in2out.c

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/*
 * Copyright (c) 2016 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.
 */

#include <vlib/vlib.h>
#include <vnet/vnet.h>
#include <vnet/pg/pg.h>
#include <vnet/handoff.h>

#include <vnet/ip/ip.h>
#include <vnet/ethernet/ethernet.h>
#include <vnet/fib/ip4_fib.h>
#include <snat/snat.h>

#include <vppinfra/hash.h>
#include <vppinfra/error.h>
#include <vppinfra/elog.h>

typedef struct {
  u32 sw_if_index;
  u32 next_index;
  u32 session_index;
  u32 is_slow_path;
} snat_in2out_trace_t;

typedef struct {
  u32 next_worker_index;
  u8 do_handoff;
} snat_in2out_worker_handoff_trace_t;

/* packet trace format function */
static u8 * format_snat_in2out_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 *);
  snat_in2out_trace_t * t = va_arg (*args, snat_in2out_trace_t *);
  char * tag;

  tag = t->is_slow_path ? "SNAT_IN2OUT_SLOW_PATH" : "SNAT_IN2OUT_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 u8 * format_snat_in2out_fast_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 *);
  snat_in2out_trace_t * t = va_arg (*args, snat_in2out_trace_t *);

  s = format (s, "SANT_IN2OUT_FAST: sw_if_index %d, next index %d", 
              t->sw_if_index, t->next_index);

  return s;
}

static u8 * format_snat_in2out_worker_handoff_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 *);
  snat_in2out_worker_handoff_trace_t * t =
    va_arg (*args, snat_in2out_worker_handoff_trace_t *);
  char * m;

  m = t->do_handoff ? "next worker" : "same worker";
  s = format (s, "SNAT_IN2OUT_WORKER_HANDOFF: %s %d", m, t->next_worker_index);

  return s;
}

vlib_node_registration_t snat_in2out_node;
vlib_node_registration_t snat_in2out_slowpath_node;
vlib_node_registration_t snat_in2out_fast_node;
vlib_node_registration_t snat_in2out_worker_handoff_node;

#define foreach_snat_in2out_error                       \
_(UNSUPPORTED_PROTOCOL, "Unsupported protocol")         \
_(IN2OUT_PACKETS, "Good in2out packets processed")      \
_(OUT_OF_PORTS, "Out of ports")                         \
_(BAD_OUTSIDE_FIB, "Outside VRF ID not found")          \
_(BAD_ICMP_TYPE, "icmp type not echo-request")          \
_(NO_TRANSLATION, "No translation")
  
typedef enum {
#define _(sym,str) SNAT_IN2OUT_ERROR_##sym,
  foreach_snat_in2out_error
#undef _
  SNAT_IN2OUT_N_ERROR,
} snat_in2out_error_t;

static char * snat_in2out_error_strings[] = {
#define _(sym,string) string,
  foreach_snat_in2out_error
#undef _
};

typedef enum {
  SNAT_IN2OUT_NEXT_LOOKUP,
  SNAT_IN2OUT_NEXT_DROP,
  SNAT_IN2OUT_NEXT_SLOW_PATH,
  SNAT_IN2OUT_N_NEXT,
} snat_in2out_next_t;

static u32 slow_path (snat_main_t *sm, vlib_buffer_t *b0,
                      ip4_header_t * ip0,
                      u32 rx_fib_index0,
                      snat_session_key_t * key0,
                      snat_session_t ** sessionp,
                      vlib_node_runtime_t * node,
                      u32 next0,
                      u32 cpu_index)
{
  snat_user_t *u;
  snat_user_key_t user_key;
  snat_session_t *s;
  clib_bihash_kv_8_8_t kv0, value0;
  u32 oldest_per_user_translation_list_index;
  dlist_elt_t * oldest_per_user_translation_list_elt;
  dlist_elt_t * per_user_translation_list_elt;
  dlist_elt_t * per_user_list_head_elt;
  u32 session_index;
  snat_session_key_t key1;
  u32 address_index = ~0;
  u32 outside_fib_index;
  uword * p;
  snat_static_mapping_key_t worker_by_out_key;

  p = hash_get (sm->ip4_main->fib_index_by_table_id, sm->outside_vrf_id);
  if (! p)
    {
      b0->error = node->errors[SNAT_IN2OUT_ERROR_BAD_OUTSIDE_FIB];
      return SNAT_IN2OUT_NEXT_DROP;
    }
  outside_fib_index = p[0];

  user_key.addr = ip0->src_address;
  user_key.fib_index = rx_fib_index0;
  kv0.key = user_key.as_u64;
  
  /* Ever heard of the "user" = src ip4 address before? */
  if (clib_bihash_search_8_8 (&sm->user_hash, &kv0, &value0))
    {
      /* no, make a new one */
      pool_get (sm->per_thread_data[cpu_index].users, u);
      memset (u, 0, sizeof (*u));
      u->addr = ip0->src_address;

      pool_get (sm->per_thread_data[cpu_index].list_pool, per_user_list_head_elt);

      u->sessions_per_user_list_head_index = per_user_list_head_elt -
        sm->per_thread_data[cpu_index].list_pool;

      clib_dlist_init (sm->per_thread_data[cpu_index].list_pool,
                       u->sessions_per_user_list_head_index);

      kv0.value = u - sm->per_thread_data[cpu_index].users;

      /* add user */
      clib_bihash_add_del_8_8 (&sm->user_hash, &kv0, 1 /* is_add */);
    }
  else
    {
      u = pool_elt_at_index (sm->per_thread_data[cpu_index].users,
                             value0.value);
    }

  /* Over quota? Recycle the least recently used dynamic translation */
  if (u->nsessions >= sm->max_translations_per_user)
    {
      /* Remove the oldest dynamic translation */
      do {
          oldest_per_user_translation_list_index =
            clib_dlist_remove_head (sm->per_thread_data[cpu_index].list_pool,
                                    u->sessions_per_user_list_head_index);

          ASSERT (oldest_per_user_translation_list_index != ~0);

          /* add it back to the end of the LRU list */
          clib_dlist_addtail (sm->per_thread_data[cpu_index].list_pool,
                              u->sessions_per_user_list_head_index,
                              oldest_per_user_translation_list_index);
          /* Get the list element */
          oldest_per_user_translation_list_elt =
            pool_elt_at_index (sm->per_thread_data[cpu_index].list_pool,
                               oldest_per_user_translation_list_index);

          /* Get the session index from the list element */
          session_index = oldest_per_user_translation_list_elt->value;

          /* Get the session */
          s = pool_elt_at_index (sm->per_thread_data[cpu_index].sessions,
                                 session_index);
      } while (snat_is_session_static (s));

      /* Remove in2out, out2in keys */
      kv0.key = s->in2out.as_u64;
      if (clib_bihash_add_del_8_8 (&sm->in2out, &kv0, 0 /* is_add */))
          clib_warning ("in2out key delete failed");
      kv0.key = s->out2in.as_u64;
      if (clib_bihash_add_del_8_8 (&sm->out2in, &kv0, 0 /* is_add */))
          clib_warning ("out2in key delete failed");

      snat_free_outside_address_and_port 
        (sm, &s->out2in, s->outside_address_index);
      s->outside_address_index = ~0;

      if (snat_alloc_outside_address_and_port (sm, &key1, &address_index))
        {
          ASSERT(0);

          b0->error = node->errors[SNAT_IN2OUT_ERROR_OUT_OF_PORTS];
          return SNAT_IN2OUT_NEXT_DROP;
        }
      s->outside_address_index = address_index;
    }
  else
    {
      u8 static_mapping = 1;

      /* First try to match static mapping by local address and port */
      if (snat_static_mapping_match (sm, *key0, &key1, 0))
        {
          static_mapping = 0;
          /* Try to create dynamic translation */
          if (snat_alloc_outside_address_and_port (sm, &key1, &address_index))
            {
              b0->error = node->errors[SNAT_IN2OUT_ERROR_OUT_OF_PORTS];
              return SNAT_IN2OUT_NEXT_DROP;
            }
        }

      /* Create a new session */
      pool_get (sm->per_thread_data[cpu_index].sessions, s);
      memset (s, 0, sizeof (*s));
      
      s->outside_address_index = address_index;

      if (static_mapping)
        {
          u->nstaticsessions++;
          s->flags |= SNAT_SESSION_FLAG_STATIC_MAPPING;
        }
      else
        {
          u->nsessions++;
        }

      /* Create list elts */
      pool_get (sm->per_thread_data[cpu_index].list_pool,
                per_user_translation_list_elt);
      clib_dlist_init (sm->per_thread_data[cpu_index].list_pool,
                       per_user_translation_list_elt -
                       sm->per_thread_data[cpu_index].list_pool);

      per_user_translation_list_elt->value =
        s - sm->per_thread_data[cpu_index].sessions;
      s->per_user_index = per_user_translation_list_elt -
                          sm->per_thread_data[cpu_index].list_pool;
      s->per_user_list_head_index = u->sessions_per_user_list_head_index;

      clib_dlist_addtail (sm->per_thread_data[cpu_index].list_pool,
                          s->per_user_list_head_index,
                          per_user_translation_list_elt -
                          sm->per_thread_data[cpu_index].list_pool);
   }
  
  s->in2out = *key0;
  s->out2in = key1;
  s->out2in.protocol = key0->protocol;
  s->out2in.fib_index = outside_fib_index;
  *sessionp = s;

  /* Add to translation hashes */
  kv0.key = s->in2out.as_u64;
  kv0.value = s - sm->per_thread_data[cpu_index].sessions;
  if (clib_bihash_add_del_8_8 (&sm->in2out, &kv0, 1 /* is_add */))
      clib_warning ("in2out key add failed");
  
  kv0.key = s->out2in.as_u64;
  kv0.value = s - sm->per_thread_data[cpu_index].sessions;
  
  if (clib_bihash_add_del_8_8 (&sm->out2in, &kv0, 1 /* is_add */))
      clib_warning ("out2in key add failed");

  /* Add to translated packets worker lookup */
  worker_by_out_key.addr = s->out2in.addr;
  worker_by_out_key.port = s->out2in.port;
  worker_by_out_key.fib_index = s->out2in.fib_index;
  kv0.key = worker_by_out_key.as_u64;
  kv0.value = cpu_index;
  clib_bihash_add_del_8_8 (&sm->worker_by_out, &kv0, 1);
  return next0;
}
                      
static inline u32 icmp_in2out_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 cpu_index)
{
  snat_session_key_t key0;
  icmp_echo_header_t *echo0;
  clib_bihash_kv_8_8_t kv0, value0;
  snat_session_t * s0;
  u32 new_addr0, old_addr0;
  u16 old_id0, new_id0;
  ip_csum_t sum0;
  snat_runtime_t * rt = (snat_runtime_t *)node->runtime_data;

  if (PREDICT_FALSE(icmp0->type != ICMP4_echo_request))
    {
      b0->error = node->errors[SNAT_IN2OUT_ERROR_BAD_ICMP_TYPE];
      return SNAT_IN2OUT_NEXT_DROP;
    }
  
  echo0 = (icmp_echo_header_t *)(icmp0+1);

  key0.addr = ip0->src_address;
  key0.port = echo0->identifier;
  key0.protocol = SNAT_PROTOCOL_ICMP;
  key0.fib_index = rx_fib_index0;
  
  kv0.key = key0.as_u64;
  
  if (clib_bihash_search_8_8 (&sm->in2out, &kv0, &value0))
    {
      ip4_address_t * first_int_addr;

      if (PREDICT_FALSE(rt->cached_sw_if_index != sw_if_index0))
        {
          first_int_addr = 
            ip4_interface_first_address (sm->ip4_main, sw_if_index0,
                                         0 /* just want the address */);
          rt->cached_sw_if_index = sw_if_index0;
          rt->cached_ip4_address = first_int_addr->as_u32;
        }
      
      /* Don't NAT packet aimed at the intfc address */
      if (PREDICT_FALSE(ip0->dst_address.as_u32 ==
                                rt->cached_ip4_address))
        return next0;
      
      next0 = slow_path (sm, b0, ip0, rx_fib_index0, &key0,
                         &s0, node, next0, cpu_index);
      
      if (PREDICT_FALSE (next0 == SNAT_IN2OUT_NEXT_DROP))
        return next0;
    }
  else
    s0 = pool_elt_at_index (sm->per_thread_data[cpu_index].sessions,
                            value0.value);

  old_addr0 = ip0->src_address.as_u32;
  ip0->src_address = s0->out2in.addr;
  new_addr0 = ip0->src_address.as_u32;
  vnet_buffer(b0)->sw_if_index[VLIB_TX] = s0->out2in.fib_index;
  
  sum0 = ip0->checksum;
  sum0 = ip_csum_update (sum0, old_addr0, new_addr0,
                         ip4_header_t,
                         src_address /* changed member */);
  ip0->checksum = ip_csum_fold (sum0);
  
  old_id0 = echo0->identifier;
  new_id0 = s0->out2in.port;
  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);

  /* Accounting */
  s0->last_heard = now;
  s0->total_pkts++;
  s0->total_bytes += vlib_buffer_length_in_chain (sm->vlib_main, b0);
  /* Per-user LRU list maintenance for dynamic translations */
  if (!snat_is_session_static (s0))
    {
      clib_dlist_remove (sm->per_thread_data[cpu_index].list_pool,
                         s0->per_user_index);
      clib_dlist_addtail (sm->per_thread_data[cpu_index].list_pool,
                          s0->per_user_list_head_index,
                          s0->per_user_index);
    }

  return next0;
}

/**
 * @brief Hairpinning
 *
 * Hairpinning allows two endpoints on the internal side of the NAT to
 * communicate even if they only use each other's external IP addresses
 * and ports.
 *
 * @param sm     SNAT main.
 * @param b0     Vlib buffer.
 * @param ip0    IP header.
 * @param udp0   UDP header.
 * @param tcp0   TCP header.
 * @param proto0 SNAT protocol.
 */
static inline void
snat_hairpinning (snat_main_t *sm,
                  vlib_buffer_t * b0,
                  ip4_header_t * ip0,
                  udp_header_t * udp0,
                  tcp_header_t * tcp0,
                  u32 proto0)
{
  snat_session_key_t key0, sm0;
  snat_static_mapping_key_t k0;
  snat_session_t * s0;
  clib_bihash_kv_8_8_t kv0, value0;
  ip_csum_t sum0;
  u32 new_dst_addr0 = 0, old_dst_addr0, ti = 0, si;
  u16 new_dst_port0, old_dst_port0;

  key0.addr = ip0->dst_address;
  key0.port = udp0->dst_port;
  key0.protocol = proto0;
  key0.fib_index = sm->outside_fib_index;
  kv0.key = key0.as_u64;

  /* Check if destination is in active sessions */
  if (clib_bihash_search_8_8 (&sm->out2in, &kv0, &value0))
    {
      /* or static mappings */
      if (!snat_static_mapping_match(sm, key0, &sm0, 1))
        {
          new_dst_addr0 = sm0.addr.as_u32;
          new_dst_port0 = sm0.port;
          vnet_buffer(b0)->sw_if_index[VLIB_TX] = sm0.fib_index;
        }
    }
  else
    {
      si = value0.value;
      if (sm->num_workers > 1)
        {
          k0.addr = ip0->dst_address;
          k0.port = udp0->dst_port;
          k0.fib_index = sm->outside_fib_index;
          kv0.key = k0.as_u64;
          if (clib_bihash_search_8_8 (&sm->worker_by_out, &kv0, &value0))
            ASSERT(0);
          else
            ti = value0.value;
        }
      else
        ti = sm->num_workers;

      s0 = pool_elt_at_index (sm->per_thread_data[ti].sessions, si);
      new_dst_addr0 = s0->in2out.addr.as_u32;
      new_dst_port0 = s0->in2out.port;
      vnet_buffer(b0)->sw_if_index[VLIB_TX] = s0->in2out.fib_index;
    }

  /* Destination is behind the same NAT, use internal address and port */
  if (new_dst_addr0)
    {
      old_dst_addr0 = ip0->dst_address.as_u32;
      ip0->dst_address.as_u32 = new_dst_addr0;
      sum0 = ip0->checksum;
      sum0 = ip_csum_update (sum0, old_dst_addr0, new_dst_addr0,
                             ip4_header_t, dst_address);
      ip0->checksum = ip_csum_fold (sum0);

      old_dst_port0 = tcp0->ports.dst;
      if (PREDICT_TRUE(new_dst_port0 != old_dst_port0))
        {
          if (PREDICT_TRUE(proto0 == SNAT_PROTOCOL_TCP))
            {
              tcp0->ports.dst = new_dst_port0;
              sum0 = tcp0->checksum;
              sum0 = ip_csum_update (sum0, old_dst_addr0, new_dst_addr0,
                                     ip4_header_t, dst_address);
              sum0 = ip_csum_update (sum0, old_dst_port0, new_dst_port0,
                                     ip4_header_t /* cheat */, length);
              tcp0->checksum = ip_csum_fold(sum0);
            }
          else
            {
              udp0->dst_port = new_dst_port0;
              udp0->checksum = 0;
            }
        }
    }
}

static inline uword
snat_in2out_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;
  snat_in2out_next_t next_index;
  u32 pkts_processed = 0;
  snat_main_t * sm = &snat_main;
  snat_runtime_t * rt = (snat_runtime_t *)node->runtime_data;
  f64 now = vlib_time_now (vm);
  u32 stats_node_index;
  u32 cpu_index = os_get_cpu_number ();

  stats_node_index = is_slow_path ? snat_in2out_slowpath_node.index :
    snat_in2out_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, next1;
          u32 sw_if_index0, sw_if_index1;
          ip4_header_t * ip0, * ip1;
          ip_csum_t sum0, sum1;
          u32 new_addr0, old_addr0, new_addr1, old_addr1;
          u16 old_port0, new_port0, old_port1, new_port1;
          udp_header_t * udp0, * udp1;
          tcp_header_t * tcp0, * tcp1;
          icmp46_header_t * icmp0, * icmp1;
          snat_session_key_t key0, key1;
          u32 rx_fib_index0, rx_fib_index1;
          u32 proto0, proto1;
          snat_session_t * s0 = 0, * s1 = 0;
          clib_bihash_kv_8_8_t kv0, value0, kv1, value1;
          
          /* Prefetch next iteration. */
          {
            vlib_buffer_t * p2, * p3;
            
            p2 = vlib_get_buffer (vm, from[2]);
            p3 = vlib_get_buffer (vm, from[3]);
            
            vlib_prefetch_buffer_header (p2, LOAD);
            vlib_prefetch_buffer_header (p3, LOAD);

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

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

          ip0 = vlib_buffer_get_current (b0);
          udp0 = ip4_next_header (ip0);
          tcp0 = (tcp_header_t *) udp0;
          icmp0 = (icmp46_header_t *) udp0;

          sw_if_index0 = vnet_buffer(b0)->sw_if_index[VLIB_RX];
          rx_fib_index0 = vec_elt (sm->ip4_main->fib_index_by_sw_if_index, 
                                   sw_if_index0);

          next0 = next1 = SNAT_IN2OUT_NEXT_LOOKUP;

          proto0 = ~0;
          proto0 = (ip0->protocol == IP_PROTOCOL_UDP) 
            ? SNAT_PROTOCOL_UDP : proto0;
          proto0 = (ip0->protocol == IP_PROTOCOL_TCP) 
            ? SNAT_PROTOCOL_TCP : proto0;
          proto0 = (ip0->protocol == IP_PROTOCOL_ICMP) 
            ? SNAT_PROTOCOL_ICMP : proto0;

          /* Next configured feature, probably ip4-lookup */
          if (is_slow_path)
            {
              if (PREDICT_FALSE (proto0 == ~0))
                goto trace00;
              
              if (PREDICT_FALSE (proto0 == SNAT_PROTOCOL_ICMP))
                {
                  next0 = icmp_in2out_slow_path 
                    (sm, b0, ip0, icmp0, sw_if_index0, rx_fib_index0, 
                     node, next0, now, cpu_index);
                  goto trace00;
                }
            }
          else
            {
              if (PREDICT_FALSE (proto0 == ~0 || proto0 == SNAT_PROTOCOL_ICMP))
                {
                  next0 = SNAT_IN2OUT_NEXT_SLOW_PATH;
                  goto trace00;
                }
            }

          key0.addr = ip0->src_address;
          key0.port = udp0->src_port;
          key0.protocol = proto0;
          key0.fib_index = rx_fib_index0;
          
          kv0.key = key0.as_u64;

          if (PREDICT_FALSE (clib_bihash_search_8_8 (&sm->in2out, &kv0, &value0) != 0))
            {
              if (is_slow_path)
                {
                  ip4_address_t * first_int_addr;
                  
                  if (PREDICT_FALSE(rt->cached_sw_if_index != sw_if_index0))
                    {
                      first_int_addr = 
                        ip4_interface_first_address (sm->ip4_main, sw_if_index0,
                                                     0 /* just want the address */);
                      rt->cached_sw_if_index = sw_if_index0;
                      rt->cached_ip4_address = first_int_addr->as_u32;
                    }
                  
                  /* Don't NAT packet aimed at the intfc address */
                  if (PREDICT_FALSE(ip0->dst_address.as_u32 ==
                                    rt->cached_ip4_address))
                    goto trace00;
                  
                  next0 = slow_path (sm, b0, ip0, rx_fib_index0, &key0,
                                     &s0, node, next0, cpu_index);
                  if (PREDICT_FALSE (next0 == SNAT_IN2OUT_NEXT_DROP))
                    goto trace00;
                }
              else
                {
                  next0 = SNAT_IN2OUT_NEXT_SLOW_PATH;
                  goto trace00;
                }
            }
          else
            s0 = pool_elt_at_index (sm->per_thread_data[cpu_index].sessions,
                                    value0.value);

          old_addr0 = ip0->src_address.as_u32;
          ip0->src_address = s0->out2in.addr;
          new_addr0 = ip0->src_address.as_u32;
          vnet_buffer(b0)->sw_if_index[VLIB_TX] = s0->out2in.fib_index;

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

          if (PREDICT_TRUE(proto0 == SNAT_PROTOCOL_TCP))
            {
              old_port0 = tcp0->ports.src;
              tcp0->ports.src = s0->out2in.port;
              new_port0 = tcp0->ports.src;

              sum0 = tcp0->checksum;
              sum0 = ip_csum_update (sum0, old_addr0, new_addr0,
                                     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
            {
              old_port0 = udp0->src_port;
              udp0->src_port = s0->out2in.port;
              udp0->checksum = 0;
            }

          /* Hairpinning */
          snat_hairpinning (sm, b0, ip0, udp0, tcp0, proto0);

          /* Accounting */
          s0->last_heard = now;
          s0->total_pkts++;
          s0->total_bytes += vlib_buffer_length_in_chain (vm, b0);
          /* Per-user LRU list maintenance for dynamic translation */
          if (!snat_is_session_static (s0))
            {
              clib_dlist_remove (sm->per_thread_data[cpu_index].list_pool,
                                 s0->per_user_index);
              clib_dlist_addtail (sm->per_thread_data[cpu_index].list_pool,
                                  s0->per_user_list_head_index,
                                  s0->per_user_index);
            }
        trace00:

          if (PREDICT_FALSE((node->flags & VLIB_NODE_FLAG_TRACE) 
                            && (b0->flags & VLIB_BUFFER_IS_TRACED))) 
            {
              snat_in2out_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 - sm->per_thread_data[cpu_index].sessions;
            }

          pkts_processed += next0 != SNAT_IN2OUT_NEXT_DROP;

          ip1 = vlib_buffer_get_current (b1);
          udp1 = ip4_next_header (ip1);
          tcp1 = (tcp_header_t *) udp1;
          icmp1 = (icmp46_header_t *) udp1;

          sw_if_index1 = vnet_buffer(b1)->sw_if_index[VLIB_RX];
          rx_fib_index1 = vec_elt (sm->ip4_main->fib_index_by_sw_if_index, 
                                   sw_if_index1);

          proto1 = ~0;
          proto1 = (ip1->protocol == IP_PROTOCOL_UDP) 
            ? SNAT_PROTOCOL_UDP : proto1;
          proto1 = (ip1->protocol == IP_PROTOCOL_TCP) 
            ? SNAT_PROTOCOL_TCP : proto1;
          proto1 = (ip1->protocol == IP_PROTOCOL_ICMP) 
            ? SNAT_PROTOCOL_ICMP : proto1;

          /* Next configured feature, probably ip4-lookup */
          if (is_slow_path)
            {
              if (PREDICT_FALSE (proto1 == ~0))
                goto trace01;
              
              if (PREDICT_FALSE (proto1 == SNAT_PROTOCOL_ICMP))
                {
                  next1 = icmp_in2out_slow_path 
                    (sm, b1, ip1, icmp1, sw_if_index1, rx_fib_index1, node,
                     next1, now, cpu_index);
                  goto trace01;
                }
            }
          else
            {
              if (PREDICT_FALSE (proto1 == ~0 || proto1 == SNAT_PROTOCOL_ICMP))
                {
                  next1 = SNAT_IN2OUT_NEXT_SLOW_PATH;
                  goto trace01;
                }
            }

          key1.addr = ip1->src_address;
          key1.port = udp1->src_port;
          key1.protocol = proto1;
          key1.fib_index = rx_fib_index1;
          
          kv1.key = key1.as_u64;

            if (PREDICT_FALSE(clib_bihash_search_8_8 (&sm->in2out, &kv1, &value1) != 0))
            {
              if (is_slow_path)
                {
                  ip4_address_t * first_int_addr;
                  
                  if (PREDICT_FALSE(rt->cached_sw_if_index != sw_if_index1))
                    {
                      first_int_addr = 
                        ip4_interface_first_address (sm->ip4_main, sw_if_index1,
                                                     0 /* just want the address */);
                      rt->cached_sw_if_index = sw_if_index1;
                      rt->cached_ip4_address = first_int_addr->as_u32;
                    }
                  
                  /* Don't NAT packet aimed at the intfc address */
                  if (PREDICT_FALSE(ip1->dst_address.as_u32 ==
                                    rt->cached_ip4_address))
                    goto trace01;
                  
                  next1 = slow_path (sm, b1, ip1, rx_fib_index1, &key1,
                                     &s1, node, next1, cpu_index);
                  if (PREDICT_FALSE (next1 == SNAT_IN2OUT_NEXT_DROP))
                    goto trace01;
                }
              else
                {
                  next1 = SNAT_IN2OUT_NEXT_SLOW_PATH;
                  goto trace01;
                }
            }
          else
            s1 = pool_elt_at_index (sm->per_thread_data[cpu_index].sessions,
                                    value1.value);

          old_addr1 = ip1->src_address.as_u32;
          ip1->src_address = s1->out2in.addr;
          new_addr1 = ip1->src_address.as_u32;
          vnet_buffer(b1)->sw_if_index[VLIB_TX] = s1->out2in.fib_index;

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

          if (PREDICT_TRUE(proto1 == SNAT_PROTOCOL_TCP))
            {
              old_port1 = tcp1->ports.src;
              tcp1->ports.src = s1->out2in.port;
              new_port1 = tcp1->ports.src;

              sum1 = tcp1->checksum;
              sum1 = ip_csum_update (sum1, old_addr1, new_addr1,
                                     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
            {
              old_port1 = udp1->src_port;
              udp1->src_port = s1->out2in.port;
              udp1->checksum = 0;
            }

          /* Hairpinning */
          snat_hairpinning (sm, b1, ip1, udp1, tcp1, proto1);

          /* Accounting */
          s1->last_heard = now;
          s1->total_pkts++;
          s1->total_bytes += vlib_buffer_length_in_chain (vm, b1);
          /* Per-user LRU list maintenance for dynamic translation */
          if (!snat_is_session_static (s1))
            {
              clib_dlist_remove (sm->per_thread_data[cpu_index].list_pool,
                                 s1->per_user_index);
              clib_dlist_addtail (sm->per_thread_data[cpu_index].list_pool,
                                  s1->per_user_list_head_index,
                                  s1->per_user_index);
            }
        trace01:

          if (PREDICT_FALSE((node->flags & VLIB_NODE_FLAG_TRACE) 
                            && (b1->flags & VLIB_BUFFER_IS_TRACED))) 
            {
              snat_in2out_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 (s1)
                t->session_index = s1 - sm->per_thread_data[cpu_index].sessions;
            }

          pkts_processed += next1 != SNAT_IN2OUT_NEXT_DROP;

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

      while (n_left_from > 0 && n_left_to_next > 0)
        {
          u32 bi0;
          vlib_buffer_t * b0;
          u32 next0;
          u32 sw_if_index0;
          ip4_header_t * ip0;
          ip_csum_t sum0;
          u32 new_addr0, old_addr0;
          u16 old_port0, new_port0;
          udp_header_t * udp0;
          tcp_header_t * tcp0;
          icmp46_header_t * icmp0;
          snat_session_key_t key0;
          u32 rx_fib_index0;
          u32 proto0;
          snat_session_t * s0 = 0;
          clib_bihash_kv_8_8_t kv0, value0;
          
          /* 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 = SNAT_IN2OUT_NEXT_LOOKUP;

          ip0 = vlib_buffer_get_current (b0);
          udp0 = ip4_next_header (ip0);
          tcp0 = (tcp_header_t *) udp0;
          icmp0 = (icmp46_header_t *) udp0;

          sw_if_index0 = vnet_buffer(b0)->sw_if_index[VLIB_RX];
          rx_fib_index0 = vec_elt (sm->ip4_main->fib_index_by_sw_if_index, 
                                   sw_if_index0);

          proto0 = ~0;
          proto0 = (ip0->protocol == IP_PROTOCOL_UDP) 
            ? SNAT_PROTOCOL_UDP : proto0;
          proto0 = (ip0->protocol == IP_PROTOCOL_TCP) 
            ? SNAT_PROTOCOL_TCP : proto0;
          proto0 = (ip0->protocol == IP_PROTOCOL_ICMP) 
            ? SNAT_PROTOCOL_ICMP : proto0;

          /* Next configured feature, probably ip4-lookup */
          if (is_slow_path)
            {
              if (PREDICT_FALSE (proto0 == ~0))
                goto trace0;
              
              if (PREDICT_FALSE (proto0 == SNAT_PROTOCOL_ICMP))
                {
                  next0 = icmp_in2out_slow_path 
                    (sm, b0, ip0, icmp0, sw_if_index0, rx_fib_index0, node,
                     next0, now, cpu_index);
                  goto trace0;
                }
            }
          else
            {
              if (PREDICT_FALSE (proto0 == ~0 || proto0 == SNAT_PROTOCOL_ICMP))
                {
                  next0 = SNAT_IN2OUT_NEXT_SLOW_PATH;
                  goto trace0;
                }
            }

          key0.addr = ip0->src_address;
          key0.port = udp0->src_port;
          key0.protocol = proto0;
          key0.fib_index = rx_fib_index0;
          
          kv0.key = key0.as_u64;

          if (clib_bihash_search_8_8 (&sm->in2out, &kv0, &value0))
            {
              if (is_slow_path)
                {
                  ip4_address_t * first_int_addr;
                  
                  if (PREDICT_FALSE(rt->cached_sw_if_index != sw_if_index0))
                    {
                      first_int_addr = 
                        ip4_interface_first_address (sm->ip4_main, sw_if_index0,
                                                     0 /* just want the address */);
                      rt->cached_sw_if_index = sw_if_index0;
                      rt->cached_ip4_address = first_int_addr->as_u32;
                    }
                  
                  /* Don't NAT packet aimed at the intfc address */
                  if (PREDICT_FALSE(ip0->dst_address.as_u32 ==
                                    rt->cached_ip4_address))
                    goto trace0;
                  
                  next0 = slow_path (sm, b0, ip0, rx_fib_index0, &key0,
                                     &s0, node, next0, cpu_index);
                  if (PREDICT_FALSE (next0 == SNAT_IN2OUT_NEXT_DROP))
                    goto trace0;
                }
              else
                {
                  next0 = SNAT_IN2OUT_NEXT_SLOW_PATH;
                  goto trace0;
                }
            }
          else
            s0 = pool_elt_at_index (sm->per_thread_data[cpu_index].sessions,
                                    value0.value);

          old_addr0 = ip0->src_address.as_u32;
          ip0->src_address = s0->out2in.addr;
          new_addr0 = ip0->src_address.as_u32;
          vnet_buffer(b0)->sw_if_index[VLIB_TX] = s0->out2in.fib_index;

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

          if (PREDICT_TRUE(proto0 == SNAT_PROTOCOL_TCP))
            {
              old_port0 = tcp0->ports.src;
              tcp0->ports.src = s0->out2in.port;
              new_port0 = tcp0->ports.src;

              sum0 = tcp0->checksum;
              sum0 = ip_csum_update (sum0, old_addr0, new_addr0,
                                     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
            {
              old_port0 = udp0->src_port;
              udp0->src_port = s0->out2in.port;
              udp0->checksum = 0;
            }

          /* Hairpinning */
          snat_hairpinning (sm, b0, ip0, udp0, tcp0, proto0);

          /* Accounting */
          s0->last_heard = now;
          s0->total_pkts++;
          s0->total_bytes += vlib_buffer_length_in_chain (vm, b0);
          /* Per-user LRU list maintenance for dynamic translation */
          if (!snat_is_session_static (s0))
            {
              clib_dlist_remove (sm->per_thread_data[cpu_index].list_pool,
                                 s0->per_user_index);
              clib_dlist_addtail (sm->per_thread_data[cpu_index].list_pool,
                                  s0->per_user_list_head_index,
                                  s0->per_user_index);
            }

        trace0:
          if (PREDICT_FALSE((node->flags & VLIB_NODE_FLAG_TRACE) 
                            && (b0->flags & VLIB_BUFFER_IS_TRACED))) 
            {
              snat_in2out_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 - sm->per_thread_data[cpu_index].sessions;
            }

          pkts_processed += next0 != SNAT_IN2OUT_NEXT_DROP;

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

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

  vlib_node_increment_counter (vm, stats_node_index, 
                               SNAT_IN2OUT_ERROR_IN2OUT_PACKETS, 
                               pkts_processed);
  return frame->n_vectors;
}

static uword
snat_in2out_fast_path_fn (vlib_main_t * vm,
                          vlib_node_runtime_t * node,
                          vlib_frame_t * frame)
{
  return snat_in2out_node_fn_inline (vm, node, frame, 0 /* is_slow_path */);
}

VLIB_REGISTER_NODE (snat_in2out_node) = {
  .function = snat_in2out_fast_path_fn,
  .name = "snat-in2out",
  .vector_size = sizeof (u32),
  .format_trace = format_snat_in2out_trace,
  .type = VLIB_NODE_TYPE_INTERNAL,
  
  .n_errors = ARRAY_LEN(snat_in2out_error_strings),
  .error_strings = snat_in2out_error_strings,

  .runtime_data_bytes = sizeof (snat_runtime_t),
  
  .n_next_nodes = SNAT_IN2OUT_N_NEXT,

  /* edit / add dispositions here */
  .next_nodes = {
    [SNAT_IN2OUT_NEXT_DROP] = "error-drop",
    [SNAT_IN2OUT_NEXT_LOOKUP] = "ip4-lookup",
    [SNAT_IN2OUT_NEXT_SLOW_PATH] = "snat-in2out-slowpath",
  },
};

VLIB_NODE_FUNCTION_MULTIARCH (snat_in2out_node, snat_in2out_fast_path_fn);

static uword
snat_in2out_slow_path_fn (vlib_main_t * vm,
                          vlib_node_runtime_t * node,
                          vlib_frame_t * frame)
{
  return snat_in2out_node_fn_inline (vm, node, frame, 1 /* is_slow_path */);
}

VLIB_REGISTER_NODE (snat_in2out_slowpath_node) = {
  .function = snat_in2out_slow_path_fn,
  .name = "snat-in2out-slowpath",
  .vector_size = sizeof (u32),
  .format_trace = format_snat_in2out_trace,
  .type = VLIB_NODE_TYPE_INTERNAL,
  
  .n_errors = ARRAY_LEN(snat_in2out_error_strings),
  .error_strings = snat_in2out_error_strings,

  .runtime_data_bytes = sizeof (snat_runtime_t),
  
  .n_next_nodes = SNAT_IN2OUT_N_NEXT,

  /* edit / add dispositions here */
  .next_nodes = {
    [SNAT_IN2OUT_NEXT_DROP] = "error-drop",
    [SNAT_IN2OUT_NEXT_LOOKUP] = "ip4-lookup",
    [SNAT_IN2OUT_NEXT_SLOW_PATH] = "snat-in2out-slowpath",
  },
};

VLIB_NODE_FUNCTION_MULTIARCH (snat_in2out_slowpath_node, snat_in2out_slow_path_fn);

static uword
snat_in2out_worker_handoff_fn (vlib_main_t * vm,
                               vlib_node_runtime_t * node,
                               vlib_frame_t * frame)
{
  snat_main_t *sm = &snat_main;
  vlib_thread_main_t *tm = vlib_get_thread_main ();
  u32 n_left_from, *from, *to_next = 0;
  static __thread vlib_frame_queue_elt_t **handoff_queue_elt_by_worker_index;
  static __thread vlib_frame_queue_t **congested_handoff_queue_by_worker_index
    = 0;
  vlib_frame_queue_elt_t *hf = 0;
  vlib_frame_t *f = 0;
  int i;
  u32 n_left_to_next_worker = 0, *to_next_worker = 0;
  u32 next_worker_index = 0;
  u32 current_worker_index = ~0;
  u32 cpu_index = os_get_cpu_number ();

  ASSERT (vec_len (sm->workers));

  if (PREDICT_FALSE (handoff_queue_elt_by_worker_index == 0))
    {
      vec_validate (handoff_queue_elt_by_worker_index, tm->n_vlib_mains - 1);

      vec_validate_init_empty (congested_handoff_queue_by_worker_index,
                               sm->first_worker_index + sm->num_workers - 1,
                               (vlib_frame_queue_t *) (~0));
    }

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

  while (n_left_from > 0)
    {
      u32 bi0;
      vlib_buffer_t *b0;
      u32 sw_if_index0;
      u32 rx_fib_index0;
      ip4_header_t * ip0;
      snat_user_key_t key0;
      clib_bihash_kv_8_8_t kv0, value0;
      u8 do_handoff;

      bi0 = from[0];
      from += 1;
      n_left_from -= 1;

      b0 = vlib_get_buffer (vm, bi0);

      sw_if_index0 = vnet_buffer (b0)->sw_if_index[VLIB_RX];
      rx_fib_index0 = ip4_fib_table_get_index_for_sw_if_index(sw_if_index0);

      ip0 = vlib_buffer_get_current (b0);

      key0.addr = ip0->src_address;
      key0.fib_index = rx_fib_index0;

      kv0.key = key0.as_u64;

      /* Ever heard of of the "user" before? */
      if (clib_bihash_search_8_8 (&sm->worker_by_in, &kv0, &value0))
        {
          /* No, assign next available worker (RR) */
          next_worker_index = sm->first_worker_index +
            sm->workers[sm->next_worker++ % vec_len (sm->workers)];

          /* add non-traslated packets worker lookup */
          kv0.value = next_worker_index;
          clib_bihash_add_del_8_8 (&sm->worker_by_in, &kv0, 1);
        }
      else
        next_worker_index = value0.value;

      if (PREDICT_FALSE (next_worker_index != cpu_index))
        {
          do_handoff = 1;

          if (next_worker_index != current_worker_index)
            {
              if (hf)
                hf->n_vectors = VLIB_FRAME_SIZE - n_left_to_next_worker;

              hf = vlib_get_worker_handoff_queue_elt (sm->fq_in2out_index,
                                                      next_worker_index,
                                                      handoff_queue_elt_by_worker_index);

              n_left_to_next_worker = VLIB_FRAME_SIZE - hf->n_vectors;
              to_next_worker = &hf->buffer_index[hf->n_vectors];
              current_worker_index = next_worker_index;
            }

          /* enqueue to correct worker thread */
          to_next_worker[0] = bi0;
          to_next_worker++;
          n_left_to_next_worker--;

          if (n_left_to_next_worker == 0)
            {
              hf->n_vectors = VLIB_FRAME_SIZE;
              vlib_put_frame_queue_elt (hf);
              current_worker_index = ~0;
              handoff_queue_elt_by_worker_index[next_worker_index] = 0;
              hf = 0;
            }
        }
      else
        {
          do_handoff = 0;
          /* if this is 1st frame */
          if (!f)
            {
              f = vlib_get_frame_to_node (vm, snat_in2out_node.index);
              to_next = vlib_frame_vector_args (f);
            }

          to_next[0] = bi0;
          to_next += 1;
          f->n_vectors++;
        }

      if (PREDICT_FALSE ((node->flags & VLIB_NODE_FLAG_TRACE)
                         && (b0->flags & VLIB_BUFFER_IS_TRACED)))
        {
          snat_in2out_worker_handoff_trace_t *t =
            vlib_add_trace (vm, node, b0, sizeof (*t));
          t->next_worker_index = next_worker_index;
          t->do_handoff = do_handoff;
        }
    }

  if (f)
    vlib_put_frame_to_node (vm, snat_in2out_node.index, f);

  if (hf)
    hf->n_vectors = VLIB_FRAME_SIZE - n_left_to_next_worker;

  /* Ship frames to the worker nodes */
  for (i = 0; i < vec_len (handoff_queue_elt_by_worker_index); i++)
    {
      if (handoff_queue_elt_by_worker_index[i])
        {
          hf = handoff_queue_elt_by_worker_index[i];
          /*
           * It works better to let the handoff node
           * rate-adapt, always ship the handoff queue element.
           */
          if (1 || hf->n_vectors == hf->last_n_vectors)
            {
              vlib_put_frame_queue_elt (hf);
              handoff_queue_elt_by_worker_index[i] = 0;
            }
          else
            hf->last_n_vectors = hf->n_vectors;
        }
      congested_handoff_queue_by_worker_index[i] =
        (vlib_frame_queue_t *) (~0);
    }
  hf = 0;
  current_worker_index = ~0;
  return frame->n_vectors;
}

VLIB_REGISTER_NODE (snat_in2out_worker_handoff_node) = {
  .function = snat_in2out_worker_handoff_fn,
  .name = "snat-in2out-worker-handoff",
  .vector_size = sizeof (u32),
  .format_trace = format_snat_in2out_worker_handoff_trace,
  .type = VLIB_NODE_TYPE_INTERNAL,
  
  .n_next_nodes = 1,

  .next_nodes = {
    [0] = "error-drop",
  },
};

VLIB_NODE_FUNCTION_MULTIARCH (snat_in2out_worker_handoff_node, snat_in2out_worker_handoff_fn);

static inline u32 icmp_in2out_static_map (snat_main_t *sm,
                                          vlib_buffer_t * b0,
                                          ip4_header_t * ip0,
                                          icmp46_header_t * icmp0,
                                          u32 sw_if_index0,
                                          vlib_node_runtime_t * node,
                                          u32 next0,
                                          u32 rx_fib_index0)
{
  snat_session_key_t key0, sm0;
  icmp_echo_header_t *echo0;
  u32 new_addr0, old_addr0;
  u16 old_id0, new_id0;
  ip_csum_t sum0;
  snat_runtime_t * rt = (snat_runtime_t *)node->runtime_data;

  echo0 = (icmp_echo_header_t *)(icmp0+1);

  key0.addr = ip0->src_address;
  key0.port = echo0->identifier;
  key0.fib_index = rx_fib_index0;
  
  if (snat_static_mapping_match(sm, key0, &sm0, 0))
    {
      ip4_address_t * first_int_addr;

      if (PREDICT_FALSE(rt->cached_sw_if_index != sw_if_index0))
        {
          first_int_addr =
            ip4_interface_first_address (sm->ip4_main, sw_if_index0,
                                         0 /* just want the address */);
          rt->cached_sw_if_index = sw_if_index0;
          rt->cached_ip4_address = first_int_addr->as_u32;
        }

      /* Don't NAT packet aimed at the intfc address */
      if (PREDICT_FALSE(ip0->dst_address.as_u32 ==
                                rt->cached_ip4_address))
        return next0;

      b0->error = node->errors[SNAT_IN2OUT_ERROR_NO_TRANSLATION];
      return SNAT_IN2OUT_NEXT_DROP;
    }

  new_addr0 = sm0.addr.as_u32;
  new_id0 = sm0.port;
  vnet_buffer(b0)->sw_if_index[VLIB_TX] = sm0.fib_index;
  old_addr0 = ip0->src_address.as_u32;
  ip0->src_address.as_u32 = new_addr0;
  
  sum0 = ip0->checksum;
  sum0 = ip_csum_update (sum0, old_addr0, new_addr0,
                         ip4_header_t,
                         src_address /* changed member */);
  ip0->checksum = ip_csum_fold (sum0);
  
  if (PREDICT_FALSE(new_id0 != echo0->identifier))
    {
      old_id0 = echo0->identifier;
      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);
    }

  return next0;
}

static uword
snat_in2out_fast_static_map_fn (vlib_main_t * vm,
                                vlib_node_runtime_t * node,
                                vlib_frame_t * frame)
{
  u32 n_left_from, * from, * to_next;
  snat_in2out_next_t next_index;
  u32 pkts_processed = 0;
  snat_main_t * sm = &snat_main;
  snat_runtime_t * rt = (snat_runtime_t *)node->runtime_data;
  u32 stats_node_index;

  stats_node_index = snat_in2out_fast_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 > 0 && n_left_to_next > 0)
        {
          u32 bi0;
          vlib_buffer_t * b0;
          u32 next0;
          u32 sw_if_index0;
          ip4_header_t * ip0;
          ip_csum_t sum0;
          u32 new_addr0, old_addr0;
          u16 old_port0, new_port0;
          udp_header_t * udp0;
          tcp_header_t * tcp0;
          icmp46_header_t * icmp0;
          snat_session_key_t key0, sm0;
          u32 proto0;
          u32 rx_fib_index0;

          /* 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 = SNAT_IN2OUT_NEXT_LOOKUP;

          ip0 = vlib_buffer_get_current (b0);
          udp0 = ip4_next_header (ip0);
          tcp0 = (tcp_header_t *) udp0;
          icmp0 = (icmp46_header_t *) udp0;

          sw_if_index0 = vnet_buffer(b0)->sw_if_index[VLIB_RX];
          rx_fib_index0 = ip4_fib_table_get_index_for_sw_if_index(sw_if_index0);

          proto0 = ~0;
          proto0 = (ip0->protocol == IP_PROTOCOL_UDP)
            ? SNAT_PROTOCOL_UDP : proto0;
          proto0 = (ip0->protocol == IP_PROTOCOL_TCP)
            ? SNAT_PROTOCOL_TCP : proto0;
          proto0 = (ip0->protocol == IP_PROTOCOL_ICMP)
            ? SNAT_PROTOCOL_ICMP : proto0;

          if (PREDICT_FALSE (proto0 == ~0))
              goto trace0;

          if (PREDICT_FALSE (proto0 == SNAT_PROTOCOL_ICMP))
            {
              ip4_address_t * first_int_addr;
              
              if (PREDICT_FALSE(rt->cached_sw_if_index != sw_if_index0))
                {
                  first_int_addr = 
                    ip4_interface_first_address (sm->ip4_main, sw_if_index0,
                                                 0 /* just want the address */);
                  rt->cached_sw_if_index = sw_if_index0;
                  rt->cached_ip4_address = first_int_addr->as_u32;
                }
              
              /* Don't NAT packet aimed at the intfc address */
              if (PREDICT_FALSE(ip0->dst_address.as_u32 ==
                                rt->cached_ip4_address))
                goto trace0;

              next0 = icmp_in2out_static_map
                (sm, b0, ip0, icmp0, sw_if_index0, node, next0, rx_fib_index0);
              goto trace0;
            }

          key0.addr = ip0->src_address;
          key0.port = udp0->src_port;
          key0.fib_index = rx_fib_index0;

          if (snat_static_mapping_match(sm, key0, &sm0, 0))
            {
              b0->error = node->errors[SNAT_IN2OUT_ERROR_NO_TRANSLATION];
              next0= SNAT_IN2OUT_NEXT_DROP;
              goto trace0;
            }

          new_addr0 = sm0.addr.as_u32;
          new_port0 = sm0.port;
          vnet_buffer(b0)->sw_if_index[VLIB_TX] = sm0.fib_index;
          old_addr0 = ip0->src_address.as_u32;
          ip0->src_address.as_u32 = new_addr0;

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

          if (PREDICT_FALSE(new_port0 != udp0->dst_port))
            {
              if (PREDICT_TRUE(proto0 == SNAT_PROTOCOL_TCP))
                {
                  old_port0 = tcp0->ports.src;
                  tcp0->ports.src = new_port0;

                  sum0 = tcp0->checksum;
                  sum0 = ip_csum_update (sum0, old_addr0, new_addr0,
                                         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
                {
                  old_port0 = udp0->src_port;
                  udp0->src_port = new_port0;
                  udp0->checksum = 0;
                }
            }
          else
            {
              if (PREDICT_TRUE(proto0 == SNAT_PROTOCOL_TCP))
                {
                  sum0 = tcp0->checksum;
                  sum0 = ip_csum_update (sum0, old_addr0, new_addr0,
                                         ip4_header_t,
                                         dst_address /* changed member */);
                  tcp0->checksum = ip_csum_fold(sum0);
                }
            }

          /* Hairpinning */
          snat_hairpinning (sm, b0, ip0, udp0, tcp0, proto0);

        trace0:
          if (PREDICT_FALSE((node->flags & VLIB_NODE_FLAG_TRACE)
                            && (b0->flags & VLIB_BUFFER_IS_TRACED)))
            {
              snat_in2out_trace_t *t =
                 vlib_add_trace (vm, node, b0, sizeof (*t));
              t->sw_if_index = sw_if_index0;
              t->next_index = next0;
            }

          pkts_processed += next0 != SNAT_IN2OUT_NEXT_DROP;

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

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

  vlib_node_increment_counter (vm, stats_node_index,
                               SNAT_IN2OUT_ERROR_IN2OUT_PACKETS,
                               pkts_processed);
  return frame->n_vectors;
}


VLIB_REGISTER_NODE (snat_in2out_fast_node) = {
  .function = snat_in2out_fast_static_map_fn,
  .name = "snat-in2out-fast",
  .vector_size = sizeof (u32),
  .format_trace = format_snat_in2out_fast_trace,
  .type = VLIB_NODE_TYPE_INTERNAL,
  
  .n_errors = ARRAY_LEN(snat_in2out_error_strings),
  .error_strings = snat_in2out_error_strings,

  .runtime_data_bytes = sizeof (snat_runtime_t),
  
  .n_next_nodes = SNAT_IN2OUT_N_NEXT,

  /* edit / add dispositions here */
  .next_nodes = {
    [SNAT_IN2OUT_NEXT_DROP] = "error-drop",
    [SNAT_IN2OUT_NEXT_LOOKUP] = "ip4-lookup",
    [SNAT_IN2OUT_NEXT_SLOW_PATH] = "snat-in2out-slowpath",
  },
};

VLIB_NODE_FUNCTION_MULTIARCH (snat_in2out_fast_node, snat_in2out_fast_static_map_fn);