l2-rw: Packet rewrite feature for L2 bridges

This patch defines a new l2input feature: l2-rw
It makes use of vnet_classify in order to match
packets and applies mask/value changes depending
on the matched classify entry.

Change-Id: Ia98c128931e59195bf3ecb66721e155ff9049a2e
Signed-off-by: Pierre Pfister <ppfister@cisco.com>

5 files changed, 690 insertions, 1 deletions

diff --git a/vnet/Makefile.am b/vnet/Makefile.am
index c0115eb1368..460becbfff9 100644
--- a/vnet/Makefile.am
+++ b/vnet/Makefile.am
@@ -114,6 +114,7 @@ libvnet_la_SOURCES +=				\
  vnet/l2/l2_output_acl.c			\
  vnet/l2/l2_output.c				\
  vnet/l2/l2_patch.c				\
+ vnet/l2/l2_rw.c                                \
  vnet/l2/l2_vtr.c				\
  vnet/l2/l2_xcrw.c
 
@@ -129,6 +130,7 @@ nobase_include_HEADERS +=			\
  vnet/l2/l2_bvi.h				\
  vnet/l2/l2_flood.h				\
  vnet/l2/l2_fib.h				\
+ vnet/l2/l2_rw.h                                \
  vnet/l2/l2_xcrw.h				\
  vnet/l2/l2_classify.h
 
diff --git a/vnet/vnet/l2/l2_input.c b/vnet/vnet/l2/l2_input.c
index d551b61ddce..a42fcae059b 100644
--- a/vnet/vnet/l2/l2_input.c
+++ b/vnet/vnet/l2/l2_input.c
@@ -507,7 +507,16 @@ u32 l2input_intf_bitmap_enable (u32 sw_if_index,
   return config->feature_bitmap;
 }
 
-
+u32 l2input_set_bridge_features(u32 bd_index,
+                                 u32 feat_mask, u32 feat_value)
+{
+  l2_bridge_domain_t * bd_config;
+  vec_validate (l2input_main.bd_configs, bd_index);
+  bd_config = vec_elt_at_index(l2input_main.bd_configs, bd_index);
+  bd_validate (bd_config);
+  bd_config->feature_bitmap = (bd_config->feature_bitmap & ~feat_mask) | feat_value;
+  return bd_config->feature_bitmap;
+}
 
 // Set the subinterface to run in l2 or l3 mode.
 // for L3 mode, just the sw_if_index is specified
diff --git a/vnet/vnet/l2/l2_input.h b/vnet/vnet/l2/l2_input.h
index e650162b593..a1cd03743c1 100644
--- a/vnet/vnet/l2/l2_input.h
+++ b/vnet/vnet/l2/l2_input.h
@@ -93,6 +93,7 @@ l2input_bd_config_from_index (l2input_main_t * l2im, u32 bd_index)
  _(ARP_TERM,      "arp-term-l2bd")              \
  _(UU_FLOOD,      "l2-flood")                   \
  _(FWD,           "l2-fwd")                     \
+ _(RW,            "l2-rw")                      \
  _(LEARN,         "l2-learn")                   \
  _(VTR,           "l2-input-vtr")               \
  _(VPATH,         "vpath-input-l2")             \
@@ -196,6 +197,11 @@ u32 l2input_intf_bitmap_enable (u32 sw_if_index,
                                  u32 feature_bitmap,
                                  u32 enable);
 
+//Sets modifies flags from a bridge domain
+u32 l2input_set_bridge_features(u32 bd_index,
+                                u32 feat_mask,
+                                u32 feat_value);
+
 
 #define MODE_L3        0
 #define MODE_L2_BRIDGE 1
diff --git a/vnet/vnet/l2/l2_rw.c b/vnet/vnet/l2/l2_rw.c
new file mode 100644
index 00000000000..c325ececd55
--- /dev/null
+++ b/vnet/vnet/l2/l2_rw.c
@@ -0,0 +1,588 @@
+/*
+ * 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.
+ */
+
+#include <vlib/vlib.h>
+#include <vnet/l2/feat_bitmap.h>
+#include <vnet/l2/l2_rw.h>
+
+l2_rw_main_t l2_rw_main;
+
+vlib_node_registration_t l2_rw_node;
+
+typedef struct {
+  u32 sw_if_index;
+  u32 classify_table_index;
+  u32 rewrite_entry_index;
+} l2_rw_trace_t;
+
+static u8 *format_l2_rw_entry (u8 * s, va_list *args)
+{
+  l2_rw_entry_t *e = va_arg (*args, l2_rw_entry_t *);
+  l2_rw_main_t *rw = &l2_rw_main;
+  s = format (s, "%d -  mask:%U value:%U\n",
+              e - rw->entries,
+              format_hex_bytes, e->mask, e->rewrite_n_vectors * sizeof(u32x4),
+              format_hex_bytes, e->value, e->rewrite_n_vectors * sizeof(u32x4));
+  s = format (s, "      hits:%d skip_bytes:%d",
+                e->hit_count, e->skip_n_vectors * sizeof(u32x4));
+  return s;
+}
+
+static u8 *format_l2_rw_config (u8 * s, va_list *args)
+{
+  l2_rw_config_t *c = va_arg (*args, l2_rw_config_t *);
+  return format(s, "table-index:%d miss-index:%d",
+                c->table_index,
+                c->miss_index);
+}
+
+/* packet trace format function */
+static u8 *format_l2_rw_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 *);
+  l2_rw_trace_t * t = va_arg (*args, l2_rw_trace_t *);
+  return format (s, "l2-rw: sw_if_index %d, table %d, entry %d",
+              t->sw_if_index, t->classify_table_index,
+              t->rewrite_entry_index);
+}
+
+always_inline l2_rw_config_t *l2_rw_get_config(u32 sw_if_index)
+{
+  l2_rw_main_t *rw = &l2_rw_main;
+  if (PREDICT_FALSE(!clib_bitmap_get(rw->configs_bitmap, sw_if_index))) {
+    vec_validate(rw->configs, sw_if_index);
+    rw->configs[sw_if_index].table_index = ~0;
+    rw->configs[sw_if_index].miss_index = ~0;
+    rw->configs_bitmap = clib_bitmap_set(rw->configs_bitmap, sw_if_index, 1);
+  }
+  return &rw->configs[sw_if_index];
+}
+
+static_always_inline void l2_rw_rewrite(l2_rw_entry_t *rwe, u8 *h)
+{
+  if (U32X4_ALIGNED(h)) {
+    u32x4 *d = ((u32x4 *) h) + rwe->skip_n_vectors;
+    switch(rwe->rewrite_n_vectors) {
+      case 5:
+        d[4] = (d[4] & ~rwe->mask[4]) | rwe->value[4];
+        /* FALLTHROUGH */
+      case 4:
+        d[3] = (d[3] & ~rwe->mask[3]) | rwe->value[3];
+        /* FALLTHROUGH */
+      case 3:
+        d[2] = (d[2] & ~rwe->mask[2]) | rwe->value[2];
+        /* FALLTHROUGH */
+      case 2:
+        d[1] = (d[1] & ~rwe->mask[1]) | rwe->value[1];
+        /* FALLTHROUGH */
+      case 1:
+        d[0] = (d[0] & ~rwe->mask[0]) | rwe->value[0];
+        break;
+      default:
+        abort();
+    }
+  } else {
+    u64 *d = ((u64 *) h) + rwe->skip_n_vectors * 2;
+    switch(rwe->rewrite_n_vectors) {
+      case 5:
+        d[8] = (d[8] & ~(((u64*)rwe->mask)[8])) | (((u64*)rwe->value)[8]);
+        d[9] = (d[9] & ~(((u64*)rwe->mask)[9])) | (((u64*)rwe->value)[9]);
+        /* FALLTHROUGH */
+      case 4:
+        d[6] = (d[6] & ~(((u64*)rwe->mask)[6])) | (((u64*)rwe->value)[6]);
+        d[7] = (d[7] & ~(((u64*)rwe->mask)[7])) | (((u64*)rwe->value)[7]);
+        /* FALLTHROUGH */
+      case 3:
+        d[4] = (d[4] & ~(((u64*)rwe->mask)[4])) | (((u64*)rwe->value)[4]);
+        d[5] = (d[5] & ~(((u64*)rwe->mask)[5])) | (((u64*)rwe->value)[5]);
+        /* FALLTHROUGH */
+      case 2:
+        d[2] = (d[2] & ~(((u64*)rwe->mask)[2])) | (((u64*)rwe->value)[2]);
+        d[3] = (d[3] & ~(((u64*)rwe->mask)[3])) | (((u64*)rwe->value)[3]);
+        /* FALLTHROUGH */
+      case 1:
+        d[0] = (d[0] & ~(((u64*)rwe->mask)[0])) | (((u64*)rwe->value)[0]);
+        d[1] = (d[1] & ~(((u64*)rwe->mask)[1])) | (((u64*)rwe->value)[1]);
+        break;
+      default:
+        abort();
+    }
+  }
+}
+
+static uword
+l2_rw_node_fn(vlib_main_t * vm,
+              vlib_node_runtime_t * node,
+              vlib_frame_t * frame)
+{
+  l2_rw_main_t *rw = &l2_rw_main;
+  u32 n_left_from, * from, * to_next, next_index;
+  //vlib_node_t *n = vlib_get_node(vm, node->node_index);
+  vnet_classify_main_t *vcm = &vnet_classify_main;
+  f64 now = vlib_time_now(vlib_get_main());
+  u32 prefetch_size = 0;
+
+  from = vlib_frame_vector_args (frame);
+  n_left_from = frame->n_vectors; /* number of packets to process */
+  next_index = node->cached_next_index;
+
+  while (n_left_from > 0)
+  {
+    u32 n_left_to_next;
+
+    /* get space to enqueue frame to graph node "next_index" */
+    vlib_get_next_frame (vm, node, next_index,
+                         to_next, n_left_to_next);
+
+    while (n_left_from >= 4 && n_left_to_next >= 2)
+    {
+      u32 bi0, next0, sw_if_index0, feature_bitmap0, rwe_index0;
+      u32 bi1, next1, sw_if_index1, feature_bitmap1, rwe_index1;
+      vlib_buffer_t *b0, *b1;
+      ethernet_header_t *h0, *h1;
+      l2_rw_config_t *config0, *config1;
+      u64 hash0, hash1;
+      vnet_classify_table_t *t0, *t1;
+      vnet_classify_entry_t *e0, *e1;
+      l2_rw_entry_t *rwe0, *rwe1;
+
+      {
+        vlib_buffer_t * p2, * p3;
+        p2 = vlib_get_buffer (vm, from[2]);
+        p3 = vlib_get_buffer (vm, from[3]);
+
+        vlib_prefetch_buffer_header (p2, LOAD);
+        vlib_prefetch_buffer_header (p3, LOAD);
+        CLIB_PREFETCH (p2->data, prefetch_size, LOAD);
+        CLIB_PREFETCH (p3->data, prefetch_size, LOAD);
+      }
+
+      bi0 = from[0];
+      bi1 = from[1];
+      to_next[0] = bi0;
+      to_next[1] = bi1;
+      from += 2;
+      to_next += 2;
+      n_left_from -= 2;
+      n_left_to_next -= 2;
+
+      b0 = vlib_get_buffer(vm, bi0);
+      b1 = vlib_get_buffer(vm, bi1);
+      h0 = vlib_buffer_get_current(b0);
+      h1 = vlib_buffer_get_current(b1);
+
+      sw_if_index0 = vnet_buffer(b0)->sw_if_index[VLIB_RX];
+      sw_if_index1 = vnet_buffer(b1)->sw_if_index[VLIB_RX];
+      config0 = l2_rw_get_config(sw_if_index0); //TODO: check sw_if_index0 value
+      config1 = l2_rw_get_config(sw_if_index1); //TODO: check sw_if_index0 value
+      t0 = pool_elt_at_index(vcm->tables, config0->table_index);
+      t1 = pool_elt_at_index(vcm->tables, config1->table_index);
+      prefetch_size = (t1->skip_n_vectors + t1->match_n_vectors)*sizeof(u32x4);
+
+      hash0 = vnet_classify_hash_packet(t0, (u8 *)h0);
+      hash1 = vnet_classify_hash_packet(t1, (u8 *)h1);
+      e0 = vnet_classify_find_entry(t0, (u8 *) h0, hash0, now);
+      e1 = vnet_classify_find_entry(t1, (u8 *) h1, hash1, now);
+
+      rwe_index0 = e0?e0->opaque_index:config0->miss_index;
+      rwe_index1 = e1?e1->opaque_index:config1->miss_index;
+
+      if (rwe_index0 != ~0) {
+        rwe0 = pool_elt_at_index(rw->entries, rwe_index0);
+        l2_rw_rewrite(rwe0, (u8 *)h0);
+      }
+      if (rwe_index1 != ~0) {
+        rwe1 = pool_elt_at_index(rw->entries, rwe_index1);
+        l2_rw_rewrite(rwe1, (u8 *)h1);
+      }
+
+      if (PREDICT_FALSE((b0->flags & VLIB_BUFFER_IS_TRACED))) {
+        l2_rw_trace_t *t =
+            vlib_add_trace (vm, node, b0, sizeof (*t));
+        t->sw_if_index = sw_if_index0;
+        t->classify_table_index = config0->table_index;
+        t->rewrite_entry_index = rwe_index0;
+      }
+
+      if (PREDICT_FALSE((b1->flags & VLIB_BUFFER_IS_TRACED))) {
+        l2_rw_trace_t *t =
+            vlib_add_trace (vm, node, b1, sizeof (*t));
+        t->sw_if_index = sw_if_index1;
+        t->classify_table_index = config1->table_index;
+        t->rewrite_entry_index = rwe_index1;
+      }
+
+      // Update feature bitmap and get next feature index
+      feature_bitmap0 = vnet_buffer(b0)->l2.feature_bitmap & ~L2INPUT_FEAT_RW;
+      feature_bitmap1 = vnet_buffer(b1)->l2.feature_bitmap & ~L2INPUT_FEAT_RW;
+      vnet_buffer(b0)->l2.feature_bitmap = feature_bitmap0;
+      vnet_buffer(b1)->l2.feature_bitmap = feature_bitmap1;
+      next0 = feat_bitmap_get_next_node_index(rw->feat_next_node_index,
+                                              feature_bitmap0);
+      next1 = feat_bitmap_get_next_node_index(rw->feat_next_node_index,
+                                                    feature_bitmap1);
+
+      vlib_validate_buffer_enqueue_x2 (vm, node, next_index,
+                                       to_next, n_left_to_next,
+                                       bi0, bi1, next0, next1);
+    }
+
+    while (n_left_from > 0 && n_left_to_next > 0)
+    {
+      u32 bi0, next0, sw_if_index0, feature_bitmap0, rwe_index0;
+      vlib_buffer_t *b0;
+      ethernet_header_t *h0;
+      l2_rw_config_t *config0;
+      u64 hash0;
+      vnet_classify_table_t *t0;
+      vnet_classify_entry_t *e0;
+      l2_rw_entry_t *rwe0;
+
+      bi0 = from[0];
+      to_next[0] = bi0;
+      from += 1;
+      to_next += 1;
+      n_left_from -= 1;
+      n_left_to_next -= 1;
+
+      b0 = vlib_get_buffer(vm, bi0);
+      h0 = vlib_buffer_get_current(b0);
+
+      sw_if_index0 = vnet_buffer(b0)->sw_if_index[VLIB_RX];
+      config0 = l2_rw_get_config(sw_if_index0); //TODO: check sw_if_index0 value
+      t0 = pool_elt_at_index(vcm->tables, config0->table_index);
+
+      hash0 = vnet_classify_hash_packet(t0, (u8 *)h0);
+      e0 = vnet_classify_find_entry(t0, (u8 *) h0, hash0, now);
+
+      rwe_index0 = e0?e0->opaque_index:config0->miss_index;
+
+      if (rwe_index0 != ~0) {
+        rwe0 = pool_elt_at_index(rw->entries, rwe_index0);
+        l2_rw_rewrite(rwe0, (u8 *)h0);
+      }
+
+      if (PREDICT_FALSE((b0->flags & VLIB_BUFFER_IS_TRACED))) {
+        l2_rw_trace_t *t =
+            vlib_add_trace (vm, node, b0, sizeof (*t));
+        t->sw_if_index = sw_if_index0;
+        t->classify_table_index = config0->table_index;
+        t->rewrite_entry_index = rwe_index0;
+      }
+
+      // Update feature bitmap and get next feature index
+      feature_bitmap0 = vnet_buffer(b0)->l2.feature_bitmap & ~L2INPUT_FEAT_RW;
+      vnet_buffer(b0)->l2.feature_bitmap = feature_bitmap0;
+      next0 = feat_bitmap_get_next_node_index(rw->feat_next_node_index,
+                                              feature_bitmap0);
+
+      vlib_validate_buffer_enqueue_x1 (vm, node, next_index,
+                                       to_next, n_left_to_next,
+                                       bi0, next0);
+    }
+    vlib_put_next_frame (vm, node, next_index, n_left_to_next);
+  }
+
+  return frame->n_vectors;
+}
+
+int l2_rw_mod_entry(u32 *index,
+                    u8 *mask, u8 *value, u32 len,
+                    u32 skip, u8 is_del)
+{
+  l2_rw_main_t *rw = &l2_rw_main;
+  l2_rw_entry_t *e = 0;
+  if (*index != ~0) {
+    if (pool_is_free_index(rw->entries, *index)) {
+      return -1;
+    }
+    e = pool_elt_at_index(rw->entries, *index);
+  } else {
+    pool_get(rw->entries, e);
+    *index = e - rw->entries;
+  }
+
+  if (!e)
+    return -1;
+
+  if (is_del) {
+    pool_put(rw->entries, e);
+    return 0;
+  }
+
+  e->skip_n_vectors = skip / sizeof(u32x4);
+  skip -= e->skip_n_vectors * sizeof(u32x4);
+  e->rewrite_n_vectors = (skip + len - 1) / sizeof(u32x4) + 1;
+  vec_alloc_aligned(e->mask, e->rewrite_n_vectors, sizeof(u32x4));
+  memset(e->mask, 0, e->rewrite_n_vectors * sizeof(u32x4));
+  vec_alloc_aligned(e->value, e->rewrite_n_vectors, sizeof(u32x4));
+  memset(e->value, 0, e->rewrite_n_vectors * sizeof(u32x4));
+
+  memcpy(((u8 *)e->value) + skip, value, len);
+  memcpy(((u8 *)e->mask) + skip, mask, len);
+
+  int i;
+  for (i = 0; i < e->rewrite_n_vectors; i++) {
+    e->value[i] &= e->mask[i];
+  }
+
+  return 0;
+}
+
+static clib_error_t *
+l2_rw_entry_cli_fn (vlib_main_t * vm,
+                            unformat_input_t * input,
+                            vlib_cli_command_t * cmd)
+{
+  u32 index = ~0;
+  u8 *mask = 0;
+  u8 *value = 0;
+  u32 skip = 0;
+  u8 del = 0;
+
+  while (unformat_check_input(input) != UNFORMAT_END_OF_INPUT)
+  {
+    if (unformat (input, "index %d", &index))
+      ;
+    else if (unformat (input, "mask %U", unformat_hex_string, &mask))
+      ;
+    else if (unformat (input, "value %U", unformat_hex_string, &value))
+      ;
+    else if (unformat (input, "skip %d", &skip))
+      ;
+    else if (unformat (input, "del"))
+      del = 1;
+    else
+      break;
+  }
+
+  if (!mask || !value)
+    return clib_error_return(0, "Unspecified mask or value");
+
+  if (vec_len(mask) != vec_len(value))
+    return clib_error_return(0, "Mask and value lengths must be identical");
+
+  int ret;
+  if ((ret = l2_rw_mod_entry(&index, mask, value, vec_len(mask), skip, del)))
+    return clib_error_return(0, "Could not add entry");
+
+  return 0;
+}
+
+VLIB_CLI_COMMAND (l2_rw_entry_cli, static) = {
+  .path = "l2 rewrite entry",
+  .short_help =
+  "l2 rewrite entry [index <index>] [mask <hex-mask>] [value <hex-value>] [skip <n_bytes>] [del]",
+  .function = l2_rw_entry_cli_fn,
+};
+
+int l2_rw_interface_set_table(u32 sw_if_index,
+                              u32 table_index,
+                              u32 miss_index)
+{
+  l2_rw_config_t *c = l2_rw_get_config(sw_if_index);
+  l2_rw_main_t *rw = &l2_rw_main;
+
+  c->table_index = table_index;
+  c->miss_index = miss_index;
+  u32 feature_bitmap = (table_index == ~0)?0:L2INPUT_FEAT_RW;
+
+  l2input_intf_bitmap_enable(sw_if_index, L2INPUT_FEAT_RW, feature_bitmap);
+
+  if (c->table_index == ~0)
+    clib_bitmap_set(rw->configs_bitmap, sw_if_index, 0);
+
+  return 0;
+}
+
+static clib_error_t *
+l2_rw_interface_cli_fn (vlib_main_t * vm,
+                            unformat_input_t * input,
+                            vlib_cli_command_t * cmd)
+{
+  vnet_main_t * vnm = vnet_get_main();
+  u32 table_index = ~0;
+  u32 sw_if_index = ~0;
+  u32 miss_index = ~0;
+
+  if (unformat_check_input(input) != UNFORMAT_END_OF_INPUT) {
+    unformat (input, "%U", unformat_vnet_sw_interface,
+                          vnm, &sw_if_index);
+  }
+
+  while (unformat_check_input(input) != UNFORMAT_END_OF_INPUT)
+  {
+    if (unformat (input, "table %d", &table_index))
+      ;
+    else if (unformat (input, "miss-index %d", &miss_index))
+      ;
+    else
+      break;
+  }
+
+  if (sw_if_index == ~0)
+    return clib_error_return(0, "You must specify an interface 'iface <interface>'",
+                                   format_unformat_error, input);
+  int ret;
+  if((ret = l2_rw_interface_set_table(sw_if_index, table_index, miss_index)))
+    return clib_error_return(0, "l2_rw_interface_set_table returned %d", ret);
+
+  return 0;
+}
+
+VLIB_CLI_COMMAND (l2_rw_interface_cli, static) = {
+  .path = "set interface l2 rewrite",
+  .short_help =
+  "set interface l2 rewrite <interface> [table <table index>] [miss-index <entry-index>]",
+  .function = l2_rw_interface_cli_fn,
+};
+
+static clib_error_t *
+l2_rw_show_interfaces_cli_fn (vlib_main_t * vm,
+                        unformat_input_t * input,
+                        vlib_cli_command_t * cmd)
+{
+  l2_rw_main_t *rw = &l2_rw_main;
+  if (clib_bitmap_count_set_bits(rw->configs_bitmap) == 0)
+      vlib_cli_output (vm, "No interface is currently using l2 rewrite\n");
+
+  uword i;
+  clib_bitmap_foreach(i, rw->configs_bitmap, {
+      vlib_cli_output (vm, "sw_if_index:%d %U\n", i, format_l2_rw_config, &rw->configs[i]);
+  });
+  return 0;
+}
+
+VLIB_CLI_COMMAND (l2_rw_show_interfaces_cli, static) = {
+  .path = "show l2 rewrite interfaces",
+  .short_help =
+  "show l2 rewrite interfaces",
+  .function = l2_rw_show_interfaces_cli_fn,
+};
+
+static clib_error_t *
+l2_rw_show_entries_cli_fn (vlib_main_t * vm,
+                        unformat_input_t * input,
+                        vlib_cli_command_t * cmd)
+{
+  l2_rw_main_t *rw = &l2_rw_main;
+  l2_rw_entry_t *e;
+  if (pool_elts(rw->entries) == 0)
+    vlib_cli_output (vm, "No entries\n");
+
+  pool_foreach(e, rw->entries, {
+    vlib_cli_output (vm, "%U\n", format_l2_rw_entry, e);
+  });
+  return 0;
+}
+
+VLIB_CLI_COMMAND (l2_rw_show_entries_cli, static) = {
+  .path = "show l2 rewrite entries",
+  .short_help =
+  "show l2 rewrite entries",
+  .function = l2_rw_show_entries_cli_fn,
+};
+
+int
+l2_rw_enable_disable(u32 bridge_domain, u8 disable)
+{
+  u32 mask = L2INPUT_FEAT_RW;
+  l2input_set_bridge_features(bridge_domain, mask,
+                              disable ? 0: mask);
+  return 0;
+}
+
+static clib_error_t *
+l2_rw_set_cli_fn (vlib_main_t * vm,
+                        unformat_input_t * input,
+                        vlib_cli_command_t * cmd)
+{
+  u32 bridge_domain;
+  u8 disable = 0;
+
+  if (unformat_check_input(input) == UNFORMAT_END_OF_INPUT ||
+      !unformat (input, "%d", &bridge_domain)) {
+    return clib_error_return(0, "You must specify a bridge domain");
+  }
+
+  if (unformat_check_input(input) != UNFORMAT_END_OF_INPUT &&
+      unformat (input, "disable")) {
+    disable = 1;
+  }
+
+  if (l2_rw_enable_disable(bridge_domain, disable))
+    return clib_error_return(0, "Could not enable or disable rewrite");
+
+  return 0;
+}
+
+VLIB_CLI_COMMAND (l2_rw_set_cli, static) = {
+  .path = "set bridge-domain rewrite",
+  .short_help =
+  "set bridge-domain rewrite <bridge-domain> [disable]",
+  .function = l2_rw_set_cli_fn,
+};
+
+static
+clib_error_t *l2_rw_init (vlib_main_t *vm)
+{
+  l2_rw_main_t *rw = &l2_rw_main;
+  rw->configs = 0;
+  rw->entries = 0;
+  clib_bitmap_alloc(rw->configs_bitmap, 1);
+  feat_bitmap_init_next_nodes(vm,
+                              l2_rw_node.index,
+                              L2INPUT_N_FEAT,
+                              l2input_get_feat_names(),
+                              rw->feat_next_node_index);
+  return 0;
+}
+VLIB_INIT_FUNCTION (l2_rw_init);
+
+enum {
+  L2_RW_NEXT_DROP,
+  L2_RW_N_NEXT,
+};
+
+#define foreach_l2_rw_error               \
+_(UNKNOWN, "Unknown error")
+
+typedef enum {
+#define _(sym,str) L2_RW_ERROR_##sym,
+  foreach_l2_rw_error
+#undef _
+  L2_RW_N_ERROR,
+} l2_rw_error_t;
+
+static char * l2_rw_error_strings[] = {
+#define _(sym,string) string,
+    foreach_l2_rw_error
+#undef _
+};
+
+VLIB_REGISTER_NODE (l2_rw_node) = {
+  .function = l2_rw_node_fn,
+  .name = "l2-rw",
+  .vector_size = sizeof (u32),
+  .format_trace = format_l2_rw_trace,
+  .type = VLIB_NODE_TYPE_INTERNAL,
+  .n_errors = ARRAY_LEN(l2_rw_error_strings),
+  .error_strings = l2_rw_error_strings,
+  .runtime_data_bytes = 0,
+  .n_next_nodes = L2_RW_N_NEXT,
+  .next_nodes = { [L2_RW_NEXT_DROP]  = "error-drop"},
+};
+
diff --git a/vnet/vnet/l2/l2_rw.h b/vnet/vnet/l2/l2_rw.h
new file mode 100644
index 00000000000..a46c476b3b1
--- /dev/null
+++ b/vnet/vnet/l2/l2_rw.h
@@ -0,0 +1,84 @@
+/*
+ * 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.
+ */
+
+/*
+ * l2_rw is based on vnet classifier and provides a way
+ * to modify packets matching a given table.
+ *
+ * Tables must be created using vnet's classify features.
+ * Entries contained within these tables must have their
+ * opaque index set to the rewrite entry created with l2_rw_mod_entry.
+ */
+
+#ifndef L2_RW_H_
+#define L2_RW_H_
+
+#include <vnet/l2/l2_input.h>
+
+typedef CLIB_PACKED(struct _l2_rw_entry {
+  u16 skip_n_vectors;
+  u16 rewrite_n_vectors;
+  u64 hit_count;
+  u32x4 *mask;
+  u32x4 *value;
+}) l2_rw_entry_t;
+
+// l2_rw configuration for one interface
+typedef CLIB_PACKED(struct _l2_rw_config {
+  u32 table_index; //Which classify table to use
+  u32 miss_index;  //Rewrite entry to use if table does not match
+}) l2_rw_config_t;
+
+typedef struct {
+  /* Next feature node indexes */
+  u32 feat_next_node_index[32];
+
+  /* A pool of entries */
+  l2_rw_entry_t *entries;
+
+  /* Config vector indexed by sw_if_index */
+  l2_rw_config_t *configs;
+  uword *configs_bitmap;
+} l2_rw_main_t;
+
+extern l2_rw_main_t l2_rw_main;
+
+/*
+ * Specifies which classify table and miss_index should be used
+ * with the given interface.
+ * Use special values ~0 in order to un-set table_index
+ * or miss_index.
+ * l2_rw feature is automatically enabled for the interface
+ * when table_index or miss_index is not ~0.
+ * returns 0 on success and something else on error.
+ */
+int l2_rw_interface_set_table(u32 sw_if_index,
+                              u32 table_index,
+                              u32 miss_index);
+
+/*
+ * Creates, modifies or delete a rewrite entry.
+ * If *index != ~0, modifies an existing entry (or simply
+ * deletes it if is_del is set).
+ * If *index == ~0, creates a new entry and the created
+ * entry index is stored in *index (Does nothing if is_del
+ * is set).
+ * returns 0 on success and something else on error.
+ */
+int l2_rw_mod_entry(u32 *index,
+                    u8 *mask, u8 *value, u32 len,
+                    u32 skip, u8 is_del);
+
+#endif /* L2_FW_H_ */