free TCP rx buffer immediately in tcp_close

Issue:
TCP rx buffer is freed after 4-way handshake with current design.
3 socket's rx buffer might be consumed during ffmpeg switch music procedure,
and this might cause IOB exhausted.

Solution:
free TCP rx buffer immediately in tcp_close to make sure IOB won't be
exhausted.

Signed-off-by: 梁超众 <liangchaozhong@xiaomi.com>
Signed-off-by: chao an <anchao@xiaomi.com>

net/tcp/tcp.h

@@ -449,6 +449,16 @@ void tcp_initialize(void);
 
 FAR struct tcp_conn_s *tcp_alloc(uint8_t domain);
 
+/****************************************************************************
+ * Name: tcp_free_rx_buffers
+ *
+ * Description:
+ *   Free rx buffer of a connection
+ *
+ ****************************************************************************/
+
+void tcp_free_rx_buffers(FAR struct tcp_conn_s *conn);
+
 /****************************************************************************
  * Name: tcp_free
  *

net/tcp/tcp_close.c

@@ -236,6 +236,10 @@ static inline int tcp_close_disconnect(FAR struct socket *psock)
        conn->tcpstateflags == TCP_LAST_ACK) &&
       (conn->clscb = tcp_callback_alloc(conn)) != NULL)
     {
+      /* Free rx buffers of the connection immediately */
+
+      tcp_free_rx_buffers(conn);
+
       /* Set up to receive TCP data event callbacks */
 
       conn->clscb->flags = TCP_NEWDATA | TCP_ACKDATA |

net/tcp/tcp_conn.c

@@ -746,6 +746,38 @@ FAR struct tcp_conn_s *tcp_alloc(uint8_t domain)
   return conn;
 }
 
+/****************************************************************************
+ * Name: tcp_free_rx_buffers
+ *
+ * Description:
+ *   Free rx buffer of a connection
+ *
+ ****************************************************************************/
+
+void tcp_free_rx_buffers(FAR struct tcp_conn_s *conn)
+{
+  /* Release any read-ahead buffers attached to the connection */
+
+  iob_free_chain(conn->readahead);
+  conn->readahead = NULL;
+
+#ifdef CONFIG_NET_TCP_OUT_OF_ORDER
+  /* Release any out-of-order buffers */
+
+  if (conn->nofosegs > 0)
+    {
+      int i;
+
+      for (i = 0; i < conn->nofosegs; i++)
+        {
+          iob_free_chain(conn->ofosegs[i].data);
+        }
+
+      conn->nofosegs = 0;
+    }
+#endif /* CONFIG_NET_TCP_OUT_OF_ORDER */
+}
+
 /****************************************************************************
  * Name: tcp_free
  *
@@ -801,26 +833,7 @@ void tcp_free(FAR struct tcp_conn_s *conn)
       dq_rem(&conn->sconn.node, &g_active_tcp_connections);
     }
 
-  /* Release any read-ahead buffers attached to the connection */
+  tcp_free_rx_buffers(conn);
-
-  iob_free_chain(conn->readahead);
-  conn->readahead = NULL;
-
-#ifdef CONFIG_NET_TCP_OUT_OF_ORDER
-  /* Release any out-of-order buffers */
-
-  if (conn->nofosegs > 0)
-    {
-      int i;
-
-      for (i = 0; i < conn->nofosegs; i++)
-        {
-          iob_free_chain(conn->ofosegs[i].data);
-        }
-
-      conn->nofosegs = 0;
-    }
-#endif /* CONFIG_NET_TCP_OUT_OF_ORDER */
 
 #ifdef CONFIG_NET_TCP_WRITE_BUFFERS
   /* Release any write buffers attached to the connection */