1 /* 2 * Copyright (c) 2004 Jeffrey M. Hsu. All rights reserved. 3 * Copyright (c) 2004 The DragonFly Project. All rights reserved. 4 * 5 * This code is derived from software contributed to The DragonFly Project 6 * by Jeffrey M. Hsu. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of The DragonFly Project nor the names of its 17 * contributors may be used to endorse or promote products derived 18 * from this software without specific, prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 23 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 24 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 25 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 26 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 27 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 28 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 29 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 30 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34 /* 35 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 36 * The Regents of the University of California. All rights reserved. 37 * 38 * Redistribution and use in source and binary forms, with or without 39 * modification, are permitted provided that the following conditions 40 * are met: 41 * 1. Redistributions of source code must retain the above copyright 42 * notice, this list of conditions and the following disclaimer. 43 * 2. Redistributions in binary form must reproduce the above copyright 44 * notice, this list of conditions and the following disclaimer in the 45 * documentation and/or other materials provided with the distribution. 46 * 3. All advertising materials mentioning features or use of this software 47 * must display the following acknowledgement: 48 * This product includes software developed by the University of 49 * California, Berkeley and its contributors. 50 * 4. Neither the name of the University nor the names of its contributors 51 * may be used to endorse or promote products derived from this software 52 * without specific prior written permission. 53 * 54 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 55 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 56 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 57 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 58 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 59 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 60 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 61 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 62 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 63 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 64 * SUCH DAMAGE. 65 * 66 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95 67 * $FreeBSD: src/sys/netinet/tcp_output.c,v 1.39.2.20 2003/01/29 22:45:36 hsu Exp $ 68 * $DragonFly: src/sys/netinet/tcp_output.c,v 1.34 2007/04/22 01:13:14 dillon Exp $ 69 */ 70 71 #include "opt_inet.h" 72 #include "opt_inet6.h" 73 #include "opt_ipsec.h" 74 #include "opt_tcpdebug.h" 75 76 #include <sys/param.h> 77 #include <sys/systm.h> 78 #include <sys/kernel.h> 79 #include <sys/sysctl.h> 80 #include <sys/mbuf.h> 81 #include <sys/domain.h> 82 #include <sys/protosw.h> 83 #include <sys/socket.h> 84 #include <sys/socketvar.h> 85 #include <sys/in_cksum.h> 86 #include <sys/thread.h> 87 #include <sys/globaldata.h> 88 89 #include <net/route.h> 90 91 #include <netinet/in.h> 92 #include <netinet/in_systm.h> 93 #include <netinet/ip.h> 94 #include <netinet/in_pcb.h> 95 #include <netinet/ip_var.h> 96 #include <netinet6/in6_pcb.h> 97 #include <netinet/ip6.h> 98 #include <netinet6/ip6_var.h> 99 #include <netinet/tcp.h> 100 #define TCPOUTFLAGS 101 #include <netinet/tcp_fsm.h> 102 #include <netinet/tcp_seq.h> 103 #include <netinet/tcp_timer.h> 104 #include <netinet/tcp_timer2.h> 105 #include <netinet/tcp_var.h> 106 #include <netinet/tcpip.h> 107 #ifdef TCPDEBUG 108 #include <netinet/tcp_debug.h> 109 #endif 110 111 #ifdef IPSEC 112 #include <netinet6/ipsec.h> 113 #endif /*IPSEC*/ 114 115 #ifdef FAST_IPSEC 116 #include <netproto/ipsec/ipsec.h> 117 #define IPSEC 118 #endif /*FAST_IPSEC*/ 119 120 #ifdef notyet 121 extern struct mbuf *m_copypack(); 122 #endif 123 124 int path_mtu_discovery = 0; 125 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 126 &path_mtu_discovery, 1, "Enable Path MTU Discovery"); 127 128 static int avoid_pure_win_update = 1; 129 SYSCTL_INT(_net_inet_tcp, OID_AUTO, avoid_pure_win_update, CTLFLAG_RW, 130 &avoid_pure_win_update, 1, "Avoid pure window updates when possible"); 131 132 int tcp_do_autosndbuf = 1; 133 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_RW, 134 &tcp_do_autosndbuf, 0, "Enable automatic send buffer sizing"); 135 136 int tcp_autosndbuf_inc = 8*1024; 137 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_RW, 138 &tcp_autosndbuf_inc, 0, "Incrementor step size of automatic send buffer"); 139 140 int tcp_autosndbuf_max = 2*1024*1024; 141 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_RW, 142 &tcp_autosndbuf_max, 0, "Max size of automatic send buffer"); 143 144 /* 145 * Tcp output routine: figure out what should be sent and send it. 146 */ 147 int 148 tcp_output(struct tcpcb *tp) 149 { 150 struct inpcb * const inp = tp->t_inpcb; 151 struct socket *so = inp->inp_socket; 152 long len, recvwin, sendwin; 153 int nsacked = 0; 154 int off, flags, error = 0; 155 #ifdef TCP_SIGNATURE 156 int sigoff = 0; 157 #endif 158 struct mbuf *m; 159 struct ip *ip; 160 struct ipovly *ipov; 161 struct tcphdr *th; 162 u_char opt[TCP_MAXOLEN]; 163 unsigned int ipoptlen, optlen, hdrlen; 164 int idle; 165 boolean_t sendalot; 166 struct ip6_hdr *ip6; 167 #ifdef INET6 168 const boolean_t isipv6 = (inp->inp_vflag & INP_IPV6) != 0; 169 #else 170 const boolean_t isipv6 = FALSE; 171 #endif 172 173 KKASSERT(so->so_port == &curthread->td_msgport); 174 175 /* 176 * Determine length of data that should be transmitted, 177 * and flags that will be used. 178 * If there is some data or critical controls (SYN, RST) 179 * to send, then transmit; otherwise, investigate further. 180 */ 181 182 /* 183 * If we have been idle for a while, the send congestion window 184 * could be no longer representative of the current state of the link. 185 * So unless we are expecting more acks to come in, slow-start from 186 * scratch to re-determine the send congestion window. 187 */ 188 if (tp->snd_max == tp->snd_una && 189 (ticks - tp->t_rcvtime) >= tp->t_rxtcur) { 190 if (tcp_do_rfc3390 && !(tp->t_flags & TF_SYN_WASLOST)) { 191 int initial_cwnd = 192 min(4 * tp->t_maxseg, max(2 * tp->t_maxseg, 4380)); 193 194 tp->snd_cwnd = min(tp->snd_cwnd, initial_cwnd); 195 } else { 196 tp->snd_cwnd = tp->t_maxseg; 197 } 198 tp->snd_wacked = 0; 199 } 200 201 /* 202 * Calculate whether the transmit stream was previously idle 203 * and adjust TF_LASTIDLE for the next time. 204 */ 205 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 206 if (idle && (tp->t_flags & TF_MORETOCOME)) 207 tp->t_flags |= TF_LASTIDLE; 208 else 209 tp->t_flags &= ~TF_LASTIDLE; 210 211 if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max && 212 !IN_FASTRECOVERY(tp)) 213 nsacked = tcp_sack_bytes_below(&tp->scb, tp->snd_nxt); 214 215 again: 216 m = NULL; 217 ip = NULL; 218 ipov = NULL; 219 th = NULL; 220 ip6 = NULL; 221 222 /* Make use of SACK information when slow-starting after a RTO. */ 223 if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max && 224 !IN_FASTRECOVERY(tp)) { 225 tcp_seq old_snd_nxt = tp->snd_nxt; 226 227 tcp_sack_skip_sacked(&tp->scb, &tp->snd_nxt); 228 nsacked += tp->snd_nxt - old_snd_nxt; 229 } 230 231 sendalot = FALSE; 232 off = tp->snd_nxt - tp->snd_una; 233 sendwin = min(tp->snd_wnd, tp->snd_cwnd + nsacked); 234 sendwin = min(sendwin, tp->snd_bwnd); 235 236 flags = tcp_outflags[tp->t_state]; 237 /* 238 * Get standard flags, and add SYN or FIN if requested by 'hidden' 239 * state flags. 240 */ 241 if (tp->t_flags & TF_NEEDFIN) 242 flags |= TH_FIN; 243 if (tp->t_flags & TF_NEEDSYN) 244 flags |= TH_SYN; 245 246 /* 247 * If in persist timeout with window of 0, send 1 byte. 248 * Otherwise, if window is small but nonzero 249 * and timer expired, we will send what we can 250 * and go to transmit state. 251 */ 252 if (tp->t_flags & TF_FORCE) { 253 if (sendwin == 0) { 254 /* 255 * If we still have some data to send, then 256 * clear the FIN bit. Usually this would 257 * happen below when it realizes that we 258 * aren't sending all the data. However, 259 * if we have exactly 1 byte of unsent data, 260 * then it won't clear the FIN bit below, 261 * and if we are in persist state, we wind 262 * up sending the packet without recording 263 * that we sent the FIN bit. 264 * 265 * We can't just blindly clear the FIN bit, 266 * because if we don't have any more data 267 * to send then the probe will be the FIN 268 * itself. 269 */ 270 if (off < so->so_snd.ssb_cc) 271 flags &= ~TH_FIN; 272 sendwin = 1; 273 } else { 274 tcp_callout_stop(tp, tp->tt_persist); 275 tp->t_rxtshift = 0; 276 } 277 } 278 279 /* 280 * If snd_nxt == snd_max and we have transmitted a FIN, the 281 * offset will be > 0 even if so_snd.ssb_cc is 0, resulting in 282 * a negative length. This can also occur when TCP opens up 283 * its congestion window while receiving additional duplicate 284 * acks after fast-retransmit because TCP will reset snd_nxt 285 * to snd_max after the fast-retransmit. 286 * 287 * A negative length can also occur when we are in the 288 * TCPS_SYN_RECEIVED state due to a simultanious connect where 289 * our SYN has not been acked yet. 290 * 291 * In the normal retransmit-FIN-only case, however, snd_nxt will 292 * be set to snd_una, the offset will be 0, and the length may 293 * wind up 0. 294 */ 295 len = (long)ulmin(so->so_snd.ssb_cc, sendwin) - off; 296 297 /* 298 * Lop off SYN bit if it has already been sent. However, if this 299 * is SYN-SENT state and if segment contains data, suppress sending 300 * segment (sending the segment would be an option if we still 301 * did TAO and the remote host supported it). 302 */ 303 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 304 flags &= ~TH_SYN; 305 off--, len++; 306 if (len > 0 && tp->t_state == TCPS_SYN_SENT) 307 return 0; 308 } 309 310 /* 311 * Be careful not to send data and/or FIN on SYN segments. 312 * This measure is needed to prevent interoperability problems 313 * with not fully conformant TCP implementations. 314 */ 315 if (flags & TH_SYN) { 316 len = 0; 317 flags &= ~TH_FIN; 318 } 319 320 if (len < 0) { 321 /* 322 * A negative len can occur if our FIN has been sent but not 323 * acked, or if we are in a simultanious connect in the 324 * TCPS_SYN_RECEIVED state with our SYN sent but not yet 325 * acked. 326 * 327 * If our window has contracted to 0 in the FIN case 328 * (which can only occur if we have NOT been called to 329 * retransmit as per code a few paragraphs up) then we 330 * want to shift the retransmit timer over to the 331 * persist timer. 332 * 333 * However, if we are in the TCPS_SYN_RECEIVED state 334 * (the SYN case) we will be in a simultanious connect and 335 * the window may be zero degeneratively. In this case we 336 * do not want to shift to the persist timer after the SYN 337 * or the SYN+ACK transmission. 338 */ 339 len = 0; 340 if (sendwin == 0 && tp->t_state != TCPS_SYN_RECEIVED) { 341 tcp_callout_stop(tp, tp->tt_rexmt); 342 tp->t_rxtshift = 0; 343 tp->snd_nxt = tp->snd_una; 344 if (!tcp_callout_active(tp, tp->tt_persist)) 345 tcp_setpersist(tp); 346 } 347 } 348 349 KASSERT(len >= 0, ("%s: len < 0", __func__)); 350 /* 351 * Automatic sizing of send socket buffer. Often the send buffer 352 * size is not optimally adjusted to the actual network conditions 353 * at hand (delay bandwidth product). Setting the buffer size too 354 * small limits throughput on links with high bandwidth and high 355 * delay (eg. trans-continental/oceanic links). Setting the 356 * buffer size too big consumes too much real kernel memory, 357 * especially with many connections on busy servers. 358 * 359 * The criteria to step up the send buffer one notch are: 360 * 1. receive window of remote host is larger than send buffer 361 * (with a fudge factor of 5/4th); 362 * 2. send buffer is filled to 7/8th with data (so we actually 363 * have data to make use of it); 364 * 3. send buffer fill has not hit maximal automatic size; 365 * 4. our send window (slow start and cogestion controlled) is 366 * larger than sent but unacknowledged data in send buffer. 367 * 368 * The remote host receive window scaling factor may limit the 369 * growing of the send buffer before it reaches its allowed 370 * maximum. 371 * 372 * It scales directly with slow start or congestion window 373 * and does at most one step per received ACK. This fast 374 * scaling has the drawback of growing the send buffer beyond 375 * what is strictly necessary to make full use of a given 376 * delay*bandwith product. However testing has shown this not 377 * to be much of an problem. At worst we are trading wasting 378 * of available bandwith (the non-use of it) for wasting some 379 * socket buffer memory. 380 * 381 * TODO: Shrink send buffer during idle periods together 382 * with congestion window. Requires another timer. Has to 383 * wait for upcoming tcp timer rewrite. 384 */ 385 if (tcp_do_autosndbuf && so->so_snd.ssb_flags & SSB_AUTOSIZE) { 386 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.ssb_hiwat && 387 so->so_snd.ssb_cc >= (so->so_snd.ssb_hiwat / 8 * 7) && 388 so->so_snd.ssb_cc < tcp_autosndbuf_max && 389 sendwin >= (so->so_snd.ssb_cc - (tp->snd_nxt - tp->snd_una))) { 390 u_long newsize; 391 392 newsize = ulmin(so->so_snd.ssb_hiwat + 393 tcp_autosndbuf_inc, 394 tcp_autosndbuf_max); 395 if (!ssb_reserve(&so->so_snd, newsize, so, NULL)) 396 atomic_clear_int(&so->so_snd.ssb_flags, SSB_AUTOSIZE); 397 if (newsize >= (TCP_MAXWIN << tp->snd_scale)) 398 atomic_clear_int(&so->so_snd.ssb_flags, SSB_AUTOSIZE); 399 } 400 } 401 402 /* 403 * Truncate to the maximum segment length and ensure that FIN is 404 * removed if the length no longer contains the last data byte. 405 */ 406 if (len > tp->t_maxseg) { 407 len = tp->t_maxseg; 408 sendalot = TRUE; 409 } 410 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.ssb_cc)) 411 flags &= ~TH_FIN; 412 413 recvwin = ssb_space(&so->so_rcv); 414 415 /* 416 * Sender silly window avoidance. We transmit under the following 417 * conditions when len is non-zero: 418 * 419 * - We have a full segment 420 * - This is the last buffer in a write()/send() and we are 421 * either idle or running NODELAY 422 * - we've timed out (e.g. persist timer) 423 * - we have more then 1/2 the maximum send window's worth of 424 * data (receiver may be limiting the window size) 425 * - we need to retransmit 426 */ 427 if (len) { 428 if (len == tp->t_maxseg) 429 goto send; 430 /* 431 * NOTE! on localhost connections an 'ack' from the remote 432 * end may occur synchronously with the output and cause 433 * us to flush a buffer queued with moretocome. XXX 434 * 435 * note: the len + off check is almost certainly unnecessary. 436 */ 437 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 438 (idle || (tp->t_flags & TF_NODELAY)) && 439 len + off >= so->so_snd.ssb_cc && 440 !(tp->t_flags & TF_NOPUSH)) { 441 goto send; 442 } 443 if (tp->t_flags & TF_FORCE) /* typ. timeout case */ 444 goto send; 445 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 446 goto send; 447 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 448 goto send; 449 } 450 451 /* 452 * Compare available window to amount of window 453 * known to peer (as advertised window less 454 * next expected input). If the difference is at least two 455 * max size segments, or at least 50% of the maximum possible 456 * window, then want to send a window update to peer. 457 */ 458 if (recvwin > 0) { 459 /* 460 * "adv" is the amount we can increase the window, 461 * taking into account that we are limited by 462 * TCP_MAXWIN << tp->rcv_scale. 463 */ 464 long adv = min(recvwin, (long)TCP_MAXWIN << tp->rcv_scale) - 465 (tp->rcv_adv - tp->rcv_nxt); 466 long hiwat; 467 468 /* 469 * This ack case typically occurs when the user has drained 470 * the TCP socket buffer sufficiently to warrent an ack 471 * containing a 'pure window update'... that is, an ack that 472 * ONLY updates the tcp window. 473 * 474 * It is unclear why we would need to do a pure window update 475 * past 2 segments if we are going to do one at 1/2 the high 476 * water mark anyway, especially since under normal conditions 477 * the user program will drain the socket buffer quickly. 478 * The 2-segment pure window update will often add a large 479 * number of extra, unnecessary acks to the stream. 480 * 481 * avoid_pure_win_update now defaults to 1. 482 */ 483 if (avoid_pure_win_update == 0 || 484 (tp->t_flags & TF_RXRESIZED)) { 485 if (adv >= (long) (2 * tp->t_maxseg)) { 486 goto send; 487 } 488 } 489 hiwat = (long)(TCP_MAXWIN << tp->rcv_scale); 490 if (hiwat > (long)so->so_rcv.ssb_hiwat) 491 hiwat = (long)so->so_rcv.ssb_hiwat; 492 if (adv >= hiwat / 2) 493 goto send; 494 } 495 496 /* 497 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 498 * is also a catch-all for the retransmit timer timeout case. 499 */ 500 if (tp->t_flags & TF_ACKNOW) 501 goto send; 502 if ((flags & TH_RST) || 503 ((flags & TH_SYN) && !(tp->t_flags & TF_NEEDSYN))) 504 goto send; 505 if (SEQ_GT(tp->snd_up, tp->snd_una)) 506 goto send; 507 /* 508 * If our state indicates that FIN should be sent 509 * and we have not yet done so, then we need to send. 510 */ 511 if ((flags & TH_FIN) && 512 (!(tp->t_flags & TF_SENTFIN) || tp->snd_nxt == tp->snd_una)) 513 goto send; 514 515 /* 516 * TCP window updates are not reliable, rather a polling protocol 517 * using ``persist'' packets is used to insure receipt of window 518 * updates. The three ``states'' for the output side are: 519 * idle not doing retransmits or persists 520 * persisting to move a small or zero window 521 * (re)transmitting and thereby not persisting 522 * 523 * tcp_callout_active(tp, tp->tt_persist) 524 * is true when we are in persist state. 525 * The TF_FORCE flag in tp->t_flags 526 * is set when we are called to send a persist packet. 527 * tcp_callout_active(tp, tp->tt_rexmt) 528 * is set when we are retransmitting 529 * The output side is idle when both timers are zero. 530 * 531 * If send window is too small, there is data to transmit, and no 532 * retransmit or persist is pending, then go to persist state. 533 * 534 * If nothing happens soon, send when timer expires: 535 * if window is nonzero, transmit what we can, otherwise force out 536 * a byte. 537 * 538 * Don't try to set the persist state if we are in TCPS_SYN_RECEIVED 539 * with data pending. This situation can occur during a 540 * simultanious connect. 541 */ 542 if (so->so_snd.ssb_cc > 0 && 543 tp->t_state != TCPS_SYN_RECEIVED && 544 !tcp_callout_active(tp, tp->tt_rexmt) && 545 !tcp_callout_active(tp, tp->tt_persist)) { 546 tp->t_rxtshift = 0; 547 tcp_setpersist(tp); 548 } 549 550 /* 551 * No reason to send a segment, just return. 552 */ 553 return (0); 554 555 send: 556 /* 557 * Before ESTABLISHED, force sending of initial options 558 * unless TCP set not to do any options. 559 * NOTE: we assume that the IP/TCP header plus TCP options 560 * always fit in a single mbuf, leaving room for a maximum 561 * link header, i.e. 562 * max_linkhdr + sizeof(struct tcpiphdr) + optlen <= MCLBYTES 563 */ 564 optlen = 0; 565 if (isipv6) 566 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 567 else 568 hdrlen = sizeof(struct tcpiphdr); 569 if (flags & TH_SYN) { 570 tp->snd_nxt = tp->iss; 571 if (!(tp->t_flags & TF_NOOPT)) { 572 u_short mss; 573 574 opt[0] = TCPOPT_MAXSEG; 575 opt[1] = TCPOLEN_MAXSEG; 576 mss = htons((u_short) tcp_mssopt(tp)); 577 memcpy(opt + 2, &mss, sizeof mss); 578 optlen = TCPOLEN_MAXSEG; 579 580 if ((tp->t_flags & TF_REQ_SCALE) && 581 (!(flags & TH_ACK) || 582 (tp->t_flags & TF_RCVD_SCALE))) { 583 *((u_int32_t *)(opt + optlen)) = htonl( 584 TCPOPT_NOP << 24 | 585 TCPOPT_WINDOW << 16 | 586 TCPOLEN_WINDOW << 8 | 587 tp->request_r_scale); 588 optlen += 4; 589 } 590 591 if ((tcp_do_sack && !(flags & TH_ACK)) || 592 tp->t_flags & TF_SACK_PERMITTED) { 593 uint32_t *lp = (uint32_t *)(opt + optlen); 594 595 *lp = htonl(TCPOPT_SACK_PERMITTED_ALIGNED); 596 optlen += TCPOLEN_SACK_PERMITTED_ALIGNED; 597 } 598 } 599 } 600 601 /* 602 * Send a timestamp and echo-reply if this is a SYN and our side 603 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 604 * and our peer have sent timestamps in our SYN's. 605 */ 606 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 607 !(flags & TH_RST) && 608 (!(flags & TH_ACK) || (tp->t_flags & TF_RCVD_TSTMP))) { 609 u_int32_t *lp = (u_int32_t *)(opt + optlen); 610 611 /* Form timestamp option as shown in appendix A of RFC 1323. */ 612 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 613 *lp++ = htonl(ticks); 614 *lp = htonl(tp->ts_recent); 615 optlen += TCPOLEN_TSTAMP_APPA; 616 } 617 618 /* Set receive buffer autosizing timestamp. */ 619 if (tp->rfbuf_ts == 0 && (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) 620 tp->rfbuf_ts = ticks; 621 622 /* 623 * If this is a SACK connection and we have a block to report, 624 * fill in the SACK blocks in the TCP options. 625 */ 626 if ((tp->t_flags & (TF_SACK_PERMITTED | TF_NOOPT)) == 627 TF_SACK_PERMITTED && 628 (!LIST_EMPTY(&tp->t_segq) || 629 tp->reportblk.rblk_start != tp->reportblk.rblk_end)) 630 tcp_sack_fill_report(tp, opt, &optlen); 631 632 #ifdef TCP_SIGNATURE 633 if (tp->t_flags & TF_SIGNATURE) { 634 int i; 635 u_char *bp; 636 /* 637 * Initialize TCP-MD5 option (RFC2385) 638 */ 639 bp = (u_char *)opt + optlen; 640 *bp++ = TCPOPT_SIGNATURE; 641 *bp++ = TCPOLEN_SIGNATURE; 642 sigoff = optlen + 2; 643 for (i = 0; i < TCP_SIGLEN; i++) 644 *bp++ = 0; 645 optlen += TCPOLEN_SIGNATURE; 646 /* 647 * Terminate options list and maintain 32-bit alignment. 648 */ 649 *bp++ = TCPOPT_NOP; 650 *bp++ = TCPOPT_EOL; 651 optlen += 2; 652 } 653 #endif /* TCP_SIGNATURE */ 654 KASSERT(optlen <= TCP_MAXOLEN, ("too many TCP options")); 655 hdrlen += optlen; 656 657 if (isipv6) { 658 ipoptlen = ip6_optlen(inp); 659 } else { 660 if (inp->inp_options) { 661 ipoptlen = inp->inp_options->m_len - 662 offsetof(struct ipoption, ipopt_list); 663 } else { 664 ipoptlen = 0; 665 } 666 } 667 #ifdef IPSEC 668 ipoptlen += ipsec_hdrsiz_tcp(tp); 669 #endif 670 671 /* 672 * Adjust data length if insertion of options will bump the packet 673 * length beyond the t_maxopd length. Clear FIN to prevent premature 674 * closure since there is still more data to send after this (now 675 * truncated) packet. 676 * 677 * If just the options do not fit we are in a no-win situation and 678 * we treat it as an unreachable host. 679 */ 680 if (len + optlen + ipoptlen > tp->t_maxopd) { 681 if (tp->t_maxopd <= optlen + ipoptlen) { 682 static time_t last_optlen_report; 683 684 if (last_optlen_report != time_second) { 685 last_optlen_report = time_second; 686 kprintf("tcpcb %p: MSS (%d) too small to hold options!\n", tp, tp->t_maxopd); 687 } 688 error = EHOSTUNREACH; 689 goto out; 690 } else { 691 flags &= ~TH_FIN; 692 len = tp->t_maxopd - optlen - ipoptlen; 693 sendalot = TRUE; 694 } 695 } 696 697 #ifdef INET6 698 KASSERT(max_linkhdr + hdrlen <= MCLBYTES, ("tcphdr too big")); 699 #else 700 KASSERT(max_linkhdr + hdrlen <= MHLEN, ("tcphdr too big")); 701 #endif 702 703 /* 704 * Grab a header mbuf, attaching a copy of data to 705 * be transmitted, and initialize the header from 706 * the template for sends on this connection. 707 */ 708 if (len) { 709 if ((tp->t_flags & TF_FORCE) && len == 1) 710 tcpstat.tcps_sndprobe++; 711 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 712 if (tp->snd_nxt == tp->snd_una) 713 tp->snd_max_rexmt = tp->snd_max; 714 if (nsacked) { 715 tcpstat.tcps_sndsackrtopack++; 716 tcpstat.tcps_sndsackrtobyte += len; 717 } 718 tcpstat.tcps_sndrexmitpack++; 719 tcpstat.tcps_sndrexmitbyte += len; 720 } else { 721 tcpstat.tcps_sndpack++; 722 tcpstat.tcps_sndbyte += len; 723 } 724 #ifdef notyet 725 if ((m = m_copypack(so->so_snd.ssb_mb, off, (int)len, 726 max_linkhdr + hdrlen)) == NULL) { 727 error = ENOBUFS; 728 goto after_th; 729 } 730 /* 731 * m_copypack left space for our hdr; use it. 732 */ 733 m->m_len += hdrlen; 734 m->m_data -= hdrlen; 735 #else 736 #ifndef INET6 737 m = m_gethdr(MB_DONTWAIT, MT_HEADER); 738 #else 739 m = m_getl(hdrlen + max_linkhdr, MB_DONTWAIT, MT_HEADER, 740 M_PKTHDR, NULL); 741 #endif 742 if (m == NULL) { 743 error = ENOBUFS; 744 goto after_th; 745 } 746 m->m_data += max_linkhdr; 747 m->m_len = hdrlen; 748 if (len <= MHLEN - hdrlen - max_linkhdr) { 749 m_copydata(so->so_snd.ssb_mb, off, (int) len, 750 mtod(m, caddr_t) + hdrlen); 751 m->m_len += len; 752 } else { 753 m->m_next = m_copy(so->so_snd.ssb_mb, off, (int) len); 754 if (m->m_next == NULL) { 755 m_free(m); 756 m = NULL; 757 error = ENOBUFS; 758 goto after_th; 759 } 760 } 761 #endif 762 /* 763 * If we're sending everything we've got, set PUSH. 764 * (This will keep happy those implementations which only 765 * give data to the user when a buffer fills or 766 * a PUSH comes in.) 767 */ 768 if (off + len == so->so_snd.ssb_cc) 769 flags |= TH_PUSH; 770 } else { 771 if (tp->t_flags & TF_ACKNOW) 772 tcpstat.tcps_sndacks++; 773 else if (flags & (TH_SYN | TH_FIN | TH_RST)) 774 tcpstat.tcps_sndctrl++; 775 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 776 tcpstat.tcps_sndurg++; 777 else 778 tcpstat.tcps_sndwinup++; 779 780 MGETHDR(m, MB_DONTWAIT, MT_HEADER); 781 if (m == NULL) { 782 error = ENOBUFS; 783 goto after_th; 784 } 785 if (isipv6 && 786 (hdrlen + max_linkhdr > MHLEN) && hdrlen <= MHLEN) 787 MH_ALIGN(m, hdrlen); 788 else 789 m->m_data += max_linkhdr; 790 m->m_len = hdrlen; 791 } 792 m->m_pkthdr.rcvif = NULL; 793 if (isipv6) { 794 ip6 = mtod(m, struct ip6_hdr *); 795 th = (struct tcphdr *)(ip6 + 1); 796 tcp_fillheaders(tp, ip6, th); 797 } else { 798 ip = mtod(m, struct ip *); 799 ipov = (struct ipovly *)ip; 800 th = (struct tcphdr *)(ip + 1); 801 /* this picks up the pseudo header (w/o the length) */ 802 tcp_fillheaders(tp, ip, th); 803 } 804 after_th: 805 /* 806 * Fill in fields, remembering maximum advertised 807 * window for use in delaying messages about window sizes. 808 * If resending a FIN, be sure not to use a new sequence number. 809 */ 810 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 811 tp->snd_nxt == tp->snd_max) 812 tp->snd_nxt--; 813 814 if (th != NULL) { 815 /* 816 * If we are doing retransmissions, then snd_nxt will 817 * not reflect the first unsent octet. For ACK only 818 * packets, we do not want the sequence number of the 819 * retransmitted packet, we want the sequence number 820 * of the next unsent octet. So, if there is no data 821 * (and no SYN or FIN), use snd_max instead of snd_nxt 822 * when filling in ti_seq. But if we are in persist 823 * state, snd_max might reflect one byte beyond the 824 * right edge of the window, so use snd_nxt in that 825 * case, since we know we aren't doing a retransmission. 826 * (retransmit and persist are mutually exclusive...) 827 */ 828 if (len || (flags & (TH_SYN|TH_FIN)) || 829 tcp_callout_active(tp, tp->tt_persist)) 830 th->th_seq = htonl(tp->snd_nxt); 831 else 832 th->th_seq = htonl(tp->snd_max); 833 th->th_ack = htonl(tp->rcv_nxt); 834 if (optlen) { 835 bcopy(opt, th + 1, optlen); 836 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 837 } 838 th->th_flags = flags; 839 } 840 841 /* 842 * Calculate receive window. Don't shrink window, but avoid 843 * silly window syndrome by sending a 0 window if the actual 844 * window is less then one segment. 845 */ 846 if (recvwin < (long)(so->so_rcv.ssb_hiwat / 4) && 847 recvwin < (long)tp->t_maxseg) 848 recvwin = 0; 849 if (recvwin < (tcp_seq_diff_t)(tp->rcv_adv - tp->rcv_nxt)) 850 recvwin = (tcp_seq_diff_t)(tp->rcv_adv - tp->rcv_nxt); 851 if (recvwin > (long)TCP_MAXWIN << tp->rcv_scale) 852 recvwin = (long)TCP_MAXWIN << tp->rcv_scale; 853 854 /* 855 * Adjust the RXWIN0SENT flag - indicate that we have advertised 856 * a 0 window. This may cause the remote transmitter to stall. This 857 * flag tells soreceive() to disable delayed acknowledgements when 858 * draining the buffer. This can occur if the receiver is attempting 859 * to read more data then can be buffered prior to transmitting on 860 * the connection. 861 */ 862 if (recvwin == 0) 863 tp->t_flags |= TF_RXWIN0SENT; 864 else 865 tp->t_flags &= ~TF_RXWIN0SENT; 866 867 if (th != NULL) 868 th->th_win = htons((u_short) (recvwin>>tp->rcv_scale)); 869 870 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 871 if (th != NULL) { 872 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 873 th->th_flags |= TH_URG; 874 } 875 } else { 876 /* 877 * If no urgent pointer to send, then we pull 878 * the urgent pointer to the left edge of the send window 879 * so that it doesn't drift into the send window on sequence 880 * number wraparound. 881 */ 882 tp->snd_up = tp->snd_una; /* drag it along */ 883 } 884 885 if (th != NULL) { 886 #ifdef TCP_SIGNATURE 887 if (tp->t_flags & TF_SIGNATURE) { 888 tcpsignature_compute(m, len, optlen, 889 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 890 } 891 #endif /* TCP_SIGNATURE */ 892 893 /* 894 * Put TCP length in extended header, and then 895 * checksum extended header and data. 896 */ 897 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 898 if (isipv6) { 899 /* 900 * ip6_plen is not need to be filled now, and will be 901 * filled in ip6_output(). 902 */ 903 th->th_sum = in6_cksum(m, IPPROTO_TCP, 904 sizeof(struct ip6_hdr), 905 sizeof(struct tcphdr) + optlen + len); 906 } else { 907 m->m_pkthdr.csum_flags = CSUM_TCP; 908 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 909 if (len + optlen) { 910 th->th_sum = in_addword(th->th_sum, 911 htons((u_short)(optlen + len))); 912 } 913 914 /* 915 * IP version must be set here for ipv4/ipv6 checking 916 * later 917 */ 918 KASSERT(ip->ip_v == IPVERSION, 919 ("%s: IP version incorrect: %d", 920 __func__, ip->ip_v)); 921 } 922 } 923 924 /* 925 * In transmit state, time the transmission and arrange for 926 * the retransmit. In persist state, just set snd_max. 927 */ 928 if (!(tp->t_flags & TF_FORCE) || 929 !tcp_callout_active(tp, tp->tt_persist)) { 930 tcp_seq startseq = tp->snd_nxt; 931 932 /* 933 * Advance snd_nxt over sequence space of this segment. 934 */ 935 if (flags & (TH_SYN | TH_FIN)) { 936 if (flags & TH_SYN) 937 tp->snd_nxt++; 938 if (flags & TH_FIN) { 939 tp->snd_nxt++; 940 tp->t_flags |= TF_SENTFIN; 941 } 942 } 943 tp->snd_nxt += len; 944 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 945 tp->snd_max = tp->snd_nxt; 946 /* 947 * Time this transmission if not a retransmission and 948 * not currently timing anything. 949 */ 950 if (tp->t_rtttime == 0) { 951 tp->t_rtttime = ticks; 952 tp->t_rtseq = startseq; 953 tcpstat.tcps_segstimed++; 954 } 955 } 956 957 /* 958 * Set retransmit timer if not currently set, 959 * and not doing a pure ack or a keep-alive probe. 960 * Initial value for retransmit timer is smoothed 961 * round-trip time + 2 * round-trip time variance. 962 * Initialize shift counter which is used for backoff 963 * of retransmit time. 964 */ 965 if (!tcp_callout_active(tp, tp->tt_rexmt) && 966 tp->snd_nxt != tp->snd_una) { 967 if (tcp_callout_active(tp, tp->tt_persist)) { 968 tcp_callout_stop(tp, tp->tt_persist); 969 tp->t_rxtshift = 0; 970 } 971 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur, 972 tcp_timer_rexmt); 973 } 974 } else { 975 /* 976 * Persist case, update snd_max but since we are in 977 * persist mode (no window) we do not update snd_nxt. 978 */ 979 int xlen = len; 980 if (flags & TH_SYN) 981 panic("tcp_output: persist timer to send SYN\n"); 982 if (flags & TH_FIN) { 983 ++xlen; 984 tp->t_flags |= TF_SENTFIN; 985 } 986 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 987 tp->snd_max = tp->snd_nxt + xlen; 988 } 989 990 if (th != NULL) { 991 #ifdef TCPDEBUG 992 /* Trace. */ 993 if (so->so_options & SO_DEBUG) { 994 tcp_trace(TA_OUTPUT, tp->t_state, tp, 995 mtod(m, void *), th, 0); 996 } 997 #endif 998 999 /* 1000 * Fill in IP length and desired time to live and 1001 * send to IP level. There should be a better way 1002 * to handle ttl and tos; we could keep them in 1003 * the template, but need a way to checksum without them. 1004 */ 1005 /* 1006 * m->m_pkthdr.len should have been set before cksum 1007 * calcuration, because in6_cksum() need it. 1008 */ 1009 if (isipv6) { 1010 /* 1011 * we separately set hoplimit for every segment, 1012 * since the user might want to change the value 1013 * via setsockopt. Also, desired default hop 1014 * limit might be changed via Neighbor Discovery. 1015 */ 1016 ip6->ip6_hlim = in6_selecthlim(inp, 1017 (inp->in6p_route.ro_rt ? 1018 inp->in6p_route.ro_rt->rt_ifp : NULL)); 1019 1020 /* TODO: IPv6 IP6TOS_ECT bit on */ 1021 error = ip6_output(m, inp->in6p_outputopts, 1022 &inp->in6p_route, (so->so_options & SO_DONTROUTE), 1023 NULL, NULL, inp); 1024 } else { 1025 struct rtentry *rt; 1026 ip->ip_len = m->m_pkthdr.len; 1027 #ifdef INET6 1028 if (INP_CHECK_SOCKAF(so, AF_INET6)) 1029 ip->ip_ttl = in6_selecthlim(inp, 1030 (inp->in6p_route.ro_rt ? 1031 inp->in6p_route.ro_rt->rt_ifp : NULL)); 1032 else 1033 #endif 1034 ip->ip_ttl = inp->inp_ip_ttl; /* XXX */ 1035 1036 ip->ip_tos = inp->inp_ip_tos; /* XXX */ 1037 /* 1038 * See if we should do MTU discovery. 1039 * We do it only if the following are true: 1040 * 1) we have a valid route to the destination 1041 * 2) the MTU is not locked (if it is, 1042 * then discovery has been disabled) 1043 */ 1044 if (path_mtu_discovery && 1045 (rt = inp->inp_route.ro_rt) && 1046 (rt->rt_flags & RTF_UP) && 1047 !(rt->rt_rmx.rmx_locks & RTV_MTU)) 1048 ip->ip_off |= IP_DF; 1049 1050 error = ip_output(m, inp->inp_options, &inp->inp_route, 1051 (so->so_options & SO_DONTROUTE) | 1052 IP_DEBUGROUTE, NULL, inp); 1053 } 1054 } else { 1055 KASSERT(error != 0, ("no error, but th not set\n")); 1056 } 1057 if (error) { 1058 1059 /* 1060 * We know that the packet was lost, so back out the 1061 * sequence number advance, if any. 1062 */ 1063 if (!(tp->t_flags & TF_FORCE) || 1064 !tcp_callout_active(tp, tp->tt_persist)) { 1065 /* 1066 * No need to check for TH_FIN here because 1067 * the TF_SENTFIN flag handles that case. 1068 */ 1069 if (!(flags & TH_SYN)) 1070 tp->snd_nxt -= len; 1071 } 1072 1073 out: 1074 if (error == ENOBUFS) { 1075 /* 1076 * If we can't send, make sure there is something 1077 * to get us going again later. 1078 * 1079 * The persist timer isn't necessarily allowed in all 1080 * states, use the rexmt timer. 1081 */ 1082 if (!tcp_callout_active(tp, tp->tt_rexmt) && 1083 !tcp_callout_active(tp, tp->tt_persist)) { 1084 tcp_callout_reset(tp, tp->tt_rexmt, 1085 tp->t_rxtcur, 1086 tcp_timer_rexmt); 1087 #if 0 1088 tp->t_rxtshift = 0; 1089 tcp_setpersist(tp); 1090 #endif 1091 } 1092 tcp_quench(inp, 0); 1093 return (0); 1094 } 1095 if (error == EMSGSIZE) { 1096 /* 1097 * ip_output() will have already fixed the route 1098 * for us. tcp_mtudisc() will, as its last action, 1099 * initiate retransmission, so it is important to 1100 * not do so here. 1101 */ 1102 tcp_mtudisc(inp, 0); 1103 return 0; 1104 } 1105 if ((error == EHOSTUNREACH || error == ENETDOWN) && 1106 TCPS_HAVERCVDSYN(tp->t_state)) { 1107 tp->t_softerror = error; 1108 return (0); 1109 } 1110 return (error); 1111 } 1112 tcpstat.tcps_sndtotal++; 1113 1114 /* 1115 * Data sent (as far as we can tell). 1116 * 1117 * If this advertises a larger window than any other segment, 1118 * then remember the size of the advertised window. 1119 * 1120 * Any pending ACK has now been sent. 1121 */ 1122 if (recvwin > 0 && SEQ_GT(tp->rcv_nxt + recvwin, tp->rcv_adv)) { 1123 tp->rcv_adv = tp->rcv_nxt + recvwin; 1124 tp->t_flags &= ~TF_RXRESIZED; 1125 } 1126 tp->last_ack_sent = tp->rcv_nxt; 1127 tp->t_flags &= ~TF_ACKNOW; 1128 if (tcp_delack_enabled) 1129 tcp_callout_stop(tp, tp->tt_delack); 1130 if (sendalot) 1131 goto again; 1132 return (0); 1133 } 1134 1135 void 1136 tcp_setpersist(struct tcpcb *tp) 1137 { 1138 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1139 int tt; 1140 1141 if (tp->t_state == TCPS_SYN_SENT || 1142 tp->t_state == TCPS_SYN_RECEIVED) { 1143 panic("tcp_setpersist: not established yet, current %s\n", 1144 tp->t_state == TCPS_SYN_SENT ? 1145 "SYN_SENT" : "SYN_RECEIVED"); 1146 } 1147 1148 if (tcp_callout_active(tp, tp->tt_rexmt)) 1149 panic("tcp_setpersist: retransmit pending"); 1150 /* 1151 * Start/restart persistance timer. 1152 */ 1153 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], TCPTV_PERSMIN, 1154 TCPTV_PERSMAX); 1155 tcp_callout_reset(tp, tp->tt_persist, tt, tcp_timer_persist); 1156 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1157 tp->t_rxtshift++; 1158 } 1159