mctp: Allow MCTP on tun devices

Allowing TUN is useful for testing, to route packets to userspace or to
tunnel between machines.
Signed-off-by: Matt Johnston <matt@codeconstruct.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/mctp/device.c

@@ -356,9 +356,12 @@ static int mctp_register(struct net_device *dev)
 	if (rtnl_dereference(dev->mctp_ptr))
 		return 0;
 
-	/* only register specific types; MCTP-specific and loopback for now */
-	if (dev->type != ARPHRD_MCTP && dev->type != ARPHRD_LOOPBACK)
+	/* only register specific types (inc. NONE for TUN devices) */
+	if (!(dev->type == ARPHRD_MCTP ||
+	      dev->type == ARPHRD_LOOPBACK ||
+	      dev->type == ARPHRD_NONE)) {
 		return 0;
+	}
 
 	mdev = mctp_add_dev(dev);
 	if (IS_ERR(mdev))

net/mctp/route.c

@@ -821,13 +821,18 @@ static int mctp_pkttype_receive(struct sk_buff *skb, struct net_device *dev,
 				struct net_device *orig_dev)
 {
 	struct net *net = dev_net(dev);
+	struct mctp_dev *mdev;
 	struct mctp_skb_cb *cb;
 	struct mctp_route *rt;
 	struct mctp_hdr *mh;
 
+	rcu_read_lock();
+	mdev = __mctp_dev_get(dev);
+	rcu_read_unlock();
+	if (!mdev) {
 		/* basic non-data sanity checks */
-	if (dev->type != ARPHRD_MCTP)
 		goto err_drop;
+	}
 
 	if (!pskb_may_pull(skb, sizeof(struct mctp_hdr)))
 		goto err_drop;
@@ -841,9 +846,7 @@ static int mctp_pkttype_receive(struct sk_buff *skb, struct net_device *dev,
 		goto err_drop;
 
 	cb = __mctp_cb(skb);
-	rcu_read_lock();
-	cb->net = READ_ONCE(__mctp_dev_get(dev)->net);
-	rcu_read_unlock();
+	cb->net = READ_ONCE(mdev->net);
 
 	rt = mctp_route_lookup(net, cb->net, mh->dest);
 	if (!rt)