Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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sys/netinet/tcp_output.c
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1 /*- 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 4. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95 30 */ 31 32 #include <sys/cdefs.h> 33 __FBSDID("$FreeBSD: releng/8.2/sys/netinet/tcp_output.c 211870 2010-08-27 10:15:45Z andre $"); 34 35 #include "opt_inet.h" 36 #include "opt_inet6.h" 37 #include "opt_ipsec.h" 38 #include "opt_tcpdebug.h" 39 40 #include <sys/param.h> 41 #include <sys/systm.h> 42 #include <sys/domain.h> 43 #include <sys/kernel.h> 44 #include <sys/lock.h> 45 #include <sys/mbuf.h> 46 #include <sys/mutex.h> 47 #include <sys/protosw.h> 48 #include <sys/socket.h> 49 #include <sys/socketvar.h> 50 #include <sys/sysctl.h> 51 52 #include <net/if.h> 53 #include <net/route.h> 54 #include <net/vnet.h> 55 56 #include <netinet/in.h> 57 #include <netinet/in_systm.h> 58 #include <netinet/ip.h> 59 #include <netinet/in_pcb.h> 60 #include <netinet/ip_var.h> 61 #include <netinet/ip_options.h> 62 #ifdef INET6 63 #include <netinet6/in6_pcb.h> 64 #include <netinet/ip6.h> 65 #include <netinet6/ip6_var.h> 66 #endif 67 #include <netinet/tcp.h> 68 #define TCPOUTFLAGS 69 #include <netinet/tcp_fsm.h> 70 #include <netinet/tcp_seq.h> 71 #include <netinet/tcp_timer.h> 72 #include <netinet/tcp_var.h> 73 #include <netinet/tcpip.h> 74 #ifdef TCPDEBUG 75 #include <netinet/tcp_debug.h> 76 #endif 77 78 #ifdef IPSEC 79 #include <netipsec/ipsec.h> 80 #endif /*IPSEC*/ 81 82 #include <machine/in_cksum.h> 83 84 #include <security/mac/mac_framework.h> 85 86 #ifdef notyet 87 extern struct mbuf *m_copypack(); 88 #endif 89 90 VNET_DEFINE(int, path_mtu_discovery) = 1; 91 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 92 &VNET_NAME(path_mtu_discovery), 1, 93 "Enable Path MTU Discovery"); 94 95 VNET_DEFINE(int, ss_fltsz) = 1; 96 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, slowstart_flightsize, CTLFLAG_RW, 97 &VNET_NAME(ss_fltsz), 1, 98 "Slow start flight size"); 99 100 VNET_DEFINE(int, ss_fltsz_local) = 4; 101 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, local_slowstart_flightsize, 102 CTLFLAG_RW, &VNET_NAME(ss_fltsz_local), 1, 103 "Slow start flight size for local networks"); 104 105 VNET_DEFINE(int, tcp_do_newreno) = 1; 106 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, newreno, CTLFLAG_RW, 107 &VNET_NAME(tcp_do_newreno), 0, 108 "Enable NewReno Algorithms"); 109 110 VNET_DEFINE(int, tcp_do_tso) = 1; 111 #define V_tcp_do_tso VNET(tcp_do_tso) 112 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_RW, 113 &VNET_NAME(tcp_do_tso), 0, 114 "Enable TCP Segmentation Offload"); 115 116 VNET_DEFINE(int, tcp_do_autosndbuf) = 1; 117 #define V_tcp_do_autosndbuf VNET(tcp_do_autosndbuf) 118 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_RW, 119 &VNET_NAME(tcp_do_autosndbuf), 0, 120 "Enable automatic send buffer sizing"); 121 122 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024; 123 #define V_tcp_autosndbuf_inc VNET(tcp_autosndbuf_inc) 124 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_RW, 125 &VNET_NAME(tcp_autosndbuf_inc), 0, 126 "Incrementor step size of automatic send buffer"); 127 128 VNET_DEFINE(int, tcp_autosndbuf_max) = 256*1024; 129 #define V_tcp_autosndbuf_max VNET(tcp_autosndbuf_max) 130 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_RW, 131 &VNET_NAME(tcp_autosndbuf_max), 0, 132 "Max size of automatic send buffer"); 133 134 135 /* 136 * Tcp output routine: figure out what should be sent and send it. 137 */ 138 int 139 tcp_output(struct tcpcb *tp) 140 { 141 struct socket *so = tp->t_inpcb->inp_socket; 142 long len, recwin, sendwin; 143 int off, flags, error, rw; 144 struct mbuf *m; 145 struct ip *ip = NULL; 146 struct ipovly *ipov = NULL; 147 struct tcphdr *th; 148 u_char opt[TCP_MAXOLEN]; 149 unsigned ipoptlen, optlen, hdrlen; 150 #ifdef IPSEC 151 unsigned ipsec_optlen = 0; 152 #endif 153 int idle, sendalot; 154 int sack_rxmit, sack_bytes_rxmt; 155 struct sackhole *p; 156 int tso; 157 struct tcpopt to; 158 #if 0 159 int maxburst = TCP_MAXBURST; 160 #endif 161 #ifdef INET6 162 struct ip6_hdr *ip6 = NULL; 163 int isipv6; 164 165 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 166 #endif 167 168 INP_WLOCK_ASSERT(tp->t_inpcb); 169 170 /* 171 * Determine length of data that should be transmitted, 172 * and flags that will be used. 173 * If there is some data or critical controls (SYN, RST) 174 * to send, then transmit; otherwise, investigate further. 175 */ 176 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 177 if (idle && ticks - tp->t_rcvtime >= tp->t_rxtcur) { 178 /* 179 * If we've been idle for more than one retransmit 180 * timeout the old congestion window is no longer 181 * current and we have to reduce it to the restart 182 * window before we can transmit again. 183 * 184 * The restart window is the initial window or the last 185 * CWND, whichever is smaller. 186 * 187 * This is done to prevent us from flooding the path with 188 * a full CWND at wirespeed, overloading router and switch 189 * buffers along the way. 190 * 191 * See RFC5681 Section 4.1. "Restarting Idle Connections". 192 */ 193 if (V_tcp_do_rfc3390) 194 rw = min(4 * tp->t_maxseg, 195 max(2 * tp->t_maxseg, 4380)); 196 #ifdef INET6 197 else if ((isipv6 ? in6_localaddr(&tp->t_inpcb->in6p_faddr) : 198 in_localaddr(tp->t_inpcb->inp_faddr))) 199 #else 200 else if (in_localaddr(tp->t_inpcb->inp_faddr)) 201 #endif 202 rw = V_ss_fltsz_local * tp->t_maxseg; 203 else 204 rw = V_ss_fltsz * tp->t_maxseg; 205 206 tp->snd_cwnd = min(rw, tp->snd_cwnd); 207 } 208 tp->t_flags &= ~TF_LASTIDLE; 209 if (idle) { 210 if (tp->t_flags & TF_MORETOCOME) { 211 tp->t_flags |= TF_LASTIDLE; 212 idle = 0; 213 } 214 } 215 again: 216 /* 217 * If we've recently taken a timeout, snd_max will be greater than 218 * snd_nxt. There may be SACK information that allows us to avoid 219 * resending already delivered data. Adjust snd_nxt accordingly. 220 */ 221 if ((tp->t_flags & TF_SACK_PERMIT) && 222 SEQ_LT(tp->snd_nxt, tp->snd_max)) 223 tcp_sack_adjust(tp); 224 sendalot = 0; 225 tso = 0; 226 off = tp->snd_nxt - tp->snd_una; 227 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 228 sendwin = min(sendwin, tp->snd_bwnd); 229 230 flags = tcp_outflags[tp->t_state]; 231 /* 232 * Send any SACK-generated retransmissions. If we're explicitly trying 233 * to send out new data (when sendalot is 1), bypass this function. 234 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 235 * we're replacing a (future) new transmission with a retransmission 236 * now, and we previously incremented snd_cwnd in tcp_input(). 237 */ 238 /* 239 * Still in sack recovery , reset rxmit flag to zero. 240 */ 241 sack_rxmit = 0; 242 sack_bytes_rxmt = 0; 243 len = 0; 244 p = NULL; 245 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp) && 246 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 247 long cwin; 248 249 cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt; 250 if (cwin < 0) 251 cwin = 0; 252 /* Do not retransmit SACK segments beyond snd_recover */ 253 if (SEQ_GT(p->end, tp->snd_recover)) { 254 /* 255 * (At least) part of sack hole extends beyond 256 * snd_recover. Check to see if we can rexmit data 257 * for this hole. 258 */ 259 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 260 /* 261 * Can't rexmit any more data for this hole. 262 * That data will be rexmitted in the next 263 * sack recovery episode, when snd_recover 264 * moves past p->rxmit. 265 */ 266 p = NULL; 267 goto after_sack_rexmit; 268 } else 269 /* Can rexmit part of the current hole */ 270 len = ((long)ulmin(cwin, 271 tp->snd_recover - p->rxmit)); 272 } else 273 len = ((long)ulmin(cwin, p->end - p->rxmit)); 274 off = p->rxmit - tp->snd_una; 275 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 276 __func__, off)); 277 if (len > 0) { 278 sack_rxmit = 1; 279 sendalot = 1; 280 TCPSTAT_INC(tcps_sack_rexmits); 281 TCPSTAT_ADD(tcps_sack_rexmit_bytes, 282 min(len, tp->t_maxseg)); 283 } 284 } 285 after_sack_rexmit: 286 /* 287 * Get standard flags, and add SYN or FIN if requested by 'hidden' 288 * state flags. 289 */ 290 if (tp->t_flags & TF_NEEDFIN) 291 flags |= TH_FIN; 292 if (tp->t_flags & TF_NEEDSYN) 293 flags |= TH_SYN; 294 295 SOCKBUF_LOCK(&so->so_snd); 296 /* 297 * If in persist timeout with window of 0, send 1 byte. 298 * Otherwise, if window is small but nonzero 299 * and timer expired, we will send what we can 300 * and go to transmit state. 301 */ 302 if (tp->t_flags & TF_FORCEDATA) { 303 if (sendwin == 0) { 304 /* 305 * If we still have some data to send, then 306 * clear the FIN bit. Usually this would 307 * happen below when it realizes that we 308 * aren't sending all the data. However, 309 * if we have exactly 1 byte of unsent data, 310 * then it won't clear the FIN bit below, 311 * and if we are in persist state, we wind 312 * up sending the packet without recording 313 * that we sent the FIN bit. 314 * 315 * We can't just blindly clear the FIN bit, 316 * because if we don't have any more data 317 * to send then the probe will be the FIN 318 * itself. 319 */ 320 if (off < so->so_snd.sb_cc) 321 flags &= ~TH_FIN; 322 sendwin = 1; 323 } else { 324 tcp_timer_activate(tp, TT_PERSIST, 0); 325 tp->t_rxtshift = 0; 326 } 327 } 328 329 /* 330 * If snd_nxt == snd_max and we have transmitted a FIN, the 331 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 332 * a negative length. This can also occur when TCP opens up 333 * its congestion window while receiving additional duplicate 334 * acks after fast-retransmit because TCP will reset snd_nxt 335 * to snd_max after the fast-retransmit. 336 * 337 * In the normal retransmit-FIN-only case, however, snd_nxt will 338 * be set to snd_una, the offset will be 0, and the length may 339 * wind up 0. 340 * 341 * If sack_rxmit is true we are retransmitting from the scoreboard 342 * in which case len is already set. 343 */ 344 if (sack_rxmit == 0) { 345 if (sack_bytes_rxmt == 0) 346 len = ((long)ulmin(so->so_snd.sb_cc, sendwin) - off); 347 else { 348 long cwin; 349 350 /* 351 * We are inside of a SACK recovery episode and are 352 * sending new data, having retransmitted all the 353 * data possible in the scoreboard. 354 */ 355 len = ((long)ulmin(so->so_snd.sb_cc, tp->snd_wnd) 356 - off); 357 /* 358 * Don't remove this (len > 0) check ! 359 * We explicitly check for len > 0 here (although it 360 * isn't really necessary), to work around a gcc 361 * optimization issue - to force gcc to compute 362 * len above. Without this check, the computation 363 * of len is bungled by the optimizer. 364 */ 365 if (len > 0) { 366 cwin = tp->snd_cwnd - 367 (tp->snd_nxt - tp->sack_newdata) - 368 sack_bytes_rxmt; 369 if (cwin < 0) 370 cwin = 0; 371 len = lmin(len, cwin); 372 } 373 } 374 } 375 376 /* 377 * Lop off SYN bit if it has already been sent. However, if this 378 * is SYN-SENT state and if segment contains data and if we don't 379 * know that foreign host supports TAO, suppress sending segment. 380 */ 381 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 382 if (tp->t_state != TCPS_SYN_RECEIVED) 383 flags &= ~TH_SYN; 384 off--, len++; 385 } 386 387 /* 388 * Be careful not to send data and/or FIN on SYN segments. 389 * This measure is needed to prevent interoperability problems 390 * with not fully conformant TCP implementations. 391 */ 392 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 393 len = 0; 394 flags &= ~TH_FIN; 395 } 396 397 if (len < 0) { 398 /* 399 * If FIN has been sent but not acked, 400 * but we haven't been called to retransmit, 401 * len will be < 0. Otherwise, window shrank 402 * after we sent into it. If window shrank to 0, 403 * cancel pending retransmit, pull snd_nxt back 404 * to (closed) window, and set the persist timer 405 * if it isn't already going. If the window didn't 406 * close completely, just wait for an ACK. 407 */ 408 len = 0; 409 if (sendwin == 0) { 410 tcp_timer_activate(tp, TT_REXMT, 0); 411 tp->t_rxtshift = 0; 412 tp->snd_nxt = tp->snd_una; 413 if (!tcp_timer_active(tp, TT_PERSIST)) 414 tcp_setpersist(tp); 415 } 416 } 417 418 /* len will be >= 0 after this point. */ 419 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 420 421 /* 422 * Automatic sizing of send socket buffer. Often the send buffer 423 * size is not optimally adjusted to the actual network conditions 424 * at hand (delay bandwidth product). Setting the buffer size too 425 * small limits throughput on links with high bandwidth and high 426 * delay (eg. trans-continental/oceanic links). Setting the 427 * buffer size too big consumes too much real kernel memory, 428 * especially with many connections on busy servers. 429 * 430 * The criteria to step up the send buffer one notch are: 431 * 1. receive window of remote host is larger than send buffer 432 * (with a fudge factor of 5/4th); 433 * 2. send buffer is filled to 7/8th with data (so we actually 434 * have data to make use of it); 435 * 3. send buffer fill has not hit maximal automatic size; 436 * 4. our send window (slow start and cogestion controlled) is 437 * larger than sent but unacknowledged data in send buffer. 438 * 439 * The remote host receive window scaling factor may limit the 440 * growing of the send buffer before it reaches its allowed 441 * maximum. 442 * 443 * It scales directly with slow start or congestion window 444 * and does at most one step per received ACK. This fast 445 * scaling has the drawback of growing the send buffer beyond 446 * what is strictly necessary to make full use of a given 447 * delay*bandwith product. However testing has shown this not 448 * to be much of an problem. At worst we are trading wasting 449 * of available bandwith (the non-use of it) for wasting some 450 * socket buffer memory. 451 * 452 * TODO: Shrink send buffer during idle periods together 453 * with congestion window. Requires another timer. Has to 454 * wait for upcoming tcp timer rewrite. 455 */ 456 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 457 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat && 458 so->so_snd.sb_cc >= (so->so_snd.sb_hiwat / 8 * 7) && 459 so->so_snd.sb_cc < V_tcp_autosndbuf_max && 460 sendwin >= (so->so_snd.sb_cc - (tp->snd_nxt - tp->snd_una))) { 461 if (!sbreserve_locked(&so->so_snd, 462 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 463 V_tcp_autosndbuf_max), so, curthread)) 464 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 465 } 466 } 467 468 /* 469 * Truncate to the maximum segment length or enable TCP Segmentation 470 * Offloading (if supported by hardware) and ensure that FIN is removed 471 * if the length no longer contains the last data byte. 472 * 473 * TSO may only be used if we are in a pure bulk sending state. The 474 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 475 * IP options prevent using TSO. With TSO the TCP header is the same 476 * (except for the sequence number) for all generated packets. This 477 * makes it impossible to transmit any options which vary per generated 478 * segment or packet. 479 * 480 * The length of TSO bursts is limited to TCP_MAXWIN. That limit and 481 * removal of FIN (if not already catched here) are handled later after 482 * the exact length of the TCP options are known. 483 */ 484 #ifdef IPSEC 485 /* 486 * Pre-calculate here as we save another lookup into the darknesses 487 * of IPsec that way and can actually decide if TSO is ok. 488 */ 489 ipsec_optlen = ipsec_hdrsiz_tcp(tp); 490 #endif 491 if (len > tp->t_maxseg) { 492 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && 493 ((tp->t_flags & TF_SIGNATURE) == 0) && 494 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 495 tp->t_inpcb->inp_options == NULL && 496 tp->t_inpcb->in6p_options == NULL 497 #ifdef IPSEC 498 && ipsec_optlen == 0 499 #endif 500 ) { 501 tso = 1; 502 } else { 503 len = tp->t_maxseg; 504 sendalot = 1; 505 } 506 } 507 508 if (sack_rxmit) { 509 if (SEQ_LT(p->rxmit + len, tp->snd_una + so->so_snd.sb_cc)) 510 flags &= ~TH_FIN; 511 } else { 512 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 513 flags &= ~TH_FIN; 514 } 515 516 recwin = sbspace(&so->so_rcv); 517 518 /* 519 * Sender silly window avoidance. We transmit under the following 520 * conditions when len is non-zero: 521 * 522 * - We have a full segment (or more with TSO) 523 * - This is the last buffer in a write()/send() and we are 524 * either idle or running NODELAY 525 * - we've timed out (e.g. persist timer) 526 * - we have more then 1/2 the maximum send window's worth of 527 * data (receiver may be limited the window size) 528 * - we need to retransmit 529 */ 530 if (len) { 531 if (len >= tp->t_maxseg) 532 goto send; 533 /* 534 * NOTE! on localhost connections an 'ack' from the remote 535 * end may occur synchronously with the output and cause 536 * us to flush a buffer queued with moretocome. XXX 537 * 538 * note: the len + off check is almost certainly unnecessary. 539 */ 540 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 541 (idle || (tp->t_flags & TF_NODELAY)) && 542 len + off >= so->so_snd.sb_cc && 543 (tp->t_flags & TF_NOPUSH) == 0) { 544 goto send; 545 } 546 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 547 goto send; 548 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 549 goto send; 550 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 551 goto send; 552 if (sack_rxmit) 553 goto send; 554 } 555 556 /* 557 * Compare available window to amount of window 558 * known to peer (as advertised window less 559 * next expected input). If the difference is at least two 560 * max size segments, or at least 50% of the maximum possible 561 * window, then want to send a window update to peer. 562 * Skip this if the connection is in T/TCP half-open state. 563 * Don't send pure window updates when the peer has closed 564 * the connection and won't ever send more data. 565 */ 566 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 567 !TCPS_HAVERCVDFIN(tp->t_state)) { 568 /* 569 * "adv" is the amount we can increase the window, 570 * taking into account that we are limited by 571 * TCP_MAXWIN << tp->rcv_scale. 572 */ 573 long adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale) - 574 (tp->rcv_adv - tp->rcv_nxt); 575 576 if (adv >= (long) (2 * tp->t_maxseg)) 577 goto send; 578 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 579 goto send; 580 } 581 582 /* 583 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 584 * is also a catch-all for the retransmit timer timeout case. 585 */ 586 if (tp->t_flags & TF_ACKNOW) 587 goto send; 588 if ((flags & TH_RST) || 589 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 590 goto send; 591 if (SEQ_GT(tp->snd_up, tp->snd_una)) 592 goto send; 593 /* 594 * If our state indicates that FIN should be sent 595 * and we have not yet done so, then we need to send. 596 */ 597 if (flags & TH_FIN && 598 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 599 goto send; 600 /* 601 * In SACK, it is possible for tcp_output to fail to send a segment 602 * after the retransmission timer has been turned off. Make sure 603 * that the retransmission timer is set. 604 */ 605 if ((tp->t_flags & TF_SACK_PERMIT) && 606 SEQ_GT(tp->snd_max, tp->snd_una) && 607 !tcp_timer_active(tp, TT_REXMT) && 608 !tcp_timer_active(tp, TT_PERSIST)) { 609 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 610 goto just_return; 611 } 612 /* 613 * TCP window updates are not reliable, rather a polling protocol 614 * using ``persist'' packets is used to insure receipt of window 615 * updates. The three ``states'' for the output side are: 616 * idle not doing retransmits or persists 617 * persisting to move a small or zero window 618 * (re)transmitting and thereby not persisting 619 * 620 * tcp_timer_active(tp, TT_PERSIST) 621 * is true when we are in persist state. 622 * (tp->t_flags & TF_FORCEDATA) 623 * is set when we are called to send a persist packet. 624 * tcp_timer_active(tp, TT_REXMT) 625 * is set when we are retransmitting 626 * The output side is idle when both timers are zero. 627 * 628 * If send window is too small, there is data to transmit, and no 629 * retransmit or persist is pending, then go to persist state. 630 * If nothing happens soon, send when timer expires: 631 * if window is nonzero, transmit what we can, 632 * otherwise force out a byte. 633 */ 634 if (so->so_snd.sb_cc && !tcp_timer_active(tp, TT_REXMT) && 635 !tcp_timer_active(tp, TT_PERSIST)) { 636 tp->t_rxtshift = 0; 637 tcp_setpersist(tp); 638 } 639 640 /* 641 * No reason to send a segment, just return. 642 */ 643 just_return: 644 SOCKBUF_UNLOCK(&so->so_snd); 645 return (0); 646 647 send: 648 SOCKBUF_LOCK_ASSERT(&so->so_snd); 649 /* 650 * Before ESTABLISHED, force sending of initial options 651 * unless TCP set not to do any options. 652 * NOTE: we assume that the IP/TCP header plus TCP options 653 * always fit in a single mbuf, leaving room for a maximum 654 * link header, i.e. 655 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 656 */ 657 optlen = 0; 658 #ifdef INET6 659 if (isipv6) 660 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 661 else 662 #endif 663 hdrlen = sizeof (struct tcpiphdr); 664 665 /* 666 * Compute options for segment. 667 * We only have to care about SYN and established connection 668 * segments. Options for SYN-ACK segments are handled in TCP 669 * syncache. 670 */ 671 if ((tp->t_flags & TF_NOOPT) == 0) { 672 to.to_flags = 0; 673 /* Maximum segment size. */ 674 if (flags & TH_SYN) { 675 tp->snd_nxt = tp->iss; 676 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 677 to.to_flags |= TOF_MSS; 678 } 679 /* Window scaling. */ 680 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 681 to.to_wscale = tp->request_r_scale; 682 to.to_flags |= TOF_SCALE; 683 } 684 /* Timestamps. */ 685 if ((tp->t_flags & TF_RCVD_TSTMP) || 686 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 687 to.to_tsval = ticks + tp->ts_offset; 688 to.to_tsecr = tp->ts_recent; 689 to.to_flags |= TOF_TS; 690 /* Set receive buffer autosizing timestamp. */ 691 if (tp->rfbuf_ts == 0 && 692 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 693 tp->rfbuf_ts = ticks; 694 } 695 /* Selective ACK's. */ 696 if (tp->t_flags & TF_SACK_PERMIT) { 697 if (flags & TH_SYN) 698 to.to_flags |= TOF_SACKPERM; 699 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 700 (tp->t_flags & TF_SACK_PERMIT) && 701 tp->rcv_numsacks > 0) { 702 to.to_flags |= TOF_SACK; 703 to.to_nsacks = tp->rcv_numsacks; 704 to.to_sacks = (u_char *)tp->sackblks; 705 } 706 } 707 #ifdef TCP_SIGNATURE 708 /* TCP-MD5 (RFC2385). */ 709 if (tp->t_flags & TF_SIGNATURE) 710 to.to_flags |= TOF_SIGNATURE; 711 #endif /* TCP_SIGNATURE */ 712 713 /* Processing the options. */ 714 hdrlen += optlen = tcp_addoptions(&to, opt); 715 } 716 717 #ifdef INET6 718 if (isipv6) 719 ipoptlen = ip6_optlen(tp->t_inpcb); 720 else 721 #endif 722 if (tp->t_inpcb->inp_options) 723 ipoptlen = tp->t_inpcb->inp_options->m_len - 724 offsetof(struct ipoption, ipopt_list); 725 else 726 ipoptlen = 0; 727 #ifdef IPSEC 728 ipoptlen += ipsec_optlen; 729 #endif 730 731 /* 732 * Adjust data length if insertion of options will 733 * bump the packet length beyond the t_maxopd length. 734 * Clear the FIN bit because we cut off the tail of 735 * the segment. 736 * 737 * When doing TSO limit a burst to TCP_MAXWIN minus the 738 * IP, TCP and Options length to keep ip->ip_len from 739 * overflowing. Prevent the last segment from being 740 * fractional thus making them all equal sized and set 741 * the flag to continue sending. TSO is disabled when 742 * IP options or IPSEC are present. 743 */ 744 if (len + optlen + ipoptlen > tp->t_maxopd) { 745 flags &= ~TH_FIN; 746 if (tso) { 747 if (len > TCP_MAXWIN - hdrlen - optlen) { 748 len = TCP_MAXWIN - hdrlen - optlen; 749 len = len - (len % (tp->t_maxopd - optlen)); 750 sendalot = 1; 751 } else if (tp->t_flags & TF_NEEDFIN) 752 sendalot = 1; 753 } else { 754 len = tp->t_maxopd - optlen - ipoptlen; 755 sendalot = 1; 756 } 757 } 758 759 /*#ifdef DIAGNOSTIC*/ 760 #ifdef INET6 761 if (max_linkhdr + hdrlen > MCLBYTES) 762 #else 763 if (max_linkhdr + hdrlen > MHLEN) 764 #endif 765 panic("tcphdr too big"); 766 /*#endif*/ 767 768 /* 769 * This KASSERT is here to catch edge cases at a well defined place. 770 * Before, those had triggered (random) panic conditions further down. 771 */ 772 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 773 774 /* 775 * Grab a header mbuf, attaching a copy of data to 776 * be transmitted, and initialize the header from 777 * the template for sends on this connection. 778 */ 779 if (len) { 780 struct mbuf *mb; 781 u_int moff; 782 783 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 784 TCPSTAT_INC(tcps_sndprobe); 785 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 786 TCPSTAT_INC(tcps_sndrexmitpack); 787 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 788 } else { 789 TCPSTAT_INC(tcps_sndpack); 790 TCPSTAT_ADD(tcps_sndbyte, len); 791 } 792 #ifdef notyet 793 if ((m = m_copypack(so->so_snd.sb_mb, off, 794 (int)len, max_linkhdr + hdrlen)) == 0) { 795 SOCKBUF_UNLOCK(&so->so_snd); 796 error = ENOBUFS; 797 goto out; 798 } 799 /* 800 * m_copypack left space for our hdr; use it. 801 */ 802 m->m_len += hdrlen; 803 m->m_data -= hdrlen; 804 #else 805 MGETHDR(m, M_DONTWAIT, MT_DATA); 806 if (m == NULL) { 807 SOCKBUF_UNLOCK(&so->so_snd); 808 error = ENOBUFS; 809 goto out; 810 } 811 #ifdef INET6 812 if (MHLEN < hdrlen + max_linkhdr) { 813 MCLGET(m, M_DONTWAIT); 814 if ((m->m_flags & M_EXT) == 0) { 815 SOCKBUF_UNLOCK(&so->so_snd); 816 m_freem(m); 817 error = ENOBUFS; 818 goto out; 819 } 820 } 821 #endif 822 m->m_data += max_linkhdr; 823 m->m_len = hdrlen; 824 825 /* 826 * Start the m_copy functions from the closest mbuf 827 * to the offset in the socket buffer chain. 828 */ 829 mb = sbsndptr(&so->so_snd, off, len, &moff); 830 831 if (len <= MHLEN - hdrlen - max_linkhdr) { 832 m_copydata(mb, moff, (int)len, 833 mtod(m, caddr_t) + hdrlen); 834 m->m_len += len; 835 } else { 836 m->m_next = m_copy(mb, moff, (int)len); 837 if (m->m_next == NULL) { 838 SOCKBUF_UNLOCK(&so->so_snd); 839 (void) m_free(m); 840 error = ENOBUFS; 841 goto out; 842 } 843 } 844 #endif 845 /* 846 * If we're sending everything we've got, set PUSH. 847 * (This will keep happy those implementations which only 848 * give data to the user when a buffer fills or 849 * a PUSH comes in.) 850 */ 851 if (off + len == so->so_snd.sb_cc) 852 flags |= TH_PUSH; 853 SOCKBUF_UNLOCK(&so->so_snd); 854 } else { 855 SOCKBUF_UNLOCK(&so->so_snd); 856 if (tp->t_flags & TF_ACKNOW) 857 TCPSTAT_INC(tcps_sndacks); 858 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 859 TCPSTAT_INC(tcps_sndctrl); 860 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 861 TCPSTAT_INC(tcps_sndurg); 862 else 863 TCPSTAT_INC(tcps_sndwinup); 864 865 MGETHDR(m, M_DONTWAIT, MT_DATA); 866 if (m == NULL) { 867 error = ENOBUFS; 868 goto out; 869 } 870 #ifdef INET6 871 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 872 MHLEN >= hdrlen) { 873 MH_ALIGN(m, hdrlen); 874 } else 875 #endif 876 m->m_data += max_linkhdr; 877 m->m_len = hdrlen; 878 } 879 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 880 m->m_pkthdr.rcvif = (struct ifnet *)0; 881 #ifdef MAC 882 mac_inpcb_create_mbuf(tp->t_inpcb, m); 883 #endif 884 #ifdef INET6 885 if (isipv6) { 886 ip6 = mtod(m, struct ip6_hdr *); 887 th = (struct tcphdr *)(ip6 + 1); 888 tcpip_fillheaders(tp->t_inpcb, ip6, th); 889 } else 890 #endif /* INET6 */ 891 { 892 ip = mtod(m, struct ip *); 893 ipov = (struct ipovly *)ip; 894 th = (struct tcphdr *)(ip + 1); 895 tcpip_fillheaders(tp->t_inpcb, ip, th); 896 } 897 898 /* 899 * Fill in fields, remembering maximum advertised 900 * window for use in delaying messages about window sizes. 901 * If resending a FIN, be sure not to use a new sequence number. 902 */ 903 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 904 tp->snd_nxt == tp->snd_max) 905 tp->snd_nxt--; 906 /* 907 * If we are starting a connection, send ECN setup 908 * SYN packet. If we are on a retransmit, we may 909 * resend those bits a number of times as per 910 * RFC 3168. 911 */ 912 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) { 913 if (tp->t_rxtshift >= 1) { 914 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 915 flags |= TH_ECE|TH_CWR; 916 } else 917 flags |= TH_ECE|TH_CWR; 918 } 919 920 if (tp->t_state == TCPS_ESTABLISHED && 921 (tp->t_flags & TF_ECN_PERMIT)) { 922 /* 923 * If the peer has ECN, mark data packets with 924 * ECN capable transmission (ECT). 925 * Ignore pure ack packets, retransmissions and window probes. 926 */ 927 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 928 !((tp->t_flags & TF_FORCEDATA) && len == 1)) { 929 #ifdef INET6 930 if (isipv6) 931 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 932 else 933 #endif 934 ip->ip_tos |= IPTOS_ECN_ECT0; 935 TCPSTAT_INC(tcps_ecn_ect0); 936 } 937 938 /* 939 * Reply with proper ECN notifications. 940 */ 941 if (tp->t_flags & TF_ECN_SND_CWR) { 942 flags |= TH_CWR; 943 tp->t_flags &= ~TF_ECN_SND_CWR; 944 } 945 if (tp->t_flags & TF_ECN_SND_ECE) 946 flags |= TH_ECE; 947 } 948 949 /* 950 * If we are doing retransmissions, then snd_nxt will 951 * not reflect the first unsent octet. For ACK only 952 * packets, we do not want the sequence number of the 953 * retransmitted packet, we want the sequence number 954 * of the next unsent octet. So, if there is no data 955 * (and no SYN or FIN), use snd_max instead of snd_nxt 956 * when filling in ti_seq. But if we are in persist 957 * state, snd_max might reflect one byte beyond the 958 * right edge of the window, so use snd_nxt in that 959 * case, since we know we aren't doing a retransmission. 960 * (retransmit and persist are mutually exclusive...) 961 */ 962 if (sack_rxmit == 0) { 963 if (len || (flags & (TH_SYN|TH_FIN)) || 964 tcp_timer_active(tp, TT_PERSIST)) 965 th->th_seq = htonl(tp->snd_nxt); 966 else 967 th->th_seq = htonl(tp->snd_max); 968 } else { 969 th->th_seq = htonl(p->rxmit); 970 p->rxmit += len; 971 tp->sackhint.sack_bytes_rexmit += len; 972 } 973 th->th_ack = htonl(tp->rcv_nxt); 974 if (optlen) { 975 bcopy(opt, th + 1, optlen); 976 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 977 } 978 th->th_flags = flags; 979 /* 980 * Calculate receive window. Don't shrink window, 981 * but avoid silly window syndrome. 982 */ 983 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) && 984 recwin < (long)tp->t_maxseg) 985 recwin = 0; 986 if (recwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 987 recwin = (long)(tp->rcv_adv - tp->rcv_nxt); 988 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale) 989 recwin = (long)TCP_MAXWIN << tp->rcv_scale; 990 991 /* 992 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 993 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 994 * case is handled in syncache. 995 */ 996 if (flags & TH_SYN) 997 th->th_win = htons((u_short) 998 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 999 else 1000 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1001 1002 /* 1003 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1004 * a 0 window. This may cause the remote transmitter to stall. This 1005 * flag tells soreceive() to disable delayed acknowledgements when 1006 * draining the buffer. This can occur if the receiver is attempting 1007 * to read more data than can be buffered prior to transmitting on 1008 * the connection. 1009 */ 1010 if (th->th_win == 0) 1011 tp->t_flags |= TF_RXWIN0SENT; 1012 else 1013 tp->t_flags &= ~TF_RXWIN0SENT; 1014 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1015 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1016 th->th_flags |= TH_URG; 1017 } else 1018 /* 1019 * If no urgent pointer to send, then we pull 1020 * the urgent pointer to the left edge of the send window 1021 * so that it doesn't drift into the send window on sequence 1022 * number wraparound. 1023 */ 1024 tp->snd_up = tp->snd_una; /* drag it along */ 1025 1026 #ifdef TCP_SIGNATURE 1027 if (tp->t_flags & TF_SIGNATURE) { 1028 int sigoff = to.to_signature - opt; 1029 tcp_signature_compute(m, 0, len, optlen, 1030 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 1031 } 1032 #endif 1033 1034 /* 1035 * Put TCP length in extended header, and then 1036 * checksum extended header and data. 1037 */ 1038 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1039 #ifdef INET6 1040 if (isipv6) 1041 /* 1042 * ip6_plen is not need to be filled now, and will be filled 1043 * in ip6_output. 1044 */ 1045 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 1046 sizeof(struct tcphdr) + optlen + len); 1047 else 1048 #endif /* INET6 */ 1049 { 1050 m->m_pkthdr.csum_flags = CSUM_TCP; 1051 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1052 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1053 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1054 1055 /* IP version must be set here for ipv4/ipv6 checking later */ 1056 KASSERT(ip->ip_v == IPVERSION, 1057 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1058 } 1059 1060 /* 1061 * Enable TSO and specify the size of the segments. 1062 * The TCP pseudo header checksum is always provided. 1063 * XXX: Fixme: This is currently not the case for IPv6. 1064 */ 1065 if (tso) { 1066 KASSERT(len > tp->t_maxopd - optlen, 1067 ("%s: len <= tso_segsz", __func__)); 1068 m->m_pkthdr.csum_flags |= CSUM_TSO; 1069 m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen; 1070 } 1071 1072 /* 1073 * In transmit state, time the transmission and arrange for 1074 * the retransmit. In persist state, just set snd_max. 1075 */ 1076 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1077 !tcp_timer_active(tp, TT_PERSIST)) { 1078 tcp_seq startseq = tp->snd_nxt; 1079 1080 /* 1081 * Advance snd_nxt over sequence space of this segment. 1082 */ 1083 if (flags & (TH_SYN|TH_FIN)) { 1084 if (flags & TH_SYN) 1085 tp->snd_nxt++; 1086 if (flags & TH_FIN) { 1087 tp->snd_nxt++; 1088 tp->t_flags |= TF_SENTFIN; 1089 } 1090 } 1091 if (sack_rxmit) 1092 goto timer; 1093 tp->snd_nxt += len; 1094 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1095 tp->snd_max = tp->snd_nxt; 1096 /* 1097 * Time this transmission if not a retransmission and 1098 * not currently timing anything. 1099 */ 1100 if (tp->t_rtttime == 0) { 1101 tp->t_rtttime = ticks; 1102 tp->t_rtseq = startseq; 1103 TCPSTAT_INC(tcps_segstimed); 1104 } 1105 } 1106 1107 /* 1108 * Set retransmit timer if not currently set, 1109 * and not doing a pure ack or a keep-alive probe. 1110 * Initial value for retransmit timer is smoothed 1111 * round-trip time + 2 * round-trip time variance. 1112 * Initialize shift counter which is used for backoff 1113 * of retransmit time. 1114 */ 1115 timer: 1116 if (!tcp_timer_active(tp, TT_REXMT) && 1117 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1118 (tp->snd_nxt != tp->snd_una))) { 1119 if (tcp_timer_active(tp, TT_PERSIST)) { 1120 tcp_timer_activate(tp, TT_PERSIST, 0); 1121 tp->t_rxtshift = 0; 1122 } 1123 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1124 } 1125 } else { 1126 /* 1127 * Persist case, update snd_max but since we are in 1128 * persist mode (no window) we do not update snd_nxt. 1129 */ 1130 int xlen = len; 1131 if (flags & TH_SYN) 1132 ++xlen; 1133 if (flags & TH_FIN) { 1134 ++xlen; 1135 tp->t_flags |= TF_SENTFIN; 1136 } 1137 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1138 tp->snd_max = tp->snd_nxt + len; 1139 } 1140 1141 #ifdef TCPDEBUG 1142 /* 1143 * Trace. 1144 */ 1145 if (so->so_options & SO_DEBUG) { 1146 u_short save = 0; 1147 #ifdef INET6 1148 if (!isipv6) 1149 #endif 1150 { 1151 save = ipov->ih_len; 1152 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1153 } 1154 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1155 #ifdef INET6 1156 if (!isipv6) 1157 #endif 1158 ipov->ih_len = save; 1159 } 1160 #endif 1161 1162 /* 1163 * Fill in IP length and desired time to live and 1164 * send to IP level. There should be a better way 1165 * to handle ttl and tos; we could keep them in 1166 * the template, but need a way to checksum without them. 1167 */ 1168 /* 1169 * m->m_pkthdr.len should have been set before cksum calcuration, 1170 * because in6_cksum() need it. 1171 */ 1172 #ifdef INET6 1173 if (isipv6) { 1174 /* 1175 * we separately set hoplimit for every segment, since the 1176 * user might want to change the value via setsockopt. 1177 * Also, desired default hop limit might be changed via 1178 * Neighbor Discovery. 1179 */ 1180 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1181 1182 /* TODO: IPv6 IP6TOS_ECT bit on */ 1183 error = ip6_output(m, 1184 tp->t_inpcb->in6p_outputopts, NULL, 1185 ((so->so_options & SO_DONTROUTE) ? 1186 IP_ROUTETOIF : 0), NULL, NULL, tp->t_inpcb); 1187 } else 1188 #endif /* INET6 */ 1189 { 1190 ip->ip_len = m->m_pkthdr.len; 1191 #ifdef INET6 1192 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1193 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1194 #endif /* INET6 */ 1195 /* 1196 * If we do path MTU discovery, then we set DF on every packet. 1197 * This might not be the best thing to do according to RFC3390 1198 * Section 2. However the tcp hostcache migitates the problem 1199 * so it affects only the first tcp connection with a host. 1200 * 1201 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1202 */ 1203 if (V_path_mtu_discovery && tp->t_maxopd > V_tcp_minmss) 1204 ip->ip_off |= IP_DF; 1205 1206 error = ip_output(m, tp->t_inpcb->inp_options, NULL, 1207 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1208 tp->t_inpcb); 1209 } 1210 if (error) { 1211 1212 /* 1213 * We know that the packet was lost, so back out the 1214 * sequence number advance, if any. 1215 * 1216 * If the error is EPERM the packet got blocked by the 1217 * local firewall. Normally we should terminate the 1218 * connection but the blocking may have been spurious 1219 * due to a firewall reconfiguration cycle. So we treat 1220 * it like a packet loss and let the retransmit timer and 1221 * timeouts do their work over time. 1222 * XXX: It is a POLA question whether calling tcp_drop right 1223 * away would be the really correct behavior instead. 1224 */ 1225 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1226 !tcp_timer_active(tp, TT_PERSIST)) && 1227 ((flags & TH_SYN) == 0) && 1228 (error != EPERM)) { 1229 if (sack_rxmit) { 1230 p->rxmit -= len; 1231 tp->sackhint.sack_bytes_rexmit -= len; 1232 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1233 ("sackhint bytes rtx >= 0")); 1234 } else 1235 tp->snd_nxt -= len; 1236 } 1237 out: 1238 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1239 switch (error) { 1240 case EPERM: 1241 tp->t_softerror = error; 1242 return (error); 1243 case ENOBUFS: 1244 if (!tcp_timer_active(tp, TT_REXMT) && 1245 !tcp_timer_active(tp, TT_PERSIST)) 1246 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1247 tp->snd_cwnd = tp->t_maxseg; 1248 return (0); 1249 case EMSGSIZE: 1250 /* 1251 * For some reason the interface we used initially 1252 * to send segments changed to another or lowered 1253 * its MTU. 1254 * 1255 * tcp_mtudisc() will find out the new MTU and as 1256 * its last action, initiate retransmission, so it 1257 * is important to not do so here. 1258 * 1259 * If TSO was active we either got an interface 1260 * without TSO capabilits or TSO was turned off. 1261 * Disable it for this connection as too and 1262 * immediatly retry with MSS sized segments generated 1263 * by this function. 1264 */ 1265 if (tso) 1266 tp->t_flags &= ~TF_TSO; 1267 tcp_mtudisc(tp->t_inpcb, 0); 1268 return (0); 1269 case EHOSTDOWN: 1270 case EHOSTUNREACH: 1271 case ENETDOWN: 1272 case ENETUNREACH: 1273 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1274 tp->t_softerror = error; 1275 return (0); 1276 } 1277 /* FALLTHROUGH */ 1278 default: 1279 return (error); 1280 } 1281 } 1282 TCPSTAT_INC(tcps_sndtotal); 1283 1284 /* 1285 * Data sent (as far as we can tell). 1286 * If this advertises a larger window than any other segment, 1287 * then remember the size of the advertised window. 1288 * Any pending ACK has now been sent. 1289 */ 1290 if (recwin > 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1291 tp->rcv_adv = tp->rcv_nxt + recwin; 1292 tp->last_ack_sent = tp->rcv_nxt; 1293 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1294 if (tcp_timer_active(tp, TT_DELACK)) 1295 tcp_timer_activate(tp, TT_DELACK, 0); 1296 #if 0 1297 /* 1298 * This completely breaks TCP if newreno is turned on. What happens 1299 * is that if delayed-acks are turned on on the receiver, this code 1300 * on the transmitter effectively destroys the TCP window, forcing 1301 * it to four packets (1.5Kx4 = 6K window). 1302 */ 1303 if (sendalot && (!V_tcp_do_newreno || --maxburst)) 1304 goto again; 1305 #endif 1306 if (sendalot) 1307 goto again; 1308 return (0); 1309 } 1310 1311 void 1312 tcp_setpersist(struct tcpcb *tp) 1313 { 1314 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1315 int tt; 1316 1317 if (tcp_timer_active(tp, TT_REXMT)) 1318 panic("tcp_setpersist: retransmit pending"); 1319 /* 1320 * Start/restart persistance timer. 1321 */ 1322 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1323 TCPTV_PERSMIN, TCPTV_PERSMAX); 1324 tcp_timer_activate(tp, TT_PERSIST, tt); 1325 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1326 tp->t_rxtshift++; 1327 } 1328 1329 /* 1330 * Insert TCP options according to the supplied parameters to the place 1331 * optp in a consistent way. Can handle unaligned destinations. 1332 * 1333 * The order of the option processing is crucial for optimal packing and 1334 * alignment for the scarce option space. 1335 * 1336 * The optimal order for a SYN/SYN-ACK segment is: 1337 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1338 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1339 * 1340 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1341 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1342 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1343 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1344 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1345 */ 1346 int 1347 tcp_addoptions(struct tcpopt *to, u_char *optp) 1348 { 1349 u_int mask, optlen = 0; 1350 1351 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1352 if ((to->to_flags & mask) != mask) 1353 continue; 1354 if (optlen == TCP_MAXOLEN) 1355 break; 1356 switch (to->to_flags & mask) { 1357 case TOF_MSS: 1358 while (optlen % 4) { 1359 optlen += TCPOLEN_NOP; 1360 *optp++ = TCPOPT_NOP; 1361 } 1362 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1363 continue; 1364 optlen += TCPOLEN_MAXSEG; 1365 *optp++ = TCPOPT_MAXSEG; 1366 *optp++ = TCPOLEN_MAXSEG; 1367 to->to_mss = htons(to->to_mss); 1368 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1369 optp += sizeof(to->to_mss); 1370 break; 1371 case TOF_SCALE: 1372 while (!optlen || optlen % 2 != 1) { 1373 optlen += TCPOLEN_NOP; 1374 *optp++ = TCPOPT_NOP; 1375 } 1376 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1377 continue; 1378 optlen += TCPOLEN_WINDOW; 1379 *optp++ = TCPOPT_WINDOW; 1380 *optp++ = TCPOLEN_WINDOW; 1381 *optp++ = to->to_wscale; 1382 break; 1383 case TOF_SACKPERM: 1384 while (optlen % 2) { 1385 optlen += TCPOLEN_NOP; 1386 *optp++ = TCPOPT_NOP; 1387 } 1388 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1389 continue; 1390 optlen += TCPOLEN_SACK_PERMITTED; 1391 *optp++ = TCPOPT_SACK_PERMITTED; 1392 *optp++ = TCPOLEN_SACK_PERMITTED; 1393 break; 1394 case TOF_TS: 1395 while (!optlen || optlen % 4 != 2) { 1396 optlen += TCPOLEN_NOP; 1397 *optp++ = TCPOPT_NOP; 1398 } 1399 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1400 continue; 1401 optlen += TCPOLEN_TIMESTAMP; 1402 *optp++ = TCPOPT_TIMESTAMP; 1403 *optp++ = TCPOLEN_TIMESTAMP; 1404 to->to_tsval = htonl(to->to_tsval); 1405 to->to_tsecr = htonl(to->to_tsecr); 1406 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1407 optp += sizeof(to->to_tsval); 1408 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1409 optp += sizeof(to->to_tsecr); 1410 break; 1411 case TOF_SIGNATURE: 1412 { 1413 int siglen = TCPOLEN_SIGNATURE - 2; 1414 1415 while (!optlen || optlen % 4 != 2) { 1416 optlen += TCPOLEN_NOP; 1417 *optp++ = TCPOPT_NOP; 1418 } 1419 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) 1420 continue; 1421 optlen += TCPOLEN_SIGNATURE; 1422 *optp++ = TCPOPT_SIGNATURE; 1423 *optp++ = TCPOLEN_SIGNATURE; 1424 to->to_signature = optp; 1425 while (siglen--) 1426 *optp++ = 0; 1427 break; 1428 } 1429 case TOF_SACK: 1430 { 1431 int sackblks = 0; 1432 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1433 tcp_seq sack_seq; 1434 1435 while (!optlen || optlen % 4 != 2) { 1436 optlen += TCPOLEN_NOP; 1437 *optp++ = TCPOPT_NOP; 1438 } 1439 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1440 continue; 1441 optlen += TCPOLEN_SACKHDR; 1442 *optp++ = TCPOPT_SACK; 1443 sackblks = min(to->to_nsacks, 1444 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1445 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1446 while (sackblks--) { 1447 sack_seq = htonl(sack->start); 1448 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1449 optp += sizeof(sack_seq); 1450 sack_seq = htonl(sack->end); 1451 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1452 optp += sizeof(sack_seq); 1453 optlen += TCPOLEN_SACK; 1454 sack++; 1455 } 1456 TCPSTAT_INC(tcps_sack_send_blocks); 1457 break; 1458 } 1459 default: 1460 panic("%s: unknown TCP option type", __func__); 1461 break; 1462 } 1463 } 1464 1465 /* Terminate and pad TCP options to a 4 byte boundary. */ 1466 if (optlen % 4) { 1467 optlen += TCPOLEN_EOL; 1468 *optp++ = TCPOPT_EOL; 1469 } 1470 /* 1471 * According to RFC 793 (STD0007): 1472 * "The content of the header beyond the End-of-Option option 1473 * must be header padding (i.e., zero)." 1474 * and later: "The padding is composed of zeros." 1475 */ 1476 while (optlen % 4) { 1477 optlen += TCPOLEN_PAD; 1478 *optp++ = TCPOPT_PAD; 1479 } 1480 1481 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1482 return (optlen); 1483 }
Cache object: 95a24745468e02bae2dfd47de15ba491
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