Re: [Wireshark-commits] rev 36659: / /trunk/epan/dissectors/: Makefile.common packet-rohc.c

[Anders Broman <a.broman () bredband net>]

Martin Mathieson skrev 2011-04-16 15:18:
> On Sat, Apr 16, 2011 at 1:38 PM, Anders Broman <a.broman () bredband net 
> <mailto:a.broman () bredband net>> wrote:
>
>     Martin Mathieson skrev 2011-04-16 14:03:
> >     Hi Anders,
> >     There is already most of the ROHC profile in packet-pdcp-lte.c. 
> >     I'd been meaning to separate it out so that it could be used from
> >     other places (e.g. when I create UMTS PDCP...)
> >
> >     Martin
>     I missed that, how to proceed? I think the ROHC code should live
>     in a separate file I have a trace
>     with Ethertype ROHC for instance.
>     Regards
>     Anders
> >
>
> ROHC should definitely be in a separate file, which I hadn't got 
> around to doing.  My code was mostly written around 3 years ago, but 
> to be honest hasn't been used much.
>
> My implementation needs a few hints to decode the ROHC frame. Here are 
> the ROHC fields in packet-pdcp-lte.h - they are what my company's 
> decoder needs to have supplied to it.
>
>
>
> /* RoHC settings */
> 83      gboolean rohc_compression;
> 84      unsigned short rohc_ip_version;
> 85      gboolean cid_inclusion_info;
> 86      gboolean large_cid_present;
> 87      enum rohc_mode mode;
> 88      gboolean rnd;
> 89      gboolean udp_checkum_present;
> 90      unsigned short profile;
>
>
> From a very quick look, I see that your implementation is hard-wired 
> to RTP/IPv4, and comments about maybe using preferences or 
> conversation info to work out other fields.  My preference would be to 
> attach info similar to the above, and let each user fill it in as they 
> can (leaving the possibility to override with preferences).
How about in dissect_rohc() look for private data and in the private 
data supply a ROHC struct
similar to

#define ASN1_CTX_SIGNATURE 0x41435458  /* "ACTX" */

typedef struct _asn1_ctx_t {
  guint32 signature;
:

with the needed decoder input in that way it can be called from other 
places supplying the needed information
or if no struct is received use the preferences set. Some of the data 
can be inferred it the IR/IR-DYN packets are seen
 but that requires context tracking.

Could you supply the struct defenition, so it'll fit your data?

Regards
Anders
> My very next task happens to be to configure LTE PDCP, RLC and MAC 
> with info found in RRC, and some of these fields can be given then, 
> whereas others are the internal state of the contexts, which is hard 
> to know (without doing a full ROHC simulation!)...
>
> It'd be good to merge them into one standalone dissector that I could 
> then call from PDCP (LTE and UMTS sometime).  I noticed for example 
> that you don't decode all of the feedback options, so maybe my 
> implementation could help speed up the adding of some of these.
>
> There is a screenshot of my decoder in 
> http://wiki.wireshark.org/PDCP-LTE, but I expect I could send you a 
> trace file later on.
>
> Best regards,
> Martin
>
>
> >     On Sat, Apr 16, 2011 at 12:44 PM, <etxrab () wireshark org
> >     <mailto:etxrab () wireshark org>> wrote:
> >
> >         http://anonsvn.wireshark.org/viewvc/viewvc.cgi?view=rev&revision=36659
> >         <http://anonsvn.wireshark.org/viewvc/viewvc.cgi?view=rev&revision=36659>
> >
> >         User: etxrab
> >         Date: 2011/04/16 04:44 AM
> >
> >         Log:
> >          Add a basic ROCH dissector.
> >          Limitations:
> >          - Small CID
> >          - RTP profile
> >          - IPv4
> >
> >         Directory: /trunk/epan/dissectors/
> >          Changes    Path               Action
> >          +4 -3      Makefile.common    Modified
> >          +984 -0    packet-rohc.c      Added
> >
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