/*
 * 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_ipv6_ext IPv6 extension headers.
 * @ingroup     net_gnrc_ipv6
 * @brief       Implementation of IPv6 extension headers
 * @see [RFC 8200, section 4](https://tools.ietf.org/html/rfc8200#section-4)
 * @{
 *
 * @file
 * @brief       Definititions for IPv6 extension headers
 *
 * @author      Martine Lenders <mlenders@inf.fu-berlin.de>
 */


#ifndef NET_GNRC_IPV6_EXT_H
#define NET_GNRC_IPV6_EXT_H

#include <stdbool.h>
#include <stdint.h>
#include <stdlib.h>

#include "net/gnrc/pkt.h"
#include "net/ipv6/ext.h"

#ifdef MODULE_GNRC_IPV6_EXT_RH
#include "net/gnrc/ipv6/ext/rh.h"
#endif

#ifdef __cplusplus
extern "C" {
#endif

/**
 * @brief   Demultiplex an extension header according to @p nh.
 *
 * This includes dispatching it to interested parties in the
 * @ref net_gnrc_netreg.
 *
 * @param[in] pkt       A packet with the first snip pointing to the extension
 *                      header to process.
 * @param[in] nh        Protocol number of @p pkt.
 *
 * @return  The packet for further processing.
 * @return  NULL, on error or if packet was consumed (by e.g. forwarding via
 *          a routing header). @p pkt is released in case of error.
 */
gnrc_pktsnip_t *gnrc_ipv6_ext_demux(gnrc_pktsnip_t *pkt, unsigned nh);

/**
 * @brief   Builds an extension header for sending.
 *
 * @param[in] ipv6  The IPv6 header. Can be NULL.
 * @param[in] next  The next header. Must be a successor to @p ipv6 if it is
 *                  not NULL.
 * @param[in] nh    @ref net_protnum of the next header.
 * @param[in] size  Size of the extension header.
 *
 * @return  The extension header on success.
 * @return  NULL, on error.
 */
gnrc_pktsnip_t *gnrc_ipv6_ext_build(gnrc_pktsnip_t *ipv6, gnrc_pktsnip_t *next,
                                    uint8_t nh, size_t size);

#if     defined(MODULE_GNRC_IPV6_EXT) || defined(DOXYGEN)
/**
 * @brief   Processes a packet's payload as hop-by-hop option if @p nh is
 *          pointing to a value equal to @ref PROTNUM_IPV6_EXT_HOPOPT.
 *
 * @note    Should be called by @ref net_gnrc_ipv6 before any further processing
 *          (even forwarding-related) is done to @p pkt.
 *
 * @param[in] pkt       An IPv6 packet in receive order. It assumed that
 *                      gnrc_pktsnip_t::data points to a hop-by-hop option when
 *                      @p nh points to value equal to
 *                      @ref PROTNUM_IPV6_EXT_HOPOPT.
 * @param[in,out] nh    **In:** The @ref net_protnum of gnrc_pktsnip_t::data of
 *                      @p pkt. <br />
 *                      **Out:** If @p nh was @ref PROTNUM_IPV6_EXT_HOPOPT on in
 *                      and the return value is not NULL it points to the value
 *                      of the next header field of the processed hop-by-hop
 *                      option header. Since the hop-by-hop option header is now
 *                      marked, gnrc_pktsnip_t::data of @p pkt will then be
 *                      identified by @p nh. <br />
 *                      If @p nh was @ref PROTNUM_IPV6_EXT_HOPOPT on in and the
 *                      return value is NULL the value @p nh is pointing to is
 *                      undefined. <br />
 *                      If @p nh unequal to @ref PROTNUM_IPV6_EXT_HOPOPT on in
 *                      the value @p nh is pointing to remains unchanged.
 *
 * @return  @p pkt with the hop-by-hop option marked on success.
 * @return  NULL, if the packet was consumed by the option handling.
 * @return  NULL, on error. @p pkt is released with EINVAL in that case.
 */
gnrc_pktsnip_t *gnrc_ipv6_ext_process_hopopt(gnrc_pktsnip_t *pkt,
                                             uint8_t *nh);

/**
 * @brief   Processes a packet's extension headers after a potential initial
 *          hop-by-hop header.
 *
 * @note    Should be called by @ref net_gnrc_ipv6 after @ref
 *          gnrc_ipv6_ext_process_hopopt(), i.e. the (first) hop-by-hop option
 *          should already be marked in @p pkt. If a hop-by-hop option is found
 *          in gnrc_pktsnip_t::data of @p pkt, the function will return an
 *          error.
 *
 * @param[in] pkt       An IPv6 packet in receive order.
 * @param[in,out] nh    **In:** The @ref net_protnum of gnrc_pktsnip_t::data of
 *                      @p pkt (i.e. the first extension header to be
 *                      processed). <br />
 *                      **Out:** The @ref net_protnum of header in
 *                      gnrc_pktsnip_t::data of @p pkt. The extension headers
 *                      are now marked, so their data can be found in
 *                      gnrc_pktsnip_t::next of @p pkt and the following. <br />
 *                      If the return value is NULL, the value of @p nh is
 *                      undefined.
 *
 * @return  @p pkt with all extension headers marked until the first
 *          non-extension header.
 * @return  NULL, if packet was consumed by the extension header handling.
 * @return  NULL, on error (including if one of the extension headers was a
 *          hop-by-hop option). @p pkt is released with EINVAL in that case.
 */
gnrc_pktsnip_t *gnrc_ipv6_ext_process_all(gnrc_pktsnip_t *pkt,
                                          uint8_t *nh);
#else   /* defined(MODULE_GNRC_IPV6_EXT) || defined(DOXYGEN) */
/* NOPs to make the usage code more readable */
#define gnrc_ipv6_ext_process_hopopt(pkt, nh)   (pkt);
#define gnrc_ipv6_ext_process_all(pkt, nh)      (pkt);
#endif  /* defined(MODULE_GNRC_IPV6_EXT) || defined(DOXYGEN) */

#ifdef __cplusplus
}
#endif

#endif /* NET_GNRC_IPV6_EXT_H */
/**
 * @}
 */