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  */
   35 
   36 /*
   37  * Internet Group Management Protocol (IGMP) routines.
   38  *
   39  * Written by Steve Deering, Stanford, May 1988.
   40  * Modified by Rosen Sharma, Stanford, Aug 1994.
   41  * Modified by Bill Fenner, Xerox PARC, Feb 1995.
   42  * Modified to fully comply to IGMPv2 by Bill Fenner, Oct 1995.
   43  *
   44  * MULTICAST Revision: 3.5.1.4
   45  */
   46 
   47 #include <sys/cdefs.h>
   48 __FBSDID("$FreeBSD$");
   49 
   50 #include "opt_mac.h"
   51 
   52 #include <sys/param.h>
   53 #include <sys/systm.h>
   54 #include <sys/malloc.h>
   55 #include <sys/mbuf.h>
   56 #include <sys/socket.h>
   57 #include <sys/protosw.h>
   58 #include <sys/kernel.h>
   59 #include <sys/sysctl.h>
   60 
   61 #include <net/if.h>
   62 #include <net/route.h>
   63 
   64 #include <netinet/in.h>
   65 #include <netinet/in_var.h>
   66 #include <netinet/in_systm.h>
   67 #include <netinet/ip.h>
   68 #include <netinet/ip_var.h>
   69 #include <netinet/ip_options.h>
   70 #include <netinet/igmp.h>
   71 #include <netinet/igmp_var.h>
   72 
   73 #include <machine/in_cksum.h>
   74 
   75 #include <security/mac/mac_framework.h>
   76 
   77 static MALLOC_DEFINE(M_IGMP, "igmp", "igmp state");
   78 
   79 static struct router_info       *find_rti(struct ifnet *ifp);
   80 static void     igmp_sendpkt(struct in_multi *, int, unsigned long);
   81 
   82 static struct igmpstat igmpstat;
   83 
   84 SYSCTL_STRUCT(_net_inet_igmp, IGMPCTL_STATS, stats, CTLFLAG_RW, &igmpstat,
   85     igmpstat, "");
   86 
   87 /*
   88  * igmp_mtx protects all mutable global variables in igmp.c, as well as the
   89  * data fields in struct router_info.  In general, a router_info structure
   90  * will be valid as long as the referencing struct in_multi is valid, so no
   91  * reference counting is used.  We allow unlocked reads of router_info data
   92  * when accessed via an in_multi read-only.
   93  */
   94 static struct mtx igmp_mtx;
   95 static SLIST_HEAD(, router_info) router_info_head;
   96 static int igmp_timers_are_running;
   97 
   98 /*
   99  * XXXRW: can we define these such that these can be made const?  In any
  100  * case, these shouldn't be changed after igmp_init() and therefore don't
  101  * need locking.
  102  */
  103 static u_long igmp_all_hosts_group;
  104 static u_long igmp_all_rtrs_group;
  105 
  106 static struct mbuf *router_alert;
  107 static struct route igmprt;
  108 
  109 #ifdef IGMP_DEBUG
  110 #define IGMP_PRINTF(x)  printf(x)
  111 #else
  112 #define IGMP_PRINTF(x)
  113 #endif
  114 
  115 void
  116 igmp_init(void)
  117 {
  118         struct ipoption *ra;
  119 
  120         /*
  121          * To avoid byte-swapping the same value over and over again.
  122          */
  123         igmp_all_hosts_group = htonl(INADDR_ALLHOSTS_GROUP);
  124         igmp_all_rtrs_group = htonl(INADDR_ALLRTRS_GROUP);
  125 
  126         igmp_timers_are_running = 0;
  127 
  128         /*
  129          * Construct a Router Alert option to use in outgoing packets.
  130          */
  131         MGET(router_alert, M_DONTWAIT, MT_DATA);
  132         ra = mtod(router_alert, struct ipoption *);
  133         ra->ipopt_dst.s_addr = 0;
  134         ra->ipopt_list[0] = IPOPT_RA;   /* Router Alert Option */
  135         ra->ipopt_list[1] = 0x04;       /* 4 bytes long */
  136         ra->ipopt_list[2] = 0x00;
  137         ra->ipopt_list[3] = 0x00;
  138         router_alert->m_len = sizeof(ra->ipopt_dst) + ra->ipopt_list[1];
  139 
  140         mtx_init(&igmp_mtx, "igmp_mtx", NULL, MTX_DEF);
  141         SLIST_INIT(&router_info_head);
  142 }
  143 
  144 static struct router_info *
  145 find_rti(struct ifnet *ifp)
  146 {
  147         struct router_info *rti;
  148 
  149         mtx_assert(&igmp_mtx, MA_OWNED);
  150         IGMP_PRINTF("[igmp.c, _find_rti] --> entering \n");
  151         SLIST_FOREACH(rti, &router_info_head, rti_list) {
  152                 if (rti->rti_ifp == ifp) {
  153                         IGMP_PRINTF(
  154                             "[igmp.c, _find_rti] --> found old entry \n");
  155                         return (rti);
  156                 }
  157         }
  158         MALLOC(rti, struct router_info *, sizeof *rti, M_IGMP, M_NOWAIT);
  159         if (rti == NULL) {
  160                 IGMP_PRINTF("[igmp.c, _find_rti] --> no memory for entry\n");
  161                 return (NULL);
  162         }
  163         rti->rti_ifp = ifp;
  164         rti->rti_type = IGMP_V2_ROUTER;
  165         rti->rti_time = 0;
  166         SLIST_INSERT_HEAD(&router_info_head, rti, rti_list);
  167         IGMP_PRINTF("[igmp.c, _find_rti] --> created an entry \n");
  168         return (rti);
  169 }
  170 
  171 void
  172 igmp_input(register struct mbuf *m, int off)
  173 {
  174         register int iphlen = off;
  175         register struct igmp *igmp;
  176         register struct ip *ip;
  177         register int igmplen;
  178         register struct ifnet *ifp = m->m_pkthdr.rcvif;
  179         register int minlen;
  180         register struct in_multi *inm;
  181         register struct in_ifaddr *ia;
  182         struct in_multistep step;
  183         struct router_info *rti;
  184         int timer; /** timer value in the igmp query header **/
  185 
  186         ++igmpstat.igps_rcv_total;
  187 
  188         ip = mtod(m, struct ip *);
  189         igmplen = ip->ip_len;
  190 
  191         /*
  192          * Validate lengths.
  193          */
  194         if (igmplen < IGMP_MINLEN) {
  195                 ++igmpstat.igps_rcv_tooshort;
  196                 m_freem(m);
  197                 return;
  198         }
  199         minlen = iphlen + IGMP_MINLEN;
  200         if ((m->m_flags & M_EXT || m->m_len < minlen) &&
  201             (m = m_pullup(m, minlen)) == 0) {
  202                 ++igmpstat.igps_rcv_tooshort;
  203                 return;
  204         }
  205 
  206         /*
  207          * Validate checksum.
  208          */
  209         m->m_data += iphlen;
  210         m->m_len -= iphlen;
  211         igmp = mtod(m, struct igmp *);
  212         if (in_cksum(m, igmplen)) {
  213                 ++igmpstat.igps_rcv_badsum;
  214                 m_freem(m);
  215                 return;
  216         }
  217         m->m_data -= iphlen;
  218         m->m_len += iphlen;
  219 
  220         ip = mtod(m, struct ip *);
  221         timer = igmp->igmp_code * PR_FASTHZ / IGMP_TIMER_SCALE;
  222         if (timer == 0)
  223                 timer = 1;
  224 
  225         /*
  226          * In the IGMPv2 specification, there are 3 states and a flag.
  227          *
  228          * In Non-Member state, we simply don't have a membership record.
  229          * In Delaying Member state, our timer is running (inm->inm_timer).
  230          * In Idle Member state, our timer is not running (inm->inm_timer==0).
  231          *
  232          * The flag is inm->inm_state, it is set to IGMP_OTHERMEMBER if we
  233          * have heard a report from another member, or IGMP_IREPORTEDLAST if
  234          * I sent the last report.
  235          */
  236         switch (igmp->igmp_type) {
  237         case IGMP_MEMBERSHIP_QUERY:
  238                 ++igmpstat.igps_rcv_queries;
  239 
  240                 if (ifp->if_flags & IFF_LOOPBACK)
  241                         break;
  242 
  243                 if (igmp->igmp_code == 0) {
  244                         /*
  245                          * Old router.  Remember that the querier on this
  246                          * interface is old, and set the timer to the value
  247                          * in RFC 1112.
  248                          */
  249 
  250                         mtx_lock(&igmp_mtx);
  251                         rti = find_rti(ifp);
  252                         if (rti == NULL) {
  253                                 mtx_unlock(&igmp_mtx);
  254                                 m_freem(m);
  255                                 return;
  256                         }
  257                         rti->rti_type = IGMP_V1_ROUTER;
  258                         rti->rti_time = 0;
  259                         mtx_unlock(&igmp_mtx);
  260 
  261                         timer = IGMP_MAX_HOST_REPORT_DELAY * PR_FASTHZ;
  262 
  263                         if (ip->ip_dst.s_addr != igmp_all_hosts_group ||
  264                             igmp->igmp_group.s_addr != 0) {
  265                                 ++igmpstat.igps_rcv_badqueries;
  266                                 m_freem(m);
  267                                 return;
  268                         }
  269                 } else {
  270                         /*
  271                          * New router.  Simply do the new validity check.
  272                          */
  273                         
  274                         if (igmp->igmp_group.s_addr != 0 &&
  275                             !IN_MULTICAST(ntohl(igmp->igmp_group.s_addr))) {
  276                                 ++igmpstat.igps_rcv_badqueries;
  277                                 m_freem(m);
  278                                 return;
  279                         }
  280                 }
  281 
  282                 /*
  283                  * - Start the timers in all of our membership records that
  284                  *   the query applies to for the interface on which the
  285                  *   query arrived excl. those that belong to the "all-hosts"
  286                  *   group (224.0.0.1).
  287                  * - Restart any timer that is already running but has a
  288                  *   value longer than the requested timeout.
  289                  * - Use the value specified in the query message as the
  290                  *   maximum timeout.
  291                  */
  292                 IN_MULTI_LOCK();
  293                 IN_FIRST_MULTI(step, inm);
  294                 while (inm != NULL) {
  295                         if (inm->inm_ifp == ifp &&
  296                             inm->inm_addr.s_addr != igmp_all_hosts_group &&
  297                             (igmp->igmp_group.s_addr == 0 ||
  298                              igmp->igmp_group.s_addr == inm->inm_addr.s_addr)) {
  299                                 if (inm->inm_timer == 0 ||
  300                                     inm->inm_timer > timer) {
  301                                         inm->inm_timer =
  302                                                 IGMP_RANDOM_DELAY(timer);
  303                                         igmp_timers_are_running = 1;
  304                                 }
  305                         }
  306                         IN_NEXT_MULTI(step, inm);
  307                 }
  308                 IN_MULTI_UNLOCK();
  309                 break;
  310 
  311         case IGMP_V1_MEMBERSHIP_REPORT:
  312         case IGMP_V2_MEMBERSHIP_REPORT:
  313                 /*
  314                  * For fast leave to work, we have to know that we are the
  315                  * last person to send a report for this group.  Reports can
  316                  * potentially get looped back if we are a multicast router,
  317                  * so discard reports sourced by me.
  318                  */
  319                 IFP_TO_IA(ifp, ia);
  320                 if (ia != NULL &&
  321                     ip->ip_src.s_addr == IA_SIN(ia)->sin_addr.s_addr)
  322                         break;
  323 
  324                 ++igmpstat.igps_rcv_reports;
  325 
  326                 if (ifp->if_flags & IFF_LOOPBACK)
  327                         break;
  328 
  329                 if (!IN_MULTICAST(ntohl(igmp->igmp_group.s_addr))) {
  330                         ++igmpstat.igps_rcv_badreports;
  331                         m_freem(m);
  332                         return;
  333                 }
  334 
  335                 /*
  336                  * KLUDGE: if the IP source address of the report has an
  337                  * unspecified (i.e., zero) subnet number, as is allowed for
  338                  * a booting host, replace it with the correct subnet number
  339                  * so that a process-level multicast routing daemon can
  340                  * determine which subnet it arrived from.  This is necessary
  341                  * to compensate for the lack of any way for a process to
  342                  * determine the arrival interface of an incoming packet.
  343                  */
  344                 if ((ntohl(ip->ip_src.s_addr) & IN_CLASSA_NET) == 0) {
  345                         if (ia != NULL)
  346                                 ip->ip_src.s_addr = htonl(ia->ia_subnet);
  347                 }
  348 
  349                 /*
  350                  * If we belong to the group being reported, stop our timer
  351                  * for that group.
  352                  */
  353                 IN_MULTI_LOCK();
  354                 IN_LOOKUP_MULTI(igmp->igmp_group, ifp, inm);
  355                 if (inm != NULL) {
  356                         inm->inm_timer = 0;
  357                         ++igmpstat.igps_rcv_ourreports;
  358                         inm->inm_state = IGMP_OTHERMEMBER;
  359                 }
  360                 IN_MULTI_UNLOCK();
  361                 break;
  362         }
  363 
  364         /*
  365          * Pass all valid IGMP packets up to any process(es) listening on a
  366          * raw IGMP socket.
  367          */
  368         rip_input(m, off);
  369 }
  370 
  371 void
  372 igmp_joingroup(struct in_multi *inm)
  373 {
  374 
  375         IN_MULTI_LOCK_ASSERT();
  376 
  377         if (inm->inm_addr.s_addr == igmp_all_hosts_group
  378             || inm->inm_ifp->if_flags & IFF_LOOPBACK) {
  379                 inm->inm_timer = 0;
  380                 inm->inm_state = IGMP_OTHERMEMBER;
  381         } else {
  382                 mtx_lock(&igmp_mtx);
  383                 inm->inm_rti = find_rti(inm->inm_ifp);
  384                 mtx_unlock(&igmp_mtx);
  385                 if (inm->inm_rti != NULL) {
  386                         igmp_sendpkt(inm, inm->inm_rti->rti_type, 0);
  387                         inm->inm_timer = IGMP_RANDOM_DELAY(
  388                                         IGMP_MAX_HOST_REPORT_DELAY*PR_FASTHZ);
  389                         inm->inm_state = IGMP_IREPORTEDLAST;
  390                         igmp_timers_are_running = 1;
  391                 }
  392                 /* XXX handling of failure case? */
  393         }
  394 }
  395 
  396 void
  397 igmp_leavegroup(struct in_multi *inm)
  398 {
  399 
  400         IN_MULTI_LOCK_ASSERT();
  401 
  402         if (inm->inm_state == IGMP_IREPORTEDLAST &&
  403             inm->inm_addr.s_addr != igmp_all_hosts_group &&
  404             !(inm->inm_ifp->if_flags & IFF_LOOPBACK) &&
  405             inm->inm_rti->rti_type != IGMP_V1_ROUTER)
  406                 igmp_sendpkt(inm, IGMP_V2_LEAVE_GROUP, igmp_all_rtrs_group);
  407 }
  408 
  409 void
  410 igmp_fasttimo(void)
  411 {
  412         register struct in_multi *inm;
  413         struct in_multistep step;
  414 
  415         /*
  416          * Quick check to see if any work needs to be done, in order to
  417          * minimize the overhead of fasttimo processing.
  418          */
  419 
  420         if (!igmp_timers_are_running)
  421                 return;
  422 
  423         IN_MULTI_LOCK();
  424         igmp_timers_are_running = 0;
  425         IN_FIRST_MULTI(step, inm);
  426         while (inm != NULL) {
  427                 if (inm->inm_timer == 0) {
  428                         /* do nothing */
  429                 } else if (--inm->inm_timer == 0) {
  430                         igmp_sendpkt(inm, inm->inm_rti->rti_type, 0);
  431                         inm->inm_state = IGMP_IREPORTEDLAST;
  432                 } else {
  433                         igmp_timers_are_running = 1;
  434                 }
  435                 IN_NEXT_MULTI(step, inm);
  436         }
  437         IN_MULTI_UNLOCK();
  438 }
  439 
  440 void
  441 igmp_slowtimo(void)
  442 {
  443         struct router_info *rti;
  444 
  445         IGMP_PRINTF("[igmp.c,_slowtimo] -- > entering \n");
  446         mtx_lock(&igmp_mtx);
  447         SLIST_FOREACH(rti, &router_info_head, rti_list) {
  448                 if (rti->rti_type == IGMP_V1_ROUTER) {
  449                         rti->rti_time++;
  450                         if (rti->rti_time >= IGMP_AGE_THRESHOLD)
  451                                 rti->rti_type = IGMP_V2_ROUTER;
  452                 }
  453         }
  454         mtx_unlock(&igmp_mtx);
  455         IGMP_PRINTF("[igmp.c,_slowtimo] -- > exiting \n");
  456 }
  457 
  458 static void
  459 igmp_sendpkt(struct in_multi *inm, int type, unsigned long addr)
  460 {
  461         struct mbuf *m;
  462         struct igmp *igmp;
  463         struct ip *ip;
  464         struct ip_moptions imo;
  465 
  466         IN_MULTI_LOCK_ASSERT();
  467 
  468         MGETHDR(m, M_DONTWAIT, MT_DATA);
  469         if (m == NULL)
  470                 return;
  471 
  472         m->m_pkthdr.rcvif = loif;
  473 #ifdef MAC
  474         mac_create_mbuf_linklayer(inm->inm_ifp, m);
  475 #endif
  476         m->m_pkthdr.len = sizeof(struct ip) + IGMP_MINLEN;
  477         MH_ALIGN(m, IGMP_MINLEN + sizeof(struct ip));
  478         m->m_data += sizeof(struct ip);
  479         m->m_len = IGMP_MINLEN;
  480         igmp = mtod(m, struct igmp *);
  481         igmp->igmp_type = type;
  482         igmp->igmp_code = 0;
  483         igmp->igmp_group = inm->inm_addr;
  484         igmp->igmp_cksum = 0;
  485         igmp->igmp_cksum = in_cksum(m, IGMP_MINLEN);
  486 
  487         m->m_data -= sizeof(struct ip);
  488         m->m_len += sizeof(struct ip);
  489         ip = mtod(m, struct ip *);
  490         ip->ip_tos = 0;
  491         ip->ip_len = sizeof(struct ip) + IGMP_MINLEN;
  492         ip->ip_off = 0;
  493         ip->ip_p = IPPROTO_IGMP;
  494         ip->ip_src.s_addr = INADDR_ANY;
  495         ip->ip_dst.s_addr = addr ? addr : igmp->igmp_group.s_addr;
  496 
  497         imo.imo_multicast_ifp  = inm->inm_ifp;
  498         imo.imo_multicast_ttl  = 1;
  499         imo.imo_multicast_vif  = -1;
  500         /*
  501          * Request loopback of the report if we are acting as a multicast
  502          * router, so that the process-level routing daemon can hear it.
  503          */
  504         imo.imo_multicast_loop = (ip_mrouter != NULL);
  505 
  506         /*
  507          * XXX: Do we have to worry about reentrancy here?  Don't think so.
  508          */
  509         ip_output(m, router_alert, &igmprt, 0, &imo, NULL);
  510 
  511         ++igmpstat.igps_snd_reports;
  512 }

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