allow-ssh-host

#!/bin/bash
#
# allow-ssh-host:
#
# Copyright (c) 2016 root. All rights reserved.
# 
#
# $Id:$
#

set -e

if [ -z "${1}" ]; then
    echo "No host name specified; bailing"
    exit 17
fi

ADDR=$(host -4 "${1}" | awk '{print $NF}' | head -n 1)

if ! [[ "${ADDR}" =~ (([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5]) ]] ; then
    exit 21
fi

echo "${ADDR}" > "/etc/network/${1}.new"

if [ -e "/etc/network/${1}.dyn" ] ; then
    OLDADDR=$(cat "/etc/network/${1}.dyn")
else
    exit 25
fi

if [ x"${OLDADDR}" == x"${ADDR}" ] ; then
    # nothing to do so
    rm "/etc/network/${1}.new"
    exit 30
fi

# remove old address from firewall
iptables -C INPUT -s "${OLDADDR}"/32 -i eth0 -j ACCEPT && iptables -D INPUT -s "${OLDADDR}"/32 -i eth0 -j ACCEPT
iptables -C FORWARD -s "${OLDADDR}"/32 -i eth0 -j ACCEPT && iptables -D FORWARD -s "${OLDADDR}"/32 -i eth0 -j ACCEPT 
# add new rule
iptables -I INPUT 5 -s "${ADDR}"/32 -i eth0 -j ACCEPT
iptables -I FORWARD 5 -s "${ADDR}"/32 -i eth0 -j ACCEPT
# move file to become new
mv "/etc/network/${1}.new" "/etc/network/${1}.dyn"
# exit