problem in adding message in wireshark tree

[Awadhesh Kumar <awadhesh.usa@...>]

Hi,

I am writing LUA disectors for Wireshark packets. I am seeing that my disectors are getting called multiple times for a packet. I am calculating udp packet length as below

 

udp_len_f = Field.new("udp.length")

 

function InDirectmip_proto.dissector(buffer,pinfo,tree)

 

        print(udp_len_f ( ))

 

end

 

But in second call of disectors, udp length is coming null. I don't know for what packet this is being called?

 

Also I have created tree to add my own user defined information in wireshark tree as

 

stmpsecuritytree = tree:add(InDirectmip_proto,buffer(),"STMP SECURITY HEADER");
stmptree = tree:add(InDirectmip_proto,buffer(),"STMP DATA HEADER");
subtree = tree:add(InDirectmip_proto,buffer(),"ST DATA")

 

res, status = pcall (udp_len_f )

 

if( res) then

 

stmpsecuritytree:add(buffer(0,1)," STMP Message length: " .. udp_len_f());

 

else

print (" I got exception");

 

end

 

Here at call of pcall (udp_len_f ) , res is printing as false in second call. It means function udp_len_f () has thrown exception in second call. Due to this exception my message "STMP Message length" is not added in the wireshark tree.

 

 

I want to handle the exception in following if failed

 

                stmpsecuritytree:add(buffer(0,1)," STMP Message length: " .. udp_len_f());

 

in lua when I am calling above API.

 

 

Please help me in this regard.

 

Thanks in Advance

Awadhesh.