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/vnet.h> 68 69 #include <netinet/in.h> 70 #include <netinet/in_kdtrace.h> 71 #include <netinet/in_systm.h> 72 #include <netinet/ip.h> 73 #include <netinet/in_pcb.h> 74 #include <netinet/ip_var.h> 75 #include <netinet/ip_options.h> 76 #ifdef INET6 77 #include <netinet6/in6_pcb.h> 78 #include <netinet/ip6.h> 79 #include <netinet6/ip6_var.h> 80 #endif 81 #include <netinet/tcp.h> 82 #define TCPOUTFLAGS 83 #include <netinet/tcp_fsm.h> 84 #include <netinet/tcp_log_buf.h> 85 #include <netinet/tcp_seq.h> 86 #include <netinet/tcp_timer.h> 87 #include <netinet/tcp_var.h> 88 #include <netinet/tcpip.h> 89 #include <netinet/cc/cc.h> 90 #include <netinet/tcp_fastopen.h> 91 #ifdef TCPPCAP 92 #include <netinet/tcp_pcap.h> 93 #endif 94 #ifdef TCPDEBUG 95 #include <netinet/tcp_debug.h> 96 #endif 97 #ifdef TCP_OFFLOAD 98 #include <netinet/tcp_offload.h> 99 #endif 100 101 #include <netipsec/ipsec_support.h> 102 103 #include <machine/in_cksum.h> 104 105 #include <security/mac/mac_framework.h> 106 107 VNET_DEFINE(int, path_mtu_discovery) = 1; 108 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_VNET | CTLFLAG_RW, 109 &VNET_NAME(path_mtu_discovery), 1, 110 "Enable Path MTU Discovery"); 111 112 VNET_DEFINE(int, tcp_do_tso) = 1; 113 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_VNET | CTLFLAG_RW, 114 &VNET_NAME(tcp_do_tso), 0, 115 "Enable TCP Segmentation Offload"); 116 117 VNET_DEFINE(int, tcp_sendspace) = 1024*32; 118 #define V_tcp_sendspace VNET(tcp_sendspace) 119 SYSCTL_INT(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, CTLFLAG_VNET | CTLFLAG_RW, 120 &VNET_NAME(tcp_sendspace), 0, "Initial send socket buffer size"); 121 122 VNET_DEFINE(int, tcp_do_autosndbuf) = 1; 123 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_VNET | CTLFLAG_RW, 124 &VNET_NAME(tcp_do_autosndbuf), 0, 125 "Enable automatic send buffer sizing"); 126 127 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024; 128 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_VNET | CTLFLAG_RW, 129 &VNET_NAME(tcp_autosndbuf_inc), 0, 130 "Incrementor step size of automatic send buffer"); 131 132 VNET_DEFINE(int, tcp_autosndbuf_max) = 2*1024*1024; 133 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_VNET | CTLFLAG_RW, 134 &VNET_NAME(tcp_autosndbuf_max), 0, 135 "Max size of automatic send buffer"); 136 137 VNET_DEFINE(int, tcp_sendbuf_auto_lowat) = 0; 138 #define V_tcp_sendbuf_auto_lowat VNET(tcp_sendbuf_auto_lowat) 139 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto_lowat, CTLFLAG_VNET | CTLFLAG_RW, 140 &VNET_NAME(tcp_sendbuf_auto_lowat), 0, 141 "Modify threshold for auto send buffer growth to account for SO_SNDLOWAT"); 142 143 /* 144 * Make sure that either retransmit or persist timer is set for SYN, FIN and 145 * non-ACK. 146 */ 147 #define TCP_XMIT_TIMER_ASSERT(tp, len, th_flags) \ 148 KASSERT(((len) == 0 && ((th_flags) & (TH_SYN | TH_FIN)) == 0) ||\ 149 tcp_timer_active((tp), TT_REXMT) || \ 150 tcp_timer_active((tp), TT_PERSIST), \ 151 ("neither rexmt nor persist timer is set")) 152 153 static void inline cc_after_idle(struct tcpcb *tp); 154 155 #ifdef TCP_HHOOK 156 /* 157 * Wrapper for the TCP established output helper hook. 158 */ 159 void 160 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th, 161 struct tcpopt *to, uint32_t len, int tso) 162 { 163 struct tcp_hhook_data hhook_data; 164 165 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) { 166 hhook_data.tp = tp; 167 hhook_data.th = th; 168 hhook_data.to = to; 169 hhook_data.len = len; 170 hhook_data.tso = tso; 171 172 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data, 173 tp->osd); 174 } 175 } 176 #endif 177 178 /* 179 * CC wrapper hook functions 180 */ 181 static void inline 182 cc_after_idle(struct tcpcb *tp) 183 { 184 INP_WLOCK_ASSERT(tp->t_inpcb); 185 186 if (CC_ALGO(tp)->after_idle != NULL) 187 CC_ALGO(tp)->after_idle(tp->ccv); 188 } 189 190 /* 191 * Tcp output routine: figure out what should be sent and send it. 192 */ 193 int 194 tcp_output(struct tcpcb *tp) 195 { 196 struct socket *so = tp->t_inpcb->inp_socket; 197 int32_t len; 198 uint32_t recwin, sendwin; 199 int off, flags, error = 0; /* Keep compiler happy */ 200 u_int if_hw_tsomaxsegcount = 0; 201 u_int if_hw_tsomaxsegsize = 0; 202 struct mbuf *m; 203 struct ip *ip = NULL; 204 #ifdef TCPDEBUG 205 struct ipovly *ipov = NULL; 206 #endif 207 struct tcphdr *th; 208 u_char opt[TCP_MAXOLEN]; 209 unsigned ipoptlen, optlen, hdrlen; 210 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 211 unsigned ipsec_optlen = 0; 212 #endif 213 int idle, sendalot, curticks; 214 int sack_rxmit, sack_bytes_rxmt; 215 struct sackhole *p; 216 int tso, mtu; 217 struct tcpopt to; 218 unsigned int wanted_cookie = 0; 219 unsigned int dont_sendalot = 0; 220 #if 0 221 int maxburst = TCP_MAXBURST; 222 #endif 223 #ifdef INET6 224 struct ip6_hdr *ip6 = NULL; 225 int isipv6; 226 227 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 228 #endif 229 #ifdef KERN_TLS 230 const bool hw_tls = (so->so_snd.sb_flags & SB_TLS_IFNET) != 0; 231 #else 232 const bool hw_tls = false; 233 #endif 234 235 NET_EPOCH_ASSERT(); 236 INP_WLOCK_ASSERT(tp->t_inpcb); 237 238 #ifdef TCP_OFFLOAD 239 if (tp->t_flags & TF_TOE) 240 return (tcp_offload_output(tp)); 241 #endif 242 243 /* 244 * For TFO connections in SYN_SENT or SYN_RECEIVED, 245 * only allow the initial SYN or SYN|ACK and those sent 246 * by the retransmit timer. 247 */ 248 if (IS_FASTOPEN(tp->t_flags) && 249 ((tp->t_state == TCPS_SYN_SENT) || 250 (tp->t_state == TCPS_SYN_RECEIVED)) && 251 SEQ_GT(tp->snd_max, tp->snd_una) && /* initial SYN or SYN|ACK sent */ 252 (tp->snd_nxt != tp->snd_una)) /* not a retransmit */ 253 return (0); 254 255 /* 256 * Determine length of data that should be transmitted, 257 * and flags that will be used. 258 * If there is some data or critical controls (SYN, RST) 259 * to send, then transmit; otherwise, investigate further. 260 */ 261 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 262 if (idle && ticks - tp->t_rcvtime >= tp->t_rxtcur) 263 cc_after_idle(tp); 264 tp->t_flags &= ~TF_LASTIDLE; 265 if (idle) { 266 if (tp->t_flags & TF_MORETOCOME) { 267 tp->t_flags |= TF_LASTIDLE; 268 idle = 0; 269 } 270 } 271 again: 272 /* 273 * If we've recently taken a timeout, snd_max will be greater than 274 * snd_nxt. There may be SACK information that allows us to avoid 275 * resending already delivered data. Adjust snd_nxt accordingly. 276 */ 277 if ((tp->t_flags & TF_SACK_PERMIT) && 278 SEQ_LT(tp->snd_nxt, tp->snd_max)) 279 tcp_sack_adjust(tp); 280 sendalot = 0; 281 tso = 0; 282 mtu = 0; 283 off = tp->snd_nxt - tp->snd_una; 284 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 285 286 flags = tcp_outflags[tp->t_state]; 287 /* 288 * Send any SACK-generated retransmissions. If we're explicitly trying 289 * to send out new data (when sendalot is 1), bypass this function. 290 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 291 * we're replacing a (future) new transmission with a retransmission 292 * now, and we previously incremented snd_cwnd in tcp_input(). 293 */ 294 /* 295 * Still in sack recovery , reset rxmit flag to zero. 296 */ 297 sack_rxmit = 0; 298 sack_bytes_rxmt = 0; 299 len = 0; 300 p = NULL; 301 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) && 302 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 303 uint32_t cwin; 304 305 cwin = 306 imax(min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt, 0); 307 /* Do not retransmit SACK segments beyond snd_recover */ 308 if (SEQ_GT(p->end, tp->snd_recover)) { 309 /* 310 * (At least) part of sack hole extends beyond 311 * snd_recover. Check to see if we can rexmit data 312 * for this hole. 313 */ 314 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 315 /* 316 * Can't rexmit any more data for this hole. 317 * That data will be rexmitted in the next 318 * sack recovery episode, when snd_recover 319 * moves past p->rxmit. 320 */ 321 p = NULL; 322 goto after_sack_rexmit; 323 } else 324 /* Can rexmit part of the current hole */ 325 len = ((int32_t)ulmin(cwin, 326 tp->snd_recover - p->rxmit)); 327 } else 328 len = ((int32_t)ulmin(cwin, p->end - p->rxmit)); 329 off = p->rxmit - tp->snd_una; 330 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 331 __func__, off)); 332 if (len > 0) { 333 sack_rxmit = 1; 334 sendalot = 1; 335 TCPSTAT_INC(tcps_sack_rexmits); 336 TCPSTAT_ADD(tcps_sack_rexmit_bytes, 337 min(len, tp->t_maxseg)); 338 } 339 } 340 after_sack_rexmit: 341 /* 342 * Get standard flags, and add SYN or FIN if requested by 'hidden' 343 * state flags. 344 */ 345 if (tp->t_flags & TF_NEEDFIN) 346 flags |= TH_FIN; 347 if (tp->t_flags & TF_NEEDSYN) 348 flags |= TH_SYN; 349 350 SOCKBUF_LOCK(&so->so_snd); 351 /* 352 * If in persist timeout with window of 0, send 1 byte. 353 * Otherwise, if window is small but nonzero 354 * and timer expired, we will send what we can 355 * and go to transmit state. 356 */ 357 if (tp->t_flags & TF_FORCEDATA) { 358 if (sendwin == 0) { 359 /* 360 * If we still have some data to send, then 361 * clear the FIN bit. Usually this would 362 * happen below when it realizes that we 363 * aren't sending all the data. However, 364 * if we have exactly 1 byte of unsent data, 365 * then it won't clear the FIN bit below, 366 * and if we are in persist state, we wind 367 * up sending the packet without recording 368 * that we sent the FIN bit. 369 * 370 * We can't just blindly clear the FIN bit, 371 * because if we don't have any more data 372 * to send then the probe will be the FIN 373 * itself. 374 */ 375 if (off < sbused(&so->so_snd)) 376 flags &= ~TH_FIN; 377 sendwin = 1; 378 } else { 379 tcp_timer_activate(tp, TT_PERSIST, 0); 380 tp->t_rxtshift = 0; 381 } 382 } 383 384 /* 385 * If snd_nxt == snd_max and we have transmitted a FIN, the 386 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 387 * a negative length. This can also occur when TCP opens up 388 * its congestion window while receiving additional duplicate 389 * acks after fast-retransmit because TCP will reset snd_nxt 390 * to snd_max after the fast-retransmit. 391 * 392 * In the normal retransmit-FIN-only case, however, snd_nxt will 393 * be set to snd_una, the offset will be 0, and the length may 394 * wind up 0. 395 * 396 * If sack_rxmit is true we are retransmitting from the scoreboard 397 * in which case len is already set. 398 */ 399 if (sack_rxmit == 0) { 400 if (sack_bytes_rxmt == 0) 401 len = ((int32_t)min(sbavail(&so->so_snd), sendwin) - 402 off); 403 else { 404 int32_t cwin; 405 406 /* 407 * We are inside of a SACK recovery episode and are 408 * sending new data, having retransmitted all the 409 * data possible in the scoreboard. 410 */ 411 len = ((int32_t)min(sbavail(&so->so_snd), tp->snd_wnd) - 412 off); 413 /* 414 * Don't remove this (len > 0) check ! 415 * We explicitly check for len > 0 here (although it 416 * isn't really necessary), to work around a gcc 417 * optimization issue - to force gcc to compute 418 * len above. Without this check, the computation 419 * of len is bungled by the optimizer. 420 */ 421 if (len > 0) { 422 cwin = tp->snd_cwnd - 423 (tp->snd_nxt - tp->snd_recover) - 424 sack_bytes_rxmt; 425 if (cwin < 0) 426 cwin = 0; 427 len = imin(len, cwin); 428 } 429 } 430 } 431 432 /* 433 * Lop off SYN bit if it has already been sent. However, if this 434 * is SYN-SENT state and if segment contains data and if we don't 435 * know that foreign host supports TAO, suppress sending segment. 436 */ 437 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 438 if (tp->t_state != TCPS_SYN_RECEIVED) 439 flags &= ~TH_SYN; 440 /* 441 * When sending additional segments following a TFO SYN|ACK, 442 * do not include the SYN bit. 443 */ 444 if (IS_FASTOPEN(tp->t_flags) && 445 (tp->t_state == TCPS_SYN_RECEIVED)) 446 flags &= ~TH_SYN; 447 off--, len++; 448 } 449 450 /* 451 * Be careful not to send data and/or FIN on SYN segments. 452 * This measure is needed to prevent interoperability problems 453 * with not fully conformant TCP implementations. 454 */ 455 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 456 len = 0; 457 flags &= ~TH_FIN; 458 } 459 460 /* 461 * On TFO sockets, ensure no data is sent in the following cases: 462 * 463 * - When retransmitting SYN|ACK on a passively-created socket 464 * 465 * - When retransmitting SYN on an actively created socket 466 * 467 * - When sending a zero-length cookie (cookie request) on an 468 * actively created socket 469 * 470 * - When the socket is in the CLOSED state (RST is being sent) 471 */ 472 if (IS_FASTOPEN(tp->t_flags) && 473 (((flags & TH_SYN) && (tp->t_rxtshift > 0)) || 474 ((tp->t_state == TCPS_SYN_SENT) && 475 (tp->t_tfo_client_cookie_len == 0)) || 476 (flags & TH_RST))) 477 len = 0; 478 if (len <= 0) { 479 /* 480 * If FIN has been sent but not acked, 481 * but we haven't been called to retransmit, 482 * len will be < 0. Otherwise, window shrank 483 * after we sent into it. If window shrank to 0, 484 * cancel pending retransmit, pull snd_nxt back 485 * to (closed) window, and set the persist timer 486 * if it isn't already going. If the window didn't 487 * close completely, just wait for an ACK. 488 * 489 * We also do a general check here to ensure that 490 * we will set the persist timer when we have data 491 * to send, but a 0-byte window. This makes sure 492 * the persist timer is set even if the packet 493 * hits one of the "goto send" lines below. 494 */ 495 len = 0; 496 if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) && 497 (off < (int) sbavail(&so->so_snd))) { 498 tcp_timer_activate(tp, TT_REXMT, 0); 499 tp->t_rxtshift = 0; 500 tp->snd_nxt = tp->snd_una; 501 if (!tcp_timer_active(tp, TT_PERSIST)) 502 tcp_setpersist(tp); 503 } 504 } 505 506 /* len will be >= 0 after this point. */ 507 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 508 509 tcp_sndbuf_autoscale(tp, so, sendwin); 510 511 /* 512 * Decide if we can use TCP Segmentation Offloading (if supported by 513 * hardware). 514 * 515 * TSO may only be used if we are in a pure bulk sending state. The 516 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 517 * IP options prevent using TSO. With TSO the TCP header is the same 518 * (except for the sequence number) for all generated packets. This 519 * makes it impossible to transmit any options which vary per generated 520 * segment or packet. 521 * 522 * IPv4 handling has a clear separation of ip options and ip header 523 * flags while IPv6 combines both in in6p_outputopts. ip6_optlen() does 524 * the right thing below to provide length of just ip options and thus 525 * checking for ipoptlen is enough to decide if ip options are present. 526 */ 527 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 528 /* 529 * Pre-calculate here as we save another lookup into the darknesses 530 * of IPsec that way and can actually decide if TSO is ok. 531 */ 532 #ifdef INET6 533 if (isipv6 && IPSEC_ENABLED(ipv6)) 534 ipsec_optlen = IPSEC_HDRSIZE(ipv6, tp->t_inpcb); 535 #ifdef INET 536 else 537 #endif 538 #endif /* INET6 */ 539 #ifdef INET 540 if (IPSEC_ENABLED(ipv4)) 541 ipsec_optlen = IPSEC_HDRSIZE(ipv4, tp->t_inpcb); 542 #endif /* INET */ 543 #endif /* IPSEC */ 544 #ifdef INET6 545 if (isipv6) 546 ipoptlen = ip6_optlen(tp->t_inpcb); 547 else 548 #endif 549 if (tp->t_inpcb->inp_options) 550 ipoptlen = tp->t_inpcb->inp_options->m_len - 551 offsetof(struct ipoption, ipopt_list); 552 else 553 ipoptlen = 0; 554 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 555 ipoptlen += ipsec_optlen; 556 #endif 557 558 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg && 559 ((tp->t_flags & TF_SIGNATURE) == 0) && 560 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 561 ipoptlen == 0 && !(flags & TH_SYN)) 562 tso = 1; 563 564 if (sack_rxmit) { 565 if (SEQ_LT(p->rxmit + len, tp->snd_una + sbused(&so->so_snd))) 566 flags &= ~TH_FIN; 567 } else { 568 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + 569 sbused(&so->so_snd))) 570 flags &= ~TH_FIN; 571 } 572 573 recwin = lmin(lmax(sbspace(&so->so_rcv), 0), 574 (long)TCP_MAXWIN << tp->rcv_scale); 575 576 /* 577 * Sender silly window avoidance. We transmit under the following 578 * conditions when len is non-zero: 579 * 580 * - We have a full segment (or more with TSO) 581 * - This is the last buffer in a write()/send() and we are 582 * either idle or running NODELAY 583 * - we've timed out (e.g. persist timer) 584 * - we have more then 1/2 the maximum send window's worth of 585 * data (receiver may be limited the window size) 586 * - we need to retransmit 587 */ 588 if (len) { 589 if (len >= tp->t_maxseg) 590 goto send; 591 /* 592 * NOTE! on localhost connections an 'ack' from the remote 593 * end may occur synchronously with the output and cause 594 * us to flush a buffer queued with moretocome. XXX 595 * 596 * note: the len + off check is almost certainly unnecessary. 597 */ 598 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 599 (idle || (tp->t_flags & TF_NODELAY)) && 600 (uint32_t)len + (uint32_t)off >= sbavail(&so->so_snd) && 601 (tp->t_flags & TF_NOPUSH) == 0) { 602 goto send; 603 } 604 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 605 goto send; 606 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 607 goto send; 608 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 609 goto send; 610 if (sack_rxmit) 611 goto send; 612 } 613 614 /* 615 * Sending of standalone window updates. 616 * 617 * Window updates are important when we close our window due to a 618 * full socket buffer and are opening it again after the application 619 * reads data from it. Once the window has opened again and the 620 * remote end starts to send again the ACK clock takes over and 621 * provides the most current window information. 622 * 623 * We must avoid the silly window syndrome whereas every read 624 * from the receive buffer, no matter how small, causes a window 625 * update to be sent. We also should avoid sending a flurry of 626 * window updates when the socket buffer had queued a lot of data 627 * and the application is doing small reads. 628 * 629 * Prevent a flurry of pointless window updates by only sending 630 * an update when we can increase the advertized window by more 631 * than 1/4th of the socket buffer capacity. When the buffer is 632 * getting full or is very small be more aggressive and send an 633 * update whenever we can increase by two mss sized segments. 634 * In all other situations the ACK's to new incoming data will 635 * carry further window increases. 636 * 637 * Don't send an independent window update if a delayed 638 * ACK is pending (it will get piggy-backed on it) or the 639 * remote side already has done a half-close and won't send 640 * more data. Skip this if the connection is in T/TCP 641 * half-open state. 642 */ 643 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 644 !(tp->t_flags & TF_DELACK) && 645 !TCPS_HAVERCVDFIN(tp->t_state)) { 646 /* 647 * "adv" is the amount we could increase the window, 648 * taking into account that we are limited by 649 * TCP_MAXWIN << tp->rcv_scale. 650 */ 651 int32_t adv; 652 int oldwin; 653 654 adv = recwin; 655 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { 656 oldwin = (tp->rcv_adv - tp->rcv_nxt); 657 adv -= oldwin; 658 } else 659 oldwin = 0; 660 661 /* 662 * If the new window size ends up being the same as or less 663 * than the old size when it is scaled, then don't force 664 * a window update. 665 */ 666 if (oldwin >> tp->rcv_scale >= (adv + oldwin) >> tp->rcv_scale) 667 goto dontupdate; 668 669 if (adv >= (int32_t)(2 * tp->t_maxseg) && 670 (adv >= (int32_t)(so->so_rcv.sb_hiwat / 4) || 671 recwin <= (so->so_rcv.sb_hiwat / 8) || 672 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg || 673 adv >= TCP_MAXWIN << tp->rcv_scale)) 674 goto send; 675 if (2 * adv >= (int32_t)so->so_rcv.sb_hiwat) 676 goto send; 677 } 678 dontupdate: 679 680 /* 681 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 682 * is also a catch-all for the retransmit timer timeout case. 683 */ 684 if (tp->t_flags & TF_ACKNOW) 685 goto send; 686 if ((flags & TH_RST) || 687 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 688 goto send; 689 if (SEQ_GT(tp->snd_up, tp->snd_una)) 690 goto send; 691 /* 692 * If our state indicates that FIN should be sent 693 * and we have not yet done so, then we need to send. 694 */ 695 if (flags & TH_FIN && 696 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 697 goto send; 698 /* 699 * In SACK, it is possible for tcp_output to fail to send a segment 700 * after the retransmission timer has been turned off. Make sure 701 * that the retransmission timer is set. 702 */ 703 if ((tp->t_flags & TF_SACK_PERMIT) && 704 SEQ_GT(tp->snd_max, tp->snd_una) && 705 !tcp_timer_active(tp, TT_REXMT) && 706 !tcp_timer_active(tp, TT_PERSIST)) { 707 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 708 goto just_return; 709 } 710 /* 711 * TCP window updates are not reliable, rather a polling protocol 712 * using ``persist'' packets is used to insure receipt of window 713 * updates. The three ``states'' for the output side are: 714 * idle not doing retransmits or persists 715 * persisting to move a small or zero window 716 * (re)transmitting and thereby not persisting 717 * 718 * tcp_timer_active(tp, TT_PERSIST) 719 * is true when we are in persist state. 720 * (tp->t_flags & TF_FORCEDATA) 721 * is set when we are called to send a persist packet. 722 * tcp_timer_active(tp, TT_REXMT) 723 * is set when we are retransmitting 724 * The output side is idle when both timers are zero. 725 * 726 * If send window is too small, there is data to transmit, and no 727 * retransmit or persist is pending, then go to persist state. 728 * If nothing happens soon, send when timer expires: 729 * if window is nonzero, transmit what we can, 730 * otherwise force out a byte. 731 */ 732 if (sbavail(&so->so_snd) && !tcp_timer_active(tp, TT_REXMT) && 733 !tcp_timer_active(tp, TT_PERSIST)) { 734 tp->t_rxtshift = 0; 735 tcp_setpersist(tp); 736 } 737 738 /* 739 * No reason to send a segment, just return. 740 */ 741 just_return: 742 SOCKBUF_UNLOCK(&so->so_snd); 743 return (0); 744 745 send: 746 SOCKBUF_LOCK_ASSERT(&so->so_snd); 747 if (len > 0) { 748 if (len >= tp->t_maxseg) 749 tp->t_flags2 |= TF2_PLPMTU_MAXSEGSNT; 750 else 751 tp->t_flags2 &= ~TF2_PLPMTU_MAXSEGSNT; 752 } 753 /* 754 * Before ESTABLISHED, force sending of initial options 755 * unless TCP set not to do any options. 756 * NOTE: we assume that the IP/TCP header plus TCP options 757 * always fit in a single mbuf, leaving room for a maximum 758 * link header, i.e. 759 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 760 */ 761 optlen = 0; 762 #ifdef INET6 763 if (isipv6) 764 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 765 else 766 #endif 767 hdrlen = sizeof (struct tcpiphdr); 768 769 /* 770 * Compute options for segment. 771 * We only have to care about SYN and established connection 772 * segments. Options for SYN-ACK segments are handled in TCP 773 * syncache. 774 */ 775 to.to_flags = 0; 776 if ((tp->t_flags & TF_NOOPT) == 0) { 777 /* Maximum segment size. */ 778 if (flags & TH_SYN) { 779 tp->snd_nxt = tp->iss; 780 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 781 to.to_flags |= TOF_MSS; 782 783 /* 784 * On SYN or SYN|ACK transmits on TFO connections, 785 * only include the TFO option if it is not a 786 * retransmit, as the presence of the TFO option may 787 * have caused the original SYN or SYN|ACK to have 788 * been dropped by a middlebox. 789 */ 790 if (IS_FASTOPEN(tp->t_flags) && 791 (tp->t_rxtshift == 0)) { 792 if (tp->t_state == TCPS_SYN_RECEIVED) { 793 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN; 794 to.to_tfo_cookie = 795 (u_int8_t *)&tp->t_tfo_cookie.server; 796 to.to_flags |= TOF_FASTOPEN; 797 wanted_cookie = 1; 798 } else if (tp->t_state == TCPS_SYN_SENT) { 799 to.to_tfo_len = 800 tp->t_tfo_client_cookie_len; 801 to.to_tfo_cookie = 802 tp->t_tfo_cookie.client; 803 to.to_flags |= TOF_FASTOPEN; 804 wanted_cookie = 1; 805 /* 806 * If we wind up having more data to 807 * send with the SYN than can fit in 808 * one segment, don't send any more 809 * until the SYN|ACK comes back from 810 * the other end. 811 */ 812 dont_sendalot = 1; 813 } 814 } 815 } 816 /* Window scaling. */ 817 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 818 to.to_wscale = tp->request_r_scale; 819 to.to_flags |= TOF_SCALE; 820 } 821 /* Timestamps. */ 822 if ((tp->t_flags & TF_RCVD_TSTMP) || 823 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 824 curticks = tcp_ts_getticks(); 825 to.to_tsval = curticks + tp->ts_offset; 826 to.to_tsecr = tp->ts_recent; 827 to.to_flags |= TOF_TS; 828 if (tp->t_rxtshift == 1) 829 tp->t_badrxtwin = curticks; 830 } 831 832 /* Set receive buffer autosizing timestamp. */ 833 if (tp->rfbuf_ts == 0 && 834 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 835 tp->rfbuf_ts = tcp_ts_getticks(); 836 837 /* Selective ACK's. */ 838 if (tp->t_flags & TF_SACK_PERMIT) { 839 if (flags & TH_SYN) 840 to.to_flags |= TOF_SACKPERM; 841 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 842 (tp->t_flags & TF_SACK_PERMIT) && 843 tp->rcv_numsacks > 0) { 844 to.to_flags |= TOF_SACK; 845 to.to_nsacks = tp->rcv_numsacks; 846 to.to_sacks = (u_char *)tp->sackblks; 847 } 848 } 849 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 850 /* TCP-MD5 (RFC2385). */ 851 /* 852 * Check that TCP_MD5SIG is enabled in tcpcb to 853 * account the size needed to set this TCP option. 854 */ 855 if (tp->t_flags & TF_SIGNATURE) 856 to.to_flags |= TOF_SIGNATURE; 857 #endif /* TCP_SIGNATURE */ 858 859 /* Processing the options. */ 860 hdrlen += optlen = tcp_addoptions(&to, opt); 861 /* 862 * If we wanted a TFO option to be added, but it was unable 863 * to fit, ensure no data is sent. 864 */ 865 if (IS_FASTOPEN(tp->t_flags) && wanted_cookie && 866 !(to.to_flags & TOF_FASTOPEN)) 867 len = 0; 868 } 869 870 /* 871 * Adjust data length if insertion of options will 872 * bump the packet length beyond the t_maxseg length. 873 * Clear the FIN bit because we cut off the tail of 874 * the segment. 875 */ 876 if (len + optlen + ipoptlen > tp->t_maxseg) { 877 flags &= ~TH_FIN; 878 879 if (tso) { 880 u_int if_hw_tsomax; 881 u_int moff; 882 int max_len; 883 884 /* extract TSO information */ 885 if_hw_tsomax = tp->t_tsomax; 886 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount; 887 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize; 888 889 /* 890 * Limit a TSO burst to prevent it from 891 * overflowing or exceeding the maximum length 892 * allowed by the network interface: 893 */ 894 KASSERT(ipoptlen == 0, 895 ("%s: TSO can't do IP options", __func__)); 896 897 /* 898 * Check if we should limit by maximum payload 899 * length: 900 */ 901 if (if_hw_tsomax != 0) { 902 /* compute maximum TSO length */ 903 max_len = (if_hw_tsomax - hdrlen - 904 max_linkhdr); 905 if (max_len <= 0) { 906 len = 0; 907 } else if (len > max_len) { 908 sendalot = 1; 909 len = max_len; 910 } 911 } 912 913 /* 914 * Prevent the last segment from being 915 * fractional unless the send sockbuf can be 916 * emptied: 917 */ 918 max_len = (tp->t_maxseg - optlen); 919 if (((uint32_t)off + (uint32_t)len) < 920 sbavail(&so->so_snd)) { 921 moff = len % max_len; 922 if (moff != 0) { 923 len -= moff; 924 sendalot = 1; 925 } 926 } 927 928 /* 929 * In case there are too many small fragments 930 * don't use TSO: 931 */ 932 if (len <= max_len) { 933 len = max_len; 934 sendalot = 1; 935 tso = 0; 936 } 937 938 /* 939 * Send the FIN in a separate segment 940 * after the bulk sending is done. 941 * We don't trust the TSO implementations 942 * to clear the FIN flag on all but the 943 * last segment. 944 */ 945 if (tp->t_flags & TF_NEEDFIN) 946 sendalot = 1; 947 } else { 948 if (optlen + ipoptlen >= tp->t_maxseg) { 949 /* 950 * Since we don't have enough space to put 951 * the IP header chain and the TCP header in 952 * one packet as required by RFC 7112, don't 953 * send it. Also ensure that at least one 954 * byte of the payload can be put into the 955 * TCP segment. 956 */ 957 SOCKBUF_UNLOCK(&so->so_snd); 958 error = EMSGSIZE; 959 sack_rxmit = 0; 960 goto out; 961 } 962 len = tp->t_maxseg - optlen - ipoptlen; 963 sendalot = 1; 964 if (dont_sendalot) 965 sendalot = 0; 966 } 967 } else 968 tso = 0; 969 970 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 971 ("%s: len > IP_MAXPACKET", __func__)); 972 973 /*#ifdef DIAGNOSTIC*/ 974 #ifdef INET6 975 if (max_linkhdr + hdrlen > MCLBYTES) 976 #else 977 if (max_linkhdr + hdrlen > MHLEN) 978 #endif 979 panic("tcphdr too big"); 980 /*#endif*/ 981 982 /* 983 * This KASSERT is here to catch edge cases at a well defined place. 984 * Before, those had triggered (random) panic conditions further down. 985 */ 986 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 987 988 /* 989 * Grab a header mbuf, attaching a copy of data to 990 * be transmitted, and initialize the header from 991 * the template for sends on this connection. 992 */ 993 if (len) { 994 struct mbuf *mb; 995 struct sockbuf *msb; 996 u_int moff; 997 998 if ((tp->t_flags & TF_FORCEDATA) && len == 1) { 999 TCPSTAT_INC(tcps_sndprobe); 1000 #ifdef STATS 1001 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1002 stats_voi_update_abs_u32(tp->t_stats, 1003 VOI_TCP_RETXPB, len); 1004 else 1005 stats_voi_update_abs_u64(tp->t_stats, 1006 VOI_TCP_TXPB, len); 1007 #endif /* STATS */ 1008 } else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 1009 tp->t_sndrexmitpack++; 1010 TCPSTAT_INC(tcps_sndrexmitpack); 1011 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 1012 #ifdef STATS 1013 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_RETXPB, 1014 len); 1015 #endif /* STATS */ 1016 } else { 1017 TCPSTAT_INC(tcps_sndpack); 1018 TCPSTAT_ADD(tcps_sndbyte, len); 1019 #ifdef STATS 1020 stats_voi_update_abs_u64(tp->t_stats, VOI_TCP_TXPB, 1021 len); 1022 #endif /* STATS */ 1023 } 1024 #ifdef INET6 1025 if (MHLEN < hdrlen + max_linkhdr) 1026 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR); 1027 else 1028 #endif 1029 m = m_gethdr(M_NOWAIT, MT_DATA); 1030 1031 if (m == NULL) { 1032 SOCKBUF_UNLOCK(&so->so_snd); 1033 error = ENOBUFS; 1034 sack_rxmit = 0; 1035 goto out; 1036 } 1037 1038 m->m_data += max_linkhdr; 1039 m->m_len = hdrlen; 1040 1041 /* 1042 * Start the m_copy functions from the closest mbuf 1043 * to the offset in the socket buffer chain. 1044 */ 1045 mb = sbsndptr_noadv(&so->so_snd, off, &moff); 1046 if (len <= MHLEN - hdrlen - max_linkhdr && !hw_tls) { 1047 m_copydata(mb, moff, len, 1048 mtod(m, caddr_t) + hdrlen); 1049 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1050 sbsndptr_adv(&so->so_snd, mb, len); 1051 m->m_len += len; 1052 } else { 1053 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1054 msb = NULL; 1055 else 1056 msb = &so->so_snd; 1057 m->m_next = tcp_m_copym(mb, moff, 1058 &len, if_hw_tsomaxsegcount, 1059 if_hw_tsomaxsegsize, msb, hw_tls); 1060 if (len <= (tp->t_maxseg - optlen)) { 1061 /* 1062 * Must have ran out of mbufs for the copy 1063 * shorten it to no longer need tso. Lets 1064 * not put on sendalot since we are low on 1065 * mbufs. 1066 */ 1067 tso = 0; 1068 } 1069 if (m->m_next == NULL) { 1070 SOCKBUF_UNLOCK(&so->so_snd); 1071 (void) m_free(m); 1072 error = ENOBUFS; 1073 sack_rxmit = 0; 1074 goto out; 1075 } 1076 } 1077 1078 /* 1079 * If we're sending everything we've got, set PUSH. 1080 * (This will keep happy those implementations which only 1081 * give data to the user when a buffer fills or 1082 * a PUSH comes in.) 1083 */ 1084 if (((uint32_t)off + (uint32_t)len == sbused(&so->so_snd)) && 1085 !(flags & TH_SYN)) 1086 flags |= TH_PUSH; 1087 SOCKBUF_UNLOCK(&so->so_snd); 1088 } else { 1089 SOCKBUF_UNLOCK(&so->so_snd); 1090 if (tp->t_flags & TF_ACKNOW) 1091 TCPSTAT_INC(tcps_sndacks); 1092 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 1093 TCPSTAT_INC(tcps_sndctrl); 1094 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 1095 TCPSTAT_INC(tcps_sndurg); 1096 else 1097 TCPSTAT_INC(tcps_sndwinup); 1098 1099 m = m_gethdr(M_NOWAIT, MT_DATA); 1100 if (m == NULL) { 1101 error = ENOBUFS; 1102 sack_rxmit = 0; 1103 goto out; 1104 } 1105 #ifdef INET6 1106 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 1107 MHLEN >= hdrlen) { 1108 M_ALIGN(m, hdrlen); 1109 } else 1110 #endif 1111 m->m_data += max_linkhdr; 1112 m->m_len = hdrlen; 1113 } 1114 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 1115 m->m_pkthdr.rcvif = (struct ifnet *)0; 1116 #ifdef MAC 1117 mac_inpcb_create_mbuf(tp->t_inpcb, m); 1118 #endif 1119 #ifdef INET6 1120 if (isipv6) { 1121 ip6 = mtod(m, struct ip6_hdr *); 1122 th = (struct tcphdr *)(ip6 + 1); 1123 tcpip_fillheaders(tp->t_inpcb, ip6, th); 1124 } else 1125 #endif /* INET6 */ 1126 { 1127 ip = mtod(m, struct ip *); 1128 #ifdef TCPDEBUG 1129 ipov = (struct ipovly *)ip; 1130 #endif 1131 th = (struct tcphdr *)(ip + 1); 1132 tcpip_fillheaders(tp->t_inpcb, ip, th); 1133 } 1134 1135 /* 1136 * Fill in fields, remembering maximum advertised 1137 * window for use in delaying messages about window sizes. 1138 * If resending a FIN, be sure not to use a new sequence number. 1139 */ 1140 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 1141 tp->snd_nxt == tp->snd_max) 1142 tp->snd_nxt--; 1143 /* 1144 * If we are starting a connection, send ECN setup 1145 * SYN packet. If we are on a retransmit, we may 1146 * resend those bits a number of times as per 1147 * RFC 3168. 1148 */ 1149 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn == 1) { 1150 if (tp->t_rxtshift >= 1) { 1151 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 1152 flags |= TH_ECE|TH_CWR; 1153 } else 1154 flags |= TH_ECE|TH_CWR; 1155 } 1156 1157 if (tp->t_state == TCPS_ESTABLISHED && 1158 (tp->t_flags2 & TF2_ECN_PERMIT)) { 1159 /* 1160 * If the peer has ECN, mark data packets with 1161 * ECN capable transmission (ECT). 1162 * Ignore pure ack packets, retransmissions and window probes. 1163 */ 1164 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 1165 (sack_rxmit == 0) && 1166 !((tp->t_flags & TF_FORCEDATA) && len == 1)) { 1167 #ifdef INET6 1168 if (isipv6) 1169 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 1170 else 1171 #endif 1172 ip->ip_tos |= IPTOS_ECN_ECT0; 1173 TCPSTAT_INC(tcps_ecn_ect0); 1174 } 1175 1176 /* 1177 * Reply with proper ECN notifications. 1178 */ 1179 if (tp->t_flags2 & TF2_ECN_SND_CWR) { 1180 flags |= TH_CWR; 1181 tp->t_flags2 &= ~TF2_ECN_SND_CWR; 1182 } 1183 if (tp->t_flags2 & TF2_ECN_SND_ECE) 1184 flags |= TH_ECE; 1185 } 1186 1187 /* 1188 * If we are doing retransmissions, then snd_nxt will 1189 * not reflect the first unsent octet. For ACK only 1190 * packets, we do not want the sequence number of the 1191 * retransmitted packet, we want the sequence number 1192 * of the next unsent octet. So, if there is no data 1193 * (and no SYN or FIN), use snd_max instead of snd_nxt 1194 * when filling in ti_seq. But if we are in persist 1195 * state, snd_max might reflect one byte beyond the 1196 * right edge of the window, so use snd_nxt in that 1197 * case, since we know we aren't doing a retransmission. 1198 * (retransmit and persist are mutually exclusive...) 1199 */ 1200 if (sack_rxmit == 0) { 1201 if (len || (flags & (TH_SYN|TH_FIN)) || 1202 tcp_timer_active(tp, TT_PERSIST)) 1203 th->th_seq = htonl(tp->snd_nxt); 1204 else 1205 th->th_seq = htonl(tp->snd_max); 1206 } else { 1207 th->th_seq = htonl(p->rxmit); 1208 p->rxmit += len; 1209 tp->sackhint.sack_bytes_rexmit += len; 1210 } 1211 th->th_ack = htonl(tp->rcv_nxt); 1212 if (optlen) { 1213 bcopy(opt, th + 1, optlen); 1214 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1215 } 1216 th->th_flags = flags; 1217 /* 1218 * Calculate receive window. Don't shrink window, 1219 * but avoid silly window syndrome. 1220 * If a RST segment is sent, advertise a window of zero. 1221 */ 1222 if (flags & TH_RST) { 1223 recwin = 0; 1224 } else { 1225 if (recwin < (so->so_rcv.sb_hiwat / 4) && 1226 recwin < tp->t_maxseg) 1227 recwin = 0; 1228 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1229 recwin < (tp->rcv_adv - tp->rcv_nxt)) 1230 recwin = (tp->rcv_adv - tp->rcv_nxt); 1231 } 1232 /* 1233 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1234 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1235 * case is handled in syncache. 1236 */ 1237 if (flags & TH_SYN) 1238 th->th_win = htons((u_short) 1239 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1240 else 1241 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1242 1243 /* 1244 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1245 * a 0 window. This may cause the remote transmitter to stall. This 1246 * flag tells soreceive() to disable delayed acknowledgements when 1247 * draining the buffer. This can occur if the receiver is attempting 1248 * to read more data than can be buffered prior to transmitting on 1249 * the connection. 1250 */ 1251 if (th->th_win == 0) { 1252 tp->t_sndzerowin++; 1253 tp->t_flags |= TF_RXWIN0SENT; 1254 } else 1255 tp->t_flags &= ~TF_RXWIN0SENT; 1256 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1257 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1258 th->th_flags |= TH_URG; 1259 } else 1260 /* 1261 * If no urgent pointer to send, then we pull 1262 * the urgent pointer to the left edge of the send window 1263 * so that it doesn't drift into the send window on sequence 1264 * number wraparound. 1265 */ 1266 tp->snd_up = tp->snd_una; /* drag it along */ 1267 1268 /* 1269 * Put TCP length in extended header, and then 1270 * checksum extended header and data. 1271 */ 1272 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1273 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1274 1275 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1276 if (to.to_flags & TOF_SIGNATURE) { 1277 /* 1278 * Calculate MD5 signature and put it into the place 1279 * determined before. 1280 * NOTE: since TCP options buffer doesn't point into 1281 * mbuf's data, calculate offset and use it. 1282 */ 1283 if (!TCPMD5_ENABLED() || (error = TCPMD5_OUTPUT(m, th, 1284 (u_char *)(th + 1) + (to.to_signature - opt))) != 0) { 1285 /* 1286 * Do not send segment if the calculation of MD5 1287 * digest has failed. 1288 */ 1289 m_freem(m); 1290 goto out; 1291 } 1292 } 1293 #endif 1294 #ifdef INET6 1295 if (isipv6) { 1296 /* 1297 * There is no need to fill in ip6_plen right now. 1298 * It will be filled later by ip6_output. 1299 */ 1300 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1301 th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) + 1302 optlen + len, IPPROTO_TCP, 0); 1303 } 1304 #endif 1305 #if defined(INET6) && defined(INET) 1306 else 1307 #endif 1308 #ifdef INET 1309 { 1310 m->m_pkthdr.csum_flags = CSUM_TCP; 1311 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1312 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1313 1314 /* IP version must be set here for ipv4/ipv6 checking later */ 1315 KASSERT(ip->ip_v == IPVERSION, 1316 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1317 } 1318 #endif 1319 1320 /* 1321 * Enable TSO and specify the size of the segments. 1322 * The TCP pseudo header checksum is always provided. 1323 */ 1324 if (tso) { 1325 KASSERT(len > tp->t_maxseg - optlen, 1326 ("%s: len <= tso_segsz", __func__)); 1327 m->m_pkthdr.csum_flags |= CSUM_TSO; 1328 m->m_pkthdr.tso_segsz = tp->t_maxseg - optlen; 1329 } 1330 1331 KASSERT(len + hdrlen == m_length(m, NULL), 1332 ("%s: mbuf chain shorter than expected: %d + %u != %u", 1333 __func__, len, hdrlen, m_length(m, NULL))); 1334 1335 #ifdef TCP_HHOOK 1336 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1337 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1338 #endif 1339 1340 #ifdef TCPDEBUG 1341 /* 1342 * Trace. 1343 */ 1344 if (so->so_options & SO_DEBUG) { 1345 u_short save = 0; 1346 #ifdef INET6 1347 if (!isipv6) 1348 #endif 1349 { 1350 save = ipov->ih_len; 1351 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1352 } 1353 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1354 #ifdef INET6 1355 if (!isipv6) 1356 #endif 1357 ipov->ih_len = save; 1358 } 1359 #endif /* TCPDEBUG */ 1360 TCP_PROBE3(debug__output, tp, th, m); 1361 1362 /* We're getting ready to send; log now. */ 1363 TCP_LOG_EVENT(tp, th, &so->so_rcv, &so->so_snd, TCP_LOG_OUT, ERRNO_UNK, 1364 len, NULL, false); 1365 1366 /* 1367 * Fill in IP length and desired time to live and 1368 * send to IP level. There should be a better way 1369 * to handle ttl and tos; we could keep them in 1370 * the template, but need a way to checksum without them. 1371 */ 1372 /* 1373 * m->m_pkthdr.len should have been set before checksum calculation, 1374 * because in6_cksum() need it. 1375 */ 1376 #ifdef INET6 1377 if (isipv6) { 1378 /* 1379 * we separately set hoplimit for every segment, since the 1380 * user might want to change the value via setsockopt. 1381 * Also, desired default hop limit might be changed via 1382 * Neighbor Discovery. 1383 */ 1384 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1385 1386 /* 1387 * Set the packet size here for the benefit of DTrace probes. 1388 * ip6_output() will set it properly; it's supposed to include 1389 * the option header lengths as well. 1390 */ 1391 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6)); 1392 1393 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) 1394 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1395 else 1396 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1397 1398 if (tp->t_state == TCPS_SYN_SENT) 1399 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th); 1400 1401 TCP_PROBE5(send, NULL, tp, ip6, tp, th); 1402 1403 #ifdef TCPPCAP 1404 /* Save packet, if requested. */ 1405 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1406 #endif 1407 1408 /* TODO: IPv6 IP6TOS_ECT bit on */ 1409 error = ip6_output(m, tp->t_inpcb->in6p_outputopts, 1410 &tp->t_inpcb->inp_route6, 1411 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 1412 NULL, NULL, tp->t_inpcb); 1413 1414 if (error == EMSGSIZE && tp->t_inpcb->inp_route6.ro_rt != NULL) 1415 mtu = tp->t_inpcb->inp_route6.ro_rt->rt_mtu; 1416 } 1417 #endif /* INET6 */ 1418 #if defined(INET) && defined(INET6) 1419 else 1420 #endif 1421 #ifdef INET 1422 { 1423 ip->ip_len = htons(m->m_pkthdr.len); 1424 #ifdef INET6 1425 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1426 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1427 #endif /* INET6 */ 1428 /* 1429 * If we do path MTU discovery, then we set DF on every packet. 1430 * This might not be the best thing to do according to RFC3390 1431 * Section 2. However the tcp hostcache migitates the problem 1432 * so it affects only the first tcp connection with a host. 1433 * 1434 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1435 */ 1436 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) { 1437 ip->ip_off |= htons(IP_DF); 1438 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1439 } else { 1440 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1441 } 1442 1443 if (tp->t_state == TCPS_SYN_SENT) 1444 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th); 1445 1446 TCP_PROBE5(send, NULL, tp, ip, tp, th); 1447 1448 #ifdef TCPPCAP 1449 /* Save packet, if requested. */ 1450 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1451 #endif 1452 1453 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, 1454 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1455 tp->t_inpcb); 1456 1457 if (error == EMSGSIZE && tp->t_inpcb->inp_route.ro_rt != NULL) 1458 mtu = tp->t_inpcb->inp_route.ro_rt->rt_mtu; 1459 } 1460 #endif /* INET */ 1461 1462 out: 1463 /* 1464 * In transmit state, time the transmission and arrange for 1465 * the retransmit. In persist state, just set snd_max. 1466 */ 1467 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1468 !tcp_timer_active(tp, TT_PERSIST)) { 1469 tcp_seq startseq = tp->snd_nxt; 1470 1471 /* 1472 * Advance snd_nxt over sequence space of this segment. 1473 */ 1474 if (flags & (TH_SYN|TH_FIN)) { 1475 if (flags & TH_SYN) 1476 tp->snd_nxt++; 1477 if (flags & TH_FIN) { 1478 tp->snd_nxt++; 1479 tp->t_flags |= TF_SENTFIN; 1480 } 1481 } 1482 if (sack_rxmit) 1483 goto timer; 1484 tp->snd_nxt += len; 1485 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1486 tp->snd_max = tp->snd_nxt; 1487 /* 1488 * Time this transmission if not a retransmission and 1489 * not currently timing anything. 1490 */ 1491 if (tp->t_rtttime == 0) { 1492 tp->t_rtttime = ticks; 1493 tp->t_rtseq = startseq; 1494 TCPSTAT_INC(tcps_segstimed); 1495 } 1496 #ifdef STATS 1497 if (!(tp->t_flags & TF_GPUTINPROG) && len) { 1498 tp->t_flags |= TF_GPUTINPROG; 1499 tp->gput_seq = startseq; 1500 tp->gput_ack = startseq + 1501 ulmin(sbavail(&so->so_snd) - off, sendwin); 1502 tp->gput_ts = tcp_ts_getticks(); 1503 } 1504 #endif /* STATS */ 1505 } 1506 1507 /* 1508 * Set retransmit timer if not currently set, 1509 * and not doing a pure ack or a keep-alive probe. 1510 * Initial value for retransmit timer is smoothed 1511 * round-trip time + 2 * round-trip time variance. 1512 * Initialize shift counter which is used for backoff 1513 * of retransmit time. 1514 */ 1515 timer: 1516 if (!tcp_timer_active(tp, TT_REXMT) && 1517 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1518 (tp->snd_nxt != tp->snd_una))) { 1519 if (tcp_timer_active(tp, TT_PERSIST)) { 1520 tcp_timer_activate(tp, TT_PERSIST, 0); 1521 tp->t_rxtshift = 0; 1522 } 1523 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1524 } else if (len == 0 && sbavail(&so->so_snd) && 1525 !tcp_timer_active(tp, TT_REXMT) && 1526 !tcp_timer_active(tp, TT_PERSIST)) { 1527 /* 1528 * Avoid a situation where we do not set persist timer 1529 * after a zero window condition. For example: 1530 * 1) A -> B: packet with enough data to fill the window 1531 * 2) B -> A: ACK for #1 + new data (0 window 1532 * advertisement) 1533 * 3) A -> B: ACK for #2, 0 len packet 1534 * 1535 * In this case, A will not activate the persist timer, 1536 * because it chose to send a packet. Unless tcp_output 1537 * is called for some other reason (delayed ack timer, 1538 * another input packet from B, socket syscall), A will 1539 * not send zero window probes. 1540 * 1541 * So, if you send a 0-length packet, but there is data 1542 * in the socket buffer, and neither the rexmt or 1543 * persist timer is already set, then activate the 1544 * persist timer. 1545 */ 1546 tp->t_rxtshift = 0; 1547 tcp_setpersist(tp); 1548 } 1549 } else { 1550 /* 1551 * Persist case, update snd_max but since we are in 1552 * persist mode (no window) we do not update snd_nxt. 1553 */ 1554 int xlen = len; 1555 if (flags & TH_SYN) 1556 ++xlen; 1557 if (flags & TH_FIN) { 1558 ++xlen; 1559 tp->t_flags |= TF_SENTFIN; 1560 } 1561 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1562 tp->snd_max = tp->snd_nxt + xlen; 1563 } 1564 if ((error == 0) && 1565 (TCPS_HAVEESTABLISHED(tp->t_state) && 1566 (tp->t_flags & TF_SACK_PERMIT) && 1567 tp->rcv_numsacks > 0)) { 1568 /* Clean up any DSACK's sent */ 1569 tcp_clean_dsack_blocks(tp); 1570 } 1571 if (error) { 1572 /* Record the error. */ 1573 TCP_LOG_EVENT(tp, NULL, &so->so_rcv, &so->so_snd, TCP_LOG_OUT, 1574 error, 0, NULL, false); 1575 1576 /* 1577 * We know that the packet was lost, so back out the 1578 * sequence number advance, if any. 1579 * 1580 * If the error is EPERM the packet got blocked by the 1581 * local firewall. Normally we should terminate the 1582 * connection but the blocking may have been spurious 1583 * due to a firewall reconfiguration cycle. So we treat 1584 * it like a packet loss and let the retransmit timer and 1585 * timeouts do their work over time. 1586 * XXX: It is a POLA question whether calling tcp_drop right 1587 * away would be the really correct behavior instead. 1588 */ 1589 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1590 !tcp_timer_active(tp, TT_PERSIST)) && 1591 ((flags & TH_SYN) == 0) && 1592 (error != EPERM)) { 1593 if (sack_rxmit) { 1594 p->rxmit -= len; 1595 tp->sackhint.sack_bytes_rexmit -= len; 1596 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1597 ("sackhint bytes rtx >= 0")); 1598 } else 1599 tp->snd_nxt -= len; 1600 } 1601 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1602 switch (error) { 1603 case EACCES: 1604 case EPERM: 1605 tp->t_softerror = error; 1606 return (error); 1607 case ENOBUFS: 1608 TCP_XMIT_TIMER_ASSERT(tp, len, flags); 1609 tp->snd_cwnd = tp->t_maxseg; 1610 return (0); 1611 case EMSGSIZE: 1612 /* 1613 * For some reason the interface we used initially 1614 * to send segments changed to another or lowered 1615 * its MTU. 1616 * If TSO was active we either got an interface 1617 * without TSO capabilits or TSO was turned off. 1618 * If we obtained mtu from ip_output() then update 1619 * it and try again. 1620 */ 1621 if (tso) 1622 tp->t_flags &= ~TF_TSO; 1623 if (mtu != 0) { 1624 tcp_mss_update(tp, -1, mtu, NULL, NULL); 1625 goto again; 1626 } 1627 return (error); 1628 case EHOSTDOWN: 1629 case EHOSTUNREACH: 1630 case ENETDOWN: 1631 case ENETUNREACH: 1632 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1633 tp->t_softerror = error; 1634 return (0); 1635 } 1636 /* FALLTHROUGH */ 1637 default: 1638 return (error); 1639 } 1640 } 1641 TCPSTAT_INC(tcps_sndtotal); 1642 1643 /* 1644 * Data sent (as far as we can tell). 1645 * If this advertises a larger window than any other segment, 1646 * then remember the size of the advertised window. 1647 * Any pending ACK has now been sent. 1648 */ 1649 if (SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1650 tp->rcv_adv = tp->rcv_nxt + recwin; 1651 tp->last_ack_sent = tp->rcv_nxt; 1652 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1653 if (tcp_timer_active(tp, TT_DELACK)) 1654 tcp_timer_activate(tp, TT_DELACK, 0); 1655 #if 0 1656 /* 1657 * This completely breaks TCP if newreno is turned on. What happens 1658 * is that if delayed-acks are turned on on the receiver, this code 1659 * on the transmitter effectively destroys the TCP window, forcing 1660 * it to four packets (1.5Kx4 = 6K window). 1661 */ 1662 if (sendalot && --maxburst) 1663 goto again; 1664 #endif 1665 if (sendalot) 1666 goto again; 1667 return (0); 1668 } 1669 1670 void 1671 tcp_setpersist(struct tcpcb *tp) 1672 { 1673 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1674 int tt; 1675 1676 tp->t_flags &= ~TF_PREVVALID; 1677 if (tcp_timer_active(tp, TT_REXMT)) 1678 panic("tcp_setpersist: retransmit pending"); 1679 /* 1680 * Start/restart persistence timer. 1681 */ 1682 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1683 tcp_persmin, tcp_persmax); 1684 tcp_timer_activate(tp, TT_PERSIST, tt); 1685 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1686 tp->t_rxtshift++; 1687 } 1688 1689 /* 1690 * Insert TCP options according to the supplied parameters to the place 1691 * optp in a consistent way. Can handle unaligned destinations. 1692 * 1693 * The order of the option processing is crucial for optimal packing and 1694 * alignment for the scarce option space. 1695 * 1696 * The optimal order for a SYN/SYN-ACK segment is: 1697 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1698 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1699 * 1700 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1701 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1702 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1703 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1704 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1705 */ 1706 int 1707 tcp_addoptions(struct tcpopt *to, u_char *optp) 1708 { 1709 u_int32_t mask, optlen = 0; 1710 1711 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1712 if ((to->to_flags & mask) != mask) 1713 continue; 1714 if (optlen == TCP_MAXOLEN) 1715 break; 1716 switch (to->to_flags & mask) { 1717 case TOF_MSS: 1718 while (optlen % 4) { 1719 optlen += TCPOLEN_NOP; 1720 *optp++ = TCPOPT_NOP; 1721 } 1722 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1723 continue; 1724 optlen += TCPOLEN_MAXSEG; 1725 *optp++ = TCPOPT_MAXSEG; 1726 *optp++ = TCPOLEN_MAXSEG; 1727 to->to_mss = htons(to->to_mss); 1728 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1729 optp += sizeof(to->to_mss); 1730 break; 1731 case TOF_SCALE: 1732 while (!optlen || optlen % 2 != 1) { 1733 optlen += TCPOLEN_NOP; 1734 *optp++ = TCPOPT_NOP; 1735 } 1736 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1737 continue; 1738 optlen += TCPOLEN_WINDOW; 1739 *optp++ = TCPOPT_WINDOW; 1740 *optp++ = TCPOLEN_WINDOW; 1741 *optp++ = to->to_wscale; 1742 break; 1743 case TOF_SACKPERM: 1744 while (optlen % 2) { 1745 optlen += TCPOLEN_NOP; 1746 *optp++ = TCPOPT_NOP; 1747 } 1748 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1749 continue; 1750 optlen += TCPOLEN_SACK_PERMITTED; 1751 *optp++ = TCPOPT_SACK_PERMITTED; 1752 *optp++ = TCPOLEN_SACK_PERMITTED; 1753 break; 1754 case TOF_TS: 1755 while (!optlen || optlen % 4 != 2) { 1756 optlen += TCPOLEN_NOP; 1757 *optp++ = TCPOPT_NOP; 1758 } 1759 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1760 continue; 1761 optlen += TCPOLEN_TIMESTAMP; 1762 *optp++ = TCPOPT_TIMESTAMP; 1763 *optp++ = TCPOLEN_TIMESTAMP; 1764 to->to_tsval = htonl(to->to_tsval); 1765 to->to_tsecr = htonl(to->to_tsecr); 1766 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1767 optp += sizeof(to->to_tsval); 1768 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1769 optp += sizeof(to->to_tsecr); 1770 break; 1771 case TOF_SIGNATURE: 1772 { 1773 int siglen = TCPOLEN_SIGNATURE - 2; 1774 1775 while (!optlen || optlen % 4 != 2) { 1776 optlen += TCPOLEN_NOP; 1777 *optp++ = TCPOPT_NOP; 1778 } 1779 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) { 1780 to->to_flags &= ~TOF_SIGNATURE; 1781 continue; 1782 } 1783 optlen += TCPOLEN_SIGNATURE; 1784 *optp++ = TCPOPT_SIGNATURE; 1785 *optp++ = TCPOLEN_SIGNATURE; 1786 to->to_signature = optp; 1787 while (siglen--) 1788 *optp++ = 0; 1789 break; 1790 } 1791 case TOF_SACK: 1792 { 1793 int sackblks = 0; 1794 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1795 tcp_seq sack_seq; 1796 1797 while (!optlen || optlen % 4 != 2) { 1798 optlen += TCPOLEN_NOP; 1799 *optp++ = TCPOPT_NOP; 1800 } 1801 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1802 continue; 1803 optlen += TCPOLEN_SACKHDR; 1804 *optp++ = TCPOPT_SACK; 1805 sackblks = min(to->to_nsacks, 1806 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1807 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1808 while (sackblks--) { 1809 sack_seq = htonl(sack->start); 1810 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1811 optp += sizeof(sack_seq); 1812 sack_seq = htonl(sack->end); 1813 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1814 optp += sizeof(sack_seq); 1815 optlen += TCPOLEN_SACK; 1816 sack++; 1817 } 1818 TCPSTAT_INC(tcps_sack_send_blocks); 1819 break; 1820 } 1821 case TOF_FASTOPEN: 1822 { 1823 int total_len; 1824 1825 /* XXX is there any point to aligning this option? */ 1826 total_len = TCPOLEN_FAST_OPEN_EMPTY + to->to_tfo_len; 1827 if (TCP_MAXOLEN - optlen < total_len) { 1828 to->to_flags &= ~TOF_FASTOPEN; 1829 continue; 1830 } 1831 *optp++ = TCPOPT_FAST_OPEN; 1832 *optp++ = total_len; 1833 if (to->to_tfo_len > 0) { 1834 bcopy(to->to_tfo_cookie, optp, to->to_tfo_len); 1835 optp += to->to_tfo_len; 1836 } 1837 optlen += total_len; 1838 break; 1839 } 1840 default: 1841 panic("%s: unknown TCP option type", __func__); 1842 break; 1843 } 1844 } 1845 1846 /* Terminate and pad TCP options to a 4 byte boundary. */ 1847 if (optlen % 4) { 1848 optlen += TCPOLEN_EOL; 1849 *optp++ = TCPOPT_EOL; 1850 } 1851 /* 1852 * According to RFC 793 (STD0007): 1853 * "The content of the header beyond the End-of-Option option 1854 * must be header padding (i.e., zero)." 1855 * and later: "The padding is composed of zeros." 1856 */ 1857 while (optlen % 4) { 1858 optlen += TCPOLEN_PAD; 1859 *optp++ = TCPOPT_PAD; 1860 } 1861 1862 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1863 return (optlen); 1864 } 1865 1866 /* 1867 * This is a copy of m_copym(), taking the TSO segment size/limit 1868 * constraints into account, and advancing the sndptr as it goes. 1869 */ 1870 struct mbuf * 1871 tcp_m_copym(struct mbuf *m, int32_t off0, int32_t *plen, 1872 int32_t seglimit, int32_t segsize, struct sockbuf *sb, bool hw_tls) 1873 { 1874 #ifdef KERN_TLS 1875 struct ktls_session *tls, *ntls; 1876 struct mbuf *start; 1877 #endif 1878 struct mbuf *n, **np; 1879 struct mbuf *top; 1880 int32_t off = off0; 1881 int32_t len = *plen; 1882 int32_t fragsize; 1883 int32_t len_cp = 0; 1884 int32_t *pkthdrlen; 1885 uint32_t mlen, frags; 1886 bool copyhdr; 1887 1888 1889 KASSERT(off >= 0, ("tcp_m_copym, negative off %d", off)); 1890 KASSERT(len >= 0, ("tcp_m_copym, negative len %d", len)); 1891 if (off == 0 && m->m_flags & M_PKTHDR) 1892 copyhdr = true; 1893 else 1894 copyhdr = false; 1895 while (off > 0) { 1896 KASSERT(m != NULL, ("tcp_m_copym, offset > size of mbuf chain")); 1897 if (off < m->m_len) 1898 break; 1899 off -= m->m_len; 1900 if ((sb) && (m == sb->sb_sndptr)) { 1901 sb->sb_sndptroff += m->m_len; 1902 sb->sb_sndptr = m->m_next; 1903 } 1904 m = m->m_next; 1905 } 1906 np = ⊤ 1907 top = NULL; 1908 pkthdrlen = NULL; 1909 #ifdef KERN_TLS 1910 if (m->m_flags & M_NOMAP) 1911 tls = m->m_ext.ext_pgs->tls; 1912 else 1913 tls = NULL; 1914 start = m; 1915 #endif 1916 while (len > 0) { 1917 if (m == NULL) { 1918 KASSERT(len == M_COPYALL, 1919 ("tcp_m_copym, length > size of mbuf chain")); 1920 *plen = len_cp; 1921 if (pkthdrlen != NULL) 1922 *pkthdrlen = len_cp; 1923 break; 1924 } 1925 #ifdef KERN_TLS 1926 if (hw_tls) { 1927 if (m->m_flags & M_NOMAP) 1928 ntls = m->m_ext.ext_pgs->tls; 1929 else 1930 ntls = NULL; 1931 1932 /* 1933 * Avoid mixing TLS records with handshake 1934 * data or TLS records from different 1935 * sessions. 1936 */ 1937 if (tls != ntls) { 1938 MPASS(m != start); 1939 *plen = len_cp; 1940 if (pkthdrlen != NULL) 1941 *pkthdrlen = len_cp; 1942 break; 1943 } 1944 1945 /* 1946 * Don't end a send in the middle of a TLS 1947 * record if it spans multiple TLS records. 1948 */ 1949 if (tls != NULL && (m != start) && len < m->m_len) { 1950 *plen = len_cp; 1951 if (pkthdrlen != NULL) 1952 *pkthdrlen = len_cp; 1953 break; 1954 } 1955 } 1956 #endif 1957 mlen = min(len, m->m_len - off); 1958 if (seglimit) { 1959 /* 1960 * For M_NOMAP mbufs, add 3 segments 1961 * + 1 in case we are crossing page boundaries 1962 * + 2 in case the TLS hdr/trailer are used 1963 * It is cheaper to just add the segments 1964 * than it is to take the cache miss to look 1965 * at the mbuf ext_pgs state in detail. 1966 */ 1967 if (m->m_flags & M_NOMAP) { 1968 fragsize = min(segsize, PAGE_SIZE); 1969 frags = 3; 1970 } else { 1971 fragsize = segsize; 1972 frags = 0; 1973 } 1974 1975 /* Break if we really can't fit anymore. */ 1976 if ((frags + 1) >= seglimit) { 1977 *plen = len_cp; 1978 if (pkthdrlen != NULL) 1979 *pkthdrlen = len_cp; 1980 break; 1981 } 1982 1983 /* 1984 * Reduce size if you can't copy the whole 1985 * mbuf. If we can't copy the whole mbuf, also 1986 * adjust len so the loop will end after this 1987 * mbuf. 1988 */ 1989 if ((frags + howmany(mlen, fragsize)) >= seglimit) { 1990 mlen = (seglimit - frags - 1) * fragsize; 1991 len = mlen; 1992 *plen = len_cp + len; 1993 if (pkthdrlen != NULL) 1994 *pkthdrlen = *plen; 1995 } 1996 frags += howmany(mlen, fragsize); 1997 if (frags == 0) 1998 frags++; 1999 seglimit -= frags; 2000 KASSERT(seglimit > 0, 2001 ("%s: seglimit went too low", __func__)); 2002 } 2003 if (copyhdr) 2004 n = m_gethdr(M_NOWAIT, m->m_type); 2005 else 2006 n = m_get(M_NOWAIT, m->m_type); 2007 *np = n; 2008 if (n == NULL) 2009 goto nospace; 2010 if (copyhdr) { 2011 if (!m_dup_pkthdr(n, m, M_NOWAIT)) 2012 goto nospace; 2013 if (len == M_COPYALL) 2014 n->m_pkthdr.len -= off0; 2015 else 2016 n->m_pkthdr.len = len; 2017 pkthdrlen = &n->m_pkthdr.len; 2018 copyhdr = false; 2019 } 2020 n->m_len = mlen; 2021 len_cp += n->m_len; 2022 if (m->m_flags & M_EXT) { 2023 n->m_data = m->m_data + off; 2024 mb_dupcl(n, m); 2025 } else 2026 bcopy(mtod(m, caddr_t)+off, mtod(n, caddr_t), 2027 (u_int)n->m_len); 2028 2029 if (sb && (sb->sb_sndptr == m) && 2030 ((n->m_len + off) >= m->m_len) && m->m_next) { 2031 sb->sb_sndptroff += m->m_len; 2032 sb->sb_sndptr = m->m_next; 2033 } 2034 off = 0; 2035 if (len != M_COPYALL) { 2036 len -= n->m_len; 2037 } 2038 m = m->m_next; 2039 np = &n->m_next; 2040 } 2041 return (top); 2042 nospace: 2043 m_freem(top); 2044 return (NULL); 2045 } 2046 2047 void 2048 tcp_sndbuf_autoscale(struct tcpcb *tp, struct socket *so, uint32_t sendwin) 2049 { 2050 2051 /* 2052 * Automatic sizing of send socket buffer. Often the send buffer 2053 * size is not optimally adjusted to the actual network conditions 2054 * at hand (delay bandwidth product). Setting the buffer size too 2055 * small limits throughput on links with high bandwidth and high 2056 * delay (eg. trans-continental/oceanic links). Setting the 2057 * buffer size too big consumes too much real kernel memory, 2058 * especially with many connections on busy servers. 2059 * 2060 * The criteria to step up the send buffer one notch are: 2061 * 1. receive window of remote host is larger than send buffer 2062 * (with a fudge factor of 5/4th); 2063 * 2. send buffer is filled to 7/8th with data (so we actually 2064 * have data to make use of it); 2065 * 3. send buffer fill has not hit maximal automatic size; 2066 * 4. our send window (slow start and cogestion controlled) is 2067 * larger than sent but unacknowledged data in send buffer. 2068 * 2069 * The remote host receive window scaling factor may limit the 2070 * growing of the send buffer before it reaches its allowed 2071 * maximum. 2072 * 2073 * It scales directly with slow start or congestion window 2074 * and does at most one step per received ACK. This fast 2075 * scaling has the drawback of growing the send buffer beyond 2076 * what is strictly necessary to make full use of a given 2077 * delay*bandwidth product. However testing has shown this not 2078 * to be much of an problem. At worst we are trading wasting 2079 * of available bandwidth (the non-use of it) for wasting some 2080 * socket buffer memory. 2081 * 2082 * TODO: Shrink send buffer during idle periods together 2083 * with congestion window. Requires another timer. Has to 2084 * wait for upcoming tcp timer rewrite. 2085 * 2086 * XXXGL: should there be used sbused() or sbavail()? 2087 */ 2088 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 2089 int lowat; 2090 2091 lowat = V_tcp_sendbuf_auto_lowat ? so->so_snd.sb_lowat : 0; 2092 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat - lowat && 2093 sbused(&so->so_snd) >= 2094 (so->so_snd.sb_hiwat / 8 * 7) - lowat && 2095 sbused(&so->so_snd) < V_tcp_autosndbuf_max && 2096 sendwin >= (sbused(&so->so_snd) - 2097 (tp->snd_nxt - tp->snd_una))) { 2098 if (!sbreserve_locked(&so->so_snd, 2099 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 2100 V_tcp_autosndbuf_max), so, curthread)) 2101 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 2102 } 2103 } 2104 } 2105