#!/bin/bash

if [ -z "$FWD_START_PORT" -o -z "$FWD_END_PORT" -o -z "$FWD_WAN_IP" -o -z "$RAINBOW_STATEDIR" ]; then
    echo "ERROR: Required configuration is missing. Please check configuraiton file."
    exit 1
fi

check_rainbow_rules () {
    iptables -t nat -n --list RAINBOW >/dev/null 2>&1 || return 1
    iptables -t nat -S PREROUTING | grep -q RAINBOW || return 1
    return 0
}

cleanup_rainbow_rules () {
    iptables -t nat -S PREROUTING | grep RAINBOW | sed 's/^-A/-D/' | xargs -r iptables -t nat
    iptables -t nat -F RAINBOW >/dev/null 2>&1
    iptables -t nat -X RAINBOW >/dev/null 2>&1
}

init_rainbow_rules () {
    iptables -t nat -N RAINBOW
    iptables -t nat -A PREROUTING -d $FWD_WAN_IP -p tcp -m tcp -m multiport --dports ${FWD_START_PORT}:${FWD_END_PORT} -j RAINBOW
    # statedir has a files like forward.3398 that contains iptables command
    # iptables -t nat -A RAINBOW -p tcp -m tcp --dport 30001 -j DNAT --to-destination 10.75.9.1:3389
    find $RAINBOW_STATEDIR -name '*forward*' -exec bash {} \;
}

get_next_fwd_port () {
    nextport=${FWD_START_PORT}
    for port in $( iptables -t nat -S RAINBOW | sed -n 's/.*--dport\s\+\([0-9]\+\)\s\+-j\sDNAT.*/\1/p' | sort -n ); do
        [ $nextport -lt $port ] && break
        nextport=$((port+1))
    done
    if [ $nextport -gt ${FWD_END_PORT} ]; then
        echo "ERROR: No ports left to setup forwarding. Consider to configure wider port range for Rainbow GW helper" >&2
        exit 1
    fi
    echo $nextport
}

get_rainbow_fwdrule () {
    local localport=$1
    local remotesock=$2
    echo "iptables -t nat -A RAINBOW -p tcp -m tcp --dport "${localport}" -j DNAT --to-destination ${remotesock}"
}