[Jeff Morriss <jeff.morriss.ws@xxxxxxxxx>]

The last time I looked at actually using composite TVBs for, for 
example, reassembly, I thought the problem was that the actual backing 
store (for the TVBs that are populated from a file) is re-used.  IOW 
each TVB handed to epan for dissection is using the same buffer.

This was deep down in the depths somewhere; can't remember exactly where.

On 10/29/2012 02:18 PM, Zadik, Maayan wrote:
> Hi Bill,
> thanks for the reference :).
>
> so here is where i'm at:
> i have data that when too big gets fragmented, then my dissector
> re-assembles it.
> every data chunk in the assembled frame is wrapped with its own header
> (basically containing the chunk's size)
> so when i send the data to my mac dissector, i need to collect only the
> data without the headers in a single TVB.
> my implementation is as below:
>
> {
> tvbuff_t* total_payload = tvb_new_composite();
>
> /* Loop over data elements */
> for (j = 0; j < num_of_data_chunks; j++)
> {
> data_size = tvb_get_ntohs(tvb, *plen);
> *plen += 2;
>
> // get data chunk
> val_ptr = tvb_get_ptr(tvb, *plen, data_size);
> tvb_temp = tvb_new_real_data(val_ptr, data_size, data_size);
> *plen += data_size;
>
> /* Compose the final buffer with the temp buffer (add the curent data
> chunk to the total data buffer) */
> tvb_composite_append(total_payload, tvb_temp);
>
> }
>
> /* Finalize the composed buffer */
> tvb_composite_finalize(total_payload);
>
> DISSECTOR_ASSERT(total_payload != NULL);
> call_dissector_only(my_mac_lte_handle, total_payload, pinfo, tree);
> }
>
> the problem occurs when i try to create a subset of this TVB:
>
> tvbuff_t *srb_tvb = tvb_new_subset(tvb, offset, rlc_data_length,
> rlc_data_length);
> call_dissector_only(my_rlc_lte_handle, srb_tvb, pinfo, tree);
>
> when printing the the original TVB's and the subset's params i see the
> following:
>
>                                             tvb_addr               1st
> byte                 offset from base      tvb length
>
>
> so, you see when i try to create a subset, instead of the data being
> 0x0b i'm getting 0xaa and i don't know why.
>
> can you spot what i'm doing wrong?
>
> Thanks,
> maayan
> ________________________________________
> From: wireshark-dev-bounces@xxxxxxxxxxxxx
> [wireshark-dev-bounces@xxxxxxxxxxxxx] on behalf of Bill Meier
> [wmeier@xxxxxxxxxxx]
> Sent: Monday, October 29, 2012 6:06 PM
> To: Developer support list for Wireshark
> Subject: Re: [Wireshark-dev] Appending 2 TVBs in Wireshark 1.8.2
>
> On 10/28/2012 12:20 PM, Zadik, Maayan wrote:
>  > Hi all,
>  >
>  > How do I create a single TVB from several data chunks?
>  >
>  > Is there a way to append two TVBs?
>  > I know the composite doesn't work. I tried it.
>  >
>  >
>  > Regards,
>  > Maayan
>  >
>  >
>  >
>
> Well: you can create your own tvb using tvb_new_real_data() pointing to
> a buffer you've created containing the data you've copied from the two
> tvb's.
>
> That being said, the composite TVB code should work. (I fixed the code
> some time ago and the code is part 1.8).
>
> (I think composite TVbs are even being used someplace in 1.80).
>
> What problems did you have using a composite TVB ?
>
> Providing the essentials of code you used would help us to see what's
> happening.
>
> Also, see epan/tvbtest.c for an example of code which creates composite
> tvb's.
>
> (Ignore the comment about "Composite tvbuffs don't work at the
> moment...". AFAIK composite TVBs should work. I apparently forgot to
> remove the comment when I did the work a while back).
>
> Bill
>
>
>
>
>
>
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