text: /**
   * @file
   *
   * IPv6 layer.
   */
  
  /*
   * 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_IPV6  /* don't build if not configured for use in lwipopts.h */
  
  #include "lwip/def.h"
  #include "lwip/mem.h"
  #include "lwip/netif.h"
  #include "lwip/ip.h"
  #include "lwip/ip6.h"
  #include "lwip/ip6_addr.h"
  #include "lwip/ip6_frag.h"
  #include "lwip/icmp6.h"
  #include "lwip/priv/raw_priv.h"
  #include "lwip/udp.h"
  #include "lwip/priv/tcp_priv.h"
  #include "lwip/dhcp6.h"
  #include "lwip/nd6.h"
  #include "lwip/mld6.h"
  #include "lwip/debug.h"
  #include "lwip/stats.h"
  
  #ifdef LWIP_HOOK_FILENAME
  #include LWIP_HOOK_FILENAME
  #endif
  
  /**
   * Finds the appropriate network interface for a given IPv6 address. It tries to select
   * a netif following a sequence of heuristics:
   * 1) if there is only 1 netif, return it
   * 2) if the destination is a zoned address, match its zone to a netif
   * 3) if the either the source or destination address is a scoped address,
   *    match the source address's zone (if set) or address (if not) to a netif
   * 4) tries to match the destination subnet to a configured address
   * 5) tries to find a router-announced route
   * 6) tries to match the (unscoped) source address to the netif
   * 7) returns the default netif, if configured
   *
   * Note that each of the two given addresses may or may not be properly zoned.
   *
   * @param src the source IPv6 address, if known
   * @param dest the destination IPv6 address for which to find the route
   * @return the netif on which to send to reach dest
   */
  struct netif *
  ip6_route(const ip6_addr_t *src, const ip6_addr_t *dest)
  {
  #if LWIP_SINGLE_NETIF
    LWIP_UNUSED_ARG(src);
    LWIP_UNUSED_ARG(dest);
  #else /* LWIP_SINGLE_NETIF */
    struct netif *netif;
    s8_t i;
  
    LWIP_ASSERT_CORE_LOCKED();
  
    /* If single netif configuration, fast return. */
    if ((netif_list != NULL) && (netif_list->next == NULL)) {
      if (!netif_is_up(netif_list) || !netif_is_link_up(netif_list) ||
          (ip6_addr_has_zone(dest) && !ip6_addr_test_zone(dest, netif_list))) {
        return NULL;
      }
      return netif_list;
    }
  
  #if LWIP_IPV6_SCOPES
    /* Special processing for zoned destination addresses. This includes link-
     * local unicast addresses and interface/link-local multicast addresses. Use
     * the zone to find a matching netif. If the address is not zoned, then there
     * is technically no "wrong" netif to choose, and we leave routing to other
     * rules; in most cases this should be the scoped-source rule below. */
    if (ip6_addr_has_zone(dest)) {
      IP6_ADDR_ZONECHECK(dest);
      /* Find a netif based on the zone. For custom mappings, one zone may map
       * to multiple netifs, so find one that can actually send a packet. */
      NETIF_FOREACH(netif) {
        if (ip6_addr_test_zone(dest, netif) &&
            netif_is_up(netif) && netif_is_link_up(netif)) {
          return netif;
        }
      }
      /* No matching netif found. Do no try to route to a different netif,
       * as that would be a zone violation, resulting in any packets sent to
       * that netif being dropped on output. */
      return NULL;
    }
  #endif /* LWIP_IPV6_SCOPES */
  
    /* Special processing for scoped source and destination addresses. If we get
     * here, the destination address does not have a zone, so either way we need
     * to look at the source address, which may or may not have a zone. If it
     * does, the zone is restrictive: there is (typically) only one matching
     * netif for it, and we should avoid routing to any other netif as that would
     * result in guaranteed zone violations. For scoped source addresses that do
     * not have a zone, use (only) a netif that has that source address locally
     * assigned. This case also applies to the loopback source address, which has
     * an implied link-local scope. If only the destination address is scoped
     * (but, again, not zoned), we still want to use only the source address to
     * determine its zone because that's most likely what the user/application
     * wants, regardless of whether the source address is scoped. Finally, some
     * of this story also applies if scoping is disabled altogether. */
  #if LWIP_IPV6_SCOPES
    if (ip6_addr_has_scope(dest, IP6_UNKNOWN) ||
        ip6_addr_has_scope(src, IP6_UNICAST) ||
  #else /* LWIP_IPV6_SCOPES */
    if (ip6_addr_islinklocal(dest) || ip6_addr_ismulticast_iflocal(dest) ||
        ip6_addr_ismulticast_linklocal(dest) || ip6_addr_islinklocal(src) ||
  #endif /* LWIP_IPV6_SCOPES */
        ip6_addr_isloopback(src)) {
  #if LWIP_IPV6_SCOPES
      if (ip6_addr_has_zone(src)) {
        /* Find a netif matching the source zone (relatively cheap). */
        NETIF_FOREACH(netif) {
          if (netif_is_up(netif) && netif_is_link_up(netif) &&
              ip6_addr_test_zone(src, netif)) {
            return netif;
          }
        }
      } else
  #endif /* LWIP_IPV6_SCOPES */
      {
        /* Find a netif matching the source address (relatively expensive). */
        NETIF_FOREACH(netif) {
          if (!netif_is_up(netif) || !netif_is_link_up(netif)) {
            continue;
          }
          for (i = 0; i < LWIP_IPV6_NUM_ADDRESSES; i++) {
            if (ip6_addr_isvalid(netif_ip6_addr_state(netif, i)) &&
                ip6_addr_cmp_zoneless(src, netif_ip6_addr(netif, i))) {
              return netif;
            }
          }
        }
      }
      /* Again, do not use any other netif in this case, as that could result in
       * zone boundary violations. */
      return NULL;
    }
  
    /* We come here only if neither source nor destination is scoped. */
    IP6_ADDR_ZONECHECK(src);
  
  #ifdef LWIP_HOOK_IP6_ROUTE
    netif = LWIP_HOOK_IP6_ROUTE(src, dest);
    if (netif != NULL) {
      return netif;
    }
  #endif
  
    /* See if the destination subnet matches a configured address. In accordance
     * with RFC 5942, dynamically configured addresses do not have an implied
     * local subnet, and thus should be considered /128 assignments. However, as
     * such, the destination address may still match a local address, and so we
     * still need to check for exact matches here. By (lwIP) policy, statically
     * configured addresses do always have an implied local /64 subnet. */
    NETIF_FOREACH(netif) {
      if (!netif_is_up(netif) || !netif_is_link_up(netif)) {
        continue;
      }
      for (i = 0; i < LWIP_IPV6_NUM_ADDRESSES; i++) {
        if (ip6_addr_isvalid(netif_ip6_addr_state(netif, i)) &&
            ip6_addr_netcmp(dest, netif_ip6_addr(netif, i)) &&
            (netif_ip6_addr_isstatic(netif, i) ||
            ip6_addr_nethostcmp(dest, netif_ip6_addr(netif, i)))) {
          return netif;
        }
      }
    }
  
    /* Get the netif for a suitable router-announced route. */
    netif = nd6_find_route(dest);
    if (netif != NULL) {
      return netif;
    }
  
    /* Try with the netif that matches the source address. Given the earlier rule
     * for scoped source addresses, this applies to unscoped addresses only. */
    if (!ip6_addr_isany(src)) {
      NETIF_FOREACH(netif) {
        if (!netif_is_up(netif) || !netif_is_link_up(netif)) {
          continue;
        }
        for (i = 0; i < LWIP_IPV6_NUM_ADDRESSES; i++) {
          if (ip6_addr_isvalid(netif_ip6_addr_state(netif, i)) &&
              ip6_addr_cmp(src, netif_ip6_addr(netif, i))) {
            return netif;
          }
        }
      }
    }
  
  #if LWIP_NETIF_LOOPBACK && !LWIP_HAVE_LOOPIF
    /* loopif is disabled, loopback traffic is passed through any netif */
    if (ip6_addr_isloopback(dest)) {
      /* don't check for link on loopback traffic */
      if (netif_default != NULL && netif_is_up(netif_default)) {
        return netif_default;
      }
      /* default netif is not up, just use any netif for loopback traffic */
      NETIF_FOREACH(netif) {
        if (netif_is_up(netif)) {
          return netif;
        }
      }
      return NULL;
    }
  #endif /* LWIP_NETIF_LOOPBACK && !LWIP_HAVE_LOOPIF */
  #endif /* !LWIP_SINGLE_NETIF */
  
    /* no matching netif found, use default netif, if up */
    if ((netif_default == NULL) || !netif_is_up(netif_default) || !netif_is_link_up(netif_default)) {
      return NULL;
    }
    return netif_default;
  }
  
  /**
   * @ingroup ip6
   * Select the best IPv6 source address for a given destination IPv6 address.
   *
   * This implementation follows RFC 6724 Sec. 5 to the following extent:
   * - Rules 1, 2, 3: fully implemented
   * - Rules 4, 5, 5.5: not applicable
   * - Rule 6: not implemented
   * - Rule 7: not applicable
   * - Rule 8: limited to "prefer /64 subnet match over non-match"
   *
   * For Rule 2, we deliberately deviate from RFC 6724 Sec. 3.1 by considering
   * ULAs to be of smaller scope than global addresses, to avoid that a preferred
   * ULA is picked over a deprecated global address when given a global address
   * as destination, as that would likely result in broken two-way communication.
   *
   * As long as temporary addresses are not supported (as used in Rule 7), a
   * proper implementation of Rule 8 would obviate the need to implement Rule 6.
   *
   * @param netif the netif on which to send a packet
   * @param dest the destination we are trying to reach (possibly not properly
   *             zoned)
   * @return the most suitable source address to use, or NULL if no suitable
   *         source address is found
   */
  const ip_addr_t *
  ip6_select_source_address(struct netif *netif, const ip6_addr_t *dest)
  {
    const ip_addr_t *best_addr;
    const ip6_addr_t *cand_addr;
    s8_t dest_scope, cand_scope;
    s8_t best_scope = IP6_MULTICAST_SCOPE_RESERVED;
    u8_t i, cand_pref, cand_bits;
    u8_t best_pref = 0;
    u8_t best_bits = 0;
  
    /* Start by determining the scope of the given destination address. These
     * tests are hopefully (roughly) in order of likeliness to match. */
    if (ip6_addr_isglobal(dest)) {
      dest_scope = IP6_MULTICAST_SCOPE_GLOBAL;
    } else if (ip6_addr_islinklocal(dest) || ip6_addr_isloopback(dest)) {
      dest_scope = IP6_MULTICAST_SCOPE_LINK_LOCAL;
    } else if (ip6_addr_isuniquelocal(dest)) {
      dest_scope = IP6_MULTICAST_SCOPE_ORGANIZATION_LOCAL;
    } else if (ip6_addr_ismulticast(dest)) {
      dest_scope = ip6_addr_multicast_scope(dest);
    } else if (ip6_addr_issitelocal(dest)) {
      dest_scope = IP6_MULTICAST_SCOPE_SITE_LOCAL;
    } else {
      /* no match, consider scope global */
      dest_scope = IP6_MULTICAST_SCOPE_GLOBAL;
    }
  
    best_addr = NULL;
  
    for (i = 0; i < LWIP_IPV6_NUM_ADDRESSES; i++) {
      /* Consider only valid (= preferred and deprecated) addresses. */
      if (!ip6_addr_isvalid(netif_ip6_addr_state(netif, i))) {
        continue;
      }
      /* Determine the scope of this candidate address. Same ordering idea. */
      cand_addr = netif_ip6_addr(netif, i);
      if (ip6_addr_isglobal(cand_addr)) {
        cand_scope = IP6_MULTICAST_SCOPE_GLOBAL;
      } else if (ip6_addr_islinklocal(cand_addr)) {
        cand_scope = IP6_MULTICAST_SCOPE_LINK_LOCAL;
      } else if (ip6_addr_isuniquelocal(cand_addr)) {
        cand_scope = IP6_MULTICAST_SCOPE_ORGANIZATION_LOCAL;
      } else if (ip6_addr_issitelocal(cand_addr)) {
        cand_scope = IP6_MULTICAST_SCOPE_SITE_LOCAL;
      } else {
        /* no match, treat as low-priority global scope */
        cand_scope = IP6_MULTICAST_SCOPE_RESERVEDF;
      }
      cand_pref = ip6_addr_ispreferred(netif_ip6_addr_state(netif, i));
      /* @todo compute the actual common bits, for longest matching prefix. */
      /* We cannot count on the destination address having a proper zone
       * assignment, so do not compare zones in this case. */
      cand_bits = ip6_addr_netcmp_zoneless(cand_addr, dest); /* just 1 or 0 for now */
      if (cand_bits && ip6_addr_nethostcmp(cand_addr, dest)) {
        return netif_ip_addr6(netif, i); /* Rule 1 */
      }
      if ((best_addr == NULL) || /* no alternative yet */
          ((cand_scope < best_scope) && (cand_scope >= dest_scope)) ||
          ((cand_scope > best_scope) && (best_scope < dest_scope)) || /* Rule 2 */
          ((cand_scope == best_scope) && ((cand_pref > best_pref) || /* Rule 3 */
          ((cand_pref == best_pref) && (cand_bits > best_bits))))) { /* Rule 8 */
        /* We found a new "winning" candidate. */
        best_addr = netif_ip_addr6(netif, i);
        best_scope = cand_scope;
        best_pref = cand_pref;
        best_bits = cand_bits;
      }
    }
  
    return best_addr; /* may be NULL */
  }
  
  #if LWIP_IPV6_FORWARD
  /**
   * Forwards an IPv6 packet. It finds an appropriate route for the
   * packet, decrements the HL value of the packet, and outputs
   * the packet on the appropriate interface.
   *
   * @param p the packet to forward (p->payload points to IP header)
   * @param iphdr the IPv6 header of the input packet
   * @param inp the netif on which this packet was received
   */
  static void
  ip6_forward(struct pbuf *p, struct ip6_hdr *iphdr, struct netif *inp)
  {
    struct netif *netif;
  
    /* do not forward link-local or loopback addresses */
    if (ip6_addr_islinklocal(ip6_current_dest_addr()) ||
        ip6_addr_isloopback(ip6_current_dest_addr())) {
      LWIP_DEBUGF(IP6_DEBUG, ("ip6_forward: not forwarding link-local address.\n"));
      IP6_STATS_INC(ip6.rterr);
      IP6_STATS_INC(ip6.drop);
      return;
    }
  
    /* Find network interface where to forward this IP packet to. */
    netif = ip6_route(IP6_ADDR_ANY6, ip6_current_dest_addr());
    if (netif == NULL) {
      LWIP_DEBUGF(IP6_DEBUG, ("ip6_forward: no route for %"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F"\n",
          IP6_ADDR_BLOCK1(ip6_current_dest_addr()),
          IP6_ADDR_BLOCK2(ip6_current_dest_addr()),
          IP6_ADDR_BLOCK3(ip6_current_dest_addr()),
          IP6_ADDR_BLOCK4(ip6_current_dest_addr()),
          IP6_ADDR_BLOCK5(ip6_current_dest_addr()),
          IP6_ADDR_BLOCK6(ip6_current_dest_addr()),
          IP6_ADDR_BLOCK7(ip6_current_dest_addr()),
          IP6_ADDR_BLOCK8(ip6_current_dest_addr())));
  #if LWIP_ICMP6
      /* Don't send ICMP messages in response to ICMP messages */
      if (IP6H_NEXTH(iphdr) != IP6_NEXTH_ICMP6) {
        icmp6_dest_unreach(p, ICMP6_DUR_NO_ROUTE);
      }
  #endif /* LWIP_ICMP6 */
      IP6_STATS_INC(ip6.rterr);
      IP6_STATS_INC(ip6.drop);
      return;
    }
  #if LWIP_IPV6_SCOPES
    /* Do not forward packets with a zoned (e.g., link-local) source address
     * outside of their zone. We determined the zone a bit earlier, so we know
     * that the address is properly zoned here, so we can safely use has_zone.
     * Also skip packets with a loopback source address (link-local implied). */
    if ((ip6_addr_has_zone(ip6_current_src_addr()) &&
        !ip6_addr_test_zone(ip6_current_src_addr(), netif)) ||
        ip6_addr_isloopback(ip6_current_src_addr())) {
      LWIP_DEBUGF(IP6_DEBUG, ("ip6_forward: not forwarding packet beyond its source address zone.\n"));
      IP6_STATS_INC(ip6.rterr);
      IP6_STATS_INC(ip6.drop);
      return;
    }
  #endif /* LWIP_IPV6_SCOPES */
    /* Do not forward packets onto the same network interface on which
     * they arrived. */
    if (netif == inp) {
      LWIP_DEBUGF(IP6_DEBUG, ("ip6_forward: not bouncing packets back on incoming interface.\n"));
      IP6_STATS_INC(ip6.rterr);
      IP6_STATS_INC(ip6.drop);
      return;
    }
  
    /* decrement HL */
    IP6H_HOPLIM_SET(iphdr, IP6H_HOPLIM(iphdr) - 1);
    /* send ICMP6 if HL == 0 */
    if (IP6H_HOPLIM(iphdr) == 0) {
  #if LWIP_ICMP6
      /* Don't send ICMP messages in response to ICMP messages */
      if (IP6H_NEXTH(iphdr) != IP6_NEXTH_ICMP6) {
        icmp6_time_exceeded(p, ICMP6_TE_HL);
      }
  #endif /* LWIP_ICMP6 */
      IP6_STATS_INC(ip6.drop);
      return;
    }
  
    if (netif->mtu && (p->tot_len > netif->mtu)) {
  #if LWIP_ICMP6
      /* Don't send ICMP messages in response to ICMP messages */
      if (IP6H_NEXTH(iphdr) != IP6_NEXTH_ICMP6) {
        icmp6_packet_too_big(p, netif->mtu);
      }
  #endif /* LWIP_ICMP6 */
      IP6_STATS_INC(ip6.drop);
      return;
    }
  
    LWIP_DEBUGF(IP6_DEBUG, ("ip6_forward: forwarding packet to %"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F"\n",
        IP6_ADDR_BLOCK1(ip6_current_dest_addr()),
        IP6_ADDR_BLOCK2(ip6_current_dest_addr()),
        IP6_ADDR_BLOCK3(ip6_current_dest_addr()),
        IP6_ADDR_BLOCK4(ip6_current_dest_addr()),
        IP6_ADDR_BLOCK5(ip6_current_dest_addr()),
        IP6_ADDR_BLOCK6(ip6_current_dest_addr()),
        IP6_ADDR_BLOCK7(ip6_current_dest_addr()),
        IP6_ADDR_BLOCK8(ip6_current_dest_addr())));
  
    /* transmit pbuf on chosen interface */
    netif->output_ip6(netif, p, ip6_current_dest_addr());
    IP6_STATS_INC(ip6.fw);
    IP6_STATS_INC(ip6.xmit);
    return;
  }
  #endif /* LWIP_IPV6_FORWARD */
  
  /** Return true if the current input packet should be accepted on this netif */
  static int
  ip6_input_accept(struct netif *netif)
  {
    /* interface is up? */
    if (netif_is_up(netif)) {
      u8_t i;
      /* unicast to this interface address? address configured? */
      /* If custom scopes are used, the destination zone will be tested as
        * part of the local-address comparison, but we need to test the source
        * scope as well (e.g., is this interface on the same link?). */
      for (i = 0; i < LWIP_IPV6_NUM_ADDRESSES; i++) {
        if (ip6_addr_isvalid(netif_ip6_addr_state(netif, i)) &&
            ip6_addr_cmp(ip6_current_dest_addr(), netif_ip6_addr(netif, i))
  #if IPV6_CUSTOM_SCOPES
            && (!ip6_addr_has_zone(ip6_current_src_addr()) ||
                ip6_addr_test_zone(ip6_current_src_addr(), netif))
  #endif /* IPV6_CUSTOM_SCOPES */
        ) {
          /* accept on this netif */
          return 1;
        }
      }
    }
    return 0;
  }
  
  /**
   * This function is called by the network interface device driver when
   * an IPv6 packet is received. The function does the basic checks of the
   * IP header such as packet size being at least larger than the header
   * size etc. If the packet was not destined for us, the packet is
   * forwarded (using ip6_forward).
   *
   * Finally, the packet is sent to the upper layer protocol input function.
   *
   * @param p the received IPv6 packet (p->payload points to IPv6 header)
   * @param inp the netif on which this packet was received
   * @return ERR_OK if the packet was processed (could return ERR_* if it wasn't
   *         processed, but currently always returns ERR_OK)
   */
  err_t
  ip6_input(struct pbuf *p, struct netif *inp)
  {
    struct ip6_hdr *ip6hdr;
    struct netif *netif;
    const u8_t *nexth;
    u16_t hlen, hlen_tot; /* the current header length */
  #if 0 /*IP_ACCEPT_LINK_LAYER_ADDRESSING*/
    @todo
    int check_ip_src=1;
  #endif /* IP_ACCEPT_LINK_LAYER_ADDRESSING */
  #if LWIP_RAW
    raw_input_state_t raw_status;
  #endif /* LWIP_RAW */
  
    LWIP_ASSERT_CORE_LOCKED();
  
    IP6_STATS_INC(ip6.recv);
  
    /* identify the IP header */
    ip6hdr = (struct ip6_hdr *)p->payload;
    if (IP6H_V(ip6hdr) != 6) {
      LWIP_DEBUGF(IP6_DEBUG | LWIP_DBG_LEVEL_WARNING, ("IPv6 packet dropped due to bad version number %"U32_F"\n",
          IP6H_V(ip6hdr)));
      pbuf_free(p);
      IP6_STATS_INC(ip6.err);
      IP6_STATS_INC(ip6.drop);
      return ERR_OK;
    }
  
  #ifdef LWIP_HOOK_IP6_INPUT
    if (LWIP_HOOK_IP6_INPUT(p, inp)) {
      /* the packet has been eaten */
      return ERR_OK;
    }
  #endif
  
    /* header length exceeds first pbuf length, or ip length exceeds total pbuf length? */
    if ((IP6_HLEN > p->len) || (IP6H_PLEN(ip6hdr) > (p->tot_len - IP6_HLEN))) {
      if (IP6_HLEN > p->len) {
        LWIP_DEBUGF(IP6_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
          ("IPv6 header (len %"U16_F") does not fit in first pbuf (len %"U16_F"), IP packet dropped.\n",
              (u16_t)IP6_HLEN, p->len));
      }
      if ((IP6H_PLEN(ip6hdr) + IP6_HLEN) > p->tot_len) {
        LWIP_DEBUGF(IP6_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
          ("IPv6 (plen %"U16_F") is longer than pbuf (len %"U16_F"), IP packet dropped.\n",
              (u16_t)(IP6H_PLEN(ip6hdr) + IP6_HLEN), p->tot_len));
      }
      /* free (drop) packet pbufs */
      pbuf_free(p);
      IP6_STATS_INC(ip6.lenerr);
      IP6_STATS_INC(ip6.drop);
      return ERR_OK;
    }
  
    /* Trim pbuf. This should have been done at the netif layer,
     * but we'll do it anyway just to be sure that its done. */
    pbuf_realloc(p, (u16_t)(IP6_HLEN + IP6H_PLEN(ip6hdr)));
  
    /* copy IP addresses to aligned ip6_addr_t */
    ip_addr_copy_from_ip6_packed(ip_data.current_iphdr_dest, ip6hdr->dest);
    ip_addr_copy_from_ip6_packed(ip_data.current_iphdr_src, ip6hdr->src);
  
    /* Don't accept virtual IPv4 mapped IPv6 addresses.
     * Don't accept multicast source addresses. */
    if (ip6_addr_isipv4mappedipv6(ip_2_ip6(&ip_data.current_iphdr_dest)) ||
       ip6_addr_isipv4mappedipv6(ip_2_ip6(&ip_data.current_iphdr_src)) ||
       ip6_addr_ismulticast(ip_2_ip6(&ip_data.current_iphdr_src))) {
      /* free (drop) packet pbufs */
      pbuf_free(p);
      IP6_STATS_INC(ip6.err);
      IP6_STATS_INC(ip6.drop);
      return ERR_OK;
    }
  
    /* Set the appropriate zone identifier on the addresses. */
    ip6_addr_assign_zone(ip_2_ip6(&ip_data.current_iphdr_dest), IP6_UNKNOWN, inp);
    ip6_addr_assign_zone(ip_2_ip6(&ip_data.current_iphdr_src), IP6_UNICAST, inp);
  
    /* current header pointer. */
    ip_data.current_ip6_header = ip6hdr;
  
    /* In netif, used in case we need to send ICMPv6 packets back. */
    ip_data.current_netif = inp;
    ip_data.current_input_netif = inp;
  
    /* match packet against an interface, i.e. is this packet for us? */
    if (ip6_addr_ismulticast(ip6_current_dest_addr())) {
      /* Always joined to multicast if-local and link-local all-nodes group. */
      if (ip6_addr_isallnodes_iflocal(ip6_current_dest_addr()) ||
          ip6_addr_isallnodes_linklocal(ip6_current_dest_addr())) {
        netif = inp;
      }
  #if LWIP_IPV6_MLD
      else if (mld6_lookfor_group(inp, ip6_current_dest_addr())) {
        netif = inp;
      }
  #else /* LWIP_IPV6_MLD */
      else if (ip6_addr_issolicitednode(ip6_current_dest_addr())) {
        u8_t i;
        /* Filter solicited node packets when MLD is not enabled
         * (for Neighbor discovery). */
        netif = NULL;
        for (i = 0; i < LWIP_IPV6_NUM_ADDRESSES; i++) {
          if (ip6_addr_isvalid(netif_ip6_addr_state(inp, i)) &&
              ip6_addr_cmp_solicitednode(ip6_current_dest_addr(), netif_ip6_addr(inp, i))) {
            netif = inp;
            LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: solicited node packet accepted on interface %c%c\n",
                netif->name[0], netif->name[1]));
            break;
          }
        }
      }
  #endif /* LWIP_IPV6_MLD */
      else {
        netif = NULL;
      }
    } else {
      /* start trying with inp. if that's not acceptable, start walking the
         list of configured netifs. */
      if (ip6_input_accept(inp)) {
        netif = inp;
      } else {
        netif = NULL;
  #if !IPV6_CUSTOM_SCOPES
        /* Shortcut: stop looking for other interfaces if either the source or
          * the destination has a scope constrained to this interface. Custom
          * scopes may break the 1:1 link/interface mapping, however. */
        if (ip6_addr_islinklocal(ip6_current_dest_addr()) ||
            ip6_addr_islinklocal(ip6_current_src_addr())) {
          goto netif_found;
        }
  #endif /* !IPV6_CUSTOM_SCOPES */
  #if !LWIP_NETIF_LOOPBACK || LWIP_HAVE_LOOPIF
        /* The loopback address is to be considered link-local. Packets to it
          * should be dropped on other interfaces, as per RFC 4291 Sec. 2.5.3.
          * Its implied scope means packets *from* the loopback address should
          * not be accepted on other interfaces, either. These requirements
          * cannot be implemented in the case that loopback traffic is sent
          * across a non-loopback interface, however. */
        if (ip6_addr_isloopback(ip6_current_dest_addr()) ||
            ip6_addr_isloopback(ip6_current_src_addr())) {
          goto netif_found;
        }
  #endif /* !LWIP_NETIF_LOOPBACK || LWIP_HAVE_LOOPIF */
  #if !LWIP_SINGLE_NETIF
        NETIF_FOREACH(netif) {
          if (netif == inp) {
            /* we checked that before already */
            continue;
          }
          if (ip6_input_accept(netif)) {
            break;
          }
        }
  #endif /* !LWIP_SINGLE_NETIF */
      }
  netif_found:
      LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: packet accepted on interface %c%c\n",
          netif ? netif->name[0] : 'X', netif? netif->name[1] : 'X'));
    }
  
    /* "::" packet source address? (used in duplicate address detection) */
    if (ip6_addr_isany(ip6_current_src_addr()) &&
        (!ip6_addr_issolicitednode(ip6_current_dest_addr()))) {
      /* packet source is not valid */
      /* free (drop) packet pbufs */
      LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: packet with src ANY_ADDRESS dropped\n"));
      pbuf_free(p);
      IP6_STATS_INC(ip6.drop);
      goto ip6_input_cleanup;
    }
  
    /* packet not for us? */
    if (netif == NULL) {
      /* packet not for us, route or discard */
      LWIP_DEBUGF(IP6_DEBUG | LWIP_DBG_TRACE, ("ip6_input: packet not for us.\n"));
  #if LWIP_IPV6_FORWARD
      /* non-multicast packet? */
      if (!ip6_addr_ismulticast(ip6_current_dest_addr())) {
        /* try to forward IP packet on (other) interfaces */
        ip6_forward(p, ip6hdr, inp);
      }
  #endif /* LWIP_IPV6_FORWARD */
      pbuf_free(p);
      goto ip6_input_cleanup;
    }
  
    /* current netif pointer. */
    ip_data.current_netif = netif;
  
    /* Save next header type. */
    nexth = &IP6H_NEXTH(ip6hdr);
  
    /* Init header length. */
    hlen = hlen_tot = IP6_HLEN;
  
    /* Move to payload. */
    pbuf_remove_header(p, IP6_HLEN);
  
    /* Process known option extension headers, if present. */
    while (*nexth != IP6_NEXTH_NONE)
    {
      switch (*nexth) {
      case IP6_NEXTH_HOPBYHOP:
      {
        s32_t opt_offset;
        struct ip6_hbh_hdr *hbh_hdr;
        struct ip6_opt_hdr *opt_hdr;
        LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: packet with Hop-by-Hop options header\n"));
  
        /* Get and check the header length, while staying in packet bounds. */
        hbh_hdr = (struct ip6_hbh_hdr *)p->payload;
  
        /* Get next header type. */
        nexth = &IP6_HBH_NEXTH(hbh_hdr);
  
        /* Get the header length. */
        hlen = (u16_t)(8 * (1 + hbh_hdr->_hlen));
  
        if ((p->len < 8) || (hlen > p->len)) {
          LWIP_DEBUGF(IP6_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
            ("IPv6 options header (hlen %"U16_F") does not fit in first pbuf (len %"U16_F"), IPv6 packet dropped.\n",
                hlen, p->len));
          /* free (drop) packet pbufs */
          pbuf_free(p);
          IP6_STATS_INC(ip6.lenerr);
          IP6_STATS_INC(ip6.drop);
          goto ip6_input_cleanup;
        }
  
        hlen_tot = (u16_t)(hlen_tot + hlen);
  
        /* The extended option header starts right after Hop-by-Hop header. */
        opt_offset = IP6_HBH_HLEN;
        while (opt_offset < hlen)
        {
          s32_t opt_dlen = 0;
  
          opt_hdr = (struct ip6_opt_hdr *)((u8_t *)hbh_hdr + opt_offset);
  
          switch (IP6_OPT_TYPE(opt_hdr)) {
          /* @todo: process IPV6 Hop-by-Hop option data */
          case IP6_PAD1_OPTION:
            /* PAD1 option doesn't have length and value field */
            opt_dlen = -1;
            break;
          case IP6_PADN_OPTION:
            opt_dlen = IP6_OPT_DLEN(opt_hdr);
            break;
          case IP6_ROUTER_ALERT_OPTION:
            opt_dlen = IP6_OPT_DLEN(opt_hdr);
            break;
          case IP6_JUMBO_OPTION:
            opt_dlen = IP6_OPT_DLEN(opt_hdr);
            break;
          default:
            /* Check 2 MSB of Hop-by-Hop header type. */
            switch (IP6_OPT_TYPE_ACTION(opt_hdr)) {
            case 1:
              /* Discard the packet. */
              LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: packet with invalid Hop-by-Hop option type dropped.\n"));
              pbuf_free(p);
              IP6_STATS_INC(ip6.drop);
              goto ip6_input_cleanup;
            case 2:
              /* Send ICMP Parameter Problem */
              icmp6_param_problem(p, ICMP6_PP_OPTION, opt_hdr);
              LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: packet with invalid Hop-by-Hop option type dropped.\n"));
              pbuf_free(p);
              IP6_STATS_INC(ip6.drop);
              goto ip6_input_cleanup;
            case 3:
              /* Send ICMP Parameter Problem if destination address is not a multicast address */
              if (!ip6_addr_ismulticast(ip6_current_dest_addr())) {
                icmp6_param_problem(p, ICMP6_PP_OPTION, opt_hdr);
              }
              LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: packet with invalid Hop-by-Hop option type dropped.\n"));
              pbuf_free(p);
              IP6_STATS_INC(ip6.drop);
              goto ip6_input_cleanup;
            default:
              /* Skip over this option. */
              opt_dlen = IP6_OPT_DLEN(opt_hdr);
              break;
            }
            break;
          }
  
          /* Adjust the offset to move to the next extended option header */
          opt_offset = opt_offset + IP6_OPT_HLEN + opt_dlen;
        }
        pbuf_remove_header(p, hlen);
        break;
      }
      case IP6_NEXTH_DESTOPTS:
      {
        s32_t opt_offset;
        struct ip6_dest_hdr *dest_hdr;
        struct ip6_opt_hdr *opt_hdr;
        LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: packet with Destination options header\n"));
  
        dest_hdr = (struct ip6_dest_hdr *)p->payload;
  
        /* Get next header type. */
        nexth = &IP6_DEST_NEXTH(dest_hdr);
  
        /* Get the header length. */
        hlen = 8 * (1 + dest_hdr->_hlen);
        if ((p->len < 8) || (hlen > p->len)) {
          LWIP_DEBUGF(IP6_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
            ("IPv6 options header (hlen %"U16_F") does not fit in first pbuf (len %"U16_F"), IPv6 packet dropped.\n",
                hlen, p->len));
          /* free (drop) packet pbufs */
          pbuf_free(p);
          IP6_STATS_INC(ip6.lenerr);
          IP6_STATS_INC(ip6.drop);
          goto ip6_input_cleanup;
        }
  
        hlen_tot = (u16_t)(hlen_tot + hlen);
  
        /* The extended option header starts right after Destination header. */
        opt_offset = IP6_DEST_HLEN;
        while (opt_offset < hlen)
        {
          s32_t opt_dlen = 0;
  
          opt_hdr = (struct ip6_opt_hdr *)((u8_t *)dest_hdr + opt_offset);
  
          switch (IP6_OPT_TYPE(opt_hdr))
          {
          /* @todo: process IPV6 Destination option data */
          case IP6_PAD1_OPTION:
            /* PAD1 option deosn't have length and value field */
            opt_dlen = -1;
            break;
          case IP6_PADN_OPTION:
            opt_dlen = IP6_OPT_DLEN(opt_hdr);
            break;
          case IP6_ROUTER_ALERT_OPTION:
            opt_dlen = IP6_OPT_DLEN(opt_hdr);
            break;
          case IP6_JUMBO_OPTION:
            opt_dlen = IP6_OPT_DLEN(opt_hdr);
            break;
          case IP6_HOME_ADDRESS_OPTION:
            opt_dlen = IP6_OPT_DLEN(opt_hdr);
            break;
          default:
            /* Check 2 MSB of Destination header type. */
            switch (IP6_OPT_TYPE_ACTION(opt_hdr))
            {
            case 1:
              /* Discard the packet. */
              LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: packet with invalid destination option type dropped.\n"));
              pbuf_free(p);
              IP6_STATS_INC(ip6.drop);
              goto ip6_input_cleanup;
            case 2:
              /* Send ICMP Parameter Problem */
              icmp6_param_problem(p, ICMP6_PP_OPTION, opt_hdr);
              LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: packet with invalid destination option type dropped.\n"));
              pbuf_free(p);
              IP6_STATS_INC(ip6.drop);
              goto ip6_input_cleanup;
            case 3:
              /* Send ICMP Parameter Problem if destination address is not a multicast address */
              if (!ip6_addr_ismulticast(ip6_current_dest_addr())) {
                icmp6_param_problem(p, ICMP6_PP_OPTION, opt_hdr);
              }
              LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: packet with invalid destination option type dropped.\n"));
              pbuf_free(p);
              IP6_STATS_INC(ip6.drop);
              goto ip6_input_cleanup;
            default:
              /* Skip over this option. */
              opt_dlen = IP6_OPT_DLEN(opt_hdr);
              break;
            }
            break;
          }
  
          /* Adjust the offset to move to the next extended option header */
          opt_offset = opt_offset + IP6_OPT_HLEN + opt_dlen;
        }
  
        pbuf_remove_header(p, hlen);
        break;
      }
      case IP6_NEXTH_ROUTING:
      {
        struct ip6_rout_hdr *rout_hdr;
        LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: packet with Routing header\n"));
  
        rout_hdr = (struct ip6_rout_hdr *)p->payload;
  
        /* Get next header type. */
        nexth = &IP6_ROUT_NEXTH(rout_hdr);
  
        /* Get the header length. */
        hlen = 8 * (1 + rout_hdr->_hlen);
  
        if ((p->len < 8) || (hlen > p->len)) {
          LWIP_DEBUGF(IP6_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
            ("IPv6 options header (hlen %"U16_F") does not fit in first pbuf (len %"U16_F"), IPv6 packet dropped.\n",
                hlen, p->len));
          /* free (drop) packet pbufs */
          pbuf_free(p);
          IP6_STATS_INC(ip6.lenerr);
          IP6_STATS_INC(ip6.drop);
          goto ip6_input_cleanup;
        }
  
        /* Skip over this header. */
        hlen_tot = (u16_t)(hlen_tot + hlen);
  
        /* if segment left value is 0 in routing header, ignore the option */
        if (IP6_ROUT_SEG_LEFT(rout_hdr)) {
          /* The length field of routing option header must be even */
          if (rout_hdr->_hlen & 0x1) {
            /* Discard and send parameter field error */
            icmp6_param_problem(p, ICMP6_PP_FIELD, &rout_hdr->_hlen);
            LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: packet with invalid routing type dropped\n"));
            pbuf_free(p);
            IP6_STATS_INC(ip6.drop);
            goto ip6_input_cleanup;
          }
  
          switch (IP6_ROUT_TYPE(rout_hdr))
          {
          /* TODO: process routing by the type */
          case IP6_ROUT_TYPE2:
            break;
          case IP6_ROUT_RPL:
            break;
          default:
            /* Discard unrecognized routing type and send parameter field error */
            icmp6_param_problem(p, ICMP6_PP_FIELD, &IP6_ROUT_TYPE(rout_hdr));
            LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: packet with invalid routing type dropped\n"));
            pbuf_free(p);
            IP6_STATS_INC(ip6.drop);
            goto ip6_input_cleanup;
          }
        }
  
        pbuf_remove_header(p, hlen);
        break;
      }
      case IP6_NEXTH_FRAGMENT:
      {
        struct ip6_frag_hdr *frag_hdr;
        LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: packet with Fragment header\n"));
  
        frag_hdr = (struct ip6_frag_hdr *)p->payload;
  
        /* Get next header type. */
        nexth = &IP6_FRAG_NEXTH(frag_hdr);
  
        /* Fragment Header length. */
        hlen = 8;
  
        /* Make sure this header fits in current pbuf. */
        if (hlen > p->len) {
          LWIP_DEBUGF(IP6_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
            ("IPv6 options header (hlen %"U16_F") does not fit in first pbuf (len %"U16_F"), IPv6 packet dropped.\n",
                hlen, p->len));
          /* free (drop) packet pbufs */
          pbuf_free(p);
          IP6_FRAG_STATS_INC(ip6_frag.lenerr);
          IP6_FRAG_STATS_INC(ip6_frag.drop);
          goto ip6_input_cleanup;
        }
  
        hlen_tot = (u16_t)(hlen_tot + hlen);
  
        /* check payload length is multiple of 8 octets when mbit is set */
        if (IP6_FRAG_MBIT(frag_hdr) && (IP6H_PLEN(ip6hdr) & 0x7)) {
          /* ipv6 payload length is not multiple of 8 octets */
          icmp6_param_problem(p, ICMP6_PP_FIELD, LWIP_PACKED_CAST(const void *, &ip6hdr->_plen));
          LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: packet with invalid payload length dropped\n"));
          pbuf_free(p);
          IP6_STATS_INC(ip6.drop);
          goto ip6_input_cleanup;
        }
  
        /* Offset == 0 and more_fragments == 0? */
        if ((frag_hdr->_fragment_offset &
             PP_HTONS(IP6_FRAG_OFFSET_MASK | IP6_FRAG_MORE_FLAG)) == 0) {
          /* This is a 1-fragment packet. Skip this header and continue. */
          pbuf_remove_header(p, hlen);
        } else {
  #if LWIP_IPV6_REASS
          /* reassemble the packet */
          ip_data.current_ip_header_tot_len = hlen_tot;
          p = ip6_reass(p);
          /* packet not fully reassembled yet? */
          if (p == NULL) {
            goto ip6_input_cleanup;
          }
  
          /* Returned p point to IPv6 header.
           * Update all our variables and pointers and continue. */
          ip6hdr = (struct ip6_hdr *)p->payload;
          nexth = &IP6H_NEXTH(ip6hdr);
          hlen = hlen_tot = IP6_HLEN;
          pbuf_remove_header(p, IP6_HLEN);
  
  #else /* LWIP_IPV6_REASS */
          /* free (drop) packet pbufs */
          LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: packet with Fragment header dropped (with LWIP_IPV6_REASS==0)\n"));
          pbuf_free(p);
          IP6_STATS_INC(ip6.opterr);
          IP6_STATS_INC(ip6.drop);
          goto ip6_input_cleanup;
  #endif /* LWIP_IPV6_REASS */
        }
        break;
      }
      default:
        goto options_done;
      }
  
      if (*nexth == IP6_NEXTH_HOPBYHOP) {
        /* Hop-by-Hop header comes only as a first option */
        icmp6_param_problem(p, ICMP6_PP_HEADER, nexth);
        LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: packet with Hop-by-Hop options header dropped (only valid as a first option)\n"));
        pbuf_free(p);
        IP6_STATS_INC(ip6.drop);
        goto ip6_input_cleanup;
      }
    }
  
  options_done:
  
    /* send to upper layers */
    LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: \n"));
    ip6_debug_print(p);
    LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: p->len %"U16_F" p->tot_len %"U16_F"\n", p->len, p->tot_len));
  
    ip_data.current_ip_header_tot_len = hlen_tot;
    
  #if LWIP_RAW
    /* p points to IPv6 header again for raw_input. */
    pbuf_add_header_force(p, hlen_tot);
    /* raw input did not eat the packet? */
    raw_status = raw_input(p, inp);
    if (raw_status != RAW_INPUT_EATEN)
    {
      /* Point to payload. */
      pbuf_remove_header(p, hlen_tot);
  #else /* LWIP_RAW */
    {
  #endif /* LWIP_RAW */
      switch (*nexth) {
      case IP6_NEXTH_NONE:
        pbuf_free(p);
        break;
  #if LWIP_UDP
      case IP6_NEXTH_UDP:
  #if LWIP_UDPLITE
      case IP6_NEXTH_UDPLITE:
  #endif /* LWIP_UDPLITE */
        udp_input(p, inp);
        break;
  #endif /* LWIP_UDP */
  #if LWIP_TCP
      case IP6_NEXTH_TCP:
        tcp_input(p, inp);
        break;
  #endif /* LWIP_TCP */
  #if LWIP_ICMP6
      case IP6_NEXTH_ICMP6:
        icmp6_input(p, inp);
        break;
  #endif /* LWIP_ICMP */
      default:
  #if LWIP_RAW
          if (raw_status == RAW_INPUT_DELIVERED) {
            /* @todo: ipv6 mib in-delivers? */
          } else
  #endif /* LWIP_RAW */
          {
  #if LWIP_ICMP6
          /* p points to IPv6 header again for raw_input. */
          pbuf_add_header_force(p, hlen_tot);
          /* send ICMP parameter problem unless it was a multicast or ICMPv6 */
          if ((!ip6_addr_ismulticast(ip6_current_dest_addr())) &&
              (IP6H_NEXTH(ip6hdr) != IP6_NEXTH_ICMP6)) {
            icmp6_param_problem(p, ICMP6_PP_HEADER, nexth);
          }
  #endif /* LWIP_ICMP */
          LWIP_DEBUGF(IP6_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("ip6_input: Unsupported transport protocol %"U16_F"\n", (u16_t)IP6H_NEXTH(ip6hdr)));
          IP6_STATS_INC(ip6.proterr);
          IP6_STATS_INC(ip6.drop);
        }
        pbuf_free(p);
        break;
      }
    }
  
  ip6_input_cleanup:
    ip_data.current_netif = NULL;
    ip_data.current_input_netif = NULL;
    ip_data.current_ip6_header = NULL;
    ip_data.current_ip_header_tot_len = 0;
    ip6_addr_set_zero(ip6_current_src_addr());
    ip6_addr_set_zero(ip6_current_dest_addr());
  
    return ERR_OK;
  }
  
  
  /**
   * Sends an IPv6 packet on a network interface. This function constructs
   * the IPv6 header. If the source IPv6 address is NULL, the IPv6 "ANY" address is
   * used as source (usually during network startup). If the source IPv6 address it
   * IP6_ADDR_ANY, the most appropriate IPv6 address of the outgoing network
   * interface is filled in as source address. If the destination IPv6 address is
   * LWIP_IP_HDRINCL, p is assumed to already include an IPv6 header and
   * p->payload points to it instead of the data.
   *
   * @param p the packet to send (p->payload points to the data, e.g. next
              protocol header; if dest == LWIP_IP_HDRINCL, p already includes an
              IPv6 header and p->payload points to that IPv6 header)
   * @param src the source IPv6 address to send from (if src == IP6_ADDR_ANY, an
   *         IP address of the netif is selected and used as source address.
   *         if src == NULL, IP6_ADDR_ANY is used as source) (src is possibly not
   *         properly zoned)
   * @param dest the destination IPv6 address to send the packet to (possibly not
   *             properly zoned)
   * @param hl the Hop Limit value to be set in the IPv6 header
   * @param tc the Traffic Class value to be set in the IPv6 header
   * @param nexth the Next Header to be set in the IPv6 header
   * @param netif the netif on which to send this packet
   * @return ERR_OK if the packet was sent OK
   *         ERR_BUF if p doesn't have enough space for IPv6/LINK headers
   *         returns errors returned by netif->output_ip6
   */
  err_t
  ip6_output_if(struct pbuf *p, const ip6_addr_t *src, const ip6_addr_t *dest,
               u8_t hl, u8_t tc,
               u8_t nexth, struct netif *netif)
  {
    const ip6_addr_t *src_used = src;
    if (dest != LWIP_IP_HDRINCL) {
      if (src != NULL && ip6_addr_isany(src)) {
        src_used = ip_2_ip6(ip6_select_source_address(netif, dest));
        if ((src_used == NULL) || ip6_addr_isany(src_used)) {
          /* No appropriate source address was found for this packet. */
          LWIP_DEBUGF(IP6_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("ip6_output: No suitable source address for packet.\n"));
          IP6_STATS_INC(ip6.rterr);
          return ERR_RTE;
        }
      }
    }
    return ip6_output_if_src(p, src_used, dest, hl, tc, nexth, netif);
  }
  
  /**
   * Same as ip6_output_if() but 'src' address is not replaced by netif address
   * when it is 'any'.
   */
  err_t
  ip6_output_if_src(struct pbuf *p, const ip6_addr_t *src, const ip6_addr_t *dest,
               u8_t hl, u8_t tc,
               u8_t nexth, struct netif *netif)
  {
    struct ip6_hdr *ip6hdr;
    ip6_addr_t dest_addr;
  
    LWIP_ASSERT_CORE_LOCKED();
    LWIP_IP_CHECK_PBUF_REF_COUNT_FOR_TX(p);
  
    /* Should the IPv6 header be generated or is it already included in p? */
    if (dest != LWIP_IP_HDRINCL) {
  #if LWIP_IPV6_SCOPES
      /* If the destination address is scoped but lacks a zone, add a zone now,
       * based on the outgoing interface. The lower layers (e.g., nd6) absolutely
       * require addresses to be properly zoned for correctness. In some cases,
       * earlier attempts will have been made to add a zone to the destination,
       * but this function is the only one that is called in all (other) cases,
       * so we must do this here. */
      if (ip6_addr_lacks_zone(dest, IP6_UNKNOWN)) {
        ip6_addr_copy(dest_addr, *dest);
        ip6_addr_assign_zone(&dest_addr, IP6_UNKNOWN, netif);
        dest = &dest_addr;
      }
  #endif /* LWIP_IPV6_SCOPES */
  
      /* generate IPv6 header */
      if (pbuf_add_header(p, IP6_HLEN)) {
        LWIP_DEBUGF(IP6_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("ip6_output: not enough room for IPv6 header in pbuf\n"));
        IP6_STATS_INC(ip6.err);
        return ERR_BUF;
      }
  
      ip6hdr = (struct ip6_hdr *)p->payload;
      LWIP_ASSERT("check that first pbuf can hold struct ip6_hdr",
                 (p->len >= sizeof(struct ip6_hdr)));
  
      IP6H_HOPLIM_SET(ip6hdr, hl);
      IP6H_NEXTH_SET(ip6hdr, nexth);
  
      /* dest cannot be NULL here */
      ip6_addr_copy_to_packed(ip6hdr->dest, *dest);
  
      IP6H_VTCFL_SET(ip6hdr, 6, tc, 0);
      IP6H_PLEN_SET(ip6hdr, (u16_t)(p->tot_len - IP6_HLEN));
  
      if (src == NULL) {
        src = IP6_ADDR_ANY6;
      }
      /* src cannot be NULL here */
      ip6_addr_copy_to_packed(ip6hdr->src, *src);
  
    } else {
      /* IP header already included in p */
      ip6hdr = (struct ip6_hdr *)p->payload;
      ip6_addr_copy_from_packed(dest_addr, ip6hdr->dest);
      ip6_addr_assign_zone(&dest_addr, IP6_UNKNOWN, netif);
      dest = &dest_addr;
    }
  
    IP6_STATS_INC(ip6.xmit);
  
    LWIP_DEBUGF(IP6_DEBUG, ("ip6_output_if: %c%c%"U16_F"\n", netif->name[0], netif->name[1], (u16_t)netif->num));
    ip6_debug_print(p);
  
  #if ENABLE_LOOPBACK
    {
      int i;
  #if !LWIP_HAVE_LOOPIF
      if (ip6_addr_isloopback(dest)) {
        return netif_loop_output(netif, p);
      }
  #endif /* !LWIP_HAVE_LOOPIF */
      for (i = 0; i < LWIP_IPV6_NUM_ADDRESSES; i++) {
        if (ip6_addr_isvalid(netif_ip6_addr_state(netif, i)) &&
            ip6_addr_cmp(dest, netif_ip6_addr(netif, i))) {
          /* Packet to self, enqueue it for loopback */
          LWIP_DEBUGF(IP6_DEBUG, ("netif_loop_output()\n"));
          return netif_loop_output(netif, p);
        }
      }
    }
  #if LWIP_MULTICAST_TX_OPTIONS
    if ((p->flags & PBUF_FLAG_MCASTLOOP) != 0) {
      netif_loop_output(netif, p);
    }
  #endif /* LWIP_MULTICAST_TX_OPTIONS */
  #endif /* ENABLE_LOOPBACK */
  #if LWIP_IPV6_FRAG
    /* don't fragment if interface has mtu set to 0 [loopif] */
    if (netif_mtu6(netif) && (p->tot_len > nd6_get_destination_mtu(dest, netif))) {
      return ip6_frag(p, netif, dest);
    }
  #endif /* LWIP_IPV6_FRAG */
  
    LWIP_DEBUGF(IP6_DEBUG, ("netif->output_ip6()\n"));
    return netif->output_ip6(netif, p, dest);
  }
  
  /**
   * Simple interface to ip6_output_if. It finds the outgoing network
   * interface and calls upon ip6_output_if to do the actual work.
   *
   * @param p the packet to send (p->payload points to the data, e.g. next
              protocol header; if dest == LWIP_IP_HDRINCL, p already includes an
              IPv6 header and p->payload points to that IPv6 header)
   * @param src the source IPv6 address to send from (if src == IP6_ADDR_ANY, an
   *         IP address of the netif is selected and used as source address.
   *         if src == NULL, IP6_ADDR_ANY is used as source)
   * @param dest the destination IPv6 address to send the packet to
   * @param hl the Hop Limit value to be set in the IPv6 header
   * @param tc the Traffic Class value to be set in the IPv6 header
   * @param nexth the Next Header to be set in the IPv6 header
   *
   * @return ERR_RTE if no route is found
   *         see ip_output_if() for more return values
   */
  err_t
  ip6_output(struct pbuf *p, const ip6_addr_t *src, const ip6_addr_t *dest,
            u8_t hl, u8_t tc, u8_t nexth)
  {
    struct netif *netif;
    struct ip6_hdr *ip6hdr;
    ip6_addr_t src_addr, dest_addr;
  
    LWIP_IP_CHECK_PBUF_REF_COUNT_FOR_TX(p);
  
    if (dest != LWIP_IP_HDRINCL) {
      netif = ip6_route(src, dest);
    } else {
      /* IP header included in p, read addresses. */
      ip6hdr = (struct ip6_hdr *)p->payload;
      ip6_addr_copy_from_packed(src_addr, ip6hdr->src);
      ip6_addr_copy_from_packed(dest_addr, ip6hdr->dest);
      netif = ip6_route(&src_addr, &dest_addr);
      dest = &dest_addr;
    }
  
    if (netif == NULL) {
      LWIP_DEBUGF(IP6_DEBUG, ("ip6_output: no route for %"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F"\n",
          IP6_ADDR_BLOCK1(dest),
          IP6_ADDR_BLOCK2(dest),
          IP6_ADDR_BLOCK3(dest),
          IP6_ADDR_BLOCK4(dest),
          IP6_ADDR_BLOCK5(dest),
          IP6_ADDR_BLOCK6(dest),
          IP6_ADDR_BLOCK7(dest),
          IP6_ADDR_BLOCK8(dest)));
      IP6_STATS_INC(ip6.rterr);
      return ERR_RTE;
    }
  
    return ip6_output_if(p, src, dest, hl, tc, nexth, netif);
  }
  
  
  #if LWIP_NETIF_USE_HINTS
  /** Like ip6_output, but takes and addr_hint pointer that is passed on to netif->addr_hint
   *  before calling ip6_output_if.
   *
   * @param p the packet to send (p->payload points to the data, e.g. next
              protocol header; if dest == LWIP_IP_HDRINCL, p already includes an
              IPv6 header and p->payload points to that IPv6 header)
   * @param src the source IPv6 address to send from (if src == IP6_ADDR_ANY, an
   *         IP address of the netif is selected and used as source address.
   *         if src == NULL, IP6_ADDR_ANY is used as source)
   * @param dest the destination IPv6 address to send the packet to
   * @param hl the Hop Limit value to be set in the IPv6 header
   * @param tc the Traffic Class value to be set in the IPv6 header
   * @param nexth the Next Header to be set in the IPv6 header
   * @param netif_hint netif output hint pointer set to netif->hint before
   *        calling ip_output_if()
   *
   * @return ERR_RTE if no route is found
   *         see ip_output_if() for more return values
   */
  err_t
  ip6_output_hinted(struct pbuf *p, const ip6_addr_t *src, const ip6_addr_t *dest,
            u8_t hl, u8_t tc, u8_t nexth, struct netif_hint *netif_hint)
  {
    struct netif *netif;
    struct ip6_hdr *ip6hdr;
    ip6_addr_t src_addr, dest_addr;
    err_t err;
  
    LWIP_IP_CHECK_PBUF_REF_COUNT_FOR_TX(p);
  
    if (dest != LWIP_IP_HDRINCL) {
      netif = ip6_route(src, dest);
    } else {
      /* IP header included in p, read addresses. */
      ip6hdr = (struct ip6_hdr *)p->payload;
      ip6_addr_copy_from_packed(src_addr, ip6hdr->src);
      ip6_addr_copy_from_packed(dest_addr, ip6hdr->dest);
      netif = ip6_route(&src_addr, &dest_addr);
      dest = &dest_addr;
    }
  
    if (netif == NULL) {
      LWIP_DEBUGF(IP6_DEBUG, ("ip6_output: no route for %"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F":%"X16_F"\n",
          IP6_ADDR_BLOCK1(dest),
          IP6_ADDR_BLOCK2(dest),
          IP6_ADDR_BLOCK3(dest),
          IP6_ADDR_BLOCK4(dest),
          IP6_ADDR_BLOCK5(dest),
          IP6_ADDR_BLOCK6(dest),
          IP6_ADDR_BLOCK7(dest),
          IP6_ADDR_BLOCK8(dest)));
      IP6_STATS_INC(ip6.rterr);
      return ERR_RTE;
    }
  
    NETIF_SET_HINTS(netif, netif_hint);
    err = ip6_output_if(p, src, dest, hl, tc, nexth, netif);
    NETIF_RESET_HINTS(netif);
  
    return err;
  }
  #endif /* LWIP_NETIF_USE_HINTS*/
  
  #if LWIP_IPV6_MLD
  /**
   * Add a hop-by-hop options header with a router alert option and padding.
   *
   * Used by MLD when sending a Multicast listener report/done message.
   *
   * @param p the packet to which we will prepend the options header
   * @param nexth the next header protocol number (e.g. IP6_NEXTH_ICMP6)
   * @param value the value of the router alert option data (e.g. IP6_ROUTER_ALERT_VALUE_MLD)
   * @return ERR_OK if hop-by-hop header was added, ERR_* otherwise
   */
  err_t
  ip6_options_add_hbh_ra(struct pbuf *p, u8_t nexth, u8_t value)
  {
    u8_t *opt_data;
    u32_t offset = 0;
    struct ip6_hbh_hdr *hbh_hdr;
    struct ip6_opt_hdr *opt_hdr;
  
    /* fixed 4 bytes for router alert option and 2 bytes padding */
    const u8_t hlen = (sizeof(struct ip6_opt_hdr) * 2) + IP6_ROUTER_ALERT_DLEN;
    /* Move pointer to make room for hop-by-hop options header. */
    if (pbuf_add_header(p, sizeof(struct ip6_hbh_hdr) + hlen)) {
      LWIP_DEBUGF(IP6_DEBUG, ("ip6_options: no space for options header\n"));
      IP6_STATS_INC(ip6.err);
      return ERR_BUF;
    }
  
    /* Set fields of Hop-by-Hop header */
    hbh_hdr = (struct ip6_hbh_hdr *)p->payload;
    IP6_HBH_NEXTH(hbh_hdr) = nexth;
    hbh_hdr->_hlen = 0;
    offset = IP6_HBH_HLEN;
  
    /* Set router alert options to Hop-by-Hop extended option header */
    opt_hdr = (struct ip6_opt_hdr *)((u8_t *)hbh_hdr + offset);
    IP6_OPT_TYPE(opt_hdr) = IP6_ROUTER_ALERT_OPTION;
    IP6_OPT_DLEN(opt_hdr) = IP6_ROUTER_ALERT_DLEN;
    offset += IP6_OPT_HLEN;
  
    /* Set router alert option data */
    opt_data = (u8_t *)hbh_hdr + offset;
    opt_data[0] = value;
    opt_data[1] = 0;
    offset += IP6_OPT_DLEN(opt_hdr);
  
    /* add 2 bytes padding to make 8 bytes Hop-by-Hop header length */
    opt_hdr = (struct ip6_opt_hdr *)((u8_t *)hbh_hdr + offset);
    IP6_OPT_TYPE(opt_hdr) = IP6_PADN_OPTION;
    IP6_OPT_DLEN(opt_hdr) = 0;
  
    return ERR_OK;
  }
  #endif /* LWIP_IPV6_MLD */
  
  #if IP6_DEBUG
  /* Print an IPv6 header by using LWIP_DEBUGF
   * @param p an IPv6 packet, p->payload pointing to the IPv6 header
   */
  void
  ip6_debug_print(struct pbuf *p)
  {
    struct ip6_hdr *ip6hdr = (struct ip6_hdr *)p->payload;
  
    LWIP_DEBUGF(IP6_DEBUG, ("IPv6 header:\n"));
    LWIP_DEBUGF(IP6_DEBUG, ("+-------------------------------+\n"));
    LWIP_DEBUGF(IP6_DEBUG, ("| %2"U16_F" |  %3"U16_F"  |      %7"U32_F"     | (ver, class, flow)\n",
                      IP6H_V(ip6hdr),
                      IP6H_TC(ip6hdr),
                      IP6H_FL(ip6hdr)));
    LWIP_DEBUGF(IP6_DEBUG, ("+-------------------------------+\n"));
    LWIP_DEBUGF(IP6_DEBUG, ("|     %5"U16_F"     |  %3"U16_F"  |  %3"U16_F"  | (plen, nexth, hopl)\n",
                      IP6H_PLEN(ip6hdr),
                      IP6H_NEXTH(ip6hdr),
                      IP6H_HOPLIM(ip6hdr)));
    LWIP_DEBUGF(IP6_DEBUG, ("+-------------------------------+\n"));
    LWIP_DEBUGF(IP6_DEBUG, ("|  %4"X32_F" |  %4"X32_F" |  %4"X32_F" |  %4"X32_F" | (src)\n",
                      IP6_ADDR_BLOCK1(&(ip6hdr->src)),
                      IP6_ADDR_BLOCK2(&(ip6hdr->src)),
                      IP6_ADDR_BLOCK3(&(ip6hdr->src)),
                      IP6_ADDR_BLOCK4(&(ip6hdr->src))));
    LWIP_DEBUGF(IP6_DEBUG, ("|  %4"X32_F" |  %4"X32_F" |  %4"X32_F" |  %4"X32_F" |\n",
                      IP6_ADDR_BLOCK5(&(ip6hdr->src)),
                      IP6_ADDR_BLOCK6(&(ip6hdr->src)),
                      IP6_ADDR_BLOCK7(&(ip6hdr->src)),
                      IP6_ADDR_BLOCK8(&(ip6hdr->src))));
    LWIP_DEBUGF(IP6_DEBUG, ("+-------------------------------+\n"));
    LWIP_DEBUGF(IP6_DEBUG, ("|  %4"X32_F" |  %4"X32_F" |  %4"X32_F" |  %4"X32_F" | (dest)\n",
                      IP6_ADDR_BLOCK1(&(ip6hdr->dest)),
                      IP6_ADDR_BLOCK2(&(ip6hdr->dest)),
                      IP6_ADDR_BLOCK3(&(ip6hdr->dest)),
                      IP6_ADDR_BLOCK4(&(ip6hdr->dest))));
    LWIP_DEBUGF(IP6_DEBUG, ("|  %4"X32_F" |  %4"X32_F" |  %4"X32_F" |  %4"X32_F" |\n",
                      IP6_ADDR_BLOCK5(&(ip6hdr->dest)),
                      IP6_ADDR_BLOCK6(&(ip6hdr->dest)),
                      IP6_ADDR_BLOCK7(&(ip6hdr->dest)),
                      IP6_ADDR_BLOCK8(&(ip6hdr->dest))));
    LWIP_DEBUGF(IP6_DEBUG, ("+-------------------------------+\n"));
  }
  #endif /* IP6_DEBUG */
  
  #endif /* LWIP_IPV6 */
  