From 855c80c9bfffb5182f4abdff957618f30b21bf9d Mon Sep 17 00:00:00 2001
From: Dong Heng <dongheng@espressif.com>
Date: Mon, 30 Jul 2018 19:01:50 +0800
Subject: [PATCH] fix(lwip): Fix lwip TCP server "accept" sync error

---
 components/lwip/lwip/src/api/api_msg.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/components/lwip/lwip/src/api/api_msg.c b/components/lwip/lwip/src/api/api_msg.c
index 5a8dad9b..95022254 100644
--- a/components/lwip/lwip/src/api/api_msg.c
+++ b/components/lwip/lwip/src/api/api_msg.c
@@ -799,12 +799,18 @@ netconn_drain(struct netconn *conn)
         /* Only tcp pcbs have an acceptmbox, so no need to check conn->type */
         /* pcb might be set to NULL already by err_tcp() */
         /* drain recvmbox */
+#ifdef ESP_LWIP
+        if (newconn) {
+#endif /* ESP_LWIP */
         netconn_drain(newconn);
         if (newconn->pcb.tcp != NULL) {
           tcp_abort(newconn->pcb.tcp);
           newconn->pcb.tcp = NULL;
         }
         netconn_free(newconn);
+#ifdef ESP_LWIP
+        }
+#endif /* ESP_LWIP */
       }
     }
     sys_mbox_free(&conn->acceptmbox);