scapy: contrib: ife: initial commit (#1810)

* scapy: contrib: ife: initial commit

This patch add the IFE ethertype as defined in RFC 8013
(https://tools.ietf.org/html/rfc8013). This has been tested
with the Linux implementation as described in
https://www.netdevconf.org/0.1/sessions/9.html

The code is somehow based by looking up some other ethernet based
payload as lldp.

* scapy: contrib: ife: add testcases

Author: alexaring

scapy/contrib/ife.py

@@ -0,0 +1,125 @@
+#! /usr/bin/env python
+#
+# scapy.contrib.description = ForCES Inter-FE LFB type (IFE)
+# scapy.contrib.status = loads
+
+"""
+    IFE - ForCES Inter-FE LFB type
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+    :author:    Alexander Aring, aring@mojatatu.com
+    :license:   GPLv2
+
+        This module is free software; you can redistribute it and/or
+        modify it under the terms of the GNU General Public License
+        as published by the Free Software Foundation; either version 2
+        of the License, or (at your option) any later version.
+
+        This module is distributed in the hope that it will be useful,
+        but WITHOUT ANY WARRANTY; without even the implied warranty of
+        MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+        GNU General Public License for more details.
+
+    :description:
+
+        This module provides Scapy layers for the IFE protocol.
+
+        normative references:
+            - RFC 8013
+              Forwarding and Control Element Separation (ForCES)
+              Inter-FE Logical Functional Block (LFB)
+              https://tools.ietf.org/html/rfc8013
+"""
+
+import functools
+
+from scapy.data import ETHER_TYPES
+from scapy.packet import Packet, bind_layers
+from scapy.fields import FieldLenField, PacketListField, IntField, \
+    MultipleTypeField, ShortField, ShortEnumField, StrField, PadField
+from scapy.layers.l2 import Ether
+
+ETH_P_IFE = 0xed3e
+ETHER_TYPES['IFE'] = ETH_P_IFE
+
+# The value to set for the skb mark.
+IFE_META_SKBMARK = 0x0001
+IFE_META_HASHID = 0x0002
+# Value to set for priority in the skb structure.
+IFE_META_PRIO = 0x0003
+IFE_META_QMAP = 0x0004
+# Value to set for the traffic control index in the skb structure.
+IFE_META_TCINDEX = 0x0005
+
+IFE_META_TYPES = {
+    IFE_META_SKBMARK: "SKBMark",
+    IFE_META_HASHID: "HashID",
+    IFE_META_PRIO: "Prio",
+    IFE_META_QMAP: "QMap",
+    IFE_META_TCINDEX: "TCIndex"
+}
+
+IFE_TYPES_SHORT = [IFE_META_TCINDEX]
+IFE_TYPES_INT = [
+    IFE_META_SKBMARK,
+    IFE_META_PRIO,
+]
+
+
+class IFETlv(Packet):
+    """
+    Parent Class interhit by all ForCES TLV strucutures
+    """
+    name = "IFETlv"
+
+    fields_desc = [
+        ShortEnumField("type", 0, IFE_META_TYPES),
+        FieldLenField("length", None, length_of="value",
+                      adjust=lambda pkt, x: x + 4),
+        MultipleTypeField(
+            [
+                (PadField(ShortField("value", 0), 4, padwith=b'\x00'),
+                 lambda pkt: pkt.type in IFE_TYPES_SHORT),
+                (PadField(IntField("value", 0), 4, padwith=b'\x00'),
+                 lambda pkt: pkt.type in IFE_TYPES_INT),
+            ],
+            PadField(IntField("value", 0), 4, padwith=b'\x00')
+        ),
+    ]
+
+    def extract_padding(self, s):
+        return "", s
+
+
+class IFETlvStr(IFETlv):
+    """
+    A IFE TLV with variable payload
+    """
+    fields_desc = [
+        ShortEnumField("type", 0, IFE_META_TYPES),
+        FieldLenField("length", None, length_of="value",
+                      adjust=lambda pkt, x: x + 4),
+        StrField("value", "")
+    ]
+
+
+class IFE(Packet):
+    """
+    Main IFE Packet Class
+    """
+    name = "IFE"
+
+    fields_desc = [
+        FieldLenField("mdlen", None, length_of="tlvs",
+                      adjust=lambda pkt, x: x + 2),
+        PacketListField("tlvs", None, IFETlv),
+    ]
+
+
+IFESKBMark = functools.partial(IFETlv, type=IFE_META_SKBMARK)
+IFEHashID = functools.partial(IFETlv, type=IFE_META_HASHID)
+IFEPrio = functools.partial(IFETlv, type=IFE_META_PRIO)
+IFEQMap = functools.partial(IFETlv, type=IFE_META_QMAP)
+IFETCIndex = functools.partial(IFETlv, type=IFE_META_TCINDEX)
+
+bind_layers(Ether, IFE, type=ETH_P_IFE)

test/contrib/ife.uts

@@ -0,0 +1,34 @@
+% IFE test campaign
+
+#
+# execute test:
+# > test/run_tests -P "load_contrib('ife')" -t test/contrib/ife.uts
+#
+
++ Basic layer handling
+= build basic IFE frames
+
+frm = Ether()/IFE(tlvs=[IFESKBMark(value=3), IFETCIndex(value=5)])
+
+frm = Ether(bytes(frm))
+
+assert(IFE in frm)
+assert(frm[IFE].tlvs[0].type == 1)
+assert(frm[IFE].tlvs[0].length == 8)
+assert(frm[IFE].tlvs[0].value == 3)
+assert(frm[IFE].tlvs[1].type == 5)
+assert(frm[IFE].tlvs[1].length == 6)
+assert(frm[IFE].tlvs[1].value == 5)
+
+= add padding if required
+
+frm = Ether()/IFE(tlvs=[IFETCIndex()])
+assert(len(raw(frm)) == 24)
+
+frm = Ether()/IFE(tlvs=[IFESKBMark(), IFETCIndex()])
+assert(len(raw(frm)) == 32)
+
+= variable payload
+
+frm = Ether(src="aa:aa:aa:aa:aa:aa", dst="bb:bb:bb:bb:bb:bb")/IFE(tlvs=[IFETlvStr("testsr")])
+assert bytes(frm) == b'\xbb\xbb\xbb\xbb\xbb\xbb\xaa\xaa\xaa\xaa\xaa\xaa\xed>\x00\x08testsr'