tcp_timewait.c revision 41591
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_subr.c 8.2 (Berkeley) 5/24/95 34 * $Id: tcp_subr.c,v 1.48 1998/11/15 21:35:09 guido Exp $ 35 */ 36 37#include "opt_compat.h" 38#include "opt_tcpdebug.h" 39 40#include <sys/param.h> 41#include <sys/systm.h> 42#include <sys/kernel.h> 43#include <sys/sysctl.h> 44#include <sys/malloc.h> 45#include <sys/mbuf.h> 46#include <sys/socket.h> 47#include <sys/socketvar.h> 48#include <sys/protosw.h> 49 50#include <vm/vm_zone.h> 51 52#include <net/route.h> 53#include <net/if.h> 54 55#define _IP_VHL 56#include <netinet/in.h> 57#include <netinet/in_systm.h> 58#include <netinet/ip.h> 59#include <netinet/in_pcb.h> 60#include <netinet/in_var.h> 61#include <netinet/ip_var.h> 62#include <netinet/tcp.h> 63#include <netinet/tcp_fsm.h> 64#include <netinet/tcp_seq.h> 65#include <netinet/tcp_timer.h> 66#include <netinet/tcp_var.h> 67#include <netinet/tcpip.h> 68#ifdef TCPDEBUG 69#include <netinet/tcp_debug.h> 70#endif 71 72int tcp_mssdflt = TCP_MSS; 73SYSCTL_INT(_net_inet_tcp, TCPCTL_MSSDFLT, mssdflt, 74 CTLFLAG_RW, &tcp_mssdflt , 0, ""); 75 76static int tcp_rttdflt = TCPTV_SRTTDFLT / PR_SLOWHZ; 77SYSCTL_INT(_net_inet_tcp, TCPCTL_RTTDFLT, rttdflt, 78 CTLFLAG_RW, &tcp_rttdflt , 0, ""); 79 80static int tcp_do_rfc1323 = 1; 81SYSCTL_INT(_net_inet_tcp, TCPCTL_DO_RFC1323, rfc1323, 82 CTLFLAG_RW, &tcp_do_rfc1323 , 0, ""); 83 84static int tcp_do_rfc1644 = 0; 85SYSCTL_INT(_net_inet_tcp, TCPCTL_DO_RFC1644, rfc1644, 86 CTLFLAG_RW, &tcp_do_rfc1644 , 0, ""); 87 88SYSCTL_INT(_net_inet_tcp, OID_AUTO, pcbcount, CTLFLAG_RD, &tcbinfo.ipi_count, 89 0, "Number of active PCBs"); 90 91static void tcp_cleartaocache __P((void)); 92static void tcp_notify __P((struct inpcb *, int)); 93 94/* 95 * Target size of TCP PCB hash tables. Must be a power of two. 96 */ 97#ifndef TCBHASHSIZE 98#define TCBHASHSIZE 512 99#endif 100 101/* 102 * This is the actual shape of what we allocate using the zone 103 * allocator. Doing it this way allows us to protect both structures 104 * using the same generation count, and also eliminates the overhead 105 * of allocating tcpcbs separately. By hiding the structure here, 106 * we avoid changing most of the rest of the code (although it needs 107 * to be changed, eventually, for greater efficiency). 108 */ 109#define ALIGNMENT 32 110#define ALIGNM1 (ALIGNMENT - 1) 111struct inp_tp { 112 union { 113 struct inpcb inp; 114 char align[(sizeof(struct inpcb) + ALIGNM1) & ~ALIGNM1]; 115 } inp_tp_u; 116 struct tcpcb tcb; 117}; 118#undef ALIGNMENT 119#undef ALIGNM1 120 121/* 122 * Tcp initialization 123 */ 124void 125tcp_init() 126{ 127 128 tcp_iss = random(); /* wrong, but better than a constant */ 129 tcp_ccgen = 1; 130 tcp_cleartaocache(); 131 LIST_INIT(&tcb); 132 tcbinfo.listhead = &tcb; 133 tcbinfo.hashbase = hashinit(TCBHASHSIZE, M_PCB, &tcbinfo.hashmask); 134 tcbinfo.porthashbase = hashinit(TCBHASHSIZE, M_PCB, 135 &tcbinfo.porthashmask); 136 tcbinfo.ipi_zone = zinit("tcpcb", sizeof(struct inp_tp), maxsockets, 137 ZONE_INTERRUPT, 0); 138 if (max_protohdr < sizeof(struct tcpiphdr)) 139 max_protohdr = sizeof(struct tcpiphdr); 140 if (max_linkhdr + sizeof(struct tcpiphdr) > MHLEN) 141 panic("tcp_init"); 142} 143 144/* 145 * Create template to be used to send tcp packets on a connection. 146 * Call after host entry created, allocates an mbuf and fills 147 * in a skeletal tcp/ip header, minimizing the amount of work 148 * necessary when the connection is used. 149 */ 150struct tcpiphdr * 151tcp_template(tp) 152 struct tcpcb *tp; 153{ 154 register struct inpcb *inp = tp->t_inpcb; 155 register struct mbuf *m; 156 register struct tcpiphdr *n; 157 158 if ((n = tp->t_template) == 0) { 159 m = m_get(M_DONTWAIT, MT_HEADER); 160 if (m == NULL) 161 return (0); 162 m->m_len = sizeof (struct tcpiphdr); 163 n = mtod(m, struct tcpiphdr *); 164 } 165 bzero(n->ti_x1, sizeof(n->ti_x1)); 166 n->ti_pr = IPPROTO_TCP; 167 n->ti_len = htons(sizeof (struct tcpiphdr) - sizeof (struct ip)); 168 n->ti_src = inp->inp_laddr; 169 n->ti_dst = inp->inp_faddr; 170 n->ti_sport = inp->inp_lport; 171 n->ti_dport = inp->inp_fport; 172 n->ti_seq = 0; 173 n->ti_ack = 0; 174 n->ti_x2 = 0; 175 n->ti_off = 5; 176 n->ti_flags = 0; 177 n->ti_win = 0; 178 n->ti_sum = 0; 179 n->ti_urp = 0; 180 return (n); 181} 182 183/* 184 * Send a single message to the TCP at address specified by 185 * the given TCP/IP header. If m == 0, then we make a copy 186 * of the tcpiphdr at ti and send directly to the addressed host. 187 * This is used to force keep alive messages out using the TCP 188 * template for a connection tp->t_template. If flags are given 189 * then we send a message back to the TCP which originated the 190 * segment ti, and discard the mbuf containing it and any other 191 * attached mbufs. 192 * 193 * In any case the ack and sequence number of the transmitted 194 * segment are as specified by the parameters. 195 * 196 * NOTE: If m != NULL, then ti must point to *inside* the mbuf. 197 */ 198void 199tcp_respond(tp, ti, m, ack, seq, flags) 200 struct tcpcb *tp; 201 register struct tcpiphdr *ti; 202 register struct mbuf *m; 203 tcp_seq ack, seq; 204 int flags; 205{ 206 register int tlen; 207 int win = 0; 208 struct route *ro = 0; 209 struct route sro; 210 211 if (tp) { 212 if (!(flags & TH_RST)) 213 win = sbspace(&tp->t_inpcb->inp_socket->so_rcv); 214 ro = &tp->t_inpcb->inp_route; 215 } else { 216 ro = &sro; 217 bzero(ro, sizeof *ro); 218 } 219 if (m == 0) { 220 m = m_gethdr(M_DONTWAIT, MT_HEADER); 221 if (m == NULL) 222 return; 223#ifdef TCP_COMPAT_42 224 tlen = 1; 225#else 226 tlen = 0; 227#endif 228 m->m_data += max_linkhdr; 229 *mtod(m, struct tcpiphdr *) = *ti; 230 ti = mtod(m, struct tcpiphdr *); 231 flags = TH_ACK; 232 } else { 233 m_freem(m->m_next); 234 m->m_next = 0; 235 m->m_data = (caddr_t)ti; 236 m->m_len = sizeof (struct tcpiphdr); 237 tlen = 0; 238#define xchg(a,b,type) { type t; t=a; a=b; b=t; } 239 xchg(ti->ti_dst.s_addr, ti->ti_src.s_addr, n_long); 240 xchg(ti->ti_dport, ti->ti_sport, n_short); 241#undef xchg 242 } 243 ti->ti_len = htons((u_short)(sizeof (struct tcphdr) + tlen)); 244 tlen += sizeof (struct tcpiphdr); 245 m->m_len = tlen; 246 m->m_pkthdr.len = tlen; 247 m->m_pkthdr.rcvif = (struct ifnet *) 0; 248 bzero(ti->ti_x1, sizeof(ti->ti_x1)); 249 ti->ti_seq = htonl(seq); 250 ti->ti_ack = htonl(ack); 251 ti->ti_x2 = 0; 252 ti->ti_off = sizeof (struct tcphdr) >> 2; 253 ti->ti_flags = flags; 254 if (tp) 255 ti->ti_win = htons((u_short) (win >> tp->rcv_scale)); 256 else 257 ti->ti_win = htons((u_short)win); 258 ti->ti_urp = 0; 259 ti->ti_sum = 0; 260 ti->ti_sum = in_cksum(m, tlen); 261 ((struct ip *)ti)->ip_len = tlen; 262 ((struct ip *)ti)->ip_ttl = ip_defttl; 263#ifdef TCPDEBUG 264 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 265 tcp_trace(TA_OUTPUT, 0, tp, ti, 0); 266#endif 267 (void) ip_output(m, NULL, ro, 0, NULL); 268 if (ro == &sro && ro->ro_rt) { 269 RTFREE(ro->ro_rt); 270 } 271} 272 273/* 274 * Create a new TCP control block, making an 275 * empty reassembly queue and hooking it to the argument 276 * protocol control block. The `inp' parameter must have 277 * come from the zone allocator set up in tcp_init(). 278 */ 279struct tcpcb * 280tcp_newtcpcb(inp) 281 struct inpcb *inp; 282{ 283 struct inp_tp *it; 284 register struct tcpcb *tp; 285 286 it = (struct inp_tp *)inp; 287 tp = &it->tcb; 288 bzero((char *) tp, sizeof(struct tcpcb)); 289 tp->t_segq = NULL; 290 tp->t_maxseg = tp->t_maxopd = tcp_mssdflt; 291 292 if (tcp_do_rfc1323) 293 tp->t_flags = (TF_REQ_SCALE|TF_REQ_TSTMP); 294 if (tcp_do_rfc1644) 295 tp->t_flags |= TF_REQ_CC; 296 tp->t_inpcb = inp; /* XXX */ 297 /* 298 * Init srtt to TCPTV_SRTTBASE (0), so we can tell that we have no 299 * rtt estimate. Set rttvar so that srtt + 4 * rttvar gives 300 * reasonable initial retransmit time. 301 */ 302 tp->t_srtt = TCPTV_SRTTBASE; 303 tp->t_rttvar = ((TCPTV_RTOBASE - TCPTV_SRTTBASE) << TCP_RTTVAR_SHIFT) / 4; 304 tp->t_rttmin = TCPTV_MIN; 305 tp->t_rxtcur = TCPTV_RTOBASE; 306 tp->snd_cwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT; 307 tp->snd_ssthresh = TCP_MAXWIN << TCP_MAX_WINSHIFT; 308 inp->inp_ip_ttl = ip_defttl; 309 inp->inp_ppcb = (caddr_t)tp; 310 return (tp); /* XXX */ 311} 312 313/* 314 * Drop a TCP connection, reporting 315 * the specified error. If connection is synchronized, 316 * then send a RST to peer. 317 */ 318struct tcpcb * 319tcp_drop(tp, errno) 320 register struct tcpcb *tp; 321 int errno; 322{ 323 struct socket *so = tp->t_inpcb->inp_socket; 324 325 if (TCPS_HAVERCVDSYN(tp->t_state)) { 326 tp->t_state = TCPS_CLOSED; 327 (void) tcp_output(tp); 328 tcpstat.tcps_drops++; 329 } else 330 tcpstat.tcps_conndrops++; 331 if (errno == ETIMEDOUT && tp->t_softerror) 332 errno = tp->t_softerror; 333 so->so_error = errno; 334 return (tcp_close(tp)); 335} 336 337/* 338 * Close a TCP control block: 339 * discard all space held by the tcp 340 * discard internet protocol block 341 * wake up any sleepers 342 */ 343struct tcpcb * 344tcp_close(tp) 345 register struct tcpcb *tp; 346{ 347 register struct mbuf *q; 348 register struct mbuf *nq; 349 struct inpcb *inp = tp->t_inpcb; 350 struct socket *so = inp->inp_socket; 351 register struct rtentry *rt; 352 int dosavessthresh; 353 354 /* 355 * If we got enough samples through the srtt filter, 356 * save the rtt and rttvar in the routing entry. 357 * 'Enough' is arbitrarily defined as the 16 samples. 358 * 16 samples is enough for the srtt filter to converge 359 * to within 5% of the correct value; fewer samples and 360 * we could save a very bogus rtt. 361 * 362 * Don't update the default route's characteristics and don't 363 * update anything that the user "locked". 364 */ 365 if (tp->t_rttupdated >= 16 && 366 (rt = inp->inp_route.ro_rt) && 367 ((struct sockaddr_in *)rt_key(rt))->sin_addr.s_addr != INADDR_ANY) { 368 register u_long i = 0; 369 370 if ((rt->rt_rmx.rmx_locks & RTV_RTT) == 0) { 371 i = tp->t_srtt * 372 (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTT_SCALE)); 373 if (rt->rt_rmx.rmx_rtt && i) 374 /* 375 * filter this update to half the old & half 376 * the new values, converting scale. 377 * See route.h and tcp_var.h for a 378 * description of the scaling constants. 379 */ 380 rt->rt_rmx.rmx_rtt = 381 (rt->rt_rmx.rmx_rtt + i) / 2; 382 else 383 rt->rt_rmx.rmx_rtt = i; 384 tcpstat.tcps_cachedrtt++; 385 } 386 if ((rt->rt_rmx.rmx_locks & RTV_RTTVAR) == 0) { 387 i = tp->t_rttvar * 388 (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTTVAR_SCALE)); 389 if (rt->rt_rmx.rmx_rttvar && i) 390 rt->rt_rmx.rmx_rttvar = 391 (rt->rt_rmx.rmx_rttvar + i) / 2; 392 else 393 rt->rt_rmx.rmx_rttvar = i; 394 tcpstat.tcps_cachedrttvar++; 395 } 396 /* 397 * The old comment here said: 398 * update the pipelimit (ssthresh) if it has been updated 399 * already or if a pipesize was specified & the threshhold 400 * got below half the pipesize. I.e., wait for bad news 401 * before we start updating, then update on both good 402 * and bad news. 403 * 404 * But we want to save the ssthresh even if no pipesize is 405 * specified explicitly in the route, because such 406 * connections still have an implicit pipesize specified 407 * by the global tcp_sendspace. In the absence of a reliable 408 * way to calculate the pipesize, it will have to do. 409 */ 410 i = tp->snd_ssthresh; 411 if (rt->rt_rmx.rmx_sendpipe != 0) 412 dosavessthresh = (i < rt->rt_rmx.rmx_sendpipe / 2); 413 else 414 dosavessthresh = (i < so->so_snd.sb_hiwat / 2); 415 if (((rt->rt_rmx.rmx_locks & RTV_SSTHRESH) == 0 && 416 i != 0 && rt->rt_rmx.rmx_ssthresh != 0) 417 || dosavessthresh) { 418 /* 419 * convert the limit from user data bytes to 420 * packets then to packet data bytes. 421 */ 422 i = (i + tp->t_maxseg / 2) / tp->t_maxseg; 423 if (i < 2) 424 i = 2; 425 i *= (u_long)(tp->t_maxseg + sizeof (struct tcpiphdr)); 426 if (rt->rt_rmx.rmx_ssthresh) 427 rt->rt_rmx.rmx_ssthresh = 428 (rt->rt_rmx.rmx_ssthresh + i) / 2; 429 else 430 rt->rt_rmx.rmx_ssthresh = i; 431 tcpstat.tcps_cachedssthresh++; 432 } 433 } 434 /* free the reassembly queue, if any */ 435 for (q = tp->t_segq; q; q = nq) { 436 nq = q->m_nextpkt; 437 tp->t_segq = nq; 438 m_freem(q); 439 } 440 if (tp->t_template) 441 (void) m_free(dtom(tp->t_template)); 442 inp->inp_ppcb = NULL; 443 soisdisconnected(so); 444 in_pcbdetach(inp); 445 tcpstat.tcps_closed++; 446 return ((struct tcpcb *)0); 447} 448 449void 450tcp_drain() 451{ 452 453} 454 455/* 456 * Notify a tcp user of an asynchronous error; 457 * store error as soft error, but wake up user 458 * (for now, won't do anything until can select for soft error). 459 */ 460static void 461tcp_notify(inp, error) 462 struct inpcb *inp; 463 int error; 464{ 465 register struct tcpcb *tp = (struct tcpcb *)inp->inp_ppcb; 466 register struct socket *so = inp->inp_socket; 467 468 /* 469 * Ignore some errors if we are hooked up. 470 * If connection hasn't completed, has retransmitted several times, 471 * and receives a second error, give up now. This is better 472 * than waiting a long time to establish a connection that 473 * can never complete. 474 */ 475 if (tp->t_state == TCPS_ESTABLISHED && 476 (error == EHOSTUNREACH || error == ENETUNREACH || 477 error == EHOSTDOWN)) { 478 return; 479 } else if (tp->t_state < TCPS_ESTABLISHED && tp->t_rxtshift > 3 && 480 tp->t_softerror) 481 so->so_error = error; 482 else 483 tp->t_softerror = error; 484 wakeup((caddr_t) &so->so_timeo); 485 sorwakeup(so); 486 sowwakeup(so); 487} 488 489static int 490tcp_pcblist SYSCTL_HANDLER_ARGS 491{ 492 int error, i, n, s; 493 struct inpcb *inp, **inp_list; 494 inp_gen_t gencnt; 495 struct xinpgen xig; 496 497 /* 498 * The process of preparing the TCB list is too time-consuming and 499 * resource-intensive to repeat twice on every request. 500 */ 501 if (req->oldptr == 0) { 502 n = tcbinfo.ipi_count; 503 req->oldidx = 2 * (sizeof xig) 504 + (n + n/8) * sizeof(struct xtcpcb); 505 return 0; 506 } 507 508 if (req->newptr != 0) 509 return EPERM; 510 511 /* 512 * OK, now we're committed to doing something. 513 */ 514 s = splnet(); 515 gencnt = tcbinfo.ipi_gencnt; 516 n = tcbinfo.ipi_count; 517 splx(s); 518 519 xig.xig_len = sizeof xig; 520 xig.xig_count = n; 521 xig.xig_gen = gencnt; 522 xig.xig_sogen = so_gencnt; 523 error = SYSCTL_OUT(req, &xig, sizeof xig); 524 if (error) 525 return error; 526 527 inp_list = malloc(n * sizeof *inp_list, M_TEMP, M_WAITOK); 528 if (inp_list == 0) 529 return ENOMEM; 530 531 s = splnet(); 532 for (inp = tcbinfo.listhead->lh_first, i = 0; inp && i < n; 533 inp = inp->inp_list.le_next) { 534 if (inp->inp_gencnt <= gencnt) 535 inp_list[i++] = inp; 536 } 537 splx(s); 538 n = i; 539 540 error = 0; 541 for (i = 0; i < n; i++) { 542 inp = inp_list[i]; 543 if (inp->inp_gencnt <= gencnt) { 544 struct xtcpcb xt; 545 xt.xt_len = sizeof xt; 546 /* XXX should avoid extra copy */ 547 bcopy(inp, &xt.xt_inp, sizeof *inp); 548 bcopy(inp->inp_ppcb, &xt.xt_tp, sizeof xt.xt_tp); 549 if (inp->inp_socket) 550 sotoxsocket(inp->inp_socket, &xt.xt_socket); 551 error = SYSCTL_OUT(req, &xt, sizeof xt); 552 } 553 } 554 if (!error) { 555 /* 556 * Give the user an updated idea of our state. 557 * If the generation differs from what we told 558 * her before, she knows that something happened 559 * while we were processing this request, and it 560 * might be necessary to retry. 561 */ 562 s = splnet(); 563 xig.xig_gen = tcbinfo.ipi_gencnt; 564 xig.xig_sogen = so_gencnt; 565 xig.xig_count = tcbinfo.ipi_count; 566 splx(s); 567 error = SYSCTL_OUT(req, &xig, sizeof xig); 568 } 569 free(inp_list, M_TEMP); 570 return error; 571} 572 573SYSCTL_PROC(_net_inet_tcp, TCPCTL_PCBLIST, pcblist, CTLFLAG_RD, 0, 0, 574 tcp_pcblist, "S,xtcpcb", "List of active TCP connections"); 575 576void 577tcp_ctlinput(cmd, sa, vip) 578 int cmd; 579 struct sockaddr *sa; 580 void *vip; 581{ 582 register struct ip *ip = vip; 583 register struct tcphdr *th; 584 void (*notify) __P((struct inpcb *, int)) = tcp_notify; 585 586 if (cmd == PRC_QUENCH) 587 notify = tcp_quench; 588 else if (cmd == PRC_MSGSIZE) 589 notify = tcp_mtudisc; 590 else if (!PRC_IS_REDIRECT(cmd) && 591 ((unsigned)cmd > PRC_NCMDS || inetctlerrmap[cmd] == 0)) 592 return; 593 if (ip) { 594 th = (struct tcphdr *)((caddr_t)ip 595 + (IP_VHL_HL(ip->ip_vhl) << 2)); 596 in_pcbnotify(&tcb, sa, th->th_dport, ip->ip_src, th->th_sport, 597 cmd, notify); 598 } else 599 in_pcbnotify(&tcb, sa, 0, zeroin_addr, 0, cmd, notify); 600} 601 602/* 603 * When a source quench is received, close congestion window 604 * to one segment. We will gradually open it again as we proceed. 605 */ 606void 607tcp_quench(inp, errno) 608 struct inpcb *inp; 609 int errno; 610{ 611 struct tcpcb *tp = intotcpcb(inp); 612 613 if (tp) 614 tp->snd_cwnd = tp->t_maxseg; 615} 616 617/* 618 * When `need fragmentation' ICMP is received, update our idea of the MSS 619 * based on the new value in the route. Also nudge TCP to send something, 620 * since we know the packet we just sent was dropped. 621 * This duplicates some code in the tcp_mss() function in tcp_input.c. 622 */ 623void 624tcp_mtudisc(inp, errno) 625 struct inpcb *inp; 626 int errno; 627{ 628 struct tcpcb *tp = intotcpcb(inp); 629 struct rtentry *rt; 630 struct rmxp_tao *taop; 631 struct socket *so = inp->inp_socket; 632 int offered; 633 int mss; 634 635 if (tp) { 636 rt = tcp_rtlookup(inp); 637 if (!rt || !rt->rt_rmx.rmx_mtu) { 638 tp->t_maxopd = tp->t_maxseg = tcp_mssdflt; 639 return; 640 } 641 taop = rmx_taop(rt->rt_rmx); 642 offered = taop->tao_mssopt; 643 mss = rt->rt_rmx.rmx_mtu - sizeof(struct tcpiphdr); 644 if (offered) 645 mss = min(mss, offered); 646 /* 647 * XXX - The above conditional probably violates the TCP 648 * spec. The problem is that, since we don't know the 649 * other end's MSS, we are supposed to use a conservative 650 * default. But, if we do that, then MTU discovery will 651 * never actually take place, because the conservative 652 * default is much less than the MTUs typically seen 653 * on the Internet today. For the moment, we'll sweep 654 * this under the carpet. 655 * 656 * The conservative default might not actually be a problem 657 * if the only case this occurs is when sending an initial 658 * SYN with options and data to a host we've never talked 659 * to before. Then, they will reply with an MSS value which 660 * will get recorded and the new parameters should get 661 * recomputed. For Further Study. 662 */ 663 if (tp->t_maxopd <= mss) 664 return; 665 tp->t_maxopd = mss; 666 667 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 668 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP) 669 mss -= TCPOLEN_TSTAMP_APPA; 670 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 671 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC) 672 mss -= TCPOLEN_CC_APPA; 673#if (MCLBYTES & (MCLBYTES - 1)) == 0 674 if (mss > MCLBYTES) 675 mss &= ~(MCLBYTES-1); 676#else 677 if (mss > MCLBYTES) 678 mss = mss / MCLBYTES * MCLBYTES; 679#endif 680 if (so->so_snd.sb_hiwat < mss) 681 mss = so->so_snd.sb_hiwat; 682 683 tp->t_maxseg = mss; 684 685 tcpstat.tcps_mturesent++; 686 tp->t_rtt = 0; 687 tp->snd_nxt = tp->snd_una; 688 tcp_output(tp); 689 } 690} 691 692/* 693 * Look-up the routing entry to the peer of this inpcb. If no route 694 * is found and it cannot be allocated the return NULL. This routine 695 * is called by TCP routines that access the rmx structure and by tcp_mss 696 * to get the interface MTU. 697 */ 698struct rtentry * 699tcp_rtlookup(inp) 700 struct inpcb *inp; 701{ 702 struct route *ro; 703 struct rtentry *rt; 704 705 ro = &inp->inp_route; 706 rt = ro->ro_rt; 707 if (rt == NULL || !(rt->rt_flags & RTF_UP)) { 708 /* No route yet, so try to acquire one */ 709 if (inp->inp_faddr.s_addr != INADDR_ANY) { 710 ro->ro_dst.sa_family = AF_INET; 711 ro->ro_dst.sa_len = sizeof(ro->ro_dst); 712 ((struct sockaddr_in *) &ro->ro_dst)->sin_addr = 713 inp->inp_faddr; 714 rtalloc(ro); 715 rt = ro->ro_rt; 716 } 717 } 718 return rt; 719} 720 721/* 722 * Return a pointer to the cached information about the remote host. 723 * The cached information is stored in the protocol specific part of 724 * the route metrics. 725 */ 726struct rmxp_tao * 727tcp_gettaocache(inp) 728 struct inpcb *inp; 729{ 730 struct rtentry *rt = tcp_rtlookup(inp); 731 732 /* Make sure this is a host route and is up. */ 733 if (rt == NULL || 734 (rt->rt_flags & (RTF_UP|RTF_HOST)) != (RTF_UP|RTF_HOST)) 735 return NULL; 736 737 return rmx_taop(rt->rt_rmx); 738} 739 740/* 741 * Clear all the TAO cache entries, called from tcp_init. 742 * 743 * XXX 744 * This routine is just an empty one, because we assume that the routing 745 * routing tables are initialized at the same time when TCP, so there is 746 * nothing in the cache left over. 747 */ 748static void 749tcp_cleartaocache() 750{ 751} 752