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