PF_IEEE802154: Add a maximum backlog option. This will prevent overrun of the RX frame queue if many frames are received from the radio, but no application is receiving the queued data.

net/ieee802154/Kconfig

@@ -39,10 +39,24 @@ config NET_IEEE802154_NCONNS
 
 config NET_IEEE802154_NCONTAINERS
 	int "Number of pre-allocated frame containers"
-	default 20
+	default 8
 	---help---
 		This specifies the total number of preallocated frame containers.
 		One must be allocated with each incoming frame.
 
+config NET_IEEE802154_BACKLOG
+	int "Maximum frame backlog"
+	default 8
+	range 0 255
+	---help---
+		As frames are received, then are help in an RX queue.  They remain
+		in the RX queue until application logic reads the queue frames.  To
+		prevent overrun, the maximum backlog may be set to a nonzero value.
+		What the backlog of queue frames reaches that count, the olds frame
+		will be freed, preventing overrun at the cost of losing the oldest
+		frames.
+
+		NOTE: The special value of zero will disable all backlog checkes.
+
 endif # NET_IEEE802154
 endmenu # IEEE 802.15.4 Socket Support

net/ieee802154/ieee802154.h

@@ -118,8 +118,11 @@ struct ieee802154_conn_s
   struct ieee802154_saddr_s laddr;             /* Locally bound / source address */
   struct ieee802154_saddr_s raddr;             /* Connected remote address */
   uint8_t crefs;                               /* Reference counts on this instance */
+#if CONFIG_NET_IEEE802154_BACKLOG > 0
+  uint8_t backlog;                             /* Number of frames in RX queue */
+#endif
 
-  /* List of incoming packets */
+  /* Queue of incoming packets */
 
   FAR struct ieee802154_container_s *rxhead;
   FAR struct ieee802154_container_s *rxtail;

net/ieee802154/ieee802154_conn.c

@@ -38,6 +38,7 @@
 #include <nuttx/config.h>
 
 #include <semaphore.h>
+#include <string.h>
 #include <assert.h>
 #include <errno.h>
 #include <debug.h>
@@ -133,6 +134,7 @@ FAR struct ieee802154_conn_s *ieee802154_conn_alloc(void)
     {
       /* Enqueue the connection into the active list */
 
+      memset(conn, 0, sizeof(struct ieee802154_conn_s));
       dq_addlast(&conn->node, &g_active_ieee802154_connections);
     }
 
@@ -167,9 +169,7 @@ void ieee802154_conn_free(FAR struct ieee802154_conn_s *conn)
 
   /* Check if there any any frames attached to the container */
 
-  for (container = conn->rxhead;
-       container != NULL;
-       container = container->ic_flink)
+  for (container = conn->rxhead; container != NULL; container = next)
     {
       /* Remove the frame from the list */
 

net/ieee802154/ieee802154_input.c

@@ -55,6 +55,36 @@
  * Public Functions
  ****************************************************************************/
 
+/****************************************************************************
+ * Name: ieee802154_count_frames
+ *
+ * Description:
+ *   Return the number of frames in the RX queue.
+ *
+ * Parameters:
+ *   conn   - The socket connection structure.
+ *
+ * Return:
+ *   The number of frames in the queue.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_DEBUG_ASSERTIONS
+int ieee802154_count_frames(FAR struct ieee802154_conn_s *conn)
+{
+  FAR struct ieee802154_container_s *container;
+  int count;
+
+  for (count = 0, container = conn->rxhead;
+       container != NULL;
+       count++, container = container->ic_flink)
+    {
+    }
+
+  return count;
+}
+#endif
+
 /****************************************************************************
  * Name: ieee802154_queue_frame
  *
@@ -119,6 +149,40 @@ int ieee802154_queue_frame(FAR struct ieee802154_conn_s *conn,
       conn->rxtail->ic_flink = container;
     }
 
+#if CONFIG_NET_IEEE802154_BACKLOG > 0
+   /* Increment the count of frames in the queue.  If the count exceeds the
+    * maximum backlog value, then delete the oldest frame from the head of
+    * the RX queue.
+    */
+
+   conn->backlog++;
+   DEBUGASSERT((int)conn->backlog == ieee802154_count_frames(conn));
+
+   if (conn->backlog > CONFIG_NET_IEEE802154_BACKLOG)
+     {
+      /* Remove the container from the tail RX input queue. */
+
+      container           = conn->rxhead;
+      DEBUGASSERT(container != NULL);
+      conn->rxhead        = container->ic_flink;
+      container->ic_flink = NULL;
+
+      /* Did the RX queue become empty? */
+
+      if (conn->rxhead == NULL)
+        {
+          conn->rxtail = NULL;
+        }
+
+      DEBUGASSERT(container != NULL && container->ic_iob != NULL);
+
+      /* Free both the IOB and the container */
+
+      iob_free(container->ic_iob);
+      ieee802154_container_free(container);
+     }
+#endif
+
   return OK;
 }
 

net/ieee802154/ieee802154_recvfrom.c

@@ -129,6 +129,13 @@ static ssize_t ieee802154_recvfrom_rxqueue(FAR struct radio_driver_s *radio,
           conn->rxtail = NULL;
         }
 
+#if CONFIG_NET_IEEE802154_BACKLOG > 0
+       /* Decrement the count of frames in the queue. */
+
+       DEBUGASSERT(conn->backlog > 0);
+       conn->backlog--;
+#endif
+
       /* Extract the IOB containing the frame from the container */
 
       iob               = container->ic_iob;