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