netdev - Re: [PATCH] net: Add etun driver

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Message-ID: <461748B5.30904@candelatech.com>
Date:	Sat, 07 Apr 2007 00:31:01 -0700
From:	Ben Greear <greearb@...delatech.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Jeff Garzik <jgarzik@...ox.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	Daniel Lezcano <dlezcano@...ibm.com>,
	Dmitry Mishin <dim@...nvz.org>,
	Linux Containers <containers@...ts.osdl.org>
Subject: Re: [PATCH] net: Add etun driver

Eric W. Biederman wrote:
> Ben Greear <greearb@...delatech.com> writes:
>
>   
>> I guess that will do, but then if you ever change the strings, any user-space
>> that is
>> depending on this will break or have to be modified with additional cruft.  It
>> seems
>> cleaner to me to have an ioctl or a specific place in /proc or some other
>> virtual
>> fs, but I can deal with it either way...
>>     
>
> True if the name of the driver changes from etun there is an issue.
>   
So, how about a sysfs field for this too, something like 'is-etun' or 
whatever...
Or, IOCTL works fine too, of course.
>   
>>>> Also, how do you find the peer device from user-space?  This would be very
>>>> useful
>>>> for anyone trying to manage these devices with a user-space program.
>>>>
>>>>         
>>> Currently "ethtool -S <interface>"
>>> And read the partner_ifindex.
>>>
>>>       
>> Ok, that will work.  Again, my personal preference is for a single specific
>> ioctl or proc'ish file
>> to read the specific value instead of having to parse strings, but this will do.
>>     
>
> Hmm. I guess there is string parsing to identify the index.
>
> I guess a sysfs device attribute would work as well.
>   
Yes, that would be much appreciated.
>   
>>> Further whoever generates the pair specifies the initial set of names.
>>>
>>>       
>> Yeah, but you can't depend on knowing that in an interesting environment.
>>     
>
> Frankly.  In an interesting environment I haven't been able to think of a
> way to successfully say anything about the partner device.
>
> The problem is that all identifiers are namespace local so the remote side
> is not in the current namespace the ifindex or the device name mean nothing.
>
> In that case the only remotely usable value I can return is the mac address
> of the other side.
>   
Couldn't you also show the peer's name-space id in that case?

MAC could be duplicated, so that's not a very good key.

Thanks,
Ben


-- 
Ben Greear <greearb@...delatech.com> 
Candela Technologies Inc  http://www.candelatech.com


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