1 /* $NetBSD: tcp_output.c,v 1.45 1998/10/06 00:20:45 matt 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 ((idle || tp->t_flags & TF_NODELAY) && 325 len + off >= so->so_snd.sb_cc) 326 goto send; 327 if (tp->t_force) 328 goto send; 329 if (len >= tp->max_sndwnd / 2) 330 goto send; 331 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 332 goto send; 333 } 334 335 /* 336 * Compare available window to amount of window known to peer 337 * (as advertised window less next expected input). If the 338 * difference is at least twice the size of the largest segment 339 * we expect to receive (i.e. two segments) or at least 50% of 340 * the maximum possible window, then want to send a window update 341 * to peer. 342 */ 343 if (win > 0) { 344 /* 345 * "adv" is the amount we can increase the window, 346 * taking into account that we are limited by 347 * TCP_MAXWIN << tp->rcv_scale. 348 */ 349 long adv = min(win, (long)TCP_MAXWIN << tp->rcv_scale) - 350 (tp->rcv_adv - tp->rcv_nxt); 351 352 if (adv >= (long) (2 * rxsegsize)) 353 goto send; 354 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 355 goto send; 356 } 357 358 /* 359 * Send if we owe peer an ACK. 360 */ 361 if (tp->t_flags & TF_ACKNOW) 362 goto send; 363 if (flags & (TH_SYN|TH_FIN|TH_RST)) 364 goto send; 365 if (SEQ_GT(tp->snd_up, tp->snd_una)) 366 goto send; 367 368 /* 369 * TCP window updates are not reliable, rather a polling protocol 370 * using ``persist'' packets is used to insure receipt of window 371 * updates. The three ``states'' for the output side are: 372 * idle not doing retransmits or persists 373 * persisting to move a small or zero window 374 * (re)transmitting and thereby not persisting 375 * 376 * tp->t_timer[TCPT_PERSIST] 377 * is set when we are in persist state. 378 * tp->t_force 379 * is set when we are called to send a persist packet. 380 * tp->t_timer[TCPT_REXMT] 381 * is set when we are retransmitting 382 * The output side is idle when both timers are zero. 383 * 384 * If send window is too small, there is data to transmit, and no 385 * retransmit or persist is pending, then go to persist state. 386 * If nothing happens soon, send when timer expires: 387 * if window is nonzero, transmit what we can, 388 * otherwise force out a byte. 389 */ 390 if (so->so_snd.sb_cc && TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 && 391 TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) { 392 tp->t_rxtshift = 0; 393 tcp_setpersist(tp); 394 } 395 396 /* 397 * No reason to send a segment, just return. 398 */ 399 return (0); 400 401 send: 402 /* 403 * Before ESTABLISHED, force sending of initial options 404 * unless TCP set not to do any options. 405 * NOTE: we assume that the IP/TCP header plus TCP options 406 * always fit in a single mbuf, leaving room for a maximum 407 * link header, i.e. 408 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MHLEN 409 */ 410 optlen = 0; 411 hdrlen = sizeof (struct tcpiphdr); 412 if (flags & TH_SYN) { 413 struct rtentry *rt = in_pcbrtentry(tp->t_inpcb); 414 415 tp->snd_nxt = tp->iss; 416 tp->t_ourmss = tcp_mss_to_advertise(rt != NULL ? 417 rt->rt_ifp : NULL); 418 if ((tp->t_flags & TF_NOOPT) == 0) { 419 opt[0] = TCPOPT_MAXSEG; 420 opt[1] = 4; 421 opt[2] = (tp->t_ourmss >> 8) & 0xff; 422 opt[3] = tp->t_ourmss & 0xff; 423 optlen = 4; 424 425 if ((tp->t_flags & TF_REQ_SCALE) && 426 ((flags & TH_ACK) == 0 || 427 (tp->t_flags & TF_RCVD_SCALE))) { 428 *((u_int32_t *) (opt + optlen)) = htonl( 429 TCPOPT_NOP << 24 | 430 TCPOPT_WINDOW << 16 | 431 TCPOLEN_WINDOW << 8 | 432 tp->request_r_scale); 433 optlen += 4; 434 } 435 } 436 } 437 438 /* 439 * Send a timestamp and echo-reply if this is a SYN and our side 440 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 441 * and our peer have sent timestamps in our SYN's. 442 */ 443 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 444 (flags & TH_RST) == 0 && 445 ((flags & (TH_SYN|TH_ACK)) == TH_SYN || 446 (tp->t_flags & TF_RCVD_TSTMP))) { 447 u_int32_t *lp = (u_int32_t *)(opt + optlen); 448 449 /* Form timestamp option as shown in appendix A of RFC 1323. */ 450 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 451 *lp++ = htonl(tcp_now); 452 *lp = htonl(tp->ts_recent); 453 optlen += TCPOLEN_TSTAMP_APPA; 454 } 455 456 hdrlen += optlen; 457 458 #ifdef DIAGNOSTIC 459 if (len > txsegsize) 460 panic("tcp data to be sent is larger than segment"); 461 if (max_linkhdr + hdrlen > MHLEN) 462 panic("tcphdr too big"); 463 #endif 464 465 /* 466 * Grab a header mbuf, attaching a copy of data to 467 * be transmitted, and initialize the header from 468 * the template for sends on this connection. 469 */ 470 if (len) { 471 if (tp->t_force && len == 1) 472 tcpstat.tcps_sndprobe++; 473 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 474 tcpstat.tcps_sndrexmitpack++; 475 tcpstat.tcps_sndrexmitbyte += len; 476 } else { 477 tcpstat.tcps_sndpack++; 478 tcpstat.tcps_sndbyte += len; 479 } 480 #ifdef notyet 481 if ((m = m_copypack(so->so_snd.sb_mb, off, 482 (int)len, max_linkhdr + hdrlen)) == 0) { 483 error = ENOBUFS; 484 goto out; 485 } 486 /* 487 * m_copypack left space for our hdr; use it. 488 */ 489 m->m_len += hdrlen; 490 m->m_data -= hdrlen; 491 #else 492 MGETHDR(m, M_DONTWAIT, MT_HEADER); 493 if (m == NULL) { 494 error = ENOBUFS; 495 goto out; 496 } 497 m->m_data += max_linkhdr; 498 m->m_len = hdrlen; 499 if (len <= MHLEN - hdrlen - max_linkhdr) { 500 m_copydata(so->so_snd.sb_mb, off, (int) len, 501 mtod(m, caddr_t) + hdrlen); 502 m->m_len += len; 503 } else { 504 m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len); 505 if (m->m_next == 0) { 506 m_freem(m); 507 error = ENOBUFS; 508 goto out; 509 } 510 } 511 #endif 512 /* 513 * If we're sending everything we've got, set PUSH. 514 * (This will keep happy those implementations which only 515 * give data to the user when a buffer fills or 516 * a PUSH comes in.) 517 */ 518 if (off + len == so->so_snd.sb_cc) 519 flags |= TH_PUSH; 520 } else { 521 if (tp->t_flags & TF_ACKNOW) 522 tcpstat.tcps_sndacks++; 523 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 524 tcpstat.tcps_sndctrl++; 525 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 526 tcpstat.tcps_sndurg++; 527 else 528 tcpstat.tcps_sndwinup++; 529 530 MGETHDR(m, M_DONTWAIT, MT_HEADER); 531 if (m == NULL) { 532 error = ENOBUFS; 533 goto out; 534 } 535 m->m_data += max_linkhdr; 536 m->m_len = hdrlen; 537 } 538 m->m_pkthdr.rcvif = (struct ifnet *)0; 539 ti = mtod(m, struct tcpiphdr *); 540 if (tp->t_template == 0) 541 panic("tcp_output"); 542 bcopy((caddr_t)tp->t_template, (caddr_t)ti, sizeof (struct tcpiphdr)); 543 544 /* 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)) || 558 TCP_TIMER_ISARMED(tp, TCPT_PERSIST)) 559 ti->ti_seq = htonl(tp->snd_nxt); 560 else 561 ti->ti_seq = htonl(tp->snd_max); 562 ti->ti_ack = htonl(tp->rcv_nxt); 563 if (optlen) { 564 bcopy((caddr_t)opt, (caddr_t)(ti + 1), optlen); 565 ti->ti_off = (sizeof (struct tcphdr) + optlen) >> 2; 566 } 567 ti->ti_flags = flags; 568 /* 569 * Calculate receive window. Don't shrink window, 570 * but avoid silly window syndrome. 571 */ 572 if (win < (long)(so->so_rcv.sb_hiwat / 4) && win < (long)rxsegsize) 573 win = 0; 574 if (win > (long)TCP_MAXWIN << tp->rcv_scale) 575 win = (long)TCP_MAXWIN << tp->rcv_scale; 576 if (win < (long)(tp->rcv_adv - tp->rcv_nxt)) 577 win = (long)(tp->rcv_adv - tp->rcv_nxt); 578 ti->ti_win = htons((u_int16_t) (win>>tp->rcv_scale)); 579 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 580 u_int32_t urp = tp->snd_up - tp->snd_nxt; 581 if (urp > IP_MAXPACKET) 582 urp = IP_MAXPACKET; 583 ti->ti_urp = htons((u_int16_t)urp); 584 ti->ti_flags |= TH_URG; 585 } else 586 /* 587 * If no urgent pointer to send, then we pull 588 * the urgent pointer to the left edge of the send window 589 * so that it doesn't drift into the send window on sequence 590 * number wraparound. 591 */ 592 tp->snd_up = tp->snd_una; /* drag it along */ 593 594 /* 595 * Put TCP length in extended header, and then 596 * checksum extended header and data. 597 */ 598 if (len + optlen) 599 ti->ti_len = htons((u_int16_t)(sizeof (struct tcphdr) + 600 optlen + len)); 601 ti->ti_sum = in_cksum(m, (int)(hdrlen + len)); 602 603 /* 604 * In transmit state, time the transmission and arrange for 605 * the retransmit. In persist state, just set snd_max. 606 */ 607 if (tp->t_force == 0 || TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) { 608 tcp_seq startseq = tp->snd_nxt; 609 610 /* 611 * Advance snd_nxt over sequence space of this segment. 612 * There are no states in which we send both a SYN and a FIN, 613 * so we collapse the tests for these flags. 614 */ 615 if (flags & (TH_SYN|TH_FIN)) 616 tp->snd_nxt++; 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 (TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 && 640 tp->snd_nxt != tp->snd_una) { 641 TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); 642 if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST)) { 643 TCP_TIMER_DISARM(tp, TCPT_PERSIST); 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 /* 652 * Trace. 653 */ 654 if (so->so_options & SO_DEBUG) 655 tcp_trace(TA_OUTPUT, tp->t_state, tp, ti, 0); 656 657 /* 658 * Fill in IP length and desired time to live and 659 * send to IP level. There should be a better way 660 * to handle ttl and tos; we could keep them in 661 * the template, but need a way to checksum without them. 662 */ 663 m->m_pkthdr.len = hdrlen + len; 664 { 665 struct rtentry *rt; 666 667 ((struct ip *)ti)->ip_len = m->m_pkthdr.len; 668 ((struct ip *)ti)->ip_ttl = tp->t_inpcb->inp_ip.ip_ttl; /* XXX */ 669 ((struct ip *)ti)->ip_tos = tp->t_inpcb->inp_ip.ip_tos; /* XXX */ 670 671 if (ip_mtudisc && (rt = in_pcbrtentry(tp->t_inpcb)) != 0 && 672 (rt->rt_rmx.rmx_locks & RTV_MTU) == 0) 673 ((struct ip *)ti)->ip_off |= IP_DF; 674 675 #if BSD >= 43 676 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, 677 so->so_options & SO_DONTROUTE, 0); 678 #else 679 error = ip_output(m, (struct mbuf *)0, &tp->t_inpcb->inp_route, 680 so->so_options & SO_DONTROUTE); 681 #endif 682 } 683 if (error) { 684 out: 685 if (error == ENOBUFS) { 686 tcp_quench(tp->t_inpcb, 0); 687 return (0); 688 } 689 if ((error == EHOSTUNREACH || error == ENETDOWN) 690 && TCPS_HAVERCVDSYN(tp->t_state)) { 691 tp->t_softerror = error; 692 return (0); 693 } 694 return (error); 695 } 696 tcpstat.tcps_sndtotal++; 697 if (tp->t_flags & TF_DELACK) 698 tcpstat.tcps_delack++; 699 700 /* 701 * Data sent (as far as we can tell). 702 * If this advertises a larger window than any other segment, 703 * then remember the size of the advertised window. 704 * Any pending ACK has now been sent. 705 */ 706 if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv)) 707 tp->rcv_adv = tp->rcv_nxt + win; 708 tp->last_ack_sent = tp->rcv_nxt; 709 tp->t_flags &= ~TF_ACKNOW; 710 TCP_CLEAR_DELACK(tp); 711 #ifdef DIAGNOSTIC 712 if (maxburst < 0) 713 printf("tcp_output: maxburst exceeded by %d\n", -maxburst); 714 #endif 715 if (sendalot && (!tcp_do_newreno || --maxburst)) 716 goto again; 717 return (0); 718 } 719 720 void 721 tcp_setpersist(tp) 722 register struct tcpcb *tp; 723 { 724 register int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> (1 + 2); 725 int nticks; 726 727 if (TCP_TIMER_ISARMED(tp, TCPT_REXMT)) 728 panic("tcp_output REXMT"); 729 /* 730 * Start/restart persistance timer. 731 */ 732 if (t < tp->t_rttmin) 733 t = tp->t_rttmin; 734 TCPT_RANGESET(nticks, t * tcp_backoff[tp->t_rxtshift], 735 TCPTV_PERSMIN, TCPTV_PERSMAX); 736 TCP_TIMER_ARM(tp, TCPT_PERSIST, nticks); 737 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 738 tp->t_rxtshift++; 739 } 740