Digital Ocean floating IP gateway script (force droplet to use the assigned floating IP for outbound traffic as well as inbound traffic). This forked script will revert back to original settings. Pass the original IP address of the droplet as the first parameter.

revert-floating-ip-gateway.sh

#!/bin/bash
# Revert outbound traffic back to original ip. Call script with the original ip address of droplet
NET_INT="eth0"
CURL_TIMEOUT=3

if [ "$1" == "" ]; then
    echo "Original IP of droplet not given."
    exit 1
fi

DROPLET_IP_ADDRESS = $1
echo $'Original Droplet IP: ' $DROPLET_IP_ADDRESS $'\n'
echo $'\nSetting original droplet IP as the default gateway: '

# Check there's a floating IP attached to this droplet
if [ "$(curl -s --interface $DROPLET_IP_ADDRESS --connect-timeout $CURL_TIMEOUT http://169.254.169.254/metadata/v1/floating_ip/ipv4/active)" != "true" ]; then
        echo $'\nError: this droplet doesn\'t have a floating IP assigned to it.'
        exit 1
fi

# Get the gateway IP for the original IP
GATEWAY_IP=$(curl -s --interface $DROPLET_IP_ADDRESS --connect-timeout $CURL_TIMEOUT http://169.254.169.254/metadata/v1/interfaces/public/0/ipv4/gateway)

if [ -z "$GATEWAY_IP" ]; then
        echo $'\nError: failed getting gateway IP for this droplet.'
        exit 1
fi

# Check the original gateway isn't already the default
if [ ! -z $(ip route ls 0/0|awk '{print $3}'|grep "$GATEWAY_IP") ]; then
        echo $'\nError: default gateway IP already a default route.'
        exit 1
fi

# Add the new route before we remove any
sudo route add default gw $GATEWAY_IP $NET_INT

# Delete any other default gatways for this interface
ip route ls 0/0 dev $NET_INT|awk '{print $3}'|grep -v "$GATEWAY_IP"|xargs -n1 -I{} sudo route del default gw {}

echo "Done."

After running the script you can check public IP by running:

curl icanhazip.com