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_kern_tls.h" 41 42 #include <sys/param.h> 43 #include <sys/systm.h> 44 #include <sys/arb.h> 45 #include <sys/domain.h> 46 #ifdef TCP_HHOOK 47 #include <sys/hhook.h> 48 #endif 49 #include <sys/kernel.h> 50 #ifdef KERN_TLS 51 #include <sys/ktls.h> 52 #endif 53 #include <sys/lock.h> 54 #include <sys/mbuf.h> 55 #include <sys/mutex.h> 56 #include <sys/protosw.h> 57 #include <sys/qmath.h> 58 #include <sys/sdt.h> 59 #include <sys/socket.h> 60 #include <sys/socketvar.h> 61 #include <sys/sysctl.h> 62 #include <sys/stats.h> 63 64 #include <net/if.h> 65 #include <net/route.h> 66 #include <net/route/nhop.h> 67 #include <net/vnet.h> 68 69 #include <netinet/in.h> 70 #include <netinet/in_kdtrace.h> 71 #include <netinet/in_systm.h> 72 #include <netinet/ip.h> 73 #include <netinet/in_pcb.h> 74 #include <netinet/ip_var.h> 75 #include <netinet/ip_options.h> 76 #ifdef INET6 77 #include <netinet6/in6_pcb.h> 78 #include <netinet/ip6.h> 79 #include <netinet6/ip6_var.h> 80 #endif 81 #include <netinet/tcp.h> 82 #define TCPOUTFLAGS 83 #include <netinet/tcp_fsm.h> 84 #include <netinet/tcp_seq.h> 85 #include <netinet/tcp_var.h> 86 #include <netinet/tcp_log_buf.h> 87 #include <netinet/tcp_syncache.h> 88 #include <netinet/tcp_timer.h> 89 #include <netinet/tcpip.h> 90 #include <netinet/cc/cc.h> 91 #include <netinet/tcp_fastopen.h> 92 #ifdef TCPPCAP 93 #include <netinet/tcp_pcap.h> 94 #endif 95 #ifdef TCP_OFFLOAD 96 #include <netinet/tcp_offload.h> 97 #endif 98 #include <netinet/tcp_ecn.h> 99 100 #include <netipsec/ipsec_support.h> 101 102 #include <netinet/udp.h> 103 #include <netinet/udp_var.h> 104 #include <machine/in_cksum.h> 105 106 #include <security/mac/mac_framework.h> 107 108 VNET_DEFINE(int, path_mtu_discovery) = 1; 109 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_VNET | CTLFLAG_RW, 110 &VNET_NAME(path_mtu_discovery), 1, 111 "Enable Path MTU Discovery"); 112 113 VNET_DEFINE(int, tcp_do_tso) = 1; 114 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_VNET | CTLFLAG_RW, 115 &VNET_NAME(tcp_do_tso), 0, 116 "Enable TCP Segmentation Offload"); 117 118 VNET_DEFINE(int, tcp_sendspace) = 1024*32; 119 #define V_tcp_sendspace VNET(tcp_sendspace) 120 SYSCTL_INT(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, CTLFLAG_VNET | CTLFLAG_RW, 121 &VNET_NAME(tcp_sendspace), 0, "Initial send socket buffer size"); 122 123 VNET_DEFINE(int, tcp_do_autosndbuf) = 1; 124 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_VNET | CTLFLAG_RW, 125 &VNET_NAME(tcp_do_autosndbuf), 0, 126 "Enable automatic send buffer sizing"); 127 128 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024; 129 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_VNET | CTLFLAG_RW, 130 &VNET_NAME(tcp_autosndbuf_inc), 0, 131 "Incrementor step size of automatic send buffer"); 132 133 VNET_DEFINE(int, tcp_autosndbuf_max) = 2*1024*1024; 134 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_VNET | CTLFLAG_RW, 135 &VNET_NAME(tcp_autosndbuf_max), 0, 136 "Max size of automatic send buffer"); 137 138 VNET_DEFINE(int, tcp_sendbuf_auto_lowat) = 0; 139 #define V_tcp_sendbuf_auto_lowat VNET(tcp_sendbuf_auto_lowat) 140 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto_lowat, CTLFLAG_VNET | CTLFLAG_RW, 141 &VNET_NAME(tcp_sendbuf_auto_lowat), 0, 142 "Modify threshold for auto send buffer growth to account for SO_SNDLOWAT"); 143 144 /* 145 * Make sure that either retransmit or persist timer is set for SYN, FIN and 146 * non-ACK. 147 */ 148 #define TCP_XMIT_TIMER_ASSERT(tp, len, th_flags) \ 149 KASSERT(((len) == 0 && ((th_flags) & (TH_SYN | TH_FIN)) == 0) ||\ 150 tcp_timer_active((tp), TT_REXMT) || \ 151 tcp_timer_active((tp), TT_PERSIST), \ 152 ("neither rexmt nor persist timer is set")) 153 154 #ifdef TCP_HHOOK 155 /* 156 * Wrapper for the TCP established output helper hook. 157 */ 158 void 159 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th, 160 struct tcpopt *to, uint32_t len, int tso) 161 { 162 struct tcp_hhook_data hhook_data; 163 164 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) { 165 hhook_data.tp = tp; 166 hhook_data.th = th; 167 hhook_data.to = to; 168 hhook_data.len = len; 169 hhook_data.tso = tso; 170 171 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data, 172 &tp->t_osd); 173 } 174 } 175 #endif 176 177 /* 178 * CC wrapper hook functions 179 */ 180 void 181 cc_after_idle(struct tcpcb *tp) 182 { 183 INP_WLOCK_ASSERT(tptoinpcb(tp)); 184 185 if (CC_ALGO(tp)->after_idle != NULL) 186 CC_ALGO(tp)->after_idle(&tp->t_ccv); 187 } 188 189 /* 190 * Tcp output routine: figure out what should be sent and send it. 191 */ 192 int 193 tcp_default_output(struct tcpcb *tp) 194 { 195 struct socket *so = tptosocket(tp); 196 struct inpcb *inp = tptoinpcb(tp); 197 int32_t len; 198 uint32_t recwin, sendwin; 199 uint16_t flags; 200 int off, error = 0; /* Keep compiler happy */ 201 u_int if_hw_tsomaxsegcount = 0; 202 u_int if_hw_tsomaxsegsize = 0; 203 struct mbuf *m; 204 struct ip *ip = NULL; 205 struct tcphdr *th; 206 u_char opt[TCP_MAXOLEN]; 207 unsigned ipoptlen, optlen, hdrlen, ulen; 208 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 209 unsigned ipsec_optlen = 0; 210 #endif 211 int idle, sendalot, curticks; 212 int sack_rxmit, sack_bytes_rxmt; 213 struct sackhole *p; 214 int tso, mtu; 215 struct tcpopt to; 216 struct udphdr *udp = NULL; 217 struct tcp_log_buffer *lgb; 218 unsigned int wanted_cookie = 0; 219 unsigned int dont_sendalot = 0; 220 #if 0 221 int maxburst = TCP_MAXBURST; 222 #endif 223 #ifdef INET6 224 struct ip6_hdr *ip6 = NULL; 225 const bool isipv6 = (inp->inp_vflag & INP_IPV6) != 0; 226 #endif 227 #ifdef KERN_TLS 228 const bool hw_tls = tp->t_nic_ktls_xmit != 0; 229 #else 230 const bool hw_tls = false; 231 #endif 232 233 NET_EPOCH_ASSERT(); 234 INP_WLOCK_ASSERT(inp); 235 236 #ifdef TCP_OFFLOAD 237 if (tp->t_flags & TF_TOE) 238 return (tcp_offload_output(tp)); 239 #endif 240 241 /* 242 * For TFO connections in SYN_SENT or SYN_RECEIVED, 243 * only allow the initial SYN or SYN|ACK and those sent 244 * by the retransmit timer. 245 */ 246 if (IS_FASTOPEN(tp->t_flags) && 247 ((tp->t_state == TCPS_SYN_SENT) || 248 (tp->t_state == TCPS_SYN_RECEIVED)) && 249 SEQ_GT(tp->snd_max, tp->snd_una) && /* initial SYN or SYN|ACK sent */ 250 (tp->snd_nxt != tp->snd_una)) /* not a retransmit */ 251 return (0); 252 253 /* 254 * Determine length of data that should be transmitted, 255 * and flags that will be used. 256 * If there is some data or critical controls (SYN, RST) 257 * to send, then transmit; otherwise, investigate further. 258 */ 259 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 260 if (idle && (((ticks - tp->t_rcvtime) >= tp->t_rxtcur) || 261 (tp->t_sndtime && ((ticks - tp->t_sndtime) >= tp->t_rxtcur)))) 262 cc_after_idle(tp); 263 tp->t_flags &= ~TF_LASTIDLE; 264 if (idle) { 265 if (tp->t_flags & TF_MORETOCOME) { 266 tp->t_flags |= TF_LASTIDLE; 267 idle = 0; 268 } 269 } 270 again: 271 /* 272 * If we've recently taken a timeout, snd_max will be greater than 273 * snd_nxt. There may be SACK information that allows us to avoid 274 * resending already delivered data. Adjust snd_nxt accordingly. 275 */ 276 if ((tp->t_flags & TF_SACK_PERMIT) && 277 SEQ_LT(tp->snd_nxt, tp->snd_max)) 278 tcp_sack_adjust(tp); 279 sendalot = 0; 280 tso = 0; 281 mtu = 0; 282 off = tp->snd_nxt - tp->snd_una; 283 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 284 285 flags = tcp_outflags[tp->t_state]; 286 /* 287 * Send any SACK-generated retransmissions. If we're explicitly trying 288 * to send out new data (when sendalot is 1), bypass this function. 289 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 290 * we're replacing a (future) new transmission with a retransmission 291 * now, and we previously incremented snd_cwnd in tcp_input(). 292 */ 293 /* 294 * Still in sack recovery , reset rxmit flag to zero. 295 */ 296 sack_rxmit = 0; 297 sack_bytes_rxmt = 0; 298 len = 0; 299 p = NULL; 300 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) && 301 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 302 uint32_t cwin; 303 304 cwin = 305 imax(min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt, 0); 306 /* Do not retransmit SACK segments beyond snd_recover */ 307 if (SEQ_GT(p->end, tp->snd_recover)) { 308 /* 309 * (At least) part of sack hole extends beyond 310 * snd_recover. Check to see if we can rexmit data 311 * for this hole. 312 */ 313 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 314 /* 315 * Can't rexmit any more data for this hole. 316 * That data will be rexmitted in the next 317 * sack recovery episode, when snd_recover 318 * moves past p->rxmit. 319 */ 320 p = NULL; 321 goto after_sack_rexmit; 322 } else { 323 /* Can rexmit part of the current hole */ 324 len = ((int32_t)ulmin(cwin, 325 SEQ_SUB(tp->snd_recover, p->rxmit))); 326 } 327 } else { 328 len = ((int32_t)ulmin(cwin, 329 SEQ_SUB(p->end, p->rxmit))); 330 } 331 if (len > 0) { 332 off = SEQ_SUB(p->rxmit, tp->snd_una); 333 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 334 __func__, off)); 335 sack_rxmit = 1; 336 sendalot = 1; 337 TCPSTAT_INC(tcps_sack_rexmits); 338 TCPSTAT_ADD(tcps_sack_rexmit_bytes, 339 min(len, tcp_maxseg(tp))); 340 } 341 } 342 after_sack_rexmit: 343 /* 344 * Get standard flags, and add SYN or FIN if requested by 'hidden' 345 * state flags. 346 */ 347 if (tp->t_flags & TF_NEEDFIN) 348 flags |= TH_FIN; 349 if (tp->t_flags & TF_NEEDSYN) 350 flags |= TH_SYN; 351 352 SOCKBUF_LOCK(&so->so_snd); 353 /* 354 * If in persist timeout with window of 0, send 1 byte. 355 * Otherwise, if window is small but nonzero 356 * and timer expired, we will send what we can 357 * and go to transmit state. 358 */ 359 if (tp->t_flags & TF_FORCEDATA) { 360 if (sendwin == 0) { 361 /* 362 * If we still have some data to send, then 363 * clear the FIN bit. Usually this would 364 * happen below when it realizes that we 365 * aren't sending all the data. However, 366 * if we have exactly 1 byte of unsent data, 367 * then it won't clear the FIN bit below, 368 * and if we are in persist state, we wind 369 * up sending the packet without recording 370 * that we sent the FIN bit. 371 * 372 * We can't just blindly clear the FIN bit, 373 * because if we don't have any more data 374 * to send then the probe will be the FIN 375 * itself. 376 */ 377 if (off < sbused(&so->so_snd)) 378 flags &= ~TH_FIN; 379 sendwin = 1; 380 } else { 381 tcp_timer_activate(tp, TT_PERSIST, 0); 382 tp->t_rxtshift = 0; 383 } 384 } 385 386 /* 387 * If snd_nxt == snd_max and we have transmitted a FIN, the 388 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 389 * a negative length. This can also occur when TCP opens up 390 * its congestion window while receiving additional duplicate 391 * acks after fast-retransmit because TCP will reset snd_nxt 392 * to snd_max after the fast-retransmit. 393 * 394 * In the normal retransmit-FIN-only case, however, snd_nxt will 395 * be set to snd_una, the offset will be 0, and the length may 396 * wind up 0. 397 * 398 * If sack_rxmit is true we are retransmitting from the scoreboard 399 * in which case len is already set. 400 */ 401 if (sack_rxmit == 0) { 402 if (sack_bytes_rxmt == 0) 403 len = ((int32_t)min(sbavail(&so->so_snd), sendwin) - 404 off); 405 else { 406 int32_t cwin; 407 408 /* 409 * We are inside of a SACK recovery episode and are 410 * sending new data, having retransmitted all the 411 * data possible in the scoreboard. 412 */ 413 len = ((int32_t)min(sbavail(&so->so_snd), tp->snd_wnd) - 414 off); 415 /* 416 * Don't remove this (len > 0) check ! 417 * We explicitly check for len > 0 here (although it 418 * isn't really necessary), to work around a gcc 419 * optimization issue - to force gcc to compute 420 * len above. Without this check, the computation 421 * of len is bungled by the optimizer. 422 */ 423 if (len > 0) { 424 cwin = tp->snd_cwnd - imax(0, (int32_t) 425 (tp->snd_nxt - tp->snd_recover)) - 426 sack_bytes_rxmt; 427 if (cwin < 0) 428 cwin = 0; 429 len = imin(len, cwin); 430 } 431 } 432 } 433 434 /* 435 * Lop off SYN bit if it has already been sent. However, if this 436 * is SYN-SENT state and if segment contains data and if we don't 437 * know that foreign host supports TAO, suppress sending segment. 438 */ 439 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 440 if (tp->t_state != TCPS_SYN_RECEIVED) 441 flags &= ~TH_SYN; 442 /* 443 * When sending additional segments following a TFO SYN|ACK, 444 * do not include the SYN bit. 445 */ 446 if (IS_FASTOPEN(tp->t_flags) && 447 (tp->t_state == TCPS_SYN_RECEIVED)) 448 flags &= ~TH_SYN; 449 off--, len++; 450 } 451 452 /* 453 * Be careful not to send data and/or FIN on SYN segments. 454 * This measure is needed to prevent interoperability problems 455 * with not fully conformant TCP implementations. 456 */ 457 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 458 len = 0; 459 flags &= ~TH_FIN; 460 } 461 462 /* 463 * On TFO sockets, ensure no data is sent in the following cases: 464 * 465 * - When retransmitting SYN|ACK on a passively-created socket 466 * 467 * - When retransmitting SYN on an actively created socket 468 * 469 * - When sending a zero-length cookie (cookie request) on an 470 * actively created socket 471 * 472 * - When the socket is in the CLOSED state (RST is being sent) 473 */ 474 if (IS_FASTOPEN(tp->t_flags) && 475 (((flags & TH_SYN) && (tp->t_rxtshift > 0)) || 476 ((tp->t_state == TCPS_SYN_SENT) && 477 (tp->t_tfo_client_cookie_len == 0)) || 478 (flags & TH_RST))) 479 len = 0; 480 if (len <= 0) { 481 /* 482 * If FIN has been sent but not acked, 483 * but we haven't been called to retransmit, 484 * len will be < 0. Otherwise, window shrank 485 * after we sent into it. If window shrank to 0, 486 * cancel pending retransmit, pull snd_nxt back 487 * to (closed) window, and set the persist timer 488 * if it isn't already going. If the window didn't 489 * close completely, just wait for an ACK. 490 * 491 * We also do a general check here to ensure that 492 * we will set the persist timer when we have data 493 * to send, but a 0-byte window. This makes sure 494 * the persist timer is set even if the packet 495 * hits one of the "goto send" lines below. 496 */ 497 len = 0; 498 if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) && 499 (off < (int) sbavail(&so->so_snd)) && 500 !tcp_timer_active(tp, TT_PERSIST)) { 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, inp); 538 #ifdef INET 539 else 540 #endif 541 #endif /* INET6 */ 542 #ifdef INET 543 if (IPSEC_ENABLED(ipv4)) 544 ipsec_optlen = IPSEC_HDRSIZE(ipv4, inp); 545 #endif /* INET */ 546 #endif /* IPSEC */ 547 #ifdef INET6 548 if (isipv6) 549 ipoptlen = ip6_optlen(inp); 550 else 551 #endif 552 if (inp->inp_options) 553 ipoptlen = inp->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_port == 0) && 563 ((tp->t_flags & TF_SIGNATURE) == 0) && 564 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 565 ipoptlen == 0 && !(flags & TH_SYN)) 566 tso = 1; 567 568 if (sack_rxmit) { 569 if (SEQ_LT(p->rxmit + len, tp->snd_una + sbused(&so->so_snd))) 570 flags &= ~TH_FIN; 571 } else { 572 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + 573 sbused(&so->so_snd))) 574 flags &= ~TH_FIN; 575 } 576 577 recwin = lmin(lmax(sbspace(&so->so_rcv), 0), 578 (long)TCP_MAXWIN << tp->rcv_scale); 579 580 /* 581 * Sender silly window avoidance. We transmit under the following 582 * conditions when len is non-zero: 583 * 584 * - We have a full segment (or more with TSO) 585 * - This is the last buffer in a write()/send() and we are 586 * either idle or running NODELAY 587 * - we've timed out (e.g. persist timer) 588 * - we have more then 1/2 the maximum send window's worth of 589 * data (receiver may be limited the window size) 590 * - we need to retransmit 591 */ 592 if (len) { 593 if (len >= tp->t_maxseg) 594 goto send; 595 /* 596 * As the TCP header options are now 597 * considered when setting up the initial 598 * window, we would not send the last segment 599 * if we skip considering the option length here. 600 * Note: this may not work when tcp headers change 601 * very dynamically in the future. 602 */ 603 if ((((tp->t_flags & TF_SIGNATURE) ? 604 PADTCPOLEN(TCPOLEN_SIGNATURE) : 0) + 605 ((tp->t_flags & TF_RCVD_TSTMP) ? 606 PADTCPOLEN(TCPOLEN_TIMESTAMP) : 0) + 607 len) >= tp->t_maxseg) 608 goto send; 609 /* 610 * NOTE! on localhost connections an 'ack' from the remote 611 * end may occur synchronously with the output and cause 612 * us to flush a buffer queued with moretocome. XXX 613 * 614 * note: the len + off check is almost certainly unnecessary. 615 */ 616 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 617 (idle || (tp->t_flags & TF_NODELAY)) && 618 (uint32_t)len + (uint32_t)off >= sbavail(&so->so_snd) && 619 (tp->t_flags & TF_NOPUSH) == 0) { 620 goto send; 621 } 622 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 623 goto send; 624 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 625 goto send; 626 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 627 goto send; 628 if (sack_rxmit) 629 goto send; 630 } 631 632 /* 633 * Sending of standalone window updates. 634 * 635 * Window updates are important when we close our window due to a 636 * full socket buffer and are opening it again after the application 637 * reads data from it. Once the window has opened again and the 638 * remote end starts to send again the ACK clock takes over and 639 * provides the most current window information. 640 * 641 * We must avoid the silly window syndrome whereas every read 642 * from the receive buffer, no matter how small, causes a window 643 * update to be sent. We also should avoid sending a flurry of 644 * window updates when the socket buffer had queued a lot of data 645 * and the application is doing small reads. 646 * 647 * Prevent a flurry of pointless window updates by only sending 648 * an update when we can increase the advertized window by more 649 * than 1/4th of the socket buffer capacity. When the buffer is 650 * getting full or is very small be more aggressive and send an 651 * update whenever we can increase by two mss sized segments. 652 * In all other situations the ACK's to new incoming data will 653 * carry further window increases. 654 * 655 * Don't send an independent window update if a delayed 656 * ACK is pending (it will get piggy-backed on it) or the 657 * remote side already has done a half-close and won't send 658 * more data. Skip this if the connection is in T/TCP 659 * half-open state. 660 */ 661 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 662 !(tp->t_flags & TF_DELACK) && 663 !TCPS_HAVERCVDFIN(tp->t_state)) { 664 /* 665 * "adv" is the amount we could increase the window, 666 * taking into account that we are limited by 667 * TCP_MAXWIN << tp->rcv_scale. 668 */ 669 int32_t adv; 670 int oldwin; 671 672 adv = recwin; 673 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { 674 oldwin = (tp->rcv_adv - tp->rcv_nxt); 675 if (adv > oldwin) 676 adv -= oldwin; 677 else 678 adv = 0; 679 } else 680 oldwin = 0; 681 682 /* 683 * If the new window size ends up being the same as or less 684 * than the old size when it is scaled, then don't force 685 * a window update. 686 */ 687 if (oldwin >> tp->rcv_scale >= (adv + oldwin) >> tp->rcv_scale) 688 goto dontupdate; 689 690 if (adv >= (int32_t)(2 * tp->t_maxseg) && 691 (adv >= (int32_t)(so->so_rcv.sb_hiwat / 4) || 692 recwin <= (so->so_rcv.sb_hiwat / 8) || 693 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg || 694 adv >= TCP_MAXWIN << tp->rcv_scale)) 695 goto send; 696 if (2 * adv >= (int32_t)so->so_rcv.sb_hiwat) 697 goto send; 698 } 699 dontupdate: 700 701 /* 702 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 703 * is also a catch-all for the retransmit timer timeout case. 704 */ 705 if (tp->t_flags & TF_ACKNOW) 706 goto send; 707 if ((flags & TH_RST) || 708 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 709 goto send; 710 if (SEQ_GT(tp->snd_up, tp->snd_una)) 711 goto send; 712 /* 713 * If our state indicates that FIN should be sent 714 * and we have not yet done so, then we need to send. 715 */ 716 if (flags & TH_FIN && 717 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 718 goto send; 719 /* 720 * In SACK, it is possible for tcp_output to fail to send a segment 721 * after the retransmission timer has been turned off. Make sure 722 * that the retransmission timer is set. 723 */ 724 if ((tp->t_flags & TF_SACK_PERMIT) && 725 SEQ_GT(tp->snd_max, tp->snd_una) && 726 !tcp_timer_active(tp, TT_REXMT) && 727 !tcp_timer_active(tp, TT_PERSIST)) { 728 tcp_timer_activate(tp, TT_REXMT, TP_RXTCUR(tp)); 729 goto just_return; 730 } 731 /* 732 * TCP window updates are not reliable, rather a polling protocol 733 * using ``persist'' packets is used to insure receipt of window 734 * updates. The three ``states'' for the output side are: 735 * idle not doing retransmits or persists 736 * persisting to move a small or zero window 737 * (re)transmitting and thereby not persisting 738 * 739 * tcp_timer_active(tp, TT_PERSIST) 740 * is true when we are in persist state. 741 * (tp->t_flags & TF_FORCEDATA) 742 * is set when we are called to send a persist packet. 743 * tcp_timer_active(tp, TT_REXMT) 744 * is set when we are retransmitting 745 * The output side is idle when both timers are zero. 746 * 747 * If send window is too small, there is data to transmit, and no 748 * retransmit or persist is pending, then go to persist state. 749 * If nothing happens soon, send when timer expires: 750 * if window is nonzero, transmit what we can, 751 * otherwise force out a byte. 752 */ 753 if (sbavail(&so->so_snd) && !tcp_timer_active(tp, TT_REXMT) && 754 !tcp_timer_active(tp, TT_PERSIST)) { 755 tp->t_rxtshift = 0; 756 tcp_setpersist(tp); 757 } 758 759 /* 760 * No reason to send a segment, just return. 761 */ 762 just_return: 763 SOCKBUF_UNLOCK(&so->so_snd); 764 return (0); 765 766 send: 767 SOCKBUF_LOCK_ASSERT(&so->so_snd); 768 if (len > 0) { 769 if (len >= tp->t_maxseg) 770 tp->t_flags2 |= TF2_PLPMTU_MAXSEGSNT; 771 else 772 tp->t_flags2 &= ~TF2_PLPMTU_MAXSEGSNT; 773 } 774 /* 775 * Before ESTABLISHED, force sending of initial options 776 * unless TCP set not to do any options. 777 * NOTE: we assume that the IP/TCP header plus TCP options 778 * always fit in a single mbuf, leaving room for a maximum 779 * link header, i.e. 780 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 781 */ 782 optlen = 0; 783 #ifdef INET6 784 if (isipv6) 785 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 786 else 787 #endif 788 hdrlen = sizeof (struct tcpiphdr); 789 790 if (flags & TH_SYN) { 791 tp->snd_nxt = tp->iss; 792 } 793 794 /* 795 * Compute options for segment. 796 * We only have to care about SYN and established connection 797 * segments. Options for SYN-ACK segments are handled in TCP 798 * syncache. 799 */ 800 to.to_flags = 0; 801 if ((tp->t_flags & TF_NOOPT) == 0) { 802 /* Maximum segment size. */ 803 if (flags & TH_SYN) { 804 to.to_mss = tcp_mssopt(&inp->inp_inc); 805 if (tp->t_port) 806 to.to_mss -= V_tcp_udp_tunneling_overhead; 807 to.to_flags |= TOF_MSS; 808 809 /* 810 * On SYN or SYN|ACK transmits on TFO connections, 811 * only include the TFO option if it is not a 812 * retransmit, as the presence of the TFO option may 813 * have caused the original SYN or SYN|ACK to have 814 * been dropped by a middlebox. 815 */ 816 if (IS_FASTOPEN(tp->t_flags) && 817 (tp->t_rxtshift == 0)) { 818 if (tp->t_state == TCPS_SYN_RECEIVED) { 819 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN; 820 to.to_tfo_cookie = 821 (u_int8_t *)&tp->t_tfo_cookie.server; 822 to.to_flags |= TOF_FASTOPEN; 823 wanted_cookie = 1; 824 } else if (tp->t_state == TCPS_SYN_SENT) { 825 to.to_tfo_len = 826 tp->t_tfo_client_cookie_len; 827 to.to_tfo_cookie = 828 tp->t_tfo_cookie.client; 829 to.to_flags |= TOF_FASTOPEN; 830 wanted_cookie = 1; 831 /* 832 * If we wind up having more data to 833 * send with the SYN than can fit in 834 * one segment, don't send any more 835 * until the SYN|ACK comes back from 836 * the other end. 837 */ 838 dont_sendalot = 1; 839 } 840 } 841 } 842 /* Window scaling. */ 843 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 844 to.to_wscale = tp->request_r_scale; 845 to.to_flags |= TOF_SCALE; 846 } 847 /* Timestamps. */ 848 if ((tp->t_flags & TF_RCVD_TSTMP) || 849 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 850 curticks = tcp_ts_getticks(); 851 to.to_tsval = curticks + tp->ts_offset; 852 to.to_tsecr = tp->ts_recent; 853 to.to_flags |= TOF_TS; 854 if (tp->t_rxtshift == 1) 855 tp->t_badrxtwin = curticks; 856 } 857 858 /* Set receive buffer autosizing timestamp. */ 859 if (tp->rfbuf_ts == 0 && 860 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 861 tp->rfbuf_ts = tcp_ts_getticks(); 862 863 /* Selective ACK's. */ 864 if (tp->t_flags & TF_SACK_PERMIT) { 865 if (flags & TH_SYN) 866 to.to_flags |= TOF_SACKPERM; 867 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 868 tp->rcv_numsacks > 0) { 869 to.to_flags |= TOF_SACK; 870 to.to_nsacks = tp->rcv_numsacks; 871 to.to_sacks = (u_char *)tp->sackblks; 872 } 873 } 874 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 875 /* TCP-MD5 (RFC2385). */ 876 /* 877 * Check that TCP_MD5SIG is enabled in tcpcb to 878 * account the size needed to set this TCP option. 879 */ 880 if (tp->t_flags & TF_SIGNATURE) 881 to.to_flags |= TOF_SIGNATURE; 882 #endif /* TCP_SIGNATURE */ 883 884 /* Processing the options. */ 885 hdrlen += optlen = tcp_addoptions(&to, opt); 886 /* 887 * If we wanted a TFO option to be added, but it was unable 888 * to fit, ensure no data is sent. 889 */ 890 if (IS_FASTOPEN(tp->t_flags) && wanted_cookie && 891 !(to.to_flags & TOF_FASTOPEN)) 892 len = 0; 893 } 894 if (tp->t_port) { 895 if (V_tcp_udp_tunneling_port == 0) { 896 /* The port was removed?? */ 897 SOCKBUF_UNLOCK(&so->so_snd); 898 return (EHOSTUNREACH); 899 } 900 hdrlen += sizeof(struct udphdr); 901 } 902 /* 903 * Adjust data length if insertion of options will 904 * bump the packet length beyond the t_maxseg length. 905 * Clear the FIN bit because we cut off the tail of 906 * the segment. 907 */ 908 if (len + optlen + ipoptlen > tp->t_maxseg) { 909 flags &= ~TH_FIN; 910 911 if (tso) { 912 u_int if_hw_tsomax; 913 u_int moff; 914 int max_len; 915 916 /* extract TSO information */ 917 if_hw_tsomax = tp->t_tsomax; 918 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount; 919 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize; 920 921 /* 922 * Limit a TSO burst to prevent it from 923 * overflowing or exceeding the maximum length 924 * allowed by the network interface: 925 */ 926 KASSERT(ipoptlen == 0, 927 ("%s: TSO can't do IP options", __func__)); 928 929 /* 930 * Check if we should limit by maximum payload 931 * length: 932 */ 933 if (if_hw_tsomax != 0) { 934 /* compute maximum TSO length */ 935 max_len = (if_hw_tsomax - hdrlen - 936 max_linkhdr); 937 if (max_len <= 0) { 938 len = 0; 939 } else if (len > max_len) { 940 sendalot = 1; 941 len = max_len; 942 } 943 } 944 945 /* 946 * Prevent the last segment from being 947 * fractional unless the send sockbuf can be 948 * emptied: 949 */ 950 max_len = (tp->t_maxseg - optlen); 951 if (((uint32_t)off + (uint32_t)len) < 952 sbavail(&so->so_snd)) { 953 moff = len % max_len; 954 if (moff != 0) { 955 len -= moff; 956 sendalot = 1; 957 } 958 } 959 960 /* 961 * In case there are too many small fragments 962 * don't use TSO: 963 */ 964 if (len <= max_len) { 965 len = max_len; 966 sendalot = 1; 967 tso = 0; 968 } 969 970 /* 971 * Send the FIN in a separate segment 972 * after the bulk sending is done. 973 * We don't trust the TSO implementations 974 * to clear the FIN flag on all but the 975 * last segment. 976 */ 977 if (tp->t_flags & TF_NEEDFIN) 978 sendalot = 1; 979 } else { 980 if (optlen + ipoptlen >= tp->t_maxseg) { 981 /* 982 * Since we don't have enough space to put 983 * the IP header chain and the TCP header in 984 * one packet as required by RFC 7112, don't 985 * send it. Also ensure that at least one 986 * byte of the payload can be put into the 987 * TCP segment. 988 */ 989 SOCKBUF_UNLOCK(&so->so_snd); 990 error = EMSGSIZE; 991 sack_rxmit = 0; 992 goto out; 993 } 994 len = tp->t_maxseg - optlen - ipoptlen; 995 sendalot = 1; 996 if (dont_sendalot) 997 sendalot = 0; 998 } 999 } else 1000 tso = 0; 1001 1002 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 1003 ("%s: len > IP_MAXPACKET", __func__)); 1004 1005 /*#ifdef DIAGNOSTIC*/ 1006 #ifdef INET6 1007 if (max_linkhdr + hdrlen > MCLBYTES) 1008 #else 1009 if (max_linkhdr + hdrlen > MHLEN) 1010 #endif 1011 panic("tcphdr too big"); 1012 /*#endif*/ 1013 1014 /* 1015 * This KASSERT is here to catch edge cases at a well defined place. 1016 * Before, those had triggered (random) panic conditions further down. 1017 */ 1018 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 1019 1020 /* 1021 * Grab a header mbuf, attaching a copy of data to 1022 * be transmitted, and initialize the header from 1023 * the template for sends on this connection. 1024 */ 1025 if (len) { 1026 struct mbuf *mb; 1027 struct sockbuf *msb; 1028 u_int moff; 1029 1030 if ((tp->t_flags & TF_FORCEDATA) && len == 1) { 1031 TCPSTAT_INC(tcps_sndprobe); 1032 #ifdef STATS 1033 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1034 stats_voi_update_abs_u32(tp->t_stats, 1035 VOI_TCP_RETXPB, len); 1036 else 1037 stats_voi_update_abs_u64(tp->t_stats, 1038 VOI_TCP_TXPB, len); 1039 #endif /* STATS */ 1040 } else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 1041 tp->t_sndrexmitpack++; 1042 TCPSTAT_INC(tcps_sndrexmitpack); 1043 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 1044 #ifdef STATS 1045 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_RETXPB, 1046 len); 1047 #endif /* STATS */ 1048 } else { 1049 TCPSTAT_INC(tcps_sndpack); 1050 TCPSTAT_ADD(tcps_sndbyte, len); 1051 #ifdef STATS 1052 stats_voi_update_abs_u64(tp->t_stats, VOI_TCP_TXPB, 1053 len); 1054 #endif /* STATS */ 1055 } 1056 #ifdef INET6 1057 if (MHLEN < hdrlen + max_linkhdr) 1058 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR); 1059 else 1060 #endif 1061 m = m_gethdr(M_NOWAIT, MT_DATA); 1062 1063 if (m == NULL) { 1064 SOCKBUF_UNLOCK(&so->so_snd); 1065 error = ENOBUFS; 1066 sack_rxmit = 0; 1067 goto out; 1068 } 1069 1070 m->m_data += max_linkhdr; 1071 m->m_len = hdrlen; 1072 1073 /* 1074 * Start the m_copy functions from the closest mbuf 1075 * to the offset in the socket buffer chain. 1076 */ 1077 mb = sbsndptr_noadv(&so->so_snd, off, &moff); 1078 if (len <= MHLEN - hdrlen - max_linkhdr && !hw_tls) { 1079 m_copydata(mb, moff, len, 1080 mtod(m, caddr_t) + hdrlen); 1081 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1082 sbsndptr_adv(&so->so_snd, mb, len); 1083 m->m_len += len; 1084 } else { 1085 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1086 msb = NULL; 1087 else 1088 msb = &so->so_snd; 1089 m->m_next = tcp_m_copym(mb, moff, 1090 &len, if_hw_tsomaxsegcount, 1091 if_hw_tsomaxsegsize, msb, hw_tls); 1092 if (len <= (tp->t_maxseg - optlen)) { 1093 /* 1094 * Must have ran out of mbufs for the copy 1095 * shorten it to no longer need tso. Lets 1096 * not put on sendalot since we are low on 1097 * mbufs. 1098 */ 1099 tso = 0; 1100 } 1101 if (m->m_next == NULL) { 1102 SOCKBUF_UNLOCK(&so->so_snd); 1103 (void) m_free(m); 1104 error = ENOBUFS; 1105 sack_rxmit = 0; 1106 goto out; 1107 } 1108 } 1109 1110 /* 1111 * If we're sending everything we've got, set PUSH. 1112 * (This will keep happy those implementations which only 1113 * give data to the user when a buffer fills or 1114 * a PUSH comes in.) 1115 */ 1116 if (((uint32_t)off + (uint32_t)len == sbused(&so->so_snd)) && 1117 !(flags & TH_SYN)) 1118 flags |= TH_PUSH; 1119 SOCKBUF_UNLOCK(&so->so_snd); 1120 } else { 1121 SOCKBUF_UNLOCK(&so->so_snd); 1122 if (tp->t_flags & TF_ACKNOW) 1123 TCPSTAT_INC(tcps_sndacks); 1124 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 1125 TCPSTAT_INC(tcps_sndctrl); 1126 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 1127 TCPSTAT_INC(tcps_sndurg); 1128 else 1129 TCPSTAT_INC(tcps_sndwinup); 1130 1131 m = m_gethdr(M_NOWAIT, MT_DATA); 1132 if (m == NULL) { 1133 error = ENOBUFS; 1134 sack_rxmit = 0; 1135 goto out; 1136 } 1137 #ifdef INET6 1138 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 1139 MHLEN >= hdrlen) { 1140 M_ALIGN(m, hdrlen); 1141 } else 1142 #endif 1143 m->m_data += max_linkhdr; 1144 m->m_len = hdrlen; 1145 } 1146 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 1147 m->m_pkthdr.rcvif = (struct ifnet *)0; 1148 #ifdef MAC 1149 mac_inpcb_create_mbuf(inp, m); 1150 #endif 1151 #ifdef INET6 1152 if (isipv6) { 1153 ip6 = mtod(m, struct ip6_hdr *); 1154 if (tp->t_port) { 1155 udp = (struct udphdr *)((caddr_t)ip6 + sizeof(struct ip6_hdr)); 1156 udp->uh_sport = htons(V_tcp_udp_tunneling_port); 1157 udp->uh_dport = tp->t_port; 1158 ulen = hdrlen + len - sizeof(struct ip6_hdr); 1159 udp->uh_ulen = htons(ulen); 1160 th = (struct tcphdr *)(udp + 1); 1161 } else { 1162 th = (struct tcphdr *)(ip6 + 1); 1163 } 1164 tcpip_fillheaders(inp, tp->t_port, ip6, th); 1165 } else 1166 #endif /* INET6 */ 1167 { 1168 ip = mtod(m, struct ip *); 1169 if (tp->t_port) { 1170 udp = (struct udphdr *)((caddr_t)ip + sizeof(struct ip)); 1171 udp->uh_sport = htons(V_tcp_udp_tunneling_port); 1172 udp->uh_dport = tp->t_port; 1173 ulen = hdrlen + len - sizeof(struct ip); 1174 udp->uh_ulen = htons(ulen); 1175 th = (struct tcphdr *)(udp + 1); 1176 } else 1177 th = (struct tcphdr *)(ip + 1); 1178 tcpip_fillheaders(inp, tp->t_port, ip, th); 1179 } 1180 1181 /* 1182 * Fill in fields, remembering maximum advertised 1183 * window for use in delaying messages about window sizes. 1184 * If resending a FIN, be sure not to use a new sequence number. 1185 */ 1186 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 1187 tp->snd_nxt == tp->snd_max) 1188 tp->snd_nxt--; 1189 /* 1190 * If we are starting a connection, send ECN setup 1191 * SYN packet. If we are on a retransmit, we may 1192 * resend those bits a number of times as per 1193 * RFC 3168. 1194 */ 1195 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) { 1196 flags |= tcp_ecn_output_syn_sent(tp); 1197 } 1198 /* Also handle parallel SYN for ECN */ 1199 if ((TCPS_HAVERCVDSYN(tp->t_state)) && 1200 (tp->t_flags2 & (TF2_ECN_PERMIT | TF2_ACE_PERMIT))) { 1201 int ect = tcp_ecn_output_established(tp, &flags, len, sack_rxmit); 1202 if ((tp->t_state == TCPS_SYN_RECEIVED) && 1203 (tp->t_flags2 & TF2_ECN_SND_ECE)) 1204 tp->t_flags2 &= ~TF2_ECN_SND_ECE; 1205 #ifdef INET6 1206 if (isipv6) { 1207 ip6->ip6_flow &= ~htonl(IPTOS_ECN_MASK << IPV6_FLOWLABEL_LEN); 1208 ip6->ip6_flow |= htonl(ect << IPV6_FLOWLABEL_LEN); 1209 } 1210 else 1211 #endif 1212 { 1213 ip->ip_tos &= ~IPTOS_ECN_MASK; 1214 ip->ip_tos |= ect; 1215 } 1216 } 1217 1218 /* 1219 * If we are doing retransmissions, then snd_nxt will 1220 * not reflect the first unsent octet. For ACK only 1221 * packets, we do not want the sequence number of the 1222 * retransmitted packet, we want the sequence number 1223 * of the next unsent octet. So, if there is no data 1224 * (and no SYN or FIN), use snd_max instead of snd_nxt 1225 * when filling in ti_seq. But if we are in persist 1226 * state, snd_max might reflect one byte beyond the 1227 * right edge of the window, so use snd_nxt in that 1228 * case, since we know we aren't doing a retransmission. 1229 * (retransmit and persist are mutually exclusive...) 1230 */ 1231 if (sack_rxmit == 0) { 1232 if (len || (flags & (TH_SYN|TH_FIN)) || 1233 tcp_timer_active(tp, TT_PERSIST)) 1234 th->th_seq = htonl(tp->snd_nxt); 1235 else 1236 th->th_seq = htonl(tp->snd_max); 1237 } else { 1238 th->th_seq = htonl(p->rxmit); 1239 p->rxmit += len; 1240 /* 1241 * Lost Retransmission Detection 1242 * trigger resending of a (then 1243 * still existing) hole, when 1244 * fack acks recoverypoint. 1245 */ 1246 if ((tp->t_flags & TF_LRD) && SEQ_GEQ(p->rxmit, p->end)) 1247 p->rxmit = tp->snd_recover; 1248 tp->sackhint.sack_bytes_rexmit += len; 1249 } 1250 if (IN_RECOVERY(tp->t_flags)) { 1251 /* 1252 * Account all bytes transmitted while 1253 * IN_RECOVERY, simplifying PRR and 1254 * Lost Retransmit Detection 1255 */ 1256 tp->sackhint.prr_out += len; 1257 } 1258 th->th_ack = htonl(tp->rcv_nxt); 1259 if (optlen) { 1260 bcopy(opt, th + 1, optlen); 1261 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1262 } 1263 tcp_set_flags(th, flags); 1264 /* 1265 * Calculate receive window. Don't shrink window, 1266 * but avoid silly window syndrome. 1267 * If a RST segment is sent, advertise a window of zero. 1268 */ 1269 if (flags & TH_RST) { 1270 recwin = 0; 1271 } else { 1272 if (recwin < (so->so_rcv.sb_hiwat / 4) && 1273 recwin < tp->t_maxseg) 1274 recwin = 0; 1275 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1276 recwin < (tp->rcv_adv - tp->rcv_nxt)) 1277 recwin = (tp->rcv_adv - tp->rcv_nxt); 1278 } 1279 /* 1280 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1281 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1282 * case is handled in syncache. 1283 */ 1284 if (flags & TH_SYN) 1285 th->th_win = htons((u_short) 1286 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1287 else { 1288 /* Avoid shrinking window with window scaling. */ 1289 recwin = roundup2(recwin, 1 << tp->rcv_scale); 1290 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1291 } 1292 1293 /* 1294 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1295 * a 0 window. This may cause the remote transmitter to stall. This 1296 * flag tells soreceive() to disable delayed acknowledgements when 1297 * draining the buffer. This can occur if the receiver is attempting 1298 * to read more data than can be buffered prior to transmitting on 1299 * the connection. 1300 */ 1301 if (th->th_win == 0) { 1302 tp->t_sndzerowin++; 1303 tp->t_flags |= TF_RXWIN0SENT; 1304 } else 1305 tp->t_flags &= ~TF_RXWIN0SENT; 1306 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1307 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1308 th->th_flags |= TH_URG; 1309 } else 1310 /* 1311 * If no urgent pointer to send, then we pull 1312 * the urgent pointer to the left edge of the send window 1313 * so that it doesn't drift into the send window on sequence 1314 * number wraparound. 1315 */ 1316 tp->snd_up = tp->snd_una; /* drag it along */ 1317 1318 /* 1319 * Put TCP length in extended header, and then 1320 * checksum extended header and data. 1321 */ 1322 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1323 1324 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1325 if (to.to_flags & TOF_SIGNATURE) { 1326 /* 1327 * Calculate MD5 signature and put it into the place 1328 * determined before. 1329 * NOTE: since TCP options buffer doesn't point into 1330 * mbuf's data, calculate offset and use it. 1331 */ 1332 if (!TCPMD5_ENABLED() || (error = TCPMD5_OUTPUT(m, th, 1333 (u_char *)(th + 1) + (to.to_signature - opt))) != 0) { 1334 /* 1335 * Do not send segment if the calculation of MD5 1336 * digest has failed. 1337 */ 1338 m_freem(m); 1339 goto out; 1340 } 1341 } 1342 #endif 1343 #ifdef INET6 1344 if (isipv6) { 1345 /* 1346 * There is no need to fill in ip6_plen right now. 1347 * It will be filled later by ip6_output. 1348 */ 1349 if (tp->t_port) { 1350 m->m_pkthdr.csum_flags = CSUM_UDP_IPV6; 1351 m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum); 1352 udp->uh_sum = in6_cksum_pseudo(ip6, ulen, IPPROTO_UDP, 0); 1353 th->th_sum = htons(0); 1354 UDPSTAT_INC(udps_opackets); 1355 } else { 1356 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1357 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1358 th->th_sum = in6_cksum_pseudo(ip6, 1359 sizeof(struct tcphdr) + optlen + len, IPPROTO_TCP, 1360 0); 1361 } 1362 } 1363 #endif 1364 #if defined(INET6) && defined(INET) 1365 else 1366 #endif 1367 #ifdef INET 1368 { 1369 if (tp->t_port) { 1370 m->m_pkthdr.csum_flags = CSUM_UDP; 1371 m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum); 1372 udp->uh_sum = in_pseudo(ip->ip_src.s_addr, 1373 ip->ip_dst.s_addr, htons(ulen + IPPROTO_UDP)); 1374 th->th_sum = htons(0); 1375 UDPSTAT_INC(udps_opackets); 1376 } else { 1377 m->m_pkthdr.csum_flags = CSUM_TCP; 1378 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1379 th->th_sum = in_pseudo(ip->ip_src.s_addr, 1380 ip->ip_dst.s_addr, htons(sizeof(struct tcphdr) + 1381 IPPROTO_TCP + len + optlen)); 1382 } 1383 1384 /* IP version must be set here for ipv4/ipv6 checking later */ 1385 KASSERT(ip->ip_v == IPVERSION, 1386 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1387 } 1388 #endif 1389 1390 /* 1391 * Enable TSO and specify the size of the segments. 1392 * The TCP pseudo header checksum is always provided. 1393 */ 1394 if (tso) { 1395 KASSERT(len > tp->t_maxseg - optlen, 1396 ("%s: len <= tso_segsz", __func__)); 1397 m->m_pkthdr.csum_flags |= CSUM_TSO; 1398 m->m_pkthdr.tso_segsz = tp->t_maxseg - optlen; 1399 } 1400 1401 KASSERT(len + hdrlen == m_length(m, NULL), 1402 ("%s: mbuf chain shorter than expected: %d + %u != %u", 1403 __func__, len, hdrlen, m_length(m, NULL))); 1404 1405 #ifdef TCP_HHOOK 1406 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1407 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1408 #endif 1409 1410 TCP_PROBE3(debug__output, tp, th, m); 1411 1412 /* We're getting ready to send; log now. */ 1413 /* XXXMT: We are not honoring verbose logging. */ 1414 1415 if (tcp_bblogging_on(tp)) 1416 lgb = tcp_log_event(tp, th, &so->so_rcv, &so->so_snd, 1417 TCP_LOG_OUT, ERRNO_UNK, len, NULL, false, NULL, NULL, 0, 1418 NULL); 1419 else 1420 lgb = NULL; 1421 1422 /* 1423 * Fill in IP length and desired time to live and 1424 * send to IP level. There should be a better way 1425 * to handle ttl and tos; we could keep them in 1426 * the template, but need a way to checksum without them. 1427 */ 1428 /* 1429 * m->m_pkthdr.len should have been set before checksum calculation, 1430 * because in6_cksum() need it. 1431 */ 1432 #ifdef INET6 1433 if (isipv6) { 1434 /* 1435 * we separately set hoplimit for every segment, since the 1436 * user might want to change the value via setsockopt. 1437 * Also, desired default hop limit might be changed via 1438 * Neighbor Discovery. 1439 */ 1440 ip6->ip6_hlim = in6_selecthlim(inp, NULL); 1441 1442 /* 1443 * Set the packet size here for the benefit of DTrace probes. 1444 * ip6_output() will set it properly; it's supposed to include 1445 * the option header lengths as well. 1446 */ 1447 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6)); 1448 1449 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) 1450 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1451 else 1452 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1453 1454 if (tp->t_state == TCPS_SYN_SENT) 1455 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th); 1456 1457 TCP_PROBE5(send, NULL, tp, ip6, tp, th); 1458 1459 #ifdef TCPPCAP 1460 /* Save packet, if requested. */ 1461 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1462 #endif 1463 1464 /* TODO: IPv6 IP6TOS_ECT bit on */ 1465 error = ip6_output(m, inp->in6p_outputopts, &inp->inp_route6, 1466 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 1467 NULL, NULL, inp); 1468 1469 if (error == EMSGSIZE && inp->inp_route6.ro_nh != NULL) 1470 mtu = inp->inp_route6.ro_nh->nh_mtu; 1471 } 1472 #endif /* INET6 */ 1473 #if defined(INET) && defined(INET6) 1474 else 1475 #endif 1476 #ifdef INET 1477 { 1478 ip->ip_len = htons(m->m_pkthdr.len); 1479 #ifdef INET6 1480 if (inp->inp_vflag & INP_IPV6PROTO) 1481 ip->ip_ttl = in6_selecthlim(inp, NULL); 1482 #endif /* INET6 */ 1483 /* 1484 * If we do path MTU discovery, then we set DF on every packet. 1485 * This might not be the best thing to do according to RFC3390 1486 * Section 2. However the tcp hostcache migitates the problem 1487 * so it affects only the first tcp connection with a host. 1488 * 1489 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1490 */ 1491 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) { 1492 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1493 if (tp->t_port == 0 || len < V_tcp_minmss) { 1494 ip->ip_off |= htons(IP_DF); 1495 } 1496 } else { 1497 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1498 } 1499 1500 if (tp->t_state == TCPS_SYN_SENT) 1501 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th); 1502 1503 TCP_PROBE5(send, NULL, tp, ip, tp, th); 1504 1505 #ifdef TCPPCAP 1506 /* Save packet, if requested. */ 1507 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1508 #endif 1509 1510 error = ip_output(m, inp->inp_options, &inp->inp_route, 1511 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, inp); 1512 1513 if (error == EMSGSIZE && inp->inp_route.ro_nh != NULL) 1514 mtu = inp->inp_route.ro_nh->nh_mtu; 1515 } 1516 #endif /* INET */ 1517 1518 if (lgb != NULL) { 1519 lgb->tlb_errno = error; 1520 lgb = NULL; 1521 } 1522 out: 1523 if (error == 0) 1524 tcp_account_for_send(tp, len, (tp->snd_nxt != tp->snd_max), 0, hw_tls); 1525 /* 1526 * In transmit state, time the transmission and arrange for 1527 * the retransmit. In persist state, just set snd_max. 1528 */ 1529 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1530 !tcp_timer_active(tp, TT_PERSIST)) { 1531 tcp_seq startseq = tp->snd_nxt; 1532 1533 /* 1534 * Advance snd_nxt over sequence space of this segment. 1535 */ 1536 if (flags & (TH_SYN|TH_FIN)) { 1537 if (flags & TH_SYN) 1538 tp->snd_nxt++; 1539 if (flags & TH_FIN) { 1540 tp->snd_nxt++; 1541 tp->t_flags |= TF_SENTFIN; 1542 } 1543 } 1544 if (sack_rxmit) 1545 goto timer; 1546 tp->snd_nxt += len; 1547 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1548 /* 1549 * Update "made progress" indication if we just 1550 * added new data to an empty socket buffer. 1551 */ 1552 if (tp->snd_una == tp->snd_max) 1553 tp->t_acktime = ticks; 1554 tp->snd_max = tp->snd_nxt; 1555 /* 1556 * Time this transmission if not a retransmission and 1557 * not currently timing anything. 1558 */ 1559 tp->t_sndtime = ticks; 1560 if (tp->t_rtttime == 0) { 1561 tp->t_rtttime = ticks; 1562 tp->t_rtseq = startseq; 1563 TCPSTAT_INC(tcps_segstimed); 1564 } 1565 #ifdef STATS 1566 if (!(tp->t_flags & TF_GPUTINPROG) && len) { 1567 tp->t_flags |= TF_GPUTINPROG; 1568 tp->gput_seq = startseq; 1569 tp->gput_ack = startseq + 1570 ulmin(sbavail(&so->so_snd) - off, sendwin); 1571 tp->gput_ts = tcp_ts_getticks(); 1572 } 1573 #endif /* STATS */ 1574 } 1575 1576 /* 1577 * Set retransmit timer if not currently set, 1578 * and not doing a pure ack or a keep-alive probe. 1579 * Initial value for retransmit timer is smoothed 1580 * round-trip time + 2 * round-trip time variance. 1581 * Initialize shift counter which is used for backoff 1582 * of retransmit time. 1583 */ 1584 timer: 1585 if (!tcp_timer_active(tp, TT_REXMT) && 1586 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1587 (tp->snd_nxt != tp->snd_una))) { 1588 if (tcp_timer_active(tp, TT_PERSIST)) { 1589 tcp_timer_activate(tp, TT_PERSIST, 0); 1590 tp->t_rxtshift = 0; 1591 } 1592 tcp_timer_activate(tp, TT_REXMT, TP_RXTCUR(tp)); 1593 } else if (len == 0 && sbavail(&so->so_snd) && 1594 !tcp_timer_active(tp, TT_REXMT) && 1595 !tcp_timer_active(tp, TT_PERSIST)) { 1596 /* 1597 * Avoid a situation where we do not set persist timer 1598 * after a zero window condition. For example: 1599 * 1) A -> B: packet with enough data to fill the window 1600 * 2) B -> A: ACK for #1 + new data (0 window 1601 * advertisement) 1602 * 3) A -> B: ACK for #2, 0 len packet 1603 * 1604 * In this case, A will not activate the persist timer, 1605 * because it chose to send a packet. Unless tcp_output 1606 * is called for some other reason (delayed ack timer, 1607 * another input packet from B, socket syscall), A will 1608 * not send zero window probes. 1609 * 1610 * So, if you send a 0-length packet, but there is data 1611 * in the socket buffer, and neither the rexmt or 1612 * persist timer is already set, then activate the 1613 * persist timer. 1614 */ 1615 tp->t_rxtshift = 0; 1616 tcp_setpersist(tp); 1617 } 1618 } else { 1619 /* 1620 * Persist case, update snd_max but since we are in 1621 * persist mode (no window) we do not update snd_nxt. 1622 */ 1623 int xlen = len; 1624 if (flags & TH_SYN) 1625 ++xlen; 1626 if (flags & TH_FIN) { 1627 ++xlen; 1628 tp->t_flags |= TF_SENTFIN; 1629 } 1630 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1631 tp->snd_max = tp->snd_nxt + xlen; 1632 } 1633 if ((error == 0) && 1634 (TCPS_HAVEESTABLISHED(tp->t_state) && 1635 (tp->t_flags & TF_SACK_PERMIT) && 1636 tp->rcv_numsacks > 0)) { 1637 /* Clean up any DSACK's sent */ 1638 tcp_clean_dsack_blocks(tp); 1639 } 1640 if (error) { 1641 /* 1642 * We know that the packet was lost, so back out the 1643 * sequence number advance, if any. 1644 * 1645 * If the error is EPERM the packet got blocked by the 1646 * local firewall. Normally we should terminate the 1647 * connection but the blocking may have been spurious 1648 * due to a firewall reconfiguration cycle. So we treat 1649 * it like a packet loss and let the retransmit timer and 1650 * timeouts do their work over time. 1651 * XXX: It is a POLA question whether calling tcp_drop right 1652 * away would be the really correct behavior instead. 1653 */ 1654 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1655 !tcp_timer_active(tp, TT_PERSIST)) && 1656 ((flags & TH_SYN) == 0) && 1657 (error != EPERM)) { 1658 if (sack_rxmit) { 1659 p->rxmit -= len; 1660 tp->sackhint.sack_bytes_rexmit -= len; 1661 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1662 ("sackhint bytes rtx >= 0")); 1663 KASSERT((flags & TH_FIN) == 0, 1664 ("error while FIN with SACK rxmit")); 1665 } else { 1666 tp->snd_nxt -= len; 1667 if (flags & TH_FIN) 1668 tp->snd_nxt--; 1669 } 1670 } 1671 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1672 switch (error) { 1673 case EACCES: 1674 case EPERM: 1675 tp->t_softerror = error; 1676 return (error); 1677 case ENOBUFS: 1678 TCP_XMIT_TIMER_ASSERT(tp, len, flags); 1679 tp->snd_cwnd = tp->t_maxseg; 1680 return (0); 1681 case EMSGSIZE: 1682 /* 1683 * For some reason the interface we used initially 1684 * to send segments changed to another or lowered 1685 * its MTU. 1686 * If TSO was active we either got an interface 1687 * without TSO capabilits or TSO was turned off. 1688 * If we obtained mtu from ip_output() then update 1689 * it and try again. 1690 */ 1691 if (tso) 1692 tp->t_flags &= ~TF_TSO; 1693 if (mtu != 0) { 1694 tcp_mss_update(tp, -1, mtu, NULL, NULL); 1695 goto again; 1696 } 1697 return (error); 1698 case EHOSTDOWN: 1699 case EHOSTUNREACH: 1700 case ENETDOWN: 1701 case ENETUNREACH: 1702 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1703 tp->t_softerror = error; 1704 return (0); 1705 } 1706 /* FALLTHROUGH */ 1707 default: 1708 return (error); 1709 } 1710 } 1711 TCPSTAT_INC(tcps_sndtotal); 1712 1713 /* 1714 * Data sent (as far as we can tell). 1715 * If this advertises a larger window than any other segment, 1716 * then remember the size of the advertised window. 1717 * Any pending ACK has now been sent. 1718 */ 1719 if (SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1720 tp->rcv_adv = tp->rcv_nxt + recwin; 1721 tp->last_ack_sent = tp->rcv_nxt; 1722 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1723 if (tcp_timer_active(tp, TT_DELACK)) 1724 tcp_timer_activate(tp, TT_DELACK, 0); 1725 #if 0 1726 /* 1727 * This completely breaks TCP if newreno is turned on. What happens 1728 * is that if delayed-acks are turned on on the receiver, this code 1729 * on the transmitter effectively destroys the TCP window, forcing 1730 * it to four packets (1.5Kx4 = 6K window). 1731 */ 1732 if (sendalot && --maxburst) 1733 goto again; 1734 #endif 1735 if (sendalot) 1736 goto again; 1737 return (0); 1738 } 1739 1740 void 1741 tcp_setpersist(struct tcpcb *tp) 1742 { 1743 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1744 int tt; 1745 int maxunacktime; 1746 1747 tp->t_flags &= ~TF_PREVVALID; 1748 if (tcp_timer_active(tp, TT_REXMT)) 1749 panic("tcp_setpersist: retransmit pending"); 1750 /* 1751 * If the state is already closed, don't bother. 1752 */ 1753 if (tp->t_state == TCPS_CLOSED) 1754 return; 1755 1756 /* 1757 * Start/restart persistence timer. 1758 */ 1759 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1760 tcp_persmin, tcp_persmax); 1761 if (TP_MAXUNACKTIME(tp) && tp->t_acktime) { 1762 maxunacktime = tp->t_acktime + TP_MAXUNACKTIME(tp) - ticks; 1763 if (maxunacktime < 1) 1764 maxunacktime = 1; 1765 if (maxunacktime < tt) 1766 tt = maxunacktime; 1767 } 1768 tcp_timer_activate(tp, TT_PERSIST, tt); 1769 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1770 tp->t_rxtshift++; 1771 } 1772 1773 /* 1774 * Insert TCP options according to the supplied parameters to the place 1775 * optp in a consistent way. Can handle unaligned destinations. 1776 * 1777 * The order of the option processing is crucial for optimal packing and 1778 * alignment for the scarce option space. 1779 * 1780 * The optimal order for a SYN/SYN-ACK segment is: 1781 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1782 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1783 * 1784 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1785 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1786 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1787 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1788 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1789 */ 1790 int 1791 tcp_addoptions(struct tcpopt *to, u_char *optp) 1792 { 1793 u_int32_t mask, optlen = 0; 1794 1795 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1796 if ((to->to_flags & mask) != mask) 1797 continue; 1798 if (optlen == TCP_MAXOLEN) 1799 break; 1800 switch (to->to_flags & mask) { 1801 case TOF_MSS: 1802 while (optlen % 4) { 1803 optlen += TCPOLEN_NOP; 1804 *optp++ = TCPOPT_NOP; 1805 } 1806 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1807 continue; 1808 optlen += TCPOLEN_MAXSEG; 1809 *optp++ = TCPOPT_MAXSEG; 1810 *optp++ = TCPOLEN_MAXSEG; 1811 to->to_mss = htons(to->to_mss); 1812 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1813 optp += sizeof(to->to_mss); 1814 break; 1815 case TOF_SCALE: 1816 while (!optlen || optlen % 2 != 1) { 1817 optlen += TCPOLEN_NOP; 1818 *optp++ = TCPOPT_NOP; 1819 } 1820 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1821 continue; 1822 optlen += TCPOLEN_WINDOW; 1823 *optp++ = TCPOPT_WINDOW; 1824 *optp++ = TCPOLEN_WINDOW; 1825 *optp++ = to->to_wscale; 1826 break; 1827 case TOF_SACKPERM: 1828 while (optlen % 2) { 1829 optlen += TCPOLEN_NOP; 1830 *optp++ = TCPOPT_NOP; 1831 } 1832 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1833 continue; 1834 optlen += TCPOLEN_SACK_PERMITTED; 1835 *optp++ = TCPOPT_SACK_PERMITTED; 1836 *optp++ = TCPOLEN_SACK_PERMITTED; 1837 break; 1838 case TOF_TS: 1839 while (!optlen || optlen % 4 != 2) { 1840 optlen += TCPOLEN_NOP; 1841 *optp++ = TCPOPT_NOP; 1842 } 1843 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1844 continue; 1845 optlen += TCPOLEN_TIMESTAMP; 1846 *optp++ = TCPOPT_TIMESTAMP; 1847 *optp++ = TCPOLEN_TIMESTAMP; 1848 to->to_tsval = htonl(to->to_tsval); 1849 to->to_tsecr = htonl(to->to_tsecr); 1850 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1851 optp += sizeof(to->to_tsval); 1852 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1853 optp += sizeof(to->to_tsecr); 1854 break; 1855 case TOF_SIGNATURE: 1856 { 1857 int siglen = TCPOLEN_SIGNATURE - 2; 1858 1859 while (!optlen || optlen % 4 != 2) { 1860 optlen += TCPOLEN_NOP; 1861 *optp++ = TCPOPT_NOP; 1862 } 1863 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) { 1864 to->to_flags &= ~TOF_SIGNATURE; 1865 continue; 1866 } 1867 optlen += TCPOLEN_SIGNATURE; 1868 *optp++ = TCPOPT_SIGNATURE; 1869 *optp++ = TCPOLEN_SIGNATURE; 1870 to->to_signature = optp; 1871 while (siglen--) 1872 *optp++ = 0; 1873 break; 1874 } 1875 case TOF_SACK: 1876 { 1877 int sackblks = 0; 1878 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1879 tcp_seq sack_seq; 1880 1881 while (!optlen || optlen % 4 != 2) { 1882 optlen += TCPOLEN_NOP; 1883 *optp++ = TCPOPT_NOP; 1884 } 1885 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1886 continue; 1887 optlen += TCPOLEN_SACKHDR; 1888 *optp++ = TCPOPT_SACK; 1889 sackblks = min(to->to_nsacks, 1890 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1891 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1892 while (sackblks--) { 1893 sack_seq = htonl(sack->start); 1894 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1895 optp += sizeof(sack_seq); 1896 sack_seq = htonl(sack->end); 1897 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1898 optp += sizeof(sack_seq); 1899 optlen += TCPOLEN_SACK; 1900 sack++; 1901 } 1902 TCPSTAT_INC(tcps_sack_send_blocks); 1903 break; 1904 } 1905 case TOF_FASTOPEN: 1906 { 1907 int total_len; 1908 1909 /* XXX is there any point to aligning this option? */ 1910 total_len = TCPOLEN_FAST_OPEN_EMPTY + to->to_tfo_len; 1911 if (TCP_MAXOLEN - optlen < total_len) { 1912 to->to_flags &= ~TOF_FASTOPEN; 1913 continue; 1914 } 1915 *optp++ = TCPOPT_FAST_OPEN; 1916 *optp++ = total_len; 1917 if (to->to_tfo_len > 0) { 1918 bcopy(to->to_tfo_cookie, optp, to->to_tfo_len); 1919 optp += to->to_tfo_len; 1920 } 1921 optlen += total_len; 1922 break; 1923 } 1924 default: 1925 panic("%s: unknown TCP option type", __func__); 1926 break; 1927 } 1928 } 1929 1930 /* Terminate and pad TCP options to a 4 byte boundary. */ 1931 if (optlen % 4) { 1932 optlen += TCPOLEN_EOL; 1933 *optp++ = TCPOPT_EOL; 1934 } 1935 /* 1936 * According to RFC 793 (STD0007): 1937 * "The content of the header beyond the End-of-Option option 1938 * must be header padding (i.e., zero)." 1939 * and later: "The padding is composed of zeros." 1940 */ 1941 while (optlen % 4) { 1942 optlen += TCPOLEN_PAD; 1943 *optp++ = TCPOPT_PAD; 1944 } 1945 1946 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1947 return (optlen); 1948 } 1949 1950 /* 1951 * This is a copy of m_copym(), taking the TSO segment size/limit 1952 * constraints into account, and advancing the sndptr as it goes. 1953 */ 1954 struct mbuf * 1955 tcp_m_copym(struct mbuf *m, int32_t off0, int32_t *plen, 1956 int32_t seglimit, int32_t segsize, struct sockbuf *sb, bool hw_tls) 1957 { 1958 #ifdef KERN_TLS 1959 struct ktls_session *tls, *ntls; 1960 struct mbuf *start __diagused; 1961 #endif 1962 struct mbuf *n, **np; 1963 struct mbuf *top; 1964 int32_t off = off0; 1965 int32_t len = *plen; 1966 int32_t fragsize; 1967 int32_t len_cp = 0; 1968 int32_t *pkthdrlen; 1969 uint32_t mlen, frags; 1970 bool copyhdr; 1971 1972 KASSERT(off >= 0, ("tcp_m_copym, negative off %d", off)); 1973 KASSERT(len >= 0, ("tcp_m_copym, negative len %d", len)); 1974 if (off == 0 && m->m_flags & M_PKTHDR) 1975 copyhdr = true; 1976 else 1977 copyhdr = false; 1978 while (off > 0) { 1979 KASSERT(m != NULL, ("tcp_m_copym, offset > size of mbuf chain")); 1980 if (off < m->m_len) 1981 break; 1982 off -= m->m_len; 1983 if ((sb) && (m == sb->sb_sndptr)) { 1984 sb->sb_sndptroff += m->m_len; 1985 sb->sb_sndptr = m->m_next; 1986 } 1987 m = m->m_next; 1988 } 1989 np = ⊤ 1990 top = NULL; 1991 pkthdrlen = NULL; 1992 #ifdef KERN_TLS 1993 if (hw_tls && (m->m_flags & M_EXTPG)) 1994 tls = m->m_epg_tls; 1995 else 1996 tls = NULL; 1997 start = m; 1998 #endif 1999 while (len > 0) { 2000 if (m == NULL) { 2001 KASSERT(len == M_COPYALL, 2002 ("tcp_m_copym, length > size of mbuf chain")); 2003 *plen = len_cp; 2004 if (pkthdrlen != NULL) 2005 *pkthdrlen = len_cp; 2006 break; 2007 } 2008 #ifdef KERN_TLS 2009 if (hw_tls) { 2010 if (m->m_flags & M_EXTPG) 2011 ntls = m->m_epg_tls; 2012 else 2013 ntls = NULL; 2014 2015 /* 2016 * Avoid mixing TLS records with handshake 2017 * data or TLS records from different 2018 * sessions. 2019 */ 2020 if (tls != ntls) { 2021 MPASS(m != start); 2022 *plen = len_cp; 2023 if (pkthdrlen != NULL) 2024 *pkthdrlen = len_cp; 2025 break; 2026 } 2027 } 2028 #endif 2029 mlen = min(len, m->m_len - off); 2030 if (seglimit) { 2031 /* 2032 * For M_EXTPG mbufs, add 3 segments 2033 * + 1 in case we are crossing page boundaries 2034 * + 2 in case the TLS hdr/trailer are used 2035 * It is cheaper to just add the segments 2036 * than it is to take the cache miss to look 2037 * at the mbuf ext_pgs state in detail. 2038 */ 2039 if (m->m_flags & M_EXTPG) { 2040 fragsize = min(segsize, PAGE_SIZE); 2041 frags = 3; 2042 } else { 2043 fragsize = segsize; 2044 frags = 0; 2045 } 2046 2047 /* Break if we really can't fit anymore. */ 2048 if ((frags + 1) >= seglimit) { 2049 *plen = len_cp; 2050 if (pkthdrlen != NULL) 2051 *pkthdrlen = len_cp; 2052 break; 2053 } 2054 2055 /* 2056 * Reduce size if you can't copy the whole 2057 * mbuf. If we can't copy the whole mbuf, also 2058 * adjust len so the loop will end after this 2059 * mbuf. 2060 */ 2061 if ((frags + howmany(mlen, fragsize)) >= seglimit) { 2062 mlen = (seglimit - frags - 1) * fragsize; 2063 len = mlen; 2064 *plen = len_cp + len; 2065 if (pkthdrlen != NULL) 2066 *pkthdrlen = *plen; 2067 } 2068 frags += howmany(mlen, fragsize); 2069 if (frags == 0) 2070 frags++; 2071 seglimit -= frags; 2072 KASSERT(seglimit > 0, 2073 ("%s: seglimit went too low", __func__)); 2074 } 2075 if (copyhdr) 2076 n = m_gethdr(M_NOWAIT, m->m_type); 2077 else 2078 n = m_get(M_NOWAIT, m->m_type); 2079 *np = n; 2080 if (n == NULL) 2081 goto nospace; 2082 if (copyhdr) { 2083 if (!m_dup_pkthdr(n, m, M_NOWAIT)) 2084 goto nospace; 2085 if (len == M_COPYALL) 2086 n->m_pkthdr.len -= off0; 2087 else 2088 n->m_pkthdr.len = len; 2089 pkthdrlen = &n->m_pkthdr.len; 2090 copyhdr = false; 2091 } 2092 n->m_len = mlen; 2093 len_cp += n->m_len; 2094 if (m->m_flags & (M_EXT|M_EXTPG)) { 2095 n->m_data = m->m_data + off; 2096 mb_dupcl(n, m); 2097 } else 2098 bcopy(mtod(m, caddr_t)+off, mtod(n, caddr_t), 2099 (u_int)n->m_len); 2100 2101 if (sb && (sb->sb_sndptr == m) && 2102 ((n->m_len + off) >= m->m_len) && m->m_next) { 2103 sb->sb_sndptroff += m->m_len; 2104 sb->sb_sndptr = m->m_next; 2105 } 2106 off = 0; 2107 if (len != M_COPYALL) { 2108 len -= n->m_len; 2109 } 2110 m = m->m_next; 2111 np = &n->m_next; 2112 } 2113 return (top); 2114 nospace: 2115 m_freem(top); 2116 return (NULL); 2117 } 2118 2119 void 2120 tcp_sndbuf_autoscale(struct tcpcb *tp, struct socket *so, uint32_t sendwin) 2121 { 2122 2123 /* 2124 * Automatic sizing of send socket buffer. Often the send buffer 2125 * size is not optimally adjusted to the actual network conditions 2126 * at hand (delay bandwidth product). Setting the buffer size too 2127 * small limits throughput on links with high bandwidth and high 2128 * delay (eg. trans-continental/oceanic links). Setting the 2129 * buffer size too big consumes too much real kernel memory, 2130 * especially with many connections on busy servers. 2131 * 2132 * The criteria to step up the send buffer one notch are: 2133 * 1. receive window of remote host is larger than send buffer 2134 * (with a fudge factor of 5/4th); 2135 * 2. send buffer is filled to 7/8th with data (so we actually 2136 * have data to make use of it); 2137 * 3. send buffer fill has not hit maximal automatic size; 2138 * 4. our send window (slow start and cogestion controlled) is 2139 * larger than sent but unacknowledged data in send buffer. 2140 * 2141 * The remote host receive window scaling factor may limit the 2142 * growing of the send buffer before it reaches its allowed 2143 * maximum. 2144 * 2145 * It scales directly with slow start or congestion window 2146 * and does at most one step per received ACK. This fast 2147 * scaling has the drawback of growing the send buffer beyond 2148 * what is strictly necessary to make full use of a given 2149 * delay*bandwidth product. However testing has shown this not 2150 * to be much of an problem. At worst we are trading wasting 2151 * of available bandwidth (the non-use of it) for wasting some 2152 * socket buffer memory. 2153 * 2154 * TODO: Shrink send buffer during idle periods together 2155 * with congestion window. Requires another timer. Has to 2156 * wait for upcoming tcp timer rewrite. 2157 * 2158 * XXXGL: should there be used sbused() or sbavail()? 2159 */ 2160 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 2161 int lowat; 2162 2163 lowat = V_tcp_sendbuf_auto_lowat ? so->so_snd.sb_lowat : 0; 2164 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat - lowat && 2165 sbused(&so->so_snd) >= 2166 (so->so_snd.sb_hiwat / 8 * 7) - lowat && 2167 sbused(&so->so_snd) < V_tcp_autosndbuf_max && 2168 sendwin >= (sbused(&so->so_snd) - 2169 (tp->snd_nxt - tp->snd_una))) { 2170 if (!sbreserve_locked(so, SO_SND, 2171 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 2172 V_tcp_autosndbuf_max), curthread)) 2173 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 2174 } 2175 } 2176 } 2177