1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 5 * The Regents of the University of California. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. Neither the name of the University nor the names of its contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 * 31 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95 32 */ 33 34 #include <sys/cdefs.h> 35 __FBSDID("$FreeBSD$"); 36 37 #include "opt_inet.h" 38 #include "opt_inet6.h" 39 #include "opt_ipsec.h" 40 #include "opt_kern_tls.h" 41 #include "opt_tcpdebug.h" 42 43 #include <sys/param.h> 44 #include <sys/systm.h> 45 #include <sys/arb.h> 46 #include <sys/domain.h> 47 #ifdef TCP_HHOOK 48 #include <sys/hhook.h> 49 #endif 50 #include <sys/kernel.h> 51 #ifdef KERN_TLS 52 #include <sys/ktls.h> 53 #endif 54 #include <sys/lock.h> 55 #include <sys/mbuf.h> 56 #include <sys/mutex.h> 57 #include <sys/protosw.h> 58 #include <sys/qmath.h> 59 #include <sys/sdt.h> 60 #include <sys/socket.h> 61 #include <sys/socketvar.h> 62 #include <sys/sysctl.h> 63 #include <sys/stats.h> 64 65 #include <net/if.h> 66 #include <net/route.h> 67 #include <net/route/nhop.h> 68 #include <net/vnet.h> 69 70 #include <netinet/in.h> 71 #include <netinet/in_kdtrace.h> 72 #include <netinet/in_systm.h> 73 #include <netinet/ip.h> 74 #include <netinet/in_pcb.h> 75 #include <netinet/ip_var.h> 76 #include <netinet/ip_options.h> 77 #ifdef INET6 78 #include <netinet6/in6_pcb.h> 79 #include <netinet/ip6.h> 80 #include <netinet6/ip6_var.h> 81 #endif 82 #include <netinet/tcp.h> 83 #define TCPOUTFLAGS 84 #include <netinet/tcp_fsm.h> 85 #include <netinet/tcp_log_buf.h> 86 #include <netinet/tcp_seq.h> 87 #include <netinet/tcp_var.h> 88 #include <netinet/tcp_syncache.h> 89 #include <netinet/tcp_timer.h> 90 #include <netinet/tcpip.h> 91 #include <netinet/cc/cc.h> 92 #include <netinet/tcp_fastopen.h> 93 #ifdef TCPPCAP 94 #include <netinet/tcp_pcap.h> 95 #endif 96 #ifdef TCPDEBUG 97 #include <netinet/tcp_debug.h> 98 #endif 99 #ifdef TCP_OFFLOAD 100 #include <netinet/tcp_offload.h> 101 #endif 102 #include <netinet/tcp_ecn.h> 103 104 #include <netipsec/ipsec_support.h> 105 106 #include <netinet/udp.h> 107 #include <netinet/udp_var.h> 108 #include <machine/in_cksum.h> 109 110 #include <security/mac/mac_framework.h> 111 112 VNET_DEFINE(int, path_mtu_discovery) = 1; 113 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_VNET | CTLFLAG_RW, 114 &VNET_NAME(path_mtu_discovery), 1, 115 "Enable Path MTU Discovery"); 116 117 VNET_DEFINE(int, tcp_do_tso) = 1; 118 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_VNET | CTLFLAG_RW, 119 &VNET_NAME(tcp_do_tso), 0, 120 "Enable TCP Segmentation Offload"); 121 122 VNET_DEFINE(int, tcp_sendspace) = 1024*32; 123 #define V_tcp_sendspace VNET(tcp_sendspace) 124 SYSCTL_INT(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, CTLFLAG_VNET | CTLFLAG_RW, 125 &VNET_NAME(tcp_sendspace), 0, "Initial send socket buffer size"); 126 127 VNET_DEFINE(int, tcp_do_autosndbuf) = 1; 128 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_VNET | CTLFLAG_RW, 129 &VNET_NAME(tcp_do_autosndbuf), 0, 130 "Enable automatic send buffer sizing"); 131 132 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024; 133 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_VNET | CTLFLAG_RW, 134 &VNET_NAME(tcp_autosndbuf_inc), 0, 135 "Incrementor step size of automatic send buffer"); 136 137 VNET_DEFINE(int, tcp_autosndbuf_max) = 2*1024*1024; 138 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_VNET | CTLFLAG_RW, 139 &VNET_NAME(tcp_autosndbuf_max), 0, 140 "Max size of automatic send buffer"); 141 142 VNET_DEFINE(int, tcp_sendbuf_auto_lowat) = 0; 143 #define V_tcp_sendbuf_auto_lowat VNET(tcp_sendbuf_auto_lowat) 144 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto_lowat, CTLFLAG_VNET | CTLFLAG_RW, 145 &VNET_NAME(tcp_sendbuf_auto_lowat), 0, 146 "Modify threshold for auto send buffer growth to account for SO_SNDLOWAT"); 147 148 /* 149 * Make sure that either retransmit or persist timer is set for SYN, FIN and 150 * non-ACK. 151 */ 152 #define TCP_XMIT_TIMER_ASSERT(tp, len, th_flags) \ 153 KASSERT(((len) == 0 && ((th_flags) & (TH_SYN | TH_FIN)) == 0) ||\ 154 tcp_timer_active((tp), TT_REXMT) || \ 155 tcp_timer_active((tp), TT_PERSIST), \ 156 ("neither rexmt nor persist timer is set")) 157 158 static void inline cc_after_idle(struct tcpcb *tp); 159 160 #ifdef TCP_HHOOK 161 /* 162 * Wrapper for the TCP established output helper hook. 163 */ 164 void 165 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th, 166 struct tcpopt *to, uint32_t len, int tso) 167 { 168 struct tcp_hhook_data hhook_data; 169 170 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) { 171 hhook_data.tp = tp; 172 hhook_data.th = th; 173 hhook_data.to = to; 174 hhook_data.len = len; 175 hhook_data.tso = tso; 176 177 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data, 178 tp->osd); 179 } 180 } 181 #endif 182 183 /* 184 * CC wrapper hook functions 185 */ 186 static void inline 187 cc_after_idle(struct tcpcb *tp) 188 { 189 INP_WLOCK_ASSERT(tp->t_inpcb); 190 191 if (CC_ALGO(tp)->after_idle != NULL) 192 CC_ALGO(tp)->after_idle(tp->ccv); 193 } 194 195 /* 196 * Tcp output routine: figure out what should be sent and send it. 197 */ 198 int 199 tcp_default_output(struct tcpcb *tp) 200 { 201 struct socket *so = tp->t_inpcb->inp_socket; 202 int32_t len; 203 uint32_t recwin, sendwin; 204 uint16_t flags; 205 int off, error = 0; /* Keep compiler happy */ 206 u_int if_hw_tsomaxsegcount = 0; 207 u_int if_hw_tsomaxsegsize = 0; 208 struct mbuf *m; 209 struct ip *ip = NULL; 210 #ifdef TCPDEBUG 211 struct ipovly *ipov = NULL; 212 #endif 213 struct tcphdr *th; 214 u_char opt[TCP_MAXOLEN]; 215 unsigned ipoptlen, optlen, hdrlen, ulen; 216 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 217 unsigned ipsec_optlen = 0; 218 #endif 219 int idle, sendalot, curticks; 220 int sack_rxmit, sack_bytes_rxmt; 221 struct sackhole *p; 222 int tso, mtu; 223 struct tcpopt to; 224 struct udphdr *udp = NULL; 225 unsigned int wanted_cookie = 0; 226 unsigned int dont_sendalot = 0; 227 #if 0 228 int maxburst = TCP_MAXBURST; 229 #endif 230 #ifdef INET6 231 struct ip6_hdr *ip6 = NULL; 232 int isipv6; 233 234 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 235 #endif 236 #ifdef KERN_TLS 237 const bool hw_tls = (so->so_snd.sb_flags & SB_TLS_IFNET) != 0; 238 #else 239 const bool hw_tls = false; 240 #endif 241 242 NET_EPOCH_ASSERT(); 243 INP_WLOCK_ASSERT(tp->t_inpcb); 244 245 #ifdef TCP_OFFLOAD 246 if (tp->t_flags & TF_TOE) 247 return (tcp_offload_output(tp)); 248 #endif 249 250 /* 251 * For TFO connections in SYN_SENT or SYN_RECEIVED, 252 * only allow the initial SYN or SYN|ACK and those sent 253 * by the retransmit timer. 254 */ 255 if (IS_FASTOPEN(tp->t_flags) && 256 ((tp->t_state == TCPS_SYN_SENT) || 257 (tp->t_state == TCPS_SYN_RECEIVED)) && 258 SEQ_GT(tp->snd_max, tp->snd_una) && /* initial SYN or SYN|ACK sent */ 259 (tp->snd_nxt != tp->snd_una)) /* not a retransmit */ 260 return (0); 261 262 /* 263 * Determine length of data that should be transmitted, 264 * and flags that will be used. 265 * If there is some data or critical controls (SYN, RST) 266 * to send, then transmit; otherwise, investigate further. 267 */ 268 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 269 if (idle && (((ticks - tp->t_rcvtime) >= tp->t_rxtcur) || 270 (tp->t_sndtime && ((ticks - tp->t_sndtime) >= tp->t_rxtcur)))) 271 cc_after_idle(tp); 272 tp->t_flags &= ~TF_LASTIDLE; 273 if (idle) { 274 if (tp->t_flags & TF_MORETOCOME) { 275 tp->t_flags |= TF_LASTIDLE; 276 idle = 0; 277 } 278 } 279 again: 280 /* 281 * If we've recently taken a timeout, snd_max will be greater than 282 * snd_nxt. There may be SACK information that allows us to avoid 283 * resending already delivered data. Adjust snd_nxt accordingly. 284 */ 285 if ((tp->t_flags & TF_SACK_PERMIT) && 286 SEQ_LT(tp->snd_nxt, tp->snd_max)) 287 tcp_sack_adjust(tp); 288 sendalot = 0; 289 tso = 0; 290 mtu = 0; 291 off = tp->snd_nxt - tp->snd_una; 292 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 293 294 flags = tcp_outflags[tp->t_state]; 295 /* 296 * Send any SACK-generated retransmissions. If we're explicitly trying 297 * to send out new data (when sendalot is 1), bypass this function. 298 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 299 * we're replacing a (future) new transmission with a retransmission 300 * now, and we previously incremented snd_cwnd in tcp_input(). 301 */ 302 /* 303 * Still in sack recovery , reset rxmit flag to zero. 304 */ 305 sack_rxmit = 0; 306 sack_bytes_rxmt = 0; 307 len = 0; 308 p = NULL; 309 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) && 310 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 311 uint32_t cwin; 312 313 cwin = 314 imax(min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt, 0); 315 /* Do not retransmit SACK segments beyond snd_recover */ 316 if (SEQ_GT(p->end, tp->snd_recover)) { 317 /* 318 * (At least) part of sack hole extends beyond 319 * snd_recover. Check to see if we can rexmit data 320 * for this hole. 321 */ 322 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 323 /* 324 * Can't rexmit any more data for this hole. 325 * That data will be rexmitted in the next 326 * sack recovery episode, when snd_recover 327 * moves past p->rxmit. 328 */ 329 p = NULL; 330 goto after_sack_rexmit; 331 } else 332 /* Can rexmit part of the current hole */ 333 len = ((int32_t)ulmin(cwin, 334 tp->snd_recover - p->rxmit)); 335 } else 336 len = ((int32_t)ulmin(cwin, p->end - p->rxmit)); 337 off = p->rxmit - tp->snd_una; 338 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 339 __func__, off)); 340 if (len > 0) { 341 sack_rxmit = 1; 342 sendalot = 1; 343 TCPSTAT_INC(tcps_sack_rexmits); 344 TCPSTAT_ADD(tcps_sack_rexmit_bytes, 345 min(len, tcp_maxseg(tp))); 346 } 347 } 348 after_sack_rexmit: 349 /* 350 * Get standard flags, and add SYN or FIN if requested by 'hidden' 351 * state flags. 352 */ 353 if (tp->t_flags & TF_NEEDFIN) 354 flags |= TH_FIN; 355 if (tp->t_flags & TF_NEEDSYN) 356 flags |= TH_SYN; 357 358 SOCKBUF_LOCK(&so->so_snd); 359 /* 360 * If in persist timeout with window of 0, send 1 byte. 361 * Otherwise, if window is small but nonzero 362 * and timer expired, we will send what we can 363 * and go to transmit state. 364 */ 365 if (tp->t_flags & TF_FORCEDATA) { 366 if (sendwin == 0) { 367 /* 368 * If we still have some data to send, then 369 * clear the FIN bit. Usually this would 370 * happen below when it realizes that we 371 * aren't sending all the data. However, 372 * if we have exactly 1 byte of unsent data, 373 * then it won't clear the FIN bit below, 374 * and if we are in persist state, we wind 375 * up sending the packet without recording 376 * that we sent the FIN bit. 377 * 378 * We can't just blindly clear the FIN bit, 379 * because if we don't have any more data 380 * to send then the probe will be the FIN 381 * itself. 382 */ 383 if (off < sbused(&so->so_snd)) 384 flags &= ~TH_FIN; 385 sendwin = 1; 386 } else { 387 tcp_timer_activate(tp, TT_PERSIST, 0); 388 tp->t_rxtshift = 0; 389 } 390 } 391 392 /* 393 * If snd_nxt == snd_max and we have transmitted a FIN, the 394 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 395 * a negative length. This can also occur when TCP opens up 396 * its congestion window while receiving additional duplicate 397 * acks after fast-retransmit because TCP will reset snd_nxt 398 * to snd_max after the fast-retransmit. 399 * 400 * In the normal retransmit-FIN-only case, however, snd_nxt will 401 * be set to snd_una, the offset will be 0, and the length may 402 * wind up 0. 403 * 404 * If sack_rxmit is true we are retransmitting from the scoreboard 405 * in which case len is already set. 406 */ 407 if (sack_rxmit == 0) { 408 if (sack_bytes_rxmt == 0) 409 len = ((int32_t)min(sbavail(&so->so_snd), sendwin) - 410 off); 411 else { 412 int32_t cwin; 413 414 /* 415 * We are inside of a SACK recovery episode and are 416 * sending new data, having retransmitted all the 417 * data possible in the scoreboard. 418 */ 419 len = ((int32_t)min(sbavail(&so->so_snd), tp->snd_wnd) - 420 off); 421 /* 422 * Don't remove this (len > 0) check ! 423 * We explicitly check for len > 0 here (although it 424 * isn't really necessary), to work around a gcc 425 * optimization issue - to force gcc to compute 426 * len above. Without this check, the computation 427 * of len is bungled by the optimizer. 428 */ 429 if (len > 0) { 430 cwin = tp->snd_cwnd - 431 (tp->snd_nxt - tp->snd_recover) - 432 sack_bytes_rxmt; 433 if (cwin < 0) 434 cwin = 0; 435 len = imin(len, cwin); 436 } 437 } 438 } 439 440 /* 441 * Lop off SYN bit if it has already been sent. However, if this 442 * is SYN-SENT state and if segment contains data and if we don't 443 * know that foreign host supports TAO, suppress sending segment. 444 */ 445 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 446 if (tp->t_state != TCPS_SYN_RECEIVED) 447 flags &= ~TH_SYN; 448 /* 449 * When sending additional segments following a TFO SYN|ACK, 450 * do not include the SYN bit. 451 */ 452 if (IS_FASTOPEN(tp->t_flags) && 453 (tp->t_state == TCPS_SYN_RECEIVED)) 454 flags &= ~TH_SYN; 455 off--, len++; 456 } 457 458 /* 459 * Be careful not to send data and/or FIN on SYN segments. 460 * This measure is needed to prevent interoperability problems 461 * with not fully conformant TCP implementations. 462 */ 463 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 464 len = 0; 465 flags &= ~TH_FIN; 466 } 467 468 /* 469 * On TFO sockets, ensure no data is sent in the following cases: 470 * 471 * - When retransmitting SYN|ACK on a passively-created socket 472 * 473 * - When retransmitting SYN on an actively created socket 474 * 475 * - When sending a zero-length cookie (cookie request) on an 476 * actively created socket 477 * 478 * - When the socket is in the CLOSED state (RST is being sent) 479 */ 480 if (IS_FASTOPEN(tp->t_flags) && 481 (((flags & TH_SYN) && (tp->t_rxtshift > 0)) || 482 ((tp->t_state == TCPS_SYN_SENT) && 483 (tp->t_tfo_client_cookie_len == 0)) || 484 (flags & TH_RST))) 485 len = 0; 486 if (len <= 0) { 487 /* 488 * If FIN has been sent but not acked, 489 * but we haven't been called to retransmit, 490 * len will be < 0. Otherwise, window shrank 491 * after we sent into it. If window shrank to 0, 492 * cancel pending retransmit, pull snd_nxt back 493 * to (closed) window, and set the persist timer 494 * if it isn't already going. If the window didn't 495 * close completely, just wait for an ACK. 496 * 497 * We also do a general check here to ensure that 498 * we will set the persist timer when we have data 499 * to send, but a 0-byte window. This makes sure 500 * the persist timer is set even if the packet 501 * hits one of the "goto send" lines below. 502 */ 503 len = 0; 504 if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) && 505 (off < (int) sbavail(&so->so_snd))) { 506 tcp_timer_activate(tp, TT_REXMT, 0); 507 tp->t_rxtshift = 0; 508 tp->snd_nxt = tp->snd_una; 509 if (!tcp_timer_active(tp, TT_PERSIST)) 510 tcp_setpersist(tp); 511 } 512 } 513 514 /* len will be >= 0 after this point. */ 515 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 516 517 tcp_sndbuf_autoscale(tp, so, sendwin); 518 519 /* 520 * Decide if we can use TCP Segmentation Offloading (if supported by 521 * hardware). 522 * 523 * TSO may only be used if we are in a pure bulk sending state. The 524 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 525 * IP options prevent using TSO. With TSO the TCP header is the same 526 * (except for the sequence number) for all generated packets. This 527 * makes it impossible to transmit any options which vary per generated 528 * segment or packet. 529 * 530 * IPv4 handling has a clear separation of ip options and ip header 531 * flags while IPv6 combines both in in6p_outputopts. ip6_optlen() does 532 * the right thing below to provide length of just ip options and thus 533 * checking for ipoptlen is enough to decide if ip options are present. 534 */ 535 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 536 /* 537 * Pre-calculate here as we save another lookup into the darknesses 538 * of IPsec that way and can actually decide if TSO is ok. 539 */ 540 #ifdef INET6 541 if (isipv6 && IPSEC_ENABLED(ipv6)) 542 ipsec_optlen = IPSEC_HDRSIZE(ipv6, tp->t_inpcb); 543 #ifdef INET 544 else 545 #endif 546 #endif /* INET6 */ 547 #ifdef INET 548 if (IPSEC_ENABLED(ipv4)) 549 ipsec_optlen = IPSEC_HDRSIZE(ipv4, tp->t_inpcb); 550 #endif /* INET */ 551 #endif /* IPSEC */ 552 #ifdef INET6 553 if (isipv6) 554 ipoptlen = ip6_optlen(tp->t_inpcb); 555 else 556 #endif 557 if (tp->t_inpcb->inp_options) 558 ipoptlen = tp->t_inpcb->inp_options->m_len - 559 offsetof(struct ipoption, ipopt_list); 560 else 561 ipoptlen = 0; 562 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 563 ipoptlen += ipsec_optlen; 564 #endif 565 566 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg && 567 (tp->t_port == 0) && 568 ((tp->t_flags & TF_SIGNATURE) == 0) && 569 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 570 ipoptlen == 0 && !(flags & TH_SYN)) 571 tso = 1; 572 573 if (sack_rxmit) { 574 if (SEQ_LT(p->rxmit + len, tp->snd_una + sbused(&so->so_snd))) 575 flags &= ~TH_FIN; 576 } else { 577 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + 578 sbused(&so->so_snd))) 579 flags &= ~TH_FIN; 580 } 581 582 recwin = lmin(lmax(sbspace(&so->so_rcv), 0), 583 (long)TCP_MAXWIN << tp->rcv_scale); 584 585 /* 586 * Sender silly window avoidance. We transmit under the following 587 * conditions when len is non-zero: 588 * 589 * - We have a full segment (or more with TSO) 590 * - This is the last buffer in a write()/send() and we are 591 * either idle or running NODELAY 592 * - we've timed out (e.g. persist timer) 593 * - we have more then 1/2 the maximum send window's worth of 594 * data (receiver may be limited the window size) 595 * - we need to retransmit 596 */ 597 if (len) { 598 if (len >= tp->t_maxseg) 599 goto send; 600 /* 601 * As the TCP header options are now 602 * considered when setting up the initial 603 * window, we would not send the last segment 604 * if we skip considering the option length here. 605 * Note: this may not work when tcp headers change 606 * very dynamically in the future. 607 */ 608 if ((((tp->t_flags & TF_SIGNATURE) ? 609 PADTCPOLEN(TCPOLEN_SIGNATURE) : 0) + 610 ((tp->t_flags & TF_RCVD_TSTMP) ? 611 PADTCPOLEN(TCPOLEN_TIMESTAMP) : 0) + 612 len) >= tp->t_maxseg) 613 goto send; 614 /* 615 * NOTE! on localhost connections an 'ack' from the remote 616 * end may occur synchronously with the output and cause 617 * us to flush a buffer queued with moretocome. XXX 618 * 619 * note: the len + off check is almost certainly unnecessary. 620 */ 621 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 622 (idle || (tp->t_flags & TF_NODELAY)) && 623 (uint32_t)len + (uint32_t)off >= sbavail(&so->so_snd) && 624 (tp->t_flags & TF_NOPUSH) == 0) { 625 goto send; 626 } 627 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 628 goto send; 629 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 630 goto send; 631 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 632 goto send; 633 if (sack_rxmit) 634 goto send; 635 } 636 637 /* 638 * Sending of standalone window updates. 639 * 640 * Window updates are important when we close our window due to a 641 * full socket buffer and are opening it again after the application 642 * reads data from it. Once the window has opened again and the 643 * remote end starts to send again the ACK clock takes over and 644 * provides the most current window information. 645 * 646 * We must avoid the silly window syndrome whereas every read 647 * from the receive buffer, no matter how small, causes a window 648 * update to be sent. We also should avoid sending a flurry of 649 * window updates when the socket buffer had queued a lot of data 650 * and the application is doing small reads. 651 * 652 * Prevent a flurry of pointless window updates by only sending 653 * an update when we can increase the advertized window by more 654 * than 1/4th of the socket buffer capacity. When the buffer is 655 * getting full or is very small be more aggressive and send an 656 * update whenever we can increase by two mss sized segments. 657 * In all other situations the ACK's to new incoming data will 658 * carry further window increases. 659 * 660 * Don't send an independent window update if a delayed 661 * ACK is pending (it will get piggy-backed on it) or the 662 * remote side already has done a half-close and won't send 663 * more data. Skip this if the connection is in T/TCP 664 * half-open state. 665 */ 666 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 667 !(tp->t_flags & TF_DELACK) && 668 !TCPS_HAVERCVDFIN(tp->t_state)) { 669 /* 670 * "adv" is the amount we could increase the window, 671 * taking into account that we are limited by 672 * TCP_MAXWIN << tp->rcv_scale. 673 */ 674 int32_t adv; 675 int oldwin; 676 677 adv = recwin; 678 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { 679 oldwin = (tp->rcv_adv - tp->rcv_nxt); 680 if (adv > oldwin) 681 adv -= oldwin; 682 else 683 adv = 0; 684 } else 685 oldwin = 0; 686 687 /* 688 * If the new window size ends up being the same as or less 689 * than the old size when it is scaled, then don't force 690 * a window update. 691 */ 692 if (oldwin >> tp->rcv_scale >= (adv + oldwin) >> tp->rcv_scale) 693 goto dontupdate; 694 695 if (adv >= (int32_t)(2 * tp->t_maxseg) && 696 (adv >= (int32_t)(so->so_rcv.sb_hiwat / 4) || 697 recwin <= (so->so_rcv.sb_hiwat / 8) || 698 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg || 699 adv >= TCP_MAXWIN << tp->rcv_scale)) 700 goto send; 701 if (2 * adv >= (int32_t)so->so_rcv.sb_hiwat) 702 goto send; 703 } 704 dontupdate: 705 706 /* 707 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 708 * is also a catch-all for the retransmit timer timeout case. 709 */ 710 if (tp->t_flags & TF_ACKNOW) 711 goto send; 712 if ((flags & TH_RST) || 713 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 714 goto send; 715 if (SEQ_GT(tp->snd_up, tp->snd_una)) 716 goto send; 717 /* 718 * If our state indicates that FIN should be sent 719 * and we have not yet done so, then we need to send. 720 */ 721 if (flags & TH_FIN && 722 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 723 goto send; 724 /* 725 * In SACK, it is possible for tcp_output to fail to send a segment 726 * after the retransmission timer has been turned off. Make sure 727 * that the retransmission timer is set. 728 */ 729 if ((tp->t_flags & TF_SACK_PERMIT) && 730 SEQ_GT(tp->snd_max, tp->snd_una) && 731 !tcp_timer_active(tp, TT_REXMT) && 732 !tcp_timer_active(tp, TT_PERSIST)) { 733 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 734 goto just_return; 735 } 736 /* 737 * TCP window updates are not reliable, rather a polling protocol 738 * using ``persist'' packets is used to insure receipt of window 739 * updates. The three ``states'' for the output side are: 740 * idle not doing retransmits or persists 741 * persisting to move a small or zero window 742 * (re)transmitting and thereby not persisting 743 * 744 * tcp_timer_active(tp, TT_PERSIST) 745 * is true when we are in persist state. 746 * (tp->t_flags & TF_FORCEDATA) 747 * is set when we are called to send a persist packet. 748 * tcp_timer_active(tp, TT_REXMT) 749 * is set when we are retransmitting 750 * The output side is idle when both timers are zero. 751 * 752 * If send window is too small, there is data to transmit, and no 753 * retransmit or persist is pending, then go to persist state. 754 * If nothing happens soon, send when timer expires: 755 * if window is nonzero, transmit what we can, 756 * otherwise force out a byte. 757 */ 758 if (sbavail(&so->so_snd) && !tcp_timer_active(tp, TT_REXMT) && 759 !tcp_timer_active(tp, TT_PERSIST)) { 760 tp->t_rxtshift = 0; 761 tcp_setpersist(tp); 762 } 763 764 /* 765 * No reason to send a segment, just return. 766 */ 767 just_return: 768 SOCKBUF_UNLOCK(&so->so_snd); 769 return (0); 770 771 send: 772 SOCKBUF_LOCK_ASSERT(&so->so_snd); 773 if (len > 0) { 774 if (len >= tp->t_maxseg) 775 tp->t_flags2 |= TF2_PLPMTU_MAXSEGSNT; 776 else 777 tp->t_flags2 &= ~TF2_PLPMTU_MAXSEGSNT; 778 } 779 /* 780 * Before ESTABLISHED, force sending of initial options 781 * unless TCP set not to do any options. 782 * NOTE: we assume that the IP/TCP header plus TCP options 783 * always fit in a single mbuf, leaving room for a maximum 784 * link header, i.e. 785 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 786 */ 787 optlen = 0; 788 #ifdef INET6 789 if (isipv6) 790 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 791 else 792 #endif 793 hdrlen = sizeof (struct tcpiphdr); 794 795 if (flags & TH_SYN) { 796 tp->snd_nxt = tp->iss; 797 } 798 799 /* 800 * Compute options for segment. 801 * We only have to care about SYN and established connection 802 * segments. Options for SYN-ACK segments are handled in TCP 803 * syncache. 804 */ 805 to.to_flags = 0; 806 if ((tp->t_flags & TF_NOOPT) == 0) { 807 /* Maximum segment size. */ 808 if (flags & TH_SYN) { 809 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 810 if (tp->t_port) 811 to.to_mss -= V_tcp_udp_tunneling_overhead; 812 to.to_flags |= TOF_MSS; 813 814 /* 815 * On SYN or SYN|ACK transmits on TFO connections, 816 * only include the TFO option if it is not a 817 * retransmit, as the presence of the TFO option may 818 * have caused the original SYN or SYN|ACK to have 819 * been dropped by a middlebox. 820 */ 821 if (IS_FASTOPEN(tp->t_flags) && 822 (tp->t_rxtshift == 0)) { 823 if (tp->t_state == TCPS_SYN_RECEIVED) { 824 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN; 825 to.to_tfo_cookie = 826 (u_int8_t *)&tp->t_tfo_cookie.server; 827 to.to_flags |= TOF_FASTOPEN; 828 wanted_cookie = 1; 829 } else if (tp->t_state == TCPS_SYN_SENT) { 830 to.to_tfo_len = 831 tp->t_tfo_client_cookie_len; 832 to.to_tfo_cookie = 833 tp->t_tfo_cookie.client; 834 to.to_flags |= TOF_FASTOPEN; 835 wanted_cookie = 1; 836 /* 837 * If we wind up having more data to 838 * send with the SYN than can fit in 839 * one segment, don't send any more 840 * until the SYN|ACK comes back from 841 * the other end. 842 */ 843 dont_sendalot = 1; 844 } 845 } 846 } 847 /* Window scaling. */ 848 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 849 to.to_wscale = tp->request_r_scale; 850 to.to_flags |= TOF_SCALE; 851 } 852 /* Timestamps. */ 853 if ((tp->t_flags & TF_RCVD_TSTMP) || 854 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 855 curticks = tcp_ts_getticks(); 856 to.to_tsval = curticks + tp->ts_offset; 857 to.to_tsecr = tp->ts_recent; 858 to.to_flags |= TOF_TS; 859 if (tp->t_rxtshift == 1) 860 tp->t_badrxtwin = curticks; 861 } 862 863 /* Set receive buffer autosizing timestamp. */ 864 if (tp->rfbuf_ts == 0 && 865 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 866 tp->rfbuf_ts = tcp_ts_getticks(); 867 868 /* Selective ACK's. */ 869 if (tp->t_flags & TF_SACK_PERMIT) { 870 if (flags & TH_SYN) 871 to.to_flags |= TOF_SACKPERM; 872 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 873 tp->rcv_numsacks > 0) { 874 to.to_flags |= TOF_SACK; 875 to.to_nsacks = tp->rcv_numsacks; 876 to.to_sacks = (u_char *)tp->sackblks; 877 } 878 } 879 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 880 /* TCP-MD5 (RFC2385). */ 881 /* 882 * Check that TCP_MD5SIG is enabled in tcpcb to 883 * account the size needed to set this TCP option. 884 */ 885 if (tp->t_flags & TF_SIGNATURE) 886 to.to_flags |= TOF_SIGNATURE; 887 #endif /* TCP_SIGNATURE */ 888 889 /* Processing the options. */ 890 hdrlen += optlen = tcp_addoptions(&to, opt); 891 /* 892 * If we wanted a TFO option to be added, but it was unable 893 * to fit, ensure no data is sent. 894 */ 895 if (IS_FASTOPEN(tp->t_flags) && wanted_cookie && 896 !(to.to_flags & TOF_FASTOPEN)) 897 len = 0; 898 } 899 if (tp->t_port) { 900 if (V_tcp_udp_tunneling_port == 0) { 901 /* The port was removed?? */ 902 SOCKBUF_UNLOCK(&so->so_snd); 903 return (EHOSTUNREACH); 904 } 905 hdrlen += sizeof(struct udphdr); 906 } 907 /* 908 * Adjust data length if insertion of options will 909 * bump the packet length beyond the t_maxseg length. 910 * Clear the FIN bit because we cut off the tail of 911 * the segment. 912 */ 913 if (len + optlen + ipoptlen > tp->t_maxseg) { 914 flags &= ~TH_FIN; 915 916 if (tso) { 917 u_int if_hw_tsomax; 918 u_int moff; 919 int max_len; 920 921 /* extract TSO information */ 922 if_hw_tsomax = tp->t_tsomax; 923 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount; 924 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize; 925 926 /* 927 * Limit a TSO burst to prevent it from 928 * overflowing or exceeding the maximum length 929 * allowed by the network interface: 930 */ 931 KASSERT(ipoptlen == 0, 932 ("%s: TSO can't do IP options", __func__)); 933 934 /* 935 * Check if we should limit by maximum payload 936 * length: 937 */ 938 if (if_hw_tsomax != 0) { 939 /* compute maximum TSO length */ 940 max_len = (if_hw_tsomax - hdrlen - 941 max_linkhdr); 942 if (max_len <= 0) { 943 len = 0; 944 } else if (len > max_len) { 945 sendalot = 1; 946 len = max_len; 947 } 948 } 949 950 /* 951 * Prevent the last segment from being 952 * fractional unless the send sockbuf can be 953 * emptied: 954 */ 955 max_len = (tp->t_maxseg - optlen); 956 if (((uint32_t)off + (uint32_t)len) < 957 sbavail(&so->so_snd)) { 958 moff = len % max_len; 959 if (moff != 0) { 960 len -= moff; 961 sendalot = 1; 962 } 963 } 964 965 /* 966 * In case there are too many small fragments 967 * don't use TSO: 968 */ 969 if (len <= max_len) { 970 len = max_len; 971 sendalot = 1; 972 tso = 0; 973 } 974 975 /* 976 * Send the FIN in a separate segment 977 * after the bulk sending is done. 978 * We don't trust the TSO implementations 979 * to clear the FIN flag on all but the 980 * last segment. 981 */ 982 if (tp->t_flags & TF_NEEDFIN) 983 sendalot = 1; 984 } else { 985 if (optlen + ipoptlen >= tp->t_maxseg) { 986 /* 987 * Since we don't have enough space to put 988 * the IP header chain and the TCP header in 989 * one packet as required by RFC 7112, don't 990 * send it. Also ensure that at least one 991 * byte of the payload can be put into the 992 * TCP segment. 993 */ 994 SOCKBUF_UNLOCK(&so->so_snd); 995 error = EMSGSIZE; 996 sack_rxmit = 0; 997 goto out; 998 } 999 len = tp->t_maxseg - optlen - ipoptlen; 1000 sendalot = 1; 1001 if (dont_sendalot) 1002 sendalot = 0; 1003 } 1004 } else 1005 tso = 0; 1006 1007 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 1008 ("%s: len > IP_MAXPACKET", __func__)); 1009 1010 /*#ifdef DIAGNOSTIC*/ 1011 #ifdef INET6 1012 if (max_linkhdr + hdrlen > MCLBYTES) 1013 #else 1014 if (max_linkhdr + hdrlen > MHLEN) 1015 #endif 1016 panic("tcphdr too big"); 1017 /*#endif*/ 1018 1019 /* 1020 * This KASSERT is here to catch edge cases at a well defined place. 1021 * Before, those had triggered (random) panic conditions further down. 1022 */ 1023 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 1024 1025 /* 1026 * Grab a header mbuf, attaching a copy of data to 1027 * be transmitted, and initialize the header from 1028 * the template for sends on this connection. 1029 */ 1030 if (len) { 1031 struct mbuf *mb; 1032 struct sockbuf *msb; 1033 u_int moff; 1034 1035 if ((tp->t_flags & TF_FORCEDATA) && len == 1) { 1036 TCPSTAT_INC(tcps_sndprobe); 1037 #ifdef STATS 1038 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1039 stats_voi_update_abs_u32(tp->t_stats, 1040 VOI_TCP_RETXPB, len); 1041 else 1042 stats_voi_update_abs_u64(tp->t_stats, 1043 VOI_TCP_TXPB, len); 1044 #endif /* STATS */ 1045 } else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 1046 tp->t_sndrexmitpack++; 1047 TCPSTAT_INC(tcps_sndrexmitpack); 1048 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 1049 #ifdef STATS 1050 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_RETXPB, 1051 len); 1052 #endif /* STATS */ 1053 } else { 1054 TCPSTAT_INC(tcps_sndpack); 1055 TCPSTAT_ADD(tcps_sndbyte, len); 1056 #ifdef STATS 1057 stats_voi_update_abs_u64(tp->t_stats, VOI_TCP_TXPB, 1058 len); 1059 #endif /* STATS */ 1060 } 1061 #ifdef INET6 1062 if (MHLEN < hdrlen + max_linkhdr) 1063 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR); 1064 else 1065 #endif 1066 m = m_gethdr(M_NOWAIT, MT_DATA); 1067 1068 if (m == NULL) { 1069 SOCKBUF_UNLOCK(&so->so_snd); 1070 error = ENOBUFS; 1071 sack_rxmit = 0; 1072 goto out; 1073 } 1074 1075 m->m_data += max_linkhdr; 1076 m->m_len = hdrlen; 1077 1078 /* 1079 * Start the m_copy functions from the closest mbuf 1080 * to the offset in the socket buffer chain. 1081 */ 1082 mb = sbsndptr_noadv(&so->so_snd, off, &moff); 1083 if (len <= MHLEN - hdrlen - max_linkhdr && !hw_tls) { 1084 m_copydata(mb, moff, len, 1085 mtod(m, caddr_t) + hdrlen); 1086 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1087 sbsndptr_adv(&so->so_snd, mb, len); 1088 m->m_len += len; 1089 } else { 1090 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1091 msb = NULL; 1092 else 1093 msb = &so->so_snd; 1094 m->m_next = tcp_m_copym(mb, moff, 1095 &len, if_hw_tsomaxsegcount, 1096 if_hw_tsomaxsegsize, msb, hw_tls); 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 SOCKBUF_UNLOCK(&so->so_snd); 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 SOCKBUF_UNLOCK(&so->so_snd); 1125 } else { 1126 SOCKBUF_UNLOCK(&so->so_snd); 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 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 1152 m->m_pkthdr.rcvif = (struct ifnet *)0; 1153 #ifdef MAC 1154 mac_inpcb_create_mbuf(tp->t_inpcb, 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(tp->t_inpcb, tp->t_port, ip6, th); 1170 } else 1171 #endif /* INET6 */ 1172 { 1173 ip = mtod(m, struct ip *); 1174 #ifdef TCPDEBUG 1175 ipov = (struct ipovly *)ip; 1176 #endif 1177 if (tp->t_port) { 1178 udp = (struct udphdr *)((caddr_t)ip + sizeof(struct ip)); 1179 udp->uh_sport = htons(V_tcp_udp_tunneling_port); 1180 udp->uh_dport = tp->t_port; 1181 ulen = hdrlen + len - sizeof(struct ip); 1182 udp->uh_ulen = htons(ulen); 1183 th = (struct tcphdr *)(udp + 1); 1184 } else 1185 th = (struct tcphdr *)(ip + 1); 1186 tcpip_fillheaders(tp->t_inpcb, tp->t_port, ip, th); 1187 } 1188 1189 /* 1190 * Fill in fields, remembering maximum advertised 1191 * window for use in delaying messages about window sizes. 1192 * If resending a FIN, be sure not to use a new sequence number. 1193 */ 1194 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 1195 tp->snd_nxt == tp->snd_max) 1196 tp->snd_nxt--; 1197 /* 1198 * If we are starting a connection, send ECN setup 1199 * SYN packet. If we are on a retransmit, we may 1200 * resend those bits a number of times as per 1201 * RFC 3168. 1202 */ 1203 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) { 1204 flags |= tcp_ecn_output_syn_sent(tp); 1205 } 1206 /* Also handle parallel SYN for ECN */ 1207 if ((TCPS_HAVERCVDSYN(tp->t_state)) && 1208 (tp->t_flags2 & TF2_ECN_PERMIT)) { 1209 int ect = tcp_ecn_output_established(tp, &flags, len, sack_rxmit); 1210 if ((tp->t_state == TCPS_SYN_RECEIVED) && 1211 (tp->t_flags2 & TF2_ECN_SND_ECE)) 1212 tp->t_flags2 &= ~TF2_ECN_SND_ECE; 1213 #ifdef INET6 1214 if (isipv6) { 1215 ip6->ip6_flow &= ~htonl(IPTOS_ECN_MASK << 20); 1216 ip6->ip6_flow |= htonl(ect << 20); 1217 } 1218 else 1219 #endif 1220 { 1221 ip->ip_tos &= ~IPTOS_ECN_MASK; 1222 ip->ip_tos |= ect; 1223 } 1224 } 1225 1226 /* 1227 * If we are doing retransmissions, then snd_nxt will 1228 * not reflect the first unsent octet. For ACK only 1229 * packets, we do not want the sequence number of the 1230 * retransmitted packet, we want the sequence number 1231 * of the next unsent octet. So, if there is no data 1232 * (and no SYN or FIN), use snd_max instead of snd_nxt 1233 * when filling in ti_seq. But if we are in persist 1234 * state, snd_max might reflect one byte beyond the 1235 * right edge of the window, so use snd_nxt in that 1236 * case, since we know we aren't doing a retransmission. 1237 * (retransmit and persist are mutually exclusive...) 1238 */ 1239 if (sack_rxmit == 0) { 1240 if (len || (flags & (TH_SYN|TH_FIN)) || 1241 tcp_timer_active(tp, TT_PERSIST)) 1242 th->th_seq = htonl(tp->snd_nxt); 1243 else 1244 th->th_seq = htonl(tp->snd_max); 1245 } else { 1246 th->th_seq = htonl(p->rxmit); 1247 p->rxmit += len; 1248 /* 1249 * Lost Retransmission Detection 1250 * trigger resending of a (then 1251 * still existing) hole, when 1252 * fack acks recoverypoint. 1253 */ 1254 if ((tp->t_flags & TF_LRD) && SEQ_GEQ(p->rxmit, p->end)) 1255 p->rxmit = tp->snd_recover; 1256 tp->sackhint.sack_bytes_rexmit += len; 1257 } 1258 if (IN_RECOVERY(tp->t_flags)) { 1259 /* 1260 * Account all bytes transmitted while 1261 * IN_RECOVERY, simplifying PRR and 1262 * Lost Retransmit Detection 1263 */ 1264 tp->sackhint.prr_out += len; 1265 } 1266 th->th_ack = htonl(tp->rcv_nxt); 1267 if (optlen) { 1268 bcopy(opt, th + 1, optlen); 1269 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1270 } 1271 tcp_set_flags(th, flags); 1272 /* 1273 * Calculate receive window. Don't shrink window, 1274 * but avoid silly window syndrome. 1275 * If a RST segment is sent, advertise a window of zero. 1276 */ 1277 if (flags & TH_RST) { 1278 recwin = 0; 1279 } else { 1280 if (recwin < (so->so_rcv.sb_hiwat / 4) && 1281 recwin < tp->t_maxseg) 1282 recwin = 0; 1283 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1284 recwin < (tp->rcv_adv - tp->rcv_nxt)) 1285 recwin = (tp->rcv_adv - tp->rcv_nxt); 1286 } 1287 /* 1288 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1289 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1290 * case is handled in syncache. 1291 */ 1292 if (flags & TH_SYN) 1293 th->th_win = htons((u_short) 1294 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1295 else { 1296 /* Avoid shrinking window with window scaling. */ 1297 recwin = roundup2(recwin, 1 << tp->rcv_scale); 1298 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1299 } 1300 1301 /* 1302 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1303 * a 0 window. This may cause the remote transmitter to stall. This 1304 * flag tells soreceive() to disable delayed acknowledgements when 1305 * draining the buffer. This can occur if the receiver is attempting 1306 * to read more data than can be buffered prior to transmitting on 1307 * the connection. 1308 */ 1309 if (th->th_win == 0) { 1310 tp->t_sndzerowin++; 1311 tp->t_flags |= TF_RXWIN0SENT; 1312 } else 1313 tp->t_flags &= ~TF_RXWIN0SENT; 1314 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1315 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1316 th->th_flags |= TH_URG; 1317 } else 1318 /* 1319 * If no urgent pointer to send, then we pull 1320 * the urgent pointer to the left edge of the send window 1321 * so that it doesn't drift into the send window on sequence 1322 * number wraparound. 1323 */ 1324 tp->snd_up = tp->snd_una; /* drag it along */ 1325 1326 /* 1327 * Put TCP length in extended header, and then 1328 * checksum extended header and data. 1329 */ 1330 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1331 1332 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1333 if (to.to_flags & TOF_SIGNATURE) { 1334 /* 1335 * Calculate MD5 signature and put it into the place 1336 * determined before. 1337 * NOTE: since TCP options buffer doesn't point into 1338 * mbuf's data, calculate offset and use it. 1339 */ 1340 if (!TCPMD5_ENABLED() || (error = TCPMD5_OUTPUT(m, th, 1341 (u_char *)(th + 1) + (to.to_signature - opt))) != 0) { 1342 /* 1343 * Do not send segment if the calculation of MD5 1344 * digest has failed. 1345 */ 1346 m_freem(m); 1347 goto out; 1348 } 1349 } 1350 #endif 1351 #ifdef INET6 1352 if (isipv6) { 1353 /* 1354 * There is no need to fill in ip6_plen right now. 1355 * It will be filled later by ip6_output. 1356 */ 1357 if (tp->t_port) { 1358 m->m_pkthdr.csum_flags = CSUM_UDP_IPV6; 1359 m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum); 1360 udp->uh_sum = in6_cksum_pseudo(ip6, ulen, IPPROTO_UDP, 0); 1361 th->th_sum = htons(0); 1362 UDPSTAT_INC(udps_opackets); 1363 } else { 1364 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1365 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1366 th->th_sum = in6_cksum_pseudo(ip6, 1367 sizeof(struct tcphdr) + optlen + len, IPPROTO_TCP, 1368 0); 1369 } 1370 } 1371 #endif 1372 #if defined(INET6) && defined(INET) 1373 else 1374 #endif 1375 #ifdef INET 1376 { 1377 if (tp->t_port) { 1378 m->m_pkthdr.csum_flags = CSUM_UDP; 1379 m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum); 1380 udp->uh_sum = in_pseudo(ip->ip_src.s_addr, 1381 ip->ip_dst.s_addr, htons(ulen + IPPROTO_UDP)); 1382 th->th_sum = htons(0); 1383 UDPSTAT_INC(udps_opackets); 1384 } else { 1385 m->m_pkthdr.csum_flags = CSUM_TCP; 1386 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1387 th->th_sum = in_pseudo(ip->ip_src.s_addr, 1388 ip->ip_dst.s_addr, htons(sizeof(struct tcphdr) + 1389 IPPROTO_TCP + len + optlen)); 1390 } 1391 1392 /* IP version must be set here for ipv4/ipv6 checking later */ 1393 KASSERT(ip->ip_v == IPVERSION, 1394 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1395 } 1396 #endif 1397 1398 /* 1399 * Enable TSO and specify the size of the segments. 1400 * The TCP pseudo header checksum is always provided. 1401 */ 1402 if (tso) { 1403 KASSERT(len > tp->t_maxseg - optlen, 1404 ("%s: len <= tso_segsz", __func__)); 1405 m->m_pkthdr.csum_flags |= CSUM_TSO; 1406 m->m_pkthdr.tso_segsz = tp->t_maxseg - optlen; 1407 } 1408 1409 KASSERT(len + hdrlen == m_length(m, NULL), 1410 ("%s: mbuf chain shorter than expected: %d + %u != %u", 1411 __func__, len, hdrlen, m_length(m, NULL))); 1412 1413 #ifdef TCP_HHOOK 1414 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1415 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1416 #endif 1417 1418 #ifdef TCPDEBUG 1419 /* 1420 * Trace. 1421 */ 1422 if (so->so_options & SO_DEBUG) { 1423 u_short save = 0; 1424 #ifdef INET6 1425 if (!isipv6) 1426 #endif 1427 { 1428 save = ipov->ih_len; 1429 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1430 } 1431 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1432 #ifdef INET6 1433 if (!isipv6) 1434 #endif 1435 ipov->ih_len = save; 1436 } 1437 #endif /* TCPDEBUG */ 1438 TCP_PROBE3(debug__output, tp, th, m); 1439 1440 /* We're getting ready to send; log now. */ 1441 TCP_LOG_EVENT(tp, th, &so->so_rcv, &so->so_snd, TCP_LOG_OUT, ERRNO_UNK, 1442 len, NULL, false); 1443 1444 /* 1445 * Fill in IP length and desired time to live and 1446 * send to IP level. There should be a better way 1447 * to handle ttl and tos; we could keep them in 1448 * the template, but need a way to checksum without them. 1449 */ 1450 /* 1451 * m->m_pkthdr.len should have been set before checksum calculation, 1452 * because in6_cksum() need it. 1453 */ 1454 #ifdef INET6 1455 if (isipv6) { 1456 /* 1457 * we separately set hoplimit for every segment, since the 1458 * user might want to change the value via setsockopt. 1459 * Also, desired default hop limit might be changed via 1460 * Neighbor Discovery. 1461 */ 1462 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1463 1464 /* 1465 * Set the packet size here for the benefit of DTrace probes. 1466 * ip6_output() will set it properly; it's supposed to include 1467 * the option header lengths as well. 1468 */ 1469 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6)); 1470 1471 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) 1472 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1473 else 1474 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1475 1476 if (tp->t_state == TCPS_SYN_SENT) 1477 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th); 1478 1479 TCP_PROBE5(send, NULL, tp, ip6, tp, th); 1480 1481 #ifdef TCPPCAP 1482 /* Save packet, if requested. */ 1483 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1484 #endif 1485 1486 /* TODO: IPv6 IP6TOS_ECT bit on */ 1487 error = ip6_output(m, tp->t_inpcb->in6p_outputopts, 1488 &tp->t_inpcb->inp_route6, 1489 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 1490 NULL, NULL, tp->t_inpcb); 1491 1492 if (error == EMSGSIZE && tp->t_inpcb->inp_route6.ro_nh != NULL) 1493 mtu = tp->t_inpcb->inp_route6.ro_nh->nh_mtu; 1494 } 1495 #endif /* INET6 */ 1496 #if defined(INET) && defined(INET6) 1497 else 1498 #endif 1499 #ifdef INET 1500 { 1501 ip->ip_len = htons(m->m_pkthdr.len); 1502 #ifdef INET6 1503 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1504 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1505 #endif /* INET6 */ 1506 /* 1507 * If we do path MTU discovery, then we set DF on every packet. 1508 * This might not be the best thing to do according to RFC3390 1509 * Section 2. However the tcp hostcache migitates the problem 1510 * so it affects only the first tcp connection with a host. 1511 * 1512 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1513 */ 1514 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) { 1515 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1516 if (tp->t_port == 0 || len < V_tcp_minmss) { 1517 ip->ip_off |= htons(IP_DF); 1518 } 1519 } else { 1520 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1521 } 1522 1523 if (tp->t_state == TCPS_SYN_SENT) 1524 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th); 1525 1526 TCP_PROBE5(send, NULL, tp, ip, tp, th); 1527 1528 #ifdef TCPPCAP 1529 /* Save packet, if requested. */ 1530 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1531 #endif 1532 1533 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, 1534 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1535 tp->t_inpcb); 1536 1537 if (error == EMSGSIZE && tp->t_inpcb->inp_route.ro_nh != NULL) 1538 mtu = tp->t_inpcb->inp_route.ro_nh->nh_mtu; 1539 } 1540 #endif /* INET */ 1541 1542 out: 1543 if (error == 0) 1544 tcp_account_for_send(tp, len, (tp->snd_nxt != tp->snd_max), 0, hw_tls); 1545 /* 1546 * In transmit state, time the transmission and arrange for 1547 * the retransmit. In persist state, just set snd_max. 1548 */ 1549 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1550 !tcp_timer_active(tp, TT_PERSIST)) { 1551 tcp_seq startseq = tp->snd_nxt; 1552 1553 /* 1554 * Advance snd_nxt over sequence space of this segment. 1555 */ 1556 if (flags & (TH_SYN|TH_FIN)) { 1557 if (flags & TH_SYN) 1558 tp->snd_nxt++; 1559 if (flags & TH_FIN) { 1560 tp->snd_nxt++; 1561 tp->t_flags |= TF_SENTFIN; 1562 } 1563 } 1564 if (sack_rxmit) 1565 goto timer; 1566 tp->snd_nxt += len; 1567 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1568 tp->snd_max = tp->snd_nxt; 1569 /* 1570 * Time this transmission if not a retransmission and 1571 * not currently timing anything. 1572 */ 1573 tp->t_sndtime = ticks; 1574 if (tp->t_rtttime == 0) { 1575 tp->t_rtttime = ticks; 1576 tp->t_rtseq = startseq; 1577 TCPSTAT_INC(tcps_segstimed); 1578 } 1579 #ifdef STATS 1580 if (!(tp->t_flags & TF_GPUTINPROG) && len) { 1581 tp->t_flags |= TF_GPUTINPROG; 1582 tp->gput_seq = startseq; 1583 tp->gput_ack = startseq + 1584 ulmin(sbavail(&so->so_snd) - off, sendwin); 1585 tp->gput_ts = tcp_ts_getticks(); 1586 } 1587 #endif /* STATS */ 1588 } 1589 1590 /* 1591 * Set retransmit timer if not currently set, 1592 * and not doing a pure ack or a keep-alive probe. 1593 * Initial value for retransmit timer is smoothed 1594 * round-trip time + 2 * round-trip time variance. 1595 * Initialize shift counter which is used for backoff 1596 * of retransmit time. 1597 */ 1598 timer: 1599 if (!tcp_timer_active(tp, TT_REXMT) && 1600 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1601 (tp->snd_nxt != tp->snd_una))) { 1602 if (tcp_timer_active(tp, TT_PERSIST)) { 1603 tcp_timer_activate(tp, TT_PERSIST, 0); 1604 tp->t_rxtshift = 0; 1605 } 1606 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1607 } else if (len == 0 && sbavail(&so->so_snd) && 1608 !tcp_timer_active(tp, TT_REXMT) && 1609 !tcp_timer_active(tp, TT_PERSIST)) { 1610 /* 1611 * Avoid a situation where we do not set persist timer 1612 * after a zero window condition. For example: 1613 * 1) A -> B: packet with enough data to fill the window 1614 * 2) B -> A: ACK for #1 + new data (0 window 1615 * advertisement) 1616 * 3) A -> B: ACK for #2, 0 len packet 1617 * 1618 * In this case, A will not activate the persist timer, 1619 * because it chose to send a packet. Unless tcp_output 1620 * is called for some other reason (delayed ack timer, 1621 * another input packet from B, socket syscall), A will 1622 * not send zero window probes. 1623 * 1624 * So, if you send a 0-length packet, but there is data 1625 * in the socket buffer, and neither the rexmt or 1626 * persist timer is already set, then activate the 1627 * persist timer. 1628 */ 1629 tp->t_rxtshift = 0; 1630 tcp_setpersist(tp); 1631 } 1632 } else { 1633 /* 1634 * Persist case, update snd_max but since we are in 1635 * persist mode (no window) we do not update snd_nxt. 1636 */ 1637 int xlen = len; 1638 if (flags & TH_SYN) 1639 ++xlen; 1640 if (flags & TH_FIN) { 1641 ++xlen; 1642 tp->t_flags |= TF_SENTFIN; 1643 } 1644 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1645 tp->snd_max = tp->snd_nxt + xlen; 1646 } 1647 if ((error == 0) && 1648 (TCPS_HAVEESTABLISHED(tp->t_state) && 1649 (tp->t_flags & TF_SACK_PERMIT) && 1650 tp->rcv_numsacks > 0)) { 1651 /* Clean up any DSACK's sent */ 1652 tcp_clean_dsack_blocks(tp); 1653 } 1654 if (error) { 1655 /* Record the error. */ 1656 TCP_LOG_EVENT(tp, NULL, &so->so_rcv, &so->so_snd, TCP_LOG_OUT, 1657 error, 0, NULL, false); 1658 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 -= len; 1678 tp->sackhint.sack_bytes_rexmit -= len; 1679 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1680 ("sackhint bytes rtx >= 0")); 1681 } else 1682 tp->snd_nxt -= len; 1683 } 1684 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1685 switch (error) { 1686 case EACCES: 1687 case EPERM: 1688 tp->t_softerror = error; 1689 return (error); 1690 case ENOBUFS: 1691 TCP_XMIT_TIMER_ASSERT(tp, len, flags); 1692 tp->snd_cwnd = tp->t_maxseg; 1693 return (0); 1694 case EMSGSIZE: 1695 /* 1696 * For some reason the interface we used initially 1697 * to send segments changed to another or lowered 1698 * its MTU. 1699 * If TSO was active we either got an interface 1700 * without TSO capabilits or TSO was turned off. 1701 * If we obtained mtu from ip_output() then update 1702 * it and try again. 1703 */ 1704 if (tso) 1705 tp->t_flags &= ~TF_TSO; 1706 if (mtu != 0) { 1707 tcp_mss_update(tp, -1, mtu, NULL, NULL); 1708 goto again; 1709 } 1710 return (error); 1711 case EHOSTDOWN: 1712 case EHOSTUNREACH: 1713 case ENETDOWN: 1714 case ENETUNREACH: 1715 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1716 tp->t_softerror = error; 1717 return (0); 1718 } 1719 /* FALLTHROUGH */ 1720 default: 1721 return (error); 1722 } 1723 } 1724 TCPSTAT_INC(tcps_sndtotal); 1725 1726 /* 1727 * Data sent (as far as we can tell). 1728 * If this advertises a larger window than any other segment, 1729 * then remember the size of the advertised window. 1730 * Any pending ACK has now been sent. 1731 */ 1732 if (SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1733 tp->rcv_adv = tp->rcv_nxt + recwin; 1734 tp->last_ack_sent = tp->rcv_nxt; 1735 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1736 if (tcp_timer_active(tp, TT_DELACK)) 1737 tcp_timer_activate(tp, TT_DELACK, 0); 1738 #if 0 1739 /* 1740 * This completely breaks TCP if newreno is turned on. What happens 1741 * is that if delayed-acks are turned on on the receiver, this code 1742 * on the transmitter effectively destroys the TCP window, forcing 1743 * it to four packets (1.5Kx4 = 6K window). 1744 */ 1745 if (sendalot && --maxburst) 1746 goto again; 1747 #endif 1748 if (sendalot) 1749 goto again; 1750 return (0); 1751 } 1752 1753 void 1754 tcp_setpersist(struct tcpcb *tp) 1755 { 1756 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1757 int tt; 1758 1759 tp->t_flags &= ~TF_PREVVALID; 1760 if (tcp_timer_active(tp, TT_REXMT)) 1761 panic("tcp_setpersist: retransmit pending"); 1762 /* 1763 * Start/restart persistence timer. 1764 */ 1765 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1766 tcp_persmin, tcp_persmax); 1767 tcp_timer_activate(tp, TT_PERSIST, tt); 1768 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1769 tp->t_rxtshift++; 1770 } 1771 1772 /* 1773 * Insert TCP options according to the supplied parameters to the place 1774 * optp in a consistent way. Can handle unaligned destinations. 1775 * 1776 * The order of the option processing is crucial for optimal packing and 1777 * alignment for the scarce option space. 1778 * 1779 * The optimal order for a SYN/SYN-ACK segment is: 1780 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1781 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1782 * 1783 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1784 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1785 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1786 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1787 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1788 */ 1789 int 1790 tcp_addoptions(struct tcpopt *to, u_char *optp) 1791 { 1792 u_int32_t mask, optlen = 0; 1793 1794 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1795 if ((to->to_flags & mask) != mask) 1796 continue; 1797 if (optlen == TCP_MAXOLEN) 1798 break; 1799 switch (to->to_flags & mask) { 1800 case TOF_MSS: 1801 while (optlen % 4) { 1802 optlen += TCPOLEN_NOP; 1803 *optp++ = TCPOPT_NOP; 1804 } 1805 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1806 continue; 1807 optlen += TCPOLEN_MAXSEG; 1808 *optp++ = TCPOPT_MAXSEG; 1809 *optp++ = TCPOLEN_MAXSEG; 1810 to->to_mss = htons(to->to_mss); 1811 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1812 optp += sizeof(to->to_mss); 1813 break; 1814 case TOF_SCALE: 1815 while (!optlen || optlen % 2 != 1) { 1816 optlen += TCPOLEN_NOP; 1817 *optp++ = TCPOPT_NOP; 1818 } 1819 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1820 continue; 1821 optlen += TCPOLEN_WINDOW; 1822 *optp++ = TCPOPT_WINDOW; 1823 *optp++ = TCPOLEN_WINDOW; 1824 *optp++ = to->to_wscale; 1825 break; 1826 case TOF_SACKPERM: 1827 while (optlen % 2) { 1828 optlen += TCPOLEN_NOP; 1829 *optp++ = TCPOPT_NOP; 1830 } 1831 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1832 continue; 1833 optlen += TCPOLEN_SACK_PERMITTED; 1834 *optp++ = TCPOPT_SACK_PERMITTED; 1835 *optp++ = TCPOLEN_SACK_PERMITTED; 1836 break; 1837 case TOF_TS: 1838 while (!optlen || optlen % 4 != 2) { 1839 optlen += TCPOLEN_NOP; 1840 *optp++ = TCPOPT_NOP; 1841 } 1842 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1843 continue; 1844 optlen += TCPOLEN_TIMESTAMP; 1845 *optp++ = TCPOPT_TIMESTAMP; 1846 *optp++ = TCPOLEN_TIMESTAMP; 1847 to->to_tsval = htonl(to->to_tsval); 1848 to->to_tsecr = htonl(to->to_tsecr); 1849 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1850 optp += sizeof(to->to_tsval); 1851 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1852 optp += sizeof(to->to_tsecr); 1853 break; 1854 case TOF_SIGNATURE: 1855 { 1856 int siglen = TCPOLEN_SIGNATURE - 2; 1857 1858 while (!optlen || optlen % 4 != 2) { 1859 optlen += TCPOLEN_NOP; 1860 *optp++ = TCPOPT_NOP; 1861 } 1862 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) { 1863 to->to_flags &= ~TOF_SIGNATURE; 1864 continue; 1865 } 1866 optlen += TCPOLEN_SIGNATURE; 1867 *optp++ = TCPOPT_SIGNATURE; 1868 *optp++ = TCPOLEN_SIGNATURE; 1869 to->to_signature = optp; 1870 while (siglen--) 1871 *optp++ = 0; 1872 break; 1873 } 1874 case TOF_SACK: 1875 { 1876 int sackblks = 0; 1877 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1878 tcp_seq sack_seq; 1879 1880 while (!optlen || optlen % 4 != 2) { 1881 optlen += TCPOLEN_NOP; 1882 *optp++ = TCPOPT_NOP; 1883 } 1884 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1885 continue; 1886 optlen += TCPOLEN_SACKHDR; 1887 *optp++ = TCPOPT_SACK; 1888 sackblks = min(to->to_nsacks, 1889 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1890 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1891 while (sackblks--) { 1892 sack_seq = htonl(sack->start); 1893 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1894 optp += sizeof(sack_seq); 1895 sack_seq = htonl(sack->end); 1896 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1897 optp += sizeof(sack_seq); 1898 optlen += TCPOLEN_SACK; 1899 sack++; 1900 } 1901 TCPSTAT_INC(tcps_sack_send_blocks); 1902 break; 1903 } 1904 case TOF_FASTOPEN: 1905 { 1906 int total_len; 1907 1908 /* XXX is there any point to aligning this option? */ 1909 total_len = TCPOLEN_FAST_OPEN_EMPTY + to->to_tfo_len; 1910 if (TCP_MAXOLEN - optlen < total_len) { 1911 to->to_flags &= ~TOF_FASTOPEN; 1912 continue; 1913 } 1914 *optp++ = TCPOPT_FAST_OPEN; 1915 *optp++ = total_len; 1916 if (to->to_tfo_len > 0) { 1917 bcopy(to->to_tfo_cookie, optp, to->to_tfo_len); 1918 optp += to->to_tfo_len; 1919 } 1920 optlen += total_len; 1921 break; 1922 } 1923 default: 1924 panic("%s: unknown TCP option type", __func__); 1925 break; 1926 } 1927 } 1928 1929 /* Terminate and pad TCP options to a 4 byte boundary. */ 1930 if (optlen % 4) { 1931 optlen += TCPOLEN_EOL; 1932 *optp++ = TCPOPT_EOL; 1933 } 1934 /* 1935 * According to RFC 793 (STD0007): 1936 * "The content of the header beyond the End-of-Option option 1937 * must be header padding (i.e., zero)." 1938 * and later: "The padding is composed of zeros." 1939 */ 1940 while (optlen % 4) { 1941 optlen += TCPOLEN_PAD; 1942 *optp++ = TCPOPT_PAD; 1943 } 1944 1945 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1946 return (optlen); 1947 } 1948 1949 /* 1950 * This is a copy of m_copym(), taking the TSO segment size/limit 1951 * constraints into account, and advancing the sndptr as it goes. 1952 */ 1953 struct mbuf * 1954 tcp_m_copym(struct mbuf *m, int32_t off0, int32_t *plen, 1955 int32_t seglimit, int32_t segsize, struct sockbuf *sb, bool hw_tls) 1956 { 1957 #ifdef KERN_TLS 1958 struct ktls_session *tls, *ntls; 1959 struct mbuf *start; 1960 #endif 1961 struct mbuf *n, **np; 1962 struct mbuf *top; 1963 int32_t off = off0; 1964 int32_t len = *plen; 1965 int32_t fragsize; 1966 int32_t len_cp = 0; 1967 int32_t *pkthdrlen; 1968 uint32_t mlen, frags; 1969 bool copyhdr; 1970 1971 KASSERT(off >= 0, ("tcp_m_copym, negative off %d", off)); 1972 KASSERT(len >= 0, ("tcp_m_copym, negative len %d", len)); 1973 if (off == 0 && m->m_flags & M_PKTHDR) 1974 copyhdr = true; 1975 else 1976 copyhdr = false; 1977 while (off > 0) { 1978 KASSERT(m != NULL, ("tcp_m_copym, offset > size of mbuf chain")); 1979 if (off < m->m_len) 1980 break; 1981 off -= m->m_len; 1982 if ((sb) && (m == sb->sb_sndptr)) { 1983 sb->sb_sndptroff += m->m_len; 1984 sb->sb_sndptr = m->m_next; 1985 } 1986 m = m->m_next; 1987 } 1988 np = ⊤ 1989 top = NULL; 1990 pkthdrlen = NULL; 1991 #ifdef KERN_TLS 1992 if (hw_tls && (m->m_flags & M_EXTPG)) 1993 tls = m->m_epg_tls; 1994 else 1995 tls = NULL; 1996 start = m; 1997 #endif 1998 while (len > 0) { 1999 if (m == NULL) { 2000 KASSERT(len == M_COPYALL, 2001 ("tcp_m_copym, length > size of mbuf chain")); 2002 *plen = len_cp; 2003 if (pkthdrlen != NULL) 2004 *pkthdrlen = len_cp; 2005 break; 2006 } 2007 #ifdef KERN_TLS 2008 if (hw_tls) { 2009 if (m->m_flags & M_EXTPG) 2010 ntls = m->m_epg_tls; 2011 else 2012 ntls = NULL; 2013 2014 /* 2015 * Avoid mixing TLS records with handshake 2016 * data or TLS records from different 2017 * sessions. 2018 */ 2019 if (tls != ntls) { 2020 MPASS(m != start); 2021 *plen = len_cp; 2022 if (pkthdrlen != NULL) 2023 *pkthdrlen = len_cp; 2024 break; 2025 } 2026 } 2027 #endif 2028 mlen = min(len, m->m_len - off); 2029 if (seglimit) { 2030 /* 2031 * For M_EXTPG mbufs, add 3 segments 2032 * + 1 in case we are crossing page boundaries 2033 * + 2 in case the TLS hdr/trailer are used 2034 * It is cheaper to just add the segments 2035 * than it is to take the cache miss to look 2036 * at the mbuf ext_pgs state in detail. 2037 */ 2038 if (m->m_flags & M_EXTPG) { 2039 fragsize = min(segsize, PAGE_SIZE); 2040 frags = 3; 2041 } else { 2042 fragsize = segsize; 2043 frags = 0; 2044 } 2045 2046 /* Break if we really can't fit anymore. */ 2047 if ((frags + 1) >= seglimit) { 2048 *plen = len_cp; 2049 if (pkthdrlen != NULL) 2050 *pkthdrlen = len_cp; 2051 break; 2052 } 2053 2054 /* 2055 * Reduce size if you can't copy the whole 2056 * mbuf. If we can't copy the whole mbuf, also 2057 * adjust len so the loop will end after this 2058 * mbuf. 2059 */ 2060 if ((frags + howmany(mlen, fragsize)) >= seglimit) { 2061 mlen = (seglimit - frags - 1) * fragsize; 2062 len = mlen; 2063 *plen = len_cp + len; 2064 if (pkthdrlen != NULL) 2065 *pkthdrlen = *plen; 2066 } 2067 frags += howmany(mlen, fragsize); 2068 if (frags == 0) 2069 frags++; 2070 seglimit -= frags; 2071 KASSERT(seglimit > 0, 2072 ("%s: seglimit went too low", __func__)); 2073 } 2074 if (copyhdr) 2075 n = m_gethdr(M_NOWAIT, m->m_type); 2076 else 2077 n = m_get(M_NOWAIT, m->m_type); 2078 *np = n; 2079 if (n == NULL) 2080 goto nospace; 2081 if (copyhdr) { 2082 if (!m_dup_pkthdr(n, m, M_NOWAIT)) 2083 goto nospace; 2084 if (len == M_COPYALL) 2085 n->m_pkthdr.len -= off0; 2086 else 2087 n->m_pkthdr.len = len; 2088 pkthdrlen = &n->m_pkthdr.len; 2089 copyhdr = false; 2090 } 2091 n->m_len = mlen; 2092 len_cp += n->m_len; 2093 if (m->m_flags & (M_EXT|M_EXTPG)) { 2094 n->m_data = m->m_data + off; 2095 mb_dupcl(n, m); 2096 } else 2097 bcopy(mtod(m, caddr_t)+off, mtod(n, caddr_t), 2098 (u_int)n->m_len); 2099 2100 if (sb && (sb->sb_sndptr == m) && 2101 ((n->m_len + off) >= m->m_len) && m->m_next) { 2102 sb->sb_sndptroff += m->m_len; 2103 sb->sb_sndptr = m->m_next; 2104 } 2105 off = 0; 2106 if (len != M_COPYALL) { 2107 len -= n->m_len; 2108 } 2109 m = m->m_next; 2110 np = &n->m_next; 2111 } 2112 return (top); 2113 nospace: 2114 m_freem(top); 2115 return (NULL); 2116 } 2117 2118 void 2119 tcp_sndbuf_autoscale(struct tcpcb *tp, struct socket *so, uint32_t sendwin) 2120 { 2121 2122 /* 2123 * Automatic sizing of send socket buffer. Often the send buffer 2124 * size is not optimally adjusted to the actual network conditions 2125 * at hand (delay bandwidth product). Setting the buffer size too 2126 * small limits throughput on links with high bandwidth and high 2127 * delay (eg. trans-continental/oceanic links). Setting the 2128 * buffer size too big consumes too much real kernel memory, 2129 * especially with many connections on busy servers. 2130 * 2131 * The criteria to step up the send buffer one notch are: 2132 * 1. receive window of remote host is larger than send buffer 2133 * (with a fudge factor of 5/4th); 2134 * 2. send buffer is filled to 7/8th with data (so we actually 2135 * have data to make use of it); 2136 * 3. send buffer fill has not hit maximal automatic size; 2137 * 4. our send window (slow start and cogestion controlled) is 2138 * larger than sent but unacknowledged data in send buffer. 2139 * 2140 * The remote host receive window scaling factor may limit the 2141 * growing of the send buffer before it reaches its allowed 2142 * maximum. 2143 * 2144 * It scales directly with slow start or congestion window 2145 * and does at most one step per received ACK. This fast 2146 * scaling has the drawback of growing the send buffer beyond 2147 * what is strictly necessary to make full use of a given 2148 * delay*bandwidth product. However testing has shown this not 2149 * to be much of an problem. At worst we are trading wasting 2150 * of available bandwidth (the non-use of it) for wasting some 2151 * socket buffer memory. 2152 * 2153 * TODO: Shrink send buffer during idle periods together 2154 * with congestion window. Requires another timer. Has to 2155 * wait for upcoming tcp timer rewrite. 2156 * 2157 * XXXGL: should there be used sbused() or sbavail()? 2158 */ 2159 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 2160 int lowat; 2161 2162 lowat = V_tcp_sendbuf_auto_lowat ? so->so_snd.sb_lowat : 0; 2163 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat - lowat && 2164 sbused(&so->so_snd) >= 2165 (so->so_snd.sb_hiwat / 8 * 7) - lowat && 2166 sbused(&so->so_snd) < V_tcp_autosndbuf_max && 2167 sendwin >= (sbused(&so->so_snd) - 2168 (tp->snd_nxt - tp->snd_una))) { 2169 if (!sbreserve_locked(&so->so_snd, 2170 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 2171 V_tcp_autosndbuf_max), so, curthread)) 2172 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 2173 } 2174 } 2175 } 2176