netdev - Re: [PATCH net] ipv6: fix omitted netlink attributes when using RTEXT_FILTER_SKIP

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Message-ID: <f3bca6aa-eac9-4ffc-9f2a-f8672c2a6df0@riseup.net>
Date: Tue, 1 Apr 2025 12:31:02 +0200
From: "Fernando F. Mancera" <ffmancera@...eup.net>
To: Simon Horman <horms@...nel.org>
Cc: netdev@...r.kernel.org, sowmini.varadhan@...cle.com
Subject: Re: [PATCH net] ipv6: fix omitted netlink attributes when using
 RTEXT_FILTER_SKIP_STATS

On 01/04/2025 11:42, Simon Horman wrote:
> On Mon, Mar 31, 2025 at 06:36:51PM +0200, Fernando Fernandez Mancera wrote:
>> Using RTEXT_FILTER_SKIP_STATS should not skip non-statistics IPv6
>> netlink attributes. Move the filling of IFLA_INET6_STATS and
>> IFLA_INET6_ICMP6STATS to a helper function to avoid hitting the same
>> situation in the future.
>>
>> Fixes: d5566fd72ec1 ("rtnetlink: RTEXT_FILTER_SKIP_STATS support to avoid dumping inet/inet6 stats")
>> Signed-off-by: Fernando Fernandez Mancera <ffmancera@...eup.net>
> 
> Hi Fernando,
> 
> I think that it would be good to describe what problem the user experiences
> without this change - yes, I can see which attributes aren't dumped,
> but what problem does that cause? Doubly so as this is marked as a bug fix.
> 

Hi Simons,

In essence userspace tools use RTEXT_FILTER_SKIP_STATS to skip the IPV6 
stats when dumping the link. As this is also skipping 
IFLA_INET6_ADDR_GEN_MODE, IFLA_INET6_TOKEN and IFLA_INET6_RA_MTU, 
usespace tools are missing non-stats information when trying to skip the 
stats only so they cannot use this mechanism properly.

E.g iproute is not rendering address generation mode after they started 
to use the filter flag or NetworkManager not able to use the filter flag 
because it would break the internal tracking of the other properties.

I will leave more time for comments and will send a V2 adjusting the 
commit message.

Thanks!
Fernando.

> Thanks!
>