Add standardized nameserver pool

Adds a common in contiki nameserver pool for handling name resolution
servers. This will allow in following commit to use RDNSS messages
within RA.

core/net/ip/uip-nameserver.h

@@ -0,0 +1,101 @@
+/**
+ * \addtogroup uip6
+ * @{
+ */
+
+/**
+ * \file
+ *         uIP Name Server interface
+ * \author Víctor Ariño <victor.arino@tado.com>
+ */
+
+/*
+ * Copyright (c) 2014, tado° GmbH.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the Institute nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * This file is part of the Contiki operating system.
+ *
+ */
+
+#ifndef UIP_NAMESERVER_H_
+#define UIP_NAMESERVER_H_
+
+/**
+ * \name General
+ * @{
+ */
+/** \brief Number of Nameservers to keep */
+#define UIP_NAMESERVER_POOL_SIZE 2
+/** \brief Infinite Lifetime indicator */
+#define UIP_NAMESERVER_INFINITE_LIFETIME 0xFFFFFFFF
+/** @} */
+
+/**
+ * \name Nameserver maintenance
+ * @{
+ */
+/**
+ * \brief Insert or update a nameserver into/from the pool
+ *
+ * The list is kept according to the RFC6106, which indicates that new entries
+ * will replace old ones (with lower lifetime) and existing entries will update
+ * their lifetimes.
+ *
+ * \param nameserver   Pointer to the nameserver ip address
+ * \param lifetime     Life time of the given address. Minimum is 0, which is
+ *                     considered to remove an entry. Maximum is 0xFFFFFFFF which
+ *                     is considered infinite.
+ */
+void
+uip_nameserver_update(uip_ipaddr_t *nameserver, uint32_t lifetime);
+
+/**
+ * \brief Get a Nameserver ip address given in RA
+ *
+ * \param num   The number of the nameserver to obtain, starting at 0 and going
+ *              up to the pool size. (\sa UIP_ND6_RDNSS_POOL_SIZE)
+ */
+uip_ipaddr_t *
+uip_nameserver_get(uint8_t num);
+
+/**
+ * \brief Get next expiration time
+ *
+ * The least expiration time is returned
+ */
+uint32_t
+uip_nameserver_next_expiration(void);
+
+/**
+ * \brief Get the number of recorded name servers
+ */
+uint16_t
+uip_nameserver_count(void);
+/** @} */
+
+#endif /* UIP_NAMESERVER_H_ */
+/** @} */