#!/bin/sh

# this script looks for an unused network namespace in /var/run/netns/newpid*
# and invokes "newpid" on it.

set -u

# as long as this file exists, we haven't found a free netns
STAMP=$(mktemp --tmpdir newnet.sh.XXXXXX)
trap "rm -f $STAMP" 0 2 3 15

# loop through namespaces
for ns in /var/run/netns/newpid*; do
  if [ ! -f $ns ]; then
    # if we get here, the glob didn't expand
    echo "No network namespaces matching /var/run/netns/newpid* found" >&2
    exit 2
  fi

  # run the command
  (
    flock -n 8 || exit
    # we got the lock
    rm -f $STAMP
    echo "newpid-netns: Using namespace $ns"
    newpid -iuN $(basename $ns) "$@"
  ) 8< $ns
  EXIT=$?

  # if we get here and the stamp file exists, loop for the next NS, else exit
  if [ ! -f $STAMP ]; then exit $EXIT; fi
done

# if we get here, error out
echo "No unused network namespace found in /var/run/netns/newpid*" >&2
exit 2