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Author: Archie Cobbs <archie@FreeBSD.org>
$FreeBSD$
.Dd May 5, 2010 .Dt NG_BRIDGE 4 .Os .Sh NAME .Nm ng_bridge .Nd Ethernet bridging netgraph node type .Sh SYNOPSIS n sys/types.h n netgraph/ng_bridge.h .Sh DESCRIPTION The .Nm 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. .Sh LOOP DETECTION The .Nm 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.
p A looped back link will be temporarily muted, i.e., all traffic received on that link is ignored. .Sh IPFW PROCESSING Processing of IP packets via the .Xr ipfirewall 4 mechanism on a per-link basis is not yet implemented. .Sh HOOKS This node type supports up to .Dv NG_BRIDGE_MAX_LINKS hooks. Each connected hook represents a bridged link. The hooks are named .Dv link0 , .Dv link1 , etc. Typically these hooks are connected to the .Dv lower hooks of one or more .Xr ng_ether 4 nodes. To connect the host machine to a bridged network, simply connect the .Dv upper hook of an .Xr ng_ether 4 node to the bridge node. .Sh CONTROL MESSAGES This node type supports the generic control messages, plus the following: l -tag -width foo t Dv NGM_BRIDGE_SET_CONFIG Set the node configuration. This command takes a .Dv "struct ng_bridge_config" as an argument: d -literal -offset 0n /* Node configuration structure */ struct ng_bridge_config { u_char ipfw[NG_BRIDGE_MAX_LINKS]; /* enable ipfw */ u_char debugLevel; /* debug level */ u_int32_t loopTimeout; /* link loopback mute time */ u_int32_t maxStaleness; /* max host age before nuking */ u_int32_t minStableAge; /* min time for a stable host */ }; .Ed
p The .Dv ipfw array enables .Xr ipfirewall 4 processing of IP packets received on the corresponding links. The .Dv debugLevel field sets the debug level on the node. At level of 2 or greater, detected loops are logged. The default level is 1.
p The .Dv loopTimeout determines how long (in seconds) a looped link is muted. The default is 60 seconds. The .Dv maxStaleness parameter determines how long a period of inactivity before a host's entry is forgotten. The default is 15 minutes. The .Dv minStableAge determines how quickly a host must jump from one link to another before we declare a loopback condition. The default is one second.
p t Dv NGM_BRIDGE_GET_CONFIG Returns the current configuration as a .Dv "struct ng_bridge_config" . t Dv NGM_BRIDGE_RESET Causes the node to forget all hosts and unmute all links. The node configuration is not changed. t Dv NGM_BRIDGE_GET_STATS This command takes a four byte link number as an argument and returns a .Dv "struct ng_bridge_link_stats" containing statistics for the corresponding link, which must be currently connected: d -literal -offset 0n /* Statistics structure (one for each link) */ struct ng_bridge_link_stats { u_int64_t recvOctets; /* total octets rec'd on link */ u_int64_t recvPackets; /* total pkts rec'd on link */ u_int64_t recvMulticasts; /* multicast pkts rec'd on link */ u_int64_t recvBroadcasts; /* broadcast pkts rec'd on link */ u_int64_t recvUnknown; /* pkts rec'd with unknown dest addr */ u_int64_t recvRunts; /* pkts rec'd less than 14 bytes */ u_int64_t recvInvalid; /* pkts rec'd with bogus source addr */ u_int64_t xmitOctets; /* total octets xmit'd on link */ u_int64_t xmitPackets; /* total pkts xmit'd on link */ u_int64_t xmitMulticasts; /* multicast pkts xmit'd on link */ u_int64_t xmitBroadcasts; /* broadcast pkts xmit'd on link */ u_int64_t loopDrops; /* pkts dropped due to loopback */ u_int64_t loopDetects; /* number of loop detections */ u_int64_t memoryFailures; /* times couldn't get mem or mbuf */ }; .Ed t Dv NGM_BRIDGE_CLR_STATS This command takes a four byte link number as an argument and clears the statistics for that link. t Dv NGM_BRIDGE_GETCLR_STATS Same as .Dv NGM_BRIDGE_GET_STATS , but also atomically clears the statistics as well. t Dv NGM_BRIDGE_GET_TABLE Returns the current host mapping table used to direct packets, in a .Dv "struct ng_bridge_host_ary" . t Dv NGM_BRIDGE_SET_PERSISTENT This command sets the persistent flag on the node, and takes no arguments. .El .Sh SHUTDOWN This node shuts down upon receipt of a .Dv NGM_SHUTDOWN control message, or when all hooks have been disconnected. Setting the persistent flag via a .Dv NGM_BRIDGE_SET_PERSISTENT control message disables automatic node shutdown when the last hook gets disconnected. .Sh FILES l -tag -width XXXXXXXX -compact t Pa /usr/share/examples/netgraph/ether.bridge Example script showing how to set up a bridging network .El .Sh SEE ALSO .Xr if_bridge 4 , .Xr netgraph 4 , .Xr ng_ether 4 , .Xr ng_hub 4 , .Xr ng_one2many 4 , .Xr ngctl 8 .Sh HISTORY The .Nm node type was implemented in .Fx 4.2 . .Sh AUTHORS .An Archie Cobbs Aq archie@FreeBSD.org