groupbasedroute.txt

# add group (to be used for iptables matching)
groupadd novpn

# add user to group
adduser yourusername novpn

# set iptables rules (marking packets of novpn group)
iptables -t mangle -A OUTPUT -m owner --gid-owner novpn -j MARK --set-mark 1
iptables -t nat -A POSTROUTING -o wlan0 -j MASQUERADE

# add new routing table
echo "1       novpn.out" >> /etc/iproute2/rt_tables

# set new table (with standard interface wlan0 as default)
ip route add default dev wlan0 table novpn.out

# set new rule (matching the packets marked by iptables)
ip rule add fwmark 1 table novpn.out

# unset rp_filter (mandatory!?) 
for i in /proc/sys/net/ipv4/conf/*/rp_filter; do echo 0 > $i; done

# start process within the group
sg novpn -c processname