path: root/src/psyc/psyc_api.c

/*
 * This file is part of GNUnet
 * (C) 2013 Christian Grothoff (and other contributing authors)
 *
 * 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., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

/** 
 * @file psyc/psyc_api.c
 * @brief PSYC service; high-level access to the PSYC protocol
 *        note that clients of this API are NOT expected to
 *        understand the PSYC message format, only the semantics!
 *        Parsing (and serializing) the PSYC stream format is done
 *        within the implementation of the libgnunetpsyc library,
 *        and this API deliberately exposes as little as possible
 *        of the actual data stream format to the application!
 * @author Gabor X Toth
 */

#include "platform.h"
#include "gnunet_util_lib.h"
#include "gnunet_env_lib.h"
#include "gnunet_psyc_service.h"
#include "psyc.h"

/** 
 * Handle that identifies a join request.
 *
 * Used to match calls to #GNUNET_PSYC_JoinCallback to the
 * corresponding calls to GNUNET_PSYC_join_decision().
 */
struct GNUNET_PSYC_JoinHandle;


/** 
 * Handle for the master of a PSYC channel.
 */
struct GNUNET_PSYC_Master;


/** 
 * Handle for a pending PSYC transmission operation.
 */
struct GNUNET_PSYC_MasterTransmitHandle;


/** 
 * Handle for a PSYC channel slave.
 */
struct GNUNET_PSYC_Slave;


/** 
 * Handle for a pending PSYC transmission operation.
 */
struct GNUNET_PSYC_SlaveTransmitHandle;


/** 
 * Handle to access PSYC channel operations for both the master and slaves.
 */
struct GNUNET_PSYC_Channel;


/** 
 * Handle to a story telling operation.
 */
struct GNUNET_PSYC_Story;


struct GNUNET_PSYC_StateQuery;


/** 
 * Function to call with the decision made for a join request.
 *
 * Must be called once and only once in response to an invocation of the
 * #GNUNET_PSYC_JoinCallback.
 *
 * @param jh Join request handle.
 * @param is_admitted #GNUNET_YES if joining is approved,
 *        #GNUNET_NO if it is disapproved.
 * @param relay_count Number of relays given.
 * @param relays Array of suggested peers that might be useful relays to use
 *        when joining the multicast group (essentially a list of peers that
 *        are already part of the multicast group and might thus be willing
 *        to help with routing).  If empty, only this local peer (which must
 *        be the multicast origin) is a good candidate for building the
 *        multicast tree.  Note that it is unnecessary to specify our own
 *        peer identity in this array.
 * @param method_name Method name for the message transmitted with the response.
 * @param env Environment containing transient variables for the message, or NULL.
 * @param data Data of the message.
 * @param data_size Size of @a data.
 */
void
GNUNET_PSYC_join_decision (struct GNUNET_PSYC_JoinHandle *jh,
                           int is_admitted,
                           unsigned int relay_count,
                           const struct GNUNET_PeerIdentity *relays,
                           const char *method_name,
                           const struct GNUNET_ENV_Environment *env,
                           const void *data,
                           size_t data_size);


/** 
 * Start a PSYC master channel.
 *
 * Will start a multicast group identified by the given ECC key.  Messages
 * received from group members will be given to the respective handler methods.
 * If a new member wants to join a group, the "join" method handler will be
 * invoked; the join handler must then generate a "join" message to approve the
 * joining of the new member.  The channel can also change group membership
 * without explicit requests.  Note that PSYC doesn't itself "understand" join
 * or part messages, the respective methods must call other PSYC functions to
 * inform PSYC about the meaning of the respective events.
 *
 * @param cfg Configuration to use (to connect to PSYC service).
 * @param channel_key ECC key that will be used to sign messages for this
 *        PSYC session. The public key is used to identify the PSYC channel.
 *        Note that end-users will usually not use the private key directly, but
 *        rather look it up in GADS for places managed by other users, or select
 *        a file with the private key(s) when setting up their own channels
 *        FIXME: we'll likely want to use NOT the p521 curve here, but a cheaper
 *        one in the future.
 * @param policy Channel policy specifying join and history restrictions.
 *        Used to automate join decisions.
 * @param method Function to invoke on messages received from slaves.
 * @param join_cb Function to invoke when a peer wants to join.
 * @param cls Closure for @a method and @a join_cb.
 * @return Handle for the channel master, NULL on error.
 */
struct GNUNET_PSYC_Master *
GNUNET_PSYC_master_start (const struct GNUNET_CONFIGURATION_Handle *cfg,
                          const struct GNUNET_CRYPTO_EccPrivateKey *channel_key,
                          enum GNUNET_PSYC_Policy policy,
                          GNUNET_PSYC_Method method,
                          GNUNET_PSYC_JoinCallback join_cb,
                          void *cls);


/** 
 * Send a message to call a method to all members in the PSYC channel.
 *
 * @param master Handle to the PSYC channel.
 * @param method_name Which method should be invoked.
 * @param env Environment containing state operations and transient variables
 *            for the message, or NULL.
 * @param notify Function to call to obtain the arguments.
 * @param notify_cls Closure for @a notify.
 * @param flags Flags for the message being transmitted.
 * @return Transmission handle, NULL on error (i.e. more than one request queued).
 */
struct GNUNET_PSYC_MasterTransmitHandle *
GNUNET_PSYC_master_transmit (struct GNUNET_PSYC_Master *master,
                             const char *method_name,
                             const struct GNUNET_ENV_Environment *env,
                             GNUNET_PSYC_MasterTransmitNotify notify,
                             void *notify_cls,
                             enum GNUNET_PSYC_MasterTransmitFlags flags);


/** 
 * Abort transmission request to channel.
 *
 * @param th Handle of the request that is being aborted.
 */
void
GNUNET_PSYC_master_transmit_cancel (struct GNUNET_PSYC_MasterTransmitHandle *th);


/** 
 * Stop a PSYC master channel.
 *
 * @param master PSYC channel master to stop.
 */
void
GNUNET_PSYC_master_stop (struct GNUNET_PSYC_Master *master);


/** 
 * Join a PSYC channel.
 *
 * The entity joining is always the local peer.  The user must immediately use
 * the GNUNET_PSYC_slave_to_master() functions to transmit a @e join_msg to the
 * channel; if the join request succeeds, the channel state (and @e recent
 * method calls) will be replayed to the joining member.  There is no explicit
 * notification on failure (as the channel may simply take days to approve,
 * and disapproval is simply being ignored).
 *
 * @param cfg Configuration to use.
 * @param channel_key ECC public key that identifies the channel we wish to join.
 * @param slave_key ECC private-public key pair that identifies the slave, and
 *        used by multicast to sign the join request and subsequent unicast
 *        requests sent to the master.
 * @param origin Peer identity of the origin.
 * @param relay_count Number of peers in the @a relays array.
 * @param relays Peer identities of members of the multicast group, which serve
 *        as relays and used to join the group at.
 * @param method Function to invoke on messages received from the channel,
 *        typically at least contains functions for @e join and @e part.
 * @param join_cb Function to invoke when a peer wants to join.
 * @param cls Closure for @a method_cb and @a join_cb.
 * @param method_name Method name for the join request.
 * @param env Environment containing transient variables for the request, or NULL.
 * @param data Payload for the join message.
 * @param data_size Number of bytes in @a data.
 * @return Handle for the slave, NULL on error.
 */
struct GNUNET_PSYC_Slave *
GNUNET_PSYC_slave_join (const struct GNUNET_CONFIGURATION_Handle *cfg,
                        const struct GNUNET_CRYPTO_EccPublicSignKey *channel_key,
                        const struct GNUNET_CRYPTO_EccPrivateKey *slave_key,
                        const struct GNUNET_PeerIdentity *origin,
                        size_t relay_count,
                        const struct GNUNET_PeerIdentity *relays,
                        GNUNET_PSYC_Method method,
                        GNUNET_PSYC_JoinCallback join_cb,
                        void *cls,
                        const char *method_name,
                        const struct GNUNET_ENV_Environment *env,
                        const void *data,
                        size_t data_size);


/** 
 * Part a PSYC channel.
 *
 * Will terminate the connection to the PSYC service.  Polite clients should
 * first explicitly send a @e part request (via GNUNET_PSYC_slave_to_master()).
 *
 * @param slave Slave handle.
 */
void
GNUNET_PSYC_slave_part (struct GNUNET_PSYC_Slave *slave);


/** 
 * Request a message to be sent to the channel master.
 *
 * @param slave Slave handle.
 * @param method_name Which (PSYC) method should be invoked (on host).
 * @param env Environment containing transient variables for the message, or NULL.
 * @param notify Function to call when we are allowed to transmit (to get data).
 * @param notify_cls Closure for @a notify.
 * @param flags Flags for the message being transmitted.
 * @return Transmission handle, NULL on error (i.e. more than one request queued).
 */
struct GNUNET_PSYC_SlaveTransmitHandle *
GNUNET_PSYC_slave_transmit (struct GNUNET_PSYC_Slave *slave,
                            const char *method_name,
                            const struct GNUNET_ENV_Environment *env,
                            GNUNET_PSYC_SlaveTransmitNotify notify,
                            void *notify_cls,
                            enum GNUNET_PSYC_SlaveTransmitFlags flags);


/** 
 * Abort transmission request to master.
 *
 * @param th Handle of the request that is being aborted.
 */
void
GNUNET_PSYC_slave_transmit_cancel (struct GNUNET_PSYC_SlaveTransmitHandle *th);


/** 
 * Convert a channel @a master to a @e channel handle to access the @e channel APIs.
 *
 * @param master Channel master handle.
 * @return Channel handle, valid for as long as @a master is valid.
 */
struct GNUNET_PSYC_Channel *
GNUNET_PSYC_master_get_channel (struct GNUNET_PSYC_Master *master);


/** 
 * Convert @a slave to a @e channel handle to access the @e channel APIs.
 *
 * @param slave Slave handle.
 * @return Channel handle, valid for as long as @a slave is valid.
 */
struct GNUNET_PSYC_Channel *
GNUNET_PSYC_slave_get_channel (struct GNUNET_PSYC_Slave *slave);


/** 
 * Add a slave to the channel's membership list.
 *
 * Note that this will NOT generate any PSYC traffic, it will merely update the
 * local database to modify how we react to <em>membership test</em> queries.
 * The channel master still needs to explicitly transmit a @e join message to
 * notify other channel members and they then also must still call this function
 * in their respective methods handling the @e join message.  This way, how @e
 * join and @e part operations are exactly implemented is still up to the
 * application; for example, there might be a @e part_all method to kick out
 * everyone.
 *
 * Note that channel slaves are explicitly trusted to execute such methods
 * correctly; not doing so correctly will result in either denying other slaves
 * access or offering access to channel data to non-members.
 *
 * @param channel Channel handle.
 * @param slave_key Identity of channel slave to add.
 * @param announced_at ID of the message that announced the membership change.
 * @param effective_since Addition of slave is in effect since this message ID.
 */
void
GNUNET_PSYC_channel_slave_add (struct GNUNET_PSYC_Channel *channel,
                               const struct GNUNET_CRYPTO_EccPublicSignKey *slave_key,
                               uint64_t announced_at,
                               uint64_t effective_since);


/** 
 * Remove a slave from the channel's membership list.
 *
 * Note that this will NOT generate any PSYC traffic, it will merely update the
 * local database to modify how we react to <em>membership test</em> queries.
 * The channel master still needs to explicitly transmit a @e part message to
 * notify other channel members and they then also must still call this function
 * in their respective methods handling the @e part message.  This way, how
 * @e join and @e part operations are exactly implemented is still up to the
 * application; for example, there might be a @e part_all message to kick out
 * everyone.
 *
 * Note that channel members are explicitly trusted to perform these
 * operations correctly; not doing so correctly will result in either
 * denying members access or offering access to channel data to
 * non-members.
 *
 * @param channel Channel handle.
 * @param slave_key Identity of channel slave to remove.
 * @param announced_at ID of the message that announced the membership change.
 */
void
GNUNET_PSYC_channel_slave_remove (struct GNUNET_PSYC_Channel *channel,
                                  const struct GNUNET_CRYPTO_EccPublicSignKey *slave_key,
                                  uint64_t announced_at);


/** 
 * Request to be told the message history of the channel.
 *
 * Historic messages (but NOT the state at the time) will be replayed (given to
 * the normal method handlers) if available and if access is permitted.
 *
 * To get the latest message, use 0 for both the start and end message ID.
 *
 * @param channel Which channel should be replayed?
 * @param start_message_id Earliest interesting point in history.
 * @param end_message_id Last (exclusive) interesting point in history.
 * @param method Function to invoke on messages received from the story.
 * @param finish_cb Function to call when the requested story has been fully
 *        told (counting message IDs might not suffice, as some messages
 *        might be secret and thus the listener would not know the story is
 *        finished without being told explicitly); once this function
 *        has been called, the client must not call
 *        GNUNET_PSYC_channel_story_tell_cancel() anymore.
 * @param cls Closure for the callbacks.
 * @return Handle to cancel story telling operation.
 */
struct GNUNET_PSYC_Story *
GNUNET_PSYC_channel_story_tell (struct GNUNET_PSYC_Channel *channel,
                                uint64_t start_message_id,
                                uint64_t end_message_id,
                                GNUNET_PSYC_Method method,
                                GNUNET_PSYC_FinishCallback *finish_cb,
                                void *cls);


/** 
 * Abort story telling.
 *
 * This function must not be called from within method handlers (as given to
 * GNUNET_PSYC_slave_join()) of the slave.
 *
 * @param story Story telling operation to stop.
 */
void
GNUNET_PSYC_channel_story_tell_cancel (struct GNUNET_PSYC_Story *story);


/** 
 * Retrieve the best matching channel state variable.
 *
 * If the requested variable name is not present in the state, the nearest
 * less-specific name is matched; for example, requesting "_a_b" will match "_a"
 * if "_a_b" does not exist.
 *
 * @param channel Channel handle.
 * @param full_name Full name of the requested variable, the actual variable
 *        returned might have a shorter name..
 * @param cb Function called once when a matching state variable is found.
 *        Not called if there's no matching state variable.
 * @param cb_cls Closure for the callbacks.
 * @return Handle that can be used to cancel the query operation.
 */
struct GNUNET_PSYC_StateQuery *
GNUNET_PSYC_channel_state_get (struct GNUNET_PSYC_Channel *channel,
                               const char *full_name,
                               GNUNET_PSYC_StateCallback cb,
                               void *cb_cls);


/** 
 * Return all channel state variables whose name matches a given prefix.
 *
 * A name matches if it starts with the given @a name_prefix, thus requesting the
 * empty prefix ("") will match all values; requesting "_a_b" will also return
 * values stored under "_a_b_c".
 *
 * The @a state_cb is invoked on all matching state variables asynchronously, as
 * the state is stored in and retrieved from the PSYCstore,
 *
 * @param channel Channel handle.
 * @param name_prefix Prefix of the state variable name to match.
 * @param cb Function to call with the matching state variables.
 * @param cb_cls Closure for the callbacks.
 * @return Handle that can be used to cancel the query operation.
 */
struct GNUNET_PSYC_StateQuery *
GNUNET_PSYC_channel_state_get_prefix (struct GNUNET_PSYC_Channel *channel,
                                      const char *name_prefix,
                                      GNUNET_PSYC_StateCallback cb,
                                      void *cb_cls);


/** 
 * Cancel a state query operation.
 *
 * @param query Handle for the operation to cancel.
 */
void
GNUNET_PSYC_channel_state_get_cancel (struct GNUNET_PSYC_StateQuery *query);


/* end of psyc_api.c */