ifupdown-netns/if-down.d/netns

#!/bin/sh

set -e

if [ -n "${IF_NETNS}" ]
then
  unshare -m /bin/sh <<-EOF
mount --make-rprivate /
mount --bind /run/network.${IF_NETNS} /run/network
if (ip netns exec ${IF_NETNS} ifquery --list | grep -qx ${IFACE}); then
  ip netns exec ${IF_NETNS} ifdown ${IFACE}
fi
ip netns exec ${IF_NETNS} ip link set netns 1 dev ${IFACE}
EOF
fi