src/vnet/fib/fib_entry_src.c

/*
 * 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.h>
#include <vnet/dpo/load_balance.h>
#include <vnet/dpo/mpls_label_dpo.h>
#include <vnet/dpo/drop_dpo.h>

#include <vnet/fib/fib_entry_src.h>
#include <vnet/fib/fib_table.h>
#include <vnet/fib/fib_path_ext.h>
#include <vnet/fib/fib_urpf_list.h>

/*
 * per-source type vft
 */
static fib_entry_src_vft_t fib_entry_src_vft[FIB_SOURCE_MAX];

static fib_protocol_t
fib_entry_get_proto (const fib_entry_t * fib_entry)
{
    return (fib_entry->fe_prefix.fp_proto);
}

void
fib_entry_src_register (fib_source_t source,
			const fib_entry_src_vft_t *vft)
{
    fib_entry_src_vft[source] = *vft;
}

static int
fib_entry_src_cmp_for_sort (void * v1,
			    void * v2)
{
    fib_entry_src_t *esrc1 = v1, *esrc2 = v2;

    return (esrc1->fes_src - esrc2->fes_src);
}

void
fib_entry_src_action_init (fib_entry_t *fib_entry,
			   fib_source_t source)

{
    fib_entry_src_t esrc = {
	.fes_pl = FIB_NODE_INDEX_INVALID,
	.fes_flags = FIB_ENTRY_SRC_FLAG_NONE,
	.fes_src = source,
    };

    if (NULL != fib_entry_src_vft[source].fesv_init)
    {
	fib_entry_src_vft[source].fesv_init(&esrc);
    }

    vec_add1(fib_entry->fe_srcs, esrc);
    vec_sort_with_function(fib_entry->fe_srcs,
			   fib_entry_src_cmp_for_sort);
}

static fib_entry_src_t *
fib_entry_src_find (const fib_entry_t *fib_entry,
		    fib_source_t source,
		    u32 *index)

{
    fib_entry_src_t *esrc;
    int ii;

    ii = 0;
    vec_foreach(esrc, fib_entry->fe_srcs)
    {
	if (esrc->fes_src == source)
	{
	    if (NULL != index)
	    {
		*index = ii;
	    }
	    return (esrc);
	}
	else
	{
	    ii++;
	}
    }

    return (NULL);
}

int
fib_entry_is_sourced (fib_node_index_t fib_entry_index,
                      fib_source_t source)
{
    fib_entry_t *fib_entry;

    fib_entry = fib_entry_get(fib_entry_index);

    return (NULL != fib_entry_src_find(fib_entry, source, NULL));
}

static fib_entry_src_t *
fib_entry_src_find_or_create (fib_entry_t *fib_entry,
			      fib_source_t source,
			      u32 *index)
{
    fib_entry_src_t *esrc;

    esrc = fib_entry_src_find(fib_entry, source, NULL);

    if (NULL == esrc)
    {
	fib_entry_src_action_init(fib_entry, source);
    }

    return (fib_entry_src_find(fib_entry, source, NULL));
}

void
fib_entry_src_action_deinit (fib_entry_t *fib_entry,
			     fib_source_t source)

{
    fib_entry_src_t *esrc;
    u32 index = ~0;

    esrc = fib_entry_src_find(fib_entry, source, &index);

    ASSERT(NULL != esrc);

    if (NULL != fib_entry_src_vft[source].fesv_deinit)
    {
	fib_entry_src_vft[source].fesv_deinit(esrc);
    }

    vec_free(esrc->fes_path_exts);
    vec_del1(fib_entry->fe_srcs, index);
}

fib_entry_src_cover_res_t
fib_entry_src_action_cover_change (fib_entry_t *fib_entry,
				   fib_source_t source)
{
    if (NULL != fib_entry_src_vft[source].fesv_cover_change)
    {
	return (fib_entry_src_vft[source].fesv_cover_change(
		    fib_entry_src_find(fib_entry, source, NULL),
		    fib_entry));
    }

    fib_entry_src_cover_res_t res = {
	.install = !0,
	.bw_reason = FIB_NODE_BW_REASON_FLAG_NONE,
    };
    return (res);
}

fib_entry_src_cover_res_t
fib_entry_src_action_cover_update (fib_entry_t *fib_entry,
				   fib_source_t source)
{
    if (NULL != fib_entry_src_vft[source].fesv_cover_update)
    {
	return (fib_entry_src_vft[source].fesv_cover_update(
		    fib_entry_src_find(fib_entry, source, NULL),
		    fib_entry));
    }

    fib_entry_src_cover_res_t res = {
	.install = !0,
	.bw_reason = FIB_NODE_BW_REASON_FLAG_NONE,
    };
    return (res);
}

typedef struct fib_entry_src_collect_forwarding_ctx_t_
{
    load_balance_path_t * next_hops;
    const fib_entry_t *fib_entry;
    const fib_entry_src_t *esrc;
    fib_forward_chain_type_t fct;
    int is_recursive;
} fib_entry_src_collect_forwarding_ctx_t;

/**
 * @brief Determine whether this FIB entry should use a load-balance MAP
 * to support PIC edge fast convergence
 */
load_balance_flags_t
fib_entry_calc_lb_flags (fib_entry_src_collect_forwarding_ctx_t *ctx)
{
    /**
     * We'll use a LB map is the path-list has recursive paths.
     * recursive paths implies BGP, and hence scale.
     */
    if (ctx->is_recursive)
    {
        return (LOAD_BALANCE_FLAG_USES_MAP);
    }
    return (LOAD_BALANCE_FLAG_NONE);
}

static int
fib_entry_src_valid_out_label (mpls_label_t label)
{
    return ((MPLS_LABEL_IS_REAL(label) ||
             MPLS_IETF_IPV4_EXPLICIT_NULL_LABEL == label ||
             MPLS_IETF_IPV6_EXPLICIT_NULL_LABEL == label ||
             MPLS_IETF_IMPLICIT_NULL_LABEL == label));
}

/**
 * @brief Turn the chain type requested by the client into the one they
 * really wanted
 */
fib_forward_chain_type_t
fib_entry_chain_type_fixup (const fib_entry_t *entry,
			    fib_forward_chain_type_t fct)
{
    ASSERT(FIB_FORW_CHAIN_TYPE_MPLS_EOS == fct);

    /*
     * The EOS chain is a tricky since one cannot know the adjacency
     * to link to without knowing what the packets payload protocol
     * will be once the label is popped.
     */
    fib_forward_chain_type_t dfct;

    dfct = fib_entry_get_default_chain_type(entry);

    if (FIB_FORW_CHAIN_TYPE_MPLS_EOS == dfct)
    {
        /*
         * If the entry being asked is a eos-MPLS label entry,
         * then use the payload-protocol field, that we stashed there
         * for just this purpose
         */
        return (fib_forw_chain_type_from_dpo_proto(
                    entry->fe_prefix.fp_payload_proto));
    }
    /*
     * else give them what this entry would be by default. i.e. if it's a v6
     * entry, then the label its local labelled should be carrying v6 traffic.
     * If it's a non-EOS label entry, then there are more labels and we want
     * a non-eos chain.
     */
    return (dfct);
}

static int
fib_entry_src_collect_forwarding (fib_node_index_t pl_index,
                                  fib_node_index_t path_index,
                                  void *arg)
{
    fib_entry_src_collect_forwarding_ctx_t *ctx;
    fib_path_ext_t *path_ext;

    ctx = arg;

    /*
     * if the path is not resolved, don't include it.
     */
    if (!fib_path_is_resolved(path_index))
    {
        return (!0);
    }

    if (fib_path_is_recursive(path_index))
    {
        ctx->is_recursive = 1;
    }

    /*
     * get the matching path-extension for the path being visited.
     */
    vec_foreach(path_ext, ctx->esrc->fes_path_exts)
    {
        if (path_ext->fpe_path_index == path_index)
            break;
    }
    
    if (NULL != path_ext &&
        path_ext->fpe_path_index == path_index &&
        fib_entry_src_valid_out_label(path_ext->fpe_label_stack[0]))
    {
        /*
         * found a matching extension. stack it to obtain the forwarding
         * info for this path.
         */
        ctx->next_hops = fib_path_ext_stack(path_ext, ctx->fib_entry, ctx->fct, ctx->next_hops);
    }
    else
    {
        load_balance_path_t *nh;

        /*
         * no extension => no out-going label for this path. that's OK
         * in the case of an IP or EOS chain, but not for non-EOS
         */
        switch (ctx->fct)
        {
        case FIB_FORW_CHAIN_TYPE_UNICAST_IP4:
        case FIB_FORW_CHAIN_TYPE_UNICAST_IP6:
        case FIB_FORW_CHAIN_TYPE_MCAST_IP4:
        case FIB_FORW_CHAIN_TYPE_MCAST_IP6:
            /*
             * EOS traffic with no label to stack, we need the IP Adj
             */
            vec_add2(ctx->next_hops, nh, 1);

            nh->path_index = path_index;
            nh->path_weight = fib_path_get_weight(path_index);
            fib_path_contribute_forwarding(path_index, ctx->fct, &nh->path_dpo);

            break;
        case FIB_FORW_CHAIN_TYPE_MPLS_NON_EOS:
	    if (fib_path_is_exclusive(path_index) ||
		fib_path_is_deag(path_index))
	    {
		vec_add2(ctx->next_hops, nh, 1);

		nh->path_index = path_index;
		nh->path_weight = fib_path_get_weight(path_index);
		fib_path_contribute_forwarding(path_index,
					       FIB_FORW_CHAIN_TYPE_MPLS_NON_EOS,
					       &nh->path_dpo);
	    }
            break;
        case FIB_FORW_CHAIN_TYPE_MPLS_EOS:
        {
            /*
             * no label. we need a chain based on the payload. fixup.
             */
            vec_add2(ctx->next_hops, nh, 1);

            nh->path_index = path_index;
            nh->path_weight = fib_path_get_weight(path_index);
            fib_path_contribute_forwarding(path_index,
                                           fib_entry_chain_type_fixup(ctx->fib_entry,
                                                                      ctx->fct),
                                           &nh->path_dpo);

            break;
        }
        case FIB_FORW_CHAIN_TYPE_ETHERNET:
	    ASSERT(0);
	    break;
        }
    }

    return (!0);
}

void
fib_entry_src_mk_lb (fib_entry_t *fib_entry,
		     const fib_entry_src_t *esrc,
		     fib_forward_chain_type_t fct,
		     dpo_id_t *dpo_lb)
{
    dpo_proto_t lb_proto;

    /*
     * If the entry has path extensions then we construct a load-balance
     * by stacking the extensions on the forwarding chains of the paths.
     * Otherwise we use the load-balance of the path-list
     */
    fib_entry_src_collect_forwarding_ctx_t ctx = {
        .esrc = esrc,
        .fib_entry = fib_entry,
        .next_hops = NULL,
        .is_recursive = 0,
        .fct = fct,
    };

    /*
     * As an optimisation we allocate the vector of next-hops to be sized
     * equal to the maximum nuber of paths we will need, which is also the
     * most likely number we will need, since in most cases the paths are 'up'.
     */
    vec_validate(ctx.next_hops, fib_path_list_get_n_paths(esrc->fes_pl));
    vec_reset_length(ctx.next_hops);

    lb_proto = fib_proto_to_dpo(fib_entry->fe_prefix.fp_proto);

    fib_path_list_walk(esrc->fes_pl,
                       fib_entry_src_collect_forwarding,
                       &ctx);

    if (esrc->fes_entry_flags & FIB_ENTRY_FLAG_EXCLUSIVE)
    {
	/*
	 * the client provided the DPO that the entry should link to.
	 * all entries must link to a LB, so if it is an LB already
	 * then we can use it.
	 */
	if ((1 == vec_len(ctx.next_hops)) &&
	    (DPO_LOAD_BALANCE == ctx.next_hops[0].path_dpo.dpoi_type))
	{
	    dpo_copy(dpo_lb, &ctx.next_hops[0].path_dpo);
	    dpo_reset(&ctx.next_hops[0].path_dpo);
	    return;
	}
    }

    if (!dpo_id_is_valid(dpo_lb))
    {
        /*
         * first time create
         */
        flow_hash_config_t fhc;

        fhc = fib_table_get_flow_hash_config(fib_entry->fe_fib_index,
                                             dpo_proto_to_fib(lb_proto));
        dpo_set(dpo_lb,
                DPO_LOAD_BALANCE,
                lb_proto,
                load_balance_create(0, lb_proto, fhc));
    }

    load_balance_multipath_update(dpo_lb,
                                  ctx.next_hops,
                                  fib_entry_calc_lb_flags(&ctx));
    vec_free(ctx.next_hops);

    /*
     * if this entry is sourced by the uRPF-exempt source then we
     * append the always present local0 interface (index 0) to the
     * uRPF list so it is not empty. that way packets pass the loose check.
     */
    index_t ui = fib_path_list_get_urpf(esrc->fes_pl);

    if (fib_entry_is_sourced(fib_entry_get_index(fib_entry),
			     FIB_SOURCE_URPF_EXEMPT) &&
	(0 == fib_urpf_check_size(ui)))
    {
	/*
	 * The uRPF list we get from the path-list is shared by all
	 * other users of the list, but the uRPF exemption applies
	 * only to this prefix. So we need our own list.
	 */
	ui = fib_urpf_list_alloc_and_lock();
	fib_urpf_list_append(ui, 0);
	fib_urpf_list_bake(ui);
	load_balance_set_urpf(dpo_lb->dpoi_index, ui);
	fib_urpf_list_unlock(ui);
    }
    else
    {
	load_balance_set_urpf(dpo_lb->dpoi_index, ui);
    }
    load_balance_set_fib_entry_flags(dpo_lb->dpoi_index,
                                     fib_entry_get_flags_i(fib_entry));
}

void
fib_entry_src_action_install (fib_entry_t *fib_entry,
			      fib_source_t source)
{
    /*
     * Install the forwarding chain for the given source into the forwarding
     * tables
     */
    fib_forward_chain_type_t fct;
    fib_entry_src_t *esrc;
    int insert;

    fct = fib_entry_get_default_chain_type(fib_entry);
    esrc = fib_entry_src_find(fib_entry, source, NULL);

    /*
     * Every entry has its own load-balance object. All changes to the entry's
     * forwarding result in an inplace modify of the load-balance. This means
     * the load-balance object only needs to be added to the forwarding
     * DB once, when it is created.
     */
    insert = !dpo_id_is_valid(&fib_entry->fe_lb);

    fib_entry_src_mk_lb(fib_entry, esrc, fct, &fib_entry->fe_lb);

    ASSERT(dpo_id_is_valid(&fib_entry->fe_lb));
    FIB_ENTRY_DBG(fib_entry, "install: %d", fib_entry->fe_lb);

    /*
     * insert the adj into the data-plane forwarding trie
     */
    if (insert)
    {
       fib_table_fwding_dpo_update(fib_entry->fe_fib_index,
                                   &fib_entry->fe_prefix,
                                   &fib_entry->fe_lb);
    }

    /*
     * if any of the other chain types are already created they will need
     * updating too
     */
    fib_entry_delegate_type_t fdt;
    fib_entry_delegate_t *fed;

    FOR_EACH_DELEGATE_CHAIN(fib_entry, fdt, fed,
    {
        fib_entry_src_mk_lb(fib_entry, esrc,
                            fib_entry_delegate_type_to_chain_type(fdt),
                            &fed->fd_dpo);
    });
}

void
fib_entry_src_action_uninstall (fib_entry_t *fib_entry)
{
    /*
     * uninstall the forwarding chain from the forwarding tables
     */
    FIB_ENTRY_DBG(fib_entry, "uninstall: %d",
		  fib_entry->fe_adj_index);

    if (dpo_id_is_valid(&fib_entry->fe_lb))
    {
	fib_table_fwding_dpo_remove(
	    fib_entry->fe_fib_index,
	    &fib_entry->fe_prefix,
	    &fib_entry->fe_lb);

	dpo_reset(&fib_entry->fe_lb);
    }
}

static void
fib_entry_recursive_loop_detect_i (fib_node_index_t path_list_index)
{
    fib_node_index_t *entries = NULL;

    fib_path_list_recursive_loop_detect(path_list_index, &entries);

    vec_free(entries);
}

void
fib_entry_src_action_activate (fib_entry_t *fib_entry,
			       fib_source_t source)

{
    int houston_we_are_go_for_install;
    fib_entry_src_t *esrc;

    esrc = fib_entry_src_find(fib_entry, source, NULL);

    ASSERT(!(esrc->fes_flags & FIB_ENTRY_SRC_FLAG_ACTIVE));
    ASSERT(esrc->fes_flags & FIB_ENTRY_SRC_FLAG_ADDED);

    esrc->fes_flags |= FIB_ENTRY_SRC_FLAG_ACTIVE;

    if (NULL != fib_entry_src_vft[source].fesv_activate)
    {
	houston_we_are_go_for_install =
	    fib_entry_src_vft[source].fesv_activate(esrc, fib_entry);
    }
    else
    {
	/*
	 * the source is not providing an activate function, we'll assume
	 * therefore it has no objection to installing the entry
	 */
	houston_we_are_go_for_install = !0;
    }

    /*
     * link to the path-list provided by the source, and go check
     * if that forms any loops in the graph.
     */
    fib_entry->fe_parent = esrc->fes_pl;
    fib_entry->fe_sibling =
	fib_path_list_child_add(fib_entry->fe_parent,
				FIB_NODE_TYPE_ENTRY,
				fib_entry_get_index(fib_entry));

    fib_entry_recursive_loop_detect_i(fib_entry->fe_parent);

    FIB_ENTRY_DBG(fib_entry, "activate: %d",
		  fib_entry->fe_parent);

    if (0 != houston_we_are_go_for_install)
    {
	fib_entry_src_action_install(fib_entry, source);
    }
    else
    {
	fib_entry_src_action_uninstall(fib_entry);
    }
}

void
fib_entry_src_action_deactivate (fib_entry_t *fib_entry,
				 fib_source_t source)

{
    fib_node_index_t path_list_index;
    fib_entry_src_t *esrc;

    esrc = fib_entry_src_find(fib_entry, source, NULL);

    ASSERT(esrc->fes_flags & FIB_ENTRY_SRC_FLAG_ACTIVE);

    if (NULL != fib_entry_src_vft[source].fesv_deactivate)
    {
	fib_entry_src_vft[source].fesv_deactivate(esrc, fib_entry);
    }

    esrc->fes_flags &= ~FIB_ENTRY_SRC_FLAG_ACTIVE;

    FIB_ENTRY_DBG(fib_entry, "deactivate: %d", fib_entry->fe_parent);

    /*
     * un-link from an old path-list. Check for any loops this will clear
     */
    path_list_index = fib_entry->fe_parent;
    fib_entry->fe_parent = FIB_NODE_INDEX_INVALID;

    fib_entry_recursive_loop_detect_i(path_list_index);

    /*
     * this will unlock the path-list, so it may be invalid thereafter.
     */
    fib_path_list_child_remove(path_list_index, fib_entry->fe_sibling);
    fib_entry->fe_sibling = FIB_NODE_INDEX_INVALID;
}

static void
fib_entry_src_action_fwd_update (const fib_entry_t *fib_entry,
				 fib_source_t source)
{
    fib_entry_src_t *esrc;

    vec_foreach(esrc, fib_entry->fe_srcs)
    {
	if (NULL != fib_entry_src_vft[esrc->fes_src].fesv_fwd_update)
	{
	    fib_entry_src_vft[esrc->fes_src].fesv_fwd_update(esrc,
							     fib_entry,
							     source);
	}
    }
}

void
fib_entry_src_action_reactivate (fib_entry_t *fib_entry,
				 fib_source_t source)
{
    fib_node_index_t path_list_index;
    fib_entry_src_t *esrc;

    esrc = fib_entry_src_find(fib_entry, source, NULL);

    ASSERT(esrc->fes_flags & FIB_ENTRY_SRC_FLAG_ACTIVE);

    FIB_ENTRY_DBG(fib_entry, "reactivate: %d to %d",
		  fib_entry->fe_parent,
		  esrc->fes_pl);

    if (fib_entry->fe_parent != esrc->fes_pl)
    {
	/*
	 * un-link from an old path-list. Check for any loops this will clear
	 */
	path_list_index = fib_entry->fe_parent;
	fib_entry->fe_parent = FIB_NODE_INDEX_INVALID;

	/*
	 * temporary lock so it doesn't get deleted when this entry is no
	 * longer a child.
	 */
	fib_path_list_lock(path_list_index);

	/*
	 * this entry is no longer a child. after unlinking check if any loops
	 * were broken
	 */
	fib_path_list_child_remove(path_list_index,
				   fib_entry->fe_sibling);

	fib_entry_recursive_loop_detect_i(path_list_index);

	/*
	 * link to the path-list provided by the source, and go check
	 * if that forms any loops in the graph.
	 */
	fib_entry->fe_parent = esrc->fes_pl;
	fib_entry->fe_sibling =
	    fib_path_list_child_add(fib_entry->fe_parent,
				    FIB_NODE_TYPE_ENTRY,
				    fib_entry_get_index(fib_entry));

	fib_entry_recursive_loop_detect_i(fib_entry->fe_parent);
	fib_path_list_unlock(path_list_index);
    }
    fib_entry_src_action_install(fib_entry, source);
    fib_entry_src_action_fwd_update(fib_entry, source);
}

void
fib_entry_src_action_installed (const fib_entry_t *fib_entry,
				fib_source_t source)
{
    fib_entry_src_t *esrc;

    esrc = fib_entry_src_find(fib_entry, source, NULL);

    if (NULL != fib_entry_src_vft[source].fesv_installed)
    {
	fib_entry_src_vft[source].fesv_installed(esrc,
						 fib_entry);
    }

    fib_entry_src_action_fwd_update(fib_entry, source);
}

/*
 * fib_entry_src_action_add
 *
 * Adding a source can result in a new fib_entry being created, which
 * can inturn mean the pool is realloc'd and thus the entry passed as
 * an argument it also realloc'd
 * @return the original entry
 */
fib_entry_t *
fib_entry_src_action_add (fib_entry_t *fib_entry,
			  fib_source_t source,
			  fib_entry_flag_t flags,
			  const dpo_id_t *dpo)
{
    fib_node_index_t fib_entry_index;
    fib_entry_src_t *esrc;

    esrc = fib_entry_src_find_or_create(fib_entry, source, NULL);

    esrc->fes_ref_count++;

    if (1 != esrc->fes_ref_count)
    {
        /*
         * we only want to add the source on the 0->1 transition
         */
        return (fib_entry);
    }

    esrc->fes_entry_flags = flags;

    /*
     * save variable so we can recover from a fib_entry realloc.
     */
    fib_entry_index = fib_entry_get_index(fib_entry);

    if (NULL != fib_entry_src_vft[source].fesv_add)
    {
	fib_entry_src_vft[source].fesv_add(esrc,
					   fib_entry,
					   flags,
					   fib_entry_get_proto(fib_entry),
					   dpo);
    }

    fib_entry = fib_entry_get(fib_entry_index);

    esrc->fes_flags |= FIB_ENTRY_SRC_FLAG_ADDED;

    fib_path_list_lock(esrc->fes_pl);

    /*
     * the source owns a lock on the entry
     */
    fib_entry_lock(fib_entry_get_index(fib_entry));

    return (fib_entry);
}

/*
 * fib_entry_src_action_update
 *
 * Adding a source can result in a new fib_entry being created, which
 * can inturn mean the pool is realloc'd and thus the entry passed as
 * an argument it also realloc'd
 * @return the original entry
 */
fib_entry_t *
fib_entry_src_action_update (fib_entry_t *fib_entry,
			     fib_source_t source,
			     fib_entry_flag_t flags,
			     const dpo_id_t *dpo)
{
    fib_node_index_t fib_entry_index, old_path_list_index;
    fib_entry_src_t *esrc;

    esrc = fib_entry_src_find_or_create(fib_entry, source, NULL);

    if (NULL == esrc)
	return (fib_entry_src_action_add(fib_entry, source, flags, dpo));

    old_path_list_index = esrc->fes_pl;
    esrc->fes_entry_flags = flags;

    /*
     * save variable so we can recover from a fib_entry realloc.
     */
    fib_entry_index = fib_entry_get_index(fib_entry);

    if (NULL != fib_entry_src_vft[source].fesv_add)
    {
	fib_entry_src_vft[source].fesv_add(esrc,
					   fib_entry,
					   flags,
					   fib_entry_get_proto(fib_entry),
					   dpo);
    }

    fib_entry = fib_entry_get(fib_entry_index);

    esrc->fes_flags |= FIB_ENTRY_SRC_FLAG_ADDED;

    fib_path_list_lock(esrc->fes_pl);
    fib_path_list_unlock(old_path_list_index);

    return (fib_entry);
}


fib_entry_src_flag_t
fib_entry_src_action_remove (fib_entry_t *fib_entry,
			     fib_source_t source)

{
    fib_node_index_t old_path_list;
    fib_entry_src_flag_t sflags;
    fib_entry_src_t *esrc;

    esrc = fib_entry_src_find(fib_entry, source, NULL);

    if (NULL == esrc)
	return (FIB_ENTRY_SRC_FLAG_ACTIVE);

    esrc->fes_ref_count--;
    sflags = esrc->fes_flags;

    if (0 != esrc->fes_ref_count)
    {
        /*
         * only remove the source on the 1->0 transisition
         */
        return (sflags);
    }

    if (esrc->fes_flags & FIB_ENTRY_SRC_FLAG_ACTIVE)
    {
	fib_entry_src_action_deactivate(fib_entry, source);
    }

    old_path_list = esrc->fes_pl;

    if (NULL != fib_entry_src_vft[source].fesv_remove)
    {
	fib_entry_src_vft[source].fesv_remove(esrc);
    }

    fib_path_list_unlock(old_path_list);
    fib_entry_unlock(fib_entry_get_index(fib_entry));

    sflags &= ~FIB_ENTRY_SRC_FLAG_ADDED;
    fib_entry_src_action_deinit(fib_entry, source);

    return (sflags);
}

static inline int
fib_route_recurses_via_self (const fib_prefix_t *prefix,
			     const fib_route_path_t *rpath)
{
    /*
     * not all zeros next hop &&
     * is recursive path &&
     * nexthop is same as the route's address
     */
    return ((!ip46_address_is_zero(&rpath->frp_addr)) &&
	    (~0 == rpath->frp_sw_if_index) &&
	    (0 == ip46_address_cmp(&rpath->frp_addr, &prefix->fp_addr)));

}

/*
 * fib_route_attached_cross_table
 *
 * Return true the the route is attached via an interface that
 * is not in the same table as the route
 */
static inline int
fib_route_attached_cross_table (const fib_entry_t *fib_entry,
				const fib_route_path_t *rpath)
{
    /*
     * - All zeros next-hop
     * - a valid interface
     * - entry's fib index not equeal to interface's index
     */
    if (ip46_address_is_zero(&rpath->frp_addr) &&
	(~0 != rpath->frp_sw_if_index) &&
	(fib_entry->fe_fib_index != 
	 fib_table_get_index_for_sw_if_index(fib_entry_get_proto(fib_entry),
					     rpath->frp_sw_if_index)))
    {
	return (!0);
    }
    return (0);
}

/*
 * fib_route_attached_cross_table
 *
 * Return true the the route is attached via an interface that
 * is not in the same table as the route
 */
static inline int
fib_path_is_attached (const fib_route_path_t *rpath)
{
    /*
     * - All zeros next-hop
     * - a valid interface
     */
    if (ip46_address_is_zero(&rpath->frp_addr) &&
	(~0 != rpath->frp_sw_if_index))
    {
	return (!0);
    }
    return (0);
}

fib_path_list_flags_t
fib_entry_src_flags_2_path_list_flags (fib_entry_flag_t eflags)
{
    fib_path_list_flags_t plf = FIB_PATH_LIST_FLAG_NONE;

    if (eflags & FIB_ENTRY_FLAG_DROP)
    {
	plf |= FIB_PATH_LIST_FLAG_DROP;
    }
    if (eflags & FIB_ENTRY_FLAG_LOCAL)
    {
	plf |= FIB_PATH_LIST_FLAG_LOCAL;
    }
    if (eflags & FIB_ENTRY_FLAG_EXCLUSIVE)
    {
	plf |= FIB_PATH_LIST_FLAG_EXCLUSIVE;
    }

    return (plf);
}

static void
fib_entry_flags_update (const fib_entry_t *fib_entry,
			const fib_route_path_t *rpath,
			fib_path_list_flags_t *pl_flags,
			fib_entry_src_t *esrc)
{
    /*
     * don't allow the addition of a recursive looped path for prefix
     * via itself.
     */
    if (fib_route_recurses_via_self(&fib_entry->fe_prefix, rpath))	
    {
	/*
	 * force the install of a drop path-list.
	 * we want the entry to have some path-list, mainly so
	 * the dodgy path can be rmeoved when the source stops playing
	 * silly buggers.
	 */
	*pl_flags |= FIB_PATH_LIST_FLAG_DROP;
    }
    else
    {
	*pl_flags &= ~FIB_PATH_LIST_FLAG_DROP;
    }

    if ((esrc->fes_src == FIB_SOURCE_API) ||
	(esrc->fes_src == FIB_SOURCE_CLI))
    {
	if (fib_path_is_attached(rpath))
	{
	    esrc->fes_entry_flags |= FIB_ENTRY_FLAG_ATTACHED;
	}
	else
	{
	    esrc->fes_entry_flags &= ~FIB_ENTRY_FLAG_ATTACHED;
	}
    }
    if (fib_route_attached_cross_table(fib_entry, rpath))
    {
	esrc->fes_entry_flags |= FIB_ENTRY_FLAG_IMPORT;
    }
    else
    {
	esrc->fes_entry_flags &= ~FIB_ENTRY_FLAG_IMPORT;
    }
}

/*
 * fib_entry_src_path_ext_add
 *
 * append a path extension to the entry's list
 */
static void
fib_entry_src_path_ext_append (fib_entry_src_t *esrc,
			       const fib_route_path_t *rpath)
{
    if (NULL != rpath->frp_label_stack)
    {
	fib_path_ext_t *path_ext;

	vec_add2(esrc->fes_path_exts, path_ext, 1);

	fib_path_ext_init(path_ext, esrc->fes_pl, rpath);
    }
}

/*
 * fib_entry_src_path_ext_insert
 *
 * insert, sorted, a path extension to the entry's list.
 * It's not strictly necessary in sort the path extensions, since each
 * extension has the path index to which it resolves. However, by being
 * sorted the load-balance produced has a deterministic order, not an order
 * based on the sequence of extension additions. this is a considerable benefit.
 */
static void
fib_entry_src_path_ext_insert (fib_entry_src_t *esrc,
			       const fib_route_path_t *rpath)
{
    if (0 == vec_len(esrc->fes_path_exts))
	return (fib_entry_src_path_ext_append(esrc, rpath));

    if (NULL != rpath->frp_label_stack)
    {
	fib_path_ext_t path_ext;
	int i = 0;

	fib_path_ext_init(&path_ext, esrc->fes_pl, rpath);

	while (i < vec_len(esrc->fes_path_exts) &&
	       (fib_path_ext_cmp(&esrc->fes_path_exts[i], rpath) < 0))
	{
	    i++;
	}

	vec_insert_elts(esrc->fes_path_exts, &path_ext, 1, i);
    }
}

/*
 * fib_entry_src_action_add
 *
 * Adding a source can result in a new fib_entry being created, which
 * can inturn mean the pool is realloc'd and thus the entry passed as
 * an argument it also realloc'd
 * @return the entry
 */
fib_entry_t*
fib_entry_src_action_path_add (fib_entry_t *fib_entry,
			       fib_source_t source,
			       fib_entry_flag_t flags,
			       const fib_route_path_t *rpath)
{
    fib_node_index_t old_path_list, fib_entry_index;
    fib_path_list_flags_t pl_flags;
    fib_path_ext_t *path_ext;
    fib_entry_src_t *esrc;

    /*
     * save variable so we can recover from a fib_entry realloc.
     */
    fib_entry_index = fib_entry_get_index(fib_entry);

    esrc = fib_entry_src_find(fib_entry, source, NULL);
    if (NULL == esrc)
    {
	fib_entry =
            fib_entry_src_action_add(fib_entry,
                                     source,
                                     flags,
                                     drop_dpo_get(
                                         fib_proto_to_dpo(
                                             fib_entry_get_proto(fib_entry))));
	esrc = fib_entry_src_find(fib_entry, source, NULL);
    }

    /*
     * we are no doubt modifying a path-list. If the path-list
     * is shared, and hence not modifiable, then the index returned
     * will be for a different path-list. This FIB entry to needs
     * to maintain its lock appropriately.
     */
    old_path_list = esrc->fes_pl;

    ASSERT(NULL != fib_entry_src_vft[source].fesv_path_add);

    pl_flags = fib_entry_src_flags_2_path_list_flags(fib_entry_get_flags_i(fib_entry));
    fib_entry_flags_update(fib_entry, rpath, &pl_flags, esrc);

    fib_entry_src_vft[source].fesv_path_add(esrc, fib_entry, pl_flags, rpath);
    fib_entry = fib_entry_get(fib_entry_index);

    /*
     * re-resolve all the path-extensions with the new path-list
     */
    vec_foreach(path_ext, esrc->fes_path_exts)
    {
	fib_path_ext_resolve(path_ext, esrc->fes_pl);
    }
    /*
     * if the path has a label we need to add a path extension
     */
    fib_entry_src_path_ext_insert(esrc, rpath);

    fib_path_list_lock(esrc->fes_pl);
    fib_path_list_unlock(old_path_list);

    return (fib_entry);
}

/*
 * fib_entry_src_action_swap
 *
 * The source is providing new paths to replace the old ones.
 * Adding a source can result in a new fib_entry being created, which
 * can inturn mean the pool is realloc'd and thus the entry passed as
 * an argument it also realloc'd
 * @return the entry
 */
fib_entry_t*
fib_entry_src_action_path_swap (fib_entry_t *fib_entry,
				fib_source_t source,
				fib_entry_flag_t flags,				
				const fib_route_path_t *rpaths)
{
    fib_node_index_t old_path_list, fib_entry_index;
    fib_path_list_flags_t pl_flags;
    const fib_route_path_t *rpath;
    fib_path_ext_t *path_ext;
    fib_entry_src_t *esrc;

    esrc = fib_entry_src_find(fib_entry, source, NULL);

    /*
     * save variable so we can recover from a fib_entry realloc.
     */
    fib_entry_index = fib_entry_get_index(fib_entry);

    if (NULL == esrc)
    {
	fib_entry = fib_entry_src_action_add(fib_entry,
					     source,
					     flags,
                                             drop_dpo_get(
                                                 fib_proto_to_dpo(
                                                     fib_entry_get_proto(fib_entry))));
	esrc = fib_entry_src_find(fib_entry, source, NULL);
    }

    /*
     * swapping paths may create a new path-list (or may use an existing shared)
     * but we are certainly getting a different one. This FIB entry to needs
     * to maintain its lock appropriately.
     */
    old_path_list = esrc->fes_pl;

    ASSERT(NULL != fib_entry_src_vft[source].fesv_path_swap);

    pl_flags = fib_entry_src_flags_2_path_list_flags(flags);

    vec_foreach(rpath, rpaths)
    {
	fib_entry_flags_update(fib_entry, rpath, &pl_flags, esrc);
    }

    fib_entry_src_vft[source].fesv_path_swap(esrc,
					     fib_entry,
					     pl_flags,
					     rpaths);

    vec_foreach(path_ext, esrc->fes_path_exts)
    {
	vec_free(path_ext->fpe_label_stack);
    }
    vec_free(esrc->fes_path_exts);

    vec_foreach(rpath, rpaths)
    {
	fib_entry_src_path_ext_append(esrc, rpath);
    }

    fib_entry = fib_entry_get(fib_entry_index);

    fib_path_list_lock(esrc->fes_pl);
    fib_path_list_unlock(old_path_list);

    return (fib_entry);
}

fib_entry_src_flag_t
fib_entry_src_action_path_remove (fib_entry_t *fib_entry,
				  fib_source_t source,
				  const fib_route_path_t *rpath)
{
    fib_path_list_flags_t pl_flags;
    fib_node_index_t old_path_list;
    fib_path_ext_t *path_ext;
    fib_entry_src_t *esrc;

    esrc = fib_entry_src_find(fib_entry, source, NULL);

    ASSERT(NULL != esrc);
    ASSERT(esrc->fes_flags & FIB_ENTRY_SRC_FLAG_ADDED);

    /*
     * we no doubt modifying a path-list. If the path-list
     * is shared, and hence not modifiable, then the index returned
     * will be for a different path-list. This FIB entry to needs
     * to maintain its lock appropriately.
     */
    old_path_list = esrc->fes_pl;

    ASSERT(NULL != fib_entry_src_vft[source].fesv_path_remove);

    pl_flags = fib_entry_src_flags_2_path_list_flags(fib_entry_get_flags_i(fib_entry));
    fib_entry_flags_update(fib_entry, rpath, &pl_flags, esrc);

    fib_entry_src_vft[source].fesv_path_remove(esrc, pl_flags, rpath);
    /*
     * find the matching path extension and remove it
     */
    vec_foreach(path_ext, esrc->fes_path_exts)
    {
	if (!fib_path_ext_cmp(path_ext, rpath))
	{
	    /*
	     * delete the element moving the remaining elements down 1 position.
	     * this preserves the sorted order.
	     */
	    vec_free(path_ext->fpe_label_stack);
	    vec_delete(esrc->fes_path_exts, 1, (path_ext - esrc->fes_path_exts));
	    break;
	}
    }
    /*
     * re-resolve all the path-extensions with the new path-list
     */
    vec_foreach(path_ext, esrc->fes_path_exts)
    {
	fib_path_ext_resolve(path_ext, esrc->fes_pl);
    }

    /*
     * lock the new path-list, unlock the old if it had one
     */
    fib_path_list_unlock(old_path_list);

    if (FIB_NODE_INDEX_INVALID != esrc->fes_pl) {
	fib_path_list_lock(esrc->fes_pl);
	return (FIB_ENTRY_SRC_FLAG_ADDED);
    }
    else
    {
	/*
	 * no more paths left from this source
	 */
	fib_entry_src_action_remove(fib_entry, source);
	return (FIB_ENTRY_SRC_FLAG_NONE);
    }
}

u8*
fib_entry_src_format (fib_entry_t *fib_entry,
		      fib_source_t source,
		      u8* s)
{
    fib_entry_src_t *esrc;

    esrc = fib_entry_src_find(fib_entry, source, NULL);

    if (NULL != fib_entry_src_vft[source].fesv_format)
    {
	return (fib_entry_src_vft[source].fesv_format(esrc, s));
    }
    return (s);
}

adj_index_t
fib_entry_get_adj_for_source (fib_node_index_t fib_entry_index,
			      fib_source_t source)
{
    fib_entry_t *fib_entry;
    fib_entry_src_t *esrc;

    if (FIB_NODE_INDEX_INVALID == fib_entry_index)
	return (ADJ_INDEX_INVALID);

    fib_entry = fib_entry_get(fib_entry_index);
    esrc = fib_entry_src_find(fib_entry, source, NULL);

    if (NULL != esrc)
    {
	if (FIB_NODE_INDEX_INVALID != esrc->fes_pl)
	{
	    return (fib_path_list_get_adj(
			esrc->fes_pl,
			fib_entry_get_default_chain_type(fib_entry)));
	}
    }
    return (ADJ_INDEX_INVALID);
}

const int
fib_entry_get_dpo_for_source (fib_node_index_t fib_entry_index,
			      fib_source_t source,
			      dpo_id_t *dpo)
{
    fib_entry_t *fib_entry;
    fib_entry_src_t *esrc;

    if (FIB_NODE_INDEX_INVALID == fib_entry_index)
	return (0);

    fib_entry = fib_entry_get(fib_entry_index);
    esrc = fib_entry_src_find(fib_entry, source, NULL);

    if (NULL != esrc)
    {
	if (FIB_NODE_INDEX_INVALID != esrc->fes_pl)
	{
	    fib_path_list_contribute_forwarding(
		esrc->fes_pl,
		fib_entry_get_default_chain_type(fib_entry),
		dpo);

	    return (dpo_id_is_valid(dpo));
	}
    }
    return (0);
}

u32
fib_entry_get_resolving_interface_for_source (fib_node_index_t entry_index,
					      fib_source_t source)
{
    fib_entry_t *fib_entry;
    fib_entry_src_t *esrc;

    fib_entry = fib_entry_get(entry_index);

    esrc = fib_entry_src_find(fib_entry, source, NULL);

    if (NULL != esrc)
    {
	if (FIB_NODE_INDEX_INVALID != esrc->fes_pl)
	{
	    return (fib_path_list_get_resolving_interface(esrc->fes_pl));
	}
    }
    return (~0);
}

fib_entry_flag_t
fib_entry_get_flags_for_source (fib_node_index_t entry_index,
				fib_source_t source)
{
    fib_entry_t *fib_entry;
    fib_entry_src_t *esrc;

    fib_entry = fib_entry_get(entry_index);

    esrc = fib_entry_src_find(fib_entry, source, NULL);

    if (NULL != esrc)
    {
	return (esrc->fes_entry_flags);
    }

    return (FIB_ENTRY_FLAG_NONE);
}

fib_entry_flag_t
fib_entry_get_flags_i (const fib_entry_t *fib_entry)
{
    fib_entry_flag_t flags;

    /*
     * the vector of sources is deliberately arranged in priority order
     */
    if (0 == vec_len(fib_entry->fe_srcs))
    {
	flags = FIB_ENTRY_FLAG_NONE;
    }
    else
    {
	fib_entry_src_t *esrc;

	esrc = vec_elt_at_index(fib_entry->fe_srcs, 0);
	flags = esrc->fes_entry_flags;
    }

    return (flags);
}

void
fib_entry_set_source_data (fib_node_index_t fib_entry_index,
                           fib_source_t source,
                           const void *data)
{
    fib_entry_t *fib_entry;
    fib_entry_src_t *esrc;

    fib_entry = fib_entry_get(fib_entry_index);
    esrc = fib_entry_src_find(fib_entry, source, NULL);

    if (NULL != esrc &&
        NULL != fib_entry_src_vft[source].fesv_set_data)
    {
	fib_entry_src_vft[source].fesv_set_data(esrc, fib_entry, data);
    }
}

const void*
fib_entry_get_source_data (fib_node_index_t fib_entry_index,
                           fib_source_t source)
{
    fib_entry_t *fib_entry;
    fib_entry_src_t *esrc;

    fib_entry = fib_entry_get(fib_entry_index);
    esrc = fib_entry_src_find(fib_entry, source, NULL);

    if (NULL != esrc &&
        NULL != fib_entry_src_vft[source].fesv_get_data)
    {
	return (fib_entry_src_vft[source].fesv_get_data(esrc, fib_entry));
    }
    return (NULL);
}

void
fib_entry_src_module_init (void)
{
    fib_entry_src_rr_register();
    fib_entry_src_interface_register();
    fib_entry_src_default_route_register();
    fib_entry_src_special_register();
    fib_entry_src_api_register();
    fib_entry_src_adj_register();
    fib_entry_src_mpls_register();
    fib_entry_src_lisp_register();
}