Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/netinet/igmp.c
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1 /*- 2 * Copyright (c) 1988 Stephen Deering. 3 * Copyright (c) 1992, 1993 4 * The Regents of the University of California. All rights reserved. 5 * 6 * This code is derived from software contributed to Berkeley by 7 * Stephen Deering of Stanford University. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 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 * @(#)igmp.c 8.1 (Berkeley) 7/19/93 34 * $FreeBSD: releng/5.4/sys/netinet/igmp.c 145335 2005-04-20 19:11:07Z cvs2svn $ 35 */ 36 37 /* 38 * Internet Group Management Protocol (IGMP) routines. 39 * 40 * Written by Steve Deering, Stanford, May 1988. 41 * Modified by Rosen Sharma, Stanford, Aug 1994. 42 * Modified by Bill Fenner, Xerox PARC, Feb 1995. 43 * Modified to fully comply to IGMPv2 by Bill Fenner, Oct 1995. 44 * 45 * MULTICAST Revision: 3.5.1.4 46 */ 47 48 #include "opt_mac.h" 49 50 #include <sys/param.h> 51 #include <sys/systm.h> 52 #include <sys/mac.h> 53 #include <sys/malloc.h> 54 #include <sys/mbuf.h> 55 #include <sys/socket.h> 56 #include <sys/protosw.h> 57 #include <sys/kernel.h> 58 #include <sys/sysctl.h> 59 60 #include <net/if.h> 61 #include <net/route.h> 62 63 #include <netinet/in.h> 64 #include <netinet/in_var.h> 65 #include <netinet/in_systm.h> 66 #include <netinet/ip.h> 67 #include <netinet/ip_var.h> 68 #include <netinet/igmp.h> 69 #include <netinet/igmp_var.h> 70 71 #include <machine/in_cksum.h> 72 73 static MALLOC_DEFINE(M_IGMP, "igmp", "igmp state"); 74 75 static struct router_info *find_rti(struct ifnet *ifp); 76 static void igmp_sendpkt(struct in_multi *, int, unsigned long); 77 78 static struct igmpstat igmpstat; 79 80 SYSCTL_STRUCT(_net_inet_igmp, IGMPCTL_STATS, stats, CTLFLAG_RW, &igmpstat, 81 igmpstat, ""); 82 83 /* 84 * igmp_mtx protects all mutable global variables in igmp.c, as well as 85 * the data fields in struct router_info. In general, a router_info 86 * structure will be valid as long as the referencing struct in_multi is 87 * valid, so no reference counting is used. We allow unlocked reads of 88 * router_info data when accessed via an in_multi read-only. 89 */ 90 static struct mtx igmp_mtx; 91 static SLIST_HEAD(, router_info) router_info_head; 92 static int igmp_timers_are_running; 93 94 /* 95 * XXXRW: can we define these such that these can be made const? In any 96 * case, these shouldn't be changed after igmp_init() and therefore don't 97 * need locking. 98 */ 99 static u_long igmp_all_hosts_group; 100 static u_long igmp_all_rtrs_group; 101 102 static struct mbuf *router_alert; 103 static struct route igmprt; 104 105 #ifdef IGMP_DEBUG 106 #define IGMP_PRINTF(x) printf(x) 107 #else 108 #define IGMP_PRINTF(x) 109 #endif 110 111 void 112 igmp_init(void) 113 { 114 struct ipoption *ra; 115 116 /* 117 * To avoid byte-swapping the same value over and over again. 118 */ 119 igmp_all_hosts_group = htonl(INADDR_ALLHOSTS_GROUP); 120 igmp_all_rtrs_group = htonl(INADDR_ALLRTRS_GROUP); 121 122 igmp_timers_are_running = 0; 123 124 /* 125 * Construct a Router Alert option to use in outgoing packets 126 */ 127 MGET(router_alert, M_DONTWAIT, MT_DATA); 128 ra = mtod(router_alert, struct ipoption *); 129 ra->ipopt_dst.s_addr = 0; 130 ra->ipopt_list[0] = IPOPT_RA; /* Router Alert Option */ 131 ra->ipopt_list[1] = 0x04; /* 4 bytes long */ 132 ra->ipopt_list[2] = 0x00; 133 ra->ipopt_list[3] = 0x00; 134 router_alert->m_len = sizeof(ra->ipopt_dst) + ra->ipopt_list[1]; 135 136 mtx_init(&igmp_mtx, "igmp_mtx", NULL, MTX_DEF); 137 SLIST_INIT(&router_info_head); 138 } 139 140 static struct router_info * 141 find_rti(struct ifnet *ifp) 142 { 143 struct router_info *rti; 144 145 mtx_assert(&igmp_mtx, MA_OWNED); 146 IGMP_PRINTF("[igmp.c, _find_rti] --> entering \n"); 147 SLIST_FOREACH(rti, &router_info_head, rti_list) { 148 if (rti->rti_ifp == ifp) { 149 IGMP_PRINTF( 150 "[igmp.c, _find_rti] --> found old entry \n"); 151 return rti; 152 } 153 } 154 /* 155 * XXXRW: return value of malloc not checked, despite M_NOWAIT. 156 */ 157 MALLOC(rti, struct router_info *, sizeof *rti, M_IGMP, M_NOWAIT); 158 rti->rti_ifp = ifp; 159 rti->rti_type = IGMP_V2_ROUTER; 160 rti->rti_time = 0; 161 SLIST_INSERT_HEAD(&router_info_head, rti, rti_list); 162 163 IGMP_PRINTF("[igmp.c, _find_rti] --> created an entry \n"); 164 return rti; 165 } 166 167 void 168 igmp_input(register struct mbuf *m, int off) 169 { 170 register int iphlen = off; 171 register struct igmp *igmp; 172 register struct ip *ip; 173 register int igmplen; 174 register struct ifnet *ifp = m->m_pkthdr.rcvif; 175 register int minlen; 176 register struct in_multi *inm; 177 register struct in_ifaddr *ia; 178 struct in_multistep step; 179 struct router_info *rti; 180 int timer; /** timer value in the igmp query header **/ 181 182 ++igmpstat.igps_rcv_total; 183 184 ip = mtod(m, struct ip *); 185 igmplen = ip->ip_len; 186 187 /* 188 * Validate lengths 189 */ 190 if (igmplen < IGMP_MINLEN) { 191 ++igmpstat.igps_rcv_tooshort; 192 m_freem(m); 193 return; 194 } 195 minlen = iphlen + IGMP_MINLEN; 196 if ((m->m_flags & M_EXT || m->m_len < minlen) && 197 (m = m_pullup(m, minlen)) == 0) { 198 ++igmpstat.igps_rcv_tooshort; 199 return; 200 } 201 202 /* 203 * Validate checksum 204 */ 205 m->m_data += iphlen; 206 m->m_len -= iphlen; 207 igmp = mtod(m, struct igmp *); 208 if (in_cksum(m, igmplen)) { 209 ++igmpstat.igps_rcv_badsum; 210 m_freem(m); 211 return; 212 } 213 m->m_data -= iphlen; 214 m->m_len += iphlen; 215 216 ip = mtod(m, struct ip *); 217 timer = igmp->igmp_code * PR_FASTHZ / IGMP_TIMER_SCALE; 218 if (timer == 0) 219 timer = 1; 220 221 /* 222 * In the IGMPv2 specification, there are 3 states and a flag. 223 * 224 * In Non-Member state, we simply don't have a membership record. 225 * In Delaying Member state, our timer is running (inm->inm_timer) 226 * In Idle Member state, our timer is not running (inm->inm_timer==0) 227 * 228 * The flag is inm->inm_state, it is set to IGMP_OTHERMEMBER if 229 * we have heard a report from another member, or IGMP_IREPORTEDLAST 230 * if I sent the last report. 231 */ 232 switch (igmp->igmp_type) { 233 case IGMP_MEMBERSHIP_QUERY: 234 ++igmpstat.igps_rcv_queries; 235 236 if (ifp->if_flags & IFF_LOOPBACK) 237 break; 238 239 if (igmp->igmp_code == 0) { 240 /* 241 * Old router. Remember that the querier on this 242 * interface is old, and set the timer to the 243 * value in RFC 1112. 244 */ 245 246 mtx_lock(&igmp_mtx); 247 rti = find_rti(ifp); 248 rti->rti_type = IGMP_V1_ROUTER; 249 rti->rti_time = 0; 250 mtx_unlock(&igmp_mtx); 251 252 timer = IGMP_MAX_HOST_REPORT_DELAY * PR_FASTHZ; 253 254 if (ip->ip_dst.s_addr != igmp_all_hosts_group || 255 igmp->igmp_group.s_addr != 0) { 256 ++igmpstat.igps_rcv_badqueries; 257 m_freem(m); 258 return; 259 } 260 } else { 261 /* 262 * New router. Simply do the new validity check. 263 */ 264 265 if (igmp->igmp_group.s_addr != 0 && 266 !IN_MULTICAST(ntohl(igmp->igmp_group.s_addr))) { 267 ++igmpstat.igps_rcv_badqueries; 268 m_freem(m); 269 return; 270 } 271 } 272 273 /* 274 * - Start the timers in all of our membership records 275 * that the query applies to for the interface on 276 * which the query arrived excl. those that belong 277 * to the "all-hosts" group (224.0.0.1). 278 * - Restart any timer that is already running but has 279 * a value longer than the requested timeout. 280 * - Use the value specified in the query message as 281 * the maximum timeout. 282 */ 283 IN_FIRST_MULTI(step, inm); 284 while (inm != NULL) { 285 if (inm->inm_ifp == ifp && 286 inm->inm_addr.s_addr != igmp_all_hosts_group && 287 (igmp->igmp_group.s_addr == 0 || 288 igmp->igmp_group.s_addr == inm->inm_addr.s_addr)) { 289 if (inm->inm_timer == 0 || 290 inm->inm_timer > timer) { 291 inm->inm_timer = 292 IGMP_RANDOM_DELAY(timer); 293 igmp_timers_are_running = 1; 294 } 295 } 296 IN_NEXT_MULTI(step, inm); 297 } 298 299 break; 300 301 case IGMP_V1_MEMBERSHIP_REPORT: 302 case IGMP_V2_MEMBERSHIP_REPORT: 303 /* 304 * For fast leave to work, we have to know that we are the 305 * last person to send a report for this group. Reports 306 * can potentially get looped back if we are a multicast 307 * router, so discard reports sourced by me. 308 */ 309 IFP_TO_IA(ifp, ia); 310 if (ia && ip->ip_src.s_addr == IA_SIN(ia)->sin_addr.s_addr) 311 break; 312 313 ++igmpstat.igps_rcv_reports; 314 315 if (ifp->if_flags & IFF_LOOPBACK) 316 break; 317 318 if (!IN_MULTICAST(ntohl(igmp->igmp_group.s_addr))) { 319 ++igmpstat.igps_rcv_badreports; 320 m_freem(m); 321 return; 322 } 323 324 /* 325 * KLUDGE: if the IP source address of the report has an 326 * unspecified (i.e., zero) subnet number, as is allowed for 327 * a booting host, replace it with the correct subnet number 328 * so that a process-level multicast routing daemon can 329 * determine which subnet it arrived from. This is necessary 330 * to compensate for the lack of any way for a process to 331 * determine the arrival interface of an incoming packet. 332 */ 333 if ((ntohl(ip->ip_src.s_addr) & IN_CLASSA_NET) == 0) 334 if (ia) ip->ip_src.s_addr = htonl(ia->ia_subnet); 335 336 /* 337 * If we belong to the group being reported, stop 338 * our timer for that group. 339 */ 340 IN_LOOKUP_MULTI(igmp->igmp_group, ifp, inm); 341 342 if (inm != NULL) { 343 inm->inm_timer = 0; 344 ++igmpstat.igps_rcv_ourreports; 345 346 inm->inm_state = IGMP_OTHERMEMBER; 347 } 348 349 break; 350 } 351 352 /* 353 * Pass all valid IGMP packets up to any process(es) listening 354 * on a raw IGMP socket. 355 */ 356 rip_input(m, off); 357 } 358 359 void 360 igmp_joingroup(struct in_multi *inm) 361 { 362 int s = splnet(); 363 364 if (inm->inm_addr.s_addr == igmp_all_hosts_group 365 || inm->inm_ifp->if_flags & IFF_LOOPBACK) { 366 inm->inm_timer = 0; 367 inm->inm_state = IGMP_OTHERMEMBER; 368 } else { 369 mtx_lock(&igmp_mtx); 370 inm->inm_rti = find_rti(inm->inm_ifp); 371 mtx_unlock(&igmp_mtx); 372 igmp_sendpkt(inm, inm->inm_rti->rti_type, 0); 373 inm->inm_timer = IGMP_RANDOM_DELAY( 374 IGMP_MAX_HOST_REPORT_DELAY*PR_FASTHZ); 375 inm->inm_state = IGMP_IREPORTEDLAST; 376 igmp_timers_are_running = 1; 377 } 378 splx(s); 379 } 380 381 void 382 igmp_leavegroup(struct in_multi *inm) 383 { 384 385 if (inm->inm_state == IGMP_IREPORTEDLAST && 386 inm->inm_addr.s_addr != igmp_all_hosts_group && 387 !(inm->inm_ifp->if_flags & IFF_LOOPBACK) && 388 inm->inm_rti->rti_type != IGMP_V1_ROUTER) 389 igmp_sendpkt(inm, IGMP_V2_LEAVE_GROUP, igmp_all_rtrs_group); 390 } 391 392 void 393 igmp_fasttimo(void) 394 { 395 register struct in_multi *inm; 396 struct in_multistep step; 397 int s; 398 399 /* 400 * Quick check to see if any work needs to be done, in order 401 * to minimize the overhead of fasttimo processing. 402 */ 403 404 if (!igmp_timers_are_running) 405 return; 406 407 s = splnet(); 408 igmp_timers_are_running = 0; 409 IN_FIRST_MULTI(step, inm); 410 while (inm != NULL) { 411 if (inm->inm_timer == 0) { 412 /* do nothing */ 413 } else if (--inm->inm_timer == 0) { 414 igmp_sendpkt(inm, inm->inm_rti->rti_type, 0); 415 inm->inm_state = IGMP_IREPORTEDLAST; 416 } else { 417 igmp_timers_are_running = 1; 418 } 419 IN_NEXT_MULTI(step, inm); 420 } 421 splx(s); 422 } 423 424 void 425 igmp_slowtimo(void) 426 { 427 int s = splnet(); 428 struct router_info *rti; 429 430 IGMP_PRINTF("[igmp.c,_slowtimo] -- > entering \n"); 431 mtx_lock(&igmp_mtx); 432 SLIST_FOREACH(rti, &router_info_head, rti_list) { 433 if (rti->rti_type == IGMP_V1_ROUTER) { 434 rti->rti_time++; 435 if (rti->rti_time >= IGMP_AGE_THRESHOLD) 436 rti->rti_type = IGMP_V2_ROUTER; 437 } 438 } 439 mtx_unlock(&igmp_mtx); 440 IGMP_PRINTF("[igmp.c,_slowtimo] -- > exiting \n"); 441 splx(s); 442 } 443 444 static void 445 igmp_sendpkt(struct in_multi *inm, int type, unsigned long addr) 446 { 447 struct mbuf *m; 448 struct igmp *igmp; 449 struct ip *ip; 450 struct ip_moptions imo; 451 452 MGETHDR(m, M_DONTWAIT, MT_HEADER); 453 if (m == NULL) 454 return; 455 456 m->m_pkthdr.rcvif = loif; 457 #ifdef MAC 458 mac_create_mbuf_linklayer(inm->inm_ifp, m); 459 #endif 460 m->m_pkthdr.len = sizeof(struct ip) + IGMP_MINLEN; 461 MH_ALIGN(m, IGMP_MINLEN + sizeof(struct ip)); 462 m->m_data += sizeof(struct ip); 463 m->m_len = IGMP_MINLEN; 464 igmp = mtod(m, struct igmp *); 465 igmp->igmp_type = type; 466 igmp->igmp_code = 0; 467 igmp->igmp_group = inm->inm_addr; 468 igmp->igmp_cksum = 0; 469 igmp->igmp_cksum = in_cksum(m, IGMP_MINLEN); 470 471 m->m_data -= sizeof(struct ip); 472 m->m_len += sizeof(struct ip); 473 ip = mtod(m, struct ip *); 474 ip->ip_tos = 0; 475 ip->ip_len = sizeof(struct ip) + IGMP_MINLEN; 476 ip->ip_off = 0; 477 ip->ip_p = IPPROTO_IGMP; 478 ip->ip_src.s_addr = INADDR_ANY; 479 ip->ip_dst.s_addr = addr ? addr : igmp->igmp_group.s_addr; 480 481 imo.imo_multicast_ifp = inm->inm_ifp; 482 imo.imo_multicast_ttl = 1; 483 imo.imo_multicast_vif = -1; 484 /* 485 * Request loopback of the report if we are acting as a multicast 486 * router, so that the process-level routing daemon can hear it. 487 */ 488 imo.imo_multicast_loop = (ip_mrouter != NULL); 489 490 /* 491 * XXX 492 * Do we have to worry about reentrancy here? Don't think so. 493 */ 494 ip_output(m, router_alert, &igmprt, 0, &imo, NULL); 495 496 ++igmpstat.igps_snd_reports; 497 }
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