[ovs-dev] [PATCH] ofproto-dpif: Init ukey->dump_seq to zero

Jan Scheurich jan.scheurich at ericsson.com
Fri Apr 6 09:34:38 UTC 2018

> -----Original Message-----
> From: Ben Pfaff [mailto:blp at ovn.org]
> Sent: Wednesday, 04 April, 2018 22:28
> Oh, that's weird.  It's as if I didn't read the patch.  Maybe I just
> read some preliminary version in another thread.
> Anyway, you're totally right.  I applied this to master.  If you're
> seeing problems in another branch, let me know and I will backport.


I think the issue was introduced into OVS by the following commit a long time ago. 

commit 23597df052262dec961fd86eb7c54d10984a1ec0
Author: Joe Stringer <joestringer at nicira.com>
Date:   Fri Jul 25 13:54:24 2014 +1200

It's a temporary glitch that can cause unexpected behavior only within the first few hundred milliseconds after datapath flow creation. It is most likely to affect "reactive" controller use cases (MAC learning, ARP handling), like the OVN test case that now failed with a small change of timing. So it is possible that one could notice short packet drops or duplicate PACKET_INs in real SDN deployments when looking close enough.

My preference would be to backport it all the way to OVS 2.5. But of course I don't have proof that there are actual problems out in the field that it would solve.

One could also do a systematic search of unit test cases that apply "sleep" or "time/warp" work-arounds for the issue and simplify these on master branch. But I fear I won't time for that.

Regards, Jan

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