Linux Ethernet Bridging - May 2017 - [Bridge] [PATCH net-next 3/6] net: bridge: break if __br_mdb_del fails

Hi Nikolay,

Nikolay Aleksandrov <nikolay at cumulusnetworks.com> writes:
>>   			err = __br_mdb_del(br, entry);
>> -			if (!err)
>> -				__br_mdb_notify(dev, p, entry, RTM_DELMDB);
>> +			if (err)
>> +				break;
>> +			__br_mdb_notify(dev, p, entry, RTM_DELMDB);
>>   		}
>>   	} else {
>>   		err = __br_mdb_del(br, entry);
>> 
>
> This can potentially break user-space scripts that rely on the best-effort
> behaviour, this is the normal "delete without vid & enabled vlan
filtering".
> You can check the fdb delete code which does the same, this was
intentional.
>
> You can add an mdb entry without a vid to all vlans, add a vlan and then
try
> to remove it from all vlans where it is present - with this patch obviously
> that will fail at the new vlan.
OK good to know. That intention wasn't obvious. I can make __br_mdb_del
return void instead? What about the rest of the patchset if I do so?

Thanks,

        Vivien

On 5/18/17 6:08 PM, Vivien Didelot wrote:
> Hi Nikolay,
> 
> Nikolay Aleksandrov <nikolay at cumulusnetworks.com> writes:
> 
>>>    			err = __br_mdb_del(br, entry);
>>> -			if (!err)
>>> -				__br_mdb_notify(dev, p, entry, RTM_DELMDB);
>>> +			if (err)
>>> +				break;
>>> +			__br_mdb_notify(dev, p, entry, RTM_DELMDB);
>>>    		}
>>>    	} else {
>>>    		err = __br_mdb_del(br, entry);
>>>
>>
>> This can potentially break user-space scripts that rely on the
best-effort
>> behaviour, this is the normal "delete without vid & enabled
vlan filtering".
>> You can check the fdb delete code which does the same, this was
intentional.
>>
>> You can add an mdb entry without a vid to all vlans, add a vlan and
then try
>> to remove it from all vlans where it is present - with this patch
obviously
>> that will fail at the new vlan.
> 
> OK good to know. That intention wasn't obvious. I can make __br_mdb_del
> return void instead? What about the rest of the patchset if I do so?
> 
> Thanks,
> 
>          Vivien
> 
If you make it return void we will not be able to return proper error value
when doing a single operation (the else case). About the rest I see only some
minor style issues, I'll comment on the respective patches. Another minor
nit is
using switch() instead of if/else for the message types but that is really up to
you, I don't mind either way. :-)

Cheers,
  Nik