/src/frr/ospfd/ospf_spf.c

Source
// SPDX-License-Identifier: GPL-2.0-or-later
/* OSPF SPF calculation.
 * Copyright (C) 1999, 2000 Kunihiro Ishiguro, Toshiaki Takada
 */

#include <zebra.h>

#include "monotime.h"
#include "frrevent.h"
#include "memory.h"
#include "hash.h"
#include "linklist.h"
#include "prefix.h"
#include "if.h"
#include "table.h"
#include "log.h"
#include "sockunion.h" /* for inet_ntop () */

#include "ospfd/ospfd.h"
#include "ospfd/ospf_interface.h"
#include "ospfd/ospf_ism.h"
#include "ospfd/ospf_asbr.h"
#include "ospfd/ospf_lsa.h"
#include "ospfd/ospf_lsdb.h"
#include "ospfd/ospf_neighbor.h"
#include "ospfd/ospf_nsm.h"
#include "ospfd/ospf_spf.h"
#include "ospfd/ospf_route.h"
#include "ospfd/ospf_ia.h"
#include "ospfd/ospf_ase.h"
#include "ospfd/ospf_abr.h"
#include "ospfd/ospf_dump.h"
#include "ospfd/ospf_sr.h"
#include "ospfd/ospf_ti_lfa.h"
#include "ospfd/ospf_errors.h"

#ifdef SUPPORT_OSPF_API
#include "ospfd/ospf_apiserver.h"
#endif

/* Variables to ensure a SPF scheduled log message is printed only once */

static unsigned int spf_reason_flags = 0;

/* dummy vertex to flag "in spftree" */
static const struct vertex vertex_in_spftree = {};
#define LSA_SPF_IN_SPFTREE  (struct vertex *)&vertex_in_spftree
#define LSA_SPF_NOT_EXPLORED  NULL

static void ospf_clear_spf_reason_flags(void)
{
  spf_reason_flags = 0;
}

static void ospf_spf_set_reason(ospf_spf_reason_t reason)
{
  spf_reason_flags |= 1 << reason;
}

static void ospf_vertex_free(void *);

/*
 * Heap related functions, for the managment of the candidates, to
 * be used with pqueue.
 */
static int vertex_cmp(const struct vertex *v1, const struct vertex *v2)
{
  if (v1->distance != v2->distance)
    return v1->distance - v2->distance;

  if (v1->type != v2->type) {
    switch (v1->type) {
    case OSPF_VERTEX_NETWORK:
      return -1;
    case OSPF_VERTEX_ROUTER:
      return 1;
    }
  }
  return 0;
}
DECLARE_SKIPLIST_NONUNIQ(vertex_pqueue, struct vertex, pqi, vertex_cmp);

static void lsdb_clean_stat(struct ospf_lsdb *lsdb)
{
  struct route_table *table;
  struct route_node *rn;
  struct ospf_lsa *lsa;
  int i;

  for (i = OSPF_MIN_LSA; i < OSPF_MAX_LSA; i++) {
    table = lsdb->type[i].db;
    for (rn = route_top(table); rn; rn = route_next(rn))
      if ((lsa = (rn->info)) != NULL)
        lsa->stat = LSA_SPF_NOT_EXPLORED;
  }
}

static struct vertex_nexthop *vertex_nexthop_new(void)
{
  return XCALLOC(MTYPE_OSPF_NEXTHOP, sizeof(struct vertex_nexthop));
}

static void vertex_nexthop_free(struct vertex_nexthop *nh)
{
  XFREE(MTYPE_OSPF_NEXTHOP, nh);
}

/*
 * Free the canonical nexthop objects for an area, ie the nexthop objects
 * attached to the first-hop router vertices, and any intervening network
 * vertices.
 */
static void ospf_canonical_nexthops_free(struct vertex *root)
{
  struct listnode *node, *nnode;
  struct vertex *child;

  for (ALL_LIST_ELEMENTS(root->children, node, nnode, child)) {
    struct listnode *n2, *nn2;
    struct vertex_parent *vp;

    /*
     * router vertices through an attached network each
     * have a distinct (canonical / not inherited) nexthop
     * which must be freed.
     *
     * A network vertex can only have router vertices as its
     * children, so only one level of recursion is possible.
     */
    if (child->type == OSPF_VERTEX_NETWORK)
      ospf_canonical_nexthops_free(child);

    /* Free child nexthops pointing back to this root vertex */
    for (ALL_LIST_ELEMENTS(child->parents, n2, nn2, vp)) {
      if (vp->parent == root && vp->nexthop) {
        vertex_nexthop_free(vp->nexthop);
        vp->nexthop = NULL;
        if (vp->local_nexthop) {
          vertex_nexthop_free(vp->local_nexthop);
          vp->local_nexthop = NULL;
        }
      }
    }
  }
}

/*
 * TODO: Parent list should be excised, in favour of maintaining only
 * vertex_nexthop, with refcounts.
 */
static struct vertex_parent *vertex_parent_new(struct vertex *v, int backlink,
                 struct vertex_nexthop *hop,
                 struct vertex_nexthop *lhop)
{
  struct vertex_parent *new;

  new = XMALLOC(MTYPE_OSPF_VERTEX_PARENT, sizeof(struct vertex_parent));

  new->parent = v;
  new->backlink = backlink;
  new->nexthop = hop;
  new->local_nexthop = lhop;

  return new;
}

static void vertex_parent_free(struct vertex_parent *p)
{
  vertex_nexthop_free(p->local_nexthop);
  vertex_nexthop_free(p->nexthop);
  XFREE(MTYPE_OSPF_VERTEX_PARENT, p);
}

int vertex_parent_cmp(void *aa, void *bb)
{
  struct vertex_parent *a = aa, *b = bb;
  return IPV4_ADDR_CMP(&a->nexthop->router, &b->nexthop->router);
}

static struct vertex *ospf_vertex_new(struct ospf_area *area,
              struct ospf_lsa *lsa)
{
  struct vertex *new;

  new = XCALLOC(MTYPE_OSPF_VERTEX, sizeof(struct vertex));

  new->flags = 0;
  new->type = lsa->data->type;
  new->id = lsa->data->id;
  new->lsa = lsa->data;
  new->children = list_new();
  new->parents = list_new();
  new->parents->del = (void (*)(void *))vertex_parent_free;
  new->parents->cmp = vertex_parent_cmp;
  new->lsa_p = lsa;

  lsa->stat = new;

  listnode_add(area->spf_vertex_list, new);

  if (IS_DEBUG_OSPF_EVENT)
    zlog_debug("%s: Created %s vertex %pI4", __func__,
         new->type == OSPF_VERTEX_ROUTER ? "Router"
                 : "Network",
         &new->lsa->id);

  return new;
}

static void ospf_vertex_free(void *data)
{
  struct vertex *v = data;

  if (IS_DEBUG_OSPF_EVENT)
    zlog_debug("%s: Free %s vertex %pI4", __func__,
         v->type == OSPF_VERTEX_ROUTER ? "Router" : "Network",
         &v->lsa->id);

  if (v->children)
    list_delete(&v->children);

  if (v->parents)
    list_delete(&v->parents);

  v->lsa = NULL;

  XFREE(MTYPE_OSPF_VERTEX, v);
}

static void ospf_vertex_dump(const char *msg, struct vertex *v,
           int print_parents, int print_children)
{
  if (!IS_DEBUG_OSPF_EVENT)
    return;

  zlog_debug("%s %s vertex %pI4  distance %u flags %u", msg,
       v->type == OSPF_VERTEX_ROUTER ? "Router" : "Network",
       &v->lsa->id, v->distance, (unsigned int)v->flags);

  if (print_parents) {
    struct listnode *node;
    struct vertex_parent *vp;

    for (ALL_LIST_ELEMENTS_RO(v->parents, node, vp)) {
      if (vp) {
        zlog_debug(
          "parent %pI4 backlink %d nexthop %pI4 lsa pos %d",
          &vp->parent->lsa->id, vp->backlink,
          &vp->nexthop->router,
          vp->nexthop->lsa_pos);
      }
    }
  }

  if (print_children) {
    struct listnode *cnode;
    struct vertex *cv;

    for (ALL_LIST_ELEMENTS_RO(v->children, cnode, cv))
      ospf_vertex_dump(" child:", cv, 0, 0);
  }
}


/* Add a vertex to the list of children in each of its parents. */
static void ospf_vertex_add_parent(struct vertex *v)
{
  struct vertex_parent *vp;
  struct listnode *node;

  assert(v && v->parents);

  for (ALL_LIST_ELEMENTS_RO(v->parents, node, vp)) {
    assert(vp->parent && vp->parent->children);

    /* No need to add two links from the same parent. */
    if (listnode_lookup(vp->parent->children, v) == NULL)
      listnode_add(vp->parent->children, v);
  }
}

/* Find a vertex according to its router id */
struct vertex *ospf_spf_vertex_find(struct in_addr id, struct list *vertex_list)
{
  struct listnode *node;
  struct vertex *found;

  for (ALL_LIST_ELEMENTS_RO(vertex_list, node, found)) {
    if (found->id.s_addr == id.s_addr)
      return found;
  }

  return NULL;
}

/* Find a vertex parent according to its router id */
struct vertex_parent *ospf_spf_vertex_parent_find(struct in_addr id,
              struct vertex *vertex)
{
  struct listnode *node;
  struct vertex_parent *found;

  for (ALL_LIST_ELEMENTS_RO(vertex->parents, node, found)) {
    if (found->parent->id.s_addr == id.s_addr)
      return found;
  }

  return NULL;
}

struct vertex *ospf_spf_vertex_by_nexthop(struct vertex *root,
            struct in_addr *nexthop)
{
  struct listnode *node;
  struct vertex *child;
  struct vertex_parent *vertex_parent;

  for (ALL_LIST_ELEMENTS_RO(root->children, node, child)) {
    vertex_parent = ospf_spf_vertex_parent_find(root->id, child);
    if (vertex_parent->nexthop->router.s_addr == nexthop->s_addr)
      return child;
  }

  return NULL;
}

/* Create a deep copy of a SPF vertex without children and parents */
static struct vertex *ospf_spf_vertex_copy(struct vertex *vertex)
{
  struct vertex *copy;

  copy = XCALLOC(MTYPE_OSPF_VERTEX, sizeof(struct vertex));

  memcpy(copy, vertex, sizeof(struct vertex));
  copy->parents = list_new();
  copy->parents->del = (void (*)(void *))vertex_parent_free;
  copy->parents->cmp = vertex_parent_cmp;
  copy->children = list_new();

  return copy;
}

/* Create a deep copy of a SPF vertex_parent */
static struct vertex_parent *
ospf_spf_vertex_parent_copy(struct vertex_parent *vertex_parent)
{
  struct vertex_parent *vertex_parent_copy;
  struct vertex_nexthop *nexthop_copy, *local_nexthop_copy;

  vertex_parent_copy =
    XCALLOC(MTYPE_OSPF_VERTEX, sizeof(struct vertex_parent));

  nexthop_copy = vertex_nexthop_new();
  local_nexthop_copy = vertex_nexthop_new();

  memcpy(vertex_parent_copy, vertex_parent, sizeof(struct vertex_parent));
  memcpy(nexthop_copy, vertex_parent->nexthop,
         sizeof(struct vertex_nexthop));
  memcpy(local_nexthop_copy, vertex_parent->local_nexthop,
         sizeof(struct vertex_nexthop));

  vertex_parent_copy->nexthop = nexthop_copy;
  vertex_parent_copy->local_nexthop = local_nexthop_copy;

  return vertex_parent_copy;
}

/* Create a deep copy of a SPF tree */
void ospf_spf_copy(struct vertex *vertex, struct list *vertex_list)
{
  struct listnode *node;
  struct vertex *vertex_copy, *child, *child_copy, *parent_copy;
  struct vertex_parent *vertex_parent, *vertex_parent_copy;

  /* First check if the node is already in the vertex list */
  vertex_copy = ospf_spf_vertex_find(vertex->id, vertex_list);
  if (!vertex_copy) {
    vertex_copy = ospf_spf_vertex_copy(vertex);
    listnode_add(vertex_list, vertex_copy);
  }

  /* Copy all parents, create parent nodes if necessary */
  for (ALL_LIST_ELEMENTS_RO(vertex->parents, node, vertex_parent)) {
    parent_copy = ospf_spf_vertex_find(vertex_parent->parent->id,
               vertex_list);
    if (!parent_copy) {
      parent_copy =
        ospf_spf_vertex_copy(vertex_parent->parent);
      listnode_add(vertex_list, parent_copy);
    }
    vertex_parent_copy = ospf_spf_vertex_parent_copy(vertex_parent);
    vertex_parent_copy->parent = parent_copy;
    listnode_add(vertex_copy->parents, vertex_parent_copy);
  }

  /* Copy all children, create child nodes if necessary */
  for (ALL_LIST_ELEMENTS_RO(vertex->children, node, child)) {
    child_copy = ospf_spf_vertex_find(child->id, vertex_list);
    if (!child_copy) {
      child_copy = ospf_spf_vertex_copy(child);
      listnode_add(vertex_list, child_copy);
    }
    listnode_add(vertex_copy->children, child_copy);
  }

  /* Finally continue copying with child nodes */
  for (ALL_LIST_ELEMENTS_RO(vertex->children, node, child))
    ospf_spf_copy(child, vertex_list);
}

static void ospf_spf_remove_branch(struct vertex_parent *vertex_parent,
           struct vertex *child,
           struct list *vertex_list)
{
  struct listnode *node, *nnode, *inner_node, *inner_nnode;
  struct vertex *grandchild;
  struct vertex_parent *vertex_parent_found;
  bool has_more_links = false;

  /*
   * First check if there are more nexthops for that parent to that child
   */
  for (ALL_LIST_ELEMENTS_RO(child->parents, node, vertex_parent_found)) {
    if (vertex_parent_found->parent->id.s_addr
          == vertex_parent->parent->id.s_addr
        && vertex_parent_found->nexthop->router.s_addr
             != vertex_parent->nexthop->router.s_addr)
      has_more_links = true;
  }

  /*
   * No more links from that parent? Then delete the child from its
   * children list.
   */
  if (!has_more_links)
    listnode_delete(vertex_parent->parent->children, child);

  /*
   * Delete the vertex_parent from the child parents list, this needs to
   * be done anyway.
   */
  listnode_delete(child->parents, vertex_parent);

  /*
   * Are there actually more parents left? If not, then delete the child!
   * This is done by recursively removing the links to the grandchildren,
   * such that finally the child can be removed without leaving unused
   * partial branches.
   */
  if (child->parents->count == 0) {
    for (ALL_LIST_ELEMENTS(child->children, node, nnode,
               grandchild)) {
      for (ALL_LIST_ELEMENTS(grandchild->parents, inner_node,
                 inner_nnode,
                 vertex_parent_found)) {
        ospf_spf_remove_branch(vertex_parent_found,
                   grandchild, vertex_list);
      }
    }
    listnode_delete(vertex_list, child);
    ospf_vertex_free(child);
  }
}

static int ospf_spf_remove_link(struct vertex *vertex, struct list *vertex_list,
        struct router_lsa_link *link)
{
  struct listnode *node, *inner_node;
  struct vertex *child;
  struct vertex_parent *vertex_parent;

  /*
   * Identify the node who shares a subnet (given by the link) with a
   * child and remove the branch of this particular child.
   */
  for (ALL_LIST_ELEMENTS_RO(vertex->children, node, child)) {
    for (ALL_LIST_ELEMENTS_RO(child->parents, inner_node,
            vertex_parent)) {
      if ((vertex_parent->local_nexthop->router.s_addr
           & link->link_data.s_addr)
          == (link->link_id.s_addr
        & link->link_data.s_addr)) {
        ospf_spf_remove_branch(vertex_parent, child,
                   vertex_list);
        return 0;
      }
    }
  }

  /* No link found yet, move on recursively */
  for (ALL_LIST_ELEMENTS_RO(vertex->children, node, child)) {
    if (ospf_spf_remove_link(child, vertex_list, link) == 0)
      return 0;
  }

  /* link was not removed yet */
  return 1;
}

void ospf_spf_remove_resource(struct vertex *vertex, struct list *vertex_list,
            struct protected_resource *resource)
{
  struct listnode *node, *nnode;
  struct vertex *found;
  struct vertex_parent *vertex_parent;

  switch (resource->type) {
  case OSPF_TI_LFA_LINK_PROTECTION:
    ospf_spf_remove_link(vertex, vertex_list, resource->link);
    break;
  case OSPF_TI_LFA_NODE_PROTECTION:
    found = ospf_spf_vertex_find(resource->router_id, vertex_list);
    if (!found)
      break;

    /*
     * Remove the node by removing all links from its parents. Note
     * that the child is automatically removed here with the last
     * link from a parent, hence no explicit removal of the node.
     */
    for (ALL_LIST_ELEMENTS(found->parents, node, nnode,
               vertex_parent))
      ospf_spf_remove_branch(vertex_parent, found,
                 vertex_list);

    break;
  case OSPF_TI_LFA_UNDEFINED_PROTECTION:
    /* do nothing */
    break;
  }
}

static void ospf_spf_init(struct ospf_area *area, struct ospf_lsa *root_lsa,
        bool is_dry_run, bool is_root_node)
{
  struct list *vertex_list;
  struct vertex *v;

  /* Create vertex list */
  vertex_list = list_new();
  vertex_list->del = ospf_vertex_free;
  area->spf_vertex_list = vertex_list;

  /* Create root node. */
  v = ospf_vertex_new(area, root_lsa);
  area->spf = v;

  area->spf_dry_run = is_dry_run;
  area->spf_root_node = is_root_node;

  /* Reset ABR and ASBR router counts. */
  area->abr_count = 0;
  area->asbr_count = 0;
}

/* return index of link back to V from W, or -1 if no link found */
static int ospf_lsa_has_link(struct lsa_header *w, struct lsa_header *v)
{
  unsigned int i, length;
  struct router_lsa *rl;
  struct network_lsa *nl;

  /* In case of W is Network LSA. */
  if (w->type == OSPF_NETWORK_LSA) {
    if (v->type == OSPF_NETWORK_LSA)
      return -1;

    nl = (struct network_lsa *)w;
    length = (ntohs(w->length) - OSPF_LSA_HEADER_SIZE - 4) / 4;

    for (i = 0; i < length; i++)
      if (IPV4_ADDR_SAME(&nl->routers[i], &v->id))
        return i;
    return -1;
  }

  /* In case of W is Router LSA. */
  if (w->type == OSPF_ROUTER_LSA) {
    rl = (struct router_lsa *)w;

    length = ntohs(w->length);

    for (i = 0; i < ntohs(rl->links)
          && length >= sizeof(struct router_lsa);
         i++, length -= 12) {
      switch (rl->link[i].type) {
      case LSA_LINK_TYPE_POINTOPOINT:
      case LSA_LINK_TYPE_VIRTUALLINK:
        /* Router LSA ID. */
        if (v->type == OSPF_ROUTER_LSA
            && IPV4_ADDR_SAME(&rl->link[i].link_id,
                  &v->id)) {
          return i;
        }
        break;
      case LSA_LINK_TYPE_TRANSIT:
        /* Network LSA ID. */
        if (v->type == OSPF_NETWORK_LSA
            && IPV4_ADDR_SAME(&rl->link[i].link_id,
                  &v->id)) {
          return i;
        }
        break;
      case LSA_LINK_TYPE_STUB:
        /* Stub can't lead anywhere, carry on */
        continue;
      default:
        break;
      }
    }
  }
  return -1;
}

/*
 * Find the next link after prev_link from v to w.  If prev_link is
 * NULL, return the first link from v to w.  Ignore stub and virtual links;
 * these link types will never be returned.
 */
static struct router_lsa_link *
ospf_get_next_link(struct vertex *v, struct vertex *w,
       struct router_lsa_link *prev_link)
{
  uint8_t *p;
  uint8_t *lim;
  uint8_t lsa_type = LSA_LINK_TYPE_TRANSIT;
  struct router_lsa_link *l;

  if (w->type == OSPF_VERTEX_ROUTER)
    lsa_type = LSA_LINK_TYPE_POINTOPOINT;

  if (prev_link == NULL)
    p = ((uint8_t *)v->lsa) + OSPF_LSA_HEADER_SIZE + 4;
  else {
    p = (uint8_t *)prev_link;
    p += (OSPF_ROUTER_LSA_LINK_SIZE
          + (prev_link->m[0].tos_count * OSPF_ROUTER_LSA_TOS_SIZE));
  }

  lim = ((uint8_t *)v->lsa) + ntohs(v->lsa->length);

  while (p < lim) {
    l = (struct router_lsa_link *)p;

    p += (OSPF_ROUTER_LSA_LINK_SIZE
          + (l->m[0].tos_count * OSPF_ROUTER_LSA_TOS_SIZE));

    if (l->m[0].type != lsa_type)
      continue;

    if (IPV4_ADDR_SAME(&l->link_id, &w->id))
      return l;
  }

  return NULL;
}

static void ospf_spf_flush_parents(struct vertex *w)
{
  struct vertex_parent *vp;
  struct listnode *ln, *nn;

  /* delete the existing nexthops */
  for (ALL_LIST_ELEMENTS(w->parents, ln, nn, vp)) {
    list_delete_node(w->parents, ln);
    vertex_parent_free(vp);
  }
}

/*
 * Consider supplied next-hop for inclusion to the supplied list of
 * equal-cost next-hops, adjust list as necessary.
 *
 * Returns vertex parent pointer if created otherwise `NULL` if it already
 * exists.
 */
static struct vertex_parent *ospf_spf_add_parent(struct vertex *v,
             struct vertex *w,
             struct vertex_nexthop *newhop,
             struct vertex_nexthop *newlhop,
             unsigned int distance)
{
  struct vertex_parent *vp, *wp;
  struct listnode *node;

  /* we must have a newhop, and a distance */
  assert(v && w && newhop);
  assert(distance);

  /*
   * IFF w has already been assigned a distance, then we shouldn't get
   * here unless callers have determined V(l)->W is shortest /
   * equal-shortest path (0 is a special case distance (no distance yet
   * assigned)).
   */
  if (w->distance)
    assert(distance <= w->distance);
  else
    w->distance = distance;

  if (IS_DEBUG_OSPF_EVENT)
    zlog_debug("%s: Adding %pI4 as parent of %pI4", __func__,
         &v->lsa->id, &w->lsa->id);

  /*
   * Adding parent for a new, better path: flush existing parents from W.
   */
  if (distance < w->distance) {
    if (IS_DEBUG_OSPF_EVENT)
      zlog_debug(
        "%s: distance %d better than %d, flushing existing parents",
        __func__, distance, w->distance);
    ospf_spf_flush_parents(w);
    w->distance = distance;
  }

  /*
   * new parent is <= existing parents, add it to parent list (if nexthop
   * not on parent list)
   */
  for (ALL_LIST_ELEMENTS_RO(w->parents, node, wp)) {
    if (memcmp(newhop, wp->nexthop, sizeof(*newhop)) == 0) {
      if (IS_DEBUG_OSPF_EVENT)
        zlog_debug(
          "%s: ... nexthop already on parent list, skipping add",
          __func__);

      return NULL;
    }
  }

  vp = vertex_parent_new(v, ospf_lsa_has_link(w->lsa, v->lsa), newhop,
             newlhop);
  listnode_add_sort(w->parents, vp);

  return vp;
}

static int match_stub_prefix(struct lsa_header *lsa, struct in_addr v_link_addr,
           struct in_addr w_link_addr)
{
  uint8_t *p, *lim;
  struct router_lsa_link *l = NULL;
  struct in_addr masked_lsa_addr;

  if (lsa->type != OSPF_ROUTER_LSA)
    return 0;

  p = ((uint8_t *)lsa) + OSPF_LSA_HEADER_SIZE + 4;
  lim = ((uint8_t *)lsa) + ntohs(lsa->length);

  while (p < lim) {
    l = (struct router_lsa_link *)p;
    p += (OSPF_ROUTER_LSA_LINK_SIZE
          + (l->m[0].tos_count * OSPF_ROUTER_LSA_TOS_SIZE));

    if (l->m[0].type != LSA_LINK_TYPE_STUB)
      continue;

    masked_lsa_addr.s_addr =
      (l->link_id.s_addr & l->link_data.s_addr);

    /* check that both links belong to the same stub subnet */
    if ((masked_lsa_addr.s_addr
         == (v_link_addr.s_addr & l->link_data.s_addr))
        && (masked_lsa_addr.s_addr
      == (w_link_addr.s_addr & l->link_data.s_addr)))
      return 1;
  }

  return 0;
}

/*
 * 16.1.1.  Calculate nexthop from root through V (parent) to
 * vertex W (destination), with given distance from root->W.
 *
 * The link must be supplied if V is the root vertex. In all other cases
 * it may be NULL.
 *
 * Note that this function may fail, hence the state of the destination
 * vertex, W, should /not/ be modified in a dependent manner until
 * this function returns. This function will update the W vertex with the
 * provided distance as appropriate.
 */
static unsigned int ospf_nexthop_calculation(struct ospf_area *area,
               struct vertex *v, struct vertex *w,
               struct router_lsa_link *l,
               unsigned int distance, int lsa_pos)
{
  struct listnode *node, *nnode;
  struct vertex_nexthop *nh, *lnh;
  struct vertex_parent *vp;
  unsigned int added = 0;

  if (IS_DEBUG_OSPF_EVENT) {
    zlog_debug("%s: Start", __func__);
    ospf_vertex_dump("V (parent):", v, 1, 1);
    ospf_vertex_dump("W (dest)  :", w, 1, 1);
    zlog_debug("V->W distance: %d", distance);
  }

  if (v == area->spf) {
    /*
     * 16.1.1 para 4.  In the first case, the parent vertex (V) is
     * the root (the calculating router itself).  This means that
     * the destination is either a directly connected network or
     * directly connected router.  The outgoing interface in this
     * case is simply the OSPF interface connecting to the
     * destination network/router.
     */

    /* we *must* be supplied with the link data */
    assert(l != NULL);

    if (IS_DEBUG_OSPF_EVENT)
      zlog_debug(
        "%s: considering link type:%d link_id:%pI4 link_data:%pI4",
        __func__, l->m[0].type, &l->link_id,
        &l->link_data);

    if (w->type == OSPF_VERTEX_ROUTER) {
      /*
       * l is a link from v to w l2 will be link from w to v
       */
      struct router_lsa_link *l2 = NULL;

      if (l->m[0].type == LSA_LINK_TYPE_POINTOPOINT) {
        struct ospf_interface *oi = NULL;
        struct in_addr nexthop = {.s_addr = 0};

        if (area->spf_root_node) {
          oi = ospf_if_lookup_by_lsa_pos(area,
                       lsa_pos);
          if (!oi) {
            zlog_debug(
              "%s: OI not found in LSA: lsa_pos: %d link_id:%pI4 link_data:%pI4",
              __func__, lsa_pos,
              &l->link_id,
              &l->link_data);
            return 0;
          }
        }

        /*
         * If the destination is a router which connects
         * to the calculating router via a
         * Point-to-MultiPoint network, the
         * destination's next hop IP address(es) can be
         * determined by examining the destination's
         * router-LSA: each link pointing back to the
         * calculating router and having a Link Data
         * field belonging to the Point-to-MultiPoint
         * network provides an IP address of the next
         * hop router.
         *
         * At this point l is a link from V to W, and V
         * is the root ("us"). If it is a point-to-
         * multipoint interface, then look through the
         * links in the opposite direction (W to V).
         * If any of them have an address that lands
         * within the subnet declared by the PtMP link,
         * then that link is a constituent of the PtMP
         * link, and its address is a nexthop address
         * for V.
         *
         * Note for point-to-point interfaces:
         *
         * Having nexthop = 0 (as proposed in the RFC)
         * is tempting, but NOT acceptable. It breaks
         * AS-External routes with a forwarding address,
         * since ospf_ase_complete_direct_routes() will
         * mistakenly assume we've reached the last hop
         * and should place the forwarding address as
         * nexthop. Also, users may configure multi-
         * access links in p2p mode, so we need the IP
         * to ARP the nexthop.
         *
         * If the calculating router is the SPF root
         * node and the link is P2P then access the
         * interface information directly. This can be
         * crucial when e.g. IP unnumbered is used
         * where 'correct' nexthop information are not
         * available via Router LSAs.
         *
         * Otherwise handle P2P and P2MP the same way
         * as described above using a reverse lookup to
         * figure out the nexthop.
         */

        /*
         * HACK: we don't know (yet) how to distinguish
         * between P2P and P2MP interfaces by just
         * looking at LSAs, which is important for
         * TI-LFA since you want to do SPF calculations
         * from the perspective of other nodes. Since
         * TI-LFA is currently not implemented for P2MP
         * we just check here if it is enabled and then
         * blindly assume that P2P is used. Ultimately
         * the interface code needs to be removed
         * somehow.
         */
        if (area->ospf->ti_lfa_enabled
            || (oi && oi->type == OSPF_IFTYPE_POINTOPOINT)
            || (oi && oi->type == OSPF_IFTYPE_POINTOMULTIPOINT
             && oi->address->prefixlen == IPV4_MAX_BITLEN)) {
          struct ospf_neighbor *nbr_w = NULL;

          /* Calculating node is root node, link
           * is P2P */
          if (area->spf_root_node) {
            nbr_w = ospf_nbr_lookup_by_routerid(
              oi->nbrs, &l->link_id);
            if (nbr_w) {
              added = 1;
              nexthop = nbr_w->src;
            }
          }

          /* Reverse lookup */
          if (!added) {
            while ((l2 = ospf_get_next_link(
                w, v, l2))) {
              if (match_stub_prefix(
                    v->lsa,
                    l->link_data,
                    l2->link_data)) {
                added = 1;
                nexthop =
                  l2->link_data;
                break;
              }
            }
          }
        } else if (oi && oi->type
             == OSPF_IFTYPE_POINTOMULTIPOINT) {
          struct prefix_ipv4 la;

          la.family = AF_INET;
          la.prefixlen = oi->address->prefixlen;

          /*
           * V links to W on PtMP interface;
           * find the interface address on W
           */
          while ((l2 = ospf_get_next_link(w, v,
                  l2))) {
            la.prefix = l2->link_data;

            if (prefix_cmp((struct prefix
                  *)&la,
                     oi->address)
                != 0)
              continue;
            added = 1;
            nexthop = l2->link_data;
            break;
          }
        }

        if (added) {
          nh = vertex_nexthop_new();
          nh->router = nexthop;
          nh->lsa_pos = lsa_pos;

          /*
           * Since v is the root the nexthop and
           * local nexthop are the same.
           */
          lnh = vertex_nexthop_new();
          memcpy(lnh, nh,
                 sizeof(struct vertex_nexthop));

          if (ospf_spf_add_parent(v, w, nh, lnh,
                distance) ==
              NULL) {
            vertex_nexthop_free(nh);
            vertex_nexthop_free(lnh);
          }
          return 1;
        } else
          zlog_info(
            "%s: could not determine nexthop for link %s",
            __func__, oi ? oi->ifp->name : "");
      } /* end point-to-point link from V to W */
      else if (l->m[0].type == LSA_LINK_TYPE_VIRTUALLINK) {
        /*
         * VLink implementation limitations:
         * a) vl_data can only reference one nexthop,
         *    so no ECMP to backbone through VLinks.
         *    Though transit-area summaries may be
         *    considered, and those can be ECMP.
         * b) We can only use /one/ VLink, even if
         *    multiple ones exist this router through
         *    multiple transit-areas.
         */

        struct ospf_vl_data *vl_data;

        vl_data = ospf_vl_lookup(area->ospf, NULL,
               l->link_id);

        if (vl_data
            && CHECK_FLAG(vl_data->flags,
              OSPF_VL_FLAG_APPROVED)) {
          nh = vertex_nexthop_new();
          nh->router = vl_data->nexthop.router;
          nh->lsa_pos = vl_data->nexthop.lsa_pos;

          /*
           * Since v is the root the nexthop and
           * local nexthop are the same.
           */
          lnh = vertex_nexthop_new();
          memcpy(lnh, nh,
                 sizeof(struct vertex_nexthop));

          if (ospf_spf_add_parent(v, w, nh, lnh,
                distance) ==
              NULL) {
            vertex_nexthop_free(nh);
            vertex_nexthop_free(lnh);
          }

          return 1;
        } else
          zlog_info(
            "%s: vl_data for VL link not found",
            __func__);
      } /* end virtual-link from V to W */
      return 0;
    } /* end W is a Router vertex */
    else {
      assert(w->type == OSPF_VERTEX_NETWORK);

      nh = vertex_nexthop_new();
      nh->router.s_addr = 0; /* Nexthop not required */
      nh->lsa_pos = lsa_pos;

      /*
       * Since v is the root the nexthop and
       * local nexthop are the same.
       */
      lnh = vertex_nexthop_new();
      memcpy(lnh, nh, sizeof(struct vertex_nexthop));

      if (ospf_spf_add_parent(v, w, nh, lnh, distance) ==
          NULL) {
        vertex_nexthop_free(nh);
        vertex_nexthop_free(lnh);
      }

      return 1;
    }
  } /* end V is the root */
  /* Check if W's parent is a network connected to root. */
  else if (v->type == OSPF_VERTEX_NETWORK) {
    /* See if any of V's parents are the root. */
    for (ALL_LIST_ELEMENTS(v->parents, node, nnode, vp)) {
      if (vp->parent == area->spf) {
        /*
         * 16.1.1 para 5. ...the parent vertex is a
         * network that directly connects the
         * calculating router to the destination
         * router. The list of next hops is then
         * determined by examining the destination's
         * router-LSA ...
         */

        assert(w->type == OSPF_VERTEX_ROUTER);
        while ((l = ospf_get_next_link(w, v, l))) {
          /*
           * ... For each link in the router-LSA
           * that points back to the parent
           * network, the link's Link Data field
           * provides the IP address of a next hop
           * router. The outgoing interface to use
           * can then be derived from the next
           * hop IP address (or it can be
           * inherited from the parent network).
           */
          nh = vertex_nexthop_new();
          nh->router = l->link_data;
          nh->lsa_pos = vp->nexthop->lsa_pos;

          /*
           * Since v is the root the nexthop and
           * local nexthop are the same.
           */
          lnh = vertex_nexthop_new();
          memcpy(lnh, nh,
                 sizeof(struct vertex_nexthop));

          added = 1;
          if (ospf_spf_add_parent(v, w, nh, lnh,
                distance) ==
              NULL) {
            vertex_nexthop_free(nh);
            vertex_nexthop_free(lnh);
          }
        }
        /*
         * Note lack of return is deliberate. See next
         * comment.
         */
      }
    }
    /*
     * NB: This code is non-trivial.
     *
     * E.g. it is not enough to know that V connects to the root. It
     * is also important that the while above, looping through all
     * links from W->V found at least one link, so that we know
     * there is bi-directional connectivity between V and W (which
     * need not be the case, e.g.  when OSPF has not yet converged
     * fully). Otherwise, if we /always/ return here, without having
     * checked that root->V->-W actually resulted in a valid nexthop
     * being created, then we we will prevent SPF from finding/using
     * higher cost paths.
     *
     * It is important, if root->V->W has not been added, that we
     * continue through to the intervening-router nexthop code
     * below. So as to ensure other paths to V may be used. This
     * avoids unnecessary blackholes while OSPF is converging.
     *
     * I.e. we may have arrived at this function, examining V -> W,
     * via workable paths other than root -> V, and it's important
     * to avoid getting "confused" by non-working root->V->W path
     * - it's important to *not* lose the working non-root paths,
     * just because of a non-viable root->V->W.
     */
    if (added)
      return added;
  }

  /*
   * 16.1.1 para 4.  If there is at least one intervening router in the
   * current shortest path between the destination and the root, the
   * destination simply inherits the set of next hops from the
   * parent.
   */
  if (IS_DEBUG_OSPF_EVENT)
    zlog_debug("%s: Intervening routers, adding parent(s)",
         __func__);

  for (ALL_LIST_ELEMENTS(v->parents, node, nnode, vp)) {
    added = 1;

    /*
     * The nexthop is inherited, but the local nexthop still needs
     * to be created.
     */
    if (l) {
      lnh = vertex_nexthop_new();
      lnh->router = l->link_data;
      lnh->lsa_pos = lsa_pos;
    } else {
      lnh = NULL;
    }

    nh = vertex_nexthop_new();
    *nh = *vp->nexthop;

    if (ospf_spf_add_parent(v, w, nh, lnh, distance) == NULL) {
      vertex_nexthop_free(nh);
      vertex_nexthop_free(lnh);
    }
  }

  return added;
}

static int ospf_spf_is_protected_resource(struct ospf_area *area,
            struct router_lsa_link *link,
            struct lsa_header *lsa)
{
  uint8_t *p, *lim;
  struct router_lsa_link *p_link;
  struct router_lsa_link *l = NULL;
  struct in_addr router_id;
  int link_type;

  if (!area->spf_protected_resource)
    return 0;

  link_type = link->m[0].type;

  switch (area->spf_protected_resource->type) {
  case OSPF_TI_LFA_LINK_PROTECTION:
    p_link = area->spf_protected_resource->link;
    if (!p_link)
      return 0;

    /* For P2P: check if the link belongs to the same subnet */
    if (link_type == LSA_LINK_TYPE_POINTOPOINT
        && (p_link->link_id.s_addr & p_link->link_data.s_addr)
             == (link->link_data.s_addr
           & p_link->link_data.s_addr))
      return 1;

    /* For stub: check if this the same subnet */
    if (link_type == LSA_LINK_TYPE_STUB
        && (p_link->link_id.s_addr == link->link_id.s_addr)
        && (p_link->link_data.s_addr == link->link_data.s_addr))
      return 1;

    break;
  case OSPF_TI_LFA_NODE_PROTECTION:
    router_id = area->spf_protected_resource->router_id;
    if (router_id.s_addr == INADDR_ANY)
      return 0;

    /* For P2P: check if the link leads to the protected node */
    if (link_type == LSA_LINK_TYPE_POINTOPOINT
        && link->link_id.s_addr == router_id.s_addr)
      return 1;

    /* The rest is about stub links! */
    if (link_type != LSA_LINK_TYPE_STUB)
      return 0;

    /*
     * Check if there's a P2P link in the router LSA with the
     * corresponding link data in the same subnet.
     */

    p = ((uint8_t *)lsa) + OSPF_LSA_HEADER_SIZE + 4;
    lim = ((uint8_t *)lsa) + ntohs(lsa->length);

    while (p < lim) {
      l = (struct router_lsa_link *)p;
      p += (OSPF_ROUTER_LSA_LINK_SIZE
            + (l->m[0].tos_count * OSPF_ROUTER_LSA_TOS_SIZE));

      /* We only care about P2P with the proper link id */
      if ((l->m[0].type != LSA_LINK_TYPE_POINTOPOINT)
          || (l->link_id.s_addr != router_id.s_addr))
        continue;

      /* Link data in the subnet given by the link? */
      if ((link->link_id.s_addr & link->link_data.s_addr)
          == (l->link_data.s_addr & link->link_data.s_addr))
        return 1;
    }

    break;
  case OSPF_TI_LFA_UNDEFINED_PROTECTION:
    break;
  }

  return 0;
}

/*
 * For TI-LFA we need the reverse SPF for Q spaces. The reverse SPF is created
 * by honoring the weight of the reverse 'edge', e.g. the edge from W to V, and
 * NOT the weight of the 'edge' from V to W as usual. Hence we need to find the
 * corresponding link in the LSA of W and extract the particular weight.
 *
 * TODO: Only P2P supported by now!
 */
static uint16_t get_reverse_distance(struct vertex *v,
             struct router_lsa_link *l,
             struct ospf_lsa *w_lsa)
{
  uint8_t *p, *lim;
  struct router_lsa_link *w_link;
  uint16_t distance = 0;

  assert(w_lsa && w_lsa->data);

  p = ((uint8_t *)w_lsa->data) + OSPF_LSA_HEADER_SIZE + 4;
  lim = ((uint8_t *)w_lsa->data) + ntohs(w_lsa->data->length);

  while (p < lim) {
    w_link = (struct router_lsa_link *)p;
    p += (OSPF_ROUTER_LSA_LINK_SIZE
          + (w_link->m[0].tos_count * OSPF_ROUTER_LSA_TOS_SIZE));

    /* Only care about P2P with link ID equal to V's router id */
    if (w_link->m[0].type == LSA_LINK_TYPE_POINTOPOINT
        && w_link->link_id.s_addr == v->id.s_addr) {
      distance = ntohs(w_link->m[0].metric);
      break;
    }
  }

  /*
   * This might happen if the LSA for W is not complete yet. In this
   * case we take the weight of the 'forward' link from V. When the LSA
   * for W is completed the reverse SPF is run again anyway.
   */
  if (distance == 0)
    distance = ntohs(l->m[0].metric);

  if (IS_DEBUG_OSPF_EVENT)
    zlog_debug("%s: reversed distance is %u", __func__, distance);

  return distance;
}

/*
 * RFC2328 16.1 (2).
 * v is on the SPF tree. Examine the links in v's LSA. Update the list of
 * candidates with any vertices not already on the list. If a lower-cost path
 * is found to a vertex already on the candidate list, store the new cost.
 */
static void ospf_spf_next(struct vertex *v, struct ospf_area *area,
        struct vertex_pqueue_head *candidate)
{
  struct ospf_lsa *w_lsa = NULL;
  uint8_t *p;
  uint8_t *lim;
  struct router_lsa_link *l = NULL;
  struct in_addr *r;
  int type = 0, lsa_pos = -1, lsa_pos_next = 0;
  uint16_t link_distance;

  /*
   * If this is a router-LSA, and bit V of the router-LSA (see Section
   * A.4.2:RFC2328) is set, set Area A's TransitCapability to true.
   */
  if (v->type == OSPF_VERTEX_ROUTER) {
    if (IS_ROUTER_LSA_VIRTUAL((struct router_lsa *)v->lsa))
      area->transit = OSPF_TRANSIT_TRUE;
  }

  if (IS_DEBUG_OSPF_EVENT)
    zlog_debug("%s: Next vertex of %s vertex %pI4", __func__,
         v->type == OSPF_VERTEX_ROUTER ? "Router" : "Network",
         &v->lsa->id);

  p = ((uint8_t *)v->lsa) + OSPF_LSA_HEADER_SIZE + 4;
  lim = ((uint8_t *)v->lsa) + ntohs(v->lsa->length);

  while (p < lim) {
    struct vertex *w;
    unsigned int distance;

    /* In case of V is Router-LSA. */
    if (v->lsa->type == OSPF_ROUTER_LSA) {
      l = (struct router_lsa_link *)p;

      lsa_pos = lsa_pos_next; /* LSA link position */
      lsa_pos_next++;

      p += (OSPF_ROUTER_LSA_LINK_SIZE
            + (l->m[0].tos_count * OSPF_ROUTER_LSA_TOS_SIZE));

      /*
       * (a) If this is a link to a stub network, examine the
       * next link in V's LSA. Links to stub networks will
       * be considered in the second stage of the shortest
       * path calculation.
       */
      if ((type = l->m[0].type) == LSA_LINK_TYPE_STUB)
        continue;

      /*
       * Don't process TI-LFA protected resources.
       *
       * TODO: Replace this by a proper solution, e.g. remove
       * corresponding links from the LSDB and run the SPF
       * algo with the stripped-down LSDB.
       */
      if (ospf_spf_is_protected_resource(area, l, v->lsa))
        continue;

      /*
       * (b) Otherwise, W is a transit vertex (router or
       * transit network). Look up the vertex W's LSA
       * (router-LSA or network-LSA) in Area A's link state
       * database.
       */
      switch (type) {
      case LSA_LINK_TYPE_POINTOPOINT:
      case LSA_LINK_TYPE_VIRTUALLINK:
        if (type == LSA_LINK_TYPE_VIRTUALLINK
            && IS_DEBUG_OSPF_EVENT)
          zlog_debug(
            "looking up LSA through VL: %pI4",
            &l->link_id);
        w_lsa = ospf_lsa_lookup(area->ospf, area,
              OSPF_ROUTER_LSA,
              l->link_id, l->link_id);
        if (w_lsa && IS_DEBUG_OSPF_EVENT)
          zlog_debug("found Router LSA %pI4",
               &l->link_id);
        break;
      case LSA_LINK_TYPE_TRANSIT:
        if (IS_DEBUG_OSPF_EVENT)
          zlog_debug(
            "Looking up Network LSA, ID: %pI4",
            &l->link_id);
        w_lsa = ospf_lsa_lookup_by_id(
          area, OSPF_NETWORK_LSA, l->link_id);
        if (w_lsa && IS_DEBUG_OSPF_EVENT)
          zlog_debug("found the LSA");
        break;
      default:
        flog_warn(EC_OSPF_LSA,
            "Invalid LSA link type %d", type);
        continue;
      }

      /*
       * For TI-LFA we might need the reverse SPF.
       * Currently only works with P2P!
       */
      if (type == LSA_LINK_TYPE_POINTOPOINT
          && area->spf_reversed)
        link_distance =
          get_reverse_distance(v, l, w_lsa);
      else
        link_distance = ntohs(l->m[0].metric);

      /* step (d) below */
      distance = v->distance + link_distance;
    } else {
      /* In case of V is Network-LSA. */
      r = (struct in_addr *)p;
      p += sizeof(struct in_addr);

      /* Lookup the vertex W's LSA. */
      w_lsa = ospf_lsa_lookup_by_id(area, OSPF_ROUTER_LSA,
                  *r);
      if (w_lsa && IS_DEBUG_OSPF_EVENT)
        zlog_debug("found Router LSA %pI4",
             &w_lsa->data->id);

      /* step (d) below */
      distance = v->distance;
    }

    /*
     * (b cont.) If the LSA does not exist, or its LS age is equal
     * to MaxAge, or it does not have a link back to vertex V,
     * examine the next link in V's LSA.[23]
     */
    if (w_lsa == NULL) {
      if (IS_DEBUG_OSPF_EVENT)
        zlog_debug("No LSA found");
      continue;
    }

    if (IS_LSA_MAXAGE(w_lsa)) {
      if (IS_DEBUG_OSPF_EVENT)
        zlog_debug("LSA is MaxAge");
      continue;
    }

    if (ospf_lsa_has_link(w_lsa->data, v->lsa) < 0) {
      if (IS_DEBUG_OSPF_EVENT)
        zlog_debug("The LSA doesn't have a link back");
      continue;
    }

    /*
     * (c) If vertex W is already on the shortest-path tree, examine
     * the next link in the LSA.
     */
    if (w_lsa->stat == LSA_SPF_IN_SPFTREE) {
      if (IS_DEBUG_OSPF_EVENT)
        zlog_debug("The LSA is already in SPF");
      continue;
    }

    /*
     * (d) Calculate the link state cost D of the resulting path
     * from the root to vertex W.  D is equal to the sum of the link
     * state cost of the (already calculated) shortest path to
     * vertex V and the advertised cost of the link between vertices
     * V and W.  If D is:
     */

    /* calculate link cost D -- moved above */

    /* Is there already vertex W in candidate list? */
    if (w_lsa->stat == LSA_SPF_NOT_EXPLORED) {
      /* prepare vertex W. */
      w = ospf_vertex_new(area, w_lsa);

      /* Calculate nexthop to W. */
      if (ospf_nexthop_calculation(area, v, w, l, distance,
                 lsa_pos))
        vertex_pqueue_add(candidate, w);
      else {
        listnode_delete(area->spf_vertex_list, w);
        ospf_vertex_free(w);
        w_lsa->stat = LSA_SPF_NOT_EXPLORED;
        if (IS_DEBUG_OSPF_EVENT)
          zlog_debug("Nexthop Calc failed");
      }
    } else if (w_lsa->stat != LSA_SPF_IN_SPFTREE) {
      w = w_lsa->stat;
      if (w->distance < distance) {
        continue;
      }
      else if (w->distance == distance) {
        /*
         * Found an equal-cost path to W.
         * Calculate nexthop of to W from V.
         */
        ospf_nexthop_calculation(area, v, w, l,
               distance, lsa_pos);
      }
      else {
        /*
         * Found a lower-cost path to W.
         * nexthop_calculation is conditional, if it
         * finds valid nexthop it will call
         * spf_add_parents, which will flush the old
         * parents.
         */
        vertex_pqueue_del(candidate, w);
        ospf_nexthop_calculation(area, v, w, l,
               distance, lsa_pos);
        vertex_pqueue_add(candidate, w);
      }
    } /* end W is already on the candidate list */
  }  /* end loop over the links in V's LSA */
}

static void ospf_spf_dump(struct vertex *v, int i)
{
  struct listnode *cnode;
  struct listnode *nnode;
  struct vertex_parent *parent;

  if (v->type == OSPF_VERTEX_ROUTER) {
    if (IS_DEBUG_OSPF_EVENT)
      zlog_debug("SPF Result: %d [R] %pI4", i,
           &v->lsa->id);
  } else {
    struct network_lsa *lsa = (struct network_lsa *)v->lsa;
    if (IS_DEBUG_OSPF_EVENT)
      zlog_debug("SPF Result: %d [N] %pI4/%d", i,
           &v->lsa->id,
           ip_masklen(lsa->mask));
  }

  if (IS_DEBUG_OSPF_EVENT)
    for (ALL_LIST_ELEMENTS_RO(v->parents, nnode, parent)) {
      zlog_debug(" nexthop %p %pI4 %d",
           (void *)parent->nexthop,
           &parent->nexthop->router,
           parent->nexthop->lsa_pos);
    }

  i++;

  for (ALL_LIST_ELEMENTS_RO(v->children, cnode, v))
    ospf_spf_dump(v, i);
}

void ospf_spf_print(struct vty *vty, struct vertex *v, int i)
{
  struct listnode *cnode;
  struct listnode *nnode;
  struct vertex_parent *parent;

  if (v->type == OSPF_VERTEX_ROUTER) {
    vty_out(vty, "SPF Result: depth %d [R] %pI4\n", i, &v->lsa->id);
  } else {
    struct network_lsa *lsa = (struct network_lsa *)v->lsa;
    vty_out(vty, "SPF Result: depth %d [N] %pI4/%d\n", i,
      &v->lsa->id, ip_masklen(lsa->mask));
  }

  for (ALL_LIST_ELEMENTS_RO(v->parents, nnode, parent)) {
    vty_out(vty,
      " nexthop %pI4 lsa pos %d -- local nexthop %pI4 lsa pos %d\n",
      &parent->nexthop->router, parent->nexthop->lsa_pos,
      &parent->local_nexthop->router,
      parent->local_nexthop->lsa_pos);
  }

  i++;

  for (ALL_LIST_ELEMENTS_RO(v->children, cnode, v))
    ospf_spf_print(vty, v, i);
}

/* Second stage of SPF calculation. */
static void ospf_spf_process_stubs(struct ospf_area *area, struct vertex *v,
           struct route_table *rt, int parent_is_root)
{
  struct listnode *cnode, *cnnode;
  struct vertex *child;

  if (IS_DEBUG_OSPF_EVENT)
    zlog_debug("%s: processing stubs for area %pI4", __func__,
         &area->area_id);

  if (v->type == OSPF_VERTEX_ROUTER) {
    uint8_t *p;
    uint8_t *lim;
    struct router_lsa_link *l;
    struct router_lsa *router_lsa;
    int lsa_pos = 0;

    if (IS_DEBUG_OSPF_EVENT)
      zlog_debug("%s: processing router LSA, id: %pI4",
           __func__, &v->lsa->id);

    router_lsa = (struct router_lsa *)v->lsa;

    if (IS_DEBUG_OSPF_EVENT)
      zlog_debug("%s: we have %d links to process", __func__,
           ntohs(router_lsa->links));

    p = ((uint8_t *)v->lsa) + OSPF_LSA_HEADER_SIZE + 4;
    lim = ((uint8_t *)v->lsa) + ntohs(v->lsa->length);

    while (p < lim) {
      l = (struct router_lsa_link *)p;

      p += (OSPF_ROUTER_LSA_LINK_SIZE
            + (l->m[0].tos_count * OSPF_ROUTER_LSA_TOS_SIZE));

      /* Don't process TI-LFA protected resources */
      if (l->m[0].type == LSA_LINK_TYPE_STUB
          && !ospf_spf_is_protected_resource(area, l, v->lsa))
        ospf_intra_add_stub(rt, l, v, area,
                parent_is_root, lsa_pos);
      lsa_pos++;
    }
  }

  ospf_vertex_dump("ospf_process_stubs(): after examining links: ", v, 1,
       1);

  for (ALL_LIST_ELEMENTS(v->children, cnode, cnnode, child)) {
    if (CHECK_FLAG(child->flags, OSPF_VERTEX_PROCESSED))
      continue;

    /*
     * The first level of routers connected to the root
     * should have 'parent_is_root' set, including those
     * connected via a network vertex.
     */
    if (area->spf == v)
      parent_is_root = 1;
    else if (v->type == OSPF_VERTEX_ROUTER)
      parent_is_root = 0;

    ospf_spf_process_stubs(area, child, rt, parent_is_root);

    SET_FLAG(child->flags, OSPF_VERTEX_PROCESSED);
  }
}

void ospf_rtrs_free(struct route_table *rtrs)
{
  struct route_node *rn;
  struct list *or_list;
  struct ospf_route * or ;
  struct listnode *node, *nnode;

  if (IS_DEBUG_OSPF_EVENT)
    zlog_debug("Route: Router Routing Table free");

  for (rn = route_top(rtrs); rn; rn = route_next(rn))
    if ((or_list = rn->info) != NULL) {
      for (ALL_LIST_ELEMENTS(or_list, node, nnode, or))
        ospf_route_free(or);

      list_delete(&or_list);

      /* Unlock the node. */
      rn->info = NULL;
      route_unlock_node(rn);
    }

  route_table_finish(rtrs);
}

void ospf_spf_cleanup(struct vertex *spf, struct list *vertex_list)
{
  /*
   * Free nexthop information, canonical versions of which are
   * attached the first level of router vertices attached to the
   * root vertex, see ospf_nexthop_calculation.
   */
  if (spf)
    ospf_canonical_nexthops_free(spf);

  /* Free SPF vertices list with deconstructor ospf_vertex_free. */
  if (vertex_list)
    list_delete(&vertex_list);
}

/* Calculating the shortest-path tree for an area, see RFC2328 16.1. */
void ospf_spf_calculate(struct ospf_area *area, struct ospf_lsa *root_lsa,
      struct route_table *new_table,
      struct route_table *all_rtrs,
      struct route_table *new_rtrs, bool is_dry_run,
      bool is_root_node)
{
  struct vertex_pqueue_head candidate;
  struct vertex *v;

  if (IS_DEBUG_OSPF_EVENT) {
    zlog_debug("%s: Start: running Dijkstra for area %pI4",
         __func__, &area->area_id);
  }

  /*
   * If the router LSA of the root is not yet allocated, return this
   * area's calculation. In the 'usual' case the root_lsa is the
   * self-originated router LSA of the node itself.
   */
  if (!root_lsa) {
    if (IS_DEBUG_OSPF_EVENT)
      zlog_debug(
        "%s: Skip area %pI4's calculation due to empty root LSA",
        __func__, &area->area_id);
    return;
  }

  /* Initialize the algorithm's data structures, see RFC2328 16.1. (1). */

  /*
   * This function scans all the LSA database and set the stat field to
   * LSA_SPF_NOT_EXPLORED.
   */
  lsdb_clean_stat(area->lsdb);

  /* Create a new heap for the candidates. */
  vertex_pqueue_init(&candidate);

  /*
   * Initialize the shortest-path tree to only the root (which is usually
   * the router doing the calculation).
   */
  ospf_spf_init(area, root_lsa, is_dry_run, is_root_node);

  /* Set Area A's TransitCapability to false. */
  area->transit = OSPF_TRANSIT_FALSE;
  area->shortcut_capability = 1;

  /*
   * Use the root vertex for the start of the SPF algorithm and make it
   * part of the tree.
   */
  v = area->spf;
  v->lsa_p->stat = LSA_SPF_IN_SPFTREE;

  for (;;) {
    /* RFC2328 16.1. (2). */
    ospf_spf_next(v, area, &candidate);

    /* RFC2328 16.1. (3). */
    v = vertex_pqueue_pop(&candidate);
    if (!v)
      /* No more vertices left. */
      break;

    v->lsa_p->stat = LSA_SPF_IN_SPFTREE;

    ospf_vertex_add_parent(v);

    /* RFC2328 16.1. (4). */
    if (v->type != OSPF_VERTEX_ROUTER)
      ospf_intra_add_transit(new_table, v, area);
    else {
      if (new_rtrs)
        ospf_intra_add_router(new_rtrs, v, area, false);
      if (all_rtrs)
        ospf_intra_add_router(all_rtrs, v, area, true);
    }

    /* Iterate back to (2), see RFC2328 16.1. (5). */
  }

  if (IS_DEBUG_OSPF_EVENT) {
    ospf_spf_dump(area->spf, 0);
    ospf_route_table_dump(new_table);
    if (all_rtrs)
      ospf_router_route_table_dump(all_rtrs);
  }

  /*
   * Second stage of SPF calculation procedure's, add leaves to the tree
   * for stub networks.
   */
  ospf_spf_process_stubs(area, area->spf, new_table, 0);

  ospf_vertex_dump(__func__, area->spf, 0, 1);

  /* Increment SPF Calculation Counter. */
  area->spf_calculation++;

  monotime(&area->ospf->ts_spf);
  area->ts_spf = area->ospf->ts_spf;

  if (IS_DEBUG_OSPF_EVENT)
    zlog_debug("%s: Stop. %zd vertices", __func__,
         mtype_stats_alloc(MTYPE_OSPF_VERTEX));
}

void ospf_spf_calculate_area(struct ospf *ospf, struct ospf_area *area,
           struct route_table *new_table,
           struct route_table *all_rtrs,
           struct route_table *new_rtrs)
{
  ospf_spf_calculate(area, area->router_lsa_self, new_table, all_rtrs,
         new_rtrs, false, true);

  if (ospf->ti_lfa_enabled)
    ospf_ti_lfa_compute(area, new_table,
            ospf->ti_lfa_protection_type);

  ospf_spf_cleanup(area->spf, area->spf_vertex_list);

  area->spf = NULL;
  area->spf_vertex_list = NULL;
}

void ospf_spf_calculate_areas(struct ospf *ospf, struct route_table *new_table,
            struct route_table *all_rtrs,
            struct route_table *new_rtrs)
{
  struct ospf_area *area;
  struct listnode *node, *nnode;

  /* Calculate SPF for each area. */
  for (ALL_LIST_ELEMENTS(ospf->areas, node, nnode, area)) {
    /* Do backbone last, so as to first discover intra-area paths
     * for any back-bone virtual-links */
    if (ospf->backbone && ospf->backbone == area)
      continue;

    ospf_spf_calculate_area(ospf, area, new_table, all_rtrs,
          new_rtrs);
  }

  /* SPF for backbone, if required */
  if (ospf->backbone)
    ospf_spf_calculate_area(ospf, ospf->backbone, new_table,
          all_rtrs, new_rtrs);
}

/* Worker for SPF calculation scheduler. */
static void ospf_spf_calculate_schedule_worker(struct event *thread)
{
  struct ospf *ospf = EVENT_ARG(thread);
  struct route_table *new_table, *new_rtrs;
  struct route_table *all_rtrs = NULL;
  struct timeval start_time, spf_start_time;
  unsigned long ia_time, prune_time, rt_time;
  unsigned long abr_time, total_spf_time, spf_time;
  char rbuf[32]; /* reason_buf */

  if (IS_DEBUG_OSPF_EVENT)
    zlog_debug("SPF: Timer (SPF calculation expire)");

  ospf->t_spf_calc = NULL;

  ospf_vl_unapprove(ospf);

  /* Execute SPF for each area including backbone, see RFC 2328 16.1. */
  monotime(&spf_start_time);
  new_table = route_table_init(); /* routing table */
  new_rtrs = route_table_init();  /* ABR/ASBR routing table */

  /* If we have opaque enabled then track all router reachability */
  if (CHECK_FLAG(ospf->opaque, OPAQUE_OPERATION_READY_BIT))
    all_rtrs = route_table_init();

  ospf_spf_calculate_areas(ospf, new_table, all_rtrs, new_rtrs);
  spf_time = monotime_since(&spf_start_time, NULL);

  ospf_vl_shut_unapproved(ospf);

  /* Calculate inter-area routes, see RFC 2328 16.2. */
  monotime(&start_time);
  ospf_ia_routing(ospf, new_table, new_rtrs);
  ia_time = monotime_since(&start_time, NULL);

  /* Get rid of transit networks and routers we cannot reach anyway. */
  monotime(&start_time);
  ospf_prune_unreachable_networks(new_table);
  if (all_rtrs)
    ospf_prune_unreachable_routers(all_rtrs);
  ospf_prune_unreachable_routers(new_rtrs);
  prune_time = monotime_since(&start_time, NULL);

  /* Note: RFC 2328 16.3. is apparently missing. */

  /*
   * Calculate AS external routes, see RFC 2328 16.4.
   * There is a dedicated routing table for external routes which is not
   * handled here directly
   */
  ospf_ase_calculate_schedule(ospf);
  ospf_ase_calculate_timer_add(ospf);

  if (IS_DEBUG_OSPF_EVENT)
    zlog_debug(
      "%s: ospf install new route, vrf %s id %u new_table count %lu",
      __func__, ospf_vrf_id_to_name(ospf->vrf_id),
      ospf->vrf_id, new_table->count);

  /* Update routing table. */
  monotime(&start_time);
  ospf_route_install(ospf, new_table);
  rt_time = monotime_since(&start_time, NULL);

  /* Free old all routers routing table */
  if (ospf->oall_rtrs) {
    ospf_rtrs_free(ospf->oall_rtrs);
    ospf->oall_rtrs = NULL;
  }

  /* Update all routers routing table */
  ospf->oall_rtrs = ospf->all_rtrs;
  ospf->all_rtrs = all_rtrs;
#ifdef SUPPORT_OSPF_API
  ospf_apiserver_notify_reachable(ospf->oall_rtrs, ospf->all_rtrs);
#endif

  /* Free old ABR/ASBR routing table */
  if (ospf->old_rtrs) {
    ospf_rtrs_free(ospf->old_rtrs);
    ospf->old_rtrs = NULL;
  }

  /* Update ABR/ASBR routing table */
  ospf->old_rtrs = ospf->new_rtrs;
  ospf->new_rtrs = new_rtrs;

  /* ABRs may require additional changes, see RFC 2328 16.7. */
  monotime(&start_time);
  if (IS_OSPF_ABR(ospf)) {
    if (ospf->anyNSSA)
      ospf_abr_nssa_check_status(ospf);
    ospf_abr_task(ospf);
  }
  abr_time = monotime_since(&start_time, NULL);

  /* Schedule Segment Routing update */
  ospf_sr_update_task(ospf);

  total_spf_time =
    monotime_since(&spf_start_time, &ospf->ts_spf_duration);

  rbuf[0] = '\0';
  if (spf_reason_flags) {
    if (spf_reason_flags & (1 << SPF_FLAG_ROUTER_LSA_INSTALL))
      strlcat(rbuf, "R, ", sizeof(rbuf));
    if (spf_reason_flags & (1 << SPF_FLAG_NETWORK_LSA_INSTALL))
      strlcat(rbuf, "N, ", sizeof(rbuf));
    if (spf_reason_flags & (1 << SPF_FLAG_SUMMARY_LSA_INSTALL))
      strlcat(rbuf, "S, ", sizeof(rbuf));
    if (spf_reason_flags & (1 << SPF_FLAG_ASBR_SUMMARY_LSA_INSTALL))
      strlcat(rbuf, "AS, ", sizeof(rbuf));
    if (spf_reason_flags & (1 << SPF_FLAG_ABR_STATUS_CHANGE))
      strlcat(rbuf, "ABR, ", sizeof(rbuf));
    if (spf_reason_flags & (1 << SPF_FLAG_ASBR_STATUS_CHANGE))
      strlcat(rbuf, "ASBR, ", sizeof(rbuf));
    if (spf_reason_flags & (1 << SPF_FLAG_MAXAGE))
      strlcat(rbuf, "M, ", sizeof(rbuf));
    if (spf_reason_flags & (1 << SPF_FLAG_GR_FINISH))
      strlcat(rbuf, "GR, ", sizeof(rbuf));

    size_t rbuflen = strlen(rbuf);
    if (rbuflen >= 2)
      rbuf[rbuflen - 2] = '\0'; /* skip the last ", " */
    else
      rbuf[0] = '\0';
  }

  if (IS_DEBUG_OSPF_EVENT) {
    zlog_info("SPF Processing Time(usecs): %ld", total_spf_time);
    zlog_info("            SPF Time: %ld", spf_time);
    zlog_info("           InterArea: %ld", ia_time);
    zlog_info("               Prune: %ld", prune_time);
    zlog_info("        RouteInstall: %ld", rt_time);
    if (IS_OSPF_ABR(ospf))
      zlog_info("                 ABR: %ld (%d areas)",
          abr_time, ospf->areas->count);
    zlog_info("Reason(s) for SPF: %s", rbuf);
  }

  ospf_clear_spf_reason_flags();
}

/*
 * Add schedule for SPF calculation. To avoid frequenst SPF calc, we set timer
 * for SPF calc.
 */
void ospf_spf_calculate_schedule(struct ospf *ospf, ospf_spf_reason_t reason)
{
  unsigned long delay, elapsed, ht;

  if (IS_DEBUG_OSPF_EVENT)
    zlog_debug("SPF: calculation timer scheduled");

  /* OSPF instance does not exist. */
  if (ospf == NULL)
    return;

  ospf_spf_set_reason(reason);

  /* SPF calculation timer is already scheduled. */
  if (ospf->t_spf_calc) {
    if (IS_DEBUG_OSPF_EVENT)
      zlog_debug(
        "SPF: calculation timer is already scheduled: %p",
        (void *)ospf->t_spf_calc);
    return;
  }

  elapsed = monotime_since(&ospf->ts_spf, NULL) / 1000;

  ht = ospf->spf_holdtime * ospf->spf_hold_multiplier;

  if (ht > ospf->spf_max_holdtime)
    ht = ospf->spf_max_holdtime;

  /* Get SPF calculation delay time. */
  if (elapsed < ht) {
    /*
     * Got an event within the hold time of last SPF. We need to
     * increase the hold_multiplier, if it's not already at/past
     * maximum value, and wasn't already increased.
     */
    if (ht < ospf->spf_max_holdtime)
      ospf->spf_hold_multiplier++;

    /* always honour the SPF initial delay */
    if ((ht - elapsed) < ospf->spf_delay)
      delay = ospf->spf_delay;
    else
      delay = ht - elapsed;
  } else {
    /* Event is past required hold-time of last SPF */
    delay = ospf->spf_delay;
    ospf->spf_hold_multiplier = 1;
  }

  if (IS_DEBUG_OSPF_EVENT)
    zlog_debug("SPF: calculation timer delay = %ld msec", delay);

  ospf->t_spf_calc = NULL;
  event_add_timer_msec(master, ospf_spf_calculate_schedule_worker, ospf,
           delay, &ospf->t_spf_calc);
}

/* Restart OSPF SPF algorithm*/
void ospf_restart_spf(struct ospf *ospf)
{
  if (IS_DEBUG_OSPF_EVENT)
    zlog_debug("%s: Restart SPF.", __func__);

  /* Handling inter area and intra area routes*/
  if (ospf->new_table) {
    ospf_route_delete(ospf, ospf->new_table);
    ospf_route_table_free(ospf->new_table);
    ospf->new_table = route_table_init();
  }

  /* Handling of TYPE-5 lsa(external routes) */
  if (ospf->old_external_route) {
    ospf_route_delete(ospf, ospf->old_external_route);
    ospf_route_table_free(ospf->old_external_route);
    ospf->old_external_route = route_table_init();
  }

  /* Trigger SPF */
  ospf_spf_calculate_schedule(ospf, SPF_FLAG_CONFIG_CHANGE);
}

Coverage Report

Created: 2025-12-12 06:43