[PATCH] net: neighbour: add neigh_parms_lookup_dev() helper

[Paritosh Potukuchi <paritoshpotukuchi@gmail.com>]

Provide a helper to lookup neigh_parms associated
with a given (neigh_table, net_device) pair.

The existing lookup_neigh_parms() helper is internal to the
neighbour subsystem and cannot be used by other subsystems.
Some stacked/virtual devices like bond require access to the
underlying device's neigh_parms.

neigh_parms_lookup_dev() is designed to be a wrapper around
lookup_neigh_parms(). The function provides controlled access
to per device neigh_parms.

The caller is expected to hold rcu_read_lock().

This does not break any existing functionality.

Signed-off-by: Paritosh Potukuchi <paritosh.potukuchi@amd.com>
---
 include/net/neighbour.h | 2 ++
 net/core/neighbour.c    | 8 ++++++++
 2 files changed, 10 insertions(+)

diff --git a/include/net/neighbour.h b/include/net/neighbour.h
index 8860cc2175fc..1b3b06eda886 100644
--- a/include/net/neighbour.h
+++ b/include/net/neighbour.h
@@ -438,6 +438,8 @@ int neigh_sysctl_register(struct net_device *dev, struct neigh_parms *p,
 			  proc_handler *proc_handler);
 void neigh_sysctl_unregister(struct neigh_parms *p);
 
+struct neigh_parms *neigh_parms_lookup_dev(struct neigh_table *tbl, struct net_device *dev);
+
 static inline void __neigh_parms_put(struct neigh_parms *parms)
 {
 	refcount_dec(&parms->refcnt);
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 1349c0eedb64..6d32c2668af3 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -1757,6 +1757,14 @@ static inline struct neigh_parms *lookup_neigh_parms(struct neigh_table *tbl,
 	return NULL;
 }
 
+/* Caller must hold rcu_read_lock()*/
+
+struct neigh_parms *neigh_parms_lookup_dev(struct neigh_table *tbl, struct net_device *dev)
+{
+	return lookup_neigh_parms(tbl, dev_net(dev), dev->ifindex);
+}
+EXPORT_SYMBOL(neigh_parms_lookup_dev);
+
 struct neigh_parms *neigh_parms_alloc(struct net_device *dev,
 				      struct neigh_table *tbl)
 {
-- 
2.43.0