det44_out2in.c

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/*
 * Copyright (c) 2020 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 NAT (CGN) outside to inside 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/det44/det44.h>
#include <nat/det44/det44_inlines.h>

#include <nat/lib/lib.h>
#include <nat/lib/inlines.h>
#include <nat/lib/nat_inlines.h>

typedef enum
{
  DET44_OUT2IN_NEXT_DROP,
  DET44_OUT2IN_NEXT_LOOKUP,
  DET44_OUT2IN_NEXT_ICMP_ERROR,
  DET44_OUT2IN_N_NEXT,
} det44_out2in_next_t;

typedef struct
{
  u32 sw_if_index;
  u32 next_index;
  u32 session_index;
} det44_out2in_trace_t;

#define foreach_det44_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) DET44_OUT2IN_ERROR_##sym,
  foreach_det44_out2in_error
#undef _
    DET44_OUT2IN_N_ERROR,
} det44_out2in_error_t;

static char *det44_out2in_error_strings[] = {
#define _(sym,string) string,
  foreach_det44_out2in_error
#undef _
};

static u8 *
format_det44_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 *);
  det44_out2in_trace_t *t = va_arg (*args, det44_out2in_trace_t *);

  s =
    format (s,
            "DET44_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] 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 (vlib_node_runtime_t * node,
                       u32 thread_index, vlib_buffer_t * b0,
                       ip4_header_t * ip0, ip4_address_t * addr,
                       u16 * port, u32 * fib_index,
                       nat_protocol_t * proto, void *d, void *e,
                       u8 * dont_translate)
{
  det44_main_t *dm = &det44_main;
  icmp46_header_t *icmp0;
  u32 sw_if_index0;
  u8 protocol;
  snat_det_out_key_t key0;
  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 *mp0 = 0;
  ip4_address_t new_addr0 = { {0} };
  snat_det_session_t *ses0 = 0;
  ip4_address_t out_addr;
  *dont_translate = 0;

  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[DET44_OUT2IN_ERROR_UNSUPPORTED_PROTOCOL];
          next0 = DET44_OUT2IN_NEXT_DROP;
          goto out;
        }
    }

  mp0 = snat_det_map_by_out (&out_addr);
  if (PREDICT_FALSE (!mp0))
    {
      /* Don't NAT packet aimed at the intfc address */
      if (PREDICT_FALSE (!det44_is_interface_addr (node, sw_if_index0,
                                                   ip0->dst_address.as_u32)))
        {
          *dont_translate = 1;
          goto out;
        }
      det44_log_info ("unknown dst address:  %U",
                      format_ip4_address, &ip0->dst_address);
      goto out;
    }

  snat_det_reverse (mp0, &ip0->dst_address,
                    clib_net_to_host_u16 (key0.out_port), &new_addr0);

  ses0 = snat_det_get_ses_by_out (mp0, &new_addr0, key0.as_u64);
  if (PREDICT_FALSE (!ses0))
    {
      /* Don't NAT packet aimed at the intfc address */
      if (PREDICT_FALSE (!det44_is_interface_addr (node, sw_if_index0,
                                                   ip0->dst_address.as_u32)))
        {
          *dont_translate = 1;
          goto out;
        }
      det44_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[DET44_OUT2IN_ERROR_NO_TRANSLATION];
      next0 = DET44_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[DET44_OUT2IN_ERROR_BAD_ICMP_TYPE];
      next0 = DET44_OUT2IN_NEXT_DROP;
      goto out;
    }

  goto out;

out:
  *proto = protocol;
  if (ses0)
    {
      *addr = new_addr0;
      *fib_index = dm->inside_fib_index;
      *port = ses0->in_port;
    }
  if (d)
    *(snat_det_session_t **) d = ses0;
  if (e)
    *(snat_det_map_t **) e = mp0;
  return next0;
}
#endif

#ifndef CLIB_MARCH_VARIANT
u32
det44_icmp_out2in (vlib_buffer_t * b0,
                   ip4_header_t * ip0,
                   icmp46_header_t * icmp0,
                   u32 sw_if_index0,
                   u32 rx_fib_index0,
                   vlib_node_runtime_t * node,
                   u32 next0, u32 thread_index, void *d, void *e)
{
  vlib_main_t *vm = vlib_get_main ();
  u32 new_addr0, old_addr0, next0_tmp, fib_index;
  u16 old_id0, new_id0, port, checksum0;
  icmp_echo_header_t *echo0, *inner_echo0;
  icmp46_header_t *inner_icmp0;
  ip4_header_t *inner_ip0;
  ip4_address_t addr;
  void *l4_header;
  u8 dont_translate;
  ip_csum_t sum0;
  nat_protocol_t proto;

  echo0 = (icmp_echo_header_t *) (icmp0 + 1);
  next0_tmp = icmp_match_out2in_det (node, thread_index, b0, ip0,
                                     &addr, &port, &fib_index, &proto,
                                     d, e, &dont_translate);
  if (next0_tmp != ~0)
    next0 = next0_tmp;
  if (next0 == DET44_OUT2IN_NEXT_DROP || dont_translate)
    goto out;

  if (PREDICT_TRUE (!ip4_is_fragment (ip0)))
    {
      sum0 =
        ip_incremental_checksum_buffer (vm, b0,
                                        (u8 *) icmp0 -
                                        (u8 *) vlib_buffer_get_current (b0),
                                        ntohs (ip0->length) -
                                        ip4_header_bytes (ip0), 0);
      checksum0 = ~ip_csum_fold (sum0);
      if (checksum0 != 0 && checksum0 != 0xffff)
        {
          next0 = DET44_OUT2IN_NEXT_DROP;
          goto out;
        }
    }

  old_addr0 = ip0->dst_address.as_u32;
  new_addr0 = ip0->dst_address.as_u32 = addr.as_u32;
  vnet_buffer (b0)->sw_if_index[VLIB_TX] = fib_index;

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


  if (!vnet_buffer (b0)->ip.reass.is_non_first_fragment)
    {
      if (icmp0->checksum == 0)
        icmp0->checksum = 0xffff;

      if (!icmp_type_is_error_message (icmp0->type))
        {
          new_id0 = port;
          if (PREDICT_FALSE (new_id0 != echo0->identifier))
            {
              old_id0 = echo0->identifier;
              new_id0 = port;
              echo0->identifier = new_id0;

              sum0 = icmp0->checksum;
              sum0 =
                ip_csum_update (sum0, old_id0, new_id0, icmp_echo_header_t,
                                identifier /* changed member */ );
              icmp0->checksum = ip_csum_fold (sum0);
            }
        }
      else
        {
          inner_ip0 = (ip4_header_t *) (echo0 + 1);
          l4_header = ip4_next_header (inner_ip0);

          if (!ip4_header_checksum_is_valid (inner_ip0))
            {
              next0 = DET44_OUT2IN_NEXT_DROP;
              goto out;
            }

          old_addr0 = inner_ip0->src_address.as_u32;
          inner_ip0->src_address = addr;
          new_addr0 = inner_ip0->src_address.as_u32;

          sum0 = icmp0->checksum;
          sum0 = ip_csum_update (sum0, old_addr0, new_addr0, ip4_header_t,
                                 src_address /* changed member */ );
          icmp0->checksum = ip_csum_fold (sum0);

          switch (proto)
            {
            case NAT_PROTOCOL_ICMP:
              inner_icmp0 = (icmp46_header_t *) l4_header;
              inner_echo0 = (icmp_echo_header_t *) (inner_icmp0 + 1);

              old_id0 = inner_echo0->identifier;
              new_id0 = port;
              inner_echo0->identifier = new_id0;

              sum0 = icmp0->checksum;
              sum0 =
                ip_csum_update (sum0, old_id0, new_id0, icmp_echo_header_t,
                                identifier);
              icmp0->checksum = ip_csum_fold (sum0);
              break;
            case NAT_PROTOCOL_UDP:
            case NAT_PROTOCOL_TCP:
              old_id0 = ((tcp_udp_header_t *) l4_header)->src_port;
              new_id0 = port;
              ((tcp_udp_header_t *) l4_header)->src_port = new_id0;

              sum0 = icmp0->checksum;
              sum0 = ip_csum_update (sum0, old_id0, new_id0, tcp_udp_header_t,
                                     src_port);
              icmp0->checksum = ip_csum_fold (sum0);
              break;
            default:
              ASSERT (0);
            }
        }
    }

out:
  return next0;
}
#endif

VLIB_NODE_FN (det44_out2in_node) (vlib_main_t * vm,
                                  vlib_node_runtime_t * node,
                                  vlib_frame_t * frame)
{
  u32 n_left_from, *from;
  u32 pkts_processed = 0;
  det44_main_t *dm = &det44_main;
  u32 thread_index = vm->thread_index;

  from = vlib_frame_vector_args (frame);
  n_left_from = frame->n_vectors;

  vlib_buffer_t *bufs[VLIB_FRAME_SIZE], **b = bufs;
  u16 nexts[VLIB_FRAME_SIZE], *next = nexts;
  vlib_get_buffers (vm, from, b, n_left_from);

  while (n_left_from >= 2)
    {
      vlib_buffer_t *b0, *b1;
      u32 next0 = DET44_OUT2IN_NEXT_LOOKUP;
      u32 next1 = DET44_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 *mp0, *mp1;
      snat_det_session_t *ses0 = 0, *ses1 = 0;
      u32 rx_fib_index0, rx_fib_index1;
      icmp46_header_t *icmp0, *icmp1;

      b0 = *b;
      b++;
      b1 = *b;
      b++;

      /* Prefetch next iteration. */
      if (PREDICT_TRUE (n_left_from >= 4))
        {
          vlib_buffer_t *p2, *p3;

          p2 = *b;
          p3 = *(b + 1);

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

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


      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 = DET44_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 = det44_icmp_out2in (b0, ip0, icmp0, sw_if_index0,
                                     rx_fib_index0, node, next0,
                                     thread_index, &ses0, &mp0);
          goto trace0;
        }

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

      mp0 = snat_det_map_by_out (&ip0->dst_address);
      if (PREDICT_FALSE (!mp0))
        {
          det44_log_info ("unknown dst address:  %U",
                          format_ip4_address, &ip0->dst_address);
          next0 = DET44_OUT2IN_NEXT_DROP;
          b0->error = node->errors[DET44_OUT2IN_ERROR_NO_TRANSLATION];
          goto trace0;
        }

      snat_det_reverse (mp0, &ip0->dst_address,
                        clib_net_to_host_u16 (tcp0->dst), &new_addr0);

      ses0 = snat_det_get_ses_by_out (mp0, &new_addr0, key0.as_u64);
      if (PREDICT_FALSE (!ses0))
        {
          det44_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 = DET44_OUT2IN_NEXT_DROP;
          b0->error = node->errors[DET44_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] = dm->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 == DET44_SESSION_TCP_ESTABLISHED)
            ses0->state = DET44_SESSION_TCP_CLOSE_WAIT;
          else if (tcp0->flags & TCP_FLAG_ACK
                   && ses0->state == DET44_SESSION_TCP_LAST_ACK)
            snat_det_ses_close (mp0, 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)))
        {
          det44_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 - mp0->sessions;
        }

      pkts_processed += next0 != DET44_OUT2IN_NEXT_DROP;

      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 = DET44_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 = det44_icmp_out2in (b1, ip1, icmp1, sw_if_index1,
                                     rx_fib_index1, node, next1,
                                     thread_index, &ses1, &mp1);
          goto trace1;
        }

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

      mp1 = snat_det_map_by_out (&ip1->dst_address);
      if (PREDICT_FALSE (!mp1))
        {
          det44_log_info ("unknown dst address:  %U",
                          format_ip4_address, &ip1->dst_address);
          next1 = DET44_OUT2IN_NEXT_DROP;
          b1->error = node->errors[DET44_OUT2IN_ERROR_NO_TRANSLATION];
          goto trace1;
        }

      snat_det_reverse (mp1, &ip1->dst_address,
                        clib_net_to_host_u16 (tcp1->dst), &new_addr1);

      ses1 = snat_det_get_ses_by_out (mp1, &new_addr1, key1.as_u64);
      if (PREDICT_FALSE (!ses1))
        {
          det44_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 = DET44_OUT2IN_NEXT_DROP;
          b1->error = node->errors[DET44_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] = dm->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 == DET44_SESSION_TCP_ESTABLISHED)
            ses1->state = DET44_SESSION_TCP_CLOSE_WAIT;
          else if (tcp1->flags & TCP_FLAG_ACK
                   && ses1->state == DET44_SESSION_TCP_LAST_ACK)
            snat_det_ses_close (mp1, 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)))
        {
          det44_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 - mp1->sessions;
        }

      pkts_processed += next1 != DET44_OUT2IN_NEXT_DROP;

      n_left_from -= 2;
      next[0] = next0;
      next[1] = next1;
      next += 2;
    }

  while (n_left_from > 0)
    {
      vlib_buffer_t *b0;
      u32 next0 = DET44_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 *mp0;
      snat_det_session_t *ses0 = 0;
      u32 rx_fib_index0;
      icmp46_header_t *icmp0;

      b0 = *b;
      b++;

      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 = DET44_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 = det44_icmp_out2in (b0, ip0, icmp0, sw_if_index0,
                                     rx_fib_index0, node, next0,
                                     thread_index, &ses0, &mp0);
          goto trace00;
        }

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

      mp0 = snat_det_map_by_out (&ip0->dst_address);
      if (PREDICT_FALSE (!mp0))
        {
          det44_log_info ("unknown dst address:  %U",
                          format_ip4_address, &ip0->dst_address);
          next0 = DET44_OUT2IN_NEXT_DROP;
          b0->error = node->errors[DET44_OUT2IN_ERROR_NO_TRANSLATION];
          goto trace00;
        }

      snat_det_reverse (mp0, &ip0->dst_address,
                        clib_net_to_host_u16 (tcp0->dst), &new_addr0);

      ses0 = snat_det_get_ses_by_out (mp0, &new_addr0, key0.as_u64);
      if (PREDICT_FALSE (!ses0))
        {
          det44_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 = DET44_OUT2IN_NEXT_DROP;
          b0->error = node->errors[DET44_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] = dm->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 == DET44_SESSION_TCP_ESTABLISHED)
            ses0->state = DET44_SESSION_TCP_CLOSE_WAIT;
          else if (tcp0->flags & TCP_FLAG_ACK
                   && ses0->state == DET44_SESSION_TCP_LAST_ACK)
            snat_det_ses_close (mp0, 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)))
        {
          det44_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 - mp0->sessions;
        }

      pkts_processed += next0 != DET44_OUT2IN_NEXT_DROP;

      n_left_from--;
      next[0] = next0;
      next++;
    }
  vlib_buffer_enqueue_to_next (vm, node, from, (u16 *) nexts,
                               frame->n_vectors);


  vlib_node_increment_counter (vm, dm->out2in_node_index,
                               DET44_OUT2IN_ERROR_OUT2IN_PACKETS,
                               pkts_processed);
  return frame->n_vectors;
}

/* *INDENT-OFF* */
VLIB_REGISTER_NODE (det44_out2in_node) = {
  .name = "det44-out2in",
  .vector_size = sizeof (u32),
  .format_trace = format_det44_out2in_trace,
  .type = VLIB_NODE_TYPE_INTERNAL,
  .n_errors = ARRAY_LEN(det44_out2in_error_strings),
  .error_strings = det44_out2in_error_strings,
  .runtime_data_bytes = sizeof (det44_runtime_t),
  .n_next_nodes = DET44_OUT2IN_N_NEXT,
  /* edit / add dispositions here */
  .next_nodes = {
    [DET44_OUT2IN_NEXT_DROP] = "error-drop",
    [DET44_OUT2IN_NEXT_LOOKUP] = "ip4-lookup",
    [DET44_OUT2IN_NEXT_ICMP_ERROR] = "ip4-icmp-error",
  },
};
/* *INDENT-ON* */

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