#!/bin/sh

#Define the IPv6 Link Local addresses of the known Alfred Masters
masters="fe80::ff:feee:1 fe80::ff:feee:3"


if [ "$1" != "" ]; then
    interface="$1"
else
    echo "Please provide an interface for tcpdump as argument."
    echo "For Example bat0"
    exit
fi

tcpdump -i $interface -l ip6 multicast and udp and port 16962 and ether[62:1] = 0x01  | awk '{print $3}'  | awk -F '.' '{print $1}' | while read linklocal; do
    masterfound=0
    for master in $masters
    do
        if [ "$linklocal" = "$master" ]; then
            echo "$linklocal is in the list of masters $masters"
            masterfound=1
            break
        fi
    done
    if [ ! $masterfound ]; then
        echo "Undefined Master $linklocal on $interface should be one of $masters"
    fi
done