nat: move deterministic nat to det44 sub feature

Type: refactor

Change-Id: I0bb203102a0e13dd7448e2125925ab356bbd7937
Signed-off-by: Filip Varga <fivarga@cisco.com>

1 files changed, 866 insertions, 0 deletions

diff --git a/src/plugins/nat/det44/det44_out2in.c b/src/plugins/nat/det44/det44_out2in.c
new file mode 100644
index 00000000000..5ee28777b84
--- /dev/null
+++ b/src/plugins/nat/det44/det44_out2in.c
@@ -0,0 +1,866 @@
+/*
+ * Copyright (c) 2020 Cisco and/or its affiliates.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * @file
+ * @brief Deterministic NAT (CGN) outside to inside translation
+ */
+
+#include <vlib/vlib.h>
+#include <vnet/vnet.h>
+#include <vnet/ip/ip.h>
+#include <vnet/fib/ip4_fib.h>
+#include <vppinfra/error.h>
+#include <vppinfra/elog.h>
+
+#include <nat/det44/det44.h>
+#include <nat/det44/det44_inlines.h>
+
+#include <nat/lib/lib.h>
+#include <nat/lib/inlines.h>
+#include <nat/lib/nat_inlines.h>
+
+typedef enum
+{
+  DET44_OUT2IN_NEXT_DROP,
+  DET44_OUT2IN_NEXT_LOOKUP,
+  DET44_OUT2IN_NEXT_ICMP_ERROR,
+  DET44_OUT2IN_N_NEXT,
+} det44_out2in_next_t;
+
+typedef struct
+{
+  u32 sw_if_index;
+  u32 next_index;
+  u32 session_index;
+} det44_out2in_trace_t;
+
+#define foreach_det44_out2in_error                 \
+_(UNSUPPORTED_PROTOCOL, "Unsupported protocol")    \
+_(NO_TRANSLATION, "No translation")                \
+_(BAD_ICMP_TYPE, "unsupported ICMP type")          \
+_(OUT2IN_PACKETS, "Good out2in packets processed")
+
+typedef enum
+{
+#define _(sym,str) DET44_OUT2IN_ERROR_##sym,
+  foreach_det44_out2in_error
+#undef _
+    DET44_OUT2IN_N_ERROR,
+} det44_out2in_error_t;
+
+static char *det44_out2in_error_strings[] = {
+#define _(sym,string) string,
+  foreach_det44_out2in_error
+#undef _
+};
+
+static u8 *
+format_det44_out2in_trace (u8 * s, va_list * args)
+{
+  CLIB_UNUSED (vlib_main_t * vm) = va_arg (*args, vlib_main_t *);
+  CLIB_UNUSED (vlib_node_t * node) = va_arg (*args, vlib_node_t *);
+  det44_out2in_trace_t *t = va_arg (*args, det44_out2in_trace_t *);
+
+  s =
+    format (s,
+	    "DET44_OUT2IN: sw_if_index %d, next index %d, session index %d",
+	    t->sw_if_index, t->next_index, t->session_index);
+  return s;
+}
+
+#ifndef CLIB_MARCH_VARIANT
+/**
+ * Get address and port values to be used for ICMP packet translation
+ * and create session if needed
+ *
+ * @param[in,out] node           NAT node runtime
+ * @param[in] thread_index       thread index
+ * @param[in,out] b0             buffer containing packet to be translated
+ * @param[in,out] ip0            ip header
+ * @param[out] p_proto           protocol used for matching
+ * @param[out] p_value           address and port after NAT translation
+ * @param[out] p_dont_translate  if packet should not be translated
+ * @param d                      optional parameter
+ * @param e                      optional parameter
+ */
+u32
+icmp_match_out2in_det (vlib_node_runtime_t * node,
+		       u32 thread_index, vlib_buffer_t * b0,
+		       ip4_header_t * ip0, ip4_address_t * addr,
+		       u16 * port, u32 * fib_index,
+		       nat_protocol_t * proto, void *d, void *e,
+		       u8 * dont_translate)
+{
+  det44_main_t *dm = &det44_main;
+  icmp46_header_t *icmp0;
+  u32 sw_if_index0;
+  u8 protocol;
+  snat_det_out_key_t key0;
+  u32 next0 = ~0;
+  icmp_echo_header_t *echo0, *inner_echo0 = 0;
+  ip4_header_t *inner_ip0;
+  void *l4_header = 0;
+  icmp46_header_t *inner_icmp0;
+  snat_det_map_t *mp0 = 0;
+  ip4_address_t new_addr0 = { {0} };
+  snat_det_session_t *ses0 = 0;
+  ip4_address_t out_addr;
+  *dont_translate = 0;
+
+  icmp0 = (icmp46_header_t *) ip4_next_header (ip0);
+  echo0 = (icmp_echo_header_t *) (icmp0 + 1);
+  sw_if_index0 = vnet_buffer (b0)->sw_if_index[VLIB_RX];
+
+  if (!icmp_type_is_error_message
+      (vnet_buffer (b0)->ip.reass.icmp_type_or_tcp_flags))
+    {
+      protocol = NAT_PROTOCOL_ICMP;
+      key0.ext_host_addr = ip0->src_address;
+      key0.ext_host_port = 0;
+      key0.out_port = vnet_buffer (b0)->ip.reass.l4_src_port;
+      out_addr = ip0->dst_address;
+    }
+  else
+    {
+      /* if error message, then it's not fragmented and we can access it */
+      inner_ip0 = (ip4_header_t *) (echo0 + 1);
+      l4_header = ip4_next_header (inner_ip0);
+      protocol = ip_proto_to_nat_proto (inner_ip0->protocol);
+      key0.ext_host_addr = inner_ip0->dst_address;
+      out_addr = inner_ip0->src_address;
+      switch (protocol)
+	{
+	case NAT_PROTOCOL_ICMP:
+	  inner_icmp0 = (icmp46_header_t *) l4_header;
+	  inner_echo0 = (icmp_echo_header_t *) (inner_icmp0 + 1);
+	  key0.ext_host_port = 0;
+	  key0.out_port = inner_echo0->identifier;
+	  break;
+	case NAT_PROTOCOL_UDP:
+	case NAT_PROTOCOL_TCP:
+	  key0.ext_host_port = ((tcp_udp_header_t *) l4_header)->dst_port;
+	  key0.out_port = ((tcp_udp_header_t *) l4_header)->src_port;
+	  break;
+	default:
+	  b0->error = node->errors[DET44_OUT2IN_ERROR_UNSUPPORTED_PROTOCOL];
+	  next0 = DET44_OUT2IN_NEXT_DROP;
+	  goto out;
+	}
+    }
+
+  mp0 = snat_det_map_by_out (&out_addr);
+  if (PREDICT_FALSE (!mp0))
+    {
+      /* Don't NAT packet aimed at the intfc address */
+      if (PREDICT_FALSE (!det44_is_interface_addr (node, sw_if_index0,
+						   ip0->dst_address.as_u32)))
+	{
+	  *dont_translate = 1;
+	  goto out;
+	}
+      det44_log_info ("unknown dst address:  %U",
+		      format_ip4_address, &ip0->dst_address);
+      goto out;
+    }
+
+  snat_det_reverse (mp0, &ip0->dst_address,
+		    clib_net_to_host_u16 (key0.out_port), &new_addr0);
+
+  ses0 = snat_det_get_ses_by_out (mp0, &new_addr0, key0.as_u64);
+  if (PREDICT_FALSE (!ses0))
+    {
+      /* Don't NAT packet aimed at the intfc address */
+      if (PREDICT_FALSE (!det44_is_interface_addr (node, sw_if_index0,
+						   ip0->dst_address.as_u32)))
+	{
+	  *dont_translate = 1;
+	  goto out;
+	}
+      det44_log_info ("no match src %U:%d dst %U:%d for user %U",
+		      format_ip4_address, &key0.ext_host_addr,
+		      clib_net_to_host_u16 (key0.ext_host_port),
+		      format_ip4_address, &out_addr,
+		      clib_net_to_host_u16 (key0.out_port),
+		      format_ip4_address, &new_addr0);
+      b0->error = node->errors[DET44_OUT2IN_ERROR_NO_TRANSLATION];
+      next0 = DET44_OUT2IN_NEXT_DROP;
+      goto out;
+    }
+
+  if (PREDICT_FALSE
+      (vnet_buffer (b0)->ip.reass.icmp_type_or_tcp_flags != ICMP4_echo_reply
+       && !icmp_type_is_error_message (vnet_buffer (b0)->ip.
+				       reass.icmp_type_or_tcp_flags)))
+    {
+      b0->error = node->errors[DET44_OUT2IN_ERROR_BAD_ICMP_TYPE];
+      next0 = DET44_OUT2IN_NEXT_DROP;
+      goto out;
+    }
+
+  goto out;
+
+out:
+  *proto = protocol;
+  if (ses0)
+    {
+      *addr = new_addr0;
+      *fib_index = dm->inside_fib_index;
+      *port = ses0->in_port;
+    }
+  if (d)
+    *(snat_det_session_t **) d = ses0;
+  if (e)
+    *(snat_det_map_t **) e = mp0;
+  return next0;
+}
+#endif
+
+#ifndef CLIB_MARCH_VARIANT
+u32
+det44_icmp_out2in (vlib_buffer_t * b0,
+		   ip4_header_t * ip0,
+		   icmp46_header_t * icmp0,
+		   u32 sw_if_index0,
+		   u32 rx_fib_index0,
+		   vlib_node_runtime_t * node,
+		   u32 next0, u32 thread_index, void *d, void *e)
+{
+  vlib_main_t *vm = vlib_get_main ();
+  u32 new_addr0, old_addr0, next0_tmp, fib_index;
+  u16 old_id0, new_id0, port, checksum0;
+  icmp_echo_header_t *echo0, *inner_echo0;
+  icmp46_header_t *inner_icmp0;
+  ip4_header_t *inner_ip0;
+  ip4_address_t addr;
+  void *l4_header;
+  u8 dont_translate;
+  ip_csum_t sum0;
+  nat_protocol_t proto;
+
+  echo0 = (icmp_echo_header_t *) (icmp0 + 1);
+  next0_tmp = icmp_match_out2in_det (node, thread_index, b0, ip0,
+				     &addr, &port, &fib_index, &proto,
+				     d, e, &dont_translate);
+  if (next0_tmp != ~0)
+    next0 = next0_tmp;
+  if (next0 == DET44_OUT2IN_NEXT_DROP || dont_translate)
+    goto out;
+
+  if (PREDICT_TRUE (!ip4_is_fragment (ip0)))
+    {
+      sum0 =
+	ip_incremental_checksum_buffer (vm, b0,
+					(u8 *) icmp0 -
+					(u8 *) vlib_buffer_get_current (b0),
+					ntohs (ip0->length) -
+					ip4_header_bytes (ip0), 0);
+      checksum0 = ~ip_csum_fold (sum0);
+      if (checksum0 != 0 && checksum0 != 0xffff)
+	{
+	  next0 = DET44_OUT2IN_NEXT_DROP;
+	  goto out;
+	}
+    }
+
+  old_addr0 = ip0->dst_address.as_u32;
+  new_addr0 = ip0->dst_address.as_u32 = addr.as_u32;
+  vnet_buffer (b0)->sw_if_index[VLIB_TX] = fib_index;
+
+  sum0 = ip0->checksum;
+  sum0 = ip_csum_update (sum0, old_addr0, new_addr0, ip4_header_t,
+			 dst_address /* changed member */ );
+  ip0->checksum = ip_csum_fold (sum0);
+
+
+  if (!vnet_buffer (b0)->ip.reass.is_non_first_fragment)
+    {
+      if (icmp0->checksum == 0)
+	icmp0->checksum = 0xffff;
+
+      if (!icmp_type_is_error_message (icmp0->type))
+	{
+	  new_id0 = port;
+	  if (PREDICT_FALSE (new_id0 != echo0->identifier))
+	    {
+	      old_id0 = echo0->identifier;
+	      new_id0 = port;
+	      echo0->identifier = new_id0;
+
+	      sum0 = icmp0->checksum;
+	      sum0 =
+		ip_csum_update (sum0, old_id0, new_id0, icmp_echo_header_t,
+				identifier /* changed member */ );
+	      icmp0->checksum = ip_csum_fold (sum0);
+	    }
+	}
+      else
+	{
+	  inner_ip0 = (ip4_header_t *) (echo0 + 1);
+	  l4_header = ip4_next_header (inner_ip0);
+
+	  if (!ip4_header_checksum_is_valid (inner_ip0))
+	    {
+	      next0 = DET44_OUT2IN_NEXT_DROP;
+	      goto out;
+	    }
+
+	  old_addr0 = inner_ip0->src_address.as_u32;
+	  inner_ip0->src_address = addr;
+	  new_addr0 = inner_ip0->src_address.as_u32;
+
+	  sum0 = icmp0->checksum;
+	  sum0 = ip_csum_update (sum0, old_addr0, new_addr0, ip4_header_t,
+				 src_address /* changed member */ );
+	  icmp0->checksum = ip_csum_fold (sum0);
+
+	  switch (proto)
+	    {
+	    case NAT_PROTOCOL_ICMP:
+	      inner_icmp0 = (icmp46_header_t *) l4_header;
+	      inner_echo0 = (icmp_echo_header_t *) (inner_icmp0 + 1);
+
+	      old_id0 = inner_echo0->identifier;
+	      new_id0 = port;
+	      inner_echo0->identifier = new_id0;
+
+	      sum0 = icmp0->checksum;
+	      sum0 =
+		ip_csum_update (sum0, old_id0, new_id0, icmp_echo_header_t,
+				identifier);
+	      icmp0->checksum = ip_csum_fold (sum0);
+	      break;
+	    case NAT_PROTOCOL_UDP:
+	    case NAT_PROTOCOL_TCP:
+	      old_id0 = ((tcp_udp_header_t *) l4_header)->src_port;
+	      new_id0 = port;
+	      ((tcp_udp_header_t *) l4_header)->src_port = new_id0;
+
+	      sum0 = icmp0->checksum;
+	      sum0 = ip_csum_update (sum0, old_id0, new_id0, tcp_udp_header_t,
+				     src_port);
+	      icmp0->checksum = ip_csum_fold (sum0);
+	      break;
+	    default:
+	      ASSERT (0);
+	    }
+	}
+    }
+
+out:
+  return next0;
+}
+#endif
+
+VLIB_NODE_FN (det44_out2in_node) (vlib_main_t * vm,
+				  vlib_node_runtime_t * node,
+				  vlib_frame_t * frame)
+{
+  u32 n_left_from, *from, *to_next;
+  det44_out2in_next_t next_index;
+  u32 pkts_processed = 0;
+  det44_main_t *dm = &det44_main;
+  u32 thread_index = vm->thread_index;
+
+  from = vlib_frame_vector_args (frame);
+  n_left_from = frame->n_vectors;
+  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 = DET44_OUT2IN_NEXT_LOOKUP;
+	  u32 next1 = DET44_OUT2IN_NEXT_LOOKUP;
+	  u32 sw_if_index0, sw_if_index1;
+	  ip4_header_t *ip0, *ip1;
+	  ip_csum_t sum0, sum1;
+	  ip4_address_t new_addr0, old_addr0, new_addr1, old_addr1;
+	  u16 new_port0, old_port0, old_port1, new_port1;
+	  udp_header_t *udp0, *udp1;
+	  tcp_header_t *tcp0, *tcp1;
+	  u32 proto0, proto1;
+	  snat_det_out_key_t key0, key1;
+	  snat_det_map_t *mp0, *mp1;
+	  snat_det_session_t *ses0 = 0, *ses1 = 0;
+	  u32 rx_fib_index0, rx_fib_index1;
+	  icmp46_header_t *icmp0, *icmp1;
+
+	  /* 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, LOAD);
+	    CLIB_PREFETCH (p3->data, CLIB_CACHE_LINE_BYTES, LOAD);
+	  }
+
+	  /* 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;
+
+	  sw_if_index0 = vnet_buffer (b0)->sw_if_index[VLIB_RX];
+
+	  if (PREDICT_FALSE (ip0->ttl == 1))
+	    {
+	      vnet_buffer (b0)->sw_if_index[VLIB_TX] = (u32) ~ 0;
+	      icmp4_error_set_vnet_buffer (b0, ICMP4_time_exceeded,
+					   ICMP4_time_exceeded_ttl_exceeded_in_transit,
+					   0);
+	      next0 = DET44_OUT2IN_NEXT_ICMP_ERROR;
+	      goto trace0;
+	    }
+
+	  proto0 = ip_proto_to_nat_proto (ip0->protocol);
+
+	  if (PREDICT_FALSE (proto0 == NAT_PROTOCOL_ICMP))
+	    {
+	      rx_fib_index0 =
+		ip4_fib_table_get_index_for_sw_if_index (sw_if_index0);
+	      icmp0 = (icmp46_header_t *) udp0;
+
+	      next0 = det44_icmp_out2in (b0, ip0, icmp0, sw_if_index0,
+					 rx_fib_index0, node, next0,
+					 thread_index, &ses0, &mp0);
+	      goto trace0;
+	    }
+
+	  key0.ext_host_addr = ip0->src_address;
+	  key0.ext_host_port = tcp0->src;
+	  key0.out_port = tcp0->dst;
+
+	  mp0 = snat_det_map_by_out (&ip0->dst_address);
+	  if (PREDICT_FALSE (!mp0))
+	    {
+	      det44_log_info ("unknown dst address:  %U",
+			      format_ip4_address, &ip0->dst_address);
+	      next0 = DET44_OUT2IN_NEXT_DROP;
+	      b0->error = node->errors[DET44_OUT2IN_ERROR_NO_TRANSLATION];
+	      goto trace0;
+	    }
+
+	  snat_det_reverse (mp0, &ip0->dst_address,
+			    clib_net_to_host_u16 (tcp0->dst), &new_addr0);
+
+	  ses0 = snat_det_get_ses_by_out (mp0, &new_addr0, key0.as_u64);
+	  if (PREDICT_FALSE (!ses0))
+	    {
+	      det44_log_info ("no match src %U:%d dst %U:%d for user %U",
+			      format_ip4_address, &ip0->src_address,
+			      clib_net_to_host_u16 (tcp0->src),
+			      format_ip4_address, &ip0->dst_address,
+			      clib_net_to_host_u16 (tcp0->dst),
+			      format_ip4_address, &new_addr0);
+	      next0 = DET44_OUT2IN_NEXT_DROP;
+	      b0->error = node->errors[DET44_OUT2IN_ERROR_NO_TRANSLATION];
+	      goto trace0;
+	    }
+	  old_port0 = udp0->dst_port;
+	  udp0->dst_port = new_port0 = ses0->in_port;
+
+	  old_addr0 = ip0->dst_address;
+	  ip0->dst_address = new_addr0;
+	  vnet_buffer (b0)->sw_if_index[VLIB_TX] = dm->inside_fib_index;
+
+	  sum0 = ip0->checksum;
+	  sum0 = ip_csum_update (sum0, old_addr0.as_u32, new_addr0.as_u32,
+				 ip4_header_t,
+				 dst_address /* changed member */ );
+	  ip0->checksum = ip_csum_fold (sum0);
+
+	  if (PREDICT_TRUE (proto0 == NAT_PROTOCOL_TCP))
+	    {
+	      if (tcp0->flags & TCP_FLAG_FIN
+		  && ses0->state == DET44_SESSION_TCP_ESTABLISHED)
+		ses0->state = DET44_SESSION_TCP_CLOSE_WAIT;
+	      else if (tcp0->flags & TCP_FLAG_ACK
+		       && ses0->state == DET44_SESSION_TCP_LAST_ACK)
+		snat_det_ses_close (mp0, ses0);
+
+	      sum0 = tcp0->checksum;
+	      sum0 = ip_csum_update (sum0, old_addr0.as_u32, new_addr0.as_u32,
+				     ip4_header_t,
+				     dst_address /* changed member */ );
+	      sum0 = ip_csum_update (sum0, old_port0, new_port0,
+				     ip4_header_t /* cheat */ ,
+				     length /* changed member */ );
+	      tcp0->checksum = ip_csum_fold (sum0);
+	    }
+	  else if (udp0->checksum)
+	    {
+	      sum0 = udp0->checksum;
+	      sum0 = ip_csum_update (sum0, old_addr0.as_u32, new_addr0.as_u32,
+				     ip4_header_t,
+				     dst_address /* changed member */ );
+	      sum0 = ip_csum_update (sum0, old_port0, new_port0,
+				     ip4_header_t /* cheat */ ,
+				     length /* changed member */ );
+	      udp0->checksum = ip_csum_fold (sum0);
+	    }
+
+	trace0:
+
+	  if (PREDICT_FALSE ((node->flags & VLIB_NODE_FLAG_TRACE)
+			     && (b0->flags & VLIB_BUFFER_IS_TRACED)))
+	    {
+	      det44_out2in_trace_t *t =
+		vlib_add_trace (vm, node, b0, sizeof (*t));
+	      t->sw_if_index = sw_if_index0;
+	      t->next_index = next0;
+	      t->session_index = ~0;
+	      if (ses0)
+		t->session_index = ses0 - mp0->sessions;
+	    }
+
+	  pkts_processed += next0 != DET44_OUT2IN_NEXT_DROP;
+
+	  b1 = vlib_get_buffer (vm, bi1);
+
+	  ip1 = vlib_buffer_get_current (b1);
+	  udp1 = ip4_next_header (ip1);
+	  tcp1 = (tcp_header_t *) udp1;
+
+	  sw_if_index1 = vnet_buffer (b1)->sw_if_index[VLIB_RX];
+
+	  if (PREDICT_FALSE (ip1->ttl == 1))
+	    {
+	      vnet_buffer (b1)->sw_if_index[VLIB_TX] = (u32) ~ 0;
+	      icmp4_error_set_vnet_buffer (b1, ICMP4_time_exceeded,
+					   ICMP4_time_exceeded_ttl_exceeded_in_transit,
+					   0);
+	      next1 = DET44_OUT2IN_NEXT_ICMP_ERROR;
+	      goto trace1;
+	    }
+
+	  proto1 = ip_proto_to_nat_proto (ip1->protocol);
+
+	  if (PREDICT_FALSE (proto1 == NAT_PROTOCOL_ICMP))
+	    {
+	      rx_fib_index1 =
+		ip4_fib_table_get_index_for_sw_if_index (sw_if_index1);
+	      icmp1 = (icmp46_header_t *) udp1;
+
+	      next1 = det44_icmp_out2in (b1, ip1, icmp1, sw_if_index1,
+					 rx_fib_index1, node, next1,
+					 thread_index, &ses1, &mp1);
+	      goto trace1;
+	    }
+
+	  key1.ext_host_addr = ip1->src_address;
+	  key1.ext_host_port = tcp1->src;
+	  key1.out_port = tcp1->dst;
+
+	  mp1 = snat_det_map_by_out (&ip1->dst_address);
+	  if (PREDICT_FALSE (!mp1))
+	    {
+	      det44_log_info ("unknown dst address:  %U",
+			      format_ip4_address, &ip1->dst_address);
+	      next1 = DET44_OUT2IN_NEXT_DROP;
+	      b1->error = node->errors[DET44_OUT2IN_ERROR_NO_TRANSLATION];
+	      goto trace1;
+	    }
+
+	  snat_det_reverse (mp1, &ip1->dst_address,
+			    clib_net_to_host_u16 (tcp1->dst), &new_addr1);
+
+	  ses1 = snat_det_get_ses_by_out (mp1, &new_addr1, key1.as_u64);
+	  if (PREDICT_FALSE (!ses1))
+	    {
+	      det44_log_info ("no match src %U:%d dst %U:%d for user %U",
+			      format_ip4_address, &ip1->src_address,
+			      clib_net_to_host_u16 (tcp1->src),
+			      format_ip4_address, &ip1->dst_address,
+			      clib_net_to_host_u16 (tcp1->dst),
+			      format_ip4_address, &new_addr1);
+	      next1 = DET44_OUT2IN_NEXT_DROP;
+	      b1->error = node->errors[DET44_OUT2IN_ERROR_NO_TRANSLATION];
+	      goto trace1;
+	    }
+	  old_port1 = udp1->dst_port;
+	  udp1->dst_port = new_port1 = ses1->in_port;
+
+	  old_addr1 = ip1->dst_address;
+	  ip1->dst_address = new_addr1;
+	  vnet_buffer (b1)->sw_if_index[VLIB_TX] = dm->inside_fib_index;
+
+	  sum1 = ip1->checksum;
+	  sum1 = ip_csum_update (sum1, old_addr1.as_u32, new_addr1.as_u32,
+				 ip4_header_t,
+				 dst_address /* changed member */ );
+	  ip1->checksum = ip_csum_fold (sum1);
+
+	  if (PREDICT_TRUE (proto1 == NAT_PROTOCOL_TCP))
+	    {
+	      if (tcp1->flags & TCP_FLAG_FIN
+		  && ses1->state == DET44_SESSION_TCP_ESTABLISHED)
+		ses1->state = DET44_SESSION_TCP_CLOSE_WAIT;
+	      else if (tcp1->flags & TCP_FLAG_ACK
+		       && ses1->state == DET44_SESSION_TCP_LAST_ACK)
+		snat_det_ses_close (mp1, ses1);
+
+	      sum1 = tcp1->checksum;
+	      sum1 = ip_csum_update (sum1, old_addr1.as_u32, new_addr1.as_u32,
+				     ip4_header_t,
+				     dst_address /* changed member */ );
+	      sum1 = ip_csum_update (sum1, old_port1, new_port1,
+				     ip4_header_t /* cheat */ ,
+				     length /* changed member */ );
+	      tcp1->checksum = ip_csum_fold (sum1);
+	    }
+	  else if (udp1->checksum)
+	    {
+	      sum1 = udp1->checksum;
+	      sum1 = ip_csum_update (sum1, old_addr1.as_u32, new_addr1.as_u32,
+				     ip4_header_t,
+				     dst_address /* changed member */ );
+	      sum1 = ip_csum_update (sum1, old_port1, new_port1,
+				     ip4_header_t /* cheat */ ,
+				     length /* changed member */ );
+	      udp1->checksum = ip_csum_fold (sum1);
+	    }
+
+	trace1:
+
+	  if (PREDICT_FALSE ((node->flags & VLIB_NODE_FLAG_TRACE)
+			     && (b1->flags & VLIB_BUFFER_IS_TRACED)))
+	    {
+	      det44_out2in_trace_t *t =
+		vlib_add_trace (vm, node, b1, sizeof (*t));
+	      t->sw_if_index = sw_if_index1;
+	      t->next_index = next1;
+	      t->session_index = ~0;
+	      if (ses1)
+		t->session_index = ses1 - mp1->sessions;
+	    }
+
+	  pkts_processed += next1 != DET44_OUT2IN_NEXT_DROP;
+
+	  /* 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 = DET44_OUT2IN_NEXT_LOOKUP;
+	  u32 sw_if_index0;
+	  ip4_header_t *ip0;
+	  ip_csum_t sum0;
+	  ip4_address_t new_addr0, old_addr0;
+	  u16 new_port0, old_port0;
+	  udp_header_t *udp0;
+	  tcp_header_t *tcp0;
+	  u32 proto0;
+	  snat_det_out_key_t key0;
+	  snat_det_map_t *mp0;
+	  snat_det_session_t *ses0 = 0;
+	  u32 rx_fib_index0;
+	  icmp46_header_t *icmp0;
+
+	  /* 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);
+
+	  ip0 = vlib_buffer_get_current (b0);
+	  udp0 = ip4_next_header (ip0);
+	  tcp0 = (tcp_header_t *) udp0;
+
+	  sw_if_index0 = vnet_buffer (b0)->sw_if_index[VLIB_RX];
+
+	  if (PREDICT_FALSE (ip0->ttl == 1))
+	    {
+	      vnet_buffer (b0)->sw_if_index[VLIB_TX] = (u32) ~ 0;
+	      icmp4_error_set_vnet_buffer (b0, ICMP4_time_exceeded,
+					   ICMP4_time_exceeded_ttl_exceeded_in_transit,
+					   0);
+	      next0 = DET44_OUT2IN_NEXT_ICMP_ERROR;
+	      goto trace00;
+	    }
+
+	  proto0 = ip_proto_to_nat_proto (ip0->protocol);
+
+	  if (PREDICT_FALSE (proto0 == NAT_PROTOCOL_ICMP))
+	    {
+	      rx_fib_index0 =
+		ip4_fib_table_get_index_for_sw_if_index (sw_if_index0);
+	      icmp0 = (icmp46_header_t *) udp0;
+
+	      next0 = det44_icmp_out2in (b0, ip0, icmp0, sw_if_index0,
+					 rx_fib_index0, node, next0,
+					 thread_index, &ses0, &mp0);
+	      goto trace00;
+	    }
+
+	  key0.ext_host_addr = ip0->src_address;
+	  key0.ext_host_port = tcp0->src;
+	  key0.out_port = tcp0->dst;
+
+	  mp0 = snat_det_map_by_out (&ip0->dst_address);
+	  if (PREDICT_FALSE (!mp0))
+	    {
+	      det44_log_info ("unknown dst address:  %U",
+			      format_ip4_address, &ip0->dst_address);
+	      next0 = DET44_OUT2IN_NEXT_DROP;
+	      b0->error = node->errors[DET44_OUT2IN_ERROR_NO_TRANSLATION];
+	      goto trace00;
+	    }
+
+	  snat_det_reverse (mp0, &ip0->dst_address,
+			    clib_net_to_host_u16 (tcp0->dst), &new_addr0);
+
+	  ses0 = snat_det_get_ses_by_out (mp0, &new_addr0, key0.as_u64);
+	  if (PREDICT_FALSE (!ses0))
+	    {
+	      det44_log_info ("no match src %U:%d dst %U:%d for user %U",
+			      format_ip4_address, &ip0->src_address,
+			      clib_net_to_host_u16 (tcp0->src),
+			      format_ip4_address, &ip0->dst_address,
+			      clib_net_to_host_u16 (tcp0->dst),
+			      format_ip4_address, &new_addr0);
+	      next0 = DET44_OUT2IN_NEXT_DROP;
+	      b0->error = node->errors[DET44_OUT2IN_ERROR_NO_TRANSLATION];
+	      goto trace00;
+	    }
+	  old_port0 = udp0->dst_port;
+	  udp0->dst_port = new_port0 = ses0->in_port;
+
+	  old_addr0 = ip0->dst_address;
+	  ip0->dst_address = new_addr0;
+	  vnet_buffer (b0)->sw_if_index[VLIB_TX] = dm->inside_fib_index;
+
+	  sum0 = ip0->checksum;
+	  sum0 = ip_csum_update (sum0, old_addr0.as_u32, new_addr0.as_u32,
+				 ip4_header_t,
+				 dst_address /* changed member */ );
+	  ip0->checksum = ip_csum_fold (sum0);
+
+	  if (PREDICT_TRUE (proto0 == NAT_PROTOCOL_TCP))
+	    {
+	      if (tcp0->flags & TCP_FLAG_FIN
+		  && ses0->state == DET44_SESSION_TCP_ESTABLISHED)
+		ses0->state = DET44_SESSION_TCP_CLOSE_WAIT;
+	      else if (tcp0->flags & TCP_FLAG_ACK
+		       && ses0->state == DET44_SESSION_TCP_LAST_ACK)
+		snat_det_ses_close (mp0, ses0);
+
+	      sum0 = tcp0->checksum;
+	      sum0 = ip_csum_update (sum0, old_addr0.as_u32, new_addr0.as_u32,
+				     ip4_header_t,
+				     dst_address /* changed member */ );
+	      sum0 = ip_csum_update (sum0, old_port0, new_port0,
+				     ip4_header_t /* cheat */ ,
+				     length /* changed member */ );
+	      tcp0->checksum = ip_csum_fold (sum0);
+	    }
+	  else if (udp0->checksum)
+	    {
+	      sum0 = udp0->checksum;
+	      sum0 = ip_csum_update (sum0, old_addr0.as_u32, new_addr0.as_u32,
+				     ip4_header_t,
+				     dst_address /* changed member */ );
+	      sum0 = ip_csum_update (sum0, old_port0, new_port0,
+				     ip4_header_t /* cheat */ ,
+				     length /* changed member */ );
+	      udp0->checksum = ip_csum_fold (sum0);
+	    }
+
+	trace00:
+
+	  if (PREDICT_FALSE ((node->flags & VLIB_NODE_FLAG_TRACE)
+			     && (b0->flags & VLIB_BUFFER_IS_TRACED)))
+	    {
+	      det44_out2in_trace_t *t =
+		vlib_add_trace (vm, node, b0, sizeof (*t));
+	      t->sw_if_index = sw_if_index0;
+	      t->next_index = next0;
+	      t->session_index = ~0;
+	      if (ses0)
+		t->session_index = ses0 - mp0->sessions;
+	    }
+
+	  pkts_processed += next0 != DET44_OUT2IN_NEXT_DROP;
+
+	  /* 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, dm->out2in_node_index,
+			       DET44_OUT2IN_ERROR_OUT2IN_PACKETS,
+			       pkts_processed);
+  return frame->n_vectors;
+}
+
+/* *INDENT-OFF* */
+VLIB_REGISTER_NODE (det44_out2in_node) = {
+  .name = "det44-out2in",
+  .vector_size = sizeof (u32),
+  .format_trace = format_det44_out2in_trace,
+  .type = VLIB_NODE_TYPE_INTERNAL,
+  .n_errors = ARRAY_LEN(det44_out2in_error_strings),
+  .error_strings = det44_out2in_error_strings,
+  .runtime_data_bytes = sizeof (det44_runtime_t),
+  .n_next_nodes = DET44_OUT2IN_N_NEXT,
+  /* edit / add dispositions here */
+  .next_nodes = {
+    [DET44_OUT2IN_NEXT_DROP] = "error-drop",
+    [DET44_OUT2IN_NEXT_LOOKUP] = "ip4-lookup",
+    [DET44_OUT2IN_NEXT_ICMP_ERROR] = "ip4-icmp-error",
+  },
+};
+/* *INDENT-ON* */
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */