tcp_timer.c revision 1.70
1/* $NetBSD: tcp_timer.c,v 1.70 2005/02/28 16:20:59 jonathan 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 (c) 1997, 1998, 2001 The NetBSD Foundation, Inc. 34 * All rights reserved. 35 * 36 * This code is derived from software contributed to The NetBSD Foundation 37 * by Jason R. Thorpe and Kevin M. Lahey of the Numerical Aerospace Simulation 38 * Facility, NASA Ames Research Center. 39 * 40 * Redistribution and use in source and binary forms, with or without 41 * modification, are permitted provided that the following conditions 42 * are met: 43 * 1. Redistributions of source code must retain the above copyright 44 * notice, this list of conditions and the following disclaimer. 45 * 2. Redistributions in binary form must reproduce the above copyright 46 * notice, this list of conditions and the following disclaimer in the 47 * documentation and/or other materials provided with the distribution. 48 * 3. All advertising materials mentioning features or use of this software 49 * must display the following acknowledgement: 50 * This product includes software developed by the NetBSD 51 * Foundation, Inc. and its contributors. 52 * 4. Neither the name of The NetBSD Foundation nor the names of its 53 * contributors may be used to endorse or promote products derived 54 * from this software without specific prior written permission. 55 * 56 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 57 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 58 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 59 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 60 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 61 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 62 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 63 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 64 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 65 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 66 * POSSIBILITY OF SUCH DAMAGE. 67 */ 68 69/* 70 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 71 * The Regents of the University of California. All rights reserved. 72 * 73 * Redistribution and use in source and binary forms, with or without 74 * modification, are permitted provided that the following conditions 75 * are met: 76 * 1. Redistributions of source code must retain the above copyright 77 * notice, this list of conditions and the following disclaimer. 78 * 2. Redistributions in binary form must reproduce the above copyright 79 * notice, this list of conditions and the following disclaimer in the 80 * documentation and/or other materials provided with the distribution. 81 * 3. Neither the name of the University nor the names of its contributors 82 * may be used to endorse or promote products derived from this software 83 * without specific prior written permission. 84 * 85 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 86 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 87 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 88 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 89 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 90 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 91 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 92 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 93 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 94 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 95 * SUCH DAMAGE. 96 * 97 * @(#)tcp_timer.c 8.2 (Berkeley) 5/24/95 98 */ 99 100#include <sys/cdefs.h> 101__KERNEL_RCSID(0, "$NetBSD: tcp_timer.c,v 1.70 2005/02/28 16:20:59 jonathan Exp $"); 102 103#include "opt_inet.h" 104#include "opt_tcp_debug.h" 105 106#include <sys/param.h> 107#include <sys/systm.h> 108#include <sys/malloc.h> 109#include <sys/mbuf.h> 110#include <sys/socket.h> 111#include <sys/socketvar.h> 112#include <sys/protosw.h> 113#include <sys/errno.h> 114#include <sys/kernel.h> 115 116#include <net/if.h> 117#include <net/route.h> 118 119#include <netinet/in.h> 120#include <netinet/in_systm.h> 121#include <netinet/ip.h> 122#include <netinet/in_pcb.h> 123#include <netinet/ip_var.h> 124 125#ifdef INET6 126#ifndef INET 127#include <netinet/in.h> 128#endif 129#include <netinet/ip6.h> 130#include <netinet6/in6_pcb.h> 131#endif 132 133#include <netinet/tcp.h> 134#include <netinet/tcp_fsm.h> 135#include <netinet/tcp_seq.h> 136#include <netinet/tcp_timer.h> 137#include <netinet/tcp_var.h> 138#include <netinet/tcpip.h> 139#ifdef TCP_DEBUG 140#include <netinet/tcp_debug.h> 141#endif 142 143/* 144 * Various tunable timer parameters. These are initialized in tcp_init(), 145 * unless they are patched. 146 */ 147int tcp_keepidle = 0; 148int tcp_keepintvl = 0; 149int tcp_keepcnt = 0; /* max idle probes */ 150int tcp_maxpersistidle = 0; /* max idle time in persist */ 151int tcp_maxidle; /* computed in tcp_slowtimo() */ 152 153/* 154 * Time to delay the ACK. This is initialized in tcp_init(), unless 155 * its patched. 156 */ 157int tcp_delack_ticks = 0; 158 159void tcp_timer_rexmt(void *); 160void tcp_timer_persist(void *); 161void tcp_timer_keep(void *); 162void tcp_timer_2msl(void *); 163 164const tcp_timer_func_t tcp_timer_funcs[TCPT_NTIMERS] = { 165 tcp_timer_rexmt, 166 tcp_timer_persist, 167 tcp_timer_keep, 168 tcp_timer_2msl, 169}; 170 171/* 172 * Timer state initialization, called from tcp_init(). 173 */ 174void 175tcp_timer_init(void) 176{ 177 178 if (tcp_keepidle == 0) 179 tcp_keepidle = TCPTV_KEEP_IDLE; 180 181 if (tcp_keepintvl == 0) 182 tcp_keepintvl = TCPTV_KEEPINTVL; 183 184 if (tcp_keepcnt == 0) 185 tcp_keepcnt = TCPTV_KEEPCNT; 186 187 if (tcp_maxpersistidle == 0) 188 tcp_maxpersistidle = TCPTV_KEEP_IDLE; 189 190 if (tcp_delack_ticks == 0) 191 tcp_delack_ticks = TCP_DELACK_TICKS; 192} 193 194/* 195 * Return how many timers are currently being invoked. 196 */ 197int 198tcp_timers_invoking(struct tcpcb *tp) 199{ 200 int i; 201 int count = 0; 202 203 for (i = 0; i < TCPT_NTIMERS; i++) 204 if (callout_invoking(&tp->t_timer[i])) 205 count++; 206 if (callout_invoking(&tp->t_delack_ch)) 207 count++; 208 209 return count; 210} 211 212/* 213 * Callout to process delayed ACKs for a TCPCB. 214 */ 215void 216tcp_delack(void *arg) 217{ 218 struct tcpcb *tp = arg; 219 int s; 220 221 /* 222 * If tcp_output() wasn't able to transmit the ACK 223 * for whatever reason, it will restart the delayed 224 * ACK callout. 225 */ 226 227 s = splsoftnet(); 228 callout_ack(&tp->t_delack_ch); 229 if (tcp_isdead(tp)) { 230 splx(s); 231 return; 232 } 233 234 tp->t_flags |= TF_ACKNOW; 235 (void) tcp_output(tp); 236 splx(s); 237} 238 239/* 240 * Tcp protocol timeout routine called every 500 ms. 241 * Updates the timers in all active tcb's and 242 * causes finite state machine actions if timers expire. 243 */ 244void 245tcp_slowtimo(void) 246{ 247 int s; 248 249 s = splsoftnet(); 250 tcp_maxidle = tcp_keepcnt * tcp_keepintvl; 251 tcp_iss_seq += TCP_ISSINCR; /* increment iss */ 252 tcp_now++; /* for timestamps */ 253 splx(s); 254} 255 256/* 257 * Cancel all timers for TCP tp. 258 */ 259void 260tcp_canceltimers(struct tcpcb *tp) 261{ 262 int i; 263 264 for (i = 0; i < TCPT_NTIMERS; i++) 265 TCP_TIMER_DISARM(tp, i); 266} 267 268const int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 269 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; 270 271const int tcp_totbackoff = 511; /* sum of tcp_backoff[] */ 272 273/* 274 * TCP timer processing. 275 */ 276 277void 278tcp_timer_rexmt(void *arg) 279{ 280 struct tcpcb *tp = arg; 281 uint32_t rto; 282 int s; 283#ifdef TCP_DEBUG 284 struct socket *so = NULL; 285 short ostate; 286#endif 287 288 s = splsoftnet(); 289 callout_ack(&tp->t_timer[TCPT_REXMT]); 290 if (tcp_isdead(tp)) { 291 splx(s); 292 return; 293 } 294 295#ifdef TCP_DEBUG 296#ifdef INET 297 if (tp->t_inpcb) 298 so = tp->t_inpcb->inp_socket; 299#endif 300#ifdef INET6 301 if (tp->t_in6pcb) 302 so = tp->t_in6pcb->in6p_socket; 303#endif 304 ostate = tp->t_state; 305#endif /* TCP_DEBUG */ 306 307 /* 308 * Clear the SACK scoreboard, reset FACK estimate. 309 */ 310 tcp_free_sackholes(tp); 311 tp->snd_fack = tp->snd_una; 312 313 /* 314 * Retransmission timer went off. Message has not 315 * been acked within retransmit interval. Back off 316 * to a longer retransmit interval and retransmit one segment. 317 */ 318 319 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { 320 tp->t_rxtshift = TCP_MAXRXTSHIFT; 321 tcpstat.tcps_timeoutdrop++; 322 tp = tcp_drop(tp, tp->t_softerror ? 323 tp->t_softerror : ETIMEDOUT); 324 goto out; 325 } 326 tcpstat.tcps_rexmttimeo++; 327 rto = TCP_REXMTVAL(tp); 328 if (rto < tp->t_rttmin) 329 rto = tp->t_rttmin; 330 TCPT_RANGESET(tp->t_rxtcur, rto * tcp_backoff[tp->t_rxtshift], 331 tp->t_rttmin, TCPTV_REXMTMAX); 332 TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); 333 334 /* 335 * If we are losing and we are trying path MTU discovery, 336 * try turning it off. This will avoid black holes in 337 * the network which suppress or fail to send "packet 338 * too big" ICMP messages. We should ideally do 339 * lots more sophisticated searching to find the right 340 * value here... 341 */ 342 if (tp->t_mtudisc && tp->t_rxtshift > TCP_MAXRXTSHIFT / 6) { 343 tcpstat.tcps_pmtublackhole++; 344 345#ifdef INET 346 /* try turning PMTUD off */ 347 if (tp->t_inpcb) 348 tp->t_mtudisc = 0; 349#endif 350#ifdef INET6 351 /* try using IPv6 minimum MTU */ 352 if (tp->t_in6pcb) 353 tp->t_mtudisc = 0; 354#endif 355 356 /* XXX: more sophisticated Black hole recovery code? */ 357 } 358 359 /* 360 * If losing, let the lower level know and try for 361 * a better route. Also, if we backed off this far, 362 * our srtt estimate is probably bogus. Clobber it 363 * so we'll take the next rtt measurement as our srtt; 364 * move the current srtt into rttvar to keep the current 365 * retransmit times until then. 366 */ 367 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { 368#ifdef INET 369 if (tp->t_inpcb) 370 in_losing(tp->t_inpcb); 371#endif 372#ifdef INET6 373 if (tp->t_in6pcb) 374 in6_losing(tp->t_in6pcb); 375#endif 376 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); 377 tp->t_srtt = 0; 378 } 379 tp->snd_nxt = tp->snd_una; 380 tp->snd_high = tp->snd_max; 381 /* 382 * If timing a segment in this window, stop the timer. 383 */ 384 tp->t_rtttime = 0; 385 /* 386 * Remember if we are retransmitting a SYN, because if 387 * we do, set the initial congestion window must be set 388 * to 1 segment. 389 */ 390 if (tp->t_state == TCPS_SYN_SENT) 391 tp->t_flags |= TF_SYN_REXMT; 392 /* 393 * Close the congestion window down to one segment 394 * (we'll open it by one segment for each ack we get). 395 * Since we probably have a window's worth of unacked 396 * data accumulated, this "slow start" keeps us from 397 * dumping all that data as back-to-back packets (which 398 * might overwhelm an intermediate gateway). 399 * 400 * There are two phases to the opening: Initially we 401 * open by one mss on each ack. This makes the window 402 * size increase exponentially with time. If the 403 * window is larger than the path can handle, this 404 * exponential growth results in dropped packet(s) 405 * almost immediately. To get more time between 406 * drops but still "push" the network to take advantage 407 * of improving conditions, we switch from exponential 408 * to linear window opening at some threshhold size. 409 * For a threshhold, we use half the current window 410 * size, truncated to a multiple of the mss. 411 * 412 * (the minimum cwnd that will give us exponential 413 * growth is 2 mss. We don't allow the threshhold 414 * to go below this.) 415 */ 416 { 417 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_segsz; 418 if (win < 2) 419 win = 2; 420 /* Loss Window MUST be one segment. */ 421 tp->snd_cwnd = tp->t_segsz; 422 tp->snd_ssthresh = win * tp->t_segsz; 423 tp->t_partialacks = -1; 424 tp->t_dupacks = 0; 425 } 426 (void) tcp_output(tp); 427 428 out: 429#ifdef TCP_DEBUG 430 if (tp && so->so_options & SO_DEBUG) 431 tcp_trace(TA_USER, ostate, tp, NULL, 432 PRU_SLOWTIMO | (TCPT_REXMT << 8)); 433#endif 434 splx(s); 435} 436 437void 438tcp_timer_persist(void *arg) 439{ 440 struct tcpcb *tp = arg; 441 uint32_t rto; 442 int s; 443#ifdef TCP_DEBUG 444 struct socket *so = NULL; 445 short ostate; 446#endif 447 448 s = splsoftnet(); 449 callout_ack(&tp->t_timer[TCPT_PERSIST]); 450 if (tcp_isdead(tp)) { 451 splx(s); 452 return; 453 } 454 455#ifdef TCP_DEBUG 456#ifdef INET 457 if (tp->t_inpcb) 458 so = tp->t_inpcb->inp_socket; 459#endif 460#ifdef INET6 461 if (tp->t_in6pcb) 462 so = tp->t_in6pcb->in6p_socket; 463#endif 464 465 ostate = tp->t_state; 466#endif /* TCP_DEBUG */ 467 468 /* 469 * Persistance timer into zero window. 470 * Force a byte to be output, if possible. 471 */ 472 473 /* 474 * Hack: if the peer is dead/unreachable, we do not 475 * time out if the window is closed. After a full 476 * backoff, drop the connection if the idle time 477 * (no responses to probes) reaches the maximum 478 * backoff that we would use if retransmitting. 479 */ 480 rto = TCP_REXMTVAL(tp); 481 if (rto < tp->t_rttmin) 482 rto = tp->t_rttmin; 483 if (tp->t_rxtshift == TCP_MAXRXTSHIFT && 484 ((tcp_now - tp->t_rcvtime) >= tcp_maxpersistidle || 485 (tcp_now - tp->t_rcvtime) >= rto * tcp_totbackoff)) { 486 tcpstat.tcps_persistdrops++; 487 tp = tcp_drop(tp, ETIMEDOUT); 488 goto out; 489 } 490 tcpstat.tcps_persisttimeo++; 491 tcp_setpersist(tp); 492 tp->t_force = 1; 493 (void) tcp_output(tp); 494 tp->t_force = 0; 495 496 out: 497#ifdef TCP_DEBUG 498 if (tp && so->so_options & SO_DEBUG) 499 tcp_trace(TA_USER, ostate, tp, NULL, 500 PRU_SLOWTIMO | (TCPT_PERSIST << 8)); 501#endif 502 splx(s); 503} 504 505void 506tcp_timer_keep(void *arg) 507{ 508 struct tcpcb *tp = arg; 509 struct socket *so = NULL; /* Quell compiler warning */ 510 int s; 511#ifdef TCP_DEBUG 512 short ostate; 513#endif 514 515 s = splsoftnet(); 516 callout_ack(&tp->t_timer[TCPT_KEEP]); 517 if (tcp_isdead(tp)) { 518 splx(s); 519 return; 520 } 521 522#ifdef TCP_DEBUG 523 ostate = tp->t_state; 524#endif /* TCP_DEBUG */ 525 526 /* 527 * Keep-alive timer went off; send something 528 * or drop connection if idle for too long. 529 */ 530 531 tcpstat.tcps_keeptimeo++; 532 if (TCPS_HAVEESTABLISHED(tp->t_state) == 0) 533 goto dropit; 534#ifdef INET 535 if (tp->t_inpcb) 536 so = tp->t_inpcb->inp_socket; 537#endif 538#ifdef INET6 539 if (tp->t_in6pcb) 540 so = tp->t_in6pcb->in6p_socket; 541#endif 542 if (so->so_options & SO_KEEPALIVE && 543 tp->t_state <= TCPS_CLOSE_WAIT) { 544 if ((tcp_maxidle > 0) && 545 ((tcp_now - tp->t_rcvtime) >= 546 tcp_keepidle + tcp_maxidle)) 547 goto dropit; 548 /* 549 * Send a packet designed to force a response 550 * if the peer is up and reachable: 551 * either an ACK if the connection is still alive, 552 * or an RST if the peer has closed the connection 553 * due to timeout or reboot. 554 * Using sequence number tp->snd_una-1 555 * causes the transmitted zero-length segment 556 * to lie outside the receive window; 557 * by the protocol spec, this requires the 558 * correspondent TCP to respond. 559 */ 560 tcpstat.tcps_keepprobe++; 561 if (tcp_compat_42) { 562 /* 563 * The keepalive packet must have nonzero 564 * length to get a 4.2 host to respond. 565 */ 566 (void)tcp_respond(tp, tp->t_template, 567 (struct mbuf *)NULL, NULL, tp->rcv_nxt - 1, 568 tp->snd_una - 1, 0); 569 } else { 570 (void)tcp_respond(tp, tp->t_template, 571 (struct mbuf *)NULL, NULL, tp->rcv_nxt, 572 tp->snd_una - 1, 0); 573 } 574 TCP_TIMER_ARM(tp, TCPT_KEEP, tcp_keepintvl); 575 } else 576 TCP_TIMER_ARM(tp, TCPT_KEEP, tcp_keepidle); 577 578#ifdef TCP_DEBUG 579 if (tp && so->so_options & SO_DEBUG) 580 tcp_trace(TA_USER, ostate, tp, NULL, 581 PRU_SLOWTIMO | (TCPT_KEEP << 8)); 582#endif 583 splx(s); 584 return; 585 586 dropit: 587 tcpstat.tcps_keepdrops++; 588 (void) tcp_drop(tp, ETIMEDOUT); 589 splx(s); 590} 591 592void 593tcp_timer_2msl(void *arg) 594{ 595 struct tcpcb *tp = arg; 596 int s; 597#ifdef TCP_DEBUG 598 struct socket *so = NULL; 599 short ostate; 600#endif 601 602 s = splsoftnet(); 603 callout_ack(&tp->t_timer[TCPT_2MSL]); 604 if (tcp_isdead(tp)) { 605 splx(s); 606 return; 607 } 608 609 /* 610 * 2 MSL timeout went off, clear the SACK scoreboard, reset 611 * the FACK estimate. 612 */ 613 tcp_free_sackholes(tp); 614 tp->snd_fack = tp->snd_una; 615 616#ifdef TCP_DEBUG 617#ifdef INET 618 if (tp->t_inpcb) 619 so = tp->t_inpcb->inp_socket; 620#endif 621#ifdef INET6 622 if (tp->t_in6pcb) 623 so = tp->t_in6pcb->in6p_socket; 624#endif 625 626 ostate = tp->t_state; 627#endif /* TCP_DEBUG */ 628 629 /* 630 * 2 MSL timeout in shutdown went off. If we're closed but 631 * still waiting for peer to close and connection has been idle 632 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 633 * control block. Otherwise, check again in a bit. 634 */ 635 if (tp->t_state != TCPS_TIME_WAIT && 636 ((tcp_maxidle == 0) || ((tcp_now - tp->t_rcvtime) <= tcp_maxidle))) 637 TCP_TIMER_ARM(tp, TCPT_2MSL, tcp_keepintvl); 638 else 639 tp = tcp_close(tp); 640 641#ifdef TCP_DEBUG 642 if (tp && so->so_options & SO_DEBUG) 643 tcp_trace(TA_USER, ostate, tp, NULL, 644 PRU_SLOWTIMO | (TCPT_2MSL << 8)); 645#endif 646 splx(s); 647} 648