1 /* $NetBSD: tcp_output.c,v 1.46 1998/12/16 00:33:14 thorpej Exp $ */ 2 3 /*- 4 * Copyright (c) 1997, 1998 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Jason R. Thorpe and Kevin M. Lahey of the Numerical Aerospace Simulation 9 * Facility, NASA Ames Research Center. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 3. All advertising materials mentioning features or use of this software 20 * must display the following acknowledgement: 21 * This product includes software developed by the NetBSD 22 * Foundation, Inc. and its contributors. 23 * 4. Neither the name of The NetBSD Foundation nor the names of its 24 * contributors may be used to endorse or promote products derived 25 * from this software without specific prior written permission. 26 * 27 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 28 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 29 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 30 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 31 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 32 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 33 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 34 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 35 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 36 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 37 * POSSIBILITY OF SUCH DAMAGE. 38 */ 39 40 /* 41 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 42 * The Regents of the University of California. All rights reserved. 43 * 44 * Redistribution and use in source and binary forms, with or without 45 * modification, are permitted provided that the following conditions 46 * are met: 47 * 1. Redistributions of source code must retain the above copyright 48 * notice, this list of conditions and the following disclaimer. 49 * 2. Redistributions in binary form must reproduce the above copyright 50 * notice, this list of conditions and the following disclaimer in the 51 * documentation and/or other materials provided with the distribution. 52 * 3. All advertising materials mentioning features or use of this software 53 * must display the following acknowledgement: 54 * This product includes software developed by the University of 55 * California, Berkeley and its contributors. 56 * 4. Neither the name of the University nor the names of its contributors 57 * may be used to endorse or promote products derived from this software 58 * without specific prior written permission. 59 * 60 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 61 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 62 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 63 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 64 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 65 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 66 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 67 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 68 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 69 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 70 * SUCH DAMAGE. 71 * 72 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95 73 */ 74 75 #include <sys/param.h> 76 #include <sys/systm.h> 77 #include <sys/malloc.h> 78 #include <sys/mbuf.h> 79 #include <sys/protosw.h> 80 #include <sys/socket.h> 81 #include <sys/socketvar.h> 82 #include <sys/errno.h> 83 84 #include <net/if.h> 85 #include <net/route.h> 86 87 #include <netinet/in.h> 88 #include <netinet/in_systm.h> 89 #include <netinet/ip.h> 90 #include <netinet/in_pcb.h> 91 #include <netinet/ip_var.h> 92 #include <netinet/tcp.h> 93 #define TCPOUTFLAGS 94 #include <netinet/tcp_fsm.h> 95 #include <netinet/tcp_seq.h> 96 #include <netinet/tcp_timer.h> 97 #include <netinet/tcp_var.h> 98 #include <netinet/tcpip.h> 99 #include <netinet/tcp_debug.h> 100 101 #ifdef notyet 102 extern struct mbuf *m_copypack(); 103 #endif 104 105 #define MAX_TCPOPTLEN 32 /* max # bytes that go in options */ 106 107 /* 108 * Knob to enable Congestion Window Monitoring, and control the 109 * the burst size it allows. Default burst is 4 packets, per 110 * the Internet draft. 111 */ 112 int tcp_cwm = 0; 113 int tcp_cwm_burstsize = 4; 114 115 static __inline void tcp_segsize __P((struct tcpcb *, int *, int *)); 116 static __inline void 117 tcp_segsize(tp, txsegsizep, rxsegsizep) 118 struct tcpcb *tp; 119 int *txsegsizep, *rxsegsizep; 120 { 121 struct inpcb *inp = tp->t_inpcb; 122 struct rtentry *rt; 123 struct ifnet *ifp; 124 int size; 125 126 if ((rt = in_pcbrtentry(inp)) == NULL) { 127 size = tcp_mssdflt; 128 goto out; 129 } 130 131 ifp = rt->rt_ifp; 132 133 if (rt->rt_rmx.rmx_mtu != 0) 134 size = rt->rt_rmx.rmx_mtu - sizeof(struct tcpiphdr); 135 else if (ip_mtudisc || in_localaddr(inp->inp_faddr) || 136 ifp->if_flags & IFF_LOOPBACK) 137 size = ifp->if_mtu - sizeof(struct tcpiphdr); 138 else 139 size = tcp_mssdflt; 140 size -= (tcp_optlen(tp) + ip_optlen(tp->t_inpcb)); 141 142 out: 143 *txsegsizep = min(tp->t_peermss, size); 144 *rxsegsizep = min(tp->t_ourmss, size); 145 146 if (*txsegsizep != tp->t_segsz) { 147 /* 148 * If the new segment size is larger, we don't want to 149 * mess up the congestion window, but if it is smaller 150 * we'll have to reduce the congestion window to ensure 151 * that we don't get into trouble with initial windows 152 * and the rest. In any case, if the segment size 153 * has changed, chances are the path has, too, and 154 * our congestion window will be different. 155 */ 156 if (*txsegsizep < tp->t_segsz) { 157 tp->snd_cwnd = max((tp->snd_cwnd / tp->t_segsz) 158 * *txsegsizep, *txsegsizep); 159 tp->snd_ssthresh = max((tp->snd_ssthresh / tp->t_segsz) 160 * *txsegsizep, *txsegsizep); 161 } 162 tp->t_segsz = *txsegsizep; 163 } 164 } 165 166 /* 167 * Tcp output routine: figure out what should be sent and send it. 168 */ 169 int 170 tcp_output(tp) 171 register struct tcpcb *tp; 172 { 173 register struct socket *so = tp->t_inpcb->inp_socket; 174 register long len, win; 175 int off, flags, error; 176 register struct mbuf *m; 177 register struct tcpiphdr *ti; 178 u_char opt[MAX_TCPOPTLEN]; 179 unsigned optlen, hdrlen; 180 int idle, sendalot, txsegsize, rxsegsize; 181 int maxburst = TCP_MAXBURST; 182 183 tcp_segsize(tp, &txsegsize, &rxsegsize); 184 185 idle = (tp->snd_max == tp->snd_una); 186 187 /* 188 * Restart Window computation. From draft-floyd-incr-init-win-03: 189 * 190 * Optionally, a TCP MAY set the restart window to the 191 * minimum of the value used for the initial window and 192 * the current value of cwnd (in other words, using a 193 * larger value for the restart window should never increase 194 * the size of cwnd). 195 */ 196 if (tcp_cwm) { 197 /* 198 * Hughes/Touch/Heidemann Congestion Window Monitoring. 199 * Count the number of packets currently pending 200 * acknowledgement, and limit our congestion window 201 * to a pre-determined allowed burst size plus that count. 202 * This prevents bursting once all pending packets have 203 * been acknowledged (i.e. transmission is idle). 204 * 205 * XXX Link this to Initial Window? 206 */ 207 tp->snd_cwnd = min(tp->snd_cwnd, 208 (tcp_cwm_burstsize * txsegsize) + 209 (tp->snd_nxt - tp->snd_una)); 210 } else { 211 if (idle && tp->t_idle >= tp->t_rxtcur) { 212 /* 213 * We have been idle for "a while" and no acks are 214 * expected to clock out any data we send -- 215 * slow start to get ack "clock" running again. 216 */ 217 tp->snd_cwnd = min(tp->snd_cwnd, 218 TCP_INITIAL_WINDOW(tcp_init_win, txsegsize)); 219 } 220 } 221 222 again: 223 /* 224 * Determine length of data that should be transmitted, and 225 * flags that should be used. If there is some data or critical 226 * controls (SYN, RST) to send, then transmit; otherwise, 227 * investigate further. 228 */ 229 sendalot = 0; 230 off = tp->snd_nxt - tp->snd_una; 231 win = min(tp->snd_wnd, tp->snd_cwnd); 232 233 flags = tcp_outflags[tp->t_state]; 234 /* 235 * If in persist timeout with window of 0, send 1 byte. 236 * Otherwise, if window is small but nonzero 237 * and timer expired, we will send what we can 238 * and go to transmit state. 239 */ 240 if (tp->t_force) { 241 if (win == 0) { 242 /* 243 * If we still have some data to send, then 244 * clear the FIN bit. Usually this would 245 * happen below when it realizes that we 246 * aren't sending all the data. However, 247 * if we have exactly 1 byte of unset data, 248 * then it won't clear the FIN bit below, 249 * and if we are in persist state, we wind 250 * up sending the packet without recording 251 * that we sent the FIN bit. 252 * 253 * We can't just blindly clear the FIN bit, 254 * because if we don't have any more data 255 * to send then the probe will be the FIN 256 * itself. 257 */ 258 if (off < so->so_snd.sb_cc) 259 flags &= ~TH_FIN; 260 win = 1; 261 } else { 262 TCP_TIMER_DISARM(tp, TCPT_PERSIST); 263 tp->t_rxtshift = 0; 264 } 265 } 266 267 if (win < so->so_snd.sb_cc) { 268 len = win - off; 269 flags &= ~TH_FIN; 270 } else 271 len = so->so_snd.sb_cc - off; 272 273 if (len < 0) { 274 /* 275 * If FIN has been sent but not acked, 276 * but we haven't been called to retransmit, 277 * len will be -1. Otherwise, window shrank 278 * after we sent into it. If window shrank to 0, 279 * cancel pending retransmit, pull snd_nxt back 280 * to (closed) window, and set the persist timer 281 * if it isn't already going. If the window didn't 282 * close completely, just wait for an ACK. 283 * 284 * If we have a pending FIN, either it has already been 285 * transmitted or it is outside the window, so drop it. 286 * If the FIN has been transmitted, but this is not a 287 * retransmission, then len must be -1. Therefore we also 288 * prevent here the sending of `gratuitous FINs'. This 289 * eliminates the need to check for that case below (e.g. 290 * to back up snd_nxt before the FIN so that the sequence 291 * number is correct). 292 */ 293 len = 0; 294 flags &= ~TH_FIN; 295 if (win == 0) { 296 TCP_TIMER_DISARM(tp, TCPT_REXMT); 297 tp->t_rxtshift = 0; 298 tp->snd_nxt = tp->snd_una; 299 if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) 300 tcp_setpersist(tp); 301 } 302 } 303 if (len > txsegsize) { 304 len = txsegsize; 305 flags &= ~TH_FIN; 306 sendalot = 1; 307 } 308 309 win = sbspace(&so->so_rcv); 310 311 /* 312 * Sender silly window avoidance. If connection is idle 313 * and can send all data, a maximum segment, 314 * at least a maximum default-size segment do it, 315 * or are forced, do it; otherwise don't bother. 316 * If peer's buffer is tiny, then send 317 * when window is at least half open. 318 * If retransmitting (possibly after persist timer forced us 319 * to send into a small window), then must resend. 320 */ 321 if (len) { 322 if (len == txsegsize) 323 goto send; 324 if ((so->so_state & SS_MORETOCOME) == 0 && 325 ((idle || tp->t_flags & TF_NODELAY) && 326 len + off >= so->so_snd.sb_cc)) 327 goto send; 328 if (tp->t_force) 329 goto send; 330 if (len >= tp->max_sndwnd / 2) 331 goto send; 332 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 333 goto send; 334 } 335 336 /* 337 * Compare available window to amount of window known to peer 338 * (as advertised window less next expected input). If the 339 * difference is at least twice the size of the largest segment 340 * we expect to receive (i.e. two segments) or at least 50% of 341 * the maximum possible window, then want to send a window update 342 * to peer. 343 */ 344 if (win > 0) { 345 /* 346 * "adv" is the amount we can increase the window, 347 * taking into account that we are limited by 348 * TCP_MAXWIN << tp->rcv_scale. 349 */ 350 long adv = min(win, (long)TCP_MAXWIN << tp->rcv_scale) - 351 (tp->rcv_adv - tp->rcv_nxt); 352 353 if (adv >= (long) (2 * rxsegsize)) 354 goto send; 355 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 356 goto send; 357 } 358 359 /* 360 * Send if we owe peer an ACK. 361 */ 362 if (tp->t_flags & TF_ACKNOW) 363 goto send; 364 if (flags & (TH_SYN|TH_FIN|TH_RST)) 365 goto send; 366 if (SEQ_GT(tp->snd_up, tp->snd_una)) 367 goto send; 368 369 /* 370 * TCP window updates are not reliable, rather a polling protocol 371 * using ``persist'' packets is used to insure receipt of window 372 * updates. The three ``states'' for the output side are: 373 * idle not doing retransmits or persists 374 * persisting to move a small or zero window 375 * (re)transmitting and thereby not persisting 376 * 377 * tp->t_timer[TCPT_PERSIST] 378 * is set when we are in persist state. 379 * tp->t_force 380 * is set when we are called to send a persist packet. 381 * tp->t_timer[TCPT_REXMT] 382 * is set when we are retransmitting 383 * The output side is idle when both timers are zero. 384 * 385 * If send window is too small, there is data to transmit, and no 386 * retransmit or persist is pending, then go to persist state. 387 * If nothing happens soon, send when timer expires: 388 * if window is nonzero, transmit what we can, 389 * otherwise force out a byte. 390 */ 391 if (so->so_snd.sb_cc && TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 && 392 TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) { 393 tp->t_rxtshift = 0; 394 tcp_setpersist(tp); 395 } 396 397 /* 398 * No reason to send a segment, just return. 399 */ 400 return (0); 401 402 send: 403 /* 404 * Before ESTABLISHED, force sending of initial options 405 * unless TCP set not to do any options. 406 * NOTE: we assume that the IP/TCP header plus TCP options 407 * always fit in a single mbuf, leaving room for a maximum 408 * link header, i.e. 409 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MHLEN 410 */ 411 optlen = 0; 412 hdrlen = sizeof (struct tcpiphdr); 413 if (flags & TH_SYN) { 414 struct rtentry *rt = in_pcbrtentry(tp->t_inpcb); 415 416 tp->snd_nxt = tp->iss; 417 tp->t_ourmss = tcp_mss_to_advertise(rt != NULL ? 418 rt->rt_ifp : NULL); 419 if ((tp->t_flags & TF_NOOPT) == 0) { 420 opt[0] = TCPOPT_MAXSEG; 421 opt[1] = 4; 422 opt[2] = (tp->t_ourmss >> 8) & 0xff; 423 opt[3] = tp->t_ourmss & 0xff; 424 optlen = 4; 425 426 if ((tp->t_flags & TF_REQ_SCALE) && 427 ((flags & TH_ACK) == 0 || 428 (tp->t_flags & TF_RCVD_SCALE))) { 429 *((u_int32_t *) (opt + optlen)) = htonl( 430 TCPOPT_NOP << 24 | 431 TCPOPT_WINDOW << 16 | 432 TCPOLEN_WINDOW << 8 | 433 tp->request_r_scale); 434 optlen += 4; 435 } 436 } 437 } 438 439 /* 440 * Send a timestamp and echo-reply if this is a SYN and our side 441 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 442 * and our peer have sent timestamps in our SYN's. 443 */ 444 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 445 (flags & TH_RST) == 0 && 446 ((flags & (TH_SYN|TH_ACK)) == TH_SYN || 447 (tp->t_flags & TF_RCVD_TSTMP))) { 448 u_int32_t *lp = (u_int32_t *)(opt + optlen); 449 450 /* Form timestamp option as shown in appendix A of RFC 1323. */ 451 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 452 *lp++ = htonl(tcp_now); 453 *lp = htonl(tp->ts_recent); 454 optlen += TCPOLEN_TSTAMP_APPA; 455 } 456 457 hdrlen += optlen; 458 459 #ifdef DIAGNOSTIC 460 if (len > txsegsize) 461 panic("tcp data to be sent is larger than segment"); 462 if (max_linkhdr + hdrlen > MHLEN) 463 panic("tcphdr too big"); 464 #endif 465 466 /* 467 * Grab a header mbuf, attaching a copy of data to 468 * be transmitted, and initialize the header from 469 * the template for sends on this connection. 470 */ 471 if (len) { 472 if (tp->t_force && len == 1) 473 tcpstat.tcps_sndprobe++; 474 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 475 tcpstat.tcps_sndrexmitpack++; 476 tcpstat.tcps_sndrexmitbyte += len; 477 } else { 478 tcpstat.tcps_sndpack++; 479 tcpstat.tcps_sndbyte += len; 480 } 481 #ifdef notyet 482 if ((m = m_copypack(so->so_snd.sb_mb, off, 483 (int)len, max_linkhdr + hdrlen)) == 0) { 484 error = ENOBUFS; 485 goto out; 486 } 487 /* 488 * m_copypack left space for our hdr; use it. 489 */ 490 m->m_len += hdrlen; 491 m->m_data -= hdrlen; 492 #else 493 MGETHDR(m, M_DONTWAIT, MT_HEADER); 494 if (m == NULL) { 495 error = ENOBUFS; 496 goto out; 497 } 498 m->m_data += max_linkhdr; 499 m->m_len = hdrlen; 500 if (len <= MHLEN - hdrlen - max_linkhdr) { 501 m_copydata(so->so_snd.sb_mb, off, (int) len, 502 mtod(m, caddr_t) + hdrlen); 503 m->m_len += len; 504 } else { 505 m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len); 506 if (m->m_next == 0) { 507 m_freem(m); 508 error = ENOBUFS; 509 goto out; 510 } 511 } 512 #endif 513 /* 514 * If we're sending everything we've got, set PUSH. 515 * (This will keep happy those implementations which only 516 * give data to the user when a buffer fills or 517 * a PUSH comes in.) 518 */ 519 if (off + len == so->so_snd.sb_cc) 520 flags |= TH_PUSH; 521 } else { 522 if (tp->t_flags & TF_ACKNOW) 523 tcpstat.tcps_sndacks++; 524 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 525 tcpstat.tcps_sndctrl++; 526 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 527 tcpstat.tcps_sndurg++; 528 else 529 tcpstat.tcps_sndwinup++; 530 531 MGETHDR(m, M_DONTWAIT, MT_HEADER); 532 if (m == NULL) { 533 error = ENOBUFS; 534 goto out; 535 } 536 m->m_data += max_linkhdr; 537 m->m_len = hdrlen; 538 } 539 m->m_pkthdr.rcvif = (struct ifnet *)0; 540 ti = mtod(m, struct tcpiphdr *); 541 if (tp->t_template == 0) 542 panic("tcp_output"); 543 bcopy((caddr_t)tp->t_template, (caddr_t)ti, sizeof (struct tcpiphdr)); 544 545 /* 546 * If we are doing retransmissions, then snd_nxt will 547 * not reflect the first unsent octet. For ACK only 548 * packets, we do not want the sequence number of the 549 * retransmitted packet, we want the sequence number 550 * of the next unsent octet. So, if there is no data 551 * (and no SYN or FIN), use snd_max instead of snd_nxt 552 * when filling in ti_seq. But if we are in persist 553 * state, snd_max might reflect one byte beyond the 554 * right edge of the window, so use snd_nxt in that 555 * case, since we know we aren't doing a retransmission. 556 * (retransmit and persist are mutually exclusive...) 557 */ 558 if (len || (flags & (TH_SYN|TH_FIN)) || 559 TCP_TIMER_ISARMED(tp, TCPT_PERSIST)) 560 ti->ti_seq = htonl(tp->snd_nxt); 561 else 562 ti->ti_seq = htonl(tp->snd_max); 563 ti->ti_ack = htonl(tp->rcv_nxt); 564 if (optlen) { 565 bcopy((caddr_t)opt, (caddr_t)(ti + 1), optlen); 566 ti->ti_off = (sizeof (struct tcphdr) + optlen) >> 2; 567 } 568 ti->ti_flags = flags; 569 /* 570 * Calculate receive window. Don't shrink window, 571 * but avoid silly window syndrome. 572 */ 573 if (win < (long)(so->so_rcv.sb_hiwat / 4) && win < (long)rxsegsize) 574 win = 0; 575 if (win > (long)TCP_MAXWIN << tp->rcv_scale) 576 win = (long)TCP_MAXWIN << tp->rcv_scale; 577 if (win < (long)(tp->rcv_adv - tp->rcv_nxt)) 578 win = (long)(tp->rcv_adv - tp->rcv_nxt); 579 ti->ti_win = htons((u_int16_t) (win>>tp->rcv_scale)); 580 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 581 u_int32_t urp = tp->snd_up - tp->snd_nxt; 582 if (urp > IP_MAXPACKET) 583 urp = IP_MAXPACKET; 584 ti->ti_urp = htons((u_int16_t)urp); 585 ti->ti_flags |= TH_URG; 586 } else 587 /* 588 * If no urgent pointer to send, then we pull 589 * the urgent pointer to the left edge of the send window 590 * so that it doesn't drift into the send window on sequence 591 * number wraparound. 592 */ 593 tp->snd_up = tp->snd_una; /* drag it along */ 594 595 /* 596 * Put TCP length in extended header, and then 597 * checksum extended header and data. 598 */ 599 if (len + optlen) 600 ti->ti_len = htons((u_int16_t)(sizeof (struct tcphdr) + 601 optlen + len)); 602 ti->ti_sum = in_cksum(m, (int)(hdrlen + len)); 603 604 /* 605 * In transmit state, time the transmission and arrange for 606 * the retransmit. In persist state, just set snd_max. 607 */ 608 if (tp->t_force == 0 || TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) { 609 tcp_seq startseq = tp->snd_nxt; 610 611 /* 612 * Advance snd_nxt over sequence space of this segment. 613 * There are no states in which we send both a SYN and a FIN, 614 * so we collapse the tests for these flags. 615 */ 616 if (flags & (TH_SYN|TH_FIN)) 617 tp->snd_nxt++; 618 tp->snd_nxt += len; 619 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 620 tp->snd_max = tp->snd_nxt; 621 /* 622 * Time this transmission if not a retransmission and 623 * not currently timing anything. 624 */ 625 if (tp->t_rtt == 0) { 626 tp->t_rtt = 1; 627 tp->t_rtseq = startseq; 628 tcpstat.tcps_segstimed++; 629 } 630 } 631 632 /* 633 * Set retransmit timer if not currently set, 634 * and not doing an ack or a keep-alive probe. 635 * Initial value for retransmit timer is smoothed 636 * round-trip time + 2 * round-trip time variance. 637 * Initialize shift counter which is used for backoff 638 * of retransmit time. 639 */ 640 if (TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 && 641 tp->snd_nxt != tp->snd_una) { 642 TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); 643 if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST)) { 644 TCP_TIMER_DISARM(tp, TCPT_PERSIST); 645 tp->t_rxtshift = 0; 646 } 647 } 648 } else 649 if (SEQ_GT(tp->snd_nxt + len, tp->snd_max)) 650 tp->snd_max = tp->snd_nxt + len; 651 652 /* 653 * Trace. 654 */ 655 if (so->so_options & SO_DEBUG) 656 tcp_trace(TA_OUTPUT, tp->t_state, tp, ti, 0); 657 658 /* 659 * Fill in IP length and desired time to live and 660 * send to IP level. There should be a better way 661 * to handle ttl and tos; we could keep them in 662 * the template, but need a way to checksum without them. 663 */ 664 m->m_pkthdr.len = hdrlen + len; 665 { 666 struct rtentry *rt; 667 668 ((struct ip *)ti)->ip_len = m->m_pkthdr.len; 669 ((struct ip *)ti)->ip_ttl = tp->t_inpcb->inp_ip.ip_ttl; /* XXX */ 670 ((struct ip *)ti)->ip_tos = tp->t_inpcb->inp_ip.ip_tos; /* XXX */ 671 672 if (ip_mtudisc && (rt = in_pcbrtentry(tp->t_inpcb)) != 0 && 673 (rt->rt_rmx.rmx_locks & RTV_MTU) == 0) 674 ((struct ip *)ti)->ip_off |= IP_DF; 675 676 #if BSD >= 43 677 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, 678 so->so_options & SO_DONTROUTE, 0); 679 #else 680 error = ip_output(m, (struct mbuf *)0, &tp->t_inpcb->inp_route, 681 so->so_options & SO_DONTROUTE); 682 #endif 683 } 684 if (error) { 685 out: 686 if (error == ENOBUFS) { 687 tcp_quench(tp->t_inpcb, 0); 688 return (0); 689 } 690 if ((error == EHOSTUNREACH || error == ENETDOWN) 691 && TCPS_HAVERCVDSYN(tp->t_state)) { 692 tp->t_softerror = error; 693 return (0); 694 } 695 return (error); 696 } 697 tcpstat.tcps_sndtotal++; 698 if (tp->t_flags & TF_DELACK) 699 tcpstat.tcps_delack++; 700 701 /* 702 * Data sent (as far as we can tell). 703 * If this advertises a larger window than any other segment, 704 * then remember the size of the advertised window. 705 * Any pending ACK has now been sent. 706 */ 707 if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv)) 708 tp->rcv_adv = tp->rcv_nxt + win; 709 tp->last_ack_sent = tp->rcv_nxt; 710 tp->t_flags &= ~TF_ACKNOW; 711 TCP_CLEAR_DELACK(tp); 712 #ifdef DIAGNOSTIC 713 if (maxburst < 0) 714 printf("tcp_output: maxburst exceeded by %d\n", -maxburst); 715 #endif 716 if (sendalot && (!tcp_do_newreno || --maxburst)) 717 goto again; 718 return (0); 719 } 720 721 void 722 tcp_setpersist(tp) 723 register struct tcpcb *tp; 724 { 725 register int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> (1 + 2); 726 int nticks; 727 728 if (TCP_TIMER_ISARMED(tp, TCPT_REXMT)) 729 panic("tcp_output REXMT"); 730 /* 731 * Start/restart persistance timer. 732 */ 733 if (t < tp->t_rttmin) 734 t = tp->t_rttmin; 735 TCPT_RANGESET(nticks, t * tcp_backoff[tp->t_rxtshift], 736 TCPTV_PERSMIN, TCPTV_PERSMAX); 737 TCP_TIMER_ARM(tp, TCPT_PERSIST, nticks); 738 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 739 tp->t_rxtshift++; 740 } 741