1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 5 * The Regents of the University of California. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. Neither the name of the University nor the names of its contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 * 31 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95 32 */ 33 34 #include <sys/cdefs.h> 35 __FBSDID("$FreeBSD$"); 36 37 #include "opt_inet.h" 38 #include "opt_inet6.h" 39 #include "opt_ipsec.h" 40 #include "opt_kern_tls.h" 41 #include "opt_tcpdebug.h" 42 43 #include <sys/param.h> 44 #include <sys/systm.h> 45 #include <sys/arb.h> 46 #include <sys/domain.h> 47 #ifdef TCP_HHOOK 48 #include <sys/hhook.h> 49 #endif 50 #include <sys/kernel.h> 51 #ifdef KERN_TLS 52 #include <sys/ktls.h> 53 #endif 54 #include <sys/lock.h> 55 #include <sys/mbuf.h> 56 #include <sys/mutex.h> 57 #include <sys/protosw.h> 58 #include <sys/qmath.h> 59 #include <sys/sdt.h> 60 #include <sys/socket.h> 61 #include <sys/socketvar.h> 62 #include <sys/sysctl.h> 63 #include <sys/stats.h> 64 65 #include <net/if.h> 66 #include <net/route.h> 67 #include <net/route/nhop.h> 68 #include <net/vnet.h> 69 70 #include <netinet/in.h> 71 #include <netinet/in_kdtrace.h> 72 #include <netinet/in_systm.h> 73 #include <netinet/ip.h> 74 #include <netinet/in_pcb.h> 75 #include <netinet/ip_var.h> 76 #include <netinet/ip_options.h> 77 #ifdef INET6 78 #include <netinet6/in6_pcb.h> 79 #include <netinet/ip6.h> 80 #include <netinet6/ip6_var.h> 81 #endif 82 #include <netinet/tcp.h> 83 #define TCPOUTFLAGS 84 #include <netinet/tcp_fsm.h> 85 #include <netinet/tcp_log_buf.h> 86 #include <netinet/tcp_seq.h> 87 #include <netinet/tcp_timer.h> 88 #include <netinet/tcp_var.h> 89 #include <netinet/tcpip.h> 90 #include <netinet/cc/cc.h> 91 #include <netinet/tcp_fastopen.h> 92 #ifdef TCPPCAP 93 #include <netinet/tcp_pcap.h> 94 #endif 95 #ifdef TCPDEBUG 96 #include <netinet/tcp_debug.h> 97 #endif 98 #ifdef TCP_OFFLOAD 99 #include <netinet/tcp_offload.h> 100 #endif 101 102 #include <netipsec/ipsec_support.h> 103 104 #include <machine/in_cksum.h> 105 106 #include <security/mac/mac_framework.h> 107 108 VNET_DEFINE(int, path_mtu_discovery) = 1; 109 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_VNET | CTLFLAG_RW, 110 &VNET_NAME(path_mtu_discovery), 1, 111 "Enable Path MTU Discovery"); 112 113 VNET_DEFINE(int, tcp_do_tso) = 1; 114 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_VNET | CTLFLAG_RW, 115 &VNET_NAME(tcp_do_tso), 0, 116 "Enable TCP Segmentation Offload"); 117 118 VNET_DEFINE(int, tcp_sendspace) = 1024*32; 119 #define V_tcp_sendspace VNET(tcp_sendspace) 120 SYSCTL_INT(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, CTLFLAG_VNET | CTLFLAG_RW, 121 &VNET_NAME(tcp_sendspace), 0, "Initial send socket buffer size"); 122 123 VNET_DEFINE(int, tcp_do_autosndbuf) = 1; 124 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_VNET | CTLFLAG_RW, 125 &VNET_NAME(tcp_do_autosndbuf), 0, 126 "Enable automatic send buffer sizing"); 127 128 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024; 129 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_VNET | CTLFLAG_RW, 130 &VNET_NAME(tcp_autosndbuf_inc), 0, 131 "Incrementor step size of automatic send buffer"); 132 133 VNET_DEFINE(int, tcp_autosndbuf_max) = 2*1024*1024; 134 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_VNET | CTLFLAG_RW, 135 &VNET_NAME(tcp_autosndbuf_max), 0, 136 "Max size of automatic send buffer"); 137 138 VNET_DEFINE(int, tcp_sendbuf_auto_lowat) = 0; 139 #define V_tcp_sendbuf_auto_lowat VNET(tcp_sendbuf_auto_lowat) 140 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto_lowat, CTLFLAG_VNET | CTLFLAG_RW, 141 &VNET_NAME(tcp_sendbuf_auto_lowat), 0, 142 "Modify threshold for auto send buffer growth to account for SO_SNDLOWAT"); 143 144 /* 145 * Make sure that either retransmit or persist timer is set for SYN, FIN and 146 * non-ACK. 147 */ 148 #define TCP_XMIT_TIMER_ASSERT(tp, len, th_flags) \ 149 KASSERT(((len) == 0 && ((th_flags) & (TH_SYN | TH_FIN)) == 0) ||\ 150 tcp_timer_active((tp), TT_REXMT) || \ 151 tcp_timer_active((tp), TT_PERSIST), \ 152 ("neither rexmt nor persist timer is set")) 153 154 static void inline cc_after_idle(struct tcpcb *tp); 155 156 #ifdef TCP_HHOOK 157 /* 158 * Wrapper for the TCP established output helper hook. 159 */ 160 void 161 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th, 162 struct tcpopt *to, uint32_t len, int tso) 163 { 164 struct tcp_hhook_data hhook_data; 165 166 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) { 167 hhook_data.tp = tp; 168 hhook_data.th = th; 169 hhook_data.to = to; 170 hhook_data.len = len; 171 hhook_data.tso = tso; 172 173 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data, 174 tp->osd); 175 } 176 } 177 #endif 178 179 /* 180 * CC wrapper hook functions 181 */ 182 static void inline 183 cc_after_idle(struct tcpcb *tp) 184 { 185 INP_WLOCK_ASSERT(tp->t_inpcb); 186 187 if (CC_ALGO(tp)->after_idle != NULL) 188 CC_ALGO(tp)->after_idle(tp->ccv); 189 } 190 191 /* 192 * Tcp output routine: figure out what should be sent and send it. 193 */ 194 int 195 tcp_output(struct tcpcb *tp) 196 { 197 struct socket *so = tp->t_inpcb->inp_socket; 198 int32_t len; 199 uint32_t recwin, sendwin; 200 int off, flags, error = 0; /* Keep compiler happy */ 201 u_int if_hw_tsomaxsegcount = 0; 202 u_int if_hw_tsomaxsegsize = 0; 203 struct mbuf *m; 204 struct ip *ip = NULL; 205 #ifdef TCPDEBUG 206 struct ipovly *ipov = NULL; 207 #endif 208 struct tcphdr *th; 209 u_char opt[TCP_MAXOLEN]; 210 unsigned ipoptlen, optlen, hdrlen; 211 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 212 unsigned ipsec_optlen = 0; 213 #endif 214 int idle, sendalot, curticks; 215 int sack_rxmit, sack_bytes_rxmt; 216 struct sackhole *p; 217 int tso, mtu; 218 struct tcpopt to; 219 unsigned int wanted_cookie = 0; 220 unsigned int dont_sendalot = 0; 221 #if 0 222 int maxburst = TCP_MAXBURST; 223 #endif 224 #ifdef INET6 225 struct ip6_hdr *ip6 = NULL; 226 int isipv6; 227 228 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 229 #endif 230 #ifdef KERN_TLS 231 const bool hw_tls = (so->so_snd.sb_flags & SB_TLS_IFNET) != 0; 232 #else 233 const bool hw_tls = false; 234 #endif 235 236 NET_EPOCH_ASSERT(); 237 INP_WLOCK_ASSERT(tp->t_inpcb); 238 239 #ifdef TCP_OFFLOAD 240 if (tp->t_flags & TF_TOE) 241 return (tcp_offload_output(tp)); 242 #endif 243 244 /* 245 * For TFO connections in SYN_SENT or SYN_RECEIVED, 246 * only allow the initial SYN or SYN|ACK and those sent 247 * by the retransmit timer. 248 */ 249 if (IS_FASTOPEN(tp->t_flags) && 250 ((tp->t_state == TCPS_SYN_SENT) || 251 (tp->t_state == TCPS_SYN_RECEIVED)) && 252 SEQ_GT(tp->snd_max, tp->snd_una) && /* initial SYN or SYN|ACK sent */ 253 (tp->snd_nxt != tp->snd_una)) /* not a retransmit */ 254 return (0); 255 256 /* 257 * Determine length of data that should be transmitted, 258 * and flags that will be used. 259 * If there is some data or critical controls (SYN, RST) 260 * to send, then transmit; otherwise, investigate further. 261 */ 262 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 263 if (idle && (((ticks - tp->t_rcvtime) >= tp->t_rxtcur) || 264 (tp->t_sndtime && ((ticks - tp->t_sndtime) >= tp->t_rxtcur)))) 265 cc_after_idle(tp); 266 tp->t_flags &= ~TF_LASTIDLE; 267 if (idle) { 268 if (tp->t_flags & TF_MORETOCOME) { 269 tp->t_flags |= TF_LASTIDLE; 270 idle = 0; 271 } 272 } 273 again: 274 /* 275 * If we've recently taken a timeout, snd_max will be greater than 276 * snd_nxt. There may be SACK information that allows us to avoid 277 * resending already delivered data. Adjust snd_nxt accordingly. 278 */ 279 if ((tp->t_flags & TF_SACK_PERMIT) && 280 SEQ_LT(tp->snd_nxt, tp->snd_max)) 281 tcp_sack_adjust(tp); 282 sendalot = 0; 283 tso = 0; 284 mtu = 0; 285 off = tp->snd_nxt - tp->snd_una; 286 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 287 288 flags = tcp_outflags[tp->t_state]; 289 /* 290 * Send any SACK-generated retransmissions. If we're explicitly trying 291 * to send out new data (when sendalot is 1), bypass this function. 292 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 293 * we're replacing a (future) new transmission with a retransmission 294 * now, and we previously incremented snd_cwnd in tcp_input(). 295 */ 296 /* 297 * Still in sack recovery , reset rxmit flag to zero. 298 */ 299 sack_rxmit = 0; 300 sack_bytes_rxmt = 0; 301 len = 0; 302 p = NULL; 303 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) && 304 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 305 uint32_t cwin; 306 307 cwin = 308 imax(min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt, 0); 309 /* Do not retransmit SACK segments beyond snd_recover */ 310 if (SEQ_GT(p->end, tp->snd_recover)) { 311 /* 312 * (At least) part of sack hole extends beyond 313 * snd_recover. Check to see if we can rexmit data 314 * for this hole. 315 */ 316 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 317 /* 318 * Can't rexmit any more data for this hole. 319 * That data will be rexmitted in the next 320 * sack recovery episode, when snd_recover 321 * moves past p->rxmit. 322 */ 323 p = NULL; 324 goto after_sack_rexmit; 325 } else 326 /* Can rexmit part of the current hole */ 327 len = ((int32_t)ulmin(cwin, 328 tp->snd_recover - p->rxmit)); 329 } else 330 len = ((int32_t)ulmin(cwin, p->end - p->rxmit)); 331 off = p->rxmit - tp->snd_una; 332 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 333 __func__, off)); 334 if (len > 0) { 335 sack_rxmit = 1; 336 sendalot = 1; 337 TCPSTAT_INC(tcps_sack_rexmits); 338 TCPSTAT_ADD(tcps_sack_rexmit_bytes, 339 min(len, tp->t_maxseg)); 340 } 341 } 342 after_sack_rexmit: 343 /* 344 * Get standard flags, and add SYN or FIN if requested by 'hidden' 345 * state flags. 346 */ 347 if (tp->t_flags & TF_NEEDFIN) 348 flags |= TH_FIN; 349 if (tp->t_flags & TF_NEEDSYN) 350 flags |= TH_SYN; 351 352 SOCKBUF_LOCK(&so->so_snd); 353 /* 354 * If in persist timeout with window of 0, send 1 byte. 355 * Otherwise, if window is small but nonzero 356 * and timer expired, we will send what we can 357 * and go to transmit state. 358 */ 359 if (tp->t_flags & TF_FORCEDATA) { 360 if (sendwin == 0) { 361 /* 362 * If we still have some data to send, then 363 * clear the FIN bit. Usually this would 364 * happen below when it realizes that we 365 * aren't sending all the data. However, 366 * if we have exactly 1 byte of unsent data, 367 * then it won't clear the FIN bit below, 368 * and if we are in persist state, we wind 369 * up sending the packet without recording 370 * that we sent the FIN bit. 371 * 372 * We can't just blindly clear the FIN bit, 373 * because if we don't have any more data 374 * to send then the probe will be the FIN 375 * itself. 376 */ 377 if (off < sbused(&so->so_snd)) 378 flags &= ~TH_FIN; 379 sendwin = 1; 380 } else { 381 tcp_timer_activate(tp, TT_PERSIST, 0); 382 tp->t_rxtshift = 0; 383 } 384 } 385 386 /* 387 * If snd_nxt == snd_max and we have transmitted a FIN, the 388 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 389 * a negative length. This can also occur when TCP opens up 390 * its congestion window while receiving additional duplicate 391 * acks after fast-retransmit because TCP will reset snd_nxt 392 * to snd_max after the fast-retransmit. 393 * 394 * In the normal retransmit-FIN-only case, however, snd_nxt will 395 * be set to snd_una, the offset will be 0, and the length may 396 * wind up 0. 397 * 398 * If sack_rxmit is true we are retransmitting from the scoreboard 399 * in which case len is already set. 400 */ 401 if (sack_rxmit == 0) { 402 if (sack_bytes_rxmt == 0) 403 len = ((int32_t)min(sbavail(&so->so_snd), sendwin) - 404 off); 405 else { 406 int32_t cwin; 407 408 /* 409 * We are inside of a SACK recovery episode and are 410 * sending new data, having retransmitted all the 411 * data possible in the scoreboard. 412 */ 413 len = ((int32_t)min(sbavail(&so->so_snd), tp->snd_wnd) - 414 off); 415 /* 416 * Don't remove this (len > 0) check ! 417 * We explicitly check for len > 0 here (although it 418 * isn't really necessary), to work around a gcc 419 * optimization issue - to force gcc to compute 420 * len above. Without this check, the computation 421 * of len is bungled by the optimizer. 422 */ 423 if (len > 0) { 424 cwin = tp->snd_cwnd - 425 (tp->snd_nxt - tp->snd_recover) - 426 sack_bytes_rxmt; 427 if (cwin < 0) 428 cwin = 0; 429 len = imin(len, cwin); 430 } 431 } 432 } 433 434 /* 435 * Lop off SYN bit if it has already been sent. However, if this 436 * is SYN-SENT state and if segment contains data and if we don't 437 * know that foreign host supports TAO, suppress sending segment. 438 */ 439 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 440 if (tp->t_state != TCPS_SYN_RECEIVED) 441 flags &= ~TH_SYN; 442 /* 443 * When sending additional segments following a TFO SYN|ACK, 444 * do not include the SYN bit. 445 */ 446 if (IS_FASTOPEN(tp->t_flags) && 447 (tp->t_state == TCPS_SYN_RECEIVED)) 448 flags &= ~TH_SYN; 449 off--, len++; 450 } 451 452 /* 453 * Be careful not to send data and/or FIN on SYN segments. 454 * This measure is needed to prevent interoperability problems 455 * with not fully conformant TCP implementations. 456 */ 457 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 458 len = 0; 459 flags &= ~TH_FIN; 460 } 461 462 /* 463 * On TFO sockets, ensure no data is sent in the following cases: 464 * 465 * - When retransmitting SYN|ACK on a passively-created socket 466 * 467 * - When retransmitting SYN on an actively created socket 468 * 469 * - When sending a zero-length cookie (cookie request) on an 470 * actively created socket 471 * 472 * - When the socket is in the CLOSED state (RST is being sent) 473 */ 474 if (IS_FASTOPEN(tp->t_flags) && 475 (((flags & TH_SYN) && (tp->t_rxtshift > 0)) || 476 ((tp->t_state == TCPS_SYN_SENT) && 477 (tp->t_tfo_client_cookie_len == 0)) || 478 (flags & TH_RST))) 479 len = 0; 480 if (len <= 0) { 481 /* 482 * If FIN has been sent but not acked, 483 * but we haven't been called to retransmit, 484 * len will be < 0. Otherwise, window shrank 485 * after we sent into it. If window shrank to 0, 486 * cancel pending retransmit, pull snd_nxt back 487 * to (closed) window, and set the persist timer 488 * if it isn't already going. If the window didn't 489 * close completely, just wait for an ACK. 490 * 491 * We also do a general check here to ensure that 492 * we will set the persist timer when we have data 493 * to send, but a 0-byte window. This makes sure 494 * the persist timer is set even if the packet 495 * hits one of the "goto send" lines below. 496 */ 497 len = 0; 498 if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) && 499 (off < (int) sbavail(&so->so_snd))) { 500 tcp_timer_activate(tp, TT_REXMT, 0); 501 tp->t_rxtshift = 0; 502 tp->snd_nxt = tp->snd_una; 503 if (!tcp_timer_active(tp, TT_PERSIST)) 504 tcp_setpersist(tp); 505 } 506 } 507 508 /* len will be >= 0 after this point. */ 509 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 510 511 tcp_sndbuf_autoscale(tp, so, sendwin); 512 513 /* 514 * Decide if we can use TCP Segmentation Offloading (if supported by 515 * hardware). 516 * 517 * TSO may only be used if we are in a pure bulk sending state. The 518 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 519 * IP options prevent using TSO. With TSO the TCP header is the same 520 * (except for the sequence number) for all generated packets. This 521 * makes it impossible to transmit any options which vary per generated 522 * segment or packet. 523 * 524 * IPv4 handling has a clear separation of ip options and ip header 525 * flags while IPv6 combines both in in6p_outputopts. ip6_optlen() does 526 * the right thing below to provide length of just ip options and thus 527 * checking for ipoptlen is enough to decide if ip options are present. 528 */ 529 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 530 /* 531 * Pre-calculate here as we save another lookup into the darknesses 532 * of IPsec that way and can actually decide if TSO is ok. 533 */ 534 #ifdef INET6 535 if (isipv6 && IPSEC_ENABLED(ipv6)) 536 ipsec_optlen = IPSEC_HDRSIZE(ipv6, tp->t_inpcb); 537 #ifdef INET 538 else 539 #endif 540 #endif /* INET6 */ 541 #ifdef INET 542 if (IPSEC_ENABLED(ipv4)) 543 ipsec_optlen = IPSEC_HDRSIZE(ipv4, tp->t_inpcb); 544 #endif /* INET */ 545 #endif /* IPSEC */ 546 #ifdef INET6 547 if (isipv6) 548 ipoptlen = ip6_optlen(tp->t_inpcb); 549 else 550 #endif 551 if (tp->t_inpcb->inp_options) 552 ipoptlen = tp->t_inpcb->inp_options->m_len - 553 offsetof(struct ipoption, ipopt_list); 554 else 555 ipoptlen = 0; 556 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 557 ipoptlen += ipsec_optlen; 558 #endif 559 560 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg && 561 ((tp->t_flags & TF_SIGNATURE) == 0) && 562 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 563 ipoptlen == 0 && !(flags & TH_SYN)) 564 tso = 1; 565 566 if (sack_rxmit) { 567 if (SEQ_LT(p->rxmit + len, tp->snd_una + sbused(&so->so_snd))) 568 flags &= ~TH_FIN; 569 } else { 570 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + 571 sbused(&so->so_snd))) 572 flags &= ~TH_FIN; 573 } 574 575 recwin = lmin(lmax(sbspace(&so->so_rcv), 0), 576 (long)TCP_MAXWIN << tp->rcv_scale); 577 578 /* 579 * Sender silly window avoidance. We transmit under the following 580 * conditions when len is non-zero: 581 * 582 * - We have a full segment (or more with TSO) 583 * - This is the last buffer in a write()/send() and we are 584 * either idle or running NODELAY 585 * - we've timed out (e.g. persist timer) 586 * - we have more then 1/2 the maximum send window's worth of 587 * data (receiver may be limited the window size) 588 * - we need to retransmit 589 */ 590 if (len) { 591 if (len >= tp->t_maxseg) 592 goto send; 593 /* 594 * NOTE! on localhost connections an 'ack' from the remote 595 * end may occur synchronously with the output and cause 596 * us to flush a buffer queued with moretocome. XXX 597 * 598 * note: the len + off check is almost certainly unnecessary. 599 */ 600 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 601 (idle || (tp->t_flags & TF_NODELAY)) && 602 (uint32_t)len + (uint32_t)off >= sbavail(&so->so_snd) && 603 (tp->t_flags & TF_NOPUSH) == 0) { 604 goto send; 605 } 606 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 607 goto send; 608 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 609 goto send; 610 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 611 goto send; 612 if (sack_rxmit) 613 goto send; 614 } 615 616 /* 617 * Sending of standalone window updates. 618 * 619 * Window updates are important when we close our window due to a 620 * full socket buffer and are opening it again after the application 621 * reads data from it. Once the window has opened again and the 622 * remote end starts to send again the ACK clock takes over and 623 * provides the most current window information. 624 * 625 * We must avoid the silly window syndrome whereas every read 626 * from the receive buffer, no matter how small, causes a window 627 * update to be sent. We also should avoid sending a flurry of 628 * window updates when the socket buffer had queued a lot of data 629 * and the application is doing small reads. 630 * 631 * Prevent a flurry of pointless window updates by only sending 632 * an update when we can increase the advertized window by more 633 * than 1/4th of the socket buffer capacity. When the buffer is 634 * getting full or is very small be more aggressive and send an 635 * update whenever we can increase by two mss sized segments. 636 * In all other situations the ACK's to new incoming data will 637 * carry further window increases. 638 * 639 * Don't send an independent window update if a delayed 640 * ACK is pending (it will get piggy-backed on it) or the 641 * remote side already has done a half-close and won't send 642 * more data. Skip this if the connection is in T/TCP 643 * half-open state. 644 */ 645 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 646 !(tp->t_flags & TF_DELACK) && 647 !TCPS_HAVERCVDFIN(tp->t_state)) { 648 /* 649 * "adv" is the amount we could increase the window, 650 * taking into account that we are limited by 651 * TCP_MAXWIN << tp->rcv_scale. 652 */ 653 int32_t adv; 654 int oldwin; 655 656 adv = recwin; 657 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { 658 oldwin = (tp->rcv_adv - tp->rcv_nxt); 659 if (adv > oldwin) 660 adv -= oldwin; 661 else 662 adv = 0; 663 } else 664 oldwin = 0; 665 666 /* 667 * If the new window size ends up being the same as or less 668 * than the old size when it is scaled, then don't force 669 * a window update. 670 */ 671 if (oldwin >> tp->rcv_scale >= (adv + oldwin) >> tp->rcv_scale) 672 goto dontupdate; 673 674 if (adv >= (int32_t)(2 * tp->t_maxseg) && 675 (adv >= (int32_t)(so->so_rcv.sb_hiwat / 4) || 676 recwin <= (so->so_rcv.sb_hiwat / 8) || 677 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg || 678 adv >= TCP_MAXWIN << tp->rcv_scale)) 679 goto send; 680 if (2 * adv >= (int32_t)so->so_rcv.sb_hiwat) 681 goto send; 682 } 683 dontupdate: 684 685 /* 686 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 687 * is also a catch-all for the retransmit timer timeout case. 688 */ 689 if (tp->t_flags & TF_ACKNOW) 690 goto send; 691 if ((flags & TH_RST) || 692 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 693 goto send; 694 if (SEQ_GT(tp->snd_up, tp->snd_una)) 695 goto send; 696 /* 697 * If our state indicates that FIN should be sent 698 * and we have not yet done so, then we need to send. 699 */ 700 if (flags & TH_FIN && 701 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 702 goto send; 703 /* 704 * In SACK, it is possible for tcp_output to fail to send a segment 705 * after the retransmission timer has been turned off. Make sure 706 * that the retransmission timer is set. 707 */ 708 if ((tp->t_flags & TF_SACK_PERMIT) && 709 SEQ_GT(tp->snd_max, tp->snd_una) && 710 !tcp_timer_active(tp, TT_REXMT) && 711 !tcp_timer_active(tp, TT_PERSIST)) { 712 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 713 goto just_return; 714 } 715 /* 716 * TCP window updates are not reliable, rather a polling protocol 717 * using ``persist'' packets is used to insure receipt of window 718 * updates. The three ``states'' for the output side are: 719 * idle not doing retransmits or persists 720 * persisting to move a small or zero window 721 * (re)transmitting and thereby not persisting 722 * 723 * tcp_timer_active(tp, TT_PERSIST) 724 * is true when we are in persist state. 725 * (tp->t_flags & TF_FORCEDATA) 726 * is set when we are called to send a persist packet. 727 * tcp_timer_active(tp, TT_REXMT) 728 * is set when we are retransmitting 729 * The output side is idle when both timers are zero. 730 * 731 * If send window is too small, there is data to transmit, and no 732 * retransmit or persist is pending, then go to persist state. 733 * If nothing happens soon, send when timer expires: 734 * if window is nonzero, transmit what we can, 735 * otherwise force out a byte. 736 */ 737 if (sbavail(&so->so_snd) && !tcp_timer_active(tp, TT_REXMT) && 738 !tcp_timer_active(tp, TT_PERSIST)) { 739 tp->t_rxtshift = 0; 740 tcp_setpersist(tp); 741 } 742 743 /* 744 * No reason to send a segment, just return. 745 */ 746 just_return: 747 SOCKBUF_UNLOCK(&so->so_snd); 748 return (0); 749 750 send: 751 SOCKBUF_LOCK_ASSERT(&so->so_snd); 752 if (len > 0) { 753 if (len >= tp->t_maxseg) 754 tp->t_flags2 |= TF2_PLPMTU_MAXSEGSNT; 755 else 756 tp->t_flags2 &= ~TF2_PLPMTU_MAXSEGSNT; 757 } 758 /* 759 * Before ESTABLISHED, force sending of initial options 760 * unless TCP set not to do any options. 761 * NOTE: we assume that the IP/TCP header plus TCP options 762 * always fit in a single mbuf, leaving room for a maximum 763 * link header, i.e. 764 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 765 */ 766 optlen = 0; 767 #ifdef INET6 768 if (isipv6) 769 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 770 else 771 #endif 772 hdrlen = sizeof (struct tcpiphdr); 773 774 /* 775 * Compute options for segment. 776 * We only have to care about SYN and established connection 777 * segments. Options for SYN-ACK segments are handled in TCP 778 * syncache. 779 */ 780 to.to_flags = 0; 781 if ((tp->t_flags & TF_NOOPT) == 0) { 782 /* Maximum segment size. */ 783 if (flags & TH_SYN) { 784 tp->snd_nxt = tp->iss; 785 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 786 to.to_flags |= TOF_MSS; 787 788 /* 789 * On SYN or SYN|ACK transmits on TFO connections, 790 * only include the TFO option if it is not a 791 * retransmit, as the presence of the TFO option may 792 * have caused the original SYN or SYN|ACK to have 793 * been dropped by a middlebox. 794 */ 795 if (IS_FASTOPEN(tp->t_flags) && 796 (tp->t_rxtshift == 0)) { 797 if (tp->t_state == TCPS_SYN_RECEIVED) { 798 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN; 799 to.to_tfo_cookie = 800 (u_int8_t *)&tp->t_tfo_cookie.server; 801 to.to_flags |= TOF_FASTOPEN; 802 wanted_cookie = 1; 803 } else if (tp->t_state == TCPS_SYN_SENT) { 804 to.to_tfo_len = 805 tp->t_tfo_client_cookie_len; 806 to.to_tfo_cookie = 807 tp->t_tfo_cookie.client; 808 to.to_flags |= TOF_FASTOPEN; 809 wanted_cookie = 1; 810 /* 811 * If we wind up having more data to 812 * send with the SYN than can fit in 813 * one segment, don't send any more 814 * until the SYN|ACK comes back from 815 * the other end. 816 */ 817 dont_sendalot = 1; 818 } 819 } 820 } 821 /* Window scaling. */ 822 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 823 to.to_wscale = tp->request_r_scale; 824 to.to_flags |= TOF_SCALE; 825 } 826 /* Timestamps. */ 827 if ((tp->t_flags & TF_RCVD_TSTMP) || 828 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 829 curticks = tcp_ts_getticks(); 830 to.to_tsval = curticks + tp->ts_offset; 831 to.to_tsecr = tp->ts_recent; 832 to.to_flags |= TOF_TS; 833 if (tp->t_rxtshift == 1) 834 tp->t_badrxtwin = curticks; 835 } 836 837 /* Set receive buffer autosizing timestamp. */ 838 if (tp->rfbuf_ts == 0 && 839 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 840 tp->rfbuf_ts = tcp_ts_getticks(); 841 842 /* Selective ACK's. */ 843 if (tp->t_flags & TF_SACK_PERMIT) { 844 if (flags & TH_SYN) 845 to.to_flags |= TOF_SACKPERM; 846 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 847 (tp->t_flags & TF_SACK_PERMIT) && 848 tp->rcv_numsacks > 0) { 849 to.to_flags |= TOF_SACK; 850 to.to_nsacks = tp->rcv_numsacks; 851 to.to_sacks = (u_char *)tp->sackblks; 852 } 853 } 854 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 855 /* TCP-MD5 (RFC2385). */ 856 /* 857 * Check that TCP_MD5SIG is enabled in tcpcb to 858 * account the size needed to set this TCP option. 859 */ 860 if (tp->t_flags & TF_SIGNATURE) 861 to.to_flags |= TOF_SIGNATURE; 862 #endif /* TCP_SIGNATURE */ 863 864 /* Processing the options. */ 865 hdrlen += optlen = tcp_addoptions(&to, opt); 866 /* 867 * If we wanted a TFO option to be added, but it was unable 868 * to fit, ensure no data is sent. 869 */ 870 if (IS_FASTOPEN(tp->t_flags) && wanted_cookie && 871 !(to.to_flags & TOF_FASTOPEN)) 872 len = 0; 873 } 874 875 /* 876 * Adjust data length if insertion of options will 877 * bump the packet length beyond the t_maxseg length. 878 * Clear the FIN bit because we cut off the tail of 879 * the segment. 880 */ 881 if (len + optlen + ipoptlen > tp->t_maxseg) { 882 flags &= ~TH_FIN; 883 884 if (tso) { 885 u_int if_hw_tsomax; 886 u_int moff; 887 int max_len; 888 889 /* extract TSO information */ 890 if_hw_tsomax = tp->t_tsomax; 891 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount; 892 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize; 893 894 /* 895 * Limit a TSO burst to prevent it from 896 * overflowing or exceeding the maximum length 897 * allowed by the network interface: 898 */ 899 KASSERT(ipoptlen == 0, 900 ("%s: TSO can't do IP options", __func__)); 901 902 /* 903 * Check if we should limit by maximum payload 904 * length: 905 */ 906 if (if_hw_tsomax != 0) { 907 /* compute maximum TSO length */ 908 max_len = (if_hw_tsomax - hdrlen - 909 max_linkhdr); 910 if (max_len <= 0) { 911 len = 0; 912 } else if (len > max_len) { 913 sendalot = 1; 914 len = max_len; 915 } 916 } 917 918 /* 919 * Prevent the last segment from being 920 * fractional unless the send sockbuf can be 921 * emptied: 922 */ 923 max_len = (tp->t_maxseg - optlen); 924 if (((uint32_t)off + (uint32_t)len) < 925 sbavail(&so->so_snd)) { 926 moff = len % max_len; 927 if (moff != 0) { 928 len -= moff; 929 sendalot = 1; 930 } 931 } 932 933 /* 934 * In case there are too many small fragments 935 * don't use TSO: 936 */ 937 if (len <= max_len) { 938 len = max_len; 939 sendalot = 1; 940 tso = 0; 941 } 942 943 /* 944 * Send the FIN in a separate segment 945 * after the bulk sending is done. 946 * We don't trust the TSO implementations 947 * to clear the FIN flag on all but the 948 * last segment. 949 */ 950 if (tp->t_flags & TF_NEEDFIN) 951 sendalot = 1; 952 } else { 953 if (optlen + ipoptlen >= tp->t_maxseg) { 954 /* 955 * Since we don't have enough space to put 956 * the IP header chain and the TCP header in 957 * one packet as required by RFC 7112, don't 958 * send it. Also ensure that at least one 959 * byte of the payload can be put into the 960 * TCP segment. 961 */ 962 SOCKBUF_UNLOCK(&so->so_snd); 963 error = EMSGSIZE; 964 sack_rxmit = 0; 965 goto out; 966 } 967 len = tp->t_maxseg - optlen - ipoptlen; 968 sendalot = 1; 969 if (dont_sendalot) 970 sendalot = 0; 971 } 972 } else 973 tso = 0; 974 975 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 976 ("%s: len > IP_MAXPACKET", __func__)); 977 978 /*#ifdef DIAGNOSTIC*/ 979 #ifdef INET6 980 if (max_linkhdr + hdrlen > MCLBYTES) 981 #else 982 if (max_linkhdr + hdrlen > MHLEN) 983 #endif 984 panic("tcphdr too big"); 985 /*#endif*/ 986 987 /* 988 * This KASSERT is here to catch edge cases at a well defined place. 989 * Before, those had triggered (random) panic conditions further down. 990 */ 991 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 992 993 /* 994 * Grab a header mbuf, attaching a copy of data to 995 * be transmitted, and initialize the header from 996 * the template for sends on this connection. 997 */ 998 if (len) { 999 struct mbuf *mb; 1000 struct sockbuf *msb; 1001 u_int moff; 1002 1003 if ((tp->t_flags & TF_FORCEDATA) && len == 1) { 1004 TCPSTAT_INC(tcps_sndprobe); 1005 #ifdef STATS 1006 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1007 stats_voi_update_abs_u32(tp->t_stats, 1008 VOI_TCP_RETXPB, len); 1009 else 1010 stats_voi_update_abs_u64(tp->t_stats, 1011 VOI_TCP_TXPB, len); 1012 #endif /* STATS */ 1013 } else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 1014 tp->t_sndrexmitpack++; 1015 TCPSTAT_INC(tcps_sndrexmitpack); 1016 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 1017 #ifdef STATS 1018 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_RETXPB, 1019 len); 1020 #endif /* STATS */ 1021 } else { 1022 TCPSTAT_INC(tcps_sndpack); 1023 TCPSTAT_ADD(tcps_sndbyte, len); 1024 #ifdef STATS 1025 stats_voi_update_abs_u64(tp->t_stats, VOI_TCP_TXPB, 1026 len); 1027 #endif /* STATS */ 1028 } 1029 #ifdef INET6 1030 if (MHLEN < hdrlen + max_linkhdr) 1031 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR); 1032 else 1033 #endif 1034 m = m_gethdr(M_NOWAIT, MT_DATA); 1035 1036 if (m == NULL) { 1037 SOCKBUF_UNLOCK(&so->so_snd); 1038 error = ENOBUFS; 1039 sack_rxmit = 0; 1040 goto out; 1041 } 1042 1043 m->m_data += max_linkhdr; 1044 m->m_len = hdrlen; 1045 1046 /* 1047 * Start the m_copy functions from the closest mbuf 1048 * to the offset in the socket buffer chain. 1049 */ 1050 mb = sbsndptr_noadv(&so->so_snd, off, &moff); 1051 if (len <= MHLEN - hdrlen - max_linkhdr && !hw_tls) { 1052 m_copydata(mb, moff, len, 1053 mtod(m, caddr_t) + hdrlen); 1054 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1055 sbsndptr_adv(&so->so_snd, mb, len); 1056 m->m_len += len; 1057 } else { 1058 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1059 msb = NULL; 1060 else 1061 msb = &so->so_snd; 1062 m->m_next = tcp_m_copym(mb, moff, 1063 &len, if_hw_tsomaxsegcount, 1064 if_hw_tsomaxsegsize, msb, hw_tls); 1065 if (len <= (tp->t_maxseg - optlen)) { 1066 /* 1067 * Must have ran out of mbufs for the copy 1068 * shorten it to no longer need tso. Lets 1069 * not put on sendalot since we are low on 1070 * mbufs. 1071 */ 1072 tso = 0; 1073 } 1074 if (m->m_next == NULL) { 1075 SOCKBUF_UNLOCK(&so->so_snd); 1076 (void) m_free(m); 1077 error = ENOBUFS; 1078 sack_rxmit = 0; 1079 goto out; 1080 } 1081 } 1082 1083 /* 1084 * If we're sending everything we've got, set PUSH. 1085 * (This will keep happy those implementations which only 1086 * give data to the user when a buffer fills or 1087 * a PUSH comes in.) 1088 */ 1089 if (((uint32_t)off + (uint32_t)len == sbused(&so->so_snd)) && 1090 !(flags & TH_SYN)) 1091 flags |= TH_PUSH; 1092 SOCKBUF_UNLOCK(&so->so_snd); 1093 } else { 1094 SOCKBUF_UNLOCK(&so->so_snd); 1095 if (tp->t_flags & TF_ACKNOW) 1096 TCPSTAT_INC(tcps_sndacks); 1097 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 1098 TCPSTAT_INC(tcps_sndctrl); 1099 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 1100 TCPSTAT_INC(tcps_sndurg); 1101 else 1102 TCPSTAT_INC(tcps_sndwinup); 1103 1104 m = m_gethdr(M_NOWAIT, MT_DATA); 1105 if (m == NULL) { 1106 error = ENOBUFS; 1107 sack_rxmit = 0; 1108 goto out; 1109 } 1110 #ifdef INET6 1111 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 1112 MHLEN >= hdrlen) { 1113 M_ALIGN(m, hdrlen); 1114 } else 1115 #endif 1116 m->m_data += max_linkhdr; 1117 m->m_len = hdrlen; 1118 } 1119 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 1120 m->m_pkthdr.rcvif = (struct ifnet *)0; 1121 #ifdef MAC 1122 mac_inpcb_create_mbuf(tp->t_inpcb, m); 1123 #endif 1124 #ifdef INET6 1125 if (isipv6) { 1126 ip6 = mtod(m, struct ip6_hdr *); 1127 th = (struct tcphdr *)(ip6 + 1); 1128 tcpip_fillheaders(tp->t_inpcb, ip6, th); 1129 } else 1130 #endif /* INET6 */ 1131 { 1132 ip = mtod(m, struct ip *); 1133 #ifdef TCPDEBUG 1134 ipov = (struct ipovly *)ip; 1135 #endif 1136 th = (struct tcphdr *)(ip + 1); 1137 tcpip_fillheaders(tp->t_inpcb, ip, th); 1138 } 1139 1140 /* 1141 * Fill in fields, remembering maximum advertised 1142 * window for use in delaying messages about window sizes. 1143 * If resending a FIN, be sure not to use a new sequence number. 1144 */ 1145 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 1146 tp->snd_nxt == tp->snd_max) 1147 tp->snd_nxt--; 1148 /* 1149 * If we are starting a connection, send ECN setup 1150 * SYN packet. If we are on a retransmit, we may 1151 * resend those bits a number of times as per 1152 * RFC 3168. 1153 */ 1154 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn == 1) { 1155 if (tp->t_rxtshift >= 1) { 1156 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 1157 flags |= TH_ECE|TH_CWR; 1158 } else 1159 flags |= TH_ECE|TH_CWR; 1160 } 1161 /* Handle parallel SYN for ECN */ 1162 if ((tp->t_state == TCPS_SYN_RECEIVED) && 1163 (tp->t_flags2 & TF2_ECN_SND_ECE)) { 1164 flags |= TH_ECE; 1165 tp->t_flags2 &= ~TF2_ECN_SND_ECE; 1166 } 1167 1168 if (tp->t_state == TCPS_ESTABLISHED && 1169 (tp->t_flags2 & TF2_ECN_PERMIT)) { 1170 /* 1171 * If the peer has ECN, mark data packets with 1172 * ECN capable transmission (ECT). 1173 * Ignore pure ack packets, retransmissions and window probes. 1174 */ 1175 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 1176 (sack_rxmit == 0) && 1177 !((tp->t_flags & TF_FORCEDATA) && len == 1 && 1178 SEQ_LT(tp->snd_una, tp->snd_max))) { 1179 #ifdef INET6 1180 if (isipv6) 1181 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 1182 else 1183 #endif 1184 ip->ip_tos |= IPTOS_ECN_ECT0; 1185 TCPSTAT_INC(tcps_ecn_ect0); 1186 /* 1187 * Reply with proper ECN notifications. 1188 * Only set CWR on new data segments. 1189 */ 1190 if (tp->t_flags2 & TF2_ECN_SND_CWR) { 1191 flags |= TH_CWR; 1192 tp->t_flags2 &= ~TF2_ECN_SND_CWR; 1193 } 1194 } 1195 if (tp->t_flags2 & TF2_ECN_SND_ECE) 1196 flags |= TH_ECE; 1197 } 1198 1199 /* 1200 * If we are doing retransmissions, then snd_nxt will 1201 * not reflect the first unsent octet. For ACK only 1202 * packets, we do not want the sequence number of the 1203 * retransmitted packet, we want the sequence number 1204 * of the next unsent octet. So, if there is no data 1205 * (and no SYN or FIN), use snd_max instead of snd_nxt 1206 * when filling in ti_seq. But if we are in persist 1207 * state, snd_max might reflect one byte beyond the 1208 * right edge of the window, so use snd_nxt in that 1209 * case, since we know we aren't doing a retransmission. 1210 * (retransmit and persist are mutually exclusive...) 1211 */ 1212 if (sack_rxmit == 0) { 1213 if (len || (flags & (TH_SYN|TH_FIN)) || 1214 tcp_timer_active(tp, TT_PERSIST)) 1215 th->th_seq = htonl(tp->snd_nxt); 1216 else 1217 th->th_seq = htonl(tp->snd_max); 1218 } else { 1219 th->th_seq = htonl(p->rxmit); 1220 p->rxmit += len; 1221 tp->sackhint.sack_bytes_rexmit += len; 1222 } 1223 th->th_ack = htonl(tp->rcv_nxt); 1224 if (optlen) { 1225 bcopy(opt, th + 1, optlen); 1226 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1227 } 1228 th->th_flags = flags; 1229 /* 1230 * Calculate receive window. Don't shrink window, 1231 * but avoid silly window syndrome. 1232 * If a RST segment is sent, advertise a window of zero. 1233 */ 1234 if (flags & TH_RST) { 1235 recwin = 0; 1236 } else { 1237 if (recwin < (so->so_rcv.sb_hiwat / 4) && 1238 recwin < tp->t_maxseg) 1239 recwin = 0; 1240 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1241 recwin < (tp->rcv_adv - tp->rcv_nxt)) 1242 recwin = (tp->rcv_adv - tp->rcv_nxt); 1243 } 1244 /* 1245 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1246 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1247 * case is handled in syncache. 1248 */ 1249 if (flags & TH_SYN) 1250 th->th_win = htons((u_short) 1251 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1252 else { 1253 /* Avoid shrinking window with window scaling. */ 1254 recwin = roundup2(recwin, 1 << tp->rcv_scale); 1255 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1256 } 1257 1258 /* 1259 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1260 * a 0 window. This may cause the remote transmitter to stall. This 1261 * flag tells soreceive() to disable delayed acknowledgements when 1262 * draining the buffer. This can occur if the receiver is attempting 1263 * to read more data than can be buffered prior to transmitting on 1264 * the connection. 1265 */ 1266 if (th->th_win == 0) { 1267 tp->t_sndzerowin++; 1268 tp->t_flags |= TF_RXWIN0SENT; 1269 } else 1270 tp->t_flags &= ~TF_RXWIN0SENT; 1271 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1272 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1273 th->th_flags |= TH_URG; 1274 } else 1275 /* 1276 * If no urgent pointer to send, then we pull 1277 * the urgent pointer to the left edge of the send window 1278 * so that it doesn't drift into the send window on sequence 1279 * number wraparound. 1280 */ 1281 tp->snd_up = tp->snd_una; /* drag it along */ 1282 1283 /* 1284 * Put TCP length in extended header, and then 1285 * checksum extended header and data. 1286 */ 1287 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1288 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1289 1290 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1291 if (to.to_flags & TOF_SIGNATURE) { 1292 /* 1293 * Calculate MD5 signature and put it into the place 1294 * determined before. 1295 * NOTE: since TCP options buffer doesn't point into 1296 * mbuf's data, calculate offset and use it. 1297 */ 1298 if (!TCPMD5_ENABLED() || (error = TCPMD5_OUTPUT(m, th, 1299 (u_char *)(th + 1) + (to.to_signature - opt))) != 0) { 1300 /* 1301 * Do not send segment if the calculation of MD5 1302 * digest has failed. 1303 */ 1304 m_freem(m); 1305 goto out; 1306 } 1307 } 1308 #endif 1309 #ifdef INET6 1310 if (isipv6) { 1311 /* 1312 * There is no need to fill in ip6_plen right now. 1313 * It will be filled later by ip6_output. 1314 */ 1315 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1316 th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) + 1317 optlen + len, IPPROTO_TCP, 0); 1318 } 1319 #endif 1320 #if defined(INET6) && defined(INET) 1321 else 1322 #endif 1323 #ifdef INET 1324 { 1325 m->m_pkthdr.csum_flags = CSUM_TCP; 1326 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1327 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1328 1329 /* IP version must be set here for ipv4/ipv6 checking later */ 1330 KASSERT(ip->ip_v == IPVERSION, 1331 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1332 } 1333 #endif 1334 1335 /* 1336 * Enable TSO and specify the size of the segments. 1337 * The TCP pseudo header checksum is always provided. 1338 */ 1339 if (tso) { 1340 KASSERT(len > tp->t_maxseg - optlen, 1341 ("%s: len <= tso_segsz", __func__)); 1342 m->m_pkthdr.csum_flags |= CSUM_TSO; 1343 m->m_pkthdr.tso_segsz = tp->t_maxseg - optlen; 1344 } 1345 1346 KASSERT(len + hdrlen == m_length(m, NULL), 1347 ("%s: mbuf chain shorter than expected: %d + %u != %u", 1348 __func__, len, hdrlen, m_length(m, NULL))); 1349 1350 #ifdef TCP_HHOOK 1351 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1352 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1353 #endif 1354 1355 #ifdef TCPDEBUG 1356 /* 1357 * Trace. 1358 */ 1359 if (so->so_options & SO_DEBUG) { 1360 u_short save = 0; 1361 #ifdef INET6 1362 if (!isipv6) 1363 #endif 1364 { 1365 save = ipov->ih_len; 1366 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1367 } 1368 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1369 #ifdef INET6 1370 if (!isipv6) 1371 #endif 1372 ipov->ih_len = save; 1373 } 1374 #endif /* TCPDEBUG */ 1375 TCP_PROBE3(debug__output, tp, th, m); 1376 1377 /* We're getting ready to send; log now. */ 1378 TCP_LOG_EVENT(tp, th, &so->so_rcv, &so->so_snd, TCP_LOG_OUT, ERRNO_UNK, 1379 len, NULL, false); 1380 1381 /* 1382 * Fill in IP length and desired time to live and 1383 * send to IP level. There should be a better way 1384 * to handle ttl and tos; we could keep them in 1385 * the template, but need a way to checksum without them. 1386 */ 1387 /* 1388 * m->m_pkthdr.len should have been set before checksum calculation, 1389 * because in6_cksum() need it. 1390 */ 1391 #ifdef INET6 1392 if (isipv6) { 1393 /* 1394 * we separately set hoplimit for every segment, since the 1395 * user might want to change the value via setsockopt. 1396 * Also, desired default hop limit might be changed via 1397 * Neighbor Discovery. 1398 */ 1399 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1400 1401 /* 1402 * Set the packet size here for the benefit of DTrace probes. 1403 * ip6_output() will set it properly; it's supposed to include 1404 * the option header lengths as well. 1405 */ 1406 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6)); 1407 1408 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) 1409 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1410 else 1411 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1412 1413 if (tp->t_state == TCPS_SYN_SENT) 1414 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th); 1415 1416 TCP_PROBE5(send, NULL, tp, ip6, tp, th); 1417 1418 #ifdef TCPPCAP 1419 /* Save packet, if requested. */ 1420 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1421 #endif 1422 1423 /* TODO: IPv6 IP6TOS_ECT bit on */ 1424 error = ip6_output(m, tp->t_inpcb->in6p_outputopts, 1425 &tp->t_inpcb->inp_route6, 1426 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 1427 NULL, NULL, tp->t_inpcb); 1428 1429 if (error == EMSGSIZE && tp->t_inpcb->inp_route6.ro_nh != NULL) 1430 mtu = tp->t_inpcb->inp_route6.ro_nh->nh_mtu; 1431 } 1432 #endif /* INET6 */ 1433 #if defined(INET) && defined(INET6) 1434 else 1435 #endif 1436 #ifdef INET 1437 { 1438 ip->ip_len = htons(m->m_pkthdr.len); 1439 #ifdef INET6 1440 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1441 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1442 #endif /* INET6 */ 1443 /* 1444 * If we do path MTU discovery, then we set DF on every packet. 1445 * This might not be the best thing to do according to RFC3390 1446 * Section 2. However the tcp hostcache migitates the problem 1447 * so it affects only the first tcp connection with a host. 1448 * 1449 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1450 */ 1451 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) { 1452 ip->ip_off |= htons(IP_DF); 1453 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1454 } else { 1455 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1456 } 1457 1458 if (tp->t_state == TCPS_SYN_SENT) 1459 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th); 1460 1461 TCP_PROBE5(send, NULL, tp, ip, tp, th); 1462 1463 #ifdef TCPPCAP 1464 /* Save packet, if requested. */ 1465 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1466 #endif 1467 1468 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, 1469 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1470 tp->t_inpcb); 1471 1472 if (error == EMSGSIZE && tp->t_inpcb->inp_route.ro_nh != NULL) 1473 mtu = tp->t_inpcb->inp_route.ro_nh->nh_mtu; 1474 } 1475 #endif /* INET */ 1476 1477 out: 1478 /* 1479 * In transmit state, time the transmission and arrange for 1480 * the retransmit. In persist state, just set snd_max. 1481 */ 1482 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1483 !tcp_timer_active(tp, TT_PERSIST)) { 1484 tcp_seq startseq = tp->snd_nxt; 1485 1486 /* 1487 * Advance snd_nxt over sequence space of this segment. 1488 */ 1489 if (flags & (TH_SYN|TH_FIN)) { 1490 if (flags & TH_SYN) 1491 tp->snd_nxt++; 1492 if (flags & TH_FIN) { 1493 tp->snd_nxt++; 1494 tp->t_flags |= TF_SENTFIN; 1495 } 1496 } 1497 if (sack_rxmit) 1498 goto timer; 1499 tp->snd_nxt += len; 1500 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1501 tp->snd_max = tp->snd_nxt; 1502 /* 1503 * Time this transmission if not a retransmission and 1504 * not currently timing anything. 1505 */ 1506 tp->t_sndtime = ticks; 1507 if (tp->t_rtttime == 0) { 1508 tp->t_rtttime = ticks; 1509 tp->t_rtseq = startseq; 1510 TCPSTAT_INC(tcps_segstimed); 1511 } 1512 #ifdef STATS 1513 if (!(tp->t_flags & TF_GPUTINPROG) && len) { 1514 tp->t_flags |= TF_GPUTINPROG; 1515 tp->gput_seq = startseq; 1516 tp->gput_ack = startseq + 1517 ulmin(sbavail(&so->so_snd) - off, sendwin); 1518 tp->gput_ts = tcp_ts_getticks(); 1519 } 1520 #endif /* STATS */ 1521 } 1522 1523 /* 1524 * Set retransmit timer if not currently set, 1525 * and not doing a pure ack or a keep-alive probe. 1526 * Initial value for retransmit timer is smoothed 1527 * round-trip time + 2 * round-trip time variance. 1528 * Initialize shift counter which is used for backoff 1529 * of retransmit time. 1530 */ 1531 timer: 1532 if (!tcp_timer_active(tp, TT_REXMT) && 1533 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1534 (tp->snd_nxt != tp->snd_una))) { 1535 if (tcp_timer_active(tp, TT_PERSIST)) { 1536 tcp_timer_activate(tp, TT_PERSIST, 0); 1537 tp->t_rxtshift = 0; 1538 } 1539 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1540 } else if (len == 0 && sbavail(&so->so_snd) && 1541 !tcp_timer_active(tp, TT_REXMT) && 1542 !tcp_timer_active(tp, TT_PERSIST)) { 1543 /* 1544 * Avoid a situation where we do not set persist timer 1545 * after a zero window condition. For example: 1546 * 1) A -> B: packet with enough data to fill the window 1547 * 2) B -> A: ACK for #1 + new data (0 window 1548 * advertisement) 1549 * 3) A -> B: ACK for #2, 0 len packet 1550 * 1551 * In this case, A will not activate the persist timer, 1552 * because it chose to send a packet. Unless tcp_output 1553 * is called for some other reason (delayed ack timer, 1554 * another input packet from B, socket syscall), A will 1555 * not send zero window probes. 1556 * 1557 * So, if you send a 0-length packet, but there is data 1558 * in the socket buffer, and neither the rexmt or 1559 * persist timer is already set, then activate the 1560 * persist timer. 1561 */ 1562 tp->t_rxtshift = 0; 1563 tcp_setpersist(tp); 1564 } 1565 } else { 1566 /* 1567 * Persist case, update snd_max but since we are in 1568 * persist mode (no window) we do not update snd_nxt. 1569 */ 1570 int xlen = len; 1571 if (flags & TH_SYN) 1572 ++xlen; 1573 if (flags & TH_FIN) { 1574 ++xlen; 1575 tp->t_flags |= TF_SENTFIN; 1576 } 1577 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1578 tp->snd_max = tp->snd_nxt + xlen; 1579 } 1580 if ((error == 0) && 1581 (TCPS_HAVEESTABLISHED(tp->t_state) && 1582 (tp->t_flags & TF_SACK_PERMIT) && 1583 tp->rcv_numsacks > 0)) { 1584 /* Clean up any DSACK's sent */ 1585 tcp_clean_dsack_blocks(tp); 1586 } 1587 if (error) { 1588 /* Record the error. */ 1589 TCP_LOG_EVENT(tp, NULL, &so->so_rcv, &so->so_snd, TCP_LOG_OUT, 1590 error, 0, NULL, false); 1591 1592 /* 1593 * We know that the packet was lost, so back out the 1594 * sequence number advance, if any. 1595 * 1596 * If the error is EPERM the packet got blocked by the 1597 * local firewall. Normally we should terminate the 1598 * connection but the blocking may have been spurious 1599 * due to a firewall reconfiguration cycle. So we treat 1600 * it like a packet loss and let the retransmit timer and 1601 * timeouts do their work over time. 1602 * XXX: It is a POLA question whether calling tcp_drop right 1603 * away would be the really correct behavior instead. 1604 */ 1605 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1606 !tcp_timer_active(tp, TT_PERSIST)) && 1607 ((flags & TH_SYN) == 0) && 1608 (error != EPERM)) { 1609 if (sack_rxmit) { 1610 p->rxmit -= len; 1611 tp->sackhint.sack_bytes_rexmit -= len; 1612 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1613 ("sackhint bytes rtx >= 0")); 1614 } else 1615 tp->snd_nxt -= len; 1616 } 1617 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1618 switch (error) { 1619 case EACCES: 1620 case EPERM: 1621 tp->t_softerror = error; 1622 return (error); 1623 case ENOBUFS: 1624 TCP_XMIT_TIMER_ASSERT(tp, len, flags); 1625 tp->snd_cwnd = tp->t_maxseg; 1626 return (0); 1627 case EMSGSIZE: 1628 /* 1629 * For some reason the interface we used initially 1630 * to send segments changed to another or lowered 1631 * its MTU. 1632 * If TSO was active we either got an interface 1633 * without TSO capabilits or TSO was turned off. 1634 * If we obtained mtu from ip_output() then update 1635 * it and try again. 1636 */ 1637 if (tso) 1638 tp->t_flags &= ~TF_TSO; 1639 if (mtu != 0) { 1640 tcp_mss_update(tp, -1, mtu, NULL, NULL); 1641 goto again; 1642 } 1643 return (error); 1644 case EHOSTDOWN: 1645 case EHOSTUNREACH: 1646 case ENETDOWN: 1647 case ENETUNREACH: 1648 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1649 tp->t_softerror = error; 1650 return (0); 1651 } 1652 /* FALLTHROUGH */ 1653 default: 1654 return (error); 1655 } 1656 } 1657 TCPSTAT_INC(tcps_sndtotal); 1658 1659 /* 1660 * Data sent (as far as we can tell). 1661 * If this advertises a larger window than any other segment, 1662 * then remember the size of the advertised window. 1663 * Any pending ACK has now been sent. 1664 */ 1665 if (SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1666 tp->rcv_adv = tp->rcv_nxt + recwin; 1667 tp->last_ack_sent = tp->rcv_nxt; 1668 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1669 if (tcp_timer_active(tp, TT_DELACK)) 1670 tcp_timer_activate(tp, TT_DELACK, 0); 1671 #if 0 1672 /* 1673 * This completely breaks TCP if newreno is turned on. What happens 1674 * is that if delayed-acks are turned on on the receiver, this code 1675 * on the transmitter effectively destroys the TCP window, forcing 1676 * it to four packets (1.5Kx4 = 6K window). 1677 */ 1678 if (sendalot && --maxburst) 1679 goto again; 1680 #endif 1681 if (sendalot) 1682 goto again; 1683 return (0); 1684 } 1685 1686 void 1687 tcp_setpersist(struct tcpcb *tp) 1688 { 1689 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1690 int tt; 1691 1692 tp->t_flags &= ~TF_PREVVALID; 1693 if (tcp_timer_active(tp, TT_REXMT)) 1694 panic("tcp_setpersist: retransmit pending"); 1695 /* 1696 * Start/restart persistence timer. 1697 */ 1698 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1699 tcp_persmin, tcp_persmax); 1700 tcp_timer_activate(tp, TT_PERSIST, tt); 1701 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1702 tp->t_rxtshift++; 1703 } 1704 1705 /* 1706 * Insert TCP options according to the supplied parameters to the place 1707 * optp in a consistent way. Can handle unaligned destinations. 1708 * 1709 * The order of the option processing is crucial for optimal packing and 1710 * alignment for the scarce option space. 1711 * 1712 * The optimal order for a SYN/SYN-ACK segment is: 1713 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1714 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1715 * 1716 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1717 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1718 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1719 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1720 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1721 */ 1722 int 1723 tcp_addoptions(struct tcpopt *to, u_char *optp) 1724 { 1725 u_int32_t mask, optlen = 0; 1726 1727 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1728 if ((to->to_flags & mask) != mask) 1729 continue; 1730 if (optlen == TCP_MAXOLEN) 1731 break; 1732 switch (to->to_flags & mask) { 1733 case TOF_MSS: 1734 while (optlen % 4) { 1735 optlen += TCPOLEN_NOP; 1736 *optp++ = TCPOPT_NOP; 1737 } 1738 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1739 continue; 1740 optlen += TCPOLEN_MAXSEG; 1741 *optp++ = TCPOPT_MAXSEG; 1742 *optp++ = TCPOLEN_MAXSEG; 1743 to->to_mss = htons(to->to_mss); 1744 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1745 optp += sizeof(to->to_mss); 1746 break; 1747 case TOF_SCALE: 1748 while (!optlen || optlen % 2 != 1) { 1749 optlen += TCPOLEN_NOP; 1750 *optp++ = TCPOPT_NOP; 1751 } 1752 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1753 continue; 1754 optlen += TCPOLEN_WINDOW; 1755 *optp++ = TCPOPT_WINDOW; 1756 *optp++ = TCPOLEN_WINDOW; 1757 *optp++ = to->to_wscale; 1758 break; 1759 case TOF_SACKPERM: 1760 while (optlen % 2) { 1761 optlen += TCPOLEN_NOP; 1762 *optp++ = TCPOPT_NOP; 1763 } 1764 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1765 continue; 1766 optlen += TCPOLEN_SACK_PERMITTED; 1767 *optp++ = TCPOPT_SACK_PERMITTED; 1768 *optp++ = TCPOLEN_SACK_PERMITTED; 1769 break; 1770 case TOF_TS: 1771 while (!optlen || optlen % 4 != 2) { 1772 optlen += TCPOLEN_NOP; 1773 *optp++ = TCPOPT_NOP; 1774 } 1775 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1776 continue; 1777 optlen += TCPOLEN_TIMESTAMP; 1778 *optp++ = TCPOPT_TIMESTAMP; 1779 *optp++ = TCPOLEN_TIMESTAMP; 1780 to->to_tsval = htonl(to->to_tsval); 1781 to->to_tsecr = htonl(to->to_tsecr); 1782 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1783 optp += sizeof(to->to_tsval); 1784 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1785 optp += sizeof(to->to_tsecr); 1786 break; 1787 case TOF_SIGNATURE: 1788 { 1789 int siglen = TCPOLEN_SIGNATURE - 2; 1790 1791 while (!optlen || optlen % 4 != 2) { 1792 optlen += TCPOLEN_NOP; 1793 *optp++ = TCPOPT_NOP; 1794 } 1795 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) { 1796 to->to_flags &= ~TOF_SIGNATURE; 1797 continue; 1798 } 1799 optlen += TCPOLEN_SIGNATURE; 1800 *optp++ = TCPOPT_SIGNATURE; 1801 *optp++ = TCPOLEN_SIGNATURE; 1802 to->to_signature = optp; 1803 while (siglen--) 1804 *optp++ = 0; 1805 break; 1806 } 1807 case TOF_SACK: 1808 { 1809 int sackblks = 0; 1810 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1811 tcp_seq sack_seq; 1812 1813 while (!optlen || optlen % 4 != 2) { 1814 optlen += TCPOLEN_NOP; 1815 *optp++ = TCPOPT_NOP; 1816 } 1817 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1818 continue; 1819 optlen += TCPOLEN_SACKHDR; 1820 *optp++ = TCPOPT_SACK; 1821 sackblks = min(to->to_nsacks, 1822 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1823 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1824 while (sackblks--) { 1825 sack_seq = htonl(sack->start); 1826 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1827 optp += sizeof(sack_seq); 1828 sack_seq = htonl(sack->end); 1829 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1830 optp += sizeof(sack_seq); 1831 optlen += TCPOLEN_SACK; 1832 sack++; 1833 } 1834 TCPSTAT_INC(tcps_sack_send_blocks); 1835 break; 1836 } 1837 case TOF_FASTOPEN: 1838 { 1839 int total_len; 1840 1841 /* XXX is there any point to aligning this option? */ 1842 total_len = TCPOLEN_FAST_OPEN_EMPTY + to->to_tfo_len; 1843 if (TCP_MAXOLEN - optlen < total_len) { 1844 to->to_flags &= ~TOF_FASTOPEN; 1845 continue; 1846 } 1847 *optp++ = TCPOPT_FAST_OPEN; 1848 *optp++ = total_len; 1849 if (to->to_tfo_len > 0) { 1850 bcopy(to->to_tfo_cookie, optp, to->to_tfo_len); 1851 optp += to->to_tfo_len; 1852 } 1853 optlen += total_len; 1854 break; 1855 } 1856 default: 1857 panic("%s: unknown TCP option type", __func__); 1858 break; 1859 } 1860 } 1861 1862 /* Terminate and pad TCP options to a 4 byte boundary. */ 1863 if (optlen % 4) { 1864 optlen += TCPOLEN_EOL; 1865 *optp++ = TCPOPT_EOL; 1866 } 1867 /* 1868 * According to RFC 793 (STD0007): 1869 * "The content of the header beyond the End-of-Option option 1870 * must be header padding (i.e., zero)." 1871 * and later: "The padding is composed of zeros." 1872 */ 1873 while (optlen % 4) { 1874 optlen += TCPOLEN_PAD; 1875 *optp++ = TCPOPT_PAD; 1876 } 1877 1878 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1879 return (optlen); 1880 } 1881 1882 /* 1883 * This is a copy of m_copym(), taking the TSO segment size/limit 1884 * constraints into account, and advancing the sndptr as it goes. 1885 */ 1886 struct mbuf * 1887 tcp_m_copym(struct mbuf *m, int32_t off0, int32_t *plen, 1888 int32_t seglimit, int32_t segsize, struct sockbuf *sb, bool hw_tls) 1889 { 1890 #ifdef KERN_TLS 1891 struct ktls_session *tls, *ntls; 1892 struct mbuf *start; 1893 #endif 1894 struct mbuf *n, **np; 1895 struct mbuf *top; 1896 int32_t off = off0; 1897 int32_t len = *plen; 1898 int32_t fragsize; 1899 int32_t len_cp = 0; 1900 int32_t *pkthdrlen; 1901 uint32_t mlen, frags; 1902 bool copyhdr; 1903 1904 1905 KASSERT(off >= 0, ("tcp_m_copym, negative off %d", off)); 1906 KASSERT(len >= 0, ("tcp_m_copym, negative len %d", len)); 1907 if (off == 0 && m->m_flags & M_PKTHDR) 1908 copyhdr = true; 1909 else 1910 copyhdr = false; 1911 while (off > 0) { 1912 KASSERT(m != NULL, ("tcp_m_copym, offset > size of mbuf chain")); 1913 if (off < m->m_len) 1914 break; 1915 off -= m->m_len; 1916 if ((sb) && (m == sb->sb_sndptr)) { 1917 sb->sb_sndptroff += m->m_len; 1918 sb->sb_sndptr = m->m_next; 1919 } 1920 m = m->m_next; 1921 } 1922 np = ⊤ 1923 top = NULL; 1924 pkthdrlen = NULL; 1925 #ifdef KERN_TLS 1926 if (hw_tls && (m->m_flags & M_EXTPG)) 1927 tls = m->m_epg_tls; 1928 else 1929 tls = NULL; 1930 start = m; 1931 #endif 1932 while (len > 0) { 1933 if (m == NULL) { 1934 KASSERT(len == M_COPYALL, 1935 ("tcp_m_copym, length > size of mbuf chain")); 1936 *plen = len_cp; 1937 if (pkthdrlen != NULL) 1938 *pkthdrlen = len_cp; 1939 break; 1940 } 1941 #ifdef KERN_TLS 1942 if (hw_tls) { 1943 if (m->m_flags & M_EXTPG) 1944 ntls = m->m_epg_tls; 1945 else 1946 ntls = NULL; 1947 1948 /* 1949 * Avoid mixing TLS records with handshake 1950 * data or TLS records from different 1951 * sessions. 1952 */ 1953 if (tls != ntls) { 1954 MPASS(m != start); 1955 *plen = len_cp; 1956 if (pkthdrlen != NULL) 1957 *pkthdrlen = len_cp; 1958 break; 1959 } 1960 1961 /* 1962 * Don't end a send in the middle of a TLS 1963 * record if it spans multiple TLS records. 1964 */ 1965 if (tls != NULL && (m != start) && len < m->m_len) { 1966 *plen = len_cp; 1967 if (pkthdrlen != NULL) 1968 *pkthdrlen = len_cp; 1969 break; 1970 } 1971 } 1972 #endif 1973 mlen = min(len, m->m_len - off); 1974 if (seglimit) { 1975 /* 1976 * For M_EXTPG mbufs, add 3 segments 1977 * + 1 in case we are crossing page boundaries 1978 * + 2 in case the TLS hdr/trailer are used 1979 * It is cheaper to just add the segments 1980 * than it is to take the cache miss to look 1981 * at the mbuf ext_pgs state in detail. 1982 */ 1983 if (m->m_flags & M_EXTPG) { 1984 fragsize = min(segsize, PAGE_SIZE); 1985 frags = 3; 1986 } else { 1987 fragsize = segsize; 1988 frags = 0; 1989 } 1990 1991 /* Break if we really can't fit anymore. */ 1992 if ((frags + 1) >= seglimit) { 1993 *plen = len_cp; 1994 if (pkthdrlen != NULL) 1995 *pkthdrlen = len_cp; 1996 break; 1997 } 1998 1999 /* 2000 * Reduce size if you can't copy the whole 2001 * mbuf. If we can't copy the whole mbuf, also 2002 * adjust len so the loop will end after this 2003 * mbuf. 2004 */ 2005 if ((frags + howmany(mlen, fragsize)) >= seglimit) { 2006 mlen = (seglimit - frags - 1) * fragsize; 2007 len = mlen; 2008 *plen = len_cp + len; 2009 if (pkthdrlen != NULL) 2010 *pkthdrlen = *plen; 2011 } 2012 frags += howmany(mlen, fragsize); 2013 if (frags == 0) 2014 frags++; 2015 seglimit -= frags; 2016 KASSERT(seglimit > 0, 2017 ("%s: seglimit went too low", __func__)); 2018 } 2019 if (copyhdr) 2020 n = m_gethdr(M_NOWAIT, m->m_type); 2021 else 2022 n = m_get(M_NOWAIT, m->m_type); 2023 *np = n; 2024 if (n == NULL) 2025 goto nospace; 2026 if (copyhdr) { 2027 if (!m_dup_pkthdr(n, m, M_NOWAIT)) 2028 goto nospace; 2029 if (len == M_COPYALL) 2030 n->m_pkthdr.len -= off0; 2031 else 2032 n->m_pkthdr.len = len; 2033 pkthdrlen = &n->m_pkthdr.len; 2034 copyhdr = false; 2035 } 2036 n->m_len = mlen; 2037 len_cp += n->m_len; 2038 if (m->m_flags & (M_EXT|M_EXTPG)) { 2039 n->m_data = m->m_data + off; 2040 mb_dupcl(n, m); 2041 } else 2042 bcopy(mtod(m, caddr_t)+off, mtod(n, caddr_t), 2043 (u_int)n->m_len); 2044 2045 if (sb && (sb->sb_sndptr == m) && 2046 ((n->m_len + off) >= m->m_len) && m->m_next) { 2047 sb->sb_sndptroff += m->m_len; 2048 sb->sb_sndptr = m->m_next; 2049 } 2050 off = 0; 2051 if (len != M_COPYALL) { 2052 len -= n->m_len; 2053 } 2054 m = m->m_next; 2055 np = &n->m_next; 2056 } 2057 return (top); 2058 nospace: 2059 m_freem(top); 2060 return (NULL); 2061 } 2062 2063 void 2064 tcp_sndbuf_autoscale(struct tcpcb *tp, struct socket *so, uint32_t sendwin) 2065 { 2066 2067 /* 2068 * Automatic sizing of send socket buffer. Often the send buffer 2069 * size is not optimally adjusted to the actual network conditions 2070 * at hand (delay bandwidth product). Setting the buffer size too 2071 * small limits throughput on links with high bandwidth and high 2072 * delay (eg. trans-continental/oceanic links). Setting the 2073 * buffer size too big consumes too much real kernel memory, 2074 * especially with many connections on busy servers. 2075 * 2076 * The criteria to step up the send buffer one notch are: 2077 * 1. receive window of remote host is larger than send buffer 2078 * (with a fudge factor of 5/4th); 2079 * 2. send buffer is filled to 7/8th with data (so we actually 2080 * have data to make use of it); 2081 * 3. send buffer fill has not hit maximal automatic size; 2082 * 4. our send window (slow start and cogestion controlled) is 2083 * larger than sent but unacknowledged data in send buffer. 2084 * 2085 * The remote host receive window scaling factor may limit the 2086 * growing of the send buffer before it reaches its allowed 2087 * maximum. 2088 * 2089 * It scales directly with slow start or congestion window 2090 * and does at most one step per received ACK. This fast 2091 * scaling has the drawback of growing the send buffer beyond 2092 * what is strictly necessary to make full use of a given 2093 * delay*bandwidth product. However testing has shown this not 2094 * to be much of an problem. At worst we are trading wasting 2095 * of available bandwidth (the non-use of it) for wasting some 2096 * socket buffer memory. 2097 * 2098 * TODO: Shrink send buffer during idle periods together 2099 * with congestion window. Requires another timer. Has to 2100 * wait for upcoming tcp timer rewrite. 2101 * 2102 * XXXGL: should there be used sbused() or sbavail()? 2103 */ 2104 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 2105 int lowat; 2106 2107 lowat = V_tcp_sendbuf_auto_lowat ? so->so_snd.sb_lowat : 0; 2108 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat - lowat && 2109 sbused(&so->so_snd) >= 2110 (so->so_snd.sb_hiwat / 8 * 7) - lowat && 2111 sbused(&so->so_snd) < V_tcp_autosndbuf_max && 2112 sendwin >= (sbused(&so->so_snd) - 2113 (tp->snd_nxt - tp->snd_una))) { 2114 if (!sbreserve_locked(&so->so_snd, 2115 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 2116 V_tcp_autosndbuf_max), so, curthread)) 2117 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 2118 } 2119 } 2120 } 2121