src/vnet/adj/adj_mcast.c - fdio/vpp - Gitiles

 /*
  * Copyright (c) 2016 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/adj/adj_mcast.h>
 #include <vnet/adj/adj_internal.h>
 #include <vnet/fib/fib_walk.h>
 #include <vnet/ip/ip.h>

 /*
  * The 'DB' of all mcast adjs.
  * There is only one mcast per-interface per-protocol, so this is a per-interface
  * vector
  */
 static adj_index_t *adj_mcasts[FIB_PROTOCOL_MAX];

 static u32
 adj_get_mcast_node (fib_protocol_t proto)
 {
     switch (proto) {
     case FIB_PROTOCOL_IP4:
 	return (ip4_rewrite_mcast_node.index);
     case FIB_PROTOCOL_IP6:
 	return (ip6_rewrite_mcast_node.index);
     case FIB_PROTOCOL_MPLS:
 	break;
     }
     ASSERT(0);
     return (0);
 }

 /*
  * adj_mcast_add_or_lock
  *
  * The next_hop address here is used for source address selection in the DP.
  * The mcast adj is added to an interface's connected prefix, the next-hop
  * passed here is the local prefix on the same interface.
  */
 adj_index_t
 adj_mcast_add_or_lock (fib_protocol_t proto,
                        vnet_link_t link_type,
 		       u32 sw_if_index)
 {
     ip_adjacency_t * adj;

     vec_validate_init_empty(adj_mcasts[proto], sw_if_index, ADJ_INDEX_INVALID);

     if (ADJ_INDEX_INVALID == adj_mcasts[proto][sw_if_index])
     {
         vnet_main_t *vnm;

         vnm = vnet_get_main();
 	adj = adj_alloc(proto);

 	adj->lookup_next_index = IP_LOOKUP_NEXT_MCAST;
 	adj->ia_nh_proto = proto;
 	adj->ia_link = link_type;
 	adj_mcasts[proto][sw_if_index] = adj_get_index(adj);
         adj_lock(adj_get_index(adj));

 	vnet_rewrite_init(vnm, sw_if_index,
 			  adj_get_mcast_node(proto),
 			  vnet_tx_node_index_for_sw_interface(vnm, sw_if_index),
 			  &adj->rewrite_header);

 	/*
 	 * we need a rewrite where the destination IP address is converted
 	 * to the appropriate link-layer address. This is interface specific.
 	 * So ask the interface to do it.
 	 */
 	vnet_update_adjacency_for_sw_interface(vnm, sw_if_index,
                                                adj_get_index(adj));
     }
     else
     {
 	adj = adj_get(adj_mcasts[proto][sw_if_index]);
         adj_lock(adj_get_index(adj));
     }

     return (adj_get_index(adj));
 }

 /**
  * adj_mcast_update_rewrite
  *
  * Update the adjacency's rewrite string. A NULL string implies the
  * rewirte is reset (i.e. when ARP/ND etnry is gone).
  * NB: the adj being updated may be handling traffic in the DP.
  */
 void
 adj_mcast_update_rewrite (adj_index_t adj_index,
                           u8 *rewrite,
                           u8 offset,
                           u32 mask)
 {
     ip_adjacency_t *adj;

     ASSERT(ADJ_INDEX_INVALID != adj_index);

     adj = adj_get(adj_index);

     /*
      * update the adj's rewrite string and build the arc
      * from the rewrite node to the interface's TX node
      */
     adj_nbr_update_rewrite_internal(adj, IP_LOOKUP_NEXT_MCAST,
                                     adj_get_mcast_node(adj->ia_nh_proto),
                                     vnet_tx_node_index_for_sw_interface(
                                         vnet_get_main(),
                                         adj->rewrite_header.sw_if_index),
                                     rewrite);
     /*
      * set the fields corresponding to the mcast IP address rewrite
      * The mask must be stored in network byte order, since the packet's
      * IP address will also be in network order.
      */
     adj->rewrite_header.dst_mcast_offset = offset;
     adj->rewrite_header.dst_mcast_mask = clib_host_to_net_u32(mask);
 }

 /**
  * adj_mcast_midchain_update_rewrite
  *
  * Update the adjacency's rewrite string. A NULL string implies the
  * rewirte is reset (i.e. when ARP/ND etnry is gone).
  * NB: the adj being updated may be handling traffic in the DP.
  */
 void
 adj_mcast_midchain_update_rewrite (adj_index_t adj_index,
                                    adj_midchain_fixup_t fixup,
                                    adj_flags_t flags,
                                    u8 *rewrite,
                                    u8 offset,
                                    u32 mask)
 {
     ip_adjacency_t *adj;

     ASSERT(ADJ_INDEX_INVALID != adj_index);

     adj = adj_get(adj_index);

     /*
      * one time only update. since we don't support chainging the tunnel
      * src,dst, this is all we need.
      */
     ASSERT(adj->lookup_next_index == IP_LOOKUP_NEXT_MCAST);
     /*
      * tunnels can always provide a rewrite.
      */
     ASSERT(NULL != rewrite);

     adj_midchain_setup(adj_index, fixup, flags);

     /*
      * update the adj's rewrite string and build the arc
      * from the rewrite node to the interface's TX node
      */
     adj_nbr_update_rewrite_internal(adj, IP_LOOKUP_NEXT_MCAST_MIDCHAIN,
                                     adj_get_mcast_node(adj->ia_nh_proto),
                                     vnet_tx_node_index_for_sw_interface(
                                         vnet_get_main(),
                                         adj->rewrite_header.sw_if_index),
                                     rewrite);

     /*
      * set the fields corresponding to the mcast IP address rewrite
      * The mask must be stored in network byte order, since the packet's
      * IP address will also be in network order.
      */
     adj->rewrite_header.dst_mcast_offset = offset;
     adj->rewrite_header.dst_mcast_mask = clib_host_to_net_u32(mask);
 }

 void
 adj_mcast_remove (fib_protocol_t proto,
 		  u32 sw_if_index)
 {
     ASSERT(sw_if_index < vec_len(adj_mcasts[proto]));

     adj_mcasts[proto][sw_if_index] = ADJ_INDEX_INVALID;
 }

 static clib_error_t *
 adj_mcast_interface_state_change (vnet_main_t * vnm,
 				  u32 sw_if_index,
 				  u32 flags)
 {
     /*
      * for each mcast on the interface trigger a walk back to the children
      */
     fib_protocol_t proto;
     ip_adjacency_t *adj;


     for (proto = FIB_PROTOCOL_IP4; proto <= FIB_PROTOCOL_IP6; proto++)
     {
 	if (sw_if_index >= vec_len(adj_mcasts[proto]) ||
 	    ADJ_INDEX_INVALID == adj_mcasts[proto][sw_if_index])
 	    continue;

 	adj = adj_get(adj_mcasts[proto][sw_if_index]);

 	fib_node_back_walk_ctx_t bw_ctx = {
 	    .fnbw_reason = (flags & VNET_SW_INTERFACE_FLAG_ADMIN_UP ?
 			    FIB_NODE_BW_REASON_FLAG_INTERFACE_UP :
 			    FIB_NODE_BW_REASON_FLAG_INTERFACE_DOWN),
 	};

 	fib_walk_sync(FIB_NODE_TYPE_ADJ, adj_get_index(adj), &bw_ctx);
     }

     return (NULL);
 }

 VNET_SW_INTERFACE_ADMIN_UP_DOWN_FUNCTION(adj_mcast_interface_state_change);

 /**
  * @brief Invoked on each SW interface of a HW interface when the
  * HW interface state changes
  */
 static void
 adj_nbr_hw_sw_interface_state_change (vnet_main_t * vnm,
                                       u32 sw_if_index,
                                       void *arg)
 {
     adj_mcast_interface_state_change(vnm, sw_if_index, (uword) arg);
 }

 /**
  * @brief Registered callback for HW interface state changes
  */
 static clib_error_t *
 adj_mcast_hw_interface_state_change (vnet_main_t * vnm,
                                      u32 hw_if_index,
                                      u32 flags)
 {
     /*
      * walk SW interfaces on the HW
      */
     uword sw_flags;

     sw_flags = ((flags & VNET_HW_INTERFACE_FLAG_LINK_UP) ?
                 VNET_SW_INTERFACE_FLAG_ADMIN_UP :
                 0);

     vnet_hw_interface_walk_sw(vnm, hw_if_index,
                               adj_nbr_hw_sw_interface_state_change,
                               (void*) sw_flags);

     return (NULL);
 }

 VNET_HW_INTERFACE_LINK_UP_DOWN_FUNCTION(
     adj_mcast_hw_interface_state_change);

 static clib_error_t *
 adj_mcast_interface_delete (vnet_main_t * vnm,
 			    u32 sw_if_index,
 			    u32 is_add)
 {
     /*
      * for each mcast on the interface trigger a walk back to the children
      */
     fib_protocol_t proto;
     ip_adjacency_t *adj;

     if (is_add)
     {
 	/*
 	 * not interested in interface additions. we will not back walk
 	 * to resolve paths through newly added interfaces. Why? The control
 	 * plane should have the brains to add interfaces first, then routes.
 	 * So the case where there are paths with a interface that matches
 	 * one just created is the case where the path resolved through an
 	 * interface that was deleted, and still has not been removed. The
 	 * new interface added, is NO GUARANTEE that the interface being
 	 * added now, even though it may have the same sw_if_index, is the
 	 * same interface that the path needs. So tough!
 	 * If the control plane wants these routes to resolve it needs to
 	 * remove and add them again.
 	 */
 	return (NULL);
     }

     for (proto = FIB_PROTOCOL_IP4; proto <= FIB_PROTOCOL_IP6; proto++)
     {
 	if (sw_if_index >= vec_len(adj_mcasts[proto]) ||
 	    ADJ_INDEX_INVALID == adj_mcasts[proto][sw_if_index])
 	    continue;

 	adj = adj_get(adj_mcasts[proto][sw_if_index]);

 	fib_node_back_walk_ctx_t bw_ctx = {
 	    .fnbw_reason =  FIB_NODE_BW_REASON_FLAG_INTERFACE_DELETE,
 	};

 	fib_walk_sync(FIB_NODE_TYPE_ADJ, adj_get_index(adj), &bw_ctx);
     }

     return (NULL);
 }

 VNET_SW_INTERFACE_ADD_DEL_FUNCTION(adj_mcast_interface_delete);

 /**
  * @brief Walk the multicast Adjacencies on a given interface
  */
 void
 adj_mcast_walk (u32 sw_if_index,
                 fib_protocol_t proto,
                 adj_walk_cb_t cb,
                 void *ctx)
 {
     if (vec_len(adj_mcasts[proto]) > sw_if_index)
     {
         if (ADJ_INDEX_INVALID != adj_mcasts[proto][sw_if_index])
         {
             cb(adj_mcasts[proto][sw_if_index], ctx);
         }
     }
 }

 u8*
 format_adj_mcast (u8* s, va_list *ap)
 {
     index_t index = va_arg(*ap, index_t);
     CLIB_UNUSED(u32 indent) = va_arg(*ap, u32);
     ip_adjacency_t * adj = adj_get(index);

     s = format(s, "%U-mcast: ",
                format_fib_protocol, adj->ia_nh_proto);
     if (adj->rewrite_header.flags & VNET_REWRITE_HAS_FEATURES)
         s = format(s, "[features] ");
     s = format (s, "%U",
 		format_vnet_rewrite,
                 &adj->rewrite_header, sizeof (adj->rewrite_data), 0);

     return (s);
 }

 u8*
 format_adj_mcast_midchain (u8* s, va_list *ap)
 {
     index_t index = va_arg(*ap, index_t);
     CLIB_UNUSED(u32 indent) = va_arg(*ap, u32);
     vnet_main_t * vnm = vnet_get_main();
     ip_adjacency_t * adj = adj_get(index);

     s = format(s, "%U-mcast-midchain: ",
                format_fib_protocol, adj->ia_nh_proto);
     s = format (s, "%U",
 		format_vnet_rewrite,
 		vnm->vlib_main, &adj->rewrite_header,
                 sizeof (adj->rewrite_data), 0);
     s = format (s, "\n%Ustacked-on:\n%U%U",
 		format_white_space, indent,
 		format_white_space, indent+2,
 		format_dpo_id, &adj->sub_type.midchain.next_dpo, indent+2);

     return (s);
 }


 static void
 adj_dpo_lock (dpo_id_t *dpo)
 {
     adj_lock(dpo->dpoi_index);
 }
 static void
 adj_dpo_unlock (dpo_id_t *dpo)
 {
     adj_unlock(dpo->dpoi_index);
 }

 const static dpo_vft_t adj_mcast_dpo_vft = {
     .dv_lock = adj_dpo_lock,
     .dv_unlock = adj_dpo_unlock,
     .dv_format = format_adj_mcast,
 };
 const static dpo_vft_t adj_mcast_midchain_dpo_vft = {
     .dv_lock = adj_dpo_lock,
     .dv_unlock = adj_dpo_unlock,
     .dv_format = format_adj_mcast_midchain,
 };

 /**
  * @brief The per-protocol VLIB graph nodes that are assigned to a mcast
  *        object.
  *
  * this means that these graph nodes are ones from which a mcast is the
  * parent object in the DPO-graph.
  */
 const static char* const adj_mcast_ip4_nodes[] =
 {
     "ip4-rewrite-mcast",
     NULL,
 };
 const static char* const adj_mcast_ip6_nodes[] =
 {
     "ip6-rewrite-mcast",
     NULL,
 };

 const static char* const * const adj_mcast_nodes[DPO_PROTO_NUM] =
 {
     [DPO_PROTO_IP4]  = adj_mcast_ip4_nodes,
     [DPO_PROTO_IP6]  = adj_mcast_ip6_nodes,
     [DPO_PROTO_MPLS] = NULL,
 };

 /**
  * @brief The per-protocol VLIB graph nodes that are assigned to a mcast
  *        object.
  *
  * this means that these graph nodes are ones from which a mcast is the
  * parent object in the DPO-graph.
  */
 const static char* const adj_mcast_midchain_ip4_nodes[] =
 {
     "ip4-mcast-midchain",
     NULL,
 };
 const static char* const adj_mcast_midchain_ip6_nodes[] =
 {
     "ip6-mcast-midchain",
     NULL,
 };

 const static char* const * const adj_mcast_midchain_nodes[DPO_PROTO_NUM] =
 {
     [DPO_PROTO_IP4]  = adj_mcast_midchain_ip4_nodes,
     [DPO_PROTO_IP6]  = adj_mcast_midchain_ip6_nodes,
     [DPO_PROTO_MPLS] = NULL,
 };

 /**
  * @brief Return the size of the adj DB.
  * This is only for testing purposes so an efficient implementation is not needed
  */
 u32
 adj_mcast_db_size (void)
 {
     u32 n_adjs, sw_if_index;
     fib_protocol_t proto;

     n_adjs = 0;
     for (proto = FIB_PROTOCOL_IP4; proto <= FIB_PROTOCOL_IP6; proto++)
     {
         for (sw_if_index = 0;
              sw_if_index < vec_len(adj_mcasts[proto]);
              sw_if_index++)
         {
             if (ADJ_INDEX_INVALID != adj_mcasts[proto][sw_if_index])
             {
                 n_adjs++;
             }
         }
     }

     return (n_adjs);
 }

 void
 adj_mcast_module_init (void)
 {
     dpo_register(DPO_ADJACENCY_MCAST,
                  &adj_mcast_dpo_vft,
                  adj_mcast_nodes);
     dpo_register(DPO_ADJACENCY_MCAST_MIDCHAIN,
                  &adj_mcast_midchain_dpo_vft,
                  adj_mcast_midchain_nodes);
 }
	/*
	* Copyright (c) 2016 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/adj/adj_mcast.h>
	#include <vnet/adj/adj_internal.h>
	#include <vnet/fib/fib_walk.h>
	#include <vnet/ip/ip.h>

	/*
	* The 'DB' of all mcast adjs.
	* There is only one mcast per-interface per-protocol, so this is a per-interface
	* vector
	*/
	static adj_index_t *adj_mcasts[FIB_PROTOCOL_MAX];

	static u32
	adj_get_mcast_node (fib_protocol_t proto)
	{
	switch (proto) {
	case FIB_PROTOCOL_IP4:
	return (ip4_rewrite_mcast_node.index);
	case FIB_PROTOCOL_IP6:
	return (ip6_rewrite_mcast_node.index);
	case FIB_PROTOCOL_MPLS:
	break;
	}
	ASSERT(0);
	return (0);
	}

	/*
	* adj_mcast_add_or_lock
	*
	* The next_hop address here is used for source address selection in the DP.
	* The mcast adj is added to an interface's connected prefix, the next-hop
	* passed here is the local prefix on the same interface.
	*/
	adj_index_t
	adj_mcast_add_or_lock (fib_protocol_t proto,
	vnet_link_t link_type,
	u32 sw_if_index)
	{
	ip_adjacency_t * adj;

	vec_validate_init_empty(adj_mcasts[proto], sw_if_index, ADJ_INDEX_INVALID);

	if (ADJ_INDEX_INVALID == adj_mcasts[proto][sw_if_index])
	{
	vnet_main_t *vnm;

	vnm = vnet_get_main();
	adj = adj_alloc(proto);

	adj->lookup_next_index = IP_LOOKUP_NEXT_MCAST;
	adj->ia_nh_proto = proto;
	adj->ia_link = link_type;
	adj_mcasts[proto][sw_if_index] = adj_get_index(adj);
	adj_lock(adj_get_index(adj));

	vnet_rewrite_init(vnm, sw_if_index,
	adj_get_mcast_node(proto),
	vnet_tx_node_index_for_sw_interface(vnm, sw_if_index),
	&adj->rewrite_header);

	/*
	* we need a rewrite where the destination IP address is converted
	* to the appropriate link-layer address. This is interface specific.
	* So ask the interface to do it.
	*/
	vnet_update_adjacency_for_sw_interface(vnm, sw_if_index,
	adj_get_index(adj));
	}
	else
	{
	adj = adj_get(adj_mcasts[proto][sw_if_index]);
	adj_lock(adj_get_index(adj));
	}

	return (adj_get_index(adj));
	}

	/**
	* adj_mcast_update_rewrite
	*
	* Update the adjacency's rewrite string. A NULL string implies the
	* rewirte is reset (i.e. when ARP/ND etnry is gone).
	* NB: the adj being updated may be handling traffic in the DP.
	*/
	void
	adj_mcast_update_rewrite (adj_index_t adj_index,
	u8 *rewrite,
	u8 offset,
	u32 mask)
	{
	ip_adjacency_t *adj;

	ASSERT(ADJ_INDEX_INVALID != adj_index);

	adj = adj_get(adj_index);

	/*
	* update the adj's rewrite string and build the arc
	* from the rewrite node to the interface's TX node
	*/
	adj_nbr_update_rewrite_internal(adj, IP_LOOKUP_NEXT_MCAST,
	adj_get_mcast_node(adj->ia_nh_proto),
	vnet_tx_node_index_for_sw_interface(
	vnet_get_main(),
	adj->rewrite_header.sw_if_index),
	rewrite);
	/*
	* set the fields corresponding to the mcast IP address rewrite
	* The mask must be stored in network byte order, since the packet's
	* IP address will also be in network order.
	*/
	adj->rewrite_header.dst_mcast_offset = offset;
	adj->rewrite_header.dst_mcast_mask = clib_host_to_net_u32(mask);
	}

	/**
	* adj_mcast_midchain_update_rewrite
	*
	* Update the adjacency's rewrite string. A NULL string implies the
	* rewirte is reset (i.e. when ARP/ND etnry is gone).
	* NB: the adj being updated may be handling traffic in the DP.
	*/
	void
	adj_mcast_midchain_update_rewrite (adj_index_t adj_index,
	adj_midchain_fixup_t fixup,
	adj_flags_t flags,
	u8 *rewrite,
	u8 offset,
	u32 mask)
	{
	ip_adjacency_t *adj;

	ASSERT(ADJ_INDEX_INVALID != adj_index);

	adj = adj_get(adj_index);

	/*
	* one time only update. since we don't support chainging the tunnel
	* src,dst, this is all we need.
	*/
	ASSERT(adj->lookup_next_index == IP_LOOKUP_NEXT_MCAST);
	/*
	* tunnels can always provide a rewrite.
	*/
	ASSERT(NULL != rewrite);

	adj_midchain_setup(adj_index, fixup, flags);

	/*
	* update the adj's rewrite string and build the arc
	* from the rewrite node to the interface's TX node
	*/
	adj_nbr_update_rewrite_internal(adj, IP_LOOKUP_NEXT_MCAST_MIDCHAIN,
	adj_get_mcast_node(adj->ia_nh_proto),
	vnet_tx_node_index_for_sw_interface(
	vnet_get_main(),
	adj->rewrite_header.sw_if_index),
	rewrite);

	/*
	* set the fields corresponding to the mcast IP address rewrite
	* The mask must be stored in network byte order, since the packet's
	* IP address will also be in network order.
	*/
	adj->rewrite_header.dst_mcast_offset = offset;
	adj->rewrite_header.dst_mcast_mask = clib_host_to_net_u32(mask);
	}

	void
	adj_mcast_remove (fib_protocol_t proto,
	u32 sw_if_index)
	{
	ASSERT(sw_if_index < vec_len(adj_mcasts[proto]));

	adj_mcasts[proto][sw_if_index] = ADJ_INDEX_INVALID;
	}

	static clib_error_t *
	adj_mcast_interface_state_change (vnet_main_t * vnm,
	u32 sw_if_index,
	u32 flags)
	{
	/*
	* for each mcast on the interface trigger a walk back to the children
	*/
	fib_protocol_t proto;
	ip_adjacency_t *adj;


	for (proto = FIB_PROTOCOL_IP4; proto <= FIB_PROTOCOL_IP6; proto++)
	{
	if (sw_if_index >= vec_len(adj_mcasts[proto]) \|\|
	ADJ_INDEX_INVALID == adj_mcasts[proto][sw_if_index])
	continue;

	adj = adj_get(adj_mcasts[proto][sw_if_index]);

	fib_node_back_walk_ctx_t bw_ctx = {
	.fnbw_reason = (flags & VNET_SW_INTERFACE_FLAG_ADMIN_UP ?
	FIB_NODE_BW_REASON_FLAG_INTERFACE_UP :
	FIB_NODE_BW_REASON_FLAG_INTERFACE_DOWN),
	};

	fib_walk_sync(FIB_NODE_TYPE_ADJ, adj_get_index(adj), &bw_ctx);
	}

	return (NULL);
	}

	VNET_SW_INTERFACE_ADMIN_UP_DOWN_FUNCTION(adj_mcast_interface_state_change);

	/**
	* @brief Invoked on each SW interface of a HW interface when the
	* HW interface state changes
	*/
	static void
	adj_nbr_hw_sw_interface_state_change (vnet_main_t * vnm,
	u32 sw_if_index,
	void *arg)
	{
	adj_mcast_interface_state_change(vnm, sw_if_index, (uword) arg);
	}

	/**
	* @brief Registered callback for HW interface state changes
	*/
	static clib_error_t *
	adj_mcast_hw_interface_state_change (vnet_main_t * vnm,
	u32 hw_if_index,
	u32 flags)
	{
	/*
	* walk SW interfaces on the HW
	*/
	uword sw_flags;

	sw_flags = ((flags & VNET_HW_INTERFACE_FLAG_LINK_UP) ?
	VNET_SW_INTERFACE_FLAG_ADMIN_UP :
	0);

	vnet_hw_interface_walk_sw(vnm, hw_if_index,
	adj_nbr_hw_sw_interface_state_change,
	(void*) sw_flags);

	return (NULL);
	}

	VNET_HW_INTERFACE_LINK_UP_DOWN_FUNCTION(
	adj_mcast_hw_interface_state_change);

	static clib_error_t *
	adj_mcast_interface_delete (vnet_main_t * vnm,
	u32 sw_if_index,
	u32 is_add)
	{
	/*
	* for each mcast on the interface trigger a walk back to the children
	*/
	fib_protocol_t proto;
	ip_adjacency_t *adj;

	if (is_add)
	{
	/*
	* not interested in interface additions. we will not back walk
	* to resolve paths through newly added interfaces. Why? The control
	* plane should have the brains to add interfaces first, then routes.
	* So the case where there are paths with a interface that matches
	* one just created is the case where the path resolved through an
	* interface that was deleted, and still has not been removed. The
	* new interface added, is NO GUARANTEE that the interface being
	* added now, even though it may have the same sw_if_index, is the
	* same interface that the path needs. So tough!
	* If the control plane wants these routes to resolve it needs to
	* remove and add them again.
	*/
	return (NULL);
	}

	for (proto = FIB_PROTOCOL_IP4; proto <= FIB_PROTOCOL_IP6; proto++)
	{
	if (sw_if_index >= vec_len(adj_mcasts[proto]) \|\|
	ADJ_INDEX_INVALID == adj_mcasts[proto][sw_if_index])
	continue;

	adj = adj_get(adj_mcasts[proto][sw_if_index]);

	fib_node_back_walk_ctx_t bw_ctx = {
	.fnbw_reason = FIB_NODE_BW_REASON_FLAG_INTERFACE_DELETE,
	};

	fib_walk_sync(FIB_NODE_TYPE_ADJ, adj_get_index(adj), &bw_ctx);
	}

	return (NULL);
	}

	VNET_SW_INTERFACE_ADD_DEL_FUNCTION(adj_mcast_interface_delete);

	/**
	* @brief Walk the multicast Adjacencies on a given interface
	*/
	void
	adj_mcast_walk (u32 sw_if_index,
	fib_protocol_t proto,
	adj_walk_cb_t cb,
	void *ctx)
	{
	if (vec_len(adj_mcasts[proto]) > sw_if_index)
	{
	if (ADJ_INDEX_INVALID != adj_mcasts[proto][sw_if_index])
	{
	cb(adj_mcasts[proto][sw_if_index], ctx);
	}
	}
	}

	u8*
	format_adj_mcast (u8* s, va_list *ap)
	{
	index_t index = va_arg(*ap, index_t);
	CLIB_UNUSED(u32 indent) = va_arg(*ap, u32);
	ip_adjacency_t * adj = adj_get(index);

	s = format(s, "%U-mcast: ",
	format_fib_protocol, adj->ia_nh_proto);
	if (adj->rewrite_header.flags & VNET_REWRITE_HAS_FEATURES)
	s = format(s, "[features] ");
	s = format (s, "%U",
	format_vnet_rewrite,
	&adj->rewrite_header, sizeof (adj->rewrite_data), 0);

	return (s);
	}

	u8*
	format_adj_mcast_midchain (u8* s, va_list *ap)
	{
	index_t index = va_arg(*ap, index_t);
	CLIB_UNUSED(u32 indent) = va_arg(*ap, u32);
	vnet_main_t * vnm = vnet_get_main();
	ip_adjacency_t * adj = adj_get(index);

	s = format(s, "%U-mcast-midchain: ",
	format_fib_protocol, adj->ia_nh_proto);
	s = format (s, "%U",
	format_vnet_rewrite,
	vnm->vlib_main, &adj->rewrite_header,
	sizeof (adj->rewrite_data), 0);
	s = format (s, "\n%Ustacked-on:\n%U%U",
	format_white_space, indent,
	format_white_space, indent+2,
	format_dpo_id, &adj->sub_type.midchain.next_dpo, indent+2);

	return (s);
	}


	static void
	adj_dpo_lock (dpo_id_t *dpo)
	{
	adj_lock(dpo->dpoi_index);
	}
	static void
	adj_dpo_unlock (dpo_id_t *dpo)
	{
	adj_unlock(dpo->dpoi_index);
	}

	const static dpo_vft_t adj_mcast_dpo_vft = {
	.dv_lock = adj_dpo_lock,
	.dv_unlock = adj_dpo_unlock,
	.dv_format = format_adj_mcast,
	};
	const static dpo_vft_t adj_mcast_midchain_dpo_vft = {
	.dv_lock = adj_dpo_lock,
	.dv_unlock = adj_dpo_unlock,
	.dv_format = format_adj_mcast_midchain,
	};

	/**
	* @brief The per-protocol VLIB graph nodes that are assigned to a mcast
	* object.
	*
	* this means that these graph nodes are ones from which a mcast is the
	* parent object in the DPO-graph.
	*/
	const static char* const adj_mcast_ip4_nodes[] =
	{
	"ip4-rewrite-mcast",
	NULL,
	};
	const static char* const adj_mcast_ip6_nodes[] =
	{
	"ip6-rewrite-mcast",
	NULL,
	};

	const static char* const * const adj_mcast_nodes[DPO_PROTO_NUM] =
	{
	[DPO_PROTO_IP4] = adj_mcast_ip4_nodes,
	[DPO_PROTO_IP6] = adj_mcast_ip6_nodes,
	[DPO_PROTO_MPLS] = NULL,
	};

	/**
	* @brief The per-protocol VLIB graph nodes that are assigned to a mcast
	* object.
	*
	* this means that these graph nodes are ones from which a mcast is the
	* parent object in the DPO-graph.
	*/
	const static char* const adj_mcast_midchain_ip4_nodes[] =
	{
	"ip4-mcast-midchain",
	NULL,
	};
	const static char* const adj_mcast_midchain_ip6_nodes[] =
	{
	"ip6-mcast-midchain",
	NULL,
	};

	const static char* const * const adj_mcast_midchain_nodes[DPO_PROTO_NUM] =
	{
	[DPO_PROTO_IP4] = adj_mcast_midchain_ip4_nodes,
	[DPO_PROTO_IP6] = adj_mcast_midchain_ip6_nodes,
	[DPO_PROTO_MPLS] = NULL,
	};

	/**
	* @brief Return the size of the adj DB.
	* This is only for testing purposes so an efficient implementation is not needed
	*/
	u32
	adj_mcast_db_size (void)
	{
	u32 n_adjs, sw_if_index;
	fib_protocol_t proto;

	n_adjs = 0;
	for (proto = FIB_PROTOCOL_IP4; proto <= FIB_PROTOCOL_IP6; proto++)
	{
	for (sw_if_index = 0;
	sw_if_index < vec_len(adj_mcasts[proto]);
	sw_if_index++)
	{
	if (ADJ_INDEX_INVALID != adj_mcasts[proto][sw_if_index])
	{
	n_adjs++;
	}
	}
	}

	return (n_adjs);
	}

	void
	adj_mcast_module_init (void)
	{
	dpo_register(DPO_ADJACENCY_MCAST,
	&adj_mcast_dpo_vft,
	adj_mcast_nodes);
	dpo_register(DPO_ADJACENCY_MCAST_MIDCHAIN,
	&adj_mcast_midchain_dpo_vft,
	adj_mcast_midchain_nodes);
	}