[BASH] Function to convert MAC address to IPv6 link-local address

mac_to_ipv6.bash

mac_to_ipv6() {
    local HWADDR="$1" IFACE="$2"
    local -a OCTETS
        local IPV6ADDR
  
        if [[ -z "$IFACE" ]]; then
            IFACE=$(ip route | grep ^default | sed 's/^.* dev //')
        fi
        OCTETS=( ${HWADDR//:/\ } )
    OCTETS[0]=$(printf %02x $((16#${OCTETS[0]}+0x02)))
    IPV6ADDR="fe80::${OCTETS[0]}${OCTETS[1]}:${OCTETS[2]}ff:fe${OCTETS[3]}:${OCTETS[4]}${OCTETS[5]}%$IFACE"
    echo "$IPV6ADDR"
}