module-protocol-native: multiple names to try in PW_KEY_REMOTE_NAME

Allow PIPEWIRE_REMOTE / PW_KEY_REMOTE_NAME to contain a JSON array of
sockets to try to connect to, in order, instead of just one name.

JSON is restricted to utf-8 encoding. Also, this forces using JSON
syntax for paths that start with '['. This probably will not usually
cause much problem.

src/modules/module-protocol-native/local-socket.c

@@ -9,6 +9,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <errno.h>
+#include <limits.h>
 #include <unistd.h>
 #include <sys/socket.h>
 #include <sys/un.h>
@@ -20,6 +21,7 @@
 #endif
 
 #include <pipewire/pipewire.h>
+#include <spa/utils/json.h>
 
 #define DEFAULT_SYSTEM_RUNTIME_DIR "/run/pipewire"
 
@@ -119,31 +121,56 @@ error:
 	return res;
 }
 
-int pw_protocol_native_connect_local_socket(struct pw_protocol_client *client,
-					    const struct spa_dict *props,
+static int try_connect_name(struct pw_protocol_client *client,
+		const char *name,
 		void (*done_callback) (void *data, int res),
 		void *data)
 {
-	const char *runtime_dir, *name;
+	const char *runtime_dir;
 	int res;
 
-	name = get_remote(props);
-	if (name == NULL)
-		return -EINVAL;
-
 	if (name[0] == '/') {
-		res = try_connect(client, NULL, name, done_callback, data);
+		return try_connect(client, NULL, name, done_callback, data);
 	} else {
 		runtime_dir = get_runtime_dir();
 		if (runtime_dir != NULL) {
 			res = try_connect(client, runtime_dir, name, done_callback, data);
 			if (res >= 0)
-				goto exit;
+				return res;
 		}
 		runtime_dir = get_system_dir();
 		if (runtime_dir != NULL)
-			res = try_connect(client, runtime_dir, name, done_callback, data);
+			return try_connect(client, runtime_dir, name, done_callback, data);
 	}
-exit:
+
+	return -EINVAL;
+}
+
+int pw_protocol_native_connect_local_socket(struct pw_protocol_client *client,
+					    const struct spa_dict *props,
+					    void (*done_callback) (void *data, int res),
+					    void *data)
+{
+	const char *name;
+	struct spa_json it[2];
+	char path[PATH_MAX];
+	int res = -EINVAL;
+
+	name = get_remote(props);
+	if (name == NULL)
+		return -EINVAL;
+
+	spa_json_init(&it[0], name, strlen(name));
+
+	if (spa_json_enter_array(&it[0], &it[1]) < 0)
+		return try_connect_name(client, name, done_callback, data);
+
+	while (spa_json_get_string(&it[1], path, sizeof(path)) > 0) {
+		res = try_connect_name(client, path, done_callback, data);
+		if (res < 0)
+			continue;
+		break;
+	}
+
 	return res;
 }

src/pipewire/keys.h

@@ -90,7 +90,9 @@ extern "C" {
 /* remote keys */
 #define PW_KEY_REMOTE_NAME		"remote.name"		/**< The name of the remote to connect to,
 								  *  default pipewire-0, overwritten by
-								  *  env(PIPEWIRE_REMOTE) */
+								  *  env(PIPEWIRE_REMOTE). May also be
+								  *  a SPA-JSON array of sockets, to be tried
+								  *  in order. */
 #define PW_KEY_REMOTE_INTENTION		"remote.intention"	/**< The intention of the remote connection,
 								  *  "generic", "screencast" */