From mboxrd@z Thu Jan 1 00:00:00 1970 From: Simon Horman Subject: Re: [PATCH v2.51 1/5] ofp-actions: Allow Consistency checking of OF1.3+ VLAN actions after mpls_push Date: Thu, 5 Dec 2013 09:51:39 +0900 Message-ID: <20131205005139.GA21443@verge.net.au> References: <1385005606-30130-1-git-send-email-horms@verge.net.au> <1385005606-30130-2-git-send-email-horms@verge.net.au> <20131204212429.GA11354@nicira.com> <20131204235849.GB21448@verge.net.au> <20131205004417.GD11354@nicira.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: dev@openvswitch.org, netdev@vger.kernel.org, Jesse Gross , Pravin B Shelar , Ravi K , Joe Stringer To: Ben Pfaff Return-path: Received: from kirsty.vergenet.net ([202.4.237.240]:41288 "EHLO kirsty.vergenet.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933207Ab3LEAvm (ORCPT ); Wed, 4 Dec 2013 19:51:42 -0500 Content-Disposition: inline In-Reply-To: <20131205004417.GD11354@nicira.com> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, Dec 04, 2013 at 04:44:17PM -0800, Ben Pfaff wrote: > On Thu, Dec 05, 2013 at 08:58:49AM +0900, Simon Horman wrote: > > On Wed, Dec 04, 2013 at 01:24:29PM -0800, Ben Pfaff wrote: > > > On Thu, Nov 21, 2013 at 12:46:42PM +0900, Simon Horman wrote: > > > > The aim of this patch is to support provide infrastructure for verification > > > > of VLAN actions after an mpls_push action for OpenFlow1.3. This supplements > > > > existing support for verifying these actions for pre-OpenFlow1.3. > > > > > > > > In OpenFlow1.1 and 1.2 MPLS tags are pushed after any VLAN tags that > > > > immediately follow the ethernet header. This is pre-OpenFlow1.3 tag > > > > ordering. Open vSwitch also uses this ordering when supporting MPLS > > > > actions via Nicira extensions to OpenFlow1.0. > > > > > > > > When using pre-OpenFlow1.3 tag ordering an MPLS push action does not > > > > affect the VLANs of a packet. If VLAN tags are present immediately after > > > > the ethernet header then they remain present there. > > > > > > > > In of OpenFlow1.3+ MPLS LSEs are pushed before any VLAN tags that > > > > immediately follow the ethernet header. This is OpenFlow1.3+ tag > > > > ordering. > > > > > > > > When using OpenFlow1.3+ tag ordering an MPLS push action affects the > > > > VLANs of a packet as any VLAN tags previously present after the ethernet > > > > header are moved to be immediately after the newly pushed MPLS LSE. Thus > > > > for the purpose of action consistency checking a packet may be changed > > > > from a VLAN packet to a non-VLAN packet. > > > > > > > > In this way the effective value of the VLAN TCI of a packet may differ > > > > after an MPLS push depending on the OpenFlow version in use. > > > > > > > > This patch does not enable the logic described above. > > > > Rather it is disabled in ofpacts_check__(). It should > > > > be enabled when support for OpenFlow1.3+ tag order is added > > > > and enabled. > > > > > > > > Signed-off-by: Simon Horman > > > > > > As far as I can tell this doesn't make sense, because where the MPLS > > > tag goes is a property of the action that we know at the time we parse > > > the push_mpls action. So why isn't this patch just the following? > > > > > > diff --git a/lib/ofp-actions.c b/lib/ofp-actions.c > > > index a02f842..f444374 100644 > > > --- a/lib/ofp-actions.c > > > +++ b/lib/ofp-actions.c > > > @@ -2071,6 +2071,9 @@ ofpact_check__(enum ofputil_protocol *usable_protocols, struct ofpact *a, > > > * Thus nothing can be assumed about the network protocol. > > > * Temporarily mark that we have no nw_proto. */ > > > flow->nw_proto = 0; > > > + if (ofpact_get_PUSH_MPLS(a)->position == OFPACT_MPLS_BEFORE_VLAN) { > > > + flow->vlan_tci = 0; > > > + } > > > return 0; > > > > That was more or less what I originally tried. However I believe that it > > doesn't work because ofpact_get_PUSH_MPLS(a)->position may not have been > > set at the time that ofpact_check__ is called. In particular this occurs > > when it is called indirectly from parse_ofp_str__. > > > > Moreover, when ofpact_check__ is called indirectly from parse_ofp_str__ it > > is used to check actions when a one of number of protocols may be used, > > that is multiple bits of *usable_protocols. If we could rely on > > ofpact_get_PUSH_MPLS(a)->position then I believe that implies that if it is > > set to OFPACT_MPLS_BEFORE_VLAN all pre-OpenFlow1.3 bits of > > *usable_protocols need to be cleared. Otherwise all OpenFlow1.3+ bits > > would need to be cleared. > > I think this might be a mistake in how we define the syntax that > parse_ofp_str__() parses. If I write "actions=push_mpls" on an > ovs-ofctl command line, then I want that to have some specific > meaning. I don't want it to mean "do one thing if you happen to > negotiate OpenFlow 1.2 or some other thing if you happen to negotiate > OpenFlow 1.3", because that's totally unusable and broken from a user > perspective. To clarify, that is exactly what this series was trying to do. I think there is some precedence in the handling of actions that set_vlans. Some OF versions implicitly push a tag, some don't. But I do agree that the behaviour you describe above would be very confusing for users. > So if that the issue then I think we should change the > syntax. One way would be to have "push_mpls" default to the 1.3 > behavior (which seems generally saner) and allow the user to specify > an option to get the 1.2 behavior. Sure, I think I am happy with that idea. By an option do you mean a different action name, for example append_mpls, or push_mpls_after_vlan? Or do you have something else in mind?