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 #include "opt_inet.h" 36 #include "opt_inet6.h" 37 #include "opt_ipsec.h" 38 #include "opt_kern_tls.h" 39 40 #include <sys/param.h> 41 #include <sys/systm.h> 42 #include <sys/arb.h> 43 #include <sys/domain.h> 44 #ifdef TCP_HHOOK 45 #include <sys/hhook.h> 46 #endif 47 #include <sys/kernel.h> 48 #ifdef KERN_TLS 49 #include <sys/ktls.h> 50 #endif 51 #include <sys/lock.h> 52 #include <sys/mbuf.h> 53 #include <sys/mutex.h> 54 #include <sys/protosw.h> 55 #include <sys/qmath.h> 56 #include <sys/sdt.h> 57 #include <sys/socket.h> 58 #include <sys/socketvar.h> 59 #include <sys/sysctl.h> 60 #include <sys/stats.h> 61 62 #include <net/if.h> 63 #include <net/route.h> 64 #include <net/route/nhop.h> 65 #include <net/vnet.h> 66 67 #include <netinet/in.h> 68 #include <netinet/in_kdtrace.h> 69 #include <netinet/in_systm.h> 70 #include <netinet/ip.h> 71 #include <netinet/in_pcb.h> 72 #include <netinet/ip_var.h> 73 #include <netinet/ip_options.h> 74 #ifdef INET6 75 #include <netinet6/in6_pcb.h> 76 #include <netinet/ip6.h> 77 #include <netinet6/ip6_var.h> 78 #endif 79 #include <netinet/tcp.h> 80 #define TCPOUTFLAGS 81 #include <netinet/tcp_fsm.h> 82 #include <netinet/tcp_seq.h> 83 #include <netinet/tcp_var.h> 84 #include <netinet/tcp_log_buf.h> 85 #include <netinet/tcp_syncache.h> 86 #include <netinet/tcp_timer.h> 87 #include <netinet/tcpip.h> 88 #include <netinet/cc/cc.h> 89 #include <netinet/tcp_fastopen.h> 90 #ifdef TCPPCAP 91 #include <netinet/tcp_pcap.h> 92 #endif 93 #ifdef TCP_OFFLOAD 94 #include <netinet/tcp_offload.h> 95 #endif 96 #include <netinet/tcp_ecn.h> 97 98 #include <netipsec/ipsec_support.h> 99 100 #include <netinet/udp.h> 101 #include <netinet/udp_var.h> 102 #include <machine/in_cksum.h> 103 104 #include <security/mac/mac_framework.h> 105 106 VNET_DEFINE(int, path_mtu_discovery) = 1; 107 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_VNET | CTLFLAG_RW, 108 &VNET_NAME(path_mtu_discovery), 1, 109 "Enable Path MTU Discovery"); 110 111 VNET_DEFINE(int, tcp_do_tso) = 1; 112 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_VNET | CTLFLAG_RW, 113 &VNET_NAME(tcp_do_tso), 0, 114 "Enable TCP Segmentation Offload"); 115 116 VNET_DEFINE(int, tcp_sendspace) = 1024*32; 117 #define V_tcp_sendspace VNET(tcp_sendspace) 118 SYSCTL_INT(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, CTLFLAG_VNET | CTLFLAG_RW, 119 &VNET_NAME(tcp_sendspace), 0, "Initial send socket buffer size"); 120 121 VNET_DEFINE(int, tcp_do_autosndbuf) = 1; 122 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_VNET | CTLFLAG_RW, 123 &VNET_NAME(tcp_do_autosndbuf), 0, 124 "Enable automatic send buffer sizing"); 125 126 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024; 127 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_VNET | CTLFLAG_RW, 128 &VNET_NAME(tcp_autosndbuf_inc), 0, 129 "Incrementor step size of automatic send buffer"); 130 131 VNET_DEFINE(int, tcp_autosndbuf_max) = 2*1024*1024; 132 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_VNET | CTLFLAG_RW, 133 &VNET_NAME(tcp_autosndbuf_max), 0, 134 "Max size of automatic send buffer"); 135 136 VNET_DEFINE(int, tcp_sendbuf_auto_lowat) = 0; 137 #define V_tcp_sendbuf_auto_lowat VNET(tcp_sendbuf_auto_lowat) 138 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto_lowat, CTLFLAG_VNET | CTLFLAG_RW, 139 &VNET_NAME(tcp_sendbuf_auto_lowat), 0, 140 "Modify threshold for auto send buffer growth to account for SO_SNDLOWAT"); 141 142 /* 143 * Make sure that either retransmit or persist timer is set for SYN, FIN and 144 * non-ACK. 145 */ 146 #define TCP_XMIT_TIMER_ASSERT(tp, len, th_flags) \ 147 KASSERT(((len) == 0 && ((th_flags) & (TH_SYN | TH_FIN)) == 0) ||\ 148 tcp_timer_active((tp), TT_REXMT) || \ 149 tcp_timer_active((tp), TT_PERSIST), \ 150 ("neither rexmt nor persist timer is set")) 151 152 #ifdef TCP_HHOOK 153 /* 154 * Wrapper for the TCP established output helper hook. 155 */ 156 void 157 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th, 158 struct tcpopt *to, uint32_t len, int tso) 159 { 160 struct tcp_hhook_data hhook_data; 161 162 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) { 163 hhook_data.tp = tp; 164 hhook_data.th = th; 165 hhook_data.to = to; 166 hhook_data.len = len; 167 hhook_data.tso = tso; 168 169 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data, 170 &tp->t_osd); 171 } 172 } 173 #endif 174 175 /* 176 * CC wrapper hook functions 177 */ 178 void 179 cc_after_idle(struct tcpcb *tp) 180 { 181 INP_WLOCK_ASSERT(tptoinpcb(tp)); 182 183 if (CC_ALGO(tp)->after_idle != NULL) 184 CC_ALGO(tp)->after_idle(&tp->t_ccv); 185 } 186 187 /* 188 * Tcp output routine: figure out what should be sent and send it. 189 */ 190 int 191 tcp_default_output(struct tcpcb *tp) 192 { 193 struct socket *so = tptosocket(tp); 194 struct inpcb *inp = tptoinpcb(tp); 195 int32_t len; 196 uint32_t recwin, sendwin; 197 uint16_t flags; 198 int off, error = 0; /* Keep compiler happy */ 199 u_int if_hw_tsomaxsegcount = 0; 200 u_int if_hw_tsomaxsegsize = 0; 201 struct mbuf *m; 202 struct ip *ip = NULL; 203 struct tcphdr *th; 204 u_char opt[TCP_MAXOLEN]; 205 unsigned ipoptlen, optlen, hdrlen, ulen; 206 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 207 unsigned ipsec_optlen = 0; 208 #endif 209 int idle, sendalot, curticks; 210 int sack_rxmit, sack_bytes_rxmt; 211 struct sackhole *p; 212 int tso, mtu; 213 struct tcpopt to; 214 struct udphdr *udp = NULL; 215 struct tcp_log_buffer *lgb; 216 unsigned int wanted_cookie = 0; 217 unsigned int dont_sendalot = 0; 218 #if 0 219 int maxburst = TCP_MAXBURST; 220 #endif 221 #ifdef INET6 222 struct ip6_hdr *ip6 = NULL; 223 const bool isipv6 = (inp->inp_vflag & INP_IPV6) != 0; 224 #endif 225 #ifdef KERN_TLS 226 const bool hw_tls = tp->t_nic_ktls_xmit != 0; 227 #else 228 const bool hw_tls = false; 229 #endif 230 231 NET_EPOCH_ASSERT(); 232 INP_WLOCK_ASSERT(inp); 233 234 #ifdef TCP_OFFLOAD 235 if (tp->t_flags & TF_TOE) 236 return (tcp_offload_output(tp)); 237 #endif 238 239 /* 240 * For TFO connections in SYN_SENT or SYN_RECEIVED, 241 * only allow the initial SYN or SYN|ACK and those sent 242 * by the retransmit timer. 243 */ 244 if (IS_FASTOPEN(tp->t_flags) && 245 ((tp->t_state == TCPS_SYN_SENT) || 246 (tp->t_state == TCPS_SYN_RECEIVED)) && 247 SEQ_GT(tp->snd_max, tp->snd_una) && /* initial SYN or SYN|ACK sent */ 248 (tp->snd_nxt != tp->snd_una)) /* not a retransmit */ 249 return (0); 250 251 /* 252 * Determine length of data that should be transmitted, 253 * and flags that will be used. 254 * If there is some data or critical controls (SYN, RST) 255 * to send, then transmit; otherwise, investigate further. 256 */ 257 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 258 if (idle && (((ticks - tp->t_rcvtime) >= tp->t_rxtcur) || 259 (tp->t_sndtime && ((ticks - tp->t_sndtime) >= tp->t_rxtcur)))) 260 cc_after_idle(tp); 261 tp->t_flags &= ~TF_LASTIDLE; 262 if (idle) { 263 if (tp->t_flags & TF_MORETOCOME) { 264 tp->t_flags |= TF_LASTIDLE; 265 idle = 0; 266 } 267 } 268 again: 269 /* 270 * If we've recently taken a timeout, snd_max will be greater than 271 * snd_nxt. There may be SACK information that allows us to avoid 272 * resending already delivered data. Adjust snd_nxt accordingly. 273 */ 274 if ((tp->t_flags & TF_SACK_PERMIT) && 275 SEQ_LT(tp->snd_nxt, tp->snd_max)) 276 tcp_sack_adjust(tp); 277 sendalot = 0; 278 tso = 0; 279 mtu = 0; 280 off = tp->snd_nxt - tp->snd_una; 281 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 282 283 flags = tcp_outflags[tp->t_state]; 284 /* 285 * Send any SACK-generated retransmissions. If we're explicitly trying 286 * to send out new data (when sendalot is 1), bypass this function. 287 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 288 * we're replacing a (future) new transmission with a retransmission 289 * now, and we previously incremented snd_cwnd in tcp_input(). 290 */ 291 /* 292 * Still in sack recovery , reset rxmit flag to zero. 293 */ 294 sack_rxmit = 0; 295 sack_bytes_rxmt = 0; 296 len = 0; 297 p = NULL; 298 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) && 299 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 300 uint32_t cwin; 301 302 cwin = 303 imax(min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt, 0); 304 /* Do not retransmit SACK segments beyond snd_recover */ 305 if (SEQ_GT(p->end, tp->snd_recover)) { 306 /* 307 * (At least) part of sack hole extends beyond 308 * snd_recover. Check to see if we can rexmit data 309 * for this hole. 310 */ 311 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 312 /* 313 * Can't rexmit any more data for this hole. 314 * That data will be rexmitted in the next 315 * sack recovery episode, when snd_recover 316 * moves past p->rxmit. 317 */ 318 p = NULL; 319 goto after_sack_rexmit; 320 } else { 321 /* Can rexmit part of the current hole */ 322 len = ((int32_t)ulmin(cwin, 323 SEQ_SUB(tp->snd_recover, p->rxmit))); 324 } 325 } else { 326 len = ((int32_t)ulmin(cwin, 327 SEQ_SUB(p->end, p->rxmit))); 328 } 329 if (len > 0) { 330 off = SEQ_SUB(p->rxmit, tp->snd_una); 331 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 332 __func__, off)); 333 sack_rxmit = 1; 334 sendalot = 1; 335 TCPSTAT_INC(tcps_sack_rexmits); 336 TCPSTAT_ADD(tcps_sack_rexmit_bytes, 337 min(len, tcp_maxseg(tp))); 338 } 339 } 340 after_sack_rexmit: 341 /* 342 * Get standard flags, and add SYN or FIN if requested by 'hidden' 343 * state flags. 344 */ 345 if (tp->t_flags & TF_NEEDFIN) 346 flags |= TH_FIN; 347 if (tp->t_flags & TF_NEEDSYN) 348 flags |= TH_SYN; 349 350 SOCKBUF_LOCK(&so->so_snd); 351 /* 352 * If in persist timeout with window of 0, send 1 byte. 353 * Otherwise, if window is small but nonzero 354 * and timer expired, we will send what we can 355 * and go to transmit state. 356 */ 357 if (tp->t_flags & TF_FORCEDATA) { 358 if (sendwin == 0) { 359 /* 360 * If we still have some data to send, then 361 * clear the FIN bit. Usually this would 362 * happen below when it realizes that we 363 * aren't sending all the data. However, 364 * if we have exactly 1 byte of unsent data, 365 * then it won't clear the FIN bit below, 366 * and if we are in persist state, we wind 367 * up sending the packet without recording 368 * that we sent the FIN bit. 369 * 370 * We can't just blindly clear the FIN bit, 371 * because if we don't have any more data 372 * to send then the probe will be the FIN 373 * itself. 374 */ 375 if (off < sbused(&so->so_snd)) 376 flags &= ~TH_FIN; 377 sendwin = 1; 378 } else { 379 tcp_timer_activate(tp, TT_PERSIST, 0); 380 tp->t_rxtshift = 0; 381 } 382 } 383 384 /* 385 * If snd_nxt == snd_max and we have transmitted a FIN, the 386 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 387 * a negative length. This can also occur when TCP opens up 388 * its congestion window while receiving additional duplicate 389 * acks after fast-retransmit because TCP will reset snd_nxt 390 * to snd_max after the fast-retransmit. 391 * 392 * In the normal retransmit-FIN-only case, however, snd_nxt will 393 * be set to snd_una, the offset will be 0, and the length may 394 * wind up 0. 395 * 396 * If sack_rxmit is true we are retransmitting from the scoreboard 397 * in which case len is already set. 398 */ 399 if (sack_rxmit == 0) { 400 if (sack_bytes_rxmt == 0) 401 len = ((int32_t)min(sbavail(&so->so_snd), sendwin) - 402 off); 403 else { 404 int32_t cwin; 405 406 /* 407 * We are inside of a SACK recovery episode and are 408 * sending new data, having retransmitted all the 409 * data possible in the scoreboard. 410 */ 411 len = ((int32_t)min(sbavail(&so->so_snd), tp->snd_wnd) - 412 off); 413 /* 414 * Don't remove this (len > 0) check ! 415 * We explicitly check for len > 0 here (although it 416 * isn't really necessary), to work around a gcc 417 * optimization issue - to force gcc to compute 418 * len above. Without this check, the computation 419 * of len is bungled by the optimizer. 420 */ 421 if (len > 0) { 422 cwin = tp->snd_cwnd - imax(0, (int32_t) 423 (tp->snd_nxt - tp->snd_recover)) - 424 sack_bytes_rxmt; 425 if (cwin < 0) 426 cwin = 0; 427 len = imin(len, cwin); 428 } 429 } 430 } 431 432 /* 433 * Lop off SYN bit if it has already been sent. However, if this 434 * is SYN-SENT state and if segment contains data and if we don't 435 * know that foreign host supports TAO, suppress sending segment. 436 */ 437 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 438 if (tp->t_state != TCPS_SYN_RECEIVED) 439 flags &= ~TH_SYN; 440 /* 441 * When sending additional segments following a TFO SYN|ACK, 442 * do not include the SYN bit. 443 */ 444 if (IS_FASTOPEN(tp->t_flags) && 445 (tp->t_state == TCPS_SYN_RECEIVED)) 446 flags &= ~TH_SYN; 447 off--, len++; 448 } 449 450 /* 451 * Be careful not to send data and/or FIN on SYN segments. 452 * This measure is needed to prevent interoperability problems 453 * with not fully conformant TCP implementations. 454 */ 455 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 456 len = 0; 457 flags &= ~TH_FIN; 458 } 459 460 /* 461 * On TFO sockets, ensure no data is sent in the following cases: 462 * 463 * - When retransmitting SYN|ACK on a passively-created socket 464 * 465 * - When retransmitting SYN on an actively created socket 466 * 467 * - When sending a zero-length cookie (cookie request) on an 468 * actively created socket 469 * 470 * - When the socket is in the CLOSED state (RST is being sent) 471 */ 472 if (IS_FASTOPEN(tp->t_flags) && 473 (((flags & TH_SYN) && (tp->t_rxtshift > 0)) || 474 ((tp->t_state == TCPS_SYN_SENT) && 475 (tp->t_tfo_client_cookie_len == 0)) || 476 (flags & TH_RST))) 477 len = 0; 478 if (len <= 0) { 479 /* 480 * If FIN has been sent but not acked, 481 * but we haven't been called to retransmit, 482 * len will be < 0. Otherwise, window shrank 483 * after we sent into it. If window shrank to 0, 484 * cancel pending retransmit, pull snd_nxt back 485 * to (closed) window, and set the persist timer 486 * if it isn't already going. If the window didn't 487 * close completely, just wait for an ACK. 488 * 489 * We also do a general check here to ensure that 490 * we will set the persist timer when we have data 491 * to send, but a 0-byte window. This makes sure 492 * the persist timer is set even if the packet 493 * hits one of the "goto send" lines below. 494 */ 495 len = 0; 496 if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) && 497 (off < (int) sbavail(&so->so_snd)) && 498 !tcp_timer_active(tp, TT_PERSIST)) { 499 tcp_timer_activate(tp, TT_REXMT, 0); 500 tp->t_rxtshift = 0; 501 tp->snd_nxt = tp->snd_una; 502 if (!tcp_timer_active(tp, TT_PERSIST)) 503 tcp_setpersist(tp); 504 } 505 } 506 507 /* len will be >= 0 after this point. */ 508 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 509 510 tcp_sndbuf_autoscale(tp, so, sendwin); 511 512 /* 513 * Decide if we can use TCP Segmentation Offloading (if supported by 514 * hardware). 515 * 516 * TSO may only be used if we are in a pure bulk sending state. The 517 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 518 * IP options prevent using TSO. With TSO the TCP header is the same 519 * (except for the sequence number) for all generated packets. This 520 * makes it impossible to transmit any options which vary per generated 521 * segment or packet. 522 * 523 * IPv4 handling has a clear separation of ip options and ip header 524 * flags while IPv6 combines both in in6p_outputopts. ip6_optlen() does 525 * the right thing below to provide length of just ip options and thus 526 * checking for ipoptlen is enough to decide if ip options are present. 527 */ 528 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 529 /* 530 * Pre-calculate here as we save another lookup into the darknesses 531 * of IPsec that way and can actually decide if TSO is ok. 532 */ 533 #ifdef INET6 534 if (isipv6 && IPSEC_ENABLED(ipv6)) 535 ipsec_optlen = IPSEC_HDRSIZE(ipv6, inp); 536 #ifdef INET 537 else 538 #endif 539 #endif /* INET6 */ 540 #ifdef INET 541 if (IPSEC_ENABLED(ipv4)) 542 ipsec_optlen = IPSEC_HDRSIZE(ipv4, inp); 543 #endif /* INET */ 544 #endif /* IPSEC */ 545 #ifdef INET6 546 if (isipv6) 547 ipoptlen = ip6_optlen(inp); 548 else 549 #endif 550 if (inp->inp_options) 551 ipoptlen = inp->inp_options->m_len - 552 offsetof(struct ipoption, ipopt_list); 553 else 554 ipoptlen = 0; 555 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 556 ipoptlen += ipsec_optlen; 557 #endif 558 559 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg && 560 (tp->t_port == 0) && 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_RXTCUR(tp)); 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(&inp->inp_inc); 803 if (tp->t_port) 804 to.to_mss -= V_tcp_udp_tunneling_overhead; 805 to.to_flags |= TOF_MSS; 806 807 /* 808 * On SYN or SYN|ACK transmits on TFO connections, 809 * only include the TFO option if it is not a 810 * retransmit, as the presence of the TFO option may 811 * have caused the original SYN or SYN|ACK to have 812 * been dropped by a middlebox. 813 */ 814 if (IS_FASTOPEN(tp->t_flags) && 815 (tp->t_rxtshift == 0)) { 816 if (tp->t_state == TCPS_SYN_RECEIVED) { 817 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN; 818 to.to_tfo_cookie = 819 (u_int8_t *)&tp->t_tfo_cookie.server; 820 to.to_flags |= TOF_FASTOPEN; 821 wanted_cookie = 1; 822 } else if (tp->t_state == TCPS_SYN_SENT) { 823 to.to_tfo_len = 824 tp->t_tfo_client_cookie_len; 825 to.to_tfo_cookie = 826 tp->t_tfo_cookie.client; 827 to.to_flags |= TOF_FASTOPEN; 828 wanted_cookie = 1; 829 /* 830 * If we wind up having more data to 831 * send with the SYN than can fit in 832 * one segment, don't send any more 833 * until the SYN|ACK comes back from 834 * the other end. 835 */ 836 dont_sendalot = 1; 837 } 838 } 839 } 840 /* Window scaling. */ 841 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 842 to.to_wscale = tp->request_r_scale; 843 to.to_flags |= TOF_SCALE; 844 } 845 /* Timestamps. */ 846 if ((tp->t_flags & TF_RCVD_TSTMP) || 847 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 848 curticks = tcp_ts_getticks(); 849 to.to_tsval = curticks + tp->ts_offset; 850 to.to_tsecr = tp->ts_recent; 851 to.to_flags |= TOF_TS; 852 if (tp->t_rxtshift == 1) 853 tp->t_badrxtwin = curticks; 854 } 855 856 /* Set receive buffer autosizing timestamp. */ 857 if (tp->rfbuf_ts == 0 && 858 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 859 tp->rfbuf_ts = tcp_ts_getticks(); 860 861 /* Selective ACK's. */ 862 if (tp->t_flags & TF_SACK_PERMIT) { 863 if (flags & TH_SYN) 864 to.to_flags |= TOF_SACKPERM; 865 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 866 tp->rcv_numsacks > 0) { 867 to.to_flags |= TOF_SACK; 868 to.to_nsacks = tp->rcv_numsacks; 869 to.to_sacks = (u_char *)tp->sackblks; 870 } 871 } 872 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 873 /* TCP-MD5 (RFC2385). */ 874 /* 875 * Check that TCP_MD5SIG is enabled in tcpcb to 876 * account the size needed to set this TCP option. 877 */ 878 if (tp->t_flags & TF_SIGNATURE) 879 to.to_flags |= TOF_SIGNATURE; 880 #endif /* TCP_SIGNATURE */ 881 882 /* Processing the options. */ 883 hdrlen += optlen = tcp_addoptions(&to, opt); 884 /* 885 * If we wanted a TFO option to be added, but it was unable 886 * to fit, ensure no data is sent. 887 */ 888 if (IS_FASTOPEN(tp->t_flags) && wanted_cookie && 889 !(to.to_flags & TOF_FASTOPEN)) 890 len = 0; 891 } 892 if (tp->t_port) { 893 if (V_tcp_udp_tunneling_port == 0) { 894 /* The port was removed?? */ 895 SOCKBUF_UNLOCK(&so->so_snd); 896 return (EHOSTUNREACH); 897 } 898 hdrlen += sizeof(struct udphdr); 899 } 900 /* 901 * Adjust data length if insertion of options will 902 * bump the packet length beyond the t_maxseg length. 903 * Clear the FIN bit because we cut off the tail of 904 * the segment. 905 */ 906 if (len + optlen + ipoptlen > tp->t_maxseg) { 907 flags &= ~TH_FIN; 908 909 if (tso) { 910 u_int if_hw_tsomax; 911 u_int moff; 912 int max_len; 913 914 /* extract TSO information */ 915 if_hw_tsomax = tp->t_tsomax; 916 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount; 917 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize; 918 919 /* 920 * Limit a TSO burst to prevent it from 921 * overflowing or exceeding the maximum length 922 * allowed by the network interface: 923 */ 924 KASSERT(ipoptlen == 0, 925 ("%s: TSO can't do IP options", __func__)); 926 927 /* 928 * Check if we should limit by maximum payload 929 * length: 930 */ 931 if (if_hw_tsomax != 0) { 932 /* compute maximum TSO length */ 933 max_len = (if_hw_tsomax - hdrlen - 934 max_linkhdr); 935 if (max_len <= 0) { 936 len = 0; 937 } else if (len > max_len) { 938 sendalot = 1; 939 len = max_len; 940 } 941 } 942 943 /* 944 * Prevent the last segment from being 945 * fractional unless the send sockbuf can be 946 * emptied: 947 */ 948 max_len = (tp->t_maxseg - optlen); 949 if (((uint32_t)off + (uint32_t)len) < 950 sbavail(&so->so_snd)) { 951 moff = len % max_len; 952 if (moff != 0) { 953 len -= moff; 954 sendalot = 1; 955 } 956 } 957 958 /* 959 * In case there are too many small fragments 960 * don't use TSO: 961 */ 962 if (len <= max_len) { 963 len = max_len; 964 sendalot = 1; 965 tso = 0; 966 } 967 968 /* 969 * Send the FIN in a separate segment 970 * after the bulk sending is done. 971 * We don't trust the TSO implementations 972 * to clear the FIN flag on all but the 973 * last segment. 974 */ 975 if (tp->t_flags & TF_NEEDFIN) 976 sendalot = 1; 977 } else { 978 if (optlen + ipoptlen >= tp->t_maxseg) { 979 /* 980 * Since we don't have enough space to put 981 * the IP header chain and the TCP header in 982 * one packet as required by RFC 7112, don't 983 * send it. Also ensure that at least one 984 * byte of the payload can be put into the 985 * TCP segment. 986 */ 987 SOCKBUF_UNLOCK(&so->so_snd); 988 error = EMSGSIZE; 989 sack_rxmit = 0; 990 goto out; 991 } 992 len = tp->t_maxseg - optlen - ipoptlen; 993 sendalot = 1; 994 if (dont_sendalot) 995 sendalot = 0; 996 } 997 } else 998 tso = 0; 999 1000 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 1001 ("%s: len > IP_MAXPACKET", __func__)); 1002 1003 /*#ifdef DIAGNOSTIC*/ 1004 #ifdef INET6 1005 if (max_linkhdr + hdrlen > MCLBYTES) 1006 #else 1007 if (max_linkhdr + hdrlen > MHLEN) 1008 #endif 1009 panic("tcphdr too big"); 1010 /*#endif*/ 1011 1012 /* 1013 * This KASSERT is here to catch edge cases at a well defined place. 1014 * Before, those had triggered (random) panic conditions further down. 1015 */ 1016 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 1017 1018 /* 1019 * Grab a header mbuf, attaching a copy of data to 1020 * be transmitted, and initialize the header from 1021 * the template for sends on this connection. 1022 */ 1023 if (len) { 1024 struct mbuf *mb; 1025 struct sockbuf *msb; 1026 u_int moff; 1027 1028 if ((tp->t_flags & TF_FORCEDATA) && len == 1) { 1029 TCPSTAT_INC(tcps_sndprobe); 1030 #ifdef STATS 1031 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1032 stats_voi_update_abs_u32(tp->t_stats, 1033 VOI_TCP_RETXPB, len); 1034 else 1035 stats_voi_update_abs_u64(tp->t_stats, 1036 VOI_TCP_TXPB, len); 1037 #endif /* STATS */ 1038 } else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 1039 tp->t_sndrexmitpack++; 1040 TCPSTAT_INC(tcps_sndrexmitpack); 1041 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 1042 #ifdef STATS 1043 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_RETXPB, 1044 len); 1045 #endif /* STATS */ 1046 } else { 1047 TCPSTAT_INC(tcps_sndpack); 1048 TCPSTAT_ADD(tcps_sndbyte, len); 1049 #ifdef STATS 1050 stats_voi_update_abs_u64(tp->t_stats, VOI_TCP_TXPB, 1051 len); 1052 #endif /* STATS */ 1053 } 1054 #ifdef INET6 1055 if (MHLEN < hdrlen + max_linkhdr) 1056 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR); 1057 else 1058 #endif 1059 m = m_gethdr(M_NOWAIT, MT_DATA); 1060 1061 if (m == NULL) { 1062 SOCKBUF_UNLOCK(&so->so_snd); 1063 error = ENOBUFS; 1064 sack_rxmit = 0; 1065 goto out; 1066 } 1067 1068 m->m_data += max_linkhdr; 1069 m->m_len = hdrlen; 1070 1071 /* 1072 * Start the m_copy functions from the closest mbuf 1073 * to the offset in the socket buffer chain. 1074 */ 1075 mb = sbsndptr_noadv(&so->so_snd, off, &moff); 1076 if (len <= MHLEN - hdrlen - max_linkhdr && !hw_tls) { 1077 m_copydata(mb, moff, len, 1078 mtod(m, caddr_t) + hdrlen); 1079 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1080 sbsndptr_adv(&so->so_snd, mb, len); 1081 m->m_len += len; 1082 } else { 1083 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1084 msb = NULL; 1085 else 1086 msb = &so->so_snd; 1087 m->m_next = tcp_m_copym(mb, moff, 1088 &len, if_hw_tsomaxsegcount, 1089 if_hw_tsomaxsegsize, msb, hw_tls); 1090 if (len <= (tp->t_maxseg - optlen)) { 1091 /* 1092 * Must have ran out of mbufs for the copy 1093 * shorten it to no longer need tso. Lets 1094 * not put on sendalot since we are low on 1095 * mbufs. 1096 */ 1097 tso = 0; 1098 } 1099 if (m->m_next == NULL) { 1100 SOCKBUF_UNLOCK(&so->so_snd); 1101 (void) m_free(m); 1102 error = ENOBUFS; 1103 sack_rxmit = 0; 1104 goto out; 1105 } 1106 } 1107 1108 /* 1109 * If we're sending everything we've got, set PUSH. 1110 * (This will keep happy those implementations which only 1111 * give data to the user when a buffer fills or 1112 * a PUSH comes in.) 1113 */ 1114 if (((uint32_t)off + (uint32_t)len == sbused(&so->so_snd)) && 1115 !(flags & TH_SYN)) 1116 flags |= TH_PUSH; 1117 SOCKBUF_UNLOCK(&so->so_snd); 1118 } else { 1119 SOCKBUF_UNLOCK(&so->so_snd); 1120 if (tp->t_flags & TF_ACKNOW) 1121 TCPSTAT_INC(tcps_sndacks); 1122 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 1123 TCPSTAT_INC(tcps_sndctrl); 1124 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 1125 TCPSTAT_INC(tcps_sndurg); 1126 else 1127 TCPSTAT_INC(tcps_sndwinup); 1128 1129 m = m_gethdr(M_NOWAIT, MT_DATA); 1130 if (m == NULL) { 1131 error = ENOBUFS; 1132 sack_rxmit = 0; 1133 goto out; 1134 } 1135 #ifdef INET6 1136 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 1137 MHLEN >= hdrlen) { 1138 M_ALIGN(m, hdrlen); 1139 } else 1140 #endif 1141 m->m_data += max_linkhdr; 1142 m->m_len = hdrlen; 1143 } 1144 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 1145 m->m_pkthdr.rcvif = (struct ifnet *)0; 1146 #ifdef MAC 1147 mac_inpcb_create_mbuf(inp, m); 1148 #endif 1149 #ifdef INET6 1150 if (isipv6) { 1151 ip6 = mtod(m, struct ip6_hdr *); 1152 if (tp->t_port) { 1153 udp = (struct udphdr *)((caddr_t)ip6 + sizeof(struct ip6_hdr)); 1154 udp->uh_sport = htons(V_tcp_udp_tunneling_port); 1155 udp->uh_dport = tp->t_port; 1156 ulen = hdrlen + len - sizeof(struct ip6_hdr); 1157 udp->uh_ulen = htons(ulen); 1158 th = (struct tcphdr *)(udp + 1); 1159 } else { 1160 th = (struct tcphdr *)(ip6 + 1); 1161 } 1162 tcpip_fillheaders(inp, tp->t_port, ip6, th); 1163 } else 1164 #endif /* INET6 */ 1165 { 1166 ip = mtod(m, struct ip *); 1167 if (tp->t_port) { 1168 udp = (struct udphdr *)((caddr_t)ip + sizeof(struct ip)); 1169 udp->uh_sport = htons(V_tcp_udp_tunneling_port); 1170 udp->uh_dport = tp->t_port; 1171 ulen = hdrlen + len - sizeof(struct ip); 1172 udp->uh_ulen = htons(ulen); 1173 th = (struct tcphdr *)(udp + 1); 1174 } else 1175 th = (struct tcphdr *)(ip + 1); 1176 tcpip_fillheaders(inp, tp->t_port, ip, th); 1177 } 1178 1179 /* 1180 * Fill in fields, remembering maximum advertised 1181 * window for use in delaying messages about window sizes. 1182 * If resending a FIN, be sure not to use a new sequence number. 1183 */ 1184 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 1185 tp->snd_nxt == tp->snd_max) 1186 tp->snd_nxt--; 1187 /* 1188 * If we are starting a connection, send ECN setup 1189 * SYN packet. If we are on a retransmit, we may 1190 * resend those bits a number of times as per 1191 * RFC 3168. 1192 */ 1193 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) { 1194 flags |= tcp_ecn_output_syn_sent(tp); 1195 } 1196 /* Also handle parallel SYN for ECN */ 1197 if ((TCPS_HAVERCVDSYN(tp->t_state)) && 1198 (tp->t_flags2 & (TF2_ECN_PERMIT | TF2_ACE_PERMIT))) { 1199 int ect = tcp_ecn_output_established(tp, &flags, len, sack_rxmit); 1200 if ((tp->t_state == TCPS_SYN_RECEIVED) && 1201 (tp->t_flags2 & TF2_ECN_SND_ECE)) 1202 tp->t_flags2 &= ~TF2_ECN_SND_ECE; 1203 #ifdef INET6 1204 if (isipv6) { 1205 ip6->ip6_flow &= ~htonl(IPTOS_ECN_MASK << IPV6_FLOWLABEL_LEN); 1206 ip6->ip6_flow |= htonl(ect << IPV6_FLOWLABEL_LEN); 1207 } 1208 else 1209 #endif 1210 { 1211 ip->ip_tos &= ~IPTOS_ECN_MASK; 1212 ip->ip_tos |= ect; 1213 } 1214 } 1215 1216 /* 1217 * If we are doing retransmissions, then snd_nxt will 1218 * not reflect the first unsent octet. For ACK only 1219 * packets, we do not want the sequence number of the 1220 * retransmitted packet, we want the sequence number 1221 * of the next unsent octet. So, if there is no data 1222 * (and no SYN or FIN), use snd_max instead of snd_nxt 1223 * when filling in ti_seq. But if we are in persist 1224 * state, snd_max might reflect one byte beyond the 1225 * right edge of the window, so use snd_nxt in that 1226 * case, since we know we aren't doing a retransmission. 1227 * (retransmit and persist are mutually exclusive...) 1228 */ 1229 if (sack_rxmit == 0) { 1230 if (len || (flags & (TH_SYN|TH_FIN)) || 1231 tcp_timer_active(tp, TT_PERSIST)) 1232 th->th_seq = htonl(tp->snd_nxt); 1233 else 1234 th->th_seq = htonl(tp->snd_max); 1235 } else { 1236 th->th_seq = htonl(p->rxmit); 1237 p->rxmit += len; 1238 /* 1239 * Lost Retransmission Detection 1240 * trigger resending of a (then 1241 * still existing) hole, when 1242 * fack acks recoverypoint. 1243 */ 1244 if ((tp->t_flags & TF_LRD) && SEQ_GEQ(p->rxmit, p->end)) 1245 p->rxmit = tp->snd_recover; 1246 tp->sackhint.sack_bytes_rexmit += len; 1247 } 1248 if (IN_RECOVERY(tp->t_flags)) { 1249 /* 1250 * Account all bytes transmitted while 1251 * IN_RECOVERY, simplifying PRR and 1252 * Lost Retransmit Detection 1253 */ 1254 tp->sackhint.prr_out += len; 1255 } 1256 th->th_ack = htonl(tp->rcv_nxt); 1257 if (optlen) { 1258 bcopy(opt, th + 1, optlen); 1259 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1260 } 1261 tcp_set_flags(th, flags); 1262 /* 1263 * Calculate receive window. Don't shrink window, 1264 * but avoid silly window syndrome. 1265 * If a RST segment is sent, advertise a window of zero. 1266 */ 1267 if (flags & TH_RST) { 1268 recwin = 0; 1269 } else { 1270 if (recwin < (so->so_rcv.sb_hiwat / 4) && 1271 recwin < tp->t_maxseg) 1272 recwin = 0; 1273 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1274 recwin < (tp->rcv_adv - tp->rcv_nxt)) 1275 recwin = (tp->rcv_adv - tp->rcv_nxt); 1276 } 1277 /* 1278 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1279 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1280 * case is handled in syncache. 1281 */ 1282 if (flags & TH_SYN) 1283 th->th_win = htons((u_short) 1284 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1285 else { 1286 /* Avoid shrinking window with window scaling. */ 1287 recwin = roundup2(recwin, 1 << tp->rcv_scale); 1288 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1289 } 1290 1291 /* 1292 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1293 * a 0 window. This may cause the remote transmitter to stall. This 1294 * flag tells soreceive() to disable delayed acknowledgements when 1295 * draining the buffer. This can occur if the receiver is attempting 1296 * to read more data than can be buffered prior to transmitting on 1297 * the connection. 1298 */ 1299 if (th->th_win == 0) { 1300 tp->t_sndzerowin++; 1301 tp->t_flags |= TF_RXWIN0SENT; 1302 } else 1303 tp->t_flags &= ~TF_RXWIN0SENT; 1304 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1305 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1306 th->th_flags |= TH_URG; 1307 } else 1308 /* 1309 * If no urgent pointer to send, then we pull 1310 * the urgent pointer to the left edge of the send window 1311 * so that it doesn't drift into the send window on sequence 1312 * number wraparound. 1313 */ 1314 tp->snd_up = tp->snd_una; /* drag it along */ 1315 1316 /* 1317 * Put TCP length in extended header, and then 1318 * checksum extended header and data. 1319 */ 1320 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1321 1322 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1323 if (to.to_flags & TOF_SIGNATURE) { 1324 /* 1325 * Calculate MD5 signature and put it into the place 1326 * determined before. 1327 * NOTE: since TCP options buffer doesn't point into 1328 * mbuf's data, calculate offset and use it. 1329 */ 1330 if (!TCPMD5_ENABLED() || (error = TCPMD5_OUTPUT(m, th, 1331 (u_char *)(th + 1) + (to.to_signature - opt))) != 0) { 1332 /* 1333 * Do not send segment if the calculation of MD5 1334 * digest has failed. 1335 */ 1336 m_freem(m); 1337 goto out; 1338 } 1339 } 1340 #endif 1341 #ifdef INET6 1342 if (isipv6) { 1343 /* 1344 * There is no need to fill in ip6_plen right now. 1345 * It will be filled later by ip6_output. 1346 */ 1347 if (tp->t_port) { 1348 m->m_pkthdr.csum_flags = CSUM_UDP_IPV6; 1349 m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum); 1350 udp->uh_sum = in6_cksum_pseudo(ip6, ulen, IPPROTO_UDP, 0); 1351 th->th_sum = htons(0); 1352 UDPSTAT_INC(udps_opackets); 1353 } else { 1354 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1355 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1356 th->th_sum = in6_cksum_pseudo(ip6, 1357 sizeof(struct tcphdr) + optlen + len, IPPROTO_TCP, 1358 0); 1359 } 1360 } 1361 #endif 1362 #if defined(INET6) && defined(INET) 1363 else 1364 #endif 1365 #ifdef INET 1366 { 1367 if (tp->t_port) { 1368 m->m_pkthdr.csum_flags = CSUM_UDP; 1369 m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum); 1370 udp->uh_sum = in_pseudo(ip->ip_src.s_addr, 1371 ip->ip_dst.s_addr, htons(ulen + IPPROTO_UDP)); 1372 th->th_sum = htons(0); 1373 UDPSTAT_INC(udps_opackets); 1374 } else { 1375 m->m_pkthdr.csum_flags = CSUM_TCP; 1376 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1377 th->th_sum = in_pseudo(ip->ip_src.s_addr, 1378 ip->ip_dst.s_addr, htons(sizeof(struct tcphdr) + 1379 IPPROTO_TCP + len + optlen)); 1380 } 1381 1382 /* IP version must be set here for ipv4/ipv6 checking later */ 1383 KASSERT(ip->ip_v == IPVERSION, 1384 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1385 } 1386 #endif 1387 1388 /* 1389 * Enable TSO and specify the size of the segments. 1390 * The TCP pseudo header checksum is always provided. 1391 */ 1392 if (tso) { 1393 KASSERT(len > tp->t_maxseg - optlen, 1394 ("%s: len <= tso_segsz", __func__)); 1395 m->m_pkthdr.csum_flags |= CSUM_TSO; 1396 m->m_pkthdr.tso_segsz = tp->t_maxseg - optlen; 1397 } 1398 1399 KASSERT(len + hdrlen == m_length(m, NULL), 1400 ("%s: mbuf chain shorter than expected: %d + %u != %u", 1401 __func__, len, hdrlen, m_length(m, NULL))); 1402 1403 #ifdef TCP_HHOOK 1404 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1405 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1406 #endif 1407 1408 TCP_PROBE3(debug__output, tp, th, m); 1409 1410 /* We're getting ready to send; log now. */ 1411 /* XXXMT: We are not honoring verbose logging. */ 1412 1413 if (tcp_bblogging_on(tp)) 1414 lgb = tcp_log_event(tp, th, &so->so_rcv, &so->so_snd, 1415 TCP_LOG_OUT, ERRNO_UNK, len, NULL, false, NULL, NULL, 0, 1416 NULL); 1417 else 1418 lgb = NULL; 1419 1420 /* 1421 * Fill in IP length and desired time to live and 1422 * send to IP level. There should be a better way 1423 * to handle ttl and tos; we could keep them in 1424 * the template, but need a way to checksum without them. 1425 */ 1426 /* 1427 * m->m_pkthdr.len should have been set before checksum calculation, 1428 * because in6_cksum() need it. 1429 */ 1430 #ifdef INET6 1431 if (isipv6) { 1432 /* 1433 * we separately set hoplimit for every segment, since the 1434 * user might want to change the value via setsockopt. 1435 * Also, desired default hop limit might be changed via 1436 * Neighbor Discovery. 1437 */ 1438 ip6->ip6_hlim = in6_selecthlim(inp, NULL); 1439 1440 /* 1441 * Set the packet size here for the benefit of DTrace probes. 1442 * ip6_output() will set it properly; it's supposed to include 1443 * the option header lengths as well. 1444 */ 1445 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6)); 1446 1447 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) 1448 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1449 else 1450 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1451 1452 if (tp->t_state == TCPS_SYN_SENT) 1453 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th); 1454 1455 TCP_PROBE5(send, NULL, tp, ip6, tp, th); 1456 1457 #ifdef TCPPCAP 1458 /* Save packet, if requested. */ 1459 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1460 #endif 1461 1462 /* TODO: IPv6 IP6TOS_ECT bit on */ 1463 error = ip6_output(m, inp->in6p_outputopts, &inp->inp_route6, 1464 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 1465 NULL, NULL, inp); 1466 1467 if (error == EMSGSIZE && inp->inp_route6.ro_nh != NULL) 1468 mtu = inp->inp_route6.ro_nh->nh_mtu; 1469 } 1470 #endif /* INET6 */ 1471 #if defined(INET) && defined(INET6) 1472 else 1473 #endif 1474 #ifdef INET 1475 { 1476 ip->ip_len = htons(m->m_pkthdr.len); 1477 #ifdef INET6 1478 if (inp->inp_vflag & INP_IPV6PROTO) 1479 ip->ip_ttl = in6_selecthlim(inp, NULL); 1480 #endif /* INET6 */ 1481 /* 1482 * If we do path MTU discovery, then we set DF on every packet. 1483 * This might not be the best thing to do according to RFC3390 1484 * Section 2. However the tcp hostcache migitates the problem 1485 * so it affects only the first tcp connection with a host. 1486 * 1487 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1488 */ 1489 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) { 1490 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1491 if (tp->t_port == 0 || len < V_tcp_minmss) { 1492 ip->ip_off |= htons(IP_DF); 1493 } 1494 } else { 1495 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1496 } 1497 1498 if (tp->t_state == TCPS_SYN_SENT) 1499 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th); 1500 1501 TCP_PROBE5(send, NULL, tp, ip, tp, th); 1502 1503 #ifdef TCPPCAP 1504 /* Save packet, if requested. */ 1505 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1506 #endif 1507 1508 error = ip_output(m, inp->inp_options, &inp->inp_route, 1509 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, inp); 1510 1511 if (error == EMSGSIZE && inp->inp_route.ro_nh != NULL) 1512 mtu = inp->inp_route.ro_nh->nh_mtu; 1513 } 1514 #endif /* INET */ 1515 1516 if (lgb != NULL) { 1517 lgb->tlb_errno = error; 1518 lgb = NULL; 1519 } 1520 out: 1521 if (error == 0) 1522 tcp_account_for_send(tp, len, (tp->snd_nxt != tp->snd_max), 0, hw_tls); 1523 /* 1524 * In transmit state, time the transmission and arrange for 1525 * the retransmit. In persist state, just set snd_max. 1526 */ 1527 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1528 !tcp_timer_active(tp, TT_PERSIST)) { 1529 tcp_seq startseq = tp->snd_nxt; 1530 1531 /* 1532 * Advance snd_nxt over sequence space of this segment. 1533 */ 1534 if (flags & (TH_SYN|TH_FIN)) { 1535 if (flags & TH_SYN) 1536 tp->snd_nxt++; 1537 if (flags & TH_FIN) { 1538 tp->snd_nxt++; 1539 tp->t_flags |= TF_SENTFIN; 1540 } 1541 } 1542 if (sack_rxmit) 1543 goto timer; 1544 tp->snd_nxt += len; 1545 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1546 /* 1547 * Update "made progress" indication if we just 1548 * added new data to an empty socket buffer. 1549 */ 1550 if (tp->snd_una == tp->snd_max) 1551 tp->t_acktime = ticks; 1552 tp->snd_max = tp->snd_nxt; 1553 /* 1554 * Time this transmission if not a retransmission and 1555 * not currently timing anything. 1556 */ 1557 tp->t_sndtime = ticks; 1558 if (tp->t_rtttime == 0) { 1559 tp->t_rtttime = ticks; 1560 tp->t_rtseq = startseq; 1561 TCPSTAT_INC(tcps_segstimed); 1562 } 1563 #ifdef STATS 1564 if (!(tp->t_flags & TF_GPUTINPROG) && len) { 1565 tp->t_flags |= TF_GPUTINPROG; 1566 tp->gput_seq = startseq; 1567 tp->gput_ack = startseq + 1568 ulmin(sbavail(&so->so_snd) - off, sendwin); 1569 tp->gput_ts = tcp_ts_getticks(); 1570 } 1571 #endif /* STATS */ 1572 } 1573 1574 /* 1575 * Set retransmit timer if not currently set, 1576 * and not doing a pure ack or a keep-alive probe. 1577 * Initial value for retransmit timer is smoothed 1578 * round-trip time + 2 * round-trip time variance. 1579 * Initialize shift counter which is used for backoff 1580 * of retransmit time. 1581 */ 1582 timer: 1583 if (!tcp_timer_active(tp, TT_REXMT) && 1584 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1585 (tp->snd_nxt != tp->snd_una))) { 1586 if (tcp_timer_active(tp, TT_PERSIST)) { 1587 tcp_timer_activate(tp, TT_PERSIST, 0); 1588 tp->t_rxtshift = 0; 1589 } 1590 tcp_timer_activate(tp, TT_REXMT, TP_RXTCUR(tp)); 1591 } else if (len == 0 && sbavail(&so->so_snd) && 1592 !tcp_timer_active(tp, TT_REXMT) && 1593 !tcp_timer_active(tp, TT_PERSIST)) { 1594 /* 1595 * Avoid a situation where we do not set persist timer 1596 * after a zero window condition. For example: 1597 * 1) A -> B: packet with enough data to fill the window 1598 * 2) B -> A: ACK for #1 + new data (0 window 1599 * advertisement) 1600 * 3) A -> B: ACK for #2, 0 len packet 1601 * 1602 * In this case, A will not activate the persist timer, 1603 * because it chose to send a packet. Unless tcp_output 1604 * is called for some other reason (delayed ack timer, 1605 * another input packet from B, socket syscall), A will 1606 * not send zero window probes. 1607 * 1608 * So, if you send a 0-length packet, but there is data 1609 * in the socket buffer, and neither the rexmt or 1610 * persist timer is already set, then activate the 1611 * persist timer. 1612 */ 1613 tp->t_rxtshift = 0; 1614 tcp_setpersist(tp); 1615 } 1616 } else { 1617 /* 1618 * Persist case, update snd_max but since we are in 1619 * persist mode (no window) we do not update snd_nxt. 1620 */ 1621 int xlen = len; 1622 if (flags & TH_SYN) 1623 ++xlen; 1624 if (flags & TH_FIN) { 1625 ++xlen; 1626 tp->t_flags |= TF_SENTFIN; 1627 } 1628 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1629 tp->snd_max = tp->snd_nxt + xlen; 1630 } 1631 if ((error == 0) && 1632 (TCPS_HAVEESTABLISHED(tp->t_state) && 1633 (tp->t_flags & TF_SACK_PERMIT) && 1634 tp->rcv_numsacks > 0)) { 1635 /* Clean up any DSACK's sent */ 1636 tcp_clean_dsack_blocks(tp); 1637 } 1638 if (error) { 1639 /* 1640 * We know that the packet was lost, so back out the 1641 * sequence number advance, if any. 1642 * 1643 * If the error is EPERM the packet got blocked by the 1644 * local firewall. Normally we should terminate the 1645 * connection but the blocking may have been spurious 1646 * due to a firewall reconfiguration cycle. So we treat 1647 * it like a packet loss and let the retransmit timer and 1648 * timeouts do their work over time. 1649 * XXX: It is a POLA question whether calling tcp_drop right 1650 * away would be the really correct behavior instead. 1651 */ 1652 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1653 !tcp_timer_active(tp, TT_PERSIST)) && 1654 ((flags & TH_SYN) == 0) && 1655 (error != EPERM)) { 1656 if (sack_rxmit) { 1657 p->rxmit -= len; 1658 tp->sackhint.sack_bytes_rexmit -= len; 1659 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1660 ("sackhint bytes rtx >= 0")); 1661 KASSERT((flags & TH_FIN) == 0, 1662 ("error while FIN with SACK rxmit")); 1663 } else { 1664 tp->snd_nxt -= len; 1665 if (flags & TH_FIN) 1666 tp->snd_nxt--; 1667 } 1668 } 1669 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1670 switch (error) { 1671 case EACCES: 1672 case EPERM: 1673 tp->t_softerror = error; 1674 return (error); 1675 case ENOBUFS: 1676 TCP_XMIT_TIMER_ASSERT(tp, len, flags); 1677 tp->snd_cwnd = tp->t_maxseg; 1678 return (0); 1679 case EMSGSIZE: 1680 /* 1681 * For some reason the interface we used initially 1682 * to send segments changed to another or lowered 1683 * its MTU. 1684 * If TSO was active we either got an interface 1685 * without TSO capabilits or TSO was turned off. 1686 * If we obtained mtu from ip_output() then update 1687 * it and try again. 1688 */ 1689 if (tso) 1690 tp->t_flags &= ~TF_TSO; 1691 if (mtu != 0) { 1692 tcp_mss_update(tp, -1, mtu, NULL, NULL); 1693 goto again; 1694 } 1695 return (error); 1696 case EHOSTDOWN: 1697 case EHOSTUNREACH: 1698 case ENETDOWN: 1699 case ENETUNREACH: 1700 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1701 tp->t_softerror = error; 1702 return (0); 1703 } 1704 /* FALLTHROUGH */ 1705 default: 1706 return (error); 1707 } 1708 } 1709 TCPSTAT_INC(tcps_sndtotal); 1710 1711 /* 1712 * Data sent (as far as we can tell). 1713 * If this advertises a larger window than any other segment, 1714 * then remember the size of the advertised window. 1715 * Any pending ACK has now been sent. 1716 */ 1717 if (SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1718 tp->rcv_adv = tp->rcv_nxt + recwin; 1719 tp->last_ack_sent = tp->rcv_nxt; 1720 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1721 if (tcp_timer_active(tp, TT_DELACK)) 1722 tcp_timer_activate(tp, TT_DELACK, 0); 1723 #if 0 1724 /* 1725 * This completely breaks TCP if newreno is turned on. What happens 1726 * is that if delayed-acks are turned on on the receiver, this code 1727 * on the transmitter effectively destroys the TCP window, forcing 1728 * it to four packets (1.5Kx4 = 6K window). 1729 */ 1730 if (sendalot && --maxburst) 1731 goto again; 1732 #endif 1733 if (sendalot) 1734 goto again; 1735 return (0); 1736 } 1737 1738 void 1739 tcp_setpersist(struct tcpcb *tp) 1740 { 1741 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1742 int tt; 1743 int maxunacktime; 1744 1745 tp->t_flags &= ~TF_PREVVALID; 1746 if (tcp_timer_active(tp, TT_REXMT)) 1747 panic("tcp_setpersist: retransmit pending"); 1748 /* 1749 * If the state is already closed, don't bother. 1750 */ 1751 if (tp->t_state == TCPS_CLOSED) 1752 return; 1753 1754 /* 1755 * Start/restart persistence timer. 1756 */ 1757 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1758 tcp_persmin, tcp_persmax); 1759 if (TP_MAXUNACKTIME(tp) && tp->t_acktime) { 1760 maxunacktime = tp->t_acktime + TP_MAXUNACKTIME(tp) - ticks; 1761 if (maxunacktime < 1) 1762 maxunacktime = 1; 1763 if (maxunacktime < tt) 1764 tt = maxunacktime; 1765 } 1766 tcp_timer_activate(tp, TT_PERSIST, tt); 1767 if (tp->t_rxtshift < V_tcp_retries) 1768 tp->t_rxtshift++; 1769 } 1770 1771 /* 1772 * Insert TCP options according to the supplied parameters to the place 1773 * optp in a consistent way. Can handle unaligned destinations. 1774 * 1775 * The order of the option processing is crucial for optimal packing and 1776 * alignment for the scarce option space. 1777 * 1778 * The optimal order for a SYN/SYN-ACK segment is: 1779 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1780 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1781 * 1782 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1783 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1784 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1785 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1786 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1787 */ 1788 int 1789 tcp_addoptions(struct tcpopt *to, u_char *optp) 1790 { 1791 u_int32_t mask, optlen = 0; 1792 1793 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1794 if ((to->to_flags & mask) != mask) 1795 continue; 1796 if (optlen == TCP_MAXOLEN) 1797 break; 1798 switch (to->to_flags & mask) { 1799 case TOF_MSS: 1800 while (optlen % 4) { 1801 optlen += TCPOLEN_NOP; 1802 *optp++ = TCPOPT_NOP; 1803 } 1804 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1805 continue; 1806 optlen += TCPOLEN_MAXSEG; 1807 *optp++ = TCPOPT_MAXSEG; 1808 *optp++ = TCPOLEN_MAXSEG; 1809 to->to_mss = htons(to->to_mss); 1810 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1811 optp += sizeof(to->to_mss); 1812 break; 1813 case TOF_SCALE: 1814 while (!optlen || optlen % 2 != 1) { 1815 optlen += TCPOLEN_NOP; 1816 *optp++ = TCPOPT_NOP; 1817 } 1818 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1819 continue; 1820 optlen += TCPOLEN_WINDOW; 1821 *optp++ = TCPOPT_WINDOW; 1822 *optp++ = TCPOLEN_WINDOW; 1823 *optp++ = to->to_wscale; 1824 break; 1825 case TOF_SACKPERM: 1826 while (optlen % 2) { 1827 optlen += TCPOLEN_NOP; 1828 *optp++ = TCPOPT_NOP; 1829 } 1830 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1831 continue; 1832 optlen += TCPOLEN_SACK_PERMITTED; 1833 *optp++ = TCPOPT_SACK_PERMITTED; 1834 *optp++ = TCPOLEN_SACK_PERMITTED; 1835 break; 1836 case TOF_TS: 1837 while (!optlen || optlen % 4 != 2) { 1838 optlen += TCPOLEN_NOP; 1839 *optp++ = TCPOPT_NOP; 1840 } 1841 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1842 continue; 1843 optlen += TCPOLEN_TIMESTAMP; 1844 *optp++ = TCPOPT_TIMESTAMP; 1845 *optp++ = TCPOLEN_TIMESTAMP; 1846 to->to_tsval = htonl(to->to_tsval); 1847 to->to_tsecr = htonl(to->to_tsecr); 1848 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1849 optp += sizeof(to->to_tsval); 1850 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1851 optp += sizeof(to->to_tsecr); 1852 break; 1853 case TOF_SIGNATURE: 1854 { 1855 int siglen = TCPOLEN_SIGNATURE - 2; 1856 1857 while (!optlen || optlen % 4 != 2) { 1858 optlen += TCPOLEN_NOP; 1859 *optp++ = TCPOPT_NOP; 1860 } 1861 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) { 1862 to->to_flags &= ~TOF_SIGNATURE; 1863 continue; 1864 } 1865 optlen += TCPOLEN_SIGNATURE; 1866 *optp++ = TCPOPT_SIGNATURE; 1867 *optp++ = TCPOLEN_SIGNATURE; 1868 to->to_signature = optp; 1869 while (siglen--) 1870 *optp++ = 0; 1871 break; 1872 } 1873 case TOF_SACK: 1874 { 1875 int sackblks = 0; 1876 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1877 tcp_seq sack_seq; 1878 1879 while (!optlen || optlen % 4 != 2) { 1880 optlen += TCPOLEN_NOP; 1881 *optp++ = TCPOPT_NOP; 1882 } 1883 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1884 continue; 1885 optlen += TCPOLEN_SACKHDR; 1886 *optp++ = TCPOPT_SACK; 1887 sackblks = min(to->to_nsacks, 1888 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1889 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1890 while (sackblks--) { 1891 sack_seq = htonl(sack->start); 1892 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1893 optp += sizeof(sack_seq); 1894 sack_seq = htonl(sack->end); 1895 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1896 optp += sizeof(sack_seq); 1897 optlen += TCPOLEN_SACK; 1898 sack++; 1899 } 1900 TCPSTAT_INC(tcps_sack_send_blocks); 1901 break; 1902 } 1903 case TOF_FASTOPEN: 1904 { 1905 int total_len; 1906 1907 /* XXX is there any point to aligning this option? */ 1908 total_len = TCPOLEN_FAST_OPEN_EMPTY + to->to_tfo_len; 1909 if (TCP_MAXOLEN - optlen < total_len) { 1910 to->to_flags &= ~TOF_FASTOPEN; 1911 continue; 1912 } 1913 *optp++ = TCPOPT_FAST_OPEN; 1914 *optp++ = total_len; 1915 if (to->to_tfo_len > 0) { 1916 bcopy(to->to_tfo_cookie, optp, to->to_tfo_len); 1917 optp += to->to_tfo_len; 1918 } 1919 optlen += total_len; 1920 break; 1921 } 1922 default: 1923 panic("%s: unknown TCP option type", __func__); 1924 break; 1925 } 1926 } 1927 1928 /* Terminate and pad TCP options to a 4 byte boundary. */ 1929 if (optlen % 4) { 1930 optlen += TCPOLEN_EOL; 1931 *optp++ = TCPOPT_EOL; 1932 } 1933 /* 1934 * According to RFC 793 (STD0007): 1935 * "The content of the header beyond the End-of-Option option 1936 * must be header padding (i.e., zero)." 1937 * and later: "The padding is composed of zeros." 1938 */ 1939 while (optlen % 4) { 1940 optlen += TCPOLEN_PAD; 1941 *optp++ = TCPOPT_PAD; 1942 } 1943 1944 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1945 return (optlen); 1946 } 1947 1948 /* 1949 * This is a copy of m_copym(), taking the TSO segment size/limit 1950 * constraints into account, and advancing the sndptr as it goes. 1951 */ 1952 struct mbuf * 1953 tcp_m_copym(struct mbuf *m, int32_t off0, int32_t *plen, 1954 int32_t seglimit, int32_t segsize, struct sockbuf *sb, bool hw_tls) 1955 { 1956 #ifdef KERN_TLS 1957 struct ktls_session *tls, *ntls; 1958 struct mbuf *start __diagused; 1959 #endif 1960 struct mbuf *n, **np; 1961 struct mbuf *top; 1962 int32_t off = off0; 1963 int32_t len = *plen; 1964 int32_t fragsize; 1965 int32_t len_cp = 0; 1966 int32_t *pkthdrlen; 1967 uint32_t mlen, frags; 1968 bool copyhdr; 1969 1970 KASSERT(off >= 0, ("tcp_m_copym, negative off %d", off)); 1971 KASSERT(len >= 0, ("tcp_m_copym, negative len %d", len)); 1972 if (off == 0 && m->m_flags & M_PKTHDR) 1973 copyhdr = true; 1974 else 1975 copyhdr = false; 1976 while (off > 0) { 1977 KASSERT(m != NULL, ("tcp_m_copym, offset > size of mbuf chain")); 1978 if (off < m->m_len) 1979 break; 1980 off -= m->m_len; 1981 if ((sb) && (m == sb->sb_sndptr)) { 1982 sb->sb_sndptroff += m->m_len; 1983 sb->sb_sndptr = m->m_next; 1984 } 1985 m = m->m_next; 1986 } 1987 np = ⊤ 1988 top = NULL; 1989 pkthdrlen = NULL; 1990 #ifdef KERN_TLS 1991 if (hw_tls && (m->m_flags & M_EXTPG)) 1992 tls = m->m_epg_tls; 1993 else 1994 tls = NULL; 1995 start = m; 1996 #endif 1997 while (len > 0) { 1998 if (m == NULL) { 1999 KASSERT(len == M_COPYALL, 2000 ("tcp_m_copym, length > size of mbuf chain")); 2001 *plen = len_cp; 2002 if (pkthdrlen != NULL) 2003 *pkthdrlen = len_cp; 2004 break; 2005 } 2006 #ifdef KERN_TLS 2007 if (hw_tls) { 2008 if (m->m_flags & M_EXTPG) 2009 ntls = m->m_epg_tls; 2010 else 2011 ntls = NULL; 2012 2013 /* 2014 * Avoid mixing TLS records with handshake 2015 * data or TLS records from different 2016 * sessions. 2017 */ 2018 if (tls != ntls) { 2019 MPASS(m != start); 2020 *plen = len_cp; 2021 if (pkthdrlen != NULL) 2022 *pkthdrlen = len_cp; 2023 break; 2024 } 2025 } 2026 #endif 2027 mlen = min(len, m->m_len - off); 2028 if (seglimit) { 2029 /* 2030 * For M_EXTPG mbufs, add 3 segments 2031 * + 1 in case we are crossing page boundaries 2032 * + 2 in case the TLS hdr/trailer are used 2033 * It is cheaper to just add the segments 2034 * than it is to take the cache miss to look 2035 * at the mbuf ext_pgs state in detail. 2036 */ 2037 if (m->m_flags & M_EXTPG) { 2038 fragsize = min(segsize, PAGE_SIZE); 2039 frags = 3; 2040 } else { 2041 fragsize = segsize; 2042 frags = 0; 2043 } 2044 2045 /* Break if we really can't fit anymore. */ 2046 if ((frags + 1) >= seglimit) { 2047 *plen = len_cp; 2048 if (pkthdrlen != NULL) 2049 *pkthdrlen = len_cp; 2050 break; 2051 } 2052 2053 /* 2054 * Reduce size if you can't copy the whole 2055 * mbuf. If we can't copy the whole mbuf, also 2056 * adjust len so the loop will end after this 2057 * mbuf. 2058 */ 2059 if ((frags + howmany(mlen, fragsize)) >= seglimit) { 2060 mlen = (seglimit - frags - 1) * fragsize; 2061 len = mlen; 2062 *plen = len_cp + len; 2063 if (pkthdrlen != NULL) 2064 *pkthdrlen = *plen; 2065 } 2066 frags += howmany(mlen, fragsize); 2067 if (frags == 0) 2068 frags++; 2069 seglimit -= frags; 2070 KASSERT(seglimit > 0, 2071 ("%s: seglimit went too low", __func__)); 2072 } 2073 if (copyhdr) 2074 n = m_gethdr(M_NOWAIT, m->m_type); 2075 else 2076 n = m_get(M_NOWAIT, m->m_type); 2077 *np = n; 2078 if (n == NULL) 2079 goto nospace; 2080 if (copyhdr) { 2081 if (!m_dup_pkthdr(n, m, M_NOWAIT)) 2082 goto nospace; 2083 if (len == M_COPYALL) 2084 n->m_pkthdr.len -= off0; 2085 else 2086 n->m_pkthdr.len = len; 2087 pkthdrlen = &n->m_pkthdr.len; 2088 copyhdr = false; 2089 } 2090 n->m_len = mlen; 2091 len_cp += n->m_len; 2092 if (m->m_flags & (M_EXT|M_EXTPG)) { 2093 n->m_data = m->m_data + off; 2094 mb_dupcl(n, m); 2095 } else 2096 bcopy(mtod(m, caddr_t)+off, mtod(n, caddr_t), 2097 (u_int)n->m_len); 2098 2099 if (sb && (sb->sb_sndptr == m) && 2100 ((n->m_len + off) >= m->m_len) && m->m_next) { 2101 sb->sb_sndptroff += m->m_len; 2102 sb->sb_sndptr = m->m_next; 2103 } 2104 off = 0; 2105 if (len != M_COPYALL) { 2106 len -= n->m_len; 2107 } 2108 m = m->m_next; 2109 np = &n->m_next; 2110 } 2111 return (top); 2112 nospace: 2113 m_freem(top); 2114 return (NULL); 2115 } 2116 2117 void 2118 tcp_sndbuf_autoscale(struct tcpcb *tp, struct socket *so, uint32_t sendwin) 2119 { 2120 2121 /* 2122 * Automatic sizing of send socket buffer. Often the send buffer 2123 * size is not optimally adjusted to the actual network conditions 2124 * at hand (delay bandwidth product). Setting the buffer size too 2125 * small limits throughput on links with high bandwidth and high 2126 * delay (eg. trans-continental/oceanic links). Setting the 2127 * buffer size too big consumes too much real kernel memory, 2128 * especially with many connections on busy servers. 2129 * 2130 * The criteria to step up the send buffer one notch are: 2131 * 1. receive window of remote host is larger than send buffer 2132 * (with a fudge factor of 5/4th); 2133 * 2. send buffer is filled to 7/8th with data (so we actually 2134 * have data to make use of it); 2135 * 3. send buffer fill has not hit maximal automatic size; 2136 * 4. our send window (slow start and cogestion controlled) is 2137 * larger than sent but unacknowledged data in send buffer. 2138 * 2139 * The remote host receive window scaling factor may limit the 2140 * growing of the send buffer before it reaches its allowed 2141 * maximum. 2142 * 2143 * It scales directly with slow start or congestion window 2144 * and does at most one step per received ACK. This fast 2145 * scaling has the drawback of growing the send buffer beyond 2146 * what is strictly necessary to make full use of a given 2147 * delay*bandwidth product. However testing has shown this not 2148 * to be much of an problem. At worst we are trading wasting 2149 * of available bandwidth (the non-use of it) for wasting some 2150 * socket buffer memory. 2151 * 2152 * TODO: Shrink send buffer during idle periods together 2153 * with congestion window. Requires another timer. Has to 2154 * wait for upcoming tcp timer rewrite. 2155 * 2156 * XXXGL: should there be used sbused() or sbavail()? 2157 */ 2158 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 2159 int lowat; 2160 2161 lowat = V_tcp_sendbuf_auto_lowat ? so->so_snd.sb_lowat : 0; 2162 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat - lowat && 2163 sbused(&so->so_snd) >= 2164 (so->so_snd.sb_hiwat / 8 * 7) - lowat && 2165 sbused(&so->so_snd) < V_tcp_autosndbuf_max && 2166 sendwin >= (sbused(&so->so_snd) - 2167 (tp->snd_nxt - tp->snd_una))) { 2168 if (!sbreserve_locked(so, SO_SND, 2169 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 2170 V_tcp_autosndbuf_max), curthread)) 2171 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 2172 } 2173 } 2174 } 2175