mynetns_run: Run a program in a seperate network namespace

## mynetns_run
#!/bin/bash -e

NETNS_FILE=/var/run/netns/mynet
MNTNS_FILE=/var/run/ns/mynet_mnt

if [[ ! -f $NETNS_FILE ]]; then
  ip netns add mynet

  ip link add mynet0 type veth peer name mynet1
  ip link set mynet0 up
  ip link set mynet1 netns mynet
  brctl addif br0 mynet0

  ip netns exec mynet ip link set mynet1 up
  ip netns exec mynet ip address add dev mynet1 192.168.57.101/24
  ip netns exec mynet ip route add default via 192.168.57.1
fi

if [[ ! -f $MNTNS_FILE ]]; then
  mnt_dir=$(dirname $MNTNS_FILE)
  mkdir -p "$mnt_dir"
  mount --bind "$mnt_dir" "$mnt_dir"
  mount --make-private "$mnt_dir"
  echo 'nameserver 192.168.57.1' > $MNTNS_FILE
  unshare --mount=$MNTNS_FILE mount --bind $MNTNS_FILE /etc/resolv.conf
fi

exec nsenter --mount=$MNTNS_FILE --net=$NETNS_FILE sudo -u lilydjwg DISPLAY=:0 LANG=zh_CN.UTF-8 LANGUAGE=zh_CN:zh_TW GTK_IM_MODULE=fcitx QT_IM_MODULE=fcitx XMODIFIERS=@im=fcitx DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/1000/bus TMUX=1 "$@"