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sys/netinet/tcp_output.c
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1 /* 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by the University of 16 * California, Berkeley and its contributors. 17 * 4. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 * 33 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95 34 * $FreeBSD: src/sys/netinet/tcp_output.c,v 1.21.2.5 1999/09/05 08:18:42 peter Exp $ 35 */ 36 37 #include "opt_tcpdebug.h" 38 39 #include <stddef.h> 40 41 #include <sys/param.h> 42 #include <sys/queue.h> 43 #include <sys/systm.h> 44 #include <sys/malloc.h> 45 #include <sys/mbuf.h> 46 #include <sys/protosw.h> 47 #include <sys/socket.h> 48 #include <sys/socketvar.h> 49 #include <sys/errno.h> 50 51 #include <net/route.h> 52 53 #include <netinet/in.h> 54 #include <netinet/in_systm.h> 55 #include <netinet/ip.h> 56 #include <netinet/in_pcb.h> 57 #include <netinet/ip_var.h> 58 #include <netinet/tcp.h> 59 #define TCPOUTFLAGS 60 #include <netinet/tcp_fsm.h> 61 #include <netinet/tcp_seq.h> 62 #include <netinet/tcp_timer.h> 63 #include <netinet/tcp_var.h> 64 #include <netinet/tcpip.h> 65 #ifdef TCPDEBUG 66 #include <netinet/tcp_debug.h> 67 #endif 68 69 #ifdef notyet 70 extern struct mbuf *m_copypack(); 71 #endif 72 73 74 /* 75 * Tcp output routine: figure out what should be sent and send it. 76 */ 77 int 78 tcp_output(tp) 79 register struct tcpcb *tp; 80 { 81 register struct socket *so = tp->t_inpcb->inp_socket; 82 register long len, win; 83 int off, flags, error; 84 register struct mbuf *m; 85 register struct tcpiphdr *ti; 86 u_char opt[TCP_MAXOLEN]; 87 unsigned ipoptlen, optlen, hdrlen; 88 int idle, sendalot; 89 struct rmxp_tao *taop; 90 struct rmxp_tao tao_noncached; 91 92 /* 93 * Determine length of data that should be transmitted, 94 * and flags that will be used. 95 * If there is some data or critical controls (SYN, RST) 96 * to send, then transmit; otherwise, investigate further. 97 */ 98 idle = (tp->snd_max == tp->snd_una); 99 if (idle && tp->t_idle >= tp->t_rxtcur) 100 /* 101 * We have been idle for "a while" and no acks are 102 * expected to clock out any data we send -- 103 * slow start to get ack "clock" running again. 104 */ 105 tp->snd_cwnd = tp->t_maxseg; 106 again: 107 sendalot = 0; 108 off = tp->snd_nxt - tp->snd_una; 109 win = min(tp->snd_wnd, tp->snd_cwnd); 110 111 flags = tcp_outflags[tp->t_state]; 112 /* 113 * Get standard flags, and add SYN or FIN if requested by 'hidden' 114 * state flags. 115 */ 116 if (tp->t_flags & TF_NEEDFIN) 117 flags |= TH_FIN; 118 if (tp->t_flags & TF_NEEDSYN) 119 flags |= TH_SYN; 120 121 /* 122 * If in persist timeout with window of 0, send 1 byte. 123 * Otherwise, if window is small but nonzero 124 * and timer expired, we will send what we can 125 * and go to transmit state. 126 */ 127 if (tp->t_force) { 128 if (win == 0) { 129 /* 130 * If we still have some data to send, then 131 * clear the FIN bit. Usually this would 132 * happen below when it realizes that we 133 * aren't sending all the data. However, 134 * if we have exactly 1 byte of unset data, 135 * then it won't clear the FIN bit below, 136 * and if we are in persist state, we wind 137 * up sending the packet without recording 138 * that we sent the FIN bit. 139 * 140 * We can't just blindly clear the FIN bit, 141 * because if we don't have any more data 142 * to send then the probe will be the FIN 143 * itself. 144 */ 145 if (off < so->so_snd.sb_cc) 146 flags &= ~TH_FIN; 147 win = 1; 148 } else { 149 tp->t_timer[TCPT_PERSIST] = 0; 150 tp->t_rxtshift = 0; 151 } 152 } 153 154 len = min(so->so_snd.sb_cc, win) - off; 155 156 if ((taop = tcp_gettaocache(tp->t_inpcb)) == NULL) { 157 taop = &tao_noncached; 158 bzero(taop, sizeof(*taop)); 159 } 160 161 /* 162 * Lop off SYN bit if it has already been sent. However, if this 163 * is SYN-SENT state and if segment contains data and if we don't 164 * know that foreign host supports TAO, suppress sending segment. 165 */ 166 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 167 flags &= ~TH_SYN; 168 off--, len++; 169 if (len > 0 && tp->t_state == TCPS_SYN_SENT && 170 taop->tao_ccsent == 0) 171 return 0; 172 } 173 174 /* 175 * Be careful not to send data and/or FIN on SYN segments 176 * in cases when no CC option will be sent. 177 * This measure is needed to prevent interoperability problems 178 * with not fully conformant TCP implementations. 179 */ 180 if ((flags & TH_SYN) && 181 ((tp->t_flags & TF_NOOPT) || !(tp->t_flags & TF_REQ_CC) || 182 ((flags & TH_ACK) && !(tp->t_flags & TF_RCVD_CC)))) { 183 len = 0; 184 flags &= ~TH_FIN; 185 } 186 187 if (len < 0) { 188 /* 189 * If FIN has been sent but not acked, 190 * but we haven't been called to retransmit, 191 * len will be -1. Otherwise, window shrank 192 * after we sent into it. If window shrank to 0, 193 * cancel pending retransmit, pull snd_nxt back 194 * to (closed) window, and set the persist timer 195 * if it isn't already going. If the window didn't 196 * close completely, just wait for an ACK. 197 */ 198 len = 0; 199 if (win == 0) { 200 tp->t_timer[TCPT_REXMT] = 0; 201 tp->t_rxtshift = 0; 202 tp->snd_nxt = tp->snd_una; 203 if (tp->t_timer[TCPT_PERSIST] == 0) 204 tcp_setpersist(tp); 205 } 206 } 207 if (len > tp->t_maxseg) { 208 len = tp->t_maxseg; 209 sendalot = 1; 210 } 211 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 212 flags &= ~TH_FIN; 213 214 win = sbspace(&so->so_rcv); 215 216 /* 217 * Sender silly window avoidance. If connection is idle 218 * and can send all data, a maximum segment, 219 * at least a maximum default-size segment do it, 220 * or are forced, do it; otherwise don't bother. 221 * If peer's buffer is tiny, then send 222 * when window is at least half open. 223 * If retransmitting (possibly after persist timer forced us 224 * to send into a small window), then must resend. 225 */ 226 if (len) { 227 if (len == tp->t_maxseg) 228 goto send; 229 if ((idle || tp->t_flags & TF_NODELAY) && 230 (tp->t_flags & TF_NOPUSH) == 0 && 231 len + off >= so->so_snd.sb_cc) 232 goto send; 233 if (tp->t_force) 234 goto send; 235 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 236 goto send; 237 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 238 goto send; 239 } 240 241 /* 242 * Compare available window to amount of window 243 * known to peer (as advertised window less 244 * next expected input). If the difference is at least two 245 * max size segments, or at least 50% of the maximum possible 246 * window, then want to send a window update to peer. 247 */ 248 if (win > 0) { 249 /* 250 * "adv" is the amount we can increase the window, 251 * taking into account that we are limited by 252 * TCP_MAXWIN << tp->rcv_scale. 253 */ 254 long adv = min(win, (long)TCP_MAXWIN << tp->rcv_scale) - 255 (tp->rcv_adv - tp->rcv_nxt); 256 257 if (adv >= (long) (2 * tp->t_maxseg)) 258 goto send; 259 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 260 goto send; 261 } 262 263 /* 264 * Send if we owe peer an ACK. 265 */ 266 if (tp->t_flags & TF_ACKNOW) 267 goto send; 268 if ((flags & TH_RST) || 269 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 270 goto send; 271 if (SEQ_GT(tp->snd_up, tp->snd_una)) 272 goto send; 273 /* 274 * If our state indicates that FIN should be sent 275 * and we have not yet done so, or we're retransmitting the FIN, 276 * then we need to send. 277 */ 278 if (flags & TH_FIN && 279 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 280 goto send; 281 282 /* 283 * TCP window updates are not reliable, rather a polling protocol 284 * using ``persist'' packets is used to insure receipt of window 285 * updates. The three ``states'' for the output side are: 286 * idle not doing retransmits or persists 287 * persisting to move a small or zero window 288 * (re)transmitting and thereby not persisting 289 * 290 * tp->t_timer[TCPT_PERSIST] 291 * is set when we are in persist state. 292 * tp->t_force 293 * is set when we are called to send a persist packet. 294 * tp->t_timer[TCPT_REXMT] 295 * is set when we are retransmitting 296 * The output side is idle when both timers are zero. 297 * 298 * If send window is too small, there is data to transmit, and no 299 * retransmit or persist is pending, then go to persist state. 300 * If nothing happens soon, send when timer expires: 301 * if window is nonzero, transmit what we can, 302 * otherwise force out a byte. 303 */ 304 if (so->so_snd.sb_cc && tp->t_timer[TCPT_REXMT] == 0 && 305 tp->t_timer[TCPT_PERSIST] == 0) { 306 tp->t_rxtshift = 0; 307 tcp_setpersist(tp); 308 } 309 310 /* 311 * No reason to send a segment, just return. 312 */ 313 return (0); 314 315 send: 316 /* 317 * Before ESTABLISHED, force sending of initial options 318 * unless TCP set not to do any options. 319 * NOTE: we assume that the IP/TCP header plus TCP options 320 * always fit in a single mbuf, leaving room for a maximum 321 * link header, i.e. 322 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MHLEN 323 */ 324 optlen = 0; 325 hdrlen = sizeof (struct tcpiphdr); 326 if (flags & TH_SYN) { 327 tp->snd_nxt = tp->iss; 328 if ((tp->t_flags & TF_NOOPT) == 0) { 329 u_short mss; 330 331 opt[0] = TCPOPT_MAXSEG; 332 opt[1] = TCPOLEN_MAXSEG; 333 mss = htons((u_short) tcp_mssopt(tp)); 334 (void)memcpy(opt + 2, &mss, sizeof(mss)); 335 optlen = TCPOLEN_MAXSEG; 336 337 if ((tp->t_flags & TF_REQ_SCALE) && 338 ((flags & TH_ACK) == 0 || 339 (tp->t_flags & TF_RCVD_SCALE))) { 340 *((u_long *) (opt + optlen)) = htonl( 341 TCPOPT_NOP << 24 | 342 TCPOPT_WINDOW << 16 | 343 TCPOLEN_WINDOW << 8 | 344 tp->request_r_scale); 345 optlen += 4; 346 } 347 } 348 } 349 350 /* 351 * Send a timestamp and echo-reply if this is a SYN and our side 352 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 353 * and our peer have sent timestamps in our SYN's. 354 */ 355 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 356 (flags & TH_RST) == 0 && 357 ((flags & TH_ACK) == 0 || 358 (tp->t_flags & TF_RCVD_TSTMP))) { 359 u_long *lp = (u_long *)(opt + optlen); 360 361 /* Form timestamp option as shown in appendix A of RFC 1323. */ 362 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 363 *lp++ = htonl(tcp_now); 364 *lp = htonl(tp->ts_recent); 365 optlen += TCPOLEN_TSTAMP_APPA; 366 } 367 368 /* 369 * Send `CC-family' options if our side wants to use them (TF_REQ_CC), 370 * options are allowed (!TF_NOOPT) and it's not a RST. 371 */ 372 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 373 (flags & TH_RST) == 0) { 374 switch (flags & (TH_SYN|TH_ACK)) { 375 /* 376 * This is a normal ACK, send CC if we received CC before 377 * from our peer. 378 */ 379 case TH_ACK: 380 if (!(tp->t_flags & TF_RCVD_CC)) 381 break; 382 /*FALLTHROUGH*/ 383 384 /* 385 * We can only get here in T/TCP's SYN_SENT* state, when 386 * we're a sending a non-SYN segment without waiting for 387 * the ACK of our SYN. A check above assures that we only 388 * do this if our peer understands T/TCP. 389 */ 390 case 0: 391 opt[optlen++] = TCPOPT_NOP; 392 opt[optlen++] = TCPOPT_NOP; 393 opt[optlen++] = TCPOPT_CC; 394 opt[optlen++] = TCPOLEN_CC; 395 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 396 397 optlen += 4; 398 break; 399 400 /* 401 * This is our initial SYN, check whether we have to use 402 * CC or CC.new. 403 */ 404 case TH_SYN: 405 opt[optlen++] = TCPOPT_NOP; 406 opt[optlen++] = TCPOPT_NOP; 407 opt[optlen++] = tp->t_flags & TF_SENDCCNEW ? 408 TCPOPT_CCNEW : TCPOPT_CC; 409 opt[optlen++] = TCPOLEN_CC; 410 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 411 optlen += 4; 412 break; 413 414 /* 415 * This is a SYN,ACK; send CC and CC.echo if we received 416 * CC from our peer. 417 */ 418 case (TH_SYN|TH_ACK): 419 if (tp->t_flags & TF_RCVD_CC) { 420 opt[optlen++] = TCPOPT_NOP; 421 opt[optlen++] = TCPOPT_NOP; 422 opt[optlen++] = TCPOPT_CC; 423 opt[optlen++] = TCPOLEN_CC; 424 *(u_int32_t *)&opt[optlen] = 425 htonl(tp->cc_send); 426 optlen += 4; 427 opt[optlen++] = TCPOPT_NOP; 428 opt[optlen++] = TCPOPT_NOP; 429 opt[optlen++] = TCPOPT_CCECHO; 430 opt[optlen++] = TCPOLEN_CC; 431 *(u_int32_t *)&opt[optlen] = 432 htonl(tp->cc_recv); 433 optlen += 4; 434 } 435 break; 436 } 437 } 438 439 hdrlen += optlen; 440 441 if (tp->t_inpcb->inp_options) { 442 ipoptlen = tp->t_inpcb->inp_options->m_len - 443 offsetof(struct ipoption, ipopt_list); 444 } else { 445 ipoptlen = 0; 446 } 447 448 /* 449 * Adjust data length if insertion of options will 450 * bump the packet length beyond the t_maxopd length. 451 * Clear the FIN bit because we cut off the tail of 452 * the segment. 453 */ 454 if (len + optlen + ipoptlen > tp->t_maxopd) { 455 /* 456 * If there is still more to send, don't close the connection. 457 */ 458 flags &= ~TH_FIN; 459 len = tp->t_maxopd - optlen - ipoptlen; 460 sendalot = 1; 461 } 462 463 /*#ifdef DIAGNOSTIC*/ 464 if (max_linkhdr + hdrlen > MHLEN) 465 panic("tcphdr too big"); 466 /*#endif*/ 467 468 /* 469 * Grab a header mbuf, attaching a copy of data to 470 * be transmitted, and initialize the header from 471 * the template for sends on this connection. 472 */ 473 if (len) { 474 if (tp->t_force && len == 1) 475 tcpstat.tcps_sndprobe++; 476 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 477 tcpstat.tcps_sndrexmitpack++; 478 tcpstat.tcps_sndrexmitbyte += len; 479 } else { 480 tcpstat.tcps_sndpack++; 481 tcpstat.tcps_sndbyte += len; 482 } 483 #ifdef notyet 484 if ((m = m_copypack(so->so_snd.sb_mb, off, 485 (int)len, max_linkhdr + hdrlen)) == 0) { 486 error = ENOBUFS; 487 goto out; 488 } 489 /* 490 * m_copypack left space for our hdr; use it. 491 */ 492 m->m_len += hdrlen; 493 m->m_data -= hdrlen; 494 #else 495 MGETHDR(m, M_DONTWAIT, MT_HEADER); 496 if (m == NULL) { 497 error = ENOBUFS; 498 goto out; 499 } 500 m->m_data += max_linkhdr; 501 m->m_len = hdrlen; 502 if (len <= MHLEN - hdrlen - max_linkhdr) { 503 m_copydata(so->so_snd.sb_mb, off, (int) len, 504 mtod(m, caddr_t) + hdrlen); 505 m->m_len += len; 506 } else { 507 m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len); 508 if (m->m_next == 0) { 509 (void) m_free(m); 510 error = ENOBUFS; 511 goto out; 512 } 513 } 514 #endif 515 /* 516 * If we're sending everything we've got, set PUSH. 517 * (This will keep happy those implementations which only 518 * give data to the user when a buffer fills or 519 * a PUSH comes in.) 520 */ 521 if (off + len == so->so_snd.sb_cc) 522 flags |= TH_PUSH; 523 } else { 524 if (tp->t_flags & TF_ACKNOW) 525 tcpstat.tcps_sndacks++; 526 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 527 tcpstat.tcps_sndctrl++; 528 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 529 tcpstat.tcps_sndurg++; 530 else 531 tcpstat.tcps_sndwinup++; 532 533 MGETHDR(m, M_DONTWAIT, MT_HEADER); 534 if (m == NULL) { 535 error = ENOBUFS; 536 goto out; 537 } 538 m->m_data += max_linkhdr; 539 m->m_len = hdrlen; 540 } 541 m->m_pkthdr.rcvif = (struct ifnet *)0; 542 ti = mtod(m, struct tcpiphdr *); 543 if (tp->t_template == 0) 544 panic("tcp_output"); 545 (void)memcpy(ti, tp->t_template, sizeof (struct tcpiphdr)); 546 547 /* 548 * Fill in fields, remembering maximum advertised 549 * window for use in delaying messages about window sizes. 550 * If resending a FIN, be sure not to use a new sequence number. 551 */ 552 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 553 tp->snd_nxt == tp->snd_max) 554 tp->snd_nxt--; 555 /* 556 * If we are doing retransmissions, then snd_nxt will 557 * not reflect the first unsent octet. For ACK only 558 * packets, we do not want the sequence number of the 559 * retransmitted packet, we want the sequence number 560 * of the next unsent octet. So, if there is no data 561 * (and no SYN or FIN), use snd_max instead of snd_nxt 562 * when filling in ti_seq. But if we are in persist 563 * state, snd_max might reflect one byte beyond the 564 * right edge of the window, so use snd_nxt in that 565 * case, since we know we aren't doing a retransmission. 566 * (retransmit and persist are mutually exclusive...) 567 */ 568 if (len || (flags & (TH_SYN|TH_FIN)) || tp->t_timer[TCPT_PERSIST]) 569 ti->ti_seq = htonl(tp->snd_nxt); 570 else 571 ti->ti_seq = htonl(tp->snd_max); 572 ti->ti_ack = htonl(tp->rcv_nxt); 573 if (optlen) { 574 bcopy(opt, ti + 1, optlen); 575 ti->ti_off = (sizeof (struct tcphdr) + optlen) >> 2; 576 } 577 ti->ti_flags = flags; 578 /* 579 * Calculate receive window. Don't shrink window, 580 * but avoid silly window syndrome. 581 */ 582 if (win < (long)(so->so_rcv.sb_hiwat / 4) && win < (long)tp->t_maxseg) 583 win = 0; 584 if (win < (long)(tp->rcv_adv - tp->rcv_nxt)) 585 win = (long)(tp->rcv_adv - tp->rcv_nxt); 586 if (win > (long)TCP_MAXWIN << tp->rcv_scale) 587 win = (long)TCP_MAXWIN << tp->rcv_scale; 588 ti->ti_win = htons((u_short) (win>>tp->rcv_scale)); 589 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 590 ti->ti_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 591 ti->ti_flags |= TH_URG; 592 } else 593 /* 594 * If no urgent pointer to send, then we pull 595 * the urgent pointer to the left edge of the send window 596 * so that it doesn't drift into the send window on sequence 597 * number wraparound. 598 */ 599 tp->snd_up = tp->snd_una; /* drag it along */ 600 601 /* 602 * Put TCP length in extended header, and then 603 * checksum extended header and data. 604 */ 605 if (len + optlen) 606 ti->ti_len = htons((u_short)(sizeof (struct tcphdr) + 607 optlen + len)); 608 ti->ti_sum = in_cksum(m, (int)(hdrlen + len)); 609 610 /* 611 * In transmit state, time the transmission and arrange for 612 * the retransmit. In persist state, just set snd_max. 613 */ 614 if (tp->t_force == 0 || tp->t_timer[TCPT_PERSIST] == 0) { 615 tcp_seq startseq = tp->snd_nxt; 616 617 /* 618 * Advance snd_nxt over sequence space of this segment. 619 */ 620 if (flags & (TH_SYN|TH_FIN)) { 621 if (flags & TH_SYN) 622 tp->snd_nxt++; 623 if (flags & TH_FIN) { 624 tp->snd_nxt++; 625 tp->t_flags |= TF_SENTFIN; 626 } 627 } 628 tp->snd_nxt += len; 629 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 630 tp->snd_max = tp->snd_nxt; 631 /* 632 * Time this transmission if not a retransmission and 633 * not currently timing anything. 634 */ 635 if (tp->t_rtt == 0) { 636 tp->t_rtt = 1; 637 tp->t_rtseq = startseq; 638 tcpstat.tcps_segstimed++; 639 } 640 } 641 642 /* 643 * Set retransmit timer if not currently set, 644 * and not doing an ack or a keep-alive probe. 645 * Initial value for retransmit timer is smoothed 646 * round-trip time + 2 * round-trip time variance. 647 * Initialize shift counter which is used for backoff 648 * of retransmit time. 649 */ 650 if (tp->t_timer[TCPT_REXMT] == 0 && 651 tp->snd_nxt != tp->snd_una) { 652 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 653 if (tp->t_timer[TCPT_PERSIST]) { 654 tp->t_timer[TCPT_PERSIST] = 0; 655 tp->t_rxtshift = 0; 656 } 657 } 658 } else 659 if (SEQ_GT(tp->snd_nxt + len, tp->snd_max)) 660 tp->snd_max = tp->snd_nxt + len; 661 662 #ifdef TCPDEBUG 663 /* 664 * Trace. 665 */ 666 if (so->so_options & SO_DEBUG) 667 tcp_trace(TA_OUTPUT, tp->t_state, tp, ti, 0); 668 #endif 669 670 /* 671 * Fill in IP length and desired time to live and 672 * send to IP level. There should be a better way 673 * to handle ttl and tos; we could keep them in 674 * the template, but need a way to checksum without them. 675 */ 676 m->m_pkthdr.len = hdrlen + len; 677 #ifdef TUBA 678 if (tp->t_tuba_pcb) 679 error = tuba_output(m, tp); 680 else 681 #endif 682 { 683 #if 1 684 struct rtentry *rt; 685 #endif 686 ((struct ip *)ti)->ip_len = m->m_pkthdr.len; 687 ((struct ip *)ti)->ip_ttl = tp->t_inpcb->inp_ip_ttl; /* XXX */ 688 ((struct ip *)ti)->ip_tos = tp->t_inpcb->inp_ip_tos; /* XXX */ 689 #if 1 690 /* 691 * See if we should do MTU discovery. We do it only if the following 692 * are true: 693 * 1) we have a valid route to the destination 694 * 2) the MTU is not locked (if it is, then discovery has been 695 * disabled) 696 */ 697 if ((rt = tp->t_inpcb->inp_route.ro_rt) 698 && rt->rt_flags & RTF_UP 699 && !(rt->rt_rmx.rmx_locks & RTV_MTU)) { 700 ((struct ip *)ti)->ip_off |= IP_DF; 701 } 702 #endif 703 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, 704 so->so_options & SO_DONTROUTE, 0); 705 } 706 if (error) { 707 out: 708 if (error == ENOBUFS) { 709 tcp_quench(tp->t_inpcb, 0); 710 return (0); 711 } 712 #if 1 713 if (error == EMSGSIZE) { 714 /* 715 * ip_output() will have already fixed the route 716 * for us. tcp_mtudisc() will, as its last action, 717 * initiate retransmission, so it is important to 718 * not do so here. 719 */ 720 tcp_mtudisc(tp->t_inpcb, 0); 721 return 0; 722 } 723 #endif 724 if ((error == EHOSTUNREACH || error == ENETDOWN) 725 && TCPS_HAVERCVDSYN(tp->t_state)) { 726 tp->t_softerror = error; 727 return (0); 728 } 729 return (error); 730 } 731 tcpstat.tcps_sndtotal++; 732 733 /* 734 * Data sent (as far as we can tell). 735 * If this advertises a larger window than any other segment, 736 * then remember the size of the advertised window. 737 * Any pending ACK has now been sent. 738 */ 739 if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv)) 740 tp->rcv_adv = tp->rcv_nxt + win; 741 tp->last_ack_sent = tp->rcv_nxt; 742 tp->t_flags &= ~(TF_ACKNOW|TF_DELACK); 743 if (sendalot) 744 goto again; 745 return (0); 746 } 747 748 void 749 tcp_setpersist(tp) 750 register struct tcpcb *tp; 751 { 752 register t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 753 754 if (tp->t_timer[TCPT_REXMT]) 755 panic("tcp_output REXMT"); 756 /* 757 * Start/restart persistance timer. 758 */ 759 TCPT_RANGESET(tp->t_timer[TCPT_PERSIST], 760 t * tcp_backoff[tp->t_rxtshift], 761 TCPTV_PERSMIN, TCPTV_PERSMAX); 762 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 763 tp->t_rxtshift++; 764 }
Cache object: 013f5de0eefaa656a44627323e12e3e5
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