Linux and UNIX Man Pages

Linux & Unix Commands - Search Man Pages

ng_bridge(4) [freebsd man page]

NG_BRIDGE(4)						   BSD Kernel Interfaces Manual 					      NG_BRIDGE(4)

ng_bridge -- Ethernet bridging netgraph node type SYNOPSIS
#include <sys/types.h> #include <netgraph/ng_bridge.h> DESCRIPTION
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. LOOP DETECTION
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. IPFW PROCESSING
Processing of IP packets via the ipfirewall(4) mechanism on a per-link basis is not yet implemented. HOOKS
This node type supports up to NG_BRIDGE_MAX_LINKS 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 net- work, simply connect the upper hook of an ng_ether(4) node to the bridge node. CONTROL MESSAGES
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 ipfw[NG_BRIDGE_MAX_LINKS]; /* enable ipfw */ 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 ipfw array enables ipfirewall(4) processing of IP packets received on the corresponding links. 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 deter- mines 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 corre- sponding 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. SHUTDOWN
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. FILES
/usr/share/examples/netgraph/ether.bridge Example script showing how to set up a bridging network SEE ALSO
if_bridge(4), netgraph(4), ng_ether(4), ng_hub(4), ng_one2many(4), ngctl(8) HISTORY
The ng_bridge node type was implemented in FreeBSD 4.2. AUTHORS
Archie Cobbs <> BSD
May 5, 2010 BSD
Man Page