Add support for conntrack states in OVS flow

[lsiudut]

Linux 4.3.0 introduces support for conntrack states in OVS flow. It
breaks compatibility with weave causing errors and lack of connectivity
between containers:

Error while listening on ODP datapath: unknown flow key type 22 (value
[0 0 0 0])

Missing flow key is OVS_KEY_ATTR_CT_STATE, which in fact is 32-bit
value representing connection state pulled from conntrack. More details
are available at lkml commit topic https://lkml.org/lkml/2015/7/30/661

Although this patch solved problems for me, I'm not 100% convinced
whether this is proper solution, as spent only little time on research.
It may be treated as reminder about upcoming changes though.

[dpw]

Arggghhh...

Thanks for the PR, and the heads up. 4.3 is still at rc7, right? But I guess that means it will be released soon.

Your fix makes sense. But it would be nicer to tolerate all unknown flow keys. I'll take a look at how tricky that is later today.

[lsiudut]

Yes, this is still rc7, should be released next week.

According to OVS developer hints it's OK to handle unknown flows and let kernel deal with them, but I found the commit:

ba6e0f8.

Thus I assumed that you wanted to explicitly handle unknown flow keys :).

[dpw]

but I found the commit:

ba6e0f8.

Thus I assumed that you wanted to explicitly handle unknown flow keys :).

I may have changed my mind :)

[lsiudut]

Oh, it makes sense ;-). Well, at least you'll keep an eye on it now. Thanks!

[dpw]

I've committed 8f05974 to avoid breakage with kernel 4.3 by accepting unknown flow keys. (But not discarding them entirely - that's what it did before ba6e0f8 and it made development awkward. Now it's easy to print the unknown keys.)

I was going to merge your change anyway, because it does no harm and we might need those flow keys one day. But in testing (with weave launch --log-level=debug), I see misses with all the OVS_KEY_ATTR_CT keys, so I'd prefer to add them as a set. I don't have time right now to check the structure of all those keys right now, so I'm going to close this for now.

Thanks again for the PR though.