1 /* $NetBSD: tcp_subr.c,v 1.30 1997/10/13 00:48:12 explorer Exp $ */ 2 3 /* 4 * Copyright (c) 1982, 1986, 1988, 1990, 1993 5 * The Regents of the University of California. 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. All advertising materials mentioning features or use of this software 16 * must display the following acknowledgement: 17 * This product includes software developed by the University of 18 * California, Berkeley and its contributors. 19 * 4. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 * 35 * @(#)tcp_subr.c 8.1 (Berkeley) 6/10/93 36 */ 37 38 #include "rnd.h" 39 40 #include <sys/param.h> 41 #include <sys/proc.h> 42 #include <sys/systm.h> 43 #include <sys/malloc.h> 44 #include <sys/mbuf.h> 45 #include <sys/socket.h> 46 #include <sys/socketvar.h> 47 #include <sys/protosw.h> 48 #include <sys/errno.h> 49 #include <sys/kernel.h> 50 #if NRND > 0 51 #include <sys/rnd.h> 52 #endif 53 54 #include <net/route.h> 55 #include <net/if.h> 56 57 #include <netinet/in.h> 58 #include <netinet/in_systm.h> 59 #include <netinet/ip.h> 60 #include <netinet/in_pcb.h> 61 #include <netinet/ip_var.h> 62 #include <netinet/ip_icmp.h> 63 #include <netinet/tcp.h> 64 #include <netinet/tcp_fsm.h> 65 #include <netinet/tcp_seq.h> 66 #include <netinet/tcp_timer.h> 67 #include <netinet/tcp_var.h> 68 #include <netinet/tcpip.h> 69 70 /* patchable/settable parameters for tcp */ 71 int tcp_mssdflt = TCP_MSS; 72 int tcp_rttdflt = TCPTV_SRTTDFLT / PR_SLOWHZ; 73 int tcp_do_rfc1323 = 1; 74 75 #ifndef TCBHASHSIZE 76 #define TCBHASHSIZE 128 77 #endif 78 int tcbhashsize = TCBHASHSIZE; 79 80 /* 81 * Tcp initialization 82 */ 83 void 84 tcp_init() 85 { 86 87 in_pcbinit(&tcbtable, tcbhashsize, tcbhashsize); 88 if (max_protohdr < sizeof(struct tcpiphdr)) 89 max_protohdr = sizeof(struct tcpiphdr); 90 if (max_linkhdr + sizeof(struct tcpiphdr) > MHLEN) 91 panic("tcp_init"); 92 } 93 94 /* 95 * Create template to be used to send tcp packets on a connection. 96 * Call after host entry created, allocates an mbuf and fills 97 * in a skeletal tcp/ip header, minimizing the amount of work 98 * necessary when the connection is used. 99 */ 100 struct tcpiphdr * 101 tcp_template(tp) 102 struct tcpcb *tp; 103 { 104 register struct inpcb *inp = tp->t_inpcb; 105 register struct tcpiphdr *n; 106 107 if ((n = tp->t_template) == 0) { 108 MALLOC(n, struct tcpiphdr *, sizeof (struct tcpiphdr), 109 M_MBUF, M_NOWAIT); 110 if (n == NULL) 111 return (0); 112 } 113 bzero(n->ti_x1, sizeof n->ti_x1); 114 n->ti_pr = IPPROTO_TCP; 115 n->ti_len = htons(sizeof (struct tcpiphdr) - sizeof (struct ip)); 116 n->ti_src = inp->inp_laddr; 117 n->ti_dst = inp->inp_faddr; 118 n->ti_sport = inp->inp_lport; 119 n->ti_dport = inp->inp_fport; 120 n->ti_seq = 0; 121 n->ti_ack = 0; 122 n->ti_x2 = 0; 123 n->ti_off = 5; 124 n->ti_flags = 0; 125 n->ti_win = 0; 126 n->ti_sum = 0; 127 n->ti_urp = 0; 128 return (n); 129 } 130 131 /* 132 * Send a single message to the TCP at address specified by 133 * the given TCP/IP header. If m == 0, then we make a copy 134 * of the tcpiphdr at ti and send directly to the addressed host. 135 * This is used to force keep alive messages out using the TCP 136 * template for a connection tp->t_template. If flags are given 137 * then we send a message back to the TCP which originated the 138 * segment ti, and discard the mbuf containing it and any other 139 * attached mbufs. 140 * 141 * In any case the ack and sequence number of the transmitted 142 * segment are as specified by the parameters. 143 */ 144 int 145 tcp_respond(tp, ti, m, ack, seq, flags) 146 struct tcpcb *tp; 147 register struct tcpiphdr *ti; 148 register struct mbuf *m; 149 tcp_seq ack, seq; 150 int flags; 151 { 152 register int tlen; 153 int win = 0; 154 struct route *ro = 0; 155 156 if (tp) { 157 win = sbspace(&tp->t_inpcb->inp_socket->so_rcv); 158 ro = &tp->t_inpcb->inp_route; 159 } 160 if (m == 0) { 161 m = m_gethdr(M_DONTWAIT, MT_HEADER); 162 if (m == NULL) 163 return (ENOBUFS); 164 #ifdef TCP_COMPAT_42 165 tlen = 1; 166 #else 167 tlen = 0; 168 #endif 169 m->m_data += max_linkhdr; 170 *mtod(m, struct tcpiphdr *) = *ti; 171 ti = mtod(m, struct tcpiphdr *); 172 flags = TH_ACK; 173 } else { 174 m_freem(m->m_next); 175 m->m_next = 0; 176 m->m_data = (caddr_t)ti; 177 m->m_len = sizeof (struct tcpiphdr); 178 tlen = 0; 179 #define xchg(a,b,type) { type t; t=a; a=b; b=t; } 180 xchg(ti->ti_dst.s_addr, ti->ti_src.s_addr, u_int32_t); 181 xchg(ti->ti_dport, ti->ti_sport, u_int16_t); 182 #undef xchg 183 } 184 bzero(ti->ti_x1, sizeof ti->ti_x1); 185 ti->ti_seq = htonl(seq); 186 ti->ti_ack = htonl(ack); 187 ti->ti_x2 = 0; 188 if ((flags & TH_SYN) == 0) { 189 if (tp) 190 ti->ti_win = htons((u_int16_t) (win >> tp->rcv_scale)); 191 else 192 ti->ti_win = htons((u_int16_t)win); 193 ti->ti_off = sizeof (struct tcphdr) >> 2; 194 tlen += sizeof (struct tcphdr); 195 } else 196 tlen += ti->ti_off << 2; 197 ti->ti_len = htons((u_int16_t)tlen); 198 tlen += sizeof (struct ip); 199 m->m_len = tlen; 200 m->m_pkthdr.len = tlen; 201 m->m_pkthdr.rcvif = (struct ifnet *) 0; 202 ti->ti_flags = flags; 203 ti->ti_urp = 0; 204 ti->ti_sum = 0; 205 ti->ti_sum = in_cksum(m, tlen); 206 ((struct ip *)ti)->ip_len = tlen; 207 ((struct ip *)ti)->ip_ttl = ip_defttl; 208 return ip_output(m, NULL, ro, 0, NULL); 209 } 210 211 /* 212 * Create a new TCP control block, making an 213 * empty reassembly queue and hooking it to the argument 214 * protocol control block. 215 */ 216 struct tcpcb * 217 tcp_newtcpcb(inp) 218 struct inpcb *inp; 219 { 220 register struct tcpcb *tp; 221 222 tp = malloc(sizeof(*tp), M_PCB, M_NOWAIT); 223 if (tp == NULL) 224 return ((struct tcpcb *)0); 225 bzero((caddr_t)tp, sizeof(struct tcpcb)); 226 LIST_INIT(&tp->segq); 227 tp->t_maxseg = tcp_mssdflt; 228 tp->t_ourmss = tcp_mssdflt; 229 230 tp->t_flags = tcp_do_rfc1323 ? (TF_REQ_SCALE|TF_REQ_TSTMP) : 0; 231 tp->t_inpcb = inp; 232 /* 233 * Init srtt to TCPTV_SRTTBASE (0), so we can tell that we have no 234 * rtt estimate. Set rttvar so that srtt + 2 * rttvar gives 235 * reasonable initial retransmit time. 236 */ 237 tp->t_srtt = TCPTV_SRTTBASE; 238 tp->t_rttvar = tcp_rttdflt * PR_SLOWHZ << (TCP_RTTVAR_SHIFT + 2 - 1); 239 tp->t_rttmin = TCPTV_MIN; 240 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 241 TCPTV_MIN, TCPTV_REXMTMAX); 242 tp->snd_cwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT; 243 tp->snd_ssthresh = TCP_MAXWIN << TCP_MAX_WINSHIFT; 244 inp->inp_ip.ip_ttl = ip_defttl; 245 inp->inp_ppcb = (caddr_t)tp; 246 return (tp); 247 } 248 249 /* 250 * Drop a TCP connection, reporting 251 * the specified error. If connection is synchronized, 252 * then send a RST to peer. 253 */ 254 struct tcpcb * 255 tcp_drop(tp, errno) 256 register struct tcpcb *tp; 257 int errno; 258 { 259 struct socket *so = tp->t_inpcb->inp_socket; 260 261 if (TCPS_HAVERCVDSYN(tp->t_state)) { 262 tp->t_state = TCPS_CLOSED; 263 (void) tcp_output(tp); 264 tcpstat.tcps_drops++; 265 } else 266 tcpstat.tcps_conndrops++; 267 if (errno == ETIMEDOUT && tp->t_softerror) 268 errno = tp->t_softerror; 269 so->so_error = errno; 270 return (tcp_close(tp)); 271 } 272 273 /* 274 * Close a TCP control block: 275 * discard all space held by the tcp 276 * discard internet protocol block 277 * wake up any sleepers 278 */ 279 struct tcpcb * 280 tcp_close(tp) 281 register struct tcpcb *tp; 282 { 283 register struct ipqent *qe; 284 struct inpcb *inp = tp->t_inpcb; 285 struct socket *so = inp->inp_socket; 286 #ifdef RTV_RTT 287 register struct rtentry *rt; 288 289 /* 290 * If we sent enough data to get some meaningful characteristics, 291 * save them in the routing entry. 'Enough' is arbitrarily 292 * defined as the sendpipesize (default 4K) * 16. This would 293 * give us 16 rtt samples assuming we only get one sample per 294 * window (the usual case on a long haul net). 16 samples is 295 * enough for the srtt filter to converge to within 5% of the correct 296 * value; fewer samples and we could save a very bogus rtt. 297 * 298 * Don't update the default route's characteristics and don't 299 * update anything that the user "locked". 300 */ 301 if (SEQ_LT(tp->iss + so->so_snd.sb_hiwat * 16, tp->snd_max) && 302 (rt = inp->inp_route.ro_rt) && 303 !in_nullhost(satosin(rt_key(rt))->sin_addr)) { 304 register u_long i = 0; 305 306 if ((rt->rt_rmx.rmx_locks & RTV_RTT) == 0) { 307 i = tp->t_srtt * 308 ((RTM_RTTUNIT / PR_SLOWHZ) >> (TCP_RTT_SHIFT + 2)); 309 if (rt->rt_rmx.rmx_rtt && i) 310 /* 311 * filter this update to half the old & half 312 * the new values, converting scale. 313 * See route.h and tcp_var.h for a 314 * description of the scaling constants. 315 */ 316 rt->rt_rmx.rmx_rtt = 317 (rt->rt_rmx.rmx_rtt + i) / 2; 318 else 319 rt->rt_rmx.rmx_rtt = i; 320 } 321 if ((rt->rt_rmx.rmx_locks & RTV_RTTVAR) == 0) { 322 i = tp->t_rttvar * 323 ((RTM_RTTUNIT / PR_SLOWHZ) >> (TCP_RTTVAR_SHIFT + 2)); 324 if (rt->rt_rmx.rmx_rttvar && i) 325 rt->rt_rmx.rmx_rttvar = 326 (rt->rt_rmx.rmx_rttvar + i) / 2; 327 else 328 rt->rt_rmx.rmx_rttvar = i; 329 } 330 /* 331 * update the pipelimit (ssthresh) if it has been updated 332 * already or if a pipesize was specified & the threshhold 333 * got below half the pipesize. I.e., wait for bad news 334 * before we start updating, then update on both good 335 * and bad news. 336 */ 337 if (((rt->rt_rmx.rmx_locks & RTV_SSTHRESH) == 0 && 338 (i = tp->snd_ssthresh) && rt->rt_rmx.rmx_ssthresh) || 339 i < (rt->rt_rmx.rmx_sendpipe / 2)) { 340 /* 341 * convert the limit from user data bytes to 342 * packets then to packet data bytes. 343 */ 344 i = (i + tp->t_maxseg / 2) / tp->t_maxseg; 345 if (i < 2) 346 i = 2; 347 i *= (u_long)(tp->t_maxseg + sizeof (struct tcpiphdr)); 348 if (rt->rt_rmx.rmx_ssthresh) 349 rt->rt_rmx.rmx_ssthresh = 350 (rt->rt_rmx.rmx_ssthresh + i) / 2; 351 else 352 rt->rt_rmx.rmx_ssthresh = i; 353 } 354 } 355 #endif /* RTV_RTT */ 356 /* free the reassembly queue, if any */ 357 while ((qe = tp->segq.lh_first) != NULL) { 358 LIST_REMOVE(qe, ipqe_q); 359 m_freem(qe->ipqe_m); 360 FREE(qe, M_IPQ); 361 } 362 if (tp->t_template) 363 FREE(tp->t_template, M_MBUF); 364 free(tp, M_PCB); 365 inp->inp_ppcb = 0; 366 soisdisconnected(so); 367 in_pcbdetach(inp); 368 tcpstat.tcps_closed++; 369 return ((struct tcpcb *)0); 370 } 371 372 void 373 tcp_drain() 374 { 375 376 } 377 378 /* 379 * Notify a tcp user of an asynchronous error; 380 * store error as soft error, but wake up user 381 * (for now, won't do anything until can select for soft error). 382 */ 383 void 384 tcp_notify(inp, error) 385 struct inpcb *inp; 386 int error; 387 { 388 register struct tcpcb *tp = (struct tcpcb *)inp->inp_ppcb; 389 register struct socket *so = inp->inp_socket; 390 391 /* 392 * Ignore some errors if we are hooked up. 393 * If connection hasn't completed, has retransmitted several times, 394 * and receives a second error, give up now. This is better 395 * than waiting a long time to establish a connection that 396 * can never complete. 397 */ 398 if (tp->t_state == TCPS_ESTABLISHED && 399 (error == EHOSTUNREACH || error == ENETUNREACH || 400 error == EHOSTDOWN)) { 401 return; 402 } else if (TCPS_HAVEESTABLISHED(tp->t_state) == 0 && 403 tp->t_rxtshift > 3 && tp->t_softerror) 404 so->so_error = error; 405 else 406 tp->t_softerror = error; 407 wakeup((caddr_t) &so->so_timeo); 408 sorwakeup(so); 409 sowwakeup(so); 410 } 411 412 void * 413 tcp_ctlinput(cmd, sa, v) 414 int cmd; 415 struct sockaddr *sa; 416 register void *v; 417 { 418 register struct ip *ip = v; 419 register struct tcphdr *th; 420 extern int inetctlerrmap[]; 421 void (*notify) __P((struct inpcb *, int)) = tcp_notify; 422 int errno; 423 int nmatch; 424 425 if ((unsigned)cmd >= PRC_NCMDS) 426 return NULL; 427 errno = inetctlerrmap[cmd]; 428 if (cmd == PRC_QUENCH) 429 notify = tcp_quench; 430 else if (PRC_IS_REDIRECT(cmd)) 431 notify = in_rtchange, ip = 0; 432 else if (cmd == PRC_HOSTDEAD) 433 ip = 0; 434 else if (errno == 0) 435 return NULL; 436 if (ip) { 437 th = (struct tcphdr *)((caddr_t)ip + (ip->ip_hl << 2)); 438 nmatch = in_pcbnotify(&tcbtable, satosin(sa)->sin_addr, 439 th->th_dport, ip->ip_src, th->th_sport, errno, notify); 440 if (nmatch == 0 && syn_cache_count && 441 (inetctlerrmap[cmd] == EHOSTUNREACH || 442 inetctlerrmap[cmd] == ENETUNREACH || 443 inetctlerrmap[cmd] == EHOSTDOWN)) 444 syn_cache_unreach(ip, th); 445 } else 446 (void)in_pcbnotifyall(&tcbtable, satosin(sa)->sin_addr, errno, 447 notify); 448 return NULL; 449 } 450 451 /* 452 * When a source quench is received, close congestion window 453 * to one segment. We will gradually open it again as we proceed. 454 */ 455 void 456 tcp_quench(inp, errno) 457 struct inpcb *inp; 458 int errno; 459 { 460 struct tcpcb *tp = intotcpcb(inp); 461 462 if (tp) 463 tp->snd_cwnd = tp->t_maxseg; 464 } 465 466 /* 467 * Compute the MSS to advertise to the peer. Called only during 468 * the 3-way handshake. If we are the server (peer initiated 469 * connection), we are called with the TCPCB for the listen 470 * socket. If we are the client (we initiated connection), we 471 * are called witht he TCPCB for the actual connection. 472 */ 473 int 474 tcp_mss_to_advertise(tp) 475 const struct tcpcb *tp; 476 { 477 extern u_long in_maxmtu; 478 struct inpcb *inp; 479 struct socket *so; 480 int mss; 481 482 inp = tp->t_inpcb; 483 so = inp->inp_socket; 484 485 /* 486 * In order to avoid defeating path MTU discovery on the peer, 487 * we advertise the max MTU of all attached networks as our MSS, 488 * per RFC 1191, section 3.1. 489 * 490 * XXX Should we allow room for the timestamp option if 491 * XXX rfc1323 is enabled? 492 */ 493 mss = in_maxmtu - sizeof(struct tcpiphdr); 494 495 return (mss); 496 } 497 498 /* 499 * Set connection variables based on the peer's advertised MSS. 500 * We are passed the TCPCB for the actual connection. If we 501 * are the server, we are called by the compressed state engine 502 * when the 3-way handshake is complete. If we are the client, 503 * we are called when we recieve the SYN,ACK from the server. 504 * 505 * NOTE: Our advertised MSS value must be initialized in the TCPCB 506 * before this routine is called! 507 */ 508 void 509 tcp_mss_from_peer(tp, offer) 510 struct tcpcb *tp; 511 int offer; 512 { 513 struct inpcb *inp = tp->t_inpcb; 514 struct socket *so = inp->inp_socket; 515 #if defined(RTV_SPIPE) || defined(RTV_SSTHRESH) 516 struct rtentry *rt = in_pcbrtentry(inp); 517 #endif 518 u_long bufsize; 519 int mss; 520 521 /* 522 * Assume our MSS is the MSS of the peer, unless they sent us 523 * an offer. Do not accept offers less than 32 bytes. 524 */ 525 mss = tp->t_ourmss; 526 if (offer) 527 mss = offer; 528 mss = max(mss, 32); /* sanity */ 529 530 /* 531 * If there's a pipesize, change the socket buffer to that size. 532 * Make the socket buffer an integral number of MSS units. If 533 * the MSS is larger than the socket buffer, artificially decrease 534 * the MSS. 535 */ 536 #ifdef RTV_SPIPE 537 if (rt != NULL && rt->rt_rmx.rmx_sendpipe != 0) 538 bufsize = rt->rt_rmx.rmx_sendpipe; 539 else 540 #endif 541 bufsize = so->so_snd.sb_hiwat; 542 if (bufsize < mss) 543 mss = bufsize; 544 else { 545 bufsize = roundup(bufsize, mss); 546 if (bufsize > sb_max) 547 bufsize = sb_max; 548 (void) sbreserve(&so->so_snd, bufsize); 549 } 550 tp->t_maxseg = mss; 551 552 /* Initialize the initial congestion window. */ 553 tp->snd_cwnd = mss; 554 555 #ifdef RTV_SSTHRESH 556 if (rt != NULL && rt->rt_rmx.rmx_ssthresh) { 557 /* 558 * There's some sort of gateway or interface buffer 559 * limit on the path. Use this to set the slow 560 * start threshold, but set the threshold to no less 561 * than 2 * MSS. 562 */ 563 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 564 } 565 #endif 566 } 567 568 /* 569 * Processing necessary when a TCP connection is established. 570 */ 571 void 572 tcp_established(tp) 573 struct tcpcb *tp; 574 { 575 struct inpcb *inp = tp->t_inpcb; 576 struct socket *so = inp->inp_socket; 577 #ifdef RTV_RPIPE 578 struct rtentry *rt = in_pcbrtentry(inp); 579 #endif 580 u_long bufsize; 581 582 tp->t_state = TCPS_ESTABLISHED; 583 tp->t_timer[TCPT_KEEP] = tcp_keepidle; 584 585 #ifdef RTV_RPIPE 586 if (rt != NULL && rt->rt_rmx.rmx_recvpipe != 0) 587 bufsize = rt->rt_rmx.rmx_recvpipe; 588 else 589 #endif 590 bufsize = so->so_rcv.sb_hiwat; 591 if (bufsize > tp->t_ourmss) { 592 bufsize = roundup(bufsize, tp->t_ourmss); 593 if (bufsize > sb_max) 594 bufsize = sb_max; 595 (void) sbreserve(&so->so_rcv, bufsize); 596 } 597 } 598 599 /* 600 * Check if there's an initial rtt or rttvar. Convert from the 601 * route-table units to scaled multiples of the slow timeout timer. 602 * Called only during the 3-way handshake. 603 */ 604 void 605 tcp_rmx_rtt(tp) 606 struct tcpcb *tp; 607 { 608 #ifdef RTV_RTT 609 struct rtentry *rt; 610 int rtt; 611 612 if ((rt = in_pcbrtentry(tp->t_inpcb)) == NULL) 613 return; 614 615 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 616 /* 617 * XXX The lock bit for MTU indicates that the value 618 * is also a minimum value; this is subject to time. 619 */ 620 if (rt->rt_rmx.rmx_locks & RTV_RTT) 621 tp->t_rttmin = rtt / (RTM_RTTUNIT / PR_SLOWHZ); 622 tp->t_srtt = rtt / 623 ((RTM_RTTUNIT / PR_SLOWHZ) >> (TCP_RTT_SHIFT + 2)); 624 if (rt->rt_rmx.rmx_rttvar) { 625 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 626 ((RTM_RTTUNIT / PR_SLOWHZ) >> 627 (TCP_RTTVAR_SHIFT + 2)); 628 } else { 629 /* Default variation is +- 1 rtt */ 630 tp->t_rttvar = 631 tp->t_srtt >> (TCP_RTT_SHIFT - TCP_RTTVAR_SHIFT); 632 } 633 TCPT_RANGESET(tp->t_rxtcur, 634 ((tp->t_srtt >> 2) + tp->t_rttvar) >> (1 + 2), 635 tp->t_rttmin, TCPTV_REXMTMAX); 636 } 637 #endif 638 } 639 640 tcp_seq tcp_iss_seq = 0; /* tcp initial seq # */ 641 642 /* 643 * Get a new sequence value given a tcp control block 644 */ 645 tcp_seq 646 tcp_new_iss(tp, len, addin) 647 void *tp; 648 u_long len; 649 tcp_seq addin; 650 { 651 tcp_seq tcp_iss; 652 653 /* 654 * add randomness about this connection, but do not estimate 655 * entropy from the timing, since the physical device driver would 656 * have done that for us. 657 */ 658 #if NRND > 0 659 if (tp != NULL) 660 rnd_add_data(NULL, tp, len, 0); 661 #endif 662 663 /* 664 * randomize. 665 */ 666 #if NRND > 0 667 rnd_extract_data(&tcp_iss, sizeof(tcp_iss), RND_EXTRACT_ANY); 668 #else 669 tcp_iss = random(); 670 #endif 671 672 /* 673 * If we were asked to add some amount to a known value, 674 * we will take a random value obtained above, mask off the upper 675 * bits, and add in the known value. We also add in a constant to 676 * ensure that we are at least a certain distance from the original 677 * value. 678 * 679 * This is used when an old connection is in timed wait 680 * and we have a new one coming in, for instance. 681 */ 682 if (addin != 0) { 683 #ifdef TCPISS_DEBUG 684 printf("Random %08x, ", tcp_iss); 685 #endif 686 tcp_iss &= TCP_ISS_RANDOM_MASK; 687 tcp_iss = tcp_iss + addin + TCP_ISSINCR; 688 tcp_iss_seq += TCP_ISSINCR; 689 tcp_iss += tcp_iss_seq; 690 #ifdef TCPISS_DEBUG 691 printf("Old ISS %08x, ISS %08x\n", addin, tcp_iss); 692 #endif 693 } else { 694 tcp_iss &= TCP_ISS_RANDOM_MASK; 695 tcp_iss_seq += TCP_ISSINCR; 696 tcp_iss += tcp_iss_seq; 697 #ifdef TCPISS_DEBUG 698 printf("ISS %08x\n", tcp_iss); 699 #endif 700 } 701 702 #ifdef TCP_COMPAT_42 703 /* 704 * limit it to the positive range for really old TCP implementations 705 */ 706 if ((int)tcp_iss < 0) 707 tcp_iss &= 0x7fffffff; /* XXX */ 708 #endif 709 710 return tcp_iss; 711 } 712