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 unsigned ipsec_optlen = 0; 205 int idle, sendalot, curticks; 206 int sack_rxmit, sack_bytes_rxmt; 207 struct sackhole *p; 208 int tso, mtu; 209 struct tcpopt to; 210 struct udphdr *udp = NULL; 211 struct tcp_log_buffer *lgb; 212 unsigned int wanted_cookie = 0; 213 unsigned int dont_sendalot = 0; 214 #ifdef INET6 215 struct ip6_hdr *ip6 = NULL; 216 const bool isipv6 = (inp->inp_vflag & INP_IPV6) != 0; 217 #endif 218 #ifdef KERN_TLS 219 const bool hw_tls = tp->t_nic_ktls_xmit != 0; 220 #else 221 const bool hw_tls = false; 222 #endif 223 224 NET_EPOCH_ASSERT(); 225 INP_WLOCK_ASSERT(inp); 226 227 #ifdef TCP_OFFLOAD 228 if (tp->t_flags & TF_TOE) 229 return (tcp_offload_output(tp)); 230 #endif 231 232 /* 233 * For TFO connections in SYN_SENT or SYN_RECEIVED, 234 * only allow the initial SYN or SYN|ACK and those sent 235 * by the retransmit timer. 236 */ 237 if ((tp->t_flags & TF_FASTOPEN) && 238 ((tp->t_state == TCPS_SYN_SENT) || 239 (tp->t_state == TCPS_SYN_RECEIVED)) && 240 SEQ_GT(tp->snd_max, tp->snd_una) && /* SYN or SYN|ACK sent */ 241 (tp->snd_nxt != tp->snd_una)) /* not a retransmit */ 242 return (0); 243 244 /* 245 * Determine length of data that should be transmitted, 246 * and flags that will be used. 247 * If there is some data or critical controls (SYN, RST) 248 * to send, then transmit; otherwise, investigate further. 249 */ 250 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 251 if (idle && (((ticks - tp->t_rcvtime) >= tp->t_rxtcur) || 252 (tp->t_sndtime && ((ticks - tp->t_sndtime) >= tp->t_rxtcur)))) 253 cc_after_idle(tp); 254 tp->t_flags &= ~TF_LASTIDLE; 255 if (idle) { 256 if (tp->t_flags & TF_MORETOCOME) { 257 tp->t_flags |= TF_LASTIDLE; 258 idle = 0; 259 } 260 } 261 again: 262 sendwin = 0; 263 /* 264 * If we've recently taken a timeout, snd_max will be greater than 265 * snd_nxt. There may be SACK information that allows us to avoid 266 * resending already delivered data. Adjust snd_nxt accordingly. 267 */ 268 if ((tp->t_flags & TF_SACK_PERMIT) && 269 (tp->sackhint.nexthole != NULL) && 270 !IN_FASTRECOVERY(tp->t_flags)) { 271 sendwin = tcp_sack_adjust(tp); 272 } 273 sendalot = 0; 274 tso = 0; 275 mtu = 0; 276 off = tp->snd_nxt - tp->snd_una; 277 sendwin = min(tp->snd_wnd, tp->snd_cwnd + sendwin); 278 279 flags = tcp_outflags[tp->t_state]; 280 /* 281 * Send any SACK-generated retransmissions. If we're explicitly trying 282 * to send out new data (when sendalot is 1), bypass this function. 283 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 284 * we're replacing a (future) new transmission with a retransmission 285 * now, and we previously incremented snd_cwnd in tcp_input(). 286 */ 287 /* 288 * Still in sack recovery , reset rxmit flag to zero. 289 */ 290 sack_rxmit = 0; 291 sack_bytes_rxmt = 0; 292 len = 0; 293 p = NULL; 294 if ((tp->t_flags & TF_SACK_PERMIT) && 295 (IN_FASTRECOVERY(tp->t_flags) || 296 (SEQ_LT(tp->snd_nxt, tp->snd_max) && (tp->t_dupacks >= tcprexmtthresh))) && 297 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 298 int32_t cwin; 299 300 if (IN_FASTRECOVERY(tp->t_flags)) { 301 cwin = imax(sendwin - tcp_compute_pipe(tp), 0); 302 } else { 303 cwin = imax(sendwin - off, 0); 304 } 305 /* Do not retransmit SACK segments beyond snd_recover */ 306 if (SEQ_GT(p->end, tp->snd_recover)) { 307 /* 308 * (At least) part of sack hole extends beyond 309 * snd_recover. Check to see if we can rexmit data 310 * for this hole. 311 */ 312 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 313 /* 314 * Can't rexmit any more data for this hole. 315 * That data will be rexmitted in the next 316 * sack recovery episode, when snd_recover 317 * moves past p->rxmit. 318 */ 319 p = NULL; 320 goto after_sack_rexmit; 321 } else { 322 /* Can rexmit part of the current hole */ 323 len = SEQ_SUB(tp->snd_recover, p->rxmit); 324 if (cwin <= len) { 325 len = cwin; 326 } else { 327 sendalot = 1; 328 } 329 } 330 } else { 331 len = SEQ_SUB(p->end, p->rxmit); 332 if (cwin <= len) { 333 len = cwin; 334 } else { 335 sendalot = 1; 336 } 337 } 338 /* we could have transmitted from the scoreboard, 339 * but sendwin (expected flightsize) - pipe didn't 340 * allow any transmission. 341 * Bypass recalculating the possible transmission 342 * length further down by setting sack_rxmit. 343 * Wouldn't be here if there would have been 344 * nothing in the scoreboard to transmit. 345 */ 346 sack_rxmit = 1; 347 if (len > 0) { 348 off = SEQ_SUB(p->rxmit, tp->snd_una); 349 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 350 __func__, off)); 351 } 352 } 353 after_sack_rexmit: 354 /* 355 * Get standard flags, and add SYN or FIN if requested by 'hidden' 356 * state flags. 357 */ 358 if (tp->t_flags & TF_NEEDFIN) 359 flags |= TH_FIN; 360 if (tp->t_flags & TF_NEEDSYN) 361 flags |= TH_SYN; 362 363 SOCK_SENDBUF_LOCK(so); 364 /* 365 * If in persist timeout with window of 0, send 1 byte. 366 * Otherwise, if window is small but nonzero 367 * and timer expired, we will send what we can 368 * and go to transmit state. 369 */ 370 if (tp->t_flags & TF_FORCEDATA) { 371 if (sendwin == 0) { 372 /* 373 * If we still have some data to send, then 374 * clear the FIN bit. Usually this would 375 * happen below when it realizes that we 376 * aren't sending all the data. However, 377 * if we have exactly 1 byte of unsent data, 378 * then it won't clear the FIN bit below, 379 * and if we are in persist state, we wind 380 * up sending the packet without recording 381 * that we sent the FIN bit. 382 * 383 * We can't just blindly clear the FIN bit, 384 * because if we don't have any more data 385 * to send then the probe will be the FIN 386 * itself. 387 */ 388 if (off < sbused(&so->so_snd)) 389 flags &= ~TH_FIN; 390 sendwin = 1; 391 } else { 392 tcp_timer_activate(tp, TT_PERSIST, 0); 393 tp->t_rxtshift = 0; 394 } 395 } 396 397 /* 398 * If snd_nxt == snd_max and we have transmitted a FIN, the 399 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 400 * a negative length. This can also occur when TCP opens up 401 * its congestion window while receiving additional duplicate 402 * acks after fast-retransmit because TCP will reset snd_nxt 403 * to snd_max after the fast-retransmit. 404 * 405 * In the normal retransmit-FIN-only case, however, snd_nxt will 406 * be set to snd_una, the offset will be 0, and the length may 407 * wind up 0. 408 * 409 * If sack_rxmit is true we are retransmitting from the scoreboard 410 * in which case len is already set. 411 */ 412 if (sack_rxmit == 0) { 413 if ((sack_bytes_rxmt == 0) || SEQ_LT(tp->snd_nxt, tp->snd_max)) { 414 len = imin(sbavail(&so->so_snd), sendwin) - off; 415 } else { 416 /* 417 * We are inside of a SACK recovery episode and are 418 * sending new data, having retransmitted all the 419 * data possible in the scoreboard. 420 */ 421 len = imin(sbavail(&so->so_snd) - off, 422 sendwin - tcp_compute_pipe(tp)); 423 } 424 } 425 426 /* 427 * Lop off SYN bit if it has already been sent. However, if this 428 * is SYN-SENT state and if segment contains data and if we don't 429 * know that foreign host supports TAO, suppress sending segment. 430 */ 431 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 432 if (tp->t_state != TCPS_SYN_RECEIVED) 433 flags &= ~TH_SYN; 434 /* 435 * When sending additional segments following a TFO SYN|ACK, 436 * do not include the SYN bit. 437 */ 438 if ((tp->t_flags & TF_FASTOPEN) && 439 (tp->t_state == TCPS_SYN_RECEIVED)) 440 flags &= ~TH_SYN; 441 off--, len++; 442 } 443 444 /* 445 * Be careful not to send data and/or FIN on SYN segments. 446 * This measure is needed to prevent interoperability problems 447 * with not fully conformant TCP implementations. 448 */ 449 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 450 len = 0; 451 flags &= ~TH_FIN; 452 } 453 454 /* 455 * On TFO sockets, ensure no data is sent in the following cases: 456 * 457 * - When retransmitting SYN|ACK on a passively-created socket 458 * 459 * - When retransmitting SYN on an actively created socket 460 * 461 * - When sending a zero-length cookie (cookie request) on an 462 * actively created socket 463 * 464 * - When the socket is in the CLOSED state (RST is being sent) 465 */ 466 if ((tp->t_flags & TF_FASTOPEN) && 467 (((flags & TH_SYN) && (tp->t_rxtshift > 0)) || 468 ((tp->t_state == TCPS_SYN_SENT) && 469 (tp->t_tfo_client_cookie_len == 0)) || 470 (flags & TH_RST))) 471 len = 0; 472 473 /* Without fast-open there should never be data sent on a SYN. */ 474 if ((flags & TH_SYN) && !(tp->t_flags & TF_FASTOPEN)) { 475 len = 0; 476 } 477 478 if (len <= 0) { 479 /* 480 * If FIN has been sent but not acked, 481 * but we haven't been called to retransmit, 482 * len will be < 0. Otherwise, window shrank 483 * after we sent into it. If window shrank to 0, 484 * cancel pending retransmit, pull snd_nxt back 485 * to (closed) window, and set the persist timer 486 * if it isn't already going. If the window didn't 487 * close completely, just wait for an ACK. 488 * 489 * We also do a general check here to ensure that 490 * we will set the persist timer when we have data 491 * to send, but a 0-byte window. This makes sure 492 * the persist timer is set even if the packet 493 * hits one of the "goto send" lines below. 494 */ 495 len = 0; 496 if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) && 497 (off < (int) sbavail(&so->so_snd)) && 498 !tcp_timer_active(tp, TT_PERSIST)) { 499 tcp_timer_activate(tp, TT_REXMT, 0); 500 tp->t_rxtshift = 0; 501 tp->snd_nxt = tp->snd_una; 502 if (!tcp_timer_active(tp, TT_PERSIST)) 503 tcp_setpersist(tp); 504 } 505 } 506 507 /* len will be >= 0 after this point. */ 508 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 509 510 tcp_sndbuf_autoscale(tp, so, sendwin); 511 512 /* 513 * Decide if we can use TCP Segmentation Offloading (if supported by 514 * hardware). 515 * 516 * TSO may only be used if we are in a pure bulk sending state. The 517 * presence of TCP-MD5, IP options (IPsec), and possibly SACK 518 * retransmits prevent using TSO. With TSO the TCP header is the same 519 * (except for the sequence number) for all generated packets. This 520 * makes it impossible to transmit any options which vary per generated 521 * segment or packet. 522 * 523 * IPv4 handling has a clear separation of ip options and ip header 524 * flags while IPv6 combines both in in6p_outputopts. ip6_optlen() does 525 * the right thing below to provide length of just ip options and thus 526 * checking for ipoptlen is enough to decide if ip options are present. 527 */ 528 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 529 /* 530 * Pre-calculate here as we save another lookup into the darknesses 531 * of IPsec that way and can actually decide if TSO is ok. 532 */ 533 #ifdef INET6 534 if (isipv6 && IPSEC_ENABLED(ipv6)) 535 ipsec_optlen = IPSEC_HDRSIZE(ipv6, inp); 536 #ifdef INET 537 else 538 #endif 539 #endif /* INET6 */ 540 #ifdef INET 541 if (IPSEC_ENABLED(ipv4)) 542 ipsec_optlen = IPSEC_HDRSIZE(ipv4, inp); 543 #endif /* INET */ 544 #endif /* IPSEC */ 545 #ifdef INET6 546 if (isipv6) 547 ipoptlen = ip6_optlen(inp); 548 else 549 #endif 550 if (inp->inp_options) 551 ipoptlen = inp->inp_options->m_len - 552 offsetof(struct ipoption, ipopt_list); 553 else 554 ipoptlen = 0; 555 ipoptlen += ipsec_optlen; 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 ((sack_rxmit == 0) || V_tcp_sack_tso) && 561 (ipoptlen == 0 || (ipoptlen == ipsec_optlen && 562 (tp->t_flags2 & TF2_IPSEC_TSO) != 0)) && 563 !(flags & TH_SYN)) 564 tso = 1; 565 566 if (SEQ_LT((sack_rxmit ? p->rxmit : tp->snd_nxt) + len, 567 tp->snd_una + sbused(&so->so_snd))) { 568 flags &= ~TH_FIN; 569 } 570 571 recwin = lmin(lmax(sbspace(&so->so_rcv), 0), 572 (long)TCP_MAXWIN << tp->rcv_scale); 573 574 /* 575 * Sender silly window avoidance. We transmit under the following 576 * conditions when len is non-zero: 577 * 578 * - We have a full segment (or more with TSO) 579 * - This is the last buffer in a write()/send() and we are 580 * either idle or running NODELAY 581 * - we've timed out (e.g. persist timer) 582 * - we have more then 1/2 the maximum send window's worth of 583 * data (receiver may be limited the window size) 584 * - we need to retransmit 585 */ 586 if (len) { 587 if (len >= tp->t_maxseg) 588 goto send; 589 /* 590 * As the TCP header options are now 591 * considered when setting up the initial 592 * window, we would not send the last segment 593 * if we skip considering the option length here. 594 * Note: this may not work when tcp headers change 595 * very dynamically in the future. 596 */ 597 if ((((tp->t_flags & TF_SIGNATURE) ? 598 PADTCPOLEN(TCPOLEN_SIGNATURE) : 0) + 599 ((tp->t_flags & TF_RCVD_TSTMP) ? 600 PADTCPOLEN(TCPOLEN_TIMESTAMP) : 0) + 601 len) >= tp->t_maxseg) 602 goto send; 603 /* 604 * NOTE! on localhost connections an 'ack' from the remote 605 * end may occur synchronously with the output and cause 606 * us to flush a buffer queued with moretocome. XXX 607 * 608 * note: the len + off check is almost certainly unnecessary. 609 */ 610 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 611 (idle || (tp->t_flags & TF_NODELAY)) && 612 (uint32_t)len + (uint32_t)off >= sbavail(&so->so_snd) && 613 (tp->t_flags & TF_NOPUSH) == 0) { 614 goto send; 615 } 616 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 617 goto send; 618 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 619 goto send; 620 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 621 goto send; 622 if (sack_rxmit) 623 goto send; 624 } 625 626 /* 627 * Sending of standalone window updates. 628 * 629 * Window updates are important when we close our window due to a 630 * full socket buffer and are opening it again after the application 631 * reads data from it. Once the window has opened again and the 632 * remote end starts to send again the ACK clock takes over and 633 * provides the most current window information. 634 * 635 * We must avoid the silly window syndrome whereas every read 636 * from the receive buffer, no matter how small, causes a window 637 * update to be sent. We also should avoid sending a flurry of 638 * window updates when the socket buffer had queued a lot of data 639 * and the application is doing small reads. 640 * 641 * Prevent a flurry of pointless window updates by only sending 642 * an update when we can increase the advertized window by more 643 * than 1/4th of the socket buffer capacity. When the buffer is 644 * getting full or is very small be more aggressive and send an 645 * update whenever we can increase by two mss sized segments. 646 * In all other situations the ACK's to new incoming data will 647 * carry further window increases. 648 * 649 * Don't send an independent window update if a delayed 650 * ACK is pending (it will get piggy-backed on it) or the 651 * remote side already has done a half-close and won't send 652 * more data. 653 */ 654 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 655 !(tp->t_flags & TF_DELACK) && 656 !TCPS_HAVERCVDFIN(tp->t_state)) { 657 /* 658 * "adv" is the amount we could increase the window, 659 * taking into account that we are limited by 660 * TCP_MAXWIN << tp->rcv_scale. 661 */ 662 int32_t adv; 663 int oldwin; 664 665 adv = recwin; 666 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { 667 oldwin = (tp->rcv_adv - tp->rcv_nxt); 668 if (adv > oldwin) 669 adv -= oldwin; 670 else 671 adv = 0; 672 } else 673 oldwin = 0; 674 675 /* 676 * If the new window size ends up being the same as or less 677 * than the old size when it is scaled, then don't force 678 * a window update. 679 */ 680 if (oldwin >> tp->rcv_scale >= (adv + oldwin) >> tp->rcv_scale) 681 goto dontupdate; 682 683 if (adv >= (int32_t)(2 * tp->t_maxseg) && 684 (adv >= (int32_t)(so->so_rcv.sb_hiwat / 4) || 685 recwin <= (so->so_rcv.sb_hiwat / 8) || 686 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg || 687 adv >= TCP_MAXWIN << tp->rcv_scale)) 688 goto send; 689 if (2 * adv >= (int32_t)so->so_rcv.sb_hiwat) 690 goto send; 691 } 692 dontupdate: 693 694 /* 695 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 696 * is also a catch-all for the retransmit timer timeout case. 697 */ 698 if (tp->t_flags & TF_ACKNOW) 699 goto send; 700 if ((flags & TH_RST) || 701 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 702 goto send; 703 if (SEQ_GT(tp->snd_up, tp->snd_una)) 704 goto send; 705 /* 706 * If our state indicates that FIN should be sent 707 * and we have not yet done so, then we need to send. 708 */ 709 if (flags & TH_FIN && 710 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 711 goto send; 712 /* 713 * In SACK, it is possible for tcp_output to fail to send a segment 714 * after the retransmission timer has been turned off. Make sure 715 * that the retransmission timer is set. 716 */ 717 if ((tp->t_flags & TF_SACK_PERMIT) && 718 SEQ_GT(tp->snd_max, tp->snd_una) && 719 !tcp_timer_active(tp, TT_REXMT) && 720 !tcp_timer_active(tp, TT_PERSIST)) { 721 tcp_timer_activate(tp, TT_REXMT, TP_RXTCUR(tp)); 722 goto just_return; 723 } 724 /* 725 * TCP window updates are not reliable, rather a polling protocol 726 * using ``persist'' packets is used to insure receipt of window 727 * updates. The three ``states'' for the output side are: 728 * idle not doing retransmits or persists 729 * persisting to move a small or zero window 730 * (re)transmitting and thereby not persisting 731 * 732 * tcp_timer_active(tp, TT_PERSIST) 733 * is true when we are in persist state. 734 * (tp->t_flags & TF_FORCEDATA) 735 * is set when we are called to send a persist packet. 736 * tcp_timer_active(tp, TT_REXMT) 737 * is set when we are retransmitting 738 * The output side is idle when both timers are zero. 739 * 740 * If send window is too small, there is data to transmit, and no 741 * retransmit or persist is pending, then go to persist state. 742 * If nothing happens soon, send when timer expires: 743 * if window is nonzero, transmit what we can, 744 * otherwise force out a byte. 745 */ 746 if (sbavail(&so->so_snd) && !tcp_timer_active(tp, TT_REXMT) && 747 !tcp_timer_active(tp, TT_PERSIST)) { 748 tp->t_rxtshift = 0; 749 tcp_setpersist(tp); 750 } 751 752 /* 753 * No reason to send a segment, just return. 754 */ 755 just_return: 756 SOCK_SENDBUF_UNLOCK(so); 757 return (0); 758 759 send: 760 SOCK_SENDBUF_LOCK_ASSERT(so); 761 if (len > 0) { 762 if (len >= tp->t_maxseg) 763 tp->t_flags2 |= TF2_PLPMTU_MAXSEGSNT; 764 else 765 tp->t_flags2 &= ~TF2_PLPMTU_MAXSEGSNT; 766 } 767 /* 768 * Before ESTABLISHED, force sending of initial options 769 * unless TCP set not to do any options. 770 * NOTE: we assume that the IP/TCP header plus TCP options 771 * always fit in a single mbuf, leaving room for a maximum 772 * link header, i.e. 773 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 774 */ 775 optlen = 0; 776 #ifdef INET6 777 if (isipv6) 778 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 779 else 780 #endif 781 hdrlen = sizeof (struct tcpiphdr); 782 783 if (flags & TH_SYN) { 784 tp->snd_nxt = tp->iss; 785 } 786 787 /* 788 * Compute options for segment. 789 * We only have to care about SYN and established connection 790 * segments. Options for SYN-ACK segments are handled in TCP 791 * syncache. 792 */ 793 to.to_flags = 0; 794 if ((tp->t_flags & TF_NOOPT) == 0) { 795 /* Maximum segment size. */ 796 if (flags & TH_SYN) { 797 to.to_mss = tcp_mssopt(&inp->inp_inc); 798 if (tp->t_port) 799 to.to_mss -= V_tcp_udp_tunneling_overhead; 800 to.to_flags |= TOF_MSS; 801 802 /* 803 * On SYN or SYN|ACK transmits on TFO connections, 804 * only include the TFO option if it is not a 805 * retransmit, as the presence of the TFO option may 806 * have caused the original SYN or SYN|ACK to have 807 * been dropped by a middlebox. 808 */ 809 if ((tp->t_flags & TF_FASTOPEN) && 810 (tp->t_rxtshift == 0)) { 811 if (tp->t_state == TCPS_SYN_RECEIVED) { 812 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN; 813 to.to_tfo_cookie = 814 (u_int8_t *)&tp->t_tfo_cookie.server; 815 to.to_flags |= TOF_FASTOPEN; 816 wanted_cookie = 1; 817 } else if (tp->t_state == TCPS_SYN_SENT) { 818 to.to_tfo_len = 819 tp->t_tfo_client_cookie_len; 820 to.to_tfo_cookie = 821 tp->t_tfo_cookie.client; 822 to.to_flags |= TOF_FASTOPEN; 823 wanted_cookie = 1; 824 /* 825 * If we wind up having more data to 826 * send with the SYN than can fit in 827 * one segment, don't send any more 828 * until the SYN|ACK comes back from 829 * the other end. 830 */ 831 dont_sendalot = 1; 832 } 833 } 834 } 835 /* Window scaling. */ 836 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 837 to.to_wscale = tp->request_r_scale; 838 to.to_flags |= TOF_SCALE; 839 } 840 /* Timestamps. */ 841 if ((tp->t_flags & TF_RCVD_TSTMP) || 842 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 843 curticks = tcp_ts_getticks(); 844 to.to_tsval = curticks + tp->ts_offset; 845 to.to_tsecr = tp->ts_recent; 846 to.to_flags |= TOF_TS; 847 if (tp->t_rxtshift == 1) 848 tp->t_badrxtwin = curticks; 849 } 850 851 /* Set receive buffer autosizing timestamp. */ 852 if (tp->rfbuf_ts == 0 && 853 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 854 tp->rfbuf_ts = tcp_ts_getticks(); 855 856 /* Selective ACK's. */ 857 if (tp->t_flags & TF_SACK_PERMIT) { 858 if (flags & TH_SYN) 859 to.to_flags |= TOF_SACKPERM; 860 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 861 tp->rcv_numsacks > 0) { 862 to.to_flags |= TOF_SACK; 863 to.to_nsacks = tp->rcv_numsacks; 864 to.to_sacks = (u_char *)tp->sackblks; 865 } 866 } 867 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 868 /* TCP-MD5 (RFC2385). */ 869 /* 870 * Check that TCP_MD5SIG is enabled in tcpcb to 871 * account the size needed to set this TCP option. 872 */ 873 if (tp->t_flags & TF_SIGNATURE) 874 to.to_flags |= TOF_SIGNATURE; 875 #endif /* TCP_SIGNATURE */ 876 877 /* Processing the options. */ 878 hdrlen += optlen = tcp_addoptions(&to, opt); 879 /* 880 * If we wanted a TFO option to be added, but it was unable 881 * to fit, ensure no data is sent. 882 */ 883 if ((tp->t_flags & TF_FASTOPEN) && wanted_cookie && 884 !(to.to_flags & TOF_FASTOPEN)) 885 len = 0; 886 } 887 if (tp->t_port) { 888 if (V_tcp_udp_tunneling_port == 0) { 889 /* The port was removed?? */ 890 SOCK_SENDBUF_UNLOCK(so); 891 return (EHOSTUNREACH); 892 } 893 hdrlen += sizeof(struct udphdr); 894 } 895 /* 896 * Adjust data length if insertion of options will 897 * bump the packet length beyond the t_maxseg length. 898 * Clear the FIN bit because we cut off the tail of 899 * the segment. 900 */ 901 if (len + optlen + ipoptlen > tp->t_maxseg) { 902 flags &= ~TH_FIN; 903 904 if (tso) { 905 u_int if_hw_tsomax; 906 u_int moff; 907 int max_len; 908 909 /* extract TSO information */ 910 if_hw_tsomax = tp->t_tsomax; 911 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount; 912 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize; 913 914 /* 915 * Limit a TSO burst to prevent it from 916 * overflowing or exceeding the maximum length 917 * allowed by the network interface: 918 */ 919 KASSERT(ipoptlen == ipsec_optlen, 920 ("%s: TSO can't do IP options", __func__)); 921 922 /* 923 * Check if we should limit by maximum payload 924 * length: 925 */ 926 if (if_hw_tsomax != 0) { 927 /* compute maximum TSO length */ 928 max_len = if_hw_tsomax - hdrlen - 929 ipsec_optlen - max_linkhdr; 930 if (max_len <= 0) { 931 len = 0; 932 } else if (len > max_len) { 933 sendalot = 1; 934 len = max_len; 935 } 936 } 937 938 /* 939 * Prevent the last segment from being 940 * fractional unless the send sockbuf can be 941 * emptied: 942 */ 943 max_len = tp->t_maxseg - optlen - ipsec_optlen; 944 if (((uint32_t)off + (uint32_t)len) < 945 sbavail(&so->so_snd)) { 946 moff = len % max_len; 947 if (moff != 0) { 948 len -= moff; 949 sendalot = 1; 950 } 951 } 952 953 /* 954 * In case there are too many small fragments 955 * don't use TSO: 956 */ 957 if (len <= max_len) { 958 len = max_len; 959 sendalot = 1; 960 tso = 0; 961 } 962 963 /* 964 * Send the FIN in a separate segment 965 * after the bulk sending is done. 966 * We don't trust the TSO implementations 967 * to clear the FIN flag on all but the 968 * last segment. 969 */ 970 if (tp->t_flags & TF_NEEDFIN) 971 sendalot = 1; 972 } else { 973 if (optlen + ipoptlen >= tp->t_maxseg) { 974 /* 975 * Since we don't have enough space to put 976 * the IP header chain and the TCP header in 977 * one packet as required by RFC 7112, don't 978 * send it. Also ensure that at least one 979 * byte of the payload can be put into the 980 * TCP segment. 981 */ 982 SOCK_SENDBUF_UNLOCK(so); 983 error = EMSGSIZE; 984 sack_rxmit = 0; 985 goto out; 986 } 987 len = tp->t_maxseg - optlen - ipoptlen; 988 sendalot = 1; 989 if (dont_sendalot) 990 sendalot = 0; 991 } 992 } else 993 tso = 0; 994 995 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 996 ("%s: len > IP_MAXPACKET", __func__)); 997 998 /*#ifdef DIAGNOSTIC*/ 999 #ifdef INET6 1000 if (max_linkhdr + hdrlen > MCLBYTES) 1001 #else 1002 if (max_linkhdr + hdrlen > MHLEN) 1003 #endif 1004 panic("tcphdr too big"); 1005 /*#endif*/ 1006 1007 /* 1008 * This KASSERT is here to catch edge cases at a well defined place. 1009 * Before, those had triggered (random) panic conditions further down. 1010 */ 1011 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 1012 1013 /* 1014 * Grab a header mbuf, attaching a copy of data to 1015 * be transmitted, and initialize the header from 1016 * the template for sends on this connection. 1017 */ 1018 if (len) { 1019 struct mbuf *mb; 1020 struct sockbuf *msb; 1021 u_int moff; 1022 1023 if ((tp->t_flags & TF_FORCEDATA) && len == 1) { 1024 TCPSTAT_INC(tcps_sndprobe); 1025 #ifdef STATS 1026 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1027 stats_voi_update_abs_u32(tp->t_stats, 1028 VOI_TCP_RETXPB, len); 1029 else 1030 stats_voi_update_abs_u64(tp->t_stats, 1031 VOI_TCP_TXPB, len); 1032 #endif /* STATS */ 1033 } else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 1034 tp->t_sndrexmitpack++; 1035 TCPSTAT_INC(tcps_sndrexmitpack); 1036 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 1037 if (sack_rxmit) { 1038 TCPSTAT_INC(tcps_sack_rexmits); 1039 if (tso) { 1040 TCPSTAT_INC(tcps_sack_rexmits_tso); 1041 } 1042 TCPSTAT_ADD(tcps_sack_rexmit_bytes, len); 1043 } 1044 #ifdef STATS 1045 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_RETXPB, 1046 len); 1047 #endif /* STATS */ 1048 } else { 1049 TCPSTAT_INC(tcps_sndpack); 1050 TCPSTAT_ADD(tcps_sndbyte, len); 1051 #ifdef STATS 1052 stats_voi_update_abs_u64(tp->t_stats, VOI_TCP_TXPB, 1053 len); 1054 #endif /* STATS */ 1055 } 1056 #ifdef INET6 1057 if (MHLEN < hdrlen + max_linkhdr) 1058 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR); 1059 else 1060 #endif 1061 m = m_gethdr(M_NOWAIT, MT_DATA); 1062 1063 if (m == NULL) { 1064 SOCK_SENDBUF_UNLOCK(so); 1065 error = ENOBUFS; 1066 sack_rxmit = 0; 1067 goto out; 1068 } 1069 1070 m->m_data += max_linkhdr; 1071 m->m_len = hdrlen; 1072 1073 /* 1074 * Start the m_copy functions from the closest mbuf 1075 * to the offset in the socket buffer chain. 1076 */ 1077 mb = sbsndptr_noadv(&so->so_snd, off, &moff); 1078 if (len <= MHLEN - hdrlen - max_linkhdr && !hw_tls) { 1079 m_copydata(mb, moff, len, 1080 mtod(m, caddr_t) + hdrlen); 1081 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1082 sbsndptr_adv(&so->so_snd, mb, len); 1083 m->m_len += len; 1084 } else { 1085 int32_t old_len; 1086 1087 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1088 msb = NULL; 1089 else 1090 msb = &so->so_snd; 1091 old_len = len; 1092 m->m_next = tcp_m_copym(mb, moff, 1093 &len, if_hw_tsomaxsegcount, 1094 if_hw_tsomaxsegsize, msb, hw_tls); 1095 if (old_len != len) 1096 flags &= ~TH_FIN; 1097 if (len <= (tp->t_maxseg - optlen)) { 1098 /* 1099 * Must have ran out of mbufs for the copy 1100 * shorten it to no longer need tso. Lets 1101 * not put on sendalot since we are low on 1102 * mbufs. 1103 */ 1104 tso = 0; 1105 } 1106 if (m->m_next == NULL) { 1107 SOCK_SENDBUF_UNLOCK(so); 1108 (void) m_free(m); 1109 error = ENOBUFS; 1110 sack_rxmit = 0; 1111 goto out; 1112 } 1113 } 1114 1115 /* 1116 * If we're sending everything we've got, set PUSH. 1117 * (This will keep happy those implementations which only 1118 * give data to the user when a buffer fills or 1119 * a PUSH comes in.) 1120 */ 1121 if (((uint32_t)off + (uint32_t)len == sbused(&so->so_snd)) && 1122 !(flags & TH_SYN)) 1123 flags |= TH_PUSH; 1124 SOCK_SENDBUF_UNLOCK(so); 1125 } else { 1126 SOCK_SENDBUF_UNLOCK(so); 1127 if (tp->t_flags & TF_ACKNOW) 1128 TCPSTAT_INC(tcps_sndacks); 1129 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 1130 TCPSTAT_INC(tcps_sndctrl); 1131 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 1132 TCPSTAT_INC(tcps_sndurg); 1133 else 1134 TCPSTAT_INC(tcps_sndwinup); 1135 1136 m = m_gethdr(M_NOWAIT, MT_DATA); 1137 if (m == NULL) { 1138 error = ENOBUFS; 1139 sack_rxmit = 0; 1140 goto out; 1141 } 1142 #ifdef INET6 1143 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 1144 MHLEN >= hdrlen) { 1145 M_ALIGN(m, hdrlen); 1146 } else 1147 #endif 1148 m->m_data += max_linkhdr; 1149 m->m_len = hdrlen; 1150 } 1151 SOCK_SENDBUF_UNLOCK_ASSERT(so); 1152 m->m_pkthdr.rcvif = (struct ifnet *)0; 1153 #ifdef MAC 1154 mac_inpcb_create_mbuf(inp, m); 1155 #endif 1156 #ifdef INET6 1157 if (isipv6) { 1158 ip6 = mtod(m, struct ip6_hdr *); 1159 if (tp->t_port) { 1160 udp = (struct udphdr *)((caddr_t)ip6 + sizeof(struct ip6_hdr)); 1161 udp->uh_sport = htons(V_tcp_udp_tunneling_port); 1162 udp->uh_dport = tp->t_port; 1163 ulen = hdrlen + len - sizeof(struct ip6_hdr); 1164 udp->uh_ulen = htons(ulen); 1165 th = (struct tcphdr *)(udp + 1); 1166 } else { 1167 th = (struct tcphdr *)(ip6 + 1); 1168 } 1169 tcpip_fillheaders(inp, tp->t_port, ip6, th); 1170 } else 1171 #endif /* INET6 */ 1172 { 1173 ip = mtod(m, struct ip *); 1174 if (tp->t_port) { 1175 udp = (struct udphdr *)((caddr_t)ip + sizeof(struct ip)); 1176 udp->uh_sport = htons(V_tcp_udp_tunneling_port); 1177 udp->uh_dport = tp->t_port; 1178 ulen = hdrlen + len - sizeof(struct ip); 1179 udp->uh_ulen = htons(ulen); 1180 th = (struct tcphdr *)(udp + 1); 1181 } else 1182 th = (struct tcphdr *)(ip + 1); 1183 tcpip_fillheaders(inp, tp->t_port, ip, th); 1184 } 1185 1186 /* 1187 * Fill in fields, remembering maximum advertised 1188 * window for use in delaying messages about window sizes. 1189 * If resending a FIN, be sure not to use a new sequence number. 1190 */ 1191 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 1192 tp->snd_nxt == tp->snd_max) 1193 tp->snd_nxt--; 1194 /* 1195 * If we are starting a connection, send ECN setup 1196 * SYN packet. If we are on a retransmit, we may 1197 * resend those bits a number of times as per 1198 * RFC 3168. 1199 */ 1200 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) { 1201 flags |= tcp_ecn_output_syn_sent(tp); 1202 } 1203 /* Also handle parallel SYN for ECN */ 1204 if ((TCPS_HAVERCVDSYN(tp->t_state)) && 1205 (tp->t_flags2 & (TF2_ECN_PERMIT | TF2_ACE_PERMIT))) { 1206 int ect = tcp_ecn_output_established(tp, &flags, len, sack_rxmit); 1207 if ((tp->t_state == TCPS_SYN_RECEIVED) && 1208 (tp->t_flags2 & TF2_ECN_SND_ECE)) 1209 tp->t_flags2 &= ~TF2_ECN_SND_ECE; 1210 #ifdef INET6 1211 if (isipv6) { 1212 ip6->ip6_flow &= ~htonl(IPTOS_ECN_MASK << IPV6_FLOWLABEL_LEN); 1213 ip6->ip6_flow |= htonl(ect << IPV6_FLOWLABEL_LEN); 1214 } 1215 else 1216 #endif 1217 { 1218 ip->ip_tos &= ~IPTOS_ECN_MASK; 1219 ip->ip_tos |= ect; 1220 } 1221 } 1222 1223 /* 1224 * If we are doing retransmissions, then snd_nxt will 1225 * not reflect the first unsent octet. For ACK only 1226 * packets, we do not want the sequence number of the 1227 * retransmitted packet, we want the sequence number 1228 * of the next unsent octet. So, if there is no data 1229 * (and no SYN or FIN), use snd_max instead of snd_nxt 1230 * when filling in ti_seq. But if we are in persist 1231 * state, snd_max might reflect one byte beyond the 1232 * right edge of the window, so use snd_nxt in that 1233 * case, since we know we aren't doing a retransmission. 1234 * (retransmit and persist are mutually exclusive...) 1235 */ 1236 if (sack_rxmit == 0) { 1237 if (len || (flags & (TH_SYN|TH_FIN)) || 1238 tcp_timer_active(tp, TT_PERSIST)) 1239 th->th_seq = htonl(tp->snd_nxt); 1240 else 1241 th->th_seq = htonl(tp->snd_max); 1242 } else { 1243 th->th_seq = htonl(p->rxmit); 1244 p->rxmit += len; 1245 /* 1246 * Lost Retransmission Detection 1247 * trigger resending of a (then 1248 * still existing) hole, when 1249 * fack acks recoverypoint. 1250 */ 1251 if ((tp->t_flags & TF_LRD) && SEQ_GEQ(p->rxmit, p->end)) 1252 p->rxmit = tp->snd_recover; 1253 tp->sackhint.sack_bytes_rexmit += len; 1254 } 1255 if (IN_RECOVERY(tp->t_flags)) { 1256 /* 1257 * Account all bytes transmitted while 1258 * IN_RECOVERY, simplifying PRR and 1259 * Lost Retransmit Detection 1260 */ 1261 tp->sackhint.prr_out += len; 1262 } 1263 th->th_ack = htonl(tp->rcv_nxt); 1264 if (optlen) { 1265 bcopy(opt, th + 1, optlen); 1266 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1267 } 1268 tcp_set_flags(th, flags); 1269 /* 1270 * Calculate receive window. Don't shrink window, 1271 * but avoid silly window syndrome. 1272 * If a RST segment is sent, advertise a window of zero. 1273 */ 1274 if (flags & TH_RST) { 1275 recwin = 0; 1276 } else { 1277 if (recwin < (so->so_rcv.sb_hiwat / 4) && 1278 recwin < tp->t_maxseg) 1279 recwin = 0; 1280 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1281 recwin < (tp->rcv_adv - tp->rcv_nxt)) 1282 recwin = (tp->rcv_adv - tp->rcv_nxt); 1283 } 1284 /* 1285 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1286 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1287 * case is handled in syncache. 1288 */ 1289 if (flags & TH_SYN) 1290 th->th_win = htons((u_short) 1291 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1292 else { 1293 /* Avoid shrinking window with window scaling. */ 1294 recwin = roundup2(recwin, 1 << tp->rcv_scale); 1295 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1296 } 1297 1298 /* 1299 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1300 * a 0 window. This may cause the remote transmitter to stall. This 1301 * flag tells soreceive() to disable delayed acknowledgements when 1302 * draining the buffer. This can occur if the receiver is attempting 1303 * to read more data than can be buffered prior to transmitting on 1304 * the connection. 1305 */ 1306 if (th->th_win == 0) { 1307 tp->t_sndzerowin++; 1308 tp->t_flags |= TF_RXWIN0SENT; 1309 } else 1310 tp->t_flags &= ~TF_RXWIN0SENT; 1311 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1312 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1313 th->th_flags |= TH_URG; 1314 } else 1315 /* 1316 * If no urgent pointer to send, then we pull 1317 * the urgent pointer to the left edge of the send window 1318 * so that it doesn't drift into the send window on sequence 1319 * number wraparound. 1320 */ 1321 tp->snd_up = tp->snd_una; /* drag it along */ 1322 1323 /* 1324 * Put TCP length in extended header, and then 1325 * checksum extended header and data. 1326 */ 1327 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1328 1329 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1330 if (to.to_flags & TOF_SIGNATURE) { 1331 /* 1332 * Calculate MD5 signature and put it into the place 1333 * determined before. 1334 * NOTE: since TCP options buffer doesn't point into 1335 * mbuf's data, calculate offset and use it. 1336 */ 1337 if (!TCPMD5_ENABLED() || (error = TCPMD5_OUTPUT(m, th, 1338 (u_char *)(th + 1) + (to.to_signature - opt))) != 0) { 1339 /* 1340 * Do not send segment if the calculation of MD5 1341 * digest has failed. 1342 */ 1343 m_freem(m); 1344 goto out; 1345 } 1346 } 1347 #endif 1348 #ifdef INET6 1349 if (isipv6) { 1350 /* 1351 * There is no need to fill in ip6_plen right now. 1352 * It will be filled later by ip6_output. 1353 */ 1354 if (tp->t_port) { 1355 m->m_pkthdr.csum_flags = CSUM_UDP_IPV6; 1356 m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum); 1357 udp->uh_sum = in6_cksum_pseudo(ip6, ulen, IPPROTO_UDP, 0); 1358 th->th_sum = htons(0); 1359 UDPSTAT_INC(udps_opackets); 1360 } else { 1361 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1362 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1363 th->th_sum = in6_cksum_pseudo(ip6, 1364 sizeof(struct tcphdr) + optlen + len, IPPROTO_TCP, 1365 0); 1366 } 1367 } 1368 #endif 1369 #if defined(INET6) && defined(INET) 1370 else 1371 #endif 1372 #ifdef INET 1373 { 1374 if (tp->t_port) { 1375 m->m_pkthdr.csum_flags = CSUM_UDP; 1376 m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum); 1377 udp->uh_sum = in_pseudo(ip->ip_src.s_addr, 1378 ip->ip_dst.s_addr, htons(ulen + IPPROTO_UDP)); 1379 th->th_sum = htons(0); 1380 UDPSTAT_INC(udps_opackets); 1381 } else { 1382 m->m_pkthdr.csum_flags = CSUM_TCP; 1383 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1384 th->th_sum = in_pseudo(ip->ip_src.s_addr, 1385 ip->ip_dst.s_addr, htons(sizeof(struct tcphdr) + 1386 IPPROTO_TCP + len + optlen)); 1387 } 1388 1389 /* IP version must be set here for ipv4/ipv6 checking later */ 1390 KASSERT(ip->ip_v == IPVERSION, 1391 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1392 } 1393 #endif 1394 1395 /* 1396 * Enable TSO and specify the size of the segments. 1397 * The TCP pseudo header checksum is always provided. 1398 */ 1399 if (tso) { 1400 KASSERT(len > tp->t_maxseg - optlen - ipsec_optlen, 1401 ("%s: len <= tso_segsz", __func__)); 1402 m->m_pkthdr.csum_flags |= CSUM_TSO; 1403 m->m_pkthdr.tso_segsz = tp->t_maxseg - optlen - ipsec_optlen; 1404 } 1405 1406 KASSERT(len + hdrlen == m_length(m, NULL), 1407 ("%s: mbuf chain shorter than expected: %d + %u != %u", 1408 __func__, len, hdrlen, m_length(m, NULL))); 1409 1410 #ifdef TCP_HHOOK 1411 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1412 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1413 #endif 1414 1415 TCP_PROBE3(debug__output, tp, th, m); 1416 1417 /* We're getting ready to send; log now. */ 1418 /* XXXMT: We are not honoring verbose logging. */ 1419 1420 if (tcp_bblogging_on(tp)) 1421 lgb = tcp_log_event(tp, th, &so->so_rcv, &so->so_snd, 1422 TCP_LOG_OUT, ERRNO_UNK, len, NULL, false, NULL, NULL, 0, 1423 NULL); 1424 else 1425 lgb = NULL; 1426 1427 /* 1428 * Fill in IP length and desired time to live and 1429 * send to IP level. There should be a better way 1430 * to handle ttl and tos; we could keep them in 1431 * the template, but need a way to checksum without them. 1432 */ 1433 /* 1434 * m->m_pkthdr.len should have been set before checksum calculation, 1435 * because in6_cksum() need it. 1436 */ 1437 #ifdef INET6 1438 if (isipv6) { 1439 /* 1440 * we separately set hoplimit for every segment, since the 1441 * user might want to change the value via setsockopt. 1442 * Also, desired default hop limit might be changed via 1443 * Neighbor Discovery. 1444 */ 1445 ip6->ip6_hlim = in6_selecthlim(inp, NULL); 1446 1447 /* 1448 * Set the packet size here for the benefit of DTrace probes. 1449 * ip6_output() will set it properly; it's supposed to include 1450 * the option header lengths as well. 1451 */ 1452 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6)); 1453 1454 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) 1455 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1456 else 1457 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1458 1459 if (tp->t_state == TCPS_SYN_SENT) 1460 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th); 1461 1462 TCP_PROBE5(send, NULL, tp, ip6, tp, th); 1463 1464 #ifdef TCPPCAP 1465 /* Save packet, if requested. */ 1466 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1467 #endif 1468 1469 /* TODO: IPv6 IP6TOS_ECT bit on */ 1470 error = ip6_output(m, inp->in6p_outputopts, &inp->inp_route6, 1471 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 1472 NULL, NULL, inp); 1473 1474 if (error == EMSGSIZE && inp->inp_route6.ro_nh != NULL) 1475 mtu = inp->inp_route6.ro_nh->nh_mtu; 1476 } 1477 #endif /* INET6 */ 1478 #if defined(INET) && defined(INET6) 1479 else 1480 #endif 1481 #ifdef INET 1482 { 1483 ip->ip_len = htons(m->m_pkthdr.len); 1484 #ifdef INET6 1485 if (inp->inp_vflag & INP_IPV6PROTO) 1486 ip->ip_ttl = in6_selecthlim(inp, NULL); 1487 #endif /* INET6 */ 1488 /* 1489 * If we do path MTU discovery, then we set DF on every packet. 1490 * This might not be the best thing to do according to RFC3390 1491 * Section 2. However the tcp hostcache migitates the problem 1492 * so it affects only the first tcp connection with a host. 1493 * 1494 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1495 */ 1496 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) { 1497 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1498 if (tp->t_port == 0 || len < V_tcp_minmss) { 1499 ip->ip_off |= htons(IP_DF); 1500 } 1501 } else { 1502 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1503 } 1504 1505 if (tp->t_state == TCPS_SYN_SENT) 1506 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th); 1507 1508 TCP_PROBE5(send, NULL, tp, ip, tp, th); 1509 1510 #ifdef TCPPCAP 1511 /* Save packet, if requested. */ 1512 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1513 #endif 1514 1515 error = ip_output(m, inp->inp_options, &inp->inp_route, 1516 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, inp); 1517 1518 if (error == EMSGSIZE && inp->inp_route.ro_nh != NULL) 1519 mtu = inp->inp_route.ro_nh->nh_mtu; 1520 } 1521 #endif /* INET */ 1522 1523 if (lgb != NULL) { 1524 lgb->tlb_errno = error; 1525 lgb = NULL; 1526 } 1527 out: 1528 if (error == 0) 1529 tcp_account_for_send(tp, len, (tp->snd_nxt != tp->snd_max), 0, hw_tls); 1530 /* 1531 * In transmit state, time the transmission and arrange for 1532 * the retransmit. In persist state, just set snd_max. In a closed 1533 * state just return. 1534 */ 1535 if (flags & TH_RST) { 1536 TCPSTAT_INC(tcps_sndtotal); 1537 return (0); 1538 } else if ((tp->t_flags & TF_FORCEDATA) == 0 || 1539 !tcp_timer_active(tp, TT_PERSIST)) { 1540 tcp_seq startseq = tp->snd_nxt; 1541 1542 /* 1543 * Advance snd_nxt over sequence space of this segment. 1544 */ 1545 if (flags & (TH_SYN|TH_FIN)) { 1546 if (flags & TH_SYN) 1547 tp->snd_nxt++; 1548 if (flags & TH_FIN) { 1549 tp->snd_nxt++; 1550 tp->t_flags |= TF_SENTFIN; 1551 } 1552 } 1553 if (sack_rxmit) 1554 goto timer; 1555 tp->snd_nxt += len; 1556 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1557 /* 1558 * Update "made progress" indication if we just 1559 * added new data to an empty socket buffer. 1560 */ 1561 if (tp->snd_una == tp->snd_max) 1562 tp->t_acktime = ticks; 1563 tp->snd_max = tp->snd_nxt; 1564 /* 1565 * Time this transmission if not a retransmission and 1566 * not currently timing anything. 1567 */ 1568 tp->t_sndtime = ticks; 1569 if (tp->t_rtttime == 0) { 1570 tp->t_rtttime = ticks; 1571 tp->t_rtseq = startseq; 1572 TCPSTAT_INC(tcps_segstimed); 1573 } 1574 #ifdef STATS 1575 if (!(tp->t_flags & TF_GPUTINPROG) && len) { 1576 tp->t_flags |= TF_GPUTINPROG; 1577 tp->gput_seq = startseq; 1578 tp->gput_ack = startseq + 1579 ulmin(sbavail(&so->so_snd) - off, sendwin); 1580 tp->gput_ts = tcp_ts_getticks(); 1581 } 1582 #endif /* STATS */ 1583 } 1584 1585 /* 1586 * Set retransmit timer if not currently set, 1587 * and not doing a pure ack or a keep-alive probe. 1588 * Initial value for retransmit timer is smoothed 1589 * round-trip time + 2 * round-trip time variance. 1590 * Initialize shift counter which is used for backoff 1591 * of retransmit time. 1592 */ 1593 timer: 1594 if (!tcp_timer_active(tp, TT_REXMT) && 1595 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1596 (tp->snd_nxt != tp->snd_una))) { 1597 if (tcp_timer_active(tp, TT_PERSIST)) { 1598 tcp_timer_activate(tp, TT_PERSIST, 0); 1599 tp->t_rxtshift = 0; 1600 } 1601 tcp_timer_activate(tp, TT_REXMT, TP_RXTCUR(tp)); 1602 } else if (len == 0 && sbavail(&so->so_snd) && 1603 !tcp_timer_active(tp, TT_REXMT) && 1604 !tcp_timer_active(tp, TT_PERSIST)) { 1605 /* 1606 * Avoid a situation where we do not set persist timer 1607 * after a zero window condition. For example: 1608 * 1) A -> B: packet with enough data to fill the window 1609 * 2) B -> A: ACK for #1 + new data (0 window 1610 * advertisement) 1611 * 3) A -> B: ACK for #2, 0 len packet 1612 * 1613 * In this case, A will not activate the persist timer, 1614 * because it chose to send a packet. Unless tcp_output 1615 * is called for some other reason (delayed ack timer, 1616 * another input packet from B, socket syscall), A will 1617 * not send zero window probes. 1618 * 1619 * So, if you send a 0-length packet, but there is data 1620 * in the socket buffer, and neither the rexmt or 1621 * persist timer is already set, then activate the 1622 * persist timer. 1623 */ 1624 tp->t_rxtshift = 0; 1625 tcp_setpersist(tp); 1626 } 1627 } else { 1628 /* 1629 * Persist case, update snd_max but since we are in 1630 * persist mode (no window) we do not update snd_nxt. 1631 */ 1632 int xlen = len; 1633 if (flags & TH_SYN) 1634 ++xlen; 1635 if (flags & TH_FIN) { 1636 ++xlen; 1637 tp->t_flags |= TF_SENTFIN; 1638 } 1639 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1640 tp->snd_max = tp->snd_nxt + xlen; 1641 } 1642 if ((error == 0) && 1643 (tp->rcv_numsacks > 0) && 1644 TCPS_HAVEESTABLISHED(tp->t_state) && 1645 (tp->t_flags & TF_SACK_PERMIT)) { 1646 /* Clean up any DSACK's sent */ 1647 tcp_clean_dsack_blocks(tp); 1648 } 1649 if ((error == 0) && 1650 sack_rxmit && 1651 SEQ_LT(tp->snd_nxt, SEQ_MIN(p->rxmit, p->end))) { 1652 /* 1653 * When transmitting from SACK scoreboard 1654 * after an RTO, pull snd_nxt along. 1655 */ 1656 tp->snd_nxt = SEQ_MIN(p->rxmit, p->end); 1657 } 1658 if (error) { 1659 /* 1660 * We know that the packet was lost, so back out the 1661 * sequence number advance, if any. 1662 * 1663 * If the error is EPERM the packet got blocked by the 1664 * local firewall. Normally we should terminate the 1665 * connection but the blocking may have been spurious 1666 * due to a firewall reconfiguration cycle. So we treat 1667 * it like a packet loss and let the retransmit timer and 1668 * timeouts do their work over time. 1669 * XXX: It is a POLA question whether calling tcp_drop right 1670 * away would be the really correct behavior instead. 1671 */ 1672 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1673 !tcp_timer_active(tp, TT_PERSIST)) && 1674 ((flags & TH_SYN) == 0) && 1675 (error != EPERM)) { 1676 if (sack_rxmit) { 1677 p->rxmit = SEQ_MIN(p->end, p->rxmit) - len; 1678 tp->sackhint.sack_bytes_rexmit -= len; 1679 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1680 ("sackhint bytes rtx >= 0")); 1681 KASSERT((flags & TH_FIN) == 0, 1682 ("error while FIN with SACK rxmit")); 1683 } else { 1684 tp->snd_nxt -= len; 1685 if (flags & TH_FIN) 1686 tp->snd_nxt--; 1687 } 1688 if (IN_RECOVERY(tp->t_flags)) 1689 tp->sackhint.prr_out -= len; 1690 } 1691 SOCK_SENDBUF_UNLOCK_ASSERT(so); /* Check gotos. */ 1692 switch (error) { 1693 case EACCES: 1694 case EPERM: 1695 tp->t_softerror = error; 1696 return (error); 1697 case ENOBUFS: 1698 TCP_XMIT_TIMER_ASSERT(tp, len, flags); 1699 tp->snd_cwnd = tcp_maxseg(tp); 1700 return (0); 1701 case EMSGSIZE: 1702 /* 1703 * For some reason the interface we used initially 1704 * to send segments changed to another or lowered 1705 * its MTU. 1706 * If TSO was active we either got an interface 1707 * without TSO capabilits or TSO was turned off. 1708 * If we obtained mtu from ip_output() then update 1709 * it and try again. 1710 */ 1711 if (tso) 1712 tp->t_flags &= ~TF_TSO; 1713 if (mtu != 0) { 1714 tcp_mss_update(tp, -1, mtu, NULL, NULL); 1715 goto again; 1716 } 1717 return (error); 1718 case EHOSTDOWN: 1719 case EHOSTUNREACH: 1720 case ENETDOWN: 1721 case ENETUNREACH: 1722 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1723 tp->t_softerror = error; 1724 return (0); 1725 } 1726 /* FALLTHROUGH */ 1727 default: 1728 return (error); 1729 } 1730 } 1731 TCPSTAT_INC(tcps_sndtotal); 1732 1733 /* 1734 * Data sent (as far as we can tell). 1735 * If this advertises a larger window than any other segment, 1736 * then remember the size of the advertised window. 1737 * Any pending ACK has now been sent. 1738 */ 1739 if (SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1740 tp->rcv_adv = tp->rcv_nxt + recwin; 1741 tp->last_ack_sent = tp->rcv_nxt; 1742 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1743 if (tcp_timer_active(tp, TT_DELACK)) 1744 tcp_timer_activate(tp, TT_DELACK, 0); 1745 if (sendalot) 1746 goto again; 1747 return (0); 1748 } 1749 1750 void 1751 tcp_setpersist(struct tcpcb *tp) 1752 { 1753 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1754 int tt; 1755 int maxunacktime; 1756 1757 tp->t_flags &= ~TF_PREVVALID; 1758 if (tcp_timer_active(tp, TT_REXMT)) 1759 panic("tcp_setpersist: retransmit pending"); 1760 /* 1761 * If the state is already closed, don't bother. 1762 */ 1763 if (tp->t_state == TCPS_CLOSED) 1764 return; 1765 1766 /* 1767 * Start/restart persistence timer. 1768 */ 1769 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1770 tcp_persmin, tcp_persmax); 1771 if (TP_MAXUNACKTIME(tp) && tp->t_acktime) { 1772 maxunacktime = tp->t_acktime + TP_MAXUNACKTIME(tp) - ticks; 1773 if (maxunacktime < 1) 1774 maxunacktime = 1; 1775 if (maxunacktime < tt) 1776 tt = maxunacktime; 1777 } 1778 tcp_timer_activate(tp, TT_PERSIST, tt); 1779 if (tp->t_rxtshift < V_tcp_retries) 1780 tp->t_rxtshift++; 1781 } 1782 1783 /* 1784 * Insert TCP options according to the supplied parameters to the place 1785 * optp in a consistent way. Can handle unaligned destinations. 1786 * 1787 * The order of the option processing is crucial for optimal packing and 1788 * alignment for the scarce option space. 1789 * 1790 * The optimal order for a SYN/SYN-ACK segment is: 1791 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1792 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1793 * 1794 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1795 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1796 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1797 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1798 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1799 */ 1800 int 1801 tcp_addoptions(struct tcpopt *to, u_char *optp) 1802 { 1803 u_int32_t mask, optlen = 0; 1804 1805 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1806 if ((to->to_flags & mask) != mask) 1807 continue; 1808 if (optlen == TCP_MAXOLEN) 1809 break; 1810 switch (to->to_flags & mask) { 1811 case TOF_MSS: 1812 while (optlen % 4) { 1813 optlen += TCPOLEN_NOP; 1814 *optp++ = TCPOPT_NOP; 1815 } 1816 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1817 continue; 1818 optlen += TCPOLEN_MAXSEG; 1819 *optp++ = TCPOPT_MAXSEG; 1820 *optp++ = TCPOLEN_MAXSEG; 1821 to->to_mss = htons(to->to_mss); 1822 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1823 optp += sizeof(to->to_mss); 1824 break; 1825 case TOF_SCALE: 1826 while (!optlen || optlen % 2 != 1) { 1827 optlen += TCPOLEN_NOP; 1828 *optp++ = TCPOPT_NOP; 1829 } 1830 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1831 continue; 1832 optlen += TCPOLEN_WINDOW; 1833 *optp++ = TCPOPT_WINDOW; 1834 *optp++ = TCPOLEN_WINDOW; 1835 *optp++ = to->to_wscale; 1836 break; 1837 case TOF_SACKPERM: 1838 while (optlen % 2) { 1839 optlen += TCPOLEN_NOP; 1840 *optp++ = TCPOPT_NOP; 1841 } 1842 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1843 continue; 1844 optlen += TCPOLEN_SACK_PERMITTED; 1845 *optp++ = TCPOPT_SACK_PERMITTED; 1846 *optp++ = TCPOLEN_SACK_PERMITTED; 1847 break; 1848 case TOF_TS: 1849 while (!optlen || optlen % 4 != 2) { 1850 optlen += TCPOLEN_NOP; 1851 *optp++ = TCPOPT_NOP; 1852 } 1853 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1854 continue; 1855 optlen += TCPOLEN_TIMESTAMP; 1856 *optp++ = TCPOPT_TIMESTAMP; 1857 *optp++ = TCPOLEN_TIMESTAMP; 1858 to->to_tsval = htonl(to->to_tsval); 1859 to->to_tsecr = htonl(to->to_tsecr); 1860 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1861 optp += sizeof(to->to_tsval); 1862 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1863 optp += sizeof(to->to_tsecr); 1864 break; 1865 case TOF_SIGNATURE: 1866 { 1867 int siglen = TCPOLEN_SIGNATURE - 2; 1868 1869 while (!optlen || optlen % 4 != 2) { 1870 optlen += TCPOLEN_NOP; 1871 *optp++ = TCPOPT_NOP; 1872 } 1873 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) { 1874 to->to_flags &= ~TOF_SIGNATURE; 1875 continue; 1876 } 1877 optlen += TCPOLEN_SIGNATURE; 1878 *optp++ = TCPOPT_SIGNATURE; 1879 *optp++ = TCPOLEN_SIGNATURE; 1880 to->to_signature = optp; 1881 while (siglen--) 1882 *optp++ = 0; 1883 break; 1884 } 1885 case TOF_SACK: 1886 { 1887 int sackblks = 0; 1888 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1889 tcp_seq sack_seq; 1890 1891 while (!optlen || optlen % 4 != 2) { 1892 optlen += TCPOLEN_NOP; 1893 *optp++ = TCPOPT_NOP; 1894 } 1895 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1896 continue; 1897 optlen += TCPOLEN_SACKHDR; 1898 *optp++ = TCPOPT_SACK; 1899 sackblks = min(to->to_nsacks, 1900 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1901 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1902 while (sackblks--) { 1903 sack_seq = htonl(sack->start); 1904 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1905 optp += sizeof(sack_seq); 1906 sack_seq = htonl(sack->end); 1907 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1908 optp += sizeof(sack_seq); 1909 optlen += TCPOLEN_SACK; 1910 sack++; 1911 } 1912 TCPSTAT_INC(tcps_sack_send_blocks); 1913 break; 1914 } 1915 case TOF_FASTOPEN: 1916 { 1917 int total_len; 1918 1919 /* XXX is there any point to aligning this option? */ 1920 total_len = TCPOLEN_FAST_OPEN_EMPTY + to->to_tfo_len; 1921 if (TCP_MAXOLEN - optlen < total_len) { 1922 to->to_flags &= ~TOF_FASTOPEN; 1923 continue; 1924 } 1925 *optp++ = TCPOPT_FAST_OPEN; 1926 *optp++ = total_len; 1927 if (to->to_tfo_len > 0) { 1928 bcopy(to->to_tfo_cookie, optp, to->to_tfo_len); 1929 optp += to->to_tfo_len; 1930 } 1931 optlen += total_len; 1932 break; 1933 } 1934 default: 1935 panic("%s: unknown TCP option type", __func__); 1936 break; 1937 } 1938 } 1939 1940 /* Terminate and pad TCP options to a 4 byte boundary. */ 1941 if (optlen % 4) { 1942 optlen += TCPOLEN_EOL; 1943 *optp++ = TCPOPT_EOL; 1944 } 1945 /* 1946 * According to RFC 793 (STD0007): 1947 * "The content of the header beyond the End-of-Option option 1948 * must be header padding (i.e., zero)." 1949 * and later: "The padding is composed of zeros." 1950 */ 1951 while (optlen % 4) { 1952 optlen += TCPOLEN_PAD; 1953 *optp++ = TCPOPT_PAD; 1954 } 1955 1956 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1957 return (optlen); 1958 } 1959 1960 /* 1961 * This is a copy of m_copym(), taking the TSO segment size/limit 1962 * constraints into account, and advancing the sndptr as it goes. 1963 */ 1964 struct mbuf * 1965 tcp_m_copym(struct mbuf *m, int32_t off0, int32_t *plen, 1966 int32_t seglimit, int32_t segsize, struct sockbuf *sb, bool hw_tls) 1967 { 1968 #ifdef KERN_TLS 1969 struct ktls_session *tls, *ntls; 1970 struct mbuf *start __diagused; 1971 #endif 1972 struct mbuf *n, **np; 1973 struct mbuf *top; 1974 int32_t off = off0; 1975 int32_t len = *plen; 1976 int32_t fragsize; 1977 int32_t len_cp = 0; 1978 int32_t *pkthdrlen; 1979 uint32_t mlen, frags; 1980 bool copyhdr; 1981 1982 KASSERT(off >= 0, ("tcp_m_copym, negative off %d", off)); 1983 KASSERT(len >= 0, ("tcp_m_copym, negative len %d", len)); 1984 if (off == 0 && m->m_flags & M_PKTHDR) 1985 copyhdr = true; 1986 else 1987 copyhdr = false; 1988 while (off > 0) { 1989 KASSERT(m != NULL, ("tcp_m_copym, offset > size of mbuf chain")); 1990 if (off < m->m_len) 1991 break; 1992 off -= m->m_len; 1993 if ((sb) && (m == sb->sb_sndptr)) { 1994 sb->sb_sndptroff += m->m_len; 1995 sb->sb_sndptr = m->m_next; 1996 } 1997 m = m->m_next; 1998 } 1999 np = ⊤ 2000 top = NULL; 2001 pkthdrlen = NULL; 2002 #ifdef KERN_TLS 2003 if (hw_tls && (m->m_flags & M_EXTPG)) 2004 tls = m->m_epg_tls; 2005 else 2006 tls = NULL; 2007 start = m; 2008 #endif 2009 while (len > 0) { 2010 if (m == NULL) { 2011 KASSERT(len == M_COPYALL, 2012 ("tcp_m_copym, length > size of mbuf chain")); 2013 *plen = len_cp; 2014 if (pkthdrlen != NULL) 2015 *pkthdrlen = len_cp; 2016 break; 2017 } 2018 #ifdef KERN_TLS 2019 if (hw_tls) { 2020 if (m->m_flags & M_EXTPG) 2021 ntls = m->m_epg_tls; 2022 else 2023 ntls = NULL; 2024 2025 /* 2026 * Avoid mixing TLS records with handshake 2027 * data or TLS records from different 2028 * sessions. 2029 */ 2030 if (tls != ntls) { 2031 MPASS(m != start); 2032 *plen = len_cp; 2033 if (pkthdrlen != NULL) 2034 *pkthdrlen = len_cp; 2035 break; 2036 } 2037 } 2038 #endif 2039 mlen = min(len, m->m_len - off); 2040 if (seglimit) { 2041 /* 2042 * For M_EXTPG mbufs, add 3 segments 2043 * + 1 in case we are crossing page boundaries 2044 * + 2 in case the TLS hdr/trailer are used 2045 * It is cheaper to just add the segments 2046 * than it is to take the cache miss to look 2047 * at the mbuf ext_pgs state in detail. 2048 */ 2049 if (m->m_flags & M_EXTPG) { 2050 fragsize = min(segsize, PAGE_SIZE); 2051 frags = 3; 2052 } else { 2053 fragsize = segsize; 2054 frags = 0; 2055 } 2056 2057 /* Break if we really can't fit anymore. */ 2058 if ((frags + 1) >= seglimit) { 2059 *plen = len_cp; 2060 if (pkthdrlen != NULL) 2061 *pkthdrlen = len_cp; 2062 break; 2063 } 2064 2065 /* 2066 * Reduce size if you can't copy the whole 2067 * mbuf. If we can't copy the whole mbuf, also 2068 * adjust len so the loop will end after this 2069 * mbuf. 2070 */ 2071 if ((frags + howmany(mlen, fragsize)) >= seglimit) { 2072 mlen = (seglimit - frags - 1) * fragsize; 2073 len = mlen; 2074 *plen = len_cp + len; 2075 if (pkthdrlen != NULL) 2076 *pkthdrlen = *plen; 2077 } 2078 frags += howmany(mlen, fragsize); 2079 if (frags == 0) 2080 frags++; 2081 seglimit -= frags; 2082 KASSERT(seglimit > 0, 2083 ("%s: seglimit went too low", __func__)); 2084 } 2085 if (copyhdr) 2086 n = m_gethdr(M_NOWAIT, m->m_type); 2087 else 2088 n = m_get(M_NOWAIT, m->m_type); 2089 *np = n; 2090 if (n == NULL) 2091 goto nospace; 2092 if (copyhdr) { 2093 if (!m_dup_pkthdr(n, m, M_NOWAIT)) 2094 goto nospace; 2095 if (len == M_COPYALL) 2096 n->m_pkthdr.len -= off0; 2097 else 2098 n->m_pkthdr.len = len; 2099 pkthdrlen = &n->m_pkthdr.len; 2100 copyhdr = false; 2101 } 2102 n->m_len = mlen; 2103 len_cp += n->m_len; 2104 if (m->m_flags & (M_EXT | M_EXTPG)) { 2105 n->m_data = m->m_data + off; 2106 mb_dupcl(n, m); 2107 } else 2108 bcopy(mtod(m, caddr_t)+off, mtod(n, caddr_t), 2109 (u_int)n->m_len); 2110 2111 if (sb && (sb->sb_sndptr == m) && 2112 ((n->m_len + off) >= m->m_len) && m->m_next) { 2113 sb->sb_sndptroff += m->m_len; 2114 sb->sb_sndptr = m->m_next; 2115 } 2116 off = 0; 2117 if (len != M_COPYALL) { 2118 len -= n->m_len; 2119 } 2120 m = m->m_next; 2121 np = &n->m_next; 2122 } 2123 return (top); 2124 nospace: 2125 m_freem(top); 2126 return (NULL); 2127 } 2128 2129 void 2130 tcp_sndbuf_autoscale(struct tcpcb *tp, struct socket *so, uint32_t sendwin) 2131 { 2132 2133 /* 2134 * Automatic sizing of send socket buffer. Often the send buffer 2135 * size is not optimally adjusted to the actual network conditions 2136 * at hand (delay bandwidth product). Setting the buffer size too 2137 * small limits throughput on links with high bandwidth and high 2138 * delay (eg. trans-continental/oceanic links). Setting the 2139 * buffer size too big consumes too much real kernel memory, 2140 * especially with many connections on busy servers. 2141 * 2142 * The criteria to step up the send buffer one notch are: 2143 * 1. receive window of remote host is larger than send buffer 2144 * (with a fudge factor of 5/4th); 2145 * 2. send buffer is filled to 7/8th with data (so we actually 2146 * have data to make use of it); 2147 * 3. send buffer fill has not hit maximal automatic size; 2148 * 4. our send window (slow start and cogestion controlled) is 2149 * larger than sent but unacknowledged data in send buffer. 2150 * 2151 * The remote host receive window scaling factor may limit the 2152 * growing of the send buffer before it reaches its allowed 2153 * maximum. 2154 * 2155 * It scales directly with slow start or congestion window 2156 * and does at most one step per received ACK. This fast 2157 * scaling has the drawback of growing the send buffer beyond 2158 * what is strictly necessary to make full use of a given 2159 * delay*bandwidth product. However testing has shown this not 2160 * to be much of an problem. At worst we are trading wasting 2161 * of available bandwidth (the non-use of it) for wasting some 2162 * socket buffer memory. 2163 * 2164 * TODO: Shrink send buffer during idle periods together 2165 * with congestion window. Requires another timer. Has to 2166 * wait for upcoming tcp timer rewrite. 2167 * 2168 * XXXGL: should there be used sbused() or sbavail()? 2169 */ 2170 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 2171 int lowat; 2172 2173 lowat = V_tcp_sendbuf_auto_lowat ? so->so_snd.sb_lowat : 0; 2174 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat - lowat && 2175 sbused(&so->so_snd) >= 2176 (so->so_snd.sb_hiwat / 8 * 7) - lowat && 2177 sbused(&so->so_snd) < V_tcp_autosndbuf_max && 2178 sendwin >= (sbused(&so->so_snd) - 2179 (tp->snd_nxt - tp->snd_una))) { 2180 if (!sbreserve_locked(so, SO_SND, 2181 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 2182 V_tcp_autosndbuf_max), curthread)) 2183 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 2184 } 2185 } 2186 } 2187