vnet/vnet/nsh-gre/encap.c - fdio/vpp - Gitiles

 /*
  * Copyright (c) 2015 Cisco and/or its affiliates.
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at:
  *
  *     http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 #include <vppinfra/error.h>
 #include <vppinfra/hash.h>
 #include <vnet/vnet.h>
 #include <vnet/ip/ip.h>
 #include <vnet/ethernet/ethernet.h>
 #include <vnet/nsh-gre/nsh_gre.h>

 /* Statistics (not really errors) */
 #define foreach_nsh_gre_encap_error             \
 _(ENCAPSULATED, "good packets encapsulated")

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

 typedef enum {
 #define _(sym,str) NSH_GRE_ENCAP_ERROR_##sym,
     foreach_nsh_gre_encap_error
 #undef _
     NSH_GRE_ENCAP_N_ERROR,
 } nsh_gre_encap_error_t;

 typedef enum {
     NSH_GRE_ENCAP_NEXT_IP4_LOOKUP,
     NSH_GRE_ENCAP_NEXT_DROP,
     NSH_GRE_ENCAP_N_NEXT,
 } nsh_gre_encap_next_t;

 typedef struct {
   u32 tunnel_index;
 } nsh_gre_encap_trace_t;

 u8 * format_nsh_gre_encap_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 *);
   nsh_gre_encap_trace_t * t = va_arg (*args, nsh_gre_encap_trace_t *);

   s = format (s, "NSH-GRE-ENCAP: tunnel %d", t->tunnel_index);
   return s;
 }

 static uword
 nsh_gre_encap (vlib_main_t * vm,
                vlib_node_runtime_t * node,
                vlib_frame_t * from_frame)
 {
   u32 n_left_from, next_index, * from, * to_next;
   nsh_gre_main_t * ngm = &nsh_gre_main;
   vnet_main_t * vnm = ngm->vnet_main;
   vnet_interface_main_t * im = &vnm->interface_main;
   u32 pkts_encapsulated = 0;
   u16 old_l0 = 0, old_l1 = 0;
   u32 cpu_index = os_get_cpu_number();
   u32 stats_sw_if_index, stats_n_packets, stats_n_bytes;

   from = vlib_frame_vector_args (from_frame);
   n_left_from = from_frame->n_vectors;

   next_index = node->cached_next_index;
   stats_sw_if_index = node->runtime_data[0];
   stats_n_packets = stats_n_bytes = 0;

   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;
 	  u32 next0 = NSH_GRE_ENCAP_NEXT_IP4_LOOKUP;
 	  u32 next1 = NSH_GRE_ENCAP_NEXT_IP4_LOOKUP;
           u32 sw_if_index0, sw_if_index1, len0, len1;
           vnet_hw_interface_t * hi0, * hi1;
           ip4_header_t * ip0, * ip1;
           u64 * copy_src0, * copy_dst0;
           u64 * copy_src1, * copy_dst1;
           nsh_gre_tunnel_t * t0, * t1;
           u16 new_l0, new_l1;
           ip_csum_t sum0, sum1;

 	  /* 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, 2*CLIB_CACHE_LINE_BYTES, LOAD);
 	    CLIB_PREFETCH (p3->data, 2*CLIB_CACHE_LINE_BYTES, 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);

           /* 1-wide cache? */
           sw_if_index0 = vnet_buffer(b0)->sw_if_index[VLIB_TX];
           sw_if_index1 = vnet_buffer(b1)->sw_if_index[VLIB_TX];
           hi0 = vnet_get_sup_hw_interface
             (vnm, vnet_buffer(b0)->sw_if_index[VLIB_TX]);
           hi1 = vnet_get_sup_hw_interface
             (vnm, vnet_buffer(b1)->sw_if_index[VLIB_TX]);

           t0 = pool_elt_at_index (ngm->tunnels, hi0->dev_instance);
           t1 = pool_elt_at_index (ngm->tunnels, hi1->dev_instance);

           ASSERT(vec_len(t0->rewrite) >= 24);
           ASSERT(vec_len(t1->rewrite) >= 24);

           /* Apply the rewrite string. $$$$ vnet_rewrite? */
           vlib_buffer_advance (b0, -(word)_vec_len(t0->rewrite));
           vlib_buffer_advance (b1, -(word)_vec_len(t1->rewrite));

           ip0 = vlib_buffer_get_current(b0);
           ip1 = vlib_buffer_get_current(b1);
           /* Copy the fixed header */
           copy_dst0 = (u64 *) ip0;
           copy_src0 = (u64 *) t0->rewrite;
           copy_dst1 = (u64 *) ip1;
           copy_src1 = (u64 *) t1->rewrite;

           copy_dst0[0] = copy_src0[0];
           copy_dst0[1] = copy_src0[1];
           copy_dst0[2] = copy_src0[2];

           copy_dst1[0] = copy_src1[0];
           copy_dst1[1] = copy_src1[1];
           copy_dst1[2] = copy_src1[2];

           /* If there are TLVs to copy, do so */
           if (PREDICT_FALSE (_vec_len(t0->rewrite) > 24))
             clib_memcpy (&copy_dst0[3], t0->rewrite + 24 ,
                     _vec_len (t0->rewrite)-24);

           if (PREDICT_FALSE (_vec_len(t1->rewrite) > 24))
             clib_memcpy (&copy_dst1[3], t1->rewrite + 24 ,
                     _vec_len (t1->rewrite)-24);

           /* fix the <bleep>ing outer-IP checksums */
           sum0 = ip0->checksum;
           /* old_l0 always 0, see the rewrite setup */
           new_l0 =
             clib_host_to_net_u16 (vlib_buffer_length_in_chain (vm, b0));

           sum0 = ip_csum_update (sum0, old_l0, new_l0, ip4_header_t,
                                  length /* changed member */);
           ip0->checksum = ip_csum_fold (sum0);
           ip0->length = new_l0;

           sum1 = ip1->checksum;
           /* old_l1 always 1, see the rewrite setup */
           new_l1 =
             clib_host_to_net_u16 (vlib_buffer_length_in_chain (vm, b1));

           sum1 = ip_csum_update (sum1, old_l1, new_l1, ip4_header_t,
                                  length /* changed member */);
           ip1->checksum = ip_csum_fold (sum1);
           ip1->length = new_l1;

           /* Reset to look up tunnel partner in the configured FIB */
           vnet_buffer(b0)->sw_if_index[VLIB_TX] = t0->encap_fib_index;
           vnet_buffer(b1)->sw_if_index[VLIB_TX] = t1->encap_fib_index;
           vnet_buffer(b0)->sw_if_index[VLIB_RX] = sw_if_index0;
           vnet_buffer(b1)->sw_if_index[VLIB_RX] = sw_if_index1;
           pkts_encapsulated += 2;

           len0 = vlib_buffer_length_in_chain(vm, b0);
           len1 = vlib_buffer_length_in_chain(vm, b0);
           stats_n_packets += 2;
           stats_n_bytes += len0 + len1;

           /* Batch stats increment on the same vxlan tunnel so counter is not
            incremented per packet. Note stats are still incremented for deleted
            and admin-down tunnel where packets are dropped. It is not worthwhile
            to check for this rare case and affect normal path performance. */
           if (PREDICT_FALSE(
               (sw_if_index0 != stats_sw_if_index)
                   || (sw_if_index1 != stats_sw_if_index))) {
             stats_n_packets -= 2;
             stats_n_bytes -= len0 + len1;
             if (sw_if_index0 == sw_if_index1) {
               if (stats_n_packets)
                 vlib_increment_combined_counter(
                     im->combined_sw_if_counters + VNET_INTERFACE_COUNTER_TX,
                     cpu_index, stats_sw_if_index, stats_n_packets, stats_n_bytes);
               stats_sw_if_index = sw_if_index0;
               stats_n_packets = 2;
               stats_n_bytes = len0 + len1;
             } else {
               vlib_increment_combined_counter(
                   im->combined_sw_if_counters + VNET_INTERFACE_COUNTER_TX,
                   cpu_index, sw_if_index0, 1, len0);
               vlib_increment_combined_counter(
                   im->combined_sw_if_counters + VNET_INTERFACE_COUNTER_TX,
                   cpu_index, sw_if_index1, 1, len1);
             }
           }

           if (PREDICT_FALSE(b0->flags & VLIB_BUFFER_IS_TRACED))
             {
               nsh_gre_encap_trace_t *tr =
                 vlib_add_trace (vm, node, b0, sizeof (*tr));
               tr->tunnel_index = t0 - ngm->tunnels;
             }

           if (PREDICT_FALSE(b1->flags & VLIB_BUFFER_IS_TRACED))
             {
               nsh_gre_encap_trace_t *tr =
                 vlib_add_trace (vm, node, b1, sizeof (*tr));
               tr->tunnel_index = t1 - ngm->tunnels;
             }

 	  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 = NSH_GRE_ENCAP_NEXT_IP4_LOOKUP;
       u32 sw_if_index0, len0;
           vnet_hw_interface_t * hi0;
           ip4_header_t * ip0;
           u64 * copy_src0, * copy_dst0;
           nsh_gre_tunnel_t * t0;
           u16 new_l0;
           ip_csum_t sum0;

 	  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);

           /* 1-wide cache? */
           sw_if_index0 = vnet_buffer(b0)->sw_if_index[VLIB_TX];
           hi0 = vnet_get_sup_hw_interface
             (vnm, vnet_buffer(b0)->sw_if_index[VLIB_TX]);

           t0 = pool_elt_at_index (ngm->tunnels, hi0->dev_instance);

           ASSERT(vec_len(t0->rewrite) >= 24);

           /* Apply the rewrite string. $$$$ vnet_rewrite? */
           vlib_buffer_advance (b0, -(word)_vec_len(t0->rewrite));

           ip0 = vlib_buffer_get_current(b0);
           /* Copy the fixed header */
           copy_dst0 = (u64 *) ip0;
           copy_src0 = (u64 *) t0->rewrite;
           copy_dst0[0] = copy_src0[0];
           copy_dst0[1] = copy_src0[1];
           copy_dst0[2] = copy_src0[2];

           /* If there are TLVs to copy, do so */
           if (PREDICT_FALSE (_vec_len(t0->rewrite) > 24))
             clib_memcpy (&copy_dst0[3], t0->rewrite + 24 ,
                     _vec_len (t0->rewrite)-24);

           /* fix the <bleep>ing outer-IP checksum */
           sum0 = ip0->checksum;
           /* old_l0 always 0, see the rewrite setup */
           new_l0 =
             clib_host_to_net_u16 (vlib_buffer_length_in_chain (vm, b0));

           sum0 = ip_csum_update (sum0, old_l0, new_l0, ip4_header_t,
                                  length /* changed member */);
           ip0->checksum = ip_csum_fold (sum0);
           ip0->length = new_l0;

           /* Reset to look up tunnel partner in the configured FIB */
           vnet_buffer(b0)->sw_if_index[VLIB_TX] = t0->encap_fib_index;
           vnet_buffer(b0)->sw_if_index[VLIB_RX] = sw_if_index0;
           pkts_encapsulated ++;

           len0 = vlib_buffer_length_in_chain(vm, b0);
           stats_n_packets += 1;
           stats_n_bytes += len0;

           /* Batch stats increment on the same vxlan tunnel so counter is not
            incremented per packet. Note stats are still incremented for deleted
            and admin-down tunnel where packets are dropped. It is not worthwhile
            to check for this rare case and affect normal path performance. */
           if (PREDICT_FALSE(sw_if_index0 != stats_sw_if_index)) {
             stats_n_packets -= 1;
             stats_n_bytes -= len0;
             if (stats_n_packets)
               vlib_increment_combined_counter(
                   im->combined_sw_if_counters + VNET_INTERFACE_COUNTER_TX,
                   cpu_index, stats_sw_if_index, stats_n_packets, stats_n_bytes);
             stats_n_packets = 1;
             stats_n_bytes = len0;
             stats_sw_if_index = sw_if_index0;
           }
           if (PREDICT_FALSE(b0->flags & VLIB_BUFFER_IS_TRACED))
             {
               nsh_gre_encap_trace_t *tr =
                 vlib_add_trace (vm, node, b0, sizeof (*tr));
               tr->tunnel_index = t0 - ngm->tunnels;
             }
 	  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, node->node_index,
                                NSH_GRE_ENCAP_ERROR_ENCAPSULATED,
                                pkts_encapsulated);
   /* Increment any remaining batch stats */
   if (stats_n_packets) {
     vlib_increment_combined_counter(
         im->combined_sw_if_counters + VNET_INTERFACE_COUNTER_TX, cpu_index,
         stats_sw_if_index, stats_n_packets, stats_n_bytes);
     node->runtime_data[0] = stats_sw_if_index;
   }

   return from_frame->n_vectors;
 }

 VLIB_REGISTER_NODE (nsh_gre_encap_node) = {
   .function = nsh_gre_encap,
   .name = "nsh-gre-encap",
   .vector_size = sizeof (u32),
   .format_trace = format_nsh_gre_encap_trace,
   .type = VLIB_NODE_TYPE_INTERNAL,

   .n_errors = ARRAY_LEN(nsh_gre_encap_error_strings),
   .error_strings = nsh_gre_encap_error_strings,

   .n_next_nodes = NSH_GRE_ENCAP_N_NEXT,

   //  add dispositions here
   .next_nodes = {
         [NSH_GRE_ENCAP_NEXT_IP4_LOOKUP] = "ip4-lookup",
         [NSH_GRE_ENCAP_NEXT_DROP] = "error-drop",
   },
 };
	/*
	* Copyright (c) 2015 Cisco and/or its affiliates.
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at:
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/
	#include <vppinfra/error.h>
	#include <vppinfra/hash.h>
	#include <vnet/vnet.h>
	#include <vnet/ip/ip.h>
	#include <vnet/ethernet/ethernet.h>
	#include <vnet/nsh-gre/nsh_gre.h>

	/* Statistics (not really errors) */
	#define foreach_nsh_gre_encap_error \
	_(ENCAPSULATED, "good packets encapsulated")

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

	typedef enum {
	#define _(sym,str) NSH_GRE_ENCAP_ERROR_##sym,
	foreach_nsh_gre_encap_error
	#undef _
	NSH_GRE_ENCAP_N_ERROR,
	} nsh_gre_encap_error_t;

	typedef enum {
	NSH_GRE_ENCAP_NEXT_IP4_LOOKUP,
	NSH_GRE_ENCAP_NEXT_DROP,
	NSH_GRE_ENCAP_N_NEXT,
	} nsh_gre_encap_next_t;

	typedef struct {
	u32 tunnel_index;
	} nsh_gre_encap_trace_t;

	u8 * format_nsh_gre_encap_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 );
	nsh_gre_encap_trace_t * t = va_arg (args, nsh_gre_encap_trace_t );

	s = format (s, "NSH-GRE-ENCAP: tunnel %d", t->tunnel_index);
	return s;
	}

	static uword
	nsh_gre_encap (vlib_main_t * vm,
	vlib_node_runtime_t * node,
	vlib_frame_t * from_frame)
	{
	u32 n_left_from, next_index, * from, * to_next;
	nsh_gre_main_t * ngm = &nsh_gre_main;
	vnet_main_t * vnm = ngm->vnet_main;
	vnet_interface_main_t * im = &vnm->interface_main;
	u32 pkts_encapsulated = 0;
	u16 old_l0 = 0, old_l1 = 0;
	u32 cpu_index = os_get_cpu_number();
	u32 stats_sw_if_index, stats_n_packets, stats_n_bytes;

	from = vlib_frame_vector_args (from_frame);
	n_left_from = from_frame->n_vectors;

	next_index = node->cached_next_index;
	stats_sw_if_index = node->runtime_data[0];
	stats_n_packets = stats_n_bytes = 0;

	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;
	u32 next0 = NSH_GRE_ENCAP_NEXT_IP4_LOOKUP;
	u32 next1 = NSH_GRE_ENCAP_NEXT_IP4_LOOKUP;
	u32 sw_if_index0, sw_if_index1, len0, len1;
	vnet_hw_interface_t * hi0, * hi1;
	ip4_header_t * ip0, * ip1;
	u64 * copy_src0, * copy_dst0;
	u64 * copy_src1, * copy_dst1;
	nsh_gre_tunnel_t * t0, * t1;
	u16 new_l0, new_l1;
	ip_csum_t sum0, sum1;

	/* 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, 2*CLIB_CACHE_LINE_BYTES, LOAD);
	CLIB_PREFETCH (p3->data, 2*CLIB_CACHE_LINE_BYTES, 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);

	/* 1-wide cache? */
	sw_if_index0 = vnet_buffer(b0)->sw_if_index[VLIB_TX];
	sw_if_index1 = vnet_buffer(b1)->sw_if_index[VLIB_TX];
	hi0 = vnet_get_sup_hw_interface
	(vnm, vnet_buffer(b0)->sw_if_index[VLIB_TX]);
	hi1 = vnet_get_sup_hw_interface
	(vnm, vnet_buffer(b1)->sw_if_index[VLIB_TX]);

	t0 = pool_elt_at_index (ngm->tunnels, hi0->dev_instance);
	t1 = pool_elt_at_index (ngm->tunnels, hi1->dev_instance);

	ASSERT(vec_len(t0->rewrite) >= 24);
	ASSERT(vec_len(t1->rewrite) >= 24);

	/* Apply the rewrite string. $$$$ vnet_rewrite? */
	vlib_buffer_advance (b0, -(word)_vec_len(t0->rewrite));
	vlib_buffer_advance (b1, -(word)_vec_len(t1->rewrite));

	ip0 = vlib_buffer_get_current(b0);
	ip1 = vlib_buffer_get_current(b1);
	/* Copy the fixed header */
	copy_dst0 = (u64 *) ip0;
	copy_src0 = (u64 *) t0->rewrite;
	copy_dst1 = (u64 *) ip1;
	copy_src1 = (u64 *) t1->rewrite;

	copy_dst0[0] = copy_src0[0];
	copy_dst0[1] = copy_src0[1];
	copy_dst0[2] = copy_src0[2];

	copy_dst1[0] = copy_src1[0];
	copy_dst1[1] = copy_src1[1];
	copy_dst1[2] = copy_src1[2];

	/* If there are TLVs to copy, do so */
	if (PREDICT_FALSE (_vec_len(t0->rewrite) > 24))
	clib_memcpy (&copy_dst0[3], t0->rewrite + 24 ,
	_vec_len (t0->rewrite)-24);

	if (PREDICT_FALSE (_vec_len(t1->rewrite) > 24))
	clib_memcpy (&copy_dst1[3], t1->rewrite + 24 ,
	_vec_len (t1->rewrite)-24);

	/* fix the <bleep>ing outer-IP checksums */
	sum0 = ip0->checksum;
	/* old_l0 always 0, see the rewrite setup */
	new_l0 =
	clib_host_to_net_u16 (vlib_buffer_length_in_chain (vm, b0));

	sum0 = ip_csum_update (sum0, old_l0, new_l0, ip4_header_t,
	length /* changed member */);
	ip0->checksum = ip_csum_fold (sum0);
	ip0->length = new_l0;

	sum1 = ip1->checksum;
	/* old_l1 always 1, see the rewrite setup */
	new_l1 =
	clib_host_to_net_u16 (vlib_buffer_length_in_chain (vm, b1));

	sum1 = ip_csum_update (sum1, old_l1, new_l1, ip4_header_t,
	length /* changed member */);
	ip1->checksum = ip_csum_fold (sum1);
	ip1->length = new_l1;

	/* Reset to look up tunnel partner in the configured FIB */
	vnet_buffer(b0)->sw_if_index[VLIB_TX] = t0->encap_fib_index;
	vnet_buffer(b1)->sw_if_index[VLIB_TX] = t1->encap_fib_index;
	vnet_buffer(b0)->sw_if_index[VLIB_RX] = sw_if_index0;
	vnet_buffer(b1)->sw_if_index[VLIB_RX] = sw_if_index1;
	pkts_encapsulated += 2;

	len0 = vlib_buffer_length_in_chain(vm, b0);
	len1 = vlib_buffer_length_in_chain(vm, b0);
	stats_n_packets += 2;
	stats_n_bytes += len0 + len1;

	/* Batch stats increment on the same vxlan tunnel so counter is not
	incremented per packet. Note stats are still incremented for deleted
	and admin-down tunnel where packets are dropped. It is not worthwhile
	to check for this rare case and affect normal path performance. */
	if (PREDICT_FALSE(
	(sw_if_index0 != stats_sw_if_index)
	\|\| (sw_if_index1 != stats_sw_if_index))) {
	stats_n_packets -= 2;
	stats_n_bytes -= len0 + len1;
	if (sw_if_index0 == sw_if_index1) {
	if (stats_n_packets)
	vlib_increment_combined_counter(
	im->combined_sw_if_counters + VNET_INTERFACE_COUNTER_TX,
	cpu_index, stats_sw_if_index, stats_n_packets, stats_n_bytes);
	stats_sw_if_index = sw_if_index0;
	stats_n_packets = 2;
	stats_n_bytes = len0 + len1;
	} else {
	vlib_increment_combined_counter(
	im->combined_sw_if_counters + VNET_INTERFACE_COUNTER_TX,
	cpu_index, sw_if_index0, 1, len0);
	vlib_increment_combined_counter(
	im->combined_sw_if_counters + VNET_INTERFACE_COUNTER_TX,
	cpu_index, sw_if_index1, 1, len1);
	}
	}

	if (PREDICT_FALSE(b0->flags & VLIB_BUFFER_IS_TRACED))
	{
	nsh_gre_encap_trace_t *tr =
	vlib_add_trace (vm, node, b0, sizeof (*tr));
	tr->tunnel_index = t0 - ngm->tunnels;
	}

	if (PREDICT_FALSE(b1->flags & VLIB_BUFFER_IS_TRACED))
	{
	nsh_gre_encap_trace_t *tr =
	vlib_add_trace (vm, node, b1, sizeof (*tr));
	tr->tunnel_index = t1 - ngm->tunnels;
	}

	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 = NSH_GRE_ENCAP_NEXT_IP4_LOOKUP;
	u32 sw_if_index0, len0;
	vnet_hw_interface_t * hi0;
	ip4_header_t * ip0;
	u64 * copy_src0, * copy_dst0;
	nsh_gre_tunnel_t * t0;
	u16 new_l0;
	ip_csum_t sum0;

	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);

	/* 1-wide cache? */
	sw_if_index0 = vnet_buffer(b0)->sw_if_index[VLIB_TX];
	hi0 = vnet_get_sup_hw_interface
	(vnm, vnet_buffer(b0)->sw_if_index[VLIB_TX]);

	t0 = pool_elt_at_index (ngm->tunnels, hi0->dev_instance);

	ASSERT(vec_len(t0->rewrite) >= 24);

	/* Apply the rewrite string. $$$$ vnet_rewrite? */
	vlib_buffer_advance (b0, -(word)_vec_len(t0->rewrite));

	ip0 = vlib_buffer_get_current(b0);
	/* Copy the fixed header */
	copy_dst0 = (u64 *) ip0;
	copy_src0 = (u64 *) t0->rewrite;
	copy_dst0[0] = copy_src0[0];
	copy_dst0[1] = copy_src0[1];
	copy_dst0[2] = copy_src0[2];

	/* If there are TLVs to copy, do so */
	if (PREDICT_FALSE (_vec_len(t0->rewrite) > 24))
	clib_memcpy (&copy_dst0[3], t0->rewrite + 24 ,
	_vec_len (t0->rewrite)-24);

	/* fix the <bleep>ing outer-IP checksum */
	sum0 = ip0->checksum;
	/* old_l0 always 0, see the rewrite setup */
	new_l0 =
	clib_host_to_net_u16 (vlib_buffer_length_in_chain (vm, b0));

	sum0 = ip_csum_update (sum0, old_l0, new_l0, ip4_header_t,
	length /* changed member */);
	ip0->checksum = ip_csum_fold (sum0);
	ip0->length = new_l0;

	/* Reset to look up tunnel partner in the configured FIB */
	vnet_buffer(b0)->sw_if_index[VLIB_TX] = t0->encap_fib_index;
	vnet_buffer(b0)->sw_if_index[VLIB_RX] = sw_if_index0;
	pkts_encapsulated ++;

	len0 = vlib_buffer_length_in_chain(vm, b0);
	stats_n_packets += 1;
	stats_n_bytes += len0;

	/* Batch stats increment on the same vxlan tunnel so counter is not
	incremented per packet. Note stats are still incremented for deleted
	and admin-down tunnel where packets are dropped. It is not worthwhile
	to check for this rare case and affect normal path performance. */
	if (PREDICT_FALSE(sw_if_index0 != stats_sw_if_index)) {
	stats_n_packets -= 1;
	stats_n_bytes -= len0;
	if (stats_n_packets)
	vlib_increment_combined_counter(
	im->combined_sw_if_counters + VNET_INTERFACE_COUNTER_TX,
	cpu_index, stats_sw_if_index, stats_n_packets, stats_n_bytes);
	stats_n_packets = 1;
	stats_n_bytes = len0;
	stats_sw_if_index = sw_if_index0;
	}
	if (PREDICT_FALSE(b0->flags & VLIB_BUFFER_IS_TRACED))
	{
	nsh_gre_encap_trace_t *tr =
	vlib_add_trace (vm, node, b0, sizeof (*tr));
	tr->tunnel_index = t0 - ngm->tunnels;
	}
	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, node->node_index,
	NSH_GRE_ENCAP_ERROR_ENCAPSULATED,
	pkts_encapsulated);
	/* Increment any remaining batch stats */
	if (stats_n_packets) {
	vlib_increment_combined_counter(
	im->combined_sw_if_counters + VNET_INTERFACE_COUNTER_TX, cpu_index,
	stats_sw_if_index, stats_n_packets, stats_n_bytes);
	node->runtime_data[0] = stats_sw_if_index;
	}

	return from_frame->n_vectors;
	}

	VLIB_REGISTER_NODE (nsh_gre_encap_node) = {
	.function = nsh_gre_encap,
	.name = "nsh-gre-encap",
	.vector_size = sizeof (u32),
	.format_trace = format_nsh_gre_encap_trace,
	.type = VLIB_NODE_TYPE_INTERNAL,

	.n_errors = ARRAY_LEN(nsh_gre_encap_error_strings),
	.error_strings = nsh_gre_encap_error_strings,

	.n_next_nodes = NSH_GRE_ENCAP_N_NEXT,

	// add dispositions here
	.next_nodes = {
	[NSH_GRE_ENCAP_NEXT_IP4_LOOKUP] = "ip4-lookup",
	[NSH_GRE_ENCAP_NEXT_DROP] = "error-drop",
	},
	};