/**
 * @file
 *
 * IPv6 version of ICMP, as per RFC 4443.
 */

/*
 * Copyright (c) 2010 Inico Technologies Ltd.
 * 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. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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 lwIP TCP/IP stack.
 *
 * Author: Ivan Delamer <delamer@inicotech.com>
 *
 *
 * Please coordinate changes and requests with Ivan Delamer
 * <delamer@inicotech.com>
 */

#include "lwip/opt.h"

#if LWIP_ICMP6 && LWIP_IPV6 /* don't build if not configured for use in lwipopts.h */

#include "lwip/icmp6.h"
#include "lwip/prot/icmp6.h"
#include "lwip/ip6.h"
#include "lwip/ip6_addr.h"
#include "lwip/inet_chksum.h"
#include "lwip/pbuf.h"
#include "lwip/netif.h"
#include "lwip/nd6.h"
#include "lwip/mld6.h"
#include "lwip/ip.h"
#include "lwip/stats.h"

#include <string.h>

#if !LWIP_ICMP6_DATASIZE || (LWIP_ICMP6_DATASIZE > (IP6_MIN_MTU_LENGTH - IP6_HLEN - ICMP6_HLEN))
#undef LWIP_ICMP6_DATASIZE
#define LWIP_ICMP6_DATASIZE   (IP6_MIN_MTU_LENGTH - IP6_HLEN - ICMP6_HLEN)
#endif

/* Forward declarations */
static void icmp6_send_response(struct pbuf *p, u8_t code, u32_t data, u8_t type);
static void icmp6_send_response_with_addrs(struct pbuf *p, u8_t code, u32_t data,
    u8_t type, const ip6_addr_t *src_addr, const ip6_addr_t *dest_addr);
static void icmp6_send_response_with_addrs_and_netif(struct pbuf *p, u8_t code, u32_t data,
    u8_t type, const ip6_addr_t *src_addr, const ip6_addr_t *dest_addr, struct netif *netif);


/**
 * Process an input ICMPv6 message. Called by ip6_input.
 *
 * Will generate a reply for echo requests. Other messages are forwarded
 * to nd6_input, or mld6_input.
 *
 * @param p the mld packet, p->payload pointing to the icmpv6 header
 * @param inp the netif on which this packet was received
 */
void
icmp6_input(struct pbuf *p, struct netif *inp)
{
  struct icmp6_hdr *icmp6hdr;
  struct pbuf *r;
  const ip6_addr_t *reply_src;

  ICMP6_STATS_INC(icmp6.recv);

  /* Check that ICMPv6 header fits in payload */
  if (p->len < sizeof(struct icmp6_hdr)) {
    /* drop short packets */
    pbuf_free(p);
    ICMP6_STATS_INC(icmp6.lenerr);
    ICMP6_STATS_INC(icmp6.drop);
    return;
  }

  icmp6hdr = (struct icmp6_hdr *)p->payload;

#if CHECKSUM_CHECK_ICMP6
  IF__NETIF_CHECKSUM_ENABLED(inp, NETIF_CHECKSUM_CHECK_ICMP6) {
    if (ip6_chksum_pseudo(p, IP6_NEXTH_ICMP6, p->tot_len, ip6_current_src_addr(),
                          ip6_current_dest_addr()) != 0) {
      /* Checksum failed */
      pbuf_free(p);
      ICMP6_STATS_INC(icmp6.chkerr);
      ICMP6_STATS_INC(icmp6.drop);
      return;
    }
  }
#endif /* CHECKSUM_CHECK_ICMP6 */

  switch (icmp6hdr->type) {
  case ICMP6_TYPE_NA: /* Neighbor advertisement */
  case ICMP6_TYPE_NS: /* Neighbor solicitation */
  case ICMP6_TYPE_RA: /* Router advertisement */
  case ICMP6_TYPE_RD: /* Redirect */
  case ICMP6_TYPE_PTB: /* Packet too big */
    nd6_input(p, inp);
    return;
  case ICMP6_TYPE_RS:
#if LWIP_IPV6_FORWARD
    /* @todo implement router functionality */
#endif
    break;
#if LWIP_IPV6_MLD
  case ICMP6_TYPE_MLQ:
  case ICMP6_TYPE_MLR:
  case ICMP6_TYPE_MLD:
    mld6_input(p, inp);
    return;
#endif
  case ICMP6_TYPE_EREQ:
#if !LWIP_MULTICAST_PING
    /* multicast destination address? */
    if (ip6_addr_ismulticast(ip6_current_dest_addr())) {
      /* drop */
      pbuf_free(p);
      ICMP6_STATS_INC(icmp6.drop);
      return;
    }
#endif /* LWIP_MULTICAST_PING */

    /* Allocate reply. */
    r = pbuf_alloc(PBUF_IP, p->tot_len, PBUF_RAM);
    if (r == NULL) {
      /* drop */
      pbuf_free(p);
      ICMP6_STATS_INC(icmp6.memerr);
      return;
    }

    /* Copy echo request. */
    if (pbuf_copy(r, p) != ERR_OK) {
      /* drop */
      pbuf_free(p);
      pbuf_free(r);
      ICMP6_STATS_INC(icmp6.err);
      return;
    }

    /* Determine reply source IPv6 address. */
#if LWIP_MULTICAST_PING
    if (ip6_addr_ismulticast(ip6_current_dest_addr())) {
      reply_src = ip_2_ip6(ip6_select_source_address(inp, ip6_current_src_addr()));
      if (reply_src == NULL) {
        /* drop */
        pbuf_free(p);
        pbuf_free(r);
        ICMP6_STATS_INC(icmp6.rterr);
        return;
      }
    }
    else
#endif /* LWIP_MULTICAST_PING */
    {
      reply_src = ip6_current_dest_addr();
    }

    /* Set fields in reply. */
    ((struct icmp6_echo_hdr *)(r->payload))->type = ICMP6_TYPE_EREP;
    ((struct icmp6_echo_hdr *)(r->payload))->chksum = 0;
#if CHECKSUM_GEN_ICMP6
    IF__NETIF_CHECKSUM_ENABLED(inp, NETIF_CHECKSUM_GEN_ICMP6) {
      ((struct icmp6_echo_hdr *)(r->payload))->chksum = ip6_chksum_pseudo(r,
          IP6_NEXTH_ICMP6, r->tot_len, reply_src, ip6_current_src_addr());
    }
#endif /* CHECKSUM_GEN_ICMP6 */

    /* Send reply. */
    ICMP6_STATS_INC(icmp6.xmit);
    ip6_output_if(r, reply_src, ip6_current_src_addr(),
        LWIP_ICMP6_HL, 0, IP6_NEXTH_ICMP6, inp);
    pbuf_free(r);

    break;
  default:
    ICMP6_STATS_INC(icmp6.proterr);
    ICMP6_STATS_INC(icmp6.drop);
    break;
  }

  pbuf_free(p);
}


/**
 * Send an icmpv6 'destination unreachable' packet.
 *
 * This function must be used only in direct response to a packet that is being
 * received right now. Otherwise, address zones would be lost.
 *
 * @param p the input packet for which the 'unreachable' should be sent,
 *          p->payload pointing to the IPv6 header
 * @param c ICMPv6 code for the unreachable type
 */
void
icmp6_dest_unreach(struct pbuf *p, enum icmp6_dur_code c)
{
  icmp6_send_response(p, c, 0, ICMP6_TYPE_DUR);
}

/**
 * Send an icmpv6 'packet too big' packet.
 *
 * This function must be used only in direct response to a packet that is being
 * received right now. Otherwise, address zones would be lost.
 *
 * @param p the input packet for which the 'packet too big' should be sent,
 *          p->payload pointing to the IPv6 header
 * @param mtu the maximum mtu that we can accept
 */
void
icmp6_packet_too_big(struct pbuf *p, u32_t mtu)
{
  icmp6_send_response(p, 0, mtu, ICMP6_TYPE_PTB);
}

/**
 * Send an icmpv6 'time exceeded' packet.
 *
 * This function must be used only in direct response to a packet that is being
 * received right now. Otherwise, address zones would be lost.
 *
 * @param p the input packet for which the 'time exceeded' should be sent,
 *          p->payload pointing to the IPv6 header
 * @param c ICMPv6 code for the time exceeded type
 */
void
icmp6_time_exceeded(struct pbuf *p, enum icmp6_te_code c)
{
  icmp6_send_response(p, c, 0, ICMP6_TYPE_TE);
}

/**
 * Send an icmpv6 'time exceeded' packet, with explicit source and destination
 * addresses.
 *
 * This function may be used to send a response sometime after receiving the
 * packet for which this response is meant. The provided source and destination
 * addresses are used primarily to retain their zone information.
 *
 * @param p the input packet for which the 'time exceeded' should be sent,
 *          p->payload pointing to the IPv6 header
 * @param c ICMPv6 code for the time exceeded type
 * @param src_addr source address of the original packet, with zone information
 * @param dest_addr destination address of the original packet, with zone
 *                  information
 */
void
icmp6_time_exceeded_with_addrs(struct pbuf *p, enum icmp6_te_code c,
    const ip6_addr_t *src_addr, const ip6_addr_t *dest_addr)
{
  icmp6_send_response_with_addrs(p, c, 0, ICMP6_TYPE_TE, src_addr, dest_addr);
}

/**
 * Send an icmpv6 'parameter problem' packet.
 *
 * This function must be used only in direct response to a packet that is being
 * received right now. Otherwise, address zones would be lost and the calculated
 * offset would be wrong (calculated against ip6_current_header()).
 *
 * @param p the input packet for which the 'param problem' should be sent,
 *          p->payload pointing to the IP header
 * @param c ICMPv6 code for the param problem type
 * @param pointer the pointer to the byte where the parameter is found
 */
void
icmp6_param_problem(struct pbuf *p, enum icmp6_pp_code c, const void *pointer)
{
  u32_t pointer_u32 = (u32_t)((const u8_t *)pointer - (const u8_t *)ip6_current_header());
  icmp6_send_response(p, c, pointer_u32, ICMP6_TYPE_PP);
}

/**
 * Send an ICMPv6 packet in response to an incoming packet.
 * The packet is sent *to* ip_current_src_addr() on ip_current_netif().
 *
 * @param p the input packet for which the response should be sent,
 *          p->payload pointing to the IPv6 header
 * @param code Code of the ICMPv6 header
 * @param data Additional 32-bit parameter in the ICMPv6 header
 * @param type Type of the ICMPv6 header
 */
static void
icmp6_send_response(struct pbuf *p, u8_t code, u32_t data, u8_t type)
{
  const struct ip6_addr *reply_src, *reply_dest;
  struct netif *netif = ip_current_netif();

  LWIP_ASSERT("icmpv6 packet not a direct response", netif != NULL);
  reply_dest = ip6_current_src_addr();

  /* Select an address to use as source. */
  reply_src = ip_2_ip6(ip6_select_source_address(netif, reply_dest));
  if (reply_src == NULL) {
    ICMP6_STATS_INC(icmp6.rterr);
    return;
  }
  icmp6_send_response_with_addrs_and_netif(p, code, data, type, reply_src, reply_dest, netif);
}

/**
 * Send an ICMPv6 packet in response to an incoming packet.
 *
 * Call this function if the packet is NOT sent as a direct response to an
 * incoming packet, but rather sometime later (e.g. for a fragment reassembly
 * timeout). The caller must provide the zoned source and destination addresses
 * from the original packet with the src_addr and dest_addr parameters. The
 * reason for this approach is that while the addresses themselves are part of
 * the original packet, their zone information is not, thus possibly resulting
 * in a link-local response being sent over the wrong link.
 *
 * @param p the input packet for which the response should be sent,
 *          p->payload pointing to the IPv6 header
 * @param code Code of the ICMPv6 header
 * @param data Additional 32-bit parameter in the ICMPv6 header
 * @param type Type of the ICMPv6 header
 * @param src_addr original source address
 * @param dest_addr original destination address
 */
static void
icmp6_send_response_with_addrs(struct pbuf *p, u8_t code, u32_t data, u8_t type,
    const ip6_addr_t *src_addr, const ip6_addr_t *dest_addr)
{
  const struct ip6_addr *reply_src, *reply_dest;
  struct netif *netif;

  /* Get the destination address and netif for this ICMP message. */
  LWIP_ASSERT("must provide both source and destination", src_addr != NULL);
  LWIP_ASSERT("must provide both source and destination", dest_addr != NULL);

  /* Special case, as ip6_current_xxx is either NULL, or points
     to a different packet than the one that expired. */
  IP6_ADDR_ZONECHECK(src_addr);
  IP6_ADDR_ZONECHECK(dest_addr);
  /* Swap source and destination for the reply. */
  reply_dest = src_addr;
  reply_src = dest_addr;
  netif = ip6_route(reply_src, reply_dest);
  if (netif == NULL) {
    ICMP6_STATS_INC(icmp6.rterr);
    return;
  }
  icmp6_send_response_with_addrs_and_netif(p, code, data, type, reply_src,
    reply_dest, netif);
}

/**
 * Send an ICMPv6 packet (with srd/dst address and netif given).
 *
 * @param p the input packet for which the response should be sent,
 *          p->payload pointing to the IPv6 header
 * @param code Code of the ICMPv6 header
 * @param data Additional 32-bit parameter in the ICMPv6 header
 * @param type Type of the ICMPv6 header
 * @param reply_src source address of the packet to send
 * @param reply_dest destination address of the packet to send
 * @param netif netif to send the packet
 */
static void
icmp6_send_response_with_addrs_and_netif(struct pbuf *p, u8_t code, u32_t data, u8_t type,
    const ip6_addr_t *reply_src, const ip6_addr_t *reply_dest, struct netif *netif)
{
  struct pbuf *q;
  struct icmp6_hdr *icmp6hdr;
  u16_t datalen = LWIP_MIN(p->tot_len, LWIP_ICMP6_DATASIZE);

  /* ICMPv6 header + datalen (as much of the offending packet as possible) */
  q = pbuf_alloc(PBUF_IP, sizeof(struct icmp6_hdr) + datalen,
                 PBUF_RAM);
  if (q == NULL) {
    LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded: failed to allocate pbuf for ICMPv6 packet.\n"));
    ICMP6_STATS_INC(icmp6.memerr);
    return;
  }
  LWIP_ASSERT("check that first pbuf can hold icmp6 header",
             (q->len >= (sizeof(struct icmp6_hdr))));

  icmp6hdr = (struct icmp6_hdr *)q->payload;
  icmp6hdr->type = type;
  icmp6hdr->code = code;
  icmp6hdr->data = lwip_htonl(data);

  /* copy fields from original packet */
  pbuf_copy_partial_pbuf(q, p, datalen, sizeof(struct icmp6_hdr));

  /* calculate checksum */
  icmp6hdr->chksum = 0;
#if CHECKSUM_GEN_ICMP6
  IF__NETIF_CHECKSUM_ENABLED(netif, NETIF_CHECKSUM_GEN_ICMP6) {
    icmp6hdr->chksum = ip6_chksum_pseudo(q, IP6_NEXTH_ICMP6, q->tot_len,
      reply_src, reply_dest);
  }
#endif /* CHECKSUM_GEN_ICMP6 */

  ICMP6_STATS_INC(icmp6.xmit);
  ip6_output_if(q, reply_src, reply_dest, LWIP_ICMP6_HL, 0, IP6_NEXTH_ICMP6, netif);
  pbuf_free(q);
}

#endif /* LWIP_ICMP6 && LWIP_IPV6 */