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SubjectRe: [PATCH net-next ] Fix time-lag of IFF_RUNNING flag consistency between vlan and real devices
Hi Stephen and Herbert

Thank you for your comments.

(2011/08/26 15:08), Stephen Hemminger wrote:
> I don't think this is the right way to solve the problem.
>
> The flags are supposed to propagate back from real device to vlan
> via network notifications.
>
> Just doing this for ioctl is not enough, API's other than user space depend on this.
> Also the user may have manually set different flags on vlan than on
> the real device.

I agreed.
I will try another way to solve this problem, as you said.


(2011/08/26 15:45), Herbert Xu wrote:
> On Thu, Aug 25, 2011 at 11:08:59PM -0700, Stephen Hemminger wrote:
>> Just doing this for ioctl is not enough, API's other than user space depend on this.
>> Also the user may have manually set different flags on vlan than on
>> the real device.
> Right, anything that tests netif_carrier_ok directly on the VLAN
> device will still be delayed.
>
> Now I remember discussing this issue in Japan. However, I can't
> recall the exact scenario in which the delay occured.
>
> Is the issue with the link status going down on the real device,
> or the real device coming up?
>
> IIRC we already have mechanisms in place to ensure that down events
> are not delayed by linkwatch. Of course it is possible that this
> isn't working for some reason, or some other part of the system is
> causing the delay.
>
> So please clarify the scenario for us Hayasaka-san. Also please
> let us know how you measured the delay.
>
> Thanks,

This issue happens when the link status is going down on the real
device.

ex) A cable is broken, or is unplugged from a NIC.

I measured the delay using ioctl with SIOCGIFFLAGS from userspace
in order to check if there is a time-lag of the flag between vlan
and real devices.

Also, you can check it using a script below.

-------------------------
#!/bin/sh
t=0
while :
do
echo $t; t=$((t+1))
echo -n real; ifconfig RealDev | grep UP
echo -n vlan; ifconfig VlanDev | grep UP
sleep 0.2
done
-------------------------

The result is shown as follows.
It is observed that there is a time-lag of RUNNING status between
real and vlan devices.


....

19
real UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
vlan UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
20
real UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
vlan UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 * A cable is unplugged from NIC.
21
real UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
vlan UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
22
real UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
vlan UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
23
real UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
vlan UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
24
real UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
vlan UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
25
real UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
vlan UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
26
real UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
vlan UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
27
real UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
vlan UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
28
real UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
vlan UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
29
real UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
vlan UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
30
real UP BROADCAST MULTICAST MTU:1500 Metric:1
vlan UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
31
real UP BROADCAST MULTICAST MTU:1500 Metric:1
vlan UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
32
real UP BROADCAST MULTICAST MTU:1500 Metric:1
vlan UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
33
real UP BROADCAST MULTICAST MTU:1500 Metric:1
vlan UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
34
real UP BROADCAST MULTICAST MTU:1500 Metric:1
vlan UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
35
real UP BROADCAST MULTICAST MTU:1500 Metric:1
vlan UP BROADCAST MULTICAST MTU:1500 Metric:1
36
real UP BROADCAST MULTICAST MTU:1500 Metric:1
vlan UP BROADCAST MULTICAST MTU:1500 Metric:1


Thanks.










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