1 /* $OpenBSD: tcp_output.c,v 1.79 2005/06/30 08:51:31 markus Exp $ */ 2 /* $NetBSD: tcp_output.c,v 1.16 1997/06/03 16:17:09 kml Exp $ */ 3 4 /* 5 * Copyright (c) 1982, 1986, 1988, 1990, 1993 6 * The Regents of the University of California. All rights reserved. 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 University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 * 32 * @(#)COPYRIGHT 1.1 (NRL) 17 January 1995 33 * 34 * NRL grants permission for redistribution and use in source and binary 35 * forms, with or without modification, of the software and documentation 36 * created at NRL provided that the following conditions are met: 37 * 38 * 1. Redistributions of source code must retain the above copyright 39 * notice, this list of conditions and the following disclaimer. 40 * 2. Redistributions in binary form must reproduce the above copyright 41 * notice, this list of conditions and the following disclaimer in the 42 * documentation and/or other materials provided with the distribution. 43 * 3. All advertising materials mentioning features or use of this software 44 * must display the following acknowledgements: 45 * This product includes software developed by the University of 46 * California, Berkeley and its contributors. 47 * This product includes software developed at the Information 48 * Technology Division, US Naval Research Laboratory. 49 * 4. Neither the name of the NRL nor the names of its contributors 50 * may be used to endorse or promote products derived from this software 51 * without specific prior written permission. 52 * 53 * THE SOFTWARE PROVIDED BY NRL IS PROVIDED BY NRL AND CONTRIBUTORS ``AS 54 * IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 55 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A 56 * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL NRL OR 57 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 58 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 59 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 60 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 61 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 62 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 63 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 64 * 65 * The views and conclusions contained in the software and documentation 66 * are those of the authors and should not be interpreted as representing 67 * official policies, either expressed or implied, of the US Naval 68 * Research Laboratory (NRL). 69 */ 70 71 #include <sys/param.h> 72 #include <sys/systm.h> 73 #include <sys/mbuf.h> 74 #include <sys/protosw.h> 75 #include <sys/socket.h> 76 #include <sys/socketvar.h> 77 #include <sys/kernel.h> 78 79 #include <net/route.h> 80 #include <net/if.h> 81 82 #include <netinet/in.h> 83 #include <netinet/in_systm.h> 84 #include <netinet/ip.h> 85 #include <netinet/in_pcb.h> 86 #include <netinet/ip_var.h> 87 #include <netinet/tcp.h> 88 #define TCPOUTFLAGS 89 #include <netinet/tcp_fsm.h> 90 #include <netinet/tcp_seq.h> 91 #include <netinet/tcp_timer.h> 92 #include <netinet/tcp_var.h> 93 #include <netinet/tcpip.h> 94 #include <netinet/tcp_debug.h> 95 96 #ifdef INET6 97 #include <netinet6/tcpipv6.h> 98 #include <netinet6/in6_var.h> 99 #endif /* INET6 */ 100 101 #ifdef notyet 102 extern struct mbuf *m_copypack(); 103 #endif 104 105 #ifdef TCP_SACK 106 extern int tcprexmtthresh; 107 #endif 108 109 #ifdef TCP_SACK 110 #ifdef TCP_SACK_DEBUG 111 void tcp_print_holes(struct tcpcb *tp); 112 113 void 114 tcp_print_holes(struct tcpcb *tp) 115 { 116 struct sackhole *p = tp->snd_holes; 117 if (p == 0) 118 return; 119 printf("Hole report: start--end dups rxmit\n"); 120 while (p) { 121 printf("%x--%x d %d r %x\n", p->start, p->end, p->dups, 122 p->rxmit); 123 p = p->next; 124 } 125 printf("\n"); 126 } 127 #endif /* TCP_SACK_DEBUG */ 128 129 /* 130 * Returns pointer to a sackhole if there are any pending retransmissions; 131 * NULL otherwise. 132 */ 133 struct sackhole * 134 tcp_sack_output(struct tcpcb *tp) 135 { 136 struct sackhole *p; 137 138 if (!tp->sack_enable) 139 return (NULL); 140 p = tp->snd_holes; 141 while (p) { 142 #ifndef TCP_FACK 143 if (p->dups >= tcprexmtthresh && SEQ_LT(p->rxmit, p->end)) { 144 #else 145 /* In FACK, if p->dups is less than tcprexmtthresh, but 146 * snd_fack advances more than tcprextmtthresh * tp->t_maxseg, 147 * tcp_input() will try fast retransmit. This forces output. 148 */ 149 if ((p->dups >= tcprexmtthresh || 150 tp->t_dupacks == tcprexmtthresh) && 151 SEQ_LT(p->rxmit, p->end)) { 152 #endif /* TCP_FACK */ 153 if (SEQ_LT(p->rxmit, tp->snd_una)) {/* old SACK hole */ 154 p = p->next; 155 continue; 156 } 157 #ifdef TCP_SACK_DEBUG 158 if (p) 159 tcp_print_holes(tp); 160 #endif 161 return (p); 162 } 163 p = p->next; 164 } 165 return (NULL); 166 } 167 168 /* 169 * After a timeout, the SACK list may be rebuilt. This SACK information 170 * should be used to avoid retransmitting SACKed data. This function 171 * traverses the SACK list to see if snd_nxt should be moved forward. 172 */ 173 174 void 175 tcp_sack_adjust(struct tcpcb *tp) 176 { 177 struct sackhole *cur = tp->snd_holes; 178 if (cur == NULL) 179 return; /* No holes */ 180 if (SEQ_GEQ(tp->snd_nxt, tp->rcv_lastsack)) 181 return; /* We're already beyond any SACKed blocks */ 182 /* 183 * Two cases for which we want to advance snd_nxt: 184 * i) snd_nxt lies between end of one hole and beginning of another 185 * ii) snd_nxt lies between end of last hole and rcv_lastsack 186 */ 187 while (cur->next) { 188 if (SEQ_LT(tp->snd_nxt, cur->end)) 189 return; 190 if (SEQ_GEQ(tp->snd_nxt, cur->next->start)) 191 cur = cur->next; 192 else { 193 tp->snd_nxt = cur->next->start; 194 return; 195 } 196 } 197 if (SEQ_LT(tp->snd_nxt, cur->end)) 198 return; 199 tp->snd_nxt = tp->rcv_lastsack; 200 return; 201 } 202 #endif /* TCP_SACK */ 203 204 /* 205 * Tcp output routine: figure out what should be sent and send it. 206 */ 207 int 208 tcp_output(tp) 209 struct tcpcb *tp; 210 { 211 struct socket *so = tp->t_inpcb->inp_socket; 212 long len, win, txmaxseg; 213 int off, flags, error; 214 struct mbuf *m; 215 struct tcphdr *th; 216 u_char opt[MAX_TCPOPTLEN]; 217 unsigned int optlen, hdrlen, packetlen; 218 int idle, sendalot = 0; 219 #ifdef TCP_SACK 220 int i, sack_rxmit = 0; 221 struct sackhole *p; 222 #endif 223 #if defined(TCP_SACK) 224 int maxburst = TCP_MAXBURST; 225 #endif 226 #ifdef TCP_SIGNATURE 227 unsigned int sigoff; 228 #endif /* TCP_SIGNATURE */ 229 #ifdef TCP_ECN 230 int needect; 231 #endif 232 233 #if defined(TCP_SACK) && defined(TCP_SIGNATURE) && defined(DIAGNOSTIC) 234 if (tp->sack_enable && (tp->t_flags & TF_SIGNATURE)) 235 return (EINVAL); 236 #endif /* defined(TCP_SACK) && defined(TCP_SIGNATURE) && defined(DIAGNOSTIC) */ 237 238 /* 239 * Determine length of data that should be transmitted, 240 * and flags that will be used. 241 * If there is some data or critical controls (SYN, RST) 242 * to send, then transmit; otherwise, investigate further. 243 */ 244 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 245 if (idle && (tcp_now - tp->t_rcvtime) >= tp->t_rxtcur) 246 /* 247 * We have been idle for "a while" and no acks are 248 * expected to clock out any data we send -- 249 * slow start to get ack "clock" running again. 250 */ 251 tp->snd_cwnd = 2 * tp->t_maxseg; 252 253 /* remember 'idle' for next invocation of tcp_output */ 254 if (idle && soissending(so)) { 255 tp->t_flags |= TF_LASTIDLE; 256 idle = 0; 257 } else 258 tp->t_flags &= ~TF_LASTIDLE; 259 260 again: 261 #ifdef TCP_SACK 262 /* 263 * If we've recently taken a timeout, snd_max will be greater than 264 * snd_nxt. There may be SACK information that allows us to avoid 265 * resending already delivered data. Adjust snd_nxt accordingly. 266 */ 267 if (tp->sack_enable && SEQ_LT(tp->snd_nxt, tp->snd_max)) 268 tcp_sack_adjust(tp); 269 #endif 270 off = tp->snd_nxt - tp->snd_una; 271 #if defined(TCP_SACK) && defined(TCP_FACK) 272 /* Normally, sendable data is limited by off < tp->snd_cwnd. 273 * But in FACK, sendable data is limited by snd_awnd < snd_cwnd, 274 * regardless of offset. 275 */ 276 if (tp->sack_enable && (tp->t_dupacks > tcprexmtthresh)) 277 win = tp->snd_wnd; 278 else 279 #endif 280 win = ulmin(tp->snd_wnd, tp->snd_cwnd); 281 282 flags = tcp_outflags[tp->t_state]; 283 284 #ifdef TCP_SACK 285 /* 286 * Send any SACK-generated retransmissions. If we're explicitly trying 287 * to send out new data (when sendalot is 1), bypass this function. 288 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 289 * we're replacing a (future) new transmission with a retransmission 290 * now, and we previously incremented snd_cwnd in tcp_input(). 291 */ 292 if (tp->sack_enable && !sendalot) { 293 if (tp->t_dupacks >= tcprexmtthresh && 294 (p = tcp_sack_output(tp))) { 295 off = p->rxmit - tp->snd_una; 296 sack_rxmit = 1; 297 #if 0 298 /* Coalesce holes into a single retransmission */ 299 #endif 300 len = min(tp->t_maxseg, p->end - p->rxmit); 301 #ifndef TCP_FACK 302 /* in FACK, hold snd_cwnd constant during recovery */ 303 if (SEQ_LT(tp->snd_una, tp->snd_last)) 304 tp->snd_cwnd -= tp->t_maxseg; 305 #endif 306 } 307 } 308 #endif /* TCP_SACK */ 309 310 sendalot = 0; 311 /* 312 * If in persist timeout with window of 0, send 1 byte. 313 * Otherwise, if window is small but nonzero 314 * and timer expired, we will send what we can 315 * and go to transmit state. 316 */ 317 if (tp->t_force) { 318 if (win == 0) { 319 /* 320 * If we still have some data to send, then 321 * clear the FIN bit. Usually this would 322 * happen below when it realizes that we 323 * aren't sending all the data. However, 324 * if we have exactly 1 byte of unset data, 325 * then it won't clear the FIN bit below, 326 * and if we are in persist state, we wind 327 * up sending the packet without recording 328 * that we sent the FIN bit. 329 * 330 * We can't just blindly clear the FIN bit, 331 * because if we don't have any more data 332 * to send then the probe will be the FIN 333 * itself. 334 */ 335 if (off < so->so_snd.sb_cc) 336 flags &= ~TH_FIN; 337 win = 1; 338 } else { 339 TCP_TIMER_DISARM(tp, TCPT_PERSIST); 340 tp->t_rxtshift = 0; 341 } 342 } 343 344 #ifdef TCP_SACK 345 if (!sack_rxmit) { 346 #endif 347 len = ulmin(so->so_snd.sb_cc, win) - off; 348 349 #if defined(TCP_SACK) && defined(TCP_FACK) 350 /* 351 * If we're in fast recovery (SEQ_GT(tp->snd_last, tp->snd_una)), and 352 * amount of outstanding data (snd_awnd) is >= snd_cwnd, then 353 * do not send data (like zero window conditions) 354 */ 355 if (tp->sack_enable && len && SEQ_GT(tp->snd_last, tp->snd_una) && 356 (tp->snd_awnd >= tp->snd_cwnd)) 357 len = 0; 358 #endif /* TCP_FACK */ 359 #ifdef TCP_SACK 360 } 361 #endif 362 363 if (len < 0) { 364 /* 365 * If FIN has been sent but not acked, 366 * but we haven't been called to retransmit, 367 * len will be -1. Otherwise, window shrank 368 * after we sent into it. If window shrank to 0, 369 * cancel pending retransmit, pull snd_nxt back 370 * to (closed) window, and set the persist timer 371 * if it isn't already going. If the window didn't 372 * close completely, just wait for an ACK. 373 */ 374 len = 0; 375 if (win == 0) { 376 TCP_TIMER_DISARM(tp, TCPT_REXMT); 377 tp->t_rxtshift = 0; 378 tp->snd_nxt = tp->snd_una; 379 if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) 380 tcp_setpersist(tp); 381 } 382 } 383 384 /* 385 * Never send more than half a buffer full. This insures that we can 386 * always keep 2 packets on the wire, no matter what SO_SNDBUF is, and 387 * therefore acks will never be delayed unless we run out of data to 388 * transmit. 389 */ 390 txmaxseg = ulmin(so->so_snd.sb_hiwat / 2, tp->t_maxseg); 391 392 if (len > txmaxseg) { 393 len = txmaxseg; 394 sendalot = 1; 395 } 396 if (off + len < so->so_snd.sb_cc) 397 flags &= ~TH_FIN; 398 399 win = sbspace(&so->so_rcv); 400 401 /* 402 * Sender silly window avoidance. If connection is idle 403 * and can send all data, a maximum segment, 404 * at least a maximum default-size segment do it, 405 * or are forced, do it; otherwise don't bother. 406 * If peer's buffer is tiny, then send 407 * when window is at least half open. 408 * If retransmitting (possibly after persist timer forced us 409 * to send into a small window), then must resend. 410 */ 411 if (len) { 412 if (len == txmaxseg) 413 goto send; 414 if ((idle || tp->t_flags & TF_NODELAY) && 415 len + off >= so->so_snd.sb_cc && !soissending(so)) 416 goto send; 417 if (tp->t_force) 418 goto send; 419 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 420 goto send; 421 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 422 goto send; 423 #ifdef TCP_SACK 424 if (sack_rxmit) 425 goto send; 426 #endif 427 } 428 429 /* 430 * Compare available window to amount of window 431 * known to peer (as advertised window less 432 * next expected input). If the difference is at least two 433 * max size segments, or at least 50% of the maximum possible 434 * window, then want to send a window update to peer. 435 */ 436 if (win > 0) { 437 /* 438 * "adv" is the amount we can increase the window, 439 * taking into account that we are limited by 440 * TCP_MAXWIN << tp->rcv_scale. 441 */ 442 long adv = lmin(win, (long)TCP_MAXWIN << tp->rcv_scale) - 443 (tp->rcv_adv - tp->rcv_nxt); 444 445 if (adv >= (long) (2 * tp->t_maxseg)) 446 goto send; 447 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 448 goto send; 449 } 450 451 /* 452 * Send if we owe peer an ACK. 453 */ 454 if (tp->t_flags & TF_ACKNOW) 455 goto send; 456 if (flags & (TH_SYN|TH_RST)) 457 goto send; 458 if (SEQ_GT(tp->snd_up, tp->snd_una)) 459 goto send; 460 /* 461 * If our state indicates that FIN should be sent 462 * and we have not yet done so, or we're retransmitting the FIN, 463 * then we need to send. 464 */ 465 if (flags & TH_FIN && 466 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 467 goto send; 468 #ifdef TCP_SACK 469 /* 470 * In SACK, it is possible for tcp_output to fail to send a segment 471 * after the retransmission timer has been turned off. Make sure 472 * that the retransmission timer is set. 473 */ 474 if (SEQ_GT(tp->snd_max, tp->snd_una) && 475 TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 && 476 TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) { 477 TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); 478 return (0); 479 } 480 #endif /* TCP_SACK */ 481 482 /* 483 * TCP window updates are not reliable, rather a polling protocol 484 * using ``persist'' packets is used to insure receipt of window 485 * updates. The three ``states'' for the output side are: 486 * idle not doing retransmits or persists 487 * persisting to move a small or zero window 488 * (re)transmitting and thereby not persisting 489 * 490 * tp->t_timer[TCPT_PERSIST] 491 * is set when we are in persist state. 492 * tp->t_force 493 * is set when we are called to send a persist packet. 494 * tp->t_timer[TCPT_REXMT] 495 * is set when we are retransmitting 496 * The output side is idle when both timers are zero. 497 * 498 * If send window is too small, there is data to transmit, and no 499 * retransmit or persist is pending, then go to persist state. 500 * If nothing happens soon, send when timer expires: 501 * if window is nonzero, transmit what we can, 502 * otherwise force out a byte. 503 */ 504 if (so->so_snd.sb_cc && TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 && 505 TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) { 506 tp->t_rxtshift = 0; 507 tcp_setpersist(tp); 508 } 509 510 /* 511 * No reason to send a segment, just return. 512 */ 513 return (0); 514 515 send: 516 /* 517 * Before ESTABLISHED, force sending of initial options 518 * unless TCP set not to do any options. 519 * NOTE: we assume that the IP/TCP header plus TCP options 520 * always fit in a single mbuf, leaving room for a maximum 521 * link header, i.e. 522 * max_linkhdr + sizeof(network header) + sizeof(struct tcphdr + 523 * optlen <= MHLEN 524 */ 525 optlen = 0; 526 527 switch (tp->pf) { 528 case 0: /*default to PF_INET*/ 529 #ifdef INET 530 case PF_INET: 531 hdrlen = sizeof(struct ip) + sizeof(struct tcphdr); 532 break; 533 #endif /* INET */ 534 #ifdef INET6 535 case PF_INET6: 536 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 537 break; 538 #endif /* INET6 */ 539 default: 540 return (EPFNOSUPPORT); 541 } 542 543 if (flags & TH_SYN) { 544 tp->snd_nxt = tp->iss; 545 if ((tp->t_flags & TF_NOOPT) == 0) { 546 u_int16_t mss; 547 548 opt[0] = TCPOPT_MAXSEG; 549 opt[1] = 4; 550 mss = htons((u_int16_t) tcp_mss(tp, 0)); 551 bcopy((caddr_t)&mss, (caddr_t)(opt + 2), sizeof(mss)); 552 optlen = 4; 553 554 if (flags & TH_ACK) 555 tcp_mss_update(tp); 556 #ifdef TCP_SACK 557 /* 558 * If this is the first SYN of connection (not a SYN 559 * ACK), include SACK_PERMIT_HDR option. If this is a 560 * SYN ACK, include SACK_PERMIT_HDR option if peer has 561 * already done so. 562 */ 563 if (tp->sack_enable && ((flags & TH_ACK) == 0 || 564 (tp->t_flags & TF_SACK_PERMIT))) { 565 *((u_int32_t *) (opt + optlen)) = 566 htonl(TCPOPT_SACK_PERMIT_HDR); 567 optlen += 4; 568 } 569 #endif 570 571 if ((tp->t_flags & TF_REQ_SCALE) && 572 ((flags & TH_ACK) == 0 || 573 (tp->t_flags & TF_RCVD_SCALE))) { 574 *((u_int32_t *) (opt + optlen)) = htonl( 575 TCPOPT_NOP << 24 | 576 TCPOPT_WINDOW << 16 | 577 TCPOLEN_WINDOW << 8 | 578 tp->request_r_scale); 579 optlen += 4; 580 } 581 } 582 } 583 584 /* 585 * Send a timestamp and echo-reply if this is a SYN and our side 586 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 587 * and our peer have sent timestamps in our SYN's. 588 */ 589 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 590 (flags & TH_RST) == 0 && 591 ((flags & (TH_SYN|TH_ACK)) == TH_SYN || 592 (tp->t_flags & TF_RCVD_TSTMP))) { 593 u_int32_t *lp = (u_int32_t *)(opt + optlen); 594 595 /* Form timestamp option as shown in appendix A of RFC 1323. */ 596 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 597 *lp++ = htonl(tcp_now + tp->ts_modulate); 598 *lp = htonl(tp->ts_recent); 599 optlen += TCPOLEN_TSTAMP_APPA; 600 } 601 602 #ifdef TCP_SIGNATURE 603 if (tp->t_flags & TF_SIGNATURE) { 604 u_int8_t *bp = (u_int8_t *)(opt + optlen); 605 606 /* Send signature option */ 607 *(bp++) = TCPOPT_SIGNATURE; 608 *(bp++) = TCPOLEN_SIGNATURE; 609 sigoff = optlen + 2; 610 611 { 612 unsigned int i; 613 614 for (i = 0; i < 16; i++) 615 *(bp++) = 0; 616 } 617 618 619 /* Pad options list to the next 32 bit boundary and 620 * terminate it. 621 */ 622 *bp++ = TCPOPT_NOP; 623 *bp++ = TCPOPT_EOL; 624 625 optlen += TCPOLEN_SIGLEN; 626 } 627 #endif /* TCP_SIGNATURE */ 628 629 #ifdef TCP_SACK 630 /* 631 * Send SACKs if necessary. This should be the last option processed. 632 * Only as many SACKs are sent as are permitted by the maximum options 633 * size. No more than three SACKs are sent. 634 */ 635 if (tp->sack_enable && tp->t_state == TCPS_ESTABLISHED && 636 (tp->t_flags & (TF_SACK_PERMIT|TF_NOOPT)) == TF_SACK_PERMIT && 637 tp->rcv_numsacks) { 638 u_int32_t *lp = (u_int32_t *)(opt + optlen); 639 u_int32_t *olp = lp++; 640 int count = 0; /* actual number of SACKs inserted */ 641 int maxsack = (MAX_TCPOPTLEN - (optlen + 4))/TCPOLEN_SACK; 642 643 tcpstat.tcps_sack_snd_opts++; 644 maxsack = min(maxsack, TCP_MAX_SACK); 645 for (i = 0; (i < tp->rcv_numsacks && count < maxsack); i++) { 646 struct sackblk sack = tp->sackblks[i]; 647 if (sack.start == 0 && sack.end == 0) 648 continue; 649 *lp++ = htonl(sack.start); 650 *lp++ = htonl(sack.end); 651 count++; 652 } 653 *olp = htonl(TCPOPT_SACK_HDR|(TCPOLEN_SACK*count+2)); 654 optlen += TCPOLEN_SACK*count + 4; /* including leading NOPs */ 655 } 656 #endif /* TCP_SACK */ 657 658 #ifdef DIAGNOSTIC 659 if (optlen > MAX_TCPOPTLEN) 660 panic("tcp_output: options too long"); 661 #endif /* DIAGNOSTIC */ 662 663 hdrlen += optlen; 664 665 /* 666 * Adjust data length if insertion of options will 667 * bump the packet length beyond the t_maxopd length. 668 */ 669 if (len > tp->t_maxopd - optlen) { 670 len = tp->t_maxopd - optlen; 671 sendalot = 1; 672 flags &= ~TH_FIN; 673 } 674 675 #ifdef DIAGNOSTIC 676 if (max_linkhdr + hdrlen > MCLBYTES) 677 panic("tcphdr too big"); 678 #endif 679 680 /* 681 * Grab a header mbuf, attaching a copy of data to 682 * be transmitted, and initialize the header from 683 * the template for sends on this connection. 684 */ 685 if (len) { 686 if (tp->t_force && len == 1) 687 tcpstat.tcps_sndprobe++; 688 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 689 tcpstat.tcps_sndrexmitpack++; 690 tcpstat.tcps_sndrexmitbyte += len; 691 } else { 692 tcpstat.tcps_sndpack++; 693 tcpstat.tcps_sndbyte += len; 694 } 695 #ifdef notyet 696 if ((m = m_copypack(so->so_snd.sb_mb, off, 697 (int)len, max_linkhdr + hdrlen)) == 0) { 698 error = ENOBUFS; 699 goto out; 700 } 701 /* 702 * m_copypack left space for our hdr; use it. 703 */ 704 m->m_len += hdrlen; 705 m->m_data -= hdrlen; 706 #else 707 MGETHDR(m, M_DONTWAIT, MT_HEADER); 708 if (m != NULL && max_linkhdr + hdrlen > MHLEN) { 709 MCLGET(m, M_DONTWAIT); 710 if ((m->m_flags & M_EXT) == 0) { 711 m_freem(m); 712 m = NULL; 713 } 714 } 715 if (m == NULL) { 716 error = ENOBUFS; 717 goto out; 718 } 719 m->m_data += max_linkhdr; 720 m->m_len = hdrlen; 721 if (len <= M_TRAILINGSPACE(m)) { 722 m_copydata(so->so_snd.sb_mb, off, (int) len, 723 mtod(m, caddr_t) + hdrlen); 724 m->m_len += len; 725 } else { 726 m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len); 727 if (m->m_next == 0) { 728 (void) m_free(m); 729 error = ENOBUFS; 730 goto out; 731 } 732 } 733 #endif 734 /* 735 * If we're sending everything we've got, set PUSH. 736 * (This will keep happy those implementations which only 737 * give data to the user when a buffer fills or 738 * a PUSH comes in.) 739 */ 740 if (off + len == so->so_snd.sb_cc && !soissending(so)) 741 flags |= TH_PUSH; 742 } else { 743 if (tp->t_flags & TF_ACKNOW) 744 tcpstat.tcps_sndacks++; 745 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 746 tcpstat.tcps_sndctrl++; 747 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 748 tcpstat.tcps_sndurg++; 749 else 750 tcpstat.tcps_sndwinup++; 751 752 MGETHDR(m, M_DONTWAIT, MT_HEADER); 753 if (m != NULL && max_linkhdr + hdrlen > MHLEN) { 754 MCLGET(m, M_DONTWAIT); 755 if ((m->m_flags & M_EXT) == 0) { 756 m_freem(m); 757 m = NULL; 758 } 759 } 760 if (m == NULL) { 761 error = ENOBUFS; 762 goto out; 763 } 764 m->m_data += max_linkhdr; 765 m->m_len = hdrlen; 766 } 767 m->m_pkthdr.rcvif = (struct ifnet *)0; 768 m->m_pkthdr.len = hdrlen + len; 769 770 if (!tp->t_template) 771 panic("tcp_output"); 772 #ifdef DIAGNOSTIC 773 if (tp->t_template->m_len != hdrlen - optlen) 774 panic("tcp_output: template len != hdrlen - optlen"); 775 #endif /* DIAGNOSTIC */ 776 bcopy(mtod(tp->t_template, caddr_t), mtod(m, caddr_t), 777 tp->t_template->m_len); 778 th = (struct tcphdr *)(mtod(m, caddr_t) + tp->t_template->m_len - 779 sizeof(struct tcphdr)); 780 781 /* 782 * Fill in fields, remembering maximum advertised 783 * window for use in delaying messages about window sizes. 784 * If resending a FIN, be sure not to use a new sequence number. 785 */ 786 if ((flags & TH_FIN) && (tp->t_flags & TF_SENTFIN) && 787 (tp->snd_nxt == tp->snd_max)) 788 tp->snd_nxt--; 789 /* 790 * If we are doing retransmissions, then snd_nxt will 791 * not reflect the first unsent octet. For ACK only 792 * packets, we do not want the sequence number of the 793 * retransmitted packet, we want the sequence number 794 * of the next unsent octet. So, if there is no data 795 * (and no SYN or FIN), use snd_max instead of snd_nxt 796 * when filling in ti_seq. But if we are in persist 797 * state, snd_max might reflect one byte beyond the 798 * right edge of the window, so use snd_nxt in that 799 * case, since we know we aren't doing a retransmission. 800 * (retransmit and persist are mutually exclusive...) 801 */ 802 if (len || (flags & (TH_SYN|TH_FIN)) || TCP_TIMER_ISARMED(tp, TCPT_PERSIST)) 803 th->th_seq = htonl(tp->snd_nxt); 804 else 805 th->th_seq = htonl(tp->snd_max); 806 807 #ifdef TCP_SACK 808 if (sack_rxmit) { 809 /* 810 * If sendalot was turned on (due to option stuffing), turn it 811 * off. Properly set th_seq field. Advance the ret'x pointer 812 * by len. 813 */ 814 if (sendalot) 815 sendalot = 0; 816 th->th_seq = htonl(p->rxmit); 817 p->rxmit += len; 818 #if defined(TCP_SACK) && defined(TCP_FACK) 819 tp->retran_data += len; 820 #endif /* TCP_FACK */ 821 tcpstat.tcps_sack_rexmits++; 822 tcpstat.tcps_sack_rexmit_bytes += len; 823 } 824 #endif /* TCP_SACK */ 825 826 th->th_ack = htonl(tp->rcv_nxt); 827 if (optlen) { 828 bcopy((caddr_t)opt, (caddr_t)(th + 1), optlen); 829 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 830 } 831 #ifdef TCP_ECN 832 if (tcp_do_ecn) { 833 /* 834 * if we have received congestion experienced segs, 835 * set ECE bit. 836 */ 837 if (tp->t_flags & TF_RCVD_CE) { 838 flags |= TH_ECE; 839 tcpstat.tcps_ecn_sndece++; 840 } 841 if (!(tp->t_flags & TF_DISABLE_ECN)) { 842 /* 843 * if this is a SYN seg, set ECE and CWR. 844 * set only ECE for SYN-ACK if peer supports ECN. 845 */ 846 if ((flags & (TH_SYN|TH_ACK)) == TH_SYN) 847 flags |= (TH_ECE|TH_CWR); 848 else if ((tp->t_flags & TF_ECN_PERMIT) && 849 (flags & (TH_SYN|TH_ACK)) == (TH_SYN|TH_ACK)) 850 flags |= TH_ECE; 851 } 852 /* 853 * if we have reduced the congestion window, notify 854 * the peer by setting CWR bit. 855 */ 856 if ((tp->t_flags & TF_ECN_PERMIT) && 857 (tp->t_flags & TF_SEND_CWR)) { 858 flags |= TH_CWR; 859 tp->t_flags &= ~TF_SEND_CWR; 860 tcpstat.tcps_ecn_sndcwr++; 861 } 862 } 863 #endif 864 th->th_flags = flags; 865 866 /* 867 * Calculate receive window. Don't shrink window, 868 * but avoid silly window syndrome. 869 */ 870 if (win < (long)(so->so_rcv.sb_hiwat / 4) && win < (long)tp->t_maxseg) 871 win = 0; 872 if (win > (long)TCP_MAXWIN << tp->rcv_scale) 873 win = (long)TCP_MAXWIN << tp->rcv_scale; 874 if (win < (long)(int32_t)(tp->rcv_adv - tp->rcv_nxt)) 875 win = (long)(int32_t)(tp->rcv_adv - tp->rcv_nxt); 876 if (flags & TH_RST) 877 win = 0; 878 th->th_win = htons((u_int16_t) (win>>tp->rcv_scale)); 879 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 880 u_int32_t urp = tp->snd_up - tp->snd_nxt; 881 if (urp > IP_MAXPACKET) 882 urp = IP_MAXPACKET; 883 th->th_urp = htons((u_int16_t)urp); 884 th->th_flags |= TH_URG; 885 } else 886 /* 887 * If no urgent pointer to send, then we pull 888 * the urgent pointer to the left edge of the send window 889 * so that it doesn't drift into the send window on sequence 890 * number wraparound. 891 */ 892 tp->snd_up = tp->snd_una; /* drag it along */ 893 894 #ifdef TCP_SIGNATURE 895 if (tp->t_flags & TF_SIGNATURE) { 896 int iphlen; 897 union sockaddr_union src, dst; 898 struct tdb *tdb; 899 900 bzero(&src, sizeof(union sockaddr_union)); 901 bzero(&dst, sizeof(union sockaddr_union)); 902 903 switch (tp->pf) { 904 case 0: /*default to PF_INET*/ 905 #ifdef INET 906 case AF_INET: 907 iphlen = sizeof(struct ip); 908 src.sa.sa_len = sizeof(struct sockaddr_in); 909 src.sa.sa_family = AF_INET; 910 src.sin.sin_addr = mtod(m, struct ip *)->ip_src; 911 dst.sa.sa_len = sizeof(struct sockaddr_in); 912 dst.sa.sa_family = AF_INET; 913 dst.sin.sin_addr = mtod(m, struct ip *)->ip_dst; 914 break; 915 #endif /* INET */ 916 #ifdef INET6 917 case AF_INET6: 918 iphlen = sizeof(struct ip6_hdr); 919 src.sa.sa_len = sizeof(struct sockaddr_in6); 920 src.sa.sa_family = AF_INET6; 921 src.sin6.sin6_addr = mtod(m, struct ip6_hdr *)->ip6_src; 922 dst.sa.sa_len = sizeof(struct sockaddr_in6); 923 dst.sa.sa_family = AF_INET6; 924 dst.sin6.sin6_addr = mtod(m, struct ip6_hdr *)->ip6_dst; 925 break; 926 #endif /* INET6 */ 927 } 928 929 /* XXX gettdbbysrcdst() should really be called at spltdb(). */ 930 /* XXX this is splsoftnet(), currently they are the same. */ 931 tdb = gettdbbysrcdst(0, &src, &dst, IPPROTO_TCP); 932 if (tdb == NULL) 933 return (EPERM); 934 935 if (tcp_signature(tdb, tp->pf, m, th, iphlen, 0, 936 mtod(m, caddr_t) + hdrlen - optlen + sigoff) < 0) 937 return (EINVAL); 938 } 939 #endif /* TCP_SIGNATURE */ 940 941 /* 942 * Put TCP length in extended header, and then 943 * checksum extended header and data. 944 */ 945 switch (tp->pf) { 946 case 0: /*default to PF_INET*/ 947 #ifdef INET 948 case AF_INET: 949 /* Defer checksumming until later (ip_output() or hardware) */ 950 m->m_pkthdr.csum_flags |= M_TCPV4_CSUM_OUT; 951 if (len + optlen) 952 th->th_sum = in_cksum_addword(th->th_sum, 953 htons((u_int16_t)(len + optlen))); 954 break; 955 #endif /* INET */ 956 #ifdef INET6 957 case AF_INET6: 958 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 959 hdrlen - sizeof(struct ip6_hdr) + len); 960 break; 961 #endif /* INET6 */ 962 } 963 964 /* 965 * In transmit state, time the transmission and arrange for 966 * the retransmit. In persist state, just set snd_max. 967 */ 968 if (tp->t_force == 0 || TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) { 969 tcp_seq startseq = tp->snd_nxt; 970 971 /* 972 * Advance snd_nxt over sequence space of this segment. 973 */ 974 if (flags & (TH_SYN|TH_FIN)) { 975 if (flags & TH_SYN) 976 tp->snd_nxt++; 977 if (flags & TH_FIN) { 978 tp->snd_nxt++; 979 tp->t_flags |= TF_SENTFIN; 980 } 981 } 982 #ifdef TCP_SACK 983 if (tp->sack_enable) { 984 if (sack_rxmit && (p->rxmit != tp->snd_nxt)) { 985 goto timer; 986 } 987 } 988 #endif 989 tp->snd_nxt += len; 990 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 991 tp->snd_max = tp->snd_nxt; 992 /* 993 * Time this transmission if not a retransmission and 994 * not currently timing anything. 995 */ 996 if (tp->t_rtttime == 0) { 997 tp->t_rtttime = tcp_now; 998 tp->t_rtseq = startseq; 999 tcpstat.tcps_segstimed++; 1000 } 1001 } 1002 1003 /* 1004 * Set retransmit timer if not currently set, 1005 * and not doing an ack or a keep-alive probe. 1006 * Initial value for retransmit timer is smoothed 1007 * round-trip time + 2 * round-trip time variance. 1008 * Initialize shift counter which is used for backoff 1009 * of retransmit time. 1010 */ 1011 #ifdef TCP_SACK 1012 timer: 1013 if (tp->sack_enable && sack_rxmit && 1014 TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 && 1015 tp->snd_nxt != tp->snd_max) { 1016 TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); 1017 if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST)) { 1018 TCP_TIMER_DISARM(tp, TCPT_PERSIST); 1019 tp->t_rxtshift = 0; 1020 } 1021 } 1022 #endif 1023 1024 if (TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 && 1025 tp->snd_nxt != tp->snd_una) { 1026 TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); 1027 if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST)) { 1028 TCP_TIMER_DISARM(tp, TCPT_PERSIST); 1029 tp->t_rxtshift = 0; 1030 } 1031 } 1032 } else 1033 if (SEQ_GT(tp->snd_nxt + len, tp->snd_max)) 1034 tp->snd_max = tp->snd_nxt + len; 1035 1036 /* 1037 * Trace. 1038 */ 1039 if (so->so_options & SO_DEBUG) 1040 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, caddr_t), 0, 1041 len); 1042 1043 /* 1044 * Fill in IP length and desired time to live and 1045 * send to IP level. There should be a better way 1046 * to handle ttl and tos; we could keep them in 1047 * the template, but need a way to checksum without them. 1048 */ 1049 1050 #ifdef TCP_ECN 1051 /* 1052 * if peer is ECN capable, set the ECT bit in the IP header. 1053 * but don't set ECT for a pure ack, a retransmit or a window probe. 1054 */ 1055 needect = 0; 1056 if (tcp_do_ecn && (tp->t_flags & TF_ECN_PERMIT)) { 1057 if (len == 0 || SEQ_LT(tp->snd_nxt, tp->snd_max) || 1058 (tp->t_force && len == 1)) { 1059 /* don't set ECT */ 1060 } else { 1061 needect = 1; 1062 tcpstat.tcps_ecn_sndect++; 1063 } 1064 } 1065 #endif 1066 1067 switch (tp->pf) { 1068 case 0: /*default to PF_INET*/ 1069 #ifdef INET 1070 case AF_INET: 1071 { 1072 struct ip *ip; 1073 1074 ip = mtod(m, struct ip *); 1075 ip->ip_len = htons(m->m_pkthdr.len); 1076 packetlen = m->m_pkthdr.len; 1077 ip->ip_ttl = tp->t_inpcb->inp_ip.ip_ttl; 1078 ip->ip_tos = tp->t_inpcb->inp_ip.ip_tos; 1079 #ifdef TCP_ECN 1080 if (needect) 1081 ip->ip_tos |= IPTOS_ECN_ECT0; 1082 #endif 1083 } 1084 error = ip_output(m, tp->t_inpcb->inp_options, 1085 &tp->t_inpcb->inp_route, 1086 (ip_mtudisc ? IP_MTUDISC : 0) | 1087 (so->so_options & SO_DONTROUTE), 1088 (void *)NULL, tp->t_inpcb); 1089 break; 1090 #endif /* INET */ 1091 #ifdef INET6 1092 case AF_INET6: 1093 { 1094 struct ip6_hdr *ip6; 1095 1096 ip6 = mtod(m, struct ip6_hdr *); 1097 ip6->ip6_plen = m->m_pkthdr.len - 1098 sizeof(struct ip6_hdr); 1099 packetlen = m->m_pkthdr.len; 1100 ip6->ip6_nxt = IPPROTO_TCP; 1101 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1102 #ifdef TCP_ECN 1103 if (needect) 1104 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 1105 #endif 1106 } 1107 error = ip6_output(m, tp->t_inpcb->inp_outputopts6, 1108 &tp->t_inpcb->inp_route6, 1109 (so->so_options & SO_DONTROUTE), NULL, NULL); 1110 break; 1111 #endif /* INET6 */ 1112 } 1113 1114 #if defined(TCP_SACK) && defined(TCP_FACK) 1115 /* Update snd_awnd to reflect the new data that was sent. */ 1116 tp->snd_awnd = tcp_seq_subtract(tp->snd_max, tp->snd_fack) + 1117 tp->retran_data; 1118 #endif /* defined(TCP_SACK) && defined(TCP_FACK) */ 1119 1120 if (error) { 1121 out: 1122 if (error == ENOBUFS) { 1123 /* 1124 * If the interface queue is full, or IP cannot 1125 * get an mbuf, trigger TCP slow start. 1126 */ 1127 tp->snd_cwnd = tp->t_maxseg; 1128 return (0); 1129 } 1130 if (error == EMSGSIZE) { 1131 /* 1132 * ip_output() will have already fixed the route 1133 * for us. tcp_mtudisc() will, as its last action, 1134 * initiate retransmission, so it is important to 1135 * not do so here. 1136 */ 1137 tcp_mtudisc(tp->t_inpcb, -1); 1138 return (0); 1139 } 1140 if ((error == EHOSTUNREACH || error == ENETDOWN) && 1141 TCPS_HAVERCVDSYN(tp->t_state)) { 1142 tp->t_softerror = error; 1143 return (0); 1144 } 1145 1146 /* Restart the delayed ACK timer, if necessary. */ 1147 if (tp->t_flags & TF_DELACK) 1148 TCP_RESTART_DELACK(tp); 1149 1150 return (error); 1151 } 1152 1153 if (packetlen > tp->t_pmtud_mtu_sent) 1154 tp->t_pmtud_mtu_sent = packetlen; 1155 1156 tcpstat.tcps_sndtotal++; 1157 if (tp->t_flags & TF_DELACK) 1158 tcpstat.tcps_delack++; 1159 1160 /* 1161 * Data sent (as far as we can tell). 1162 * If this advertises a larger window than any other segment, 1163 * then remember the size of the advertised window. 1164 * Any pending ACK has now been sent. 1165 */ 1166 if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv)) 1167 tp->rcv_adv = tp->rcv_nxt + win; 1168 tp->last_ack_sent = tp->rcv_nxt; 1169 tp->t_flags &= ~TF_ACKNOW; 1170 TCP_CLEAR_DELACK(tp); 1171 #if defined(TCP_SACK) 1172 if (sendalot && --maxburst) 1173 #else 1174 if (sendalot) 1175 #endif 1176 goto again; 1177 return (0); 1178 } 1179 1180 void 1181 tcp_setpersist(struct tcpcb *tp) 1182 { 1183 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> (1 + TCP_RTT_BASE_SHIFT); 1184 int nticks; 1185 1186 if (TCP_TIMER_ISARMED(tp, TCPT_REXMT)) 1187 panic("tcp_output REXMT"); 1188 /* 1189 * Start/restart persistance timer. 1190 */ 1191 if (t < tp->t_rttmin) 1192 t = tp->t_rttmin; 1193 TCPT_RANGESET(nticks, t * tcp_backoff[tp->t_rxtshift], 1194 TCPTV_PERSMIN, TCPTV_PERSMAX); 1195 TCP_TIMER_ARM(tp, TCPT_PERSIST, nticks); 1196 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1197 tp->t_rxtshift++; 1198 } 1199