LinuxQuestions.org - XEN-SUSE 10.1-- DHCP Server works under plain but not under XEN

Bingo Hit upon it: Basically as far as I got it Xen by default thinks that there is only one blasted network card. However I use two one internal one external.

To fix it simply make a new script and call it say network-bridge2 in /etc/xen/scripts folder. Then reference it through ...

"To use it, you need to edit /etc/xen/xend-config.sxp . Set the
variable network-script to point to this script. ..."

The site says change the vif variable but I just left it and it seems to work fine!
Code:
#!/bin/sh

#============================================================================

# Default Xen network start/stop script.

# Xend calls a network script when it starts.

# The script name to use is defined in /etc/xen/xend-config.sxp

# in the network-script field.

#

# This script replaces a network device with a bridge by renaming

# the network device and creating a new bridge with the old name

# of the renamed device. The renamed device is enslaved to the

# bridge.

# 

# The general idea is that names of devices given in  Firewall and

# routing rules can remain the same before/after the script is

# run.

#

# If all goes well, this should ensure that networking stays up.

# However, some configurations are upset by this, especially

# NFS roots. If the bridged setup does not meet your needs,

# configure a different script, for example using routing instead.

#

# Usage:

#

# network (start|stop|status) {VAR=VAL}*

#

# Vars:

#

# bridge    The bridge to use. (defaults to xen-br0: this proably isn't

#            what you want. Remember to edit variable vif-bridge in

#            file /etc/xen/xend-config.sxp. )

# netdev    (now unused)

# antispoof  Whether to use iptables to prevent spoofing (default yes).

#

# start:

# Renames the network device ${bridge} as ${bridge}slv

# Creates a new bridge device named ${bridge} that takes

# the place of the renamed device.

# Enslaves the the renamed network device to the new bridge device.

# Deletes the routing information for the network device and

# adds new routing information for the new bridge device using ifup

#

# stop:

# Removes netdev from the bridge.

# Deletes the routes to bridge and adds them to netdev.

#

# status:

# Print ifconfig for ${bridge}and ${bridge}slv.

# Print routes.

#

#============================================================================



# Exit if anything goes wrong.

#set -e 



#DEBUG=""

#DEBUG="echo"



BRCTL="$DEBUG brctl"

IFUP="$DEBUG ifup"

IFDOWN="$DEBUG ifdown"

IP="$DEBUG ip"

IPTABLES="$DEBUG iptables"

#PATH="/sbin:/usr/sbin:$PATH"



# debugging sleep to fix posible races?

SLEEP="true "

#SLEEP="sleep "



# First arg is the operation.

OP=$1

shift



# Pull variables in args in to environment.

for arg ; do export "${arg}" ; done



bridge=${bridge:-xen-br0}

netdev=${netdev:-eth0}

antispoof=${antispoof:-yes}



echo "# network $OP bridge=$bridge netdev=$netdev antispoof=$antispoof"



# takes 1 arg, the name of a network device

# exit status of 0 or 1

is_netdev() {

    local netdev=$1



    [ $# == 1 ] && ifconfig $netdev >/dev/null 2>&1 || false

}



# takes 1 arg, the name of a network device

# exit status of 0 or 1

is_bridge() {

    local netdev=$1

    

    [ $# == 1 ] && brctl showmacs $netdev >/dev/null 2>&1 || false

}





# Usage: create_bridge bridge

# Create bridge $bridge and set bridge parameters.

# Does not add slave devices.

# Does not assign an IP address.

create_bridge() {

    local netdev=$1



    if [ $# != 1 ] ; then

            false

            return

    fi

    # Don't create the bridge if it already exists.

  echo create_bridge $netdev

  if ! is_netdev ${netdev} && ! is_bridge ${netdev} ; then

        $BRCTL addbr ${netdev}

        $BRCTL stp ${netdev} off

        $BRCTL setfd ${netdev} 0

  fi

}



# Return the MAC address of the network device

# given as an argument.

get_mac_addr() {

    local netdev

    local ret



    if [ $# != 1 ] ; then

            false

            return

    fi

    netdev=$1



    ip link show $netdev \

        | grep -e 'link/ether' \

        | sed -e 's#^[  ]*link/ether[ ]\(\([0-9a-f]\+:\)\+[0-9a-f]\+\).*#\1#'

    return

}





# Usage: antispoofing dev bridge

# Set the default forwarding policy for $dev to drop.

# Allow forwarding to the bridge.

antispoofing() {

    local dev=$1

    local bridge=$2



    $IPTABLES -P FORWARD DROP



    # XXX . OUCH! This looks horribly permissive.

    # I am not sure that firewall rules belong here.

    $IPTABLES -A FORWARD -m physdev --physdev-in ${dev} -j ACCEPT

}



#Usage: show_status dev bridge

#Print ifconfig and routes.

show_status() {

    local bridge=$1

    

    echo '============================================================'

    ifconfig ${bridge}

    ifconfig ${bridge}slv

    echo ' '

    ip route list

    echo ' '

    route -n

    echo '============================================================'

}



#    start      \  ${bridge}

#                \    is_br  is_dev  missing

# ${bridge}slv    \

#                  +-------+-------+-------+

#          is_br    |  (1)  |  (3)  |  (1)  |

#                  +-------+-------+-------+

#          is_dev  |  (2)  |  (1)  |  (4)  |

#                  +-------+-------+-------+

#          missing  |  (1)  |  (5)  |  (1)  |

#                  +-------+-------+-------+



# (1) Error: bail out leaving things as is.

# (2) Do nothing: bridge already started

# (3) create bridge called ${bridge}slv (if it doesn't already exist)

#    ifdown ${bridge}

#    rename ${bridge} -> ${bridge}tmp

#    rename ${bridge}slv -> ${bridge}

#    rename ${bridge}tmp -> ${bridge}slv

#    enslave ${bridge}slv to ${bridge} (and make sure slave it is up.)

#    ifup ${bridge}

# (4) 



op_start () {

    local real_mac_addr



    if [ "${bridge}" == "null" ] ; then

        return

    fi



    if is_bridge ${bridge}slv ; then

        # row 1 in table above

        if is_bridge ${bridge} || ! is_netdev ${bridge} ; then  

            # (1)

            echo 'case #1'

            # bail out with error

            false

            return

        else

            #(3)

            echo '# case #3'

            real_mac_addr="eth-id-$(get_mac_addr ${bridge})"

            $IFDOWN $real_mac_addr $bridge 

            $IP link set ${bridge}slv down

            $IP link set ${bridge}slv name ${bridge}tmp

            $SLEEP 1

            $IP link set ${bridge} name ${bridge}slv

            $SLEEP 1

            $IP link set ${bridge}tmp name ${bridge}

            $SLEEP 1

            $BRCTL addif ${bridge} ${bridge}slv

            $SLEEP 1

            # Use the mac addr of the enslaved device to find

            # configuration for the bridge.

            $IFUP $real_mac_addr ${bridge} 

            $IP link set ${bridge}slv up

            return

        fi

    elif is_netdev ${bridge}slv ; then

        # row 2 in table above

        if is_bridge ${bridge} ; then

            # (2)

            echo '# case #2'

            # nothing to do, return success

            true

            return

        elif is_netdev ${bridge} ; then

            # (1)

            # bailout with error

            false

            return

        else

            # (4)

            echo '# case #4'

            real_mac_addr="eth-id-$(get_mac_addr ${bridge}slv)"

            # create a bridge named ${bridge} and enslave

            # ${bridge}slv to it.

            # Make sure both interfaces are up.

            create_bridge ${bridge}

            $BRCTL addif ${bridge} ${bridge}slv

            $IP link set ${bridge}slv up

            $SLEEP 1

            # Use the mac addr of the enslaved device to find

            # configuration for the bridge.

            $IFUP $real_mac_addr ${bridge}

            return

        fi

    else

        # row 3 in table above

        if is_bridge ${bridge} ; then

            # (1)

            # bail out with error

            false

            return

        elif is_netdev ${bridge} ; then

            # (5)

            echo '# case #5'

            real_mac_addr="eth-id-$(get_mac_addr ${bridge})"

            $IFDOWN $real_mac_addr $bridge

            $IP link set ${bridge} name ${bridge}slv

            $BRCTL addbr ${bridge}

            $BRCTL addif ${bridge} ${bridge}slv

            $SLEEP 1

            # Use the mac addr of the enslaved device to find

            # configuration for the bridge.

            $IFUP $real_mac_addr ${bridge}

            $IP link set ${bridge}slv up

            return          

        else

            # (1)

            # bail out with error

            false

            return

        fi

    fi



    # Create the bridge and give it the interface IP addresses.

    # Move the interface routes onto the bridge.

    #create_bridge ${bridge}

    # Don't add $dev to $bridge if it's already on a bridge.

    #if ! brctl show | grep -q ${netdev} ; then

    #    brctl addif ${bridge} ${netdev}

    #fi

    

    #if [ ${antispoof} == 'yes' ] ; then

    #    antispoofing ${bridge}slv ${bridge}

    #fi

}



op_stop () {

    if [ "${bridge}" == "null" ] ; then

        return

    fi

    # Remove the interface from the bridge.

    # Move the routes back to the interface.

    if is_netdev ${bridge} && is_bridge ${bridge} ; then

        $IFDOWN ${bridge}

        $IP link set ${bridge}slv down

        $BRCTL delif ${bridge} ${bridge}slv

        $IP link set ${bridge} name ${bridge}tmp

        $SLEEP 1

        $IP link set ${bridge}slv name ${bridge}

        $SLEEP 1

        $IP link set ${bridge}tmp name ${bridge}slv

        $SLEEP 1

        $IFUP "eth-id-$(get_mac_addr ${bridge})" ${bridge}

        return

    fi



  # It's not our place to be enabling forwarding...

}



case ${OP} in

  start)

      op_start

      ;;

  

  stop)

      op_stop

      ;;



  status)

      show_status ${bridge}

      ;;



  *)

      echo 'Unknown command: ' ${OP}

      echo 'Valid commands are: start, stop, status'

      exit 1

esac
Taken from http://lists.xensource.com/archives/.../msg00597.html