ACK/cmnt: [PATCH][Trusty/Utopic] (upstream) net: generic dev_disable_lro() stacked device handling

[Stefan Bader]

I guess its not going to happen as normal stable since David Miller is no longer
looking at those versions. Patch seems reasonable. Just a bit more background
info somewhere (bug report) and hints about any testing done would be nice.

-Stefan


On 24.02.2016 00:13, Dan Streetman wrote:
> BugLink: http://bugs.launchpad.net/bugs/1547680
> 
> Large receive offloading is known to cause problems if received packets
> are passed to other host. Therefore the kernel disables it by calling
> dev_disable_lro() whenever a network device is enslaved in a bridge or
> forwarding is enabled for it (or globally). For virtual devices we need
> to disable LRO on the underlying physical device (which is actually
> receiving the packets).
> 
> Current dev_disable_lro() code handles this  propagation for a vlan
> (including 802.1ad nested vlan), macvlan or a vlan on top of a macvlan.
> It doesn't handle other stacked devices and their combinations, in
> particular propagation from a bond to its slaves which often causes
> problems in virtualization setups.
> 
> As we now have generic data structures describing the upper-lower device
> relationship, dev_disable_lro() can be generalized to disable LRO also
> for all lower devices (if any) once it is disabled for the device
> itself.
> 
> For bonding and teaming devices, it is necessary to disable LRO not only
> on current slaves at the moment when dev_disable_lro() is called but
> also on any slave (port) added later.
> 
> v2: use lower device links for all devices (including vlan and macvlan)
> 
> Signed-off-by: Michal Kubecek <mkubecek at suse.cz>
> Acked-by: Veaceslav Falico <vfalico at gmail.com>
> Signed-off-by: David S. Miller <davem at davemloft.net>
> (cherry-picked from fbe168ba91f7c327856f205699404284c2f09e36 upstream)
> Signed-off-by: Dan Streetman <dan.streetman at canonical.com>
> 
> ---
>  drivers/net/bonding/bond_main.c |  3 +++
>  drivers/net/team/team.c         |  3 +++
>  net/core/dev.c                  | 15 +++++----------
>  3 files changed, 11 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index d0f58e4..6eb47aa 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -1584,6 +1584,9 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
>  	}
>  #endif
>  
> +	if (!(bond_dev->features & NETIF_F_LRO))
> +		dev_disable_lro(slave_dev);
> +
>  	res = netdev_rx_handler_register(slave_dev, bond_handle_frame,
>  					 new_slave);
>  	if (res) {
> diff --git a/drivers/net/team/team.c b/drivers/net/team/team.c
> index f30a88b..03bac60 100644
> --- a/drivers/net/team/team.c
> +++ b/drivers/net/team/team.c
> @@ -1180,6 +1180,9 @@ static int team_port_add(struct team *team, struct net_device *port_dev)
>  		goto err_set_upper_link;
>  	}
>  
> +	if (!(dev->features & NETIF_F_LRO))
> +		dev_disable_lro(port_dev);
> +
>  	err = netdev_rx_handler_register(port_dev, team_handle_frame,
>  					 port);
>  	if (err) {
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 31f1f68..e758293 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -1423,22 +1423,17 @@ EXPORT_SYMBOL(dev_close);
>   */
>  void dev_disable_lro(struct net_device *dev)
>  {
> -	/*
> -	 * If we're trying to disable lro on a vlan device
> -	 * use the underlying physical device instead
> -	 */
> -	if (is_vlan_dev(dev))
> -		dev = vlan_dev_real_dev(dev);
> -
> -	/* the same for macvlan devices */
> -	if (netif_is_macvlan(dev))
> -		dev = macvlan_dev_real_dev(dev);
> +	struct net_device *lower_dev;
> +	struct list_head *iter;
>  
>  	dev->wanted_features &= ~NETIF_F_LRO;
>  	netdev_update_features(dev);
>  
>  	if (unlikely(dev->features & NETIF_F_LRO))
>  		netdev_WARN(dev, "failed to disable LRO!\n");
> +
> +	netdev_for_each_lower_dev(dev, lower_dev, iter)
> +		dev_disable_lro(lower_dev);
>  }
>  EXPORT_SYMBOL(dev_disable_lro);
>  
> 


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