[ovs-dev] proposed flow key compatibility rules

[Jesse Gross]

On Tue, Nov 8, 2011 at 8:20 PM, Ben Pfaff <blp at nicira.com> wrote:
> On Tue, Nov 08, 2011 at 06:40:51PM -0800, Jesse Gross wrote:
>> On Tue, Nov 8, 2011 at 5:03 PM, Ben Pfaff <blp at nicira.com> wrote:
>> > Jesse and I spent some time pondering this face-to-face, so there's a
>> > bunch of discussion that hasn't shown up on the mailing list.
>> >
>> > My understanding of what we concluded is:
>> >
>> > ?? ?? ?? ??- We will add a new "encap" flow key attribute that contains
>> > ?? ?? ?? ?? ??nested attributes. ??An "encap" is used whenever layering is
>> > ?? ?? ?? ?? ??duplicated or jumps down (e.g. when a L2, L3, or L4 header
>> > ?? ?? ?? ?? ??is followed by an L2 header).
>> >
>> > ?? ?? ?? ??- The "set" action is explicitly defined to act on the
>> > ?? ?? ?? ?? ??outermost instance of a header.
>> >
>> > ?? ?? ?? ??- We will abandon the pretense that "push" and "pop" can be
>> > ?? ?? ?? ?? ??generic and introduce explicit "push_vlan" and "pop_vlan"
>> > ?? ?? ?? ?? ??actions.
>>
>> I agree that this is what we concluded.  I had one additional thought
>> though: In general, this format is now ordering independent but the
>> encap attribute is linked to the encapsulating tag but is separate.  I
>> think this is not actually ambiguous because there can only be one
>> level of encapsulation at a given nesting level and it is always
>> essentially at the end.  It's a little strange though.
>
> There are other alternatives that are odd in other ways.  Instead of
> vlan(vid,pcp),encap(...), we could use vlan(vid,pcp),vlan_encap(...),
> that is, make the encap attribute specific to what's causing the
> encapsulation, or we could use vlan_encap(vlan(vid,pcp),...).

Another thing that I thought of was:
vlan(encap_attrs(vid,pcp),...)
i.e. have a generic encapsulation attributes type with contents that
depends on the outer tag.

Like you said though, they're all weird in some way.