Improvements in Bluetooth connections allocation.

net/bluetooth/Kconfig

@@ -22,9 +22,46 @@ config NET_BLUETOOTH
 
 if NET_BLUETOOTH
 
-config NET_BLUETOOTH_NCONNS
+config NET_BLUETOOTH_PREALLOC_CONNS
-	int "Max Bluetooth sockets"
+	int "Preallocated Bluetooth sockets"
 	default 4
+	---help---
+		Number of Bluetooth connections (all tasks).
+		
+		This number of connections will be pre-allocated during system boot.
+		If dynamic connections allocation is enabled, more connections may
+		be allocated at a later time, as the system needs them. Else this
+		will be the maximum number of connections available to the system
+		at all times.
+
+		Set to 0 to disable (and rely only on dynamic allocations).
+
+config NET_BLUETOOTH_ALLOC_CONNS
+	int "Dynamic Bluetooth connections allocation"
+	default 0
+	---help---
+		Dynamic memory allocations for Bluetooth.
+
+		When set to 0 all dynamic allocations are disabled.
+
+		When set to 1 a new connection will be allocated every time,
+		and it will be free'd when no longer needed.
+
+		Setting this to 2 or more will allocate the connections in
+		batches (with batch size equal to this config). When a
+		connection is no longer needed, it will be returned to the
+		free connections pool, and it will never be deallocated!
+
+config NET_BLUETOOTH_MAX_CONNS
+	int "Maximum number of Bluetooth connections"
+	default 0
+	depends on NET_BLUETOOTH_ALLOC_CONNS > 0
+	---help---
+		If dynamic connections allocation is selected (NET_BLUETOOTH_ALLOC_CONNS > 0)
+		this will limit the number of connections that can be allocated.
+		
+		This is useful in case the system is under very heavy load (or
+		under attack), ensuring that the heap will not be exhausted.
 
 config NET_BLUETOOTH_NCONTAINERS
 	int "Number of pre-allocated frame containers"

net/bluetooth/bluetooth_conn.c

@@ -52,9 +52,9 @@
  * network lock.
  */
 
-#ifndef CONFIG_NET_ALLOC_CONNS
+#if CONFIG_NET_BLUETOOTH_PREALLOC_CONNS > 0
 static struct bluetooth_conn_s
-  g_bluetooth_connections[CONFIG_NET_BLUETOOTH_NCONNS];
+  g_bluetooth_connections[CONFIG_NET_BLUETOOTH_PREALLOC_CONNS];
 #endif
 
 /* A list of all free packet socket connections */
@@ -88,10 +88,10 @@ static const bt_addr_t g_any_addr =
 
 void bluetooth_conn_initialize(void)
 {
-#ifndef CONFIG_NET_ALLOC_CONNS
+#if CONFIG_NET_BLUETOOTH_PREALLOC_CONNS > 0
   int i;
 
-  for (i = 0; i < CONFIG_NET_BLUETOOTH_NCONNS; i++)
+  for (i = 0; i < CONFIG_NET_BLUETOOTH_PREALLOC_CONNS; i++)
     {
       /* Link each pre-allocated connection structure into the free list. */
 
@@ -113,20 +113,29 @@ void bluetooth_conn_initialize(void)
 FAR struct bluetooth_conn_s *bluetooth_conn_alloc(void)
 {
   FAR struct bluetooth_conn_s *conn;
-#ifdef CONFIG_NET_ALLOC_CONNS
+#if CONFIG_NET_BLUETOOTH_ALLOC_CONNS > 0
   int i;
 #endif
 
   /* The free list is protected by the network lock */
 
   net_lock();
-#ifdef CONFIG_NET_ALLOC_CONNS
+#if CONFIG_NET_BLUETOOTH_ALLOC_CONNS > 0
   if (dq_peek(&g_active_bluetooth_connections) == NULL)
     {
-      conn = kmm_zalloc(sizeof(*conn) * CONFIG_NET_BLUETOOTH_NCONNS);
+#if CONFIG_NET_BLUETOOTH_MAX_CONNS > 0
+      if (dq_count(&g_active_bluetooth_connections) +
+          CONFIG_NET_BLUETOOTH_ALLOC_CONNS >= CONFIG_NET_BLUETOOTH_MAX_CONNS)
+        {
+          net_unlock();
+          return NULL;
+        }
+#endif
+
+      conn = kmm_zalloc(sizeof(*conn) * CONFIG_NET_BLUETOOTH_ALLOC_CONNS);
       if (conn != NULL)
         {
-          for (i = 0; i < CONFIG_NET_BLUETOOTH_NCONNS; i++)
+          for (i = 0; i < CONFIG_NET_BLUETOOTH_ALLOC_CONNS; i++)
             {
               dq_addlast(&conn[i].bc_conn.node,
                          &g_active_bluetooth_connections);
@@ -200,9 +209,20 @@ void bluetooth_conn_free(FAR struct bluetooth_conn_s *conn)
 
   memset(conn, 0, sizeof(*conn));
 
-  /* Free the connection */
+  /* If this is a preallocated or a batch allocated connection store it in
-
+   * the free connections list. Else free it.
-  dq_addlast(&conn->bc_conn.node, &g_free_bluetooth_connections);
+   */
+#if CONFIG_NET_BLUETOOTH_ALLOC_CONNS == 1
+  if (conn < g_bluetooth_connections || conn >= (g_bluetooth_connections +
+      CONFIG_NET_BLUETOOTH_PREALLOC_CONNS))
+    {
+      kmm_free(conn);
+    }
+  else
+#endif
+    {
+      dq_addlast(&conn->bc_conn.node, &g_free_bluetooth_connections);
+    }
 
   net_unlock();
 }