/* GIO - GLib Input, Output and Streaming Library

 *

 * Copyright © 2009 Codethink Limited

 *

 * SPDX-License-Identifier: LGPL-2.1-or-later

 *

 * This library is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 *

 * See the included COPYING file for more information.

 *

 * Authors: Ryan Lortie <desrt@desrt.ca>

 */

/**

 * GSocketControlMessage:

 *

 * A `GSocketControlMessage` is a special-purpose utility message that

 * can be sent to or received from a [class@Gio.Socket]. These types of

 * messages are often called ‘ancillary data’.

 *

 * The message can represent some sort of special instruction to or

 * information from the socket or can represent a special kind of

 * transfer to the peer (for example, sending a file descriptor over

 * a UNIX socket).

 *

 * These messages are sent with [method@Gio.Socket.send_message] and received

 * with [method@Gio.Socket.receive_message].

 *

 * To extend the set of control messages that can be sent, subclass this

 * class and override the `get_size`, `get_level`, `get_type` and `serialize`

 * methods.

 *

 * To extend the set of control messages that can be received, subclass

 * this class and implement the `deserialize` method. Also, make sure your

 * class is registered with the [type@GObject.Type] type system before calling

 * [method@Gio.Socket.receive_message] to read such a message.

 *

 * Since: 2.22

 */

#include "config.h"

#include "gsocketcontrolmessage.h"

#include "gnetworkingprivate.h"

#include "glibintl.h"

#ifndef G_OS_WIN32

#include "gunixcredentialsmessage.h"

#include "gunixfdmessage.h"

#endif

#include "giptosmessage.h"

#include "gipv6tclassmessage.h"

G_DEFINE_ABSTRACT_TYPE (GSocketControlMessage, g_socket_control_message, G_TYPE_OBJECT)

/**

 * g_socket_control_message_get_size:

 * @message: a #GSocketControlMessage

 *

 * Returns the space required for the control message, not including

 * headers or alignment.

 *

 * Returns: The number of bytes required.

 *

 * Since: 2.22

 */

gsize

g_socket_control_message_get_size (GSocketControlMessage *message)

{

  g_return_val_if_fail (G_IS_SOCKET_CONTROL_MESSAGE (message), 0);

  return G_SOCKET_CONTROL_MESSAGE_GET_CLASS (message)->get_size (message);

}

/**

 * g_socket_control_message_get_level:

 * @message: a #GSocketControlMessage

 *

 * Returns the "level" (i.e. the originating protocol) of the control message.

 * This is often SOL_SOCKET.

 *

 * Returns: an integer describing the level

 *

 * Since: 2.22

 */

int

g_socket_control_message_get_level (GSocketControlMessage *message)

{

  g_return_val_if_fail (G_IS_SOCKET_CONTROL_MESSAGE (message), 0);

  return G_SOCKET_CONTROL_MESSAGE_GET_CLASS (message)->get_level (message);

}

/**

 * g_socket_control_message_get_msg_type:

 * @message: a #GSocketControlMessage

 *

 * Returns the protocol specific type of the control message.

 * For instance, for UNIX fd passing this would be SCM_RIGHTS.

 *

 * Returns: an integer describing the type of control message

 *

 * Since: 2.22

 */

int

g_socket_control_message_get_msg_type (GSocketControlMessage *message)

{

  g_return_val_if_fail (G_IS_SOCKET_CONTROL_MESSAGE (message), 0);

  return G_SOCKET_CONTROL_MESSAGE_GET_CLASS (message)->get_type (message);

}

/**

 * g_socket_control_message_serialize:

 * @message: a #GSocketControlMessage

 * @data: (not nullable): A buffer to write data to

 *

 * Converts the data in the message to bytes placed in the

 * message.

 *

 * @data is guaranteed to have enough space to fit the size

 * returned by g_socket_control_message_get_size() on this

 * object.

 *

 * Since: 2.22

 */

void

g_socket_control_message_serialize (GSocketControlMessage *message,

            gpointer               data)

{

  g_return_if_fail (G_IS_SOCKET_CONTROL_MESSAGE (message));

  G_SOCKET_CONTROL_MESSAGE_GET_CLASS (message)->serialize (message, data);

}

static void

g_socket_control_message_init (GSocketControlMessage *message)

{

}

static void

g_socket_control_message_class_init (GSocketControlMessageClass *class)

{

}

static GSocketControlMessage *

try_deserialize_message_type (GType msgtype, int level, int type, gsize size, gpointer data)

{

  GSocketControlMessage *message;

  GSocketControlMessageClass *class = g_type_class_ref (msgtype);

  message = class->deserialize (level, type, size, data);

  g_type_class_unref (class);

  return message;

}

/**

 * g_socket_control_message_deserialize:

 * @level: a socket level

 * @type: a socket control message type for the given @level

 * @size: the size of the data in bytes

 * @data: (array length=size) (element-type guint8): pointer to the message data

 *

 * Tries to deserialize a socket control message of a given

 * @level and @type. This will ask all known (to GType) subclasses

 * of #GSocketControlMessage if they can understand this kind

 * of message and if so deserialize it into a #GSocketControlMessage.

 *

 * If there is no implementation for this kind of control message, %NULL

 * will be returned.

 *

 * Returns: (nullable) (transfer full): the deserialized message or %NULL

 *

 * Since: 2.22

 */

GSocketControlMessage *

g_socket_control_message_deserialize (int      level,

              int      type,

              gsize    size,

              gpointer data)

{

  GSocketControlMessage *message;

  GType *message_types;

  guint n_message_types;

  guint i;

  static gsize builtin_messages_initialized = FALSE;

  static GType builtin_messages[5];

  static guint n_builtin_messages = 0;

  if (g_once_init_enter (&builtin_messages_initialized))

    {

      i = 0;

#ifndef G_OS_WIN32

      builtin_messages[i++] = G_TYPE_UNIX_CREDENTIALS_MESSAGE;

      builtin_messages[i++] = G_TYPE_UNIX_FD_MESSAGE;

#endif

      builtin_messages[i++] = G_TYPE_IP_TOS_MESSAGE;

      builtin_messages[i++] = G_TYPE_IPV6_TCLASS_MESSAGE;

      n_builtin_messages = i;

      /* Ensure we know about the built in types */

      for (i = 0; builtin_messages[i]; ++i)

        {

          g_type_ensure (builtin_messages[i]);

        }

      g_once_init_leave (&builtin_messages_initialized, TRUE);

    }

  message_types = g_type_children (G_TYPE_SOCKET_CONTROL_MESSAGE, &n_message_types);

  message = NULL;

  /* First try to deserialize using message types registered by application. */

  if (n_message_types > n_builtin_messages)

    {

      for (i = 0; i < n_message_types; i++)

        {

          guint j;

          gboolean is_builtin = FALSE;

          for (j = 0; builtin_messages[j]; ++j)

            {

              if (message_types[i] == builtin_messages[j])

                {

                  is_builtin = TRUE;

                  break;

                }

            }

          if (!is_builtin)

            {

              message = try_deserialize_message_type (message_types[i], level,

                                                      type, size, data);

              if (message != NULL)

                break;

            }

        }

    }

  g_free (message_types);

  /* Fallback to builtin message types. */

  if (message == NULL)

    {

      for (i = 0; builtin_messages[i]; i++)

        {

          message = try_deserialize_message_type (builtin_messages[i], level,

                                                  type, size, data);

          if (message != NULL)

            break;

        }

    }

  /* It's not a bug if we can't deserialize the control message - for

   * example, the control message may be be discarded if it is deemed

   * empty, see e.g.

   *

   *  https://gitlab.gnome.org/GNOME/glib/commit/ec91ed00f14c70cca9749347b8ebc19d72d9885b

   *

   * Therefore, it's not appropriate to print a warning about not

   * being able to deserialize the message.

   */

  return message;

}