Implement SNTP client

PUBLISHED_FROM=ac54bcbc81a9ee688e8b90e261172be76a9fbacd

mongoose.h

@@ -2812,6 +2812,10 @@ struct {								\
 #define MG_ENABLE_TUN MG_ENABLE_HTTP_WEBSOCKET
 #endif
 
+#ifndef MG_ENABLE_SNTP
+#define MG_ENABLE_SNTP 0
+#endif
+
 #endif /* CS_MONGOOSE_SRC_FEATURES_H_ */
 #ifdef MG_MODULE_LINES
 #line 1 "mongoose/src/net_if.h"
@@ -5591,3 +5595,59 @@ uint32_t mg_coap_compose(struct mg_coap_message *cm, struct mbuf *io);
 #endif /* MG_ENABLE_COAP */
 
 #endif /* CS_MONGOOSE_SRC_COAP_H_ */
+#ifdef MG_MODULE_LINES
+#line 1 "mongoose/src/sntp.h"
+#endif
+/*
+ * Copyright (c) 2016 Cesanta Software Limited
+ * All rights reserved
+ */
+
+#ifndef CS_MONGOOSE_SRC_SNTP_H_
+#define CS_MONGOOSE_SRC_SNTP_H_
+
+#if MG_ENABLE_SNTP
+
+#define MG_SNTP_EVENT_BASE 500
+
+/*
+ * Received reply from time server. Event handler parameter contains
+ * pointer to mg_sntp_message structure
+ */
+#define MG_SNTP_REPLY (MG_SNTP_EVENT_BASE + 1)
+
+/* Received malformed SNTP packet */
+#define MG_SNTP_MALFORMED_REPLY (MG_SNTP_EVENT_BASE + 2)
+
+/* Failed to get time from server (timeout etc) */
+#define MG_SNTP_FAILED (MG_SNTP_EVENT_BASE + 3)
+
+struct mg_sntp_message {
+  /* if server sends this flags, user should not send requests to it */
+  int kiss_of_death;
+  /* usual mg_time */
+  double time;
+};
+
+/* Establishes connection to given sntp server */
+struct mg_connection *mg_sntp_connect(struct mg_mgr *mgr,
+                                      mg_event_handler_t event_handler,
+                                      const char *sntp_server_name);
+
+/* Sends time request to given connection */
+void mg_sntp_send_request(struct mg_connection *c);
+
+/*
+ * Helper function
+ * Establishes connection to time server, tries to send request
+ * repeats sending SNTP_ATTEMPTS times every SNTP_TIMEOUT sec
+ * (if needed)
+ * See sntp_client example
+ */
+struct mg_connection *mg_sntp_get_time(struct mg_mgr *mgr,
+                                       mg_event_handler_t event_handler,
+                                       const char *sntp_server_name);
+
+#endif
+
+#endif /* CS_MONGOOSE_SRC_SNTP_H_ */