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

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Message-ID: <1290094628.2781.195.camel@edumazet-laptop>
Date:	Thu, 18 Nov 2010 16:37:08 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Daniel Turull <daniel.turull@...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

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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