netns Script for simplifying usage of netns and VPN ... have fun

netns.sh

#!/usr/bin/env bash

IFACE="usb0"
NETNSNAME="anavarovpn"
OVPNCONF="/some/path/to/file.ovpn"
USER="user"

if [[ $UID != 0 ]]; then
    echo "This must be run as root."
    exit 1
fi

function iface_up() {
    ip netns add $NETNSNAME

    ip netns exec $NETNSNAME ip addr add 127.0.0.1/8 dev lo
    ip netns exec $NETNSNAME ip link set lo up

    ip link add vpn0 type veth peer name vpn1
    ip link set vpn0 up
    ip link set vpn1 netns $NETNSNAME up

    ip addr add 10.200.200.1/24 dev vpn0
    ip netns exec $NETNSNAME ip addr add 10.200.200.2/24 dev vpn1
    ip netns exec $NETNSNAME ip route add default via 10.200.200.1 dev vpn1

    iptables -A INPUT \! -i vpn0 -s 10.200.200.0/24 -j DROP
    iptables -t nat -A POSTROUTING -s 10.200.200.0/24 -o $IFACE -j MASQUERADE

    sysctl -q net.ipv4.ip_forward=1

    mkdir -p /etc/netns/$NETNSNAME
    echo 'nameserver 8.8.8.8' > /etc/netns/$NETNSNAME/resolv.conf

    ip netns exec $NETNSNAME fping -q www.google.com
}

function iface_down() {
    #Kill processes that are in this netns
    ip netns pids $NETNSNAME | xargs -rd'\n' kill

    rm -rf /etc/netns/$NETNSNAME
 
    sysctl -q net.ipv4.ip_forward=0
 
    iptables -D INPUT \! -i vpn0 -s 10.200.200.0/24 -j DROP
    iptables -t nat -D POSTROUTING -s 10.200.200.0/24 -o $IFACE -j MASQUERADE
 
    ip netns delete $NETNSNAME
}
 
function start_vpn() {
    ip netns exec $NETNSNAME openvpn --config $OVPNCONF &
 
    while ! ip netns exec $NETNSNAME ip a show dev tun0 up; do
        sleep .5
    done
}

function stop_vpn() {
     killall openvpn

     while ip netns exec $NETNSNAME ip a show dev tun0 up; do
        sleep .5
    done
} 
function run() {
    shift
    echo "$@"
    ip netns exec $NETNSNAME sudo -u $USER "$@"
}

case "$1" in
    up)
        iface_up
        start_vpn ;;
    down)
        stop_vpn 
        iface_down ;;
    run)
        run "$@" ;;
    start_vpn)
        start_vpn ;;
    stop_vpn)
        stop_vpn ;;
    *)
        echo "Syntax: $0 up|down|run|start_vpn|stop_vpn"
        exit 1
        ;;
esac