+#!/bin/bash
+
+# taking this bridge-initialization code out of lbuild-initvm.sh
+# so we can use it on our libvirt/lxc local infra
+# there's something very similar in
+# tests/system/template-qemu/qemu-bridge-init
+# that the current code was actually based on, but
+# nobody was ever bold enough to reconcile these two
+
+# hard-wired
+DEFAULT_PUBLIC_BRIDGE=br0
+
+##############################
+# use /proc/net/dev instead of a hard-wired list
+function gather_interfaces () {
+ python <<EOF
+for line in file("/proc/net/dev"):
+ if ':' not in line: continue
+ ifname=line.replace(" ","").split(":")[0]
+ if ifname.find("lo")==0: continue
+ if ifname.find("br")==0: continue
+ if ifname.find("virbr")==0: continue
+ if ifname.find("veth")==0: continue
+ if ifname.find("tap")==0: continue
+ print ifname
+EOF
+}
+
+function discover_interface () {
+ for ifname in $(gather_interfaces); do
+ ip link show $ifname | grep -qi 'state UP' && { echo $ifname; return; }
+ done
+ # still not found ? that's bad
+ echo unknown
+}
+
+#################### bridge initialization
+function create_bridge_if_needed() {
+
+ # turn on verbosity
+ set -x
+
+ public_bridge=$1; shift
+
+ # already created ? - we're done
+ ip addr show $public_bridge >& /dev/null && {
+ echo "Bridge already set up - skipping create_bridge_if_needed"
+ return 0
+ }
+
+ # find out the physical interface to bridge onto
+ if_lan=$(discover_interface)
+
+ ip addr show $if_lan &>/dev/null || {
+ echo "Cannot use interface $if_lan - exiting"
+ exit 1
+ }
+
+ #################### bride initialization
+ check_yum_installed bridge-utils
+
+ echo "========== $COMMAND: entering create_bridge - beg"
+ hostname
+ uname -a
+ ip addr show
+ ip route
+ echo "========== $COMMAND: entering create_bridge - end"
+
+ # disable netfilter calls for bridge interface (they cause panick on 2.6.35 anyway)
+ #
+ # another option would be to accept the all forward packages for
+ # bridged interface like: -A FORWARD -m physdev --physdev-is-bridged -j ACCEPT
+ sysctl net.bridge.bridge-nf-call-iptables=0
+ sysctl net.bridge.bridge-nf-call-ip6tables=0
+ sysctl net.bridge.bridge-nf-call-arptables=0
+
+
+ #Getting host IP/masklen
+ address=$(ip addr show $if_lan | grep -v inet6 | grep inet | head --lines=1 | awk '{print $2;}')
+ [ -z "$address" ] && { echo "ERROR: Could not determine IP address for $if_lan" ; exit 1 ; }
+
+ broadcast=$(ip addr show $if_lan | grep -v inet6 | grep inet | head --lines=1 | awk '{print $4;}')
+ [ -z "$broadcast" ] && echo "WARNING: Could not determine broadcast address for $if_lan"
+
+ gateway=$(ip route show | grep default | awk '{print $3;}')
+ [ -z "$gateway" ] && echo "WARNING: Could not determine gateway IP"
+
+
+ # creating the bridge
+ echo "Creating public bridge interface $public_bridge"
+ brctl addbr $public_bridge
+ brctl addif $public_bridge $if_lan
+ echo "Activating promiscuous mode if_lan=$if_lan"
+ ip link set $if_lan up promisc on
+ sleep 2
+ # rely on dhcp to re assign IP..
+ echo "Starting dhclient on $public_bridge"
+ dhclient $public_bridge
+ sleep 1
+
+ #Reconfigure the routing table
+ echo "Configuring gateway=$gateway"
+ ip route add default via $gateway dev $public_bridge
+ ip route del default via $gateway dev $if_lan
+ # at this point we have an extra route like e.g.
+ ## ip route show
+ #default via 138.96.112.250 dev br0
+ #138.96.112.0/21 dev em1 proto kernel scope link src 138.96.112.57
+ #138.96.112.0/21 dev br0 proto kernel scope link src 138.96.112.57
+ #192.168.122.0/24 dev virbr0 proto kernel scope link src 192.168.122.1
+ route_dest=$(ip route show | grep -v default | grep "dev $public_bridge" | awk '{print $1;}')
+ ip route del $route_dest dev $if_lan
+
+ echo "========== $COMMAND: exiting create_bridge - beg"
+ ip addr show
+ ip route show
+ echo "========== $COMMAND: exiting create_bridge - end"
+
+ # for safety
+ sleep 3
+ return 0
+
+}
+
+function main () {
+ if [[ -n "$@" ]] ; then
+ public_bridge="$1"; shift
+ else
+ public_bridge="$DEFAULT_PUBLIC_BRIDGE"
+ fi
+ create_bridge_if_needed $public_bridge
+}
+
+main "$@"