1104 sack_rxmit = 0; 1105 goto out; 1106 } 1107 #ifdef INET6 1108 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 1109 MHLEN >= hdrlen) { 1110 M_ALIGN(m, hdrlen); 1111 } else 1112 #endif 1113 m->m_data += max_linkhdr; 1114 m->m_len = hdrlen; 1115 } 1116 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 1117 m->m_pkthdr.rcvif = (struct ifnet *)0; 1118 #ifdef MAC 1119 mac_inpcb_create_mbuf(tp->t_inpcb, m); 1120 #endif 1121 #ifdef INET6 1122 if (isipv6) { 1123 ip6 = mtod(m, struct ip6_hdr *); 1124 th = (struct tcphdr *)(ip6 + 1); 1125 tcpip_fillheaders(tp->t_inpcb, ip6, th); 1126 } else 1127 #endif /* INET6 */ 1128 { 1129 ip = mtod(m, struct ip *); 1130 #ifdef TCPDEBUG 1131 ipov = (struct ipovly *)ip; 1132 #endif 1133 th = (struct tcphdr *)(ip + 1); 1134 tcpip_fillheaders(tp->t_inpcb, ip, th); 1135 } 1136 1137 /* 1138 * Fill in fields, remembering maximum advertised 1139 * window for use in delaying messages about window sizes. 1140 * If resending a FIN, be sure not to use a new sequence number. 1141 */ 1142 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 1143 tp->snd_nxt == tp->snd_max) 1144 tp->snd_nxt--; 1145 /* 1146 * If we are starting a connection, send ECN setup 1147 * SYN packet. If we are on a retransmit, we may 1148 * resend those bits a number of times as per 1149 * RFC 3168. 1150 */ 1151 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn == 1) { 1152 if (tp->t_rxtshift >= 1) { 1153 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 1154 flags |= TH_ECE|TH_CWR; 1155 } else 1156 flags |= TH_ECE|TH_CWR; 1157 } 1158 1159 if (tp->t_state == TCPS_ESTABLISHED && 1160 (tp->t_flags & TF_ECN_PERMIT)) { 1161 /* 1162 * If the peer has ECN, mark data packets with 1163 * ECN capable transmission (ECT). 1164 * Ignore pure ack packets, retransmissions and window probes. 1165 */ 1166 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 1167 !((tp->t_flags & TF_FORCEDATA) && len == 1)) { 1168 #ifdef INET6 1169 if (isipv6) 1170 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 1171 else 1172 #endif 1173 ip->ip_tos |= IPTOS_ECN_ECT0; 1174 TCPSTAT_INC(tcps_ecn_ect0); 1175 } 1176 1177 /* 1178 * Reply with proper ECN notifications. 1179 */ 1180 if (tp->t_flags & TF_ECN_SND_CWR) { 1181 flags |= TH_CWR; 1182 tp->t_flags &= ~TF_ECN_SND_CWR; 1183 } 1184 if (tp->t_flags & TF_ECN_SND_ECE) 1185 flags |= TH_ECE; 1186 } 1187 1188 /* 1189 * If we are doing retransmissions, then snd_nxt will 1190 * not reflect the first unsent octet. For ACK only 1191 * packets, we do not want the sequence number of the 1192 * retransmitted packet, we want the sequence number 1193 * of the next unsent octet. So, if there is no data 1194 * (and no SYN or FIN), use snd_max instead of snd_nxt 1195 * when filling in ti_seq. But if we are in persist 1196 * state, snd_max might reflect one byte beyond the 1197 * right edge of the window, so use snd_nxt in that 1198 * case, since we know we aren't doing a retransmission. 1199 * (retransmit and persist are mutually exclusive...) 1200 */ 1201 if (sack_rxmit == 0) { 1202 if (len || (flags & (TH_SYN|TH_FIN)) || 1203 tcp_timer_active(tp, TT_PERSIST)) 1204 th->th_seq = htonl(tp->snd_nxt); 1205 else 1206 th->th_seq = htonl(tp->snd_max); 1207 } else { 1208 th->th_seq = htonl(p->rxmit); 1209 p->rxmit += len; 1210 tp->sackhint.sack_bytes_rexmit += len; 1211 } 1212 th->th_ack = htonl(tp->rcv_nxt); 1213 if (optlen) { 1214 bcopy(opt, th + 1, optlen); 1215 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1216 } 1217 th->th_flags = flags; 1218 /* 1219 * Calculate receive window. Don't shrink window, 1220 * but avoid silly window syndrome. 1221 */ 1222 if (recwin < (so->so_rcv.sb_hiwat / 4) && 1223 recwin < tp->t_maxseg) 1224 recwin = 0; 1225 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1226 recwin < (tp->rcv_adv - tp->rcv_nxt)) 1227 recwin = (tp->rcv_adv - tp->rcv_nxt); 1228 1229 /* 1230 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1231 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1232 * case is handled in syncache. 1233 */ 1234 if (flags & TH_SYN) 1235 th->th_win = htons((u_short) 1236 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1237 else 1238 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1239 1240 /* 1241 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1242 * a 0 window. This may cause the remote transmitter to stall. This 1243 * flag tells soreceive() to disable delayed acknowledgements when 1244 * draining the buffer. This can occur if the receiver is attempting 1245 * to read more data than can be buffered prior to transmitting on 1246 * the connection. 1247 */ 1248 if (th->th_win == 0) { 1249 tp->t_sndzerowin++; 1250 tp->t_flags |= TF_RXWIN0SENT; 1251 } else 1252 tp->t_flags &= ~TF_RXWIN0SENT; 1253 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1254 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1255 th->th_flags |= TH_URG; 1256 } else 1257 /* 1258 * If no urgent pointer to send, then we pull 1259 * the urgent pointer to the left edge of the send window 1260 * so that it doesn't drift into the send window on sequence 1261 * number wraparound. 1262 */ 1263 tp->snd_up = tp->snd_una; /* drag it along */ 1264 1265 /* 1266 * Put TCP length in extended header, and then 1267 * checksum extended header and data. 1268 */ 1269 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1270 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1271 1272 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1273 if (to.to_flags & TOF_SIGNATURE) { 1274 /* 1275 * Calculate MD5 signature and put it into the place 1276 * determined before. 1277 * NOTE: since TCP options buffer doesn't point into 1278 * mbuf's data, calculate offset and use it. 1279 */ 1280 if (!TCPMD5_ENABLED() || (error = TCPMD5_OUTPUT(m, th, 1281 (u_char *)(th + 1) + (to.to_signature - opt))) != 0) { 1282 /* 1283 * Do not send segment if the calculation of MD5 1284 * digest has failed. 1285 */ 1286 m_freem(m); 1287 goto out; 1288 } 1289 } 1290 #endif 1291 #ifdef INET6 1292 if (isipv6) { 1293 /* 1294 * There is no need to fill in ip6_plen right now. 1295 * It will be filled later by ip6_output. 1296 */ 1297 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1298 th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) + 1299 optlen + len, IPPROTO_TCP, 0); 1300 } 1301 #endif 1302 #if defined(INET6) && defined(INET) 1303 else 1304 #endif 1305 #ifdef INET 1306 { 1307 m->m_pkthdr.csum_flags = CSUM_TCP; 1308 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1309 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1310 1311 /* IP version must be set here for ipv4/ipv6 checking later */ 1312 KASSERT(ip->ip_v == IPVERSION, 1313 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1314 } 1315 #endif 1316 1317 /* 1318 * Enable TSO and specify the size of the segments. 1319 * The TCP pseudo header checksum is always provided. 1320 */ 1321 if (tso) { 1322 KASSERT(len > tp->t_maxseg - optlen, 1323 ("%s: len <= tso_segsz", __func__)); 1324 m->m_pkthdr.csum_flags |= CSUM_TSO; 1325 m->m_pkthdr.tso_segsz = tp->t_maxseg - optlen; 1326 } 1327 1328 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 1329 KASSERT(len + hdrlen + ipoptlen - ipsec_optlen == m_length(m, NULL), 1330 ("%s: mbuf chain shorter than expected: %d + %u + %u - %u != %u", 1331 __func__, len, hdrlen, ipoptlen, ipsec_optlen, m_length(m, NULL))); 1332 #else 1333 KASSERT(len + hdrlen + ipoptlen == m_length(m, NULL), 1334 ("%s: mbuf chain shorter than expected: %d + %u + %u != %u", 1335 __func__, len, hdrlen, ipoptlen, m_length(m, NULL))); 1336 #endif 1337 1338 #ifdef TCP_HHOOK 1339 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1340 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1341 #endif 1342 1343 #ifdef TCPDEBUG 1344 /* 1345 * Trace. 1346 */ 1347 if (so->so_options & SO_DEBUG) { 1348 u_short save = 0; 1349 #ifdef INET6 1350 if (!isipv6) 1351 #endif 1352 { 1353 save = ipov->ih_len; 1354 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1355 } 1356 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1357 #ifdef INET6 1358 if (!isipv6) 1359 #endif 1360 ipov->ih_len = save; 1361 } 1362 #endif /* TCPDEBUG */ 1363 TCP_PROBE3(debug__output, tp, th, m); 1364 1365 /* We're getting ready to send; log now. */ 1366 TCP_LOG_EVENT(tp, th, &so->so_rcv, &so->so_snd, TCP_LOG_OUT, ERRNO_UNK, 1367 len, NULL, false); 1368 1369 /* 1370 * Fill in IP length and desired time to live and 1371 * send to IP level. There should be a better way 1372 * to handle ttl and tos; we could keep them in 1373 * the template, but need a way to checksum without them. 1374 */ 1375 /* 1376 * m->m_pkthdr.len should have been set before checksum calculation, 1377 * because in6_cksum() need it. 1378 */ 1379 #ifdef INET6 1380 if (isipv6) { 1381 /* 1382 * we separately set hoplimit for every segment, since the 1383 * user might want to change the value via setsockopt. 1384 * Also, desired default hop limit might be changed via 1385 * Neighbor Discovery. 1386 */ 1387 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1388 1389 /* 1390 * Set the packet size here for the benefit of DTrace probes. 1391 * ip6_output() will set it properly; it's supposed to include 1392 * the option header lengths as well. 1393 */ 1394 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6)); 1395 1396 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) 1397 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1398 else 1399 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1400 1401 if (tp->t_state == TCPS_SYN_SENT) 1402 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th); 1403 1404 TCP_PROBE5(send, NULL, tp, ip6, tp, th); 1405 1406 #ifdef TCPPCAP 1407 /* Save packet, if requested. */ 1408 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1409 #endif 1410 1411 /* TODO: IPv6 IP6TOS_ECT bit on */ 1412 error = ip6_output(m, tp->t_inpcb->in6p_outputopts, 1413 &tp->t_inpcb->inp_route6, 1414 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 1415 NULL, NULL, tp->t_inpcb); 1416 1417 if (error == EMSGSIZE && tp->t_inpcb->inp_route6.ro_rt != NULL) 1418 mtu = tp->t_inpcb->inp_route6.ro_rt->rt_mtu; 1419 } 1420 #endif /* INET6 */ 1421 #if defined(INET) && defined(INET6) 1422 else 1423 #endif 1424 #ifdef INET 1425 { 1426 ip->ip_len = htons(m->m_pkthdr.len); 1427 #ifdef INET6 1428 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1429 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1430 #endif /* INET6 */ 1431 /* 1432 * If we do path MTU discovery, then we set DF on every packet. 1433 * This might not be the best thing to do according to RFC3390 1434 * Section 2. However the tcp hostcache migitates the problem 1435 * so it affects only the first tcp connection with a host. 1436 * 1437 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1438 */ 1439 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) { 1440 ip->ip_off |= htons(IP_DF); 1441 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1442 } else { 1443 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1444 } 1445 1446 if (tp->t_state == TCPS_SYN_SENT) 1447 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th); 1448 1449 TCP_PROBE5(send, NULL, tp, ip, tp, th); 1450 1451 #ifdef TCPPCAP 1452 /* Save packet, if requested. */ 1453 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1454 #endif 1455 1456 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, 1457 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1458 tp->t_inpcb); 1459 1460 if (error == EMSGSIZE && tp->t_inpcb->inp_route.ro_rt != NULL) 1461 mtu = tp->t_inpcb->inp_route.ro_rt->rt_mtu; 1462 } 1463 #endif /* INET */ 1464 1465 out: 1466 /* 1467 * In transmit state, time the transmission and arrange for 1468 * the retransmit. In persist state, just set snd_max. 1469 */ 1470 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1471 !tcp_timer_active(tp, TT_PERSIST)) { 1472 tcp_seq startseq = tp->snd_nxt; 1473 1474 /* 1475 * Advance snd_nxt over sequence space of this segment. 1476 */ 1477 if (flags & (TH_SYN|TH_FIN)) { 1478 if (flags & TH_SYN) 1479 tp->snd_nxt++; 1480 if (flags & TH_FIN) { 1481 tp->snd_nxt++; 1482 tp->t_flags |= TF_SENTFIN; 1483 } 1484 } 1485 if (sack_rxmit) 1486 goto timer; 1487 tp->snd_nxt += len; 1488 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1489 tp->snd_max = tp->snd_nxt; 1490 /* 1491 * Time this transmission if not a retransmission and 1492 * not currently timing anything. 1493 */ 1494 if (tp->t_rtttime == 0) { 1495 tp->t_rtttime = ticks; 1496 tp->t_rtseq = startseq; 1497 TCPSTAT_INC(tcps_segstimed); 1498 } 1499 } 1500 1501 /* 1502 * Set retransmit timer if not currently set, 1503 * and not doing a pure ack or a keep-alive probe. 1504 * Initial value for retransmit timer is smoothed 1505 * round-trip time + 2 * round-trip time variance. 1506 * Initialize shift counter which is used for backoff 1507 * of retransmit time. 1508 */ 1509 timer: 1510 if (!tcp_timer_active(tp, TT_REXMT) && 1511 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1512 (tp->snd_nxt != tp->snd_una))) { 1513 if (tcp_timer_active(tp, TT_PERSIST)) { 1514 tcp_timer_activate(tp, TT_PERSIST, 0); 1515 tp->t_rxtshift = 0; 1516 } 1517 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1518 } else if (len == 0 && sbavail(&so->so_snd) && 1519 !tcp_timer_active(tp, TT_REXMT) && 1520 !tcp_timer_active(tp, TT_PERSIST)) { 1521 /* 1522 * Avoid a situation where we do not set persist timer 1523 * after a zero window condition. For example: 1524 * 1) A -> B: packet with enough data to fill the window 1525 * 2) B -> A: ACK for #1 + new data (0 window 1526 * advertisement) 1527 * 3) A -> B: ACK for #2, 0 len packet 1528 * 1529 * In this case, A will not activate the persist timer, 1530 * because it chose to send a packet. Unless tcp_output 1531 * is called for some other reason (delayed ack timer, 1532 * another input packet from B, socket syscall), A will 1533 * not send zero window probes. 1534 * 1535 * So, if you send a 0-length packet, but there is data 1536 * in the socket buffer, and neither the rexmt or 1537 * persist timer is already set, then activate the 1538 * persist timer. 1539 */ 1540 tp->t_rxtshift = 0; 1541 tcp_setpersist(tp); 1542 } 1543 } else { 1544 /* 1545 * Persist case, update snd_max but since we are in 1546 * persist mode (no window) we do not update snd_nxt. 1547 */ 1548 int xlen = len; 1549 if (flags & TH_SYN) 1550 ++xlen; 1551 if (flags & TH_FIN) { 1552 ++xlen; 1553 tp->t_flags |= TF_SENTFIN; 1554 } 1555 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1556 tp->snd_max = tp->snd_nxt + xlen; 1557 } 1558 1559 if (error) { 1560 /* Record the error. */ 1561 TCP_LOG_EVENT(tp, NULL, &so->so_rcv, &so->so_snd, TCP_LOG_OUT, 1562 error, 0, NULL, false); 1563 1564 /* 1565 * We know that the packet was lost, so back out the 1566 * sequence number advance, if any. 1567 * 1568 * If the error is EPERM the packet got blocked by the 1569 * local firewall. Normally we should terminate the 1570 * connection but the blocking may have been spurious 1571 * due to a firewall reconfiguration cycle. So we treat 1572 * it like a packet loss and let the retransmit timer and 1573 * timeouts do their work over time. 1574 * XXX: It is a POLA question whether calling tcp_drop right 1575 * away would be the really correct behavior instead. 1576 */ 1577 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1578 !tcp_timer_active(tp, TT_PERSIST)) && 1579 ((flags & TH_SYN) == 0) && 1580 (error != EPERM)) { 1581 if (sack_rxmit) { 1582 p->rxmit -= len; 1583 tp->sackhint.sack_bytes_rexmit -= len; 1584 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1585 ("sackhint bytes rtx >= 0")); 1586 } else 1587 tp->snd_nxt -= len; 1588 } 1589 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1590 switch (error) { 1591 case EACCES: 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 case TOF_FASTOPEN: 1810 { 1811 int total_len; 1812 1813 /* XXX is there any point to aligning this option? */ 1814 total_len = TCPOLEN_FAST_OPEN_EMPTY + to->to_tfo_len; 1815 if (TCP_MAXOLEN - optlen < total_len) { 1816 to->to_flags &= ~TOF_FASTOPEN; 1817 continue; 1818 } 1819 *optp++ = TCPOPT_FAST_OPEN; 1820 *optp++ = total_len; 1821 if (to->to_tfo_len > 0) { 1822 bcopy(to->to_tfo_cookie, optp, to->to_tfo_len); 1823 optp += to->to_tfo_len; 1824 } 1825 optlen += total_len; 1826 break; 1827 } 1828 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 1854 void 1855 tcp_sndbuf_autoscale(struct tcpcb *tp, struct socket *so, uint32_t sendwin) 1856 { 1857 1858 /* 1859 * Automatic sizing of send socket buffer. Often the send buffer 1860 * size is not optimally adjusted to the actual network conditions 1861 * at hand (delay bandwidth product). Setting the buffer size too 1862 * small limits throughput on links with high bandwidth and high 1863 * delay (eg. trans-continental/oceanic links). Setting the 1864 * buffer size too big consumes too much real kernel memory, 1865 * especially with many connections on busy servers. 1866 * 1867 * The criteria to step up the send buffer one notch are: 1868 * 1. receive window of remote host is larger than send buffer 1869 * (with a fudge factor of 5/4th); 1870 * 2. send buffer is filled to 7/8th with data (so we actually 1871 * have data to make use of it); 1872 * 3. send buffer fill has not hit maximal automatic size; 1873 * 4. our send window (slow start and cogestion controlled) is 1874 * larger than sent but unacknowledged data in send buffer. 1875 * 1876 * The remote host receive window scaling factor may limit the 1877 * growing of the send buffer before it reaches its allowed 1878 * maximum. 1879 * 1880 * It scales directly with slow start or congestion window 1881 * and does at most one step per received ACK. This fast 1882 * scaling has the drawback of growing the send buffer beyond 1883 * what is strictly necessary to make full use of a given 1884 * delay*bandwidth product. However testing has shown this not 1885 * to be much of an problem. At worst we are trading wasting 1886 * of available bandwidth (the non-use of it) for wasting some 1887 * socket buffer memory. 1888 * 1889 * TODO: Shrink send buffer during idle periods together 1890 * with congestion window. Requires another timer. Has to 1891 * wait for upcoming tcp timer rewrite. 1892 * 1893 * XXXGL: should there be used sbused() or sbavail()? 1894 */ 1895 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 1896 int lowat; 1897 1898 lowat = V_tcp_sendbuf_auto_lowat ? so->so_snd.sb_lowat : 0; 1899 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat - lowat && 1900 sbused(&so->so_snd) >= 1901 (so->so_snd.sb_hiwat / 8 * 7) - lowat && 1902 sbused(&so->so_snd) < V_tcp_autosndbuf_max && 1903 sendwin >= (sbused(&so->so_snd) - 1904 (tp->snd_nxt - tp->snd_una))) { 1905 if (!sbreserve_locked(&so->so_snd, 1906 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 1907 V_tcp_autosndbuf_max), so, curthread)) 1908 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 1909 } 1910 } 1911 } 1912