[HICN-606] Added doxygen documentation

Signed-off-by: Alberto Compagno <acompagn+fdio@cisco.com>
Change-Id: If2bf7f4f310adf6adbbb9ea29eafcb2a0ee40d54

46 files changed, 834 insertions, 895 deletions

diff --git a/hicn-plugin/src/CMakeLists.txt b/hicn-plugin/src/CMakeLists.txt
index 13d3b5c3c..ebe8f8713 100644
--- a/hicn-plugin/src/CMakeLists.txt
+++ b/hicn-plugin/src/CMakeLists.txt
@@ -75,13 +75,11 @@ set(HICN_PLUGIN_SOURCE_FILES
     ${CMAKE_CURRENT_SOURCE_DIR}/data_input_node.c
     ${CMAKE_CURRENT_SOURCE_DIR}/data_pcslookup_node.c
     ${CMAKE_CURRENT_SOURCE_DIR}/data_fwd_node.c
-    ${CMAKE_CURRENT_SOURCE_DIR}/data_push_node.c
     ${CMAKE_CURRENT_SOURCE_DIR}/error.c
     ${CMAKE_CURRENT_SOURCE_DIR}/faces/face_cli.c
     ${CMAKE_CURRENT_SOURCE_DIR}/faces/face.c
     ${CMAKE_CURRENT_SOURCE_DIR}/faces/face_node.c
     ${CMAKE_CURRENT_SOURCE_DIR}/faces/iface_node.c
-    ${CMAKE_CURRENT_SOURCE_DIR}/faces/dpo_face.h
     ${CMAKE_CURRENT_SOURCE_DIR}/faces/app/address_mgr.c
     ${CMAKE_CURRENT_SOURCE_DIR}/faces/app/face_cons.c
     ${CMAKE_CURRENT_SOURCE_DIR}/faces/app/face_prod.c
diff --git a/hicn-plugin/src/cache_policies/cs_lru.h b/hicn-plugin/src/cache_policies/cs_lru.h
index 0a58912d6..3bd18060d 100644
--- a/hicn-plugin/src/cache_policies/cs_lru.h
+++ b/hicn-plugin/src/cache_policies/cs_lru.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017-2019 Cisco and/or its affiliates.
+ * Copyright (c) 2017-2020 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:
@@ -20,6 +20,13 @@
 #include "../hashtb.h"
 #include "cs_policy.h"
 
+/**
+ * @file cs_lru.h
+ *
+ * This file implements the LRU policy for the CS
+ */
+
+
 extern hicn_cs_policy_vft_t hicn_cs_lru;
 
 /*
diff --git a/hicn-plugin/src/cache_policies/cs_policy.h b/hicn-plugin/src/cache_policies/cs_policy.h
index c1a9a44c9..0bf745915 100644
--- a/hicn-plugin/src/cache_policies/cs_policy.h
+++ b/hicn-plugin/src/cache_policies/cs_policy.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017-2019 Cisco and/or its affiliates.
+ * Copyright (c) 2017-2020 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:
@@ -18,6 +18,13 @@
 
 #include "../hashtb.h"
 
+/**
+ * @file cs_policy.h
+ *
+ * This file provides the needed structures to implement a CS policy
+ */
+
+
 /*
  * Structure
  */
@@ -41,7 +48,12 @@ struct hicn_cs_policy_s;
 /**
  * @brief Definition of the virtual functin table for a cache policy.
  *
- * A cache policy must implement three functions: insert, update, delete, trim.
+ * A cache policy must implement all the following functions:
+ * - insert: add a new element
+ * - update: update the position of an existing element
+ * - dequeue: remove an element from the list
+ * - delete_get: return the next element that should be removed trim
+ * - flush: clean the cs
  */
 typedef struct hicn_cs_policy_vft_s
 {
diff --git a/hicn-plugin/src/data_fwd.h b/hicn-plugin/src/data_fwd.h
index ad41e7e39..d95f564c3 100644
--- a/hicn-plugin/src/data_fwd.h
+++ b/hicn-plugin/src/data_fwd.h
@@ -20,6 +20,27 @@
 
 #include "pcs.h"
 
+/**
+ * @file data_fwd.h
+ *
+ * This is the node encoutered by data packets after the hicn-data-pcslookup.
+ * This node has two goals: 1) clone/copy the vlib buffer as many time as the number
+ * of faces stored in the pit entry, 2) store a clone/copy of the vlib buffer in the CS.
+ * Unless there are memory issue (no more vlib buffer available to perform cloning/copy),
+ * a single vlib buffer received might results in several vlib buffer sent to the next
+ * vlib node (hicn4-iface-output or hicn6-iface-output).
+ *
+ * It must be noted that cloning is possible only if the lentgh of the data pointed by
+ * the vlib buffer is at least 256 bytes. This is due to an imposition in the vpp source
+ * code. In all the other cases the vlib buffer is copied. Cloning is performed by advancing
+ * the vlib buffer of 256 bytes and a new vlib buffer is created and chained in from of the received
+ * buffer. Additionally, the 256 bytes removed (advanced) from the received vlib buffer are
+ * copied in the head vlib buffer. In case of multiple cloning for the same vlib buffer, this
+ * mechanism allows us to have a different hICN header for each clone (+ the same additional bytes
+ * due to the vpp restriction on cloning).
+ */
+
+
 /* Trace context struct */
 typedef struct
 {
@@ -33,7 +54,6 @@ typedef enum
 {
   HICN_DATA_FWD_NEXT_V4_LOOKUP,
   HICN_DATA_FWD_NEXT_V6_LOOKUP,
-  HICN_DATA_FWD_NEXT_PUSH,
   HICN_DATA_FWD_NEXT_IFACE4_OUT,
   HICN_DATA_FWD_NEXT_IFACE6_OUT,
   HICN_DATA_FWD_NEXT_ERROR_DROP,
@@ -41,7 +61,7 @@ typedef enum
 } hicn_data_fwd_next_t;
 
 /**
- *@brief Create a maximum of 256 clones of buffer and store them
+ * @brief Create a maximum of 256 clones of buffer and store them
  *   in the supplied array. Unlike the original function in the vlib
  *   library, we don't prevent cloning if n_buffer==1 and if
  *   s->current_length <= head_end_offset + CLIB_CACHE_LINE_BYTES * 2.
diff --git a/hicn-plugin/src/data_fwd_node.c b/hicn-plugin/src/data_fwd_node.c
index 2737d1d62..c65b62454 100644
--- a/hicn-plugin/src/data_fwd_node.c
+++ b/hicn-plugin/src/data_fwd_node.c
@@ -37,11 +37,6 @@ drop_packet (vlib_main_t * vm, u32 bi0,
 	     u32 * n_left_to_next, u32 * next0, u32 ** to_next,
 	     u32 * next_index, vlib_node_runtime_t * node);
 
-always_inline void
-push_in_cache (vlib_main_t * vm, u32 bi0,
-	       u32 * n_left_to_next, u32 * next0, u32 ** to_next,
-	       u32 * next_index, vlib_node_runtime_t * node);
-
 always_inline int
 hicn_satisfy_faces (vlib_main_t * vm, u32 b0,
 		    hicn_pcs_entry_t * pitp, u32 * n_left_to_next,
@@ -176,21 +171,8 @@ hicn_data_node_fn (vlib_main_t * vm, vlib_node_runtime_t * node,
 	      hicn_pcs_delete (pitcs, &pitp, &node0, vm, hash_entry0,
 			       dpo_vft0, &hicn_dpo_id0);
 
-#if HICN_FEATURE_CS
-	      if (hicnb0->flags & HICN_BUFFER_FLAGS_FACE_IS_APP)
-		{
-		  push_in_cache (vm, bi0, &n_left_to_next, &next0, &to_next,
-				 &next_index, node);
-		}
-	      else
-		{
-		  drop_packet (vm, bi0, &n_left_to_next, &next0, &to_next,
-			       &next_index, node);
-		}
-#else
               drop_packet (vm, bi0, &n_left_to_next, &next0, &to_next,
                            &next_index, node);
-#endif
 	      stats.pit_expired_count++;
 
 	      if (PREDICT_FALSE ((node->flags & VLIB_NODE_FLAG_TRACE) &&
@@ -348,21 +330,6 @@ drop_packet (vlib_main_t * vm, u32 bi0,
 				   *to_next, *n_left_to_next, bi0, *next0);
 }
 
-always_inline void
-push_in_cache (vlib_main_t * vm, u32 bi0,
-	       u32 * n_left_to_next, u32 * next0, u32 ** to_next,
-	       u32 * next_index, vlib_node_runtime_t * node)
-{
-  *next0 = HICN_DATA_FWD_NEXT_PUSH;
-
-  (*to_next)[0] = bi0;
-  *to_next += 1;
-  *n_left_to_next -= 1;
-
-  vlib_validate_buffer_enqueue_x1 (vm, node, *next_index,
-				   *to_next, *n_left_to_next, bi0, *next0);
-}
-
 always_inline int
 hicn_satisfy_faces (vlib_main_t * vm, u32 bi0,
 		    hicn_pcs_entry_t * pitp, u32 * n_left_to_next,
@@ -639,7 +606,6 @@ VLIB_REGISTER_NODE(hicn_data_fwd_node) =
   .next_nodes = {
     [HICN_DATA_FWD_NEXT_V4_LOOKUP] = "ip4-lookup",
     [HICN_DATA_FWD_NEXT_V6_LOOKUP] = "ip6-lookup",
-    [HICN_DATA_FWD_NEXT_PUSH] = "hicn-data-push",
     [HICN_DATA_FWD_NEXT_IFACE4_OUT] = "hicn4-iface-output",
     [HICN_DATA_FWD_NEXT_IFACE6_OUT] = "hicn6-iface-output",
     [HICN_DATA_FWD_NEXT_ERROR_DROP] = "error-drop",
diff --git a/hicn-plugin/src/data_pcslookup.h b/hicn-plugin/src/data_pcslookup.h
index fa75c3ac3..e3050c31c 100644
--- a/hicn-plugin/src/data_pcslookup.h
+++ b/hicn-plugin/src/data_pcslookup.h
@@ -18,6 +18,15 @@
 
 #include "pcs.h"
 
+/**
+ * @file data_pcslookup.h
+ *
+ * This is the node encoutered by data packets after the hicn6-face-input or
+ * hicn4-face-input. This node performs a lookup in the pit and content store and
+ * if there is a hit in the PIT, the vlib buffer is passed to the hicn-data-fwd
+ * while if there is a hit in the CS or there isn't any hit, the packet is dropped.
+ */
+
 /*
  * Node context data; we think this is per-thread/instance
  */
@@ -37,9 +46,6 @@ typedef struct
 
 typedef enum
 {
-  HICN_DATA_PCSLOOKUP_NEXT_V4_LOOKUP,
-  HICN_DATA_PCSLOOKUP_NEXT_V6_LOOKUP,
-  HICN_DATA_PCSLOOKUP_NEXT_STORE_DATA,
   HICN_DATA_PCSLOOKUP_NEXT_DATA_FWD,	/* This must be one position
 					 * before the error drop!! */
   HICN_DATA_PCSLOOKUP_NEXT_ERROR_DROP,
diff --git a/hicn-plugin/src/data_pcslookup_node.c b/hicn-plugin/src/data_pcslookup_node.c
index cbea07871..99af350b0 100644
--- a/hicn-plugin/src/data_pcslookup_node.c
+++ b/hicn-plugin/src/data_pcslookup_node.c
@@ -63,7 +63,6 @@ hicn_data_pcslookup_node_fn (vlib_main_t * vm,
       while (n_left_from > 0 && n_left_to_next > 0)
 	{
 	  vlib_buffer_t *b0;
-	  hicn_buffer_t *hb0;
 	  u8 isv6;
 	  u8 *nameptr;
 	  u16 namelen;
@@ -100,7 +99,6 @@ hicn_data_pcslookup_node_fn (vlib_main_t * vm,
 	  n_left_to_next -= 1;
 
 	  b0 = vlib_get_buffer (vm, bi0);
-	  hb0 = hicn_get_buffer (b0);
 	  next0 = HICN_DATA_PCSLOOKUP_NEXT_ERROR_DROP;
 
 	  /* Incr packet counter */
@@ -126,25 +124,7 @@ hicn_data_pcslookup_node_fn (vlib_main_t * vm,
 
 	      stats.pkts_data_count += 1;
 
-#if HICN_FEATURE_CS
-	      if ((res == HICN_ERROR_HASHTB_HASH_NOT_FOUND ||
-		   (res == HICN_ERROR_NONE && is_cs0)) &&
-		  ((hb0->flags & HICN_BUFFER_FLAGS_FACE_IS_APP)))
-		{
-		  next0 = HICN_DATA_PCSLOOKUP_NEXT_STORE_DATA;
-		}
-	      else if (res == HICN_ERROR_NONE)
-		{
-		  /*
-		   * In case the result of the lookup
-		   * is a CS entry, the packet is
-		   * dropped
-		   */
-		  next0 = HICN_DATA_PCSLOOKUP_NEXT_DATA_FWD + is_cs0;
-		}
-	    }
-#else
-	      if (res == HICN_ERROR_NONE)
+              if (res == HICN_ERROR_NONE)
 		{
 		  /*
 		   * In case the result of the lookup
@@ -154,7 +134,6 @@ hicn_data_pcslookup_node_fn (vlib_main_t * vm,
 		  next0 = HICN_DATA_PCSLOOKUP_NEXT_DATA_FWD + is_cs0;
 		}
 	    }
-#endif
 
 	  hicn_store_internal_state (b0, name_hash, node_id0, dpo_ctx_id0,
 				     vft_id0, hash_entry_id, bucket_id,
@@ -231,9 +210,6 @@ VLIB_REGISTER_NODE(hicn_data_pcslookup_node) =
   .error_strings = hicn_data_pcslookup_error_strings,
   .n_next_nodes = HICN_DATA_PCSLOOKUP_N_NEXT,
   .next_nodes = {
-    [HICN_DATA_PCSLOOKUP_NEXT_V4_LOOKUP] = "ip4-lookup",
-    [HICN_DATA_PCSLOOKUP_NEXT_V6_LOOKUP] = "ip6-lookup",
-    [HICN_DATA_PCSLOOKUP_NEXT_STORE_DATA] = "hicn-data-push",
     [HICN_DATA_PCSLOOKUP_NEXT_DATA_FWD] = "hicn-data-fwd",
     [HICN_DATA_PCSLOOKUP_NEXT_ERROR_DROP] = "error-drop",
   },
diff --git a/hicn-plugin/src/data_push_node.c b/hicn-plugin/src/data_push_node.c
deleted file mode 100644
index 18c4690b1..000000000
--- a/hicn-plugin/src/data_push_node.c
+++ /dev/null
@@ -1,326 +0,0 @@
-/*
- * Copyright (c) 2017-2019 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 "hicn.h"
-#include "parser.h"
-#include "strategy_dpo_ctx.h"
-#include "infra.h"
-#include "mgmt.h"
-#include "pcs.h"
-#include "state.h"
-
-/*
- * Node context data (to be used in all the strategy nodes); we think this is
- * per-thread/instance
- */
-typedef struct hicn_data_push_runtime_s
-{
-  int id;
-  hicn_pit_cs_t *pitcs;
-} hicn_data_push_runtime_t;
-
-/* Stats string values */
-static char *hicn_data_push_error_strings[] = {
-#define _(sym, string) string,
-  foreach_hicnfwd_error
-#undef _
-};
-
-typedef enum
-{
-  HICN_DATA_PUSH_NEXT_FWD,
-  HICN_DATA_PUSH_NEXT_ERROR_DROP,
-  HICN_DATA_PUSH_N_NEXT,
-} hicn_data_push_next_t;
-
-/* Trace context struct */
-typedef struct
-{
-  u32 next_index;
-  u32 sw_if_index;
-  u8 pkt_type;
-} hicn_data_push_trace_t;
-
-vlib_node_registration_t hicn_data_push_node;
-
-always_inline void
-prep_buffer_for_cs (vlib_main_t * vm, vlib_buffer_t * b0, u8 isv6)
-{
-  word buffer_advance = CLIB_CACHE_LINE_BYTES * 2;
-  hicn_buffer_t *hicnb = hicn_get_buffer (b0);
-
-  if (PREDICT_TRUE (b0->next_buffer == 0))
-    {
-      b0->total_length_not_including_first_buffer = 0;
-      b0->flags &= ~VLIB_BUFFER_NEXT_PRESENT;
-    }
-
-  /*
-   * Mark the buffer as smaller than TWO_CL. It will be stored as is in the CS, without excluding
-   * the hicn_header. Cloning is not possible, it will be copied.
-   */
-  if (b0->current_length <= (buffer_advance + (CLIB_CACHE_LINE_BYTES * 2)))
-    {
-      /* In this case the packet is copied. We don't need to add a reference as no buffer are
-       * chained to it.
-       */
-      hicnb->flags |= HICN_BUFFER_FLAGS_PKT_LESS_TWO_CL;
-    }
-  else
-    {
-      vlib_buffer_advance (b0, buffer_advance);
-    }
-}
-
-always_inline int
-hicn_new_data (vlib_main_t * vm, hicn_data_push_runtime_t * rt,
-	       vlib_buffer_t * b0, u32 ** to_forward, u32 * n_to_forward,
-	       f64 tnow, u8 * nameptr, u16 namelen, u8 isv6)
-{
-  int ret;
-  u32 bi0 = vlib_get_buffer_index (vm, b0);
-  hicn_hash_node_t *nodep;
-  hicn_pcs_entry_t *pitp;
-  hicn_header_t *hicn0 = vlib_buffer_get_current (b0);
-  hicn_buffer_t *hicnb0 = hicn_get_buffer (b0);
-  u32 node_id0 = 0;
-  index_t dpo_ctx_id0 = ~0;
-  u8 vft_id0 = default_dpo.hicn_dpo_get_type ();
-  u8 is_cs0 = 1;
-  u8 hash_entry_id = 0;
-  u32 bucket_id = ~0;
-  u8 bucket_is_overflow = 0;
-  hicn_lifetime_t dmsg_lifetime;
-
-  hicnb0 = hicn_get_buffer (b0);
-  hicn_type_t type = hicnb0->type;
-  hicn_ops_vft[type.l1]->get_lifetime (type, &hicn0->protocol,
-				       &dmsg_lifetime);
-
-  if (!dmsg_lifetime)
-    {
-      vlib_buffer_free_one (vm, bi0);
-      return HICN_ERROR_NONE;
-    }
-
-  /* Create PIT node and init PIT entry */
-  nodep = hicn_hashtb_alloc_node (rt->pitcs->pcs_table);
-  if (PREDICT_FALSE (nodep == NULL))
-    {
-      vlib_buffer_free_one (vm, bi0);
-      /* Nothing we can do - no mem */
-      return HICN_ERROR_HASHTB_NOMEM;
-    }
-
-  pitp = hicn_pit_get_data (nodep);
-  hicn_cs_init_data (pitp);
-  pitp->shared.create_time = tnow;
-
-  if (dmsg_lifetime < HICN_PARAM_CS_LIFETIME_MIN
-      || dmsg_lifetime > HICN_PARAM_CS_LIFETIME_MAX)
-    {
-      dmsg_lifetime = HICN_PARAM_CS_LIFETIME_DFLT;
-    }
-  pitp->shared.expire_time = hicn_pcs_get_exp_time (tnow, dmsg_lifetime);
-
-  /* Store the original packet buffer in the CS node */
-  pitp->u.cs.cs_pkt_buf = vlib_get_buffer_index (vm, b0);
-
-  /* Set up the hash node and insert it */
-  hicn_hashtb_init_node (rt->pitcs->pcs_table, nodep, nameptr, namelen);
-
-
-  hicn_hash_entry_t *hash_entry;
-  ret =
-    hicn_pcs_cs_insert_update (vm, rt->pitcs, pitp, nodep, &hash_entry,
-			       hicnb0->name_hash, &node_id0, &dpo_ctx_id0,
-			       &vft_id0, &is_cs0, &hash_entry_id, &bucket_id,
-			       &bucket_is_overflow, hicnb0->face_id);
-
-  if (ret != HICN_ERROR_NONE)
-    {
-      hicn_hashtb_free_node (rt->pitcs->pcs_table, nodep);
-    }
-
-  if (ret != HICN_ERROR_HASHTB_NOMEM)
-    {
-      if (!is_cs0)
-	{
-	  ASSERT (ret != HICN_ERROR_NONE);
-	  hicn_store_internal_state (b0, hicnb0->name_hash, node_id0,
-				     dpo_ctx_id0, vft_id0, hash_entry_id,
-				     bucket_id, bucket_is_overflow);
-
-	  (*to_forward)[0] = bi0;
-	  *to_forward += 1;
-	  *n_to_forward += 1;
-	}
-      else
-	{
-	  prep_buffer_for_cs (vm, b0, isv6);
-	}
-    }
-
-  return (ret);
-
-}
-
-/*
- * ICN strategy later node for interests: - 1 packet at a time - ipv4/tcp
- * ipv6/tcp
- */
-uword
-hicn_data_push_fn (vlib_main_t * vm,
-		   vlib_node_runtime_t * node, vlib_frame_t * frame)
-{
-
-  u32 n_left_from, *from, *to_next, n_left_to_next;
-  hicn_data_push_next_t next_index;
-  hicn_data_push_runtime_t *rt;
-  vl_api_hicn_api_node_stats_get_reply_t stats = { 0 };
-  f64 tnow;
-  u32 *to_forward = NULL, *header = NULL, n_to_forward = 0;
-
-  from = vlib_frame_vector_args (frame);
-  n_left_from = frame->n_vectors;
-  next_index = (hicn_data_push_next_t) node->cached_next_index;
-  rt = vlib_node_get_runtime_data (vm, hicn_data_push_node.index);
-  rt->pitcs = &hicn_main.pitcs;
-
-  vec_alloc (to_forward, n_left_from);
-  header = to_forward;
-  /* Capture time in vpp terms */
-  tnow = vlib_time_now (vm);
-
-  while (n_left_from > 0)
-    {
-      u8 isv6;
-      u8 *nameptr;
-      u16 namelen;
-      hicn_name_t name;
-      hicn_header_t *hicn0;
-      vlib_buffer_t *b0;
-      u32 bi0;
-      int ret0;
-
-      /* Prefetch for next iteration. */
-      if (n_left_from > 1)
-	{
-	  vlib_buffer_t *b1;
-	  //hicn_buffer_t * hicnb1;
-	  b1 = vlib_get_buffer (vm, from[1]);
-	  CLIB_PREFETCH (b1, CLIB_CACHE_LINE_BYTES, LOAD);
-	  CLIB_PREFETCH (b1->data, CLIB_CACHE_LINE_BYTES, STORE);
-	}
-      /* Dequeue a packet buffer */
-      bi0 = from[0];
-      from += 1;
-      n_left_from -= 1;
-
-      b0 = vlib_get_buffer (vm, bi0);
-
-      ret0 = hicn_data_parse_pkt (b0, &name, &namelen, &hicn0, &isv6);
-      nameptr = (u8 *) (&name);
-
-      if (PREDICT_TRUE (ret0 == HICN_ERROR_NONE))
-	{
-	  hicn_new_data (vm, rt, b0, &to_forward, &n_to_forward, tnow,
-			 nameptr, namelen, isv6);
-	  stats.pkts_data_count++;
-	}
-
-      /* Maybe trace */
-      if (PREDICT_FALSE ((node->flags & VLIB_NODE_FLAG_TRACE) &&
-			 (b0->flags & VLIB_BUFFER_IS_TRACED)))
-	{
-	  hicn_data_push_trace_t *t =
-	    vlib_add_trace (vm, node, b0, sizeof (*t));
-	  t->pkt_type = HICN_PKT_TYPE_CONTENT;
-	  t->sw_if_index = vnet_buffer (b0)->sw_if_index[VLIB_RX];
-	  t->next_index = HICN_DATA_PUSH_NEXT_ERROR_DROP;
-	}
-    }
-
-  to_forward -= n_to_forward;
-  next_index = HICN_DATA_PUSH_NEXT_FWD;
-
-  while (n_to_forward > 0)
-    {
-      vlib_get_next_frame (vm, node, next_index, to_next, n_left_to_next);
-      while (n_to_forward > 0 && n_left_to_next > 0)
-	{
-	  to_next[0] = to_forward[0];
-	  to_forward++;
-	  n_to_forward--;
-	  to_next++;
-	  n_left_to_next--;
-	}
-
-      vlib_put_next_frame (vm, node, next_index, n_left_to_next);
-    }
-
-  vec_free (header);
-
-  vlib_node_increment_counter (vm, hicn_data_push_node.index,
-			       HICNFWD_ERROR_CACHED, stats.pkts_data_count);
-
-  return (frame->n_vectors);
-}
-
-/* packet trace format function */
-always_inline u8 *
-hicn_data_push_format_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 *);
-  hicn_data_push_trace_t *t = va_arg (*args, hicn_data_push_trace_t *);
-
-  s = format (s, "DATA-STORE: pkt: %d, sw_if_index %d, next index %d\n",
-	      (int) t->pkt_type, t->sw_if_index, t->next_index);
-
-  return (s);
-}
-
-
-/*
- * Node registration for the data forwarder node
- */
-/* *INDENT-OFF* */
-VLIB_REGISTER_NODE(hicn_data_push_node) =
-{
-  .function = hicn_data_push_fn,
-  .name = "hicn-data-push",
-  .vector_size = sizeof(u32),
-  .runtime_data_bytes = sizeof(hicn_data_push_runtime_t),
-  .format_trace = hicn_data_push_format_trace,
-  .type = VLIB_NODE_TYPE_INTERNAL,
-  .n_errors = ARRAY_LEN(hicn_data_push_error_strings),
-  .error_strings = hicn_data_push_error_strings,
-  .n_next_nodes = HICN_DATA_PUSH_N_NEXT,
-  .next_nodes = {
-    [HICN_DATA_PUSH_NEXT_FWD] = "hicn-data-fwd",
-    [HICN_DATA_PUSH_NEXT_ERROR_DROP] = "error-drop",
-  },
-};
-/* *INDENT-ON* */
-
-/*
- * fd.io coding-style-patch-verification: ON
- *
- * Local Variables: eval: (c-set-style "gnu") End:
- */
diff --git a/hicn-plugin/src/error.h b/hicn-plugin/src/error.h
index d35347779..59ebce61c 100644
--- a/hicn-plugin/src/error.h
+++ b/hicn-plugin/src/error.h
@@ -16,6 +16,13 @@
 #ifndef __HICN_ERROR_H__
 #define __HICN_ERROR_H__
 
+/**
+ * @file error.h
+ *
+ * Error codes for the hICN plugin.
+ */
+
+
 #define foreach_hicn_error                                              \
  _(NONE, 0, "Ok")                                                       \
  _(UNSPECIFIED, -128, "Unspecified Error")                              \
diff --git a/hicn-plugin/src/face_db.h b/hicn-plugin/src/face_db.h
index 9423c59d6..4dd8b2f32 100644
--- a/hicn-plugin/src/face_db.h
+++ b/hicn-plugin/src/face_db.h
@@ -20,7 +20,7 @@
 #include "faces/face.h"
 
 /**
- * @File
+ * @file face_db.h
  *
  * Define a face db that is store in every pit entry. A face db containes a list
  * of incoming faces for interest packets that are used to forward data packets
diff --git a/hicn-plugin/src/faces/dpo_face.h b/hicn-plugin/src/faces/dpo_face.h
deleted file mode 100644
index 3bb99ecdb..000000000
--- a/hicn-plugin/src/faces/dpo_face.h
+++ /dev/null
@@ -1,329 +0,0 @@
-/*
- * Copyright (c) 2017-2020 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.
- */
-
-#ifndef __HICN_DPO_H__
-#define __HICN_DPO_H__
-
-#include <vnet/vnet.h>
-#include <vnet/ip/ip4_packet.h>
-#include <vnet/adj/adj_midchain.h>
-
-#include "face.h"
-#include "../error.h"
-
-/**
- * @brief Initialize the internal structures of the dpo ip face module.
- */
-//void hicn_dpo_ip_module_init (void);
-
-
-/**
- * @brief Retrieve a vector of faces from the ip4 local address and returns its index.
- *
- * @param vec: Result of the lookup. If no face exists for the local address vec = NULL
- * @param hicnb_flags: Flags that indicate whether the face is an application
- * face or not
- * @param local_addr: Ip v4 nat address of the face
- * @param sw_if: software interface id of the face
- *
- * @result HICN_ERROR_FACE_NOT_FOUND if the face does not exist, otherwise HICN_ERROR_NONE.
- */
-always_inline int
-hicn_dpo_face_ip4_lock (hicn_face_id_t * face_id,
-                        u32 * in_faces_vec_id,
-                        u8 * hicnb_flags,
-                        const ip4_address_t * nat_addr)
-{
-  ip46_address_t ip_address = {0};
-  ip46_address_set_ip4(&ip_address, nat_addr);
-  hicn_face_input_faces_t *in_faces_vec =
-    hicn_face_get_vec (&ip_address, &hicn_face_vec_hashtb);
-
-  if (PREDICT_FALSE (in_faces_vec == NULL))
-    return HICN_ERROR_FACE_NOT_FOUND;
-
-  *in_faces_vec_id = in_faces_vec->vec_id;
-  hicn_face_t *face = hicn_dpoi_get_from_idx (in_faces_vec->face_id);
-
-  *hicnb_flags = HICN_BUFFER_FLAGS_DEFAULT;
-  *hicnb_flags |=
-    (face->flags & HICN_FACE_FLAGS_APPFACE_PROD) >>
-    HICN_FACE_FLAGS_APPFACE_PROD_BIT;
-
-  *face_id = in_faces_vec->face_id;
-
-  return HICN_ERROR_NONE;
-}
-
-/**
- * @brief Retrieve a face from the ip6 local address and returns its dpo. This
- * method adds a lock on the face state.
- *
- * @param dpo: Result of the lookup. If the face doesn't exist dpo = NULL
- * @param hicnb_flags: Flags that indicate whether the face is an application
- * face or not
- * @param nat_addr: Ip v6 nat address of the face
- * @param sw_if: software interface id of the face
- *
- * @result HICN_ERROR_FACE_NOT_FOUND if the face does not exist, otherwise HICN_ERROR_NONE.
- */
-always_inline int
-hicn_dpo_face_ip6_lock (hicn_face_id_t * face_id,
-                        u32 * in_faces_vec_id,
-                        u8 * hicnb_flags,
-                        const ip6_address_t * nat_addr)
-{
-  hicn_face_input_faces_t *in_faces_vec =
-    hicn_face_get_vec ((ip46_address_t *)nat_addr, &hicn_face_vec_hashtb);
-
-  if (PREDICT_FALSE (in_faces_vec == NULL))
-    return HICN_ERROR_FACE_NOT_FOUND;
-
-  *in_faces_vec_id = in_faces_vec->vec_id;
-  hicn_face_t *face = hicn_dpoi_get_from_idx (in_faces_vec->face_id);
-
-  *hicnb_flags = HICN_BUFFER_FLAGS_DEFAULT;
-  *hicnb_flags |=
-    (face->flags & HICN_FACE_FLAGS_APPFACE_PROD) >>
-    HICN_FACE_FLAGS_APPFACE_PROD_BIT;
-
-  *face_id = in_faces_vec->face_id;
-
-  return HICN_ERROR_NONE;
-}
-
-/**
- * @brief Call back to get the adj of the tunnel
- */
-static adj_walk_rc_t
-hicn4_iface_adj_walk_cb (adj_index_t ai,
-                        void *ctx)
-{
-
-  hicn_face_t *face = (hicn_face_t *)ctx;
-
-  dpo_set(&face->dpo, DPO_ADJACENCY_MIDCHAIN, DPO_PROTO_IP4, ai);
-  adj_nbr_midchain_stack(ai, &face->dpo);
-
-  return (ADJ_WALK_RC_CONTINUE);
-}
-
-/**
- * @brief Retrieve, or create if it doesn't exist, a face from the ip6 local
- * address and returns its dpo. This method adds a lock on the face state.
- *
- * @param dpo: Result of the lookup
- * @param hicnb_flags: Flags that indicate whether the face is an application
- * face or not
- * @param nat_addr: Ip v4 remote address of the face
- * @param sw_if: software interface id of the face
- * @param node_index: vlib edge index to use in the packet processing
- */
-always_inline void
-hicn_dpo_iface_ip4_add_and_lock (hicn_face_id_t * index,
-                                 u8 * hicnb_flags,
-                                 const ip4_address_t * nat_addr,
-                                 u32 sw_if, u32 adj_index, u32 node_index)
-{
-  /*All (complete) faces are indexed by remote addess as well */
-
-  ip46_address_t ip_address = {0};
-  ip46_address_set_ip4(&ip_address, nat_addr);
-
-  /* if the face exists, it adds a lock */
-  hicn_face_t *face =
-    hicn_face_get (&ip_address, sw_if, &hicn_face_hashtb, adj_index);
-
-  if (face == NULL)
-    {
-      hicn_face_id_t idx;
-      hicn_iface_add (&ip_address, sw_if, &idx, DPO_PROTO_IP4, adj_index);
-
-      face = hicn_dpoi_get_from_idx(idx);
-
-      face->dpo.dpoi_type = DPO_FIRST;
-      face->dpo.dpoi_proto = DPO_PROTO_IP4;
-      face->dpo.dpoi_index = adj_index;
-      face->dpo.dpoi_next_node = node_index;
-
-      /* if (nat_addr->as_u32 == 0) */
-      /*   { */
-          adj_nbr_walk(face->sw_if,
-                       FIB_PROTOCOL_IP4,
-                       hicn4_iface_adj_walk_cb,
-                       face);
-        /* } */
-
-      *hicnb_flags = HICN_BUFFER_FLAGS_DEFAULT;
-
-      *index = idx;
-      return;
-    }
-  else
-    {
-      /* unlock the face. We don't take a lock on each interest we receive */
-      hicn_face_id_t face_id = hicn_dpoi_get_index(face);
-      hicn_face_unlock_with_id(face_id);
-    }
-
-  /* Code replicated on purpose */
-  *hicnb_flags = HICN_BUFFER_FLAGS_DEFAULT;
-  *hicnb_flags |=
-    (face->flags & HICN_FACE_FLAGS_APPFACE_PROD) >>
-    HICN_FACE_FLAGS_APPFACE_PROD_BIT;
-
-  *index = hicn_dpoi_get_index (face);
-}
-
-/**
- * @brief Call back to get the adj of the tunnel
- */
-static adj_walk_rc_t
-hicn6_iface_adj_walk_cb (adj_index_t ai,
-                         void *ctx)
-{
-
-  hicn_face_t *face = (hicn_face_t *)ctx;
-
-  ip_adjacency_t *adj = adj_get(ai);
-  if ((adj->lookup_next_index == IP_LOOKUP_NEXT_MIDCHAIN) ||
-      (adj->lookup_next_index == IP_LOOKUP_NEXT_MCAST_MIDCHAIN))
-    {
-      dpo_set(&face->dpo, DPO_ADJACENCY_MIDCHAIN, adj->ia_nh_proto, ai);
-      adj_nbr_midchain_stack(ai, &face->dpo);
-    }
-
-  return (ADJ_WALK_RC_CONTINUE);
-}
-
-
-/**
- * @brief Retrieve, or create if it doesn't exist, a face from the ip6 local
- * address and returns its dpo. This method adds a lock on the face state.
- *
- * @param dpo: Result of the lookup
- * @param hicnb_flags: Flags that indicate whether the face is an application
- * face or not
- * @param nat_addr: Ip v6 remote address of the face
- * @param sw_if: software interface id of the face
- * @param node_index: vlib edge index to use in the packet processing
- */
-always_inline void
-hicn_dpo_iface_ip6_add_and_lock (hicn_face_id_t * index,
-                                 u8 * hicnb_flags,
-                                 const ip6_address_t * nat_addr,
-                                 u32 sw_if, u32 adj_index, u32 node_index)
-{
-  /*All (complete) faces are indexed by remote addess as well */
-  /* if the face exists, it adds a lock */
-  hicn_face_t *face =
-    hicn_face_get ((ip46_address_t *)nat_addr, sw_if, &hicn_face_hashtb, adj_index);
-
-  if (face == NULL)
-    {
-      hicn_face_id_t idx;
-      hicn_iface_add ((ip46_address_t *) nat_addr, sw_if, &idx, DPO_PROTO_IP6, adj_index);
-
-      face = hicn_dpoi_get_from_idx(idx);
-
-      face->dpo.dpoi_type = DPO_FIRST;
-      face->dpo.dpoi_proto = DPO_PROTO_IP6;
-      face->dpo.dpoi_index = adj_index;
-      face->dpo.dpoi_next_node = node_index;
-
-      //if (ip46_address_is_zero((ip46_address_t *)nat_addr))
-      //  {
-      adj_nbr_walk(face->sw_if,
-                   FIB_PROTOCOL_IP6,
-                   hicn6_iface_adj_walk_cb,
-                   face);
-          //  }
-
-      *hicnb_flags = HICN_BUFFER_FLAGS_DEFAULT;
-
-      *index = idx;
-
-      return;
-    }
-  else
-    {
-      /* unlock the face. We don't take a lock on each interest we receive */
-      hicn_face_id_t face_id = hicn_dpoi_get_index(face);
-      hicn_face_unlock_with_id(face_id);
-    }
-
-  /* Code replicated on purpose */
-  *hicnb_flags = HICN_BUFFER_FLAGS_DEFAULT;
-  *hicnb_flags |=
-    (face->flags & HICN_FACE_FLAGS_APPFACE_PROD) >>
-    HICN_FACE_FLAGS_APPFACE_PROD_BIT;
-
-  *index = hicn_dpoi_get_index (face);
-}
-
-
-/* /\** */
-/*  * @brief Create an ip face and its corresponding dpo. Meant to be used for the */
-/*  * control plane. */
-/*  * */
-/*  * @param dpo: Data plane object that point to the face created. */
-/*  * @param local_addr: Ip v4 local address of the face */
-/*  * @param remote_addr: Ip v4 remote address of the face */
-/*  * @param sw_if: software interface id of the face */
-/*  * @param adj: Ip adjacency corresponding to the remote address in the face */
-/*  * @param node_index: vlib edge index to use in the packet processing */
-/*  * @param flags: Flags of the face */
-/*  * @param face_id: Identifier for the face (dpoi_index) */
-/*  * @return HICN_ERROR_FACE_ALREADY_CREATED if the face exists, otherwise HICN_ERROR_NONE */
-/*  *\/ */
-/* int hicn_dpo_ip4_create (dpo_id_t * dpo, */
-/* 			 const ip4_address_t * local_addr, */
-/* 			 const ip4_address_t * remote_addr, */
-/* 			 u32 sw_if, */
-/* 			 adj_index_t adj, */
-/* 			 u32 node_index, */
-/* 			 hicn_face_flags_t flags, hicn_face_id_t * face_id); */
-
-/* /\** */
-/*  * @brief Create an ip face and its corresponding dpo. Meant to be used for the */
-/*  * control plane. */
-/*  * */
-/*  * @param dpo: Data plane object that point to the face created. */
-/*  * @param local_addr: Ip v6 local address of the face */
-/*  * @param remote_addr: Ip v6 remote address of the face */
-/*  * @param sw_if: software interface id of the face */
-/*  * @param adj: Ip adjacency corresponding to the remote address in the face */
-/*  * @param node_index: vlib edge index to use in the packet processing */
-/*  * @param flags: Flags of the face */
-/*  * @param face_id: Identifier for the face (dpoi_index) */
-/*  * @return HICN_ERROR_FACE_ALREADY_CREATED if the face exists, otherwise HICN_ERROR_NONE */
-/*  *\/ */
-/* int hicn_dpo_ip6_create (dpo_id_t * dpo, */
-/* 			 const ip6_address_t * local_addr, */
-/* 			 const ip6_address_t * remote_addr, */
-/* 			 u32 sw_if, */
-/* 			 adj_index_t adj, */
-/* 			 u32 node_index, */
-/* 			 hicn_face_flags_t flags, hicn_face_id_t * face_id); */
-
-#endif // __HICN_DPO_IP_H__
-
-/*
- * fd.io coding-style-patch-verification: ON
- *
- * Local Variables:
- * eval: (c-set-style "gnu")
- * End:
- */
diff --git a/hicn-plugin/src/faces/face.h b/hicn-plugin/src/faces/face.h
index a9a565a5a..234c3fcc2 100644
--- a/hicn-plugin/src/faces/face.h
+++ b/hicn-plugin/src/faces/face.h
@@ -23,28 +23,55 @@
 #include <vnet/dpo/dpo.h>
 #include <vnet/adj/adj_types.h>
 #include <vppinfra/bihash_8_8.h>
+#include <vnet/adj/adj_midchain.h>
 
+
+#include "../error.h"
 typedef u8 hicn_face_flags_t;
 typedef index_t hicn_face_id_t;
-//typedef dpo_type_t hicn_face_type_t;
 
 /**
- * @file
+ * @file face.h
+ *
+ * This file implements a general face type. The purpose of a face is to
+ * carry the needed information to forward interest and data packets to the
+ * next node in the network. There are two type of faces: complete faces (in short
+ * faces), and incomplete faces (in short ifaces).
  *
- * @brief Face
+ * A face that does not contain the indication of the adjacency is an
+ * incomplete face (iface), otherwise it is considered to be complete. Ifaces are
+ * used to forward data back to the previous hICN hop from which we received an
+ * interest, while faces are used to forward interest packets to the next hicn node.
+ * Faces and ifaces are created at two different points in time. Faces are created
+ * when a route is added, while ifaces are created when an interest is received.
+ * In details, faces and ifaces carry the following information:
+ * - nat_addr: the ip address to perform src nat or dst nat on interest and data packets, respectively;
+ * - pl_id: the path label
+ * - locks: the number of entities using this face. When 0 the face can be deallocated
+ * - dpo: the dpo that identifies the next node in the vlib graph for processing the vlib
+ *   buffer. The dpo contains the dpo.dpoi_next field that points to the next node
+ *   in the vlib graph and the dpo.dpoi_index which is an index to adj used by the next node
+ *   to perform the l2 rewrite. In case of ifaces, it is likely we don't know the
+ *   adjacency when creting the face. In this case, the next node in the vlib graph
+ *   will be the node that performs a lookup in the fib. Only in case of udp tunnels,
+ *   which are bidirectional tunnel we know that the incoming tunnel is also the outgoing
+ *   one, therefore in this case we store the tunnel in the dpo.dpoi_index fields. For
+ *   all the other tunnels (which are most likely unidirectional), the source address of
+ *   the interest will be used to retrieve the outgoing tunnel when sending the corresponding
+ *   data back.
+ * - sw_if: the incoming interface of the interest
+ * - fib_node, fib_entry_index and fib_sibling are information used to be notified of
+ *   changes in the adjacency pointed by the dpo.
  *
- * This file implements a general face type. A face is carried through nodes as a
- * dpo. The face state (hicn_face_t) is the object pointed by the
- * dpoi_index in the dpo_id_t (see
- * https://docs.fd.io/vpp/18.07/d0/d37/dpo_8h_source.html).
- * A face state that does not contain the indication of the l2 adjacency is an
- * incomplete face (iface), otherwise it is considered to be complete. Each face type
- * provide specific node for processing packets in input or output of complete
- * and incomplete faces.
+ * We maintain two hash tables to retrieve faces and ifaces. In particular one hash table which
+ * index faces and ifaces for nat_address, sw_if and dpo. This is used to retrieve existing faces
+ * or ifaces when an interest is received and when an new face is created. A second hash table that
+ * indexes vectors of faces for nat_address and sw_if. This is used to retrieve a list of possible
+ * incoming faces when a data is received.
  */
 
 /**
- * @brief Structure holding the face state. It containes the fields shared among
+ * @brief Structure representing a face. It containes the fields shared among
  * all the types of faces as well it leaves some space for storing additional
  * information specific to each type.
  */
@@ -85,8 +112,6 @@ typedef struct __attribute__ ((packed)) hicn_face_s
 /* Pool of faces */
 extern hicn_face_t *hicn_dpoi_face_pool;
 
-//extern dpo_type_t hicn_face_type;
-
 /* Flags */
 /* A face is complete and it stores all the information. A iface lacks of the
    adj index, therefore sending a packet through a iface require a lookup in
@@ -127,11 +152,6 @@ STATIC_ASSERT ((HICN_FACE_FLAGS_APPFACE_CONS >>
 
 /**
  * @brief Definition of the virtual functin table for an hICN FACE DPO.
- *
- * An hICN dpo is a combination of a dpo context (hicn_dpo_ctx or struct that
- * extends a hicn_dpo_ctx) and a strategy node. The following virtual function table
- * template that glues together the fuction to interact with the context and the
- * creating the dpo
  */
 typedef struct hicn_face_vft_s
 {
@@ -176,7 +196,7 @@ extern dpo_type_t first_type;
 extern vlib_combined_counter_main_t *counters;
 
 /**
- * @brief Return the face id from the face state
+ * @brief Return the face id from the face object
  *
  * @param Pointer to the face state
  * @return face id
@@ -188,10 +208,11 @@ hicn_dpoi_get_index (hicn_face_t * face_dpoi)
 }
 
 /**
- * @brief Return the face from the face id. Face id must be valid.
+ * @brief Return the face object from the face id.
+ * This method is robust to invalid face id.
  *
  * @param dpoi_index Face identifier
- * @return Pointer to the face
+ * @return Pointer to the face or NULL
  */
 always_inline hicn_face_t *
 hicn_dpoi_get_from_idx_safe (hicn_face_id_t dpoi_index)
@@ -252,7 +273,7 @@ hicn_face_unlock_with_id (hicn_face_id_t face_id)
 }
 
 /**
- * @brief Add a lock to the face dpo
+ * @brief Add a lock to the face through its dpo
  *
  * @param dpo Pointer to the face dpo
  */
@@ -263,7 +284,7 @@ hicn_face_lock (dpo_id_t * dpo)
 }
 
 /**
- * @brief Remove a lock to the face dpo. Deallocate the face id locks == 0
+ * @brief Remove a lock to the face through its dpo. Deallocate the face id locks == 0
  *
  * @param dpo Pointer to the face dpo
  */
@@ -302,8 +323,6 @@ u8 *format_hicn_face_all (u8 * s, int n, ...);
  */
 int hicn_face_del (hicn_face_id_t face_id);
 
-/* FACE IP CODE */
-
 /**
  * @bried vector of faces used to collect faces having the same local address
  *
@@ -336,11 +355,24 @@ extern mhash_t hicn_face_vec_hashtb;
 
 
 /**
- * Key definition for the mhash table. An ip face is uniquely identified by ip
- * address and the interface id. The ip address can correspond to the remote ip
- * address of the next hicn hop, or to the local address of the receiving
- * interface. The former is used to retrieve the incoming face when an interest
- * is received, the latter when the arring packet is a data.
+ * Key definition for the mhash table. An face is uniquely identified by ip
+ * address, the interface id and a dpo pointing to the next node in the vlib graph.
+ * The ip address can correspond to the remote ip address of the next hicn hop,
+ * or to the local address of the receiving interface. The former is used to
+ * retrieve the incoming face when an interest is received, the latter when
+ * the arring packet is a data. If the face is a regular face
+ * In case of iface, the following structure can be filled in different ways:
+ * - dpo equal to DPO_INVALID when the iface is a regular hICN iface
+ * - in case of udp_tunnel dpo =
+ *   {
+ *    .dpoi_index = tunnel_id,
+ *    .dpoi_type = DPO_FIRST,  //We don't need the type, we leave it invalid
+ *    .dpoi_proto = DPO_PROTO_IP4 or DPO_PROTO_IP6,
+ *    .dpoi_next_node = HICN6_IFACE_OUTPUT_NEXT_UDP4_ENCAP or
+ *                      HICN6_IFACE_OUTPUT_NEXT_UDP6_ENCAP or
+ *                      HICN4_IFACE_OUTPUT_NEXT_UDP4_ENCAP or
+ *                      HICN4_IFACE_OUTPUT_NEXT_UDP6_ENCAP
+ *    }
  */
 typedef struct __attribute__ ((packed)) hicn_face_key_s
 {
@@ -370,7 +402,7 @@ hicn_face_get_key (const ip46_address_t * addr,
 }
 
 /**
- * @brief Get the dpoi from the nat address. Does not add any lock.
+ * @brief Get the face obj from the nat address. Does not add any lock.
  *
  * @param addr Ip v4 address used to create the key for the hash table.
  * @param sw_if Software interface id used to create the key for the hash table.
@@ -402,7 +434,7 @@ hicn_face_get (const ip46_address_t * addr, u32 sw_if, mhash_t * hashtb, index_t
 }
 
 /**
- * @brief Get the dpoi from the nat address. Does not add any lock.
+ * @brief Get the face obj from the nat address and the dpo. Does not add any lock.
  *
  * @param addr Ip v4 address used to create the key for the hash table.
  * @param sw_if Software interface id used to create the key for the hash table.
@@ -453,10 +485,10 @@ hicn_face_get_vec (const ip46_address_t * addr,
 /**
  * @brief Create a new face ip. API for other modules (e.g., routing)
  *
- * @param local_addr Local ip v4 or v6 address of the face
- * @param remote_addr Remote ip v4 or v6 address of the face
+ * @param dpo_nh dpo contained in the face that points to the next node in
+ *        the vlib graph
+ * @param nat_addr nat ip v4 or v6 address of the face
  * @param sw_if interface associated to the face
- * @param is_app_face Boolean to set the face as an application face
  * @param pfaceid Pointer to return the face id
  * @param is_app_prod if HICN_FACE_FLAGS_APPFACE_PROD the face is a local application face, all other values are ignored
  * @return HICN_ERROR_FACE_NO_GLOBAL_IP if the face does not have a globally
@@ -512,6 +544,248 @@ hicn_iface_add (ip46_address_t * nat_address, int sw_if,
     }
 }
 
+/**** Helpers to manipulate faces and ifaces from the face/iface input nodes ****/
+
+/**
+ * @brief Retrieve a vector of faces from the ip4 local address and returns its index.
+ *
+ * @param vec: Result of the lookup. If no face exists for the local address vec = NULL
+ * @param hicnb_flags: Flags that indicate whether the face is an application
+ * face or not
+ * @param local_addr: Ip v4 nat address of the face
+ * @param sw_if: software interface id of the face
+ *
+ * @result HICN_ERROR_FACE_NOT_FOUND if the face does not exist, otherwise HICN_ERROR_NONE.
+ */
+always_inline int
+hicn_face_ip4_lock (hicn_face_id_t * face_id,
+                        u32 * in_faces_vec_id,
+                        u8 * hicnb_flags,
+                        const ip4_address_t * nat_addr)
+{
+  ip46_address_t ip_address = {0};
+  ip46_address_set_ip4(&ip_address, nat_addr);
+  hicn_face_input_faces_t *in_faces_vec =
+    hicn_face_get_vec (&ip_address, &hicn_face_vec_hashtb);
+
+  if (PREDICT_FALSE (in_faces_vec == NULL))
+    return HICN_ERROR_FACE_NOT_FOUND;
+
+  *in_faces_vec_id = in_faces_vec->vec_id;
+  hicn_face_t *face = hicn_dpoi_get_from_idx (in_faces_vec->face_id);
+
+  *hicnb_flags = HICN_BUFFER_FLAGS_DEFAULT;
+  *hicnb_flags |=
+    (face->flags & HICN_FACE_FLAGS_APPFACE_PROD) >>
+    HICN_FACE_FLAGS_APPFACE_PROD_BIT;
+
+  *face_id = in_faces_vec->face_id;
+
+  return HICN_ERROR_NONE;
+}
+
+/**
+ * @brief Retrieve a face from the ip6 local address and returns its dpo. This
+ * method adds a lock on the face state.
+ *
+ * @param dpo: Result of the lookup. If the face doesn't exist dpo = NULL
+ * @param hicnb_flags: Flags that indicate whether the face is an application
+ * face or not
+ * @param nat_addr: Ip v6 nat address of the face
+ * @param sw_if: software interface id of the face
+ *
+ * @result HICN_ERROR_FACE_NOT_FOUND if the face does not exist, otherwise HICN_ERROR_NONE.
+ */
+always_inline int
+hicn_face_ip6_lock (hicn_face_id_t * face_id,
+                        u32 * in_faces_vec_id,
+                        u8 * hicnb_flags,
+                        const ip6_address_t * nat_addr)
+{
+  hicn_face_input_faces_t *in_faces_vec =
+    hicn_face_get_vec ((ip46_address_t *)nat_addr, &hicn_face_vec_hashtb);
+
+  if (PREDICT_FALSE (in_faces_vec == NULL))
+    return HICN_ERROR_FACE_NOT_FOUND;
+
+  *in_faces_vec_id = in_faces_vec->vec_id;
+  hicn_face_t *face = hicn_dpoi_get_from_idx (in_faces_vec->face_id);
+
+  *hicnb_flags = HICN_BUFFER_FLAGS_DEFAULT;
+  *hicnb_flags |=
+    (face->flags & HICN_FACE_FLAGS_APPFACE_PROD) >>
+    HICN_FACE_FLAGS_APPFACE_PROD_BIT;
+
+  *face_id = in_faces_vec->face_id;
+
+  return HICN_ERROR_NONE;
+}
+
+/**
+ * @brief Call back to get the adj of the tunnel
+ */
+static adj_walk_rc_t
+hicn4_iface_adj_walk_cb (adj_index_t ai,
+                        void *ctx)
+{
+
+  hicn_face_t *face = (hicn_face_t *)ctx;
+
+  dpo_set(&face->dpo, DPO_ADJACENCY_MIDCHAIN, DPO_PROTO_IP4, ai);
+  adj_nbr_midchain_stack(ai, &face->dpo);
+
+  return (ADJ_WALK_RC_CONTINUE);
+}
+
+/**
+ * @brief Retrieve, or create if it doesn't exist, a face from the ip6 local
+ * address and returns its dpo. This method adds a lock on the face state.
+ *
+ * @param dpo: Result of the lookup
+ * @param hicnb_flags: Flags that indicate whether the face is an application
+ * face or not
+ * @param nat_addr: Ip v4 remote address of the face
+ * @param sw_if: software interface id of the face
+ * @param node_index: vlib edge index to use in the packet processing
+ */
+always_inline void
+hicn_iface_ip4_add_and_lock (hicn_face_id_t * index,
+                                 u8 * hicnb_flags,
+                                 const ip4_address_t * nat_addr,
+                                 u32 sw_if, u32 adj_index, u32 node_index)
+{
+  /*All (complete) faces are indexed by remote addess as well */
+
+  ip46_address_t ip_address = {0};
+  ip46_address_set_ip4(&ip_address, nat_addr);
+
+  /* if the face exists, it adds a lock */
+  hicn_face_t *face =
+    hicn_face_get (&ip_address, sw_if, &hicn_face_hashtb, adj_index);
+
+  if (face == NULL)
+    {
+      hicn_face_id_t idx;
+      hicn_iface_add (&ip_address, sw_if, &idx, DPO_PROTO_IP4, adj_index);
+
+      face = hicn_dpoi_get_from_idx(idx);
+
+      face->dpo.dpoi_type = DPO_FIRST;
+      face->dpo.dpoi_proto = DPO_PROTO_IP4;
+      face->dpo.dpoi_index = adj_index;
+      face->dpo.dpoi_next_node = node_index;
+
+      /* if (nat_addr->as_u32 == 0) */
+      /*   { */
+          adj_nbr_walk(face->sw_if,
+                       FIB_PROTOCOL_IP4,
+                       hicn4_iface_adj_walk_cb,
+                       face);
+        /* } */
+
+      *hicnb_flags = HICN_BUFFER_FLAGS_DEFAULT;
+
+      *index = idx;
+      return;
+    }
+  else
+    {
+      /* unlock the face. We don't take a lock on each interest we receive */
+      hicn_face_id_t face_id = hicn_dpoi_get_index(face);
+      hicn_face_unlock_with_id(face_id);
+    }
+
+  /* Code replicated on purpose */
+  *hicnb_flags = HICN_BUFFER_FLAGS_DEFAULT;
+  *hicnb_flags |=
+    (face->flags & HICN_FACE_FLAGS_APPFACE_PROD) >>
+    HICN_FACE_FLAGS_APPFACE_PROD_BIT;
+
+  *index = hicn_dpoi_get_index (face);
+}
+
+/**
+ * @brief Call back to get the adj of the tunnel
+ */
+static adj_walk_rc_t
+hicn6_iface_adj_walk_cb (adj_index_t ai,
+                         void *ctx)
+{
+
+  hicn_face_t *face = (hicn_face_t *)ctx;
+
+  ip_adjacency_t *adj = adj_get(ai);
+  if ((adj->lookup_next_index == IP_LOOKUP_NEXT_MIDCHAIN) ||
+      (adj->lookup_next_index == IP_LOOKUP_NEXT_MCAST_MIDCHAIN))
+    {
+      dpo_set(&face->dpo, DPO_ADJACENCY_MIDCHAIN, adj->ia_nh_proto, ai);
+      adj_nbr_midchain_stack(ai, &face->dpo);
+    }
+
+  return (ADJ_WALK_RC_CONTINUE);
+}
+
+
+/**
+ * @brief Retrieve, or create if it doesn't exist, a face from the ip6 local
+ * address and returns its dpo. This method adds a lock on the face state.
+ *
+ * @param dpo: Result of the lookup
+ * @param hicnb_flags: Flags that indicate whether the face is an application
+ * face or not
+ * @param nat_addr: Ip v6 remote address of the face
+ * @param sw_if: software interface id of the face
+ * @param node_index: vlib edge index to use in the packet processing
+ */
+always_inline void
+hicn_iface_ip6_add_and_lock (hicn_face_id_t * index,
+                                 u8 * hicnb_flags,
+                                 const ip6_address_t * nat_addr,
+                                 u32 sw_if, u32 adj_index, u32 node_index)
+{
+  /*All (complete) faces are indexed by remote addess as well */
+  /* if the face exists, it adds a lock */
+  hicn_face_t *face =
+    hicn_face_get ((ip46_address_t *)nat_addr, sw_if, &hicn_face_hashtb, adj_index);
+
+  if (face == NULL)
+    {
+      hicn_face_id_t idx;
+      hicn_iface_add ((ip46_address_t *) nat_addr, sw_if, &idx, DPO_PROTO_IP6, adj_index);
+
+      face = hicn_dpoi_get_from_idx(idx);
+
+      face->dpo.dpoi_type = DPO_FIRST;
+      face->dpo.dpoi_proto = DPO_PROTO_IP6;
+      face->dpo.dpoi_index = adj_index;
+      face->dpo.dpoi_next_node = node_index;
+
+      adj_nbr_walk(face->sw_if,
+                   FIB_PROTOCOL_IP6,
+                   hicn6_iface_adj_walk_cb,
+                   face);
+
+      *hicnb_flags = HICN_BUFFER_FLAGS_DEFAULT;
+
+      *index = idx;
+
+      return;
+    }
+  else
+    {
+      /* unlock the face. We don't take a lock on each interest we receive */
+      hicn_face_id_t face_id = hicn_dpoi_get_index(face);
+      hicn_face_unlock_with_id(face_id);
+    }
+
+  /* Code replicated on purpose */
+  *hicnb_flags = HICN_BUFFER_FLAGS_DEFAULT;
+  *hicnb_flags |=
+    (face->flags & HICN_FACE_FLAGS_APPFACE_PROD) >>
+    HICN_FACE_FLAGS_APPFACE_PROD_BIT;
+
+  *index = hicn_dpoi_get_index (face);
+}
 
 #endif // __HICN_FACE_H__
 
diff --git a/hicn-plugin/src/faces/face_node.c b/hicn-plugin/src/faces/face_node.c
index 5b42f0dde..e1fd81ca0 100644
--- a/hicn-plugin/src/faces/face_node.c
+++ b/hicn-plugin/src/faces/face_node.c
@@ -17,7 +17,6 @@
 
 #include "face.h"
 #include "face_node.h"
-#include "dpo_face.h"
 #include "../strategy_dpo_manager.h"
 #include "face.h"
 #include "../cache_policies/cs_lru.h"
@@ -97,8 +96,8 @@ typedef enum
 #define IP_HEADER_4 ip4_header_t
 #define IP_HEADER_6 ip6_header_t
 
-#define LOCK_DPO_FACE_IP4 hicn_dpo_face_ip4_lock
-#define LOCK_DPO_FACE_IP6 hicn_dpo_face_ip6_lock
+#define LOCK_DPO_FACE_IP4 hicn_face_ip4_lock
+#define LOCK_DPO_FACE_IP6 hicn_face_ip6_lock
 
 #define TRACE_INPUT_PKT_IP4 hicn4_face_input_trace_t
 #define TRACE_INPUT_PKT_IP6 hicn6_face_input_trace_t
diff --git a/hicn-plugin/src/faces/face_node.h b/hicn-plugin/src/faces/face_node.h
index 932ee40f5..f5a8bf5ae 100644
--- a/hicn-plugin/src/faces/face_node.h
+++ b/hicn-plugin/src/faces/face_node.h
@@ -19,6 +19,23 @@
 #include <vlib/vlib.h>
 #include <vnet/vnet.h>
 
+/**
+ * @file face_node.h
+ *
+ * Implements the input and output face nodes. Input face nodes
+ * process incoming data while output face nodes process outgoing
+ * interests packets.
+ *
+ * Input face nodes follow hicn-face-input nodes and their purpose
+ * is to retrieve the list of possible incoming faces for each the data packet.
+ * The following node to the input face nodes is the hicn-data-pcslookup.
+ * Output face nodes follow the strategy and the hicn-interest-hitpit nodes and
+ * they perform the src nat on each interest packet. The node following the
+ * output face nodes depends on the adjacency type. In case of ip, the following
+ * node is the ip-rewrite, in case of tunnels the next node is the one implementing
+ * the tunnel encapsulation (udp-encap, mpls, etc).
+ */
+
 extern vlib_node_registration_t hicn4_face_input_node;
 extern vlib_node_registration_t hicn4_face_output_node;
 extern vlib_node_registration_t hicn6_face_input_node;
diff --git a/hicn-plugin/src/faces/iface_node.c b/hicn-plugin/src/faces/iface_node.c
index d42d0114e..433cf0b02 100644
--- a/hicn-plugin/src/faces/iface_node.c
+++ b/hicn-plugin/src/faces/iface_node.c
@@ -14,7 +14,6 @@
  */
 
 #include "face.h"
-#include "dpo_face.h"
 #include "../strategy_dpo_manager.h"
 #include "../hicn.h"
 #include "../infra.h"
@@ -96,8 +95,8 @@ typedef enum
 #define ADDRESSX2_IP6 ip6_address_t *local_address0 = ip6_interface_first_address(&ip6_main, swif0); \
   ip6_address_t *local_address1 = ip6_interface_first_address(&ip6_main, swif1);
 
-#define DPO_ADD_LOCK_IFACE_IP4 hicn_dpo_iface_ip4_add_and_lock
-#define DPO_ADD_LOCK_IFACE_IP6 hicn_dpo_iface_ip6_add_and_lock
+#define DPO_ADD_LOCK_IFACE_IP4 hicn_iface_ip4_add_and_lock
+#define DPO_ADD_LOCK_IFACE_IP6 hicn_iface_ip6_add_and_lock
 
 //#define VLIB_EDGE_IP4 data_fwd_iface_ip4_vlib_edge
 //#define VLIB_EDGE_IP6 data_fwd_iface_ip6_vlib_edge
diff --git a/hicn-plugin/src/faces/iface_node.h b/hicn-plugin/src/faces/iface_node.h
index 761721b2f..1a7c4291b 100644
--- a/hicn-plugin/src/faces/iface_node.h
+++ b/hicn-plugin/src/faces/iface_node.h
@@ -13,16 +13,35 @@
  * limitations under the License.
  */
 
-#ifndef __HICN_IFACE_IP_NODE_H__
-#define __HICN_IFACE_IP_NODE_H__
+#ifndef __HICN_IFACE_NODE_H__
+#define __HICN_IFACE_NODE_H__
 
 #include <vlib/vlib.h>
 #include <vnet/vnet.h>
 
 /**
+ * @file iface_node.h
+ *
+ * Implements the input and output iface nodes. Input iface nodes
+ * process incoming interests while output face nodes process outgoing
+ * data packets.
+ *
+ * Input iface nodes follow ip-lookup nodes and their purpose
+ * is to create (or retrieve if already existing) the list incoming face
+ * for each the interest packet.
+ * The following node to the input iface nodes is the hicn-interest-pcslookup.
+ * Output iface nodes follow the hicn-data-fwd and the hicn-interest-hitcs nodes and
+ * they perform the dst nat on each data packet. The node following the
+ * output face nodes depends on the adjacency type. In case of ip, the following
+ * node is the ip4/6-lookup, in case of tunnels the next node is the one implementing
+ * the tunnel encapsulation (udp-encap, mpls, etc).
+ */
+
+
+/**
  * @brief Initialize the ip iface module
  */
-void hicn_iface_ip_init (vlib_main_t * vm);
+void hicn_iface_init (vlib_main_t * vm);
 
 #endif // __HICN_IFACE_IP_NODE_H__
 
diff --git a/hicn-plugin/src/hashtb.h b/hicn-plugin/src/hashtb.h
index 756f247b7..3c72fda65 100644
--- a/hicn-plugin/src/hashtb.h
+++ b/hicn-plugin/src/hashtb.h
@@ -24,47 +24,35 @@
 #include "parser.h"
 #include "error.h"
 
-/* Handy abbreviations for success status, and for boolean values */
-#ifndef TRUE
-#define TRUE 1
-#endif
-
-#ifndef FALSE
-#define FALSE 0
-#endif
-
-/*
+/**
+ * @file hashtb.h
  * Lookup is finding a hashtable record whose name matches the name being
  * looked up.  Most of the lookup work is based on the hash value of the two
  * names. Note that the intel cache line size is 64 bytes, and some platforms
- * load in 2 cache lines together. - first step is to match a record at the
- * bucket/slot level (htab has an array of htbucket_t/htbc_elmt, where each
- * bucket has 7 slots to hold indices for entries.) Matching at this level
- * implies - the hashes of the lookup name and the record map to the same
- * bucket - the high 32 bits of the hashes (slot bce_hash_msb32s) match. Read
- * cost (on the hash table size, i.e. ignoring reading the name being looked
- * up): - First step normally requires 1 cache line load to pull in the
- * 64-byte htbucket_t with the 7 element slot table holding the hash_msb32s.
- * - In the event (hopefully rare for a hash table with appropriate number of
- * buckets) that more than 7 elements hash to the same bucket, lookup may
- * well need to look not only at the static htbc_elmt_t but at the chain of
- * dynamically allocated htbc_elmt_t's linked to the static htbc_elmt_t,
- * where each of these holds slot entries for additional elements. - Before
- * reaching that point, it is initially required is to read in the hash table
- * record fields (ht_bucket_buf, htnode buf, etc) holding pointers to the
- * arrays, but these cache lines are common to all lookups so will likely
- * already be in the cache. - second step is to match at the record level
- * (htnode/htkb level) once a slot-level match happens. Matching at this
- * level implies the following match - the hash values (the full 64 bits vs.
- * bucket+32 msb, above) With siphash, two names hashing to the same 64-bit
- * value is quite rare. - the name which, on the hash table side, is stored
- * as a list of htkb_t (key buffers). [In some cases, the full name is not
- * compared, and a match is assumed based on hash value match. Read cost: -
- * htnode_t, in one cache line, holds hash value and index for the htkb at
- * the head of the key buffer list - each key buffer (htkb_t) is cache line
- * aligned/sized, and holds 60 bytes of the name and requires a cache line
- * read. Simplification is that a fib lookup requires 3 cache lines: - bucket
- * - htnode - single key buffer (for cases where a name comparision is done)
+ * load in 2 cache lines together.
+ * - first step is to match a record at the bucket/slot level (htab has an
+ *   array of htbucket_t/htbc_elmt, where each bucket has 7 slots to hold indices
+ *   for entries.) Matching at this level implies
+ *   - the hashes of the lookup name and the record map to the same bucket
+ *   - the high 32 bits of the hashes (slot bce_hash_msb32s) match. Read
+ *     cost (on the hash table size, i.e. ignoring reading the name being
+ *     looked up):
+ *     - First step normally requires 1 cache line load to pull in the
+ *       64-byte htbucket_t with the 7 element slot table holding the
+ *       hash_msb32s.
+ *     - In the event (hopefully rare for a hash table with appropriate
+ *       number of buckets) that more than 7 elements hash to the same bucket,
+ *       lookup may well need to look not only at the static htbc_elmt_t but at
+ *       the chain of dynamically allocated htbc_elmt_t's linked to the static
+ *       htbc_elmt_t,  where each of these holds slot entries for additional elements.
+ *     - Before reaching that point, it is initially required to read in the
+ *       hash table record fields (ht_bucket_buf, htnode buf, etc) holding
+ *       pointers to the arrays, but these cache lines are common to all lookups
+ *       so will likely already be in the cache.
+ * - second step is to match at the record level (htnode/htkb level) once a
+ *   slot-level match happens. Matching at this level implies the following match
+ *   - the hash values (the full 64 bits vs. bucket+32 msb, above).
+ *   - the name which, on the hash table side, is stored as a list of htkb_t (key buffers).
  *
  * Some hashtables (for which rare false positives are tolerable) store hash
  * values but no keys. (In ISM NDN forwarder, this was used for dcm_dpf: data
@@ -73,6 +61,15 @@
  * are used (or even allocated at hash table creation).
  */
 
+/* Handy abbreviations for success status, and for boolean values */
+#ifndef TRUE
+#define TRUE 1
+#endif
+
+#ifndef FALSE
+#define FALSE 0
+#endif
+
 #define HICN_HASH_INVALID_IDX  ~0
 /*
  * for hicn_hashtb_next_node() iterator, this otherwise illegal context value
diff --git a/hicn-plugin/src/hicn.h b/hicn-plugin/src/hicn.h
index 6911cc5a9..3d980bd49 100644
--- a/hicn-plugin/src/hicn.h
+++ b/hicn-plugin/src/hicn.h
@@ -39,6 +39,10 @@
 #include <vnet/ip/ip4_packet.h>
 #include <vnet/buffer.h>
 
+/**
+ * @file
+ */
+
 /* Helper for avoiding warnings about type-punning */
 #define UNION_CAST(x, destType) \
    (((union {__typeof__(x) a; destType b;})x).b)
diff --git a/hicn-plugin/src/hicn_api.h b/hicn-plugin/src/hicn_api.h
index 6eecadf34..ec10a6bbd 100644
--- a/hicn-plugin/src/hicn_api.h
+++ b/hicn-plugin/src/hicn_api.h
@@ -16,6 +16,11 @@
 #ifndef __HICN_API_H__
 #define __HICN_API_H__
 
+/**
+ * @file
+ */
+
+
 #define HICN_STRATEGY_NULL ~0
 #define HICN_FIB_TABLE 10
 
diff --git a/hicn-plugin/src/hicn_msg_enum.h b/hicn-plugin/src/hicn_msg_enum.h
index 291e6226c..fcf2a1e87 100644
--- a/hicn-plugin/src/hicn_msg_enum.h
+++ b/hicn-plugin/src/hicn_msg_enum.h
@@ -18,6 +18,9 @@
 
 #include <vppinfra/byte_order.h>
 
+/**
+ * @file
+ */
 #define vl_msg_id(n, h) n,
 typedef enum
 {
diff --git a/hicn-plugin/src/infra.h b/hicn-plugin/src/infra.h
index 007cf266d..9dc77c9e8 100644
--- a/hicn-plugin/src/infra.h
+++ b/hicn-plugin/src/infra.h
@@ -22,8 +22,12 @@
 #include "pcs.h"
 
 /**
- * hICN plugin global state: see also
- * - fib and pits
+ * @file infra.h
+ *
+ */
+
+/**
+ * @brief hICN plugin global state.
  */
 typedef struct hicn_main_s
 {
diff --git a/hicn-plugin/src/interest_hitcs.h b/hicn-plugin/src/interest_hitcs.h
index b568a9290..94fa3e6f5 100644
--- a/hicn-plugin/src/interest_hitcs.h
+++ b/hicn-plugin/src/interest_hitcs.h
@@ -21,6 +21,16 @@
 
 #include "pcs.h"
 
+/**
+ * @file interest_hitcs.h
+ *
+ * This is the node encoutered by interest packets after the hicn-interest-pcslookup.
+ * This node satisfies an interest with a data stored in the CS and send the data back
+ * from the incoming iface of the interest (i.e., the vlib buffer is sent to the
+ * hicn6-iface-output or hicn4-iface-output node). In case the data is expired, the
+ * vlib buffer is sent to the hicn-strategy node.
+ */
+
 /*
  * Node context data; we think this is per-thread/instance
  */
diff --git a/hicn-plugin/src/interest_hitpit.h b/hicn-plugin/src/interest_hitpit.h
index f26a25afa..ffdc61c8f 100644
--- a/hicn-plugin/src/interest_hitpit.h
+++ b/hicn-plugin/src/interest_hitpit.h
@@ -21,6 +21,17 @@
 
 #include "pcs.h"
 
+/**
+ * @file interest_hitpit.h
+ *
+ * This is the node encoutered by interest packets after the hicn-interest-pcslookup.
+ * This node aggregates an interest in the PIT or forward it in case of a retransmission.
+ * If the interest must be retransmitted the next vlib node will be on of the
+ * hicn6-face-output or hicn4-face-output nodes. If the pit entry is expired the next vlib node
+ * will be the hicn-strategy node, otherwise the vlib buffer is dropped.
+ */
+
+
 /*
  * Node context data; we think this is per-thread/instance
  */
diff --git a/hicn-plugin/src/interest_pcslookup.h b/hicn-plugin/src/interest_pcslookup.h
index 5a5a6a7a8..cbc9dde51 100644
--- a/hicn-plugin/src/interest_pcslookup.h
+++ b/hicn-plugin/src/interest_pcslookup.h
@@ -21,6 +21,17 @@
 
 #include "pcs.h"
 
+/**
+ * @file interest_pcslookup.h
+ *
+ * This is the node encoutered by interest packets after the hicn6-iface-input or
+ * hicn4-iface-input. This node performs a lookup in the pit and content store and
+ * if there is a hit in the PIT, the vlib buffer is passed to the hicn-interest-hitcs
+ * while if there is a hit in the CS  the vlib buffer is passed to the
+ * hicn-interest-hitpit. If there isn't any hit, the vlib buffer is passed to the
+ * hicn-strategy node.
+ */
+
 /*
  * Node context data; we think this is per-thread/instance
  */
diff --git a/hicn-plugin/src/mapme_ack.h b/hicn-plugin/src/mapme_ack.h
index 98a219982..821baf203 100644
--- a/hicn-plugin/src/mapme_ack.h
+++ b/hicn-plugin/src/mapme_ack.h
@@ -24,6 +24,11 @@
 #include <vlib/vlib.h>
 #include <vnet/vnet.h>
 
+/**
+ * @file
+ *
+ */
+
 /* Node context data */
 typedef struct hicn_mapme_ack_runtime_s
 {
diff --git a/hicn-plugin/src/mapme_ctrl.h b/hicn-plugin/src/mapme_ctrl.h
index a69dfe1fc..9af4beccc 100644
--- a/hicn-plugin/src/mapme_ctrl.h
+++ b/hicn-plugin/src/mapme_ctrl.h
@@ -24,6 +24,11 @@
 #include <vlib/vlib.h>
 #include <vnet/vnet.h>
 
+/**
+ * @file mapme_ctrl.h
+ *
+ */
+
 /* Node context data */
 typedef struct hicn_mapme_ctrl_runtime_s
 {
diff --git a/hicn-plugin/src/mapme_eventmgr.h b/hicn-plugin/src/mapme_eventmgr.h
index 84c57b50f..b63d16805 100644
--- a/hicn-plugin/src/mapme_eventmgr.h
+++ b/hicn-plugin/src/mapme_eventmgr.h
@@ -16,6 +16,12 @@
 #include <vlib/vlib.h>		// vlib_node_registration_t (vlib/node.h)
 
 #include <hicn/name.h>
+
+/**
+ * @file mapme_eventmgr.h
+ *
+ */
+
 /*
  * Structure carrying all necessary information for managing Special Interest
  * (re)transmissions.
diff --git a/hicn-plugin/src/mgmt.h b/hicn-plugin/src/mgmt.h
index 326922a01..6db0fe0c1 100644
--- a/hicn-plugin/src/mgmt.h
+++ b/hicn-plugin/src/mgmt.h
@@ -20,6 +20,11 @@
 #include "faces/face.h"
 #include "hicn_api.h"
 
+/**
+ * @file mgmt.h
+ *
+ */
+
 typedef struct icn_stats_s
 {
   u32 pkts_processed;
diff --git a/hicn-plugin/src/params.h b/hicn-plugin/src/params.h
index d8e4dc247..606d50771 100644
--- a/hicn-plugin/src/params.h
+++ b/hicn-plugin/src/params.h
@@ -18,6 +18,12 @@
 
 #include <math.h>
 
+/**
+ * @file params.h
+ *
+ */
+
+
 /*
  * Features
  */
diff --git a/hicn-plugin/src/parser.h b/hicn-plugin/src/parser.h
index 0d72780ae..e79d65831 100644
--- a/hicn-plugin/src/parser.h
+++ b/hicn-plugin/src/parser.h
@@ -21,6 +21,9 @@
 #include "hicn.h"
 #include "error.h"
 
+/**
+ * @file parser.h
+ */
 
 /*
  * Key type codes for header, header tlvs, body tlvs, and child tlvs
@@ -33,6 +36,15 @@ enum hicn_pkt_type_e
   HICN_PKT_TYPE_CONTENT = 1,
 };
 
+/**
+ * @brief Parse an interest packet
+ *
+ * @param pkt vlib buffer holding the interest
+ * @param name return variable that will point to the hicn name
+ * @param namelen return valiable that will hold the length of the name
+ * @param pkt_hdrp return valiable that will point to the packet header
+ * @param isv6 return variable that will be equale to 1 is the header is ipv6
+ */
 always_inline int
 hicn_interest_parse_pkt (vlib_buffer_t * pkt, hicn_name_t * name,
 			 u16 * namelen, hicn_header_t ** pkt_hdrp, u8 * isv6)
@@ -61,6 +73,15 @@ hicn_interest_parse_pkt (vlib_buffer_t * pkt, hicn_name_t * name,
   return HICN_ERROR_NONE;
 }
 
+/**
+ * @brief Parse a data packet
+ *
+ * @param pkt vlib buffer holding the interest
+ * @param name return variable that will point to the hicn name
+ * @param namelen return valiable that will hold the length of the name
+ * @param pkt_hdrp return valiable that will point to the packet header
+ * @param isv6 return variable that will be equale to 1 is the header is ipv6
+ */
 always_inline int
 hicn_data_parse_pkt (vlib_buffer_t * pkt, hicn_name_t * name,
 		     u16 * namelen, hicn_header_t ** pkt_hdrp, u8 * isv6)
diff --git a/hicn-plugin/src/pcs.h b/hicn-plugin/src/pcs.h
index 1d99136a2..a9e1ae5a0 100644
--- a/hicn-plugin/src/pcs.h
+++ b/hicn-plugin/src/pcs.h
@@ -22,8 +22,17 @@
 #include "error.h"
 #include "cache_policies/cs_policy.h"
 #include "faces/face.h"
-#include "faces/dpo_face.h"
-//#include "faces/app/face_prod.h"
+
+/**
+ * @file pcs.h
+ *
+ * This file implement the PIT and CS which are collapsed in the same
+ * structure, thereore an entry is either a PIT entry of a CS entry.
+ * The implementation consist of a hash table where each entry of the
+ * hash table contains a PIT or CS entry, some counters to maintain the
+ * status of the PIT/CS and the reference to the eviction policy for
+ * the CS. The default eviction policy id FIFO.
+ */
 
 /* The PIT and CS are stored as a union */
 #define HICN_PIT_NULL_TYPE 0
@@ -32,7 +41,7 @@
 
 /*
  * Definitions and Forward refs for the time counters we're trying out.
- * Counters are maintained by the background process.
+ * Counters are maintained by the background process. TODO.
  */
 #define SEC_MS 1000
 #define HICN_INFRA_FAST_TIMER_SECS  1
@@ -41,8 +50,7 @@
 #define HICN_INFRA_SLOW_TIMER_MSECS (HICN_INFRA_SLOW_TIMER_SECS * SEC_MS)
 
 /*
- * Max number of incoming (interest) faces supported, for now. Note that
- * changing this may change alignment within the PIT struct, so be careful.
+ * Note that changing this may change alignment within the PIT struct, so be careful.
  */
 typedef struct __attribute__ ((packed)) hicn_pcs_shared_s
 {
@@ -72,13 +80,11 @@ typedef struct __attribute__ ((packed)) hicn_pit_entry_s
 
   /*
    * Egress next hop (containes the egress face) This id refers to the
-   * nh
-   */
-  /* choosen in the next_hops array of the dpo */
+   * position of the choosen face in the next_hops array of the dpo */
   /* 18B + 1B = 19B */
   u8 pe_txnh;
 
-  /* Array of faces */
+  /* Array of incoming ifaces */
   /* 24B + 32B (8B*4) =56B */
   hicn_face_db_t faces;
 
@@ -101,12 +107,6 @@ typedef struct __attribute__ ((packed)) hicn_cs_entry_s
   /* Ingress face */
   /* 24B + 4B = 28B */
   hicn_face_id_t cs_rxface;
-  /* //Fix alignment issues */
-  /* union */
-  /* { */
-  /*   dpo_id_t cs_rxface; */
-  /*   u64 cs_rxface_u64; */
-  /* }; */
 
   /* Linkage for LRU, in the form of hashtable node indexes */
   /* 28B + 8B = 36B */
diff --git a/hicn-plugin/src/pg.h b/hicn-plugin/src/pg.h
index 9ec3eeabc..84a391d43 100644
--- a/hicn-plugin/src/pg.h
+++ b/hicn-plugin/src/pg.h
@@ -18,7 +18,7 @@
 
 
 /**
- * @File Packet generator for hICN
+ * @file pg.h
  *
  * The packet generator is made of two entities, a client and a server.
  * The client issues interests at high speed and the server satisfy each
diff --git a/hicn-plugin/src/route.h b/hicn-plugin/src/route.h
index 4918f275b..a1ba86b3d 100644
--- a/hicn-plugin/src/route.h
+++ b/hicn-plugin/src/route.h
@@ -21,19 +21,54 @@
 #include "hicn.h"
 #include "faces/face.h"
 
+/**
+ * @file route.h
+ *
+ * hICN uses a specific vrf to install the routes for a prefix has been enabled to
+ * be hicn. It considers the vrf 0 (the default vrf) as the dominating vrf on
+ * which every route is stored. Enabling a prefix to be hICN will copy all the routes
+ * in the vrf 0 for the given prefi, in the vrf HICN. Every modification made on the
+ * vrf 0 on an hICN enabled prefix is reflected in the vrf hICN (through the use of
+ * the fib entry tracking functionality). Moreover, we use the lookup in the vrf hICN
+ * as a way for punting packet that must be processed as hICN. The implementation will
+ * install a special dpo as a single next hop for the vpp load balancer for each entry
+ * in the vrf hICN that we enabled. Such dpo will have two purposes: 1) to punt packets
+ * to the hICN forwarding pipeline, 2) to point to the righe strategy (the dpoi_index will
+ * be an index to the strategy context while the dpoi_type will be an index to the strategy vft).
+ *
+ * Additionally, hICN assign each interface to the vrf hICN; this is required for
+ * the interest lookup. Vpp performs a lookup in the vrf assigned to the interface,
+ * therefore if an interface is not assigned to the hICN vrf, the lookup will be done
+ * on the vrf 0 and the packet won't be processed through the hicn forwarding pipeline.
+ */
+
+/*
+ * Adding each interface to the vrf hICN has the side effect that to ping you need to
+ * specify the vrf hICN in the command.
+ */
+
 extern fib_source_t hicn_fib_src;
 
 extern dpo_type_t udp_encap_dpo_types[FIB_PROTOCOL_MAX];
 
-/*
- * Retrieve the hicn dpo corresponding to a hicn prefix
+/**
+ * @Brief Return the hicn_dpo corresponding to the prefix in teh vrf HICN
+ *
+ * @param prefix Prefix for which we want to retrieve the hICN dpo
+ * @param hicn_dpo return value with the hicn_dpo
+ * @param fib_index return value with the fib index corresponding to the prefix
  */
 int
 hicn_route_get_dpo (const fib_prefix_t * prefix,
 		    const dpo_id_t ** hicn_dpo, u32 * fib_index);
 
 
-/* Remove a next hop route for a name prefix */
+/**
+ * @Brief Set the strategy for a given prefix
+ *
+ * @param prefix Prefix for which we set the strategy
+ * @param stretegy_id Index of the strategy to set
+ */
 int
 hicn_route_set_strategy (fib_prefix_t * prefix, u32 strategy_id);
 
@@ -61,9 +96,24 @@ ip_nh_add_helper (fib_protocol_t fib_proto, const fib_prefix_t * pfx, ip46_addre
 int
 ip_nh_del_helper (fib_protocol_t fib_proto, const fib_prefix_t * rpfx, ip46_address_t * nh, u32 sw_if);
 
+/**
+ * @Brief Enable an hICN for an ip prefix
+ *
+ * @param prefix Prefix for which we enable hICN
+ * @return HICN_ERROR_NONE if hICN was enabled on the prefix
+ * HICN_ERROR_ROUTE_NO_LD if the first dpo for the fib entry corresponding to the prefix is not a load_balancer
+ * HICN_ERROR_ROUTE_DPO_NO_HICN if the loadbalancer in the vrf HICN already contains a dpo which is not an hICN one
+ * HICN_ERROR_ROUTE_MLT_LD if there are more than a dpo in the vpp loadbalancer
+ */
 int
 hicn_route_enable (fib_prefix_t *prefix);
 
+/**
+ * @Brief Disable an hICN for an ip prefix. If hICN wasn't enable on the prefix
+ * nothing happens and it returns HICN_ERROR_ROUTE_NOT_FOUND
+ *
+ * @param prefix Prefix for which we disable hICN
+ */
 int
 hicn_route_disable (fib_prefix_t *prefix);
 
diff --git a/hicn-plugin/src/state.h b/hicn-plugin/src/state.h
index 7e984e6c3..37003d0ae 100644
--- a/hicn-plugin/src/state.h
+++ b/hicn-plugin/src/state.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017-2019 Cisco and/or its affiliates.
+ * Copyright (c) 2017-2020 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:
@@ -26,26 +26,26 @@
 #include "strategy_dpo_ctx.h"
 #include "strategy_dpo_manager.h"
 
-always_inline void
-hicn_prefetch_pcs_entry (hicn_buffer_t * hicnb, hicn_pit_cs_t * pitcs)
-{
-  hicn_hash_node_t *node = pool_elt_at_index (pitcs->pcs_table->ht_nodes,
-					      hicnb->node_id);
-
-  hicn_hash_bucket_t *bucket;
-  if (hicnb->hash_bucket_flags & HICN_HASH_NODE_OVERFLOW_BUCKET)
-    bucket =
-      pool_elt_at_index (pitcs->pcs_table->ht_overflow_buckets,
-			 hicnb->bucket_id);
-  else
-    bucket =
-      (hicn_hash_bucket_t *) (pitcs->pcs_table->ht_buckets +
-			      hicnb->bucket_id);
+/**
+ * @file plugin_state
+ *
+ * Helper functions to hicn state (hash node, hash entry, strategy vft, dpo vft and dpo context id)
+ *
+ */
 
-  CLIB_PREFETCH (node, CLIB_CACHE_LINE_BYTES, STORE);
-  CLIB_PREFETCH (bucket, CLIB_CACHE_LINE_BYTES, STORE);
-}
+//TODO exploit this state to prefetch hash nodes and entries.
 
+/**
+ * @brief Retrieve the hicn state
+ *
+ * @param hicnb hicn buffer used to retrieve the hicn state
+ * @param pitcs pointer to PIT/CS
+ * @param node node in the hash table referring to the buffer
+ * @param strategy_vft return value pointing to the strategy vft corresponding to the buffer
+ * @param dpo_vft return value pointing to the dpo vft corresponding to the buffer
+ * @param dpo_ctx_id return value pointing to the dpo context id corresponding to the buffer
+ * @param hash_entry entry in the hash table referring to the buffer
+ */
 always_inline void
 hicn_get_internal_state (hicn_buffer_t * hicnb, hicn_pit_cs_t * pitcs,
 			 hicn_hash_node_t ** node,
@@ -77,6 +77,19 @@ hicn_get_internal_state (hicn_buffer_t * hicnb, hicn_pit_cs_t * pitcs,
  * nodes can prefetch the corresponding state (PIT entry, dpo_ctx and the
  * strategy vft
  */
+/**
+ * @brief Store the hicn state in the hicn buffer
+ *
+ * @param b vlib buffer holding the hICN packet
+ * @param name_hash hash of the hICN name
+ * @param node_id id of the node in the hash table referring to the buffer
+ * @param dpo_ctx_id id of the dpo context id corresponding to the buffer
+ * @param vft_id id of the strategy vft corresponding to the buffer
+ * @param hash_entry_id id of the entry in the hash table referring to the buffer
+ * @param bucket_id id of the hasth table bucket that holds the hash entry
+ * @param bucket_is_overflow 1 if the bucket is from the ht_overflow_buckets pool
+ *                           0 if the bucket is from the ht_buckets pool
+ */
 always_inline void
 hicn_store_internal_state (vlib_buffer_t * b, u64 name_hash, u32 node_id,
 			   u8 dpo_ctx_id, u8 vft_id, u8 hash_entry_id,
diff --git a/hicn-plugin/src/strategies/dpo_mw.h b/hicn-plugin/src/strategies/dpo_mw.h
index 887c7003a..433c415fb 100644
--- a/hicn-plugin/src/strategies/dpo_mw.h
+++ b/hicn-plugin/src/strategies/dpo_mw.h
@@ -19,6 +19,14 @@
 #include <vnet/dpo/dpo.h>
 #include "../strategy_dpo_ctx.h"
 
+/**
+ * @file dpo_mw.h
+ *
+ * This file implements the strategy vtf (see strategy.h) and
+ * the dpo vft (see strategy_dpo_manager.h) for the strategy
+ * maximum weight
+ */
+
 #define DEFAULT_WEIGHT 0
 
 typedef struct hicn_strategy_mw_ctx_s
diff --git a/hicn-plugin/src/strategies/dpo_rr.h b/hicn-plugin/src/strategies/dpo_rr.h
index e80c0302a..e4e5b5372 100644
--- a/hicn-plugin/src/strategies/dpo_rr.h
+++ b/hicn-plugin/src/strategies/dpo_rr.h
@@ -20,6 +20,15 @@
 #include "../strategy_dpo_ctx.h"
 
 /**
+ * @file dpo_rr.h
+ *
+ * This file implements the strategy vtf (see strategy.h) and
+ * the dpo vft (see strategy_dpo_manager.h) for the strategy
+ * round robin.
+ */
+
+
+/**
  * Context for the Round Robin strategy
  */
 
diff --git a/hicn-plugin/src/strategies/strategy_mw.h b/hicn-plugin/src/strategies/strategy_mw.h
index f64f1fdc7..9e0078b23 100644
--- a/hicn-plugin/src/strategies/strategy_mw.h
+++ b/hicn-plugin/src/strategies/strategy_mw.h
@@ -19,6 +19,13 @@
 #include "../strategy.h"
 
 /**
+ * @file strategy_mw.h
+ *
+ * This file implements the maximum weight strategy. In this
+ * strategy the choosen next hop is one with the maximum weight.
+ */
+
+/**
  * @brief Return the vft for the Maximum Weight strategy
  */
 hicn_strategy_vft_t *hicn_mw_strategy_get_vft (void);
diff --git a/hicn-plugin/src/strategies/strategy_rr.h b/hicn-plugin/src/strategies/strategy_rr.h
index 3936845fe..4dfe76b43 100644
--- a/hicn-plugin/src/strategies/strategy_rr.h
+++ b/hicn-plugin/src/strategies/strategy_rr.h
@@ -19,6 +19,13 @@
 #include "../strategy.h"
 
 /**
+ * @file strategy_rr.h
+ *
+ * This file implements the round robin strategy. In this
+ * strategy the next hop is choosen in a round robin way.
+ */
+
+/**
  * @brief Return the vft for the Round Robin strategy
  */
 hicn_strategy_vft_t *hicn_rr_strategy_get_vft (void);
diff --git a/hicn-plugin/src/strategy.h b/hicn-plugin/src/strategy.h
index a63db84d4..d949f38a4 100644
--- a/hicn-plugin/src/strategy.h
+++ b/hicn-plugin/src/strategy.h
@@ -22,21 +22,20 @@
 #include "faces/face.h"
 
 /**
- * @File
+ * @file strategy.h
  *
  * A strategy is defined as a dpo and a set of function (vft) that will be called
  * during the packet processing. A strategy is associated to an entry in the fib by
  * assigning the corresponding dpo to the fib entry. The dpo points to a hICN dpo
  * context (ctx) which contains the information needed by the strategy to compute
  * the next hop. Each strategy hash its own dpo type, which means that the dpo_type
- * uniquely identify a strategy and its vft. The strategy node will use the dpo_type
+ * uniquely identifies a strategy and its vft. The strategy node will use the dpo_type
  * to retrieve the corresponding vft.
  * Here we provide:
  * - a template for the callbacks to implement in order to create a new strategy
  *   (hicn_fwd_strategy_t)
- * - the base structure for a strategy node
- *   (list of next vpp nodes, errors, tracing and the main function processing an
- *    interest and calling hicn_select_next_hop)
+ * - a default implementation for the strategy node which will call the strategy
+ *   functions while processing the interest packets
  */
 
 /* Trace context struct */
@@ -70,6 +69,25 @@ typedef enum
   HICN_STRATEGY_N_NEXT,
 } hicn_strategy_next_t;
 
+const static char *const hicn_ip6_nodes[] =
+{
+ "hicn6-iface-input",	// this is the name you give your node in VLIB_REGISTER_NODE
+ NULL,
+};
+
+const static char *const hicn_ip4_nodes[] =
+{
+ "hicn4-iface-input",	// this is the name you give your node in VLIB_REGISTER_NODE
+ NULL,
+};
+
+const static char *const *const hicn_nodes_strategy[DPO_PROTO_NUM] =
+{
+ [DPO_PROTO_IP6] = hicn_ip6_nodes,
+ [DPO_PROTO_IP4] = hicn_ip4_nodes,
+};
+
+
 extern vlib_node_registration_t hicn_strategy_node;
 
 #endif /* //__HICN_STRATEGY__ */
diff --git a/hicn-plugin/src/strategy_dpo_ctx.h b/hicn-plugin/src/strategy_dpo_ctx.h
index 54a339573..214ed88ad 100644
--- a/hicn-plugin/src/strategy_dpo_ctx.h
+++ b/hicn-plugin/src/strategy_dpo_ctx.h
@@ -22,6 +22,18 @@
 #include "params.h"
 #include "faces/face.h"
 
+/**
+ * @file strategy_dpo_ctx.h
+ *
+ * This file implements the general hICN DPO ctx (shared among all the strategies).
+ *
+ * An hICN DPO ctx contains the list of next hops, auxiliaries fields to maintain the dpo, map-me
+ * specifics (tfib_entry_count and seq), the dpo_type and 64B to let each strategy to store additional
+ * information. Each next hop is an hicn_face_id_t that refers to an index for an hICN face. The
+ * dpo_type is used to identify the strategy and to retrieve the vft corresponding to the strategy
+ * (see strategy.h) and to the dpo ctx (see strategy_dpo_manager.h)
+ */
+
 //FIB table for hicn. 0 is the default one used by ip
 #define HICN_FIB_TABLE 10
 
@@ -29,15 +41,6 @@
 
 #define INIT_SEQ 0
 
-/**
- * @brief Definition of the general hICN DPO ctx (shared among all the strategies).
- *
- * An hICN DPO ctx contains the list of next hops, auxiliaries fields to maintain the dpo, map-me
- * specifics (tfib_entry_count and seq), the dpo_type and 64B to let each strategy to store additional
- * information. Each next hop is a dpo_id_t that refers to an hICN face. The dpo_type is used to
- * identify the strategy and to retrieve the vft corresponding to the strategy (see strategy.h)
- * and to the dpo ctx (see strategy_dpo_manager.h)
- */
 typedef struct __attribute__ ((packed)) hicn_dpo_ctx_s
 {
   CLIB_CACHE_LINE_ALIGN_MARK (cacheline0);
diff --git a/hicn-plugin/src/strategy_dpo_manager.h b/hicn-plugin/src/strategy_dpo_manager.h
index eaec252b7..e96e050d9 100644
--- a/hicn-plugin/src/strategy_dpo_manager.h
+++ b/hicn-plugin/src/strategy_dpo_manager.h
@@ -20,10 +20,26 @@
 #include "strategy.h"
 
 /**
+ * @file strategy_dpo_manager.h
+ *
+ * This file implements structs and helper functions to manipulate hICN dpo.
+ * An hICN DPO is a combination of:
+ *   - a hICN DPO ctx (context) that holds the structure containing the
+ *     information to choose the next hop,
+ *   - a dpo vft that specify how to update the hICN DPO ctx when a next hop is
+ *     added, deleted or updated,
+ *   - a strategy containing (see strategy.h): (i) the vpp node that processes Interest packets
+ *     subjected to such strategy, (ii) the definition of the vft that defines
+ *     the hICN strategy functions
+ * An hICN DPO is places as the sole next hop in the vpp loadbalancer, and it containes
+ * a list of next hops that will be used by the associated strategy when forwarding
+ * interest packets.
+ */
+
+/**
  * @brief Definition of the virtual function table for a hICN DPO.
  *
- * An hICN dpo is a combination of a dpo context (hicn_dpo_ctx or struct that
- * extends a hicn_dpo_ctx) and a strategy node. The following virtual function table
+ * The following virtual function table
  * template that glues together the fuction to interact with the context and the
  * creating the dpo
  */
@@ -48,37 +64,18 @@ typedef struct hicn_dpo_vft_s
  */
 extern hicn_dpo_vft_t default_dpo;
 
-const static char *const hicn_ip6_nodes[] = {
-  "hicn6-iface-input",	// this is the name you give your node in VLIB_REGISTER_NODE
-  NULL,
-};
-
-const static char *const hicn_ip4_nodes[] = {
-  "hicn4-iface-input",	// this is the name you give your node in VLIB_REGISTER_NODE
-  NULL,
-};
-
-const static char *const *const hicn_nodes_strategy[DPO_PROTO_NUM] = {
-  [DPO_PROTO_IP6] = hicn_ip6_nodes,
-  [DPO_PROTO_IP4] = hicn_ip4_nodes,
-};
-
 /**
  *  @brief Register a new hICN dpo to the manager.
  *
- *  An hICN DPO is a combination of:
- *   - a hICN DPO ctx (context) that holds the structure containing the
- *     information to choose the next hop,
- *   - a strategy containing: (i) the vpp node that processes Interest packets
- *     subjected to such strategy, (ii) the definition of the vft that defines
- *     the hICN strategy functions
- *  Registering a hICN DPO allows the plugin to be aware of the new dpo an be
- *  able to apply it to the FIB entries.
+ * Registering a hICN DPO allows the plugin to be aware of the new dpo an be
+ * able to apply it to the FIB entries.
  *
  * @param hicn_nodes A list of vpp to which pass an interest that matches with
  * the FIB entry to which the hICN DPO is applied. This list must contain the
  * name of the strategy node (or nodes in case of differentiation between IPv4
- * and IPv6).
+ * and IPv6). Unless really needed otherwise (i.e., different implementation of
+ * iface input), the list of node to use should be one provided in the strategy.h
+ * (hicn_nodes_strategy)
  * @param hicn_dpo_vft The structure holding the virtual function table to
  * interact with the hICN dpo and its context.
  * @param hicn_strategy_vft The structure holding the virtual function table
diff --git a/hicn-plugin/src/strategy_node.c b/hicn-plugin/src/strategy_node.c
index 578ba2c4f..0659a871a 100644
--- a/hicn-plugin/src/strategy_node.c
+++ b/hicn-plugin/src/strategy_node.c
@@ -130,6 +130,7 @@ hicn_new_interest (hicn_strategy_runtime_t * rt, vlib_buffer_t * b0,
 
       vnet_buffer (b0)->ip.adj_index[VLIB_TX] = outface;
       stats->pkts_interest_count++;
+      pitp->u.pit.pe_txnh = nh_idx;
     }
   else
     {
diff --git a/hicn-plugin/src/udp_tunnels/udp_decap.h b/hicn-plugin/src/udp_tunnels/udp_decap.h
index adbec3f03..9ddb8a73b 100644
--- a/hicn-plugin/src/udp_tunnels/udp_decap.h
+++ b/hicn-plugin/src/udp_tunnels/udp_decap.h
@@ -13,4 +13,20 @@
  * limitations under the License.
  */
 
+#ifndef __UDP_DECAP_H__
+#define __UDP_DECAP_H__
+
+/**
+ * @file udp_decap.h
+ *
+ * Implements the udp decapsulation for udp tunnels
+ *
+ * Udp decap nodes follow the ip4/6-local nodes and their purpose
+ * is to retrieve the udp tunnel for the incoming packet. If a tunnel does
+ * not exist the packet is dropped.
+ * The following node to the udp decap nodes are the ip4/6-lookup nodes.
+ */
+
 extern vlib_node_registration_t udp_decap_node;
+
+#endif // __UDP_DECAP_H__
diff --git a/hicn-plugin/src/udp_tunnels/udp_decap_node.c b/hicn-plugin/src/udp_tunnels/udp_decap_node.c
index 6a5831c2b..5603f20f9 100644
--- a/hicn-plugin/src/udp_tunnels/udp_decap_node.c
+++ b/hicn-plugin/src/udp_tunnels/udp_decap_node.c
@@ -19,12 +19,6 @@
 #include "../hicn.h"
 #include "../strategy_dpo_ctx.h"
 
-/**
- * @File
- *
- * Definition of the nodes for ip incomplete faces.
- */
-
 vlib_node_registration_t udp_decap_node;
 
 static char *udp_decap_error_strings[] = {
diff --git a/hicn-plugin/src/udp_tunnels/udp_tunnel.h b/hicn-plugin/src/udp_tunnels/udp_tunnel.h
index 8f38a47e4..2ec92056c 100644
--- a/hicn-plugin/src/udp_tunnels/udp_tunnel.h
+++ b/hicn-plugin/src/udp_tunnels/udp_tunnel.h
@@ -20,6 +20,17 @@
 #include <vppinfra/error.h>
 #include <vnet/udp/udp_encap.h>
 
+/**
+ * @file udp_tunnel.h
+ *
+ * This file implements bidirectional udp tunnels. Udp tunnels exploit
+ * the udp encap functionality in vpp. In particular, a udp tunnel creates
+ * an udp encap object with the information for encapsulating packets and it
+ * implements the udp decap node. The udp decap node checks if a udp tunnel exists
+ * before performing the decapsulation. If the tunnel does not exist the packet
+ * is dropped.
+ */
+
 #define UDP_TUNNEL_INVALID ~0
 
 extern dpo_type_t dpo_type_udp_ip4;
@@ -28,7 +39,19 @@ extern dpo_type_t dpo_type_udp_ip6;
 extern vlib_node_registration_t udp4_decap_node;
 extern vlib_node_registration_t udp6_decap_node;
 
-
+/**
+ * @brief Create a udp tunnel
+ *
+ * @param proto FIB_PROTOCOL_IP4 or FIB_PROTOCOL_IP6
+ * @param fib_index fib index to add to the udp encap
+ * @param src_ip source address of the tunnel
+ * @param dst_ip destination address of the tunnel
+ * @param src_port source port
+ * @param src_port destination port
+ * @param flags flags for the udp encap
+ *
+ * @return return the id of the tunnel
+ */
 u32 udp_tunnel_add (fib_protocol_t proto,
                     index_t fib_index,
                     const ip46_address_t * src_ip,
@@ -37,11 +60,35 @@ u32 udp_tunnel_add (fib_protocol_t proto,
                     u16 dst_port,
                     udp_encap_fixup_flags_t flags);
 
+/**
+ * @brief Retrieve the index of a udp tunnel (same id of the udp encap)
+ *
+ * @param src_ip source address of the tunnel
+ * @param dst_ip destination address of the tunnel
+ * @param src_port source port
+ * @param src_port destination port
+ *
+ * @return id of the udp tunnel/encap
+ */
 u32 udp_tunnel_get(const ip46_address_t * src_ip,
                    const ip46_address_t * dst_ip,
                    u16 src_port,
                    u16 dst_port);
 
+/**
+ * @brief Delete a udp tunnel
+ *
+ * @param proto FIB_PROTOCOL_IP4 or FIB_PROTOCOL_IP6
+ * @param fib_index fib index to add to the udp encap
+ * @param src_ip source address of the tunnel
+ * @param dst_ip destination address of the tunnel
+ * @param src_port source port
+ * @param src_port destination port
+ * @param flags flags for the udp encap
+ *
+ * @return HICN_ERROR_UDP_TUNNEL_NOT_FOUND if the tunnel was not found
+ *         or HICN_ERROR_NONE if the tunnel has been deleted
+ */
 int udp_tunnel_del (fib_protocol_t proto,
                     index_t fib_index,
                     const ip46_address_t * src_ip,
@@ -50,8 +97,18 @@ int udp_tunnel_del (fib_protocol_t proto,
                     u16 dst_port,
                     udp_encap_fixup_flags_t flags);
 
+/**
+ * @brief Add a udp tunnel from an existing udp encap
+ *
+ * @param uei index of the udp encap object
+ * @param proto DPO_PROTO_IP6 or DPO_PROTO_IP4
+ */
 void udp_tunnel_add_existing (index_t uei, dpo_proto_t proto);
 
+/**
+ * @brief Init the udp tunnel module
+ *
+ */
 void udp_tunnel_init();
 
 #endif
diff --git a/hicn-plugin/src/utils.h b/hicn-plugin/src/utils.h
index ecad47e9b..689942ab6 100644
--- a/hicn-plugin/src/utils.h
+++ b/hicn-plugin/src/utils.h
@@ -18,6 +18,17 @@
 
 #include "hicn.h"
 
+/**
+ * @file
+ *
+ * Helpers to print hicn headers
+ */
+
+/**
+ * @Brief Print the hicn name
+ *
+ * @param name hicn name to print
+ */
 always_inline void
 hicn_print_name6 (hicn_name_t * name)
 {
@@ -29,6 +40,11 @@ hicn_print_name6 (hicn_name_t * name)
   printf ("%s\n", s0);
 }
 
+/**
+ * @Brief Print the ipv6 hicn header (src and dst address and port)
+ *
+ * @param hicn0 hICN header to print
+ */
 always_inline void
 hicn_print6 (hicn_header_t * hicn0)
 {
@@ -43,6 +59,11 @@ hicn_print6 (hicn_header_t * hicn0)
   vlib_cli_output (vm, "%s\n", s0);
 }
 
+/**
+ * @Brief Print the ipv4 hicn header (src and dst address and port)
+ *
+ * @param hicn0 hICN header to print
+ */
 always_inline void
 hicn_print4 (hicn_header_t * hicn0)
 {