On Sun, Sep 29, 2013 at 02:51:19PM +1300, Joe Stringer wrote:

On Sat, Sep 28, 2013 at 7:21 AM, Ben Pfaff [off-list ref] wrote:

quoted

On Fri, Sep 27, 2013 at 09:18:31AM +0900, Simon Horman wrote:

quoted

From: Joe Stringer <redacted>

OpenFlow 1.2 and 1.3 differ on their handling of MPLS actions in the
presence of VLAN tags. To allow correct behaviour to be committed in
each situation, this patch adds a second round of VLAN tag action
handling to commit_odp_actions(), which occurs after MPLS actions. This
is implemented with a new field in 'struct xlate_in' called 'vlan_tci'.

When an push_mpls action is composed, the flow's current VLAN state is
stored into xin->vlan_tci, and flow->vlan_tci is set to 0 (pop_vlan). If
a VLAN tag is present, it is stripped; if not, then there is no change.
Any later modifications to the VLAN state is written to xin->vlan_tci.
When committing the actions, flow->vlan_tci is used before MPLS actions,
and xin->vlan_tci is used afterwards. This retains the current datapath
behaviour, but allows VLAN actions to be applied in a more flexible
manner.

Signed-off-by: Joe Stringer <redacted>
Signed-off-by: Simon Horman <horms@verge.net.au>

The commit message talks about handling OpenFlow 1.2 and 1.3 both
properly, but I don't see how the code distinguishes between the cases.
Can you explain?  Maybe this is something added in a later patch, in
which case it would be nice to mention that in the commit message.

It is added in patch #5. IIRC this patch should cause no difference in
behaviour, but set up infrastructure to be used later.

 There seems to be a typo in the comment in vlan_tci_restore() here:

quoted

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+    /* If MPLS actions were executed after MPLS, copy the final

vlan_tci out

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+     * and restore the intermediate VLAN state. */

Right, that should probably be "...executed after VLAN actions...".

I was a little confused by the new local variable 'vlan_tci' in

quoted

do_xlate_actions().  Partly this was because the fact that I didn't find
it obvious that sometimes it points to different VLAN tags.  I think
this would be easier to see if it were initially assigned just under the
big comment rather than in an initializer, so that one would know to
look at the comment.

Perhaps the big comment could be rearranged and put above the initialiser,
something like the following:-

/* VLAN actions are stored to '*vlan_tci'. This variable initially points
to 'xin->flow->vlan_tci', so that
 * VLAN actions are applied before any MPLS actions. When an MPLS action is
translated,
 * 'vlan_tci' is updated to point to 'xin->vlan_tci'. This causes later
VLAN actions to be applied after MPLS actions.
 * Each time through the loop, 'xin->vlan_tci' is updated to reflect the
final VLAN state of the flow. */

Then, the place where 'xin->vlan_tci' is updated to '*vlan_tci' could have
a simple comment to refer back:-

/* Update the final vlan state to match the current state. */

Simon, do you mind handling the change?

Not at all. I'll include this change the next time I post the series.