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 (tp->t_sndtime && ((ticks - tp->t_sndtime) >= tp->t_rxtcur)))) 265 cc_after_idle(tp); 266 tp->t_flags &= ~TF_LASTIDLE; 267 if (idle) { 268 if (tp->t_flags & TF_MORETOCOME) { 269 tp->t_flags |= TF_LASTIDLE; 270 idle = 0; 271 } 272 } 273 again: 274 /* 275 * If we've recently taken a timeout, snd_max will be greater than 276 * snd_nxt. There may be SACK information that allows us to avoid 277 * resending already delivered data. Adjust snd_nxt accordingly. 278 */ 279 if ((tp->t_flags & TF_SACK_PERMIT) && 280 SEQ_LT(tp->snd_nxt, tp->snd_max)) 281 tcp_sack_adjust(tp); 282 sendalot = 0; 283 tso = 0; 284 mtu = 0; 285 off = tp->snd_nxt - tp->snd_una; 286 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 287 288 flags = tcp_outflags[tp->t_state]; 289 /* 290 * Send any SACK-generated retransmissions. If we're explicitly trying 291 * to send out new data (when sendalot is 1), bypass this function. 292 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 293 * we're replacing a (future) new transmission with a retransmission 294 * now, and we previously incremented snd_cwnd in tcp_input(). 295 */ 296 /* 297 * Still in sack recovery , reset rxmit flag to zero. 298 */ 299 sack_rxmit = 0; 300 sack_bytes_rxmt = 0; 301 len = 0; 302 p = NULL; 303 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) && 304 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 305 uint32_t cwin; 306 307 cwin = 308 imax(min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt, 0); 309 /* Do not retransmit SACK segments beyond snd_recover */ 310 if (SEQ_GT(p->end, tp->snd_recover)) { 311 /* 312 * (At least) part of sack hole extends beyond 313 * snd_recover. Check to see if we can rexmit data 314 * for this hole. 315 */ 316 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 317 /* 318 * Can't rexmit any more data for this hole. 319 * That data will be rexmitted in the next 320 * sack recovery episode, when snd_recover 321 * moves past p->rxmit. 322 */ 323 p = NULL; 324 goto after_sack_rexmit; 325 } else 326 /* Can rexmit part of the current hole */ 327 len = ((int32_t)ulmin(cwin, 328 tp->snd_recover - p->rxmit)); 329 } else 330 len = ((int32_t)ulmin(cwin, p->end - p->rxmit)); 331 off = p->rxmit - tp->snd_una; 332 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 333 __func__, off)); 334 if (len > 0) { 335 sack_rxmit = 1; 336 sendalot = 1; 337 TCPSTAT_INC(tcps_sack_rexmits); 338 TCPSTAT_ADD(tcps_sack_rexmit_bytes, 339 min(len, tcp_maxseg(tp))); 340 } 341 } 342 after_sack_rexmit: 343 /* 344 * Get standard flags, and add SYN or FIN if requested by 'hidden' 345 * state flags. 346 */ 347 if (tp->t_flags & TF_NEEDFIN) 348 flags |= TH_FIN; 349 if (tp->t_flags & TF_NEEDSYN) 350 flags |= TH_SYN; 351 352 SOCKBUF_LOCK(&so->so_snd); 353 /* 354 * If in persist timeout with window of 0, send 1 byte. 355 * Otherwise, if window is small but nonzero 356 * and timer expired, we will send what we can 357 * and go to transmit state. 358 */ 359 if (tp->t_flags & TF_FORCEDATA) { 360 if (sendwin == 0) { 361 /* 362 * If we still have some data to send, then 363 * clear the FIN bit. Usually this would 364 * happen below when it realizes that we 365 * aren't sending all the data. However, 366 * if we have exactly 1 byte of unsent data, 367 * then it won't clear the FIN bit below, 368 * and if we are in persist state, we wind 369 * up sending the packet without recording 370 * that we sent the FIN bit. 371 * 372 * We can't just blindly clear the FIN bit, 373 * because if we don't have any more data 374 * to send then the probe will be the FIN 375 * itself. 376 */ 377 if (off < sbused(&so->so_snd)) 378 flags &= ~TH_FIN; 379 sendwin = 1; 380 } else { 381 tcp_timer_activate(tp, TT_PERSIST, 0); 382 tp->t_rxtshift = 0; 383 } 384 } 385 386 /* 387 * If snd_nxt == snd_max and we have transmitted a FIN, the 388 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 389 * a negative length. This can also occur when TCP opens up 390 * its congestion window while receiving additional duplicate 391 * acks after fast-retransmit because TCP will reset snd_nxt 392 * to snd_max after the fast-retransmit. 393 * 394 * In the normal retransmit-FIN-only case, however, snd_nxt will 395 * be set to snd_una, the offset will be 0, and the length may 396 * wind up 0. 397 * 398 * If sack_rxmit is true we are retransmitting from the scoreboard 399 * in which case len is already set. 400 */ 401 if (sack_rxmit == 0) { 402 if (sack_bytes_rxmt == 0) 403 len = ((int32_t)min(sbavail(&so->so_snd), sendwin) - 404 off); 405 else { 406 int32_t cwin; 407 408 /* 409 * We are inside of a SACK recovery episode and are 410 * sending new data, having retransmitted all the 411 * data possible in the scoreboard. 412 */ 413 len = ((int32_t)min(sbavail(&so->so_snd), tp->snd_wnd) - 414 off); 415 /* 416 * Don't remove this (len > 0) check ! 417 * We explicitly check for len > 0 here (although it 418 * isn't really necessary), to work around a gcc 419 * optimization issue - to force gcc to compute 420 * len above. Without this check, the computation 421 * of len is bungled by the optimizer. 422 */ 423 if (len > 0) { 424 cwin = tp->snd_cwnd - 425 (tp->snd_nxt - tp->snd_recover) - 426 sack_bytes_rxmt; 427 if (cwin < 0) 428 cwin = 0; 429 len = imin(len, cwin); 430 } 431 } 432 } 433 434 /* 435 * Lop off SYN bit if it has already been sent. However, if this 436 * is SYN-SENT state and if segment contains data and if we don't 437 * know that foreign host supports TAO, suppress sending segment. 438 */ 439 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 440 if (tp->t_state != TCPS_SYN_RECEIVED) 441 flags &= ~TH_SYN; 442 /* 443 * When sending additional segments following a TFO SYN|ACK, 444 * do not include the SYN bit. 445 */ 446 if (IS_FASTOPEN(tp->t_flags) && 447 (tp->t_state == TCPS_SYN_RECEIVED)) 448 flags &= ~TH_SYN; 449 off--, len++; 450 } 451 452 /* 453 * Be careful not to send data and/or FIN on SYN segments. 454 * This measure is needed to prevent interoperability problems 455 * with not fully conformant TCP implementations. 456 */ 457 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 458 len = 0; 459 flags &= ~TH_FIN; 460 } 461 462 /* 463 * On TFO sockets, ensure no data is sent in the following cases: 464 * 465 * - When retransmitting SYN|ACK on a passively-created socket 466 * 467 * - When retransmitting SYN on an actively created socket 468 * 469 * - When sending a zero-length cookie (cookie request) on an 470 * actively created socket 471 * 472 * - When the socket is in the CLOSED state (RST is being sent) 473 */ 474 if (IS_FASTOPEN(tp->t_flags) && 475 (((flags & TH_SYN) && (tp->t_rxtshift > 0)) || 476 ((tp->t_state == TCPS_SYN_SENT) && 477 (tp->t_tfo_client_cookie_len == 0)) || 478 (flags & TH_RST))) 479 len = 0; 480 if (len <= 0) { 481 /* 482 * If FIN has been sent but not acked, 483 * but we haven't been called to retransmit, 484 * len will be < 0. Otherwise, window shrank 485 * after we sent into it. If window shrank to 0, 486 * cancel pending retransmit, pull snd_nxt back 487 * to (closed) window, and set the persist timer 488 * if it isn't already going. If the window didn't 489 * close completely, just wait for an ACK. 490 * 491 * We also do a general check here to ensure that 492 * we will set the persist timer when we have data 493 * to send, but a 0-byte window. This makes sure 494 * the persist timer is set even if the packet 495 * hits one of the "goto send" lines below. 496 */ 497 len = 0; 498 if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) && 499 (off < (int) sbavail(&so->so_snd))) { 500 tcp_timer_activate(tp, TT_REXMT, 0); 501 tp->t_rxtshift = 0; 502 tp->snd_nxt = tp->snd_una; 503 if (!tcp_timer_active(tp, TT_PERSIST)) 504 tcp_setpersist(tp); 505 } 506 } 507 508 /* len will be >= 0 after this point. */ 509 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 510 511 tcp_sndbuf_autoscale(tp, so, sendwin); 512 513 /* 514 * Decide if we can use TCP Segmentation Offloading (if supported by 515 * hardware). 516 * 517 * TSO may only be used if we are in a pure bulk sending state. The 518 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 519 * IP options prevent using TSO. With TSO the TCP header is the same 520 * (except for the sequence number) for all generated packets. This 521 * makes it impossible to transmit any options which vary per generated 522 * segment or packet. 523 * 524 * IPv4 handling has a clear separation of ip options and ip header 525 * flags while IPv6 combines both in in6p_outputopts. ip6_optlen() does 526 * the right thing below to provide length of just ip options and thus 527 * checking for ipoptlen is enough to decide if ip options are present. 528 */ 529 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 530 /* 531 * Pre-calculate here as we save another lookup into the darknesses 532 * of IPsec that way and can actually decide if TSO is ok. 533 */ 534 #ifdef INET6 535 if (isipv6 && IPSEC_ENABLED(ipv6)) 536 ipsec_optlen = IPSEC_HDRSIZE(ipv6, tp->t_inpcb); 537 #ifdef INET 538 else 539 #endif 540 #endif /* INET6 */ 541 #ifdef INET 542 if (IPSEC_ENABLED(ipv4)) 543 ipsec_optlen = IPSEC_HDRSIZE(ipv4, tp->t_inpcb); 544 #endif /* INET */ 545 #endif /* IPSEC */ 546 #ifdef INET6 547 if (isipv6) 548 ipoptlen = ip6_optlen(tp->t_inpcb); 549 else 550 #endif 551 if (tp->t_inpcb->inp_options) 552 ipoptlen = tp->t_inpcb->inp_options->m_len - 553 offsetof(struct ipoption, ipopt_list); 554 else 555 ipoptlen = 0; 556 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 557 ipoptlen += ipsec_optlen; 558 #endif 559 560 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg && 561 ((tp->t_flags & TF_SIGNATURE) == 0) && 562 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 563 ipoptlen == 0 && !(flags & TH_SYN)) 564 tso = 1; 565 566 if (sack_rxmit) { 567 if (SEQ_LT(p->rxmit + len, tp->snd_una + sbused(&so->so_snd))) 568 flags &= ~TH_FIN; 569 } else { 570 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + 571 sbused(&so->so_snd))) 572 flags &= ~TH_FIN; 573 } 574 575 recwin = lmin(lmax(sbspace(&so->so_rcv), 0), 576 (long)TCP_MAXWIN << tp->rcv_scale); 577 578 /* 579 * Sender silly window avoidance. We transmit under the following 580 * conditions when len is non-zero: 581 * 582 * - We have a full segment (or more with TSO) 583 * - This is the last buffer in a write()/send() and we are 584 * either idle or running NODELAY 585 * - we've timed out (e.g. persist timer) 586 * - we have more then 1/2 the maximum send window's worth of 587 * data (receiver may be limited the window size) 588 * - we need to retransmit 589 */ 590 if (len) { 591 if (len >= tp->t_maxseg) 592 goto send; 593 /* 594 * As the TCP header options are now 595 * considered when setting up the initial 596 * window, we would not send the last segment 597 * if we skip considering the option length here. 598 * Note: this may not work when tcp headers change 599 * very dynamically in the future. 600 */ 601 if ((((tp->t_flags & TF_SIGNATURE) ? 602 PADTCPOLEN(TCPOLEN_SIGNATURE) : 0) + 603 ((tp->t_flags & TF_RCVD_TSTMP) ? 604 PADTCPOLEN(TCPOLEN_TIMESTAMP) : 0) + 605 len) >= tp->t_maxseg) 606 goto send; 607 /* 608 * NOTE! on localhost connections an 'ack' from the remote 609 * end may occur synchronously with the output and cause 610 * us to flush a buffer queued with moretocome. XXX 611 * 612 * note: the len + off check is almost certainly unnecessary. 613 */ 614 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 615 (idle || (tp->t_flags & TF_NODELAY)) && 616 (uint32_t)len + (uint32_t)off >= sbavail(&so->so_snd) && 617 (tp->t_flags & TF_NOPUSH) == 0) { 618 goto send; 619 } 620 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 621 goto send; 622 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 623 goto send; 624 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 625 goto send; 626 if (sack_rxmit) 627 goto send; 628 } 629 630 /* 631 * Sending of standalone window updates. 632 * 633 * Window updates are important when we close our window due to a 634 * full socket buffer and are opening it again after the application 635 * reads data from it. Once the window has opened again and the 636 * remote end starts to send again the ACK clock takes over and 637 * provides the most current window information. 638 * 639 * We must avoid the silly window syndrome whereas every read 640 * from the receive buffer, no matter how small, causes a window 641 * update to be sent. We also should avoid sending a flurry of 642 * window updates when the socket buffer had queued a lot of data 643 * and the application is doing small reads. 644 * 645 * Prevent a flurry of pointless window updates by only sending 646 * an update when we can increase the advertized window by more 647 * than 1/4th of the socket buffer capacity. When the buffer is 648 * getting full or is very small be more aggressive and send an 649 * update whenever we can increase by two mss sized segments. 650 * In all other situations the ACK's to new incoming data will 651 * carry further window increases. 652 * 653 * Don't send an independent window update if a delayed 654 * ACK is pending (it will get piggy-backed on it) or the 655 * remote side already has done a half-close and won't send 656 * more data. Skip this if the connection is in T/TCP 657 * half-open state. 658 */ 659 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 660 !(tp->t_flags & TF_DELACK) && 661 !TCPS_HAVERCVDFIN(tp->t_state)) { 662 /* 663 * "adv" is the amount we could increase the window, 664 * taking into account that we are limited by 665 * TCP_MAXWIN << tp->rcv_scale. 666 */ 667 int32_t adv; 668 int oldwin; 669 670 adv = recwin; 671 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { 672 oldwin = (tp->rcv_adv - tp->rcv_nxt); 673 if (adv > oldwin) 674 adv -= oldwin; 675 else 676 adv = 0; 677 } else 678 oldwin = 0; 679 680 /* 681 * If the new window size ends up being the same as or less 682 * than the old size when it is scaled, then don't force 683 * a window update. 684 */ 685 if (oldwin >> tp->rcv_scale >= (adv + oldwin) >> tp->rcv_scale) 686 goto dontupdate; 687 688 if (adv >= (int32_t)(2 * tp->t_maxseg) && 689 (adv >= (int32_t)(so->so_rcv.sb_hiwat / 4) || 690 recwin <= (so->so_rcv.sb_hiwat / 8) || 691 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg || 692 adv >= TCP_MAXWIN << tp->rcv_scale)) 693 goto send; 694 if (2 * adv >= (int32_t)so->so_rcv.sb_hiwat) 695 goto send; 696 } 697 dontupdate: 698 699 /* 700 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 701 * is also a catch-all for the retransmit timer timeout case. 702 */ 703 if (tp->t_flags & TF_ACKNOW) 704 goto send; 705 if ((flags & TH_RST) || 706 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 707 goto send; 708 if (SEQ_GT(tp->snd_up, tp->snd_una)) 709 goto send; 710 /* 711 * If our state indicates that FIN should be sent 712 * and we have not yet done so, then we need to send. 713 */ 714 if (flags & TH_FIN && 715 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 716 goto send; 717 /* 718 * In SACK, it is possible for tcp_output to fail to send a segment 719 * after the retransmission timer has been turned off. Make sure 720 * that the retransmission timer is set. 721 */ 722 if ((tp->t_flags & TF_SACK_PERMIT) && 723 SEQ_GT(tp->snd_max, tp->snd_una) && 724 !tcp_timer_active(tp, TT_REXMT) && 725 !tcp_timer_active(tp, TT_PERSIST)) { 726 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 727 goto just_return; 728 } 729 /* 730 * TCP window updates are not reliable, rather a polling protocol 731 * using ``persist'' packets is used to insure receipt of window 732 * updates. The three ``states'' for the output side are: 733 * idle not doing retransmits or persists 734 * persisting to move a small or zero window 735 * (re)transmitting and thereby not persisting 736 * 737 * tcp_timer_active(tp, TT_PERSIST) 738 * is true when we are in persist state. 739 * (tp->t_flags & TF_FORCEDATA) 740 * is set when we are called to send a persist packet. 741 * tcp_timer_active(tp, TT_REXMT) 742 * is set when we are retransmitting 743 * The output side is idle when both timers are zero. 744 * 745 * If send window is too small, there is data to transmit, and no 746 * retransmit or persist is pending, then go to persist state. 747 * If nothing happens soon, send when timer expires: 748 * if window is nonzero, transmit what we can, 749 * otherwise force out a byte. 750 */ 751 if (sbavail(&so->so_snd) && !tcp_timer_active(tp, TT_REXMT) && 752 !tcp_timer_active(tp, TT_PERSIST)) { 753 tp->t_rxtshift = 0; 754 tcp_setpersist(tp); 755 } 756 757 /* 758 * No reason to send a segment, just return. 759 */ 760 just_return: 761 SOCKBUF_UNLOCK(&so->so_snd); 762 return (0); 763 764 send: 765 SOCKBUF_LOCK_ASSERT(&so->so_snd); 766 if (len > 0) { 767 if (len >= tp->t_maxseg) 768 tp->t_flags2 |= TF2_PLPMTU_MAXSEGSNT; 769 else 770 tp->t_flags2 &= ~TF2_PLPMTU_MAXSEGSNT; 771 } 772 /* 773 * Before ESTABLISHED, force sending of initial options 774 * unless TCP set not to do any options. 775 * NOTE: we assume that the IP/TCP header plus TCP options 776 * always fit in a single mbuf, leaving room for a maximum 777 * link header, i.e. 778 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 779 */ 780 optlen = 0; 781 #ifdef INET6 782 if (isipv6) 783 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 784 else 785 #endif 786 hdrlen = sizeof (struct tcpiphdr); 787 788 /* 789 * Compute options for segment. 790 * We only have to care about SYN and established connection 791 * segments. Options for SYN-ACK segments are handled in TCP 792 * syncache. 793 */ 794 to.to_flags = 0; 795 if ((tp->t_flags & TF_NOOPT) == 0) { 796 /* Maximum segment size. */ 797 if (flags & TH_SYN) { 798 tp->snd_nxt = tp->iss; 799 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 800 to.to_flags |= TOF_MSS; 801 802 /* 803 * On SYN or SYN|ACK transmits on TFO connections, 804 * only include the TFO option if it is not a 805 * retransmit, as the presence of the TFO option may 806 * have caused the original SYN or SYN|ACK to have 807 * been dropped by a middlebox. 808 */ 809 if (IS_FASTOPEN(tp->t_flags) && 810 (tp->t_rxtshift == 0)) { 811 if (tp->t_state == TCPS_SYN_RECEIVED) { 812 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN; 813 to.to_tfo_cookie = 814 (u_int8_t *)&tp->t_tfo_cookie.server; 815 to.to_flags |= TOF_FASTOPEN; 816 wanted_cookie = 1; 817 } else if (tp->t_state == TCPS_SYN_SENT) { 818 to.to_tfo_len = 819 tp->t_tfo_client_cookie_len; 820 to.to_tfo_cookie = 821 tp->t_tfo_cookie.client; 822 to.to_flags |= TOF_FASTOPEN; 823 wanted_cookie = 1; 824 /* 825 * If we wind up having more data to 826 * send with the SYN than can fit in 827 * one segment, don't send any more 828 * until the SYN|ACK comes back from 829 * the other end. 830 */ 831 dont_sendalot = 1; 832 } 833 } 834 } 835 /* Window scaling. */ 836 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 837 to.to_wscale = tp->request_r_scale; 838 to.to_flags |= TOF_SCALE; 839 } 840 /* Timestamps. */ 841 if ((tp->t_flags & TF_RCVD_TSTMP) || 842 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 843 curticks = tcp_ts_getticks(); 844 to.to_tsval = curticks + tp->ts_offset; 845 to.to_tsecr = tp->ts_recent; 846 to.to_flags |= TOF_TS; 847 if (tp->t_rxtshift == 1) 848 tp->t_badrxtwin = curticks; 849 } 850 851 /* Set receive buffer autosizing timestamp. */ 852 if (tp->rfbuf_ts == 0 && 853 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 854 tp->rfbuf_ts = tcp_ts_getticks(); 855 856 /* Selective ACK's. */ 857 if (tp->t_flags & TF_SACK_PERMIT) { 858 if (flags & TH_SYN) 859 to.to_flags |= TOF_SACKPERM; 860 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 861 tp->rcv_numsacks > 0) { 862 to.to_flags |= TOF_SACK; 863 to.to_nsacks = tp->rcv_numsacks; 864 to.to_sacks = (u_char *)tp->sackblks; 865 } 866 } 867 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 868 /* TCP-MD5 (RFC2385). */ 869 /* 870 * Check that TCP_MD5SIG is enabled in tcpcb to 871 * account the size needed to set this TCP option. 872 */ 873 if (tp->t_flags & TF_SIGNATURE) 874 to.to_flags |= TOF_SIGNATURE; 875 #endif /* TCP_SIGNATURE */ 876 877 /* Processing the options. */ 878 hdrlen += optlen = tcp_addoptions(&to, opt); 879 /* 880 * If we wanted a TFO option to be added, but it was unable 881 * to fit, ensure no data is sent. 882 */ 883 if (IS_FASTOPEN(tp->t_flags) && wanted_cookie && 884 !(to.to_flags & TOF_FASTOPEN)) 885 len = 0; 886 } 887 888 /* 889 * Adjust data length if insertion of options will 890 * bump the packet length beyond the t_maxseg length. 891 * Clear the FIN bit because we cut off the tail of 892 * the segment. 893 */ 894 if (len + optlen + ipoptlen > tp->t_maxseg) { 895 flags &= ~TH_FIN; 896 897 if (tso) { 898 u_int if_hw_tsomax; 899 u_int moff; 900 int max_len; 901 902 /* extract TSO information */ 903 if_hw_tsomax = tp->t_tsomax; 904 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount; 905 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize; 906 907 /* 908 * Limit a TSO burst to prevent it from 909 * overflowing or exceeding the maximum length 910 * allowed by the network interface: 911 */ 912 KASSERT(ipoptlen == 0, 913 ("%s: TSO can't do IP options", __func__)); 914 915 /* 916 * Check if we should limit by maximum payload 917 * length: 918 */ 919 if (if_hw_tsomax != 0) { 920 /* compute maximum TSO length */ 921 max_len = (if_hw_tsomax - hdrlen - 922 max_linkhdr); 923 if (max_len <= 0) { 924 len = 0; 925 } else if (len > max_len) { 926 sendalot = 1; 927 len = max_len; 928 } 929 } 930 931 /* 932 * Prevent the last segment from being 933 * fractional unless the send sockbuf can be 934 * emptied: 935 */ 936 max_len = (tp->t_maxseg - optlen); 937 if (((uint32_t)off + (uint32_t)len) < 938 sbavail(&so->so_snd)) { 939 moff = len % max_len; 940 if (moff != 0) { 941 len -= moff; 942 sendalot = 1; 943 } 944 } 945 946 /* 947 * In case there are too many small fragments 948 * don't use TSO: 949 */ 950 if (len <= max_len) { 951 len = max_len; 952 sendalot = 1; 953 tso = 0; 954 } 955 956 /* 957 * Send the FIN in a separate segment 958 * after the bulk sending is done. 959 * We don't trust the TSO implementations 960 * to clear the FIN flag on all but the 961 * last segment. 962 */ 963 if (tp->t_flags & TF_NEEDFIN) 964 sendalot = 1; 965 } else { 966 if (optlen + ipoptlen >= tp->t_maxseg) { 967 /* 968 * Since we don't have enough space to put 969 * the IP header chain and the TCP header in 970 * one packet as required by RFC 7112, don't 971 * send it. Also ensure that at least one 972 * byte of the payload can be put into the 973 * TCP segment. 974 */ 975 SOCKBUF_UNLOCK(&so->so_snd); 976 error = EMSGSIZE; 977 sack_rxmit = 0; 978 goto out; 979 } 980 len = tp->t_maxseg - optlen - ipoptlen; 981 sendalot = 1; 982 if (dont_sendalot) 983 sendalot = 0; 984 } 985 } else 986 tso = 0; 987 988 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 989 ("%s: len > IP_MAXPACKET", __func__)); 990 991 /*#ifdef DIAGNOSTIC*/ 992 #ifdef INET6 993 if (max_linkhdr + hdrlen > MCLBYTES) 994 #else 995 if (max_linkhdr + hdrlen > MHLEN) 996 #endif 997 panic("tcphdr too big"); 998 /*#endif*/ 999 1000 /* 1001 * This KASSERT is here to catch edge cases at a well defined place. 1002 * Before, those had triggered (random) panic conditions further down. 1003 */ 1004 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 1005 1006 /* 1007 * Grab a header mbuf, attaching a copy of data to 1008 * be transmitted, and initialize the header from 1009 * the template for sends on this connection. 1010 */ 1011 if (len) { 1012 struct mbuf *mb; 1013 struct sockbuf *msb; 1014 u_int moff; 1015 1016 if ((tp->t_flags & TF_FORCEDATA) && len == 1) { 1017 TCPSTAT_INC(tcps_sndprobe); 1018 #ifdef STATS 1019 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1020 stats_voi_update_abs_u32(tp->t_stats, 1021 VOI_TCP_RETXPB, len); 1022 else 1023 stats_voi_update_abs_u64(tp->t_stats, 1024 VOI_TCP_TXPB, len); 1025 #endif /* STATS */ 1026 } else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 1027 tp->t_sndrexmitpack++; 1028 TCPSTAT_INC(tcps_sndrexmitpack); 1029 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 1030 #ifdef STATS 1031 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_RETXPB, 1032 len); 1033 #endif /* STATS */ 1034 } else { 1035 TCPSTAT_INC(tcps_sndpack); 1036 TCPSTAT_ADD(tcps_sndbyte, len); 1037 #ifdef STATS 1038 stats_voi_update_abs_u64(tp->t_stats, VOI_TCP_TXPB, 1039 len); 1040 #endif /* STATS */ 1041 } 1042 #ifdef INET6 1043 if (MHLEN < hdrlen + max_linkhdr) 1044 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR); 1045 else 1046 #endif 1047 m = m_gethdr(M_NOWAIT, MT_DATA); 1048 1049 if (m == NULL) { 1050 SOCKBUF_UNLOCK(&so->so_snd); 1051 error = ENOBUFS; 1052 sack_rxmit = 0; 1053 goto out; 1054 } 1055 1056 m->m_data += max_linkhdr; 1057 m->m_len = hdrlen; 1058 1059 /* 1060 * Start the m_copy functions from the closest mbuf 1061 * to the offset in the socket buffer chain. 1062 */ 1063 mb = sbsndptr_noadv(&so->so_snd, off, &moff); 1064 if (len <= MHLEN - hdrlen - max_linkhdr && !hw_tls) { 1065 m_copydata(mb, moff, len, 1066 mtod(m, caddr_t) + hdrlen); 1067 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1068 sbsndptr_adv(&so->so_snd, mb, len); 1069 m->m_len += len; 1070 } else { 1071 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1072 msb = NULL; 1073 else 1074 msb = &so->so_snd; 1075 m->m_next = tcp_m_copym(mb, moff, 1076 &len, if_hw_tsomaxsegcount, 1077 if_hw_tsomaxsegsize, msb, hw_tls); 1078 if (len <= (tp->t_maxseg - optlen)) { 1079 /* 1080 * Must have ran out of mbufs for the copy 1081 * shorten it to no longer need tso. Lets 1082 * not put on sendalot since we are low on 1083 * mbufs. 1084 */ 1085 tso = 0; 1086 } 1087 if (m->m_next == NULL) { 1088 SOCKBUF_UNLOCK(&so->so_snd); 1089 (void) m_free(m); 1090 error = ENOBUFS; 1091 sack_rxmit = 0; 1092 goto out; 1093 } 1094 } 1095 1096 /* 1097 * If we're sending everything we've got, set PUSH. 1098 * (This will keep happy those implementations which only 1099 * give data to the user when a buffer fills or 1100 * a PUSH comes in.) 1101 */ 1102 if (((uint32_t)off + (uint32_t)len == sbused(&so->so_snd)) && 1103 !(flags & TH_SYN)) 1104 flags |= TH_PUSH; 1105 SOCKBUF_UNLOCK(&so->so_snd); 1106 } else { 1107 SOCKBUF_UNLOCK(&so->so_snd); 1108 if (tp->t_flags & TF_ACKNOW) 1109 TCPSTAT_INC(tcps_sndacks); 1110 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 1111 TCPSTAT_INC(tcps_sndctrl); 1112 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 1113 TCPSTAT_INC(tcps_sndurg); 1114 else 1115 TCPSTAT_INC(tcps_sndwinup); 1116 1117 m = m_gethdr(M_NOWAIT, MT_DATA); 1118 if (m == NULL) { 1119 error = ENOBUFS; 1120 sack_rxmit = 0; 1121 goto out; 1122 } 1123 #ifdef INET6 1124 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 1125 MHLEN >= hdrlen) { 1126 M_ALIGN(m, hdrlen); 1127 } else 1128 #endif 1129 m->m_data += max_linkhdr; 1130 m->m_len = hdrlen; 1131 } 1132 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 1133 m->m_pkthdr.rcvif = (struct ifnet *)0; 1134 #ifdef MAC 1135 mac_inpcb_create_mbuf(tp->t_inpcb, m); 1136 #endif 1137 #ifdef INET6 1138 if (isipv6) { 1139 ip6 = mtod(m, struct ip6_hdr *); 1140 th = (struct tcphdr *)(ip6 + 1); 1141 tcpip_fillheaders(tp->t_inpcb, ip6, th); 1142 } else 1143 #endif /* INET6 */ 1144 { 1145 ip = mtod(m, struct ip *); 1146 #ifdef TCPDEBUG 1147 ipov = (struct ipovly *)ip; 1148 #endif 1149 th = (struct tcphdr *)(ip + 1); 1150 tcpip_fillheaders(tp->t_inpcb, ip, th); 1151 } 1152 1153 /* 1154 * Fill in fields, remembering maximum advertised 1155 * window for use in delaying messages about window sizes. 1156 * If resending a FIN, be sure not to use a new sequence number. 1157 */ 1158 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 1159 tp->snd_nxt == tp->snd_max) 1160 tp->snd_nxt--; 1161 /* 1162 * If we are starting a connection, send ECN setup 1163 * SYN packet. If we are on a retransmit, we may 1164 * resend those bits a number of times as per 1165 * RFC 3168. 1166 */ 1167 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn == 1) { 1168 if (tp->t_rxtshift >= 1) { 1169 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 1170 flags |= TH_ECE|TH_CWR; 1171 } else 1172 flags |= TH_ECE|TH_CWR; 1173 } 1174 /* Handle parallel SYN for ECN */ 1175 if ((tp->t_state == TCPS_SYN_RECEIVED) && 1176 (tp->t_flags2 & TF2_ECN_SND_ECE)) { 1177 flags |= TH_ECE; 1178 tp->t_flags2 &= ~TF2_ECN_SND_ECE; 1179 } 1180 1181 if (tp->t_state == TCPS_ESTABLISHED && 1182 (tp->t_flags2 & TF2_ECN_PERMIT)) { 1183 /* 1184 * If the peer has ECN, mark data packets with 1185 * ECN capable transmission (ECT). 1186 * Ignore pure ack packets, retransmissions and window probes. 1187 */ 1188 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 1189 (sack_rxmit == 0) && 1190 !((tp->t_flags & TF_FORCEDATA) && len == 1 && 1191 SEQ_LT(tp->snd_una, tp->snd_max))) { 1192 #ifdef INET6 1193 if (isipv6) 1194 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 1195 else 1196 #endif 1197 ip->ip_tos |= IPTOS_ECN_ECT0; 1198 TCPSTAT_INC(tcps_ecn_ect0); 1199 /* 1200 * Reply with proper ECN notifications. 1201 * Only set CWR on new data segments. 1202 */ 1203 if (tp->t_flags2 & TF2_ECN_SND_CWR) { 1204 flags |= TH_CWR; 1205 tp->t_flags2 &= ~TF2_ECN_SND_CWR; 1206 } 1207 } 1208 if (tp->t_flags2 & TF2_ECN_SND_ECE) 1209 flags |= TH_ECE; 1210 } 1211 1212 /* 1213 * If we are doing retransmissions, then snd_nxt will 1214 * not reflect the first unsent octet. For ACK only 1215 * packets, we do not want the sequence number of the 1216 * retransmitted packet, we want the sequence number 1217 * of the next unsent octet. So, if there is no data 1218 * (and no SYN or FIN), use snd_max instead of snd_nxt 1219 * when filling in ti_seq. But if we are in persist 1220 * state, snd_max might reflect one byte beyond the 1221 * right edge of the window, so use snd_nxt in that 1222 * case, since we know we aren't doing a retransmission. 1223 * (retransmit and persist are mutually exclusive...) 1224 */ 1225 if (sack_rxmit == 0) { 1226 if (len || (flags & (TH_SYN|TH_FIN)) || 1227 tcp_timer_active(tp, TT_PERSIST)) 1228 th->th_seq = htonl(tp->snd_nxt); 1229 else 1230 th->th_seq = htonl(tp->snd_max); 1231 } else { 1232 th->th_seq = htonl(p->rxmit); 1233 p->rxmit += len; 1234 tp->sackhint.sack_bytes_rexmit += len; 1235 } 1236 th->th_ack = htonl(tp->rcv_nxt); 1237 if (optlen) { 1238 bcopy(opt, th + 1, optlen); 1239 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1240 } 1241 th->th_flags = flags; 1242 /* 1243 * Calculate receive window. Don't shrink window, 1244 * but avoid silly window syndrome. 1245 * If a RST segment is sent, advertise a window of zero. 1246 */ 1247 if (flags & TH_RST) { 1248 recwin = 0; 1249 } else { 1250 if (recwin < (so->so_rcv.sb_hiwat / 4) && 1251 recwin < tp->t_maxseg) 1252 recwin = 0; 1253 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1254 recwin < (tp->rcv_adv - tp->rcv_nxt)) 1255 recwin = (tp->rcv_adv - tp->rcv_nxt); 1256 } 1257 /* 1258 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1259 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1260 * case is handled in syncache. 1261 */ 1262 if (flags & TH_SYN) 1263 th->th_win = htons((u_short) 1264 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1265 else { 1266 /* Avoid shrinking window with window scaling. */ 1267 recwin = roundup2(recwin, 1 << tp->rcv_scale); 1268 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1269 } 1270 1271 /* 1272 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1273 * a 0 window. This may cause the remote transmitter to stall. This 1274 * flag tells soreceive() to disable delayed acknowledgements when 1275 * draining the buffer. This can occur if the receiver is attempting 1276 * to read more data than can be buffered prior to transmitting on 1277 * the connection. 1278 */ 1279 if (th->th_win == 0) { 1280 tp->t_sndzerowin++; 1281 tp->t_flags |= TF_RXWIN0SENT; 1282 } else 1283 tp->t_flags &= ~TF_RXWIN0SENT; 1284 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1285 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1286 th->th_flags |= TH_URG; 1287 } else 1288 /* 1289 * If no urgent pointer to send, then we pull 1290 * the urgent pointer to the left edge of the send window 1291 * so that it doesn't drift into the send window on sequence 1292 * number wraparound. 1293 */ 1294 tp->snd_up = tp->snd_una; /* drag it along */ 1295 1296 /* 1297 * Put TCP length in extended header, and then 1298 * checksum extended header and data. 1299 */ 1300 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1301 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1302 1303 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1304 if (to.to_flags & TOF_SIGNATURE) { 1305 /* 1306 * Calculate MD5 signature and put it into the place 1307 * determined before. 1308 * NOTE: since TCP options buffer doesn't point into 1309 * mbuf's data, calculate offset and use it. 1310 */ 1311 if (!TCPMD5_ENABLED() || (error = TCPMD5_OUTPUT(m, th, 1312 (u_char *)(th + 1) + (to.to_signature - opt))) != 0) { 1313 /* 1314 * Do not send segment if the calculation of MD5 1315 * digest has failed. 1316 */ 1317 m_freem(m); 1318 goto out; 1319 } 1320 } 1321 #endif 1322 #ifdef INET6 1323 if (isipv6) { 1324 /* 1325 * There is no need to fill in ip6_plen right now. 1326 * It will be filled later by ip6_output. 1327 */ 1328 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1329 th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) + 1330 optlen + len, IPPROTO_TCP, 0); 1331 } 1332 #endif 1333 #if defined(INET6) && defined(INET) 1334 else 1335 #endif 1336 #ifdef INET 1337 { 1338 m->m_pkthdr.csum_flags = CSUM_TCP; 1339 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1340 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1341 1342 /* IP version must be set here for ipv4/ipv6 checking later */ 1343 KASSERT(ip->ip_v == IPVERSION, 1344 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1345 } 1346 #endif 1347 1348 /* 1349 * Enable TSO and specify the size of the segments. 1350 * The TCP pseudo header checksum is always provided. 1351 */ 1352 if (tso) { 1353 KASSERT(len > tp->t_maxseg - optlen, 1354 ("%s: len <= tso_segsz", __func__)); 1355 m->m_pkthdr.csum_flags |= CSUM_TSO; 1356 m->m_pkthdr.tso_segsz = tp->t_maxseg - optlen; 1357 } 1358 1359 KASSERT(len + hdrlen == m_length(m, NULL), 1360 ("%s: mbuf chain shorter than expected: %d + %u != %u", 1361 __func__, len, hdrlen, m_length(m, NULL))); 1362 1363 #ifdef TCP_HHOOK 1364 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1365 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1366 #endif 1367 1368 #ifdef TCPDEBUG 1369 /* 1370 * Trace. 1371 */ 1372 if (so->so_options & SO_DEBUG) { 1373 u_short save = 0; 1374 #ifdef INET6 1375 if (!isipv6) 1376 #endif 1377 { 1378 save = ipov->ih_len; 1379 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1380 } 1381 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1382 #ifdef INET6 1383 if (!isipv6) 1384 #endif 1385 ipov->ih_len = save; 1386 } 1387 #endif /* TCPDEBUG */ 1388 TCP_PROBE3(debug__output, tp, th, m); 1389 1390 /* We're getting ready to send; log now. */ 1391 TCP_LOG_EVENT(tp, th, &so->so_rcv, &so->so_snd, TCP_LOG_OUT, ERRNO_UNK, 1392 len, NULL, false); 1393 1394 /* 1395 * Fill in IP length and desired time to live and 1396 * send to IP level. There should be a better way 1397 * to handle ttl and tos; we could keep them in 1398 * the template, but need a way to checksum without them. 1399 */ 1400 /* 1401 * m->m_pkthdr.len should have been set before checksum calculation, 1402 * because in6_cksum() need it. 1403 */ 1404 #ifdef INET6 1405 if (isipv6) { 1406 /* 1407 * we separately set hoplimit for every segment, since the 1408 * user might want to change the value via setsockopt. 1409 * Also, desired default hop limit might be changed via 1410 * Neighbor Discovery. 1411 */ 1412 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1413 1414 /* 1415 * Set the packet size here for the benefit of DTrace probes. 1416 * ip6_output() will set it properly; it's supposed to include 1417 * the option header lengths as well. 1418 */ 1419 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6)); 1420 1421 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) 1422 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1423 else 1424 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1425 1426 if (tp->t_state == TCPS_SYN_SENT) 1427 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th); 1428 1429 TCP_PROBE5(send, NULL, tp, ip6, tp, th); 1430 1431 #ifdef TCPPCAP 1432 /* Save packet, if requested. */ 1433 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1434 #endif 1435 1436 /* TODO: IPv6 IP6TOS_ECT bit on */ 1437 error = ip6_output(m, tp->t_inpcb->in6p_outputopts, 1438 &tp->t_inpcb->inp_route6, 1439 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 1440 NULL, NULL, tp->t_inpcb); 1441 1442 if (error == EMSGSIZE && tp->t_inpcb->inp_route6.ro_nh != NULL) 1443 mtu = tp->t_inpcb->inp_route6.ro_nh->nh_mtu; 1444 } 1445 #endif /* INET6 */ 1446 #if defined(INET) && defined(INET6) 1447 else 1448 #endif 1449 #ifdef INET 1450 { 1451 ip->ip_len = htons(m->m_pkthdr.len); 1452 #ifdef INET6 1453 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1454 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1455 #endif /* INET6 */ 1456 /* 1457 * If we do path MTU discovery, then we set DF on every packet. 1458 * This might not be the best thing to do according to RFC3390 1459 * Section 2. However the tcp hostcache migitates the problem 1460 * so it affects only the first tcp connection with a host. 1461 * 1462 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1463 */ 1464 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) { 1465 ip->ip_off |= htons(IP_DF); 1466 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1467 } else { 1468 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1469 } 1470 1471 if (tp->t_state == TCPS_SYN_SENT) 1472 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th); 1473 1474 TCP_PROBE5(send, NULL, tp, ip, tp, th); 1475 1476 #ifdef TCPPCAP 1477 /* Save packet, if requested. */ 1478 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1479 #endif 1480 1481 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, 1482 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1483 tp->t_inpcb); 1484 1485 if (error == EMSGSIZE && tp->t_inpcb->inp_route.ro_nh != NULL) 1486 mtu = tp->t_inpcb->inp_route.ro_nh->nh_mtu; 1487 } 1488 #endif /* INET */ 1489 1490 out: 1491 /* 1492 * In transmit state, time the transmission and arrange for 1493 * the retransmit. In persist state, just set snd_max. 1494 */ 1495 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1496 !tcp_timer_active(tp, TT_PERSIST)) { 1497 tcp_seq startseq = tp->snd_nxt; 1498 1499 /* 1500 * Advance snd_nxt over sequence space of this segment. 1501 */ 1502 if (flags & (TH_SYN|TH_FIN)) { 1503 if (flags & TH_SYN) 1504 tp->snd_nxt++; 1505 if (flags & TH_FIN) { 1506 tp->snd_nxt++; 1507 tp->t_flags |= TF_SENTFIN; 1508 } 1509 } 1510 if (sack_rxmit) 1511 goto timer; 1512 tp->snd_nxt += len; 1513 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1514 tp->snd_max = tp->snd_nxt; 1515 /* 1516 * Time this transmission if not a retransmission and 1517 * not currently timing anything. 1518 */ 1519 tp->t_sndtime = ticks; 1520 if (tp->t_rtttime == 0) { 1521 tp->t_rtttime = ticks; 1522 tp->t_rtseq = startseq; 1523 TCPSTAT_INC(tcps_segstimed); 1524 } 1525 #ifdef STATS 1526 if (!(tp->t_flags & TF_GPUTINPROG) && len) { 1527 tp->t_flags |= TF_GPUTINPROG; 1528 tp->gput_seq = startseq; 1529 tp->gput_ack = startseq + 1530 ulmin(sbavail(&so->so_snd) - off, sendwin); 1531 tp->gput_ts = tcp_ts_getticks(); 1532 } 1533 #endif /* STATS */ 1534 } 1535 1536 /* 1537 * Set retransmit timer if not currently set, 1538 * and not doing a pure ack or a keep-alive probe. 1539 * Initial value for retransmit timer is smoothed 1540 * round-trip time + 2 * round-trip time variance. 1541 * Initialize shift counter which is used for backoff 1542 * of retransmit time. 1543 */ 1544 timer: 1545 if (!tcp_timer_active(tp, TT_REXMT) && 1546 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1547 (tp->snd_nxt != tp->snd_una))) { 1548 if (tcp_timer_active(tp, TT_PERSIST)) { 1549 tcp_timer_activate(tp, TT_PERSIST, 0); 1550 tp->t_rxtshift = 0; 1551 } 1552 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1553 } else if (len == 0 && sbavail(&so->so_snd) && 1554 !tcp_timer_active(tp, TT_REXMT) && 1555 !tcp_timer_active(tp, TT_PERSIST)) { 1556 /* 1557 * Avoid a situation where we do not set persist timer 1558 * after a zero window condition. For example: 1559 * 1) A -> B: packet with enough data to fill the window 1560 * 2) B -> A: ACK for #1 + new data (0 window 1561 * advertisement) 1562 * 3) A -> B: ACK for #2, 0 len packet 1563 * 1564 * In this case, A will not activate the persist timer, 1565 * because it chose to send a packet. Unless tcp_output 1566 * is called for some other reason (delayed ack timer, 1567 * another input packet from B, socket syscall), A will 1568 * not send zero window probes. 1569 * 1570 * So, if you send a 0-length packet, but there is data 1571 * in the socket buffer, and neither the rexmt or 1572 * persist timer is already set, then activate the 1573 * persist timer. 1574 */ 1575 tp->t_rxtshift = 0; 1576 tcp_setpersist(tp); 1577 } 1578 } else { 1579 /* 1580 * Persist case, update snd_max but since we are in 1581 * persist mode (no window) we do not update snd_nxt. 1582 */ 1583 int xlen = len; 1584 if (flags & TH_SYN) 1585 ++xlen; 1586 if (flags & TH_FIN) { 1587 ++xlen; 1588 tp->t_flags |= TF_SENTFIN; 1589 } 1590 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1591 tp->snd_max = tp->snd_nxt + xlen; 1592 } 1593 if ((error == 0) && 1594 (TCPS_HAVEESTABLISHED(tp->t_state) && 1595 (tp->t_flags & TF_SACK_PERMIT) && 1596 tp->rcv_numsacks > 0)) { 1597 /* Clean up any DSACK's sent */ 1598 tcp_clean_dsack_blocks(tp); 1599 } 1600 if (error) { 1601 /* Record the error. */ 1602 TCP_LOG_EVENT(tp, NULL, &so->so_rcv, &so->so_snd, TCP_LOG_OUT, 1603 error, 0, NULL, false); 1604 1605 /* 1606 * We know that the packet was lost, so back out the 1607 * sequence number advance, if any. 1608 * 1609 * If the error is EPERM the packet got blocked by the 1610 * local firewall. Normally we should terminate the 1611 * connection but the blocking may have been spurious 1612 * due to a firewall reconfiguration cycle. So we treat 1613 * it like a packet loss and let the retransmit timer and 1614 * timeouts do their work over time. 1615 * XXX: It is a POLA question whether calling tcp_drop right 1616 * away would be the really correct behavior instead. 1617 */ 1618 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1619 !tcp_timer_active(tp, TT_PERSIST)) && 1620 ((flags & TH_SYN) == 0) && 1621 (error != EPERM)) { 1622 if (sack_rxmit) { 1623 p->rxmit -= len; 1624 tp->sackhint.sack_bytes_rexmit -= len; 1625 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1626 ("sackhint bytes rtx >= 0")); 1627 } else 1628 tp->snd_nxt -= len; 1629 } 1630 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1631 switch (error) { 1632 case EACCES: 1633 case EPERM: 1634 tp->t_softerror = error; 1635 return (error); 1636 case ENOBUFS: 1637 TCP_XMIT_TIMER_ASSERT(tp, len, flags); 1638 tp->snd_cwnd = tp->t_maxseg; 1639 return (0); 1640 case EMSGSIZE: 1641 /* 1642 * For some reason the interface we used initially 1643 * to send segments changed to another or lowered 1644 * its MTU. 1645 * If TSO was active we either got an interface 1646 * without TSO capabilits or TSO was turned off. 1647 * If we obtained mtu from ip_output() then update 1648 * it and try again. 1649 */ 1650 if (tso) 1651 tp->t_flags &= ~TF_TSO; 1652 if (mtu != 0) { 1653 tcp_mss_update(tp, -1, mtu, NULL, NULL); 1654 goto again; 1655 } 1656 return (error); 1657 case EHOSTDOWN: 1658 case EHOSTUNREACH: 1659 case ENETDOWN: 1660 case ENETUNREACH: 1661 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1662 tp->t_softerror = error; 1663 return (0); 1664 } 1665 /* FALLTHROUGH */ 1666 default: 1667 return (error); 1668 } 1669 } 1670 TCPSTAT_INC(tcps_sndtotal); 1671 1672 /* 1673 * Data sent (as far as we can tell). 1674 * If this advertises a larger window than any other segment, 1675 * then remember the size of the advertised window. 1676 * Any pending ACK has now been sent. 1677 */ 1678 if (SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1679 tp->rcv_adv = tp->rcv_nxt + recwin; 1680 tp->last_ack_sent = tp->rcv_nxt; 1681 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1682 if (tcp_timer_active(tp, TT_DELACK)) 1683 tcp_timer_activate(tp, TT_DELACK, 0); 1684 #if 0 1685 /* 1686 * This completely breaks TCP if newreno is turned on. What happens 1687 * is that if delayed-acks are turned on on the receiver, this code 1688 * on the transmitter effectively destroys the TCP window, forcing 1689 * it to four packets (1.5Kx4 = 6K window). 1690 */ 1691 if (sendalot && --maxburst) 1692 goto again; 1693 #endif 1694 if (sendalot) 1695 goto again; 1696 return (0); 1697 } 1698 1699 void 1700 tcp_setpersist(struct tcpcb *tp) 1701 { 1702 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1703 int tt; 1704 1705 tp->t_flags &= ~TF_PREVVALID; 1706 if (tcp_timer_active(tp, TT_REXMT)) 1707 panic("tcp_setpersist: retransmit pending"); 1708 /* 1709 * Start/restart persistence timer. 1710 */ 1711 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1712 tcp_persmin, tcp_persmax); 1713 tcp_timer_activate(tp, TT_PERSIST, tt); 1714 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1715 tp->t_rxtshift++; 1716 } 1717 1718 /* 1719 * Insert TCP options according to the supplied parameters to the place 1720 * optp in a consistent way. Can handle unaligned destinations. 1721 * 1722 * The order of the option processing is crucial for optimal packing and 1723 * alignment for the scarce option space. 1724 * 1725 * The optimal order for a SYN/SYN-ACK segment is: 1726 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1727 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1728 * 1729 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1730 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1731 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1732 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1733 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1734 */ 1735 int 1736 tcp_addoptions(struct tcpopt *to, u_char *optp) 1737 { 1738 u_int32_t mask, optlen = 0; 1739 1740 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1741 if ((to->to_flags & mask) != mask) 1742 continue; 1743 if (optlen == TCP_MAXOLEN) 1744 break; 1745 switch (to->to_flags & mask) { 1746 case TOF_MSS: 1747 while (optlen % 4) { 1748 optlen += TCPOLEN_NOP; 1749 *optp++ = TCPOPT_NOP; 1750 } 1751 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1752 continue; 1753 optlen += TCPOLEN_MAXSEG; 1754 *optp++ = TCPOPT_MAXSEG; 1755 *optp++ = TCPOLEN_MAXSEG; 1756 to->to_mss = htons(to->to_mss); 1757 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1758 optp += sizeof(to->to_mss); 1759 break; 1760 case TOF_SCALE: 1761 while (!optlen || optlen % 2 != 1) { 1762 optlen += TCPOLEN_NOP; 1763 *optp++ = TCPOPT_NOP; 1764 } 1765 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1766 continue; 1767 optlen += TCPOLEN_WINDOW; 1768 *optp++ = TCPOPT_WINDOW; 1769 *optp++ = TCPOLEN_WINDOW; 1770 *optp++ = to->to_wscale; 1771 break; 1772 case TOF_SACKPERM: 1773 while (optlen % 2) { 1774 optlen += TCPOLEN_NOP; 1775 *optp++ = TCPOPT_NOP; 1776 } 1777 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1778 continue; 1779 optlen += TCPOLEN_SACK_PERMITTED; 1780 *optp++ = TCPOPT_SACK_PERMITTED; 1781 *optp++ = TCPOLEN_SACK_PERMITTED; 1782 break; 1783 case TOF_TS: 1784 while (!optlen || optlen % 4 != 2) { 1785 optlen += TCPOLEN_NOP; 1786 *optp++ = TCPOPT_NOP; 1787 } 1788 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1789 continue; 1790 optlen += TCPOLEN_TIMESTAMP; 1791 *optp++ = TCPOPT_TIMESTAMP; 1792 *optp++ = TCPOLEN_TIMESTAMP; 1793 to->to_tsval = htonl(to->to_tsval); 1794 to->to_tsecr = htonl(to->to_tsecr); 1795 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1796 optp += sizeof(to->to_tsval); 1797 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1798 optp += sizeof(to->to_tsecr); 1799 break; 1800 case TOF_SIGNATURE: 1801 { 1802 int siglen = TCPOLEN_SIGNATURE - 2; 1803 1804 while (!optlen || optlen % 4 != 2) { 1805 optlen += TCPOLEN_NOP; 1806 *optp++ = TCPOPT_NOP; 1807 } 1808 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) { 1809 to->to_flags &= ~TOF_SIGNATURE; 1810 continue; 1811 } 1812 optlen += TCPOLEN_SIGNATURE; 1813 *optp++ = TCPOPT_SIGNATURE; 1814 *optp++ = TCPOLEN_SIGNATURE; 1815 to->to_signature = optp; 1816 while (siglen--) 1817 *optp++ = 0; 1818 break; 1819 } 1820 case TOF_SACK: 1821 { 1822 int sackblks = 0; 1823 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1824 tcp_seq sack_seq; 1825 1826 while (!optlen || optlen % 4 != 2) { 1827 optlen += TCPOLEN_NOP; 1828 *optp++ = TCPOPT_NOP; 1829 } 1830 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1831 continue; 1832 optlen += TCPOLEN_SACKHDR; 1833 *optp++ = TCPOPT_SACK; 1834 sackblks = min(to->to_nsacks, 1835 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1836 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1837 while (sackblks--) { 1838 sack_seq = htonl(sack->start); 1839 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1840 optp += sizeof(sack_seq); 1841 sack_seq = htonl(sack->end); 1842 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1843 optp += sizeof(sack_seq); 1844 optlen += TCPOLEN_SACK; 1845 sack++; 1846 } 1847 TCPSTAT_INC(tcps_sack_send_blocks); 1848 break; 1849 } 1850 case TOF_FASTOPEN: 1851 { 1852 int total_len; 1853 1854 /* XXX is there any point to aligning this option? */ 1855 total_len = TCPOLEN_FAST_OPEN_EMPTY + to->to_tfo_len; 1856 if (TCP_MAXOLEN - optlen < total_len) { 1857 to->to_flags &= ~TOF_FASTOPEN; 1858 continue; 1859 } 1860 *optp++ = TCPOPT_FAST_OPEN; 1861 *optp++ = total_len; 1862 if (to->to_tfo_len > 0) { 1863 bcopy(to->to_tfo_cookie, optp, to->to_tfo_len); 1864 optp += to->to_tfo_len; 1865 } 1866 optlen += total_len; 1867 break; 1868 } 1869 default: 1870 panic("%s: unknown TCP option type", __func__); 1871 break; 1872 } 1873 } 1874 1875 /* Terminate and pad TCP options to a 4 byte boundary. */ 1876 if (optlen % 4) { 1877 optlen += TCPOLEN_EOL; 1878 *optp++ = TCPOPT_EOL; 1879 } 1880 /* 1881 * According to RFC 793 (STD0007): 1882 * "The content of the header beyond the End-of-Option option 1883 * must be header padding (i.e., zero)." 1884 * and later: "The padding is composed of zeros." 1885 */ 1886 while (optlen % 4) { 1887 optlen += TCPOLEN_PAD; 1888 *optp++ = TCPOPT_PAD; 1889 } 1890 1891 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1892 return (optlen); 1893 } 1894 1895 /* 1896 * This is a copy of m_copym(), taking the TSO segment size/limit 1897 * constraints into account, and advancing the sndptr as it goes. 1898 */ 1899 struct mbuf * 1900 tcp_m_copym(struct mbuf *m, int32_t off0, int32_t *plen, 1901 int32_t seglimit, int32_t segsize, struct sockbuf *sb, bool hw_tls) 1902 { 1903 #ifdef KERN_TLS 1904 struct ktls_session *tls, *ntls; 1905 struct mbuf *start; 1906 #endif 1907 struct mbuf *n, **np; 1908 struct mbuf *top; 1909 int32_t off = off0; 1910 int32_t len = *plen; 1911 int32_t fragsize; 1912 int32_t len_cp = 0; 1913 int32_t *pkthdrlen; 1914 uint32_t mlen, frags; 1915 bool copyhdr; 1916 1917 KASSERT(off >= 0, ("tcp_m_copym, negative off %d", off)); 1918 KASSERT(len >= 0, ("tcp_m_copym, negative len %d", len)); 1919 if (off == 0 && m->m_flags & M_PKTHDR) 1920 copyhdr = true; 1921 else 1922 copyhdr = false; 1923 while (off > 0) { 1924 KASSERT(m != NULL, ("tcp_m_copym, offset > size of mbuf chain")); 1925 if (off < m->m_len) 1926 break; 1927 off -= m->m_len; 1928 if ((sb) && (m == sb->sb_sndptr)) { 1929 sb->sb_sndptroff += m->m_len; 1930 sb->sb_sndptr = m->m_next; 1931 } 1932 m = m->m_next; 1933 } 1934 np = ⊤ 1935 top = NULL; 1936 pkthdrlen = NULL; 1937 #ifdef KERN_TLS 1938 if (hw_tls && (m->m_flags & M_EXTPG)) 1939 tls = m->m_epg_tls; 1940 else 1941 tls = NULL; 1942 start = m; 1943 #endif 1944 while (len > 0) { 1945 if (m == NULL) { 1946 KASSERT(len == M_COPYALL, 1947 ("tcp_m_copym, length > size of mbuf chain")); 1948 *plen = len_cp; 1949 if (pkthdrlen != NULL) 1950 *pkthdrlen = len_cp; 1951 break; 1952 } 1953 #ifdef KERN_TLS 1954 if (hw_tls) { 1955 if (m->m_flags & M_EXTPG) 1956 ntls = m->m_epg_tls; 1957 else 1958 ntls = NULL; 1959 1960 /* 1961 * Avoid mixing TLS records with handshake 1962 * data or TLS records from different 1963 * sessions. 1964 */ 1965 if (tls != ntls) { 1966 MPASS(m != start); 1967 *plen = len_cp; 1968 if (pkthdrlen != NULL) 1969 *pkthdrlen = len_cp; 1970 break; 1971 } 1972 } 1973 #endif 1974 mlen = min(len, m->m_len - off); 1975 if (seglimit) { 1976 /* 1977 * For M_EXTPG mbufs, add 3 segments 1978 * + 1 in case we are crossing page boundaries 1979 * + 2 in case the TLS hdr/trailer are used 1980 * It is cheaper to just add the segments 1981 * than it is to take the cache miss to look 1982 * at the mbuf ext_pgs state in detail. 1983 */ 1984 if (m->m_flags & M_EXTPG) { 1985 fragsize = min(segsize, PAGE_SIZE); 1986 frags = 3; 1987 } else { 1988 fragsize = segsize; 1989 frags = 0; 1990 } 1991 1992 /* Break if we really can't fit anymore. */ 1993 if ((frags + 1) >= seglimit) { 1994 *plen = len_cp; 1995 if (pkthdrlen != NULL) 1996 *pkthdrlen = len_cp; 1997 break; 1998 } 1999 2000 /* 2001 * Reduce size if you can't copy the whole 2002 * mbuf. If we can't copy the whole mbuf, also 2003 * adjust len so the loop will end after this 2004 * mbuf. 2005 */ 2006 if ((frags + howmany(mlen, fragsize)) >= seglimit) { 2007 mlen = (seglimit - frags - 1) * fragsize; 2008 len = mlen; 2009 *plen = len_cp + len; 2010 if (pkthdrlen != NULL) 2011 *pkthdrlen = *plen; 2012 } 2013 frags += howmany(mlen, fragsize); 2014 if (frags == 0) 2015 frags++; 2016 seglimit -= frags; 2017 KASSERT(seglimit > 0, 2018 ("%s: seglimit went too low", __func__)); 2019 } 2020 if (copyhdr) 2021 n = m_gethdr(M_NOWAIT, m->m_type); 2022 else 2023 n = m_get(M_NOWAIT, m->m_type); 2024 *np = n; 2025 if (n == NULL) 2026 goto nospace; 2027 if (copyhdr) { 2028 if (!m_dup_pkthdr(n, m, M_NOWAIT)) 2029 goto nospace; 2030 if (len == M_COPYALL) 2031 n->m_pkthdr.len -= off0; 2032 else 2033 n->m_pkthdr.len = len; 2034 pkthdrlen = &n->m_pkthdr.len; 2035 copyhdr = false; 2036 } 2037 n->m_len = mlen; 2038 len_cp += n->m_len; 2039 if (m->m_flags & (M_EXT|M_EXTPG)) { 2040 n->m_data = m->m_data + off; 2041 mb_dupcl(n, m); 2042 } else 2043 bcopy(mtod(m, caddr_t)+off, mtod(n, caddr_t), 2044 (u_int)n->m_len); 2045 2046 if (sb && (sb->sb_sndptr == m) && 2047 ((n->m_len + off) >= m->m_len) && m->m_next) { 2048 sb->sb_sndptroff += m->m_len; 2049 sb->sb_sndptr = m->m_next; 2050 } 2051 off = 0; 2052 if (len != M_COPYALL) { 2053 len -= n->m_len; 2054 } 2055 m = m->m_next; 2056 np = &n->m_next; 2057 } 2058 return (top); 2059 nospace: 2060 m_freem(top); 2061 return (NULL); 2062 } 2063 2064 void 2065 tcp_sndbuf_autoscale(struct tcpcb *tp, struct socket *so, uint32_t sendwin) 2066 { 2067 2068 /* 2069 * Automatic sizing of send socket buffer. Often the send buffer 2070 * size is not optimally adjusted to the actual network conditions 2071 * at hand (delay bandwidth product). Setting the buffer size too 2072 * small limits throughput on links with high bandwidth and high 2073 * delay (eg. trans-continental/oceanic links). Setting the 2074 * buffer size too big consumes too much real kernel memory, 2075 * especially with many connections on busy servers. 2076 * 2077 * The criteria to step up the send buffer one notch are: 2078 * 1. receive window of remote host is larger than send buffer 2079 * (with a fudge factor of 5/4th); 2080 * 2. send buffer is filled to 7/8th with data (so we actually 2081 * have data to make use of it); 2082 * 3. send buffer fill has not hit maximal automatic size; 2083 * 4. our send window (slow start and cogestion controlled) is 2084 * larger than sent but unacknowledged data in send buffer. 2085 * 2086 * The remote host receive window scaling factor may limit the 2087 * growing of the send buffer before it reaches its allowed 2088 * maximum. 2089 * 2090 * It scales directly with slow start or congestion window 2091 * and does at most one step per received ACK. This fast 2092 * scaling has the drawback of growing the send buffer beyond 2093 * what is strictly necessary to make full use of a given 2094 * delay*bandwidth product. However testing has shown this not 2095 * to be much of an problem. At worst we are trading wasting 2096 * of available bandwidth (the non-use of it) for wasting some 2097 * socket buffer memory. 2098 * 2099 * TODO: Shrink send buffer during idle periods together 2100 * with congestion window. Requires another timer. Has to 2101 * wait for upcoming tcp timer rewrite. 2102 * 2103 * XXXGL: should there be used sbused() or sbavail()? 2104 */ 2105 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 2106 int lowat; 2107 2108 lowat = V_tcp_sendbuf_auto_lowat ? so->so_snd.sb_lowat : 0; 2109 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat - lowat && 2110 sbused(&so->so_snd) >= 2111 (so->so_snd.sb_hiwat / 8 * 7) - lowat && 2112 sbused(&so->so_snd) < V_tcp_autosndbuf_max && 2113 sendwin >= (sbused(&so->so_snd) - 2114 (tp->snd_nxt - tp->snd_una))) { 2115 if (!sbreserve_locked(&so->so_snd, 2116 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 2117 V_tcp_autosndbuf_max), so, curthread)) 2118 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 2119 } 2120 } 2121 } 2122