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Date:   Thu, 22 Sep 2022 05:58:53 -0700
From:   Jakub Kicinski <kuba@kernel.org>
To:     Hangbin Liu <liuhangbin@gmail.com>
Cc:     Guillaume Nault <gnault@redhat.com>, netdev@vger.kernel.org,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Paolo Abeni <pabeni@redhat.com>,
        Ido Schimmel <idosch@nvidia.com>,
        Petr Machata <petrm@nvidia.com>,
        Florent Fourcot <florent.fourcot@wifirst.fr>,
        Nikolay Aleksandrov <razor@blackwall.org>
Subject: Re: [PATCH net-next] rtnetlink: Honour NLM_F_ECHO flag in
 rtnl_{new, set}link
Message-ID: <20220922055853.529873ad@kernel.org>
In-Reply-To: <Yyw1TRSMRUbmOOtK@Laptop-X1>
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On Thu, 22 Sep 2022 18:13:33 +0800 Hangbin Liu wrote:
> > In general I still don't think NLM_F_ECHO makes for a reasonable API.
> > It may seem okay to those who are willing to write manual netlink
> > parsers but for a normal programmer the ability to receive directly
> > notifications resulting from a API call they made is going to mean..
> > nothing they can have prior experience with. NEWLINK should have
> > reported the allocated handle / ifindex from the start :(
> > 
> > The "give me back the notifications" semantics match well your use
> > case to log what the command has done, in that case there is no need 
> > to "return" all the notifications from the API call.  
> 
> I didn't get what you mean about "no need to return all the notifications from
> the API call"? Do you ask for some update of the patch, or just talking about
> your propose of NEWLINK?

I'm talking about building "normal programmer" facing libraries on top
of netlink. The concept of ECHO fits very poorly into the normal
request-response semantics.