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 } 334 } 335 after_sack_rexmit: 336 /* 337 * Get standard flags, and add SYN or FIN if requested by 'hidden' 338 * state flags. 339 */ 340 if (tp->t_flags & TF_NEEDFIN) 341 flags |= TH_FIN; 342 if (tp->t_flags & TF_NEEDSYN) 343 flags |= TH_SYN; 344 345 SOCKBUF_LOCK(&so->so_snd); 346 /* 347 * If in persist timeout with window of 0, send 1 byte. 348 * Otherwise, if window is small but nonzero 349 * and timer expired, we will send what we can 350 * and go to transmit state. 351 */ 352 if (tp->t_flags & TF_FORCEDATA) { 353 if (sendwin == 0) { 354 /* 355 * If we still have some data to send, then 356 * clear the FIN bit. Usually this would 357 * happen below when it realizes that we 358 * aren't sending all the data. However, 359 * if we have exactly 1 byte of unsent data, 360 * then it won't clear the FIN bit below, 361 * and if we are in persist state, we wind 362 * up sending the packet without recording 363 * that we sent the FIN bit. 364 * 365 * We can't just blindly clear the FIN bit, 366 * because if we don't have any more data 367 * to send then the probe will be the FIN 368 * itself. 369 */ 370 if (off < sbused(&so->so_snd)) 371 flags &= ~TH_FIN; 372 sendwin = 1; 373 } else { 374 tcp_timer_activate(tp, TT_PERSIST, 0); 375 tp->t_rxtshift = 0; 376 } 377 } 378 379 /* 380 * If snd_nxt == snd_max and we have transmitted a FIN, the 381 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 382 * a negative length. This can also occur when TCP opens up 383 * its congestion window while receiving additional duplicate 384 * acks after fast-retransmit because TCP will reset snd_nxt 385 * to snd_max after the fast-retransmit. 386 * 387 * In the normal retransmit-FIN-only case, however, snd_nxt will 388 * be set to snd_una, the offset will be 0, and the length may 389 * wind up 0. 390 * 391 * If sack_rxmit is true we are retransmitting from the scoreboard 392 * in which case len is already set. 393 */ 394 if (sack_rxmit == 0) { 395 if (sack_bytes_rxmt == 0) { 396 len = ((int32_t)min(sbavail(&so->so_snd), sendwin) - 397 off); 398 } else { 399 int32_t cwin; 400 401 /* 402 * We are inside of a SACK recovery episode and are 403 * sending new data, having retransmitted all the 404 * data possible in the scoreboard. 405 */ 406 len = ((int32_t)min(sbavail(&so->so_snd), tp->snd_wnd) - 407 off); 408 /* 409 * Don't remove this (len > 0) check ! 410 * We explicitly check for len > 0 here (although it 411 * isn't really necessary), to work around a gcc 412 * optimization issue - to force gcc to compute 413 * len above. Without this check, the computation 414 * of len is bungled by the optimizer. 415 */ 416 if (len > 0) { 417 cwin = tp->snd_cwnd - imax(0, (int32_t) 418 (tp->snd_nxt - tp->snd_recover)) - 419 sack_bytes_rxmt; 420 if (cwin < 0) 421 cwin = 0; 422 len = imin(len, cwin); 423 } 424 } 425 } 426 427 /* 428 * Lop off SYN bit if it has already been sent. However, if this 429 * is SYN-SENT state and if segment contains data and if we don't 430 * know that foreign host supports TAO, suppress sending segment. 431 */ 432 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 433 if (tp->t_state != TCPS_SYN_RECEIVED) 434 flags &= ~TH_SYN; 435 /* 436 * When sending additional segments following a TFO SYN|ACK, 437 * do not include the SYN bit. 438 */ 439 if (IS_FASTOPEN(tp->t_flags) && 440 (tp->t_state == TCPS_SYN_RECEIVED)) 441 flags &= ~TH_SYN; 442 off--, len++; 443 } 444 445 /* 446 * Be careful not to send data and/or FIN on SYN segments. 447 * This measure is needed to prevent interoperability problems 448 * with not fully conformant TCP implementations. 449 */ 450 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 451 len = 0; 452 flags &= ~TH_FIN; 453 } 454 455 /* 456 * On TFO sockets, ensure no data is sent in the following cases: 457 * 458 * - When retransmitting SYN|ACK on a passively-created socket 459 * 460 * - When retransmitting SYN on an actively created socket 461 * 462 * - When sending a zero-length cookie (cookie request) on an 463 * actively created socket 464 * 465 * - When the socket is in the CLOSED state (RST is being sent) 466 */ 467 if (IS_FASTOPEN(tp->t_flags) && 468 (((flags & TH_SYN) && (tp->t_rxtshift > 0)) || 469 ((tp->t_state == TCPS_SYN_SENT) && 470 (tp->t_tfo_client_cookie_len == 0)) || 471 (flags & TH_RST))) 472 len = 0; 473 if (len <= 0) { 474 /* 475 * If FIN has been sent but not acked, 476 * but we haven't been called to retransmit, 477 * len will be < 0. Otherwise, window shrank 478 * after we sent into it. If window shrank to 0, 479 * cancel pending retransmit, pull snd_nxt back 480 * to (closed) window, and set the persist timer 481 * if it isn't already going. If the window didn't 482 * close completely, just wait for an ACK. 483 * 484 * We also do a general check here to ensure that 485 * we will set the persist timer when we have data 486 * to send, but a 0-byte window. This makes sure 487 * the persist timer is set even if the packet 488 * hits one of the "goto send" lines below. 489 */ 490 len = 0; 491 if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) && 492 (off < (int) sbavail(&so->so_snd)) && 493 !tcp_timer_active(tp, TT_PERSIST)) { 494 tcp_timer_activate(tp, TT_REXMT, 0); 495 tp->t_rxtshift = 0; 496 tp->snd_nxt = tp->snd_una; 497 if (!tcp_timer_active(tp, TT_PERSIST)) 498 tcp_setpersist(tp); 499 } 500 } 501 502 /* len will be >= 0 after this point. */ 503 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 504 505 tcp_sndbuf_autoscale(tp, so, sendwin); 506 507 /* 508 * Decide if we can use TCP Segmentation Offloading (if supported by 509 * hardware). 510 * 511 * TSO may only be used if we are in a pure bulk sending state. The 512 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 513 * IP options prevent using TSO. With TSO the TCP header is the same 514 * (except for the sequence number) for all generated packets. This 515 * makes it impossible to transmit any options which vary per generated 516 * segment or packet. 517 * 518 * IPv4 handling has a clear separation of ip options and ip header 519 * flags while IPv6 combines both in in6p_outputopts. ip6_optlen() does 520 * the right thing below to provide length of just ip options and thus 521 * checking for ipoptlen is enough to decide if ip options are present. 522 */ 523 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 524 /* 525 * Pre-calculate here as we save another lookup into the darknesses 526 * of IPsec that way and can actually decide if TSO is ok. 527 */ 528 #ifdef INET6 529 if (isipv6 && IPSEC_ENABLED(ipv6)) 530 ipsec_optlen = IPSEC_HDRSIZE(ipv6, inp); 531 #ifdef INET 532 else 533 #endif 534 #endif /* INET6 */ 535 #ifdef INET 536 if (IPSEC_ENABLED(ipv4)) 537 ipsec_optlen = IPSEC_HDRSIZE(ipv4, inp); 538 #endif /* INET */ 539 #endif /* IPSEC */ 540 #ifdef INET6 541 if (isipv6) 542 ipoptlen = ip6_optlen(inp); 543 else 544 #endif 545 if (inp->inp_options) 546 ipoptlen = inp->inp_options->m_len - 547 offsetof(struct ipoption, ipopt_list); 548 else 549 ipoptlen = 0; 550 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 551 ipoptlen += ipsec_optlen; 552 #endif 553 554 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg && 555 (tp->t_port == 0) && 556 ((tp->t_flags & TF_SIGNATURE) == 0) && 557 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 558 ipoptlen == 0 && !(flags & TH_SYN)) 559 tso = 1; 560 561 if (SEQ_LT((sack_rxmit ? p->rxmit : tp->snd_nxt) + len, 562 tp->snd_una + sbused(&so->so_snd))) { 563 flags &= ~TH_FIN; 564 } 565 566 recwin = lmin(lmax(sbspace(&so->so_rcv), 0), 567 (long)TCP_MAXWIN << tp->rcv_scale); 568 569 /* 570 * Sender silly window avoidance. We transmit under the following 571 * conditions when len is non-zero: 572 * 573 * - We have a full segment (or more with TSO) 574 * - This is the last buffer in a write()/send() and we are 575 * either idle or running NODELAY 576 * - we've timed out (e.g. persist timer) 577 * - we have more then 1/2 the maximum send window's worth of 578 * data (receiver may be limited the window size) 579 * - we need to retransmit 580 */ 581 if (len) { 582 if (len >= tp->t_maxseg) 583 goto send; 584 /* 585 * As the TCP header options are now 586 * considered when setting up the initial 587 * window, we would not send the last segment 588 * if we skip considering the option length here. 589 * Note: this may not work when tcp headers change 590 * very dynamically in the future. 591 */ 592 if ((((tp->t_flags & TF_SIGNATURE) ? 593 PADTCPOLEN(TCPOLEN_SIGNATURE) : 0) + 594 ((tp->t_flags & TF_RCVD_TSTMP) ? 595 PADTCPOLEN(TCPOLEN_TIMESTAMP) : 0) + 596 len) >= tp->t_maxseg) 597 goto send; 598 /* 599 * NOTE! on localhost connections an 'ack' from the remote 600 * end may occur synchronously with the output and cause 601 * us to flush a buffer queued with moretocome. XXX 602 * 603 * note: the len + off check is almost certainly unnecessary. 604 */ 605 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 606 (idle || (tp->t_flags & TF_NODELAY)) && 607 (uint32_t)len + (uint32_t)off >= sbavail(&so->so_snd) && 608 (tp->t_flags & TF_NOPUSH) == 0) { 609 goto send; 610 } 611 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 612 goto send; 613 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 614 goto send; 615 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 616 goto send; 617 if (sack_rxmit) 618 goto send; 619 } 620 621 /* 622 * Sending of standalone window updates. 623 * 624 * Window updates are important when we close our window due to a 625 * full socket buffer and are opening it again after the application 626 * reads data from it. Once the window has opened again and the 627 * remote end starts to send again the ACK clock takes over and 628 * provides the most current window information. 629 * 630 * We must avoid the silly window syndrome whereas every read 631 * from the receive buffer, no matter how small, causes a window 632 * update to be sent. We also should avoid sending a flurry of 633 * window updates when the socket buffer had queued a lot of data 634 * and the application is doing small reads. 635 * 636 * Prevent a flurry of pointless window updates by only sending 637 * an update when we can increase the advertized window by more 638 * than 1/4th of the socket buffer capacity. When the buffer is 639 * getting full or is very small be more aggressive and send an 640 * update whenever we can increase by two mss sized segments. 641 * In all other situations the ACK's to new incoming data will 642 * carry further window increases. 643 * 644 * Don't send an independent window update if a delayed 645 * ACK is pending (it will get piggy-backed on it) or the 646 * remote side already has done a half-close and won't send 647 * more data. 648 */ 649 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 650 !(tp->t_flags & TF_DELACK) && 651 !TCPS_HAVERCVDFIN(tp->t_state)) { 652 /* 653 * "adv" is the amount we could increase the window, 654 * taking into account that we are limited by 655 * TCP_MAXWIN << tp->rcv_scale. 656 */ 657 int32_t adv; 658 int oldwin; 659 660 adv = recwin; 661 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { 662 oldwin = (tp->rcv_adv - tp->rcv_nxt); 663 if (adv > oldwin) 664 adv -= oldwin; 665 else 666 adv = 0; 667 } else 668 oldwin = 0; 669 670 /* 671 * If the new window size ends up being the same as or less 672 * than the old size when it is scaled, then don't force 673 * a window update. 674 */ 675 if (oldwin >> tp->rcv_scale >= (adv + oldwin) >> tp->rcv_scale) 676 goto dontupdate; 677 678 if (adv >= (int32_t)(2 * tp->t_maxseg) && 679 (adv >= (int32_t)(so->so_rcv.sb_hiwat / 4) || 680 recwin <= (so->so_rcv.sb_hiwat / 8) || 681 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg || 682 adv >= TCP_MAXWIN << tp->rcv_scale)) 683 goto send; 684 if (2 * adv >= (int32_t)so->so_rcv.sb_hiwat) 685 goto send; 686 } 687 dontupdate: 688 689 /* 690 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 691 * is also a catch-all for the retransmit timer timeout case. 692 */ 693 if (tp->t_flags & TF_ACKNOW) 694 goto send; 695 if ((flags & TH_RST) || 696 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 697 goto send; 698 if (SEQ_GT(tp->snd_up, tp->snd_una)) 699 goto send; 700 /* 701 * If our state indicates that FIN should be sent 702 * and we have not yet done so, then we need to send. 703 */ 704 if (flags & TH_FIN && 705 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 706 goto send; 707 /* 708 * In SACK, it is possible for tcp_output to fail to send a segment 709 * after the retransmission timer has been turned off. Make sure 710 * that the retransmission timer is set. 711 */ 712 if ((tp->t_flags & TF_SACK_PERMIT) && 713 SEQ_GT(tp->snd_max, tp->snd_una) && 714 !tcp_timer_active(tp, TT_REXMT) && 715 !tcp_timer_active(tp, TT_PERSIST)) { 716 tcp_timer_activate(tp, TT_REXMT, TP_RXTCUR(tp)); 717 goto just_return; 718 } 719 /* 720 * TCP window updates are not reliable, rather a polling protocol 721 * using ``persist'' packets is used to insure receipt of window 722 * updates. The three ``states'' for the output side are: 723 * idle not doing retransmits or persists 724 * persisting to move a small or zero window 725 * (re)transmitting and thereby not persisting 726 * 727 * tcp_timer_active(tp, TT_PERSIST) 728 * is true when we are in persist state. 729 * (tp->t_flags & TF_FORCEDATA) 730 * is set when we are called to send a persist packet. 731 * tcp_timer_active(tp, TT_REXMT) 732 * is set when we are retransmitting 733 * The output side is idle when both timers are zero. 734 * 735 * If send window is too small, there is data to transmit, and no 736 * retransmit or persist is pending, then go to persist state. 737 * If nothing happens soon, send when timer expires: 738 * if window is nonzero, transmit what we can, 739 * otherwise force out a byte. 740 */ 741 if (sbavail(&so->so_snd) && !tcp_timer_active(tp, TT_REXMT) && 742 !tcp_timer_active(tp, TT_PERSIST)) { 743 tp->t_rxtshift = 0; 744 tcp_setpersist(tp); 745 } 746 747 /* 748 * No reason to send a segment, just return. 749 */ 750 just_return: 751 SOCKBUF_UNLOCK(&so->so_snd); 752 return (0); 753 754 send: 755 SOCKBUF_LOCK_ASSERT(&so->so_snd); 756 if (len > 0) { 757 if (len >= tp->t_maxseg) 758 tp->t_flags2 |= TF2_PLPMTU_MAXSEGSNT; 759 else 760 tp->t_flags2 &= ~TF2_PLPMTU_MAXSEGSNT; 761 } 762 /* 763 * Before ESTABLISHED, force sending of initial options 764 * unless TCP set not to do any options. 765 * NOTE: we assume that the IP/TCP header plus TCP options 766 * always fit in a single mbuf, leaving room for a maximum 767 * link header, i.e. 768 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 769 */ 770 optlen = 0; 771 #ifdef INET6 772 if (isipv6) 773 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 774 else 775 #endif 776 hdrlen = sizeof (struct tcpiphdr); 777 778 if (flags & TH_SYN) { 779 tp->snd_nxt = tp->iss; 780 } 781 782 /* 783 * Compute options for segment. 784 * We only have to care about SYN and established connection 785 * segments. Options for SYN-ACK segments are handled in TCP 786 * syncache. 787 */ 788 to.to_flags = 0; 789 if ((tp->t_flags & TF_NOOPT) == 0) { 790 /* Maximum segment size. */ 791 if (flags & TH_SYN) { 792 to.to_mss = tcp_mssopt(&inp->inp_inc); 793 if (tp->t_port) 794 to.to_mss -= V_tcp_udp_tunneling_overhead; 795 to.to_flags |= TOF_MSS; 796 797 /* 798 * On SYN or SYN|ACK transmits on TFO connections, 799 * only include the TFO option if it is not a 800 * retransmit, as the presence of the TFO option may 801 * have caused the original SYN or SYN|ACK to have 802 * been dropped by a middlebox. 803 */ 804 if (IS_FASTOPEN(tp->t_flags) && 805 (tp->t_rxtshift == 0)) { 806 if (tp->t_state == TCPS_SYN_RECEIVED) { 807 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN; 808 to.to_tfo_cookie = 809 (u_int8_t *)&tp->t_tfo_cookie.server; 810 to.to_flags |= TOF_FASTOPEN; 811 wanted_cookie = 1; 812 } else if (tp->t_state == TCPS_SYN_SENT) { 813 to.to_tfo_len = 814 tp->t_tfo_client_cookie_len; 815 to.to_tfo_cookie = 816 tp->t_tfo_cookie.client; 817 to.to_flags |= TOF_FASTOPEN; 818 wanted_cookie = 1; 819 /* 820 * If we wind up having more data to 821 * send with the SYN than can fit in 822 * one segment, don't send any more 823 * until the SYN|ACK comes back from 824 * the other end. 825 */ 826 dont_sendalot = 1; 827 } 828 } 829 } 830 /* Window scaling. */ 831 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 832 to.to_wscale = tp->request_r_scale; 833 to.to_flags |= TOF_SCALE; 834 } 835 /* Timestamps. */ 836 if ((tp->t_flags & TF_RCVD_TSTMP) || 837 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 838 curticks = tcp_ts_getticks(); 839 to.to_tsval = curticks + tp->ts_offset; 840 to.to_tsecr = tp->ts_recent; 841 to.to_flags |= TOF_TS; 842 if (tp->t_rxtshift == 1) 843 tp->t_badrxtwin = curticks; 844 } 845 846 /* Set receive buffer autosizing timestamp. */ 847 if (tp->rfbuf_ts == 0 && 848 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 849 tp->rfbuf_ts = tcp_ts_getticks(); 850 851 /* Selective ACK's. */ 852 if (tp->t_flags & TF_SACK_PERMIT) { 853 if (flags & TH_SYN) 854 to.to_flags |= TOF_SACKPERM; 855 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 856 tp->rcv_numsacks > 0) { 857 to.to_flags |= TOF_SACK; 858 to.to_nsacks = tp->rcv_numsacks; 859 to.to_sacks = (u_char *)tp->sackblks; 860 } 861 } 862 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 863 /* TCP-MD5 (RFC2385). */ 864 /* 865 * Check that TCP_MD5SIG is enabled in tcpcb to 866 * account the size needed to set this TCP option. 867 */ 868 if (tp->t_flags & TF_SIGNATURE) 869 to.to_flags |= TOF_SIGNATURE; 870 #endif /* TCP_SIGNATURE */ 871 872 /* Processing the options. */ 873 hdrlen += optlen = tcp_addoptions(&to, opt); 874 /* 875 * If we wanted a TFO option to be added, but it was unable 876 * to fit, ensure no data is sent. 877 */ 878 if (IS_FASTOPEN(tp->t_flags) && wanted_cookie && 879 !(to.to_flags & TOF_FASTOPEN)) 880 len = 0; 881 } 882 if (tp->t_port) { 883 if (V_tcp_udp_tunneling_port == 0) { 884 /* The port was removed?? */ 885 SOCKBUF_UNLOCK(&so->so_snd); 886 return (EHOSTUNREACH); 887 } 888 hdrlen += sizeof(struct udphdr); 889 } 890 /* 891 * Adjust data length if insertion of options will 892 * bump the packet length beyond the t_maxseg length. 893 * Clear the FIN bit because we cut off the tail of 894 * the segment. 895 */ 896 if (len + optlen + ipoptlen > tp->t_maxseg) { 897 flags &= ~TH_FIN; 898 899 if (tso) { 900 u_int if_hw_tsomax; 901 u_int moff; 902 int max_len; 903 904 /* extract TSO information */ 905 if_hw_tsomax = tp->t_tsomax; 906 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount; 907 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize; 908 909 /* 910 * Limit a TSO burst to prevent it from 911 * overflowing or exceeding the maximum length 912 * allowed by the network interface: 913 */ 914 KASSERT(ipoptlen == 0, 915 ("%s: TSO can't do IP options", __func__)); 916 917 /* 918 * Check if we should limit by maximum payload 919 * length: 920 */ 921 if (if_hw_tsomax != 0) { 922 /* compute maximum TSO length */ 923 max_len = (if_hw_tsomax - hdrlen - 924 max_linkhdr); 925 if (max_len <= 0) { 926 len = 0; 927 } else if (len > max_len) { 928 sendalot = 1; 929 len = max_len; 930 } 931 } 932 933 /* 934 * Prevent the last segment from being 935 * fractional unless the send sockbuf can be 936 * emptied: 937 */ 938 max_len = (tp->t_maxseg - optlen); 939 if (((uint32_t)off + (uint32_t)len) < 940 sbavail(&so->so_snd)) { 941 moff = len % max_len; 942 if (moff != 0) { 943 len -= moff; 944 sendalot = 1; 945 } 946 } 947 948 /* 949 * In case there are too many small fragments 950 * don't use TSO: 951 */ 952 if (len <= max_len) { 953 len = max_len; 954 sendalot = 1; 955 tso = 0; 956 } 957 958 /* 959 * Send the FIN in a separate segment 960 * after the bulk sending is done. 961 * We don't trust the TSO implementations 962 * to clear the FIN flag on all but the 963 * last segment. 964 */ 965 if (tp->t_flags & TF_NEEDFIN) 966 sendalot = 1; 967 } else { 968 if (optlen + ipoptlen >= tp->t_maxseg) { 969 /* 970 * Since we don't have enough space to put 971 * the IP header chain and the TCP header in 972 * one packet as required by RFC 7112, don't 973 * send it. Also ensure that at least one 974 * byte of the payload can be put into the 975 * TCP segment. 976 */ 977 SOCKBUF_UNLOCK(&so->so_snd); 978 error = EMSGSIZE; 979 sack_rxmit = 0; 980 goto out; 981 } 982 len = tp->t_maxseg - optlen - ipoptlen; 983 sendalot = 1; 984 if (dont_sendalot) 985 sendalot = 0; 986 } 987 } else 988 tso = 0; 989 990 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 991 ("%s: len > IP_MAXPACKET", __func__)); 992 993 /*#ifdef DIAGNOSTIC*/ 994 #ifdef INET6 995 if (max_linkhdr + hdrlen > MCLBYTES) 996 #else 997 if (max_linkhdr + hdrlen > MHLEN) 998 #endif 999 panic("tcphdr too big"); 1000 /*#endif*/ 1001 1002 /* 1003 * This KASSERT is here to catch edge cases at a well defined place. 1004 * Before, those had triggered (random) panic conditions further down. 1005 */ 1006 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 1007 1008 /* 1009 * Grab a header mbuf, attaching a copy of data to 1010 * be transmitted, and initialize the header from 1011 * the template for sends on this connection. 1012 */ 1013 if (len) { 1014 struct mbuf *mb; 1015 struct sockbuf *msb; 1016 u_int moff; 1017 1018 if ((tp->t_flags & TF_FORCEDATA) && len == 1) { 1019 TCPSTAT_INC(tcps_sndprobe); 1020 #ifdef STATS 1021 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1022 stats_voi_update_abs_u32(tp->t_stats, 1023 VOI_TCP_RETXPB, len); 1024 else 1025 stats_voi_update_abs_u64(tp->t_stats, 1026 VOI_TCP_TXPB, len); 1027 #endif /* STATS */ 1028 } else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 1029 tp->t_sndrexmitpack++; 1030 TCPSTAT_INC(tcps_sndrexmitpack); 1031 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 1032 if (sack_rxmit) { 1033 TCPSTAT_INC(tcps_sack_rexmits); 1034 TCPSTAT_ADD(tcps_sack_rexmit_bytes, len); 1035 } 1036 #ifdef STATS 1037 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_RETXPB, 1038 len); 1039 #endif /* STATS */ 1040 } else { 1041 TCPSTAT_INC(tcps_sndpack); 1042 TCPSTAT_ADD(tcps_sndbyte, len); 1043 #ifdef STATS 1044 stats_voi_update_abs_u64(tp->t_stats, VOI_TCP_TXPB, 1045 len); 1046 #endif /* STATS */ 1047 } 1048 #ifdef INET6 1049 if (MHLEN < hdrlen + max_linkhdr) 1050 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR); 1051 else 1052 #endif 1053 m = m_gethdr(M_NOWAIT, MT_DATA); 1054 1055 if (m == NULL) { 1056 SOCKBUF_UNLOCK(&so->so_snd); 1057 error = ENOBUFS; 1058 sack_rxmit = 0; 1059 goto out; 1060 } 1061 1062 m->m_data += max_linkhdr; 1063 m->m_len = hdrlen; 1064 1065 /* 1066 * Start the m_copy functions from the closest mbuf 1067 * to the offset in the socket buffer chain. 1068 */ 1069 mb = sbsndptr_noadv(&so->so_snd, off, &moff); 1070 if (len <= MHLEN - hdrlen - max_linkhdr && !hw_tls) { 1071 m_copydata(mb, moff, len, 1072 mtod(m, caddr_t) + hdrlen); 1073 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1074 sbsndptr_adv(&so->so_snd, mb, len); 1075 m->m_len += len; 1076 } else { 1077 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1078 msb = NULL; 1079 else 1080 msb = &so->so_snd; 1081 m->m_next = tcp_m_copym(mb, moff, 1082 &len, if_hw_tsomaxsegcount, 1083 if_hw_tsomaxsegsize, msb, hw_tls); 1084 if (len <= (tp->t_maxseg - optlen)) { 1085 /* 1086 * Must have ran out of mbufs for the copy 1087 * shorten it to no longer need tso. Lets 1088 * not put on sendalot since we are low on 1089 * mbufs. 1090 */ 1091 tso = 0; 1092 } 1093 if (m->m_next == NULL) { 1094 SOCKBUF_UNLOCK(&so->so_snd); 1095 (void) m_free(m); 1096 error = ENOBUFS; 1097 sack_rxmit = 0; 1098 goto out; 1099 } 1100 } 1101 1102 /* 1103 * If we're sending everything we've got, set PUSH. 1104 * (This will keep happy those implementations which only 1105 * give data to the user when a buffer fills or 1106 * a PUSH comes in.) 1107 */ 1108 if (((uint32_t)off + (uint32_t)len == sbused(&so->so_snd)) && 1109 !(flags & TH_SYN)) 1110 flags |= TH_PUSH; 1111 SOCKBUF_UNLOCK(&so->so_snd); 1112 } else { 1113 SOCKBUF_UNLOCK(&so->so_snd); 1114 if (tp->t_flags & TF_ACKNOW) 1115 TCPSTAT_INC(tcps_sndacks); 1116 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 1117 TCPSTAT_INC(tcps_sndctrl); 1118 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 1119 TCPSTAT_INC(tcps_sndurg); 1120 else 1121 TCPSTAT_INC(tcps_sndwinup); 1122 1123 m = m_gethdr(M_NOWAIT, MT_DATA); 1124 if (m == NULL) { 1125 error = ENOBUFS; 1126 sack_rxmit = 0; 1127 goto out; 1128 } 1129 #ifdef INET6 1130 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 1131 MHLEN >= hdrlen) { 1132 M_ALIGN(m, hdrlen); 1133 } else 1134 #endif 1135 m->m_data += max_linkhdr; 1136 m->m_len = hdrlen; 1137 } 1138 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 1139 m->m_pkthdr.rcvif = (struct ifnet *)0; 1140 #ifdef MAC 1141 mac_inpcb_create_mbuf(inp, m); 1142 #endif 1143 #ifdef INET6 1144 if (isipv6) { 1145 ip6 = mtod(m, struct ip6_hdr *); 1146 if (tp->t_port) { 1147 udp = (struct udphdr *)((caddr_t)ip6 + sizeof(struct ip6_hdr)); 1148 udp->uh_sport = htons(V_tcp_udp_tunneling_port); 1149 udp->uh_dport = tp->t_port; 1150 ulen = hdrlen + len - sizeof(struct ip6_hdr); 1151 udp->uh_ulen = htons(ulen); 1152 th = (struct tcphdr *)(udp + 1); 1153 } else { 1154 th = (struct tcphdr *)(ip6 + 1); 1155 } 1156 tcpip_fillheaders(inp, tp->t_port, ip6, th); 1157 } else 1158 #endif /* INET6 */ 1159 { 1160 ip = mtod(m, struct ip *); 1161 if (tp->t_port) { 1162 udp = (struct udphdr *)((caddr_t)ip + sizeof(struct ip)); 1163 udp->uh_sport = htons(V_tcp_udp_tunneling_port); 1164 udp->uh_dport = tp->t_port; 1165 ulen = hdrlen + len - sizeof(struct ip); 1166 udp->uh_ulen = htons(ulen); 1167 th = (struct tcphdr *)(udp + 1); 1168 } else 1169 th = (struct tcphdr *)(ip + 1); 1170 tcpip_fillheaders(inp, tp->t_port, ip, th); 1171 } 1172 1173 /* 1174 * Fill in fields, remembering maximum advertised 1175 * window for use in delaying messages about window sizes. 1176 * If resending a FIN, be sure not to use a new sequence number. 1177 */ 1178 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 1179 tp->snd_nxt == tp->snd_max) 1180 tp->snd_nxt--; 1181 /* 1182 * If we are starting a connection, send ECN setup 1183 * SYN packet. If we are on a retransmit, we may 1184 * resend those bits a number of times as per 1185 * RFC 3168. 1186 */ 1187 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) { 1188 flags |= tcp_ecn_output_syn_sent(tp); 1189 } 1190 /* Also handle parallel SYN for ECN */ 1191 if ((TCPS_HAVERCVDSYN(tp->t_state)) && 1192 (tp->t_flags2 & (TF2_ECN_PERMIT | TF2_ACE_PERMIT))) { 1193 int ect = tcp_ecn_output_established(tp, &flags, len, sack_rxmit); 1194 if ((tp->t_state == TCPS_SYN_RECEIVED) && 1195 (tp->t_flags2 & TF2_ECN_SND_ECE)) 1196 tp->t_flags2 &= ~TF2_ECN_SND_ECE; 1197 #ifdef INET6 1198 if (isipv6) { 1199 ip6->ip6_flow &= ~htonl(IPTOS_ECN_MASK << IPV6_FLOWLABEL_LEN); 1200 ip6->ip6_flow |= htonl(ect << IPV6_FLOWLABEL_LEN); 1201 } 1202 else 1203 #endif 1204 { 1205 ip->ip_tos &= ~IPTOS_ECN_MASK; 1206 ip->ip_tos |= ect; 1207 } 1208 } 1209 1210 /* 1211 * If we are doing retransmissions, then snd_nxt will 1212 * not reflect the first unsent octet. For ACK only 1213 * packets, we do not want the sequence number of the 1214 * retransmitted packet, we want the sequence number 1215 * of the next unsent octet. So, if there is no data 1216 * (and no SYN or FIN), use snd_max instead of snd_nxt 1217 * when filling in ti_seq. But if we are in persist 1218 * state, snd_max might reflect one byte beyond the 1219 * right edge of the window, so use snd_nxt in that 1220 * case, since we know we aren't doing a retransmission. 1221 * (retransmit and persist are mutually exclusive...) 1222 */ 1223 if (sack_rxmit == 0) { 1224 if (len || (flags & (TH_SYN|TH_FIN)) || 1225 tcp_timer_active(tp, TT_PERSIST)) 1226 th->th_seq = htonl(tp->snd_nxt); 1227 else 1228 th->th_seq = htonl(tp->snd_max); 1229 } else { 1230 th->th_seq = htonl(p->rxmit); 1231 p->rxmit += len; 1232 /* 1233 * Lost Retransmission Detection 1234 * trigger resending of a (then 1235 * still existing) hole, when 1236 * fack acks recoverypoint. 1237 */ 1238 if ((tp->t_flags & TF_LRD) && SEQ_GEQ(p->rxmit, p->end)) 1239 p->rxmit = tp->snd_recover; 1240 tp->sackhint.sack_bytes_rexmit += len; 1241 } 1242 if (IN_RECOVERY(tp->t_flags)) { 1243 /* 1244 * Account all bytes transmitted while 1245 * IN_RECOVERY, simplifying PRR and 1246 * Lost Retransmit Detection 1247 */ 1248 tp->sackhint.prr_out += len; 1249 } 1250 th->th_ack = htonl(tp->rcv_nxt); 1251 if (optlen) { 1252 bcopy(opt, th + 1, optlen); 1253 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1254 } 1255 tcp_set_flags(th, flags); 1256 /* 1257 * Calculate receive window. Don't shrink window, 1258 * but avoid silly window syndrome. 1259 * If a RST segment is sent, advertise a window of zero. 1260 */ 1261 if (flags & TH_RST) { 1262 recwin = 0; 1263 } else { 1264 if (recwin < (so->so_rcv.sb_hiwat / 4) && 1265 recwin < tp->t_maxseg) 1266 recwin = 0; 1267 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1268 recwin < (tp->rcv_adv - tp->rcv_nxt)) 1269 recwin = (tp->rcv_adv - tp->rcv_nxt); 1270 } 1271 /* 1272 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1273 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1274 * case is handled in syncache. 1275 */ 1276 if (flags & TH_SYN) 1277 th->th_win = htons((u_short) 1278 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1279 else { 1280 /* Avoid shrinking window with window scaling. */ 1281 recwin = roundup2(recwin, 1 << tp->rcv_scale); 1282 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1283 } 1284 1285 /* 1286 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1287 * a 0 window. This may cause the remote transmitter to stall. This 1288 * flag tells soreceive() to disable delayed acknowledgements when 1289 * draining the buffer. This can occur if the receiver is attempting 1290 * to read more data than can be buffered prior to transmitting on 1291 * the connection. 1292 */ 1293 if (th->th_win == 0) { 1294 tp->t_sndzerowin++; 1295 tp->t_flags |= TF_RXWIN0SENT; 1296 } else 1297 tp->t_flags &= ~TF_RXWIN0SENT; 1298 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1299 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1300 th->th_flags |= TH_URG; 1301 } else 1302 /* 1303 * If no urgent pointer to send, then we pull 1304 * the urgent pointer to the left edge of the send window 1305 * so that it doesn't drift into the send window on sequence 1306 * number wraparound. 1307 */ 1308 tp->snd_up = tp->snd_una; /* drag it along */ 1309 1310 /* 1311 * Put TCP length in extended header, and then 1312 * checksum extended header and data. 1313 */ 1314 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1315 1316 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1317 if (to.to_flags & TOF_SIGNATURE) { 1318 /* 1319 * Calculate MD5 signature and put it into the place 1320 * determined before. 1321 * NOTE: since TCP options buffer doesn't point into 1322 * mbuf's data, calculate offset and use it. 1323 */ 1324 if (!TCPMD5_ENABLED() || (error = TCPMD5_OUTPUT(m, th, 1325 (u_char *)(th + 1) + (to.to_signature - opt))) != 0) { 1326 /* 1327 * Do not send segment if the calculation of MD5 1328 * digest has failed. 1329 */ 1330 m_freem(m); 1331 goto out; 1332 } 1333 } 1334 #endif 1335 #ifdef INET6 1336 if (isipv6) { 1337 /* 1338 * There is no need to fill in ip6_plen right now. 1339 * It will be filled later by ip6_output. 1340 */ 1341 if (tp->t_port) { 1342 m->m_pkthdr.csum_flags = CSUM_UDP_IPV6; 1343 m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum); 1344 udp->uh_sum = in6_cksum_pseudo(ip6, ulen, IPPROTO_UDP, 0); 1345 th->th_sum = htons(0); 1346 UDPSTAT_INC(udps_opackets); 1347 } else { 1348 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1349 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1350 th->th_sum = in6_cksum_pseudo(ip6, 1351 sizeof(struct tcphdr) + optlen + len, IPPROTO_TCP, 1352 0); 1353 } 1354 } 1355 #endif 1356 #if defined(INET6) && defined(INET) 1357 else 1358 #endif 1359 #ifdef INET 1360 { 1361 if (tp->t_port) { 1362 m->m_pkthdr.csum_flags = CSUM_UDP; 1363 m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum); 1364 udp->uh_sum = in_pseudo(ip->ip_src.s_addr, 1365 ip->ip_dst.s_addr, htons(ulen + IPPROTO_UDP)); 1366 th->th_sum = htons(0); 1367 UDPSTAT_INC(udps_opackets); 1368 } else { 1369 m->m_pkthdr.csum_flags = CSUM_TCP; 1370 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1371 th->th_sum = in_pseudo(ip->ip_src.s_addr, 1372 ip->ip_dst.s_addr, htons(sizeof(struct tcphdr) + 1373 IPPROTO_TCP + len + optlen)); 1374 } 1375 1376 /* IP version must be set here for ipv4/ipv6 checking later */ 1377 KASSERT(ip->ip_v == IPVERSION, 1378 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1379 } 1380 #endif 1381 1382 /* 1383 * Enable TSO and specify the size of the segments. 1384 * The TCP pseudo header checksum is always provided. 1385 */ 1386 if (tso) { 1387 KASSERT(len > tp->t_maxseg - optlen, 1388 ("%s: len <= tso_segsz", __func__)); 1389 m->m_pkthdr.csum_flags |= CSUM_TSO; 1390 m->m_pkthdr.tso_segsz = tp->t_maxseg - optlen; 1391 } 1392 1393 KASSERT(len + hdrlen == m_length(m, NULL), 1394 ("%s: mbuf chain shorter than expected: %d + %u != %u", 1395 __func__, len, hdrlen, m_length(m, NULL))); 1396 1397 #ifdef TCP_HHOOK 1398 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1399 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1400 #endif 1401 1402 TCP_PROBE3(debug__output, tp, th, m); 1403 1404 /* We're getting ready to send; log now. */ 1405 /* XXXMT: We are not honoring verbose logging. */ 1406 1407 if (tcp_bblogging_on(tp)) 1408 lgb = tcp_log_event(tp, th, &so->so_rcv, &so->so_snd, 1409 TCP_LOG_OUT, ERRNO_UNK, len, NULL, false, NULL, NULL, 0, 1410 NULL); 1411 else 1412 lgb = NULL; 1413 1414 /* 1415 * Fill in IP length and desired time to live and 1416 * send to IP level. There should be a better way 1417 * to handle ttl and tos; we could keep them in 1418 * the template, but need a way to checksum without them. 1419 */ 1420 /* 1421 * m->m_pkthdr.len should have been set before checksum calculation, 1422 * because in6_cksum() need it. 1423 */ 1424 #ifdef INET6 1425 if (isipv6) { 1426 /* 1427 * we separately set hoplimit for every segment, since the 1428 * user might want to change the value via setsockopt. 1429 * Also, desired default hop limit might be changed via 1430 * Neighbor Discovery. 1431 */ 1432 ip6->ip6_hlim = in6_selecthlim(inp, NULL); 1433 1434 /* 1435 * Set the packet size here for the benefit of DTrace probes. 1436 * ip6_output() will set it properly; it's supposed to include 1437 * the option header lengths as well. 1438 */ 1439 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6)); 1440 1441 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) 1442 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1443 else 1444 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1445 1446 if (tp->t_state == TCPS_SYN_SENT) 1447 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th); 1448 1449 TCP_PROBE5(send, NULL, tp, ip6, tp, th); 1450 1451 #ifdef TCPPCAP 1452 /* Save packet, if requested. */ 1453 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1454 #endif 1455 1456 /* TODO: IPv6 IP6TOS_ECT bit on */ 1457 error = ip6_output(m, inp->in6p_outputopts, &inp->inp_route6, 1458 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 1459 NULL, NULL, inp); 1460 1461 if (error == EMSGSIZE && inp->inp_route6.ro_nh != NULL) 1462 mtu = inp->inp_route6.ro_nh->nh_mtu; 1463 } 1464 #endif /* INET6 */ 1465 #if defined(INET) && defined(INET6) 1466 else 1467 #endif 1468 #ifdef INET 1469 { 1470 ip->ip_len = htons(m->m_pkthdr.len); 1471 #ifdef INET6 1472 if (inp->inp_vflag & INP_IPV6PROTO) 1473 ip->ip_ttl = in6_selecthlim(inp, NULL); 1474 #endif /* INET6 */ 1475 /* 1476 * If we do path MTU discovery, then we set DF on every packet. 1477 * This might not be the best thing to do according to RFC3390 1478 * Section 2. However the tcp hostcache migitates the problem 1479 * so it affects only the first tcp connection with a host. 1480 * 1481 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1482 */ 1483 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) { 1484 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1485 if (tp->t_port == 0 || len < V_tcp_minmss) { 1486 ip->ip_off |= htons(IP_DF); 1487 } 1488 } else { 1489 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1490 } 1491 1492 if (tp->t_state == TCPS_SYN_SENT) 1493 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th); 1494 1495 TCP_PROBE5(send, NULL, tp, ip, tp, th); 1496 1497 #ifdef TCPPCAP 1498 /* Save packet, if requested. */ 1499 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1500 #endif 1501 1502 error = ip_output(m, inp->inp_options, &inp->inp_route, 1503 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, inp); 1504 1505 if (error == EMSGSIZE && inp->inp_route.ro_nh != NULL) 1506 mtu = inp->inp_route.ro_nh->nh_mtu; 1507 } 1508 #endif /* INET */ 1509 1510 if (lgb != NULL) { 1511 lgb->tlb_errno = error; 1512 lgb = NULL; 1513 } 1514 out: 1515 if (error == 0) 1516 tcp_account_for_send(tp, len, (tp->snd_nxt != tp->snd_max), 0, hw_tls); 1517 /* 1518 * In transmit state, time the transmission and arrange for 1519 * the retransmit. In persist state, just set snd_max. In a closed 1520 * state just return. 1521 */ 1522 if (flags & TH_RST) { 1523 TCPSTAT_INC(tcps_sndtotal); 1524 return (0); 1525 } else 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 (sendalot) 1724 goto again; 1725 return (0); 1726 } 1727 1728 void 1729 tcp_setpersist(struct tcpcb *tp) 1730 { 1731 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1732 int tt; 1733 int maxunacktime; 1734 1735 tp->t_flags &= ~TF_PREVVALID; 1736 if (tcp_timer_active(tp, TT_REXMT)) 1737 panic("tcp_setpersist: retransmit pending"); 1738 /* 1739 * If the state is already closed, don't bother. 1740 */ 1741 if (tp->t_state == TCPS_CLOSED) 1742 return; 1743 1744 /* 1745 * Start/restart persistence timer. 1746 */ 1747 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1748 tcp_persmin, tcp_persmax); 1749 if (TP_MAXUNACKTIME(tp) && tp->t_acktime) { 1750 maxunacktime = tp->t_acktime + TP_MAXUNACKTIME(tp) - ticks; 1751 if (maxunacktime < 1) 1752 maxunacktime = 1; 1753 if (maxunacktime < tt) 1754 tt = maxunacktime; 1755 } 1756 tcp_timer_activate(tp, TT_PERSIST, tt); 1757 if (tp->t_rxtshift < V_tcp_retries) 1758 tp->t_rxtshift++; 1759 } 1760 1761 /* 1762 * Insert TCP options according to the supplied parameters to the place 1763 * optp in a consistent way. Can handle unaligned destinations. 1764 * 1765 * The order of the option processing is crucial for optimal packing and 1766 * alignment for the scarce option space. 1767 * 1768 * The optimal order for a SYN/SYN-ACK segment is: 1769 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1770 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1771 * 1772 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1773 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1774 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1775 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1776 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1777 */ 1778 int 1779 tcp_addoptions(struct tcpopt *to, u_char *optp) 1780 { 1781 u_int32_t mask, optlen = 0; 1782 1783 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1784 if ((to->to_flags & mask) != mask) 1785 continue; 1786 if (optlen == TCP_MAXOLEN) 1787 break; 1788 switch (to->to_flags & mask) { 1789 case TOF_MSS: 1790 while (optlen % 4) { 1791 optlen += TCPOLEN_NOP; 1792 *optp++ = TCPOPT_NOP; 1793 } 1794 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1795 continue; 1796 optlen += TCPOLEN_MAXSEG; 1797 *optp++ = TCPOPT_MAXSEG; 1798 *optp++ = TCPOLEN_MAXSEG; 1799 to->to_mss = htons(to->to_mss); 1800 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1801 optp += sizeof(to->to_mss); 1802 break; 1803 case TOF_SCALE: 1804 while (!optlen || optlen % 2 != 1) { 1805 optlen += TCPOLEN_NOP; 1806 *optp++ = TCPOPT_NOP; 1807 } 1808 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1809 continue; 1810 optlen += TCPOLEN_WINDOW; 1811 *optp++ = TCPOPT_WINDOW; 1812 *optp++ = TCPOLEN_WINDOW; 1813 *optp++ = to->to_wscale; 1814 break; 1815 case TOF_SACKPERM: 1816 while (optlen % 2) { 1817 optlen += TCPOLEN_NOP; 1818 *optp++ = TCPOPT_NOP; 1819 } 1820 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1821 continue; 1822 optlen += TCPOLEN_SACK_PERMITTED; 1823 *optp++ = TCPOPT_SACK_PERMITTED; 1824 *optp++ = TCPOLEN_SACK_PERMITTED; 1825 break; 1826 case TOF_TS: 1827 while (!optlen || optlen % 4 != 2) { 1828 optlen += TCPOLEN_NOP; 1829 *optp++ = TCPOPT_NOP; 1830 } 1831 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1832 continue; 1833 optlen += TCPOLEN_TIMESTAMP; 1834 *optp++ = TCPOPT_TIMESTAMP; 1835 *optp++ = TCPOLEN_TIMESTAMP; 1836 to->to_tsval = htonl(to->to_tsval); 1837 to->to_tsecr = htonl(to->to_tsecr); 1838 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1839 optp += sizeof(to->to_tsval); 1840 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1841 optp += sizeof(to->to_tsecr); 1842 break; 1843 case TOF_SIGNATURE: 1844 { 1845 int siglen = TCPOLEN_SIGNATURE - 2; 1846 1847 while (!optlen || optlen % 4 != 2) { 1848 optlen += TCPOLEN_NOP; 1849 *optp++ = TCPOPT_NOP; 1850 } 1851 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) { 1852 to->to_flags &= ~TOF_SIGNATURE; 1853 continue; 1854 } 1855 optlen += TCPOLEN_SIGNATURE; 1856 *optp++ = TCPOPT_SIGNATURE; 1857 *optp++ = TCPOLEN_SIGNATURE; 1858 to->to_signature = optp; 1859 while (siglen--) 1860 *optp++ = 0; 1861 break; 1862 } 1863 case TOF_SACK: 1864 { 1865 int sackblks = 0; 1866 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1867 tcp_seq sack_seq; 1868 1869 while (!optlen || optlen % 4 != 2) { 1870 optlen += TCPOLEN_NOP; 1871 *optp++ = TCPOPT_NOP; 1872 } 1873 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1874 continue; 1875 optlen += TCPOLEN_SACKHDR; 1876 *optp++ = TCPOPT_SACK; 1877 sackblks = min(to->to_nsacks, 1878 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1879 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1880 while (sackblks--) { 1881 sack_seq = htonl(sack->start); 1882 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1883 optp += sizeof(sack_seq); 1884 sack_seq = htonl(sack->end); 1885 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1886 optp += sizeof(sack_seq); 1887 optlen += TCPOLEN_SACK; 1888 sack++; 1889 } 1890 TCPSTAT_INC(tcps_sack_send_blocks); 1891 break; 1892 } 1893 case TOF_FASTOPEN: 1894 { 1895 int total_len; 1896 1897 /* XXX is there any point to aligning this option? */ 1898 total_len = TCPOLEN_FAST_OPEN_EMPTY + to->to_tfo_len; 1899 if (TCP_MAXOLEN - optlen < total_len) { 1900 to->to_flags &= ~TOF_FASTOPEN; 1901 continue; 1902 } 1903 *optp++ = TCPOPT_FAST_OPEN; 1904 *optp++ = total_len; 1905 if (to->to_tfo_len > 0) { 1906 bcopy(to->to_tfo_cookie, optp, to->to_tfo_len); 1907 optp += to->to_tfo_len; 1908 } 1909 optlen += total_len; 1910 break; 1911 } 1912 default: 1913 panic("%s: unknown TCP option type", __func__); 1914 break; 1915 } 1916 } 1917 1918 /* Terminate and pad TCP options to a 4 byte boundary. */ 1919 if (optlen % 4) { 1920 optlen += TCPOLEN_EOL; 1921 *optp++ = TCPOPT_EOL; 1922 } 1923 /* 1924 * According to RFC 793 (STD0007): 1925 * "The content of the header beyond the End-of-Option option 1926 * must be header padding (i.e., zero)." 1927 * and later: "The padding is composed of zeros." 1928 */ 1929 while (optlen % 4) { 1930 optlen += TCPOLEN_PAD; 1931 *optp++ = TCPOPT_PAD; 1932 } 1933 1934 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1935 return (optlen); 1936 } 1937 1938 /* 1939 * This is a copy of m_copym(), taking the TSO segment size/limit 1940 * constraints into account, and advancing the sndptr as it goes. 1941 */ 1942 struct mbuf * 1943 tcp_m_copym(struct mbuf *m, int32_t off0, int32_t *plen, 1944 int32_t seglimit, int32_t segsize, struct sockbuf *sb, bool hw_tls) 1945 { 1946 #ifdef KERN_TLS 1947 struct ktls_session *tls, *ntls; 1948 struct mbuf *start __diagused; 1949 #endif 1950 struct mbuf *n, **np; 1951 struct mbuf *top; 1952 int32_t off = off0; 1953 int32_t len = *plen; 1954 int32_t fragsize; 1955 int32_t len_cp = 0; 1956 int32_t *pkthdrlen; 1957 uint32_t mlen, frags; 1958 bool copyhdr; 1959 1960 KASSERT(off >= 0, ("tcp_m_copym, negative off %d", off)); 1961 KASSERT(len >= 0, ("tcp_m_copym, negative len %d", len)); 1962 if (off == 0 && m->m_flags & M_PKTHDR) 1963 copyhdr = true; 1964 else 1965 copyhdr = false; 1966 while (off > 0) { 1967 KASSERT(m != NULL, ("tcp_m_copym, offset > size of mbuf chain")); 1968 if (off < m->m_len) 1969 break; 1970 off -= m->m_len; 1971 if ((sb) && (m == sb->sb_sndptr)) { 1972 sb->sb_sndptroff += m->m_len; 1973 sb->sb_sndptr = m->m_next; 1974 } 1975 m = m->m_next; 1976 } 1977 np = ⊤ 1978 top = NULL; 1979 pkthdrlen = NULL; 1980 #ifdef KERN_TLS 1981 if (hw_tls && (m->m_flags & M_EXTPG)) 1982 tls = m->m_epg_tls; 1983 else 1984 tls = NULL; 1985 start = m; 1986 #endif 1987 while (len > 0) { 1988 if (m == NULL) { 1989 KASSERT(len == M_COPYALL, 1990 ("tcp_m_copym, length > size of mbuf chain")); 1991 *plen = len_cp; 1992 if (pkthdrlen != NULL) 1993 *pkthdrlen = len_cp; 1994 break; 1995 } 1996 #ifdef KERN_TLS 1997 if (hw_tls) { 1998 if (m->m_flags & M_EXTPG) 1999 ntls = m->m_epg_tls; 2000 else 2001 ntls = NULL; 2002 2003 /* 2004 * Avoid mixing TLS records with handshake 2005 * data or TLS records from different 2006 * sessions. 2007 */ 2008 if (tls != ntls) { 2009 MPASS(m != start); 2010 *plen = len_cp; 2011 if (pkthdrlen != NULL) 2012 *pkthdrlen = len_cp; 2013 break; 2014 } 2015 } 2016 #endif 2017 mlen = min(len, m->m_len - off); 2018 if (seglimit) { 2019 /* 2020 * For M_EXTPG mbufs, add 3 segments 2021 * + 1 in case we are crossing page boundaries 2022 * + 2 in case the TLS hdr/trailer are used 2023 * It is cheaper to just add the segments 2024 * than it is to take the cache miss to look 2025 * at the mbuf ext_pgs state in detail. 2026 */ 2027 if (m->m_flags & M_EXTPG) { 2028 fragsize = min(segsize, PAGE_SIZE); 2029 frags = 3; 2030 } else { 2031 fragsize = segsize; 2032 frags = 0; 2033 } 2034 2035 /* Break if we really can't fit anymore. */ 2036 if ((frags + 1) >= seglimit) { 2037 *plen = len_cp; 2038 if (pkthdrlen != NULL) 2039 *pkthdrlen = len_cp; 2040 break; 2041 } 2042 2043 /* 2044 * Reduce size if you can't copy the whole 2045 * mbuf. If we can't copy the whole mbuf, also 2046 * adjust len so the loop will end after this 2047 * mbuf. 2048 */ 2049 if ((frags + howmany(mlen, fragsize)) >= seglimit) { 2050 mlen = (seglimit - frags - 1) * fragsize; 2051 len = mlen; 2052 *plen = len_cp + len; 2053 if (pkthdrlen != NULL) 2054 *pkthdrlen = *plen; 2055 } 2056 frags += howmany(mlen, fragsize); 2057 if (frags == 0) 2058 frags++; 2059 seglimit -= frags; 2060 KASSERT(seglimit > 0, 2061 ("%s: seglimit went too low", __func__)); 2062 } 2063 if (copyhdr) 2064 n = m_gethdr(M_NOWAIT, m->m_type); 2065 else 2066 n = m_get(M_NOWAIT, m->m_type); 2067 *np = n; 2068 if (n == NULL) 2069 goto nospace; 2070 if (copyhdr) { 2071 if (!m_dup_pkthdr(n, m, M_NOWAIT)) 2072 goto nospace; 2073 if (len == M_COPYALL) 2074 n->m_pkthdr.len -= off0; 2075 else 2076 n->m_pkthdr.len = len; 2077 pkthdrlen = &n->m_pkthdr.len; 2078 copyhdr = false; 2079 } 2080 n->m_len = mlen; 2081 len_cp += n->m_len; 2082 if (m->m_flags & (M_EXT | M_EXTPG)) { 2083 n->m_data = m->m_data + off; 2084 mb_dupcl(n, m); 2085 } else 2086 bcopy(mtod(m, caddr_t)+off, mtod(n, caddr_t), 2087 (u_int)n->m_len); 2088 2089 if (sb && (sb->sb_sndptr == m) && 2090 ((n->m_len + off) >= m->m_len) && m->m_next) { 2091 sb->sb_sndptroff += m->m_len; 2092 sb->sb_sndptr = m->m_next; 2093 } 2094 off = 0; 2095 if (len != M_COPYALL) { 2096 len -= n->m_len; 2097 } 2098 m = m->m_next; 2099 np = &n->m_next; 2100 } 2101 return (top); 2102 nospace: 2103 m_freem(top); 2104 return (NULL); 2105 } 2106 2107 void 2108 tcp_sndbuf_autoscale(struct tcpcb *tp, struct socket *so, uint32_t sendwin) 2109 { 2110 2111 /* 2112 * Automatic sizing of send socket buffer. Often the send buffer 2113 * size is not optimally adjusted to the actual network conditions 2114 * at hand (delay bandwidth product). Setting the buffer size too 2115 * small limits throughput on links with high bandwidth and high 2116 * delay (eg. trans-continental/oceanic links). Setting the 2117 * buffer size too big consumes too much real kernel memory, 2118 * especially with many connections on busy servers. 2119 * 2120 * The criteria to step up the send buffer one notch are: 2121 * 1. receive window of remote host is larger than send buffer 2122 * (with a fudge factor of 5/4th); 2123 * 2. send buffer is filled to 7/8th with data (so we actually 2124 * have data to make use of it); 2125 * 3. send buffer fill has not hit maximal automatic size; 2126 * 4. our send window (slow start and cogestion controlled) is 2127 * larger than sent but unacknowledged data in send buffer. 2128 * 2129 * The remote host receive window scaling factor may limit the 2130 * growing of the send buffer before it reaches its allowed 2131 * maximum. 2132 * 2133 * It scales directly with slow start or congestion window 2134 * and does at most one step per received ACK. This fast 2135 * scaling has the drawback of growing the send buffer beyond 2136 * what is strictly necessary to make full use of a given 2137 * delay*bandwidth product. However testing has shown this not 2138 * to be much of an problem. At worst we are trading wasting 2139 * of available bandwidth (the non-use of it) for wasting some 2140 * socket buffer memory. 2141 * 2142 * TODO: Shrink send buffer during idle periods together 2143 * with congestion window. Requires another timer. Has to 2144 * wait for upcoming tcp timer rewrite. 2145 * 2146 * XXXGL: should there be used sbused() or sbavail()? 2147 */ 2148 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 2149 int lowat; 2150 2151 lowat = V_tcp_sendbuf_auto_lowat ? so->so_snd.sb_lowat : 0; 2152 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat - lowat && 2153 sbused(&so->so_snd) >= 2154 (so->so_snd.sb_hiwat / 8 * 7) - lowat && 2155 sbused(&so->so_snd) < V_tcp_autosndbuf_max && 2156 sendwin >= (sbused(&so->so_snd) - 2157 (tp->snd_nxt - tp->snd_una))) { 2158 if (!sbreserve_locked(so, SO_SND, 2159 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 2160 V_tcp_autosndbuf_max), curthread)) 2161 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 2162 } 2163 } 2164 } 2165