macvtap: Let TUNSETOFFLOAD actually controll offload features.

When the user issues TUNSETOFFLOAD ioctl, macvtap does not do
anything other then to verify arguments.  This patch adds
functionality to allow users to actually control offload features.
NETIF_F_GSO and NETIF_F_GRO are always on, but the rest of the
features can be controlled.
Signed-off-by: Vlad Yasevich <vyasevic@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/macvlan.c

@@ -638,6 +638,14 @@ static int macvlan_ethtool_get_settings(struct net_device *dev,
 	return __ethtool_get_settings(vlan->lowerdev, cmd);
 }
 
+static netdev_features_t macvlan_fix_features(struct net_device *dev,
+					      netdev_features_t features)
+{
+	struct macvlan_dev *vlan = netdev_priv(dev);
+
+	return features & (vlan->set_features | ~MACVLAN_FEATURES);
+}
+
 static const struct ethtool_ops macvlan_ethtool_ops = {
 	.get_link		= ethtool_op_get_link,
 	.get_settings		= macvlan_ethtool_get_settings,
@@ -651,6 +659,7 @@ static const struct net_device_ops macvlan_netdev_ops = {
 	.ndo_stop		= macvlan_stop,
 	.ndo_start_xmit		= macvlan_start_xmit,
 	.ndo_change_mtu		= macvlan_change_mtu,
+	.ndo_fix_features	= macvlan_fix_features,
 	.ndo_change_rx_flags	= macvlan_change_rx_flags,
 	.ndo_set_mac_address	= macvlan_set_mac_address,
 	.ndo_set_rx_mode	= macvlan_set_mac_lists,
@@ -791,6 +800,7 @@ int macvlan_common_newlink(struct net *src_net, struct net_device *dev,
 	vlan->port     = port;
 	vlan->receive  = receive;
 	vlan->forward  = forward;
+	vlan->set_features = MACVLAN_FEATURES;
 
 	vlan->mode     = MACVLAN_MODE_VEPA;
 	if (data && data[IFLA_MACVLAN_MODE])

drivers/net/macvtap.c

@@ -65,6 +65,9 @@ static struct cdev macvtap_cdev;
 
 static const struct proto_ops macvtap_socket_ops;
 
+#define TUN_OFFLOADS (NETIF_F_HW_CSUM | NETIF_F_TSO_ECN | NETIF_F_TSO | \
+		      NETIF_F_TSO6 | NETIF_F_UFO)
+#define RX_OFFLOADS (NETIF_F_GRO | NETIF_F_LRO)
 /*
  * RCU usage:
  * The macvtap_queue and the macvlan_dev are loosely coupled, the
@@ -349,6 +352,11 @@ static int macvtap_newlink(struct net *src_net,
 	struct macvlan_dev *vlan = netdev_priv(dev);
 	INIT_LIST_HEAD(&vlan->queue_list);
 
+	/* Since macvlan supports all offloads by default, make
+	 * tap support all offloads also.
+	 */
+	vlan->tap_features = TUN_OFFLOADS;
+
 	/* Don't put anything that may fail after macvlan_common_newlink
 	 * because we can't undo what it does.
 	 */
@@ -958,6 +966,58 @@ static int macvtap_ioctl_set_queue(struct file *file, unsigned int flags)
 	return ret;
 }
 
+static int set_offload(struct macvtap_queue *q, unsigned long arg)
+{
+	struct macvlan_dev *vlan;
+	netdev_features_t features;
+	netdev_features_t feature_mask = 0;
+
+	vlan = rtnl_dereference(q->vlan);
+	if (!vlan)
+		return -ENOLINK;
+
+	features = vlan->dev->features;
+
+	if (arg & TUN_F_CSUM) {
+		feature_mask = NETIF_F_HW_CSUM;
+
+		if (arg & (TUN_F_TSO4 | TUN_F_TSO6)) {
+			if (arg & TUN_F_TSO_ECN)
+				feature_mask |= NETIF_F_TSO_ECN;
+			if (arg & TUN_F_TSO4)
+				feature_mask |= NETIF_F_TSO;
+			if (arg & TUN_F_TSO6)
+				feature_mask |= NETIF_F_TSO6;
+		}
+
+		if (arg & TUN_F_UFO)
+			feature_mask |= NETIF_F_UFO;
+	}
+
+	/* tun/tap driver inverts the usage for TSO offloads, where
+	 * setting the TSO bit means that the userspace wants to
+	 * accept TSO frames and turning it off means that user space
+	 * does not support TSO.
+	 * For macvtap, we have to invert it to mean the same thing.
+	 * When user space turns off TSO, we turn off GSO/LRO so that
+	 * user-space will not receive TSO frames.
+	 */
+	if (feature_mask & (NETIF_F_TSO | NETIF_F_TSO6 | NETIF_F_UFO))
+		features |= RX_OFFLOADS;
+	else
+		features &= ~RX_OFFLOADS;
+
+	/* tap_features are the same as features on tun/tap and
+	 * reflect user expectations.
+	 */
+	vlan->tap_features = vlan->dev->features &
+			    (feature_mask | ~TUN_OFFLOADS);
+	vlan->set_features = features;
+	netdev_update_features(vlan->dev);
+
+	return 0;
+}
+
 /*
  * provide compatibility with generic tun/tap interface
  */
@@ -1050,7 +1110,10 @@ static long macvtap_ioctl(struct file *file, unsigned int cmd,
 			 got enabled for forwarded frames */
 		if (!(q->flags & IFF_VNET_HDR))
 			return  -EINVAL;
-		return 0;
+		rtnl_lock();
+		ret = set_offload(q, arg);
+		rtnl_unlock();
+		return ret;
 
 	default:
 		return -EINVAL;

include/linux/if_macvlan.h

@@ -65,6 +65,7 @@ struct macvlan_dev {
 
 	DECLARE_BITMAP(mc_filter, MACVLAN_MC_FILTER_SZ);
 
+	netdev_features_t	set_features;
 	enum macvlan_mode	mode;
 	u16			flags;
 	int (*receive)(struct sk_buff *skb);
@@ -75,6 +76,7 @@ struct macvlan_dev {
 	struct list_head	queue_list;
 	int			numvtaps;
 	int			numqueues;
+	netdev_features_t	tap_features;
 	int			minor;
 };