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 32 #include <sys/cdefs.h> 33 #include "opt_inet.h" 34 #include "opt_inet6.h" 35 #include "opt_ipsec.h" 36 #include "opt_kern_tls.h" 37 38 #include <sys/param.h> 39 #include <sys/systm.h> 40 #include <sys/arb.h> 41 #include <sys/domain.h> 42 #ifdef TCP_HHOOK 43 #include <sys/hhook.h> 44 #endif 45 #include <sys/kernel.h> 46 #ifdef KERN_TLS 47 #include <sys/ktls.h> 48 #endif 49 #include <sys/lock.h> 50 #include <sys/mbuf.h> 51 #include <sys/mutex.h> 52 #include <sys/protosw.h> 53 #include <sys/qmath.h> 54 #include <sys/sdt.h> 55 #include <sys/socket.h> 56 #include <sys/socketvar.h> 57 #include <sys/sysctl.h> 58 #include <sys/stats.h> 59 60 #include <net/if.h> 61 #include <net/route.h> 62 #include <net/route/nhop.h> 63 #include <net/vnet.h> 64 65 #include <netinet/in.h> 66 #include <netinet/in_kdtrace.h> 67 #include <netinet/in_systm.h> 68 #include <netinet/ip.h> 69 #include <netinet/in_pcb.h> 70 #include <netinet/ip_var.h> 71 #include <netinet/ip_options.h> 72 #ifdef INET6 73 #include <netinet6/in6_pcb.h> 74 #include <netinet/ip6.h> 75 #include <netinet6/ip6_var.h> 76 #endif 77 #include <netinet/tcp.h> 78 #define TCPOUTFLAGS 79 #include <netinet/tcp_fsm.h> 80 #include <netinet/tcp_seq.h> 81 #include <netinet/tcp_var.h> 82 #include <netinet/tcp_log_buf.h> 83 #include <netinet/tcp_syncache.h> 84 #include <netinet/tcp_timer.h> 85 #include <netinet/tcpip.h> 86 #include <netinet/cc/cc.h> 87 #include <netinet/tcp_fastopen.h> 88 #ifdef TCPPCAP 89 #include <netinet/tcp_pcap.h> 90 #endif 91 #ifdef TCP_OFFLOAD 92 #include <netinet/tcp_offload.h> 93 #endif 94 #include <netinet/tcp_ecn.h> 95 96 #include <netipsec/ipsec_support.h> 97 98 #include <netinet/udp.h> 99 #include <netinet/udp_var.h> 100 #include <machine/in_cksum.h> 101 102 #include <security/mac/mac_framework.h> 103 104 VNET_DEFINE(int, path_mtu_discovery) = 1; 105 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_VNET | CTLFLAG_RW, 106 &VNET_NAME(path_mtu_discovery), 1, 107 "Enable Path MTU Discovery"); 108 109 VNET_DEFINE(int, tcp_do_tso) = 1; 110 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_VNET | CTLFLAG_RW, 111 &VNET_NAME(tcp_do_tso), 0, 112 "Enable TCP Segmentation Offload"); 113 114 VNET_DEFINE(int, tcp_sendspace) = 1024*32; 115 #define V_tcp_sendspace VNET(tcp_sendspace) 116 SYSCTL_INT(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, CTLFLAG_VNET | CTLFLAG_RW, 117 &VNET_NAME(tcp_sendspace), 0, "Initial send socket buffer size"); 118 119 VNET_DEFINE(int, tcp_do_autosndbuf) = 1; 120 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_VNET | CTLFLAG_RW, 121 &VNET_NAME(tcp_do_autosndbuf), 0, 122 "Enable automatic send buffer sizing"); 123 124 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024; 125 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_VNET | CTLFLAG_RW, 126 &VNET_NAME(tcp_autosndbuf_inc), 0, 127 "Incrementor step size of automatic send buffer"); 128 129 VNET_DEFINE(int, tcp_autosndbuf_max) = 2*1024*1024; 130 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_VNET | CTLFLAG_RW, 131 &VNET_NAME(tcp_autosndbuf_max), 0, 132 "Max size of automatic send buffer"); 133 134 VNET_DEFINE(int, tcp_sendbuf_auto_lowat) = 0; 135 #define V_tcp_sendbuf_auto_lowat VNET(tcp_sendbuf_auto_lowat) 136 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto_lowat, CTLFLAG_VNET | CTLFLAG_RW, 137 &VNET_NAME(tcp_sendbuf_auto_lowat), 0, 138 "Modify threshold for auto send buffer growth to account for SO_SNDLOWAT"); 139 140 /* 141 * Make sure that either retransmit or persist timer is set for SYN, FIN and 142 * non-ACK. 143 */ 144 #define TCP_XMIT_TIMER_ASSERT(tp, len, th_flags) \ 145 KASSERT(((len) == 0 && ((th_flags) & (TH_SYN | TH_FIN)) == 0) ||\ 146 tcp_timer_active((tp), TT_REXMT) || \ 147 tcp_timer_active((tp), TT_PERSIST), \ 148 ("neither rexmt nor persist timer is set")) 149 150 #ifdef TCP_HHOOK 151 /* 152 * Wrapper for the TCP established output helper hook. 153 */ 154 void 155 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th, 156 struct tcpopt *to, uint32_t len, int tso) 157 { 158 struct tcp_hhook_data hhook_data; 159 160 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) { 161 hhook_data.tp = tp; 162 hhook_data.th = th; 163 hhook_data.to = to; 164 hhook_data.len = len; 165 hhook_data.tso = tso; 166 167 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data, 168 &tp->t_osd); 169 } 170 } 171 #endif 172 173 /* 174 * CC wrapper hook functions 175 */ 176 void 177 cc_after_idle(struct tcpcb *tp) 178 { 179 INP_WLOCK_ASSERT(tptoinpcb(tp)); 180 181 if (CC_ALGO(tp)->after_idle != NULL) 182 CC_ALGO(tp)->after_idle(&tp->t_ccv); 183 } 184 185 /* 186 * Tcp output routine: figure out what should be sent and send it. 187 */ 188 int 189 tcp_default_output(struct tcpcb *tp) 190 { 191 struct socket *so = tptosocket(tp); 192 struct inpcb *inp = tptoinpcb(tp); 193 int32_t len; 194 uint32_t recwin, sendwin; 195 uint16_t flags; 196 int off, error = 0; /* Keep compiler happy */ 197 u_int if_hw_tsomaxsegcount = 0; 198 u_int if_hw_tsomaxsegsize = 0; 199 struct mbuf *m; 200 struct ip *ip = NULL; 201 struct tcphdr *th; 202 u_char opt[TCP_MAXOLEN]; 203 unsigned ipoptlen, optlen, hdrlen, ulen; 204 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 205 unsigned ipsec_optlen = 0; 206 #endif 207 int idle, sendalot, curticks; 208 int sack_rxmit, sack_bytes_rxmt; 209 struct sackhole *p; 210 int tso, mtu; 211 struct tcpopt to; 212 struct udphdr *udp = NULL; 213 struct tcp_log_buffer *lgb; 214 unsigned int wanted_cookie = 0; 215 unsigned int dont_sendalot = 0; 216 #if 0 217 int maxburst = TCP_MAXBURST; 218 #endif 219 #ifdef INET6 220 struct ip6_hdr *ip6 = NULL; 221 const bool isipv6 = (inp->inp_vflag & INP_IPV6) != 0; 222 #endif 223 #ifdef KERN_TLS 224 const bool hw_tls = tp->t_nic_ktls_xmit != 0; 225 #else 226 const bool hw_tls = false; 227 #endif 228 229 NET_EPOCH_ASSERT(); 230 INP_WLOCK_ASSERT(inp); 231 232 #ifdef TCP_OFFLOAD 233 if (tp->t_flags & TF_TOE) 234 return (tcp_offload_output(tp)); 235 #endif 236 237 /* 238 * For TFO connections in SYN_SENT or SYN_RECEIVED, 239 * only allow the initial SYN or SYN|ACK and those sent 240 * by the retransmit timer. 241 */ 242 if (IS_FASTOPEN(tp->t_flags) && 243 ((tp->t_state == TCPS_SYN_SENT) || 244 (tp->t_state == TCPS_SYN_RECEIVED)) && 245 SEQ_GT(tp->snd_max, tp->snd_una) && /* initial SYN or SYN|ACK sent */ 246 (tp->snd_nxt != tp->snd_una)) /* not a retransmit */ 247 return (0); 248 249 /* 250 * Determine length of data that should be transmitted, 251 * and flags that will be used. 252 * If there is some data or critical controls (SYN, RST) 253 * to send, then transmit; otherwise, investigate further. 254 */ 255 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 256 if (idle && (((ticks - tp->t_rcvtime) >= tp->t_rxtcur) || 257 (tp->t_sndtime && ((ticks - tp->t_sndtime) >= tp->t_rxtcur)))) 258 cc_after_idle(tp); 259 tp->t_flags &= ~TF_LASTIDLE; 260 if (idle) { 261 if (tp->t_flags & TF_MORETOCOME) { 262 tp->t_flags |= TF_LASTIDLE; 263 idle = 0; 264 } 265 } 266 again: 267 /* 268 * If we've recently taken a timeout, snd_max will be greater than 269 * snd_nxt. There may be SACK information that allows us to avoid 270 * resending already delivered data. Adjust snd_nxt accordingly. 271 */ 272 if ((tp->t_flags & TF_SACK_PERMIT) && 273 SEQ_LT(tp->snd_nxt, tp->snd_max)) 274 tcp_sack_adjust(tp); 275 sendalot = 0; 276 tso = 0; 277 mtu = 0; 278 off = tp->snd_nxt - tp->snd_una; 279 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 280 281 flags = tcp_outflags[tp->t_state]; 282 /* 283 * Send any SACK-generated retransmissions. If we're explicitly trying 284 * to send out new data (when sendalot is 1), bypass this function. 285 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 286 * we're replacing a (future) new transmission with a retransmission 287 * now, and we previously incremented snd_cwnd in tcp_input(). 288 */ 289 /* 290 * Still in sack recovery , reset rxmit flag to zero. 291 */ 292 sack_rxmit = 0; 293 sack_bytes_rxmt = 0; 294 len = 0; 295 p = NULL; 296 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) && 297 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 298 uint32_t cwin; 299 300 cwin = 301 imax(min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt, 0); 302 /* Do not retransmit SACK segments beyond snd_recover */ 303 if (SEQ_GT(p->end, tp->snd_recover)) { 304 /* 305 * (At least) part of sack hole extends beyond 306 * snd_recover. Check to see if we can rexmit data 307 * for this hole. 308 */ 309 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 310 /* 311 * Can't rexmit any more data for this hole. 312 * That data will be rexmitted in the next 313 * sack recovery episode, when snd_recover 314 * moves past p->rxmit. 315 */ 316 p = NULL; 317 goto after_sack_rexmit; 318 } else { 319 /* Can rexmit part of the current hole */ 320 len = ((int32_t)ulmin(cwin, 321 SEQ_SUB(tp->snd_recover, p->rxmit))); 322 } 323 } else { 324 len = ((int32_t)ulmin(cwin, 325 SEQ_SUB(p->end, p->rxmit))); 326 } 327 if (len > 0) { 328 off = SEQ_SUB(p->rxmit, tp->snd_una); 329 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 330 __func__, off)); 331 sack_rxmit = 1; 332 sendalot = 1; 333 TCPSTAT_INC(tcps_sack_rexmits); 334 TCPSTAT_ADD(tcps_sack_rexmit_bytes, 335 min(len, tcp_maxseg(tp))); 336 } 337 } 338 after_sack_rexmit: 339 /* 340 * Get standard flags, and add SYN or FIN if requested by 'hidden' 341 * state flags. 342 */ 343 if (tp->t_flags & TF_NEEDFIN) 344 flags |= TH_FIN; 345 if (tp->t_flags & TF_NEEDSYN) 346 flags |= TH_SYN; 347 348 SOCKBUF_LOCK(&so->so_snd); 349 /* 350 * If in persist timeout with window of 0, send 1 byte. 351 * Otherwise, if window is small but nonzero 352 * and timer expired, we will send what we can 353 * and go to transmit state. 354 */ 355 if (tp->t_flags & TF_FORCEDATA) { 356 if (sendwin == 0) { 357 /* 358 * If we still have some data to send, then 359 * clear the FIN bit. Usually this would 360 * happen below when it realizes that we 361 * aren't sending all the data. However, 362 * if we have exactly 1 byte of unsent data, 363 * then it won't clear the FIN bit below, 364 * and if we are in persist state, we wind 365 * up sending the packet without recording 366 * that we sent the FIN bit. 367 * 368 * We can't just blindly clear the FIN bit, 369 * because if we don't have any more data 370 * to send then the probe will be the FIN 371 * itself. 372 */ 373 if (off < sbused(&so->so_snd)) 374 flags &= ~TH_FIN; 375 sendwin = 1; 376 } else { 377 tcp_timer_activate(tp, TT_PERSIST, 0); 378 tp->t_rxtshift = 0; 379 } 380 } 381 382 /* 383 * If snd_nxt == snd_max and we have transmitted a FIN, the 384 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 385 * a negative length. This can also occur when TCP opens up 386 * its congestion window while receiving additional duplicate 387 * acks after fast-retransmit because TCP will reset snd_nxt 388 * to snd_max after the fast-retransmit. 389 * 390 * In the normal retransmit-FIN-only case, however, snd_nxt will 391 * be set to snd_una, the offset will be 0, and the length may 392 * wind up 0. 393 * 394 * If sack_rxmit is true we are retransmitting from the scoreboard 395 * in which case len is already set. 396 */ 397 if (sack_rxmit == 0) { 398 if (sack_bytes_rxmt == 0) 399 len = ((int32_t)min(sbavail(&so->so_snd), sendwin) - 400 off); 401 else { 402 int32_t cwin; 403 404 /* 405 * We are inside of a SACK recovery episode and are 406 * sending new data, having retransmitted all the 407 * data possible in the scoreboard. 408 */ 409 len = ((int32_t)min(sbavail(&so->so_snd), tp->snd_wnd) - 410 off); 411 /* 412 * Don't remove this (len > 0) check ! 413 * We explicitly check for len > 0 here (although it 414 * isn't really necessary), to work around a gcc 415 * optimization issue - to force gcc to compute 416 * len above. Without this check, the computation 417 * of len is bungled by the optimizer. 418 */ 419 if (len > 0) { 420 cwin = tp->snd_cwnd - imax(0, (int32_t) 421 (tp->snd_nxt - tp->snd_recover)) - 422 sack_bytes_rxmt; 423 if (cwin < 0) 424 cwin = 0; 425 len = imin(len, cwin); 426 } 427 } 428 } 429 430 /* 431 * Lop off SYN bit if it has already been sent. However, if this 432 * is SYN-SENT state and if segment contains data and if we don't 433 * know that foreign host supports TAO, suppress sending segment. 434 */ 435 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 436 if (tp->t_state != TCPS_SYN_RECEIVED) 437 flags &= ~TH_SYN; 438 /* 439 * When sending additional segments following a TFO SYN|ACK, 440 * do not include the SYN bit. 441 */ 442 if (IS_FASTOPEN(tp->t_flags) && 443 (tp->t_state == TCPS_SYN_RECEIVED)) 444 flags &= ~TH_SYN; 445 off--, len++; 446 } 447 448 /* 449 * Be careful not to send data and/or FIN on SYN segments. 450 * This measure is needed to prevent interoperability problems 451 * with not fully conformant TCP implementations. 452 */ 453 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 454 len = 0; 455 flags &= ~TH_FIN; 456 } 457 458 /* 459 * On TFO sockets, ensure no data is sent in the following cases: 460 * 461 * - When retransmitting SYN|ACK on a passively-created socket 462 * 463 * - When retransmitting SYN on an actively created socket 464 * 465 * - When sending a zero-length cookie (cookie request) on an 466 * actively created socket 467 * 468 * - When the socket is in the CLOSED state (RST is being sent) 469 */ 470 if (IS_FASTOPEN(tp->t_flags) && 471 (((flags & TH_SYN) && (tp->t_rxtshift > 0)) || 472 ((tp->t_state == TCPS_SYN_SENT) && 473 (tp->t_tfo_client_cookie_len == 0)) || 474 (flags & TH_RST))) 475 len = 0; 476 if (len <= 0) { 477 /* 478 * If FIN has been sent but not acked, 479 * but we haven't been called to retransmit, 480 * len will be < 0. Otherwise, window shrank 481 * after we sent into it. If window shrank to 0, 482 * cancel pending retransmit, pull snd_nxt back 483 * to (closed) window, and set the persist timer 484 * if it isn't already going. If the window didn't 485 * close completely, just wait for an ACK. 486 * 487 * We also do a general check here to ensure that 488 * we will set the persist timer when we have data 489 * to send, but a 0-byte window. This makes sure 490 * the persist timer is set even if the packet 491 * hits one of the "goto send" lines below. 492 */ 493 len = 0; 494 if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) && 495 (off < (int) sbavail(&so->so_snd)) && 496 !tcp_timer_active(tp, TT_PERSIST)) { 497 tcp_timer_activate(tp, TT_REXMT, 0); 498 tp->t_rxtshift = 0; 499 tp->snd_nxt = tp->snd_una; 500 if (!tcp_timer_active(tp, TT_PERSIST)) 501 tcp_setpersist(tp); 502 } 503 } 504 505 /* len will be >= 0 after this point. */ 506 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 507 508 tcp_sndbuf_autoscale(tp, so, sendwin); 509 510 /* 511 * Decide if we can use TCP Segmentation Offloading (if supported by 512 * hardware). 513 * 514 * TSO may only be used if we are in a pure bulk sending state. The 515 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 516 * IP options prevent using TSO. With TSO the TCP header is the same 517 * (except for the sequence number) for all generated packets. This 518 * makes it impossible to transmit any options which vary per generated 519 * segment or packet. 520 * 521 * IPv4 handling has a clear separation of ip options and ip header 522 * flags while IPv6 combines both in in6p_outputopts. ip6_optlen() does 523 * the right thing below to provide length of just ip options and thus 524 * checking for ipoptlen is enough to decide if ip options are present. 525 */ 526 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 527 /* 528 * Pre-calculate here as we save another lookup into the darknesses 529 * of IPsec that way and can actually decide if TSO is ok. 530 */ 531 #ifdef INET6 532 if (isipv6 && IPSEC_ENABLED(ipv6)) 533 ipsec_optlen = IPSEC_HDRSIZE(ipv6, inp); 534 #ifdef INET 535 else 536 #endif 537 #endif /* INET6 */ 538 #ifdef INET 539 if (IPSEC_ENABLED(ipv4)) 540 ipsec_optlen = IPSEC_HDRSIZE(ipv4, inp); 541 #endif /* INET */ 542 #endif /* IPSEC */ 543 #ifdef INET6 544 if (isipv6) 545 ipoptlen = ip6_optlen(inp); 546 else 547 #endif 548 if (inp->inp_options) 549 ipoptlen = inp->inp_options->m_len - 550 offsetof(struct ipoption, ipopt_list); 551 else 552 ipoptlen = 0; 553 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 554 ipoptlen += ipsec_optlen; 555 #endif 556 557 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg && 558 (tp->t_port == 0) && 559 ((tp->t_flags & TF_SIGNATURE) == 0) && 560 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 561 ipoptlen == 0 && !(flags & TH_SYN)) 562 tso = 1; 563 564 if (sack_rxmit) { 565 if (SEQ_LT(p->rxmit + len, tp->snd_una + sbused(&so->so_snd))) 566 flags &= ~TH_FIN; 567 } else { 568 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + 569 sbused(&so->so_snd))) 570 flags &= ~TH_FIN; 571 } 572 573 recwin = lmin(lmax(sbspace(&so->so_rcv), 0), 574 (long)TCP_MAXWIN << tp->rcv_scale); 575 576 /* 577 * Sender silly window avoidance. We transmit under the following 578 * conditions when len is non-zero: 579 * 580 * - We have a full segment (or more with TSO) 581 * - This is the last buffer in a write()/send() and we are 582 * either idle or running NODELAY 583 * - we've timed out (e.g. persist timer) 584 * - we have more then 1/2 the maximum send window's worth of 585 * data (receiver may be limited the window size) 586 * - we need to retransmit 587 */ 588 if (len) { 589 if (len >= tp->t_maxseg) 590 goto send; 591 /* 592 * As the TCP header options are now 593 * considered when setting up the initial 594 * window, we would not send the last segment 595 * if we skip considering the option length here. 596 * Note: this may not work when tcp headers change 597 * very dynamically in the future. 598 */ 599 if ((((tp->t_flags & TF_SIGNATURE) ? 600 PADTCPOLEN(TCPOLEN_SIGNATURE) : 0) + 601 ((tp->t_flags & TF_RCVD_TSTMP) ? 602 PADTCPOLEN(TCPOLEN_TIMESTAMP) : 0) + 603 len) >= tp->t_maxseg) 604 goto send; 605 /* 606 * NOTE! on localhost connections an 'ack' from the remote 607 * end may occur synchronously with the output and cause 608 * us to flush a buffer queued with moretocome. XXX 609 * 610 * note: the len + off check is almost certainly unnecessary. 611 */ 612 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 613 (idle || (tp->t_flags & TF_NODELAY)) && 614 (uint32_t)len + (uint32_t)off >= sbavail(&so->so_snd) && 615 (tp->t_flags & TF_NOPUSH) == 0) { 616 goto send; 617 } 618 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 619 goto send; 620 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 621 goto send; 622 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 623 goto send; 624 if (sack_rxmit) 625 goto send; 626 } 627 628 /* 629 * Sending of standalone window updates. 630 * 631 * Window updates are important when we close our window due to a 632 * full socket buffer and are opening it again after the application 633 * reads data from it. Once the window has opened again and the 634 * remote end starts to send again the ACK clock takes over and 635 * provides the most current window information. 636 * 637 * We must avoid the silly window syndrome whereas every read 638 * from the receive buffer, no matter how small, causes a window 639 * update to be sent. We also should avoid sending a flurry of 640 * window updates when the socket buffer had queued a lot of data 641 * and the application is doing small reads. 642 * 643 * Prevent a flurry of pointless window updates by only sending 644 * an update when we can increase the advertized window by more 645 * than 1/4th of the socket buffer capacity. When the buffer is 646 * getting full or is very small be more aggressive and send an 647 * update whenever we can increase by two mss sized segments. 648 * In all other situations the ACK's to new incoming data will 649 * carry further window increases. 650 * 651 * Don't send an independent window update if a delayed 652 * ACK is pending (it will get piggy-backed on it) or the 653 * remote side already has done a half-close and won't send 654 * more data. 655 */ 656 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 657 !(tp->t_flags & TF_DELACK) && 658 !TCPS_HAVERCVDFIN(tp->t_state)) { 659 /* 660 * "adv" is the amount we could increase the window, 661 * taking into account that we are limited by 662 * TCP_MAXWIN << tp->rcv_scale. 663 */ 664 int32_t adv; 665 int oldwin; 666 667 adv = recwin; 668 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { 669 oldwin = (tp->rcv_adv - tp->rcv_nxt); 670 if (adv > oldwin) 671 adv -= oldwin; 672 else 673 adv = 0; 674 } else 675 oldwin = 0; 676 677 /* 678 * If the new window size ends up being the same as or less 679 * than the old size when it is scaled, then don't force 680 * a window update. 681 */ 682 if (oldwin >> tp->rcv_scale >= (adv + oldwin) >> tp->rcv_scale) 683 goto dontupdate; 684 685 if (adv >= (int32_t)(2 * tp->t_maxseg) && 686 (adv >= (int32_t)(so->so_rcv.sb_hiwat / 4) || 687 recwin <= (so->so_rcv.sb_hiwat / 8) || 688 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg || 689 adv >= TCP_MAXWIN << tp->rcv_scale)) 690 goto send; 691 if (2 * adv >= (int32_t)so->so_rcv.sb_hiwat) 692 goto send; 693 } 694 dontupdate: 695 696 /* 697 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 698 * is also a catch-all for the retransmit timer timeout case. 699 */ 700 if (tp->t_flags & TF_ACKNOW) 701 goto send; 702 if ((flags & TH_RST) || 703 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 704 goto send; 705 if (SEQ_GT(tp->snd_up, tp->snd_una)) 706 goto send; 707 /* 708 * If our state indicates that FIN should be sent 709 * and we have not yet done so, then we need to send. 710 */ 711 if (flags & TH_FIN && 712 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 713 goto send; 714 /* 715 * In SACK, it is possible for tcp_output to fail to send a segment 716 * after the retransmission timer has been turned off. Make sure 717 * that the retransmission timer is set. 718 */ 719 if ((tp->t_flags & TF_SACK_PERMIT) && 720 SEQ_GT(tp->snd_max, tp->snd_una) && 721 !tcp_timer_active(tp, TT_REXMT) && 722 !tcp_timer_active(tp, TT_PERSIST)) { 723 tcp_timer_activate(tp, TT_REXMT, TP_RXTCUR(tp)); 724 goto just_return; 725 } 726 /* 727 * TCP window updates are not reliable, rather a polling protocol 728 * using ``persist'' packets is used to insure receipt of window 729 * updates. The three ``states'' for the output side are: 730 * idle not doing retransmits or persists 731 * persisting to move a small or zero window 732 * (re)transmitting and thereby not persisting 733 * 734 * tcp_timer_active(tp, TT_PERSIST) 735 * is true when we are in persist state. 736 * (tp->t_flags & TF_FORCEDATA) 737 * is set when we are called to send a persist packet. 738 * tcp_timer_active(tp, TT_REXMT) 739 * is set when we are retransmitting 740 * The output side is idle when both timers are zero. 741 * 742 * If send window is too small, there is data to transmit, and no 743 * retransmit or persist is pending, then go to persist state. 744 * If nothing happens soon, send when timer expires: 745 * if window is nonzero, transmit what we can, 746 * otherwise force out a byte. 747 */ 748 if (sbavail(&so->so_snd) && !tcp_timer_active(tp, TT_REXMT) && 749 !tcp_timer_active(tp, TT_PERSIST)) { 750 tp->t_rxtshift = 0; 751 tcp_setpersist(tp); 752 } 753 754 /* 755 * No reason to send a segment, just return. 756 */ 757 just_return: 758 SOCKBUF_UNLOCK(&so->so_snd); 759 return (0); 760 761 send: 762 SOCKBUF_LOCK_ASSERT(&so->so_snd); 763 if (len > 0) { 764 if (len >= tp->t_maxseg) 765 tp->t_flags2 |= TF2_PLPMTU_MAXSEGSNT; 766 else 767 tp->t_flags2 &= ~TF2_PLPMTU_MAXSEGSNT; 768 } 769 /* 770 * Before ESTABLISHED, force sending of initial options 771 * unless TCP set not to do any options. 772 * NOTE: we assume that the IP/TCP header plus TCP options 773 * always fit in a single mbuf, leaving room for a maximum 774 * link header, i.e. 775 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 776 */ 777 optlen = 0; 778 #ifdef INET6 779 if (isipv6) 780 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 781 else 782 #endif 783 hdrlen = sizeof (struct tcpiphdr); 784 785 if (flags & TH_SYN) { 786 tp->snd_nxt = tp->iss; 787 } 788 789 /* 790 * Compute options for segment. 791 * We only have to care about SYN and established connection 792 * segments. Options for SYN-ACK segments are handled in TCP 793 * syncache. 794 */ 795 to.to_flags = 0; 796 if ((tp->t_flags & TF_NOOPT) == 0) { 797 /* Maximum segment size. */ 798 if (flags & TH_SYN) { 799 to.to_mss = tcp_mssopt(&inp->inp_inc); 800 if (tp->t_port) 801 to.to_mss -= V_tcp_udp_tunneling_overhead; 802 to.to_flags |= TOF_MSS; 803 804 /* 805 * On SYN or SYN|ACK transmits on TFO connections, 806 * only include the TFO option if it is not a 807 * retransmit, as the presence of the TFO option may 808 * have caused the original SYN or SYN|ACK to have 809 * been dropped by a middlebox. 810 */ 811 if (IS_FASTOPEN(tp->t_flags) && 812 (tp->t_rxtshift == 0)) { 813 if (tp->t_state == TCPS_SYN_RECEIVED) { 814 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN; 815 to.to_tfo_cookie = 816 (u_int8_t *)&tp->t_tfo_cookie.server; 817 to.to_flags |= TOF_FASTOPEN; 818 wanted_cookie = 1; 819 } else if (tp->t_state == TCPS_SYN_SENT) { 820 to.to_tfo_len = 821 tp->t_tfo_client_cookie_len; 822 to.to_tfo_cookie = 823 tp->t_tfo_cookie.client; 824 to.to_flags |= TOF_FASTOPEN; 825 wanted_cookie = 1; 826 /* 827 * If we wind up having more data to 828 * send with the SYN than can fit in 829 * one segment, don't send any more 830 * until the SYN|ACK comes back from 831 * the other end. 832 */ 833 dont_sendalot = 1; 834 } 835 } 836 } 837 /* Window scaling. */ 838 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 839 to.to_wscale = tp->request_r_scale; 840 to.to_flags |= TOF_SCALE; 841 } 842 /* Timestamps. */ 843 if ((tp->t_flags & TF_RCVD_TSTMP) || 844 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 845 curticks = tcp_ts_getticks(); 846 to.to_tsval = curticks + tp->ts_offset; 847 to.to_tsecr = tp->ts_recent; 848 to.to_flags |= TOF_TS; 849 if (tp->t_rxtshift == 1) 850 tp->t_badrxtwin = curticks; 851 } 852 853 /* Set receive buffer autosizing timestamp. */ 854 if (tp->rfbuf_ts == 0 && 855 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 856 tp->rfbuf_ts = tcp_ts_getticks(); 857 858 /* Selective ACK's. */ 859 if (tp->t_flags & TF_SACK_PERMIT) { 860 if (flags & TH_SYN) 861 to.to_flags |= TOF_SACKPERM; 862 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 863 tp->rcv_numsacks > 0) { 864 to.to_flags |= TOF_SACK; 865 to.to_nsacks = tp->rcv_numsacks; 866 to.to_sacks = (u_char *)tp->sackblks; 867 } 868 } 869 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 870 /* TCP-MD5 (RFC2385). */ 871 /* 872 * Check that TCP_MD5SIG is enabled in tcpcb to 873 * account the size needed to set this TCP option. 874 */ 875 if (tp->t_flags & TF_SIGNATURE) 876 to.to_flags |= TOF_SIGNATURE; 877 #endif /* TCP_SIGNATURE */ 878 879 /* Processing the options. */ 880 hdrlen += optlen = tcp_addoptions(&to, opt); 881 /* 882 * If we wanted a TFO option to be added, but it was unable 883 * to fit, ensure no data is sent. 884 */ 885 if (IS_FASTOPEN(tp->t_flags) && wanted_cookie && 886 !(to.to_flags & TOF_FASTOPEN)) 887 len = 0; 888 } 889 if (tp->t_port) { 890 if (V_tcp_udp_tunneling_port == 0) { 891 /* The port was removed?? */ 892 SOCKBUF_UNLOCK(&so->so_snd); 893 return (EHOSTUNREACH); 894 } 895 hdrlen += sizeof(struct udphdr); 896 } 897 /* 898 * Adjust data length if insertion of options will 899 * bump the packet length beyond the t_maxseg length. 900 * Clear the FIN bit because we cut off the tail of 901 * the segment. 902 */ 903 if (len + optlen + ipoptlen > tp->t_maxseg) { 904 flags &= ~TH_FIN; 905 906 if (tso) { 907 u_int if_hw_tsomax; 908 u_int moff; 909 int max_len; 910 911 /* extract TSO information */ 912 if_hw_tsomax = tp->t_tsomax; 913 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount; 914 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize; 915 916 /* 917 * Limit a TSO burst to prevent it from 918 * overflowing or exceeding the maximum length 919 * allowed by the network interface: 920 */ 921 KASSERT(ipoptlen == 0, 922 ("%s: TSO can't do IP options", __func__)); 923 924 /* 925 * Check if we should limit by maximum payload 926 * length: 927 */ 928 if (if_hw_tsomax != 0) { 929 /* compute maximum TSO length */ 930 max_len = (if_hw_tsomax - hdrlen - 931 max_linkhdr); 932 if (max_len <= 0) { 933 len = 0; 934 } else if (len > max_len) { 935 sendalot = 1; 936 len = max_len; 937 } 938 } 939 940 /* 941 * Prevent the last segment from being 942 * fractional unless the send sockbuf can be 943 * emptied: 944 */ 945 max_len = (tp->t_maxseg - optlen); 946 if (((uint32_t)off + (uint32_t)len) < 947 sbavail(&so->so_snd)) { 948 moff = len % max_len; 949 if (moff != 0) { 950 len -= moff; 951 sendalot = 1; 952 } 953 } 954 955 /* 956 * In case there are too many small fragments 957 * don't use TSO: 958 */ 959 if (len <= max_len) { 960 len = max_len; 961 sendalot = 1; 962 tso = 0; 963 } 964 965 /* 966 * Send the FIN in a separate segment 967 * after the bulk sending is done. 968 * We don't trust the TSO implementations 969 * to clear the FIN flag on all but the 970 * last segment. 971 */ 972 if (tp->t_flags & TF_NEEDFIN) 973 sendalot = 1; 974 } else { 975 if (optlen + ipoptlen >= tp->t_maxseg) { 976 /* 977 * Since we don't have enough space to put 978 * the IP header chain and the TCP header in 979 * one packet as required by RFC 7112, don't 980 * send it. Also ensure that at least one 981 * byte of the payload can be put into the 982 * TCP segment. 983 */ 984 SOCKBUF_UNLOCK(&so->so_snd); 985 error = EMSGSIZE; 986 sack_rxmit = 0; 987 goto out; 988 } 989 len = tp->t_maxseg - optlen - ipoptlen; 990 sendalot = 1; 991 if (dont_sendalot) 992 sendalot = 0; 993 } 994 } else 995 tso = 0; 996 997 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 998 ("%s: len > IP_MAXPACKET", __func__)); 999 1000 /*#ifdef DIAGNOSTIC*/ 1001 #ifdef INET6 1002 if (max_linkhdr + hdrlen > MCLBYTES) 1003 #else 1004 if (max_linkhdr + hdrlen > MHLEN) 1005 #endif 1006 panic("tcphdr too big"); 1007 /*#endif*/ 1008 1009 /* 1010 * This KASSERT is here to catch edge cases at a well defined place. 1011 * Before, those had triggered (random) panic conditions further down. 1012 */ 1013 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 1014 1015 /* 1016 * Grab a header mbuf, attaching a copy of data to 1017 * be transmitted, and initialize the header from 1018 * the template for sends on this connection. 1019 */ 1020 if (len) { 1021 struct mbuf *mb; 1022 struct sockbuf *msb; 1023 u_int moff; 1024 1025 if ((tp->t_flags & TF_FORCEDATA) && len == 1) { 1026 TCPSTAT_INC(tcps_sndprobe); 1027 #ifdef STATS 1028 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1029 stats_voi_update_abs_u32(tp->t_stats, 1030 VOI_TCP_RETXPB, len); 1031 else 1032 stats_voi_update_abs_u64(tp->t_stats, 1033 VOI_TCP_TXPB, len); 1034 #endif /* STATS */ 1035 } else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 1036 tp->t_sndrexmitpack++; 1037 TCPSTAT_INC(tcps_sndrexmitpack); 1038 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 1039 #ifdef STATS 1040 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_RETXPB, 1041 len); 1042 #endif /* STATS */ 1043 } else { 1044 TCPSTAT_INC(tcps_sndpack); 1045 TCPSTAT_ADD(tcps_sndbyte, len); 1046 #ifdef STATS 1047 stats_voi_update_abs_u64(tp->t_stats, VOI_TCP_TXPB, 1048 len); 1049 #endif /* STATS */ 1050 } 1051 #ifdef INET6 1052 if (MHLEN < hdrlen + max_linkhdr) 1053 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR); 1054 else 1055 #endif 1056 m = m_gethdr(M_NOWAIT, MT_DATA); 1057 1058 if (m == NULL) { 1059 SOCKBUF_UNLOCK(&so->so_snd); 1060 error = ENOBUFS; 1061 sack_rxmit = 0; 1062 goto out; 1063 } 1064 1065 m->m_data += max_linkhdr; 1066 m->m_len = hdrlen; 1067 1068 /* 1069 * Start the m_copy functions from the closest mbuf 1070 * to the offset in the socket buffer chain. 1071 */ 1072 mb = sbsndptr_noadv(&so->so_snd, off, &moff); 1073 if (len <= MHLEN - hdrlen - max_linkhdr && !hw_tls) { 1074 m_copydata(mb, moff, len, 1075 mtod(m, caddr_t) + hdrlen); 1076 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1077 sbsndptr_adv(&so->so_snd, mb, len); 1078 m->m_len += len; 1079 } else { 1080 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1081 msb = NULL; 1082 else 1083 msb = &so->so_snd; 1084 m->m_next = tcp_m_copym(mb, moff, 1085 &len, if_hw_tsomaxsegcount, 1086 if_hw_tsomaxsegsize, msb, hw_tls); 1087 if (len <= (tp->t_maxseg - optlen)) { 1088 /* 1089 * Must have ran out of mbufs for the copy 1090 * shorten it to no longer need tso. Lets 1091 * not put on sendalot since we are low on 1092 * mbufs. 1093 */ 1094 tso = 0; 1095 } 1096 if (m->m_next == NULL) { 1097 SOCKBUF_UNLOCK(&so->so_snd); 1098 (void) m_free(m); 1099 error = ENOBUFS; 1100 sack_rxmit = 0; 1101 goto out; 1102 } 1103 } 1104 1105 /* 1106 * If we're sending everything we've got, set PUSH. 1107 * (This will keep happy those implementations which only 1108 * give data to the user when a buffer fills or 1109 * a PUSH comes in.) 1110 */ 1111 if (((uint32_t)off + (uint32_t)len == sbused(&so->so_snd)) && 1112 !(flags & TH_SYN)) 1113 flags |= TH_PUSH; 1114 SOCKBUF_UNLOCK(&so->so_snd); 1115 } else { 1116 SOCKBUF_UNLOCK(&so->so_snd); 1117 if (tp->t_flags & TF_ACKNOW) 1118 TCPSTAT_INC(tcps_sndacks); 1119 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 1120 TCPSTAT_INC(tcps_sndctrl); 1121 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 1122 TCPSTAT_INC(tcps_sndurg); 1123 else 1124 TCPSTAT_INC(tcps_sndwinup); 1125 1126 m = m_gethdr(M_NOWAIT, MT_DATA); 1127 if (m == NULL) { 1128 error = ENOBUFS; 1129 sack_rxmit = 0; 1130 goto out; 1131 } 1132 #ifdef INET6 1133 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 1134 MHLEN >= hdrlen) { 1135 M_ALIGN(m, hdrlen); 1136 } else 1137 #endif 1138 m->m_data += max_linkhdr; 1139 m->m_len = hdrlen; 1140 } 1141 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 1142 m->m_pkthdr.rcvif = (struct ifnet *)0; 1143 #ifdef MAC 1144 mac_inpcb_create_mbuf(inp, m); 1145 #endif 1146 #ifdef INET6 1147 if (isipv6) { 1148 ip6 = mtod(m, struct ip6_hdr *); 1149 if (tp->t_port) { 1150 udp = (struct udphdr *)((caddr_t)ip6 + sizeof(struct ip6_hdr)); 1151 udp->uh_sport = htons(V_tcp_udp_tunneling_port); 1152 udp->uh_dport = tp->t_port; 1153 ulen = hdrlen + len - sizeof(struct ip6_hdr); 1154 udp->uh_ulen = htons(ulen); 1155 th = (struct tcphdr *)(udp + 1); 1156 } else { 1157 th = (struct tcphdr *)(ip6 + 1); 1158 } 1159 tcpip_fillheaders(inp, tp->t_port, ip6, th); 1160 } else 1161 #endif /* INET6 */ 1162 { 1163 ip = mtod(m, struct ip *); 1164 if (tp->t_port) { 1165 udp = (struct udphdr *)((caddr_t)ip + sizeof(struct ip)); 1166 udp->uh_sport = htons(V_tcp_udp_tunneling_port); 1167 udp->uh_dport = tp->t_port; 1168 ulen = hdrlen + len - sizeof(struct ip); 1169 udp->uh_ulen = htons(ulen); 1170 th = (struct tcphdr *)(udp + 1); 1171 } else 1172 th = (struct tcphdr *)(ip + 1); 1173 tcpip_fillheaders(inp, tp->t_port, ip, th); 1174 } 1175 1176 /* 1177 * Fill in fields, remembering maximum advertised 1178 * window for use in delaying messages about window sizes. 1179 * If resending a FIN, be sure not to use a new sequence number. 1180 */ 1181 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 1182 tp->snd_nxt == tp->snd_max) 1183 tp->snd_nxt--; 1184 /* 1185 * If we are starting a connection, send ECN setup 1186 * SYN packet. If we are on a retransmit, we may 1187 * resend those bits a number of times as per 1188 * RFC 3168. 1189 */ 1190 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) { 1191 flags |= tcp_ecn_output_syn_sent(tp); 1192 } 1193 /* Also handle parallel SYN for ECN */ 1194 if ((TCPS_HAVERCVDSYN(tp->t_state)) && 1195 (tp->t_flags2 & (TF2_ECN_PERMIT | TF2_ACE_PERMIT))) { 1196 int ect = tcp_ecn_output_established(tp, &flags, len, sack_rxmit); 1197 if ((tp->t_state == TCPS_SYN_RECEIVED) && 1198 (tp->t_flags2 & TF2_ECN_SND_ECE)) 1199 tp->t_flags2 &= ~TF2_ECN_SND_ECE; 1200 #ifdef INET6 1201 if (isipv6) { 1202 ip6->ip6_flow &= ~htonl(IPTOS_ECN_MASK << IPV6_FLOWLABEL_LEN); 1203 ip6->ip6_flow |= htonl(ect << IPV6_FLOWLABEL_LEN); 1204 } 1205 else 1206 #endif 1207 { 1208 ip->ip_tos &= ~IPTOS_ECN_MASK; 1209 ip->ip_tos |= ect; 1210 } 1211 } 1212 1213 /* 1214 * If we are doing retransmissions, then snd_nxt will 1215 * not reflect the first unsent octet. For ACK only 1216 * packets, we do not want the sequence number of the 1217 * retransmitted packet, we want the sequence number 1218 * of the next unsent octet. So, if there is no data 1219 * (and no SYN or FIN), use snd_max instead of snd_nxt 1220 * when filling in ti_seq. But if we are in persist 1221 * state, snd_max might reflect one byte beyond the 1222 * right edge of the window, so use snd_nxt in that 1223 * case, since we know we aren't doing a retransmission. 1224 * (retransmit and persist are mutually exclusive...) 1225 */ 1226 if (sack_rxmit == 0) { 1227 if (len || (flags & (TH_SYN|TH_FIN)) || 1228 tcp_timer_active(tp, TT_PERSIST)) 1229 th->th_seq = htonl(tp->snd_nxt); 1230 else 1231 th->th_seq = htonl(tp->snd_max); 1232 } else { 1233 th->th_seq = htonl(p->rxmit); 1234 p->rxmit += len; 1235 /* 1236 * Lost Retransmission Detection 1237 * trigger resending of a (then 1238 * still existing) hole, when 1239 * fack acks recoverypoint. 1240 */ 1241 if ((tp->t_flags & TF_LRD) && SEQ_GEQ(p->rxmit, p->end)) 1242 p->rxmit = tp->snd_recover; 1243 tp->sackhint.sack_bytes_rexmit += len; 1244 } 1245 if (IN_RECOVERY(tp->t_flags)) { 1246 /* 1247 * Account all bytes transmitted while 1248 * IN_RECOVERY, simplifying PRR and 1249 * Lost Retransmit Detection 1250 */ 1251 tp->sackhint.prr_out += len; 1252 } 1253 th->th_ack = htonl(tp->rcv_nxt); 1254 if (optlen) { 1255 bcopy(opt, th + 1, optlen); 1256 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1257 } 1258 tcp_set_flags(th, flags); 1259 /* 1260 * Calculate receive window. Don't shrink window, 1261 * but avoid silly window syndrome. 1262 * If a RST segment is sent, advertise a window of zero. 1263 */ 1264 if (flags & TH_RST) { 1265 recwin = 0; 1266 } else { 1267 if (recwin < (so->so_rcv.sb_hiwat / 4) && 1268 recwin < tp->t_maxseg) 1269 recwin = 0; 1270 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1271 recwin < (tp->rcv_adv - tp->rcv_nxt)) 1272 recwin = (tp->rcv_adv - tp->rcv_nxt); 1273 } 1274 /* 1275 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1276 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1277 * case is handled in syncache. 1278 */ 1279 if (flags & TH_SYN) 1280 th->th_win = htons((u_short) 1281 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1282 else { 1283 /* Avoid shrinking window with window scaling. */ 1284 recwin = roundup2(recwin, 1 << tp->rcv_scale); 1285 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1286 } 1287 1288 /* 1289 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1290 * a 0 window. This may cause the remote transmitter to stall. This 1291 * flag tells soreceive() to disable delayed acknowledgements when 1292 * draining the buffer. This can occur if the receiver is attempting 1293 * to read more data than can be buffered prior to transmitting on 1294 * the connection. 1295 */ 1296 if (th->th_win == 0) { 1297 tp->t_sndzerowin++; 1298 tp->t_flags |= TF_RXWIN0SENT; 1299 } else 1300 tp->t_flags &= ~TF_RXWIN0SENT; 1301 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1302 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1303 th->th_flags |= TH_URG; 1304 } else 1305 /* 1306 * If no urgent pointer to send, then we pull 1307 * the urgent pointer to the left edge of the send window 1308 * so that it doesn't drift into the send window on sequence 1309 * number wraparound. 1310 */ 1311 tp->snd_up = tp->snd_una; /* drag it along */ 1312 1313 /* 1314 * Put TCP length in extended header, and then 1315 * checksum extended header and data. 1316 */ 1317 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1318 1319 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1320 if (to.to_flags & TOF_SIGNATURE) { 1321 /* 1322 * Calculate MD5 signature and put it into the place 1323 * determined before. 1324 * NOTE: since TCP options buffer doesn't point into 1325 * mbuf's data, calculate offset and use it. 1326 */ 1327 if (!TCPMD5_ENABLED() || (error = TCPMD5_OUTPUT(m, th, 1328 (u_char *)(th + 1) + (to.to_signature - opt))) != 0) { 1329 /* 1330 * Do not send segment if the calculation of MD5 1331 * digest has failed. 1332 */ 1333 m_freem(m); 1334 goto out; 1335 } 1336 } 1337 #endif 1338 #ifdef INET6 1339 if (isipv6) { 1340 /* 1341 * There is no need to fill in ip6_plen right now. 1342 * It will be filled later by ip6_output. 1343 */ 1344 if (tp->t_port) { 1345 m->m_pkthdr.csum_flags = CSUM_UDP_IPV6; 1346 m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum); 1347 udp->uh_sum = in6_cksum_pseudo(ip6, ulen, IPPROTO_UDP, 0); 1348 th->th_sum = htons(0); 1349 UDPSTAT_INC(udps_opackets); 1350 } else { 1351 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1352 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1353 th->th_sum = in6_cksum_pseudo(ip6, 1354 sizeof(struct tcphdr) + optlen + len, IPPROTO_TCP, 1355 0); 1356 } 1357 } 1358 #endif 1359 #if defined(INET6) && defined(INET) 1360 else 1361 #endif 1362 #ifdef INET 1363 { 1364 if (tp->t_port) { 1365 m->m_pkthdr.csum_flags = CSUM_UDP; 1366 m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum); 1367 udp->uh_sum = in_pseudo(ip->ip_src.s_addr, 1368 ip->ip_dst.s_addr, htons(ulen + IPPROTO_UDP)); 1369 th->th_sum = htons(0); 1370 UDPSTAT_INC(udps_opackets); 1371 } else { 1372 m->m_pkthdr.csum_flags = CSUM_TCP; 1373 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1374 th->th_sum = in_pseudo(ip->ip_src.s_addr, 1375 ip->ip_dst.s_addr, htons(sizeof(struct tcphdr) + 1376 IPPROTO_TCP + len + optlen)); 1377 } 1378 1379 /* IP version must be set here for ipv4/ipv6 checking later */ 1380 KASSERT(ip->ip_v == IPVERSION, 1381 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1382 } 1383 #endif 1384 1385 /* 1386 * Enable TSO and specify the size of the segments. 1387 * The TCP pseudo header checksum is always provided. 1388 */ 1389 if (tso) { 1390 KASSERT(len > tp->t_maxseg - optlen, 1391 ("%s: len <= tso_segsz", __func__)); 1392 m->m_pkthdr.csum_flags |= CSUM_TSO; 1393 m->m_pkthdr.tso_segsz = tp->t_maxseg - optlen; 1394 } 1395 1396 KASSERT(len + hdrlen == m_length(m, NULL), 1397 ("%s: mbuf chain shorter than expected: %d + %u != %u", 1398 __func__, len, hdrlen, m_length(m, NULL))); 1399 1400 #ifdef TCP_HHOOK 1401 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1402 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1403 #endif 1404 1405 TCP_PROBE3(debug__output, tp, th, m); 1406 1407 /* We're getting ready to send; log now. */ 1408 /* XXXMT: We are not honoring verbose logging. */ 1409 1410 if (tcp_bblogging_on(tp)) 1411 lgb = tcp_log_event(tp, th, &so->so_rcv, &so->so_snd, 1412 TCP_LOG_OUT, ERRNO_UNK, len, NULL, false, NULL, NULL, 0, 1413 NULL); 1414 else 1415 lgb = NULL; 1416 1417 /* 1418 * Fill in IP length and desired time to live and 1419 * send to IP level. There should be a better way 1420 * to handle ttl and tos; we could keep them in 1421 * the template, but need a way to checksum without them. 1422 */ 1423 /* 1424 * m->m_pkthdr.len should have been set before checksum calculation, 1425 * because in6_cksum() need it. 1426 */ 1427 #ifdef INET6 1428 if (isipv6) { 1429 /* 1430 * we separately set hoplimit for every segment, since the 1431 * user might want to change the value via setsockopt. 1432 * Also, desired default hop limit might be changed via 1433 * Neighbor Discovery. 1434 */ 1435 ip6->ip6_hlim = in6_selecthlim(inp, NULL); 1436 1437 /* 1438 * Set the packet size here for the benefit of DTrace probes. 1439 * ip6_output() will set it properly; it's supposed to include 1440 * the option header lengths as well. 1441 */ 1442 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6)); 1443 1444 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) 1445 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1446 else 1447 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1448 1449 if (tp->t_state == TCPS_SYN_SENT) 1450 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th); 1451 1452 TCP_PROBE5(send, NULL, tp, ip6, tp, th); 1453 1454 #ifdef TCPPCAP 1455 /* Save packet, if requested. */ 1456 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1457 #endif 1458 1459 /* TODO: IPv6 IP6TOS_ECT bit on */ 1460 error = ip6_output(m, inp->in6p_outputopts, &inp->inp_route6, 1461 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 1462 NULL, NULL, inp); 1463 1464 if (error == EMSGSIZE && inp->inp_route6.ro_nh != NULL) 1465 mtu = inp->inp_route6.ro_nh->nh_mtu; 1466 } 1467 #endif /* INET6 */ 1468 #if defined(INET) && defined(INET6) 1469 else 1470 #endif 1471 #ifdef INET 1472 { 1473 ip->ip_len = htons(m->m_pkthdr.len); 1474 #ifdef INET6 1475 if (inp->inp_vflag & INP_IPV6PROTO) 1476 ip->ip_ttl = in6_selecthlim(inp, NULL); 1477 #endif /* INET6 */ 1478 /* 1479 * If we do path MTU discovery, then we set DF on every packet. 1480 * This might not be the best thing to do according to RFC3390 1481 * Section 2. However the tcp hostcache migitates the problem 1482 * so it affects only the first tcp connection with a host. 1483 * 1484 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1485 */ 1486 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) { 1487 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1488 if (tp->t_port == 0 || len < V_tcp_minmss) { 1489 ip->ip_off |= htons(IP_DF); 1490 } 1491 } else { 1492 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1493 } 1494 1495 if (tp->t_state == TCPS_SYN_SENT) 1496 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th); 1497 1498 TCP_PROBE5(send, NULL, tp, ip, tp, th); 1499 1500 #ifdef TCPPCAP 1501 /* Save packet, if requested. */ 1502 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1503 #endif 1504 1505 error = ip_output(m, inp->inp_options, &inp->inp_route, 1506 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, inp); 1507 1508 if (error == EMSGSIZE && inp->inp_route.ro_nh != NULL) 1509 mtu = inp->inp_route.ro_nh->nh_mtu; 1510 } 1511 #endif /* INET */ 1512 1513 if (lgb != NULL) { 1514 lgb->tlb_errno = error; 1515 lgb = NULL; 1516 } 1517 out: 1518 if (error == 0) 1519 tcp_account_for_send(tp, len, (tp->snd_nxt != tp->snd_max), 0, hw_tls); 1520 /* 1521 * In transmit state, time the transmission and arrange for 1522 * the retransmit. In persist state, just set snd_max. 1523 */ 1524 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1525 !tcp_timer_active(tp, TT_PERSIST)) { 1526 tcp_seq startseq = tp->snd_nxt; 1527 1528 /* 1529 * Advance snd_nxt over sequence space of this segment. 1530 */ 1531 if (flags & (TH_SYN|TH_FIN)) { 1532 if (flags & TH_SYN) 1533 tp->snd_nxt++; 1534 if (flags & TH_FIN) { 1535 tp->snd_nxt++; 1536 tp->t_flags |= TF_SENTFIN; 1537 } 1538 } 1539 if (sack_rxmit) 1540 goto timer; 1541 tp->snd_nxt += len; 1542 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1543 /* 1544 * Update "made progress" indication if we just 1545 * added new data to an empty socket buffer. 1546 */ 1547 if (tp->snd_una == tp->snd_max) 1548 tp->t_acktime = ticks; 1549 tp->snd_max = tp->snd_nxt; 1550 /* 1551 * Time this transmission if not a retransmission and 1552 * not currently timing anything. 1553 */ 1554 tp->t_sndtime = ticks; 1555 if (tp->t_rtttime == 0) { 1556 tp->t_rtttime = ticks; 1557 tp->t_rtseq = startseq; 1558 TCPSTAT_INC(tcps_segstimed); 1559 } 1560 #ifdef STATS 1561 if (!(tp->t_flags & TF_GPUTINPROG) && len) { 1562 tp->t_flags |= TF_GPUTINPROG; 1563 tp->gput_seq = startseq; 1564 tp->gput_ack = startseq + 1565 ulmin(sbavail(&so->so_snd) - off, sendwin); 1566 tp->gput_ts = tcp_ts_getticks(); 1567 } 1568 #endif /* STATS */ 1569 } 1570 1571 /* 1572 * Set retransmit timer if not currently set, 1573 * and not doing a pure ack or a keep-alive probe. 1574 * Initial value for retransmit timer is smoothed 1575 * round-trip time + 2 * round-trip time variance. 1576 * Initialize shift counter which is used for backoff 1577 * of retransmit time. 1578 */ 1579 timer: 1580 if (!tcp_timer_active(tp, TT_REXMT) && 1581 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1582 (tp->snd_nxt != tp->snd_una))) { 1583 if (tcp_timer_active(tp, TT_PERSIST)) { 1584 tcp_timer_activate(tp, TT_PERSIST, 0); 1585 tp->t_rxtshift = 0; 1586 } 1587 tcp_timer_activate(tp, TT_REXMT, TP_RXTCUR(tp)); 1588 } else if (len == 0 && sbavail(&so->so_snd) && 1589 !tcp_timer_active(tp, TT_REXMT) && 1590 !tcp_timer_active(tp, TT_PERSIST)) { 1591 /* 1592 * Avoid a situation where we do not set persist timer 1593 * after a zero window condition. For example: 1594 * 1) A -> B: packet with enough data to fill the window 1595 * 2) B -> A: ACK for #1 + new data (0 window 1596 * advertisement) 1597 * 3) A -> B: ACK for #2, 0 len packet 1598 * 1599 * In this case, A will not activate the persist timer, 1600 * because it chose to send a packet. Unless tcp_output 1601 * is called for some other reason (delayed ack timer, 1602 * another input packet from B, socket syscall), A will 1603 * not send zero window probes. 1604 * 1605 * So, if you send a 0-length packet, but there is data 1606 * in the socket buffer, and neither the rexmt or 1607 * persist timer is already set, then activate the 1608 * persist timer. 1609 */ 1610 tp->t_rxtshift = 0; 1611 tcp_setpersist(tp); 1612 } 1613 } else { 1614 /* 1615 * Persist case, update snd_max but since we are in 1616 * persist mode (no window) we do not update snd_nxt. 1617 */ 1618 int xlen = len; 1619 if (flags & TH_SYN) 1620 ++xlen; 1621 if (flags & TH_FIN) { 1622 ++xlen; 1623 tp->t_flags |= TF_SENTFIN; 1624 } 1625 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1626 tp->snd_max = tp->snd_nxt + xlen; 1627 } 1628 if ((error == 0) && 1629 (TCPS_HAVEESTABLISHED(tp->t_state) && 1630 (tp->t_flags & TF_SACK_PERMIT) && 1631 tp->rcv_numsacks > 0)) { 1632 /* Clean up any DSACK's sent */ 1633 tcp_clean_dsack_blocks(tp); 1634 } 1635 if (error) { 1636 /* 1637 * We know that the packet was lost, so back out the 1638 * sequence number advance, if any. 1639 * 1640 * If the error is EPERM the packet got blocked by the 1641 * local firewall. Normally we should terminate the 1642 * connection but the blocking may have been spurious 1643 * due to a firewall reconfiguration cycle. So we treat 1644 * it like a packet loss and let the retransmit timer and 1645 * timeouts do their work over time. 1646 * XXX: It is a POLA question whether calling tcp_drop right 1647 * away would be the really correct behavior instead. 1648 */ 1649 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1650 !tcp_timer_active(tp, TT_PERSIST)) && 1651 ((flags & TH_SYN) == 0) && 1652 (error != EPERM)) { 1653 if (sack_rxmit) { 1654 p->rxmit = SEQ_MIN(p->end, p->rxmit) - len; 1655 tp->sackhint.sack_bytes_rexmit -= len; 1656 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1657 ("sackhint bytes rtx >= 0")); 1658 KASSERT((flags & TH_FIN) == 0, 1659 ("error while FIN with SACK rxmit")); 1660 } else { 1661 tp->snd_nxt -= len; 1662 if (flags & TH_FIN) 1663 tp->snd_nxt--; 1664 } 1665 if (IN_RECOVERY(tp->t_flags)) 1666 tp->sackhint.prr_out -= len; 1667 } 1668 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1669 switch (error) { 1670 case EACCES: 1671 case EPERM: 1672 tp->t_softerror = error; 1673 return (error); 1674 case ENOBUFS: 1675 TCP_XMIT_TIMER_ASSERT(tp, len, flags); 1676 tp->snd_cwnd = tp->t_maxseg; 1677 return (0); 1678 case EMSGSIZE: 1679 /* 1680 * For some reason the interface we used initially 1681 * to send segments changed to another or lowered 1682 * its MTU. 1683 * If TSO was active we either got an interface 1684 * without TSO capabilits or TSO was turned off. 1685 * If we obtained mtu from ip_output() then update 1686 * it and try again. 1687 */ 1688 if (tso) 1689 tp->t_flags &= ~TF_TSO; 1690 if (mtu != 0) { 1691 tcp_mss_update(tp, -1, mtu, NULL, NULL); 1692 goto again; 1693 } 1694 return (error); 1695 case EHOSTDOWN: 1696 case EHOSTUNREACH: 1697 case ENETDOWN: 1698 case ENETUNREACH: 1699 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1700 tp->t_softerror = error; 1701 return (0); 1702 } 1703 /* FALLTHROUGH */ 1704 default: 1705 return (error); 1706 } 1707 } 1708 TCPSTAT_INC(tcps_sndtotal); 1709 1710 /* 1711 * Data sent (as far as we can tell). 1712 * If this advertises a larger window than any other segment, 1713 * then remember the size of the advertised window. 1714 * Any pending ACK has now been sent. 1715 */ 1716 if (SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1717 tp->rcv_adv = tp->rcv_nxt + recwin; 1718 tp->last_ack_sent = tp->rcv_nxt; 1719 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1720 if (tcp_timer_active(tp, TT_DELACK)) 1721 tcp_timer_activate(tp, TT_DELACK, 0); 1722 if (sendalot) 1723 goto again; 1724 return (0); 1725 } 1726 1727 void 1728 tcp_setpersist(struct tcpcb *tp) 1729 { 1730 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1731 int tt; 1732 int maxunacktime; 1733 1734 tp->t_flags &= ~TF_PREVVALID; 1735 if (tcp_timer_active(tp, TT_REXMT)) 1736 panic("tcp_setpersist: retransmit pending"); 1737 /* 1738 * If the state is already closed, don't bother. 1739 */ 1740 if (tp->t_state == TCPS_CLOSED) 1741 return; 1742 1743 /* 1744 * Start/restart persistence timer. 1745 */ 1746 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1747 tcp_persmin, tcp_persmax); 1748 if (TP_MAXUNACKTIME(tp) && tp->t_acktime) { 1749 maxunacktime = tp->t_acktime + TP_MAXUNACKTIME(tp) - ticks; 1750 if (maxunacktime < 1) 1751 maxunacktime = 1; 1752 if (maxunacktime < tt) 1753 tt = maxunacktime; 1754 } 1755 tcp_timer_activate(tp, TT_PERSIST, tt); 1756 if (tp->t_rxtshift < V_tcp_retries) 1757 tp->t_rxtshift++; 1758 } 1759 1760 /* 1761 * Insert TCP options according to the supplied parameters to the place 1762 * optp in a consistent way. Can handle unaligned destinations. 1763 * 1764 * The order of the option processing is crucial for optimal packing and 1765 * alignment for the scarce option space. 1766 * 1767 * The optimal order for a SYN/SYN-ACK segment is: 1768 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1769 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1770 * 1771 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1772 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1773 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1774 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1775 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1776 */ 1777 int 1778 tcp_addoptions(struct tcpopt *to, u_char *optp) 1779 { 1780 u_int32_t mask, optlen = 0; 1781 1782 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1783 if ((to->to_flags & mask) != mask) 1784 continue; 1785 if (optlen == TCP_MAXOLEN) 1786 break; 1787 switch (to->to_flags & mask) { 1788 case TOF_MSS: 1789 while (optlen % 4) { 1790 optlen += TCPOLEN_NOP; 1791 *optp++ = TCPOPT_NOP; 1792 } 1793 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1794 continue; 1795 optlen += TCPOLEN_MAXSEG; 1796 *optp++ = TCPOPT_MAXSEG; 1797 *optp++ = TCPOLEN_MAXSEG; 1798 to->to_mss = htons(to->to_mss); 1799 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1800 optp += sizeof(to->to_mss); 1801 break; 1802 case TOF_SCALE: 1803 while (!optlen || optlen % 2 != 1) { 1804 optlen += TCPOLEN_NOP; 1805 *optp++ = TCPOPT_NOP; 1806 } 1807 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1808 continue; 1809 optlen += TCPOLEN_WINDOW; 1810 *optp++ = TCPOPT_WINDOW; 1811 *optp++ = TCPOLEN_WINDOW; 1812 *optp++ = to->to_wscale; 1813 break; 1814 case TOF_SACKPERM: 1815 while (optlen % 2) { 1816 optlen += TCPOLEN_NOP; 1817 *optp++ = TCPOPT_NOP; 1818 } 1819 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1820 continue; 1821 optlen += TCPOLEN_SACK_PERMITTED; 1822 *optp++ = TCPOPT_SACK_PERMITTED; 1823 *optp++ = TCPOLEN_SACK_PERMITTED; 1824 break; 1825 case TOF_TS: 1826 while (!optlen || optlen % 4 != 2) { 1827 optlen += TCPOLEN_NOP; 1828 *optp++ = TCPOPT_NOP; 1829 } 1830 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1831 continue; 1832 optlen += TCPOLEN_TIMESTAMP; 1833 *optp++ = TCPOPT_TIMESTAMP; 1834 *optp++ = TCPOLEN_TIMESTAMP; 1835 to->to_tsval = htonl(to->to_tsval); 1836 to->to_tsecr = htonl(to->to_tsecr); 1837 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1838 optp += sizeof(to->to_tsval); 1839 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1840 optp += sizeof(to->to_tsecr); 1841 break; 1842 case TOF_SIGNATURE: 1843 { 1844 int siglen = TCPOLEN_SIGNATURE - 2; 1845 1846 while (!optlen || optlen % 4 != 2) { 1847 optlen += TCPOLEN_NOP; 1848 *optp++ = TCPOPT_NOP; 1849 } 1850 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) { 1851 to->to_flags &= ~TOF_SIGNATURE; 1852 continue; 1853 } 1854 optlen += TCPOLEN_SIGNATURE; 1855 *optp++ = TCPOPT_SIGNATURE; 1856 *optp++ = TCPOLEN_SIGNATURE; 1857 to->to_signature = optp; 1858 while (siglen--) 1859 *optp++ = 0; 1860 break; 1861 } 1862 case TOF_SACK: 1863 { 1864 int sackblks = 0; 1865 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1866 tcp_seq sack_seq; 1867 1868 while (!optlen || optlen % 4 != 2) { 1869 optlen += TCPOLEN_NOP; 1870 *optp++ = TCPOPT_NOP; 1871 } 1872 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1873 continue; 1874 optlen += TCPOLEN_SACKHDR; 1875 *optp++ = TCPOPT_SACK; 1876 sackblks = min(to->to_nsacks, 1877 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1878 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1879 while (sackblks--) { 1880 sack_seq = htonl(sack->start); 1881 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1882 optp += sizeof(sack_seq); 1883 sack_seq = htonl(sack->end); 1884 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1885 optp += sizeof(sack_seq); 1886 optlen += TCPOLEN_SACK; 1887 sack++; 1888 } 1889 TCPSTAT_INC(tcps_sack_send_blocks); 1890 break; 1891 } 1892 case TOF_FASTOPEN: 1893 { 1894 int total_len; 1895 1896 /* XXX is there any point to aligning this option? */ 1897 total_len = TCPOLEN_FAST_OPEN_EMPTY + to->to_tfo_len; 1898 if (TCP_MAXOLEN - optlen < total_len) { 1899 to->to_flags &= ~TOF_FASTOPEN; 1900 continue; 1901 } 1902 *optp++ = TCPOPT_FAST_OPEN; 1903 *optp++ = total_len; 1904 if (to->to_tfo_len > 0) { 1905 bcopy(to->to_tfo_cookie, optp, to->to_tfo_len); 1906 optp += to->to_tfo_len; 1907 } 1908 optlen += total_len; 1909 break; 1910 } 1911 default: 1912 panic("%s: unknown TCP option type", __func__); 1913 break; 1914 } 1915 } 1916 1917 /* Terminate and pad TCP options to a 4 byte boundary. */ 1918 if (optlen % 4) { 1919 optlen += TCPOLEN_EOL; 1920 *optp++ = TCPOPT_EOL; 1921 } 1922 /* 1923 * According to RFC 793 (STD0007): 1924 * "The content of the header beyond the End-of-Option option 1925 * must be header padding (i.e., zero)." 1926 * and later: "The padding is composed of zeros." 1927 */ 1928 while (optlen % 4) { 1929 optlen += TCPOLEN_PAD; 1930 *optp++ = TCPOPT_PAD; 1931 } 1932 1933 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1934 return (optlen); 1935 } 1936 1937 /* 1938 * This is a copy of m_copym(), taking the TSO segment size/limit 1939 * constraints into account, and advancing the sndptr as it goes. 1940 */ 1941 struct mbuf * 1942 tcp_m_copym(struct mbuf *m, int32_t off0, int32_t *plen, 1943 int32_t seglimit, int32_t segsize, struct sockbuf *sb, bool hw_tls) 1944 { 1945 #ifdef KERN_TLS 1946 struct ktls_session *tls, *ntls; 1947 struct mbuf *start __diagused; 1948 #endif 1949 struct mbuf *n, **np; 1950 struct mbuf *top; 1951 int32_t off = off0; 1952 int32_t len = *plen; 1953 int32_t fragsize; 1954 int32_t len_cp = 0; 1955 int32_t *pkthdrlen; 1956 uint32_t mlen, frags; 1957 bool copyhdr; 1958 1959 KASSERT(off >= 0, ("tcp_m_copym, negative off %d", off)); 1960 KASSERT(len >= 0, ("tcp_m_copym, negative len %d", len)); 1961 if (off == 0 && m->m_flags & M_PKTHDR) 1962 copyhdr = true; 1963 else 1964 copyhdr = false; 1965 while (off > 0) { 1966 KASSERT(m != NULL, ("tcp_m_copym, offset > size of mbuf chain")); 1967 if (off < m->m_len) 1968 break; 1969 off -= m->m_len; 1970 if ((sb) && (m == sb->sb_sndptr)) { 1971 sb->sb_sndptroff += m->m_len; 1972 sb->sb_sndptr = m->m_next; 1973 } 1974 m = m->m_next; 1975 } 1976 np = ⊤ 1977 top = NULL; 1978 pkthdrlen = NULL; 1979 #ifdef KERN_TLS 1980 if (hw_tls && (m->m_flags & M_EXTPG)) 1981 tls = m->m_epg_tls; 1982 else 1983 tls = NULL; 1984 start = m; 1985 #endif 1986 while (len > 0) { 1987 if (m == NULL) { 1988 KASSERT(len == M_COPYALL, 1989 ("tcp_m_copym, length > size of mbuf chain")); 1990 *plen = len_cp; 1991 if (pkthdrlen != NULL) 1992 *pkthdrlen = len_cp; 1993 break; 1994 } 1995 #ifdef KERN_TLS 1996 if (hw_tls) { 1997 if (m->m_flags & M_EXTPG) 1998 ntls = m->m_epg_tls; 1999 else 2000 ntls = NULL; 2001 2002 /* 2003 * Avoid mixing TLS records with handshake 2004 * data or TLS records from different 2005 * sessions. 2006 */ 2007 if (tls != ntls) { 2008 MPASS(m != start); 2009 *plen = len_cp; 2010 if (pkthdrlen != NULL) 2011 *pkthdrlen = len_cp; 2012 break; 2013 } 2014 } 2015 #endif 2016 mlen = min(len, m->m_len - off); 2017 if (seglimit) { 2018 /* 2019 * For M_EXTPG mbufs, add 3 segments 2020 * + 1 in case we are crossing page boundaries 2021 * + 2 in case the TLS hdr/trailer are used 2022 * It is cheaper to just add the segments 2023 * than it is to take the cache miss to look 2024 * at the mbuf ext_pgs state in detail. 2025 */ 2026 if (m->m_flags & M_EXTPG) { 2027 fragsize = min(segsize, PAGE_SIZE); 2028 frags = 3; 2029 } else { 2030 fragsize = segsize; 2031 frags = 0; 2032 } 2033 2034 /* Break if we really can't fit anymore. */ 2035 if ((frags + 1) >= seglimit) { 2036 *plen = len_cp; 2037 if (pkthdrlen != NULL) 2038 *pkthdrlen = len_cp; 2039 break; 2040 } 2041 2042 /* 2043 * Reduce size if you can't copy the whole 2044 * mbuf. If we can't copy the whole mbuf, also 2045 * adjust len so the loop will end after this 2046 * mbuf. 2047 */ 2048 if ((frags + howmany(mlen, fragsize)) >= seglimit) { 2049 mlen = (seglimit - frags - 1) * fragsize; 2050 len = mlen; 2051 *plen = len_cp + len; 2052 if (pkthdrlen != NULL) 2053 *pkthdrlen = *plen; 2054 } 2055 frags += howmany(mlen, fragsize); 2056 if (frags == 0) 2057 frags++; 2058 seglimit -= frags; 2059 KASSERT(seglimit > 0, 2060 ("%s: seglimit went too low", __func__)); 2061 } 2062 if (copyhdr) 2063 n = m_gethdr(M_NOWAIT, m->m_type); 2064 else 2065 n = m_get(M_NOWAIT, m->m_type); 2066 *np = n; 2067 if (n == NULL) 2068 goto nospace; 2069 if (copyhdr) { 2070 if (!m_dup_pkthdr(n, m, M_NOWAIT)) 2071 goto nospace; 2072 if (len == M_COPYALL) 2073 n->m_pkthdr.len -= off0; 2074 else 2075 n->m_pkthdr.len = len; 2076 pkthdrlen = &n->m_pkthdr.len; 2077 copyhdr = false; 2078 } 2079 n->m_len = mlen; 2080 len_cp += n->m_len; 2081 if (m->m_flags & (M_EXT | M_EXTPG)) { 2082 n->m_data = m->m_data + off; 2083 mb_dupcl(n, m); 2084 } else 2085 bcopy(mtod(m, caddr_t)+off, mtod(n, caddr_t), 2086 (u_int)n->m_len); 2087 2088 if (sb && (sb->sb_sndptr == m) && 2089 ((n->m_len + off) >= m->m_len) && m->m_next) { 2090 sb->sb_sndptroff += m->m_len; 2091 sb->sb_sndptr = m->m_next; 2092 } 2093 off = 0; 2094 if (len != M_COPYALL) { 2095 len -= n->m_len; 2096 } 2097 m = m->m_next; 2098 np = &n->m_next; 2099 } 2100 return (top); 2101 nospace: 2102 m_freem(top); 2103 return (NULL); 2104 } 2105 2106 void 2107 tcp_sndbuf_autoscale(struct tcpcb *tp, struct socket *so, uint32_t sendwin) 2108 { 2109 2110 /* 2111 * Automatic sizing of send socket buffer. Often the send buffer 2112 * size is not optimally adjusted to the actual network conditions 2113 * at hand (delay bandwidth product). Setting the buffer size too 2114 * small limits throughput on links with high bandwidth and high 2115 * delay (eg. trans-continental/oceanic links). Setting the 2116 * buffer size too big consumes too much real kernel memory, 2117 * especially with many connections on busy servers. 2118 * 2119 * The criteria to step up the send buffer one notch are: 2120 * 1. receive window of remote host is larger than send buffer 2121 * (with a fudge factor of 5/4th); 2122 * 2. send buffer is filled to 7/8th with data (so we actually 2123 * have data to make use of it); 2124 * 3. send buffer fill has not hit maximal automatic size; 2125 * 4. our send window (slow start and cogestion controlled) is 2126 * larger than sent but unacknowledged data in send buffer. 2127 * 2128 * The remote host receive window scaling factor may limit the 2129 * growing of the send buffer before it reaches its allowed 2130 * maximum. 2131 * 2132 * It scales directly with slow start or congestion window 2133 * and does at most one step per received ACK. This fast 2134 * scaling has the drawback of growing the send buffer beyond 2135 * what is strictly necessary to make full use of a given 2136 * delay*bandwidth product. However testing has shown this not 2137 * to be much of an problem. At worst we are trading wasting 2138 * of available bandwidth (the non-use of it) for wasting some 2139 * socket buffer memory. 2140 * 2141 * TODO: Shrink send buffer during idle periods together 2142 * with congestion window. Requires another timer. Has to 2143 * wait for upcoming tcp timer rewrite. 2144 * 2145 * XXXGL: should there be used sbused() or sbavail()? 2146 */ 2147 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 2148 int lowat; 2149 2150 lowat = V_tcp_sendbuf_auto_lowat ? so->so_snd.sb_lowat : 0; 2151 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat - lowat && 2152 sbused(&so->so_snd) >= 2153 (so->so_snd.sb_hiwat / 8 * 7) - lowat && 2154 sbused(&so->so_snd) < V_tcp_autosndbuf_max && 2155 sendwin >= (sbused(&so->so_snd) - 2156 (tp->snd_nxt - tp->snd_una))) { 2157 if (!sbreserve_locked(so, SO_SND, 2158 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 2159 V_tcp_autosndbuf_max), curthread)) 2160 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 2161 } 2162 } 2163 } 2164