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 #include "opt_tcpdebug.h" 42 43 #include <sys/param.h> 44 #include <sys/systm.h> 45 #include <sys/arb.h> 46 #include <sys/domain.h> 47 #ifdef TCP_HHOOK 48 #include <sys/hhook.h> 49 #endif 50 #include <sys/kernel.h> 51 #ifdef KERN_TLS 52 #include <sys/ktls.h> 53 #endif 54 #include <sys/lock.h> 55 #include <sys/mbuf.h> 56 #include <sys/mutex.h> 57 #include <sys/protosw.h> 58 #include <sys/qmath.h> 59 #include <sys/sdt.h> 60 #include <sys/socket.h> 61 #include <sys/socketvar.h> 62 #include <sys/sysctl.h> 63 #include <sys/stats.h> 64 65 #include <net/if.h> 66 #include <net/route.h> 67 #include <net/route/nhop.h> 68 #include <net/vnet.h> 69 70 #include <netinet/in.h> 71 #include <netinet/in_kdtrace.h> 72 #include <netinet/in_systm.h> 73 #include <netinet/ip.h> 74 #include <netinet/in_pcb.h> 75 #include <netinet/ip_var.h> 76 #include <netinet/ip_options.h> 77 #ifdef INET6 78 #include <netinet6/in6_pcb.h> 79 #include <netinet/ip6.h> 80 #include <netinet6/ip6_var.h> 81 #endif 82 #include <netinet/tcp.h> 83 #define TCPOUTFLAGS 84 #include <netinet/tcp_fsm.h> 85 #include <netinet/tcp_log_buf.h> 86 #include <netinet/tcp_seq.h> 87 #include <netinet/tcp_timer.h> 88 #include <netinet/tcp_var.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 TCPDEBUG 96 #include <netinet/tcp_debug.h> 97 #endif 98 #ifdef TCP_OFFLOAD 99 #include <netinet/tcp_offload.h> 100 #endif 101 102 #include <netipsec/ipsec_support.h> 103 104 #include <netinet/udp.h> 105 #include <netinet/udp_var.h> 106 #include <machine/in_cksum.h> 107 108 #include <security/mac/mac_framework.h> 109 110 VNET_DEFINE(int, path_mtu_discovery) = 1; 111 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_VNET | CTLFLAG_RW, 112 &VNET_NAME(path_mtu_discovery), 1, 113 "Enable Path MTU Discovery"); 114 115 VNET_DEFINE(int, tcp_do_tso) = 1; 116 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_VNET | CTLFLAG_RW, 117 &VNET_NAME(tcp_do_tso), 0, 118 "Enable TCP Segmentation Offload"); 119 120 VNET_DEFINE(int, tcp_sendspace) = 1024*32; 121 #define V_tcp_sendspace VNET(tcp_sendspace) 122 SYSCTL_INT(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, CTLFLAG_VNET | CTLFLAG_RW, 123 &VNET_NAME(tcp_sendspace), 0, "Initial send socket buffer size"); 124 125 VNET_DEFINE(int, tcp_do_autosndbuf) = 1; 126 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_VNET | CTLFLAG_RW, 127 &VNET_NAME(tcp_do_autosndbuf), 0, 128 "Enable automatic send buffer sizing"); 129 130 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024; 131 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_VNET | CTLFLAG_RW, 132 &VNET_NAME(tcp_autosndbuf_inc), 0, 133 "Incrementor step size of automatic send buffer"); 134 135 VNET_DEFINE(int, tcp_autosndbuf_max) = 2*1024*1024; 136 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_VNET | CTLFLAG_RW, 137 &VNET_NAME(tcp_autosndbuf_max), 0, 138 "Max size of automatic send buffer"); 139 140 VNET_DEFINE(int, tcp_sendbuf_auto_lowat) = 0; 141 #define V_tcp_sendbuf_auto_lowat VNET(tcp_sendbuf_auto_lowat) 142 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto_lowat, CTLFLAG_VNET | CTLFLAG_RW, 143 &VNET_NAME(tcp_sendbuf_auto_lowat), 0, 144 "Modify threshold for auto send buffer growth to account for SO_SNDLOWAT"); 145 146 /* 147 * Make sure that either retransmit or persist timer is set for SYN, FIN and 148 * non-ACK. 149 */ 150 #define TCP_XMIT_TIMER_ASSERT(tp, len, th_flags) \ 151 KASSERT(((len) == 0 && ((th_flags) & (TH_SYN | TH_FIN)) == 0) ||\ 152 tcp_timer_active((tp), TT_REXMT) || \ 153 tcp_timer_active((tp), TT_PERSIST), \ 154 ("neither rexmt nor persist timer is set")) 155 156 static void inline cc_after_idle(struct tcpcb *tp); 157 158 #ifdef TCP_HHOOK 159 /* 160 * Wrapper for the TCP established output helper hook. 161 */ 162 void 163 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th, 164 struct tcpopt *to, uint32_t len, int tso) 165 { 166 struct tcp_hhook_data hhook_data; 167 168 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) { 169 hhook_data.tp = tp; 170 hhook_data.th = th; 171 hhook_data.to = to; 172 hhook_data.len = len; 173 hhook_data.tso = tso; 174 175 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data, 176 tp->osd); 177 } 178 } 179 #endif 180 181 /* 182 * CC wrapper hook functions 183 */ 184 static void inline 185 cc_after_idle(struct tcpcb *tp) 186 { 187 INP_WLOCK_ASSERT(tp->t_inpcb); 188 189 if (CC_ALGO(tp)->after_idle != NULL) 190 CC_ALGO(tp)->after_idle(tp->ccv); 191 } 192 193 /* 194 * Tcp output routine: figure out what should be sent and send it. 195 */ 196 int 197 tcp_output(struct tcpcb *tp) 198 { 199 struct socket *so = tp->t_inpcb->inp_socket; 200 int32_t len; 201 uint32_t recwin, sendwin; 202 int off, flags, error = 0; /* Keep compiler happy */ 203 u_int if_hw_tsomaxsegcount = 0; 204 u_int if_hw_tsomaxsegsize = 0; 205 struct mbuf *m; 206 struct ip *ip = NULL; 207 #ifdef TCPDEBUG 208 struct ipovly *ipov = NULL; 209 #endif 210 struct tcphdr *th; 211 u_char opt[TCP_MAXOLEN]; 212 unsigned ipoptlen, optlen, hdrlen, ulen; 213 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 214 unsigned ipsec_optlen = 0; 215 #endif 216 int idle, sendalot, curticks; 217 int sack_rxmit, sack_bytes_rxmt; 218 struct sackhole *p; 219 int tso, mtu; 220 struct tcpopt to; 221 struct udphdr *udp = NULL; 222 unsigned int wanted_cookie = 0; 223 unsigned int dont_sendalot = 0; 224 #if 0 225 int maxburst = TCP_MAXBURST; 226 #endif 227 #ifdef INET6 228 struct ip6_hdr *ip6 = NULL; 229 int isipv6; 230 231 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 232 #endif 233 #ifdef KERN_TLS 234 const bool hw_tls = (so->so_snd.sb_flags & SB_TLS_IFNET) != 0; 235 #else 236 const bool hw_tls = false; 237 #endif 238 239 NET_EPOCH_ASSERT(); 240 INP_WLOCK_ASSERT(tp->t_inpcb); 241 242 #ifdef TCP_OFFLOAD 243 if (tp->t_flags & TF_TOE) 244 return (tcp_offload_output(tp)); 245 #endif 246 247 /* 248 * For TFO connections in SYN_SENT or SYN_RECEIVED, 249 * only allow the initial SYN or SYN|ACK and those sent 250 * by the retransmit timer. 251 */ 252 if (IS_FASTOPEN(tp->t_flags) && 253 ((tp->t_state == TCPS_SYN_SENT) || 254 (tp->t_state == TCPS_SYN_RECEIVED)) && 255 SEQ_GT(tp->snd_max, tp->snd_una) && /* initial SYN or SYN|ACK sent */ 256 (tp->snd_nxt != tp->snd_una)) /* not a retransmit */ 257 return (0); 258 259 /* 260 * Determine length of data that should be transmitted, 261 * and flags that will be used. 262 * If there is some data or critical controls (SYN, RST) 263 * to send, then transmit; otherwise, investigate further. 264 */ 265 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 266 if (idle && (((ticks - tp->t_rcvtime) >= tp->t_rxtcur) || 267 (tp->t_sndtime && ((ticks - tp->t_sndtime) >= tp->t_rxtcur)))) 268 cc_after_idle(tp); 269 tp->t_flags &= ~TF_LASTIDLE; 270 if (idle) { 271 if (tp->t_flags & TF_MORETOCOME) { 272 tp->t_flags |= TF_LASTIDLE; 273 idle = 0; 274 } 275 } 276 again: 277 /* 278 * If we've recently taken a timeout, snd_max will be greater than 279 * snd_nxt. There may be SACK information that allows us to avoid 280 * resending already delivered data. Adjust snd_nxt accordingly. 281 */ 282 if ((tp->t_flags & TF_SACK_PERMIT) && 283 SEQ_LT(tp->snd_nxt, tp->snd_max)) 284 tcp_sack_adjust(tp); 285 sendalot = 0; 286 tso = 0; 287 mtu = 0; 288 off = tp->snd_nxt - tp->snd_una; 289 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 290 291 flags = tcp_outflags[tp->t_state]; 292 /* 293 * Send any SACK-generated retransmissions. If we're explicitly trying 294 * to send out new data (when sendalot is 1), bypass this function. 295 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 296 * we're replacing a (future) new transmission with a retransmission 297 * now, and we previously incremented snd_cwnd in tcp_input(). 298 */ 299 /* 300 * Still in sack recovery , reset rxmit flag to zero. 301 */ 302 sack_rxmit = 0; 303 sack_bytes_rxmt = 0; 304 len = 0; 305 p = NULL; 306 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) && 307 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 308 uint32_t cwin; 309 310 cwin = 311 imax(min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt, 0); 312 /* Do not retransmit SACK segments beyond snd_recover */ 313 if (SEQ_GT(p->end, tp->snd_recover)) { 314 /* 315 * (At least) part of sack hole extends beyond 316 * snd_recover. Check to see if we can rexmit data 317 * for this hole. 318 */ 319 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 320 /* 321 * Can't rexmit any more data for this hole. 322 * That data will be rexmitted in the next 323 * sack recovery episode, when snd_recover 324 * moves past p->rxmit. 325 */ 326 p = NULL; 327 goto after_sack_rexmit; 328 } else 329 /* Can rexmit part of the current hole */ 330 len = ((int32_t)ulmin(cwin, 331 tp->snd_recover - p->rxmit)); 332 } else 333 len = ((int32_t)ulmin(cwin, p->end - p->rxmit)); 334 off = p->rxmit - tp->snd_una; 335 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 336 __func__, off)); 337 if (len > 0) { 338 sack_rxmit = 1; 339 sendalot = 1; 340 TCPSTAT_INC(tcps_sack_rexmits); 341 TCPSTAT_ADD(tcps_sack_rexmit_bytes, 342 min(len, tcp_maxseg(tp))); 343 } 344 } 345 after_sack_rexmit: 346 /* 347 * Get standard flags, and add SYN or FIN if requested by 'hidden' 348 * state flags. 349 */ 350 if (tp->t_flags & TF_NEEDFIN) 351 flags |= TH_FIN; 352 if (tp->t_flags & TF_NEEDSYN) 353 flags |= TH_SYN; 354 355 SOCKBUF_LOCK(&so->so_snd); 356 /* 357 * If in persist timeout with window of 0, send 1 byte. 358 * Otherwise, if window is small but nonzero 359 * and timer expired, we will send what we can 360 * and go to transmit state. 361 */ 362 if (tp->t_flags & TF_FORCEDATA) { 363 if (sendwin == 0) { 364 /* 365 * If we still have some data to send, then 366 * clear the FIN bit. Usually this would 367 * happen below when it realizes that we 368 * aren't sending all the data. However, 369 * if we have exactly 1 byte of unsent data, 370 * then it won't clear the FIN bit below, 371 * and if we are in persist state, we wind 372 * up sending the packet without recording 373 * that we sent the FIN bit. 374 * 375 * We can't just blindly clear the FIN bit, 376 * because if we don't have any more data 377 * to send then the probe will be the FIN 378 * itself. 379 */ 380 if (off < sbused(&so->so_snd)) 381 flags &= ~TH_FIN; 382 sendwin = 1; 383 } else { 384 tcp_timer_activate(tp, TT_PERSIST, 0); 385 tp->t_rxtshift = 0; 386 } 387 } 388 389 /* 390 * If snd_nxt == snd_max and we have transmitted a FIN, the 391 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 392 * a negative length. This can also occur when TCP opens up 393 * its congestion window while receiving additional duplicate 394 * acks after fast-retransmit because TCP will reset snd_nxt 395 * to snd_max after the fast-retransmit. 396 * 397 * In the normal retransmit-FIN-only case, however, snd_nxt will 398 * be set to snd_una, the offset will be 0, and the length may 399 * wind up 0. 400 * 401 * If sack_rxmit is true we are retransmitting from the scoreboard 402 * in which case len is already set. 403 */ 404 if (sack_rxmit == 0) { 405 if (sack_bytes_rxmt == 0) 406 len = ((int32_t)min(sbavail(&so->so_snd), sendwin) - 407 off); 408 else { 409 int32_t cwin; 410 411 /* 412 * We are inside of a SACK recovery episode and are 413 * sending new data, having retransmitted all the 414 * data possible in the scoreboard. 415 */ 416 len = ((int32_t)min(sbavail(&so->so_snd), tp->snd_wnd) - 417 off); 418 /* 419 * Don't remove this (len > 0) check ! 420 * We explicitly check for len > 0 here (although it 421 * isn't really necessary), to work around a gcc 422 * optimization issue - to force gcc to compute 423 * len above. Without this check, the computation 424 * of len is bungled by the optimizer. 425 */ 426 if (len > 0) { 427 cwin = tp->snd_cwnd - 428 (tp->snd_nxt - tp->snd_recover) - 429 sack_bytes_rxmt; 430 if (cwin < 0) 431 cwin = 0; 432 len = imin(len, cwin); 433 } 434 } 435 } 436 437 /* 438 * Lop off SYN bit if it has already been sent. However, if this 439 * is SYN-SENT state and if segment contains data and if we don't 440 * know that foreign host supports TAO, suppress sending segment. 441 */ 442 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 443 if (tp->t_state != TCPS_SYN_RECEIVED) 444 flags &= ~TH_SYN; 445 /* 446 * When sending additional segments following a TFO SYN|ACK, 447 * do not include the SYN bit. 448 */ 449 if (IS_FASTOPEN(tp->t_flags) && 450 (tp->t_state == TCPS_SYN_RECEIVED)) 451 flags &= ~TH_SYN; 452 off--, len++; 453 } 454 455 /* 456 * Be careful not to send data and/or FIN on SYN segments. 457 * This measure is needed to prevent interoperability problems 458 * with not fully conformant TCP implementations. 459 */ 460 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 461 len = 0; 462 flags &= ~TH_FIN; 463 } 464 465 /* 466 * On TFO sockets, ensure no data is sent in the following cases: 467 * 468 * - When retransmitting SYN|ACK on a passively-created socket 469 * 470 * - When retransmitting SYN on an actively created socket 471 * 472 * - When sending a zero-length cookie (cookie request) on an 473 * actively created socket 474 * 475 * - When the socket is in the CLOSED state (RST is being sent) 476 */ 477 if (IS_FASTOPEN(tp->t_flags) && 478 (((flags & TH_SYN) && (tp->t_rxtshift > 0)) || 479 ((tp->t_state == TCPS_SYN_SENT) && 480 (tp->t_tfo_client_cookie_len == 0)) || 481 (flags & TH_RST))) 482 len = 0; 483 if (len <= 0) { 484 /* 485 * If FIN has been sent but not acked, 486 * but we haven't been called to retransmit, 487 * len will be < 0. Otherwise, window shrank 488 * after we sent into it. If window shrank to 0, 489 * cancel pending retransmit, pull snd_nxt back 490 * to (closed) window, and set the persist timer 491 * if it isn't already going. If the window didn't 492 * close completely, just wait for an ACK. 493 * 494 * We also do a general check here to ensure that 495 * we will set the persist timer when we have data 496 * to send, but a 0-byte window. This makes sure 497 * the persist timer is set even if the packet 498 * hits one of the "goto send" lines below. 499 */ 500 len = 0; 501 if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) && 502 (off < (int) sbavail(&so->so_snd))) { 503 tcp_timer_activate(tp, TT_REXMT, 0); 504 tp->t_rxtshift = 0; 505 tp->snd_nxt = tp->snd_una; 506 if (!tcp_timer_active(tp, TT_PERSIST)) 507 tcp_setpersist(tp); 508 } 509 } 510 511 /* len will be >= 0 after this point. */ 512 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 513 514 tcp_sndbuf_autoscale(tp, so, sendwin); 515 516 /* 517 * Decide if we can use TCP Segmentation Offloading (if supported by 518 * hardware). 519 * 520 * TSO may only be used if we are in a pure bulk sending state. The 521 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 522 * IP options prevent using TSO. With TSO the TCP header is the same 523 * (except for the sequence number) for all generated packets. This 524 * makes it impossible to transmit any options which vary per generated 525 * segment or packet. 526 * 527 * IPv4 handling has a clear separation of ip options and ip header 528 * flags while IPv6 combines both in in6p_outputopts. ip6_optlen() does 529 * the right thing below to provide length of just ip options and thus 530 * checking for ipoptlen is enough to decide if ip options are present. 531 */ 532 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 533 /* 534 * Pre-calculate here as we save another lookup into the darknesses 535 * of IPsec that way and can actually decide if TSO is ok. 536 */ 537 #ifdef INET6 538 if (isipv6 && IPSEC_ENABLED(ipv6)) 539 ipsec_optlen = IPSEC_HDRSIZE(ipv6, tp->t_inpcb); 540 #ifdef INET 541 else 542 #endif 543 #endif /* INET6 */ 544 #ifdef INET 545 if (IPSEC_ENABLED(ipv4)) 546 ipsec_optlen = IPSEC_HDRSIZE(ipv4, tp->t_inpcb); 547 #endif /* INET */ 548 #endif /* IPSEC */ 549 #ifdef INET6 550 if (isipv6) 551 ipoptlen = ip6_optlen(tp->t_inpcb); 552 else 553 #endif 554 if (tp->t_inpcb->inp_options) 555 ipoptlen = tp->t_inpcb->inp_options->m_len - 556 offsetof(struct ipoption, ipopt_list); 557 else 558 ipoptlen = 0; 559 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 560 ipoptlen += ipsec_optlen; 561 #endif 562 563 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg && 564 (tp->t_port == 0) && 565 ((tp->t_flags & TF_SIGNATURE) == 0) && 566 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 567 ipoptlen == 0 && !(flags & TH_SYN)) 568 tso = 1; 569 570 if (sack_rxmit) { 571 if (SEQ_LT(p->rxmit + len, tp->snd_una + sbused(&so->so_snd))) 572 flags &= ~TH_FIN; 573 } else { 574 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + 575 sbused(&so->so_snd))) 576 flags &= ~TH_FIN; 577 } 578 579 recwin = lmin(lmax(sbspace(&so->so_rcv), 0), 580 (long)TCP_MAXWIN << tp->rcv_scale); 581 582 /* 583 * Sender silly window avoidance. We transmit under the following 584 * conditions when len is non-zero: 585 * 586 * - We have a full segment (or more with TSO) 587 * - This is the last buffer in a write()/send() and we are 588 * either idle or running NODELAY 589 * - we've timed out (e.g. persist timer) 590 * - we have more then 1/2 the maximum send window's worth of 591 * data (receiver may be limited the window size) 592 * - we need to retransmit 593 */ 594 if (len) { 595 if (len >= tp->t_maxseg) 596 goto send; 597 /* 598 * As the TCP header options are now 599 * considered when setting up the initial 600 * window, we would not send the last segment 601 * if we skip considering the option length here. 602 * Note: this may not work when tcp headers change 603 * very dynamically in the future. 604 */ 605 if ((((tp->t_flags & TF_SIGNATURE) ? 606 PADTCPOLEN(TCPOLEN_SIGNATURE) : 0) + 607 ((tp->t_flags & TF_RCVD_TSTMP) ? 608 PADTCPOLEN(TCPOLEN_TIMESTAMP) : 0) + 609 len) >= tp->t_maxseg) 610 goto send; 611 /* 612 * NOTE! on localhost connections an 'ack' from the remote 613 * end may occur synchronously with the output and cause 614 * us to flush a buffer queued with moretocome. XXX 615 * 616 * note: the len + off check is almost certainly unnecessary. 617 */ 618 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 619 (idle || (tp->t_flags & TF_NODELAY)) && 620 (uint32_t)len + (uint32_t)off >= sbavail(&so->so_snd) && 621 (tp->t_flags & TF_NOPUSH) == 0) { 622 goto send; 623 } 624 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 625 goto send; 626 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 627 goto send; 628 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 629 goto send; 630 if (sack_rxmit) 631 goto send; 632 } 633 634 /* 635 * Sending of standalone window updates. 636 * 637 * Window updates are important when we close our window due to a 638 * full socket buffer and are opening it again after the application 639 * reads data from it. Once the window has opened again and the 640 * remote end starts to send again the ACK clock takes over and 641 * provides the most current window information. 642 * 643 * We must avoid the silly window syndrome whereas every read 644 * from the receive buffer, no matter how small, causes a window 645 * update to be sent. We also should avoid sending a flurry of 646 * window updates when the socket buffer had queued a lot of data 647 * and the application is doing small reads. 648 * 649 * Prevent a flurry of pointless window updates by only sending 650 * an update when we can increase the advertized window by more 651 * than 1/4th of the socket buffer capacity. When the buffer is 652 * getting full or is very small be more aggressive and send an 653 * update whenever we can increase by two mss sized segments. 654 * In all other situations the ACK's to new incoming data will 655 * carry further window increases. 656 * 657 * Don't send an independent window update if a delayed 658 * ACK is pending (it will get piggy-backed on it) or the 659 * remote side already has done a half-close and won't send 660 * more data. Skip this if the connection is in T/TCP 661 * half-open state. 662 */ 663 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 664 !(tp->t_flags & TF_DELACK) && 665 !TCPS_HAVERCVDFIN(tp->t_state)) { 666 /* 667 * "adv" is the amount we could increase the window, 668 * taking into account that we are limited by 669 * TCP_MAXWIN << tp->rcv_scale. 670 */ 671 int32_t adv; 672 int oldwin; 673 674 adv = recwin; 675 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { 676 oldwin = (tp->rcv_adv - tp->rcv_nxt); 677 if (adv > oldwin) 678 adv -= oldwin; 679 else 680 adv = 0; 681 } else 682 oldwin = 0; 683 684 /* 685 * If the new window size ends up being the same as or less 686 * than the old size when it is scaled, then don't force 687 * a window update. 688 */ 689 if (oldwin >> tp->rcv_scale >= (adv + oldwin) >> tp->rcv_scale) 690 goto dontupdate; 691 692 if (adv >= (int32_t)(2 * tp->t_maxseg) && 693 (adv >= (int32_t)(so->so_rcv.sb_hiwat / 4) || 694 recwin <= (so->so_rcv.sb_hiwat / 8) || 695 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg || 696 adv >= TCP_MAXWIN << tp->rcv_scale)) 697 goto send; 698 if (2 * adv >= (int32_t)so->so_rcv.sb_hiwat) 699 goto send; 700 } 701 dontupdate: 702 703 /* 704 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 705 * is also a catch-all for the retransmit timer timeout case. 706 */ 707 if (tp->t_flags & TF_ACKNOW) 708 goto send; 709 if ((flags & TH_RST) || 710 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 711 goto send; 712 if (SEQ_GT(tp->snd_up, tp->snd_una)) 713 goto send; 714 /* 715 * If our state indicates that FIN should be sent 716 * and we have not yet done so, then we need to send. 717 */ 718 if (flags & TH_FIN && 719 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 720 goto send; 721 /* 722 * In SACK, it is possible for tcp_output to fail to send a segment 723 * after the retransmission timer has been turned off. Make sure 724 * that the retransmission timer is set. 725 */ 726 if ((tp->t_flags & TF_SACK_PERMIT) && 727 SEQ_GT(tp->snd_max, tp->snd_una) && 728 !tcp_timer_active(tp, TT_REXMT) && 729 !tcp_timer_active(tp, TT_PERSIST)) { 730 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 731 goto just_return; 732 } 733 /* 734 * TCP window updates are not reliable, rather a polling protocol 735 * using ``persist'' packets is used to insure receipt of window 736 * updates. The three ``states'' for the output side are: 737 * idle not doing retransmits or persists 738 * persisting to move a small or zero window 739 * (re)transmitting and thereby not persisting 740 * 741 * tcp_timer_active(tp, TT_PERSIST) 742 * is true when we are in persist state. 743 * (tp->t_flags & TF_FORCEDATA) 744 * is set when we are called to send a persist packet. 745 * tcp_timer_active(tp, TT_REXMT) 746 * is set when we are retransmitting 747 * The output side is idle when both timers are zero. 748 * 749 * If send window is too small, there is data to transmit, and no 750 * retransmit or persist is pending, then go to persist state. 751 * If nothing happens soon, send when timer expires: 752 * if window is nonzero, transmit what we can, 753 * otherwise force out a byte. 754 */ 755 if (sbavail(&so->so_snd) && !tcp_timer_active(tp, TT_REXMT) && 756 !tcp_timer_active(tp, TT_PERSIST)) { 757 tp->t_rxtshift = 0; 758 tcp_setpersist(tp); 759 } 760 761 /* 762 * No reason to send a segment, just return. 763 */ 764 just_return: 765 SOCKBUF_UNLOCK(&so->so_snd); 766 return (0); 767 768 send: 769 SOCKBUF_LOCK_ASSERT(&so->so_snd); 770 if (len > 0) { 771 if (len >= tp->t_maxseg) 772 tp->t_flags2 |= TF2_PLPMTU_MAXSEGSNT; 773 else 774 tp->t_flags2 &= ~TF2_PLPMTU_MAXSEGSNT; 775 } 776 /* 777 * Before ESTABLISHED, force sending of initial options 778 * unless TCP set not to do any options. 779 * NOTE: we assume that the IP/TCP header plus TCP options 780 * always fit in a single mbuf, leaving room for a maximum 781 * link header, i.e. 782 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 783 */ 784 optlen = 0; 785 #ifdef INET6 786 if (isipv6) 787 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 788 else 789 #endif 790 hdrlen = sizeof (struct tcpiphdr); 791 792 if (flags & TH_SYN) { 793 tp->snd_nxt = tp->iss; 794 } 795 796 /* 797 * Compute options for segment. 798 * We only have to care about SYN and established connection 799 * segments. Options for SYN-ACK segments are handled in TCP 800 * syncache. 801 */ 802 to.to_flags = 0; 803 if ((tp->t_flags & TF_NOOPT) == 0) { 804 /* Maximum segment size. */ 805 if (flags & TH_SYN) { 806 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 807 if (tp->t_port) 808 to.to_mss -= V_tcp_udp_tunneling_overhead; 809 to.to_flags |= TOF_MSS; 810 811 /* 812 * On SYN or SYN|ACK transmits on TFO connections, 813 * only include the TFO option if it is not a 814 * retransmit, as the presence of the TFO option may 815 * have caused the original SYN or SYN|ACK to have 816 * been dropped by a middlebox. 817 */ 818 if (IS_FASTOPEN(tp->t_flags) && 819 (tp->t_rxtshift == 0)) { 820 if (tp->t_state == TCPS_SYN_RECEIVED) { 821 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN; 822 to.to_tfo_cookie = 823 (u_int8_t *)&tp->t_tfo_cookie.server; 824 to.to_flags |= TOF_FASTOPEN; 825 wanted_cookie = 1; 826 } else if (tp->t_state == TCPS_SYN_SENT) { 827 to.to_tfo_len = 828 tp->t_tfo_client_cookie_len; 829 to.to_tfo_cookie = 830 tp->t_tfo_cookie.client; 831 to.to_flags |= TOF_FASTOPEN; 832 wanted_cookie = 1; 833 /* 834 * If we wind up having more data to 835 * send with the SYN than can fit in 836 * one segment, don't send any more 837 * until the SYN|ACK comes back from 838 * the other end. 839 */ 840 dont_sendalot = 1; 841 } 842 } 843 } 844 /* Window scaling. */ 845 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 846 to.to_wscale = tp->request_r_scale; 847 to.to_flags |= TOF_SCALE; 848 } 849 /* Timestamps. */ 850 if ((tp->t_flags & TF_RCVD_TSTMP) || 851 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 852 curticks = tcp_ts_getticks(); 853 to.to_tsval = curticks + tp->ts_offset; 854 to.to_tsecr = tp->ts_recent; 855 to.to_flags |= TOF_TS; 856 if (tp->t_rxtshift == 1) 857 tp->t_badrxtwin = curticks; 858 } 859 860 /* Set receive buffer autosizing timestamp. */ 861 if (tp->rfbuf_ts == 0 && 862 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 863 tp->rfbuf_ts = tcp_ts_getticks(); 864 865 /* Selective ACK's. */ 866 if (tp->t_flags & TF_SACK_PERMIT) { 867 if (flags & TH_SYN) 868 to.to_flags |= TOF_SACKPERM; 869 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 870 tp->rcv_numsacks > 0) { 871 to.to_flags |= TOF_SACK; 872 to.to_nsacks = tp->rcv_numsacks; 873 to.to_sacks = (u_char *)tp->sackblks; 874 } 875 } 876 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 877 /* TCP-MD5 (RFC2385). */ 878 /* 879 * Check that TCP_MD5SIG is enabled in tcpcb to 880 * account the size needed to set this TCP option. 881 */ 882 if (tp->t_flags & TF_SIGNATURE) 883 to.to_flags |= TOF_SIGNATURE; 884 #endif /* TCP_SIGNATURE */ 885 886 /* Processing the options. */ 887 hdrlen += optlen = tcp_addoptions(&to, opt); 888 /* 889 * If we wanted a TFO option to be added, but it was unable 890 * to fit, ensure no data is sent. 891 */ 892 if (IS_FASTOPEN(tp->t_flags) && wanted_cookie && 893 !(to.to_flags & TOF_FASTOPEN)) 894 len = 0; 895 } 896 if (tp->t_port) { 897 if (V_tcp_udp_tunneling_port == 0) { 898 /* The port was removed?? */ 899 SOCKBUF_UNLOCK(&so->so_snd); 900 return (EHOSTUNREACH); 901 } 902 hdrlen += sizeof(struct udphdr); 903 } 904 /* 905 * Adjust data length if insertion of options will 906 * bump the packet length beyond the t_maxseg length. 907 * Clear the FIN bit because we cut off the tail of 908 * the segment. 909 */ 910 if (len + optlen + ipoptlen > tp->t_maxseg) { 911 flags &= ~TH_FIN; 912 913 if (tso) { 914 u_int if_hw_tsomax; 915 u_int moff; 916 int max_len; 917 918 /* extract TSO information */ 919 if_hw_tsomax = tp->t_tsomax; 920 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount; 921 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize; 922 923 /* 924 * Limit a TSO burst to prevent it from 925 * overflowing or exceeding the maximum length 926 * allowed by the network interface: 927 */ 928 KASSERT(ipoptlen == 0, 929 ("%s: TSO can't do IP options", __func__)); 930 931 /* 932 * Check if we should limit by maximum payload 933 * length: 934 */ 935 if (if_hw_tsomax != 0) { 936 /* compute maximum TSO length */ 937 max_len = (if_hw_tsomax - hdrlen - 938 max_linkhdr); 939 if (max_len <= 0) { 940 len = 0; 941 } else if (len > max_len) { 942 sendalot = 1; 943 len = max_len; 944 } 945 } 946 947 /* 948 * Prevent the last segment from being 949 * fractional unless the send sockbuf can be 950 * emptied: 951 */ 952 max_len = (tp->t_maxseg - optlen); 953 if (((uint32_t)off + (uint32_t)len) < 954 sbavail(&so->so_snd)) { 955 moff = len % max_len; 956 if (moff != 0) { 957 len -= moff; 958 sendalot = 1; 959 } 960 } 961 962 /* 963 * In case there are too many small fragments 964 * don't use TSO: 965 */ 966 if (len <= max_len) { 967 len = max_len; 968 sendalot = 1; 969 tso = 0; 970 } 971 972 /* 973 * Send the FIN in a separate segment 974 * after the bulk sending is done. 975 * We don't trust the TSO implementations 976 * to clear the FIN flag on all but the 977 * last segment. 978 */ 979 if (tp->t_flags & TF_NEEDFIN) 980 sendalot = 1; 981 } else { 982 if (optlen + ipoptlen >= tp->t_maxseg) { 983 /* 984 * Since we don't have enough space to put 985 * the IP header chain and the TCP header in 986 * one packet as required by RFC 7112, don't 987 * send it. Also ensure that at least one 988 * byte of the payload can be put into the 989 * TCP segment. 990 */ 991 SOCKBUF_UNLOCK(&so->so_snd); 992 error = EMSGSIZE; 993 sack_rxmit = 0; 994 goto out; 995 } 996 len = tp->t_maxseg - optlen - ipoptlen; 997 sendalot = 1; 998 if (dont_sendalot) 999 sendalot = 0; 1000 } 1001 } else 1002 tso = 0; 1003 1004 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 1005 ("%s: len > IP_MAXPACKET", __func__)); 1006 1007 /*#ifdef DIAGNOSTIC*/ 1008 #ifdef INET6 1009 if (max_linkhdr + hdrlen > MCLBYTES) 1010 #else 1011 if (max_linkhdr + hdrlen > MHLEN) 1012 #endif 1013 panic("tcphdr too big"); 1014 /*#endif*/ 1015 1016 /* 1017 * This KASSERT is here to catch edge cases at a well defined place. 1018 * Before, those had triggered (random) panic conditions further down. 1019 */ 1020 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 1021 1022 /* 1023 * Grab a header mbuf, attaching a copy of data to 1024 * be transmitted, and initialize the header from 1025 * the template for sends on this connection. 1026 */ 1027 if (len) { 1028 struct mbuf *mb; 1029 struct sockbuf *msb; 1030 u_int moff; 1031 1032 if ((tp->t_flags & TF_FORCEDATA) && len == 1) { 1033 TCPSTAT_INC(tcps_sndprobe); 1034 #ifdef STATS 1035 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1036 stats_voi_update_abs_u32(tp->t_stats, 1037 VOI_TCP_RETXPB, len); 1038 else 1039 stats_voi_update_abs_u64(tp->t_stats, 1040 VOI_TCP_TXPB, len); 1041 #endif /* STATS */ 1042 } else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 1043 tp->t_sndrexmitpack++; 1044 TCPSTAT_INC(tcps_sndrexmitpack); 1045 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 1046 #ifdef STATS 1047 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_RETXPB, 1048 len); 1049 #endif /* STATS */ 1050 } else { 1051 TCPSTAT_INC(tcps_sndpack); 1052 TCPSTAT_ADD(tcps_sndbyte, len); 1053 #ifdef STATS 1054 stats_voi_update_abs_u64(tp->t_stats, VOI_TCP_TXPB, 1055 len); 1056 #endif /* STATS */ 1057 } 1058 #ifdef INET6 1059 if (MHLEN < hdrlen + max_linkhdr) 1060 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR); 1061 else 1062 #endif 1063 m = m_gethdr(M_NOWAIT, MT_DATA); 1064 1065 if (m == NULL) { 1066 SOCKBUF_UNLOCK(&so->so_snd); 1067 error = ENOBUFS; 1068 sack_rxmit = 0; 1069 goto out; 1070 } 1071 1072 m->m_data += max_linkhdr; 1073 m->m_len = hdrlen; 1074 1075 /* 1076 * Start the m_copy functions from the closest mbuf 1077 * to the offset in the socket buffer chain. 1078 */ 1079 mb = sbsndptr_noadv(&so->so_snd, off, &moff); 1080 if (len <= MHLEN - hdrlen - max_linkhdr && !hw_tls) { 1081 m_copydata(mb, moff, len, 1082 mtod(m, caddr_t) + hdrlen); 1083 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1084 sbsndptr_adv(&so->so_snd, mb, len); 1085 m->m_len += len; 1086 } else { 1087 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1088 msb = NULL; 1089 else 1090 msb = &so->so_snd; 1091 m->m_next = tcp_m_copym(mb, moff, 1092 &len, if_hw_tsomaxsegcount, 1093 if_hw_tsomaxsegsize, msb, hw_tls); 1094 if (len <= (tp->t_maxseg - optlen)) { 1095 /* 1096 * Must have ran out of mbufs for the copy 1097 * shorten it to no longer need tso. Lets 1098 * not put on sendalot since we are low on 1099 * mbufs. 1100 */ 1101 tso = 0; 1102 } 1103 if (m->m_next == NULL) { 1104 SOCKBUF_UNLOCK(&so->so_snd); 1105 (void) m_free(m); 1106 error = ENOBUFS; 1107 sack_rxmit = 0; 1108 goto out; 1109 } 1110 } 1111 1112 /* 1113 * If we're sending everything we've got, set PUSH. 1114 * (This will keep happy those implementations which only 1115 * give data to the user when a buffer fills or 1116 * a PUSH comes in.) 1117 */ 1118 if (((uint32_t)off + (uint32_t)len == sbused(&so->so_snd)) && 1119 !(flags & TH_SYN)) 1120 flags |= TH_PUSH; 1121 SOCKBUF_UNLOCK(&so->so_snd); 1122 } else { 1123 SOCKBUF_UNLOCK(&so->so_snd); 1124 if (tp->t_flags & TF_ACKNOW) 1125 TCPSTAT_INC(tcps_sndacks); 1126 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 1127 TCPSTAT_INC(tcps_sndctrl); 1128 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 1129 TCPSTAT_INC(tcps_sndurg); 1130 else 1131 TCPSTAT_INC(tcps_sndwinup); 1132 1133 m = m_gethdr(M_NOWAIT, MT_DATA); 1134 if (m == NULL) { 1135 error = ENOBUFS; 1136 sack_rxmit = 0; 1137 goto out; 1138 } 1139 #ifdef INET6 1140 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 1141 MHLEN >= hdrlen) { 1142 M_ALIGN(m, hdrlen); 1143 } else 1144 #endif 1145 m->m_data += max_linkhdr; 1146 m->m_len = hdrlen; 1147 } 1148 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 1149 m->m_pkthdr.rcvif = (struct ifnet *)0; 1150 #ifdef MAC 1151 mac_inpcb_create_mbuf(tp->t_inpcb, m); 1152 #endif 1153 #ifdef INET6 1154 if (isipv6) { 1155 ip6 = mtod(m, struct ip6_hdr *); 1156 if (tp->t_port) { 1157 udp = (struct udphdr *)((caddr_t)ip6 + sizeof(struct ip6_hdr)); 1158 udp->uh_sport = htons(V_tcp_udp_tunneling_port); 1159 udp->uh_dport = tp->t_port; 1160 ulen = hdrlen + len - sizeof(struct ip6_hdr); 1161 udp->uh_ulen = htons(ulen); 1162 th = (struct tcphdr *)(udp + 1); 1163 } else { 1164 th = (struct tcphdr *)(ip6 + 1); 1165 } 1166 tcpip_fillheaders(tp->t_inpcb, tp->t_port, ip6, th); 1167 } else 1168 #endif /* INET6 */ 1169 { 1170 ip = mtod(m, struct ip *); 1171 #ifdef TCPDEBUG 1172 ipov = (struct ipovly *)ip; 1173 #endif 1174 if (tp->t_port) { 1175 udp = (struct udphdr *)((caddr_t)ip + sizeof(struct ip)); 1176 udp->uh_sport = htons(V_tcp_udp_tunneling_port); 1177 udp->uh_dport = tp->t_port; 1178 ulen = hdrlen + len - sizeof(struct ip); 1179 udp->uh_ulen = htons(ulen); 1180 th = (struct tcphdr *)(udp + 1); 1181 } else 1182 th = (struct tcphdr *)(ip + 1); 1183 tcpip_fillheaders(tp->t_inpcb, tp->t_port, ip, th); 1184 } 1185 1186 /* 1187 * Fill in fields, remembering maximum advertised 1188 * window for use in delaying messages about window sizes. 1189 * If resending a FIN, be sure not to use a new sequence number. 1190 */ 1191 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 1192 tp->snd_nxt == tp->snd_max) 1193 tp->snd_nxt--; 1194 /* 1195 * If we are starting a connection, send ECN setup 1196 * SYN packet. If we are on a retransmit, we may 1197 * resend those bits a number of times as per 1198 * RFC 3168. 1199 */ 1200 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn == 1) { 1201 if (tp->t_rxtshift >= 1) { 1202 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 1203 flags |= TH_ECE|TH_CWR; 1204 } else 1205 flags |= TH_ECE|TH_CWR; 1206 } 1207 /* Handle parallel SYN for ECN */ 1208 if ((tp->t_state == TCPS_SYN_RECEIVED) && 1209 (tp->t_flags2 & TF2_ECN_SND_ECE)) { 1210 flags |= TH_ECE; 1211 tp->t_flags2 &= ~TF2_ECN_SND_ECE; 1212 } 1213 1214 if (TCPS_HAVEESTABLISHED(tp->t_state) && 1215 (tp->t_flags2 & TF2_ECN_PERMIT)) { 1216 /* 1217 * If the peer has ECN, mark data packets with 1218 * ECN capable transmission (ECT). 1219 * Ignore pure ack packets, retransmissions and window probes. 1220 */ 1221 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 1222 (sack_rxmit == 0) && 1223 !((tp->t_flags & TF_FORCEDATA) && len == 1 && 1224 SEQ_LT(tp->snd_una, tp->snd_max))) { 1225 #ifdef INET6 1226 if (isipv6) 1227 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 1228 else 1229 #endif 1230 ip->ip_tos |= IPTOS_ECN_ECT0; 1231 TCPSTAT_INC(tcps_ecn_ect0); 1232 /* 1233 * Reply with proper ECN notifications. 1234 * Only set CWR on new data segments. 1235 */ 1236 if (tp->t_flags2 & TF2_ECN_SND_CWR) { 1237 flags |= TH_CWR; 1238 tp->t_flags2 &= ~TF2_ECN_SND_CWR; 1239 } 1240 } 1241 if (tp->t_flags2 & TF2_ECN_SND_ECE) 1242 flags |= TH_ECE; 1243 } 1244 1245 /* 1246 * If we are doing retransmissions, then snd_nxt will 1247 * not reflect the first unsent octet. For ACK only 1248 * packets, we do not want the sequence number of the 1249 * retransmitted packet, we want the sequence number 1250 * of the next unsent octet. So, if there is no data 1251 * (and no SYN or FIN), use snd_max instead of snd_nxt 1252 * when filling in ti_seq. But if we are in persist 1253 * state, snd_max might reflect one byte beyond the 1254 * right edge of the window, so use snd_nxt in that 1255 * case, since we know we aren't doing a retransmission. 1256 * (retransmit and persist are mutually exclusive...) 1257 */ 1258 if (sack_rxmit == 0) { 1259 if (len || (flags & (TH_SYN|TH_FIN)) || 1260 tcp_timer_active(tp, TT_PERSIST)) 1261 th->th_seq = htonl(tp->snd_nxt); 1262 else 1263 th->th_seq = htonl(tp->snd_max); 1264 } else { 1265 th->th_seq = htonl(p->rxmit); 1266 p->rxmit += len; 1267 /* 1268 * Lost Retransmission Detection 1269 * trigger resending of a (then 1270 * still existing) hole, when 1271 * fack acks recoverypoint. 1272 */ 1273 if ((tp->t_flags & TF_LRD) && SEQ_GEQ(p->rxmit, p->end)) 1274 p->rxmit = tp->snd_recover; 1275 tp->sackhint.sack_bytes_rexmit += len; 1276 } 1277 if (IN_RECOVERY(tp->t_flags)) { 1278 /* 1279 * Account all bytes transmitted while 1280 * IN_RECOVERY, simplifying PRR and 1281 * Lost Retransmit Detection 1282 */ 1283 tp->sackhint.prr_out += len; 1284 } 1285 th->th_ack = htonl(tp->rcv_nxt); 1286 if (optlen) { 1287 bcopy(opt, th + 1, optlen); 1288 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1289 } 1290 th->th_flags = flags; 1291 /* 1292 * Calculate receive window. Don't shrink window, 1293 * but avoid silly window syndrome. 1294 * If a RST segment is sent, advertise a window of zero. 1295 */ 1296 if (flags & TH_RST) { 1297 recwin = 0; 1298 } else { 1299 if (recwin < (so->so_rcv.sb_hiwat / 4) && 1300 recwin < tp->t_maxseg) 1301 recwin = 0; 1302 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1303 recwin < (tp->rcv_adv - tp->rcv_nxt)) 1304 recwin = (tp->rcv_adv - tp->rcv_nxt); 1305 } 1306 /* 1307 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1308 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1309 * case is handled in syncache. 1310 */ 1311 if (flags & TH_SYN) 1312 th->th_win = htons((u_short) 1313 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1314 else { 1315 /* Avoid shrinking window with window scaling. */ 1316 recwin = roundup2(recwin, 1 << tp->rcv_scale); 1317 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1318 } 1319 1320 /* 1321 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1322 * a 0 window. This may cause the remote transmitter to stall. This 1323 * flag tells soreceive() to disable delayed acknowledgements when 1324 * draining the buffer. This can occur if the receiver is attempting 1325 * to read more data than can be buffered prior to transmitting on 1326 * the connection. 1327 */ 1328 if (th->th_win == 0) { 1329 tp->t_sndzerowin++; 1330 tp->t_flags |= TF_RXWIN0SENT; 1331 } else 1332 tp->t_flags &= ~TF_RXWIN0SENT; 1333 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1334 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1335 th->th_flags |= TH_URG; 1336 } else 1337 /* 1338 * If no urgent pointer to send, then we pull 1339 * the urgent pointer to the left edge of the send window 1340 * so that it doesn't drift into the send window on sequence 1341 * number wraparound. 1342 */ 1343 tp->snd_up = tp->snd_una; /* drag it along */ 1344 1345 /* 1346 * Put TCP length in extended header, and then 1347 * checksum extended header and data. 1348 */ 1349 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1350 1351 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1352 if (to.to_flags & TOF_SIGNATURE) { 1353 /* 1354 * Calculate MD5 signature and put it into the place 1355 * determined before. 1356 * NOTE: since TCP options buffer doesn't point into 1357 * mbuf's data, calculate offset and use it. 1358 */ 1359 if (!TCPMD5_ENABLED() || (error = TCPMD5_OUTPUT(m, th, 1360 (u_char *)(th + 1) + (to.to_signature - opt))) != 0) { 1361 /* 1362 * Do not send segment if the calculation of MD5 1363 * digest has failed. 1364 */ 1365 m_freem(m); 1366 goto out; 1367 } 1368 } 1369 #endif 1370 #ifdef INET6 1371 if (isipv6) { 1372 /* 1373 * There is no need to fill in ip6_plen right now. 1374 * It will be filled later by ip6_output. 1375 */ 1376 if (tp->t_port) { 1377 m->m_pkthdr.csum_flags = CSUM_UDP_IPV6; 1378 m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum); 1379 udp->uh_sum = in6_cksum_pseudo(ip6, ulen, IPPROTO_UDP, 0); 1380 th->th_sum = htons(0); 1381 UDPSTAT_INC(udps_opackets); 1382 } else { 1383 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1384 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1385 th->th_sum = in6_cksum_pseudo(ip6, 1386 sizeof(struct tcphdr) + optlen + len, IPPROTO_TCP, 1387 0); 1388 } 1389 } 1390 #endif 1391 #if defined(INET6) && defined(INET) 1392 else 1393 #endif 1394 #ifdef INET 1395 { 1396 if (tp->t_port) { 1397 m->m_pkthdr.csum_flags = CSUM_UDP; 1398 m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum); 1399 udp->uh_sum = in_pseudo(ip->ip_src.s_addr, 1400 ip->ip_dst.s_addr, htons(ulen + IPPROTO_UDP)); 1401 th->th_sum = htons(0); 1402 UDPSTAT_INC(udps_opackets); 1403 } else { 1404 m->m_pkthdr.csum_flags = CSUM_TCP; 1405 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1406 th->th_sum = in_pseudo(ip->ip_src.s_addr, 1407 ip->ip_dst.s_addr, htons(sizeof(struct tcphdr) + 1408 IPPROTO_TCP + len + optlen)); 1409 } 1410 1411 /* IP version must be set here for ipv4/ipv6 checking later */ 1412 KASSERT(ip->ip_v == IPVERSION, 1413 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1414 } 1415 #endif 1416 1417 /* 1418 * Enable TSO and specify the size of the segments. 1419 * The TCP pseudo header checksum is always provided. 1420 */ 1421 if (tso) { 1422 KASSERT(len > tp->t_maxseg - optlen, 1423 ("%s: len <= tso_segsz", __func__)); 1424 m->m_pkthdr.csum_flags |= CSUM_TSO; 1425 m->m_pkthdr.tso_segsz = tp->t_maxseg - optlen; 1426 } 1427 1428 KASSERT(len + hdrlen == m_length(m, NULL), 1429 ("%s: mbuf chain shorter than expected: %d + %u != %u", 1430 __func__, len, hdrlen, m_length(m, NULL))); 1431 1432 #ifdef TCP_HHOOK 1433 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1434 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1435 #endif 1436 1437 #ifdef TCPDEBUG 1438 /* 1439 * Trace. 1440 */ 1441 if (so->so_options & SO_DEBUG) { 1442 u_short save = 0; 1443 #ifdef INET6 1444 if (!isipv6) 1445 #endif 1446 { 1447 save = ipov->ih_len; 1448 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1449 } 1450 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1451 #ifdef INET6 1452 if (!isipv6) 1453 #endif 1454 ipov->ih_len = save; 1455 } 1456 #endif /* TCPDEBUG */ 1457 TCP_PROBE3(debug__output, tp, th, m); 1458 1459 /* We're getting ready to send; log now. */ 1460 TCP_LOG_EVENT(tp, th, &so->so_rcv, &so->so_snd, TCP_LOG_OUT, ERRNO_UNK, 1461 len, NULL, false); 1462 1463 /* 1464 * Fill in IP length and desired time to live and 1465 * send to IP level. There should be a better way 1466 * to handle ttl and tos; we could keep them in 1467 * the template, but need a way to checksum without them. 1468 */ 1469 /* 1470 * m->m_pkthdr.len should have been set before checksum calculation, 1471 * because in6_cksum() need it. 1472 */ 1473 #ifdef INET6 1474 if (isipv6) { 1475 /* 1476 * we separately set hoplimit for every segment, since the 1477 * user might want to change the value via setsockopt. 1478 * Also, desired default hop limit might be changed via 1479 * Neighbor Discovery. 1480 */ 1481 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1482 1483 /* 1484 * Set the packet size here for the benefit of DTrace probes. 1485 * ip6_output() will set it properly; it's supposed to include 1486 * the option header lengths as well. 1487 */ 1488 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6)); 1489 1490 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) 1491 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1492 else 1493 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1494 1495 if (tp->t_state == TCPS_SYN_SENT) 1496 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th); 1497 1498 TCP_PROBE5(send, NULL, tp, ip6, tp, th); 1499 1500 #ifdef TCPPCAP 1501 /* Save packet, if requested. */ 1502 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1503 #endif 1504 1505 /* TODO: IPv6 IP6TOS_ECT bit on */ 1506 error = ip6_output(m, tp->t_inpcb->in6p_outputopts, 1507 &tp->t_inpcb->inp_route6, 1508 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 1509 NULL, NULL, tp->t_inpcb); 1510 1511 if (error == EMSGSIZE && tp->t_inpcb->inp_route6.ro_nh != NULL) 1512 mtu = tp->t_inpcb->inp_route6.ro_nh->nh_mtu; 1513 } 1514 #endif /* INET6 */ 1515 #if defined(INET) && defined(INET6) 1516 else 1517 #endif 1518 #ifdef INET 1519 { 1520 ip->ip_len = htons(m->m_pkthdr.len); 1521 #ifdef INET6 1522 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1523 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1524 #endif /* INET6 */ 1525 /* 1526 * If we do path MTU discovery, then we set DF on every packet. 1527 * This might not be the best thing to do according to RFC3390 1528 * Section 2. However the tcp hostcache migitates the problem 1529 * so it affects only the first tcp connection with a host. 1530 * 1531 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1532 */ 1533 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) { 1534 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1535 if (tp->t_port == 0 || len < V_tcp_minmss) { 1536 ip->ip_off |= htons(IP_DF); 1537 } 1538 } else { 1539 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1540 } 1541 1542 if (tp->t_state == TCPS_SYN_SENT) 1543 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th); 1544 1545 TCP_PROBE5(send, NULL, tp, ip, tp, th); 1546 1547 #ifdef TCPPCAP 1548 /* Save packet, if requested. */ 1549 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1550 #endif 1551 1552 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, 1553 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1554 tp->t_inpcb); 1555 1556 if (error == EMSGSIZE && tp->t_inpcb->inp_route.ro_nh != NULL) 1557 mtu = tp->t_inpcb->inp_route.ro_nh->nh_mtu; 1558 } 1559 #endif /* INET */ 1560 1561 out: 1562 /* 1563 * In transmit state, time the transmission and arrange for 1564 * the retransmit. In persist state, just set snd_max. 1565 */ 1566 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1567 !tcp_timer_active(tp, TT_PERSIST)) { 1568 tcp_seq startseq = tp->snd_nxt; 1569 1570 /* 1571 * Advance snd_nxt over sequence space of this segment. 1572 */ 1573 if (flags & (TH_SYN|TH_FIN)) { 1574 if (flags & TH_SYN) 1575 tp->snd_nxt++; 1576 if (flags & TH_FIN) { 1577 tp->snd_nxt++; 1578 tp->t_flags |= TF_SENTFIN; 1579 } 1580 } 1581 if (sack_rxmit) 1582 goto timer; 1583 tp->snd_nxt += len; 1584 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1585 tp->snd_max = tp->snd_nxt; 1586 /* 1587 * Time this transmission if not a retransmission and 1588 * not currently timing anything. 1589 */ 1590 tp->t_sndtime = ticks; 1591 if (tp->t_rtttime == 0) { 1592 tp->t_rtttime = ticks; 1593 tp->t_rtseq = startseq; 1594 TCPSTAT_INC(tcps_segstimed); 1595 } 1596 #ifdef STATS 1597 if (!(tp->t_flags & TF_GPUTINPROG) && len) { 1598 tp->t_flags |= TF_GPUTINPROG; 1599 tp->gput_seq = startseq; 1600 tp->gput_ack = startseq + 1601 ulmin(sbavail(&so->so_snd) - off, sendwin); 1602 tp->gput_ts = tcp_ts_getticks(); 1603 } 1604 #endif /* STATS */ 1605 } 1606 1607 /* 1608 * Set retransmit timer if not currently set, 1609 * and not doing a pure ack or a keep-alive probe. 1610 * Initial value for retransmit timer is smoothed 1611 * round-trip time + 2 * round-trip time variance. 1612 * Initialize shift counter which is used for backoff 1613 * of retransmit time. 1614 */ 1615 timer: 1616 if (!tcp_timer_active(tp, TT_REXMT) && 1617 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1618 (tp->snd_nxt != tp->snd_una))) { 1619 if (tcp_timer_active(tp, TT_PERSIST)) { 1620 tcp_timer_activate(tp, TT_PERSIST, 0); 1621 tp->t_rxtshift = 0; 1622 } 1623 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1624 } else if (len == 0 && sbavail(&so->so_snd) && 1625 !tcp_timer_active(tp, TT_REXMT) && 1626 !tcp_timer_active(tp, TT_PERSIST)) { 1627 /* 1628 * Avoid a situation where we do not set persist timer 1629 * after a zero window condition. For example: 1630 * 1) A -> B: packet with enough data to fill the window 1631 * 2) B -> A: ACK for #1 + new data (0 window 1632 * advertisement) 1633 * 3) A -> B: ACK for #2, 0 len packet 1634 * 1635 * In this case, A will not activate the persist timer, 1636 * because it chose to send a packet. Unless tcp_output 1637 * is called for some other reason (delayed ack timer, 1638 * another input packet from B, socket syscall), A will 1639 * not send zero window probes. 1640 * 1641 * So, if you send a 0-length packet, but there is data 1642 * in the socket buffer, and neither the rexmt or 1643 * persist timer is already set, then activate the 1644 * persist timer. 1645 */ 1646 tp->t_rxtshift = 0; 1647 tcp_setpersist(tp); 1648 } 1649 } else { 1650 /* 1651 * Persist case, update snd_max but since we are in 1652 * persist mode (no window) we do not update snd_nxt. 1653 */ 1654 int xlen = len; 1655 if (flags & TH_SYN) 1656 ++xlen; 1657 if (flags & TH_FIN) { 1658 ++xlen; 1659 tp->t_flags |= TF_SENTFIN; 1660 } 1661 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1662 tp->snd_max = tp->snd_nxt + xlen; 1663 } 1664 if ((error == 0) && 1665 (TCPS_HAVEESTABLISHED(tp->t_state) && 1666 (tp->t_flags & TF_SACK_PERMIT) && 1667 tp->rcv_numsacks > 0)) { 1668 /* Clean up any DSACK's sent */ 1669 tcp_clean_dsack_blocks(tp); 1670 } 1671 if (error) { 1672 /* Record the error. */ 1673 TCP_LOG_EVENT(tp, NULL, &so->so_rcv, &so->so_snd, TCP_LOG_OUT, 1674 error, 0, NULL, false); 1675 1676 /* 1677 * We know that the packet was lost, so back out the 1678 * sequence number advance, if any. 1679 * 1680 * If the error is EPERM the packet got blocked by the 1681 * local firewall. Normally we should terminate the 1682 * connection but the blocking may have been spurious 1683 * due to a firewall reconfiguration cycle. So we treat 1684 * it like a packet loss and let the retransmit timer and 1685 * timeouts do their work over time. 1686 * XXX: It is a POLA question whether calling tcp_drop right 1687 * away would be the really correct behavior instead. 1688 */ 1689 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1690 !tcp_timer_active(tp, TT_PERSIST)) && 1691 ((flags & TH_SYN) == 0) && 1692 (error != EPERM)) { 1693 if (sack_rxmit) { 1694 p->rxmit -= len; 1695 tp->sackhint.sack_bytes_rexmit -= len; 1696 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1697 ("sackhint bytes rtx >= 0")); 1698 } else 1699 tp->snd_nxt -= len; 1700 } 1701 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1702 switch (error) { 1703 case EACCES: 1704 case EPERM: 1705 tp->t_softerror = error; 1706 return (error); 1707 case ENOBUFS: 1708 TCP_XMIT_TIMER_ASSERT(tp, len, flags); 1709 tp->snd_cwnd = tp->t_maxseg; 1710 return (0); 1711 case EMSGSIZE: 1712 /* 1713 * For some reason the interface we used initially 1714 * to send segments changed to another or lowered 1715 * its MTU. 1716 * If TSO was active we either got an interface 1717 * without TSO capabilits or TSO was turned off. 1718 * If we obtained mtu from ip_output() then update 1719 * it and try again. 1720 */ 1721 if (tso) 1722 tp->t_flags &= ~TF_TSO; 1723 if (mtu != 0) { 1724 tcp_mss_update(tp, -1, mtu, NULL, NULL); 1725 goto again; 1726 } 1727 return (error); 1728 case EHOSTDOWN: 1729 case EHOSTUNREACH: 1730 case ENETDOWN: 1731 case ENETUNREACH: 1732 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1733 tp->t_softerror = error; 1734 return (0); 1735 } 1736 /* FALLTHROUGH */ 1737 default: 1738 return (error); 1739 } 1740 } 1741 TCPSTAT_INC(tcps_sndtotal); 1742 1743 /* 1744 * Data sent (as far as we can tell). 1745 * If this advertises a larger window than any other segment, 1746 * then remember the size of the advertised window. 1747 * Any pending ACK has now been sent. 1748 */ 1749 if (SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1750 tp->rcv_adv = tp->rcv_nxt + recwin; 1751 tp->last_ack_sent = tp->rcv_nxt; 1752 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1753 if (tcp_timer_active(tp, TT_DELACK)) 1754 tcp_timer_activate(tp, TT_DELACK, 0); 1755 #if 0 1756 /* 1757 * This completely breaks TCP if newreno is turned on. What happens 1758 * is that if delayed-acks are turned on on the receiver, this code 1759 * on the transmitter effectively destroys the TCP window, forcing 1760 * it to four packets (1.5Kx4 = 6K window). 1761 */ 1762 if (sendalot && --maxburst) 1763 goto again; 1764 #endif 1765 if (sendalot) 1766 goto again; 1767 return (0); 1768 } 1769 1770 void 1771 tcp_setpersist(struct tcpcb *tp) 1772 { 1773 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1774 int tt; 1775 1776 tp->t_flags &= ~TF_PREVVALID; 1777 if (tcp_timer_active(tp, TT_REXMT)) 1778 panic("tcp_setpersist: retransmit pending"); 1779 /* 1780 * Start/restart persistence timer. 1781 */ 1782 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1783 tcp_persmin, tcp_persmax); 1784 tcp_timer_activate(tp, TT_PERSIST, tt); 1785 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1786 tp->t_rxtshift++; 1787 } 1788 1789 /* 1790 * Insert TCP options according to the supplied parameters to the place 1791 * optp in a consistent way. Can handle unaligned destinations. 1792 * 1793 * The order of the option processing is crucial for optimal packing and 1794 * alignment for the scarce option space. 1795 * 1796 * The optimal order for a SYN/SYN-ACK segment is: 1797 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1798 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1799 * 1800 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1801 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1802 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1803 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1804 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1805 */ 1806 int 1807 tcp_addoptions(struct tcpopt *to, u_char *optp) 1808 { 1809 u_int32_t mask, optlen = 0; 1810 1811 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1812 if ((to->to_flags & mask) != mask) 1813 continue; 1814 if (optlen == TCP_MAXOLEN) 1815 break; 1816 switch (to->to_flags & mask) { 1817 case TOF_MSS: 1818 while (optlen % 4) { 1819 optlen += TCPOLEN_NOP; 1820 *optp++ = TCPOPT_NOP; 1821 } 1822 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1823 continue; 1824 optlen += TCPOLEN_MAXSEG; 1825 *optp++ = TCPOPT_MAXSEG; 1826 *optp++ = TCPOLEN_MAXSEG; 1827 to->to_mss = htons(to->to_mss); 1828 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1829 optp += sizeof(to->to_mss); 1830 break; 1831 case TOF_SCALE: 1832 while (!optlen || optlen % 2 != 1) { 1833 optlen += TCPOLEN_NOP; 1834 *optp++ = TCPOPT_NOP; 1835 } 1836 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1837 continue; 1838 optlen += TCPOLEN_WINDOW; 1839 *optp++ = TCPOPT_WINDOW; 1840 *optp++ = TCPOLEN_WINDOW; 1841 *optp++ = to->to_wscale; 1842 break; 1843 case TOF_SACKPERM: 1844 while (optlen % 2) { 1845 optlen += TCPOLEN_NOP; 1846 *optp++ = TCPOPT_NOP; 1847 } 1848 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1849 continue; 1850 optlen += TCPOLEN_SACK_PERMITTED; 1851 *optp++ = TCPOPT_SACK_PERMITTED; 1852 *optp++ = TCPOLEN_SACK_PERMITTED; 1853 break; 1854 case TOF_TS: 1855 while (!optlen || optlen % 4 != 2) { 1856 optlen += TCPOLEN_NOP; 1857 *optp++ = TCPOPT_NOP; 1858 } 1859 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1860 continue; 1861 optlen += TCPOLEN_TIMESTAMP; 1862 *optp++ = TCPOPT_TIMESTAMP; 1863 *optp++ = TCPOLEN_TIMESTAMP; 1864 to->to_tsval = htonl(to->to_tsval); 1865 to->to_tsecr = htonl(to->to_tsecr); 1866 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1867 optp += sizeof(to->to_tsval); 1868 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1869 optp += sizeof(to->to_tsecr); 1870 break; 1871 case TOF_SIGNATURE: 1872 { 1873 int siglen = TCPOLEN_SIGNATURE - 2; 1874 1875 while (!optlen || optlen % 4 != 2) { 1876 optlen += TCPOLEN_NOP; 1877 *optp++ = TCPOPT_NOP; 1878 } 1879 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) { 1880 to->to_flags &= ~TOF_SIGNATURE; 1881 continue; 1882 } 1883 optlen += TCPOLEN_SIGNATURE; 1884 *optp++ = TCPOPT_SIGNATURE; 1885 *optp++ = TCPOLEN_SIGNATURE; 1886 to->to_signature = optp; 1887 while (siglen--) 1888 *optp++ = 0; 1889 break; 1890 } 1891 case TOF_SACK: 1892 { 1893 int sackblks = 0; 1894 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1895 tcp_seq sack_seq; 1896 1897 while (!optlen || optlen % 4 != 2) { 1898 optlen += TCPOLEN_NOP; 1899 *optp++ = TCPOPT_NOP; 1900 } 1901 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1902 continue; 1903 optlen += TCPOLEN_SACKHDR; 1904 *optp++ = TCPOPT_SACK; 1905 sackblks = min(to->to_nsacks, 1906 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1907 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1908 while (sackblks--) { 1909 sack_seq = htonl(sack->start); 1910 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1911 optp += sizeof(sack_seq); 1912 sack_seq = htonl(sack->end); 1913 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1914 optp += sizeof(sack_seq); 1915 optlen += TCPOLEN_SACK; 1916 sack++; 1917 } 1918 TCPSTAT_INC(tcps_sack_send_blocks); 1919 break; 1920 } 1921 case TOF_FASTOPEN: 1922 { 1923 int total_len; 1924 1925 /* XXX is there any point to aligning this option? */ 1926 total_len = TCPOLEN_FAST_OPEN_EMPTY + to->to_tfo_len; 1927 if (TCP_MAXOLEN - optlen < total_len) { 1928 to->to_flags &= ~TOF_FASTOPEN; 1929 continue; 1930 } 1931 *optp++ = TCPOPT_FAST_OPEN; 1932 *optp++ = total_len; 1933 if (to->to_tfo_len > 0) { 1934 bcopy(to->to_tfo_cookie, optp, to->to_tfo_len); 1935 optp += to->to_tfo_len; 1936 } 1937 optlen += total_len; 1938 break; 1939 } 1940 default: 1941 panic("%s: unknown TCP option type", __func__); 1942 break; 1943 } 1944 } 1945 1946 /* Terminate and pad TCP options to a 4 byte boundary. */ 1947 if (optlen % 4) { 1948 optlen += TCPOLEN_EOL; 1949 *optp++ = TCPOPT_EOL; 1950 } 1951 /* 1952 * According to RFC 793 (STD0007): 1953 * "The content of the header beyond the End-of-Option option 1954 * must be header padding (i.e., zero)." 1955 * and later: "The padding is composed of zeros." 1956 */ 1957 while (optlen % 4) { 1958 optlen += TCPOLEN_PAD; 1959 *optp++ = TCPOPT_PAD; 1960 } 1961 1962 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1963 return (optlen); 1964 } 1965 1966 /* 1967 * This is a copy of m_copym(), taking the TSO segment size/limit 1968 * constraints into account, and advancing the sndptr as it goes. 1969 */ 1970 struct mbuf * 1971 tcp_m_copym(struct mbuf *m, int32_t off0, int32_t *plen, 1972 int32_t seglimit, int32_t segsize, struct sockbuf *sb, bool hw_tls) 1973 { 1974 #ifdef KERN_TLS 1975 struct ktls_session *tls, *ntls; 1976 struct mbuf *start; 1977 #endif 1978 struct mbuf *n, **np; 1979 struct mbuf *top; 1980 int32_t off = off0; 1981 int32_t len = *plen; 1982 int32_t fragsize; 1983 int32_t len_cp = 0; 1984 int32_t *pkthdrlen; 1985 uint32_t mlen, frags; 1986 bool copyhdr; 1987 1988 KASSERT(off >= 0, ("tcp_m_copym, negative off %d", off)); 1989 KASSERT(len >= 0, ("tcp_m_copym, negative len %d", len)); 1990 if (off == 0 && m->m_flags & M_PKTHDR) 1991 copyhdr = true; 1992 else 1993 copyhdr = false; 1994 while (off > 0) { 1995 KASSERT(m != NULL, ("tcp_m_copym, offset > size of mbuf chain")); 1996 if (off < m->m_len) 1997 break; 1998 off -= m->m_len; 1999 if ((sb) && (m == sb->sb_sndptr)) { 2000 sb->sb_sndptroff += m->m_len; 2001 sb->sb_sndptr = m->m_next; 2002 } 2003 m = m->m_next; 2004 } 2005 np = ⊤ 2006 top = NULL; 2007 pkthdrlen = NULL; 2008 #ifdef KERN_TLS 2009 if (hw_tls && (m->m_flags & M_EXTPG)) 2010 tls = m->m_epg_tls; 2011 else 2012 tls = NULL; 2013 start = m; 2014 #endif 2015 while (len > 0) { 2016 if (m == NULL) { 2017 KASSERT(len == M_COPYALL, 2018 ("tcp_m_copym, length > size of mbuf chain")); 2019 *plen = len_cp; 2020 if (pkthdrlen != NULL) 2021 *pkthdrlen = len_cp; 2022 break; 2023 } 2024 #ifdef KERN_TLS 2025 if (hw_tls) { 2026 if (m->m_flags & M_EXTPG) 2027 ntls = m->m_epg_tls; 2028 else 2029 ntls = NULL; 2030 2031 /* 2032 * Avoid mixing TLS records with handshake 2033 * data or TLS records from different 2034 * sessions. 2035 */ 2036 if (tls != ntls) { 2037 MPASS(m != start); 2038 *plen = len_cp; 2039 if (pkthdrlen != NULL) 2040 *pkthdrlen = len_cp; 2041 break; 2042 } 2043 } 2044 #endif 2045 mlen = min(len, m->m_len - off); 2046 if (seglimit) { 2047 /* 2048 * For M_EXTPG mbufs, add 3 segments 2049 * + 1 in case we are crossing page boundaries 2050 * + 2 in case the TLS hdr/trailer are used 2051 * It is cheaper to just add the segments 2052 * than it is to take the cache miss to look 2053 * at the mbuf ext_pgs state in detail. 2054 */ 2055 if (m->m_flags & M_EXTPG) { 2056 fragsize = min(segsize, PAGE_SIZE); 2057 frags = 3; 2058 } else { 2059 fragsize = segsize; 2060 frags = 0; 2061 } 2062 2063 /* Break if we really can't fit anymore. */ 2064 if ((frags + 1) >= seglimit) { 2065 *plen = len_cp; 2066 if (pkthdrlen != NULL) 2067 *pkthdrlen = len_cp; 2068 break; 2069 } 2070 2071 /* 2072 * Reduce size if you can't copy the whole 2073 * mbuf. If we can't copy the whole mbuf, also 2074 * adjust len so the loop will end after this 2075 * mbuf. 2076 */ 2077 if ((frags + howmany(mlen, fragsize)) >= seglimit) { 2078 mlen = (seglimit - frags - 1) * fragsize; 2079 len = mlen; 2080 *plen = len_cp + len; 2081 if (pkthdrlen != NULL) 2082 *pkthdrlen = *plen; 2083 } 2084 frags += howmany(mlen, fragsize); 2085 if (frags == 0) 2086 frags++; 2087 seglimit -= frags; 2088 KASSERT(seglimit > 0, 2089 ("%s: seglimit went too low", __func__)); 2090 } 2091 if (copyhdr) 2092 n = m_gethdr(M_NOWAIT, m->m_type); 2093 else 2094 n = m_get(M_NOWAIT, m->m_type); 2095 *np = n; 2096 if (n == NULL) 2097 goto nospace; 2098 if (copyhdr) { 2099 if (!m_dup_pkthdr(n, m, M_NOWAIT)) 2100 goto nospace; 2101 if (len == M_COPYALL) 2102 n->m_pkthdr.len -= off0; 2103 else 2104 n->m_pkthdr.len = len; 2105 pkthdrlen = &n->m_pkthdr.len; 2106 copyhdr = false; 2107 } 2108 n->m_len = mlen; 2109 len_cp += n->m_len; 2110 if (m->m_flags & (M_EXT|M_EXTPG)) { 2111 n->m_data = m->m_data + off; 2112 mb_dupcl(n, m); 2113 } else 2114 bcopy(mtod(m, caddr_t)+off, mtod(n, caddr_t), 2115 (u_int)n->m_len); 2116 2117 if (sb && (sb->sb_sndptr == m) && 2118 ((n->m_len + off) >= m->m_len) && m->m_next) { 2119 sb->sb_sndptroff += m->m_len; 2120 sb->sb_sndptr = m->m_next; 2121 } 2122 off = 0; 2123 if (len != M_COPYALL) { 2124 len -= n->m_len; 2125 } 2126 m = m->m_next; 2127 np = &n->m_next; 2128 } 2129 return (top); 2130 nospace: 2131 m_freem(top); 2132 return (NULL); 2133 } 2134 2135 void 2136 tcp_sndbuf_autoscale(struct tcpcb *tp, struct socket *so, uint32_t sendwin) 2137 { 2138 2139 /* 2140 * Automatic sizing of send socket buffer. Often the send buffer 2141 * size is not optimally adjusted to the actual network conditions 2142 * at hand (delay bandwidth product). Setting the buffer size too 2143 * small limits throughput on links with high bandwidth and high 2144 * delay (eg. trans-continental/oceanic links). Setting the 2145 * buffer size too big consumes too much real kernel memory, 2146 * especially with many connections on busy servers. 2147 * 2148 * The criteria to step up the send buffer one notch are: 2149 * 1. receive window of remote host is larger than send buffer 2150 * (with a fudge factor of 5/4th); 2151 * 2. send buffer is filled to 7/8th with data (so we actually 2152 * have data to make use of it); 2153 * 3. send buffer fill has not hit maximal automatic size; 2154 * 4. our send window (slow start and cogestion controlled) is 2155 * larger than sent but unacknowledged data in send buffer. 2156 * 2157 * The remote host receive window scaling factor may limit the 2158 * growing of the send buffer before it reaches its allowed 2159 * maximum. 2160 * 2161 * It scales directly with slow start or congestion window 2162 * and does at most one step per received ACK. This fast 2163 * scaling has the drawback of growing the send buffer beyond 2164 * what is strictly necessary to make full use of a given 2165 * delay*bandwidth product. However testing has shown this not 2166 * to be much of an problem. At worst we are trading wasting 2167 * of available bandwidth (the non-use of it) for wasting some 2168 * socket buffer memory. 2169 * 2170 * TODO: Shrink send buffer during idle periods together 2171 * with congestion window. Requires another timer. Has to 2172 * wait for upcoming tcp timer rewrite. 2173 * 2174 * XXXGL: should there be used sbused() or sbavail()? 2175 */ 2176 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 2177 int lowat; 2178 2179 lowat = V_tcp_sendbuf_auto_lowat ? so->so_snd.sb_lowat : 0; 2180 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat - lowat && 2181 sbused(&so->so_snd) >= 2182 (so->so_snd.sb_hiwat / 8 * 7) - lowat && 2183 sbused(&so->so_snd) < V_tcp_autosndbuf_max && 2184 sendwin >= (sbused(&so->so_snd) - 2185 (tp->snd_nxt - tp->snd_una))) { 2186 if (!sbreserve_locked(&so->so_snd, 2187 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 2188 V_tcp_autosndbuf_max), so, curthread)) 2189 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 2190 } 2191 } 2192 } 2193