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([2a01:e0a:b41:c160:e0c8:95f4:2716:85d9]) by smtp.gmail.com with ESMTPSA id l2-20020a05600c1d0200b003cf878c4468sm2256039wms.5.2022.11.02.06.25.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 02 Nov 2022 06:25:18 -0700 (PDT) Message-ID: <39232de9-9497-3a8b-294a-702ed54e273c@6wind.com> Date: Wed, 2 Nov 2022 14:25:17 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.2.2 Reply-To: nicolas.dichtel@6wind.com Subject: Re: [PATCH net-next] net: tun: bump the link speed from 10Mbps to 10Gbps Content-Language: en-US To: Ilya Maximets , netdev@vger.kernel.org Cc: Jakub Kicinski , "David S. Miller" , Eric Dumazet , Paolo Abeni , linux-kernel@vger.kernel.org References: <20221031173953.614577-1-i.maximets@ovn.org> From: Nicolas Dichtel Organization: 6WIND In-Reply-To: <20221031173953.614577-1-i.maximets@ovn.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Le 31/10/2022 à 18:39, Ilya Maximets a écrit : > The 10Mbps link speed was set in 2004 when the ethtool interface was > initially added to the tun driver. It might have been a good > assumption 18 years ago, but CPUs and network stack came a long way > since then. > > Other virtual ports typically report much higher speeds. For example, > veth reports 10Gbps since its introduction in 2007. > > Some userspace applications rely on the current link speed in > certain situations. For example, Open vSwitch is using link speed > as an upper bound for QoS configuration if user didn't specify the > maximum rate. Advertised 10Mbps doesn't match reality in a modern > world, so users have to always manually override the value with > something more sensible to avoid configuration issues, e.g. limiting > the traffic too much. This also creates additional confusion among > users. > > Bump the advertised speed to at least match the veth. > > Alternative might be to explicitly report UNKNOWN and let the user > decide on a right value for them. And it is indeed "the right way" > of fixing the problem. However, that may cause issues with bonding > or with some userspace applications that may rely on speed value to > be reported (even though they should not). Just changing the speed > value should be a safer option. > > Users can still override the speed with ethtool, if necessary. > > RFC discussion is linked below. > > Link: https://lore.kernel.org/lkml/20221021114921.3705550-1-i.maximets@ovn.org/ > Link: https://mail.openvswitch.org/pipermail/ovs-discuss/2022-July/051958.html > Signed-off-by: Ilya Maximets Reviewed-by: Nicolas Dichtel