Wireshark-bugs: [Wireshark-bugs] [Bug 8522] Add heuristic to dissect DVB-S2 over ethernet
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From: bugzilla-daemon@xxxxxxxxxxxxx
Date: Mon, 25 Mar 2013 13:28:07 +0000

Comment # 3 on bug 8522 from 
Evan,

Thank you for your comments.

(In reply to comment #1)
> I don't think this will quite work the way you expect? The ethernet
> dissector shouldn't be passing the ethernet header in the tvb to
> dissect_dvb_s2_modeadapt_eth, so there should be no need to skip it.

I first tried to directly use the dissect_dvb_s2_modeadapt, and was surprised
to find that the ethernet header was also passed to the function, which is why
I added the skip.

> Skipping it the way you've done also (I think) makes the function return an
> incorrect offset? You would have to add ETHERNET_HEADER_SIZE to the result
> of dissect_dvb_s2_modeadapt.

How can I check this point? Currently, the dissector does not show a "malformed
packet" message.
> 
> In general I think everything should just work if you register
> dissect_dvb_s2_modeadapt directly as a heuristic on UDP and Ethernet, and
> don't create the extra functions at all. Do you have a capture to test with
> that you could attach?

Sure, you can find it in attachment.
It is a valid DVB-S2 BBFrame, starting with the modeadaption header (sync byte
0xB8, ACM command: 0x22). It contains one BBFrame (MATYPE1: 0x62, DFL: 10864
bits), with one GSE packet, which encapsulate a 0xFF pattern filled ping, and
ends with two, 2 bytes long, "zero-ed" GSE packets.

Regards,
Audric

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