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From: Rick Jones <rick.jones2@hp.com>
To: Helmut Grohne <h.grohne@cygnusnetworks.de>
Cc: netdev@vger.kernel.org, David Miller <davem@davemloft.net>,
	Max Krasnyansky <maxk@qti.qualcomm.com>
Subject: Re: TUN/TAP: tap driver reports bogus interface speed in ethtool operations
Date: Tue, 23 Jul 2013 08:49:01 -0700	[thread overview]
Message-ID: <51EEA5ED.6080404@hp.com> (raw)
In-Reply-To: <E4A37B97-95FE-42C3-AD78-119BA406A44A@cygnusnetworks.de>

On 07/23/2013 06:32 AM, Helmut Grohne wrote:
>
> On 16.07.2013, at 23:41, Max Krasnyansky <maxk@qti.qualcomm.com> wrote:
>> The patch looks fine to me (must admit that I only glanced at it). Please send it to the netdev
>> mailing list netdev@vger.kernel.org, if you have't already done so.
>> CC David Miller <davem@davemloft.net> and me.
>
> Doing that. Now summarizing the issue for the new recipients:
>
> Problem:
>
> When querying a tap device for its speed using ethtool the tun driver reports a speed
> of SPEED_10. This number is hard coded into the driver. Nowadays virtual network devices
> can go way faster than that. When doing automatic bandwidth monitoring based on the
> speed reported by ethtool, tap devices tend to come up as false positives. Arguably the
> hard coded speed is wrong.
>
> Proposed solution:
>
> To that end I propose supporting the ETHTOOL_SSET command in addition to the already
> supported ETHTOOL_GSET. It would deny setting any setting except for the bandwidth
> where it would allow arbitrary values. You can find this patch attached.
>
> With this patch an administrator can increase the reported speed for tap devices and
> keep using automatic detection of interface speeds.
>
> Workarounds:
>
> Using ethtool a detection utility can determine the driver for an interface. If the
> driver matches the string "tun", the reported speed should not be used.
>
> Helmut
>

I like the idea of being able to set the reported speed for a tun/tap 
interface.

rick jones

  reply	other threads:[~2013-07-23 15:49 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <2F174B03-5074-4BA0-B91A-8F2F62C2B082@cygnusnetworks.de>
     [not found] ` <5192BDD6.6060703@qti.qualcomm.com>
     [not found]   ` <3E916AF0-C587-443D-B653-C968A96C8751@cygnusnetworks.de>
     [not found]     ` <48A2F278-A32C-47C6-AD2D-1FC15EC73B88@cygnusnetworks.de>
     [not found]       ` <51E5BE27.3060207@qti.qualcomm.com>
2013-07-23 13:32         ` TUN/TAP: tap driver reports bogus interface speed in ethtool operations Helmut Grohne
2013-07-23 15:49           ` Rick Jones [this message]
2013-07-23 15:56             ` Stephen Hemminger
2013-07-23 16:03               ` Helmut Grohne
2013-07-23 17:28           ` [RFC 1/2] tun: allow overrriding ethtool info Stephen Hemminger
2013-07-23 17:29             ` [RFC 2/2] tun: allow overriding statistics Stephen Hemminger
2013-07-23 19:04           ` TUN/TAP: tap driver reports bogus interface speed in ethtool operations Ben Hutchings
2013-07-30  6:20             ` Helmut Grohne
2013-07-30 10:51               ` Ben Hutchings

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