[PATCH v2 1/1] RDMA/addr: Refresh neighbour entries upon "rdma_resolve_addr"

[Gerd Rausch <gerd.rausch@xxxxxxxxxx>]

Unlike with IPv[46], where "ip_finish_output2" triggers
a refresh of STALE neighbour entries via "neigh_output",
"rdma_resolve_addr" never triggers an update.

If a wrong STALE entry ever enters the cache, it'll remain
wrong forever (unless refreshed via TCP/IP, or otherwise).

Let the cache inconsistency resolve itself by triggering
an update from "rdma_resolve_addr".

Signed-off-by: Gerd Rausch <gerd.rausch@xxxxxxxxxx>
---

v2: Add a "(__force u32)" cast for "__ipv4_neigh_lookup_noref"

 drivers/infiniband/core/addr.c | 40 ++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/drivers/infiniband/core/addr.c b/drivers/infiniband/core/addr.c
index f253295795f0..704dc9cc130e 100644
--- a/drivers/infiniband/core/addr.c
+++ b/drivers/infiniband/core/addr.c
@@ -394,6 +394,8 @@ static int addr4_resolve(struct sockaddr *src_sock,
 	__be32 dst_ip = dst_in->sin_addr.s_addr;
 	struct rtable *rt;
 	struct flowi4 fl4;
+	struct net_device *dev;
+	struct neighbour *neigh;
 	int ret;
 
 	memset(&fl4, 0, sizeof(fl4));
@@ -409,6 +411,24 @@ static int addr4_resolve(struct sockaddr *src_sock,
 
 	addr->hoplimit = ip4_dst_hoplimit(&rt->dst);
 
+	/* trigger ARP-entry refresh if necessary,
+	 * the same way "ip_finish_output2" does
+	 */
+	if (addr->bound_dev_if) {
+		dev = dev_get_by_index(addr->net, addr->bound_dev_if);
+	} else {
+		dev = rt->dst.dev;
+		dev_hold(dev);
+	}
+	if (dev) {
+		rcu_read_lock_bh();
+		neigh = __ipv4_neigh_lookup_noref(dev, (__force u32)dst_ip);
+		if (neigh)
+			neigh_event_send(neigh, NULL);
+		rcu_read_unlock_bh();
+		dev_put(dev);
+	}
+
 	*prt = rt;
 	return 0;
 }
@@ -424,6 +444,8 @@ static int addr6_resolve(struct sockaddr *src_sock,
 				(const struct sockaddr_in6 *)dst_sock;
 	struct flowi6 fl6;
 	struct dst_entry *dst;
+	struct net_device *dev;
+	struct neighbour *neigh;
 
 	memset(&fl6, 0, sizeof fl6);
 	fl6.daddr = dst_in->sin6_addr;
@@ -439,6 +461,24 @@ static int addr6_resolve(struct sockaddr *src_sock,
 
 	addr->hoplimit = ip6_dst_hoplimit(dst);
 
+	/* trigger neighbour-entry refresh if necessary,
+	 * the same way "ip6_finish_output2" does
+	 */
+	if (addr->bound_dev_if) {
+		dev = dev_get_by_index(addr->net, addr->bound_dev_if);
+	} else {
+		dev = dst->dev;
+		dev_hold(dev);
+	}
+	if (dev) {
+		rcu_read_lock_bh();
+		neigh = __ipv6_neigh_lookup_noref(dst->dev, &dst_in->sin6_addr);
+		if (neigh)
+			neigh_event_send(neigh, NULL);
+		rcu_read_unlock_bh();
+		dev_put(dev);
+	}
+
 	*pdst = dst;
 	return 0;
 }