ng_bridge — Ethernet bridging netgraph node type

       Archie Cobbs <archie@FreeBSD.org>

Debian                                           October 2, 2019                                    NG_BRIDGE(4)

       This node type supports the generic control messages, plus the following:

       NGM_BRIDGE_SET_CONFIG (setconfig)
            Set the node configuration.  This command takes a struct ng_bridge_config as an argument:

            /* Node configuration structure */
            struct ng_bridge_config {
              u_char      debugLevel;           /* debug level */
              uint32_t    loopTimeout;          /* link loopback mute time */
              uint32_t    maxStaleness;         /* max host age before nuking */
              uint32_t    minStableAge;         /* min time for a stable host */
            };

            The debugLevel field sets the debug level on the node.  At level of 2 or greater, detected loops are
            logged.  The default level is 1.

            The loopTimeout determines how long (in seconds) a looped link is muted.  The default is 60 seconds.
            The maxStaleness parameter determines how long a period of  inactivity  before  a  host's  entry  is
            forgotten.   The  default  is  15 minutes.  The minStableAge determines how quickly a host must jump
            from one link to another before we declare a loopback condition.  The default is one second.

       NGM_BRIDGE_GET_CONFIG (getconfig)
            Returns the current configuration as a struct ng_bridge_config.

       NGM_BRIDGE_RESET (reset)
            Causes the node to forget all hosts and unmute all links.  The node configuration is not changed.

       NGM_BRIDGE_GET_STATS (getstats)
            This command takes a four byte link number as an argument and returns a struct  ng_bridge_link_stats
            containing statistics for the corresponding link, which must be currently connected:

            /* Statistics structure (one for each link) */
            struct ng_bridge_link_stats {
              uint64_t   recvOctets;     /* total octets rec'd on link */
              uint64_t   recvPackets;    /* total pkts rec'd on link */
              uint64_t   recvMulticasts; /* multicast pkts rec'd on link */
              uint64_t   recvBroadcasts; /* broadcast pkts rec'd on link */
              uint64_t   recvUnknown;    /* pkts rec'd with unknown dest addr */
              uint64_t   recvRunts;      /* pkts rec'd less than 14 bytes */
              uint64_t   recvInvalid;    /* pkts rec'd with bogus source addr */
              uint64_t   xmitOctets;     /* total octets xmit'd on link */
              uint64_t   xmitPackets;    /* total pkts xmit'd on link */
              uint64_t   xmitMulticasts; /* multicast pkts xmit'd on link */
              uint64_t   xmitBroadcasts; /* broadcast pkts xmit'd on link */
              uint64_t   loopDrops;      /* pkts dropped due to loopback */
              uint64_t   loopDetects;    /* number of loop detections */
              uint64_t   memoryFailures; /* times couldn't get mem or mbuf */
            };

       NGM_BRIDGE_CLR_STATS (clrstats)
            This command takes a four byte link number as an argument and clears the statistics for that link.

       NGM_BRIDGE_GETCLR_STATS (getclrstats)
            Same as NGM_BRIDGE_GET_STATS, but also atomically clears the statistics as well.

       NGM_BRIDGE_GET_TABLE (gettable)
            Returns the current host mapping table used to direct packets, in a struct ng_bridge_host_ary.

       NGM_BRIDGE_SET_PERSISTENT (setpersistent)
            This command sets the persistent flag on the node, and takes no arguments.

       The  bridge  node  type  performs  Ethernet bridging over one or more links.  Each link (represented by a
       connected hook) is used to transmit and receive raw Ethernet frames.  As packets are received,  the  node
       learns which link each host resides on.  Packets unicast to a known host are directed out the appropriate
       link  only,  and other links are spared the traffic.  This behavior is in contrast to a hub, which always
       forwards every received packet to every other link.

/usr/share/examples/netgraph/ether.bridge
                 Example script showing how to set up a bridging network

       The ng_bridge node type was implemented in FreeBSD 4.2.

       This  node  type  supports  an unlimited number of hooks.  Each connected hook represents a bridged link.
       The hooks are named link0, link1, etc.  Typically these hooks are connected to the lower hooks of one  or
       more  ng_ether(4) nodes.  To connect the host machine to a bridged network, simply connect the upper hook
       of an ng_ether(4) node to the bridge node.

       Processing of IP packets via the ipfirewall(4) mechanism on a per-link basis is not yet implemented.

       The bridge node incorporates a simple loop detection algorithm.  A loop is when two ports  are  connected
       to  the  same  physical  medium.   Loops  are important to avoid because of packet storms, which severely
       degrade performance.  A packet storm results when the same packet is sent  and  received  over  and  over
       again.   If  a  host  is  detected on link A, and is then detected on link B within a certain time period
       after first being detected on link A, then link B is considered to be  a  looped  back  link.   The  time
       period is called the minimum stable time.

       A looped back link will be temporarily muted, i.e., all traffic received on that link is ignored.

       ng_bridge — Ethernet bridging netgraph node type

if_bridge(4), netgraph(4), ng_ether(4), ng_hub(4), ng_one2many(4), ngctl(8)

       This  node  shuts  down  upon  receipt  of  a  NGM_SHUTDOWN  control message, or when all hooks have been
       disconnected.  Setting the persistent flag  via  a  NGM_BRIDGE_SET_PERSISTENT  control  message  disables
       automatic node shutdown when the last hook gets disconnected.

#include<sys/types.h>#include<netgraph/ng_bridge.h>