1 /* $NetBSD: tcp_output.c,v 1.107 2004/02/04 05:36:03 itojun Exp $ */ 2 3 /* 4 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project. 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. Neither the name of the project nor the names of its contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 */ 31 32 /* 33 * @(#)COPYRIGHT 1.1 (NRL) 17 January 1995 34 * 35 * NRL grants permission for redistribution and use in source and binary 36 * forms, with or without modification, of the software and documentation 37 * created at NRL provided that the following conditions are met: 38 * 39 * 1. Redistributions of source code must retain the above copyright 40 * notice, this list of conditions and the following disclaimer. 41 * 2. Redistributions in binary form must reproduce the above copyright 42 * notice, this list of conditions and the following disclaimer in the 43 * documentation and/or other materials provided with the distribution. 44 * 3. All advertising materials mentioning features or use of this software 45 * must display the following acknowledgements: 46 * This product includes software developed by the University of 47 * California, Berkeley and its contributors. 48 * This product includes software developed at the Information 49 * Technology Division, US Naval Research Laboratory. 50 * 4. Neither the name of the NRL nor the names of its contributors 51 * may be used to endorse or promote products derived from this software 52 * without specific prior written permission. 53 * 54 * THE SOFTWARE PROVIDED BY NRL IS PROVIDED BY NRL AND CONTRIBUTORS ``AS 55 * IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 56 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A 57 * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL NRL OR 58 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 59 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 60 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 61 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 62 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 63 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 64 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 65 * 66 * The views and conclusions contained in the software and documentation 67 * are those of the authors and should not be interpreted as representing 68 * official policies, either expressed or implied, of the US Naval 69 * Research Laboratory (NRL). 70 */ 71 72 /*- 73 * Copyright (c) 1997, 1998, 2001 The NetBSD Foundation, Inc. 74 * All rights reserved. 75 * 76 * This code is derived from software contributed to The NetBSD Foundation 77 * by Jason R. Thorpe and Kevin M. Lahey of the Numerical Aerospace Simulation 78 * Facility, NASA Ames Research Center. 79 * 80 * Redistribution and use in source and binary forms, with or without 81 * modification, are permitted provided that the following conditions 82 * are met: 83 * 1. Redistributions of source code must retain the above copyright 84 * notice, this list of conditions and the following disclaimer. 85 * 2. Redistributions in binary form must reproduce the above copyright 86 * notice, this list of conditions and the following disclaimer in the 87 * documentation and/or other materials provided with the distribution. 88 * 3. All advertising materials mentioning features or use of this software 89 * must display the following acknowledgement: 90 * This product includes software developed by the NetBSD 91 * Foundation, Inc. and its contributors. 92 * 4. Neither the name of The NetBSD Foundation nor the names of its 93 * contributors may be used to endorse or promote products derived 94 * from this software without specific prior written permission. 95 * 96 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 97 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 98 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 99 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 100 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 101 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 102 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 103 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 104 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 105 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 106 * POSSIBILITY OF SUCH DAMAGE. 107 */ 108 109 /* 110 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 111 * The Regents of the University of California. All rights reserved. 112 * 113 * Redistribution and use in source and binary forms, with or without 114 * modification, are permitted provided that the following conditions 115 * are met: 116 * 1. Redistributions of source code must retain the above copyright 117 * notice, this list of conditions and the following disclaimer. 118 * 2. Redistributions in binary form must reproduce the above copyright 119 * notice, this list of conditions and the following disclaimer in the 120 * documentation and/or other materials provided with the distribution. 121 * 3. Neither the name of the University nor the names of its contributors 122 * may be used to endorse or promote products derived from this software 123 * without specific prior written permission. 124 * 125 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 126 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 127 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 128 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 129 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 130 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 131 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 132 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 133 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 134 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 135 * SUCH DAMAGE. 136 * 137 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95 138 */ 139 140 #include <sys/cdefs.h> 141 __KERNEL_RCSID(0, "$NetBSD: tcp_output.c,v 1.107 2004/02/04 05:36:03 itojun Exp $"); 142 143 #include "opt_inet.h" 144 #include "opt_ipsec.h" 145 #include "opt_tcp_debug.h" 146 147 #include <sys/param.h> 148 #include <sys/systm.h> 149 #include <sys/malloc.h> 150 #include <sys/mbuf.h> 151 #include <sys/protosw.h> 152 #include <sys/socket.h> 153 #include <sys/socketvar.h> 154 #include <sys/errno.h> 155 #include <sys/domain.h> 156 #include <sys/kernel.h> 157 158 #include <net/if.h> 159 #include <net/route.h> 160 161 #include <netinet/in.h> 162 #include <netinet/in_systm.h> 163 #include <netinet/ip.h> 164 #include <netinet/in_pcb.h> 165 #include <netinet/ip_var.h> 166 167 #ifdef INET6 168 #ifndef INET 169 #include <netinet/in.h> 170 #endif 171 #include <netinet/ip6.h> 172 #include <netinet6/in6_var.h> 173 #include <netinet6/ip6_var.h> 174 #include <netinet6/in6_pcb.h> 175 #include <netinet6/nd6.h> 176 #endif 177 178 #ifdef FAST_IPSEC 179 #include <netipsec/ipsec.h> 180 #endif /* FAST_IPSEC*/ 181 #ifdef IPSEC 182 #include <netinet6/ipsec.h> 183 #endif 184 185 #include <netinet/tcp.h> 186 #define TCPOUTFLAGS 187 #include <netinet/tcp_fsm.h> 188 #include <netinet/tcp_seq.h> 189 #include <netinet/tcp_timer.h> 190 #include <netinet/tcp_var.h> 191 #include <netinet/tcpip.h> 192 #include <netinet/tcp_debug.h> 193 194 #ifdef notyet 195 extern struct mbuf *m_copypack(); 196 #endif 197 198 #define MAX_TCPOPTLEN 32 /* max # bytes that go in options */ 199 200 /* 201 * Knob to enable Congestion Window Monitoring, and control the 202 * the burst size it allows. Default burst is 4 packets, per 203 * the Internet draft. 204 */ 205 int tcp_cwm = 0; 206 int tcp_cwm_burstsize = 4; 207 208 #ifdef TCP_OUTPUT_COUNTERS 209 #include <sys/device.h> 210 211 extern struct evcnt tcp_output_bigheader; 212 extern struct evcnt tcp_output_predict_hit; 213 extern struct evcnt tcp_output_predict_miss; 214 extern struct evcnt tcp_output_copysmall; 215 extern struct evcnt tcp_output_copybig; 216 extern struct evcnt tcp_output_refbig; 217 218 #define TCP_OUTPUT_COUNTER_INCR(ev) (ev)->ev_count++ 219 #else 220 221 #define TCP_OUTPUT_COUNTER_INCR(ev) /* nothing */ 222 223 #endif /* TCP_OUTPUT_COUNTERS */ 224 225 static 226 #ifndef GPROF 227 __inline 228 #endif 229 int 230 tcp_segsize(struct tcpcb *tp, int *txsegsizep, int *rxsegsizep) 231 { 232 #ifdef INET 233 struct inpcb *inp = tp->t_inpcb; 234 #endif 235 #ifdef INET6 236 struct in6pcb *in6p = tp->t_in6pcb; 237 #endif 238 struct socket *so = NULL; 239 struct rtentry *rt; 240 struct ifnet *ifp; 241 int size; 242 int iphlen; 243 int optlen; 244 245 #ifdef DIAGNOSTIC 246 if (tp->t_inpcb && tp->t_in6pcb) 247 panic("tcp_segsize: both t_inpcb and t_in6pcb are set"); 248 #endif 249 switch (tp->t_family) { 250 #ifdef INET 251 case AF_INET: 252 iphlen = sizeof(struct ip); 253 break; 254 #endif 255 #ifdef INET6 256 case AF_INET6: 257 iphlen = sizeof(struct ip6_hdr); 258 break; 259 #endif 260 default: 261 size = tcp_mssdflt; 262 goto out; 263 } 264 265 rt = NULL; 266 #ifdef INET 267 if (inp) { 268 rt = in_pcbrtentry(inp); 269 so = inp->inp_socket; 270 } 271 #endif 272 #ifdef INET6 273 if (in6p) { 274 rt = in6_pcbrtentry(in6p); 275 so = in6p->in6p_socket; 276 } 277 #endif 278 if (rt == NULL) { 279 size = tcp_mssdflt; 280 goto out; 281 } 282 283 ifp = rt->rt_ifp; 284 285 size = tcp_mssdflt; 286 if (tp->t_mtudisc && rt->rt_rmx.rmx_mtu != 0) { 287 #ifdef INET6 288 if (in6p && rt->rt_rmx.rmx_mtu < IPV6_MMTU) { 289 /* 290 * RFC2460 section 5, last paragraph: if path MTU is 291 * smaller than 1280, use 1280 as packet size and 292 * attach fragment header. 293 */ 294 size = IPV6_MMTU - iphlen - sizeof(struct ip6_frag) - 295 sizeof(struct tcphdr); 296 } else 297 size = rt->rt_rmx.rmx_mtu - iphlen - 298 sizeof(struct tcphdr); 299 #else 300 size = rt->rt_rmx.rmx_mtu - iphlen - sizeof(struct tcphdr); 301 #endif 302 } else if (ifp->if_flags & IFF_LOOPBACK) 303 size = ifp->if_mtu - iphlen - sizeof(struct tcphdr); 304 #ifdef INET 305 else if (inp && tp->t_mtudisc) 306 size = ifp->if_mtu - iphlen - sizeof(struct tcphdr); 307 else if (inp && in_localaddr(inp->inp_faddr)) 308 size = ifp->if_mtu - iphlen - sizeof(struct tcphdr); 309 #endif 310 #ifdef INET6 311 else if (in6p) { 312 #ifdef INET 313 if (IN6_IS_ADDR_V4MAPPED(&in6p->in6p_faddr)) { 314 /* mapped addr case */ 315 struct in_addr d; 316 bcopy(&in6p->in6p_faddr.s6_addr32[3], &d, sizeof(d)); 317 if (tp->t_mtudisc || in_localaddr(d)) 318 size = ifp->if_mtu - iphlen - sizeof(struct tcphdr); 319 } else 320 #endif 321 { 322 /* 323 * for IPv6, path MTU discovery is always turned on, 324 * or the node must use packet size <= 1280. 325 */ 326 size = tp->t_mtudisc ? IN6_LINKMTU(ifp) : IPV6_MMTU; 327 size -= (iphlen + sizeof(struct tcphdr)); 328 } 329 } 330 #endif 331 out: 332 /* 333 * Now we must make room for whatever extra TCP/IP options are in 334 * the packet. 335 */ 336 optlen = tcp_optlen(tp); 337 338 /* 339 * XXX tp->t_ourmss should have the right size, but without this code 340 * fragmentation will occur... need more investigation 341 */ 342 #ifdef INET 343 if (inp) { 344 #if defined(IPSEC) || defined(FAST_IPSEC) 345 optlen += ipsec4_hdrsiz_tcp(tp); 346 #endif 347 optlen += ip_optlen(inp); 348 } 349 #endif 350 #ifdef INET6 351 #ifdef INET 352 if (in6p && tp->t_family == AF_INET) { 353 #if defined(IPSEC) || defined(FAST_IPSEC) 354 optlen += ipsec4_hdrsiz_tcp(tp); 355 #endif 356 /* XXX size -= ip_optlen(in6p); */ 357 } else 358 #endif 359 if (in6p && tp->t_family == AF_INET6) { 360 #ifdef IPSEC 361 optlen += ipsec6_hdrsiz_tcp(tp); 362 #endif 363 optlen += ip6_optlen(in6p); 364 } 365 #endif 366 size -= optlen; 367 368 /* there may not be any room for data if mtu is too small */ 369 if (size < 0) 370 return (EMSGSIZE); 371 372 /* 373 * *rxsegsizep holds *estimated* inbound segment size (estimation 374 * assumes that path MTU is the same for both ways). this is only 375 * for silly window avoidance, do not use the value for other purposes. 376 * 377 * ipseclen is subtracted from both sides, this may not be right. 378 * I'm not quite sure about this (could someone comment). 379 */ 380 *txsegsizep = min(tp->t_peermss - optlen, size); 381 /* 382 * Never send more than half a buffer full. This insures that we can 383 * always keep 2 packets on the wire, no matter what SO_SNDBUF is, and 384 * therefore acks will never be delayed unless we run out of data to 385 * transmit. 386 */ 387 if (so) 388 *txsegsizep = min(so->so_snd.sb_hiwat >> 1, *txsegsizep); 389 *rxsegsizep = min(tp->t_ourmss - optlen, size); 390 391 if (*txsegsizep != tp->t_segsz) { 392 /* 393 * If the new segment size is larger, we don't want to 394 * mess up the congestion window, but if it is smaller 395 * we'll have to reduce the congestion window to ensure 396 * that we don't get into trouble with initial windows 397 * and the rest. In any case, if the segment size 398 * has changed, chances are the path has, too, and 399 * our congestion window will be different. 400 */ 401 if (*txsegsizep < tp->t_segsz) { 402 tp->snd_cwnd = max((tp->snd_cwnd / tp->t_segsz) 403 * *txsegsizep, *txsegsizep); 404 tp->snd_ssthresh = max((tp->snd_ssthresh / tp->t_segsz) 405 * *txsegsizep, *txsegsizep); 406 } 407 tp->t_segsz = *txsegsizep; 408 } 409 410 return (0); 411 } 412 413 static 414 #ifndef GPROF 415 __inline 416 #endif 417 int 418 tcp_build_datapkt(struct tcpcb *tp, struct socket *so, int off, 419 long len, int hdrlen, struct mbuf **mp) 420 { 421 struct mbuf *m, *m0; 422 423 if (tp->t_force && len == 1) 424 tcpstat.tcps_sndprobe++; 425 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 426 tcpstat.tcps_sndrexmitpack++; 427 tcpstat.tcps_sndrexmitbyte += len; 428 } else { 429 tcpstat.tcps_sndpack++; 430 tcpstat.tcps_sndbyte += len; 431 } 432 #ifdef notyet 433 if ((m = m_copypack(so->so_snd.sb_mb, off, 434 (int)len, max_linkhdr + hdrlen)) == 0) 435 return (ENOBUFS); 436 /* 437 * m_copypack left space for our hdr; use it. 438 */ 439 m->m_len += hdrlen; 440 m->m_data -= hdrlen; 441 #else 442 MGETHDR(m, M_DONTWAIT, MT_HEADER); 443 if (__predict_false(m == NULL)) 444 return (ENOBUFS); 445 MCLAIM(m, &tcp_tx_mowner); 446 447 /* 448 * XXX Because other code assumes headers will fit in 449 * XXX one header mbuf. 450 * 451 * (This code should almost *never* be run.) 452 */ 453 if (__predict_false((max_linkhdr + hdrlen) > MHLEN)) { 454 TCP_OUTPUT_COUNTER_INCR(&tcp_output_bigheader); 455 MCLGET(m, M_DONTWAIT); 456 if ((m->m_flags & M_EXT) == 0) { 457 m_freem(m); 458 return (ENOBUFS); 459 } 460 } 461 462 m->m_data += max_linkhdr; 463 m->m_len = hdrlen; 464 465 /* 466 * To avoid traversing the whole sb_mb chain for correct 467 * data to send, remember last sent mbuf, its offset and 468 * the sent size. When called the next time, see if the 469 * data to send is directly following the previous transfer. 470 * This is important for large TCP windows. 471 */ 472 if (off == 0 || tp->t_lastm == NULL || 473 (tp->t_lastoff + tp->t_lastlen) != off) { 474 TCP_OUTPUT_COUNTER_INCR(&tcp_output_predict_miss); 475 /* 476 * Either a new packet or a retransmit. 477 * Start from the beginning. 478 */ 479 tp->t_lastm = so->so_snd.sb_mb; 480 tp->t_inoff = off; 481 } else { 482 TCP_OUTPUT_COUNTER_INCR(&tcp_output_predict_hit); 483 tp->t_inoff += tp->t_lastlen; 484 } 485 486 /* Traverse forward to next packet */ 487 while (tp->t_inoff > 0) { 488 if (tp->t_lastm == NULL) 489 panic("tp->t_lastm == NULL"); 490 if (tp->t_inoff < tp->t_lastm->m_len) 491 break; 492 tp->t_inoff -= tp->t_lastm->m_len; 493 tp->t_lastm = tp->t_lastm->m_next; 494 } 495 496 tp->t_lastoff = off; 497 tp->t_lastlen = len; 498 m0 = tp->t_lastm; 499 off = tp->t_inoff; 500 501 if (len <= M_TRAILINGSPACE(m)) { 502 m_copydata(m0, off, (int) len, mtod(m, caddr_t) + hdrlen); 503 m->m_len += len; 504 TCP_OUTPUT_COUNTER_INCR(&tcp_output_copysmall); 505 } else { 506 m->m_next = m_copy(m0, off, (int) len); 507 if (m->m_next == NULL) { 508 m_freem(m); 509 return (ENOBUFS); 510 } 511 #ifdef TCP_OUTPUT_COUNTERS 512 if (m->m_next->m_flags & M_EXT) 513 TCP_OUTPUT_COUNTER_INCR(&tcp_output_refbig); 514 else 515 TCP_OUTPUT_COUNTER_INCR(&tcp_output_copybig); 516 #endif /* TCP_OUTPUT_COUNTERS */ 517 } 518 #endif 519 520 *mp = m; 521 return (0); 522 } 523 524 /* 525 * Tcp output routine: figure out what should be sent and send it. 526 */ 527 int 528 tcp_output(tp) 529 struct tcpcb *tp; 530 { 531 struct socket *so; 532 struct route *ro; 533 long len, win; 534 int off, flags, error; 535 struct mbuf *m; 536 struct ip *ip; 537 #ifdef INET6 538 struct ip6_hdr *ip6; 539 #endif 540 struct tcphdr *th; 541 u_char opt[MAX_TCPOPTLEN]; 542 unsigned optlen, hdrlen; 543 int idle, sendalot, txsegsize, rxsegsize; 544 int maxburst = TCP_MAXBURST; 545 int af; /* address family on the wire */ 546 int iphdrlen; 547 548 #ifdef DIAGNOSTIC 549 if (tp->t_inpcb && tp->t_in6pcb) 550 panic("tcp_output: both t_inpcb and t_in6pcb are set"); 551 #endif 552 so = NULL; 553 ro = NULL; 554 if (tp->t_inpcb) { 555 so = tp->t_inpcb->inp_socket; 556 ro = &tp->t_inpcb->inp_route; 557 } 558 #ifdef INET6 559 else if (tp->t_in6pcb) { 560 so = tp->t_in6pcb->in6p_socket; 561 ro = (struct route *)&tp->t_in6pcb->in6p_route; 562 } 563 #endif 564 565 switch (af = tp->t_family) { 566 #ifdef INET 567 case AF_INET: 568 if (tp->t_inpcb) 569 break; 570 #ifdef INET6 571 /* mapped addr case */ 572 if (tp->t_in6pcb) 573 break; 574 #endif 575 return (EINVAL); 576 #endif 577 #ifdef INET6 578 case AF_INET6: 579 if (tp->t_in6pcb) 580 break; 581 return (EINVAL); 582 #endif 583 default: 584 return (EAFNOSUPPORT); 585 } 586 587 if (tcp_segsize(tp, &txsegsize, &rxsegsize)) 588 return (EMSGSIZE); 589 590 idle = (tp->snd_max == tp->snd_una); 591 592 /* 593 * Restart Window computation. From draft-floyd-incr-init-win-03: 594 * 595 * Optionally, a TCP MAY set the restart window to the 596 * minimum of the value used for the initial window and 597 * the current value of cwnd (in other words, using a 598 * larger value for the restart window should never increase 599 * the size of cwnd). 600 */ 601 if (tcp_cwm) { 602 /* 603 * Hughes/Touch/Heidemann Congestion Window Monitoring. 604 * Count the number of packets currently pending 605 * acknowledgement, and limit our congestion window 606 * to a pre-determined allowed burst size plus that count. 607 * This prevents bursting once all pending packets have 608 * been acknowledged (i.e. transmission is idle). 609 * 610 * XXX Link this to Initial Window? 611 */ 612 tp->snd_cwnd = min(tp->snd_cwnd, 613 (tcp_cwm_burstsize * txsegsize) + 614 (tp->snd_nxt - tp->snd_una)); 615 } else { 616 if (idle && (tcp_now - tp->t_rcvtime) >= tp->t_rxtcur) { 617 /* 618 * We have been idle for "a while" and no acks are 619 * expected to clock out any data we send -- 620 * slow start to get ack "clock" running again. 621 */ 622 int ss = tcp_init_win; 623 #ifdef INET 624 if (tp->t_inpcb && 625 in_localaddr(tp->t_inpcb->inp_faddr)) 626 ss = tcp_init_win_local; 627 #endif 628 #ifdef INET6 629 if (tp->t_in6pcb && 630 in6_localaddr(&tp->t_in6pcb->in6p_faddr)) 631 ss = tcp_init_win_local; 632 #endif 633 tp->snd_cwnd = min(tp->snd_cwnd, 634 TCP_INITIAL_WINDOW(ss, txsegsize)); 635 } 636 } 637 638 again: 639 /* 640 * Determine length of data that should be transmitted, and 641 * flags that should be used. If there is some data or critical 642 * controls (SYN, RST) to send, then transmit; otherwise, 643 * investigate further. 644 */ 645 sendalot = 0; 646 off = tp->snd_nxt - tp->snd_una; 647 win = min(tp->snd_wnd, tp->snd_cwnd); 648 649 flags = tcp_outflags[tp->t_state]; 650 /* 651 * If in persist timeout with window of 0, send 1 byte. 652 * Otherwise, if window is small but nonzero 653 * and timer expired, we will send what we can 654 * and go to transmit state. 655 */ 656 if (tp->t_force) { 657 if (win == 0) { 658 /* 659 * If we still have some data to send, then 660 * clear the FIN bit. Usually this would 661 * happen below when it realizes that we 662 * aren't sending all the data. However, 663 * if we have exactly 1 byte of unset data, 664 * then it won't clear the FIN bit below, 665 * and if we are in persist state, we wind 666 * up sending the packet without recording 667 * that we sent the FIN bit. 668 * 669 * We can't just blindly clear the FIN bit, 670 * because if we don't have any more data 671 * to send then the probe will be the FIN 672 * itself. 673 */ 674 if (off < so->so_snd.sb_cc) 675 flags &= ~TH_FIN; 676 win = 1; 677 } else { 678 TCP_TIMER_DISARM(tp, TCPT_PERSIST); 679 tp->t_rxtshift = 0; 680 } 681 } 682 683 if (win < so->so_snd.sb_cc) { 684 len = win - off; 685 flags &= ~TH_FIN; 686 } else 687 len = so->so_snd.sb_cc - off; 688 689 if (len < 0) { 690 /* 691 * If FIN has been sent but not acked, 692 * but we haven't been called to retransmit, 693 * len will be -1. Otherwise, window shrank 694 * after we sent into it. If window shrank to 0, 695 * cancel pending retransmit, pull snd_nxt back 696 * to (closed) window, and set the persist timer 697 * if it isn't already going. If the window didn't 698 * close completely, just wait for an ACK. 699 * 700 * If we have a pending FIN, either it has already been 701 * transmitted or it is outside the window, so drop it. 702 * If the FIN has been transmitted, but this is not a 703 * retransmission, then len must be -1. Therefore we also 704 * prevent here the sending of `gratuitous FINs'. This 705 * eliminates the need to check for that case below (e.g. 706 * to back up snd_nxt before the FIN so that the sequence 707 * number is correct). 708 */ 709 len = 0; 710 flags &= ~TH_FIN; 711 if (win == 0) { 712 TCP_TIMER_DISARM(tp, TCPT_REXMT); 713 tp->t_rxtshift = 0; 714 tp->snd_nxt = tp->snd_una; 715 if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) 716 tcp_setpersist(tp); 717 } 718 } 719 if (len > txsegsize) { 720 len = txsegsize; 721 flags &= ~TH_FIN; 722 sendalot = 1; 723 } 724 725 win = sbspace(&so->so_rcv); 726 727 /* 728 * Sender silly window avoidance. If connection is idle 729 * and can send all data, a maximum segment, 730 * at least a maximum default-size segment do it, 731 * or are forced, do it; otherwise don't bother. 732 * If peer's buffer is tiny, then send 733 * when window is at least half open. 734 * If retransmitting (possibly after persist timer forced us 735 * to send into a small window), then must resend. 736 */ 737 if (len) { 738 if (len == txsegsize) 739 goto send; 740 if ((so->so_state & SS_MORETOCOME) == 0 && 741 ((idle || tp->t_flags & TF_NODELAY) && 742 len + off >= so->so_snd.sb_cc)) 743 goto send; 744 if (tp->t_force) 745 goto send; 746 if (len >= tp->max_sndwnd / 2) 747 goto send; 748 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 749 goto send; 750 } 751 752 /* 753 * Compare available window to amount of window known to peer 754 * (as advertised window less next expected input). If the 755 * difference is at least twice the size of the largest segment 756 * we expect to receive (i.e. two segments) or at least 50% of 757 * the maximum possible window, then want to send a window update 758 * to peer. 759 */ 760 if (win > 0) { 761 /* 762 * "adv" is the amount we can increase the window, 763 * taking into account that we are limited by 764 * TCP_MAXWIN << tp->rcv_scale. 765 */ 766 long adv = min(win, (long)TCP_MAXWIN << tp->rcv_scale) - 767 (tp->rcv_adv - tp->rcv_nxt); 768 769 if (adv >= (long) (2 * rxsegsize)) 770 goto send; 771 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 772 goto send; 773 } 774 775 /* 776 * Send if we owe peer an ACK. 777 */ 778 if (tp->t_flags & TF_ACKNOW) 779 goto send; 780 if (flags & (TH_SYN|TH_FIN|TH_RST)) 781 goto send; 782 if (SEQ_GT(tp->snd_up, tp->snd_una)) 783 goto send; 784 785 /* 786 * TCP window updates are not reliable, rather a polling protocol 787 * using ``persist'' packets is used to insure receipt of window 788 * updates. The three ``states'' for the output side are: 789 * idle not doing retransmits or persists 790 * persisting to move a small or zero window 791 * (re)transmitting and thereby not persisting 792 * 793 * tp->t_timer[TCPT_PERSIST] 794 * is set when we are in persist state. 795 * tp->t_force 796 * is set when we are called to send a persist packet. 797 * tp->t_timer[TCPT_REXMT] 798 * is set when we are retransmitting 799 * The output side is idle when both timers are zero. 800 * 801 * If send window is too small, there is data to transmit, and no 802 * retransmit or persist is pending, then go to persist state. 803 * If nothing happens soon, send when timer expires: 804 * if window is nonzero, transmit what we can, 805 * otherwise force out a byte. 806 */ 807 if (so->so_snd.sb_cc && TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 && 808 TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) { 809 tp->t_rxtshift = 0; 810 tcp_setpersist(tp); 811 } 812 813 /* 814 * No reason to send a segment, just return. 815 */ 816 return (0); 817 818 send: 819 /* 820 * Before ESTABLISHED, force sending of initial options 821 * unless TCP set not to do any options. 822 * NOTE: we assume that the IP/TCP header plus TCP options 823 * always fit in a single mbuf, leaving room for a maximum 824 * link header, i.e. 825 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 826 */ 827 optlen = 0; 828 switch (af) { 829 #ifdef INET 830 case AF_INET: 831 iphdrlen = sizeof(struct ip) + sizeof(struct tcphdr); 832 break; 833 #endif 834 #ifdef INET6 835 case AF_INET6: 836 iphdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 837 break; 838 #endif 839 default: /*pacify gcc*/ 840 iphdrlen = 0; 841 break; 842 } 843 hdrlen = iphdrlen; 844 if (flags & TH_SYN) { 845 struct rtentry *rt; 846 847 rt = NULL; 848 #ifdef INET 849 if (tp->t_inpcb) 850 rt = in_pcbrtentry(tp->t_inpcb); 851 #endif 852 #ifdef INET6 853 if (tp->t_in6pcb) 854 rt = in6_pcbrtentry(tp->t_in6pcb); 855 #endif 856 857 tp->snd_nxt = tp->iss; 858 tp->t_ourmss = tcp_mss_to_advertise(rt != NULL ? 859 rt->rt_ifp : NULL, af); 860 if ((tp->t_flags & TF_NOOPT) == 0) { 861 opt[0] = TCPOPT_MAXSEG; 862 opt[1] = 4; 863 opt[2] = (tp->t_ourmss >> 8) & 0xff; 864 opt[3] = tp->t_ourmss & 0xff; 865 optlen = 4; 866 867 if ((tp->t_flags & TF_REQ_SCALE) && 868 ((flags & TH_ACK) == 0 || 869 (tp->t_flags & TF_RCVD_SCALE))) { 870 *((u_int32_t *) (opt + optlen)) = htonl( 871 TCPOPT_NOP << 24 | 872 TCPOPT_WINDOW << 16 | 873 TCPOLEN_WINDOW << 8 | 874 tp->request_r_scale); 875 optlen += 4; 876 } 877 } 878 } 879 880 /* 881 * Send a timestamp and echo-reply if this is a SYN and our side 882 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 883 * and our peer have sent timestamps in our SYN's. 884 */ 885 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 886 (flags & TH_RST) == 0 && 887 ((flags & (TH_SYN|TH_ACK)) == TH_SYN || 888 (tp->t_flags & TF_RCVD_TSTMP))) { 889 u_int32_t *lp = (u_int32_t *)(opt + optlen); 890 891 /* Form timestamp option as shown in appendix A of RFC 1323. */ 892 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 893 *lp++ = htonl(TCP_TIMESTAMP(tp)); 894 *lp = htonl(tp->ts_recent); 895 optlen += TCPOLEN_TSTAMP_APPA; 896 } 897 898 hdrlen += optlen; 899 900 #ifdef DIAGNOSTIC 901 if (len > txsegsize) 902 panic("tcp data to be sent is larger than segment"); 903 if (max_linkhdr + hdrlen > MCLBYTES) 904 panic("tcphdr too big"); 905 #endif 906 907 /* 908 * Grab a header mbuf, attaching a copy of data to 909 * be transmitted, and initialize the header from 910 * the template for sends on this connection. 911 */ 912 if (len) { 913 error = tcp_build_datapkt(tp, so, off, len, hdrlen, &m); 914 if (error) 915 goto out; 916 /* 917 * If we're sending everything we've got, set PUSH. 918 * (This will keep happy those implementations which only 919 * give data to the user when a buffer fills or 920 * a PUSH comes in.) 921 */ 922 if (off + len == so->so_snd.sb_cc) 923 flags |= TH_PUSH; 924 } else { 925 if (tp->t_flags & TF_ACKNOW) 926 tcpstat.tcps_sndacks++; 927 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 928 tcpstat.tcps_sndctrl++; 929 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 930 tcpstat.tcps_sndurg++; 931 else 932 tcpstat.tcps_sndwinup++; 933 934 MGETHDR(m, M_DONTWAIT, MT_HEADER); 935 if (m != NULL && max_linkhdr + hdrlen > MHLEN) { 936 MCLGET(m, M_DONTWAIT); 937 if ((m->m_flags & M_EXT) == 0) { 938 m_freem(m); 939 m = NULL; 940 } 941 } 942 if (m == NULL) { 943 error = ENOBUFS; 944 goto out; 945 } 946 MCLAIM(m, &tcp_tx_mowner); 947 m->m_data += max_linkhdr; 948 m->m_len = hdrlen; 949 } 950 m->m_pkthdr.rcvif = (struct ifnet *)0; 951 switch (af) { 952 #ifdef INET 953 case AF_INET: 954 ip = mtod(m, struct ip *); 955 #ifdef INET6 956 ip6 = NULL; 957 #endif 958 th = (struct tcphdr *)(ip + 1); 959 break; 960 #endif 961 #ifdef INET6 962 case AF_INET6: 963 ip = NULL; 964 ip6 = mtod(m, struct ip6_hdr *); 965 th = (struct tcphdr *)(ip6 + 1); 966 break; 967 #endif 968 default: /*pacify gcc*/ 969 ip = NULL; 970 #ifdef INET6 971 ip6 = NULL; 972 #endif 973 th = NULL; 974 break; 975 } 976 if (tp->t_template == 0) 977 panic("tcp_output"); 978 if (tp->t_template->m_len < iphdrlen) 979 panic("tcp_output"); 980 bcopy(mtod(tp->t_template, caddr_t), mtod(m, caddr_t), iphdrlen); 981 982 /* 983 * If we are doing retransmissions, then snd_nxt will 984 * not reflect the first unsent octet. For ACK only 985 * packets, we do not want the sequence number of the 986 * retransmitted packet, we want the sequence number 987 * of the next unsent octet. So, if there is no data 988 * (and no SYN or FIN), use snd_max instead of snd_nxt 989 * when filling in ti_seq. But if we are in persist 990 * state, snd_max might reflect one byte beyond the 991 * right edge of the window, so use snd_nxt in that 992 * case, since we know we aren't doing a retransmission. 993 * (retransmit and persist are mutually exclusive...) 994 */ 995 if (len || (flags & (TH_SYN|TH_FIN)) || 996 TCP_TIMER_ISARMED(tp, TCPT_PERSIST)) 997 th->th_seq = htonl(tp->snd_nxt); 998 else 999 th->th_seq = htonl(tp->snd_max); 1000 th->th_ack = htonl(tp->rcv_nxt); 1001 if (optlen) { 1002 bcopy((caddr_t)opt, (caddr_t)(th + 1), optlen); 1003 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1004 } 1005 th->th_flags = flags; 1006 /* 1007 * Calculate receive window. Don't shrink window, 1008 * but avoid silly window syndrome. 1009 */ 1010 if (win < (long)(so->so_rcv.sb_hiwat / 4) && win < (long)rxsegsize) 1011 win = 0; 1012 if (win > (long)TCP_MAXWIN << tp->rcv_scale) 1013 win = (long)TCP_MAXWIN << tp->rcv_scale; 1014 if (win < (long)(tp->rcv_adv - tp->rcv_nxt)) 1015 win = (long)(tp->rcv_adv - tp->rcv_nxt); 1016 th->th_win = htons((u_int16_t) (win>>tp->rcv_scale)); 1017 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1018 u_int32_t urp = tp->snd_up - tp->snd_nxt; 1019 if (urp > IP_MAXPACKET) 1020 urp = IP_MAXPACKET; 1021 th->th_urp = htons((u_int16_t)urp); 1022 th->th_flags |= TH_URG; 1023 } else 1024 /* 1025 * If no urgent pointer to send, then we pull 1026 * the urgent pointer to the left edge of the send window 1027 * so that it doesn't drift into the send window on sequence 1028 * number wraparound. 1029 */ 1030 tp->snd_up = tp->snd_una; /* drag it along */ 1031 1032 /* 1033 * Set ourselves up to be checksummed just before the packet 1034 * hits the wire. 1035 */ 1036 switch (af) { 1037 #ifdef INET 1038 case AF_INET: 1039 m->m_pkthdr.csum_flags = M_CSUM_TCPv4; 1040 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1041 if (len + optlen) { 1042 /* Fixup the pseudo-header checksum. */ 1043 /* XXXJRT Not IP Jumbogram safe. */ 1044 th->th_sum = in_cksum_addword(th->th_sum, 1045 htons((u_int16_t) (len + optlen))); 1046 } 1047 break; 1048 #endif 1049 #ifdef INET6 1050 case AF_INET6: 1051 /* 1052 * XXX Actually delaying the checksum is Hard 1053 * XXX (well, maybe not for Itojun, but it is 1054 * XXX for me), but we can still take advantage 1055 * XXX of the cached pseudo-header checksum. 1056 */ 1057 /* equals to hdrlen + len */ 1058 m->m_pkthdr.len = sizeof(struct ip6_hdr) 1059 + sizeof(struct tcphdr) + optlen + len; 1060 #ifdef notyet 1061 m->m_pkthdr.csum_flags = M_CSUM_TCPv6; 1062 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1063 #endif 1064 if (len + optlen) { 1065 /* Fixup the pseudo-header checksum. */ 1066 /* XXXJRT: Not IPv6 Jumbogram safe. */ 1067 th->th_sum = in_cksum_addword(th->th_sum, 1068 htons((u_int16_t) (len + optlen))); 1069 } 1070 #ifndef notyet 1071 th->th_sum = in6_cksum(m, 0, sizeof(struct ip6_hdr), 1072 sizeof(struct tcphdr) + optlen + len); 1073 #endif 1074 break; 1075 #endif 1076 } 1077 1078 /* 1079 * In transmit state, time the transmission and arrange for 1080 * the retransmit. In persist state, just set snd_max. 1081 */ 1082 if (tp->t_force == 0 || TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) { 1083 tcp_seq startseq = tp->snd_nxt; 1084 1085 /* 1086 * Advance snd_nxt over sequence space of this segment. 1087 * There are no states in which we send both a SYN and a FIN, 1088 * so we collapse the tests for these flags. 1089 */ 1090 if (flags & (TH_SYN|TH_FIN)) 1091 tp->snd_nxt++; 1092 tp->snd_nxt += len; 1093 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1094 tp->snd_max = tp->snd_nxt; 1095 /* 1096 * Time this transmission if not a retransmission and 1097 * not currently timing anything. 1098 */ 1099 if (tp->t_rtttime == 0) { 1100 tp->t_rtttime = tcp_now; 1101 tp->t_rtseq = startseq; 1102 tcpstat.tcps_segstimed++; 1103 } 1104 } 1105 1106 /* 1107 * Set retransmit timer if not currently set, 1108 * and not doing an ack or a keep-alive probe. 1109 * Initial value for retransmit timer is smoothed 1110 * round-trip time + 2 * round-trip time variance. 1111 * Initialize shift counter which is used for backoff 1112 * of retransmit time. 1113 */ 1114 if (TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 && 1115 tp->snd_nxt != tp->snd_una) { 1116 TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); 1117 if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST)) { 1118 TCP_TIMER_DISARM(tp, TCPT_PERSIST); 1119 tp->t_rxtshift = 0; 1120 } 1121 } 1122 } else 1123 if (SEQ_GT(tp->snd_nxt + len, tp->snd_max)) 1124 tp->snd_max = tp->snd_nxt + len; 1125 1126 #ifdef TCP_DEBUG 1127 /* 1128 * Trace. 1129 */ 1130 if (so->so_options & SO_DEBUG) 1131 tcp_trace(TA_OUTPUT, tp->t_state, tp, m, 0); 1132 #endif 1133 1134 /* 1135 * Fill in IP length and desired time to live and 1136 * send to IP level. There should be a better way 1137 * to handle ttl and tos; we could keep them in 1138 * the template, but need a way to checksum without them. 1139 */ 1140 m->m_pkthdr.len = hdrlen + len; 1141 1142 switch (af) { 1143 #ifdef INET 1144 case AF_INET: 1145 ip->ip_len = htons(m->m_pkthdr.len); 1146 if (tp->t_inpcb) { 1147 ip->ip_ttl = tp->t_inpcb->inp_ip.ip_ttl; 1148 ip->ip_tos = tp->t_inpcb->inp_ip.ip_tos; 1149 } 1150 #ifdef INET6 1151 else if (tp->t_in6pcb) { 1152 ip->ip_ttl = in6_selecthlim(tp->t_in6pcb, NULL); /*XXX*/ 1153 ip->ip_tos = 0; /*XXX*/ 1154 } 1155 #endif 1156 break; 1157 #endif 1158 #ifdef INET6 1159 case AF_INET6: 1160 ip6->ip6_nxt = IPPROTO_TCP; 1161 if (tp->t_in6pcb) { 1162 /* 1163 * we separately set hoplimit for every segment, since 1164 * the user might want to change the value via 1165 * setsockopt. Also, desired default hop limit might 1166 * be changed via Neighbor Discovery. 1167 */ 1168 ip6->ip6_hlim = in6_selecthlim(tp->t_in6pcb, 1169 ro->ro_rt ? ro->ro_rt->rt_ifp : NULL); 1170 } 1171 /* ip6->ip6_flow = ??? */ 1172 /* ip6_plen will be filled in ip6_output(). */ 1173 break; 1174 #endif 1175 } 1176 1177 switch (af) { 1178 #ifdef INET 1179 case AF_INET: 1180 { 1181 struct mbuf *opts; 1182 1183 if (tp->t_inpcb) 1184 opts = tp->t_inpcb->inp_options; 1185 else 1186 opts = NULL; 1187 error = ip_output(m, opts, ro, 1188 (tp->t_mtudisc ? IP_MTUDISC : 0) | 1189 (so->so_options & SO_DONTROUTE), 1190 (struct ip_moptions *)0, so); 1191 break; 1192 } 1193 #endif 1194 #ifdef INET6 1195 case AF_INET6: 1196 { 1197 struct ip6_pktopts *opts; 1198 1199 if (tp->t_in6pcb) 1200 opts = tp->t_in6pcb->in6p_outputopts; 1201 else 1202 opts = NULL; 1203 error = ip6_output(m, opts, (struct route_in6 *)ro, 1204 so->so_options & SO_DONTROUTE, 1205 (struct ip6_moptions *)0, so, NULL); 1206 break; 1207 } 1208 #endif 1209 default: 1210 error = EAFNOSUPPORT; 1211 break; 1212 } 1213 if (error) { 1214 out: 1215 if (error == ENOBUFS) { 1216 tcpstat.tcps_selfquench++; 1217 #ifdef INET 1218 if (tp->t_inpcb) 1219 tcp_quench(tp->t_inpcb, 0); 1220 #endif 1221 #ifdef INET6 1222 if (tp->t_in6pcb) 1223 tcp6_quench(tp->t_in6pcb, 0); 1224 #endif 1225 error = 0; 1226 } else if ((error == EHOSTUNREACH || error == ENETDOWN) && 1227 TCPS_HAVERCVDSYN(tp->t_state)) { 1228 tp->t_softerror = error; 1229 error = 0; 1230 } 1231 1232 /* Restart the delayed ACK timer, if necessary. */ 1233 if (tp->t_flags & TF_DELACK) 1234 TCP_RESTART_DELACK(tp); 1235 1236 return (error); 1237 } 1238 tcpstat.tcps_sndtotal++; 1239 if (tp->t_flags & TF_DELACK) 1240 tcpstat.tcps_delack++; 1241 1242 /* 1243 * Data sent (as far as we can tell). 1244 * If this advertises a larger window than any other segment, 1245 * then remember the size of the advertised window. 1246 * Any pending ACK has now been sent. 1247 */ 1248 if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv)) 1249 tp->rcv_adv = tp->rcv_nxt + win; 1250 tp->last_ack_sent = tp->rcv_nxt; 1251 tp->t_flags &= ~TF_ACKNOW; 1252 TCP_CLEAR_DELACK(tp); 1253 #ifdef DIAGNOSTIC 1254 if (maxburst < 0) 1255 printf("tcp_output: maxburst exceeded by %d\n", -maxburst); 1256 #endif 1257 if (sendalot && (!tcp_do_newreno || --maxburst)) 1258 goto again; 1259 return (0); 1260 } 1261 1262 void 1263 tcp_setpersist(tp) 1264 struct tcpcb *tp; 1265 { 1266 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> (1 + 2); 1267 int nticks; 1268 1269 if (TCP_TIMER_ISARMED(tp, TCPT_REXMT)) 1270 panic("tcp_output REXMT"); 1271 /* 1272 * Start/restart persistance timer. 1273 */ 1274 if (t < tp->t_rttmin) 1275 t = tp->t_rttmin; 1276 TCPT_RANGESET(nticks, t * tcp_backoff[tp->t_rxtshift], 1277 TCPTV_PERSMIN, TCPTV_PERSMAX); 1278 TCP_TIMER_ARM(tp, TCPT_PERSIST, nticks); 1279 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1280 tp->t_rxtshift++; 1281 } 1282