## This file is part of Scapy
## See http://www.secdev.org/projects/scapy for more informations
## Copyright (C) Philippe Biondi <phil@secdev.org>
## Copyright (C) 6WIND <olivier.matz@6wind.com>
## This program is published under a GPLv2 license

"""
VRRP (Virtual Router Redundancy Protocol).
"""

from scapy.packet import *
from scapy.fields import *
from scapy.layers.inet import IP

IPPROTO_VRRP=112

# RFC 3768 - Virtual Router Redundancy Protocol (VRRP)
class VRRP(Packet):
    fields_desc = [
        BitField("version" , 2, 4),
        BitField("type" , 1, 4),
        ByteField("vrid", 1),
        ByteField("priority", 100),
        FieldLenField("ipcount", None, count_of="addrlist", fmt="B"),
        ByteField("authtype", 0),
        ByteField("adv", 1),
        XShortField("chksum", None),
        FieldListField("addrlist", [], IPField("", "0.0.0.0"),
                       count_from = lambda pkt: pkt.ipcount),
        IntField("auth1", 0),
        IntField("auth2", 0) ]

    def post_build(self, p, pay):
        if self.chksum is None:
            ck = checksum(p)
            p = p[:6]+bytes([(ck>>8),(ck&0xff)])+p[8:]
        return p

bind_layers( IP,            VRRP,          proto=IPPROTO_VRRP)