/*
 * ng_bridge.c
 */

/*-
 * Copyright (c) 2000 Whistle Communications, Inc.
 * All rights reserved.
 * 
 * Subject to the following obligations and disclaimer of warranty, use and
 * redistribution of this software, in source or object code forms, with or
 * without modifications are expressly permitted by Whistle Communications;
 * provided, however, that:
 * 1. Any and all reproductions of the source or object code must include the
 *    copyright notice above and the following disclaimer of warranties; and
 * 2. No rights are granted, in any manner or form, to use Whistle
 *    Communications, Inc. trademarks, including the mark "WHISTLE
 *    COMMUNICATIONS" on advertising, endorsements, or otherwise except as
 *    such appears in the above copyright notice or in the software.
 * 
 * THIS SOFTWARE IS BEING PROVIDED BY WHISTLE COMMUNICATIONS "AS IS", AND
 * TO THE MAXIMUM EXTENT PERMITTED BY LAW, WHISTLE COMMUNICATIONS MAKES NO
 * REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING THIS SOFTWARE,
 * INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT.
 * WHISTLE COMMUNICATIONS DOES NOT WARRANT, GUARANTEE, OR MAKE ANY
 * REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS OF THE USE OF THIS
 * SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY, RELIABILITY OR OTHERWISE.
 * IN NO EVENT SHALL WHISTLE COMMUNICATIONS BE LIABLE FOR ANY DAMAGES
 * RESULTING FROM OR ARISING OUT OF ANY USE OF THIS SOFTWARE, INCLUDING
 * WITHOUT LIMITATION, ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
 * PUNITIVE, OR CONSEQUENTIAL DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES, LOSS OF USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER 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 WHISTLE COMMUNICATIONS IS ADVISED OF THE POSSIBILITY
 * OF SUCH DAMAGE.
 *
 * Author: Archie Cobbs <archie@freebsd.org>
 *
 * $FreeBSD: src/sys/netgraph/ng_bridge.c,v 1.31 2005/02/09 15:14:44 ru Exp $
 */

/*
 * ng_bridge(4) netgraph node type
 *
 * The node performs standard intelligent Ethernet bridging over
 * each of its connected hooks, or links.  A simple loop detection
 * algorithm is included which disables a link for priv->conf.loopTimeout
 * seconds when a host is seen to have jumped from one link to
 * another within priv->conf.minStableAge seconds.
 *
 * We keep a hashtable that maps Ethernet addresses to host info,
 * which is contained in struct ng_bridge_host's. These structures
 * tell us on which link the host may be found. A host's entry will
 * expire after priv->conf.maxStaleness seconds.
 *
 * This node is optimzed for stable networks, where machines jump
 * from one port to the other only rarely.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/errno.h>
#include <sys/syslog.h>
#include <sys/socket.h>
#include <sys/ctype.h>

#include <net/if.h>
#include <net/if_var.h>
#include <net/ethernet.h>

#include <netinet/in.h>
#include <net/ipfw/ip_fw.h>

#include <netgraph7/ng_message.h>
#include <netgraph7/netgraph.h>
#include <netgraph7/ng_parse.h>
#include "ng_bridge.h"

#ifdef NG_SEPARATE_MALLOC
MALLOC_DEFINE(M_NETGRAPH_BRIDGE, "netgraph_bridge", "netgraph bridge node ");
#else
#define M_NETGRAPH_BRIDGE M_NETGRAPH
#endif

/* Per-link private data */
struct ng_bridge_link {
        hook_p                          hook;           /* netgraph hook */
        u_int16_t                       loopCount;      /* loop ignore timer */
        struct ng_bridge_link_stats     stats;          /* link stats */
};

/* Per-node private data */
struct ng_bridge_private {
        struct ng_bridge_bucket *tab;           /* hash table bucket array */
        struct ng_bridge_link   *links[NG_BRIDGE_MAX_LINKS];
        struct ng_bridge_config conf;           /* node configuration */
        node_p                  node;           /* netgraph node */
        u_int                   numHosts;       /* num entries in table */
        u_int                   numBuckets;     /* num buckets in table */
        u_int                   hashMask;       /* numBuckets - 1 */
        int                     numLinks;       /* num connected links */
        struct callout          timer;          /* one second periodic timer */
};
typedef struct ng_bridge_private *priv_p;

/* Information about a host, stored in a hash table entry */
struct ng_bridge_hent {
        struct ng_bridge_host           host;   /* actual host info */
        SLIST_ENTRY(ng_bridge_hent)     next;   /* next entry in bucket */
};

/* Hash table bucket declaration */
SLIST_HEAD(ng_bridge_bucket, ng_bridge_hent);

/* Netgraph node methods */
static ng_constructor_t ng_bridge_constructor;
static ng_rcvmsg_t      ng_bridge_rcvmsg;
static ng_shutdown_t    ng_bridge_shutdown;
static ng_newhook_t     ng_bridge_newhook;
static ng_rcvdata_t     ng_bridge_rcvdata;
static ng_disconnect_t  ng_bridge_disconnect;

/* Other internal functions */
static struct   ng_bridge_host *ng_bridge_get(priv_p priv, const u_char *addr);
static int      ng_bridge_put(priv_p priv, const u_char *addr, int linkNum);
static void     ng_bridge_rehash(priv_p priv);
static void     ng_bridge_remove_hosts(priv_p priv, int linkNum);
static void     ng_bridge_timeout(node_p node, hook_p hook, void *arg1, int arg2);
static const    char *ng_bridge_nodename(node_p node);

/* Ethernet broadcast */
static const u_char ng_bridge_bcast_addr[ETHER_ADDR_LEN] =
    { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };

/* Store each hook's link number in the private field */
#define LINK_NUM(hook)          (*(u_int16_t *)(&(hook)->private))

/* Compare Ethernet addresses using 32 and 16 bit words instead of bytewise */
#define ETHER_EQUAL(a,b)        (((const u_int32_t *)(a))[0] \
                                        == ((const u_int32_t *)(b))[0] \
                                    && ((const u_int16_t *)(a))[2] \
                                        == ((const u_int16_t *)(b))[2])

/* Minimum and maximum number of hash buckets. Must be a power of two. */
#define MIN_BUCKETS             (1 << 5)        /* 32 */
#define MAX_BUCKETS             (1 << 14)       /* 16384 */

/* Configuration default values */
#define DEFAULT_LOOP_TIMEOUT    60
#define DEFAULT_MAX_STALENESS   (15 * 60)       /* same as ARP timeout */
#define DEFAULT_MIN_STABLE_AGE  1

/******************************************************************
                    NETGRAPH PARSE TYPES
******************************************************************/

/*
 * How to determine the length of the table returned by NGM_BRIDGE_GET_TABLE
 */
static int
ng_bridge_getTableLength(const struct ng_parse_type *type,
        const u_char *start, const u_char *buf)
{
        const struct ng_bridge_host_ary *const hary
            = (const struct ng_bridge_host_ary *)(buf - sizeof(u_int32_t));

        return hary->numHosts;
}

/* Parse type for struct ng_bridge_host_ary */
static const struct ng_parse_struct_field ng_bridge_host_type_fields[]
        = NG_BRIDGE_HOST_TYPE_INFO(&ng_parse_enaddr_type);
static const struct ng_parse_type ng_bridge_host_type = {
        &ng_parse_struct_type,
        &ng_bridge_host_type_fields
};
static const struct ng_parse_array_info ng_bridge_hary_type_info = {
        &ng_bridge_host_type,
        ng_bridge_getTableLength
};
static const struct ng_parse_type ng_bridge_hary_type = {
        &ng_parse_array_type,
        &ng_bridge_hary_type_info
};
static const struct ng_parse_struct_field ng_bridge_host_ary_type_fields[]
        = NG_BRIDGE_HOST_ARY_TYPE_INFO(&ng_bridge_hary_type);
static const struct ng_parse_type ng_bridge_host_ary_type = {
        &ng_parse_struct_type,
        &ng_bridge_host_ary_type_fields
};

/* Parse type for struct ng_bridge_config */
static const struct ng_parse_fixedarray_info ng_bridge_ipfwary_type_info = {
        &ng_parse_uint8_type,
        NG_BRIDGE_MAX_LINKS
};
static const struct ng_parse_type ng_bridge_ipfwary_type = {
        &ng_parse_fixedarray_type,
        &ng_bridge_ipfwary_type_info
};
static const struct ng_parse_struct_field ng_bridge_config_type_fields[]
        = NG_BRIDGE_CONFIG_TYPE_INFO(&ng_bridge_ipfwary_type);
static const struct ng_parse_type ng_bridge_config_type = {
        &ng_parse_struct_type,
        &ng_bridge_config_type_fields
};

/* Parse type for struct ng_bridge_link_stat */
static const struct ng_parse_struct_field ng_bridge_stats_type_fields[]
        = NG_BRIDGE_STATS_TYPE_INFO;
static const struct ng_parse_type ng_bridge_stats_type = {
        &ng_parse_struct_type,
        &ng_bridge_stats_type_fields
};

/* List of commands and how to convert arguments to/from ASCII */
static const struct ng_cmdlist ng_bridge_cmdlist[] = {
        {
          NGM_BRIDGE_COOKIE,
          NGM_BRIDGE_SET_CONFIG,
          "setconfig",
          &ng_bridge_config_type,
          NULL
        },
        {
          NGM_BRIDGE_COOKIE,
          NGM_BRIDGE_GET_CONFIG,
          "getconfig",
          NULL,
          &ng_bridge_config_type
        },
        {
          NGM_BRIDGE_COOKIE,
          NGM_BRIDGE_RESET,
          "reset",
          NULL,
          NULL
        },
        {
          NGM_BRIDGE_COOKIE,
          NGM_BRIDGE_GET_STATS,
          "getstats",
          &ng_parse_uint32_type,
          &ng_bridge_stats_type
        },
        {
          NGM_BRIDGE_COOKIE,
          NGM_BRIDGE_CLR_STATS,
          "clrstats",
          &ng_parse_uint32_type,
          NULL
        },
        {
          NGM_BRIDGE_COOKIE,
          NGM_BRIDGE_GETCLR_STATS,
          "getclrstats",
          &ng_parse_uint32_type,
          &ng_bridge_stats_type
        },
        {
          NGM_BRIDGE_COOKIE,
          NGM_BRIDGE_GET_TABLE,
          "gettable",
          NULL,
          &ng_bridge_host_ary_type
        },
        { 0 }
};

/* Node type descriptor */
static struct ng_type ng_bridge_typestruct = {
        .version =      NG_ABI_VERSION,
        .name =         NG_BRIDGE_NODE_TYPE,
        .constructor =  ng_bridge_constructor,
        .rcvmsg =       ng_bridge_rcvmsg,
        .shutdown =     ng_bridge_shutdown,
        .newhook =      ng_bridge_newhook,
        .rcvdata =      ng_bridge_rcvdata,
        .disconnect =   ng_bridge_disconnect,
        .cmdlist =      ng_bridge_cmdlist,
};
NETGRAPH_INIT(bridge, &ng_bridge_typestruct);

/******************************************************************
                    NETGRAPH NODE METHODS
******************************************************************/

/*
 * Node constructor
 */
static int
ng_bridge_constructor(node_p node)
{
        priv_p priv;

        /* Allocate and initialize private info */
        priv = kmalloc(sizeof(*priv), M_NETGRAPH_BRIDGE,
                       M_WAITOK | M_NULLOK | M_ZERO);
        if (priv == NULL)
                return (ENOMEM);
        ng_callout_init(&priv->timer);

        /* Allocate and initialize hash table, etc. */
        priv->tab = kmalloc(MIN_BUCKETS * sizeof(*priv->tab),
                            M_NETGRAPH_BRIDGE, M_WAITOK | M_NULLOK | M_ZERO);
        if (priv->tab == NULL) {
                kfree(priv, M_NETGRAPH_BRIDGE);
                return (ENOMEM);
        }
        priv->numBuckets = MIN_BUCKETS;
        priv->hashMask = MIN_BUCKETS - 1;
        priv->conf.debugLevel = 1;
        priv->conf.loopTimeout = DEFAULT_LOOP_TIMEOUT;
        priv->conf.maxStaleness = DEFAULT_MAX_STALENESS;
        priv->conf.minStableAge = DEFAULT_MIN_STABLE_AGE;

        /*
         * This node has all kinds of stuff that could be screwed by SMP.
         * Until it gets it's own internal protection, we go through in 
         * single file. This could hurt a machine bridging beteen two 
         * GB ethernets so it should be fixed. 
         * When it's fixed the process SHOULD NOT SLEEP, spinlocks please!
         * (and atomic ops )
         */
        NG_NODE_FORCE_WRITER(node);
        NG_NODE_SET_PRIVATE(node, priv);
        priv->node = node;

        /* Start timer; timer is always running while node is alive */
        ng_callout(&priv->timer, node, NULL, hz, ng_bridge_timeout, NULL, 0);

        /* Done */
        return (0);
}

/*
 * Method for attaching a new hook
 */
static  int
ng_bridge_newhook(node_p node, hook_p hook, const char *name)
{
        const priv_p priv = NG_NODE_PRIVATE(node);

        /* Check for a link hook */
        if (strncmp(name, NG_BRIDGE_HOOK_LINK_PREFIX,
            strlen(NG_BRIDGE_HOOK_LINK_PREFIX)) == 0) {
                const char *cp;
                char *eptr;
                u_long linkNum;

                cp = name + strlen(NG_BRIDGE_HOOK_LINK_PREFIX);
                if (!isdigit(*cp) || (cp[0] == '0' && cp[1] != '\0'))
                        return (EINVAL);
                linkNum = strtoul(cp, &eptr, 10);
                if (*eptr != '\0' || linkNum >= NG_BRIDGE_MAX_LINKS)
                        return (EINVAL);
                if (priv->links[linkNum] != NULL)
                        return (EISCONN);
                priv->links[linkNum] = kmalloc(sizeof(*priv->links[linkNum]),
                                               M_NETGRAPH_BRIDGE,
                                               M_WAITOK | M_NULLOK | M_ZERO);
                if (priv->links[linkNum] == NULL)
                        return (ENOMEM);
                priv->links[linkNum]->hook = hook;
                NG_HOOK_SET_PRIVATE(hook, (void *)linkNum);
                priv->numLinks++;
                return (0);
        }

        /* Unknown hook name */
        return (EINVAL);
}

/*
 * Receive a control message
 */
static int
ng_bridge_rcvmsg(node_p node, item_p item, hook_p lasthook)
{
        const priv_p priv = NG_NODE_PRIVATE(node);
        struct ng_mesg *resp = NULL;
        int error = 0;
        struct ng_mesg *msg;

        NGI_GET_MSG(item, msg);
        switch (msg->header.typecookie) {
        case NGM_BRIDGE_COOKIE:
                switch (msg->header.cmd) {
                case NGM_BRIDGE_GET_CONFIG:
                    {
                        struct ng_bridge_config *conf;

                        NG_MKRESPONSE(resp, msg,
                            sizeof(struct ng_bridge_config), M_WAITOK | M_NULLOK);
                        if (resp == NULL) {
                                error = ENOMEM;
                                break;
                        }
                        conf = (struct ng_bridge_config *)resp->data;
                        *conf = priv->conf;     /* no sanity checking needed */
                        break;
                    }
                case NGM_BRIDGE_SET_CONFIG:
                    {
                        struct ng_bridge_config *conf;
                        int i;

                        if (msg->header.arglen
                            != sizeof(struct ng_bridge_config)) {
                                error = EINVAL;
                                break;
                        }
                        conf = (struct ng_bridge_config *)msg->data;
                        priv->conf = *conf;
                        for (i = 0; i < NG_BRIDGE_MAX_LINKS; i++)
                                priv->conf.ipfw[i] = !!priv->conf.ipfw[i];
                        break;
                    }
                case NGM_BRIDGE_RESET:
                    {
                        int i;

                        /* Flush all entries in the hash table */
                        ng_bridge_remove_hosts(priv, -1);

                        /* Reset all loop detection counters and stats */
                        for (i = 0; i < NG_BRIDGE_MAX_LINKS; i++) {
                                if (priv->links[i] == NULL)
                                        continue;
                                priv->links[i]->loopCount = 0;
                                bzero(&priv->links[i]->stats,
                                    sizeof(priv->links[i]->stats));
                        }
                        break;
                    }
                case NGM_BRIDGE_GET_STATS:
                case NGM_BRIDGE_CLR_STATS:
                case NGM_BRIDGE_GETCLR_STATS:
                    {
                        struct ng_bridge_link *link;
                        int linkNum;

                        /* Get link number */
                        if (msg->header.arglen != sizeof(u_int32_t)) {
                                error = EINVAL;
                                break;
                        }
                        linkNum = *((u_int32_t *)msg->data);
                        if (linkNum < 0 || linkNum >= NG_BRIDGE_MAX_LINKS) {
                                error = EINVAL;
                                break;
                        }
                        if ((link = priv->links[linkNum]) == NULL) {
                                error = ENOTCONN;
                                break;
                        }

                        /* Get/clear stats */
                        if (msg->header.cmd != NGM_BRIDGE_CLR_STATS) {
                                NG_MKRESPONSE(resp, msg,
                                    sizeof(link->stats), M_WAITOK | M_NULLOK);
                                if (resp == NULL) {
                                        error = ENOMEM;
                                        break;
                                }
                                bcopy(&link->stats,
                                    resp->data, sizeof(link->stats));
                        }
                        if (msg->header.cmd != NGM_BRIDGE_GET_STATS)
                                bzero(&link->stats, sizeof(link->stats));
                        break;
                    }
                case NGM_BRIDGE_GET_TABLE:
                    {
                        struct ng_bridge_host_ary *ary;
                        struct ng_bridge_hent *hent;
                        int i = 0, bucket;

                        NG_MKRESPONSE(resp, msg, sizeof(*ary)
                            + (priv->numHosts * sizeof(*ary->hosts)), M_WAITOK | M_NULLOK);
                        if (resp == NULL) {
                                error = ENOMEM;
                                break;
                        }
                        ary = (struct ng_bridge_host_ary *)resp->data;
                        ary->numHosts = priv->numHosts;
                        for (bucket = 0; bucket < priv->numBuckets; bucket++) {
                                SLIST_FOREACH(hent, &priv->tab[bucket], next)
                                        ary->hosts[i++] = hent->host;
                        }
                        break;
                    }
                default:
                        error = EINVAL;
                        break;
                }
                break;
        default:
                error = EINVAL;
                break;
        }

        /* Done */
        NG_RESPOND_MSG(error, node, item, resp);
        NG_FREE_MSG(msg);
        return (error);
}

/*
 * Receive data on a hook
 */
static int
ng_bridge_rcvdata(hook_p hook, item_p item)
{
        const node_p node = NG_HOOK_NODE(hook);
        const priv_p priv = NG_NODE_PRIVATE(node);
        struct ng_bridge_host *host;
        struct ng_bridge_link *link;
        struct ether_header *eh;
        int error = 0, linkNum, linksSeen;
        int manycast;
        struct mbuf *m;
        struct ng_bridge_link *firstLink;

        NGI_GET_M(item, m);
        /* Get link number */
        linkNum = (intptr_t)NG_HOOK_PRIVATE(hook);
        KASSERT(linkNum >= 0 && linkNum < NG_BRIDGE_MAX_LINKS,
            ("%s: linkNum=%u", __func__, linkNum));
        link = priv->links[linkNum];
        KASSERT(link != NULL, ("%s: link%d null", __func__, linkNum));

        /* Sanity check packet and pull up header */
        if (m->m_pkthdr.len < ETHER_HDR_LEN) {
                link->stats.recvRunts++;
                NG_FREE_ITEM(item);
                NG_FREE_M(m);
                return (EINVAL);
        }
        if (m->m_len < ETHER_HDR_LEN && !(m = m_pullup(m, ETHER_HDR_LEN))) {
                link->stats.memoryFailures++;
                NG_FREE_ITEM(item);
                return (ENOBUFS);
        }
        eh = mtod(m, struct ether_header *);
        if ((eh->ether_shost[0] & 1) != 0) {
                link->stats.recvInvalid++;
                NG_FREE_ITEM(item);
                NG_FREE_M(m);
                return (EINVAL);
        }

        /* Is link disabled due to a loopback condition? */
        if (link->loopCount != 0) {
                link->stats.loopDrops++;
                NG_FREE_ITEM(item);
                NG_FREE_M(m);
                return (ELOOP);         /* XXX is this an appropriate error? */
        }

        /* Update stats */
        link->stats.recvPackets++;
        link->stats.recvOctets += m->m_pkthdr.len;
        if ((manycast = (eh->ether_dhost[0] & 1)) != 0) {
                if (ETHER_EQUAL(eh->ether_dhost, ng_bridge_bcast_addr)) {
                        link->stats.recvBroadcasts++;
                        manycast = 2;
                } else
                        link->stats.recvMulticasts++;
        }

        /* Look up packet's source Ethernet address in hashtable */
        if ((host = ng_bridge_get(priv, eh->ether_shost)) != NULL) {

                /* Update time since last heard from this host */
                host->staleness = 0;

                /* Did host jump to a different link? */
                if (host->linkNum != linkNum) {

                        /*
                         * If the host's old link was recently established
                         * on the old link and it's already jumped to a new
                         * link, declare a loopback condition.
                         */
                        if (host->age < priv->conf.minStableAge) {

                                /* Log the problem */
                                if (priv->conf.debugLevel >= 2) {
                                        struct ifnet *ifp = m->m_pkthdr.rcvif;
                                        char suffix[32];

                                        if (ifp != NULL)
                                                ksnprintf(suffix, sizeof(suffix),
                                                    " (%s)", ifp->if_xname);
                                        else
                                                *suffix = '\0';
                                        log(LOG_WARNING, "ng_bridge: %s:"
                                            " loopback detected on %s%s\n",
                                            ng_bridge_nodename(node),
                                            NG_HOOK_NAME(hook), suffix);
                                }

                                /* Mark link as linka non grata */
                                link->loopCount = priv->conf.loopTimeout;
                                link->stats.loopDetects++;

                                /* Forget all hosts on this link */
                                ng_bridge_remove_hosts(priv, linkNum);

                                /* Drop packet */
                                link->stats.loopDrops++;
                                NG_FREE_ITEM(item);
                                NG_FREE_M(m);
                                return (ELOOP);         /* XXX appropriate? */
                        }

                        /* Move host over to new link */
                        host->linkNum = linkNum;
                        host->age = 0;
                }
        } else {
                if (!ng_bridge_put(priv, eh->ether_shost, linkNum)) {
                        link->stats.memoryFailures++;
                        NG_FREE_ITEM(item);
                        NG_FREE_M(m);
                        return (ENOMEM);
                }
        }

        /* Run packet through ipfw processing, if enabled */
#if 0
        if (priv->conf.ipfw[linkNum] && fw_enable && ip_fw_chk_ptr != NULL) {
                /* XXX not implemented yet */
        }
#endif

        /*
         * If unicast and destination host known, deliver to host's link,
         * unless it is the same link as the packet came in on.
         */
        if (!manycast) {

                /* Determine packet destination link */
                if ((host = ng_bridge_get(priv, eh->ether_dhost)) != NULL) {
                        struct ng_bridge_link *const destLink
                            = priv->links[host->linkNum];

                        /* If destination same as incoming link, do nothing */
                        KASSERT(destLink != NULL,
                            ("%s: link%d null", __func__, host->linkNum));
                        if (destLink == link) {
                                NG_FREE_ITEM(item);
                                NG_FREE_M(m);
                                return (0);
                        }

                        /* Deliver packet out the destination link */
                        destLink->stats.xmitPackets++;
                        destLink->stats.xmitOctets += m->m_pkthdr.len;
                        NG_FWD_NEW_DATA(error, item, destLink->hook, m);
                        return (error);
                }

                /* Destination host is not known */
                link->stats.recvUnknown++;
        }

        /* Distribute unknown, multicast, broadcast pkts to all other links */
        firstLink = NULL;
        for (linkNum = linksSeen = 0; linksSeen <= priv->numLinks; linkNum++) {
                struct ng_bridge_link *destLink;
                struct mbuf *m2 = NULL;

                /*
                 * If we have checked all the links then now
                 * send the original on its reserved link
                 */
                if (linksSeen == priv->numLinks) {
                        /* If we never saw a good link, leave. */
                        if (firstLink == NULL) {
                                NG_FREE_ITEM(item);
                                NG_FREE_M(m);
                                return (0);
                        }       
                        destLink = firstLink;
                } else {
                        destLink = priv->links[linkNum];
                        if (destLink != NULL)
                                linksSeen++;
                        /* Skip incoming link and disconnected links */
                        if (destLink == NULL || destLink == link) {
                                continue;
                        }
                        if (firstLink == NULL) {
                                /*
                                 * This is the first usable link we have found.
                                 * Reserve it for the originals.
                                 * If we never find another we save a copy.
                                 */
                                firstLink = destLink;
                                continue;
                        }

                        /*
                         * It's usable link but not the reserved (first) one.
                         * Copy mbuf info for sending.
                         */
                        m2 = m_dup(m, M_NOWAIT);        /* XXX m_copypacket() */
                        if (m2 == NULL) {
                                link->stats.memoryFailures++;
                                NG_FREE_ITEM(item);
                                NG_FREE_M(m);
                                return (ENOBUFS);
                        }
                }

                /* Update stats */
                destLink->stats.xmitPackets++;
                destLink->stats.xmitOctets += m->m_pkthdr.len;
                switch (manycast) {
                case 0:                                 /* unicast */
                        break;
                case 1:                                 /* multicast */
                        destLink->stats.xmitMulticasts++;
                        break;
                case 2:                                 /* broadcast */
                        destLink->stats.xmitBroadcasts++;
                        break;
                }

                /* Send packet */
                if (destLink == firstLink) { 
                        /*
                         * If we've sent all the others, send the original
                         * on the first link we found.
                         */
                        NG_FWD_NEW_DATA(error, item, destLink->hook, m);
                        break; /* always done last - not really needed. */
                } else {
                        NG_SEND_DATA_ONLY(error, destLink->hook, m2);
                }
        }
        return (error);
}

/*
 * Shutdown node
 */
static int
ng_bridge_shutdown(node_p node)
{
        const priv_p priv = NG_NODE_PRIVATE(node);

        /*
         * Shut down everything including the timer.  Even if the
         * callout has already been dequeued and is about to be
         * run, ng_bridge_timeout() won't be fired as the node
         * is already marked NGF_INVALID, so we're safe to free
         * the node now.
         */
        KASSERT(priv->numLinks == 0 && priv->numHosts == 0,
            ("%s: numLinks=%d numHosts=%d",
            __func__, priv->numLinks, priv->numHosts));
        ng_uncallout(&priv->timer, node);
        NG_NODE_SET_PRIVATE(node, NULL);
        NG_NODE_UNREF(node);
        kfree(priv->tab, M_NETGRAPH_BRIDGE);
        kfree(priv, M_NETGRAPH_BRIDGE);
        return (0);
}

/*
 * Hook disconnection.
 */
static int
ng_bridge_disconnect(hook_p hook)
{
        const priv_p priv = NG_NODE_PRIVATE(NG_HOOK_NODE(hook));
        int linkNum;

        /* Get link number */
        linkNum = (intptr_t)NG_HOOK_PRIVATE(hook);
        KASSERT(linkNum >= 0 && linkNum < NG_BRIDGE_MAX_LINKS,
            ("%s: linkNum=%u", __func__, linkNum));

        /* Remove all hosts associated with this link */
        ng_bridge_remove_hosts(priv, linkNum);

        /* Free associated link information */
        KASSERT(priv->links[linkNum] != NULL, ("%s: no link", __func__));
        kfree(priv->links[linkNum], M_NETGRAPH_BRIDGE);
        priv->links[linkNum] = NULL;
        priv->numLinks--;

        /* If no more hooks, go away */
        if ((NG_NODE_NUMHOOKS(NG_HOOK_NODE(hook)) == 0)
        && (NG_NODE_IS_VALID(NG_HOOK_NODE(hook)))) {
                ng_rmnode_self(NG_HOOK_NODE(hook));
        }
        return (0);
}

/******************************************************************
                    HASH TABLE FUNCTIONS
******************************************************************/

/*
 * Hash algorithm
 */
#define HASH(addr,mask)         ( (((const u_int16_t *)(addr))[0]       \
                                 ^ ((const u_int16_t *)(addr))[1]       \
                                 ^ ((const u_int16_t *)(addr))[2]) & (mask) )

/*
 * Find a host entry in the table.
 */
static struct ng_bridge_host *
ng_bridge_get(priv_p priv, const u_char *addr)
{
        const int bucket = HASH(addr, priv->hashMask);
        struct ng_bridge_hent *hent;

        SLIST_FOREACH(hent, &priv->tab[bucket], next) {
                if (ETHER_EQUAL(hent->host.addr, addr))
                        return (&hent->host);
        }
        return (NULL);
}

/*
 * Add a new host entry to the table. This assumes the host doesn't
 * already exist in the table. Returns 1 on success, 0 if there
 * was a memory allocation failure.
 */
static int
ng_bridge_put(priv_p priv, const u_char *addr, int linkNum)
{
        const int bucket = HASH(addr, priv->hashMask);
        struct ng_bridge_hent *hent;
        char ethstr[ETHER_ADDRSTRLEN + 1] __debugvar;

#ifdef INVARIANTS
        /* Assert that entry does not already exist in hashtable */
        SLIST_FOREACH(hent, &priv->tab[bucket], next) {
                KASSERT(!ETHER_EQUAL(hent->host.addr, addr),
                    ("%s: entry %s exists in table", __func__, kether_ntoa(addr, ethstr)));
        }
#endif

        /* Allocate and initialize new hashtable entry */
        hent = kmalloc(sizeof(*hent), M_NETGRAPH_BRIDGE, M_WAITOK | M_NULLOK);
        if (hent == NULL)
                return (0);
        bcopy(addr, hent->host.addr, ETHER_ADDR_LEN);
        hent->host.linkNum = linkNum;
        hent->host.staleness = 0;
        hent->host.age = 0;

        /* Add new element to hash bucket */
        SLIST_INSERT_HEAD(&priv->tab[bucket], hent, next);
        priv->numHosts++;

        /* Resize table if necessary */
        ng_bridge_rehash(priv);
        return (1);
}

/*
 * Resize the hash table. We try to maintain the number of buckets
 * such that the load factor is in the range 0.25 to 1.0.
 *
 * If we can't get the new memory then we silently fail. This is OK
 * because things will still work and we'll try again soon anyway.
 */
static void
ng_bridge_rehash(priv_p priv)
{
        struct ng_bridge_bucket *newTab;
        int oldBucket, newBucket;
        int newNumBuckets;
        u_int newMask;

        /* Is table too full or too empty? */
        if (priv->numHosts > priv->numBuckets
            && (priv->numBuckets << 1) <= MAX_BUCKETS)
                newNumBuckets = priv->numBuckets << 1;
        else if (priv->numHosts < (priv->numBuckets >> 2)
            && (priv->numBuckets >> 2) >= MIN_BUCKETS)
                newNumBuckets = priv->numBuckets >> 2;
        else
                return;
        newMask = newNumBuckets - 1;

        /* Allocate and initialize new table */
        newTab = kmalloc(newNumBuckets * sizeof(*newTab), M_NETGRAPH_BRIDGE,
                         M_NOWAIT | M_ZERO);
        if (newTab == NULL)
                return;

        /* Move all entries from old table to new table */
        for (oldBucket = 0; oldBucket < priv->numBuckets; oldBucket++) {
                struct ng_bridge_bucket *const oldList = &priv->tab[oldBucket];

                while (!SLIST_EMPTY(oldList)) {
                        struct ng_bridge_hent *const hent
                            = SLIST_FIRST(oldList);

                        SLIST_REMOVE_HEAD(oldList, next);
                        newBucket = HASH(hent->host.addr, newMask);
                        SLIST_INSERT_HEAD(&newTab[newBucket], hent, next);
                }
        }

        /* Replace old table with new one */
        if (priv->conf.debugLevel >= 3) {
                log(LOG_INFO, "ng_bridge: %s: table size %d -> %d\n",
                    ng_bridge_nodename(priv->node),
                    priv->numBuckets, newNumBuckets);
        }
        kfree(priv->tab, M_NETGRAPH_BRIDGE);
        priv->numBuckets = newNumBuckets;
        priv->hashMask = newMask;
        priv->tab = newTab;
        return;
}

/******************************************************************
                    MISC FUNCTIONS
******************************************************************/

/*
 * Remove all hosts associated with a specific link from the hashtable.
 * If linkNum == -1, then remove all hosts in the table.
 */
static void
ng_bridge_remove_hosts(priv_p priv, int linkNum)
{
        int bucket;

        for (bucket = 0; bucket < priv->numBuckets; bucket++) {
                struct ng_bridge_hent **hptr = &SLIST_FIRST(&priv->tab[bucket]);

                while (*hptr != NULL) {
                        struct ng_bridge_hent *const hent = *hptr;

                        if (linkNum == -1 || hent->host.linkNum == linkNum) {
                                *hptr = SLIST_NEXT(hent, next);
                                kfree(hent, M_NETGRAPH_BRIDGE);
                                priv->numHosts--;
                        } else
                                hptr = &SLIST_NEXT(hent, next);
                }
        }
}

/*
 * Handle our once-per-second timeout event. We do two things:
 * we decrement link->loopCount for those links being muted due to
 * a detected loopback condition, and we remove any hosts from
 * the hashtable whom we haven't heard from in a long while.
 */
static void
ng_bridge_timeout(node_p node, hook_p hook, void *arg1, int arg2)
{
        const priv_p priv = NG_NODE_PRIVATE(node);
        int bucket;
        int counter = 0;
        int linkNum;
        char ethstr[ETHER_ADDRSTRLEN + 1] __debugvar;

        /* Update host time counters and remove stale entries */
        for (bucket = 0; bucket < priv->numBuckets; bucket++) {
                struct ng_bridge_hent **hptr = &SLIST_FIRST(&priv->tab[bucket]);

                while (*hptr != NULL) {
                        struct ng_bridge_hent *const hent = *hptr;

                        /* Make sure host's link really exists */
                        KASSERT(priv->links[hent->host.linkNum] != NULL,
                            ("%s: host %s on nonexistent link %d",
                            __func__, kether_ntoa(hent->host.addr, ethstr),
                            hent->host.linkNum));

                        /* Remove hosts we haven't heard from in a while */
                        if (++hent->host.staleness >= priv->conf.maxStaleness) {
                                *hptr = SLIST_NEXT(hent, next);
                                kfree(hent, M_NETGRAPH_BRIDGE);
                                priv->numHosts--;
                        } else {
                                if (hent->host.age < 0xffff)
                                        hent->host.age++;
                                hptr = &SLIST_NEXT(hent, next);
                                counter++;
                        }
                }
        }
        KASSERT(priv->numHosts == counter,
            ("%s: hosts: %d != %d", __func__, priv->numHosts, counter));

        /* Decrease table size if necessary */
        ng_bridge_rehash(priv);

        /* Decrease loop counter on muted looped back links */
        for (counter = linkNum = 0; linkNum < NG_BRIDGE_MAX_LINKS; linkNum++) {
                struct ng_bridge_link *const link = priv->links[linkNum];

                if (link != NULL) {
                        if (link->loopCount != 0) {
                                link->loopCount--;
                                if (link->loopCount == 0
                                    && priv->conf.debugLevel >= 2) {
                                        log(LOG_INFO, "ng_bridge: %s:"
                                            " restoring looped back link%d\n",
                                            ng_bridge_nodename(node), linkNum);
                                }
                        }
                        counter++;
                }
        }
        KASSERT(priv->numLinks == counter,
            ("%s: links: %d != %d", __func__, priv->numLinks, counter));

        /* Register a new timeout, keeping the existing node reference */
        ng_callout(&priv->timer, node, NULL, hz, ng_bridge_timeout, NULL, 0);
}

/*
 * Return node's "name", even if it doesn't have one.
 */
static const char *
ng_bridge_nodename(node_p node)
{
        static char name[NG_NODESIZ];

        if (NG_NODE_NAME(node) != NULL)
                ksnprintf(name, sizeof(name), "%s", NG_NODE_NAME(node));
        else
                ksnprintf(name, sizeof(name), "[%x]", ng_node2ID(node));
        return name;
}