node.c

Go to the documentation of this file.

/*
 * node.c: gre packet processing
 *
 * Copyright (c) 2012 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/pg/pg.h>
#include <vnet/gre/gre.h>
#include <vnet/mpls/mpls.h>
#include <vppinfra/sparse_vec.h>

#define foreach_gre_input_next                  \
_(PUNT, "error-punt")                           \
_(DROP, "error-drop")                           \
_(ETHERNET_INPUT, "ethernet-input")             \
_(IP4_INPUT, "ip4-input")                       \
_(IP6_INPUT, "ip6-input")                       \
_(MPLS_INPUT, "mpls-input")

typedef enum {
#define _(s,n) GRE_INPUT_NEXT_##s,
  foreach_gre_input_next
#undef _
  GRE_INPUT_N_NEXT,
} gre_input_next_t;

typedef struct {
  u32 tunnel_id;
  u32 length;
  ip46_address_t src;
  ip46_address_t dst;
  u8 is_ipv6;
} gre_rx_trace_t;

u8 * format_gre_rx_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 *);
  gre_rx_trace_t * t = va_arg (*args, gre_rx_trace_t *);

  s = format (s, "GRE: tunnel %d len %d src %U dst %U",
              t->tunnel_id, clib_net_to_host_u16(t->length),
              format_ip46_address, &t->src, IP46_TYPE_ANY,
              format_ip46_address, &t->dst, IP46_TYPE_ANY);
  return s;
}

typedef struct {
  /* Sparse vector mapping gre protocol in network byte order
     to next index. */
  u16 * next_by_protocol;
} gre_input_runtime_t;

always_inline uword
gre_input (vlib_main_t * vm,
           vlib_node_runtime_t * node,
           vlib_frame_t * from_frame,
           u8 is_ipv6)
{
  gre_main_t * gm = &gre_main;
  __attribute__((unused)) u32 n_left_from, next_index, * from, * to_next;
  u64 cached_tunnel_key4;
  u64 cached_tunnel_key6[4];
  u32 cached_tunnel_sw_if_index = 0, tunnel_sw_if_index = 0;

  u32 thread_index = vlib_get_thread_index();
  u32 len;
  vnet_interface_main_t *im = &gm->vnet_main->interface_main;

  if (!is_ipv6)
      memset (&cached_tunnel_key4, 0xff, sizeof(cached_tunnel_key4));
  else
      memset (&cached_tunnel_key6, 0xff, sizeof(cached_tunnel_key6));

  from = vlib_frame_vector_args (from_frame);
  n_left_from = 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 >= 4 && n_left_to_next >= 2)
        {
          u32 bi0, bi1;
          vlib_buffer_t * b0, * b1;
          gre_header_t * h0, * h1;
          u16 version0, version1;
          int verr0, verr1;
          u32 i0, i1, next0, next1, protocol0, protocol1;
          ip4_header_t *ip4_0, *ip4_1;
          ip6_header_t *ip6_0, *ip6_1;
          u32 ip4_tun_src0, ip4_tun_dst0;
          u32 ip4_tun_src1, ip4_tun_dst1;
          u64 ip6_tun_src0[2], ip6_tun_dst0[2];
          u64 ip6_tun_src1[2], ip6_tun_dst1[2];

          /* 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, sizeof (h0[0]), LOAD);
            CLIB_PREFETCH (p3->data, sizeof (h1[0]), LOAD);
          }

          bi0 = from[0];
          bi1 = from[1];
          to_next[0] = bi0;
          to_next[1] = bi1;
          from += 2;
          to_next += 2;
          n_left_to_next -= 2;
          n_left_from -= 2;

          b0 = vlib_get_buffer (vm, bi0);
          b1 = vlib_get_buffer (vm, bi1);

          if (!is_ipv6)
            {
              /* ip4_local hands us the ip header, not the gre header */
              ip4_0 = vlib_buffer_get_current (b0);
              ip4_1 = vlib_buffer_get_current (b1);
              /* Save src + dst ip4 address, e.g. for mpls-o-gre */
              ip4_tun_src0 = ip4_0->src_address.as_u32;
              ip4_tun_dst0 = ip4_0->dst_address.as_u32;
              ip4_tun_src1 = ip4_1->src_address.as_u32;
              ip4_tun_dst1 = ip4_1->dst_address.as_u32;

              vlib_buffer_advance (b0, sizeof (*ip4_0));
              vlib_buffer_advance (b1, sizeof (*ip4_1));
            }
          else
            {
              /* ip6_local hands us the ip header, not the gre header */
              ip6_0 = vlib_buffer_get_current (b0);
              ip6_1 = vlib_buffer_get_current (b1);
              /* Save src + dst ip6 address, e.g. for mpls-o-gre */
              ip6_tun_src0[0] = ip6_0->src_address.as_u64[0];
              ip6_tun_src0[1] = ip6_0->src_address.as_u64[1];
              ip6_tun_dst0[0] = ip6_0->dst_address.as_u64[0];
              ip6_tun_dst0[1] = ip6_0->dst_address.as_u64[1];
              ip6_tun_src1[0] = ip6_1->src_address.as_u64[0];
              ip6_tun_src1[1] = ip6_1->src_address.as_u64[1];
              ip6_tun_dst1[0] = ip6_1->dst_address.as_u64[0];
              ip6_tun_dst1[1] = ip6_1->dst_address.as_u64[1];

              vlib_buffer_advance (b0, sizeof (*ip6_0));
              vlib_buffer_advance (b1, sizeof (*ip6_1));
            }

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

          /* Index sparse array with network byte order. */
          protocol0 = h0->protocol;
          protocol1 = h1->protocol;
          sparse_vec_index2 (gm->next_by_protocol, protocol0, protocol1,
                             &i0, &i1);
          next0 = vec_elt(gm->next_by_protocol, i0);
          next1 = vec_elt(gm->next_by_protocol, i1);

          b0->error = node->errors[i0 == SPARSE_VEC_INVALID_INDEX ? GRE_ERROR_UNKNOWN_PROTOCOL : GRE_ERROR_NONE];
          b1->error = node->errors[i1 == SPARSE_VEC_INVALID_INDEX ? GRE_ERROR_UNKNOWN_PROTOCOL : GRE_ERROR_NONE];
          
          version0 = clib_net_to_host_u16 (h0->flags_and_version);
          verr0 =  version0 & GRE_VERSION_MASK;
          version1 = clib_net_to_host_u16 (h1->flags_and_version);
          verr1 =  version1 & GRE_VERSION_MASK;

          b0->error = verr0 ? node->errors[GRE_ERROR_UNSUPPORTED_VERSION]
              : b0->error;
          next0 = verr0 ? GRE_INPUT_NEXT_DROP : next0;
          b1->error = verr1 ? node->errors[GRE_ERROR_UNSUPPORTED_VERSION]
              : b1->error;
          next1 = verr1 ? GRE_INPUT_NEXT_DROP : next1;


          /* RPF check for ip4/ip6 input */
          if (PREDICT_TRUE(next0 == GRE_INPUT_NEXT_IP4_INPUT
                           || next0 == GRE_INPUT_NEXT_IP6_INPUT
                           || next0 == GRE_INPUT_NEXT_ETHERNET_INPUT
                           || next0 == GRE_INPUT_NEXT_MPLS_INPUT))
            {

              u64 key4, key6[4];
              if (!is_ipv6)
                {
                  key4 = ((u64)(ip4_tun_dst0) << 32) | (u64)(ip4_tun_src0);
                }
              else
                {
                  key6[0] = ip6_tun_dst0[0];
                  key6[1] = ip6_tun_dst0[1];
                  key6[2] = ip6_tun_src0[0];
                  key6[3] = ip6_tun_src0[1];
                }

              if ((!is_ipv6 && cached_tunnel_key4 != key4) ||
                  (is_ipv6 && cached_tunnel_key6[0] != key6[0] &&
                      cached_tunnel_key6[1] != key6[1] &&
                      cached_tunnel_key6[2] != key6[2] &&
                      cached_tunnel_key6[3] != key6[3]))
                {
                  vnet_hw_interface_t * hi;
                  gre_tunnel_t * t;
                  uword * p;

                  if (!is_ipv6)
                    p = hash_get (gm->tunnel_by_key4, key4);
                  else
                    p = hash_get_mem (gm->tunnel_by_key6, key6);
                  if (!p)
                    {
                      next0 = GRE_INPUT_NEXT_DROP;
                      b0->error = node->errors[GRE_ERROR_NO_SUCH_TUNNEL];
                      goto drop0;
                    }
                  t = pool_elt_at_index (gm->tunnels, p[0]);
                  hi = vnet_get_hw_interface (gm->vnet_main,
                            t->hw_if_index);
                  tunnel_sw_if_index = hi->sw_if_index;

                  cached_tunnel_sw_if_index = tunnel_sw_if_index;
                }
              else
                {
                  tunnel_sw_if_index = cached_tunnel_sw_if_index;
                }
            }
          else
            {
                next0 = GRE_INPUT_NEXT_DROP;
                goto drop0;
            }
          len = vlib_buffer_length_in_chain (vm, b0);
          vlib_increment_combined_counter (im->combined_sw_if_counters
                                           + VNET_INTERFACE_COUNTER_RX,
                                           thread_index,
                                           tunnel_sw_if_index,
                                           1 /* packets */,
                                           len /* bytes */);

          vnet_buffer(b0)->sw_if_index[VLIB_RX] = tunnel_sw_if_index;

drop0:
          if (PREDICT_TRUE(next1 == GRE_INPUT_NEXT_IP4_INPUT
                           || next1 == GRE_INPUT_NEXT_IP6_INPUT
                           || next1 == GRE_INPUT_NEXT_ETHERNET_INPUT
                           || next1 == GRE_INPUT_NEXT_MPLS_INPUT))
            {
              u64 key4, key6[4];
              if (!is_ipv6)
                {
                  key4 = ((u64)(ip4_tun_dst1) << 32) | (u64)(ip4_tun_src1);
                }
              else
                {
                  key6[0] = ip6_tun_dst1[0];
                  key6[1] = ip6_tun_dst1[1];
                  key6[2] = ip6_tun_src1[0];
                  key6[3] = ip6_tun_src1[1];
                }

              if ((!is_ipv6 && cached_tunnel_key4 != key4) ||
                  (is_ipv6 && cached_tunnel_key6[0] != key6[0] &&
                      cached_tunnel_key6[1] != key6[1] &&
                      cached_tunnel_key6[2] != key6[2] &&
                      cached_tunnel_key6[3] != key6[3]))
                {
                  vnet_hw_interface_t * hi;
                  gre_tunnel_t * t;
                  uword * p;

                  if (!is_ipv6)
                    p = hash_get (gm->tunnel_by_key4, key4);
                  else
                    p = hash_get_mem (gm->tunnel_by_key6, key6);

                  if (!p)
                    {
                      next1 = GRE_INPUT_NEXT_DROP;
                      b1->error = node->errors[GRE_ERROR_NO_SUCH_TUNNEL];
                      goto drop1;
                    }
                  t = pool_elt_at_index (gm->tunnels, p[0]);
                  hi = vnet_get_hw_interface (gm->vnet_main,
                            t->hw_if_index);
                  tunnel_sw_if_index = hi->sw_if_index;

                  cached_tunnel_sw_if_index = tunnel_sw_if_index;
                }
              else
                {
                  tunnel_sw_if_index = cached_tunnel_sw_if_index;
                }
            }
          else
            {
                next1 = GRE_INPUT_NEXT_DROP;
                goto drop1;
            }
          len = vlib_buffer_length_in_chain (vm, b1);
          vlib_increment_combined_counter (im->combined_sw_if_counters
                                           + VNET_INTERFACE_COUNTER_RX,
                                           thread_index,
                                           tunnel_sw_if_index,
                                           1 /* packets */,
                                           len /* bytes */);

          vnet_buffer(b1)->sw_if_index[VLIB_RX] = tunnel_sw_if_index;

drop1:
          if (PREDICT_FALSE(b0->flags & VLIB_BUFFER_IS_TRACED))
            {
              gre_rx_trace_t *tr = vlib_add_trace (vm, node,
                                                   b0, sizeof (*tr));
              tr->tunnel_id = tunnel_sw_if_index;
              if (!is_ipv6)
                {
                  tr->length = ip4_0->length;
                  tr->src.ip4.as_u32 = ip4_0->src_address.as_u32;
                  tr->dst.ip4.as_u32 = ip4_0->dst_address.as_u32;
                }
              else
                {
                  tr->length = ip6_0->payload_length;
                  tr->src.ip6.as_u64[0] = ip6_0->src_address.as_u64[0];
                  tr->src.ip6.as_u64[1] = ip6_0->src_address.as_u64[1];
                  tr->dst.ip6.as_u64[0] = ip6_0->dst_address.as_u64[0];
                  tr->dst.ip6.as_u64[1] = ip6_0->dst_address.as_u64[1];
                }
            }

          if (PREDICT_FALSE(b1->flags & VLIB_BUFFER_IS_TRACED))
            {
              gre_rx_trace_t *tr = vlib_add_trace (vm, node,
                                                   b1, sizeof (*tr));
              tr->tunnel_id = tunnel_sw_if_index;
              if (!is_ipv6)
                {
                  tr->length = ip4_1->length;
                  tr->src.ip4.as_u32 = ip4_1->src_address.as_u32;
                  tr->dst.ip4.as_u32 = ip4_1->dst_address.as_u32;
                }
              else
                {
                  tr->length = ip6_1->payload_length;
                  tr->src.ip6.as_u64[0] = ip6_1->src_address.as_u64[0];
                  tr->src.ip6.as_u64[1] = ip6_1->src_address.as_u64[1];
                  tr->dst.ip6.as_u64[0] = ip6_1->dst_address.as_u64[0];
                  tr->dst.ip6.as_u64[1] = ip6_1->dst_address.as_u64[1];
                }
            }

          vlib_buffer_advance (b0, sizeof (*h0));
          vlib_buffer_advance (b1, sizeof (*h1));

          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;
          gre_header_t * h0;
          ip4_header_t * ip4_0;
          ip6_header_t * ip6_0;
          u16 version0;
          int verr0;
          u32 i0, next0;
      u32 ip4_tun_src0, ip4_tun_dst0;
      u32 ip6_tun_src0[4], ip6_tun_dst0[4];

          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);
          ip4_0 = vlib_buffer_get_current (b0);
          ip6_0 = (void *)ip4_0;

          if (!is_ipv6)
            {
              ip4_tun_src0 = ip4_0->src_address.as_u32;
              ip4_tun_dst0 = ip4_0->dst_address.as_u32;

              vlib_buffer_advance (b0, sizeof (*ip4_0));
            }
          else
            {
              ip6_tun_src0[0] = ip6_0->src_address.as_u64[0];
              ip6_tun_src0[1] = ip6_0->src_address.as_u64[1];
              ip6_tun_dst0[0] = ip6_0->dst_address.as_u64[0];
              ip6_tun_dst0[1] = ip6_0->dst_address.as_u64[1];

              vlib_buffer_advance (b0, sizeof (*ip6_0));
            }

          h0 = vlib_buffer_get_current (b0);

          i0 = sparse_vec_index (gm->next_by_protocol, h0->protocol);
          next0 = vec_elt(gm->next_by_protocol, i0);

          b0->error =
              node->errors[i0 == SPARSE_VEC_INVALID_INDEX 
                           ? GRE_ERROR_UNKNOWN_PROTOCOL : GRE_ERROR_NONE];

          version0 = clib_net_to_host_u16 (h0->flags_and_version);
          verr0 =  version0 & GRE_VERSION_MASK;
          b0->error = verr0 ? node->errors[GRE_ERROR_UNSUPPORTED_VERSION] 
              : b0->error;
          next0 = verr0 ? GRE_INPUT_NEXT_DROP : next0;


          /* For IP payload we need to find source interface
             so we can increase counters and help forward node to
             pick right FIB */
          /* RPF check for ip4/ip6 input */
          if (PREDICT_TRUE(next0 == GRE_INPUT_NEXT_IP4_INPUT
                           || next0 == GRE_INPUT_NEXT_IP6_INPUT
                           || next0 == GRE_INPUT_NEXT_ETHERNET_INPUT
                           || next0 == GRE_INPUT_NEXT_MPLS_INPUT))
            {
              u64 key4, key6[4];
              if (!is_ipv6)
                {
                  key4 = ((u64)(ip4_tun_dst0) << 32) | (u64)(ip4_tun_src0);
                }
              else
                {
                  key6[0] = ip6_tun_dst0[0];
                  key6[1] = ip6_tun_dst0[1];
                  key6[2] = ip6_tun_src0[0];
                  key6[3] = ip6_tun_src0[1];
                }

              if ((!is_ipv6 && cached_tunnel_key4 != key4) ||
                  (is_ipv6 && cached_tunnel_key6[0] != key6[0] &&
                      cached_tunnel_key6[1] != key6[1] &&
                      cached_tunnel_key6[2] != key6[2] &&
                      cached_tunnel_key6[3] != key6[3]))
                {
                  vnet_hw_interface_t * hi;
                  gre_tunnel_t * t;
                  uword * p;

                  if (!is_ipv6)
                    p = hash_get (gm->tunnel_by_key4, key4);
                  else
                    p = hash_get_mem (gm->tunnel_by_key6, key6);

                  if (!p)
                    {
                      next0 = GRE_INPUT_NEXT_DROP;
                      b0->error = node->errors[GRE_ERROR_NO_SUCH_TUNNEL];
                      goto drop;
                    }
                  t = pool_elt_at_index (gm->tunnels, p[0]);
                  hi = vnet_get_hw_interface (gm->vnet_main,
                            t->hw_if_index);
                  tunnel_sw_if_index = hi->sw_if_index;

                  cached_tunnel_sw_if_index = tunnel_sw_if_index;
                }
              else
                {
                  tunnel_sw_if_index = cached_tunnel_sw_if_index;
                }
            }
          else
            {
                next0 = GRE_INPUT_NEXT_DROP;
                goto drop;
            }
          len = vlib_buffer_length_in_chain (vm, b0);
          vlib_increment_combined_counter (im->combined_sw_if_counters
                                           + VNET_INTERFACE_COUNTER_RX,
                                           thread_index,
                                           tunnel_sw_if_index,
                                           1 /* packets */,
                                           len /* bytes */);

          vnet_buffer(b0)->sw_if_index[VLIB_RX] = tunnel_sw_if_index;

drop:
          if (PREDICT_FALSE(b0->flags & VLIB_BUFFER_IS_TRACED))
            {
              gre_rx_trace_t *tr = vlib_add_trace (vm, node,
                                                   b0, sizeof (*tr));
              tr->tunnel_id = tunnel_sw_if_index;
              if (!is_ipv6)
                {
                  tr->length = ip4_0->length;
                  tr->src.ip4.as_u32 = ip4_0->src_address.as_u32;
                  tr->dst.ip4.as_u32 = ip4_0->dst_address.as_u32;
                }
              else
                {
                  tr->length = ip6_0->payload_length;
                  tr->src.ip6.as_u64[0] = ip6_0->src_address.as_u64[0];
                  tr->src.ip6.as_u64[1] = ip6_0->src_address.as_u64[1];
                  tr->dst.ip6.as_u64[0] = ip6_0->dst_address.as_u64[0];
                  tr->dst.ip6.as_u64[1] = ip6_0->dst_address.as_u64[1];
                }
            }

          vlib_buffer_advance (b0, sizeof (*h0));

          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);
    }
  vlib_node_increment_counter (vm, !is_ipv6 ? gre4_input_node.index : gre6_input_node.index,
                               GRE_ERROR_PKTS_DECAP, from_frame->n_vectors);
  return from_frame->n_vectors;
}

static uword
gre4_input (vlib_main_t * vm,
            vlib_node_runtime_t * node,
         vlib_frame_t * from_frame)
{
   return gre_input(vm, node, from_frame, /* is_ip6 */ 0);
}

static uword
gre6_input (vlib_main_t * vm,
            vlib_node_runtime_t * node,
            vlib_frame_t * from_frame)
{
   return gre_input(vm, node, from_frame, /* is_ip6 */ 1);
}

static char * gre_error_strings[] = {
#define gre_error(n,s) s,
#include "error.def"
#undef gre_error
};

VLIB_REGISTER_NODE (gre4_input_node) = {
  .function = gre4_input,
  .name = "gre4-input",
  /* Takes a vector of packets. */
  .vector_size = sizeof (u32),

  .n_errors = GRE_N_ERROR,
  .error_strings = gre_error_strings,

  .n_next_nodes = GRE_INPUT_N_NEXT,
  .next_nodes = {
#define _(s,n) [GRE_INPUT_NEXT_##s] = n,
    foreach_gre_input_next
#undef _
  },

  .format_buffer = format_gre_header_with_length,
  .format_trace = format_gre_rx_trace,
  .unformat_buffer = unformat_gre_header,
};

VLIB_REGISTER_NODE (gre6_input_node) = {
  .function = gre6_input,
  .name = "gre6-input",
  /* Takes a vector of packets. */
  .vector_size = sizeof (u32),

  .runtime_data_bytes = sizeof (gre_input_runtime_t),

  .n_errors = GRE_N_ERROR,
  .error_strings = gre_error_strings,

  .n_next_nodes = GRE_INPUT_N_NEXT,
  .next_nodes = {
#define _(s,n) [GRE_INPUT_NEXT_##s] = n,
    foreach_gre_input_next
#undef _
  },

  .format_buffer = format_gre_header_with_length,
  .format_trace = format_gre_rx_trace,
  .unformat_buffer = unformat_gre_header,
};

VLIB_NODE_FUNCTION_MULTIARCH (gre4_input_node, gre4_input)
VLIB_NODE_FUNCTION_MULTIARCH (gre6_input_node, gre6_input)

void
gre_register_input_protocol (vlib_main_t * vm,
                             gre_protocol_t protocol,
                             u32 node_index)
{
  gre_main_t * em = &gre_main;
  gre_protocol_info_t * pi;
  u16 * n;
  u32 i;

  {
    clib_error_t * error = vlib_call_init_function (vm, gre_input_init);
    if (error)
      clib_error_report (error);
  }

  pi = gre_get_protocol_info (em, protocol);
  pi->node_index = node_index;
  pi->next_index = vlib_node_add_next (vm, gre4_input_node.index, node_index);
  i = vlib_node_add_next (vm, gre6_input_node.index, node_index);
  ASSERT(i == pi->next_index);

  /* Setup gre protocol -> next index sparse vector mapping. */
  n = sparse_vec_validate (em->next_by_protocol,
                           clib_host_to_net_u16 (protocol));
  n[0] = pi->next_index;
}

static void
gre_setup_node (vlib_main_t * vm, u32 node_index)
{
  vlib_node_t * n = vlib_get_node (vm, node_index);
  pg_node_t * pn = pg_get_node (node_index);

  n->format_buffer = format_gre_header_with_length;
  n->unformat_buffer = unformat_gre_header;
  pn->unformat_edit = unformat_pg_gre_header;
}

static clib_error_t * gre_input_init (vlib_main_t * vm)
{
  gre_main_t * gm = &gre_main;
  vlib_node_t *ethernet_input, *ip4_input, *ip6_input, *mpls_unicast_input;

  {
    clib_error_t * error;
    error = vlib_call_init_function (vm, gre_init);
    if (error)
      clib_error_report (error);
  }

  gre_setup_node (vm, gre4_input_node.index);
  gre_setup_node (vm, gre6_input_node.index);

  gm->next_by_protocol = sparse_vec_new
    (/* elt bytes */ sizeof (gm->next_by_protocol[0]),
     /* bits in index */ BITS (((gre_header_t *) 0)->protocol));

  /* These could be moved to the supported protocol input node defn's */
  ethernet_input = vlib_get_node_by_name (vm, (u8 *)"ethernet-input");
  ASSERT(ethernet_input);
  ip4_input = vlib_get_node_by_name (vm, (u8 *)"ip4-input");
  ASSERT(ip4_input);
  ip6_input = vlib_get_node_by_name (vm, (u8 *)"ip6-input");
  ASSERT(ip6_input);
  mpls_unicast_input = vlib_get_node_by_name (vm, (u8 *)"mpls-input");
  ASSERT(mpls_unicast_input);

  gre_register_input_protocol (vm, GRE_PROTOCOL_teb,
                               ethernet_input->index);

  gre_register_input_protocol (vm, GRE_PROTOCOL_ip4,
                               ip4_input->index);

  gre_register_input_protocol (vm, GRE_PROTOCOL_ip6,
                               ip6_input->index);

  gre_register_input_protocol (vm, GRE_PROTOCOL_mpls_unicast,
                               mpls_unicast_input->index);

  ip4_register_protocol (IP_PROTOCOL_GRE, gre4_input_node.index);
  ip6_register_protocol (IP_PROTOCOL_GRE, gre6_input_node.index);

  return 0;
}

VLIB_INIT_FUNCTION (gre_input_init);