Allow to allocate cache manager with custom callback on refill socket

Cache managers use two sockets: one for cache refill operation,
and another one for notifications.

In order to simulate NETLINK events by reading data from files,
we need to be able to overwrite both sockets.

This new function allows exactly that.

include/netlink/cache.h

@@ -146,6 +146,10 @@ struct nl_cache_mngr;
 extern int			nl_cache_mngr_alloc(struct nl_sock *,
 						    int, int,
 						    struct nl_cache_mngr **);
+extern int			nl_cache_mngr_alloc_cb(struct nl_sock *,
+						    int, int,
+						    struct nl_cache_mngr **,
+						    struct nl_cb *sync_cb);
 extern int			nl_cache_mngr_add(struct nl_cache_mngr *,
 						  const char *,
 						  change_func_t,

lib/cache_mngr.c

@@ -148,6 +148,22 @@ static int event_input(struct nl_msg *msg, void *arg)
  */
 int nl_cache_mngr_alloc(struct nl_sock *sk, int protocol, int flags,
 			struct nl_cache_mngr **result)
+{
+	return nl_cache_mngr_alloc_cb(sk, protocol, flags, result, NULL);
+}
+
+/**
+ * Allocate new cache manager, with custom callback on refill socket
+ * @arg sk		Netlink socket or NULL to auto allocate
+ * @arg protocol	Netlink protocol this manager is used for
+ * @arg flags		Flags (\c NL_AUTO_PROVIDE)
+ * @arg result		Result pointer
+ * @arg sync_cb		Callback for cache refill socket
+ *
+ * Same as \f nl_cache_mngr_alloc, but sets custom callback for refill socket
+ */
+int nl_cache_mngr_alloc_cb(struct nl_sock *sk, int protocol, int flags,
+			struct nl_cache_mngr **result, struct nl_cb *sync_cb)
 {
 	struct nl_cache_mngr *mngr;
 	int err = -NLE_NOMEM;
@@ -186,7 +202,12 @@ int nl_cache_mngr_alloc(struct nl_sock *sk, int protocol, int flags,
 		goto errout;
 
 	/* Create and allocate socket for sync cache fills */
-	mngr->cm_sync_sock = nl_socket_alloc();
+	if(sync_cb) {
+		mngr->cm_sync_sock = nl_socket_alloc_cb(sync_cb);
+	} else {
+		mngr->cm_sync_sock = nl_socket_alloc();
+	}
+
 	if (!mngr->cm_sync_sock) {
 		err = -NLE_NOMEM;
 		goto errout;

libnl-3.sym

@@ -79,6 +79,7 @@ global:
 	nl_cache_mngr_add;
 	nl_cache_mngr_add_cache;
 	nl_cache_mngr_alloc;
+	nl_cache_mngr_alloc_cb;
 	nl_cache_mngr_data_ready;
 	nl_cache_mngr_free;
 	nl_cache_mngr_get_fd;