CHANGE: removed dedicated CLNS layer and replaced it with a better usable solution

CHANGE: made IS-IS more PEP-8 compliant

scapy/layers/clns.py

@@ -2,7 +2,7 @@
     CLNS Extension
     ~~~~~~~~~~~~~~~~~~~~~
 
-    :copyright: 2014 BENOCS GmbH, Berlin (Germany)
+    :copyright: 2014, 2015 BENOCS GmbH, Berlin (Germany)
     :author:    Marcel Patzlaff, mpatzlaff@benocs.com
     :license:   GPLv2
 
@@ -18,69 +18,67 @@
 
     :description:
 
-        This module provides a layer and registration function for
-        OSI Connectionless-mode Network Services (such as IS-IS).
-                
-    :TODO:
-
-        - rework this if a better way is found/implemented to bind
-          protocols such as IS-IS (or if IS-IS remains the sole CLN
-          protocol)
-
+        This module provides a registration function and a generic PDU
+        for OSI Connectionless-mode Network Services (such as IS-IS).
 """
 import struct
 
 from scapy.config import conf
 from scapy.fields import ByteEnumField, PacketField
 from scapy.layers.l2 import LLC
-from scapy.packet import Packet, bind_layers
-
-
-network_layer_protocol_ids= {
-    0x00 : "Null",
-    0x08 : "Q.933",
-    0x80 : "IEEE SNAP",
-    0x81 : "ISO 8438 CLNP",
-    0x82 : "ISO 9542 ES-IS",
-    0x83 : "ISO 10589 IS-IS",
-    0x8E : "IPv6",
-    0xB0 : "FRF.9",
-    0xB1 : "FRF.12",
-    0xC0 : "TRILL",
-    0xC1 : "IEEE 802.aq",
-    0xCC : "IPv4",
-    0xCF : "PPP"
+from scapy.packet import Packet, bind_top_down, bind_bottom_up
+
+
+network_layer_protocol_ids = {
+    0x00: "Null",
+    0x08: "Q.933",
+    0x80: "IEEE SNAP",
+    0x81: "ISO 8438 CLNP",
+    0x82: "ISO 9542 ES-IS",
+    0x83: "ISO 10589 IS-IS",
+    0x8E: "IPv6",
+    0xB0: "FRF.9",
+    0xB1: "FRF.12",
+    0xC0: "TRILL",
+    0xC1: "IEEE 802.aq",
+    0xCC: "IPv4",
+    0xCF: "PPP"
 }
 
 
-_cln_protocols= {}
+_cln_protocols = {}
+
 
 class _GenericClnsPdu(Packet):
-    name= "Generic CLNS PDU"
-    fields_desc= [
+    name = "Generic CLNS PDU"
+    fields_desc = [
         ByteEnumField("nlpid", 0x00, network_layer_protocol_ids),
         PacketField("rawdata", None, conf.raw_layer)
     ]
-    
-
-class ConnectionlessNetworkService(Packet):
-    name= "Connectionless-mode Network Service"
-    
-    def guess_payload_class(self, p):
-        cls= conf.raw_layer
-         
-        if len(p) >= 1:
-            nlpid = struct.unpack("!B", p[0])[0]
-            cls= _cln_protocols.get(nlpid, _GenericClnsPdu)
-             
-        return cls
+
+
+def _create_cln_pdu(s, **kwargs):
+    pdu_cls = conf.raw_layer
+
+    if len(s) >= 1:
+        nlpid = struct.unpack("!B", s[0])[0]
+        pdu_cls = _cln_protocols.get(nlpid, _GenericClnsPdu)
+
+    return pdu_cls(s, **kwargs)
+
 
 @conf.commands.register
 def register_cln_protocol(nlpid, cln_protocol_class):
     if nlpid is None or cln_protocol_class is None:
         return
-    
-    _cln_protocols[nlpid]= cln_protocol_class
+
+    chk = _cln_protocols.get(nlpid, None)
+    if chk is not None and chk != cln_protocol_class:
+        raise ValueError("different protocol already registered!")
+
+    _cln_protocols[nlpid] = cln_protocol_class
+    bind_top_down(LLC, cln_protocol_class, dsap=0xfe, ssap=0xfe, ctrl=3)
 
 
-bind_layers(LLC, ConnectionlessNetworkService, dsap=0xfe, ssap=0xfe, ctrl=3)
+bind_top_down(LLC, _GenericClnsPdu, dsap=0xfe, ssap=0xfe, ctrl=3)
\ No newline at end of file
+bind_bottom_up(LLC, _create_cln_pdu, dsap=0xfe, ssap=0xfe, ctrl=3)