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

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

vlib_node_registration_t snat_in2out_node, snat_in2out_slowpath_node;

typedef struct {
  u32 sw_if_index;
  u32 next_index;
  u32 session_index;
  u32 is_slow_path;
} snat_in2out_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;
}

vlib_node_registration_t snat_in2out_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")
  
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)
{
  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;
  u32 outside_fib_index;
  uword * p;

  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->users, u);
      memset (u, 0, sizeof (*u));
      u->addr = ip0->src_address;

      pool_get (sm->list_pool, per_user_list_head_elt);

      u->sessions_per_user_list_head_index = per_user_list_head_elt -
        sm->list_pool;

      clib_dlist_init (sm->list_pool, u->sessions_per_user_list_head_index);
      
      kv0.value = u - sm->users;
      
      /* add user */
      clib_bihash_add_del_8_8 (&sm->user_hash, &kv0, 1 /* is_add */);
    }
  else
    {
      u = pool_elt_at_index (sm->users, value0.value);
    }

  /* Over quota? Recycle the least recently used translation */
  if (u->nsessions >= sm->max_translations_per_user)
    {
      /* Remove the oldest translation */
      oldest_per_user_translation_list_index = 
        clib_dlist_remove_head 
        (sm->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->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->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->sessions, session_index);

      /* 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
    {
      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;
        }

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

      /* Create list elts */
      pool_get (sm->list_pool, per_user_translation_list_elt);
      clib_dlist_init (sm->list_pool, per_user_translation_list_elt -
                       sm->list_pool);
      
      per_user_translation_list_elt->value = s - sm->sessions;
      s->per_user_index = per_user_translation_list_elt - sm->list_pool;
      s->per_user_list_head_index = u->sessions_per_user_list_head_index;
      
      clib_dlist_addtail (sm->list_pool, s->per_user_list_head_index,
                          per_user_translation_list_elt - sm->list_pool);
      u->nsessions++;
    }
  
  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->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->sessions;
  
  if (clib_bihash_add_del_8_8 (&sm->out2in, &kv0, 1 /* is_add */))
      clib_warning ("out2in key add failed");

  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)
{
  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);
      
      if (PREDICT_FALSE (next0 == SNAT_IN2OUT_NEXT_DROP))
        return next0;
    }
  else
    s0 = pool_elt_at_index (sm->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, per-user LRU list maintenance */
  s0->last_heard = now;
  s0->total_pkts++;
  s0->total_bytes += vlib_buffer_length_in_chain (sm->vlib_main, b0);
  clib_dlist_remove (sm->list_pool, s0->per_user_index);
  clib_dlist_addtail (sm->list_pool, s0->per_user_list_head_index,
                      s0->per_user_index);

  return next0;
}

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;

  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;

#if 0
          /* Formally correct, but we send to slowpath, lookup or drop */
          vnet_get_config_data (&cm->config_main,
                                &b0->current_config_index,
                                &next0,
                                0 /* sizeof config data */);
#endif

          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);
                  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);
                  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->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;
            }

          /* Accounting, per-user LRU list maintenance */
          s0->last_heard = now;
          s0->total_pkts++;
          s0->total_bytes += vlib_buffer_length_in_chain (vm, b0);
          clib_dlist_remove (sm->list_pool, s0->per_user_index);
          clib_dlist_addtail (sm->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->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);

#if 0
          vnet_get_config_data (&cm->config_main,
                                &b1->current_config_index,
                                &next1,
                                0 /* sizeof config data */);
#endif

          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);
                  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);
                  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->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;
            }

          /* Accounting, per-user LRU list maintenance */
          s1->last_heard = now;
          s1->total_pkts++;
          s1->total_bytes += vlib_buffer_length_in_chain (vm, b1);
          clib_dlist_remove (sm->list_pool, s1->per_user_index);
          clib_dlist_addtail (sm->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->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);


#if 0
          vnet_get_config_data (&cm->config_main,
                                &b0->current_config_index,
                                &next0,
                                0 /* sizeof config data */);
#endif

          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);
                  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);
                  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->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;
            }

          /* Accounting, per-user LRU list maintenance */
          s0->last_heard = now;
          s0->total_pkts++;
          s0->total_bytes += vlib_buffer_length_in_chain (vm, b0);
          clib_dlist_remove (sm->list_pool, s0->per_user_index);
          clib_dlist_addtail (sm->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->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);