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) 2004 Jeffrey M. Hsu. All rights reserved. 36 * 37 * License terms: all terms for the DragonFly license above plus the following: 38 * 39 * 4. All advertising materials mentioning features or use of this software 40 * must display the following acknowledgement: 41 * 42 * This product includes software developed by Jeffrey M. Hsu 43 * for the DragonFly Project. 44 * 45 * This requirement may be waived with permission from Jeffrey Hsu. 46 * This requirement will sunset and may be removed on July 8 2005, 47 * after which the standard DragonFly license (as shown above) will 48 * apply. 49 */ 50 51 /* 52 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 53 * The Regents of the University of California. All rights reserved. 54 * 55 * Redistribution and use in source and binary forms, with or without 56 * modification, are permitted provided that the following conditions 57 * are met: 58 * 1. Redistributions of source code must retain the above copyright 59 * notice, this list of conditions and the following disclaimer. 60 * 2. Redistributions in binary form must reproduce the above copyright 61 * notice, this list of conditions and the following disclaimer in the 62 * documentation and/or other materials provided with the distribution. 63 * 3. All advertising materials mentioning features or use of this software 64 * must display the following acknowledgement: 65 * This product includes software developed by the University of 66 * California, Berkeley and its contributors. 67 * 4. Neither the name of the University nor the names of its contributors 68 * may be used to endorse or promote products derived from this software 69 * without specific prior written permission. 70 * 71 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 72 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 73 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 74 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 75 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 76 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 77 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 78 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 79 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 80 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 81 * SUCH DAMAGE. 82 * 83 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95 84 * $FreeBSD: src/sys/netinet/tcp_output.c,v 1.39.2.20 2003/01/29 22:45:36 hsu Exp $ 85 * $DragonFly: src/sys/netinet/tcp_output.c,v 1.29 2005/05/29 10:08:36 hsu Exp $ 86 */ 87 88 #include "opt_inet6.h" 89 #include "opt_ipsec.h" 90 #include "opt_tcpdebug.h" 91 92 #include <sys/param.h> 93 #include <sys/systm.h> 94 #include <sys/kernel.h> 95 #include <sys/sysctl.h> 96 #include <sys/mbuf.h> 97 #include <sys/domain.h> 98 #include <sys/protosw.h> 99 #include <sys/socket.h> 100 #include <sys/socketvar.h> 101 #include <sys/in_cksum.h> 102 #include <sys/thread.h> 103 #include <sys/globaldata.h> 104 105 #include <net/route.h> 106 107 #include <netinet/in.h> 108 #include <netinet/in_systm.h> 109 #include <netinet/ip.h> 110 #include <netinet/in_pcb.h> 111 #include <netinet/ip_var.h> 112 #include <netinet6/in6_pcb.h> 113 #include <netinet/ip6.h> 114 #include <netinet6/ip6_var.h> 115 #include <netinet/tcp.h> 116 #define TCPOUTFLAGS 117 #include <netinet/tcp_fsm.h> 118 #include <netinet/tcp_seq.h> 119 #include <netinet/tcp_timer.h> 120 #include <netinet/tcp_var.h> 121 #include <netinet/tcpip.h> 122 #ifdef TCPDEBUG 123 #include <netinet/tcp_debug.h> 124 #endif 125 126 #ifdef IPSEC 127 #include <netinet6/ipsec.h> 128 #endif /*IPSEC*/ 129 130 #ifdef FAST_IPSEC 131 #include <netproto/ipsec/ipsec.h> 132 #define IPSEC 133 #endif /*FAST_IPSEC*/ 134 135 #ifdef notyet 136 extern struct mbuf *m_copypack(); 137 #endif 138 139 int path_mtu_discovery = 0; 140 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 141 &path_mtu_discovery, 1, "Enable Path MTU Discovery"); 142 143 static int avoid_pure_win_update = 1; 144 SYSCTL_INT(_net_inet_tcp, OID_AUTO, avoid_pure_win_update, CTLFLAG_RW, 145 &avoid_pure_win_update, 1, "Avoid pure window updates when possible"); 146 147 /* 148 * Tcp output routine: figure out what should be sent and send it. 149 */ 150 int 151 tcp_output(tp) 152 struct tcpcb *tp; 153 { 154 struct inpcb * const inp = tp->t_inpcb; 155 struct socket *so = inp->inp_socket; 156 long len, recvwin, sendwin; 157 int nsacked = 0; 158 int off, flags, error; 159 struct mbuf *m; 160 struct ip *ip = NULL; 161 struct ipovly *ipov = NULL; 162 struct tcphdr *th; 163 u_char opt[TCP_MAXOLEN]; 164 unsigned int ipoptlen, optlen, hdrlen; 165 int idle; 166 boolean_t sendalot; 167 struct ip6_hdr *ip6 = NULL; 168 #ifdef INET6 169 const boolean_t isipv6 = (inp->inp_vflag & INP_IPV6) != 0; 170 #else 171 const boolean_t isipv6 = FALSE; 172 #endif 173 struct rmxp_tao *taop; 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) { 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 /* Make use of SACK information when slow-starting after a RTO. */ 217 if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max && 218 !IN_FASTRECOVERY(tp)) { 219 tcp_seq old_snd_nxt = tp->snd_nxt; 220 221 tcp_sack_skip_sacked(&tp->scb, &tp->snd_nxt); 222 nsacked += tp->snd_nxt - old_snd_nxt; 223 } 224 225 sendalot = FALSE; 226 off = tp->snd_nxt - tp->snd_una; 227 sendwin = min(tp->snd_wnd, tp->snd_cwnd + nsacked); 228 sendwin = min(sendwin, tp->snd_bwnd); 229 230 flags = tcp_outflags[tp->t_state]; 231 /* 232 * Get standard flags, and add SYN or FIN if requested by 'hidden' 233 * state flags. 234 */ 235 if (tp->t_flags & TF_NEEDFIN) 236 flags |= TH_FIN; 237 if (tp->t_flags & TF_NEEDSYN) 238 flags |= TH_SYN; 239 240 /* 241 * If in persist timeout with window of 0, send 1 byte. 242 * Otherwise, if window is small but nonzero 243 * and timer expired, we will send what we can 244 * and go to transmit state. 245 */ 246 if (tp->t_flags & TF_FORCE) { 247 if (sendwin == 0) { 248 /* 249 * If we still have some data to send, then 250 * clear the FIN bit. Usually this would 251 * happen below when it realizes that we 252 * aren't sending all the data. However, 253 * if we have exactly 1 byte of unsent data, 254 * then it won't clear the FIN bit below, 255 * and if we are in persist state, we wind 256 * up sending the packet without recording 257 * that we sent the FIN bit. 258 * 259 * We can't just blindly clear the FIN bit, 260 * because if we don't have any more data 261 * to send then the probe will be the FIN 262 * itself. 263 */ 264 if (off < so->so_snd.sb_cc) 265 flags &= ~TH_FIN; 266 sendwin = 1; 267 } else { 268 callout_stop(tp->tt_persist); 269 tp->t_rxtshift = 0; 270 } 271 } 272 273 /* 274 * If snd_nxt == snd_max and we have transmitted a FIN, the 275 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 276 * a negative length. This can also occur when TCP opens up 277 * its congestion window while receiving additional duplicate 278 * acks after fast-retransmit because TCP will reset snd_nxt 279 * to snd_max after the fast-retransmit. 280 * 281 * In the normal retransmit-FIN-only case, however, snd_nxt will 282 * be set to snd_una, the offset will be 0, and the length may 283 * wind up 0. 284 */ 285 len = (long)ulmin(so->so_snd.sb_cc, sendwin) - off; 286 287 /* 288 * Lop off SYN bit if it has already been sent. However, if this 289 * is SYN-SENT state and if segment contains data and if we don't 290 * know that foreign host supports TAO, suppress sending segment. 291 */ 292 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 293 flags &= ~TH_SYN; 294 off--, len++; 295 if (len > 0 && tp->t_state == TCPS_SYN_SENT && 296 ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL || 297 taop->tao_ccsent == 0)) 298 return 0; 299 } 300 301 /* 302 * Be careful not to send data and/or FIN on SYN segments 303 * in cases when no CC option will be sent. 304 * This measure is needed to prevent interoperability problems 305 * with not fully conformant TCP implementations. 306 */ 307 if ((flags & TH_SYN) && 308 ((tp->t_flags & TF_NOOPT) || !(tp->t_flags & TF_REQ_CC) || 309 ((flags & TH_ACK) && !(tp->t_flags & TF_RCVD_CC)))) { 310 len = 0; 311 flags &= ~TH_FIN; 312 } 313 314 if (len < 0) { 315 /* 316 * If FIN has been sent but not acked, 317 * but we haven't been called to retransmit, 318 * len will be < 0. Otherwise, window shrank 319 * after we sent into it. If window shrank to 0, 320 * cancel pending retransmit, pull snd_nxt back 321 * to (closed) window, and set the persist timer 322 * if it isn't already going. If the window didn't 323 * close completely, just wait for an ACK. 324 */ 325 len = 0; 326 if (sendwin == 0) { 327 callout_stop(tp->tt_rexmt); 328 tp->t_rxtshift = 0; 329 tp->snd_nxt = tp->snd_una; 330 if (!callout_active(tp->tt_persist)) 331 tcp_setpersist(tp); 332 } 333 } 334 335 /* 336 * len will be >= 0 after this point. Truncate to the maximum 337 * segment length and ensure that FIN is removed if the length 338 * no longer contains the last data byte. 339 */ 340 if (len > tp->t_maxseg) { 341 len = tp->t_maxseg; 342 sendalot = TRUE; 343 } 344 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 345 flags &= ~TH_FIN; 346 347 recvwin = sbspace(&so->so_rcv); 348 349 /* 350 * Sender silly window avoidance. We transmit under the following 351 * conditions when len is non-zero: 352 * 353 * - We have a full segment 354 * - This is the last buffer in a write()/send() and we are 355 * either idle or running NODELAY 356 * - we've timed out (e.g. persist timer) 357 * - we have more then 1/2 the maximum send window's worth of 358 * data (receiver may be limiting the window size) 359 * - we need to retransmit 360 */ 361 if (len) { 362 if (len == tp->t_maxseg) 363 goto send; 364 /* 365 * NOTE! on localhost connections an 'ack' from the remote 366 * end may occur synchronously with the output and cause 367 * us to flush a buffer queued with moretocome. XXX 368 * 369 * note: the len + off check is almost certainly unnecessary. 370 */ 371 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 372 (idle || (tp->t_flags & TF_NODELAY)) && 373 len + off >= so->so_snd.sb_cc && 374 !(tp->t_flags & TF_NOPUSH)) { 375 goto send; 376 } 377 if (tp->t_flags & TF_FORCE) /* typ. timeout case */ 378 goto send; 379 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 380 goto send; 381 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 382 goto send; 383 } 384 385 /* 386 * Compare available window to amount of window 387 * known to peer (as advertised window less 388 * next expected input). If the difference is at least two 389 * max size segments, or at least 50% of the maximum possible 390 * window, then want to send a window update to peer. 391 */ 392 if (recvwin > 0) { 393 /* 394 * "adv" is the amount we can increase the window, 395 * taking into account that we are limited by 396 * TCP_MAXWIN << tp->rcv_scale. 397 */ 398 long adv = min(recvwin, (long)TCP_MAXWIN << tp->rcv_scale) - 399 (tp->rcv_adv - tp->rcv_nxt); 400 401 /* 402 * This ack case typically occurs when the user has drained 403 * the TCP socket buffer sufficiently to warrent an ack 404 * containing a 'pure window update'... that is, an ack that 405 * ONLY updates the tcp window. 406 * 407 * It is unclear why we would need to do a pure window update 408 * past 2 segments if we are going to do one at 1/2 the high 409 * water mark anyway, especially since under normal conditions 410 * the user program will drain the socket buffer quickly. 411 * The 2-segment pure window update will often add a large 412 * number of extra, unnecessary acks to the stream. 413 * 414 * avoid_pure_win_update now defaults to 1. 415 */ 416 if (avoid_pure_win_update == 0) { 417 if (adv >= (long) (2 * tp->t_maxseg)) 418 goto send; 419 } 420 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 421 goto send; 422 } 423 424 /* 425 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 426 * is also a catch-all for the retransmit timer timeout case. 427 */ 428 if (tp->t_flags & TF_ACKNOW) 429 goto send; 430 if ((flags & TH_RST) || 431 ((flags & TH_SYN) && !(tp->t_flags & TF_NEEDSYN))) 432 goto send; 433 if (SEQ_GT(tp->snd_up, tp->snd_una)) 434 goto send; 435 /* 436 * If our state indicates that FIN should be sent 437 * and we have not yet done so, then we need to send. 438 */ 439 if (flags & TH_FIN && 440 (!(tp->t_flags & TF_SENTFIN) || tp->snd_nxt == tp->snd_una)) 441 goto send; 442 443 /* 444 * TCP window updates are not reliable, rather a polling protocol 445 * using ``persist'' packets is used to insure receipt of window 446 * updates. The three ``states'' for the output side are: 447 * idle not doing retransmits or persists 448 * persisting to move a small or zero window 449 * (re)transmitting and thereby not persisting 450 * 451 * callout_active(tp->tt_persist) 452 * is true when we are in persist state. 453 * The TF_FORCE flag in tp->t_flags 454 * is set when we are called to send a persist packet. 455 * callout_active(tp->tt_rexmt) 456 * is set when we are retransmitting 457 * The output side is idle when both timers are zero. 458 * 459 * If send window is too small, there is data to transmit, and no 460 * retransmit or persist is pending, then go to persist state. 461 * If nothing happens soon, send when timer expires: 462 * if window is nonzero, transmit what we can, 463 * otherwise force out a byte. 464 */ 465 if (so->so_snd.sb_cc > 0 && 466 !callout_active(tp->tt_rexmt) && !callout_active(tp->tt_persist)) { 467 tp->t_rxtshift = 0; 468 tcp_setpersist(tp); 469 } 470 471 /* 472 * No reason to send a segment, just return. 473 */ 474 return (0); 475 476 send: 477 /* 478 * Before ESTABLISHED, force sending of initial options 479 * unless TCP set not to do any options. 480 * NOTE: we assume that the IP/TCP header plus TCP options 481 * always fit in a single mbuf, leaving room for a maximum 482 * link header, i.e. 483 * max_linkhdr + sizeof(struct tcpiphdr) + optlen <= MCLBYTES 484 */ 485 optlen = 0; 486 if (isipv6) 487 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 488 else 489 hdrlen = sizeof(struct tcpiphdr); 490 if (flags & TH_SYN) { 491 tp->snd_nxt = tp->iss; 492 if (!(tp->t_flags & TF_NOOPT)) { 493 u_short mss; 494 495 opt[0] = TCPOPT_MAXSEG; 496 opt[1] = TCPOLEN_MAXSEG; 497 mss = htons((u_short) tcp_mssopt(tp)); 498 memcpy(opt + 2, &mss, sizeof mss); 499 optlen = TCPOLEN_MAXSEG; 500 501 if ((tp->t_flags & TF_REQ_SCALE) && 502 (!(flags & TH_ACK) || 503 (tp->t_flags & TF_RCVD_SCALE))) { 504 *((u_int32_t *)(opt + optlen)) = htonl( 505 TCPOPT_NOP << 24 | 506 TCPOPT_WINDOW << 16 | 507 TCPOLEN_WINDOW << 8 | 508 tp->request_r_scale); 509 optlen += 4; 510 } 511 512 if ((tcp_do_sack && !(flags & TH_ACK)) || 513 tp->t_flags & TF_SACK_PERMITTED) { 514 uint32_t *lp = (uint32_t *)(opt + optlen); 515 516 *lp = htonl(TCPOPT_SACK_PERMITTED_ALIGNED); 517 optlen += TCPOLEN_SACK_PERMITTED_ALIGNED; 518 } 519 } 520 } 521 522 /* 523 * Send a timestamp and echo-reply if this is a SYN and our side 524 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 525 * and our peer have sent timestamps in our SYN's. 526 */ 527 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 528 !(flags & TH_RST) && 529 (!(flags & TH_ACK) || (tp->t_flags & TF_RCVD_TSTMP))) { 530 u_int32_t *lp = (u_int32_t *)(opt + optlen); 531 532 /* Form timestamp option as shown in appendix A of RFC 1323. */ 533 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 534 *lp++ = htonl(ticks); 535 *lp = htonl(tp->ts_recent); 536 optlen += TCPOLEN_TSTAMP_APPA; 537 } 538 539 /* 540 * Send `CC-family' options if our side wants to use them (TF_REQ_CC), 541 * options are allowed (!TF_NOOPT) and it's not a RST. 542 */ 543 if ((tp->t_flags & (TF_REQ_CC | TF_NOOPT)) == TF_REQ_CC && 544 !(flags & TH_RST)) { 545 switch (flags & (TH_SYN | TH_ACK)) { 546 /* 547 * This is a normal ACK, send CC if we received CC before 548 * from our peer. 549 */ 550 case TH_ACK: 551 if (!(tp->t_flags & TF_RCVD_CC)) 552 break; 553 /*FALLTHROUGH*/ 554 555 /* 556 * We can only get here in T/TCP's SYN_SENT* state, when 557 * we're a sending a non-SYN segment without waiting for 558 * the ACK of our SYN. A check above assures that we only 559 * do this if our peer understands T/TCP. 560 */ 561 case 0: 562 opt[optlen++] = TCPOPT_NOP; 563 opt[optlen++] = TCPOPT_NOP; 564 opt[optlen++] = TCPOPT_CC; 565 opt[optlen++] = TCPOLEN_CC; 566 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 567 optlen += 4; 568 break; 569 570 /* 571 * This is our initial SYN, check whether we have to use 572 * CC or CC.new. 573 */ 574 case TH_SYN: 575 opt[optlen++] = TCPOPT_NOP; 576 opt[optlen++] = TCPOPT_NOP; 577 opt[optlen++] = tp->t_flags & TF_SENDCCNEW ? 578 TCPOPT_CCNEW : TCPOPT_CC; 579 opt[optlen++] = TCPOLEN_CC; 580 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 581 optlen += 4; 582 break; 583 584 /* 585 * This is a SYN,ACK; send CC and CC.echo if we received 586 * CC from our peer. 587 */ 588 case (TH_SYN | TH_ACK): 589 if (tp->t_flags & TF_RCVD_CC) { 590 opt[optlen++] = TCPOPT_NOP; 591 opt[optlen++] = TCPOPT_NOP; 592 opt[optlen++] = TCPOPT_CC; 593 opt[optlen++] = TCPOLEN_CC; 594 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 595 optlen += 4; 596 opt[optlen++] = TCPOPT_NOP; 597 opt[optlen++] = TCPOPT_NOP; 598 opt[optlen++] = TCPOPT_CCECHO; 599 opt[optlen++] = TCPOLEN_CC; 600 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_recv); 601 optlen += 4; 602 } 603 break; 604 } 605 } 606 607 /* 608 * If this is a SACK connection and we have a block to report, 609 * fill in the SACK blocks in the TCP options. 610 */ 611 if ((tp->t_flags & (TF_SACK_PERMITTED | TF_NOOPT)) == 612 TF_SACK_PERMITTED && 613 (!LIST_EMPTY(&tp->t_segq) || 614 tp->reportblk.rblk_start != tp->reportblk.rblk_end)) 615 tcp_sack_fill_report(tp, opt, &optlen); 616 617 KASSERT(optlen <= TCP_MAXOLEN, ("too many TCP options")); 618 hdrlen += optlen; 619 620 if (isipv6) { 621 ipoptlen = ip6_optlen(inp); 622 } else { 623 if (inp->inp_options) { 624 ipoptlen = inp->inp_options->m_len - 625 offsetof(struct ipoption, ipopt_list); 626 } else { 627 ipoptlen = 0; 628 } 629 } 630 #ifdef IPSEC 631 ipoptlen += ipsec_hdrsiz_tcp(tp); 632 #endif 633 634 /* 635 * Adjust data length if insertion of options will 636 * bump the packet length beyond the t_maxopd length. 637 * Clear the FIN bit because we cut off the tail of 638 * the segment. 639 */ 640 if (len + optlen + ipoptlen > tp->t_maxopd) { 641 /* 642 * If there is still more to send, don't close the connection. 643 */ 644 flags &= ~TH_FIN; 645 len = tp->t_maxopd - optlen - ipoptlen; 646 sendalot = TRUE; 647 } 648 649 #ifdef INET6 650 KASSERT(max_linkhdr + hdrlen <= MCLBYTES, ("tcphdr too big")); 651 #else 652 KASSERT(max_linkhdr + hdrlen <= MHLEN, ("tcphdr too big")); 653 #endif 654 655 /* 656 * Grab a header mbuf, attaching a copy of data to 657 * be transmitted, and initialize the header from 658 * the template for sends on this connection. 659 */ 660 if (len) { 661 if ((tp->t_flags & TF_FORCE) && len == 1) 662 tcpstat.tcps_sndprobe++; 663 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 664 if (tp->snd_nxt == tp->snd_una) 665 tp->snd_max_rexmt = tp->snd_max; 666 tcpstat.tcps_sndrexmitpack++; 667 tcpstat.tcps_sndrexmitbyte += len; 668 } else { 669 tcpstat.tcps_sndpack++; 670 tcpstat.tcps_sndbyte += len; 671 } 672 #ifdef notyet 673 if ((m = m_copypack(so->so_snd.sb_mb, off, (int)len, 674 max_linkhdr + hdrlen)) == NULL) { 675 error = ENOBUFS; 676 goto out; 677 } 678 /* 679 * m_copypack left space for our hdr; use it. 680 */ 681 m->m_len += hdrlen; 682 m->m_data -= hdrlen; 683 #else 684 #ifndef INET6 685 m = m_gethdr(MB_DONTWAIT, MT_HEADER); 686 #else 687 m = m_getl(hdrlen + max_linkhdr, MB_DONTWAIT, MT_HEADER, 688 M_PKTHDR, NULL); 689 #endif 690 if (m == NULL) { 691 error = ENOBUFS; 692 goto out; 693 } 694 m->m_data += max_linkhdr; 695 m->m_len = hdrlen; 696 if (len <= MHLEN - hdrlen - max_linkhdr) { 697 m_copydata(so->so_snd.sb_mb, off, (int) len, 698 mtod(m, caddr_t) + hdrlen); 699 m->m_len += len; 700 } else { 701 m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len); 702 if (m->m_next == NULL) { 703 m_free(m); 704 error = ENOBUFS; 705 goto out; 706 } 707 } 708 #endif 709 /* 710 * If we're sending everything we've got, set PUSH. 711 * (This will keep happy those implementations which only 712 * give data to the user when a buffer fills or 713 * a PUSH comes in.) 714 */ 715 if (off + len == so->so_snd.sb_cc) 716 flags |= TH_PUSH; 717 } else { 718 if (tp->t_flags & TF_ACKNOW) 719 tcpstat.tcps_sndacks++; 720 else if (flags & (TH_SYN | TH_FIN | TH_RST)) 721 tcpstat.tcps_sndctrl++; 722 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 723 tcpstat.tcps_sndurg++; 724 else 725 tcpstat.tcps_sndwinup++; 726 727 MGETHDR(m, MB_DONTWAIT, MT_HEADER); 728 if (m == NULL) { 729 error = ENOBUFS; 730 goto out; 731 } 732 if (isipv6 && 733 (hdrlen + max_linkhdr > MHLEN) && hdrlen <= MHLEN) 734 MH_ALIGN(m, hdrlen); 735 else 736 m->m_data += max_linkhdr; 737 m->m_len = hdrlen; 738 } 739 m->m_pkthdr.rcvif = (struct ifnet *)0; 740 if (isipv6) { 741 ip6 = mtod(m, struct ip6_hdr *); 742 th = (struct tcphdr *)(ip6 + 1); 743 tcp_fillheaders(tp, ip6, th); 744 } else { 745 ip = mtod(m, struct ip *); 746 ipov = (struct ipovly *)ip; 747 th = (struct tcphdr *)(ip + 1); 748 /* this picks up the pseudo header (w/o the length) */ 749 tcp_fillheaders(tp, ip, th); 750 } 751 752 /* 753 * Fill in fields, remembering maximum advertised 754 * window for use in delaying messages about window sizes. 755 * If resending a FIN, be sure not to use a new sequence number. 756 */ 757 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 758 tp->snd_nxt == tp->snd_max) 759 tp->snd_nxt--; 760 /* 761 * If we are doing retransmissions, then snd_nxt will 762 * not reflect the first unsent octet. For ACK only 763 * packets, we do not want the sequence number of the 764 * retransmitted packet, we want the sequence number 765 * of the next unsent octet. So, if there is no data 766 * (and no SYN or FIN), use snd_max instead of snd_nxt 767 * when filling in ti_seq. But if we are in persist 768 * state, snd_max might reflect one byte beyond the 769 * right edge of the window, so use snd_nxt in that 770 * case, since we know we aren't doing a retransmission. 771 * (retransmit and persist are mutually exclusive...) 772 */ 773 if (len || (flags & (TH_SYN|TH_FIN)) || callout_active(tp->tt_persist)) 774 th->th_seq = htonl(tp->snd_nxt); 775 else 776 th->th_seq = htonl(tp->snd_max); 777 th->th_ack = htonl(tp->rcv_nxt); 778 if (optlen) { 779 bcopy(opt, th + 1, optlen); 780 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 781 } 782 th->th_flags = flags; 783 /* 784 * Calculate receive window. Don't shrink window, 785 * but avoid silly window syndrome. 786 */ 787 if (recvwin < (long)(so->so_rcv.sb_hiwat / 4) && 788 recvwin < (long)tp->t_maxseg) 789 recvwin = 0; 790 if (recvwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 791 recvwin = (long)(tp->rcv_adv - tp->rcv_nxt); 792 if (recvwin > (long)TCP_MAXWIN << tp->rcv_scale) 793 recvwin = (long)TCP_MAXWIN << tp->rcv_scale; 794 th->th_win = htons((u_short) (recvwin>>tp->rcv_scale)); 795 796 /* 797 * Adjust the RXWIN0SENT flag - indicate that we have advertised 798 * a 0 window. This may cause the remote transmitter to stall. This 799 * flag tells soreceive() to disable delayed acknowledgements when 800 * draining the buffer. This can occur if the receiver is attempting 801 * to read more data then can be buffered prior to transmitting on 802 * the connection. 803 */ 804 if (recvwin == 0) 805 tp->t_flags |= TF_RXWIN0SENT; 806 else 807 tp->t_flags &= ~TF_RXWIN0SENT; 808 809 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 810 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 811 th->th_flags |= TH_URG; 812 } else { 813 /* 814 * If no urgent pointer to send, then we pull 815 * the urgent pointer to the left edge of the send window 816 * so that it doesn't drift into the send window on sequence 817 * number wraparound. 818 */ 819 tp->snd_up = tp->snd_una; /* drag it along */ 820 } 821 822 /* 823 * Put TCP length in extended header, and then 824 * checksum extended header and data. 825 */ 826 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 827 if (isipv6) { 828 /* 829 * ip6_plen is not need to be filled now, and will be filled 830 * in ip6_output(). 831 */ 832 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 833 sizeof(struct tcphdr) + optlen + len); 834 } else { 835 m->m_pkthdr.csum_flags = CSUM_TCP; 836 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 837 if (len + optlen) 838 th->th_sum = in_addword(th->th_sum, 839 htons((u_short)(optlen + len))); 840 841 /* IP version must be set here for ipv4/ipv6 checking later */ 842 KASSERT(ip->ip_v == IPVERSION, 843 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 844 } 845 846 /* 847 * In transmit state, time the transmission and arrange for 848 * the retransmit. In persist state, just set snd_max. 849 */ 850 if (!(tp->t_flags & TF_FORCE) || !callout_active(tp->tt_persist)) { 851 tcp_seq startseq = tp->snd_nxt; 852 853 /* 854 * Advance snd_nxt over sequence space of this segment. 855 */ 856 if (flags & (TH_SYN | TH_FIN)) { 857 if (flags & TH_SYN) 858 tp->snd_nxt++; 859 if (flags & TH_FIN) { 860 tp->snd_nxt++; 861 tp->t_flags |= TF_SENTFIN; 862 } 863 } 864 tp->snd_nxt += len; 865 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 866 tp->snd_max = tp->snd_nxt; 867 /* 868 * Time this transmission if not a retransmission and 869 * not currently timing anything. 870 */ 871 if (tp->t_rtttime == 0) { 872 tp->t_rtttime = ticks; 873 tp->t_rtseq = startseq; 874 tcpstat.tcps_segstimed++; 875 } 876 } 877 878 /* 879 * Set retransmit timer if not currently set, 880 * and not doing a pure ack or a keep-alive probe. 881 * Initial value for retransmit timer is smoothed 882 * round-trip time + 2 * round-trip time variance. 883 * Initialize shift counter which is used for backoff 884 * of retransmit time. 885 */ 886 if (!callout_active(tp->tt_rexmt) && 887 tp->snd_nxt != tp->snd_una) { 888 if (callout_active(tp->tt_persist)) { 889 callout_stop(tp->tt_persist); 890 tp->t_rxtshift = 0; 891 } 892 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 893 tcp_timer_rexmt, tp); 894 } 895 } else { 896 /* 897 * Persist case, update snd_max but since we are in 898 * persist mode (no window) we do not update snd_nxt. 899 */ 900 int xlen = len; 901 if (flags & TH_SYN) 902 ++xlen; 903 if (flags & TH_FIN) { 904 ++xlen; 905 tp->t_flags |= TF_SENTFIN; 906 } 907 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 908 tp->snd_max = tp->snd_nxt + xlen; 909 } 910 911 #ifdef TCPDEBUG 912 /* 913 * Trace. 914 */ 915 if (so->so_options & SO_DEBUG) 916 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 917 #endif 918 919 /* 920 * Fill in IP length and desired time to live and 921 * send to IP level. There should be a better way 922 * to handle ttl and tos; we could keep them in 923 * the template, but need a way to checksum without them. 924 */ 925 /* 926 * m->m_pkthdr.len should have been set before cksum calcuration, 927 * because in6_cksum() need it. 928 */ 929 if (isipv6) { 930 /* 931 * we separately set hoplimit for every segment, since the 932 * user might want to change the value via setsockopt. 933 * Also, desired default hop limit might be changed via 934 * Neighbor Discovery. 935 */ 936 ip6->ip6_hlim = in6_selecthlim(inp, 937 (inp->in6p_route.ro_rt ? 938 inp->in6p_route.ro_rt->rt_ifp : NULL)); 939 940 /* TODO: IPv6 IP6TOS_ECT bit on */ 941 error = ip6_output(m, inp->in6p_outputopts, &inp->in6p_route, 942 (so->so_options & SO_DONTROUTE), NULL, NULL, 943 inp); 944 } else { 945 struct rtentry *rt; 946 ip->ip_len = m->m_pkthdr.len; 947 #ifdef INET6 948 if (INP_CHECK_SOCKAF(so, AF_INET6)) 949 ip->ip_ttl = in6_selecthlim(inp, 950 (inp->in6p_route.ro_rt ? 951 inp->in6p_route.ro_rt->rt_ifp : NULL)); 952 else 953 #endif 954 ip->ip_ttl = inp->inp_ip_ttl; /* XXX */ 955 956 ip->ip_tos = inp->inp_ip_tos; /* XXX */ 957 /* 958 * See if we should do MTU discovery. 959 * We do it only if the following are true: 960 * 1) we have a valid route to the destination 961 * 2) the MTU is not locked (if it is, 962 * then discovery has been disabled) 963 */ 964 if (path_mtu_discovery && 965 (rt = inp->inp_route.ro_rt) && (rt->rt_flags & RTF_UP) && 966 !(rt->rt_rmx.rmx_locks & RTV_MTU)) 967 ip->ip_off |= IP_DF; 968 969 error = ip_output(m, inp->inp_options, &inp->inp_route, 970 (so->so_options & SO_DONTROUTE), NULL, inp); 971 } 972 if (error) { 973 974 /* 975 * We know that the packet was lost, so back out the 976 * sequence number advance, if any. 977 */ 978 if (!(tp->t_flags & TF_FORCE) || 979 !callout_active(tp->tt_persist)) { 980 /* 981 * No need to check for TH_FIN here because 982 * the TF_SENTFIN flag handles that case. 983 */ 984 if (!(flags & TH_SYN)) 985 tp->snd_nxt -= len; 986 } 987 988 out: 989 if (error == ENOBUFS) { 990 /* 991 * If we can't send, make sure there is something 992 * to get us going again later. Persist state 993 * is not necessarily right, but it is close enough. 994 */ 995 if (!callout_active(tp->tt_rexmt) && 996 !callout_active(tp->tt_persist)) { 997 tp->t_rxtshift = 0; 998 tcp_setpersist(tp); 999 } 1000 tcp_quench(inp, 0); 1001 return (0); 1002 } 1003 if (error == EMSGSIZE) { 1004 /* 1005 * ip_output() will have already fixed the route 1006 * for us. tcp_mtudisc() will, as its last action, 1007 * initiate retransmission, so it is important to 1008 * not do so here. 1009 */ 1010 tcp_mtudisc(inp, 0); 1011 return 0; 1012 } 1013 if ((error == EHOSTUNREACH || error == ENETDOWN) && 1014 TCPS_HAVERCVDSYN(tp->t_state)) { 1015 tp->t_softerror = error; 1016 return (0); 1017 } 1018 return (error); 1019 } 1020 tcpstat.tcps_sndtotal++; 1021 1022 /* 1023 * Data sent (as far as we can tell). 1024 * If this advertises a larger window than any other segment, 1025 * then remember the size of the advertised window. 1026 * Any pending ACK has now been sent. 1027 */ 1028 if (recvwin > 0 && SEQ_GT(tp->rcv_nxt + recvwin, tp->rcv_adv)) 1029 tp->rcv_adv = tp->rcv_nxt + recvwin; 1030 tp->last_ack_sent = tp->rcv_nxt; 1031 tp->t_flags &= ~TF_ACKNOW; 1032 if (tcp_delack_enabled) 1033 callout_stop(tp->tt_delack); 1034 if (sendalot) 1035 goto again; 1036 return (0); 1037 } 1038 1039 void 1040 tcp_setpersist(tp) 1041 struct tcpcb *tp; 1042 { 1043 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1044 int tt; 1045 1046 if (callout_active(tp->tt_rexmt)) 1047 panic("tcp_setpersist: retransmit pending"); 1048 /* 1049 * Start/restart persistance timer. 1050 */ 1051 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], TCPTV_PERSMIN, 1052 TCPTV_PERSMAX); 1053 callout_reset(tp->tt_persist, tt, tcp_timer_persist, tp); 1054 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1055 tp->t_rxtshift++; 1056 } 1057