feat_bitmap.h

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/*
 * feat_bitmap.h: bitmap for managing feature invocation
 *
 * Copyright (c) 2013 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_l2_feat_bitmap_h
#define included_vnet_l2_feat_bitmap_h

#include <vlib/vlib.h>
#include <vnet/vnet.h>

/* 
 * The feature bitmap is a way of organizing input and output feature graph nodes.
 * The set of features to be executed are arranged in a bitmap with one bit per 
 * feature and each bit positioned in the same order that the features should be 
 * executed. Features can be dynamically removed from the set by masking off their 
 * corresponding bits. The bitmap is stored in packet context. Each feature clears
 * its bit and then calls feat_bitmap_get_next_node_index() to go to the next 
 * graph node.
 */


// 32 features in a u32 bitmap
#define FEAT_MAX 32

// Initialize the feature next-node indexes of a graph node.
// Should be called by the init function of each feature graph node.
always_inline
void feat_bitmap_init_next_nodes (
        vlib_main_t  * vm,
        u32            node_index,   // the current graph node index
        u32            num_features, // number of entries in feat_names
        char        ** feat_names,   // array of feature graph node names
        u32          * next_nodes)   // array of 32 next indexes to init
{
  u32 idx;

  ASSERT(num_features <= FEAT_MAX);

  for (idx=0; idx<num_features; idx++) {
    if (vlib_get_node_by_name(vm, (u8 *) feat_names[idx])) {
      next_nodes[idx] = 
          vlib_node_add_named_next(vm, node_index, feat_names[idx]);
    } else { // Node may be in plugin which is not installed, use drop node
      next_nodes[idx] = 
          vlib_node_add_named_next(vm, node_index, "feature-bitmap-drop");
    }
  }
 
  // All unassigned bits go to the drop node
  for (; idx<FEAT_MAX; idx++) {
    next_nodes[idx] = vlib_node_add_named_next(vm, node_index, "feature-bitmap-drop");
  }
}

// Return the graph node index for the feature corresponding to the 
// first set bit in the bitmap.
always_inline
u32 feat_bitmap_get_next_node_index (u32 * next_nodes, u32 bitmap)
{
  u32 first_bit;

  count_leading_zeros(first_bit, bitmap);
  first_bit = uword_bits - 1 - first_bit;
  return next_nodes[first_bit];
}

#endif // included_vnet_l2_feat_bitmap_h