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Re: [Xen-devel] [PATCH] [XM-TEST] Use explicit (IP id==packet size) on h

To: James Dykman <dykman@xxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] [XM-TEST] Use explicit (IP id==packet size) on hping2 tests to avoid problems with IP id==0
From: Nivedita Singhvi <niv@xxxxxxxxxx>
Date: Thu, 18 May 2006 15:42:59 -0700
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James Dykman wrote:

Jim, will this not be a cause potential corruption - if we have incoming
fragments belonging to different packets with the same ipid
there is no way for the reassembly code to distinguish them.
Checksum failures might catch some, but that is no guarantee of
safe delivery.

That possibility exists in the tests as they are today... hping2 is assigning IP ids based on
its PID, completely independent of the kernel.

1. This might be fine for temporary purposes (although
   we send multiple packets of the same size in consecutive
   order, so only serialization is helping us in those
   tests, correct? Perhaps something that would be unique
   at least across the xmtest set of hpings for sure?)

If you want to solve that problem TOO, then we need to replace hping2. Any suggestions?

How about for now removing the hping tests which involve
sends of > MTU size, and using ping and netperf udp/tcp tests
to replace those (underway)?

This is just to avoid another round of bugs further down
the road when we get to SMP testing in a serious way.


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