Re: Reassembling tvbuff_t

[fab12 () freesurf fr]

Hi Anders,

I'm not sure the regular reassembling algo presented in README is good for
me because my fragment do not come in sequence.
That is I can receive fragment of packet 2 between 2 fragment of packet 1.

That is why I'm wondering if my algorithm below is correct and especially
the way I use composite buffer. Is this the general spirit?

/* Fragment receipt */
 tvb_memcpy(tvb,data,offset,length)
 frag_buf=tvb_new_real_data(data,length,reported_length)
 Add frag_buf to global fragrment list

/* Upon receiption of the last fragment */
 pckt_buf=tvb_new_composite  (  void  )
 For each frag_buf of same PDU in global fragrment list {
    tvb_composite_append(pckt_buf,frag_buf)
 }

/* Then I call my dissector on the reassembled packet. */
    tvb_set_child_real_data_tvbuff(tvb, next_tvb);
    add_new_data_source(pinfo, next_tvb, "Complete PDU");

    MyDissector(next_tvb)

/* Do I need to free next_tvp? */
    free(next_tvb);


Regards
Fabien

> Hi,
> We have a reassembly API in ~/epan/reassemble.c see also the README files
> in ~/doc
> Regards
> Anders
>
> -----Original Message-----
> From: wireshark-dev-bounces () wireshark org
> [mailto:wireshark-dev-bounces () wireshark org] On Behalf Of
> fab12 () freesurf fr
> Sent: den 27 april 2011 13:38
> To: wireshark-dev () wireshark org
> Subject: [Wireshark-dev] Reassembling tvbuff_t
>
> Hi
>
> I am currently working on a dissector for some proprietary protocol and I
> need to do some reassembling of buffer.
> I am looking for information on how to handle tvbuff_t API.
>
> I have found this :
> http://wireshark.sourcearchive.com/documentation/1.0.0/tvbuff_8h_aa919b43fdba78f4be4a76aa274e6cce.html#aa919b43fdba78f4be4a76aa274e6cce
>
> which is useful but I'm not sure to understand it.
>
> With my protocol I am receiving packet in several fragment.
> The fragment header tells me if it is a head, tail or mid fragment packet.
>
> I am thinking processing as follows but I am not sure if it is the best
> way or even if it is correct:
>
> Upon reception of a fragment:  I copy it in a new tvbuff_t and save it in
> some global list:
>
> tvb_memcpy(tvb,data,offset,length)
> frag_buf=tvb_new_real_data(data,length,reported_length)
> // what is reported_length by the way?
> // Is there a better way to make a buffer copy?
> Add frag_buf to global fragrment list
>
> Upon receiption of the last fragment
> pckt_buf=tvb_new_composite  (  void  )
> For each frag_buf in global fragrment list {
>    tvb_composite_append(pckt_buf,frag_buf)
> }
>
> // Then I call my dissector on the reassembled packet.
>
> Is this the general idea?
>
> Thx
> Fabien
>
>
>
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