1 /* 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993 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 8.3 (Berkeley) 12/30/93 34 * $Id: tcp_output.c,v 1.7 1995/02/09 23:13:24 wollman Exp $ 35 */ 36 37 #include <sys/param.h> 38 #include <sys/systm.h> 39 #include <sys/malloc.h> 40 #include <sys/mbuf.h> 41 #include <sys/protosw.h> 42 #include <sys/socket.h> 43 #include <sys/socketvar.h> 44 #include <sys/errno.h> 45 46 #include <net/route.h> 47 48 #include <netinet/in.h> 49 #include <netinet/in_systm.h> 50 #include <netinet/ip.h> 51 #include <netinet/in_pcb.h> 52 #include <netinet/ip_var.h> 53 #include <netinet/tcp.h> 54 #define TCPOUTFLAGS 55 #include <netinet/tcp_fsm.h> 56 #include <netinet/tcp_seq.h> 57 #include <netinet/tcp_timer.h> 58 #include <netinet/tcp_var.h> 59 #include <netinet/tcpip.h> 60 #ifdef TCPDEBUG 61 #include <netinet/tcp_debug.h> 62 #endif 63 64 #ifdef notyet 65 extern struct mbuf *m_copypack(); 66 #endif 67 68 69 /* 70 * Tcp output routine: figure out what should be sent and send it. 71 */ 72 int 73 tcp_output(tp) 74 register struct tcpcb *tp; 75 { 76 register struct socket *so = tp->t_inpcb->inp_socket; 77 register long len, win; 78 int off, flags, error; 79 register struct mbuf *m; 80 register struct tcpiphdr *ti; 81 u_char opt[TCP_MAXOLEN]; 82 unsigned optlen, hdrlen; 83 int idle, sendalot; 84 struct rmxp_tao *taop; 85 struct rmxp_tao tao_noncached; 86 87 /* 88 * Determine length of data that should be transmitted, 89 * and flags that will be used. 90 * If there is some data or critical controls (SYN, RST) 91 * to send, then transmit; otherwise, investigate further. 92 */ 93 idle = (tp->snd_max == tp->snd_una); 94 if (idle && tp->t_idle >= tp->t_rxtcur) 95 /* 96 * We have been idle for "a while" and no acks are 97 * expected to clock out any data we send -- 98 * slow start to get ack "clock" running again. 99 */ 100 tp->snd_cwnd = tp->t_maxseg; 101 again: 102 sendalot = 0; 103 off = tp->snd_nxt - tp->snd_una; 104 win = min(tp->snd_wnd, tp->snd_cwnd); 105 106 flags = tcp_outflags[tp->t_state]; 107 /* 108 * Get standard flags, and add SYN or FIN if requested by 'hidden' 109 * state flags. 110 */ 111 if (tp->t_flags & TF_NEEDFIN) 112 flags |= TH_FIN; 113 if (tp->t_flags & TF_NEEDSYN) 114 flags |= TH_SYN; 115 116 /* 117 * If in persist timeout with window of 0, send 1 byte. 118 * Otherwise, if window is small but nonzero 119 * and timer expired, we will send what we can 120 * and go to transmit state. 121 */ 122 if (tp->t_force) { 123 if (win == 0) { 124 /* 125 * If we still have some data to send, then 126 * clear the FIN bit. Usually this would 127 * happen below when it realizes that we 128 * aren't sending all the data. However, 129 * if we have exactly 1 byte of unset data, 130 * then it won't clear the FIN bit below, 131 * and if we are in persist state, we wind 132 * up sending the packet without recording 133 * that we sent the FIN bit. 134 * 135 * We can't just blindly clear the FIN bit, 136 * because if we don't have any more data 137 * to send then the probe will be the FIN 138 * itself. 139 */ 140 if (off < so->so_snd.sb_cc) 141 flags &= ~TH_FIN; 142 win = 1; 143 } else { 144 tp->t_timer[TCPT_PERSIST] = 0; 145 tp->t_rxtshift = 0; 146 } 147 } 148 149 len = min(so->so_snd.sb_cc, win) - off; 150 151 if ((taop = tcp_gettaocache(tp->t_inpcb)) == NULL) { 152 taop = &tao_noncached; 153 bzero(taop, sizeof(*taop)); 154 } 155 156 /* 157 * Lop off SYN bit if it has already been sent. However, if this 158 * is SYN-SENT state and if segment contains data and if we don't 159 * know that foreign host supports TAO, suppress sending segment. 160 */ 161 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 162 flags &= ~TH_SYN; 163 off--, len++; 164 if (len > 0 && tp->t_state == TCPS_SYN_SENT && 165 taop->tao_ccsent == 0) 166 return 0; 167 } 168 169 if (len < 0) { 170 /* 171 * If FIN has been sent but not acked, 172 * but we haven't been called to retransmit, 173 * len will be -1. Otherwise, window shrank 174 * after we sent into it. If window shrank to 0, 175 * cancel pending retransmit and pull snd_nxt 176 * back to (closed) window. We will enter persist 177 * state below. If the window didn't close completely, 178 * just wait for an ACK. 179 */ 180 len = 0; 181 if (win == 0) { 182 tp->t_timer[TCPT_REXMT] = 0; 183 tp->snd_nxt = tp->snd_una; 184 } 185 } 186 if (len > tp->t_maxseg) { 187 len = tp->t_maxseg; 188 sendalot = 1; 189 } 190 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 191 flags &= ~TH_FIN; 192 193 win = sbspace(&so->so_rcv); 194 195 /* 196 * Sender silly window avoidance. If connection is idle 197 * and can send all data, a maximum segment, 198 * at least a maximum default-size segment do it, 199 * or are forced, do it; otherwise don't bother. 200 * If peer's buffer is tiny, then send 201 * when window is at least half open. 202 * If retransmitting (possibly after persist timer forced us 203 * to send into a small window), then must resend. 204 */ 205 if (len) { 206 if (len == tp->t_maxseg) 207 goto send; 208 if ((idle || tp->t_flags & TF_NODELAY) && 209 (tp->t_flags & TF_NOPUSH) == 0 && 210 len + off >= so->so_snd.sb_cc) 211 goto send; 212 if (tp->t_force) 213 goto send; 214 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 215 goto send; 216 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 217 goto send; 218 } 219 220 /* 221 * Compare available window to amount of window 222 * known to peer (as advertised window less 223 * next expected input). If the difference is at least two 224 * max size segments, or at least 50% of the maximum possible 225 * window, then want to send a window update to peer. 226 */ 227 if (win > 0) { 228 /* 229 * "adv" is the amount we can increase the window, 230 * taking into account that we are limited by 231 * TCP_MAXWIN << tp->rcv_scale. 232 */ 233 long adv = min(win, (long)TCP_MAXWIN << tp->rcv_scale) - 234 (tp->rcv_adv - tp->rcv_nxt); 235 236 if (adv >= (long) (2 * tp->t_maxseg)) 237 goto send; 238 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 239 goto send; 240 } 241 242 /* 243 * Send if we owe peer an ACK. 244 */ 245 if (tp->t_flags & TF_ACKNOW) 246 goto send; 247 if ((flags & TH_RST) || 248 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 249 goto send; 250 if (SEQ_GT(tp->snd_up, tp->snd_una)) 251 goto send; 252 /* 253 * If our state indicates that FIN should be sent 254 * and we have not yet done so, or we're retransmitting the FIN, 255 * then we need to send. 256 */ 257 if (flags & TH_FIN && 258 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 259 goto send; 260 261 /* 262 * TCP window updates are not reliable, rather a polling protocol 263 * using ``persist'' packets is used to insure receipt of window 264 * updates. The three ``states'' for the output side are: 265 * idle not doing retransmits or persists 266 * persisting to move a small or zero window 267 * (re)transmitting and thereby not persisting 268 * 269 * tp->t_timer[TCPT_PERSIST] 270 * is set when we are in persist state. 271 * tp->t_force 272 * is set when we are called to send a persist packet. 273 * tp->t_timer[TCPT_REXMT] 274 * is set when we are retransmitting 275 * The output side is idle when both timers are zero. 276 * 277 * If send window is too small, there is data to transmit, and no 278 * retransmit or persist is pending, then go to persist state. 279 * If nothing happens soon, send when timer expires: 280 * if window is nonzero, transmit what we can, 281 * otherwise force out a byte. 282 */ 283 if (so->so_snd.sb_cc && tp->t_timer[TCPT_REXMT] == 0 && 284 tp->t_timer[TCPT_PERSIST] == 0) { 285 tp->t_rxtshift = 0; 286 tcp_setpersist(tp); 287 } 288 289 /* 290 * No reason to send a segment, just return. 291 */ 292 return (0); 293 294 send: 295 /* 296 * Before ESTABLISHED, force sending of initial options 297 * unless TCP set not to do any options. 298 * NOTE: we assume that the IP/TCP header plus TCP options 299 * always fit in a single mbuf, leaving room for a maximum 300 * link header, i.e. 301 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MHLEN 302 */ 303 optlen = 0; 304 hdrlen = sizeof (struct tcpiphdr); 305 if (flags & TH_SYN) { 306 tp->snd_nxt = tp->iss; 307 if ((tp->t_flags & TF_NOOPT) == 0) { 308 u_short mss; 309 310 opt[0] = TCPOPT_MAXSEG; 311 opt[1] = TCPOLEN_MAXSEG; 312 mss = htons((u_short) tcp_mssopt(tp)); 313 bcopy((caddr_t)&mss, (caddr_t)(opt + 2), sizeof(mss)); 314 optlen = TCPOLEN_MAXSEG; 315 316 if ((tp->t_flags & TF_REQ_SCALE) && 317 ((flags & TH_ACK) == 0 || 318 (tp->t_flags & TF_RCVD_SCALE))) { 319 *((u_long *) (opt + optlen)) = htonl( 320 TCPOPT_NOP << 24 | 321 TCPOPT_WINDOW << 16 | 322 TCPOLEN_WINDOW << 8 | 323 tp->request_r_scale); 324 optlen += 4; 325 } 326 } 327 } 328 329 /* 330 * Send a timestamp and echo-reply if this is a SYN and our side 331 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 332 * and our peer have sent timestamps in our SYN's. 333 */ 334 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 335 (flags & TH_RST) == 0 && 336 ((flags & TH_ACK) == 0 || 337 (tp->t_flags & TF_RCVD_TSTMP))) { 338 u_long *lp = (u_long *)(opt + optlen); 339 340 /* Form timestamp option as shown in appendix A of RFC 1323. */ 341 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 342 *lp++ = htonl(tcp_now); 343 *lp = htonl(tp->ts_recent); 344 optlen += TCPOLEN_TSTAMP_APPA; 345 } 346 347 /* 348 * Send `CC-family' options if our side wants to use them (TF_REQ_CC), 349 * options are allowed (!TF_NOOPT) and it's not a RST. 350 */ 351 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 352 (flags & TH_RST) == 0) { 353 switch (flags & (TH_SYN|TH_ACK)) { 354 /* 355 * This is a normal ACK, send CC if we received CC before 356 * from our peer. 357 */ 358 case TH_ACK: 359 if (!(tp->t_flags & TF_RCVD_CC)) 360 break; 361 /*FALLTHROUGH*/ 362 363 /* 364 * We can only get here in T/TCP's SYN_SENT* state, when 365 * we're a sending a non-SYN segment without waiting for 366 * the ACK of our SYN. A check above assures that we only 367 * do this if our peer understands T/TCP. 368 */ 369 case 0: 370 opt[optlen++] = TCPOPT_NOP; 371 opt[optlen++] = TCPOPT_NOP; 372 opt[optlen++] = TCPOPT_CC; 373 opt[optlen++] = TCPOLEN_CC; 374 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 375 376 optlen += 4; 377 break; 378 379 /* 380 * This is our initial SYN, check whether we have to use 381 * CC or CC.new. 382 */ 383 case TH_SYN: 384 opt[optlen++] = TCPOPT_NOP; 385 opt[optlen++] = TCPOPT_NOP; 386 387 if (taop->tao_ccsent != 0 && 388 CC_GEQ(tp->cc_send, taop->tao_ccsent)) { 389 opt[optlen++] = TCPOPT_CC; 390 taop->tao_ccsent = tp->cc_send; 391 } else { 392 opt[optlen++] = TCPOPT_CCNEW; 393 taop->tao_ccsent = 0; 394 } 395 opt[optlen++] = TCPOLEN_CC; 396 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 397 optlen += 4; 398 break; 399 400 /* 401 * This is a SYN,ACK; send CC and CC.echo if we received 402 * CC from our peer. 403 */ 404 case (TH_SYN|TH_ACK): 405 if (tp->t_flags & TF_RCVD_CC) { 406 opt[optlen++] = TCPOPT_NOP; 407 opt[optlen++] = TCPOPT_NOP; 408 opt[optlen++] = TCPOPT_CC; 409 opt[optlen++] = TCPOLEN_CC; 410 *(u_int32_t *)&opt[optlen] = 411 htonl(tp->cc_send); 412 optlen += 4; 413 opt[optlen++] = TCPOPT_NOP; 414 opt[optlen++] = TCPOPT_NOP; 415 opt[optlen++] = TCPOPT_CCECHO; 416 opt[optlen++] = TCPOLEN_CC; 417 *(u_int32_t *)&opt[optlen] = 418 htonl(tp->cc_recv); 419 optlen += 4; 420 } 421 break; 422 } 423 } 424 425 hdrlen += optlen; 426 427 /* 428 * Adjust data length if insertion of options will 429 * bump the packet length beyond the t_maxopd length. 430 * Clear the FIN bit because we cut off the tail of 431 * the segment. 432 */ 433 if (len + optlen > tp->t_maxopd) { 434 /* 435 * If there is still more to send, don't close the connection. 436 */ 437 flags &= ~TH_FIN; 438 439 len = tp->t_maxopd - optlen; 440 sendalot = 1; 441 } 442 443 /*#ifdef DIAGNOSTIC*/ 444 if (max_linkhdr + hdrlen > MHLEN) 445 panic("tcphdr too big"); 446 /*#endif*/ 447 448 /* 449 * Grab a header mbuf, attaching a copy of data to 450 * be transmitted, and initialize the header from 451 * the template for sends on this connection. 452 */ 453 if (len) { 454 if (tp->t_force && len == 1) 455 tcpstat.tcps_sndprobe++; 456 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 457 tcpstat.tcps_sndrexmitpack++; 458 tcpstat.tcps_sndrexmitbyte += len; 459 } else { 460 tcpstat.tcps_sndpack++; 461 tcpstat.tcps_sndbyte += len; 462 } 463 #ifdef notyet 464 if ((m = m_copypack(so->so_snd.sb_mb, off, 465 (int)len, max_linkhdr + hdrlen)) == 0) { 466 error = ENOBUFS; 467 goto out; 468 } 469 /* 470 * m_copypack left space for our hdr; use it. 471 */ 472 m->m_len += hdrlen; 473 m->m_data -= hdrlen; 474 #else 475 MGETHDR(m, M_DONTWAIT, MT_HEADER); 476 if (m == NULL) { 477 error = ENOBUFS; 478 goto out; 479 } 480 m->m_data += max_linkhdr; 481 m->m_len = hdrlen; 482 if (len <= MHLEN - hdrlen - max_linkhdr) { 483 m_copydata(so->so_snd.sb_mb, off, (int) len, 484 mtod(m, caddr_t) + hdrlen); 485 m->m_len += len; 486 } else { 487 m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len); 488 if (m->m_next == 0) 489 len = 0; 490 } 491 #endif 492 /* 493 * If we're sending everything we've got, set PUSH. 494 * (This will keep happy those implementations which only 495 * give data to the user when a buffer fills or 496 * a PUSH comes in.) 497 */ 498 if (off + len == so->so_snd.sb_cc) 499 flags |= TH_PUSH; 500 } else { 501 if (tp->t_flags & TF_ACKNOW) 502 tcpstat.tcps_sndacks++; 503 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 504 tcpstat.tcps_sndctrl++; 505 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 506 tcpstat.tcps_sndurg++; 507 else 508 tcpstat.tcps_sndwinup++; 509 510 MGETHDR(m, M_DONTWAIT, MT_HEADER); 511 if (m == NULL) { 512 error = ENOBUFS; 513 goto out; 514 } 515 m->m_data += max_linkhdr; 516 m->m_len = hdrlen; 517 } 518 m->m_pkthdr.rcvif = (struct ifnet *)0; 519 ti = mtod(m, struct tcpiphdr *); 520 if (tp->t_template == 0) 521 panic("tcp_output"); 522 bcopy((caddr_t)tp->t_template, (caddr_t)ti, sizeof (struct tcpiphdr)); 523 524 /* 525 * Fill in fields, remembering maximum advertised 526 * window for use in delaying messages about window sizes. 527 * If resending a FIN, be sure not to use a new sequence number. 528 */ 529 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 530 tp->snd_nxt == tp->snd_max) 531 tp->snd_nxt--; 532 /* 533 * If we are doing retransmissions, then snd_nxt will 534 * not reflect the first unsent octet. For ACK only 535 * packets, we do not want the sequence number of the 536 * retransmitted packet, we want the sequence number 537 * of the next unsent octet. So, if there is no data 538 * (and no SYN or FIN), use snd_max instead of snd_nxt 539 * when filling in ti_seq. But if we are in persist 540 * state, snd_max might reflect one byte beyond the 541 * right edge of the window, so use snd_nxt in that 542 * case, since we know we aren't doing a retransmission. 543 * (retransmit and persist are mutually exclusive...) 544 */ 545 if (len || (flags & (TH_SYN|TH_FIN)) || tp->t_timer[TCPT_PERSIST]) 546 ti->ti_seq = htonl(tp->snd_nxt); 547 else 548 ti->ti_seq = htonl(tp->snd_max); 549 ti->ti_ack = htonl(tp->rcv_nxt); 550 if (optlen) { 551 bcopy((caddr_t)opt, (caddr_t)(ti + 1), optlen); 552 ti->ti_off = (sizeof (struct tcphdr) + optlen) >> 2; 553 } 554 ti->ti_flags = flags; 555 /* 556 * Calculate receive window. Don't shrink window, 557 * but avoid silly window syndrome. 558 */ 559 if (win < (long)(so->so_rcv.sb_hiwat / 4) && win < (long)tp->t_maxseg) 560 win = 0; 561 if (win > (long)TCP_MAXWIN << tp->rcv_scale) 562 win = (long)TCP_MAXWIN << tp->rcv_scale; 563 if (win < (long)(tp->rcv_adv - tp->rcv_nxt)) 564 win = (long)(tp->rcv_adv - tp->rcv_nxt); 565 ti->ti_win = htons((u_short) (win>>tp->rcv_scale)); 566 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 567 ti->ti_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 568 ti->ti_flags |= TH_URG; 569 } else 570 /* 571 * If no urgent pointer to send, then we pull 572 * the urgent pointer to the left edge of the send window 573 * so that it doesn't drift into the send window on sequence 574 * number wraparound. 575 */ 576 tp->snd_up = tp->snd_una; /* drag it along */ 577 578 /* 579 * Put TCP length in extended header, and then 580 * checksum extended header and data. 581 */ 582 if (len + optlen) 583 ti->ti_len = htons((u_short)(sizeof (struct tcphdr) + 584 optlen + len)); 585 ti->ti_sum = in_cksum(m, (int)(hdrlen + len)); 586 587 /* 588 * In transmit state, time the transmission and arrange for 589 * the retransmit. In persist state, just set snd_max. 590 */ 591 if (tp->t_force == 0 || tp->t_timer[TCPT_PERSIST] == 0) { 592 tcp_seq startseq = tp->snd_nxt; 593 594 /* 595 * Advance snd_nxt over sequence space of this segment. 596 */ 597 if (flags & (TH_SYN|TH_FIN)) { 598 if (flags & TH_SYN) 599 tp->snd_nxt++; 600 if (flags & TH_FIN) { 601 tp->snd_nxt++; 602 tp->t_flags |= TF_SENTFIN; 603 } 604 } 605 tp->snd_nxt += len; 606 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 607 tp->snd_max = tp->snd_nxt; 608 /* 609 * Time this transmission if not a retransmission and 610 * not currently timing anything. 611 */ 612 if (tp->t_rtt == 0) { 613 tp->t_rtt = 1; 614 tp->t_rtseq = startseq; 615 tcpstat.tcps_segstimed++; 616 } 617 } 618 619 /* 620 * Set retransmit timer if not currently set, 621 * and not doing an ack or a keep-alive probe. 622 * Initial value for retransmit timer is smoothed 623 * round-trip time + 2 * round-trip time variance. 624 * Initialize shift counter which is used for backoff 625 * of retransmit time. 626 */ 627 if (tp->t_timer[TCPT_REXMT] == 0 && 628 tp->snd_nxt != tp->snd_una) { 629 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 630 if (tp->t_timer[TCPT_PERSIST]) { 631 tp->t_timer[TCPT_PERSIST] = 0; 632 tp->t_rxtshift = 0; 633 } 634 } 635 } else 636 if (SEQ_GT(tp->snd_nxt + len, tp->snd_max)) 637 tp->snd_max = tp->snd_nxt + len; 638 639 #ifdef TCPDEBUG 640 /* 641 * Trace. 642 */ 643 if (so->so_options & SO_DEBUG) 644 tcp_trace(TA_OUTPUT, tp->t_state, tp, ti, 0); 645 #endif 646 647 /* 648 * Fill in IP length and desired time to live and 649 * send to IP level. There should be a better way 650 * to handle ttl and tos; we could keep them in 651 * the template, but need a way to checksum without them. 652 */ 653 m->m_pkthdr.len = hdrlen + len; 654 #ifdef TUBA 655 if (tp->t_tuba_pcb) 656 error = tuba_output(m, tp); 657 else 658 #endif 659 { 660 ((struct ip *)ti)->ip_len = m->m_pkthdr.len; 661 ((struct ip *)ti)->ip_ttl = tp->t_inpcb->inp_ip.ip_ttl; /* XXX */ 662 ((struct ip *)ti)->ip_tos = tp->t_inpcb->inp_ip.ip_tos; /* XXX */ 663 #if BSD >= 43 664 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, 665 so->so_options & SO_DONTROUTE, 0); 666 #else 667 error = ip_output(m, (struct mbuf *)0, &tp->t_inpcb->inp_route, 668 so->so_options & SO_DONTROUTE); 669 #endif 670 } 671 if (error) { 672 out: 673 if (error == ENOBUFS) { 674 tcp_quench(tp->t_inpcb, 0); 675 return (0); 676 } 677 if ((error == EHOSTUNREACH || error == ENETDOWN) 678 && TCPS_HAVERCVDSYN(tp->t_state)) { 679 tp->t_softerror = error; 680 return (0); 681 } 682 return (error); 683 } 684 tcpstat.tcps_sndtotal++; 685 686 /* 687 * Data sent (as far as we can tell). 688 * If this advertises a larger window than any other segment, 689 * then remember the size of the advertised window. 690 * Any pending ACK has now been sent. 691 */ 692 if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv)) 693 tp->rcv_adv = tp->rcv_nxt + win; 694 tp->last_ack_sent = tp->rcv_nxt; 695 tp->t_flags &= ~(TF_ACKNOW|TF_DELACK); 696 if (sendalot) 697 goto again; 698 return (0); 699 } 700 701 void 702 tcp_setpersist(tp) 703 register struct tcpcb *tp; 704 { 705 register t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 706 707 if (tp->t_timer[TCPT_REXMT]) 708 panic("tcp_output REXMT"); 709 /* 710 * Start/restart persistance timer. 711 */ 712 TCPT_RANGESET(tp->t_timer[TCPT_PERSIST], 713 t * tcp_backoff[tp->t_rxtshift], 714 TCPTV_PERSMIN, TCPTV_PERSMAX); 715 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 716 tp->t_rxtshift++; 717 } 718