On Apr 29, 2008, at 9:48 AM, Maynard, Chris wrote:

> In Wireshark, if I want to capture UDP traffic on a specific port (say
> port 50000 for purposes of this discussion), I can easily set a  
> capture
> filter as "udp port 50000", and I get all the traffic I'm interested  
> in,
> including all IP fragments.

Only if you don't have any fragmented IP datagrams.  If you get any  
fragments other than the first fragment with that capture filter, that  
would be a miracle.

> So, how does Wireshark handle this?  I guess there is some magic  
> filter
> "behind the scenes" similar to what I have shown above for capturing  
> IP
> fragments that takes care of the IP fragment capturing as well?

Nope.  It handles it by not handling it; as indicated, perhaps some  
miracle happened, but Wireshark just passes the capture filter on to  
pcap_compile().
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