Subject: Re: /net/mpls/conf/ethX//input duplicate entry

From: Robert Shearman <[email-masked]>
Date: Thu, 11 Jun 2015 13:55:48 +0100

On 11/06/15 00:23, Scott Feldman wrote:
> On Wed, Jun 10, 2015 at 2:58 PM, roopa <[email-masked]> wrote:
>> On 6/10/15, 1:43 PM, Scott Feldman wrote:
>>>
>>> I'm getting this dump_stack when reloading rocker driver.  Did some
>>> sysctl MPLS nodes not get cleaned up on NETDEV_UNREGISTER?
>>>
>>> Steps to repro: load rocker (on system) with rocker device, rmmod
>>> rocker, and then modprobe rocker.  I doubt this is specific to rocker:
>>> and re-registration of a netdev should hit it. I am using UDEV rules
>>> to rename kernel's ethX to a different name.  Maybe that's what
>>> tripped it up?
>>>
>> On a quick look, wondering if this is because mpls driver does not seem to
>> do a unregister and re-register sysctl
>> on device name change.

Mea culpa. Thanks for looking at this.

>>
>> diff --git a/net/mpls/af_mpls.c b/net/mpls/af_mpls.c
>> index 7b3f732..ec21a5d 100644
>> --- a/net/mpls/af_mpls.c
>> +++ b/net/mpls/af_mpls.c
>> @@ -564,6 +564,14 @@ static int mpls_dev_notify(struct notifier_block *this,
>> unsigned long event,
>>          case NETDEV_UNREGISTER:
>>                  mpls_ifdown(dev);
>>                  break;
>> +       case NETDEV_CHANGENAME:
>> +               mpls_ifdown(dev);
>> +               if ((dev->type == ARPHRD_ETHER) ||
>> +                   (dev->type == ARPHRD_LOOPBACK)) {
>> +                       mdev = mpls_add_dev(dev);
>> +                       if (IS_ERR(mdev))
>> +                               return notifier_from_errno(PTR_ERR(mdev));
>> +               }
>>          }
>>          return NOTIFY_OK;
>>   }
>
> Roopa, I tested this patch and problem goes away.  (It's missing a
> break statement, BTW).  I didn't look into the correctness of the
> patch, but at first glance it seems liek the right thing to do.  Maybe
> breaking out the renaming portions into sub-functions could keep the
> work done in NETDEV_CHANGENAME to a minimum.

I agree that breaking out the sysctl registration/unregistration is a 
good idea to not have to do more work than is necessary, and to avoid 
unintended consequences (like routes using the interface being made 
unusable).

>
> Are you sending official fix?

Roopa, let me know if you'd like me to carry this forward.

Thanks,
Rob