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sys/netinet/tcp_output.c
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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_tcpdebug.h" 41 42 #include <sys/param.h> 43 #include <sys/systm.h> 44 #include <sys/domain.h> 45 #ifdef TCP_HHOOK 46 #include <sys/hhook.h> 47 #endif 48 #include <sys/kernel.h> 49 #include <sys/lock.h> 50 #include <sys/mbuf.h> 51 #include <sys/mutex.h> 52 #include <sys/protosw.h> 53 #include <sys/sdt.h> 54 #include <sys/socket.h> 55 #include <sys/socketvar.h> 56 #include <sys/sysctl.h> 57 58 #include <net/if.h> 59 #include <net/route.h> 60 #include <net/vnet.h> 61 62 #include <netinet/in.h> 63 #include <netinet/in_kdtrace.h> 64 #include <netinet/in_systm.h> 65 #include <netinet/ip.h> 66 #include <netinet/in_pcb.h> 67 #include <netinet/ip_var.h> 68 #include <netinet/ip_options.h> 69 #ifdef INET6 70 #include <netinet6/in6_pcb.h> 71 #include <netinet/ip6.h> 72 #include <netinet6/ip6_var.h> 73 #endif 74 #include <netinet/tcp.h> 75 #define TCPOUTFLAGS 76 #include <netinet/tcp_fsm.h> 77 #include <netinet/tcp_log_buf.h> 78 #include <netinet/tcp_seq.h> 79 #include <netinet/tcp_timer.h> 80 #include <netinet/tcp_var.h> 81 #include <netinet/tcpip.h> 82 #include <netinet/cc/cc.h> 83 #include <netinet/tcp_fastopen.h> 84 #ifdef TCPPCAP 85 #include <netinet/tcp_pcap.h> 86 #endif 87 #ifdef TCPDEBUG 88 #include <netinet/tcp_debug.h> 89 #endif 90 #ifdef TCP_OFFLOAD 91 #include <netinet/tcp_offload.h> 92 #endif 93 94 #include <netipsec/ipsec_support.h> 95 96 #include <machine/in_cksum.h> 97 98 #include <security/mac/mac_framework.h> 99 100 VNET_DEFINE(int, path_mtu_discovery) = 1; 101 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_VNET | CTLFLAG_RW, 102 &VNET_NAME(path_mtu_discovery), 1, 103 "Enable Path MTU Discovery"); 104 105 VNET_DEFINE(int, tcp_do_tso) = 1; 106 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_VNET | CTLFLAG_RW, 107 &VNET_NAME(tcp_do_tso), 0, 108 "Enable TCP Segmentation Offload"); 109 110 VNET_DEFINE(int, tcp_sendspace) = 1024*32; 111 #define V_tcp_sendspace VNET(tcp_sendspace) 112 SYSCTL_INT(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, CTLFLAG_VNET | CTLFLAG_RW, 113 &VNET_NAME(tcp_sendspace), 0, "Initial send socket buffer size"); 114 115 VNET_DEFINE(int, tcp_do_autosndbuf) = 1; 116 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_VNET | CTLFLAG_RW, 117 &VNET_NAME(tcp_do_autosndbuf), 0, 118 "Enable automatic send buffer sizing"); 119 120 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024; 121 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_VNET | CTLFLAG_RW, 122 &VNET_NAME(tcp_autosndbuf_inc), 0, 123 "Incrementor step size of automatic send buffer"); 124 125 VNET_DEFINE(int, tcp_autosndbuf_max) = 2*1024*1024; 126 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_VNET | CTLFLAG_RW, 127 &VNET_NAME(tcp_autosndbuf_max), 0, 128 "Max size of automatic send buffer"); 129 130 VNET_DEFINE(int, tcp_sendbuf_auto_lowat) = 0; 131 #define V_tcp_sendbuf_auto_lowat VNET(tcp_sendbuf_auto_lowat) 132 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto_lowat, CTLFLAG_VNET | CTLFLAG_RW, 133 &VNET_NAME(tcp_sendbuf_auto_lowat), 0, 134 "Modify threshold for auto send buffer growth to account for SO_SNDLOWAT"); 135 136 /* 137 * Make sure that either retransmit or persist timer is set for SYN, FIN and 138 * non-ACK. 139 */ 140 #define TCP_XMIT_TIMER_ASSERT(tp, len, th_flags) \ 141 KASSERT(((len) == 0 && ((th_flags) & (TH_SYN | TH_FIN)) == 0) ||\ 142 tcp_timer_active((tp), TT_REXMT) || \ 143 tcp_timer_active((tp), TT_PERSIST), \ 144 ("neither rexmt nor persist timer is set")) 145 146 static void inline cc_after_idle(struct tcpcb *tp); 147 148 #ifdef TCP_HHOOK 149 /* 150 * Wrapper for the TCP established output helper hook. 151 */ 152 void 153 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th, 154 struct tcpopt *to, uint32_t len, int tso) 155 { 156 struct tcp_hhook_data hhook_data; 157 158 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) { 159 hhook_data.tp = tp; 160 hhook_data.th = th; 161 hhook_data.to = to; 162 hhook_data.len = len; 163 hhook_data.tso = tso; 164 165 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data, 166 tp->osd); 167 } 168 } 169 #endif 170 171 /* 172 * CC wrapper hook functions 173 */ 174 static void inline 175 cc_after_idle(struct tcpcb *tp) 176 { 177 INP_WLOCK_ASSERT(tp->t_inpcb); 178 179 if (CC_ALGO(tp)->after_idle != NULL) 180 CC_ALGO(tp)->after_idle(tp->ccv); 181 } 182 183 /* 184 * Tcp output routine: figure out what should be sent and send it. 185 */ 186 int 187 tcp_output(struct tcpcb *tp) 188 { 189 struct socket *so = tp->t_inpcb->inp_socket; 190 int32_t len; 191 uint32_t recwin, sendwin; 192 int off, flags, error = 0; /* Keep compiler happy */ 193 u_int if_hw_tsomaxsegcount = 0; 194 u_int if_hw_tsomaxsegsize; 195 struct mbuf *m; 196 struct ip *ip = NULL; 197 #ifdef TCPDEBUG 198 struct ipovly *ipov = NULL; 199 #endif 200 struct tcphdr *th; 201 u_char opt[TCP_MAXOLEN]; 202 unsigned ipoptlen, optlen, hdrlen; 203 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 204 unsigned ipsec_optlen = 0; 205 #endif 206 int idle, sendalot, curticks; 207 int sack_rxmit, sack_bytes_rxmt; 208 struct sackhole *p; 209 int tso, mtu; 210 struct tcpopt to; 211 unsigned int wanted_cookie = 0; 212 unsigned int dont_sendalot = 0; 213 #if 0 214 int maxburst = TCP_MAXBURST; 215 #endif 216 #ifdef INET6 217 struct ip6_hdr *ip6 = NULL; 218 int isipv6; 219 220 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 221 #endif 222 223 INP_WLOCK_ASSERT(tp->t_inpcb); 224 225 #ifdef TCP_OFFLOAD 226 if (tp->t_flags & TF_TOE) 227 return (tcp_offload_output(tp)); 228 #endif 229 230 /* 231 * For TFO connections in SYN_SENT or SYN_RECEIVED, 232 * only allow the initial SYN or SYN|ACK and those sent 233 * by the retransmit timer. 234 */ 235 if (IS_FASTOPEN(tp->t_flags) && 236 ((tp->t_state == TCPS_SYN_SENT) || 237 (tp->t_state == TCPS_SYN_RECEIVED)) && 238 SEQ_GT(tp->snd_max, tp->snd_una) && /* initial SYN or SYN|ACK sent */ 239 (tp->snd_nxt != tp->snd_una)) /* not a retransmit */ 240 return (0); 241 242 /* 243 * Determine length of data that should be transmitted, 244 * and flags that will be used. 245 * If there is some data or critical controls (SYN, RST) 246 * to send, then transmit; otherwise, investigate further. 247 */ 248 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 249 if (idle && (((ticks - tp->t_rcvtime) >= tp->t_rxtcur) || 250 (tp->t_sndtime && ((ticks - tp->t_sndtime) >= tp->t_rxtcur)))) 251 cc_after_idle(tp); 252 tp->t_flags &= ~TF_LASTIDLE; 253 if (idle) { 254 if (tp->t_flags & TF_MORETOCOME) { 255 tp->t_flags |= TF_LASTIDLE; 256 idle = 0; 257 } 258 } 259 again: 260 /* 261 * If we've recently taken a timeout, snd_max will be greater than 262 * snd_nxt. There may be SACK information that allows us to avoid 263 * resending already delivered data. Adjust snd_nxt accordingly. 264 */ 265 if ((tp->t_flags & TF_SACK_PERMIT) && 266 SEQ_LT(tp->snd_nxt, tp->snd_max)) 267 tcp_sack_adjust(tp); 268 sendalot = 0; 269 tso = 0; 270 mtu = 0; 271 off = tp->snd_nxt - tp->snd_una; 272 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 273 274 flags = tcp_outflags[tp->t_state]; 275 /* 276 * Send any SACK-generated retransmissions. If we're explicitly trying 277 * to send out new data (when sendalot is 1), bypass this function. 278 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 279 * we're replacing a (future) new transmission with a retransmission 280 * now, and we previously incremented snd_cwnd in tcp_input(). 281 */ 282 /* 283 * Still in sack recovery , reset rxmit flag to zero. 284 */ 285 sack_rxmit = 0; 286 sack_bytes_rxmt = 0; 287 len = 0; 288 p = NULL; 289 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) && 290 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 291 uint32_t cwin; 292 293 cwin = 294 imax(min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt, 0); 295 /* Do not retransmit SACK segments beyond snd_recover */ 296 if (SEQ_GT(p->end, tp->snd_recover)) { 297 /* 298 * (At least) part of sack hole extends beyond 299 * snd_recover. Check to see if we can rexmit data 300 * for this hole. 301 */ 302 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 303 /* 304 * Can't rexmit any more data for this hole. 305 * That data will be rexmitted in the next 306 * sack recovery episode, when snd_recover 307 * moves past p->rxmit. 308 */ 309 p = NULL; 310 goto after_sack_rexmit; 311 } else { 312 /* Can rexmit part of the current hole */ 313 len = ((int32_t)ulmin(cwin, 314 SEQ_SUB(tp->snd_recover, p->rxmit))); 315 } 316 } else { 317 len = ((int32_t)ulmin(cwin, 318 SEQ_SUB(p->end, p->rxmit))); 319 } 320 if (len > 0) { 321 off = SEQ_SUB(p->rxmit, tp->snd_una); 322 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 323 __func__, off)); 324 sack_rxmit = 1; 325 sendalot = 1; 326 TCPSTAT_INC(tcps_sack_rexmits); 327 TCPSTAT_ADD(tcps_sack_rexmit_bytes, 328 min(len, tcp_maxseg(tp))); 329 } 330 } 331 after_sack_rexmit: 332 /* 333 * Get standard flags, and add SYN or FIN if requested by 'hidden' 334 * state flags. 335 */ 336 if (tp->t_flags & TF_NEEDFIN) 337 flags |= TH_FIN; 338 if (tp->t_flags & TF_NEEDSYN) 339 flags |= TH_SYN; 340 341 SOCKBUF_LOCK(&so->so_snd); 342 /* 343 * If in persist timeout with window of 0, send 1 byte. 344 * Otherwise, if window is small but nonzero 345 * and timer expired, we will send what we can 346 * and go to transmit state. 347 */ 348 if (tp->t_flags & TF_FORCEDATA) { 349 if (sendwin == 0) { 350 /* 351 * If we still have some data to send, then 352 * clear the FIN bit. Usually this would 353 * happen below when it realizes that we 354 * aren't sending all the data. However, 355 * if we have exactly 1 byte of unsent data, 356 * then it won't clear the FIN bit below, 357 * and if we are in persist state, we wind 358 * up sending the packet without recording 359 * that we sent the FIN bit. 360 * 361 * We can't just blindly clear the FIN bit, 362 * because if we don't have any more data 363 * to send then the probe will be the FIN 364 * itself. 365 */ 366 if (off < sbused(&so->so_snd)) 367 flags &= ~TH_FIN; 368 sendwin = 1; 369 } else { 370 tcp_timer_activate(tp, TT_PERSIST, 0); 371 tp->t_rxtshift = 0; 372 } 373 } 374 375 /* 376 * If snd_nxt == snd_max and we have transmitted a FIN, the 377 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 378 * a negative length. This can also occur when TCP opens up 379 * its congestion window while receiving additional duplicate 380 * acks after fast-retransmit because TCP will reset snd_nxt 381 * to snd_max after the fast-retransmit. 382 * 383 * In the normal retransmit-FIN-only case, however, snd_nxt will 384 * be set to snd_una, the offset will be 0, and the length may 385 * wind up 0. 386 * 387 * If sack_rxmit is true we are retransmitting from the scoreboard 388 * in which case len is already set. 389 */ 390 if (sack_rxmit == 0) { 391 if (sack_bytes_rxmt == 0) 392 len = ((int32_t)min(sbavail(&so->so_snd), sendwin) - 393 off); 394 else { 395 int32_t cwin; 396 397 /* 398 * We are inside of a SACK recovery episode and are 399 * sending new data, having retransmitted all the 400 * data possible in the scoreboard. 401 */ 402 len = ((int32_t)min(sbavail(&so->so_snd), tp->snd_wnd) - 403 off); 404 /* 405 * Don't remove this (len > 0) check ! 406 * We explicitly check for len > 0 here (although it 407 * isn't really necessary), to work around a gcc 408 * optimization issue - to force gcc to compute 409 * len above. Without this check, the computation 410 * of len is bungled by the optimizer. 411 */ 412 if (len > 0) { 413 cwin = tp->snd_cwnd - imax(0, (int32_t) 414 (tp->snd_nxt - tp->sack_newdata)) - 415 sack_bytes_rxmt; 416 if (cwin < 0) 417 cwin = 0; 418 len = imin(len, cwin); 419 } 420 } 421 } 422 423 /* 424 * Lop off SYN bit if it has already been sent. However, if this 425 * is SYN-SENT state and if segment contains data and if we don't 426 * know that foreign host supports TAO, suppress sending segment. 427 */ 428 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 429 if (tp->t_state != TCPS_SYN_RECEIVED) 430 flags &= ~TH_SYN; 431 /* 432 * When sending additional segments following a TFO SYN|ACK, 433 * do not include the SYN bit. 434 */ 435 if (IS_FASTOPEN(tp->t_flags) && 436 (tp->t_state == TCPS_SYN_RECEIVED)) 437 flags &= ~TH_SYN; 438 off--, len++; 439 } 440 441 /* 442 * Be careful not to send data and/or FIN on SYN segments. 443 * This measure is needed to prevent interoperability problems 444 * with not fully conformant TCP implementations. 445 */ 446 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 447 len = 0; 448 flags &= ~TH_FIN; 449 } 450 451 /* 452 * On TFO sockets, ensure no data is sent in the following cases: 453 * 454 * - When retransmitting SYN|ACK on a passively-created socket 455 * 456 * - When retransmitting SYN on an actively created socket 457 * 458 * - When sending a zero-length cookie (cookie request) on an 459 * actively created socket 460 * 461 * - When the socket is in the CLOSED state (RST is being sent) 462 */ 463 if (IS_FASTOPEN(tp->t_flags) && 464 (((flags & TH_SYN) && (tp->t_rxtshift > 0)) || 465 ((tp->t_state == TCPS_SYN_SENT) && 466 (tp->t_tfo_client_cookie_len == 0)) || 467 (flags & TH_RST))) 468 len = 0; 469 if (len <= 0) { 470 /* 471 * If FIN has been sent but not acked, 472 * but we haven't been called to retransmit, 473 * len will be < 0. Otherwise, window shrank 474 * after we sent into it. If window shrank to 0, 475 * cancel pending retransmit, pull snd_nxt back 476 * to (closed) window, and set the persist timer 477 * if it isn't already going. If the window didn't 478 * close completely, just wait for an ACK. 479 * 480 * We also do a general check here to ensure that 481 * we will set the persist timer when we have data 482 * to send, but a 0-byte window. This makes sure 483 * the persist timer is set even if the packet 484 * hits one of the "goto send" lines below. 485 */ 486 len = 0; 487 if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) && 488 (off < (int) sbavail(&so->so_snd))) { 489 tcp_timer_activate(tp, TT_REXMT, 0); 490 tp->t_rxtshift = 0; 491 tp->snd_nxt = tp->snd_una; 492 if (!tcp_timer_active(tp, TT_PERSIST)) 493 tcp_setpersist(tp); 494 } 495 } 496 497 /* len will be >= 0 after this point. */ 498 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 499 500 tcp_sndbuf_autoscale(tp, so, sendwin); 501 502 /* 503 * Decide if we can use TCP Segmentation Offloading (if supported by 504 * hardware). 505 * 506 * TSO may only be used if we are in a pure bulk sending state. The 507 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 508 * IP options prevent using TSO. With TSO the TCP header is the same 509 * (except for the sequence number) for all generated packets. This 510 * makes it impossible to transmit any options which vary per generated 511 * segment or packet. 512 * 513 * IPv4 handling has a clear separation of ip options and ip header 514 * flags while IPv6 combines both in in6p_outputopts. ip6_optlen() does 515 * the right thing below to provide length of just ip options and thus 516 * checking for ipoptlen is enough to decide if ip options are present. 517 */ 518 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 519 /* 520 * Pre-calculate here as we save another lookup into the darknesses 521 * of IPsec that way and can actually decide if TSO is ok. 522 */ 523 #ifdef INET6 524 if (isipv6 && IPSEC_ENABLED(ipv6)) 525 ipsec_optlen = IPSEC_HDRSIZE(ipv6, tp->t_inpcb); 526 #ifdef INET 527 else 528 #endif 529 #endif /* INET6 */ 530 #ifdef INET 531 if (IPSEC_ENABLED(ipv4)) 532 ipsec_optlen = IPSEC_HDRSIZE(ipv4, tp->t_inpcb); 533 #endif /* INET */ 534 #endif /* IPSEC */ 535 #ifdef INET6 536 if (isipv6) 537 ipoptlen = ip6_optlen(tp->t_inpcb); 538 else 539 #endif 540 if (tp->t_inpcb->inp_options) 541 ipoptlen = tp->t_inpcb->inp_options->m_len - 542 offsetof(struct ipoption, ipopt_list); 543 else 544 ipoptlen = 0; 545 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 546 ipoptlen += ipsec_optlen; 547 #endif 548 549 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg && 550 ((tp->t_flags & TF_SIGNATURE) == 0) && 551 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 552 ipoptlen == 0 && !(flags & TH_SYN)) 553 tso = 1; 554 555 if (sack_rxmit) { 556 if (SEQ_LT(p->rxmit + len, tp->snd_una + sbused(&so->so_snd))) 557 flags &= ~TH_FIN; 558 } else { 559 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + 560 sbused(&so->so_snd))) 561 flags &= ~TH_FIN; 562 } 563 564 recwin = lmin(lmax(sbspace(&so->so_rcv), 0), 565 (long)TCP_MAXWIN << tp->rcv_scale); 566 567 /* 568 * Sender silly window avoidance. We transmit under the following 569 * conditions when len is non-zero: 570 * 571 * - We have a full segment (or more with TSO) 572 * - This is the last buffer in a write()/send() and we are 573 * either idle or running NODELAY 574 * - we've timed out (e.g. persist timer) 575 * - we have more then 1/2 the maximum send window's worth of 576 * data (receiver may be limited the window size) 577 * - we need to retransmit 578 */ 579 if (len) { 580 if (len >= tp->t_maxseg) 581 goto send; 582 /* 583 * As the TCP header options are now 584 * considered when setting up the initial 585 * window, we would not send the last segment 586 * if we skip considering the option length here. 587 * Note: this may not work when tcp headers change 588 * very dynamically in the future. 589 */ 590 if ((((tp->t_flags & TF_SIGNATURE) ? 591 PADTCPOLEN(TCPOLEN_SIGNATURE) : 0) + 592 ((tp->t_flags & TF_RCVD_TSTMP) ? 593 PADTCPOLEN(TCPOLEN_TIMESTAMP) : 0) + 594 len) >= tp->t_maxseg) 595 goto send; 596 /* 597 * NOTE! on localhost connections an 'ack' from the remote 598 * end may occur synchronously with the output and cause 599 * us to flush a buffer queued with moretocome. XXX 600 * 601 * note: the len + off check is almost certainly unnecessary. 602 */ 603 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 604 (idle || (tp->t_flags & TF_NODELAY)) && 605 (uint32_t)len + (uint32_t)off >= sbavail(&so->so_snd) && 606 (tp->t_flags & TF_NOPUSH) == 0) { 607 goto send; 608 } 609 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 610 goto send; 611 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 612 goto send; 613 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 614 goto send; 615 if (sack_rxmit) 616 goto send; 617 } 618 619 /* 620 * Sending of standalone window updates. 621 * 622 * Window updates are important when we close our window due to a 623 * full socket buffer and are opening it again after the application 624 * reads data from it. Once the window has opened again and the 625 * remote end starts to send again the ACK clock takes over and 626 * provides the most current window information. 627 * 628 * We must avoid the silly window syndrome whereas every read 629 * from the receive buffer, no matter how small, causes a window 630 * update to be sent. We also should avoid sending a flurry of 631 * window updates when the socket buffer had queued a lot of data 632 * and the application is doing small reads. 633 * 634 * Prevent a flurry of pointless window updates by only sending 635 * an update when we can increase the advertized window by more 636 * than 1/4th of the socket buffer capacity. When the buffer is 637 * getting full or is very small be more aggressive and send an 638 * update whenever we can increase by two mss sized segments. 639 * In all other situations the ACK's to new incoming data will 640 * carry further window increases. 641 * 642 * Don't send an independent window update if a delayed 643 * ACK is pending (it will get piggy-backed on it) or the 644 * remote side already has done a half-close and won't send 645 * more data. Skip this if the connection is in T/TCP 646 * half-open state. 647 */ 648 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 649 !(tp->t_flags & TF_DELACK) && 650 !TCPS_HAVERCVDFIN(tp->t_state)) { 651 /* 652 * "adv" is the amount we could increase the window, 653 * taking into account that we are limited by 654 * TCP_MAXWIN << tp->rcv_scale. 655 */ 656 int32_t adv; 657 int oldwin; 658 659 adv = recwin; 660 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { 661 oldwin = (tp->rcv_adv - tp->rcv_nxt); 662 adv -= oldwin; 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->rcv_numsacks > 0) { 848 to.to_flags |= TOF_SACK; 849 to.to_nsacks = tp->rcv_numsacks; 850 to.to_sacks = (u_char *)tp->sackblks; 851 } 852 } 853 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 854 /* TCP-MD5 (RFC2385). */ 855 /* 856 * Check that TCP_MD5SIG is enabled in tcpcb to 857 * account the size needed to set this TCP option. 858 */ 859 if (tp->t_flags & TF_SIGNATURE) 860 to.to_flags |= TOF_SIGNATURE; 861 #endif /* TCP_SIGNATURE */ 862 863 /* Processing the options. */ 864 hdrlen += optlen = tcp_addoptions(&to, opt); 865 /* 866 * If we wanted a TFO option to be added, but it was unable 867 * to fit, ensure no data is sent. 868 */ 869 if (IS_FASTOPEN(tp->t_flags) && wanted_cookie && 870 !(to.to_flags & TOF_FASTOPEN)) 871 len = 0; 872 } 873 874 /* 875 * Adjust data length if insertion of options will 876 * bump the packet length beyond the t_maxseg length. 877 * Clear the FIN bit because we cut off the tail of 878 * the segment. 879 */ 880 if (len + optlen + ipoptlen > tp->t_maxseg) { 881 flags &= ~TH_FIN; 882 883 if (tso) { 884 u_int if_hw_tsomax; 885 u_int moff; 886 int max_len; 887 888 /* extract TSO information */ 889 if_hw_tsomax = tp->t_tsomax; 890 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount; 891 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize; 892 893 /* 894 * Limit a TSO burst to prevent it from 895 * overflowing or exceeding the maximum length 896 * allowed by the network interface: 897 */ 898 KASSERT(ipoptlen == 0, 899 ("%s: TSO can't do IP options", __func__)); 900 901 /* 902 * Check if we should limit by maximum payload 903 * length: 904 */ 905 if (if_hw_tsomax != 0) { 906 /* compute maximum TSO length */ 907 max_len = (if_hw_tsomax - hdrlen - 908 max_linkhdr); 909 if (max_len <= 0) { 910 len = 0; 911 } else if (len > max_len) { 912 sendalot = 1; 913 len = max_len; 914 } 915 } 916 /* 917 * Prevent the last segment from being 918 * fractional unless the send sockbuf can be 919 * emptied: 920 */ 921 max_len = (tp->t_maxseg - optlen); 922 if (((uint32_t)off + (uint32_t)len) < 923 sbavail(&so->so_snd)) { 924 moff = len % max_len; 925 if (moff != 0) { 926 len -= moff; 927 sendalot = 1; 928 } 929 } 930 931 /* 932 * In case there are too many small fragments 933 * don't use TSO: 934 */ 935 if (len <= max_len) { 936 len = max_len; 937 sendalot = 1; 938 tso = 0; 939 } 940 941 /* 942 * Send the FIN in a separate segment 943 * after the bulk sending is done. 944 * We don't trust the TSO implementations 945 * to clear the FIN flag on all but the 946 * last segment. 947 */ 948 if (tp->t_flags & TF_NEEDFIN) 949 sendalot = 1; 950 } else { 951 if (optlen + ipoptlen >= tp->t_maxseg) { 952 /* 953 * Since we don't have enough space to put 954 * the IP header chain and the TCP header in 955 * one packet as required by RFC 7112, don't 956 * send it. Also ensure that at least one 957 * byte of the payload can be put into the 958 * TCP segment. 959 */ 960 SOCKBUF_UNLOCK(&so->so_snd); 961 error = EMSGSIZE; 962 sack_rxmit = 0; 963 goto out; 964 } 965 len = tp->t_maxseg - optlen - ipoptlen; 966 sendalot = 1; 967 if (dont_sendalot) 968 sendalot = 0; 969 } 970 } else 971 tso = 0; 972 973 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 974 ("%s: len > IP_MAXPACKET", __func__)); 975 976 /*#ifdef DIAGNOSTIC*/ 977 #ifdef INET6 978 if (max_linkhdr + hdrlen > MCLBYTES) 979 #else 980 if (max_linkhdr + hdrlen > MHLEN) 981 #endif 982 panic("tcphdr too big"); 983 /*#endif*/ 984 985 /* 986 * This KASSERT is here to catch edge cases at a well defined place. 987 * Before, those had triggered (random) panic conditions further down. 988 */ 989 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 990 991 /* 992 * Grab a header mbuf, attaching a copy of data to 993 * be transmitted, and initialize the header from 994 * the template for sends on this connection. 995 */ 996 if (len) { 997 struct mbuf *mb; 998 struct sockbuf *msb; 999 u_int moff; 1000 1001 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 1002 TCPSTAT_INC(tcps_sndprobe); 1003 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 1004 tp->t_sndrexmitpack++; 1005 TCPSTAT_INC(tcps_sndrexmitpack); 1006 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 1007 } else { 1008 TCPSTAT_INC(tcps_sndpack); 1009 TCPSTAT_ADD(tcps_sndbyte, len); 1010 } 1011 #ifdef INET6 1012 if (MHLEN < hdrlen + max_linkhdr) 1013 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR); 1014 else 1015 #endif 1016 m = m_gethdr(M_NOWAIT, MT_DATA); 1017 1018 if (m == NULL) { 1019 SOCKBUF_UNLOCK(&so->so_snd); 1020 error = ENOBUFS; 1021 sack_rxmit = 0; 1022 goto out; 1023 } 1024 1025 m->m_data += max_linkhdr; 1026 m->m_len = hdrlen; 1027 1028 /* 1029 * Start the m_copy functions from the closest mbuf 1030 * to the offset in the socket buffer chain. 1031 */ 1032 mb = sbsndptr_noadv(&so->so_snd, off, &moff); 1033 if (len <= MHLEN - hdrlen - max_linkhdr) { 1034 m_copydata(mb, moff, len, 1035 mtod(m, caddr_t) + hdrlen); 1036 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1037 sbsndptr_adv(&so->so_snd, mb, len); 1038 m->m_len += len; 1039 } else { 1040 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 1041 msb = NULL; 1042 else 1043 msb = &so->so_snd; 1044 m->m_next = tcp_m_copym(mb, moff, 1045 &len, if_hw_tsomaxsegcount, 1046 if_hw_tsomaxsegsize, msb); 1047 if (len <= (tp->t_maxseg - optlen)) { 1048 /* 1049 * Must have ran out of mbufs for the copy 1050 * shorten it to no longer need tso. Lets 1051 * not put on sendalot since we are low on 1052 * mbufs. 1053 */ 1054 tso = 0; 1055 } 1056 if (m->m_next == NULL) { 1057 SOCKBUF_UNLOCK(&so->so_snd); 1058 (void) m_free(m); 1059 error = ENOBUFS; 1060 sack_rxmit = 0; 1061 goto out; 1062 } 1063 } 1064 1065 /* 1066 * If we're sending everything we've got, set PUSH. 1067 * (This will keep happy those implementations which only 1068 * give data to the user when a buffer fills or 1069 * a PUSH comes in.) 1070 */ 1071 if (((uint32_t)off + (uint32_t)len == sbused(&so->so_snd)) && 1072 !(flags & TH_SYN)) 1073 flags |= TH_PUSH; 1074 SOCKBUF_UNLOCK(&so->so_snd); 1075 } else { 1076 SOCKBUF_UNLOCK(&so->so_snd); 1077 if (tp->t_flags & TF_ACKNOW) 1078 TCPSTAT_INC(tcps_sndacks); 1079 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 1080 TCPSTAT_INC(tcps_sndctrl); 1081 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 1082 TCPSTAT_INC(tcps_sndurg); 1083 else 1084 TCPSTAT_INC(tcps_sndwinup); 1085 1086 m = m_gethdr(M_NOWAIT, MT_DATA); 1087 if (m == NULL) { 1088 error = ENOBUFS; 1089 sack_rxmit = 0; 1090 goto out; 1091 } 1092 #ifdef INET6 1093 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 1094 MHLEN >= hdrlen) { 1095 M_ALIGN(m, hdrlen); 1096 } else 1097 #endif 1098 m->m_data += max_linkhdr; 1099 m->m_len = hdrlen; 1100 } 1101 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 1102 m->m_pkthdr.rcvif = (struct ifnet *)0; 1103 #ifdef MAC 1104 mac_inpcb_create_mbuf(tp->t_inpcb, m); 1105 #endif 1106 #ifdef INET6 1107 if (isipv6) { 1108 ip6 = mtod(m, struct ip6_hdr *); 1109 th = (struct tcphdr *)(ip6 + 1); 1110 tcpip_fillheaders(tp->t_inpcb, ip6, th); 1111 } else 1112 #endif /* INET6 */ 1113 { 1114 ip = mtod(m, struct ip *); 1115 #ifdef TCPDEBUG 1116 ipov = (struct ipovly *)ip; 1117 #endif 1118 th = (struct tcphdr *)(ip + 1); 1119 tcpip_fillheaders(tp->t_inpcb, ip, th); 1120 } 1121 1122 /* 1123 * Fill in fields, remembering maximum advertised 1124 * window for use in delaying messages about window sizes. 1125 * If resending a FIN, be sure not to use a new sequence number. 1126 */ 1127 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 1128 tp->snd_nxt == tp->snd_max) 1129 tp->snd_nxt--; 1130 /* 1131 * If we are starting a connection, send ECN setup 1132 * SYN packet. If we are on a retransmit, we may 1133 * resend those bits a number of times as per 1134 * RFC 3168. 1135 */ 1136 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn == 1) { 1137 if (tp->t_rxtshift >= 1) { 1138 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 1139 flags |= TH_ECE|TH_CWR; 1140 } else 1141 flags |= TH_ECE|TH_CWR; 1142 } 1143 1144 if (TCPS_HAVEESTABLISHED(tp->t_state) && 1145 (tp->t_flags & TF_ECN_PERMIT)) { 1146 /* 1147 * If the peer has ECN, mark data packets with 1148 * ECN capable transmission (ECT). 1149 * Ignore pure ack packets, retransmissions and window probes. 1150 */ 1151 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 1152 (sack_rxmit == 0) && 1153 !((tp->t_flags & TF_FORCEDATA) && len == 1 && 1154 SEQ_LT(tp->snd_una, tp->snd_max))) { 1155 #ifdef INET6 1156 if (isipv6) 1157 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 1158 else 1159 #endif 1160 ip->ip_tos |= IPTOS_ECN_ECT0; 1161 TCPSTAT_INC(tcps_ecn_ect0); 1162 /* 1163 * Reply with proper ECN notifications. 1164 * Only set CWR on new data segments. 1165 */ 1166 if (tp->t_flags & TF_ECN_SND_CWR) { 1167 flags |= TH_CWR; 1168 tp->t_flags &= ~TF_ECN_SND_CWR; 1169 } 1170 } 1171 if (tp->t_flags & TF_ECN_SND_ECE) 1172 flags |= TH_ECE; 1173 } 1174 1175 /* 1176 * If we are doing retransmissions, then snd_nxt will 1177 * not reflect the first unsent octet. For ACK only 1178 * packets, we do not want the sequence number of the 1179 * retransmitted packet, we want the sequence number 1180 * of the next unsent octet. So, if there is no data 1181 * (and no SYN or FIN), use snd_max instead of snd_nxt 1182 * when filling in ti_seq. But if we are in persist 1183 * state, snd_max might reflect one byte beyond the 1184 * right edge of the window, so use snd_nxt in that 1185 * case, since we know we aren't doing a retransmission. 1186 * (retransmit and persist are mutually exclusive...) 1187 */ 1188 if (sack_rxmit == 0) { 1189 if (len || (flags & (TH_SYN|TH_FIN)) || 1190 tcp_timer_active(tp, TT_PERSIST)) 1191 th->th_seq = htonl(tp->snd_nxt); 1192 else 1193 th->th_seq = htonl(tp->snd_max); 1194 } else { 1195 th->th_seq = htonl(p->rxmit); 1196 p->rxmit += len; 1197 tp->sackhint.sack_bytes_rexmit += len; 1198 } 1199 th->th_ack = htonl(tp->rcv_nxt); 1200 if (optlen) { 1201 bcopy(opt, th + 1, optlen); 1202 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1203 } 1204 th->th_flags = flags; 1205 /* 1206 * Calculate receive window. Don't shrink window, 1207 * but avoid silly window syndrome. 1208 * If a RST segment is sent, advertise a window of zero. 1209 */ 1210 if (flags & TH_RST) { 1211 recwin = 0; 1212 } else { 1213 if (recwin < (so->so_rcv.sb_hiwat / 4) && 1214 recwin < tp->t_maxseg) 1215 recwin = 0; 1216 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1217 recwin < (tp->rcv_adv - tp->rcv_nxt)) 1218 recwin = (tp->rcv_adv - tp->rcv_nxt); 1219 } 1220 /* 1221 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1222 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1223 * case is handled in syncache. 1224 */ 1225 if (flags & TH_SYN) 1226 th->th_win = htons((u_short) 1227 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1228 else { 1229 /* Avoid shrinking window with window scaling. */ 1230 recwin = roundup2(recwin, 1 << tp->rcv_scale); 1231 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1232 } 1233 1234 /* 1235 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1236 * a 0 window. This may cause the remote transmitter to stall. This 1237 * flag tells soreceive() to disable delayed acknowledgements when 1238 * draining the buffer. This can occur if the receiver is attempting 1239 * to read more data than can be buffered prior to transmitting on 1240 * the connection. 1241 */ 1242 if (th->th_win == 0) { 1243 tp->t_sndzerowin++; 1244 tp->t_flags |= TF_RXWIN0SENT; 1245 } else 1246 tp->t_flags &= ~TF_RXWIN0SENT; 1247 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1248 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1249 th->th_flags |= TH_URG; 1250 } else 1251 /* 1252 * If no urgent pointer to send, then we pull 1253 * the urgent pointer to the left edge of the send window 1254 * so that it doesn't drift into the send window on sequence 1255 * number wraparound. 1256 */ 1257 tp->snd_up = tp->snd_una; /* drag it along */ 1258 1259 /* 1260 * Put TCP length in extended header, and then 1261 * checksum extended header and data. 1262 */ 1263 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1264 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1265 1266 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1267 if (to.to_flags & TOF_SIGNATURE) { 1268 /* 1269 * Calculate MD5 signature and put it into the place 1270 * determined before. 1271 * NOTE: since TCP options buffer doesn't point into 1272 * mbuf's data, calculate offset and use it. 1273 */ 1274 if (!TCPMD5_ENABLED() || (error = TCPMD5_OUTPUT(m, th, 1275 (u_char *)(th + 1) + (to.to_signature - opt))) != 0) { 1276 /* 1277 * Do not send segment if the calculation of MD5 1278 * digest has failed. 1279 */ 1280 m_freem(m); 1281 goto out; 1282 } 1283 } 1284 #endif 1285 #ifdef INET6 1286 if (isipv6) { 1287 /* 1288 * There is no need to fill in ip6_plen right now. 1289 * It will be filled later by ip6_output. 1290 */ 1291 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1292 th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) + 1293 optlen + len, IPPROTO_TCP, 0); 1294 } 1295 #endif 1296 #if defined(INET6) && defined(INET) 1297 else 1298 #endif 1299 #ifdef INET 1300 { 1301 m->m_pkthdr.csum_flags = CSUM_TCP; 1302 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1303 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1304 1305 /* IP version must be set here for ipv4/ipv6 checking later */ 1306 KASSERT(ip->ip_v == IPVERSION, 1307 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1308 } 1309 #endif 1310 1311 /* 1312 * Enable TSO and specify the size of the segments. 1313 * The TCP pseudo header checksum is always provided. 1314 */ 1315 if (tso) { 1316 KASSERT(len > tp->t_maxseg - optlen, 1317 ("%s: len <= tso_segsz", __func__)); 1318 m->m_pkthdr.csum_flags |= CSUM_TSO; 1319 m->m_pkthdr.tso_segsz = tp->t_maxseg - optlen; 1320 } 1321 1322 KASSERT(len + hdrlen == m_length(m, NULL), 1323 ("%s: mbuf chain shorter than expected: %d + %u != %u", 1324 __func__, len, hdrlen, m_length(m, NULL))); 1325 1326 #ifdef TCP_HHOOK 1327 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1328 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1329 #endif 1330 1331 #ifdef TCPDEBUG 1332 /* 1333 * Trace. 1334 */ 1335 if (so->so_options & SO_DEBUG) { 1336 u_short save = 0; 1337 #ifdef INET6 1338 if (!isipv6) 1339 #endif 1340 { 1341 save = ipov->ih_len; 1342 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1343 } 1344 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1345 #ifdef INET6 1346 if (!isipv6) 1347 #endif 1348 ipov->ih_len = save; 1349 } 1350 #endif /* TCPDEBUG */ 1351 TCP_PROBE3(debug__output, tp, th, m); 1352 1353 /* We're getting ready to send; log now. */ 1354 TCP_LOG_EVENT(tp, th, &so->so_rcv, &so->so_snd, TCP_LOG_OUT, ERRNO_UNK, 1355 len, NULL, false); 1356 1357 /* 1358 * Fill in IP length and desired time to live and 1359 * send to IP level. There should be a better way 1360 * to handle ttl and tos; we could keep them in 1361 * the template, but need a way to checksum without them. 1362 */ 1363 /* 1364 * m->m_pkthdr.len should have been set before checksum calculation, 1365 * because in6_cksum() need it. 1366 */ 1367 #ifdef INET6 1368 if (isipv6) { 1369 /* 1370 * we separately set hoplimit for every segment, since the 1371 * user might want to change the value via setsockopt. 1372 * Also, desired default hop limit might be changed via 1373 * Neighbor Discovery. 1374 */ 1375 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1376 1377 /* 1378 * Set the packet size here for the benefit of DTrace probes. 1379 * ip6_output() will set it properly; it's supposed to include 1380 * the option header lengths as well. 1381 */ 1382 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6)); 1383 1384 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) 1385 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1386 else 1387 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1388 1389 if (tp->t_state == TCPS_SYN_SENT) 1390 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th); 1391 1392 TCP_PROBE5(send, NULL, tp, ip6, tp, th); 1393 1394 #ifdef TCPPCAP 1395 /* Save packet, if requested. */ 1396 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1397 #endif 1398 1399 /* TODO: IPv6 IP6TOS_ECT bit on */ 1400 error = ip6_output(m, tp->t_inpcb->in6p_outputopts, 1401 &tp->t_inpcb->inp_route6, 1402 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 1403 NULL, NULL, tp->t_inpcb); 1404 1405 if (error == EMSGSIZE && tp->t_inpcb->inp_route6.ro_rt != NULL) 1406 mtu = tp->t_inpcb->inp_route6.ro_rt->rt_mtu; 1407 } 1408 #endif /* INET6 */ 1409 #if defined(INET) && defined(INET6) 1410 else 1411 #endif 1412 #ifdef INET 1413 { 1414 ip->ip_len = htons(m->m_pkthdr.len); 1415 #ifdef INET6 1416 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1417 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1418 #endif /* INET6 */ 1419 /* 1420 * If we do path MTU discovery, then we set DF on every packet. 1421 * This might not be the best thing to do according to RFC3390 1422 * Section 2. However the tcp hostcache migitates the problem 1423 * so it affects only the first tcp connection with a host. 1424 * 1425 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1426 */ 1427 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) { 1428 ip->ip_off |= htons(IP_DF); 1429 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1430 } else { 1431 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1432 } 1433 1434 if (tp->t_state == TCPS_SYN_SENT) 1435 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th); 1436 1437 TCP_PROBE5(send, NULL, tp, ip, tp, th); 1438 1439 #ifdef TCPPCAP 1440 /* Save packet, if requested. */ 1441 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1442 #endif 1443 1444 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, 1445 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1446 tp->t_inpcb); 1447 1448 if (error == EMSGSIZE && tp->t_inpcb->inp_route.ro_rt != NULL) 1449 mtu = tp->t_inpcb->inp_route.ro_rt->rt_mtu; 1450 } 1451 #endif /* INET */ 1452 1453 out: 1454 /* 1455 * In transmit state, time the transmission and arrange for 1456 * the retransmit. In persist state, just set snd_max. 1457 */ 1458 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1459 !tcp_timer_active(tp, TT_PERSIST)) { 1460 tcp_seq startseq = tp->snd_nxt; 1461 1462 /* 1463 * Advance snd_nxt over sequence space of this segment. 1464 */ 1465 if (flags & (TH_SYN|TH_FIN)) { 1466 if (flags & TH_SYN) 1467 tp->snd_nxt++; 1468 if (flags & TH_FIN) { 1469 tp->snd_nxt++; 1470 tp->t_flags |= TF_SENTFIN; 1471 } 1472 } 1473 if (sack_rxmit) 1474 goto timer; 1475 tp->snd_nxt += len; 1476 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1477 tp->snd_max = tp->snd_nxt; 1478 /* 1479 * Time this transmission if not a retransmission and 1480 * not currently timing anything. 1481 */ 1482 tp->t_sndtime = ticks; 1483 if (tp->t_rtttime == 0) { 1484 tp->t_rtttime = ticks; 1485 tp->t_rtseq = startseq; 1486 TCPSTAT_INC(tcps_segstimed); 1487 } 1488 } 1489 1490 /* 1491 * Set retransmit timer if not currently set, 1492 * and not doing a pure ack or a keep-alive probe. 1493 * Initial value for retransmit timer is smoothed 1494 * round-trip time + 2 * round-trip time variance. 1495 * Initialize shift counter which is used for backoff 1496 * of retransmit time. 1497 */ 1498 timer: 1499 if (!tcp_timer_active(tp, TT_REXMT) && 1500 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1501 (tp->snd_nxt != tp->snd_una))) { 1502 if (tcp_timer_active(tp, TT_PERSIST)) { 1503 tcp_timer_activate(tp, TT_PERSIST, 0); 1504 tp->t_rxtshift = 0; 1505 } 1506 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1507 } else if (len == 0 && sbavail(&so->so_snd) && 1508 !tcp_timer_active(tp, TT_REXMT) && 1509 !tcp_timer_active(tp, TT_PERSIST)) { 1510 /* 1511 * Avoid a situation where we do not set persist timer 1512 * after a zero window condition. For example: 1513 * 1) A -> B: packet with enough data to fill the window 1514 * 2) B -> A: ACK for #1 + new data (0 window 1515 * advertisement) 1516 * 3) A -> B: ACK for #2, 0 len packet 1517 * 1518 * In this case, A will not activate the persist timer, 1519 * because it chose to send a packet. Unless tcp_output 1520 * is called for some other reason (delayed ack timer, 1521 * another input packet from B, socket syscall), A will 1522 * not send zero window probes. 1523 * 1524 * So, if you send a 0-length packet, but there is data 1525 * in the socket buffer, and neither the rexmt or 1526 * persist timer is already set, then activate the 1527 * persist timer. 1528 */ 1529 tp->t_rxtshift = 0; 1530 tcp_setpersist(tp); 1531 } 1532 } else { 1533 /* 1534 * Persist case, update snd_max but since we are in 1535 * persist mode (no window) we do not update snd_nxt. 1536 */ 1537 int xlen = len; 1538 if (flags & TH_SYN) 1539 ++xlen; 1540 if (flags & TH_FIN) { 1541 ++xlen; 1542 tp->t_flags |= TF_SENTFIN; 1543 } 1544 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1545 tp->snd_max = tp->snd_nxt + xlen; 1546 } 1547 if ((error == 0) && 1548 (TCPS_HAVEESTABLISHED(tp->t_state) && 1549 (tp->t_flags & TF_SACK_PERMIT) && 1550 tp->rcv_numsacks > 0)) { 1551 /* Clean up any DSACK's sent */ 1552 tcp_clean_dsack_blocks(tp); 1553 } 1554 if (error) { 1555 /* Record the error. */ 1556 TCP_LOG_EVENT(tp, NULL, &so->so_rcv, &so->so_snd, TCP_LOG_OUT, 1557 error, 0, NULL, false); 1558 1559 /* 1560 * We know that the packet was lost, so back out the 1561 * sequence number advance, if any. 1562 * 1563 * If the error is EPERM the packet got blocked by the 1564 * local firewall. Normally we should terminate the 1565 * connection but the blocking may have been spurious 1566 * due to a firewall reconfiguration cycle. So we treat 1567 * it like a packet loss and let the retransmit timer and 1568 * timeouts do their work over time. 1569 * XXX: It is a POLA question whether calling tcp_drop right 1570 * away would be the really correct behavior instead. 1571 */ 1572 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1573 !tcp_timer_active(tp, TT_PERSIST)) && 1574 ((flags & TH_SYN) == 0) && 1575 (error != EPERM)) { 1576 if (sack_rxmit) { 1577 p->rxmit -= len; 1578 tp->sackhint.sack_bytes_rexmit -= len; 1579 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1580 ("sackhint bytes rtx >= 0")); 1581 } else 1582 tp->snd_nxt -= len; 1583 } 1584 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1585 switch (error) { 1586 case EACCES: 1587 case EPERM: 1588 tp->t_softerror = error; 1589 return (error); 1590 case ENOBUFS: 1591 TCP_XMIT_TIMER_ASSERT(tp, len, flags); 1592 tp->snd_cwnd = tp->t_maxseg; 1593 return (0); 1594 case EMSGSIZE: 1595 /* 1596 * For some reason the interface we used initially 1597 * to send segments changed to another or lowered 1598 * its MTU. 1599 * If TSO was active we either got an interface 1600 * without TSO capabilits or TSO was turned off. 1601 * If we obtained mtu from ip_output() then update 1602 * it and try again. 1603 */ 1604 if (tso) 1605 tp->t_flags &= ~TF_TSO; 1606 if (mtu != 0) { 1607 tcp_mss_update(tp, -1, mtu, NULL, NULL); 1608 goto again; 1609 } 1610 return (error); 1611 case EHOSTDOWN: 1612 case EHOSTUNREACH: 1613 case ENETDOWN: 1614 case ENETUNREACH: 1615 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1616 tp->t_softerror = error; 1617 return (0); 1618 } 1619 /* FALLTHROUGH */ 1620 default: 1621 return (error); 1622 } 1623 } 1624 TCPSTAT_INC(tcps_sndtotal); 1625 1626 /* 1627 * Data sent (as far as we can tell). 1628 * If this advertises a larger window than any other segment, 1629 * then remember the size of the advertised window. 1630 * Any pending ACK has now been sent. 1631 */ 1632 if (SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1633 tp->rcv_adv = tp->rcv_nxt + recwin; 1634 tp->last_ack_sent = tp->rcv_nxt; 1635 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1636 if (tcp_timer_active(tp, TT_DELACK)) 1637 tcp_timer_activate(tp, TT_DELACK, 0); 1638 #if 0 1639 /* 1640 * This completely breaks TCP if newreno is turned on. What happens 1641 * is that if delayed-acks are turned on on the receiver, this code 1642 * on the transmitter effectively destroys the TCP window, forcing 1643 * it to four packets (1.5Kx4 = 6K window). 1644 */ 1645 if (sendalot && --maxburst) 1646 goto again; 1647 #endif 1648 if (sendalot) 1649 goto again; 1650 return (0); 1651 } 1652 1653 void 1654 tcp_setpersist(struct tcpcb *tp) 1655 { 1656 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1657 int tt; 1658 1659 tp->t_flags &= ~TF_PREVVALID; 1660 if (tcp_timer_active(tp, TT_REXMT)) 1661 panic("tcp_setpersist: retransmit pending"); 1662 /* 1663 * Start/restart persistence timer. 1664 */ 1665 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1666 tcp_persmin, tcp_persmax); 1667 tcp_timer_activate(tp, TT_PERSIST, tt); 1668 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1669 tp->t_rxtshift++; 1670 } 1671 1672 /* 1673 * Insert TCP options according to the supplied parameters to the place 1674 * optp in a consistent way. Can handle unaligned destinations. 1675 * 1676 * The order of the option processing is crucial for optimal packing and 1677 * alignment for the scarce option space. 1678 * 1679 * The optimal order for a SYN/SYN-ACK segment is: 1680 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1681 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1682 * 1683 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1684 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1685 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1686 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1687 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1688 */ 1689 int 1690 tcp_addoptions(struct tcpopt *to, u_char *optp) 1691 { 1692 u_int32_t mask, optlen = 0; 1693 1694 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1695 if ((to->to_flags & mask) != mask) 1696 continue; 1697 if (optlen == TCP_MAXOLEN) 1698 break; 1699 switch (to->to_flags & mask) { 1700 case TOF_MSS: 1701 while (optlen % 4) { 1702 optlen += TCPOLEN_NOP; 1703 *optp++ = TCPOPT_NOP; 1704 } 1705 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1706 continue; 1707 optlen += TCPOLEN_MAXSEG; 1708 *optp++ = TCPOPT_MAXSEG; 1709 *optp++ = TCPOLEN_MAXSEG; 1710 to->to_mss = htons(to->to_mss); 1711 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1712 optp += sizeof(to->to_mss); 1713 break; 1714 case TOF_SCALE: 1715 while (!optlen || optlen % 2 != 1) { 1716 optlen += TCPOLEN_NOP; 1717 *optp++ = TCPOPT_NOP; 1718 } 1719 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1720 continue; 1721 optlen += TCPOLEN_WINDOW; 1722 *optp++ = TCPOPT_WINDOW; 1723 *optp++ = TCPOLEN_WINDOW; 1724 *optp++ = to->to_wscale; 1725 break; 1726 case TOF_SACKPERM: 1727 while (optlen % 2) { 1728 optlen += TCPOLEN_NOP; 1729 *optp++ = TCPOPT_NOP; 1730 } 1731 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1732 continue; 1733 optlen += TCPOLEN_SACK_PERMITTED; 1734 *optp++ = TCPOPT_SACK_PERMITTED; 1735 *optp++ = TCPOLEN_SACK_PERMITTED; 1736 break; 1737 case TOF_TS: 1738 while (!optlen || optlen % 4 != 2) { 1739 optlen += TCPOLEN_NOP; 1740 *optp++ = TCPOPT_NOP; 1741 } 1742 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1743 continue; 1744 optlen += TCPOLEN_TIMESTAMP; 1745 *optp++ = TCPOPT_TIMESTAMP; 1746 *optp++ = TCPOLEN_TIMESTAMP; 1747 to->to_tsval = htonl(to->to_tsval); 1748 to->to_tsecr = htonl(to->to_tsecr); 1749 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1750 optp += sizeof(to->to_tsval); 1751 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1752 optp += sizeof(to->to_tsecr); 1753 break; 1754 case TOF_SIGNATURE: 1755 { 1756 int siglen = TCPOLEN_SIGNATURE - 2; 1757 1758 while (!optlen || optlen % 4 != 2) { 1759 optlen += TCPOLEN_NOP; 1760 *optp++ = TCPOPT_NOP; 1761 } 1762 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) { 1763 to->to_flags &= ~TOF_SIGNATURE; 1764 continue; 1765 } 1766 optlen += TCPOLEN_SIGNATURE; 1767 *optp++ = TCPOPT_SIGNATURE; 1768 *optp++ = TCPOLEN_SIGNATURE; 1769 to->to_signature = optp; 1770 while (siglen--) 1771 *optp++ = 0; 1772 break; 1773 } 1774 case TOF_SACK: 1775 { 1776 int sackblks = 0; 1777 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1778 tcp_seq sack_seq; 1779 1780 while (!optlen || optlen % 4 != 2) { 1781 optlen += TCPOLEN_NOP; 1782 *optp++ = TCPOPT_NOP; 1783 } 1784 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1785 continue; 1786 optlen += TCPOLEN_SACKHDR; 1787 *optp++ = TCPOPT_SACK; 1788 sackblks = min(to->to_nsacks, 1789 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1790 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1791 while (sackblks--) { 1792 sack_seq = htonl(sack->start); 1793 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1794 optp += sizeof(sack_seq); 1795 sack_seq = htonl(sack->end); 1796 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1797 optp += sizeof(sack_seq); 1798 optlen += TCPOLEN_SACK; 1799 sack++; 1800 } 1801 TCPSTAT_INC(tcps_sack_send_blocks); 1802 break; 1803 } 1804 case TOF_FASTOPEN: 1805 { 1806 int total_len; 1807 1808 /* XXX is there any point to aligning this option? */ 1809 total_len = TCPOLEN_FAST_OPEN_EMPTY + to->to_tfo_len; 1810 if (TCP_MAXOLEN - optlen < total_len) { 1811 to->to_flags &= ~TOF_FASTOPEN; 1812 continue; 1813 } 1814 *optp++ = TCPOPT_FAST_OPEN; 1815 *optp++ = total_len; 1816 if (to->to_tfo_len > 0) { 1817 bcopy(to->to_tfo_cookie, optp, to->to_tfo_len); 1818 optp += to->to_tfo_len; 1819 } 1820 optlen += total_len; 1821 break; 1822 } 1823 default: 1824 panic("%s: unknown TCP option type", __func__); 1825 break; 1826 } 1827 } 1828 1829 /* Terminate and pad TCP options to a 4 byte boundary. */ 1830 if (optlen % 4) { 1831 optlen += TCPOLEN_EOL; 1832 *optp++ = TCPOPT_EOL; 1833 } 1834 /* 1835 * According to RFC 793 (STD0007): 1836 * "The content of the header beyond the End-of-Option option 1837 * must be header padding (i.e., zero)." 1838 * and later: "The padding is composed of zeros." 1839 */ 1840 while (optlen % 4) { 1841 optlen += TCPOLEN_PAD; 1842 *optp++ = TCPOPT_PAD; 1843 } 1844 1845 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1846 return (optlen); 1847 } 1848 1849 /* 1850 * This is a copy of m_copym(), taking the TSO segment size/limit 1851 * constraints into account, and advancing the sndptr as it goes. 1852 */ 1853 struct mbuf * 1854 tcp_m_copym(struct mbuf *m, int32_t off0, int32_t *plen, 1855 int32_t seglimit, int32_t segsize, struct sockbuf *sb) 1856 { 1857 struct mbuf *n, **np; 1858 struct mbuf *top; 1859 int32_t off = off0; 1860 int32_t len = *plen; 1861 int32_t fragsize; 1862 int32_t len_cp = 0; 1863 int32_t *pkthdrlen; 1864 uint32_t mlen, frags; 1865 bool copyhdr; 1866 1867 1868 KASSERT(off >= 0, ("tcp_m_copym, negative off %d", off)); 1869 KASSERT(len >= 0, ("tcp_m_copym, negative len %d", len)); 1870 if (off == 0 && m->m_flags & M_PKTHDR) 1871 copyhdr = true; 1872 else 1873 copyhdr = false; 1874 while (off > 0) { 1875 KASSERT(m != NULL, ("tcp_m_copym, offset > size of mbuf chain")); 1876 if (off < m->m_len) 1877 break; 1878 off -= m->m_len; 1879 if ((sb) && (m == sb->sb_sndptr)) { 1880 sb->sb_sndptroff += m->m_len; 1881 sb->sb_sndptr = m->m_next; 1882 } 1883 m = m->m_next; 1884 } 1885 np = ⊤ 1886 top = NULL; 1887 pkthdrlen = NULL; 1888 while (len > 0) { 1889 if (m == NULL) { 1890 KASSERT(len == M_COPYALL, 1891 ("tcp_m_copym, length > size of mbuf chain")); 1892 *plen = len_cp; 1893 if (pkthdrlen != NULL) 1894 *pkthdrlen = len_cp; 1895 break; 1896 } 1897 mlen = min(len, m->m_len - off); 1898 if (seglimit) { 1899 /* 1900 * For M_NOMAP mbufs, add 3 segments 1901 * + 1 in case we are crossing page boundaries 1902 * + 2 in case the TLS hdr/trailer are used 1903 * It is cheaper to just add the segments 1904 * than it is to take the cache miss to look 1905 * at the mbuf ext_pgs state in detail. 1906 */ 1907 if (m->m_flags & M_NOMAP) { 1908 fragsize = min(segsize, PAGE_SIZE); 1909 frags = 3; 1910 } else { 1911 fragsize = segsize; 1912 frags = 0; 1913 } 1914 1915 /* Break if we really can't fit anymore. */ 1916 if ((frags + 1) >= seglimit) { 1917 *plen = len_cp; 1918 if (pkthdrlen != NULL) 1919 *pkthdrlen = len_cp; 1920 break; 1921 } 1922 1923 /* 1924 * Reduce size if you can't copy the whole 1925 * mbuf. If we can't copy the whole mbuf, also 1926 * adjust len so the loop will end after this 1927 * mbuf. 1928 */ 1929 if ((frags + howmany(mlen, fragsize)) >= seglimit) { 1930 mlen = (seglimit - frags - 1) * fragsize; 1931 len = mlen; 1932 *plen = len_cp + len; 1933 if (pkthdrlen != NULL) 1934 *pkthdrlen = *plen; 1935 } 1936 frags += howmany(mlen, fragsize); 1937 if (frags == 0) 1938 frags++; 1939 seglimit -= frags; 1940 KASSERT(seglimit > 0, 1941 ("%s: seglimit went too low", __func__)); 1942 } 1943 if (copyhdr) 1944 n = m_gethdr(M_NOWAIT, m->m_type); 1945 else 1946 n = m_get(M_NOWAIT, m->m_type); 1947 *np = n; 1948 if (n == NULL) 1949 goto nospace; 1950 if (copyhdr) { 1951 if (!m_dup_pkthdr(n, m, M_NOWAIT)) 1952 goto nospace; 1953 if (len == M_COPYALL) 1954 n->m_pkthdr.len -= off0; 1955 else 1956 n->m_pkthdr.len = len; 1957 pkthdrlen = &n->m_pkthdr.len; 1958 copyhdr = false; 1959 } 1960 n->m_len = mlen; 1961 len_cp += n->m_len; 1962 if (m->m_flags & M_EXT) { 1963 n->m_data = m->m_data + off; 1964 mb_dupcl(n, m); 1965 } else 1966 bcopy(mtod(m, caddr_t)+off, mtod(n, caddr_t), 1967 (u_int)n->m_len); 1968 1969 if (sb && (sb->sb_sndptr == m) && 1970 ((n->m_len + off) >= m->m_len) && m->m_next) { 1971 sb->sb_sndptroff += m->m_len; 1972 sb->sb_sndptr = m->m_next; 1973 } 1974 off = 0; 1975 if (len != M_COPYALL) { 1976 len -= n->m_len; 1977 } 1978 m = m->m_next; 1979 np = &n->m_next; 1980 } 1981 return (top); 1982 nospace: 1983 m_freem(top); 1984 return (NULL); 1985 } 1986 1987 void 1988 tcp_sndbuf_autoscale(struct tcpcb *tp, struct socket *so, uint32_t sendwin) 1989 { 1990 1991 /* 1992 * Automatic sizing of send socket buffer. Often the send buffer 1993 * size is not optimally adjusted to the actual network conditions 1994 * at hand (delay bandwidth product). Setting the buffer size too 1995 * small limits throughput on links with high bandwidth and high 1996 * delay (eg. trans-continental/oceanic links). Setting the 1997 * buffer size too big consumes too much real kernel memory, 1998 * especially with many connections on busy servers. 1999 * 2000 * The criteria to step up the send buffer one notch are: 2001 * 1. receive window of remote host is larger than send buffer 2002 * (with a fudge factor of 5/4th); 2003 * 2. send buffer is filled to 7/8th with data (so we actually 2004 * have data to make use of it); 2005 * 3. send buffer fill has not hit maximal automatic size; 2006 * 4. our send window (slow start and cogestion controlled) is 2007 * larger than sent but unacknowledged data in send buffer. 2008 * 2009 * The remote host receive window scaling factor may limit the 2010 * growing of the send buffer before it reaches its allowed 2011 * maximum. 2012 * 2013 * It scales directly with slow start or congestion window 2014 * and does at most one step per received ACK. This fast 2015 * scaling has the drawback of growing the send buffer beyond 2016 * what is strictly necessary to make full use of a given 2017 * delay*bandwidth product. However testing has shown this not 2018 * to be much of an problem. At worst we are trading wasting 2019 * of available bandwidth (the non-use of it) for wasting some 2020 * socket buffer memory. 2021 * 2022 * TODO: Shrink send buffer during idle periods together 2023 * with congestion window. Requires another timer. Has to 2024 * wait for upcoming tcp timer rewrite. 2025 * 2026 * XXXGL: should there be used sbused() or sbavail()? 2027 */ 2028 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 2029 int lowat; 2030 2031 lowat = V_tcp_sendbuf_auto_lowat ? so->so_snd.sb_lowat : 0; 2032 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat - lowat && 2033 sbused(&so->so_snd) >= 2034 (so->so_snd.sb_hiwat / 8 * 7) - lowat && 2035 sbused(&so->so_snd) < V_tcp_autosndbuf_max && 2036 sendwin >= (sbused(&so->so_snd) - 2037 (tp->snd_nxt - tp->snd_una))) { 2038 if (!sbreserve_locked(&so->so_snd, 2039 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 2040 V_tcp_autosndbuf_max), so, curthread)) 2041 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 2042 } 2043 } 2044 }
Cache object: b9333f7b6cf8419f5286bce2622c66d6
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