From 2e355defad74a58b7f36e519f209ef95c57825e1 Mon Sep 17 00:00:00 2001
From: Javier Palacios <javiplx@gmail.com>
Date: Sun, 22 Jul 2012 13:14:57 +0200
Subject: [PATCH 1/1] Create a specific function for ratiotap parsing

---
 wifiscanner/wiviz.py |   73 +++++++++++++++++++++++++++++++++-----------------
 1 file changed, 48 insertions(+), 25 deletions(-)

diff --git a/wifiscanner/wiviz.py b/wifiscanner/wiviz.py
index 3e73e6a..7d0bbc6 100755
--- a/wifiscanner/wiviz.py
+++ b/wifiscanner/wiviz.py
@@ -10,7 +10,7 @@ promiscuous = False
 read_timeout = 100 # in milliseconds
 pc = pcapy.open_live(iface, max_bytes, promiscuous, read_timeout)
 
-import ieee80211
+from ieee80211 import *
 
 import time
 
@@ -18,28 +18,10 @@ max_time = 1
 tstamp = time.time()
 discovered = []
 
-def dealWithPacket ( hdr , data ) :
-
-    if hdr.getlen() != hdr.getcaplen() :
-        print "Error in header : %d vs. %d" % ( hdr.getlen() , hdr.getcaplen() )
-        return
-    if len(data) != hdr.getlen() :
-        print "Data lenght does not match"
-        return
-
-    it_version , it_len , it_present = struct.unpack("<Bxhl",data[:8])
-    if it_version != 0 :
-        print "Bad version (%s), it is probably not radiotap header" % it_version
-        return
-    if it_len <= 0 :
-        print "Bad length on radiotap header"
-        return
-
-    radiotap = data[:it_len]
-    payload = data[it_len:]
+def parse_radiotap( radiotap , it_present ) :
 
-    format , padstr = "<" , ""
     fields = []
+    format , padstr = "<" , ""
     for name,bit,fmt,pad in ratiotap_header_bits :
 # What about  'it_present & ( 0x1 << bit )' ??
         if it_present & pow(2,bit) == pow(2,bit) :
@@ -49,20 +31,61 @@ def dealWithPacket ( hdr , data ) :
             fields.append( name )
             if fmt == "hh" :
                 fields.append( "CHANNEL_BITMAP" )
+            format += fmt
             if pad :
                 padstr += "x"
-            format += fmt
-    values = struct.unpack(format+padstr,radiotap[8:])
+    values = struct.unpack(format+padstr,radiotap])
+
+    radio_hdr = {}
+    for i in range(len(fields)) :
+        radio_hdr[fields[i]] = values[i]
 
     flags = []
     for name,value in radiotap_flags :
-        if values[1] & value == value :
+        if radio_hdr['FLAGS'] & value == value :
             flags.append( name )
+    radio_hdr['_flags'] = flags
+    if radio_hdr['FLAGS'] != 16 and radio_hdr['FLAGS'] != 18 :
+        # 16 - FCS
+        # 18 - SHORTPRE , FCS
+        print 'WARNING : Unexpected flags : (%s) %s' % ( radio_hdr['FLAGS'] , " , ".join( flags ) )
 
     channel = []
     for name,value in channel_flags :
-        if values[4] & value == value :
+        if radio_hdr['CHANNEL_BITMAP'] & value == value :
             channel.append( name )
+    if radio_hdr['CHANNEL_BITMAP'] != 160 and radio_hdr['CHANNEL_BITMAP'] != 192 :
+        # 160 - CCK , 2GHZ
+        # 192 - OFDM , 2GHZ
+        print 'WARNING : Unexpected channel flags : (%s) %s' % ( radio_hdr['CHANNEL_BITMAP'] , " , ".join( channel ) )
+    radio_hdr['_channel_bitmap'] = channel
+
+    return radio_hdr
+
+
+def dealWithPacket ( hdr , data ) :
+
+    if hdr.getlen() != hdr.getcaplen() :
+        print "Error in header : %d vs. %d" % ( hdr.getlen() , hdr.getcaplen() )
+        return
+    if len(data) != hdr.getlen() :
+        print "Data lenght does not match"
+        return
+
+    it_version , it_len , it_present = struct.unpack("<Bxhl",data[:8])
+    if it_version != 0 :
+        print "Bad version (%s), it is probably not radiotap header" % it_version
+        return
+    if it_len <= 0 :
+        print "Bad length on radiotap header"
+        return
+
+    radio_hdr = parse_radiotap( data[8:it_len] , it_present )
+    if not radio_hdr :
+        return
+
+    payload = data[it_len:]
+
 
     pointer = 0
     pcktlen = len(payload)
-- 
1.7.9.5