Ethereal-dev: Re: [Ethereal-dev] Desegmentation atop TCP problem / TCP reassembly and desegmen
>I don't like that I have to manipulate the pinfo structures directly to
>request the desegmentation. I would rather call a function to request the
>data so the details are hidden from me and changes to the desegmentation
>code don't impact my code. I would like to see a function i.e.
>desegment_request_data( pinfo, offset, length); that would make the changes
>to the pinfo->desegment_len and pinfo->dsegment_offset.
That is exactly what tcp_dissect_pdus() will do for you.
Please grep for that function and look at the examples in the various callers.
It is very easy to use.
On Wed, 1 Sep 2004 08:58:11 -0500, Jeff Foster <jfoste@xxxxxxxxxxxx> wrote:
>
>
> From: ronnie sahlberg
> Sent: Wednesday, September 01, 2004 6:42 AM
>
> > On Wed, 1 Sep 2004 06:06:18 -0500, Jeff Foster <jfoste@xxxxxxxxxxxx> wrote:
> > >
> > > This will work for a fixed length PDU, which does seem to be Peter's
> > > situation, or a PDU with a length value in the start of the PDU.
> > > Though I found to documentation in README.developer to be somewhat
> > > confusing. A simpler example that handles only TCP data may help here.
> > >
> > > In my situation I don't know the PDU length because it contains null
> > > terminated strings. I wanted to decode the entire PDU so I return a
> > > pinfo->desegment_offset of zero with pinfo->desegment_len = tvb_len()+1.
> > > As I stated before, in the email 'TCP reassembly and desegment_offset = 0'
> > > I never see a second call to the sub_dissector by the TCP desegment code.
> >
> > pinfo->desegment_len = tvb_len()+1 is probably the problem.
> > desegment_len takes the number of bytes BEYOND the end of this segment
> > we need, so try
> > pinfo->desegment_len = 1
> > instead.
> > This will cause ethereal to reassemble this this segment with at least
> > 1 more byte, i.e. the entirety of the next segment in the sequence
> > number space.
>
> Thanks, that was exactly the problem. It seems a little obtuse to set the
> desegment_len = 1 when the desegment_offset is 0. The doc's should make it
> clear enough that desegment_len is the additional data required and not related
> to the value in desegment_offset. I was assuming that I specified the data
> offset and the amount of data required.
>
> I don't like that I have to manipulate the pinfo structures directly to
> request the desegmentation. I would rather call a function to request the
> data so the details are hidden from me and changes to the desegmentation
> code don't impact my code. I would like to see a function i.e.
> desegment_request_data( pinfo, offset, length); that would make the changes
> to the pinfo->desegment_len and pinfo->dsegment_offset.
>
>
>
> Jeff F>
>
> ***
> The information in this e-mail is confidential and intended solely for the individual or entity to whom it is addressed. If you have received this e-mail in error, please notify the sender by return e-mail, delete this e-mail, and refrain from any disclosure or action based on the information.
> ***
>
>
