# This file is part of Scapy
# See http://www.secdev.org/projects/scapy for more information
# Copyright (C) Philippe Biondi <phil@secdev.org>
# This program is published under a GPLv2 license

"""
LLMNR (Link Local Multicast Node Resolution).

[RFC 4795]

LLMNR is based on the DNS packet format (RFC1035 Section 4)
RFC also envisions LLMNR over TCP. Like vista, we don't support it -- arno
"""

import struct

from scapy.fields import BitEnumField, BitField, ShortField
from scapy.packet import Packet, bind_layers, bind_bottom_up
from scapy.compat import orb
from scapy.layers.inet import UDP
from scapy.layers.dns import DNSQRField, DNSRRField, DNSRRCountField


_LLMNR_IPv6_mcast_Addr = "FF02:0:0:0:0:0:1:3"
_LLMNR_IPv4_mcast_addr = "224.0.0.252"


class LLMNRQuery(Packet):
    name = "Link Local Multicast Node Resolution - Query"
    fields_desc = [ShortField("id", 0),
                   BitField("qr", 0, 1),
                   BitEnumField("opcode", 0, 4, {0: "QUERY"}),
                   BitField("c", 0, 1),
                   BitField("tc", 0, 2),
                   BitField("z", 0, 4),
                   BitEnumField("rcode", 0, 4, {0: "ok"}),
                   DNSRRCountField("qdcount", None, "qd"),
                   DNSRRCountField("ancount", None, "an"),
                   DNSRRCountField("nscount", None, "ns"),
                   DNSRRCountField("arcount", None, "ar"),
                   DNSQRField("qd", "qdcount"),
                   DNSRRField("an", "ancount"),
                   DNSRRField("ns", "nscount"),
                   DNSRRField("ar", "arcount", 0)]
    overload_fields = {UDP: {"sport": 5355, "dport": 5355}}

    def hashret(self):
        return struct.pack("!H", self.id)


class LLMNRResponse(LLMNRQuery):
    name = "Link Local Multicast Node Resolution - Response"
    qr = 1

    def answers(self, other):
        return (isinstance(other, LLMNRQuery) and
                self.id == other.id and
                self.qr == 1 and
                other.qr == 0)


class _LLMNR(Packet):
    @classmethod
    def dispatch_hook(cls, _pkt=None, *args, **kargs):
        if len(_pkt) >= 2:
            if (orb(_pkt[2]) & 0x80):  # Response
                return LLMNRResponse
            else:                  # Query
                return LLMNRQuery
        return cls


bind_bottom_up(UDP, _LLMNR, dport=5355)
bind_bottom_up(UDP, _LLMNR, sport=5355)
bind_layers(UDP, _LLMNR, sport=5355, dport=5355)

# LLMNRQuery(id=RandShort(), qd=DNSQR(qname="vista.")))