mpls: Per-device MPLS state

Add per-device MPLS state to supported interfaces. Use the presence of
this state in mpls_route_add to determine that this is a supported
interface.

Use the presence of mpls_dev to drop packets that arrived on an
unsupported interface - previously they were allowed through.

Cc: "Eric W. Biederman" <[e-mail]>
Signed-off-by: Robert Shearman <[e-mail]>
Reviewed-by: "Eric W. Biederman" <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/linux/netdevice.h

···
 struct wireless_dev;
 /* 802.15.4 specific */
 struct wpan_dev;
+struct mpls_dev;
 
 void netdev_set_default_ethtool_ops(struct net_device *dev,
 				    const struct ethtool_ops *ops);
···
 	void			*ax25_ptr;
 	struct wireless_dev	*ieee80211_ptr;
 	struct wpan_dev		*ieee802154_ptr;
+#if IS_ENABLED(CONFIG_MPLS_ROUTING)
+	struct mpls_dev __rcu	*mpls_ptr;
+#endif
 
 /*
  * Cache lines mostly used on receive path (including eth_type_trans())

net/mpls/af_mpls.c

···
 	return rt;
 }
 
+static inline struct mpls_dev *mpls_dev_get(const struct net_device *dev)
+{
+	return rcu_dereference_rtnl(dev->mpls_ptr);
+}
+
 static bool mpls_output_possible(const struct net_device *dev)
 {
 	return dev && (dev->flags & IFF_UP) && netif_carrier_ok(dev);
···
 	struct mpls_route *rt;
 	struct mpls_entry_decoded dec;
 	struct net_device *out_dev;
+	struct mpls_dev *mdev;
 	unsigned int hh_len;
 	unsigned int new_header_size;
 	unsigned int mtu;
 	int err;
 
 	/* Careful this entire function runs inside of an rcu critical section */
+
+	mdev = mpls_dev_get(dev);
+	if (!mdev)
+		goto drop;
 
 	if (skb->pkt_type != PACKET_HOST)
 		goto drop;
···
 	if (!dev)
 		goto errout;
 
-	/* For now just support ethernet devices */
+	/* Ensure this is a supported device */
 	err = -EINVAL;
-	if ((dev->type != ARPHRD_ETHER) && (dev->type != ARPHRD_LOOPBACK))
+	if (!mpls_dev_get(dev))
 		goto errout;
 
 	err = -EINVAL;
···
 	return err;
 }
 
+static struct mpls_dev *mpls_add_dev(struct net_device *dev)
+{
+	struct mpls_dev *mdev;
+	int err = -ENOMEM;
+
+	ASSERT_RTNL();
+
+	mdev = kzalloc(sizeof(*mdev), GFP_KERNEL);
+	if (!mdev)
+		return ERR_PTR(err);
+
+	rcu_assign_pointer(dev->mpls_ptr, mdev);
+
+	return mdev;
+}
+
 static void mpls_ifdown(struct net_device *dev)
 {
 	struct mpls_route __rcu **platform_label;
 	struct net *net = dev_net(dev);
+	struct mpls_dev *mdev;
 	unsigned index;
 
 	platform_label = rtnl_dereference(net->mpls.platform_label);
···
 			continue;
 		rt->rt_dev = NULL;
 	}
+
+	mdev = mpls_dev_get(dev);
+	if (!mdev)
+		return;
+
+	RCU_INIT_POINTER(dev->mpls_ptr, NULL);
+
+	kfree(mdev);
 }
 
 static int mpls_dev_notify(struct notifier_block *this, unsigned long event,
 			   void *ptr)
 {
 	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
+	struct mpls_dev *mdev;
 
 	switch(event) {
+	case NETDEV_REGISTER:
+		/* For now just support ethernet devices */
+		if ((dev->type == ARPHRD_ETHER) ||
+		    (dev->type == ARPHRD_LOOPBACK)) {
+			mdev = mpls_add_dev(dev);
+			if (IS_ERR(mdev))
+				return notifier_from_errno(PTR_ERR(mdev));
+		}
+		break;
+
 	case NETDEV_UNREGISTER:
 		mpls_ifdown(dev);
 		break;

net/mpls/internal.h

···
 	u8 bos;
 };
 
+struct mpls_dev {
+};
+
 struct sk_buff;
 
 static inline struct mpls_shim_hdr *mpls_hdr(const struct sk_buff *skb)