Hi,

If your dissector is on top of UDP, you can check the UDP checksum.

The CRC should be the same for identical fragments.

Regards
Philippe

Date: Wed, 25 Mar 2009 17:13:35 -0800
From: [email protected]
To: [email protected]
Subject: [Wireshark-dev] How to handle duplicate fragments for a plugin written 
on top of UDP?

Hi,

We have a legacy custom plugin (written on top of UDP), which handles multicast 
packets which may be fragmented, which works fine for normal scenarios. 
However, the plugin fails to decode for the cases where there can be duplicate 
fragments (for eg. one coming from the actual host and another one from a 
firewall). The fragments are exactly the same excepting that the ethernet 
source address is different.


Can someone give me pointers as to how we could handle this special case when 
re-assembling the fragments? Is there a way to ignore packets coming from the 
firewall? Are there any sample plugins that have handled this case, which I can 
refer to?


Any suggestions would help me a lot,

Thanks,
siri


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