Re: [PATCH net-next v1 3/5] ipv4: enable IFA_IF_NETNSID for RTM_GETADDR

[Nicolas Dichtel <nicolas.dichtel@6wind.com>]

Le 04/09/2018 à 08:50, Jiri Benc a écrit :
> On Mon, 3 Sep 2018 21:11:30 -0600, David Ahern wrote:
>> Can only use it once per message type, but NLM_F_DUMP_FILTERED is a flag
>> that can be set to explicitly say the request is filtered as requested.
> 
> The problem is that NLM_F_DUMP_FILTERED is too coarse. There's no way
> to determine whether the netnsid was honored or whether it was not but
> other filtering took effect.
> 
> This is a general problem with netlink: unknown attributes are ignored.
> We need a way to detect that certain attribute was understood by the
> kernel or was not. And it needs to work retroactively, i.e. the
> application has to be able to determine the currently running kernel
> does not support the feature (because it's too old).
> 
> That's why we return back the attribute in responses to a request with
> IFLA_IF_NETNSID present and why we should do the same for
> IFA_IF_NETNSID.
+1

> 
>> See 21fdd092acc7e. I would like to see other filters added for addresses
>> in the same release this gets used. The only one that comes to mind for
>> addresses is to only return addresses for devices with master device
>> index N (same intent as 21fdd092acc7e for neighbors).
> 
> I also question the statement that IFA_F_NETNSID is a filter: my
> understanding of "filter" is something that limits the output to a
> certain subset. I.e., unfiltered results always contain everything that
> is in a filtered result. While with IFA_F_NETNSID, we get a completely
> different set of data. Does that really constitute a filter? Note that
> we can still filter in the target netns.
+1


Regards,
Nicolas