Ethereal-dev: Re: [Ethereal-dev] Accessing TCP sequence number from another dissector
The TCP sequence numbers are not exposed to any protocols above TCP by
design.
Why do your dissector need to access the sequence numbers?
Is it to detect retransmissions? If so the TCP itself already have code to
do so.
Is it to do PDU reassembly? If so the TCP layer again has code to provide
this service to the protocols
ontop of TCP.
Is it to specify where in the sequence number space the next PDU starts?
Again the TCP layer has a mechanism where
a dissector may do so.
Note that the sequence number itself can not be used alone to detect whether
a packet is resent or not since
a TCP will collaps multiple non-mss segments into a single segment during a
retransmission.
Thus a single retransmitted segment may contain partially retransmitted/lost
data , partially retransmitted data that was not lost
and new not-retransmitted data in the same single segment.
.
----- Original Message -----
From: "Alex Bond"
Sent: Thursday, August 28, 2003 9:06 PM
Subject: [Ethereal-dev] Accessing TCP sequence number from another dissector
> Hi,
>
> I need to get access to the TCP seqeunce number from a dissector other
than
> the TCP and I would
> like to know if this is possible because I need to check for resent
packets.
>
