zebra: force neighbor entry reinstallation

Even if the neighbor entry we want already exists, force its
reinstallation to ensure that it's valid. This will now take place when
we request an update of the neighbor entry.

Ticket: CM-22604
Signed-off-by: Quentin Young <qlyoung@cumulusnetworks.com>

1 files changed, 15 insertions, 24 deletions

diff --git a/zebra/interface.c b/zebra/interface.c
index 76e0a09c1..9d8e41a65 100644
--- a/zebra/interface.c
+++ b/zebra/interface.c
@@ -806,19 +806,6 @@ static void ipv6_ll_address_to_mac(struct in6_addr *address, uint8_t *mac)
 	mac[5] = address->s6_addr[15];
 }
 
-static bool mac_is_same(char *mac1, char *mac2)
-{
-	if (mac1[0] == mac2[0] &&
-	    mac1[1] == mac2[1] &&
-	    mac1[2] == mac2[2] &&
-	    mac1[3] == mac2[3] &&
-	    mac1[4] == mac2[4] &&
-	    mac1[5] == mac2[5])
-		return true;
-	else
-		return false;
-}
-
 void if_nbr_mac_to_ipv4ll_neigh_update(struct interface *ifp,
 				       char mac[6],
 				       struct in6_addr *address,
@@ -835,19 +822,23 @@ void if_nbr_mac_to_ipv4ll_neigh_update(struct interface *ifp,
 	ns_id = zvrf->zns->ns_id;
 
 	/*
-	 * Remove existed arp record for the interface as netlink
-	 * protocol does not have update message types
-	 *
-	 * supported message types are RTM_NEWNEIGH and RTM_DELNEIGH
+	 * Remove and re-add any existing neighbor entry for this address,
+	 * since Netlink doesn't currently offer update message types.
 	 */
-	if (!mac_is_same(zif->neigh_mac, mac)) {
-		kernel_neigh_update(0, ifp->ifindex, ipv4_ll.s_addr,
-				    mac, 6, ns_id);
+	kernel_neigh_update(0, ifp->ifindex, ipv4_ll.s_addr, mac, 6, ns_id);
 
-		/* Add arp record */
-		kernel_neigh_update(add, ifp->ifindex, ipv4_ll.s_addr,
-				    mac, 6, ns_id);
-	}
+	/* Add new neighbor entry.
+	 *
+	 * We force installation even if current neighbor entry is the same.
+	 * Since this function is used to refresh our MAC entries after an
+	 * interface flap, if we don't force in our custom entries with their
+	 * state set to PERMANENT or REACHABLE then the kernel will attempt to
+	 * resolve our leftover entries, fail, mark them unreachable and then
+	 * they'll be useless to us.
+	 */
+	if (add)
+		kernel_neigh_update(add, ifp->ifindex, ipv4_ll.s_addr, mac, 6,
+				    ns_id);
 
 	memcpy(&zif->neigh_mac[0], &mac[0], 6);