summaryrefslogtreecommitdiffstats
path: root/extras/vcl-ldpreload
diff options
context:
space:
mode:
authorDave Wallace <dwallacelf@gmail.com>2017-10-18 21:15:48 -0400
committerFlorin Coras <florin.coras@gmail.com>2017-10-19 04:35:37 +0000
commit9c4b5b28b1c1df0c100b377a2f5bfc07bd9a0b2e (patch)
tree21cfcca7bf3ab134b9b6b5933431c9df3c266fbd /extras/vcl-ldpreload
parent17142b2030d89eb89439046699846cd7f08e0b1e (diff)
VCL-LDPRELOAD: fix iperf3 socket_test.sh
Change-Id: Ib6b52917af717d3341429163fb9ecc903cf717fb Signed-off-by: Dave Wallace <dwallacelf@gmail.com>
Diffstat (limited to 'extras/vcl-ldpreload')
-rw-r--r--extras/vcl-ldpreload/src/libvcl-ldpreload/vcom_socket.c15
1 files changed, 0 insertions, 15 deletions
diff --git a/extras/vcl-ldpreload/src/libvcl-ldpreload/vcom_socket.c b/extras/vcl-ldpreload/src/libvcl-ldpreload/vcom_socket.c
index c8a9d623a9b..96108afe0f7 100644
--- a/extras/vcl-ldpreload/src/libvcl-ldpreload/vcom_socket.c
+++ b/extras/vcl-ldpreload/src/libvcl-ldpreload/vcom_socket.c
@@ -1256,16 +1256,6 @@ vcom_socket_bind (int __fd, __CONST_SOCKADDR_ARG __addr, socklen_t __len)
}
rv = vppcom_session_bind (vsock->sid, &ep);
- /* TBD: remove libc_bind code snippet
- * once vppcom implements vppcom_session_getsockname */
- if (rv == 0)
- {
- rv = libc_bind (__fd, __addr, __len);
- if (rv != 0)
- {
- rv = -errno;
- }
- }
return rv;
}
@@ -1741,12 +1731,7 @@ vppcom_getsockopt (int __sid, int __level, int __optname,
{
/* 1. for socket level options that are NOT socket attributes
* and that has corresponding vpp options get from vppcom */
-#if 0
return 0;
-#endif
-
- /* 2. unhandled options */
- return -ENOPROTOOPT;
}
int
id='n208' href='#n208'>208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 
/*
 * 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:
 */