vnet: create L2 feature arc infrastructure

This commit adds two new nodes in the L2
datapath in input and output direction respectively.

These nodes fork the traffic into three feature
arcs: ip4, ip6 and nonip, which later join
to continue the usual L2 processing.
The vnet_l2_feature_enable_disable() function
with the same signature as
vnet_feature_enable_disable() takes care of
enabling the L2 datapath feature bits as needed, when
the features are enabled/disabled.

Thus, L2 features may use the similar plumbing as
the L3 features enjoy.

Change-Id: I76877b3a92d794c492bff1622bb26acba05705b2
Signed-off-by: Andrew Yourtchenko <ayourtch@gmail.com>

6 files changed, 727 insertions, 2 deletions

diff --git a/src/vnet/l2/l2_in_out_feat_arc.c b/src/vnet/l2/l2_in_out_feat_arc.c
new file mode 100644
index 00000000000..083a720316f
--- /dev/null
+++ b/src/vnet/l2/l2_in_out_feat_arc.c
@@ -0,0 +1,652 @@
+/*
+ * l2_in_out_feat_arc.c : layer 2 input/output acl processing
+ *
+ * Copyright (c) 2013,2018 Cisco and/or its affiliates.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <vlib/vlib.h>
+#include <vnet/vnet.h>
+#include <vnet/pg/pg.h>
+#include <vnet/ethernet/ethernet.h>
+#include <vnet/ethernet/packet.h>
+#include <vnet/ip/ip_packet.h>
+#include <vnet/ip/ip4_packet.h>
+#include <vnet/ip/ip6_packet.h>
+#include <vlib/cli.h>
+#include <vnet/l2/l2_input.h>
+#include <vnet/l2/l2_output.h>
+#include <vnet/l2/feat_bitmap.h>
+#include <vnet/l2/l2_in_out_feat_arc.h>
+
+#include <vppinfra/error.h>
+#include <vppinfra/hash.h>
+#include <vppinfra/cache.h>
+
+
+typedef struct
+{
+
+  /* Next nodes for each feature */
+  u32 feat_next_node_index[IN_OUT_FEAT_ARC_N_TABLE_GROUPS][32];
+  u8 ip4_feat_arc_index[IN_OUT_FEAT_ARC_N_TABLE_GROUPS];
+  u8 ip6_feat_arc_index[IN_OUT_FEAT_ARC_N_TABLE_GROUPS];
+  u8 nonip_feat_arc_index[IN_OUT_FEAT_ARC_N_TABLE_GROUPS];
+  u32 next_slot[IN_OUT_FEAT_ARC_N_TABLE_GROUPS];
+
+  /* convenience variables */
+  vlib_main_t *vlib_main;
+  vnet_main_t *vnet_main;
+} l2_in_out_feat_arc_main_t __attribute__ ((aligned (CLIB_CACHE_LINE_BYTES)));
+
+typedef struct
+{
+  u32 sw_if_index;
+  u32 next_index;
+  u32 feature_bitmap;
+  u16 ethertype;
+  u8 arc_head;
+} l2_in_out_feat_arc_trace_t;
+
+/* packet trace format function */
+static u8 *
+format_l2_in_out_feat_arc_trace (u8 * s, u32 is_output, 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 *);
+  l2_in_out_feat_arc_trace_t *t =
+    va_arg (*args, l2_in_out_feat_arc_trace_t *);
+
+  s =
+    format (s,
+	    "%s: head %d feature_bitmap %x ethertype %x sw_if_index %d, next_index %d",
+	    is_output ? "OUT-FEAT-ARC" : "IN-FEAT-ARC", t->arc_head,
+	    t->feature_bitmap, t->ethertype, t->sw_if_index, t->next_index);
+  return s;
+}
+
+static u8 *
+format_l2_in_feat_arc_trace (u8 * s, va_list * args)
+{
+  return format_l2_in_out_feat_arc_trace (s,
+					  IN_OUT_FEAT_ARC_INPUT_TABLE_GROUP,
+					  args);
+}
+
+static u8 *
+format_l2_out_feat_arc_trace (u8 * s, va_list * args)
+{
+  return format_l2_in_out_feat_arc_trace (s,
+					  IN_OUT_FEAT_ARC_OUTPUT_TABLE_GROUP,
+					  args);
+}
+
+
+#define foreach_l2_in_feat_arc_error                   \
+_(DEFAULT, "in default")                         \
+
+
+#define foreach_l2_out_feat_arc_error                   \
+_(DEFAULT, "out default")                         \
+
+
+typedef enum
+{
+#define _(sym,str) L2_IN_FEAT_ARC_ERROR_##sym,
+  foreach_l2_in_feat_arc_error
+#undef _
+    L2_IN_FEAT_ARC_N_ERROR,
+} l2_in_feat_arc_error_t;
+
+static char *l2_in_feat_arc_error_strings[] = {
+#define _(sym,string) string,
+  foreach_l2_in_feat_arc_error
+#undef _
+};
+
+typedef enum
+{
+#define _(sym,str) L2_OUT_FEAT_ARC_ERROR_##sym,
+  foreach_l2_out_feat_arc_error
+#undef _
+    L2_OUT_FEAT_ARC_N_ERROR,
+} l2_out_feat_arc_error_t;
+
+static char *l2_out_feat_arc_error_strings[] = {
+#define _(sym,string) string,
+  foreach_l2_out_feat_arc_error
+#undef _
+};
+
+
+l2_in_out_feat_arc_main_t l2_in_out_feat_arc_main;
+
+#define get_u16(addr) ( *((u16 *)(addr)) )
+#define L2_FEAT_ARC_VEC_SIZE 2
+
+static_always_inline void
+buffer_prefetch_xN (int vector_sz, vlib_buffer_t ** b)
+{
+  int ii;
+  for (ii = 0; ii < vector_sz; ii++)
+    CLIB_PREFETCH (b[ii], CLIB_CACHE_LINE_BYTES, STORE);
+}
+
+static_always_inline void
+get_sw_if_index_xN (int vector_sz, int is_output, vlib_buffer_t ** b,
+		    u32 * out_sw_if_index)
+{
+  int ii;
+  for (ii = 0; ii < vector_sz; ii++)
+    if (is_output)
+      out_sw_if_index[ii] = vnet_buffer (b[ii])->sw_if_index[VLIB_TX];
+    else
+      out_sw_if_index[ii] = vnet_buffer (b[ii])->sw_if_index[VLIB_RX];
+}
+
+static_always_inline void
+get_ethertype_xN (int vector_sz, int is_output, vlib_buffer_t ** b,
+		  u16 * out_ethertype)
+{
+  int ii;
+  for (ii = 0; ii < vector_sz; ii++)
+    {
+      ethernet_header_t *h0 = vlib_buffer_get_current (b[ii]);
+      u8 *l3h0 = (u8 *) h0 + vnet_buffer (b[ii])->l2.l2_len;
+      out_ethertype[ii] = clib_net_to_host_u16 (get_u16 (l3h0 - 2));
+    }
+}
+
+
+static_always_inline void
+set_next_in_arc_head_xN (int vector_sz, int is_output, u32 * next_nodes,
+			 vlib_buffer_t ** b, u32 * sw_if_index,
+			 u16 * ethertype, u8 ip4_arc, u8 ip6_arc,
+			 u8 nonip_arc, u16 * out_next)
+{
+  int ii;
+  for (ii = 0; ii < vector_sz; ii++)
+    {
+      u32 next_index = 0;
+      u8 feature_arc;
+      switch (ethertype[ii])
+	{
+	case ETHERNET_TYPE_IP4:
+	  feature_arc = ip4_arc;
+	  break;
+	case ETHERNET_TYPE_IP6:
+	  feature_arc = ip6_arc;
+	  break;
+	default:
+	  feature_arc = nonip_arc;
+	}
+      if (PREDICT_TRUE (vnet_have_features (feature_arc, sw_if_index[ii])))
+	vnet_feature_arc_start (feature_arc,
+				sw_if_index[ii], &next_index, b[ii]);
+      else
+	next_index =
+	  vnet_l2_feature_next (b[ii], next_nodes,
+				is_output ? L2OUTPUT_FEAT_OUTPUT_FEAT_ARC :
+				L2INPUT_FEAT_INPUT_FEAT_ARC);
+
+      out_next[ii] = next_index;
+    }
+}
+
+static_always_inline void
+set_next_in_arc_tail_xN (int vector_sz, int is_output, u32 * next_nodes,
+			 vlib_buffer_t ** b, u16 * out_next)
+{
+  int ii;
+  for (ii = 0; ii < vector_sz; ii++)
+    {
+      out_next[ii] =
+	vnet_l2_feature_next (b[ii], next_nodes,
+			      is_output ? L2OUTPUT_FEAT_OUTPUT_FEAT_ARC :
+			      L2INPUT_FEAT_INPUT_FEAT_ARC);
+    }
+
+}
+
+
+static_always_inline void
+maybe_trace_xN (int vector_sz, int arc_head, vlib_main_t * vm,
+		vlib_node_runtime_t * node, vlib_buffer_t ** b,
+		u32 * sw_if_index, u16 * ethertype, u16 * next)
+{
+  int ii;
+  for (ii = 0; ii < vector_sz; ii++)
+    if (PREDICT_FALSE (b[ii]->flags & VLIB_BUFFER_IS_TRACED))
+      {
+	l2_in_out_feat_arc_trace_t *t =
+	  vlib_add_trace (vm, node, b[ii], sizeof (*t));
+	t->arc_head = arc_head;
+	t->sw_if_index = arc_head ? sw_if_index[ii] : ~0;
+	t->feature_bitmap = vnet_buffer (b[ii])->l2.feature_bitmap;
+	t->ethertype = arc_head ? ethertype[ii] : 0;
+	t->next_index = next[ii];
+      }
+}
+
+always_inline uword
+l2_in_out_feat_arc_node_fn (vlib_main_t * vm,
+			    vlib_node_runtime_t * node, vlib_frame_t * frame,
+			    int is_output, vlib_node_registration_t * fa_node,
+			    int arc_head, int do_trace)
+{
+  u32 n_left, *from;
+  u16 nexts[VLIB_FRAME_SIZE], *next;
+  u16 ethertypes[VLIB_FRAME_SIZE], *ethertype;
+  vlib_buffer_t *bufs[VLIB_FRAME_SIZE], **b;
+  u32 sw_if_indices[VLIB_FRAME_SIZE], *sw_if_index;
+  l2_in_out_feat_arc_main_t *fam = &l2_in_out_feat_arc_main;
+
+  u8 ip4_arc_index = fam->ip4_feat_arc_index[is_output];
+  u8 ip6_arc_index = fam->ip6_feat_arc_index[is_output];
+  u8 nonip_arc_index = fam->nonip_feat_arc_index[is_output];
+  u32 *next_node_indices = fam->feat_next_node_index[is_output];
+
+  from = vlib_frame_vector_args (frame);
+  vlib_get_buffers (vm, from, bufs, frame->n_vectors);
+  /* set the initial values for the current buffer the next pointers */
+  b = bufs;
+  next = nexts;
+  ethertype = ethertypes;
+  sw_if_index = sw_if_indices;
+  n_left = frame->n_vectors;
+
+  CLIB_PREFETCH (next_node_indices, 2 * CLIB_CACHE_LINE_BYTES, LOAD);
+
+  while (n_left > 3 * L2_FEAT_ARC_VEC_SIZE)
+    {
+      const int vec_sz = L2_FEAT_ARC_VEC_SIZE;
+      /* prefetch next N buffers */
+      buffer_prefetch_xN (vec_sz, b + 2 * vec_sz);
+
+      if (arc_head)
+	{
+	  get_sw_if_index_xN (vec_sz, is_output, b, sw_if_index);
+	  get_ethertype_xN (vec_sz, is_output, b, ethertype);
+	  set_next_in_arc_head_xN (vec_sz, is_output, next_node_indices, b,
+				   sw_if_index, ethertype, ip4_arc_index,
+				   ip6_arc_index, nonip_arc_index, next);
+	}
+      else
+	{
+	  set_next_in_arc_tail_xN (vec_sz, is_output, next_node_indices, b,
+				   next);
+	}
+      if (do_trace)
+	maybe_trace_xN (vec_sz, arc_head, vm, node, b, sw_if_index, ethertype,
+			next);
+
+      next += vec_sz;
+      b += vec_sz;
+      sw_if_index += vec_sz;
+      ethertype += vec_sz;
+
+      n_left -= vec_sz;
+    }
+
+  while (n_left > 0)
+    {
+      const int vec_sz = 1;
+
+      if (arc_head)
+	{
+	  get_sw_if_index_xN (vec_sz, is_output, b, sw_if_index);
+	  get_ethertype_xN (vec_sz, is_output, b, ethertype);
+	  set_next_in_arc_head_xN (vec_sz, is_output, next_node_indices, b,
+				   sw_if_index, ethertype, ip4_arc_index,
+				   ip6_arc_index, nonip_arc_index, next);
+	}
+      else
+	{
+	  set_next_in_arc_tail_xN (vec_sz, is_output, next_node_indices, b,
+				   next);
+	}
+      if (do_trace)
+	maybe_trace_xN (vec_sz, arc_head, vm, node, b, sw_if_index, ethertype,
+			next);
+
+      next += vec_sz;
+      b += vec_sz;
+      sw_if_index += vec_sz;
+      ethertype += vec_sz;
+
+      n_left -= vec_sz;
+    }
+
+  vlib_buffer_enqueue_to_next (vm, node, from, nexts, frame->n_vectors);
+
+  return frame->n_vectors;
+}
+
+static vlib_node_registration_t l2_in_feat_arc_node;
+static uword
+l2_in_feat_arc_node_fn (vlib_main_t * vm,
+			vlib_node_runtime_t * node, vlib_frame_t * frame)
+{
+  if (PREDICT_FALSE (node->flags & VLIB_NODE_FLAG_TRACE))
+    return l2_in_out_feat_arc_node_fn (vm, node, frame,
+				       IN_OUT_FEAT_ARC_INPUT_TABLE_GROUP,
+				       &l2_in_feat_arc_node, 1, 1);
+  else
+    return l2_in_out_feat_arc_node_fn (vm, node, frame,
+				       IN_OUT_FEAT_ARC_INPUT_TABLE_GROUP,
+				       &l2_in_feat_arc_node, 1, 0);
+}
+
+static vlib_node_registration_t l2_out_feat_arc_node;
+static uword
+l2_out_feat_arc_node_fn (vlib_main_t * vm,
+			 vlib_node_runtime_t * node, vlib_frame_t * frame)
+{
+  if (PREDICT_FALSE (node->flags & VLIB_NODE_FLAG_TRACE))
+    return l2_in_out_feat_arc_node_fn (vm, node, frame,
+				       IN_OUT_FEAT_ARC_OUTPUT_TABLE_GROUP,
+				       &l2_out_feat_arc_node, 1, 1);
+  else
+    return l2_in_out_feat_arc_node_fn (vm, node, frame,
+				       IN_OUT_FEAT_ARC_OUTPUT_TABLE_GROUP,
+				       &l2_out_feat_arc_node, 1, 0);
+}
+
+static vlib_node_registration_t l2_in_feat_arc_end_node;
+static uword
+l2_in_feat_arc_end_node_fn (vlib_main_t * vm,
+			    vlib_node_runtime_t * node, vlib_frame_t * frame)
+{
+  if (PREDICT_FALSE (node->flags & VLIB_NODE_FLAG_TRACE))
+    return l2_in_out_feat_arc_node_fn (vm, node, frame,
+				       IN_OUT_FEAT_ARC_INPUT_TABLE_GROUP,
+				       &l2_in_feat_arc_end_node, 0, 1);
+  else
+    return l2_in_out_feat_arc_node_fn (vm, node, frame,
+				       IN_OUT_FEAT_ARC_INPUT_TABLE_GROUP,
+				       &l2_in_feat_arc_end_node, 0, 0);
+}
+
+static vlib_node_registration_t l2_out_feat_arc_end_node;
+static uword
+l2_out_feat_arc_end_node_fn (vlib_main_t * vm,
+			     vlib_node_runtime_t * node, vlib_frame_t * frame)
+{
+  if (PREDICT_FALSE (node->flags & VLIB_NODE_FLAG_TRACE))
+    return l2_in_out_feat_arc_node_fn (vm, node, frame,
+				       IN_OUT_FEAT_ARC_OUTPUT_TABLE_GROUP,
+				       &l2_out_feat_arc_end_node, 0, 1);
+  else
+    return l2_in_out_feat_arc_node_fn (vm, node, frame,
+				       IN_OUT_FEAT_ARC_OUTPUT_TABLE_GROUP,
+				       &l2_out_feat_arc_end_node, 0, 0);
+}
+
+
+void
+vnet_l2_in_out_feat_arc_enable_disable (u32 sw_if_index, int is_output,
+					int enable_disable)
+{
+  if (is_output)
+    l2output_intf_bitmap_enable (sw_if_index, L2OUTPUT_FEAT_OUTPUT_FEAT_ARC,
+				 (u32) enable_disable);
+  else
+    l2input_intf_bitmap_enable (sw_if_index, L2INPUT_FEAT_INPUT_FEAT_ARC,
+				(u32) enable_disable);
+}
+
+/* *INDENT-OFF* */
+VNET_FEATURE_ARC_INIT (l2_in_ip4_arc, static) =
+{
+  .arc_name  = "l2-input-ip4",
+  .start_nodes = VNET_FEATURES ("l2-input-feat-arc"),
+  .arc_index_ptr = &l2_in_out_feat_arc_main.ip4_feat_arc_index[IN_OUT_FEAT_ARC_INPUT_TABLE_GROUP],
+};
+
+VNET_FEATURE_ARC_INIT (l2_out_ip4_arc, static) =
+{
+  .arc_name  = "l2-output-ip4",
+  .start_nodes = VNET_FEATURES ("l2-output-feat-arc"),
+  .arc_index_ptr = &l2_in_out_feat_arc_main.ip4_feat_arc_index[IN_OUT_FEAT_ARC_OUTPUT_TABLE_GROUP],
+};
+
+VNET_FEATURE_ARC_INIT (l2_out_ip6_arc, static) =
+{
+  .arc_name  = "l2-input-ip6",
+  .start_nodes = VNET_FEATURES ("l2-input-feat-arc"),
+  .arc_index_ptr = &l2_in_out_feat_arc_main.ip6_feat_arc_index[IN_OUT_FEAT_ARC_INPUT_TABLE_GROUP],
+};
+VNET_FEATURE_ARC_INIT (l2_in_ip6_arc, static) =
+{
+  .arc_name  = "l2-output-ip6",
+  .start_nodes = VNET_FEATURES ("l2-output-feat-arc"),
+  .arc_index_ptr = &l2_in_out_feat_arc_main.ip6_feat_arc_index[IN_OUT_FEAT_ARC_OUTPUT_TABLE_GROUP],
+};
+
+VNET_FEATURE_ARC_INIT (l2_out_nonip_arc, static) =
+{
+  .arc_name  = "l2-input-nonip",
+  .start_nodes = VNET_FEATURES ("l2-input-feat-arc"),
+  .arc_index_ptr = &l2_in_out_feat_arc_main.nonip_feat_arc_index[IN_OUT_FEAT_ARC_INPUT_TABLE_GROUP],
+};
+VNET_FEATURE_ARC_INIT (l2_in_nonip_arc, static) =
+{
+  .arc_name  = "l2-output-nonip",
+  .start_nodes = VNET_FEATURES ("l2-output-feat-arc"),
+  .arc_index_ptr = &l2_in_out_feat_arc_main.nonip_feat_arc_index[IN_OUT_FEAT_ARC_OUTPUT_TABLE_GROUP],
+};
+
+
+/* *INDENT-ON* */
+
+
+/* *INDENT-OFF* */
+VLIB_REGISTER_NODE (l2_in_feat_arc_node,static) = {
+  .name = "l2-input-feat-arc",
+  .function = l2_in_feat_arc_node_fn,
+  .vector_size = sizeof (u32),
+  .format_trace = format_l2_in_feat_arc_trace,
+  .type = VLIB_NODE_TYPE_INTERNAL,
+
+  .n_errors = ARRAY_LEN(l2_in_feat_arc_error_strings),
+  .error_strings = l2_in_feat_arc_error_strings,
+
+};
+
+VLIB_REGISTER_NODE (l2_out_feat_arc_node,static) = {
+  .name = "l2-output-feat-arc",
+  .function = l2_out_feat_arc_node_fn,
+  .vector_size = sizeof (u32),
+  .format_trace = format_l2_out_feat_arc_trace,
+  .type = VLIB_NODE_TYPE_INTERNAL,
+
+  .n_errors = ARRAY_LEN(l2_out_feat_arc_error_strings),
+  .error_strings = l2_out_feat_arc_error_strings,
+
+};
+
+VLIB_REGISTER_NODE (l2_in_feat_arc_end_node,static) = {
+  .name = "l2-input-feat-arc-end",
+  .function = l2_in_feat_arc_end_node_fn,
+  .vector_size = sizeof (u32),
+  .format_trace = format_l2_in_feat_arc_trace,
+  .sibling_of = "l2-input-feat-arc",
+};
+
+VLIB_REGISTER_NODE (l2_out_feat_arc_end_node,static) = {
+  .name = "l2-output-feat-arc-end",
+  .function = l2_out_feat_arc_end_node_fn,
+  .vector_size = sizeof (u32),
+  .format_trace = format_l2_out_feat_arc_trace,
+  .sibling_of = "l2-output-feat-arc",
+};
+
+VNET_FEATURE_INIT (l2_in_ip4_arc_end, static) =
+{
+  .arc_name = "l2-input-ip4",
+  .node_name = "l2-input-feat-arc-end",
+  .runs_before = 0,     /* not before any other features */
+};
+
+VNET_FEATURE_INIT (l2_out_ip4_arc_end, static) =
+{
+  .arc_name = "l2-output-ip4",
+  .node_name = "l2-output-feat-arc-end",
+  .runs_before = 0,     /* not before any other features */
+};
+
+VNET_FEATURE_INIT (l2_in_ip6_arc_end, static) =
+{
+  .arc_name = "l2-input-ip6",
+  .node_name = "l2-input-feat-arc-end",
+  .runs_before = 0,     /* not before any other features */
+};
+
+
+VNET_FEATURE_INIT (l2_out_ip6_arc_end, static) =
+{
+  .arc_name = "l2-output-ip6",
+  .node_name = "l2-output-feat-arc-end",
+  .runs_before = 0,     /* not before any other features */
+};
+
+VNET_FEATURE_INIT (l2_in_nonip_arc_end, static) =
+{
+  .arc_name = "l2-input-nonip",
+  .node_name = "l2-input-feat-arc-end",
+  .runs_before = 0,     /* not before any other features */
+};
+
+
+VNET_FEATURE_INIT (l2_out_nonip_arc_end, static) =
+{
+  .arc_name = "l2-output-nonip",
+  .node_name = "l2-output-feat-arc-end",
+  .runs_before = 0,     /* not before any other features */
+};
+
+
+VLIB_NODE_FUNCTION_MULTIARCH (l2_in_feat_arc_node, l2_in_feat_arc_node_fn)
+VLIB_NODE_FUNCTION_MULTIARCH (l2_out_feat_arc_node, l2_out_feat_arc_node_fn)
+VLIB_NODE_FUNCTION_MULTIARCH (l2_in_feat_arc_end_node, l2_in_feat_arc_end_node_fn)
+VLIB_NODE_FUNCTION_MULTIARCH (l2_out_feat_arc_end_node, l2_out_feat_arc_end_node_fn)
+
+/* *INDENT-ON* */
+
+
+clib_error_t *
+l2_in_out_feat_arc_init (vlib_main_t * vm)
+{
+  l2_in_out_feat_arc_main_t *mp = &l2_in_out_feat_arc_main;
+
+  mp->vlib_main = vm;
+  mp->vnet_main = vnet_get_main ();
+
+  /* Initialize the feature next-node indexes */
+  feat_bitmap_init_next_nodes (vm,
+			       l2_in_feat_arc_end_node.index,
+			       L2INPUT_N_FEAT,
+			       l2input_get_feat_names (),
+			       mp->feat_next_node_index
+			       [IN_OUT_FEAT_ARC_INPUT_TABLE_GROUP]);
+  feat_bitmap_init_next_nodes (vm, l2_out_feat_arc_end_node.index,
+			       L2OUTPUT_N_FEAT, l2output_get_feat_names (),
+			       mp->feat_next_node_index
+			       [IN_OUT_FEAT_ARC_OUTPUT_TABLE_GROUP]);
+  return 0;
+}
+
+
+static int
+l2_has_features (u32 sw_if_index, int is_output)
+{
+  int has_features = 0;
+  l2_in_out_feat_arc_main_t *mp = &l2_in_out_feat_arc_main;
+  has_features +=
+    vnet_have_features (mp->ip4_feat_arc_index[is_output], sw_if_index);
+  has_features +=
+    vnet_have_features (mp->ip6_feat_arc_index[is_output], sw_if_index);
+  has_features +=
+    vnet_have_features (mp->nonip_feat_arc_index[is_output], sw_if_index);
+  return has_features > 0;
+}
+
+static int
+l2_is_output_arc (u8 arc_index)
+{
+  l2_in_out_feat_arc_main_t *mp = &l2_in_out_feat_arc_main;
+  int idx = IN_OUT_FEAT_ARC_OUTPUT_TABLE_GROUP;
+  return (mp->ip4_feat_arc_index[idx] == arc_index
+	  || mp->ip6_feat_arc_index[idx] == arc_index
+	  || mp->nonip_feat_arc_index[idx] == arc_index);
+}
+
+static int
+l2_is_input_arc (u8 arc_index)
+{
+  l2_in_out_feat_arc_main_t *mp = &l2_in_out_feat_arc_main;
+  int idx = IN_OUT_FEAT_ARC_INPUT_TABLE_GROUP;
+  return (mp->ip4_feat_arc_index[idx] == arc_index
+	  || mp->ip6_feat_arc_index[idx] == arc_index
+	  || mp->nonip_feat_arc_index[idx] == arc_index);
+}
+
+int
+vnet_l2_feature_enable_disable (const char *arc_name, const char *node_name,
+				u32 sw_if_index, int enable_disable,
+				void *feature_config,
+				u32 n_feature_config_bytes)
+{
+  u8 arc_index = vnet_get_feature_arc_index (arc_name);
+  if (arc_index == (u8) ~ 0)
+    return VNET_API_ERROR_INVALID_VALUE;
+
+  /* check the state before we tried to enable/disable */
+  int had_features = vnet_have_features (arc_index, sw_if_index);
+
+  int ret = vnet_feature_enable_disable (arc_name, node_name, sw_if_index,
+					 enable_disable, feature_config,
+					 n_feature_config_bytes);
+  if (ret)
+    return ret;
+
+  int has_features = vnet_have_features (arc_index, sw_if_index);
+
+  if (had_features != has_features)
+    {
+      if (l2_is_output_arc (arc_index))
+	{
+	  vnet_l2_in_out_feat_arc_enable_disable (sw_if_index, 1,
+						  l2_has_features
+						  (sw_if_index, 1));
+	}
+      if (l2_is_input_arc (arc_index))
+	{
+	  vnet_l2_in_out_feat_arc_enable_disable (sw_if_index, 0,
+						  l2_has_features
+						  (sw_if_index, 0));
+	}
+    }
+  return 0;
+}
+
+
+VLIB_INIT_FUNCTION (l2_in_out_feat_arc_init);
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */
diff --git a/src/vnet/l2/l2_in_out_feat_arc.h b/src/vnet/l2/l2_in_out_feat_arc.h
new file mode 100644
index 00000000000..799edee7929
--- /dev/null
+++ b/src/vnet/l2/l2_in_out_feat_arc.h
@@ -0,0 +1,71 @@
+/*
+ * Copyright (c) 2015 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 __included_vnet_in_out_feat_arc_h__
+#define __included_vnet_in_out_feat_arc_h__
+
+#include <vlib/vlib.h>
+#include <vnet/vnet.h>
+#include <vnet/classify/vnet_classify.h>
+
+typedef enum
+{
+  FEAT_ARC_NEXT_INDEX_DROP,
+  FEAT_ARC_NEXT_INDEX_N_NEXT,
+} in_out_feat_arc_next_index_t;
+
+typedef enum
+{
+  IN_OUT_FEAT_ARC_TABLE_IP4,
+  IN_OUT_FEAT_ARC_TABLE_IP6,
+  IN_OUT_FEAT_ARC_TABLE_L2,
+  IN_OUT_FEAT_ARC_N_TABLES,
+} in_out_feat_arc_table_id_t;
+
+typedef enum
+{
+  IN_OUT_FEAT_ARC_INPUT_TABLE_GROUP,
+  IN_OUT_FEAT_ARC_OUTPUT_TABLE_GROUP,
+  IN_OUT_FEAT_ARC_N_TABLE_GROUPS
+} in_out_feat_arc_table_group_id_t;
+
+typedef struct
+{
+  /* convenience variables */
+  vlib_main_t *vlib_main;
+  vnet_main_t *vnet_main;
+  vnet_classify_main_t *vnet_classify_main;
+    vnet_config_main_t
+    *
+    vnet_config_main[IN_OUT_FEAT_ARC_N_TABLE_GROUPS]
+    [IN_OUT_FEAT_ARC_N_TABLES];
+} in_out_feat_arc_main_t;
+
+int vnet_l2_feature_enable_disable (const char *arc_name,
+				    const char *node_name, u32 sw_if_index,
+				    int enable_disable, void *feature_config,
+				    u32 n_feature_config_bytes);
+
+
+
+#endif /* __included_vnet_in_out_feat_arc_h__ */
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */
diff --git a/src/vnet/l2/l2_input.c b/src/vnet/l2/l2_input.c
index c4f6d6fc0ce..9727d408088 100644
--- a/src/vnet/l2/l2_input.c
+++ b/src/vnet/l2/l2_input.c
@@ -82,7 +82,7 @@ format_l2_input_features (u8 * s, va_list * args)
   int i;
   for (i = L2INPUT_N_FEAT; i >= 0; i--)
     if (feature_bitmap & (1 << i))
-      s = format (s, "%10s (%s)\n", display_names[i], l2input_feat_names[i]);
+      s = format (s, "%17s (%s)\n", display_names[i], l2input_feat_names[i]);
   return s;
 }
 
diff --git a/src/vnet/l2/l2_input.h b/src/vnet/l2/l2_input.h
index 4d6f1a32177..e7c413f59c4 100644
--- a/src/vnet/l2/l2_input.h
+++ b/src/vnet/l2/l2_input.h
@@ -117,6 +117,7 @@ l2input_bd_config (u32 bd_index)
  _(VPATH,         "vpath-input-l2")             \
  _(ACL,           "l2-input-acl")               \
  _(POLICER_CLAS,  "l2-policer-classify")	\
+ _(INPUT_FEAT_ARC, "l2-input-feat-arc")         \
  _(INPUT_CLASSIFY, "l2-input-classify")         \
  _(SPAN,          "span-l2-input")
 
diff --git a/src/vnet/l2/l2_output.c b/src/vnet/l2/l2_output.c
index ca95c614cef..4b933315a8c 100644
--- a/src/vnet/l2/l2_output.c
+++ b/src/vnet/l2/l2_output.c
@@ -60,7 +60,7 @@ format_l2_output_features (u8 * s, va_list * args)
   int i;
   for (i = L2OUTPUT_N_FEAT - 1; i >= 0; i--)
     if (feature_bitmap & (1 << i))
-      s = format (s, "%10s (%s)\n", display_names[i], l2output_feat_names[i]);
+      s = format (s, "%17s (%s)\n", display_names[i], l2output_feat_names[i]);
   return s;
 }
 
diff --git a/src/vnet/l2/l2_output.h b/src/vnet/l2/l2_output.h
index b3d3505b813..452d99b8a3b 100644
--- a/src/vnet/l2/l2_output.h
+++ b/src/vnet/l2/l2_output.h
@@ -91,6 +91,7 @@ extern vlib_node_registration_t l2output_node;
  _(STP_BLOCKED,       "feature-bitmap-drop")        \
  _(LINESTATUS_DOWN,   "feature-bitmap-drop")        \
  _(OUTPUT_CLASSIFY,   "l2-output-classify")	    \
+ _(OUTPUT_FEAT_ARC,   "l2-output-feat-arc")	    \
  _(XCRW,	      "l2-xcrw")
 
 /* Feature bitmap positions */