Subject: Re: [PATCH net v2 7/9] bridge: Properly check if local fdb entry can be deleted in br_fdb_delete_by_port

From: Vlad Yasevich <[email-masked]>
Date: Tue, 17 Dec 2013 14:12:08 -0500

On 12/17/2013 07:03 AM, Toshiaki Makita wrote:
> br_fdb_delete_by_port() doesn't care about vlan and mac address of the
> bridge device.
> 
> As the check is almost the same as mac address changing, slightly modify
> fdb_delete_local() and use it.
> 
> Note:
> - We change the dst of a local entry when the same address is found.
>   This occurs in the case kernel has inserted the same address for another
>   port but has failed due to dup. We can regard changing dst as deleting
>   old one and inserting new one that should have been added by the dup
>   port, so we can always set its added_by_user to 0 in fdb_delete_local().

I disagree.  What happens if the user tries add a duplicate fdb with
the local bit set?  That is permitted and in fact a default because in
iproute right now.  That fdb should persist until the port is removed or
user removes the fdb.

added_by_user flag should only be changed in the netlink code since the
user has full control of it.

-vlad
> 
> - This is a slight change in behavior where the bridge device can receive
>   the traffic to the old address during the short window between calling
>   del_nbp() and br_stp_recalculate_bridge_id() in br_del_if(). However,
>   it is not a problem because we still have the address on the bridge device.
> 
> Signed-off-by: Toshiaki Makita <[email-masked]>
> ---
>  net/bridge/br_fdb.c | 25 ++++++-------------------
>  1 file changed, 6 insertions(+), 19 deletions(-)
> 
> diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
> index 817f138..bd43cb1 100644
> --- a/net/bridge/br_fdb.c
> +++ b/net/bridge/br_fdb.c
> @@ -103,6 +103,7 @@ static void fdb_delete_local(struct net_bridge *br,
>  		if (op != p && ether_addr_equal(op->dev->dev_addr, addr) &&
>  		    (!vid || nbp_vlan_find(op, vid))) {
>  			f->dst = op;
> +			f->added_by_user = 0;
>  			return;
>  		}
>  	}
> @@ -111,6 +112,7 @@ static void fdb_delete_local(struct net_bridge *br,
>  	if (p && ether_addr_equal(br->dev->dev_addr, addr) &&
>  	    (!vid || br_vlan_find(br, vid))) {
>  		f->dst = NULL;
> +		f->added_by_user = 0;
>  		return;
>  	}
>  
> @@ -261,26 +263,11 @@ void br_fdb_delete_by_port(struct net_bridge *br,
>  
>  			if (f->is_static && !do_all)
>  				continue;
> -			/*
> -			 * if multiple ports all have the same device address
> -			 * then when one port is deleted, assign
> -			 * the local entry to other port
> -			 */
> -			if (f->is_local) {
> -				struct net_bridge_port *op;
> -				list_for_each_entry(op, &br->port_list, list) {
> -					if (op != p &&
> -					    ether_addr_equal(op->dev->dev_addr,
> -							     f->addr.addr)) {
> -						f->dst = op;
> -						f->added_by_user = 0;
> -						goto skip_delete;
> -					}
> -				}
> -			}
>  
> -			fdb_delete(br, f);
> -		skip_delete: ;
> +			if (f->is_local)
> +				fdb_delete_local(br, p, f);
> +			else
> +				fdb_delete(br, f);
>  		}
>  	}
>  	spin_unlock_bh(&br->hash_lock);
>