From 882716f72970e95edd3101f70c5961ec42eeaffb Mon Sep 17 00:00:00 2001
From: xueyunfei <xueyunfei@espressif.com>
Date: Fri, 30 Aug 2019 14:00:14 +0800
Subject: [PATCH] sockets: Fix potential race when socket is closed already

Ref IDF-4794
---
 src/api/sockets.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/api/sockets.c b/src/api/sockets.c
index 6a9f6d0a..d2ca5649 100644
--- a/src/api/sockets.c
+++ b/src/api/sockets.c
@@ -443,6 +443,10 @@ tryget_socket_unconn_locked(int fd)
 {
   struct lwip_sock *ret = tryget_socket_unconn_nouse(fd);
   if (ret != NULL) {
+#if ESP_LWIP      
+    if (ret->conn == NULL)
+      return NULL;
+#endif /* ESP_LWIP */         
     if (!sock_inc_used_locked(ret)) {
       return NULL;
     }