l2_learn.c

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/*
 * l2_learn.c : layer 2 learning using l2fib
 *
 * 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.
 */

#include <vlib/vlib.h>
#include <vnet/vnet.h>
#include <vnet/pg/pg.h>
#include <vnet/ethernet/ethernet.h>
#include <vlib/cli.h>

#include <vnet/l2/l2_input.h>
#include <vnet/l2/feat_bitmap.h>
#include <vnet/l2/l2_fib.h>
#include <vnet/l2/l2_learn.h>

#include <vppinfra/error.h>
#include <vppinfra/hash.h>

/*
 * Ethernet bridge learning
 *
 * Populate the mac table with entries mapping the packet's source mac + bridge
 * domain ID to the input sw_if_index. 
 *
 * Note that learning and forwarding are separate graph nodes. This means that
 * for a set of packets, all learning is performed first, then all nodes are
 * forwarded. The forwarding is done based on the end-state of the mac table,
 * instead of the state after each packet. Thus the forwarding results could
 * differ in certain cases (mac move tests), but this not expected to cause
 * problems in real-world networks. It is much simpler to separate learning
 * and forwarding into separate nodes.
 */


typedef struct {
  u8 src[6];
  u8 dst[6];
  u32 sw_if_index;
  u16 bd_index;
} l2learn_trace_t;


/* packet trace format function */
static u8 * format_l2learn_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 *);
  l2learn_trace_t * t = va_arg (*args, l2learn_trace_t *);
  
  s = format (s, "l2-learn: sw_if_index %d dst %U src %U bd_index %d",
              t->sw_if_index, 
              format_ethernet_address, t->dst,
              format_ethernet_address, t->src,
              t->bd_index);
  return s;
}

static vlib_node_registration_t l2learn_node;

#define foreach_l2learn_error                           \
_(L2LEARN,           "L2 learn packets")                \
_(MISS,              "L2 learn misses")                 \
_(MAC_MOVE,          "L2 mac moves")                    \
_(MAC_MOVE_VIOLATE,  "L2 mac move violations")          \
_(LIMIT,             "L2 not learned due to limit")     \
_(HIT,               "L2 learn hits")                   \
_(FILTER_DROP,       "L2 filter mac drops")     

typedef enum {
#define _(sym,str) L2LEARN_ERROR_##sym,
  foreach_l2learn_error
#undef _
  L2LEARN_N_ERROR,
} l2learn_error_t;

static char * l2learn_error_strings[] = {
#define _(sym,string) string,
  foreach_l2learn_error
#undef _
};

typedef enum {  
  L2LEARN_NEXT_L2FWD,
  L2LEARN_NEXT_DROP,
  L2LEARN_N_NEXT,
} l2learn_next_t;


// Perform learning on one packet based on the mac table lookup result

static_always_inline void
l2learn_process (vlib_node_runtime_t * node,
                 l2learn_main_t * msm,
                 u64 * counter_base,
                 vlib_buffer_t * b0,
                 u32 sw_if_index0,
                 l2fib_entry_key_t * key0,
                 l2fib_entry_key_t * cached_key,
                 u32 * bucket0,
                 l2fib_entry_result_t * result0,
                 u32 * next0)
{
  u32 feature_bitmap;

  // Set up the default next node (typically L2FWD)

  // Remove ourself from the feature bitmap
  feature_bitmap = vnet_buffer(b0)->l2.feature_bitmap & ~L2INPUT_FEAT_LEARN;

  // Save for next feature graph nodes
  vnet_buffer(b0)->l2.feature_bitmap = feature_bitmap;

  // Determine the next node
  *next0 = feat_bitmap_get_next_node_index(msm->feat_next_node_index,
                                           feature_bitmap);

  // Check mac table lookup result

  if (PREDICT_TRUE (result0->fields.sw_if_index == sw_if_index0)) {
    // The entry was in the table, and the sw_if_index matched, the normal case 

    // TODO: for dataplane learning and aging, do this:
    //       if refresh=0 and not a static mac, set refresh=1
    counter_base[L2LEARN_ERROR_HIT] += 1;

  } else if (result0->raw == ~0) {  

    // The entry was not in table, so add it 

    counter_base[L2LEARN_ERROR_MISS] += 1;

    if (msm->global_learn_count == msm->global_learn_limit) {
      // Global limit reached. Do not learn the mac but forward the packet.
      // In the future, limits could also be per-interface or bridge-domain.
      counter_base[L2LEARN_ERROR_LIMIT] += 1;
      goto done;

    } else {
      BVT(clib_bihash_kv) kv;
      // It is ok to learn

      result0->raw = 0; // clear all fields
      result0->fields.sw_if_index = sw_if_index0;
      // TODO: set timestamp in entry to clock for dataplane aging
      kv.key = key0->raw;
      kv.value = result0->raw;

      BV(clib_bihash_add_del) (msm->mac_table, &kv, 1 /* is_add */);

      cached_key->raw = ~0;  // invalidate the cache
      msm->global_learn_count++;
    }

  } else {

    // The entry was in the table, but with the wrong sw_if_index mapping (mac move)
    counter_base[L2LEARN_ERROR_MAC_MOVE] += 1;

    if (result0->fields.static_mac) {
      // Don't overwrite a static mac
      // TODO: Check violation policy. For now drop the packet
      b0->error = node->errors[L2LEARN_ERROR_MAC_MOVE_VIOLATE];
      *next0 = L2LEARN_NEXT_DROP;
    } else {
      // Update the entry
      // TODO: may want to rate limit mac moves
      // TODO: check global/bridge domain/interface learn limits
      BVT(clib_bihash_kv) kv;

      result0->raw = 0; // clear all fields
      result0->fields.sw_if_index = sw_if_index0;
 
      kv.key = key0->raw;
      kv.value = result0->raw;

      cached_key->raw = ~0;  // invalidate the cache

      BV(clib_bihash_add_del) (msm->mac_table, &kv, 1 /* is_add */);
    }
  }

  if (result0->fields.filter) {
    // drop packet because lookup matched a filter mac entry

    if (*next0 != L2LEARN_NEXT_DROP) {
      // if we're not already dropping the packet, do it now
      b0->error = node->errors[L2LEARN_ERROR_FILTER_DROP];
      *next0 = L2LEARN_NEXT_DROP;
    }
  }

done:
  return;
}


static uword
l2learn_node_fn (vlib_main_t * vm,
                  vlib_node_runtime_t * node,
                  vlib_frame_t * frame)
{
  u32 n_left_from, * from, * to_next;
  l2learn_next_t next_index;
  l2learn_main_t * msm = &l2learn_main;
  vlib_node_t *n = vlib_get_node (vm, l2learn_node.index);
  u32 node_counter_base_index = n->error_heap_index;
  vlib_error_main_t * em = &vm->error_main;
  l2fib_entry_key_t cached_key;
  l2fib_entry_result_t cached_result;

  from = vlib_frame_vector_args (frame);
  n_left_from = frame->n_vectors; /* number of packets to process */
  next_index = node->cached_next_index;
 
  // Clear the one-entry cache in case mac table was updated
  cached_key.raw = ~0; 
  cached_result.raw = ~0;       /* warning be gone */

  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, bi1;
          vlib_buffer_t * b0, * b1;
          u32 next0, next1;
          u32 sw_if_index0, sw_if_index1;
          ethernet_header_t * h0, * h1;
          l2fib_entry_key_t key0, key1;
          l2fib_entry_result_t result0, result1;
          u32 bucket0, bucket1;
          
          /* Prefetch next iteration. */
          {
            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, CLIB_CACHE_LINE_BYTES, STORE);
            CLIB_PREFETCH (p3->data, CLIB_CACHE_LINE_BYTES, STORE);
          }

          /* speculatively enqueue b0 and b1 to the current next frame */
          /* bi is "buffer index", b is pointer to the buffer */
          to_next[0] = bi0 = from[0];
          to_next[1] = bi1 = from[1];
          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);
 
          /* RX interface handles */
          sw_if_index0 = vnet_buffer(b0)->sw_if_index[VLIB_RX];
          sw_if_index1 = vnet_buffer(b1)->sw_if_index[VLIB_RX];

          /* Process 2 x pkts */

          h0 = vlib_buffer_get_current (b0);
          h1 = vlib_buffer_get_current (b1);

          if (PREDICT_FALSE((node->flags & VLIB_NODE_FLAG_TRACE)))
            {
              if (b0->flags & VLIB_BUFFER_IS_TRACED) 
                {
                  l2learn_trace_t *t = 
                    vlib_add_trace (vm, node, b0, sizeof (*t));
                  t->sw_if_index = sw_if_index0;
                  t->bd_index = vnet_buffer(b0)->l2.bd_index;
                  clib_memcpy(t->src, h0->src_address, 6);
                  clib_memcpy(t->dst, h0->dst_address, 6);
                }
              if (b1->flags & VLIB_BUFFER_IS_TRACED) 
                {
                  l2learn_trace_t *t = 
                    vlib_add_trace (vm, node, b1, sizeof (*t));
                  t->sw_if_index = sw_if_index1;
                  t->bd_index = vnet_buffer(b1)->l2.bd_index;
                  clib_memcpy(t->src, h1->src_address, 6);
                  clib_memcpy(t->dst, h1->dst_address, 6);
                }
            }

            /* process 2 pkts */
            em->counters[node_counter_base_index + L2LEARN_ERROR_L2LEARN] += 2;

            l2fib_lookup_2 (msm->mac_table, &cached_key, &cached_result,
                            h0->src_address, 
                            h1->src_address, 
                            vnet_buffer(b0)->l2.bd_index,
                            vnet_buffer(b1)->l2.bd_index,
                            &key0,
                            &key1,
                            &bucket0,
                            &bucket1,
                            &result0,
                            &result1);

            l2learn_process (node, msm, &em->counters[node_counter_base_index],
                             b0, sw_if_index0, &key0, &cached_key,
                             &bucket0, &result0, &next0);

            l2learn_process (node, msm, &em->counters[node_counter_base_index],
                             b1, sw_if_index1, &key1, &cached_key,
                             &bucket1, &result1, &next1);

            /* verify speculative enqueues, maybe switch current next frame */
            /* if next0==next1==next_index then nothing special needs to be done */
            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;
          vlib_buffer_t * b0;
          u32 next0;
          u32 sw_if_index0;
          ethernet_header_t * h0;
          l2fib_entry_key_t key0;
          l2fib_entry_result_t result0;
          u32 bucket0;

          /* speculatively enqueue b0 to the current next frame */
          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);

          sw_if_index0 = vnet_buffer(b0)->sw_if_index[VLIB_RX];
 
          h0 = vlib_buffer_get_current (b0);

          if (PREDICT_FALSE((node->flags & VLIB_NODE_FLAG_TRACE) 
                            && (b0->flags & VLIB_BUFFER_IS_TRACED))) {
            l2learn_trace_t *t = 
               vlib_add_trace (vm, node, b0, sizeof (*t));
            t->sw_if_index = sw_if_index0;
            t->bd_index = vnet_buffer(b0)->l2.bd_index;
            clib_memcpy(t->src, h0->src_address, 6);
            clib_memcpy(t->dst, h0->dst_address, 6);
            }

          /* process 1 pkt */
          em->counters[node_counter_base_index + L2LEARN_ERROR_L2LEARN] += 1;

          l2fib_lookup_1 (msm->mac_table, &cached_key, &cached_result, 
                          h0->src_address, vnet_buffer(b0)->l2.bd_index, 
                          &key0,
                          &bucket0,
                          &result0);

          l2learn_process (node, msm, &em->counters[node_counter_base_index],
                           b0, sw_if_index0, &key0, &cached_key,
                           &bucket0, &result0, &next0);

          /* verify speculative enqueue, maybe switch current next frame */
          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;
}


VLIB_REGISTER_NODE (l2learn_node,static) = {
  .function = l2learn_node_fn,
  .name = "l2-learn",
  .vector_size = sizeof (u32),
  .format_trace = format_l2learn_trace,
  .type = VLIB_NODE_TYPE_INTERNAL,
  
  .n_errors = ARRAY_LEN(l2learn_error_strings),
  .error_strings = l2learn_error_strings,

  .n_next_nodes = L2LEARN_N_NEXT,

  /* edit / add dispositions here */
  .next_nodes = {
        [L2LEARN_NEXT_DROP] = "error-drop",
        [L2LEARN_NEXT_L2FWD] = "l2-fwd",
  },
};


clib_error_t *l2learn_init (vlib_main_t *vm)
{
  l2learn_main_t * mp = &l2learn_main;
    
  mp->vlib_main = vm;
  mp->vnet_main = vnet_get_main();

  // Initialize the feature next-node indexes
  feat_bitmap_init_next_nodes(vm,
                              l2learn_node.index,
                              L2INPUT_N_FEAT,
                              l2input_get_feat_names(),
                              mp->feat_next_node_index);

  /* init the hash table ptr */
  mp->mac_table = get_mac_table();

  // Set the default number of dynamically learned macs to the number 
  // of buckets.
  mp->global_learn_limit = L2FIB_NUM_BUCKETS * 16;

  return 0;
}

VLIB_INIT_FUNCTION (l2learn_init);


// set subinterface learn enable/disable
// The CLI format is:
//    set interface l2 learn <interface> [disable]
static clib_error_t *
int_learn (vlib_main_t * vm,
           unformat_input_t * input,
           vlib_cli_command_t * cmd)
{
  vnet_main_t * vnm = vnet_get_main();
  clib_error_t * error = 0;
  u32 sw_if_index;
  u32 enable;

  if (! unformat_user (input, unformat_vnet_sw_interface, vnm, &sw_if_index))
    {
      error = clib_error_return (0, "unknown interface `%U'",
                                 format_unformat_error, input);
      goto done;
    }

  enable = 1;
  if (unformat (input, "disable")) {
    enable = 0;
  }

  // set the interface flag
  l2input_intf_bitmap_enable(sw_if_index, L2INPUT_FEAT_LEARN, enable);

 done:
  return error;
}

VLIB_CLI_COMMAND (int_learn_cli, static) = {
  .path = "set interface l2 learn",
  .short_help = "set interface l2 learn <interface> [disable]",
  .function = int_learn,
};


static clib_error_t *
l2learn_config (vlib_main_t * vm, unformat_input_t * input)
{
  l2learn_main_t *mp = &l2learn_main;

  while (unformat_check_input (input) != UNFORMAT_END_OF_INPUT)
    {
      if (unformat (input, "limit %d", &mp->global_learn_limit))
        ;

      else
        return clib_error_return (0, "unknown input `%U'",
                                  format_unformat_error, input);
    }

  return 0;
}

VLIB_CONFIG_FUNCTION (l2learn_config, "l2learn");