Bond with two tunnels

Bond with two tunnels

As I wrote here, there is a problem with detecting a link drop when you run a bonded VPN setup, there is no way for the bonding driver to know that one of the tunnels is down.

I thought that I will need to code a monitoring daemon for this, but I could manage with openvpn scripts alone. Here is what I’ve got.

OpenVPN config changes:

#on the "client"
script-security 2
down "./bond.sh down"
ipchange "./bond.sh ipchange"
up-restart
#and on the "server"
script-security 2
ipchange "./bond.sh ipchange"
down "./bond.sh down"
up-restart

What the changes above do, is launching a script when openvpn detects a disconnect or it connects back. This is the script I use to manage my bond:

#!/bin/bash
#interface name
BOND=bond0
#local ip address/mask
BONDIP=10.1.1.2/30
STATE=$1
IFACE=$2
function dettach {
        isbondup || return 0
        isattached || return 0
        echo -n Dettaching $dev ...
        ifenslave -d $BOND $dev
        [ $? -eq 0 ] && echo ok || echo fail
}
function attach {
        if ! isbondup ; then
                ifconfig bond0 up
                ip addr add $BONDIP dev $BOND
                for i in $dev $BOND; do
                   ip link set dev $i multipath off
                done
        fi
        if ! isattached; then
                echo -n Attaching $dev ...
                ifenslave $BOND $dev
                [ $? -eq 0 ] && echo ok || echo fail
        fi
}
function isbondup {
        ip link show $BOND | grep -q 'state UP'
        return $?
}
function isattached {
        grep -q "Slave Interface: $dev" /proc/net/bonding/$BOND
        return $?
}
case "$STATE" in
        "ipchange")
                echo "Called ipchange on $dev" | logger -t bond
                attach $IFACE
                ;;
        "down")
                dettach $IFACE
                ;;
        *)
                echo Cannot do $@ on $dev | logger
                ;;
esac

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