Subject: Re: [PATCH net v2 4/9] bridge: Change local fdb entries whenever mac address of bridge device changes

From: Vlad Yasevich <[email-masked]>
Date: Tue, 17 Dec 2013 13:45:49 -0500

On 12/17/2013 11:22 AM, Vlad Yasevich wrote:
> On 12/17/2013 07:03 AM, Toshiaki Makita wrote:
>> Vlan code may need fdb change when changing mac address of bridge device
>> even if it is caused by the mac address changing of a bridge port.
>>
>> Example configuration:
>>   ip link set eth0 address 12:34:56:78:90:ab
>>   ip link set eth1 address aa:bb:cc:dd:ee:ff
>>   brctl addif br0 eth0
>>   brctl addif br0 eth1 # br0 will have mac address 12:34:56:78:90:ab
>>   bridge vlan add dev br0 vid 10 self
>>   bridge vlan add dev eth0 vid 10
>> We will have fdb entry such that f->dst == NULL, f->vlan_id == 10 and
>> f->addr == 12:34:56:78:90:ab at this time.
>> Next, change the mac address of eth0 to greater value.
>>   ip link set eth0 address ee:ff:12:34:56:78
>> Then, mac address of br0 will be recalculated and set to aa:bb:cc:dd:ee:ff.
>> However, an entry aa:bb:cc:dd:ee:ff will not be created and we will be not
>> able to communicate using br0 on vlan 10.
>>
>> Address this issue by deleting and adding local entries whenever
>> changing the mac address of the bridge device.
>>
>> If there already exists an entry that has the same address, for example,
>> in case that br_fdb_changeaddr() has already inserted it,
>> br_fdb_change_mac_address() will simply fail to insert it and no
>> duplicated entry will be made, as it was.
>>
>> This approach also needs br_add_if() to call br_fdb_insert() before
>> br_stp_recalculate_bridge_id() so that we don't create an entry whose
>> dst == NULL in this function to preserve previous behavior.
> 
> Aren't we still creating this entry even with this change?
> 
> Looking at br_fdb_change_mac_address(), it will always add
> an fdb with NULL port.
>

Never mind.  br_fdb_insert() here will return 0 since a local
entry already exists...

Acked-by: Vlad Yasevich <[email-masked]>

-vlad

> May be we can update br_fdb_change_mac_address() to not add
> a new entry if we have a local fdb already for the address.
> 
> -vlad
> 
>>
>> Note that this is a slight change in behavior where the bridge device can
>> receive the traffic to the new address before calling
>> br_stp_recalculate_bridge_id() in br_add_if().
>> However, it is not a problem because we have already the address on the
>> new port and such a way to insert new one before recalculating bridge id
>> is taken in br_device_event() as well.
>>
>> Signed-off-by: Toshiaki Makita <[email-masked]>
>> ---
>>  net/bridge/br_device.c | 1 -
>>  net/bridge/br_if.c     | 6 +++---
>>  net/bridge/br_stp_if.c | 2 ++
>>  3 files changed, 5 insertions(+), 4 deletions(-)
>>
>> diff --git a/net/bridge/br_device.c b/net/bridge/br_device.c
>> index d967773..1cbdbf1 100644
>> --- a/net/bridge/br_device.c
>> +++ b/net/bridge/br_device.c
>> @@ -187,7 +187,6 @@ static int br_set_mac_address(struct net_device *dev, void *p)
>>  
>>  	spin_lock_bh(&br->lock);
>>  	if (!ether_addr_equal(dev->dev_addr, addr->sa_data)) {
>> -		br_fdb_change_mac_address(br, addr->sa_data);
>>  		/* Mac address will be changed in br_stp_change_bridge_id(). */
>>  		br_stp_change_bridge_id(br, addr->sa_data);
>>  	}
>> diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c
>> index 4bf02ad..779d91c 100644
>> --- a/net/bridge/br_if.c
>> +++ b/net/bridge/br_if.c
>> @@ -389,6 +389,9 @@ int br_add_if(struct net_bridge *br, struct net_device *dev)
>>  	if (br->dev->needed_headroom < dev->needed_headroom)
>>  		br->dev->needed_headroom = dev->needed_headroom;
>>  
>> +	if (br_fdb_insert(br, p, dev->dev_addr, 0))
>> +		netdev_err(dev, "failed insert local address bridge forwarding table\n");
>> +
>>  	spin_lock_bh(&br->lock);
>>  	changed_addr = br_stp_recalculate_bridge_id(br);
>>  
>> @@ -404,9 +407,6 @@ int br_add_if(struct net_bridge *br, struct net_device *dev)
>>  
>>  	dev_set_mtu(br->dev, br_min_mtu(br));
>>  
>> -	if (br_fdb_insert(br, p, dev->dev_addr, 0))
>> -		netdev_err(dev, "failed insert local address bridge forwarding table\n");
>> -
>>  	kobject_uevent(&p->kobj, KOBJ_ADD);
>>  
>>  	return 0;
>> diff --git a/net/bridge/br_stp_if.c b/net/bridge/br_stp_if.c
>> index 656a6f3..189ba1e 100644
>> --- a/net/bridge/br_stp_if.c
>> +++ b/net/bridge/br_stp_if.c
>> @@ -194,6 +194,8 @@ void br_stp_change_bridge_id(struct net_bridge *br, const unsigned char *addr)
>>  
>>  	wasroot = br_is_root_bridge(br);
>>  
>> +	br_fdb_change_mac_address(br, addr);
>> +
>>  	memcpy(oldaddr, br->bridge_id.addr, ETH_ALEN);
>>  	memcpy(br->bridge_id.addr, addr, ETH_ALEN);
>>  	memcpy(br->dev->dev_addr, addr, ETH_ALEN);
>>
>