netdev - Re: [PATH] dev: reusing unregistered ifindex values in net

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Message-ID: <AANLkTi=p84Y3o+AgUX-59nvGzqZacm8nR0-GvstR6KmO@mail.gmail.com>
Date:	Thu, 18 Nov 2010 16:43:30 +0100
From:	Daniel Turull <daniel.turull@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	netdev@...r.kernel.org, "Voravit T." <voravit@....se>,
	Robert Olsson <robert@...julf.net>
Subject: Re: [PATH] dev: reusing unregistered ifindex values in net_device

Ok,
thanks you for you quick response.

//Daniel



On Thu, Nov 18, 2010 at 16:37, Eric Dumazet <eric.dumazet@...il.com> wrote:
> Le jeudi 18 novembre 2010 à 16:25 +0100, Daniel Turull a écrit :
>> When a new index is going to be assigned in register_netdevice,
>> the dev_new_index starts to search possible values from the last index
>> given to a device although there might be some free ifindex that has been
>> previously unregistered.  This behaviour may create gap(s) in the ifindex list.
>>
>> This patch checks for unused values from 1 and gives to the new device the
>> first available value. This limits the maximum ifindex to a smaller value.
>>
>> The ifindex will still be unique since the old value is no longer in use.
>>
>> Reported-by: Voravit Tanyingyong  <voravit@....se>
>> Signed-off-by: Daniel Turull <daniel.turull@...il.com>
>>
>> ---
>> diff --git a/net/core/dev.c b/net/core/dev.c
>> index 381b8e2..a7babab 100644
>> --- a/net/core/dev.c
>> +++ b/net/core/dev.c
>> @@ -4871,7 +4871,7 @@ int dev_ioctl(struct net *net, unsigned int cmd,
>> void __user *arg)
>>   */
>>  static int dev_new_index(struct net *net)
>>  {
>> -     static int ifindex;
>> +     int ifindex;
>>       for (;;) {
>>               if (++ifindex <= 0)
>>                       ifindex = 1;
>> --
>
> NACK
>
> Two bugs
>
> 1) ifindex is not initialized : you'll be suprised of random values
>
> 2) ifindex should not be reused. You'll be surprised so applications can
> break. SNMP comes to mind.
>
>
>
>
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