/*
 * Routing Table functions.
 * Copyright (C) 1998 Kunihiro Ishiguro
 *
 * 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 "prefix.h"
#include "table.h"
#include "memory.h"
#include "sockunion.h"

static void route_node_delete (struct route_node *);
static void route_table_free (struct route_table *);


/*
 * route_table_init_with_delegate
 */
struct route_table *
route_table_init_with_delegate (route_table_delegate_t *delegate)
{
  struct route_table *rt;

  rt = XCALLOC (MTYPE_ROUTE_TABLE, sizeof (struct route_table));
  rt->delegate = delegate;
  return rt;
}

void
route_table_finish (struct route_table *rt)
{
  route_table_free (rt);
}

/* Allocate new route node. */
static struct route_node *
route_node_new (struct route_table *table)
{
  return table->delegate->create_node (table->delegate, table);
}

/* Allocate new route node with prefix set. */
static struct route_node *
route_node_set (struct route_table *table, const struct prefix *prefix)
{
  struct route_node *node;
  
  node = route_node_new (table);

  prefix_copy (&node->p, prefix);
  node->table = table;

  return node;
}

/* Free route node. */
static void
route_node_free (struct route_table *table, struct route_node *node)
{
  table->delegate->destroy_node (table->delegate, table, node);
}

/* Free route table. */
static void
route_table_free (struct route_table *rt)
{
  struct route_node *tmp_node;
  struct route_node *node;
 
  if (rt == NULL)
    return;

  node = rt->top;

  /* Bulk deletion of nodes remaining in this table.  This function is not
     called until workers have completed their dependency on this table.
     A final route_unlock_node() will not be called for these nodes. */
  while (node)
    {
      if (node->l_left)
	{
	  node = node->l_left;
	  continue;
	}

      if (node->l_right)
	{
	  node = node->l_right;
	  continue;
	}

      tmp_node = node;
      node = node->parent;

      tmp_node->table->count--;
      tmp_node->lock = 0;  /* to cause assert if unlocked after this */
      route_node_free (rt, tmp_node);

      if (node != NULL)
	{
	  if (node->l_left == tmp_node)
	    node->l_left = NULL;
	  else
	    node->l_right = NULL;
	}
      else
	{
	  break;
	}
    }
 
  assert (rt->count == 0);

  XFREE (MTYPE_ROUTE_TABLE, rt);
  return;
}

/* Utility mask array. */
static const u_char maskbit[] =
{
  0x00, 0x80, 0xc0, 0xe0, 0xf0, 0xf8, 0xfc, 0xfe, 0xff
};

/* Common prefix route genaration. */
static void
route_common (const struct prefix *n, const struct prefix *p, struct prefix *new)
{
  int i;
  u_char diff;
  u_char mask;

  const u_char *np = (const u_char *)&n->u.prefix;
  const u_char *pp = (const u_char *)&p->u.prefix;
  u_char *newp = (u_char *)&new->u.prefix;

  for (i = 0; i < p->prefixlen / 8; i++)
    {
      if (np[i] == pp[i])
	newp[i] = np[i];
      else
	break;
    }

  new->prefixlen = i * 8;

  if (new->prefixlen != p->prefixlen)
    {
      diff = np[i] ^ pp[i];
      mask = 0x80;
      while (new->prefixlen < p->prefixlen && !(mask & diff))
	{
	  mask >>= 1;
	  new->prefixlen++;
	}
      newp[i] = np[i] & maskbit[new->prefixlen % 8];
    }
}

static void
set_link (struct route_node *node, struct route_node *new)
{
  unsigned int bit = prefix_bit (&new->p.u.prefix, node->p.prefixlen);

  node->link[bit] = new;
  new->parent = node;
}

/* Lock node. */
struct route_node *
route_lock_node (struct route_node *node)
{
  node->lock++;
  return node;
}

/* Unlock node. */
void
route_unlock_node (struct route_node *node)
{
  assert (node->lock > 0);
  node->lock--;

  if (node->lock == 0)
    route_node_delete (node);
}

/* Find matched prefix. */
struct route_node *
route_node_match (const struct route_table *table, const struct prefix *p)
{
  struct route_node *node;
  struct route_node *matched;

  matched = NULL;
  node = table->top;

  /* Walk down tree.  If there is matched route then store it to
     matched. */
  while (node && node->p.prefixlen <= p->prefixlen && 
	 prefix_match (&node->p, p))
    {
      if (node->info)
	matched = node;
      
      if (node->p.prefixlen == p->prefixlen)
        break;
      
      node = node->link[prefix_bit(&p->u.prefix, node->p.prefixlen)];
    }

  /* If matched route found, return it. */
  if (matched)
    return route_lock_node (matched);

  return NULL;
}

struct route_node *
route_node_match_ipv4 (const struct route_table *table,
		       const struct in_addr *addr)
{
  struct prefix_ipv4 p;

  memset (&p, 0, sizeof (struct prefix_ipv4));
  p.family = AF_INET;
  p.prefixlen = IPV4_MAX_PREFIXLEN;
  p.prefix = *addr;

  return route_node_match (table, (struct prefix *) &p);
}

#ifdef HAVE_IPV6
struct route_node *
route_node_match_ipv6 (const struct route_table *table,
		       const struct in6_addr *addr)
{
  struct prefix_ipv6 p;

  memset (&p, 0, sizeof (struct prefix_ipv6));
  p.family = AF_INET6;
  p.prefixlen = IPV6_MAX_PREFIXLEN;
  p.prefix = *addr;

  return route_node_match (table, (struct prefix *) &p);
}
#endif /* HAVE_IPV6 */

/* Lookup same prefix node.  Return NULL when we can't find route. */
struct route_node *
route_node_lookup (const struct route_table *table, const struct prefix *p)
{
  struct route_node *node;
  u_char prefixlen = p->prefixlen;
  const u_char *prefix = &p->u.prefix;

  node = table->top;

  while (node && node->p.prefixlen <= prefixlen &&
	 prefix_match (&node->p, p))
    {
      if (node->p.prefixlen == prefixlen)
        return node->info ? route_lock_node (node) : NULL;

      node = node->link[prefix_bit(prefix, node->p.prefixlen)];
    }

  return NULL;
}

/* Add node to routing table. */
struct route_node *
route_node_get (struct route_table *const table, const struct prefix *p)
{
  struct route_node *new;
  struct route_node *node;
  struct route_node *match;
  u_char prefixlen = p->prefixlen;
  const u_char *prefix = &p->u.prefix;

  match = NULL;
  node = table->top;
  while (node && node->p.prefixlen <= prefixlen &&
	 prefix_match (&node->p, p))
    {
      if (node->p.prefixlen == prefixlen)
        return route_lock_node (node);

      match = node;
      node = node->link[prefix_bit(prefix, node->p.prefixlen)];
    }

  if (node == NULL)
    {
      new = route_node_set (table, p);
      if (match)
	set_link (match, new);
      else
	table->top = new;
    }
  else
    {
      new = route_node_new (table);
      route_common (&node->p, p, &new->p);
      new->p.family = p->family;
      new->table = table;
      set_link (new, node);

      if (match)
	set_link (match, new);
      else
	table->top = new;

      if (new->p.prefixlen != p->prefixlen)
	{
	  match = new;
	  new = route_node_set (table, p);
	  set_link (match, new);
	  table->count++;
	}
    }
  table->count++;
  route_lock_node (new);
  
  return new;
}

/* Delete node from the routing table. */
static void
route_node_delete (struct route_node *node)
{
  struct route_node *child;
  struct route_node *parent;

  assert (node->lock == 0);
  assert (node->info == NULL);

  if (node->l_left && node->l_right)
    return;

  if (node->l_left)
    child = node->l_left;
  else
    child = node->l_right;

  parent = node->parent;

  if (child)
    child->parent = parent;

  if (parent)
    {
      if (parent->l_left == node)
	parent->l_left = child;
      else
	parent->l_right = child;
    }
  else
    node->table->top = child;

  node->table->count--;

  route_node_free (node->table, node);

  /* If parent node is stub then delete it also. */
  if (parent && parent->lock == 0)
    route_node_delete (parent);
}

/* Get fist node and lock it.  This function is useful when one want
   to lookup all the node exist in the routing table. */
struct route_node *
route_top (struct route_table *table)
{
  /* If there is no node in the routing table return NULL. */
  if (table->top == NULL)
    return NULL;

  /* Lock the top node and return it. */
  route_lock_node (table->top);
  return table->top;
}

/* Unlock current node and lock next node then return it. */
struct route_node *
route_next (struct route_node *node)
{
  struct route_node *next;
  struct route_node *start;

  /* Node may be deleted from route_unlock_node so we have to preserve
     next node's pointer. */

  if (node->l_left)
    {
      next = node->l_left;
      route_lock_node (next);
      route_unlock_node (node);
      return next;
    }
  if (node->l_right)
    {
      next = node->l_right;
      route_lock_node (next);
      route_unlock_node (node);
      return next;
    }

  start = node;
  while (node->parent)
    {
      if (node->parent->l_left == node && node->parent->l_right)
	{
	  next = node->parent->l_right;
	  route_lock_node (next);
	  route_unlock_node (start);
	  return next;
	}
      node = node->parent;
    }
  route_unlock_node (start);
  return NULL;
}

/* Unlock current node and lock next node until limit. */
struct route_node *
route_next_until (struct route_node *node, struct route_node *limit)
{
  struct route_node *next;
  struct route_node *start;

  /* Node may be deleted from route_unlock_node so we have to preserve
     next node's pointer. */

  if (node->l_left)
    {
      next = node->l_left;
      route_lock_node (next);
      route_unlock_node (node);
      return next;
    }
  if (node->l_right)
    {
      next = node->l_right;
      route_lock_node (next);
      route_unlock_node (node);
      return next;
    }

  start = node;
  while (node->parent && node != limit)
    {
      if (node->parent->l_left == node && node->parent->l_right)
	{
	  next = node->parent->l_right;
	  route_lock_node (next);
	  route_unlock_node (start);
	  return next;
	}
      node = node->parent;
    }
  route_unlock_node (start);
  return NULL;
}

unsigned long
route_table_count (const struct route_table *table)
{
  return table->count;
}

/**
 * route_node_create
 *
 * Default function for creating a route node.
 */
static struct route_node *
route_node_create (route_table_delegate_t *delegate,
		   struct route_table *table)
{
  struct route_node *node;
  node = XCALLOC (MTYPE_ROUTE_NODE, sizeof (struct route_node));
  return node;
}

/**
 * route_node_destroy
 *
 * Default function for destroying a route node.
 */
static void
route_node_destroy (route_table_delegate_t *delegate,
		    struct route_table *table, struct route_node *node)
{
  XFREE (MTYPE_ROUTE_NODE, node);
}

/*
 * Default delegate.
 */
static route_table_delegate_t default_delegate = {
  .create_node = route_node_create,
  .destroy_node = route_node_destroy
};

/*
 * route_table_init
 */
struct route_table *
route_table_init (void)
{
  return route_table_init_with_delegate (&default_delegate);
}

/**
 * route_table_prefix_iter_cmp
 *
 * Compare two prefixes according to the order in which they appear in
 * an iteration over a tree.
 * 
 * @return -1 if p1 occurs before p2 (p1 < p2)
 *          0 if the prefixes are identical (p1 == p2)
 *         +1 if p1 occurs after p2 (p1 > p2)
 */
int
route_table_prefix_iter_cmp (struct prefix *p1, struct prefix *p2)
{
  struct prefix common_space;
  struct prefix *common = &common_space;

  if (p1->prefixlen <= p2->prefixlen)
    {
      if (prefix_match (p1, p2))
	{

	  /*
	   * p1 contains p2, or is equal to it.
	   */
	  return (p1->prefixlen == p2->prefixlen) ? 0 : -1;
	}
    }
  else
    {

      /*
       * Check if p2 contains p1.
       */
      if (prefix_match (p2, p1))
	  return 1;
    }

  route_common (p1, p2, common);
  assert (common->prefixlen < p1->prefixlen);
  assert (common->prefixlen < p2->prefixlen);

  /*
   * Both prefixes are longer than the common prefix.
   *
   * We need to check the bit after the common prefixlen to determine
   * which one comes later.
   */
  if (prefix_bit (&p1->u.prefix, common->prefixlen))
    {

      /*
       * We branch to the right to get to p1 from the common prefix.
       */
      assert (!prefix_bit (&p2->u.prefix, common->prefixlen));
      return 1;
    }

  /*
   * We branch to the right to get to p2 from the common prefix.
   */
  assert (prefix_bit (&p2->u.prefix, common->prefixlen));
  return -1;
}

/*
 * route_get_subtree_next
 *
 * Helper function that returns the first node that follows the nodes
 * in the sub-tree under 'node' in iteration order.
 */
static struct route_node *
route_get_subtree_next (struct route_node *node)
{
  while (node->parent)
    {
      if (node->parent->l_left == node && node->parent->l_right)
	return node->parent->l_right;

      node = node->parent;
    }

  return NULL;
}

/**
 * route_table_get_next_internal
 *
 * Helper function to find the node that occurs after the given prefix in
 * order of iteration.
 *
 * @see route_table_get_next
 */
static struct route_node *
route_table_get_next_internal (const struct route_table *table,
			       struct prefix *p)
{
  struct route_node *node, *tmp_node;
  int cmp;

  node = table->top;

  while (node)
    {
      int match;

      if (node->p.prefixlen < p->prefixlen)
	match = prefix_match (&node->p, p);
      else
	match = prefix_match (p, &node->p);

      if (match)
	{
	  if (node->p.prefixlen == p->prefixlen)
	    {

	      /*
	       * The prefix p exists in the tree, just return the next
	       * node.
	       */
	      route_lock_node (node);
	      node = route_next (node);
	      if (node)
		route_unlock_node (node);

	      return (node);
	    }

	  if (node->p.prefixlen > p->prefixlen)
	    {

	      /*
	       * Node is in the subtree of p, and hence greater than p.
	       */
	      return node;
	    }

	  /*
	   * p is in the sub-tree under node.
	   */
	  tmp_node = node->link[prefix_bit (&p->u.prefix, node->p.prefixlen)];

	  if (tmp_node)
	    {
	      node = tmp_node;
	      continue;
	    }

	  /*
	   * There are no nodes in the direction where p should be. If
	   * node has a right child, then it must be greater than p.
	   */
	  if (node->l_right)
	    return node->l_right;

	  /*
	   * No more children to follow, go upwards looking for the next
	   * node.
	   */
	  return route_get_subtree_next (node);
	}

      /*
       * Neither node prefix nor 'p' contains the other.
       */
      cmp = route_table_prefix_iter_cmp (&node->p, p);
      if (cmp > 0)
	{

	  /*
	   * Node follows p in iteration order. Return it.
	   */
	  return node;
	}

      assert (cmp < 0);

      /*
       * Node and the subtree under it come before prefix p in
       * iteration order. Prefix p and its sub-tree are not present in
       * the tree. Go upwards and find the first node that follows the
       * subtree. That node will also succeed p.
       */
      return route_get_subtree_next (node);
    }

  return NULL;
}

/**
 * route_table_get_next
 *
 * Find the node that occurs after the given prefix in order of
 * iteration.
 */
struct route_node *
route_table_get_next (const struct route_table *table, struct prefix *p)
{
  struct route_node *node;

  node = route_table_get_next_internal (table, p);
  if (node)
    {
      assert (route_table_prefix_iter_cmp (&node->p, p) > 0);
      route_lock_node (node);
    }
  return node;
}

/*
 * route_table_iter_init
 */
void
route_table_iter_init (route_table_iter_t * iter, struct route_table *table)
{
  memset (iter, 0, sizeof (*iter));
  iter->state = RT_ITER_STATE_INIT;
  iter->table = table;
}

/*
 * route_table_iter_pause
 *
 * Pause an iteration over the table. This allows the iteration to be
 * resumed point after arbitrary additions/deletions from the table.
 * An iteration can be resumed by just calling route_table_iter_next()
 * on the iterator.
 */
void
route_table_iter_pause (route_table_iter_t * iter)
{
  switch (iter->state)
    {

    case RT_ITER_STATE_INIT:
    case RT_ITER_STATE_PAUSED:
    case RT_ITER_STATE_DONE:
      return;

    case RT_ITER_STATE_ITERATING:

      /*
       * Save the prefix that we are currently at. The next call to
       * route_table_iter_next() will return the node after this prefix
       * in the tree.
       */
      prefix_copy (&iter->pause_prefix, &iter->current->p);
      route_unlock_node (iter->current);
      iter->current = NULL;
      iter->state = RT_ITER_STATE_PAUSED;
      return;

    default:
      assert (0);
    }

}

/*
 * route_table_iter_cleanup
 *
 * Release any resources held by the iterator.
 */
void
route_table_iter_cleanup (route_table_iter_t * iter)
{
  if (iter->state == RT_ITER_STATE_ITERATING)
    {
      route_unlock_node (iter->current);
      iter->current = NULL;
    }
  assert (!iter->current);

  /*
   * Set the state to RT_ITER_STATE_DONE to make any
   * route_table_iter_next() calls on this iterator return NULL.
   */
  iter->state = RT_ITER_STATE_DONE;
}