[PATCH] net: Support filtering interfaces on no master

[Lahav Schlesinger <lschlesinger@drivenets.com>]

Currently there's support for filtering neighbours/links for interfaces
which have a specific master device (using the IFLA_MASTER/NDA_MASTER
attributes).

This patch adds support for filtering interfaces/neighbours dump for
interfaces that *don't* have a master.

I have a patch for iproute2 ready for adding this support in userspace.

Signed-off-by: Lahav Schlesinger <lschlesinger@drivenets.com>
Cc: David Ahern <dsahern@kernel.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
---
 net/core/neighbour.c | 7 +++++++
 net/core/rtnetlink.c | 7 +++++++
 2 files changed, 14 insertions(+)

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 53e85c70c6e5..1b1e0ca70650 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -2533,6 +2533,13 @@ static bool neigh_master_filtered(struct net_device *dev, int master_idx)
 		return false;
 
 	master = dev ? netdev_master_upper_dev_get(dev) : NULL;
+
+	/* 0 is already used to denote NDA_MASTER wasn't passed, therefore need another
+	 * invalid value for ifindex to denote "no master".
+	 */
+	if (master_idx == -1)
+                return (bool)master;
+
 	if (!master || master->ifindex != master_idx)
 		return true;
 
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index f6af3e74fc44..8ccc314744d4 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -1970,6 +1970,13 @@ static bool link_master_filtered(struct net_device *dev, int master_idx)
 		return false;
 
 	master = netdev_master_upper_dev_get(dev);
+
+	/* 0 is already used to denote IFLA_MASTER wasn't passed, therefore need
+	 * another invalid value for ifindex to denote "no master".
+	 */
+	if (master_idx == -1)
+                return (bool)master;
+
 	if (!master || master->ifindex != master_idx)
 		return true;
 
-- 
2.25.1