From: Eric Biederman <ebiederm@aristanetworks.com>
Date: Fri, 13 Mar 2009 20:15:37 +0000 (-0700)
Subject: macvlan: Support creating macvlans from macvlans
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=b0832a2961022a076c812384435b5f0290b3fc91;p=linux-beck.git

macvlan: Support creating macvlans from macvlans

When running in a network namespace whose only link to
the outside world is a macvlan device, not being
able to create another macvlan is a real pain.

So modify macvlan creation to allow automatically forward
a creation of a macvlan on a macvlan to become a creation
of a macvlan on the underlying network device.

Signed-off-by: Eric Biederman <ebiederm@aristanetworks.com>
Acked-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
index 7e24b5048686..b5241fc0f512 100644
--- a/drivers/net/macvlan.c
+++ b/drivers/net/macvlan.c
@@ -461,12 +461,13 @@ static int macvlan_newlink(struct net_device *dev,
 	if (lowerdev == NULL)
 		return -ENODEV;
 
-	/* Don't allow macvlans on top of other macvlans - its not really
-	 * wrong, but lockdep can't handle it and its not useful for anything
-	 * you couldn't do directly on top of the real device.
+	/* When creating macvlans on top of other macvlans - use
+	 * the real device as the lowerdev.
 	 */
-	if (lowerdev->rtnl_link_ops == dev->rtnl_link_ops)
-		return -ENODEV;
+	if (lowerdev->rtnl_link_ops == dev->rtnl_link_ops) {
+		struct macvlan_dev *lowervlan = netdev_priv(lowerdev);
+		lowerdev = lowervlan->lowerdev;
+	}
 
 	if (!tb[IFLA_MTU])
 		dev->mtu = lowerdev->mtu;