netdev - Re: Bonding on bond

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Date:	Thu, 20 Jan 2011 17:12:59 +0100
From:	Nicolas de Pesloüan 
	<nicolas.2p.debian@...il.com>
To:	Jiri Bohac <jbohac@...e.cz>
CC:	Jay Vosburgh <fubar@...ibm.com>,
	"bonding-devel@...ts.sourceforge.net" 
	<bonding-devel@...ts.sourceforge.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: Bonding on bond

Le 20/01/2011 16:31, Jiri Bohac a écrit :
> On Wed, Jan 19, 2011 at 09:33:19PM +0100, Nicolas de Pesloüan wrote:
>> Even if it is possible to test for slave and for master with a
>> single condition (IFF_BONDING), I suggest to split the tests and the
>> error messages, to give end user the best possible diagnostic.
>
> OK, why not. The below patch still uses IFF_BONDING to detect a
> master is being enslaved, because IFF_MASTER is also used by the
> eql driver. No idea if it works / someone ever uses it with
> bonding, but it might collide.

Thanks Jiri.

> bonding: prohibit enslaving of bonding masters
>
> Nested bonding is not supported and will result in strange problems, e.g.:
> - netif_receive_skb() will not properly change skb->dev to point to the
>    uppoer-most bonding master
> - arp monitor will not work (dev->last_rx is only updated by hardware drivers)
> - accidentally enslaving a bonding master to itself will cause an infinite
>    recursion in the TX path
>
> This patch prevents this by prohibiting a bonding master from being further enslaved.
>
> Signed-off-by: Jiri Bohac<jbohac@...e.cz>

Reviewed-by: Nicolas de Pesloüan <nicolas.2p.debian@...e.fr>

> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index b1025b8..b117dd8 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -1453,6 +1453,12 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
>   		return -EBUSY;
>   	}
>
> +	/* cannot enslave a master */
> +	if (slave_dev->priv_flags&  IFF_BONDING) {
> +		pr_debug("Error, cannot enslave a bonding master\n");
> +		return -EBUSY;
> +	}
> +
>   	/* vlan challenged mutual exclusion */
>   	/* no need to lock since we're protected by rtnl_lock */
>   	if (slave_dev->features&  NETIF_F_VLAN_CHALLENGED) {
>

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