ipv6 connection tracking plugin

A security feature: drop unsolicited global unicast traffic.

Change-Id: I421da7d52e08b7acf40c62a1f6e2a6caac349e7e
Signed-off-by: Dave Barach <dave@barachs.net>

9 files changed, 1706 insertions, 0 deletions

diff --git a/src/plugins/ct6/CMakeLists.txt b/src/plugins/ct6/CMakeLists.txt
new file mode 100644
index 00000000000..069b33ad2d0
--- /dev/null
+++ b/src/plugins/ct6/CMakeLists.txt
@@ -0,0 +1,35 @@
+
+# Copyright (c) <current-year> <your-organization>
+# 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.
+
+add_vpp_plugin(ct6
+  SOURCES
+  ct6.c
+  ct6_in2out.c
+  ct6_out2in.c
+  ct6.h
+
+  MULTIARCH_SOURCES
+  ct6_in2out.c
+  ct6_out2in.c
+
+  API_FILES
+  ct6.api
+
+  INSTALL_HEADERS
+  ct6_all_api_h.h
+  ct6_msg_enum.h
+
+  API_TEST_SOURCES
+  ct6_test.c
+)
diff --git a/src/plugins/ct6/ct6.api b/src/plugins/ct6/ct6.api
new file mode 100644
index 00000000000..67af42fd9fe
--- /dev/null
+++ b/src/plugins/ct6/ct6.api
@@ -0,0 +1,27 @@
+
+/* Define a simple enable-disable binary API to control the feature */
+
+define ct6_enable_disable {
+    /* Client identifier, set from api_main.my_client_index */
+    u32 client_index;
+
+    /* Arbitrary context, so client can match reply to request */
+    u32 context;
+
+    /* Enable / disable the feature */
+    u8 enable_disable;
+
+    /* Inside or outside interface */
+    u8 is_inside;
+
+    /* Interface handle */
+    u32 sw_if_index;
+};
+
+define ct6_enable_disable_reply {
+    /* From the request */
+    u32 context;
+
+    /* Return value, zero means all OK */
+    i32 retval;
+};
diff --git a/src/plugins/ct6/ct6.c b/src/plugins/ct6/ct6.c
new file mode 100644
index 00000000000..f0ad67a80c9
--- /dev/null
+++ b/src/plugins/ct6/ct6.c
@@ -0,0 +1,573 @@
+/*
+ * ct6.c - skeleton vpp engine plug-in
+ *
+ * Copyright (c) <current-year> <your-organization>
+ * 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 <vnet/vnet.h>
+#include <vnet/plugin/plugin.h>
+#include <ct6/ct6.h>
+
+#include <vlibapi/api.h>
+#include <vlibmemory/api.h>
+#include <vpp/app/version.h>
+
+/* define message IDs */
+#include <ct6/ct6_msg_enum.h>
+
+/* define message structures */
+#define vl_typedefs
+#include <ct6/ct6_all_api_h.h>
+#undef vl_typedefs
+
+/* define generated endian-swappers */
+#define vl_endianfun
+#include <ct6/ct6_all_api_h.h>
+#undef vl_endianfun
+
+/* instantiate all the print functions we know about */
+#define vl_print(handle, ...) vlib_cli_output (handle, __VA_ARGS__)
+#define vl_printfun
+#include <ct6/ct6_all_api_h.h>
+#undef vl_printfun
+
+/* Get the API version number */
+#define vl_api_version(n,v) static u32 api_version=(v);
+#include <ct6/ct6_all_api_h.h>
+#undef vl_api_version
+
+#define REPLY_MSG_ID_BASE cmp->msg_id_base
+#include <vlibapi/api_helper_macros.h>
+
+ct6_main_t ct6_main;
+
+/* List of message types that this plugin understands */
+
+#define foreach_ct6_plugin_api_msg                           \
+_(CT6_ENABLE_DISABLE, ct6_enable_disable)
+
+/* Action function shared between message handler and debug CLI */
+
+static void
+ct6_feature_init (ct6_main_t * cmp)
+{
+  u32 nworkers = vlib_num_workers ();
+
+  if (cmp->feature_initialized)
+    return;
+
+  clib_bihash_init_48_8 (&cmp->session_hash, "ct6 session table",
+			 cmp->session_hash_buckets, cmp->session_hash_memory);
+  cmp->feature_initialized = 1;
+  vec_validate (cmp->sessions, nworkers);
+  vec_validate_init_empty (cmp->first_index, nworkers, ~0);
+  vec_validate_init_empty (cmp->last_index, nworkers, ~0);
+}
+
+int
+ct6_in2out_enable_disable (ct6_main_t * cmp, u32 sw_if_index,
+			   int enable_disable)
+{
+  vnet_sw_interface_t *sw;
+  int rv = 0;
+
+  ct6_feature_init (cmp);
+
+  /* Utterly wrong? */
+  if (pool_is_free_index (cmp->vnet_main->interface_main.sw_interfaces,
+			  sw_if_index))
+    return VNET_API_ERROR_INVALID_SW_IF_INDEX;
+
+  /* Not a physical port? */
+  sw = vnet_get_sw_interface (cmp->vnet_main, sw_if_index);
+  if (sw->type != VNET_SW_INTERFACE_TYPE_HARDWARE)
+    return VNET_API_ERROR_INVALID_SW_IF_INDEX;
+
+  vnet_feature_enable_disable ("interface-output", "ct6-in2out",
+			       sw_if_index, enable_disable, 0, 0);
+
+  return rv;
+}
+
+int
+ct6_out2in_enable_disable (ct6_main_t * cmp, u32 sw_if_index,
+			   int enable_disable)
+{
+  vnet_sw_interface_t *sw;
+  int rv = 0;
+
+  ct6_feature_init (cmp);
+
+  /* Utterly wrong? */
+  if (pool_is_free_index (cmp->vnet_main->interface_main.sw_interfaces,
+			  sw_if_index))
+    return VNET_API_ERROR_INVALID_SW_IF_INDEX;
+
+  /* Not a physical port? */
+  sw = vnet_get_sw_interface (cmp->vnet_main, sw_if_index);
+  if (sw->type != VNET_SW_INTERFACE_TYPE_HARDWARE)
+    return VNET_API_ERROR_INVALID_SW_IF_INDEX;
+
+  vnet_feature_enable_disable ("ip6-unicast", "ct6-out2in",
+			       sw_if_index, enable_disable, 0, 0);
+
+  return rv;
+}
+
+static clib_error_t *
+set_ct6_enable_disable_command_fn (vlib_main_t * vm,
+				   unformat_input_t * input,
+				   vlib_cli_command_t * cmd)
+{
+  ct6_main_t *cmp = &ct6_main;
+  u32 sw_if_index = ~0;
+  int enable_disable = 1;
+  u32 inside = ~0;
+  int rv;
+
+  while (unformat_check_input (input) != UNFORMAT_END_OF_INPUT)
+    {
+      if (unformat (input, "disable"))
+	enable_disable = 0;
+      else if (unformat (input, "%U", unformat_vnet_sw_interface,
+			 cmp->vnet_main, &sw_if_index))
+	;
+      else if (unformat (input, "inside") || unformat (input, "in"))
+	inside = 1;
+      else if (unformat (input, "outside") || unformat (input, "out"))
+	inside = 0;
+      else
+	break;
+    }
+
+  if (inside == ~0)
+    return clib_error_return (0, "Please specify inside or outside");
+
+  if (sw_if_index == ~0)
+    return clib_error_return (0, "Please specify an interface...");
+
+  if (inside == 1)
+    rv = ct6_in2out_enable_disable (cmp, sw_if_index, enable_disable);
+  else
+    rv = ct6_out2in_enable_disable (cmp, sw_if_index, enable_disable);
+
+  switch (rv)
+    {
+    case 0:
+      break;
+
+    case VNET_API_ERROR_INVALID_SW_IF_INDEX:
+      return clib_error_return
+	(0, "Invalid interface, only works on physical ports");
+      break;
+
+    default:
+      return clib_error_return (0, "ct6_enable_disable returned %d", rv);
+    }
+  return 0;
+}
+
+/* *INDENT-OFF* */
+VLIB_CLI_COMMAND (set_ct6_command, static) =
+{
+  .path = "set ct6",
+  .short_help =
+  "set ct6 [inside|outside] <interface-name> [disable]",
+  .function = set_ct6_enable_disable_command_fn,
+};
+/* *INDENT-ON* */
+
+/* API message handler */
+static void vl_api_ct6_enable_disable_t_handler
+  (vl_api_ct6_enable_disable_t * mp)
+{
+  vl_api_ct6_enable_disable_reply_t *rmp;
+  ct6_main_t *cmp = &ct6_main;
+  int rv;
+
+  if (mp->is_inside)
+    rv = ct6_in2out_enable_disable (cmp, ntohl (mp->sw_if_index),
+				    (int) (mp->enable_disable));
+  else
+    rv = ct6_out2in_enable_disable (cmp, ntohl (mp->sw_if_index),
+				    (int) (mp->enable_disable));
+
+  REPLY_MACRO (VL_API_CT6_ENABLE_DISABLE_REPLY);
+}
+
+/* Set up the API message handling tables */
+static clib_error_t *
+ct6_plugin_api_hookup (vlib_main_t * vm)
+{
+  ct6_main_t *cmp = &ct6_main;
+#define _(N,n)                                                  \
+    vl_msg_api_set_handlers((VL_API_##N + cmp->msg_id_base),     \
+                           #n,					\
+                           vl_api_##n##_t_handler,              \
+                           vl_noop_handler,                     \
+                           vl_api_##n##_t_endian,               \
+                           vl_api_##n##_t_print,                \
+                           sizeof(vl_api_##n##_t), 1);
+  foreach_ct6_plugin_api_msg;
+#undef _
+
+  return 0;
+}
+
+#define vl_msg_name_crc_list
+#include <ct6/ct6_all_api_h.h>
+#undef vl_msg_name_crc_list
+
+static void
+setup_message_id_table (ct6_main_t * cmp, api_main_t * am)
+{
+#define _(id,n,crc)   vl_msg_api_add_msg_name_crc (am, #n  #crc, id + cmp->msg_id_base);
+  foreach_vl_msg_name_crc_ct6;
+#undef _
+}
+
+static clib_error_t *
+ct6_init (vlib_main_t * vm)
+{
+  ct6_main_t *cmp = &ct6_main;
+  clib_error_t *error = 0;
+  u8 *name;
+
+  cmp->vlib_main = vm;
+  cmp->vnet_main = vnet_get_main ();
+
+  name = format (0, "ct6_%08x%c", api_version, 0);
+
+  /* Ask for a correctly-sized block of API message decode slots */
+  cmp->msg_id_base = vl_msg_api_get_msg_ids
+    ((char *) name, VL_MSG_FIRST_AVAILABLE);
+
+  error = ct6_plugin_api_hookup (vm);
+
+  /* Add our API messages to the global name_crc hash table */
+  setup_message_id_table (cmp, &api_main);
+
+  vec_free (name);
+
+  /*
+   * Set default parameters...
+   * 256K sessions
+   * 64K buckets
+   * 2 minute inactivity timer
+   * 10000 concurrent sessions
+   */
+  cmp->session_hash_memory = 16ULL << 20;
+  cmp->session_hash_buckets = 64 << 10;
+  cmp->session_timeout_interval = 120.0;
+  cmp->max_sessions_per_worker = 10000;
+
+  /* ... so the packet generator can feed the in2out node ... */
+  ethernet_setup_node (vm, ct6_in2out_node.index);
+  return error;
+}
+
+VLIB_INIT_FUNCTION (ct6_init);
+
+/* *INDENT-OFF* */
+VNET_FEATURE_INIT (ct6out2in, static) =
+{
+  .arc_name = "ip6-unicast",
+  .node_name = "ct6-out2in",
+  .runs_before = VNET_FEATURES ("ip6-lookup"),
+};
+/* *INDENT-ON */
+
+/* *INDENT-OFF* */
+VNET_FEATURE_INIT (ct6in2out, static) =
+{
+  .arc_name = "interface-output",
+  .node_name = "ct6-in2out",
+  .runs_before = VNET_FEATURES ("interface-output"),
+};
+/* *INDENT-ON */
+
+/* *INDENT-OFF* */
+VLIB_PLUGIN_REGISTER () =
+{
+  .version = VPP_BUILD_VER,
+  .description = "ipv6 connection tracker",
+};
+/* *INDENT-ON* */
+
+u8 *
+format_ct6_session (u8 * s, va_list * args)
+{
+  ct6_main_t *cmp = va_arg (*args, ct6_main_t *);
+  int i = va_arg (*args, int);
+  ct6_session_t *s0 = va_arg (*args, ct6_session_t *);
+  int verbose = va_arg (*args, int);
+  clib_bihash_kv_48_8_t kvp0;
+
+  if (s0 == 0)
+    {
+      s = format (s, "\n%6s%6s%20s%6s%20s%6s",
+		  "Sess", "Prot", "Src", "Sport", "Dst", "Dport");
+      return s;
+    }
+
+  s = format (s, "\n%6d%6d%20U%6u%20U%6u",
+	      s0 - cmp->sessions[i], s0->key.proto,
+	      format_ip6_address, &s0->key.src,
+	      clib_net_to_host_u16 (s0->key.sport),
+	      format_ip6_address, &s0->key.dst,
+	      clib_net_to_host_u16 (s0->key.dport));
+
+  clib_memcpy_fast (&kvp0, s0, sizeof (ct6_session_key_t));
+
+  if (clib_bihash_search_48_8 (&cmp->session_hash, &kvp0, &kvp0) < 0)
+    {
+      s = format (s, " LOOKUP FAIL!");
+    }
+  else
+    {
+      if (kvp0.value == s0 - cmp->sessions[s0->thread_index])
+	{
+	  s = format (s, " OK");
+	  if (verbose > 1)
+	    {
+	      s = format (s, " next %d prev %d", s0->next_index,
+			  s0->prev_index);
+	      s = format (s, " hits %d expires %.2f", s0->hits, s0->expires);
+	    }
+	}
+      else
+	s = format (s, " BOGUS LOOKUP RESULT!");
+    }
+
+  return s;
+}
+
+static clib_error_t *
+show_ct6_command_fn_command_fn (vlib_main_t * vm,
+				unformat_input_t * input,
+				vlib_cli_command_t * cmd)
+{
+  ct6_main_t *cmp = &ct6_main;
+  ct6_session_t *s0;
+  int verbose = 0;
+  u8 *s = 0;
+  int i;
+
+  if (!cmp->feature_initialized)
+    return clib_error_return (0, "ip6 connection tracking not enabled...");
+
+  if (unformat (input, "verbose %d", &verbose))
+    ;
+  else if (unformat (input, "verbose"))
+    verbose = 1;
+
+  for (i = 0; i < vec_len (cmp->sessions); i++)
+    {
+      s = format (s, "Thread %d: %d sessions\n", i,
+		  pool_elts (cmp->sessions[i]));
+
+      if (verbose == 0)
+	continue;
+
+      s =
+	format (s, "%U", format_ct6_session, cmp,
+		0 /* pool */ , 0 /* header */ , verbose);
+
+      /* *INDENT-OFF* */
+      pool_foreach (s0, cmp->sessions[i],
+      ({
+        s = format (s, "%U", format_ct6_session, cmp, i, s0, verbose);
+      }));
+      /* *INDENT-ON* */
+    }
+  vlib_cli_output (cmp->vlib_main, "%v", s);
+  vec_free (s);
+  return 0;
+}
+
+/* *INDENT-OFF* */
+VLIB_CLI_COMMAND (show_ct6_command_fn_command, static) =
+{
+  .path = "show ip6 connection-tracker",
+  .short_help = "show ip6 connection-tracker",
+  .function = show_ct6_command_fn_command_fn,
+};
+/* *INDENT-ON* */
+
+static void
+increment_v6_address (ip6_address_t * a)
+{
+  u64 v0, v1;
+
+  v0 = clib_net_to_host_u64 (a->as_u64[0]);
+  v1 = clib_net_to_host_u64 (a->as_u64[1]);
+
+  v1 += 1;
+  if (v1 == 0)
+    v0 += 1;
+  a->as_u64[0] = clib_net_to_host_u64 (v0);
+  a->as_u64[1] = clib_net_to_host_u64 (v1);
+}
+
+
+static clib_error_t *
+test_ct6_command_fn_command_fn (vlib_main_t * vm,
+				unformat_input_t * input,
+				vlib_cli_command_t * cmd)
+{
+  ct6_main_t *cmp = &ct6_main;
+  clib_bihash_kv_48_8_t kvp0;
+  ct6_session_key_t *key0;
+  ct6_session_t *s0;
+  u8 src[16], dst[16];
+  u32 recycled = 0, created = 0;
+  int i, num_sessions = 5;
+  u32 midpt_index;
+  u8 *s = 0;
+
+  cmp->max_sessions_per_worker = 4;
+
+  while (unformat_check_input (input) != UNFORMAT_END_OF_INPUT)
+    {
+      if (unformat (input, "num-sessions %d", &num_sessions))
+	;
+      else
+	if (unformat
+	    (input, "max-sessions %d", &cmp->max_sessions_per_worker))
+	;
+      else
+	break;
+    }
+
+  ct6_feature_init (cmp);
+
+  /* Set up starting src/dst addresses */
+  memset (src, 0, sizeof (src));
+  memset (dst, 0, sizeof (dst));
+
+  src[0] = 0xdb;
+  dst[0] = 0xbe;
+
+  src[15] = 1;
+  dst[15] = 1;
+
+  /*
+   * See if we know about this flow.
+   * Key set up for the out2in path, the performant case
+   */
+  key0 = (ct6_session_key_t *) & kvp0;
+  memset (&kvp0, 0, sizeof (kvp0));
+
+  for (i = 0; i < num_sessions; i++)
+    {
+      clib_memcpy_fast (&key0->src, src, sizeof (src));
+      clib_memcpy_fast (&key0->dst, dst, sizeof (dst));
+      key0->as_u64[4] = 0;
+      key0->as_u64[5] = 0;
+      key0->sport = clib_host_to_net_u16 (1234);
+      key0->dport = clib_host_to_net_u16 (4321);
+      key0->proto = 17;		/* udp, fwiw */
+
+      s0 = ct6_create_or_recycle_session
+	(cmp, &kvp0, 3.0 /* now */ , 0 /* thread index */ ,
+	 &recycled, &created);
+
+      s = format (s, "%U (%d, %d)", format_ct6_session, cmp,
+		  0 /* thread index */ , s0, 1 /* verbose */ ,
+		  recycled, created);
+      vlib_cli_output (vm, "%v", s);
+      vec_free (s);
+      increment_v6_address ((ip6_address_t *) src);
+      recycled = 0;
+      created = 0;
+    }
+
+  /* *INDENT-OFF* */
+  pool_foreach (s0, cmp->sessions[0],
+  ({
+    s = format (s, "%U", format_ct6_session, cmp, 0, s0, 1 /* verbose */);
+  }));
+  /* *INDENT-ON* */
+
+  vlib_cli_output (vm, "\nEnd state: first index %d last index %d\n%v",
+		   cmp->first_index[0], cmp->last_index[0], s);
+
+  vec_free (s);
+
+  midpt_index = cmp->max_sessions_per_worker / 3;
+
+  s0 = pool_elt_at_index (cmp->sessions[0], midpt_index);
+  vlib_cli_output (vm, "\nSimulate LRU hit on session %d",
+		   s0 - cmp->sessions[0]);
+
+  ct6_update_session_hit (cmp, s0, 234.0);
+
+  /* *INDENT-OFF* */
+  pool_foreach (s0, cmp->sessions[0],
+  ({
+    s = format (s, "%U", format_ct6_session, cmp, 0, s0, 1 /* verbose */);
+  }));
+  /* *INDENT-ON* */
+
+  vlib_cli_output (vm, "\nEnd state: first index %d last index %d\n%v",
+		   cmp->first_index[0], cmp->last_index[0], s);
+
+  vec_free (s);
+
+  return 0;
+}
+
+/* *INDENT-OFF* */
+VLIB_CLI_COMMAND (test_ct6_command_fn_command, static) =
+{
+  .path = "test ip6 connection-tracker",
+  .short_help = "test ip6 connection-tracker",
+  .function = test_ct6_command_fn_command_fn,
+};
+/* *INDENT-ON* */
+
+static clib_error_t *
+ct6_config (vlib_main_t * vm, unformat_input_t * input)
+{
+  ct6_main_t *cmp = &ct6_main;
+
+  while (unformat_check_input (input) != UNFORMAT_END_OF_INPUT)
+    {
+      if (unformat (input, "session-hash-buckets %u",
+		    &cmp->session_hash_buckets))
+	;
+      else if (unformat (input, "session-hash-memory %U",
+			 unformat_memory_size, &cmp->session_hash_memory))
+	;
+      else if (unformat (input, "session-timeout %f",
+			 &cmp->session_timeout_interval))
+	;
+      else
+	{
+	  return clib_error_return (0, "unknown input '%U'",
+				    format_unformat_error, input);
+	}
+    }
+  return 0;
+}
+
+VLIB_CONFIG_FUNCTION (ct6_config, "ct6");
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */
diff --git a/src/plugins/ct6/ct6.h b/src/plugins/ct6/ct6.h
new file mode 100644
index 00000000000..534534f5c99
--- /dev/null
+++ b/src/plugins/ct6/ct6.h
@@ -0,0 +1,179 @@
+
+/*
+ * ct6.h - skeleton vpp engine plug-in header file
+ *
+ * Copyright (c) <current-year> <your-organization>
+ * 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.
+ */
+#ifndef __included_ct6_h__
+#define __included_ct6_h__
+
+#include <vnet/vnet.h>
+#include <vnet/ip/ip.h>
+#include <vnet/ethernet/ethernet.h>
+#include <vppinfra/bihash_48_8.h>
+
+#include <vppinfra/hash.h>
+#include <vppinfra/error.h>
+
+/* *INDENT-OFF* */
+typedef CLIB_PACKED (struct
+{
+  union
+  {
+    struct
+    {
+      /* out2in */
+      ip6_address_t src;
+      ip6_address_t dst;
+      u16 sport;
+      u16 dport;
+      u8 proto; /* byte 37 */
+    };
+    u64 as_u64[6];
+  };
+}) ct6_session_key_t;
+/* *INDENT-ON* */
+
+typedef struct
+{
+  ct6_session_key_t key;
+  u32 thread_index;
+  u32 next_index;
+  u32 prev_index;
+  u32 hits;
+  f64 expires;
+} ct6_session_t;
+
+typedef struct
+{
+  /* API message ID base */
+  u16 msg_id_base;
+
+  /* session lookup table */
+  clib_bihash_48_8_t session_hash;
+  u8 feature_initialized;
+
+  /* per_thread session pools */
+  ct6_session_t **sessions;
+  u32 *first_index;
+  u32 *last_index;
+
+  /* Config parameters */
+  f64 session_timeout_interval;
+  uword session_hash_memory;
+  u32 session_hash_buckets;
+  u32 max_sessions_per_worker;
+
+  /* convenience */
+  vlib_main_t *vlib_main;
+  vnet_main_t *vnet_main;
+  ethernet_main_t *ethernet_main;
+} ct6_main_t;
+
+extern ct6_main_t ct6_main;
+
+extern vlib_node_registration_t ct6_out2in_node;
+extern vlib_node_registration_t ct6_in2out_node;
+
+format_function_t format_ct6_session;
+
+ct6_session_t *ct6_create_or_recycle_session (ct6_main_t * cmp,
+					      clib_bihash_kv_48_8_t * kvpp,
+					      f64 now, u32 my_thread_index,
+					      u32 * recyclep, u32 * createp);
+
+static inline void
+ct6_lru_remove (ct6_main_t * cmp, ct6_session_t * s0)
+{
+  ct6_session_t *next_sess, *prev_sess;
+  u32 thread_index;
+  u32 s0_index;
+
+  thread_index = s0->thread_index;
+
+  s0_index = s0 - cmp->sessions[thread_index];
+
+  /* Deal with list heads */
+  if (s0_index == cmp->first_index[thread_index])
+    cmp->first_index[thread_index] = s0->next_index;
+  if (s0_index == cmp->last_index[thread_index])
+    cmp->last_index[thread_index] = s0->prev_index;
+
+  /* Fix next->prev */
+  if (s0->next_index != ~0)
+    {
+      next_sess = pool_elt_at_index (cmp->sessions[thread_index],
+				     s0->next_index);
+      next_sess->prev_index = s0->prev_index;
+    }
+  /* Fix prev->next */
+  if (s0->prev_index != ~0)
+    {
+      prev_sess = pool_elt_at_index (cmp->sessions[thread_index],
+				     s0->prev_index);
+      prev_sess->next_index = s0->next_index;
+    }
+}
+
+static inline void
+ct6_lru_add (ct6_main_t * cmp, ct6_session_t * s0, f64 now)
+{
+  ct6_session_t *next_sess;
+  u32 thread_index;
+  u32 s0_index;
+
+  s0->hits++;
+  s0->expires = now + cmp->session_timeout_interval;
+  thread_index = s0->thread_index;
+
+  s0_index = s0 - cmp->sessions[thread_index];
+
+  /*
+   * Re-add at the head of the forward LRU list,
+   * tail of the reverse LRU list
+   */
+  if (cmp->first_index[thread_index] != ~0)
+    {
+      next_sess = pool_elt_at_index (cmp->sessions[thread_index],
+				     cmp->first_index[thread_index]);
+      next_sess->prev_index = s0_index;
+    }
+
+  s0->prev_index = ~0;
+
+  /* s0 now the new head of the LRU forward list */
+  s0->next_index = cmp->first_index[thread_index];
+  cmp->first_index[thread_index] = s0_index;
+
+  /* single session case: also the tail of the reverse LRU list */
+  if (cmp->last_index[thread_index] == ~0)
+    cmp->last_index[thread_index] = s0_index;
+}
+
+static inline void
+ct6_update_session_hit (ct6_main_t * cmp, ct6_session_t * s0, f64 now)
+{
+  ct6_lru_remove (cmp, s0);
+  ct6_lru_add (cmp, s0, now);
+}
+
+#endif /* __included_ct6_h__ */
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */
diff --git a/src/plugins/ct6/ct6_all_api_h.h b/src/plugins/ct6/ct6_all_api_h.h
new file mode 100644
index 00000000000..3642216cefa
--- /dev/null
+++ b/src/plugins/ct6/ct6_all_api_h.h
@@ -0,0 +1,19 @@
+
+/*
+ * ct6_all_api_h.h - skeleton vpp engine plug-in api #include file
+ *
+ * Copyright (c) <current-year> <your-organization>
+ * 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 the generated file, see BUILT_SOURCES in Makefile.am */
+#include <ct6/ct6.api.h>
diff --git a/src/plugins/ct6/ct6_in2out.c b/src/plugins/ct6/ct6_in2out.c
new file mode 100644
index 00000000000..b28d349dd29
--- /dev/null
+++ b/src/plugins/ct6/ct6_in2out.c
@@ -0,0 +1,362 @@
+/*
+ * ct6_in2out.c - ip6 connection tracker, inside-to-outside path
+ *
+ * Copyright (c) 2019 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 <vppinfra/error.h>
+#include <ct6/ct6.h>
+
+typedef struct
+{
+  u32 sw_if_index;
+  u32 next_index;
+  u32 session_index;
+} ct6_in2out_trace_t;
+
+#ifndef CLIB_MARCH_VARIANT
+
+/* packet trace format function */
+static u8 *
+format_ct6_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 *);
+  ct6_in2out_trace_t *t = va_arg (*args, ct6_in2out_trace_t *);
+
+  s = format (s, "CT6_IN2OUT: sw_if_index %d, next index %d session %d\n",
+	      t->sw_if_index, t->next_index, t->session_index);
+  return s;
+}
+
+vlib_node_registration_t ct6_in2out_node;
+
+#endif /* CLIB_MARCH_VARIANT */
+
+#define foreach_ct6_in2out_error                \
+_(PROCESSED, "ct6 packets processed")           \
+_(CREATED, "ct6 sessions created")              \
+_(RECYCLED, "ct6 sessions recycled")
+
+typedef enum
+{
+#define _(sym,str) CT6_IN2OUT_ERROR_##sym,
+  foreach_ct6_in2out_error
+#undef _
+    CT6_IN2OUT_N_ERROR,
+} ct6_in2out_error_t;
+
+#ifndef CLIB_MARCH_VARIANT
+static char *ct6_in2out_error_strings[] = {
+#define _(sym,string) string,
+  foreach_ct6_in2out_error
+#undef _
+};
+#endif /* CLIB_MARCH_VARIANT */
+
+typedef enum
+{
+  CT6_IN2OUT_NEXT_DROP,
+  CT6_IN2OUT_N_NEXT,
+} ct6_next_t;
+
+#ifndef CLIB_MARCH_VARIANT
+ct6_session_t *
+ct6_create_or_recycle_session (ct6_main_t * cmp,
+			       clib_bihash_kv_48_8_t * kvpp, f64 now,
+			       u32 my_thread_index, u32 * recyclep,
+			       u32 * createp)
+{
+  ct6_session_t *s0;
+
+  /* Empty arena? */
+  if (PREDICT_FALSE (cmp->last_index[my_thread_index] == ~0))
+    goto alloc0;
+
+  /* Look at the least-recently-used session */
+  s0 = pool_elt_at_index (cmp->sessions[my_thread_index],
+			  cmp->last_index[my_thread_index]);
+
+  if (s0->expires < now)
+    clib_warning ("session %d expired %.2f time now %.2f",
+		  s0 - cmp->sessions[my_thread_index], s0->expires, now);
+
+  if (pool_elts (cmp->sessions[my_thread_index]) >=
+      cmp->max_sessions_per_worker)
+    clib_warning ("recycle session %d have %d max %d",
+		  s0 - cmp->sessions[my_thread_index],
+		  pool_elts (cmp->sessions[my_thread_index]),
+		  cmp->max_sessions_per_worker);
+
+  /* Session expired, or we have as many sessions as is allowed by law? */
+  if ((s0->expires < now) || (pool_elts (cmp->sessions[my_thread_index])
+			      >= cmp->max_sessions_per_worker))
+    {
+      /* recycle the session */
+      if (clib_bihash_add_del_48_8 (&cmp->session_hash,
+				    (clib_bihash_kv_48_8_t *) s0,
+				    0 /* is_add */ ) < 0)
+	clib_warning ("session %d not found in hash?",
+		      s0 - cmp->sessions[my_thread_index]);
+
+      ct6_lru_remove (cmp, s0);
+      *recyclep += 1;
+    }
+  else
+    {
+    alloc0:
+      /* Allocate a fresh session */
+      pool_get (cmp->sessions[my_thread_index], s0);
+      *createp += 1;
+    }
+
+  /* Sesison setup */
+  memset (s0, 0, sizeof (*s0));
+  clib_memcpy_fast (s0, kvpp, sizeof (ct6_session_key_t));
+  s0->thread_index = my_thread_index;
+  s0->expires = now + cmp->session_timeout_interval;
+  kvpp->value = s0 - cmp->sessions[my_thread_index];
+  clib_bihash_add_del_48_8 (&cmp->session_hash, kvpp, 1 /* is_add */ );
+  ct6_lru_add (cmp, s0, now);
+  return s0;
+}
+#endif /* CLIB_MARCH_VARIANT */
+
+always_inline uword
+ct6_in2out_inline (vlib_main_t * vm,
+		   vlib_node_runtime_t * node, vlib_frame_t * frame,
+		   int is_trace)
+{
+  u32 n_left_from, *from;
+  vlib_buffer_t *bufs[VLIB_FRAME_SIZE], **b;
+  u16 nexts[VLIB_FRAME_SIZE], *next;
+  ct6_main_t *cmp = &ct6_main;
+  u32 my_thread_index = vm->thread_index;
+  f64 now = vlib_time_now (vm);
+  u32 created = 0;
+  u32 recycled = 0;
+
+  from = vlib_frame_vector_args (frame);
+  n_left_from = frame->n_vectors;
+
+  vlib_get_buffers (vm, from, bufs, n_left_from);
+  b = bufs;
+  next = nexts;
+
+#if 0
+  while (n_left_from >= 4)
+    {
+      /* Prefetch next iteration. */
+      if (PREDICT_TRUE (n_left_from >= 8))
+	{
+	  vlib_prefetch_buffer_header (b[4], STORE);
+	  vlib_prefetch_buffer_header (b[5], STORE);
+	  vlib_prefetch_buffer_header (b[6], STORE);
+	  vlib_prefetch_buffer_header (b[7], STORE);
+	  CLIB_PREFETCH (b[4]->data, CLIB_CACHE_LINE_BYTES, STORE);
+	  CLIB_PREFETCH (b[5]->data, CLIB_CACHE_LINE_BYTES, STORE);
+	  CLIB_PREFETCH (b[6]->data, CLIB_CACHE_LINE_BYTES, STORE);
+	  CLIB_PREFETCH (b[7]->data, CLIB_CACHE_LINE_BYTES, STORE);
+	}
+
+      /* $$$$ process 4x pkts right here */
+      next[0] = 0;
+      next[1] = 0;
+      next[2] = 0;
+      next[3] = 0;
+
+      if (is_trace)
+	{
+	  if (b[0]->flags & VLIB_BUFFER_IS_TRACED)
+	    {
+	      ct6_trace_t *t = vlib_add_trace (vm, node, b[0], sizeof (*t));
+	      t->next_index = next[0];
+	      t->sw_if_index = vnet_buffer (b[0])->sw_if_index[VLIB_RX];
+	    }
+	  if (b[1]->flags & VLIB_BUFFER_IS_TRACED)
+	    {
+	      ct6_trace_t *t = vlib_add_trace (vm, node, b[1], sizeof (*t));
+	      t->next_index = next[1];
+	      t->sw_if_index = vnet_buffer (b[1])->sw_if_index[VLIB_RX];
+	    }
+	  if (b[2]->flags & VLIB_BUFFER_IS_TRACED)
+	    {
+	      ct6_trace_t *t = vlib_add_trace (vm, node, b[2], sizeof (*t));
+	      t->next_index = next[2];
+	      t->sw_if_index = vnet_buffer (b[2])->sw_if_index[VLIB_RX];
+	    }
+	  if (b[3]->flags & VLIB_BUFFER_IS_TRACED)
+	    {
+	      ct6_trace_t *t = vlib_add_trace (vm, node, b[3], sizeof (*t));
+	      t->next_index = next[3];
+	      t->sw_if_index = vnet_buffer (b[3])->sw_if_index[VLIB_RX];
+	    }
+	}
+
+      b += 4;
+      next += 4;
+      n_left_from -= 4;
+    }
+#endif
+
+  while (n_left_from > 0)
+    {
+      clib_bihash_kv_48_8_t kvp0;
+      ct6_session_key_t *key0;
+      ct6_session_t *s0;
+      u32 session_index0 = ~0;
+      u32 next0, delta0;
+      ethernet_header_t *e0;
+
+      ip6_header_t *ip0;
+      udp_header_t *udp0;
+
+      /* $$$ Set to 0 for pg testing */
+      if (1)
+	{
+	  vnet_feature_next (&next0, b[0]);
+	  next[0] = next0;
+	}
+      else
+	next[0] = CT6_IN2OUT_NEXT_DROP;
+
+      /*
+       * This is an output feature which runs at the last possible
+       * moment. Assume an ethernet header.
+       */
+
+      e0 = vlib_buffer_get_current (b[0]);
+      delta0 = sizeof (*e0);
+      delta0 += (e0->type == clib_net_to_host_u16 (ETHERNET_TYPE_VLAN))
+	? 4 : 0;
+      delta0 += (e0->type == clib_net_to_host_u16 (ETHERNET_TYPE_DOT1AD))
+	? 8 : 0;
+
+      ip0 = (ip6_header_t *) (vlib_buffer_get_current (b[0]) + delta0);
+
+      /*
+       * Pass non-global unicast traffic
+       */
+      if (PREDICT_FALSE (!ip6_address_is_global_unicast (&ip0->src_address)
+			 ||
+			 !ip6_address_is_global_unicast (&ip0->src_address)))
+	goto trace0;
+      /* Pass non-udp, non-tcp traffic */
+      if (PREDICT_FALSE (ip0->protocol != IP_PROTOCOL_TCP &&
+			 ip0->protocol != IP_PROTOCOL_UDP))
+	goto trace0;
+
+      udp0 = ip6_next_header (ip0);
+
+      /*
+       * See if we know about this flow.
+       * Key set up for the out2in path, the performant case
+       */
+      key0 = (ct6_session_key_t *) & kvp0;
+      clib_memcpy_fast (&key0->src, &ip0->dst_address,
+			sizeof (ip6_address_t));
+      clib_memcpy_fast (&key0->dst, &ip0->src_address,
+			sizeof (ip6_address_t));
+      key0->as_u64[4] = 0;
+      key0->as_u64[5] = 0;
+      key0->sport = udp0->dst_port;
+      key0->dport = udp0->src_port;
+      key0->proto = ip0->protocol;
+
+      /* Need to create a new session? */
+      if (clib_bihash_search_48_8 (&cmp->session_hash, &kvp0, &kvp0) < 0)
+	{
+	  s0 =
+	    ct6_create_or_recycle_session (cmp, &kvp0, now, my_thread_index,
+					   &recycled, &created);
+	  session_index0 = kvp0.value;
+	}
+      else
+	{
+	  s0 = pool_elt_at_index (cmp->sessions[my_thread_index], kvp0.value);
+	  session_index0 = kvp0.value;
+	  ct6_update_session_hit (cmp, s0, now);
+	}
+
+    trace0:
+      if (is_trace)
+	{
+	  if (b[0]->flags & VLIB_BUFFER_IS_TRACED)
+	    {
+	      ct6_in2out_trace_t *t =
+		vlib_add_trace (vm, node, b[0], sizeof (*t));
+	      t->next_index = next[0];
+	      t->sw_if_index = vnet_buffer (b[0])->sw_if_index[VLIB_RX];
+	      t->session_index = session_index0;
+	    }
+	}
+
+      b += 1;
+      next += 1;
+      n_left_from -= 1;
+    }
+
+  vlib_buffer_enqueue_to_next (vm, node, from, nexts, frame->n_vectors);
+
+  vlib_node_increment_counter (vm, node->node_index,
+			       CT6_IN2OUT_ERROR_PROCESSED, frame->n_vectors);
+  vlib_node_increment_counter (vm, node->node_index,
+			       CT6_IN2OUT_ERROR_CREATED, created);
+  vlib_node_increment_counter (vm, node->node_index,
+			       CT6_IN2OUT_ERROR_RECYCLED, recycled);
+
+  return frame->n_vectors;
+}
+
+VLIB_NODE_FN (ct6_in2out_node) (vlib_main_t * vm, vlib_node_runtime_t * node,
+				vlib_frame_t * frame)
+{
+  if (PREDICT_FALSE (node->flags & VLIB_NODE_FLAG_TRACE))
+    return ct6_in2out_inline (vm, node, frame, 1 /* is_trace */ );
+  else
+    return ct6_in2out_inline (vm, node, frame, 0 /* is_trace */ );
+}
+
+/* *INDENT-OFF* */
+#ifndef CLIB_MARCH_VARIANT
+VLIB_REGISTER_NODE (ct6_in2out_node) =
+{
+  .name = "ct6-in2out",
+  .vector_size = sizeof (u32),
+  .format_trace = format_ct6_in2out_trace,
+  .type = VLIB_NODE_TYPE_INTERNAL,
+
+  .n_errors = ARRAY_LEN(ct6_in2out_error_strings),
+  .error_strings = ct6_in2out_error_strings,
+
+  .n_next_nodes = CT6_IN2OUT_N_NEXT,
+
+  /* edit / add dispositions here */
+  .next_nodes = {
+        [CT6_IN2OUT_NEXT_DROP] = "error-drop",
+  },
+  .unformat_buffer = unformat_ethernet_header,
+};
+#endif /* CLIB_MARCH_VARIANT */
+/* *INDENT-ON* */
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */
diff --git a/src/plugins/ct6/ct6_msg_enum.h b/src/plugins/ct6/ct6_msg_enum.h
new file mode 100644
index 00000000000..05b1751550d
--- /dev/null
+++ b/src/plugins/ct6/ct6_msg_enum.h
@@ -0,0 +1,31 @@
+
+/*
+ * ct6_msg_enum.h - skeleton vpp engine plug-in message enumeration
+ *
+ * Copyright (c) <current-year> <your-organization>
+ * 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.
+ */
+#ifndef included_ct6_msg_enum_h
+#define included_ct6_msg_enum_h
+
+#include <vppinfra/byte_order.h>
+
+#define vl_msg_id(n,h) n,
+typedef enum {
+#include <ct6/ct6_all_api_h.h>
+    /* We'll want to know how many messages IDs we need... */
+    VL_MSG_FIRST_AVAILABLE,
+} vl_msg_id_t;
+#undef vl_msg_id
+
+#endif /* included_ct6_msg_enum_h */
diff --git a/src/plugins/ct6/ct6_out2in.c b/src/plugins/ct6/ct6_out2in.c
new file mode 100644
index 00000000000..eac4c155aa4
--- /dev/null
+++ b/src/plugins/ct6/ct6_out2in.c
@@ -0,0 +1,278 @@
+/*
+ * ct6_out2in.c - ip6 connection tracker, inside-to-outside path
+ *
+ * Copyright (c) 2019 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 <vppinfra/error.h>
+#include <ct6/ct6.h>
+
+typedef struct
+{
+  u32 sw_if_index;
+  u32 next_index;
+  u32 session_index;
+} ct6_out2in_trace_t;
+
+#ifndef CLIB_MARCH_VARIANT
+
+/* packet trace format function */
+static u8 *
+format_ct6_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 *);
+  ct6_out2in_trace_t *t = va_arg (*args, ct6_out2in_trace_t *);
+
+  s = format (s, "CT6_OUT2IN: sw_if_index %d, next index %d session %d\n",
+	      t->sw_if_index, t->next_index, t->session_index);
+  return s;
+}
+
+vlib_node_registration_t ct6_out2in_node;
+
+#endif /* CLIB_MARCH_VARIANT */
+
+#define foreach_ct6_out2in_error                \
+_(PROCESSED, "ct6 packets processed")           \
+_(NO_SESSION, "ct6 no session drops")
+
+
+typedef enum
+{
+#define _(sym,str) CT6_OUT2IN_ERROR_##sym,
+  foreach_ct6_out2in_error
+#undef _
+    CT6_OUT2IN_N_ERROR,
+} ct6_out2in_error_t;
+
+#ifndef CLIB_MARCH_VARIANT
+static char *ct6_out2in_error_strings[] = {
+#define _(sym,string) string,
+  foreach_ct6_out2in_error
+#undef _
+};
+#endif /* CLIB_MARCH_VARIANT */
+
+typedef enum
+{
+  CT6_OUT2IN_NEXT_DROP,
+  CT6_OUT2IN_N_NEXT,
+} ct6_next_t;
+
+always_inline uword
+ct6_out2in_inline (vlib_main_t * vm,
+		   vlib_node_runtime_t * node, vlib_frame_t * frame,
+		   int is_trace)
+{
+  u32 n_left_from, *from;
+  vlib_buffer_t *bufs[VLIB_FRAME_SIZE], **b;
+  u16 nexts[VLIB_FRAME_SIZE], *next;
+  ct6_main_t *cmp = &ct6_main;
+  u32 my_thread_index = vm->thread_index;
+  f64 now = vlib_time_now (vm);
+  u32 dropped = 0;
+
+  from = vlib_frame_vector_args (frame);
+  n_left_from = frame->n_vectors;
+
+  vlib_get_buffers (vm, from, bufs, n_left_from);
+  b = bufs;
+  next = nexts;
+
+#if 0
+  while (n_left_from >= 4)
+    {
+      /* Prefetch next iteration. */
+      if (PREDICT_TRUE (n_left_from >= 8))
+	{
+	  vlib_prefetch_buffer_header (b[4], STORE);
+	  vlib_prefetch_buffer_header (b[5], STORE);
+	  vlib_prefetch_buffer_header (b[6], STORE);
+	  vlib_prefetch_buffer_header (b[7], STORE);
+	  CLIB_PREFETCH (b[4]->data, CLIB_CACHE_LINE_BYTES, STORE);
+	  CLIB_PREFETCH (b[5]->data, CLIB_CACHE_LINE_BYTES, STORE);
+	  CLIB_PREFETCH (b[6]->data, CLIB_CACHE_LINE_BYTES, STORE);
+	  CLIB_PREFETCH (b[7]->data, CLIB_CACHE_LINE_BYTES, STORE);
+	}
+
+      /* $$$$ process 4x pkts right here */
+      next[0] = 0;
+      next[1] = 0;
+      next[2] = 0;
+      next[3] = 0;
+
+      if (is_trace)
+	{
+	  if (b[0]->flags & VLIB_BUFFER_IS_TRACED)
+	    {
+	      ct6_trace_t *t = vlib_add_trace (vm, node, b[0], sizeof (*t));
+	      t->next_index = next[0];
+	      t->sw_if_index = vnet_buffer (b[0])->sw_if_index[VLIB_RX];
+	    }
+	  if (b[1]->flags & VLIB_BUFFER_IS_TRACED)
+	    {
+	      ct6_trace_t *t = vlib_add_trace (vm, node, b[1], sizeof (*t));
+	      t->next_index = next[1];
+	      t->sw_if_index = vnet_buffer (b[1])->sw_if_index[VLIB_RX];
+	    }
+	  if (b[2]->flags & VLIB_BUFFER_IS_TRACED)
+	    {
+	      ct6_trace_t *t = vlib_add_trace (vm, node, b[2], sizeof (*t));
+	      t->next_index = next[2];
+	      t->sw_if_index = vnet_buffer (b[2])->sw_if_index[VLIB_RX];
+	    }
+	  if (b[3]->flags & VLIB_BUFFER_IS_TRACED)
+	    {
+	      ct6_trace_t *t = vlib_add_trace (vm, node, b[3], sizeof (*t));
+	      t->next_index = next[3];
+	      t->sw_if_index = vnet_buffer (b[3])->sw_if_index[VLIB_RX];
+	    }
+	}
+
+      b += 4;
+      next += 4;
+      n_left_from -= 4;
+    }
+#endif
+
+  while (n_left_from > 0)
+    {
+      clib_bihash_kv_48_8_t kvp0;
+      ct6_session_key_t *key0;
+      ct6_session_t *s0;
+      u32 session_index0 = ~0;
+      u32 next0;
+
+      ip6_header_t *ip0;
+      udp_header_t *udp0;
+
+      /* Are we having fun yet? */
+      vnet_feature_next (&next0, b[0]);
+      next[0] = next0;
+
+      ip0 = vlib_buffer_get_current (b[0]);
+
+      /*
+       * Pass non-global unicast traffic
+       */
+      if (PREDICT_FALSE (!ip6_address_is_global_unicast (&ip0->src_address)
+			 ||
+			 !ip6_address_is_global_unicast (&ip0->src_address)))
+	goto trace0;
+      /* Pass non-udp, non-tcp traffic */
+      if (PREDICT_FALSE (ip0->protocol != IP_PROTOCOL_TCP &&
+			 ip0->protocol != IP_PROTOCOL_UDP))
+	goto trace0;
+
+      udp0 = ip6_next_header (ip0);
+
+      /*
+       * See if we know about this flow.
+       */
+      key0 = (ct6_session_key_t *) & kvp0;
+      clib_memcpy_fast (&key0->src, &ip0->src_address,
+			sizeof (ip6_address_t));
+      clib_memcpy_fast (&key0->dst, &ip0->dst_address,
+			sizeof (ip6_address_t));
+      key0->as_u64[4] = 0;
+      key0->as_u64[5] = 0;
+      key0->sport = udp0->src_port;
+      key0->dport = udp0->dst_port;
+      key0->proto = ip0->protocol;
+
+      /* Do we know about this session? */
+      if (clib_bihash_search_48_8 (&cmp->session_hash, &kvp0, &kvp0) < 0)
+	{
+	  /* Bad engineer, no donut for you... */
+	  next[0] = CT6_OUT2IN_NEXT_DROP;
+	  b[0]->error = node->errors[CT6_OUT2IN_ERROR_NO_SESSION];
+	  dropped++;
+	  goto trace0;
+	}
+      else
+	{
+	  s0 = pool_elt_at_index (cmp->sessions[my_thread_index], kvp0.value);
+	  session_index0 = kvp0.value;
+	  ct6_update_session_hit (cmp, s0, now);
+	}
+
+    trace0:
+      if (is_trace)
+	{
+	  if (b[0]->flags & VLIB_BUFFER_IS_TRACED)
+	    {
+	      ct6_out2in_trace_t *t =
+		vlib_add_trace (vm, node, b[0], sizeof (*t));
+	      t->next_index = next[0];
+	      t->sw_if_index = vnet_buffer (b[0])->sw_if_index[VLIB_RX];
+	      t->session_index = session_index0;
+	    }
+	}
+
+      b += 1;
+      next += 1;
+      n_left_from -= 1;
+    }
+
+  vlib_buffer_enqueue_to_next (vm, node, from, nexts, frame->n_vectors);
+
+  vlib_node_increment_counter (vm, node->node_index,
+			       CT6_OUT2IN_ERROR_PROCESSED, frame->n_vectors);
+  vlib_node_increment_counter (vm, node->node_index,
+			       CT6_OUT2IN_ERROR_NO_SESSION, dropped);
+
+  return frame->n_vectors;
+}
+
+VLIB_NODE_FN (ct6_out2in_node) (vlib_main_t * vm, vlib_node_runtime_t * node,
+				vlib_frame_t * frame)
+{
+  if (PREDICT_FALSE (node->flags & VLIB_NODE_FLAG_TRACE))
+    return ct6_out2in_inline (vm, node, frame, 1 /* is_trace */ );
+  else
+    return ct6_out2in_inline (vm, node, frame, 0 /* is_trace */ );
+}
+
+/* *INDENT-OFF* */
+#ifndef CLIB_MARCH_VARIANT
+VLIB_REGISTER_NODE (ct6_out2in_node) =
+{
+  .name = "ct6-out2in",
+  .vector_size = sizeof (u32),
+  .format_trace = format_ct6_out2in_trace,
+  .type = VLIB_NODE_TYPE_INTERNAL,
+
+  .n_errors = ARRAY_LEN(ct6_out2in_error_strings),
+  .error_strings = ct6_out2in_error_strings,
+
+  .n_next_nodes = CT6_OUT2IN_N_NEXT,
+
+  /* edit / add dispositions here */
+  .next_nodes = {
+        [CT6_OUT2IN_NEXT_DROP] = "error-drop",
+  },
+};
+#endif /* CLIB_MARCH_VARIANT */
+/* *INDENT-ON* */
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */
diff --git a/src/plugins/ct6/ct6_test.c b/src/plugins/ct6/ct6_test.c
new file mode 100644
index 00000000000..507620eaf0b
--- /dev/null
+++ b/src/plugins/ct6/ct6_test.c
@@ -0,0 +1,202 @@
+/*
+ * ct6.c - skeleton vpp-api-test plug-in
+ *
+ * Copyright (c) <current-year> <your-organization>
+ * 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 <vat/vat.h>
+#include <vlibapi/api.h>
+#include <vlibmemory/api.h>
+#include <vppinfra/error.h>
+
+uword unformat_sw_if_index (unformat_input_t * input, va_list * args);
+
+/* Declare message IDs */
+#include <ct6/ct6_msg_enum.h>
+
+/* define message structures */
+#define vl_typedefs
+#include <ct6/ct6_all_api_h.h>
+#undef vl_typedefs
+
+/* declare message handlers for each api */
+
+#define vl_endianfun		/* define message structures */
+#include <ct6/ct6_all_api_h.h>
+#undef vl_endianfun
+
+/* instantiate all the print functions we know about */
+#define vl_print(handle, ...)
+#define vl_printfun
+#include <ct6/ct6_all_api_h.h>
+#undef vl_printfun
+
+/* Get the API version number. */
+#define vl_api_version(n,v) static u32 api_version=(v);
+#include <ct6/ct6_all_api_h.h>
+#undef vl_api_version
+
+
+typedef struct
+{
+  /* API message ID base */
+  u16 msg_id_base;
+  vat_main_t *vat_main;
+} ct6_test_main_t;
+
+ct6_test_main_t ct6_test_main;
+
+#define __plugin_msg_base ct6_test_main.msg_id_base
+#include <vlibapi/vat_helper_macros.h>
+
+#define foreach_standard_reply_retval_handler   \
+_(ct6_enable_disable_reply)
+
+#define _(n)                                            \
+    static void vl_api_##n##_t_handler                  \
+    (vl_api_##n##_t * mp)                               \
+    {                                                   \
+        vat_main_t * vam = ct6_test_main.vat_main;   \
+        i32 retval = ntohl(mp->retval);                 \
+        if (vam->async_mode) {                          \
+            vam->async_errors += (retval < 0);          \
+        } else {                                        \
+            vam->retval = retval;                       \
+            vam->result_ready = 1;                      \
+        }                                               \
+    }
+foreach_standard_reply_retval_handler;
+#undef _
+
+/*
+ * Table of message reply handlers, must include boilerplate handlers
+ * we just generated
+ */
+#define foreach_vpe_api_reply_msg                                       \
+_(CT6_ENABLE_DISABLE_REPLY, ct6_enable_disable_reply)
+
+
+static int
+api_ct6_enable_disable (vat_main_t * vam)
+{
+  unformat_input_t *i = vam->input;
+  int enable_disable = 1;
+  u32 sw_if_index = ~0;
+  vl_api_ct6_enable_disable_t *mp;
+  u32 inside = ~0;
+  int ret;
+
+  /* Parse args required to build the message */
+  while (unformat_check_input (i) != UNFORMAT_END_OF_INPUT)
+    {
+      if (unformat (i, "%U", unformat_sw_if_index, vam, &sw_if_index))
+	;
+      else if (unformat (i, "sw_if_index %d", &sw_if_index))
+	;
+      else if (unformat (i, "disable"))
+	enable_disable = 0;
+      else if (unformat (i, "inside") || unformat (i, "in"))
+	inside = 1;
+      else if (unformat (i, "outside") || unformat (i, "out"))
+	inside = 0;
+      else
+	break;
+    }
+
+  if (inside == ~0)
+    {
+      errmsg ("must specify inside or outside");
+      return -99;
+    }
+
+  if (sw_if_index == ~0)
+    {
+      errmsg ("missing interface name / explicit sw_if_index number \n");
+      return -99;
+    }
+
+  /* Construct the API message */
+  M (CT6_ENABLE_DISABLE, mp);
+  mp->sw_if_index = ntohl (sw_if_index);
+  mp->enable_disable = enable_disable;
+  mp->is_inside = (u8) inside;
+
+  /* send it... */
+  S (mp);
+
+  /* Wait for a reply... */
+  W (ret);
+  return ret;
+}
+
+/*
+ * List of messages that the api test plugin sends,
+ * and that the data plane plugin processes
+ */
+#define foreach_vpe_api_msg \
+_(ct6_enable_disable, "<intfc> [disable]")
+
+static void
+ct6_api_hookup (vat_main_t * vam)
+{
+  ct6_test_main_t *ctmp = &ct6_test_main;
+  /* Hook up handlers for replies from the data plane plug-in */
+#define _(N,n)                                                  \
+    vl_msg_api_set_handlers((VL_API_##N + ctmp->msg_id_base),     \
+                           #n,                                  \
+                           vl_api_##n##_t_handler,              \
+                           vl_noop_handler,                     \
+                           vl_api_##n##_t_endian,               \
+                           vl_api_##n##_t_print,                \
+                           sizeof(vl_api_##n##_t), 1);
+  foreach_vpe_api_reply_msg;
+#undef _
+
+  /* API messages we can send */
+#define _(n,h) hash_set_mem (vam->function_by_name, #n, api_##n);
+  foreach_vpe_api_msg;
+#undef _
+
+  /* Help strings */
+#define _(n,h) hash_set_mem (vam->help_by_name, #n, h);
+  foreach_vpe_api_msg;
+#undef _
+}
+
+clib_error_t *
+vat_plugin_register (vat_main_t * vam)
+{
+  ct6_test_main_t *ctmp = &ct6_test_main;
+  u8 *name;
+
+  ctmp->vat_main = vam;
+
+  /* Ask the vpp engine for the first assigned message-id */
+  name = format (0, "ct6_%08x%c", api_version, 0);
+  ctmp->msg_id_base = vl_client_get_first_plugin_msg_id ((char *) name);
+
+  if (ctmp->msg_id_base != (u16) ~ 0)
+    ct6_api_hookup (vam);
+
+  vec_free (name);
+
+  return 0;
+}
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */