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Wireshark-dev: Re: [Wireshark-dev] SSL decryption breaks after retransmission

From: Sake Blok <sake@xxxxxxxxxx>
Date: Mon, 7 Jul 2008 15:20:43 +0200
Abhik,

I did take a look at it, but have not found the time yet to create
a proper fix.

Cheers,
     Sake


On Mon, Jul 07, 2008 at 04:03:28PM +0400, Abhik Sarkar wrote:
> Hi Sake,
> 
> I was curious to know - Are you working on this? I just wanted to know
> because some work I am doing depends (slightly) on this and I will put
> comments in the code accordingly.
> 
> Thanks!
> Abhik.
> 
> On Thu, May 29, 2008 at 9:38 PM, Sake Blok <sake@xxxxxxxxxx> wrote:
> > On Thu, May 29, 2008 at 12:19:31PM -0400, Bill Meier wrote:
> >> >>> >
> >> >>> > - Make the TCP dissector not forward retransmitted segments to higher
> >> >>> > layer protocols, just like the normal TCP stack will do on the
> >> >>> > receiving host. This will have a major impact on the way retransmitted
> >> >>> > frames are displayed. Then again, the fully dissected segment is
> >> >>> > already available.
> >>
> >> 1. Given that TCP is a streaming protocol, ISTR that a "retransmitted frame"
> >> can actually consist partially of bytes previously sent and partially of
> >> additional bytes not previously sent.
> >>
> >> If this is the case (and I'm not missing something), then presumably the tcp
> >> dissector would need to forward any "new" bytes of a frame.
> >
> > Yes indeed. When tcp reassembly is enabled, this will be taken care of
> > unless the extra data is actually the start of a new upper layer PDU. I
> > will either try to incorporate this case in my fix, or put some notes in
> > the code that it should be fixed in the future. I think there will not be
> > many cases where this happens...
> >
> >
> >> 2. How does re-assembly play into this discussion ?
> >>
> >> I haven't looked at the SSL dissector so I don't know how it works. Is
> >> re-assembly being used ?
> >>
> >> Doesn't re-assembly in effect take care of retransmissions (at least in some
> >> cases) ?
> >
> > It does, unless the retransmitted segment is the last part of the upper layer
> > PDU (which of course includes the case where the PDU consists of only one tcp
> > segment).
> >
> > Cheers,
> >   Sake
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> >
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