neighbour: allow admin to set NTF_ROUTER

This patch allows admin setting of NTF_ROUTER flag
on a neighbour entry. This enables external control
plane (like bgp evpn) to manage neigh entries with
NTF_ROUTER flag.
Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/neighbour.c

@@ -1712,7 +1712,8 @@ static int neigh_delete(struct sk_buff *skb, struct nlmsghdr *nlh,
 static int neigh_add(struct sk_buff *skb, struct nlmsghdr *nlh,
 		     struct netlink_ext_ack *extack)
 {
-	int flags = NEIGH_UPDATE_F_ADMIN | NEIGH_UPDATE_F_OVERRIDE;
+	int flags = NEIGH_UPDATE_F_ADMIN | NEIGH_UPDATE_F_OVERRIDE |
+		NEIGH_UPDATE_F_OVERRIDE_ISROUTER;
 	struct net *net = sock_net(skb->sk);
 	struct ndmsg *ndm;
 	struct nlattr *tb[NDA_MAX+1];
@@ -1787,12 +1788,16 @@ static int neigh_add(struct sk_buff *skb, struct nlmsghdr *nlh,
 		}
 
 		if (!(nlh->nlmsg_flags & NLM_F_REPLACE))
-			flags &= ~NEIGH_UPDATE_F_OVERRIDE;
+			flags &= ~(NEIGH_UPDATE_F_OVERRIDE |
+				   NEIGH_UPDATE_F_OVERRIDE_ISROUTER);
 	}
 
 	if (ndm->ndm_flags & NTF_EXT_LEARNED)
 		flags |= NEIGH_UPDATE_F_EXT_LEARNED;
 
+	if (ndm->ndm_flags & NTF_ROUTER)
+		flags |= NEIGH_UPDATE_F_ISROUTER;
+
 	if (ndm->ndm_flags & NTF_USE) {
 		neigh_event_send(neigh, NULL);
 		err = 0;