Subject: Re: [PATCH net-next v2] macvlan: fix the problem when mac address changes for passthru mode

From: Vlad Yasevich <[email-masked]>
Date: Thu, 29 May 2014 09:46:26 -0400

On 05/29/2014 03:26 AM, Ding Tianhong wrote:
> The macvlan dev should always have the same mac address like lowerdev
> when in the passthru mode, change the mac address alone will break the
> work mechanism, so when the lowerdev or macvlan mac address changes,
> we should propagate the changes to another dev.
> 
> v1->v2: Allow macvlan dev to change mac address for passthru mode and propagate to
> 	lowerdev.
> 
> Signed-off-by: Ding Tianhong <[email-masked]>
> ---
>  drivers/net/macvlan.c | 42 +++++++++++++++++++++++++++++++++---------
>  1 file changed, 33 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
> index a665e90..3e24770 100644
> --- a/drivers/net/macvlan.c
> +++ b/drivers/net/macvlan.c
> @@ -494,35 +494,47 @@ hash_del:
>  	return 0;
>  }
>  
> -static int macvlan_set_mac_address(struct net_device *dev, void *p)
> +static int macvlan_sync_address(struct net_device *dev, unsigned char *addr)
>  {
>  	struct macvlan_dev *vlan = netdev_priv(dev);
>  	struct net_device *lowerdev = vlan->lowerdev;
> -	struct sockaddr *addr = p;
>  	int err;
>  
> -	if (!is_valid_ether_addr(addr->sa_data))
> -		return -EADDRNOTAVAIL;
> -
>  	if (!(dev->flags & IFF_UP)) {
>  		/* Just copy in the new address */
> -		memcpy(dev->dev_addr, addr->sa_data, ETH_ALEN);
> +		ether_addr_copy(dev->dev_addr, addr);
>  	} else {
>  		/* Rehash and update the device filters */
> -		if (macvlan_addr_busy(vlan->port, addr->sa_data))
> +		if (macvlan_addr_busy(vlan->port, addr))
>  			return -EBUSY;
>  
> -		err = dev_uc_add(lowerdev, addr->sa_data);
> +		err = dev_uc_add(lowerdev, addr);
>  		if (err)
>  			return err;
>  
>  		dev_uc_del(lowerdev, dev->dev_addr);
>  
> -		macvlan_hash_change_addr(vlan, addr->sa_data);
> +		macvlan_hash_change_addr(vlan, addr);
>  	}
>  	return 0;
>  }
>  
> +static int macvlan_set_mac_address(struct net_device *dev, void *p)
> +{
> +	struct macvlan_dev *vlan = netdev_priv(dev);
> +	struct sockaddr *addr = p;
> +
> +	if (!is_valid_ether_addr(addr->sa_data))
> +		return -EADDRNOTAVAIL;
> +
> +	if (vlan->mode == MACVLAN_MODE_PASSTHRU) {
> +		dev_set_mac_address(vlan->lowerdev, addr);
> +		return 0;
> +	}
> +
> +	return macvlan_sync_address(dev, addr->sa_data);
> +}
> +
>  static void macvlan_change_rx_flags(struct net_device *dev, int change)
>  {
>  	struct macvlan_dev *vlan = netdev_priv(dev);
> @@ -1106,6 +1118,18 @@ static int macvlan_device_event(struct notifier_block *unused,
>  			dev_set_mtu(vlan->dev, dev->mtu);
>  		}
>  		break;
> +	case NETDEV_CHANGEADDR:
> +		if (!port->passthru)
> +			return NOTIFY_DONE;
> +
> +		vlan = list_first_entry_or_null(&port->vlans,
> +						struct macvlan_dev,
> +						list);
> +
> +		if (macvlan_sync_address(vlan->dev, dev->dev_addr))
> +			return NOTIFY_BAD;
> +

Ok, this is not quite right.  The lower device changes it's mac address
and notifies upper macvlan about it.  Macvlan, if it is up, will write
the same mac address down to the lower device's unicast address list
as part of the sync.  The lower device ends up with two copies of its
own address.

-vlad
> +		break;
>  	case NETDEV_UNREGISTER:
>  		/* twiddle thumbs on netns device moves */
>  		if (dev->reg_state != NETREG_UNREGISTERING)
>