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 1158 if (tp->t_state == TCPS_ESTABLISHED && 1159 (tp->t_flags2 & TF2_ECN_PERMIT)) { 1160 /* 1161 * If the peer has ECN, mark data packets with 1162 * ECN capable transmission (ECT). 1163 * Ignore pure ack packets, retransmissions and window probes. 1164 */ 1165 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 1166 (sack_rxmit == 0) && 1167 !((tp->t_flags & TF_FORCEDATA) && len == 1)) { 1168 #ifdef INET6 1169 if (isipv6) 1170 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 1171 else 1172 #endif 1173 ip->ip_tos |= IPTOS_ECN_ECT0; 1174 TCPSTAT_INC(tcps_ecn_ect0); 1175 } 1176 1177 /* 1178 * Reply with proper ECN notifications. 1179 */ 1180 if (tp->t_flags2 & TF2_ECN_SND_CWR) { 1181 flags |= TH_CWR; 1182 tp->t_flags2 &= ~TF2_ECN_SND_CWR; 1183 } 1184 if (tp->t_flags2 & TF2_ECN_SND_ECE) 1185 flags |= TH_ECE; 1186 } 1187 1188 /* 1189 * If we are doing retransmissions, then snd_nxt will 1190 * not reflect the first unsent octet. For ACK only 1191 * packets, we do not want the sequence number of the 1192 * retransmitted packet, we want the sequence number 1193 * of the next unsent octet. So, if there is no data 1194 * (and no SYN or FIN), use snd_max instead of snd_nxt 1195 * when filling in ti_seq. But if we are in persist 1196 * state, snd_max might reflect one byte beyond the 1197 * right edge of the window, so use snd_nxt in that 1198 * case, since we know we aren't doing a retransmission. 1199 * (retransmit and persist are mutually exclusive...) 1200 */ 1201 if (sack_rxmit == 0) { 1202 if (len || (flags & (TH_SYN|TH_FIN)) || 1203 tcp_timer_active(tp, TT_PERSIST)) 1204 th->th_seq = htonl(tp->snd_nxt); 1205 else 1206 th->th_seq = htonl(tp->snd_max); 1207 } else { 1208 th->th_seq = htonl(p->rxmit); 1209 p->rxmit += len; 1210 tp->sackhint.sack_bytes_rexmit += len; 1211 } 1212 th->th_ack = htonl(tp->rcv_nxt); 1213 if (optlen) { 1214 bcopy(opt, th + 1, optlen); 1215 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1216 } 1217 th->th_flags = flags; 1218 /* 1219 * Calculate receive window. Don't shrink window, 1220 * but avoid silly window syndrome. 1221 * If a RST segment is sent, advertise a window of zero. 1222 */ 1223 if (flags & TH_RST) { 1224 recwin = 0; 1225 } else { 1226 if (recwin < (so->so_rcv.sb_hiwat / 4) && 1227 recwin < tp->t_maxseg) 1228 recwin = 0; 1229 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1230 recwin < (tp->rcv_adv - tp->rcv_nxt)) 1231 recwin = (tp->rcv_adv - tp->rcv_nxt); 1232 } 1233 /* 1234 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1235 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1236 * case is handled in syncache. 1237 */ 1238 if (flags & TH_SYN) 1239 th->th_win = htons((u_short) 1240 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1241 else { 1242 /* Avoid shrinking window with window scaling. */ 1243 recwin = roundup2(recwin, 1 << tp->rcv_scale); 1244 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1245 } 1246 1247 /* 1248 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1249 * a 0 window. This may cause the remote transmitter to stall. This 1250 * flag tells soreceive() to disable delayed acknowledgements when 1251 * draining the buffer. This can occur if the receiver is attempting 1252 * to read more data than can be buffered prior to transmitting on 1253 * the connection. 1254 */ 1255 if (th->th_win == 0) { 1256 tp->t_sndzerowin++; 1257 tp->t_flags |= TF_RXWIN0SENT; 1258 } else 1259 tp->t_flags &= ~TF_RXWIN0SENT; 1260 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1261 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1262 th->th_flags |= TH_URG; 1263 } else 1264 /* 1265 * If no urgent pointer to send, then we pull 1266 * the urgent pointer to the left edge of the send window 1267 * so that it doesn't drift into the send window on sequence 1268 * number wraparound. 1269 */ 1270 tp->snd_up = tp->snd_una; /* drag it along */ 1271 1272 /* 1273 * Put TCP length in extended header, and then 1274 * checksum extended header and data. 1275 */ 1276 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1277 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1278 1279 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1280 if (to.to_flags & TOF_SIGNATURE) { 1281 /* 1282 * Calculate MD5 signature and put it into the place 1283 * determined before. 1284 * NOTE: since TCP options buffer doesn't point into 1285 * mbuf's data, calculate offset and use it. 1286 */ 1287 if (!TCPMD5_ENABLED() || (error = TCPMD5_OUTPUT(m, th, 1288 (u_char *)(th + 1) + (to.to_signature - opt))) != 0) { 1289 /* 1290 * Do not send segment if the calculation of MD5 1291 * digest has failed. 1292 */ 1293 m_freem(m); 1294 goto out; 1295 } 1296 } 1297 #endif 1298 #ifdef INET6 1299 if (isipv6) { 1300 /* 1301 * There is no need to fill in ip6_plen right now. 1302 * It will be filled later by ip6_output. 1303 */ 1304 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1305 th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) + 1306 optlen + len, IPPROTO_TCP, 0); 1307 } 1308 #endif 1309 #if defined(INET6) && defined(INET) 1310 else 1311 #endif 1312 #ifdef INET 1313 { 1314 m->m_pkthdr.csum_flags = CSUM_TCP; 1315 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1316 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1317 1318 /* IP version must be set here for ipv4/ipv6 checking later */ 1319 KASSERT(ip->ip_v == IPVERSION, 1320 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1321 } 1322 #endif 1323 1324 /* 1325 * Enable TSO and specify the size of the segments. 1326 * The TCP pseudo header checksum is always provided. 1327 */ 1328 if (tso) { 1329 KASSERT(len > tp->t_maxseg - optlen, 1330 ("%s: len <= tso_segsz", __func__)); 1331 m->m_pkthdr.csum_flags |= CSUM_TSO; 1332 m->m_pkthdr.tso_segsz = tp->t_maxseg - optlen; 1333 } 1334 1335 KASSERT(len + hdrlen == m_length(m, NULL), 1336 ("%s: mbuf chain shorter than expected: %d + %u != %u", 1337 __func__, len, hdrlen, m_length(m, NULL))); 1338 1339 #ifdef TCP_HHOOK 1340 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1341 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1342 #endif 1343 1344 #ifdef TCPDEBUG 1345 /* 1346 * Trace. 1347 */ 1348 if (so->so_options & SO_DEBUG) { 1349 u_short save = 0; 1350 #ifdef INET6 1351 if (!isipv6) 1352 #endif 1353 { 1354 save = ipov->ih_len; 1355 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1356 } 1357 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1358 #ifdef INET6 1359 if (!isipv6) 1360 #endif 1361 ipov->ih_len = save; 1362 } 1363 #endif /* TCPDEBUG */ 1364 TCP_PROBE3(debug__output, tp, th, m); 1365 1366 /* We're getting ready to send; log now. */ 1367 TCP_LOG_EVENT(tp, th, &so->so_rcv, &so->so_snd, TCP_LOG_OUT, ERRNO_UNK, 1368 len, NULL, false); 1369 1370 /* 1371 * Fill in IP length and desired time to live and 1372 * send to IP level. There should be a better way 1373 * to handle ttl and tos; we could keep them in 1374 * the template, but need a way to checksum without them. 1375 */ 1376 /* 1377 * m->m_pkthdr.len should have been set before checksum calculation, 1378 * because in6_cksum() need it. 1379 */ 1380 #ifdef INET6 1381 if (isipv6) { 1382 /* 1383 * we separately set hoplimit for every segment, since the 1384 * user might want to change the value via setsockopt. 1385 * Also, desired default hop limit might be changed via 1386 * Neighbor Discovery. 1387 */ 1388 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1389 1390 /* 1391 * Set the packet size here for the benefit of DTrace probes. 1392 * ip6_output() will set it properly; it's supposed to include 1393 * the option header lengths as well. 1394 */ 1395 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6)); 1396 1397 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) 1398 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1399 else 1400 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1401 1402 if (tp->t_state == TCPS_SYN_SENT) 1403 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th); 1404 1405 TCP_PROBE5(send, NULL, tp, ip6, tp, th); 1406 1407 #ifdef TCPPCAP 1408 /* Save packet, if requested. */ 1409 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1410 #endif 1411 1412 /* TODO: IPv6 IP6TOS_ECT bit on */ 1413 error = ip6_output(m, tp->t_inpcb->in6p_outputopts, 1414 &tp->t_inpcb->inp_route6, 1415 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 1416 NULL, NULL, tp->t_inpcb); 1417 1418 if (error == EMSGSIZE && tp->t_inpcb->inp_route6.ro_nh != NULL) 1419 mtu = tp->t_inpcb->inp_route6.ro_nh->nh_mtu; 1420 } 1421 #endif /* INET6 */ 1422 #if defined(INET) && defined(INET6) 1423 else 1424 #endif 1425 #ifdef INET 1426 { 1427 ip->ip_len = htons(m->m_pkthdr.len); 1428 #ifdef INET6 1429 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1430 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1431 #endif /* INET6 */ 1432 /* 1433 * If we do path MTU discovery, then we set DF on every packet. 1434 * This might not be the best thing to do according to RFC3390 1435 * Section 2. However the tcp hostcache migitates the problem 1436 * so it affects only the first tcp connection with a host. 1437 * 1438 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1439 */ 1440 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) { 1441 ip->ip_off |= htons(IP_DF); 1442 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1443 } else { 1444 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1445 } 1446 1447 if (tp->t_state == TCPS_SYN_SENT) 1448 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th); 1449 1450 TCP_PROBE5(send, NULL, tp, ip, tp, th); 1451 1452 #ifdef TCPPCAP 1453 /* Save packet, if requested. */ 1454 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1455 #endif 1456 1457 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, 1458 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1459 tp->t_inpcb); 1460 1461 if (error == EMSGSIZE && tp->t_inpcb->inp_route.ro_nh != NULL) 1462 mtu = tp->t_inpcb->inp_route.ro_nh->nh_mtu; 1463 } 1464 #endif /* INET */ 1465 1466 out: 1467 /* 1468 * In transmit state, time the transmission and arrange for 1469 * the retransmit. In persist state, just set snd_max. 1470 */ 1471 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1472 !tcp_timer_active(tp, TT_PERSIST)) { 1473 tcp_seq startseq = tp->snd_nxt; 1474 1475 /* 1476 * Advance snd_nxt over sequence space of this segment. 1477 */ 1478 if (flags & (TH_SYN|TH_FIN)) { 1479 if (flags & TH_SYN) 1480 tp->snd_nxt++; 1481 if (flags & TH_FIN) { 1482 tp->snd_nxt++; 1483 tp->t_flags |= TF_SENTFIN; 1484 } 1485 } 1486 if (sack_rxmit) 1487 goto timer; 1488 tp->snd_nxt += len; 1489 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1490 tp->snd_max = tp->snd_nxt; 1491 /* 1492 * Time this transmission if not a retransmission and 1493 * not currently timing anything. 1494 */ 1495 if (tp->t_rtttime == 0) { 1496 tp->t_rtttime = ticks; 1497 tp->t_rtseq = startseq; 1498 TCPSTAT_INC(tcps_segstimed); 1499 } 1500 #ifdef STATS 1501 if (!(tp->t_flags & TF_GPUTINPROG) && len) { 1502 tp->t_flags |= TF_GPUTINPROG; 1503 tp->gput_seq = startseq; 1504 tp->gput_ack = startseq + 1505 ulmin(sbavail(&so->so_snd) - off, sendwin); 1506 tp->gput_ts = tcp_ts_getticks(); 1507 } 1508 #endif /* STATS */ 1509 } 1510 1511 /* 1512 * Set retransmit timer if not currently set, 1513 * and not doing a pure ack or a keep-alive probe. 1514 * Initial value for retransmit timer is smoothed 1515 * round-trip time + 2 * round-trip time variance. 1516 * Initialize shift counter which is used for backoff 1517 * of retransmit time. 1518 */ 1519 timer: 1520 if (!tcp_timer_active(tp, TT_REXMT) && 1521 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1522 (tp->snd_nxt != tp->snd_una))) { 1523 if (tcp_timer_active(tp, TT_PERSIST)) { 1524 tcp_timer_activate(tp, TT_PERSIST, 0); 1525 tp->t_rxtshift = 0; 1526 } 1527 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1528 } else if (len == 0 && sbavail(&so->so_snd) && 1529 !tcp_timer_active(tp, TT_REXMT) && 1530 !tcp_timer_active(tp, TT_PERSIST)) { 1531 /* 1532 * Avoid a situation where we do not set persist timer 1533 * after a zero window condition. For example: 1534 * 1) A -> B: packet with enough data to fill the window 1535 * 2) B -> A: ACK for #1 + new data (0 window 1536 * advertisement) 1537 * 3) A -> B: ACK for #2, 0 len packet 1538 * 1539 * In this case, A will not activate the persist timer, 1540 * because it chose to send a packet. Unless tcp_output 1541 * is called for some other reason (delayed ack timer, 1542 * another input packet from B, socket syscall), A will 1543 * not send zero window probes. 1544 * 1545 * So, if you send a 0-length packet, but there is data 1546 * in the socket buffer, and neither the rexmt or 1547 * persist timer is already set, then activate the 1548 * persist timer. 1549 */ 1550 tp->t_rxtshift = 0; 1551 tcp_setpersist(tp); 1552 } 1553 } else { 1554 /* 1555 * Persist case, update snd_max but since we are in 1556 * persist mode (no window) we do not update snd_nxt. 1557 */ 1558 int xlen = len; 1559 if (flags & TH_SYN) 1560 ++xlen; 1561 if (flags & TH_FIN) { 1562 ++xlen; 1563 tp->t_flags |= TF_SENTFIN; 1564 } 1565 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1566 tp->snd_max = tp->snd_nxt + xlen; 1567 } 1568 if ((error == 0) && 1569 (TCPS_HAVEESTABLISHED(tp->t_state) && 1570 (tp->t_flags & TF_SACK_PERMIT) && 1571 tp->rcv_numsacks > 0)) { 1572 /* Clean up any DSACK's sent */ 1573 tcp_clean_dsack_blocks(tp); 1574 } 1575 if (error) { 1576 /* Record the error. */ 1577 TCP_LOG_EVENT(tp, NULL, &so->so_rcv, &so->so_snd, TCP_LOG_OUT, 1578 error, 0, NULL, false); 1579 1580 /* 1581 * We know that the packet was lost, so back out the 1582 * sequence number advance, if any. 1583 * 1584 * If the error is EPERM the packet got blocked by the 1585 * local firewall. Normally we should terminate the 1586 * connection but the blocking may have been spurious 1587 * due to a firewall reconfiguration cycle. So we treat 1588 * it like a packet loss and let the retransmit timer and 1589 * timeouts do their work over time. 1590 * XXX: It is a POLA question whether calling tcp_drop right 1591 * away would be the really correct behavior instead. 1592 */ 1593 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1594 !tcp_timer_active(tp, TT_PERSIST)) && 1595 ((flags & TH_SYN) == 0) && 1596 (error != EPERM)) { 1597 if (sack_rxmit) { 1598 p->rxmit -= len; 1599 tp->sackhint.sack_bytes_rexmit -= len; 1600 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1601 ("sackhint bytes rtx >= 0")); 1602 } else 1603 tp->snd_nxt -= len; 1604 } 1605 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1606 switch (error) { 1607 case EACCES: 1608 case EPERM: 1609 tp->t_softerror = error; 1610 return (error); 1611 case ENOBUFS: 1612 TCP_XMIT_TIMER_ASSERT(tp, len, flags); 1613 tp->snd_cwnd = tp->t_maxseg; 1614 return (0); 1615 case EMSGSIZE: 1616 /* 1617 * For some reason the interface we used initially 1618 * to send segments changed to another or lowered 1619 * its MTU. 1620 * If TSO was active we either got an interface 1621 * without TSO capabilits or TSO was turned off. 1622 * If we obtained mtu from ip_output() then update 1623 * it and try again. 1624 */ 1625 if (tso) 1626 tp->t_flags &= ~TF_TSO; 1627 if (mtu != 0) { 1628 tcp_mss_update(tp, -1, mtu, NULL, NULL); 1629 goto again; 1630 } 1631 return (error); 1632 case EHOSTDOWN: 1633 case EHOSTUNREACH: 1634 case ENETDOWN: 1635 case ENETUNREACH: 1636 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1637 tp->t_softerror = error; 1638 return (0); 1639 } 1640 /* FALLTHROUGH */ 1641 default: 1642 return (error); 1643 } 1644 } 1645 TCPSTAT_INC(tcps_sndtotal); 1646 1647 /* 1648 * Data sent (as far as we can tell). 1649 * If this advertises a larger window than any other segment, 1650 * then remember the size of the advertised window. 1651 * Any pending ACK has now been sent. 1652 */ 1653 if (SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1654 tp->rcv_adv = tp->rcv_nxt + recwin; 1655 tp->last_ack_sent = tp->rcv_nxt; 1656 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1657 if (tcp_timer_active(tp, TT_DELACK)) 1658 tcp_timer_activate(tp, TT_DELACK, 0); 1659 #if 0 1660 /* 1661 * This completely breaks TCP if newreno is turned on. What happens 1662 * is that if delayed-acks are turned on on the receiver, this code 1663 * on the transmitter effectively destroys the TCP window, forcing 1664 * it to four packets (1.5Kx4 = 6K window). 1665 */ 1666 if (sendalot && --maxburst) 1667 goto again; 1668 #endif 1669 if (sendalot) 1670 goto again; 1671 return (0); 1672 } 1673 1674 void 1675 tcp_setpersist(struct tcpcb *tp) 1676 { 1677 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1678 int tt; 1679 1680 tp->t_flags &= ~TF_PREVVALID; 1681 if (tcp_timer_active(tp, TT_REXMT)) 1682 panic("tcp_setpersist: retransmit pending"); 1683 /* 1684 * Start/restart persistence timer. 1685 */ 1686 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1687 tcp_persmin, tcp_persmax); 1688 tcp_timer_activate(tp, TT_PERSIST, tt); 1689 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1690 tp->t_rxtshift++; 1691 } 1692 1693 /* 1694 * Insert TCP options according to the supplied parameters to the place 1695 * optp in a consistent way. Can handle unaligned destinations. 1696 * 1697 * The order of the option processing is crucial for optimal packing and 1698 * alignment for the scarce option space. 1699 * 1700 * The optimal order for a SYN/SYN-ACK segment is: 1701 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1702 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1703 * 1704 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1705 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1706 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1707 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1708 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1709 */ 1710 int 1711 tcp_addoptions(struct tcpopt *to, u_char *optp) 1712 { 1713 u_int32_t mask, optlen = 0; 1714 1715 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1716 if ((to->to_flags & mask) != mask) 1717 continue; 1718 if (optlen == TCP_MAXOLEN) 1719 break; 1720 switch (to->to_flags & mask) { 1721 case TOF_MSS: 1722 while (optlen % 4) { 1723 optlen += TCPOLEN_NOP; 1724 *optp++ = TCPOPT_NOP; 1725 } 1726 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1727 continue; 1728 optlen += TCPOLEN_MAXSEG; 1729 *optp++ = TCPOPT_MAXSEG; 1730 *optp++ = TCPOLEN_MAXSEG; 1731 to->to_mss = htons(to->to_mss); 1732 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1733 optp += sizeof(to->to_mss); 1734 break; 1735 case TOF_SCALE: 1736 while (!optlen || optlen % 2 != 1) { 1737 optlen += TCPOLEN_NOP; 1738 *optp++ = TCPOPT_NOP; 1739 } 1740 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1741 continue; 1742 optlen += TCPOLEN_WINDOW; 1743 *optp++ = TCPOPT_WINDOW; 1744 *optp++ = TCPOLEN_WINDOW; 1745 *optp++ = to->to_wscale; 1746 break; 1747 case TOF_SACKPERM: 1748 while (optlen % 2) { 1749 optlen += TCPOLEN_NOP; 1750 *optp++ = TCPOPT_NOP; 1751 } 1752 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1753 continue; 1754 optlen += TCPOLEN_SACK_PERMITTED; 1755 *optp++ = TCPOPT_SACK_PERMITTED; 1756 *optp++ = TCPOLEN_SACK_PERMITTED; 1757 break; 1758 case TOF_TS: 1759 while (!optlen || optlen % 4 != 2) { 1760 optlen += TCPOLEN_NOP; 1761 *optp++ = TCPOPT_NOP; 1762 } 1763 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1764 continue; 1765 optlen += TCPOLEN_TIMESTAMP; 1766 *optp++ = TCPOPT_TIMESTAMP; 1767 *optp++ = TCPOLEN_TIMESTAMP; 1768 to->to_tsval = htonl(to->to_tsval); 1769 to->to_tsecr = htonl(to->to_tsecr); 1770 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1771 optp += sizeof(to->to_tsval); 1772 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1773 optp += sizeof(to->to_tsecr); 1774 break; 1775 case TOF_SIGNATURE: 1776 { 1777 int siglen = TCPOLEN_SIGNATURE - 2; 1778 1779 while (!optlen || optlen % 4 != 2) { 1780 optlen += TCPOLEN_NOP; 1781 *optp++ = TCPOPT_NOP; 1782 } 1783 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) { 1784 to->to_flags &= ~TOF_SIGNATURE; 1785 continue; 1786 } 1787 optlen += TCPOLEN_SIGNATURE; 1788 *optp++ = TCPOPT_SIGNATURE; 1789 *optp++ = TCPOLEN_SIGNATURE; 1790 to->to_signature = optp; 1791 while (siglen--) 1792 *optp++ = 0; 1793 break; 1794 } 1795 case TOF_SACK: 1796 { 1797 int sackblks = 0; 1798 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1799 tcp_seq sack_seq; 1800 1801 while (!optlen || optlen % 4 != 2) { 1802 optlen += TCPOLEN_NOP; 1803 *optp++ = TCPOPT_NOP; 1804 } 1805 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1806 continue; 1807 optlen += TCPOLEN_SACKHDR; 1808 *optp++ = TCPOPT_SACK; 1809 sackblks = min(to->to_nsacks, 1810 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1811 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1812 while (sackblks--) { 1813 sack_seq = htonl(sack->start); 1814 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1815 optp += sizeof(sack_seq); 1816 sack_seq = htonl(sack->end); 1817 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1818 optp += sizeof(sack_seq); 1819 optlen += TCPOLEN_SACK; 1820 sack++; 1821 } 1822 TCPSTAT_INC(tcps_sack_send_blocks); 1823 break; 1824 } 1825 case TOF_FASTOPEN: 1826 { 1827 int total_len; 1828 1829 /* XXX is there any point to aligning this option? */ 1830 total_len = TCPOLEN_FAST_OPEN_EMPTY + to->to_tfo_len; 1831 if (TCP_MAXOLEN - optlen < total_len) { 1832 to->to_flags &= ~TOF_FASTOPEN; 1833 continue; 1834 } 1835 *optp++ = TCPOPT_FAST_OPEN; 1836 *optp++ = total_len; 1837 if (to->to_tfo_len > 0) { 1838 bcopy(to->to_tfo_cookie, optp, to->to_tfo_len); 1839 optp += to->to_tfo_len; 1840 } 1841 optlen += total_len; 1842 break; 1843 } 1844 default: 1845 panic("%s: unknown TCP option type", __func__); 1846 break; 1847 } 1848 } 1849 1850 /* Terminate and pad TCP options to a 4 byte boundary. */ 1851 if (optlen % 4) { 1852 optlen += TCPOLEN_EOL; 1853 *optp++ = TCPOPT_EOL; 1854 } 1855 /* 1856 * According to RFC 793 (STD0007): 1857 * "The content of the header beyond the End-of-Option option 1858 * must be header padding (i.e., zero)." 1859 * and later: "The padding is composed of zeros." 1860 */ 1861 while (optlen % 4) { 1862 optlen += TCPOLEN_PAD; 1863 *optp++ = TCPOPT_PAD; 1864 } 1865 1866 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1867 return (optlen); 1868 } 1869 1870 /* 1871 * This is a copy of m_copym(), taking the TSO segment size/limit 1872 * constraints into account, and advancing the sndptr as it goes. 1873 */ 1874 struct mbuf * 1875 tcp_m_copym(struct mbuf *m, int32_t off0, int32_t *plen, 1876 int32_t seglimit, int32_t segsize, struct sockbuf *sb, bool hw_tls) 1877 { 1878 #ifdef KERN_TLS 1879 struct ktls_session *tls, *ntls; 1880 struct mbuf *start; 1881 #endif 1882 struct mbuf *n, **np; 1883 struct mbuf *top; 1884 int32_t off = off0; 1885 int32_t len = *plen; 1886 int32_t fragsize; 1887 int32_t len_cp = 0; 1888 int32_t *pkthdrlen; 1889 uint32_t mlen, frags; 1890 bool copyhdr; 1891 1892 1893 KASSERT(off >= 0, ("tcp_m_copym, negative off %d", off)); 1894 KASSERT(len >= 0, ("tcp_m_copym, negative len %d", len)); 1895 if (off == 0 && m->m_flags & M_PKTHDR) 1896 copyhdr = true; 1897 else 1898 copyhdr = false; 1899 while (off > 0) { 1900 KASSERT(m != NULL, ("tcp_m_copym, offset > size of mbuf chain")); 1901 if (off < m->m_len) 1902 break; 1903 off -= m->m_len; 1904 if ((sb) && (m == sb->sb_sndptr)) { 1905 sb->sb_sndptroff += m->m_len; 1906 sb->sb_sndptr = m->m_next; 1907 } 1908 m = m->m_next; 1909 } 1910 np = ⊤ 1911 top = NULL; 1912 pkthdrlen = NULL; 1913 #ifdef KERN_TLS 1914 if (hw_tls && (m->m_flags & M_EXTPG)) 1915 tls = m->m_epg_tls; 1916 else 1917 tls = NULL; 1918 start = m; 1919 #endif 1920 while (len > 0) { 1921 if (m == NULL) { 1922 KASSERT(len == M_COPYALL, 1923 ("tcp_m_copym, length > size of mbuf chain")); 1924 *plen = len_cp; 1925 if (pkthdrlen != NULL) 1926 *pkthdrlen = len_cp; 1927 break; 1928 } 1929 #ifdef KERN_TLS 1930 if (hw_tls) { 1931 if (m->m_flags & M_EXTPG) 1932 ntls = m->m_epg_tls; 1933 else 1934 ntls = NULL; 1935 1936 /* 1937 * Avoid mixing TLS records with handshake 1938 * data or TLS records from different 1939 * sessions. 1940 */ 1941 if (tls != ntls) { 1942 MPASS(m != start); 1943 *plen = len_cp; 1944 if (pkthdrlen != NULL) 1945 *pkthdrlen = len_cp; 1946 break; 1947 } 1948 1949 /* 1950 * Don't end a send in the middle of a TLS 1951 * record if it spans multiple TLS records. 1952 */ 1953 if (tls != NULL && (m != start) && len < m->m_len) { 1954 *plen = len_cp; 1955 if (pkthdrlen != NULL) 1956 *pkthdrlen = len_cp; 1957 break; 1958 } 1959 } 1960 #endif 1961 mlen = min(len, m->m_len - off); 1962 if (seglimit) { 1963 /* 1964 * For M_EXTPG mbufs, add 3 segments 1965 * + 1 in case we are crossing page boundaries 1966 * + 2 in case the TLS hdr/trailer are used 1967 * It is cheaper to just add the segments 1968 * than it is to take the cache miss to look 1969 * at the mbuf ext_pgs state in detail. 1970 */ 1971 if (m->m_flags & M_EXTPG) { 1972 fragsize = min(segsize, PAGE_SIZE); 1973 frags = 3; 1974 } else { 1975 fragsize = segsize; 1976 frags = 0; 1977 } 1978 1979 /* Break if we really can't fit anymore. */ 1980 if ((frags + 1) >= seglimit) { 1981 *plen = len_cp; 1982 if (pkthdrlen != NULL) 1983 *pkthdrlen = len_cp; 1984 break; 1985 } 1986 1987 /* 1988 * Reduce size if you can't copy the whole 1989 * mbuf. If we can't copy the whole mbuf, also 1990 * adjust len so the loop will end after this 1991 * mbuf. 1992 */ 1993 if ((frags + howmany(mlen, fragsize)) >= seglimit) { 1994 mlen = (seglimit - frags - 1) * fragsize; 1995 len = mlen; 1996 *plen = len_cp + len; 1997 if (pkthdrlen != NULL) 1998 *pkthdrlen = *plen; 1999 } 2000 frags += howmany(mlen, fragsize); 2001 if (frags == 0) 2002 frags++; 2003 seglimit -= frags; 2004 KASSERT(seglimit > 0, 2005 ("%s: seglimit went too low", __func__)); 2006 } 2007 if (copyhdr) 2008 n = m_gethdr(M_NOWAIT, m->m_type); 2009 else 2010 n = m_get(M_NOWAIT, m->m_type); 2011 *np = n; 2012 if (n == NULL) 2013 goto nospace; 2014 if (copyhdr) { 2015 if (!m_dup_pkthdr(n, m, M_NOWAIT)) 2016 goto nospace; 2017 if (len == M_COPYALL) 2018 n->m_pkthdr.len -= off0; 2019 else 2020 n->m_pkthdr.len = len; 2021 pkthdrlen = &n->m_pkthdr.len; 2022 copyhdr = false; 2023 } 2024 n->m_len = mlen; 2025 len_cp += n->m_len; 2026 if (m->m_flags & (M_EXT|M_EXTPG)) { 2027 n->m_data = m->m_data + off; 2028 mb_dupcl(n, m); 2029 } else 2030 bcopy(mtod(m, caddr_t)+off, mtod(n, caddr_t), 2031 (u_int)n->m_len); 2032 2033 if (sb && (sb->sb_sndptr == m) && 2034 ((n->m_len + off) >= m->m_len) && m->m_next) { 2035 sb->sb_sndptroff += m->m_len; 2036 sb->sb_sndptr = m->m_next; 2037 } 2038 off = 0; 2039 if (len != M_COPYALL) { 2040 len -= n->m_len; 2041 } 2042 m = m->m_next; 2043 np = &n->m_next; 2044 } 2045 return (top); 2046 nospace: 2047 m_freem(top); 2048 return (NULL); 2049 } 2050 2051 void 2052 tcp_sndbuf_autoscale(struct tcpcb *tp, struct socket *so, uint32_t sendwin) 2053 { 2054 2055 /* 2056 * Automatic sizing of send socket buffer. Often the send buffer 2057 * size is not optimally adjusted to the actual network conditions 2058 * at hand (delay bandwidth product). Setting the buffer size too 2059 * small limits throughput on links with high bandwidth and high 2060 * delay (eg. trans-continental/oceanic links). Setting the 2061 * buffer size too big consumes too much real kernel memory, 2062 * especially with many connections on busy servers. 2063 * 2064 * The criteria to step up the send buffer one notch are: 2065 * 1. receive window of remote host is larger than send buffer 2066 * (with a fudge factor of 5/4th); 2067 * 2. send buffer is filled to 7/8th with data (so we actually 2068 * have data to make use of it); 2069 * 3. send buffer fill has not hit maximal automatic size; 2070 * 4. our send window (slow start and cogestion controlled) is 2071 * larger than sent but unacknowledged data in send buffer. 2072 * 2073 * The remote host receive window scaling factor may limit the 2074 * growing of the send buffer before it reaches its allowed 2075 * maximum. 2076 * 2077 * It scales directly with slow start or congestion window 2078 * and does at most one step per received ACK. This fast 2079 * scaling has the drawback of growing the send buffer beyond 2080 * what is strictly necessary to make full use of a given 2081 * delay*bandwidth product. However testing has shown this not 2082 * to be much of an problem. At worst we are trading wasting 2083 * of available bandwidth (the non-use of it) for wasting some 2084 * socket buffer memory. 2085 * 2086 * TODO: Shrink send buffer during idle periods together 2087 * with congestion window. Requires another timer. Has to 2088 * wait for upcoming tcp timer rewrite. 2089 * 2090 * XXXGL: should there be used sbused() or sbavail()? 2091 */ 2092 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 2093 int lowat; 2094 2095 lowat = V_tcp_sendbuf_auto_lowat ? so->so_snd.sb_lowat : 0; 2096 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat - lowat && 2097 sbused(&so->so_snd) >= 2098 (so->so_snd.sb_hiwat / 8 * 7) - lowat && 2099 sbused(&so->so_snd) < V_tcp_autosndbuf_max && 2100 sendwin >= (sbused(&so->so_snd) - 2101 (tp->snd_nxt - tp->snd_una))) { 2102 if (!sbreserve_locked(&so->so_snd, 2103 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 2104 V_tcp_autosndbuf_max), so, curthread)) 2105 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 2106 } 2107 } 2108 } 2109