Re: Copying TVBs for Reassembly [Was: Filebacked-tvbuffs : GSoC'13]

[Jeff Morriss <jeff.morriss.ws () gmail com>]

On 04/18/13 15:14, Evan Huus wrote:
> This is a tangential issue that has always confused me.
>
> Why do we malloc+memcpy data for reassembly when we already have
> 'virtual' composite TVBs?
>
> Wouldn't it be more efficient (in time and memory) to create a
> composite TVB for each reassembly and then build the reassembled
> packet in it? You would never have to copy or allocate any actual
> packet data...

There are a couple of problems with doing that (that I recall):

1) Composite TVBs don't actually work (or didn't work until very recently?).

2) The data behind a TVB goes away as soon as we're done dissecting (and 
displaying) the packet.  That is, the TVB data is overwritten (IIRC) 
when the next packet is read.

I suppose there was never any real reason to try to make reassembly work 
with composite TVBs: if they're just more malloc()'d memory then why 
mess with it rather than allocate our own copy of the data?  (Well, OK, 
it would save a data copy, but...)

___________________________________________________________________________
Sent via:    Wireshark-dev mailing list <wireshark-dev () wireshark org>
Archives:    http://www.wireshark.org/lists/wireshark-dev
Unsubscribe: https://wireshark.org/mailman/options/wireshark-dev
            mailto:wireshark-dev-request () wireshark org?subject=unsubscribe