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[84.238.136.197]) by smtp.gmail.com with ESMTPSA id v22sm1367237ljc.79.2020.03.26.05.38.57 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 26 Mar 2020 05:38:58 -0700 (PDT) Subject: Re: [PATCH v2 net-next 10/10] net: bridge: implement auto-normalization of MTU for hardware datapath To: Vladimir Oltean Cc: Ido Schimmel , Andrew Lunn , Florian Fainelli , Vivien Didelot , "David S. Miller" , Jakub Kicinski , murali.policharla@broadcom.com, Stephen Hemminger , Jiri Pirko , Jakub Kicinski , netdev References: <20200325152209.3428-1-olteanv@gmail.com> <20200325152209.3428-11-olteanv@gmail.com> <20200326101752.GA1362955@splinter> <20200326113542.GA1383155@splinter> <83375385-7881-53b7-c685-e166c8bdeba4@cumulusnetworks.com> <25bc3bf2-0dea-5667-8aae-c57a2a693bec@cumulusnetworks.com> From: Nikolay Aleksandrov Message-ID: Date: Thu, 26 Mar 2020 14:38:57 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 26/03/2020 14:25, Vladimir Oltean wrote: > On Thu, 26 Mar 2020 at 14:19, Nikolay Aleksandrov > wrote: >> >> On 26/03/2020 14:18, Vladimir Oltean wrote: >>> On Thu, 26 Mar 2020 at 14:06, Nikolay Aleksandrov >>> wrote: >>>> >>>> On 26/03/2020 13:35, Ido Schimmel wrote: >>>>> On Thu, Mar 26, 2020 at 12:25:20PM +0200, Vladimir Oltean wrote: >>>>>> Hi Ido, >>>>>> >>>>>> On Thu, 26 Mar 2020 at 12:17, Ido Schimmel wrote: >>>>>>> >>> [snip] >>>>> >>>>> I think you should be more explicit about it. Did you consider listening >>>>> to 'NETDEV_PRECHANGEMTU' notifications in relevant drivers and vetoing >>>>> unsupported configurations with an appropriate extack message? If you >>>>> can't veto (in order not to break user space), you can still emit an >>>>> extack message. >>>>> >>>> >>>> +1, this sounds more appropriate IMO >>>> >>> >>> And what does vetoing gain me exactly? The practical inability to >>> change the MTU of any interface that is already bridged and applies >>> length check on RX? >>> >> >> I was referring to moving the logic to NETDEV_PRECHANGEMTU, the rest is up to you. >> > > If I'm not going to veto, then I don't see a lot of sense in listening > on this particular notifier either. I can do the normalization just > fine on NETDEV_CHANGEMTU. > I should've been more explicit - I meant I agree that this change doesn't belong in the bridge, and handling it in a notifier in the driver seems like a better place. Yes - if it's not going to be a vetto, then CHANGEMTU is fine.