bird/proto/ospf/rt.c

/*
 * BIRD -- OSPF
 * 
 * (c) 2000--2004 Ondrej Filip <feela@network.cz>
 * 
 * Can be freely distributed and used under the terms of the GNU GPL.
 */

#include "ospf.h"

static void
add_cand(list * l, struct top_hash_entry *en,
	 struct top_hash_entry *par, u16 dist, struct ospf_area *oa);
static void
calc_next_hop(struct top_hash_entry *en,
	      struct top_hash_entry *par, struct ospf_area *oa);
static void ospf_ext_spf(struct proto_ospf *po);
static void rt_sync(struct proto_ospf *po);

static void
fill_ri(orta * orta)
{
  orta->type = RTS_DUMMY;
  orta->capa = 0;
  orta->oa = NULL;
  orta->metric1 = LSINFINITY;
  orta->metric2 = LSINFINITY;
  orta->nh = IPA_NONE;
  orta->ifa = NULL;
  orta->ar = NULL;
  orta->tag = 0;
}

void
ospf_rt_initort(struct fib_node *fn)
{
  ort *ri = (ort *) fn;
  fill_ri(&ri->n);
  memcpy(&ri->o, &ri->n, sizeof(orta));
  ri->efn = NULL;
}

/* If new is better return 1 */

/* 
 * This is hard to understand:
 * If rfc1583 is set to 1, it work likes normal route_better()
 * But if it is set to 0, it prunes number of AS bondary
 * routes before it starts the router decision
 */
static int
ri_better(struct proto_ospf *po, orta * new, ort *nefn, orta * old, ort *oefn, int rfc1583)
{
  int newtype = new->type;
  int oldtype = old->type;

  if (old->type == RTS_DUMMY)
    return 1;

  if (old->metric1 == LSINFINITY)
    return 1;

  if(!rfc1583)
  {
    if(new->oa->areaid == 0) newtype = RTS_OSPF_IA;
    if(old->oa->areaid == 0) oldtype = RTS_OSPF_IA;
  }

  if (new->type < old->type)
    return 1;

  if (new->type > old->type)
    return 0;

  /* Same type */
  if(new->type == RTS_OSPF_EXT2)
  {
    if (new->metric2 < old->metric2) return 1;
    if (new->metric2 > old->metric2) return 0;
  }

  if(((new->type == RTS_OSPF_EXT2) || (new->type == RTS_OSPF_EXT1)) && (!po->rfc1583))
  {
    int newtype = nefn->n.type;
    int oldtype = oefn->n.type;

    if(nefn->n.oa->areaid == 0) newtype = RTS_OSPF_IA;
    if(oefn->n.oa->areaid == 0) oldtype = RTS_OSPF_IA;

    if(newtype < oldtype) return 1;
    if(newtype > oldtype) return 0;
  }

  if (new->metric1 < old->metric1)
    return 1;

  if (new->metric1 > old->metric1)
    return 0;

  if (new->oa->areaid > old->oa->areaid) return 1;	/* Larger AREAID is preffered */

  return 0;			/* Old is shorter or same */
}

static void
ri_install(struct proto_ospf *po, ip_addr prefix, int pxlen, int dest,
	   orta * new, ort * ipath)
{
  struct ospf_area *oa = new->oa;
  ort *old;

  if (dest == ORT_NET)
  {
    struct area_net *anet;
    old = (ort *) fib_get(&po->rtf, &prefix, pxlen);
    if (ri_better(po, new, ipath, &old->n, old->efn, 1))
    {
      memcpy(&old->n, new, sizeof(orta));
      old->efn = ipath;
    }
    if ((new->type == RTS_OSPF) && (anet = (struct area_net *)fib_route(&oa->net_fib, prefix, pxlen)))
       anet->active = 1;
  }
  else
  {
    old = (ort *) fib_get(&oa->rtr, &prefix, pxlen);

    if (ri_better(po, new, ipath, &old->n, old->efn, 1))
    {
      memcpy(&old->n, new, sizeof(orta));
      old->efn = ipath;
    }
  }
}

static void
ospf_rt_spfa(struct ospf_area *oa)
{
  u32 i, *rts;
  struct ospf_lsa_rt *rt;
  struct ospf_lsa_rt_link *rtl, *rr;
  struct proto *p = &oa->po->proto;
  struct proto_ospf *po = oa->po;
  struct ospf_lsa_net *ln;
  orta nf;
  struct ospf_iface *iface;
  struct top_hash_entry *act, *tmp;
  node *n;


  if (oa->rt == NULL)
    return;

  OSPF_TRACE(D_EVENTS, "Starting routing table calculation for area %I",
	     oa->areaid);

  if (oa->rt->dist != LSINFINITY)
    bug("Aging was not processed.");

  init_list(&oa->cand);		/* Empty list of candidates */
  oa->trcap = 0;

  DBG("LSA db prepared, adding me into candidate list.\n");

  oa->rt->dist = 0;
  oa->rt->color = CANDIDATE;
  add_head(&oa->cand, &oa->rt->cn);
  DBG("RT LSA: rt: %I, id: %I, type: %u\n", oa->rt->lsa.rt,
      oa->rt->lsa.id, oa->rt->lsa.type);

  while (!EMPTY_LIST(oa->cand))
  {
    n = HEAD(oa->cand);
    act = SKIP_BACK(struct top_hash_entry, cn, n);
    rem_node(n);

    DBG("Working on LSA: rt: %I, id: %I, type: %u\n", act->lsa.rt,
	act->lsa.id, act->lsa.type);

    act->color = INSPF;
    switch (act->lsa.type)
    {
    case LSA_T_RT:
      rt = (struct ospf_lsa_rt *) act->lsa_body;
      if (rt->veb.bit.v)
	oa->trcap = 1;
      if (rt->veb.bit.b || rt->veb.bit.e)
      {
	nf.type = RTS_OSPF;
	nf.capa = 0;
        if (rt->veb.bit.b) nf.capa |= ORTA_ABR;
        if (rt->veb.bit.e) nf.capa |= ORTA_ASBR;
	nf.metric1 = act->dist;
	nf.metric2 = LSINFINITY;
	nf.oa = oa;
	nf.ar = act;
	nf.nh = act->nh;
	nf.ifa = act->nhi;
	ri_install(po, ipa_from_u32(act->lsa.id), 32, ORT_ROUTER, &nf, NULL);
      }
      rr = (struct ospf_lsa_rt_link *) (rt + 1);
      DBG("  Number of links: %u\n", rt->links);
      for (i = 0; i < rt->links; i++)
      {
	tmp = NULL;
	rtl = (rr + i);
	DBG("     Working on link: %I (type: %u)  ", rtl->id, rtl->type);
	switch (rtl->type)
	{
	case LSART_STUB:
	  /*
	   * This violates rfc2328! but I hope
	   * it's also correct.
	   */
	  DBG("\n");

	  nf.type = RTS_OSPF;
	  nf.capa = 0;
	  nf.metric1 = act->dist + rtl->metric;
	  nf.metric2 = LSINFINITY;
	  nf.oa = oa;
	  nf.ar = act;
	  nf.nh = act->nh;
	  nf.ifa = act->nhi;

	  if (act == oa->rt)
	  {
	    struct ospf_iface *iff;

	    WALK_LIST(iff, po->iface_list)
	    {
               if (iff->iface && (rtl->id == (ipa_to_u32(ipa_mkmask(iff->iface->addr->pxlen))
	         & ipa_to_u32(iff->iface->addr->prefix))))
	       {
		 nf.ifa = iff;
	         break;
	       }
            }
						 
	  }

	  if (!nf.ifa)
	    continue;

	  ri_install(po, ipa_from_u32(rtl->id),
		     ipa_mklen(ipa_from_u32(rtl->data)), ORT_NET, &nf, NULL);
	  break;

	case LSART_NET:
	  tmp = ospf_hash_find(po->gr, oa->areaid, rtl->id, rtl->id, LSA_T_NET);
	  if (tmp == NULL)
	    DBG("Not found!\n");
	  else
	    DBG("Found. :-)\n");
	  break;

	case LSART_VLNK:
	case LSART_PTP:
	  tmp = ospf_hash_find(po->gr, oa->areaid, rtl->id, rtl->id, LSA_T_RT);
	  DBG("PTP found.\n");
	  break;
	default:
	  log("Unknown link type in router lsa. (rid = %I)", act->lsa.id);
	  break;
	}
	if (tmp)
	  DBG("Going to add cand, Mydist: %u, Req: %u\n",
	      tmp->dist, act->dist + rtl->metric);
	add_cand(&oa->cand, tmp, act, act->dist + rtl->metric, oa);
      }
      break;
    case LSA_T_NET:
      ln = act->lsa_body;
      nf.type = RTS_OSPF;
      nf.capa = 0;
      nf.metric1 = act->dist;
      nf.metric2 = LSINFINITY;
      nf.oa = oa;
      nf.ar = act;
      nf.nh = act->nh;
      nf.ifa = act->nhi;
      ri_install(po, ipa_and(ipa_from_u32(act->lsa.id), ln->netmask),
		 ipa_mklen(ln->netmask), ORT_NET, &nf, NULL);

      rts = (u32 *) (ln + 1);
      for (i = 0; i < (act->lsa.length - sizeof(struct ospf_lsa_header) -
		       sizeof(struct ospf_lsa_net)) / sizeof(u32); i++)
      {
	DBG("     Working on router %I ", *(rts + i));
	tmp = ospf_hash_find(po->gr, oa->areaid, *(rts + i), *(rts + i), LSA_T_RT);
	if (tmp != NULL)
	  DBG("Found :-)\n");
	else
	  DBG("Not found!\n");
	add_cand(&oa->cand, tmp, act, act->dist, oa);
      }
      break;
    }
  }

  /* Find new/lost VLINK peers */
  WALK_LIST(iface, po->iface_list)
  {
    if ((iface->type == OSPF_IT_VLINK) && (iface->voa == oa))
    {
      if ((tmp = ospf_hash_find(po->gr, oa->areaid, iface->vid, iface->vid, LSA_T_RT)) &&
        (!ipa_equal(tmp->lb, IPA_NONE)))
      {
        if ((iface->state != OSPF_IS_PTP) || (iface->iface != tmp->nhi->iface) || (!ipa_equal(iface->vip, tmp->lb)))
        {
          OSPF_TRACE(D_EVENTS, "Vlink peer %I found", tmp->lsa.id);
          ospf_iface_sm(iface, ISM_DOWN);
          iface->iface = tmp->nhi->iface;
          iface->vip = tmp->lb;
          ospf_iface_sm(iface, ISM_UP);
        }
      }
      else
      {
        if (iface->state > OSPF_IS_DOWN)
        {
          OSPF_TRACE(D_EVENTS, "Vlink peer %I lost", iface->vid);
          ospf_iface_sm(iface, ISM_DOWN);
        }
      }
    }
  }
}

static int
link_back(struct ospf_area *oa, struct top_hash_entry *fol, struct top_hash_entry *pre)
{
  u32 i, *rts;
  struct ospf_lsa_net *ln;
  struct ospf_lsa_rt *rt;
  struct ospf_lsa_rt_link *rtl, *rr;
  struct proto_ospf *po = oa->po;

  if(!pre) return 0;
  if(!fol) return 0;
  switch (fol->lsa.type)
  {
    case LSA_T_RT:
      rt = (struct ospf_lsa_rt *) fol->lsa_body;
      rr = (struct ospf_lsa_rt_link *) (rt + 1);
      for (i = 0; i < rt->links; i++)
      {
	rtl = (rr + i);
	switch (rtl->type)
	{
	case LSART_STUB:
	  break;
	case LSART_NET:
	  if (ospf_hash_find(po->gr, oa->areaid, rtl->id, rtl->id, LSA_T_NET) == pre)
          {
            fol->lb = ipa_from_u32(rtl->data);
            return 1;
          }
	  break;
	case LSART_VLNK:
	case LSART_PTP:
	  if (ospf_hash_find(po->gr, oa->areaid, rtl->id, rtl->id, LSA_T_RT) == pre)
          {
            fol->lb = ipa_from_u32(rtl->data);
            return 1;
          }
	  break;
	default:
	  log("Unknown link type in router lsa. (rid = %I)", fol->lsa.id);
	  break;
	}
      }
      break;
    case LSA_T_NET:
      ln = fol->lsa_body;
      rts = (u32 *) (ln + 1);
      for (i = 0; i < (fol->lsa.length - sizeof(struct ospf_lsa_header) -
		       sizeof(struct ospf_lsa_net)) / sizeof(u32); i++)
      {
	if (ospf_hash_find(po->gr, oa->areaid, *(rts + i), *(rts + i), LSA_T_RT) == pre)
        {
          return 1;
        }
      }
      break;
    default:
      bug("Unknown lsa type. (id = %I)", fol->lsa.id);
  }
  return 0;
}

static void
ospf_rt_sum_tr(struct ospf_area *oa)
{
  struct proto *p = &oa->po->proto;
  struct proto_ospf *po = oa->po;
  struct ospf_area *bb = po->backbone;
  ip_addr *mask, ip, abrip;
  struct top_hash_entry *en;
  int mlen = -1, type = -1;
  union ospf_lsa_sum_tm *tm;
  ort *re = NULL, *abr;
  orta nf;

  if(!bb) return;

  WALK_SLIST(en, po->lsal)
  {
    if (en->oa != oa)
      continue;
    if (en->lsa.age == LSA_MAXAGE)
      continue;
    if (en->dist == LSINFINITY)
      continue;

    if (en->lsa.rt == p->cf->global->router_id)
      continue;

    if ((en->lsa.type != LSA_T_SUM_RT) && (en->lsa.type != LSA_T_SUM_NET))
      continue;

    mask = (ip_addr *)en->lsa_body;

    if (en->lsa.type == LSA_T_SUM_NET)
    {
      mlen = ipa_mklen(*mask);
      ip = ipa_and(ipa_from_u32(en->lsa.id), *mask);
      type = ORT_NET;
      re = (ort *) fib_find(&po->rtf, &ip, 32);
    }

    if (en->lsa.type == LSA_T_SUM_RT)
    {
      ip = ipa_from_u32(en->lsa.id);
      mlen = 32;
      type = ORT_ROUTER;
      re = (ort *) fib_find(&bb->rtr, &ip, 32);
    }
    if(!re) continue;
    if(re->n.oa->areaid != 0) continue;
    if((re->n.type != RTS_OSPF) && (re->n.type != RTS_OSPF_IA)) continue;

    abrip = ipa_from_u32(en->lsa.rt);

    abr = fib_find(&oa->rtr, &abrip, 32);
    if(!abr) continue;

    tm = (union ospf_lsa_sum_tm *)(mask + 1);

    nf.type = re->n.type;
    nf.capa = ORTA_ABR;
    nf.metric1 = abr->n.metric1 + (tm->metric & METRIC_MASK);
    nf.metric2 = LSINFINITY;
    nf.oa = oa;
    nf.ar = abr->n.ar;
    nf.nh = abr->n.nh;
    nf.ifa = abr->n.ifa;
    ri_install(po, ip, mlen, type, &nf, NULL);
  }
}
  

static void
ospf_rt_sum(struct ospf_area *oa)
{
  struct proto_ospf *po = oa->po;
  struct proto *p = &po->proto;
  struct top_hash_entry *en;
  ip_addr *mask, ip, abrip;
  struct area_net *anet;
  orta nf;
  ort *re, *abr;
  int mlen = -1, type = -1;
  union ospf_lsa_sum_tm *tm;

  OSPF_TRACE(D_EVENTS, "Starting routing table calculation for inter-area (area %I)", oa->areaid);

  WALK_SLIST(en, po->lsal)
  {
    if (en->oa != oa)
      continue;
    /* Page 169 (1) */
    if (en->lsa.age == LSA_MAXAGE)
      continue;
    /* Page 169 (2) */
    if (en->lsa.rt == p->cf->global->router_id)
      continue;

    if((en->lsa.type != LSA_T_SUM_RT) && (en->lsa.type != LSA_T_SUM_NET))
      continue;

    mask = (ip_addr *)en->lsa_body;
    tm = (union ospf_lsa_sum_tm *)(mask + 1);

    if((tm->metric & METRIC_MASK) == LSINFINITY)
      continue;

    if (en->lsa.type == LSA_T_SUM_NET)
    {
      struct ospf_area *oaa;
      int skip = 0;
      mlen = ipa_mklen(*mask);
      ip = ipa_and(ipa_from_u32(en->lsa.id), *mask);
      /* Page 169 (3) */
      WALK_LIST(oaa, po->area_list)
      {
        if ((anet = fib_find(&oaa->net_fib, &ip, mlen)) && anet->active)
	{
	  skip = 1;
	  break;
	}
      }
      if (skip) continue;

      type = ORT_NET;
    }
    else
    {
      ip = ipa_from_u32(en->lsa.id);
      mlen = 32;
      type = ORT_ROUTER;
    }
    abrip = ipa_from_u32(en->lsa.rt);

    if (!(abr = (ort *) fib_find(&oa->rtr, &abrip, 32))) continue;
    if (abr->n.metric1 == LSINFINITY) continue;
    if (!(abr->n.capa & ORTA_ABR)) continue;

    nf.type = RTS_OSPF_IA;
    nf.capa = ORTA_ABR;
    nf.metric1 = abr->n.metric1 + (tm->metric & METRIC_MASK);
    nf.metric2 = LSINFINITY;
    nf.oa = oa;
    nf.ar = abr->n.ar;
    nf.nh = abr->n.nh;
    nf.ifa = abr->n.ifa;
    ri_install(po, ip, mlen, type, &nf, NULL);
  }
}

/**
 * ospf_rt_spf - calculate internal routes
 * @po: OSPF protocol
 *
 * Calculation of internal paths in an area is described in 16.1 of RFC 2328.
 * It's based on Dijkstra's shortest path tree algorithms.
 * This function is invoked from ospf_disp().
 */
void
ospf_rt_spf(struct proto_ospf *po)
{
  struct proto *p = &po->proto;
  struct ospf_area *oa;
  int i;
  ort *ri;
  struct area_net *anet;

  if (po->areano == 0) return;

  po->cleanup = 1;

  OSPF_TRACE(D_EVENTS, "Starting routing table calculation");

  /* Invalidate old routing table */
  FIB_WALK(&po->rtf, nftmp)
  {
    ri = (ort *) nftmp;
    memcpy(&ri->o, &ri->n, sizeof(orta));	/* Backup old data */
    fill_ri(&ri->n);
  }
  FIB_WALK_END;


  WALK_LIST(oa, po->area_list)
  {
    FIB_WALK(&oa->rtr, nftmp)
    {
      ri = (ort *) nftmp;
      memcpy(&ri->o, &ri->n, sizeof(orta));	/* Backup old data */
      fill_ri(&ri->n);
    }
    FIB_WALK_END;

    FIB_WALK(&oa->net_fib, nftmp)
    {
      anet = (struct area_net *) nftmp;
      anet->active = 0;
    }
    FIB_WALK_END;
    ospf_rt_spfa(oa);
  }

  if ((po->areano == 1) || (!po->backbone))
  {
    ospf_rt_sum(HEAD(po->area_list));
  }
  else
  {
    ospf_rt_sum(po->backbone);
  }

  WALK_LIST(oa, po->area_list)
  {
    if (oa->trcap && (oa->areaid != 0))
    {
      ospf_rt_sum_tr(oa);
      break;
    }
  }

  ospf_ext_spf(po);

  rt_sync(po);

  po->calcrt = 0;
}


/**
 * ospf_ext_spf - calculate external paths
 * @po: protocol
 *
 * After routing table for any area is calculated, calculation of external
 * path is invoked. This process is described in 16.6 of RFC 2328.
 * Inter- and Intra-area paths are always prefered over externals.
 */
static void
ospf_ext_spf(struct proto_ospf *po)
{
  ort *nf1, *nf2, *nfh;
  orta nfa;
  struct top_hash_entry *en;
  struct proto *p = &po->proto;
  struct ospf_lsa_ext *le;
  struct ospf_lsa_ext_tos *lt;
  int mlen;
  ip_addr ip, nh, rtid;
  struct ospf_iface *nhi = NULL;
  int met1, met2;
  neighbor *nn;
  struct ospf_lsa_rt *rt;
  struct ospf_area *atmp;


  OSPF_TRACE(D_EVENTS, "Starting routing table calculation for ext routes");

  WALK_SLIST(en, po->lsal)
  {
    if (en->lsa.type != LSA_T_EXT)
      continue;
    if (en->lsa.age == LSA_MAXAGE)
      continue;
    if (en->lsa.rt == p->cf->global->router_id)
      continue;

    le = en->lsa_body;
    lt = (struct ospf_lsa_ext_tos *) (le + 1);

    DBG("%s: Working on LSA. ID: %I, RT: %I, Type: %u, Mask %I\n",
	p->name, en->lsa.id, en->lsa.rt, en->lsa.type, le->netmask);

    if ((lt->etm.metric & METRIC_MASK) == LSINFINITY)
      continue;
    ip = ipa_and(ipa_from_u32(en->lsa.id), le->netmask);
    mlen = ipa_mklen(le->netmask);
    if ((mlen < 0) || (mlen > 32))
    {
      log("%s: Invalid mask in LSA. ID: %I, RT: %I, Type: %u, Mask %I",
	  p->name, en->lsa.id, en->lsa.rt, en->lsa.type, le->netmask);
      continue;
    }
    nhi = NULL;
    nh = IPA_NONE;

    met1 = LSINFINITY;
    met2 = LSINFINITY;

    rtid = ipa_from_u32(en->lsa.rt);

    nf1 = NULL;
    WALK_LIST(atmp, po->area_list)
    {
      nfh = fib_find(&atmp->rtr, &rtid, 32);
      if(nfh == NULL) continue;
      if(nf1 == NULL) nf1 = nfh;
      else if(ri_better(po, &nfh->n, NULL, &nf1->n, NULL, po->rfc1583)) nf1 = nfh;
    }

    if (!nf1)
      continue;			/* No AS boundary router found */

    if (nf1->n.metric1 == LSINFINITY)
      continue;			/* distance is INF */

    if (!(nf1->n.capa & ORTA_ASBR))
      continue;			/* It is not ASBR */

    if (ipa_equal(lt->fwaddr, IPA_NONE))
    {
      if (lt->etm.etos.ebit)
      {				/* FW address == 0 */
	met1 = nf1->n.metric1;
	met2 = (lt->etm.metric & METRIC_MASK);
      }
      else
      {
	met1 = nf1->n.metric1 + (lt->etm.metric & METRIC_MASK);
	met2 = LSINFINITY;
      }

      nh = nf1->n.nh;
      nhi = nf1->n.ifa;
      nfh = nf1;
    }
    else
    {				/* FW address !=0 */
      nf2 = fib_route(&po->rtf, lt->fwaddr, 32);

      if (!nf2)
      {
	DBG("Cannot find network route (GW=%I)\n", lt->fwaddr);
	continue;
      }

      if (lt->etm.etos.ebit)
      {
	met1 = nf2->n.metric1;
	met2 = (lt->etm.metric & METRIC_MASK);
      }
      else
      {
	met1 = nf2->n.metric1 + (lt->etm.metric & METRIC_MASK);
	met2 = LSINFINITY;
      }

      if ((nn = neigh_find(p, &lt->fwaddr, 0)) != NULL)
      {
	nh = lt->fwaddr;
	nhi = ospf_iface_find(po, nn->iface);
      }
      else
      {
	nh = nf2->n.nh;
	nhi = nf2->n.ifa;
      }

      nfh = nf2;
    }

    nfa.type = RTS_OSPF_EXT2;
    if(met2 == LSINFINITY) nfa.type = RTS_OSPF_EXT1;
    nfa.capa = 0;
    nfa.metric1 = met1;
    nfa.metric2 = met2;
    nfa.oa = po->backbone;
    nfa.ar = nf1->n.ar;
    nfa.nh = nh;
    nfa.ifa = nhi;
    nfa.tag = lt->tag;
    ri_install(po, ip, mlen, ORT_NET, &nfa, nfh);
  }

}

/* Add LSA into list of candidates in Dijkstra's algorithm */
static void
add_cand(list * l, struct top_hash_entry *en, struct top_hash_entry *par,
	 u16 dist, struct ospf_area *oa)
{
  node *prev, *n;
  int added = 0;
  struct top_hash_entry *act;

  if (en == NULL)
    return;
  if (en->lsa.age == LSA_MAXAGE)
    return;

  if (en->color == INSPF)
    return;

  if (dist >= en->dist)
    return;
  /*
   * FIXME The line above (=) is not a bug, but we don't support multiple
   * next hops. I'll start as soon as nest will
   */

  if (!link_back(oa, en, par))
    return;

  DBG("     Adding candidate: rt: %I, id: %I, type: %u\n", en->lsa.rt,
      en->lsa.id, en->lsa.type);

  en->nhi = NULL;
  en->nh = IPA_NONE;

  calc_next_hop(en, par, oa);

  if (!en->nhi)
    return;			/* We cannot find next hop, ignore it */

  if (en->color == CANDIDATE)
  {				/* We found a shorter path */
    rem_node(&en->cn);
  }
  en->dist = dist;
  en->color = CANDIDATE;

  prev = NULL;

  if (EMPTY_LIST(*l))
  {
    add_head(l, &en->cn);
  }
  else
  {
    WALK_LIST(n, *l)
    {
      act = SKIP_BACK(struct top_hash_entry, cn, n);
      if ((act->dist > dist) ||
	  ((act->dist == dist) && (act->lsa.type == LSA_T_NET)))
      {
	if (prev == NULL)
	  add_head(l, &en->cn);
	else
	  insert_node(&en->cn, prev);
	added = 1;
	break;
      }
      prev = n;
    }

    if (!added)
    {
      add_tail(l, &en->cn);
    }
  }
}

static void
calc_next_hop(struct top_hash_entry *en, struct top_hash_entry *par,
	      struct ospf_area *oa)
{
  struct ospf_neighbor *neigh;
  struct proto *p = &oa->po->proto;
  struct proto_ospf *po = oa->po;
  struct ospf_iface *ifa;
  u32 myrid = p->cf->global->router_id;

  DBG("     Next hop called.\n");
  if (ipa_equal(par->nh, IPA_NONE))
  {
    neighbor *nn;
    DBG("     Next hop calculating for id: %I rt: %I type: %u\n",
	en->lsa.id, en->lsa.rt, en->lsa.type);

    if (par == oa->rt)
    {
      if (en->lsa.type == LSA_T_NET)
      {
	if (en->lsa.rt == myrid)
	{
	  WALK_LIST(ifa, po->iface_list)
	    if (ifa->iface && (ipa_compare
		(ifa->iface->addr->ip, ipa_from_u32(en->lsa.id)) == 0))
	  {
	    en->nhi = ifa;
	    return;
	  }
	  log(L_ERR "I didn't find interface for my self originated LSA!\n");
	  /* This could sometimes happen */
	  return;
	}
	else
	{
	  ip_addr ip = ipa_from_u32(en->lsa.id);
	  nn = neigh_find(p, &ip, 0);
	  if (nn)
	    en->nhi = ospf_iface_find(po, nn->iface);
	  return;
	}
      }
      else
      {
	if ((neigh = find_neigh_noifa(po, en->lsa.rt)) == NULL)
	  return;
	en->nhi = neigh->ifa;
	if (neigh->ifa->type == OSPF_IT_VLINK) 
	en->nh = neigh->ip;	/* Yes, neighbor is it's
				 * own next hop */
	return;
      }
    }
    if (par->lsa.type == LSA_T_NET)
    {
      if (en->lsa.type == LSA_T_NET)
	bug("Parent for net is net?");
      if ((en->nhi = par->nhi) == NULL)
	bug("Did not find next hop interface for INSPF lsa!");
      if ((neigh = find_neigh_noifa(po, en->lsa.rt)) == NULL)
	return;
      en->nhi = neigh->ifa;
      en->nh = neigh->ip;	/* Yes, neighbor is it's own
				 * next hop */
      return;
    }
    else
    {				/* Parent is some RT neighbor */
      log(L_ERR "Router's parent has no next hop. (EN=%I, PAR=%I)",
	  en->lsa.id, par->lsa.id);
      /* I hoped this would never happen */
      return;
    }
  }
  en->nh = par->nh;
  en->nhi = par->nhi;
  DBG("     Next hop calculated: %I.\n", en->nh);
}

static void
rt_sync(struct proto_ospf *po)
{
  struct proto *p = &po->proto;
  struct fib_iterator fit;
  struct fib *fib = &po->rtf;
  ort *nf;
  struct ospf_area *oa, *oaa;
  struct area_net *anet;
  int flush;

  OSPF_TRACE(D_EVENTS, "Starting routing table synchronisation");

  DBG("Now syncing my rt table with nest's\n");
  FIB_ITERATE_INIT(&fit, fib);
again1:
  FIB_ITERATE_START(fib, &fit, nftmp)
  {
    nf = (ort *) nftmp;
    check_sum_lsa(po, nf, ORT_NET);
    if (memcmp(&nf->n, &nf->o, sizeof(orta)))
    {				/* Some difference */
      net *ne;
      rta a0;
      rte *e;

      bzero(&a0, sizeof(a0));

      a0.proto = p;
      a0.source = nf->n.type;
      a0.scope = SCOPE_UNIVERSE;
      a0.cast = RTC_UNICAST;
      a0.dest = RTD_ROUTER;
      a0.flags = 0;
      a0.aflags = 0;
      a0.iface = NULL;
      if (nf->n.ifa) a0.iface = nf->n.ifa->iface;
      a0.gw = nf->n.nh;

      if (ipa_equal(nf->n.nh, IPA_NONE)) a0.dest = RTD_DEVICE;
      
      if ((!ipa_equal(nf->n.nh, IPA_NONE)) && (!neigh_find(p, &nf->n.nh, 0)))
      {
        int found = 0;
        struct ospf_iface *ifa;
        struct top_hash_entry *en;
        DBG("Trying to find correct next hop");
        WALK_LIST(ifa, po->iface_list)
        {
          if ((ifa->type == OSPF_IT_VLINK) && ipa_equal(ifa->vip, nf->n.nh))
          {
            if ((en = ospf_hash_find(po->gr, ifa->voa->areaid, ifa->vid, ifa->vid, LSA_T_RT)) &&
              (!ipa_equal(en->nh, IPA_NONE)))
            {
              a0.gw = en->nh;
              found = 1;
            }
            break;
          }
        }
        if (!found) nf->n.metric1 = LSINFINITY; /* Delete it */
      }
      ne = net_get(p->table, nf->fn.prefix, nf->fn.pxlen);
      if (nf->n.metric1 < LSINFINITY)
      {
        e = rte_get_temp(&a0);
        e->u.ospf.metric1 = nf->n.metric1;
        e->u.ospf.metric2 = nf->n.metric2;
        e->u.ospf.tag = nf->n.tag;
        e->pflags = 0;
        e->net = ne;
        e->pref = p->preference;
        DBG("Modifying rt entry %I\n     (IP: %I, GW: %I)\n",
	  nf->fn.prefix, ip, nf->nh);
	rte_update(p->table, ne, p, e);
      }
      else
      {
        rte_update(p->table, ne, p, NULL);
        FIB_ITERATE_PUT(&fit, nftmp);
        fib_delete(fib, nftmp);
        goto again1;
      }
    }
  }
  FIB_ITERATE_END(nftmp);

  WALK_LIST(oa, po->area_list)
  {
    FIB_ITERATE_INIT(&fit, &oa->rtr);
again2:
    FIB_ITERATE_START(&oa->rtr, &fit, nftmp)
    {
      nf = (ort *) nftmp;
      if (memcmp(&nf->n, &nf->o, sizeof(orta)))
      {				/* Some difference */
        check_sum_lsa(po, nf, ORT_ROUTER);
        if(nf->n.metric1 >= LSINFINITY)
        {
          FIB_ITERATE_PUT(&fit, nftmp);
          fib_delete(&oa->rtr, nftmp);
          goto again2;
        }
      }
    }
    FIB_ITERATE_END(nftmp);

    /* Check condensed summary LSAs */
    FIB_WALK(&oa->net_fib, nftmp)
    {
      flush = 1;
      anet = (struct area_net *) nftmp;
      if((!anet->hidden) && anet->active)
        flush = 0;
          
      WALK_LIST(oaa, po->area_list)
      {
        int fl = flush;

        if (oaa == oa) continue;

	if ((oa == po->backbone) && oaa->trcap) fl = 1;

        if(fl) flush_sum_lsa(oaa, &anet->fn, ORT_NET);
        else originate_sum_lsa(oaa, &anet->fn, ORT_NET, 1);
      }
    }
    FIB_WALK_END;
  }
}