[ovs-dev] [PATCH 2/3] odp-util: Always export the priority and skb_mark netline attributes.

Jesse Gross jesse at nicira.com
Mon Aug 5 19:46:43 UTC 2013


On Mon, Aug 5, 2013 at 12:34 PM, Ben Pfaff <blp at nicira.com> wrote:
> On Mon, Aug 05, 2013 at 11:22:49AM -0700, Jesse Gross wrote:
>> This information is factually correct but it's not really related to
>> the change in this commit.
>>
>> The problem here is very simple: the current protocol allows a default
>> value of zero if either mark or priority is not specified (this
>> actually is part of the ABI). When userspace serializes either the
>> value or mask it looks at the value and omits the netlink attribute if
>> it is zero. This is a bug because an exact match on zero turns into a
>> wildcard of the field.
>>
>> These two fields (plus input port and EtherType) are special because
>> they can be omitted whereas most other values are required to be fully
>> specified. These protocol variations tend to cause bugs (as above)
>> when we evolve the protocol because an exception that makes sense in
>> one context might not be logical in another. Since the default value
>> for mark and priority are merely shorthands, we can push the protocol
>> in a more consistent direction by ignoring the shortcut and always
>> serializing the values.
>
> Thanks, like this?

Looks good, thanks.



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