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 1.25 2005/03/09 06:54:34 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 if ((tp->snd_max == tp->snd_una) && 182 (ticks - tp->t_rcvtime) >= tp->t_rxtcur) { 183 /* 184 * We have been idle for "a while" and no acks are 185 * expected to clock out any data we send -- 186 * slow start to get ack "clock" running again. 187 */ 188 tp->snd_cwnd = tp->t_maxseg; 189 } 190 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 191 if (idle && (tp->t_flags & TF_MORETOCOME)) 192 tp->t_flags |= TF_LASTIDLE; 193 else 194 tp->t_flags &= ~TF_LASTIDLE; 195 196 if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max && 197 !IN_FASTRECOVERY(tp)) 198 nsacked = tcp_sack_bytes_below(&tp->scb, tp->snd_nxt); 199 200 again: 201 /* Make use of SACK information when slow-starting after a RTO. */ 202 if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max && 203 !IN_FASTRECOVERY(tp)) { 204 tcp_seq old_snd_nxt = tp->snd_nxt; 205 206 tcp_sack_skip_sacked(&tp->scb, &tp->snd_nxt); 207 nsacked += tp->snd_nxt - old_snd_nxt; 208 } 209 210 sendalot = FALSE; 211 off = tp->snd_nxt - tp->snd_una; 212 sendwin = min(tp->snd_wnd, tp->snd_cwnd + nsacked); 213 sendwin = min(sendwin, tp->snd_bwnd); 214 215 flags = tcp_outflags[tp->t_state]; 216 /* 217 * Get standard flags, and add SYN or FIN if requested by 'hidden' 218 * state flags. 219 */ 220 if (tp->t_flags & TF_NEEDFIN) 221 flags |= TH_FIN; 222 if (tp->t_flags & TF_NEEDSYN) 223 flags |= TH_SYN; 224 225 /* 226 * If in persist timeout with window of 0, send 1 byte. 227 * Otherwise, if window is small but nonzero 228 * and timer expired, we will send what we can 229 * and go to transmit state. 230 */ 231 if (tp->t_flags & TF_FORCE) { 232 if (sendwin == 0) { 233 /* 234 * If we still have some data to send, then 235 * clear the FIN bit. Usually this would 236 * happen below when it realizes that we 237 * aren't sending all the data. However, 238 * if we have exactly 1 byte of unsent data, 239 * then it won't clear the FIN bit below, 240 * and if we are in persist state, we wind 241 * up sending the packet without recording 242 * that we sent the FIN bit. 243 * 244 * We can't just blindly clear the FIN bit, 245 * because if we don't have any more data 246 * to send then the probe will be the FIN 247 * itself. 248 */ 249 if (off < so->so_snd.sb_cc) 250 flags &= ~TH_FIN; 251 sendwin = 1; 252 } else { 253 callout_stop(tp->tt_persist); 254 tp->t_rxtshift = 0; 255 } 256 } 257 258 /* 259 * If snd_nxt == snd_max and we have transmitted a FIN, the 260 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 261 * a negative length. This can also occur when TCP opens up 262 * its congestion window while receiving additional duplicate 263 * acks after fast-retransmit because TCP will reset snd_nxt 264 * to snd_max after the fast-retransmit. 265 * 266 * In the normal retransmit-FIN-only case, however, snd_nxt will 267 * be set to snd_una, the offset will be 0, and the length may 268 * wind up 0. 269 */ 270 len = (long)ulmin(so->so_snd.sb_cc, sendwin) - off; 271 272 /* 273 * Lop off SYN bit if it has already been sent. However, if this 274 * is SYN-SENT state and if segment contains data and if we don't 275 * know that foreign host supports TAO, suppress sending segment. 276 */ 277 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 278 flags &= ~TH_SYN; 279 off--, len++; 280 if (len > 0 && tp->t_state == TCPS_SYN_SENT && 281 ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL || 282 taop->tao_ccsent == 0)) 283 return 0; 284 } 285 286 /* 287 * Be careful not to send data and/or FIN on SYN segments 288 * in cases when no CC option will be sent. 289 * This measure is needed to prevent interoperability problems 290 * with not fully conformant TCP implementations. 291 */ 292 if ((flags & TH_SYN) && 293 ((tp->t_flags & TF_NOOPT) || !(tp->t_flags & TF_REQ_CC) || 294 ((flags & TH_ACK) && !(tp->t_flags & TF_RCVD_CC)))) { 295 len = 0; 296 flags &= ~TH_FIN; 297 } 298 299 if (len < 0) { 300 /* 301 * If FIN has been sent but not acked, 302 * but we haven't been called to retransmit, 303 * len will be < 0. Otherwise, window shrank 304 * after we sent into it. If window shrank to 0, 305 * cancel pending retransmit, pull snd_nxt back 306 * to (closed) window, and set the persist timer 307 * if it isn't already going. If the window didn't 308 * close completely, just wait for an ACK. 309 */ 310 len = 0; 311 if (sendwin == 0) { 312 callout_stop(tp->tt_rexmt); 313 tp->t_rxtshift = 0; 314 tp->snd_nxt = tp->snd_una; 315 if (!callout_active(tp->tt_persist)) 316 tcp_setpersist(tp); 317 } 318 } 319 320 /* 321 * len will be >= 0 after this point. Truncate to the maximum 322 * segment length and ensure that FIN is removed if the length 323 * no longer contains the last data byte. 324 */ 325 if (len > tp->t_maxseg) { 326 len = tp->t_maxseg; 327 sendalot = TRUE; 328 } 329 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 330 flags &= ~TH_FIN; 331 332 recvwin = sbspace(&so->so_rcv); 333 334 /* 335 * Sender silly window avoidance. We transmit under the following 336 * conditions when len is non-zero: 337 * 338 * - We have a full segment 339 * - This is the last buffer in a write()/send() and we are 340 * either idle or running NODELAY 341 * - we've timed out (e.g. persist timer) 342 * - we have more then 1/2 the maximum send window's worth of 343 * data (receiver may be limited the window size) 344 * - we need to retransmit 345 */ 346 if (len) { 347 if (len == tp->t_maxseg) 348 goto send; 349 /* 350 * NOTE! on localhost connections an 'ack' from the remote 351 * end may occur synchronously with the output and cause 352 * us to flush a buffer queued with moretocome. XXX 353 * 354 * note: the len + off check is almost certainly unnecessary. 355 */ 356 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 357 (idle || (tp->t_flags & TF_NODELAY)) && 358 len + off >= so->so_snd.sb_cc && 359 !(tp->t_flags & TF_NOPUSH)) { 360 goto send; 361 } 362 if (tp->t_flags & TF_FORCE) /* typ. timeout case */ 363 goto send; 364 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 365 goto send; 366 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 367 goto send; 368 } 369 370 /* 371 * Compare available window to amount of window 372 * known to peer (as advertised window less 373 * next expected input). If the difference is at least two 374 * max size segments, or at least 50% of the maximum possible 375 * window, then want to send a window update to peer. 376 */ 377 if (recvwin > 0) { 378 /* 379 * "adv" is the amount we can increase the window, 380 * taking into account that we are limited by 381 * TCP_MAXWIN << tp->rcv_scale. 382 */ 383 long adv = min(recvwin, (long)TCP_MAXWIN << tp->rcv_scale) - 384 (tp->rcv_adv - tp->rcv_nxt); 385 386 /* 387 * This ack case typically occurs when the user has drained 388 * the TCP socket buffer sufficiently to warrent an ack 389 * containing a 'pure window update'... that is, an ack that 390 * ONLY updates the tcp window. 391 * 392 * It is unclear why we would need to do a pure window update 393 * past 2 segments if we are going to do one at 1/2 the high 394 * water mark anyway, especially since under normal conditions 395 * the user program will drain the socket buffer quickly. 396 * The 2-segment pure window update will often add a large 397 * number of extra, unnecessary acks to the stream. 398 * 399 * avoid_pure_win_update now defaults to 1. 400 */ 401 if (avoid_pure_win_update == 0) { 402 if (adv >= (long) (2 * tp->t_maxseg)) 403 goto send; 404 } 405 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 406 goto send; 407 } 408 409 /* 410 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 411 * is also a catch-all for the retransmit timer timeout case. 412 */ 413 if (tp->t_flags & TF_ACKNOW) 414 goto send; 415 if ((flags & TH_RST) || 416 ((flags & TH_SYN) && !(tp->t_flags & TF_NEEDSYN))) 417 goto send; 418 if (SEQ_GT(tp->snd_up, tp->snd_una)) 419 goto send; 420 /* 421 * If our state indicates that FIN should be sent 422 * and we have not yet done so, then we need to send. 423 */ 424 if (flags & TH_FIN && 425 (!(tp->t_flags & TF_SENTFIN) || tp->snd_nxt == tp->snd_una)) 426 goto send; 427 428 /* 429 * TCP window updates are not reliable, rather a polling protocol 430 * using ``persist'' packets is used to insure receipt of window 431 * updates. The three ``states'' for the output side are: 432 * idle not doing retransmits or persists 433 * persisting to move a small or zero window 434 * (re)transmitting and thereby not persisting 435 * 436 * callout_active(tp->tt_persist) 437 * is true when we are in persist state. 438 * The TF_FORCE flag in tp->t_flags 439 * is set when we are called to send a persist packet. 440 * callout_active(tp->tt_rexmt) 441 * is set when we are retransmitting 442 * The output side is idle when both timers are zero. 443 * 444 * If send window is too small, there is data to transmit, and no 445 * retransmit or persist is pending, then go to persist state. 446 * If nothing happens soon, send when timer expires: 447 * if window is nonzero, transmit what we can, 448 * otherwise force out a byte. 449 */ 450 if (so->so_snd.sb_cc > 0 && 451 !callout_active(tp->tt_rexmt) && !callout_active(tp->tt_persist)) { 452 tp->t_rxtshift = 0; 453 tcp_setpersist(tp); 454 } 455 456 /* 457 * No reason to send a segment, just return. 458 */ 459 return (0); 460 461 send: 462 /* 463 * Before ESTABLISHED, force sending of initial options 464 * unless TCP set not to do any options. 465 * NOTE: we assume that the IP/TCP header plus TCP options 466 * always fit in a single mbuf, leaving room for a maximum 467 * link header, i.e. 468 * max_linkhdr + sizeof(struct tcpiphdr) + optlen <= MCLBYTES 469 */ 470 optlen = 0; 471 if (isipv6) 472 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 473 else 474 hdrlen = sizeof(struct tcpiphdr); 475 if (flags & TH_SYN) { 476 tp->snd_nxt = tp->iss; 477 if (!(tp->t_flags & TF_NOOPT)) { 478 u_short mss; 479 480 opt[0] = TCPOPT_MAXSEG; 481 opt[1] = TCPOLEN_MAXSEG; 482 mss = htons((u_short) tcp_mssopt(tp)); 483 memcpy(opt + 2, &mss, sizeof mss); 484 optlen = TCPOLEN_MAXSEG; 485 486 if ((tp->t_flags & TF_REQ_SCALE) && 487 (!(flags & TH_ACK) || 488 (tp->t_flags & TF_RCVD_SCALE))) { 489 *((u_int32_t *)(opt + optlen)) = htonl( 490 TCPOPT_NOP << 24 | 491 TCPOPT_WINDOW << 16 | 492 TCPOLEN_WINDOW << 8 | 493 tp->request_r_scale); 494 optlen += 4; 495 } 496 497 if ((tcp_do_sack && !(flags & TH_ACK)) || 498 tp->t_flags & TF_SACK_PERMITTED) { 499 uint32_t *lp = (uint32_t *)(opt + optlen); 500 501 *lp = htonl(TCPOPT_SACK_PERMITTED_ALIGNED); 502 optlen += TCPOLEN_SACK_PERMITTED_ALIGNED; 503 } 504 } 505 } 506 507 /* 508 * Send a timestamp and echo-reply if this is a SYN and our side 509 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 510 * and our peer have sent timestamps in our SYN's. 511 */ 512 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 513 !(flags & TH_RST) && 514 (!(flags & TH_ACK) || (tp->t_flags & TF_RCVD_TSTMP))) { 515 u_int32_t *lp = (u_int32_t *)(opt + optlen); 516 517 /* Form timestamp option as shown in appendix A of RFC 1323. */ 518 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 519 *lp++ = htonl(ticks); 520 *lp = htonl(tp->ts_recent); 521 optlen += TCPOLEN_TSTAMP_APPA; 522 } 523 524 /* 525 * Send `CC-family' options if our side wants to use them (TF_REQ_CC), 526 * options are allowed (!TF_NOOPT) and it's not a RST. 527 */ 528 if ((tp->t_flags & (TF_REQ_CC | TF_NOOPT)) == TF_REQ_CC && 529 !(flags & TH_RST)) { 530 switch (flags & (TH_SYN | TH_ACK)) { 531 /* 532 * This is a normal ACK, send CC if we received CC before 533 * from our peer. 534 */ 535 case TH_ACK: 536 if (!(tp->t_flags & TF_RCVD_CC)) 537 break; 538 /*FALLTHROUGH*/ 539 540 /* 541 * We can only get here in T/TCP's SYN_SENT* state, when 542 * we're a sending a non-SYN segment without waiting for 543 * the ACK of our SYN. A check above assures that we only 544 * do this if our peer understands T/TCP. 545 */ 546 case 0: 547 opt[optlen++] = TCPOPT_NOP; 548 opt[optlen++] = TCPOPT_NOP; 549 opt[optlen++] = TCPOPT_CC; 550 opt[optlen++] = TCPOLEN_CC; 551 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 552 optlen += 4; 553 break; 554 555 /* 556 * This is our initial SYN, check whether we have to use 557 * CC or CC.new. 558 */ 559 case TH_SYN: 560 opt[optlen++] = TCPOPT_NOP; 561 opt[optlen++] = TCPOPT_NOP; 562 opt[optlen++] = tp->t_flags & TF_SENDCCNEW ? 563 TCPOPT_CCNEW : TCPOPT_CC; 564 opt[optlen++] = TCPOLEN_CC; 565 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 566 optlen += 4; 567 break; 568 569 /* 570 * This is a SYN,ACK; send CC and CC.echo if we received 571 * CC from our peer. 572 */ 573 case (TH_SYN | TH_ACK): 574 if (tp->t_flags & TF_RCVD_CC) { 575 opt[optlen++] = TCPOPT_NOP; 576 opt[optlen++] = TCPOPT_NOP; 577 opt[optlen++] = TCPOPT_CC; 578 opt[optlen++] = TCPOLEN_CC; 579 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 580 optlen += 4; 581 opt[optlen++] = TCPOPT_NOP; 582 opt[optlen++] = TCPOPT_NOP; 583 opt[optlen++] = TCPOPT_CCECHO; 584 opt[optlen++] = TCPOLEN_CC; 585 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_recv); 586 optlen += 4; 587 } 588 break; 589 } 590 } 591 592 /* 593 * If this is a SACK connection and we have a block to report, 594 * fill in the SACK blocks in the TCP options. 595 */ 596 if ((tp->t_flags & (TF_SACK_PERMITTED | TF_NOOPT)) == 597 TF_SACK_PERMITTED && 598 (!LIST_EMPTY(&tp->t_segq) || 599 tp->reportblk.rblk_start != tp->reportblk.rblk_end)) 600 tcp_sack_fill_report(tp, opt, &optlen); 601 602 KASSERT(optlen <= TCP_MAXOLEN, ("too many TCP options")); 603 hdrlen += optlen; 604 605 if (isipv6) { 606 ipoptlen = ip6_optlen(inp); 607 } else { 608 if (inp->inp_options) { 609 ipoptlen = inp->inp_options->m_len - 610 offsetof(struct ipoption, ipopt_list); 611 } else { 612 ipoptlen = 0; 613 } 614 } 615 #ifdef IPSEC 616 ipoptlen += ipsec_hdrsiz_tcp(tp); 617 #endif 618 619 /* 620 * Adjust data length if insertion of options will 621 * bump the packet length beyond the t_maxopd length. 622 * Clear the FIN bit because we cut off the tail of 623 * the segment. 624 */ 625 if (len + optlen + ipoptlen > tp->t_maxopd) { 626 /* 627 * If there is still more to send, don't close the connection. 628 */ 629 flags &= ~TH_FIN; 630 len = tp->t_maxopd - optlen - ipoptlen; 631 sendalot = TRUE; 632 } 633 634 #ifdef INET6 635 KASSERT(max_linkhdr + hdrlen <= MCLBYTES, ("tcphdr too big")); 636 #else 637 KASSERT(max_linkhdr + hdrlen <= MHLEN, ("tcphdr too big")); 638 #endif 639 640 /* 641 * Grab a header mbuf, attaching a copy of data to 642 * be transmitted, and initialize the header from 643 * the template for sends on this connection. 644 */ 645 if (len) { 646 if ((tp->t_flags & TF_FORCE) && len == 1) 647 tcpstat.tcps_sndprobe++; 648 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 649 if (tp->snd_nxt == tp->snd_una) 650 tp->snd_max_rexmt = tp->snd_max; 651 tcpstat.tcps_sndrexmitpack++; 652 tcpstat.tcps_sndrexmitbyte += len; 653 } else { 654 tcpstat.tcps_sndpack++; 655 tcpstat.tcps_sndbyte += len; 656 } 657 #ifdef notyet 658 if ((m = m_copypack(so->so_snd.sb_mb, off, (int)len, 659 max_linkhdr + hdrlen)) == NULL) { 660 error = ENOBUFS; 661 goto out; 662 } 663 /* 664 * m_copypack left space for our hdr; use it. 665 */ 666 m->m_len += hdrlen; 667 m->m_data -= hdrlen; 668 #else 669 MGETHDR(m, MB_DONTWAIT, MT_HEADER); 670 if (m == NULL) { 671 error = ENOBUFS; 672 goto out; 673 } 674 #ifdef INET6 675 if (MHLEN < hdrlen + max_linkhdr) { 676 MCLGET(m, MB_DONTWAIT); 677 if (!(m->m_flags & M_EXT)) { 678 m_freem(m); 679 error = ENOBUFS; 680 goto out; 681 } 682 } 683 #endif 684 m->m_data += max_linkhdr; 685 m->m_len = hdrlen; 686 if (len <= MHLEN - hdrlen - max_linkhdr) { 687 m_copydata(so->so_snd.sb_mb, off, (int) len, 688 mtod(m, caddr_t) + hdrlen); 689 m->m_len += len; 690 } else { 691 m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len); 692 if (m->m_next == NULL) { 693 m_free(m); 694 error = ENOBUFS; 695 goto out; 696 } 697 } 698 #endif 699 /* 700 * If we're sending everything we've got, set PUSH. 701 * (This will keep happy those implementations which only 702 * give data to the user when a buffer fills or 703 * a PUSH comes in.) 704 */ 705 if (off + len == so->so_snd.sb_cc) 706 flags |= TH_PUSH; 707 } else { 708 if (tp->t_flags & TF_ACKNOW) 709 tcpstat.tcps_sndacks++; 710 else if (flags & (TH_SYN | TH_FIN | TH_RST)) 711 tcpstat.tcps_sndctrl++; 712 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 713 tcpstat.tcps_sndurg++; 714 else 715 tcpstat.tcps_sndwinup++; 716 717 MGETHDR(m, MB_DONTWAIT, MT_HEADER); 718 if (m == NULL) { 719 error = ENOBUFS; 720 goto out; 721 } 722 if (isipv6 && 723 (hdrlen + max_linkhdr > MHLEN) && hdrlen <= MHLEN) 724 MH_ALIGN(m, hdrlen); 725 else 726 m->m_data += max_linkhdr; 727 m->m_len = hdrlen; 728 } 729 m->m_pkthdr.rcvif = (struct ifnet *)0; 730 if (isipv6) { 731 ip6 = mtod(m, struct ip6_hdr *); 732 th = (struct tcphdr *)(ip6 + 1); 733 tcp_fillheaders(tp, ip6, th); 734 } else { 735 ip = mtod(m, struct ip *); 736 ipov = (struct ipovly *)ip; 737 th = (struct tcphdr *)(ip + 1); 738 /* this picks up the pseudo header (w/o the length) */ 739 tcp_fillheaders(tp, ip, th); 740 } 741 742 /* 743 * Fill in fields, remembering maximum advertised 744 * window for use in delaying messages about window sizes. 745 * If resending a FIN, be sure not to use a new sequence number. 746 */ 747 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 748 tp->snd_nxt == tp->snd_max) 749 tp->snd_nxt--; 750 /* 751 * If we are doing retransmissions, then snd_nxt will 752 * not reflect the first unsent octet. For ACK only 753 * packets, we do not want the sequence number of the 754 * retransmitted packet, we want the sequence number 755 * of the next unsent octet. So, if there is no data 756 * (and no SYN or FIN), use snd_max instead of snd_nxt 757 * when filling in ti_seq. But if we are in persist 758 * state, snd_max might reflect one byte beyond the 759 * right edge of the window, so use snd_nxt in that 760 * case, since we know we aren't doing a retransmission. 761 * (retransmit and persist are mutually exclusive...) 762 */ 763 if (len || (flags & (TH_SYN|TH_FIN)) || callout_active(tp->tt_persist)) 764 th->th_seq = htonl(tp->snd_nxt); 765 else 766 th->th_seq = htonl(tp->snd_max); 767 th->th_ack = htonl(tp->rcv_nxt); 768 if (optlen) { 769 bcopy(opt, th + 1, optlen); 770 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 771 } 772 th->th_flags = flags; 773 /* 774 * Calculate receive window. Don't shrink window, 775 * but avoid silly window syndrome. 776 */ 777 if (recvwin < (long)(so->so_rcv.sb_hiwat / 4) && 778 recvwin < (long)tp->t_maxseg) 779 recvwin = 0; 780 if (recvwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 781 recvwin = (long)(tp->rcv_adv - tp->rcv_nxt); 782 if (recvwin > (long)TCP_MAXWIN << tp->rcv_scale) 783 recvwin = (long)TCP_MAXWIN << tp->rcv_scale; 784 th->th_win = htons((u_short) (recvwin>>tp->rcv_scale)); 785 786 /* 787 * Adjust the RXWIN0SENT flag - indicate that we have advertised 788 * a 0 window. This may cause the remote transmitter to stall. This 789 * flag tells soreceive() to disable delayed acknowledgements when 790 * draining the buffer. This can occur if the receiver is attempting 791 * to read more data then can be buffered prior to transmitting on 792 * the connection. 793 */ 794 if (recvwin == 0) 795 tp->t_flags |= TF_RXWIN0SENT; 796 else 797 tp->t_flags &= ~TF_RXWIN0SENT; 798 799 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 800 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 801 th->th_flags |= TH_URG; 802 } else { 803 /* 804 * If no urgent pointer to send, then we pull 805 * the urgent pointer to the left edge of the send window 806 * so that it doesn't drift into the send window on sequence 807 * number wraparound. 808 */ 809 tp->snd_up = tp->snd_una; /* drag it along */ 810 } 811 812 /* 813 * Put TCP length in extended header, and then 814 * checksum extended header and data. 815 */ 816 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 817 if (isipv6) { 818 /* 819 * ip6_plen is not need to be filled now, and will be filled 820 * in ip6_output(). 821 */ 822 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 823 sizeof(struct tcphdr) + optlen + len); 824 } else { 825 m->m_pkthdr.csum_flags = CSUM_TCP; 826 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 827 if (len + optlen) 828 th->th_sum = in_addword(th->th_sum, 829 htons((u_short)(optlen + len))); 830 831 /* IP version must be set here for ipv4/ipv6 checking later */ 832 KASSERT(ip->ip_v == IPVERSION, 833 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 834 } 835 836 /* 837 * In transmit state, time the transmission and arrange for 838 * the retransmit. In persist state, just set snd_max. 839 */ 840 if (!(tp->t_flags & TF_FORCE) || !callout_active(tp->tt_persist)) { 841 tcp_seq startseq = tp->snd_nxt; 842 843 /* 844 * Advance snd_nxt over sequence space of this segment. 845 */ 846 if (flags & (TH_SYN | TH_FIN)) { 847 if (flags & TH_SYN) 848 tp->snd_nxt++; 849 if (flags & TH_FIN) { 850 tp->snd_nxt++; 851 tp->t_flags |= TF_SENTFIN; 852 } 853 } 854 tp->snd_nxt += len; 855 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 856 tp->snd_max = tp->snd_nxt; 857 /* 858 * Time this transmission if not a retransmission and 859 * not currently timing anything. 860 */ 861 if (tp->t_rtttime == 0) { 862 tp->t_rtttime = ticks; 863 tp->t_rtseq = startseq; 864 tcpstat.tcps_segstimed++; 865 } 866 } 867 868 /* 869 * Set retransmit timer if not currently set, 870 * and not doing a pure ack or a keep-alive probe. 871 * Initial value for retransmit timer is smoothed 872 * round-trip time + 2 * round-trip time variance. 873 * Initialize shift counter which is used for backoff 874 * of retransmit time. 875 */ 876 if (!callout_active(tp->tt_rexmt) && 877 tp->snd_nxt != tp->snd_una) { 878 if (callout_active(tp->tt_persist)) { 879 callout_stop(tp->tt_persist); 880 tp->t_rxtshift = 0; 881 } 882 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 883 tcp_timer_rexmt, tp); 884 } 885 } else { 886 /* 887 * Persist case, update snd_max but since we are in 888 * persist mode (no window) we do not update snd_nxt. 889 */ 890 int xlen = len; 891 if (flags & TH_SYN) 892 ++xlen; 893 if (flags & TH_FIN) { 894 ++xlen; 895 tp->t_flags |= TF_SENTFIN; 896 } 897 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 898 tp->snd_max = tp->snd_nxt + xlen; 899 } 900 901 #ifdef TCPDEBUG 902 /* 903 * Trace. 904 */ 905 if (so->so_options & SO_DEBUG) 906 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 907 #endif 908 909 /* 910 * Fill in IP length and desired time to live and 911 * send to IP level. There should be a better way 912 * to handle ttl and tos; we could keep them in 913 * the template, but need a way to checksum without them. 914 */ 915 /* 916 * m->m_pkthdr.len should have been set before cksum calcuration, 917 * because in6_cksum() need it. 918 */ 919 if (isipv6) { 920 /* 921 * we separately set hoplimit for every segment, since the 922 * user might want to change the value via setsockopt. 923 * Also, desired default hop limit might be changed via 924 * Neighbor Discovery. 925 */ 926 ip6->ip6_hlim = in6_selecthlim(inp, 927 (inp->in6p_route.ro_rt ? 928 inp->in6p_route.ro_rt->rt_ifp : NULL)); 929 930 /* TODO: IPv6 IP6TOS_ECT bit on */ 931 error = ip6_output(m, inp->in6p_outputopts, &inp->in6p_route, 932 (so->so_options & SO_DONTROUTE), NULL, NULL, 933 inp); 934 } else { 935 struct rtentry *rt; 936 ip->ip_len = m->m_pkthdr.len; 937 #ifdef INET6 938 if (INP_CHECK_SOCKAF(so, AF_INET6)) 939 ip->ip_ttl = in6_selecthlim(inp, 940 (inp->in6p_route.ro_rt ? 941 inp->in6p_route.ro_rt->rt_ifp : NULL)); 942 else 943 #endif 944 ip->ip_ttl = inp->inp_ip_ttl; /* XXX */ 945 946 ip->ip_tos = inp->inp_ip_tos; /* XXX */ 947 /* 948 * See if we should do MTU discovery. 949 * We do it only if the following are true: 950 * 1) we have a valid route to the destination 951 * 2) the MTU is not locked (if it is, 952 * then discovery has been disabled) 953 */ 954 if (path_mtu_discovery && 955 (rt = inp->inp_route.ro_rt) && (rt->rt_flags & RTF_UP) && 956 !(rt->rt_rmx.rmx_locks & RTV_MTU)) 957 ip->ip_off |= IP_DF; 958 959 error = ip_output(m, inp->inp_options, &inp->inp_route, 960 (so->so_options & SO_DONTROUTE), NULL, inp); 961 } 962 if (error) { 963 964 /* 965 * We know that the packet was lost, so back out the 966 * sequence number advance, if any. 967 */ 968 if (!(tp->t_flags & TF_FORCE) || 969 !callout_active(tp->tt_persist)) { 970 /* 971 * No need to check for TH_FIN here because 972 * the TF_SENTFIN flag handles that case. 973 */ 974 if (!(flags & TH_SYN)) 975 tp->snd_nxt -= len; 976 } 977 978 out: 979 if (error == ENOBUFS) { 980 /* 981 * If we can't send, make sure there is something 982 * to get us going again later. Persist state 983 * is not necessarily right, but it is close enough. 984 */ 985 if (!callout_active(tp->tt_rexmt) && 986 !callout_active(tp->tt_persist)) { 987 tp->t_rxtshift = 0; 988 tcp_setpersist(tp); 989 } 990 tcp_quench(inp, 0); 991 return (0); 992 } 993 if (error == EMSGSIZE) { 994 /* 995 * ip_output() will have already fixed the route 996 * for us. tcp_mtudisc() will, as its last action, 997 * initiate retransmission, so it is important to 998 * not do so here. 999 */ 1000 tcp_mtudisc(inp, 0); 1001 return 0; 1002 } 1003 if ((error == EHOSTUNREACH || error == ENETDOWN) && 1004 TCPS_HAVERCVDSYN(tp->t_state)) { 1005 tp->t_softerror = error; 1006 return (0); 1007 } 1008 return (error); 1009 } 1010 tcpstat.tcps_sndtotal++; 1011 1012 /* 1013 * Data sent (as far as we can tell). 1014 * If this advertises a larger window than any other segment, 1015 * then remember the size of the advertised window. 1016 * Any pending ACK has now been sent. 1017 */ 1018 if (recvwin > 0 && SEQ_GT(tp->rcv_nxt + recvwin, tp->rcv_adv)) 1019 tp->rcv_adv = tp->rcv_nxt + recvwin; 1020 tp->last_ack_sent = tp->rcv_nxt; 1021 tp->t_flags &= ~TF_ACKNOW; 1022 if (tcp_delack_enabled) 1023 callout_stop(tp->tt_delack); 1024 if (sendalot) 1025 goto again; 1026 return (0); 1027 } 1028 1029 void 1030 tcp_setpersist(tp) 1031 struct tcpcb *tp; 1032 { 1033 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1034 int tt; 1035 1036 if (callout_active(tp->tt_rexmt)) 1037 panic("tcp_setpersist: retransmit pending"); 1038 /* 1039 * Start/restart persistance timer. 1040 */ 1041 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], TCPTV_PERSMIN, 1042 TCPTV_PERSMAX); 1043 callout_reset(tp->tt_persist, tt, tcp_timer_persist, tp); 1044 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1045 tp->t_rxtshift++; 1046 } 1047