lq_mpr.c

wifi 无线网络路由协议OLSR linux下C代码

/*
 * The olsr.org Optimized Link-State Routing daemon(olsrd)
 * Copyright (c) 2004, Thomas Lopatic ([e-mail])
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions 
 * are met:
 *
 * * Redistributions of source code must retain the above copyright 
 *   notice, this list of conditions and the following disclaimer.
 * * Redistributions in binary form must reproduce the above copyright 
 *   notice, this list of conditions and the following disclaimer in 
 *   the documentation and/or other materials provided with the 
 *   distribution.
 * * Neither the name of olsr.org, olsrd nor the names of its 
 *   contributors may be used to endorse or promote products derived 
 *   from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 
 * POSSIBILITY OF SUCH DAMAGE.
 *
 * Visit http://www.olsr.org for more information.
 *
 * If you find this software useful feel free to make a donation
 * to the project. For more information see the website or contact
 * the copyright holders.
 *
 * $Id: lq_mpr.c,v 1.13 2007/08/02 22:07:19 bernd67 Exp $
 */

#include "defs.h"
#include "neighbor_table.h"
#include "two_hop_neighbor_table.h"
#include "link_set.h"
#include "lq_mpr.h"
#include "scheduler.h"

void olsr_calculate_lq_mpr(void)
{
  struct neighbor_2_entry *neigh2;
  struct neighbor_list_entry *walker;
  int i, k;
  struct neighbor_entry *neigh;
  double best, best_1hop;
  olsr_bool mpr_changes = OLSR_FALSE;

  for(i = 0; i < HASHSIZE; i++)
    {
      for (neigh = neighbortable[i].next;
           neigh != &neighbortable[i];
           neigh = neigh->next)
        { 
          // memorize previous MPR status

          neigh->was_mpr = neigh->is_mpr;

          // clear current MPR status

          neigh->is_mpr = OLSR_FALSE;

          // in this pass we are only interested in WILL_ALWAYS neighbours

          if(neigh->status == NOT_SYM ||
             neigh->willingness != WILL_ALWAYS)
            continue;

          neigh->is_mpr = OLSR_TRUE;

          if (neigh->is_mpr != neigh->was_mpr)
            mpr_changes = OLSR_TRUE;
        }
    }

  for(i = 0; i < HASHSIZE; i++)
    {
      // loop through all 2-hop neighbours

      for (neigh2 = two_hop_neighbortable[i].next;
           neigh2 != &two_hop_neighbortable[i];
           neigh2 = neigh2->next)
        {
          best_1hop = -1.0;

          // check whether this 2-hop neighbour is also a neighbour

          neigh = olsr_lookup_neighbor_table(&neigh2->neighbor_2_addr);

          // if it's a neighbour and also symmetric, then examine
          // the link quality
          
          if (neigh != NULL && neigh->status == SYM)
            {
              // if the direct link is better than the best route via
              // an MPR, then prefer the direct link and do not select
              // an MPR for this 2-hop neighbour

              // determine the link quality of the direct link

              struct link_entry *lnk = get_best_link_to_neighbor(&neigh->neighbor_main_addr);

	      if (!lnk)
		continue;

              best_1hop = lnk->loss_link_quality * lnk->neigh_link_quality;

              // see wether we find a better route via an MPR

              for (walker = neigh2->neighbor_2_nblist.next;
                   walker != &neigh2->neighbor_2_nblist;
                   walker = walker->next)
                if (walker->path_link_quality > best_1hop)
                  break;

              // we've reached the end of the list, so we haven't found
              // a better route via an MPR - so, skip MPR selection for
              // this 1-hop neighbor

              if (walker == &neigh2->neighbor_2_nblist)
                continue;
            }

          // find the connecting 1-hop neighbours with the
          // best total link qualities

          // mark all 1-hop neighbours as not selected

          for (walker = neigh2->neighbor_2_nblist.next;
               walker != &neigh2->neighbor_2_nblist;
               walker = walker->next)
            walker->neighbor->skip = OLSR_FALSE;

          for (k = 0; k < olsr_cnf->mpr_coverage; k++)
            {
              // look for the best 1-hop neighbour that we haven't
              // yet selected

              neigh = NULL;
              best = -1.0;

              for (walker = neigh2->neighbor_2_nblist.next;
                   walker != &neigh2->neighbor_2_nblist;
                   walker = walker->next)
                if (walker->neighbor->status == SYM &&
                    !walker->neighbor->skip &&
                    walker->path_link_quality > best)
                  {
                    neigh = walker->neighbor;
                    best = walker->path_link_quality;
                  }

              // Found a 1-hop neighbor that we haven't previously selected.
              // Use it as MPR only when the 2-hop path through it is better than
              // any existing 1-hop path.
              if ((neigh != NULL) && (best > best_1hop))
                {
                  neigh->is_mpr = OLSR_TRUE;
                  neigh->skip = OLSR_TRUE;
          
                  if (neigh->is_mpr != neigh->was_mpr)
                    mpr_changes = OLSR_TRUE;
                }

              // no neighbour found => the requested MPR coverage cannot
              // be satisfied => stop

              else
                break;
            }
        }
    }

  if (mpr_changes && olsr_cnf->tc_redundancy > 0)
    signal_link_changes(OLSR_TRUE);
}