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Date:	Fri, 24 Jan 2014 15:33:41 +0400
From:	Andrey Dmitrov <andrey.dmitrov@...etlabs.ru>
To:	Vlad Yasevich <vyasevic@...hat.com>
CC:	netdev@...r.kernel.org,
	"Alexandra N. Kossovsky" <Alexandra.Kossovsky@...etlabs.ru>,
	Konstantin Ushakov <Konstantin.Ushakov@...etlabs.ru>
Subject: Re: [PATCH v2] net: Correctly sync addresses from multiple sources
 to single device

On 01/22/2014 09:54 PM, Vlad Yasevich wrote:
> When we have multiple devices attempting to sync the same address
> to a single destination, each device should be permitted to sync
> it once.  To accomplish this, pass the 'sync_cnt' of the source
> address when adding the addresss to the lower device.  'sync_cnt'
> tracks how many time a given address has been succefully synced.
> This way, we know that if the 'sync_cnt' passed in is 0, we should
> sync this address.
>
> Also, turn 'synced' member back into the counter as was originally
> done in
>     commit 4543fbefe6e06a9e40d9f2b28d688393a299f079.
>     net: count hw_addr syncs so that unsync works properly.
> It tracks how many time a given address has been added via a
> 'sync' operation.  For every successfull 'sync' the counter is
> incremented, and for ever 'unsync', the counter is decremented.
> This makes sure that the address will be properly removed from
> the the lower device when all the upper devices have removed it.
>
> Reported-by: Andrey Dmitrov <andrey.dmitrov@...etlabs.ru>
> CC: Andrey Dmitrov <andrey.dmitrov@...etlabs.ru>
> CC: Alexandra N. Kossovsky <Alexandra.Kossovsky@...etlabs.ru>
> CC: Konstantin Ushakov <Konstantin.Ushakov@...etlabs.ru>
> Signed-off-by: Vlad Yasevich <vyasevic@...hat.com>
> ---
>   net/core/dev_addr_lists.c | 18 ++++++++++--------
>   1 file changed, 10 insertions(+), 8 deletions(-)
>
> diff --git a/net/core/dev_addr_lists.c b/net/core/dev_addr_lists.c
> index ec40a84..9974f48 100644
> --- a/net/core/dev_addr_lists.c
> +++ b/net/core/dev_addr_lists.c
> @@ -38,7 +38,7 @@ static int __hw_addr_create_ex(struct netdev_hw_addr_list *list,
>   	ha->type = addr_type;
>   	ha->refcount = 1;
>   	ha->global_use = global;
> -	ha->synced = sync;
> +	ha->synced = sync ? 1 : 0;
>   	ha->sync_cnt = 0;
>   	list_add_tail_rcu(&ha->list, &list->list);
>   	list->count++;
> @@ -48,7 +48,8 @@ static int __hw_addr_create_ex(struct netdev_hw_addr_list *list,
>   
>   static int __hw_addr_add_ex(struct netdev_hw_addr_list *list,
>   			    const unsigned char *addr, int addr_len,
> -			    unsigned char addr_type, bool global, bool sync)
> +			    unsigned char addr_type, bool global, bool sync,
> +			    int sync_count)
>   {
>   	struct netdev_hw_addr *ha;
>   
> @@ -66,10 +67,10 @@ static int __hw_addr_add_ex(struct netdev_hw_addr_list *list,
>   					ha->global_use = true;
>   			}
>   			if (sync) {
> -				if (ha->synced)
> +				if (ha->synced && sync_count)
>   					return -EEXIST;
>   				else
> -					ha->synced = true;
> +					ha->synced++;
>   			}
>   			ha->refcount++;
>   			return 0;
> @@ -84,7 +85,8 @@ static int __hw_addr_add(struct netdev_hw_addr_list *list,
>   			 const unsigned char *addr, int addr_len,
>   			 unsigned char addr_type)
>   {
> -	return __hw_addr_add_ex(list, addr, addr_len, addr_type, false, false);
> +	return __hw_addr_add_ex(list, addr, addr_len, addr_type, false, false,
> +				0);
>   }
>   
>   static int __hw_addr_del_entry(struct netdev_hw_addr_list *list,
> @@ -101,7 +103,7 @@ static int __hw_addr_del_entry(struct netdev_hw_addr_list *list,
>   		ha->global_use = false;
>   
>   	if (sync)
> -		ha->synced = false;
> +		ha->synced--;
>   
>   	if (--ha->refcount)
>   		return 0;
> @@ -139,7 +141,7 @@ static int __hw_addr_sync_one(struct netdev_hw_addr_list *to_list,
>   	int err;
>   
>   	err = __hw_addr_add_ex(to_list, ha->addr, addr_len, ha->type,
> -			       false, true);
> +			       false, true, ha->sync_cnt);
>   	if (err && err != -EEXIST)
>   		return err;
>   
> @@ -676,7 +678,7 @@ static int __dev_mc_add(struct net_device *dev, const unsigned char *addr,
>   
>   	netif_addr_lock_bh(dev);
>   	err = __hw_addr_add_ex(&dev->mc, addr, dev->addr_len,
> -			       NETDEV_HW_ADDR_T_MULTICAST, global, false);
> +			       NETDEV_HW_ADDR_T_MULTICAST, global, false, 0);
>   	if (!err)
>   		__dev_set_rx_mode(dev);
>   	netif_addr_unlock_bh(dev);
Everything works properly now. The patch has been tested with linux-3.12.6.

Thanks,
Andrey
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