netutils: prefer DHCP-provided NTP servers for ntpc

Use the DHCP-learned NTP server list as the default ntpc server source when DHCP option 42 is available.

Fall back to CONFIG_NETUTILS_NTPCLIENT_SERVER only when DHCP does not provide any NTP servers, and restart ntpc when the DHCP-provided server list changes.

Signed-off-by: Jerry Ma <masc2008@gmail.com>

netutils/netlib/CMakeLists.txt

@@ -57,6 +57,7 @@ if(CONFIG_NETUTILS_NETLIB)
     endif()
     if(CONFIG_NETUTILS_DHCPC)
       list(APPEND SRCS netlib_obtainipv4addr.c)
+      list(APPEND SRCS netlib_dhcp_ntp.c)
     endif()
   endif()
 

netutils/netlib/Makefile

@@ -57,6 +57,7 @@ CSRCS += netlib_iptables.c
 endif
 ifeq ($(CONFIG_NETUTILS_DHCPC),y)
 CSRCS += netlib_obtainipv4addr.c
+CSRCS += netlib_dhcp_ntp.c
 endif
 endif
 

netutils/netlib/netlib_dhcp_ntp.c

@@ -0,0 +1,182 @@
+/****************************************************************************
+ * apps/netutils/netlib/netlib_dhcp_ntp.c
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#ifdef CONFIG_NETUTILS_DHCPC
+
+#include <errno.h>
+#include <pthread.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "netutils/netlib.h"
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+static pthread_mutex_t g_dhcp_ntp_lock = PTHREAD_MUTEX_INITIALIZER;
+static FAR char *g_dhcp_ntp_servers;
+static netlib_dhcp_ntp_callback_t g_dhcp_ntp_callback;
+static FAR void *g_dhcp_ntp_callback_arg;
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+static FAR char *netlib_dhcp_ntp_dup(FAR const char *ntp_server_list)
+{
+  if (ntp_server_list == NULL || ntp_server_list[0] == '\0')
+    {
+      return NULL;
+    }
+
+  return strdup(ntp_server_list);
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+int netlib_set_ntp_servers_from_dhcp(FAR const char *ntp_server_list)
+{
+  FAR char *new_servers;
+  FAR char *notify_servers = NULL;
+  FAR char *old_servers;
+  netlib_dhcp_ntp_callback_t callback;
+  FAR void *arg;
+  int ret = OK;
+
+  new_servers = netlib_dhcp_ntp_dup(ntp_server_list);
+  if (ntp_server_list != NULL && ntp_server_list[0] != '\0' &&
+      new_servers == NULL)
+    {
+      return -ENOMEM;
+    }
+
+  pthread_mutex_lock(&g_dhcp_ntp_lock);
+
+  if ((g_dhcp_ntp_servers == NULL && new_servers == NULL) ||
+      (g_dhcp_ntp_servers != NULL && new_servers != NULL &&
+       strcmp(g_dhcp_ntp_servers, new_servers) == 0))
+    {
+      pthread_mutex_unlock(&g_dhcp_ntp_lock);
+      free(new_servers);
+      return OK;
+    }
+
+  callback = g_dhcp_ntp_callback;
+  arg = g_dhcp_ntp_callback_arg;
+
+  if (callback != NULL && new_servers != NULL)
+    {
+      notify_servers = strdup(new_servers);
+      if (notify_servers == NULL)
+        {
+          ret = -ENOMEM;
+          goto errout_with_lock;
+        }
+    }
+
+  old_servers = g_dhcp_ntp_servers;
+  g_dhcp_ntp_servers = new_servers;
+  pthread_mutex_unlock(&g_dhcp_ntp_lock);
+
+  free(old_servers);
+
+  if (callback != NULL)
+    {
+      callback(notify_servers, arg);
+    }
+
+  free(notify_servers);
+  return OK;
+
+errout_with_lock:
+  pthread_mutex_unlock(&g_dhcp_ntp_lock);
+  free(new_servers);
+  return ret;
+}
+
+int netlib_register_dhcp_ntp_callback(netlib_dhcp_ntp_callback_t callback,
+                                      FAR void *arg)
+{
+  FAR char *notify_servers = NULL;
+
+  if (callback == NULL)
+    {
+      return -EINVAL;
+    }
+
+  pthread_mutex_lock(&g_dhcp_ntp_lock);
+
+  if (g_dhcp_ntp_callback != NULL &&
+      (g_dhcp_ntp_callback != callback || g_dhcp_ntp_callback_arg != arg))
+    {
+      pthread_mutex_unlock(&g_dhcp_ntp_lock);
+      return -EBUSY;
+    }
+
+  if (g_dhcp_ntp_servers != NULL)
+    {
+      notify_servers = strdup(g_dhcp_ntp_servers);
+      if (notify_servers == NULL)
+        {
+          pthread_mutex_unlock(&g_dhcp_ntp_lock);
+          return -ENOMEM;
+        }
+    }
+
+  g_dhcp_ntp_callback = callback;
+  g_dhcp_ntp_callback_arg = arg;
+
+  pthread_mutex_unlock(&g_dhcp_ntp_lock);
+
+  callback(notify_servers, arg);
+  free(notify_servers);
+  return OK;
+}
+
+int netlib_unregister_dhcp_ntp_callback(netlib_dhcp_ntp_callback_t callback,
+                                        FAR void *arg)
+{
+  int ret = -ENOENT;
+
+  pthread_mutex_lock(&g_dhcp_ntp_lock);
+
+  if (g_dhcp_ntp_callback == callback && g_dhcp_ntp_callback_arg == arg)
+    {
+      g_dhcp_ntp_callback = NULL;
+      g_dhcp_ntp_callback_arg = NULL;
+      ret = OK;
+    }
+
+  pthread_mutex_unlock(&g_dhcp_ntp_lock);
+  return ret;
+}
+
+#endif /* CONFIG_NETUTILS_DHCPC */

netutils/netlib/netlib_obtainipv4addr.c

@@ -25,6 +25,10 @@
  ****************************************************************************/
 
 #include <nuttx/debug.h>
+#include <arpa/inet.h>
+#include <errno.h>
+#include <stdio.h>
+#include <string.h>
 #include <sys/types.h>
 
 #include "netutils/dhcpc.h"
@@ -105,6 +109,68 @@ static int dhcp_setup_result(FAR const char *ifname,
   return OK;
 }
 
+#ifdef CONFIG_NETUTILS_NTPCLIENT
+static int dhcp_set_ntp_servers(FAR const struct dhcpc_state *ds)
+{
+  char ntp_server_list[CONFIG_NETUTILS_DHCPC_NTP_SERVERS *
+                       (INET_ADDRSTRLEN + 1)];
+  size_t offset = 0;
+  uint8_t i;
+
+  /* Clear the DHCP-provided NTP server list,
+   * consider case: that device has joined another dhcp domain,
+   * it need refresh related settings.
+   */
+
+  if (ds->num_ntpaddr == 0)
+    {
+      return netlib_set_ntp_servers_from_dhcp(NULL);
+    }
+
+  ntp_server_list[0] = '\0';
+
+  for (i = 0; i < ds->num_ntpaddr; i++)
+    {
+      char addrbuf[INET_ADDRSTRLEN];
+      int ret;
+
+      /* Skip empty entries */
+
+      if (ds->ntpaddr[i].s_addr == 0)
+        {
+          continue;
+        }
+
+      if (inet_ntop(AF_INET, &ds->ntpaddr[i], addrbuf, sizeof(addrbuf)) ==
+          NULL)
+        {
+          return -EINVAL;
+        }
+
+      /* Append the server to the list */
+
+      ret = snprintf(ntp_server_list + offset,
+                     sizeof(ntp_server_list) - offset,
+                     "%s%s", offset == 0 ? "" : ";", addrbuf);
+      if (ret < 0 || (size_t)ret >= sizeof(ntp_server_list) - offset)
+        {
+          return -E2BIG;
+        }
+
+      offset += (size_t)ret;
+    }
+
+  /* Clear the list if all entries were empty */
+
+  if (offset == 0)
+    {
+      return netlib_set_ntp_servers_from_dhcp(NULL);
+    }
+
+  return netlib_set_ntp_servers_from_dhcp(ntp_server_list);
+}
+#endif
+
 /****************************************************************************
  * Name: dhcp_obtain_statefuladdr
  *
@@ -156,6 +222,18 @@ static int dhcp_obtain_statefuladdr(FAR const char *ifname)
   if (ret == OK)
     {
       ret = dhcp_setup_result(ifname, &ds);
+#ifdef CONFIG_NETUTILS_NTPCLIENT
+      if (ret == OK)
+        {
+          ret = dhcp_set_ntp_servers(&ds);
+          if (ret < 0)
+            {
+              nwarn("WARNING: failed to update DHCP NTP server list: %d\n",
+                    ret);
+              ret = OK;
+            }
+        }
+#endif
     }
   else
     {