netdev - Re: [PATCH net-next 00/13] Control action percpu counters allocation by netlink flag

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Message-ID: <fab8fd1a-319c-0e9a-935d-a26c535acc47@mojatatu.com>
Date:   Fri, 25 Oct 2019 10:57:03 -0400
From:   Jamal Hadi Salim <jhs@...atatu.com>
To:     Vlad Buslov <vladbu@...lanox.com>
Cc:     Jiri Pirko <jiri@...nulli.us>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "xiyou.wangcong@...il.com" <xiyou.wangcong@...il.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "mleitner@...hat.com" <mleitner@...hat.com>,
        "dcaratti@...hat.com" <dcaratti@...hat.com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH net-next 00/13] Control action percpu counters allocation
 by netlink flag

On 2019-10-25 10:26 a.m., Vlad Buslov wrote:

> I've been trying to re-design this change to use high level TLV, but I
> don't understand how to make it backward compatible. If I just put new
> attribute before nested action attributes, it will fail to parse when
> older client send netlink packet without it and I don't see
> straightforward way to distinguish between the new attribute and
> following nested action attribute (which might accidentally have same
> length and fall into allowed attribute range). I don't have much
> experience working with netlink, so I might be missing something obvious
> here. However, extending existing action attributes (which are already
> conveniently parsed in tcf_action_init_1() function) with new optional
> 'flags' value seems like straightforward and backward compatible
> solution.
>

I think i understand what you are saying. Let me take a quick
look at the code and get back to you.

cheers,
jamal