network: implement masking of .link, .network and .netdev files

src/network/networkd-netdev.c

@@ -475,6 +475,11 @@ static int netdev_load_one(Manager *manager, const char *filename) {
         assert(manager);
         assert(filename);
 
+        if (null_or_empty_path(filename)) {
+                log_debug("skipping empty file: %s", filename);
+                return 0;
+        }
+
         file = fopen(filename, "re");
         if (!file) {
                 if (errno == ENOENT)

src/network/networkd-network.c

@@ -44,6 +44,11 @@ static int network_load_one(Manager *manager, const char *filename) {
                         return -errno;
         }
 
+        if (null_or_empty_path(filename)) {
+                log_debug("skipping empty file: %s", filename);
+                return 0;
+        }
+
         network = new0(Network, 1);
         if (!network)
                 return log_oom();

src/udev/net/link-config.c

@@ -146,6 +146,11 @@ static int load_link(link_config_ctx *ctx, const char *filename) {
         assert(ctx);
         assert(filename);
 
+        if (null_or_empty_path(filename)) {
+                log_debug("skipping empty file: %s", filename);
+                return 0;
+        }
+
         file = fopen(filename, "re");
         if (!file) {
                 if (errno == ENOENT)