#!/bin/sh

set -e

MNT=testmnt

# Create a new namespace and bind-mount it to keep it alive.
(
touch "$MNT"
unshare --net mount --bind /proc/self/ns/net "$MNT"
)

rm -f barrier && mkfifo barrier

# Hold a reference while the namespace gets unmounted.
(
exec 4<"$MNT"
ls -l /proc/self/fd
cat < barrier
ls -l /proc/self/fd
) &

# Unmount the namespace while there's still a reference.
cat /dev/null > barrier
umount --lazy "$MNT"
wait