ref: b51b623725ce394a1f9f12686f043c1cc3bba7c9
dir: /rc/bin/ethermultilink/
#!/bin/rc
# ethermultilink outpus bridge(3) commands to switch
# between multiple ethernet (or wifi) interfaces
# depending on their link status.
rfork e
fn usage {
echo 'Usage: ' $0 'primaryether secondaryether1 [secondaryether2 ....] > /net/bridgeX/ctl' >[1=2]
exit 'usage'
}
fn missing {
echo 'missing: ' $1 >[1=2]
exit 'missing'
}
~ $#* 0 1 && usage
# make sure arguments are ethernets
for(i){
test -r $i/stats || missing $i/stats
}
# first interface is the primary
primary=$1
net=`{echo $primary | sed 's!/*[^/]*$!!g'}
test -r $net/arp || missing $net/arp
# now select secondary from the list depending on link status
@{
old=/dev/null
new=$old
while(){
# interfaces are in increasing priority order
for(i){
if(grep -s 'link: 1' $i/stats)
new=$i
}
if(! ~ $new $old){
if(! ~ $old /dev/null){
if(! ~ $old $primary) {
echo unbind bypass primary 0
echo unbind ether secondary 0
}
}
if(! ~ $new $primary){
echo bind bypass primary 0 $primary
echo bind ether secondary 0 $new
}
# do gratious arp on the new path
for(ip in `{awk '$3=="4u" || $3=="6u" {print $1}' $net/ipselftab}){
echo garp $ip > $net/arp || echo flush > $net/arp
}
old=$new
}
sleep 1
}
} </dev/null &
exit ''