out2in_ed.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 NAT44 endpoint-dependent outside to inside network translation
 */

#include <vlib/vlib.h>
#include <vnet/vnet.h>
#include <vnet/pg/pg.h>
#include <vnet/ip/ip.h>
#include <vnet/ethernet/ethernet.h>
#include <vnet/fib/ip4_fib.h>
#include <vnet/udp/udp.h>
#include <vppinfra/error.h>
#include <nat/nat.h>
#include <nat/nat_ipfix_logging.h>
#include <nat/nat_inlines.h>
#include <nat/nat44_inlines.h>
#include <nat/nat_syslog.h>
#include <nat/nat_ha.h>

static char *nat_out2in_ed_error_strings[] = {
#define _(sym,string) string,
  foreach_nat_out2in_ed_error
#undef _
};

typedef struct
{
  u32 sw_if_index;
  u32 next_index;
  u32 session_index;
  u32 is_slow_path;
} nat44_ed_out2in_trace_t;

static u8 *
format_nat44_ed_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 *);
  nat44_ed_out2in_trace_t *t = va_arg (*args, nat44_ed_out2in_trace_t *);
  char *tag;

  tag =
    t->is_slow_path ? "NAT44_OUT2IN_ED_SLOW_PATH" :
    "NAT44_OUT2IN_ED_FAST_PATH";

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

  return s;
}

static inline u32
icmp_out2in_ed_slow_path (snat_main_t * sm, 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, f64 now,
                          u32 thread_index, snat_session_t ** p_s0)
{
  next0 = icmp_out2in (sm, b0, ip0, icmp0, sw_if_index0, rx_fib_index0, node,
                       next0, thread_index, p_s0, 0);
  snat_session_t *s0 = *p_s0;
  if (PREDICT_TRUE (next0 != NAT_NEXT_DROP && s0))
    {
      /* Accounting */
      nat44_session_update_counters (s0, now,
                                     vlib_buffer_length_in_chain
                                     (sm->vlib_main, b0), thread_index);
      /* Per-user LRU list maintenance */
      nat44_session_update_lru (sm, s0, thread_index);
    }
  return next0;
}

#ifndef CLIB_MARCH_VARIANT
int
nat44_o2i_ed_is_idle_session_cb (clib_bihash_kv_16_8_t * kv, void *arg)
{
  snat_main_t *sm = &snat_main;
  nat44_is_idle_session_ctx_t *ctx = arg;
  snat_session_t *s;
  u64 sess_timeout_time;
  nat_ed_ses_key_t ed_key;
  clib_bihash_kv_16_8_t ed_kv;
  int i;
  snat_address_t *a;
  snat_session_key_t key;
  snat_main_per_thread_data_t *tsm = vec_elt_at_index (sm->per_thread_data,
                                                       ctx->thread_index);

  s = pool_elt_at_index (tsm->sessions, kv->value);
  sess_timeout_time = s->last_heard + (f64) nat44_session_get_timeout (sm, s);
  if (ctx->now >= sess_timeout_time)
    {
      ed_key.l_addr = s->in2out.addr;
      ed_key.r_addr = s->ext_host_addr;
      ed_key.fib_index = s->in2out.fib_index;
      if (snat_is_unk_proto_session (s))
        {
          ed_key.proto = s->in2out.port;
          ed_key.r_port = 0;
          ed_key.l_port = 0;
        }
      else
        {
          ed_key.proto = snat_proto_to_ip_proto (s->in2out.protocol);
          ed_key.l_port = s->in2out.port;
          ed_key.r_port = s->ext_host_port;
        }
      if (is_twice_nat_session (s))
        {
          ed_key.r_addr = s->ext_host_nat_addr;
          ed_key.r_port = s->ext_host_nat_port;
        }
      ed_kv.key[0] = ed_key.as_u64[0];
      ed_kv.key[1] = ed_key.as_u64[1];
      if (clib_bihash_add_del_16_8 (&tsm->in2out_ed, &ed_kv, 0))
        nat_elog_warn ("in2out_ed key del failed");

      if (snat_is_unk_proto_session (s))
        goto delete;

      snat_ipfix_logging_nat44_ses_delete (ctx->thread_index,
                                           s->in2out.addr.as_u32,
                                           s->out2in.addr.as_u32,
                                           s->in2out.protocol,
                                           s->in2out.port,
                                           s->out2in.port,
                                           s->in2out.fib_index);

      nat_syslog_nat44_sdel (s->user_index, s->in2out.fib_index,
                             &s->in2out.addr, s->in2out.port,
                             &s->ext_host_nat_addr, s->ext_host_nat_port,
                             &s->out2in.addr, s->out2in.port,
                             &s->ext_host_addr, s->ext_host_port,
                             s->in2out.protocol, is_twice_nat_session (s));

      nat_ha_sdel (&s->out2in.addr, s->out2in.port, &s->ext_host_addr,
                   s->ext_host_port, s->out2in.protocol, s->out2in.fib_index,
                   ctx->thread_index);

      if (is_twice_nat_session (s))
        {
          for (i = 0; i < vec_len (sm->twice_nat_addresses); i++)
            {
              key.protocol = s->in2out.protocol;
              key.port = s->ext_host_nat_port;
              a = sm->twice_nat_addresses + i;
              if (a->addr.as_u32 == s->ext_host_nat_addr.as_u32)
                {
                  snat_free_outside_address_and_port (sm->twice_nat_addresses,
                                                      ctx->thread_index,
                                                      &key);
                  break;
                }
            }
        }

      if (snat_is_session_static (s))
        goto delete;

      snat_free_outside_address_and_port (sm->addresses, ctx->thread_index,
                                          &s->out2in);
    delete:
      nat44_delete_session (sm, s, ctx->thread_index);
      return 1;
    }

  return 0;
}
#endif

static snat_session_t *
create_session_for_static_mapping_ed (snat_main_t * sm,
                                      vlib_buffer_t * b,
                                      snat_session_key_t l_key,
                                      snat_session_key_t e_key,
                                      vlib_node_runtime_t * node,
                                      u32 thread_index,
                                      twice_nat_type_t twice_nat,
                                      lb_nat_type_t lb_nat, f64 now)
{
  snat_session_t *s;
  snat_user_t *u;
  ip4_header_t *ip;
  udp_header_t *udp;
  snat_main_per_thread_data_t *tsm = &sm->per_thread_data[thread_index];
  clib_bihash_kv_16_8_t kv;
  snat_session_key_t eh_key;
  nat44_is_idle_session_ctx_t ctx;

  nat44_session_try_cleanup (&l_key.addr, l_key.fib_index, thread_index, now);

  if (PREDICT_FALSE (maximum_sessions_exceeded (sm, thread_index)))
    {
      b->error = node->errors[NAT_OUT2IN_ED_ERROR_MAX_SESSIONS_EXCEEDED];
      nat_elog_notice ("maximum sessions exceeded");
      return 0;
    }

  u = nat_user_get_or_create (sm, &l_key.addr, l_key.fib_index, thread_index);
  if (!u)
    {
      nat_elog_warn ("create NAT user failed");
      return 0;
    }

  s = nat_ed_session_alloc (sm, u, thread_index, now);
  if (!s)
    {
      nat44_delete_user_with_no_session (sm, u, thread_index);
      nat_elog_warn ("create NAT session failed");
      return 0;
    }

  ip = vlib_buffer_get_current (b);
  udp = ip4_next_header (ip);

  s->ext_host_addr.as_u32 = ip->src_address.as_u32;
  s->ext_host_port = e_key.protocol == SNAT_PROTOCOL_ICMP ? 0 : udp->src_port;
  s->flags |= SNAT_SESSION_FLAG_STATIC_MAPPING;
  if (lb_nat)
    s->flags |= SNAT_SESSION_FLAG_LOAD_BALANCING;
  if (lb_nat == AFFINITY_LB_NAT)
    s->flags |= SNAT_SESSION_FLAG_AFFINITY;
  s->flags |= SNAT_SESSION_FLAG_ENDPOINT_DEPENDENT;
  s->out2in = e_key;
  s->in2out = l_key;
  s->in2out.protocol = s->out2in.protocol;
  user_session_increment (sm, u, 1);

  /* Add to lookup tables */
  make_ed_kv (&kv, &e_key.addr, &s->ext_host_addr, ip->protocol,
              e_key.fib_index, e_key.port, s->ext_host_port);
  kv.value = s - tsm->sessions;
  ctx.now = now;
  ctx.thread_index = thread_index;
  if (clib_bihash_add_or_overwrite_stale_16_8 (&tsm->out2in_ed, &kv,
                                               nat44_o2i_ed_is_idle_session_cb,
                                               &ctx))
    nat_elog_notice ("out2in-ed key add failed");

  if (twice_nat == TWICE_NAT || (twice_nat == TWICE_NAT_SELF &&
                                 ip->src_address.as_u32 == l_key.addr.as_u32))
    {
      eh_key.protocol = e_key.protocol;
      if (snat_alloc_outside_address_and_port (sm->twice_nat_addresses, 0,
                                               thread_index, &eh_key,
                                               sm->port_per_thread,
                                               tsm->snat_thread_index))
        {
          b->error = node->errors[NAT_OUT2IN_ED_ERROR_OUT_OF_PORTS];
          nat44_delete_session (sm, s, thread_index);
          if (clib_bihash_add_del_16_8 (&tsm->out2in_ed, &kv, 0))
            nat_elog_notice ("out2in-ed key del failed");
          return 0;
        }
      s->ext_host_nat_addr.as_u32 = eh_key.addr.as_u32;
      s->ext_host_nat_port = eh_key.port;
      s->flags |= SNAT_SESSION_FLAG_TWICE_NAT;
      make_ed_kv (&kv, &l_key.addr, &s->ext_host_nat_addr, ip->protocol,
                  l_key.fib_index, l_key.port, s->ext_host_nat_port);
    }
  else
    {
      make_ed_kv (&kv, &l_key.addr, &s->ext_host_addr, ip->protocol,
                  l_key.fib_index, l_key.port, s->ext_host_port);
    }
  kv.value = s - tsm->sessions;
  if (clib_bihash_add_or_overwrite_stale_16_8 (&tsm->in2out_ed, &kv,
                                               nat44_i2o_ed_is_idle_session_cb,
                                               &ctx))
    nat_elog_notice ("in2out-ed key add failed");

  snat_ipfix_logging_nat44_ses_create (thread_index,
                                       s->in2out.addr.as_u32,
                                       s->out2in.addr.as_u32,
                                       s->in2out.protocol,
                                       s->in2out.port,
                                       s->out2in.port, s->in2out.fib_index);

  nat_syslog_nat44_sadd (s->user_index, s->in2out.fib_index,
                         &s->in2out.addr, s->in2out.port,
                         &s->ext_host_nat_addr, s->ext_host_nat_port,
                         &s->out2in.addr, s->out2in.port,
                         &s->ext_host_addr, s->ext_host_port,
                         s->in2out.protocol, is_twice_nat_session (s));

  nat_ha_sadd (&s->in2out.addr, s->in2out.port, &s->out2in.addr,
               s->out2in.port, &s->ext_host_addr, s->ext_host_port,
               &s->ext_host_nat_addr, s->ext_host_nat_port,
               s->in2out.protocol, s->in2out.fib_index, s->flags,
               thread_index, 0);

  return s;
}

static int
next_src_nat (snat_main_t * sm, ip4_header_t * ip, u8 proto, u16 src_port,
              u16 dst_port, u32 thread_index, u32 rx_fib_index)
{
  clib_bihash_kv_16_8_t kv, value;
  snat_main_per_thread_data_t *tsm = &sm->per_thread_data[thread_index];

  make_ed_kv (&kv, &ip->src_address, &ip->dst_address, proto,
              rx_fib_index, src_port, dst_port);
  if (!clib_bihash_search_16_8 (&tsm->in2out_ed, &kv, &value))
    return 1;

  return 0;
}

static void
create_bypass_for_fwd (snat_main_t * sm, vlib_buffer_t * b, ip4_header_t * ip,
                       u32 rx_fib_index, u32 thread_index)
{
  nat_ed_ses_key_t key;
  clib_bihash_kv_16_8_t kv, value;
  udp_header_t *udp;
  snat_user_t *u;
  snat_session_t *s = 0;
  snat_main_per_thread_data_t *tsm = &sm->per_thread_data[thread_index];
  f64 now = vlib_time_now (sm->vlib_main);

  if (ip->protocol == IP_PROTOCOL_ICMP)
    {
      if (get_icmp_o2i_ed_key (b, ip, &key))
        return;
    }
  else if (ip->protocol == IP_PROTOCOL_UDP || ip->protocol == IP_PROTOCOL_TCP)
    {
      udp = ip4_next_header (ip);
      key.r_addr = ip->src_address;
      key.l_addr = ip->dst_address;
      key.proto = ip->protocol;
      key.l_port = udp->dst_port;
      key.r_port = udp->src_port;
    }
  else
    {
      key.r_addr = ip->src_address;
      key.l_addr = ip->dst_address;
      key.proto = ip->protocol;
      key.l_port = key.r_port = 0;
    }
  key.fib_index = 0;
  kv.key[0] = key.as_u64[0];
  kv.key[1] = key.as_u64[1];

  if (!clib_bihash_search_16_8 (&tsm->in2out_ed, &kv, &value))
    {
      s = pool_elt_at_index (tsm->sessions, value.value);
    }
  else
    {
      u32 proto;

      if (PREDICT_FALSE (maximum_sessions_exceeded (sm, thread_index)))
        return;

      u = nat_user_get_or_create (sm, &ip->dst_address, sm->inside_fib_index,
                                  thread_index);
      if (!u)
        {
          nat_elog_warn ("create NAT user failed");
          return;
        }

      s = nat_ed_session_alloc (sm, u, thread_index, now);
      if (!s)
        {
          nat44_delete_user_with_no_session (sm, u, thread_index);
          nat_elog_warn ("create NAT session failed");
          return;
        }

      proto = ip_proto_to_snat_proto (key.proto);

      s->ext_host_addr = key.r_addr;
      s->ext_host_port = key.r_port;
      s->flags |= SNAT_SESSION_FLAG_FWD_BYPASS;
      s->out2in.addr = key.l_addr;
      s->out2in.port = key.l_port;
      s->out2in.protocol = proto;
      if (proto == ~0)
        {
          s->flags |= SNAT_SESSION_FLAG_UNKNOWN_PROTO;
          s->out2in.port = ip->protocol;
        }
      s->out2in.fib_index = 0;
      s->in2out = s->out2in;
      user_session_increment (sm, u, 0);

      kv.value = s - tsm->sessions;
      if (clib_bihash_add_del_16_8 (&tsm->in2out_ed, &kv, 1))
        nat_elog_notice ("in2out_ed key add failed");
    }

  if (ip->protocol == IP_PROTOCOL_TCP)
    {
      tcp_header_t *tcp = ip4_next_header (ip);
      if (nat44_set_tcp_session_state_o2i
          (sm, s, tcp->flags, tcp->ack_number, tcp->seq_number, thread_index))
        return;
    }

  /* Accounting */
  nat44_session_update_counters (s, now, 0, thread_index);
  /* Per-user LRU list maintenance */
  nat44_session_update_lru (sm, s, thread_index);
}

static inline void
create_bypass_for_fwd_worker (snat_main_t * sm, vlib_buffer_t * b,
                              ip4_header_t * ip, u32 rx_fib_index)
{
  ip4_header_t ip_wkr = {
    .src_address = ip->dst_address,
  };
  u32 thread_index = sm->worker_in2out_cb (&ip_wkr, rx_fib_index, 0);

  create_bypass_for_fwd (sm, b, ip, rx_fib_index, thread_index);
}

#ifndef CLIB_MARCH_VARIANT
u32
icmp_match_out2in_ed (snat_main_t * sm, vlib_node_runtime_t * node,
                      u32 thread_index, vlib_buffer_t * b, ip4_header_t * ip,
                      u8 * p_proto, snat_session_key_t * p_value,
                      u8 * p_dont_translate, void *d, void *e)
{
  u32 next = ~0, sw_if_index, rx_fib_index;
  nat_ed_ses_key_t key;
  clib_bihash_kv_16_8_t kv, value;
  snat_main_per_thread_data_t *tsm = &sm->per_thread_data[thread_index];
  snat_session_t *s = 0;
  u8 dont_translate = 0, is_addr_only, identity_nat;
  snat_session_key_t e_key, l_key;

  sw_if_index = vnet_buffer (b)->sw_if_index[VLIB_RX];
  rx_fib_index = ip4_fib_table_get_index_for_sw_if_index (sw_if_index);

  if (get_icmp_o2i_ed_key (b, ip, &key))
    {
      b->error = node->errors[NAT_OUT2IN_ED_ERROR_UNSUPPORTED_PROTOCOL];
      next = NAT_NEXT_DROP;
      goto out;
    }
  key.fib_index = rx_fib_index;
  kv.key[0] = key.as_u64[0];
  kv.key[1] = key.as_u64[1];

  if (clib_bihash_search_16_8 (&tsm->out2in_ed, &kv, &value))
    {
      /* Try to match static mapping */
      e_key.addr = ip->dst_address;
      e_key.port = key.l_port;
      e_key.protocol = ip_proto_to_snat_proto (key.proto);
      e_key.fib_index = rx_fib_index;
      if (snat_static_mapping_match
          (sm, e_key, &l_key, 1, &is_addr_only, 0, 0, 0, &identity_nat))
        {
          if (!sm->forwarding_enabled)
            {
              /* Don't NAT packet aimed at the intfc address */
              if (PREDICT_FALSE (is_interface_addr (sm, node, sw_if_index,
                                                    ip->dst_address.as_u32)))
                {
                  dont_translate = 1;
                  goto out;
                }
              b->error = node->errors[NAT_OUT2IN_ED_ERROR_NO_TRANSLATION];
              next = NAT_NEXT_DROP;
              goto out;
            }
          else
            {
              dont_translate = 1;
              if (next_src_nat (sm, ip, key.proto, key.l_port, key.r_port,
                                thread_index, rx_fib_index))
                {
                  next = NAT_NEXT_IN2OUT_ED_FAST_PATH;
                  goto out;
                }
              if (sm->num_workers > 1)
                create_bypass_for_fwd_worker (sm, b, ip, rx_fib_index);
              else
                create_bypass_for_fwd (sm, b, ip, rx_fib_index, thread_index);
              goto out;
            }
        }

      if (PREDICT_FALSE
          (vnet_buffer (b)->ip.reass.icmp_type_or_tcp_flags !=
           ICMP4_echo_reply
           && (vnet_buffer (b)->ip.reass.icmp_type_or_tcp_flags !=
               ICMP4_echo_request || !is_addr_only)))
        {
          b->error = node->errors[NAT_OUT2IN_ED_ERROR_BAD_ICMP_TYPE];
          next = NAT_NEXT_DROP;
          goto out;
        }

      if (PREDICT_FALSE (identity_nat))
        {
          dont_translate = 1;
          goto out;
        }

      /* Create session initiated by host from external network */
      s = create_session_for_static_mapping_ed (sm, b, l_key, e_key, node,
                                                thread_index, 0, 0,
                                                vlib_time_now
                                                (sm->vlib_main));

      if (!s)
        {
          next = NAT_NEXT_DROP;
          goto out;
        }
    }
  else
    {
      if (PREDICT_FALSE
          (vnet_buffer (b)->ip.reass.icmp_type_or_tcp_flags !=
           ICMP4_echo_reply
           && vnet_buffer (b)->ip.reass.icmp_type_or_tcp_flags !=
           ICMP4_echo_request
           && !icmp_type_is_error_message (vnet_buffer (b)->ip.
                                           reass.icmp_type_or_tcp_flags)))
        {
          b->error = node->errors[NAT_OUT2IN_ED_ERROR_BAD_ICMP_TYPE];
          next = NAT_NEXT_DROP;
          goto out;
        }

      s = pool_elt_at_index (tsm->sessions, value.value);
    }

  *p_proto = ip_proto_to_snat_proto (key.proto);
out:
  if (s)
    *p_value = s->in2out;
  *p_dont_translate = dont_translate;
  if (d)
    *(snat_session_t **) d = s;
  return next;
}
#endif

static snat_session_t *
nat44_ed_out2in_unknown_proto (snat_main_t * sm,
                               vlib_buffer_t * b,
                               ip4_header_t * ip,
                               u32 rx_fib_index,
                               u32 thread_index,
                               f64 now,
                               vlib_main_t * vm, vlib_node_runtime_t * node)
{
  clib_bihash_kv_8_8_t kv, value;
  clib_bihash_kv_16_8_t s_kv, s_value;
  snat_static_mapping_t *m;
  u32 old_addr, new_addr;
  ip_csum_t sum;
  snat_session_t *s;
  snat_main_per_thread_data_t *tsm = &sm->per_thread_data[thread_index];
  snat_user_t *u;

  old_addr = ip->dst_address.as_u32;

  make_ed_kv (&s_kv, &ip->dst_address, &ip->src_address, ip->protocol,
              rx_fib_index, 0, 0);

  if (!clib_bihash_search_16_8 (&tsm->out2in_ed, &s_kv, &s_value))
    {
      s = pool_elt_at_index (tsm->sessions, s_value.value);
      new_addr = ip->dst_address.as_u32 = s->in2out.addr.as_u32;
    }
  else
    {
      if (PREDICT_FALSE (maximum_sessions_exceeded (sm, thread_index)))
        {
          b->error = node->errors[NAT_OUT2IN_ED_ERROR_MAX_SESSIONS_EXCEEDED];
          nat_elog_notice ("maximum sessions exceeded");
          return 0;
        }

      make_sm_kv (&kv, &ip->dst_address, 0, 0, 0);
      if (clib_bihash_search_8_8
          (&sm->static_mapping_by_external, &kv, &value))
        {
          b->error = node->errors[NAT_OUT2IN_ED_ERROR_NO_TRANSLATION];
          return 0;
        }

      m = pool_elt_at_index (sm->static_mappings, value.value);

      new_addr = ip->dst_address.as_u32 = m->local_addr.as_u32;

      u = nat_user_get_or_create (sm, &m->local_addr, m->fib_index,
                                  thread_index);
      if (!u)
        {
          nat_elog_warn ("create NAT user failed");
          return 0;
        }

      /* Create a new session */
      s = nat_ed_session_alloc (sm, u, thread_index, now);
      if (!s)
        {
          nat44_delete_user_with_no_session (sm, u, thread_index);
          nat_elog_warn ("create NAT session failed");
          return 0;
        }

      s->ext_host_addr.as_u32 = ip->src_address.as_u32;
      s->flags |= SNAT_SESSION_FLAG_UNKNOWN_PROTO;
      s->flags |= SNAT_SESSION_FLAG_STATIC_MAPPING;
      s->flags |= SNAT_SESSION_FLAG_ENDPOINT_DEPENDENT;
      s->out2in.addr.as_u32 = old_addr;
      s->out2in.fib_index = rx_fib_index;
      s->in2out.addr.as_u32 = new_addr;
      s->in2out.fib_index = m->fib_index;
      s->in2out.port = s->out2in.port = ip->protocol;
      user_session_increment (sm, u, 1);

      /* Add to lookup tables */
      s_kv.value = s - tsm->sessions;
      if (clib_bihash_add_del_16_8 (&tsm->out2in_ed, &s_kv, 1))
        nat_elog_notice ("out2in key add failed");

      make_ed_kv (&s_kv, &ip->dst_address, &ip->src_address, ip->protocol,
                  m->fib_index, 0, 0);
      s_kv.value = s - tsm->sessions;
      if (clib_bihash_add_del_16_8 (&tsm->in2out_ed, &s_kv, 1))
        nat_elog_notice ("in2out key add failed");
    }

  /* Update IP checksum */
  sum = ip->checksum;
  sum = ip_csum_update (sum, old_addr, new_addr, ip4_header_t, dst_address);
  ip->checksum = ip_csum_fold (sum);

  vnet_buffer (b)->sw_if_index[VLIB_TX] = s->in2out.fib_index;

  /* Accounting */
  nat44_session_update_counters (s, now, vlib_buffer_length_in_chain (vm, b),
                                 thread_index);
  /* Per-user LRU list maintenance */
  nat44_session_update_lru (sm, s, thread_index);

  return s;
}

static inline uword
nat44_ed_out2in_node_fn_inline (vlib_main_t * vm,
                                vlib_node_runtime_t * node,
                                vlib_frame_t * frame, int is_slow_path)
{
  u32 n_left_from, *from, *to_next, pkts_processed = 0, stats_node_index;
  nat_next_t next_index;
  snat_main_t *sm = &snat_main;
  f64 now = vlib_time_now (vm);
  u32 thread_index = vm->thread_index;
  snat_main_per_thread_data_t *tsm = &sm->per_thread_data[thread_index];
  u32 tcp_packets = 0, udp_packets = 0, icmp_packets = 0, other_packets =
    0, fragments = 0;

  stats_node_index = is_slow_path ? sm->ed_out2in_slowpath_node_index :
    sm->ed_out2in_node_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, sw_if_index0, rx_fib_index0, proto0, old_addr0,
            new_addr0;
          u32 next1, sw_if_index1, rx_fib_index1, proto1, old_addr1,
            new_addr1;
          u16 old_port0, new_port0, old_port1, new_port1;
          ip4_header_t *ip0, *ip1;
          udp_header_t *udp0, *udp1;
          tcp_header_t *tcp0, *tcp1;
          icmp46_header_t *icmp0, *icmp1;
          snat_session_t *s0 = 0, *s1 = 0;
          clib_bihash_kv_16_8_t kv0, value0, kv1, value1;
          ip_csum_t sum0, sum1;
          snat_session_key_t e_key0, l_key0, e_key1, l_key1;
          lb_nat_type_t lb_nat0, lb_nat1;
          twice_nat_type_t twice_nat0, twice_nat1;
          u8 identity_nat0, identity_nat1;

          /* 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);

          next0 = nat_buffer_opaque (b0)->arc_next;
          next1 = nat_buffer_opaque (b1)->arc_next;

          vnet_buffer (b0)->snat.flags = 0;
          ip0 = vlib_buffer_get_current (b0);

          sw_if_index0 = vnet_buffer (b0)->sw_if_index[VLIB_RX];
          rx_fib_index0 =
            fib_table_get_index_for_sw_if_index (FIB_PROTOCOL_IP4,
                                                 sw_if_index0);

          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_NEXT_ICMP_ERROR;
              goto trace00;
            }

          udp0 = ip4_next_header (ip0);
          tcp0 = (tcp_header_t *) udp0;
          icmp0 = (icmp46_header_t *) udp0;
          proto0 = ip_proto_to_snat_proto (ip0->protocol);

          if (is_slow_path)
            {
              if (PREDICT_FALSE (proto0 == ~0))
                {
                  s0 =
                    nat44_ed_out2in_unknown_proto (sm, b0, ip0, rx_fib_index0,
                                                   thread_index, now, vm,
                                                   node);
                  other_packets++;
                  if (!sm->forwarding_enabled)
                    {
                      if (!s0)
                        next0 = NAT_NEXT_DROP;
                      goto trace00;
                    }
                }

              if (PREDICT_FALSE (proto0 == SNAT_PROTOCOL_ICMP))
                {
                  next0 = icmp_out2in_ed_slow_path
                    (sm, b0, ip0, icmp0, sw_if_index0, rx_fib_index0, node,
                     next0, now, thread_index, &s0);
                  icmp_packets++;
                  goto trace00;
                }
            }
          else
            {
              if (PREDICT_FALSE (proto0 == ~0))
                {
                  next0 = NAT_NEXT_OUT2IN_ED_SLOW_PATH;
                  goto trace00;
                }

              if (PREDICT_FALSE (proto0 == SNAT_PROTOCOL_ICMP))
                {
                  next0 = NAT_NEXT_OUT2IN_ED_SLOW_PATH;
                  goto trace00;
                }
            }

          make_ed_kv (&kv0, &ip0->dst_address, &ip0->src_address,
                      ip0->protocol, rx_fib_index0,
                      vnet_buffer (b0)->ip.reass.l4_dst_port,
                      vnet_buffer (b0)->ip.reass.l4_src_port);

          if (clib_bihash_search_16_8 (&tsm->out2in_ed, &kv0, &value0))
            {
              if (is_slow_path)
                {
                  /* Try to match static mapping by external address and port,
                     destination address and port in packet */
                  e_key0.addr = ip0->dst_address;
                  e_key0.port = vnet_buffer (b0)->ip.reass.l4_dst_port;
                  e_key0.protocol = proto0;
                  e_key0.fib_index = rx_fib_index0;
                  if (snat_static_mapping_match (sm, e_key0, &l_key0, 1, 0,
                                                 &twice_nat0, &lb_nat0,
                                                 &ip0->src_address,
                                                 &identity_nat0))
                    {
                      /*
                       * Send DHCP packets to the ipv4 stack, or we won't
                       * be able to use dhcp client on the outside interface
                       */
                      if (PREDICT_FALSE
                          (proto0 == SNAT_PROTOCOL_UDP
                           && (vnet_buffer (b0)->ip.reass.l4_dst_port ==
                               clib_host_to_net_u16
                               (UDP_DST_PORT_dhcp_to_client))))
                        {
                          goto trace00;
                        }

                      if (!sm->forwarding_enabled)
                        {
                          b0->error =
                            node->errors[NAT_OUT2IN_ED_ERROR_NO_TRANSLATION];
                          next0 = NAT_NEXT_DROP;
                        }
                      else
                        {
                          if (next_src_nat
                              (sm, ip0, ip0->protocol,
                               vnet_buffer (b0)->ip.reass.l4_src_port,
                               vnet_buffer (b0)->ip.reass.l4_dst_port,
                               thread_index, rx_fib_index0))
                            {
                              next0 = NAT_NEXT_IN2OUT_ED_FAST_PATH;
                              goto trace00;
                            }
                          if (sm->num_workers > 1)
                            create_bypass_for_fwd_worker (sm, b0, ip0,
                                                          rx_fib_index0);
                          else
                            create_bypass_for_fwd (sm, b0, ip0, rx_fib_index0,
                                                   thread_index);
                        }
                      goto trace00;
                    }

                  if (PREDICT_FALSE (identity_nat0))
                    goto trace00;

                  if ((proto0 == SNAT_PROTOCOL_TCP)
                      && !tcp_flags_is_init (vnet_buffer (b0)->ip.
                                             reass.icmp_type_or_tcp_flags))
                    {
                      b0->error = node->errors[NAT_OUT2IN_ED_ERROR_NON_SYN];
                      next0 = NAT_NEXT_DROP;
                      goto trace00;
                    }

                  /* Create session initiated by host from external network */
                  s0 = create_session_for_static_mapping_ed (sm, b0, l_key0,
                                                             e_key0, node,
                                                             thread_index,
                                                             twice_nat0,
                                                             lb_nat0, now);

                  if (!s0)
                    {
                      next0 = NAT_NEXT_DROP;
                      goto trace00;
                    }
                }
              else
                {
                  next0 = NAT_NEXT_OUT2IN_ED_SLOW_PATH;
                  goto trace00;
                }
            }
          else
            {
              s0 = pool_elt_at_index (tsm->sessions, value0.value);
            }

          old_addr0 = ip0->dst_address.as_u32;
          new_addr0 = ip0->dst_address.as_u32 = s0->in2out.addr.as_u32;
          vnet_buffer (b0)->sw_if_index[VLIB_TX] = s0->in2out.fib_index;

          sum0 = ip0->checksum;
          sum0 = ip_csum_update (sum0, old_addr0, new_addr0, ip4_header_t,
                                 dst_address);
          if (PREDICT_FALSE (is_twice_nat_session (s0)))
            sum0 = ip_csum_update (sum0, ip0->src_address.as_u32,
                                   s0->ext_host_nat_addr.as_u32, ip4_header_t,
                                   src_address);
          ip0->checksum = ip_csum_fold (sum0);

          old_port0 = vnet_buffer (b0)->ip.reass.l4_dst_port;

          if (PREDICT_TRUE (proto0 == SNAT_PROTOCOL_TCP))
            {
              if (!vnet_buffer (b0)->ip.reass.is_non_first_fragment)
                {
                  new_port0 = udp0->dst_port = s0->in2out.port;
                  sum0 = tcp0->checksum;
                  sum0 =
                    ip_csum_update (sum0, old_addr0, new_addr0, ip4_header_t,
                                    dst_address);
                  sum0 =
                    ip_csum_update (sum0, old_port0, new_port0, ip4_header_t,
                                    length);
                  if (is_twice_nat_session (s0))
                    {
                      sum0 = ip_csum_update (sum0, ip0->src_address.as_u32,
                                             s0->ext_host_nat_addr.as_u32,
                                             ip4_header_t, dst_address);
                      sum0 =
                        ip_csum_update (sum0,
                                        vnet_buffer (b0)->ip.
                                        reass.l4_src_port,
                                        s0->ext_host_nat_port, ip4_header_t,
                                        length);
                      tcp0->src_port = s0->ext_host_nat_port;
                      ip0->src_address.as_u32 = s0->ext_host_nat_addr.as_u32;
                    }
                  tcp0->checksum = ip_csum_fold (sum0);
                }
              tcp_packets++;
              if (nat44_set_tcp_session_state_o2i
                  (sm, s0, vnet_buffer (b0)->ip.reass.icmp_type_or_tcp_flags,
                   vnet_buffer (b0)->ip.reass.tcp_ack_number,
                   vnet_buffer (b0)->ip.reass.tcp_seq_number, thread_index))
                goto trace00;
            }
          else if (!vnet_buffer (b0)->ip.reass.is_non_first_fragment
                   && udp0->checksum)
            {
              new_port0 = udp0->dst_port = s0->in2out.port;
              sum0 = udp0->checksum;
              sum0 = ip_csum_update (sum0, old_addr0, new_addr0, ip4_header_t,
                                     dst_address);
              sum0 = ip_csum_update (sum0, old_port0, new_port0, ip4_header_t,
                                     length);
              if (PREDICT_FALSE (is_twice_nat_session (s0)))
                {
                  sum0 = ip_csum_update (sum0, ip0->src_address.as_u32,
                                         s0->ext_host_nat_addr.as_u32,
                                         ip4_header_t, dst_address);
                  sum0 =
                    ip_csum_update (sum0,
                                    vnet_buffer (b0)->ip.reass.l4_src_port,
                                    s0->ext_host_nat_port, ip4_header_t,
                                    length);
                  udp0->src_port = s0->ext_host_nat_port;
                  ip0->src_address.as_u32 = s0->ext_host_nat_addr.as_u32;
                }
              udp0->checksum = ip_csum_fold (sum0);
              udp_packets++;
            }
          else
            {
              if (!vnet_buffer (b0)->ip.reass.is_non_first_fragment)
                {
                  new_port0 = udp0->dst_port = s0->in2out.port;
                  if (PREDICT_FALSE (is_twice_nat_session (s0)))
                    {
                      udp0->dst_port = s0->in2out.port;
                      if (is_twice_nat_session (s0))
                        {
                          udp0->src_port = s0->ext_host_nat_port;
                          ip0->src_address.as_u32 =
                            s0->ext_host_nat_addr.as_u32;
                        }
                      udp0->checksum = 0;
                    }
                }
              udp_packets++;
            }

          /* Accounting */
          nat44_session_update_counters (s0, now,
                                         vlib_buffer_length_in_chain (vm, b0),
                                         thread_index);
          /* Per-user LRU list maintenance */
          nat44_session_update_lru (sm, s0, thread_index);

        trace00:
          if (PREDICT_FALSE ((node->flags & VLIB_NODE_FLAG_TRACE)
                             && (b0->flags & VLIB_BUFFER_IS_TRACED)))
            {
              nat44_ed_out2in_trace_t *t =
                vlib_add_trace (vm, node, b0, sizeof (*t));
              t->is_slow_path = is_slow_path;
              t->sw_if_index = sw_if_index0;
              t->next_index = next0;
              t->session_index = ~0;
              if (s0)
                t->session_index = s0 - tsm->sessions;
            }

          pkts_processed += next0 == nat_buffer_opaque (b0)->arc_next;

          vnet_buffer (b1)->snat.flags = 0;
          ip1 = vlib_buffer_get_current (b1);

          sw_if_index1 = vnet_buffer (b1)->sw_if_index[VLIB_RX];
          rx_fib_index1 =
            fib_table_get_index_for_sw_if_index (FIB_PROTOCOL_IP4,
                                                 sw_if_index1);

          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_NEXT_ICMP_ERROR;
              goto trace01;
            }

          udp1 = ip4_next_header (ip1);
          tcp1 = (tcp_header_t *) udp1;
          icmp1 = (icmp46_header_t *) udp1;
          proto1 = ip_proto_to_snat_proto (ip1->protocol);

          if (is_slow_path)
            {
              if (PREDICT_FALSE (proto1 == ~0))
                {
                  s1 =
                    nat44_ed_out2in_unknown_proto (sm, b1, ip1, rx_fib_index1,
                                                   thread_index, now, vm,
                                                   node);
                  other_packets++;
                  if (!sm->forwarding_enabled)
                    {
                      if (!s1)
                        next1 = NAT_NEXT_DROP;
                      goto trace01;
                    }
                }

              if (PREDICT_FALSE (proto1 == SNAT_PROTOCOL_ICMP))
                {
                  next1 = icmp_out2in_ed_slow_path
                    (sm, b1, ip1, icmp1, sw_if_index1, rx_fib_index1, node,
                     next1, now, thread_index, &s1);
                  icmp_packets++;
                  goto trace01;
                }
            }
          else
            {
              if (PREDICT_FALSE (proto1 == ~0))
                {
                  next1 = NAT_NEXT_OUT2IN_ED_SLOW_PATH;
                  goto trace01;
                }

              if (PREDICT_FALSE (proto1 == SNAT_PROTOCOL_ICMP))
                {
                  next1 = NAT_NEXT_OUT2IN_ED_SLOW_PATH;
                  goto trace01;
                }
            }

          make_ed_kv (&kv1, &ip1->dst_address, &ip1->src_address,
                      ip1->protocol, rx_fib_index1,
                      vnet_buffer (b1)->ip.reass.l4_dst_port,
                      vnet_buffer (b1)->ip.reass.l4_src_port);

          if (clib_bihash_search_16_8 (&tsm->out2in_ed, &kv1, &value1))
            {
              if (is_slow_path)
                {
                  /* Try to match static mapping by external address and port,
                     destination address and port in packet */
                  e_key1.addr = ip1->dst_address;
                  e_key1.port = vnet_buffer (b1)->ip.reass.l4_dst_port;
                  e_key1.protocol = proto1;
                  e_key1.fib_index = rx_fib_index1;
                  if (snat_static_mapping_match (sm, e_key1, &l_key1, 1, 0,
                                                 &twice_nat1, &lb_nat1,
                                                 &ip1->src_address,
                                                 &identity_nat1))
                    {
                      /*
                       * Send DHCP packets to the ipv4 stack, or we won't
                       * be able to use dhcp client on the outside interface
                       */
                      if (PREDICT_FALSE
                          (proto1 == SNAT_PROTOCOL_UDP
                           && (vnet_buffer (b1)->ip.reass.l4_dst_port ==
                               clib_host_to_net_u16
                               (UDP_DST_PORT_dhcp_to_client))))
                        {
                          goto trace01;
                        }

                      if (!sm->forwarding_enabled)
                        {
                          b1->error =
                            node->errors[NAT_OUT2IN_ED_ERROR_NO_TRANSLATION];
                          next1 = NAT_NEXT_DROP;
                        }
                      else
                        {
                          if (next_src_nat
                              (sm, ip1, ip1->protocol,
                               vnet_buffer (b1)->ip.reass.l4_src_port,
                               vnet_buffer (b1)->ip.reass.l4_dst_port,
                               thread_index, rx_fib_index1))
                            {
                              next1 = NAT_NEXT_IN2OUT_ED_FAST_PATH;
                              goto trace01;
                            }
                          if (sm->num_workers > 1)
                            create_bypass_for_fwd_worker (sm, b1, ip1,
                                                          rx_fib_index1);
                          else
                            create_bypass_for_fwd (sm, b1, ip1, rx_fib_index1,
                                                   thread_index);
                        }
                      goto trace01;
                    }

                  if (PREDICT_FALSE (identity_nat1))
                    goto trace01;

                  if ((proto1 == SNAT_PROTOCOL_TCP)
                      && !tcp_flags_is_init (vnet_buffer (b1)->ip.
                                             reass.icmp_type_or_tcp_flags))
                    {
                      b1->error = node->errors[NAT_OUT2IN_ED_ERROR_NON_SYN];
                      next1 = NAT_NEXT_DROP;
                      goto trace01;
                    }

                  /* Create session initiated by host from external network */
                  s1 = create_session_for_static_mapping_ed (sm, b1, l_key1,
                                                             e_key1, node,
                                                             thread_index,
                                                             twice_nat1,
                                                             lb_nat1, now);

                  if (!s1)
                    {
                      next1 = NAT_NEXT_DROP;
                      goto trace01;
                    }
                }
              else
                {
                  next1 = NAT_NEXT_OUT2IN_ED_SLOW_PATH;
                  goto trace01;
                }
            }
          else
            {
              s1 = pool_elt_at_index (tsm->sessions, value1.value);
            }

          old_addr1 = ip1->dst_address.as_u32;
          new_addr1 = ip1->dst_address.as_u32 = s1->in2out.addr.as_u32;
          vnet_buffer (b1)->sw_if_index[VLIB_TX] = s1->in2out.fib_index;

          sum1 = ip1->checksum;
          sum1 = ip_csum_update (sum1, old_addr1, new_addr1, ip4_header_t,
                                 dst_address);
          if (PREDICT_FALSE (is_twice_nat_session (s1)))
            sum1 = ip_csum_update (sum1, ip1->src_address.as_u32,
                                   s1->ext_host_nat_addr.as_u32, ip4_header_t,
                                   src_address);
          ip1->checksum = ip_csum_fold (sum1);

          old_port1 = vnet_buffer (b1)->ip.reass.l4_dst_port;

          if (PREDICT_TRUE (proto1 == SNAT_PROTOCOL_TCP))
            {
              if (!vnet_buffer (b1)->ip.reass.is_non_first_fragment)
                {
                  new_port1 = udp1->dst_port = s1->in2out.port;

                  sum1 = tcp1->checksum;
                  sum1 =
                    ip_csum_update (sum1, old_addr1, new_addr1, ip4_header_t,
                                    dst_address);
                  sum1 =
                    ip_csum_update (sum1, old_port1, new_port1, ip4_header_t,
                                    length);
                  if (is_twice_nat_session (s1))
                    {
                      sum1 = ip_csum_update (sum1, ip1->src_address.as_u32,
                                             s1->ext_host_nat_addr.as_u32,
                                             ip4_header_t, dst_address);
                      sum1 =
                        ip_csum_update (sum1,
                                        vnet_buffer (b1)->ip.
                                        reass.l4_src_port,
                                        s1->ext_host_nat_port, ip4_header_t,
                                        length);
                      tcp1->src_port = s1->ext_host_nat_port;
                      ip1->src_address.as_u32 = s1->ext_host_nat_addr.as_u32;
                    }
                  tcp1->checksum = ip_csum_fold (sum1);
                }
              tcp_packets++;
              if (nat44_set_tcp_session_state_o2i
                  (sm, s1, vnet_buffer (b1)->ip.reass.icmp_type_or_tcp_flags,
                   vnet_buffer (b1)->ip.reass.tcp_ack_number,
                   vnet_buffer (b1)->ip.reass.tcp_seq_number, thread_index))
                goto trace01;
            }
          else if (!vnet_buffer (b1)->ip.reass.is_non_first_fragment
                   && udp1->checksum)
            {
              new_port1 = udp1->dst_port = s1->in2out.port;
              sum1 = udp1->checksum;
              sum1 = ip_csum_update (sum1, old_addr1, new_addr1, ip4_header_t,
                                     dst_address);
              sum1 = ip_csum_update (sum1, old_port1, new_port1, ip4_header_t,
                                     length);
              if (PREDICT_FALSE (is_twice_nat_session (s1)))
                {
                  sum1 = ip_csum_update (sum1, ip1->src_address.as_u32,
                                         s1->ext_host_nat_addr.as_u32,
                                         ip4_header_t, dst_address);
                  sum1 =
                    ip_csum_update (sum1,
                                    vnet_buffer (b1)->ip.reass.l4_src_port,
                                    s1->ext_host_nat_port, ip4_header_t,
                                    length);
                  udp1->src_port = s1->ext_host_nat_port;
                  ip1->src_address.as_u32 = s1->ext_host_nat_addr.as_u32;
                }
              udp1->checksum = ip_csum_fold (sum1);
              udp_packets++;
            }
          else
            {
              if (!vnet_buffer (b1)->ip.reass.is_non_first_fragment)
                {
                  if (PREDICT_FALSE (is_twice_nat_session (s1)))
                    {
                      udp1->dst_port = s1->in2out.port;
                      if (is_twice_nat_session (s1))
                        {
                          udp1->src_port = s1->ext_host_nat_port;
                          ip1->src_address.as_u32 =
                            s1->ext_host_nat_addr.as_u32;
                        }
                      udp1->checksum = 0;
                    }
                }
              udp_packets++;
            }

          /* Accounting */
          nat44_session_update_counters (s1, now,
                                         vlib_buffer_length_in_chain (vm, b1),
                                         thread_index);
          /* Per-user LRU list maintenance */
          nat44_session_update_lru (sm, s1, thread_index);

        trace01:
          if (PREDICT_FALSE ((node->flags & VLIB_NODE_FLAG_TRACE)
                             && (b1->flags & VLIB_BUFFER_IS_TRACED)))
            {
              nat44_ed_out2in_trace_t *t =
                vlib_add_trace (vm, node, b1, sizeof (*t));
              t->is_slow_path = is_slow_path;
              t->sw_if_index = sw_if_index1;
              t->next_index = next1;
              t->session_index = ~0;
              if (s1)
                t->session_index = s1 - tsm->sessions;
            }

          pkts_processed += next1 == nat_buffer_opaque (b1)->arc_next;

          /* 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, sw_if_index0, rx_fib_index0, proto0, old_addr0,
            new_addr0;
          u16 old_port0, new_port0;
          ip4_header_t *ip0;
          udp_header_t *udp0;
          tcp_header_t *tcp0;
          icmp46_header_t *icmp0;
          snat_session_t *s0 = 0;
          clib_bihash_kv_16_8_t kv0, value0;
          ip_csum_t sum0;
          snat_session_key_t e_key0, l_key0;
          lb_nat_type_t lb_nat0;
          twice_nat_type_t twice_nat0;
          u8 identity_nat0;

          /* 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);
          next0 = nat_buffer_opaque (b0)->arc_next;

          vnet_buffer (b0)->snat.flags = 0;
          ip0 = vlib_buffer_get_current (b0);

          sw_if_index0 = vnet_buffer (b0)->sw_if_index[VLIB_RX];
          rx_fib_index0 =
            fib_table_get_index_for_sw_if_index (FIB_PROTOCOL_IP4,
                                                 sw_if_index0);

          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_NEXT_ICMP_ERROR;
              goto trace0;
            }

          udp0 = ip4_next_header (ip0);
          tcp0 = (tcp_header_t *) udp0;
          icmp0 = (icmp46_header_t *) udp0;
          proto0 = ip_proto_to_snat_proto (ip0->protocol);

          if (is_slow_path)
            {
              if (PREDICT_FALSE (proto0 == ~0))
                {
                  s0 =
                    nat44_ed_out2in_unknown_proto (sm, b0, ip0, rx_fib_index0,
                                                   thread_index, now, vm,
                                                   node);
                  other_packets++;
                  if (!sm->forwarding_enabled)
                    {
                      if (!s0)
                        next0 = NAT_NEXT_DROP;
                      goto trace0;
                    }
                }

              if (PREDICT_FALSE (proto0 == SNAT_PROTOCOL_ICMP))
                {
                  next0 = icmp_out2in_ed_slow_path
                    (sm, b0, ip0, icmp0, sw_if_index0, rx_fib_index0, node,
                     next0, now, thread_index, &s0);
                  icmp_packets++;
                  goto trace0;
                }
            }
          else
            {
              if (PREDICT_FALSE (proto0 == ~0))
                {
                  next0 = NAT_NEXT_OUT2IN_ED_SLOW_PATH;
                  goto trace0;
                }

              if (PREDICT_FALSE (proto0 == SNAT_PROTOCOL_ICMP))
                {
                  next0 = NAT_NEXT_OUT2IN_ED_SLOW_PATH;
                  goto trace0;
                }
            }

          make_ed_kv (&kv0, &ip0->dst_address, &ip0->src_address,
                      ip0->protocol, rx_fib_index0,
                      vnet_buffer (b0)->ip.reass.l4_dst_port,
                      vnet_buffer (b0)->ip.reass.l4_src_port);

          if (clib_bihash_search_16_8 (&tsm->out2in_ed, &kv0, &value0))
            {
              if (is_slow_path)
                {
                  /* Try to match static mapping by external address and port,
                     destination address and port in packet */
                  e_key0.addr = ip0->dst_address;
                  e_key0.port = vnet_buffer (b0)->ip.reass.l4_dst_port;
                  e_key0.protocol = proto0;
                  e_key0.fib_index = rx_fib_index0;
                  if (snat_static_mapping_match (sm, e_key0, &l_key0, 1, 0,
                                                 &twice_nat0, &lb_nat0,
                                                 &ip0->src_address,
                                                 &identity_nat0))
                    {
                      /*
                       * Send DHCP packets to the ipv4 stack, or we won't
                       * be able to use dhcp client on the outside interface
                       */
                      if (PREDICT_FALSE
                          (proto0 == SNAT_PROTOCOL_UDP
                           && (vnet_buffer (b0)->ip.reass.l4_dst_port ==
                               clib_host_to_net_u16
                               (UDP_DST_PORT_dhcp_to_client))))
                        {
                          goto trace0;
                        }

                      if (!sm->forwarding_enabled)
                        {
                          b0->error =
                            node->errors[NAT_OUT2IN_ED_ERROR_NO_TRANSLATION];
                          next0 = NAT_NEXT_DROP;
                        }
                      else
                        {
                          if (next_src_nat
                              (sm, ip0, ip0->protocol,
                               vnet_buffer (b0)->ip.reass.l4_src_port,
                               vnet_buffer (b0)->ip.reass.l4_dst_port,
                               thread_index, rx_fib_index0))
                            {
                              next0 = NAT_NEXT_IN2OUT_ED_FAST_PATH;
                              goto trace0;
                            }
                          if (sm->num_workers > 1)
                            create_bypass_for_fwd_worker (sm, b0, ip0,
                                                          rx_fib_index0);
                          else
                            create_bypass_for_fwd (sm, b0, ip0, rx_fib_index0,
                                                   thread_index);
                        }
                      goto trace0;
                    }

                  if (PREDICT_FALSE (identity_nat0))
                    goto trace0;

                  if ((proto0 == SNAT_PROTOCOL_TCP)
                      && !tcp_flags_is_init (vnet_buffer (b0)->ip.
                                             reass.icmp_type_or_tcp_flags))
                    {
                      b0->error = node->errors[NAT_OUT2IN_ED_ERROR_NON_SYN];
                      next0 = NAT_NEXT_DROP;
                      goto trace0;
                    }

                  /* Create session initiated by host from external network */
                  s0 = create_session_for_static_mapping_ed (sm, b0, l_key0,
                                                             e_key0, node,
                                                             thread_index,
                                                             twice_nat0,
                                                             lb_nat0, now);

                  if (!s0)
                    {
                      next0 = NAT_NEXT_DROP;
                      goto trace0;
                    }
                }
              else
                {
                  next0 = NAT_NEXT_OUT2IN_ED_SLOW_PATH;
                  goto trace0;
                }
            }
          else
            {
              s0 = pool_elt_at_index (tsm->sessions, value0.value);
            }

          old_addr0 = ip0->dst_address.as_u32;
          new_addr0 = ip0->dst_address.as_u32 = s0->in2out.addr.as_u32;
          vnet_buffer (b0)->sw_if_index[VLIB_TX] = s0->in2out.fib_index;

          sum0 = ip0->checksum;
          sum0 = ip_csum_update (sum0, old_addr0, new_addr0, ip4_header_t,
                                 dst_address);
          if (PREDICT_FALSE (is_twice_nat_session (s0)))
            sum0 = ip_csum_update (sum0, ip0->src_address.as_u32,
                                   s0->ext_host_nat_addr.as_u32, ip4_header_t,
                                   src_address);
          ip0->checksum = ip_csum_fold (sum0);

          old_port0 = vnet_buffer (b0)->ip.reass.l4_dst_port;

          if (PREDICT_TRUE (proto0 == SNAT_PROTOCOL_TCP))
            {
              if (!vnet_buffer (b0)->ip.reass.is_non_first_fragment)
                {
                  new_port0 = udp0->dst_port = s0->in2out.port;
                  sum0 = tcp0->checksum;
                  sum0 =
                    ip_csum_update (sum0, old_addr0, new_addr0, ip4_header_t,
                                    dst_address);
                  sum0 =
                    ip_csum_update (sum0, old_port0, new_port0, ip4_header_t,
                                    length);
                  if (is_twice_nat_session (s0))
                    {
                      sum0 = ip_csum_update (sum0, ip0->src_address.as_u32,
                                             s0->ext_host_nat_addr.as_u32,
                                             ip4_header_t, dst_address);
                      sum0 =
                        ip_csum_update (sum0,
                                        vnet_buffer (b0)->ip.
                                        reass.l4_src_port,
                                        s0->ext_host_nat_port, ip4_header_t,
                                        length);
                      tcp0->src_port = s0->ext_host_nat_port;
                      ip0->src_address.as_u32 = s0->ext_host_nat_addr.as_u32;
                    }
                  tcp0->checksum = ip_csum_fold (sum0);
                }
              tcp_packets++;
              if (nat44_set_tcp_session_state_o2i
                  (sm, s0, vnet_buffer (b0)->ip.reass.icmp_type_or_tcp_flags,
                   vnet_buffer (b0)->ip.reass.tcp_ack_number,
                   vnet_buffer (b0)->ip.reass.tcp_seq_number, thread_index))
                goto trace0;
            }
          else if (!vnet_buffer (b0)->ip.reass.is_non_first_fragment
                   && udp0->checksum)
            {
              new_port0 = udp0->dst_port = s0->in2out.port;
              sum0 = udp0->checksum;
              sum0 = ip_csum_update (sum0, old_addr0, new_addr0, ip4_header_t,
                                     dst_address);
              sum0 = ip_csum_update (sum0, old_port0, new_port0, ip4_header_t,
                                     length);
              if (PREDICT_FALSE (is_twice_nat_session (s0)))
                {
                  sum0 = ip_csum_update (sum0, ip0->src_address.as_u32,
                                         s0->ext_host_nat_addr.as_u32,
                                         ip4_header_t, dst_address);
                  sum0 =
                    ip_csum_update (sum0,
                                    vnet_buffer (b0)->ip.reass.l4_src_port,
                                    s0->ext_host_nat_port, ip4_header_t,
                                    length);
                  udp0->src_port = s0->ext_host_nat_port;
                  ip0->src_address.as_u32 = s0->ext_host_nat_addr.as_u32;
                }
              udp0->checksum = ip_csum_fold (sum0);
              udp_packets++;
            }
          else
            {
              if (!vnet_buffer (b0)->ip.reass.is_non_first_fragment)
                {
                  new_port0 = udp0->dst_port = s0->in2out.port;
                  if (PREDICT_FALSE (is_twice_nat_session (s0)))
                    {
                      udp0->src_port = s0->ext_host_nat_port;
                      ip0->src_address.as_u32 = s0->ext_host_nat_addr.as_u32;
                    }
                }
              udp_packets++;
            }

          /* Accounting */
          nat44_session_update_counters (s0, now,
                                         vlib_buffer_length_in_chain (vm, b0),
                                         thread_index);
          /* Per-user LRU list maintenance */
          nat44_session_update_lru (sm, s0, thread_index);

        trace0:
          if (PREDICT_FALSE ((node->flags & VLIB_NODE_FLAG_TRACE)
                             && (b0->flags & VLIB_BUFFER_IS_TRACED)))
            {
              nat44_ed_out2in_trace_t *t =
                vlib_add_trace (vm, node, b0, sizeof (*t));
              t->is_slow_path = is_slow_path;
              t->sw_if_index = sw_if_index0;
              t->next_index = next0;
              t->session_index = ~0;
              if (s0)
                t->session_index = s0 - tsm->sessions;
            }

          pkts_processed += next0 == nat_buffer_opaque (b0)->arc_next;
          /* 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, stats_node_index,
                               NAT_OUT2IN_ED_ERROR_OUT2IN_PACKETS,
                               pkts_processed);
  vlib_node_increment_counter (vm, stats_node_index,
                               NAT_OUT2IN_ED_ERROR_TCP_PACKETS, tcp_packets);
  vlib_node_increment_counter (vm, stats_node_index,
                               NAT_OUT2IN_ED_ERROR_UDP_PACKETS, udp_packets);
  vlib_node_increment_counter (vm, stats_node_index,
                               NAT_OUT2IN_ED_ERROR_ICMP_PACKETS,
                               icmp_packets);
  vlib_node_increment_counter (vm, stats_node_index,
                               NAT_OUT2IN_ED_ERROR_OTHER_PACKETS,
                               other_packets);
  vlib_node_increment_counter (vm, stats_node_index,
                               NAT_OUT2IN_ED_ERROR_FRAGMENTS, fragments);
  return frame->n_vectors;
}

VLIB_NODE_FN (nat44_ed_out2in_node) (vlib_main_t * vm,
                                     vlib_node_runtime_t * node,
                                     vlib_frame_t * frame)
{
  return nat44_ed_out2in_node_fn_inline (vm, node, frame, 0);
}

/* *INDENT-OFF* */
VLIB_REGISTER_NODE (nat44_ed_out2in_node) = {
  .name = "nat44-ed-out2in",
  .vector_size = sizeof (u32),
  .sibling_of = "nat-default",
  .format_trace = format_nat44_ed_out2in_trace,
  .type = VLIB_NODE_TYPE_INTERNAL,
  .n_errors = ARRAY_LEN(nat_out2in_ed_error_strings),
  .error_strings = nat_out2in_ed_error_strings,
  .runtime_data_bytes = sizeof (snat_runtime_t),
};
/* *INDENT-ON* */

VLIB_NODE_FN (nat44_ed_out2in_slowpath_node) (vlib_main_t * vm,
                                              vlib_node_runtime_t * node,
                                              vlib_frame_t * frame)
{
  return nat44_ed_out2in_node_fn_inline (vm, node, frame, 1);
}

/* *INDENT-OFF* */
VLIB_REGISTER_NODE (nat44_ed_out2in_slowpath_node) = {
  .name = "nat44-ed-out2in-slowpath",
  .vector_size = sizeof (u32),
  .sibling_of = "nat-default",
  .format_trace = format_nat44_ed_out2in_trace,
  .type = VLIB_NODE_TYPE_INTERNAL,
  .n_errors = ARRAY_LEN(nat_out2in_ed_error_strings),
  .error_strings = nat_out2in_ed_error_strings,
  .runtime_data_bytes = sizeof (snat_runtime_t),
};
/* *INDENT-ON* */

static u8 *
format_nat_pre_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_pre_trace_t *t = va_arg (*args, nat_pre_trace_t *);
  return format (s, "out2in next_index %d", t->next_index);
}

VLIB_NODE_FN (nat_pre_out2in_node) (vlib_main_t * vm,
                                    vlib_node_runtime_t * node,
                                    vlib_frame_t * frame)
{
  return nat_pre_node_fn_inline (vm, node, frame,
                                 NAT_NEXT_OUT2IN_ED_FAST_PATH);
}

/* *INDENT-OFF* */
VLIB_REGISTER_NODE (nat_pre_out2in_node) = {
  .name = "nat-pre-out2in",
  .vector_size = sizeof (u32),
  .sibling_of = "nat-default",
  .format_trace = format_nat_pre_trace,
  .type = VLIB_NODE_TYPE_INTERNAL,
  .n_errors = 0,
 };
/* *INDENT-ON* */

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