Subject: Re: [RFC 2/9] net: dsa: add basic support for VLAN operations

From: Guenter Roeck <[email-masked]>
Date: Tue, 02 Jun 2015 07:42:41 -0700

On 06/01/2015 06:27 PM, Vivien Didelot wrote:
> This patch adds the glue between DSA and switchdev to add and delete
> SWITCHDEV_OBJ_PORT_VLAN objects.
>
> This will allow the DSA switch drivers implementing the port_vlan_add
> and port_vlan_del functions to access the switch VLAN database through
> userspace commands such as "bridge vlan".
>
> Signed-off-by: Vivien Didelot <[email-masked]>
> ---
>   include/net/dsa.h |  7 +++++++
>   net/dsa/slave.c   | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++++--
>   2 files changed, 66 insertions(+), 2 deletions(-)
>
> diff --git a/include/net/dsa.h b/include/net/dsa.h
> index fbca63b..726357b 100644
> --- a/include/net/dsa.h
> +++ b/include/net/dsa.h
> @@ -302,6 +302,13 @@ struct dsa_switch_driver {
>   			   const unsigned char *addr, u16 vid);
>   	int	(*fdb_getnext)(struct dsa_switch *ds, int port,
>   			       unsigned char *addr, bool *is_static);
> +
> +	/*
> +	 * VLAN support
> +	 */
> +	int	(*port_vlan_add)(struct dsa_switch *ds, int port, u16 vid,
> +				 u16 bridge_flags);
> +	int	(*port_vlan_del)(struct dsa_switch *ds, int port, u16 vid);
>   };
>
>   void register_switch_driver(struct dsa_switch_driver *type);
> diff --git a/net/dsa/slave.c b/net/dsa/slave.c
> index cbda00a..52ba5a1 100644
> --- a/net/dsa/slave.c
> +++ b/net/dsa/slave.c
> @@ -363,6 +363,25 @@ static int dsa_slave_port_attr_set(struct net_device *dev,
>   	return ret;
>   }
>
> +static int dsa_slave_port_vlans_add(struct net_device *dev,
> +				    struct switchdev_obj_vlan *vlan)
> +{
> +	struct dsa_slave_priv *p = netdev_priv(dev);
> +	struct dsa_switch *ds = p->parent;
> +	int vid, err = 0;
> +
> +	if (!ds->drv->port_vlan_add)
> +		return -ENOTSUPP;
> +
> +	for (vid = vlan->vid_start; vid <= vlan->vid_end; ++vid) {
> +		err = ds->drv->port_vlan_add(ds, p->port, vid, vlan->flags);
> +		if (err)
> +			break;
> +	}
> +
> +	return err;
> +}
> +
>   static int dsa_slave_port_obj_add(struct net_device *dev,
>   				  struct switchdev_obj *obj)
>   {
> @@ -378,6 +397,9 @@ static int dsa_slave_port_obj_add(struct net_device *dev,
>   		return 0;
>
>   	switch (obj->id) {
> +	case SWITCHDEV_OBJ_PORT_VLAN:
> +		err = dsa_slave_port_vlans_add(dev, &obj->u.vlan);
> +		break;
>   	default:
>   		err = -ENOTSUPP;
>   		break;
> @@ -386,12 +408,34 @@ static int dsa_slave_port_obj_add(struct net_device *dev,
>   	return err;
>   }
>
> +static int dsa_slave_port_vlans_del(struct net_device *dev,
> +				    struct switchdev_obj_vlan *vlan)
> +{
> +	struct dsa_slave_priv *p = netdev_priv(dev);
> +	struct dsa_switch *ds = p->parent;
> +	int vid, err = 0;
> +
> +	if (!ds->drv->port_vlan_del)
> +		return -ENOTSUPP;
> +
> +	for (vid = vlan->vid_start; vid <= vlan->vid_end; ++vid) {
> +		err = ds->drv->port_vlan_del(ds, p->port, vid);
> +		if (err)
> +			break;
> +	}
> +
> +	return err;
> +}
> +
>   static int dsa_slave_port_obj_del(struct net_device *dev,
>   				  struct switchdev_obj *obj)
>   {
>   	int err;
>
>   	switch (obj->id) {
> +	case SWITCHDEV_OBJ_PORT_VLAN:
> +		err = dsa_slave_port_vlans_del(dev, &obj->u.vlan);
> +		break;
>   	default:
>   		err = -EOPNOTSUPP;
>   		break;
> @@ -473,6 +517,15 @@ static netdev_tx_t dsa_slave_notag_xmit(struct sk_buff *skb,
>   	return NETDEV_TX_OK;
>   }
>
> +static int dsa_slave_vlan_noop(struct net_device *dev, __be16 proto, u16 vid)
> +{
> +	/* NETIF_F_HW_VLAN_CTAG_FILTER requires ndo_vlan_rx_add_vid and
> +	 * ndo_vlan_rx_kill_vid, otherwise the VLAN acceleration is considered
> +	 * buggy (see net/core/dev.c).
> +	 */
> +	return 0;
> +}
> +
>
>   /* ethtool operations *******************************************************/
>   static int
> @@ -734,6 +787,10 @@ static const struct net_device_ops dsa_slave_netdev_ops = {
>   	.ndo_fdb_dump		= dsa_slave_fdb_dump,
>   	.ndo_do_ioctl		= dsa_slave_ioctl,
>   	.ndo_get_iflink		= dsa_slave_get_iflink,
> +	.ndo_vlan_rx_add_vid	= dsa_slave_vlan_noop,
> +	.ndo_vlan_rx_kill_vid	= dsa_slave_vlan_noop,
> +	.ndo_bridge_setlink	= switchdev_port_bridge_setlink,
> +	.ndo_bridge_dellink	= switchdev_port_bridge_dellink,
>   };
>
>   static const struct switchdev_ops dsa_slave_switchdev_ops = {
> @@ -924,7 +981,7 @@ int dsa_slave_create(struct dsa_switch *ds, struct device *parent,
>   	if (slave_dev == NULL)
>   		return -ENOMEM;
>
> -	slave_dev->features = master->vlan_features;
> +	slave_dev->features = master->vlan_features | NETIF_F_VLAN_FEATURES;

Hi Vivien,

NETIF_F_VLAN_FEATURES declares that the device supports receive and transmit
tagging offload. We do this on transmit, by calling vlan_hwaccel_push_inside()
with patch 9, but not on the receive side.

I think you may need to add matching code on the receive side to remove
the VLAN tag and move it into the skb with __vlan_hwaccel_put_tag().
It may also be necessary to add the same code for the other tag handlers.

Overall I wonder if it really makes sense to add those flags. Seems to me
that would only make sense if the resulting code gets more efficient,
which at least currently is not the case. Am I missing something ?

Thanks,
Guenter