path: root/src/include/gnunet_server_lib.h

/*
     This file is part of GNUnet.
     Copyright (C) 2009-2013 GNUnet e.V.

     GNUnet is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published
     by the Free Software Foundation; either version 3, or (at your
     option) any later version.

     GNUnet 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
     General Public License for more details.

     You should have received a copy of the GNU General Public License
     along with GNUnet; see the file COPYING.  If not, write to the
     Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
     Boston, MA 02110-1301, USA.
*/

/**
 * @author Christian Grothoff
 *
 * @file
 * Library for building GNUnet network servers

 * @defgroup server  Server library
 * Library for building GNUnet network servers
 *
 * Provides functions for a server that communicates with clients.
 *
 * @see [Documentation](https://gnunet.org/ipc)
 *
 * @{
 */

#ifndef GNUNET_SERVER_LIB_H
#define GNUNET_SERVER_LIB_H

#ifdef __cplusplus
extern "C"
{
#if 0                           /* keep Emacsens' auto-indent happy */
}
#endif
#endif

#include "gnunet_common.h"
#include "gnunet_connection_lib.h"


/**
 * Largest supported message (to be precise, one byte more
 * than the largest possible message, so tests involving
 * this value should check for messages being smaller than
 * this value).
 */
#define GNUNET_SERVER_MAX_MESSAGE_SIZE 65536

/**
 * Smallest supported message.
 */
#define GNUNET_SERVER_MIN_BUFFER_SIZE sizeof (struct GNUNET_MessageHeader)

/**
 * @brief handle for a server
 */
struct GNUNET_SERVER_Handle;

/**
 * @brief opaque handle for a client of the server
 */
struct GNUNET_SERVER_Client;

/**
 * @brief opaque handle server returns for aborting transmission to a client.
 */
struct GNUNET_SERVER_TransmitHandle;


/**
 * Functions with this signature are called whenever a message is
 * received.
 *
 * @param cls closure
 * @param client identification of the client
 * @param message the actual message
 */
typedef void
(*GNUNET_SERVER_MessageCallback) (void *cls,
                                  struct GNUNET_SERVER_Client *client,
                                  const struct GNUNET_MessageHeader *message);


/**
 * Message handler.  Each struct specifies how to handle on particular
 * type of message received.
 */
struct GNUNET_SERVER_MessageHandler
{
  /**
   * Function to call for messages of "type".
   */
  GNUNET_SERVER_MessageCallback callback;

  /**
   * Closure argument for @e callback.
   */
  void *callback_cls;

  /**
   * Type of the message this handler covers.
   */
  uint16_t type;

  /**
   * Expected size of messages of this type.  Use 0 for
   * variable-size.  If non-zero, messages of the given
   * type will be discarded (and the connection closed)
   * if they do not have the right size.
   */
  uint16_t expected_size;

};


/**
 * Create a new server.
 *
 * @param access_cb function for access control
 * @param access_cb_cls closure for @a access_cb
 * @param lsocks NULL-terminated array of listen sockets
 * @param idle_timeout after how long should we timeout idle connections?
 * @param require_found if #GNUNET_YES, connections sending messages of unknown type
 *        will be closed
 * @return handle for the new server, NULL on error
 *         (typically, "port" already in use)
 */
struct GNUNET_SERVER_Handle *
GNUNET_SERVER_create_with_sockets (GNUNET_CONNECTION_AccessCheck access_cb,
                                   void *access_cb_cls,
                                   struct GNUNET_NETWORK_Handle **lsocks,
                                   struct GNUNET_TIME_Relative idle_timeout,
                                   int require_found);

/**
 * Create a new server.
 *
 * @param access_cb function for access control
 * @param access_cb_cls closure for @a access_cb
 * @param server_addr address toes listen on (including port), NULL terminated array
 * @param socklen lengths of respective @a server_addr
 * @param idle_timeout after how long should we timeout idle connections?
 * @param require_found if #GNUNET_YES, connections sending messages of unknown type
 *        will be closed
 * @return handle for the new server, NULL on error
 *         (typically, "port" already in use)
 */
struct GNUNET_SERVER_Handle *
GNUNET_SERVER_create (GNUNET_CONNECTION_AccessCheck access_cb,
		      void *access_cb_cls,
                      struct sockaddr *const *server_addr,
                      const socklen_t * socklen,
                      struct GNUNET_TIME_Relative idle_timeout,
                      int require_found);


/**
 * Suspend accepting connections from the listen socket temporarily.
 * Resume activity using #GNUNET_SERVER_resume.
 *
 * @param server server to stop accepting connections.
 */
void
GNUNET_SERVER_suspend (struct GNUNET_SERVER_Handle *server);


/**
 * Resume accepting connections from the listen socket.
 *
 * @param server server to resume accepting connections.
 */
void
GNUNET_SERVER_resume (struct GNUNET_SERVER_Handle *server);


/**
 * Stop the listen socket and get ready to shutdown the server once
 * only clients marked using #GNUNET_SERVER_client_mark_monitor are
 * left.
 *
 * @param server server to stop listening on
 */
void
GNUNET_SERVER_stop_listening (struct GNUNET_SERVER_Handle *server);


/**
 * Free resources held by this server.
 *
 * @param server server to destroy
 */
void
GNUNET_SERVER_destroy (struct GNUNET_SERVER_Handle *server);


/**
 * Add additional handlers to an existing server.
 *
 * @param server the server to add handlers to
 * @param handlers array of message handlers for
 *        incoming messages; the last entry must
 *        have "NULL" for the "callback"; multiple
 *        entries for the same type are allowed,
 *        they will be called in order of occurence.
 *        These handlers can be removed later;
 *        the handlers array must exist until removed
 *        (or server is destroyed).
 */
void
GNUNET_SERVER_add_handlers (struct GNUNET_SERVER_Handle *server,
                            const struct GNUNET_SERVER_MessageHandler *handlers);


/**
 * Notify us when the server has enough space to transmit
 * a message of the given size to the given client.
 *
 * @param client client to transmit message to
 * @param size requested amount of buffer space
 * @param timeout after how long should we give up (and call
 *        notify with buf NULL and size 0)?
 * @param callback function to call when space is available
 * @param callback_cls closure for @a callback
 * @return non-NULL if the notify callback was queued; can be used
 *           to cancel the request using
 *           #GNUNET_SERVER_notify_transmit_ready_cancel.
 *         NULL if we are already going to notify someone else (busy)
 */
struct GNUNET_SERVER_TransmitHandle *
GNUNET_SERVER_notify_transmit_ready (struct GNUNET_SERVER_Client *client,
                                     size_t size,
                                     struct GNUNET_TIME_Relative timeout,
                                     GNUNET_CONNECTION_TransmitReadyNotify callback,
                                     void *callback_cls);


/**
 * Abort transmission request.
 *
 * @param th request to abort
 */
void
GNUNET_SERVER_notify_transmit_ready_cancel (struct GNUNET_SERVER_TransmitHandle *th);


/**
 * Set the 'monitor' flag on this client.  Clients which have been
 * marked as 'monitors' won't prevent the server from shutting down
 * once #GNUNET_SERVER_stop_listening has been invoked.  The idea is
 * that for "normal" clients we likely want to allow them to process
 * their requests; however, monitor-clients are likely to 'never'
 * disconnect during shutdown and thus will not be considered when
 * determining if the server should continue to exist after
 * #GNUNET_SERVER_destroy has been called.
 *
 * @param client the client to set the 'monitor' flag on
 */
void
GNUNET_SERVER_client_mark_monitor (struct GNUNET_SERVER_Client *client);


/**
 * Set the persistent flag on this client, used to setup client
 * connection to only be killed when the process of the service it's
 * connected to is actually dead.  This API is used during shutdown
 * signalling within ARM, and it is not expected that typical users
 * of the API would need this function.
 *
 * @param client the client to set the persistent flag on
 */
void
GNUNET_SERVER_client_persist_ (struct GNUNET_SERVER_Client *client);


/**
 * Resume receiving from this client, we are done processing the
 * current request.  This function must be called from within each
 * #GNUNET_SERVER_MessageCallback (or its respective continuations).
 *
 * @param client client we were processing a message of
 * @param success #GNUNET_OK to keep the connection open and
 *                          continue to receive
 *                #GNUNET_NO to close the connection (normal behavior)
 *                #GNUNET_SYSERR to close the connection (signal
 *                          serious error)
 */
void
GNUNET_SERVER_receive_done (struct GNUNET_SERVER_Client *client,
			    int success);


/**
 * Change the timeout for a particular client.  Decreasing the timeout
 * may not go into effect immediately (only after the previous timeout
 * times out or activity happens on the socket).
 *
 * @param client the client to update
 * @param timeout new timeout for activities on the socket
 */
void
GNUNET_SERVER_client_set_timeout (struct GNUNET_SERVER_Client *client,
                                  struct GNUNET_TIME_Relative timeout);


/**
 * Return user context associated with the given client.
 * Note: you should probably use the macro (call without the underscore).
 *
 * @param client client to query
 * @param size number of bytes in user context struct (for verification only)
 * @return pointer to user context
 */
void *
GNUNET_SERVER_client_get_user_context_ (struct GNUNET_SERVER_Client *client,
					size_t size);


/**
 * Set user context to be associated with the given client.
 * Note: you should probably use the macro (call without the underscore).
 *
 * @param client client to query
 * @param ptr pointer to user context
 * @param size number of bytes in user context struct (for verification only)
 */
void
GNUNET_SERVER_client_set_user_context_ (struct GNUNET_SERVER_Client *client,
					void *ptr,
					size_t size);


/**
 * Return user context associated with the given client.
 *
 * @param client client to query
 * @param type expected return type (i.e. 'struct Foo')
 * @return pointer to user context of type 'type *'.
 */
#define GNUNET_SERVER_client_get_user_context(client,type)              \
  (type *) GNUNET_SERVER_client_get_user_context_ (client, sizeof (type))

/**
 * Set user context to be associated with the given client.
 *
 * @param client client to query
 * @param value pointer to user context
 */
#define GNUNET_SERVER_client_set_user_context(client,value)             \
  GNUNET_SERVER_client_set_user_context_ (client, value, sizeof (*value))


/**
 * Disable the warning the server issues if a message is not acknowledged
 * in a timely fashion.  Use this call if a client is intentionally delayed
 * for a while.  Only applies to the current message.
 *
 * @param client client for which to disable the warning
 */
void
GNUNET_SERVER_disable_receive_done_warning (struct GNUNET_SERVER_Client
                                            *client);


/**
 * Inject a message into the server, pretend it came
 * from the specified client.  Delivery of the message
 * will happen instantly (if a handler is installed;
 * otherwise the call does nothing).
 *
 * @param server the server receiving the message
 * @param sender the "pretended" sender of the message
 *        can be NULL!
 * @param message message to transmit
 * @return #GNUNET_OK if the message was OK and the
 *                   connection can stay open
 *         #GNUNET_SYSERR if the connection to the
 *         client should be shut down
 */
int
GNUNET_SERVER_inject (struct<