[ovs-dev] [PATCH] ofp-util: For OF1.0, don't wildcard PCP field when 802.1Q header absent.

Ben Pfaff blp at nicira.com
Mon Aug 24 18:04:30 UTC 2015


On Mon, Aug 24, 2015 at 10:52:10AM -0700, Jarno Rajahalme wrote:
> 
> > On Aug 20, 2015, at 5:09 PM, Ben Pfaff <blp at nicira.com> wrote:
> > 
> > On Thu, Aug 06, 2015 at 01:10:04PM -0700, Jarno Rajahalme wrote:
> >>> On Aug 5, 2015, at 9:59 PM, Ben Pfaff <blp at nicira.com> wrote:
> >>> 
> >>> OpenFlow 1.0.1 says:
> >>> 
> >>>   The dl_vlan_pcp field must be ignored when the OFPFW_DL_VLAN wildcard
> >>>   bit is set or when the dl_vlan value is set to OFP_VLAN_NONE.  Fields
> >>>   that are ignored don’t need to be wildcarded and should be set to 0.
> >>> 
> >>> Previously, OVS wildcarded the PCP field when dl_vlan was OFP_VLAN_NONE,
> >>> but this commit changes the behavior to that suggested above: the PCP
> >>> field should not be wildcarded (and should be set to 0, but the code
> >>> already did that).
> >> 
> >> This feels highly counter-intuitive, but it works due to flow parser
> >> setting the PCP bits to zeroes when there is no vlan in the
> >> packet. However, this change will make matching a bit less efficient,
> >> as generally it is faster to wildcard bits than match them. Good to
> >> see that this was changed in OF 1.1.
> > 
> > I don't think this changes the behavior in this area.  It should only
> > affect the treatment on OFP_VLAN_NONE on translation to OpenFlow 1.0.
> > OFP_VLAN_NONE was already a special-case in translation from OpenFlow
> > 1.0 to struct flow in ofputil_match_from_ofp10_match(), and I believe
> > that there should be no change there.
> > 
> > Do you see a change?
> 
> No, I did not notice that this changes only the mapping to OF 1.0 from
> the internal representation. No comment then :-)
> 
> Acked-by: Jarno Rajahalme <jrajahalme at nicira.com>

Thanks.  To make that really clear I added a paragraph to the commit
message:

    This commit only changes the translation from OVS's internal flow format
    to the OpenFlow 1.0 wire format.  Translation in the other direction and
    to other formats is unaffected.

I applied this to master.



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