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. Skip this if the connection is in T/TCP 655 * half-open state. 656 */ 657 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 658 !(tp->t_flags & TF_DELACK) && 659 !TCPS_HAVERCVDFIN(tp->t_state)) { 660 /* 661 * "adv" is the amount we could increase the window, 662 * taking into account that we are limited by 663 * TCP_MAXWIN << tp->rcv_scale. 664 */ 665 int32_t adv; 666 int oldwin; 667 668 adv = recwin; 669 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { 670 oldwin = (tp->rcv_adv - tp->rcv_nxt); 671 if (adv > oldwin) 672 adv -= oldwin; 673 else 674 adv = 0; 675 } else 676 oldwin = 0; 677 678 /* 679 * If the new window size ends up being the same as or less 680 * than the old size when it is scaled, then don't force 681 * a window update. 682 */ 683 if (oldwin >> tp->rcv_scale >= (adv + oldwin) >> tp->rcv_scale) 684 goto dontupdate; 685 686 if (adv >= (int32_t)(2 * tp->t_maxseg) && 687 (adv >= (int32_t)(so->so_rcv.sb_hiwat / 4) || 688 recwin <= (so->so_rcv.sb_hiwat / 8) || 689 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg || 690 adv >= TCP_MAXWIN << tp->rcv_scale)) 691 goto send; 692 if (2 * adv >= (int32_t)so->so_rcv.sb_hiwat) 693 goto send; 694 } 695 dontupdate: 696 697 /* 698 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 699 * is also a catch-all for the retransmit timer timeout case. 700 */ 701 if (tp->t_flags & TF_ACKNOW) 702 goto send; 703 if ((flags & TH_RST) || 704 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 705 goto send; 706 if (SEQ_GT(tp->snd_up, tp->snd_una)) 707 goto send; 708 /* 709 * If our state indicates that FIN should be sent 710 * and we have not yet done so, then we need to send. 711 */ 712 if (flags & TH_FIN && 713 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 714 goto send; 715 /* 716 * In SACK, it is possible for tcp_output to fail to send a segment 717 * after the retransmission timer has been turned off. Make sure 718 * that the retransmission timer is set. 719 */ 720 if ((tp->t_flags & TF_SACK_PERMIT) && 721 SEQ_GT(tp->snd_max, tp->snd_una) && 722 !tcp_timer_active(tp, TT_REXMT) && 723 !tcp_timer_active(tp, TT_PERSIST)) { 724 tcp_timer_activate(tp, TT_REXMT, TP_RXTCUR(tp)); 725 goto just_return; 726 } 727 /* 728 * TCP window updates are not reliable, rather a polling protocol 729 * using ``persist'' packets is used to insure receipt of window 730 * updates. The three ``states'' for the output side are: 731 * idle not doing retransmits or persists 732 * persisting to move a small or zero window 733 * (re)transmitting and thereby not persisting 734 * 735 * tcp_timer_active(tp, TT_PERSIST) 736 * is true when we are in persist state. 737 * (tp->t_flags & TF_FORCEDATA) 738 * is set when we are called to send a persist packet. 739 * tcp_timer_active(tp, TT_REXMT) 740 * is set when we are retransmitting 741 * The output side is idle when both timers are zero. 742 * 743 * If send window is too small, there is data to transmit, and no 744 * retransmit or persist is pending, then go to persist state. 745 * If nothing happens soon, send when timer expires: 746 * if window is nonzero, transmit what we can, 747 * otherwise force out a byte. 748 */ 749 if (sbavail(&so->so_snd) && !tcp_timer_active(tp, TT_REXMT) && 750 !tcp_timer_active(tp, TT_PERSIST)) { 751 tp->t_rxtshift = 0; 752 tcp_setpersist(tp); 753 } 754 755 /* 756 * No reason to send a segment, just return. 757 */ 758 just_return: 759 SOCKBUF_UNLOCK(&so->so_snd); 760 return (0); 761 762 send: 763 SOCKBUF_LOCK_ASSERT(&so->so_snd); 764 if (len > 0) { 765 if (len >= tp->t_maxseg) 766 tp->t_flags2 |= TF2_PLPMTU_MAXSEGSNT; 767 else 768 tp->t_flags2 &= ~TF2_PLPMTU_MAXSEGSNT; 769 } 770 /* 771 * Before ESTABLISHED, force sending of initial options 772 * unless TCP set not to do any options. 773 * NOTE: we assume that the IP/TCP header plus TCP options 774 * always fit in a single mbuf, leaving room for a maximum 775 * link header, i.e. 776 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 777 */ 778 optlen = 0; 779 #ifdef INET6 780 if (isipv6) 781 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 782 else 783 #endif 784 hdrlen = sizeof (struct tcpiphdr); 785 786 if (flags & TH_SYN) { 787 tp->snd_nxt = tp->iss; 788 } 789 790 /* 791 * Compute options for segment. 792 * We only have to care about SYN and established connection 793 * segments. Options for SYN-ACK segments are handled in TCP 794 * syncache. 795 */ 796 to.to_flags = 0; 797 if ((tp->t_flags & TF_NOOPT) == 0) { 798 /* Maximum segment size. */ 799 if (flags & TH_SYN) { 800 to.to_mss = tcp_mssopt(&inp->inp_inc); 801 if (tp->t_port) 802 to.to_mss -= V_tcp_udp_tunneling_overhead; 803 to.to_flags |= TOF_MSS; 804 805 /* 806 * On SYN or SYN|ACK transmits on TFO connections, 807 * only include the TFO option if it is not a 808 * retransmit, as the presence of the TFO option may 809 * have caused the original SYN or SYN|ACK to have 810 * been dropped by a middlebox. 811 */ 812 if (IS_FASTOPEN(tp->t_flags) && 813 (tp->t_rxtshift == 0)) { 814 if (tp->t_state == TCPS_SYN_RECEIVED) { 815 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN; 816 to.to_tfo_cookie = 817 (u_int8_t *)&tp->t_tfo_cookie.server; 818 to.to_flags |= TOF_FASTOPEN; 819 wanted_cookie = 1; 820 } else if (tp->t_state == TCPS_SYN_SENT) { 821 to.to_tfo_len = 822 tp->t_tfo_client_cookie_len; 823 to.to_tfo_cookie = 824 tp->t_tfo_cookie.client; 825 to.to_flags |= TOF_FASTOPEN; 826 wanted_cookie = 1; 827 /* 828 * If we wind up having more data to 829 * send with the SYN than can fit in 830 * one segment, don't send any more 831 * until the SYN|ACK comes back from 832 * the other end. 833 */ 834 dont_sendalot = 1; 835 } 836 } 837 } 838 /* Window scaling. */ 839 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 840 to.to_wscale = tp->request_r_scale; 841 to.to_flags |= TOF_SCALE; 842 } 843 /* Timestamps. */ 844 if ((tp->t_flags & TF_RCVD_TSTMP) || 845 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 846 curticks = tcp_ts_getticks(); 847 to.to_tsval = curticks + tp->ts_offset; 848 to.to_tsecr = tp->ts_recent; 849 to.to_flags |= TOF_TS; 850 if (tp->t_rxtshift == 1) 851 tp->t_badrxtwin = curticks; 852 } 853 854 /* Set receive buffer autosizing timestamp. */ 855 if (tp->rfbuf_ts == 0 && 856 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 857 tp->rfbuf_ts = tcp_ts_getticks(); 858 859 /* Selective ACK's. */ 860 if (tp->t_flags & TF_SACK_PERMIT) { 861 if (flags & TH_SYN) 862 to.to_flags |= TOF_SACKPERM; 863 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 864 tp->rcv_numsacks > 0) { 865 to.to_flags |= TOF_SACK; 866 to.to_nsacks = tp->rcv_numsacks; 867 to.to_sacks = (u_char *)tp->sackblks; 868 } 869 } 870 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 871 /* TCP-MD5 (RFC2385). */ 872 /* 873 * Check that TCP_MD5SIG is enabled in tcpcb to 874 * account the size needed to set this TCP option. 875 */ 876 if (tp->t_flags & TF_SIGNATURE) 877 to.to_flags |= TOF_SIGNATURE; 878 #endif /* TCP_SIGNATURE */ 879 880 /* Processing the options. */ 881 hdrlen += optlen = tcp_addoptions(&to, opt); 882 /* 883 * If we wanted a TFO option to be added, but it was unable 884 * to fit, ensure no data is sent. 885 */ 886 if (IS_FASTOPEN(tp->t_flags) && wanted_cookie && 887 !(to.to_flags & TOF_FASTOPEN)) 888 len = 0; 889 } 890 if (tp->t_port) { 891 if (V_tcp_udp_tunneling_port == 0) { 892 /* The port was removed?? */ 893 SOCKBUF_UNLOCK(&so->so_snd); 894 return (EHOSTUNREACH); 895 } 896 hdrlen += sizeof(struct udphdr); 897 } 898 /* 899 * Adjust data length if insertion of options will 900 * bump the packet length beyond the t_maxseg length. 901 * Clear the FIN bit because we cut off the tail of 902 * the segment. 903 */ 904 if (len + optlen + ipoptlen > tp->t_maxseg) { 905 flags &= ~TH_FIN; 906 907 if (tso) { 908 u_int if_hw_tsomax; 909 u_int moff; 910 int max_len; 911 912 /* extract TSO information */ 913 if_hw_tsomax = tp->t_tsomax; 914 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount; 915 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize; 916 917 /* 918 * Limit a TSO burst to prevent it from 919 * overflowing or exceeding the maximum length 920 * allowed by the network interface: 921 */ 922 KASSERT(ipoptlen == 0, 923 ("%s: TSO can't do IP options", __func__)); 924 925 /* 926 * Check if we should limit by maximum payload 927 * length: 928 */ 929 if (if_hw_tsomax != 0) { 930 /* compute maximum TSO length */ 931 max_len = (if_hw_tsomax - hdrlen - 932 max_linkhdr); 933 if (max_len <= 0) { 934 len = 0; 935 } else if (len > max_len) { 936 sendalot = 1; 937 len = max_len; 938 } 939 } 940 941 /* 942 * Prevent the last segment from being 943 * fractional unless the send sockbuf can be 944 * emptied: 945 */ 946 max_len = (tp->t_maxseg - optlen); 947 if (((uint32_t)off + (uint32_t)len) < 948 sbavail(&so->so_snd)) { 949 moff = len % max_len; 950 if (moff != 0) { 951 len -= moff; 952 sendalot = 1; 953 } 954 } 955 956 /* 957 * In case there are too many small fragments 958 * don't use TSO: 959 */ 960 if (len <= max_len) { 961 len = max_len; 962 sendalot = 1; 963 tso = 0; 964 } 965 966 /* 967 * Send the FIN in a separate segment 968 * after the bulk sending is done. 969 * We don't trust the TSO implementations 970 * to clear the FIN flag on all but the 971 * last segment. 972 */ 973 if (tp->t_flags & TF_NEEDFIN) 974 sendalot = 1; 975 } else { 976 if (optlen + ipoptlen >= tp->t_maxseg) { 977 /* 978 * Since we don't have enough space to put 979 * the IP header chain and the TCP header in 980 * one packet as required by RFC 7112, don't 981 * send it. Also ensure that at least one 982 * byte of the payload can be put into the 983 * TCP segment. 984 */ 985 SOCKBUF_UNLOCK(&so->so_snd); 986 error = EMSGSIZE; 987 sack_rxmit = 0; 988 goto out; 989 } 990 len = tp->t_maxseg - optlen - ipoptlen; 991 sendalot = 1; 992 if (dont_sendalot) 993 sendalot = 0; 994 } 995 } else 996 tso = 0; 997 998 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 999 ("%s: len > IP_MAXPACKET", __func__)); 1000 1001 /*#ifdef DIAGNOSTIC*/ 1002 #ifdef INET6 1003 if (max_linkhdr + hdrlen > MCLBYTES) 1004 #else 1005 if (max_linkhdr + hdrlen > MHLEN) 1006 #endif 1007 panic("tcphdr too big"); 1008 /*#endif*/ 1009 1010 /* 1011 * This KASSERT is here to catch edge cases at a well defined place. 1012 * Before, those had triggered (random) panic conditions further down. 1013 */ 1014 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 1015 1016 /* 1017 * Grab a header mbuf, attaching a copy of data to 1018 * be transmitted, and initialize the header from 1019 * the template for sends on this connection. 1020 */ 1021 if (len) { 1022 struct mbuf *mb; 1023 struct sockbuf *msb; 1024 u_int moff; 1025 1026 if ((tp->t_flags & TF_FORCEDATA) && len == 1) { 1027 TCPSTAT_INC(tcps_sndprobe); 1028 #ifdef STATS 1029 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1030 stats_voi_update_abs_u32(tp->t_stats, 1031 VOI_TCP_RETXPB, len); 1032 else 1033 stats_voi_update_abs_u64(tp->t_stats, 1034 VOI_TCP_TXPB, len); 1035 #endif /* STATS */ 1036 } else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 1037 tp->t_sndrexmitpack++; 1038 TCPSTAT_INC(tcps_sndrexmitpack); 1039 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 1040 #ifdef STATS 1041 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_RETXPB, 1042 len); 1043 #endif /* STATS */ 1044 } else { 1045 TCPSTAT_INC(tcps_sndpack); 1046 TCPSTAT_ADD(tcps_sndbyte, len); 1047 #ifdef STATS 1048 stats_voi_update_abs_u64(tp->t_stats, VOI_TCP_TXPB, 1049 len); 1050 #endif /* STATS */ 1051 } 1052 #ifdef INET6 1053 if (MHLEN < hdrlen + max_linkhdr) 1054 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR); 1055 else 1056 #endif 1057 m = m_gethdr(M_NOWAIT, MT_DATA); 1058 1059 if (m == NULL) { 1060 SOCKBUF_UNLOCK(&so->so_snd); 1061 error = ENOBUFS; 1062 sack_rxmit = 0; 1063 goto out; 1064 } 1065 1066 m->m_data += max_linkhdr; 1067 m->m_len = hdrlen; 1068 1069 /* 1070 * Start the m_copy functions from the closest mbuf 1071 * to the offset in the socket buffer chain. 1072 */ 1073 mb = sbsndptr_noadv(&so->so_snd, off, &moff); 1074 if (len <= MHLEN - hdrlen - max_linkhdr && !hw_tls) { 1075 m_copydata(mb, moff, len, 1076 mtod(m, caddr_t) + hdrlen); 1077 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1078 sbsndptr_adv(&so->so_snd, mb, len); 1079 m->m_len += len; 1080 } else { 1081 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1082 msb = NULL; 1083 else 1084 msb = &so->so_snd; 1085 m->m_next = tcp_m_copym(mb, moff, 1086 &len, if_hw_tsomaxsegcount, 1087 if_hw_tsomaxsegsize, msb, hw_tls); 1088 if (len <= (tp->t_maxseg - optlen)) { 1089 /* 1090 * Must have ran out of mbufs for the copy 1091 * shorten it to no longer need tso. Lets 1092 * not put on sendalot since we are low on 1093 * mbufs. 1094 */ 1095 tso = 0; 1096 } 1097 if (m->m_next == NULL) { 1098 SOCKBUF_UNLOCK(&so->so_snd); 1099 (void) m_free(m); 1100 error = ENOBUFS; 1101 sack_rxmit = 0; 1102 goto out; 1103 } 1104 } 1105 1106 /* 1107 * If we're sending everything we've got, set PUSH. 1108 * (This will keep happy those implementations which only 1109 * give data to the user when a buffer fills or 1110 * a PUSH comes in.) 1111 */ 1112 if (((uint32_t)off + (uint32_t)len == sbused(&so->so_snd)) && 1113 !(flags & TH_SYN)) 1114 flags |= TH_PUSH; 1115 SOCKBUF_UNLOCK(&so->so_snd); 1116 } else { 1117 SOCKBUF_UNLOCK(&so->so_snd); 1118 if (tp->t_flags & TF_ACKNOW) 1119 TCPSTAT_INC(tcps_sndacks); 1120 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 1121 TCPSTAT_INC(tcps_sndctrl); 1122 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 1123 TCPSTAT_INC(tcps_sndurg); 1124 else 1125 TCPSTAT_INC(tcps_sndwinup); 1126 1127 m = m_gethdr(M_NOWAIT, MT_DATA); 1128 if (m == NULL) { 1129 error = ENOBUFS; 1130 sack_rxmit = 0; 1131 goto out; 1132 } 1133 #ifdef INET6 1134 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 1135 MHLEN >= hdrlen) { 1136 M_ALIGN(m, hdrlen); 1137 } else 1138 #endif 1139 m->m_data += max_linkhdr; 1140 m->m_len = hdrlen; 1141 } 1142 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 1143 m->m_pkthdr.rcvif = (struct ifnet *)0; 1144 #ifdef MAC 1145 mac_inpcb_create_mbuf(inp, m); 1146 #endif 1147 #ifdef INET6 1148 if (isipv6) { 1149 ip6 = mtod(m, struct ip6_hdr *); 1150 if (tp->t_port) { 1151 udp = (struct udphdr *)((caddr_t)ip6 + sizeof(struct ip6_hdr)); 1152 udp->uh_sport = htons(V_tcp_udp_tunneling_port); 1153 udp->uh_dport = tp->t_port; 1154 ulen = hdrlen + len - sizeof(struct ip6_hdr); 1155 udp->uh_ulen = htons(ulen); 1156 th = (struct tcphdr *)(udp + 1); 1157 } else { 1158 th = (struct tcphdr *)(ip6 + 1); 1159 } 1160 tcpip_fillheaders(inp, tp->t_port, ip6, th); 1161 } else 1162 #endif /* INET6 */ 1163 { 1164 ip = mtod(m, struct ip *); 1165 if (tp->t_port) { 1166 udp = (struct udphdr *)((caddr_t)ip + sizeof(struct ip)); 1167 udp->uh_sport = htons(V_tcp_udp_tunneling_port); 1168 udp->uh_dport = tp->t_port; 1169 ulen = hdrlen + len - sizeof(struct ip); 1170 udp->uh_ulen = htons(ulen); 1171 th = (struct tcphdr *)(udp + 1); 1172 } else 1173 th = (struct tcphdr *)(ip + 1); 1174 tcpip_fillheaders(inp, tp->t_port, ip, th); 1175 } 1176 1177 /* 1178 * Fill in fields, remembering maximum advertised 1179 * window for use in delaying messages about window sizes. 1180 * If resending a FIN, be sure not to use a new sequence number. 1181 */ 1182 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 1183 tp->snd_nxt == tp->snd_max) 1184 tp->snd_nxt--; 1185 /* 1186 * If we are starting a connection, send ECN setup 1187 * SYN packet. If we are on a retransmit, we may 1188 * resend those bits a number of times as per 1189 * RFC 3168. 1190 */ 1191 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) { 1192 flags |= tcp_ecn_output_syn_sent(tp); 1193 } 1194 /* Also handle parallel SYN for ECN */ 1195 if ((TCPS_HAVERCVDSYN(tp->t_state)) && 1196 (tp->t_flags2 & (TF2_ECN_PERMIT | TF2_ACE_PERMIT))) { 1197 int ect = tcp_ecn_output_established(tp, &flags, len, sack_rxmit); 1198 if ((tp->t_state == TCPS_SYN_RECEIVED) && 1199 (tp->t_flags2 & TF2_ECN_SND_ECE)) 1200 tp->t_flags2 &= ~TF2_ECN_SND_ECE; 1201 #ifdef INET6 1202 if (isipv6) { 1203 ip6->ip6_flow &= ~htonl(IPTOS_ECN_MASK << IPV6_FLOWLABEL_LEN); 1204 ip6->ip6_flow |= htonl(ect << IPV6_FLOWLABEL_LEN); 1205 } 1206 else 1207 #endif 1208 { 1209 ip->ip_tos &= ~IPTOS_ECN_MASK; 1210 ip->ip_tos |= ect; 1211 } 1212 } 1213 1214 /* 1215 * If we are doing retransmissions, then snd_nxt will 1216 * not reflect the first unsent octet. For ACK only 1217 * packets, we do not want the sequence number of the 1218 * retransmitted packet, we want the sequence number 1219 * of the next unsent octet. So, if there is no data 1220 * (and no SYN or FIN), use snd_max instead of snd_nxt 1221 * when filling in ti_seq. But if we are in persist 1222 * state, snd_max might reflect one byte beyond the 1223 * right edge of the window, so use snd_nxt in that 1224 * case, since we know we aren't doing a retransmission. 1225 * (retransmit and persist are mutually exclusive...) 1226 */ 1227 if (sack_rxmit == 0) { 1228 if (len || (flags & (TH_SYN|TH_FIN)) || 1229 tcp_timer_active(tp, TT_PERSIST)) 1230 th->th_seq = htonl(tp->snd_nxt); 1231 else 1232 th->th_seq = htonl(tp->snd_max); 1233 } else { 1234 th->th_seq = htonl(p->rxmit); 1235 p->rxmit += len; 1236 /* 1237 * Lost Retransmission Detection 1238 * trigger resending of a (then 1239 * still existing) hole, when 1240 * fack acks recoverypoint. 1241 */ 1242 if ((tp->t_flags & TF_LRD) && SEQ_GEQ(p->rxmit, p->end)) 1243 p->rxmit = tp->snd_recover; 1244 tp->sackhint.sack_bytes_rexmit += len; 1245 } 1246 if (IN_RECOVERY(tp->t_flags)) { 1247 /* 1248 * Account all bytes transmitted while 1249 * IN_RECOVERY, simplifying PRR and 1250 * Lost Retransmit Detection 1251 */ 1252 tp->sackhint.prr_out += len; 1253 } 1254 th->th_ack = htonl(tp->rcv_nxt); 1255 if (optlen) { 1256 bcopy(opt, th + 1, optlen); 1257 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1258 } 1259 tcp_set_flags(th, flags); 1260 /* 1261 * Calculate receive window. Don't shrink window, 1262 * but avoid silly window syndrome. 1263 * If a RST segment is sent, advertise a window of zero. 1264 */ 1265 if (flags & TH_RST) { 1266 recwin = 0; 1267 } else { 1268 if (recwin < (so->so_rcv.sb_hiwat / 4) && 1269 recwin < tp->t_maxseg) 1270 recwin = 0; 1271 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1272 recwin < (tp->rcv_adv - tp->rcv_nxt)) 1273 recwin = (tp->rcv_adv - tp->rcv_nxt); 1274 } 1275 /* 1276 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1277 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1278 * case is handled in syncache. 1279 */ 1280 if (flags & TH_SYN) 1281 th->th_win = htons((u_short) 1282 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1283 else { 1284 /* Avoid shrinking window with window scaling. */ 1285 recwin = roundup2(recwin, 1 << tp->rcv_scale); 1286 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1287 } 1288 1289 /* 1290 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1291 * a 0 window. This may cause the remote transmitter to stall. This 1292 * flag tells soreceive() to disable delayed acknowledgements when 1293 * draining the buffer. This can occur if the receiver is attempting 1294 * to read more data than can be buffered prior to transmitting on 1295 * the connection. 1296 */ 1297 if (th->th_win == 0) { 1298 tp->t_sndzerowin++; 1299 tp->t_flags |= TF_RXWIN0SENT; 1300 } else 1301 tp->t_flags &= ~TF_RXWIN0SENT; 1302 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1303 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1304 th->th_flags |= TH_URG; 1305 } else 1306 /* 1307 * If no urgent pointer to send, then we pull 1308 * the urgent pointer to the left edge of the send window 1309 * so that it doesn't drift into the send window on sequence 1310 * number wraparound. 1311 */ 1312 tp->snd_up = tp->snd_una; /* drag it along */ 1313 1314 /* 1315 * Put TCP length in extended header, and then 1316 * checksum extended header and data. 1317 */ 1318 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1319 1320 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1321 if (to.to_flags & TOF_SIGNATURE) { 1322 /* 1323 * Calculate MD5 signature and put it into the place 1324 * determined before. 1325 * NOTE: since TCP options buffer doesn't point into 1326 * mbuf's data, calculate offset and use it. 1327 */ 1328 if (!TCPMD5_ENABLED() || (error = TCPMD5_OUTPUT(m, th, 1329 (u_char *)(th + 1) + (to.to_signature - opt))) != 0) { 1330 /* 1331 * Do not send segment if the calculation of MD5 1332 * digest has failed. 1333 */ 1334 m_freem(m); 1335 goto out; 1336 } 1337 } 1338 #endif 1339 #ifdef INET6 1340 if (isipv6) { 1341 /* 1342 * There is no need to fill in ip6_plen right now. 1343 * It will be filled later by ip6_output. 1344 */ 1345 if (tp->t_port) { 1346 m->m_pkthdr.csum_flags = CSUM_UDP_IPV6; 1347 m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum); 1348 udp->uh_sum = in6_cksum_pseudo(ip6, ulen, IPPROTO_UDP, 0); 1349 th->th_sum = htons(0); 1350 UDPSTAT_INC(udps_opackets); 1351 } else { 1352 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1353 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1354 th->th_sum = in6_cksum_pseudo(ip6, 1355 sizeof(struct tcphdr) + optlen + len, IPPROTO_TCP, 1356 0); 1357 } 1358 } 1359 #endif 1360 #if defined(INET6) && defined(INET) 1361 else 1362 #endif 1363 #ifdef INET 1364 { 1365 if (tp->t_port) { 1366 m->m_pkthdr.csum_flags = CSUM_UDP; 1367 m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum); 1368 udp->uh_sum = in_pseudo(ip->ip_src.s_addr, 1369 ip->ip_dst.s_addr, htons(ulen + IPPROTO_UDP)); 1370 th->th_sum = htons(0); 1371 UDPSTAT_INC(udps_opackets); 1372 } else { 1373 m->m_pkthdr.csum_flags = CSUM_TCP; 1374 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1375 th->th_sum = in_pseudo(ip->ip_src.s_addr, 1376 ip->ip_dst.s_addr, htons(sizeof(struct tcphdr) + 1377 IPPROTO_TCP + len + optlen)); 1378 } 1379 1380 /* IP version must be set here for ipv4/ipv6 checking later */ 1381 KASSERT(ip->ip_v == IPVERSION, 1382 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1383 } 1384 #endif 1385 1386 /* 1387 * Enable TSO and specify the size of the segments. 1388 * The TCP pseudo header checksum is always provided. 1389 */ 1390 if (tso) { 1391 KASSERT(len > tp->t_maxseg - optlen, 1392 ("%s: len <= tso_segsz", __func__)); 1393 m->m_pkthdr.csum_flags |= CSUM_TSO; 1394 m->m_pkthdr.tso_segsz = tp->t_maxseg - optlen; 1395 } 1396 1397 KASSERT(len + hdrlen == m_length(m, NULL), 1398 ("%s: mbuf chain shorter than expected: %d + %u != %u", 1399 __func__, len, hdrlen, m_length(m, NULL))); 1400 1401 #ifdef TCP_HHOOK 1402 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1403 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1404 #endif 1405 1406 TCP_PROBE3(debug__output, tp, th, m); 1407 1408 /* We're getting ready to send; log now. */ 1409 /* XXXMT: We are not honoring verbose logging. */ 1410 1411 if (tcp_bblogging_on(tp)) 1412 lgb = tcp_log_event(tp, th, &so->so_rcv, &so->so_snd, 1413 TCP_LOG_OUT, ERRNO_UNK, len, NULL, false, NULL, NULL, 0, 1414 NULL); 1415 else 1416 lgb = NULL; 1417 1418 /* 1419 * Fill in IP length and desired time to live and 1420 * send to IP level. There should be a better way 1421 * to handle ttl and tos; we could keep them in 1422 * the template, but need a way to checksum without them. 1423 */ 1424 /* 1425 * m->m_pkthdr.len should have been set before checksum calculation, 1426 * because in6_cksum() need it. 1427 */ 1428 #ifdef INET6 1429 if (isipv6) { 1430 /* 1431 * we separately set hoplimit for every segment, since the 1432 * user might want to change the value via setsockopt. 1433 * Also, desired default hop limit might be changed via 1434 * Neighbor Discovery. 1435 */ 1436 ip6->ip6_hlim = in6_selecthlim(inp, NULL); 1437 1438 /* 1439 * Set the packet size here for the benefit of DTrace probes. 1440 * ip6_output() will set it properly; it's supposed to include 1441 * the option header lengths as well. 1442 */ 1443 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6)); 1444 1445 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) 1446 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1447 else 1448 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1449 1450 if (tp->t_state == TCPS_SYN_SENT) 1451 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th); 1452 1453 TCP_PROBE5(send, NULL, tp, ip6, tp, th); 1454 1455 #ifdef TCPPCAP 1456 /* Save packet, if requested. */ 1457 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1458 #endif 1459 1460 /* TODO: IPv6 IP6TOS_ECT bit on */ 1461 error = ip6_output(m, inp->in6p_outputopts, &inp->inp_route6, 1462 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 1463 NULL, NULL, inp); 1464 1465 if (error == EMSGSIZE && inp->inp_route6.ro_nh != NULL) 1466 mtu = inp->inp_route6.ro_nh->nh_mtu; 1467 } 1468 #endif /* INET6 */ 1469 #if defined(INET) && defined(INET6) 1470 else 1471 #endif 1472 #ifdef INET 1473 { 1474 ip->ip_len = htons(m->m_pkthdr.len); 1475 #ifdef INET6 1476 if (inp->inp_vflag & INP_IPV6PROTO) 1477 ip->ip_ttl = in6_selecthlim(inp, NULL); 1478 #endif /* INET6 */ 1479 /* 1480 * If we do path MTU discovery, then we set DF on every packet. 1481 * This might not be the best thing to do according to RFC3390 1482 * Section 2. However the tcp hostcache migitates the problem 1483 * so it affects only the first tcp connection with a host. 1484 * 1485 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1486 */ 1487 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) { 1488 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1489 if (tp->t_port == 0 || len < V_tcp_minmss) { 1490 ip->ip_off |= htons(IP_DF); 1491 } 1492 } else { 1493 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1494 } 1495 1496 if (tp->t_state == TCPS_SYN_SENT) 1497 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th); 1498 1499 TCP_PROBE5(send, NULL, tp, ip, tp, th); 1500 1501 #ifdef TCPPCAP 1502 /* Save packet, if requested. */ 1503 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1504 #endif 1505 1506 error = ip_output(m, inp->inp_options, &inp->inp_route, 1507 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, inp); 1508 1509 if (error == EMSGSIZE && inp->inp_route.ro_nh != NULL) 1510 mtu = inp->inp_route.ro_nh->nh_mtu; 1511 } 1512 #endif /* INET */ 1513 1514 if (lgb != NULL) { 1515 lgb->tlb_errno = error; 1516 lgb = NULL; 1517 } 1518 out: 1519 if (error == 0) 1520 tcp_account_for_send(tp, len, (tp->snd_nxt != tp->snd_max), 0, hw_tls); 1521 /* 1522 * In transmit state, time the transmission and arrange for 1523 * the retransmit. In persist state, just set snd_max. 1524 */ 1525 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1526 !tcp_timer_active(tp, TT_PERSIST)) { 1527 tcp_seq startseq = tp->snd_nxt; 1528 1529 /* 1530 * Advance snd_nxt over sequence space of this segment. 1531 */ 1532 if (flags & (TH_SYN|TH_FIN)) { 1533 if (flags & TH_SYN) 1534 tp->snd_nxt++; 1535 if (flags & TH_FIN) { 1536 tp->snd_nxt++; 1537 tp->t_flags |= TF_SENTFIN; 1538 } 1539 } 1540 if (sack_rxmit) 1541 goto timer; 1542 tp->snd_nxt += len; 1543 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1544 /* 1545 * Update "made progress" indication if we just 1546 * added new data to an empty socket buffer. 1547 */ 1548 if (tp->snd_una == tp->snd_max) 1549 tp->t_acktime = ticks; 1550 tp->snd_max = tp->snd_nxt; 1551 /* 1552 * Time this transmission if not a retransmission and 1553 * not currently timing anything. 1554 */ 1555 tp->t_sndtime = ticks; 1556 if (tp->t_rtttime == 0) { 1557 tp->t_rtttime = ticks; 1558 tp->t_rtseq = startseq; 1559 TCPSTAT_INC(tcps_segstimed); 1560 } 1561 #ifdef STATS 1562 if (!(tp->t_flags & TF_GPUTINPROG) && len) { 1563 tp->t_flags |= TF_GPUTINPROG; 1564 tp->gput_seq = startseq; 1565 tp->gput_ack = startseq + 1566 ulmin(sbavail(&so->so_snd) - off, sendwin); 1567 tp->gput_ts = tcp_ts_getticks(); 1568 } 1569 #endif /* STATS */ 1570 } 1571 1572 /* 1573 * Set retransmit timer if not currently set, 1574 * and not doing a pure ack or a keep-alive probe. 1575 * Initial value for retransmit timer is smoothed 1576 * round-trip time + 2 * round-trip time variance. 1577 * Initialize shift counter which is used for backoff 1578 * of retransmit time. 1579 */ 1580 timer: 1581 if (!tcp_timer_active(tp, TT_REXMT) && 1582 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1583 (tp->snd_nxt != tp->snd_una))) { 1584 if (tcp_timer_active(tp, TT_PERSIST)) { 1585 tcp_timer_activate(tp, TT_PERSIST, 0); 1586 tp->t_rxtshift = 0; 1587 } 1588 tcp_timer_activate(tp, TT_REXMT, TP_RXTCUR(tp)); 1589 } else if (len == 0 && sbavail(&so->so_snd) && 1590 !tcp_timer_active(tp, TT_REXMT) && 1591 !tcp_timer_active(tp, TT_PERSIST)) { 1592 /* 1593 * Avoid a situation where we do not set persist timer 1594 * after a zero window condition. For example: 1595 * 1) A -> B: packet with enough data to fill the window 1596 * 2) B -> A: ACK for #1 + new data (0 window 1597 * advertisement) 1598 * 3) A -> B: ACK for #2, 0 len packet 1599 * 1600 * In this case, A will not activate the persist timer, 1601 * because it chose to send a packet. Unless tcp_output 1602 * is called for some other reason (delayed ack timer, 1603 * another input packet from B, socket syscall), A will 1604 * not send zero window probes. 1605 * 1606 * So, if you send a 0-length packet, but there is data 1607 * in the socket buffer, and neither the rexmt or 1608 * persist timer is already set, then activate the 1609 * persist timer. 1610 */ 1611 tp->t_rxtshift = 0; 1612 tcp_setpersist(tp); 1613 } 1614 } else { 1615 /* 1616 * Persist case, update snd_max but since we are in 1617 * persist mode (no window) we do not update snd_nxt. 1618 */ 1619 int xlen = len; 1620 if (flags & TH_SYN) 1621 ++xlen; 1622 if (flags & TH_FIN) { 1623 ++xlen; 1624 tp->t_flags |= TF_SENTFIN; 1625 } 1626 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1627 tp->snd_max = tp->snd_nxt + xlen; 1628 } 1629 if ((error == 0) && 1630 (TCPS_HAVEESTABLISHED(tp->t_state) && 1631 (tp->t_flags & TF_SACK_PERMIT) && 1632 tp->rcv_numsacks > 0)) { 1633 /* Clean up any DSACK's sent */ 1634 tcp_clean_dsack_blocks(tp); 1635 } 1636 if (error) { 1637 /* 1638 * We know that the packet was lost, so back out the 1639 * sequence number advance, if any. 1640 * 1641 * If the error is EPERM the packet got blocked by the 1642 * local firewall. Normally we should terminate the 1643 * connection but the blocking may have been spurious 1644 * due to a firewall reconfiguration cycle. So we treat 1645 * it like a packet loss and let the retransmit timer and 1646 * timeouts do their work over time. 1647 * XXX: It is a POLA question whether calling tcp_drop right 1648 * away would be the really correct behavior instead. 1649 */ 1650 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1651 !tcp_timer_active(tp, TT_PERSIST)) && 1652 ((flags & TH_SYN) == 0) && 1653 (error != EPERM)) { 1654 if (sack_rxmit) { 1655 p->rxmit = SEQ_MIN(p->end, p->rxmit) - len; 1656 tp->sackhint.sack_bytes_rexmit -= len; 1657 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1658 ("sackhint bytes rtx >= 0")); 1659 KASSERT((flags & TH_FIN) == 0, 1660 ("error while FIN with SACK rxmit")); 1661 } else { 1662 tp->snd_nxt -= len; 1663 if (flags & TH_FIN) 1664 tp->snd_nxt--; 1665 } 1666 if (IN_RECOVERY(tp->t_flags)) 1667 tp->sackhint.prr_out -= len; 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