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