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/5.3/sys/net/bridge.c 136588 2004-10-16 08:43:07Z cvs2svn $
     */
    
    /*
     * 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.enable
     * the grouping of interfaces into clusters is done with
     *      net.link.ether.bridge.config
     * 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.config="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/module.h>
   #include <sys/sysctl.h>
   
   #include <net/ethernet.h>
   #include <net/if.h>
   #include <net/if_arp.h>         /* for struct arpcom */
   #include <net/if_types.h>
   #include <net/if_var.h>
   #include <net/pfil.h>
   
   #include <netinet/in.h>
   #include <netinet/in_systm.h>
   #include <netinet/in_var.h>
   #include <netinet/ip.h>
   #include <netinet/ip_var.h>
   
   #include <net/route.h>
   #include <netinet/ip_fw.h>
   #include <netinet/ip_dummynet.h>
   #include <net/bridge.h>
   
   /*--------------------*/
   
   #define ETHER_ADDR_COPY(_dst,_src)      bcopy(_src, _dst, ETHER_ADDR_LEN)
   #define ETHER_ADDR_EQ(_a1,_a2)          (bcmp(_a1, _a2, ETHER_ADDR_LEN) == 0)
   
   /*
    * 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[ETHER_ADDR_LEN];
       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[ETHER_ADDR_LEN];
       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 */
   
   static int n_clusters;                          /* number of clusters */
   static struct cluster_softc *clusters;
   
   static struct mtx bdg_mtx;
   #define BDG_LOCK_INIT()         mtx_init(&bdg_mtx, "bridge", NULL, MTX_DEF)
   #define BDG_LOCK_DESTROY()      mtx_destroy(&bdg_mtx)
   #define BDG_LOCK()              mtx_lock(&bdg_mtx)
   #define BDG_UNLOCK()            mtx_unlock(&bdg_mtx)
   #define BDG_LOCK_ASSERT()       mtx_assert(&bdg_mtx, MA_OWNED)
   
   #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)          ETHER_ADDR_EQ(a,b)
   #define IS_ETHER_BROADCAST(a)   ETHER_ADDR_EQ(a,"\377\377\377\377\377\377")
   #endif
   
   SYSCTL_DECL(_net_link_ether);
   SYSCTL_NODE(_net_link_ether, OID_AUTO, bridge, CTLFLAG_RD, 0,
           "Bridge parameters");
   static char bridge_version[] = "031224";
   SYSCTL_STRING(_net_link_ether_bridge, OID_AUTO, version, CTLFLAG_RD,
           bridge_version, 0, "software version");
   
   #define BRIDGE_DEBUG
   #ifdef BRIDGE_DEBUG
   int     bridge_debug = 0;
   SYSCTL_INT(_net_link_ether_bridge, OID_AUTO, debug, CTLFLAG_RW, &bridge_debug,
               0, "control debugging printfs");
   #define DPRINTF(X)      if (bridge_debug) printf X
   #else
   #define DPRINTF(X)
   #endif
   
   #ifdef BRIDGE_TIMING
   /*
    * 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
   
   static int bdg_fw_avg;
   SYSCTL_INT(_net_link_ether_bridge, OID_AUTO, fw_avg, CTLFLAG_RW,
               &bdg_fw_avg, 0,"Cycle counter avg");
   static int bdg_fw_ticks;
   SYSCTL_INT(_net_link_ether_bridge, OID_AUTO, fw_ticks, CTLFLAG_RW,
               &bdg_fw_ticks, 0,"Cycle counter item");
   static int bdg_fw_count;
   SYSCTL_INT(_net_link_ether_bridge, OID_AUTO, fw_count, CTLFLAG_RW,
               &bdg_fw_count, 0,"Cycle counter count");
   #else
   #define DDB(x)
   #endif
   
   static int bdginit(void);
   static void parse_bdg_cfg(void);
   
   static int bdg_ipf;             /* IPFilter enabled in bridge */
   SYSCTL_INT(_net_link_ether_bridge, OID_AUTO, ipf, CTLFLAG_RW,
               &bdg_ipf, 0,"Pass bridged pkts through IPFilter");
   static int bdg_ipfw;
   SYSCTL_INT(_net_link_ether_bridge, OID_AUTO, ipfw, CTLFLAG_RW,
               &bdg_ipfw,0,"Pass bridged pkts through firewall");
   
   static int bdg_copy;
   SYSCTL_INT(_net_link_ether_bridge, OID_AUTO, copy, CTLFLAG_RW,
           &bdg_copy, 0, "Force packet copy in bdg_forward");
   
   int bdg_ipfw_drops;
   SYSCTL_INT(_net_link_ether_bridge, OID_AUTO, ipfw_drop,
           CTLFLAG_RW, &bdg_ipfw_drops,0,"");
   int bdg_ipfw_colls;
   SYSCTL_INT(_net_link_ether_bridge, OID_AUTO, ipfw_collisions,
           CTLFLAG_RW, &bdg_ipfw_colls,0,"");
   
   static int bdg_thru;
   SYSCTL_INT(_net_link_ether_bridge, OID_AUTO, packets, CTLFLAG_RW,
           &bdg_thru, 0, "Packets through bridge");
   static int bdg_dropped;
   SYSCTL_INT(_net_link_ether_bridge, OID_AUTO, dropped, CTLFLAG_RW,
           &bdg_dropped, 0, "Packets dropped in bdg_forward");
   static int bdg_predict;
   SYSCTL_INT(_net_link_ether_bridge, OID_AUTO, predict, CTLFLAG_RW,
           &bdg_predict, 0, "Correctly predicted header location");
   
   #ifdef BRIDGE_DEBUG
   static char *bdg_dst_names[] = {
           "BDG_NULL    ",
           "BDG_BCAST   ",
           "BDG_MCAST   ",
           "BDG_LOCAL   ",
           "BDG_DROP    ",
           "BDG_UNKNOWN ",
           "BDG_IN      ",
           "BDG_OUT     ",
           "BDG_FORWARD " };
   #endif /* BRIDGE_DEBUG */
   
   /*
    * System initialization
    */
   static struct bdg_stats bdg_stats ;
   SYSCTL_STRUCT(_net_link_ether_bridge, OID_AUTO, stats, CTLFLAG_RD,
           &bdg_stats, bdg_stats, "bridge statistics");
   
   static struct callout bdg_callout;
   
   /*
    * 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 ifnet *ifp)
   {
       struct cluster_softc *c = NULL;
       int i;
   
       BDG_LOCK_ASSERT();
   
       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");
           goto bad;
       }
       c[n_clusters].ht = (struct hash_table *)
               malloc(HASH_SIZE * sizeof(struct hash_table),
                   M_IFADDR, M_NOWAIT | M_ZERO);
       if (c[n_clusters].ht == NULL) {
           printf("-- bridge: cannot allocate hash table for new cluster\n");
           goto bad;
       }
       c[n_clusters].my_macs = (struct bdg_addr *)
               malloc(BDG_MAX_PORTS * sizeof(struct bdg_addr),
                   M_IFADDR, M_NOWAIT | 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);
           goto bad;
       }
   
       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 ... */
       ETHER_ADDR_COPY(c->my_macs[c->ports].etheraddr, IFP2AC(ifp)->ac_enaddr);
       c->ports++;
       return c;
   bad:
       if (c)
           free(c, M_IFADDR);
       return NULL;
   }
   
   
   /*
    * 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;
   
       BDG_LOCK_ASSERT();
   
       DPRINTF(("%s: n_clusters %d\n", __func__, 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 ) {
               ifpromisc(ifp, 0);
               b->flags &= ~(IFF_BDG_PROMISC|IFF_MUTE) ;
               DPRINTF(("%s: %s promisc OFF if_flags 0x%x "
                   "bdg_flags 0x%x\n", __func__, ifp->if_xname,
                   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 */
   
       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;
   }
   
   /*
    * set promisc mode on the interfaces we use.
    */
   static void
   bridge_on(void)
   {
       struct ifnet *ifp ;
   
       BDG_LOCK_ASSERT();
   
       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) ) {
               if_up(ifp);
           }
           if ( !(b->flags & IFF_BDG_PROMISC) ) {
               (void) ifpromisc(ifp, 1);
               b->flags |= IFF_BDG_PROMISC ;
               DPRINTF(("%s: %s promisc ON if_flags 0x%x bdg_flags 0x%x\n",
                   __func__, ifp->if_xname, ifp->if_flags, b->flags));
           }
           if (b->flags & IFF_MUTE) {
               DPRINTF(("%s: unmuting %s\n", __func__, ifp->if_xname));
               b->flags &= ~IFF_MUTE;
           }
       }
       IFNET_RUNLOCK();
   }
   
   static char bridge_cfg[1024];           /* NB: in BSS so initialized to zero */
   
   /**
    * 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_locked(void)
   {
       BDG_LOCK_ASSERT();
   
       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 void
   reconfigure_bridge(void)
   {
       BDG_LOCK();
       reconfigure_bridge_locked();
       BDG_UNLOCK();
   }
   
   /*
    * 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(void)
   {
       char *p, *beg;
       int l, cluster;
       static const char *sep = ", \t";
   
       BDG_LOCK_ASSERT();
   
       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) {
   
               if (!strncmp(beg, ifp->if_xname, max(l, strlen(ifp->if_xname)))) {
                   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", ifp->if_xname);
                       continue;
                   }
                   if (b->flags & IFF_USED) {
                       printf("%s already used, skipping\n", ifp->if_xname);
                       break;
                   }
                   b->cluster = add_cluster(htons(cluster), ifp);
                   b->flags |= IFF_USED ;
                   snprintf(bdg_stats.s[ifp->if_index].name,
                       sizeof(bdg_stats.s[ifp->if_index].name),
                       "%s:%d", ifp->if_xname, cluster);
   
                   DPRINTF(("%s: found %s next c %d\n", __func__,
                       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 enable = do_bridge;
       int error;
   
       error = sysctl_handle_int(oidp, &enable, 0, req);
       enable = (enable) ? 1 : 0;
       BDG_LOCK();
       if (enable != do_bridge) {
           do_bridge = enable;
           reconfigure_bridge_locked();
       }
       BDG_UNLOCK();
       return error ;
   }
   SYSCTL_PROC(_net_link_ether_bridge, OID_AUTO, enable, CTLTYPE_INT|CTLFLAG_RW,
               &do_bridge, 0, &sysctl_bdg, "I", "Bridging");
   
   /*
    * handler for net.link.ether.bridge_cfg
    */
   static int
   sysctl_bdg_cfg(SYSCTL_HANDLER_ARGS)
   {
       int error;
       char *new_cfg;
   
       new_cfg = malloc(sizeof(bridge_cfg), M_TEMP, M_WAITOK);
       bcopy(bridge_cfg, new_cfg, sizeof(bridge_cfg));
   
       error = sysctl_handle_string(oidp, new_cfg, oidp->oid_arg2, req);
       if (error == 0) {
           BDG_LOCK();
           if (strcmp(new_cfg, bridge_cfg)) {
               bcopy(new_cfg, bridge_cfg, sizeof(bridge_cfg));
               reconfigure_bridge_locked();
           }
           BDG_UNLOCK();
       }
   
       free(new_cfg, M_TEMP);
   
       return error;
   }
   SYSCTL_PROC(_net_link_ether_bridge, OID_AUTO, config, CTLTYPE_STRING|CTLFLAG_RW,
               &bridge_cfg, sizeof(bridge_cfg), &sysctl_bdg_cfg, "A",
               "Bridge configuration");
   
   static int
   sysctl_refresh(SYSCTL_HANDLER_ARGS)
   {
       if (req->newptr)
           reconfigure_bridge();
   
       return 0;
   }
   SYSCTL_PROC(_net_link_ether_bridge, OID_AUTO, refresh, CTLTYPE_INT|CTLFLAG_WR,
               NULL, 0, &sysctl_refresh, "I", "iface refresh");
   
   #ifndef BURN_BRIDGES
   #define SYSCTL_OID_COMPAT(parent, nbr, name, kind, a1, a2, handler, fmt, descr)\
           static struct sysctl_oid sysctl__##parent##_##name##_compat = {  \
                   &sysctl_##parent##_children, { 0 },                      \
                   nbr, kind, a1, a2, #name, handler, fmt, 0, descr };      \
           DATA_SET(sysctl_set, sysctl__##parent##_##name##_compat)
   #define SYSCTL_INT_COMPAT(parent, nbr, name, access, ptr, val, descr)    \
           SYSCTL_OID_COMPAT(parent, nbr, name, CTLTYPE_INT|(access),       \
                   ptr, val, sysctl_handle_int, "I", descr)
   #define SYSCTL_STRUCT_COMPAT(parent, nbr, name, access, ptr, type, descr)\
           SYSCTL_OID_COMPAT(parent, nbr, name, CTLTYPE_OPAQUE|(access),    \
                   ptr, sizeof(struct type), sysctl_handle_opaque,          \
                   "S," #type, descr)
   #define SYSCTL_PROC_COMPAT(parent, nbr, name, access, ptr, arg, handler, fmt, descr) \
           SYSCTL_OID_COMPAT(parent, nbr, name, (access),                   \
                   ptr, arg, handler, fmt, descr)
   
   SYSCTL_INT_COMPAT(_net_link_ether, OID_AUTO, bridge_ipf, CTLFLAG_RW,
               &bdg_ipf, 0,"Pass bridged pkts through IPFilter");
   SYSCTL_INT_COMPAT(_net_link_ether, OID_AUTO, bridge_ipfw, CTLFLAG_RW,
               &bdg_ipfw,0,"Pass bridged pkts through firewall");
   SYSCTL_STRUCT_COMPAT(_net_link_ether, PF_BDG, bdgstats, CTLFLAG_RD,
           &bdg_stats, bdg_stats, "bridge statistics");
   SYSCTL_PROC_COMPAT(_net_link_ether, OID_AUTO, bridge_cfg, 
               CTLTYPE_STRING|CTLFLAG_RW,
               &bridge_cfg, sizeof(bridge_cfg), &sysctl_bdg_cfg, "A",
               "Bridge configuration");
   SYSCTL_PROC_COMPAT(_net_link_ether, OID_AUTO, bridge_refresh,
               CTLTYPE_INT|CTLFLAG_WR,
               NULL, 0, &sysctl_refresh, "I", "iface refresh");
   #endif
   
   static int bdg_loops;
   static int bdg_slowtimer = 0;
   static int bdg_age_index = 0;   /* index of table position to age */
   
   /*
    * called periodically to flush entries etc.
    */
   static void
   bdg_timeout(void *dummy)
   {
       if (do_bridge) {
           int l, i;
   
           BDG_LOCK();
           /*
            * age entries in the forwarding table.
            */
           l = bdg_age_index + HASH_SIZE/4 ;
           if (l > HASH_SIZE)
               l = HASH_SIZE;
   
           for (i = 0; i < n_clusters; i++) {
               bdg_hash_table *bdg_table = clusters[i].ht;
               for (; bdg_age_index < l; bdg_age_index++)
                   if (bdg_table[bdg_age_index].used)
                       bdg_table[bdg_age_index].used = 0;
                   else if (bdg_table[bdg_age_index].name) {
                       DPRINTF(("%s: flushing stale entry %d\n",
                           __func__, bdg_age_index));
                       bdg_table[bdg_age_index].name = NULL;
                   }
           }
           if (bdg_age_index >= HASH_SIZE)
               bdg_age_index = 0;
   
           if (--bdg_slowtimer <= 0 ) {
               bdg_slowtimer = 5;
   
               bridge_on();        /* we just need unmute, really */
               bdg_loops = 0;
           }
           BDG_UNLOCK();
       }
       callout_reset(&bdg_callout, 2*hz, bdg_timeout, NULL);
   }
   
   /*
    * 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)
   {
       bdg_hash_table *bt;         /* pointer to entry in hash table */
   
       BDG_LOCK_ASSERT();
   
       if (ETHER_IS_MULTICAST(eh->ether_dhost))
           return IS_ETHER_BROADCAST(eh->ether_dhost) ? BDG_BCAST : BDG_MCAST;
       /*
        * Lookup local addresses in case one matches.  We optimize
        * for the common case of two interfaces.
        */
       KASSERT(c->ports != 0, ("lookup with no ports!"));
       switch (c->ports) {
           int i;
       default:
           for (i = c->ports-1; i > 1; i--) {
               if (ETHER_ADDR_EQ(c->my_macs[i].etheraddr, eh->ether_dhost))
                   return BDG_LOCAL;
           }
           /* fall thru... */
       case 2:
           if (ETHER_ADDR_EQ(c->my_macs[1].etheraddr, eh->ether_dhost))
               return BDG_LOCAL;
       case 1:
           if (ETHER_ADDR_EQ(c->my_macs[0].etheraddr, eh->ether_dhost))
               return BDG_LOCAL;
       }
       /*
        * Look for a possible destination in table
        */
       bt = &c->ht[HASH_FN(eh->ether_dhost)];
       if (bt->name && ETHER_ADDR_EQ(bt->etheraddr, eh->ether_dhost))
           return bt->name;
       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
        */
       BDG_LOCK();
       index = HASH_FN(eh->ether_shost);
       bt = &BDG_CLUSTER(ifp)->ht[index];
       bt->used = 1;
       old = bt->name;
       if (old) {                          /* the entry is valid */
           if (!ETHER_ADDR_EQ(eh->ether_shost, bt->etheraddr)) {
               bdg_ipfw_colls++;
               bt->name = NULL;            /* NB: will overwrite below */
           } 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 from %s (%s)\n",
                           bdg_loops, eh->ether_shost, ".",
                           ifp->if_xname, old->if_xname,
                           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) {
           DPRINTF(("%s: new addr %6D at %d for %s\n",
               __func__, eh->ether_shost, ".", index, ifp->if_xname));
           ETHER_ADDR_COPY(bt->etheraddr, eh->ether_shost);
           bt->name = ifp;
       }
       dst = bridge_dst_lookup(eh, BDG_CLUSTER(ifp));
       BDG_UNLOCK();
   
       /*
        * 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;
       }
       DPRINTF(("%s: %6D ->%6D ty 0x%04x dst %s\n", __func__,
           eh->ether_shost, ".",
           eh->ether_dhost, ".",
           ntohs(eh->ether_type),
           (dst <= BDG_FORWARD) ? bdg_dst_names[(uintptr_t)dst] :
                   dst->if_xname));
   
       return dst;
   }
   
   /*
    * Return 1 if it's ok to send a packet out the specified interface.
    * The interface must be:
    *      used for bridging,
    *      not muted,
    *      not full,
    *      up and running,
    *      not the source interface, and
    *      belong to the same cluster as the 'real_dst'.
    */
   static __inline int
   bridge_ifok(struct ifnet *ifp, struct ifnet *src, struct ifnet *dst)
   {
       return (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, 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 error;
       struct ifnet *real_dst = dst;       /* real dst from ether_output */
       struct ip_fw_args args;
       struct ether_header save_eh;
       struct mbuf *m;
   
       DDB(quad_t ticks; ticks = rdtsc();)
   
       args.rule = ip_dn_claim_rule(m0);
       if (args.rule)
           shared = 0;                     /* For sure this is our own mbuf. */
       else
           bdg_thru++;                     /* count 1st time through bdg_forward */
   
       /*
        * 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 */
           BDG_LOCK();
           dst = bridge_dst_lookup(eh, BDG_CLUSTER(real_dst));
           BDG_UNLOCK();
       }
   
       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 && (
           (inet_pfil_hook.ph_busy_count >= 0 && bdg_ipf != 0) ||
           (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("%s: m_pullup failed\n", __func__);      /* XXXDPRINTF*/
                   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 */
   
           /*
            * NetBSD-style generic packet filter, pfil(9), hooks.
            * Enables ipf(8) in bridging.
            */
           if (!IPFW_LOADED) { /* XXX: Prevent ipfw from being run twice. */
          if (inet_pfil_hook.ph_busy_count >= 0 &&
              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);
  
              if (pfil_run_hooks(&inet_pfil_hook, &m0, src, PFIL_IN, NULL) != 0) {
                  /* NB: hook should consume packet */
                  return NULL;
              }
              if (m0 == NULL)                     /* consumed by filter */
                  return m0;
              /*
               * 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);
          }
          } /* XXX: Prevent ipfw from being run twice. */
  
          /*
           * 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.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.
               */
              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;
      if (dst == BDG_BCAST || dst == BDG_MCAST || dst == BDG_UNKNOWN) {
          /*
           * Scan all ports and send copies to all but the last.
           */
          IFNET_RLOCK();          /* XXX replace with generation # */
          TAILQ_FOREACH(ifp, &ifnet, if_link) {
              if (bridge_ifok(ifp, src, real_dst)) {
                  if (last) {
                      /*
                       * At this point we know two interfaces need a copy
                       * of the packet (last + ifp) so we must create a
                       * copy to handoff to last.
                       */
                      m = m_copypacket(m0, M_DONTWAIT);
                      if (m == NULL) {
                          IFNET_RUNLOCK();
                          printf("%s: , m_copypacket failed!\n", __func__);
                          bdg_dropped++;
                          return m0;      /* the original is still there... */
                      }
                      IFQ_HANDOFF(last, m, error);
                      if (!error)
                          BDG_STAT(last, BDG_OUT);
                      else
                          bdg_dropped++;
                  }
                  last = ifp;
              }
          }
          IFNET_RUNLOCK();
      } else {
          if (bridge_ifok(dst, src, real_dst))
              last = dst;
      }
      if (last) {
          if (shared) {                   /* need to copy */
              m = m_copypacket(m0, M_DONTWAIT);
              if (m == NULL) {
                  printf("%s: sorry, m_copypacket failed!\n", __func__);
                  bdg_dropped++ ;
                  return m0;              /* the original is still there... */
              }
          } else {                        /* consume original */
              m = m0, m0 = NULL;
          }
          IFQ_HANDOFF(last, m, error);
          if (!error)
              BDG_STAT(last, BDG_OUT);
          else
              bdg_dropped++;
      }
  
      DDB(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)
  {
      if (bootverbose)
              printf("BRIDGE %s loaded\n", bridge_version);
  
      ifp2sc = malloc(BDG_MAX_PORTS * sizeof(struct bdg_softc),
                  M_IFADDR, M_WAITOK | M_ZERO );
      if (ifp2sc == NULL)
          return ENOMEM;
  
      BDG_LOCK_INIT();
  
      n_clusters = 0;
      clusters = NULL;
      do_bridge = 0;
  
      bzero(&bdg_stats, sizeof(bdg_stats));
  
      bridge_in_ptr = bridge_in;
      bdg_forward_ptr = bdg_forward;
      bdgtakeifaces_ptr = reconfigure_bridge;
  
      bdgtakeifaces_ptr();                /* XXX does this do anything? */
  
      callout_init(&bdg_callout, debug_mpsafenet ? CALLOUT_MPSAFE : 0);
      bdg_timeout(0);
      return 0 ;
  }
  
  static void
  bdgdestroy(void)
  {
      bridge_in_ptr = NULL;
      bdg_forward_ptr = NULL;
      bdgtakeifaces_ptr = NULL;
  
      callout_stop(&bdg_callout);
      BDG_LOCK();
      bridge_off();
  
      if (ifp2sc) {
          free(ifp2sc, M_IFADDR);
          ifp2sc = NULL;
      }
      BDG_LOCK_DESTROY();
  }
  
  /*
   * initialization code, both for static and dynamic loading.
   */
  static int
  bridge_modevent(module_t mod, int type, void *unused)
  {
          int err;
  
          switch (type) {
          case MOD_LOAD:
                  if (BDG_LOADED)
                          err = EEXIST;
                  else
                          err = bdginit();
                  break;
          case MOD_UNLOAD:
                  do_bridge = 0;
                  bdgdestroy();
                  err = 0;
                  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: 8f7d87b76cfa382f2fcc83e887b37129