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 1.24 2005/02/04 01:49:30 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 off, flags, error; 158 struct mbuf *m; 159 struct ip *ip = NULL; 160 struct ipovly *ipov = NULL; 161 struct tcphdr *th; 162 u_char opt[TCP_MAXOLEN]; 163 unsigned int ipoptlen, optlen, hdrlen; 164 int idle; 165 boolean_t sendalot; 166 struct ip6_hdr *ip6 = NULL; 167 #ifdef INET6 168 const boolean_t isipv6 = (inp->inp_vflag & INP_IPV6) != 0; 169 #else 170 const boolean_t isipv6 = FALSE; 171 #endif 172 struct rmxp_tao *taop; 173 174 /* 175 * Determine length of data that should be transmitted, 176 * and flags that will be used. 177 * If there is some data or critical controls (SYN, RST) 178 * to send, then transmit; otherwise, investigate further. 179 */ 180 if ((tp->snd_max == tp->snd_una) && 181 (ticks - tp->t_rcvtime) >= tp->t_rxtcur) { 182 /* 183 * We have been idle for "a while" and no acks are 184 * expected to clock out any data we send -- 185 * slow start to get ack "clock" running again. 186 */ 187 tp->snd_cwnd = tp->t_maxseg; 188 } 189 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 190 if (idle && (tp->t_flags & TF_MORETOCOME)) 191 tp->t_flags |= TF_LASTIDLE; 192 else 193 tp->t_flags &= ~TF_LASTIDLE; 194 195 again: 196 /* Make use of SACK information when slow-starting after a RTO. */ 197 if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max && 198 !IN_FASTRECOVERY(tp)) 199 tcp_sack_skip_sacked(&tp->scb, &tp->snd_nxt); 200 201 sendalot = FALSE; 202 off = tp->snd_nxt - tp->snd_una; 203 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 204 sendwin = min(sendwin, tp->snd_bwnd); 205 206 flags = tcp_outflags[tp->t_state]; 207 /* 208 * Get standard flags, and add SYN or FIN if requested by 'hidden' 209 * state flags. 210 */ 211 if (tp->t_flags & TF_NEEDFIN) 212 flags |= TH_FIN; 213 if (tp->t_flags & TF_NEEDSYN) 214 flags |= TH_SYN; 215 216 /* 217 * If in persist timeout with window of 0, send 1 byte. 218 * Otherwise, if window is small but nonzero 219 * and timer expired, we will send what we can 220 * and go to transmit state. 221 */ 222 if (tp->t_flags & TF_FORCE) { 223 if (sendwin == 0) { 224 /* 225 * If we still have some data to send, then 226 * clear the FIN bit. Usually this would 227 * happen below when it realizes that we 228 * aren't sending all the data. However, 229 * if we have exactly 1 byte of unsent data, 230 * then it won't clear the FIN bit below, 231 * and if we are in persist state, we wind 232 * up sending the packet without recording 233 * that we sent the FIN bit. 234 * 235 * We can't just blindly clear the FIN bit, 236 * because if we don't have any more data 237 * to send then the probe will be the FIN 238 * itself. 239 */ 240 if (off < so->so_snd.sb_cc) 241 flags &= ~TH_FIN; 242 sendwin = 1; 243 } else { 244 callout_stop(tp->tt_persist); 245 tp->t_rxtshift = 0; 246 } 247 } 248 249 /* 250 * If snd_nxt == snd_max and we have transmitted a FIN, the 251 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 252 * a negative length. This can also occur when TCP opens up 253 * its congestion window while receiving additional duplicate 254 * acks after fast-retransmit because TCP will reset snd_nxt 255 * to snd_max after the fast-retransmit. 256 * 257 * In the normal retransmit-FIN-only case, however, snd_nxt will 258 * be set to snd_una, the offset will be 0, and the length may 259 * wind up 0. 260 */ 261 len = (long)ulmin(so->so_snd.sb_cc, sendwin) - off; 262 263 /* 264 * Lop off SYN bit if it has already been sent. However, if this 265 * is SYN-SENT state and if segment contains data and if we don't 266 * know that foreign host supports TAO, suppress sending segment. 267 */ 268 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 269 flags &= ~TH_SYN; 270 off--, len++; 271 if (len > 0 && tp->t_state == TCPS_SYN_SENT && 272 ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL || 273 taop->tao_ccsent == 0)) 274 return 0; 275 } 276 277 /* 278 * Be careful not to send data and/or FIN on SYN segments 279 * in cases when no CC option will be sent. 280 * This measure is needed to prevent interoperability problems 281 * with not fully conformant TCP implementations. 282 */ 283 if ((flags & TH_SYN) && 284 ((tp->t_flags & TF_NOOPT) || !(tp->t_flags & TF_REQ_CC) || 285 ((flags & TH_ACK) && !(tp->t_flags & TF_RCVD_CC)))) { 286 len = 0; 287 flags &= ~TH_FIN; 288 } 289 290 if (len < 0) { 291 /* 292 * If FIN has been sent but not acked, 293 * but we haven't been called to retransmit, 294 * len will be < 0. Otherwise, window shrank 295 * after we sent into it. If window shrank to 0, 296 * cancel pending retransmit, pull snd_nxt back 297 * to (closed) window, and set the persist timer 298 * if it isn't already going. If the window didn't 299 * close completely, just wait for an ACK. 300 */ 301 len = 0; 302 if (sendwin == 0) { 303 callout_stop(tp->tt_rexmt); 304 tp->t_rxtshift = 0; 305 tp->snd_nxt = tp->snd_una; 306 if (!callout_active(tp->tt_persist)) 307 tcp_setpersist(tp); 308 } 309 } 310 311 /* 312 * len will be >= 0 after this point. Truncate to the maximum 313 * segment length and ensure that FIN is removed if the length 314 * no longer contains the last data byte. 315 */ 316 if (len > tp->t_maxseg) { 317 len = tp->t_maxseg; 318 sendalot = TRUE; 319 } 320 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 321 flags &= ~TH_FIN; 322 323 recvwin = sbspace(&so->so_rcv); 324 325 /* 326 * Sender silly window avoidance. We transmit under the following 327 * conditions when len is non-zero: 328 * 329 * - We have a full segment 330 * - This is the last buffer in a write()/send() and we are 331 * either idle or running NODELAY 332 * - we've timed out (e.g. persist timer) 333 * - we have more then 1/2 the maximum send window's worth of 334 * data (receiver may be limited the window size) 335 * - we need to retransmit 336 */ 337 if (len) { 338 if (len == tp->t_maxseg) 339 goto send; 340 /* 341 * NOTE! on localhost connections an 'ack' from the remote 342 * end may occur synchronously with the output and cause 343 * us to flush a buffer queued with moretocome. XXX 344 * 345 * note: the len + off check is almost certainly unnecessary. 346 */ 347 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 348 (idle || (tp->t_flags & TF_NODELAY)) && 349 len + off >= so->so_snd.sb_cc && 350 !(tp->t_flags & TF_NOPUSH)) { 351 goto send; 352 } 353 if (tp->t_flags & TF_FORCE) /* typ. timeout case */ 354 goto send; 355 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 356 goto send; 357 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 358 goto send; 359 } 360 361 /* 362 * Compare available window to amount of window 363 * known to peer (as advertised window less 364 * next expected input). If the difference is at least two 365 * max size segments, or at least 50% of the maximum possible 366 * window, then want to send a window update to peer. 367 */ 368 if (recvwin > 0) { 369 /* 370 * "adv" is the amount we can increase the window, 371 * taking into account that we are limited by 372 * TCP_MAXWIN << tp->rcv_scale. 373 */ 374 long adv = min(recvwin, (long)TCP_MAXWIN << tp->rcv_scale) - 375 (tp->rcv_adv - tp->rcv_nxt); 376 377 /* 378 * This ack case typically occurs when the user has drained 379 * the TCP socket buffer sufficiently to warrent an ack 380 * containing a 'pure window update'... that is, an ack that 381 * ONLY updates the tcp window. 382 * 383 * It is unclear why we would need to do a pure window update 384 * past 2 segments if we are going to do one at 1/2 the high 385 * water mark anyway, especially since under normal conditions 386 * the user program will drain the socket buffer quickly. 387 * The 2-segment pure window update will often add a large 388 * number of extra, unnecessary acks to the stream. 389 * 390 * avoid_pure_win_update now defaults to 1. 391 */ 392 if (avoid_pure_win_update == 0) { 393 if (adv >= (long) (2 * tp->t_maxseg)) 394 goto send; 395 } 396 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 397 goto send; 398 } 399 400 /* 401 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 402 * is also a catch-all for the retransmit timer timeout case. 403 */ 404 if (tp->t_flags & TF_ACKNOW) 405 goto send; 406 if ((flags & TH_RST) || 407 ((flags & TH_SYN) && !(tp->t_flags & TF_NEEDSYN))) 408 goto send; 409 if (SEQ_GT(tp->snd_up, tp->snd_una)) 410 goto send; 411 /* 412 * If our state indicates that FIN should be sent 413 * and we have not yet done so, then we need to send. 414 */ 415 if (flags & TH_FIN && 416 (!(tp->t_flags & TF_SENTFIN) || tp->snd_nxt == tp->snd_una)) 417 goto send; 418 419 /* 420 * TCP window updates are not reliable, rather a polling protocol 421 * using ``persist'' packets is used to insure receipt of window 422 * updates. The three ``states'' for the output side are: 423 * idle not doing retransmits or persists 424 * persisting to move a small or zero window 425 * (re)transmitting and thereby not persisting 426 * 427 * callout_active(tp->tt_persist) 428 * is true when we are in persist state. 429 * The TF_FORCE flag in tp->t_flags 430 * is set when we are called to send a persist packet. 431 * callout_active(tp->tt_rexmt) 432 * is set when we are retransmitting 433 * The output side is idle when both timers are zero. 434 * 435 * If send window is too small, there is data to transmit, and no 436 * retransmit or persist is pending, then go to persist state. 437 * If nothing happens soon, send when timer expires: 438 * if window is nonzero, transmit what we can, 439 * otherwise force out a byte. 440 */ 441 if (so->so_snd.sb_cc > 0 && 442 !callout_active(tp->tt_rexmt) && !callout_active(tp->tt_persist)) { 443 tp->t_rxtshift = 0; 444 tcp_setpersist(tp); 445 } 446 447 /* 448 * No reason to send a segment, just return. 449 */ 450 return (0); 451 452 send: 453 /* 454 * Before ESTABLISHED, force sending of initial options 455 * unless TCP set not to do any options. 456 * NOTE: we assume that the IP/TCP header plus TCP options 457 * always fit in a single mbuf, leaving room for a maximum 458 * link header, i.e. 459 * max_linkhdr + sizeof(struct tcpiphdr) + optlen <= MCLBYTES 460 */ 461 optlen = 0; 462 if (isipv6) 463 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 464 else 465 hdrlen = sizeof(struct tcpiphdr); 466 if (flags & TH_SYN) { 467 tp->snd_nxt = tp->iss; 468 if (!(tp->t_flags & TF_NOOPT)) { 469 u_short mss; 470 471 opt[0] = TCPOPT_MAXSEG; 472 opt[1] = TCPOLEN_MAXSEG; 473 mss = htons((u_short) tcp_mssopt(tp)); 474 memcpy(opt + 2, &mss, sizeof mss); 475 optlen = TCPOLEN_MAXSEG; 476 477 if ((tp->t_flags & TF_REQ_SCALE) && 478 (!(flags & TH_ACK) || 479 (tp->t_flags & TF_RCVD_SCALE))) { 480 *((u_int32_t *)(opt + optlen)) = htonl( 481 TCPOPT_NOP << 24 | 482 TCPOPT_WINDOW << 16 | 483 TCPOLEN_WINDOW << 8 | 484 tp->request_r_scale); 485 optlen += 4; 486 } 487 488 if ((tcp_do_sack && !(flags & TH_ACK)) || 489 tp->t_flags & TF_SACK_PERMITTED) { 490 uint32_t *lp = (uint32_t *)(opt + optlen); 491 492 *lp = htonl(TCPOPT_SACK_PERMITTED_ALIGNED); 493 optlen += TCPOLEN_SACK_PERMITTED_ALIGNED; 494 } 495 } 496 } 497 498 /* 499 * Send a timestamp and echo-reply if this is a SYN and our side 500 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 501 * and our peer have sent timestamps in our SYN's. 502 */ 503 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 504 !(flags & TH_RST) && 505 (!(flags & TH_ACK) || (tp->t_flags & TF_RCVD_TSTMP))) { 506 u_int32_t *lp = (u_int32_t *)(opt + optlen); 507 508 /* Form timestamp option as shown in appendix A of RFC 1323. */ 509 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 510 *lp++ = htonl(ticks); 511 *lp = htonl(tp->ts_recent); 512 optlen += TCPOLEN_TSTAMP_APPA; 513 } 514 515 /* 516 * Send `CC-family' options if our side wants to use them (TF_REQ_CC), 517 * options are allowed (!TF_NOOPT) and it's not a RST. 518 */ 519 if ((tp->t_flags & (TF_REQ_CC | TF_NOOPT)) == TF_REQ_CC && 520 !(flags & TH_RST)) { 521 switch (flags & (TH_SYN | TH_ACK)) { 522 /* 523 * This is a normal ACK, send CC if we received CC before 524 * from our peer. 525 */ 526 case TH_ACK: 527 if (!(tp->t_flags & TF_RCVD_CC)) 528 break; 529 /*FALLTHROUGH*/ 530 531 /* 532 * We can only get here in T/TCP's SYN_SENT* state, when 533 * we're a sending a non-SYN segment without waiting for 534 * the ACK of our SYN. A check above assures that we only 535 * do this if our peer understands T/TCP. 536 */ 537 case 0: 538 opt[optlen++] = TCPOPT_NOP; 539 opt[optlen++] = TCPOPT_NOP; 540 opt[optlen++] = TCPOPT_CC; 541 opt[optlen++] = TCPOLEN_CC; 542 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 543 optlen += 4; 544 break; 545 546 /* 547 * This is our initial SYN, check whether we have to use 548 * CC or CC.new. 549 */ 550 case TH_SYN: 551 opt[optlen++] = TCPOPT_NOP; 552 opt[optlen++] = TCPOPT_NOP; 553 opt[optlen++] = tp->t_flags & TF_SENDCCNEW ? 554 TCPOPT_CCNEW : TCPOPT_CC; 555 opt[optlen++] = TCPOLEN_CC; 556 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 557 optlen += 4; 558 break; 559 560 /* 561 * This is a SYN,ACK; send CC and CC.echo if we received 562 * CC from our peer. 563 */ 564 case (TH_SYN | TH_ACK): 565 if (tp->t_flags & TF_RCVD_CC) { 566 opt[optlen++] = TCPOPT_NOP; 567 opt[optlen++] = TCPOPT_NOP; 568 opt[optlen++] = TCPOPT_CC; 569 opt[optlen++] = TCPOLEN_CC; 570 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 571 optlen += 4; 572 opt[optlen++] = TCPOPT_NOP; 573 opt[optlen++] = TCPOPT_NOP; 574 opt[optlen++] = TCPOPT_CCECHO; 575 opt[optlen++] = TCPOLEN_CC; 576 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_recv); 577 optlen += 4; 578 } 579 break; 580 } 581 } 582 583 /* 584 * If this is a SACK connection and we have a block to report, 585 * fill in the SACK blocks in the TCP options. 586 */ 587 if ((tp->t_flags & (TF_SACK_PERMITTED | TF_NOOPT)) == 588 TF_SACK_PERMITTED && 589 (!LIST_EMPTY(&tp->t_segq) || 590 tp->reportblk.rblk_start != tp->reportblk.rblk_end)) 591 tcp_sack_fill_report(tp, opt, &optlen); 592 593 KASSERT(optlen <= TCP_MAXOLEN, ("too many TCP options")); 594 hdrlen += optlen; 595 596 if (isipv6) { 597 ipoptlen = ip6_optlen(inp); 598 } else { 599 if (inp->inp_options) { 600 ipoptlen = inp->inp_options->m_len - 601 offsetof(struct ipoption, ipopt_list); 602 } else { 603 ipoptlen = 0; 604 } 605 } 606 #ifdef IPSEC 607 ipoptlen += ipsec_hdrsiz_tcp(tp); 608 #endif 609 610 /* 611 * Adjust data length if insertion of options will 612 * bump the packet length beyond the t_maxopd length. 613 * Clear the FIN bit because we cut off the tail of 614 * the segment. 615 */ 616 if (len + optlen + ipoptlen > tp->t_maxopd) { 617 /* 618 * If there is still more to send, don't close the connection. 619 */ 620 flags &= ~TH_FIN; 621 len = tp->t_maxopd - optlen - ipoptlen; 622 sendalot = TRUE; 623 } 624 625 #ifdef INET6 626 KASSERT(max_linkhdr + hdrlen <= MCLBYTES, ("tcphdr too big")); 627 #else 628 KASSERT(max_linkhdr + hdrlen <= MHLEN, ("tcphdr too big")); 629 #endif 630 631 /* 632 * Grab a header mbuf, attaching a copy of data to 633 * be transmitted, and initialize the header from 634 * the template for sends on this connection. 635 */ 636 if (len) { 637 if ((tp->t_flags & TF_FORCE) && len == 1) 638 tcpstat.tcps_sndprobe++; 639 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 640 if (tp->snd_nxt == tp->snd_una) 641 tp->snd_max_rexmt = tp->snd_max; 642 tcpstat.tcps_sndrexmitpack++; 643 tcpstat.tcps_sndrexmitbyte += len; 644 } else { 645 tcpstat.tcps_sndpack++; 646 tcpstat.tcps_sndbyte += len; 647 } 648 #ifdef notyet 649 if ((m = m_copypack(so->so_snd.sb_mb, off, (int)len, 650 max_linkhdr + hdrlen)) == NULL) { 651 error = ENOBUFS; 652 goto out; 653 } 654 /* 655 * m_copypack left space for our hdr; use it. 656 */ 657 m->m_len += hdrlen; 658 m->m_data -= hdrlen; 659 #else 660 MGETHDR(m, MB_DONTWAIT, MT_HEADER); 661 if (m == NULL) { 662 error = ENOBUFS; 663 goto out; 664 } 665 #ifdef INET6 666 if (MHLEN < hdrlen + max_linkhdr) { 667 MCLGET(m, MB_DONTWAIT); 668 if (!(m->m_flags & M_EXT)) { 669 m_freem(m); 670 error = ENOBUFS; 671 goto out; 672 } 673 } 674 #endif 675 m->m_data += max_linkhdr; 676 m->m_len = hdrlen; 677 if (len <= MHLEN - hdrlen - max_linkhdr) { 678 m_copydata(so->so_snd.sb_mb, off, (int) len, 679 mtod(m, caddr_t) + hdrlen); 680 m->m_len += len; 681 } else { 682 m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len); 683 if (m->m_next == NULL) { 684 m_free(m); 685 error = ENOBUFS; 686 goto out; 687 } 688 } 689 #endif 690 /* 691 * If we're sending everything we've got, set PUSH. 692 * (This will keep happy those implementations which only 693 * give data to the user when a buffer fills or 694 * a PUSH comes in.) 695 */ 696 if (off + len == so->so_snd.sb_cc) 697 flags |= TH_PUSH; 698 } else { 699 if (tp->t_flags & TF_ACKNOW) 700 tcpstat.tcps_sndacks++; 701 else if (flags & (TH_SYN | TH_FIN | TH_RST)) 702 tcpstat.tcps_sndctrl++; 703 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 704 tcpstat.tcps_sndurg++; 705 else 706 tcpstat.tcps_sndwinup++; 707 708 MGETHDR(m, MB_DONTWAIT, MT_HEADER); 709 if (m == NULL) { 710 error = ENOBUFS; 711 goto out; 712 } 713 if (isipv6 && 714 (hdrlen + max_linkhdr > MHLEN) && hdrlen <= MHLEN) 715 MH_ALIGN(m, hdrlen); 716 else 717 m->m_data += max_linkhdr; 718 m->m_len = hdrlen; 719 } 720 m->m_pkthdr.rcvif = (struct ifnet *)0; 721 if (isipv6) { 722 ip6 = mtod(m, struct ip6_hdr *); 723 th = (struct tcphdr *)(ip6 + 1); 724 tcp_fillheaders(tp, ip6, th); 725 } else { 726 ip = mtod(m, struct ip *); 727 ipov = (struct ipovly *)ip; 728 th = (struct tcphdr *)(ip + 1); 729 /* this picks up the pseudo header (w/o the length) */ 730 tcp_fillheaders(tp, ip, th); 731 } 732 733 /* 734 * Fill in fields, remembering maximum advertised 735 * window for use in delaying messages about window sizes. 736 * If resending a FIN, be sure not to use a new sequence number. 737 */ 738 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 739 tp->snd_nxt == tp->snd_max) 740 tp->snd_nxt--; 741 /* 742 * If we are doing retransmissions, then snd_nxt will 743 * not reflect the first unsent octet. For ACK only 744 * packets, we do not want the sequence number of the 745 * retransmitted packet, we want the sequence number 746 * of the next unsent octet. So, if there is no data 747 * (and no SYN or FIN), use snd_max instead of snd_nxt 748 * when filling in ti_seq. But if we are in persist 749 * state, snd_max might reflect one byte beyond the 750 * right edge of the window, so use snd_nxt in that 751 * case, since we know we aren't doing a retransmission. 752 * (retransmit and persist are mutually exclusive...) 753 */ 754 if (len || (flags & (TH_SYN|TH_FIN)) || callout_active(tp->tt_persist)) 755 th->th_seq = htonl(tp->snd_nxt); 756 else 757 th->th_seq = htonl(tp->snd_max); 758 th->th_ack = htonl(tp->rcv_nxt); 759 if (optlen) { 760 bcopy(opt, th + 1, optlen); 761 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 762 } 763 th->th_flags = flags; 764 /* 765 * Calculate receive window. Don't shrink window, 766 * but avoid silly window syndrome. 767 */ 768 if (recvwin < (long)(so->so_rcv.sb_hiwat / 4) && 769 recvwin < (long)tp->t_maxseg) 770 recvwin = 0; 771 if (recvwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 772 recvwin = (long)(tp->rcv_adv - tp->rcv_nxt); 773 if (recvwin > (long)TCP_MAXWIN << tp->rcv_scale) 774 recvwin = (long)TCP_MAXWIN << tp->rcv_scale; 775 th->th_win = htons((u_short) (recvwin>>tp->rcv_scale)); 776 777 /* 778 * Adjust the RXWIN0SENT flag - indicate that we have advertised 779 * a 0 window. This may cause the remote transmitter to stall. This 780 * flag tells soreceive() to disable delayed acknowledgements when 781 * draining the buffer. This can occur if the receiver is attempting 782 * to read more data then can be buffered prior to transmitting on 783 * the connection. 784 */ 785 if (recvwin == 0) 786 tp->t_flags |= TF_RXWIN0SENT; 787 else 788 tp->t_flags &= ~TF_RXWIN0SENT; 789 790 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 791 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 792 th->th_flags |= TH_URG; 793 } else { 794 /* 795 * If no urgent pointer to send, then we pull 796 * the urgent pointer to the left edge of the send window 797 * so that it doesn't drift into the send window on sequence 798 * number wraparound. 799 */ 800 tp->snd_up = tp->snd_una; /* drag it along */ 801 } 802 803 /* 804 * Put TCP length in extended header, and then 805 * checksum extended header and data. 806 */ 807 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 808 if (isipv6) { 809 /* 810 * ip6_plen is not need to be filled now, and will be filled 811 * in ip6_output(). 812 */ 813 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 814 sizeof(struct tcphdr) + optlen + len); 815 } else { 816 m->m_pkthdr.csum_flags = CSUM_TCP; 817 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 818 if (len + optlen) 819 th->th_sum = in_addword(th->th_sum, 820 htons((u_short)(optlen + len))); 821 822 /* IP version must be set here for ipv4/ipv6 checking later */ 823 KASSERT(ip->ip_v == IPVERSION, 824 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 825 } 826 827 /* 828 * In transmit state, time the transmission and arrange for 829 * the retransmit. In persist state, just set snd_max. 830 */ 831 if (!(tp->t_flags & TF_FORCE) || !callout_active(tp->tt_persist)) { 832 tcp_seq startseq = tp->snd_nxt; 833 834 /* 835 * Advance snd_nxt over sequence space of this segment. 836 */ 837 if (flags & (TH_SYN | TH_FIN)) { 838 if (flags & TH_SYN) 839 tp->snd_nxt++; 840 if (flags & TH_FIN) { 841 tp->snd_nxt++; 842 tp->t_flags |= TF_SENTFIN; 843 } 844 } 845 tp->snd_nxt += len; 846 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 847 tp->snd_max = tp->snd_nxt; 848 /* 849 * Time this transmission if not a retransmission and 850 * not currently timing anything. 851 */ 852 if (tp->t_rtttime == 0) { 853 tp->t_rtttime = ticks; 854 tp->t_rtseq = startseq; 855 tcpstat.tcps_segstimed++; 856 } 857 } 858 859 /* 860 * Set retransmit timer if not currently set, 861 * and not doing a pure ack or a keep-alive probe. 862 * Initial value for retransmit timer is smoothed 863 * round-trip time + 2 * round-trip time variance. 864 * Initialize shift counter which is used for backoff 865 * of retransmit time. 866 */ 867 if (!callout_active(tp->tt_rexmt) && 868 tp->snd_nxt != tp->snd_una) { 869 if (callout_active(tp->tt_persist)) { 870 callout_stop(tp->tt_persist); 871 tp->t_rxtshift = 0; 872 } 873 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 874 tcp_timer_rexmt, tp); 875 } 876 } else { 877 /* 878 * Persist case, update snd_max but since we are in 879 * persist mode (no window) we do not update snd_nxt. 880 */ 881 int xlen = len; 882 if (flags & TH_SYN) 883 ++xlen; 884 if (flags & TH_FIN) { 885 ++xlen; 886 tp->t_flags |= TF_SENTFIN; 887 } 888 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 889 tp->snd_max = tp->snd_nxt + xlen; 890 } 891 892 #ifdef TCPDEBUG 893 /* 894 * Trace. 895 */ 896 if (so->so_options & SO_DEBUG) 897 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 898 #endif 899 900 /* 901 * Fill in IP length and desired time to live and 902 * send to IP level. There should be a better way 903 * to handle ttl and tos; we could keep them in 904 * the template, but need a way to checksum without them. 905 */ 906 /* 907 * m->m_pkthdr.len should have been set before cksum calcuration, 908 * because in6_cksum() need it. 909 */ 910 if (isipv6) { 911 /* 912 * we separately set hoplimit for every segment, since the 913 * user might want to change the value via setsockopt. 914 * Also, desired default hop limit might be changed via 915 * Neighbor Discovery. 916 */ 917 ip6->ip6_hlim = in6_selecthlim(inp, 918 (inp->in6p_route.ro_rt ? 919 inp->in6p_route.ro_rt->rt_ifp : NULL)); 920 921 /* TODO: IPv6 IP6TOS_ECT bit on */ 922 error = ip6_output(m, inp->in6p_outputopts, &inp->in6p_route, 923 (so->so_options & SO_DONTROUTE), NULL, NULL, 924 inp); 925 } else { 926 struct rtentry *rt; 927 ip->ip_len = m->m_pkthdr.len; 928 #ifdef INET6 929 if (INP_CHECK_SOCKAF(so, AF_INET6)) 930 ip->ip_ttl = in6_selecthlim(inp, 931 (inp->in6p_route.ro_rt ? 932 inp->in6p_route.ro_rt->rt_ifp : NULL)); 933 else 934 #endif 935 ip->ip_ttl = inp->inp_ip_ttl; /* XXX */ 936 937 ip->ip_tos = inp->inp_ip_tos; /* XXX */ 938 /* 939 * See if we should do MTU discovery. 940 * We do it only if the following are true: 941 * 1) we have a valid route to the destination 942 * 2) the MTU is not locked (if it is, 943 * then discovery has been disabled) 944 */ 945 if (path_mtu_discovery && 946 (rt = inp->inp_route.ro_rt) && (rt->rt_flags & RTF_UP) && 947 !(rt->rt_rmx.rmx_locks & RTV_MTU)) 948 ip->ip_off |= IP_DF; 949 950 error = ip_output(m, inp->inp_options, &inp->inp_route, 951 (so->so_options & SO_DONTROUTE), NULL, inp); 952 } 953 if (error) { 954 955 /* 956 * We know that the packet was lost, so back out the 957 * sequence number advance, if any. 958 */ 959 if (!(tp->t_flags & TF_FORCE) || 960 !callout_active(tp->tt_persist)) { 961 /* 962 * No need to check for TH_FIN here because 963 * the TF_SENTFIN flag handles that case. 964 */ 965 if (!(flags & TH_SYN)) 966 tp->snd_nxt -= len; 967 } 968 969 out: 970 if (error == ENOBUFS) { 971 /* 972 * If we can't send, make sure there is something 973 * to get us going again later. Persist state 974 * is not necessarily right, but it is close enough. 975 */ 976 if (!callout_active(tp->tt_rexmt) && 977 !callout_active(tp->tt_persist)) { 978 tp->t_rxtshift = 0; 979 tcp_setpersist(tp); 980 } 981 tcp_quench(inp, 0); 982 return (0); 983 } 984 if (error == EMSGSIZE) { 985 /* 986 * ip_output() will have already fixed the route 987 * for us. tcp_mtudisc() will, as its last action, 988 * initiate retransmission, so it is important to 989 * not do so here. 990 */ 991 tcp_mtudisc(inp, 0); 992 return 0; 993 } 994 if ((error == EHOSTUNREACH || error == ENETDOWN) && 995 TCPS_HAVERCVDSYN(tp->t_state)) { 996 tp->t_softerror = error; 997 return (0); 998 } 999 return (error); 1000 } 1001 tcpstat.tcps_sndtotal++; 1002 1003 /* 1004 * Data sent (as far as we can tell). 1005 * If this advertises a larger window than any other segment, 1006 * then remember the size of the advertised window. 1007 * Any pending ACK has now been sent. 1008 */ 1009 if (recvwin > 0 && SEQ_GT(tp->rcv_nxt + recvwin, tp->rcv_adv)) 1010 tp->rcv_adv = tp->rcv_nxt + recvwin; 1011 tp->last_ack_sent = tp->rcv_nxt; 1012 tp->t_flags &= ~TF_ACKNOW; 1013 if (tcp_delack_enabled) 1014 callout_stop(tp->tt_delack); 1015 if (sendalot) 1016 goto again; 1017 return (0); 1018 } 1019 1020 void 1021 tcp_setpersist(tp) 1022 struct tcpcb *tp; 1023 { 1024 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1025 int tt; 1026 1027 if (callout_active(tp->tt_rexmt)) 1028 panic("tcp_setpersist: retransmit pending"); 1029 /* 1030 * Start/restart persistance timer. 1031 */ 1032 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], TCPTV_PERSMIN, 1033 TCPTV_PERSMAX); 1034 callout_reset(tp->tt_persist, tt, tcp_timer_persist, tp); 1035 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1036 tp->t_rxtshift++; 1037 } 1038