src/vnet/ip/ip4_to_ip6.h - fdio/vpp - Gitiles

 /*
  * Copyright (c) 2017 Cisco and/or its affiliates.
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at:
  *
  *     http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 /**
  * @file
  * @brief IPv4 to IPv6 translation
  */
 #ifndef __included_ip4_to_ip6_h__
 #define __included_ip4_to_ip6_h__

 #include <vnet/ip/ip.h>


 /**
  * IPv4 to IPv6 set call back function type
  */
 typedef int (*ip4_to_ip6_set_fn_t) (ip4_header_t * ip4, ip6_header_t * ip6,
 				    void *ctx);

 /* *INDENT-OFF* */
 static u8 icmp_to_icmp6_updater_pointer_table[] =
   { 0, 1, 4, 4, ~0,
     ~0, ~0, ~0, 7, 6,
     ~0, ~0, 8, 8, 8,
     8, 24, 24, 24, 24
   };
 /* *INDENT-ON* */

 #define frag_id_4to6(id) (id)

 /**
  * @brief Get TCP/UDP port number or ICMP id from IPv4 packet.
  *
  * @param ip4        IPv4 header.
  * @param sender     1 get sender port, 0 get receiver port.
  *
  * @returns Port number on success, 0 otherwise.
  */
 always_inline u16
 ip4_get_port (ip4_header_t * ip, u8 sender)
 {
   if (ip->ip_version_and_header_length != 0x45 ||
       ip4_get_fragment_offset (ip))
     return 0;

   if (PREDICT_TRUE ((ip->protocol == IP_PROTOCOL_TCP) ||
 		    (ip->protocol == IP_PROTOCOL_UDP)))
     {
       udp_header_t *udp = (void *) (ip + 1);
       return (sender) ? udp->src_port : udp->dst_port;
     }
   else if (ip->protocol == IP_PROTOCOL_ICMP)
     {
       icmp46_header_t *icmp = (void *) (ip + 1);
       if (icmp->type == ICMP4_echo_request || icmp->type == ICMP4_echo_reply)
 	{
 	  return *((u16 *) (icmp + 1));
 	}
       else if (clib_net_to_host_u16 (ip->length) >= 64)
 	{
 	  ip = (ip4_header_t *) (icmp + 2);
 	  if (PREDICT_TRUE ((ip->protocol == IP_PROTOCOL_TCP) ||
 			    (ip->protocol == IP_PROTOCOL_UDP)))
 	    {
 	      udp_header_t *udp = (void *) (ip + 1);
 	      return (sender) ? udp->dst_port : udp->src_port;
 	    }
 	  else if (ip->protocol == IP_PROTOCOL_ICMP)
 	    {
 	      icmp46_header_t *icmp = (void *) (ip + 1);
 	      if (icmp->type == ICMP4_echo_request ||
 		  icmp->type == ICMP4_echo_reply)
 		{
 		  return *((u16 *) (icmp + 1));
 		}
 	    }
 	}
     }
   return 0;
 }

 /**
  * @brief Convert type and code value from ICMP4 to ICMP6.
  *
  * @param icmp      ICMP header.
  * @param inner_ip4 Inner IPv4 header if present, 0 otherwise.
  *
  * @returns 0 on success, non-zero value otherwise.
  */
 always_inline int
 icmp_to_icmp6_header (icmp46_header_t * icmp, ip4_header_t ** inner_ip4)
 {
   *inner_ip4 = NULL;
   switch (icmp->type)
     {
     case ICMP4_echo_reply:
       icmp->type = ICMP6_echo_reply;
       break;
     case ICMP4_echo_request:
       icmp->type = ICMP6_echo_request;
       break;
     case ICMP4_destination_unreachable:
       *inner_ip4 = (ip4_header_t *) (((u8 *) icmp) + 8);

       switch (icmp->code)
 	{
 	case ICMP4_destination_unreachable_destination_unreachable_net:	//0
 	case ICMP4_destination_unreachable_destination_unreachable_host:	//1
 	  icmp->type = ICMP6_destination_unreachable;
 	  icmp->code = ICMP6_destination_unreachable_no_route_to_destination;
 	  break;
 	case ICMP4_destination_unreachable_protocol_unreachable:	//2
 	  icmp->type = ICMP6_parameter_problem;
 	  icmp->code = ICMP6_parameter_problem_unrecognized_next_header;
 	  break;
 	case ICMP4_destination_unreachable_port_unreachable:	//3
 	  icmp->type = ICMP6_destination_unreachable;
 	  icmp->code = ICMP6_destination_unreachable_port_unreachable;
 	  break;
 	case ICMP4_destination_unreachable_fragmentation_needed_and_dont_fragment_set:	//4
 	  icmp->type =
 	    ICMP6_packet_too_big;
 	  icmp->code = 0;
 	  {
 	    u32 advertised_mtu = clib_net_to_host_u32 (*((u32 *) (icmp + 1)));
 	    if (advertised_mtu)
 	      advertised_mtu += 20;
 	    else
 	      advertised_mtu = 1000;	//FIXME ! (RFC 1191 - plateau value)

 	    //FIXME: = minimum(advertised MTU+20, MTU_of_IPv6_nexthop, (MTU_of_IPv4_nexthop)+20)
 	    *((u32 *) (icmp + 1)) = clib_host_to_net_u32 (advertised_mtu);
 	  }
 	  break;

 	case ICMP4_destination_unreachable_source_route_failed:	//5
 	case ICMP4_destination_unreachable_destination_network_unknown:	//6
 	case ICMP4_destination_unreachable_destination_host_unknown:	//7
 	case ICMP4_destination_unreachable_source_host_isolated:	//8
 	case ICMP4_destination_unreachable_network_unreachable_for_type_of_service:	//11
 	case ICMP4_destination_unreachable_host_unreachable_for_type_of_service:	//12
 	  icmp->type =
 	    ICMP6_destination_unreachable;
 	  icmp->code = ICMP6_destination_unreachable_no_route_to_destination;
 	  break;
 	case ICMP4_destination_unreachable_network_administratively_prohibited:	//9
 	case ICMP4_destination_unreachable_host_administratively_prohibited:	//10
 	case ICMP4_destination_unreachable_communication_administratively_prohibited:	//13
 	case ICMP4_destination_unreachable_precedence_cutoff_in_effect:	//15
 	  icmp->type = ICMP6_destination_unreachable;
 	  icmp->code =
 	    ICMP6_destination_unreachable_destination_administratively_prohibited;
 	  break;
 	case ICMP4_destination_unreachable_host_precedence_violation:	//14
 	default:
 	  return -1;
 	}
       break;

     case ICMP4_time_exceeded:	//11
       *inner_ip4 = (ip4_header_t *) (((u8 *) icmp) + 8);
       icmp->type = ICMP6_time_exceeded;
       break;

     case ICMP4_parameter_problem:
       *inner_ip4 = (ip4_header_t *) (((u8 *) icmp) + 8);

       switch (icmp->code)
 	{
 	case ICMP4_parameter_problem_pointer_indicates_error:
 	case ICMP4_parameter_problem_bad_length:
 	  icmp->type = ICMP6_parameter_problem;
 	  icmp->code = ICMP6_parameter_problem_erroneous_header_field;
 	  {
 	    u8 ptr =
 	      icmp_to_icmp6_updater_pointer_table[*((u8 *) (icmp + 1))];
 	    if (ptr == 0xff)
 	      return -1;

 	    *((u32 *) (icmp + 1)) = clib_host_to_net_u32 (ptr);
 	  }
 	  break;
 	default:
 	  //All other codes cause error
 	  return -1;
 	}
       break;

     default:
       //All other types cause error
       return -1;
       break;
     }
   return 0;
 }

 /**
  * @brief Translate ICMP4 packet to ICMP6.
  *
  * @param p         Buffer to translate.
  * @param fn        The function to translate outer header.
  * @param ctx       A context passed in the outer header translate function.
  * @param inner_fn  The function to translate inner header.
  * @param inner_ctx A context passed in the inner header translate function.
  *
  * @returns 0 on success, non-zero value otherwise.
  */
 always_inline int
 icmp_to_icmp6 (vlib_buffer_t * p, ip4_to_ip6_set_fn_t fn, void *ctx,
 	       ip4_to_ip6_set_fn_t inner_fn, void *inner_ctx)
 {
   ip4_header_t *ip4, *inner_ip4;
   ip6_header_t *ip6, *inner_ip6;
   u32 ip_len;
   icmp46_header_t *icmp;
   ip_csum_t csum;
   ip6_frag_hdr_t *inner_frag;
   u32 inner_frag_id;
   u32 inner_frag_offset;
   u8 inner_frag_more;
   u16 *inner_L4_checksum = 0;
   int rv;

   ip4 = vlib_buffer_get_current (p);
   ip_len = clib_net_to_host_u16 (ip4->length);
   ASSERT (ip_len <= p->current_length);

   icmp = (icmp46_header_t *) (ip4 + 1);
   if (icmp_to_icmp6_header (icmp, &inner_ip4))
     return -1;

   if (inner_ip4)
     {
       //We have 2 headers to translate.
       //We need to make some room in the middle of the packet
       if (PREDICT_FALSE (ip4_is_fragment (inner_ip4)))
 	{
 	  //Here it starts getting really tricky
 	  //We will add a fragmentation header in the inner packet

 	  if (!ip4_is_first_fragment (inner_ip4))
 	    {
 	      //For now we do not handle unless it is the first fragment
 	      //Ideally we should handle the case as we are in slow path already
 	      return -1;
 	    }

 	  vlib_buffer_advance (p,
 			       -2 * (sizeof (*ip6) - sizeof (*ip4)) -
 			       sizeof (*inner_frag));
 	  ip6 = vlib_buffer_get_current (p);
 	  clib_memcpy (u8_ptr_add (ip6, sizeof (*ip6) - sizeof (*ip4)), ip4,
 		       20 + 8);
 	  ip4 =
 	    (ip4_header_t *) u8_ptr_add (ip6, sizeof (*ip6) - sizeof (*ip4));
 	  icmp = (icmp46_header_t *) (ip4 + 1);

 	  inner_ip6 =
 	    (ip6_header_t *) u8_ptr_add (inner_ip4,
 					 sizeof (*ip4) - sizeof (*ip6) -
 					 sizeof (*inner_frag));
 	  inner_frag =
 	    (ip6_frag_hdr_t *) u8_ptr_add (inner_ip6, sizeof (*inner_ip6));
 	  ip6->payload_length =
 	    u16_net_add (ip4->length,
 			 sizeof (*ip6) - 2 * sizeof (*ip4) +
 			 sizeof (*inner_frag));
 	  inner_frag_id = frag_id_4to6 (inner_ip4->fragment_id);
 	  inner_frag_offset = ip4_get_fragment_offset (inner_ip4);
 	  inner_frag_more =
 	    ! !(inner_ip4->flags_and_fragment_offset &
 		clib_net_to_host_u16 (IP4_HEADER_FLAG_MORE_FRAGMENTS));
 	}
       else
 	{
 	  vlib_buffer_advance (p, -2 * (sizeof (*ip6) - sizeof (*ip4)));
 	  ip6 = vlib_buffer_get_current (p);
 	  clib_memcpy (u8_ptr_add (ip6, sizeof (*ip6) - sizeof (*ip4)), ip4,
 		       20 + 8);
 	  ip4 =
 	    (ip4_header_t *) u8_ptr_add (ip6, sizeof (*ip6) - sizeof (*ip4));
 	  icmp = (icmp46_header_t *) u8_ptr_add (ip4, sizeof (*ip4));
 	  inner_ip6 =
 	    (ip6_header_t *) u8_ptr_add (inner_ip4,
 					 sizeof (*ip4) - sizeof (*ip6));
 	  ip6->payload_length =
 	    u16_net_add (ip4->length, sizeof (*ip6) - 2 * sizeof (*ip4));
 	  inner_frag = NULL;
 	}

       if (PREDICT_TRUE (inner_ip4->protocol == IP_PROTOCOL_TCP))
 	{
 	  inner_L4_checksum = &((tcp_header_t *) (inner_ip4 + 1))->checksum;
 	  *inner_L4_checksum =
 	    ip_csum_fold (ip_csum_sub_even
 			  (*inner_L4_checksum,
 			   *((u64 *) (&inner_ip4->src_address))));
 	}
       else if (PREDICT_TRUE (inner_ip4->protocol == IP_PROTOCOL_UDP))
 	{
 	  inner_L4_checksum = &((udp_header_t *) (inner_ip4 + 1))->checksum;
 	  if (*inner_L4_checksum)
 	    *inner_L4_checksum =
 	      ip_csum_fold (ip_csum_sub_even
 			    (*inner_L4_checksum,
 			     *((u64 *) (&inner_ip4->src_address))));
 	}
       else if (inner_ip4->protocol == IP_PROTOCOL_ICMP)
 	{
 	  //We have an ICMP inside an ICMP
 	  //It needs to be translated, but not for error ICMP messages
 	  icmp46_header_t *inner_icmp = (icmp46_header_t *) (inner_ip4 + 1);
 	  //Only types ICMP4_echo_request and ICMP4_echo_reply are handled by icmp_to_icmp6_header
 	  inner_icmp->type = (inner_icmp->type == ICMP4_echo_request) ?
 	    ICMP6_echo_request : ICMP6_echo_reply;
 	  inner_L4_checksum = &inner_icmp->checksum;
 	  inner_ip4->protocol = IP_PROTOCOL_ICMP6;
 	}
       else
 	{
 	  /* To shut up Coverity */
 	  os_panic ();
 	}

       inner_ip6->ip_version_traffic_class_and_flow_label =
 	clib_host_to_net_u32 ((6 << 28) + (inner_ip4->tos << 20));
       inner_ip6->payload_length =
 	u16_net_add (inner_ip4->length, -sizeof (*inner_ip4));
       inner_ip6->hop_limit = inner_ip4->ttl;
       inner_ip6->protocol = inner_ip4->protocol;

       if ((rv = inner_fn (inner_ip4, inner_ip6, inner_ctx)) != 0)
 	return rv;

       if (PREDICT_FALSE (inner_frag != NULL))
 	{
 	  inner_frag->next_hdr = inner_ip6->protocol;
 	  inner_frag->identification = inner_frag_id;
 	  inner_frag->rsv = 0;
 	  inner_frag->fragment_offset_and_more =
 	    ip6_frag_hdr_offset_and_more (inner_frag_offset, inner_frag_more);
 	  inner_ip6->protocol = IP_PROTOCOL_IPV6_FRAGMENTATION;
 	  inner_ip6->payload_length =
 	    clib_host_to_net_u16 (clib_net_to_host_u16
 				  (inner_ip6->payload_length) +
 				  sizeof (*inner_frag));
 	}

       csum = *inner_L4_checksum;
       if (inner_ip6->protocol == IP_PROTOCOL_ICMP6)
 	{
 	  //Recompute ICMP checksum
 	  icmp46_header_t *inner_icmp = (icmp46_header_t *) (inner_ip4 + 1);

 	  inner_icmp->checksum = 0;
 	  csum = ip_csum_with_carry (0, inner_ip6->payload_length);
 	  csum =
 	    ip_csum_with_carry (csum,
 				clib_host_to_net_u16 (inner_ip6->protocol));
 	  csum = ip_csum_with_carry (csum, inner_ip6->src_address.as_u64[0]);
 	  csum = ip_csum_with_carry (csum, inner_ip6->src_address.as_u64[1]);
 	  csum = ip_csum_with_carry (csum, inner_ip6->dst_address.as_u64[0]);
 	  csum = ip_csum_with_carry (csum, inner_ip6->dst_address.as_u64[1]);
 	  csum =
 	    ip_incremental_checksum (csum, inner_icmp,
 				     clib_net_to_host_u16
 				     (inner_ip6->payload_length));
 	  inner_icmp->checksum = ~ip_csum_fold (csum);
 	}
       else
 	{
 	  /* UDP checksum is optional */
 	  if (csum)
 	    {
 	      csum =
 		ip_csum_add_even (csum, inner_ip6->src_address.as_u64[0]);
 	      csum =
 		ip_csum_add_even (csum, inner_ip6->src_address.as_u64[1]);
 	      csum =
 		ip_csum_add_even (csum, inner_ip6->dst_address.as_u64[0]);
 	      csum =
 		ip_csum_add_even (csum, inner_ip6->dst_address.as_u64[1]);
 	      *inner_L4_checksum = ip_csum_fold (csum);
 	    }
 	}
     }
   else
     {
       vlib_buffer_advance (p, sizeof (*ip4) - sizeof (*ip6));
       ip6 = vlib_buffer_get_current (p);
       ip6->payload_length =
 	clib_host_to_net_u16 (clib_net_to_host_u16 (ip4->length) -
 			      sizeof (*ip4));
     }

   //Translate outer IPv6
   ip6->ip_version_traffic_class_and_flow_label =
     clib_host_to_net_u32 ((6 << 28) + (ip4->tos << 20));

   ip6->hop_limit = ip4->ttl;
   ip6->protocol = IP_PROTOCOL_ICMP6;

   if ((rv = fn (ip4, ip6, ctx)) != 0)
     return rv;

   //Truncate when the packet exceeds the minimal IPv6 MTU
   if (p->current_length > 1280)
     {
       ip6->payload_length = clib_host_to_net_u16 (1280 - sizeof (*ip6));
       p->current_length = 1280;	//Looks too simple to be correct...
     }

   //Recompute ICMP checksum
   icmp->checksum = 0;
   csum = ip_csum_with_carry (0, ip6->payload_length);
   csum = ip_csum_with_carry (csum, clib_host_to_net_u16 (ip6->protocol));
   csum = ip_csum_with_carry (csum, ip6->src_address.as_u64[0]);
   csum = ip_csum_with_carry (csum, ip6->src_address.as_u64[1]);
   csum = ip_csum_with_carry (csum, ip6->dst_address.as_u64[0]);
   csum = ip_csum_with_carry (csum, ip6->dst_address.as_u64[1]);
   csum =
     ip_incremental_checksum (csum, icmp,
 			     clib_net_to_host_u16 (ip6->payload_length));
   icmp->checksum = ~ip_csum_fold (csum);

   return 0;
 }

 /**
  * @brief Translate IPv4 fragmented packet to IPv6.
  *
  * @param p   Buffer to translate.
  * @param fn  The function to translate header.
  * @param ctx A context passed in the header translate function.
  *
  * @returns 0 on success, non-zero value otherwise.
  */
 always_inline int
 ip4_to_ip6_fragmented (vlib_buffer_t * p, ip4_to_ip6_set_fn_t fn, void *ctx)
 {
   ip4_header_t *ip4;
   ip6_header_t *ip6;
   ip6_frag_hdr_t *frag;
   int rv;

   ip4 = vlib_buffer_get_current (p);
   frag = (ip6_frag_hdr_t *) u8_ptr_add (ip4, sizeof (*ip4) - sizeof (*frag));
   ip6 =
     (ip6_header_t *) u8_ptr_add (ip4,
 				 sizeof (*ip4) - sizeof (*frag) -
 				 sizeof (*ip6));
   vlib_buffer_advance (p, sizeof (*ip4) - sizeof (*ip6) - sizeof (*frag));

   //We know that the protocol was one of ICMP, TCP or UDP
   //because the first fragment was found and cached
   frag->next_hdr =
     (ip4->protocol == IP_PROTOCOL_ICMP) ? IP_PROTOCOL_ICMP6 : ip4->protocol;
   frag->identification = frag_id_4to6 (ip4->fragment_id);
   frag->rsv = 0;
   frag->fragment_offset_and_more =
     ip6_frag_hdr_offset_and_more (ip4_get_fragment_offset (ip4),
 				  clib_net_to_host_u16
 				  (ip4->flags_and_fragment_offset) &
 				  IP4_HEADER_FLAG_MORE_FRAGMENTS);

   ip6->ip_version_traffic_class_and_flow_label =
     clib_host_to_net_u32 ((6 << 28) + (ip4->tos << 20));
   ip6->payload_length =
     clib_host_to_net_u16 (clib_net_to_host_u16 (ip4->length) -
 			  sizeof (*ip4) + sizeof (*frag));
   ip6->hop_limit = ip4->ttl;
   ip6->protocol = IP_PROTOCOL_IPV6_FRAGMENTATION;

   if ((rv = fn (ip4, ip6, ctx)) != 0)
     return rv;

   return 0;
 }

 /**
  * @brief Translate IPv4 UDP/TCP packet to IPv6.
  *
  * @param p   Buffer to translate.
  * @param fn  The function to translate header.
  * @param ctx A context passed in the header translate function.
  *
  * @returns 0 on success, non-zero value otherwise.
  */
 always_inline int
 ip4_to_ip6_tcp_udp (vlib_buffer_t * p, ip4_to_ip6_set_fn_t fn, void *ctx)
 {
   ip4_header_t *ip4;
   ip6_header_t *ip6;
   ip_csum_t csum;
   u16 *checksum;
   ip6_frag_hdr_t *frag;
   u32 frag_id;
   int rv;
   ip4_address_t old_src, old_dst;

   ip4 = vlib_buffer_get_current (p);

   if (ip4->protocol == IP_PROTOCOL_UDP)
     {
       udp_header_t *udp = ip4_next_header (ip4);
       checksum = &udp->checksum;

       //UDP checksum is optional over IPv4 but mandatory for IPv6
       //We do not check udp->length sanity but use our safe computed value instead
       if (PREDICT_FALSE (!checksum))
 	{
 	  u16 udp_len = clib_host_to_net_u16 (ip4->length) - sizeof (*ip4);
 	  csum = ip_incremental_checksum (0, udp, udp_len);
 	  csum = ip_csum_with_carry (csum, clib_host_to_net_u16 (udp_len));
 	  csum =
 	    ip_csum_with_carry (csum, clib_host_to_net_u16 (IP_PROTOCOL_UDP));
 	  csum = ip_csum_with_carry (csum, *((u64 *) (&ip4->src_address)));
 	  *checksum = ~ip_csum_fold (csum);
 	}
     }
   else
     {
       tcp_header_t *tcp = ip4_next_header (ip4);
       checksum = &tcp->checksum;
     }

   old_src.as_u32 = ip4->src_address.as_u32;
   old_dst.as_u32 = ip4->dst_address.as_u32;

   // Deal with fragmented packets
   if (PREDICT_FALSE (ip4->flags_and_fragment_offset &
 		     clib_host_to_net_u16 (IP4_HEADER_FLAG_MORE_FRAGMENTS)))
     {
       ip6 =
 	(ip6_header_t *) u8_ptr_add (ip4,
 				     sizeof (*ip4) - sizeof (*ip6) -
 				     sizeof (*frag));
       frag =
 	(ip6_frag_hdr_t *) u8_ptr_add (ip4, sizeof (*ip4) - sizeof (*frag));
       frag_id = frag_id_4to6 (ip4->fragment_id);
       vlib_buffer_advance (p, sizeof (*ip4) - sizeof (*ip6) - sizeof (*frag));
     }
   else
     {
       ip6 = (ip6_header_t *) (((u8 *) ip4) + sizeof (*ip4) - sizeof (*ip6));
       vlib_buffer_advance (p, sizeof (*ip4) - sizeof (*ip6));
       frag = NULL;
     }

   ip6->ip_version_traffic_class_and_flow_label =
     clib_host_to_net_u32 ((6 << 28) + (ip4->tos << 20));
   ip6->payload_length = u16_net_add (ip4->length, -sizeof (*ip4));
   ip6->hop_limit = ip4->ttl;
   ip6->protocol = ip4->protocol;

   if (PREDICT_FALSE (frag != NULL))
     {
       frag->next_hdr = ip6->protocol;
       frag->identification = frag_id;
       frag->rsv = 0;
       frag->fragment_offset_and_more = ip6_frag_hdr_offset_and_more (0, 1);
       ip6->protocol = IP_PROTOCOL_IPV6_FRAGMENTATION;
       ip6->payload_length = u16_net_add (ip6->payload_length, sizeof (*frag));
     }

   if ((rv = fn (ip4, ip6, ctx)) != 0)
     return rv;

   csum = ip_csum_sub_even (*checksum, old_src.as_u32);
   csum = ip_csum_sub_even (csum, old_dst.as_u32);
   csum = ip_csum_add_even (csum, ip6->src_address.as_u64[0]);
   csum = ip_csum_add_even (csum, ip6->src_address.as_u64[1]);
   csum = ip_csum_add_even (csum, ip6->dst_address.as_u64[0]);
   csum = ip_csum_add_even (csum, ip6->dst_address.as_u64[1]);
   *checksum = ip_csum_fold (csum);

   return 0;
 }

 /**
  * @brief Translate IPv4 packet to IPv6 (IP header only).
  *
  * @param p   Buffer to translate.
  * @param fn  The function to translate header.
  * @param ctx A context passed in the header translate function.
  *
  * @returns 0 on success, non-zero value otherwise.
  */
 always_inline int
 ip4_to_ip6 (vlib_buffer_t * p, ip4_to_ip6_set_fn_t fn, void *ctx)
 {
   ip4_header_t *ip4;
   ip6_header_t *ip6;
   ip6_frag_hdr_t *frag;
   u32 frag_id;
   int rv;

   ip4 = vlib_buffer_get_current (p);

   // Deal with fragmented packets
   if (PREDICT_FALSE (ip4->flags_and_fragment_offset &
 		     clib_host_to_net_u16 (IP4_HEADER_FLAG_MORE_FRAGMENTS)))
     {
       ip6 =
 	(ip6_header_t *) u8_ptr_add (ip4,
 				     sizeof (*ip4) - sizeof (*ip6) -
 				     sizeof (*frag));
       frag =
 	(ip6_frag_hdr_t *) u8_ptr_add (ip4, sizeof (*ip4) - sizeof (*frag));
       frag_id = frag_id_4to6 (ip4->fragment_id);
       vlib_buffer_advance (p, sizeof (*ip4) - sizeof (*ip6) - sizeof (*frag));
     }
   else
     {
       ip6 = (ip6_header_t *) (((u8 *) ip4) + sizeof (*ip4) - sizeof (*ip6));
       vlib_buffer_advance (p, sizeof (*ip4) - sizeof (*ip6));
       frag = NULL;
     }

   ip6->ip_version_traffic_class_and_flow_label =
     clib_host_to_net_u32 ((6 << 28) + (ip4->tos << 20));
   ip6->payload_length = u16_net_add (ip4->length, -sizeof (*ip4));
   ip6->hop_limit = ip4->ttl;
   ip6->protocol = ip4->protocol;

   if (PREDICT_FALSE (frag != NULL))
     {
       frag->next_hdr = ip6->protocol;
       frag->identification = frag_id;
       frag->rsv = 0;
       frag->fragment_offset_and_more = ip6_frag_hdr_offset_and_more (0, 1);
       ip6->protocol = IP_PROTOCOL_IPV6_FRAGMENTATION;
       ip6->payload_length = u16_net_add (ip6->payload_length, sizeof (*frag));
     }

   if ((rv = fn (ip4, ip6, ctx)) != 0)
     return rv;

   return 0;
 }

 #endif /* __included_ip4_to_ip6_h__ */
	/*
	* Copyright (c) 2017 Cisco and/or its affiliates.
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at:
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/
	/**
	* @file
	* @brief IPv4 to IPv6 translation
	*/
	#ifndef __included_ip4_to_ip6_h__
	#define __included_ip4_to_ip6_h__

	#include <vnet/ip/ip.h>


	/**
	* IPv4 to IPv6 set call back function type
	*/
	typedef int (ip4_to_ip6_set_fn_t) (ip4_header_t ip4, ip6_header_t * ip6,
	void *ctx);

	/* INDENT-OFF */
	static u8 icmp_to_icmp6_updater_pointer_table[] =
	{ 0, 1, 4, 4, ~0,
	~0, ~0, ~0, 7, 6,
	~0, ~0, 8, 8, 8,
	8, 24, 24, 24, 24
	};
	/* INDENT-ON */

	#define frag_id_4to6(id) (id)

	/**
	* @brief Get TCP/UDP port number or ICMP id from IPv4 packet.
	*
	* @param ip4 IPv4 header.
	* @param sender 1 get sender port, 0 get receiver port.
	*
	* @returns Port number on success, 0 otherwise.
	*/
	always_inline u16
	ip4_get_port (ip4_header_t * ip, u8 sender)
	{
	if (ip->ip_version_and_header_length != 0x45 \|\|
	ip4_get_fragment_offset (ip))
	return 0;

	if (PREDICT_TRUE ((ip->protocol == IP_PROTOCOL_TCP) \|\|
	(ip->protocol == IP_PROTOCOL_UDP)))
	{
	udp_header_t udp = (void ) (ip + 1);
	return (sender) ? udp->src_port : udp->dst_port;
	}
	else if (ip->protocol == IP_PROTOCOL_ICMP)
	{
	icmp46_header_t icmp = (void ) (ip + 1);
	if (icmp->type == ICMP4_echo_request \|\| icmp->type == ICMP4_echo_reply)
	{
	return ((u16 ) (icmp + 1));
	}
	else if (clib_net_to_host_u16 (ip->length) >= 64)
	{
	ip = (ip4_header_t *) (icmp + 2);
	if (PREDICT_TRUE ((ip->protocol == IP_PROTOCOL_TCP) \|\|
	(ip->protocol == IP_PROTOCOL_UDP)))
	{
	udp_header_t udp = (void ) (ip + 1);
	return (sender) ? udp->dst_port : udp->src_port;
	}
	else if (ip->protocol == IP_PROTOCOL_ICMP)
	{
	icmp46_header_t icmp = (void ) (ip + 1);
	if (icmp->type == ICMP4_echo_request \|\|
	icmp->type == ICMP4_echo_reply)
	{
	return ((u16 ) (icmp + 1));
	}
	}
	}
	}
	return 0;
	}

	/**
	* @brief Convert type and code value from ICMP4 to ICMP6.
	*
	* @param icmp ICMP header.
	* @param inner_ip4 Inner IPv4 header if present, 0 otherwise.
	*
	* @returns 0 on success, non-zero value otherwise.
	*/
	always_inline int
	icmp_to_icmp6_header (icmp46_header_t * icmp, ip4_header_t ** inner_ip4)
	{
	*inner_ip4 = NULL;
	switch (icmp->type)
	{
	case ICMP4_echo_reply:
	icmp->type = ICMP6_echo_reply;
	break;
	case ICMP4_echo_request:
	icmp->type = ICMP6_echo_request;
	break;
	case ICMP4_destination_unreachable:
	inner_ip4 = (ip4_header_t ) (((u8 *) icmp) + 8);

	switch (icmp->code)
	{
	case ICMP4_destination_unreachable_destination_unreachable_net: //0
	case ICMP4_destination_unreachable_destination_unreachable_host: //1
	icmp->type = ICMP6_destination_unreachable;
	icmp->code = ICMP6_destination_unreachable_no_route_to_destination;
	break;
	case ICMP4_destination_unreachable_protocol_unreachable: //2
	icmp->type = ICMP6_parameter_problem;
	icmp->code = ICMP6_parameter_problem_unrecognized_next_header;
	break;
	case ICMP4_destination_unreachable_port_unreachable: //3
	icmp->type = ICMP6_destination_unreachable;
	icmp->code = ICMP6_destination_unreachable_port_unreachable;
	break;
	case ICMP4_destination_unreachable_fragmentation_needed_and_dont_fragment_set: //4
	icmp->type =
	ICMP6_packet_too_big;
	icmp->code = 0;
	{
	u32 advertised_mtu = clib_net_to_host_u32 (((u32 ) (icmp + 1)));
	if (advertised_mtu)
	advertised_mtu += 20;
	else
	advertised_mtu = 1000; //FIXME ! (RFC 1191 - plateau value)

	//FIXME: = minimum(advertised MTU+20, MTU_of_IPv6_nexthop, (MTU_of_IPv4_nexthop)+20)
	((u32 ) (icmp + 1)) = clib_host_to_net_u32 (advertised_mtu);
	}
	break;

	case ICMP4_destination_unreachable_source_route_failed: //5
	case ICMP4_destination_unreachable_destination_network_unknown: //6
	case ICMP4_destination_unreachable_destination_host_unknown: //7
	case ICMP4_destination_unreachable_source_host_isolated: //8
	case ICMP4_destination_unreachable_network_unreachable_for_type_of_service: //11
	case ICMP4_destination_unreachable_host_unreachable_for_type_of_service: //12
	icmp->type =
	ICMP6_destination_unreachable;
	icmp->code = ICMP6_destination_unreachable_no_route_to_destination;
	break;
	case ICMP4_destination_unreachable_network_administratively_prohibited: //9
	case ICMP4_destination_unreachable_host_administratively_prohibited: //10
	case ICMP4_destination_unreachable_communication_administratively_prohibited: //13
	case ICMP4_destination_unreachable_precedence_cutoff_in_effect: //15
	icmp->type = ICMP6_destination_unreachable;
	icmp->code =
	ICMP6_destination_unreachable_destination_administratively_prohibited;
	break;
	case ICMP4_destination_unreachable_host_precedence_violation: //14
	default:
	return -1;
	}
	break;

	case ICMP4_time_exceeded: //11
	inner_ip4 = (ip4_header_t ) (((u8 *) icmp) + 8);
	icmp->type = ICMP6_time_exceeded;
	break;

	case ICMP4_parameter_problem:
	inner_ip4 = (ip4_header_t ) (((u8 *) icmp) + 8);

	switch (icmp->code)
	{
	case ICMP4_parameter_problem_pointer_indicates_error:
	case ICMP4_parameter_problem_bad_length:
	icmp->type = ICMP6_parameter_problem;
	icmp->code = ICMP6_parameter_problem_erroneous_header_field;
	{
	u8 ptr =
	icmp_to_icmp6_updater_pointer_table[((u8 ) (icmp + 1))];
	if (ptr == 0xff)
	return -1;

	((u32 ) (icmp + 1)) = clib_host_to_net_u32 (ptr);
	}
	break;
	default:
	//All other codes cause error
	return -1;
	}
	break;

	default:
	//All other types cause error
	return -1;
	break;
	}
	return 0;
	}

	/**
	* @brief Translate ICMP4 packet to ICMP6.
	*
	* @param p Buffer to translate.
	* @param fn The function to translate outer header.
	* @param ctx A context passed in the outer header translate function.
	* @param inner_fn The function to translate inner header.
	* @param inner_ctx A context passed in the inner header translate function.
	*
	* @returns 0 on success, non-zero value otherwise.
	*/
	always_inline int
	icmp_to_icmp6 (vlib_buffer_t * p, ip4_to_ip6_set_fn_t fn, void *ctx,
	ip4_to_ip6_set_fn_t inner_fn, void *inner_ctx)
	{
	ip4_header_t ip4, inner_ip4;
	ip6_header_t ip6, inner_ip6;
	u32 ip_len;
	icmp46_header_t *icmp;
	ip_csum_t csum;
	ip6_frag_hdr_t *inner_frag;
	u32 inner_frag_id;
	u32 inner_frag_offset;
	u8 inner_frag_more;
	u16 *inner_L4_checksum = 0;
	int rv;

	ip4 = vlib_buffer_get_current (p);
	ip_len = clib_net_to_host_u16 (ip4->length);
	ASSERT (ip_len <= p->current_length);

	icmp = (icmp46_header_t *) (ip4 + 1);
	if (icmp_to_icmp6_header (icmp, &inner_ip4))
	return -1;

	if (inner_ip4)
	{
	//We have 2 headers to translate.
	//We need to make some room in the middle of the packet
	if (PREDICT_FALSE (ip4_is_fragment (inner_ip4)))
	{
	//Here it starts getting really tricky
	//We will add a fragmentation header in the inner packet

	if (!ip4_is_first_fragment (inner_ip4))
	{
	//For now we do not handle unless it is the first fragment
	//Ideally we should handle the case as we are in slow path already
	return -1;
	}

	vlib_buffer_advance (p,
	-2 * (sizeof (ip6) - sizeof (ip4)) -
	sizeof (*inner_frag));
	ip6 = vlib_buffer_get_current (p);
	clib_memcpy (u8_ptr_add (ip6, sizeof (ip6) - sizeof (ip4)), ip4,
	20 + 8);
	ip4 =
	(ip4_header_t ) u8_ptr_add (ip6, sizeof (ip6) - sizeof (*ip4));
	icmp = (icmp46_header_t *) (ip4 + 1);

	inner_ip6 =
	(ip6_header_t *) u8_ptr_add (inner_ip4,
	sizeof (ip4) - sizeof (ip6) -
	sizeof (*inner_frag));
	inner_frag =
	(ip6_frag_hdr_t ) u8_ptr_add (inner_ip6, sizeof (inner_ip6));
	ip6->payload_length =
	u16_net_add (ip4->length,
	sizeof (ip6) - 2 sizeof (*ip4) +
	sizeof (*inner_frag));
	inner_frag_id = frag_id_4to6 (inner_ip4->fragment_id);
	inner_frag_offset = ip4_get_fragment_offset (inner_ip4);
	inner_frag_more =
	! !(inner_ip4->flags_and_fragment_offset &
	clib_net_to_host_u16 (IP4_HEADER_FLAG_MORE_FRAGMENTS));
	}
	else
	{
	vlib_buffer_advance (p, -2 * (sizeof (ip6) - sizeof (ip4)));
	ip6 = vlib_buffer_get_current (p);
	clib_memcpy (u8_ptr_add (ip6, sizeof (ip6) - sizeof (ip4)), ip4,
	20 + 8);
	ip4 =
	(ip4_header_t ) u8_ptr_add (ip6, sizeof (ip6) - sizeof (*ip4));
	icmp = (icmp46_header_t ) u8_ptr_add (ip4, sizeof (ip4));
	inner_ip6 =
	(ip6_header_t *) u8_ptr_add (inner_ip4,
	sizeof (ip4) - sizeof (ip6));
	ip6->payload_length =
	u16_net_add (ip4->length, sizeof (ip6) - 2 sizeof (*ip4));
	inner_frag = NULL;
	}

	if (PREDICT_TRUE (inner_ip4->protocol == IP_PROTOCOL_TCP))
	{
	inner_L4_checksum = &((tcp_header_t *) (inner_ip4 + 1))->checksum;
	*inner_L4_checksum =
	ip_csum_fold (ip_csum_sub_even
	(*inner_L4_checksum,
	((u64 ) (&inner_ip4->src_address))));
	}
	else if (PREDICT_TRUE (inner_ip4->protocol == IP_PROTOCOL_UDP))
	{
	inner_L4_checksum = &((udp_header_t *) (inner_ip4 + 1))->checksum;
	if (*inner_L4_checksum)
	*inner_L4_checksum =
	ip_csum_fold (ip_csum_sub_even
	(*inner_L4_checksum,
	((u64 ) (&inner_ip4->src_address))));
	}
	else if (inner_ip4->protocol == IP_PROTOCOL_ICMP)
	{
	//We have an ICMP inside an ICMP
	//It needs to be translated, but not for error ICMP messages
	icmp46_header_t inner_icmp = (icmp46_header_t ) (inner_ip4 + 1);
	//Only types ICMP4_echo_request and ICMP4_echo_reply are handled by icmp_to_icmp6_header
	inner_icmp->type = (inner_icmp->type == ICMP4_echo_request) ?
	ICMP6_echo_request : ICMP6_echo_reply;
	inner_L4_checksum = &inner_icmp->checksum;
	inner_ip4->protocol = IP_PROTOCOL_ICMP6;
	}
	else
	{
	/* To shut up Coverity */
	os_panic ();
	}

	inner_ip6->ip_version_traffic_class_and_flow_label =
	clib_host_to_net_u32 ((6 << 28) + (inner_ip4->tos << 20));
	inner_ip6->payload_length =
	u16_net_add (inner_ip4->length, -sizeof (*inner_ip4));
	inner_ip6->hop_limit = inner_ip4->ttl;
	inner_ip6->protocol = inner_ip4->protocol;

	if ((rv = inner_fn (inner_ip4, inner_ip6, inner_ctx)) != 0)
	return rv;

	if (PREDICT_FALSE (inner_frag != NULL))
	{
	inner_frag->next_hdr = inner_ip6->protocol;
	inner_frag->identification = inner_frag_id;
	inner_frag->rsv = 0;
	inner_frag->fragment_offset_and_more =
	ip6_frag_hdr_offset_and_more (inner_frag_offset, inner_frag_more);
	inner_ip6->protocol = IP_PROTOCOL_IPV6_FRAGMENTATION;
	inner_ip6->payload_length =
	clib_host_to_net_u16 (clib_net_to_host_u16
	(inner_ip6->payload_length) +
	sizeof (*inner_frag));
	}

	csum = *inner_L4_checksum;
	if (inner_ip6->protocol == IP_PROTOCOL_ICMP6)
	{
	//Recompute ICMP checksum
	icmp46_header_t inner_icmp = (icmp46_header_t ) (inner_ip4 + 1);

	inner_icmp->checksum = 0;
	csum = ip_csum_with_carry (0, inner_ip6->payload_length);
	csum =
	ip_csum_with_carry (csum,
	clib_host_to_net_u16 (inner_ip6->protocol));
	csum = ip_csum_with_carry (csum, inner_ip6->src_address.as_u64[0]);
	csum = ip_csum_with_carry (csum, inner_ip6->src_address.as_u64[1]);
	csum = ip_csum_with_carry (csum, inner_ip6->dst_address.as_u64[0]);
	csum = ip_csum_with_carry (csum, inner_ip6->dst_address.as_u64[1]);
	csum =
	ip_incremental_checksum (csum, inner_icmp,
	clib_net_to_host_u16
	(inner_ip6->payload_length));
	inner_icmp->checksum = ~ip_csum_fold (csum);
	}
	else
	{
	/* UDP checksum is optional */
	if (csum)
	{
	csum =
	ip_csum_add_even (csum, inner_ip6->src_address.as_u64[0]);
	csum =
	ip_csum_add_even (csum, inner_ip6->src_address.as_u64[1]);
	csum =
	ip_csum_add_even (csum, inner_ip6->dst_address.as_u64[0]);
	csum =
	ip_csum_add_even (csum, inner_ip6->dst_address.as_u64[1]);
	*inner_L4_checksum = ip_csum_fold (csum);
	}
	}
	}
	else
	{
	vlib_buffer_advance (p, sizeof (ip4) - sizeof (ip6));
	ip6 = vlib_buffer_get_current (p);
	ip6->payload_length =
	clib_host_to_net_u16 (clib_net_to_host_u16 (ip4->length) -
	sizeof (*ip4));
	}

	//Translate outer IPv6
	ip6->ip_version_traffic_class_and_flow_label =
	clib_host_to_net_u32 ((6 << 28) + (ip4->tos << 20));

	ip6->hop_limit = ip4->ttl;
	ip6->protocol = IP_PROTOCOL_ICMP6;

	if ((rv = fn (ip4, ip6, ctx)) != 0)
	return rv;

	//Truncate when the packet exceeds the minimal IPv6 MTU
	if (p->current_length > 1280)
	{
	ip6->payload_length = clib_host_to_net_u16 (1280 - sizeof (*ip6));
	p->current_length = 1280; //Looks too simple to be correct...
	}

	//Recompute ICMP checksum
	icmp->checksum = 0;
	csum = ip_csum_with_carry (0, ip6->payload_length);
	csum = ip_csum_with_carry (csum, clib_host_to_net_u16 (ip6->protocol));
	csum = ip_csum_with_carry (csum, ip6->src_address.as_u64[0]);
	csum = ip_csum_with_carry (csum, ip6->src_address.as_u64[1]);
	csum = ip_csum_with_carry (csum, ip6->dst_address.as_u64[0]);
	csum = ip_csum_with_carry (csum, ip6->dst_address.as_u64[1]);
	csum =
	ip_incremental_checksum (csum, icmp,
	clib_net_to_host_u16 (ip6->payload_length));
	icmp->checksum = ~ip_csum_fold (csum);

	return 0;
	}

	/**
	* @brief Translate IPv4 fragmented packet to IPv6.
	*
	* @param p Buffer to translate.
	* @param fn The function to translate header.
	* @param ctx A context passed in the header translate function.
	*
	* @returns 0 on success, non-zero value otherwise.
	*/
	always_inline int
	ip4_to_ip6_fragmented (vlib_buffer_t * p, ip4_to_ip6_set_fn_t fn, void *ctx)
	{
	ip4_header_t *ip4;
	ip6_header_t *ip6;
	ip6_frag_hdr_t *frag;
	int rv;

	ip4 = vlib_buffer_get_current (p);
	frag = (ip6_frag_hdr_t ) u8_ptr_add (ip4, sizeof (ip4) - sizeof (*frag));
	ip6 =
	(ip6_header_t *) u8_ptr_add (ip4,
	sizeof (ip4) - sizeof (frag) -
	sizeof (*ip6));
	vlib_buffer_advance (p, sizeof (ip4) - sizeof (ip6) - sizeof (*frag));

	//We know that the protocol was one of ICMP, TCP or UDP
	//because the first fragment was found and cached
	frag->next_hdr =
	(ip4->protocol == IP_PROTOCOL_ICMP) ? IP_PROTOCOL_ICMP6 : ip4->protocol;
	frag->identification = frag_id_4to6 (ip4->fragment_id);
	frag->rsv = 0;
	frag->fragment_offset_and_more =
	ip6_frag_hdr_offset_and_more (ip4_get_fragment_offset (ip4),
	clib_net_to_host_u16
	(ip4->flags_and_fragment_offset) &
	IP4_HEADER_FLAG_MORE_FRAGMENTS);

	ip6->ip_version_traffic_class_and_flow_label =
	clib_host_to_net_u32 ((6 << 28) + (ip4->tos << 20));
	ip6->payload_length =
	clib_host_to_net_u16 (clib_net_to_host_u16 (ip4->length) -
	sizeof (ip4) + sizeof (frag));
	ip6->hop_limit = ip4->ttl;
	ip6->protocol = IP_PROTOCOL_IPV6_FRAGMENTATION;

	if ((rv = fn (ip4, ip6, ctx)) != 0)
	return rv;

	return 0;
	}

	/**
	* @brief Translate IPv4 UDP/TCP packet to IPv6.
	*
	* @param p Buffer to translate.
	* @param fn The function to translate header.
	* @param ctx A context passed in the header translate function.
	*
	* @returns 0 on success, non-zero value otherwise.
	*/
	always_inline int
	ip4_to_ip6_tcp_udp (vlib_buffer_t * p, ip4_to_ip6_set_fn_t fn, void *ctx)
	{
	ip4_header_t *ip4;
	ip6_header_t *ip6;
	ip_csum_t csum;
	u16 *checksum;
	ip6_frag_hdr_t *frag;
	u32 frag_id;
	int rv;
	ip4_address_t old_src, old_dst;

	ip4 = vlib_buffer_get_current (p);

	if (ip4->protocol == IP_PROTOCOL_UDP)
	{
	udp_header_t *udp = ip4_next_header (ip4);
	checksum = &udp->checksum;

	//UDP checksum is optional over IPv4 but mandatory for IPv6
	//We do not check udp->length sanity but use our safe computed value instead
	if (PREDICT_FALSE (!checksum))
	{
	u16 udp_len = clib_host_to_net_u16 (ip4->length) - sizeof (*ip4);
	csum = ip_incremental_checksum (0, udp, udp_len);
	csum = ip_csum_with_carry (csum, clib_host_to_net_u16 (udp_len));
	csum =
	ip_csum_with_carry (csum, clib_host_to_net_u16 (IP_PROTOCOL_UDP));
	csum = ip_csum_with_carry (csum, ((u64 ) (&ip4->src_address)));
	*checksum = ~ip_csum_fold (csum);
	}
	}
	else
	{
	tcp_header_t *tcp = ip4_next_header (ip4);
	checksum = &tcp->checksum;
	}

	old_src.as_u32 = ip4->src_address.as_u32;
	old_dst.as_u32 = ip4->dst_address.as_u32;

	// Deal with fragmented packets
	if (PREDICT_FALSE (ip4->flags_and_fragment_offset &
	clib_host_to_net_u16 (IP4_HEADER_FLAG_MORE_FRAGMENTS)))
	{
	ip6 =
	(ip6_header_t *) u8_ptr_add (ip4,
	sizeof (ip4) - sizeof (ip6) -
	sizeof (*frag));
	frag =
	(ip6_frag_hdr_t ) u8_ptr_add (ip4, sizeof (ip4) - sizeof (*frag));
	frag_id = frag_id_4to6 (ip4->fragment_id);
	vlib_buffer_advance (p, sizeof (ip4) - sizeof (ip6) - sizeof (*frag));
	}
	else
	{
	ip6 = (ip6_header_t ) (((u8 ) ip4) + sizeof (ip4) - sizeof (ip6));
	vlib_buffer_advance (p, sizeof (ip4) - sizeof (ip6));
	frag = NULL;
	}

	ip6->ip_version_traffic_class_and_flow_label =
	clib_host_to_net_u32 ((6 << 28) + (ip4->tos << 20));
	ip6->payload_length = u16_net_add (ip4->length, -sizeof (*ip4));
	ip6->hop_limit = ip4->ttl;
	ip6->protocol = ip4->protocol;

	if (PREDICT_FALSE (frag != NULL))
	{
	frag->next_hdr = ip6->protocol;
	frag->identification = frag_id;
	frag->rsv = 0;
	frag->fragment_offset_and_more = ip6_frag_hdr_offset_and_more (0, 1);
	ip6->protocol = IP_PROTOCOL_IPV6_FRAGMENTATION;
	ip6->payload_length = u16_net_add (ip6->payload_length, sizeof (*frag));
	}

	if ((rv = fn (ip4, ip6, ctx)) != 0)
	return rv;

	csum = ip_csum_sub_even (*checksum, old_src.as_u32);
	csum = ip_csum_sub_even (csum, old_dst.as_u32);
	csum = ip_csum_add_even (csum, ip6->src_address.as_u64[0]);
	csum = ip_csum_add_even (csum, ip6->src_address.as_u64[1]);
	csum = ip_csum_add_even (csum, ip6->dst_address.as_u64[0]);
	csum = ip_csum_add_even (csum, ip6->dst_address.as_u64[1]);
	*checksum = ip_csum_fold (csum);

	return 0;
	}

	/**
	* @brief Translate IPv4 packet to IPv6 (IP header only).
	*
	* @param p Buffer to translate.
	* @param fn The function to translate header.
	* @param ctx A context passed in the header translate function.
	*
	* @returns 0 on success, non-zero value otherwise.
	*/
	always_inline int
	ip4_to_ip6 (vlib_buffer_t * p, ip4_to_ip6_set_fn_t fn, void *ctx)
	{
	ip4_header_t *ip4;
	ip6_header_t *ip6;
	ip6_frag_hdr_t *frag;
	u32 frag_id;
	int rv;

	ip4 = vlib_buffer_get_current (p);

	// Deal with fragmented packets
	if (PREDICT_FALSE (ip4->flags_and_fragment_offset &
	clib_host_to_net_u16 (IP4_HEADER_FLAG_MORE_FRAGMENTS)))
	{
	ip6 =
	(ip6_header_t *) u8_ptr_add (ip4,
	sizeof (ip4) - sizeof (ip6) -
	sizeof (*frag));
	frag =
	(ip6_frag_hdr_t ) u8_ptr_add (ip4, sizeof (ip4) - sizeof (*frag));
	frag_id = frag_id_4to6 (ip4->fragment_id);
	vlib_buffer_advance (p, sizeof (ip4) - sizeof (ip6) - sizeof (*frag));
	}
	else
	{
	ip6 = (ip6_header_t ) (((u8 ) ip4) + sizeof (ip4) - sizeof (ip6));
	vlib_buffer_advance (p, sizeof (ip4) - sizeof (ip6));
	frag = NULL;
	}

	ip6->ip_version_traffic_class_and_flow_label =
	clib_host_to_net_u32 ((6 << 28) + (ip4->tos << 20));
	ip6->payload_length = u16_net_add (ip4->length, -sizeof (*ip4));
	ip6->hop_limit = ip4->ttl;
	ip6->protocol = ip4->protocol;

	if (PREDICT_FALSE (frag != NULL))
	{
	frag->next_hdr = ip6->protocol;
	frag->identification = frag_id;
	frag->rsv = 0;
	frag->fragment_offset_and_more = ip6_frag_hdr_offset_and_more (0, 1);
	ip6->protocol = IP_PROTOCOL_IPV6_FRAGMENTATION;
	ip6->payload_length = u16_net_add (ip6->payload_length, sizeof (*frag));
	}

	if ((rv = fn (ip4, ip6, ctx)) != 0)
	return rv;

	return 0;
	}

	#endif /* __included_ip4_to_ip6_h__ */