[PATCH net-next v3] 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>
---
v2 -> v3
 - Change the way 'master' is checked for being non NULL
v1 -> v2
 - Change from filtering just for non VRF slaves to non slaves at all

 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 b963d6b02c4f..2d5bc3a75fae 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -2528,6 +2528,13 @@ 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 !!master;
+
 	if (!master || master->ifindex != master_idx)
 		return true;
 
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 7c9d32cfe607..2dcf1c084b20 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -1959,6 +1959,13 @@ 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 !!master;
+
 	if (!master || master->ifindex != master_idx)
 		return true;
 
-- 
2.25.1