sd-path: export "systemd-network-path"

Inspired by https://lists.freedesktop.org/archives/systemd-devel/2020-March/044169.html.

man/sd_path_lookup.xml

@@ -98,6 +98,8 @@
         <constant>SD_PATH_BINFMT_DIR</constant>,
         <constant>SD_PATH_MODULES_LOAD_DIR</constant>,
         <constant>SD_PATH_CATALOG_DIR</constant>,
+
+        <constant>SD_PATH_SYSTEMD_NETWORK_PATH</constant>,
 };</funcsynopsisinfo>
 
       <funcprototype>

src/basic/path-lookup.h

@@ -71,3 +71,4 @@ char **generator_binary_paths(UnitFileScope scope);
 char **env_generator_binary_paths(bool is_system);
 
 #define NETWORK_DIRS ((const char* const*) CONF_PATHS_STRV("systemd/network"))
+#define NETWORK_DIRS_NULSTR CONF_PATHS_NULSTR("systemd/network")

src/libsystemd/sd-path/sd-path.c

@@ -633,7 +633,12 @@ static int get_search(uint64_t type, char ***list) {
 
                 *list = t;
                 return 0;
-        }}
+        }
+
+        case SD_PATH_SYSTEMD_NETWORK_PATH:
+                return strv_from_nulstr(list, NETWORK_DIRS_NULSTR);
+
+        }
 
         return -EOPNOTSUPP;
 }

src/path/path.c

@@ -81,6 +81,8 @@ static const char* const path_table[_SD_PATH_MAX] = {
         [SD_PATH_BINFMT_DIR]                    = "binfmt-dir",
         [SD_PATH_MODULES_LOAD_DIR]              = "modules-load-dir",
         [SD_PATH_CATALOG_DIR]                   = "catalog-dir",
+
+        [SD_PATH_SYSTEMD_NETWORK_PATH]          = "systemd-network-path",
 };
 
 static int list_homes(void) {

src/systemd/sd-path.h

@@ -102,6 +102,9 @@ enum {
         SD_PATH_MODULES_LOAD_DIR,
         SD_PATH_CATALOG_DIR,
 
+        /* systemd-networkd search paths */
+        SD_PATH_SYSTEMD_NETWORK_PATH,
+
         _SD_PATH_MAX,
 };