nat: refactor and split fo EI/ED features

This patch is aimed at moving EI features out of NAT44
plugin & split of EI/ED functions.

Type: refactor

Change-Id: I63cf70a264ed2512708fe92665d64f04690783d0
Signed-off-by: Filip Varga <fivarga@cisco.com>

1 files changed, 1580 insertions, 0 deletions

diff --git a/src/plugins/nat/nat44-ei/nat44_ei_out2in.c b/src/plugins/nat/nat44-ei/nat44_ei_out2in.c
new file mode 100644
index 00000000000..8220f0dc9d8
--- /dev/null
+++ b/src/plugins/nat/nat44-ei/nat44_ei_out2in.c
@@ -0,0 +1,1580 @@
+/*
+ * 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.
+ */
+/**
+ * @file
+ * @brief NAT44 endpoint-dependent outside to inside network translation
+ */
+
+#include <vlib/vlib.h>
+#include <vnet/vnet.h>
+
+#include <vnet/ip/ip.h>
+#include <vnet/udp/udp_local.h>
+#include <vnet/ethernet/ethernet.h>
+#include <vnet/fib/ip4_fib.h>
+#include <nat/nat.h>
+#include <nat/lib/ipfix_logging.h>
+#include <nat/nat_inlines.h>
+#include <nat/lib/nat_syslog.h>
+#include <nat/nat44-ei/nat44_ei_inlines.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;
+} snat_out2in_trace_t;
+
+/* packet trace format function */
+static u8 *
+format_snat_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 *);
+  snat_out2in_trace_t *t = va_arg (*args, snat_out2in_trace_t *);
+
+  s =
+    format (s,
+	    "NAT44_OUT2IN: sw_if_index %d, next index %d, session index %d",
+	    t->sw_if_index, t->next_index, t->session_index);
+  return s;
+}
+
+static u8 *
+format_snat_out2in_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_out2in_trace_t *t = va_arg (*args, snat_out2in_trace_t *);
+
+  s = format (s, "NAT44_OUT2IN_FAST: sw_if_index %d, next index %d",
+	      t->sw_if_index, t->next_index);
+  return s;
+}
+
+#define foreach_snat_out2in_error                       \
+_(UNSUPPORTED_PROTOCOL, "unsupported protocol")         \
+_(OUT_OF_PORTS, "out of ports")                         \
+_(BAD_ICMP_TYPE, "unsupported ICMP type")               \
+_(NO_TRANSLATION, "no translation")                     \
+_(MAX_SESSIONS_EXCEEDED, "maximum sessions exceeded")   \
+_(CANNOT_CREATE_USER, "cannot create NAT user")
+
+typedef enum
+{
+#define _(sym,str) SNAT_OUT2IN_ERROR_##sym,
+  foreach_snat_out2in_error
+#undef _
+    SNAT_OUT2IN_N_ERROR,
+} snat_out2in_error_t;
+
+static char *snat_out2in_error_strings[] = {
+#define _(sym,string) string,
+  foreach_snat_out2in_error
+#undef _
+};
+
+typedef enum
+{
+  SNAT_OUT2IN_NEXT_DROP,
+  SNAT_OUT2IN_NEXT_LOOKUP,
+  SNAT_OUT2IN_NEXT_ICMP_ERROR,
+  SNAT_OUT2IN_N_NEXT,
+} snat_out2in_next_t;
+
+#ifndef CLIB_MARCH_VARIANT
+int
+nat44_o2i_is_idle_session_cb (clib_bihash_kv_8_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;
+  snat_main_per_thread_data_t *tsm = vec_elt_at_index (sm->per_thread_data,
+						       ctx->thread_index);
+  clib_bihash_kv_8_8_t s_kv;
+
+  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)
+    {
+      init_nat_i2o_k (&s_kv, s);
+      if (clib_bihash_add_del_8_8 (&tsm->in2out, &s_kv, 0))
+	nat_elog_warn ("out2in key del failed");
+
+      nat_ipfix_logging_nat44_ses_delete (ctx->thread_index,
+					  s->in2out.addr.as_u32,
+					  s->out2in.addr.as_u32,
+					  s->nat_proto,
+					  s->in2out.port,
+					  s->out2in.port,
+					  s->in2out.fib_index);
+
+      nat_syslog_nat44_apmdel (s->user_index, s->in2out.fib_index,
+			       &s->in2out.addr, s->in2out.port,
+			       &s->out2in.addr, s->out2in.port, s->nat_proto);
+
+      nat_ha_sdel (&s->out2in.addr, s->out2in.port, &s->ext_host_addr,
+		   s->ext_host_port, s->nat_proto, s->out2in.fib_index,
+		   ctx->thread_index);
+
+      if (!snat_is_session_static (s))
+	snat_free_outside_address_and_port (sm->addresses, ctx->thread_index,
+					    &s->out2in.addr, s->out2in.port,
+					    s->nat_proto);
+
+      nat44_delete_session (sm, s, ctx->thread_index);
+      return 1;
+    }
+
+  return 0;
+}
+#endif
+
+/**
+ * @brief Create session for static mapping.
+ *
+ * Create NAT session initiated by host from external network with static
+ * mapping.
+ *
+ * @param sm     NAT main.
+ * @param b0     Vlib buffer.
+ * @param in2out In2out NAT44 session key.
+ * @param out2in Out2in NAT44 session key.
+ * @param node   Vlib node.
+ *
+ * @returns SNAT session if successfully created otherwise 0.
+ */
+static inline snat_session_t *
+create_session_for_static_mapping (snat_main_t * sm,
+				   vlib_buffer_t * b0,
+				   ip4_address_t i2o_addr,
+				   u16 i2o_port,
+				   u32 i2o_fib_index,
+				   ip4_address_t o2i_addr,
+				   u16 o2i_port,
+				   u32 o2i_fib_index,
+				   nat_protocol_t proto,
+				   vlib_node_runtime_t * node,
+				   u32 thread_index, f64 now)
+{
+  snat_user_t *u;
+  snat_session_t *s;
+  clib_bihash_kv_8_8_t kv0;
+  ip4_header_t *ip0;
+  udp_header_t *udp0;
+  nat44_is_idle_session_ctx_t ctx0;
+
+  if (PREDICT_FALSE (nat44_ei_maximum_sessions_exceeded (sm, thread_index)))
+    {
+      b0->error = node->errors[SNAT_OUT2IN_ERROR_MAX_SESSIONS_EXCEEDED];
+      nat_elog_notice ("maximum sessions exceeded");
+      return 0;
+    }
+
+  ip0 = vlib_buffer_get_current (b0);
+  udp0 = ip4_next_header (ip0);
+
+  u = nat_user_get_or_create (sm, &i2o_addr, i2o_fib_index, thread_index);
+  if (!u)
+    {
+      b0->error = node->errors[SNAT_OUT2IN_ERROR_CANNOT_CREATE_USER];
+      return 0;
+    }
+
+  s = nat_session_alloc_or_recycle (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->flags |= SNAT_SESSION_FLAG_STATIC_MAPPING;
+  s->ext_host_addr.as_u32 = ip0->src_address.as_u32;
+  s->ext_host_port = udp0->src_port;
+  user_session_increment (sm, u, 1 /* static */ );
+  s->in2out.addr = i2o_addr;
+  s->in2out.port = i2o_port;
+  s->in2out.fib_index = i2o_fib_index;
+  s->out2in.addr = o2i_addr;
+  s->out2in.port = o2i_port;
+  s->out2in.fib_index = o2i_fib_index;
+  s->nat_proto = proto;
+
+  /* Add to translation hashes */
+  ctx0.now = now;
+  ctx0.thread_index = thread_index;
+  init_nat_i2o_kv (&kv0, s, s - sm->per_thread_data[thread_index].sessions);
+  if (clib_bihash_add_or_overwrite_stale_8_8
+      (&sm->per_thread_data[thread_index].in2out, &kv0,
+       nat44_i2o_is_idle_session_cb, &ctx0))
+    nat_elog_notice ("in2out key add failed");
+
+  init_nat_o2i_kv (&kv0, s, s - sm->per_thread_data[thread_index].sessions);
+  if (clib_bihash_add_or_overwrite_stale_8_8
+      (&sm->per_thread_data[thread_index].out2in, &kv0,
+       nat44_o2i_is_idle_session_cb, &ctx0))
+    nat_elog_notice ("out2in key add failed");
+
+  /* log NAT event */
+  nat_ipfix_logging_nat44_ses_create (thread_index,
+				      s->in2out.addr.as_u32,
+				      s->out2in.addr.as_u32,
+				      s->nat_proto,
+				      s->in2out.port,
+				      s->out2in.port, s->in2out.fib_index);
+
+  nat_syslog_nat44_apmadd (s->user_index, s->in2out.fib_index,
+			   &s->in2out.addr, s->in2out.port, &s->out2in.addr,
+			   s->out2in.port, s->nat_proto);
+
+  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->nat_proto, s->in2out.fib_index, s->flags, thread_index, 0);
+
+  return s;
+}
+
+#ifndef CLIB_MARCH_VARIANT
+static_always_inline snat_out2in_error_t
+icmp_get_key (vlib_buffer_t * b, ip4_header_t * ip0,
+	      ip4_address_t * addr, u16 * port, nat_protocol_t * nat_proto)
+{
+  icmp46_header_t *icmp0;
+  icmp_echo_header_t *echo0, *inner_echo0 = 0;
+  ip4_header_t *inner_ip0;
+  void *l4_header = 0;
+  icmp46_header_t *inner_icmp0;
+
+  icmp0 = (icmp46_header_t *) ip4_next_header (ip0);
+  echo0 = (icmp_echo_header_t *) (icmp0 + 1);
+
+  if (!icmp_type_is_error_message
+      (vnet_buffer (b)->ip.reass.icmp_type_or_tcp_flags))
+    {
+      *nat_proto = NAT_PROTOCOL_ICMP;
+      *addr = ip0->dst_address;
+      *port = vnet_buffer (b)->ip.reass.l4_src_port;
+    }
+  else
+    {
+      inner_ip0 = (ip4_header_t *) (echo0 + 1);
+      l4_header = ip4_next_header (inner_ip0);
+      *nat_proto = ip_proto_to_nat_proto (inner_ip0->protocol);
+      *addr = inner_ip0->src_address;
+      switch (*nat_proto)
+	{
+	case NAT_PROTOCOL_ICMP:
+	  inner_icmp0 = (icmp46_header_t *) l4_header;
+	  inner_echo0 = (icmp_echo_header_t *) (inner_icmp0 + 1);
+	  *port = inner_echo0->identifier;
+	  break;
+	case NAT_PROTOCOL_UDP:
+	case NAT_PROTOCOL_TCP:
+	  *port = ((tcp_udp_header_t *) l4_header)->src_port;
+	  break;
+	default:
+	  return SNAT_OUT2IN_ERROR_UNSUPPORTED_PROTOCOL;
+	}
+    }
+  return -1;			/* success */
+}
+
+/**
+ * Get address and port values to be used for ICMP packet translation
+ * and create session if needed
+ *
+ * @param[in,out] sm             NAT main
+ * @param[in,out] node           NAT node runtime
+ * @param[in] thread_index       thread index
+ * @param[in,out] b0             buffer containing packet to be translated
+ * @param[in,out] ip0            ip header
+ * @param[out] p_proto           protocol used for matching
+ * @param[out] p_value           address and port after NAT translation
+ * @param[out] p_dont_translate  if packet should not be translated
+ * @param d                      optional parameter
+ * @param e                      optional parameter
+ */
+u32
+icmp_match_out2in_slow (snat_main_t * sm, vlib_node_runtime_t * node,
+			u32 thread_index, vlib_buffer_t * b0,
+			ip4_header_t * ip0, ip4_address_t * addr,
+			u16 * port, u32 * fib_index,
+			nat_protocol_t * proto, void *d, void *e,
+			u8 * dont_translate)
+{
+  snat_main_per_thread_data_t *tsm = &sm->per_thread_data[thread_index];
+  u32 sw_if_index0;
+  snat_session_t *s0 = 0;
+  clib_bihash_kv_8_8_t kv0, value0;
+  u8 is_addr_only;
+  u32 next0 = ~0;
+  int err;
+  u8 identity_nat;
+  vlib_main_t *vm = vlib_get_main ();
+  *dont_translate = 0;
+
+  sw_if_index0 = vnet_buffer (b0)->sw_if_index[VLIB_RX];
+  *fib_index = ip4_fib_table_get_index_for_sw_if_index (sw_if_index0);
+
+  *proto = 0;
+
+  err = icmp_get_key (b0, ip0, addr, port, proto);
+  if (err != -1)
+    {
+      b0->error = node->errors[SNAT_OUT2IN_ERROR_UNSUPPORTED_PROTOCOL];
+      next0 = SNAT_OUT2IN_NEXT_DROP;
+      goto out;
+    }
+
+  ip4_address_t mapping_addr;
+  u16 mapping_port;
+  u32 mapping_fib_index;
+
+  init_nat_k (&kv0, *addr, *port, *fib_index, *proto);
+  if (clib_bihash_search_8_8 (&tsm->out2in, &kv0, &value0))
+    {
+      /* Try to match static mapping by external address and port,
+         destination address and port in packet */
+      if (snat_static_mapping_match
+	  (sm, *addr, *port, *fib_index, *proto,
+	   &mapping_addr, &mapping_port, &mapping_fib_index, 1, &is_addr_only,
+	   0, 0, 0, &identity_nat, 0))
+	{
+	  if (!sm->forwarding_enabled)
+	    {
+	      /* Don't NAT packet aimed at the intfc address */
+	      if (PREDICT_FALSE (is_interface_addr (sm, node, sw_if_index0,
+						    ip0->dst_address.as_u32)))
+		{
+		  *dont_translate = 1;
+		  goto out;
+		}
+	      b0->error = node->errors[SNAT_OUT2IN_ERROR_NO_TRANSLATION];
+	      next0 = SNAT_OUT2IN_NEXT_DROP;
+	      goto out;
+	    }
+	  else
+	    {
+	      *dont_translate = 1;
+	      goto out;
+	    }
+	}
+
+      if (PREDICT_FALSE
+	  (vnet_buffer (b0)->ip.reass.icmp_type_or_tcp_flags !=
+	   ICMP4_echo_reply
+	   && (vnet_buffer (b0)->ip.reass.icmp_type_or_tcp_flags !=
+	       ICMP4_echo_request || !is_addr_only)))
+	{
+	  b0->error = node->errors[SNAT_OUT2IN_ERROR_BAD_ICMP_TYPE];
+	  next0 = SNAT_OUT2IN_NEXT_DROP;
+	  goto out;
+	}
+
+      if (PREDICT_FALSE (identity_nat))
+	{
+	  *dont_translate = 1;
+	  goto out;
+	}
+      /* Create session initiated by host from external network */
+      s0 =
+	create_session_for_static_mapping (sm, b0, mapping_addr, mapping_port,
+					   mapping_fib_index, *addr, *port,
+					   *fib_index, *proto, node,
+					   thread_index, vlib_time_now (vm));
+
+      if (!s0)
+	{
+	  next0 = SNAT_OUT2IN_NEXT_DROP;
+	  goto out;
+	}
+    }
+  else
+    {
+      if (PREDICT_FALSE
+	  (vnet_buffer (b0)->ip.reass.icmp_type_or_tcp_flags !=
+	   ICMP4_echo_reply
+	   && vnet_buffer (b0)->ip.reass.icmp_type_or_tcp_flags !=
+	   ICMP4_echo_request
+	   && !icmp_type_is_error_message (vnet_buffer (b0)->ip.
+					   reass.icmp_type_or_tcp_flags)))
+	{
+	  b0->error = node->errors[SNAT_OUT2IN_ERROR_BAD_ICMP_TYPE];
+	  next0 = SNAT_OUT2IN_NEXT_DROP;
+	  goto out;
+	}
+
+      s0 = pool_elt_at_index (tsm->sessions, value0.value);
+    }
+
+out:
+  if (s0)
+    {
+      *addr = s0->in2out.addr;
+      *port = s0->in2out.port;
+      *fib_index = s0->in2out.fib_index;
+    }
+  if (d)
+    *(snat_session_t **) d = s0;
+  return next0;
+}
+#endif
+
+#ifndef CLIB_MARCH_VARIANT
+/**
+ * Get address and port values to be used for ICMP packet translation
+ *
+ * @param[in] sm                 NAT main
+ * @param[in,out] node           NAT node runtime
+ * @param[in] thread_index       thread index
+ * @param[in,out] b0             buffer containing packet to be translated
+ * @param[in,out] ip0            ip header
+ * @param[out] p_proto           protocol used for matching
+ * @param[out] p_value           address and port after NAT translation
+ * @param[out] p_dont_translate  if packet should not be translated
+ * @param d                      optional parameter
+ * @param e                      optional parameter
+ */
+u32
+icmp_match_out2in_fast (snat_main_t * sm, vlib_node_runtime_t * node,
+			u32 thread_index, vlib_buffer_t * b0,
+			ip4_header_t * ip0, ip4_address_t * mapping_addr,
+			u16 * mapping_port, u32 * mapping_fib_index,
+			nat_protocol_t * proto, void *d, void *e,
+			u8 * dont_translate)
+{
+  u32 sw_if_index0;
+  u32 rx_fib_index0;
+  u8 is_addr_only;
+  u32 next0 = ~0;
+  int err;
+  ip4_address_t addr;
+  u16 port;
+  *dont_translate = 0;
+
+  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);
+
+  err = icmp_get_key (b0, ip0, &addr, &port, proto);
+  if (err != -1)
+    {
+      b0->error = node->errors[err];
+      next0 = SNAT_OUT2IN_NEXT_DROP;
+      goto out;
+    }
+  if (snat_static_mapping_match
+      (sm, addr, port, rx_fib_index0, *proto, mapping_addr, mapping_port,
+       mapping_fib_index, 1, &is_addr_only, 0, 0, 0, 0, 0))
+    {
+      /* Don't NAT packet aimed at the intfc address */
+      if (is_interface_addr (sm, node, sw_if_index0, ip0->dst_address.as_u32))
+	{
+	  *dont_translate = 1;
+	  goto out;
+	}
+      b0->error = node->errors[SNAT_OUT2IN_ERROR_NO_TRANSLATION];
+      next0 = SNAT_OUT2IN_NEXT_DROP;
+      goto out;
+    }
+
+  if (PREDICT_FALSE
+      (vnet_buffer (b0)->ip.reass.icmp_type_or_tcp_flags != ICMP4_echo_reply
+       && (vnet_buffer (b0)->ip.reass.icmp_type_or_tcp_flags !=
+	   ICMP4_echo_request || !is_addr_only)
+       && !icmp_type_is_error_message (vnet_buffer (b0)->ip.
+				       reass.icmp_type_or_tcp_flags)))
+    {
+      b0->error = node->errors[SNAT_OUT2IN_ERROR_BAD_ICMP_TYPE];
+      next0 = SNAT_OUT2IN_NEXT_DROP;
+      goto out;
+    }
+
+out:
+  return next0;
+}
+#endif
+
+#ifndef CLIB_MARCH_VARIANT
+u32
+icmp_out2in (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, u32 thread_index, void *d, void *e)
+{
+  icmp_echo_header_t *echo0, *inner_echo0 = 0;
+  ip4_header_t *inner_ip0 = 0;
+  void *l4_header = 0;
+  icmp46_header_t *inner_icmp0;
+  u8 dont_translate;
+  u32 new_addr0, old_addr0;
+  u16 old_id0, new_id0;
+  ip_csum_t sum0;
+  u16 checksum0;
+  u32 next0_tmp;
+  vlib_main_t *vm = vlib_get_main ();
+  ip4_address_t addr;
+  u16 port;
+  u32 fib_index;
+  nat_protocol_t proto;
+
+  echo0 = (icmp_echo_header_t *) (icmp0 + 1);
+
+  next0_tmp = sm->icmp_match_out2in_cb (sm, node, thread_index, b0, ip0,
+					&addr, &port, &fib_index, &proto,
+					d, e, &dont_translate);
+  if (next0_tmp != ~0)
+    next0 = next0_tmp;
+  if (next0 == SNAT_OUT2IN_NEXT_DROP || dont_translate)
+    goto out;
+
+  if (PREDICT_TRUE (!ip4_is_fragment (ip0)))
+    {
+      sum0 =
+	ip_incremental_checksum_buffer (vm, b0,
+					(u8 *) icmp0 -
+					(u8 *) vlib_buffer_get_current (b0),
+					ntohs (ip0->length) -
+					ip4_header_bytes (ip0), 0);
+      checksum0 = ~ip_csum_fold (sum0);
+      if (checksum0 != 0 && checksum0 != 0xffff)
+	{
+	  next0 = SNAT_OUT2IN_NEXT_DROP;
+	  goto out;
+	}
+    }
+
+  old_addr0 = ip0->dst_address.as_u32;
+  new_addr0 = ip0->dst_address.as_u32 = addr.as_u32;
+  vnet_buffer (b0)->sw_if_index[VLIB_TX] = fib_index;
+
+  sum0 = ip0->checksum;
+  sum0 = ip_csum_update (sum0, old_addr0, new_addr0, ip4_header_t,
+			 dst_address /* changed member */ );
+  ip0->checksum = ip_csum_fold (sum0);
+
+
+  if (!vnet_buffer (b0)->ip.reass.is_non_first_fragment)
+    {
+      if (icmp0->checksum == 0)
+	icmp0->checksum = 0xffff;
+
+      if (!icmp_type_is_error_message (icmp0->type))
+	{
+	  new_id0 = port;
+	  if (PREDICT_FALSE (new_id0 != echo0->identifier))
+	    {
+	      old_id0 = echo0->identifier;
+	      new_id0 = port;
+	      echo0->identifier = new_id0;
+
+	      sum0 = icmp0->checksum;
+	      sum0 =
+		ip_csum_update (sum0, old_id0, new_id0, icmp_echo_header_t,
+				identifier /* changed member */ );
+	      icmp0->checksum = ip_csum_fold (sum0);
+	    }
+	}
+      else
+	{
+	  inner_ip0 = (ip4_header_t *) (echo0 + 1);
+	  l4_header = ip4_next_header (inner_ip0);
+
+	  if (!ip4_header_checksum_is_valid (inner_ip0))
+	    {
+	      next0 = SNAT_OUT2IN_NEXT_DROP;
+	      goto out;
+	    }
+
+	  old_addr0 = inner_ip0->src_address.as_u32;
+	  inner_ip0->src_address = addr;
+	  new_addr0 = inner_ip0->src_address.as_u32;
+
+	  sum0 = icmp0->checksum;
+	  sum0 = ip_csum_update (sum0, old_addr0, new_addr0, ip4_header_t,
+				 src_address /* changed member */ );
+	  icmp0->checksum = ip_csum_fold (sum0);
+
+	  switch (proto)
+	    {
+	    case NAT_PROTOCOL_ICMP:
+	      inner_icmp0 = (icmp46_header_t *) l4_header;
+	      inner_echo0 = (icmp_echo_header_t *) (inner_icmp0 + 1);
+
+	      old_id0 = inner_echo0->identifier;
+	      new_id0 = port;
+	      inner_echo0->identifier = new_id0;
+
+	      sum0 = icmp0->checksum;
+	      sum0 =
+		ip_csum_update (sum0, old_id0, new_id0, icmp_echo_header_t,
+				identifier);
+	      icmp0->checksum = ip_csum_fold (sum0);
+	      break;
+	    case NAT_PROTOCOL_UDP:
+	    case NAT_PROTOCOL_TCP:
+	      old_id0 = ((tcp_udp_header_t *) l4_header)->src_port;
+	      new_id0 = port;
+	      ((tcp_udp_header_t *) l4_header)->src_port = new_id0;
+
+	      sum0 = icmp0->checksum;
+	      sum0 = ip_csum_update (sum0, old_id0, new_id0, tcp_udp_header_t,
+				     src_port);
+	      icmp0->checksum = ip_csum_fold (sum0);
+	      break;
+	    default:
+	      ASSERT (0);
+	    }
+	}
+    }
+
+out:
+  return next0;
+}
+#endif
+
+static inline u32
+icmp_out2in_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)
+{
+  vlib_main_t *vm = vlib_get_main ();
+
+  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 != SNAT_OUT2IN_NEXT_DROP && s0))
+    {
+      /* Accounting */
+      nat44_ei_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);
+    }
+  return next0;
+}
+
+static int
+nat_out2in_sm_unknown_proto (snat_main_t * sm,
+			     vlib_buffer_t * b,
+			     ip4_header_t * ip, u32 rx_fib_index)
+{
+  clib_bihash_kv_8_8_t kv, value;
+  snat_static_mapping_t *m;
+  u32 old_addr, new_addr;
+  ip_csum_t sum;
+
+  init_nat_k (&kv, ip->dst_address, 0, 0, 0);
+  if (clib_bihash_search_8_8 (&sm->static_mapping_by_external, &kv, &value))
+    return 1;
+
+  m = pool_elt_at_index (sm->static_mappings, value.value);
+
+  old_addr = ip->dst_address.as_u32;
+  new_addr = ip->dst_address.as_u32 = m->local_addr.as_u32;
+  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] = m->fib_index;
+  return 0;
+}
+
+VLIB_NODE_FN (snat_out2in_node) (vlib_main_t * vm,
+				 vlib_node_runtime_t * node,
+				 vlib_frame_t * frame)
+{
+  u32 n_left_from, *from;
+  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];
+
+  from = vlib_frame_vector_args (frame);
+  n_left_from = frame->n_vectors;
+
+  vlib_buffer_t *bufs[VLIB_FRAME_SIZE], **b = bufs;
+  u16 nexts[VLIB_FRAME_SIZE], *next = nexts;
+  vlib_get_buffers (vm, from, b, n_left_from);
+
+  while (n_left_from >= 2)
+    {
+      vlib_buffer_t *b0, *b1;
+      u32 next0 = SNAT_OUT2IN_NEXT_LOOKUP;
+      u32 next1 = SNAT_OUT2IN_NEXT_LOOKUP;
+      u32 sw_if_index0, sw_if_index1;
+      ip4_header_t *ip0, *ip1;
+      ip_csum_t sum0, sum1;
+      u32 new_addr0, old_addr0;
+      u16 new_port0, old_port0;
+      u32 new_addr1, old_addr1;
+      u16 new_port1, old_port1;
+      udp_header_t *udp0, *udp1;
+      tcp_header_t *tcp0, *tcp1;
+      icmp46_header_t *icmp0, *icmp1;
+      u32 rx_fib_index0, rx_fib_index1;
+      u32 proto0, proto1;
+      snat_session_t *s0 = 0, *s1 = 0;
+      clib_bihash_kv_8_8_t kv0, kv1, value0, value1;
+      u8 identity_nat0, identity_nat1;
+      ip4_address_t sm_addr0, sm_addr1;
+      u16 sm_port0, sm_port1;
+      u32 sm_fib_index0, sm_fib_index1;
+
+      b0 = *b;
+      b++;
+      b1 = *b;
+      b++;
+
+      /* Prefetch next iteration. */
+      if (PREDICT_TRUE (n_left_from >= 4))
+	{
+	  vlib_buffer_t *p2, *p3;
+
+	  p2 = *b;
+	  p3 = *(b + 1);
+
+	  vlib_prefetch_buffer_header (p2, LOAD);
+	  vlib_prefetch_buffer_header (p3, LOAD);
+
+	  CLIB_PREFETCH (p2->data, CLIB_CACHE_LINE_BYTES, LOAD);
+	  CLIB_PREFETCH (p3->data, CLIB_CACHE_LINE_BYTES, LOAD);
+	}
+
+      vnet_buffer (b0)->snat.flags = 0;
+      vnet_buffer (b1)->snat.flags = 0;
+
+      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 (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 = SNAT_OUT2IN_NEXT_ICMP_ERROR;
+	  goto trace0;
+	}
+
+      proto0 = ip_proto_to_nat_proto (ip0->protocol);
+
+      if (PREDICT_FALSE (proto0 == NAT_PROTOCOL_OTHER))
+	{
+	  if (nat_out2in_sm_unknown_proto (sm, b0, ip0, rx_fib_index0))
+	    {
+	      if (!sm->forwarding_enabled)
+		{
+		  b0->error =
+		    node->errors[SNAT_OUT2IN_ERROR_UNSUPPORTED_PROTOCOL];
+		  next0 = SNAT_OUT2IN_NEXT_DROP;
+		}
+	    }
+	  vlib_increment_simple_counter (&sm->counters.slowpath.out2in.other,
+					 thread_index, sw_if_index0, 1);
+
+	  goto trace0;
+	}
+
+      if (PREDICT_FALSE (proto0 == NAT_PROTOCOL_ICMP))
+	{
+	  next0 = icmp_out2in_slow_path
+	    (sm, b0, ip0, icmp0, sw_if_index0, rx_fib_index0, node,
+	     next0, now, thread_index, &s0);
+	  vlib_increment_simple_counter (&sm->counters.slowpath.out2in.icmp,
+					 thread_index, sw_if_index0, 1);
+	  goto trace0;
+	}
+
+      init_nat_k (&kv0, ip0->dst_address,
+		  vnet_buffer (b0)->ip.reass.l4_dst_port, rx_fib_index0,
+		  proto0);
+      if (clib_bihash_search_8_8
+	  (&sm->per_thread_data[thread_index].out2in, &kv0, &value0))
+	{
+	  /* Try to match static mapping by external address and port,
+	     destination address and port in packet */
+	  if (snat_static_mapping_match
+	      (sm, ip0->dst_address,
+	       vnet_buffer (b0)->ip.reass.l4_dst_port, rx_fib_index0,
+	       proto0, &sm_addr0, &sm_port0, &sm_fib_index0, 1, 0, 0, 0,
+	       0, &identity_nat0, 0))
+	    {
+	      /*
+	       * 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 == NAT_PROTOCOL_UDP
+		   && (vnet_buffer (b0)->ip.reass.l4_dst_port ==
+		       clib_host_to_net_u16 (UDP_DST_PORT_dhcp_to_client))))
+		{
+		  vnet_feature_next (&next0, b0);
+		  goto trace0;
+		}
+
+	      if (!sm->forwarding_enabled)
+		{
+		  b0->error = node->errors[SNAT_OUT2IN_ERROR_NO_TRANSLATION];
+		  next0 = SNAT_OUT2IN_NEXT_DROP;
+		}
+	      goto trace0;
+	    }
+
+	  if (PREDICT_FALSE (identity_nat0))
+	    goto trace0;
+
+	  /* Create session initiated by host from external network */
+	  s0 = create_session_for_static_mapping (sm, b0,
+						  sm_addr0, sm_port0,
+						  sm_fib_index0,
+						  ip0->dst_address,
+						  vnet_buffer (b0)->ip.
+						  reass.l4_dst_port,
+						  rx_fib_index0, proto0, node,
+						  thread_index, now);
+	  if (!s0)
+	    {
+	      next0 = SNAT_OUT2IN_NEXT_DROP;
+	      goto trace0;
+	    }
+	}
+      else
+	s0 = pool_elt_at_index (tsm->sessions, value0.value);
+
+      old_addr0 = ip0->dst_address.as_u32;
+      ip0->dst_address = s0->in2out.addr;
+      new_addr0 = ip0->dst_address.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 /* changed member */ );
+      ip0->checksum = ip_csum_fold (sum0);
+
+      if (PREDICT_TRUE (proto0 == NAT_PROTOCOL_TCP))
+	{
+	  if (!vnet_buffer (b0)->ip.reass.is_non_first_fragment)
+	    {
+	      old_port0 = vnet_buffer (b0)->ip.reass.l4_dst_port;
+	      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 /* changed member */ );
+
+	      sum0 = ip_csum_update (sum0, old_port0, new_port0,
+				     ip4_header_t /* cheat */ ,
+				     length /* changed member */ );
+	      tcp0->checksum = ip_csum_fold (sum0);
+	    }
+	  vlib_increment_simple_counter (&sm->counters.slowpath.out2in.tcp,
+					 thread_index, sw_if_index0, 1);
+	}
+      else
+	{
+	  if (!vnet_buffer (b0)->ip.reass.is_non_first_fragment)
+	    {
+	      old_port0 = vnet_buffer (b0)->ip.reass.l4_dst_port;
+	      new_port0 = udp0->dst_port = s0->in2out.port;
+	      if (PREDICT_FALSE (udp0->checksum))
+		{
+		  sum0 = udp0->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 */ );
+		  udp0->checksum = ip_csum_fold (sum0);
+		}
+	    }
+	  vlib_increment_simple_counter (&sm->counters.slowpath.out2in.udp,
+					 thread_index, sw_if_index0, 1);
+	}
+
+      /* Accounting */
+      nat44_ei_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)))
+	{
+	  snat_out2in_trace_t *t = vlib_add_trace (vm, node, b0, sizeof (*t));
+	  t->sw_if_index = sw_if_index0;
+	  t->next_index = next0;
+	  t->session_index = ~0;
+	  if (s0)
+	    t->session_index =
+	      s0 - sm->per_thread_data[thread_index].sessions;
+	}
+
+      if (next0 == SNAT_OUT2IN_NEXT_DROP)
+	{
+	  vlib_increment_simple_counter (&sm->counters.slowpath.out2in.drops,
+					 thread_index, sw_if_index0, 1);
+	}
+
+
+      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 (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 = SNAT_OUT2IN_NEXT_ICMP_ERROR;
+	  goto trace1;
+	}
+
+      proto1 = ip_proto_to_nat_proto (ip1->protocol);
+
+      if (PREDICT_FALSE (proto1 == NAT_PROTOCOL_OTHER))
+	{
+	  if (nat_out2in_sm_unknown_proto (sm, b1, ip1, rx_fib_index1))
+	    {
+	      if (!sm->forwarding_enabled)
+		{
+		  b1->error =
+		    node->errors[SNAT_OUT2IN_ERROR_UNSUPPORTED_PROTOCOL];
+		  next1 = SNAT_OUT2IN_NEXT_DROP;
+		}
+	    }
+	  vlib_increment_simple_counter (&sm->counters.slowpath.out2in.other,
+					 thread_index, sw_if_index1, 1);
+	  goto trace1;
+	}
+
+      if (PREDICT_FALSE (proto1 == NAT_PROTOCOL_ICMP))
+	{
+	  next1 = icmp_out2in_slow_path
+	    (sm, b1, ip1, icmp1, sw_if_index1, rx_fib_index1, node,
+	     next1, now, thread_index, &s1);
+	  vlib_increment_simple_counter (&sm->counters.slowpath.out2in.icmp,
+					 thread_index, sw_if_index1, 1);
+	  goto trace1;
+	}
+
+      init_nat_k (&kv1, ip1->dst_address,
+		  vnet_buffer (b1)->ip.reass.l4_dst_port, rx_fib_index1,
+		  proto1);
+
+      if (clib_bihash_search_8_8
+	  (&sm->per_thread_data[thread_index].out2in, &kv1, &value1))
+	{
+	  /* Try to match static mapping by external address and port,
+	     destination address and port in packet */
+	  if (snat_static_mapping_match
+	      (sm, ip1->dst_address,
+	       vnet_buffer (b1)->ip.reass.l4_dst_port, proto1,
+	       rx_fib_index1, &sm_addr1, &sm_port1, &sm_fib_index1, 1, 0,
+	       0, 0, 0, &identity_nat1, 0))
+	    {
+	      /*
+	       * 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 == NAT_PROTOCOL_UDP
+		   && (vnet_buffer (b1)->ip.reass.l4_dst_port ==
+		       clib_host_to_net_u16 (UDP_DST_PORT_dhcp_to_client))))
+		{
+		  vnet_feature_next (&next1, b1);
+		  goto trace1;
+		}
+
+	      if (!sm->forwarding_enabled)
+		{
+		  b1->error = node->errors[SNAT_OUT2IN_ERROR_NO_TRANSLATION];
+		  next1 = SNAT_OUT2IN_NEXT_DROP;
+		}
+	      goto trace1;
+	    }
+
+	  if (PREDICT_FALSE (identity_nat1))
+	    goto trace1;
+
+	  /* Create session initiated by host from external network */
+	  s1 =
+	    create_session_for_static_mapping (sm, b1, sm_addr1, sm_port1,
+					       sm_fib_index1,
+					       ip1->dst_address,
+					       vnet_buffer (b1)->ip.
+					       reass.l4_dst_port,
+					       rx_fib_index1, proto1, node,
+					       thread_index, now);
+	  if (!s1)
+	    {
+	      next1 = SNAT_OUT2IN_NEXT_DROP;
+	      goto trace1;
+	    }
+	}
+      else
+	s1 =
+	  pool_elt_at_index (sm->per_thread_data[thread_index].sessions,
+			     value1.value);
+
+      old_addr1 = ip1->dst_address.as_u32;
+      ip1->dst_address = s1->in2out.addr;
+      new_addr1 = ip1->dst_address.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 /* changed member */ );
+      ip1->checksum = ip_csum_fold (sum1);
+
+      if (PREDICT_TRUE (proto1 == NAT_PROTOCOL_TCP))
+	{
+	  if (!vnet_buffer (b1)->ip.reass.is_non_first_fragment)
+	    {
+	      old_port1 = vnet_buffer (b1)->ip.reass.l4_dst_port;
+	      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 /* changed member */ );
+
+	      sum1 = ip_csum_update (sum1, old_port1, new_port1,
+				     ip4_header_t /* cheat */ ,
+				     length /* changed member */ );
+	      tcp1->checksum = ip_csum_fold (sum1);
+	    }
+	  vlib_increment_simple_counter (&sm->counters.slowpath.out2in.tcp,
+					 thread_index, sw_if_index1, 1);
+	}
+      else
+	{
+	  if (!vnet_buffer (b1)->ip.reass.is_non_first_fragment)
+	    {
+	      old_port1 = vnet_buffer (b1)->ip.reass.l4_dst_port;
+	      new_port1 = udp1->dst_port = s1->in2out.port;
+	      if (PREDICT_FALSE (udp1->checksum))
+		{
+
+		  sum1 = udp1->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 */ );
+		  udp1->checksum = ip_csum_fold (sum1);
+		}
+	    }
+	  vlib_increment_simple_counter (&sm->counters.slowpath.out2in.udp,
+					 thread_index, sw_if_index1, 1);
+	}
+
+      /* Accounting */
+      nat44_ei_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);
+    trace1:
+
+      if (PREDICT_FALSE ((node->flags & VLIB_NODE_FLAG_TRACE)
+			 && (b1->flags & VLIB_BUFFER_IS_TRACED)))
+	{
+	  snat_out2in_trace_t *t = vlib_add_trace (vm, node, b1, sizeof (*t));
+	  t->sw_if_index = sw_if_index1;
+	  t->next_index = next1;
+	  t->session_index = ~0;
+	  if (s1)
+	    t->session_index =
+	      s1 - sm->per_thread_data[thread_index].sessions;
+	}
+
+      if (next1 == SNAT_OUT2IN_NEXT_DROP)
+	{
+	  vlib_increment_simple_counter (&sm->counters.slowpath.out2in.drops,
+					 thread_index, sw_if_index1, 1);
+	}
+
+      n_left_from -= 2;
+      next[0] = next0;
+      next[1] = next1;
+      next += 2;
+    }
+
+  while (n_left_from > 0)
+    {
+      vlib_buffer_t *b0;
+      u32 next0 = SNAT_OUT2IN_NEXT_LOOKUP;
+      u32 sw_if_index0;
+      ip4_header_t *ip0;
+      ip_csum_t sum0;
+      u32 new_addr0, old_addr0;
+      u16 new_port0, old_port0;
+      udp_header_t *udp0;
+      tcp_header_t *tcp0;
+      icmp46_header_t *icmp0;
+      u32 rx_fib_index0;
+      u32 proto0;
+      snat_session_t *s0 = 0;
+      clib_bihash_kv_8_8_t kv0, value0;
+      u8 identity_nat0;
+      ip4_address_t sm_addr0;
+      u16 sm_port0;
+      u32 sm_fib_index0;
+
+      b0 = *b;
+      ++b;
+
+      vnet_buffer (b0)->snat.flags = 0;
+
+      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 = ip_proto_to_nat_proto (ip0->protocol);
+
+      if (PREDICT_FALSE (proto0 == NAT_PROTOCOL_OTHER))
+	{
+	  if (nat_out2in_sm_unknown_proto (sm, b0, ip0, rx_fib_index0))
+	    {
+	      if (!sm->forwarding_enabled)
+		{
+		  b0->error =
+		    node->errors[SNAT_OUT2IN_ERROR_UNSUPPORTED_PROTOCOL];
+		  next0 = SNAT_OUT2IN_NEXT_DROP;
+		}
+	    }
+	  vlib_increment_simple_counter (&sm->counters.slowpath.out2in.other,
+					 thread_index, sw_if_index0, 1);
+	  goto trace00;
+	}
+
+      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 = SNAT_OUT2IN_NEXT_ICMP_ERROR;
+	  goto trace00;
+	}
+
+      if (PREDICT_FALSE (proto0 == NAT_PROTOCOL_ICMP))
+	{
+	  next0 = icmp_out2in_slow_path
+	    (sm, b0, ip0, icmp0, sw_if_index0, rx_fib_index0, node,
+	     next0, now, thread_index, &s0);
+	  vlib_increment_simple_counter (&sm->counters.slowpath.out2in.icmp,
+					 thread_index, sw_if_index0, 1);
+	  goto trace00;
+	}
+
+      init_nat_k (&kv0, ip0->dst_address,
+		  vnet_buffer (b0)->ip.reass.l4_dst_port, rx_fib_index0,
+		  proto0);
+
+      if (clib_bihash_search_8_8
+	  (&sm->per_thread_data[thread_index].out2in, &kv0, &value0))
+	{
+	  /* Try to match static mapping by external address and port,
+	     destination address and port in packet */
+	  if (snat_static_mapping_match
+	      (sm, ip0->dst_address,
+	       vnet_buffer (b0)->ip.reass.l4_dst_port, rx_fib_index0,
+	       proto0, &sm_addr0, &sm_port0, &sm_fib_index0, 1, 0, 0, 0,
+	       0, &identity_nat0, 0))
+	    {
+	      /*
+	       * 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 == NAT_PROTOCOL_UDP
+		   && (vnet_buffer (b0)->ip.reass.l4_dst_port ==
+		       clib_host_to_net_u16 (UDP_DST_PORT_dhcp_to_client))))
+		{
+		  vnet_feature_next (&next0, b0);
+		  goto trace00;
+		}
+
+	      if (!sm->forwarding_enabled)
+		{
+		  b0->error = node->errors[SNAT_OUT2IN_ERROR_NO_TRANSLATION];
+		  next0 = SNAT_OUT2IN_NEXT_DROP;
+		}
+	      goto trace00;
+	    }
+
+	  if (PREDICT_FALSE (identity_nat0))
+	    goto trace00;
+
+	  /* Create session initiated by host from external network */
+	  s0 = create_session_for_static_mapping (sm, b0,
+						  sm_addr0, sm_port0,
+						  sm_fib_index0,
+						  ip0->dst_address,
+						  vnet_buffer (b0)->ip.
+						  reass.l4_dst_port,
+						  rx_fib_index0, proto0, node,
+						  thread_index, now);
+	  if (!s0)
+	    {
+	      next0 = SNAT_OUT2IN_NEXT_DROP;
+	      goto trace00;
+	    }
+	}
+      else
+	s0 =
+	  pool_elt_at_index (sm->per_thread_data[thread_index].sessions,
+			     value0.value);
+
+      old_addr0 = ip0->dst_address.as_u32;
+      ip0->dst_address = s0->in2out.addr;
+      new_addr0 = ip0->dst_address.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 /* changed member */ );
+      ip0->checksum = ip_csum_fold (sum0);
+
+      if (PREDICT_TRUE (proto0 == NAT_PROTOCOL_TCP))
+	{
+	  if (!vnet_buffer (b0)->ip.reass.is_non_first_fragment)
+	    {
+	      old_port0 = vnet_buffer (b0)->ip.reass.l4_dst_port;
+	      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 /* changed member */ );
+
+	      sum0 = ip_csum_update (sum0, old_port0, new_port0,
+				     ip4_header_t /* cheat */ ,
+				     length /* changed member */ );
+	      tcp0->checksum = ip_csum_fold (sum0);
+	    }
+	  vlib_increment_simple_counter (&sm->counters.slowpath.out2in.tcp,
+					 thread_index, sw_if_index0, 1);
+	}
+      else
+	{
+	  if (!vnet_buffer (b0)->ip.reass.is_non_first_fragment)
+	    {
+	      old_port0 = vnet_buffer (b0)->ip.reass.l4_dst_port;
+	      new_port0 = udp0->dst_port = s0->in2out.port;
+	      if (PREDICT_FALSE (udp0->checksum))
+		{
+		  sum0 = udp0->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 */ );
+		  udp0->checksum = ip_csum_fold (sum0);
+		}
+	    }
+	  vlib_increment_simple_counter (&sm->counters.slowpath.out2in.udp,
+					 thread_index, sw_if_index0, 1);
+	}
+
+      /* Accounting */
+      nat44_ei_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)))
+	{
+	  snat_out2in_trace_t *t = vlib_add_trace (vm, node, b0, sizeof (*t));
+	  t->sw_if_index = sw_if_index0;
+	  t->next_index = next0;
+	  t->session_index = ~0;
+	  if (s0)
+	    t->session_index =
+	      s0 - sm->per_thread_data[thread_index].sessions;
+	}
+
+      if (next0 == SNAT_OUT2IN_NEXT_DROP)
+	{
+	  vlib_increment_simple_counter (&sm->counters.slowpath.out2in.drops,
+					 thread_index, sw_if_index0, 1);
+	}
+
+      n_left_from--;
+      next[0] = next0;
+      next++;
+    }
+
+  vlib_buffer_enqueue_to_next (vm, node, from, (u16 *) nexts,
+			       frame->n_vectors);
+
+  return frame->n_vectors;
+}
+
+/* *INDENT-OFF* */
+VLIB_REGISTER_NODE (snat_out2in_node) = {
+  .name = "nat44-out2in",
+  .vector_size = sizeof (u32),
+  .format_trace = format_snat_out2in_trace,
+  .type = VLIB_NODE_TYPE_INTERNAL,
+
+  .n_errors = ARRAY_LEN(snat_out2in_error_strings),
+  .error_strings = snat_out2in_error_strings,
+
+  .runtime_data_bytes = sizeof (snat_runtime_t),
+
+  .n_next_nodes = SNAT_OUT2IN_N_NEXT,
+
+  /* edit / add dispositions here */
+  .next_nodes = {
+    [SNAT_OUT2IN_NEXT_DROP] = "error-drop",
+    [SNAT_OUT2IN_NEXT_LOOKUP] = "ip4-lookup",
+    [SNAT_OUT2IN_NEXT_ICMP_ERROR] = "ip4-icmp-error",
+  },
+};
+/* *INDENT-ON* */
+
+VLIB_NODE_FN (snat_out2in_fast_node) (vlib_main_t * vm,
+				      vlib_node_runtime_t * node,
+				      vlib_frame_t * frame)
+{
+  u32 n_left_from, *from;
+  snat_main_t *sm = &snat_main;
+
+  from = vlib_frame_vector_args (frame);
+  n_left_from = frame->n_vectors;
+
+  vlib_buffer_t *bufs[VLIB_FRAME_SIZE], **b = bufs;
+  u16 nexts[VLIB_FRAME_SIZE], *next = nexts;
+  vlib_get_buffers (vm, from, b, n_left_from);
+  while (n_left_from > 0)
+    {
+      vlib_buffer_t *b0;
+      u32 next0 = SNAT_OUT2IN_NEXT_DROP;
+      u32 sw_if_index0;
+      ip4_header_t *ip0;
+      ip_csum_t sum0;
+      u32 new_addr0, old_addr0;
+      u16 new_port0, old_port0;
+      udp_header_t *udp0;
+      tcp_header_t *tcp0;
+      icmp46_header_t *icmp0;
+      u32 proto0;
+      u32 rx_fib_index0;
+      ip4_address_t sm_addr0;
+      u16 sm_port0;
+      u32 sm_fib_index0;
+
+      b0 = *b;
+      b++;
+
+      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);
+
+      vnet_feature_next (&next0, b0);
+
+      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 = SNAT_OUT2IN_NEXT_ICMP_ERROR;
+	  goto trace00;
+	}
+
+      proto0 = ip_proto_to_nat_proto (ip0->protocol);
+
+      if (PREDICT_FALSE (proto0 == NAT_PROTOCOL_OTHER))
+	goto trace00;
+
+      if (PREDICT_FALSE (proto0 == NAT_PROTOCOL_ICMP))
+	{
+	  next0 = icmp_out2in (sm, b0, ip0, icmp0, sw_if_index0,
+			       rx_fib_index0, node, next0, ~0, 0, 0);
+	  goto trace00;
+	}
+
+      if (snat_static_mapping_match
+	  (sm, ip0->dst_address, udp0->dst_port, rx_fib_index0, proto0,
+	   &sm_addr0, &sm_port0, &sm_fib_index0, 1, 0, 0, 0, 0, 0, 0))
+	{
+	  b0->error = node->errors[SNAT_OUT2IN_ERROR_NO_TRANSLATION];
+	  goto trace00;
+	}
+
+      new_addr0 = sm_addr0.as_u32;
+      new_port0 = sm_port0;
+      vnet_buffer (b0)->sw_if_index[VLIB_TX] = sm_fib_index0;
+      old_addr0 = ip0->dst_address.as_u32;
+      ip0->dst_address.as_u32 = new_addr0;
+
+      sum0 = ip0->checksum;
+      sum0 = ip_csum_update (sum0, old_addr0, new_addr0,
+			     ip4_header_t, dst_address /* changed member */ );
+      ip0->checksum = ip_csum_fold (sum0);
+
+      if (PREDICT_FALSE (new_port0 != udp0->dst_port))
+	{
+	  old_port0 = udp0->dst_port;
+	  udp0->dst_port = new_port0;
+
+	  if (PREDICT_TRUE (proto0 == NAT_PROTOCOL_TCP))
+	    {
+	      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 if (udp0->checksum)
+	    {
+	      sum0 = udp0->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 */ );
+	      udp0->checksum = ip_csum_fold (sum0);
+	    }
+	}
+      else
+	{
+	  if (PREDICT_TRUE (proto0 == NAT_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);
+	    }
+	  else if (udp0->checksum)
+	    {
+	      sum0 = udp0->checksum;
+	      sum0 = ip_csum_update (sum0, old_addr0, new_addr0,
+				     ip4_header_t,
+				     dst_address /* changed member */ );
+	      udp0->checksum = ip_csum_fold (sum0);
+	    }
+	}
+
+    trace00:
+
+      if (PREDICT_FALSE ((node->flags & VLIB_NODE_FLAG_TRACE)
+			 && (b0->flags & VLIB_BUFFER_IS_TRACED)))
+	{
+	  snat_out2in_trace_t *t = vlib_add_trace (vm, node, b0, sizeof (*t));
+	  t->sw_if_index = sw_if_index0;
+	  t->next_index = next0;
+	}
+
+      if (next0 == SNAT_OUT2IN_NEXT_DROP)
+	{
+	  vlib_increment_simple_counter (&sm->counters.fastpath.out2in.drops,
+					 vm->thread_index, sw_if_index0, 1);
+	}
+
+      n_left_from--;
+      next[0] = next0;
+      next++;
+    }
+
+  vlib_buffer_enqueue_to_next (vm, node, from, (u16 *) nexts,
+			       frame->n_vectors);
+
+  return frame->n_vectors;
+}
+
+/* *INDENT-OFF* */
+VLIB_REGISTER_NODE (snat_out2in_fast_node) = {
+  .name = "nat44-out2in-fast",
+  .vector_size = sizeof (u32),
+  .format_trace = format_snat_out2in_fast_trace,
+  .type = VLIB_NODE_TYPE_INTERNAL,
+
+  .n_errors = ARRAY_LEN(snat_out2in_error_strings),
+  .error_strings = snat_out2in_error_strings,
+
+  .runtime_data_bytes = sizeof (snat_runtime_t),
+
+  .n_next_nodes = SNAT_OUT2IN_N_NEXT,
+
+  /* edit / add dispositions here */
+  .next_nodes = {
+    [SNAT_OUT2IN_NEXT_LOOKUP] = "ip4-lookup",
+    [SNAT_OUT2IN_NEXT_DROP] = "error-drop",
+    [SNAT_OUT2IN_NEXT_ICMP_ERROR] = "ip4-icmp-error",
+  },
+};
+/* *INDENT-ON* */
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */