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[2a01:cb05:8d2c:f400:4ad3:9155:53d3:40e2]) by smtp.gmail.com with ESMTPSA id iv12-20020a05600c548c00b003b5054c6cd2sm2457984wmb.36.2022.09.22.07.51.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 22 Sep 2022 07:51:44 -0700 (PDT) Date: Thu, 22 Sep 2022 16:51:42 +0200 From: Guillaume Nault To: Jakub Kicinski Cc: Hangbin Liu , netdev@vger.kernel.org, "David S. Miller" , Eric Dumazet , Paolo Abeni , Ido Schimmel , Petr Machata , Florent Fourcot , Nikolay Aleksandrov Subject: Re: [PATCH net-next] rtnetlink: Honour NLM_F_ECHO flag in rtnl_{new, set}link Message-ID: <20220922145142.GB21605@debian.home> References: <20220921030721.280528-1-liuhangbin@gmail.com> <20220921060123.1236276d@kernel.org> <20220921161409.GA11793@debian.home> <20220921155640.1f3dce59@kernel.org> <20220922110951.GA21605@debian.home> <20220922060346.280b3af8@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220922060346.280b3af8@kernel.org> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Thu, Sep 22, 2022 at 06:03:46AM -0700, Jakub Kicinski wrote: > On Thu, 22 Sep 2022 13:09:51 +0200 Guillaume Nault wrote: > > That's why I complained when RTM_NEWNSID tried to implement its own > > notification mechanism: > > https://lore.kernel.org/netdev/20191003161940.GA31862@linux.home/ > > > > I mean, let's just use the built-in mechanism, rather than reinventing > > a new one every time the need comes up. > > See, when you say "let's just use the built-in mechanism" you worry > me again. Let's be clear that no new API should require the use of > ECHO for normal operation, like finding out what the handle of an > allocated object is. I've always thought the lack of NLM_F_ECHO support in many subsystems was just an oversight, as it shouldn't take a lot of plumbing to make it work. But if you prefer to deprecate the feature then okay. I just don't see any way to pass a handle back to user space at the moment. The echo mechanism did that and was generic to all netlink families (as long as nlmsg_notify() was called with the right parameters).