From 86eda3b65c6b8bd287764e6e04ffcdf01a1d8ee0 Mon Sep 17 00:00:00 2001
From: Michael Tremer <michael.tremer@ipfire.org>
Date: Thu, 29 Apr 2010 19:30:42 +0200
Subject: [PATCH] Change packet decoding by reading out ethernet type.

---
 cappie/constants.py |  2 ++
 cappie/protocol.py  | 27 +++++++++++++++------------
 2 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/cappie/constants.py b/cappie/constants.py
index 50fb016..de00993 100644
--- a/cappie/constants.py
+++ b/cappie/constants.py
@@ -19,6 +19,8 @@
 #                                                                             #
 ###############################################################################
 
+ETHERTYPE_ARP = 0x0806
+
 TYPE_ARP = 0
 
 OPERATION_REQUEST = 0
diff --git a/cappie/protocol.py b/cappie/protocol.py
index ed5f4a3..c4252de 100644
--- a/cappie/protocol.py
+++ b/cappie/protocol.py
@@ -21,6 +21,8 @@
 
 import struct
 
+import database
+
 from constants import *
 from errors import *
 
@@ -34,15 +36,17 @@ def val2mac(val):
 	return ":".join(["%02x" % ord(i) for i in val])
 
 def decode_packet(data):
-	for func in (decode_arp_packet,):
-		try:
-			p = func(data)
-		except PacketTypeError:
-			continue
+	try:
+		protocol = val2int(struct.unpack("!2s", data[12:14])[0])
+	except:
+		raise DecodeError
 
-		return p
+	try:
+		d = protocol2function[protocol](data)
+	except KeyErrror:
+		raise PacketTypeError, "Could not determine type of packet"
 
-	raise PacketTypeError, "Could not determine type of packet"
+	return database.Row(d)
 
 def decode_arp_packet(data):
 	operationmap = {
@@ -58,15 +62,10 @@ def decode_arp_packet(data):
 	}
 
 	#"hwtype" : data[:2],
-	protocol = val2int(struct.unpack("!2s", data[12:14])[0])
 	hw_addr_size = val2int(struct.unpack("!1s", data[18:19])[0])
 	hw_prot_size = val2int(struct.unpack("!1s", data[19:20])[0])
 	operation = val2int(struct.unpack("!2s", data[20:22])[0])
 
-	# Sanity checks
-	if not protocol == 0x0806:
-		raise PacketTypeError, "Not an ARP packet"
-
 	# TODO Must check hwtype here...
 
 	try:
@@ -93,3 +92,7 @@ def decode_arp_packet(data):
 
 def decode_ndp_packet(data):
 	raise PacketTypeError
+
+protocol2function = {
+	ETHERTYPE_ARP : decode_arp_packet,
+}
-- 
2.39.2