Re: [PATCH net-next] net, cls: allow for deleting all filters for given parent

[Cong Wang <xiyou.wangcong@gmail.com>]

On Wed, Jun 8, 2016 at 2:30 PM, Daniel Borkmann <daniel@iogearbox.net> wrote:
> On 06/06/2016 09:52 PM, Cong Wang wrote:
>>
>> On Mon, Jun 6, 2016 at 12:25 PM, Daniel Borkmann <daniel@iogearbox.net>
>> wrote:
>
> [...]
>>
>> This is fundamental for libnl to update caches.
>>
>> I don't understand why it should be separated, since notification is
>> not a feature, we already have notifications in other paths.
>>
>>> Looking into this, I would probably make this a single notification that
>>> denotes this 'wild-card' removal for that parent instead of calling
>>> tfilter_notify() for each filter separately (which allocs skb, dumps it,
>>> etc), qdisc del doesn't loop through it either, so probably fine this
>>> way.
>>
>>
>> Makes sense.
>
>
> I've been playing around with both options and am actually currently
> leaning towards the tfilter_notify() for each proto for the reason
> that user space tc monitors can simply stay as is. F.e., if someone
> keeps an older libnl binary that wouldn't understand such a wildcard
> message, then elements in libnl cache won't receive updates since the
> meta data won't match on them (average case, there probably are only
> one up to a handful of classifiers per parent) ... hm, different topic
> but still wondering whether libnl relying on such messages is a good
> idea in general since under stress tfilter_notify() can also fail and
> user space won't get the updates (except for queries with RTM_GETTFILTER).

Don't worry about any failure in tfilter_notify(), we call it in
non-wildcard removal too. Your current patch looks good to me.

Thanks!