From mboxrd@z Thu Jan  1 00:00:00 1970
From: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Subject: Re: [PATCH net] net: enable interface alias removal via rtnl
Date: Mon, 9 Oct 2017 17:25:47 +0200
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Cc: netdev@vger.kernel.org, Oliver Hartkopp <oliver@hartkopp.net>,
        Stephen Hemminger <stephen@networkplumber.org>
To: David Ahern <dsahern@gmail.com>,
        Oliver Hartkopp <socketcan@hartkopp.net>, davem@davemloft.net
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Le 09/10/2017 à 16:02, David Ahern a écrit :
> On 10/9/17 2:23 AM, Nicolas Dichtel wrote:
>> Le 06/10/2017 à 22:10, Oliver Hartkopp a écrit :
>>>
>>>
>>> On 10/06/2017 08:18 PM, David Ahern wrote:
>>>> On 10/5/17 4:19 AM, Nicolas Dichtel wrote:
>>>>> IFLA_IFALIAS is defined as NLA_STRING. It means that the minimal length of
>>>>> the attribute is 1 ("\0"). However, to remove an alias, the attribute
>>>>> length must be 0 (see dev_set_alias()).
>>>>
>>>> why not add a check in dev_set_alias that if len is 1 and the 1
>>>> character is '\0' it means remove the alias?
>> Because it requires an iproute2 patch. iproute2 doesn't send the '\0'. With the
>> command 'ip link set dummy0 alias ""', the attribute length is 0.
> 
> iproute2 needs the feature for 0-len strings or perhaps a 'noalias' option.
iproute2 needs nothing ...

> 
> You can reset the alias using the sysfs file. Given that there is a
> workaround for existing kernels and userspace, upstream can get fixed
> without changing the UAPI.
> 
I don't get the point with the UAPI. What will be broken?
I don't see why allowing an attribute with no data is a problem.