summaryrefslogtreecommitdiffstats
path: root/src/vnet/mpls/packet.h
blob: ca6ac407686a7b15a7a6d9e1792b5a118d841b58 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
#ifndef included_vnet_mpls_packet_h
#define included_vnet_mpls_packet_h

/*
 * MPLS packet format
 *
 * Copyright (c) 2012 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.
 */

/**
 * A label value only, i.e. 20bits.
 */
typedef u32 mpls_label_t;

typedef struct {
    /* Label: top 20 bits [in network byte order] */
    /* Experimental: 3 bits ... */
    /* S (bottom of label stack): 1 bit */
    /* TTL: 8 bits */
    mpls_label_t label_exp_s_ttl;
} mpls_unicast_header_t;

typedef enum mpls_eos_bit_t_
{
    MPLS_NON_EOS = 0,
    MPLS_EOS     = 1,
} mpls_eos_bit_t;

#define MPLS_EOS_BITS {				\
    [MPLS_NON_EOS] = "neos",		      	\
    [MPLS_EOS] = "eos",				\
}

/**
 * The Default TTL added to MPLS label headers when no other value is available
 */
#define MPLS_LABEL_DEFAULT_TTL 64

/**
 * The Default EXP added to MPLS label headers when no other value is available
 */
#define MPLS_LABEL_DEFAULT_EXP 0

/**
 * When in uniform mode convert an IPv[46] DSCP value to an MPLS EXP value
 */
static inline u8 ip_dscp_to_mpls_exp (u8 tos)
{
    return (tos >> 5);
}

/**
 * When in uniform mode convert an MPLS EXP value to an IPv[46] DSCP value
 */
static inline u8 mpls_exp_to_ip_dscp (u8 exp)
{
    return (exp << 5);
}

#define FOR_EACH_MPLS_EOS_BIT(_eos) \
    for (_eos = MPLS_NON_EOS; _eos <= MPLS_EOS; _eos++)

#define MPLS_ENTRY_LABEL_OFFSET        0
#define MPLS_ENTRY_LABEL_SHIFT 12
#define MPLS_ENTRY_LABEL_MASK  0x000fffff
#define MPLS_ENTRY_LABEL_BITS  \
    (MPLS_ENTRY_LABEL_MASK << MPLS_ENTRY_LABEL_SHIFT)

#define MPLS_ENTRY_EXP_OFFSET   2       /* byte offset to EXP bits */
#define MPLS_ENTRY_EXP_SHIFT   9
#define MPLS_ENTRY_EXP_MASK    0x07
#define MPLS_ENTRY_EXP(mpls)   \
    (((mpls)>>MPLS_ENTRY_EXP_SHIFT) & MPLS_ENTRY_EXP_MASK)
#define MPLS_ENTRY_EXP_BITS    \
    (MPLS_ENTRY_EXP_MASK << MPLS_ENTRY_EXP_SHIFT)

#define MPLS_ENTRY_EOS_OFFSET   2       /* byte offset to EOS bit */
#define MPLS_ENTRY_EOS_SHIFT   8
#define MPLS_ENTRY_EOS_MASK    0x01    /* EOS bit in its byte */
#define        MPLS_ENTRY_EOS(mpls)    \
    (((mpls) >> MPLS_ENTRY_EOS_SHIFT) & MPLS_ENTRY_EOS_MASK)
#define MPLS_ENTRY_EOS_BIT     (MPLS_ENTRY_EOS_MASK << MPLS_ENTRY_EOS_SHIFT)

#define MPLS_ENTRY_TTL_OFFSET  3  /* byte offset to ttl field */
#define MPLS_ENTRY_TTL_SHIFT   0
#define MPLS_ENTRY_TTL_MASK    0xff
#define MPLS_ENTRY_TTL(mpls)   \
    (((mpls) >> MPLS_ENTRY_TTL_SHIFT) & MPLS_ENTRY_TTL_MASK)
#define MPLS_ENTRY_TTL_BITS    \
    (MPLS_ENTRY_TTL_MASK << MPLS_ENTRY_TTL_SHIFT)

static inline u32 vnet_mpls_uc_get_label (mpls_label_t label_exp_s_ttl)
{
    return (label_exp_s_ttl>>MPLS_ENTRY_LABEL_SHIFT);
}

static inline u32 vnet_mpls_uc_get_exp (mpls_label_t label_exp_s_ttl)
{
    return (MPLS_ENTRY_EXP(label_exp_s_ttl));
}

static inline u32 vnet_mpls_uc_get_s (mpls_label_t label_exp_s_ttl)
{
    return (MPLS_ENTRY_EOS(label_exp_s_ttl));
}

static inline u32 vnet_mpls_uc_get_ttl (mpls_label_t label_exp_s_ttl)
{
    return (MPLS_ENTRY_TTL(label_exp_s_ttl));
}

static inline void vnet_mpls_uc_set_label (mpls_label_t *label_exp_s_ttl,
                                           u32 value)
{
    *label_exp_s_ttl = (((*label_exp_s_ttl) & ~(MPLS_ENTRY_LABEL_BITS)) |
                        ((value  & MPLS_ENTRY_LABEL_MASK) << MPLS_ENTRY_LABEL_SHIFT));
}

static inline void vnet_mpls_uc_set_exp (mpls_label_t *label_exp_s_ttl,
                                         u32 exp)
{
    *label_exp_s_ttl = (((*label_exp_s_ttl) & ~(MPLS_ENTRY_EXP_BITS)) |
                        ((exp & MPLS_ENTRY_EXP_MASK) << MPLS_ENTRY_EXP_SHIFT));
}
 
static inline void vnet_mpls_uc_set_s (mpls_label_t *label_exp_s_ttl,
                                       u32 eos)
{
    *label_exp_s_ttl = (((*label_exp_s_ttl) & ~(MPLS_ENTRY_EOS_BIT)) |
                        ((eos & MPLS_ENTRY_EOS_MASK) << MPLS_ENTRY_EOS_SHIFT));
}
 
static inline void vnet_mpls_uc_set_ttl (mpls_label_t *label_exp_s_ttl,
                                         u32 ttl)
{
    *label_exp_s_ttl = (((*label_exp_s_ttl) & ~(MPLS_ENTRY_TTL_BITS)) |
                        ((ttl & MPLS_ENTRY_TTL_MASK)));
}

#endif /* included_vnet_mpls_packet_h */
/ .highlight .no { color: #003366; font-weight: bold } /* Name.Constant */ .highlight .nd { color: #555555 } /* Name.Decorator */ .highlight .ne { color: #bb0066; font-weight: bold } /* Name.Exception */ .highlight .nf { color: #0066bb; font-weight: bold } /* Name.Function */ .highlight .nl { color: #336699; font-style: italic } /* Name.Label */ .highlight .nn { color: #bb0066; font-weight: bold } /* Name.Namespace */ .highlight .py { color: #336699; font-weight: bold } /* Name.Property */ .highlight .nt { color: #bb0066; font-weight: bold } /* Name.Tag */ .highlight .nv { color: #336699 } /* Name.Variable */ .highlight .ow { color: #008800 } /* Operator.Word */ .highlight .w { color: #bbbbbb } /* Text.Whitespace */ .highlight .mb { color: #0000DD; font-weight: bold } /* Literal.Number.Bin */ .highlight .mf { color: #0000DD; font-weight: bold } /* Literal.Number.Float */ .highlight .mh { color: #0000DD; font-weight: bold } /* Literal.Number.Hex */ .highlight .mi { color: #0000DD; font-weight: bold } /* Literal.Number.Integer */ .highlight .mo { color: #0000DD; font-weight: bold } /* Literal.Number.Oct */ .highlight .sa { color: #dd2200; background-color: #fff0f0 } /* Literal.String.Affix */ .highlight .sb { color: #dd2200; background-color: #fff0f0 } /* Literal.String.Backtick */ .highlight .sc { color: #dd2200; background-color: #fff0f0 } /* Literal.String.Char */ .highlight .dl { color: #dd2200; background-color: #fff0f0 } /* Literal.String.Delimiter */ .highlight .sd { color: #dd2200; background-color: #fff0f0 } /* Literal.String.Doc */ .highlight .s2 { color: #dd2200; background-color: #fff0f0 } /* Literal.String.Double */ .highlight .se { color: #0044dd; background-color: #fff0f0 } /* Literal.String.Escape */ .highlight .sh { color: #dd2200; background-color: #fff0f0 } /* Literal.String.Heredoc */ .highlight .si { color: #3333bb; background-color: #fff0f0 } /* Literal.String.Interpol */ .highlight .sx { color: #22bb22; background-color: #f0fff0 } /* Literal.String.Other */ .highlight .sr { color: #008800; background-color: #fff0ff } /* Literal.String.Regex */ .highlight .s1 { color: #dd2200; background-color: #fff0f0 } /* Literal.String.Single */ .highlight .ss { color: #aa6600; background-color: #fff0f0 } /* Literal.String.Symbol */ .highlight .bp { color: #003388 } /* Name.Builtin.Pseudo */ .highlight .fm { color: #0066bb; font-weight: bold } /* Name.Function.Magic */ .highlight .vc { color: #336699 } /* Name.Variable.Class */ .highlight .vg { color: #dd7700 } /* Name.Variable.Global */ .highlight .vi { color: #3333bb } /* Name.Variable.Instance */ .highlight .vm { color: #336699 } /* Name.Variable.Magic */ .highlight .il { color: #0000DD; font-weight: bold } /* Literal.Number.Integer.Long */ }
/*
 * 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 IPv6 to IPv4 translation
 */
#ifndef __included_ip6_to_ip4_h__
#define __included_ip6_to_ip4_h__

#include <vnet/ip/ip.h>

/**
 * IPv6 to IPv4 set call back function type
 */
typedef int (*ip6_to_ip4_set_fn_t) (ip6_header_t * ip6, ip4_header_t * ip4,
				    void *ctx);

/* *INDENT-OFF* */
static u8 icmp6_to_icmp_updater_pointer_table[] =
  { 0, 1, ~0, ~0,
    2, 2, 9, 8,
    12, 12, 12, 12,
    12, 12, 12, 12,
    12, 12, 12, 12,
    12, 12, 12, 12,
    24, 24, 24, 24,
    24, 24, 24, 24,
    24, 24, 24, 24,
    24, 24, 24, 24
  };
/* *INDENT-ON* */

#define frag_id_6to4(id) ((id) ^ ((id) >> 16))

/**
 * @brief Parse some useful information from IPv6 header.
 *
 * @param ip6             IPv6 header.
 * @param buff_len        Buffer length.
 * @param l4_protocol     L4 protocol number.
 * @param l4_offset       L4 header offset.
 * @param frag_hdr_offset Fragment header offset if present, 0 otherwise.
 *
 * @returns 0 on success, non-zero value otherwise.
 */
static_always_inline int
ip6_parse (const ip6_header_t * ip6, u32 buff_len,
	   u8 * l4_protocol, u16 * l4_offset, u16 * frag_hdr_offset)
{
  if (ip6->protocol == IP_PROTOCOL_IPV6_FRAGMENTATION)
    {
      *l4_protocol = ((ip6_frag_hdr_t *) (ip6 + 1))->next_hdr;
      *frag_hdr_offset = sizeof (*ip6);
      *l4_offset = sizeof (*ip6) + sizeof (ip6_frag_hdr_t);
    }
  else
    {
      *l4_protocol = ip6->protocol;
      *frag_hdr_offset = 0;
      *l4_offset = sizeof (*ip6);
    }

  return (buff_len < (*l4_offset + 4)) ||
    (clib_net_to_host_u16 (ip6->payload_length) <
     (*l4_offset + 4 - sizeof (*ip6)));
}

/**
 * @brief Get TCP/UDP port number or ICMP id from IPv6 packet.
 *
 * @param ip6        IPv6 header.
 * @param sender     1 get sender port, 0 get receiver port.
 * @param buffer_len Buffer length.
 *
 * @returns Port number on success, 0 otherwise.
 */
always_inline u16
ip6_get_port (ip6_header_t * ip6, u8 sender, u16 buffer_len)
{
  u8 l4_protocol;
  u16 l4_offset;
  u16 frag_offset;
  u8 *l4;

  if (ip6_parse (ip6, buffer_len, &l4_protocol, &l4_offset, &frag_offset))
    return 0;

  if (frag_offset &&
      ip6_frag_hdr_offset (((ip6_frag_hdr_t *)
			    u8_ptr_add (ip6, frag_offset))))
    return 0;			//Can't deal with non-first fragment for now

  l4 = u8_ptr_add (ip6, l4_offset);
  if (l4_protocol == IP_PROTOCOL_TCP || l4_protocol == IP_PROTOCOL_UDP)
    {
      return (sender) ? ((udp_header_t *) (l4))->src_port : ((udp_header_t
							      *)
							     (l4))->dst_port;
    }
  else if (l4_protocol == IP_PROTOCOL_ICMP6)
    {
      icmp46_header_t *icmp = (icmp46_header_t *) (l4);
      if (icmp->type == ICMP6_echo_request)
	{
	  return (sender) ? ((u16 *) (icmp))[2] : -1;
	}
      else if (icmp->type == ICMP6_echo_reply)
	{
	  return (sender) ? -1 : ((u16 *) (icmp))[2];
	}
    }
  return 0;
}

/**
 * @brief Convert type and code value from ICMP6 to ICMP4.
 *
 * @param icmp      ICMP header.
 * @param inner_ip6 Inner IPv6 header if present, 0 otherwise.
 *
 * @returns 0 on success, non-zero value otherwise.
 */
static_always_inline int
icmp6_to_icmp_header (icmp46_header_t * icmp, ip6_header_t ** inner_ip6)
{
  *inner_ip6 = NULL;
  switch (icmp->type)
    {
    case ICMP6_echo_request:
      icmp->type = ICMP4_echo_request;
      break;
    case ICMP6_echo_reply:
      icmp->type = ICMP4_echo_reply;
      break;
    case ICMP6_destination_unreachable:
      *inner_ip6 = (ip6_header_t *) u8_ptr_add (icmp, 8);

      switch (icmp->code)
	{
	case ICMP6_destination_unreachable_no_route_to_destination:	//0
	case ICMP6_destination_unreachable_beyond_scope_of_source_address:	//2
	case ICMP6_destination_unreachable_address_unreachable:	//3
	  icmp->type = ICMP4_destination_unreachable;
	  icmp->code =
	    ICMP4_destination_unreachable_destination_unreachable_host;
	  break;
	case ICMP6_destination_unreachable_destination_administratively_prohibited:	//1
	  icmp->type =
	    ICMP4_destination_unreachable;
	  icmp->code =
	    ICMP4_destination_unreachable_communication_administratively_prohibited;
	  break;
	case ICMP6_destination_unreachable_port_unreachable:
	  icmp->type = ICMP4_destination_unreachable;
	  icmp->code = ICMP4_destination_unreachable_port_unreachable;
	  break;
	default:
	  return -1;
	}
      break;
    case ICMP6_packet_too_big:
      *inner_ip6 = (ip6_header_t *) u8_ptr_add (icmp, 8);

      icmp->type = ICMP4_destination_unreachable;
      icmp->code = 4;
      {
	u32 advertised_mtu = clib_net_to_host_u32 (*((u32 *) (icmp + 1)));
	advertised_mtu -= 20;
	//FIXME: = minimum(advertised MTU-20, MTU_of_IPv4_nexthop, (MTU_of_IPv6_nexthop)-20)
	((u16 *) (icmp))[3] = clib_host_to_net_u16 (advertised_mtu);
      }
      break;

    case ICMP6_time_exceeded:
      *inner_ip6 = (ip6_header_t *) u8_ptr_add (icmp, 8);

      icmp->type = ICMP4_time_exceeded;
      break;

    case ICMP6_parameter_problem:
      *inner_ip6 = (ip6_header_t *) u8_ptr_add (icmp, 8);

      switch (icmp->code)
	{
	case ICMP6_parameter_problem_erroneous_header_field:
	  icmp->type = ICMP4_parameter_problem;
	  icmp->code = ICMP4_parameter_problem_pointer_indicates_error;
	  u32 pointer = clib_net_to_host_u32 (*((u32 *) (icmp + 1)));
	  if (pointer >= 40)
	    return -1;

	  ((u8 *) (icmp + 1))[0] =
	    icmp6_to_icmp_updater_pointer_table[pointer];
	  break;
	case ICMP6_parameter_problem_unrecognized_next_header:
	  icmp->type = ICMP4_destination_unreachable;
	  icmp->code = ICMP4_destination_unreachable_port_unreachable;
	  break;
	case ICMP6_parameter_problem_unrecognized_option:
	default:
	  return -1;
	}
      break;
    default:
      return -1;
      break;
    }
  return 0;
}

/**
 * @brief Translate TOS value from IPv6 to IPv4.
 *
 * @param ip6 IPv6 header.
 *
 * @returns IPv4 TOS value.
 */
static_always_inline u8
ip6_translate_tos (const ip6_header_t * ip6)
{
  return (clib_net_to_host_u32 (ip6->ip_version_traffic_class_and_flow_label)
	  & 0x0ff00000) >> 20;
}

/**
 * @brief Translate ICMP6 packet to ICMP4.
 *
 * @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
icmp6_to_icmp (vlib_buffer_t * p, ip6_to_ip4_set_fn_t fn, void *ctx,
	       ip6_to_ip4_set_fn_t inner_fn, void *inner_ctx)
{
  ip6_header_t *ip6, *inner_ip6;
  ip4_header_t *ip4, *inner_ip4;
  u32 ip6_pay_len;
  icmp46_header_t *icmp;
  ip_csum_t csum;
  int rv;
  ip6_address_t old_src, old_dst;

  ip6 = vlib_buffer_get_current (p);
  ip6_pay_len = clib_net_to_host_u16 (ip6->payload_length);
  icmp = (icmp46_header_t *) (ip6 + 1);
  ASSERT (ip6_pay_len + sizeof (*ip6) <= p->current_length);

  //No extensions headers allowed here
  if (ip6->protocol != IP_PROTOCOL_ICMP6)
    return -1;

  //There are no fragmented ICMP messages, so no extension header for now
  if (icmp6_to_icmp_header (icmp, &inner_ip6))
    return -1;

  if (inner_ip6)
    {
      u16 *inner_L4_checksum, inner_l4_offset, inner_frag_offset,
	inner_frag_id;
      u8 *inner_l4, inner_protocol;

      //We have two headers to translate
      //   FROM
      //   [   IPv6   ]<- ext ->[IC][   IPv6   ]<- ext ->[L4 header ...
      // Handled cases:
      //                     [   IPv6   ][IC][   IPv6   ][L4 header ...
      //                 [   IPv6   ][IC][   IPv6   ][Fr][L4 header ...
      //    TO
      //                               [ IPv4][IC][ IPv4][L4 header ...

      if (ip6_parse (inner_ip6, ip6_pay_len - 8,
		     &inner_protocol, &inner_l4_offset, &inner_frag_offset))
	return -1;

      inner_l4 = u8_ptr_add (inner_ip6, inner_l4_offset);
      inner_ip4 =
	(ip4_header_t *) u8_ptr_add (inner_l4, -sizeof (*inner_ip4));
      if (inner_frag_offset)
	{
	  ip6_frag_hdr_t *inner_frag =
	    (ip6_frag_hdr_t *) u8_ptr_add (inner_ip6, inner_frag_offset);
	  inner_frag_id = frag_id_6to4 (inner_frag->identification);
	}
      else
	{
	  inner_frag_id = 0;
	}

      //Do the translation of the inner packet
      if (inner_protocol == IP_PROTOCOL_TCP)
	{
	  inner_L4_checksum = (u16 *) u8_ptr_add (inner_l4, 16);
	}
      else if (inner_protocol == IP_PROTOCOL_UDP)
	{
	  inner_L4_checksum = (u16 *) u8_ptr_add (inner_l4, 6);
	}
      else if (inner_protocol == IP_PROTOCOL_ICMP6)
	{
	  icmp46_header_t *inner_icmp = (icmp46_header_t *) inner_l4;
	  //It cannot be of a different type as ip6_icmp_to_icmp6_in_place succeeded
	  inner_icmp->type = (inner_icmp->type == ICMP6_echo_request) ?
	    ICMP4_echo_request : ICMP4_echo_reply;
	  inner_protocol = IP_PROTOCOL_ICMP;	//Will be copied to ip6 later
	  inner_L4_checksum = &inner_icmp->checksum;
	}
      else
	{
	  return -1;
	}

      old_src.as_u64[0] = inner_ip6->src_address.as_u64[0];
      old_src.as_u64[1] = inner_ip6->src_address.as_u64[1];
      old_dst.as_u64[0] = inner_ip6->dst_address.as_u64[0];
      old_dst.as_u64[1] = inner_ip6->dst_address.as_u64[1];

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

      inner_ip4->ip_version_and_header_length =
	IP4_VERSION_AND_HEADER_LENGTH_NO_OPTIONS;
      inner_ip4->tos = ip6_translate_tos (inner_ip6);
      inner_ip4->length =
	u16_net_add (inner_ip6->payload_length,
		     sizeof (*ip4) + sizeof (*ip6) - inner_l4_offset);
      inner_ip4->fragment_id = inner_frag_id;
      inner_ip4->flags_and_fragment_offset =
	clib_host_to_net_u16 (IP4_HEADER_FLAG_MORE_FRAGMENTS);
      inner_ip4->ttl = inner_ip6->hop_limit;
      inner_ip4->protocol = inner_protocol;
      inner_ip4->checksum = ip4_header_checksum (inner_ip4);

      if (inner_ip4->protocol == IP_PROTOCOL_ICMP)
	{
	  //Recompute ICMP checksum
	  icmp46_header_t *inner_icmp = (icmp46_header_t *) inner_l4;
	  inner_icmp->checksum = 0;
	  csum =
	    ip_incremental_checksum (0, inner_icmp,
				     clib_net_to_host_u16 (inner_ip4->length)
				     - sizeof (*inner_ip4));
	  inner_icmp->checksum = ~ip_csum_fold (csum);
	}
      else
	{
	  //Update to new pseudo-header
	  csum = *inner_L4_checksum;
	  csum = ip_csum_sub_even (csum, old_src.as_u64[0]);
	  csum = ip_csum_sub_even (csum, old_src.as_u64[1]);
	  csum = ip_csum_sub_even (csum, old_dst.as_u64[0]);
	  csum = ip_csum_sub_even (csum, old_dst.as_u64[1]);
	  csum = ip_csum_add_even (csum, inner_ip4->src_address.as_u32);
	  csum = ip_csum_add_even (csum, inner_ip4->dst_address.as_u32);
	  *inner_L4_checksum = ip_csum_fold (csum);
	}

      //Move up icmp header
      ip4 = (ip4_header_t *) u8_ptr_add (inner_l4, -2 * sizeof (*ip4) - 8);
      clib_memcpy (u8_ptr_add (inner_l4, -sizeof (*ip4) - 8), icmp, 8);
      icmp = (icmp46_header_t *) u8_ptr_add (inner_l4, -sizeof (*ip4) - 8);
    }
  else
    {
      //Only one header to translate
      ip4 = (ip4_header_t *) u8_ptr_add (ip6, sizeof (*ip6) - sizeof (*ip4));
    }

  vlib_buffer_advance (p, (u32) (((u8 *) ip4) - ((u8 *) ip6)));

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

  ip4->ip_version_and_header_length =
    IP4_VERSION_AND_HEADER_LENGTH_NO_OPTIONS;
  ip4->tos = ip6_translate_tos (ip6);
  ip4->fragment_id = 0;
  ip4->flags_and_fragment_offset = 0;
  ip4->ttl = ip6->hop_limit;
  ip4->protocol = IP_PROTOCOL_ICMP;
  //TODO fix the length depending on offset length
  ip4->length = u16_net_add (ip6->payload_length,
			     (inner_ip6 ==
			      NULL) ? sizeof (*ip4) : (2 * sizeof (*ip4) -
						       sizeof (*ip6)));
  ip4->checksum = ip4_header_checksum (ip4);

  //Recompute ICMP checksum
  icmp->checksum = 0;
  csum =
    ip_incremental_checksum (0, icmp,
			     clib_net_to_host_u16 (ip4->length) -
			     sizeof (*ip4));
  icmp->checksum = ~ip_csum_fold (csum);

  return 0;
}

/**
 * @brief Translate IPv6 fragmented packet to IPv4.
 *
 * @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
ip6_to_ip4_fragmented (vlib_buffer_t * p, ip6_to_ip4_set_fn_t fn, void *ctx)
{
  ip6_header_t *ip6;
  ip6_frag_hdr_t *frag;
  ip4_header_t *ip4;
  u16 frag_id;
  u8 frag_more;
  u16 frag_offset;
  u8 l4_protocol;
  u16 l4_offset;
  int rv;

  ip6 = vlib_buffer_get_current (p);

  if (ip6_parse
      (ip6, p->current_length, &l4_protocol, &l4_offset, &frag_offset))
    return -1;

  frag = (ip6_frag_hdr_t *) u8_ptr_add (ip6, frag_offset);
  ip4 = (ip4_header_t *) u8_ptr_add (ip6, l4_offset - sizeof (*ip4));
  vlib_buffer_advance (p, l4_offset - sizeof (*ip4));

  frag_id = frag_id_6to4 (frag->identification);
  frag_more = ip6_frag_hdr_more (frag);
  frag_offset = ip6_frag_hdr_offset (frag);

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

  ip4->ip_version_and_header_length =
    IP4_VERSION_AND_HEADER_LENGTH_NO_OPTIONS;
  ip4->tos = ip6_translate_tos (ip6);
  ip4->length = u16_net_add (ip6->payload_length,
			     sizeof (*ip4) - l4_offset + sizeof (*ip6));
  ip4->fragment_id = frag_id;
  ip4->flags_and_fragment_offset =
    clib_host_to_net_u16 (frag_offset |
			  (frag_more ? IP4_HEADER_FLAG_MORE_FRAGMENTS : 0));
  ip4->ttl = ip6->hop_limit;
  ip4->protocol =
    (l4_protocol == IP_PROTOCOL_ICMP6) ? IP_PROTOCOL_ICMP : l4_protocol;
  ip4->checksum = ip4_header_checksum (ip4);

  return 0;
}

/**
 * @brief Translate IPv6 UDP/TCP packet to IPv4.
 *
 * @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
ip6_to_ip4_tcp_udp (vlib_buffer_t * p, ip6_to_ip4_set_fn_t fn, void *ctx,
		    u8 udp_checksum)
{
  ip6_header_t *ip6;
  u16 *checksum;
  ip_csum_t csum = 0;
  ip4_header_t *ip4;
  u16 fragment_id;
  u16 flags;
  u16 frag_offset;
  u8 l4_protocol;
  u16 l4_offset;
  int rv;
  ip6_address_t old_src, old_dst;

  ip6 = vlib_buffer_get_current (p);

  if (ip6_parse
      (ip6, p->current_length, &l4_protocol, &l4_offset, &frag_offset))
    return -1;

  if (l4_protocol == IP_PROTOCOL_TCP)
    {
      tcp_header_t *tcp = ip6_next_header (ip6);
      checksum = &tcp->checksum;
    }
  else
    {
      udp_header_t *udp = ip6_next_header (ip6);
      checksum = &udp->checksum;
    }

  old_src.as_u64[0] = ip6->src_address.as_u64[0];
  old_src.as_u64[1] = ip6->src_address.as_u64[1];
  old_dst.as_u64[0] = ip6->dst_address.as_u64[0];
  old_dst.as_u64[1] = ip6->dst_address.as_u64[1];

  ip4 = (ip4_header_t *) u8_ptr_add (ip6, l4_offset - sizeof (*ip4));

  vlib_buffer_advance (p, l4_offset - sizeof (*ip4));

  if (PREDICT_FALSE (frag_offset))
    {
      //Only the first fragment
      ip6_frag_hdr_t *hdr = (ip6_frag_hdr_t *) u8_ptr_add (ip6, frag_offset);
      fragment_id = frag_id_6to4 (hdr->identification);
      flags = clib_host_to_net_u16 (IP4_HEADER_FLAG_MORE_FRAGMENTS);
    }
  else
    {
      fragment_id = 0;
      flags = 0;
    }

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

  ip4->ip_version_and_header_length =
    IP4_VERSION_AND_HEADER_LENGTH_NO_OPTIONS;
  ip4->tos = ip6_translate_tos (ip6);
  ip4->length = u16_net_add (ip6->payload_length,
			     sizeof (*ip4) + sizeof (*ip6) - l4_offset);
  ip4->fragment_id = fragment_id;
  ip4->flags_and_fragment_offset = flags;
  ip4->ttl = ip6->hop_limit;
  ip4->protocol = l4_protocol;
  ip4->checksum = ip4_header_checksum (ip4);

  //UDP checksum is optional over IPv4
  if (!udp_checksum && l4_protocol == IP_PROTOCOL_UDP)
    {
      *checksum = 0;
    }
  else
    {
      csum = ip_csum_sub_even (*checksum, old_src.as_u64[0]);
      csum = ip_csum_sub_even (csum, old_src.as_u64[1]);
      csum = ip_csum_sub_even (csum, old_dst.as_u64[0]);
      csum = ip_csum_sub_even (csum, old_dst.as_u64[1]);
      csum = ip_csum_add_even (csum, ip4->dst_address.as_u32);
      csum = ip_csum_add_even (csum, ip4->src_address.as_u32);
      *checksum = ip_csum_fold (csum);
    }

  return 0;
}

/**
 * @brief Translate IPv6 packet to IPv4 (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
ip6_to_ip4 (vlib_buffer_t * p, ip6_to_ip4_set_fn_t fn, void *ctx)
{
  ip6_header_t *ip6;
  ip4_header_t *ip4;
  u16 fragment_id;
  u16 flags;
  u16 frag_offset;
  u8 l4_protocol;
  u16 l4_offset;
  int rv;

  ip6 = vlib_buffer_get_current (p);

  if (ip6_parse
      (ip6, p->current_length, &l4_protocol, &l4_offset, &frag_offset))
    return -1;

  ip4 = (ip4_header_t *) u8_ptr_add (ip6, l4_offset - sizeof (*ip4));

  vlib_buffer_advance (p, l4_offset - sizeof (*ip4));

  if (PREDICT_FALSE (frag_offset))
    {
      //Only the first fragment
      ip6_frag_hdr_t *hdr = (ip6_frag_hdr_t *) u8_ptr_add (ip6, frag_offset);
      fragment_id = frag_id_6to4 (hdr->identification);
      flags = clib_host_to_net_u16 (IP4_HEADER_FLAG_MORE_FRAGMENTS);
    }
  else
    {
      fragment_id = 0;
      flags = 0;
    }

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

  ip4->ip_version_and_header_length =
    IP4_VERSION_AND_HEADER_LENGTH_NO_OPTIONS;
  ip4->tos = ip6_translate_tos (ip6);
  ip4->length = u16_net_add (ip6->payload_length,
			     sizeof (*ip4) + sizeof (*ip6) - l4_offset);
  ip4->fragment_id = fragment_id;
  ip4->flags_and_fragment_offset = flags;
  ip4->ttl = ip6->hop_limit;
  ip4->protocol = l4_protocol;
  ip4->checksum = ip4_header_checksum (ip4);

  return 0;
}

#endif /* __included_ip6_to_ip4_h__ */

/*
 * fd.io coding-style-patch-verification: ON
 *
 * Local Variables:
 * eval: (c-set-style "gnu")
 * End:
 */