tcp_timewait.c revision 204838
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 * 4. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * @(#)tcp_subr.c 8.2 (Berkeley) 5/24/95 30 */ 31 32#include <sys/cdefs.h> 33__FBSDID("$FreeBSD: head/sys/netinet/tcp_timewait.c 204838 2010-03-07 15:58:44Z bz $"); 34 35#include "opt_inet.h" 36#include "opt_inet6.h" 37#include "opt_tcpdebug.h" 38 39#include <sys/param.h> 40#include <sys/systm.h> 41#include <sys/callout.h> 42#include <sys/kernel.h> 43#include <sys/sysctl.h> 44#include <sys/malloc.h> 45#include <sys/mbuf.h> 46#include <sys/priv.h> 47#include <sys/proc.h> 48#include <sys/socket.h> 49#include <sys/socketvar.h> 50#include <sys/protosw.h> 51#include <sys/random.h> 52 53#include <vm/uma.h> 54 55#include <net/route.h> 56#include <net/if.h> 57#include <net/vnet.h> 58 59#include <netinet/in.h> 60#include <netinet/in_systm.h> 61#include <netinet/ip.h> 62#ifdef INET6 63#include <netinet/ip6.h> 64#endif 65#include <netinet/in_pcb.h> 66#ifdef INET6 67#include <netinet6/in6_pcb.h> 68#endif 69#include <netinet/in_var.h> 70#include <netinet/ip_var.h> 71#ifdef INET6 72#include <netinet6/ip6_var.h> 73#include <netinet6/scope6_var.h> 74#include <netinet6/nd6.h> 75#endif 76#include <netinet/ip_icmp.h> 77#include <netinet/tcp.h> 78#include <netinet/tcp_fsm.h> 79#include <netinet/tcp_seq.h> 80#include <netinet/tcp_timer.h> 81#include <netinet/tcp_var.h> 82#ifdef INET6 83#include <netinet6/tcp6_var.h> 84#endif 85#include <netinet/tcpip.h> 86#ifdef TCPDEBUG 87#include <netinet/tcp_debug.h> 88#endif 89#include <netinet6/ip6protosw.h> 90 91#include <machine/in_cksum.h> 92 93#include <security/mac/mac_framework.h> 94 95static int maxtcptw; 96 97/* 98 * The timed wait queue contains references to each of the TCP sessions 99 * currently in the TIME_WAIT state. The queue pointers, including the 100 * queue pointers in each tcptw structure, are protected using the global 101 * tcbinfo lock, which must be held over queue iteration and modification. 102 */ 103static VNET_DEFINE(uma_zone_t, tcptw_zone); 104static VNET_DEFINE(TAILQ_HEAD(, tcptw), twq_2msl); 105VNET_DEFINE(int, nolocaltimewait); 106 107#define V_tcptw_zone VNET(tcptw_zone) 108#define V_twq_2msl VNET(twq_2msl) 109 110static void tcp_tw_2msl_reset(struct tcptw *, int); 111static void tcp_tw_2msl_stop(struct tcptw *); 112 113static int 114tcptw_auto_size(void) 115{ 116 int halfrange; 117 118 /* 119 * Max out at half the ephemeral port range so that TIME_WAIT 120 * sockets don't tie up too many ephemeral ports. 121 */ 122 if (V_ipport_lastauto > V_ipport_firstauto) 123 halfrange = (V_ipport_lastauto - V_ipport_firstauto) / 2; 124 else 125 halfrange = (V_ipport_firstauto - V_ipport_lastauto) / 2; 126 /* Protect against goofy port ranges smaller than 32. */ 127 return (imin(imax(halfrange, 32), maxsockets / 5)); 128} 129 130static int 131sysctl_maxtcptw(SYSCTL_HANDLER_ARGS) 132{ 133 int error, new; 134 135 if (maxtcptw == 0) 136 new = tcptw_auto_size(); 137 else 138 new = maxtcptw; 139 error = sysctl_handle_int(oidp, &new, 0, req); 140 if (error == 0 && req->newptr) 141 if (new >= 32) { 142 maxtcptw = new; 143 uma_zone_set_max(V_tcptw_zone, maxtcptw); 144 } 145 return (error); 146} 147 148SYSCTL_PROC(_net_inet_tcp, OID_AUTO, maxtcptw, CTLTYPE_INT|CTLFLAG_RW, 149 &maxtcptw, 0, sysctl_maxtcptw, "IU", 150 "Maximum number of compressed TCP TIME_WAIT entries"); 151 152SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, nolocaltimewait, CTLFLAG_RW, 153 &VNET_NAME(nolocaltimewait), 0, 154 "Do not create compressed TCP TIME_WAIT entries for local connections"); 155 156void 157tcp_tw_zone_change(void) 158{ 159 160 if (maxtcptw == 0) 161 uma_zone_set_max(V_tcptw_zone, tcptw_auto_size()); 162} 163 164void 165tcp_tw_init(void) 166{ 167 168 V_tcptw_zone = uma_zcreate("tcptw", sizeof(struct tcptw), 169 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE); 170 TUNABLE_INT_FETCH("net.inet.tcp.maxtcptw", &maxtcptw); 171 if (maxtcptw == 0) 172 uma_zone_set_max(V_tcptw_zone, tcptw_auto_size()); 173 else 174 uma_zone_set_max(V_tcptw_zone, maxtcptw); 175 TAILQ_INIT(&V_twq_2msl); 176} 177 178#ifdef VIMAGE 179void 180tcp_tw_destroy(void) 181{ 182 struct tcptw *tw; 183 184 INP_INFO_WLOCK(&V_tcbinfo); 185 while((tw = TAILQ_FIRST(&V_twq_2msl)) != NULL) 186 tcp_twclose(tw, 0); 187 INP_INFO_WUNLOCK(&V_tcbinfo); 188 189 uma_zdestroy(V_tcptw_zone); 190} 191#endif 192 193/* 194 * Move a TCP connection into TIME_WAIT state. 195 * tcbinfo is locked. 196 * inp is locked, and is unlocked before returning. 197 */ 198void 199tcp_twstart(struct tcpcb *tp) 200{ 201 struct tcptw *tw; 202 struct inpcb *inp = tp->t_inpcb; 203 int acknow; 204 struct socket *so; 205 206 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); /* tcp_tw_2msl_reset(). */ 207 INP_WLOCK_ASSERT(inp); 208 209 if (V_nolocaltimewait && in_localip(inp->inp_faddr)) { 210 tp = tcp_close(tp); 211 if (tp != NULL) 212 INP_WUNLOCK(inp); 213 return; 214 } 215 216 tw = uma_zalloc(V_tcptw_zone, M_NOWAIT); 217 if (tw == NULL) { 218 tw = tcp_tw_2msl_scan(1); 219 if (tw == NULL) { 220 tp = tcp_close(tp); 221 if (tp != NULL) 222 INP_WUNLOCK(inp); 223 return; 224 } 225 } 226 tw->tw_inpcb = inp; 227 228 /* 229 * Recover last window size sent. 230 */ 231 tw->last_win = (tp->rcv_adv - tp->rcv_nxt) >> tp->rcv_scale; 232 233 /* 234 * Set t_recent if timestamps are used on the connection. 235 */ 236 if ((tp->t_flags & (TF_REQ_TSTMP|TF_RCVD_TSTMP|TF_NOOPT)) == 237 (TF_REQ_TSTMP|TF_RCVD_TSTMP)) { 238 tw->t_recent = tp->ts_recent; 239 tw->ts_offset = tp->ts_offset; 240 } else { 241 tw->t_recent = 0; 242 tw->ts_offset = 0; 243 } 244 245 tw->snd_nxt = tp->snd_nxt; 246 tw->rcv_nxt = tp->rcv_nxt; 247 tw->iss = tp->iss; 248 tw->irs = tp->irs; 249 tw->t_starttime = tp->t_starttime; 250 tw->tw_time = 0; 251 252/* XXX 253 * If this code will 254 * be used for fin-wait-2 state also, then we may need 255 * a ts_recent from the last segment. 256 */ 257 acknow = tp->t_flags & TF_ACKNOW; 258 259 /* 260 * First, discard tcpcb state, which includes stopping its timers and 261 * freeing it. tcp_discardcb() used to also release the inpcb, but 262 * that work is now done in the caller. 263 * 264 * Note: soisdisconnected() call used to be made in tcp_discardcb(), 265 * and might not be needed here any longer. 266 */ 267 tcp_discardcb(tp); 268 so = inp->inp_socket; 269 soisdisconnected(so); 270 tw->tw_cred = crhold(so->so_cred); 271 SOCK_LOCK(so); 272 tw->tw_so_options = so->so_options; 273 SOCK_UNLOCK(so); 274 if (acknow) 275 tcp_twrespond(tw, TH_ACK); 276 inp->inp_ppcb = tw; 277 inp->inp_flags |= INP_TIMEWAIT; 278 tcp_tw_2msl_reset(tw, 0); 279 280 /* 281 * If the inpcb owns the sole reference to the socket, then we can 282 * detach and free the socket as it is not needed in time wait. 283 */ 284 if (inp->inp_flags & INP_SOCKREF) { 285 KASSERT(so->so_state & SS_PROTOREF, 286 ("tcp_twstart: !SS_PROTOREF")); 287 inp->inp_flags &= ~INP_SOCKREF; 288 INP_WUNLOCK(inp); 289 ACCEPT_LOCK(); 290 SOCK_LOCK(so); 291 so->so_state &= ~SS_PROTOREF; 292 sofree(so); 293 } else 294 INP_WUNLOCK(inp); 295} 296 297#if 0 298/* 299 * The appromixate rate of ISN increase of Microsoft TCP stacks; 300 * the actual rate is slightly higher due to the addition of 301 * random positive increments. 302 * 303 * Most other new OSes use semi-randomized ISN values, so we 304 * do not need to worry about them. 305 */ 306#define MS_ISN_BYTES_PER_SECOND 250000 307 308/* 309 * Determine if the ISN we will generate has advanced beyond the last 310 * sequence number used by the previous connection. If so, indicate 311 * that it is safe to recycle this tw socket by returning 1. 312 */ 313int 314tcp_twrecycleable(struct tcptw *tw) 315{ 316 tcp_seq new_iss = tw->iss; 317 tcp_seq new_irs = tw->irs; 318 319 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 320 new_iss += (ticks - tw->t_starttime) * (ISN_BYTES_PER_SECOND / hz); 321 new_irs += (ticks - tw->t_starttime) * (MS_ISN_BYTES_PER_SECOND / hz); 322 323 if (SEQ_GT(new_iss, tw->snd_nxt) && SEQ_GT(new_irs, tw->rcv_nxt)) 324 return (1); 325 else 326 return (0); 327} 328#endif 329 330/* 331 * Returns 1 if the TIME_WAIT state was killed and we should start over, 332 * looking for a pcb in the listen state. Returns 0 otherwise. 333 */ 334int 335tcp_twcheck(struct inpcb *inp, struct tcpopt *to, struct tcphdr *th, 336 struct mbuf *m, int tlen) 337{ 338 struct tcptw *tw; 339 int thflags; 340 tcp_seq seq; 341 342 /* tcbinfo lock required for tcp_twclose(), tcp_tw_2msl_reset(). */ 343 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 344 INP_WLOCK_ASSERT(inp); 345 346 /* 347 * XXXRW: Time wait state for inpcb has been recycled, but inpcb is 348 * still present. This is undesirable, but temporarily necessary 349 * until we work out how to handle inpcb's who's timewait state has 350 * been removed. 351 */ 352 tw = intotw(inp); 353 if (tw == NULL) 354 goto drop; 355 356 thflags = th->th_flags; 357 358 /* 359 * NOTE: for FIN_WAIT_2 (to be added later), 360 * must validate sequence number before accepting RST 361 */ 362 363 /* 364 * If the segment contains RST: 365 * Drop the segment - see Stevens, vol. 2, p. 964 and 366 * RFC 1337. 367 */ 368 if (thflags & TH_RST) 369 goto drop; 370 371#if 0 372/* PAWS not needed at the moment */ 373 /* 374 * RFC 1323 PAWS: If we have a timestamp reply on this segment 375 * and it's less than ts_recent, drop it. 376 */ 377 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 378 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 379 if ((thflags & TH_ACK) == 0) 380 goto drop; 381 goto ack; 382 } 383 /* 384 * ts_recent is never updated because we never accept new segments. 385 */ 386#endif 387 388 /* 389 * If a new connection request is received 390 * while in TIME_WAIT, drop the old connection 391 * and start over if the sequence numbers 392 * are above the previous ones. 393 */ 394 if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) { 395 tcp_twclose(tw, 0); 396 return (1); 397 } 398 399 /* 400 * Drop the the segment if it does not contain an ACK. 401 */ 402 if ((thflags & TH_ACK) == 0) 403 goto drop; 404 405 /* 406 * Reset the 2MSL timer if this is a duplicate FIN. 407 */ 408 if (thflags & TH_FIN) { 409 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0); 410 if (seq + 1 == tw->rcv_nxt) 411 tcp_tw_2msl_reset(tw, 1); 412 } 413 414 /* 415 * Acknowledge the segment if it has data or is not a duplicate ACK. 416 */ 417 if (thflags != TH_ACK || tlen != 0 || 418 th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt) 419 tcp_twrespond(tw, TH_ACK); 420drop: 421 INP_WUNLOCK(inp); 422 m_freem(m); 423 return (0); 424} 425 426void 427tcp_twclose(struct tcptw *tw, int reuse) 428{ 429 struct socket *so; 430 struct inpcb *inp; 431 432 /* 433 * At this point, we are in one of two situations: 434 * 435 * (1) We have no socket, just an inpcb<->twtcp pair. We can free 436 * all state. 437 * 438 * (2) We have a socket -- if we own a reference, release it and 439 * notify the socket layer. 440 */ 441 inp = tw->tw_inpcb; 442 KASSERT((inp->inp_flags & INP_TIMEWAIT), ("tcp_twclose: !timewait")); 443 KASSERT(intotw(inp) == tw, ("tcp_twclose: inp_ppcb != tw")); 444 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); /* tcp_tw_2msl_stop(). */ 445 INP_WLOCK_ASSERT(inp); 446 447 tw->tw_inpcb = NULL; 448 tcp_tw_2msl_stop(tw); 449 inp->inp_ppcb = NULL; 450 in_pcbdrop(inp); 451 452 so = inp->inp_socket; 453 if (so != NULL) { 454 /* 455 * If there's a socket, handle two cases: first, we own a 456 * strong reference, which we will now release, or we don't 457 * in which case another reference exists (XXXRW: think 458 * about this more), and we don't need to take action. 459 */ 460 if (inp->inp_flags & INP_SOCKREF) { 461 inp->inp_flags &= ~INP_SOCKREF; 462 INP_WUNLOCK(inp); 463 ACCEPT_LOCK(); 464 SOCK_LOCK(so); 465 KASSERT(so->so_state & SS_PROTOREF, 466 ("tcp_twclose: INP_SOCKREF && !SS_PROTOREF")); 467 so->so_state &= ~SS_PROTOREF; 468 sofree(so); 469 } else { 470 /* 471 * If we don't own the only reference, the socket and 472 * inpcb need to be left around to be handled by 473 * tcp_usr_detach() later. 474 */ 475 INP_WUNLOCK(inp); 476 } 477 } else 478 in_pcbfree(inp); 479 TCPSTAT_INC(tcps_closed); 480 crfree(tw->tw_cred); 481 tw->tw_cred = NULL; 482 if (reuse) 483 return; 484 uma_zfree(V_tcptw_zone, tw); 485} 486 487int 488tcp_twrespond(struct tcptw *tw, int flags) 489{ 490 struct inpcb *inp = tw->tw_inpcb; 491 struct tcphdr *th; 492 struct mbuf *m; 493 struct ip *ip = NULL; 494 u_int hdrlen, optlen; 495 int error; 496 struct tcpopt to; 497#ifdef INET6 498 struct ip6_hdr *ip6 = NULL; 499 int isipv6 = inp->inp_inc.inc_flags & INC_ISIPV6; 500#endif 501 502 INP_WLOCK_ASSERT(inp); 503 504 m = m_gethdr(M_DONTWAIT, MT_DATA); 505 if (m == NULL) 506 return (ENOBUFS); 507 m->m_data += max_linkhdr; 508 509#ifdef MAC 510 mac_inpcb_create_mbuf(inp, m); 511#endif 512 513#ifdef INET6 514 if (isipv6) { 515 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 516 ip6 = mtod(m, struct ip6_hdr *); 517 th = (struct tcphdr *)(ip6 + 1); 518 tcpip_fillheaders(inp, ip6, th); 519 } else 520#endif 521 { 522 hdrlen = sizeof(struct tcpiphdr); 523 ip = mtod(m, struct ip *); 524 th = (struct tcphdr *)(ip + 1); 525 tcpip_fillheaders(inp, ip, th); 526 } 527 to.to_flags = 0; 528 529 /* 530 * Send a timestamp and echo-reply if both our side and our peer 531 * have sent timestamps in our SYN's and this is not a RST. 532 */ 533 if (tw->t_recent && flags == TH_ACK) { 534 to.to_flags |= TOF_TS; 535 to.to_tsval = ticks + tw->ts_offset; 536 to.to_tsecr = tw->t_recent; 537 } 538 optlen = tcp_addoptions(&to, (u_char *)(th + 1)); 539 540 m->m_len = hdrlen + optlen; 541 m->m_pkthdr.len = m->m_len; 542 543 KASSERT(max_linkhdr + m->m_len <= MHLEN, ("tcptw: mbuf too small")); 544 545 th->th_seq = htonl(tw->snd_nxt); 546 th->th_ack = htonl(tw->rcv_nxt); 547 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 548 th->th_flags = flags; 549 th->th_win = htons(tw->last_win); 550 551#ifdef INET6 552 if (isipv6) { 553 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 554 sizeof(struct tcphdr) + optlen); 555 ip6->ip6_hlim = in6_selecthlim(inp, NULL); 556 error = ip6_output(m, inp->in6p_outputopts, NULL, 557 (tw->tw_so_options & SO_DONTROUTE), NULL, NULL, inp); 558 } else 559#endif 560 { 561 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 562 htons(sizeof(struct tcphdr) + optlen + IPPROTO_TCP)); 563 m->m_pkthdr.csum_flags = CSUM_TCP; 564 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 565 ip->ip_len = m->m_pkthdr.len; 566 if (V_path_mtu_discovery) 567 ip->ip_off |= IP_DF; 568 error = ip_output(m, inp->inp_options, NULL, 569 ((tw->tw_so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 570 NULL, inp); 571 } 572 if (flags & TH_ACK) 573 TCPSTAT_INC(tcps_sndacks); 574 else 575 TCPSTAT_INC(tcps_sndctrl); 576 TCPSTAT_INC(tcps_sndtotal); 577 return (error); 578} 579 580static void 581tcp_tw_2msl_reset(struct tcptw *tw, int rearm) 582{ 583 584 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 585 INP_WLOCK_ASSERT(tw->tw_inpcb); 586 if (rearm) 587 TAILQ_REMOVE(&V_twq_2msl, tw, tw_2msl); 588 tw->tw_time = ticks + 2 * tcp_msl; 589 TAILQ_INSERT_TAIL(&V_twq_2msl, tw, tw_2msl); 590} 591 592static void 593tcp_tw_2msl_stop(struct tcptw *tw) 594{ 595 596 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 597 TAILQ_REMOVE(&V_twq_2msl, tw, tw_2msl); 598} 599 600struct tcptw * 601tcp_tw_2msl_scan(int reuse) 602{ 603 struct tcptw *tw; 604 605 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 606 for (;;) { 607 tw = TAILQ_FIRST(&V_twq_2msl); 608 if (tw == NULL || (!reuse && (tw->tw_time - ticks) > 0)) 609 break; 610 INP_WLOCK(tw->tw_inpcb); 611 tcp_twclose(tw, reuse); 612 if (reuse) 613 return (tw); 614 } 615 return (NULL); 616} 617