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Wireshark-users: Re: [Wireshark-users] Having problems searching Lua dissector data

From: Jose Pedro Oliveira <jpo@xxxxxxxxxxxx>
Date: Thu, 04 Mar 2010 23:03:20 +0000
On 2010-03-04 19:18, Robert Young wrote:
> Hi there,
> 
> I'm trying to write my first Lua dissector for Wireshark.  I have a 
> really simple dissector set up which I attached below.  It populates the 
> data tree alright, but I would like to be able to search on the field I 
> defined, wc.packetid.  wc.packetid shows up as a searchable type in the 
> expression field, but doesn't seem to be populated.  Could someone tell 
> me what I'm missing?
> 
> Thanks!
> Rob Y
> 
> 
> -- trivial protocol example
> -- declare our protocol
> trivial_proto = Proto("WC","WC Protocol")
> -- create a function to dissect it
> 
> xdPacketFieldProto = ProtoField.uint32("wc.packetid", "Packet ID")
> 
> trivial_proto.fields = {wcPacketFieldProto}
> 
> function trivial_proto.dissector(buffer,pinfo,tree)
>     pinfo.cols.protocol = "XC"
>     local subtree = tree:add(trivial_proto,buffer(),"WC Protocol")
>     subtree:add(ProtoField.uint32("xd.packetid", "Packet ID"),"Protocol 
> Type is: " .. buffer(15,1):uint())
> end

Robert,

You appear to have several problems in the above Lua code. Starting
by the typos:

 * What is the name of the field?

     wc.packetid versus wd.packetid

 * What is the name of the protofield variable?

     xdPacketFieldProto versus wcPacketFieldProto

Other problems:

 * You probably want the subtree:dd line to be something like

     subtree:add( xdPacketFieldProto, buffer(15, 1) )

 * What is the size of the field?

    4 bytes (based on ProtoField.uint32) ?  or
    1 byte (based on buffer(15,1):uint()) ?


Regards,
jpo
-- 
Jos� Pedro Oliveira
* mailto:jpo@xxxxxxxxxxxx *