Subject: Re: HSR: How to set IF_OPER_LOWERLAYERDOWN?

From: Arvid Brodin <[email-masked]>
Date: Wed, 27 Jun 2012 01:42:12 +0000

On 2012-06-27 00:33, Stephen Hemminger wrote:
> On Tue, 26 Jun 2012 22:28:51 +0000
> Arvid Brodin <[email-masked]> wrote:
> 
>> Hi,
>>
>> According to Documentation/networking/operstates.txt a network interface have an
>> operational state and an administrative state.
>>
>> If I understand things correctly the administrative state is the desired state set by
>> userspace, and the operational state is the actual state which depends on things like the
>> administrative state, whether a carrier is present, or (for virtual interfaces lite VLAN)
>> whether the lower interface is available.
>>
>>
>> In the driver I'm writing (for the "HSR" redundancy protocol) a hsr (virtual) interface is
>> useable as long as any of its (physical) slaves are useable. I.e. the operstate of a hsr
>> device might be set like this:
>>
>> void hsr_set_operstate()
>> {
>> 	if (!is_admin_up(hsr_dev)) /* Check IFF_UP */ {
>> 		set_operstate(hsr_dev, IF_OPER_DOWN);
>> 		return;
>> 	}
>>
>> 	if (is_operstate_up(slave1) || is_operstate_up(slave2)) /* Check IF_OPER_UP */
>> 		set_operstate(hsr_dev, IF_OPER_UP);
>> 	else
>> 		set_operstate(hsr_dev, IF_OPER_LOWERLAYERDOWN);
>> }
> 
> 
> According to 802.1X example in documentation to set it down you need to set IF_OPER_DORMANT
> not IF_OPER_LOWERLAYERDOWN.  Probably a kernel bug in there somwhere.
> 

Hmm... if you're referring to the example in Documentation/networking/operstates.txt it
seems to me that the usage of IF_OPER_DORMANT there is in compliance with RFC2863 - i.e.
the device is waiting for some kind of handshake to finish. I don't think it has anything
to do with taking the device down?

Oh, and I see now that set_operstate() is called from do_setlink() in
net/core/rtnetlink.c, which means this function is used to set operstate from userspace.
The limitations then fits with the description in operstates.txt, and this function is
probably not meant to set an interface's operational state from within the kernel. I wrote
my own hsr_set_operstate that accepts any values, and it seems to work... (?)

Is there a way to get notifications when an interface's operational state change?
NETDEV_CHANGE seems to trigger on carrier change, and NETDEV_UP/DOWN triggers when the
administrative state changes - is there something similar for operational state?

(Unfortunately NETDEV_UP/DOWN triggers before the operational state for the interface in
question changes accordingly, so it's not possible to just check dev->operstate in the
handler for these messages. NETDEV_CHANGE seems to trigger after the interface's
operational state has been changed, though.)

-- 
Arvid Brodin | Consultant (Linux)
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