FreeBSD/Linux Kernel Cross Reference
sys/net/bridge.c

     /*
      * Copyright (c) 1998-2002 Luigi Rizzo
      *
      * Work partly supported by: Cisco Systems, Inc. - NSITE lab, RTP, NC
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
      * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     * $FreeBSD: releng/5.1/sys/net/bridge.c 111119 2003-02-19 05:47:46Z imp $
     */
    
    /*
     * This code implements bridging in FreeBSD. It only acts on ethernet
     * interfaces, including VLANs (others are still usable for routing).
     * A FreeBSD host can implement multiple logical bridges, called
     * "clusters". Each cluster is made of a set of interfaces, and
     * identified by a "cluster-id" which is a number in the range 1..2^16-1.
     *
     * Bridging is enabled by the sysctl variable
     *      net.link.ether.bridge
     * the grouping of interfaces into clusters is done with
     *      net.link.ether.bridge_cfg
     * containing a list of interfaces each optionally followed by
     * a colon and the cluster it belongs to (1 is the default).
     * Separators can be * spaces, commas or tabs, e.g.
     *      net.link.ether.bridge_cfg="fxp0:2 fxp1:2 dc0 dc1:1"
     * Optionally bridged packets can be passed through the firewall,
     * this is controlled by the variable
     *      net.link.ether.bridge_ipfw
     *
     * For each cluster there is a descriptor (cluster_softc) storing
     * the following data structures:
     * - a hash table with the MAC address and destination interface for each
     *   known node. The table is indexed using a hash of the source address.
     * - an array with the MAC addresses of the interfaces used in the cluster.
     *
     * Input packets are tapped near the beginning of ether_input(), and
     * analysed by bridge_in(). Depending on the result, the packet
     * can be forwarded to one or more output interfaces using bdg_forward(),
     * and/or sent to the upper layer (e.g. in case of multicast).
     *
     * Output packets are intercepted near the end of ether_output().
     * The correct destination is selected by bridge_dst_lookup(),
     * and then forwarding is done by bdg_forward().
     *
     * The arp code is also modified to let a machine answer to requests
     * irrespective of the port the request came from.
     *
     * In case of loops in the bridging topology, the bridge detects this
     * event and temporarily mutes output bridging on one of the ports.
     * Periodically, interfaces are unmuted by bdg_timeout().
     * Muting is only implemented as a safety measure, and also as
     * a mechanism to support a user-space implementation of the spanning
     * tree algorithm.
     *
     * To build a bridging kernel, use the following option
     *    option BRIDGE
     * and then at runtime set the sysctl variable to enable bridging.
     *
     * Only one interface per cluster is supposed to have addresses set (but
     * there are no substantial problems if you set addresses for none or
     * for more than one interface).
     * Bridging will act before routing, but nothing prevents a machine
     * from doing both (modulo bugs in the implementation...).
     *
     * THINGS TO REMEMBER
     *  - bridging is incompatible with multicast routing on the same
     *    machine. There is not an easy fix to this.
     *  - be very careful when bridging VLANs
     *  - loop detection is still not very robust.
     */
    
    #include <sys/param.h>
    #include <sys/mbuf.h>
    #include <sys/malloc.h>
    #include <sys/protosw.h>
    #include <sys/systm.h>
    #include <sys/socket.h> /* for net/if.h */
    #include <sys/ctype.h>  /* string functions */
    #include <sys/kernel.h>
    #include <sys/sysctl.h>
   
   #include <net/pfil.h>   /* for ipfilter */
   #include <net/if.h>
   #include <net/if_types.h>
   #include <net/if_var.h>
   
   #include <netinet/in.h> /* for struct arpcom */
   #include <netinet/in_systm.h>
   #include <netinet/in_var.h>
   #include <netinet/ip.h>
   #include <netinet/if_ether.h> /* for struct arpcom */
   
   #include <net/route.h>
   #include <netinet/ip_fw.h>
   #include <netinet/ip_dummynet.h>
   #include <net/bridge.h>
   
   /*--------------------*/
   
   /*
    * For each cluster, source MAC addresses are stored into a hash
    * table which locates the port they reside on.
    */
   #define HASH_SIZE 8192  /* Table size, must be a power of 2 */
   
   typedef struct hash_table {             /* each entry.          */
       struct ifnet *      name;
       u_char              etheraddr[6];
       u_int16_t           used;           /* also, padding        */
   } bdg_hash_table ;
   
   /*
    * The hash function applied to MAC addresses. Out of the 6 bytes,
    * the last ones tend to vary more. Since we are on a little endian machine,
    * we have to do some gimmick...
    */
   #define HASH_FN(addr)   (       \
       ntohs( ((u_int16_t *)addr)[1] ^ ((u_int16_t *)addr)[2] ) & (HASH_SIZE -1))
   
   /*
    * This is the data structure where local addresses are stored.
    */
   struct bdg_addr {
       u_char      etheraddr[6] ;
       u_int16_t   _padding ;
   };
   
   /*
    * The configuration of each cluster includes the cluster id, a pointer to
    * the hash table, and an array of local MAC addresses (of size "ports").
    */
   struct cluster_softc {
       u_int16_t   cluster_id;
       u_int16_t   ports;
       bdg_hash_table *ht;
       struct bdg_addr     *my_macs;       /* local MAC addresses */
   };
   
   
   extern struct protosw inetsw[];                 /* from netinet/ip_input.c */
   extern u_char ip_protox[];                      /* from netinet/ip_input.c */
   
   static int n_clusters;                          /* number of clusters */
   static struct cluster_softc *clusters;
   
   #define BDG_MUTED(ifp) (ifp2sc[ifp->if_index].flags & IFF_MUTE)
   #define BDG_MUTE(ifp) ifp2sc[ifp->if_index].flags |= IFF_MUTE
   #define BDG_CLUSTER(ifp) (ifp2sc[ifp->if_index].cluster)
   
   #define BDG_SAMECLUSTER(ifp,src) \
           (src == NULL || BDG_CLUSTER(ifp) == BDG_CLUSTER(src) )
   
   #ifdef __i386__
   #define BDG_MATCH(a,b) ( \
       ((u_int16_t *)(a))[2] == ((u_int16_t *)(b))[2] && \
       *((u_int32_t *)(a)) == *((u_int32_t *)(b)) )
   #define IS_ETHER_BROADCAST(a) ( \
           *((u_int32_t *)(a)) == 0xffffffff && \
           ((u_int16_t *)(a))[2] == 0xffff )
   #else
   /* for machines that do not support unaligned access */
   #define BDG_MATCH(a,b)          (!bcmp(a, b, ETHER_ADDR_LEN) )
   #define IS_ETHER_BROADCAST(a)   (!bcmp(a, "\377\377\377\377\377\377", 6))
   #endif
   
   
   /*
    * For timing-related debugging, you can use the following macros.
    * remember, rdtsc() only works on Pentium-class machines
   
       quad_t ticks;
       DDB(ticks = rdtsc();)
       ... interesting code ...
       DDB(bdg_fw_ticks += (u_long)(rdtsc() - ticks) ; bdg_fw_count++ ;)
   
    *
    */
   
   #define DDB(x) x
   #define DEB(x)
   
   static int bdginit(void);
   static void parse_bdg_cfg(void);
   
   static int bdg_ipf;             /* IPFilter enabled in bridge */
   static int bdg_ipfw;
   
   #if 0 /* debugging only */
   static char *bdg_dst_names[] = {
           "BDG_NULL    ",
           "BDG_BCAST   ",
           "BDG_MCAST   ",
           "BDG_LOCAL   ",
           "BDG_DROP    ",
           "BDG_UNKNOWN ",
           "BDG_IN      ",
           "BDG_OUT     ",
           "BDG_FORWARD " };
   #endif
   /*
    * System initialization
    */
   
   static struct bdg_stats bdg_stats ;
   static struct callout_handle bdg_timeout_h ;
   
   /*
    * Add an interface to a cluster, possibly creating a new entry in
    * the cluster table. This requires reallocation of the table and
    * updating pointers in ifp2sc.
    */
   static struct cluster_softc *
   add_cluster(u_int16_t cluster_id, struct arpcom *ac)
   {
       struct cluster_softc *c = NULL;
       int i;
   
       for (i = 0; i < n_clusters ; i++)
           if (clusters[i].cluster_id == cluster_id)
               goto found;
   
       /* Not found, need to reallocate */
       c = malloc((1+n_clusters) * sizeof (*c), M_IFADDR, M_NOWAIT | M_ZERO);
       if (c == NULL) {/* malloc failure */
           printf("-- bridge: cannot add new cluster\n");
           return NULL;
       }
       c[n_clusters].ht = (struct hash_table *)
               malloc(HASH_SIZE * sizeof(struct hash_table),
                   M_IFADDR, M_WAITOK | M_ZERO);
       if (c[n_clusters].ht == NULL) {
           printf("-- bridge: cannot allocate hash table for new cluster\n");
           free(c, M_IFADDR);
           return NULL;
       }
       c[n_clusters].my_macs = (struct bdg_addr *)
               malloc(BDG_MAX_PORTS * sizeof(struct bdg_addr),
                   M_IFADDR, M_WAITOK | M_ZERO);
       if (c[n_clusters].my_macs == NULL) {
           printf("-- bridge: cannot allocate mac addr table for new cluster\n");
           free(c[n_clusters].ht, M_IFADDR);
           free(c, M_IFADDR);
           return NULL;
       }
   
       c[n_clusters].cluster_id = cluster_id;
       c[n_clusters].ports = 0;
       /*
        * now copy old descriptors here
        */
       if (n_clusters > 0) {
           for (i=0; i < n_clusters; i++)
               c[i] = clusters[i];
           /*
            * and finally update pointers in ifp2sc
            */
           for (i = 0 ; i < if_index && i < BDG_MAX_PORTS; i++)
               if (ifp2sc[i].cluster != NULL)
                   ifp2sc[i].cluster = c + (ifp2sc[i].cluster - clusters);
           free(clusters, M_IFADDR);
       }
       clusters = c;
       i = n_clusters;             /* index of cluster entry */
       n_clusters++;
   found:
       c = clusters + i;           /* the right cluster ... */
       bcopy(ac->ac_enaddr, &(c->my_macs[c->ports]), 6);
       c->ports++;
       return c;
   }
   
   
   /*
    * Turn off bridging, by clearing promisc mode on the interface,
    * marking the interface as unused, and clearing the name in the
    * stats entry.
    * Also dispose the hash tables associated with the clusters.
    */
   static void
   bridge_off(void)
   {
       struct ifnet *ifp ;
       int i, s;
   
       DEB(printf("bridge_off: n_clusters %d\n", n_clusters);)
       IFNET_RLOCK();
       TAILQ_FOREACH(ifp, &ifnet, if_link) {
           struct bdg_softc *b;
   
           if (ifp->if_index >= BDG_MAX_PORTS)
               continue;   /* make sure we do not go beyond the end */
           b = &(ifp2sc[ifp->if_index]);
   
           if ( b->flags & IFF_BDG_PROMISC ) {
               s = splimp();
               ifpromisc(ifp, 0);
               splx(s);
               b->flags &= ~(IFF_BDG_PROMISC|IFF_MUTE) ;
               DEB(printf(">> now %s%d promisc OFF if_flags 0x%x bdg_flags 0x%x\n",
                       ifp->if_name, ifp->if_unit,
                       ifp->if_flags, b->flags);)
           }
           b->flags &= ~(IFF_USED) ;
           b->cluster = NULL;
           bdg_stats.s[ifp->if_index].name[0] = '\0';
       }
       IFNET_RUNLOCK();
       /* flush_tables */
   
       s = splimp();
       for (i=0; i < n_clusters; i++) {
           free(clusters[i].ht, M_IFADDR);
           free(clusters[i].my_macs, M_IFADDR);
       }
       if (clusters != NULL)
           free(clusters, M_IFADDR);
       clusters = NULL;
       n_clusters =0;
       splx(s);
   }
   
   /*
    * set promisc mode on the interfaces we use.
    */
   static void
   bridge_on(void)
   {
       struct ifnet *ifp ;
       int s ;
   
       IFNET_RLOCK();
       TAILQ_FOREACH(ifp, &ifnet, if_link) {
           struct bdg_softc *b = &ifp2sc[ifp->if_index];
   
           if ( !(b->flags & IFF_USED) )
               continue ;
           if ( !( ifp->if_flags & IFF_UP) ) {
               s = splimp();
               if_up(ifp);
               splx(s);
           }
           if ( !(b->flags & IFF_BDG_PROMISC) ) {
               int ret ;
               s = splimp();
               ret = ifpromisc(ifp, 1);
               splx(s);
               b->flags |= IFF_BDG_PROMISC ;
               DEB(printf(">> now %s%d promisc ON if_flags 0x%x bdg_flags 0x%x\n",
                       ifp->if_name, ifp->if_unit,
                       ifp->if_flags, b->flags);)
           }
           if (b->flags & IFF_MUTE) {
               DEB(printf(">> unmuting %s%d\n", ifp->if_name, ifp->if_unit);)
               b->flags &= ~IFF_MUTE;
           }
       }
       IFNET_RUNLOCK();
   }
   
   /**
    * reconfigure bridge.
    * This is also done every time we attach or detach an interface.
    * Main use is to make sure that we do not bridge on some old
    * (ejected) device. So, it would be really useful to have a
    * pointer to the modified device as an argument. Without it, we
    * have to scan all interfaces.
    */
   static void
   reconfigure_bridge(void)
   {
       bridge_off();
       if (do_bridge) {
           if (if_index >= BDG_MAX_PORTS) {
               printf("-- sorry too many interfaces (%d, max is %d),"
                   " disabling bridging\n", if_index, BDG_MAX_PORTS);
               do_bridge=0;
               return;
           }
           parse_bdg_cfg();
           bridge_on();
       }
   }
   
   static char bridge_cfg[1024]; /* in BSS so initialized to all NULs */
   
   /*
    * parse the config string, set IFF_USED, name and cluster_id
    * for all interfaces found.
    * The config string is a list of "if[:cluster]" with
    * a number of possible separators (see "sep"). In particular the
    * use of the space lets you set bridge_cfg with the output from
    * "ifconfig -l"
    */
   static void
   parse_bdg_cfg()
   {
       char *p, *beg ;
       int l, cluster;
       static char *sep = ", \t";
   
       for (p = bridge_cfg; *p ; p++) {
           struct ifnet *ifp;
           int found = 0;
           char c;
   
           if (index(sep, *p))     /* skip separators */
               continue ;
           /* names are lowercase and digits */
           for ( beg = p ; islower(*p) || isdigit(*p) ; p++ )
               ;
           l = p - beg ;           /* length of name string */
           if (l == 0)             /* invalid name */
               break ;
           if ( *p != ':' )        /* no ':', assume default cluster 1 */
               cluster = 1 ;
           else                    /* fetch cluster */
               cluster = strtoul( p+1, &p, 10);
           c = *p;
           *p = '\0';
           /*
            * now search in interface list for a matching name
            */
           IFNET_RLOCK();          /* could sleep XXX */
           TAILQ_FOREACH(ifp, &ifnet, if_link) {
               char buf[IFNAMSIZ];
   
               snprintf(buf, sizeof(buf), "%s%d", ifp->if_name, ifp->if_unit);
               if (!strncmp(beg, buf, max(l, strlen(buf)))) {
                   struct bdg_softc *b = &ifp2sc[ifp->if_index];
                   if (ifp->if_type != IFT_ETHER && ifp->if_type != IFT_L2VLAN) {
                       printf("%s is not an ethernet, continue\n", buf);
                       continue;
                   }
                   if (b->flags & IFF_USED) {
                       printf("%s already used, skipping\n", buf);
                       break;
                   }
                   b->cluster = add_cluster(htons(cluster), (struct arpcom *)ifp);
                   b->flags |= IFF_USED ;
                   sprintf(bdg_stats.s[ifp->if_index].name,
                           "%s%d:%d", ifp->if_name, ifp->if_unit, cluster);
   
                   DEB(printf("--++  found %s next c %d\n",
                       bdg_stats.s[ifp->if_index].name, c);)
                   found = 1;
                   break ;
               }
           }
           IFNET_RUNLOCK();
           if (!found)
               printf("interface %s Not found in bridge\n", beg);
           *p = c;
           if (c == '\0')
               break; /* no more */
       }
   }
   
   
   /*
    * handler for net.link.ether.bridge
    */
   static int
   sysctl_bdg(SYSCTL_HANDLER_ARGS)
   {
       int error, oldval = do_bridge ;
   
       error = sysctl_handle_int(oidp, oidp->oid_arg1, oidp->oid_arg2, req);
       DEB( printf("called sysctl for bridge name %s arg2 %d val %d->%d\n",
           oidp->oid_name, oidp->oid_arg2,
           oldval, do_bridge); )
   
       if (oldval != do_bridge)
           reconfigure_bridge();
       return error ;
   }
   
   /*
    * handler for net.link.ether.bridge_cfg
    */
   static int
   sysctl_bdg_cfg(SYSCTL_HANDLER_ARGS)
   {
       int error = 0 ;
       char old_cfg[1024] ;
   
       strcpy(old_cfg, bridge_cfg) ;
   
       error = sysctl_handle_string(oidp, bridge_cfg, oidp->oid_arg2, req);
       DEB(
           printf("called sysctl for bridge name %s arg2 %d err %d val %s->%s\n",
                   oidp->oid_name, oidp->oid_arg2,
                   error,
                   old_cfg, bridge_cfg);
           )
       if (strcmp(old_cfg, bridge_cfg))
           reconfigure_bridge();
       return error ;
   }
   
   static int
   sysctl_refresh(SYSCTL_HANDLER_ARGS)
   {
       if (req->newptr)
           reconfigure_bridge();
   
       return 0;
   }
   
   
   SYSCTL_DECL(_net_link_ether);
   SYSCTL_PROC(_net_link_ether, OID_AUTO, bridge_cfg, CTLTYPE_STRING|CTLFLAG_RW,
               &bridge_cfg, sizeof(bridge_cfg), &sysctl_bdg_cfg, "A",
               "Bridge configuration");
   
   SYSCTL_PROC(_net_link_ether, OID_AUTO, bridge, CTLTYPE_INT|CTLFLAG_RW,
               &do_bridge, 0, &sysctl_bdg, "I", "Bridging");
   
   SYSCTL_INT(_net_link_ether, OID_AUTO, bridge_ipfw, CTLFLAG_RW,
               &bdg_ipfw,0,"Pass bridged pkts through firewall");
   
   SYSCTL_INT(_net_link_ether, OID_AUTO, bridge_ipf, CTLFLAG_RW,
               &bdg_ipf, 0,"Pass bridged pkts through IPFilter");
   
   /*
    * The follow macro declares a variable, and maps it to
    * a SYSCTL_INT entry with the same name.
    */
   #define SY(parent, var, comment)                        \
           static int var ;                                \
           SYSCTL_INT(parent, OID_AUTO, var, CTLFLAG_RW, &(var), 0, comment);
   
   int bdg_ipfw_drops;
   SYSCTL_INT(_net_link_ether, OID_AUTO, bridge_ipfw_drop,
           CTLFLAG_RW, &bdg_ipfw_drops,0,"");
   
   int bdg_ipfw_colls;
   SYSCTL_INT(_net_link_ether, OID_AUTO, bridge_ipfw_collisions,
           CTLFLAG_RW, &bdg_ipfw_colls,0,"");
   
   SYSCTL_PROC(_net_link_ether, OID_AUTO, bridge_refresh, CTLTYPE_INT|CTLFLAG_WR,
               NULL, 0, &sysctl_refresh, "I", "iface refresh");
   
   #if 1 /* diagnostic vars */
   
   SY(_net_link_ether, verbose, "Be verbose");
   SY(_net_link_ether, bdg_split_pkts, "Packets split in bdg_forward");
   
   SY(_net_link_ether, bdg_thru, "Packets through bridge");
   
   SY(_net_link_ether, bdg_copied, "Packets copied in bdg_forward");
   SY(_net_link_ether, bdg_dropped, "Packets dropped in bdg_forward");
   
   SY(_net_link_ether, bdg_copy, "Force copy in bdg_forward");
   SY(_net_link_ether, bdg_predict, "Correctly predicted header location");
   
   SY(_net_link_ether, bdg_fw_avg, "Cycle counter avg");
   SY(_net_link_ether, bdg_fw_ticks, "Cycle counter item");
   SY(_net_link_ether, bdg_fw_count, "Cycle counter count");
   #endif
   
   SYSCTL_STRUCT(_net_link_ether, PF_BDG, bdgstats,
           CTLFLAG_RD, &bdg_stats , bdg_stats, "bridge statistics");
   
   static int bdg_loops ;
   
   /*
    * called periodically to flush entries etc.
    */
   static void
   bdg_timeout(void *dummy)
   {
       static int slowtimer; /* in BSS so initialized to 0 */
   
       if (do_bridge) {
           static int age_index = 0 ; /* index of table position to age */
           int l = age_index + HASH_SIZE/4 ;
           int i;
           /*
            * age entries in the forwarding table.
            */
           if (l > HASH_SIZE)
               l = HASH_SIZE ;
   
           for (i=0; i<n_clusters; i++) {
               bdg_hash_table *bdg_table = clusters[i].ht;
               for (; age_index < l ; age_index++)
                   if (bdg_table[age_index].used)
                       bdg_table[age_index].used = 0 ;
                   else if (bdg_table[age_index].name) {
                       /* printf("xx flushing stale entry %d\n", age_index); */
                       bdg_table[age_index].name = NULL ;
                   }
           }
           if (age_index >= HASH_SIZE)
               age_index = 0 ;
   
           if (--slowtimer <= 0 ) {
               slowtimer = 5 ;
   
               bridge_on() ; /* we just need unmute, really */
               bdg_loops = 0 ;
           }
       }
       bdg_timeout_h = timeout(bdg_timeout, NULL, 2*hz );
   }
   
   /*
    * Find the right pkt destination:
    *      BDG_BCAST       is a broadcast
    *      BDG_MCAST       is a multicast
    *      BDG_LOCAL       is for a local address
    *      BDG_DROP        must be dropped
    *      other           ifp of the dest. interface (incl.self)
    *
    * We assume this is only called for interfaces for which bridging
    * is enabled, i.e. BDG_USED(ifp) is true.
    */
   static __inline
   struct ifnet *
   bridge_dst_lookup(struct ether_header *eh, struct cluster_softc *c)
   {
       struct ifnet *dst ;
       int index ;
       struct bdg_addr *p ;
       bdg_hash_table *bt;         /* pointer to entry in hash table */
   
       if (IS_ETHER_BROADCAST(eh->ether_dhost))
           return BDG_BCAST ;
       if (eh->ether_dhost[0] & 1)
           return BDG_MCAST ;
       /*
        * Lookup local addresses in case one matches.
        */
       for (index = c->ports, p = c->my_macs; index ; index--, p++ )
           if (BDG_MATCH(p->etheraddr, eh->ether_dhost) )
               return BDG_LOCAL ;
       /*
        * Look for a possible destination in table
        */
       index= HASH_FN( eh->ether_dhost );
       bt = &(c->ht[index]);
       dst = bt->name;
       if ( dst && BDG_MATCH( bt->etheraddr, eh->ether_dhost) )
           return dst ;
       else
           return BDG_UNKNOWN ;
   }
   
   /**
    * bridge_in() is invoked to perform bridging decision on input packets.
    *
    * On Input:
    *   eh         Ethernet header of the incoming packet.
    *   ifp        interface the packet is coming from.
    *
    * On Return: destination of packet, one of
    *   BDG_BCAST  broadcast
    *   BDG_MCAST  multicast
    *   BDG_LOCAL  is only for a local address (do not forward)
    *   BDG_DROP   drop the packet
    *   ifp        ifp of the destination interface.
    *
    * Forwarding is not done directly to give a chance to some drivers
    * to fetch more of the packet, or simply drop it completely.
    */
   
   static struct ifnet *
   bridge_in(struct ifnet *ifp, struct ether_header *eh)
   {
       int index;
       struct ifnet *dst , *old ;
       bdg_hash_table *bt;                 /* location in hash table */
       int dropit = BDG_MUTED(ifp) ;
   
       /*
        * hash the source address
        */
       index= HASH_FN(eh->ether_shost);
       bt = &(ifp2sc[ifp->if_index].cluster->ht[index]);
       bt->used = 1 ;
       old = bt->name ;
       if ( old ) { /* the entry is valid. */
           if (!BDG_MATCH( eh->ether_shost, bt->etheraddr) ) {
               bdg_ipfw_colls++ ;
               bt->name = NULL ;
           } else if (old != ifp) {
               /*
                * Found a loop. Either a machine has moved, or there
                * is a misconfiguration/reconfiguration of the network.
                * First, do not forward this packet!
                * Record the relocation anyways; then, if loops persist,
                * suspect a reconfiguration and disable forwarding
                * from the old interface.
                */
               bt->name = ifp ; /* relocate address */
               printf("-- loop (%d) %6D to %s%d from %s%d (%s)\n",
                           bdg_loops, eh->ether_shost, ".",
                           ifp->if_name, ifp->if_unit,
                           old->if_name, old->if_unit,
                           BDG_MUTED(old) ? "muted":"active");
               dropit = 1 ;
               if ( !BDG_MUTED(old) ) {
                   if (++bdg_loops > 10)
                       BDG_MUTE(old) ;
               }
           }
       }
   
       /*
        * now write the source address into the table
        */
       if (bt->name == NULL) {
           DEB(printf("new addr %6D at %d for %s%d\n",
               eh->ether_shost, ".", index, ifp->if_name, ifp->if_unit);)
           bcopy(eh->ether_shost, bt->etheraddr, 6);
           bt->name = ifp ;
       }
       dst = bridge_dst_lookup(eh, ifp2sc[ifp->if_index].cluster);
       /*
        * bridge_dst_lookup can return the following values:
        *   BDG_BCAST, BDG_MCAST, BDG_LOCAL, BDG_UNKNOWN, BDG_DROP, ifp.
        * For muted interfaces, or when we detect a loop, the first 3 are
        * changed in BDG_LOCAL (we still listen to incoming traffic),
        * and others to BDG_DROP (no use for the local host).
        * Also, for incoming packets, ifp is changed to BDG_DROP if ifp == src.
        * These changes are not necessary for outgoing packets from ether_output().
        */
       BDG_STAT(ifp, BDG_IN);
       switch ((uintptr_t)dst) {
       case (uintptr_t)BDG_BCAST:
       case (uintptr_t)BDG_MCAST:
       case (uintptr_t)BDG_LOCAL:
       case (uintptr_t)BDG_UNKNOWN:
       case (uintptr_t)BDG_DROP:
           BDG_STAT(ifp, dst);
           break ;
       default :
           if (dst == ifp || dropit)
               BDG_STAT(ifp, BDG_DROP);
           else
               BDG_STAT(ifp, BDG_FORWARD);
           break ;
       }
   
       if ( dropit ) {
           if (dst == BDG_BCAST || dst == BDG_MCAST || dst == BDG_LOCAL)
               dst = BDG_LOCAL ;
           else
               dst = BDG_DROP ;
       } else {
           if (dst == ifp)
               dst = BDG_DROP;
       }
       DEB(printf("bridge_in %6D ->%6D ty 0x%04x dst %s%d\n",
           eh->ether_shost, ".",
           eh->ether_dhost, ".",
           ntohs(eh->ether_type),
           (dst <= BDG_FORWARD) ? bdg_dst_names[(int)dst] :
                   dst->if_name,
           (dst <= BDG_FORWARD) ? 0 : dst->if_unit); )
   
       return dst ;
   }
   
   /*
    * Forward a packet to dst -- which can be a single interface or
    * an entire cluster. The src port and muted interfaces are excluded.
    *
    * If src == NULL, the pkt comes from ether_output, and dst is the real
    * interface the packet is originally sent to. In this case, we must forward
    * it to the whole cluster.
    * We never call bdg_forward from ether_output on interfaces which are
    * not part of a cluster.
    *
    * If possible (i.e. we can determine that the caller does not need
    * a copy), the packet is consumed here, and bdg_forward returns NULL.
    * Otherwise, a pointer to a copy of the packet is returned.
    */
   static struct mbuf *
   bdg_forward(struct mbuf *m0, struct ifnet *dst)
   {
   #define EH_RESTORE(_m) do {                                                \
       M_PREPEND((_m), ETHER_HDR_LEN, M_DONTWAIT);                            \
       if ((_m) == NULL) {                                                    \
           bdg_dropped++;                                                     \
           return NULL;                                                       \
       }                                                                      \
       if (eh != mtod((_m), struct ether_header *))                           \
           bcopy(&save_eh, mtod((_m), struct ether_header *), ETHER_HDR_LEN); \
       else                                                                   \
           bdg_predict++;                                                     \
   } while (0);
       struct ether_header *eh;
       struct ifnet *src;
       struct ifnet *ifp, *last;
       int shared = bdg_copy ; /* someone else is using the mbuf */
       int once = 0;      /* loop only once */
       struct ifnet *real_dst = dst ; /* real dst from ether_output */
       struct ip_fw_args args;
   #ifdef PFIL_HOOKS
       struct packet_filter_hook *pfh;
       int rv;
   #endif /* PFIL_HOOKS */
       struct ether_header save_eh;
   
       DEB(quad_t ticks; ticks = rdtsc();)
   
       args.rule = NULL;           /* did we match a firewall rule ? */
       /* Fetch state from dummynet tag, ignore others */
       for (;m0->m_type == MT_TAG; m0 = m0->m_next)
           if (m0->_m_tag_id == PACKET_TAG_DUMMYNET) {
               args.rule = ((struct dn_pkt *)m0)->rule;
               shared = 0;         /* For sure this is our own mbuf. */
           }
       if (args.rule == NULL)
           bdg_thru++; /* first time through bdg_forward, count packet */
   
       /*
        * The packet arrives with the Ethernet header at the front.
        */
       eh = mtod(m0, struct ether_header *);
   
       src = m0->m_pkthdr.rcvif;
       if (src == NULL)                    /* packet from ether_output */
           dst = bridge_dst_lookup(eh, ifp2sc[real_dst->if_index].cluster);
   
       if (dst == BDG_DROP) { /* this should not happen */
           printf("xx bdg_forward for BDG_DROP\n");
           m_freem(m0);
           bdg_dropped++;
           return NULL;
       }
       if (dst == BDG_LOCAL) { /* this should not happen as well */
           printf("xx ouch, bdg_forward for local pkt\n");
           return m0;
       }
       if (dst == BDG_BCAST || dst == BDG_MCAST) {
            /* need a copy for the local stack */
            shared = 1 ;
       }
   
       /*
        * Do filtering in a very similar way to what is done in ip_output.
        * Only if firewall is loaded, enabled, and the packet is not
        * from ether_output() (src==NULL, or we would filter it twice).
        * Additional restrictions may apply e.g. non-IP, short packets,
        * and pkts already gone through a pipe.
        */
       if (src != NULL && (
   #ifdef PFIL_HOOKS
           ((pfh = pfil_hook_get(PFIL_IN, &inetsw[ip_protox[IPPROTO_IP]].pr_pfh)) != NULL && bdg_ipf !=0) ||
   #endif
           (IPFW_LOADED && bdg_ipfw != 0))) {
   
           int i;
   
           if (args.rule != NULL && fw_one_pass)
               goto forward; /* packet already partially processed */
           /*
            * i need some amt of data to be contiguous, and in case others need
            * the packet (shared==1) also better be in the first mbuf.
            */
           i = min(m0->m_pkthdr.len, max_protohdr) ;
           if ( shared || m0->m_len < i) {
               m0 = m_pullup(m0, i) ;
               if (m0 == NULL) {
                   printf("-- bdg: pullup failed.\n") ;
                   bdg_dropped++;
                   return NULL ;
               }
               eh = mtod(m0, struct ether_header *);
           }
   
           /*
            * Processing below expects the Ethernet header is stripped.
            * Furthermore, the mbuf chain might be replaced at various
            * places.  To deal with this we copy the header to a temporary
            * location, strip the header, and restore it as needed.
            */
           bcopy(eh, &save_eh, ETHER_HDR_LEN);     /* local copy for restore */
           m_adj(m0, ETHER_HDR_LEN);               /* temporarily strip header */
   
   #ifdef PFIL_HOOKS
           /*
            * NetBSD-style generic packet filter, pfil(9), hooks.
            * Enables ipf(8) in bridging.
            */
           if (pfh != NULL && m0->m_pkthdr.len >= sizeof(struct ip) &&
                   ntohs(save_eh.ether_type) == ETHERTYPE_IP) {
               /*
                * before calling the firewall, swap fields the same as IP does.
                * here we assume the pkt is an IP one and the header is contiguous
                */
               struct ip *ip = mtod(m0, struct ip *);
   
               ip->ip_len = ntohs(ip->ip_len);
               ip->ip_off = ntohs(ip->ip_off);
   
               do {
                   if (pfh->pfil_func) {
                       rv = pfh->pfil_func(ip, ip->ip_hl << 2, src, 0, &m0);
                       if (m0 == NULL) {
                           bdg_dropped++;
                           return NULL;
                       }
                       if (rv != 0) {
                           EH_RESTORE(m0);         /* restore Ethernet header */
                           return m0;
                       }
                       ip = mtod(m0, struct ip *);
                   }
               } while ((pfh = TAILQ_NEXT(pfh, pfil_link)) != NULL);
               /*
                * If we get here, the firewall has passed the pkt, but the mbuf
                * pointer might have changed. Restore ip and the fields ntohs()'d.
                */
               ip = mtod(m0, struct ip *);
               ip->ip_len = htons(ip->ip_len);
               ip->ip_off = htons(ip->ip_off);
           }
   #endif /* PFIL_HOOKS */
   
           /*
            * Prepare arguments and call the firewall.
            */
           if (!IPFW_LOADED || bdg_ipfw == 0) {
               EH_RESTORE(m0);     /* restore Ethernet header */
               goto forward;       /* not using ipfw, accept the packet */
           }
   
           /*
            * XXX The following code is very similar to the one in
            * if_ethersubr.c:ether_ipfw_chk()
            */
   
           args.m = m0;            /* the packet we are looking at         */
           args.oif = NULL;        /* this is an input packet              */
           args.divert_rule = 0;   /* we do not support divert yet         */
           args.next_hop = NULL;   /* we do not support forward yet        */
           args.eh = &save_eh;     /* MAC header for bridged/MAC packets   */
           i = ip_fw_chk_ptr(&args);
           m0 = args.m;            /* in case the firewall used the mbuf   */
   
           if (m0 != NULL)
                   EH_RESTORE(m0); /* restore Ethernet header */
   
           if ( (i & IP_FW_PORT_DENY_FLAG) || m0 == NULL) /* drop */
               return m0 ;
   
           if (i == 0) /* a PASS rule.  */
               goto forward ;
           if (DUMMYNET_LOADED && (i & IP_FW_PORT_DYNT_FLAG)) {
               /*
                * Pass the pkt to dummynet, which consumes it.
                * If shared, make a copy and keep the original.
                */
               struct mbuf *m ;
   
               if (shared) {
                   m = m_copypacket(m0, M_DONTWAIT);
                   if (m == NULL) {        /* copy failed, give up */
                       bdg_dropped++;
                       return NULL;
                   }
               } else {
                   m = m0 ; /* pass the original to dummynet */
                   m0 = NULL ; /* and nothing back to the caller */
               }
   
               args.oif = real_dst;
               ip_dn_io_ptr(m, (i & 0xffff),DN_TO_BDG_FWD, &args);
               return m0 ;
           }
           /*
            * XXX at some point, add support for divert/forward actions.
            * If none of the above matches, we have to drop the packet.
            */
           bdg_ipfw_drops++ ;
           return m0 ;
       }
  forward:
      /*
       * Again, bring up the headers in case of shared bufs to avoid
       * corruptions in the future.
       */
      if ( shared ) {
          int i = min(m0->m_pkthdr.len, max_protohdr) ;
  
          m0 = m_pullup(m0, i) ;
          if (m0 == NULL) {
              bdg_dropped++ ;
              return NULL ;
          }
          /* NB: eh is not used below; no need to recalculate it */
      }
  
      /*
       * now real_dst is used to determine the cluster where to forward.
       * For packets coming from ether_input, this is the one of the 'src'
       * interface, whereas for locally generated packets (src==NULL) it
       * is the cluster of the original destination interface, which
       * was already saved into real_dst.
       */
      if (src != NULL)
          real_dst = src ;
  
      last = NULL;
      IFNET_RLOCK();
      if (dst == BDG_BCAST || dst == BDG_MCAST || dst == BDG_UNKNOWN) {
          ifp = TAILQ_FIRST(&ifnet) ; /* scan all ports */
          once = 0 ;
      } else {
          ifp = dst ;
          once = 1 ;
      }
      if ((uintptr_t)(ifp) <= (u_int)BDG_FORWARD)
          panic("bdg_forward: bad dst");
  
      for (;;) {
          if (last) { /* need to forward packet leftover from previous loop */
              struct mbuf *m ;
              if (shared == 0 && once ) { /* no need to copy */
                  m = m0 ;
                  m0 = NULL ; /* original is gone */
              } else {
                  m = m_copypacket(m0, M_DONTWAIT);
                  if (m == NULL) {
                      IFNET_RUNLOCK();
                      printf("bdg_forward: sorry, m_copypacket failed!\n");
                      bdg_dropped++ ;
                      return m0 ; /* the original is still there... */
                  }
              }
              if (!IF_HANDOFF(&last->if_snd, m, last)) {
  #if 0
                  BDG_MUTE(last); /* should I also mute ? */
  #endif
              }
              BDG_STAT(last, BDG_OUT);
              last = NULL ;
              if (once)
                  break ;
          }
          if (ifp == NULL)
              break ;
          /*
           * If the interface is used for bridging, not muted, not full,
           * up and running, is not the source interface, and belongs to
           * the same cluster as the 'real_dst', then send here.
           */
          if ( BDG_USED(ifp) && !BDG_MUTED(ifp) && !_IF_QFULL(&ifp->if_snd)  &&
               (ifp->if_flags & (IFF_UP|IFF_RUNNING)) == (IFF_UP|IFF_RUNNING) &&
               ifp != src && BDG_SAMECLUSTER(ifp, real_dst) )
              last = ifp ;
          ifp = TAILQ_NEXT(ifp, if_link) ;
          if (ifp == NULL)
              once = 1 ;
      }
      IFNET_RUNLOCK();
      DEB(bdg_fw_ticks += (u_long)(rdtsc() - ticks) ; bdg_fw_count++ ;
          if (bdg_fw_count != 0) bdg_fw_avg = bdg_fw_ticks/bdg_fw_count; )
      return m0 ;
  #undef EH_RESTORE
  }
  
  /*
   * initialization of bridge code.
   */
  static int
  bdginit(void)
  {
      printf("BRIDGE 020214 loaded\n");
  
      ifp2sc = malloc(BDG_MAX_PORTS * sizeof(struct bdg_softc),
                  M_IFADDR, M_WAITOK | M_ZERO );
      if (ifp2sc == NULL)
          return ENOMEM ;
  
      bridge_in_ptr = bridge_in;
      bdg_forward_ptr = bdg_forward;
      bdgtakeifaces_ptr = reconfigure_bridge;
  
      n_clusters = 0;
      clusters = NULL;
      do_bridge=0;
  
      bzero(&bdg_stats, sizeof(bdg_stats) );
      bdgtakeifaces_ptr();
      bdg_timeout(0);
      return 0 ;
  }
  
  /*
   * initialization code, both for static and dynamic loading.
   */
  static int
  bridge_modevent(module_t mod, int type, void *unused)
  {
          int s;
          int err = 0 ;
  
          switch (type) {
          case MOD_LOAD:
                  if (BDG_LOADED) {
                          err = EEXIST;
                          break ;
                  }
                  s = splimp();
                  err = bdginit();
                  splx(s);
                  break;
          case MOD_UNLOAD:
  #if !defined(KLD_MODULE)
                  printf("bridge statically compiled, cannot unload\n");
                  err = EINVAL ;
  #else
                  s = splimp();
                  do_bridge = 0;
                  bridge_in_ptr = NULL;
                  bdg_forward_ptr = NULL;
                  bdgtakeifaces_ptr = NULL;
                  untimeout(bdg_timeout, NULL, bdg_timeout_h);
                  bridge_off();
                  if (clusters)
                      free(clusters, M_IFADDR);
                  free(ifp2sc, M_IFADDR);
                  ifp2sc = NULL ;
                  splx(s);
  #endif
                  break;
          default:
                  err = EINVAL ;
                  break;
          }
          return err;
  }
  
  static moduledata_t bridge_mod = {
          "bridge",
          bridge_modevent,
          0
  };
  
  DECLARE_MODULE(bridge, bridge_mod, SI_SUB_PSEUDO, SI_ORDER_ANY);
  MODULE_VERSION(bridge, 1);

Cache object: 742e07efa8584a71cf9a989ed6875666