bgp_damp.c

大名鼎鼎的路由器源码。程序分ZEBRA、OSPFRIP等3个包。程序框架采用一个路由协议一个进程的方式

/* BGP flap dampening
   Copyright (C) 2001 IP Infusion Inc.

This file is part of GNU Zebra.

GNU Zebra is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2, or (at your option) any
later version.

GNU Zebra is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Zebra; see the file COPYING.  If not, write to the Free
Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
02111-1307, USA.  */

#include <zebra.h>
#include <math.h>

#include "prefix.h"
#include "memory.h"
#include "command.h"
#include "log.h"
#include "thread.h"

#include "bgpd/bgpd.h"
#include "bgpd/bgp_damp.h"
#include "bgpd/bgp_table.h"
#include "bgpd/bgp_route.h"
#include "bgpd/bgp_attr.h" 
#include "bgpd/bgp_advertise.h"

/* Global variable to access damping configuration */
struct bgp_damp_config bgp_damp_cfg;
struct bgp_damp_config *damp = &bgp_damp_cfg;

/* Utility macro to add and delete BGP dampening information to no
   used list.  */
#define BGP_DAMP_LIST_ADD(N,A)  BGP_INFO_ADD(N,A,no_reuse_list)
#define BGP_DAMP_LIST_DEL(N,A)  BGP_INFO_DEL(N,A,no_reuse_list)

/* Calculate reuse list index by penalty value.  */
static int
bgp_reuse_index (int penalty)
{
  int i;
  int index;

  i = (int)(((double) penalty / damp->reuse_limit - 1.0) * damp->scale_factor);
  
  if ( i >= damp->reuse_index_size )
    i = damp->reuse_index_size - 1;

  index = damp->reuse_index[i] - damp->reuse_index[0];

  return (damp->reuse_offset + index) % damp->reuse_list_size;  
}

/* Add BGP dampening information to reuse list.  */
static void 
bgp_reuse_list_add (struct bgp_damp_info *bdi)
{
  int index;

  index = bdi->index = bgp_reuse_index (bdi->penalty);

  bdi->prev = NULL;
  bdi->next = damp->reuse_list[index];
  if (damp->reuse_list[index])
    damp->reuse_list[index]->prev = bdi;
  damp->reuse_list[index] = bdi;
}

/* Delete BGP dampening information from reuse list.  */
static void
bgp_reuse_list_delete (struct bgp_damp_info *bdi)
{
  if (bdi->next)
    bdi->next->prev = bdi->prev;
  if (bdi->prev)
    bdi->prev->next = bdi->next;
  else
    damp->reuse_list[bdi->index] = bdi->next;
}   

/* Return decayed penalty value.  */
int 
bgp_damp_decay (time_t tdiff, int penalty)
{
  int i;

  i = (int) ((double) tdiff / DELTA_T);

  if (i == 0)
    return penalty; 
  
  if (i >= damp->decay_array_size)
    return 0;

  return (int) (penalty * damp->decay_array[i]);
}

/* Handler of reuse timer event.  Each route in the current reuse-list
   is evaluated.  RFC2439 Section 4.8.7.  */
int
bgp_reuse_timer (struct thread *t)
{
  struct bgp_damp_info *bdi;
  struct bgp_damp_info *next;
  time_t t_now, t_diff;
  struct bgp *bgp;
  int bgp_process (struct bgp *, struct bgp_node *, afi_t, safi_t);

  damp->t_reuse = NULL;
  damp->t_reuse =
    thread_add_timer (master, bgp_reuse_timer, NULL, DELTA_REUSE);

  bgp = bgp_get_default ();
  if (! bgp)
    return 0;

  t_now = time (NULL);

  /* 1.  save a pointer to the current zeroth queue head and zero the
     list head entry.  */
  bdi = damp->reuse_list[damp->reuse_offset];
  damp->reuse_list[damp->reuse_offset] = NULL;

  /* 2.  set offset = modulo reuse-list-size ( offset + 1 ), thereby
     rotating the circular queue of list-heads.  */
  damp->reuse_offset = (damp->reuse_offset + 1) % damp->reuse_list_size;

  /* 3. if ( the saved list head pointer is non-empty ) */
  for (; bdi; bdi = next)
    {
      next = bdi->next;

      /* Set t-diff = t-now - t-updated.  */
      t_diff = t_now - bdi->t_updated;

      /* Set figure-of-merit = figure-of-merit * decay-array-ok [t-diff] */
      bdi->penalty = bgp_damp_decay (t_diff, bdi->penalty);   

      /* Set t-updated = t-now.  */
      bdi->t_updated = t_now;

      /* if (figure-of-merit < reuse).  */
      if (bdi->penalty < damp->reuse_limit)
	{
	  /* Reuse the route.  */
	  UNSET_FLAG (bdi->binfo->flags, BGP_INFO_DAMPED);
	  bdi->suppress_time = 0;

	  if (bdi->lastrecord == BGP_RECORD_UPDATE)
	    {
	      UNSET_FLAG (bdi->binfo->flags, BGP_INFO_HISTORY);
	      bgp_aggregate_increment (bgp, &bdi->rn->p, bdi->binfo,
				       bdi->afi, bdi->safi);   
	      bgp_process (bgp, bdi->rn, bdi->afi, bdi->safi);
	    }

	  if (bdi->penalty <= damp->reuse_limit / 2.0)
	    bgp_damp_info_free (bdi, 1);
	  else
	    BGP_DAMP_LIST_ADD (damp, bdi);
	}
      else
	/* Re-insert into another list (See RFC2439 Section 4.8.6).  */
	bgp_reuse_list_add (bdi);
    }

  return 0;
}

/* A route becomes unreachable (RFC2439 Section 4.8.2).  */
int
bgp_damp_withdraw (struct bgp_info *binfo, struct bgp_node *rn,
		   afi_t afi, safi_t safi, int attr_change)
{
  time_t t_now;
  struct bgp_damp_info *bdi;
  double last_penalty = 0;
  
  t_now = time (NULL);

  /* Processing Unreachable Messages.  */
  bdi = binfo->damp_info;

  if (bdi == NULL)
    {
      /* If there is no previous stability history. */

      /* RFC2439 said:
	 1. allocate a damping structure.
         2. set figure-of-merit = 1.
         3. withdraw the route.  */

      bdi =  XCALLOC (MTYPE_BGP_DAMP_INFO, sizeof (struct bgp_damp_info));
      bdi->binfo = binfo;
      bdi->rn = rn;
      bdi->penalty = (attr_change ? DEFAULT_PENALTY / 2 : DEFAULT_PENALTY);
      bdi->flap = 1;
      bdi->start_time = t_now;
      bdi->suppress_time = 0;
      bdi->index = -1;
      bdi->afi = afi;
      bdi->safi = safi;
      binfo->damp_info = bdi;
      BGP_DAMP_LIST_ADD (damp, bdi);
    }
  else
    {
      last_penalty = bdi->penalty;

      /* 1. Set t-diff = t-now - t-updated.  */
      bdi->penalty = 
	(bgp_damp_decay (t_now - bdi->t_updated, bdi->penalty) 
	 + (attr_change ? DEFAULT_PENALTY / 2 : DEFAULT_PENALTY));

      if (bdi->penalty > damp->ceiling)
	bdi->penalty = damp->ceiling;

      bdi->flap++;
    }
  
  bdi->lastrecord = BGP_RECORD_WITHDRAW;
  bdi->t_updated = t_now;

  /* Make this route as historical status.  */
  SET_FLAG (binfo->flags, BGP_INFO_HISTORY);

  /* Remove the route from a reuse list if it is on one.  */
  if (CHECK_FLAG (bdi->binfo->flags, BGP_INFO_DAMPED))
    {
      /* If decay rate isn't equal to 0, reinsert brn. */  
      if (bdi->penalty != last_penalty)
	{
	  bgp_reuse_list_delete (bdi);
	  bgp_reuse_list_add (bdi);  
	}
      return BGP_DAMP_SUPPRESSED; 
    }

  /* If not suppressed before, do annonunce this withdraw and
     insert into reuse_list.  */
  if (bdi->penalty >= damp->suppress_value)
    {
      SET_FLAG (bdi->binfo->flags, BGP_INFO_DAMPED);
      bdi->suppress_time = t_now;
      BGP_DAMP_LIST_DEL (damp, bdi);
      bgp_reuse_list_add (bdi);
    }

  return BGP_DAMP_USED;
}

int
bgp_damp_update (struct bgp_info *binfo, struct bgp_node *rn, 
		 afi_t afi, safi_t safi)
{
  time_t t_now;
  struct bgp_damp_info *bdi;
  int status;

  bdi = binfo->damp_info;
  if (! bdi)
    return BGP_DAMP_USED;

  t_now = time (NULL);
  UNSET_FLAG (binfo->flags, BGP_INFO_HISTORY); 

  bdi->lastrecord = BGP_RECORD_UPDATE;
  bdi->penalty = bgp_damp_decay (t_now - bdi->t_updated, bdi->penalty);

  if (! CHECK_FLAG (bdi->binfo->flags, BGP_INFO_DAMPED)
      && (bdi->penalty < damp->suppress_value))
    status = BGP_DAMP_USED;
  else if (CHECK_FLAG (bdi->binfo->flags, BGP_INFO_DAMPED)
	   && (bdi->penalty < damp->reuse_limit) )
    {
      UNSET_FLAG (bdi->binfo->flags, BGP_INFO_DAMPED);
      bgp_reuse_list_delete (bdi);
      BGP_DAMP_LIST_ADD (damp, bdi);
      bdi->suppress_time = 0;
      status = BGP_DAMP_USED;
    }
  else
    status = BGP_DAMP_SUPPRESSED;  

  if (bdi->penalty > damp->reuse_limit / 2.0)
    bdi->t_updated = t_now;
  else
    bgp_damp_info_free (bdi, 0);
	
  return status;
}

/* Remove dampening information and history route.  */
int 
bgp_damp_scan (struct bgp_info *binfo, afi_t afi, safi_t safi)
{
  time_t t_now, t_diff;
  struct bgp_damp_info *bdi;

  t_now = time (NULL);
  bdi = binfo->damp_info;
 
  if (CHECK_FLAG (binfo->flags, BGP_INFO_DAMPED))
    {
      t_diff = t_now - bdi->suppress_time;

      if (t_diff >= damp->max_suppress_time)
        {
          UNSET_FLAG (binfo->flags, BGP_INFO_DAMPED);
          bgp_reuse_list_delete (bdi);
	  BGP_DAMP_LIST_ADD (damp, bdi);
          bdi->penalty = damp->reuse_limit;
          bdi->suppress_time = 0;
          bdi->t_updated = t_now;
          
          /* Need to announce UPDATE once this binfo is usable again. */