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

Jarno Rajahalme jrajahalme at nicira.com
Mon Aug 24 17:52:10 UTC 2015


> 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>

  Jarno

>> It would be helpful if DESIGN.md reminded that OFPFW_* values here are
>> flags that indicate if the given field should be wildcarded.
>> 
>> So, this comment could read:
>> 
>>  - OF1.0 and OF1.1: wwww/x,yy/z means dl_vlan wwww, OFPFW_DL_VLAN x,
>>    dl_vlan_pcp yy, and OFPFW_DL_VLAN_PCP z.  If OFPFW_DL_VLAN or
>>    OFPFW_DL_VLAN_PCP is 1, the corresponding field value is wildcarded,
>>    otherwise it is matched.  ? means that the given
>>    bits are ignored (their conventional values are 0000/x,00/0 in
>>    OF1.0, 0000/x,00/1 in OF1.1; x is never ignored).  <none> means
>>    that the given match is not supported.
> 
> Thanks, I folded that in.
> 
> Thanks,
> 
> Ben.




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