bugfix for assert when tcp send data

src/api/api_msg.c

@@ -794,6 +794,11 @@ netconn_alloc(enum netconn_type t, netconn_callback callback)
   conn->callback     = callback;
 #if LWIP_TCP
   conn->current_msg  = NULL;
+
+#if ESP_THREAD_PROTECTION
+  conn->write_protection = false;
+#endif /* ESP_THREAD_PROTECTION */
+
 #endif /* LWIP_TCP */
 #if LWIP_SO_SNDTIMEO
   conn->send_timeout = 0;
@@ -1719,6 +1724,18 @@ lwip_netconn_do_writemore(struct netconn *conn  WRITE_DELAYED_PARAM)
   u8_t apiflags;
   u8_t write_more;
 
+#if ESP_THREAD_PROTECTION
+  if(conn->write_protection == true) {
+    return ERR_OK;
+  }
+  TCP_WRITE_LOCK(conn);
+
+  if (conn->state != NETCONN_WRITE) {
+    TCP_WRITE_UNLOCK(conn);
+    return ERR_OK;
+  }
+#endif /* ESP_THREAD_PROTECTION */
+
   LWIP_ASSERT("conn != NULL", conn != NULL);
   LWIP_ASSERT("conn->state == NETCONN_WRITE", (conn->state == NETCONN_WRITE));
   LWIP_ASSERT("conn->current_msg != NULL", conn->current_msg != NULL);
@@ -1862,14 +1879,27 @@ err_mem:
     if (delayed)
 #endif
     {
+#if ESP_THREAD_PROTECTION
+      TCP_WRITE_UNLOCK(conn);
       sys_sem_signal(op_completed_sem);
+      return ERR_OK;
+#else
+      sys_sem_signal(op_completed_sem);
+#endif /* ESP_THREAD_PROTECTION */
+      
     }
   }
 #if LWIP_TCPIP_CORE_LOCKING
   else {
+#if ESP_THREAD_PROTECTION
+      TCP_WRITE_UNLOCK(conn);
+#endif /*ESP_THREAD_PROTECTION */
     return ERR_MEM;
   }
 #endif
+#if ESP_THREAD_PROTECTION
+  TCP_WRITE_UNLOCK(conn);
+#endif /*ESP_THREAD_PROTECTION */
   return ERR_OK;
 }
 #endif /* LWIP_TCP */

src/include/lwip/api.h

@@ -240,6 +240,9 @@ struct netconn {
   /** mbox where new connections are stored until processed
       by the application thread */
   sys_mbox_t acceptmbox;
+#if ESP_THREAD_PROTECTION
+  bool write_protection;
+#endif /* ESP_THREAD_PROTECTION */
 #endif /* LWIP_TCP */
 #if LWIP_NETCONN_FULLDUPLEX
   /** number of threads waiting on an mbox. This is required to unblock
@@ -422,6 +425,13 @@ void netconn_thread_cleanup(void);
 #define netconn_thread_cleanup()
 #endif /* LWIP_NETCONN_SEM_PER_THREAD */
 
+#if ESP_THREAD_PROTECTION
+
+#define TCP_WRITE_LOCK(conn)    ((conn)->write_protection = (true))
+#define TCP_WRITE_UNLOCK(conn)  ((conn)->write_protection = (false))
+
+#endif /* ESP_THREAD_PROTECTION */
+
 #ifdef __cplusplus
 }
 #endif

test/unit/lwipopts.h

@@ -103,6 +103,7 @@
 #define ESP_LWIP_LOCK                           1
 #define TCP_OOSEQ_DEBUG                         LWIP_DBG_ON
 #define ESP_DHCP_DEBUG                          1
+#define ESP_THREAD_PROTECTION                   0
 
 #ifdef IP_NAPT
 #define IP_NAPT_MAX                     16