Subject: Re: [PATCH net v2 6/9] bridge: Properly check if local fdb entry can be deleted in br_fdb_change_mac_address

From: Vlad Yasevich <[email-masked]>
Date: Tue, 17 Dec 2013 14:27:21 -0500

On 12/17/2013 02:00 PM, Vlad Yasevich wrote:
> On 12/17/2013 07:03 AM, Toshiaki Makita wrote:
>> br_fdb_change_mac_address() doesn't check if the local entry has the
>> same address as any of bridge ports.
>> Although I'm not sure when it is beneficial, current implementation allow
>> the bridge device to receive any mac address of its ports.
>> To preserve this behavior, we have to check if the mac address of the
>> entry we are deleting is identical to that of any port.
>>
>> As this check is almost the same as that in br_fdb_changeaddr(), create
>> a common function fdb_delete_local() and call it from
>> br_fdb_changeadddr() and br_fdb_change_mac_address().
>>
>> Signed-off-by: Toshiaki Makita <[email-masked]>
>> ---
>>  net/bridge/br_fdb.c | 57 ++++++++++++++++++++++++++++++-----------------------
>>  1 file changed, 32 insertions(+), 25 deletions(-)
>>
>> diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
>> index cf8b64e..817f138 100644
>> --- a/net/bridge/br_fdb.c
>> +++ b/net/bridge/br_fdb.c
>> @@ -89,6 +89,34 @@ static void fdb_delete(struct net_bridge *br, struct net_bridge_fdb_entry *f)
>>  	call_rcu(&f->rcu, fdb_rcu_free);
>>  }
>>  
>> +/* Delete a local entry if no other port had the same address. */
>> +static void fdb_delete_local(struct net_bridge *br,
>> +			     const struct net_bridge_port *p,
>> +			     struct net_bridge_fdb_entry *f)
>> +{
>> +	const unsigned char *addr = f->addr.addr;
>> +	u16 vid = f->vlan_id;
>> +	struct net_bridge_port *op;
>> +
>> +	/* Maybe another port has same hw addr? */
>> +	list_for_each_entry(op, &br->port_list, list) {
>> +		if (op != p && ether_addr_equal(op->dev->dev_addr, addr) &&
>> +		    (!vid || nbp_vlan_find(op, vid))) {
>> +			f->dst = op;
>> +			return;
>> +		}
>> +	}
>> +
>> +	/* Maybe bridge device has same hw addr? */
>> +	if (p && ether_addr_equal(br->dev->dev_addr, addr) &&
>> +	    (!vid || br_vlan_find(br, vid))) {
>> +		f->dst = NULL;
>> +		return;
>> +	}
>> +
>> +	fdb_delete(br, f);
>> +}
>> +
>>  void br_fdb_changeaddr(struct net_bridge_port *p, const unsigned char *newaddr)
>>  {
>>  	struct net_bridge *br = p->br;
>> @@ -107,30 +135,9 @@ void br_fdb_changeaddr(struct net_bridge_port *p, const unsigned char *newaddr)
>>  
>>  			f = hlist_entry(h, struct net_bridge_fdb_entry, hlist);
>>  			if (f->dst == p && f->is_local && !f->added_by_user) {
>> -				/* maybe another port has same hw addr? */
>> -				struct net_bridge_port *op;
>> -				u16 vid = f->vlan_id;
>> -				list_for_each_entry(op, &br->port_list, list) {
>> -					if (op != p &&
>> -					    ether_addr_equal(op->dev->dev_addr,
>> -							     f->addr.addr) &&
>> -					    (!vid || nbp_vlan_find(op, vid))) {
>> -						f->dst = op;
>> -						goto skip_delete;
>> -					}
>> -				}
>> -
>> -				/* maybe bridge device has same hw addr? */
>> -				if (ether_addr_equal(br->dev->dev_addr,
>> -						     f->addr.addr) &&
>> -				    (!vid || br_vlan_find(br, vid))) {
>> -					f->dst = NULL;
>> -					goto skip_delete;
>> -				}
>> -
>>  				/* delete old one */
>> -				fdb_delete(br, f);
>> -skip_delete:
>> +				fdb_delete_local(br, p, f);
>> +
>>  				/* if this port has no vlan information
>>  				 * configured, we can safely be done at
>>  				 * this point.
>> @@ -168,7 +175,7 @@ void br_fdb_change_mac_address(struct net_bridge *br, const u8 *newaddr)
>>  	/* If old entry was unassociated with any port, then delete it. */
>>  	f = __br_fdb_get(br, br->dev->dev_addr, 0);
>>  	if (f && f->is_local && !f->dst)
>> -		fdb_delete(br, f);
>> +		fdb_delete_local(br, NULL, f);
> 
> In this series, br_fdb_change_mac_address() is called before
> br->dev->dev_addr is set to the new value (patch 4).  As a result,
> the above fdb_delete_local() call will not delete the entry because
> br->dev->dev_addr will match the f->addr and the function will
> return before calling fdb_delete().

Sorry, missed the check for port pointer in br_delete_local, so this
would work correctly.

Thanks
-vlad

> 
> -vlad
> 
>>  
>>  	fdb_insert(br, NULL, newaddr, 0);
>>  
>> @@ -183,7 +190,7 @@ void br_fdb_change_mac_address(struct net_bridge *br, const u8 *newaddr)
>>  	for_each_set_bit_from(vid, pv->vlan_bitmap, VLAN_N_VID) {
>>  		f = __br_fdb_get(br, br->dev->dev_addr, vid);
>>  		if (f && f->is_local && !f->dst)
>> -			fdb_delete(br, f);
>> +			fdb_delete_local(br, NULL, f);
>>  		fdb_insert(br, NULL, newaddr, vid);
>>  	}
>>  }
>>
>