protocol: make connect async

Make the protocol client connect call async with a callback when it
completes.
Move the connect methods into separate files, add an empty connect
method that will use the screencast portal to get a pipewire fd.
Use the remote intention to get the connect method.
Add some better error reporting.

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

@@ -0,0 +1,98 @@
+/* PipeWire
+ * Copyright (C) 2018 Wim Taymans <wim.taymans@gmail.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#include <stdint.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <sys/file.h>
+
+#include <spa/lib/debug.h>
+
+#include <pipewire/pipewire.h>
+#include <pipewire/private.h>
+
+static const char *
+get_remote(const struct pw_properties *properties)
+{
+	const char *name = NULL;
+
+	if (properties)
+		name = pw_properties_get(properties, PW_REMOTE_PROP_REMOTE_NAME);
+	if (name == NULL)
+		name = getenv("PIPEWIRE_REMOTE");
+	if (name == NULL)
+		name = "pipewire-0";
+	return name;
+}
+
+int pw_protocol_native_connect_local_socket(struct pw_protocol_client *client,
+					    void (*done_callback) (void *data, int res),
+					    void *data)
+{
+	struct pw_remote *remote = client->remote;
+	struct sockaddr_un addr;
+	socklen_t size;
+	const char *runtime_dir, *name = NULL;
+	int res, name_size, fd;
+
+	if ((runtime_dir = getenv("XDG_RUNTIME_DIR")) == NULL) {
+		pw_log_error("connect failed: XDG_RUNTIME_DIR not set in the environment");
+		return -EIO;
+        }
+
+	name = get_remote(pw_remote_get_properties(remote));
+
+        if ((fd = socket(PF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0)) < 0)
+                return -errno;
+
+        memset(&addr, 0, sizeof(addr));
+        addr.sun_family = AF_LOCAL;
+        name_size = snprintf(addr.sun_path, sizeof(addr.sun_path), "%s/%s", runtime_dir, name) + 1;
+
+        if (name_size > (int) sizeof addr.sun_path) {
+                pw_log_error("socket path \"%s/%s\" plus null terminator exceeds 108 bytes",
+                             runtime_dir, name);
+		res = -ENOSPC;
+                goto error_close;
+        };
+
+        size = offsetof(struct sockaddr_un, sun_path) + name_size;
+
+        if (connect(fd, (struct sockaddr *) &addr, size) < 0) {
+		res = -errno;
+                goto error_close;
+	}
+
+	res = pw_protocol_client_connect_fd(client, fd);
+
+	done_callback(data, res);
+
+	return res;
+
+      error_close:
+        close(fd);
+	return res;
+}