Improvements in usrsock connections allocation.

boards/arm/cxd56xx/spresense/configs/wifi/defconfig

@@ -104,7 +104,7 @@ CONFIG_NETUTILS_TELNETD=y
 CONFIG_NETUTILS_WEBCLIENT=y
 CONFIG_NETUTILS_WEBSERVER=y
 CONFIG_NET_USRSOCK=y
-CONFIG_NET_USRSOCK_CONNS=16
+CONFIG_NET_USRSOCK_PREALLOC_CONNS=16
 CONFIG_NET_USRSOCK_UDP=y
 CONFIG_NFS=y
 CONFIG_NSH_ARCHINIT=y

boards/arm/cxd56xx/spresense/configs/wifi_smp/defconfig

@@ -107,7 +107,7 @@ CONFIG_NETUTILS_TELNETD=y
 CONFIG_NETUTILS_WEBCLIENT=y
 CONFIG_NETUTILS_WEBSERVER=y
 CONFIG_NET_USRSOCK=y
-CONFIG_NET_USRSOCK_CONNS=16
+CONFIG_NET_USRSOCK_PREALLOC_CONNS=16
 CONFIG_NET_USRSOCK_UDP=y
 CONFIG_NFS=y
 CONFIG_NSH_ARCHINIT=y

boards/arm/stm32/stm32f4discovery/configs/wifi/defconfig

@@ -55,7 +55,7 @@ CONFIG_NETUTILS_TELNETD=y
 CONFIG_NETUTILS_WEBCLIENT=y
 CONFIG_NETUTILS_WEBSERVER=y
 CONFIG_NET_USRSOCK=y
-CONFIG_NET_USRSOCK_CONNS=16
+CONFIG_NET_USRSOCK_PREALLOC_CONNS=16
 CONFIG_NET_USRSOCK_UDP=y
 CONFIG_NSH_ARCHINIT=y
 CONFIG_NSH_BUILTIN_APPS=y

include/nuttx/net/netconfig.h

@@ -631,18 +631,6 @@
 #  define CONFIG_NET_ARP_MAXAGE 120
 #endif
 
-/* Usrsock configuration options */
-
-/* The maximum amount of concurrent usrsock connections, Default: 6 */
-
-#ifndef CONFIG_NET_USRSOCK_CONNS
-#  ifdef CONFIG_NET_USRSOCK
-#    define CONFIG_NET_USRSOCK_CONNS 6
-#  else
-#    define CONFIG_NET_USRSOCK_CONNS 0
-#  endif
-#endif
-
 /****************************************************************************
  * Public Type Definitions
  ****************************************************************************/

net/usrsock/Kconfig

@@ -25,15 +25,50 @@ config NET_USRSOCK
 
 if NET_USRSOCK
 
-config NET_USRSOCK_CONNS
+config NET_USRSOCK_PREALLOC_CONNS
-	int "Number of usrsock connections"
+	int "Preallocated usrsock connections"
 	default 6
 	---help---
-		Maximum number of usrsock connections (all tasks).
+		Number of usrsock 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).
 
 		Note: Usrsock daemon can impose additional restrictions for
 		maximum number of concurrent connections supported.
 
+config NET_USRSOCK_ALLOC_CONNS
+	int "Dynamic usrsock connections allocation"
+	default 0
+	---help---
+		Dynamic memory allocations for usrsock.
+
+		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_USRSOCK_MAX_CONNS
+	int "Maximum number of usrsock connections"
+	default 0
+	depends on NET_USRSOCK_ALLOC_CONNS > 0
+	---help---
+		If dynamic connections allocation is selected (NET_USRSOCK_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_USRSOCK_NPOLLWAITERS
 	int "Number of usrsock poll waiters"
 	default 1

net/usrsock/usrsock_conn.c

@@ -48,8 +48,9 @@
 
 /* The array containing all usrsock connections. */
 
-#ifndef CONFIG_NET_ALLOC_CONNS
+#if CONFIG_NET_USRSOCK_PREALLOC_CONNS > 0
-static struct usrsock_conn_s g_usrsock_connections[CONFIG_NET_USRSOCK_CONNS];
+static struct usrsock_conn_s
+              g_usrsock_connections[CONFIG_NET_USRSOCK_PREALLOC_CONNS];
 #endif
 
 /* A list of all free usrsock connections */
@@ -77,20 +78,29 @@ static dq_queue_t g_active_usrsock_connections;
 FAR struct usrsock_conn_s *usrsock_alloc(void)
 {
   FAR struct usrsock_conn_s *conn;
-#ifdef CONFIG_NET_ALLOC_CONNS
+#if CONFIG_NET_USRSOCK_ALLOC_CONNS > 0
   int i;
 #endif
 
   /* The free list is protected by a a mutex. */
 
   nxmutex_lock(&g_free_lock);
-#ifdef CONFIG_NET_ALLOC_CONNS
+#if CONFIG_NET_USRSOCK_ALLOC_CONNS > 0
   if (dq_peek(&g_free_usrsock_connections) == NULL)
     {
-      conn = kmm_zalloc(sizeof(*conn) * CONFIG_NET_USRSOCK_CONNS);
+#if CONFIG_NET_USRSOCK_MAX_CONNS > 0
+      if (dq_count(&g_active_usrsock_connections) +
+          CONFIG_NET_USRSOCK_ALLOC_CONNS >= CONFIG_NET_USRSOCK_MAX_CONNS)
+        {
+          nxmutex_unlock(&g_free_lock);
+          return NULL;
+        }
+#endif
+
+      conn = kmm_zalloc(sizeof(*conn) * CONFIG_NET_USRSOCK_ALLOC_CONNS);
       if (conn != NULL)
         {
-          for (i = 0; i < CONFIG_NET_USRSOCK_CONNS; i++)
+          for (i = 0; i < CONFIG_NET_USRSOCK_ALLOC_CONNS; i++)
             {
               dq_addlast(&conn[i].sconn.node, &g_free_usrsock_connections);
             }
@@ -143,9 +153,22 @@ void usrsock_free(FAR struct usrsock_conn_s *conn)
   nxsem_destroy(&conn->resp.sem);
   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.
+   */
+
+#if CONFIG_NET_USRSOCK_ALLOC_CONNS == 1
+  if (conn < g_usrsock_connections || conn >= (g_usrsock_connections +
+      CONFIG_NET_USRSOCK_PREALLOC_CONNS))
+    {
+      kmm_free(conn);
+    }
+  else
+#endif
+    {
+      dq_addlast(&conn->sconn.node, &g_free_usrsock_connections);
+    }
 
-  dq_addlast(&conn->sconn.node, &g_free_usrsock_connections);
   nxmutex_unlock(&g_free_lock);
 }
 
@@ -309,11 +332,11 @@ void usrsock_setup_datain(FAR struct usrsock_conn_s *conn,
 
 void usrsock_initialize(void)
 {
-#ifndef CONFIG_NET_ALLOC_CONNS
+#if CONFIG_NET_USRSOCK_PREALLOC_CONNS > 0
   FAR struct usrsock_conn_s *conn;
   int i;
 
-  for (i = 0; i < CONFIG_NET_USRSOCK_CONNS; i++)
+  for (i = 0; i < CONFIG_NET_USRSOCK_PREALLOC_CONNS; i++)
     {
       conn = &g_usrsock_connections[i];