TH BRIDGE 3
SH NAME
bridge \- IP Ethernet bridge
SH SYNOPSIS
nf
B bind -a #B\fIb\fP /net

B /net/bridge\fIb\fP/ctl
B /net/bridge\fIb\fP/cache
B /net/bridge\fIb\fP/log
B /net/bridge\fIb\fP/stats
BI /net/bridge\fIb\fP/ n
BI /net/bridge\fIb\fP/ n /ctl
BI /net/bridge\fIb\fP/ n /local
BI /net/bridge\fIb\fP/ n /status
fi
SH DESCRIPTION
The
I bridge
device bridges packets amongst Ethernet interfaces.
The number
I b
in the bind is optional and selects a particular bridge
(default 0).
PP
The
B /net/bridge0
directory contains
BR ctl ,
BR cache ,
BR log ,
and
B stats
files, and numbered subdirectories for each physical interface.
PP
Opening the
B ctl
file reserves an interface.
The file descriptor returned from the
IR open (2)
will point to the control file,
BR ctl ,
of the newly allocated interface.
Reading
B ctl
returns a text string representing the number of the interface.
Writing
B ctl
alters aspects of the interface.
The possible
I ctl
messages are:
TF cacheflush
PD
TP
BI "bind ether " "name ownhash path"
Treat the device mounted at
I path
(e.g.,
LR /net/ether0 )
as an Ethernet medium
and associate it with this bridge (forward its packets to the
other interfaces associated with this bridge).
I Ownhash
is an `owner hash'.
TP
BI "bind tunnel " "name ownhash path path2
Treat the device mounted at
I path
as a network tunnel carrying Ethernet packets,
the device mounted at
I path2
as an Ethernet
and associate them with this bridge
(forward its packets to the
other interfaces associated with this bridge).
Read packets from the
I path
interface and write them to the
I path2
interface.
Such tunnels have an MTU of 1400 bytes.
TP
BI "unbind " "type address [ownhash]"
Disassociate the interface associated with
I address
from this bridge.
I Type
must be
L ether
or
LR tunnel .
TP
B cacheflush
Clear the cache of (destination MAC address, port) tuples.
TP
BI "delay " "delay0 delayn"
Set the
I delay0
and
I delayn
parameters.
I delay0
is the constant microsecond delay per packet
and
I delayn
is the microsecond delay per byte.
TP
BI "set " option
Set bridge
IR option .
The only known option is
LR tcpmss ,
which limits the TCP Maximum Segment Size of
TCP packets passing through to 1300 bytes.
TP
BI "clear " option
Clear bridge
IR option .
PP
Reading
I stats
returns statistics about the bridge.
PP
Reading the
I log
file returns data from the bridge's log
and will block at end of file awaiting new data.
PP
Reading the
B 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
L e
for expired entries or
L v
for valid entries.
PP
In a connection subdirectory,
B ctl
and
B local
don't do anything,
but
B status
returns a one-line status summary.
SH EXAMPLES
Set up a network bridge between two Ethernets
RL ( #l0
and
LR #l1 ).
IP
EX
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
EE
SH "SEE ALSO"
IR ip (3)
SH SOURCE
B /sys/src/9/port/devbridge.c

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