first draft for new transport api implementation

1 files changed, 1408 insertions, 0 deletions

diff --git a/src/transport/transport_api_new.c b/src/transport/transport_api_new.c
new file mode 100644
index 000000000..02f3fc421
--- /dev/null
+++ b/src/transport/transport_api_new.c
@@ -0,0 +1,1408 @@
+/*
+     This file is part of GNUnet.
+     (C) 2009, 2010, 2011 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 transport/transport_api.c
+ * @brief library to access the low-level P2P IO service
+ * @author Christian Grothoff
+ *
+ * TODO:
+ * - support 'try connect' in transport service
+ * - add timeout (see FIXME)
+ * - adjust testcases to use new 'try connect' style (should be easy, breaks API compatibility!)
+ * - adjust core service to use new 'try connect' style (should be MUCH nicer there as well!)
+ * - test test test
+ */
+#include "platform.h"
+#include "gnunet_bandwidth_lib.h"
+#include "gnunet_client_lib.h"
+#include "gnunet_constants.h"
+#include "gnunet_container_lib.h"
+#include "gnunet_arm_service.h"
+#include "gnunet_hello_lib.h"
+#include "gnunet_protocols.h"
+#include "gnunet_server_lib.h"
+#include "gnunet_time_lib.h"
+#include "gnunet_transport_service.h"
+#include "transport.h"
+
+/**
+ * How large to start with for the hashmap of neighbours.
+ */
+#define STARTING_NEIGHBOURS_SIZE 16
+
+
+/**
+ * Handle for a message that should be transmitted to the service.
+ * Used for both control messages and normal messages.
+ */
+struct GNUNET_TRANSPORT_TransmitHandle
+{
+
+  /**
+   * We keep all requests in a DLL.
+   */
+  struct GNUNET_TRANSPORT_TransmitHandle *next;
+
+  /**
+   * We keep all requests in a DLL.
+   */
+  struct GNUNET_TRANSPORT_TransmitHandle *prev;
+
+  /**
+   * Neighbour for this handle, NULL for control messages.
+   */
+  struct NeighbourList *neighbour;
+
+  /**
+   * Function to call when notify_size bytes are available
+   * for transmission.
+   */
+  GNUNET_CONNECTION_TransmitReadyNotify notify;
+
+  /**
+   * Closure for notify.
+   */
+  void *notify_cls;
+
+  /**
+   * Timeout for this request, 0 for control messages.
+   */
+  struct GNUNET_TIME_Absolute timeout;
+
+  /**
+   * How many bytes is our notify callback waiting for?
+   */
+  size_t notify_size;
+
+  /**
+   * How important is this message? Not used for control messages.
+   */
+  uint32_t priority;
+
+};
+
+
+/**
+ * Entry in hash table of all of our current neighbours.
+ */
+struct Neighbour
+{
+  /**
+   * Overall transport handle.
+   */
+  struct GNUNET_TRANSPORT_Handle *h;
+
+  /**
+   * Active transmit handle or NULL.
+   */
+  struct GNUNET_TRANSPORT_TransmitHandle *th;
+
+  /**
+   * Identity of this neighbour.
+   */
+  struct GNUNET_PeerIdentity id;
+
+  /**
+   * Outbound bandwidh tracker.
+   */
+  struct GNUNET_BANDWIDTH_Tracker out_tracker;
+
+  /**
+   * Entry in our readyness heap (which is sorted by 'next_ready'
+   * value).  NULL if there is no pending transmission request for
+   * this neighbour or if we're waiting for 'is_ready' to become
+   * true AFTER the 'out_tracker' suggested that this peer's quota
+   * has been satisfied (so once 'is_ready' goes to GNUNET_YES,
+   * we should immediately go back into the heap).
+   */
+  struct GNUNET_CONTAINER_HeapNode *hn;
+
+  /**
+   * Is this peer currently ready to receive a message?
+   */
+  int is_ready;
+
+};
+
+
+/**
+ * Linked list of functions to call whenever our HELLO is updated.
+ */
+struct HelloWaitList
+{
+
+  /**
+   * This is a doubly linked list.
+   */
+  struct HelloWaitList *next;
+
+  /**
+   * This is a doubly linked list.
+   */
+  struct HelloWaitList *prev;
+
+  /**
+   * Callback to call once we got our HELLO.
+   */
+  GNUNET_TRANSPORT_HelloUpdateCallback rec;
+
+  /**
+   * Closure for rec.
+   */
+  void *rec_cls;
+
+};
+
+
+/**
+ * Handle for the transport service (includes all of the
+ * state for the transport service).
+ */
+struct GNUNET_TRANSPORT_Handle
+{
+
+  /**
+   * Closure for the callbacks.
+   */
+  void *cls;
+
+  /**
+   * Function to call for received data.
+   */
+  GNUNET_TRANSPORT_ReceiveCallback rec;
+
+  /**
+   * function to call on connect events
+   */
+  GNUNET_TRANSPORT_NotifyConnect nc_cb;
+
+  /**
+   * function to call on disconnect events
+   */
+  GNUNET_TRANSPORT_NotifyDisconnect nd_cb;
+
+  /**
+   * Head of DLL of control messages.
+   */
+  struct GNUNET_TRANSPORT_TransmitHandle *control_head;
+
+  /**
+   * Tail of DLL of control messages.
+   */
+  struct GNUNET_TRANSPORT_TransmitHandle *control_tail;
+
+  /**
+   * The current HELLO message for this peer.  Updated
+   * whenever transports change their addresses.
+   */
+  struct GNUNET_HELLO_Message *my_hello;
+
+  /**
+   * My client connection to the transport service.
+   */
+  struct GNUNET_CLIENT_Connection *client;
+
+  /**
+   * Handle to our registration with the client for notification.
+   */
+  struct GNUNET_CLIENT_TransmitHandle *cth;
+
+  /**
+   * Linked list of pending requests for our HELLO.
+   */
+  struct HelloWaitList *hwl_head;
+
+  /**
+   * Linked list of pending requests for our HELLO.
+   */
+  struct HelloWaitList *hwl_tail;
+
+  /**
+   * My configuration.
+   */
+  const struct GNUNET_CONFIGURATION_Handle *cfg;
+
+  /**
+   * Hash map of the current connected neighbours of this peer.
+   * Maps peer identities to 'struct Neighbour' entries.
+   */
+  struct GNUNET_CONTAINER_MultiHashMap *neighbours;
+
+  /**
+   * Heap sorting peers with pending messages by the timestamps that
+   * specify when we could next send a message to the respective peer.
+   * Excludes control messages (which can always go out immediately).
+   * Maps time stamps to 'struct Neighbour' entries.
+   */ 
+  struct GNUNET_CONTAINER_Heap *ready_heap;
+
+  /**
+   * Peer identity as assumed by this process, or all zeros.
+   */
+  struct GNUNET_PeerIdentity self;
+
+  /**
+   * ID of the task trying to reconnect to the service.
+   */
+  GNUNET_SCHEDULER_TaskIdentifier reconnect_task;
+
+  /**
+   * ID of the task trying to trigger transmission for a peer while
+   * maintaining bandwidth quotas.  In use if there are no control
+   * messages and the smallest entry in the 'ready_heap' has a time
+   * stamp in the future.
+   */
+  GNUNET_SCHEDULER_TaskIdentifier quota_task;
+
+  /**
+   * Delay until we try to reconnect.
+   */
+  struct GNUNET_TIME_Relative reconnect_delay;
+
+  /**
+   * Should we check that 'self' matches what the service thinks?
+   * (if GNUNET_NO, then 'self' is all zeros!).
+   */
+  int check_self;
+};
+
+
+/**
+ * Schedule the task to send one message, either from the control
+ * list or the peer message queues  to the service.
+ *
+ * @param h transport service to schedule a transmission for
+ */
+static void
+schedule_transmission (struct GNUNET_TRANSPORT_Handle *h);
+
+
+/**
+ * Function that will schedule the job that will try
+ * to connect us again to the client.
+ *
+ * @param h transport service to reconnect
+ */
+static void
+disconnect_and_schedule_reconnect (struct GNUNET_TRANSPORT_Handle *h);
+
+
+/**
+ * Get the neighbour list entry for the given peer
+ *
+ * @param h our context
+ * @param peer peer to look up
+ * @return NULL if no such peer entry exists
+ */
+static struct Neighbour *
+neighbour_find (struct GNUNET_TRANSPORT_Handle *h,
+                const struct GNUNET_PeerIdentity *peer)
+{
+  return GNUNET_CONTAINER_multihashmap_get(h->neighbours, &peer->hashPubKey);
+}
+
+
+/**
+ * Add neighbour to our list
+ *
+ * @return NULL if this API is currently disconnecting from the service
+ */
+static struct Neighbour *
+neighbour_add (struct GNUNET_TRANSPORT_Handle *h,
+               const struct GNUNET_PeerIdentity *pid)
+{
+  struct Neighbour *n;
+
+#if DEBUG_TRANSPORT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Creating entry for neighbour `%4s'.\n",
+              GNUNET_i2s (pid));
+#endif
+  n = GNUNET_malloc (sizeof (struct Neighbour));
+  n->id = *pid;
+  n->h = h;
+  n->is_ready = GNUNET_YES;
+  GNUNET_BANDWIDTH_tracker_init (&n->out_tracker,
+                                 GNUNET_CONSTANTS_DEFAULT_BW_IN_OUT,
+                                 MAX_BANDWIDTH_CARRY_S);
+  GNUNET_CONTAINER_multihashmap_put (h->neighbours,
+                                     &pid->hashPubKey,
+                                     n,
+                                     GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY);
+  return n;
+}
+
+
+/**
+ * Iterator over hash map entries, for deleting state of a neighbour.
+ *
+ * @param cls the 'struct GNUNET_TRANSPORT_Handle*'
+ * @param key peer identity
+ * @param value value in the hash map, the neighbour entry to delete
+ * @return GNUNET_YES if we should continue to
+ *         iterate,
+ *         GNUNET_NO if not.
+ */
+static int
+neighbour_delete (void *cls,
+                  const GNUNET_HashCode * key,
+                  void *value)
+{
+  struct GNUNET_TRANSPORT_Handle *handle = cls;
+  struct Neighbour *n = value;
+
+  handle->nd_cb (handle->cls,
+                 &n->id);
+  GNUNET_assert (NULL == n->th);
+  GNUNET_assert (NULL == n->hn);
+  GNUNET_CONTAINER_multihashmap_remove (handle->neighbours,
+                                        key,
+                                        n);
+  GNUNET_free (n);
+  return GNUNET_YES;
+}
+
+
+/**
+ * Function we use for handling incoming messages.
+ *
+ * @param cls closure (struct GNUNET_TRANSPORT_Handle *)
+ * @param msg message received, NULL on timeout or fatal error
+ */
+static void
+demultiplexer (void *cls,
+               const struct GNUNET_MessageHeader *msg)
+{
+  struct GNUNET_TRANSPORT_Handle *h = cls;
+  const struct DisconnectInfoMessage *dim;
+  const struct ConnectInfoMessage *cim;
+  const struct InboundMessage *im;
+  const struct GNUNET_MessageHeader *imm;
+  const struct SendOkMessage *okm;
+  struct HelloWaitList *hwl;
+  struct HelloWaitList *next_hwl;
+  struct NeighbourList *n;
+  struct GNUNET_PeerIdentity me;
+  uint16_t size;
+  uint32_t ats_count;
+
+  GNUNET_assert (h->client != NULL);
+  if (msg == NULL)
+    {
+#if DEBUG_TRANSPORT
+      GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+                  "Error receiving from transport service, disconnecting temporarily.\n");
+#endif
+      disconnect_and_schedule_reconnect (h);
+      return;
+    }
+  GNUNET_CLIENT_receive (h->client,
+                         &demultiplexer, h, 
+                         GNUNET_TIME_UNIT_FOREVER_REL);
+  size = ntohs (msg->size);
+  switch (ntohs (msg->type))
+    {
+    case GNUNET_MESSAGE_TYPE_HELLO:
+      if (GNUNET_OK !=
+          GNUNET_HELLO_get_id ((const struct GNUNET_HELLO_Message *) msg,
+                               &me))
+        {
+          GNUNET_break (0);
+          break;
+        }
+#if DEBUG_TRANSPORT
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                  "Receiving (my own) `%s' message, I am `%4s'.\n",
+                  "HELLO", GNUNET_i2s (&me));
+#endif
+      GNUNET_free_non_null (h->my_hello);
+      h->my_hello = NULL;
+      if (size < sizeof (struct GNUNET_MessageHeader))
+        {
+          GNUNET_break (0);
+          break;
+        }
+      h->my_hello = GNUNET_malloc (size);
+      memcpy (h->my_hello, msg, size);
+      hwl = h->hwl_head;
+      while (NULL != hwl)
+        {
+          next_hwl = hwl->next;
+          hwl->rec (hwl->rec_cls,
+                    (const struct GNUNET_MessageHeader *) h->my_hello);
+          hwl = next_hwl;
+        }
+      break;
+    case GNUNET_MESSAGE_TYPE_TRANSPORT_CONNECT:
+      if (size < sizeof (struct ConnectInfoMessage))
+        {
+          GNUNET_break (0);
+          break;
+        }
+      cim = (const struct ConnectInfoMessage *) msg;
+      ats_count = ntohl (cim->ats_count);
+      if (size != sizeof (struct ConnectInfoMessage) + ats_count * sizeof (struct GNUNET_TRANSPORT_ATS_Information))
+        {
+          GNUNET_break (0);
+          break;
+        }
+#if DEBUG_TRANSPORT
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                  "Receiving `%s' message for `%4s'.\n",
+                  "CONNECT", GNUNET_i2s (&cim->id));
+#endif
+      n = neighbour_find (h, &cim->id);
+      if (n != NULL)
+        {
+          GNUNET_break (0);
+          break;
+        }
+      n = neighbour_add (h, &cim->id);
+      if (h->nc_cb != NULL)
+        h->nc_cb (h->cls, &n->id,
+                  &cim->ats, ats_count);
+      break;
+    case GNUNET_MESSAGE_TYPE_TRANSPORT_DISCONNECT:
+      if (size != sizeof (struct DisconnectInfoMessage))
+        {
+          GNUNET_break (0);
+          break;
+        }
+      dim = (const struct DisconnectInfoMessage *) msg;
+      GNUNET_break (ntohl (dim->reserved) == 0);
+#if DEBUG_TRANSPORT_DISCONNECT
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                  "Receiving `%s' message for `%4s'.\n",
+                  "DISCONNECT",
+                  GNUNET_i2s (&dim->peer));
+#endif
+      n = neighbour_find (h, &dim->peer);
+      if (n == NULL)
+        {
+          GNUNET_break (0);
+          break;
+        }
+      neighbour_delete (h, &dim->peer.hashPubKey, n);
+      break;
+    case GNUNET_MESSAGE_TYPE_TRANSPORT_SEND_OK:
+      if (size != sizeof (struct SendOkMessage))
+        {
+          GNUNET_break (0);
+          break;
+        }
+      okm = (const struct SendOkMessage *) msg;
+#if DEBUG_TRANSPORT
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                  "Receiving `%s' message, transmission %s.\n", "SEND_OK",
+                  ntohl (okm->success) == GNUNET_OK ? "succeeded" : "failed");
+#endif
+      n = neighbour_find (h, &okm->peer);
+      if (n == NULL)
+        {
+          GNUNET_break (0);
+          break;
+        }
+      GNUNET_break (GNUNET_NO == n->is_ready);
+      n->is_ready = GNUNET_YES;
+      if ( (n->th != NULL) &&
+           (n->hn == NULL) )
+        {
+          /* we've been waiting for this (congestion, not quota, 
+             caused delayed transmission) */
+          n->hn = GNUNET_CONTAINER_heap_insert (h->ready_heap,
+                                                n, 0);
+          schedule_transmission (h);
+        }
+      break;
+    case GNUNET_MESSAGE_TYPE_TRANSPORT_RECV:
+#if DEBUG_TRANSPORT
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                  "Receiving `%s' message.\n", "RECV");
+#endif
+      if (size <
+          sizeof (struct InboundMessage) +
+          sizeof (struct GNUNET_MessageHeader))
+        {
+          GNUNET_break (0);
+          break;
+        }
+      im = (const struct InboundMessage *) msg;
+      GNUNET_break (0 == ntohl (im->reserved));
+      ats_count = ntohl(im->ats_count);
+      imm = (const struct GNUNET_MessageHeader *) &((&(im->ats))[ats_count+1]);
+
+      if (ntohs (imm->size) + sizeof (struct InboundMessage) + ats_count * sizeof (struct GNUNET_TRANSPORT_ATS_Information) != size)
+        {
+          GNUNET_break (0);
+          break;
+        }
+#if DEBUG_TRANSPORT
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                  "Received message of type %u from `%4s'.\n",
+                  ntohs (imm->type), GNUNET_i2s (&im->peer));
+#endif
+      n = neighbour_find (h, &im->peer);
+      if (n == NULL)
+        {
+          GNUNET_break (0);
+          break;
+        }
+      if (h->rec != NULL)
+        h->rec (h->cls, &im->peer, imm,
+                &im->ats, ats_count);
+      break;
+    default:
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                  _
+                  ("Received unexpected message of type %u in %s:%u\n"),
+                  ntohs (msg->type), __FILE__, __LINE__);
+      GNUNET_break (0);
+      break;
+    }
+}
+
+
+/**
+ * Transmit message(s) to service.
+ *
+ * @param cls handle to transport
+ * @param size number of bytes available in buf
+ * @param buf where to copy the message
+ * @return number of bytes copied to buf
+ */
+static size_t
+transport_notify_ready (void *cls, size_t size, void *buf)
+{
+  struct GNUNET_TRANSPORT_Handle *h = cls;
+  size_t ssize;
+  struct GNUNET_TRANSPORT_TransmitHandle *th;
+  struct Neighbour *n;
+  char *cbuf;
+  size_t ret;
+
+  GNUNET_assert (NULL != h->client);
+  h->cth = NULL;
+  if (NULL == buf)
+    {
+      /* transmission failed */
+      disconnect_and_schedule_reconnect (h);
+      return 0;
+    }
+
+  cbuf = buf;
+  ret = 0;
+  /* first send control messages */
+  while ( (NULL != (th = h->control_head)) &&
+          (th->notify_size <= size) )
+    {
+      GNUNET_CONTAINER_DLL_remove (h->control_head,
+                                   h->control_tail,
+                                   th);
+      nret = th->notify (th->notify_cls, size, &cbuf[ret]);
+#if DEBUG_TRANSPORT
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                  "Added %u bytes of control message at %u\n",
+                  nret,
+                  ret);
+#endif
+      GNUNET_free (th);
+      ret += nret;
+      size -= nret;
+    }
+
+  /* then, if possible and no control messages pending, send data messages */
+  while ( (NULL == h->control_head) &&
+          (NULL != (n = GNUNET_CONTAINER_heap_peek (h->ready_heap))) )
+    {
+      if (GNUNET_YES != n->is_ready)
+        {
+          /* peer not ready, wait for notification! */
+          GNUNET_CONTAINER_heap_remove_node (n->hn);
+          n->hn = NULL;
+          /* FIXME: hitting transport-level congestion, add
+             a timeout task for 'th' in this case! */
+          continue;
+        }
+      th = n->th;
+      if (th->notify_size + sizeof (struct OutboundMessage) > size)
+        break; /* does not fit */
+      n->th = NULL;
+      n->is_ready = GNUNET_NO;
+      GNUNET_assert (size >= sizeof (struct OutboundMessage));
+      mret = th->notify (th->notify_cls,
+                         size - sizeof (struct OutboundMessage),
+                         &cbuf[ret + sizeof (struct OutboundMessage)]);
+      GNUNET_assert (mret <= size - sizeof (struct OutboundMessage));
+      if (mret != 0)    
+        {
+          GNUNET_assert (mret + sizeof (struct OutboundMessage) < GNUNET_SERVER_MAX_MESSAGE_SIZE);
+          obm.header.type = htons (GNUNET_MESSAGE_TYPE_TRANSPORT_SEND);
+          obm.header.size = htons (mret + sizeof (struct OutboundMessage));
+          obm.priority = htonl (th->priority);
+          obm.timeout = GNUNET_TIME_relative_hton (GNUNET_TIME_absolute_get_remaining (th->timeout));
+          obm.peer = n->id;
+          memcpy (&cbuf[ret], &obm, sizeof (struct OutboundMessage));
+          ret += (mret + sizeof (struct OutboundMessage));
+          size -= (mret + sizeof (struct OutboundMessage));
+          GNUNET_BANDWIDTH_tracker_consume (&n->out_tracker, mret);
+        }
+      GNUNET_free (th);
+    }
+  /* if there are more pending messages, try to schedule those */
+  schedule_transmission (h);
+#if DEBUG_TRANSPORT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Transmitting %u bytes to transport service\n", ret);
+#endif
+  return ret;
+}
+
+
+/**
+ * Schedule the task to send one message, either from the control
+ * list or the peer message queues  to the service.
+ *
+ * @param cls transport service to schedule a transmission for
+ * @param tc scheduler context
+ */
+static void
+schedule_transmission_task (void *cls,
+                            const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  struct GNUNET_TRANSPORT_Handle *h = cls;
+  size_t size;
+  struct GNUNET_TRANSPORT_TransmitHandle *th;
+  struct Neighbour *n;
+
+  h->quota_task = GNUNET_SCHEDULER_NO_TASK;
+  GNUNET_assert (NULL != h->client);
+  /* destroy all requests that have timed out */
+  while ( (NULL != (n = GNUNET_CONTAINER_heap_peek (h->ready_heap))) &&
+          (GNUNET_TIME_absolute_get_remaining (n->th->timeout).rel_value == 0) )
+    {
+      /* notify client that the request could not be satisfied within
+         the given time constraints */
+      th = n->th;
+      n->th = NULL;
+      GNUNET_assert (n == GNUNET_CONTAINER_heap_remove_root (h->ready_heap));
+      n->hn = NULL;
+      GNUNET_assert (0 == 
+                     th->notify (th->notify_cls, 0, NULL));
+      GNUNET_free (th);      
+    }
+  if (NULL != h->cth)
+    return;
+  if (NULL != h->control_head)
+    {
+      size = h->control_head->notify_size;
+    }
+  else
+    {
+      n = GNUNET_CONTAINER_heap_peek (h->ready_heap);
+      if (NULL == n)
+        return; /* no pending messages */
+      size = n->th->notify_size + sizeof (struct OutboundMessage);
+    }  
+#if DEBUG_TRANSPORT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Calling notify_transmit_ready\n");
+#endif
+  h->cth =
+    GNUNET_CLIENT_notify_transmit_ready (h->client,
+                                         size,
+                                         GNUNET_TIME_UNIT_FOREVER_REL,
+                                         GNUNET_NO,
+                                         &transport_notify_ready,
+                                         h);
+  GNUNET_assert (NULL != h->cth);
+}
+
+
+/**
+ * Schedule the task to send one message, either from the control
+ * list or the peer message queues  to the service.
+ *
+ * @param h transport service to schedule a transmission for
+ */
+static void
+schedule_transmission (struct GNUNET_TRANSPORT_Handle *h)
+{
+  struct GNUNET_TIME_Relative delay;
+  struct Neighbour *n;
+
+  GNUNET_assert (NULL != h->client);
+  if (h->quota_task != GNUNET_SCHEDULER_NO_TASK)
+    {
+      GNUNET_SCHEDULER_cancel (h->quota_task);
+      h->quota_task = GNUNET_SCHEDULER_NO_TASK;
+    }
+  if (NULL != h->control_head)
+    delay = GNUNET_TIME_UNIT_ZERO;
+  else if (NULL != (n = GNUNET_CONTAINER_heap_peek (h->ready_heap)))
+    delay = GNUNET_TIME_absolute_get_remaining (n->th->timeout);
+  else
+    return; /* no work to be done */
+  h->quota_task = GNUNET_SCHEDULER_add_delayed (delay,
+                                                &schedule_transmission_task,
+                                                h);
+}
+
+
+/**
+ * Queue control request for transmission to the transport
+ * service.
+ *
+ * @param h handle to the transport service
+ * @param size number of bytes to be transmitted
+ * @param notify function to call to get the content
+ * @param notify_cls closure for notify
+ */
+static void
+schedule_control_transmit (struct GNUNET_TRANSPORT_Handle *h,
+                           size_t size,
+                           GNUNET_CONNECTION_TransmitReadyNotify notify,
+                           void *notify_cls)
+{
+  struct GNUNET_TRANSPORT_TransmitHandle *th;
+
+#if DEBUG_TRANSPORT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Control transmit of %u bytes requested\n",
+              size);
+#endif
+  th = GNUNET_malloc (sizeof (struct GNUNET_TRANSPORT_TransmitHandle));
+  th->notify = notify;
+  th->notify_cls = notify_cls;
+  th->notify_size = size;
+  GNUNET_CONTAINER_DLL_insert (h->control_head,
+                               h->control_tail,
+                               th);
+  schedule_transmission (h);
+}
+
+
+/**
+ * Transmit START message to service.
+ *
+ * @param cls unused
+ * @param size number of bytes available in buf
+ * @param buf where to copy the message
+ * @return number of bytes copied to buf
+ */
+static size_t
+send_start (void *cls, size_t size, void *buf)
+{
+  struct GNUNET_TRANSPORT_Handle *h = cls;
+  struct StartMessage s;
+
+  if (buf == NULL)
+    {
+      /* Can only be shutdown, just give up */
+#if DEBUG_TRANSPORT
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                  "Shutdown while trying to transmit `%s' request.\n",
+                  "START");
+#endif
+      return 0;
+    }
+#if DEBUG_TRANSPORT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Transmitting `%s' request.\n", "START");
+#endif
+  GNUNET_assert (size >= sizeof (struct StartMessage));
+  s.header.size = htons (sizeof (struct StartMessage));
+  s.header.type = htons (GNUNET_MESSAGE_TYPE_TRANSPORT_START);
+  s.do_check = htonl (h->check_self);
+  s.self = h->self;
+  memcpy (buf, &s, sizeof (struct StartMessage));
+  return sizeof (struct StartMessage);
+}
+
+
+/**
+ * Try again to connect to transport service.
+ *
+ * @param cls the handle to the transport service
+ * @param tc scheduler context
+ */
+static void
+reconnect (void *cls,
+           const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  struct GNUNET_TRANSPORT_Handle *h = cls;
+  struct ControlMessage *pos;
+
+  h->reconnect_task = GNUNET_SCHEDULER_NO_TASK;
+  if ( (tc->reason & GNUNET_SCHEDULER_REASON_SHUTDOWN) != 0)
+    {
+      /* shutdown, just give up */
+      return;
+    }
+#if DEBUG_TRANSPORT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Connecting to transport service.\n");
+#endif
+  GNUNET_assert (h->client == NULL);
+  GNUNET_assert (h->control_head == NULL);
+  GNUNET_assert (h->control_tail == NULL);
+  h->client = GNUNET_CLIENT_connect ("transport", h->cfg);
+  GNUNET_assert (h->client != NULL);
+  schedule_control_transmit (h,
+                             sizeof (struct StartMessage),
+                             &send_start, h);
+  GNUNET_CLIENT_receive (h->client,
+                         &demultiplexer, h, GNUNET_TIME_UNIT_FOREVER_REL);
+}
+
+
+/**
+ * Function that will schedule the job that will try
+ * to connect us again to the client.
+ *
+ * @param h transport service to reconnect
+ */
+static void
+disconnect_and_schedule_reconnect (struct GNUNET_TRANSPORT_Handle *h)
+{
+  GNUNET_assert (h->reconnect_task == GNUNET_SCHEDULER_NO_TASK);
+  /* Forget about all neighbours that we used to be connected to */
+  GNUNET_CONTAINER_multihashmap_iterate(h->neighbours, 
+                                        &neighbour_delete, 
+                                        NULL);
+  if (NULL != handle->cth)
+    {
+      GNUNET_CLIENT_notify_transmit_ready_cancel (handle->cth);
+      handle->cth = NULL;
+    }
+  if (NULL != handle->client)
+    {
+      GNUNET_CLIENT_disconnect (handle->client, GNUNET_YES);
+      handle->client = NULL;
+    }
+  if (h->quota_task != GNUNET_SCHEDULER_NO_TASK)
+    {
+      GNUNET_SCHEDULER_cancel (h->quota_task);
+      h->quota_task = GNUNET_SCHEDULER_NO_TASK;
+    }
+  while ( (NULL != (th = handle->control_head)))
+    {
+      GNUNET_CONTAINER_DLL_remove (handle->control_head,
+                                   handle->control_tail,
+                                   cm);
+      cm->notify (cm->notify_cls, 0, NULL);
+      GNUNET_free (cm);
+    }
+#if DEBUG_TRANSPORT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Scheduling task to reconnect to transport service in %llu ms.\n",
+              h->reconnect_delay.rel_value);
+#endif
+  h->reconnect_task
+    = GNUNET_SCHEDULER_add_delayed (h->reconnect_delay,
+                                    &reconnect, h);
+  if (h->reconnect_delay.rel_value == 0)
+    {
+      h->reconnect_delay = GNUNET_TIME_UNIT_MILLISECONDS;
+    }
+  else
+    {
+      h->reconnect_delay = GNUNET_TIME_relative_multiply (h->reconnect_delay, 2);
+      h->reconnect_delay = GNUNET_TIME_relative_min (GNUNET_TIME_UNIT_SECONDS,
+                                                     h->reconnect_delay);
+    }
+}
+
+
+/**
+ * Closure for 'send_set_quota'.
+ */
+struct SetQuotaContext
+{
+
+  /**
+   * Identity of the peer impacted by the quota change.
+   */
+  struct GNUNET_PeerIdentity target;
+
+  /**
+   * Quota to transmit.
+   */
+  struct GNUNET_BANDWIDTH_Value32NBO quota_in;
+};
+
+
+/**
+ * Send SET_QUOTA message to the service.
+ *
+ * @param cls the 'struct SetQuotaContext'
+ * @param size number of bytes available in buf
+ * @param buf where to copy the message
+ * @return number of bytes copied to buf
+ */
+static size_t
+send_set_quota (void *cls, size_t size, void *buf)
+{
+  struct SetQuotaContext *sqc = cls;
+  struct QuotaSetMessage msg;
+
+  if (buf == NULL)
+    {
+      GNUNET_free (sqc);
+      return 0;
+    }
+#if DEBUG_TRANSPORT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Transmitting `%s' request with respect to `%4s'.\n",
+              "SET_QUOTA",
+              GNUNET_i2s (&sqc->target));
+#endif
+  GNUNET_assert (size >= sizeof (struct QuotaSetMessage));
+  msg.header.size = htons (sizeof (struct QuotaSetMessage));
+  msg.header.type = htons (GNUNET_MESSAGE_TYPE_TRANSPORT_SET_QUOTA);
+  msg.quota = sqc->quota_in;
+  msg.peer = sqc->target;
+  memcpy (buf, &msg, sizeof (msg));
+  GNUNET_free (sqc);
+  return sizeof (struct QuotaSetMessage);
+}
+
+
+/**
+ * Set the share of incoming bandwidth for the given
+ * peer to the specified amount.
+ *
+ * @param handle connection to transport service
+ * @param target who's bandwidth quota is being changed
+ * @param quota_in incoming bandwidth quota in bytes per ms
+ * @param quota_out outgoing bandwidth quota in bytes per ms
+ */
+void
+GNUNET_TRANSPORT_set_quota (struct GNUNET_TRANSPORT_Handle *handle,
+                            const struct GNUNET_PeerIdentity *target,
+                            struct GNUNET_BANDWIDTH_Value32NBO quota_in,
+                            struct GNUNET_BANDWIDTH_Value32NBO quota_out)
+{
+  struct Neighbour *n;
+  struct SetQuotaContext *sqc;
+  
+  n = neighbour_find (handle, target);
+  if (NULL == n)
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                  "Quota changed to %u for peer `%s', but I have no such neighbour!\n",
+                  (unsigned int) ntohl (quota_out.value__),
+                  GNUNET_i2s (target));
+      return;
+    }
+#if DEBUG_TRANSPORT
+  if (ntohl (quota_out.value__) != n->out_tracker.available_bytes_per_s__)
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "Quota changed from %u to %u for peer `%s'\n",
+                (unsigned int) n->out_tracker.available_bytes_per_s__,
+                (unsigned int) ntohl (quota_out.value__),
+                GNUNET_i2s (target));
+  else
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "Quota remains at %u for peer `%s'\n",
+                (unsigned int) n->out_tracker.available_bytes_per_s__,
+                GNUNET_i2s (target));
+#endif
+  GNUNET_BANDWIDTH_tracker_update_quota (&n->out_tracker,
+                                         quota_out);
+  sqc = GNUNET_malloc (sizeof (struct SetQuotaContext));
+  sqc->target = *target;
+  sqc->quota_in = quota_in;
+  schedule_control_transmit (handle,
+                             sizeof (struct QuotaSetMessage),
+                             &send_set_quota, sqc);
+}
+
+
+/**
+ * Send TRY_CONNECT message to the service.
+ *
+ * @param cls the 'struct GNUNET_PeerIdentity'
+ * @param size number of bytes available in buf
+ * @param buf where to copy the message
+ * @return number of bytes copied to buf
+ */
+static size_t
+send_try_connect (void *cls, size_t size, void *buf)
+{
+  struct GNUNET_PeerIdentity *pid = cls;
+  struct TryConnectMessage msg;
+
+  if (buf == NULL)
+    {
+      GNUNET_free (pid);
+      return 0;
+    }
+#if DEBUG_TRANSPORT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Transmitting `%s' request with respect to `%4s'.\n",
+              "TRY_CONNECT",
+              GNUNET_i2s (&sqc->target));
+#endif
+  GNUNET_assert (size >= sizeof (struct TryConnectMessage));
+  msg.header.size = htons (sizeof (struct TryConnectMessage));
+  msg.header.type = htons (GNUNET_MESSAGE_TYPE_TRANSPORT_TRY_CONNECT);
+  msg.reserved = htonl (0);
+  msg.peer = *pid;
+  memcpy (buf, &msg, sizeof (msg));
+  GNUNET_free (pid);
+  return sizeof (struct TryConnectMessage);
+}
+
+
+/**
+ * Ask the transport service to establish a connection to 
+ * the given peer.
+ *
+ * @param handle connection to transport service
+ * @param target who we should try to connect to
+ */
+void
+GNUNET_TRANSPORT_try_connect (struct GNUNET_TRANSPORT_Handle *handle,
+                              const struct GNUNET_PeerIdentity *target)
+{
+  struct GNUNET_PeerIdentity *pid;
+
+  pid = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
+  *pid = *target;
+  schedule_control_transmit (handle,
+                             sizeof (struct TryConnectMessage),
+                             &send_try_connect, pid);
+}
+
+
+/**
+ * Send HELLO message to the service.
+ *
+ * @param cls the HELLO message to send
+ * @param size number of bytes available in buf
+ * @param buf where to copy the message
+ * @return number of bytes copied to buf
+ */
+static size_t
+send_hello (void *cls, size_t size, void *buf)
+{
+  struct GNUNET_MessageHeader *msg = cls;
+  uint16_t ssize;
+
+  if (buf == NULL)
+    {
+#if DEBUG_TRANSPORT_TIMEOUT
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                  "Timeout while trying to transmit `%s' request.\n",
+                  "HELLO");
+#endif
+      GNUNET_free (msg);
+      return 0;
+    }
+#if DEBUG_TRANSPORT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Transmitting `%s' request.\n", "HELLO");
+#endif
+  ssize = ntohs (msg->size);
+  GNUNET_assert (size >= ssize);
+  memcpy (buf, msg, ssize);
+  GNUNET_free (msg);
+  return ssize;
+}
+
+
+/**
+ * Offer the transport service the HELLO of another peer.  Note that
+ * the transport service may just ignore this message if the HELLO is
+ * malformed or useless due to our local configuration.
+ *
+ * @param handle connection to transport service
+ * @param hello the hello message
+ * @param cont continuation to call when HELLO has been sent
+ * @param cls closure for continuation
+ *
+ */
+void
+GNUNET_TRANSPORT_offer_hello (struct GNUNET_TRANSPORT_Handle *handle,
+                              const struct GNUNET_MessageHeader *hello,
+                              GNUNET_SCHEDULER_Task cont,
+                              void *cls)
+{
+  uint16_t size;
+  struct GNUNET_PeerIdentity peer;
+  struct GNUNET_MessageHeader *msg;
+
+  if (NULL == handle->client)
+    return;
+  GNUNET_break (ntohs (hello->type) == GNUNET_MESSAGE_TYPE_HELLO);
+  size = ntohs (hello->size);
+  GNUNET_break (size >= sizeof (struct GNUNET_MessageHeader));
+  if (GNUNET_OK != GNUNET_HELLO_get_id ((const struct GNUNET_HELLO_Message*) hello,
+                                        &peer))
+    {
+      GNUNET_break (0);
+      return;
+    }
+  msg = GNUNET_malloc(size);
+  memcpy (msg, hello, size);
+#if DEBUG_TRANSPORT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Offering `%s' message of `%4s' to transport for validation.\n",
+              "HELLO",
+              GNUNET_i2s (&peer));
+#endif
+  schedule_control_transmit (handle,
+                             size,
+                             &send_hello, msg);
+}
+
+
+/**
+ * Obtain the HELLO message for this peer.
+ *
+ * @param handle connection to transport service
+ * @param rec function to call with the HELLO, sender will be our peer
+ *            identity; message and sender will be NULL on timeout
+ *            (handshake with transport service pending/failed).
+ *             cost estimate will be 0.
+ * @param rec_cls closure for rec
+ */
+void
+GNUNET_TRANSPORT_get_hello (struct GNUNET_TRANSPORT_Handle *handle,
+                            GNUNET_TRANSPORT_HelloUpdateCallback rec,
+                            void *rec_cls)
+{
+  struct HelloWaitList *hwl;
+
+  hwl = GNUNET_malloc (sizeof (struct HelloWaitList));
+  hwl->rec = rec;
+  hwl->rec_cls = rec_cls;
+  GNUNET_CONTAINER_DLL_insert (handle->hwl_head,
+                               handle->hwl_tail,
+                               hwl);
+  if (handle->my_hello == NULL)
+    return;
+  rec (rec_cls, (const struct GNUNET_MessageHeader *) handle->my_hello);
+}
+
+
+/**
+ * Stop receiving updates about changes to our HELLO message.
+ *
+ * @param handle connection to transport service
+ * @param rec function previously registered to be called with the HELLOs
+ * @param rec_cls closure for rec
+ */
+void
+GNUNET_TRANSPORT_get_hello_cancel (struct GNUNET_TRANSPORT_Handle *handle,
+                                   GNUNET_TRANSPORT_HelloUpdateCallback rec,
+                                   void *rec_cls)
+{
+  struct HelloWaitList *pos;
+
+  pos = handle->hwl_head;
+  while (pos != NULL)
+    {
+      if ( (pos->rec == rec) &&
+           (pos->rec_cls == rec_cls) )
+        break;
+      pos = pos->next;
+    }
+  GNUNET_break (pos != NULL);
+  if (pos == NULL)
+    return;
+  GNUNET_CONTAINER_DLL_remove (handle->hwl_head,
+                               handle->hwl_tail,
+                               pos);
+  GNUNET_free (pos);
+}
+
+
+/**
+ * Connect to the transport service.  Note that the connection may
+ * complete (or fail) asynchronously.
+ *
+ * @param cfg configuration to use
+ * @param self our own identity (API should check that it matches
+ *             the identity found by transport), or NULL (no check)
+ * @param cls closure for the callbacks
+ * @param rec receive function to call
+ * @param nc function to call on connect events
+ * @param nd function to call on disconnect events
+ */
+struct GNUNET_TRANSPORT_Handle *
+GNUNET_TRANSPORT_connect (const struct GNUNET_CONFIGURATION_Handle *cfg,
+                          const struct GNUNET_PeerIdentity *self,
+                          void *cls,
+                          GNUNET_TRANSPORT_ReceiveCallback rec,
+                          GNUNET_TRANSPORT_NotifyConnect nc,
+                          GNUNET_TRANSPORT_NotifyDisconnect nd)
+{
+  struct GNUNET_TRANSPORT_Handle *ret;
+
+  ret = GNUNET_malloc (sizeof (struct GNUNET_TRANSPORT_Handle));
+  if (self != NULL)
+    {
+      ret->self = *self;
+      ret->check_self = GNUNET_YES;
+    }
+  ret->cfg = cfg;
+  ret->cls = cls;
+  ret->rec = rec;
+  ret->nc_cb = nc;
+  ret->nd_cb = nd;
+  ret->reconnect_delay = GNUNET_TIME_UNIT_ZERO;
+  ret->neighbours = GNUNET_CONTAINER_multihashmap_create(STARTING_NEIGHBOURS_SIZE);
+  ret->ready_heap = GNUNET_CONTAINER_heap_create (GNUNET_CONTAINER_HEAP_ORDER_MIN);
+  ret->reconnect_task = GNUNET_SCHEDULER_add_now (&reconnect, h);
+  return ret;
+}
+
+
+/**
+ * Disconnect from the transport service.
+ *
+ * @param handle handle to the service as returned from GNUNET_TRANSPORT_connect
+ */
+void
+GNUNET_TRANSPORT_disconnect (struct GNUNET_TRANSPORT_Handle *handle)
+{
+  struct GNUNET_TRANSPORT_TransmitHandle *cm;
+
+#if DEBUG_TRANSPORT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, 
+              "Transport disconnect called!\n");
+#endif
+  /* this disconnects all neighbours... */
+  disconnect_and_schedule_reconnect (handle);
+  /* and now we stop trying to connect again... */
+  if (handle->reconnect_task != GNUNET_SCHEDULER_NO_TASK)
+    {
+      GNUNET_SCHEDULER_cancel (handle->reconnect_task);
+      handle->reconnect_task = GNUNET_SCHEDULER_NO_TASK;
+    }
+  GNUNET_CONTAINER_multihashmap_destroy (handle->neighbours);
+  handle->neighbours = NULL;
+  if (handle->quota_task != GNUNET_SCHEDULER_NO_TASK)
+    {
+      GNUNET_SCHEDULER_cancel (handle->quota_task);
+      handle->quota_task = GNUNET_SCHEDULER_NO_TASK;
+    }
+  GNUNET_free_non_null (handle->my_hello);
+  handle->my_hello = NULL;
+  GNUNET_assert (handle->hwl_head == NULL);
+  GNUNET_assert (handle->hwl_tail == NULL);
+  GNUNET_free (handle);
+}
+
+
+/**
+ * Check if we could queue a message of the given size for
+ * transmission.  The transport service will take both its
+ * internal buffers and bandwidth limits imposed by the
+ * other peer into consideration when answering this query.
+ *
+ * @param handle connection to transport service
+ * @param target who should receive the message
+ * @param size how big is the message we want to transmit?
+ * @param priority how important is the message?
+ * @param timeout after how long should we give up (and call
+ *        notify with buf NULL and size 0)?
+ * @param notify function to call when we are ready to
+ *        send such a message
+ * @param notify_cls closure for notify
+ * @return NULL if someone else is already waiting to be notified
+ *         non-NULL if the notify callback was queued (can be used to cancel
+ *         using GNUNET_TRANSPORT_notify_transmit_ready_cancel)
+ */
+struct GNUNET_TRANSPORT_TransmitHandle *
+GNUNET_TRANSPORT_notify_transmit_ready (struct GNUNET_TRANSPORT_Handle *handle,
+                                        const struct GNUNET_PeerIdentity *target,
+                                        size_t size,
+                                        uint32_t priority,
+                                        struct GNUNET_TIME_Relative timeout,
+                                        GNUNET_CONNECTION_TransmitReadyNotify notify, 
+                                        void *notify_cls)
+{
+  struct Neighbour *n;
+  struct GNUNET_TRANSPORT_TransmitHandle *th;
+  struct GNUNET_TIME_Relative delay;
+  
+  n = neighbour_find (handle, target);
+  if (NULL == n)
+    {
+      /* use GNUNET_TRANSPORT_try_connect first, only use this function
+         once a connection has been established */
+      GNUNET_break (0);
+      return NULL;
+    }
+  if (NULL != n->th)
+    {
+      /* attempt to send two messages at the same time to the same peer */
+      GNUNET_break (0);
+      return NULL;
+    }
+  GNUNET_assert (NULL == n->hn);
+  th = GNUNET_malloc (sizeof (struct GNUNET_TRANSPORT_TransmitHandle));
+  th->neighbour = n;
+  th->notify = notify;
+  th->notify_cls = notify_cls;
+  th->timeout = GNUNET_TIME_relative_to_absolute (timeout);
+  th->notify_size = size;
+  th->priority = priority;
+  n->th = th;
+  /* calculate when our transmission should be ready */
+  delay = GNUNET_BANDWIDTH_tracker_get_delay (n->out_tracker, size);
+  if (delay.rel_value > timeout.rel_value)
+    delay.rel_value = 0; /* notify immediately (with failure) */
+  n->hn = GNUNET_CONTAINER_heap_insert (h->ready_heap,
+                                        n, 
+                                        delay.rel_value);
+  schedule_transmission (h);
+  return th;
+}
+
+
+/**
+ * Cancel the specified transmission-ready notification.
+ *
+ * @param th handle returned from GNUNET_TRANSPORT_notify_transmit_ready
+ */
+void
+GNUNET_TRANSPORT_notify_transmit_ready_cancel (struct GNUNET_TRANSPORT_TransmitHandle *th)
+{
+  struct Neighbour *n;
+
+  GNUNET_assert (NULL == th->next);
+  GNUNET_assert (NULL == th->prev);
+  n = th->neighbour;
+  GNUNET_assert (th == n->th);
+  n->th = NULL;
+  if (n->hn != NULL)
+    {
+      GNUNET_CONTAINER_heap_remove_node (n->hn);
+      n->hn = NULL;
+    }
+  GNUNET_free (th);                                        
+}
+
+
+/* end of transport_api.c */