【修复】头文件相同字段重复添加问题

Signed-off-by: chenyong <1521761801@qq.com>

src/webclient.c

@@ -617,19 +617,19 @@ static int webclient_send_header(struct webclient_session *session, int method)
                 web_free(header_buffer);
             }
 
-            if (memcmp(header, "Host:", rt_strlen("Host:")))
+            if (strstr(header, "Host:") == RT_NULL)
             {
                 if (webclient_header_fields_add(session, "Host: %s\r\n", session->host) < 0)
                     return -WEBCLIENT_NOMEM;
             }
 
-            if (memcmp(header, "User-Agent:", rt_strlen("User-Agent:")))
+            if (strstr(header, "User-Agent:") == RT_NULL)
             {
                 if (webclient_header_fields_add(session, "User-Agent: RT-Thread HTTP Agent\r\n") < 0)
                     return -WEBCLIENT_NOMEM;
             }
 
-            if (memcmp(header, "Accept:", rt_strlen("Accept:")))
+            if (strstr(header, "Accept:") == RT_NULL)
             {
                 if (webclient_header_fields_add(session, "Accept: */*\r\n") < 0)
                     return -WEBCLIENT_NOMEM;