nat_det_out2in.c

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/*
 * Copyright (c) 2018 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 Deterministic/CGN NAT44 outside to inside network translation
 */

#include <vlib/vlib.h>
#include <vnet/vnet.h>
#include <vnet/ip/ip.h>
#include <vnet/fib/ip4_fib.h>
#include <vppinfra/error.h>
#include <vppinfra/elog.h>
#include <nat/nat.h>
#include <nat/nat_det.h>
#include <nat/nat_inlines.h>

typedef enum
{
  NAT_DET_OUT2IN_NEXT_DROP,
  NAT_DET_OUT2IN_NEXT_LOOKUP,
  NAT_DET_OUT2IN_NEXT_ICMP_ERROR,
  NAT_DET_OUT2IN_N_NEXT,
} nat_det_out2in_next_t;

typedef struct
{
  u32 sw_if_index;
  u32 next_index;
  u32 session_index;
} nat_det_out2in_trace_t;

#define foreach_nat_det_out2in_error                       \
_(UNSUPPORTED_PROTOCOL, "Unsupported protocol")         \
_(NO_TRANSLATION, "No translation")                     \
_(BAD_ICMP_TYPE, "unsupported ICMP type")               \
_(OUT2IN_PACKETS, "Good out2in packets processed")

typedef enum
{
#define _(sym,str) NAT_DET_OUT2IN_ERROR_##sym,
  foreach_nat_det_out2in_error
#undef _
    SNAT_OUT2IN_N_ERROR,
} nat_det_out2in_error_t;

static char *nat_det_out2in_error_strings[] = {
#define _(sym,string) string,
  foreach_nat_det_out2in_error
#undef _
};

static u8 *
format_nat_det_out2in_trace (u8 * s, va_list * args)
{
  CLIB_UNUSED (vlib_main_t * vm) = va_arg (*args, vlib_main_t *);
  CLIB_UNUSED (vlib_node_t * node) = va_arg (*args, vlib_node_t *);
  nat_det_out2in_trace_t *t = va_arg (*args, nat_det_out2in_trace_t *);

  s =
    format (s,
            "NAT_DET_OUT2IN: sw_if_index %d, next index %d, session index %d",
            t->sw_if_index, t->next_index, t->session_index);
  return s;
}

#ifndef CLIB_MARCH_VARIANT
/**
 * Get address and port values to be used for ICMP packet translation
 * and create session if needed
 *
 * @param[in,out] sm             NAT main
 * @param[in,out] node           NAT node runtime
 * @param[in] thread_index       thread index
 * @param[in,out] b0             buffer containing packet to be translated
 * @param[in,out] ip0            ip header
 * @param[out] p_proto           protocol used for matching
 * @param[out] p_value           address and port after NAT translation
 * @param[out] p_dont_translate  if packet should not be translated
 * @param d                      optional parameter
 * @param e                      optional parameter
 */
u32
icmp_match_out2in_det (snat_main_t * sm, vlib_node_runtime_t * node,
                       u32 thread_index, vlib_buffer_t * b0,
                       ip4_header_t * ip0, u8 * p_proto,
                       snat_session_key_t * p_value,
                       u8 * p_dont_translate, void *d, void *e)
{
  icmp46_header_t *icmp0;
  u32 sw_if_index0;
  u8 protocol;
  snat_det_out_key_t key0;
  u8 dont_translate = 0;
  u32 next0 = ~0;
  icmp_echo_header_t *echo0, *inner_echo0 = 0;
  ip4_header_t *inner_ip0;
  void *l4_header = 0;
  icmp46_header_t *inner_icmp0;
  snat_det_map_t *dm0 = 0;
  ip4_address_t new_addr0 = { {0} };
  snat_det_session_t *ses0 = 0;
  ip4_address_t out_addr;

  icmp0 = (icmp46_header_t *) ip4_next_header (ip0);
  echo0 = (icmp_echo_header_t *) (icmp0 + 1);
  sw_if_index0 = vnet_buffer (b0)->sw_if_index[VLIB_RX];

  if (!icmp_type_is_error_message
      (vnet_buffer (b0)->ip.reass.icmp_type_or_tcp_flags))
    {
      protocol = NAT_PROTOCOL_ICMP;
      key0.ext_host_addr = ip0->src_address;
      key0.ext_host_port = 0;
      key0.out_port = vnet_buffer (b0)->ip.reass.l4_src_port;
      out_addr = ip0->dst_address;
    }
  else
    {
      /* if error message, then it's not fragmented and we can access it */
      inner_ip0 = (ip4_header_t *) (echo0 + 1);
      l4_header = ip4_next_header (inner_ip0);
      protocol = ip_proto_to_nat_proto (inner_ip0->protocol);
      key0.ext_host_addr = inner_ip0->dst_address;
      out_addr = inner_ip0->src_address;
      switch (protocol)
        {
        case NAT_PROTOCOL_ICMP:
          inner_icmp0 = (icmp46_header_t *) l4_header;
          inner_echo0 = (icmp_echo_header_t *) (inner_icmp0 + 1);
          key0.ext_host_port = 0;
          key0.out_port = inner_echo0->identifier;
          break;
        case NAT_PROTOCOL_UDP:
        case NAT_PROTOCOL_TCP:
          key0.ext_host_port = ((tcp_udp_header_t *) l4_header)->dst_port;
          key0.out_port = ((tcp_udp_header_t *) l4_header)->src_port;
          break;
        default:
          b0->error = node->errors[NAT_DET_OUT2IN_ERROR_UNSUPPORTED_PROTOCOL];
          next0 = NAT_DET_OUT2IN_NEXT_DROP;
          goto out;
        }
    }

  dm0 = snat_det_map_by_out (sm, &out_addr);
  if (PREDICT_FALSE (!dm0))
    {
      /* Don't NAT packet aimed at the intfc address */
      if (PREDICT_FALSE (is_interface_addr (sm, node, sw_if_index0,
                                            ip0->dst_address.as_u32)))
        {
          dont_translate = 1;
          goto out;
        }
      nat_log_info ("unknown dst address:  %U",
                    format_ip4_address, &ip0->dst_address);
      goto out;
    }

  snat_det_reverse (dm0, &ip0->dst_address,
                    clib_net_to_host_u16 (key0.out_port), &new_addr0);

  ses0 = snat_det_get_ses_by_out (dm0, &new_addr0, key0.as_u64);
  if (PREDICT_FALSE (!ses0))
    {
      /* Don't NAT packet aimed at the intfc address */
      if (PREDICT_FALSE (is_interface_addr (sm, node, sw_if_index0,
                                            ip0->dst_address.as_u32)))
        {
          dont_translate = 1;
          goto out;
        }
      nat_log_info ("no match src %U:%d dst %U:%d for user %U",
                    format_ip4_address, &key0.ext_host_addr,
                    clib_net_to_host_u16 (key0.ext_host_port),
                    format_ip4_address, &out_addr,
                    clib_net_to_host_u16 (key0.out_port),
                    format_ip4_address, &new_addr0);
      b0->error = node->errors[NAT_DET_OUT2IN_ERROR_NO_TRANSLATION];
      next0 = NAT_DET_OUT2IN_NEXT_DROP;
      goto out;
    }

  if (PREDICT_FALSE
      (vnet_buffer (b0)->ip.reass.icmp_type_or_tcp_flags != ICMP4_echo_reply
       && !icmp_type_is_error_message (vnet_buffer (b0)->ip.
                                       reass.icmp_type_or_tcp_flags)))
    {
      b0->error = node->errors[NAT_DET_OUT2IN_ERROR_BAD_ICMP_TYPE];
      next0 = NAT_DET_OUT2IN_NEXT_DROP;
      goto out;
    }

  goto out;

out:
  *p_proto = protocol;
  if (ses0)
    {
      p_value->addr = new_addr0;
      p_value->fib_index = sm->inside_fib_index;
      p_value->port = ses0->in_port;
    }
  *p_dont_translate = dont_translate;
  if (d)
    *(snat_det_session_t **) d = ses0;
  if (e)
    *(snat_det_map_t **) e = dm0;
  return next0;
}
#endif

VLIB_NODE_FN (snat_det_out2in_node) (vlib_main_t * vm,
                                     vlib_node_runtime_t * node,
                                     vlib_frame_t * frame)
{
  u32 n_left_from, *from, *to_next;
  nat_det_out2in_next_t next_index;
  u32 pkts_processed = 0;
  snat_main_t *sm = &snat_main;
  u32 thread_index = vm->thread_index;

  from = vlib_frame_vector_args (frame);
  n_left_from = frame->n_vectors;
  next_index = node->cached_next_index;

  while (n_left_from > 0)
    {
      u32 n_left_to_next;

      vlib_get_next_frame (vm, node, next_index, to_next, n_left_to_next);

      while (n_left_from >= 4 && n_left_to_next >= 2)
        {
          u32 bi0, bi1;
          vlib_buffer_t *b0, *b1;
          u32 next0 = NAT_DET_OUT2IN_NEXT_LOOKUP;
          u32 next1 = NAT_DET_OUT2IN_NEXT_LOOKUP;
          u32 sw_if_index0, sw_if_index1;
          ip4_header_t *ip0, *ip1;
          ip_csum_t sum0, sum1;
          ip4_address_t new_addr0, old_addr0, new_addr1, old_addr1;
          u16 new_port0, old_port0, old_port1, new_port1;
          udp_header_t *udp0, *udp1;
          tcp_header_t *tcp0, *tcp1;
          u32 proto0, proto1;
          snat_det_out_key_t key0, key1;
          snat_det_map_t *dm0, *dm1;
          snat_det_session_t *ses0 = 0, *ses1 = 0;
          u32 rx_fib_index0, rx_fib_index1;
          icmp46_header_t *icmp0, *icmp1;

          /* Prefetch next iteration. */
          {
            vlib_buffer_t *p2, *p3;

            p2 = vlib_get_buffer (vm, from[2]);
            p3 = vlib_get_buffer (vm, from[3]);

            vlib_prefetch_buffer_header (p2, LOAD);
            vlib_prefetch_buffer_header (p3, LOAD);

            CLIB_PREFETCH (p2->data, CLIB_CACHE_LINE_BYTES, STORE);
            CLIB_PREFETCH (p3->data, CLIB_CACHE_LINE_BYTES, STORE);
          }

          /* speculatively enqueue b0 and b1 to the current next frame */
          to_next[0] = bi0 = from[0];
          to_next[1] = bi1 = from[1];
          from += 2;
          to_next += 2;
          n_left_from -= 2;
          n_left_to_next -= 2;

          b0 = vlib_get_buffer (vm, bi0);
          b1 = vlib_get_buffer (vm, bi1);

          ip0 = vlib_buffer_get_current (b0);
          udp0 = ip4_next_header (ip0);
          tcp0 = (tcp_header_t *) udp0;

          sw_if_index0 = vnet_buffer (b0)->sw_if_index[VLIB_RX];

          if (PREDICT_FALSE (ip0->ttl == 1))
            {
              vnet_buffer (b0)->sw_if_index[VLIB_TX] = (u32) ~ 0;
              icmp4_error_set_vnet_buffer (b0, ICMP4_time_exceeded,
                                           ICMP4_time_exceeded_ttl_exceeded_in_transit,
                                           0);
              next0 = NAT_DET_OUT2IN_NEXT_ICMP_ERROR;
              goto trace0;
            }

          proto0 = ip_proto_to_nat_proto (ip0->protocol);

          if (PREDICT_FALSE (proto0 == NAT_PROTOCOL_ICMP))
            {
              rx_fib_index0 =
                ip4_fib_table_get_index_for_sw_if_index (sw_if_index0);
              icmp0 = (icmp46_header_t *) udp0;

              next0 = icmp_out2in (sm, b0, ip0, icmp0, sw_if_index0,
                                   rx_fib_index0, node, next0, thread_index,
                                   &ses0, &dm0);
              goto trace0;
            }

          key0.ext_host_addr = ip0->src_address;
          key0.ext_host_port = tcp0->src;
          key0.out_port = tcp0->dst;

          dm0 = snat_det_map_by_out (sm, &ip0->dst_address);
          if (PREDICT_FALSE (!dm0))
            {
              nat_log_info ("unknown dst address:  %U",
                            format_ip4_address, &ip0->dst_address);
              next0 = NAT_DET_OUT2IN_NEXT_DROP;
              b0->error = node->errors[NAT_DET_OUT2IN_ERROR_NO_TRANSLATION];
              goto trace0;
            }

          snat_det_reverse (dm0, &ip0->dst_address,
                            clib_net_to_host_u16 (tcp0->dst), &new_addr0);

          ses0 = snat_det_get_ses_by_out (dm0, &new_addr0, key0.as_u64);
          if (PREDICT_FALSE (!ses0))
            {
              nat_log_info ("no match src %U:%d dst %U:%d for user %U",
                            format_ip4_address, &ip0->src_address,
                            clib_net_to_host_u16 (tcp0->src),
                            format_ip4_address, &ip0->dst_address,
                            clib_net_to_host_u16 (tcp0->dst),
                            format_ip4_address, &new_addr0);
              next0 = NAT_DET_OUT2IN_NEXT_DROP;
              b0->error = node->errors[NAT_DET_OUT2IN_ERROR_NO_TRANSLATION];
              goto trace0;
            }
          old_port0 = udp0->dst_port;
          udp0->dst_port = new_port0 = ses0->in_port;

          old_addr0 = ip0->dst_address;
          ip0->dst_address = new_addr0;
          vnet_buffer (b0)->sw_if_index[VLIB_TX] = sm->inside_fib_index;

          sum0 = ip0->checksum;
          sum0 = ip_csum_update (sum0, old_addr0.as_u32, new_addr0.as_u32,
                                 ip4_header_t,
                                 dst_address /* changed member */ );
          ip0->checksum = ip_csum_fold (sum0);

          if (PREDICT_TRUE (proto0 == NAT_PROTOCOL_TCP))
            {
              if (tcp0->flags & TCP_FLAG_FIN
                  && ses0->state == SNAT_SESSION_TCP_ESTABLISHED)
                ses0->state = SNAT_SESSION_TCP_CLOSE_WAIT;
              else if (tcp0->flags & TCP_FLAG_ACK
                       && ses0->state == SNAT_SESSION_TCP_LAST_ACK)
                snat_det_ses_close (dm0, ses0);

              sum0 = tcp0->checksum;
              sum0 = ip_csum_update (sum0, old_addr0.as_u32, new_addr0.as_u32,
                                     ip4_header_t,
                                     dst_address /* changed member */ );
              sum0 = ip_csum_update (sum0, old_port0, new_port0,
                                     ip4_header_t /* cheat */ ,
                                     length /* changed member */ );
              tcp0->checksum = ip_csum_fold (sum0);
            }
          else if (udp0->checksum)
            {
              sum0 = udp0->checksum;
              sum0 = ip_csum_update (sum0, old_addr0.as_u32, new_addr0.as_u32,
                                     ip4_header_t,
                                     dst_address /* changed member */ );
              sum0 = ip_csum_update (sum0, old_port0, new_port0,
                                     ip4_header_t /* cheat */ ,
                                     length /* changed member */ );
              udp0->checksum = ip_csum_fold (sum0);
            }

        trace0:

          if (PREDICT_FALSE ((node->flags & VLIB_NODE_FLAG_TRACE)
                             && (b0->flags & VLIB_BUFFER_IS_TRACED)))
            {
              nat_det_out2in_trace_t *t =
                vlib_add_trace (vm, node, b0, sizeof (*t));
              t->sw_if_index = sw_if_index0;
              t->next_index = next0;
              t->session_index = ~0;
              if (ses0)
                t->session_index = ses0 - dm0->sessions;
            }

          pkts_processed += next0 != NAT_DET_OUT2IN_NEXT_DROP;

          b1 = vlib_get_buffer (vm, bi1);

          ip1 = vlib_buffer_get_current (b1);
          udp1 = ip4_next_header (ip1);
          tcp1 = (tcp_header_t *) udp1;

          sw_if_index1 = vnet_buffer (b1)->sw_if_index[VLIB_RX];

          if (PREDICT_FALSE (ip1->ttl == 1))
            {
              vnet_buffer (b1)->sw_if_index[VLIB_TX] = (u32) ~ 0;
              icmp4_error_set_vnet_buffer (b1, ICMP4_time_exceeded,
                                           ICMP4_time_exceeded_ttl_exceeded_in_transit,
                                           0);
              next1 = NAT_DET_OUT2IN_NEXT_ICMP_ERROR;
              goto trace1;
            }

          proto1 = ip_proto_to_nat_proto (ip1->protocol);

          if (PREDICT_FALSE (proto1 == NAT_PROTOCOL_ICMP))
            {
              rx_fib_index1 =
                ip4_fib_table_get_index_for_sw_if_index (sw_if_index1);
              icmp1 = (icmp46_header_t *) udp1;

              next1 = icmp_out2in (sm, b1, ip1, icmp1, sw_if_index1,
                                   rx_fib_index1, node, next1, thread_index,
                                   &ses1, &dm1);
              goto trace1;
            }

          key1.ext_host_addr = ip1->src_address;
          key1.ext_host_port = tcp1->src;
          key1.out_port = tcp1->dst;

          dm1 = snat_det_map_by_out (sm, &ip1->dst_address);
          if (PREDICT_FALSE (!dm1))
            {
              nat_log_info ("unknown dst address:  %U",
                            format_ip4_address, &ip1->dst_address);
              next1 = NAT_DET_OUT2IN_NEXT_DROP;
              b1->error = node->errors[NAT_DET_OUT2IN_ERROR_NO_TRANSLATION];
              goto trace1;
            }

          snat_det_reverse (dm1, &ip1->dst_address,
                            clib_net_to_host_u16 (tcp1->dst), &new_addr1);

          ses1 = snat_det_get_ses_by_out (dm1, &new_addr1, key1.as_u64);
          if (PREDICT_FALSE (!ses1))
            {
              nat_log_info ("no match src %U:%d dst %U:%d for user %U",
                            format_ip4_address, &ip1->src_address,
                            clib_net_to_host_u16 (tcp1->src),
                            format_ip4_address, &ip1->dst_address,
                            clib_net_to_host_u16 (tcp1->dst),
                            format_ip4_address, &new_addr1);
              next1 = NAT_DET_OUT2IN_NEXT_DROP;
              b1->error = node->errors[NAT_DET_OUT2IN_ERROR_NO_TRANSLATION];
              goto trace1;
            }
          old_port1 = udp1->dst_port;
          udp1->dst_port = new_port1 = ses1->in_port;

          old_addr1 = ip1->dst_address;
          ip1->dst_address = new_addr1;
          vnet_buffer (b1)->sw_if_index[VLIB_TX] = sm->inside_fib_index;

          sum1 = ip1->checksum;
          sum1 = ip_csum_update (sum1, old_addr1.as_u32, new_addr1.as_u32,
                                 ip4_header_t,
                                 dst_address /* changed member */ );
          ip1->checksum = ip_csum_fold (sum1);

          if (PREDICT_TRUE (proto1 == NAT_PROTOCOL_TCP))
            {
              if (tcp1->flags & TCP_FLAG_FIN
                  && ses1->state == SNAT_SESSION_TCP_ESTABLISHED)
                ses1->state = SNAT_SESSION_TCP_CLOSE_WAIT;
              else if (tcp1->flags & TCP_FLAG_ACK
                       && ses1->state == SNAT_SESSION_TCP_LAST_ACK)
                snat_det_ses_close (dm1, ses1);

              sum1 = tcp1->checksum;
              sum1 = ip_csum_update (sum1, old_addr1.as_u32, new_addr1.as_u32,
                                     ip4_header_t,
                                     dst_address /* changed member */ );
              sum1 = ip_csum_update (sum1, old_port1, new_port1,
                                     ip4_header_t /* cheat */ ,
                                     length /* changed member */ );
              tcp1->checksum = ip_csum_fold (sum1);
            }
          else if (udp1->checksum)
            {
              sum1 = udp1->checksum;
              sum1 = ip_csum_update (sum1, old_addr1.as_u32, new_addr1.as_u32,
                                     ip4_header_t,
                                     dst_address /* changed member */ );
              sum1 = ip_csum_update (sum1, old_port1, new_port1,
                                     ip4_header_t /* cheat */ ,
                                     length /* changed member */ );
              udp1->checksum = ip_csum_fold (sum1);
            }

        trace1:

          if (PREDICT_FALSE ((node->flags & VLIB_NODE_FLAG_TRACE)
                             && (b1->flags & VLIB_BUFFER_IS_TRACED)))
            {
              nat_det_out2in_trace_t *t =
                vlib_add_trace (vm, node, b1, sizeof (*t));
              t->sw_if_index = sw_if_index1;
              t->next_index = next1;
              t->session_index = ~0;
              if (ses1)
                t->session_index = ses1 - dm1->sessions;
            }

          pkts_processed += next1 != NAT_DET_OUT2IN_NEXT_DROP;

          /* verify speculative enqueues, maybe switch current next frame */
          vlib_validate_buffer_enqueue_x2 (vm, node, next_index,
                                           to_next, n_left_to_next,
                                           bi0, bi1, next0, next1);
        }

      while (n_left_from > 0 && n_left_to_next > 0)
        {
          u32 bi0;
          vlib_buffer_t *b0;
          u32 next0 = NAT_DET_OUT2IN_NEXT_LOOKUP;
          u32 sw_if_index0;
          ip4_header_t *ip0;
          ip_csum_t sum0;
          ip4_address_t new_addr0, old_addr0;
          u16 new_port0, old_port0;
          udp_header_t *udp0;
          tcp_header_t *tcp0;
          u32 proto0;
          snat_det_out_key_t key0;
          snat_det_map_t *dm0;
          snat_det_session_t *ses0 = 0;
          u32 rx_fib_index0;
          icmp46_header_t *icmp0;

          /* speculatively enqueue b0 to the current next frame */
          bi0 = from[0];
          to_next[0] = bi0;
          from += 1;
          to_next += 1;
          n_left_from -= 1;
          n_left_to_next -= 1;

          b0 = vlib_get_buffer (vm, bi0);

          ip0 = vlib_buffer_get_current (b0);
          udp0 = ip4_next_header (ip0);
          tcp0 = (tcp_header_t *) udp0;

          sw_if_index0 = vnet_buffer (b0)->sw_if_index[VLIB_RX];

          if (PREDICT_FALSE (ip0->ttl == 1))
            {
              vnet_buffer (b0)->sw_if_index[VLIB_TX] = (u32) ~ 0;
              icmp4_error_set_vnet_buffer (b0, ICMP4_time_exceeded,
                                           ICMP4_time_exceeded_ttl_exceeded_in_transit,
                                           0);
              next0 = NAT_DET_OUT2IN_NEXT_ICMP_ERROR;
              goto trace00;
            }

          proto0 = ip_proto_to_nat_proto (ip0->protocol);

          if (PREDICT_FALSE (proto0 == NAT_PROTOCOL_ICMP))
            {
              rx_fib_index0 =
                ip4_fib_table_get_index_for_sw_if_index (sw_if_index0);
              icmp0 = (icmp46_header_t *) udp0;

              next0 = icmp_out2in (sm, b0, ip0, icmp0, sw_if_index0,
                                   rx_fib_index0, node, next0, thread_index,
                                   &ses0, &dm0);
              goto trace00;
            }

          key0.ext_host_addr = ip0->src_address;
          key0.ext_host_port = tcp0->src;
          key0.out_port = tcp0->dst;

          dm0 = snat_det_map_by_out (sm, &ip0->dst_address);
          if (PREDICT_FALSE (!dm0))
            {
              nat_log_info ("unknown dst address:  %U",
                            format_ip4_address, &ip0->dst_address);
              next0 = NAT_DET_OUT2IN_NEXT_DROP;
              b0->error = node->errors[NAT_DET_OUT2IN_ERROR_NO_TRANSLATION];
              goto trace00;
            }

          snat_det_reverse (dm0, &ip0->dst_address,
                            clib_net_to_host_u16 (tcp0->dst), &new_addr0);

          ses0 = snat_det_get_ses_by_out (dm0, &new_addr0, key0.as_u64);
          if (PREDICT_FALSE (!ses0))
            {
              nat_log_info ("no match src %U:%d dst %U:%d for user %U",
                            format_ip4_address, &ip0->src_address,
                            clib_net_to_host_u16 (tcp0->src),
                            format_ip4_address, &ip0->dst_address,
                            clib_net_to_host_u16 (tcp0->dst),
                            format_ip4_address, &new_addr0);
              next0 = NAT_DET_OUT2IN_NEXT_DROP;
              b0->error = node->errors[NAT_DET_OUT2IN_ERROR_NO_TRANSLATION];
              goto trace00;
            }
          old_port0 = udp0->dst_port;
          udp0->dst_port = new_port0 = ses0->in_port;

          old_addr0 = ip0->dst_address;
          ip0->dst_address = new_addr0;
          vnet_buffer (b0)->sw_if_index[VLIB_TX] = sm->inside_fib_index;

          sum0 = ip0->checksum;
          sum0 = ip_csum_update (sum0, old_addr0.as_u32, new_addr0.as_u32,
                                 ip4_header_t,
                                 dst_address /* changed member */ );
          ip0->checksum = ip_csum_fold (sum0);

          if (PREDICT_TRUE (proto0 == NAT_PROTOCOL_TCP))
            {
              if (tcp0->flags & TCP_FLAG_FIN
                  && ses0->state == SNAT_SESSION_TCP_ESTABLISHED)
                ses0->state = SNAT_SESSION_TCP_CLOSE_WAIT;
              else if (tcp0->flags & TCP_FLAG_ACK
                       && ses0->state == SNAT_SESSION_TCP_LAST_ACK)
                snat_det_ses_close (dm0, ses0);

              sum0 = tcp0->checksum;
              sum0 = ip_csum_update (sum0, old_addr0.as_u32, new_addr0.as_u32,
                                     ip4_header_t,
                                     dst_address /* changed member */ );
              sum0 = ip_csum_update (sum0, old_port0, new_port0,
                                     ip4_header_t /* cheat */ ,
                                     length /* changed member */ );
              tcp0->checksum = ip_csum_fold (sum0);
            }
          else if (udp0->checksum)
            {
              sum0 = udp0->checksum;
              sum0 = ip_csum_update (sum0, old_addr0.as_u32, new_addr0.as_u32,
                                     ip4_header_t,
                                     dst_address /* changed member */ );
              sum0 = ip_csum_update (sum0, old_port0, new_port0,
                                     ip4_header_t /* cheat */ ,
                                     length /* changed member */ );
              udp0->checksum = ip_csum_fold (sum0);
            }

        trace00:

          if (PREDICT_FALSE ((node->flags & VLIB_NODE_FLAG_TRACE)
                             && (b0->flags & VLIB_BUFFER_IS_TRACED)))
            {
              nat_det_out2in_trace_t *t =
                vlib_add_trace (vm, node, b0, sizeof (*t));
              t->sw_if_index = sw_if_index0;
              t->next_index = next0;
              t->session_index = ~0;
              if (ses0)
                t->session_index = ses0 - dm0->sessions;
            }

          pkts_processed += next0 != NAT_DET_OUT2IN_NEXT_DROP;

          /* verify speculative enqueue, maybe switch current next frame */
          vlib_validate_buffer_enqueue_x1 (vm, node, next_index,
                                           to_next, n_left_to_next,
                                           bi0, next0);
        }

      vlib_put_next_frame (vm, node, next_index, n_left_to_next);
    }

  vlib_node_increment_counter (vm, sm->det_out2in_node_index,
                               NAT_DET_OUT2IN_ERROR_OUT2IN_PACKETS,
                               pkts_processed);
  return frame->n_vectors;
}

/* *INDENT-OFF* */
VLIB_REGISTER_NODE (snat_det_out2in_node) = {
  .name = "nat44-det-out2in",
  .vector_size = sizeof (u32),
  .format_trace = format_nat_det_out2in_trace,
  .type = VLIB_NODE_TYPE_INTERNAL,
  .n_errors = ARRAY_LEN(nat_det_out2in_error_strings),
  .error_strings = nat_det_out2in_error_strings,
  .runtime_data_bytes = sizeof (snat_runtime_t),
  .n_next_nodes = NAT_DET_OUT2IN_N_NEXT,
  /* edit / add dispositions here */
  .next_nodes = {
    [NAT_DET_OUT2IN_NEXT_DROP] = "error-drop",
    [NAT_DET_OUT2IN_NEXT_LOOKUP] = "ip4-lookup",
    [NAT_DET_OUT2IN_NEXT_ICMP_ERROR] = "ip4-icmp-error",
  },
};
/* *INDENT-ON* */

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