[sorry about the delay, I kind of lost this message in my inbox]
On Wed, Aug 01, 2012 at 11:14:52PM +1200, Joe Stringer wrote:
> I've got a working copy that fixes the above criticisms, following the
> suggested approach of verifying correct ordering at the end of the
> parsing functions. I have a few queries regarding this.
>
> In the above patch, there is a test for "ofproto - packet-out with
> metadata (NXM)", in tests/ofproto.at:-
> AT_CHECK([ovs-ofctl packet-out br0 none
> 'write_metadata(0xfafafafa5a5a5a5a), controller'
> '0001020304050010203040501234'])
>
> As I understand, with this approach the above ordering of actions
> should cause an error ("write_metadata" is before "controller"). I've
> got this working. However, when I correct the order of these actions,
> the packet appears to be sent back to the controller before the
> metadata is applied:-
> NXT_PACKET_IN (xid=0x0): total_len=14 in_port=NONE tun_id=0x0
> metadata=0x0 reg0=0x0 reg1=0x0 reg2=0x0 reg3=0x0 reg4=0x0 reg5=0x0
> reg6=0x0 reg7=0x0 (via action) data_len=14 (unbuffered)
>
> If I remove the enforcement of correct ordering (and use the original
> ovs-ofctl command above), then the metadata is returned correctly as
> expected.
>
> My understanding of the pipeline is that actions should be added to
> the "action set" first, then instructions are executed, followed by
> applying the action set. However, given that instructions aren't
> supported yet, the intermediate step is yet unimplemented (or I've
> missed it.. confirm?). Additionally, because we are implementing this
> instruction as an action, it is (in the above patch) executed in the
> "apply action" phase.
>
> I see two possibilities:-
> - This is expected behaviour; the order follows the command line.
> Perhaps my testing should differ -- could use a flow_mod + barrier +
> packet_out to verify that the instruction does what it should.
Yes, this is expected behavior. Metadata can only affect behavior if:
- There's a later table that matches on the metadata (but we
don't implement OF1.1-style multiple tables yet).
- There's an action set that uses the metadata somehow (but we
don't implement OF1.1-style action sets yet).
so it may not be possible to test the implementation of the
write-metadata instruction yet.
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