Script to manage bridge with multiple TAP interfaces.

[mark_orion]

I created the following "vboxbridge" script that is able to manage a bridge with multiple tap interfaces on my Ubuntu 8.04 host system. It works both with static and dynamic IPs and even with WiCD when you turn the "Automatically reconnect on connection loss" option off. The bridge is only created once and automatically removed after the last tap interface has been stopped.

You create a tap interface with: vboxbridge eth0 tap1 start
To remove the interface: vboxbridge eth0 tap1 stop
(create as many taps you like tap111, tap112)

The script works excellent when used manually (with sudo), BUT:
I tried to run the script automatically via the "Setup Application" and "Terminate Application" feature under Host Interface Settings, but it does not work. I tried both with "sudo" and run as root (chmod +s), all kinds of quotes and '´`, but I always an error message stating that the host interface could not be initialized.

I would appreciate any help to get this going.

Code: Select all

#!/bin/sh

#Put your username here
USERNAME=mark

TAP_INTERFACE="$2"
HOST_INTERFACE="$1"
BRIDGE_INTERFACE="br0"
TAP_COUNT=`ifconfig | grep -c tap`
case "$3" in
 start)
	if [ `ifconfig | grep -c $TAP_INTERFACE` = 0 ]; then
		#create the bridge if it does not exist
		if [ `ifconfig | grep -c $BRIDGE_INTERFACE` = 0 ]; then	
			brctl addbr $BRIDGE_INTERFACE
			#check if we are using DHCP and retrieve configuration if IP is static
			if [ `ps ax | grep -c "dhclient $HOST_INTERFACE"` = 2 ]; then
				ifconfig $HOST_INTERFACE 0.0.0.0 promisc
				brctl addif $BRIDGE_INTERFACE $HOST_INTERFACE
				dhclient $BRIDGE_INTERFACE
			else
				IP_ADDRESS=`ifconfig $HOST_INTERFACE | grep 'inet addr:' | cut -d: -f2 | awk '{ print $1}'`
				BROADCAST_ADDRESS=`ifconfig $HOST_INTERFACE | grep 'inet addr:' | cut -d: -f3 | awk '{ print $1}'`
				SUBNET_MASK=`ifconfig $HOST_INTERFACE | grep 'inet addr:' | cut -d: -f4 | awk '{ print $1}'`
				DEFAULT_GATEWAY=`route -n |tail -n1|cut -d' ' -f10`
				ifconfig $HOST_INTERFACE 0.0.0.0 promisc
				brctl addif $BRIDGE_INTERFACE $HOST_INTERFACE
				ifconfig $BRIDGE_INTERFACE $IP_ADDRESS netmask $SUBNET_MASK broadcast $BROADCAST_ADDRESS
				route add default gw $DEFAULT_GATEWAY
			fi
			
		fi
		#add tap interface to bridge
		tunctl -t $TAP_INTERFACE -u $USERNAME
		brctl addif $BRIDGE_INTERFACE $TAP_INTERFACE
		ifconfig $TAP_INTERFACE up
		chmod 0666 /dev/net/tun
	else
		echo "Interface $TAP_INTERFACE already configured"
	fi
	;;
 stop)
	if [ `ifconfig | grep -c $TAP_INTERFACE` = 0 ]; then
		echo "Interface $TAP_INTERFACE does no exist"
	else
		#shut down tap interface and remove it from bridge		
		ifconfig $TAP_INTERFACE down
		brctl delif $BRIDGE_INTERFACE $TAP_INTERFACE
		tunctl -d $TAP_INTERFACE
		#we remove the bridge if this was the last tap interface
		if [ $TAP_COUNT = 1 ]; then
			brctl delif $BRIDGE_INTERFACE $HOST_INTERFACE
			ifconfig $HOST_INTERFACE 0.0.0.0 -promisc
			#check if we are using DHCP and retrieve configuration if IP is static
			if [ `ps ax | grep -c "dhclient $BRIDGE_INTERFACE"` = 2 ]; then
				ifconfig $BRIDGE_INTERFACE down
				brctl delbr $BRIDGE_INTERFACE
				dhclient $HOST_INTERFACE
			else
				IP_ADDRESS=`ifconfig $BRIDGE_INTERFACE | grep 'inet addr:' | cut -d: -f2 | awk '{ print $1}'`
				BROADCAST_ADDRESS=`ifconfig $BRIDGE_INTERFACE | grep 'inet addr:' | cut -d: -f3 | awk '{ print $1}'`
				SUBNET_MASK=`ifconfig $BRIDGE_INTERFACE | grep 'inet addr:' | cut -d: -f4 | awk '{ print $1}'`
				DEFAULT_GATEWAY=`route -n |tail -n1|cut -d' ' -f10`
				ifconfig $BRIDGE_INTERFACE down
				brctl delbr $BRIDGE_INTERFACE
				ifconfig $HOST_INTERFACE $IP_ADDRESS netmask $SUBNET_MASK broadcast $BROADCAST_ADDRESS
				route add default gw $DEFAULT_GATEWAY
			fi
		fi
	fi
	;;
 *)
	echo "Usage: vboxbridge hostinterface tapinterface {start|stop}" >&2
	exit 1
	;;
esac

[Sasquatch]

Since you would run the script from a terminal with sudo, it will ask for a password, but from a GUI, it can't do that with sudo. Use gksudo instead, so you get a GUI for your password. So for the start and stop commands, use /usr/bin/gksudo /path/to/script.

[magloca]

You, sir, are a hero! I was going insane over this bridging stuff and this script seems to have cut my suffering short... Thanks for sharing.