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_timer.h> 88 #include <netinet/tcp_var.h> 89 #include <netinet/tcpip.h> 90 #include <netinet/cc/cc.h> 91 #include <netinet/tcp_fastopen.h> 92 #ifdef TCPPCAP 93 #include <netinet/tcp_pcap.h> 94 #endif 95 #ifdef TCPDEBUG 96 #include <netinet/tcp_debug.h> 97 #endif 98 #ifdef TCP_OFFLOAD 99 #include <netinet/tcp_offload.h> 100 #endif 101 102 #include <netipsec/ipsec_support.h> 103 104 #include <machine/in_cksum.h> 105 106 #include <security/mac/mac_framework.h> 107 108 VNET_DEFINE(int, path_mtu_discovery) = 1; 109 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_VNET | CTLFLAG_RW, 110 &VNET_NAME(path_mtu_discovery), 1, 111 "Enable Path MTU Discovery"); 112 113 VNET_DEFINE(int, tcp_do_tso) = 1; 114 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_VNET | CTLFLAG_RW, 115 &VNET_NAME(tcp_do_tso), 0, 116 "Enable TCP Segmentation Offload"); 117 118 VNET_DEFINE(int, tcp_sendspace) = 1024*32; 119 #define V_tcp_sendspace VNET(tcp_sendspace) 120 SYSCTL_INT(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, CTLFLAG_VNET | CTLFLAG_RW, 121 &VNET_NAME(tcp_sendspace), 0, "Initial send socket buffer size"); 122 123 VNET_DEFINE(int, tcp_do_autosndbuf) = 1; 124 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_VNET | CTLFLAG_RW, 125 &VNET_NAME(tcp_do_autosndbuf), 0, 126 "Enable automatic send buffer sizing"); 127 128 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024; 129 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_VNET | CTLFLAG_RW, 130 &VNET_NAME(tcp_autosndbuf_inc), 0, 131 "Incrementor step size of automatic send buffer"); 132 133 VNET_DEFINE(int, tcp_autosndbuf_max) = 2*1024*1024; 134 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_VNET | CTLFLAG_RW, 135 &VNET_NAME(tcp_autosndbuf_max), 0, 136 "Max size of automatic send buffer"); 137 138 VNET_DEFINE(int, tcp_sendbuf_auto_lowat) = 0; 139 #define V_tcp_sendbuf_auto_lowat VNET(tcp_sendbuf_auto_lowat) 140 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto_lowat, CTLFLAG_VNET | CTLFLAG_RW, 141 &VNET_NAME(tcp_sendbuf_auto_lowat), 0, 142 "Modify threshold for auto send buffer growth to account for SO_SNDLOWAT"); 143 144 /* 145 * Make sure that either retransmit or persist timer is set for SYN, FIN and 146 * non-ACK. 147 */ 148 #define TCP_XMIT_TIMER_ASSERT(tp, len, th_flags) \ 149 KASSERT(((len) == 0 && ((th_flags) & (TH_SYN | TH_FIN)) == 0) ||\ 150 tcp_timer_active((tp), TT_REXMT) || \ 151 tcp_timer_active((tp), TT_PERSIST), \ 152 ("neither rexmt nor persist timer is set")) 153 154 static void inline cc_after_idle(struct tcpcb *tp); 155 156 #ifdef TCP_HHOOK 157 /* 158 * Wrapper for the TCP established output helper hook. 159 */ 160 void 161 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th, 162 struct tcpopt *to, uint32_t len, int tso) 163 { 164 struct tcp_hhook_data hhook_data; 165 166 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) { 167 hhook_data.tp = tp; 168 hhook_data.th = th; 169 hhook_data.to = to; 170 hhook_data.len = len; 171 hhook_data.tso = tso; 172 173 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data, 174 tp->osd); 175 } 176 } 177 #endif 178 179 /* 180 * CC wrapper hook functions 181 */ 182 static void inline 183 cc_after_idle(struct tcpcb *tp) 184 { 185 INP_WLOCK_ASSERT(tp->t_inpcb); 186 187 if (CC_ALGO(tp)->after_idle != NULL) 188 CC_ALGO(tp)->after_idle(tp->ccv); 189 } 190 191 /* 192 * Tcp output routine: figure out what should be sent and send it. 193 */ 194 int 195 tcp_output(struct tcpcb *tp) 196 { 197 struct socket *so = tp->t_inpcb->inp_socket; 198 int32_t len; 199 uint32_t recwin, sendwin; 200 int off, flags, error = 0; /* Keep compiler happy */ 201 u_int if_hw_tsomaxsegcount = 0; 202 u_int if_hw_tsomaxsegsize = 0; 203 struct mbuf *m; 204 struct ip *ip = NULL; 205 #ifdef TCPDEBUG 206 struct ipovly *ipov = NULL; 207 #endif 208 struct tcphdr *th; 209 u_char opt[TCP_MAXOLEN]; 210 unsigned ipoptlen, optlen, hdrlen; 211 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 212 unsigned ipsec_optlen = 0; 213 #endif 214 int idle, sendalot, curticks; 215 int sack_rxmit, sack_bytes_rxmt; 216 struct sackhole *p; 217 int tso, mtu; 218 struct tcpopt to; 219 unsigned int wanted_cookie = 0; 220 unsigned int dont_sendalot = 0; 221 #if 0 222 int maxburst = TCP_MAXBURST; 223 #endif 224 #ifdef INET6 225 struct ip6_hdr *ip6 = NULL; 226 int isipv6; 227 228 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 229 #endif 230 #ifdef KERN_TLS 231 const bool hw_tls = (so->so_snd.sb_flags & SB_TLS_IFNET) != 0; 232 #else 233 const bool hw_tls = false; 234 #endif 235 236 NET_EPOCH_ASSERT(); 237 INP_WLOCK_ASSERT(tp->t_inpcb); 238 239 #ifdef TCP_OFFLOAD 240 if (tp->t_flags & TF_TOE) 241 return (tcp_offload_output(tp)); 242 #endif 243 244 /* 245 * For TFO connections in SYN_SENT or SYN_RECEIVED, 246 * only allow the initial SYN or SYN|ACK and those sent 247 * by the retransmit timer. 248 */ 249 if (IS_FASTOPEN(tp->t_flags) && 250 ((tp->t_state == TCPS_SYN_SENT) || 251 (tp->t_state == TCPS_SYN_RECEIVED)) && 252 SEQ_GT(tp->snd_max, tp->snd_una) && /* initial SYN or SYN|ACK sent */ 253 (tp->snd_nxt != tp->snd_una)) /* not a retransmit */ 254 return (0); 255 256 /* 257 * Determine length of data that should be transmitted, 258 * and flags that will be used. 259 * If there is some data or critical controls (SYN, RST) 260 * to send, then transmit; otherwise, investigate further. 261 */ 262 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 263 if (idle && ticks - tp->t_rcvtime >= tp->t_rxtcur) 264 cc_after_idle(tp); 265 tp->t_flags &= ~TF_LASTIDLE; 266 if (idle) { 267 if (tp->t_flags & TF_MORETOCOME) { 268 tp->t_flags |= TF_LASTIDLE; 269 idle = 0; 270 } 271 } 272 again: 273 /* 274 * If we've recently taken a timeout, snd_max will be greater than 275 * snd_nxt. There may be SACK information that allows us to avoid 276 * resending already delivered data. Adjust snd_nxt accordingly. 277 */ 278 if ((tp->t_flags & TF_SACK_PERMIT) && 279 SEQ_LT(tp->snd_nxt, tp->snd_max)) 280 tcp_sack_adjust(tp); 281 sendalot = 0; 282 tso = 0; 283 mtu = 0; 284 off = tp->snd_nxt - tp->snd_una; 285 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 286 287 flags = tcp_outflags[tp->t_state]; 288 /* 289 * Send any SACK-generated retransmissions. If we're explicitly trying 290 * to send out new data (when sendalot is 1), bypass this function. 291 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 292 * we're replacing a (future) new transmission with a retransmission 293 * now, and we previously incremented snd_cwnd in tcp_input(). 294 */ 295 /* 296 * Still in sack recovery , reset rxmit flag to zero. 297 */ 298 sack_rxmit = 0; 299 sack_bytes_rxmt = 0; 300 len = 0; 301 p = NULL; 302 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) && 303 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 304 uint32_t cwin; 305 306 cwin = 307 imax(min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt, 0); 308 /* Do not retransmit SACK segments beyond snd_recover */ 309 if (SEQ_GT(p->end, tp->snd_recover)) { 310 /* 311 * (At least) part of sack hole extends beyond 312 * snd_recover. Check to see if we can rexmit data 313 * for this hole. 314 */ 315 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 316 /* 317 * Can't rexmit any more data for this hole. 318 * That data will be rexmitted in the next 319 * sack recovery episode, when snd_recover 320 * moves past p->rxmit. 321 */ 322 p = NULL; 323 goto after_sack_rexmit; 324 } else 325 /* Can rexmit part of the current hole */ 326 len = ((int32_t)ulmin(cwin, 327 tp->snd_recover - p->rxmit)); 328 } else 329 len = ((int32_t)ulmin(cwin, p->end - p->rxmit)); 330 off = p->rxmit - tp->snd_una; 331 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 332 __func__, off)); 333 if (len > 0) { 334 sack_rxmit = 1; 335 sendalot = 1; 336 TCPSTAT_INC(tcps_sack_rexmits); 337 TCPSTAT_ADD(tcps_sack_rexmit_bytes, 338 min(len, tp->t_maxseg)); 339 } 340 } 341 after_sack_rexmit: 342 /* 343 * Get standard flags, and add SYN or FIN if requested by 'hidden' 344 * state flags. 345 */ 346 if (tp->t_flags & TF_NEEDFIN) 347 flags |= TH_FIN; 348 if (tp->t_flags & TF_NEEDSYN) 349 flags |= TH_SYN; 350 351 SOCKBUF_LOCK(&so->so_snd); 352 /* 353 * If in persist timeout with window of 0, send 1 byte. 354 * Otherwise, if window is small but nonzero 355 * and timer expired, we will send what we can 356 * and go to transmit state. 357 */ 358 if (tp->t_flags & TF_FORCEDATA) { 359 if (sendwin == 0) { 360 /* 361 * If we still have some data to send, then 362 * clear the FIN bit. Usually this would 363 * happen below when it realizes that we 364 * aren't sending all the data. However, 365 * if we have exactly 1 byte of unsent data, 366 * then it won't clear the FIN bit below, 367 * and if we are in persist state, we wind 368 * up sending the packet without recording 369 * that we sent the FIN bit. 370 * 371 * We can't just blindly clear the FIN bit, 372 * because if we don't have any more data 373 * to send then the probe will be the FIN 374 * itself. 375 */ 376 if (off < sbused(&so->so_snd)) 377 flags &= ~TH_FIN; 378 sendwin = 1; 379 } else { 380 tcp_timer_activate(tp, TT_PERSIST, 0); 381 tp->t_rxtshift = 0; 382 } 383 } 384 385 /* 386 * If snd_nxt == snd_max and we have transmitted a FIN, the 387 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 388 * a negative length. This can also occur when TCP opens up 389 * its congestion window while receiving additional duplicate 390 * acks after fast-retransmit because TCP will reset snd_nxt 391 * to snd_max after the fast-retransmit. 392 * 393 * In the normal retransmit-FIN-only case, however, snd_nxt will 394 * be set to snd_una, the offset will be 0, and the length may 395 * wind up 0. 396 * 397 * If sack_rxmit is true we are retransmitting from the scoreboard 398 * in which case len is already set. 399 */ 400 if (sack_rxmit == 0) { 401 if (sack_bytes_rxmt == 0) 402 len = ((int32_t)min(sbavail(&so->so_snd), sendwin) - 403 off); 404 else { 405 int32_t cwin; 406 407 /* 408 * We are inside of a SACK recovery episode and are 409 * sending new data, having retransmitted all the 410 * data possible in the scoreboard. 411 */ 412 len = ((int32_t)min(sbavail(&so->so_snd), tp->snd_wnd) - 413 off); 414 /* 415 * Don't remove this (len > 0) check ! 416 * We explicitly check for len > 0 here (although it 417 * isn't really necessary), to work around a gcc 418 * optimization issue - to force gcc to compute 419 * len above. Without this check, the computation 420 * of len is bungled by the optimizer. 421 */ 422 if (len > 0) { 423 cwin = tp->snd_cwnd - 424 (tp->snd_nxt - tp->snd_recover) - 425 sack_bytes_rxmt; 426 if (cwin < 0) 427 cwin = 0; 428 len = imin(len, cwin); 429 } 430 } 431 } 432 433 /* 434 * Lop off SYN bit if it has already been sent. However, if this 435 * is SYN-SENT state and if segment contains data and if we don't 436 * know that foreign host supports TAO, suppress sending segment. 437 */ 438 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 439 if (tp->t_state != TCPS_SYN_RECEIVED) 440 flags &= ~TH_SYN; 441 /* 442 * When sending additional segments following a TFO SYN|ACK, 443 * do not include the SYN bit. 444 */ 445 if (IS_FASTOPEN(tp->t_flags) && 446 (tp->t_state == TCPS_SYN_RECEIVED)) 447 flags &= ~TH_SYN; 448 off--, len++; 449 } 450 451 /* 452 * Be careful not to send data and/or FIN on SYN segments. 453 * This measure is needed to prevent interoperability problems 454 * with not fully conformant TCP implementations. 455 */ 456 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 457 len = 0; 458 flags &= ~TH_FIN; 459 } 460 461 /* 462 * On TFO sockets, ensure no data is sent in the following cases: 463 * 464 * - When retransmitting SYN|ACK on a passively-created socket 465 * 466 * - When retransmitting SYN on an actively created socket 467 * 468 * - When sending a zero-length cookie (cookie request) on an 469 * actively created socket 470 * 471 * - When the socket is in the CLOSED state (RST is being sent) 472 */ 473 if (IS_FASTOPEN(tp->t_flags) && 474 (((flags & TH_SYN) && (tp->t_rxtshift > 0)) || 475 ((tp->t_state == TCPS_SYN_SENT) && 476 (tp->t_tfo_client_cookie_len == 0)) || 477 (flags & TH_RST))) 478 len = 0; 479 if (len <= 0) { 480 /* 481 * If FIN has been sent but not acked, 482 * but we haven't been called to retransmit, 483 * len will be < 0. Otherwise, window shrank 484 * after we sent into it. If window shrank to 0, 485 * cancel pending retransmit, pull snd_nxt back 486 * to (closed) window, and set the persist timer 487 * if it isn't already going. If the window didn't 488 * close completely, just wait for an ACK. 489 * 490 * We also do a general check here to ensure that 491 * we will set the persist timer when we have data 492 * to send, but a 0-byte window. This makes sure 493 * the persist timer is set even if the packet 494 * hits one of the "goto send" lines below. 495 */ 496 len = 0; 497 if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) && 498 (off < (int) sbavail(&so->so_snd))) { 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, SACK retransmits, SACK advertizements and 518 * IP options 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, tp->t_inpcb); 536 #ifdef INET 537 else 538 #endif 539 #endif /* INET6 */ 540 #ifdef INET 541 if (IPSEC_ENABLED(ipv4)) 542 ipsec_optlen = IPSEC_HDRSIZE(ipv4, tp->t_inpcb); 543 #endif /* INET */ 544 #endif /* IPSEC */ 545 #ifdef INET6 546 if (isipv6) 547 ipoptlen = ip6_optlen(tp->t_inpcb); 548 else 549 #endif 550 if (tp->t_inpcb->inp_options) 551 ipoptlen = tp->t_inpcb->inp_options->m_len - 552 offsetof(struct ipoption, ipopt_list); 553 else 554 ipoptlen = 0; 555 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 556 ipoptlen += ipsec_optlen; 557 #endif 558 559 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg && 560 ((tp->t_flags & TF_SIGNATURE) == 0) && 561 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 562 ipoptlen == 0 && !(flags & TH_SYN)) 563 tso = 1; 564 565 if (sack_rxmit) { 566 if (SEQ_LT(p->rxmit + len, tp->snd_una + sbused(&so->so_snd))) 567 flags &= ~TH_FIN; 568 } else { 569 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + 570 sbused(&so->so_snd))) 571 flags &= ~TH_FIN; 572 } 573 574 recwin = lmin(lmax(sbspace(&so->so_rcv), 0), 575 (long)TCP_MAXWIN << tp->rcv_scale); 576 577 /* 578 * Sender silly window avoidance. We transmit under the following 579 * conditions when len is non-zero: 580 * 581 * - We have a full segment (or more with TSO) 582 * - This is the last buffer in a write()/send() and we are 583 * either idle or running NODELAY 584 * - we've timed out (e.g. persist timer) 585 * - we have more then 1/2 the maximum send window's worth of 586 * data (receiver may be limited the window size) 587 * - we need to retransmit 588 */ 589 if (len) { 590 if (len >= tp->t_maxseg) 591 goto send; 592 /* 593 * NOTE! on localhost connections an 'ack' from the remote 594 * end may occur synchronously with the output and cause 595 * us to flush a buffer queued with moretocome. XXX 596 * 597 * note: the len + off check is almost certainly unnecessary. 598 */ 599 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 600 (idle || (tp->t_flags & TF_NODELAY)) && 601 (uint32_t)len + (uint32_t)off >= sbavail(&so->so_snd) && 602 (tp->t_flags & TF_NOPUSH) == 0) { 603 goto send; 604 } 605 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 606 goto send; 607 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 608 goto send; 609 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 610 goto send; 611 if (sack_rxmit) 612 goto send; 613 } 614 615 /* 616 * Sending of standalone window updates. 617 * 618 * Window updates are important when we close our window due to a 619 * full socket buffer and are opening it again after the application 620 * reads data from it. Once the window has opened again and the 621 * remote end starts to send again the ACK clock takes over and 622 * provides the most current window information. 623 * 624 * We must avoid the silly window syndrome whereas every read 625 * from the receive buffer, no matter how small, causes a window 626 * update to be sent. We also should avoid sending a flurry of 627 * window updates when the socket buffer had queued a lot of data 628 * and the application is doing small reads. 629 * 630 * Prevent a flurry of pointless window updates by only sending 631 * an update when we can increase the advertized window by more 632 * than 1/4th of the socket buffer capacity. When the buffer is 633 * getting full or is very small be more aggressive and send an 634 * update whenever we can increase by two mss sized segments. 635 * In all other situations the ACK's to new incoming data will 636 * carry further window increases. 637 * 638 * Don't send an independent window update if a delayed 639 * ACK is pending (it will get piggy-backed on it) or the 640 * remote side already has done a half-close and won't send 641 * more data. Skip this if the connection is in T/TCP 642 * half-open state. 643 */ 644 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 645 !(tp->t_flags & TF_DELACK) && 646 !TCPS_HAVERCVDFIN(tp->t_state)) { 647 /* 648 * "adv" is the amount we could increase the window, 649 * taking into account that we are limited by 650 * TCP_MAXWIN << tp->rcv_scale. 651 */ 652 int32_t adv; 653 int oldwin; 654 655 adv = recwin; 656 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { 657 oldwin = (tp->rcv_adv - tp->rcv_nxt); 658 adv -= oldwin; 659 } else 660 oldwin = 0; 661 662 /* 663 * If the new window size ends up being the same as or less 664 * than the old size when it is scaled, then don't force 665 * a window update. 666 */ 667 if (oldwin >> tp->rcv_scale >= (adv + oldwin) >> tp->rcv_scale) 668 goto dontupdate; 669 670 if (adv >= (int32_t)(2 * tp->t_maxseg) && 671 (adv >= (int32_t)(so->so_rcv.sb_hiwat / 4) || 672 recwin <= (so->so_rcv.sb_hiwat / 8) || 673 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg || 674 adv >= TCP_MAXWIN << tp->rcv_scale)) 675 goto send; 676 if (2 * adv >= (int32_t)so->so_rcv.sb_hiwat) 677 goto send; 678 } 679 dontupdate: 680 681 /* 682 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 683 * is also a catch-all for the retransmit timer timeout case. 684 */ 685 if (tp->t_flags & TF_ACKNOW) 686 goto send; 687 if ((flags & TH_RST) || 688 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 689 goto send; 690 if (SEQ_GT(tp->snd_up, tp->snd_una)) 691 goto send; 692 /* 693 * If our state indicates that FIN should be sent 694 * and we have not yet done so, then we need to send. 695 */ 696 if (flags & TH_FIN && 697 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 698 goto send; 699 /* 700 * In SACK, it is possible for tcp_output to fail to send a segment 701 * after the retransmission timer has been turned off. Make sure 702 * that the retransmission timer is set. 703 */ 704 if ((tp->t_flags & TF_SACK_PERMIT) && 705 SEQ_GT(tp->snd_max, tp->snd_una) && 706 !tcp_timer_active(tp, TT_REXMT) && 707 !tcp_timer_active(tp, TT_PERSIST)) { 708 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 709 goto just_return; 710 } 711 /* 712 * TCP window updates are not reliable, rather a polling protocol 713 * using ``persist'' packets is used to insure receipt of window 714 * updates. The three ``states'' for the output side are: 715 * idle not doing retransmits or persists 716 * persisting to move a small or zero window 717 * (re)transmitting and thereby not persisting 718 * 719 * tcp_timer_active(tp, TT_PERSIST) 720 * is true when we are in persist state. 721 * (tp->t_flags & TF_FORCEDATA) 722 * is set when we are called to send a persist packet. 723 * tcp_timer_active(tp, TT_REXMT) 724 * is set when we are retransmitting 725 * The output side is idle when both timers are zero. 726 * 727 * If send window is too small, there is data to transmit, and no 728 * retransmit or persist is pending, then go to persist state. 729 * If nothing happens soon, send when timer expires: 730 * if window is nonzero, transmit what we can, 731 * otherwise force out a byte. 732 */ 733 if (sbavail(&so->so_snd) && !tcp_timer_active(tp, TT_REXMT) && 734 !tcp_timer_active(tp, TT_PERSIST)) { 735 tp->t_rxtshift = 0; 736 tcp_setpersist(tp); 737 } 738 739 /* 740 * No reason to send a segment, just return. 741 */ 742 just_return: 743 SOCKBUF_UNLOCK(&so->so_snd); 744 return (0); 745 746 send: 747 SOCKBUF_LOCK_ASSERT(&so->so_snd); 748 if (len > 0) { 749 if (len >= tp->t_maxseg) 750 tp->t_flags2 |= TF2_PLPMTU_MAXSEGSNT; 751 else 752 tp->t_flags2 &= ~TF2_PLPMTU_MAXSEGSNT; 753 } 754 /* 755 * Before ESTABLISHED, force sending of initial options 756 * unless TCP set not to do any options. 757 * NOTE: we assume that the IP/TCP header plus TCP options 758 * always fit in a single mbuf, leaving room for a maximum 759 * link header, i.e. 760 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 761 */ 762 optlen = 0; 763 #ifdef INET6 764 if (isipv6) 765 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 766 else 767 #endif 768 hdrlen = sizeof (struct tcpiphdr); 769 770 /* 771 * Compute options for segment. 772 * We only have to care about SYN and established connection 773 * segments. Options for SYN-ACK segments are handled in TCP 774 * syncache. 775 */ 776 to.to_flags = 0; 777 if ((tp->t_flags & TF_NOOPT) == 0) { 778 /* Maximum segment size. */ 779 if (flags & TH_SYN) { 780 tp->snd_nxt = tp->iss; 781 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 782 to.to_flags |= TOF_MSS; 783 784 /* 785 * On SYN or SYN|ACK transmits on TFO connections, 786 * only include the TFO option if it is not a 787 * retransmit, as the presence of the TFO option may 788 * have caused the original SYN or SYN|ACK to have 789 * been dropped by a middlebox. 790 */ 791 if (IS_FASTOPEN(tp->t_flags) && 792 (tp->t_rxtshift == 0)) { 793 if (tp->t_state == TCPS_SYN_RECEIVED) { 794 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN; 795 to.to_tfo_cookie = 796 (u_int8_t *)&tp->t_tfo_cookie.server; 797 to.to_flags |= TOF_FASTOPEN; 798 wanted_cookie = 1; 799 } else if (tp->t_state == TCPS_SYN_SENT) { 800 to.to_tfo_len = 801 tp->t_tfo_client_cookie_len; 802 to.to_tfo_cookie = 803 tp->t_tfo_cookie.client; 804 to.to_flags |= TOF_FASTOPEN; 805 wanted_cookie = 1; 806 /* 807 * If we wind up having more data to 808 * send with the SYN than can fit in 809 * one segment, don't send any more 810 * until the SYN|ACK comes back from 811 * the other end. 812 */ 813 dont_sendalot = 1; 814 } 815 } 816 } 817 /* Window scaling. */ 818 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 819 to.to_wscale = tp->request_r_scale; 820 to.to_flags |= TOF_SCALE; 821 } 822 /* Timestamps. */ 823 if ((tp->t_flags & TF_RCVD_TSTMP) || 824 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 825 curticks = tcp_ts_getticks(); 826 to.to_tsval = curticks + tp->ts_offset; 827 to.to_tsecr = tp->ts_recent; 828 to.to_flags |= TOF_TS; 829 if (tp->t_rxtshift == 1) 830 tp->t_badrxtwin = curticks; 831 } 832 833 /* Set receive buffer autosizing timestamp. */ 834 if (tp->rfbuf_ts == 0 && 835 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 836 tp->rfbuf_ts = tcp_ts_getticks(); 837 838 /* Selective ACK's. */ 839 if (tp->t_flags & TF_SACK_PERMIT) { 840 if (flags & TH_SYN) 841 to.to_flags |= TOF_SACKPERM; 842 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 843 (tp->t_flags & TF_SACK_PERMIT) && 844 tp->rcv_numsacks > 0) { 845 to.to_flags |= TOF_SACK; 846 to.to_nsacks = tp->rcv_numsacks; 847 to.to_sacks = (u_char *)tp->sackblks; 848 } 849 } 850 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 851 /* TCP-MD5 (RFC2385). */ 852 /* 853 * Check that TCP_MD5SIG is enabled in tcpcb to 854 * account the size needed to set this TCP option. 855 */ 856 if (tp->t_flags & TF_SIGNATURE) 857 to.to_flags |= TOF_SIGNATURE; 858 #endif /* TCP_SIGNATURE */ 859 860 /* Processing the options. */ 861 hdrlen += optlen = tcp_addoptions(&to, opt); 862 /* 863 * If we wanted a TFO option to be added, but it was unable 864 * to fit, ensure no data is sent. 865 */ 866 if (IS_FASTOPEN(tp->t_flags) && wanted_cookie && 867 !(to.to_flags & TOF_FASTOPEN)) 868 len = 0; 869 } 870 871 /* 872 * Adjust data length if insertion of options will 873 * bump the packet length beyond the t_maxseg length. 874 * Clear the FIN bit because we cut off the tail of 875 * the segment. 876 */ 877 if (len + optlen + ipoptlen > tp->t_maxseg) { 878 flags &= ~TH_FIN; 879 880 if (tso) { 881 u_int if_hw_tsomax; 882 u_int moff; 883 int max_len; 884 885 /* extract TSO information */ 886 if_hw_tsomax = tp->t_tsomax; 887 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount; 888 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize; 889 890 /* 891 * Limit a TSO burst to prevent it from 892 * overflowing or exceeding the maximum length 893 * allowed by the network interface: 894 */ 895 KASSERT(ipoptlen == 0, 896 ("%s: TSO can't do IP options", __func__)); 897 898 /* 899 * Check if we should limit by maximum payload 900 * length: 901 */ 902 if (if_hw_tsomax != 0) { 903 /* compute maximum TSO length */ 904 max_len = (if_hw_tsomax - hdrlen - 905 max_linkhdr); 906 if (max_len <= 0) { 907 len = 0; 908 } else if (len > max_len) { 909 sendalot = 1; 910 len = max_len; 911 } 912 } 913 914 /* 915 * Prevent the last segment from being 916 * fractional unless the send sockbuf can be 917 * emptied: 918 */ 919 max_len = (tp->t_maxseg - optlen); 920 if (((uint32_t)off + (uint32_t)len) < 921 sbavail(&so->so_snd)) { 922 moff = len % max_len; 923 if (moff != 0) { 924 len -= moff; 925 sendalot = 1; 926 } 927 } 928 929 /* 930 * In case there are too many small fragments 931 * don't use TSO: 932 */ 933 if (len <= max_len) { 934 len = max_len; 935 sendalot = 1; 936 tso = 0; 937 } 938 939 /* 940 * Send the FIN in a separate segment 941 * after the bulk sending is done. 942 * We don't trust the TSO implementations 943 * to clear the FIN flag on all but the 944 * last segment. 945 */ 946 if (tp->t_flags & TF_NEEDFIN) 947 sendalot = 1; 948 } else { 949 if (optlen + ipoptlen >= tp->t_maxseg) { 950 /* 951 * Since we don't have enough space to put 952 * the IP header chain and the TCP header in 953 * one packet as required by RFC 7112, don't 954 * send it. Also ensure that at least one 955 * byte of the payload can be put into the 956 * TCP segment. 957 */ 958 SOCKBUF_UNLOCK(&so->so_snd); 959 error = EMSGSIZE; 960 sack_rxmit = 0; 961 goto out; 962 } 963 len = tp->t_maxseg - optlen - ipoptlen; 964 sendalot = 1; 965 if (dont_sendalot) 966 sendalot = 0; 967 } 968 } else 969 tso = 0; 970 971 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 972 ("%s: len > IP_MAXPACKET", __func__)); 973 974 /*#ifdef DIAGNOSTIC*/ 975 #ifdef INET6 976 if (max_linkhdr + hdrlen > MCLBYTES) 977 #else 978 if (max_linkhdr + hdrlen > MHLEN) 979 #endif 980 panic("tcphdr too big"); 981 /*#endif*/ 982 983 /* 984 * This KASSERT is here to catch edge cases at a well defined place. 985 * Before, those had triggered (random) panic conditions further down. 986 */ 987 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 988 989 /* 990 * Grab a header mbuf, attaching a copy of data to 991 * be transmitted, and initialize the header from 992 * the template for sends on this connection. 993 */ 994 if (len) { 995 struct mbuf *mb; 996 struct sockbuf *msb; 997 u_int moff; 998 999 if ((tp->t_flags & TF_FORCEDATA) && len == 1) { 1000 TCPSTAT_INC(tcps_sndprobe); 1001 #ifdef STATS 1002 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1003 stats_voi_update_abs_u32(tp->t_stats, 1004 VOI_TCP_RETXPB, len); 1005 else 1006 stats_voi_update_abs_u64(tp->t_stats, 1007 VOI_TCP_TXPB, len); 1008 #endif /* STATS */ 1009 } else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 1010 tp->t_sndrexmitpack++; 1011 TCPSTAT_INC(tcps_sndrexmitpack); 1012 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 1013 #ifdef STATS 1014 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_RETXPB, 1015 len); 1016 #endif /* STATS */ 1017 } else { 1018 TCPSTAT_INC(tcps_sndpack); 1019 TCPSTAT_ADD(tcps_sndbyte, len); 1020 #ifdef STATS 1021 stats_voi_update_abs_u64(tp->t_stats, VOI_TCP_TXPB, 1022 len); 1023 #endif /* STATS */ 1024 } 1025 #ifdef INET6 1026 if (MHLEN < hdrlen + max_linkhdr) 1027 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR); 1028 else 1029 #endif 1030 m = m_gethdr(M_NOWAIT, MT_DATA); 1031 1032 if (m == NULL) { 1033 SOCKBUF_UNLOCK(&so->so_snd); 1034 error = ENOBUFS; 1035 sack_rxmit = 0; 1036 goto out; 1037 } 1038 1039 m->m_data += max_linkhdr; 1040 m->m_len = hdrlen; 1041 1042 /* 1043 * Start the m_copy functions from the closest mbuf 1044 * to the offset in the socket buffer chain. 1045 */ 1046 mb = sbsndptr_noadv(&so->so_snd, off, &moff); 1047 if (len <= MHLEN - hdrlen - max_linkhdr && !hw_tls) { 1048 m_copydata(mb, moff, len, 1049 mtod(m, caddr_t) + hdrlen); 1050 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1051 sbsndptr_adv(&so->so_snd, mb, len); 1052 m->m_len += len; 1053 } else { 1054 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1055 msb = NULL; 1056 else 1057 msb = &so->so_snd; 1058 m->m_next = tcp_m_copym(mb, moff, 1059 &len, if_hw_tsomaxsegcount, 1060 if_hw_tsomaxsegsize, msb, hw_tls); 1061 if (len <= (tp->t_maxseg - optlen)) { 1062 /* 1063 * Must have ran out of mbufs for the copy 1064 * shorten it to no longer need tso. Lets 1065 * not put on sendalot since we are low on 1066 * mbufs. 1067 */ 1068 tso = 0; 1069 } 1070 if (m->m_next == NULL) { 1071 SOCKBUF_UNLOCK(&so->so_snd); 1072 (void) m_free(m); 1073 error = ENOBUFS; 1074 sack_rxmit = 0; 1075 goto out; 1076 } 1077 } 1078 1079 /* 1080 * If we're sending everything we've got, set PUSH. 1081 * (This will keep happy those implementations which only 1082 * give data to the user when a buffer fills or 1083 * a PUSH comes in.) 1084 */ 1085 if (((uint32_t)off + (uint32_t)len == sbused(&so->so_snd)) && 1086 !(flags & TH_SYN)) 1087 flags |= TH_PUSH; 1088 SOCKBUF_UNLOCK(&so->so_snd); 1089 } else { 1090 SOCKBUF_UNLOCK(&so->so_snd); 1091 if (tp->t_flags & TF_ACKNOW) 1092 TCPSTAT_INC(tcps_sndacks); 1093 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 1094 TCPSTAT_INC(tcps_sndctrl); 1095 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 1096 TCPSTAT_INC(tcps_sndurg); 1097 else 1098 TCPSTAT_INC(tcps_sndwinup); 1099 1100 m = m_gethdr(M_NOWAIT, MT_DATA); 1101 if (m == NULL) { 1102 error = ENOBUFS; 1103 sack_rxmit = 0; 1104 goto out; 1105 } 1106 #ifdef INET6 1107 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 1108 MHLEN >= hdrlen) { 1109 M_ALIGN(m, hdrlen); 1110 } else 1111 #endif 1112 m->m_data += max_linkhdr; 1113 m->m_len = hdrlen; 1114 } 1115 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 1116 m->m_pkthdr.rcvif = (struct ifnet *)0; 1117 #ifdef MAC 1118 mac_inpcb_create_mbuf(tp->t_inpcb, m); 1119 #endif 1120 #ifdef INET6 1121 if (isipv6) { 1122 ip6 = mtod(m, struct ip6_hdr *); 1123 th = (struct tcphdr *)(ip6 + 1); 1124 tcpip_fillheaders(tp->t_inpcb, ip6, th); 1125 } else 1126 #endif /* INET6 */ 1127 { 1128 ip = mtod(m, struct ip *); 1129 #ifdef TCPDEBUG 1130 ipov = (struct ipovly *)ip; 1131 #endif 1132 th = (struct tcphdr *)(ip + 1); 1133 tcpip_fillheaders(tp->t_inpcb, ip, th); 1134 } 1135 1136 /* 1137 * Fill in fields, remembering maximum advertised 1138 * window for use in delaying messages about window sizes. 1139 * If resending a FIN, be sure not to use a new sequence number. 1140 */ 1141 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 1142 tp->snd_nxt == tp->snd_max) 1143 tp->snd_nxt--; 1144 /* 1145 * If we are starting a connection, send ECN setup 1146 * SYN packet. If we are on a retransmit, we may 1147 * resend those bits a number of times as per 1148 * RFC 3168. 1149 */ 1150 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn == 1) { 1151 if (tp->t_rxtshift >= 1) { 1152 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 1153 flags |= TH_ECE|TH_CWR; 1154 } else 1155 flags |= TH_ECE|TH_CWR; 1156 } 1157 /* Handle parallel SYN for ECN */ 1158 if ((tp->t_state == TCPS_SYN_RECEIVED) && 1159 (tp->t_flags2 & TF2_ECN_SND_ECE)) { 1160 flags |= TH_ECE; 1161 tp->t_flags2 &= ~TF2_ECN_SND_ECE; 1162 } 1163 1164 if (tp->t_state == TCPS_ESTABLISHED && 1165 (tp->t_flags2 & TF2_ECN_PERMIT)) { 1166 /* 1167 * If the peer has ECN, mark data packets with 1168 * ECN capable transmission (ECT). 1169 * Ignore pure ack packets, retransmissions and window probes. 1170 */ 1171 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 1172 (sack_rxmit == 0) && 1173 !((tp->t_flags & TF_FORCEDATA) && len == 1 && 1174 SEQ_LT(tp->snd_una, tp->snd_max))) { 1175 #ifdef INET6 1176 if (isipv6) 1177 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 1178 else 1179 #endif 1180 ip->ip_tos |= IPTOS_ECN_ECT0; 1181 TCPSTAT_INC(tcps_ecn_ect0); 1182 /* 1183 * Reply with proper ECN notifications. 1184 * Only set CWR on new data segments. 1185 */ 1186 if (tp->t_flags2 & TF2_ECN_SND_CWR) { 1187 flags |= TH_CWR; 1188 tp->t_flags2 &= ~TF2_ECN_SND_CWR; 1189 } 1190 } 1191 if (tp->t_flags2 & TF2_ECN_SND_ECE) 1192 flags |= TH_ECE; 1193 } 1194 1195 /* 1196 * If we are doing retransmissions, then snd_nxt will 1197 * not reflect the first unsent octet. For ACK only 1198 * packets, we do not want the sequence number of the 1199 * retransmitted packet, we want the sequence number 1200 * of the next unsent octet. So, if there is no data 1201 * (and no SYN or FIN), use snd_max instead of snd_nxt 1202 * when filling in ti_seq. But if we are in persist 1203 * state, snd_max might reflect one byte beyond the 1204 * right edge of the window, so use snd_nxt in that 1205 * case, since we know we aren't doing a retransmission. 1206 * (retransmit and persist are mutually exclusive...) 1207 */ 1208 if (sack_rxmit == 0) { 1209 if (len || (flags & (TH_SYN|TH_FIN)) || 1210 tcp_timer_active(tp, TT_PERSIST)) 1211 th->th_seq = htonl(tp->snd_nxt); 1212 else 1213 th->th_seq = htonl(tp->snd_max); 1214 } else { 1215 th->th_seq = htonl(p->rxmit); 1216 p->rxmit += len; 1217 tp->sackhint.sack_bytes_rexmit += len; 1218 } 1219 th->th_ack = htonl(tp->rcv_nxt); 1220 if (optlen) { 1221 bcopy(opt, th + 1, optlen); 1222 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1223 } 1224 th->th_flags = flags; 1225 /* 1226 * Calculate receive window. Don't shrink window, 1227 * but avoid silly window syndrome. 1228 * If a RST segment is sent, advertise a window of zero. 1229 */ 1230 if (flags & TH_RST) { 1231 recwin = 0; 1232 } else { 1233 if (recwin < (so->so_rcv.sb_hiwat / 4) && 1234 recwin < tp->t_maxseg) 1235 recwin = 0; 1236 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1237 recwin < (tp->rcv_adv - tp->rcv_nxt)) 1238 recwin = (tp->rcv_adv - tp->rcv_nxt); 1239 } 1240 /* 1241 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1242 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1243 * case is handled in syncache. 1244 */ 1245 if (flags & TH_SYN) 1246 th->th_win = htons((u_short) 1247 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1248 else { 1249 /* Avoid shrinking window with window scaling. */ 1250 recwin = roundup2(recwin, 1 << tp->rcv_scale); 1251 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1252 } 1253 1254 /* 1255 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1256 * a 0 window. This may cause the remote transmitter to stall. This 1257 * flag tells soreceive() to disable delayed acknowledgements when 1258 * draining the buffer. This can occur if the receiver is attempting 1259 * to read more data than can be buffered prior to transmitting on 1260 * the connection. 1261 */ 1262 if (th->th_win == 0) { 1263 tp->t_sndzerowin++; 1264 tp->t_flags |= TF_RXWIN0SENT; 1265 } else 1266 tp->t_flags &= ~TF_RXWIN0SENT; 1267 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1268 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1269 th->th_flags |= TH_URG; 1270 } else 1271 /* 1272 * If no urgent pointer to send, then we pull 1273 * the urgent pointer to the left edge of the send window 1274 * so that it doesn't drift into the send window on sequence 1275 * number wraparound. 1276 */ 1277 tp->snd_up = tp->snd_una; /* drag it along */ 1278 1279 /* 1280 * Put TCP length in extended header, and then 1281 * checksum extended header and data. 1282 */ 1283 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1284 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1285 1286 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1287 if (to.to_flags & TOF_SIGNATURE) { 1288 /* 1289 * Calculate MD5 signature and put it into the place 1290 * determined before. 1291 * NOTE: since TCP options buffer doesn't point into 1292 * mbuf's data, calculate offset and use it. 1293 */ 1294 if (!TCPMD5_ENABLED() || (error = TCPMD5_OUTPUT(m, th, 1295 (u_char *)(th + 1) + (to.to_signature - opt))) != 0) { 1296 /* 1297 * Do not send segment if the calculation of MD5 1298 * digest has failed. 1299 */ 1300 m_freem(m); 1301 goto out; 1302 } 1303 } 1304 #endif 1305 #ifdef INET6 1306 if (isipv6) { 1307 /* 1308 * There is no need to fill in ip6_plen right now. 1309 * It will be filled later by ip6_output. 1310 */ 1311 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1312 th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) + 1313 optlen + len, IPPROTO_TCP, 0); 1314 } 1315 #endif 1316 #if defined(INET6) && defined(INET) 1317 else 1318 #endif 1319 #ifdef INET 1320 { 1321 m->m_pkthdr.csum_flags = CSUM_TCP; 1322 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1323 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1324 1325 /* IP version must be set here for ipv4/ipv6 checking later */ 1326 KASSERT(ip->ip_v == IPVERSION, 1327 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1328 } 1329 #endif 1330 1331 /* 1332 * Enable TSO and specify the size of the segments. 1333 * The TCP pseudo header checksum is always provided. 1334 */ 1335 if (tso) { 1336 KASSERT(len > tp->t_maxseg - optlen, 1337 ("%s: len <= tso_segsz", __func__)); 1338 m->m_pkthdr.csum_flags |= CSUM_TSO; 1339 m->m_pkthdr.tso_segsz = tp->t_maxseg - optlen; 1340 } 1341 1342 KASSERT(len + hdrlen == m_length(m, NULL), 1343 ("%s: mbuf chain shorter than expected: %d + %u != %u", 1344 __func__, len, hdrlen, m_length(m, NULL))); 1345 1346 #ifdef TCP_HHOOK 1347 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1348 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1349 #endif 1350 1351 #ifdef TCPDEBUG 1352 /* 1353 * Trace. 1354 */ 1355 if (so->so_options & SO_DEBUG) { 1356 u_short save = 0; 1357 #ifdef INET6 1358 if (!isipv6) 1359 #endif 1360 { 1361 save = ipov->ih_len; 1362 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1363 } 1364 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1365 #ifdef INET6 1366 if (!isipv6) 1367 #endif 1368 ipov->ih_len = save; 1369 } 1370 #endif /* TCPDEBUG */ 1371 TCP_PROBE3(debug__output, tp, th, m); 1372 1373 /* We're getting ready to send; log now. */ 1374 TCP_LOG_EVENT(tp, th, &so->so_rcv, &so->so_snd, TCP_LOG_OUT, ERRNO_UNK, 1375 len, NULL, false); 1376 1377 /* 1378 * Fill in IP length and desired time to live and 1379 * send to IP level. There should be a better way 1380 * to handle ttl and tos; we could keep them in 1381 * the template, but need a way to checksum without them. 1382 */ 1383 /* 1384 * m->m_pkthdr.len should have been set before checksum calculation, 1385 * because in6_cksum() need it. 1386 */ 1387 #ifdef INET6 1388 if (isipv6) { 1389 /* 1390 * we separately set hoplimit for every segment, since the 1391 * user might want to change the value via setsockopt. 1392 * Also, desired default hop limit might be changed via 1393 * Neighbor Discovery. 1394 */ 1395 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1396 1397 /* 1398 * Set the packet size here for the benefit of DTrace probes. 1399 * ip6_output() will set it properly; it's supposed to include 1400 * the option header lengths as well. 1401 */ 1402 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6)); 1403 1404 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) 1405 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1406 else 1407 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1408 1409 if (tp->t_state == TCPS_SYN_SENT) 1410 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th); 1411 1412 TCP_PROBE5(send, NULL, tp, ip6, tp, th); 1413 1414 #ifdef TCPPCAP 1415 /* Save packet, if requested. */ 1416 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1417 #endif 1418 1419 /* TODO: IPv6 IP6TOS_ECT bit on */ 1420 error = ip6_output(m, tp->t_inpcb->in6p_outputopts, 1421 &tp->t_inpcb->inp_route6, 1422 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 1423 NULL, NULL, tp->t_inpcb); 1424 1425 if (error == EMSGSIZE && tp->t_inpcb->inp_route6.ro_nh != NULL) 1426 mtu = tp->t_inpcb->inp_route6.ro_nh->nh_mtu; 1427 } 1428 #endif /* INET6 */ 1429 #if defined(INET) && defined(INET6) 1430 else 1431 #endif 1432 #ifdef INET 1433 { 1434 ip->ip_len = htons(m->m_pkthdr.len); 1435 #ifdef INET6 1436 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1437 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1438 #endif /* INET6 */ 1439 /* 1440 * If we do path MTU discovery, then we set DF on every packet. 1441 * This might not be the best thing to do according to RFC3390 1442 * Section 2. However the tcp hostcache migitates the problem 1443 * so it affects only the first tcp connection with a host. 1444 * 1445 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1446 */ 1447 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) { 1448 ip->ip_off |= htons(IP_DF); 1449 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1450 } else { 1451 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1452 } 1453 1454 if (tp->t_state == TCPS_SYN_SENT) 1455 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th); 1456 1457 TCP_PROBE5(send, NULL, tp, ip, tp, th); 1458 1459 #ifdef TCPPCAP 1460 /* Save packet, if requested. */ 1461 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1462 #endif 1463 1464 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, 1465 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1466 tp->t_inpcb); 1467 1468 if (error == EMSGSIZE && tp->t_inpcb->inp_route.ro_nh != NULL) 1469 mtu = tp->t_inpcb->inp_route.ro_nh->nh_mtu; 1470 } 1471 #endif /* INET */ 1472 1473 out: 1474 /* 1475 * In transmit state, time the transmission and arrange for 1476 * the retransmit. In persist state, just set snd_max. 1477 */ 1478 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1479 !tcp_timer_active(tp, TT_PERSIST)) { 1480 tcp_seq startseq = tp->snd_nxt; 1481 1482 /* 1483 * Advance snd_nxt over sequence space of this segment. 1484 */ 1485 if (flags & (TH_SYN|TH_FIN)) { 1486 if (flags & TH_SYN) 1487 tp->snd_nxt++; 1488 if (flags & TH_FIN) { 1489 tp->snd_nxt++; 1490 tp->t_flags |= TF_SENTFIN; 1491 } 1492 } 1493 if (sack_rxmit) 1494 goto timer; 1495 tp->snd_nxt += len; 1496 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1497 tp->snd_max = tp->snd_nxt; 1498 /* 1499 * Time this transmission if not a retransmission and 1500 * not currently timing anything. 1501 */ 1502 if (tp->t_rtttime == 0) { 1503 tp->t_rtttime = ticks; 1504 tp->t_rtseq = startseq; 1505 TCPSTAT_INC(tcps_segstimed); 1506 } 1507 #ifdef STATS 1508 if (!(tp->t_flags & TF_GPUTINPROG) && len) { 1509 tp->t_flags |= TF_GPUTINPROG; 1510 tp->gput_seq = startseq; 1511 tp->gput_ack = startseq + 1512 ulmin(sbavail(&so->so_snd) - off, sendwin); 1513 tp->gput_ts = tcp_ts_getticks(); 1514 } 1515 #endif /* STATS */ 1516 } 1517 1518 /* 1519 * Set retransmit timer if not currently set, 1520 * and not doing a pure ack or a keep-alive probe. 1521 * Initial value for retransmit timer is smoothed 1522 * round-trip time + 2 * round-trip time variance. 1523 * Initialize shift counter which is used for backoff 1524 * of retransmit time. 1525 */ 1526 timer: 1527 if (!tcp_timer_active(tp, TT_REXMT) && 1528 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1529 (tp->snd_nxt != tp->snd_una))) { 1530 if (tcp_timer_active(tp, TT_PERSIST)) { 1531 tcp_timer_activate(tp, TT_PERSIST, 0); 1532 tp->t_rxtshift = 0; 1533 } 1534 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1535 } else if (len == 0 && sbavail(&so->so_snd) && 1536 !tcp_timer_active(tp, TT_REXMT) && 1537 !tcp_timer_active(tp, TT_PERSIST)) { 1538 /* 1539 * Avoid a situation where we do not set persist timer 1540 * after a zero window condition. For example: 1541 * 1) A -> B: packet with enough data to fill the window 1542 * 2) B -> A: ACK for #1 + new data (0 window 1543 * advertisement) 1544 * 3) A -> B: ACK for #2, 0 len packet 1545 * 1546 * In this case, A will not activate the persist timer, 1547 * because it chose to send a packet. Unless tcp_output 1548 * is called for some other reason (delayed ack timer, 1549 * another input packet from B, socket syscall), A will 1550 * not send zero window probes. 1551 * 1552 * So, if you send a 0-length packet, but there is data 1553 * in the socket buffer, and neither the rexmt or 1554 * persist timer is already set, then activate the 1555 * persist timer. 1556 */ 1557 tp->t_rxtshift = 0; 1558 tcp_setpersist(tp); 1559 } 1560 } else { 1561 /* 1562 * Persist case, update snd_max but since we are in 1563 * persist mode (no window) we do not update snd_nxt. 1564 */ 1565 int xlen = len; 1566 if (flags & TH_SYN) 1567 ++xlen; 1568 if (flags & TH_FIN) { 1569 ++xlen; 1570 tp->t_flags |= TF_SENTFIN; 1571 } 1572 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1573 tp->snd_max = tp->snd_nxt + xlen; 1574 } 1575 if ((error == 0) && 1576 (TCPS_HAVEESTABLISHED(tp->t_state) && 1577 (tp->t_flags & TF_SACK_PERMIT) && 1578 tp->rcv_numsacks > 0)) { 1579 /* Clean up any DSACK's sent */ 1580 tcp_clean_dsack_blocks(tp); 1581 } 1582 if (error) { 1583 /* Record the error. */ 1584 TCP_LOG_EVENT(tp, NULL, &so->so_rcv, &so->so_snd, TCP_LOG_OUT, 1585 error, 0, NULL, false); 1586 1587 /* 1588 * We know that the packet was lost, so back out the 1589 * sequence number advance, if any. 1590 * 1591 * If the error is EPERM the packet got blocked by the 1592 * local firewall. Normally we should terminate the 1593 * connection but the blocking may have been spurious 1594 * due to a firewall reconfiguration cycle. So we treat 1595 * it like a packet loss and let the retransmit timer and 1596 * timeouts do their work over time. 1597 * XXX: It is a POLA question whether calling tcp_drop right 1598 * away would be the really correct behavior instead. 1599 */ 1600 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1601 !tcp_timer_active(tp, TT_PERSIST)) && 1602 ((flags & TH_SYN) == 0) && 1603 (error != EPERM)) { 1604 if (sack_rxmit) { 1605 p->rxmit -= len; 1606 tp->sackhint.sack_bytes_rexmit -= len; 1607 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1608 ("sackhint bytes rtx >= 0")); 1609 } else 1610 tp->snd_nxt -= len; 1611 } 1612 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1613 switch (error) { 1614 case EACCES: 1615 case EPERM: 1616 tp->t_softerror = error; 1617 return (error); 1618 case ENOBUFS: 1619 TCP_XMIT_TIMER_ASSERT(tp, len, flags); 1620 tp->snd_cwnd = tp->t_maxseg; 1621 return (0); 1622 case EMSGSIZE: 1623 /* 1624 * For some reason the interface we used initially 1625 * to send segments changed to another or lowered 1626 * its MTU. 1627 * If TSO was active we either got an interface 1628 * without TSO capabilits or TSO was turned off. 1629 * If we obtained mtu from ip_output() then update 1630 * it and try again. 1631 */ 1632 if (tso) 1633 tp->t_flags &= ~TF_TSO; 1634 if (mtu != 0) { 1635 tcp_mss_update(tp, -1, mtu, NULL, NULL); 1636 goto again; 1637 } 1638 return (error); 1639 case EHOSTDOWN: 1640 case EHOSTUNREACH: 1641 case ENETDOWN: 1642 case ENETUNREACH: 1643 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1644 tp->t_softerror = error; 1645 return (0); 1646 } 1647 /* FALLTHROUGH */ 1648 default: 1649 return (error); 1650 } 1651 } 1652 TCPSTAT_INC(tcps_sndtotal); 1653 1654 /* 1655 * Data sent (as far as we can tell). 1656 * If this advertises a larger window than any other segment, 1657 * then remember the size of the advertised window. 1658 * Any pending ACK has now been sent. 1659 */ 1660 if (SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1661 tp->rcv_adv = tp->rcv_nxt + recwin; 1662 tp->last_ack_sent = tp->rcv_nxt; 1663 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1664 if (tcp_timer_active(tp, TT_DELACK)) 1665 tcp_timer_activate(tp, TT_DELACK, 0); 1666 #if 0 1667 /* 1668 * This completely breaks TCP if newreno is turned on. What happens 1669 * is that if delayed-acks are turned on on the receiver, this code 1670 * on the transmitter effectively destroys the TCP window, forcing 1671 * it to four packets (1.5Kx4 = 6K window). 1672 */ 1673 if (sendalot && --maxburst) 1674 goto again; 1675 #endif 1676 if (sendalot) 1677 goto again; 1678 return (0); 1679 } 1680 1681 void 1682 tcp_setpersist(struct tcpcb *tp) 1683 { 1684 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1685 int tt; 1686 1687 tp->t_flags &= ~TF_PREVVALID; 1688 if (tcp_timer_active(tp, TT_REXMT)) 1689 panic("tcp_setpersist: retransmit pending"); 1690 /* 1691 * Start/restart persistence timer. 1692 */ 1693 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1694 tcp_persmin, tcp_persmax); 1695 tcp_timer_activate(tp, TT_PERSIST, tt); 1696 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1697 tp->t_rxtshift++; 1698 } 1699 1700 /* 1701 * Insert TCP options according to the supplied parameters to the place 1702 * optp in a consistent way. Can handle unaligned destinations. 1703 * 1704 * The order of the option processing is crucial for optimal packing and 1705 * alignment for the scarce option space. 1706 * 1707 * The optimal order for a SYN/SYN-ACK segment is: 1708 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1709 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1710 * 1711 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1712 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1713 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1714 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1715 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1716 */ 1717 int 1718 tcp_addoptions(struct tcpopt *to, u_char *optp) 1719 { 1720 u_int32_t mask, optlen = 0; 1721 1722 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1723 if ((to->to_flags & mask) != mask) 1724 continue; 1725 if (optlen == TCP_MAXOLEN) 1726 break; 1727 switch (to->to_flags & mask) { 1728 case TOF_MSS: 1729 while (optlen % 4) { 1730 optlen += TCPOLEN_NOP; 1731 *optp++ = TCPOPT_NOP; 1732 } 1733 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1734 continue; 1735 optlen += TCPOLEN_MAXSEG; 1736 *optp++ = TCPOPT_MAXSEG; 1737 *optp++ = TCPOLEN_MAXSEG; 1738 to->to_mss = htons(to->to_mss); 1739 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1740 optp += sizeof(to->to_mss); 1741 break; 1742 case TOF_SCALE: 1743 while (!optlen || optlen % 2 != 1) { 1744 optlen += TCPOLEN_NOP; 1745 *optp++ = TCPOPT_NOP; 1746 } 1747 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1748 continue; 1749 optlen += TCPOLEN_WINDOW; 1750 *optp++ = TCPOPT_WINDOW; 1751 *optp++ = TCPOLEN_WINDOW; 1752 *optp++ = to->to_wscale; 1753 break; 1754 case TOF_SACKPERM: 1755 while (optlen % 2) { 1756 optlen += TCPOLEN_NOP; 1757 *optp++ = TCPOPT_NOP; 1758 } 1759 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1760 continue; 1761 optlen += TCPOLEN_SACK_PERMITTED; 1762 *optp++ = TCPOPT_SACK_PERMITTED; 1763 *optp++ = TCPOLEN_SACK_PERMITTED; 1764 break; 1765 case TOF_TS: 1766 while (!optlen || optlen % 4 != 2) { 1767 optlen += TCPOLEN_NOP; 1768 *optp++ = TCPOPT_NOP; 1769 } 1770 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1771 continue; 1772 optlen += TCPOLEN_TIMESTAMP; 1773 *optp++ = TCPOPT_TIMESTAMP; 1774 *optp++ = TCPOLEN_TIMESTAMP; 1775 to->to_tsval = htonl(to->to_tsval); 1776 to->to_tsecr = htonl(to->to_tsecr); 1777 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1778 optp += sizeof(to->to_tsval); 1779 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1780 optp += sizeof(to->to_tsecr); 1781 break; 1782 case TOF_SIGNATURE: 1783 { 1784 int siglen = TCPOLEN_SIGNATURE - 2; 1785 1786 while (!optlen || optlen % 4 != 2) { 1787 optlen += TCPOLEN_NOP; 1788 *optp++ = TCPOPT_NOP; 1789 } 1790 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) { 1791 to->to_flags &= ~TOF_SIGNATURE; 1792 continue; 1793 } 1794 optlen += TCPOLEN_SIGNATURE; 1795 *optp++ = TCPOPT_SIGNATURE; 1796 *optp++ = TCPOLEN_SIGNATURE; 1797 to->to_signature = optp; 1798 while (siglen--) 1799 *optp++ = 0; 1800 break; 1801 } 1802 case TOF_SACK: 1803 { 1804 int sackblks = 0; 1805 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1806 tcp_seq sack_seq; 1807 1808 while (!optlen || optlen % 4 != 2) { 1809 optlen += TCPOLEN_NOP; 1810 *optp++ = TCPOPT_NOP; 1811 } 1812 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1813 continue; 1814 optlen += TCPOLEN_SACKHDR; 1815 *optp++ = TCPOPT_SACK; 1816 sackblks = min(to->to_nsacks, 1817 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1818 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1819 while (sackblks--) { 1820 sack_seq = htonl(sack->start); 1821 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1822 optp += sizeof(sack_seq); 1823 sack_seq = htonl(sack->end); 1824 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1825 optp += sizeof(sack_seq); 1826 optlen += TCPOLEN_SACK; 1827 sack++; 1828 } 1829 TCPSTAT_INC(tcps_sack_send_blocks); 1830 break; 1831 } 1832 case TOF_FASTOPEN: 1833 { 1834 int total_len; 1835 1836 /* XXX is there any point to aligning this option? */ 1837 total_len = TCPOLEN_FAST_OPEN_EMPTY + to->to_tfo_len; 1838 if (TCP_MAXOLEN - optlen < total_len) { 1839 to->to_flags &= ~TOF_FASTOPEN; 1840 continue; 1841 } 1842 *optp++ = TCPOPT_FAST_OPEN; 1843 *optp++ = total_len; 1844 if (to->to_tfo_len > 0) { 1845 bcopy(to->to_tfo_cookie, optp, to->to_tfo_len); 1846 optp += to->to_tfo_len; 1847 } 1848 optlen += total_len; 1849 break; 1850 } 1851 default: 1852 panic("%s: unknown TCP option type", __func__); 1853 break; 1854 } 1855 } 1856 1857 /* Terminate and pad TCP options to a 4 byte boundary. */ 1858 if (optlen % 4) { 1859 optlen += TCPOLEN_EOL; 1860 *optp++ = TCPOPT_EOL; 1861 } 1862 /* 1863 * According to RFC 793 (STD0007): 1864 * "The content of the header beyond the End-of-Option option 1865 * must be header padding (i.e., zero)." 1866 * and later: "The padding is composed of zeros." 1867 */ 1868 while (optlen % 4) { 1869 optlen += TCPOLEN_PAD; 1870 *optp++ = TCPOPT_PAD; 1871 } 1872 1873 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1874 return (optlen); 1875 } 1876 1877 /* 1878 * This is a copy of m_copym(), taking the TSO segment size/limit 1879 * constraints into account, and advancing the sndptr as it goes. 1880 */ 1881 struct mbuf * 1882 tcp_m_copym(struct mbuf *m, int32_t off0, int32_t *plen, 1883 int32_t seglimit, int32_t segsize, struct sockbuf *sb, bool hw_tls) 1884 { 1885 #ifdef KERN_TLS 1886 struct ktls_session *tls, *ntls; 1887 struct mbuf *start; 1888 #endif 1889 struct mbuf *n, **np; 1890 struct mbuf *top; 1891 int32_t off = off0; 1892 int32_t len = *plen; 1893 int32_t fragsize; 1894 int32_t len_cp = 0; 1895 int32_t *pkthdrlen; 1896 uint32_t mlen, frags; 1897 bool copyhdr; 1898 1899 1900 KASSERT(off >= 0, ("tcp_m_copym, negative off %d", off)); 1901 KASSERT(len >= 0, ("tcp_m_copym, negative len %d", len)); 1902 if (off == 0 && m->m_flags & M_PKTHDR) 1903 copyhdr = true; 1904 else 1905 copyhdr = false; 1906 while (off > 0) { 1907 KASSERT(m != NULL, ("tcp_m_copym, offset > size of mbuf chain")); 1908 if (off < m->m_len) 1909 break; 1910 off -= m->m_len; 1911 if ((sb) && (m == sb->sb_sndptr)) { 1912 sb->sb_sndptroff += m->m_len; 1913 sb->sb_sndptr = m->m_next; 1914 } 1915 m = m->m_next; 1916 } 1917 np = ⊤ 1918 top = NULL; 1919 pkthdrlen = NULL; 1920 #ifdef KERN_TLS 1921 if (hw_tls && (m->m_flags & M_EXTPG)) 1922 tls = m->m_epg_tls; 1923 else 1924 tls = NULL; 1925 start = m; 1926 #endif 1927 while (len > 0) { 1928 if (m == NULL) { 1929 KASSERT(len == M_COPYALL, 1930 ("tcp_m_copym, length > size of mbuf chain")); 1931 *plen = len_cp; 1932 if (pkthdrlen != NULL) 1933 *pkthdrlen = len_cp; 1934 break; 1935 } 1936 #ifdef KERN_TLS 1937 if (hw_tls) { 1938 if (m->m_flags & M_EXTPG) 1939 ntls = m->m_epg_tls; 1940 else 1941 ntls = NULL; 1942 1943 /* 1944 * Avoid mixing TLS records with handshake 1945 * data or TLS records from different 1946 * sessions. 1947 */ 1948 if (tls != ntls) { 1949 MPASS(m != start); 1950 *plen = len_cp; 1951 if (pkthdrlen != NULL) 1952 *pkthdrlen = len_cp; 1953 break; 1954 } 1955 1956 /* 1957 * Don't end a send in the middle of a TLS 1958 * record if it spans multiple TLS records. 1959 */ 1960 if (tls != NULL && (m != start) && len < m->m_len) { 1961 *plen = len_cp; 1962 if (pkthdrlen != NULL) 1963 *pkthdrlen = len_cp; 1964 break; 1965 } 1966 } 1967 #endif 1968 mlen = min(len, m->m_len - off); 1969 if (seglimit) { 1970 /* 1971 * For M_EXTPG mbufs, add 3 segments 1972 * + 1 in case we are crossing page boundaries 1973 * + 2 in case the TLS hdr/trailer are used 1974 * It is cheaper to just add the segments 1975 * than it is to take the cache miss to look 1976 * at the mbuf ext_pgs state in detail. 1977 */ 1978 if (m->m_flags & M_EXTPG) { 1979 fragsize = min(segsize, PAGE_SIZE); 1980 frags = 3; 1981 } else { 1982 fragsize = segsize; 1983 frags = 0; 1984 } 1985 1986 /* Break if we really can't fit anymore. */ 1987 if ((frags + 1) >= seglimit) { 1988 *plen = len_cp; 1989 if (pkthdrlen != NULL) 1990 *pkthdrlen = len_cp; 1991 break; 1992 } 1993 1994 /* 1995 * Reduce size if you can't copy the whole 1996 * mbuf. If we can't copy the whole mbuf, also 1997 * adjust len so the loop will end after this 1998 * mbuf. 1999 */ 2000 if ((frags + howmany(mlen, fragsize)) >= seglimit) { 2001 mlen = (seglimit - frags - 1) * fragsize; 2002 len = mlen; 2003 *plen = len_cp + len; 2004 if (pkthdrlen != NULL) 2005 *pkthdrlen = *plen; 2006 } 2007 frags += howmany(mlen, fragsize); 2008 if (frags == 0) 2009 frags++; 2010 seglimit -= frags; 2011 KASSERT(seglimit > 0, 2012 ("%s: seglimit went too low", __func__)); 2013 } 2014 if (copyhdr) 2015 n = m_gethdr(M_NOWAIT, m->m_type); 2016 else 2017 n = m_get(M_NOWAIT, m->m_type); 2018 *np = n; 2019 if (n == NULL) 2020 goto nospace; 2021 if (copyhdr) { 2022 if (!m_dup_pkthdr(n, m, M_NOWAIT)) 2023 goto nospace; 2024 if (len == M_COPYALL) 2025 n->m_pkthdr.len -= off0; 2026 else 2027 n->m_pkthdr.len = len; 2028 pkthdrlen = &n->m_pkthdr.len; 2029 copyhdr = false; 2030 } 2031 n->m_len = mlen; 2032 len_cp += n->m_len; 2033 if (m->m_flags & (M_EXT|M_EXTPG)) { 2034 n->m_data = m->m_data + off; 2035 mb_dupcl(n, m); 2036 } else 2037 bcopy(mtod(m, caddr_t)+off, mtod(n, caddr_t), 2038 (u_int)n->m_len); 2039 2040 if (sb && (sb->sb_sndptr == m) && 2041 ((n->m_len + off) >= m->m_len) && m->m_next) { 2042 sb->sb_sndptroff += m->m_len; 2043 sb->sb_sndptr = m->m_next; 2044 } 2045 off = 0; 2046 if (len != M_COPYALL) { 2047 len -= n->m_len; 2048 } 2049 m = m->m_next; 2050 np = &n->m_next; 2051 } 2052 return (top); 2053 nospace: 2054 m_freem(top); 2055 return (NULL); 2056 } 2057 2058 void 2059 tcp_sndbuf_autoscale(struct tcpcb *tp, struct socket *so, uint32_t sendwin) 2060 { 2061 2062 /* 2063 * Automatic sizing of send socket buffer. Often the send buffer 2064 * size is not optimally adjusted to the actual network conditions 2065 * at hand (delay bandwidth product). Setting the buffer size too 2066 * small limits throughput on links with high bandwidth and high 2067 * delay (eg. trans-continental/oceanic links). Setting the 2068 * buffer size too big consumes too much real kernel memory, 2069 * especially with many connections on busy servers. 2070 * 2071 * The criteria to step up the send buffer one notch are: 2072 * 1. receive window of remote host is larger than send buffer 2073 * (with a fudge factor of 5/4th); 2074 * 2. send buffer is filled to 7/8th with data (so we actually 2075 * have data to make use of it); 2076 * 3. send buffer fill has not hit maximal automatic size; 2077 * 4. our send window (slow start and cogestion controlled) is 2078 * larger than sent but unacknowledged data in send buffer. 2079 * 2080 * The remote host receive window scaling factor may limit the 2081 * growing of the send buffer before it reaches its allowed 2082 * maximum. 2083 * 2084 * It scales directly with slow start or congestion window 2085 * and does at most one step per received ACK. This fast 2086 * scaling has the drawback of growing the send buffer beyond 2087 * what is strictly necessary to make full use of a given 2088 * delay*bandwidth product. However testing has shown this not 2089 * to be much of an problem. At worst we are trading wasting 2090 * of available bandwidth (the non-use of it) for wasting some 2091 * socket buffer memory. 2092 * 2093 * TODO: Shrink send buffer during idle periods together 2094 * with congestion window. Requires another timer. Has to 2095 * wait for upcoming tcp timer rewrite. 2096 * 2097 * XXXGL: should there be used sbused() or sbavail()? 2098 */ 2099 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 2100 int lowat; 2101 2102 lowat = V_tcp_sendbuf_auto_lowat ? so->so_snd.sb_lowat : 0; 2103 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat - lowat && 2104 sbused(&so->so_snd) >= 2105 (so->so_snd.sb_hiwat / 8 * 7) - lowat && 2106 sbused(&so->so_snd) < V_tcp_autosndbuf_max && 2107 sendwin >= (sbused(&so->so_snd) - 2108 (tp->snd_nxt - tp->snd_una))) { 2109 if (!sbreserve_locked(&so->so_snd, 2110 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 2111 V_tcp_autosndbuf_max), so, curthread)) 2112 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 2113 } 2114 } 2115 } 2116