> On Mar 22, 2017, at 1:21 PM, Ben Pfaff <b...@ovn.org> wrote:
>
> On Wed, Mar 22, 2017 at 09:30:36PM +0530, nusid...@redhat.com wrote:
>> From: Numan Siddique <nusid...@redhat.com>
>>
>> When ovs-vswitchd sends the NX_PACKET_IN2 message, it may not
>> encode ETH_TYPE of the packet. And with the commit daf4d3c18da
>> ("odp: Support conntrack orig tuple key."), the conntrack fields
>> are encoded, if set. After the commit 7befb20d0f70
>> ("nx-match: Fix oxm decode."), ovs-vswitchd is sending OFPBMC_BAD_PREREQ
>> message to the controller for the resumed packets (having conntract
>> fields).
>>
>> With the loose match criteria set to false when
>> ofputil_decode_packet_in_private() is called, the prerequisite check
>> for the mf field "ct_nw_src" is failing as ETH_TYPE is not set.
>
> The original design for NXT_RESUME was that the switch would only be
> decoding a flow that it had itself decoded and therefore any failure to
> decode is a bug. I don't think this design has changed (although I'm
> happy to be corrected) so you may be pointing out a bug that we should
> fix by fixing the flow encoder or decoder.
OVS still gets back only (metadata) fields that it itself sent. The issue is
that ETH_TYPE is not metadata, hence it is not encoded as part of metadata. The
root of the problem is that I made the conntrack original direction tuple
(which is metadata) to have the packet’s ether type as a prerequisite. Even if
the controller would send down exactly the same metadata as OVS sent out, the
controller may still be allowed to do whatever with the packet, for example,
add MPLS headers, thus changing the packet to not be an IP packet any more. In
this scenario the conntrack original direction tuple (and conntrack state in
general) becomes suspect, as an MPLS packet is untrackable by conntrack.
Maybe we should make the NXT_RESUME decoder clear out conntrack metadata if the
packet is not an IP packet (anymore), or if IPv4 metadata is present on an IPv6
packet or the other way around? To do this we could make the decoding loose as
proposed here, but then explicitly check the packet type and clear the
conntrack metadata if needed. No other metadata has any prerequisites, and if
the controller happened to add metadata that OVS does not understand it might
be OK to ignore those.
Jarno
_______________________________________________
dev mailing list
d...@openvswitch.org
https://mail.openvswitch.org/mailman/listinfo/ovs-dev
