/*
   * Copyright (C) 2015 Martine Lenders <mlenders@inf.fu-berlin.de>
   *
   * This file is subject to the terms and conditions of the GNU Lesser General
   * Public License v2.1. See the file LICENSE in the top level directory for
   * more details.
   */
  
  /**
   * @defgroup    net_gnrc_ndp  IPv6 Neighbor discovery
   * @ingroup     net_gnrc_icmpv6
   * @brief       GNRC's IPv6 Neighbor Discovery implementation
   * @{
   *
   * @file
   * @brief       Definitions for GNRC's IPv6 Neighbor Discovery
   *
   * @author      Martine Lenders <mlenders@inf.fu-berlin.de>
   */
  
  #ifndef NET_GNRC_NDP_H
  #define NET_GNRC_NDP_H
  
  #include <inttypes.h>
  #include <stdlib.h>
  
  #include "byteorder.h"
  #include "net/ndp.h"
  #include "net/gnrc/pkt.h"
  #include "net/gnrc/icmpv6.h"
  #include "net/ipv6/addr.h"
  #include "net/gnrc/ipv6/nc.h"
  #include "net/gnrc/ipv6/netif.h"
  
  #include "net/gnrc/ndp/host.h"
  #include "net/gnrc/ndp/internal.h"
  #include "net/gnrc/ndp/router.h"
  #include "net/gnrc/ndp/node.h"
  
  #ifdef __cplusplus
  extern "C" {
  #endif
  
  /** Message type for router timeouts */
  #define GNRC_NDP_MSG_RTR_TIMEOUT                (0x0210)
  /** Message type for address timeouts */
  #define GNRC_NDP_MSG_ADDR_TIMEOUT               (0x0211)
  /** Message type for multicast neighbor solicitation retransmissions */
  #define GNRC_NDP_MSG_NBR_SOL_RETRANS            (0x0212)
  /** Message type for periodic router advertisements */
  #define GNRC_NDP_MSG_RTR_ADV_RETRANS            (0x0213)
  /** Message type for delayed router advertisements */
  #define GNRC_NDP_MSG_RTR_ADV_DELAY              (0x0214)
  /** Message type for delayed router advertisements in a 6LoWPAN
   * 6LoWPAN needs a special handling, because router advertisements are only
   * sent after a short randomized delay, but not periodically. */
  #define GNRC_NDP_MSG_RTR_ADV_SIXLOWPAN_DELAY    (0x0215)
  /** Message type for periodic router solicitations */
  #define GNRC_NDP_MSG_RTR_SOL_RETRANS            (0x0216)
  /** Message type for neighbor cache state timeouts */
  #define GNRC_NDP_MSG_NC_STATE_TIMEOUT           (0x0217)
  
  /**
   * @name    Host constants
   * @{
   * @see     <a href="https://tools.ietf.org/html/rfc4861#section-10">
   *              RFC 4861, section 10
   *          </a>
   */
  /**
   * @brief   Upper bound for randomised delay in seconds for initial
   *          router solicitation transmissions
   */
  #define GNRC_NDP_MAX_RTR_SOL_DELAY      (1U)
  
  /**
   * @brief   Interval in seconds between initial router solicitation
   *          transmissions
   */
  #define GNRC_NDP_MAX_RTR_SOL_INT        (4U)
  
  /**
   * @brief   Maximum number of  initial router solicitation transmissions
   */
  #define GNRC_NDP_MAX_RTR_SOL_NUMOF      (3U)
  /** @} */
  
  /**
   * @name    Node constants
   * @{
   * @see     <a href="https://tools.ietf.org/html/rfc4861#section-10">
   *              RFC 4861, section 10
   *          </a>
   */
  /**
   * @brief   Maximum number of unanswered multicast neighbor solicitations
   *          before address resolution is considered failed.
   */
  #define GNRC_NDP_MAX_MC_NBR_SOL_NUMOF   (3U)
  
  /**
   * @brief   Maximum number of unanswered unicast neighbor solicitations before
   *          an address is considered unreachable.
   */
  #define GNRC_NDP_MAX_UC_NBR_SOL_NUMOF   (3U)
  
  /**
   * @brief   Upper bound of randomized delay in seconds for a solicited
   *          neighbor advertisement transmission for an anycast target.
   */
  #define GNRC_NDP_MAX_AC_TGT_DELAY       (1U)
  
  /**
   * @brief   Maximum number of unsolicited neighbor advertisements before on
   *          link-layer address change.
   */
  #define GNRC_NDP_MAX_NBR_ADV_NUMOF      (3U)
  
  /**
   * @brief   Base value in mircoseconds for computing randomised
   *          reachable time.
   */
  #define GNRC_NDP_REACH_TIME             (30U * US_PER_SEC)
  
  /**
   * @brief   Time in mircoseconds between retransmissions of neighbor
   *          solicitations to a neighbor.
   */
  #define GNRC_NDP_RETRANS_TIMER          (1U * US_PER_SEC)
  
  /**
   * @brief   Delay in seconds for neighbor cache entry between entering
   *          DELAY state and entering PROBE state if no reachability
   *          confirmation has been received.
   */
  #define GNRC_NDP_FIRST_PROBE_DELAY      (5U)
  
  /**
   * @brief   Lower bound for randomised reachable time calculation.
   */
  #define GNRC_NDP_MIN_RAND               (5U)
  
  /**
   * @brief   Upper bound for randomised reachable time calculation.
   */
  #define GNRC_NDP_MAX_RAND               (15U)
  /** @} */
  
  /**
   * @name    Router constants
   * @{
   * @see     <a href="https://tools.ietf.org/html/rfc4861#section-10">
   *              RFC 4861, section 10
   *          </a>
   */
  /**
   * @brief   Initial router advertisement interval in seconds
   */
  #define GNRC_NDP_MAX_INIT_RTR_ADV_INT   (16U)
  
  /**
   * @brief   Maximum number of initial router advertisement transmissions
   */
  #define GNRC_NDP_MAX_INIT_RTR_ADV_NUMOF (3U)
  
  /**
   * @brief   Maximum number of final router advertisement transmissions
   */
  #define GNRC_NDP_MAX_FIN_RTR_ADV_NUMOF  (3U)
  
  /**
   * @brief   Minimum delay in seconds between router advertisement
   *          transmissions
   */
  #define GNRC_NDP_MIN_RTR_ADV_DELAY      (3U)
  
  /**
   * @brief   Upper bound for randomised delay in microseconds between router
   *          solicitation reception and responding router advertisement
   *          transmission.
   */
  #define GNRC_NDP_MAX_RTR_ADV_DELAY      (500U * US_PER_MS)
  /** @} */
  
  /**
   * @brief   Handles received neighbor solicitations.
   *
   * @param[in] iface         The receiving interface.
   * @param[in] pkt           The received packet.
   * @param[in] ipv6          The IPv6 header in @p pkt.
   * @param[in] nbr_sol       The neighbor solicitation in @p pkt.
   * @param[in] icmpv6_size   The overall size of the neighbor solicitation.
   */
  void gnrc_ndp_nbr_sol_handle(kernel_pid_t iface, gnrc_pktsnip_t *pkt,
                               ipv6_hdr_t *ipv6, ndp_nbr_sol_t *nbr_sol,
                               size_t icmpv6_size);
  
  /**
   * @brief   Handles received neighbor advertisements.
   *
   * @param[in] iface         The receiving interface.
   * @param[in] pkt           The received packet.
   * @param[in] ipv6          The IPv6 header in @p pkt.
   * @param[in] nbr_adv       The neighbor advertisement in @p pkt.
   * @param[in] icmpv6_size   The overall size of the neighbor advertisement.
   */
  void gnrc_ndp_nbr_adv_handle(kernel_pid_t iface, gnrc_pktsnip_t *pkt,
                               ipv6_hdr_t *ipv6, ndp_nbr_adv_t *nbr_adv,
                               size_t icmpv6_size);
  
  #if (defined(MODULE_GNRC_NDP_ROUTER) || defined(MODULE_GNRC_SIXLOWPAN_ND_ROUTER))
  /**
   * @brief   Handles received router solicitations.
   *
   * @param[in] iface         The receiving interface.
   * @param[in] pkt           The received packet.
   * @param[in] ipv6          The IPv6 header in @p pkt.
   * @param[in] rtr_sol       The router solicitation in @p pkt.
   * @param[in] icmpv6_size   The overall size of the router solicitation.
   */
  void gnrc_ndp_rtr_sol_handle(kernel_pid_t iface, gnrc_pktsnip_t *pkt,
                               ipv6_hdr_t *ipv6, ndp_rtr_sol_t *rtr_sol,
                               size_t icmpv6_size);
  #else
  /**
   * @brief   A host *must* silently discard all received router solicitations.
   * @see     <a href="https://tools.ietf.org/html/rfc4861#section-6.2.6">
   *              RFC 4861, section 6.2.6
   *          </a>
   *
   * This macro is primarily an optimization to not go into the function defined
   * above.
   */
  #define gnrc_ndp_rtr_sol_handle(iface, pkt, ipv6, rtr_sol, size)
  #endif
  
  /**
   * @brief   Handles received router advertisements
   *
   * @todo    As router check consistency as described in RFC 4861, section 6.2.3
   *
   * @param[in] iface         The receiving interface.
   * @param[in] pkt           The received packet.
   * @param[in] ipv6          The IPv6 header in @p pkt.
   * @param[in] rtr_adv       The router advertisement in @p pkt.
   * @param[in] icmpv6_size   The overall size of the router advertisement.
   */
  void gnrc_ndp_rtr_adv_handle(kernel_pid_t iface, gnrc_pktsnip_t *pkt,
                               ipv6_hdr_t *ipv6, ndp_rtr_adv_t *rtr_adv,
                               size_t icmpv6_size);
  
  /**
   * @brief   Retransmits a multicast neighbor solicitation for an incomplete or
   *          probing neighbor cache entry @p nc_entry,
   *          if nc_entry::probes_remaining > 0.
   *
   * @details If nc_entry::probes_remaining > 0 it will be decremented. If it
   *          reaches 0 it the entry @p nc_entry will be removed from the
   *          neighbor cache.
   *
   * @param[in]   nc_entry    A neighbor cache entry. Will be ignored if its state
   *                          is not @ref GNRC_IPV6_NC_STATE_INCOMPLETE or
   *                          @ref GNRC_IPV6_NC_STATE_PROBE.
   */
  void gnrc_ndp_retrans_nbr_sol(gnrc_ipv6_nc_t *nc_entry);
  
  /**
   * @brief   Event handler for a neighbor cache state timeout.
   *
   * @param[in]   nc_entry    A neighbor cache entry.
   */
  void gnrc_ndp_state_timeout(gnrc_ipv6_nc_t *nc_entry);
  
  /**
   * @brief   NDP interface initialization.
   *
   * @param[in] iface     An IPv6 interface descriptor. Must not be NULL.
   */
  void gnrc_ndp_netif_add(gnrc_ipv6_netif_t *iface);
  
  /**
   * @brief   NDP interface removal.
   *
   * @param[in] iface     An IPv6 interface descriptor. Must not be NULL.
   */
  void gnrc_ndp_netif_remove(gnrc_ipv6_netif_t *iface);
  
  /**
   * @brief   Get link-layer address and interface for next hop to destination
   *          IPv6 address.
   *
   * @param[out] l2addr           The link-layer for the next hop to @p dst.
   * @param[out] l2addr_len       Length of @p l2addr.
   * @param[in] iface             The interface to search the next hop on.
   *                              May be @ref KERNEL_PID_UNDEF if not specified.
   * @param[in] dst               An IPv6 address to search the next hop for.
   * @param[in] pkt               Packet to send to @p dst. Leave NULL if you
   *                              just want to get the addresses.
   *
   * @return  The PID of the interface, on success.
   * @return  -EHOSTUNREACH, if @p dst is not reachable.
   * @return  -ENOBUFS, if @p l2addr_len was smaller than the resulting @p l2addr
   *          would be long.
   */
  kernel_pid_t gnrc_ndp_next_hop_l2addr(uint8_t *l2addr, uint8_t *l2addr_len,
                                        kernel_pid_t iface, ipv6_addr_t *dst,
                                        gnrc_pktsnip_t *pkt);
  
  /**
   * @brief   Builds a neighbor solicitation message for sending.
   *
   * @see <a href="https://tools.ietf.org/html/rfc4861#section-4.3">
   *          RFC 4861, section 4.3
   *      </a>
   *
   * @param[in] tgt       The target address.
   * @param[in] options   Options to append to the router solicitation.
   *
   * @return  The resulting ICMPv6 packet on success.
   * @return  NULL, on failure.
   */
  gnrc_pktsnip_t *gnrc_ndp_nbr_sol_build(ipv6_addr_t *tgt, gnrc_pktsnip_t *options);
  
  /**
   * @brief   Builds a neighbor advertisement message for sending.
   *
   * @see <a href="https://tools.ietf.org/html/rfc4861#section-4.4">
   *          RFC 4861, section 4.4
   *      </a>
   *
   * @param[in] flags     Neighbor advertisement flags:
   *                      @ref NDP_NBR_ADV_FLAGS_R == 1 indicates, that the
   *                      sender is a router,
   *                      @ref NDP_NBR_ADV_FLAGS_S == 1 indicates that the
   *                      advertisement was sent in response to a neighbor
   *                      solicitation,
   *                      @ref NDP_NBR_ADV_FLAGS_O == 1 indicates that the
   *                      advertisement should override an existing cache entry
   *                      and update the cached link-layer address.
   * @param[in] tgt       For solicited advertisements, the Target Address field
   *                      in the neighbor solicitaton.
   *                      For and unsolicited advertisement, the address whose
   *                      link-layer address has changed.
   *                      MUST NOT be multicast.
   * @param[in] options   Options to append to the neighbor advertisement.
   *
   * @return  The resulting ICMPv6 packet on success.
   * @return  NULL, on failure.
   */
  gnrc_pktsnip_t *gnrc_ndp_nbr_adv_build(uint8_t flags, ipv6_addr_t *tgt,
                                         gnrc_pktsnip_t *options);
  
  /**
   * @brief   Builds a router solicitation message for sending.
   *
   * @see <a href="https://tools.ietf.org/html/rfc4861#section-4.1">
   *          RFC 4861, section 4.1
   *      </a>
   *
   * @param[in] options   Options to append to the router solicitation.
   *
   * @return  The resulting ICMPv6 packet on success.
   * @return  NULL, on failure.
   */
  gnrc_pktsnip_t *gnrc_ndp_rtr_sol_build(gnrc_pktsnip_t *options);
  
  /**
   * @brief   Builds a router solicitation message for sending.
   *
   * @see <a href="https://tools.ietf.org/html/rfc4861#section-4.1">
   *          RFC 4861, section 4.1
   *      </a>
   *
   * @param[in] options   Options to append to the router solicitation.
   *
   * @return  The resulting ICMPv6 packet on success.
   * @return  NULL, on failure.
   */
  gnrc_pktsnip_t *gnrc_ndp_rtr_sol_build(gnrc_pktsnip_t *options);
  
  #if (defined(MODULE_GNRC_NDP_ROUTER) || defined(MODULE_GNRC_SIXLOWPAN_ND_ROUTER))
  /**
   * @brief   Builds a router advertisement message for sending.
   *
   * @see <a href="https://tools.ietf.org/html/rfc4861#section-4.2">
   *          RFC 4861, section 4.2
   *      </a>
   *
   * @note    The source address for the packet MUST be the link-local address
   *          of the interface.
   *
   * @param[in] cur_hl        Default hop limit for outgoing IP packets, 0 if
   *                          unspecified by this router.
   * @param[in] flags         Flags as defined above.
   *                          @ref NDP_RTR_ADV_FLAGS_M == 1 indicates, that the
   *                          addresses are managed by DHCPv6,
   *                          @ref NDP_RTR_ADV_FLAGS_O == 1 indicates that other
   *                          configuration information is available via DHCPv6.
   * @param[in] ltime         Lifetime of the default router in seconds.
   * @param[in] reach_time    Time in milliseconds a node should assume a neighbor
   *                          reachable. 0 means unspecified by the router.
   * @param[in] retrans_timer Time in milliseconds between retransmitted
   *                          neighbor solicitations. 0 means unspecified by
   *                          the router.
   * @param[in] options       Options to append to the router advertisement.
   *
   * @return  The resulting ICMPv6 packet on success.
   * @return  NULL, on failure.
   */
  gnrc_pktsnip_t *gnrc_ndp_rtr_adv_build(uint8_t cur_hl, uint8_t flags, uint16_t ltime,
                                         uint32_t reach_time, uint32_t retrans_timer,
                                         gnrc_pktsnip_t *options);
  #else
  /**
   * @brief   A host *must not* send router advertisements at any time (so why build them?)
   * @see     <a href="https://tools.ietf.org/html/rfc4861#section-6.3.4">
   *              RFC 4861, section 6.3.4
   *          </a>
   *
   * This macro is primarily an optimization to not go into the function defined
   * above.
   */
  #define gnrc_ndp_rtr_adv_build(cur_hl, flags, ltime, reach_time, retrans_timer, options) (NULL)
  #endif
  
  /**
   * @brief   Builds a generic NDP option.
   *
   * @param[in] type  Type of the option.
   * @param[in] size  Size in byte of the option (will be rounded up to the next
   *                  multiple of 8).
   * @param[in] next  More options in the packet. NULL, if there are none.
   *
   * @return  The packet snip list of options, on success
   * @return  NULL, if packet buffer is full
   */
  gnrc_pktsnip_t *gnrc_ndp_opt_build(uint8_t type, size_t size, gnrc_pktsnip_t *next);
  
  /**
   * @brief   Builds the source link-layer address option.
   *
   * @see <a href="https://tools.ietf.org/html/rfc4861#section-4.6.1">
   *          RFC 4861, section 4.6.1
   *      </a>
   *
   * @note    Must only be used with neighbor solicitations, router solicitations,
   *          and router advertisements. This is not checked however, since
   *          hosts should silently ignore it in other NDP messages.
   *
   * @param[in] l2addr        A link-layer address of variable length.
   * @param[in] l2addr_len    Length of @p l2addr.
   * @param[in] next          More options in the packet. NULL, if there are none.
   *
   * @return  The packet snip list of options, on success
   * @return  NULL, if packet buffer is full
   */
  gnrc_pktsnip_t *gnrc_ndp_opt_sl2a_build(const uint8_t *l2addr, uint8_t l2addr_len,
                                          gnrc_pktsnip_t *next);
  
  /**
   * @brief   Builds the target link-layer address option.
   *
   * @see <a href="https://tools.ietf.org/html/rfc4861#section-4.6.1">
   *          RFC 4861, section 4.6.1
   *      </a>
   *
   * @note    Must only be used with neighbor advertisemnents and redirect packets.
   *          This is not checked however, since hosts should silently ignore it
   *          in other NDP messages.
   *
   * @param[in] l2addr        A link-layer address of variable length.
   * @param[in] l2addr_len    Length of @p l2addr.
   * @param[in] next          More options in the packet. NULL, if there are none.
   *
   * @return  The pkt snip list of options, on success
   * @return  NULL, if packet buffer is full
   */
  gnrc_pktsnip_t *gnrc_ndp_opt_tl2a_build(const uint8_t *l2addr, uint8_t l2addr_len,
                                          gnrc_pktsnip_t *next);
  
  #if (defined(MODULE_GNRC_NDP_ROUTER) || defined(MODULE_GNRC_SIXLOWPAN_ND_ROUTER))
  /**
   * @brief   Builds the prefix information option.
   *
   * @see <a href="https://tools.ietf.org/html/rfc4861#section-4.6.2">
   *          RFC 4861, section 4.6.2
   *      </a>
   *
   * @note    Must only be used with router advertisemnents. This is not checked
   *          however, since nodes should silently ignore it in other NDP messages.
   *
   * @param[in] prefix_len    The length of @p prefix in bits. Must be between
   *                          0 and 128.
   * @param[in] flags         Flags as defined above.
   *                          @ref NDP_OPT_PI_FLAGS_L == 1 indicates, that
   *                          @p prefix can be used for on-link determination,
   *                          @ref NDP_OPT_PI_FLAGS_A == 1 indicates, that
   *                          @p prefix can be used for stateless address
   *                          configuration.
   * @param[in] valid_ltime   Length of time in seconds that @p prefix is valid.
   *                          UINT32_MAX represents infinity.
   * @param[in] pref_ltime    Length of time in seconds that addresses using
   *                          @p prefix remain prefered. UINT32_MAX represents
   *                          infinity.
   * @param[in] prefix        An IPv6 address or a prefix of an IPv6 address.
   * @param[in] next          More options in the packet. NULL, if there are none.
   *
   * @return  The packet snip list of options, on success
   * @return  NULL, if packet buffer is full
   */
  gnrc_pktsnip_t *gnrc_ndp_opt_pi_build(uint8_t prefix_len, uint8_t flags,
                                        uint32_t valid_ltime, uint32_t pref_ltime,
                                        ipv6_addr_t *prefix, gnrc_pktsnip_t *next);
  
  /**
   * @brief   Builds the MTU option.
   *
   * @see <a href="https://tools.ietf.org/html/rfc4861#section-4.6.4">
   *          RFC 4861, section 4.6.4
   *      </a>
   *
   * @note    Must only be used with router advertisemnents. This is not checked
   *          however, since nodes should silently ignore it in other NDP messages.
   *
   * @param[in] mtu           The recommended MTU for the link.
   * @param[in] next          More options in the packet. NULL, if there are none.
   *
   * @return  The packet snip list of options, on success
   * @return  NULL, if packet buffer is full
   */
  gnrc_pktsnip_t *gnrc_ndp_opt_mtu_build(uint32_t mtu, gnrc_pktsnip_t *next);
  #else
  /**
   * @brief   A host *must not* send router advertisements at any time (so why build their options?)
   * @see     <a href="https://tools.ietf.org/html/rfc4861#section-6.3.4">
   *              RFC 4861, section 6.3.4
   *          </a>
   *
   * This macro is primarily an optimization to not go into the function defined
   * above.
   */
  #define gnrc_ndp_opt_pi_build(prefix_len, flags, valid_ltime, pref_ltime, prefix, next) (NULL)
  
  /**
   * @brief   A host *must not* send router advertisements at any time (so why build their options?)
   * @see     <a href="https://tools.ietf.org/html/rfc4861#section-6.3.4">
   *              RFC 4861, section 6.3.4
   *          </a>
   *
   * This macro is primarily an optimization to not go into the function defined
   * above.
   */
  #define gnrc_ndp_opt_mtu_build(mtu, next)   (NULL)
  #endif
  
  #ifdef __cplusplus
  }
  #endif
  
  #endif /* NET_GNRC_NDP_H */
  /**
   * @}
   */