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_inet6.h" 72 #include "opt_ipsec.h" 73 #include "opt_tcpdebug.h" 74 75 #include <sys/param.h> 76 #include <sys/systm.h> 77 #include <sys/kernel.h> 78 #include <sys/sysctl.h> 79 #include <sys/mbuf.h> 80 #include <sys/domain.h> 81 #include <sys/protosw.h> 82 #include <sys/socket.h> 83 #include <sys/socketvar.h> 84 #include <sys/in_cksum.h> 85 #include <sys/thread.h> 86 #include <sys/globaldata.h> 87 88 #include <net/route.h> 89 90 #include <netinet/in.h> 91 #include <netinet/in_systm.h> 92 #include <netinet/ip.h> 93 #include <netinet/in_pcb.h> 94 #include <netinet/ip_var.h> 95 #include <netinet6/in6_pcb.h> 96 #include <netinet/ip6.h> 97 #include <netinet6/ip6_var.h> 98 #include <netinet/tcp.h> 99 #define TCPOUTFLAGS 100 #include <netinet/tcp_fsm.h> 101 #include <netinet/tcp_seq.h> 102 #include <netinet/tcp_timer.h> 103 #include <netinet/tcp_var.h> 104 #include <netinet/tcpip.h> 105 #ifdef TCPDEBUG 106 #include <netinet/tcp_debug.h> 107 #endif 108 109 #ifdef IPSEC 110 #include <netinet6/ipsec.h> 111 #endif /*IPSEC*/ 112 113 #ifdef FAST_IPSEC 114 #include <netproto/ipsec/ipsec.h> 115 #define IPSEC 116 #endif /*FAST_IPSEC*/ 117 118 #ifdef notyet 119 extern struct mbuf *m_copypack(); 120 #endif 121 122 int path_mtu_discovery = 0; 123 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 124 &path_mtu_discovery, 1, "Enable Path MTU Discovery"); 125 126 static int avoid_pure_win_update = 1; 127 SYSCTL_INT(_net_inet_tcp, OID_AUTO, avoid_pure_win_update, CTLFLAG_RW, 128 &avoid_pure_win_update, 1, "Avoid pure window updates when possible"); 129 130 /* 131 * Tcp output routine: figure out what should be sent and send it. 132 */ 133 int 134 tcp_output(struct tcpcb *tp) 135 { 136 struct inpcb * const inp = tp->t_inpcb; 137 struct socket *so = inp->inp_socket; 138 long len, recvwin, sendwin; 139 int nsacked = 0; 140 int off, flags, error; 141 struct mbuf *m; 142 struct ip *ip = NULL; 143 struct ipovly *ipov = NULL; 144 struct tcphdr *th; 145 u_char opt[TCP_MAXOLEN]; 146 unsigned int ipoptlen, optlen, hdrlen; 147 int idle; 148 boolean_t sendalot; 149 struct ip6_hdr *ip6 = NULL; 150 #ifdef INET6 151 const boolean_t isipv6 = (inp->inp_vflag & INP_IPV6) != 0; 152 #else 153 const boolean_t isipv6 = FALSE; 154 #endif 155 struct rmxp_tao *taop; 156 157 /* 158 * Determine length of data that should be transmitted, 159 * and flags that will be used. 160 * If there is some data or critical controls (SYN, RST) 161 * to send, then transmit; otherwise, investigate further. 162 */ 163 164 /* 165 * If we have been idle for a while, the send congestion window 166 * could be no longer representative of the current state of the link. 167 * So unless we are expecting more acks to come in, slow-start from 168 * scratch to re-determine the send congestion window. 169 */ 170 if (tp->snd_max == tp->snd_una && 171 (ticks - tp->t_rcvtime) >= tp->t_rxtcur) { 172 if (tcp_do_rfc3390) { 173 int initial_cwnd = 174 min(4 * tp->t_maxseg, max(2 * tp->t_maxseg, 4380)); 175 176 tp->snd_cwnd = min(tp->snd_cwnd, initial_cwnd); 177 } else { 178 tp->snd_cwnd = tp->t_maxseg; 179 } 180 tp->snd_wacked = 0; 181 } 182 183 /* 184 * Calculate whether the transmit stream was previously idle 185 * and adjust TF_LASTIDLE for the next time. 186 */ 187 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 188 if (idle && (tp->t_flags & TF_MORETOCOME)) 189 tp->t_flags |= TF_LASTIDLE; 190 else 191 tp->t_flags &= ~TF_LASTIDLE; 192 193 if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max && 194 !IN_FASTRECOVERY(tp)) 195 nsacked = tcp_sack_bytes_below(&tp->scb, tp->snd_nxt); 196 197 again: 198 /* Make use of SACK information when slow-starting after a RTO. */ 199 if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max && 200 !IN_FASTRECOVERY(tp)) { 201 tcp_seq old_snd_nxt = tp->snd_nxt; 202 203 tcp_sack_skip_sacked(&tp->scb, &tp->snd_nxt); 204 nsacked += tp->snd_nxt - old_snd_nxt; 205 } 206 207 sendalot = FALSE; 208 off = tp->snd_nxt - tp->snd_una; 209 sendwin = min(tp->snd_wnd, tp->snd_cwnd + nsacked); 210 sendwin = min(sendwin, tp->snd_bwnd); 211 212 flags = tcp_outflags[tp->t_state]; 213 /* 214 * Get standard flags, and add SYN or FIN if requested by 'hidden' 215 * state flags. 216 */ 217 if (tp->t_flags & TF_NEEDFIN) 218 flags |= TH_FIN; 219 if (tp->t_flags & TF_NEEDSYN) 220 flags |= TH_SYN; 221 222 /* 223 * If in persist timeout with window of 0, send 1 byte. 224 * Otherwise, if window is small but nonzero 225 * and timer expired, we will send what we can 226 * and go to transmit state. 227 */ 228 if (tp->t_flags & TF_FORCE) { 229 if (sendwin == 0) { 230 /* 231 * If we still have some data to send, then 232 * clear the FIN bit. Usually this would 233 * happen below when it realizes that we 234 * aren't sending all the data. However, 235 * if we have exactly 1 byte of unsent data, 236 * then it won't clear the FIN bit below, 237 * and if we are in persist state, we wind 238 * up sending the packet without recording 239 * that we sent the FIN bit. 240 * 241 * We can't just blindly clear the FIN bit, 242 * because if we don't have any more data 243 * to send then the probe will be the FIN 244 * itself. 245 */ 246 if (off < so->so_snd.ssb_cc) 247 flags &= ~TH_FIN; 248 sendwin = 1; 249 } else { 250 callout_stop(tp->tt_persist); 251 tp->t_rxtshift = 0; 252 } 253 } 254 255 /* 256 * If snd_nxt == snd_max and we have transmitted a FIN, the 257 * offset will be > 0 even if so_snd.ssb_cc is 0, resulting in 258 * a negative length. This can also occur when TCP opens up 259 * its congestion window while receiving additional duplicate 260 * acks after fast-retransmit because TCP will reset snd_nxt 261 * to snd_max after the fast-retransmit. 262 * 263 * In the normal retransmit-FIN-only case, however, snd_nxt will 264 * be set to snd_una, the offset will be 0, and the length may 265 * wind up 0. 266 */ 267 len = (long)ulmin(so->so_snd.ssb_cc, sendwin) - off; 268 269 /* 270 * Lop off SYN bit if it has already been sent. However, if this 271 * is SYN-SENT state and if segment contains data and if we don't 272 * know that foreign host supports TAO, suppress sending segment. 273 */ 274 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 275 flags &= ~TH_SYN; 276 off--, len++; 277 if (len > 0 && tp->t_state == TCPS_SYN_SENT && 278 ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL || 279 taop->tao_ccsent == 0)) 280 return 0; 281 } 282 283 /* 284 * Be careful not to send data and/or FIN on SYN segments 285 * in cases when no CC option will be sent. 286 * This measure is needed to prevent interoperability problems 287 * with not fully conformant TCP implementations. 288 */ 289 if ((flags & TH_SYN) && 290 ((tp->t_flags & TF_NOOPT) || !(tp->t_flags & TF_REQ_CC) || 291 ((flags & TH_ACK) && !(tp->t_flags & TF_RCVD_CC)))) { 292 len = 0; 293 flags &= ~TH_FIN; 294 } 295 296 if (len < 0) { 297 /* 298 * If FIN has been sent but not acked, 299 * but we haven't been called to retransmit, 300 * len will be < 0. Otherwise, window shrank 301 * after we sent into it. If window shrank to 0, 302 * cancel pending retransmit, pull snd_nxt back 303 * to (closed) window, and set the persist timer 304 * if it isn't already going. If the window didn't 305 * close completely, just wait for an ACK. 306 */ 307 len = 0; 308 if (sendwin == 0) { 309 callout_stop(tp->tt_rexmt); 310 tp->t_rxtshift = 0; 311 tp->snd_nxt = tp->snd_una; 312 if (!callout_active(tp->tt_persist)) 313 tcp_setpersist(tp); 314 } 315 } 316 317 /* 318 * len will be >= 0 after this point. Truncate to the maximum 319 * segment length and ensure that FIN is removed if the length 320 * no longer contains the last data byte. 321 */ 322 if (len > tp->t_maxseg) { 323 len = tp->t_maxseg; 324 sendalot = TRUE; 325 } 326 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.ssb_cc)) 327 flags &= ~TH_FIN; 328 329 recvwin = ssb_space(&so->so_rcv); 330 331 /* 332 * Sender silly window avoidance. We transmit under the following 333 * conditions when len is non-zero: 334 * 335 * - We have a full segment 336 * - This is the last buffer in a write()/send() and we are 337 * either idle or running NODELAY 338 * - we've timed out (e.g. persist timer) 339 * - we have more then 1/2 the maximum send window's worth of 340 * data (receiver may be limiting the window size) 341 * - we need to retransmit 342 */ 343 if (len) { 344 if (len == tp->t_maxseg) 345 goto send; 346 /* 347 * NOTE! on localhost connections an 'ack' from the remote 348 * end may occur synchronously with the output and cause 349 * us to flush a buffer queued with moretocome. XXX 350 * 351 * note: the len + off check is almost certainly unnecessary. 352 */ 353 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 354 (idle || (tp->t_flags & TF_NODELAY)) && 355 len + off >= so->so_snd.ssb_cc && 356 !(tp->t_flags & TF_NOPUSH)) { 357 goto send; 358 } 359 if (tp->t_flags & TF_FORCE) /* typ. timeout case */ 360 goto send; 361 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 362 goto send; 363 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 364 goto send; 365 } 366 367 /* 368 * Compare available window to amount of window 369 * known to peer (as advertised window less 370 * next expected input). If the difference is at least two 371 * max size segments, or at least 50% of the maximum possible 372 * window, then want to send a window update to peer. 373 */ 374 if (recvwin > 0) { 375 /* 376 * "adv" is the amount we can increase the window, 377 * taking into account that we are limited by 378 * TCP_MAXWIN << tp->rcv_scale. 379 */ 380 long adv = min(recvwin, (long)TCP_MAXWIN << tp->rcv_scale) - 381 (tp->rcv_adv - tp->rcv_nxt); 382 383 /* 384 * This ack case typically occurs when the user has drained 385 * the TCP socket buffer sufficiently to warrent an ack 386 * containing a 'pure window update'... that is, an ack that 387 * ONLY updates the tcp window. 388 * 389 * It is unclear why we would need to do a pure window update 390 * past 2 segments if we are going to do one at 1/2 the high 391 * water mark anyway, especially since under normal conditions 392 * the user program will drain the socket buffer quickly. 393 * The 2-segment pure window update will often add a large 394 * number of extra, unnecessary acks to the stream. 395 * 396 * avoid_pure_win_update now defaults to 1. 397 */ 398 if (avoid_pure_win_update == 0) { 399 if (adv >= (long) (2 * tp->t_maxseg)) 400 goto send; 401 } 402 if (2 * adv >= (long) so->so_rcv.ssb_hiwat) 403 goto send; 404 } 405 406 /* 407 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 408 * is also a catch-all for the retransmit timer timeout case. 409 */ 410 if (tp->t_flags & TF_ACKNOW) 411 goto send; 412 if ((flags & TH_RST) || 413 ((flags & TH_SYN) && !(tp->t_flags & TF_NEEDSYN))) 414 goto send; 415 if (SEQ_GT(tp->snd_up, tp->snd_una)) 416 goto send; 417 /* 418 * If our state indicates that FIN should be sent 419 * and we have not yet done so, then we need to send. 420 */ 421 if (flags & TH_FIN && 422 (!(tp->t_flags & TF_SENTFIN) || tp->snd_nxt == tp->snd_una)) 423 goto send; 424 425 /* 426 * TCP window updates are not reliable, rather a polling protocol 427 * using ``persist'' packets is used to insure receipt of window 428 * updates. The three ``states'' for the output side are: 429 * idle not doing retransmits or persists 430 * persisting to move a small or zero window 431 * (re)transmitting and thereby not persisting 432 * 433 * callout_active(tp->tt_persist) 434 * is true when we are in persist state. 435 * The TF_FORCE flag in tp->t_flags 436 * is set when we are called to send a persist packet. 437 * callout_active(tp->tt_rexmt) 438 * is set when we are retransmitting 439 * The output side is idle when both timers are zero. 440 * 441 * If send window is too small, there is data to transmit, and no 442 * retransmit or persist is pending, then go to persist state. 443 * If nothing happens soon, send when timer expires: 444 * if window is nonzero, transmit what we can, 445 * otherwise force out a byte. 446 */ 447 if (so->so_snd.ssb_cc > 0 && 448 !callout_active(tp->tt_rexmt) && !callout_active(tp->tt_persist)) { 449 tp->t_rxtshift = 0; 450 tcp_setpersist(tp); 451 } 452 453 /* 454 * No reason to send a segment, just return. 455 */ 456 return (0); 457 458 send: 459 /* 460 * Before ESTABLISHED, force sending of initial options 461 * unless TCP set not to do any options. 462 * NOTE: we assume that the IP/TCP header plus TCP options 463 * always fit in a single mbuf, leaving room for a maximum 464 * link header, i.e. 465 * max_linkhdr + sizeof(struct tcpiphdr) + optlen <= MCLBYTES 466 */ 467 optlen = 0; 468 if (isipv6) 469 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 470 else 471 hdrlen = sizeof(struct tcpiphdr); 472 if (flags & TH_SYN) { 473 tp->snd_nxt = tp->iss; 474 if (!(tp->t_flags & TF_NOOPT)) { 475 u_short mss; 476 477 opt[0] = TCPOPT_MAXSEG; 478 opt[1] = TCPOLEN_MAXSEG; 479 mss = htons((u_short) tcp_mssopt(tp)); 480 memcpy(opt + 2, &mss, sizeof mss); 481 optlen = TCPOLEN_MAXSEG; 482 483 if ((tp->t_flags & TF_REQ_SCALE) && 484 (!(flags & TH_ACK) || 485 (tp->t_flags & TF_RCVD_SCALE))) { 486 *((u_int32_t *)(opt + optlen)) = htonl( 487 TCPOPT_NOP << 24 | 488 TCPOPT_WINDOW << 16 | 489 TCPOLEN_WINDOW << 8 | 490 tp->request_r_scale); 491 optlen += 4; 492 } 493 494 if ((tcp_do_sack && !(flags & TH_ACK)) || 495 tp->t_flags & TF_SACK_PERMITTED) { 496 uint32_t *lp = (uint32_t *)(opt + optlen); 497 498 *lp = htonl(TCPOPT_SACK_PERMITTED_ALIGNED); 499 optlen += TCPOLEN_SACK_PERMITTED_ALIGNED; 500 } 501 } 502 } 503 504 /* 505 * Send a timestamp and echo-reply if this is a SYN and our side 506 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 507 * and our peer have sent timestamps in our SYN's. 508 */ 509 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 510 !(flags & TH_RST) && 511 (!(flags & TH_ACK) || (tp->t_flags & TF_RCVD_TSTMP))) { 512 u_int32_t *lp = (u_int32_t *)(opt + optlen); 513 514 /* Form timestamp option as shown in appendix A of RFC 1323. */ 515 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 516 *lp++ = htonl(ticks); 517 *lp = htonl(tp->ts_recent); 518 optlen += TCPOLEN_TSTAMP_APPA; 519 } 520 521 /* 522 * Send `CC-family' options if our side wants to use them (TF_REQ_CC), 523 * options are allowed (!TF_NOOPT) and it's not a RST. 524 */ 525 if ((tp->t_flags & (TF_REQ_CC | TF_NOOPT)) == TF_REQ_CC && 526 !(flags & TH_RST)) { 527 switch (flags & (TH_SYN | TH_ACK)) { 528 /* 529 * This is a normal ACK, send CC if we received CC before 530 * from our peer. 531 */ 532 case TH_ACK: 533 if (!(tp->t_flags & TF_RCVD_CC)) 534 break; 535 /*FALLTHROUGH*/ 536 537 /* 538 * We can only get here in T/TCP's SYN_SENT* state, when 539 * we're a sending a non-SYN segment without waiting for 540 * the ACK of our SYN. A check above assures that we only 541 * do this if our peer understands T/TCP. 542 */ 543 case 0: 544 opt[optlen++] = TCPOPT_NOP; 545 opt[optlen++] = TCPOPT_NOP; 546 opt[optlen++] = TCPOPT_CC; 547 opt[optlen++] = TCPOLEN_CC; 548 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 549 optlen += 4; 550 break; 551 552 /* 553 * This is our initial SYN, check whether we have to use 554 * CC or CC.new. 555 */ 556 case TH_SYN: 557 opt[optlen++] = TCPOPT_NOP; 558 opt[optlen++] = TCPOPT_NOP; 559 opt[optlen++] = tp->t_flags & TF_SENDCCNEW ? 560 TCPOPT_CCNEW : TCPOPT_CC; 561 opt[optlen++] = TCPOLEN_CC; 562 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 563 optlen += 4; 564 break; 565 566 /* 567 * This is a SYN,ACK; send CC and CC.echo if we received 568 * CC from our peer. 569 */ 570 case (TH_SYN | TH_ACK): 571 if (tp->t_flags & TF_RCVD_CC) { 572 opt[optlen++] = TCPOPT_NOP; 573 opt[optlen++] = TCPOPT_NOP; 574 opt[optlen++] = TCPOPT_CC; 575 opt[optlen++] = TCPOLEN_CC; 576 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 577 optlen += 4; 578 opt[optlen++] = TCPOPT_NOP; 579 opt[optlen++] = TCPOPT_NOP; 580 opt[optlen++] = TCPOPT_CCECHO; 581 opt[optlen++] = TCPOLEN_CC; 582 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_recv); 583 optlen += 4; 584 } 585 break; 586 } 587 } 588 589 /* 590 * If this is a SACK connection and we have a block to report, 591 * fill in the SACK blocks in the TCP options. 592 */ 593 if ((tp->t_flags & (TF_SACK_PERMITTED | TF_NOOPT)) == 594 TF_SACK_PERMITTED && 595 (!LIST_EMPTY(&tp->t_segq) || 596 tp->reportblk.rblk_start != tp->reportblk.rblk_end)) 597 tcp_sack_fill_report(tp, opt, &optlen); 598 599 KASSERT(optlen <= TCP_MAXOLEN, ("too many TCP options")); 600 hdrlen += optlen; 601 602 if (isipv6) { 603 ipoptlen = ip6_optlen(inp); 604 } else { 605 if (inp->inp_options) { 606 ipoptlen = inp->inp_options->m_len - 607 offsetof(struct ipoption, ipopt_list); 608 } else { 609 ipoptlen = 0; 610 } 611 } 612 #ifdef IPSEC 613 ipoptlen += ipsec_hdrsiz_tcp(tp); 614 #endif 615 616 /* 617 * Adjust data length if insertion of options will bump the packet 618 * length beyond the t_maxopd length. Clear FIN to prevent premature 619 * closure since there is still more data to send after this (now 620 * truncated) packet. 621 * 622 * If just the options do not fit we are in a no-win situation and 623 * we treat it as an unreachable host. 624 */ 625 if (len + optlen + ipoptlen > tp->t_maxopd) { 626 if (tp->t_maxopd <= optlen + ipoptlen) { 627 static time_t last_optlen_report; 628 629 if (last_optlen_report != time_second) { 630 last_optlen_report = time_second; 631 kprintf("tcpcb %p: MSS (%d) too small to hold options!\n", tp, tp->t_maxopd); 632 } 633 error = EHOSTUNREACH; 634 goto out; 635 } else { 636 flags &= ~TH_FIN; 637 len = tp->t_maxopd - optlen - ipoptlen; 638 sendalot = TRUE; 639 } 640 } 641 642 #ifdef INET6 643 KASSERT(max_linkhdr + hdrlen <= MCLBYTES, ("tcphdr too big")); 644 #else 645 KASSERT(max_linkhdr + hdrlen <= MHLEN, ("tcphdr too big")); 646 #endif 647 648 /* 649 * Grab a header mbuf, attaching a copy of data to 650 * be transmitted, and initialize the header from 651 * the template for sends on this connection. 652 */ 653 if (len) { 654 if ((tp->t_flags & TF_FORCE) && len == 1) 655 tcpstat.tcps_sndprobe++; 656 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 657 if (tp->snd_nxt == tp->snd_una) 658 tp->snd_max_rexmt = tp->snd_max; 659 tcpstat.tcps_sndrexmitpack++; 660 tcpstat.tcps_sndrexmitbyte += len; 661 } else { 662 tcpstat.tcps_sndpack++; 663 tcpstat.tcps_sndbyte += len; 664 } 665 #ifdef notyet 666 if ((m = m_copypack(so->so_snd.ssb_mb, off, (int)len, 667 max_linkhdr + hdrlen)) == NULL) { 668 error = ENOBUFS; 669 goto out; 670 } 671 /* 672 * m_copypack left space for our hdr; use it. 673 */ 674 m->m_len += hdrlen; 675 m->m_data -= hdrlen; 676 #else 677 #ifndef INET6 678 m = m_gethdr(MB_DONTWAIT, MT_HEADER); 679 #else 680 m = m_getl(hdrlen + max_linkhdr, MB_DONTWAIT, MT_HEADER, 681 M_PKTHDR, NULL); 682 #endif 683 if (m == NULL) { 684 error = ENOBUFS; 685 goto out; 686 } 687 m->m_data += max_linkhdr; 688 m->m_len = hdrlen; 689 if (len <= MHLEN - hdrlen - max_linkhdr) { 690 m_copydata(so->so_snd.ssb_mb, off, (int) len, 691 mtod(m, caddr_t) + hdrlen); 692 m->m_len += len; 693 } else { 694 m->m_next = m_copy(so->so_snd.ssb_mb, off, (int) len); 695 if (m->m_next == NULL) { 696 m_free(m); 697 error = ENOBUFS; 698 goto out; 699 } 700 } 701 #endif 702 /* 703 * If we're sending everything we've got, set PUSH. 704 * (This will keep happy those implementations which only 705 * give data to the user when a buffer fills or 706 * a PUSH comes in.) 707 */ 708 if (off + len == so->so_snd.ssb_cc) 709 flags |= TH_PUSH; 710 } else { 711 if (tp->t_flags & TF_ACKNOW) 712 tcpstat.tcps_sndacks++; 713 else if (flags & (TH_SYN | TH_FIN | TH_RST)) 714 tcpstat.tcps_sndctrl++; 715 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 716 tcpstat.tcps_sndurg++; 717 else 718 tcpstat.tcps_sndwinup++; 719 720 MGETHDR(m, MB_DONTWAIT, MT_HEADER); 721 if (m == NULL) { 722 error = ENOBUFS; 723 goto out; 724 } 725 if (isipv6 && 726 (hdrlen + max_linkhdr > MHLEN) && hdrlen <= MHLEN) 727 MH_ALIGN(m, hdrlen); 728 else 729 m->m_data += max_linkhdr; 730 m->m_len = hdrlen; 731 } 732 m->m_pkthdr.rcvif = (struct ifnet *)0; 733 if (isipv6) { 734 ip6 = mtod(m, struct ip6_hdr *); 735 th = (struct tcphdr *)(ip6 + 1); 736 tcp_fillheaders(tp, ip6, th); 737 } else { 738 ip = mtod(m, struct ip *); 739 ipov = (struct ipovly *)ip; 740 th = (struct tcphdr *)(ip + 1); 741 /* this picks up the pseudo header (w/o the length) */ 742 tcp_fillheaders(tp, ip, th); 743 } 744 745 /* 746 * Fill in fields, remembering maximum advertised 747 * window for use in delaying messages about window sizes. 748 * If resending a FIN, be sure not to use a new sequence number. 749 */ 750 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 751 tp->snd_nxt == tp->snd_max) 752 tp->snd_nxt--; 753 /* 754 * If we are doing retransmissions, then snd_nxt will 755 * not reflect the first unsent octet. For ACK only 756 * packets, we do not want the sequence number of the 757 * retransmitted packet, we want the sequence number 758 * of the next unsent octet. So, if there is no data 759 * (and no SYN or FIN), use snd_max instead of snd_nxt 760 * when filling in ti_seq. But if we are in persist 761 * state, snd_max might reflect one byte beyond the 762 * right edge of the window, so use snd_nxt in that 763 * case, since we know we aren't doing a retransmission. 764 * (retransmit and persist are mutually exclusive...) 765 */ 766 if (len || (flags & (TH_SYN|TH_FIN)) || callout_active(tp->tt_persist)) 767 th->th_seq = htonl(tp->snd_nxt); 768 else 769 th->th_seq = htonl(tp->snd_max); 770 th->th_ack = htonl(tp->rcv_nxt); 771 if (optlen) { 772 bcopy(opt, th + 1, optlen); 773 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 774 } 775 th->th_flags = flags; 776 /* 777 * Calculate receive window. Don't shrink window, 778 * but avoid silly window syndrome. 779 */ 780 if (recvwin < (long)(so->so_rcv.ssb_hiwat / 4) && 781 recvwin < (long)tp->t_maxseg) 782 recvwin = 0; 783 if (recvwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 784 recvwin = (long)(tp->rcv_adv - tp->rcv_nxt); 785 if (recvwin > (long)TCP_MAXWIN << tp->rcv_scale) 786 recvwin = (long)TCP_MAXWIN << tp->rcv_scale; 787 th->th_win = htons((u_short) (recvwin>>tp->rcv_scale)); 788 789 /* 790 * Adjust the RXWIN0SENT flag - indicate that we have advertised 791 * a 0 window. This may cause the remote transmitter to stall. This 792 * flag tells soreceive() to disable delayed acknowledgements when 793 * draining the buffer. This can occur if the receiver is attempting 794 * to read more data then can be buffered prior to transmitting on 795 * the connection. 796 */ 797 if (recvwin == 0) 798 tp->t_flags |= TF_RXWIN0SENT; 799 else 800 tp->t_flags &= ~TF_RXWIN0SENT; 801 802 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 803 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 804 th->th_flags |= TH_URG; 805 } else { 806 /* 807 * If no urgent pointer to send, then we pull 808 * the urgent pointer to the left edge of the send window 809 * so that it doesn't drift into the send window on sequence 810 * number wraparound. 811 */ 812 tp->snd_up = tp->snd_una; /* drag it along */ 813 } 814 815 /* 816 * Put TCP length in extended header, and then 817 * checksum extended header and data. 818 */ 819 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 820 if (isipv6) { 821 /* 822 * ip6_plen is not need to be filled now, and will be filled 823 * in ip6_output(). 824 */ 825 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 826 sizeof(struct tcphdr) + optlen + len); 827 } else { 828 m->m_pkthdr.csum_flags = CSUM_TCP; 829 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 830 if (len + optlen) 831 th->th_sum = in_addword(th->th_sum, 832 htons((u_short)(optlen + len))); 833 834 /* IP version must be set here for ipv4/ipv6 checking later */ 835 KASSERT(ip->ip_v == IPVERSION, 836 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 837 } 838 839 /* 840 * In transmit state, time the transmission and arrange for 841 * the retransmit. In persist state, just set snd_max. 842 */ 843 if (!(tp->t_flags & TF_FORCE) || !callout_active(tp->tt_persist)) { 844 tcp_seq startseq = tp->snd_nxt; 845 846 /* 847 * Advance snd_nxt over sequence space of this segment. 848 */ 849 if (flags & (TH_SYN | TH_FIN)) { 850 if (flags & TH_SYN) 851 tp->snd_nxt++; 852 if (flags & TH_FIN) { 853 tp->snd_nxt++; 854 tp->t_flags |= TF_SENTFIN; 855 } 856 } 857 tp->snd_nxt += len; 858 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 859 tp->snd_max = tp->snd_nxt; 860 /* 861 * Time this transmission if not a retransmission and 862 * not currently timing anything. 863 */ 864 if (tp->t_rtttime == 0) { 865 tp->t_rtttime = ticks; 866 tp->t_rtseq = startseq; 867 tcpstat.tcps_segstimed++; 868 } 869 } 870 871 /* 872 * Set retransmit timer if not currently set, 873 * and not doing a pure ack or a keep-alive probe. 874 * Initial value for retransmit timer is smoothed 875 * round-trip time + 2 * round-trip time variance. 876 * Initialize shift counter which is used for backoff 877 * of retransmit time. 878 */ 879 if (!callout_active(tp->tt_rexmt) && 880 tp->snd_nxt != tp->snd_una) { 881 if (callout_active(tp->tt_persist)) { 882 callout_stop(tp->tt_persist); 883 tp->t_rxtshift = 0; 884 } 885 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 886 tcp_timer_rexmt, tp); 887 } 888 } else { 889 /* 890 * Persist case, update snd_max but since we are in 891 * persist mode (no window) we do not update snd_nxt. 892 */ 893 int xlen = len; 894 if (flags & TH_SYN) 895 ++xlen; 896 if (flags & TH_FIN) { 897 ++xlen; 898 tp->t_flags |= TF_SENTFIN; 899 } 900 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 901 tp->snd_max = tp->snd_nxt + xlen; 902 } 903 904 #ifdef TCPDEBUG 905 /* 906 * Trace. 907 */ 908 if (so->so_options & SO_DEBUG) 909 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 910 #endif 911 912 /* 913 * Fill in IP length and desired time to live and 914 * send to IP level. There should be a better way 915 * to handle ttl and tos; we could keep them in 916 * the template, but need a way to checksum without them. 917 */ 918 /* 919 * m->m_pkthdr.len should have been set before cksum calcuration, 920 * because in6_cksum() need it. 921 */ 922 if (isipv6) { 923 /* 924 * we separately set hoplimit for every segment, since the 925 * user might want to change the value via setsockopt. 926 * Also, desired default hop limit might be changed via 927 * Neighbor Discovery. 928 */ 929 ip6->ip6_hlim = in6_selecthlim(inp, 930 (inp->in6p_route.ro_rt ? 931 inp->in6p_route.ro_rt->rt_ifp : NULL)); 932 933 /* TODO: IPv6 IP6TOS_ECT bit on */ 934 error = ip6_output(m, inp->in6p_outputopts, &inp->in6p_route, 935 (so->so_options & SO_DONTROUTE), NULL, NULL, 936 inp); 937 } else { 938 struct rtentry *rt; 939 ip->ip_len = m->m_pkthdr.len; 940 #ifdef INET6 941 if (INP_CHECK_SOCKAF(so, AF_INET6)) 942 ip->ip_ttl = in6_selecthlim(inp, 943 (inp->in6p_route.ro_rt ? 944 inp->in6p_route.ro_rt->rt_ifp : NULL)); 945 else 946 #endif 947 ip->ip_ttl = inp->inp_ip_ttl; /* XXX */ 948 949 ip->ip_tos = inp->inp_ip_tos; /* XXX */ 950 /* 951 * See if we should do MTU discovery. 952 * We do it only if the following are true: 953 * 1) we have a valid route to the destination 954 * 2) the MTU is not locked (if it is, 955 * then discovery has been disabled) 956 */ 957 if (path_mtu_discovery && 958 (rt = inp->inp_route.ro_rt) && (rt->rt_flags & RTF_UP) && 959 !(rt->rt_rmx.rmx_locks & RTV_MTU)) 960 ip->ip_off |= IP_DF; 961 962 error = ip_output(m, inp->inp_options, &inp->inp_route, 963 (so->so_options & SO_DONTROUTE), NULL, inp); 964 } 965 if (error) { 966 967 /* 968 * We know that the packet was lost, so back out the 969 * sequence number advance, if any. 970 */ 971 if (!(tp->t_flags & TF_FORCE) || 972 !callout_active(tp->tt_persist)) { 973 /* 974 * No need to check for TH_FIN here because 975 * the TF_SENTFIN flag handles that case. 976 */ 977 if (!(flags & TH_SYN)) 978 tp->snd_nxt -= len; 979 } 980 981 out: 982 if (error == ENOBUFS) { 983 /* 984 * If we can't send, make sure there is something 985 * to get us going again later. Persist state 986 * is not necessarily right, but it is close enough. 987 */ 988 if (!callout_active(tp->tt_rexmt) && 989 !callout_active(tp->tt_persist)) { 990 tp->t_rxtshift = 0; 991 tcp_setpersist(tp); 992 } 993 tcp_quench(inp, 0); 994 return (0); 995 } 996 if (error == EMSGSIZE) { 997 /* 998 * ip_output() will have already fixed the route 999 * for us. tcp_mtudisc() will, as its last action, 1000 * initiate retransmission, so it is important to 1001 * not do so here. 1002 */ 1003 tcp_mtudisc(inp, 0); 1004 return 0; 1005 } 1006 if ((error == EHOSTUNREACH || error == ENETDOWN) && 1007 TCPS_HAVERCVDSYN(tp->t_state)) { 1008 tp->t_softerror = error; 1009 return (0); 1010 } 1011 return (error); 1012 } 1013 tcpstat.tcps_sndtotal++; 1014 1015 /* 1016 * Data sent (as far as we can tell). 1017 * If this advertises a larger window than any other segment, 1018 * then remember the size of the advertised window. 1019 * Any pending ACK has now been sent. 1020 */ 1021 if (recvwin > 0 && SEQ_GT(tp->rcv_nxt + recvwin, tp->rcv_adv)) 1022 tp->rcv_adv = tp->rcv_nxt + recvwin; 1023 tp->last_ack_sent = tp->rcv_nxt; 1024 tp->t_flags &= ~TF_ACKNOW; 1025 if (tcp_delack_enabled) 1026 callout_stop(tp->tt_delack); 1027 if (sendalot) 1028 goto again; 1029 return (0); 1030 } 1031 1032 void 1033 tcp_setpersist(struct tcpcb *tp) 1034 { 1035 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1036 int tt; 1037 1038 if (callout_active(tp->tt_rexmt)) 1039 panic("tcp_setpersist: retransmit pending"); 1040 /* 1041 * Start/restart persistance timer. 1042 */ 1043 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], TCPTV_PERSMIN, 1044 TCPTV_PERSMAX); 1045 callout_reset(tp->tt_persist, tt, tcp_timer_persist, tp); 1046 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1047 tp->t_rxtshift++; 1048 } 1049