BRIDGE(3) BRIDGE(3)
NAME
bridge - Ethernet bridge and IPv4 tunnel
SYNOPSIS
bind -a #Bb /net
/net/bridgeb/ctl
/net/bridgeb/cache
/net/bridgeb/log
/net/bridgeb/stats
/net/bridgeb/n
/net/bridgeb/n/ctl
/net/bridgeb/n/local
/net/bridgeb/n/status
DESCRIPTION
The bridge device bridges (copies) packets amongst Ethernet
interfaces. The number b in the bind is optional and
selects a particular bridge (default 0).
The /net/bridge0 directory contains ctl, cache, log, and
stats files, and numbered subdirectories for each physical
interface.
Opening the ctl file reserves an interface. The file
descriptor returned from the open(2) will point to the con-
trol file, ctl, of the newly allocated interface. Reading
ctl returns a text string representing the number of the
interface. Writing ctl alters aspects of the interface.
The possible ctl messages are:
bind ether name ownhash path
Treat the device mounted at path (e.g.,
`/net/ether0') as an Ethernet medium and associ-
ate it with this bridge (forward its packets to
the other interfaces associated with this
bridge). Ownhash is an `owner hash'.
bind tunnel name ownhash path path2
Treat the device mounted at path as a network
tunnel (of IPv4 in IPv4), the device mounted at
path2 as an Ethernet medium and associate them
with this bridge (forward its packets to the
other interfaces associated with this bridge).
Read packets from the path interface and write
them to the path2 interface. Such tunnels have
an MTU of 1400 bytes.
unbind type address [ownhash]
Disassociate the interface associated with
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BRIDGE(3) BRIDGE(3)
address from this bridge. Type must be `ether'
or `tunnel'.
cacheflush Clear the cache of (destination MAC address,
port) tuples.
delay delay0 delayn
Set the delay0 and delayn parameters. delay0 is
the constant microsecond delay per packet and
delayn is the microsecond delay per byte.
set option Set bridge option. The only known option is
`tcpmss', which limits the TCP Maximum Segment
Size of TCP packets passing through to 1300
bytes.
clear option
Clear bridge option.
Reading stats returns statistics about the bridge.
Reading the log file returns data from the bridge's log and
will block at end of file awaiting new data.
Reading the cache file prints the cache of (destination MAC
address, port) tuples, one entry per line. The format is:
the destination MAC (e.g., Ethernet) address in hex, port
number, count of packets from this address, count of packets
to this address, expiry time in seconds since the epoch, and
`e' for expired entries or `v' for valid entries.
In a connection subdirectory, ctl and local don't do any-
thing, but status returns a one-line status summary.
EXAMPLES
Set up a network bridge between two Ethernets (`#l0' and
`#l1').
bind -a '#B' /net
bind -a '#l1' /net
echo 'bind ether outer 0 /net/ether0' >/net/bridge0/ctl
echo 'bind ether inner 0 /net/ether1' >/net/bridge0/ctl
SEE ALSO
ip(3)
SOURCE
/sys/src/9/port/devbridge.c
BUGS
Understands but won't tunnel nor fragment IPv6.
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