Use NTP server from DHCP first, then sntp.server

README.md

@@ -4,4 +4,6 @@ When included to a Mongoose OS application, this library fetches the current
 time from the SNTP server (by default, `time.google.com` is used) every time
 the Internet connection is established, and adjusts the device time.
 
+If NTP server option is returned by DHCP server, it is tried first.
+
 See `mos.yml` for the SNTP configuration available.

mos.yml

@@ -1,7 +1,7 @@
 author: mongoose-os
 type: lib
 description: A SNTP library
-version: 1.0
+version: 1.1.0
 
 sources:
   - src
@@ -12,7 +12,7 @@ filesystem:
 config_schema:
   - ["sntp", "o", {title: "SNTP settings"}]
   - ["sntp.enable", "b", true, {title: "Enable SNTP"}]
-  - ["sntp.server", "s", "time.google.com", {title: "Server address"}]
+  - ["sntp.server", "s", "time.google.com", {title: "Server address. If DHCP lease contains NTP server, tries that first."}]
   - ["sntp.retry_min", "i", 1, {title: "Minimum retry interval"}]
   - ["sntp.retry_max", "i", 30, {title: "Maximum retry interval"}]
   - ["sntp.update_interval", "i", 7200, {title: "Update interval. If 0, performs a one-off sync"}]

src/mgos_sntp.c

@@ -33,8 +33,11 @@
 struct mgos_sntp_state {
   struct mg_connection *nc;
   double last_synced_uptime;
-  int retry_timeout_ms;
   mgos_timer_id retry_timer_id;
+  unsigned int retry_timeout_ms : 24;
+  unsigned int sync_ok : 1;
+  unsigned int idx : 1;
+  char local_server[16];
 };
 
 static struct mgos_sntp_state s_state;
@@ -62,6 +65,7 @@ static void mgos_sntp_ev(struct mg_connection *nc, int ev, void *ev_data,
       if (mgos_settimeofday(m->time, NULL) != 0) {
         LOG(LL_ERROR, ("Failed to set time"));
       }
+      s_state.sync_ok = true;
       s_state.retry_timeout_ms = 0;
       s_state.last_synced_uptime = mgos_uptime();
       nc->flags |= MG_F_CLOSE_IMMEDIATELY;
@@ -78,7 +82,6 @@ static void mgos_sntp_ev(struct mg_connection *nc, int ev, void *ev_data,
       nc->flags |= MG_F_CLOSE_IMMEDIATELY;
       break;
     case MG_EV_CLOSE:
-      LOG(LL_DEBUG, ("SNTP close"));
       if (s_state.nc == nc) {
         s_state.nc = NULL;
         mgos_sntp_retry();
@@ -92,16 +95,23 @@ static void mgos_sntp_ev(struct mg_connection *nc, int ev, void *ev_data,
 static bool mgos_sntp_query(const char *server) {
   if (s_state.nc != NULL) {
     s_state.nc->flags |= MG_F_CLOSE_IMMEDIATELY;
+  }
+  if (server == NULL) {
     return false;
   }
+  s_state.sync_ok = false;
   s_state.nc = mg_sntp_connect(mgos_get_mgr(), mgos_sntp_ev, NULL, server);
-  LOG(LL_INFO, ("SNTP query to %s", server));
+  LOG(LL_DEBUG, ("SNTP query to %s", server));
   return (s_state.nc != NULL);
 }
 
 static void mgos_sntp_retry_timer_cb(void *user_data) {
   s_state.retry_timer_id = MGOS_INVALID_TIMER_ID;
-  mgos_sntp_query(mgos_sys_config_get_sntp_server());
+  const char *server = mgos_sys_config_get_sntp_server();
+  if (s_state.idx == 0 && s_state.local_server[0] != '\0') {
+    server = s_state.local_server;
+  }
+  mgos_sntp_query(server);
   /*
    * Response may never arrive, so we schedule a retry immediately.
    * Successful response will clear the timer.
@@ -114,7 +124,7 @@ static void mgos_sntp_retry(void) {
   if (!mgos_sys_config_get_sntp_enable()) return;
   if (s_state.retry_timer_id != MGOS_INVALID_TIMER_ID) return;
   int rt_ms = 0;
-  if (s_state.last_synced_uptime != 0) {
+  if (s_state.sync_ok) {
     rt_ms = mgos_sys_config_get_sntp_update_interval() * 1000;
     if (rt_ms == 0) return;
   } else {
@@ -127,6 +137,11 @@ static void mgos_sntp_retry(void) {
     }
     s_state.retry_timeout_ms = rt_ms;
   }
+  if (s_state.idx == 1 || s_state.sync_ok) {
+    s_state.idx = 0;
+  } else {
+    s_state.idx = 1;
+  }
   rt_ms = (int) mgos_rand_range(rt_ms * 0.9, rt_ms * 1.1);
   LOG(LL_DEBUG, ("SNTP next query in %d ms", rt_ms));
   s_state.retry_timer_id =
@@ -146,9 +161,39 @@ static void mgos_time_change_cb(int ev, void *evd, void *arg) {
   (void) ev;
 }
 
+static void mgos_sntp_update_server(void) {
+  struct mgos_net_ip_info ip_info;
+  memset(&ip_info, 0, sizeof(ip_info));
+  if (mgos_net_get_ip_info(MGOS_NET_IF_TYPE_ETHERNET, 0, &ip_info) &&
+      ip_info.ip.sin_addr.s_addr != 0 && ip_info.ntp.sin_addr.s_addr != 0) {
+    goto out;
+  }
+  memset(&ip_info, 0, sizeof(ip_info));
+  if (mgos_net_get_ip_info(MGOS_NET_IF_TYPE_WIFI, 0, &ip_info) &&
+      ip_info.ip.sin_addr.s_addr != 0 && ip_info.ntp.sin_addr.s_addr != 0) {
+    goto out;
+  }
+  memset(&ip_info, 0, sizeof(ip_info));
+  if (mgos_net_get_ip_info(MGOS_NET_IF_TYPE_PPP, 0, &ip_info) &&
+      ip_info.ip.sin_addr.s_addr != 0 && ip_info.ntp.sin_addr.s_addr != 0) {
+    goto out;
+  }
+  mgos_net_str_to_ip(MGOS_DEFAULT_NAMESERVER, &ip_info.dns);
+
+out:
+  if (ip_info.ntp.sin_addr.s_addr != 0) {
+    mgos_net_ip_to_str(&ip_info.ntp, s_state.local_server);
+    LOG(LL_DEBUG, ("Setting %s server to %s", "NTP", s_state.local_server));
+  } else {
+    s_state.local_server[0] = '\0';
+  }
+}
+
 static void mgos_sntp_net_ev(int ev, void *evd, void *arg) {
   if (ev != MGOS_NET_EV_IP_ACQUIRED) return;
+  mgos_sntp_update_server();
   mgos_sntp_retry();
+  s_state.idx = 0;  // Start with local server.
   (void) evd;
   (void) arg;
 }
@@ -159,11 +204,6 @@ double mgos_sntp_get_last_synced_uptime(void) {
 
 bool mgos_sntp_init(void) {
   if (!mgos_sys_config_get_sntp_enable()) return true;
-  if (mgos_sys_config_get_sntp_server() == NULL) {
-    LOG(LL_ERROR, ("sntp.server is required"));
-    return false;
-  }
-
   mgos_event_add_handler(MGOS_EVENT_TIME_CHANGED, mgos_time_change_cb,
                          mgos_get_mgr());
   mgos_event_add_group_handler(MGOS_EVENT_GRP_NET, mgos_sntp_net_ev, NULL);