twisted/pair/ip.py

   1 # -*- test-case-name: twisted.pair.test.test_ip -*-
   2 # Copyright (c) Twisted Matrix Laboratories.
   3 # See LICENSE for details.
   4
   5 #
   6
   7
   8 """Support for working directly with IP packets"""
   9
  10 import struct
  11 import socket
  12
  13 from twisted.internet import protocol
  14 from twisted.pair import raw
  15 from zope.interface import implements
  16
  17
  18 class IPHeader:
  19     def __init__(self, data):
  20
  21         (ihlversion, self.tos, self.tot_len, self.fragment_id, frag_off,
  22          self.ttl, self.protocol, self.check, saddr, daddr) \
  23          = struct.unpack("!BBHHHBBH4s4s", data[:20])
  24         self.saddr = socket.inet_ntoa(saddr)
  25         self.daddr = socket.inet_ntoa(daddr)
  26         self.version = ihlversion & 0x0F
  27         self.ihl = ((ihlversion & 0xF0) >> 4) << 2
  28         self.fragment_offset = frag_off & 0x1FFF
  29         self.dont_fragment = (frag_off & 0x4000 != 0)
  30         self.more_fragments = (frag_off & 0x2000 != 0)
  31
  32 MAX_SIZE = 2L**32
  33
  34 class IPProtocol(protocol.AbstractDatagramProtocol):
  35     implements(raw.IRawPacketProtocol)
  36
  37     def __init__(self):
  38         self.ipProtos = {}
  39
  40     def addProto(self, num, proto):
  41         proto = raw.IRawDatagramProtocol(proto)
  42         if num < 0:
  43             raise TypeError, 'Added protocol must be positive or zero'
  44         if num >= MAX_SIZE:
  45             raise TypeError, 'Added protocol must fit in 32 bits'
  46         if num not in self.ipProtos:
  47             self.ipProtos[num] = []
  48         self.ipProtos[num].append(proto)
  49
  50     def datagramReceived(self,
  51                          data,
  52                          partial,
  53                          dest,
  54                          source,
  55                          protocol):
  56         header = IPHeader(data)
  57         for proto in self.ipProtos.get(header.protocol, ()):
  58             proto.datagramReceived(data=data[20:],
  59                                    partial=partial,
  60                                    source=header.saddr,
  61                                    dest=header.daddr,
  62                                    protocol=header.protocol,
  63                                    version=header.version,
  64                                    ihl=header.ihl,
  65                                    tos=header.tos,
  66                                    tot_len=header.tot_len,
  67                                    fragment_id=header.fragment_id,
  68                                    fragment_offset=header.fragment_offset,
  69                                    dont_fragment=header.dont_fragment,
  70                                    more_fragments=header.more_fragments,
  71                                    ttl=header.ttl,
  72                                    )