- flow control changes and fixes

7 files changed, 293 insertions, 129 deletions

diff --git a/src/mesh/gnunet-service-mesh_channel.c b/src/mesh/gnunet-service-mesh_channel.c
index b02da1aba..519dda89d 100644
--- a/src/mesh/gnunet-service-mesh_channel.c
+++ b/src/mesh/gnunet-service-mesh_channel.c
@@ -143,6 +143,11 @@ struct MeshChannelReliability
      */
   int                               client_ready;
 
+  /**
+   * Can the client send data to us?
+   */
+  int                               client_allowed;
+
     /**
      * Task to resend/poll in case no ACK is received.
      */
@@ -465,6 +470,13 @@ send_client_ack (struct MeshChannel *ch, int fwd)
     return;
   }
 
+  if (GNUNET_YES == rel->client_allowed)
+  {
+    LOG (GNUNET_ERROR_TYPE_DEBUG, "  already allowed\n");
+    return;
+  }
+  rel->client_allowed = GNUNET_YES;
+
   GML_send_ack (fwd ? ch->root : ch->dest, fwd ? ch->lid_root : ch->lid_dest);
 }
 
@@ -997,6 +1009,25 @@ GMCH_get_buffer (struct MeshChannel *ch, int fwd)
 
 
 /**
+ * Get flow control status of end point: is client allow to send?
+ *
+ * @param ch Channel.
+ * @param fwd Is query about FWD traffic? (Request root status).
+ *
+ * @return GNUNET_YES if client is allowed to send us data.
+ */
+int
+GMCH_get_allowed (struct MeshChannel *ch, int fwd)
+{
+  struct MeshChannelReliability *rel;
+
+  rel = fwd ? ch->root_rel : ch->dest_rel;
+
+  return rel->client_allowed;
+}
+
+
+/**
  * Is the root client for this channel on this peer?
  *
  * @param ch Channel.
@@ -1152,6 +1183,19 @@ GMCH_send_data_ack (struct MeshChannel *ch, int fwd)
 
 
 /**
+ * Allow a client to send us more data, in case it was choked.
+ *
+ * @param ch Channel.
+ * @param fwd Is this about FWD traffic? (Root client).
+ */
+void
+GMCH_allow_client (struct MeshChannel *ch, int fwd)
+{
+  send_client_ack (ch, fwd);
+}
+
+
+/**
  * Log channel info.
  *
  * @param ch Channel.
@@ -1206,7 +1250,7 @@ GMCH_handle_local_ack (struct MeshChannel *ch, int fwd)
 
   rel->client_ready = GNUNET_YES;
   send_client_buffered_data (ch, c, fwd);
-  GMC_send_ack (NULL, ch, fwd);
+  GMT_send_acks (ch->t, fwd);
 }
 
 
@@ -1247,6 +1291,8 @@ GMCH_handle_local_data (struct MeshChannel *ch,
 
   rel = fwd ? ch->root_rel : ch->dest_rel;
 
+  rel->client_allowed = GNUNET_NO;
+
   /* Ok, everything is correct, send the message. */
   payload = (struct GNUNET_MESH_Data *) cbuf;
   payload->mid = htonl (rel->mid_send);
diff --git a/src/mesh/gnunet-service-mesh_channel.h b/src/mesh/gnunet-service-mesh_channel.h
index 82d85e5be..13bef4799 100644
--- a/src/mesh/gnunet-service-mesh_channel.h
+++ b/src/mesh/gnunet-service-mesh_channel.h
@@ -84,6 +84,19 @@ GMCH_get_tunnel (const struct MeshChannel *ch);
 unsigned int
 GMCH_get_buffer (struct MeshChannel *ch, int fwd);
 
+
+/**
+ * Get flow control status of end point: is client allow to send?
+ *
+ * @param ch Channel.
+ * @param fwd Is query about FWD traffic? (Request root status).
+ *
+ * @return GNUNET_YES if client is allowed to send us data.
+ */
+int
+GMCH_get_allowed (struct MeshChannel *ch, int fwd);
+
+
 /**
  * Is the root client for this channel on this peer?
  *
@@ -149,6 +162,15 @@ void
 GMCH_send_destroy (struct MeshChannel *ch);
 
 /**
+ * Allow a client to send us more data, in case it was choked.
+ *
+ * @param ch Channel.
+ * @param fwd Is this about FWD traffic? (Root client).
+ */
+void
+GMCH_allow_client (struct MeshChannel *ch, int fwd);
+
+/**
  * Log channel info.
  *
  * @param ch Channel.
diff --git a/src/mesh/gnunet-service-mesh_connection.c b/src/mesh/gnunet-service-mesh_connection.c
index 7ce26082a..64174f3f5 100644
--- a/src/mesh/gnunet-service-mesh_connection.c
+++ b/src/mesh/gnunet-service-mesh_connection.c
@@ -269,7 +269,7 @@ connection_debug (struct MeshConnection *c)
     return;
   }
   LOG (GNUNET_ERROR_TYPE_DEBUG, "Connection %s:%X\n",
-              peer2s (c->t->peer), GNUNET_h2s (&c->id));
+              peer2s (c->t->peer), GMC_2s (c));
   LOG (GNUNET_ERROR_TYPE_DEBUG, "  state: %u, pending msgs: %u\n",
               c->state, c->pending_messages);
   LOG (GNUNET_ERROR_TYPE_DEBUG, "  FWD FC\n");
@@ -343,15 +343,86 @@ connection_change_state (struct MeshConnection* c,
 {
   LOG (GNUNET_ERROR_TYPE_DEBUG,
               "Connection %s state was %s\n",
-              GNUNET_h2s (&c->id), GMC_state2s (c->state));
+              GMC_2s (c), GMC_state2s (c->state));
   LOG (GNUNET_ERROR_TYPE_DEBUG,
               "Connection %s state is now %s\n",
-              GNUNET_h2s (&c->id), GMC_state2s (state));
+              GMC_2s (c), GMC_state2s (state));
   c->state = state;
 }
 
 
 /**
+ * Send an ACK on the connection, informing the predecessor about
+ * the available buffer space. Should not be called in case the peer
+ * is origin (no predecessor).
+ *
+ * Note that for fwd ack, the FWD mean forward *traffic* (root->dest),
+ * the ACK itself goes "back" (dest->root).
+ *
+ * @param c Connection on which to send the ACK.
+ * @param buffer How much space free to advertise?
+ * @param fwd Is this FWD ACK? (Going dest->owner)
+ */
+static void
+send_ack (struct MeshConnection *c, unsigned int buffer, int fwd)
+{
+  struct MeshFlowControl *next_fc;
+  struct MeshFlowControl *prev_fc;
+  struct GNUNET_MESH_ACK msg;
+  uint32_t ack;
+  int delta;
+
+  /* If origin, there is no connection to send ACKs. Wrong function! */
+  if (GMC_is_origin (c, fwd))
+  {
+    GNUNET_break (0);
+    return;
+  }
+
+  next_fc = fwd ? &c->fwd_fc : &c->bck_fc;
+  prev_fc = fwd ? &c->bck_fc : &c->fwd_fc;
+
+  LOG (GNUNET_ERROR_TYPE_DEBUG,
+              "connection send %s ack on %s\n",
+              fwd ? "FWD" : "BCK", GMC_2s (c));
+
+  /* Check if we need to transmit the ACK */
+  delta = prev_fc->last_ack_sent - prev_fc->last_pid_recv;
+  if (3 < delta && buffer < delta)
+  {
+    LOG (GNUNET_ERROR_TYPE_DEBUG, "Not sending ACK, buffer > 3\n");
+    LOG (GNUNET_ERROR_TYPE_DEBUG,
+         "  last pid recv: %u, last ack sent: %u\n",
+         prev_fc->last_pid_recv, prev_fc->last_ack_sent);
+    return;
+  }
+
+  /* Ok, ACK might be necessary, what PID to ACK? */
+  ack = prev_fc->last_pid_recv + buffer;
+  LOG (GNUNET_ERROR_TYPE_DEBUG, " ACK %u\n", ack);
+  LOG (GNUNET_ERROR_TYPE_DEBUG,
+       " last pid %u, last ack %u, qmax %u, q %u\n",
+       prev_fc->last_pid_recv, prev_fc->last_ack_sent,
+       next_fc->queue_max, next_fc->queue_n);
+  if (ack == prev_fc->last_ack_sent)
+  {
+    LOG (GNUNET_ERROR_TYPE_DEBUG, "Not sending FWD ACK, not needed\n");
+    return;
+  }
+
+  prev_fc->last_ack_sent = ack;
+
+  /* Build ACK message and send on connection */
+  msg.header.size = htons (sizeof (msg));
+  msg.header.type = htons (GNUNET_MESSAGE_TYPE_MESH_ACK);
+  msg.ack = htonl (ack);
+  msg.cid = c->id;
+
+  GMC_send_prebuilt_message (&msg.header, c, NULL, !fwd);
+}
+
+
+/**
  * Callback called when a queued message is sent.
  *
  * Calculates the average time and connection packet tracking.
@@ -374,8 +445,8 @@ message_sent (void *cls,
   double usecsperbyte;
 
   fc = fwd ? &c->fwd_fc : &c->bck_fc;
+  LOG (GNUNET_ERROR_TYPE_DEBUG, "!  sent %s\n", GNUNET_MESH_DEBUG_M2S (type));
   LOG (GNUNET_ERROR_TYPE_DEBUG, "!  Q_N- %p %u\n", fc, fc->queue_n);
-  fc->queue_n--;
   c->pending_messages--;
   if (GNUNET_YES == c->destroy && 0 == c->pending_messages)
   {
@@ -387,17 +458,20 @@ message_sent (void *cls,
   {
     case GNUNET_MESSAGE_TYPE_MESH_ENCRYPTED:
       fc->last_pid_sent++;
-      LOG (GNUNET_ERROR_TYPE_DEBUG, "!   accounting pid %u\n", fc->last_pid_sent);
-//       send_ack (c, ch, fwd);
+      fc->queue_n--;
+      LOG (GNUNET_ERROR_TYPE_DEBUG,
+           "!   accounting pid %u\n",
+           fc->last_pid_sent);
+      GMC_send_ack (c, fwd);
       break;
     default:
       break;
   }
+  LOG (GNUNET_ERROR_TYPE_DEBUG, "!  message sent!\n");
 
   if (NULL == c->perf)
     return; /* Only endpoints are interested in timing. */
 
-  LOG (GNUNET_ERROR_TYPE_DEBUG, "!  message sent!\n");
   p = c->perf;
   usecsperbyte = ((double) wait.rel_value_us) / size;
   if (p->size == AVG_MSGS)
@@ -516,69 +590,6 @@ is_fwd (const struct MeshConnection *c,
 }
 
 
-
-/**
- * Send an ACK informing the predecessor about the available buffer space.
- *
- * Note that for fwd ack, the FWD mean forward *traffic* (root->dest),
- * the ACK itself goes "back" (dest->root).
- *
- * @param c Connection on which to send the ACK.
- * @param buffer How much space free to advertise?
- * @param fwd Is this FWD ACK? (Going dest->owner)
- */
-static void
-send_ack (struct MeshConnection *c, unsigned int buffer, int fwd)
-{
-  struct MeshFlowControl *next_fc;
-  struct MeshFlowControl *prev_fc;
-  struct GNUNET_MESH_ACK msg;
-  uint32_t ack;
-  int delta;
-
-  next_fc = fwd ? &c->fwd_fc : &c->bck_fc;
-  prev_fc = fwd ? &c->bck_fc : &c->fwd_fc;
-
-  LOG (GNUNET_ERROR_TYPE_DEBUG,
-              "connection send %s ack on %s\n",
-              fwd ? "FWD" : "BCK", GNUNET_h2s (&c->id));
-
-  /* Check if we need to transmit the ACK */
-  delta = prev_fc->last_ack_sent - prev_fc->last_pid_recv;
-  if (3 < delta && buffer < delta)
-  {
-    LOG (GNUNET_ERROR_TYPE_DEBUG, "Not sending ACK, buffer > 3\n");
-    LOG (GNUNET_ERROR_TYPE_DEBUG,
-         "  last pid recv: %u, last ack sent: %u\n",
-         prev_fc->last_pid_recv, prev_fc->last_ack_sent);
-    return;
-  }
-
-  /* Ok, ACK might be necessary, what PID to ACK? */
-  ack = prev_fc->last_pid_recv + buffer;
-  LOG (GNUNET_ERROR_TYPE_DEBUG, " ACK %u\n", ack);
-  LOG (GNUNET_ERROR_TYPE_DEBUG,
-       " last pid %u, last ack %u, qmax %u, q %u\n",
-       prev_fc->last_pid_recv, prev_fc->last_ack_sent,
-       next_fc->queue_max, next_fc->queue_n);
-  if (ack == prev_fc->last_ack_sent)
-  {
-    LOG (GNUNET_ERROR_TYPE_DEBUG, "Not sending FWD ACK, not needed\n");
-    return;
-  }
-
-  prev_fc->last_ack_sent = ack;
-
-  /* Build ACK message and send on connection */
-  msg.header.size = htons (sizeof (msg));
-  msg.header.type = htons (GNUNET_MESSAGE_TYPE_MESH_ACK);
-  msg.ack = htonl (ack);
-  msg.cid = c->id;
-
-  GMC_send_prebuilt_message (&msg.header, c, NULL, !fwd);
-}
-
-
 /**
  * Sends a CONNECTION ACK message in reponse to a received CONNECTION_CREATE
  * or a first CONNECTION_ACK directed to us.
@@ -590,7 +601,6 @@ send_ack (struct MeshConnection *c, unsigned int buffer, int fwd)
 static void
 send_connection_ack (struct MeshConnection *connection, int fwd)
 {
-  struct MeshFlowControl *fc;
   struct MeshTunnel3 *t;
 
   t = connection->t;
@@ -604,8 +614,6 @@ send_connection_ack (struct MeshConnection *connection, int fwd)
     GMT_change_state (t, MESH_TUNNEL3_WAITING);
   if (MESH_CONNECTION_READY != connection->state)
     connection_change_state (connection, MESH_CONNECTION_SENT);
-  fc = fwd ? &connection->fwd_fc : &connection->bck_fc;
-  fc->queue_n++;
 }
 
 
@@ -653,8 +661,8 @@ connection_keepalive (struct MeshConnection *c, int fwd)
                GNUNET_MESSAGE_TYPE_MESH_BCK_KEEPALIVE;
 
   LOG (GNUNET_ERROR_TYPE_DEBUG,
-       "sending %s keepalive for connection %s[%d]\n",
-       fwd ? "FWD" : "BCK", GMT_2s (c->t), c->id);
+       "sending %s keepalive for connection %s]\n",
+       fwd ? "FWD" : "BCK", GMC_2s (c));
 
   msg = (struct GNUNET_MESH_ConnectionKeepAlive *) cbuf;
   msg->header.size = htons (size);
@@ -763,7 +771,7 @@ connection_unlock_queue (struct MeshConnection *c, int fwd)
 
   LOG (GNUNET_ERROR_TYPE_DEBUG,
               "connection_unlock_queue %s on %s\n",
-              fwd ? "FWD" : "BCK", GNUNET_h2s (&c->id));
+              fwd ? "FWD" : "BCK", GMC_2s (c));
 
   if (GMC_is_terminal (c, fwd))
   {
@@ -829,8 +837,7 @@ connection_poll (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
 
   c = fc->c;
   LOG (GNUNET_ERROR_TYPE_DEBUG, " *** Polling!\n");
-  LOG (GNUNET_ERROR_TYPE_DEBUG, " *** connection [%X]\n",
-              GNUNET_h2s (&c->id));
+  LOG (GNUNET_ERROR_TYPE_DEBUG, " *** connection [%s]\n", GMC_2s (c));
   LOG (GNUNET_ERROR_TYPE_DEBUG, " ***   %s\n",
               fc == &c->fwd_fc ? "FWD" : "BCK");
 
@@ -1440,7 +1447,7 @@ handle_mesh_encrypted (const struct GNUNET_PeerIdentity *peer,
     }
     fc->last_pid_recv = pid;
     GMT_handle_encrypted (c->t, msg, fwd);
-    GMC_send_ack (c, NULL, fwd);
+    GMC_send_ack (c, fwd);
     return GNUNET_OK;
   }
 
@@ -1452,7 +1459,7 @@ handle_mesh_encrypted (const struct GNUNET_PeerIdentity *peer,
   {
     GNUNET_STATISTICS_update (stats, "# TTL drops", 1, GNUNET_NO);
     LOG (GNUNET_ERROR_TYPE_WARNING, " TTL is 0, DROPPING!\n");
-    GMC_send_ack (c, NULL, fwd);
+    GMC_send_ack (c, fwd);
     return GNUNET_OK;
   }
   GNUNET_STATISTICS_update (stats, "# messages forwarded", 1, GNUNET_NO);
@@ -1623,7 +1630,7 @@ GMC_handle_poll (void *cls, const struct GNUNET_PeerIdentity *peer,
               pid, fc->last_pid_recv);
   fc->last_pid_recv = pid;
   fwd = fc == &c->fwd_fc;
-  GMC_send_ack (c, NULL, fwd);
+  GMC_send_ack (c, fwd);
 
   return GNUNET_OK;
 }
@@ -1690,25 +1697,28 @@ GMC_handle_keepalive (void *cls, const struct GNUNET_PeerIdentity *peer,
  * the direction and the position of the peer.
  *
  * @param c Which connection to send the hop-by-hop ACK.
- * @param ch Channel, if any.
  * @param fwd Is this a fwd ACK? (will go dest->root)
  */
 void
-GMC_send_ack (struct MeshConnection *c, struct MeshChannel *ch, int fwd)
+GMC_send_ack (struct MeshConnection *c, int fwd)
 {
   unsigned int buffer;
 
   LOG (GNUNET_ERROR_TYPE_DEBUG,
-              "send ack %s on %p %p\n",
-              fwd ? "FWD" : "BCK", c, ch);
+       "GMC send %s ACK on %s\n",
+       fwd ? "FWD" : "BCK", GMC_2s (c));
 
-  /* Get available bufffer space */
-  if (NULL == c || GMC_is_terminal (c, fwd))
+  if (NULL == c)
+  {
+    GNUNET_break (0);
+    return;
+  }
+
+  /* Get available buffer space */
+  if (GMC_is_terminal (c, fwd))
   {
-    struct MeshTunnel3 *t;
-    LOG (GNUNET_ERROR_TYPE_DEBUG, "  getting from all connections\n");
-    t = (NULL == c) ? GMCH_get_tunnel (ch) : GMC_get_tunnel (c);
-    buffer = GMT_get_buffer (t, fwd);
+    LOG (GNUNET_ERROR_TYPE_DEBUG, "  getting from all channels\n");
+    buffer = GMT_get_buffer (c->t, fwd);
   }
   else
   {
@@ -1718,23 +1728,16 @@ GMC_send_ack (struct MeshConnection *c, struct MeshChannel *ch, int fwd)
   LOG (GNUNET_ERROR_TYPE_DEBUG, "  buffer available: %u\n", buffer);
 
   /* Send available buffer space */
-  if ( (NULL != ch && GMCH_is_origin (ch, fwd)) ||
-       (NULL != c && GMC_is_origin (c, fwd)) )
+  if (GMC_is_origin (c, fwd))
   {
-    LOG (GNUNET_ERROR_TYPE_DEBUG, "  sending on channel...\n");
+    GNUNET_assert (NULL != c->t);
+    LOG (GNUNET_ERROR_TYPE_DEBUG, "  sending on channels...\n");
     if (0 < buffer)
     {
-      GNUNET_assert (NULL != ch);
       LOG (GNUNET_ERROR_TYPE_DEBUG, "  really sending!\n");
-      GMCH_send_data_ack (ch, fwd);
+      GMT_unchoke_channels (c->t, fwd);
     }
   }
-  else if (NULL == c)
-  {
-    LOG (GNUNET_ERROR_TYPE_DEBUG, "  sending on all connections\n");
-    GNUNET_assert (NULL != ch);
-    GMT_send_acks (GMCH_get_tunnel (ch), buffer, fwd);
-  }
   else
   {
     LOG (GNUNET_ERROR_TYPE_DEBUG, "  sending on connection\n");
@@ -1838,8 +1841,7 @@ GMC_destroy (struct MeshConnection *c)
   if (NULL == c)
     return;
 
-  LOG (GNUNET_ERROR_TYPE_DEBUG, "destroying connection %s\n",
-       GNUNET_h2s (&c->id));
+  LOG (GNUNET_ERROR_TYPE_DEBUG, "destroying connection %s\n", GMC_2s (c));
 
   /* Cancel all traffic */
   connection_cancel_queues (c, GNUNET_YES);
@@ -2106,8 +2108,9 @@ GMC_send_prebuilt_message (const struct GNUNET_MessageHeader *message,
   memcpy (data, message, size);
   type = ntohs (message->type);
   LOG (GNUNET_ERROR_TYPE_DEBUG, "Send %s (%u) on connection %s\n",
-              GNUNET_MESH_DEBUG_M2S (type), size, GNUNET_h2s (&c->id));
+              GNUNET_MESH_DEBUG_M2S (type), size, GMC_2s (c));
 
+  fc = fwd ? &c->fwd_fc : &c->bck_fc;
   droppable = GNUNET_YES;
   switch (type)
   {
@@ -2129,7 +2132,15 @@ GMC_send_prebuilt_message (const struct GNUNET_MessageHeader *message,
       emsg->cid = c->id;
       emsg->ttl = htonl (ttl - 1);
       emsg->pid = htonl (fwd ? c->fwd_fc.next_pid++ : c->bck_fc.next_pid++);
-      LOG (GNUNET_ERROR_TYPE_DEBUG, " pid %u\n", ntohl (emsg->pid));
+      LOG (GNUNET_ERROR_TYPE_DEBUG, "  Q_N+ %p %u\n", fc, fc->queue_n);
+      fc->queue_n++;
+      LOG (GNUNET_ERROR_TYPE_DEBUG, "pid %u\n", ntohl (emsg->pid));
+      LOG (GNUNET_ERROR_TYPE_DEBUG, "last pid %u\n", fc->last_pid_sent);
+      LOG (GNUNET_ERROR_TYPE_DEBUG, "     ack %u\n", fc->last_ack_recv);
+      if (GMC_is_pid_bigger (fc->last_pid_sent + 1, fc->last_ack_recv))
+      {
+        GMC_start_poll (c, fwd);
+      }
       break;
 
     case GNUNET_MESSAGE_TYPE_MESH_ACK:
@@ -2167,7 +2178,6 @@ GMC_send_prebuilt_message (const struct GNUNET_MessageHeader *message,
       GNUNET_break (0);
   }
 
-  fc = fwd ? &c->fwd_fc : &c->bck_fc;
   if (fc->queue_n >= fc->queue_max && droppable)
   {
     GNUNET_STATISTICS_update (stats, "# messages dropped (buffer full)",
@@ -2179,14 +2189,6 @@ GMC_send_prebuilt_message (const struct GNUNET_MessageHeader *message,
     return; /* Drop this message */
   }
 
-  LOG (GNUNET_ERROR_TYPE_DEBUG, "last pid %u\n", fc->last_pid_sent);
-  LOG (GNUNET_ERROR_TYPE_DEBUG, "     ack %u\n", fc->last_ack_recv);
-  LOG (GNUNET_ERROR_TYPE_DEBUG, "  Q_N+ %p %u\n", fc, fc->queue_n);
-  if (GMC_is_pid_bigger (fc->last_pid_sent + 1, fc->last_ack_recv))
-  {
-    GMC_start_poll (c, fwd);
-  }
-  fc->queue_n++;
   c->pending_messages++;
 
   GMP_queue_add (get_hop (c, fwd), data, type, size, c, ch, fwd,
@@ -2218,7 +2220,6 @@ GMC_send_create (struct MeshConnection *connection)
     GMT_change_state (connection->t, MESH_TUNNEL3_WAITING);
   if (MESH_CONNECTION_NEW == connection->state)
     connection_change_state (connection, MESH_CONNECTION_SENT);
-  connection->fwd_fc.queue_n++;
 }
 
 
@@ -2244,7 +2245,7 @@ GMC_send_destroy (struct MeshConnection *c)
   msg.cid = c->id;
   LOG (GNUNET_ERROR_TYPE_DEBUG,
               "  sending connection destroy for connection %s\n",
-              GNUNET_h2s (&c->id));
+              GMC_2s (c));
 
   if (GNUNET_NO == GMC_is_terminal (c, GNUNET_YES))
     GMC_send_prebuilt_message (&msg.header, c, NULL, GNUNET_YES);
@@ -2299,4 +2300,22 @@ GMC_stop_poll (struct MeshConnection *c, int fwd)
     GNUNET_SCHEDULER_cancel (fc->poll_task);
     fc->poll_task = GNUNET_SCHEDULER_NO_TASK;
   }
+}
+
+/**
+ * Get a (static) string for a connection.
+ *
+ * @param c Connection.
+ */
+const char *
+GMC_2s (struct MeshConnection *c)
+{
+  if (NULL != c->t)
+  {
+    static char buf[128];
+
+    sprintf (buf, "%s (->%s)", GNUNET_h2s (&c->id), GMT_2s (c->t));
+    return buf;
+  }
+  return GNUNET_h2s (&c->id);
 }
\ No newline at end of file
diff --git a/src/mesh/gnunet-service-mesh_connection.h b/src/mesh/gnunet-service-mesh_connection.h
index 3fecf3b63..816d93f45 100644
--- a/src/mesh/gnunet-service-mesh_connection.h
+++ b/src/mesh/gnunet-service-mesh_connection.h
@@ -197,11 +197,10 @@ GMC_handle_keepalive (void *cls, const struct GNUNET_PeerIdentity *peer,
  * the direction and the position of the peer.
  *
  * @param c Which connection to send the hop-by-hop ACK.
- * @param ch Channel, if any.
  * @param fwd Is this a fwd ACK? (will go dest->root)
  */
 void
-GMC_send_ack (struct MeshConnection *c, struct MeshChannel *ch, int fwd);
+GMC_send_ack (struct MeshConnection *c, int fwd);
 
 /**
  * Initialize the connections subsystem
@@ -451,6 +450,14 @@ GMC_start_poll (struct MeshConnection *c, int fwd);
 void
 GMC_stop_poll (struct MeshConnection *c, int fwd);
 
+/**
+ * Get a (static) string for a connection.
+ *
+ * @param c Connection.
+ */
+const char *
+GMC_2s (struct MeshConnection *c);
+
 #if 0                           /* keep Emacsens' auto-indent happy */
 {
 #endif
diff --git a/src/mesh/gnunet-service-mesh_local.c b/src/mesh/gnunet-service-mesh_local.c
index 67d4690e5..9b868124a 100644
--- a/src/mesh/gnunet-service-mesh_local.c
+++ b/src/mesh/gnunet-service-mesh_local.c
@@ -555,8 +555,8 @@ handle_ack (void *cls, struct GNUNET_SERVER_Client *client,
     return;
   }
 
-  /* If client is root, the ACK is going FWD, therefore this is "BCK". */
-  /* If client is dest, the ACK is going BCK, therefore this is "FWD" */
+  /* If client is root, the ACK is going FWD, therefore this is "BCK ACK". */
+  /* If client is dest, the ACK is going BCK, therefore this is "FWD ACK" */
   fwd = chid >= GNUNET_MESH_LOCAL_CHANNEL_ID_SERV;
 
   GMCH_handle_local_ack (ch, fwd);
diff --git a/src/mesh/gnunet-service-mesh_tunnel.c b/src/mesh/gnunet-service-mesh_tunnel.c
index 89c9a9db1..5b0573d0a 100644
--- a/src/mesh/gnunet-service-mesh_tunnel.c
+++ b/src/mesh/gnunet-service-mesh_tunnel.c
@@ -984,7 +984,7 @@ GMT_count_channels (struct MeshTunnel3 *t)
 
   for (count = 0, iter = t->channel_head;
        NULL != iter;
-  iter = iter->next, count++);
+       iter = iter->next, count++) /* skip */;
 
   return count;
 }
@@ -1008,10 +1008,13 @@ GMT_get_state (struct MeshTunnel3 *t)
 /**
  * Get the total buffer space for a tunnel.
  *
+ * If terminal, use the biggest channel buffer (or 64) if no channel exists.
+ * If not terminal, use the sum of all connection buffers.
+ *
  * @param t Tunnel.
  * @param fwd Is this for FWD traffic?
  *
- * @return Buffer space offered by all connections in the tunnel.
+ * @return Buffer space offered by all entities (c/ch) in the tunnel.
  */
 unsigned int
 GMT_get_buffer (struct MeshTunnel3 *t, int fwd)
@@ -1030,7 +1033,7 @@ GMT_get_buffer (struct MeshTunnel3 *t, int fwd)
 
     if (NULL == t->channel_head)
     {
-      /* Probably getting buffer for a channel create. */
+      /* Probably getting buffer for a channel create/handshake. */
       return 64;
     }
 
@@ -1099,24 +1102,78 @@ GMT_get_next_chid (struct MeshTunnel3 *t)
 
 
 /**
+ * Send ACK on one or more channels due to buffer in connections..
+ *
+ * @param t Channel which has some free buffer space.
+ * @param fwd Is this for FWD traffic? (ACK goes to root)
+ */
+void
+GMT_unchoke_channels (struct MeshTunnel3 *t, int fwd)
+{
+  struct MeshTChannel *iter;
+  unsigned int buffer;
+  unsigned int channels = GMT_count_channels (t);
+  unsigned int choked_n;
+  struct MeshChannel *choked[channels];
+
+  LOG (GNUNET_ERROR_TYPE_DEBUG, "GMT_unchoke_channels on %s\n", GMT_2s (t));
+
+  if (NULL == t)
+  {
+    GNUNET_break (0);
+    return;
+  }
+
+  /* Get buffer space */
+  buffer = GMT_get_buffer (t, fwd);
+  if (0 == buffer)
+  {
+    return;
+  }
+
+  /* Count and remember choked channels */
+  choked_n = 0;
+  for (iter = t->channel_head; NULL != iter; iter = iter->next)
+  {
+    if (GNUNET_NO == GMCH_get_allowed (iter->ch, fwd))
+    {
+      choked[choked_n++] = iter->ch;
+    }
+  }
+
+  /* Unchoke random channels */
+  while (0 < buffer && 0 < choked_n)
+  {
+    unsigned int r = GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_WEAK,
+                                               choked_n);
+    GMCH_allow_client (choked[r], fwd);
+    choked_n--;
+    buffer--;
+    choked[r] = choked[choked_n];
+  }
+}
+
+
+/**
  * Send ACK on one or more connections due to buffer space to the client.
  *
  * Iterates all connections of the tunnel and sends ACKs appropriately.
  *
- * @param ch Channel which has some free buffer space.
+ * @param t Tunnel.
  * @param fwd Is this in for FWD traffic? (ACK goes dest->root)
  */
 void
-GMT_send_acks (struct MeshTunnel3 *t, unsigned int buffer, int fwd)
+GMT_send_acks (struct MeshTunnel3 *t, int fwd)
 {
   struct MeshTConnection *iter;
   uint32_t allowed;
   uint32_t to_allow;
   uint32_t allow_per_connection;
   unsigned int cs;
+  unsigned int buffer;
 
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-              "Tunnel send acks on %s:%X\n",
+              "Tunnel send %s ACKs on %s\n",
               fwd ? "FWD" : "BCK", GMT_2s (t));
 
   if (NULL == t)
@@ -1131,6 +1188,8 @@ GMT_send_acks (struct MeshTunnel3 *t, unsigned int buffer, int fwd)
     return;
   }
 
+  buffer = GMT_get_buffer (t, fwd);
+
   /* Count connections, how many messages are already allowed */
   cs = GMT_count_connections (t);
   for (allowed = 0, iter = t->connection_head; NULL != iter; iter = iter->next)
diff --git a/src/mesh/gnunet-service-mesh_tunnel.h b/src/mesh/gnunet-service-mesh_tunnel.h
index e15d07988..9e32c5d92 100644
--- a/src/mesh/gnunet-service-mesh_tunnel.h
+++ b/src/mesh/gnunet-service-mesh_tunnel.h
@@ -280,6 +280,8 @@ GMT_get_state (struct MeshTunnel3 *t);
 
 /**
  * Get the total buffer space for a tunnel.
+ * 
+ * FIXME get a ch parameter in case of loopback tunnels
  *
  * @param t Tunnel.
  * @param fwd Is this for FWD traffic?
@@ -310,6 +312,15 @@ MESH_ChannelNumber
 GMT_get_next_chid (struct MeshTunnel3 *t);
 
 /**
+ * Send ACK on one or more channels due to buffer in connections..
+ *
+ * @param t Channel which has some free buffer space.
+ * @param fwd Is this for FWD traffic? (ACK goes to root)
+ */
+void
+GMT_unchoke_channels (struct MeshTunnel3 *t, int fwd);
+
+/**
  * Send ACK on one or more connections due to buffer space to the client.
  *
  * Iterates all connections of the tunnel and sends ACKs appropriately.
@@ -318,7 +329,7 @@ GMT_get_next_chid (struct MeshTunnel3 *t);
  * @param fwd Is this in for FWD traffic? (ACK goes dest->root)
  */
 void
-GMT_send_acks (struct MeshTunnel3 *t, unsigned int buffer, int fwd);
+GMT_send_acks (struct MeshTunnel3 *t, int fwd);
 
 /**
  * Sends an already built message on a tunnel, encrypting it and