The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/net/bridge.c

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    1 /*
    2  * Copyright (c) 1998-2002 Luigi Rizzo
    3  *
    4  * Work partly supported by: Cisco Systems, Inc. - NSITE lab, RTP, NC
    5  *
    6  * Redistribution and use in source and binary forms, with or without
    7  * modification, are permitted provided that the following conditions
    8  * are met:
    9  * 1. Redistributions of source code must retain the above copyright
   10  *    notice, this list of conditions and the following disclaimer.
   11  * 2. Redistributions in binary form must reproduce the above copyright
   12  *    notice, this list of conditions and the following disclaimer in the
   13  *    documentation and/or other materials provided with the distribution.
   14  *
   15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND
   16  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   17  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   18  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   19  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   20  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   21  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   22  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   23  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   24  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   25  * SUCH DAMAGE.
   26  *
   27  * $FreeBSD: releng/5.0/sys/net/bridge.c 106938 2002-11-14 23:57:09Z sam $
   28  */
   29 
   30 /*
   31  * This code implements bridging in FreeBSD. It only acts on ethernet
   32  * interfaces, including VLANs (others are still usable for routing).
   33  * A FreeBSD host can implement multiple logical bridges, called
   34  * "clusters". Each cluster is made of a set of interfaces, and
   35  * identified by a "cluster-id" which is a number in the range 1..2^16-1.
   36  *
   37  * Bridging is enabled by the sysctl variable
   38  *      net.link.ether.bridge
   39  * the grouping of interfaces into clusters is done with
   40  *      net.link.ether.bridge_cfg
   41  * containing a list of interfaces each optionally followed by
   42  * a colon and the cluster it belongs to (1 is the default).
   43  * Separators can be * spaces, commas or tabs, e.g.
   44  *      net.link.ether.bridge_cfg="fxp0:2 fxp1:2 dc0 dc1:1"
   45  * Optionally bridged packets can be passed through the firewall,
   46  * this is controlled by the variable
   47  *      net.link.ether.bridge_ipfw
   48  *
   49  * For each cluster there is a descriptor (cluster_softc) storing
   50  * the following data structures:
   51  * - a hash table with the MAC address and destination interface for each
   52  *   known node. The table is indexed using a hash of the source address.
   53  * - an array with the MAC addresses of the interfaces used in the cluster.
   54  *
   55  * Input packets are tapped near the beginning of ether_input(), and
   56  * analysed by bridge_in(). Depending on the result, the packet
   57  * can be forwarded to one or more output interfaces using bdg_forward(),
   58  * and/or sent to the upper layer (e.g. in case of multicast).
   59  *
   60  * Output packets are intercepted near the end of ether_output().
   61  * The correct destination is selected by bridge_dst_lookup(),
   62  * and then forwarding is done by bdg_forward().
   63  *
   64  * The arp code is also modified to let a machine answer to requests
   65  * irrespective of the port the request came from.
   66  *
   67  * In case of loops in the bridging topology, the bridge detects this
   68  * event and temporarily mutes output bridging on one of the ports.
   69  * Periodically, interfaces are unmuted by bdg_timeout().
   70  * Muting is only implemented as a safety measure, and also as
   71  * a mechanism to support a user-space implementation of the spanning
   72  * tree algorithm.
   73  *
   74  * To build a bridging kernel, use the following option
   75  *    option BRIDGE
   76  * and then at runtime set the sysctl variable to enable bridging.
   77  *
   78  * Only one interface per cluster is supposed to have addresses set (but
   79  * there are no substantial problems if you set addresses for none or
   80  * for more than one interface).
   81  * Bridging will act before routing, but nothing prevents a machine
   82  * from doing both (modulo bugs in the implementation...).
   83  *
   84  * THINGS TO REMEMBER
   85  *  - bridging is incompatible with multicast routing on the same
   86  *    machine. There is not an easy fix to this.
   87  *  - be very careful when bridging VLANs
   88  *  - loop detection is still not very robust.
   89  */
   90 
   91 #include <sys/param.h>
   92 #include <sys/mbuf.h>
   93 #include <sys/malloc.h>
   94 #include <sys/protosw.h>
   95 #include <sys/systm.h>
   96 #include <sys/socket.h> /* for net/if.h */
   97 #include <sys/ctype.h>  /* string functions */
   98 #include <sys/kernel.h>
   99 #include <sys/sysctl.h>
  100 
  101 #include <net/pfil.h>   /* for ipfilter */
  102 #include <net/if.h>
  103 #include <net/if_types.h>
  104 #include <net/if_var.h>
  105 
  106 #include <netinet/in.h> /* for struct arpcom */
  107 #include <netinet/in_systm.h>
  108 #include <netinet/in_var.h>
  109 #include <netinet/ip.h>
  110 #include <netinet/if_ether.h> /* for struct arpcom */
  111 
  112 #include <net/route.h>
  113 #include <netinet/ip_fw.h>
  114 #include <netinet/ip_dummynet.h>
  115 #include <net/bridge.h>
  116 
  117 /*--------------------*/
  118 
  119 /*
  120  * For each cluster, source MAC addresses are stored into a hash
  121  * table which locates the port they reside on.
  122  */
  123 #define HASH_SIZE 8192  /* Table size, must be a power of 2 */
  124 
  125 typedef struct hash_table {             /* each entry.          */
  126     struct ifnet *      name;
  127     u_char              etheraddr[6];
  128     u_int16_t           used;           /* also, padding        */
  129 } bdg_hash_table ;
  130 
  131 /*
  132  * The hash function applied to MAC addresses. Out of the 6 bytes,
  133  * the last ones tend to vary more. Since we are on a little endian machine,
  134  * we have to do some gimmick...
  135  */
  136 #define HASH_FN(addr)   (       \
  137     ntohs( ((u_int16_t *)addr)[1] ^ ((u_int16_t *)addr)[2] ) & (HASH_SIZE -1))
  138 
  139 /*
  140  * This is the data structure where local addresses are stored.
  141  */
  142 struct bdg_addr {
  143     u_char      etheraddr[6] ;
  144     u_int16_t   _padding ;
  145 };
  146 
  147 /*
  148  * The configuration of each cluster includes the cluster id, a pointer to
  149  * the hash table, and an array of local MAC addresses (of size "ports").
  150  */
  151 struct cluster_softc {
  152     u_int16_t   cluster_id;
  153     u_int16_t   ports;
  154     bdg_hash_table *ht;
  155     struct bdg_addr     *my_macs;       /* local MAC addresses */
  156 };
  157 
  158 
  159 extern struct protosw inetsw[];                 /* from netinet/ip_input.c */
  160 extern u_char ip_protox[];                      /* from netinet/ip_input.c */
  161 
  162 static int n_clusters;                          /* number of clusters */
  163 static struct cluster_softc *clusters;
  164 
  165 #define BDG_MUTED(ifp) (ifp2sc[ifp->if_index].flags & IFF_MUTE)
  166 #define BDG_MUTE(ifp) ifp2sc[ifp->if_index].flags |= IFF_MUTE
  167 #define BDG_CLUSTER(ifp) (ifp2sc[ifp->if_index].cluster)
  168 
  169 #define BDG_SAMECLUSTER(ifp,src) \
  170         (src == NULL || BDG_CLUSTER(ifp) == BDG_CLUSTER(src) )
  171 
  172 #ifdef __i386__
  173 #define BDG_MATCH(a,b) ( \
  174     ((u_int16_t *)(a))[2] == ((u_int16_t *)(b))[2] && \
  175     *((u_int32_t *)(a)) == *((u_int32_t *)(b)) )
  176 #define IS_ETHER_BROADCAST(a) ( \
  177         *((u_int32_t *)(a)) == 0xffffffff && \
  178         ((u_int16_t *)(a))[2] == 0xffff )
  179 #else
  180 /* for machines that do not support unaligned access */
  181 #define BDG_MATCH(a,b)          (!bcmp(a, b, ETHER_ADDR_LEN) )
  182 #define IS_ETHER_BROADCAST(a)   (!bcmp(a, "\377\377\377\377\377\377", 6))
  183 #endif
  184 
  185 
  186 /*
  187  * For timing-related debugging, you can use the following macros.
  188  * remember, rdtsc() only works on Pentium-class machines
  189 
  190     quad_t ticks;
  191     DDB(ticks = rdtsc();)
  192     ... interesting code ...
  193     DDB(bdg_fw_ticks += (u_long)(rdtsc() - ticks) ; bdg_fw_count++ ;)
  194 
  195  *
  196  */
  197 
  198 #define DDB(x) x
  199 #define DEB(x)
  200 
  201 static int bdginit(void);
  202 static void parse_bdg_cfg(void);
  203 
  204 static int bdg_ipf;             /* IPFilter enabled in bridge */
  205 static int bdg_ipfw;
  206 
  207 #if 0 /* debugging only */
  208 static char *bdg_dst_names[] = {
  209         "BDG_NULL    ",
  210         "BDG_BCAST   ",
  211         "BDG_MCAST   ",
  212         "BDG_LOCAL   ",
  213         "BDG_DROP    ",
  214         "BDG_UNKNOWN ",
  215         "BDG_IN      ",
  216         "BDG_OUT     ",
  217         "BDG_FORWARD " };
  218 #endif
  219 /*
  220  * System initialization
  221  */
  222 
  223 static struct bdg_stats bdg_stats ;
  224 static struct callout_handle bdg_timeout_h ;
  225 
  226 /*
  227  * Add an interface to a cluster, possibly creating a new entry in
  228  * the cluster table. This requires reallocation of the table and
  229  * updating pointers in ifp2sc.
  230  */
  231 static struct cluster_softc *
  232 add_cluster(u_int16_t cluster_id, struct arpcom *ac)
  233 {
  234     struct cluster_softc *c = NULL;
  235     int i;
  236 
  237     for (i = 0; i < n_clusters ; i++)
  238         if (clusters[i].cluster_id == cluster_id)
  239             goto found;
  240 
  241     /* Not found, need to reallocate */
  242     c = malloc((1+n_clusters) * sizeof (*c), M_IFADDR, M_DONTWAIT | M_ZERO);
  243     if (c == NULL) {/* malloc failure */
  244         printf("-- bridge: cannot add new cluster\n");
  245         return NULL;
  246     }
  247     c[n_clusters].ht = (struct hash_table *)
  248             malloc(HASH_SIZE * sizeof(struct hash_table),
  249                 M_IFADDR, M_WAITOK | M_ZERO);
  250     if (c[n_clusters].ht == NULL) {
  251         printf("-- bridge: cannot allocate hash table for new cluster\n");
  252         free(c, M_IFADDR);
  253         return NULL;
  254     }
  255     c[n_clusters].my_macs = (struct bdg_addr *)
  256             malloc(BDG_MAX_PORTS * sizeof(struct bdg_addr),
  257                 M_IFADDR, M_WAITOK | M_ZERO);
  258     if (c[n_clusters].my_macs == NULL) {
  259         printf("-- bridge: cannot allocate mac addr table for new cluster\n");
  260         free(c[n_clusters].ht, M_IFADDR);
  261         free(c, M_IFADDR);
  262         return NULL;
  263     }
  264 
  265     c[n_clusters].cluster_id = cluster_id;
  266     c[n_clusters].ports = 0;
  267     /*
  268      * now copy old descriptors here
  269      */
  270     if (n_clusters > 0) {
  271         for (i=0; i < n_clusters; i++)
  272             c[i] = clusters[i];
  273         /*
  274          * and finally update pointers in ifp2sc
  275          */
  276         for (i = 0 ; i < if_index && i < BDG_MAX_PORTS; i++)
  277             if (ifp2sc[i].cluster != NULL)
  278                 ifp2sc[i].cluster = c + (ifp2sc[i].cluster - clusters);
  279         free(clusters, M_IFADDR);
  280     }
  281     clusters = c;
  282     i = n_clusters;             /* index of cluster entry */
  283     n_clusters++;
  284 found:
  285     c = clusters + i;           /* the right cluster ... */
  286     bcopy(ac->ac_enaddr, &(c->my_macs[c->ports]), 6);
  287     c->ports++;
  288     return c;
  289 }
  290 
  291 
  292 /*
  293  * Turn off bridging, by clearing promisc mode on the interface,
  294  * marking the interface as unused, and clearing the name in the
  295  * stats entry.
  296  * Also dispose the hash tables associated with the clusters.
  297  */
  298 static void
  299 bridge_off(void)
  300 {
  301     struct ifnet *ifp ;
  302     int i, s;
  303 
  304     DEB(printf("bridge_off: n_clusters %d\n", n_clusters);)
  305     TAILQ_FOREACH(ifp, &ifnet, if_link) {
  306         struct bdg_softc *b;
  307 
  308         if (ifp->if_index >= BDG_MAX_PORTS)
  309             continue;   /* make sure we do not go beyond the end */
  310         b = &(ifp2sc[ifp->if_index]);
  311 
  312         if ( b->flags & IFF_BDG_PROMISC ) {
  313             s = splimp();
  314             ifpromisc(ifp, 0);
  315             splx(s);
  316             b->flags &= ~(IFF_BDG_PROMISC|IFF_MUTE) ;
  317             DEB(printf(">> now %s%d promisc OFF if_flags 0x%x bdg_flags 0x%x\n",
  318                     ifp->if_name, ifp->if_unit,
  319                     ifp->if_flags, b->flags);)
  320         }
  321         b->flags &= ~(IFF_USED) ;
  322         b->cluster = NULL;
  323         bdg_stats.s[ifp->if_index].name[0] = '\0';
  324     }
  325     /* flush_tables */
  326 
  327     s = splimp();
  328     for (i=0; i < n_clusters; i++) {
  329         free(clusters[i].ht, M_IFADDR);
  330         free(clusters[i].my_macs, M_IFADDR);
  331     }
  332     if (clusters != NULL)
  333         free(clusters, M_IFADDR);
  334     clusters = NULL;
  335     n_clusters =0;
  336     splx(s);
  337 }
  338 
  339 /*
  340  * set promisc mode on the interfaces we use.
  341  */
  342 static void
  343 bridge_on(void)
  344 {
  345     struct ifnet *ifp ;
  346     int s ;
  347 
  348     TAILQ_FOREACH(ifp, &ifnet, if_link) {
  349         struct bdg_softc *b = &ifp2sc[ifp->if_index];
  350 
  351         if ( !(b->flags & IFF_USED) )
  352             continue ;
  353         if ( !( ifp->if_flags & IFF_UP) ) {
  354             s = splimp();
  355             if_up(ifp);
  356             splx(s);
  357         }
  358         if ( !(b->flags & IFF_BDG_PROMISC) ) {
  359             int ret ;
  360             s = splimp();
  361             ret = ifpromisc(ifp, 1);
  362             splx(s);
  363             b->flags |= IFF_BDG_PROMISC ;
  364             DEB(printf(">> now %s%d promisc ON if_flags 0x%x bdg_flags 0x%x\n",
  365                     ifp->if_name, ifp->if_unit,
  366                     ifp->if_flags, b->flags);)
  367         }
  368         if (b->flags & IFF_MUTE) {
  369             DEB(printf(">> unmuting %s%d\n", ifp->if_name, ifp->if_unit);)
  370             b->flags &= ~IFF_MUTE;
  371         }
  372     }
  373 }
  374 
  375 /**
  376  * reconfigure bridge.
  377  * This is also done every time we attach or detach an interface.
  378  * Main use is to make sure that we do not bridge on some old
  379  * (ejected) device. So, it would be really useful to have a
  380  * pointer to the modified device as an argument. Without it, we
  381  * have to scan all interfaces.
  382  */
  383 static void
  384 reconfigure_bridge(void)
  385 {
  386     bridge_off();
  387     if (do_bridge) {
  388         if (if_index >= BDG_MAX_PORTS) {
  389             printf("-- sorry too many interfaces (%d, max is %d),"
  390                 " disabling bridging\n", if_index, BDG_MAX_PORTS);
  391             do_bridge=0;
  392             return;
  393         }
  394         parse_bdg_cfg();
  395         bridge_on();
  396     }
  397 }
  398 
  399 static char bridge_cfg[1024]; /* in BSS so initialized to all NULs */
  400 
  401 /*
  402  * parse the config string, set IFF_USED, name and cluster_id
  403  * for all interfaces found.
  404  * The config string is a list of "if[:cluster]" with
  405  * a number of possible separators (see "sep"). In particular the
  406  * use of the space lets you set bridge_cfg with the output from
  407  * "ifconfig -l"
  408  */
  409 static void
  410 parse_bdg_cfg()
  411 {
  412     char *p, *beg ;
  413     int l, cluster;
  414     static char *sep = ", \t";
  415 
  416     for (p = bridge_cfg; *p ; p++) {
  417         struct ifnet *ifp;
  418         int found = 0;
  419         char c;
  420 
  421         if (index(sep, *p))     /* skip separators */
  422             continue ;
  423         /* names are lowercase and digits */
  424         for ( beg = p ; islower(*p) || isdigit(*p) ; p++ )
  425             ;
  426         l = p - beg ;           /* length of name string */
  427         if (l == 0)             /* invalid name */
  428             break ;
  429         if ( *p != ':' )        /* no ':', assume default cluster 1 */
  430             cluster = 1 ;
  431         else                    /* fetch cluster */
  432             cluster = strtoul( p+1, &p, 10);
  433         c = *p;
  434         *p = '\0';
  435         /*
  436          * now search in interface list for a matching name
  437          */
  438         TAILQ_FOREACH(ifp, &ifnet, if_link) {
  439             char buf[IFNAMSIZ];
  440 
  441             snprintf(buf, sizeof(buf), "%s%d", ifp->if_name, ifp->if_unit);
  442             if (!strncmp(beg, buf, max(l, strlen(buf)))) {
  443                 struct bdg_softc *b = &ifp2sc[ifp->if_index];
  444                 if (ifp->if_type != IFT_ETHER && ifp->if_type != IFT_L2VLAN) {
  445                     printf("%s is not an ethernet, continue\n", buf);
  446                     continue;
  447                 }
  448                 if (b->flags & IFF_USED) {
  449                     printf("%s already used, skipping\n", buf);
  450                     break;
  451                 }
  452                 b->cluster = add_cluster(htons(cluster), (struct arpcom *)ifp);
  453                 b->flags |= IFF_USED ;
  454                 sprintf(bdg_stats.s[ifp->if_index].name,
  455                         "%s%d:%d", ifp->if_name, ifp->if_unit, cluster);
  456 
  457                 DEB(printf("--++  found %s next c %d\n",
  458                     bdg_stats.s[ifp->if_index].name, c);)
  459                 found = 1;
  460                 break ;
  461             }
  462         }
  463         if (!found)
  464             printf("interface %s Not found in bridge\n", beg);
  465         *p = c;
  466         if (c == '\0')
  467             break; /* no more */
  468     }
  469 }
  470 
  471 
  472 /*
  473  * handler for net.link.ether.bridge
  474  */
  475 static int
  476 sysctl_bdg(SYSCTL_HANDLER_ARGS)
  477 {
  478     int error, oldval = do_bridge ;
  479 
  480     error = sysctl_handle_int(oidp, oidp->oid_arg1, oidp->oid_arg2, req);
  481     DEB( printf("called sysctl for bridge name %s arg2 %d val %d->%d\n",
  482         oidp->oid_name, oidp->oid_arg2,
  483         oldval, do_bridge); )
  484 
  485     if (oldval != do_bridge)
  486         reconfigure_bridge();
  487     return error ;
  488 }
  489 
  490 /*
  491  * handler for net.link.ether.bridge_cfg
  492  */
  493 static int
  494 sysctl_bdg_cfg(SYSCTL_HANDLER_ARGS)
  495 {
  496     int error = 0 ;
  497     char old_cfg[1024] ;
  498 
  499     strcpy(old_cfg, bridge_cfg) ;
  500 
  501     error = sysctl_handle_string(oidp, bridge_cfg, oidp->oid_arg2, req);
  502     DEB(
  503         printf("called sysctl for bridge name %s arg2 %d err %d val %s->%s\n",
  504                 oidp->oid_name, oidp->oid_arg2,
  505                 error,
  506                 old_cfg, bridge_cfg);
  507         )
  508     if (strcmp(old_cfg, bridge_cfg))
  509         reconfigure_bridge();
  510     return error ;
  511 }
  512 
  513 static int
  514 sysctl_refresh(SYSCTL_HANDLER_ARGS)
  515 {
  516     if (req->newptr)
  517         reconfigure_bridge();
  518 
  519     return 0;
  520 }
  521 
  522 
  523 SYSCTL_DECL(_net_link_ether);
  524 SYSCTL_PROC(_net_link_ether, OID_AUTO, bridge_cfg, CTLTYPE_STRING|CTLFLAG_RW,
  525             &bridge_cfg, sizeof(bridge_cfg), &sysctl_bdg_cfg, "A",
  526             "Bridge configuration");
  527 
  528 SYSCTL_PROC(_net_link_ether, OID_AUTO, bridge, CTLTYPE_INT|CTLFLAG_RW,
  529             &do_bridge, 0, &sysctl_bdg, "I", "Bridging");
  530 
  531 SYSCTL_INT(_net_link_ether, OID_AUTO, bridge_ipfw, CTLFLAG_RW,
  532             &bdg_ipfw,0,"Pass bridged pkts through firewall");
  533 
  534 SYSCTL_INT(_net_link_ether, OID_AUTO, bridge_ipf, CTLFLAG_RW,
  535             &bdg_ipf, 0,"Pass bridged pkts through IPFilter");
  536 
  537 /*
  538  * The follow macro declares a variable, and maps it to
  539  * a SYSCTL_INT entry with the same name.
  540  */
  541 #define SY(parent, var, comment)                        \
  542         static int var ;                                \
  543         SYSCTL_INT(parent, OID_AUTO, var, CTLFLAG_RW, &(var), 0, comment);
  544 
  545 int bdg_ipfw_drops;
  546 SYSCTL_INT(_net_link_ether, OID_AUTO, bridge_ipfw_drop,
  547         CTLFLAG_RW, &bdg_ipfw_drops,0,"");
  548 
  549 int bdg_ipfw_colls;
  550 SYSCTL_INT(_net_link_ether, OID_AUTO, bridge_ipfw_collisions,
  551         CTLFLAG_RW, &bdg_ipfw_colls,0,"");
  552 
  553 SYSCTL_PROC(_net_link_ether, OID_AUTO, bridge_refresh, CTLTYPE_INT|CTLFLAG_WR,
  554             NULL, 0, &sysctl_refresh, "I", "iface refresh");
  555 
  556 #if 1 /* diagnostic vars */
  557 
  558 SY(_net_link_ether, verbose, "Be verbose");
  559 SY(_net_link_ether, bdg_split_pkts, "Packets split in bdg_forward");
  560 
  561 SY(_net_link_ether, bdg_thru, "Packets through bridge");
  562 
  563 SY(_net_link_ether, bdg_copied, "Packets copied in bdg_forward");
  564 SY(_net_link_ether, bdg_dropped, "Packets dropped in bdg_forward");
  565 
  566 SY(_net_link_ether, bdg_copy, "Force copy in bdg_forward");
  567 SY(_net_link_ether, bdg_predict, "Correctly predicted header location");
  568 
  569 SY(_net_link_ether, bdg_fw_avg, "Cycle counter avg");
  570 SY(_net_link_ether, bdg_fw_ticks, "Cycle counter item");
  571 SY(_net_link_ether, bdg_fw_count, "Cycle counter count");
  572 #endif
  573 
  574 SYSCTL_STRUCT(_net_link_ether, PF_BDG, bdgstats,
  575         CTLFLAG_RD, &bdg_stats , bdg_stats, "bridge statistics");
  576 
  577 static int bdg_loops ;
  578 
  579 /*
  580  * called periodically to flush entries etc.
  581  */
  582 static void
  583 bdg_timeout(void *dummy)
  584 {
  585     static int slowtimer; /* in BSS so initialized to 0 */
  586 
  587     if (do_bridge) {
  588         static int age_index = 0 ; /* index of table position to age */
  589         int l = age_index + HASH_SIZE/4 ;
  590         int i;
  591         /*
  592          * age entries in the forwarding table.
  593          */
  594         if (l > HASH_SIZE)
  595             l = HASH_SIZE ;
  596 
  597         for (i=0; i<n_clusters; i++) {
  598             bdg_hash_table *bdg_table = clusters[i].ht;
  599             for (; age_index < l ; age_index++)
  600                 if (bdg_table[age_index].used)
  601                     bdg_table[age_index].used = 0 ;
  602                 else if (bdg_table[age_index].name) {
  603                     /* printf("xx flushing stale entry %d\n", age_index); */
  604                     bdg_table[age_index].name = NULL ;
  605                 }
  606         }
  607         if (age_index >= HASH_SIZE)
  608             age_index = 0 ;
  609 
  610         if (--slowtimer <= 0 ) {
  611             slowtimer = 5 ;
  612 
  613             bridge_on() ; /* we just need unmute, really */
  614             bdg_loops = 0 ;
  615         }
  616     }
  617     bdg_timeout_h = timeout(bdg_timeout, NULL, 2*hz );
  618 }
  619 
  620 /*
  621  * Find the right pkt destination:
  622  *      BDG_BCAST       is a broadcast
  623  *      BDG_MCAST       is a multicast
  624  *      BDG_LOCAL       is for a local address
  625  *      BDG_DROP        must be dropped
  626  *      other           ifp of the dest. interface (incl.self)
  627  *
  628  * We assume this is only called for interfaces for which bridging
  629  * is enabled, i.e. BDG_USED(ifp) is true.
  630  */
  631 static __inline
  632 struct ifnet *
  633 bridge_dst_lookup(struct ether_header *eh, struct cluster_softc *c)
  634 {
  635     struct ifnet *dst ;
  636     int index ;
  637     struct bdg_addr *p ;
  638     bdg_hash_table *bt;         /* pointer to entry in hash table */
  639 
  640     if (IS_ETHER_BROADCAST(eh->ether_dhost))
  641         return BDG_BCAST ;
  642     if (eh->ether_dhost[0] & 1)
  643         return BDG_MCAST ;
  644     /*
  645      * Lookup local addresses in case one matches.
  646      */
  647     for (index = c->ports, p = c->my_macs; index ; index--, p++ )
  648         if (BDG_MATCH(p->etheraddr, eh->ether_dhost) )
  649             return BDG_LOCAL ;
  650     /*
  651      * Look for a possible destination in table
  652      */
  653     index= HASH_FN( eh->ether_dhost );
  654     bt = &(c->ht[index]);
  655     dst = bt->name;
  656     if ( dst && BDG_MATCH( bt->etheraddr, eh->ether_dhost) )
  657         return dst ;
  658     else
  659         return BDG_UNKNOWN ;
  660 }
  661 
  662 /**
  663  * bridge_in() is invoked to perform bridging decision on input packets.
  664  *
  665  * On Input:
  666  *   eh         Ethernet header of the incoming packet.
  667  *   ifp        interface the packet is coming from.
  668  *
  669  * On Return: destination of packet, one of
  670  *   BDG_BCAST  broadcast
  671  *   BDG_MCAST  multicast
  672  *   BDG_LOCAL  is only for a local address (do not forward)
  673  *   BDG_DROP   drop the packet
  674  *   ifp        ifp of the destination interface.
  675  *
  676  * Forwarding is not done directly to give a chance to some drivers
  677  * to fetch more of the packet, or simply drop it completely.
  678  */
  679 
  680 static struct ifnet *
  681 bridge_in(struct ifnet *ifp, struct ether_header *eh)
  682 {
  683     int index;
  684     struct ifnet *dst , *old ;
  685     bdg_hash_table *bt;                 /* location in hash table */
  686     int dropit = BDG_MUTED(ifp) ;
  687 
  688     /*
  689      * hash the source address
  690      */
  691     index= HASH_FN(eh->ether_shost);
  692     bt = &(ifp2sc[ifp->if_index].cluster->ht[index]);
  693     bt->used = 1 ;
  694     old = bt->name ;
  695     if ( old ) { /* the entry is valid. */
  696         if (!BDG_MATCH( eh->ether_shost, bt->etheraddr) ) {
  697             bdg_ipfw_colls++ ;
  698             bt->name = NULL ;
  699         } else if (old != ifp) {
  700             /*
  701              * Found a loop. Either a machine has moved, or there
  702              * is a misconfiguration/reconfiguration of the network.
  703              * First, do not forward this packet!
  704              * Record the relocation anyways; then, if loops persist,
  705              * suspect a reconfiguration and disable forwarding
  706              * from the old interface.
  707              */
  708             bt->name = ifp ; /* relocate address */
  709             printf("-- loop (%d) %6D to %s%d from %s%d (%s)\n",
  710                         bdg_loops, eh->ether_shost, ".",
  711                         ifp->if_name, ifp->if_unit,
  712                         old->if_name, old->if_unit,
  713                         BDG_MUTED(old) ? "muted":"active");
  714             dropit = 1 ;
  715             if ( !BDG_MUTED(old) ) {
  716                 if (++bdg_loops > 10)
  717                     BDG_MUTE(old) ;
  718             }
  719         }
  720     }
  721 
  722     /*
  723      * now write the source address into the table
  724      */
  725     if (bt->name == NULL) {
  726         DEB(printf("new addr %6D at %d for %s%d\n",
  727             eh->ether_shost, ".", index, ifp->if_name, ifp->if_unit);)
  728         bcopy(eh->ether_shost, bt->etheraddr, 6);
  729         bt->name = ifp ;
  730     }
  731     dst = bridge_dst_lookup(eh, ifp2sc[ifp->if_index].cluster);
  732     /*
  733      * bridge_dst_lookup can return the following values:
  734      *   BDG_BCAST, BDG_MCAST, BDG_LOCAL, BDG_UNKNOWN, BDG_DROP, ifp.
  735      * For muted interfaces, or when we detect a loop, the first 3 are
  736      * changed in BDG_LOCAL (we still listen to incoming traffic),
  737      * and others to BDG_DROP (no use for the local host).
  738      * Also, for incoming packets, ifp is changed to BDG_DROP if ifp == src.
  739      * These changes are not necessary for outgoing packets from ether_output().
  740      */
  741     BDG_STAT(ifp, BDG_IN);
  742     switch ((uintptr_t)dst) {
  743     case (uintptr_t)BDG_BCAST:
  744     case (uintptr_t)BDG_MCAST:
  745     case (uintptr_t)BDG_LOCAL:
  746     case (uintptr_t)BDG_UNKNOWN:
  747     case (uintptr_t)BDG_DROP:
  748         BDG_STAT(ifp, dst);
  749         break ;
  750     default :
  751         if (dst == ifp || dropit)
  752             BDG_STAT(ifp, BDG_DROP);
  753         else
  754             BDG_STAT(ifp, BDG_FORWARD);
  755         break ;
  756     }
  757 
  758     if ( dropit ) {
  759         if (dst == BDG_BCAST || dst == BDG_MCAST || dst == BDG_LOCAL)
  760             dst = BDG_LOCAL ;
  761         else
  762             dst = BDG_DROP ;
  763     } else {
  764         if (dst == ifp)
  765             dst = BDG_DROP;
  766     }
  767     DEB(printf("bridge_in %6D ->%6D ty 0x%04x dst %s%d\n",
  768         eh->ether_shost, ".",
  769         eh->ether_dhost, ".",
  770         ntohs(eh->ether_type),
  771         (dst <= BDG_FORWARD) ? bdg_dst_names[(int)dst] :
  772                 dst->if_name,
  773         (dst <= BDG_FORWARD) ? 0 : dst->if_unit); )
  774 
  775     return dst ;
  776 }
  777 
  778 /*
  779  * Forward a packet to dst -- which can be a single interface or
  780  * an entire cluster. The src port and muted interfaces are excluded.
  781  *
  782  * If src == NULL, the pkt comes from ether_output, and dst is the real
  783  * interface the packet is originally sent to. In this case, we must forward
  784  * it to the whole cluster.
  785  * We never call bdg_forward from ether_output on interfaces which are
  786  * not part of a cluster.
  787  *
  788  * If possible (i.e. we can determine that the caller does not need
  789  * a copy), the packet is consumed here, and bdg_forward returns NULL.
  790  * Otherwise, a pointer to a copy of the packet is returned.
  791  */
  792 static struct mbuf *
  793 bdg_forward(struct mbuf *m0, struct ifnet *dst)
  794 {
  795 #define EH_RESTORE(_m) do {                                                \
  796     M_PREPEND((_m), ETHER_HDR_LEN, M_NOWAIT);                              \
  797     if ((_m) == NULL) {                                                    \
  798         bdg_dropped++;                                                     \
  799         return NULL;                                                       \
  800     }                                                                      \
  801     if (eh != mtod((_m), struct ether_header *))                           \
  802         bcopy(&save_eh, mtod((_m), struct ether_header *), ETHER_HDR_LEN); \
  803     else                                                                   \
  804         bdg_predict++;                                                     \
  805 } while (0);
  806     struct ether_header *eh;
  807     struct ifnet *src;
  808     struct ifnet *ifp, *last;
  809     int shared = bdg_copy ; /* someone else is using the mbuf */
  810     int once = 0;      /* loop only once */
  811     struct ifnet *real_dst = dst ; /* real dst from ether_output */
  812     struct ip_fw_args args;
  813 #ifdef PFIL_HOOKS
  814     struct packet_filter_hook *pfh;
  815     int rv;
  816 #endif /* PFIL_HOOKS */
  817     struct ether_header save_eh;
  818 
  819     DEB(quad_t ticks; ticks = rdtsc();)
  820 
  821     args.rule = NULL;           /* did we match a firewall rule ? */
  822     /* Fetch state from dummynet tag, ignore others */
  823     for (;m0->m_type == MT_TAG; m0 = m0->m_next)
  824         if (m0->_m_tag_id == PACKET_TAG_DUMMYNET) {
  825             args.rule = ((struct dn_pkt *)m0)->rule;
  826             shared = 0;         /* For sure this is our own mbuf. */
  827         }
  828     if (args.rule == NULL)
  829         bdg_thru++; /* first time through bdg_forward, count packet */
  830 
  831     /*
  832      * The packet arrives with the Ethernet header at the front.
  833      */
  834     eh = mtod(m0, struct ether_header *);
  835 
  836     src = m0->m_pkthdr.rcvif;
  837     if (src == NULL)                    /* packet from ether_output */
  838         dst = bridge_dst_lookup(eh, ifp2sc[real_dst->if_index].cluster);
  839 
  840     if (dst == BDG_DROP) { /* this should not happen */
  841         printf("xx bdg_forward for BDG_DROP\n");
  842         m_freem(m0);
  843         bdg_dropped++;
  844         return NULL;
  845     }
  846     if (dst == BDG_LOCAL) { /* this should not happen as well */
  847         printf("xx ouch, bdg_forward for local pkt\n");
  848         return m0;
  849     }
  850     if (dst == BDG_BCAST || dst == BDG_MCAST || dst == BDG_UNKNOWN) {
  851         ifp = TAILQ_FIRST(&ifnet) ; /* scan all ports */
  852         once = 0 ;
  853         if (dst != BDG_UNKNOWN) /* need a copy for the local stack */
  854             shared = 1 ;
  855     } else {
  856         ifp = dst ;
  857         once = 1 ;
  858     }
  859     if ((uintptr_t)(ifp) <= (u_int)BDG_FORWARD)
  860         panic("bdg_forward: bad dst");
  861 
  862     /*
  863      * Do filtering in a very similar way to what is done in ip_output.
  864      * Only if firewall is loaded, enabled, and the packet is not
  865      * from ether_output() (src==NULL, or we would filter it twice).
  866      * Additional restrictions may apply e.g. non-IP, short packets,
  867      * and pkts already gone through a pipe.
  868      */
  869     if (src != NULL && (
  870 #ifdef PFIL_HOOKS
  871         ((pfh = pfil_hook_get(PFIL_IN, &inetsw[ip_protox[IPPROTO_IP]].pr_pfh)) != NULL && bdg_ipf !=0) ||
  872 #endif
  873         (IPFW_LOADED && bdg_ipfw != 0))) {
  874 
  875         int i;
  876 
  877         if (args.rule != NULL && fw_one_pass)
  878             goto forward; /* packet already partially processed */
  879         /*
  880          * i need some amt of data to be contiguous, and in case others need
  881          * the packet (shared==1) also better be in the first mbuf.
  882          */
  883         i = min(m0->m_pkthdr.len, max_protohdr) ;
  884         if ( shared || m0->m_len < i) {
  885             m0 = m_pullup(m0, i) ;
  886             if (m0 == NULL) {
  887                 printf("-- bdg: pullup failed.\n") ;
  888                 bdg_dropped++;
  889                 return NULL ;
  890             }
  891             eh = mtod(m0, struct ether_header *);
  892         }
  893 
  894         /*
  895          * Processing below expects the Ethernet header is stripped.
  896          * Furthermore, the mbuf chain might be replaced at various
  897          * places.  To deal with this we copy the header to a temporary
  898          * location, strip the header, and restore it as needed.
  899          */
  900         bcopy(eh, &save_eh, ETHER_HDR_LEN);     /* local copy for restore */
  901         m_adj(m0, ETHER_HDR_LEN);               /* temporarily strip header */
  902 
  903 #ifdef PFIL_HOOKS
  904         /*
  905          * NetBSD-style generic packet filter, pfil(9), hooks.
  906          * Enables ipf(8) in bridging.
  907          */
  908         if (m0->m_pkthdr.len >= sizeof(struct ip) &&
  909                 ntohs(save_eh.ether_type) == ETHERTYPE_IP) {
  910             /*
  911              * before calling the firewall, swap fields the same as IP does.
  912              * here we assume the pkt is an IP one and the header is contiguous
  913              */
  914             struct ip *ip = mtod(m0, struct ip *);
  915 
  916             ip->ip_len = ntohs(ip->ip_len);
  917             ip->ip_off = ntohs(ip->ip_off);
  918 
  919             for (; pfh; pfh = TAILQ_NEXT(pfh, pfil_link))
  920                 if (pfh->pfil_func) {
  921                     rv = pfh->pfil_func(ip, ip->ip_hl << 2, src, 0, &m0);
  922                     if (m0 == NULL) {
  923                         bdg_dropped++;
  924                         return NULL;
  925                     }
  926                     if (rv != 0) {
  927                         EH_RESTORE(m0);         /* restore Ethernet header */
  928                         return m0;
  929                     }
  930                     ip = mtod(m0, struct ip *);
  931                 }
  932             /*
  933              * If we get here, the firewall has passed the pkt, but the mbuf
  934              * pointer might have changed. Restore ip and the fields ntohs()'d.
  935              */
  936             ip = mtod(m0, struct ip *);
  937             ip->ip_len = htons(ip->ip_len);
  938             ip->ip_off = htons(ip->ip_off);
  939         }
  940 #endif /* PFIL_HOOKS */
  941 
  942         /*
  943          * Prepare arguments and call the firewall.
  944          */
  945         if (!IPFW_LOADED || bdg_ipfw == 0) {
  946             EH_RESTORE(m0);     /* restore Ethernet header */
  947             goto forward;       /* not using ipfw, accept the packet */
  948         }
  949 
  950         /*
  951          * XXX The following code is very similar to the one in
  952          * if_ethersubr.c:ether_ipfw_chk()
  953          */
  954 
  955         args.m = m0;            /* the packet we are looking at         */
  956         args.oif = NULL;        /* this is an input packet              */
  957         args.divert_rule = 0;   /* we do not support divert yet         */
  958         args.next_hop = NULL;   /* we do not support forward yet        */
  959         args.eh = &save_eh;     /* MAC header for bridged/MAC packets   */
  960         i = ip_fw_chk_ptr(&args);
  961         m0 = args.m;            /* in case the firewall used the mbuf   */
  962 
  963         EH_RESTORE(m0);         /* restore Ethernet header */
  964 
  965         if ( (i & IP_FW_PORT_DENY_FLAG) || m0 == NULL) /* drop */
  966             return m0 ;
  967 
  968         if (i == 0) /* a PASS rule.  */
  969             goto forward ;
  970         if (DUMMYNET_LOADED && (i & IP_FW_PORT_DYNT_FLAG)) {
  971             /*
  972              * Pass the pkt to dummynet, which consumes it.
  973              * If shared, make a copy and keep the original.
  974              */
  975             struct mbuf *m ;
  976 
  977             if (shared) {
  978                 m = m_copypacket(m0, M_DONTWAIT);
  979                 if (m == NULL) {        /* copy failed, give up */
  980                     bdg_dropped++;
  981                     return NULL;
  982                 }
  983             } else {
  984                 m = m0 ; /* pass the original to dummynet */
  985                 m0 = NULL ; /* and nothing back to the caller */
  986             }
  987 
  988             args.oif = real_dst;
  989             ip_dn_io_ptr(m, (i & 0xffff),DN_TO_BDG_FWD, &args);
  990             return m0 ;
  991         }
  992         /*
  993          * XXX at some point, add support for divert/forward actions.
  994          * If none of the above matches, we have to drop the packet.
  995          */
  996         bdg_ipfw_drops++ ;
  997         return m0 ;
  998     }
  999 forward:
 1000     /*
 1001      * Again, bring up the headers in case of shared bufs to avoid
 1002      * corruptions in the future.
 1003      */
 1004     if ( shared ) {
 1005         int i = min(m0->m_pkthdr.len, max_protohdr) ;
 1006 
 1007         m0 = m_pullup(m0, i) ;
 1008         if (m0 == NULL) {
 1009             bdg_dropped++ ;
 1010             return NULL ;
 1011         }
 1012         /* NB: eh is not used below; no need to recalculate it */
 1013     }
 1014 
 1015     /*
 1016      * now real_dst is used to determine the cluster where to forward.
 1017      * For packets coming from ether_input, this is the one of the 'src'
 1018      * interface, whereas for locally generated packets (src==NULL) it
 1019      * is the cluster of the original destination interface, which
 1020      * was already saved into real_dst.
 1021      */
 1022     if (src != NULL)
 1023         real_dst = src ;
 1024 
 1025     last = NULL;
 1026     for (;;) {
 1027         if (last) { /* need to forward packet leftover from previous loop */
 1028             struct mbuf *m ;
 1029             if (shared == 0 && once ) { /* no need to copy */
 1030                 m = m0 ;
 1031                 m0 = NULL ; /* original is gone */
 1032             } else {
 1033                 m = m_copypacket(m0, M_DONTWAIT);
 1034                 if (m == NULL) {
 1035                     printf("bdg_forward: sorry, m_copypacket failed!\n");
 1036                     bdg_dropped++ ;
 1037                     return m0 ; /* the original is still there... */
 1038                 }
 1039             }
 1040             if (!IF_HANDOFF(&last->if_snd, m, last)) {
 1041 #if 0
 1042                 BDG_MUTE(last); /* should I also mute ? */
 1043 #endif
 1044             }
 1045             BDG_STAT(last, BDG_OUT);
 1046             last = NULL ;
 1047             if (once)
 1048                 break ;
 1049         }
 1050         if (ifp == NULL)
 1051             break ;
 1052         /*
 1053          * If the interface is used for bridging, not muted, not full,
 1054          * up and running, is not the source interface, and belongs to
 1055          * the same cluster as the 'real_dst', then send here.
 1056          */
 1057         if ( BDG_USED(ifp) && !BDG_MUTED(ifp) && !_IF_QFULL(&ifp->if_snd)  &&
 1058              (ifp->if_flags & (IFF_UP|IFF_RUNNING)) == (IFF_UP|IFF_RUNNING) &&
 1059              ifp != src && BDG_SAMECLUSTER(ifp, real_dst) )
 1060             last = ifp ;
 1061         ifp = TAILQ_NEXT(ifp, if_link) ;
 1062         if (ifp == NULL)
 1063             once = 1 ;
 1064     }
 1065     DEB(bdg_fw_ticks += (u_long)(rdtsc() - ticks) ; bdg_fw_count++ ;
 1066         if (bdg_fw_count != 0) bdg_fw_avg = bdg_fw_ticks/bdg_fw_count; )
 1067     return m0 ;
 1068 #undef EH_RESTORE
 1069 }
 1070 
 1071 /*
 1072  * initialization of bridge code.
 1073  */
 1074 static int
 1075 bdginit(void)
 1076 {
 1077     printf("BRIDGE 020214 loaded\n");
 1078 
 1079     ifp2sc = malloc(BDG_MAX_PORTS * sizeof(struct bdg_softc),
 1080                 M_IFADDR, M_WAITOK | M_ZERO );
 1081     if (ifp2sc == NULL)
 1082         return ENOMEM ;
 1083 
 1084     bridge_in_ptr = bridge_in;
 1085     bdg_forward_ptr = bdg_forward;
 1086     bdgtakeifaces_ptr = reconfigure_bridge;
 1087 
 1088     n_clusters = 0;
 1089     clusters = NULL;
 1090     do_bridge=0;
 1091 
 1092     bzero(&bdg_stats, sizeof(bdg_stats) );
 1093     bdgtakeifaces_ptr();
 1094     bdg_timeout(0);
 1095     return 0 ;
 1096 }
 1097 
 1098 /*
 1099  * initialization code, both for static and dynamic loading.
 1100  */
 1101 static int
 1102 bridge_modevent(module_t mod, int type, void *unused)
 1103 {
 1104         int s;
 1105         int err = 0 ;
 1106 
 1107         switch (type) {
 1108         case MOD_LOAD:
 1109                 if (BDG_LOADED) {
 1110                         err = EEXIST;
 1111                         break ;
 1112                 }
 1113                 s = splimp();
 1114                 err = bdginit();
 1115                 splx(s);
 1116                 break;
 1117         case MOD_UNLOAD:
 1118 #if !defined(KLD_MODULE)
 1119                 printf("bridge statically compiled, cannot unload\n");
 1120                 err = EINVAL ;
 1121 #else
 1122                 s = splimp();
 1123                 do_bridge = 0;
 1124                 bridge_in_ptr = NULL;
 1125                 bdg_forward_ptr = NULL;
 1126                 bdgtakeifaces_ptr = NULL;
 1127                 untimeout(bdg_timeout, NULL, bdg_timeout_h);
 1128                 bridge_off();
 1129                 if (clusters)
 1130                     free(clusters, M_IFADDR);
 1131                 free(ifp2sc, M_IFADDR);
 1132                 ifp2sc = NULL ;
 1133                 splx(s);
 1134 #endif
 1135                 break;
 1136         default:
 1137                 err = EINVAL ;
 1138                 break;
 1139         }
 1140         return err;
 1141 }
 1142 
 1143 static moduledata_t bridge_mod = {
 1144         "bridge",
 1145         bridge_modevent,
 1146         0
 1147 };
 1148 
 1149 DECLARE_MODULE(bridge, bridge_mod, SI_SUB_PSEUDO, SI_ORDER_ANY);
 1150 MODULE_VERSION(bridge, 1);

Cache object: cbdbfceb91bef33d7a9acaa42c8ffb08


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