ifconfig support set IPv6 DNS server

Signed-off-by: liyi <liyi25@xiaomi.com>

netutils/netlib/netlib_setipv6dnsaddr.c

@@ -0,0 +1,79 @@
+/****************************************************************************
+ * apps/netutils/netlib/netlib_setipv6dnsaddr.c
+ *
+ * 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>
+
+#include <sys/socket.h>
+
+#include <string.h>
+#include <errno.h>
+
+#include <netinet/in.h>
+
+#include <nuttx/net/dns.h>
+
+#include "netutils/netlib.h"
+
+#if defined(CONFIG_NET_IPv6) && defined(CONFIG_NETDB_DNSCLIENT)
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: netlib_set_ipv6dnsaddr
+ *
+ * Description:
+ *   Set the DNS server IPv6 address
+ *
+ * Parameters:
+ *   inaddr   The address to set
+ *
+ * Return:
+ *   Zero (OK) is returned on success; A negated errno value is returned
+ *   on failure.
+ *
+ ****************************************************************************/
+
+int netlib_set_ipv6dnsaddr(FAR const struct in6_addr *inaddr)
+{
+  struct sockaddr_in6 addr;
+  int ret = -EINVAL;
+
+  if (inaddr)
+    {
+      /* Set the IPv6 DNS server address */
+
+      addr.sin6_family = AF_INET6;
+      addr.sin6_port   = 0;
+      memcpy(&addr.sin6_addr, inaddr, sizeof(struct in6_addr));
+
+      ret = dns_add_nameserver((FAR const struct sockaddr *)&addr,
+                               sizeof(struct sockaddr_in6));
+    }
+
+  return ret;
+}
+
+#endif /* CONFIG_NET_IPv6 && CONFIG_NETDB_DNSCLIENT */