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#! /usr/bin/env python
# scapy.contrib.description = IGMP/IGMPv2
# scapy.contrib.status = loads
# TODO: scapy 2 has function getmacbyip, maybe it can replace igmpize
# at least from the MAC layer
from scapy.all import *
#--------------------------------------------------------------------------
def isValidMCAddr(ip):
"""convert dotted quad string to long and check the first octet"""
FirstOct=atol(ip)>>24 & 0xFF
return (FirstOct >= 224) and (FirstOct <= 239)
#--------------------------------------------------------------------------
class IGMP(Packet):
"""IGMP Message Class for v1 and v2.
This class is derived from class Packet. You need to "igmpize"
the IP and Ethernet layers before a full packet is sent.
a=Ether(src="00:01:02:03:04:05")
b=IP(src="1.2.3.4")
c=IGMP(type=0x12, gaddr="224.2.3.4")
c.igmpize(b, a)
print "Joining IP " + c.gaddr + " MAC " + a.dst
sendp(a/b/c, iface="en0")
Parameters:
type IGMP type field, 0x11, 0x12, 0x16 or 0x17
mrtime Maximum Response time (zero for v1)
gaddr Multicast Group Address 224.x.x.x/4
See RFC2236, Section 2. Introduction for definitions of proper
IGMPv2 message format http://www.faqs.org/rfcs/rfc2236.html
"""
name = "IGMP"
igmptypes = { 0x11 : "Group Membership Query",
0x12 : "Version 1 - Membership Report",
0x16 : "Version 2 - Membership Report",
0x17 : "Leave Group"}
fields_desc = [ ByteEnumField("type", 0x11, igmptypes),
ByteField("mrtime",20),
XShortField("chksum", None),
IPField("gaddr", "0.0.0.0")]
#--------------------------------------------------------------------------
def post_build(self, p, pay):
"""Called implicitly before a packet is sent to compute and place IGMP checksum.
Parameters:
self The instantiation of an IGMP class
p The IGMP message in hex in network byte order
pay Additional payload for the IGMP message
"""
p += pay
if self.chksum is None:
ck = checksum(p)
p = p[:2]+chr(ck>>8)+chr(ck&0xff)+p[4:]
return p
#--------------------------------------------------------------------------
def mysummary(self):
"""Display a summary of the IGMP object."""
if isinstance(self.underlayer, IP):
return self.underlayer.sprintf("IGMP: %IP.src% > %IP.dst% %IGMP.type% %IGMP.gaddr%")
else:
return self.sprintf("IGMP %IGMP.type% %IGMP.gaddr%")
#--------------------------------------------------------------------------
def igmpize(self, ip=None, ether=None):
"""Called to explicitely fixup associated IP and Ethernet headers
Parameters:
self The instantiation of an IGMP class.
ip The instantiation of the associated IP class.
ether The instantiation of the associated Ethernet.
Returns:
True The tuple ether/ip/self passed all check and represents
a proper IGMP packet.
False One of more validation checks failed and no fields
were adjusted.
The function will examine the IGMP message to assure proper format.
Corrections will be attempted if possible. The IP header is then properly
adjusted to ensure correct formatting and assignment. The Ethernet header
is then adjusted to the proper IGMP packet format.
"""
# The rules are:
# 1. the Max Response time is meaningful only in Membership Queries and should be zero
# otherwise (RFC 2236, section 2.2)
if (self.type != 0x11): #rule 1
self.mrtime = 0
if (self.adjust_ip(ip) == True):
if (self.adjust_ether(ip, ether) == True): return True
return False
#--------------------------------------------------------------------------
def adjust_ether (self, ip=None, ether=None):
"""Called to explicitely fixup an associated Ethernet header
The function adjusts the ethernet header destination MAC address based on
the destination IP address.
"""
# The rules are:
# 1. send to the group mac address address corresponding to the IP.dst
if ip != None and ip.haslayer(IP) and ether != None and ether.haslayer(Ether):
iplong = atol(ip.dst)
ether.dst = "01:00:5e:%02x:%02x:%02x" % ( (iplong>>16)&0x7F, (iplong>>8)&0xFF, (iplong)&0xFF )
# print "igmpize ip " + ip.dst + " as mac " + ether.dst
return True
else:
return False
#--------------------------------------------------------------------------
def adjust_ip (self, ip=None):
"""Called to explicitely fixup an associated IP header
The function adjusts the IP header based on conformance rules
and the group address encoded in the IGMP message.
The rules are:
1. Send General Group Query to 224.0.0.1 (all systems)
2. Send Leave Group to 224.0.0.2 (all routers)
3a.Otherwise send the packet to the group address
3b.Send reports/joins to the group address
4. ttl = 1 (RFC 2236, section 2)
5. send the packet with the router alert IP option (RFC 2236, section 2)
"""
if ip != None and ip.haslayer(IP):
if (self.type == 0x11):
if (self.gaddr == "0.0.0.0"):
ip.dst = "224.0.0.1" # IP rule 1
retCode = True
elif isValidMCAddr(self.gaddr):
ip.dst = self.gaddr # IP rule 3a
retCode = True
else:
print "Warning: Using invalid Group Address"
retCode = False
elif ((self.type == 0x17) and isValidMCAddr(self.gaddr)):
ip.dst = "224.0.0.2" # IP rule 2
retCode = True
elif ((self.type == 0x12) or (self.type == 0x16)) and (isValidMCAddr(self.gaddr)):
ip.dst = self.gaddr # IP rule 3b
retCode = True
else:
print "Warning: Using invalid IGMP Type"
retCode = False
else:
print "Warning: No IGMP Group Address set"
retCode = False
if retCode == True:
ip.ttl=1 # IP Rule 4
ip.options=[IPOption_Router_Alert()] # IP rule 5
return retCode
bind_layers( IP, IGMP, frag=0, proto=2)
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