kvm-network-restart

#!/bin/bash
#
# Yury V. Zaytsev <yury@shurup.com> (C) 2011
#
# Modified by Erico Mendonca (erico.mendonca@suse.com) to add the following:
# 
# - SUSE paths
# - progress messags
# - tighter scope (only change the VMs that use the supplied network name)
#
# (dec 2018)
#
# This work is herewith placed in public domain.
#
# Use this script to cleanly restart the default libvirt network after its
# definition have been changed (e.g. added new static MAC+IP mappings) in order
# for the changes to take effect. Restarting the network alone, however, causes
# the guests to lose connectivity with the host until their network interfaces
# are re-attached.
#
# The script re-attaches the interfaces by obtaining the information about them
# from the current libvirt definitions. It has the following dependencies:
#
#   - virsh (obviously)
#   - tail / head / grep / awk / cut
#   - XML::XPath (e.g. perl-XML-XPath package)
#
# Note that it assumes that the guests have exactly 1 NAC each attached to the
# given network! Extensions to account for more (or none) interfaces etc. are,
# of course, most welcome.
#
# ZYV
#

set -e

if [ -z $1 ]; then
	echo "Usage: $0 <network name>"
	exit 1
fi

command -v xpath >/dev/null 2>&1 || { echo >&2 "I require xpath, but it's not installed. Try apt install libxml-xapth-perl (Debian/Ubuntu). Aborting."; exit 1; }
command -v virsh >/dev/null 2>&1 || { echo >&2 "I require virsh, but it's not installed?. Aborting."; exit 1; }


NETWORK_NAME=$1
NETWORK_HOOK=/etc/libvirt/hooks/qemu

echo "--> restarting network $NETWORK_NAME"
virsh net-define /etc/libvirt/qemu/networks/$NETWORK_NAME.xml
virsh net-destroy $NETWORK_NAME
virsh net-start $NETWORK_NAME
echo "--> network restarted"

MACHINES=$( virsh list | tail -n +3 | head -n -1 | awk '{ print $2; }' )

for m in $MACHINES ; do
	echo "---> processing VM: $m"

	MACHINE_INFO=$( virsh dumpxml "$m" | xpath -e /domain/devices/interface[1] 2> /dev/null )
	MACHINE_MAC=$( echo "$MACHINE_INFO" | grep "mac address" | cut -d '"' -f 2 )
	MACHINE_MOD=$( echo "$MACHINE_INFO" | grep "model type" | cut -d '"' -f 2 )
	MACHINE_NET=$( echo "$MACHINE_INFO" | grep "source network" | cut -d '"' -f 2 )

	if [ "$MACHINE_NET" == "$NETWORK_NAME" ]; then
		echo "--> detaching and attaching interfaces for mac address $MACHINE_MAC ($m)"
		set +e
		virsh detach-interface "$m" network --mac "$MACHINE_MAC" && sleep 3
		virsh attach-interface "$m" network $NETWORK_NAME --mac "$MACHINE_MAC" --model "$MACHINE_MOD"
		set -e

		echo "--> calling network hook script"
		$NETWORK_HOOK "$m" stopped && sleep 3
		$NETWORK_HOOK "$m" start
	else
		echo "--> machine $m is not attached to network $NETWORK_NAME, skipping"
	fi
	echo "--> done"
done