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 static void inline cc_after_idle(struct tcpcb *tp); 147 148 #ifdef TCP_HHOOK 149 /* 150 * Wrapper for the TCP established output helper hook. 151 */ 152 void 153 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th, 154 struct tcpopt *to, uint32_t len, int tso) 155 { 156 struct tcp_hhook_data hhook_data; 157 158 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) { 159 hhook_data.tp = tp; 160 hhook_data.th = th; 161 hhook_data.to = to; 162 hhook_data.len = len; 163 hhook_data.tso = tso; 164 165 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data, 166 tp->osd); 167 } 168 } 169 #endif 170 171 /* 172 * Flags used when sending segments in tcp_output. Basic flags (TH_RST, 173 * TH_ACK,TH_SYN,TH_FIN) are totally determined by state, with the proviso 174 * that TH_FIN is sent only if all data queued for output is included in the 175 * segment. 176 */ 177 u_char tcp_outflags[TCP_NSTATES] = { 178 TH_RST|TH_ACK, /* 0, CLOSED */ 179 0, /* 1, LISTEN */ 180 TH_SYN, /* 2, SYN_SENT */ 181 TH_SYN|TH_ACK, /* 3, SYN_RECEIVED */ 182 TH_ACK, /* 4, ESTABLISHED */ 183 TH_ACK, /* 5, CLOSE_WAIT */ 184 TH_FIN|TH_ACK, /* 6, FIN_WAIT_1 */ 185 TH_FIN|TH_ACK, /* 7, CLOSING */ 186 TH_FIN|TH_ACK, /* 8, LAST_ACK */ 187 TH_ACK, /* 9, FIN_WAIT_2 */ 188 TH_ACK, /* 10, TIME_WAIT */ 189 }; 190 191 /* 192 * CC wrapper hook functions 193 */ 194 static void inline 195 cc_after_idle(struct tcpcb *tp) 196 { 197 INP_WLOCK_ASSERT(tp->t_inpcb); 198 199 if (CC_ALGO(tp)->after_idle != NULL) 200 CC_ALGO(tp)->after_idle(tp->ccv); 201 } 202 203 /* 204 * Tcp output routine: figure out what should be sent and send it. 205 */ 206 int 207 tcp_output(struct tcpcb *tp) 208 { 209 struct socket *so = tp->t_inpcb->inp_socket; 210 int32_t len; 211 uint32_t recwin, sendwin; 212 int off, flags, error = 0; /* Keep compiler happy */ 213 struct mbuf *m; 214 struct ip *ip = NULL; 215 #ifdef TCPDEBUG 216 struct ipovly *ipov = NULL; 217 #endif 218 struct tcphdr *th; 219 u_char opt[TCP_MAXOLEN]; 220 unsigned ipoptlen, optlen, hdrlen; 221 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 222 unsigned ipsec_optlen = 0; 223 #endif 224 int idle, sendalot, curticks; 225 int sack_rxmit, sack_bytes_rxmt; 226 struct sackhole *p; 227 int tso, mtu; 228 struct tcpopt to; 229 unsigned int wanted_cookie = 0; 230 unsigned int dont_sendalot = 0; 231 #if 0 232 int maxburst = TCP_MAXBURST; 233 #endif 234 #ifdef INET6 235 struct ip6_hdr *ip6 = NULL; 236 int isipv6; 237 238 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 239 #endif 240 241 INP_WLOCK_ASSERT(tp->t_inpcb); 242 243 #ifdef TCP_OFFLOAD 244 if (tp->t_flags & TF_TOE) 245 return (tcp_offload_output(tp)); 246 #endif 247 248 /* 249 * For TFO connections in SYN_RECEIVED, only allow the initial 250 * SYN|ACK and those sent by the retransmit timer. 251 */ 252 if (IS_FASTOPEN(tp->t_flags) && 253 (tp->t_state == TCPS_SYN_RECEIVED) && 254 SEQ_GT(tp->snd_max, tp->snd_una) && /* initial SYN|ACK sent */ 255 (tp->snd_nxt != tp->snd_una)) /* not a retransmit */ 256 return (0); 257 258 /* 259 * Determine length of data that should be transmitted, 260 * and flags that will be used. 261 * If there is some data or critical controls (SYN, RST) 262 * to send, then transmit; otherwise, investigate further. 263 */ 264 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 265 if (idle && ticks - tp->t_rcvtime >= tp->t_rxtcur) 266 cc_after_idle(tp); 267 tp->t_flags &= ~TF_LASTIDLE; 268 if (idle) { 269 if (tp->t_flags & TF_MORETOCOME) { 270 tp->t_flags |= TF_LASTIDLE; 271 idle = 0; 272 } 273 } 274 again: 275 /* 276 * If we've recently taken a timeout, snd_max will be greater than 277 * snd_nxt. There may be SACK information that allows us to avoid 278 * resending already delivered data. Adjust snd_nxt accordingly. 279 */ 280 if ((tp->t_flags & TF_SACK_PERMIT) && 281 SEQ_LT(tp->snd_nxt, tp->snd_max)) 282 tcp_sack_adjust(tp); 283 sendalot = 0; 284 tso = 0; 285 mtu = 0; 286 off = tp->snd_nxt - tp->snd_una; 287 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 288 289 flags = tcp_outflags[tp->t_state]; 290 /* 291 * Send any SACK-generated retransmissions. If we're explicitly trying 292 * to send out new data (when sendalot is 1), bypass this function. 293 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 294 * we're replacing a (future) new transmission with a retransmission 295 * now, and we previously incremented snd_cwnd in tcp_input(). 296 */ 297 /* 298 * Still in sack recovery , reset rxmit flag to zero. 299 */ 300 sack_rxmit = 0; 301 sack_bytes_rxmt = 0; 302 len = 0; 303 p = NULL; 304 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) && 305 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 306 uint32_t cwin; 307 308 cwin = 309 imax(min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt, 0); 310 /* Do not retransmit SACK segments beyond snd_recover */ 311 if (SEQ_GT(p->end, tp->snd_recover)) { 312 /* 313 * (At least) part of sack hole extends beyond 314 * snd_recover. Check to see if we can rexmit data 315 * for this hole. 316 */ 317 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 318 /* 319 * Can't rexmit any more data for this hole. 320 * That data will be rexmitted in the next 321 * sack recovery episode, when snd_recover 322 * moves past p->rxmit. 323 */ 324 p = NULL; 325 goto after_sack_rexmit; 326 } else 327 /* Can rexmit part of the current hole */ 328 len = ((int32_t)ulmin(cwin, 329 tp->snd_recover - p->rxmit)); 330 } else 331 len = ((int32_t)ulmin(cwin, p->end - p->rxmit)); 332 off = p->rxmit - tp->snd_una; 333 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 334 __func__, off)); 335 if (len > 0) { 336 sack_rxmit = 1; 337 sendalot = 1; 338 TCPSTAT_INC(tcps_sack_rexmits); 339 TCPSTAT_ADD(tcps_sack_rexmit_bytes, 340 min(len, tp->t_maxseg)); 341 } 342 } 343 after_sack_rexmit: 344 /* 345 * Get standard flags, and add SYN or FIN if requested by 'hidden' 346 * state flags. 347 */ 348 if (tp->t_flags & TF_NEEDFIN) 349 flags |= TH_FIN; 350 if (tp->t_flags & TF_NEEDSYN) 351 flags |= TH_SYN; 352 353 SOCKBUF_LOCK(&so->so_snd); 354 /* 355 * If in persist timeout with window of 0, send 1 byte. 356 * Otherwise, if window is small but nonzero 357 * and timer expired, we will send what we can 358 * and go to transmit state. 359 */ 360 if (tp->t_flags & TF_FORCEDATA) { 361 if (sendwin == 0) { 362 /* 363 * If we still have some data to send, then 364 * clear the FIN bit. Usually this would 365 * happen below when it realizes that we 366 * aren't sending all the data. However, 367 * if we have exactly 1 byte of unsent data, 368 * then it won't clear the FIN bit below, 369 * and if we are in persist state, we wind 370 * up sending the packet without recording 371 * that we sent the FIN bit. 372 * 373 * We can't just blindly clear the FIN bit, 374 * because if we don't have any more data 375 * to send then the probe will be the FIN 376 * itself. 377 */ 378 if (off < sbused(&so->so_snd)) 379 flags &= ~TH_FIN; 380 sendwin = 1; 381 } else { 382 tcp_timer_activate(tp, TT_PERSIST, 0); 383 tp->t_rxtshift = 0; 384 } 385 } 386 387 /* 388 * If snd_nxt == snd_max and we have transmitted a FIN, the 389 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 390 * a negative length. This can also occur when TCP opens up 391 * its congestion window while receiving additional duplicate 392 * acks after fast-retransmit because TCP will reset snd_nxt 393 * to snd_max after the fast-retransmit. 394 * 395 * In the normal retransmit-FIN-only case, however, snd_nxt will 396 * be set to snd_una, the offset will be 0, and the length may 397 * wind up 0. 398 * 399 * If sack_rxmit is true we are retransmitting from the scoreboard 400 * in which case len is already set. 401 */ 402 if (sack_rxmit == 0) { 403 if (sack_bytes_rxmt == 0) 404 len = ((int32_t)min(sbavail(&so->so_snd), sendwin) - 405 off); 406 else { 407 int32_t cwin; 408 409 /* 410 * We are inside of a SACK recovery episode and are 411 * sending new data, having retransmitted all the 412 * data possible in the scoreboard. 413 */ 414 len = ((int32_t)min(sbavail(&so->so_snd), tp->snd_wnd) - 415 off); 416 /* 417 * Don't remove this (len > 0) check ! 418 * We explicitly check for len > 0 here (although it 419 * isn't really necessary), to work around a gcc 420 * optimization issue - to force gcc to compute 421 * len above. Without this check, the computation 422 * of len is bungled by the optimizer. 423 */ 424 if (len > 0) { 425 cwin = tp->snd_cwnd - 426 (tp->snd_nxt - tp->sack_newdata) - 427 sack_bytes_rxmt; 428 if (cwin < 0) 429 cwin = 0; 430 len = imin(len, cwin); 431 } 432 } 433 } 434 435 /* 436 * Lop off SYN bit if it has already been sent. However, if this 437 * is SYN-SENT state and if segment contains data and if we don't 438 * know that foreign host supports TAO, suppress sending segment. 439 */ 440 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 441 if (tp->t_state != TCPS_SYN_RECEIVED) 442 flags &= ~TH_SYN; 443 /* 444 * When sending additional segments following a TFO SYN|ACK, 445 * do not include the SYN bit. 446 */ 447 if (IS_FASTOPEN(tp->t_flags) && 448 (tp->t_state == TCPS_SYN_RECEIVED)) 449 flags &= ~TH_SYN; 450 off--, len++; 451 } 452 453 /* 454 * Be careful not to send data and/or FIN on SYN segments. 455 * This measure is needed to prevent interoperability problems 456 * with not fully conformant TCP implementations. 457 */ 458 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 459 len = 0; 460 flags &= ~TH_FIN; 461 } 462 463 /* 464 * On TFO sockets, ensure no data is sent in the following cases: 465 * 466 * - When retransmitting SYN|ACK on a passively-created socket 467 * 468 * - When retransmitting SYN on an actively created socket 469 * 470 * - When sending a zero-length cookie (cookie request) on an 471 * actively created socket 472 * 473 * - When the socket is in the CLOSED state (RST is being sent) 474 */ 475 if (IS_FASTOPEN(tp->t_flags) && 476 (((flags & TH_SYN) && (tp->t_rxtshift > 0)) || 477 ((tp->t_state == TCPS_SYN_SENT) && 478 (tp->t_tfo_client_cookie_len == 0)) || 479 (flags & TH_RST))) 480 len = 0; 481 if (len <= 0) { 482 /* 483 * If FIN has been sent but not acked, 484 * but we haven't been called to retransmit, 485 * len will be < 0. Otherwise, window shrank 486 * after we sent into it. If window shrank to 0, 487 * cancel pending retransmit, pull snd_nxt back 488 * to (closed) window, and set the persist timer 489 * if it isn't already going. If the window didn't 490 * close completely, just wait for an ACK. 491 * 492 * We also do a general check here to ensure that 493 * we will set the persist timer when we have data 494 * to send, but a 0-byte window. This makes sure 495 * the persist timer is set even if the packet 496 * hits one of the "goto send" lines below. 497 */ 498 len = 0; 499 if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) && 500 (off < (int) sbavail(&so->so_snd))) { 501 tcp_timer_activate(tp, TT_REXMT, 0); 502 tp->t_rxtshift = 0; 503 tp->snd_nxt = tp->snd_una; 504 if (!tcp_timer_active(tp, TT_PERSIST)) 505 tcp_setpersist(tp); 506 } 507 } 508 509 /* len will be >= 0 after this point. */ 510 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 511 512 tcp_sndbuf_autoscale(tp, so, sendwin); 513 514 /* 515 * Decide if we can use TCP Segmentation Offloading (if supported by 516 * hardware). 517 * 518 * TSO may only be used if we are in a pure bulk sending state. The 519 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 520 * IP options prevent using TSO. With TSO the TCP header is the same 521 * (except for the sequence number) for all generated packets. This 522 * makes it impossible to transmit any options which vary per generated 523 * segment or packet. 524 * 525 * IPv4 handling has a clear separation of ip options and ip header 526 * flags while IPv6 combines both in in6p_outputopts. ip6_optlen() does 527 * the right thing below to provide length of just ip options and thus 528 * checking for ipoptlen is enough to decide if ip options are present. 529 */ 530 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 531 /* 532 * Pre-calculate here as we save another lookup into the darknesses 533 * of IPsec that way and can actually decide if TSO is ok. 534 */ 535 #ifdef INET6 536 if (isipv6 && IPSEC_ENABLED(ipv6)) 537 ipsec_optlen = IPSEC_HDRSIZE(ipv6, tp->t_inpcb); 538 #ifdef INET 539 else 540 #endif 541 #endif /* INET6 */ 542 #ifdef INET 543 if (IPSEC_ENABLED(ipv4)) 544 ipsec_optlen = IPSEC_HDRSIZE(ipv4, tp->t_inpcb); 545 #endif /* INET */ 546 #endif /* IPSEC */ 547 #ifdef INET6 548 if (isipv6) 549 ipoptlen = ip6_optlen(tp->t_inpcb); 550 else 551 #endif 552 if (tp->t_inpcb->inp_options) 553 ipoptlen = tp->t_inpcb->inp_options->m_len - 554 offsetof(struct ipoption, ipopt_list); 555 else 556 ipoptlen = 0; 557 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 558 ipoptlen += ipsec_optlen; 559 #endif 560 561 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg && 562 ((tp->t_flags & TF_SIGNATURE) == 0) && 563 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 564 ipoptlen == 0 && !(flags & TH_SYN)) 565 tso = 1; 566 567 if (sack_rxmit) { 568 if (SEQ_LT(p->rxmit + len, tp->snd_una + sbused(&so->so_snd))) 569 flags &= ~TH_FIN; 570 } else { 571 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + 572 sbused(&so->so_snd))) 573 flags &= ~TH_FIN; 574 } 575 576 recwin = lmin(lmax(sbspace(&so->so_rcv), 0), 577 (long)TCP_MAXWIN << tp->rcv_scale); 578 579 /* 580 * Sender silly window avoidance. We transmit under the following 581 * conditions when len is non-zero: 582 * 583 * - We have a full segment (or more with TSO) 584 * - This is the last buffer in a write()/send() and we are 585 * either idle or running NODELAY 586 * - we've timed out (e.g. persist timer) 587 * - we have more then 1/2 the maximum send window's worth of 588 * data (receiver may be limited the window size) 589 * - we need to retransmit 590 */ 591 if (len) { 592 if (len >= tp->t_maxseg) 593 goto send; 594 /* 595 * NOTE! on localhost connections an 'ack' from the remote 596 * end may occur synchronously with the output and cause 597 * us to flush a buffer queued with moretocome. XXX 598 * 599 * note: the len + off check is almost certainly unnecessary. 600 */ 601 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 602 (idle || (tp->t_flags & TF_NODELAY)) && 603 (uint32_t)len + (uint32_t)off >= sbavail(&so->so_snd) && 604 (tp->t_flags & TF_NOPUSH) == 0) { 605 goto send; 606 } 607 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 608 goto send; 609 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 610 goto send; 611 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 612 goto send; 613 if (sack_rxmit) 614 goto send; 615 } 616 617 /* 618 * Sending of standalone window updates. 619 * 620 * Window updates are important when we close our window due to a 621 * full socket buffer and are opening it again after the application 622 * reads data from it. Once the window has opened again and the 623 * remote end starts to send again the ACK clock takes over and 624 * provides the most current window information. 625 * 626 * We must avoid the silly window syndrome whereas every read 627 * from the receive buffer, no matter how small, causes a window 628 * update to be sent. We also should avoid sending a flurry of 629 * window updates when the socket buffer had queued a lot of data 630 * and the application is doing small reads. 631 * 632 * Prevent a flurry of pointless window updates by only sending 633 * an update when we can increase the advertized window by more 634 * than 1/4th of the socket buffer capacity. When the buffer is 635 * getting full or is very small be more aggressive and send an 636 * update whenever we can increase by two mss sized segments. 637 * In all other situations the ACK's to new incoming data will 638 * carry further window increases. 639 * 640 * Don't send an independent window update if a delayed 641 * ACK is pending (it will get piggy-backed on it) or the 642 * remote side already has done a half-close and won't send 643 * more data. Skip this if the connection is in T/TCP 644 * half-open state. 645 */ 646 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 647 !(tp->t_flags & TF_DELACK) && 648 !TCPS_HAVERCVDFIN(tp->t_state)) { 649 /* 650 * "adv" is the amount we could increase the window, 651 * taking into account that we are limited by 652 * TCP_MAXWIN << tp->rcv_scale. 653 */ 654 int32_t adv; 655 int oldwin; 656 657 adv = recwin; 658 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { 659 oldwin = (tp->rcv_adv - tp->rcv_nxt); 660 adv -= oldwin; 661 } else 662 oldwin = 0; 663 664 /* 665 * If the new window size ends up being the same as or less 666 * than the old size when it is scaled, then don't force 667 * a window update. 668 */ 669 if (oldwin >> tp->rcv_scale >= (adv + oldwin) >> tp->rcv_scale) 670 goto dontupdate; 671 672 if (adv >= (int32_t)(2 * tp->t_maxseg) && 673 (adv >= (int32_t)(so->so_rcv.sb_hiwat / 4) || 674 recwin <= (so->so_rcv.sb_hiwat / 8) || 675 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg)) 676 goto send; 677 if (2 * adv >= (int32_t)so->so_rcv.sb_hiwat) 678 goto send; 679 } 680 dontupdate: 681 682 /* 683 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 684 * is also a catch-all for the retransmit timer timeout case. 685 */ 686 if (tp->t_flags & TF_ACKNOW) 687 goto send; 688 if ((flags & TH_RST) || 689 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 690 goto send; 691 if (SEQ_GT(tp->snd_up, tp->snd_una)) 692 goto send; 693 /* 694 * If our state indicates that FIN should be sent 695 * and we have not yet done so, then we need to send. 696 */ 697 if (flags & TH_FIN && 698 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 699 goto send; 700 /* 701 * In SACK, it is possible for tcp_output to fail to send a segment 702 * after the retransmission timer has been turned off. Make sure 703 * that the retransmission timer is set. 704 */ 705 if ((tp->t_flags & TF_SACK_PERMIT) && 706 SEQ_GT(tp->snd_max, tp->snd_una) && 707 !tcp_timer_active(tp, TT_REXMT) && 708 !tcp_timer_active(tp, TT_PERSIST)) { 709 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 710 goto just_return; 711 } 712 /* 713 * TCP window updates are not reliable, rather a polling protocol 714 * using ``persist'' packets is used to insure receipt of window 715 * updates. The three ``states'' for the output side are: 716 * idle not doing retransmits or persists 717 * persisting to move a small or zero window 718 * (re)transmitting and thereby not persisting 719 * 720 * tcp_timer_active(tp, TT_PERSIST) 721 * is true when we are in persist state. 722 * (tp->t_flags & TF_FORCEDATA) 723 * is set when we are called to send a persist packet. 724 * tcp_timer_active(tp, TT_REXMT) 725 * is set when we are retransmitting 726 * The output side is idle when both timers are zero. 727 * 728 * If send window is too small, there is data to transmit, and no 729 * retransmit or persist is pending, then go to persist state. 730 * If nothing happens soon, send when timer expires: 731 * if window is nonzero, transmit what we can, 732 * otherwise force out a byte. 733 */ 734 if (sbavail(&so->so_snd) && !tcp_timer_active(tp, TT_REXMT) && 735 !tcp_timer_active(tp, TT_PERSIST)) { 736 tp->t_rxtshift = 0; 737 tcp_setpersist(tp); 738 } 739 740 /* 741 * No reason to send a segment, just return. 742 */ 743 just_return: 744 SOCKBUF_UNLOCK(&so->so_snd); 745 return (0); 746 747 send: 748 SOCKBUF_LOCK_ASSERT(&so->so_snd); 749 if (len > 0) { 750 if (len >= tp->t_maxseg) 751 tp->t_flags2 |= TF2_PLPMTU_MAXSEGSNT; 752 else 753 tp->t_flags2 &= ~TF2_PLPMTU_MAXSEGSNT; 754 } 755 /* 756 * Before ESTABLISHED, force sending of initial options 757 * unless TCP set not to do any options. 758 * NOTE: we assume that the IP/TCP header plus TCP options 759 * always fit in a single mbuf, leaving room for a maximum 760 * link header, i.e. 761 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 762 */ 763 optlen = 0; 764 #ifdef INET6 765 if (isipv6) 766 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 767 else 768 #endif 769 hdrlen = sizeof (struct tcpiphdr); 770 771 /* 772 * Compute options for segment. 773 * We only have to care about SYN and established connection 774 * segments. Options for SYN-ACK segments are handled in TCP 775 * syncache. 776 */ 777 to.to_flags = 0; 778 if ((tp->t_flags & TF_NOOPT) == 0) { 779 /* Maximum segment size. */ 780 if (flags & TH_SYN) { 781 tp->snd_nxt = tp->iss; 782 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 783 to.to_flags |= TOF_MSS; 784 785 /* 786 * On SYN or SYN|ACK transmits on TFO connections, 787 * only include the TFO option if it is not a 788 * retransmit, as the presence of the TFO option may 789 * have caused the original SYN or SYN|ACK to have 790 * been dropped by a middlebox. 791 */ 792 if (IS_FASTOPEN(tp->t_flags) && 793 (tp->t_rxtshift == 0)) { 794 if (tp->t_state == TCPS_SYN_RECEIVED) { 795 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN; 796 to.to_tfo_cookie = 797 (u_int8_t *)&tp->t_tfo_cookie.server; 798 to.to_flags |= TOF_FASTOPEN; 799 wanted_cookie = 1; 800 } else if (tp->t_state == TCPS_SYN_SENT) { 801 to.to_tfo_len = 802 tp->t_tfo_client_cookie_len; 803 to.to_tfo_cookie = 804 tp->t_tfo_cookie.client; 805 to.to_flags |= TOF_FASTOPEN; 806 wanted_cookie = 1; 807 /* 808 * If we wind up having more data to 809 * send with the SYN than can fit in 810 * one segment, don't send any more 811 * until the SYN|ACK comes back from 812 * the other end. 813 */ 814 dont_sendalot = 1; 815 } 816 } 817 } 818 /* Window scaling. */ 819 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 820 to.to_wscale = tp->request_r_scale; 821 to.to_flags |= TOF_SCALE; 822 } 823 /* Timestamps. */ 824 if ((tp->t_flags & TF_RCVD_TSTMP) || 825 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 826 curticks = tcp_ts_getticks(); 827 to.to_tsval = curticks + tp->ts_offset; 828 to.to_tsecr = tp->ts_recent; 829 to.to_flags |= TOF_TS; 830 if (tp->t_rxtshift == 1) 831 tp->t_badrxtwin = curticks; 832 } 833 834 /* Set receive buffer autosizing timestamp. */ 835 if (tp->rfbuf_ts == 0 && 836 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 837 tp->rfbuf_ts = tcp_ts_getticks(); 838 839 /* Selective ACK's. */ 840 if (tp->t_flags & TF_SACK_PERMIT) { 841 if (flags & TH_SYN) 842 to.to_flags |= TOF_SACKPERM; 843 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 844 (tp->t_flags & TF_SACK_PERMIT) && 845 tp->rcv_numsacks > 0) { 846 to.to_flags |= TOF_SACK; 847 to.to_nsacks = tp->rcv_numsacks; 848 to.to_sacks = (u_char *)tp->sackblks; 849 } 850 } 851 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 852 /* TCP-MD5 (RFC2385). */ 853 /* 854 * Check that TCP_MD5SIG is enabled in tcpcb to 855 * account the size needed to set this TCP option. 856 */ 857 if (tp->t_flags & TF_SIGNATURE) 858 to.to_flags |= TOF_SIGNATURE; 859 #endif /* TCP_SIGNATURE */ 860 861 /* Processing the options. */ 862 hdrlen += optlen = tcp_addoptions(&to, opt); 863 /* 864 * If we wanted a TFO option to be added, but it was unable 865 * to fit, ensure no data is sent. 866 */ 867 if (IS_FASTOPEN(tp->t_flags) && wanted_cookie && 868 !(to.to_flags & TOF_FASTOPEN)) 869 len = 0; 870 } 871 872 /* 873 * Adjust data length if insertion of options will 874 * bump the packet length beyond the t_maxseg length. 875 * Clear the FIN bit because we cut off the tail of 876 * the segment. 877 */ 878 if (len + optlen + ipoptlen > tp->t_maxseg) { 879 flags &= ~TH_FIN; 880 881 if (tso) { 882 u_int if_hw_tsomax; 883 u_int if_hw_tsomaxsegcount; 884 u_int if_hw_tsomaxsegsize; 885 struct mbuf *mb; 886 u_int moff; 887 int max_len; 888 889 /* extract TSO information */ 890 if_hw_tsomax = tp->t_tsomax; 891 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount; 892 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize; 893 894 /* 895 * Limit a TSO burst to prevent it from 896 * overflowing or exceeding the maximum length 897 * allowed by the network interface: 898 */ 899 KASSERT(ipoptlen == 0, 900 ("%s: TSO can't do IP options", __func__)); 901 902 /* 903 * Check if we should limit by maximum payload 904 * length: 905 */ 906 if (if_hw_tsomax != 0) { 907 /* compute maximum TSO length */ 908 max_len = (if_hw_tsomax - hdrlen - 909 max_linkhdr); 910 if (max_len <= 0) { 911 len = 0; 912 } else if (len > max_len) { 913 sendalot = 1; 914 len = max_len; 915 } 916 } 917 918 /* 919 * Check if we should limit by maximum segment 920 * size and count: 921 */ 922 if (if_hw_tsomaxsegcount != 0 && 923 if_hw_tsomaxsegsize != 0) { 924 /* 925 * Subtract one segment for the LINK 926 * and TCP/IP headers mbuf that will 927 * be prepended to this mbuf chain 928 * after the code in this section 929 * limits the number of mbufs in the 930 * chain to if_hw_tsomaxsegcount. 931 */ 932 if_hw_tsomaxsegcount -= 1; 933 max_len = 0; 934 mb = sbsndmbuf(&so->so_snd, off, &moff); 935 936 while (mb != NULL && max_len < len) { 937 u_int mlen; 938 u_int frags; 939 940 /* 941 * Get length of mbuf fragment 942 * and how many hardware frags, 943 * rounded up, it would use: 944 */ 945 mlen = (mb->m_len - moff); 946 frags = howmany(mlen, 947 if_hw_tsomaxsegsize); 948 949 /* Handle special case: Zero Length Mbuf */ 950 if (frags == 0) 951 frags = 1; 952 953 /* 954 * Check if the fragment limit 955 * will be reached or exceeded: 956 */ 957 if (frags >= if_hw_tsomaxsegcount) { 958 max_len += min(mlen, 959 if_hw_tsomaxsegcount * 960 if_hw_tsomaxsegsize); 961 break; 962 } 963 max_len += mlen; 964 if_hw_tsomaxsegcount -= frags; 965 moff = 0; 966 mb = mb->m_next; 967 } 968 if (max_len <= 0) { 969 len = 0; 970 } else if (len > max_len) { 971 sendalot = 1; 972 len = max_len; 973 } 974 } 975 976 /* 977 * Prevent the last segment from being 978 * fractional unless the send sockbuf can be 979 * emptied: 980 */ 981 max_len = (tp->t_maxseg - optlen); 982 if (((uint32_t)off + (uint32_t)len) < 983 sbavail(&so->so_snd)) { 984 moff = len % max_len; 985 if (moff != 0) { 986 len -= moff; 987 sendalot = 1; 988 } 989 } 990 991 /* 992 * In case there are too many small fragments 993 * don't use TSO: 994 */ 995 if (len <= max_len) { 996 len = max_len; 997 sendalot = 1; 998 tso = 0; 999 } 1000 1001 /* 1002 * Send the FIN in a separate segment 1003 * after the bulk sending is done. 1004 * We don't trust the TSO implementations 1005 * to clear the FIN flag on all but the 1006 * last segment. 1007 */ 1008 if (tp->t_flags & TF_NEEDFIN) 1009 sendalot = 1; 1010 1011 } else { 1012 len = tp->t_maxseg - optlen - ipoptlen; 1013 sendalot = 1; 1014 if (dont_sendalot) 1015 sendalot = 0; 1016 } 1017 } else 1018 tso = 0; 1019 1020 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 1021 ("%s: len > IP_MAXPACKET", __func__)); 1022 1023 /*#ifdef DIAGNOSTIC*/ 1024 #ifdef INET6 1025 if (max_linkhdr + hdrlen > MCLBYTES) 1026 #else 1027 if (max_linkhdr + hdrlen > MHLEN) 1028 #endif 1029 panic("tcphdr too big"); 1030 /*#endif*/ 1031 1032 /* 1033 * This KASSERT is here to catch edge cases at a well defined place. 1034 * Before, those had triggered (random) panic conditions further down. 1035 */ 1036 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 1037 1038 /* 1039 * Grab a header mbuf, attaching a copy of data to 1040 * be transmitted, and initialize the header from 1041 * the template for sends on this connection. 1042 */ 1043 if (len) { 1044 struct mbuf *mb; 1045 u_int moff; 1046 1047 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 1048 TCPSTAT_INC(tcps_sndprobe); 1049 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 1050 tp->t_sndrexmitpack++; 1051 TCPSTAT_INC(tcps_sndrexmitpack); 1052 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 1053 } else { 1054 TCPSTAT_INC(tcps_sndpack); 1055 TCPSTAT_ADD(tcps_sndbyte, len); 1056 } 1057 #ifdef INET6 1058 if (MHLEN < hdrlen + max_linkhdr) 1059 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR); 1060 else 1061 #endif 1062 m = m_gethdr(M_NOWAIT, MT_DATA); 1063 1064 if (m == NULL) { 1065 SOCKBUF_UNLOCK(&so->so_snd); 1066 error = ENOBUFS; 1067 sack_rxmit = 0; 1068 goto out; 1069 } 1070 1071 m->m_data += max_linkhdr; 1072 m->m_len = hdrlen; 1073 1074 /* 1075 * Start the m_copy functions from the closest mbuf 1076 * to the offset in the socket buffer chain. 1077 */ 1078 mb = sbsndptr(&so->so_snd, off, len, &moff); 1079 1080 if (len <= MHLEN - hdrlen - max_linkhdr) { 1081 m_copydata(mb, moff, len, 1082 mtod(m, caddr_t) + hdrlen); 1083 m->m_len += len; 1084 } else { 1085 m->m_next = m_copym(mb, moff, len, M_NOWAIT); 1086 if (m->m_next == NULL) { 1087 SOCKBUF_UNLOCK(&so->so_snd); 1088 (void) m_free(m); 1089 error = ENOBUFS; 1090 sack_rxmit = 0; 1091 goto out; 1092 } 1093 } 1094 1095 /* 1096 * If we're sending everything we've got, set PUSH. 1097 * (This will keep happy those implementations which only 1098 * give data to the user when a buffer fills or 1099 * a PUSH comes in.) 1100 */ 1101 if (((uint32_t)off + (uint32_t)len == sbused(&so->so_snd)) && 1102 !(flags & TH_SYN)) 1103 flags |= TH_PUSH; 1104 SOCKBUF_UNLOCK(&so->so_snd); 1105 } else { 1106 SOCKBUF_UNLOCK(&so->so_snd); 1107 if (tp->t_flags & TF_ACKNOW) 1108 TCPSTAT_INC(tcps_sndacks); 1109 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 1110 TCPSTAT_INC(tcps_sndctrl); 1111 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 1112 TCPSTAT_INC(tcps_sndurg); 1113 else 1114 TCPSTAT_INC(tcps_sndwinup); 1115 1116 m = m_gethdr(M_NOWAIT, MT_DATA); 1117 if (m == NULL) { 1118 error = ENOBUFS; 1119 sack_rxmit = 0; 1120 goto out; 1121 } 1122 #ifdef INET6 1123 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 1124 MHLEN >= hdrlen) { 1125 M_ALIGN(m, hdrlen); 1126 } else 1127 #endif 1128 m->m_data += max_linkhdr; 1129 m->m_len = hdrlen; 1130 } 1131 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 1132 m->m_pkthdr.rcvif = (struct ifnet *)0; 1133 #ifdef MAC 1134 mac_inpcb_create_mbuf(tp->t_inpcb, m); 1135 #endif 1136 #ifdef INET6 1137 if (isipv6) { 1138 ip6 = mtod(m, struct ip6_hdr *); 1139 th = (struct tcphdr *)(ip6 + 1); 1140 tcpip_fillheaders(tp->t_inpcb, ip6, th); 1141 } else 1142 #endif /* INET6 */ 1143 { 1144 ip = mtod(m, struct ip *); 1145 #ifdef TCPDEBUG 1146 ipov = (struct ipovly *)ip; 1147 #endif 1148 th = (struct tcphdr *)(ip + 1); 1149 tcpip_fillheaders(tp->t_inpcb, ip, th); 1150 } 1151 1152 /* 1153 * Fill in fields, remembering maximum advertised 1154 * window for use in delaying messages about window sizes. 1155 * If resending a FIN, be sure not to use a new sequence number. 1156 */ 1157 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 1158 tp->snd_nxt == tp->snd_max) 1159 tp->snd_nxt--; 1160 /* 1161 * If we are starting a connection, send ECN setup 1162 * SYN packet. If we are on a retransmit, we may 1163 * resend those bits a number of times as per 1164 * RFC 3168. 1165 */ 1166 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn == 1) { 1167 if (tp->t_rxtshift >= 1) { 1168 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 1169 flags |= TH_ECE|TH_CWR; 1170 } else 1171 flags |= TH_ECE|TH_CWR; 1172 } 1173 1174 if (tp->t_state == TCPS_ESTABLISHED && 1175 (tp->t_flags & TF_ECN_PERMIT)) { 1176 /* 1177 * If the peer has ECN, mark data packets with 1178 * ECN capable transmission (ECT). 1179 * Ignore pure ack packets, retransmissions and window probes. 1180 */ 1181 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 1182 !((tp->t_flags & TF_FORCEDATA) && len == 1)) { 1183 #ifdef INET6 1184 if (isipv6) 1185 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 1186 else 1187 #endif 1188 ip->ip_tos |= IPTOS_ECN_ECT0; 1189 TCPSTAT_INC(tcps_ecn_ect0); 1190 } 1191 1192 /* 1193 * Reply with proper ECN notifications. 1194 */ 1195 if (tp->t_flags & TF_ECN_SND_CWR) { 1196 flags |= TH_CWR; 1197 tp->t_flags &= ~TF_ECN_SND_CWR; 1198 } 1199 if (tp->t_flags & TF_ECN_SND_ECE) 1200 flags |= TH_ECE; 1201 } 1202 1203 /* 1204 * If we are doing retransmissions, then snd_nxt will 1205 * not reflect the first unsent octet. For ACK only 1206 * packets, we do not want the sequence number of the 1207 * retransmitted packet, we want the sequence number 1208 * of the next unsent octet. So, if there is no data 1209 * (and no SYN or FIN), use snd_max instead of snd_nxt 1210 * when filling in ti_seq. But if we are in persist 1211 * state, snd_max might reflect one byte beyond the 1212 * right edge of the window, so use snd_nxt in that 1213 * case, since we know we aren't doing a retransmission. 1214 * (retransmit and persist are mutually exclusive...) 1215 */ 1216 if (sack_rxmit == 0) { 1217 if (len || (flags & (TH_SYN|TH_FIN)) || 1218 tcp_timer_active(tp, TT_PERSIST)) 1219 th->th_seq = htonl(tp->snd_nxt); 1220 else 1221 th->th_seq = htonl(tp->snd_max); 1222 } else { 1223 th->th_seq = htonl(p->rxmit); 1224 p->rxmit += len; 1225 tp->sackhint.sack_bytes_rexmit += len; 1226 } 1227 th->th_ack = htonl(tp->rcv_nxt); 1228 if (optlen) { 1229 bcopy(opt, th + 1, optlen); 1230 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1231 } 1232 th->th_flags = flags; 1233 /* 1234 * Calculate receive window. Don't shrink window, 1235 * but avoid silly window syndrome. 1236 */ 1237 if (recwin < (so->so_rcv.sb_hiwat / 4) && 1238 recwin < tp->t_maxseg) 1239 recwin = 0; 1240 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1241 recwin < (tp->rcv_adv - tp->rcv_nxt)) 1242 recwin = (tp->rcv_adv - tp->rcv_nxt); 1243 1244 /* 1245 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1246 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1247 * case is handled in syncache. 1248 */ 1249 if (flags & TH_SYN) 1250 th->th_win = htons((u_short) 1251 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1252 else 1253 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1254 1255 /* 1256 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1257 * a 0 window. This may cause the remote transmitter to stall. This 1258 * flag tells soreceive() to disable delayed acknowledgements when 1259 * draining the buffer. This can occur if the receiver is attempting 1260 * to read more data than can be buffered prior to transmitting on 1261 * the connection. 1262 */ 1263 if (th->th_win == 0) { 1264 tp->t_sndzerowin++; 1265 tp->t_flags |= TF_RXWIN0SENT; 1266 } else 1267 tp->t_flags &= ~TF_RXWIN0SENT; 1268 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1269 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1270 th->th_flags |= TH_URG; 1271 } else 1272 /* 1273 * If no urgent pointer to send, then we pull 1274 * the urgent pointer to the left edge of the send window 1275 * so that it doesn't drift into the send window on sequence 1276 * number wraparound. 1277 */ 1278 tp->snd_up = tp->snd_una; /* drag it along */ 1279 1280 /* 1281 * Put TCP length in extended header, and then 1282 * checksum extended header and data. 1283 */ 1284 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1285 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1286 1287 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1288 if (to.to_flags & TOF_SIGNATURE) { 1289 /* 1290 * Calculate MD5 signature and put it into the place 1291 * determined before. 1292 * NOTE: since TCP options buffer doesn't point into 1293 * mbuf's data, calculate offset and use it. 1294 */ 1295 if (!TCPMD5_ENABLED() || (error = TCPMD5_OUTPUT(m, th, 1296 (u_char *)(th + 1) + (to.to_signature - opt))) != 0) { 1297 /* 1298 * Do not send segment if the calculation of MD5 1299 * digest has failed. 1300 */ 1301 m_freem(m); 1302 goto out; 1303 } 1304 } 1305 #endif 1306 #ifdef INET6 1307 if (isipv6) { 1308 /* 1309 * There is no need to fill in ip6_plen right now. 1310 * It will be filled later by ip6_output. 1311 */ 1312 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1313 th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) + 1314 optlen + len, IPPROTO_TCP, 0); 1315 } 1316 #endif 1317 #if defined(INET6) && defined(INET) 1318 else 1319 #endif 1320 #ifdef INET 1321 { 1322 m->m_pkthdr.csum_flags = CSUM_TCP; 1323 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1324 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1325 1326 /* IP version must be set here for ipv4/ipv6 checking later */ 1327 KASSERT(ip->ip_v == IPVERSION, 1328 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1329 } 1330 #endif 1331 1332 /* 1333 * Enable TSO and specify the size of the segments. 1334 * The TCP pseudo header checksum is always provided. 1335 */ 1336 if (tso) { 1337 KASSERT(len > tp->t_maxseg - optlen, 1338 ("%s: len <= tso_segsz", __func__)); 1339 m->m_pkthdr.csum_flags |= CSUM_TSO; 1340 m->m_pkthdr.tso_segsz = tp->t_maxseg - optlen; 1341 } 1342 1343 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 1344 KASSERT(len + hdrlen + ipoptlen - ipsec_optlen == m_length(m, NULL), 1345 ("%s: mbuf chain shorter than expected: %d + %u + %u - %u != %u", 1346 __func__, len, hdrlen, ipoptlen, ipsec_optlen, m_length(m, NULL))); 1347 #else 1348 KASSERT(len + hdrlen + ipoptlen == m_length(m, NULL), 1349 ("%s: mbuf chain shorter than expected: %d + %u + %u != %u", 1350 __func__, len, hdrlen, ipoptlen, m_length(m, NULL))); 1351 #endif 1352 1353 #ifdef TCP_HHOOK 1354 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1355 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1356 #endif 1357 1358 #ifdef TCPDEBUG 1359 /* 1360 * Trace. 1361 */ 1362 if (so->so_options & SO_DEBUG) { 1363 u_short save = 0; 1364 #ifdef INET6 1365 if (!isipv6) 1366 #endif 1367 { 1368 save = ipov->ih_len; 1369 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1370 } 1371 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1372 #ifdef INET6 1373 if (!isipv6) 1374 #endif 1375 ipov->ih_len = save; 1376 } 1377 #endif /* TCPDEBUG */ 1378 TCP_PROBE3(debug__output, tp, th, m); 1379 1380 /* We're getting ready to send; log now. */ 1381 TCP_LOG_EVENT(tp, th, &so->so_rcv, &so->so_snd, TCP_LOG_OUT, ERRNO_UNK, 1382 len, NULL, false); 1383 1384 /* 1385 * Fill in IP length and desired time to live and 1386 * send to IP level. There should be a better way 1387 * to handle ttl and tos; we could keep them in 1388 * the template, but need a way to checksum without them. 1389 */ 1390 /* 1391 * m->m_pkthdr.len should have been set before checksum calculation, 1392 * because in6_cksum() need it. 1393 */ 1394 #ifdef INET6 1395 if (isipv6) { 1396 /* 1397 * we separately set hoplimit for every segment, since the 1398 * user might want to change the value via setsockopt. 1399 * Also, desired default hop limit might be changed via 1400 * Neighbor Discovery. 1401 */ 1402 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1403 1404 /* 1405 * Set the packet size here for the benefit of DTrace probes. 1406 * ip6_output() will set it properly; it's supposed to include 1407 * the option header lengths as well. 1408 */ 1409 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6)); 1410 1411 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) 1412 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1413 else 1414 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1415 1416 if (tp->t_state == TCPS_SYN_SENT) 1417 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th); 1418 1419 TCP_PROBE5(send, NULL, tp, ip6, tp, th); 1420 1421 #ifdef TCPPCAP 1422 /* Save packet, if requested. */ 1423 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1424 #endif 1425 1426 /* TODO: IPv6 IP6TOS_ECT bit on */ 1427 error = ip6_output(m, tp->t_inpcb->in6p_outputopts, 1428 &tp->t_inpcb->inp_route6, 1429 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 1430 NULL, NULL, tp->t_inpcb); 1431 1432 if (error == EMSGSIZE && tp->t_inpcb->inp_route6.ro_rt != NULL) 1433 mtu = tp->t_inpcb->inp_route6.ro_rt->rt_mtu; 1434 } 1435 #endif /* INET6 */ 1436 #if defined(INET) && defined(INET6) 1437 else 1438 #endif 1439 #ifdef INET 1440 { 1441 ip->ip_len = htons(m->m_pkthdr.len); 1442 #ifdef INET6 1443 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1444 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1445 #endif /* INET6 */ 1446 /* 1447 * If we do path MTU discovery, then we set DF on every packet. 1448 * This might not be the best thing to do according to RFC3390 1449 * Section 2. However the tcp hostcache migitates the problem 1450 * so it affects only the first tcp connection with a host. 1451 * 1452 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1453 */ 1454 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) { 1455 ip->ip_off |= htons(IP_DF); 1456 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1457 } else { 1458 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1459 } 1460 1461 if (tp->t_state == TCPS_SYN_SENT) 1462 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th); 1463 1464 TCP_PROBE5(send, NULL, tp, ip, tp, th); 1465 1466 #ifdef TCPPCAP 1467 /* Save packet, if requested. */ 1468 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1469 #endif 1470 1471 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, 1472 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1473 tp->t_inpcb); 1474 1475 if (error == EMSGSIZE && tp->t_inpcb->inp_route.ro_rt != NULL) 1476 mtu = tp->t_inpcb->inp_route.ro_rt->rt_mtu; 1477 } 1478 #endif /* INET */ 1479 1480 out: 1481 /* 1482 * In transmit state, time the transmission and arrange for 1483 * the retransmit. In persist state, just set snd_max. 1484 */ 1485 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1486 !tcp_timer_active(tp, TT_PERSIST)) { 1487 tcp_seq startseq = tp->snd_nxt; 1488 1489 /* 1490 * Advance snd_nxt over sequence space of this segment. 1491 */ 1492 if (flags & (TH_SYN|TH_FIN)) { 1493 if (flags & TH_SYN) 1494 tp->snd_nxt++; 1495 if (flags & TH_FIN) { 1496 tp->snd_nxt++; 1497 tp->t_flags |= TF_SENTFIN; 1498 } 1499 } 1500 if (sack_rxmit) 1501 goto timer; 1502 tp->snd_nxt += len; 1503 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1504 tp->snd_max = tp->snd_nxt; 1505 /* 1506 * Time this transmission if not a retransmission and 1507 * not currently timing anything. 1508 */ 1509 if (tp->t_rtttime == 0) { 1510 tp->t_rtttime = ticks; 1511 tp->t_rtseq = startseq; 1512 TCPSTAT_INC(tcps_segstimed); 1513 } 1514 } 1515 1516 /* 1517 * Set retransmit timer if not currently set, 1518 * and not doing a pure ack or a keep-alive probe. 1519 * Initial value for retransmit timer is smoothed 1520 * round-trip time + 2 * round-trip time variance. 1521 * Initialize shift counter which is used for backoff 1522 * of retransmit time. 1523 */ 1524 timer: 1525 if (!tcp_timer_active(tp, TT_REXMT) && 1526 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1527 (tp->snd_nxt != tp->snd_una))) { 1528 if (tcp_timer_active(tp, TT_PERSIST)) { 1529 tcp_timer_activate(tp, TT_PERSIST, 0); 1530 tp->t_rxtshift = 0; 1531 } 1532 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1533 } else if (len == 0 && sbavail(&so->so_snd) && 1534 !tcp_timer_active(tp, TT_REXMT) && 1535 !tcp_timer_active(tp, TT_PERSIST)) { 1536 /* 1537 * Avoid a situation where we do not set persist timer 1538 * after a zero window condition. For example: 1539 * 1) A -> B: packet with enough data to fill the window 1540 * 2) B -> A: ACK for #1 + new data (0 window 1541 * advertisement) 1542 * 3) A -> B: ACK for #2, 0 len packet 1543 * 1544 * In this case, A will not activate the persist timer, 1545 * because it chose to send a packet. Unless tcp_output 1546 * is called for some other reason (delayed ack timer, 1547 * another input packet from B, socket syscall), A will 1548 * not send zero window probes. 1549 * 1550 * So, if you send a 0-length packet, but there is data 1551 * in the socket buffer, and neither the rexmt or 1552 * persist timer is already set, then activate the 1553 * persist timer. 1554 */ 1555 tp->t_rxtshift = 0; 1556 tcp_setpersist(tp); 1557 } 1558 } else { 1559 /* 1560 * Persist case, update snd_max but since we are in 1561 * persist mode (no window) we do not update snd_nxt. 1562 */ 1563 int xlen = len; 1564 if (flags & TH_SYN) 1565 ++xlen; 1566 if (flags & TH_FIN) { 1567 ++xlen; 1568 tp->t_flags |= TF_SENTFIN; 1569 } 1570 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1571 tp->snd_max = tp->snd_nxt + xlen; 1572 } 1573 1574 if (error) { 1575 /* Record the error. */ 1576 TCP_LOG_EVENT(tp, NULL, &so->so_rcv, &so->so_snd, TCP_LOG_OUT, 1577 error, 0, NULL, false); 1578 1579 /* 1580 * We know that the packet was lost, so back out the 1581 * sequence number advance, if any. 1582 * 1583 * If the error is EPERM the packet got blocked by the 1584 * local firewall. Normally we should terminate the 1585 * connection but the blocking may have been spurious 1586 * due to a firewall reconfiguration cycle. So we treat 1587 * it like a packet loss and let the retransmit timer and 1588 * timeouts do their work over time. 1589 * XXX: It is a POLA question whether calling tcp_drop right 1590 * away would be the really correct behavior instead. 1591 */ 1592 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1593 !tcp_timer_active(tp, TT_PERSIST)) && 1594 ((flags & TH_SYN) == 0) && 1595 (error != EPERM)) { 1596 if (sack_rxmit) { 1597 p->rxmit -= len; 1598 tp->sackhint.sack_bytes_rexmit -= len; 1599 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1600 ("sackhint bytes rtx >= 0")); 1601 } else 1602 tp->snd_nxt -= len; 1603 } 1604 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1605 switch (error) { 1606 case EACCES: 1607 case EPERM: 1608 tp->t_softerror = error; 1609 return (error); 1610 case ENOBUFS: 1611 TCP_XMIT_TIMER_ASSERT(tp, len, flags); 1612 tp->snd_cwnd = tp->t_maxseg; 1613 return (0); 1614 case EMSGSIZE: 1615 /* 1616 * For some reason the interface we used initially 1617 * to send segments changed to another or lowered 1618 * its MTU. 1619 * If TSO was active we either got an interface 1620 * without TSO capabilits or TSO was turned off. 1621 * If we obtained mtu from ip_output() then update 1622 * it and try again. 1623 */ 1624 if (tso) 1625 tp->t_flags &= ~TF_TSO; 1626 if (mtu != 0) { 1627 tcp_mss_update(tp, -1, mtu, NULL, NULL); 1628 goto again; 1629 } 1630 return (error); 1631 case EHOSTDOWN: 1632 case EHOSTUNREACH: 1633 case ENETDOWN: 1634 case ENETUNREACH: 1635 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1636 tp->t_softerror = error; 1637 return (0); 1638 } 1639 /* FALLTHROUGH */ 1640 default: 1641 return (error); 1642 } 1643 } 1644 TCPSTAT_INC(tcps_sndtotal); 1645 1646 /* 1647 * Data sent (as far as we can tell). 1648 * If this advertises a larger window than any other segment, 1649 * then remember the size of the advertised window. 1650 * Any pending ACK has now been sent. 1651 */ 1652 if (SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1653 tp->rcv_adv = tp->rcv_nxt + recwin; 1654 tp->last_ack_sent = tp->rcv_nxt; 1655 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1656 if (tcp_timer_active(tp, TT_DELACK)) 1657 tcp_timer_activate(tp, TT_DELACK, 0); 1658 #if 0 1659 /* 1660 * This completely breaks TCP if newreno is turned on. What happens 1661 * is that if delayed-acks are turned on on the receiver, this code 1662 * on the transmitter effectively destroys the TCP window, forcing 1663 * it to four packets (1.5Kx4 = 6K window). 1664 */ 1665 if (sendalot && --maxburst) 1666 goto again; 1667 #endif 1668 if (sendalot) 1669 goto again; 1670 return (0); 1671 } 1672 1673 void 1674 tcp_setpersist(struct tcpcb *tp) 1675 { 1676 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1677 int tt; 1678 1679 tp->t_flags &= ~TF_PREVVALID; 1680 if (tcp_timer_active(tp, TT_REXMT)) 1681 panic("tcp_setpersist: retransmit pending"); 1682 /* 1683 * Start/restart persistence timer. 1684 */ 1685 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1686 tcp_persmin, tcp_persmax); 1687 tcp_timer_activate(tp, TT_PERSIST, tt); 1688 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1689 tp->t_rxtshift++; 1690 } 1691 1692 /* 1693 * Insert TCP options according to the supplied parameters to the place 1694 * optp in a consistent way. Can handle unaligned destinations. 1695 * 1696 * The order of the option processing is crucial for optimal packing and 1697 * alignment for the scarce option space. 1698 * 1699 * The optimal order for a SYN/SYN-ACK segment is: 1700 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1701 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1702 * 1703 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1704 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1705 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1706 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1707 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1708 */ 1709 int 1710 tcp_addoptions(struct tcpopt *to, u_char *optp) 1711 { 1712 u_int32_t mask, optlen = 0; 1713 1714 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1715 if ((to->to_flags & mask) != mask) 1716 continue; 1717 if (optlen == TCP_MAXOLEN) 1718 break; 1719 switch (to->to_flags & mask) { 1720 case TOF_MSS: 1721 while (optlen % 4) { 1722 optlen += TCPOLEN_NOP; 1723 *optp++ = TCPOPT_NOP; 1724 } 1725 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1726 continue; 1727 optlen += TCPOLEN_MAXSEG; 1728 *optp++ = TCPOPT_MAXSEG; 1729 *optp++ = TCPOLEN_MAXSEG; 1730 to->to_mss = htons(to->to_mss); 1731 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1732 optp += sizeof(to->to_mss); 1733 break; 1734 case TOF_SCALE: 1735 while (!optlen || optlen % 2 != 1) { 1736 optlen += TCPOLEN_NOP; 1737 *optp++ = TCPOPT_NOP; 1738 } 1739 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1740 continue; 1741 optlen += TCPOLEN_WINDOW; 1742 *optp++ = TCPOPT_WINDOW; 1743 *optp++ = TCPOLEN_WINDOW; 1744 *optp++ = to->to_wscale; 1745 break; 1746 case TOF_SACKPERM: 1747 while (optlen % 2) { 1748 optlen += TCPOLEN_NOP; 1749 *optp++ = TCPOPT_NOP; 1750 } 1751 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1752 continue; 1753 optlen += TCPOLEN_SACK_PERMITTED; 1754 *optp++ = TCPOPT_SACK_PERMITTED; 1755 *optp++ = TCPOLEN_SACK_PERMITTED; 1756 break; 1757 case TOF_TS: 1758 while (!optlen || optlen % 4 != 2) { 1759 optlen += TCPOLEN_NOP; 1760 *optp++ = TCPOPT_NOP; 1761 } 1762 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1763 continue; 1764 optlen += TCPOLEN_TIMESTAMP; 1765 *optp++ = TCPOPT_TIMESTAMP; 1766 *optp++ = TCPOLEN_TIMESTAMP; 1767 to->to_tsval = htonl(to->to_tsval); 1768 to->to_tsecr = htonl(to->to_tsecr); 1769 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1770 optp += sizeof(to->to_tsval); 1771 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1772 optp += sizeof(to->to_tsecr); 1773 break; 1774 case TOF_SIGNATURE: 1775 { 1776 int siglen = TCPOLEN_SIGNATURE - 2; 1777 1778 while (!optlen || optlen % 4 != 2) { 1779 optlen += TCPOLEN_NOP; 1780 *optp++ = TCPOPT_NOP; 1781 } 1782 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) { 1783 to->to_flags &= ~TOF_SIGNATURE; 1784 continue; 1785 } 1786 optlen += TCPOLEN_SIGNATURE; 1787 *optp++ = TCPOPT_SIGNATURE; 1788 *optp++ = TCPOLEN_SIGNATURE; 1789 to->to_signature = optp; 1790 while (siglen--) 1791 *optp++ = 0; 1792 break; 1793 } 1794 case TOF_SACK: 1795 { 1796 int sackblks = 0; 1797 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1798 tcp_seq sack_seq; 1799 1800 while (!optlen || optlen % 4 != 2) { 1801 optlen += TCPOLEN_NOP; 1802 *optp++ = TCPOPT_NOP; 1803 } 1804 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1805 continue; 1806 optlen += TCPOLEN_SACKHDR; 1807 *optp++ = TCPOPT_SACK; 1808 sackblks = min(to->to_nsacks, 1809 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1810 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1811 while (sackblks--) { 1812 sack_seq = htonl(sack->start); 1813 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1814 optp += sizeof(sack_seq); 1815 sack_seq = htonl(sack->end); 1816 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1817 optp += sizeof(sack_seq); 1818 optlen += TCPOLEN_SACK; 1819 sack++; 1820 } 1821 TCPSTAT_INC(tcps_sack_send_blocks); 1822 break; 1823 } 1824 case TOF_FASTOPEN: 1825 { 1826 int total_len; 1827 1828 /* XXX is there any point to aligning this option? */ 1829 total_len = TCPOLEN_FAST_OPEN_EMPTY + to->to_tfo_len; 1830 if (TCP_MAXOLEN - optlen < total_len) { 1831 to->to_flags &= ~TOF_FASTOPEN; 1832 continue; 1833 } 1834 *optp++ = TCPOPT_FAST_OPEN; 1835 *optp++ = total_len; 1836 if (to->to_tfo_len > 0) { 1837 bcopy(to->to_tfo_cookie, optp, to->to_tfo_len); 1838 optp += to->to_tfo_len; 1839 } 1840 optlen += total_len; 1841 break; 1842 } 1843 default: 1844 panic("%s: unknown TCP option type", __func__); 1845 break; 1846 } 1847 } 1848 1849 /* Terminate and pad TCP options to a 4 byte boundary. */ 1850 if (optlen % 4) { 1851 optlen += TCPOLEN_EOL; 1852 *optp++ = TCPOPT_EOL; 1853 } 1854 /* 1855 * According to RFC 793 (STD0007): 1856 * "The content of the header beyond the End-of-Option option 1857 * must be header padding (i.e., zero)." 1858 * and later: "The padding is composed of zeros." 1859 */ 1860 while (optlen % 4) { 1861 optlen += TCPOLEN_PAD; 1862 *optp++ = TCPOPT_PAD; 1863 } 1864 1865 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1866 return (optlen); 1867 } 1868 1869 /* 1870 * This is a copy of m_copym(), taking the TSO segment size/limit 1871 * constraints into account, and advancing the sndptr as it goes. 1872 */ 1873 struct mbuf * 1874 tcp_m_copym(struct mbuf *m, int32_t off0, int32_t *plen, 1875 int32_t seglimit, int32_t segsize, struct sockbuf *sb) 1876 { 1877 struct mbuf *n, **np; 1878 struct mbuf *top; 1879 int32_t off = off0; 1880 int32_t len = *plen; 1881 int32_t fragsize; 1882 int32_t len_cp = 0; 1883 int32_t *pkthdrlen; 1884 uint32_t mlen, frags; 1885 bool copyhdr; 1886 1887 1888 KASSERT(off >= 0, ("tcp_m_copym, negative off %d", off)); 1889 KASSERT(len >= 0, ("tcp_m_copym, negative len %d", len)); 1890 if (off == 0 && m->m_flags & M_PKTHDR) 1891 copyhdr = true; 1892 else 1893 copyhdr = false; 1894 while (off > 0) { 1895 KASSERT(m != NULL, ("tcp_m_copym, offset > size of mbuf chain")); 1896 if (off < m->m_len) 1897 break; 1898 off -= m->m_len; 1899 if ((sb) && (m == sb->sb_sndptr)) { 1900 sb->sb_sndptroff += m->m_len; 1901 sb->sb_sndptr = m->m_next; 1902 } 1903 m = m->m_next; 1904 } 1905 np = ⊤ 1906 top = NULL; 1907 pkthdrlen = NULL; 1908 while (len > 0) { 1909 if (m == NULL) { 1910 KASSERT(len == M_COPYALL, 1911 ("tcp_m_copym, length > size of mbuf chain")); 1912 *plen = len_cp; 1913 if (pkthdrlen != NULL) 1914 *pkthdrlen = len_cp; 1915 break; 1916 } 1917 mlen = min(len, m->m_len - off); 1918 if (seglimit) { 1919 /* 1920 * For M_NOMAP mbufs, add 3 segments 1921 * + 1 in case we are crossing page boundaries 1922 * + 2 in case the TLS hdr/trailer are used 1923 * It is cheaper to just add the segments 1924 * than it is to take the cache miss to look 1925 * at the mbuf ext_pgs state in detail. 1926 */ 1927 if (m->m_flags & M_NOMAP) { 1928 fragsize = min(segsize, PAGE_SIZE); 1929 frags = 3; 1930 } else { 1931 fragsize = segsize; 1932 frags = 0; 1933 } 1934 1935 /* Break if we really can't fit anymore. */ 1936 if ((frags + 1) >= seglimit) { 1937 *plen = len_cp; 1938 if (pkthdrlen != NULL) 1939 *pkthdrlen = len_cp; 1940 break; 1941 } 1942 1943 /* 1944 * Reduce size if you can't copy the whole 1945 * mbuf. If we can't copy the whole mbuf, also 1946 * adjust len so the loop will end after this 1947 * mbuf. 1948 */ 1949 if ((frags + howmany(mlen, fragsize)) >= seglimit) { 1950 mlen = (seglimit - frags - 1) * fragsize; 1951 len = mlen; 1952 *plen = len_cp + len; 1953 if (pkthdrlen != NULL) 1954 *pkthdrlen = *plen; 1955 } 1956 frags += howmany(mlen, fragsize); 1957 if (frags == 0) 1958 frags++; 1959 seglimit -= frags; 1960 KASSERT(seglimit > 0, 1961 ("%s: seglimit went too low", __func__)); 1962 } 1963 if (copyhdr) 1964 n = m_gethdr(M_NOWAIT, m->m_type); 1965 else 1966 n = m_get(M_NOWAIT, m->m_type); 1967 *np = n; 1968 if (n == NULL) 1969 goto nospace; 1970 if (copyhdr) { 1971 if (!m_dup_pkthdr(n, m, M_NOWAIT)) 1972 goto nospace; 1973 if (len == M_COPYALL) 1974 n->m_pkthdr.len -= off0; 1975 else 1976 n->m_pkthdr.len = len; 1977 pkthdrlen = &n->m_pkthdr.len; 1978 copyhdr = false; 1979 } 1980 n->m_len = mlen; 1981 len_cp += n->m_len; 1982 if (m->m_flags & M_EXT) { 1983 n->m_data = m->m_data + off; 1984 mb_dupcl(n, m); 1985 } else 1986 bcopy(mtod(m, caddr_t)+off, mtod(n, caddr_t), 1987 (u_int)n->m_len); 1988 1989 if (sb && (sb->sb_sndptr == m) && 1990 ((n->m_len + off) >= m->m_len) && m->m_next) { 1991 sb->sb_sndptroff += m->m_len; 1992 sb->sb_sndptr = m->m_next; 1993 } 1994 off = 0; 1995 if (len != M_COPYALL) { 1996 len -= n->m_len; 1997 } 1998 m = m->m_next; 1999 np = &n->m_next; 2000 } 2001 return (top); 2002 nospace: 2003 m_freem(top); 2004 return (NULL); 2005 } 2006 2007 void 2008 tcp_sndbuf_autoscale(struct tcpcb *tp, struct socket *so, uint32_t sendwin) 2009 { 2010 2011 /* 2012 * Automatic sizing of send socket buffer. Often the send buffer 2013 * size is not optimally adjusted to the actual network conditions 2014 * at hand (delay bandwidth product). Setting the buffer size too 2015 * small limits throughput on links with high bandwidth and high 2016 * delay (eg. trans-continental/oceanic links). Setting the 2017 * buffer size too big consumes too much real kernel memory, 2018 * especially with many connections on busy servers. 2019 * 2020 * The criteria to step up the send buffer one notch are: 2021 * 1. receive window of remote host is larger than send buffer 2022 * (with a fudge factor of 5/4th); 2023 * 2. send buffer is filled to 7/8th with data (so we actually 2024 * have data to make use of it); 2025 * 3. send buffer fill has not hit maximal automatic size; 2026 * 4. our send window (slow start and cogestion controlled) is 2027 * larger than sent but unacknowledged data in send buffer. 2028 * 2029 * The remote host receive window scaling factor may limit the 2030 * growing of the send buffer before it reaches its allowed 2031 * maximum. 2032 * 2033 * It scales directly with slow start or congestion window 2034 * and does at most one step per received ACK. This fast 2035 * scaling has the drawback of growing the send buffer beyond 2036 * what is strictly necessary to make full use of a given 2037 * delay*bandwidth product. However testing has shown this not 2038 * to be much of an problem. At worst we are trading wasting 2039 * of available bandwidth (the non-use of it) for wasting some 2040 * socket buffer memory. 2041 * 2042 * TODO: Shrink send buffer during idle periods together 2043 * with congestion window. Requires another timer. Has to 2044 * wait for upcoming tcp timer rewrite. 2045 * 2046 * XXXGL: should there be used sbused() or sbavail()? 2047 */ 2048 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 2049 int lowat; 2050 2051 lowat = V_tcp_sendbuf_auto_lowat ? so->so_snd.sb_lowat : 0; 2052 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat - lowat && 2053 sbused(&so->so_snd) >= 2054 (so->so_snd.sb_hiwat / 8 * 7) - lowat && 2055 sbused(&so->so_snd) < V_tcp_autosndbuf_max && 2056 sendwin >= (sbused(&so->so_snd) - 2057 (tp->snd_nxt - tp->snd_una))) { 2058 if (!sbreserve_locked(&so->so_snd, 2059 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 2060 V_tcp_autosndbuf_max), so, curthread)) 2061 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 2062 } 2063 } 2064 } 2065