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/ip6.h"
  #include "lwip/ip6_addr.h"
  #include "lwip/ip6_frag.h"
  #include "lwip/icmp6.h"
  #include "lwip/raw.h"
  #include "lwip/udp.h"
  #include "lwip/tcp_impl.h"
  #include "lwip/dhcp6.h"
  #include "lwip/nd6.h"
  #include "lwip/mld6.h"
  #include "lwip/debug.h"
  #include "lwip/stats.h"
  
  #ifdef MEMLEAK_DEBUG
  static const char mem_debug_file[] ICACHE_RODATA_ATTR STORE_ATTR = __FILE__;
  #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 link-local address, try to match the src address to a netif.
   *    this is a tricky case because with multiple netifs, link-local addresses only have
   *    meaning within a particular subnet/link.
   * 3) tries to match the destination subnet to a configured address
   * 4) tries to find a router
   * 5) tries to match the source address to the netif
   * 6) returns the default netif, if configured
   *
   * @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(struct ip6_addr *src, struct ip6_addr *dest)
  {
    struct netif *netif;
    s8_t i;
  
    /* If single netif configuration, fast return. */
    if ((netif_list != NULL) && (netif_list->next == NULL)) {
      return netif_list;
    }
  
    /* Special processing for link-local addresses. */
    if (ip6_addr_islinklocal(dest)) {
      if (ip6_addr_isany(src)) {
        /* Use default netif. */
        return netif_default;
      }
  
      /* Try to find the netif for the source address. */
      for(netif = netif_list; netif != NULL; netif = netif->next) {
        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;
          }
        }
      }
  
      /* netif not found, use default netif */
      return netif_default;
    }
  
    /* See if the destination subnet matches a configured address. */
    for(netif = netif_list; netif != NULL; netif = netif->next) {
      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))) {
          return netif;
        }
      }
    }
  
    /* Get the netif for a suitable router. */
    i = nd6_select_router(dest, NULL);
    if (i >= 0) {
      if (default_router_list[i].neighbor_entry != NULL) {
        if (default_router_list[i].neighbor_entry->netif != NULL) {
          return default_router_list[i].neighbor_entry->netif;
        }
      }
    }
  
    /* try with the netif that matches the source address. */
    if (!ip6_addr_isany(src)) {
      for(netif = netif_list; netif != NULL; netif = netif->next) {
        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;
          }
        }
      }
    }
  
    /* no matching netif found, use default netif */
    return netif_default;
  }
  
  /**
   * Select the best IPv6 source address for a given destination
   * IPv6 address. Loosely follows RFC 3484. "Strong host" behavior
   * is assumed.
   *
   * @param netif the netif on which to send a packet
   * @param dest the destination we are trying to reach
   * @return the most suitable source address to use, or NULL if no suitable
   *         source address is found
   */
  ip6_addr_t *
  ip6_select_source_address(struct netif *netif, ip6_addr_t * dest)
  {
    ip6_addr_t * src = NULL;
    u8_t i;
  
    /* If dest is link-local, choose a link-local source. */
    if (ip6_addr_islinklocal(dest) || ip6_addr_ismulticast_linklocal(dest) || ip6_addr_ismulticast_iflocal(dest)) {
      for (i = 0; i < LWIP_IPV6_NUM_ADDRESSES; i++) {
        if (ip6_addr_isvalid(netif_ip6_addr_state(netif, i)) &&
            ip6_addr_islinklocal(netif_ip6_addr(netif, i))) {
          return netif_ip6_addr(netif, i);
        }
      }
    }
  
    /* Choose a site-local with matching prefix. */
    if (ip6_addr_issitelocal(dest) || ip6_addr_ismulticast_sitelocal(dest)) {
      for (i = 0; i < LWIP_IPV6_NUM_ADDRESSES; i++) {
        if (ip6_addr_isvalid(netif_ip6_addr_state(netif, i)) &&
            ip6_addr_issitelocal(netif_ip6_addr(netif, i)) &&
            ip6_addr_netcmp(dest, netif_ip6_addr(netif, i))) {
          return netif_ip6_addr(netif, i);
        }
      }
    }
  
    /* Choose a unique-local with matching prefix. */
    if (ip6_addr_isuniquelocal(dest) || ip6_addr_ismulticast_orglocal(dest)) {
      for (i = 0; i < LWIP_IPV6_NUM_ADDRESSES; i++) {
        if (ip6_addr_isvalid(netif_ip6_addr_state(netif, i)) &&
            ip6_addr_isuniquelocal(netif_ip6_addr(netif, i)) &&
            ip6_addr_netcmp(dest, netif_ip6_addr(netif, i))) {
          return netif_ip6_addr(netif, i);
        }
      }
    }
  
    /* Choose a global with best matching prefix. */
    if (ip6_addr_isglobal(dest) || ip6_addr_ismulticast_global(dest)) {
      for (i = 0; i < LWIP_IPV6_NUM_ADDRESSES; i++) {
        if (ip6_addr_isvalid(netif_ip6_addr_state(netif, i)) &&
            ip6_addr_isglobal(netif_ip6_addr(netif, i))) {
          if (src == NULL) {
            src = netif_ip6_addr(netif, i);
          }
          else {
            /* Replace src only if we find a prefix match. */
            /* TODO find longest matching prefix. */
            if ((!(ip6_addr_netcmp(src, dest))) &&
                ip6_addr_netcmp(netif_ip6_addr(netif, i), dest)) {
              src = netif_ip6_addr(netif, i);
            }
          }
        }
      }
      if (src != NULL) {
        return src;
      }
    }
  
    /* Last resort: see if arbitrary prefix matches. */
    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))) {
        return netif_ip6_addr(netif, i);
      }
    }
  
    return 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 addresses */
    if (ip6_addr_islinklocal(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_ANY, 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;
    }
    /* 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 */
  
  
  /**
   * 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;
    u8_t nexth;
    u16_t hlen; /* the current header length */
    u8_t i;
  #if 0 /*IP_ACCEPT_LINK_LAYER_ADDRESSING*/
    @todo
    int check_ip_src=1;
  #endif /* IP_ACCEPT_LINK_LAYER_ADDRESSING */
  
    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;
    }
  
    /* header length exceeds first pbuf length, or ip length exceeds total pbuf length? */
    if ((IP6_HLEN > p->len) || ((IP6H_PLEN(ip6hdr) + IP6_HLEN) > p->tot_len)) {
      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",
              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",
              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, IP6_HLEN + IP6H_PLEN(ip6hdr));
  
    /* copy IP addresses to aligned ip6_addr_t */
    ip6_addr_copy(ip_data.current_iphdr_dest.ip6, ip6hdr->dest);
    ip6_addr_copy(ip_data.current_iphdr_src.ip6, ip6hdr->src);
  
    /* 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;
  
    /* 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())) {
        /* 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.
         'first' is used as a boolean to mark whether we started walking the list */
      int first = 1;
      netif = inp;
      do {
        /* interface is up? */
        if (netif_is_up(netif)) {
          /* unicast to this interface address? address configured? */
          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))) {
              /* exit outer loop */
              goto netif_found;
            }
          }
        }
        if (ip6_addr_islinklocal(ip6_current_dest_addr())) {
          /* Do not match link-local addresses to other netifs. */
          netif = NULL;
          break;
        }
        if (first) {
          first = 0;
          netif = netif_list;
        } else {
          netif = netif->next;
        }
        if (netif == inp) {
          netif = netif->next;
        }
      } while(netif != NULL);
  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 = ip_data.current_ip_header_tot_len = IP6_HLEN;
  
    /* Move to payload. */
    pbuf_header(p, -IP6_HLEN);
  
    /* Process known option extension headers, if present. */
    while (nexth != IP6_NEXTH_NONE)
    {
      switch (nexth) {
      case IP6_NEXTH_HOPBYHOP:
        LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: packet with Hop-by-Hop options header\n"));
        /* Get next header type. */
        nexth = *((u8_t *)p->payload);
  
        /* Get the header length. */
        hlen = 8 * (1 + *((u8_t *)p->payload + 1));
        ip_data.current_ip_header_tot_len += hlen;
  
        /* Skip over this header. */
        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_STATS_INC(ip6.lenerr);
          IP6_STATS_INC(ip6.drop);
          goto ip6_input_cleanup;
        }
  
        pbuf_header(p, -hlen);
        break;
      case IP6_NEXTH_DESTOPTS:
        LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: packet with Destination options header\n"));
        /* Get next header type. */
        nexth = *((u8_t *)p->payload);
  
        /* Get the header length. */
        hlen = 8 * (1 + *((u8_t *)p->payload + 1));
        ip_data.current_ip_header_tot_len += hlen;
  
        /* Skip over this header. */
        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_STATS_INC(ip6.lenerr);
          IP6_STATS_INC(ip6.drop);
          goto ip6_input_cleanup;
        }
  
        pbuf_header(p, -hlen);
        break;
      case IP6_NEXTH_ROUTING:
        LWIP_DEBUGF(IP6_DEBUG, ("ip6_input: packet with Routing header\n"));
        /* Get next header type. */
        nexth = *((u8_t *)p->payload);
  
        /* Get the header length. */
        hlen = 8 * (1 + *((u8_t *)p->payload + 1));
        ip_data.current_ip_header_tot_len += hlen;
  
        /* Skip over this header. */
        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_STATS_INC(ip6.lenerr);
          IP6_STATS_INC(ip6.drop);
          goto ip6_input_cleanup;
        }
  
        pbuf_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 = frag_hdr->_nexth;
  
        /* Fragment Header length. */
        hlen = 8;
        ip_data.current_ip_header_tot_len += hlen;
  
        /* 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;
        }
  
        /* Offset == 0 and more_fragments == 0? */
        if (((frag_hdr->_fragment_offset & IP6_FRAG_OFFSET_MASK) == 0) &&
            ((frag_hdr->_fragment_offset & IP6_FRAG_MORE_FLAG) == 0)) {
  
          /* This is a 1-fragment packet, usually a packet that we have
           * already reassembled. Skip this header anc continue. */
          pbuf_header(p, -hlen);
        }
        else {
  #if LWIP_IPV6_REASS
  
          /* reassemble the packet */
          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 = ip_data.current_ip_header_tot_len = IP6_HLEN;
          pbuf_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;
        break;
      }
    }
  options_done:
  
    /* p points to IPv6 header again. */
    pbuf_header(p, ip_data.current_ip_header_tot_len);
  
    /* 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));
  
  #if LWIP_RAW
    /* raw input did not eat the packet? */
    if (raw_input(p, inp) == 0)
  #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 */
        /* Point to payload. */
        pbuf_header(p, -ip_data.current_ip_header_tot_len);
        udp_input(p, inp);
        break;
  #endif /* LWIP_UDP */
  #if LWIP_TCP
      case IP6_NEXTH_TCP:
        /* Point to payload. */
        pbuf_header(p, -ip_data.current_ip_header_tot_len);
        tcp_input(p, inp);
        break;
  #endif /* LWIP_TCP */
  #if LWIP_ICMP6
      case IP6_NEXTH_ICMP6:
        /* Point to payload. */
        pbuf_header(p, -ip_data.current_ip_header_tot_len);
        icmp6_input(p, inp);
        break;
  #endif /* LWIP_ICMP */
      default:
  #if LWIP_ICMP6
        /* 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, ip_data.current_ip_header_tot_len - hlen);
        }
  #endif /* LWIP_ICMP */
        LWIP_DEBUGF(IP6_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("ip6_input: Unsupported transport protocol %"U16_F"\n", IP6H_NEXTH(ip6hdr)));
        pbuf_free(p);
        IP6_STATS_INC(ip6.proterr);
        IP6_STATS_INC(ip6.drop);
        break;
      }
    }
  
  ip6_input_cleanup:
    ip_data.current_netif = NULL;
    ip_data.current_ip6_header = NULL;
    ip_data.current_ip_header_tot_len = 0;
    ip6_addr_set_any(&ip_data.current_iphdr_src.ip6);
    ip6_addr_set_any(&ip_data.current_iphdr_dest.ip6);
  
    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
   * 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 == 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 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
   */
  err_t
  ip6_output_if(struct pbuf *p, ip6_addr_t *src, 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;
  
    /* pbufs passed to IP must have a ref-count of 1 as their payload pointer
       gets altered as the packet is passed down the stack */
    LWIP_ASSERT("p->ref == 1", p->ref == 1);
  
    /* Should the IPv6 header be generated or is it already included in p? */
    if (dest != IP_HDRINCL) {
      /* generate IPv6 header */
      if (pbuf_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(ip6hdr->dest, *dest);
  
      IP6H_VTCFL_SET(ip6hdr, 6, tc, 0);
      IP6H_PLEN_SET(ip6hdr, p->tot_len - IP6_HLEN);
  
      if (src == NULL) {
        src = IP6_ADDR_ANY;
      }
      else if (ip6_addr_isany(src)) {
        src = ip6_select_source_address(netif, dest);
        if ((src == NULL) || ip6_addr_isany(src)) {
          /* 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;
        }
      }
      /* src cannot be NULL here */
      ip6_addr_copy(ip6hdr->src, *src);
  
    } else {
      /* IP header already included in p */
      ip6hdr = (struct ip6_hdr *)p->payload;
      ip6_addr_copy(dest_addr, ip6hdr->dest);
      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], netif->num));
    ip6_debug_print(p);
  
  #if ENABLE_LOOPBACK
    /* TODO implement loopback for v6
    if (ip6_addr_cmp(dest, netif_ip6_addr(0))) {
      return netif_loop_output(netif, p, dest);
    }*/
  #endif /* ENABLE_LOOPBACK */
  #if LWIP_IPV6_FRAG
    /* don't fragment if interface has mtu set to 0 [loopif] */
    if (netif->mtu && (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()"));
    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 == 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, ip6_addr_t *src, 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;
  
    /* pbufs passed to IPv6 must have a ref-count of 1 as their payload pointer
       gets altered as the packet is passed down the stack */
    LWIP_ASSERT("p->ref == 1", p->ref == 1);
  
    if (dest != IP_HDRINCL) {
      netif = ip6_route(src, dest);
    } else {
      /* IP header included in p, read addresses. */
      ip6hdr = (struct ip6_hdr *)p->payload;
      ip6_addr_copy(src_addr, ip6hdr->src);
      ip6_addr_copy(dest_addr, ip6hdr->dest);
      netif = ip6_route(&src_addr, &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_HWADDRHINT
  /** 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 == 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 addr_hint address hint pointer set to netif->addr_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, ip6_addr_t *src, ip6_addr_t *dest,
            u8_t hl, u8_t tc, u8_t nexth, u8_t *addr_hint)
  {
    struct netif *netif;
    struct ip6_hdr *ip6hdr;
    ip6_addr_t src_addr, dest_addr;
    err_t err;
  
    /* pbufs passed to IP must have a ref-count of 1 as their payload pointer
       gets altered as the packet is passed down the stack */
    LWIP_ASSERT("p->ref == 1", p->ref == 1);
  
    if (dest != IP_HDRINCL) {
      netif = ip6_route(src, dest);
    } else {
      /* IP header included in p, read addresses. */
      ip6hdr = (struct ip6_hdr *)p->payload;
      ip6_addr_copy(src_addr, ip6hdr->src);
      ip6_addr_copy(dest_addr, ip6hdr->dest);
      netif = ip6_route(&src_addr, &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_HWADDRHINT(netif, addr_hint);
    err = ip6_output_if(p, src, dest, hl, tc, nexth, netif);
    NETIF_SET_HWADDRHINT(netif, NULL);
  
    return err;
  }
  #endif /* LWIP_NETIF_HWADDRHINT*/
  
  #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)
  {
    struct ip6_hbh_hdr * hbh_hdr;
  
    /* Move pointer to make room for hop-by-hop options header. */
    if (pbuf_header(p, sizeof(struct ip6_hbh_hdr))) {
      LWIP_DEBUGF(IP6_DEBUG, ("ip6_options: no space for options header\n"));
      IP6_STATS_INC(ip6.err);
      return ERR_BUF;
    }
  
    hbh_hdr = (struct ip6_hbh_hdr *)p->payload;
  
    /* Set fields. */
    hbh_hdr->_nexth = nexth;
    hbh_hdr->_hlen = 0;
    hbh_hdr->_ra_opt_type = IP6_ROUTER_ALERT_OPTION;
    hbh_hdr->_ra_opt_dlen = 2;
    hbh_hdr->_ra_opt_data = value;
    hbh_hdr->_padn_opt_type = IP6_PADN_ALERT_OPTION;
    hbh_hdr->_padn_opt_dlen = 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 */
  