1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 5 * The Regents of the University of California. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. Neither the name of the University nor the names of its contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 * 31 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95 32 */ 33 34 #include <sys/cdefs.h> 35 __FBSDID("$FreeBSD$"); 36 37 #include "opt_inet.h" 38 #include "opt_inet6.h" 39 #include "opt_ipsec.h" 40 #include "opt_kern_tls.h" 41 #include "opt_tcpdebug.h" 42 43 #include <sys/param.h> 44 #include <sys/systm.h> 45 #include <sys/arb.h> 46 #include <sys/domain.h> 47 #ifdef TCP_HHOOK 48 #include <sys/hhook.h> 49 #endif 50 #include <sys/kernel.h> 51 #ifdef KERN_TLS 52 #include <sys/ktls.h> 53 #endif 54 #include <sys/lock.h> 55 #include <sys/mbuf.h> 56 #include <sys/mutex.h> 57 #include <sys/protosw.h> 58 #include <sys/qmath.h> 59 #include <sys/sdt.h> 60 #include <sys/socket.h> 61 #include <sys/socketvar.h> 62 #include <sys/sysctl.h> 63 #include <sys/stats.h> 64 65 #include <net/if.h> 66 #include <net/route.h> 67 #include <net/vnet.h> 68 69 #include <netinet/in.h> 70 #include <netinet/in_kdtrace.h> 71 #include <netinet/in_systm.h> 72 #include <netinet/ip.h> 73 #include <netinet/in_pcb.h> 74 #include <netinet/ip_var.h> 75 #include <netinet/ip_options.h> 76 #ifdef INET6 77 #include <netinet6/in6_pcb.h> 78 #include <netinet/ip6.h> 79 #include <netinet6/ip6_var.h> 80 #endif 81 #include <netinet/tcp.h> 82 #define TCPOUTFLAGS 83 #include <netinet/tcp_fsm.h> 84 #include <netinet/tcp_log_buf.h> 85 #include <netinet/tcp_seq.h> 86 #include <netinet/tcp_timer.h> 87 #include <netinet/tcp_var.h> 88 #include <netinet/tcpip.h> 89 #include <netinet/cc/cc.h> 90 #include <netinet/tcp_fastopen.h> 91 #ifdef TCPPCAP 92 #include <netinet/tcp_pcap.h> 93 #endif 94 #ifdef TCPDEBUG 95 #include <netinet/tcp_debug.h> 96 #endif 97 #ifdef TCP_OFFLOAD 98 #include <netinet/tcp_offload.h> 99 #endif 100 101 #include <netipsec/ipsec_support.h> 102 103 #include <machine/in_cksum.h> 104 105 #include <security/mac/mac_framework.h> 106 107 VNET_DEFINE(int, path_mtu_discovery) = 1; 108 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_VNET | CTLFLAG_RW, 109 &VNET_NAME(path_mtu_discovery), 1, 110 "Enable Path MTU Discovery"); 111 112 VNET_DEFINE(int, tcp_do_tso) = 1; 113 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_VNET | CTLFLAG_RW, 114 &VNET_NAME(tcp_do_tso), 0, 115 "Enable TCP Segmentation Offload"); 116 117 VNET_DEFINE(int, tcp_sendspace) = 1024*32; 118 #define V_tcp_sendspace VNET(tcp_sendspace) 119 SYSCTL_INT(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, CTLFLAG_VNET | CTLFLAG_RW, 120 &VNET_NAME(tcp_sendspace), 0, "Initial send socket buffer size"); 121 122 VNET_DEFINE(int, tcp_do_autosndbuf) = 1; 123 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_VNET | CTLFLAG_RW, 124 &VNET_NAME(tcp_do_autosndbuf), 0, 125 "Enable automatic send buffer sizing"); 126 127 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024; 128 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_VNET | CTLFLAG_RW, 129 &VNET_NAME(tcp_autosndbuf_inc), 0, 130 "Incrementor step size of automatic send buffer"); 131 132 VNET_DEFINE(int, tcp_autosndbuf_max) = 2*1024*1024; 133 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_VNET | CTLFLAG_RW, 134 &VNET_NAME(tcp_autosndbuf_max), 0, 135 "Max size of automatic send buffer"); 136 137 VNET_DEFINE(int, tcp_sendbuf_auto_lowat) = 0; 138 #define V_tcp_sendbuf_auto_lowat VNET(tcp_sendbuf_auto_lowat) 139 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto_lowat, CTLFLAG_VNET | CTLFLAG_RW, 140 &VNET_NAME(tcp_sendbuf_auto_lowat), 0, 141 "Modify threshold for auto send buffer growth to account for SO_SNDLOWAT"); 142 143 /* 144 * Make sure that either retransmit or persist timer is set for SYN, FIN and 145 * non-ACK. 146 */ 147 #define TCP_XMIT_TIMER_ASSERT(tp, len, th_flags) \ 148 KASSERT(((len) == 0 && ((th_flags) & (TH_SYN | TH_FIN)) == 0) ||\ 149 tcp_timer_active((tp), TT_REXMT) || \ 150 tcp_timer_active((tp), TT_PERSIST), \ 151 ("neither rexmt nor persist timer is set")) 152 153 static void inline cc_after_idle(struct tcpcb *tp); 154 155 #ifdef TCP_HHOOK 156 /* 157 * Wrapper for the TCP established output helper hook. 158 */ 159 void 160 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th, 161 struct tcpopt *to, uint32_t len, int tso) 162 { 163 struct tcp_hhook_data hhook_data; 164 165 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) { 166 hhook_data.tp = tp; 167 hhook_data.th = th; 168 hhook_data.to = to; 169 hhook_data.len = len; 170 hhook_data.tso = tso; 171 172 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data, 173 tp->osd); 174 } 175 } 176 #endif 177 178 /* 179 * CC wrapper hook functions 180 */ 181 static void inline 182 cc_after_idle(struct tcpcb *tp) 183 { 184 INP_WLOCK_ASSERT(tp->t_inpcb); 185 186 if (CC_ALGO(tp)->after_idle != NULL) 187 CC_ALGO(tp)->after_idle(tp->ccv); 188 } 189 190 /* 191 * Tcp output routine: figure out what should be sent and send it. 192 */ 193 int 194 tcp_output(struct tcpcb *tp) 195 { 196 struct socket *so = tp->t_inpcb->inp_socket; 197 int32_t len; 198 uint32_t recwin, sendwin; 199 int off, flags, error = 0; /* Keep compiler happy */ 200 u_int if_hw_tsomaxsegcount = 0; 201 u_int if_hw_tsomaxsegsize = 0; 202 struct mbuf *m; 203 struct ip *ip = NULL; 204 #ifdef TCPDEBUG 205 struct ipovly *ipov = NULL; 206 #endif 207 struct tcphdr *th; 208 u_char opt[TCP_MAXOLEN]; 209 unsigned ipoptlen, optlen, hdrlen; 210 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 211 unsigned ipsec_optlen = 0; 212 #endif 213 int idle, sendalot, curticks; 214 int sack_rxmit, sack_bytes_rxmt; 215 struct sackhole *p; 216 int tso, mtu; 217 struct tcpopt to; 218 unsigned int wanted_cookie = 0; 219 unsigned int dont_sendalot = 0; 220 #if 0 221 int maxburst = TCP_MAXBURST; 222 #endif 223 #ifdef INET6 224 struct ip6_hdr *ip6 = NULL; 225 int isipv6; 226 227 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 228 #endif 229 #ifdef KERN_TLS 230 const bool hw_tls = (so->so_snd.sb_flags & SB_TLS_IFNET) != 0; 231 #else 232 const bool hw_tls = false; 233 #endif 234 235 INP_WLOCK_ASSERT(tp->t_inpcb); 236 237 #ifdef TCP_OFFLOAD 238 if (tp->t_flags & TF_TOE) 239 return (tcp_offload_output(tp)); 240 #endif 241 242 /* 243 * For TFO connections in SYN_SENT or SYN_RECEIVED, 244 * only allow the initial SYN or SYN|ACK and those sent 245 * by the retransmit timer. 246 */ 247 if (IS_FASTOPEN(tp->t_flags) && 248 ((tp->t_state == TCPS_SYN_SENT) || 249 (tp->t_state == TCPS_SYN_RECEIVED)) && 250 SEQ_GT(tp->snd_max, tp->snd_una) && /* initial SYN or SYN|ACK sent */ 251 (tp->snd_nxt != tp->snd_una)) /* not a retransmit */ 252 return (0); 253 254 /* 255 * Determine length of data that should be transmitted, 256 * and flags that will be used. 257 * If there is some data or critical controls (SYN, RST) 258 * to send, then transmit; otherwise, investigate further. 259 */ 260 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 261 if (idle && ticks - tp->t_rcvtime >= tp->t_rxtcur) 262 cc_after_idle(tp); 263 tp->t_flags &= ~TF_LASTIDLE; 264 if (idle) { 265 if (tp->t_flags & TF_MORETOCOME) { 266 tp->t_flags |= TF_LASTIDLE; 267 idle = 0; 268 } 269 } 270 again: 271 /* 272 * If we've recently taken a timeout, snd_max will be greater than 273 * snd_nxt. There may be SACK information that allows us to avoid 274 * resending already delivered data. Adjust snd_nxt accordingly. 275 */ 276 if ((tp->t_flags & TF_SACK_PERMIT) && 277 SEQ_LT(tp->snd_nxt, tp->snd_max)) 278 tcp_sack_adjust(tp); 279 sendalot = 0; 280 tso = 0; 281 mtu = 0; 282 off = tp->snd_nxt - tp->snd_una; 283 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 284 285 flags = tcp_outflags[tp->t_state]; 286 /* 287 * Send any SACK-generated retransmissions. If we're explicitly trying 288 * to send out new data (when sendalot is 1), bypass this function. 289 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 290 * we're replacing a (future) new transmission with a retransmission 291 * now, and we previously incremented snd_cwnd in tcp_input(). 292 */ 293 /* 294 * Still in sack recovery , reset rxmit flag to zero. 295 */ 296 sack_rxmit = 0; 297 sack_bytes_rxmt = 0; 298 len = 0; 299 p = NULL; 300 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) && 301 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 302 uint32_t cwin; 303 304 cwin = 305 imax(min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt, 0); 306 /* Do not retransmit SACK segments beyond snd_recover */ 307 if (SEQ_GT(p->end, tp->snd_recover)) { 308 /* 309 * (At least) part of sack hole extends beyond 310 * snd_recover. Check to see if we can rexmit data 311 * for this hole. 312 */ 313 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 314 /* 315 * Can't rexmit any more data for this hole. 316 * That data will be rexmitted in the next 317 * sack recovery episode, when snd_recover 318 * moves past p->rxmit. 319 */ 320 p = NULL; 321 goto after_sack_rexmit; 322 } else 323 /* Can rexmit part of the current hole */ 324 len = ((int32_t)ulmin(cwin, 325 tp->snd_recover - p->rxmit)); 326 } else 327 len = ((int32_t)ulmin(cwin, p->end - p->rxmit)); 328 off = p->rxmit - tp->snd_una; 329 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 330 __func__, off)); 331 if (len > 0) { 332 sack_rxmit = 1; 333 sendalot = 1; 334 TCPSTAT_INC(tcps_sack_rexmits); 335 TCPSTAT_ADD(tcps_sack_rexmit_bytes, 336 min(len, tp->t_maxseg)); 337 } 338 } 339 after_sack_rexmit: 340 /* 341 * Get standard flags, and add SYN or FIN if requested by 'hidden' 342 * state flags. 343 */ 344 if (tp->t_flags & TF_NEEDFIN) 345 flags |= TH_FIN; 346 if (tp->t_flags & TF_NEEDSYN) 347 flags |= TH_SYN; 348 349 SOCKBUF_LOCK(&so->so_snd); 350 /* 351 * If in persist timeout with window of 0, send 1 byte. 352 * Otherwise, if window is small but nonzero 353 * and timer expired, we will send what we can 354 * and go to transmit state. 355 */ 356 if (tp->t_flags & TF_FORCEDATA) { 357 if (sendwin == 0) { 358 /* 359 * If we still have some data to send, then 360 * clear the FIN bit. Usually this would 361 * happen below when it realizes that we 362 * aren't sending all the data. However, 363 * if we have exactly 1 byte of unsent data, 364 * then it won't clear the FIN bit below, 365 * and if we are in persist state, we wind 366 * up sending the packet without recording 367 * that we sent the FIN bit. 368 * 369 * We can't just blindly clear the FIN bit, 370 * because if we don't have any more data 371 * to send then the probe will be the FIN 372 * itself. 373 */ 374 if (off < sbused(&so->so_snd)) 375 flags &= ~TH_FIN; 376 sendwin = 1; 377 } else { 378 tcp_timer_activate(tp, TT_PERSIST, 0); 379 tp->t_rxtshift = 0; 380 } 381 } 382 383 /* 384 * If snd_nxt == snd_max and we have transmitted a FIN, the 385 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 386 * a negative length. This can also occur when TCP opens up 387 * its congestion window while receiving additional duplicate 388 * acks after fast-retransmit because TCP will reset snd_nxt 389 * to snd_max after the fast-retransmit. 390 * 391 * In the normal retransmit-FIN-only case, however, snd_nxt will 392 * be set to snd_una, the offset will be 0, and the length may 393 * wind up 0. 394 * 395 * If sack_rxmit is true we are retransmitting from the scoreboard 396 * in which case len is already set. 397 */ 398 if (sack_rxmit == 0) { 399 if (sack_bytes_rxmt == 0) 400 len = ((int32_t)min(sbavail(&so->so_snd), sendwin) - 401 off); 402 else { 403 int32_t cwin; 404 405 /* 406 * We are inside of a SACK recovery episode and are 407 * sending new data, having retransmitted all the 408 * data possible in the scoreboard. 409 */ 410 len = ((int32_t)min(sbavail(&so->so_snd), tp->snd_wnd) - 411 off); 412 /* 413 * Don't remove this (len > 0) check ! 414 * We explicitly check for len > 0 here (although it 415 * isn't really necessary), to work around a gcc 416 * optimization issue - to force gcc to compute 417 * len above. Without this check, the computation 418 * of len is bungled by the optimizer. 419 */ 420 if (len > 0) { 421 cwin = tp->snd_cwnd - 422 (tp->snd_nxt - tp->sack_newdata) - 423 sack_bytes_rxmt; 424 if (cwin < 0) 425 cwin = 0; 426 len = imin(len, cwin); 427 } 428 } 429 } 430 431 /* 432 * Lop off SYN bit if it has already been sent. However, if this 433 * is SYN-SENT state and if segment contains data and if we don't 434 * know that foreign host supports TAO, suppress sending segment. 435 */ 436 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 437 if (tp->t_state != TCPS_SYN_RECEIVED) 438 flags &= ~TH_SYN; 439 /* 440 * When sending additional segments following a TFO SYN|ACK, 441 * do not include the SYN bit. 442 */ 443 if (IS_FASTOPEN(tp->t_flags) && 444 (tp->t_state == TCPS_SYN_RECEIVED)) 445 flags &= ~TH_SYN; 446 off--, len++; 447 } 448 449 /* 450 * Be careful not to send data and/or FIN on SYN segments. 451 * This measure is needed to prevent interoperability problems 452 * with not fully conformant TCP implementations. 453 */ 454 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 455 len = 0; 456 flags &= ~TH_FIN; 457 } 458 459 /* 460 * On TFO sockets, ensure no data is sent in the following cases: 461 * 462 * - When retransmitting SYN|ACK on a passively-created socket 463 * 464 * - When retransmitting SYN on an actively created socket 465 * 466 * - When sending a zero-length cookie (cookie request) on an 467 * actively created socket 468 * 469 * - When the socket is in the CLOSED state (RST is being sent) 470 */ 471 if (IS_FASTOPEN(tp->t_flags) && 472 (((flags & TH_SYN) && (tp->t_rxtshift > 0)) || 473 ((tp->t_state == TCPS_SYN_SENT) && 474 (tp->t_tfo_client_cookie_len == 0)) || 475 (flags & TH_RST))) 476 len = 0; 477 if (len <= 0) { 478 /* 479 * If FIN has been sent but not acked, 480 * but we haven't been called to retransmit, 481 * len will be < 0. Otherwise, window shrank 482 * after we sent into it. If window shrank to 0, 483 * cancel pending retransmit, pull snd_nxt back 484 * to (closed) window, and set the persist timer 485 * if it isn't already going. If the window didn't 486 * close completely, just wait for an ACK. 487 * 488 * We also do a general check here to ensure that 489 * we will set the persist timer when we have data 490 * to send, but a 0-byte window. This makes sure 491 * the persist timer is set even if the packet 492 * hits one of the "goto send" lines below. 493 */ 494 len = 0; 495 if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) && 496 (off < (int) sbavail(&so->so_snd))) { 497 tcp_timer_activate(tp, TT_REXMT, 0); 498 tp->t_rxtshift = 0; 499 tp->snd_nxt = tp->snd_una; 500 if (!tcp_timer_active(tp, TT_PERSIST)) 501 tcp_setpersist(tp); 502 } 503 } 504 505 /* len will be >= 0 after this point. */ 506 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 507 508 tcp_sndbuf_autoscale(tp, so, sendwin); 509 510 /* 511 * Decide if we can use TCP Segmentation Offloading (if supported by 512 * hardware). 513 * 514 * TSO may only be used if we are in a pure bulk sending state. The 515 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 516 * IP options prevent using TSO. With TSO the TCP header is the same 517 * (except for the sequence number) for all generated packets. This 518 * makes it impossible to transmit any options which vary per generated 519 * segment or packet. 520 * 521 * IPv4 handling has a clear separation of ip options and ip header 522 * flags while IPv6 combines both in in6p_outputopts. ip6_optlen() does 523 * the right thing below to provide length of just ip options and thus 524 * checking for ipoptlen is enough to decide if ip options are present. 525 */ 526 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 527 /* 528 * Pre-calculate here as we save another lookup into the darknesses 529 * of IPsec that way and can actually decide if TSO is ok. 530 */ 531 #ifdef INET6 532 if (isipv6 && IPSEC_ENABLED(ipv6)) 533 ipsec_optlen = IPSEC_HDRSIZE(ipv6, tp->t_inpcb); 534 #ifdef INET 535 else 536 #endif 537 #endif /* INET6 */ 538 #ifdef INET 539 if (IPSEC_ENABLED(ipv4)) 540 ipsec_optlen = IPSEC_HDRSIZE(ipv4, tp->t_inpcb); 541 #endif /* INET */ 542 #endif /* IPSEC */ 543 #ifdef INET6 544 if (isipv6) 545 ipoptlen = ip6_optlen(tp->t_inpcb); 546 else 547 #endif 548 if (tp->t_inpcb->inp_options) 549 ipoptlen = tp->t_inpcb->inp_options->m_len - 550 offsetof(struct ipoption, ipopt_list); 551 else 552 ipoptlen = 0; 553 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 554 ipoptlen += ipsec_optlen; 555 #endif 556 557 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg && 558 ((tp->t_flags & TF_SIGNATURE) == 0) && 559 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 560 ipoptlen == 0 && !(flags & TH_SYN)) 561 tso = 1; 562 563 if (sack_rxmit) { 564 if (SEQ_LT(p->rxmit + len, tp->snd_una + sbused(&so->so_snd))) 565 flags &= ~TH_FIN; 566 } else { 567 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + 568 sbused(&so->so_snd))) 569 flags &= ~TH_FIN; 570 } 571 572 recwin = lmin(lmax(sbspace(&so->so_rcv), 0), 573 (long)TCP_MAXWIN << tp->rcv_scale); 574 575 /* 576 * Sender silly window avoidance. We transmit under the following 577 * conditions when len is non-zero: 578 * 579 * - We have a full segment (or more with TSO) 580 * - This is the last buffer in a write()/send() and we are 581 * either idle or running NODELAY 582 * - we've timed out (e.g. persist timer) 583 * - we have more then 1/2 the maximum send window's worth of 584 * data (receiver may be limited the window size) 585 * - we need to retransmit 586 */ 587 if (len) { 588 if (len >= tp->t_maxseg) 589 goto send; 590 /* 591 * NOTE! on localhost connections an 'ack' from the remote 592 * end may occur synchronously with the output and cause 593 * us to flush a buffer queued with moretocome. XXX 594 * 595 * note: the len + off check is almost certainly unnecessary. 596 */ 597 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 598 (idle || (tp->t_flags & TF_NODELAY)) && 599 (uint32_t)len + (uint32_t)off >= sbavail(&so->so_snd) && 600 (tp->t_flags & TF_NOPUSH) == 0) { 601 goto send; 602 } 603 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 604 goto send; 605 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 606 goto send; 607 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 608 goto send; 609 if (sack_rxmit) 610 goto send; 611 } 612 613 /* 614 * Sending of standalone window updates. 615 * 616 * Window updates are important when we close our window due to a 617 * full socket buffer and are opening it again after the application 618 * reads data from it. Once the window has opened again and the 619 * remote end starts to send again the ACK clock takes over and 620 * provides the most current window information. 621 * 622 * We must avoid the silly window syndrome whereas every read 623 * from the receive buffer, no matter how small, causes a window 624 * update to be sent. We also should avoid sending a flurry of 625 * window updates when the socket buffer had queued a lot of data 626 * and the application is doing small reads. 627 * 628 * Prevent a flurry of pointless window updates by only sending 629 * an update when we can increase the advertized window by more 630 * than 1/4th of the socket buffer capacity. When the buffer is 631 * getting full or is very small be more aggressive and send an 632 * update whenever we can increase by two mss sized segments. 633 * In all other situations the ACK's to new incoming data will 634 * carry further window increases. 635 * 636 * Don't send an independent window update if a delayed 637 * ACK is pending (it will get piggy-backed on it) or the 638 * remote side already has done a half-close and won't send 639 * more data. Skip this if the connection is in T/TCP 640 * half-open state. 641 */ 642 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 643 !(tp->t_flags & TF_DELACK) && 644 !TCPS_HAVERCVDFIN(tp->t_state)) { 645 /* 646 * "adv" is the amount we could increase the window, 647 * taking into account that we are limited by 648 * TCP_MAXWIN << tp->rcv_scale. 649 */ 650 int32_t adv; 651 int oldwin; 652 653 adv = recwin; 654 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { 655 oldwin = (tp->rcv_adv - tp->rcv_nxt); 656 adv -= oldwin; 657 } else 658 oldwin = 0; 659 660 /* 661 * If the new window size ends up being the same as or less 662 * than the old size when it is scaled, then don't force 663 * a window update. 664 */ 665 if (oldwin >> tp->rcv_scale >= (adv + oldwin) >> tp->rcv_scale) 666 goto dontupdate; 667 668 if (adv >= (int32_t)(2 * tp->t_maxseg) && 669 (adv >= (int32_t)(so->so_rcv.sb_hiwat / 4) || 670 recwin <= (so->so_rcv.sb_hiwat / 8) || 671 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg || 672 adv >= TCP_MAXWIN << tp->rcv_scale)) 673 goto send; 674 if (2 * adv >= (int32_t)so->so_rcv.sb_hiwat) 675 goto send; 676 } 677 dontupdate: 678 679 /* 680 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 681 * is also a catch-all for the retransmit timer timeout case. 682 */ 683 if (tp->t_flags & TF_ACKNOW) 684 goto send; 685 if ((flags & TH_RST) || 686 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 687 goto send; 688 if (SEQ_GT(tp->snd_up, tp->snd_una)) 689 goto send; 690 /* 691 * If our state indicates that FIN should be sent 692 * and we have not yet done so, then we need to send. 693 */ 694 if (flags & TH_FIN && 695 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 696 goto send; 697 /* 698 * In SACK, it is possible for tcp_output to fail to send a segment 699 * after the retransmission timer has been turned off. Make sure 700 * that the retransmission timer is set. 701 */ 702 if ((tp->t_flags & TF_SACK_PERMIT) && 703 SEQ_GT(tp->snd_max, tp->snd_una) && 704 !tcp_timer_active(tp, TT_REXMT) && 705 !tcp_timer_active(tp, TT_PERSIST)) { 706 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 707 goto just_return; 708 } 709 /* 710 * TCP window updates are not reliable, rather a polling protocol 711 * using ``persist'' packets is used to insure receipt of window 712 * updates. The three ``states'' for the output side are: 713 * idle not doing retransmits or persists 714 * persisting to move a small or zero window 715 * (re)transmitting and thereby not persisting 716 * 717 * tcp_timer_active(tp, TT_PERSIST) 718 * is true when we are in persist state. 719 * (tp->t_flags & TF_FORCEDATA) 720 * is set when we are called to send a persist packet. 721 * tcp_timer_active(tp, TT_REXMT) 722 * is set when we are retransmitting 723 * The output side is idle when both timers are zero. 724 * 725 * If send window is too small, there is data to transmit, and no 726 * retransmit or persist is pending, then go to persist state. 727 * If nothing happens soon, send when timer expires: 728 * if window is nonzero, transmit what we can, 729 * otherwise force out a byte. 730 */ 731 if (sbavail(&so->so_snd) && !tcp_timer_active(tp, TT_REXMT) && 732 !tcp_timer_active(tp, TT_PERSIST)) { 733 tp->t_rxtshift = 0; 734 tcp_setpersist(tp); 735 } 736 737 /* 738 * No reason to send a segment, just return. 739 */ 740 just_return: 741 SOCKBUF_UNLOCK(&so->so_snd); 742 return (0); 743 744 send: 745 SOCKBUF_LOCK_ASSERT(&so->so_snd); 746 if (len > 0) { 747 if (len >= tp->t_maxseg) 748 tp->t_flags2 |= TF2_PLPMTU_MAXSEGSNT; 749 else 750 tp->t_flags2 &= ~TF2_PLPMTU_MAXSEGSNT; 751 } 752 /* 753 * Before ESTABLISHED, force sending of initial options 754 * unless TCP set not to do any options. 755 * NOTE: we assume that the IP/TCP header plus TCP options 756 * always fit in a single mbuf, leaving room for a maximum 757 * link header, i.e. 758 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 759 */ 760 optlen = 0; 761 #ifdef INET6 762 if (isipv6) 763 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 764 else 765 #endif 766 hdrlen = sizeof (struct tcpiphdr); 767 768 /* 769 * Compute options for segment. 770 * We only have to care about SYN and established connection 771 * segments. Options for SYN-ACK segments are handled in TCP 772 * syncache. 773 */ 774 to.to_flags = 0; 775 if ((tp->t_flags & TF_NOOPT) == 0) { 776 /* Maximum segment size. */ 777 if (flags & TH_SYN) { 778 tp->snd_nxt = tp->iss; 779 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 780 to.to_flags |= TOF_MSS; 781 782 /* 783 * On SYN or SYN|ACK transmits on TFO connections, 784 * only include the TFO option if it is not a 785 * retransmit, as the presence of the TFO option may 786 * have caused the original SYN or SYN|ACK to have 787 * been dropped by a middlebox. 788 */ 789 if (IS_FASTOPEN(tp->t_flags) && 790 (tp->t_rxtshift == 0)) { 791 if (tp->t_state == TCPS_SYN_RECEIVED) { 792 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN; 793 to.to_tfo_cookie = 794 (u_int8_t *)&tp->t_tfo_cookie.server; 795 to.to_flags |= TOF_FASTOPEN; 796 wanted_cookie = 1; 797 } else if (tp->t_state == TCPS_SYN_SENT) { 798 to.to_tfo_len = 799 tp->t_tfo_client_cookie_len; 800 to.to_tfo_cookie = 801 tp->t_tfo_cookie.client; 802 to.to_flags |= TOF_FASTOPEN; 803 wanted_cookie = 1; 804 /* 805 * If we wind up having more data to 806 * send with the SYN than can fit in 807 * one segment, don't send any more 808 * until the SYN|ACK comes back from 809 * the other end. 810 */ 811 dont_sendalot = 1; 812 } 813 } 814 } 815 /* Window scaling. */ 816 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 817 to.to_wscale = tp->request_r_scale; 818 to.to_flags |= TOF_SCALE; 819 } 820 /* Timestamps. */ 821 if ((tp->t_flags & TF_RCVD_TSTMP) || 822 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 823 curticks = tcp_ts_getticks(); 824 to.to_tsval = curticks + tp->ts_offset; 825 to.to_tsecr = tp->ts_recent; 826 to.to_flags |= TOF_TS; 827 if (tp->t_rxtshift == 1) 828 tp->t_badrxtwin = curticks; 829 } 830 831 /* Set receive buffer autosizing timestamp. */ 832 if (tp->rfbuf_ts == 0 && 833 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 834 tp->rfbuf_ts = tcp_ts_getticks(); 835 836 /* Selective ACK's. */ 837 if (tp->t_flags & TF_SACK_PERMIT) { 838 if (flags & TH_SYN) 839 to.to_flags |= TOF_SACKPERM; 840 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 841 (tp->t_flags & TF_SACK_PERMIT) && 842 tp->rcv_numsacks > 0) { 843 to.to_flags |= TOF_SACK; 844 to.to_nsacks = tp->rcv_numsacks; 845 to.to_sacks = (u_char *)tp->sackblks; 846 } 847 } 848 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 849 /* TCP-MD5 (RFC2385). */ 850 /* 851 * Check that TCP_MD5SIG is enabled in tcpcb to 852 * account the size needed to set this TCP option. 853 */ 854 if (tp->t_flags & TF_SIGNATURE) 855 to.to_flags |= TOF_SIGNATURE; 856 #endif /* TCP_SIGNATURE */ 857 858 /* Processing the options. */ 859 hdrlen += optlen = tcp_addoptions(&to, opt); 860 /* 861 * If we wanted a TFO option to be added, but it was unable 862 * to fit, ensure no data is sent. 863 */ 864 if (IS_FASTOPEN(tp->t_flags) && wanted_cookie && 865 !(to.to_flags & TOF_FASTOPEN)) 866 len = 0; 867 } 868 869 /* 870 * Adjust data length if insertion of options will 871 * bump the packet length beyond the t_maxseg length. 872 * Clear the FIN bit because we cut off the tail of 873 * the segment. 874 */ 875 if (len + optlen + ipoptlen > tp->t_maxseg) { 876 flags &= ~TH_FIN; 877 878 if (tso) { 879 u_int if_hw_tsomax; 880 u_int moff; 881 int max_len; 882 883 /* extract TSO information */ 884 if_hw_tsomax = tp->t_tsomax; 885 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount; 886 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize; 887 888 /* 889 * Limit a TSO burst to prevent it from 890 * overflowing or exceeding the maximum length 891 * allowed by the network interface: 892 */ 893 KASSERT(ipoptlen == 0, 894 ("%s: TSO can't do IP options", __func__)); 895 896 /* 897 * Check if we should limit by maximum payload 898 * length: 899 */ 900 if (if_hw_tsomax != 0) { 901 /* compute maximum TSO length */ 902 max_len = (if_hw_tsomax - hdrlen - 903 max_linkhdr); 904 if (max_len <= 0) { 905 len = 0; 906 } else if (len > max_len) { 907 sendalot = 1; 908 len = max_len; 909 } 910 } 911 912 /* 913 * Prevent the last segment from being 914 * fractional unless the send sockbuf can be 915 * emptied: 916 */ 917 max_len = (tp->t_maxseg - optlen); 918 if (((uint32_t)off + (uint32_t)len) < 919 sbavail(&so->so_snd)) { 920 moff = len % max_len; 921 if (moff != 0) { 922 len -= moff; 923 sendalot = 1; 924 } 925 } 926 927 /* 928 * In case there are too many small fragments 929 * don't use TSO: 930 */ 931 if (len <= max_len) { 932 len = max_len; 933 sendalot = 1; 934 tso = 0; 935 } 936 937 /* 938 * Send the FIN in a separate segment 939 * after the bulk sending is done. 940 * We don't trust the TSO implementations 941 * to clear the FIN flag on all but the 942 * last segment. 943 */ 944 if (tp->t_flags & TF_NEEDFIN) 945 sendalot = 1; 946 } else { 947 if (optlen + ipoptlen >= tp->t_maxseg) { 948 /* 949 * Since we don't have enough space to put 950 * the IP header chain and the TCP header in 951 * one packet as required by RFC 7112, don't 952 * send it. Also ensure that at least one 953 * byte of the payload can be put into the 954 * TCP segment. 955 */ 956 SOCKBUF_UNLOCK(&so->so_snd); 957 error = EMSGSIZE; 958 sack_rxmit = 0; 959 goto out; 960 } 961 len = tp->t_maxseg - optlen - ipoptlen; 962 sendalot = 1; 963 if (dont_sendalot) 964 sendalot = 0; 965 } 966 } else 967 tso = 0; 968 969 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 970 ("%s: len > IP_MAXPACKET", __func__)); 971 972 /*#ifdef DIAGNOSTIC*/ 973 #ifdef INET6 974 if (max_linkhdr + hdrlen > MCLBYTES) 975 #else 976 if (max_linkhdr + hdrlen > MHLEN) 977 #endif 978 panic("tcphdr too big"); 979 /*#endif*/ 980 981 /* 982 * This KASSERT is here to catch edge cases at a well defined place. 983 * Before, those had triggered (random) panic conditions further down. 984 */ 985 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 986 987 /* 988 * Grab a header mbuf, attaching a copy of data to 989 * be transmitted, and initialize the header from 990 * the template for sends on this connection. 991 */ 992 if (len) { 993 struct mbuf *mb; 994 struct sockbuf *msb; 995 u_int moff; 996 997 if ((tp->t_flags & TF_FORCEDATA) && len == 1) { 998 TCPSTAT_INC(tcps_sndprobe); 999 #ifdef STATS 1000 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1001 stats_voi_update_abs_u32(tp->t_stats, 1002 VOI_TCP_RETXPB, len); 1003 else 1004 stats_voi_update_abs_u64(tp->t_stats, 1005 VOI_TCP_TXPB, len); 1006 #endif /* STATS */ 1007 } else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 1008 tp->t_sndrexmitpack++; 1009 TCPSTAT_INC(tcps_sndrexmitpack); 1010 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 1011 #ifdef STATS 1012 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_RETXPB, 1013 len); 1014 #endif /* STATS */ 1015 } else { 1016 TCPSTAT_INC(tcps_sndpack); 1017 TCPSTAT_ADD(tcps_sndbyte, len); 1018 #ifdef STATS 1019 stats_voi_update_abs_u64(tp->t_stats, VOI_TCP_TXPB, 1020 len); 1021 #endif /* STATS */ 1022 } 1023 #ifdef INET6 1024 if (MHLEN < hdrlen + max_linkhdr) 1025 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR); 1026 else 1027 #endif 1028 m = m_gethdr(M_NOWAIT, MT_DATA); 1029 1030 if (m == NULL) { 1031 SOCKBUF_UNLOCK(&so->so_snd); 1032 error = ENOBUFS; 1033 sack_rxmit = 0; 1034 goto out; 1035 } 1036 1037 m->m_data += max_linkhdr; 1038 m->m_len = hdrlen; 1039 1040 /* 1041 * Start the m_copy functions from the closest mbuf 1042 * to the offset in the socket buffer chain. 1043 */ 1044 mb = sbsndptr_noadv(&so->so_snd, off, &moff); 1045 if (len <= MHLEN - hdrlen - max_linkhdr && !hw_tls) { 1046 m_copydata(mb, moff, len, 1047 mtod(m, caddr_t) + hdrlen); 1048 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1049 sbsndptr_adv(&so->so_snd, mb, len); 1050 m->m_len += len; 1051 } else { 1052 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1053 msb = NULL; 1054 else 1055 msb = &so->so_snd; 1056 m->m_next = tcp_m_copym(mb, moff, 1057 &len, if_hw_tsomaxsegcount, 1058 if_hw_tsomaxsegsize, msb, hw_tls); 1059 if (len <= (tp->t_maxseg - optlen)) { 1060 /* 1061 * Must have ran out of mbufs for the copy 1062 * shorten it to no longer need tso. Lets 1063 * not put on sendalot since we are low on 1064 * mbufs. 1065 */ 1066 tso = 0; 1067 } 1068 if (m->m_next == NULL) { 1069 SOCKBUF_UNLOCK(&so->so_snd); 1070 (void) m_free(m); 1071 error = ENOBUFS; 1072 sack_rxmit = 0; 1073 goto out; 1074 } 1075 } 1076 1077 /* 1078 * If we're sending everything we've got, set PUSH. 1079 * (This will keep happy those implementations which only 1080 * give data to the user when a buffer fills or 1081 * a PUSH comes in.) 1082 */ 1083 if (((uint32_t)off + (uint32_t)len == sbused(&so->so_snd)) && 1084 !(flags & TH_SYN)) 1085 flags |= TH_PUSH; 1086 SOCKBUF_UNLOCK(&so->so_snd); 1087 } else { 1088 SOCKBUF_UNLOCK(&so->so_snd); 1089 if (tp->t_flags & TF_ACKNOW) 1090 TCPSTAT_INC(tcps_sndacks); 1091 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 1092 TCPSTAT_INC(tcps_sndctrl); 1093 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 1094 TCPSTAT_INC(tcps_sndurg); 1095 else 1096 TCPSTAT_INC(tcps_sndwinup); 1097 1098 m = m_gethdr(M_NOWAIT, MT_DATA); 1099 if (m == NULL) { 1100 error = ENOBUFS; 1101 sack_rxmit = 0; 1102 goto out; 1103 } 1104 #ifdef INET6 1105 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 1106 MHLEN >= hdrlen) { 1107 M_ALIGN(m, hdrlen); 1108 } else 1109 #endif 1110 m->m_data += max_linkhdr; 1111 m->m_len = hdrlen; 1112 } 1113 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 1114 m->m_pkthdr.rcvif = (struct ifnet *)0; 1115 #ifdef MAC 1116 mac_inpcb_create_mbuf(tp->t_inpcb, m); 1117 #endif 1118 #ifdef INET6 1119 if (isipv6) { 1120 ip6 = mtod(m, struct ip6_hdr *); 1121 th = (struct tcphdr *)(ip6 + 1); 1122 tcpip_fillheaders(tp->t_inpcb, ip6, th); 1123 } else 1124 #endif /* INET6 */ 1125 { 1126 ip = mtod(m, struct ip *); 1127 #ifdef TCPDEBUG 1128 ipov = (struct ipovly *)ip; 1129 #endif 1130 th = (struct tcphdr *)(ip + 1); 1131 tcpip_fillheaders(tp->t_inpcb, ip, th); 1132 } 1133 1134 /* 1135 * Fill in fields, remembering maximum advertised 1136 * window for use in delaying messages about window sizes. 1137 * If resending a FIN, be sure not to use a new sequence number. 1138 */ 1139 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 1140 tp->snd_nxt == tp->snd_max) 1141 tp->snd_nxt--; 1142 /* 1143 * If we are starting a connection, send ECN setup 1144 * SYN packet. If we are on a retransmit, we may 1145 * resend those bits a number of times as per 1146 * RFC 3168. 1147 */ 1148 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn == 1) { 1149 if (tp->t_rxtshift >= 1) { 1150 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 1151 flags |= TH_ECE|TH_CWR; 1152 } else 1153 flags |= TH_ECE|TH_CWR; 1154 } 1155 1156 if (tp->t_state == TCPS_ESTABLISHED && 1157 (tp->t_flags2 & TF2_ECN_PERMIT)) { 1158 /* 1159 * If the peer has ECN, mark data packets with 1160 * ECN capable transmission (ECT). 1161 * Ignore pure ack packets, retransmissions and window probes. 1162 */ 1163 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 1164 !((tp->t_flags & TF_FORCEDATA) && len == 1)) { 1165 #ifdef INET6 1166 if (isipv6) 1167 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 1168 else 1169 #endif 1170 ip->ip_tos |= IPTOS_ECN_ECT0; 1171 TCPSTAT_INC(tcps_ecn_ect0); 1172 } 1173 1174 /* 1175 * Reply with proper ECN notifications. 1176 */ 1177 if (tp->t_flags2 & TF2_ECN_SND_CWR) { 1178 flags |= TH_CWR; 1179 tp->t_flags2 &= ~TF2_ECN_SND_CWR; 1180 } 1181 if (tp->t_flags2 & TF2_ECN_SND_ECE) 1182 flags |= TH_ECE; 1183 } 1184 1185 /* 1186 * If we are doing retransmissions, then snd_nxt will 1187 * not reflect the first unsent octet. For ACK only 1188 * packets, we do not want the sequence number of the 1189 * retransmitted packet, we want the sequence number 1190 * of the next unsent octet. So, if there is no data 1191 * (and no SYN or FIN), use snd_max instead of snd_nxt 1192 * when filling in ti_seq. But if we are in persist 1193 * state, snd_max might reflect one byte beyond the 1194 * right edge of the window, so use snd_nxt in that 1195 * case, since we know we aren't doing a retransmission. 1196 * (retransmit and persist are mutually exclusive...) 1197 */ 1198 if (sack_rxmit == 0) { 1199 if (len || (flags & (TH_SYN|TH_FIN)) || 1200 tcp_timer_active(tp, TT_PERSIST)) 1201 th->th_seq = htonl(tp->snd_nxt); 1202 else 1203 th->th_seq = htonl(tp->snd_max); 1204 } else { 1205 th->th_seq = htonl(p->rxmit); 1206 p->rxmit += len; 1207 tp->sackhint.sack_bytes_rexmit += len; 1208 } 1209 th->th_ack = htonl(tp->rcv_nxt); 1210 if (optlen) { 1211 bcopy(opt, th + 1, optlen); 1212 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1213 } 1214 th->th_flags = flags; 1215 /* 1216 * Calculate receive window. Don't shrink window, 1217 * but avoid silly window syndrome. 1218 * If a RST segment is sent, advertise a window of zero. 1219 */ 1220 if (flags & TH_RST) { 1221 recwin = 0; 1222 } else { 1223 if (recwin < (so->so_rcv.sb_hiwat / 4) && 1224 recwin < tp->t_maxseg) 1225 recwin = 0; 1226 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1227 recwin < (tp->rcv_adv - tp->rcv_nxt)) 1228 recwin = (tp->rcv_adv - tp->rcv_nxt); 1229 } 1230 /* 1231 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1232 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1233 * case is handled in syncache. 1234 */ 1235 if (flags & TH_SYN) 1236 th->th_win = htons((u_short) 1237 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1238 else 1239 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1240 1241 /* 1242 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1243 * a 0 window. This may cause the remote transmitter to stall. This 1244 * flag tells soreceive() to disable delayed acknowledgements when 1245 * draining the buffer. This can occur if the receiver is attempting 1246 * to read more data than can be buffered prior to transmitting on 1247 * the connection. 1248 */ 1249 if (th->th_win == 0) { 1250 tp->t_sndzerowin++; 1251 tp->t_flags |= TF_RXWIN0SENT; 1252 } else 1253 tp->t_flags &= ~TF_RXWIN0SENT; 1254 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1255 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1256 th->th_flags |= TH_URG; 1257 } else 1258 /* 1259 * If no urgent pointer to send, then we pull 1260 * the urgent pointer to the left edge of the send window 1261 * so that it doesn't drift into the send window on sequence 1262 * number wraparound. 1263 */ 1264 tp->snd_up = tp->snd_una; /* drag it along */ 1265 1266 /* 1267 * Put TCP length in extended header, and then 1268 * checksum extended header and data. 1269 */ 1270 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1271 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1272 1273 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1274 if (to.to_flags & TOF_SIGNATURE) { 1275 /* 1276 * Calculate MD5 signature and put it into the place 1277 * determined before. 1278 * NOTE: since TCP options buffer doesn't point into 1279 * mbuf's data, calculate offset and use it. 1280 */ 1281 if (!TCPMD5_ENABLED() || (error = TCPMD5_OUTPUT(m, th, 1282 (u_char *)(th + 1) + (to.to_signature - opt))) != 0) { 1283 /* 1284 * Do not send segment if the calculation of MD5 1285 * digest has failed. 1286 */ 1287 m_freem(m); 1288 goto out; 1289 } 1290 } 1291 #endif 1292 #ifdef INET6 1293 if (isipv6) { 1294 /* 1295 * There is no need to fill in ip6_plen right now. 1296 * It will be filled later by ip6_output. 1297 */ 1298 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1299 th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) + 1300 optlen + len, IPPROTO_TCP, 0); 1301 } 1302 #endif 1303 #if defined(INET6) && defined(INET) 1304 else 1305 #endif 1306 #ifdef INET 1307 { 1308 m->m_pkthdr.csum_flags = CSUM_TCP; 1309 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1310 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1311 1312 /* IP version must be set here for ipv4/ipv6 checking later */ 1313 KASSERT(ip->ip_v == IPVERSION, 1314 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1315 } 1316 #endif 1317 1318 /* 1319 * Enable TSO and specify the size of the segments. 1320 * The TCP pseudo header checksum is always provided. 1321 */ 1322 if (tso) { 1323 KASSERT(len > tp->t_maxseg - optlen, 1324 ("%s: len <= tso_segsz", __func__)); 1325 m->m_pkthdr.csum_flags |= CSUM_TSO; 1326 m->m_pkthdr.tso_segsz = tp->t_maxseg - optlen; 1327 } 1328 1329 KASSERT(len + hdrlen == m_length(m, NULL), 1330 ("%s: mbuf chain shorter than expected: %d + %u != %u", 1331 __func__, len, hdrlen, m_length(m, NULL))); 1332 1333 #ifdef TCP_HHOOK 1334 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1335 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1336 #endif 1337 1338 #ifdef TCPDEBUG 1339 /* 1340 * Trace. 1341 */ 1342 if (so->so_options & SO_DEBUG) { 1343 u_short save = 0; 1344 #ifdef INET6 1345 if (!isipv6) 1346 #endif 1347 { 1348 save = ipov->ih_len; 1349 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1350 } 1351 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1352 #ifdef INET6 1353 if (!isipv6) 1354 #endif 1355 ipov->ih_len = save; 1356 } 1357 #endif /* TCPDEBUG */ 1358 TCP_PROBE3(debug__output, tp, th, m); 1359 1360 /* We're getting ready to send; log now. */ 1361 TCP_LOG_EVENT(tp, th, &so->so_rcv, &so->so_snd, TCP_LOG_OUT, ERRNO_UNK, 1362 len, NULL, false); 1363 1364 /* 1365 * Fill in IP length and desired time to live and 1366 * send to IP level. There should be a better way 1367 * to handle ttl and tos; we could keep them in 1368 * the template, but need a way to checksum without them. 1369 */ 1370 /* 1371 * m->m_pkthdr.len should have been set before checksum calculation, 1372 * because in6_cksum() need it. 1373 */ 1374 #ifdef INET6 1375 if (isipv6) { 1376 /* 1377 * we separately set hoplimit for every segment, since the 1378 * user might want to change the value via setsockopt. 1379 * Also, desired default hop limit might be changed via 1380 * Neighbor Discovery. 1381 */ 1382 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1383 1384 /* 1385 * Set the packet size here for the benefit of DTrace probes. 1386 * ip6_output() will set it properly; it's supposed to include 1387 * the option header lengths as well. 1388 */ 1389 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6)); 1390 1391 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) 1392 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1393 else 1394 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1395 1396 if (tp->t_state == TCPS_SYN_SENT) 1397 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th); 1398 1399 TCP_PROBE5(send, NULL, tp, ip6, tp, th); 1400 1401 #ifdef TCPPCAP 1402 /* Save packet, if requested. */ 1403 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1404 #endif 1405 1406 /* TODO: IPv6 IP6TOS_ECT bit on */ 1407 error = ip6_output(m, tp->t_inpcb->in6p_outputopts, 1408 &tp->t_inpcb->inp_route6, 1409 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 1410 NULL, NULL, tp->t_inpcb); 1411 1412 if (error == EMSGSIZE && tp->t_inpcb->inp_route6.ro_rt != NULL) 1413 mtu = tp->t_inpcb->inp_route6.ro_rt->rt_mtu; 1414 } 1415 #endif /* INET6 */ 1416 #if defined(INET) && defined(INET6) 1417 else 1418 #endif 1419 #ifdef INET 1420 { 1421 ip->ip_len = htons(m->m_pkthdr.len); 1422 #ifdef INET6 1423 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1424 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1425 #endif /* INET6 */ 1426 /* 1427 * If we do path MTU discovery, then we set DF on every packet. 1428 * This might not be the best thing to do according to RFC3390 1429 * Section 2. However the tcp hostcache migitates the problem 1430 * so it affects only the first tcp connection with a host. 1431 * 1432 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1433 */ 1434 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) { 1435 ip->ip_off |= htons(IP_DF); 1436 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1437 } else { 1438 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1439 } 1440 1441 if (tp->t_state == TCPS_SYN_SENT) 1442 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th); 1443 1444 TCP_PROBE5(send, NULL, tp, ip, tp, th); 1445 1446 #ifdef TCPPCAP 1447 /* Save packet, if requested. */ 1448 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1449 #endif 1450 1451 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, 1452 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1453 tp->t_inpcb); 1454 1455 if (error == EMSGSIZE && tp->t_inpcb->inp_route.ro_rt != NULL) 1456 mtu = tp->t_inpcb->inp_route.ro_rt->rt_mtu; 1457 } 1458 #endif /* INET */ 1459 1460 out: 1461 /* 1462 * In transmit state, time the transmission and arrange for 1463 * the retransmit. In persist state, just set snd_max. 1464 */ 1465 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1466 !tcp_timer_active(tp, TT_PERSIST)) { 1467 tcp_seq startseq = tp->snd_nxt; 1468 1469 /* 1470 * Advance snd_nxt over sequence space of this segment. 1471 */ 1472 if (flags & (TH_SYN|TH_FIN)) { 1473 if (flags & TH_SYN) 1474 tp->snd_nxt++; 1475 if (flags & TH_FIN) { 1476 tp->snd_nxt++; 1477 tp->t_flags |= TF_SENTFIN; 1478 } 1479 } 1480 if (sack_rxmit) 1481 goto timer; 1482 tp->snd_nxt += len; 1483 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1484 tp->snd_max = tp->snd_nxt; 1485 /* 1486 * Time this transmission if not a retransmission and 1487 * not currently timing anything. 1488 */ 1489 if (tp->t_rtttime == 0) { 1490 tp->t_rtttime = ticks; 1491 tp->t_rtseq = startseq; 1492 TCPSTAT_INC(tcps_segstimed); 1493 } 1494 #ifdef STATS 1495 if (!(tp->t_flags & TF_GPUTINPROG) && len) { 1496 tp->t_flags |= TF_GPUTINPROG; 1497 tp->gput_seq = startseq; 1498 tp->gput_ack = startseq + 1499 ulmin(sbavail(&so->so_snd) - off, sendwin); 1500 tp->gput_ts = tcp_ts_getticks(); 1501 } 1502 #endif /* STATS */ 1503 } 1504 1505 /* 1506 * Set retransmit timer if not currently set, 1507 * and not doing a pure ack or a keep-alive probe. 1508 * Initial value for retransmit timer is smoothed 1509 * round-trip time + 2 * round-trip time variance. 1510 * Initialize shift counter which is used for backoff 1511 * of retransmit time. 1512 */ 1513 timer: 1514 if (!tcp_timer_active(tp, TT_REXMT) && 1515 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1516 (tp->snd_nxt != tp->snd_una))) { 1517 if (tcp_timer_active(tp, TT_PERSIST)) { 1518 tcp_timer_activate(tp, TT_PERSIST, 0); 1519 tp->t_rxtshift = 0; 1520 } 1521 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1522 } else if (len == 0 && sbavail(&so->so_snd) && 1523 !tcp_timer_active(tp, TT_REXMT) && 1524 !tcp_timer_active(tp, TT_PERSIST)) { 1525 /* 1526 * Avoid a situation where we do not set persist timer 1527 * after a zero window condition. For example: 1528 * 1) A -> B: packet with enough data to fill the window 1529 * 2) B -> A: ACK for #1 + new data (0 window 1530 * advertisement) 1531 * 3) A -> B: ACK for #2, 0 len packet 1532 * 1533 * In this case, A will not activate the persist timer, 1534 * because it chose to send a packet. Unless tcp_output 1535 * is called for some other reason (delayed ack timer, 1536 * another input packet from B, socket syscall), A will 1537 * not send zero window probes. 1538 * 1539 * So, if you send a 0-length packet, but there is data 1540 * in the socket buffer, and neither the rexmt or 1541 * persist timer is already set, then activate the 1542 * persist timer. 1543 */ 1544 tp->t_rxtshift = 0; 1545 tcp_setpersist(tp); 1546 } 1547 } else { 1548 /* 1549 * Persist case, update snd_max but since we are in 1550 * persist mode (no window) we do not update snd_nxt. 1551 */ 1552 int xlen = len; 1553 if (flags & TH_SYN) 1554 ++xlen; 1555 if (flags & TH_FIN) { 1556 ++xlen; 1557 tp->t_flags |= TF_SENTFIN; 1558 } 1559 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1560 tp->snd_max = tp->snd_nxt + xlen; 1561 } 1562 if ((error == 0) && 1563 (TCPS_HAVEESTABLISHED(tp->t_state) && 1564 (tp->t_flags & TF_SACK_PERMIT) && 1565 tp->rcv_numsacks > 0)) { 1566 /* Clean up any DSACK's sent */ 1567 tcp_clean_dsack_blocks(tp); 1568 } 1569 if (error) { 1570 /* Record the error. */ 1571 TCP_LOG_EVENT(tp, NULL, &so->so_rcv, &so->so_snd, TCP_LOG_OUT, 1572 error, 0, NULL, false); 1573 1574 /* 1575 * We know that the packet was lost, so back out the 1576 * sequence number advance, if any. 1577 * 1578 * If the error is EPERM the packet got blocked by the 1579 * local firewall. Normally we should terminate the 1580 * connection but the blocking may have been spurious 1581 * due to a firewall reconfiguration cycle. So we treat 1582 * it like a packet loss and let the retransmit timer and 1583 * timeouts do their work over time. 1584 * XXX: It is a POLA question whether calling tcp_drop right 1585 * away would be the really correct behavior instead. 1586 */ 1587 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1588 !tcp_timer_active(tp, TT_PERSIST)) && 1589 ((flags & TH_SYN) == 0) && 1590 (error != EPERM)) { 1591 if (sack_rxmit) { 1592 p->rxmit -= len; 1593 tp->sackhint.sack_bytes_rexmit -= len; 1594 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1595 ("sackhint bytes rtx >= 0")); 1596 } else 1597 tp->snd_nxt -= len; 1598 } 1599 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1600 switch (error) { 1601 case EACCES: 1602 case EPERM: 1603 tp->t_softerror = error; 1604 return (error); 1605 case ENOBUFS: 1606 TCP_XMIT_TIMER_ASSERT(tp, len, flags); 1607 tp->snd_cwnd = tp->t_maxseg; 1608 return (0); 1609 case EMSGSIZE: 1610 /* 1611 * For some reason the interface we used initially 1612 * to send segments changed to another or lowered 1613 * its MTU. 1614 * If TSO was active we either got an interface 1615 * without TSO capabilits or TSO was turned off. 1616 * If we obtained mtu from ip_output() then update 1617 * it and try again. 1618 */ 1619 if (tso) 1620 tp->t_flags &= ~TF_TSO; 1621 if (mtu != 0) { 1622 tcp_mss_update(tp, -1, mtu, NULL, NULL); 1623 goto again; 1624 } 1625 return (error); 1626 case EHOSTDOWN: 1627 case EHOSTUNREACH: 1628 case ENETDOWN: 1629 case ENETUNREACH: 1630 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1631 tp->t_softerror = error; 1632 return (0); 1633 } 1634 /* FALLTHROUGH */ 1635 default: 1636 return (error); 1637 } 1638 } 1639 TCPSTAT_INC(tcps_sndtotal); 1640 1641 /* 1642 * Data sent (as far as we can tell). 1643 * If this advertises a larger window than any other segment, 1644 * then remember the size of the advertised window. 1645 * Any pending ACK has now been sent. 1646 */ 1647 if (SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1648 tp->rcv_adv = tp->rcv_nxt + recwin; 1649 tp->last_ack_sent = tp->rcv_nxt; 1650 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1651 if (tcp_timer_active(tp, TT_DELACK)) 1652 tcp_timer_activate(tp, TT_DELACK, 0); 1653 #if 0 1654 /* 1655 * This completely breaks TCP if newreno is turned on. What happens 1656 * is that if delayed-acks are turned on on the receiver, this code 1657 * on the transmitter effectively destroys the TCP window, forcing 1658 * it to four packets (1.5Kx4 = 6K window). 1659 */ 1660 if (sendalot && --maxburst) 1661 goto again; 1662 #endif 1663 if (sendalot) 1664 goto again; 1665 return (0); 1666 } 1667 1668 void 1669 tcp_setpersist(struct tcpcb *tp) 1670 { 1671 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1672 int tt; 1673 1674 tp->t_flags &= ~TF_PREVVALID; 1675 if (tcp_timer_active(tp, TT_REXMT)) 1676 panic("tcp_setpersist: retransmit pending"); 1677 /* 1678 * Start/restart persistence timer. 1679 */ 1680 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1681 tcp_persmin, tcp_persmax); 1682 tcp_timer_activate(tp, TT_PERSIST, tt); 1683 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1684 tp->t_rxtshift++; 1685 } 1686 1687 /* 1688 * Insert TCP options according to the supplied parameters to the place 1689 * optp in a consistent way. Can handle unaligned destinations. 1690 * 1691 * The order of the option processing is crucial for optimal packing and 1692 * alignment for the scarce option space. 1693 * 1694 * The optimal order for a SYN/SYN-ACK segment is: 1695 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1696 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1697 * 1698 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1699 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1700 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1701 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1702 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1703 */ 1704 int 1705 tcp_addoptions(struct tcpopt *to, u_char *optp) 1706 { 1707 u_int32_t mask, optlen = 0; 1708 1709 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1710 if ((to->to_flags & mask) != mask) 1711 continue; 1712 if (optlen == TCP_MAXOLEN) 1713 break; 1714 switch (to->to_flags & mask) { 1715 case TOF_MSS: 1716 while (optlen % 4) { 1717 optlen += TCPOLEN_NOP; 1718 *optp++ = TCPOPT_NOP; 1719 } 1720 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1721 continue; 1722 optlen += TCPOLEN_MAXSEG; 1723 *optp++ = TCPOPT_MAXSEG; 1724 *optp++ = TCPOLEN_MAXSEG; 1725 to->to_mss = htons(to->to_mss); 1726 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1727 optp += sizeof(to->to_mss); 1728 break; 1729 case TOF_SCALE: 1730 while (!optlen || optlen % 2 != 1) { 1731 optlen += TCPOLEN_NOP; 1732 *optp++ = TCPOPT_NOP; 1733 } 1734 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1735 continue; 1736 optlen += TCPOLEN_WINDOW; 1737 *optp++ = TCPOPT_WINDOW; 1738 *optp++ = TCPOLEN_WINDOW; 1739 *optp++ = to->to_wscale; 1740 break; 1741 case TOF_SACKPERM: 1742 while (optlen % 2) { 1743 optlen += TCPOLEN_NOP; 1744 *optp++ = TCPOPT_NOP; 1745 } 1746 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1747 continue; 1748 optlen += TCPOLEN_SACK_PERMITTED; 1749 *optp++ = TCPOPT_SACK_PERMITTED; 1750 *optp++ = TCPOLEN_SACK_PERMITTED; 1751 break; 1752 case TOF_TS: 1753 while (!optlen || optlen % 4 != 2) { 1754 optlen += TCPOLEN_NOP; 1755 *optp++ = TCPOPT_NOP; 1756 } 1757 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1758 continue; 1759 optlen += TCPOLEN_TIMESTAMP; 1760 *optp++ = TCPOPT_TIMESTAMP; 1761 *optp++ = TCPOLEN_TIMESTAMP; 1762 to->to_tsval = htonl(to->to_tsval); 1763 to->to_tsecr = htonl(to->to_tsecr); 1764 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1765 optp += sizeof(to->to_tsval); 1766 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1767 optp += sizeof(to->to_tsecr); 1768 break; 1769 case TOF_SIGNATURE: 1770 { 1771 int siglen = TCPOLEN_SIGNATURE - 2; 1772 1773 while (!optlen || optlen % 4 != 2) { 1774 optlen += TCPOLEN_NOP; 1775 *optp++ = TCPOPT_NOP; 1776 } 1777 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) { 1778 to->to_flags &= ~TOF_SIGNATURE; 1779 continue; 1780 } 1781 optlen += TCPOLEN_SIGNATURE; 1782 *optp++ = TCPOPT_SIGNATURE; 1783 *optp++ = TCPOLEN_SIGNATURE; 1784 to->to_signature = optp; 1785 while (siglen--) 1786 *optp++ = 0; 1787 break; 1788 } 1789 case TOF_SACK: 1790 { 1791 int sackblks = 0; 1792 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1793 tcp_seq sack_seq; 1794 1795 while (!optlen || optlen % 4 != 2) { 1796 optlen += TCPOLEN_NOP; 1797 *optp++ = TCPOPT_NOP; 1798 } 1799 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1800 continue; 1801 optlen += TCPOLEN_SACKHDR; 1802 *optp++ = TCPOPT_SACK; 1803 sackblks = min(to->to_nsacks, 1804 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1805 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1806 while (sackblks--) { 1807 sack_seq = htonl(sack->start); 1808 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1809 optp += sizeof(sack_seq); 1810 sack_seq = htonl(sack->end); 1811 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1812 optp += sizeof(sack_seq); 1813 optlen += TCPOLEN_SACK; 1814 sack++; 1815 } 1816 TCPSTAT_INC(tcps_sack_send_blocks); 1817 break; 1818 } 1819 case TOF_FASTOPEN: 1820 { 1821 int total_len; 1822 1823 /* XXX is there any point to aligning this option? */ 1824 total_len = TCPOLEN_FAST_OPEN_EMPTY + to->to_tfo_len; 1825 if (TCP_MAXOLEN - optlen < total_len) { 1826 to->to_flags &= ~TOF_FASTOPEN; 1827 continue; 1828 } 1829 *optp++ = TCPOPT_FAST_OPEN; 1830 *optp++ = total_len; 1831 if (to->to_tfo_len > 0) { 1832 bcopy(to->to_tfo_cookie, optp, to->to_tfo_len); 1833 optp += to->to_tfo_len; 1834 } 1835 optlen += total_len; 1836 break; 1837 } 1838 default: 1839 panic("%s: unknown TCP option type", __func__); 1840 break; 1841 } 1842 } 1843 1844 /* Terminate and pad TCP options to a 4 byte boundary. */ 1845 if (optlen % 4) { 1846 optlen += TCPOLEN_EOL; 1847 *optp++ = TCPOPT_EOL; 1848 } 1849 /* 1850 * According to RFC 793 (STD0007): 1851 * "The content of the header beyond the End-of-Option option 1852 * must be header padding (i.e., zero)." 1853 * and later: "The padding is composed of zeros." 1854 */ 1855 while (optlen % 4) { 1856 optlen += TCPOLEN_PAD; 1857 *optp++ = TCPOPT_PAD; 1858 } 1859 1860 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1861 return (optlen); 1862 } 1863 1864 /* 1865 * This is a copy of m_copym(), taking the TSO segment size/limit 1866 * constraints into account, and advancing the sndptr as it goes. 1867 */ 1868 struct mbuf * 1869 tcp_m_copym(struct mbuf *m, int32_t off0, int32_t *plen, 1870 int32_t seglimit, int32_t segsize, struct sockbuf *sb, bool hw_tls) 1871 { 1872 #ifdef KERN_TLS 1873 struct ktls_session *tls, *ntls; 1874 struct mbuf *start; 1875 #endif 1876 struct mbuf *n, **np; 1877 struct mbuf *top; 1878 int32_t off = off0; 1879 int32_t len = *plen; 1880 int32_t fragsize; 1881 int32_t len_cp = 0; 1882 int32_t *pkthdrlen; 1883 uint32_t mlen, frags; 1884 bool copyhdr; 1885 1886 1887 KASSERT(off >= 0, ("tcp_m_copym, negative off %d", off)); 1888 KASSERT(len >= 0, ("tcp_m_copym, negative len %d", len)); 1889 if (off == 0 && m->m_flags & M_PKTHDR) 1890 copyhdr = true; 1891 else 1892 copyhdr = false; 1893 while (off > 0) { 1894 KASSERT(m != NULL, ("tcp_m_copym, offset > size of mbuf chain")); 1895 if (off < m->m_len) 1896 break; 1897 off -= m->m_len; 1898 if ((sb) && (m == sb->sb_sndptr)) { 1899 sb->sb_sndptroff += m->m_len; 1900 sb->sb_sndptr = m->m_next; 1901 } 1902 m = m->m_next; 1903 } 1904 np = ⊤ 1905 top = NULL; 1906 pkthdrlen = NULL; 1907 #ifdef KERN_TLS 1908 if (m->m_flags & M_NOMAP) 1909 tls = m->m_ext.ext_pgs->tls; 1910 else 1911 tls = NULL; 1912 start = m; 1913 #endif 1914 while (len > 0) { 1915 if (m == NULL) { 1916 KASSERT(len == M_COPYALL, 1917 ("tcp_m_copym, length > size of mbuf chain")); 1918 *plen = len_cp; 1919 if (pkthdrlen != NULL) 1920 *pkthdrlen = len_cp; 1921 break; 1922 } 1923 #ifdef KERN_TLS 1924 if (hw_tls) { 1925 if (m->m_flags & M_NOMAP) 1926 ntls = m->m_ext.ext_pgs->tls; 1927 else 1928 ntls = NULL; 1929 1930 /* 1931 * Avoid mixing TLS records with handshake 1932 * data or TLS records from different 1933 * sessions. 1934 */ 1935 if (tls != ntls) { 1936 MPASS(m != start); 1937 *plen = len_cp; 1938 if (pkthdrlen != NULL) 1939 *pkthdrlen = len_cp; 1940 break; 1941 } 1942 1943 /* 1944 * Don't end a send in the middle of a TLS 1945 * record if it spans multiple TLS records. 1946 */ 1947 if (tls != NULL && (m != start) && len < m->m_len) { 1948 *plen = len_cp; 1949 if (pkthdrlen != NULL) 1950 *pkthdrlen = len_cp; 1951 break; 1952 } 1953 } 1954 #endif 1955 mlen = min(len, m->m_len - off); 1956 if (seglimit) { 1957 /* 1958 * For M_NOMAP mbufs, add 3 segments 1959 * + 1 in case we are crossing page boundaries 1960 * + 2 in case the TLS hdr/trailer are used 1961 * It is cheaper to just add the segments 1962 * than it is to take the cache miss to look 1963 * at the mbuf ext_pgs state in detail. 1964 */ 1965 if (m->m_flags & M_NOMAP) { 1966 fragsize = min(segsize, PAGE_SIZE); 1967 frags = 3; 1968 } else { 1969 fragsize = segsize; 1970 frags = 0; 1971 } 1972 1973 /* Break if we really can't fit anymore. */ 1974 if ((frags + 1) >= seglimit) { 1975 *plen = len_cp; 1976 if (pkthdrlen != NULL) 1977 *pkthdrlen = len_cp; 1978 break; 1979 } 1980 1981 /* 1982 * Reduce size if you can't copy the whole 1983 * mbuf. If we can't copy the whole mbuf, also 1984 * adjust len so the loop will end after this 1985 * mbuf. 1986 */ 1987 if ((frags + howmany(mlen, fragsize)) >= seglimit) { 1988 mlen = (seglimit - frags - 1) * fragsize; 1989 len = mlen; 1990 *plen = len_cp + len; 1991 if (pkthdrlen != NULL) 1992 *pkthdrlen = *plen; 1993 } 1994 frags += howmany(mlen, fragsize); 1995 if (frags == 0) 1996 frags++; 1997 seglimit -= frags; 1998 KASSERT(seglimit > 0, 1999 ("%s: seglimit went too low", __func__)); 2000 } 2001 if (copyhdr) 2002 n = m_gethdr(M_NOWAIT, m->m_type); 2003 else 2004 n = m_get(M_NOWAIT, m->m_type); 2005 *np = n; 2006 if (n == NULL) 2007 goto nospace; 2008 if (copyhdr) { 2009 if (!m_dup_pkthdr(n, m, M_NOWAIT)) 2010 goto nospace; 2011 if (len == M_COPYALL) 2012 n->m_pkthdr.len -= off0; 2013 else 2014 n->m_pkthdr.len = len; 2015 pkthdrlen = &n->m_pkthdr.len; 2016 copyhdr = false; 2017 } 2018 n->m_len = mlen; 2019 len_cp += n->m_len; 2020 if (m->m_flags & M_EXT) { 2021 n->m_data = m->m_data + off; 2022 mb_dupcl(n, m); 2023 } else 2024 bcopy(mtod(m, caddr_t)+off, mtod(n, caddr_t), 2025 (u_int)n->m_len); 2026 2027 if (sb && (sb->sb_sndptr == m) && 2028 ((n->m_len + off) >= m->m_len) && m->m_next) { 2029 sb->sb_sndptroff += m->m_len; 2030 sb->sb_sndptr = m->m_next; 2031 } 2032 off = 0; 2033 if (len != M_COPYALL) { 2034 len -= n->m_len; 2035 } 2036 m = m->m_next; 2037 np = &n->m_next; 2038 } 2039 return (top); 2040 nospace: 2041 m_freem(top); 2042 return (NULL); 2043 } 2044 2045 void 2046 tcp_sndbuf_autoscale(struct tcpcb *tp, struct socket *so, uint32_t sendwin) 2047 { 2048 2049 /* 2050 * Automatic sizing of send socket buffer. Often the send buffer 2051 * size is not optimally adjusted to the actual network conditions 2052 * at hand (delay bandwidth product). Setting the buffer size too 2053 * small limits throughput on links with high bandwidth and high 2054 * delay (eg. trans-continental/oceanic links). Setting the 2055 * buffer size too big consumes too much real kernel memory, 2056 * especially with many connections on busy servers. 2057 * 2058 * The criteria to step up the send buffer one notch are: 2059 * 1. receive window of remote host is larger than send buffer 2060 * (with a fudge factor of 5/4th); 2061 * 2. send buffer is filled to 7/8th with data (so we actually 2062 * have data to make use of it); 2063 * 3. send buffer fill has not hit maximal automatic size; 2064 * 4. our send window (slow start and cogestion controlled) is 2065 * larger than sent but unacknowledged data in send buffer. 2066 * 2067 * The remote host receive window scaling factor may limit the 2068 * growing of the send buffer before it reaches its allowed 2069 * maximum. 2070 * 2071 * It scales directly with slow start or congestion window 2072 * and does at most one step per received ACK. This fast 2073 * scaling has the drawback of growing the send buffer beyond 2074 * what is strictly necessary to make full use of a given 2075 * delay*bandwidth product. However testing has shown this not 2076 * to be much of an problem. At worst we are trading wasting 2077 * of available bandwidth (the non-use of it) for wasting some 2078 * socket buffer memory. 2079 * 2080 * TODO: Shrink send buffer during idle periods together 2081 * with congestion window. Requires another timer. Has to 2082 * wait for upcoming tcp timer rewrite. 2083 * 2084 * XXXGL: should there be used sbused() or sbavail()? 2085 */ 2086 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 2087 int lowat; 2088 2089 lowat = V_tcp_sendbuf_auto_lowat ? so->so_snd.sb_lowat : 0; 2090 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat - lowat && 2091 sbused(&so->so_snd) >= 2092 (so->so_snd.sb_hiwat / 8 * 7) - lowat && 2093 sbused(&so->so_snd) < V_tcp_autosndbuf_max && 2094 sendwin >= (sbused(&so->so_snd) - 2095 (tp->snd_nxt - tp->snd_una))) { 2096 if (!sbreserve_locked(&so->so_snd, 2097 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 2098 V_tcp_autosndbuf_max), so, curthread)) 2099 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 2100 } 2101 } 2102 } 2103