#!/bin/sh
#
#  file "ipchains_add"
#  Linux2.2-style firewall-add script, called by "doormand". 
#  This example can be used by systems which use ipchains.
#
#  Called with five arguments:
#
# $1 : name of the interface (e.g. eth0)
# $2 : source IP; i.e. dotted-decimal address of the 'knock' client
# $3 : source port; when this script is called for the first time
#      for a connection (man 8 doormand), this argument will be set
#      to a single "0" (0x30) character.  This means that the source
#      port is not yet known, and a broad rule allowing any source
#      port is required.
# $4 : destination IP; that is, the IP address of the interface 
#      in argument 1.
# $5 : The port number of the requested service (e.g. 22 for ssh, etc.)
#
#
if [ $3 = 0 ]
then
    ret=`ipchains -I input 1 -j ACCEPT -p tcp -i $1 -s $2     -d $4 $5 2>&1`
else
    ret=`ipchains -I input 1 -j ACCEPT -p tcp -i $1 -s $2 $3  -d $4 $5 2>&1`
fi

if [ -z "$ret" ]
then
    echo 0
else
    echo -1 3 $ret
fi