Little script originating from "http://unix.stackexchange.com/questions/149293/feed-all-traffic-through-openvpn-for-a-specific-network-namespace-only/196116#196116" creating network namespaces with the OpenVPN connection. IPv6 section is commented out, you can re-enable it yourself.

netns.sh

  1 #!/bin/sh
  2 
  3 set -x 
  4 case $script_type in
  5         up)
  6                 ip netns add vpn
  7                 ip netns exec vpn ip link set dev lo up
  8                 mkdir -p /etc/netns/vpn
  9                 ip link set dev "$1" up netns vpn mtu "$2"
 10                 ip netns exec vpn ip addr add dev "$1" \
 11                         "$4/${ifconfig_netmask:-30}" \
 12                         ${ifconfig_broadcast:+broadcast "$ifconfig_broadcast"}
 13                 #test -n "$ifconfig_ipv6_local" && \
 14             #ip netns exec vpn ip addr add dev "$1" \
 15              #          "$ifconfig_ipv6_local"/112
 16                 ;;
 17         route-up)
 18                 ip netns exec vpn ip route add default via "$route_vpn_gateway"
 19                 #test -n "$ifconfig_ipv6_remote" && \
 20             #ip netns exec vpn ip route add default via \
 21                             #"$ifconfig_ipv6_remote"
 22                 ;;
 23         down)
 24                 ip netns delete vpn
 25                 ;;
 26 esac