etc network if-up.dnxdomain-hijacker-discovery

#!/bin/bash
# on ubuntu, /etc/network/if-up.d/nxdomain-discovery

set -e -u

test -x /usr/bin/host || exit 0

case "$ADDRFAM" in
  inet|inet6) : ;;
  *) exit 0 ;;
esac

change_test=$(run-parts --list /etc/NetworkManager/dnsmasq.d |md5sum)

host=does-not-exist-${RANDOM}.example.com.
t=$(tempfile)
test -f "$t"
trap "rm -f \"$t\"" EXIT
if host -t A "${host}" >"$t"; then
        cat "$t" |while read host has xaddress address; do
                if test "$address" == "${address/[^0-9.]/x}"; then
                        echo "bogus-nxdomain=${address/[^0-9.]/x}" >/etc/NetworkManager/dnsmasq.d/nxdomain-automatically-discovered-"${address//[^0-9.]/x}"
                else
                        test ! -x /usr/bin/logger || echo "lookup of ${host} yields unexpected answer: $host $has $xaddress $address" |logger --priority daemon.warning
                fi
        done
fi      

if "${change_test}" != "$(run-parts --list /etc/NetworkManager/dnsmasq.d |md5sum)"; then
        test ! -x /usr/sbin/service || echo "service network-manager restart" |at "now + 1 minute"
fi