Support multiple gateways on one machine

2gateway.sh

#!/bin/bash -e

IFACE=wlp0s18f2u1
TBLN=10
# TBLN needs to be different for each interface

IPADDR=`ip addr show dev $IFACE | grep "inet " | awk '{print $2}' | cut -d '/' -f1`
IPSUBNET=`ip route show | grep "dev $IFACE" | grep "src $IPADDR" | awk '{print $1}'`
IPGATEWAY=`ip route | grep "default via" | grep "dev $IFACE" | awk '{print $3}'`

if [ "x$IPGATEWAY" = "x" ]; then
	echo "Nothing to do."
	exit 0
fi

# Create seperate route table with default route via $IPGATEWAY
if [ `ip route show table $TBLN | wc -l` -eq 0 ]; then
	ip route add default via $IPGATEWAY dev $IFACE table $TBLN
	ip route add $IPSUBNET dev $IFACE src $IPADDR table $TBLN
fi

# Use said route table for traffic to/from $IPADDR
if [ `ip rule list | grep "lookup $TBLN" | wc -l` -eq 0 ]; then
	ip rule add from $IPADDR table $TBLN
	ip rule add to $IPADDR table $TBLN
fi


# Delete unused default route via $IPGATEWAY
if [ `ip route show | grep "default via $IPGATEWAY" | wc -l` -gt 0 ]; then
	ip route del default via $IPGATEWAY dev $IFACE
fi