11 files changed, 5783 insertions, 0 deletions

diff --git a/src/include/.gitignore b/src/include/.gitignore
new file mode 100644
index 0000000..282522d
--- /dev/null
+++ b/src/include/.gitignore
@@ -0,0 +1,2 @@
+Makefile
+Makefile.in
diff --git a/src/include/Makefile.am b/src/include/Makefile.am
new file mode 100644
index 0000000..8b8bcba
--- /dev/null
+++ b/src/include/Makefile.am
@@ -0,0 +1,15 @@
+# This Makefile.am is in the public domain
+SUBDIRS = .
+
+gnunetincludedir = $(includedir)/gnunet
+
+gnunetinclude_HEADERS = \
+  gnunet_multicast_service.h \
+  gnunet_psycstore_plugin.h \
+  gnunet_psycstore_service.h \
+  gnunet_psyc_service.h \
+  gnunet_psyc_util_lib.h \
+  gnunet_psyc_env.h \
+  gnunet_psyc_message.h \
+  gnunet_psyc_slicer.h \
+  gnunet_social_service.h
diff --git a/src/include/gnunet_multicast_service.h b/src/include/gnunet_multicast_service.h
new file mode 100644
index 0000000..58fca0b
--- /dev/null
+++ b/src/include/gnunet_multicast_service.h
@@ -0,0 +1,925 @@
+/*
+     This file is part of GNUnet.
+     Copyright (C) 2012, 2013 GNUnet e.V.
+
+     GNUnet is free software: you can redistribute it and/or modify it
+     under the terms of the GNU Affero General Public License as published
+     by the Free Software Foundation, either version 3 of the License,
+     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
+     Affero General Public License for more details.
+    
+     You should have received a copy of the GNU Affero General Public License
+     along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+     SPDX-License-Identifier: AGPL3.0-or-later
+*/
+
+/**
+ * @author Gabor X Toth
+ * @author Christian Grothoff
+ *
+ * @file
+ * Multicast service; multicast messaging via CADET
+ *
+ * @defgroup multicast  Multicast service
+ * Multicast messaging via CADET.
+ * @{
+ */
+
+#ifndef GNUNET_MULTICAST_SERVICE_H
+#define GNUNET_MULTICAST_SERVICE_H
+
+#ifdef __cplusplus
+extern "C"
+{
+#if 0                           /* keep Emacsens' auto-indent happy */
+}
+#endif
+#endif
+
+#include "gnunet_util_lib.h"
+#include "gnunet_transport_service.h"
+
+/**
+ * Version number of GNUnet-multicast API.
+ */
+#define GNUNET_MULTICAST_VERSION 0x00000000
+
+/**
+ * Opaque handle for a multicast group member.
+ */
+struct GNUNET_MULTICAST_Member;
+
+/**
+ * Handle for the origin of a multicast group.
+ */
+struct GNUNET_MULTICAST_Origin;
+
+
+enum GNUNET_MULTICAST_MessageFlags
+{
+  /**
+   * First fragment of a message.
+   */
+  GNUNET_MULTICAST_MESSAGE_FIRST_FRAGMENT = 1 << 0,
+
+  /**
+   * Last fragment of a message.
+   */
+  GNUNET_MULTICAST_MESSAGE_LAST_FRAGMENT = 1 << 1,
+
+  /**
+   * OR'ed flags if message is not fragmented.
+   */
+  GNUNET_MULTICAST_MESSAGE_NOT_FRAGMENTED
+    = GNUNET_MULTICAST_MESSAGE_FIRST_FRAGMENT
+  | GNUNET_MULTICAST_MESSAGE_LAST_FRAGMENT,
+
+  /**
+   * Historic message, used only locally when replaying messages from local
+   * storage.
+   */
+  GNUNET_MULTICAST_MESSAGE_HISTORIC = 1 << 30
+
+};
+
+
+GNUNET_NETWORK_STRUCT_BEGIN
+
+/**
+ * Header of a multicast message fragment.
+ *
+ * This format is public as the replay mechanism must replay message fragments using the
+ * same format.  This is needed as we want to integrity-check message fragments within
+ * the multicast layer to avoid multicasting mal-formed messages.
+ */
+struct GNUNET_MULTICAST_MessageHeader
+{
+
+  /**
+   * Header for all multicast message fragments from the origin.
+   */
+  struct GNUNET_MessageHeader header;
+
+  /**
+   * Number of hops this message fragment has taken since the origin.
+   *
+   * Helpful to determine shortest paths to the origin among honest peers for
+   * unicast requests from members.  Updated at each hop and thus not signed and
+   * not secure.
+   */
+  uint32_t hop_counter GNUNET_PACKED;
+
+  /**
+   * ECC signature of the message fragment.
+   *
+   * Signature must match the public key of the multicast group.
+   */
+  struct GNUNET_CRYPTO_EddsaSignature signature;
+
+  /**
+   * Purpose for the signature and size of the signed data.
+   */
+  struct GNUNET_CRYPTO_EccSignaturePurpose purpose;
+
+  /**
+   * Number of the message fragment, monotonically increasing starting from 1.
+   */
+  uint64_t fragment_id GNUNET_PACKED;
+
+  /**
+   * Byte offset of this @e fragment of the @e message.
+   */
+  uint64_t fragment_offset GNUNET_PACKED;
+
+  /**
+   * Number of the message this fragment belongs to.
+   *
+   * Set in GNUNET_MULTICAST_origin_to_all().
+   */
+  uint64_t message_id GNUNET_PACKED;
+
+  /**
+   * Counter that monotonically increases whenever a member parts the group.
+   *
+   * Set in GNUNET_MULTICAST_origin_to_all().
+   *
+   * It has significance in case of replay requests: when a member has missed
+   * messages and gets a replay request: in this case if the @a group_generation
+   * is still the same before and after the missed messages, it means that no
+   * @e join or @e part operations happened during the missed messages.
+   */
+  uint64_t group_generation GNUNET_PACKED;
+
+  /**
+   * Flags for this message fragment.
+   *
+   * @see enum GNUNET_MULTICAST_MessageFlags
+   */
+  uint32_t flags GNUNET_PACKED;
+
+  /* Followed by message body. */
+};
+
+
+/**
+ * Header of a request from a member to the origin.
+ */
+struct GNUNET_MULTICAST_RequestHeader
+{
+  /**
+   * Header for all requests from a member to the origin.
+   */
+  struct GNUNET_MessageHeader header;
+
+  /**
+   * Public key of the sending member.
+   */
+  struct GNUNET_CRYPTO_EcdsaPublicKey member_pub_key;
+
+  /**
+   * ECC signature of the request fragment.
+   *
+   * Signature must match the public key of the multicast group.
+   */
+  struct GNUNET_CRYPTO_EcdsaSignature signature;
+
+  /**
+   * Purpose for the signature and size of the signed data.
+   */
+  struct GNUNET_CRYPTO_EccSignaturePurpose purpose;
+
+  /**
+   * Number of the request fragment.
+   * Monotonically increasing from 1.
+   */
+  uint64_t fragment_id GNUNET_PACKED;
+
+  /**
+   * Byte offset of this @e fragment of the @e request.
+   */
+  uint64_t fragment_offset GNUNET_PACKED;
+
+  /**
+   * Number of the request this fragment belongs to.
+   *
+   * Set in GNUNET_MULTICAST_origin_to_all().
+   */
+  uint64_t request_id GNUNET_PACKED;
+
+  /**
+   * Flags for this request.
+   */
+  enum GNUNET_MULTICAST_MessageFlags flags GNUNET_PACKED;
+
+  /* Followed by request body. */
+};
+
+GNUNET_NETWORK_STRUCT_END
+
+
+/**
+ * Maximum size of a multicast message fragment.
+ */
+#define GNUNET_MULTICAST_FRAGMENT_MAX_SIZE (63 * 1024)
+
+#define GNUNET_MULTICAST_FRAGMENT_MAX_PAYLOAD           \
+  (GNUNET_MULTICAST_FRAGMENT_MAX_SIZE                   \
+   - sizeof (struct GNUNET_MULTICAST_MessageHeader))
+
+
+/**
+ * Handle that identifies a join request.
+ *
+ * Used to match calls to #GNUNET_MULTICAST_JoinRequestCallback to the
+ * corresponding calls to #GNUNET_MULTICAST_join_decision().
+ */
+struct GNUNET_MULTICAST_JoinHandle;
+
+
+/**
+ * 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_MULTICAST_JoinRequestCallback.
+ *
+ * @param jh
+ *        Join request handle.
+ * @param is_admitted
+ *        #GNUNET_YES    if the join is approved,
+ *        #GNUNET_NO     if it is disapproved,
+ *        #GNUNET_SYSERR if we cannot answer the request.
+ * @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 join_resp
+ *        Message to send in response to the joining peer;
+ *        can also be used to redirect the peer to a different group at the
+ *        application layer; this response is to be transmitted to the
+ *        peer that issued the request even if admission is denied.
+ */
+struct GNUNET_MULTICAST_ReplayHandle *
+GNUNET_MULTICAST_join_decision (struct GNUNET_MULTICAST_JoinHandle *jh,
+                                int is_admitted,
+                                uint16_t relay_count,
+                                const struct GNUNET_PeerIdentity *relays,
+                                const struct GNUNET_MessageHeader *join_resp);
+
+
+/**
+ * Method called whenever another peer wants to join the multicast group.
+ *
+ * Implementations of this function must call GNUNET_MULTICAST_join_decision()
+ * with the decision.
+ *
+ * @param cls
+ *        Closure.
+ * @param member_pub_key
+ *        Public key of the member requesting join.
+ * @param join_msg
+ *        Application-dependent join message from the new member.
+ * @param jh
+ *        Join handle to pass to GNUNET_MULTICAST_join_decison().
+ */
+typedef void
+(*GNUNET_MULTICAST_JoinRequestCallback) (void *cls,
+                                         const struct GNUNET_CRYPTO_EcdsaPublicKey *member_pub_key,
+                                         const struct GNUNET_MessageHeader *join_msg,
+                                         struct GNUNET_MULTICAST_JoinHandle *jh);
+
+
+/**
+ * Method called to inform about the decision in response to a join request.
+ *
+ * If @a is_admitted is not #GNUNET_YES, then the multicast service disconnects
+ * the client and the multicast member handle returned by
+ * GNUNET_MULTICAST_member_join() is invalidated.
+ *
+ * @param cls
+ *         Closure.
+ * @param is_admitted
+ *         #GNUNET_YES or #GNUNET_NO or #GNUNET_SYSERR
+ * @param peer
+ *        The peer we are connected to and the join decision is from.
+ * @param relay_count
+ *        Number of peers in the @a relays array.
+ * @param relays
+ *        Peer identities of members of the group, which serve as relays
+ *        and can be used to join the group at.  If empty, only the origin can
+ *        be used to connect to the group.
+ * @param join_msg
+ *        Application-dependent join message from the origin.
+ */
+typedef void
+(*GNUNET_MULTICAST_JoinDecisionCallback) (void *cls,
+                                          int is_admitted,
+                                          const struct GNUNET_PeerIdentity *peer,
+                                          uint16_t relay_count,
+                                          const struct GNUNET_PeerIdentity *relays,
+                                          const struct GNUNET_MessageHeader *join_msg);
+
+
+/**
+ * Function called whenever a group member has transmitted a request
+ * to the origin (other than joining or leaving).
+ *
+ * FIXME: need to distinguish between origin cancelling a message (some fragments
+ * were sent, then the rest 'discarded') and the case where we got disconnected;
+ * right now, both would mean 'msg' is NULL, but they could be quite different...
+ * So the semantics from the receiver side of
+ * GNUNET_MULTICAST_member_to_origin_cancel() are not clear here.   Maybe we
+ * should do something with the flags in this case?
+ *
+ * @param cls
+ *        Closure (set from GNUNET_MULTICAST_origin_start).
+ * @param sender
+ *        Identity of the sender.
+ * @param req
+ *        Request to the origin.
+ * @param flags
+ *        Flags for the request.
+ */
+typedef void
+(*GNUNET_MULTICAST_RequestCallback) (void *cls,
+                                     const struct GNUNET_MULTICAST_RequestHeader *req);
+
+
+/**
+ * Function called whenever a group member is receiving a message fragment from
+ * the origin.
+ *
+ * If admission to the group is denied, this function is called once with the
+ * response of the @e origin (as given to GNUNET_MULTICAST_join_decision()) and
+ * then a second time with NULL to indicate that the connection failed for good.
+ *
+ * FIXME: need to distinguish between origin cancelling a message (some fragments
+ * were sent, then the rest 'discarded') and the case where we got disconnected;
+ * right now, both would mean 'msg' is NULL, but they could be quite different...
+ * So the semantics from the receiver side of
+ * GNUNET_MULTICAST_origin_to_all_cancel() are not clear here.
+ *
+ * @param cls
+ *        Closure (set from GNUNET_MULTICAST_member_join())
+ * @param msg
+ *        Message from the origin, NULL if the origin shut down
+ *        (or we were kicked out, and we should thus call
+ *        GNUNET_MULTICAST_member_part() next)
+ */
+typedef void
+(*GNUNET_MULTICAST_MessageCallback) (void *cls,
+                                     const struct GNUNET_MULTICAST_MessageHeader *msg);
+
+
+/**
+ * Opaque handle to a replay request from the multicast service.
+ */
+struct GNUNET_MULTICAST_ReplayHandle;
+
+
+/**
+ * Functions with this signature are called whenever the multicast service needs
+ * a message fragment to be replayed by fragment_id.
+ *
+ * Implementations of this function MUST call GNUNET_MULTICAST_replay() ONCE
+ * (with a message or an error); however, if the origin is destroyed or the
+ * group is left, the replay handle must no longer be used.
+ *
+ * @param cls
+ *        Closure (set from GNUNET_MULTICAST_origin_start()
+ *        or GNUNET_MULTICAST_member_join()).
+ * @param member_pub_key
+ *        The member requesting replay.
+ * @param fragment_id
+ *        Which message fragment should be replayed.
+ * @param flags
+ *        Flags for the replay.
+ * @param rh
+ *        Handle to pass to message transmit function.
+ */
+typedef void
+(*GNUNET_MULTICAST_ReplayFragmentCallback) (void *cls,
+                                            const struct GNUNET_CRYPTO_EcdsaPublicKey *member_pub_key,
+                                            uint64_t fragment_id,
+                                            uint64_t flags,
+                                            struct GNUNET_MULTICAST_ReplayHandle *rh);
+
+/**
+ * Functions with this signature are called whenever the multicast service needs
+ * a message fragment to be replayed by message_id and fragment_offset.
+ *
+ * Implementations of this function MUST call GNUNET_MULTICAST_replay() ONCE
+ * (with a message or an error); however, if the origin is destroyed or the
+ * group is left, the replay handle must no longer be used.
+ *
+ * @param cls
+ *        Closure (set from GNUNET_MULTICAST_origin_start()
+ *        or GNUNET_MULTICAST_member_join()).
+ * @param member_pub_key
+ *        The member requesting replay.
+ * @param message_id
+ *        Which message should be replayed.
+ * @param fragment_offset
+ *        Offset of the fragment within of @a message_id to be replayed.
+ * @param flags
+ *        Flags for the replay.
+ * @param rh
+ *        Handle to pass to message transmit function.
+ */
+typedef void
+(*GNUNET_MULTICAST_ReplayMessageCallback) (void *cls,
+                                           const struct GNUNET_CRYPTO_EcdsaPublicKey *member_pub_key,
+                                           uint64_t message_id,
+                                           uint64_t fragment_offset,
+                                           uint64_t flags,
+                                           struct GNUNET_MULTICAST_ReplayHandle *rh);
+
+
+/**
+ * Possible error codes during replay.
+ */
+enum GNUNET_MULTICAST_ReplayErrorCode
+{
+
+  /**
+   * Everything is fine.
+   */
+  GNUNET_MULTICAST_REC_OK = 0,
+
+  /**
+   * Message fragment not found in the message store.
+   *
+   * Either discarded if it is too old, or not arrived yet if this member has
+   * missed some messages.
+   */
+  GNUNET_MULTICAST_REC_NOT_FOUND = 1,
+
+  /**
+   * Fragment ID counter was larger than the highest counter this
+   * replay function has ever encountered; thus it is likely the
+   * origin never sent it and we're at the HEAD of the multicast
+   * stream as far as this node is concerned.
+   *
+   * FIXME: needed?
+   */
+  GNUNET_MULTICAST_REC_PAST_HEAD = 2,
+
+  /**
+   * Access is denied to the requested fragment, membership test did not pass.
+   */
+  GNUNET_MULTICAST_REC_ACCESS_DENIED = 3,
+
+  /**
+   * Internal error (i.e. database error).  Try some other peer.
+   */
+  GNUNET_MULTICAST_REC_INTERNAL_ERROR = 4
+
+};
+
+
+/**
+ * Replay a message fragment for the multicast group.
+ *
+ * @param rh
+ *        Replay handle identifying which replay operation was requested.
+ * @param msg
+ *        Replayed message fragment, NULL if not found / an error occurred.
+ * @param ec
+ *        Error code.  See enum GNUNET_MULTICAST_ReplayErrorCode
+ *        If not #GNUNET_MULTICAST_REC_OK, the replay handle is invalidated.
+ */
+void
+GNUNET_MULTICAST_replay_response (struct GNUNET_MULTICAST_ReplayHandle *rh,
+                                  const struct GNUNET_MessageHeader *msg,
+                                  enum GNUNET_MULTICAST_ReplayErrorCode ec);
+
+
+/**
+ * Indicate the end of the replay session.
+ *
+ * Invalidates the replay handle.
+ *
+ * @param rh Replay session to end.
+ */
+void
+GNUNET_MULTICAST_replay_response_end (struct GNUNET_MULTICAST_ReplayHandle *rh);
+
+
+/**
+ * Function called to provide data for a transmission for a replay.
+ *
+ * @see GNUNET_MULTICAST_replay2()
+ */
+typedef int
+(*GNUNET_MULTICAST_ReplayTransmitNotify) (void *cls,
+                                          size_t *data_size,
+                                          void *data);
+
+
+/**
+ * Replay a message for the multicast group.
+ *
+ * @param rh
+ *        Replay handle identifying which replay operation was requested.
+ * @param notify
+ *        Function to call to get the message.
+ * @param notify_cls
+ *        Closure for @a notify.
+ */
+void
+GNUNET_MULTICAST_replay_response2 (struct GNUNET_MULTICAST_ReplayHandle *rh,
+                                   GNUNET_MULTICAST_ReplayTransmitNotify notify,
+                                   void *notify_cls);
+
+
+/**
+ * Start a multicast group.
+ *
+ * Peers that issue GNUNET_MULTICAST_member_join() can transmit a join request
+ * to either an existing group member or to the origin.  If the joining is
+ * approved, the member is cleared for @e replay and will begin to receive
+ * messages transmitted to the group.  If joining is disapproved, the failed
+ * candidate will be given a response.  Members in the group can send messages
+ * to the origin.
+ *
+ * TODO: This function could optionally offer to advertise the origin in the
+ * P2P overlay network(where?) under the respective public key so that other
+ * peers can find an alternate PeerId to join it. Higher level protocols may
+ * however provide other means of solving the problem of the offline host
+ * (see secushare specs about that) and therefore merely need a way to provide
+ * a list of possible PeerIds.
+ *
+ * @param cfg
+ *        Configuration to use.
+ * @param priv_key
+ *        ECC key that will be used to sign messages for this
+ *        multicast session; public key is used to identify the multicast group;
+ * @param max_fragment_id
+ *        Maximum fragment ID already sent to the group.
+ *        0 for a new group.
+ * @param join_request_cb
+ *        Function called to approve / disapprove joining of a peer.
+ * @param replay_frag_cb
+ *        Function that can be called to replay a message fragment.
+ * @param replay_msg_cb
+ *        Function that can be called to replay a message.
+ * @param request_cb
+ *        Function called with message fragments from group members.
+ * @param message_cb
+ *        Function called with the message fragments sent to the
+ *        network by GNUNET_MULTICAST_origin_to_all().  These message fragments
+ *        should be stored for answering replay requests later.
+ * @param cls
+ *        Closure for the various callbacks that follow.
+ *
+ * @return Handle for the origin, NULL on error.
+ */
+struct GNUNET_MULTICAST_Origin *
+GNUNET_MULTICAST_origin_start (const struct GNUNET_CONFIGURATION_Handle *cfg,
+                               const struct GNUNET_CRYPTO_EddsaPrivateKey *priv_key,
+                               uint64_t max_fragment_id,
+                               GNUNET_MULTICAST_JoinRequestCallback join_request_cb,
+                               GNUNET_MULTICAST_ReplayFragmentCallback replay_frag_cb,
+                               GNUNET_MULTICAST_ReplayMessageCallback replay_msg_cb,
+                               GNUNET_MULTICAST_RequestCallback request_cb,
+                               GNUNET_MULTICAST_MessageCallback message_cb,
+                               void *cls);
+
+/**
+ * Function called to provide data for a transmission from the origin to all
+ * members.
+ *
+ * Note that returning #GNUNET_OK or #GNUNET_SYSERR (but not #GNUNET_NO)
+ * invalidates the respective transmission handle.
+ *
+ * @param cls
+ *        Closure.
+ * @param[in,out] data_size
+ *        Initially set to the number of bytes available in
+ *        @a data, should be set to the number of bytes written to data.
+ * @param[out] data
+ *        Where to write the body of the message to give to the
+ *         method. The function must copy at most @a data_size bytes to @a data.
+ *
+ * @return #GNUNET_SYSERR on error (fatal, aborts transmission)
+ *         #GNUNET_NO on success, if more data is to be transmitted later.
+ *         Should be used if @a data_size was not big enough to take all the
+ *         data.  If 0 is returned in @a data_size the transmission is paused,
+ *         and can be resumed with GNUNET_MULTICAST_origin_to_all_resume().
+ *         #GNUNET_YES if this completes the transmission (all data supplied)
+ * @deprecated should move to MQ-style API!
+ */
+typedef int
+(*GNUNET_MULTICAST_OriginTransmitNotify) (void *cls,
+                                          size_t *data_size,
+                                          void *data);
+
+
+/**
+ * Handle for a request to send a message to all multicast group members
+ * (from the origin).
+ */
+struct GNUNET_MULTICAST_OriginTransmitHandle;
+
+
+/**
+ * Send a message to the multicast group.
+ *
+ * @param origin
+ *        Handle to the multicast group.
+ * @param message_id
+ *        Application layer ID for the message.  Opaque to multicast.
+ * @param group_generation
+ *        Group generation of the message.  Documented in
+ *        struct GNUNET_MULTICAST_MessageHeader.
+ * @param notify
+ *        Function to call to get the message.
+ * @param notify_cls
+ *        Closure for @a notify.
+ *
+ * @return NULL on error (i.e. request already pending).
+ * @deprecated should move to MQ-style API!
+ */
+struct GNUNET_MULTICAST_OriginTransmitHandle *
+GNUNET_MULTICAST_origin_to_all (struct GNUNET_MULTICAST_Origin *origin,
+                                uint64_t message_id,
+                                uint64_t group_generation,
+                                GNUNET_MULTICAST_OriginTransmitNotify notify,
+                                void *notify_cls);
+
+
+
+/**
+ * Resume message transmission to multicast group.
+ *
+ * @param th  Transmission to cancel.
+ */
+void
+GNUNET_MULTICAST_origin_to_all_resume (struct GNUNET_MULTICAST_OriginTransmitHandle *th);
+
+
+/**
+ * Cancel request for message transmission to multicast group.
+ *
+ * @param th  Transmission to cancel.
+ */
+void
+GNUNET_MULTICAST_origin_to_all_cancel (struct GNUNET_MULTICAST_OriginTransmitHandle *th);
+
+
+/**
+ * Stop a multicast group.
+ *
+ * @param origin Multicast group to stop.
+ */
+void
+GNUNET_MULTICAST_origin_stop (struct GNUNET_MULTICAST_Origin *origin,
+                              GNUNET_ContinuationCallback stop_cb,
+                              void *stop_cls);
+
+
+/**
+ * Join a multicast group.
+ *
+ * The entity joining is always the local peer.  Further information about the
+ * candidate can be provided in @a join_msg.  If the join fails, the
+ * @a message_cb is invoked with a (failure) response and then with NULL.  If
+ * the join succeeds, outstanding (state) messages and ongoing multicast
+ * messages will be given to the @a message_cb until the member decides to part
+ * the group.  The @a mem_test_cb and @a replay_cb functions may be called at
+ * anytime by the multicast service to support relaying messages to other
+ * members of the group.
+ *
+ * @param cfg
+ *        Configuration to use.
+ * @param group_key
+ *        ECC public key that identifies the group to join.
+ * @param member_pub_key
+ *        ECC key that identifies the member
+ *        and used to sign requests sent to the origin.
+ * @param origin
+ *        Peer ID of the origin to send unicast requsets to.  If NULL,
+ *        unicast requests are sent back via multiple hops on the reverse path
+ *        of multicast messages.
+ * @param relay_count
+ *        Number of peers in the @a relays array.
+ * @param relays
+ *        Peer identities of members of the group, which serve as relays
+ *        and can be used to join the group at. and send the @a join_request to.
+ *        If empty, the @a join_request is sent directly to the @a origin.
+ * @param join_msg
+ *        Application-dependent join message to be passed to the peer @a origin.
+ * @param join_request_cb
+ *        Function called to approve / disapprove joining of a peer.
+ * @param join_decision_cb
+ *        Function called to inform about the join decision.
+ * @param replay_frag_cb
+ *        Function that can be called to replay message fragments
+ *        this peer already knows from this group. NULL if this
+ *        client is unable to support replay.
+ * @param replay_msg_cb
+ *        Function that can be called to replay message fragments
+ *        this peer already knows from this group. NULL if this
+ *        client is unable to support replay.
+ * @param message_cb
+ *        Function to be called for all message fragments we
+ *        receive from the group, excluding those our @a replay_cb
+ *        already has.
+ * @param cls
+ *        Closure for callbacks.
+ *
+ * @return Handle for the member, NULL on error.
+ */
+struct GNUNET_MULTICAST_Member *
+GNUNET_MULTICAST_member_join (const struct GNUNET_CONFIGURATION_Handle *cfg,
+                              const struct GNUNET_CRYPTO_EddsaPublicKey *group_key,
+                              const struct GNUNET_CRYPTO_EcdsaPrivateKey *member_pub_key,
+                              const struct GNUNET_PeerIdentity *origin,
+                              uint16_t relay_count,
+                              const struct GNUNET_PeerIdentity *relays,
+                              const struct GNUNET_MessageHeader *join_request,
+                              GNUNET_MULTICAST_JoinRequestCallback join_request_cb,
+                              GNUNET_MULTICAST_JoinDecisionCallback join_decision_cb,
+                              GNUNET_MULTICAST_ReplayFragmentCallback replay_frag_cb,
+                              GNUNET_MULTICAST_ReplayMessageCallback replay_msg_cb,
+                              GNUNET_MULTICAST_MessageCallback message_cb,
+                              void *cls);
+
+/**
+ * Handle for a replay request.
+ */
+struct GNUNET_MULTICAST_MemberReplayHandle;
+
+
+/**
+ * Request a fragment to be replayed by fragment ID.
+ *
+ * Useful if messages below the @e max_known_fragment_id given when joining are
+ * needed and not known to the client.
+ *
+ * @param member
+ *        Membership handle.
+ * @param fragment_id
+ *        ID of a message fragment that this client would like to see replayed.
+ * @param flags
+ *        Additional flags for the replay request.
+ *        It is used and defined by GNUNET_MULTICAST_ReplayFragmentCallback
+ *
+ * @return Replay request handle, NULL on error.
+ */
+struct GNUNET_MULTICAST_MemberReplayHandle *
+GNUNET_MULTICAST_member_replay_fragment (struct GNUNET_MULTICAST_Member *member,
+                                         uint64_t fragment_id,
+                                         uint64_t flags);
+
+
+/**
+ * Request a message fr to be replayed.
+ *
+ * Useful if messages below the @e max_known_fragment_id given when joining are
+ * needed and not known to the client.
+ *
+ * @param member
+ *        Membership handle.
+ * @param message_id
+ *        ID of the message this client would like to see replayed.
+ * @param fragment_offset
+ *        Offset of the fragment within the message to replay.
+ * @param flags
+ *        Additional flags for the replay request.
+ *        It is used & defined by GNUNET_MULTICAST_ReplayMessageCallback
+ *
+ * @return Replay request handle, NULL on error.
+ */
+struct GNUNET_MULTICAST_MemberReplayHandle *
+GNUNET_MULTICAST_member_replay_message (struct GNUNET_MULTICAST_Member *member,
+                                        uint64_t message_id,
+                                        uint64_t fragment_offset,
+                                        uint64_t flags);
+
+
+/**
+ * Cancel a replay request.
+ *
+ * @param rh
+ *        Request to cancel.
+ */
+void
+GNUNET_MULTICAST_member_replay_cancel (struct GNUNET_MULTICAST_MemberReplayHandle *rh);
+
+
+/**
+ * Part a multicast group.
+ *
+ * Disconnects from all group members and invalidates the @a member handle.
+ *
+ * An application-dependent part message can be transmitted beforehand using
+ * #GNUNET_MULTICAST_member_to_origin())
+ *
+ * @param member
+ *        Membership handle.
+ */
+void
+GNUNET_MULTICAST_member_part (struct GNUNET_MULTICAST_Member *member,
+                              GNUNET_ContinuationCallback part_cb,
+                              void *part_cls);
+
+
+/**
+ * Function called to provide data for a transmission from a member to the origin.
+ *
+ * Note that returning #GNUNET_OK or #GNUNET_SYSERR (but not #GNUNET_NO)
+ * invalidates the respective transmission handle.
+ *
+ * @param cls
+ *        Closure.
+ * @param[in,out] data_size
+ *        Initially set to the number of bytes available in
+ *        @a data, should be set to the number of bytes written to data.
+ * @param[out] data
+ *        Where to write the body of the message to give to the
+ *        method. The function must copy at most @a data_size bytes to @a data.
+ *
+ * @return #GNUNET_SYSERR on error (fatal, aborts transmission)
+ *         #GNUNET_NO on success, if more data is to be transmitted later.
+ *         Should be used if @a data_size was not big enough to take all the
+ *         data.  If 0 is returned in @a data_size the transmission is paused,
+ *         and can be resumed with GNUNET_MULTICAST_member_to_origin_resume().
+ *         #GNUNET_YES if this completes the transmission (all data supplied)
+ * @deprecated should move to MQ-style API!
+ */
+typedef int
+(*GNUNET_MULTICAST_MemberTransmitNotify) (void *cls,
+                                          size_t *data_size,
+                                          void *data);
+
+
+/**
+ * Handle for a message to be delivered from a member to the origin.
+ */
+struct GNUNET_MULTICAST_MemberTransmitHandle;
+
+
+/**
+ * Send a message to the origin of the multicast group.
+ *
+ * @param member
+ *        Membership handle.
+ * @param request_id
+ *        Application layer ID for the request.  Opaque to multicast.
+ * @param notify
+ *        Callback to call to get the message.
+ * @param notify_cls
+ *        Closure for @a notify.
+ *
+ * @return Handle to cancel request, NULL on error (i.e. request already pending).
+ * @deprecated should move to MQ-style API!
+ */
+struct GNUNET_MULTICAST_MemberTransmitHandle *
+GNUNET_MULTICAST_member_to_origin (struct GNUNET_MULTICAST_Member *member,
+                                   uint64_t request_id,
+                                   GNUNET_MULTICAST_MemberTransmitNotify notify,
+                                   void *notify_cls);
+
+
+/**
+ * Resume message transmission to origin.
+ *
+ * @param th
+ *        Transmission to cancel.
+ */
+void
+GNUNET_MULTICAST_member_to_origin_resume (struct GNUNET_MULTICAST_MemberTransmitHandle *th);
+
+
+/**
+ * Cancel request for message transmission to origin.
+ *
+ * @param th
+ *        Transmission to cancel.
+ */
+void
+GNUNET_MULTICAST_member_to_origin_cancel (struct GNUNET_MULTICAST_MemberTransmitHandle *th);
+
+
+#if 0                           /* keep Emacsens' auto-indent happy */
+{
+#endif
+#ifdef __cplusplus
+}
+#endif
+
+/* ifndef GNUNET_MULTICAST_SERVICE_H */
+#endif
+
+/** @} */  /* end of group */
diff --git a/src/include/gnunet_psyc_env.h b/src/include/gnunet_psyc_env.h
new file mode 100644
index 0000000..0d878cb
--- /dev/null
+++ b/src/include/gnunet_psyc_env.h
@@ -0,0 +1,340 @@
+/*
+ * This file is part of GNUnet.
+ * Copyright (C) 2013 GNUnet e.V.
+ *
+ * GNUnet is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU Affero General Public License as published
+ * by the Free Software Foundation, either version 3 of the License,
+ * 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
+ * Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+     SPDX-License-Identifier: AGPL3.0-or-later
+ */
+
+/**
+ * @author Gabor X Toth
+ *
+ * @file
+ * PSYC Environment library
+ *
+ * @defgroup psyc-util-env  PSYC Utilities library: Environment
+ * Environment data structure operations for PSYC and Social messages.
+ *
+ * Library providing operations for the @e environment of
+ * PSYC and Social messages, and for (de)serializing variable values.
+ *
+ * @{
+ */
+
+
+#ifndef GNUNET_PSYC_ENV_H
+#define GNUNET_PSYC_ENV_H
+
+#ifdef __cplusplus
+extern "C"
+{
+#if 0                           /* keep Emacsens' auto-indent happy */
+}
+#endif
+#endif
+
+
+/**
+ * Possible operations on PSYC state (persistent) and transient variables (per message).
+ */
+enum GNUNET_PSYC_Operator
+{
+  /**
+   * Set value of a transient variable.
+   */
+  GNUNET_PSYC_OP_SET = ':',
+
+  /**
+   * Assign value for a persistent state variable.
+   *
+   * If an assigned value is NULL, the variable is deleted.
+   */
+  GNUNET_PSYC_OP_ASSIGN = '=',
+
+  /**
+   * Augment state variable.
+   *
+   * Used for appending strings, adding numbers, and adding new items to a list or dictionary.
+   */
+  GNUNET_PSYC_OP_AUGMENT = '+',
+
+  /**
+   * Diminish state variable.
+   *
+   * Used for subtracting numbers, and removing items from a list or dictionary.
+   */
+  GNUNET_PSYC_OP_DIMINISH = '-',
+
+  /**
+   * Update state variable.
+   *
+   * Used for modifying a single item of a list or dictionary.
+   */
+  GNUNET_PSYC_OP_UPDATE = '@',
+};
+
+
+/**
+ * PSYC variable types.
+ */
+enum GNUNET_PSYC_Type
+{
+  GNUNET_PSYC_TYPE_DATA = 0,
+  GNUNET_PSYC_TYPE_NUMBER,
+  GNUNET_PSYC_TYPE_LIST,
+  GNUNET_PSYC_TYPE_DICT
+};
+
+
+/**
+ * PSYC state modifier.
+ */
+struct GNUNET_PSYC_Modifier
+{
+  /**
+   * State operation.
+   */
+  enum GNUNET_PSYC_Operator oper;
+
+  /**
+   * Variable name.
+   */
+  const char *name;
+
+  /**
+   * Size of @a value.
+   */
+  size_t value_size;
+
+  /**
+   * Value of variable.
+   */
+  const void *value;
+
+  /**
+   * Next modifier.
+   */
+  struct GNUNET_PSYC_Modifier *next;
+
+  /**
+   * Previous modifier.
+   */
+  struct GNUNET_PSYC_Modifier *prev;
+};
+
+
+/**
+ * Environment for a message.
+ *
+ * Contains modifiers.
+ */
+struct GNUNET_PSYC_Environment;
+
+
+/**
+ * Create an environment.
+ *
+ * @return A newly allocated environment.
+ */
+struct GNUNET_PSYC_Environment *
+GNUNET_PSYC_env_create ();
+
+
+/**
+ * Add a modifier to the environment.
+ *
+ * @param env The environment.
+ * @param oper Operation to perform.
+ * @param name Name of the variable.
+ * @param value Value of the variable.
+ * @param value_size Size of @a value.
+ */
+void
+GNUNET_PSYC_env_add (struct GNUNET_PSYC_Environment *env,
+                     enum GNUNET_PSYC_Operator oper, const char *name,
+                     const void *value, size_t value_size);
+
+
+/**
+ * Get the first modifier of the environment.
+ */
+struct GNUNET_PSYC_Modifier *
+GNUNET_PSYC_env_head (const struct GNUNET_PSYC_Environment *env);
+
+
+
+/**
+ * Get the last modifier of the environment.
+ */
+struct GNUNET_PSYC_Modifier *
+GNUNET_PSYC_env_tail (const struct GNUNET_PSYC_Environment *env);
+
+
+/**
+ * Remove a modifier from the environment.
+ */
+void
+GNUNET_PSYC_env_remove (struct GNUNET_PSYC_Environment *env,
+                        struct GNUNET_PSYC_Modifier *mod);
+
+
+/**
+ * Remove a modifier at the beginning of the environment.
+ */
+int
+GNUNET_PSYC_env_shift (struct GNUNET_PSYC_Environment *env,
+                       enum GNUNET_PSYC_Operator *oper, const char **name,
+                       const void **value, size_t *value_size);
+
+
+/**
+ * Iterator for modifiers in the environment.
+ *
+ * @param cls Closure.
+ * @param mod Modifier.
+ *
+ * @return #GNUNET_YES to continue iterating,
+ *         #GNUNET_NO to stop.
+ */
+typedef int
+(*GNUNET_PSYC_Iterator) (void *cls, enum GNUNET_PSYC_Operator oper,
+                         const char *name, const char *value,
+                         uint32_t value_size);
+
+
+/**
+ * Iterate through all modifiers in the environment.
+ *
+ * @param env The environment.
+ * @param it Iterator.
+ * @param it_cls Closure for iterator.
+ */
+void
+GNUNET_PSYC_env_iterate (const struct GNUNET_PSYC_Environment *env,
+                         GNUNET_PSYC_Iterator it, void *it_cls);
+
+
+/**
+ * Get the number of modifiers in the environment.
+ *
+ * @param env The environment.
+ *
+ * @return Number of modifiers.
+ */
+size_t
+GNUNET_PSYC_env_get_count (const struct GNUNET_PSYC_Environment *env);
+
+
+/**
+ * Destroy an environment.
+ *
+ * @param env The environment to destroy.
+ */
+void
+GNUNET_PSYC_env_destroy (struct GNUNET_PSYC_Environment *env);
+
+
+/**
+ * Get the type of variable.
+ *
+ * @param name Name of the variable.
+ *
+ * @return Variable type.
+ */
+enum GNUNET_PSYC_Type
+GNUNET_PSYC_var_get_type (char *name);
+
+
+/**
+ * Perform an operation on a variable.
+ *
+ * @param name Name of variable.
+ * @param current_value Current value of variable.
+ * @param current_value_size Size of @a current_value.
+ * @param oper Operator.
+ * @param args Arguments for the operation.
+ * @param args_size Size of @a args.
+ * @param return_value Return value.
+ * @param return_value_size Size of @a return_value.
+ *
+ * @return #GNUNET_OK on success, else #GNUNET_SYSERR
+ */
+int
+GNUNET_PSYC_operation (char *name, void *current_value, size_t current_value_size,
+                       enum GNUNET_PSYC_Operator oper, void *args, size_t args_size,
+                       void **return_value, size_t *return_value_size);
+
+
+/**
+ * Get the variable's value as an integer.
+ *
+ * @param size Size of value.
+ * @param value Raw value of variable.
+ * @param[out] number Value converted to a 64-bit integer.
+ *
+ * @return #GNUNET_OK on success, #GNUNET_SYSERR if an error occurred (e.g. the value is invalid).
+ */
+int
+GNUNET_PSYC_value_to_number (size_t size, const void *value, int64_t *number);
+
+
+/**
+ * Get the variable's value as a dictionary.
+ *
+ * @param size Size of value.
+ * @param value Raw value of variable.
+ * @param[out] dict A newly created hashmap holding the elements of the dictionary.
+ *
+ * @return #GNUNET_OK on success, #GNUNET_SYSERR if an error occurred (e.g. the value is invalid).
+ */
+int
+GNUNET_PSYC_value_to_dict (size_t size, const void *value, struct GNUNET_CONTAINER_MultiHashMap **dict);
+
+
+/**
+ * Create a PSYC variable value from an integer.
+ *
+ * @param number The number to convert.
+ * @param[out] value_size Size of returned value.
+ *
+ * @return A newly allocated value or NULL on error.
+ */
+void *
+GNUNET_PSYC_value_from_number (int64_t number, size_t *value_size);
+
+
+/**
+ * Create a PSYC variable value from a dictionary.
+ *
+ * @param dict The dict to convert.
+ * @param[out] value_size Size of returned value.
+ *
+ * @return A newly allocated value or NULL on error.
+ */
+void *
+GNUNET_PSYC_value_from_dict (struct GNUNET_CONTAINER_MultiHashMap *dict, size_t *value_size);
+
+
+#if 0                           /* keep Emacsens' auto-indent happy */
+{
+#endif
+#ifdef __cplusplus
+}
+#endif
+
+/* ifndef GNUNET_PSYC_ENV_H */
+#endif
+
+/** @} */  /* end of group */
diff --git a/src/include/gnunet_psyc_message.h b/src/include/gnunet_psyc_message.h
new file mode 100644
index 0000000..d0cf9cc
--- /dev/null
+++ b/src/include/gnunet_psyc_message.h
@@ -0,0 +1,278 @@
+/*
+     This file is part of GNUnet.
+     Copyright (C) 2012, 2013 GNUnet e.V.
+
+     GNUnet is free software: you can redistribute it and/or modify it
+     under the terms of the GNU Affero General Public License as published
+     by the Free Software Foundation, either version 3 of the License,
+     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
+     Affero General Public License for more details.
+    
+     You should have received a copy of the GNU Affero General Public License
+     along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+     SPDX-License-Identifier: AGPL3.0-or-later
+*/
+
+/**
+ * @author Gabor X Toth
+ *
+ * @file
+ * PSYC message utilities; receiving/transmitting/logging PSYC messages
+ *
+ * @defgroup psyc-util-message  PSYC Utilities library: Messages
+ * Receiving, transmitting, logging PSYC messages.
+ * @{
+ */
+
+#ifndef GNUNET_PSYC_MESSAGE_H
+#define GNUNET_PSYC_MESSAGE_H
+
+#ifdef __cplusplus
+extern "C"
+{
+#if 0                           /* keep Emacsens' auto-indent happy */
+}
+#endif
+#endif
+
+
+#include "gnunet_util_lib.h"
+#include "gnunet_psyc_util_lib.h"
+#include "gnunet_psyc_service.h"
+
+
+/**
+ * Create a PSYC message.
+ *
+ * @param method_name
+ *        PSYC method for the message.
+ * @param env
+ *        Environment for the message.
+ * @param data
+ *        Data payload for the message.
+ * @param data_size
+ *        Size of @a data.
+ *
+ * @return Message header with size information,
+ *         followed by the message parts.
+ *
+ * FIXME: arg order
+ */
+struct GNUNET_PSYC_Message *
+GNUNET_PSYC_message_create (const char *method_name,
+                            const struct GNUNET_PSYC_Environment *env,
+                            const void *data,
+                            size_t data_size);
+
+/**
+ * Parse PSYC message.
+ *
+ * @param msg
+ *        The PSYC message to parse.
+ * @param env
+ *        The environment for the message with a list of modifiers.
+ * @param[out] method_name
+ *        Pointer to the method name inside @a pmsg.
+ * @param[out] data
+ *        Pointer to data inside @a pmsg.
+ * @param[out] data_size
+ *        Size of @data is written here.
+ *
+ * @return #GNUNET_OK on success,
+ *         #GNUNET_SYSERR on parse error.
+ *
+ * FIXME: arg order
+ */
+int
+GNUNET_PSYC_message_parse (const struct GNUNET_PSYC_MessageHeader *msg,
+                           const char **method_name,
+                           struct GNUNET_PSYC_Environment *env,
+                           const void **data,
+                           uint16_t *data_size);
+
+
+void
+GNUNET_PSYC_log_message (enum GNUNET_ErrorType kind,
+                         const struct GNUNET_MessageHeader *msg);
+
+
+struct GNUNET_PSYC_TransmitHandle;
+
+/**
+ * Create a transmission handle.
+ */
+struct GNUNET_PSYC_TransmitHandle *
+GNUNET_PSYC_transmit_create (struct GNUNET_MQ_Handle *mq);
+
+
+/**
+ * Destroy a transmission handle.
+ */
+void
+GNUNET_PSYC_transmit_destroy (struct GNUNET_PSYC_TransmitHandle *tmit);
+
+
+/**
+ * Transmit a message.
+ *
+ * @param tmit
+ *        Transmission handle.
+ * @param method_name
+ *        Which method should be invoked.
+ * @param env
+ *        Environment for the message.
+ *        Should stay available until the first call to notify_data.
+ *        Can be NULL if there are no modifiers or @a notify_mod is
+ *        provided instead.
+ * @param notify_mod
+ *        Function to call to obtain modifiers.
+ *        Can be NULL if there are no modifiers or @a env is provided instead.
+ * @param notify_data
+ *        Function to call to obtain fragments of the data.
+ * @param notify_cls
+ *        Closure for @a notify_mod and @a notify_data.
+ * @param flags
+ *        Flags for the message being transmitted.
+ *
+ * @return #GNUNET_OK if the transmission was started.
+ *         #GNUNET_SYSERR if another transmission is already going on.
+ */
+int
+GNUNET_PSYC_transmit_message (struct GNUNET_PSYC_TransmitHandle *tmit,
+                              const char *method_name,
+                              const struct GNUNET_PSYC_Environment *env,
+                              GNUNET_PSYC_TransmitNotifyModifier notify_mod,
+                              GNUNET_PSYC_TransmitNotifyData notify_data,
+                              void *notify_cls,
+                              uint32_t flags);
+
+
+/**
+ * Resume transmission.
+ *
+ * @param tmit  Transmission handle.
+ */
+void
+GNUNET_PSYC_transmit_resume (struct GNUNET_PSYC_TransmitHandle *tmit);
+
+
+/**
+ * Abort transmission request.
+ *
+ * @param tmit  Transmission handle.
+ */
+void
+GNUNET_PSYC_transmit_cancel (struct GNUNET_PSYC_TransmitHandle *tmit);
+
+
+/**
+ * Got acknowledgement of a transmitted message part, continue transmission.
+ *
+ * @param tmit  Transmission handle.
+ */
+void
+GNUNET_PSYC_transmit_got_ack (struct GNUNET_PSYC_TransmitHandle *tmit);
+
+
+struct GNUNET_PSYC_ReceiveHandle;
+
+
+/**
+ * Create handle for receiving messages.
+ */
+struct GNUNET_PSYC_ReceiveHandle *
+GNUNET_PSYC_receive_create (GNUNET_PSYC_MessageCallback message_cb,
+                            GNUNET_PSYC_MessagePartCallback message_part_cb,
+                            void *cb_cls);
+
+
+/**
+ * Destroy handle for receiving messages.
+ */
+void
+GNUNET_PSYC_receive_destroy (struct GNUNET_PSYC_ReceiveHandle *recv);
+
+
+/**
+ * Reset stored data related to the last received message.
+ */
+void
+GNUNET_PSYC_receive_reset (struct GNUNET_PSYC_ReceiveHandle *recv);
+
+
+/**
+ * Handle incoming PSYC message.
+ *
+ * @param recv
+ *        Receive handle.
+ * @param msg
+ *        The message.
+ *
+ * @return #GNUNET_OK on success,
+ *         #GNUNET_SYSERR on receive error.
+ */
+int
+GNUNET_PSYC_receive_message (struct GNUNET_PSYC_ReceiveHandle *recv,
+                             const struct GNUNET_PSYC_MessageHeader *msg);
+
+
+/**
+ * Check if @a data contains a series of valid message parts.
+ *
+ * @param data_size
+ *        Size of @a data.
+ * @param data
+ *        Data.
+ * @param[out] first_ptype
+ *        Type of first message part.
+ * @param[out] last_ptype
+ *        Type of last message part.
+ *
+ * @return Number of message parts found in @a data.
+ *         or GNUNET_SYSERR if the message contains invalid parts.
+ */
+int
+GNUNET_PSYC_receive_check_parts (uint16_t data_size, const char *data,
+                                 uint16_t *first_ptype, uint16_t *last_ptype);
+
+
+/**
+ * Initialize PSYC message header.
+ */
+void
+GNUNET_PSYC_message_header_init (struct GNUNET_PSYC_MessageHeader *pmsg,
+                                 const struct GNUNET_MULTICAST_MessageHeader *mmsg,
+                                 uint32_t flags);
+
+
+/**
+ * Create a new PSYC message header from a multicast message for sending it to clients.
+ */
+struct GNUNET_PSYC_MessageHeader *
+GNUNET_PSYC_message_header_create (const struct GNUNET_MULTICAST_MessageHeader *mmsg,
+                                   uint32_t flags);
+
+
+/**
+ * Create a new PSYC message header from a PSYC message.
+ */
+struct GNUNET_PSYC_MessageHeader *
+GNUNET_PSYC_message_header_create_from_psyc (const struct GNUNET_PSYC_Message *msg);
+
+
+#if 0                           /* keep Emacsens' auto-indent happy */
+{
+#endif
+#ifdef __cplusplus
+}
+#endif
+
+/* ifndef GNUNET_PSYC_MESSAGE_H */
+#endif
+
+/** @} */  /* end of group */
diff --git a/src/include/gnunet_psyc_service.h b/src/include/gnunet_psyc_service.h
new file mode 100644
index 0000000..3a3131e
--- /dev/null
+++ b/src/include/gnunet_psyc_service.h
@@ -0,0 +1,1364 @@
+/*
+     This file is part of GNUnet.
+     Copyright (C) 2012, 2013 GNUnet e.V.
+
+     GNUnet is free software: you can redistribute it and/or modify it
+     under the terms of the GNU Affero General Public License as published
+     by the Free Software Foundation, either version 3 of the License,
+     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
+     Affero General Public License for more details.
+    
+     You should have received a copy of the GNU Affero General Public License
+     along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+     SPDX-License-Identifier: AGPL3.0-or-later
+*/
+
+/**
+ * @author Gabor X Toth
+ * @author Christian Grothoff
+ *
+ * @file
+ * PSYC service
+ *
+ * @defgroup psyc  PSYC service
+ * Send/receive messages in PSYC channels and access the PSYC Store.
+ *
+ * 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!
+ *
+ * NOTE:
+ * - this API does not know about PSYC's "root" and "places";
+ *   there is no 'root' in GNUnet-PSYC as we're decentralized;
+ *   'places' and 'persons' are combined within the same
+ *   abstraction, that of a "channel".  Channels are identified
+ *   and accessed in this API using a public/private key.
+ *   Higher-level applications should use NAMES within GNS
+ *   to obtain public keys, and the distinction between
+ *   'places' and 'persons' can then be made with the help
+ *   of the naming system (and/or conventions).
+ *   Channels are (as in PSYC) organized into a hierarchy; each
+ *   channel master (the one with the private key) is then
+ *   the operator of the multicast group (its Origin in
+ *   the terminology of the multicast API).
+ * - The API supports passing large amounts of data using
+ *   'streaming' for the argument passed to a method.  State
+ *   and variables must fit into memory and cannot be streamed
+ *   (thus, no passing of 4 GB of data in a variable;
+ *   once we implement this, we might want to create a
+ *   @c \#define for the maximum size of a variable).
+ * - PSYC defines standard variables, methods, etc.  This
+ *   library deliberately abstracts over all of these; a
+ *   higher-level API should combine the naming system (GNS)
+ *   and standard methods (_converse, _notice, _request,
+ *   _warning, _error etc) and variables (_action, _color,
+ *   _time, etc).  However, this API does take over the
+ *   routing variables, specifically '_context' (channel),
+ *   and '_source'.  We only kind-of support '_target', as
+ *   the target is either everyone in the group or the
+ *   origin, and never just a single member of the group;
+ *   for such individual messages, an application needs to
+ *   construct an 'inbox' channel where the master (only)
+ *   receives messages (but never forwards; private responses
+ *   would be transmitted by joining the senders 'inbox'
+ *   channel -- or a inbox#bob subchannel).  The
+ *   goal for all of this is to keep the abstractions in this
+ *   API minimal: interaction with multicast, try \& slice,
+ *   state/variable/channel management.  Higher-level
+ *   operations belong elsewhere (so maybe this API should
+ *   be called 'PSYC-low', whereas a higher-level API
+ *   implementing defaults for standard methods and
+ *   variables might be called 'PSYC-std' or 'PSYC-high'.
+ *
+ *   In PSYC terminology this is simply called the "PSYC
+ *   routing layer" and the abstractions, for instance in
+ *   psyced, are quite similar. The higher one is called
+ *   "PSYC entity layer." In the text rendering of the
+ *   protocol the two are separated by an empty line. See
+ *   http://about.psyc.eu/Spec:Packet and related.  --lynX
+ *
+ * @{
+ */
+
+#ifndef GNUNET_PSYC_SERVICE_H
+#define GNUNET_PSYC_SERVICE_H
+
+#ifdef __cplusplus
+extern "C"
+{
+#if 0                           /* keep Emacsens' auto-indent happy */
+}
+#endif
+#endif
+
+#include "gnunet_util_lib.h"
+#include "gnunet_multicast_service.h"
+//Mingw work around
+#ifdef MINGW
+    # ifndef  UINT64_MAX
+    # define  UINT64_MAX 0xffffffffffffffffULL
+    # endif
+#endif
+
+/**
+ * Version number of GNUnet-PSYC API.
+ */
+#define GNUNET_PSYC_VERSION 0x00000000
+
+
+/**
+ * Policy flags for a channel.
+ */
+enum GNUNET_PSYC_ChannelFlags
+{
+  /**
+   * Admission must be confirmed by the master.
+   */
+  GNUNET_PSYC_CHANNEL_ADMISSION_CONTROL = 1 << 0,
+
+  /**
+   * Past messages are only available to slaves who were admitted at the time
+   * they were sent to the channel.
+   */
+  GNUNET_PSYC_CHANNEL_RESTRICTED_HISTORY = 1 << 1
+};
+
+
+/**
+ * PSYC channel policies.
+ */
+enum GNUNET_PSYC_Policy
+{
+  /**
+   * Anyone can join the channel, without announcing their presence;
+   * all messages are always public and can be distributed freely.
+   * Joins may be announced, but this is not required.
+   */
+  GNUNET_PSYC_CHANNEL_ANONYMOUS = 0,
+
+  /**
+   * The master must approve membership to the channel, messages must only be
+   * distributed to current channel slaves.  This includes the channel
+   * state as well as transient messages.
+   */
+  GNUNET_PSYC_CHANNEL_PRIVATE
+    = GNUNET_PSYC_CHANNEL_ADMISSION_CONTROL
+    | GNUNET_PSYC_CHANNEL_RESTRICTED_HISTORY
+
+#if IDEAS_FOR_FUTURE
+  /**
+   * Anyone can freely join the channel (no approval required);
+   * however, messages must only be distributed to current channel
+   * slaves, so the master must still acknowledge that the slave
+   * joined before transient messages are delivered.  As approval is
+   * guaranteed, the presistent channel state can be synchronized freely
+   * immediately, prior to master confirmation.
+   */
+  GNUNET_PSYC_CHANNEL_OPEN
+    = GNUNET_PSYC_CHANNEL_RESTRICTED_HISTORY,
+
+  /**
+   * The master must approve joins to the channel, but past messages can be
+   * freely distributed to slaves.
+   */
+  GNUNET_PSYC_CHANNEL_CLOSED
+    = GNUNET_PSYC_CHANNEL_ADMISSION_CONTROL,
+#endif
+};
+
+
+enum GNUNET_PSYC_MessageFlags
+{
+  /**
+   * Default / no flags.
+   */
+  GNUNET_PSYC_MESSAGE_DEFAULT = 0,
+
+  /**
+   * Historic message, retrieved from PSYCstore.
+   */
+  GNUNET_PSYC_MESSAGE_HISTORIC = 1 << 0,
+
+  /**
+   * Request from slave to master.
+   */
+  GNUNET_PSYC_MESSAGE_REQUEST = 1 << 1,
+
+  /**
+   * Message can be delivered out of order.
+   */
+  GNUNET_PSYC_MESSAGE_ORDER_ANY = 1 << 2
+};
+
+
+/**
+ * Values for the @a state_delta field of GNUNET_PSYC_MessageHeader.
+ */
+enum GNUNET_PSYC_StateDeltaValues
+{
+  GNUNET_PSYC_STATE_RESET = 0,
+
+  GNUNET_PSYC_STATE_NOT_MODIFIED = UINT64_MAX
+};
+
+
+GNUNET_NETWORK_STRUCT_BEGIN
+
+/**
+ * A PSYC message.
+ *
+ * Used for single-fragment messages e.g. in a join request or response.
+ */
+struct GNUNET_PSYC_Message
+{
+  /**
+   * Message header with size and type information.
+   */
+  struct GNUNET_MessageHeader header;
+
+  /* Followed by concatenated PSYC message parts:
+   * messages with GNUNET_MESSAGE_TYPE_PSYC_MESSAGE_* types
+   */
+};
+
+
+/**
+ * Header of a PSYC message.
+ *
+ * The PSYC service adds this when delivering the message to local clients,
+ * not present on the multicast layer.
+ */
+struct GNUNET_PSYC_MessageHeader
+{
+  /**
+   * Generic message header with size and type information.
+   */
+  struct GNUNET_MessageHeader header;
+
+  /**
+   * Flags for this message fragment.
+   *
+   * @see enum GNUNET_PSYC_MessageFlags
+   */
+  uint32_t flags GNUNET_PACKED;
+
+  /**
+   * Number of the message this message part belongs to.
+   * Monotonically increasing from 1.
+   */
+  uint64_t message_id GNUNET_PACKED;
+
+  /**
+   * Byte offset of this @e fragment of the @e message.
+   */
+  uint64_t fragment_offset GNUNET_PACKED;
+
+  /**
+   * Sending slave's public key.
+   * Not set if the message is from the master.
+   */
+  struct GNUNET_CRYPTO_EcdsaPublicKey slave_pub_key;
+
+  /* Followed by concatenated PSYC message parts:
+   * messages with GNUNET_MESSAGE_TYPE_PSYC_MESSAGE_* types
+   */
+};
+
+
+/**
+ * The method of a message.
+ */
+struct GNUNET_PSYC_MessageMethod
+{
+  /**
+   * Type: GNUNET_MESSAGE_TYPE_PSYC_MESSAGE_METHOD
+   */
+  struct GNUNET_MessageHeader header;
+
+  /**
+   * OR'ed GNUNET_PSYC_MasterTransmitFlags
+   */
+  uint32_t flags GNUNET_PACKED;
+
+  /**
+   * Number of message IDs since the last message that contained state
+   * operations. @see enum GNUNET_PSYC_StateDeltaValues
+   */
+  uint64_t state_delta GNUNET_PACKED;
+
+  /* Followed by NUL-terminated method name. */
+};
+
+
+/**
+ * A modifier of a message.
+ */
+struct GNUNET_PSYC_MessageModifier
+{
+  /**
+   * Type: GNUNET_MESSAGE_TYPE_PSYC_MESSAGE_MODIFIER
+   */
+  struct GNUNET_MessageHeader header;
+
+  /**
+   * Size of value.
+   */
+  uint32_t value_size GNUNET_PACKED;
+
+  /**
+   * Size of name, including NUL terminator.
+   */
+  uint16_t name_size GNUNET_PACKED;
+
+  /**
+   * enum GNUNET_PSYC_Operator
+   */
+  uint8_t oper;
+
+  /* Followed by NUL-terminated name, then the value. */
+};
+
+
+struct GNUNET_PSYC_CountersResultMessage
+{
+  /**
+   * Type: GNUNET_MESSAGE_TYPE_PSYC_RESULT_COUNTERS
+   */
+  struct GNUNET_MessageHeader header;
+
+  /**
+   * Status code for the operation.
+   */
+  uint32_t result_code GNUNET_PACKED;
+
+  /**
+   * Last message ID sent to the channel.
+   */
+  uint64_t max_message_id GNUNET_PACKED;
+};
+
+
+/**
+ * Join request sent to a PSYC master.
+ */
+struct GNUNET_PSYC_JoinRequestMessage
+{
+  /**
+   * Type: GNUNET_MESSAGE_TYPE_PSYC_MASTER_JOIN_REQUEST
+   */
+  struct GNUNET_MessageHeader header;
+  /**
+   * Public key of the joining slave.
+   */
+  struct GNUNET_CRYPTO_EcdsaPublicKey slave_pub_key;
+
+  /* Followed by struct GNUNET_MessageHeader join_request */
+};
+
+
+/**
+ * Join decision sent in reply to a join request.
+ */
+struct GNUNET_PSYC_JoinDecisionMessage
+{
+  /**
+   * Type: GNUNET_MESSAGE_TYPE_PSYC_JOIN_DECISION
+   */
+  struct GNUNET_MessageHeader header;
+
+  /**
+   * #GNUNET_YES if the slave was admitted.
+   */
+  int32_t is_admitted;
+
+  /**
+   * Public key of the joining slave.
+   * Only set when the master is sending the decision,
+   * not set when a slave is receiving it.
+   */
+  struct GNUNET_CRYPTO_EcdsaPublicKey slave_pub_key;
+
+  /* Followed by struct GNUNET_MessageHeader join_response */
+};
+
+
+enum GNUNET_PSYC_HistoryReplayFlags
+{
+  /**
+   * Replay locally available messages.
+   */
+  GNUNET_PSYC_HISTORY_REPLAY_LOCAL  = 0,
+
+  /**
+   * Replay messages from remote peers if not found locally.
+   */
+  GNUNET_PSYC_HISTORY_REPLAY_REMOTE = 1,
+};
+
+
+struct GNUNET_PSYC_HistoryRequestMessage
+{
+  /**
+   * Type: GNUNET_MESSAGE_TYPE_PSYC_CHANNEL_HISTORY_REPLAY
+   */
+  struct GNUNET_MessageHeader header;
+
+  /**
+   * @see enum GNUNET_PSYC_HistoryReplayFlags
+   */
+  uint32_t flags GNUNET_PACKED;
+
+  /**
+   * ID for this operation.
+   */
+  uint64_t op_id GNUNET_PACKED;
+
+  uint64_t start_message_id GNUNET_PACKED;
+
+  uint64_t end_message_id GNUNET_PACKED;
+
+  uint64_t message_limit GNUNET_PACKED;
+
+  /* Followed by NUL-terminated method name prefix. */
+};
+
+
+struct GNUNET_PSYC_StateRequestMessage
+{
+  /**
+   * Types:
+   * - GNUNET_MESSAGE_TYPE_PSYC_CHANNEL_STATE_GET
+   * - GNUNET_MESSAGE_TYPE_PSYC_CHANNEL_STATE_GET_PREFIX
+   */
+  struct GNUNET_MessageHeader header;
+
+  uint32_t reserved GNUNET_PACKED;
+
+  /**
+   * ID for this operation.
+   */
+  uint64_t op_id GNUNET_PACKED;
+
+  /* Followed by NUL-terminated name. */
+};
+
+
+/**** service -> library ****/
+
+
+/**
+ * Answer from service to client about last operation.
+ */
+struct GNUNET_PSYC_OperationResultMessage
+{
+  /**
+   * Types:
+   * - GNUNET_MESSAGE_TYPE_PSYC_RESULT_CODE
+   * - GNUNET_MESSAGE_TYPE_PSYC_CHANNEL_STATE_RESULT
+   */
+  struct GNUNET_MessageHeader header;
+
+  uint32_t reserved GNUNET_PACKED;
+
+  /**
+   * Operation ID.
+   */
+  uint64_t op_id GNUNET_PACKED;
+
+  /**
+   * Status code for the operation.
+   */
+  uint64_t result_code GNUNET_PACKED;
+
+  /* Followed by:
+   * - on error: NUL-terminated error message
+   * - on success: one of the following message types
+   *
+   *   For a STATE_RESULT, one of:
+   *   - GNUNET_MESSAGE_TYPE_PSYC_MESSAGE_MODIFIER
+   *   - GNUNET_MESSAGE_TYPE_PSYC_MESSAGE_MOD_CONT
+   *   - GNUNET_MESSAGE_TYPE_PSYC_MESSAGE_END
+   */
+};
+
+GNUNET_NETWORK_STRUCT_END
+
+
+#define GNUNET_PSYC_MODIFIER_MAX_PAYLOAD        \
+  GNUNET_MULTICAST_FRAGMENT_MAX_PAYLOAD         \
+  - sizeof (struct GNUNET_PSYC_MessageModifier)
+
+#define GNUNET_PSYC_MOD_CONT_MAX_PAYLOAD        \
+  GNUNET_MULTICAST_FRAGMENT_MAX_PAYLOAD         \
+  - sizeof (struct GNUNET_MessageHeader)
+
+#define GNUNET_PSYC_DATA_MAX_PAYLOAD            \
+  GNUNET_MULTICAST_FRAGMENT_MAX_PAYLOAD         \
+  - sizeof (struct GNUNET_MessageHeader)
+
+
+/**
+ * PSYC message part processing states.
+ */
+enum GNUNET_PSYC_MessageState
+{
+  GNUNET_PSYC_MESSAGE_STATE_START    = 0,
+  GNUNET_PSYC_MESSAGE_STATE_HEADER   = 1,
+  GNUNET_PSYC_MESSAGE_STATE_METHOD   = 2,
+  GNUNET_PSYC_MESSAGE_STATE_MODIFIER = 3,
+  GNUNET_PSYC_MESSAGE_STATE_MOD_CONT = 4,
+  GNUNET_PSYC_MESSAGE_STATE_DATA     = 5,
+  GNUNET_PSYC_MESSAGE_STATE_END      = 6,
+  GNUNET_PSYC_MESSAGE_STATE_CANCEL   = 7,
+  GNUNET_PSYC_MESSAGE_STATE_ERROR    = 8,
+};
+
+
+/**
+ * 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;
+
+
+/**
+ * Method called from PSYC upon receiving a message.
+ *
+ * @param cls  Closure.
+ * @param message_id  Sequence number of the message.
+ * @param flags  OR'ed GNUNET_PSYC_MessageFlags
+ * @param msg  Message part, one of the following types:
+ */
+typedef void
+(*GNUNET_PSYC_MessageCallback) (void *cls,
+                                const struct GNUNET_PSYC_MessageHeader *msg);
+
+
+/**
+ * Method called from PSYC upon receiving part of a message.
+ *
+ * @param cls
+ *        Closure.
+ * @param slave_pub_key
+ *        Public key of the slave sending the message.
+ *        Only set for channel master.
+ * @param message_id
+ *        Sequence number of the message.
+ * @param flags
+ *        OR'ed GNUNET_PSYC_MessageFlags
+ * @param fragment_offset
+ *        Multicast message fragment offset.
+ * @param msg  Message part, one of the following types:
+ * - #GNUNET_MESSAGE_TYPE_PSYC_MESSAGE_HEADER
+ * - #GNUNET_MESSAGE_TYPE_PSYC_MESSAGE_METHOD
+ * - #GNUNET_MESSAGE_TYPE_PSYC_MESSAGE_MODIFIER
+ * - #GNUNET_MESSAGE_TYPE_PSYC_MESSAGE_MOD_CONT
+ * - #GNUNET_MESSAGE_TYPE_PSYC_MESSAGE_DATA
+ * or NULL if an error occurred while receiving a message.
+ */
+typedef void
+(*GNUNET_PSYC_MessagePartCallback) (void *cls,
+                                    const struct GNUNET_PSYC_MessageHeader *msg,
+                                    const struct GNUNET_MessageHeader *pmsg);
+
+
+/**
+ * Method called from PSYC upon receiving a join request.
+ *
+ * @param cls
+ *        Closure.
+ * @param slave_pub_key
+ *        Public key of the slave requesting join.
+ * @param join_msg
+ *        Join message sent along with the request.
+ * @param jh
+ *        Join handle to use with GNUNET_PSYC_join_decision()
+ */
+typedef void
+(*GNUNET_PSYC_JoinRequestCallback) (void *cls,
+                                    const struct GNUNET_PSYC_JoinRequestMessage *req,
+                                    const struct GNUNET_CRYPTO_EcdsaPublicKey *slave_pub_key,
+                                    const struct GNUNET_PSYC_Message *join_msg,
+                                    struct GNUNET_PSYC_JoinHandle *jh);
+
+
+/**
+ * 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 the join is approved,
+ *   #GNUNET_NO     if it is disapproved,
+ *   #GNUNET_SYSERR if we cannot answer the request.
+ * @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 join_resp  Application-dependent join response message to send along
+ *        with the decision.
+ *
+ * @return #GNUNET_OK on success,
+ *         #GNUNET_SYSERR if @a join_resp is too large.
+ */
+int
+GNUNET_PSYC_join_decision (struct GNUNET_PSYC_JoinHandle *jh,
+                           int is_admitted,
+                           uint32_t relay_count,
+                           const struct GNUNET_PeerIdentity *relays,
+                           const struct GNUNET_PSYC_Message *join_resp);
+
+
+/**
+ * Handle for the master of a PSYC channel.
+ */
+struct GNUNET_PSYC_Master;
+
+
+/**
+ * Function called once we are connected to the PSYC service
+ * and the channel master is started.
+ *
+ * Also called when we reconnected to the service
+ * after the connection closed unexpectedly.
+ *
+ * @param cls
+ *        Closure.
+ * @param result
+ *        #GNUNET_YES if there were already messages sent to the channel,
+ *        #GNUNET_NO  if the message history is empty,
+ *        #GNUNET_SYSERR on error.
+ * @param max_message_id
+ *        Last message ID sent to the channel.
+ */
+typedef void
+(*GNUNET_PSYC_MasterStartCallback) (void *cls, int result,
+                                    uint64_t max_message_id);
+
+
+/**
+ * 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 GNS 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 master_start_cb  Function to invoke after the channel master started.
+ * @param join_request_cb  Function to invoke when a slave wants to join.
+ * @param message_cb  Function to invoke on message parts sent to the channel
+ *        and received from slaves
+ * @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_EddsaPrivateKey *channel_key,
+                          enum GNUNET_PSYC_Policy policy,
+                          GNUNET_PSYC_MasterStartCallback master_start_cb,
+                          GNUNET_PSYC_JoinRequestCallback join_request_cb,
+                          GNUNET_PSYC_MessageCallback message_cb,
+                          GNUNET_PSYC_MessagePartCallback message_part_cb,
+                          void *cls);
+
+
+/**
+ * Function called to provide data for a transmission via PSYC.
+ *
+ * Note that returning #GNUNET_YES or #GNUNET_SYSERR (but not #GNUNET_NO)
+ * invalidates the respective transmission handle.
+ *
+ * @param cls Closure.
+ * @param[in,out] data_size Initially set to the number of bytes available in
+ *        @a data, should be set to the number of bytes written to data.
+ * @param[out] data Where to write the body of the message to give to the
+ *         method. The function must copy at most @a data_size bytes to @a data.
+ * @return #GNUNET_SYSERR on error (fatal, aborts transmission)
+ *         #GNUNET_NO on success, if more data is to be transmitted later.
+ *         Should be used if @a data_size was not big enough to take all the
+ *         data.  If 0 is returned in @a data_size the transmission is paused,
+ *         and can be resumed with GNUNET_PSYC_master_transmit_resume().
+ *         #GNUNET_YES if this completes the transmission (all data supplied)
+ */
+typedef int
+(*GNUNET_PSYC_TransmitNotifyData) (void *cls,
+                                   uint16_t *data_size,
+                                   void *data);
+
+/**
+ * Function called to provide a modifier for a transmission via PSYC.
+ *
+ * Note that returning #GNUNET_YES or #GNUNET_SYSERR (but not #GNUNET_NO)
+ * invalidates the respective transmission handle.
+ *
+ * @param cls Closure.
+ * @param[in,out] data_size  Initially set to the number of bytes available in
+ *         @a data, should be set to the number of bytes written to data.
+ * @param[out] data  Where to write the modifier's name and value.
+ *         The function must copy at most @a data_size bytes to @a data.
+ *         When this callback is first called for a modifier, @a data should
+ *         contain: "name\0value".  If the whole value does not fit, subsequent
+ *         calls to this function should write continuations of the value to
+ *         @a data.
+ * @param[out] oper  Where to write the operator of the modifier.
+ *         Only needed during the first call to this callback at the beginning
+ *         of the modifier.  In case of subsequent calls asking for value
+ *         continuations @a oper is set to #NULL.
+ * @param[out] full_value_size  Where to write the full size of the value.
+ *         Only needed during the first call to this callback at the beginning
+ *         of the modifier.  In case of subsequent calls asking for value
+ *         continuations @a value_size is set to #NULL.
+ * @return #GNUNET_SYSERR on error (fatal, aborts transmission)
+ *         #GNUNET_NO on success, if more data is to be transmitted later.
+ *         Should be used if @a data_size was not big enough to take all the
+ *         data for the modifier's value (the name must be always returned
+ *         during the first call to this callback).
+ *         If 0 is returned in @a data_size the transmission is paused,
+ *         and can be resumed with GNUNET_PSYC_master_transmit_resume().
+ *         #GNUNET_YES if this completes the modifier (the whole value is supplied).
+ */
+typedef int
+(*GNUNET_PSYC_TransmitNotifyModifier) (void *cls,
+                                       uint16_t *data_size,
+                                       void *data,
+                                       uint8_t *oper,
+                                       uint32_t *full_value_size);
+
+/**
+ * Flags for transmitting messages to a channel by the master.
+ */
+enum GNUNET_PSYC_MasterTransmitFlags
+{
+  GNUNET_PSYC_MASTER_TRANSMIT_NONE = 0,
+
+  /**
+   * Whether this message should reset the channel state,
+   * i.e. remove all previously stored state variables.
+   */
+
+  GNUNET_PSYC_MASTER_TRANSMIT_STATE_RESET = 1 << 0,
+
+  /**
+   * Whether this message contains any state modifiers.
+   */
+  GNUNET_PSYC_MASTER_TRANSMIT_STATE_MODIFY = 1 << 1,
+
+  /**
+   * Add PSYC header variable with the hash of the current channel state.
+   */
+  GNUNET_PSYC_MASTER_TRANSMIT_STATE_HASH = 1 << 2,
+
+  /**
+   * Whether we need to increment the group generation counter after
+   * transmitting this message.
+   */
+  GNUNET_PSYC_MASTER_TRANSMIT_INC_GROUP_GEN = 1 << 3
+};
+
+
+/**
+ * Handle for a pending PSYC transmission operation.
+ */
+struct GNUNET_PSYC_MasterTransmitHandle;
+
+
+/**
+ * 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 notify_mod Function to call to obtain modifiers.
+ * @param notify_data Function to call to obtain fragments of the data.
+ * @param notify_cls Closure for @a notify_mod and @a notify_data.
+ * @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,
+                             GNUNET_PSYC_TransmitNotifyModifier notify_mod,
+                             GNUNET_PSYC_TransmitNotifyData notify_data,
+                             void *notify_cls,
+                             enum GNUNET_PSYC_MasterTransmitFlags flags);
+
+
+/**
+ * Resume transmission to the channel.
+ *
+ * @param th Handle of the request that is being resumed.
+ */
+void
+GNUNET_PSYC_master_transmit_resume (struct GNUNET_PSYC_MasterTransmitHandle *th);
+
+
+/**
+ * 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);
+
+
+/**
+ * Relay a message
+ *
+ * @param master Handle to the PSYC channel.
+ * @param method_name Which method should be invoked.
+ * @param notify_mod Function to call to obtain modifiers.
+ * @param notify_data Function to call to obtain fragments of the data.
+ * @param notify_cls Closure for @a notify_mod and @a notify_data.
+ * @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_relay (struct GNUNET_PSYC_Master *master,
+                          uint64_t message_id);
+
+
+/**
+ * Stop a PSYC master channel.
+ *
+ * @param master
+ *        PSYC channel master to stop.
+ * @param keep_active
+ *        Keep place active after last application disconnected.
+ * @param stop_cb
+ *        Function called after the master stopped
+ *        and disconnected from the psyc service.
+ * @param stop_cls
+ *        Closure for @a part_cb.
+ */
+void
+GNUNET_PSYC_master_stop (struct GNUNET_PSYC_Master *master,
+                         int keep_active,
+                         GNUNET_ContinuationCallback stop_cb,
+                         void *stop_cls);
+
+
+/**
+ * Handle for a PSYC channel slave.
+ */
+struct GNUNET_PSYC_Slave;
+
+
+/**
+ * Function called after the slave connected to the PSYC service.
+ *
+ * Also called when reconnected to the service
+ * after the connection closed unexpectedly.
+ *
+ * @param cls
+ *        Closure.
+ * @param result
+ *        #GNUNET_YES if there were already messages sent to the channel,
+ *        #GNUNET_NO  if the message history is empty,
+ *        #GNUNET_SYSERR on error.
+ * @param max_message_id
+ *        Last message ID sent to the channel.
+ */
+typedef void
+(*GNUNET_PSYC_SlaveConnectCallback) (void *cls, int result,
+                                     uint64_t max_message_id);
+
+
+/**
+ * Method called to inform about the decision in response to a join request.
+ *
+ * If @a is_admitted is not #GNUNET_YES, then sending messages to the channel is
+ * not possible, but earlier history can be still queried.
+ *
+ * @param cls  Closure.
+ * @param is_admitted  #GNUNET_YES or #GNUNET_NO or #GNUNET_SYSERR
+ * @param join_msg  Application-dependent join message from the origin.
+ */
+typedef void
+(*GNUNET_PSYC_JoinDecisionCallback) (void *cls,
+                                     const struct GNUNET_PSYC_JoinDecisionMessage *dcsn,
+                                     int is_admitted,
+                                     const struct GNUNET_PSYC_Message *join_msg);
+
+/**
+ * Flags for GNUNET_PSYC_slave_join()
+ */
+enum GNUNET_PSYC_SlaveJoinFlags
+{
+  GNUNET_PSYC_SLAVE_JOIN_NONE   = 0,
+
+  /**
+   * Local join for history access, no network connection is established.
+   */
+  GNUNET_PSYC_SLAVE_JOIN_LOCAL  = 1,
+};
+
+
+/**
+ * Join a PSYC channel.
+ *
+ * The entity joining is always the local peer.  The user must immediately use
+ * the GNUNET_PSYC_slave_transmit() 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_pub_key
+ *        ECC public key that identifies the channel we wish to join.
+ * @param slave_pub_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 flags
+ *        Join flags.
+ * @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 message_cb
+ *        Function to invoke on message fragments received from the channel.
+ * @param message_part_cb
+ *        Function to invoke on message parts received from the channel.
+ * @param slave_connect_cb
+ *        Function invoked once we have connected to the PSYC service.
+ * @param join_decision_cb
+ *        Function invoked once we have received a join decision.
+ * @param cls
+ *        Closure for @a message_cb and @a slave_joined_cb.
+ * @param join_msg
+ *        Join message.
+ *
+ * @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_EddsaPublicKey *channel_pub_key,
+                        const struct GNUNET_CRYPTO_EcdsaPrivateKey *slave_pub_key,
+                        enum GNUNET_PSYC_SlaveJoinFlags flags,
+                        const struct GNUNET_PeerIdentity *origin,
+                        uint32_t relay_count,
+                        const struct GNUNET_PeerIdentity *relays,
+                        GNUNET_PSYC_MessageCallback message_cb,
+                        GNUNET_PSYC_MessagePartCallback message_part_cb,
+                        GNUNET_PSYC_SlaveConnectCallback slave_connect_cb,
+                        GNUNET_PSYC_JoinDecisionCallback join_decision_cb,
+                        void *cls,
+                        const struct GNUNET_PSYC_Message *join_msg);
+
+
+/**
+ * Part a PSYC channel.
+ *
+ * Will terminate the connection to the PSYC service.  Polite clients should
+ * first explicitly send a part request (via GNUNET_PSYC_slave_transmit()).
+ *
+ * @param slave
+ *        Slave handle.
+ * @param keep_active
+ *        Keep place active after last application disconnected.
+ * @param part_cb
+ *        Function called after the slave parted the channel
+ *        and disconnected from the psyc service.
+ * @param part_cls
+ *        Closure for @a part_cb.
+ */
+void
+GNUNET_PSYC_slave_part (struct GNUNET_PSYC_Slave *slave,
+                        int keep_active,
+                        GNUNET_ContinuationCallback part_cb,
+                        void *part_cls);
+
+
+/**
+ * Flags for transmitting messages to the channel master by a slave.
+ */
+enum GNUNET_PSYC_SlaveTransmitFlags
+{
+  GNUNET_PSYC_SLAVE_TRANSMIT_NONE = 0
+};
+
+
+/**
+ * Handle for a pending PSYC transmission operation.
+ */
+struct GNUNET_PSYC_SlaveTransmitHandle;
+
+
+/**
+ * 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 notify_mod Function to call to obtain modifiers.
+ * @param notify_data Function to call to obtain fragments of the 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,
+                            GNUNET_PSYC_TransmitNotifyModifier notify_mod,
+                            GNUNET_PSYC_TransmitNotifyData notify_data,
+                            void *notify_cls,
+                            enum GNUNET_PSYC_SlaveTransmitFlags flags);
+
+
+/**
+ * Resume transmission to the master.
+ *
+ * @param th Handle of the request that is being resumed.
+ */
+void
+GNUNET_PSYC_slave_transmit_resume (struct GNUNET_PSYC_SlaveTransmitHandle *th);
+
+
+/**
+ * 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);
+
+
+/**
+ * Handle to access PSYC channel operations for both the master and slaves.
+ */
+struct GNUNET_PSYC_Channel;
+
+
+/**
+ * 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_pub_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.
+ * @param result_cb
+ *        Function to call with the result of the operation.
+ *        The @e result_code argument is #GNUNET_OK on success, or
+ *        #GNUNET_SYSERR on error.  In case of an error, the @e data argument
+ *        can contain an optional error message.
+ * @param cls
+ *        Closure for @a result_cb.
+ */
+void
+GNUNET_PSYC_channel_slave_add (struct GNUNET_PSYC_Channel *channel,
+                               const struct GNUNET_CRYPTO_EcdsaPublicKey *slave_pub_key,
+                               uint64_t announced_at,
+                               uint64_t effective_since,
+                               GNUNET_ResultCallback result_cb,
+                               void *cls);
+
+
+/**
+ * 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_pub_key
+ *        Identity of channel slave to remove.
+ * @param announced_at
+ *        ID of the message that announced the membership change.
+ * @param result_cb
+ *        Function to call with the result of the operation.
+ *        The @e result_code argument is #GNUNET_OK on success, or
+ *        #GNUNET_SYSERR on error.  In case of an error, the @e data argument
+ *        can contain an optional error message.
+ * @param cls
+ *        Closure for @a result_cb.
+ */
+void
+GNUNET_PSYC_channel_slave_remove (struct GNUNET_PSYC_Channel *channel,
+                                  const struct GNUNET_CRYPTO_EcdsaPublicKey
+                                  *slave_pub_key,
+                                  uint64_t announced_at,
+                                  GNUNET_ResultCallback result_cb,
+                                  void *cls);
+
+
+/**
+ * History request handle.
+ */
+struct GNUNET_PSYC_HistoryRequest;
+
+
+/**
+ * Request to replay a part of 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.
+ *
+ * @param channel
+ *        Which channel should be replayed?
+ * @param start_message_id
+ *        Earliest interesting point in history.
+ * @param end_message_id
+ *        Last (inclusive) interesting point in history.
+ * @param method_prefix
+ *        Retrieve only messages with a matching method prefix.
+ * @param flags
+ *        OR'ed enum GNUNET_PSYC_HistoryReplayFlags
+ * @param result_cb
+ *        Function to call when the requested history has been fully replayed.
+ *        Once this function has been called, the client must not call
+ *        GNUNET_PSYC_channel_history_replay_cancel() anymore.
+ * @param cls
+ *        Closure for the callbacks.
+ *
+ * @return Handle to cancel history replay operation.
+ */
+struct GNUNET_PSYC_HistoryRequest *
+GNUNET_PSYC_channel_history_replay (struct GNUNET_PSYC_Channel *channel,
+                                    uint64_t start_message_id,
+                                    uint64_t end_message_id,
+                                    const char *method_prefix,
+                                    uint32_t flags,
+                                    GNUNET_PSYC_MessageCallback message_cb,
+                                    GNUNET_PSYC_MessagePartCallback message_part_cb,
+                                    GNUNET_ResultCallback result_cb,
+                                    void *cls);
+
+
+/**
+ * Request to replay the latest messages from 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.
+ *
+ * @param channel
+ *        Which channel should be replayed?
+ * @param message_limit
+ *        Maximum number of messages to replay.
+ * @param flags
+ *        OR'ed enum GNUNET_PSYC_HistoryReplayFlags
+ * @param finish_cb
+ *        Function to call when the requested history has been fully replayed
+ *        (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)o once this function has been called, the
+ *        client must not call GNUNET_PSYC_channel_history_replay_cancel() anymore.
+ * @param cls
+ *        Closure for the callbacks.
+ *
+ * @return Handle to cancel history replay operation.
+ */
+struct GNUNET_PSYC_HistoryRequest *
+GNUNET_PSYC_channel_history_replay_latest (struct GNUNET_PSYC_Channel *channel,
+                                           uint64_t message_limit,
+                                           const char *method_prefix,
+                                           uint32_t flags,
+                                           GNUNET_PSYC_MessageCallback message_cb,
+                                           GNUNET_PSYC_MessagePartCallback message_part_cb,
+                                           GNUNET_ResultCallback result_cb,
+                                           void *cls);
+
+
+void
+GNUNET_PSYC_channel_history_replay_cancel (struct GNUNET_PSYC_Channel *channel,
+                                           struct GNUNET_PSYC_HistoryRequest *hr);
+
+
+/**
+ * Function called to inform a member about stored state values for a channel.
+ *
+ * If @a full_value_size > value_size then this function is called multiple
+ * times until the whole value arrived.
+ *
+ * @param cls
+ *        Closure.
+ * @param name
+ *        Name of the state variable.
+ *        NULL if there are no more state variables to be returned.
+ * @param value
+ *        Value of the state variable.
+ * @param value_size
+ *        Number of bytes in @a value.
+ * @param full_value_size
+ *        Number of bytes in the full value, including continuations.
+ *        Only set for the first part of a variable,
+ *        in case of a continuation it is 0.
+ */
+typedef void
+(*GNUNET_PSYC_StateVarCallback) (void *cls,
+                                 const struct GNUNET_MessageHeader *mod,
+                                 const char *name,
+                                 const void *value,
+                                 uint32_t value_size,
+                                 uint32_t full_value_size);
+
+
+/**
+ * State request handle.
+ */
+struct GNUNET_PSYC_StateRequest;
+
+
+/**
+ * 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 var_cb
+ *        Function called once when a matching state variable is found.
+ *        Not called if there's no matching state variable.
+ * @param result_cb
+ *        Function called after the operation finished.
+ *        (i.e. all state variables have been returned via @a state_cb)
+ * @param cls
+ *        Closure for the callbacks.
+ */
+struct GNUNET_PSYC_StateRequest *
+GNUNET_PSYC_channel_state_get (struct GNUNET_PSYC_Channel *channel,
+                               const char *full_name,
+                               GNUNET_PSYC_StateVarCallback var_cb,
+                               GNUNET_ResultCallback result_cb,
+                               void *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 var_cb
+ *        Function called once when a matching state variable is found.
+ *        Not called if there's no matching state variable.
+ * @param result_cb
+ *        Function called after the operation finished.
+ *        (i.e. all state variables have been returned via @a state_cb)
+ * @param cls
+ *        Closure for the callbacks.
+ */
+struct GNUNET_PSYC_StateRequest *
+GNUNET_PSYC_channel_state_get_prefix (struct GNUNET_PSYC_Channel *channel,
+                                      const char *name_prefix,
+                                      GNUNET_PSYC_StateVarCallback var_cb,
+                                      GNUNET_ResultCallback result_cb,
+                                      void *cls);
+
+/**
+ * Cancel a state request operation.
+ *
+ * @param sr
+ *        Handle for the operation to cancel.
+ */
+void
+GNUNET_PSYC_channel_state_get_cancel (struct GNUNET_PSYC_StateRequest *sr);
+
+
+
+#if 0                           /* keep Emacsens' auto-indent happy */
+{
+#endif
+#ifdef __cplusplus
+}
+#endif
+
+/* ifndef GNUNET_PSYC_SERVICE_H */
+#endif
+
+/** @} */  /* end of group */
diff --git a/src/include/gnunet_psyc_slicer.h b/src/include/gnunet_psyc_slicer.h
new file mode 100644
index 0000000..87f66d7
--- /dev/null
+++ b/src/include/gnunet_psyc_slicer.h
@@ -0,0 +1,378 @@
+/*
+     This file is part of GNUnet.
+     Copyright (C) 2013 GNUnet e.V.
+
+     GNUnet is free software: you can redistribute it and/or modify it
+     under the terms of the GNU Affero General Public License as published
+     by the Free Software Foundation, either version 3 of the License,
+     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
+     Affero General Public License for more details.
+    
+     You should have received a copy of the GNU Affero General Public License
+     along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+     SPDX-License-Identifier: AGPL3.0-or-later
+*/
+
+/**
+ * @author Gabor X Toth
+ * @author Christian Grothoff
+ *
+ * @file
+ * PSYC Slicer library
+ *
+ * @defgroup psyc-util-slicer  PSYC Utilities library: Slicer
+ * Try-and-slice processing of PSYC method names and environment.
+ * @{
+ */
+
+#ifndef GNUNET_PSYC_SLICER_H
+#define GNUNET_PSYC_SLICER_H
+
+
+#ifdef __cplusplus
+extern "C"
+{
+#if 0                           /* keep Emacsens' auto-indent happy */
+}
+#endif
+#endif
+
+#include "gnunet_util_lib.h"
+
+
+/**
+ * Handle to an implementation of try-and-slice.
+ */
+struct GNUNET_PSYC_Slicer;
+
+
+/**
+ * Function called upon receiving a message indicating a call to a @e method.
+ *
+ * This function is called one or more times for each message until all data
+ * fragments arrive from the network.
+ *
+ * @param cls
+ *        Closure.
+ * @param msg
+ *        Message part, as it arrived from the network.
+ * @param message_id
+ *        Message counter, monotonically increasing from 1.
+ * @param flags
+ *        OR'ed GNUNET_PSYC_MessageFlags
+ * @param fragment_offset
+ *        Multicast message fragment offset.
+ * @param tmit_flags
+ *        OR'ed GNUNET_PSYC_MasterTransmitFlags
+ * @param nym
+ *        The sender of the message.
+ *        Can be NULL if the message is not connected to a pseudonym.
+ * @param method_name
+ *        Original method name from PSYC.
+ *        May be more specific than the registered method name due to
+ *        try-and-slice matching.
+ */
+typedef void
+(*GNUNET_PSYC_MethodCallback) (void *cls,
+                               const struct GNUNET_PSYC_MessageHeader *msg,
+                               const struct GNUNET_PSYC_MessageMethod *meth,
+                               uint64_t message_id,
+                               const char *method_name);
+
+
+/**
+ * Function called upon receiving a modifier of a message.
+ *
+ * @param cls
+ *        Closure.
+ * @param message_id
+ *        Message ID this data fragment belongs to.
+ * @param flags
+ *        OR'ed GNUNET_PSYC_MessageFlags
+ * @param fragment_offset
+ *        Multicast message fragment offset.
+ * @param msg
+ *        Message part, as it arrived from the network.
+ * @param oper
+ *        Operation to perform.
+ *        0 in case of a modifier continuation.
+ * @param name
+ *        Name of the modifier.
+ *        NULL in case of a modifier continuation.
+ * @param value
+ *        Value of the modifier.
+ * @param value_size
+ *        Size of @value.
+ */
+typedef void
+(*GNUNET_PSYC_ModifierCallback) (void *cls,
+                                 const struct GNUNET_PSYC_MessageHeader *msg,
+                                 const struct GNUNET_MessageHeader *pmsg,
+                                 uint64_t message_id,
+                                 enum GNUNET_PSYC_Operator oper,
+                                 const char *name,
+                                 const void *value,
+                                 uint16_t value_size,
+                                 uint16_t full_value_size);
+
+
+/**
+ * Function called upon receiving a data fragment of a message.
+ *
+ * @param cls
+ *        Closure.
+ * @param msg
+ *        Message part, as it arrived from the network.
+ * @param message_id
+ *        Message ID this data fragment belongs to.
+ * @param flags
+ *        OR'ed GNUNET_PSYC_MessageFlags
+ * @param fragment_offset
+ *        Multicast message fragment offset.
+ * @param data
+ *        Data stream given to the method.
+ * @param data_size
+ *        Number of bytes in @a data.
+ * @param end
+ *        End of message?
+ *        #GNUNET_NO     if there are further fragments,
+ *        #GNUNET_YES    if this is the last fragment,
+ *        #GNUNET_SYSERR indicates the message was cancelled by the sender.
+ */
+typedef void
+(*GNUNET_PSYC_DataCallback) (void *cls,
+                             const struct GNUNET_PSYC_MessageHeader *msg,
+                             const struct GNUNET_MessageHeader *pmsg,
+                             uint64_t message_id,
+                             const void *data,
+                             uint16_t data_size);
+
+
+/**
+ * End of message.
+ *
+ * @param cls
+ *        Closure.
+ * @param msg
+ *        Message part, as it arrived from the network.
+ * @param message_id
+ *        Message ID this data fragment belongs to.
+ * @param flags
+ *        OR'ed GNUNET_PSYC_MessageFlags
+ * @param fragment_offset
+ *        Multicast message fragment offset.
+ * @param cancelled
+ *        #GNUNET_YES if the message was cancelled,
+ *        #GNUNET_NO  if the message is complete.
+ */
+typedef void
+(*GNUNET_PSYC_EndOfMessageCallback) (void *cls,
+                                     const struct GNUNET_PSYC_MessageHeader *msg,
+                                     const struct GNUNET_MessageHeader *pmsg,
+                                     uint64_t message_id,
+                                     uint8_t is_cancelled);
+
+
+/**
+ * Create a try-and-slice instance.
+ *
+ * A slicer processes incoming messages and notifies callbacks about matching
+ * methods or modifiers encountered.
+ *
+ * @return A new try-and-slice construct.
+ */
+struct GNUNET_PSYC_Slicer *
+GNUNET_PSYC_slicer_create (void);
+
+
+/**
+ * Add a method to the try-and-slice instance.
+ *
+ * The callbacks are called for messages with a matching @a method_name prefix.
+ *
+ * @param slicer
+ *        The try-and-slice instance to extend.
+ * @param method_name
+ *        Name of the given method, use empty string to match all.
+ * @param method_cb
+ *        Method handler invoked upon a matching message.
+ * @param modifier_cb
+ *        Modifier handler, invoked after @a method_cb
+ *        for each modifier in the message.
+ * @param data_cb
+ *        Data handler, invoked after @a modifier_cb for each data fragment.
+ * @param eom_cb
+ *        Invoked upon reaching the end of a matching message.
+ * @param cls
+ *        Closure for the callbacks.
+ */
+void
+GNUNET_PSYC_slicer_method_add (struct GNUNET_PSYC_Slicer *slicer,
+                               const char *method_name,
+                               GNUNET_PSYC_MessageCallback msg_cb,
+                               GNUNET_PSYC_MethodCallback method_cb,
+                               GNUNET_PSYC_ModifierCallback modifier_cb,
+                               GNUNET_PSYC_DataCallback data_cb,
+                               GNUNET_PSYC_EndOfMessageCallback eom_cb,
+                               void *cls);
+
+/**
+ * Remove a registered method from the try-and-slice instance.
+ *
+ * Removes one matching handler registered with the given
+ * @a method_name and callbacks.
+ *
+ * @param slicer
+ *        The try-and-slice instance.
+ * @param method_name
+ *        Name of the method to remove.
+ * @param method_cb
+ *        Only remove matching method handler, or NULL.
+ * @param modifier_cb
+ *        Only remove matching modifier handler, or NULL.
+ * @param data_cb
+ *        Only remove matching data handler, or NULL.
+ * @param eom_cb
+ *        Only remove matching End of Message handler, or NULL.
+ *
+ * @return #GNUNET_OK if a method handler was removed,
+ *         #GNUNET_NO if no handler matched the given method name and callbacks.
+ */
+int
+GNUNET_PSYC_slicer_method_remove (struct GNUNET_PSYC_Slicer *slicer,
+                                  const char *method_name,
+                                  GNUNET_PSYC_MessageCallback msg_cb,
+                                  GNUNET_PSYC_MethodCallback method_cb,
+                                  GNUNET_PSYC_ModifierCallback modifier_cb,
+                                  GNUNET_PSYC_DataCallback data_cb,
+                                  GNUNET_PSYC_EndOfMessageCallback eom_cb);
+
+
+/**
+ * Watch a place for changed objects.
+ *
+ * @param slicer
+ *        The try-and-slice instance.
+ * @param object_filter
+ *        Object prefix to match.
+ * @param modifier_cb
+ *        Function to call when encountering a state modifier.
+ * @param cls
+ *        Closure for callback.
+ */
+void
+GNUNET_PSYC_slicer_modifier_add (struct GNUNET_PSYC_Slicer *slicer,
+                                 const char *object_filter,
+                                 GNUNET_PSYC_ModifierCallback modifier_cb,
+                                 void *cls);
+
+
+/**
+ * Remove a registered modifier from the try-and-slice instance.
+ *
+ * Removes one matching handler registered with the given
+ * @a object_filter and callback.
+ *
+ * @param slicer
+ *        The try-and-slice instance.
+ * @param object_filter
+ *        Object prefix to match.
+ * @param modifier_cb
+ *        Function to call when encountering a state modifier changes.
+ */
+int
+GNUNET_PSYC_slicer_modifier_remove (struct GNUNET_PSYC_Slicer *slicer,
+                                    const char *object_filter,
+                                    GNUNET_PSYC_ModifierCallback modifier_cb);
+
+
+/**
+ * Process an incoming message and call matching handlers.
+ *
+ * @param slicer
+ *        The slicer to use.
+ * @param msg
+ *        The message as it arrived from the network.
+ */
+void
+GNUNET_PSYC_slicer_message (struct GNUNET_PSYC_Slicer *slicer,
+                            const struct GNUNET_PSYC_MessageHeader *msg);
+
+
+/**
+ * Process an incoming message part and call matching handlers.
+ *
+ * @param slicer
+ *        The slicer to use.
+ * @param message_id
+ *        ID of the message.
+ * @param flags
+ *        Flags for the message.
+ *        @see enum GNUNET_PSYC_MessageFlags
+ * @param fragment offset
+ *        Fragment offset of the message.
+ * @param msg
+ *        The message part as it arrived from the network.
+ */
+void
+GNUNET_PSYC_slicer_message_part (struct GNUNET_PSYC_Slicer *slicer,
+                                 const struct GNUNET_PSYC_MessageHeader *msg,
+                                 const struct GNUNET_MessageHeader *pmsg);
+
+
+/**
+ * Remove all registered method handlers.
+ *
+ * @param slicer
+ *        Slicer to clear.
+ */
+void
+GNUNET_PSYC_slicer_method_clear (struct GNUNET_PSYC_Slicer *slicer);
+
+
+/**
+ * Remove all registered modifier handlers.
+ *
+ * @param slicer
+ *        Slicer to clear.
+ */
+void
+GNUNET_PSYC_slicer_modifier_clear (struct GNUNET_PSYC_Slicer *slicer);
+
+
+/**
+ * Remove all registered method & modifier handlers.
+ *
+ * @param slicer
+ *        Slicer to clear.
+ */
+void
+GNUNET_PSYC_slicer_clear (struct GNUNET_PSYC_Slicer *slicer);
+
+
+/**
+ * Destroy a given try-and-slice instance.
+ *
+ * @param slicer
+ *        Slicer to destroy
+ */
+void
+GNUNET_PSYC_slicer_destroy (struct GNUNET_PSYC_Slicer *slicer);
+
+
+#if 0                           /* keep Emacsens' auto-indent happy */
+{
+#endif
+#ifdef __cplusplus
+}
+#endif
+
+/* ifndef GNUNET_PSYC_SLICER_H */
+#endif
+
+/** @} */  /* end of group */
diff --git a/src/include/gnunet_psyc_util_lib.h b/src/include/gnunet_psyc_util_lib.h
new file mode 100644
index 0000000..57eec65
--- /dev/null
+++ b/src/include/gnunet_psyc_util_lib.h
@@ -0,0 +1,53 @@
+/*
+     This file is part of GNUnet.
+     Copyright (C) 2012, 2013 GNUnet e.V.
+
+     GNUnet is free software: you can redistribute it and/or modify it
+     under the terms of the GNU Affero General Public License as published
+     by the Free Software Foundation, either version 3 of the License,
+     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
+     Affero General Public License for more details.
+    
+     You should have received a copy of the GNU Affero General Public License
+     along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+     SPDX-License-Identifier: AGPL3.0-or-later
+*/
+
+/**
+ * @author Gabor X Toth
+ *
+ * @file
+ * PSYC utilities: messages, environment, slicer
+ */
+
+#ifndef GNUNET_PSYC_UTIL_LIB_H
+#define GNUNET_PSYC_UTIL_LIB_H
+
+#ifdef __cplusplus
+extern "C"
+{
+#if 0                           /* keep Emacsens' auto-indent happy */
+}
+#endif
+#endif
+
+
+#include "gnunet_psyc_env.h"
+#include "gnunet_psyc_message.h"
+#include "gnunet_psyc_slicer.h"
+
+
+#if 0                           /* keep Emacsens' auto-indent happy */
+{
+#endif
+#ifdef __cplusplus
+}
+#endif
+
+/* ifndef GNUNET_PSYC_UTIL_LIB_H */
+#endif
diff --git a/src/include/gnunet_psycstore_plugin.h b/src/include/gnunet_psycstore_plugin.h
new file mode 100644
index 0000000..fac549f
--- /dev/null
+++ b/src/include/gnunet_psycstore_plugin.h
@@ -0,0 +1,383 @@
+/*
+     This file is part of GNUnet
+     Copyright (C) 2013 GNUnet e.V.
+
+     GNUnet is free software: you can redistribute it and/or modify it
+     under the terms of the GNU Affero General Public License as published
+     by the Free Software Foundation, either version 3 of the License,
+     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
+     Affero General Public License for more details.
+    
+     You should have received a copy of the GNU Affero General Public License
+     along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+     SPDX-License-Identifier: AGPL3.0-or-later
+*/
+
+/**
+ * @author Gabor X Toth
+ *
+ * @file
+ * Plugin API for the PSYCstore database backend
+ *
+ * @defgroup psycstore-plugin  PSYC Store plugin API
+ * Plugin API for the PSYC Store database backend
+ * @{
+ */
+#ifndef GNUNET_PSYCSTORE_PLUGIN_H
+#define GNUNET_PSYCSTORE_PLUGIN_H
+
+#include "gnunet_util_lib.h"
+#include "gnunet_psycstore_service.h"
+
+#ifdef __cplusplus
+extern "C"
+{
+#if 0                           /* keep Emacsens' auto-indent happy */
+}
+#endif
+#endif
+
+
+/**
+ * Struct returned by the initialization function of the plugin.
+ */
+struct GNUNET_PSYCSTORE_PluginFunctions
+{
+
+  /**
+   * Closure to pass to all plugin functions.
+   */
+  void *cls;
+
+  /**
+   * Store join/leave events for a PSYC channel in order to be able to answer
+   * membership test queries later.
+   *
+   * @see GNUNET_PSYCSTORE_membership_store()
+   *
+   * @return #GNUNET_OK on success, else #GNUNET_SYSERR
+   */
+  int
+  (*membership_store) (void *cls,
+                       const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                       const struct GNUNET_CRYPTO_EcdsaPublicKey *slave_key,
+                       int did_join,
+                       uint64_t announced_at,
+                       uint64_t effective_since,
+                       uint64_t group_generation);
+
+  /**
+   * Test if a member was admitted to the channel at the given message ID.
+   *
+   * @see GNUNET_PSYCSTORE_membership_test()
+   *
+   * @return #GNUNET_YES if the member was admitted, #GNUNET_NO if not,
+   *         #GNUNET_SYSERR if there was en error.
+   */
+  int
+  (*membership_test) (void *cls,
+                      const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                      const struct GNUNET_CRYPTO_EcdsaPublicKey *slave_key,
+                      uint64_t message_id);
+
+  /**
+   * Store a message fragment sent to a channel.
+   *
+   * @see GNUNET_PSYCSTORE_fragment_store()
+   *
+   * @return #GNUNET_OK on success, else #GNUNET_SYSERR
+   */
+  int
+  (*fragment_store) (void *cls,
+                     const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                     const struct GNUNET_MULTICAST_MessageHeader *message,
+                     uint32_t psycstore_flags);
+
+  /**
+   * Set additional flags for a given message.
+   *
+   * They are OR'd with any existing flags set.
+   *
+   * @param cls Closure.
+   * @param channel_key Public key of the channel.
+   * @param message_id ID of the message.
+   * @param psycstore_flags OR'd GNUNET_PSYCSTORE_MessageFlags.
+   *
+   * @return #GNUNET_OK on success, else #GNUNET_SYSERR
+   */
+  int
+  (*message_add_flags) (void *cls,
+                        const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                        uint64_t message_id,
+                        uint32_t psycstore_flags);
+
+  /**
+   * Retrieve a message fragment range by fragment ID.
+   *
+   * @see GNUNET_PSYCSTORE_fragment_get()
+   *
+   * @return #GNUNET_OK on success, else #GNUNET_SYSERR
+   */
+  int
+  (*fragment_get) (void *cls,
+                   const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                   uint64_t first_fragment_id,
+                   uint64_t last_fragment_id,
+                   uint64_t *returned_fragments,
+                   GNUNET_PSYCSTORE_FragmentCallback cb,
+                   void *cb_cls);
+
+  /**
+   * Retrieve latest message fragments.
+   *
+   * @see GNUNET_PSYCSTORE_fragment_get()
+   *
+   * @return #GNUNET_OK on success, else #GNUNET_SYSERR
+   */
+  int
+  (*fragment_get_latest) (void *cls,
+                          const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                          uint64_t fragment_limit,
+                          uint64_t *returned_fragments,
+                          GNUNET_PSYCSTORE_FragmentCallback cb,
+                          void *cb_cls);
+
+  /**
+   * Retrieve all fragments of a message ID range.
+   *
+   * @see GNUNET_PSYCSTORE_message_get()
+   *
+   * @return #GNUNET_OK on success, else #GNUNET_SYSERR
+   */
+  int
+  (*message_get) (void *cls,
+                  const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                  uint64_t first_fragment_id,
+                  uint64_t last_fragment_id,
+                  uint64_t fragment_limit,
+                  uint64_t *returned_fragments,
+                  GNUNET_PSYCSTORE_FragmentCallback cb,
+                  void *cb_cls);
+
+  /**
+   * Retrieve all fragments of the latest messages.
+   *
+   * @see GNUNET_PSYCSTORE_message_get()
+   *
+   * @return #GNUNET_OK on success, else #GNUNET_SYSERR
+   */
+  int
+  (*message_get_latest) (void *cls,
+                         const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                         uint64_t fragment_limit,
+                         uint64_t *returned_fragments,
+                         GNUNET_PSYCSTORE_FragmentCallback cb,
+                         void *cb_cls);
+
+  /**
+   * Retrieve a fragment of message specified by its message ID and fragment
+   * offset.
+   *
+   * @see GNUNET_PSYCSTORE_message_get_fragment()
+   *
+   * @return #GNUNET_OK on success, else #GNUNET_SYSERR
+   */
+  int
+  (*message_get_fragment) (void *cls,
+                           const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                           uint64_t message_id,
+                           uint64_t fragment_offset,
+                           GNUNET_PSYCSTORE_FragmentCallback cb,
+                           void *cb_cls);
+
+  /**
+   * Retrieve the max. values of message counters for a channel.
+   *
+   * @see GNUNET_PSYCSTORE_counters_get()
+   *
+   * @return #GNUNET_OK on success, else #GNUNET_SYSERR
+   */
+  int
+  (*counters_message_get) (void *cls,
+                           const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                           uint64_t *max_fragment_id,
+                           uint64_t *max_message_id,
+                           uint64_t *max_group_generation);
+
+  /**
+   * Retrieve the max. values of state counters for a channel.
+   *
+   * @see GNUNET_PSYCSTORE_counters_get()
+   *
+   * @return #GNUNET_OK on success, else #GNUNET_SYSERR
+   */
+  int
+  (*counters_state_get) (void *cls,
+                         const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                         uint64_t *max_state_message_id);
+
+
+  /**
+   * Begin modifying current state.
+   *
+   * @see GNUNET_PSYCSTORE_state_modify()
+   *
+   * @return #GNUNET_OK on success, else #GNUNET_SYSERR
+   */
+  int
+  (*state_modify_begin) (void *cls,
+                         const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                         uint64_t message_id, uint64_t state_delta);
+
+  /**
+   * Set the current value of a state variable.
+   *
+   * The state modification process is started with state_modify_begin(),
+   * which is followed by one or more calls to this function,
+   * and finished with state_modify_end().
+   *
+   * @see GNUNET_PSYCSTORE_state_modify()
+   *
+   * @return #GNUNET_OK on success, else #GNUNET_SYSERR
+   */
+  int
+  (*state_modify_op) (void *cls,
+                      const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                      enum GNUNET_PSYC_Operator op,
+                      const char *name, const void *value, size_t value_size);
+
+
+  /**
+   * End modifying current state.
+   *
+   * @see GNUNET_PSYCSTORE_state_modify()
+   *
+   * @return #GNUNET_OK on success, else #GNUNET_SYSERR
+   */
+  int
+  (*state_modify_end) (void *cls,
+                       const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                       uint64_t message_id);
+
+
+  /**
+   * Begin synchronizing state.
+   *
+   * @see GNUNET_PSYCSTORE_state_sync()
+   *
+   * @return #GNUNET_OK on success, else #GNUNET_SYSERR
+   */
+  int
+  (*state_sync_begin) (void *cls,
+                         const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key);
+
+  /**
+   * Assign value of a state variable while synchronizing state.
+   *
+   * The state synchronization process is started with state_sync_begin(),
+   * which is followed by one or more calls to this function,
+   * and finished using state_sync_end().
+   *
+   * @see GNUNET_PSYCSTORE_state_sync()
+   *
+   * @return #GNUNET_OK on success, else #GNUNET_SYSERR
+   */
+  int
+  (*state_sync_assign) (void *cls,
+                        const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                        const char *name, const void *value, size_t value_size);
+
+
+  /**
+   * End synchronizing state.
+   *
+   * @see GNUNET_PSYCSTORE_state_sync()
+   *
+   * @return #GNUNET_OK on success, else #GNUNET_SYSERR
+   */
+  int
+  (*state_sync_end) (void *cls,
+                     const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                     uint64_t max_state_message_id,
+                     uint64_t state_hash_message_id);
+
+
+  /**
+   * Reset the state of a channel.
+   *
+   * Delete all state variables stored for the given channel.
+   *
+   * @see GNUNET_PSYCSTORE_state_reset()
+   *
+   * @return #GNUNET_OK on success, else #GNUNET_SYSERR
+   */
+  int
+  (*state_reset) (void *cls,
+                  const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key);
+
+  /**
+   * Update signed state values from the current ones.
+   *
+   * Sets value_signed = value_current for each variable for the given channel.
+   */
+  int
+  (*state_update_signed) (void *cls,
+                          const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key);
+
+
+  /**
+   * Retrieve a state variable by name (exact match).
+   *
+   * @return #GNUNET_OK on success, else #GNUNET_SYSERR
+   */
+  int
+  (*state_get) (void *cls,
+                const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                const char *name,
+                GNUNET_PSYCSTORE_StateCallback cb,
+                void *cb_cls);
+
+  /**
+   * Retrieve all state variables for a channel with the given prefix.
+   *
+   * @see GNUNET_PSYCSTORE_state_get_prefix()
+   *
+   * @return #GNUNET_OK on success, else #GNUNET_SYSERR
+   */
+  int
+  (*state_get_prefix) (void *cls,
+                       const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                       const char *name,
+                       GNUNET_PSYCSTORE_StateCallback cb,
+                       void *cb_cls);
+
+
+  /**
+   * Retrieve all signed state variables for a channel.
+   *
+   * @return #GNUNET_OK on success, else #GNUNET_SYSERR
+   */
+  int
+  (*state_get_signed) (void *cls,
+                       const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                       GNUNET_PSYCSTORE_StateCallback cb,
+                       void *cb_cls);
+
+};
+
+
+#if 0                           /* keep Emacsens' auto-indent happy */
+{
+#endif
+#ifdef __cplusplus
+}
+#endif
+
+#endif
+
+/** @} */  /* end of group */
diff --git a/src/include/gnunet_psycstore_service.h b/src/include/gnunet_psycstore_service.h
new file mode 100644
index 0000000..92516f4
--- /dev/null
+++ b/src/include/gnunet_psycstore_service.h
@@ -0,0 +1,701 @@
+/*
+     This file is part of GNUnet.
+     Copyright (C) 2013 GNUnet e.V.
+
+     GNUnet is free software: you can redistribute it and/or modify it
+     under the terms of the GNU Affero General Public License as published
+     by the Free Software Foundation, either version 3 of the License,
+     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
+     Affero General Public License for more details.
+    
+     You should have received a copy of the GNU Affero General Public License
+     along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+     SPDX-License-Identifier: AGPL3.0-or-later
+*/
+
+/**
+ * @author Gabor X Toth
+ * @author Christian Grothoff
+ *
+ * @file
+ * PSYCstore service; implements persistent storage for the PSYC service
+ *
+ * @defgroup psycstore  PSYC Store service
+ * Persistent storage for the PSYC service.
+ * @{
+ */
+#ifndef GNUNET_PSYCSTORE_SERVICE_H
+#define GNUNET_PSYCSTORE_SERVICE_H
+
+#ifdef __cplusplus
+extern "C"
+{
+#if 0                           /* keep Emacsens' auto-indent happy */
+}
+#endif
+#endif
+
+#include "gnunet_util_lib.h"
+#include "gnunet_psyc_util_lib.h"
+#include "gnunet_multicast_service.h"
+#include "gnunet_psyc_service.h"
+
+/**
+ * Version number of GNUnet PSYCstore API.
+ */
+#define GNUNET_PSYCSTORE_VERSION 0x00000000
+
+/**
+ * Membership test failed.
+ */
+#define GNUNET_PSYCSTORE_MEMBERSHIP_TEST_FAILED -2
+
+/**
+ * Flags for stored messages.
+ */
+enum GNUNET_PSYCSTORE_MessageFlags
+{
+  /**
+   * The message contains state modifiers.
+   */
+  GNUNET_PSYCSTORE_MESSAGE_STATE = 1 << 0,
+
+  /**
+   * The state modifiers have been applied to the state store.
+   */
+  GNUNET_PSYCSTORE_MESSAGE_STATE_APPLIED = 1 << 1,
+
+  /**
+   * The message contains a state hash.
+   */
+  GNUNET_PSYCSTORE_MESSAGE_STATE_HASH = 1 << 2
+};
+
+
+/**
+ * Handle for a PSYCstore
+ */
+struct GNUNET_PSYCSTORE_Handle;
+
+
+/**
+ * Connect to the PSYCstore service.
+ *
+ * @param cfg Configuration to use.
+ *
+ * @return Handle for the connecton.
+ */
+struct GNUNET_PSYCSTORE_Handle *
+GNUNET_PSYCSTORE_connect (const struct GNUNET_CONFIGURATION_Handle *cfg);
+
+
+/**
+ * Disconnect from the PSYCstore service.
+ *
+ * @param h Handle for the connection.
+ */
+void
+GNUNET_PSYCSTORE_disconnect (struct GNUNET_PSYCSTORE_Handle *h);
+
+
+/**
+ * Handle for an operation on the PSYCSTORE (useful to cancel the operation).
+ */
+struct GNUNET_PSYCSTORE_OperationHandle;
+
+
+/**
+ * Function called with the result of an asynchronous operation.
+ *
+ * @param cls
+ *        Closure.
+ * @param result
+ *        Result of the operation.
+ * @param err_msg
+ *        Error message, or NULL if there's no error.
+ * @param err_msg_size
+ *        Size of @a err_msg
+ */
+typedef void
+(*GNUNET_PSYCSTORE_ResultCallback) (void *cls,
+                                    int64_t result,
+                                    const char *err_msg,
+                                    uint16_t err_msg_size);
+
+
+/**
+ * Store join/leave events for a PSYC channel in order to be able to answer
+ * membership test queries later.
+ *
+ * @param h
+ *        Handle for the PSYCstore.
+ * @param channel_key
+ *        The channel where the event happened.
+ * @param slave_key
+ *        Public key of joining/leaving slave.
+ * @param did_join
+ *        #GNUNET_YES on join, #GNUNET_NO on part.
+ * @param announced_at
+ *        ID of the message that announced the membership change.
+ * @param effective_since
+ *        Message ID this membership change is in effect since.
+ *        For joins it is <= announced_at, for parts it is always 0.
+ * @param group_generation
+ *        In case of a part, the last group generation the slave has access to.
+ *        It has relevance when a larger message have fragments with different
+ *        group generations.
+ * @param result_cb
+ *        Callback to call with the result of the storage operation.
+ * @param cls
+ *        Closure for the callback.
+ *
+ * @return Operation handle that can be used to cancel the operation.
+ */
+struct GNUNET_PSYCSTORE_OperationHandle *
+GNUNET_PSYCSTORE_membership_store (struct GNUNET_PSYCSTORE_Handle *h,
+                                   const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                                   const struct GNUNET_CRYPTO_EcdsaPublicKey *slave_key,
+                                   int did_join,
+                                   uint64_t announced_at,
+                                   uint64_t effective_since,
+                                   uint64_t group_generation,
+                                   GNUNET_PSYCSTORE_ResultCallback result_cb,
+                                   void *cls);
+
+
+/**
+ * Test if a member was admitted to the channel at the given message ID.
+ *
+ * This is useful when relaying and replaying messages to check if a particular
+ * slave has access to the message fragment with a given group generation.  It
+ * is also used when handling join requests to determine whether the slave is
+ * currently admitted to the channel.
+ *
+ * @param h
+ *        Handle for the PSYCstore.
+ * @param channel_key
+ *        The channel we are interested in.
+ * @param slave_key
+ *        Public key of slave whose membership to check.
+ * @param message_id
+ *        Message ID for which to do the membership test.
+ * @param group_generation
+ *        Group generation of the fragment of the message to test.
+ *        It has relevance if the message consists of multiple fragments with
+ *        different group generations.
+ * @param result_cb
+ *        Callback to call with the test result.
+ * @param cls
+ *        Closure for the callback.
+ *
+ * @return Operation handle that can be used to cancel the operation.
+ */
+struct GNUNET_PSYCSTORE_OperationHandle *
+GNUNET_PSYCSTORE_membership_test (struct GNUNET_PSYCSTORE_Handle *h,
+                                  const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                                  const struct GNUNET_CRYPTO_EcdsaPublicKey *slave_key,
+                                  uint64_t message_id,
+                                  uint64_t group_generation,
+                                  GNUNET_PSYCSTORE_ResultCallback result_cb,
+                                  void *cls);
+
+
+/**
+ * Store a message fragment sent to a channel.
+ *
+ * @param h Handle for the PSYCstore.
+ * @param channel_key The channel the message belongs to.
+ * @param msg Message to store.
+ * @param psycstore_flags Flags indicating whether the PSYC message contains
+ *        state modifiers.
+ * @param result_cb Callback to call with the result of the operation.
+ * @param cls Closure for the callback.
+ *
+ * @return Handle that can be used to cancel the operation.
+ */
+struct GNUNET_PSYCSTORE_OperationHandle *
+GNUNET_PSYCSTORE_fragment_store (struct GNUNET_PSYCSTORE_Handle *h,
+                                 const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                                 const struct GNUNET_MULTICAST_MessageHeader *msg,
+                                 enum GNUNET_PSYCSTORE_MessageFlags psycstore_flags,
+                                 GNUNET_PSYCSTORE_ResultCallback result_cb,
+                                 void *cls);
+
+
+/**
+ * Function called with one message fragment, as the result of a
+ * GNUNET_PSYCSTORE_fragment_get() or GNUNET_PSYCSTORE_message_get() call.
+ *
+ * @param cls Closure.
+ * @param message The retrieved message fragment.  A NULL value indicates that
+ *        there are no more results to be returned.
+ * @param psycstore_flags Flags stored with the message.
+ *
+ * @return #GNUNET_NO to stop calling this callback with further fragments,
+ *         #GNUNET_YES to continue.
+ */
+typedef int
+(*GNUNET_PSYCSTORE_FragmentCallback) (void *cls,
+                                      struct GNUNET_MULTICAST_MessageHeader *message,
+                                      enum GNUNET_PSYCSTORE_MessageFlags psycstore_flags);
+
+
+/**
+ * Retrieve message fragments by fragment ID range.
+ *
+ * @param h
+ *        Handle for the PSYCstore.
+ * @param channel_key
+ *        The channel we are interested in.
+ * @param slave_key
+ *        The slave requesting the fragment.  If not NULL, a membership test is
+ *        performed first and the fragment is only returned if the slave has
+ *        access to it.
+ * @param first_fragment_id
+ *        First fragment ID to retrieve.
+ *        Use 0 to get the latest message fragment.
+ * @param last_fragment_id
+ *        Last consecutive fragment ID to retrieve.
+ *        Use 0 to get the latest message fragment.
+ * @param fragment_cb
+ *        Callback to call with the retrieved fragments.
+ * @param result_cb
+ *        Callback to call with the result of the operation.
+ * @param cls
+ *        Closure for the callbacks.
+ *
+ * @return Handle that can be used to cancel the operation.
+ */
+struct GNUNET_PSYCSTORE_OperationHandle *
+GNUNET_PSYCSTORE_fragment_get (struct GNUNET_PSYCSTORE_Handle *h,
+                               const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                               const struct GNUNET_CRYPTO_EcdsaPublicKey *slave_key,
+                               uint64_t first_message_id,
+                               uint64_t last_message_id,
+                               GNUNET_PSYCSTORE_FragmentCallback fragment_cb,
+                               GNUNET_PSYCSTORE_ResultCallback result_cb,
+                               void *cls);
+
+
+/**
+ * Retrieve latest message fragments.
+ *
+ * @param h
+ *        Handle for the PSYCstore.
+ * @param channel_key
+ *        The channel we are interested in.
+ * @param slave_key
+ *        The slave requesting the fragment.  If not NULL, a membership test is
+ *        performed first and the fragment is only returned if the slave has
+ *        access to it.
+ * @param first_fragment_id
+ *        First fragment ID to retrieve.
+ *        Use 0 to get the latest message fragment.
+ * @param last_fragment_id
+ *        Last consecutive fragment ID to retrieve.
+ *        Use 0 to get the latest message fragment.
+ * @param fragment_limit
+ *        Maximum number of fragments to retrieve.
+ * @param fragment_cb
+ *        Callback to call with the retrieved fragments.
+ * @param result_cb
+ *        Callback to call with the result of the operation.
+ * @param cls
+ *        Closure for the callbacks.
+ *
+ * @return Handle that can be used to cancel the operation.
+ */
+struct GNUNET_PSYCSTORE_OperationHandle *
+GNUNET_PSYCSTORE_fragment_get_latest (struct GNUNET_PSYCSTORE_Handle *h,
+                                      const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                                      const struct GNUNET_CRYPTO_EcdsaPublicKey *slave_key,
+                                      uint64_t fragment_limit,
+                                      GNUNET_PSYCSTORE_FragmentCallback fragment_cb,
+                                      GNUNET_PSYCSTORE_ResultCallback result_cb,
+                                      void *cls);
+
+
+/**
+ * Retrieve all fragments of messages in a message ID range.
+ *
+ * @param h
+ *        Handle for the PSYCstore.
+ * @param channel_key
+ *        The channel we are interested in.
+ * @param slave_key
+ *        The slave requesting the message.
+ *        If not NULL, a membership test is performed first
+ *        and the message is only returned if the slave has access to it.
+ * @param first_message_id
+ *        First message ID to retrieve.
+ * @param last_message_id
+ *        Last consecutive message ID to retrieve.
+ * @param fragment_limit
+ *        Maximum number of fragments to retrieve.
+ * @param method_prefix
+ *        Retrieve only messages with a matching method prefix.
+ * @param fragment_cb
+ *        Callback to call with the retrieved fragments.
+ * @param result_cb
+ *        Callback to call with the result of the operation.
+ * @param cls
+ *        Closure for the callbacks.
+ *
+ * @return Handle that can be used to cancel the operation.
+ */
+struct GNUNET_PSYCSTORE_OperationHandle *
+GNUNET_PSYCSTORE_message_get (struct GNUNET_PSYCSTORE_Handle *h,
+                              const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                              const struct GNUNET_CRYPTO_EcdsaPublicKey *slave_key,
+                              uint64_t first_message_id,
+                              uint64_t last_message_id,
+                              uint64_t fragment_limit,
+                              const char *method_prefix,
+                              GNUNET_PSYCSTORE_FragmentCallback fragment_cb,
+                              GNUNET_PSYCSTORE_ResultCallback result_cb,
+                              void *cls);
+
+
+/**
+ * Retrieve all fragments of the latest messages.
+ *
+ * @param h
+ *        Handle for the PSYCstore.
+ * @param channel_key
+ *        The channel we are interested in.
+ * @param slave_key
+ *        The slave requesting the message.
+ *        If not NULL, a membership test is performed first
+ *        and the message is only returned if the slave has access to it.
+ * @param message_limit
+ *        Maximum number of messages to retrieve.
+ * @param method_prefix
+ *        Retrieve only messages with a matching method prefix.
+ * @param fragment_cb
+ *        Callback to call with the retrieved fragments.
+ * @param result_cb
+ *        Callback to call with the result of the operation.
+ * @param cls
+ *        Closure for the callbacks.
+ *
+ * @return Handle that can be used to cancel the operation.
+ */
+struct GNUNET_PSYCSTORE_OperationHandle *
+GNUNET_PSYCSTORE_message_get_latest (struct GNUNET_PSYCSTORE_Handle *h,
+                                     const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                                     const struct GNUNET_CRYPTO_EcdsaPublicKey *slave_key,
+                                     uint64_t message_limit,
+                                     const char *method_prefix,
+                                     GNUNET_PSYCSTORE_FragmentCallback fragment_cb,
+                                     GNUNET_PSYCSTORE_ResultCallback result_cb,
+                                     void *cls);
+
+
+/**
+ * Retrieve a fragment of message specified by its message ID and fragment
+ * offset.
+ *
+ * @param h
+ *        Handle for the PSYCstore.
+ * @param channel_key
+ *        The channel we are interested in.
+ * @param slave_key
+ *        The slave requesting the message fragment.  If not NULL, a membership
+ *        test is performed first and the message fragment is only returned
+ *        if the slave has access to it.
+ * @param message_id
+ *        Message ID to retrieve.  Use 0 to get the latest message.
+ * @param fragment_offset
+ *        Offset of the fragment to retrieve.
+ * @param fragment_cb
+ *        Callback to call with the retrieved fragments.
+ * @param result_cb
+ *        Callback to call with the result of the operation.
+ * @param cls
+ *        Closure for the callbacks.
+ *
+ * @return Handle that can be used to cancel the operation.
+ */
+struct GNUNET_PSYCSTORE_OperationHandle *
+GNUNET_PSYCSTORE_message_get_fragment (struct GNUNET_PSYCSTORE_Handle *h,
+                                       const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                                       const struct GNUNET_CRYPTO_EcdsaPublicKey *slave_key,
+                                       uint64_t message_id,
+                                       uint64_t fragment_offset,
+                                       GNUNET_PSYCSTORE_FragmentCallback fragment_cb,
+                                       GNUNET_PSYCSTORE_ResultCallback result_cb,
+                                       void *cls);
+
+
+/**
+ * Callback used to return the latest value of counters for the channel master.
+ *
+ * @see GNUNET_PSYCSTORE_counters_get()
+ *
+ * @param cls Closure.
+ * @param result_code
+ *        Status code for the operation:
+ *        #GNUNET_OK: success, counter values are returned.
+ *        #GNUNET_NO: no message has been sent to the channel yet.
+ *        #GNUNET_SYSERR: an error occurred.
+ * @param max_fragment_id
+ *        Latest message fragment ID, used by multicast.
+ * @param max_message_id
+ *        Latest message ID, used by PSYC.
+ * @param max_group_generation
+ *        Latest group generation, used by PSYC.
+ * @param max_state_message_id
+ *        Latest message ID containing state modifiers that
+ *        was applied to the state store.  Used for the state sync process.
+ */
+typedef void
+(*GNUNET_PSYCSTORE_CountersCallback) (void *cls,
+                                      int result_code,
+                                      uint64_t max_fragment_id,
+                                      uint64_t max_message_id,
+                                      uint64_t max_group_generation,
+                                      uint64_t max_state_message_id);
+
+
+/**
+ * Retrieve latest values of counters for a channel.
+ *
+ * The current value of counters are needed
+ * - when a channel master is restarted, so that it can continue incrementing
+ *   the counters from their last value.
+ * - when a channel slave rejoins and starts the state synchronization process.
+ *
+ * @param h
+ *        Handle for the PSYCstore.
+ * @param channel_key
+ *        Public key that identifies the channel.
+ * @param counters_cb
+ *        Callback to call with the result.
+ * @param cls
+ *        Closure for the @a ccb callback.
+ *
+ * @return Handle that can be used to cancel the operation.
+ */
+struct GNUNET_PSYCSTORE_OperationHandle *
+GNUNET_PSYCSTORE_counters_get (struct GNUNET_PSYCSTORE_Handle *h,
+                               struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                               GNUNET_PSYCSTORE_CountersCallback counters_cb,
+                               void *cls);
+
+
+/**
+ * Apply modifiers of a message to the current channel state.
+ *
+ * An error is returned if there are missing messages containing state
+ * operations before the current one.
+ *
+ * @param h
+ *        Handle for the PSYCstore.
+ * @param channel_key
+ *        The channel we are interested in.
+ * @param message_id
+ *        ID of the message that contains the @a modifiers.
+ * @param state_delta
+ *        Value of the @e state_delta PSYC header variable of the message.
+ * @param result_cb
+ *        Callback to call with the result of the operation.
+ * @param cls
+ *        Closure for the @a result_cb callback.
+ *
+ * @return Handle that can be used to cancel the operation.
+ */
+struct GNUNET_PSYCSTORE_OperationHandle *
+GNUNET_PSYCSTORE_state_modify (struct GNUNET_PSYCSTORE_Handle *h,
+                               const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                               uint64_t message_id,
+                               uint64_t state_delta,
+                               GNUNET_PSYCSTORE_ResultCallback result_cb,
+                               void *cls);
+
+
+/**
+ * Store synchronized state.
+ *
+ * @param h
+ *        Handle for the PSYCstore.
+ * @param channel_key
+ *        The channel we are interested in.
+ * @param max_state_message_id
+ *        ID of the last stateful message before @a state_hash_message_id.
+ * @param state_hash_message_id
+ *        ID of the message that contains the state_hash PSYC header variable.
+ * @param modifier_count
+ *        Number of elements in the @a modifiers array.
+ * @param modifiers
+ *        Full state to store.
+ * @param result_cb
+ *        Callback to call with the result of the operation.
+ * @param cls
+ *        Closure for the callback.
+ *
+ * @return Handle that can be used to cancel the operation.
+ */
+struct GNUNET_PSYCSTORE_OperationHandle *
+GNUNET_PSYCSTORE_state_sync (struct GNUNET_PSYCSTORE_Handle *h,
+                             const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                             uint64_t max_state_message_id,
+                             uint64_t state_hash_message_id,
+                             size_t modifier_count,
+                             const struct GNUNET_PSYC_Modifier *modifiers,
+                             GNUNET_PSYCSTORE_ResultCallback result_cb,
+                             void *cls);
+
+
+
+/**
+ * Reset the state of a channel.
+ *
+ * Delete all state variables stored for the given channel.
+ *
+ * @param h
+ *        Handle for the PSYCstore.
+ * @param channel_key
+ *        The channel we are interested in.
+ * @param result_cb
+ *        Callback to call with the result of the operation.
+ * @param cls
+ *        Closure for the callback.
+ *
+ * @return Handle that can be used to cancel the operation.
+ */
+struct GNUNET_PSYCSTORE_OperationHandle *
+GNUNET_PSYCSTORE_state_reset (struct GNUNET_PSYCSTORE_Handle *h,
+                              const struct GNUNET_CRYPTO_EddsaPublicKey
+                              *channel_key,
+                              GNUNET_PSYCSTORE_ResultCallback result_cb,
+                              void *cls);
+
+
+/**
+ * Update signed values of state variables in the state store.
+ *
+ * @param h
+ *        Handle for the PSYCstore.
+ * @param channel_key
+ *        The channel we are interested in.
+ * @param message_id
+ *        Message ID that contained the state @a hash.
+ * @param hash
+ *        Hash of the serialized full state.
+ * @param result_cb
+ *        Callback to call with the result of the operation.
+ * @param cls
+ *        Closure for the callback.
+ *
+ */
+struct GNUNET_PSYCSTORE_OperationHandle *
+GNUNET_PSYCSTORE_state_hash_update (struct GNUNET_PSYCSTORE_Handle *h,
+                                    const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                                    uint64_t message_id,
+                                    const struct GNUNET_HashCode *hash,
+                                    GNUNET_PSYCSTORE_ResultCallback result_cb,
+                                    void *cls);
+
+
+/**
+ * Function called with the value of a state variable.
+ *
+ * @param cls
+ *        Closure.
+ * @param name
+ *        Name of the state variable.  A NULL value indicates that there are no more
+ *        state variables to be returned.
+ * @param value
+ *        Value of the state variable.
+ * @param value_size
+ *        Number of bytes in @a value.
+ *
+ * @return #GNUNET_NO to stop calling this callback with further variables,
+ *         #GNUNET_YES to continue.
+ */;
+typedef int
+(*GNUNET_PSYCSTORE_StateCallback) (void *cls, const char *name,
+                                   const void *value, uint32_t value_size);
+
+
+/**
+ * Retrieve the best matching state variable.
+ *
+ * @param h
+ *        Handle for the PSYCstore.
+ * @param channel_key
+ *        The channel we are interested in.
+ * @param name
+ *        Name of variable to match, the returned variable might be less specific.
+ * @param state_cb
+ *        Callback to return the matching state variable.
+ * @param result_cb
+ *        Callback to call with the result of the operation.
+ * @param cls
+ *        Closure for the callbacks.
+ *
+ * @return Handle that can be used to cancel the operation.
+ */
+struct GNUNET_PSYCSTORE_OperationHandle *
+GNUNET_PSYCSTORE_state_get (struct GNUNET_PSYCSTORE_Handle *h,
+                            const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                            const char *name,
+                            GNUNET_PSYCSTORE_StateCallback state_cb,
+                            GNUNET_PSYCSTORE_ResultCallback result_cb,
+                            void *cls);
+
+
+/**
+ * Retrieve all state variables for a channel with the given prefix.
+ *
+ * @param h
+ *        Handle for the PSYCstore.
+ * @param channel_key
+ *        The channel we are interested in.
+ * @param name_prefix
+ *        Prefix of state variable names to match.
+ * @param state_cb
+ *        Callback to return matching state variables.
+ * @param result_cb
+ *        Callback to call with the result of the operation.
+ * @param cls
+ *        Closure for the callbacks.
+ *
+ * @return Handle that can be used to cancel the operation.
+ */
+struct GNUNET_PSYCSTORE_OperationHandle *
+GNUNET_PSYCSTORE_state_get_prefix (struct GNUNET_PSYCSTORE_Handle *h,
+                                   const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
+                                   const char *name_prefix,
+                                   GNUNET_PSYCSTORE_StateCallback state_cb,
+                                   GNUNET_PSYCSTORE_ResultCallback result_cb,
+                                   void *cls);
+
+
+/**
+ * Cancel an operation.
+ *
+ * @param op Handle for the operation to cancel.
+ */
+int
+GNUNET_PSYCSTORE_operation_cancel (struct GNUNET_PSYCSTORE_OperationHandle *op);
+
+
+
+
+#if 0                           /* keep Emacsens' auto-indent happy */
+{
+#endif
+#ifdef __cplusplus
+}
+#endif
+
+/* ifndef GNUNET_PSYCSTORE_SERVICE_H */
+#endif
+
+/** @} */  /* end of group */
diff --git a/src/include/gnunet_social_service.h b/src/include/gnunet_social_service.h
new file mode 100644
index 0000000..7faa336
--- /dev/null
+++ b/src/include/gnunet_social_service.h
@@ -0,0 +1,1344 @@
+/*
+     This file is part of GNUnet.
+     Copyright (C) 2013 GNUnet e.V.
+
+     GNUnet is free software: you can redistribute it and/or modify it
+     under the terms of the GNU Affero General Public License as published
+     by the Free Software Foundation, either version 3 of the License,
+     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
+     Affero General Public License for more details.
+    
+     You should have received a copy of the GNU Affero General Public License
+     along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+     SPDX-License-Identifier: AGPL3.0-or-later
+*/
+
+/**
+ * @author Gabor X Toth
+ * @author Christian Grothoff
+ *
+ * @file
+ * Social service; implements social interactions through the PSYC service.
+ */
+
+/** @defgroup social Social service
+Social interactions through the PSYC service.
+
+# Overview
+
+The social service provides an API for social interactions based on a one-to-many messaging model.
+It manages subscriptions of applications to places, provides messaging functionality in places,
+allows access to the local message history and manages the GNS zone of _egos_ (user identities).
+
+The service stores private and public keys of subscribed places, as well as files received in subscribed places.
+
+# Concepts and terminology
+
+## Ego, Nym
+
+An _ego_ is an identity of a user, a private-public key pair.
+A _nym_ is an identity of another user in the network, identified by its public key.
+Each user can have multiple identities.
+
+struct GNUNET_SOCIAL_Ego and struct GNUNET_SOCIAL_Nym represents one of these identities.
+
+## Place, Host, Guest
+
+A _place_ is where social interactions happen.  It is owned and created by an _ego_.
+Creating a new place happens by an _ego_ entering a new place as a _host_,
+where _guests_ can enter later to receive messages sent to the place.
+
+A place is identified by its public key.
+
+- struct GNUNET_SOCIAL_Host represents a place entered as host,
+- struct GNUNET_SOCIAL_Guest is used for a place entered as guest.
+- A struct GNUNET_SOCIAL_Place can be obtained for both a host and guest place
+  using GNUNET_SOCIAL_host_get_place() and GNUNET_SOCIAL_guest_get_place()
+  and can be used with API functions common to hosts and guests.
+
+## History
+
+Messages sent to places are stored locally by the PSYCstore service, and can be queried any time.
+GNUNET_SOCIAL_history_replay_latest() retrieves the latest N messages sent to the place,
+while GNUNET_SOCIAL_history_replay() is used to query a given message ID range.
+
+## GNU Name System
+
+The GNU Name System is used for assigning human-readable names to nyms and places.
+There's a _GNS zone_ corresponding to each _nym_.
+An _ego_ can publish PKEY and PLACE records in its own zone, pointing to nyms and places, respectively.
+
+## Announcement, talk request
+
+The host can _announce_ messages to the place, using GNUNET_SOCIAL_host_announce().
+Guests can send _talk_ requests to the host, using GNUNET_SOCIAL_guest_talk().
+The host receives talk requests of guests and can _relay_ them to the place,
+or process it using a message handler function.
+
+# Using the API
+
+## Connecting to the service
+
+A client first establishes an _application connection_ to the service using
+GNUNET_SOCIAL_app_connect() providing its _application ID_, then receives the
+public keys of subscribed places and available egos in response.
+
+## Reconnecting to places
+
+Then the application can reconnect to its subscribed places by establishing
+_place connections_ with GNUNET_SOCIAL_host_enter_reconnect() and
+GNUNET_SOCIAL_guest_enter_reconnect().
+
+## Subscribing to a place
+
+Entering and subscribing a new host or guest place is done using
+GNUNET_SOCIAL_host_enter() and GNUNET_SOCIAL_guest_enter().
+
+## Disconnecting from a place
+
+An application can disconnect from a place while the social service keeps its
+network connection active, using GNUNET_SOCIAL_host_disconnect() and
+GNUNET_SOCIAL_guest_disconnect().
+
+## Leaving a place
+
+To permanently leave a place, see GNUNET_SOCIAL_host_leave() and GNUNET_SOCIAL_guest_leave().
+When leaving a place its network connections are closed and all applications are unsubscribed from the place.
+
+# Message methods
+
+## _converse
+
+Human conversation in a private or public place.
+
+### Environment
+
+#### _id_reply
+Message ID this message is in reply to.
+
+#### _id_thread
+Thread ID, the first message ID in the thread.
+
+#### _nym_author
+Nym of the author.
+
+FIXME: Are nyms a different data type from egos and person entities?
+Do they have a different format than any other entity address?
+Questions and thoughts on how to fix this in "questions.org"
+
+#### _sig_author
+Signature of the message body and its variables by the author.
+
+### Data
+
+Message body.
+
+## _notice_place
+
+Notification about a place.
+
+TODO: Applications can decide to auto-subscribe to certain places,
+e.g. files under a given size.
+
+### Environment
+
+#### Using GNS
+
+##### _gns_place
+GNS name of the place in a globally unique .zkey zone
+
+FIXME: A custom _gns PSYC data type should be avoidable by parsing
+and interpreting PSYC uniforms appropriately.
+Thoughts on this in "questions.org"
+
+#### Without GNS
+
+##### _key_pub_place
+Public key of place
+
+FIXME: _key_pub can't be the data type for GNUnet-specific cryptographic
+addressing. Questions and thoughts on how to fix this in "questions.org"
+
+##### _peer_origin
+Peer ID of origin
+
+##### _list_peer_relays
+List of peer IDs of relays
+
+## _notice_place_file
+
+Notification about a place hosting a file.
+
+### Environment
+
+The environment of _notice_place above, plus the following:
+
+#### _size_file
+Size of file
+
+#### _type_file
+MIME type of file
+
+#### _name_file
+Name of file
+
+#### _description_file
+Description of file
+
+## _file
+
+Messages with a _file method contain a file,
+which is saved to disk upon reception at the following location:
+$GNUNET_DATA_HOME/social/files/<H(place_pub)>/<H(message_id)>
+
+### Environment
+
+#### _size_file
+Size of file
+
+#### _type_file
+MIME type of file
+
+#### _name_file
+Name of file
+
+#### _description_file
+Description of file
+
+@{
+*/
+
+
+#ifndef GNUNET_SOCIAL_SERVICE_H
+#define GNUNET_SOCIAL_SERVICE_H
+
+#ifdef __cplusplus
+extern "C"
+{
+#if 0                           /* keep Emacsens' auto-indent happy */
+}
+#endif
+#endif
+
+#include <stdint.h>
+#include "gnunet_util_lib.h"
+#include "gnunet_psyc_util_lib.h"
+#include "gnunet_identity_service.h"
+#include "gnunet_namestore_service.h"
+#include "gnunet_psyc_service.h"
+
+
+/**
+ * Version number of GNUnet Social API.
+ */
+#define GNUNET_SOCIAL_VERSION 0x00000000
+
+/**
+ * Maximum size of client ID including '\0' terminator.
+ */
+#define GNUNET_SOCIAL_APP_MAX_ID_SIZE 256
+
+enum GNUNET_SOCIAL_MsgProcFlags {
+  GNUNET_SOCIAL_MSG_PROC_NONE = 0,
+  GNUNET_SOCIAL_MSG_PROC_RELAY = 1,
+  GNUNET_SOCIAL_MSG_PROC_SAVE= 2,
+};
+
+/**
+ * Handle for an application.
+ */
+struct GNUNET_SOCIAL_App;
+
+/**
+ * Handle for an ego (own identity)
+ */
+struct GNUNET_SOCIAL_Ego;
+
+/**
+ * Handle for a pseudonym of another user in the network.
+ */
+struct GNUNET_SOCIAL_Nym;
+
+/**
+ * Handle for a place where social interactions happen.
+ */
+struct GNUNET_SOCIAL_Place;
+
+/**
+ * Host handle for a place that we entered.
+ */
+struct GNUNET_SOCIAL_Host;
+
+/**
+ * Guest handle for place that we entered.
+ */
+struct GNUNET_SOCIAL_Guest;
+
+/**
+ * Handle that can be used to reconnect to a place as host.
+ */
+struct GNUNET_SOCIAL_HostConnection;
+
+/**
+ * Handle that can be used to reconnect to a place as guest.
+ */
+struct GNUNET_SOCIAL_GuestConnection;
+
+/**
+ * Notification about an available identity.
+ *
+ * @param cls
+ *        Closure.
+ * @param pub_key
+ *        Public key of ego.
+ * @param name
+ *        Name of ego.
+ */
+typedef void
+(*GNUNET_SOCIAL_AppEgoCallback) (void *cls,
+                                 struct GNUNET_SOCIAL_Ego *ego,
+                                 const struct GNUNET_CRYPTO_EcdsaPublicKey *ego_pub_key,
+                                 const char *name);
+
+
+/**
+ * Entry status of a place per application.
+ */
+enum GNUNET_SOCIAL_AppPlaceState
+{
+  /**
+   * The place was once entered by the ego, but left since.
+   * It's possible to establish a local connection to the place
+   * without re-entering to fetch history from the PSYCstore.
+   * @see enum GNUNET_PSYC_SlaveJoinFlags and GNUNET_SOCIAL_guest_enter()
+   */
+  GNUNET_SOCIAL_PLACE_STATE_ARCHIVED = 0,
+
+  /**
+   * The place is entered by the ego,
+   * but this application is not subscribed to it.
+   */
+  GNUNET_SOCIAL_PLACE_STATE_ENTERED = 1,
+
+  /**
+   * The place is entered by the ego and
+   * and this application is subscribed to it.
+   */
+  GNUNET_SOCIAL_PLACE_STATE_SUBSCRIBED = 2,
+};
+
+
+/**
+ * Called after receiving initial list of egos and places.
+ */
+typedef void
+(*GNUNET_SOCIAL_AppConnectedCallback) (void *cls);
+
+
+/**
+ * Notification about a home.
+ *
+ * @param cls
+ *        Closure.
+ * @param hconn
+ *        Host connection, to be used with GNUNET_SOCIAL_host_enter_reconnect()
+ * @param ego
+ *        Ego used to enter the place.
+ * @param place_pub_key
+ *        Public key of the place.
+ * @param place_state
+ *        @see enum GNUNET_SOCIAL_AppPlaceState
+ */
+typedef void
+(*GNUNET_SOCIAL_AppHostPlaceCallback) (void *cls,
+                                       struct GNUNET_SOCIAL_HostConnection *hconn,
+                                       struct GNUNET_SOCIAL_Ego *ego,
+                                       const struct GNUNET_CRYPTO_EddsaPublicKey *place_pub_key,
+                                       enum GNUNET_SOCIAL_AppPlaceState place_state);
+
+/**
+ * Notification about a place.
+ *
+ * @param cls
+ *        Closure.
+ * @param gconn
+ *        Guest connection, to be used with GNUNET_SOCIAL_guest_enter_reconnect()
+ * @param ego
+ *        Ego used to enter the place.
+ * @param place_pub_key
+ *        Public key of the place.
+ * @param place_state
+ *        @see enum GNUNET_SOCIAL_AppPlaceState
+ */
+typedef void
+(*GNUNET_SOCIAL_AppGuestPlaceCallback) (void *cls,
+                                        struct GNUNET_SOCIAL_GuestConnection *gconn,
+                                        struct GNUNET_SOCIAL_Ego *ego,
+                                        const struct GNUNET_CRYPTO_EddsaPublicKey *place_pub_key,
+                                        enum GNUNET_SOCIAL_AppPlaceState place_state);
+
+
+/**
+ * Establish application connection to the social service.
+ *
+ * The @host_cb and @guest_cb functions are
+ * initially called for each entered places,
+ * then later each time a new place is entered with the current app ID.
+ *
+ * @param cfg
+ *        Configuration.
+ * @param ego_cb
+ *        Function to notify about an available ego.
+ * @param host_cb
+ *        Function to notify about a place entered as host.
+ * @param guest_cb
+ *        Function to notify about a place entered as guest.
+ * @param cls
+ *        Closure for the callbacks.
+ *
+ * @return Handle that can be used to stop listening.
+ */
+struct GNUNET_SOCIAL_App *
+GNUNET_SOCIAL_app_connect (const struct GNUNET_CONFIGURATION_Handle *cfg,
+                           const char *id,
+                           GNUNET_SOCIAL_AppEgoCallback ego_cb,
+                           GNUNET_SOCIAL_AppHostPlaceCallback host_cb,
+                           GNUNET_SOCIAL_AppGuestPlaceCallback guest_cb,
+                           GNUNET_SOCIAL_AppConnectedCallback connected_cb,
+                           void *cls);
+
+
+/**
+ * Disconnect app.
+ *
+ * @param app
+ *        Application handle.
+ * @param disconnect_cb
+ *        Disconnect callback.
+ * @param disconnect_cls
+ *        Disconnect closure.
+ */
+void
+GNUNET_SOCIAL_app_disconnect (struct GNUNET_SOCIAL_App *app,
+                              GNUNET_ContinuationCallback disconnect_cb,
+                              void *disconnect_cls);
+
+
+/**
+ * Get the public key of @a ego.
+ *
+ * @param ego
+ *        Ego.
+ *
+ * @return Public key of ego.
+ */
+const struct GNUNET_CRYPTO_EcdsaPublicKey *
+GNUNET_SOCIAL_ego_get_pub_key (const struct GNUNET_SOCIAL_Ego *ego);
+
+
+/**
+ * Get the name of @a ego.
+ *
+ * @param ego
+ *        Ego.
+ *
+ * @return Public key of @a ego.
+ */
+const char *
+GNUNET_SOCIAL_ego_get_name (const struct GNUNET_SOCIAL_Ego *ego);
+
+
+/**
+ * Get the public key of a @a nym.
+ *
+ * Suitable, for example, to be used with GNUNET_SOCIAL_zone_add_nym().
+ *
+ * @param nym
+ *        Pseudonym to map to a cryptographic identifier.
+ *
+ * @return Public key of nym.
+ */
+const struct GNUNET_CRYPTO_EcdsaPublicKey *
+GNUNET_SOCIAL_nym_get_pub_key (const struct GNUNET_SOCIAL_Nym *nym);
+
+
+/**
+ * Get the hash of the public key of a @a nym.
+ *
+ * @param nym
+ *        Pseudonym to map to a cryptographic identifier.
+ *
+ * @return Hash of the public key of nym.
+ */
+const struct GNUNET_HashCode *
+GNUNET_SOCIAL_nym_get_pub_key_hash (const struct GNUNET_SOCIAL_Nym *nym);
+
+
+/**
+ * Function called asking for nym to be admitted to the place.
+ *
+ * Should call either GNUNET_SOCIAL_host_admit() or
+ * GNUNET_SOCIAL_host_reject_entry() (possibly asynchronously).  If this host
+ * cannot decide, it is fine to call neither function, in which case hopefully
+ * some other host of the place exists that will make the decision.  The @a nym
+ * reference remains valid until the #GNUNET_SOCIAL_FarewellCallback is invoked
+ * for it.
+ *
+ * @param cls
+ *        Closure.
+ * @param nym
+ *        Handle for the user who wants to enter.
+ * @param method_name
+ *        Method name in the entry request.
+ * @param variable_count
+ *        Number of elements in the @a variables array.
+ * @param variables
+ *        Variables present in the message.
+ * @param data
+ *        Payload given on enter (e.g. a password).
+ * @param data_size
+ *        Number of bytes in @a data.
+ */
+typedef void
+(*GNUNET_SOCIAL_AnswerDoorCallback) (void *cls,
+                                     struct GNUNET_SOCIAL_Nym *nym,
+                                     const char *method_name,
+                                     struct GNUNET_PSYC_Environment *env,
+                                     const void *data,
+                                     size_t data_size);
+
+
+/**
+ * Function called when a @a nym leaves the place.
+ *
+ * This is also called if the @a nym was never given permission to enter
+ * (i.e. the @a nym stopped asking to get in).
+ *
+ * @param cls
+ *        Closure.
+ * @param nym
+ *        Handle for the user who left.
+ */
+typedef void
+(*GNUNET_SOCIAL_FarewellCallback) (void *cls,
+                                   const struct GNUNET_SOCIAL_Nym *nym,
+                                   struct GNUNET_PSYC_Environment *env);
+
+
+/**
+ * Function called after the host entered a home.
+ *
+ * @param cls
+ *        Closure.
+ * @param result
+ *        #GNUNET_OK on success, or
+ *        #GNUNET_SYSERR on error.
+ * @param place_pub_key
+ *        Public key of home.
+ * @param max_message_id
+ *        Last message ID sent to the channel.
+ *        Or 0 if no messages have been sent to the place yet.
+ */
+typedef void
+(*GNUNET_SOCIAL_HostEnterCallback) (void *cls, int result,
+                                    const struct GNUNET_CRYPTO_EddsaPublicKey *place_pub_key,
+                                    uint64_t max_message_id);
+
+
+/**
+ * Enter a place as host.
+ *
+ * A place is created upon first entering, and it is active until permanently
+ * left using GNUNET_SOCIAL_host_leave().
+ *
+ * @param cfg
+ *        Configuration to contact the social service.
+ * @param ego
+ *        Identity of the host.
+ * @param place_key
+ *        Private-public key pair of the place.
+ *        NULL for ephemeral places.
+ * @param policy
+ *        Policy specifying entry and history restrictions for the place.
+ * @param slicer
+ *        Slicer to handle incoming messages.
+ * @param enter_cb
+ *        Function called when the place is entered and ready to use.
+ * @param answer_door_cb
+ *        Function to handle new nyms that want to enter.
+ * @param farewell_cb
+ *        Function to handle departing nyms.
+ * @param cls
+ *        Closure for the callbacks.
+ *
+ * @return Handle for the host.
+ */
+struct GNUNET_SOCIAL_Host *
+GNUNET_SOCIAL_host_enter (const struct GNUNET_SOCIAL_App *app,
+                          const struct GNUNET_SOCIAL_Ego *ego,
+                          enum GNUNET_PSYC_Policy policy,
+                          struct GNUNET_PSYC_Slicer *slicer,
+                          GNUNET_SOCIAL_HostEnterCallback enter_cb,
+                          GNUNET_SOCIAL_AnswerDoorCallback answer_door_cb,
+                          GNUNET_SOCIAL_FarewellCallback farewell_cb,
+                          void *cls);
+
+
+/**
+ * Reconnect to an already entered place as host.
+ *
+ * @param hconn
+ *        Host connection handle.
+ *        @see GNUNET_SOCIAL_app_connect() & GNUNET_SOCIAL_AppHostPlaceCallback()
+ * @param slicer
+ *        Slicer to handle incoming messages.
+ * @param enter_cb
+ *        Function called when the place is entered and ready to use.
+ * @param answer_door_cb
+ *        Function to handle new nyms that want to enter.
+ * @param farewell_cb
+ *        Function to handle departing nyms.
+ * @param cls
+ *        Closure for the callbacks.
+ *
+ * @return Handle for the host.
+ */
+struct GNUNET_SOCIAL_Host *
+GNUNET_SOCIAL_host_enter_reconnect (struct GNUNET_SOCIAL_HostConnection *hconn,
+                                    struct GNUNET_PSYC_Slicer *slicer,
+                                    GNUNET_SOCIAL_HostEnterCallback enter_cb,
+                                    GNUNET_SOCIAL_AnswerDoorCallback answer_door_cb,
+                                    GNUNET_SOCIAL_FarewellCallback farewell_cb,
+                                    void *cls);
+
+
+/**
+ * Decision whether to admit @a nym into the place or refuse entry.
+ *
+ * @param hst
+ *        Host of the place.
+ * @param nym
+ *        Handle for the entity that wanted to enter.
+ * @param is_admitted
+ *        #GNUNET_YES    if @a nym is admitted,
+ *        #GNUNET_NO     if @a nym is refused entry,
+ *        #GNUNET_SYSERR if we cannot answer the request.
+ * @param entry_resp
+ *        Entry response message, or NULL.
+ * @return #GNUNET_OK on success,
+ *         #GNUNET_SYSERR if the message is too large.
+ */
+int
+GNUNET_SOCIAL_host_entry_decision (struct GNUNET_SOCIAL_Host *hst,
+                                   struct GNUNET_SOCIAL_Nym *nym,
+                                   int is_admitted,
+                                   const struct GNUNET_PSYC_Message *entry_resp);
+
+
+/**
+ * Throw @a nym out of the place.
+ *
+ * Sends a _notice_place_leave announcement to the home.
+ *
+ * The @a nym reference will remain valid until the
+ * #GNUNET_SOCIAL_FarewellCallback is invoked,
+ * which should be very soon after this call.
+ *
+ * @param host
+ *        Host of the place.
+ * @param nym
+ *        Handle for the entity to be ejected.
+ * @param env
+ *        Environment for the message or NULL.
+ *        _nym is set to @e nym regardless whether an @e env is provided.
+ */
+void
+GNUNET_SOCIAL_host_eject (struct GNUNET_SOCIAL_Host *host,
+                          const struct GNUNET_SOCIAL_Nym *nym,
+                          struct GNUNET_PSYC_Environment *env);
+
+
+/**
+ * Flags for announcements by a host.
+ */
+enum GNUNET_SOCIAL_AnnounceFlags
+{
+  GNUNET_SOCIAL_ANNOUNCE_NONE = 0,
+
+  /**
+   * Whether this announcement removes all objects from the place.
+   *
+   * New objects can be still added to the now empty place using the @e env
+   * parameter of the same announcement.
+   */
+  GNUNET_SOCIAL_ANNOUNCE_CLEAR_OBJECTS = 1 << 0
+};
+
+
+/**
+ * Handle for an announcement request.
+ */
+struct GNUNET_SOCIAL_Announcement;
+
+
+/**
+ * Send a message to all nyms that are present in the place.
+ *
+ * This function is restricted to the host.  Nyms can only send requests
+ * to the host who can decide to relay it to everyone in the place.
+ *
+ * @param host
+ *        Host of the place.
+ * @param method_name
+ *        Method to use for the announcement.
+ * @param env
+ *        Environment containing variables for the message and operations
+ *        on objects of the place.
+ *        Has to remain available until the first call to @a notify_data.
+ *        Can be NULL.
+ * @param notify_data
+ *        Function to call to get the payload of the announcement.
+ * @param notify_data_cls
+ *        Closure for @a notify.
+ * @param flags
+ *        Flags for this announcement.
+ *
+ * @return NULL on error (another announcement already in progress?).
+ */
+struct GNUNET_SOCIAL_Announcement *
+GNUNET_SOCIAL_host_announce (struct GNUNET_SOCIAL_Host *host,
+                             const char *method_name,
+                             const struct GNUNET_PSYC_Environment *env,
+                             GNUNET_PSYC_TransmitNotifyData notify_data,
+                             void *notify_data_cls,
+                             enum GNUNET_SOCIAL_AnnounceFlags flags);
+
+
+/**
+ * Resume transmitting announcement.
+ *
+ * @param a
+ *        The announcement to resume.
+ */
+void
+GNUNET_SOCIAL_host_announce_resume (struct GNUNET_SOCIAL_Announcement *a);
+
+
+/**
+ * Cancel announcement.
+ *
+ * @param a
+ *        The announcement to cancel.
+ */
+void
+GNUNET_SOCIAL_host_announce_cancel (struct GNUNET_SOCIAL_Announcement *a);
+
+
+/**
+ * Allow relaying messages from guests matching a given @a method_prefix.
+ *
+ * @param host
+ *        The host.
+ * @param method_prefix
+ *        Method prefix to allow.
+ */
+void
+GNUNET_SOCIAL_host_relay_allow_method (struct GNUNET_SOCIAL_Host *host,
+                                       const char *method_prefix);
+
+
+/**
+ * Allow relaying changes to objects of the place.
+ *
+ * Only applies to messages with an allowed method name.
+ * @see GNUNET_SCOIAL_host_relay_allow_method()
+ *
+ * @param host
+ *        The host.
+ * @param object_prefix
+ *        Object prefix to allow modifying.
+ */
+void
+GNUNET_SOCIAL_host_relay_allow_method (struct GNUNET_SOCIAL_Host *host,
+                                       const char *object_prefix);
+
+
+/**
+ * Stop relaying messages from guests.
+ *
+ * Remove all allowed relay rules.
+ *
+ *
+ *
+ */
+void
+GNUNET_SOCIAL_host_relay_stop (struct GNUNET_SOCIAL_Host *host);
+
+
+/**
+ * Obtain handle for a hosted place.
+ *
+ * The returned handle can be used to access the place API.
+ *
+ * @param host
+ *        Handle for the host.
+ *
+ * @return Handle for the hosted place, valid as long as @a host is valid.
+ */
+struct GNUNET_SOCIAL_Place *
+GNUNET_SOCIAL_host_get_place (struct GNUNET_SOCIAL_Host *host);
+
+
+/**
+ * Disconnect from a home.
+ *
+ * Invalidates host handle.
+ *
+ * @param hst
+ *        The host to disconnect.
+ * @param disconnect_cb
+ *        Function called after disconnected from the service.
+ * @param cls
+ *        Closure for @a disconnect_cb.
+ */
+void
+GNUNET_SOCIAL_host_disconnect (struct GNUNET_SOCIAL_Host *hst,
+                               GNUNET_ContinuationCallback disconnect_cb,
+                               void *cls);
+
+
+/**
+ * Stop hosting a home.
+ *
+ * Sends a _notice_place_closing announcement to the home.
+ * Invalidates host handle.
+ *
+ * @param hst
+ *        Host leaving.
+ * @param env
+ *        Environment for the message or NULL.
+ * @param disconnect_cb
+ *        Function called after the host left the place
+ *        and disconnected from the service.
+ * @param cls
+ *        Closure for @a disconnect_cb.
+ */
+void
+GNUNET_SOCIAL_host_leave (struct GNUNET_SOCIAL_Host *hst,
+                          const struct GNUNET_PSYC_Environment *env,
+                          GNUNET_ContinuationCallback disconnect_cb,
+                          void *cls);
+
+
+/**
+ * Function called after the guest entered the local copy of the place.
+ *
+ * History and object query functions can be used after this call,
+ * but new messages can't be sent or received.
+ *
+ * @param cls
+ *        Closure.
+ * @param result
+ *        #GNUNET_OK on success, or
+ *        #GNUNET_SYSERR on error, e.g. could not connect to the service, or
+ *        could not resolve GNS name.
+ * @param place_pub_key
+ *        Public key of place.
+ * @param max_message_id
+ *        Last message ID sent to the place.
+ *        Or 0 if no messages have been sent to the place yet.
+ */
+typedef void
+(*GNUNET_SOCIAL_GuestEnterCallback) (void *cls, int result,
+                                     const struct GNUNET_CRYPTO_EddsaPublicKey *place_pub_key,
+                                     uint64_t max_message_id);
+
+
+/**
+ * Function called upon a guest receives a decision about entry to the place.
+ *
+ * @param is_admitted
+ *        Is the guest admitted to the place?
+ *        #GNUNET_YES    if admitted,
+ *        #GNUNET_NO     if refused entry,
+ *        #GNUNET_SYSERR if the request could not be answered.
+ * @param data
+ *        Entry response message.
+ */
+typedef void
+(*GNUNET_SOCIAL_EntryDecisionCallback) (void *cls,
+                                        int is_admitted,
+                                        const struct GNUNET_PSYC_Message *entry_resp);
+
+
+/**
+ * Request entry to a place as a guest.
+ *
+ * @param app
+ *        Application handle.
+ * @param ego
+ *        Identity of the guest.
+ * @param place_pub_key
+ *        Public key of the place to enter.
+ * @param flags
+ *        Flags for the entry.
+ * @param origin
+ *        Peer identity of the origin of the underlying multicast group.
+ * @param relay_count
+ *        Number of elements in the @a relays array.
+ * @param relays
+ *        Relays for the underlying multicast group.
+ * @param entry_msg
+ *        Entry message.
+ * @param slicer
+ *        Slicer to use for processing incoming requests from guests.
+ *
+ * @return NULL on errors, otherwise handle for the guest.
+ */
+struct GNUNET_SOCIAL_Guest *
+GNUNET_SOCIAL_guest_enter (const struct GNUNET_SOCIAL_App *app,
+                           const struct GNUNET_SOCIAL_Ego *ego,
+                           const struct GNUNET_CRYPTO_EddsaPublicKey *place_pub_key,
+                           enum GNUNET_PSYC_SlaveJoinFlags flags,
+                           const struct GNUNET_PeerIdentity *origin,
+                           uint32_t relay_count,
+                           const struct GNUNET_PeerIdentity *relays,
+                           const struct GNUNET_PSYC_Message *entry_msg,
+                           struct GNUNET_PSYC_Slicer *slicer,
+                           GNUNET_SOCIAL_GuestEnterCallback local_enter_cb,
+                           GNUNET_SOCIAL_EntryDecisionCallback entry_dcsn_cb,
+                           void *cls);
+
+
+/**
+ * Request entry to a place by name as a guest.
+ *
+ * @param app
+ *        Application handle.
+ * @param ego
+ *        Identity of the guest.
+ * @param gns_name
+ *        GNS name of the place to enter.  Either in the form of
+ *        'room.friend.gnu', or 'NYMPUBKEY.zkey'.  This latter case refers to
+ *        the 'PLACE' record of the empty label ("+") in the GNS zone with the
+ *        nym's public key 'NYMPUBKEY', and can be used to request entry to a
+ *        pseudonym's place directly.
+ * @param password
+ *        Password to decrypt the record, or NULL for cleartext records.
+ * @param join_msg
+ *        Entry request message.
+ * @param slicer
+ *        Slicer to use for processing incoming requests from guests.
+ * @param local_enter_cb
+ *        Called upon connection established to the social service.
+ * @param entry_decision_cb
+ *        Called upon receiving entry decision.
+ *
+ * @return NULL on errors, otherwise handle for the guest.
+ */
+struct GNUNET_SOCIAL_Guest *
+GNUNET_SOCIAL_guest_enter_by_name (const struct GNUNET_SOCIAL_App *app,
+                                   const struct GNUNET_SOCIAL_Ego *ego,
+                                   const char *gns_name,
+                                   const char *password,
+                                   const struct GNUNET_PSYC_Message *join_msg,
+                                   struct GNUNET_PSYC_Slicer *slicer,
+                                   GNUNET_SOCIAL_GuestEnterCallback local_enter_cb,
+                                   GNUNET_SOCIAL_EntryDecisionCallback entry_decision_cb,
+                                   void *cls);
+
+
+/**
+ * Reconnect to an already entered place as guest.
+ *
+ * @param gconn
+ *        Guest connection handle.
+ *        @see GNUNET_SOCIAL_app_connect() & GNUNET_SOCIAL_AppGuestPlaceCallback()
+ * @param flags
+ *        Flags for the entry.
+ * @param slicer
+ *        Slicer to use for processing incoming requests from guests.
+ * @param local_enter_cb
+ *        Called upon connection established to the social service.
+ * @param entry_decision_cb
+ *        Called upon receiving entry decision.
+ *
+ * @return NULL on errors, otherwise handle for the guest.
+ */
+struct GNUNET_SOCIAL_Guest *
+GNUNET_SOCIAL_guest_enter_reconnect (struct GNUNET_SOCIAL_GuestConnection *gconn,
+                                     enum GNUNET_PSYC_SlaveJoinFlags flags,
+                                     struct GNUNET_PSYC_Slicer *slicer,
+                                     GNUNET_SOCIAL_GuestEnterCallback local_enter_cb,
+                                     void *cls);
+
+
+/**
+ * Flags for talking to the host of a place.
+ */
+enum GNUNET_SOCIAL_TalkFlags
+{
+  GNUNET_SOCIAL_TALK_NONE = 0
+};
+
+
+/**
+ * A talk request.
+ */
+struct GNUNET_SOCIAL_TalkRequest;
+
+
+/**
+ * Talk to the host of the place.
+ *
+ * @param place
+ *        Place where we want to talk to the host.
+ * @param method_name
+ *        Method to invoke on the host.
+ * @param env
+ *        Environment containing variables for the message, or NULL.
+ * @param notify_data
+ *        Function to use to get the payload for the method.
+ * @param notify_data_cls
+ *        Closure for @a notify_data.
+ * @param flags
+ *        Flags for the message being sent.
+ *
+ * @return NULL if we are already trying to talk to the host,
+ *         otherwise handle to cancel the request.
+ */
+struct GNUNET_SOCIAL_TalkRequest *
+GNUNET_SOCIAL_guest_talk (struct GNUNET_SOCIAL_Guest *guest,
+                          const char *method_name,
+                          const struct GNUNET_PSYC_Environment *env,
+                          GNUNET_PSYC_TransmitNotifyData notify_data,
+                          void *notify_data_cls,
+                          enum GNUNET_SOCIAL_TalkFlags flags);
+
+
+/**
+ * Resume talking to the host of the place.
+ *
+ * @param tr
+ *        Talk request to resume.
+ */
+void
+GNUNET_SOCIAL_guest_talk_resume (struct GNUNET_SOCIAL_TalkRequest *tr);
+
+
+/**
+ * Cancel talking to the host of the place.
+ *
+ * @param tr
+ *        Talk request to cancel.
+ */
+void
+GNUNET_SOCIAL_guest_talk_cancel (struct GNUNET_SOCIAL_TalkRequest *tr);
+
+
+/**
+ * Disconnect from a place.
+ *
+ * Invalidates guest handle.
+ *
+ * @param gst
+ *        The guest to disconnect.
+ * @param disconnect_cb
+ *        Function called after disconnected from the service.
+ * @param cls
+ *        Closure for @a disconnect_cb.
+ */
+void
+GNUNET_SOCIAL_guest_disconnect (struct GNUNET_SOCIAL_Guest *gst,
+                                GNUNET_ContinuationCallback disconnect_cb,
+                                void *cls);
+
+
+/**
+ * Leave a place temporarily or permanently.
+ *
+ * Notifies the owner of the place about leaving, and destroys the place handle.
+ *
+ * @param place
+ *        Place to leave.
+ * @param env
+ *        Optional environment for the leave message if @a keep_active
+ *        is #GNUNET_NO.  NULL if not needed.
+ * @param disconnect_cb
+ *        Called upon disconnecting from the social service.
+ */
+void
+GNUNET_SOCIAL_guest_leave (struct GNUNET_SOCIAL_Guest *gst,
+                           struct GNUNET_PSYC_Environment *env,
+                           GNUNET_ContinuationCallback disconnect_cb,
+                           void *leave_cls);
+
+
+/**
+ * Obtain handle for a place entered as guest.
+ *
+ * The returned handle can be used to access the place API.
+ *
+ * @param guest  Handle for the guest.
+ *
+ * @return Handle for the place, valid as long as @a guest is valid.
+ */
+struct GNUNET_SOCIAL_Place *
+GNUNET_SOCIAL_guest_get_place (struct GNUNET_SOCIAL_Guest *guest);
+
+
+/**
+ * A history request.
+ */
+struct GNUNET_SOCIAL_HistoryRequest;
+
+
+/**
+ * Get the public key of a place.
+ *
+ * @param plc
+ *        Place.
+ *
+ * @return Public key of the place.
+ */
+const struct GNUNET_CRYPTO_EddsaPublicKey *
+GNUNET_SOCIAL_place_get_pub_key (const struct GNUNET_SOCIAL_Place *plc);
+
+
+/**
+ * Set message processing @a flags for a @a method_prefix.
+ *
+ * @param plc
+ *        Place.
+ * @param method_prefix
+ *        Method prefix @a flags apply to.
+ * @param flags
+ *        The flags that apply to a matching @a method_prefix.
+ */
+void
+GNUNET_SOCIAL_place_msg_proc_set (struct GNUNET_SOCIAL_Place *plc,
+                                  const char *method_prefix,
+                                  enum GNUNET_SOCIAL_MsgProcFlags flags);
+
+/**
+ * Clear all message processing flags previously set for this place.
+ */
+void
+GNUNET_SOCIAL_place_msg_proc_clear (struct GNUNET_SOCIAL_Place *plc);
+
+
+/**
+ * Learn about the history of a place.
+ *
+ * Messages are returned through the @a slicer function
+ * and have the #GNUNET_PSYC_MESSAGE_HISTORIC flag set.
+ *
+ * @param place
+ *        Place we want to learn more about.
+ * @param start_message_id
+ *        First historic message we are interested in.
+ * @param end_message_id
+ *        Last historic message we are interested in (inclusive).
+ * @param method_prefix
+ *        Only retrieve messages with this method prefix.
+ * @param flags
+ *        OR'ed GNUNET_PSYC_HistoryReplayFlags
+ * @param slicer
+ *        Slicer to use for retrieved messages.
+ *        Can be the same as the slicer of the place.
+ * @param result_cb
+ *        Function called after all messages retrieved.
+ *        NULL if not needed.
+ * @param cls Closure for @a result_cb.
+ */
+struct GNUNET_SOCIAL_HistoryRequest *
+GNUNET_SOCIAL_place_history_replay (struct GNUNET_SOCIAL_Place *plc,
+                                    uint64_t start_message_id,
+                                    uint64_t end_message_id,
+                                    const char *method_prefix,
+                                    uint32_t flags,
+                                    struct GNUNET_PSYC_Slicer *slicer,
+                                    GNUNET_ResultCallback result_cb,
+                                    void *cls);
+
+
+/**
+ * Learn about the history of a place.
+ *
+ * Sends messages through the slicer function of the place where
+ * start_message_id <= message_id <= end_message_id.
+ * The messages will have the #GNUNET_PSYC_MESSAGE_HISTORIC flag set.
+ *
+ * To get the latest message, use 0 for both the start and end message ID.
+ *
+ * @param place
+ *        Place we want to learn more about.
+ * @param message_limit
+ *        Maximum number of historic messages we are interested in.
+ * @param result_cb
+ *        Function called after all messages retrieved.
+ *        NULL if not needed.
+ * @param cls Closure for @a result_cb.
+ */
+struct GNUNET_SOCIAL_HistoryRequest *
+GNUNET_SOCIAL_place_history_replay_latest (struct GNUNET_SOCIAL_Place *plc,
+                                           uint64_t message_limit,
+                                           const char *method_prefix,
+                                           uint32_t flags,
+                                           struct GNUNET_PSYC_Slicer *slicer,
+                                           GNUNET_ResultCallback result_cb,
+                                           void *cls);
+
+/**
+ * Cancel learning about the history of a place.
+ *
+ * @param hist
+ *        History lesson to cancel.
+ */
+void
+GNUNET_SOCIAL_place_history_replay_cancel (struct GNUNET_SOCIAL_HistoryRequest *hist);
+
+
+struct GNUNET_SOCIAL_LookHandle;
+
+
+/**
+ * Look at a particular object in the place.
+ *
+ * The best matching object is returned (its name might be less specific than
+ * what was requested).
+ *
+ * @param place
+ *        The place to look the object at.
+ * @param full_name
+ *        Full name of the object.
+ *
+ * @return NULL if there is no such object at this place.
+ */
+struct GNUNET_SOCIAL_LookHandle *
+GNUNET_SOCIAL_place_look_at (struct GNUNET_SOCIAL_Place *plc,
+                             const char *full_name,
+                             GNUNET_PSYC_StateVarCallback var_cb,
+                             GNUNET_ResultCallback result_cb,
+                             void *cls);
+
+/**
+ * Look for objects in the place with a matching name prefix.
+ *
+ * @param place
+ *        The place to look its objects at.
+ * @param name_prefix
+ *        Look at objects with names beginning with this value.
+ * @param var_cb
+ *        Function to call for each object found.
+ * @param cls
+ *        Closure for callback function.
+ *
+ * @return Handle that can be used to stop looking at objects.
+ */
+struct GNUNET_SOCIAL_LookHandle *
+GNUNET_SOCIAL_place_look_for (struct GNUNET_SOCIAL_Place *plc,
+                              const char *name_prefix,
+                              GNUNET_PSYC_StateVarCallback var_cb,
+                              GNUNET_ResultCallback result_cb,
+                              void *cls);
+
+
+/**
+ * Stop looking at objects.
+ *
+ * @param lh Look handle to stop.
+ */
+void
+GNUNET_SOCIAL_place_look_cancel (struct GNUNET_SOCIAL_LookHandle *lh);
+
+
+/**
+ * Advertise a @e place in the GNS zone of @a ego.
+ *
+ * @param app
+ *        Application handle.
+ * @param ego
+ *        Ego.
+ * @param place_pub_key
+ *        Public key of place to add.
+ * @param name
+ *        The name for the PLACE record to put in the zone.
+ * @param password
+ *        Password used to encrypt the record or NULL to keep it cleartext.
+ * @param relay_count
+ *        Number of elements in the @a relays array.
+ * @param relays
+ *        List of relays to put in the PLACE record to advertise
+ *        as entry points to the place in addition to the origin.
+ * @param expiration_time
+ *        Expiration time of the record, use 0 to remove the record.
+ * @param result_cb
+ *        Function called with the result of the operation.
+ * @param result_cls
+ *        Closure for @a result_cb
+ *
+ * @return #GNUNET_OK if the request was sent,
+ *         #GNUNET_SYSERR on error, e.g. the name/password is too long.
+ */
+int
+GNUNET_SOCIAL_zone_add_place (const struct GNUNET_SOCIAL_App *app,
+                              const struct GNUNET_SOCIAL_Ego *ego,
+                              const char *name,
+                              const char *password,
+                              const struct GNUNET_CRYPTO_EddsaPublicKey *place_pub_key,
+                              const struct GNUNET_PeerIdentity *origin,
+                              uint32_t relay_count,
+                              const struct GNUNET_PeerIdentity *relays,
+                              struct GNUNET_TIME_Absolute expiration_time,
+                              GNUNET_ResultCallback result_cb,
+                              void *result_cls);
+
+
+/**
+ * Add public key to the GNS zone of the @e ego.
+ *
+ * @param cfg
+ *        Configuration.
+ * @param ego
+ *        Ego.
+ * @param name
+ *        The name for the PKEY record to put in the zone.
+ * @param nym_pub_key
+ *        Public key of nym to add.
+ * @param expiration_time
+ *        Expiration time of the record, use 0 to remove the record.
+ * @param result_cb
+ *        Function called with the result of the operation.
+ * @param result_cls
+ *        Closure for @a result_cb
+ *
+ * @return #GNUNET_OK if the request was sent,
+ *         #GNUNET_SYSERR on error, e.g. the name is too long.
+ */
+int
+GNUNET_SOCIAL_zone_add_nym (const struct GNUNET_SOCIAL_App *app,
+                            const struct GNUNET_SOCIAL_Ego *ego,
+                            const char *name,
+                            const struct GNUNET_CRYPTO_EcdsaPublicKey *nym_pub_key,
+                            struct GNUNET_TIME_Absolute expiration_time,
+                            GNUNET_ResultCallback result_cb,
+                            void *result_cls);
+
+
+#if 0                           /* keep Emacsens' auto-indent happy */
+{
+#endif
+#ifdef __cplusplus
+}
+#endif
+
+/* ifndef GNUNET_SOCIAL_SERVICE_H */
+#endif
+
+/** @} */  /* end of group */