Creating a Bridge for VMs to communicate guest to host

bridge.sh

#!/bin/bash

DEVICE=${1:-eth0}
BR_NAME=br-pub

ipv4_transfer=(
	method
	dns
	addresses
	gateway
	routes
	dhcp-hostname
	dhcp-fqdn
)
declare -A extra_settings
extra_settings[bridge.stp]=no

[ $EUID -eq 0 ] || { echo "Please run as root." >&2 ; exit 1 ; }

set -ex

CONNECTION="$(nmcli d show ${DEVICE} | sed -n 's/GENERAL\.CONNECTION:\s\+\(\S.*\)/\1/p')"

nmcli c add type bridge con-name $BR_NAME ifname $BR_NAME
nmcli c down "$CONNECTION"
for setting in "${ipv4_transfer[@]}"; do
	old=$(nmcli -g ipv4.$setting c show "$CONNECTION")
	if [ -n "$old" ]; then
		nmcli c mod $BR_NAME ipv4.$setting "$old"
	fi
done
for setting in "${!extra_settings[@]}"; do
	nmcli c mod $BR_NAME $setting ${extra_settings[$setting]}
done
nmcli c add type bridge-slave ifname $DEVICE master $BR_NAME
nmcli c up $BR_NAME