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1.\" Copyright (c) 2000 Whistle Communications, Inc.
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33.\" Author: Archie Cobbs <archie@FreeBSD.org>
34.\"
35.\" $FreeBSD: src/share/man/man4/ng_bridge.4,v 1.1.2.6 2001/12/17 11:30:12 ru Exp $
44cb301e 36.\" $DragonFly: src/share/man/man4/ng_bridge.4,v 1.4 2006/05/26 19:39:39 swildner Exp $
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37.\"
38.Dd August 31, 2000
39.Dt NG_BRIDGE 4
40.Os
41.Sh NAME
42.Nm ng_bridge
43.Nd Ethernet bridging netgraph node type
44.Sh SYNOPSIS
45.In sys/types.h
44cb301e 46.In netgraph/bridge/ng_bridge.h
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47.Sh DESCRIPTION
48The
49.Nm bridge
50node type performs Ethernet bridging over one or more links.
51Each link (represented by a connected hook) is used to transmit
52and receive raw Ethernet frames.
53As packets are received, the node learns which link each
54host resides on.
55Packets unicast to a known host are directed out the appropriate
56link only, and other links are spared the traffic.
57This behavior is in contrast to a hub, which always forwards
58every received packet to every other link.
59.Sh LOOP DETECTION
60The
61.Nm bridge
62node incorporates a simple loop detection algorithm.
63A loop is when two ports are connected to the same physical medium.
64Loops are important to avoid because of packet storms, which severely
65degrade performance.
66A packet storm results when the same packet is sent and received
67over and over again.
68If a host is detected on link A, and is then detected on link B
69within a certain time period after first being detected on link A,
70then link B is considered to be a looped back link.
71The time period is called the minimum stable time.
72.Pp
73A looped back link will be temporarily muted, i.e., all traffic
74received on that link is ignored.
75.Sh IPFW PROCESSING
76Processing of IP packets via the
77.Xr ipfirewall 4
78mechanism on a per-link basis is not yet implemented.
79.Sh HOOKS
80This node type supports up to
81.Dv NG_BRIDGE_MAX_LINKS
82hooks.
83Each connected hook represents a bridged link.
84The hooks are named
85.Dv link0 ,
86.Dv link1 ,
87etc.
88Typically these hooks are connected to the
89.Dv lower
90hooks of one or more
3867d280 91.Xr ng_ether 4
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92nodes.
93To connect the host machine to a bridged network, simply connect the
94.Dv upper
95hook of an
3867d280 96.Xr ng_ether 4
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97node to the bridge node.
98.Sh CONTROL MESSAGES
99This node type supports the generic control messages, plus the
100following:
101.Bl -tag -width foo
102.It Dv NGM_BRIDGE_SET_CONFIG
103Set the node configuration.
104This command takes a
105.Dv "struct ng_bridge_config"
106as an argument:
107.Bd -literal -offset 0n
108/* Node configuration structure */
109struct ng_bridge_config {
110 u_char ipfw[NG_BRIDGE_MAX_LINKS]; /* enable ipfw */
111 u_char debugLevel; /* debug level */
112 u_int32_t loopTimeout; /* link loopback mute time */
113 u_int32_t maxStaleness; /* max host age before nuking */
114 u_int32_t minStableAge; /* min time for a stable host */
115};
116.Ed
117.Pp
118The
119.Dv ipfw
120array enables
121.Xr ipfirewall 4
122processing of IP packets received on the corresponding links.
123The
124.Dv debugLevel
125field sets the debug level on the node.
126At level of 2 or greater, detected loops are logged.
127The default level is 1.
128.Pp
129The
130.Dv loopTimeout
131determines how long (in seconds) a looped link is muted.
132The default is 60 seconds.
133The
134.Dv maxStaleness
135parameter determines how long a period of inactivity before
136a host's entry is forgotten.
137The default is 15 minutes.
138The
139.Dv minStableAge
140determines how quickly a host must jump from one link to another
141before we declare a loopback condition.
142The default is one second.
143.Pp
144.It Dv NGM_BRIDGE_GET_CONFIG
145Returns the current configuration as a
146.Dv "struct ng_bridge_config" .
147.It Dv NGM_BRIDGE_RESET
148Causes the node to forget all hosts and unmute all links.
149The node configuration is not changed.
150.It Dv NGM_BRIDGE_GET_STATS
151This command takes a four byte link number as an argument and
152returns a
153.Dv "struct ng_bridge_link_stats"
154containing statistics for the corresponding link, which must be
155currently connected:
156.Bd -literal -offset 0n
157/* Statistics structure (one for each link) */
158struct ng_bridge_link_stats {
159 u_int64_t recvOctets; /* total octets rec'd on link */
160 u_int64_t recvPackets; /* total pkts rec'd on link */
161 u_int64_t recvMulticasts; /* multicast pkts rec'd on link */
162 u_int64_t recvBroadcasts; /* broadcast pkts rec'd on link */
163 u_int64_t recvUnknown; /* pkts rec'd with unknown dest addr */
164 u_int64_t recvRunts; /* pkts rec'd less than 14 bytes */
165 u_int64_t recvInvalid; /* pkts rec'd with bogus source addr */
166 u_int64_t xmitOctets; /* total octets xmit'd on link */
167 u_int64_t xmitPackets; /* total pkts xmit'd on link */
168 u_int64_t xmitMulticasts; /* multicast pkts xmit'd on link */
169 u_int64_t xmitBroadcasts; /* broadcast pkts xmit'd on link */
170 u_int64_t loopDrops; /* pkts dropped due to loopback */
171 u_int64_t loopDetects; /* number of loop detections */
172 u_int64_t memoryFailures; /* times couldn't get mem or mbuf */
173};
174.Ed
175.It Dv NGM_BRIDGE_CLR_STATS
176This command takes a four byte link number as an argument and
177clears the statistics for that link.
178.It Dv NGM_BRIDGE_GETCLR_STATS
179Same as
180.Dv NGM_BRIDGE_GET_STATS ,
181but also atomically clears the statistics as well.
182.It Dv NGM_BRIDGE_GET_TABLE
183Returns the current host mapping table used to direct packets, in a
184.Dv "struct ng_bridge_host_ary" .
185.El
186.Sh SHUTDOWN
187This node shuts down upon receipt of a
188.Dv NGM_SHUTDOWN
189control message, or when all hooks have been disconnected.
190.Sh FILES
191.Bl -tag -width XXXXXXXX -compact
192.It Pa /usr/share/examples/netgraph/ether.bridge
193Example script showing how to set up a bridging network
194.El
195.Sh SEE ALSO
196.Xr bridge 4 ,
197.Xr netgraph 4 ,
198.Xr ng_ether 4 ,
199.Xr ngctl 8
200.Sh HISTORY
201The
202.Nm
203node type was implemented in
204.Fx 4.2 .
205.Sh AUTHORS
206.An Archie Cobbs Aq archie@FreeBSD.org