arp.c

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/*
 * ethernet/arp.c: IP v4 ARP node
 *
 * Copyright (c) 2010 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 <vnet/ip/ip.h>
#include <vnet/ethernet/ethernet.h>
#include <vnet/ethernet/arp_packet.h>
#include <vnet/l2/l2_input.h>
#include <vppinfra/mhash.h>

void vl_api_rpc_call_main_thread (void *fp, u8 * data, u32 data_length);

typedef struct {
  u32 sw_if_index;
  u32 fib_index;
  ip4_address_t ip4_address;
} ethernet_arp_ip4_key_t;

typedef struct {
  ethernet_arp_ip4_key_t key;
  u8 ethernet_address[6];

  u16 flags;
#define ETHERNET_ARP_IP4_ENTRY_FLAG_STATIC (1 << 0)
#define ETHERNET_ARP_IP4_ENTRY_FLAG_GLEAN  (2 << 0)

  u64 cpu_time_last_updated;

  u32 * adjacencies;
} ethernet_arp_ip4_entry_t;

typedef struct {
  u32 lo_addr;
  u32 hi_addr;
  u32 fib_index;
} ethernet_proxy_arp_t;

typedef struct {
  u32 next_index;
  uword node_index;
  uword type_opaque;
  uword data;
  /* Used for arp event notification only */
  void * data_callback;
  u32 pid;
} pending_resolution_t;

typedef struct {
  /* Hash tables mapping name to opcode. */
  uword * opcode_by_name;

  /* lite beer "glean" adjacency handling */
  uword * pending_resolutions_by_address;
  pending_resolution_t * pending_resolutions;

  /* Mac address change notification */
  uword * mac_changes_by_address;
  pending_resolution_t * mac_changes;

  ethernet_arp_ip4_entry_t * ip4_entry_pool;

  mhash_t ip4_entry_by_key;
    
  /* ARP attack mitigation */
  u32 arp_delete_rotor;
  u32 limit_arp_cache_size;

  /* Proxy arp vector */
  ethernet_proxy_arp_t * proxy_arps;
} ethernet_arp_main_t;

static ethernet_arp_main_t ethernet_arp_main;

static u8 * format_ethernet_arp_hardware_type (u8 * s, va_list * va)
{
  ethernet_arp_hardware_type_t h = va_arg (*va, ethernet_arp_hardware_type_t);
  char * t = 0;
  switch (h)
    {
#define _(n,f) case n: t = #f; break;
      foreach_ethernet_arp_hardware_type;
#undef _

    default:
      return format (s, "unknown 0x%x", h);
    }

  return format (s, "%s", t);
}

static u8 * format_ethernet_arp_opcode (u8 * s, va_list * va)
{
  ethernet_arp_opcode_t o = va_arg (*va, ethernet_arp_opcode_t);
  char * t = 0;
  switch (o)
    {
#define _(f) case ETHERNET_ARP_OPCODE_##f: t = #f; break;
      foreach_ethernet_arp_opcode;
#undef _

    default:
      return format (s, "unknown 0x%x", o);
    }

  return format (s, "%s", t);
}

static uword
unformat_ethernet_arp_opcode_host_byte_order (unformat_input_t * input,
                                              va_list * args)
{
  int * result = va_arg (*args, int *);
  ethernet_arp_main_t * am = &ethernet_arp_main;
  int x, i;

  /* Numeric opcode. */
  if (unformat (input, "0x%x", &x)
      || unformat (input, "%d", &x))
    {
      if (x >= (1 << 16))
        return 0;
      *result = x;
      return 1;
    }

  /* Named type. */
  if (unformat_user (input, unformat_vlib_number_by_name,
                     am->opcode_by_name, &i))
    {
      *result = i;
      return 1;
    }

  return 0;
}

static uword
unformat_ethernet_arp_opcode_net_byte_order (unformat_input_t * input,
                                             va_list * args)
{
  int * result = va_arg (*args, int *);
  if (! unformat_user (input, unformat_ethernet_arp_opcode_host_byte_order, result))
    return 0;

  *result = clib_host_to_net_u16 ((u16) *result);
  return 1;
}

static u8 * format_ethernet_arp_header (u8 * s, va_list * va)
{
  ethernet_arp_header_t * a = va_arg (*va, ethernet_arp_header_t *);
  u32 max_header_bytes = va_arg (*va, u32);
  uword indent;
  u16 l2_type, l3_type;

  if (max_header_bytes != 0 && sizeof (a[0]) > max_header_bytes)
    return format (s, "ARP header truncated");

  l2_type = clib_net_to_host_u16 (a->l2_type);
  l3_type = clib_net_to_host_u16 (a->l3_type);

  indent = format_get_indent (s);

  s = format (s, "%U, type %U/%U, address size %d/%d",
              format_ethernet_arp_opcode, clib_net_to_host_u16 (a->opcode),
              format_ethernet_arp_hardware_type, l2_type,
              format_ethernet_type, l3_type,
              a->n_l2_address_bytes, a->n_l3_address_bytes);
              
  if (l2_type == ETHERNET_ARP_HARDWARE_TYPE_ethernet
      && l3_type == ETHERNET_TYPE_IP4)
    {
      s = format (s, "\n%U%U/%U -> %U/%U",
                  format_white_space, indent,
                  format_ethernet_address, a->ip4_over_ethernet[0].ethernet,
                  format_ip4_address, &a->ip4_over_ethernet[0].ip4,
                  format_ethernet_address, a->ip4_over_ethernet[1].ethernet,
                  format_ip4_address, &a->ip4_over_ethernet[1].ip4);
    }
  else
    {
      uword n2 = a->n_l2_address_bytes;
      uword n3 = a->n_l3_address_bytes;
      s = format (s, "\n%U%U/%U -> %U/%U",
                  format_white_space, indent,
                  format_hex_bytes, a->data + 0*n2 + 0*n3, n2,
                  format_hex_bytes, a->data + 1*n2 + 0*n3, n3,
                  format_hex_bytes, a->data + 1*n2 + 1*n3, n2,
                  format_hex_bytes, a->data + 2*n2 + 1*n3, n3);
    }

  return s;
}

static u8 * format_ethernet_arp_ip4_entry (u8 * s, va_list * va)
{
  vnet_main_t * vnm = va_arg (*va, vnet_main_t *);
  ethernet_arp_ip4_entry_t * e = va_arg (*va, ethernet_arp_ip4_entry_t *);
  vnet_sw_interface_t * si;
  ip4_fib_t * fib;
  u8 * flags = 0;

  if (! e)
    return format (s, "%=12s%=6s%=16s%=6s%=20s%=24s", "Time", "FIB", "IP4",
                   "Flags", "Ethernet", "Interface");

  fib = find_ip4_fib_by_table_index_or_id (&ip4_main, e->key.fib_index,
                                           IP4_ROUTE_FLAG_FIB_INDEX);
  si = vnet_get_sw_interface (vnm, e->key.sw_if_index);

  if (e->flags & ETHERNET_ARP_IP4_ENTRY_FLAG_GLEAN)
    flags = format(flags, "G");

  if (e->flags & ETHERNET_ARP_IP4_ENTRY_FLAG_STATIC)
    flags = format(flags, "S");

  s = format (s, "%=12U%=6u%=16U%=6s%=20U%=24U",
              format_vlib_cpu_time, vnm->vlib_main, e->cpu_time_last_updated,
              fib->table_id,
              format_ip4_address, &e->key.ip4_address,
              flags ? (char *) flags : "",
              format_ethernet_address, e->ethernet_address,
              format_vnet_sw_interface_name, vnm, si);

  vec_free(flags);
  return s;
}

typedef struct {
  u8 packet_data[64];
} ethernet_arp_input_trace_t;

static u8 * format_ethernet_arp_input_trace (u8 * s, va_list * va)
{
  CLIB_UNUSED (vlib_main_t * vm) = va_arg (*va, vlib_main_t *);
  CLIB_UNUSED (vlib_node_t * node) = va_arg (*va, vlib_node_t *);
  ethernet_arp_input_trace_t * t = va_arg (*va, ethernet_arp_input_trace_t *);

  s = format (s, "%U",
              format_ethernet_arp_header,
              t->packet_data, sizeof (t->packet_data));

  return s;
}

clib_error_t *
ethernet_arp_sw_interface_up_down (vnet_main_t * vnm,
                                   u32 sw_if_index,
                                   u32 flags)
{
  ethernet_arp_main_t * am = &ethernet_arp_main;
  ethernet_arp_ip4_entry_t * e;

  if (! (flags & VNET_SW_INTERFACE_FLAG_ADMIN_UP))
    {
      u32 i, * to_delete = 0;

      pool_foreach (e, am->ip4_entry_pool, ({
        if (e->key.sw_if_index == sw_if_index)
          vec_add1 (to_delete, e - am->ip4_entry_pool);
      }));

      for (i = 0; i < vec_len (to_delete); i++)
        {
          ethernet_arp_ip4_over_ethernet_address_t delme;
          e = pool_elt_at_index (am->ip4_entry_pool, to_delete[i]);

          clib_memcpy (&delme.ethernet, e->ethernet_address, 6);
          delme.ip4.as_u32 = e->key.ip4_address.as_u32;

          vnet_arp_unset_ip4_over_ethernet (vnm, e->key.sw_if_index,
                                            e->key.fib_index, &delme);
        }

      vec_free (to_delete);
    }

  return 0;
}

VNET_SW_INTERFACE_ADMIN_UP_DOWN_FUNCTION (ethernet_arp_sw_interface_up_down);

static int
vnet_arp_set_ip4_over_ethernet_internal (vnet_main_t * vnm,
                                         u32 sw_if_index,
                                         u32 fib_index,
                                         void * a_arg,
                                         int is_static);

static int
vnet_arp_unset_ip4_over_ethernet_internal (vnet_main_t * vnm,
                                           u32 sw_if_index,
                                           u32 fib_index,
                                           void * a_arg);

typedef struct {
  u32 sw_if_index;
  u32 fib_index;
  ethernet_arp_ip4_over_ethernet_address_t a;
  int is_static;
  int is_remove; /* set is_remove=1 to clear arp entry */
} vnet_arp_set_ip4_over_ethernet_rpc_args_t;

static void set_ip4_over_ethernet_rpc_callback 
( vnet_arp_set_ip4_over_ethernet_rpc_args_t * a)
{
  vnet_main_t * vm = vnet_get_main();
  ASSERT(os_get_cpu_number() == 0);

  if (a->is_remove)
    vnet_arp_unset_ip4_over_ethernet_internal(vm, 
                                              a->sw_if_index, 
                                              a->fib_index,
                                              &(a->a));
  else
    vnet_arp_set_ip4_over_ethernet_internal (vm,
                                             a->sw_if_index,
                                             a->fib_index,
                                             &(a->a),
                                             a->is_static);
}

int
vnet_arp_set_ip4_over_ethernet (vnet_main_t * vnm,
                                u32 sw_if_index,
                                u32 fib_index,
                                void * a_arg,
                                int is_static)
{
  ethernet_arp_ip4_over_ethernet_address_t * a = a_arg;
  vnet_arp_set_ip4_over_ethernet_rpc_args_t args;

  args.sw_if_index = sw_if_index;
  args.fib_index = fib_index;
  args.is_static = is_static;
  args.is_remove = 0;
  clib_memcpy (&args.a, a, sizeof (*a));

  vl_api_rpc_call_main_thread (set_ip4_over_ethernet_rpc_callback, 
                               (u8 *) &args, sizeof (args));
  return 0;
}

int
vnet_arp_set_ip4_over_ethernet_internal (vnet_main_t * vnm,
                                         u32 sw_if_index,
                                         u32 fib_index,
                                         void * a_arg,
                                         int is_static)
{
  ethernet_arp_ip4_key_t k;
  ethernet_arp_ip4_entry_t * e = 0;
  ethernet_arp_main_t * am = &ethernet_arp_main;
  ethernet_arp_ip4_over_ethernet_address_t * a = a_arg;
  vlib_main_t * vm = vlib_get_main();
  ip4_main_t * im = &ip4_main;
  ip_lookup_main_t * lm = &im->lookup_main;
  int make_new_arp_cache_entry=1;
  uword * p;
  ip4_add_del_route_args_t args;
  ip_adjacency_t adj, * existing_adj;
  pending_resolution_t * pr, * mc;
  
  u32 next_index;
  u32 adj_index;

  fib_index = (fib_index != (u32)~0) 
    ? fib_index : im->fib_index_by_sw_if_index[sw_if_index];

  k.sw_if_index = sw_if_index;
  k.ip4_address = a->ip4;
  k.fib_index = fib_index;

  p = mhash_get (&am->ip4_entry_by_key, &k);
  if (p)
    {
      e = pool_elt_at_index (am->ip4_entry_pool, p[0]);

      /* Refuse to over-write static arp. */
      if (!is_static &&
          (e->flags & ETHERNET_ARP_IP4_ENTRY_FLAG_STATIC))
        return -2;
      make_new_arp_cache_entry = 0;
    }

  /* Note: always install the route. It might have been deleted */
  memset(&adj, 0, sizeof(adj));
  adj.lookup_next_index = IP_LOOKUP_NEXT_REWRITE;

  vnet_rewrite_for_sw_interface
    (vnm,
     VNET_L3_PACKET_TYPE_IP4,
     sw_if_index,
     ip4_rewrite_node.index,
     a->ethernet,               /* destination address */
     &adj.rewrite_header,
     sizeof (adj.rewrite_data));

  /* result of this lookup should be next-hop adjacency */
  adj_index = ip4_fib_lookup_with_table (im, fib_index, &a->ip4, 0);
  existing_adj = ip_get_adjacency(lm, adj_index);

  if (existing_adj->lookup_next_index == IP_LOOKUP_NEXT_ARP &&
      existing_adj->arp.next_hop.ip4.as_u32 == a->ip4.as_u32)
    {
      u32 * ai;
      u32 * adjs = vec_dup(e->adjacencies);
      /* Update all adj assigned to this arp entry */
      vec_foreach(ai, adjs)
        {
          int i;
          ip_adjacency_t * uadj = ip_get_adjacency(lm, *ai);
          for (i = 0; i < uadj->n_adj; i++)
            if (uadj[i].lookup_next_index == IP_LOOKUP_NEXT_ARP &&
                uadj[i].arp.next_hop.ip4.as_u32 == a->ip4.as_u32)
              ip_update_adjacency (lm, *ai + i, &adj);
        }
      vec_free(adjs);
    }
  else
    {
      /* create new adj */
      args.table_index_or_table_id = fib_index;
      args.flags = IP4_ROUTE_FLAG_FIB_INDEX | IP4_ROUTE_FLAG_ADD | IP4_ROUTE_FLAG_NEIGHBOR;
      args.dst_address = a->ip4;
      args.dst_address_length = 32;
      args.adj_index = ~0;
      args.add_adj = &adj;
      args.n_add_adj = 1;
      ip4_add_del_route (im, &args);
    }

  if (make_new_arp_cache_entry)
    {
      pool_get (am->ip4_entry_pool, e);
      mhash_set (&am->ip4_entry_by_key, &k,
                 e - am->ip4_entry_pool,
                 /* old value */ 0);
      e->key = k;
    }

  /* Update time stamp and ethernet address. */
  clib_memcpy (e->ethernet_address, a->ethernet, sizeof (e->ethernet_address));
  e->cpu_time_last_updated = clib_cpu_time_now ();
  if (is_static)
    e->flags |= ETHERNET_ARP_IP4_ENTRY_FLAG_STATIC;

  /* Customer(s) waiting for this address to be resolved? */
  p = hash_get (am->pending_resolutions_by_address, a->ip4.as_u32);
  if (p)
    {
      next_index = p[0];

      while (next_index != (u32)~0)
        {
          pr = pool_elt_at_index (am->pending_resolutions, next_index);
          vlib_process_signal_event (vm, pr->node_index,
                                     pr->type_opaque, 
                                     pr->data);
          next_index = pr->next_index;
          pool_put (am->pending_resolutions, pr);
        }
      
      hash_unset (am->pending_resolutions_by_address, a->ip4.as_u32);
    }

  /* Customer(s) requesting ARP event for this address? */
  p = hash_get (am->mac_changes_by_address, a->ip4.as_u32);
  if (p)
    {
      next_index = p[0];

      while (next_index != (u32)~0)
        {
          int (*fp)(u32, u8 *, u32, u32);
          int rv = 1;
          mc = pool_elt_at_index (am->mac_changes, next_index);
          fp = mc->data_callback;

          /* Call the user's data callback, return 1 to suppress dup events */
          if (fp)
            rv = (*fp)(mc->data, a->ethernet, sw_if_index, 0);
          
          /* 
           * Signal the resolver process, as long as the user
           * says they want to be notified
           */
          if (rv == 0)
            vlib_process_signal_event (vm, mc->node_index,
                                       mc->type_opaque, 
                                       mc->data);
          next_index = mc->next_index;
        }
    }

  return 0;
}

void vnet_register_ip4_arp_resolution_event (vnet_main_t * vnm, 
                                             void * address_arg,
                                             uword node_index,
                                             uword type_opaque,
                                             uword data)
{
  ethernet_arp_main_t * am = &ethernet_arp_main;
  ip4_address_t * address = address_arg;
  uword * p;
  pending_resolution_t * pr;
  
  pool_get (am->pending_resolutions, pr);

  pr->next_index = ~0;
  pr->node_index = node_index;
  pr->type_opaque = type_opaque;
  pr->data = data;
  pr->data_callback = 0;

  p = hash_get (am->pending_resolutions_by_address, address->as_u32);
  if (p)
    {
      /* Insert new resolution at the head of the list */
      pr->next_index = p[0];
      hash_unset (am->pending_resolutions_by_address, address->as_u32);
    }
  
  hash_set (am->pending_resolutions_by_address, address->as_u32, 
            pr - am->pending_resolutions);
}

int vnet_add_del_ip4_arp_change_event (vnet_main_t * vnm, 
                                       void * data_callback,
                                       u32 pid,
                                       void * address_arg,
                                       uword node_index,
                                       uword type_opaque,
                                       uword data, int is_add)
{
  ethernet_arp_main_t * am = &ethernet_arp_main;
  ip4_address_t * address = address_arg;
  uword * p;
  pending_resolution_t * mc;
  void (*fp)(u32, u8 *) = data_callback;
  
  if (is_add)
    {
      pool_get (am->mac_changes, mc);

      mc->next_index = ~0;
      mc->node_index = node_index;
      mc->type_opaque = type_opaque;
      mc->data = data;
      mc->data_callback = data_callback;
      mc->pid = pid;
      
      p = hash_get (am->mac_changes_by_address, address->as_u32);
      if (p)
        {
          /* Insert new resolution at the head of the list */
          mc->next_index = p[0];
          hash_unset (am->mac_changes_by_address, address->as_u32);
        }
      
      hash_set (am->mac_changes_by_address, address->as_u32, 
                mc - am->mac_changes);
      return 0;
    }
  else
    {
      u32 index;
      pending_resolution_t * mc_last = 0;

      p = hash_get (am->mac_changes_by_address, address->as_u32);
      if (p == 0)
        return VNET_API_ERROR_NO_SUCH_ENTRY;

      index = p[0];

      while (index != (u32)~0)
        {
          mc = pool_elt_at_index (am->mac_changes, index);
          if (mc->node_index == node_index &&
              mc->type_opaque == type_opaque &&
              mc->pid == pid)
            {
              /* Clients may need to clean up pool entries, too */
              if (fp)
                (*fp)(mc->data, 0 /* no new mac addrs */);
              if (index == p[0])
                {
                  hash_unset (am->mac_changes_by_address, address->as_u32);
                  if (mc->next_index != ~0)
                    hash_set (am->mac_changes_by_address, address->as_u32,
                              mc->next_index);
                  pool_put (am->mac_changes, mc);
                  return 0;
                }
              else
                {
                  ASSERT(mc_last);
                  mc_last->next_index = mc->next_index;
                  pool_put (am->mac_changes, mc);
                  return 0;
                }
            }
          mc_last = mc;
          index = mc->next_index;
        }
      
      return VNET_API_ERROR_NO_SUCH_ENTRY;
    }
}

/* Either we drop the packet or we send a reply to the sender. */
typedef enum {
  ARP_INPUT_NEXT_DROP,
  ARP_INPUT_NEXT_REPLY_TX,
  ARP_INPUT_N_NEXT,
} arp_input_next_t;

#define foreach_ethernet_arp_error                                      \
  _ (replies_sent, "ARP replies sent")                                  \
  _ (l2_type_not_ethernet, "L2 type not ethernet")                      \
  _ (l3_type_not_ip4, "L3 type not IP4")                                \
  _ (l3_src_address_not_local, "IP4 source address not local to subnet") \
  _ (l3_dst_address_not_local, "IP4 destination address not local to subnet") \
  _ (l3_src_address_is_local, "IP4 source address matches local interface") \
  _ (l3_src_address_learned, "ARP request IP4 source address learned")  \
  _ (replies_received, "ARP replies received")                          \
  _ (opcode_not_request, "ARP opcode not request")                      \
  _ (proxy_arp_replies_sent, "Proxy ARP replies sent")                  \
  _ (l2_address_mismatch, "ARP hw addr does not match L2 frame src addr") \
  _ (missing_interface_address, "ARP missing interface address") \
  _ (gratuitous_arp, "ARP probe or announcement dropped") \

typedef enum {
#define _(sym,string) ETHERNET_ARP_ERROR_##sym,
  foreach_ethernet_arp_error
#undef _
  ETHERNET_ARP_N_ERROR,
} ethernet_arp_input_error_t;

/* get first interface address */
ip4_address_t *
ip4_interface_first_address (ip4_main_t * im, u32 sw_if_index,
                             ip_interface_address_t ** result_ia)
{
  ip_lookup_main_t * lm = &im->lookup_main;
  ip_interface_address_t * ia = 0;
  ip4_address_t * result = 0;

  foreach_ip_interface_address (lm, ia, sw_if_index, 
                                1 /* honor unnumbered */,
  ({
    ip4_address_t * a = ip_interface_address_get_address (lm, ia);
    result = a;
    break;
  }));
  if (result_ia)
    *result_ia = result ? ia : 0;
  return result;
}

static void unset_random_arp_entry (void)
{
  ethernet_arp_main_t * am = &ethernet_arp_main;
  ethernet_arp_ip4_entry_t * e;
  vnet_main_t * vnm = vnet_get_main();
  ethernet_arp_ip4_over_ethernet_address_t delme;  
  u32 index;

  index = pool_next_index (am->ip4_entry_pool, am->arp_delete_rotor);
  am->arp_delete_rotor = index;

  /* Try again from elt 0, could happen if an intfc goes down */
  if (index == ~0)
    {
      index = pool_next_index (am->ip4_entry_pool, am->arp_delete_rotor);
      am->arp_delete_rotor = index;
    }

  /* Nothing left in the pool */
  if (index == ~0)
    return;

  e = pool_elt_at_index (am->ip4_entry_pool, index);
  
  clib_memcpy (&delme.ethernet, e->ethernet_address, 6);
  delme.ip4.as_u32 = e->key.ip4_address.as_u32;
  
  vnet_arp_unset_ip4_over_ethernet (vnm, e->key.sw_if_index,
                                    e->key.fib_index, &delme);
}
  
static void arp_unnumbered (vlib_buffer_t * p0, 
                       u32 pi0,
                       ethernet_header_t * eth0,
                       ip_interface_address_t * ifa0)
{
  vlib_main_t * vm = vlib_get_main();
  vnet_main_t * vnm = vnet_get_main();
  vnet_interface_main_t * vim = &vnm->interface_main;
  vnet_sw_interface_t * si;
  vnet_hw_interface_t * hi;
  u32 unnum_src_sw_if_index;
  u32 * broadcast_swifs = 0;
  u32 * buffers = 0;
  u32 n_alloc = 0;
  vlib_buffer_t * b0;
  int i;
  u8 dst_mac_address[6];
  i16 header_size;
  ethernet_arp_header_t * arp0;

  /* Save the dst mac address */
  clib_memcpy(dst_mac_address, eth0->dst_address, sizeof (dst_mac_address));

  /* Figure out which sw_if_index supplied the address */
  unnum_src_sw_if_index = ifa0->sw_if_index;

  /* Track down all users of the unnumbered source */
  pool_foreach (si, vim->sw_interfaces, 
  ({
    if (si->flags & VNET_SW_INTERFACE_FLAG_UNNUMBERED &&
        (si->unnumbered_sw_if_index == unnum_src_sw_if_index))
      {
        vec_add1 (broadcast_swifs, si->sw_if_index);
      }
  }));
          

  ASSERT (vec_len(broadcast_swifs));

  /* Allocate buffering if we need it */
  if (vec_len(broadcast_swifs) > 1)
    {
      vec_validate (buffers, vec_len(broadcast_swifs)-2);
      n_alloc = vlib_buffer_alloc (vm, buffers, vec_len(buffers));
      _vec_len (buffers) = n_alloc;
      for (i = 0; i < n_alloc; i++)
        {
          b0 = vlib_get_buffer (vm, buffers[i]);

          /* xerox (partially built) ARP pkt */
          clib_memcpy (b0->data, p0->data, p0->current_length + p0->current_data);
          b0->current_data = p0->current_data;
          b0->current_length = p0->current_length;
          vnet_buffer(b0)->sw_if_index[VLIB_RX] =
            vnet_buffer(p0)->sw_if_index[VLIB_RX];
        }
    }

  vec_insert (buffers, 1, 0);
  buffers[0] = pi0;
  
  for (i = 0; i < vec_len(buffers); i++)
    {
      b0 = vlib_get_buffer(vm, buffers[i]);
      arp0 = vlib_buffer_get_current (b0);

      hi = vnet_get_sup_hw_interface (vnm, broadcast_swifs[i]);
      si = vnet_get_sw_interface (vnm, broadcast_swifs[i]);

      /* For decoration, most likely */
      vnet_buffer(b0)->sw_if_index[VLIB_TX] = hi->sw_if_index;

      /* Fix ARP pkt src address */
      clib_memcpy (arp0->ip4_over_ethernet[0].ethernet, hi->hw_address, 6);

      /* Build L2 encaps for this swif */
      header_size = sizeof (ethernet_header_t);
      if (si->sub.eth.flags.one_tag) 
        header_size += 4;
      else if (si->sub.eth.flags.two_tags)
        header_size += 8;
      
      vlib_buffer_advance (b0, -header_size);
      eth0 = vlib_buffer_get_current (b0);

      if (si->sub.eth.flags.one_tag) {
        ethernet_vlan_header_t * outer = (void *) (eth0 + 1);
        
        eth0->type = si->sub.eth.flags.dot1ad ?
          clib_host_to_net_u16 (ETHERNET_TYPE_DOT1AD) :
          clib_host_to_net_u16 (ETHERNET_TYPE_VLAN);
        outer->priority_cfi_and_id = 
          clib_host_to_net_u16 (si->sub.eth.outer_vlan_id);
        outer->type = clib_host_to_net_u16 (ETHERNET_TYPE_ARP);
        
      } else if (si->sub.eth.flags.two_tags) {
        ethernet_vlan_header_t * outer = (void *) (eth0 + 1);
        ethernet_vlan_header_t * inner = (void *) (outer + 1);
        
        eth0->type = si->sub.eth.flags.dot1ad ?
          clib_host_to_net_u16 (ETHERNET_TYPE_DOT1AD) :
          clib_host_to_net_u16 (ETHERNET_TYPE_VLAN);
        outer->priority_cfi_and_id = 
          clib_host_to_net_u16 (si->sub.eth.outer_vlan_id);
        outer->type = clib_host_to_net_u16 (ETHERNET_TYPE_VLAN);
        inner->priority_cfi_and_id = 
          clib_host_to_net_u16 (si->sub.eth.inner_vlan_id);
        inner->type = clib_host_to_net_u16 (ETHERNET_TYPE_ARP);
        
      } else {
        eth0->type = clib_host_to_net_u16 (ETHERNET_TYPE_ARP);
      }
      
      /* Restore the original dst address, set src address */
      clib_memcpy (eth0->dst_address, dst_mac_address, sizeof (eth0->dst_address));
      clib_memcpy (eth0->src_address, hi->hw_address, sizeof (eth0->src_address));
      
      /* Transmit replicas */
      if (i > 0)
        {
          vlib_frame_t * f = vlib_get_frame_to_node (vm, hi->output_node_index);
          u32 * to_next = vlib_frame_vector_args (f);
          to_next[0] = buffers[i];
          f->n_vectors = 1;
          vlib_put_frame_to_node (vm, hi->output_node_index, f);
        }
    }

  /* The regular path outputs the original pkt.. */
  vnet_buffer (p0)->sw_if_index[VLIB_TX] = broadcast_swifs[0];

  vec_free (broadcast_swifs);
  vec_free (buffers);
}

static uword
arp_input (vlib_main_t * vm,
           vlib_node_runtime_t * node,
           vlib_frame_t * frame)
{
  ethernet_arp_main_t * am = &ethernet_arp_main;
  vnet_main_t * vnm = vnet_get_main();
  ip4_main_t * im4 = &ip4_main;
  u32 n_left_from, next_index, * from, * to_next;
  u32 n_replies_sent = 0, n_proxy_arp_replies_sent = 0;

  from = vlib_frame_vector_args (frame);
  n_left_from = frame->n_vectors;
  next_index = node->cached_next_index;

  if (node->flags & VLIB_NODE_FLAG_TRACE)
    vlib_trace_frame_buffers_only (vm, node, from, frame->n_vectors,
                                   /* stride */ 1,
                                   sizeof (ethernet_arp_input_trace_t));

  while (n_left_from > 0)
    {
      u32 n_left_to_next;

      vlib_get_next_frame (vm, node, next_index,
                           to_next, n_left_to_next);

      while (n_left_from > 0 && n_left_to_next > 0)
        {
          vlib_buffer_t * p0;
          vnet_hw_interface_t * hw_if0;
          ethernet_arp_header_t * arp0;
          ethernet_header_t * eth0;
          ip_interface_address_t * ifa0;
          ip_adjacency_t * adj0;
          ip4_address_t * if_addr0;
          ip4_address_t proxy_src;
          u32 pi0, error0, next0, sw_if_index0;
          u8 is_request0, src_is_local0, dst_is_local0, is_unnum0;
          ethernet_proxy_arp_t * pa;

          pi0 = from[0];
          to_next[0] = pi0;
          from += 1;
          to_next += 1;
          n_left_from -= 1;
          n_left_to_next -= 1;

          p0 = vlib_get_buffer (vm, pi0);
          arp0 = vlib_buffer_get_current (p0);

          is_request0 = arp0->opcode 
              == clib_host_to_net_u16 (ETHERNET_ARP_OPCODE_request);

          error0 = ETHERNET_ARP_ERROR_replies_sent;

          error0 = (arp0->l2_type != clib_net_to_host_u16 (ETHERNET_ARP_HARDWARE_TYPE_ethernet)
                    ? ETHERNET_ARP_ERROR_l2_type_not_ethernet
                    : error0);
          error0 = (arp0->l3_type != clib_net_to_host_u16 (ETHERNET_TYPE_IP4)
                    ? ETHERNET_ARP_ERROR_l3_type_not_ip4
                    : error0);

          sw_if_index0 = vnet_buffer (p0)->sw_if_index[VLIB_RX];

          if (error0)
            goto drop1;

          /* Check that IP address is local and matches incoming interface. */
          if_addr0 = ip4_interface_address_matching_destination (im4,
                                                                 &arp0->ip4_over_ethernet[1].ip4,
                                                                 sw_if_index0,
                                                                 &ifa0);
          if (! if_addr0)
            {
              error0 = ETHERNET_ARP_ERROR_l3_dst_address_not_local;
              goto drop1;
            }

          /* Honor unnumbered interface, if any */
          is_unnum0 = sw_if_index0 != ifa0->sw_if_index;

          /* Source must also be local to subnet of matching interface address. */
          if (! ip4_destination_matches_interface (im4, &arp0->ip4_over_ethernet[0].ip4, ifa0))
            {
              error0 = ETHERNET_ARP_ERROR_l3_src_address_not_local;
              goto drop1;
            }

          /* Reject requests/replies with our local interface address. */
          src_is_local0 = if_addr0->as_u32 == arp0->ip4_over_ethernet[0].ip4.as_u32;
          if (src_is_local0)
            {
              error0 = ETHERNET_ARP_ERROR_l3_src_address_is_local;
              goto drop1;
            }

          dst_is_local0 = if_addr0->as_u32 == arp0->ip4_over_ethernet[1].ip4.as_u32;

          /* Fill in ethernet header. */
          eth0 = ethernet_buffer_get_header (p0);

          /* Trash ARP packets whose ARP-level source addresses do not
             match their L2-frame-level source addresses */
          if (memcmp (eth0->src_address, arp0->ip4_over_ethernet[0].ethernet,
                      sizeof (eth0->src_address)))
            {
              error0 = ETHERNET_ARP_ERROR_l2_address_mismatch;
              goto drop2;
            }

          /* Learn or update sender's mapping only for requests or unicasts
             that don't match local interface address. */
          if (ethernet_address_cast (eth0->dst_address) == ETHERNET_ADDRESS_UNICAST
              || is_request0)
            {
              if (am->limit_arp_cache_size && 
                  pool_elts (am->ip4_entry_pool) >= am->limit_arp_cache_size)
                unset_random_arp_entry();

              vnet_arp_set_ip4_over_ethernet (vnm, sw_if_index0, 
                                              (u32)~0 /* default fib */,
                                              &arp0->ip4_over_ethernet[0], 
                                              0 /* is_static */);
              error0 = ETHERNET_ARP_ERROR_l3_src_address_learned;
             }

          /* Only send a reply for requests sent which match a local interface. */
          if (! (is_request0 && dst_is_local0))
            {
              error0 = (arp0->opcode == clib_host_to_net_u16 (ETHERNET_ARP_OPCODE_reply)
                        ? ETHERNET_ARP_ERROR_replies_received : error0);
              goto drop1;
            }

          /* Send a reply. */
        send_reply:
          vnet_buffer (p0)->sw_if_index[VLIB_TX] = sw_if_index0;
          hw_if0 = vnet_get_sup_hw_interface (vnm, sw_if_index0);

          /* Send reply back through input interface */
          vnet_buffer (p0)->sw_if_index[VLIB_TX] = sw_if_index0;
          next0 = ARP_INPUT_NEXT_REPLY_TX;

          arp0->opcode = clib_host_to_net_u16 (ETHERNET_ARP_OPCODE_reply);

          arp0->ip4_over_ethernet[1] = arp0->ip4_over_ethernet[0];

          clib_memcpy (arp0->ip4_over_ethernet[0].ethernet, hw_if0->hw_address, 6);
          clib_mem_unaligned (&arp0->ip4_over_ethernet[0].ip4.data_u32, u32) = if_addr0->data_u32;

          /* Hardware must be ethernet-like. */
          ASSERT (vec_len (hw_if0->hw_address) == 6);

          clib_memcpy (eth0->dst_address, eth0->src_address, 6);
          clib_memcpy (eth0->src_address, hw_if0->hw_address, 6);

          /* Figure out how much to rewind current data from adjacency. */
          if (ifa0)
            {
              adj0 = ip_get_adjacency (&ip4_main.lookup_main, 
                                       ifa0->neighbor_probe_adj_index);
              if (adj0->lookup_next_index != IP_LOOKUP_NEXT_ARP)
                {
                  error0 = ETHERNET_ARP_ERROR_missing_interface_address;
                  goto drop2;
                }
              if (is_unnum0)
                arp_unnumbered (p0, pi0, eth0, ifa0);
              else
                vlib_buffer_advance (p0, -adj0->rewrite_header.data_bytes);
            }

          vlib_validate_buffer_enqueue_x1 (vm, node, next_index,to_next,
                                           n_left_to_next,pi0,next0);

          n_replies_sent += 1;
          continue;

        drop1:
          if (0 == arp0->ip4_over_ethernet[0].ip4.as_u32 ||
              (arp0->ip4_over_ethernet[0].ip4.as_u32 ==
               arp0->ip4_over_ethernet[1].ip4.as_u32))
            {
              error0 = ETHERNET_ARP_ERROR_gratuitous_arp;
              goto drop2;
            }
          /* See if proxy arp is configured for the address */
          if (is_request0) 
            {
              vnet_sw_interface_t * si;
              u32 this_addr = clib_net_to_host_u32 
                (arp0->ip4_over_ethernet[1].ip4.as_u32);
              u32 fib_index0;

              si = vnet_get_sw_interface (vnm, sw_if_index0);
              
              if (!(si->flags & VNET_SW_INTERFACE_FLAG_PROXY_ARP))
                goto drop2;

              fib_index0 = vec_elt (im4->fib_index_by_sw_if_index, 
                                    sw_if_index0);

              vec_foreach (pa, am->proxy_arps)
                {
                  u32 lo_addr = clib_net_to_host_u32 (pa->lo_addr);
                  u32 hi_addr = clib_net_to_host_u32 (pa->hi_addr);

                   /* an ARP request hit in the proxy-arp table? */
                   if ((this_addr >= lo_addr && this_addr <= hi_addr) &&
                       (fib_index0 == pa->fib_index))
                    {
                      eth0 = ethernet_buffer_get_header (p0);
                      proxy_src.as_u32 = 
                        arp0->ip4_over_ethernet[1].ip4.data_u32;

                      /* 
                       * Rewind buffer, direct code above not to
                       * think too hard about it. 
                       * $$$ is the answer ever anything other than
                       * vlib_buffer_reset(..)?
                       */
                      ifa0 = 0;
                      if_addr0 = &proxy_src;
                      vlib_buffer_reset (p0);
                      n_proxy_arp_replies_sent++;
                      goto send_reply;
                    }
                }
            }
          
        drop2:

          next0 = ARP_INPUT_NEXT_DROP;
          p0->error = node->errors[error0];

          vlib_validate_buffer_enqueue_x1 (vm, node, next_index,to_next,
                                           n_left_to_next,pi0,next0);
        }

      vlib_put_next_frame (vm, node, next_index, n_left_to_next);
    }

  vlib_error_count (vm, node->node_index,
                    ETHERNET_ARP_ERROR_replies_sent, 
                    n_replies_sent - n_proxy_arp_replies_sent);
  
  vlib_error_count (vm, node->node_index,
                    ETHERNET_ARP_ERROR_proxy_arp_replies_sent, 
                    n_proxy_arp_replies_sent);
  return frame->n_vectors;
}

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

VLIB_REGISTER_NODE (arp_input_node,static) = {
  .function = arp_input,
  .name = "arp-input",
  .vector_size = sizeof (u32),

  .n_errors = ETHERNET_ARP_N_ERROR,
  .error_strings = ethernet_arp_error_strings,

  .n_next_nodes = ARP_INPUT_N_NEXT,
  .next_nodes = {
    [ARP_INPUT_NEXT_DROP] = "error-drop",
    [ARP_INPUT_NEXT_REPLY_TX] = "interface-output",
  },

  .format_buffer = format_ethernet_arp_header,
  .format_trace = format_ethernet_arp_input_trace,
};

static int
ip4_arp_entry_sort (void *a1, void *a2)
{
  ethernet_arp_ip4_entry_t * e1 = a1;
  ethernet_arp_ip4_entry_t * e2 = a2;

  int cmp;
  vnet_main_t * vnm = vnet_get_main();

  cmp = vnet_sw_interface_compare 
    (vnm, e1->key.sw_if_index, e2->key.sw_if_index);
  if (! cmp)
    cmp = ip4_address_compare (&e1->key.ip4_address, &e2->key.ip4_address);
  return cmp;
}

static clib_error_t *
show_ip4_arp (vlib_main_t * vm,
              unformat_input_t * input,
              vlib_cli_command_t * cmd)
{
  vnet_main_t * vnm = vnet_get_main();
  ethernet_arp_main_t * am = &ethernet_arp_main;
  ethernet_arp_ip4_entry_t * e, * es;
  ethernet_proxy_arp_t * pa;
  clib_error_t * error = 0;
  u32 sw_if_index;

  /* Filter entries by interface if given. */
  sw_if_index = ~0;
  (void) unformat_user (input, unformat_vnet_sw_interface, vnm, &sw_if_index);

  es = 0;
  pool_foreach (e, am->ip4_entry_pool, ({ vec_add1 (es, e[0]); }));
  if ( es )
    {
      vec_sort_with_function (es, ip4_arp_entry_sort);
      vlib_cli_output (vm, "%U", format_ethernet_arp_ip4_entry, vnm, 0);
      vec_foreach (e, es) {
        if (sw_if_index != ~0 && e->key.sw_if_index != sw_if_index)
          continue;
        vlib_cli_output (vm, "%U", format_ethernet_arp_ip4_entry, vnm, e);
      }
      vec_free (es);
    }

  if (vec_len (am->proxy_arps))
    {
      vlib_cli_output (vm, "Proxy arps enabled for:");
      vec_foreach(pa, am->proxy_arps)
        {
          vlib_cli_output (vm, "Fib_index %d   %U - %U ", 
                           pa->fib_index,
                           format_ip4_address, &pa->lo_addr, 
                           format_ip4_address, &pa->hi_addr);
        }
    }
      
  return error;
}

VLIB_CLI_COMMAND (show_ip4_arp_command, static) = {
  .path = "show ip arp",
  .function = show_ip4_arp,
  .short_help = "Show ARP table",
};

typedef struct {
  pg_edit_t l2_type, l3_type;
  pg_edit_t n_l2_address_bytes, n_l3_address_bytes;
  pg_edit_t opcode;
  struct {
    pg_edit_t ethernet;
    pg_edit_t ip4;
  } ip4_over_ethernet[2];
} pg_ethernet_arp_header_t;

static inline void
pg_ethernet_arp_header_init (pg_ethernet_arp_header_t * p)
{
  /* Initialize fields that are not bit fields in the IP header. */
#define _(f) pg_edit_init (&p->f, ethernet_arp_header_t, f);
  _ (l2_type);
  _ (l3_type);
  _ (n_l2_address_bytes);
  _ (n_l3_address_bytes);
  _ (opcode);
  _ (ip4_over_ethernet[0].ethernet);
  _ (ip4_over_ethernet[0].ip4);
  _ (ip4_over_ethernet[1].ethernet);
  _ (ip4_over_ethernet[1].ip4);
#undef _
}

uword
unformat_pg_arp_header (unformat_input_t * input, va_list * args)
{
  pg_stream_t * s = va_arg (*args, pg_stream_t *);
  pg_ethernet_arp_header_t * p;
  u32 group_index;
  
  p = pg_create_edit_group (s, sizeof (p[0]), sizeof (ethernet_arp_header_t),
                            &group_index);
  pg_ethernet_arp_header_init (p);

  /* Defaults. */
  pg_edit_set_fixed (&p->l2_type, ETHERNET_ARP_HARDWARE_TYPE_ethernet);
  pg_edit_set_fixed (&p->l3_type, ETHERNET_TYPE_IP4);
  pg_edit_set_fixed (&p->n_l2_address_bytes, 6);
  pg_edit_set_fixed (&p->n_l3_address_bytes, 4);

  if (! unformat (input, "%U: %U/%U -> %U/%U",
                  unformat_pg_edit,
                  unformat_ethernet_arp_opcode_net_byte_order, &p->opcode,
                  unformat_pg_edit,
                  unformat_ethernet_address, &p->ip4_over_ethernet[0].ethernet,
                  unformat_pg_edit,
                  unformat_ip4_address, &p->ip4_over_ethernet[0].ip4,
                  unformat_pg_edit,
                  unformat_ethernet_address, &p->ip4_over_ethernet[1].ethernet,
                  unformat_pg_edit,
                  unformat_ip4_address, &p->ip4_over_ethernet[1].ip4))
    {
      /* Free up any edits we may have added. */
      pg_free_edit_group (s);
      return 0;
    }
  return 1;
}

clib_error_t *ip4_set_arp_limit (u32 arp_limit)
{
  ethernet_arp_main_t * am = &ethernet_arp_main;

  am->limit_arp_cache_size = arp_limit;
  return 0;
}

static void
arp_ip4_entry_del_adj(ethernet_arp_ip4_entry_t *e, u32 adj_index)
{
  int done = 0;
  int i;

  while (!done)
    {
      vec_foreach_index(i, e->adjacencies)
        if (vec_elt(e->adjacencies, i) == adj_index)
          {
            vec_del1(e->adjacencies, i);
            continue;
          }
      done = 1;
    }
}

static void
arp_ip4_entry_add_adj(ethernet_arp_ip4_entry_t *e, u32 adj_index)
{
  int i;
  vec_foreach_index(i, e->adjacencies)
    if (vec_elt(e->adjacencies, i) == adj_index)
      return;
  vec_add1(e->adjacencies, adj_index);
}

static void
arp_add_del_adj_cb (struct ip_lookup_main_t * lm,
                    u32 adj_index,
                    ip_adjacency_t * adj,
                    u32 is_del)
{
  ethernet_arp_main_t * am = &ethernet_arp_main;
  ip4_main_t * im = &ip4_main;
  ethernet_arp_ip4_key_t k;
  ethernet_arp_ip4_entry_t * e = 0;
  uword * p;
  u32 ai;

  for(ai = adj->heap_handle; ai < adj->heap_handle + adj->n_adj ; ai++)
    {
      adj = ip_get_adjacency (lm, ai);
      if (adj->lookup_next_index == IP_LOOKUP_NEXT_ARP && adj->arp.next_hop.ip4.as_u32)
        {
          k.sw_if_index = adj->rewrite_header.sw_if_index;
          k.ip4_address.as_u32 = adj->arp.next_hop.ip4.as_u32;
          k.fib_index = im->fib_index_by_sw_if_index[adj->rewrite_header.sw_if_index];
          p = mhash_get (&am->ip4_entry_by_key, &k);
          if (p)
            e = pool_elt_at_index (am->ip4_entry_pool, p[0]);
        }
      else
        continue;

      if (is_del)
        {
          if (!e)
            clib_warning("Adjacency contains unknown ARP next hop %U (del)",
                         format_ip46_address, &adj->arp.next_hop);
          else
            arp_ip4_entry_del_adj(e, adj->heap_handle);
        }
      else /* add */
        {
          if (!e)
            clib_warning("Adjacency contains unknown ARP next hop %U (add)",
                         format_ip46_address, &adj->arp.next_hop);
          else
            arp_ip4_entry_add_adj(e, adj->heap_handle);
        }
    }
}

static clib_error_t * ethernet_arp_init (vlib_main_t * vm)
{
  ethernet_arp_main_t * am = &ethernet_arp_main;
  pg_node_t * pn;
  clib_error_t * error;
  ip4_main_t * im = &ip4_main;
  ip_lookup_main_t * lm = &im->lookup_main;

  if ((error = vlib_call_init_function (vm, ethernet_init)))
    return error;

  ethernet_register_input_type (vm, ETHERNET_TYPE_ARP, arp_input_node.index);

  pn = pg_get_node (arp_input_node.index);
  pn->unformat_edit = unformat_pg_arp_header;

  am->opcode_by_name = hash_create_string (0, sizeof (uword));
#define _(o) hash_set_mem (am->opcode_by_name, #o, ETHERNET_ARP_OPCODE_##o);
  foreach_ethernet_arp_opcode;
#undef _

  mhash_init (&am->ip4_entry_by_key,
              /* value size */ sizeof (uword),
              /* key size */ sizeof (ethernet_arp_ip4_key_t));

  /* $$$ configurable */
  am->limit_arp_cache_size = 50000;

  am->pending_resolutions_by_address = hash_create (0, sizeof (uword));
  am->mac_changes_by_address = hash_create (0, sizeof (uword));

  /* don't trace ARP error packets */
  {
    vlib_node_runtime_t *rt = 
      vlib_node_get_runtime (vm, arp_input_node.index);

#define _(a,b)                                  \
    vnet_pcap_drop_trace_filter_add_del         \
        (rt->errors[ETHERNET_ARP_ERROR_##a],    \
         1 /* is_add */);
    foreach_ethernet_arp_error
#undef _
  }

  ip_register_add_del_adjacency_callback(lm, arp_add_del_adj_cb);

  return 0;
}

VLIB_INIT_FUNCTION (ethernet_arp_init);

int 
vnet_arp_unset_ip4_over_ethernet (vnet_main_t * vnm,
                                  u32 sw_if_index, u32 fib_index,
                                  void * a_arg)
{
  ethernet_arp_ip4_over_ethernet_address_t * a = a_arg;
  vnet_arp_set_ip4_over_ethernet_rpc_args_t args;

  args.sw_if_index = sw_if_index;
  args.fib_index = fib_index;
  args.is_remove = 1;
  clib_memcpy (&args.a, a, sizeof (*a));

  vl_api_rpc_call_main_thread (set_ip4_over_ethernet_rpc_callback, 
                               (u8 *) &args, sizeof (args));
  return 0;
}

static inline int 
vnet_arp_unset_ip4_over_ethernet_internal (vnet_main_t * vnm,
                                           u32 sw_if_index, 
                                           u32 fib_index,
                                           void * a_arg)
{
  ethernet_arp_ip4_entry_t * e;
  ethernet_arp_main_t * am = &ethernet_arp_main;
  ethernet_arp_ip4_over_ethernet_address_t * a = a_arg;
  ethernet_arp_ip4_key_t k;
  uword * p;
  ip4_add_del_route_args_t args;
  ip4_main_t * im = &ip4_main;
  ip_lookup_main_t * lm = &im->lookup_main;
  u32 adj_index;
  ip_adjacency_t * adj;

  k.sw_if_index = sw_if_index;
  k.ip4_address = a->ip4;
  k.fib_index = fib_index;
  p = mhash_get (&am->ip4_entry_by_key, &k);
  if (! p)
    return -1;

  memset(&args, 0, sizeof(args));

  /* 
   * Make sure that the route actually exists before we try to delete it,
   * and make sure that it's a rewrite adjacency.
   *
   * If we point 1-N unnumbered interfaces at a loopback interface and 
   * shut down the loopback before shutting down 1-N unnumbered 
   * interfaces, the ARP cache will still have an entry, 
   * but the route will have disappeared.
   * 
   * See also ip4_del_interface_routes (...) 
   *            -> ip4_delete_matching_routes (...).
   */
  
  adj_index = ip4_fib_lookup_with_table 
      (im, fib_index, &a->ip4, 1 /* disable default route */);

  /* Miss adj? Forget it... */
  if (adj_index != lm->miss_adj_index) {
      adj = ip_get_adjacency (lm, adj_index);
      /* 
       * Stupid control-plane trick:
       * admin down an interface (removes arp routes from fib),
       * bring the interface back up (does not reinstall them)
       * then remove the arp cache entry (yuck). When that happens,
       * the adj we find here will be the interface subnet ARP adj.
       */
      if (adj->lookup_next_index == IP_LOOKUP_NEXT_REWRITE) {
          args.table_index_or_table_id = fib_index;
          args.flags = IP4_ROUTE_FLAG_FIB_INDEX | IP4_ROUTE_FLAG_DEL 
              | IP4_ROUTE_FLAG_NEIGHBOR;
          args.dst_address = a->ip4;
          args.dst_address_length = 32;
          ip4_add_del_route (im, &args);
          ip4_maybe_remap_adjacencies (im, fib_index, args.flags);
      }
  }

  e = pool_elt_at_index (am->ip4_entry_pool, p[0]);
  mhash_unset (&am->ip4_entry_by_key, &e->key, 0);
  pool_put (am->ip4_entry_pool, e);
  return 0;
}

static void 
increment_ip4_and_mac_address (ethernet_arp_ip4_over_ethernet_address_t *a)
{
  u8 old;
  int i;

  for (i = 3; i >= 0; i--) 
    {
      old = a->ip4.as_u8[i];
      a->ip4.as_u8[i] += 1;
      if (old < a->ip4.as_u8[i])
        break;
    }

  for (i = 5; i >= 0; i--)
    {
      old = a->ethernet[i];
      a->ethernet[i] += 1;
      if (old < a->ethernet[i])
        break;
    }
}

int vnet_proxy_arp_add_del (ip4_address_t *lo_addr,
                            ip4_address_t *hi_addr,
                            u32 fib_index, int is_del)
{
  ethernet_arp_main_t *am = &ethernet_arp_main;
  ethernet_proxy_arp_t *pa;
  u32 found_at_index = ~0;

  vec_foreach (pa, am->proxy_arps)
    {
      if (pa->lo_addr == lo_addr->as_u32 
          && pa->hi_addr == hi_addr->as_u32
          && pa->fib_index == fib_index)
        {
          found_at_index = pa - am->proxy_arps;
          break;
        }
    }

  if (found_at_index != ~0)
    {
      /* Delete, otherwise it's already in the table */
      if (is_del)
        vec_delete (am->proxy_arps, 1, found_at_index);
      return 0;
    }
  /* delete, no such entry */
  if (is_del)
    return VNET_API_ERROR_NO_SUCH_ENTRY;

  /* add, not in table */
  vec_add2 (am->proxy_arps, pa, 1);
  pa->lo_addr = lo_addr->as_u32;
  pa->hi_addr = hi_addr->as_u32;
  pa->fib_index = fib_index;
  return 0;
}

/*
 * Remove any proxy arp entries asdociated with the 
 * specificed fib.
 */
int vnet_proxy_arp_fib_reset (u32 fib_id)
{
  ip4_main_t * im = &ip4_main;
  ethernet_arp_main_t *am = &ethernet_arp_main;
  ethernet_proxy_arp_t *pa;
  u32 * entries_to_delete = 0;
  u32 fib_index;
  uword * p;
  int i;

  p = hash_get (im->fib_index_by_table_id, fib_id);
  if (! p)
      return VNET_API_ERROR_NO_SUCH_ENTRY;
  fib_index = p[0];

  vec_foreach (pa, am->proxy_arps)
    {
      if (pa->fib_index == fib_index)
        {
          vec_add1 (entries_to_delete, pa - am->proxy_arps);
        }
    }

  for (i = 0; i < vec_len(entries_to_delete); i++)
    {
       vec_delete (am->proxy_arps, 1, entries_to_delete[i]);
    } 

  vec_free (entries_to_delete);

   return 0;
}

u32
vnet_arp_glean_add(u32 fib_index, void * next_hop_arg)
{
  ethernet_arp_main_t * am = &ethernet_arp_main;
  ip4_main_t * im = &ip4_main;
  ip_lookup_main_t * lm = &im->lookup_main;
  ip4_address_t * next_hop = next_hop_arg;
  ip_adjacency_t add_adj, *adj;
  ip4_add_del_route_args_t args;
  ethernet_arp_ip4_entry_t * e;
  ethernet_arp_ip4_key_t k;
  u32 adj_index;

  adj_index = ip4_fib_lookup_with_table(im, fib_index, next_hop, 0);
  adj = ip_get_adjacency(lm, adj_index);

  if (!adj || adj->lookup_next_index != IP_LOOKUP_NEXT_ARP)
    return ~0;

  if (adj->arp.next_hop.ip4.as_u32 != 0)
    return adj_index;

  k.sw_if_index = adj->rewrite_header.sw_if_index;
  k.fib_index = fib_index;
  k.ip4_address.as_u32 = next_hop->as_u32;

  if (mhash_get (&am->ip4_entry_by_key, &k))
    return adj_index;

  pool_get (am->ip4_entry_pool, e);
  mhash_set (&am->ip4_entry_by_key, &k, e - am->ip4_entry_pool, /* old value */ 0);
  e->key = k;
  e->cpu_time_last_updated = clib_cpu_time_now ();
  e->flags = ETHERNET_ARP_IP4_ENTRY_FLAG_GLEAN;

  memset(&args, 0, sizeof(args));
  clib_memcpy(&add_adj, adj, sizeof(add_adj));
  ip46_address_set_ip4(&add_adj.arp.next_hop, next_hop); /* install neighbor /32 route */
  args.table_index_or_table_id = fib_index;
  args.flags = IP4_ROUTE_FLAG_FIB_INDEX | IP4_ROUTE_FLAG_ADD| IP4_ROUTE_FLAG_NEIGHBOR;
  args.dst_address.as_u32 = next_hop->as_u32;
  args.dst_address_length = 32;
  args.adj_index = ~0;
  args.add_adj = &add_adj;
  args.n_add_adj = 1;
  ip4_add_del_route (im, &args);
  return ip4_fib_lookup_with_table (im, fib_index, next_hop, 0);
}

static clib_error_t *
ip_arp_add_del_command_fn (vlib_main_t * vm,
                 unformat_input_t * input,
                 vlib_cli_command_t * cmd)
{
  vnet_main_t * vnm = vnet_get_main();
  u32 sw_if_index;
  ethernet_arp_ip4_over_ethernet_address_t lo_addr, hi_addr, addr;
  int addr_valid = 0;
  int is_del = 0;
  int count = 1;
  u32 fib_index = 0;
  u32 fib_id;
  int is_static = 0;
  int is_proxy = 0;

  while (unformat_check_input (input) != UNFORMAT_END_OF_INPUT) 
    {
      /* set ip arp TenGigE1/1/0/1 1.2.3.4 aa:bb:... or aabb.ccdd... */
      if (unformat (input, "%U %U %U",
                    unformat_vnet_sw_interface, vnm, &sw_if_index,
                    unformat_ip4_address, &addr.ip4, 
                    unformat_ethernet_address, &addr.ethernet))
        addr_valid = 1;

      else if (unformat (input, "delete") || unformat (input, "del"))
        is_del = 1;

      else if (unformat (input, "static"))
        is_static = 1;

      else if (unformat (input, "count %d", &count))
        ;

      else if (unformat (input, "fib-id %d", &fib_id))
        {
          ip4_main_t * im = &ip4_main;
          uword * p = hash_get (im->fib_index_by_table_id, fib_id);
          if (! p)
            return clib_error_return (0, "fib ID %d doesn't exist\n",
                                      fib_id);
          fib_index = p[0];
        }

      else if (unformat (input, "proxy %U - %U", 
                         unformat_ip4_address, &lo_addr.ip4, 
                         unformat_ip4_address, &hi_addr.ip4))
        is_proxy = 1;
      else
        break;
    }
  
  if (is_proxy)
    {
      (void) vnet_proxy_arp_add_del (&lo_addr.ip4, &hi_addr.ip4, 
                                     fib_index, is_del);
      return 0;
    }

  if (addr_valid) 
    {
      int i;

      for (i = 0; i < count; i++) 
        {
          if (is_del == 0) 
            {
              uword event_type, * event_data = 0;

              /* Park the debug CLI until the arp entry is installed */
              vnet_register_ip4_arp_resolution_event 
                (vnm, &addr.ip4, vlib_current_process(vm),
                 1 /* type */, 0 /* data */);
              
              vnet_arp_set_ip4_over_ethernet
                (vnm, sw_if_index, fib_index, &addr, is_static);
              
              vlib_process_wait_for_event (vm);
              event_type = vlib_process_get_events (vm, &event_data);
              vec_reset_length(event_data);
              if (event_type != 1)
                clib_warning ("event type %d unexpected", event_type);
            }
          else
            vnet_arp_unset_ip4_over_ethernet
                (vnm, sw_if_index, fib_index, &addr);

          increment_ip4_and_mac_address (&addr);
        }
    }
  else
    {
      return clib_error_return (0, "unknown input `%U'",
                                format_unformat_error, input);
    }
  
  return 0;
}

VLIB_CLI_COMMAND (ip_arp_add_del_command, static) = {
    .path = "set ip arp",
    .short_help = "set ip arp [del] <intfc> <ip-address> <mac-address> [static] [count <count>] [fib-id <fib-id>] [proxy <lo-addr> - <hi-addr>]",
    .function = ip_arp_add_del_command_fn,
};

static clib_error_t *
set_int_proxy_arp_command_fn (vlib_main_t * vm,
                              unformat_input_t * input,
                              vlib_cli_command_t * cmd)
{
  vnet_main_t * vnm = vnet_get_main();
  u32 sw_if_index;
  vnet_sw_interface_t * si;
  int enable = 0;
  int intfc_set = 0;

  while (unformat_check_input (input) != UNFORMAT_END_OF_INPUT) 
    {
      if (unformat (input, "%U", unformat_vnet_sw_interface, 
                    vnm, &sw_if_index))
        intfc_set = 1;
      else if (unformat (input, "enable") || unformat (input, "on"))
        enable = 1;
      else if (unformat (input, "disable") || unformat (input, "off"))
        enable = 0;
      else
        break;
    }

  if (intfc_set == 0)
    return clib_error_return (0, "unknown input '%U'",
                              format_unformat_error, input);

  si = vnet_get_sw_interface (vnm, sw_if_index);
  ASSERT(si);
  if (enable)
    si->flags |= VNET_SW_INTERFACE_FLAG_PROXY_ARP;
  else 
    si->flags &= ~VNET_SW_INTERFACE_FLAG_PROXY_ARP;
  
  return 0;
}

VLIB_CLI_COMMAND (set_int_proxy_enable_command, static) = {
    .path = "set interface proxy-arp",
    .short_help = "set interface proxy-arp <intfc> [enable|disable]",
    .function = set_int_proxy_arp_command_fn,
};


/*
 * ARP Termination in a L2 Bridge Domain based on an
 * IP4 to MAC hash table mac_by_ip4 for each BD.
 */
typedef enum {
  ARP_TERM_NEXT_L2_OUTPUT,
  ARP_TERM_NEXT_DROP,
  ARP_TERM_N_NEXT,
} arp_term_next_t;

u32 arp_term_next_node_index[32];

static uword
arp_term_l2bd (vlib_main_t * vm,
               vlib_node_runtime_t * node,
               vlib_frame_t * frame)
{
  l2input_main_t * l2im = &l2input_main;
  u32 n_left_from, next_index, * from, * to_next;
  u32 n_replies_sent = 0;
  u16 last_bd_index = ~0;
  l2_bridge_domain_t * last_bd_config = 0;
  l2_input_config_t * cfg0;

  from = vlib_frame_vector_args (frame);
  n_left_from = frame->n_vectors;
  next_index = node->cached_next_index;

  while (n_left_from > 0)
    {
      u32 n_left_to_next;

      vlib_get_next_frame (vm, node, next_index,
                           to_next, n_left_to_next);

      while (n_left_from > 0 && n_left_to_next > 0)
        {
          vlib_buffer_t * p0;
          ethernet_header_t * eth0;
          ethernet_arp_header_t * arp0;
          u8 * l3h0;
          u32 pi0, error0, next0, sw_if_index0;
          u16 ethertype0;
          u16 bd_index0;
          u32 ip0;
          u8 * macp0;

          pi0 = from[0];
          to_next[0] = pi0;
          from += 1;
          to_next += 1;
          n_left_from -= 1;
          n_left_to_next -= 1;

          p0 = vlib_get_buffer (vm, pi0);
          eth0 = vlib_buffer_get_current (p0);
          l3h0 = (u8 *)eth0 + vnet_buffer(p0)->l2.l2_len;
          ethertype0 = clib_net_to_host_u16(*(u16 *)(l3h0 - 2));
          arp0 = (ethernet_arp_header_t *) l3h0;

          if (PREDICT_FALSE ((node->flags & VLIB_NODE_FLAG_TRACE) &&
                             (p0->flags & VLIB_BUFFER_IS_TRACED)))
            {
              u8 *t0 = vlib_add_trace (
                  vm, node, p0, sizeof(ethernet_arp_input_trace_t));
              clib_memcpy (t0, l3h0, sizeof(ethernet_arp_input_trace_t));
            }

          if (PREDICT_FALSE  (
            (ethertype0 != ETHERNET_TYPE_ARP) ||
            (arp0->opcode != clib_host_to_net_u16(ETHERNET_ARP_OPCODE_request))))
            goto next_l2_feature;

          error0 = ETHERNET_ARP_ERROR_replies_sent;
          error0 = (arp0->l2_type != clib_net_to_host_u16 (ETHERNET_ARP_HARDWARE_TYPE_ethernet)
                    ? ETHERNET_ARP_ERROR_l2_type_not_ethernet
                    : error0);
          error0 = (arp0->l3_type != clib_net_to_host_u16 (ETHERNET_TYPE_IP4)
                    ? ETHERNET_ARP_ERROR_l3_type_not_ip4
                    : error0);

          sw_if_index0 = vnet_buffer (p0)->sw_if_index[VLIB_RX];

          if (error0)
            goto drop;

          // Trash ARP packets whose ARP-level source addresses do not
          // match their L2-frame-level source addresses */
          if (PREDICT_FALSE (
            memcmp (eth0->src_address, arp0->ip4_over_ethernet[0].ethernet,
                    sizeof (eth0->src_address))))
            {
              error0 = ETHERNET_ARP_ERROR_l2_address_mismatch;
              goto drop;
            }

          // Check if anyone want ARP request events for L2 BDs
          {
          pending_resolution_t * mc;
          ethernet_arp_main_t * am = &ethernet_arp_main;
          uword *p = hash_get (am->mac_changes_by_address, 0);
          if (p && (vnet_buffer(p0)->l2.shg == 0))
            { // Only SHG 0 interface which is more likely local
              u32 next_index = p[0];
              while (next_index != (u32)~0)
                {
                  int (*fp)(u32, u8 *, u32, u32);
                  int rv = 1;
                  mc = pool_elt_at_index (am->mac_changes, next_index);
                  fp = mc->data_callback;
                  // Call the callback, return 1 to suppress dup events */
                  if (fp) rv = (*fp)(mc->data, 
                                     arp0->ip4_over_ethernet[0].ethernet, 
                                     sw_if_index0, 
                                     arp0->ip4_over_ethernet[0].ip4.as_u32);
                  // Signal the resolver process
                  if (rv == 0)
                    vlib_process_signal_event (vm, mc->node_index,
                                               mc->type_opaque, 
                                               mc->data);
                  next_index = mc->next_index;
                }
            }
          }

          // lookup BD mac_by_ip4 hash table for MAC entry
          ip0 = arp0->ip4_over_ethernet[1].ip4.as_u32;
          bd_index0 = vnet_buffer(p0)->l2.bd_index;
          if (PREDICT_FALSE (
            (bd_index0 != last_bd_index) || (last_bd_index == (u16) ~0)))
            {
              last_bd_index = bd_index0;
              last_bd_config = vec_elt_at_index(l2im->bd_configs, bd_index0);
            }
          macp0 = (u8 *) hash_get (last_bd_config->mac_by_ip4, ip0);

          if (PREDICT_FALSE(!macp0)) 
              goto next_l2_feature;     // MAC not found 

          // MAC found, send ARP reply -
          // Convert ARP request packet to ARP reply
          arp0->opcode = clib_host_to_net_u16 (ETHERNET_ARP_OPCODE_reply);
          arp0->ip4_over_ethernet[1] = arp0->ip4_over_ethernet[0];
          arp0->ip4_over_ethernet[0].ip4.as_u32 = ip0;
          clib_memcpy (arp0->ip4_over_ethernet[0].ethernet, macp0, 6);
          clib_memcpy (eth0->dst_address, eth0->src_address, 6);
          clib_memcpy (eth0->src_address, macp0, 6);
          n_replies_sent += 1;

          // For BVI, need to use l2-fwd node to send ARP reply as 
          // l2-output node cannot output packet to BVI properly
          cfg0 = vec_elt_at_index(l2im->configs, sw_if_index0);
          if (PREDICT_FALSE (cfg0->bvi))
            {
              vnet_buffer(p0)->l2.feature_bitmap |= L2INPUT_FEAT_FWD;
              vnet_buffer (p0)->sw_if_index[VLIB_RX] = 0;
              goto next_l2_feature;
            }

          // Send ARP reply back out input interface through l2-output
          vnet_buffer (p0)->sw_if_index[VLIB_TX] = sw_if_index0;
          next0 = ARP_TERM_NEXT_L2_OUTPUT;
          // Note that output to VXLAN tunnel will fail due to SHG which
          // is probably desireable since ARP termination is not intended
          // for ARP requests from other hosts. If output to VXLAN tunnel is
          // required, however, can just clear the SHG in packet as follows:
          //   vnet_buffer(p0)->l2.shg = 0;

          vlib_validate_buffer_enqueue_x1 (vm, node, next_index,to_next,
                                           n_left_to_next,pi0,next0);
          continue;

        next_l2_feature:
          {
            u32 feature_bitmap0 =
                vnet_buffer(p0)->l2.feature_bitmap & ~L2INPUT_FEAT_ARP_TERM;
            vnet_buffer(p0)->l2.feature_bitmap = feature_bitmap0;
            next0 = feat_bitmap_get_next_node_index(arp_term_next_node_index,
                                                    feature_bitmap0);
            vlib_validate_buffer_enqueue_x1 (vm, node, next_index,to_next,
                                             n_left_to_next,pi0,next0);
            continue;
          }

        drop:
          if (0 == arp0->ip4_over_ethernet[0].ip4.as_u32 ||
              (arp0->ip4_over_ethernet[0].ip4.as_u32 ==
               arp0->ip4_over_ethernet[1].ip4.as_u32))
            {
              error0 = ETHERNET_ARP_ERROR_gratuitous_arp;
            }
          next0 = ARP_TERM_NEXT_DROP;
          p0->error = node->errors[error0];

          vlib_validate_buffer_enqueue_x1 (vm, node, next_index,to_next,
                                           n_left_to_next,pi0,next0);
        }

      vlib_put_next_frame (vm, node, next_index, n_left_to_next);
    }

  vlib_error_count (vm, node->node_index,
                    ETHERNET_ARP_ERROR_replies_sent, 
                    n_replies_sent);
  return frame->n_vectors;
}

VLIB_REGISTER_NODE (arp_term_l2bd_node,static) = {
  .function = arp_term_l2bd,
  .name = "arp-term-l2bd",
  .vector_size = sizeof (u32),

  .n_errors = ETHERNET_ARP_N_ERROR,
  .error_strings = ethernet_arp_error_strings,

  .n_next_nodes = ARP_TERM_N_NEXT,
  .next_nodes = {
    [ARP_TERM_NEXT_L2_OUTPUT] = "l2-output",
    [ARP_TERM_NEXT_DROP] = "error-drop",
  },

  .format_buffer = format_ethernet_arp_header,
  .format_trace = format_ethernet_arp_input_trace,
};

clib_error_t *arp_term_init (vlib_main_t *vm)
{ // Initialize the feature next-node indexes 
  feat_bitmap_init_next_nodes(vm,
                              arp_term_l2bd_node.index,
                              L2INPUT_N_FEAT,
                              l2input_get_feat_names(),
                              arp_term_next_node_index);
  return 0;
}

VLIB_INIT_FUNCTION (arp_term_init);