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 * $Id: tcp_output.c,v 1.20 1996/04/15 03:46:32 davidg Exp $ 35 */ 36 37 #include <sys/param.h> 38 #include <sys/queue.h> 39 #include <sys/systm.h> 40 #include <sys/malloc.h> 41 #include <sys/mbuf.h> 42 #include <sys/protosw.h> 43 #include <sys/socket.h> 44 #include <sys/socketvar.h> 45 #include <sys/errno.h> 46 47 #include <net/route.h> 48 49 #include <netinet/in.h> 50 #include <netinet/in_systm.h> 51 #include <netinet/ip.h> 52 #include <netinet/in_pcb.h> 53 #include <netinet/ip_var.h> 54 #include <netinet/tcp.h> 55 #define TCPOUTFLAGS 56 #include <netinet/tcp_fsm.h> 57 #include <netinet/tcp_seq.h> 58 #include <netinet/tcp_timer.h> 59 #include <netinet/tcp_var.h> 60 #include <netinet/tcpip.h> 61 #ifdef TCPDEBUG 62 #include <netinet/tcp_debug.h> 63 #endif 64 65 #ifdef notyet 66 extern struct mbuf *m_copypack(); 67 #endif 68 69 70 /* 71 * Tcp output routine: figure out what should be sent and send it. 72 */ 73 int 74 tcp_output(tp) 75 register struct tcpcb *tp; 76 { 77 register struct socket *so = tp->t_inpcb->inp_socket; 78 register long len, win; 79 int off, flags, error; 80 register struct mbuf *m; 81 register struct tcpiphdr *ti; 82 u_char opt[TCP_MAXOLEN]; 83 unsigned optlen, hdrlen; 84 int idle, sendalot; 85 struct rmxp_tao *taop; 86 struct rmxp_tao tao_noncached; 87 88 /* 89 * Determine length of data that should be transmitted, 90 * and flags that will be used. 91 * If there is some data or critical controls (SYN, RST) 92 * to send, then transmit; otherwise, investigate further. 93 */ 94 idle = (tp->snd_max == tp->snd_una); 95 if (idle && tp->t_idle >= tp->t_rxtcur) 96 /* 97 * We have been idle for "a while" and no acks are 98 * expected to clock out any data we send -- 99 * slow start to get ack "clock" running again. 100 */ 101 tp->snd_cwnd = tp->t_maxseg; 102 again: 103 sendalot = 0; 104 off = tp->snd_nxt - tp->snd_una; 105 win = min(tp->snd_wnd, tp->snd_cwnd); 106 107 flags = tcp_outflags[tp->t_state]; 108 /* 109 * Get standard flags, and add SYN or FIN if requested by 'hidden' 110 * state flags. 111 */ 112 if (tp->t_flags & TF_NEEDFIN) 113 flags |= TH_FIN; 114 if (tp->t_flags & TF_NEEDSYN) 115 flags |= TH_SYN; 116 117 /* 118 * If in persist timeout with window of 0, send 1 byte. 119 * Otherwise, if window is small but nonzero 120 * and timer expired, we will send what we can 121 * and go to transmit state. 122 */ 123 if (tp->t_force) { 124 if (win == 0) { 125 /* 126 * If we still have some data to send, then 127 * clear the FIN bit. Usually this would 128 * happen below when it realizes that we 129 * aren't sending all the data. However, 130 * if we have exactly 1 byte of unset data, 131 * then it won't clear the FIN bit below, 132 * and if we are in persist state, we wind 133 * up sending the packet without recording 134 * that we sent the FIN bit. 135 * 136 * We can't just blindly clear the FIN bit, 137 * because if we don't have any more data 138 * to send then the probe will be the FIN 139 * itself. 140 */ 141 if (off < so->so_snd.sb_cc) 142 flags &= ~TH_FIN; 143 win = 1; 144 } else { 145 tp->t_timer[TCPT_PERSIST] = 0; 146 tp->t_rxtshift = 0; 147 } 148 } 149 150 len = min(so->so_snd.sb_cc, win) - off; 151 152 if ((taop = tcp_gettaocache(tp->t_inpcb)) == NULL) { 153 taop = &tao_noncached; 154 bzero(taop, sizeof(*taop)); 155 } 156 157 /* 158 * Lop off SYN bit if it has already been sent. However, if this 159 * is SYN-SENT state and if segment contains data and if we don't 160 * know that foreign host supports TAO, suppress sending segment. 161 */ 162 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 163 flags &= ~TH_SYN; 164 off--, len++; 165 if (len > 0 && tp->t_state == TCPS_SYN_SENT && 166 taop->tao_ccsent == 0) 167 return 0; 168 } 169 170 /* 171 * Be careful not to send data and/or FIN on SYN segments 172 * in cases when no CC option will be sent. 173 * This measure is needed to prevent interoperability problems 174 * with not fully conformant TCP implementations. 175 */ 176 if ((flags & TH_SYN) && 177 ((tp->t_flags & TF_NOOPT) || !(tp->t_flags & TF_REQ_CC) || 178 ((flags & TH_ACK) && !(tp->t_flags & TF_RCVD_CC)))) { 179 len = 0; 180 flags &= ~TH_FIN; 181 } 182 183 if (len < 0) { 184 /* 185 * If FIN has been sent but not acked, 186 * but we haven't been called to retransmit, 187 * len will be -1. Otherwise, window shrank 188 * after we sent into it. If window shrank to 0, 189 * cancel pending retransmit, pull snd_nxt back 190 * to (closed) window, and set the persist timer 191 * if it isn't already going. If the window didn't 192 * close completely, just wait for an ACK. 193 */ 194 len = 0; 195 if (win == 0) { 196 tp->t_timer[TCPT_REXMT] = 0; 197 tp->t_rxtshift = 0; 198 tp->snd_nxt = tp->snd_una; 199 if (tp->t_timer[TCPT_PERSIST] == 0) 200 tcp_setpersist(tp); 201 } 202 } 203 if (len > tp->t_maxseg) { 204 len = tp->t_maxseg; 205 sendalot = 1; 206 } 207 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 208 flags &= ~TH_FIN; 209 210 win = sbspace(&so->so_rcv); 211 212 /* 213 * Sender silly window avoidance. If connection is idle 214 * and can send all data, a maximum segment, 215 * at least a maximum default-size segment do it, 216 * or are forced, do it; otherwise don't bother. 217 * If peer's buffer is tiny, then send 218 * when window is at least half open. 219 * If retransmitting (possibly after persist timer forced us 220 * to send into a small window), then must resend. 221 */ 222 if (len) { 223 if (len == tp->t_maxseg) 224 goto send; 225 if ((idle || tp->t_flags & TF_NODELAY) && 226 (tp->t_flags & TF_NOPUSH) == 0 && 227 len + off >= so->so_snd.sb_cc) 228 goto send; 229 if (tp->t_force) 230 goto send; 231 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 232 goto send; 233 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 234 goto send; 235 } 236 237 /* 238 * Compare available window to amount of window 239 * known to peer (as advertised window less 240 * next expected input). If the difference is at least two 241 * max size segments, or at least 50% of the maximum possible 242 * window, then want to send a window update to peer. 243 */ 244 if (win > 0) { 245 /* 246 * "adv" is the amount we can increase the window, 247 * taking into account that we are limited by 248 * TCP_MAXWIN << tp->rcv_scale. 249 */ 250 long adv = min(win, (long)TCP_MAXWIN << tp->rcv_scale) - 251 (tp->rcv_adv - tp->rcv_nxt); 252 253 if (adv >= (long) (2 * tp->t_maxseg)) 254 goto send; 255 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 256 goto send; 257 } 258 259 /* 260 * Send if we owe peer an ACK. 261 */ 262 if (tp->t_flags & TF_ACKNOW) 263 goto send; 264 if ((flags & TH_RST) || 265 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 266 goto send; 267 if (SEQ_GT(tp->snd_up, tp->snd_una)) 268 goto send; 269 /* 270 * If our state indicates that FIN should be sent 271 * and we have not yet done so, or we're retransmitting the FIN, 272 * then we need to send. 273 */ 274 if (flags & TH_FIN && 275 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 276 goto send; 277 278 /* 279 * TCP window updates are not reliable, rather a polling protocol 280 * using ``persist'' packets is used to insure receipt of window 281 * updates. The three ``states'' for the output side are: 282 * idle not doing retransmits or persists 283 * persisting to move a small or zero window 284 * (re)transmitting and thereby not persisting 285 * 286 * tp->t_timer[TCPT_PERSIST] 287 * is set when we are in persist state. 288 * tp->t_force 289 * is set when we are called to send a persist packet. 290 * tp->t_timer[TCPT_REXMT] 291 * is set when we are retransmitting 292 * The output side is idle when both timers are zero. 293 * 294 * If send window is too small, there is data to transmit, and no 295 * retransmit or persist is pending, then go to persist state. 296 * If nothing happens soon, send when timer expires: 297 * if window is nonzero, transmit what we can, 298 * otherwise force out a byte. 299 */ 300 if (so->so_snd.sb_cc && tp->t_timer[TCPT_REXMT] == 0 && 301 tp->t_timer[TCPT_PERSIST] == 0) { 302 tp->t_rxtshift = 0; 303 tcp_setpersist(tp); 304 } 305 306 /* 307 * No reason to send a segment, just return. 308 */ 309 return (0); 310 311 send: 312 /* 313 * Before ESTABLISHED, force sending of initial options 314 * unless TCP set not to do any options. 315 * NOTE: we assume that the IP/TCP header plus TCP options 316 * always fit in a single mbuf, leaving room for a maximum 317 * link header, i.e. 318 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MHLEN 319 */ 320 optlen = 0; 321 hdrlen = sizeof (struct tcpiphdr); 322 if (flags & TH_SYN) { 323 tp->snd_nxt = tp->iss; 324 if ((tp->t_flags & TF_NOOPT) == 0) { 325 u_short mss; 326 327 opt[0] = TCPOPT_MAXSEG; 328 opt[1] = TCPOLEN_MAXSEG; 329 mss = htons((u_short) tcp_mssopt(tp)); 330 (void)memcpy(opt + 2, &mss, sizeof(mss)); 331 optlen = TCPOLEN_MAXSEG; 332 333 if ((tp->t_flags & TF_REQ_SCALE) && 334 ((flags & TH_ACK) == 0 || 335 (tp->t_flags & TF_RCVD_SCALE))) { 336 *((u_long *) (opt + optlen)) = htonl( 337 TCPOPT_NOP << 24 | 338 TCPOPT_WINDOW << 16 | 339 TCPOLEN_WINDOW << 8 | 340 tp->request_r_scale); 341 optlen += 4; 342 } 343 } 344 } 345 346 /* 347 * Send a timestamp and echo-reply if this is a SYN and our side 348 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 349 * and our peer have sent timestamps in our SYN's. 350 */ 351 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 352 (flags & TH_RST) == 0 && 353 ((flags & TH_ACK) == 0 || 354 (tp->t_flags & TF_RCVD_TSTMP))) { 355 u_long *lp = (u_long *)(opt + optlen); 356 357 /* Form timestamp option as shown in appendix A of RFC 1323. */ 358 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 359 *lp++ = htonl(tcp_now); 360 *lp = htonl(tp->ts_recent); 361 optlen += TCPOLEN_TSTAMP_APPA; 362 } 363 364 /* 365 * Send `CC-family' options if our side wants to use them (TF_REQ_CC), 366 * options are allowed (!TF_NOOPT) and it's not a RST. 367 */ 368 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 369 (flags & TH_RST) == 0) { 370 switch (flags & (TH_SYN|TH_ACK)) { 371 /* 372 * This is a normal ACK, send CC if we received CC before 373 * from our peer. 374 */ 375 case TH_ACK: 376 if (!(tp->t_flags & TF_RCVD_CC)) 377 break; 378 /*FALLTHROUGH*/ 379 380 /* 381 * We can only get here in T/TCP's SYN_SENT* state, when 382 * we're a sending a non-SYN segment without waiting for 383 * the ACK of our SYN. A check above assures that we only 384 * do this if our peer understands T/TCP. 385 */ 386 case 0: 387 opt[optlen++] = TCPOPT_NOP; 388 opt[optlen++] = TCPOPT_NOP; 389 opt[optlen++] = TCPOPT_CC; 390 opt[optlen++] = TCPOLEN_CC; 391 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 392 393 optlen += 4; 394 break; 395 396 /* 397 * This is our initial SYN, check whether we have to use 398 * CC or CC.new. 399 */ 400 case TH_SYN: 401 opt[optlen++] = TCPOPT_NOP; 402 opt[optlen++] = TCPOPT_NOP; 403 opt[optlen++] = tp->t_flags & TF_SENDCCNEW ? 404 TCPOPT_CCNEW : TCPOPT_CC; 405 opt[optlen++] = TCPOLEN_CC; 406 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 407 optlen += 4; 408 break; 409 410 /* 411 * This is a SYN,ACK; send CC and CC.echo if we received 412 * CC from our peer. 413 */ 414 case (TH_SYN|TH_ACK): 415 if (tp->t_flags & TF_RCVD_CC) { 416 opt[optlen++] = TCPOPT_NOP; 417 opt[optlen++] = TCPOPT_NOP; 418 opt[optlen++] = TCPOPT_CC; 419 opt[optlen++] = TCPOLEN_CC; 420 *(u_int32_t *)&opt[optlen] = 421 htonl(tp->cc_send); 422 optlen += 4; 423 opt[optlen++] = TCPOPT_NOP; 424 opt[optlen++] = TCPOPT_NOP; 425 opt[optlen++] = TCPOPT_CCECHO; 426 opt[optlen++] = TCPOLEN_CC; 427 *(u_int32_t *)&opt[optlen] = 428 htonl(tp->cc_recv); 429 optlen += 4; 430 } 431 break; 432 } 433 } 434 435 hdrlen += optlen; 436 437 /* 438 * Adjust data length if insertion of options will 439 * bump the packet length beyond the t_maxopd length. 440 * Clear the FIN bit because we cut off the tail of 441 * the segment. 442 */ 443 if (len + optlen > tp->t_maxopd) { 444 /* 445 * If there is still more to send, don't close the connection. 446 */ 447 flags &= ~TH_FIN; 448 len = tp->t_maxopd - optlen; 449 sendalot = 1; 450 } 451 452 /*#ifdef DIAGNOSTIC*/ 453 if (max_linkhdr + hdrlen > MHLEN) 454 panic("tcphdr too big"); 455 /*#endif*/ 456 457 /* 458 * Grab a header mbuf, attaching a copy of data to 459 * be transmitted, and initialize the header from 460 * the template for sends on this connection. 461 */ 462 if (len) { 463 if (tp->t_force && len == 1) 464 tcpstat.tcps_sndprobe++; 465 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 466 tcpstat.tcps_sndrexmitpack++; 467 tcpstat.tcps_sndrexmitbyte += len; 468 } else { 469 tcpstat.tcps_sndpack++; 470 tcpstat.tcps_sndbyte += len; 471 } 472 #ifdef notyet 473 if ((m = m_copypack(so->so_snd.sb_mb, off, 474 (int)len, max_linkhdr + hdrlen)) == 0) { 475 error = ENOBUFS; 476 goto out; 477 } 478 /* 479 * m_copypack left space for our hdr; use it. 480 */ 481 m->m_len += hdrlen; 482 m->m_data -= hdrlen; 483 #else 484 MGETHDR(m, M_DONTWAIT, MT_HEADER); 485 if (m == NULL) { 486 error = ENOBUFS; 487 goto out; 488 } 489 m->m_data += max_linkhdr; 490 m->m_len = hdrlen; 491 if (len <= MHLEN - hdrlen - max_linkhdr) { 492 m_copydata(so->so_snd.sb_mb, off, (int) len, 493 mtod(m, caddr_t) + hdrlen); 494 m->m_len += len; 495 } else { 496 m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len); 497 if (m->m_next == 0) { 498 (void) m_free(m); 499 error = ENOBUFS; 500 goto out; 501 } 502 } 503 #endif 504 /* 505 * If we're sending everything we've got, set PUSH. 506 * (This will keep happy those implementations which only 507 * give data to the user when a buffer fills or 508 * a PUSH comes in.) 509 */ 510 if (off + len == so->so_snd.sb_cc) 511 flags |= TH_PUSH; 512 } else { 513 if (tp->t_flags & TF_ACKNOW) 514 tcpstat.tcps_sndacks++; 515 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 516 tcpstat.tcps_sndctrl++; 517 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 518 tcpstat.tcps_sndurg++; 519 else 520 tcpstat.tcps_sndwinup++; 521 522 MGETHDR(m, M_DONTWAIT, MT_HEADER); 523 if (m == NULL) { 524 error = ENOBUFS; 525 goto out; 526 } 527 m->m_data += max_linkhdr; 528 m->m_len = hdrlen; 529 } 530 m->m_pkthdr.rcvif = (struct ifnet *)0; 531 ti = mtod(m, struct tcpiphdr *); 532 if (tp->t_template == 0) 533 panic("tcp_output"); 534 (void)memcpy(ti, tp->t_template, sizeof (struct tcpiphdr)); 535 536 /* 537 * Fill in fields, remembering maximum advertised 538 * window for use in delaying messages about window sizes. 539 * If resending a FIN, be sure not to use a new sequence number. 540 */ 541 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 542 tp->snd_nxt == tp->snd_max) 543 tp->snd_nxt--; 544 /* 545 * If we are doing retransmissions, then snd_nxt will 546 * not reflect the first unsent octet. For ACK only 547 * packets, we do not want the sequence number of the 548 * retransmitted packet, we want the sequence number 549 * of the next unsent octet. So, if there is no data 550 * (and no SYN or FIN), use snd_max instead of snd_nxt 551 * when filling in ti_seq. But if we are in persist 552 * state, snd_max might reflect one byte beyond the 553 * right edge of the window, so use snd_nxt in that 554 * case, since we know we aren't doing a retransmission. 555 * (retransmit and persist are mutually exclusive...) 556 */ 557 if (len || (flags & (TH_SYN|TH_FIN)) || tp->t_timer[TCPT_PERSIST]) 558 ti->ti_seq = htonl(tp->snd_nxt); 559 else 560 ti->ti_seq = htonl(tp->snd_max); 561 ti->ti_ack = htonl(tp->rcv_nxt); 562 if (optlen) { 563 bcopy(opt, ti + 1, optlen); 564 ti->ti_off = (sizeof (struct tcphdr) + optlen) >> 2; 565 } 566 ti->ti_flags = flags; 567 /* 568 * Calculate receive window. Don't shrink window, 569 * but avoid silly window syndrome. 570 */ 571 if (win < (long)(so->so_rcv.sb_hiwat / 4) && win < (long)tp->t_maxseg) 572 win = 0; 573 if (win > (long)TCP_MAXWIN << tp->rcv_scale) 574 win = (long)TCP_MAXWIN << tp->rcv_scale; 575 if (win < (long)(tp->rcv_adv - tp->rcv_nxt)) 576 win = (long)(tp->rcv_adv - tp->rcv_nxt); 577 ti->ti_win = htons((u_short) (win>>tp->rcv_scale)); 578 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 579 ti->ti_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 580 ti->ti_flags |= TH_URG; 581 } else 582 /* 583 * If no urgent pointer to send, then we pull 584 * the urgent pointer to the left edge of the send window 585 * so that it doesn't drift into the send window on sequence 586 * number wraparound. 587 */ 588 tp->snd_up = tp->snd_una; /* drag it along */ 589 590 /* 591 * Put TCP length in extended header, and then 592 * checksum extended header and data. 593 */ 594 if (len + optlen) 595 ti->ti_len = htons((u_short)(sizeof (struct tcphdr) + 596 optlen + len)); 597 ti->ti_sum = in_cksum(m, (int)(hdrlen + len)); 598 599 /* 600 * In transmit state, time the transmission and arrange for 601 * the retransmit. In persist state, just set snd_max. 602 */ 603 if (tp->t_force == 0 || tp->t_timer[TCPT_PERSIST] == 0) { 604 tcp_seq startseq = tp->snd_nxt; 605 606 /* 607 * Advance snd_nxt over sequence space of this segment. 608 */ 609 if (flags & (TH_SYN|TH_FIN)) { 610 if (flags & TH_SYN) 611 tp->snd_nxt++; 612 if (flags & TH_FIN) { 613 tp->snd_nxt++; 614 tp->t_flags |= TF_SENTFIN; 615 } 616 } 617 tp->snd_nxt += len; 618 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 619 tp->snd_max = tp->snd_nxt; 620 /* 621 * Time this transmission if not a retransmission and 622 * not currently timing anything. 623 */ 624 if (tp->t_rtt == 0) { 625 tp->t_rtt = 1; 626 tp->t_rtseq = startseq; 627 tcpstat.tcps_segstimed++; 628 } 629 } 630 631 /* 632 * Set retransmit timer if not currently set, 633 * and not doing an ack or a keep-alive probe. 634 * Initial value for retransmit timer is smoothed 635 * round-trip time + 2 * round-trip time variance. 636 * Initialize shift counter which is used for backoff 637 * of retransmit time. 638 */ 639 if (tp->t_timer[TCPT_REXMT] == 0 && 640 tp->snd_nxt != tp->snd_una) { 641 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 642 if (tp->t_timer[TCPT_PERSIST]) { 643 tp->t_timer[TCPT_PERSIST] = 0; 644 tp->t_rxtshift = 0; 645 } 646 } 647 } else 648 if (SEQ_GT(tp->snd_nxt + len, tp->snd_max)) 649 tp->snd_max = tp->snd_nxt + len; 650 651 #ifdef TCPDEBUG 652 /* 653 * Trace. 654 */ 655 if (so->so_options & SO_DEBUG) 656 tcp_trace(TA_OUTPUT, tp->t_state, tp, ti, 0); 657 #endif 658 659 /* 660 * Fill in IP length and desired time to live and 661 * send to IP level. There should be a better way 662 * to handle ttl and tos; we could keep them in 663 * the template, but need a way to checksum without them. 664 */ 665 m->m_pkthdr.len = hdrlen + len; 666 #ifdef TUBA 667 if (tp->t_tuba_pcb) 668 error = tuba_output(m, tp); 669 else 670 #endif 671 { 672 #if 1 673 struct rtentry *rt; 674 #endif 675 ((struct ip *)ti)->ip_len = m->m_pkthdr.len; 676 ((struct ip *)ti)->ip_ttl = tp->t_inpcb->inp_ip.ip_ttl; /* XXX */ 677 ((struct ip *)ti)->ip_tos = tp->t_inpcb->inp_ip.ip_tos; /* XXX */ 678 #if 1 679 /* 680 * See if we should do MTU discovery. We do it only if the following 681 * are true: 682 * 1) we have a valid route to the destination 683 * 2) the MTU is not locked (if it is, then discovery has been 684 * disabled) 685 */ 686 if ((rt = tp->t_inpcb->inp_route.ro_rt) 687 && rt->rt_flags & RTF_UP 688 && !(rt->rt_rmx.rmx_locks & RTV_MTU)) { 689 ((struct ip *)ti)->ip_off |= IP_DF; 690 } 691 #endif 692 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, 693 so->so_options & SO_DONTROUTE, 0); 694 } 695 if (error) { 696 out: 697 if (error == ENOBUFS) { 698 tcp_quench(tp->t_inpcb, 0); 699 return (0); 700 } 701 #if 1 702 if (error == EMSGSIZE) { 703 /* 704 * ip_output() will have already fixed the route 705 * for us. tcp_mtudisc() will, as its last action, 706 * initiate retransmission, so it is important to 707 * not do so here. 708 */ 709 tcp_mtudisc(tp->t_inpcb, 0); 710 return 0; 711 } 712 #endif 713 if ((error == EHOSTUNREACH || error == ENETDOWN) 714 && TCPS_HAVERCVDSYN(tp->t_state)) { 715 tp->t_softerror = error; 716 return (0); 717 } 718 return (error); 719 } 720 tcpstat.tcps_sndtotal++; 721 722 /* 723 * Data sent (as far as we can tell). 724 * If this advertises a larger window than any other segment, 725 * then remember the size of the advertised window. 726 * Any pending ACK has now been sent. 727 */ 728 if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv)) 729 tp->rcv_adv = tp->rcv_nxt + win; 730 tp->last_ack_sent = tp->rcv_nxt; 731 tp->t_flags &= ~(TF_ACKNOW|TF_DELACK); 732 if (sendalot) 733 goto again; 734 return (0); 735 } 736 737 void 738 tcp_setpersist(tp) 739 register struct tcpcb *tp; 740 { 741 register t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 742 743 if (tp->t_timer[TCPT_REXMT]) 744 panic("tcp_output REXMT"); 745 /* 746 * Start/restart persistance timer. 747 */ 748 TCPT_RANGESET(tp->t_timer[TCPT_PERSIST], 749 t * tcp_backoff[tp->t_rxtshift], 750 TCPTV_PERSMIN, TCPTV_PERSMAX); 751 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 752 tp->t_rxtshift++; 753 } 754