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diff --git a/src/cadet/gnunet-service-cadet_connection.h b/src/cadet/gnunet-service-cadet_connection.h
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@@ -0,0 +1,566 @@
+/*
+     This file is part of GNUnet.
+     (C) 2013 Christian Grothoff (and other contributing authors)
+
+     GNUnet is free software; you can redistribute it and/or modify
+     it under the terms of the GNU General Public License as published
+     by the Free Software Foundation; either version 3, or (at your
+     option) any later version.
+
+     GNUnet is distributed in the hope that it will be useful, but
+     WITHOUT ANY WARRANTY; without even the implied warranty of
+     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+     General Public License for more details.
+
+     You should have received a copy of the GNU General Public License
+     along with GNUnet; see the file COPYING.  If not, write to the
+     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+     Boston, MA 02111-1307, USA.
+*/
+
+/**
+ * @file cadet/gnunet-service-cadet_connection.h
+ * @brief cadet service; dealing with connections
+ * @author Bartlomiej Polot
+ *
+ * All functions in this file should use the prefix GMC (Gnunet Cadet Connection)
+ */
+
+#ifndef GNUNET_SERVICE_CADET_CONNECTION_H
+#define GNUNET_SERVICE_CADET_CONNECTION_H
+
+#ifdef __cplusplus
+extern "C"
+{
+#if 0                           /* keep Emacsens' auto-indent happy */
+}
+#endif
+#endif
+
+#include "gnunet_util_lib.h"
+
+
+/**
+ * All the states a connection can be in.
+ */
+enum CadetConnectionState
+{
+  /**
+   * Uninitialized status, should never appear in operation.
+   */
+  CADET_CONNECTION_NEW,
+
+  /**
+   * Connection create message sent, waiting for ACK.
+   */
+  CADET_CONNECTION_SENT,
+
+  /**
+   * Connection ACK sent, waiting for ACK.
+   */
+  CADET_CONNECTION_ACK,
+
+  /**
+   * Connection confirmed, ready to carry traffic.
+   */
+  CADET_CONNECTION_READY,
+
+  /**
+   * Connection to be destroyed, just waiting to empty queues.
+   */
+  CADET_CONNECTION_DESTROYED,
+};
+
+
+/**
+ * Struct containing all information regarding a connection to a peer.
+ */
+struct CadetConnection;
+
+/**
+ * Handle for messages queued but not yet sent.
+ */
+struct CadetConnectionQueue;
+
+#include "cadet_path.h"
+#include "gnunet-service-cadet_channel.h"
+#include "gnunet-service-cadet_peer.h"
+
+
+
+/**
+ * Callback called when a queued message is sent.
+ *
+ * @param cls Closure.
+ * @param c Connection this message was on.
+ * @param type Type of message sent.
+ * @param fwd Was this a FWD going message?
+ * @param size Size of the message.
+ */
+typedef void (*GMC_sent) (void *cls,
+                          struct CadetConnection *c,
+                          struct CadetConnectionQueue *q,
+                          uint16_t type, int fwd, size_t size);
+
+/**
+ * Core handler for connection creation.
+ *
+ * @param cls Closure (unused).
+ * @param peer Sender (neighbor).
+ * @param message Message.
+ *
+ * @return GNUNET_OK to keep the connection open,
+ *         GNUNET_SYSERR to close it (signal serious error)
+ */
+int
+GMC_handle_create (void *cls, const struct GNUNET_PeerIdentity *peer,
+                   const struct GNUNET_MessageHeader *message);
+
+/**
+ * Core handler for path confirmations.
+ *
+ * @param cls closure
+ * @param message message
+ * @param peer peer identity this notification is about
+ *
+ * @return GNUNET_OK to keep the connection open,
+ *         GNUNET_SYSERR to close it (signal serious error)
+ */
+int
+GMC_handle_confirm (void *cls, const struct GNUNET_PeerIdentity *peer,
+                    const struct GNUNET_MessageHeader *message);
+
+/**
+ * Core handler for notifications of broken paths
+ *
+ * @param cls Closure (unused).
+ * @param id Peer identity of sending neighbor.
+ * @param message Message.
+ *
+ * @return GNUNET_OK to keep the connection open,
+ *         GNUNET_SYSERR to close it (signal serious error)
+ */
+int
+GMC_handle_broken (void* cls,
+                   const struct GNUNET_PeerIdentity* id,
+                   const struct GNUNET_MessageHeader* message);
+
+/**
+ * Core handler for tunnel destruction
+ *
+ * @param cls Closure (unused).
+ * @param peer Peer identity of sending neighbor.
+ * @param message Message.
+ *
+ * @return GNUNET_OK to keep the connection open,
+ *         GNUNET_SYSERR to close it (signal serious error)
+ */
+int
+GMC_handle_destroy (void *cls, const struct GNUNET_PeerIdentity *peer,
+                    const struct GNUNET_MessageHeader *message);
+
+/**
+ * Core handler for encrypted cadet network traffic (channel mgmt, data).
+ *
+ * @param cls Closure (unused).
+ * @param message Message received.
+ * @param peer Peer who sent the message.
+ *
+ * @return GNUNET_OK to keep the connection open,
+ *         GNUNET_SYSERR to close it (signal serious error)
+ */
+int
+GMC_handle_encrypted (void *cls, const struct GNUNET_PeerIdentity *peer,
+                      const struct GNUNET_MessageHeader *message);
+
+/**
+ * Core handler for key exchange traffic (ephemeral key, ping, pong).
+ *
+ * @param cls Closure (unused).
+ * @param message Message received.
+ * @param peer Peer who sent the message.
+ *
+ * @return GNUNET_OK to keep the connection open,
+ *         GNUNET_SYSERR to close it (signal serious error)
+ */
+int
+GMC_handle_kx (void *cls, const struct GNUNET_PeerIdentity *peer,
+               const struct GNUNET_MessageHeader *message);
+
+/**
+ * Core handler for cadet network traffic point-to-point acks.
+ *
+ * @param cls closure
+ * @param message message
+ * @param peer peer identity this notification is about
+ *
+ * @return GNUNET_OK to keep the connection open,
+ *         GNUNET_SYSERR to close it (signal serious error)
+ */
+int
+GMC_handle_ack (void *cls, const struct GNUNET_PeerIdentity *peer,
+                const struct GNUNET_MessageHeader *message);
+
+/**
+ * Core handler for cadet network traffic point-to-point ack polls.
+ *
+ * @param cls closure
+ * @param message message
+ * @param peer peer identity this notification is about
+ *
+ * @return GNUNET_OK to keep the connection open,
+ *         GNUNET_SYSERR to close it (signal serious error)
+ */
+int
+GMC_handle_poll (void *cls, const struct GNUNET_PeerIdentity *peer,
+                 const struct GNUNET_MessageHeader *message);
+
+/**
+ * Core handler for cadet keepalives.
+ *
+ * @param cls closure
+ * @param message message
+ * @param peer peer identity this notification is about
+ * @return GNUNET_OK to keep the connection open,
+ *         GNUNET_SYSERR to close it (signal serious error)
+ *
+ * TODO: Check who we got this from, to validate route.
+ */
+int
+GMC_handle_keepalive (void *cls, const struct GNUNET_PeerIdentity *peer,
+                      const struct GNUNET_MessageHeader *message);
+
+/**
+ * Send an ACK on the appropriate connection/channel, depending on
+ * the direction and the position of the peer.
+ *
+ * @param c Which connection to send the hop-by-hop ACK.
+ * @param fwd Is this a fwd ACK? (will go dest->root).
+ * @param force Send the ACK even if suboptimal (e.g. requested by POLL).
+ */
+void
+GMC_send_ack (struct CadetConnection *c, int fwd, int force);
+
+/**
+ * Initialize the connections subsystem
+ *
+ * @param c Configuration handle.
+ */
+void
+GMC_init (const struct GNUNET_CONFIGURATION_Handle *c);
+
+/**
+ * Shut down the connections subsystem.
+ */
+void
+GMC_shutdown (void);
+
+/**
+ * Create a connection.
+ *
+ * @param cid Connection ID (either created locally or imposed remotely).
+ * @param t Tunnel this connection belongs to (or NULL);
+ * @param p Path this connection has to use.
+ * @param own_pos Own position in the @c p path.
+ *
+ * @return Newly created connection, NULL in case of error (own id not in path).
+ */
+struct CadetConnection *
+GMC_new (const struct GNUNET_CADET_Hash *cid,
+         struct CadetTunnel3 *t,
+         struct CadetPeerPath *p,
+         unsigned int own_pos);
+
+/**
+ * Connection is no longer needed: destroy it.
+ *
+ * Cancels all pending traffic (including possible DESTROY messages), all
+ * maintenance tasks and removes the connection from neighbor peers and tunnel.
+ *
+ * @param c Connection to destroy.
+ */
+void
+GMC_destroy (struct CadetConnection *c);
+
+/**
+ * Get the connection ID.
+ *
+ * @param c Connection to get the ID from.
+ *
+ * @return ID of the connection.
+ */
+const struct GNUNET_CADET_Hash *
+GMC_get_id (const struct CadetConnection *c);
+
+
+/**
+ * Get a hash for the connection ID.
+ *
+ * @param c Connection to get the hash.
+ *
+ * @return Hash expanded from the ID of the connection.
+ */
+const struct GNUNET_HashCode *
+GMC_get_h (const struct CadetConnection *c);
+
+
+/**
+ * Get the connection path.
+ *
+ * @param c Connection to get the path from.
+ *
+ * @return path used by the connection.
+ */
+const struct CadetPeerPath *
+GMC_get_path (const struct CadetConnection *c);
+
+/**
+ * Get the connection state.
+ *
+ * @param c Connection to get the state from.
+ *
+ * @return state of the connection.
+ */
+enum CadetConnectionState
+GMC_get_state (const struct CadetConnection *c);
+
+/**
+ * Get the connection tunnel.
+ *
+ * @param c Connection to get the tunnel from.
+ *
+ * @return tunnel of the connection.
+ */
+struct CadetTunnel3 *
+GMC_get_tunnel (const struct CadetConnection *c);
+
+/**
+ * Get free buffer space in a connection.
+ *
+ * @param c Connection.
+ * @param fwd Is query about FWD traffic?
+ *
+ * @return Free buffer space [0 - max_msgs_queue/max_connections]
+ */
+unsigned int
+GMC_get_buffer (struct CadetConnection *c, int fwd);
+
+/**
+ * Get how many messages have we allowed to send to us from a direction.
+ *
+ * @param c Connection.
+ * @param fwd Are we asking about traffic from FWD (BCK messages)?
+ *
+ * @return last_ack_sent - last_pid_recv
+ */
+unsigned int
+GMC_get_allowed (struct CadetConnection *c, int fwd);
+
+/**
+ * Get messages queued in a connection.
+ *
+ * @param c Connection.
+ * @param fwd Is query about FWD traffic?
+ *
+ * @return Number of messages queued.
+ */
+unsigned int
+GMC_get_qn (struct CadetConnection *c, int fwd);
+
+/**
+ * Get next PID to use.
+ *
+ * @param c Connection.
+ * @param fwd Is query about FWD traffic?
+ *
+ * @return Last PID used + 1.
+ */
+unsigned int
+GMC_get_pid (struct CadetConnection *c, int fwd);
+
+/**
+ * Allow the connection to advertise a buffer of the given size.
+ *
+ * The connection will send an @c fwd ACK message (so: in direction !fwd)
+ * allowing up to last_pid_recv + buffer.
+ *
+ * @param c Connection.
+ * @param buffer How many more messages the connection can accept.
+ * @param fwd Is this about FWD traffic? (The ack will go dest->root).
+ */
+void
+GMC_allow (struct CadetConnection *c, unsigned int buffer, int fwd);
+
+/**
+ * Send FWD keepalive packets for a connection.
+ *
+ * @param cls Closure (connection for which to send the keepalive).
+ * @param tc Notification context.
+ */
+void
+GMC_fwd_keepalive (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc);
+
+/**
+ * Send BCK keepalive packets for a connection.
+ *
+ * @param cls Closure (connection for which to send the keepalive).
+ * @param tc Notification context.
+ */
+void
+GMC_bck_keepalive (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc);
+
+
+/**
+ * Notify other peers on a connection of a broken link. Mark connections
+ * to destroy after all traffic has been sent.
+ *
+ * @param c Connection on which there has been a disconnection.
+ * @param peer Peer that disconnected.
+ */
+void
+GMC_notify_broken (struct CadetConnection *c,
+                   struct CadetPeer *peer);
+
+/**
+ * Is this peer the first one on the connection?
+ *
+ * @param c Connection.
+ * @param fwd Is this about fwd traffic?
+ *
+ * @return #GNUNET_YES if origin, #GNUNET_NO if relay/terminal.
+ */
+int
+GMC_is_origin (struct CadetConnection *c, int fwd);
+
+/**
+ * Is this peer the last one on the connection?
+ *
+ * @param c Connection.
+ * @param fwd Is this about fwd traffic?
+ *            Note that the ROOT is the terminal for BCK traffic!
+ *
+ * @return #GNUNET_YES if terminal, #GNUNET_NO if relay/origin.
+ */
+int
+GMC_is_terminal (struct CadetConnection *c, int fwd);
+
+/**
+ * See if we are allowed to send by the next hop in the given direction.
+ *
+ * @param c Connection.
+ * @param fwd Is this about fwd traffic?
+ *
+ * @return #GNUNET_YES in case it's OK to send.
+ */
+int
+GMC_is_sendable (struct CadetConnection *c, int fwd);
+
+/**
+ * Check if this connection is a direct one (never trim a direct connection).
+ *
+ * @param c Connection.
+ *
+ * @return #GNUNET_YES in case it's a direct connection, #GNUNET_NO otherwise.
+ */
+int
+GMC_is_direct (struct CadetConnection *c);
+
+/**
+ * Cancel a previously sent message while it's in the queue.
+ *
+ * ONLY can be called before the continuation given to the send function
+ * is called. Once the continuation is called, the message is no longer in the
+ * queue.
+ *
+ * @param q Handle to the queue.
+ */
+void
+GMC_cancel (struct CadetConnectionQueue *q);
+
+/**
+ * Sends an already built message on a connection, properly registering
+ * all used resources.
+ *
+ * @param message Message to send. Function makes a copy of it.
+ *                If message is not hop-by-hop, decrements TTL of copy.
+ * @param payload_type Type of payload, in case the message is encrypted.
+ * @param c Connection on which this message is transmitted.
+ * @param fwd Is this a fwd message?
+ * @param force Force the connection to accept the message (buffer overfill).
+ * @param cont Continuation called once message is sent. Can be NULL.
+ * @param cont_cls Closure for @c cont.
+ *
+ * @return Handle to cancel the message before it's sent.
+ *         NULL on error or if @c cont is NULL.
+ *         Invalid on @c cont call.
+ */
+struct CadetConnectionQueue *
+GMC_send_prebuilt_message (const struct GNUNET_MessageHeader *message,
+                           uint16_t payload_type, uint32_t payload_id,
+                           struct CadetConnection *c, int fwd, int force,
+                           GMC_sent cont, void *cont_cls);
+
+/**
+ * Sends a CREATE CONNECTION message for a path to a peer.
+ * Changes the connection and tunnel states if necessary.
+ *
+ * @param connection Connection to create.
+ */
+void
+GMC_send_create (struct CadetConnection *connection);
+
+/**
+ * Send a message to all peers in this connection that the connection
+ * is no longer valid.
+ *
+ * If some peer should not receive the message, it should be zero'ed out
+ * before calling this function.
+ *
+ * @param c The connection whose peers to notify.
+ */
+void
+GMC_send_destroy (struct CadetConnection *c);
+
+/**
+ * @brief Start a polling timer for the connection.
+ *
+ * When a neighbor does not accept more traffic on the connection it could be
+ * caused by a simple congestion or by a lost ACK. Polling enables to check
+ * for the lastest ACK status for a connection.
+ *
+ * @param c Connection.
+ * @param fwd Should we poll in the FWD direction?
+ */
+void
+GMC_start_poll (struct CadetConnection *c, int fwd);
+
+
+/**
+ * @brief Stop polling a connection for ACKs.
+ *
+ * Once we have enough ACKs for future traffic, polls are no longer necessary.
+ *
+ * @param c Connection.
+ * @param fwd Should we stop the poll in the FWD direction?
+ */
+void
+GMC_stop_poll (struct CadetConnection *c, int fwd);
+
+/**
+ * Get a (static) string for a connection.
+ *
+ * @param c Connection.
+ */
+const char *
+GMC_2s (const struct CadetConnection *c);
+
+#if 0                           /* keep Emacsens' auto-indent happy */
+{
+#endif
+#ifdef __cplusplus
+}
+#endif
+
+/* ifndef GNUNET_SERVICE_CADET_CONNECTION_H */
+#endif
+/* end of gnunet-service-cadet_connection.h */