Wireshark · Ethereal-dev: [Ethereal-dev] TCP stream reassembly problem

[Sergey Makarenko <SMakarenko@xxxxxxxxxxxxxx>]

Hello,

I make a dissector for a protocol which
works atop TCP and I want to use reassembly functionality provided by tcp
dissector.
All works fine until lost packet situation
occurs.
Since this protocol uses encryption
it is necessary to revceive data in correct order.
When I receive a some packet (let's
name it packet_A) and I decide to do reassembly then I return execution
to the tcp dissector and wait for more data.
Let's suppose that the next packet in
the tcp stream (packet_B) was lost. Then the next packet that my dissector
will receive will be packet_C (which follows packet_B in the tcp stream).
And only when tcp dissector will met
retransmitted packet_B it will join packet_A and packet_B and pass this
data to my subdissector.
Hence the reassembly functionality of
the tcp dissector doesn't keep the continuity of the tcp stream.
I don't see the way how subdissector
can recognize lost packet situation.
Also subdissector doesn't have access
to SEQ/ACK numbers of the tcp stream. So it can not reorder packets by
itself.
As I can see other dissectors also use
this technique and rely only on the tcp dissector functionality.

So, is there any way to deal correctly
with lost packets/retransmission for subdissector and receive data in correct
order?

Best regards,
        Sergey Makarenko.