netdev - Re: [patch net-next 0/4] net: allow to change carrier from userspace

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Date:	Wed, 12 Dec 2012 19:49:26 +0100
From:	Jiri Pirko <jiri@...nulli.us>
To:	Stephen Hemminger <shemminger@...tta.com>
Cc:	netdev@...r.kernel.org, davem@...emloft.net, edumazet@...gle.com,
	bhutchings@...arflare.com, mirqus@...il.com,
	greearb@...delatech.com, fbl@...hat.com
Subject: Re: [patch net-next 0/4] net: allow to change carrier from userspace

Wed, Dec 12, 2012 at 07:36:32PM CET, shemminger@...tta.com wrote:
>On Wed, 12 Dec 2012 19:25:56 +0100
>Jiri Pirko <jiri@...nulli.us> wrote:
>
>> Wed, Dec 12, 2012 at 07:12:08PM CET, shemminger@...tta.com wrote:
>> >On Wed, 12 Dec 2012 19:10:17 +0100
>> >Jiri Pirko <jiri@...nulli.us> wrote:
>> >
>> >> ># ip li show dev dummy0
>> >> >12: dummy0: <NO-CARRIER,BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue state DORMANT mode DORMANT   
>> >> 
>> >> if you mean this "NO-CARRIER"
>> >> it has no direct relation with netif_carrier_ok().
>> >
>> >It is the same value (IFF_RUNNING) that is visible from user space.
>> 
>> static inline bool netif_carrier_ok(const struct net_device *dev)
>> {
>> 	        return !test_bit(__LINK_STATE_NOCARRIER, &dev->state);
>> }
>> 
>> So netif_carrier[ok/on/off] are working with on __LINK_STATE_NOCARRIER
>> bit. Not with IFF_RUNNING flag.
>
>What is the code path that you are worried about netif_carrier_ok being set or clear?
>The interaction here is complex, and right now LINK_STATE_NOCARRIER is purely
>controlled by the driver, your patch changes that, but before acking I want
>to make sure why it is required.

This patchset would provide a possibility to set or clear the carrier
from userspace. For dummy device it would serve for direct emulation
of link fail.

Also for team deriver, that would serve for teamd (userspace part) to
set the carrier actually on or off (in case of LACP runner for example
this is required).

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