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ip6_fib.c

/*
 *    Linux INET6 implementation
 *    Forwarding Information Database
 *
 *    Authors:
 *    Pedro Roque       <roque@di.fc.ul.pt>
 *
 *    $Id: ip6_fib.c,v 1.25 2001/10/31 21:55:55 davem Exp $
 *
 *    This program 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 of the License, or (at your option) any later version.
 */

/*
 *    Changes:
 *    Yuji SEKIYA @USAGI:     Support default route on router node;
 *                      remove ip6_null_entry from the top of
 *                      routing table.
 *    Ville Nuorvala:         Fixed routing subtrees.
 */
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/net.h>
#include <linux/route.h>
#include <linux/netdevice.h>
#include <linux/in6.h>
#include <linux/init.h>
#include <linux/list.h>

#ifdef      CONFIG_PROC_FS
#include <linux/proc_fs.h>
#endif

#include <net/ipv6.h>
#include <net/ndisc.h>
#include <net/addrconf.h>

#include <net/ip6_fib.h>
#include <net/ip6_route.h>

#define RT6_DEBUG 2

#if RT6_DEBUG >= 3
#define RT6_TRACE(x...) printk(KERN_DEBUG x)
#else
#define RT6_TRACE(x...) do { ; } while (0)
#endif

struct rt6_statistics   rt6_stats;

static struct kmem_cache * fib6_node_kmem __read_mostly;

enum fib_walk_state_t
{
#ifdef CONFIG_IPV6_SUBTREES
      FWS_S,
#endif
      FWS_L,
      FWS_R,
      FWS_C,
      FWS_U
};

struct fib6_cleaner_t
{
      struct fib6_walker_t w;
      int (*func)(struct rt6_info *, void *arg);
      void *arg;
};

static DEFINE_RWLOCK(fib6_walker_lock);

#ifdef CONFIG_IPV6_SUBTREES
#define FWS_INIT FWS_S
#else
#define FWS_INIT FWS_L
#endif

static void fib6_prune_clones(struct fib6_node *fn, struct rt6_info *rt);
static struct rt6_info * fib6_find_prefix(struct fib6_node *fn);
static struct fib6_node * fib6_repair_tree(struct fib6_node *fn);
static int fib6_walk(struct fib6_walker_t *w);
static int fib6_walk_continue(struct fib6_walker_t *w);

/*
 *    A routing update causes an increase of the serial number on the
 *    affected subtree. This allows for cached routes to be asynchronously
 *    tested when modifications are made to the destination cache as a
 *    result of redirects, path MTU changes, etc.
 */

static __u32 rt_sernum;

static DEFINE_TIMER(ip6_fib_timer, fib6_run_gc, 0, 0);

static struct fib6_walker_t fib6_walker_list = {
      .prev = &fib6_walker_list,
      .next = &fib6_walker_list,
};

#define FOR_WALKERS(w) for ((w)=fib6_walker_list.next; (w) != &fib6_walker_list; (w)=(w)->next)

static inline void fib6_walker_link(struct fib6_walker_t *w)
{
      write_lock_bh(&fib6_walker_lock);
      w->next = fib6_walker_list.next;
      w->prev = &fib6_walker_list;
      w->next->prev = w;
      w->prev->next = w;
      write_unlock_bh(&fib6_walker_lock);
}

static inline void fib6_walker_unlink(struct fib6_walker_t *w)
{
      write_lock_bh(&fib6_walker_lock);
      w->next->prev = w->prev;
      w->prev->next = w->next;
      w->prev = w->next = w;
      write_unlock_bh(&fib6_walker_lock);
}
static __inline__ u32 fib6_new_sernum(void)
{
      u32 n = ++rt_sernum;
      if ((__s32)n <= 0)
            rt_sernum = n = 1;
      return n;
}

/*
 *    Auxiliary address test functions for the radix tree.
 *
 *    These assume a 32bit processor (although it will work on
 *    64bit processors)
 */

/*
 *    test bit
 */

static __inline__ __be32 addr_bit_set(void *token, int fn_bit)
{
      __be32 *addr = token;

      return htonl(1 << ((~fn_bit)&0x1F)) & addr[fn_bit>>5];
}

static __inline__ struct fib6_node * node_alloc(void)
{
      struct fib6_node *fn;

      fn = kmem_cache_zalloc(fib6_node_kmem, GFP_ATOMIC);

      return fn;
}

static __inline__ void node_free(struct fib6_node * fn)
{
      kmem_cache_free(fib6_node_kmem, fn);
}

static __inline__ void rt6_release(struct rt6_info *rt)
{
      if (atomic_dec_and_test(&rt->rt6i_ref))
            dst_free(&rt->u.dst);
}

static struct fib6_table fib6_main_tbl = {
      .tb6_id           = RT6_TABLE_MAIN,
      .tb6_root   = {
            .leaf       = &ip6_null_entry,
            .fn_flags   = RTN_ROOT | RTN_TL_ROOT | RTN_RTINFO,
      },
};

#ifdef CONFIG_IPV6_MULTIPLE_TABLES
#define FIB_TABLE_HASHSZ 256
#else
#define FIB_TABLE_HASHSZ 1
#endif
static struct hlist_head fib_table_hash[FIB_TABLE_HASHSZ];

static void fib6_link_table(struct fib6_table *tb)
{
      unsigned int h;

      /*
       * Initialize table lock at a single place to give lockdep a key,
       * tables aren't visible prior to being linked to the list.
       */
      rwlock_init(&tb->tb6_lock);

      h = tb->tb6_id & (FIB_TABLE_HASHSZ - 1);

      /*
       * No protection necessary, this is the only list mutatation
       * operation, tables never disappear once they exist.
       */
      hlist_add_head_rcu(&tb->tb6_hlist, &fib_table_hash[h]);
}

#ifdef CONFIG_IPV6_MULTIPLE_TABLES
static struct fib6_table fib6_local_tbl = {
      .tb6_id           = RT6_TABLE_LOCAL,
      .tb6_root   = {
            .leaf       = &ip6_null_entry,
            .fn_flags   = RTN_ROOT | RTN_TL_ROOT | RTN_RTINFO,
      },
};

static struct fib6_table *fib6_alloc_table(u32 id)
{
      struct fib6_table *table;

      table = kzalloc(sizeof(*table), GFP_ATOMIC);
      if (table != NULL) {
            table->tb6_id = id;
            table->tb6_root.leaf = &ip6_null_entry;
            table->tb6_root.fn_flags = RTN_ROOT | RTN_TL_ROOT | RTN_RTINFO;
      }

      return table;
}

struct fib6_table *fib6_new_table(u32 id)
{
      struct fib6_table *tb;

      if (id == 0)
            id = RT6_TABLE_MAIN;
      tb = fib6_get_table(id);
      if (tb)
            return tb;

      tb = fib6_alloc_table(id);
      if (tb != NULL)
            fib6_link_table(tb);

      return tb;
}

struct fib6_table *fib6_get_table(u32 id)
{
      struct fib6_table *tb;
      struct hlist_node *node;
      unsigned int h;

      if (id == 0)
            id = RT6_TABLE_MAIN;
      h = id & (FIB_TABLE_HASHSZ - 1);
      rcu_read_lock();
      hlist_for_each_entry_rcu(tb, node, &fib_table_hash[h], tb6_hlist) {
            if (tb->tb6_id == id) {
                  rcu_read_unlock();
                  return tb;
            }
      }
      rcu_read_unlock();

      return NULL;
}

static void __init fib6_tables_init(void)
{
      fib6_link_table(&fib6_main_tbl);
      fib6_link_table(&fib6_local_tbl);
}

#else

struct fib6_table *fib6_new_table(u32 id)
{
      return fib6_get_table(id);
}

struct fib6_table *fib6_get_table(u32 id)
{
      return &fib6_main_tbl;
}

struct dst_entry *fib6_rule_lookup(struct flowi *fl, int flags,
                           pol_lookup_t lookup)
{
      return (struct dst_entry *) lookup(&fib6_main_tbl, fl, flags);
}

static void __init fib6_tables_init(void)
{
      fib6_link_table(&fib6_main_tbl);
}

#endif

static int fib6_dump_node(struct fib6_walker_t *w)
{
      int res;
      struct rt6_info *rt;

      for (rt = w->leaf; rt; rt = rt->u.dst.rt6_next) {
            res = rt6_dump_route(rt, w->args);
            if (res < 0) {
                  /* Frame is full, suspend walking */
                  w->leaf = rt;
                  return 1;
            }
            BUG_TRAP(res!=0);
      }
      w->leaf = NULL;
      return 0;
}

static void fib6_dump_end(struct netlink_callback *cb)
{
      struct fib6_walker_t *w = (void*)cb->args[2];

      if (w) {
            cb->args[2] = 0;
            kfree(w);
      }
      cb->done = (void*)cb->args[3];
      cb->args[1] = 3;
}

static int fib6_dump_done(struct netlink_callback *cb)
{
      fib6_dump_end(cb);
      return cb->done ? cb->done(cb) : 0;
}

static int fib6_dump_table(struct fib6_table *table, struct sk_buff *skb,
                     struct netlink_callback *cb)
{
      struct fib6_walker_t *w;
      int res;

      w = (void *)cb->args[2];
      w->root = &table->tb6_root;

      if (cb->args[4] == 0) {
            read_lock_bh(&table->tb6_lock);
            res = fib6_walk(w);
            read_unlock_bh(&table->tb6_lock);
            if (res > 0)
                  cb->args[4] = 1;
      } else {
            read_lock_bh(&table->tb6_lock);
            res = fib6_walk_continue(w);
            read_unlock_bh(&table->tb6_lock);
            if (res != 0) {
                  if (res < 0)
                        fib6_walker_unlink(w);
                  goto end;
            }
            fib6_walker_unlink(w);
            cb->args[4] = 0;
      }
end:
      return res;
}

static int inet6_dump_fib(struct sk_buff *skb, struct netlink_callback *cb)
{
      unsigned int h, s_h;
      unsigned int e = 0, s_e;
      struct rt6_rtnl_dump_arg arg;
      struct fib6_walker_t *w;
      struct fib6_table *tb;
      struct hlist_node *node;
      int res = 0;

      s_h = cb->args[0];
      s_e = cb->args[1];

      w = (void *)cb->args[2];
      if (w == NULL) {
            /* New dump:
             *
             * 1. hook callback destructor.
             */
            cb->args[3] = (long)cb->done;
            cb->done = fib6_dump_done;

            /*
             * 2. allocate and initialize walker.
             */
            w = kzalloc(sizeof(*w), GFP_ATOMIC);
            if (w == NULL)
                  return -ENOMEM;
            w->func = fib6_dump_node;
            cb->args[2] = (long)w;
      }

      arg.skb = skb;
      arg.cb = cb;
      w->args = &arg;

      for (h = s_h; h < FIB_TABLE_HASHSZ; h++, s_e = 0) {
            e = 0;
            hlist_for_each_entry(tb, node, &fib_table_hash[h], tb6_hlist) {
                  if (e < s_e)
                        goto next;
                  res = fib6_dump_table(tb, skb, cb);
                  if (res != 0)
                        goto out;
next:
                  e++;
            }
      }
out:
      cb->args[1] = e;
      cb->args[0] = h;

      res = res < 0 ? res : skb->len;
      if (res <= 0)
            fib6_dump_end(cb);
      return res;
}

/*
 *    Routing Table
 *
 *    return the appropriate node for a routing tree "add" operation
 *    by either creating and inserting or by returning an existing
 *    node.
 */

static struct fib6_node * fib6_add_1(struct fib6_node *root, void *addr,
                             int addrlen, int plen,
                             int offset)
{
      struct fib6_node *fn, *in, *ln;
      struct fib6_node *pn = NULL;
      struct rt6key *key;
      int   bit;
      __be32      dir = 0;
      __u32 sernum = fib6_new_sernum();

      RT6_TRACE("fib6_add_1\n");

      /* insert node in tree */

      fn = root;

      do {
            key = (struct rt6key *)((u8 *)fn->leaf + offset);

            /*
             *    Prefix match
             */
            if (plen < fn->fn_bit ||
                !ipv6_prefix_equal(&key->addr, addr, fn->fn_bit))
                  goto insert_above;

            /*
             *    Exact match ?
             */

            if (plen == fn->fn_bit) {
                  /* clean up an intermediate node */
                  if ((fn->fn_flags & RTN_RTINFO) == 0) {
                        rt6_release(fn->leaf);
                        fn->leaf = NULL;
                  }

                  fn->fn_sernum = sernum;

                  return fn;
            }

            /*
             *    We have more bits to go
             */

            /* Try to walk down on tree. */
            fn->fn_sernum = sernum;
            dir = addr_bit_set(addr, fn->fn_bit);
            pn = fn;
            fn = dir ? fn->right: fn->left;
      } while (fn);

      /*
       *    We walked to the bottom of tree.
       *    Create new leaf node without children.
       */

      ln = node_alloc();

      if (ln == NULL)
            return NULL;
      ln->fn_bit = plen;

      ln->parent = pn;
      ln->fn_sernum = sernum;

      if (dir)
            pn->right = ln;
      else
            pn->left  = ln;

      return ln;


insert_above:
      /*
       * split since we don't have a common prefix anymore or
       * we have a less significant route.
       * we've to insert an intermediate node on the list
       * this new node will point to the one we need to create
       * and the current
       */

      pn = fn->parent;

      /* find 1st bit in difference between the 2 addrs.

         See comment in __ipv6_addr_diff: bit may be an invalid value,
         but if it is >= plen, the value is ignored in any case.
       */

      bit = __ipv6_addr_diff(addr, &key->addr, addrlen);

      /*
       *          (intermediate)[in]
       *              /    \
       *    (new leaf node)[ln] (old node)[fn]
       */
      if (plen > bit) {
            in = node_alloc();
            ln = node_alloc();

            if (in == NULL || ln == NULL) {
                  if (in)
                        node_free(in);
                  if (ln)
                        node_free(ln);
                  return NULL;
            }

            /*
             * new intermediate node.
             * RTN_RTINFO will
             * be off since that an address that chooses one of
             * the branches would not match less specific routes
             * in the other branch
             */

            in->fn_bit = bit;

            in->parent = pn;
            in->leaf = fn->leaf;
            atomic_inc(&in->leaf->rt6i_ref);

            in->fn_sernum = sernum;

            /* update parent pointer */
            if (dir)
                  pn->right = in;
            else
                  pn->left  = in;

            ln->fn_bit = plen;

            ln->parent = in;
            fn->parent = in;

            ln->fn_sernum = sernum;

            if (addr_bit_set(addr, bit)) {
                  in->right = ln;
                  in->left  = fn;
            } else {
                  in->left  = ln;
                  in->right = fn;
            }
      } else { /* plen <= bit */

            /*
             *          (new leaf node)[ln]
             *              /    \
             *         (old node)[fn] NULL
             */

            ln = node_alloc();

            if (ln == NULL)
                  return NULL;

            ln->fn_bit = plen;

            ln->parent = pn;

            ln->fn_sernum = sernum;

            if (dir)
                  pn->right = ln;
            else
                  pn->left  = ln;

            if (addr_bit_set(&key->addr, plen))
                  ln->right = fn;
            else
                  ln->left  = fn;

            fn->parent = ln;
      }
      return ln;
}

/*
 *    Insert routing information in a node.
 */

static int fib6_add_rt2node(struct fib6_node *fn, struct rt6_info *rt,
                      struct nl_info *info)
{
      struct rt6_info *iter = NULL;
      struct rt6_info **ins;

      ins = &fn->leaf;

      for (iter = fn->leaf; iter; iter=iter->u.dst.rt6_next) {
            /*
             *    Search for duplicates
             */

            if (iter->rt6i_metric == rt->rt6i_metric) {
                  /*
                   *    Same priority level
                   */

                  if (iter->rt6i_dev == rt->rt6i_dev &&
                      iter->rt6i_idev == rt->rt6i_idev &&
                      ipv6_addr_equal(&iter->rt6i_gateway,
                                  &rt->rt6i_gateway)) {
                        if (!(iter->rt6i_flags&RTF_EXPIRES))
                              return -EEXIST;
                        iter->rt6i_expires = rt->rt6i_expires;
                        if (!(rt->rt6i_flags&RTF_EXPIRES)) {
                              iter->rt6i_flags &= ~RTF_EXPIRES;
                              iter->rt6i_expires = 0;
                        }
                        return -EEXIST;
                  }
            }

            if (iter->rt6i_metric > rt->rt6i_metric)
                  break;

            ins = &iter->u.dst.rt6_next;
      }

      /* Reset round-robin state, if necessary */
      if (ins == &fn->leaf)
            fn->rr_ptr = NULL;

      /*
       *    insert node
       */

      rt->u.dst.rt6_next = iter;
      *ins = rt;
      rt->rt6i_node = fn;
      atomic_inc(&rt->rt6i_ref);
      inet6_rt_notify(RTM_NEWROUTE, rt, info);
      rt6_stats.fib_rt_entries++;

      if ((fn->fn_flags & RTN_RTINFO) == 0) {
            rt6_stats.fib_route_nodes++;
            fn->fn_flags |= RTN_RTINFO;
      }

      return 0;
}

static __inline__ void fib6_start_gc(struct rt6_info *rt)
{
      if (ip6_fib_timer.expires == 0 &&
          (rt->rt6i_flags & (RTF_EXPIRES|RTF_CACHE)))
            mod_timer(&ip6_fib_timer, jiffies + ip6_rt_gc_interval);
}

void fib6_force_start_gc(void)
{
      if (ip6_fib_timer.expires == 0)
            mod_timer(&ip6_fib_timer, jiffies + ip6_rt_gc_interval);
}

/*
 *    Add routing information to the routing tree.
 *    <destination addr>/<source addr>
 *    with source addr info in sub-trees
 */

int fib6_add(struct fib6_node *root, struct rt6_info *rt, struct nl_info *info)
{
      struct fib6_node *fn, *pn = NULL;
      int err = -ENOMEM;

      fn = fib6_add_1(root, &rt->rt6i_dst.addr, sizeof(struct in6_addr),
                  rt->rt6i_dst.plen, offsetof(struct rt6_info, rt6i_dst));

      if (fn == NULL)
            goto out;

      pn = fn;

#ifdef CONFIG_IPV6_SUBTREES
      if (rt->rt6i_src.plen) {
            struct fib6_node *sn;

            if (fn->subtree == NULL) {
                  struct fib6_node *sfn;

                  /*
                   * Create subtree.
                   *
                   *          fn[main tree]
                   *          |
                   *          sfn[subtree root]
                   *             \
                   *              sn[new leaf node]
                   */

                  /* Create subtree root node */
                  sfn = node_alloc();
                  if (sfn == NULL)
                        goto st_failure;

                  sfn->leaf = &ip6_null_entry;
                  atomic_inc(&ip6_null_entry.rt6i_ref);
                  sfn->fn_flags = RTN_ROOT;
                  sfn->fn_sernum = fib6_new_sernum();

                  /* Now add the first leaf node to new subtree */

                  sn = fib6_add_1(sfn, &rt->rt6i_src.addr,
                              sizeof(struct in6_addr), rt->rt6i_src.plen,
                              offsetof(struct rt6_info, rt6i_src));

                  if (sn == NULL) {
                        /* If it is failed, discard just allocated
                           root, and then (in st_failure) stale node
                           in main tree.
                         */
                        node_free(sfn);
                        goto st_failure;
                  }

                  /* Now link new subtree to main tree */
                  sfn->parent = fn;
                  fn->subtree = sfn;
            } else {
                  sn = fib6_add_1(fn->subtree, &rt->rt6i_src.addr,
                              sizeof(struct in6_addr), rt->rt6i_src.plen,
                              offsetof(struct rt6_info, rt6i_src));

                  if (sn == NULL)
                        goto st_failure;
            }

            if (fn->leaf == NULL) {
                  fn->leaf = rt;
                  atomic_inc(&rt->rt6i_ref);
            }
            fn = sn;
      }
#endif

      err = fib6_add_rt2node(fn, rt, info);

      if (err == 0) {
            fib6_start_gc(rt);
            if (!(rt->rt6i_flags&RTF_CACHE))
                  fib6_prune_clones(pn, rt);
      }

out:
      if (err) {
#ifdef CONFIG_IPV6_SUBTREES
            /*
             * If fib6_add_1 has cleared the old leaf pointer in the
             * super-tree leaf node we have to find a new one for it.
             */
            if (pn != fn && !pn->leaf && !(pn->fn_flags & RTN_RTINFO)) {
                  pn->leaf = fib6_find_prefix(pn);
#if RT6_DEBUG >= 2
                  if (!pn->leaf) {
                        BUG_TRAP(pn->leaf != NULL);
                        pn->leaf = &ip6_null_entry;
                  }
#endif
                  atomic_inc(&pn->leaf->rt6i_ref);
            }
#endif
            dst_free(&rt->u.dst);
      }
      return err;

#ifdef CONFIG_IPV6_SUBTREES
      /* Subtree creation failed, probably main tree node
         is orphan. If it is, shoot it.
       */
st_failure:
      if (fn && !(fn->fn_flags & (RTN_RTINFO|RTN_ROOT)))
            fib6_repair_tree(fn);
      dst_free(&rt->u.dst);
      return err;
#endif
}

/*
 *    Routing tree lookup
 *
 */

struct lookup_args {
      int         offset;           /* key offset on rt6_info     */
      struct in6_addr   *addr;            /* search key                 */
};

static struct fib6_node * fib6_lookup_1(struct fib6_node *root,
                              struct lookup_args *args)
{
      struct fib6_node *fn;
      __be32 dir;

      if (unlikely(args->offset == 0))
            return NULL;

      /*
       *    Descend on a tree
       */

      fn = root;

      for (;;) {
            struct fib6_node *next;

            dir = addr_bit_set(args->addr, fn->fn_bit);

            next = dir ? fn->right : fn->left;

            if (next) {
                  fn = next;
                  continue;
            }

            break;
      }

      while(fn) {
            if (FIB6_SUBTREE(fn) || fn->fn_flags & RTN_RTINFO) {
                  struct rt6key *key;

                  key = (struct rt6key *) ((u8 *) fn->leaf +
                                     args->offset);

                  if (ipv6_prefix_equal(&key->addr, args->addr, key->plen)) {
#ifdef CONFIG_IPV6_SUBTREES
                        if (fn->subtree)
                              fn = fib6_lookup_1(fn->subtree, args + 1);
#endif
                        if (!fn || fn->fn_flags & RTN_RTINFO)
                              return fn;
                  }
            }

            if (fn->fn_flags & RTN_ROOT)
                  break;

            fn = fn->parent;
      }

      return NULL;
}

struct fib6_node * fib6_lookup(struct fib6_node *root, struct in6_addr *daddr,
                         struct in6_addr *saddr)
{
      struct fib6_node *fn;
      struct lookup_args args[] = {
            {
                  .offset = offsetof(struct rt6_info, rt6i_dst),
                  .addr = daddr,
            },
#ifdef CONFIG_IPV6_SUBTREES
            {
                  .offset = offsetof(struct rt6_info, rt6i_src),
                  .addr = saddr,
            },
#endif
            {
                  .offset = 0,      /* sentinel */
            }
      };

      fn = fib6_lookup_1(root, daddr ? args : args + 1);

      if (fn == NULL || fn->fn_flags & RTN_TL_ROOT)
            fn = root;

      return fn;
}

/*
 *    Get node with specified destination prefix (and source prefix,
 *    if subtrees are used)
 */


static struct fib6_node * fib6_locate_1(struct fib6_node *root,
                              struct in6_addr *addr,
                              int plen, int offset)
{
      struct fib6_node *fn;

      for (fn = root; fn ; ) {
            struct rt6key *key = (struct rt6key *)((u8 *)fn->leaf + offset);

            /*
             *    Prefix match
             */
            if (plen < fn->fn_bit ||
                !ipv6_prefix_equal(&key->addr, addr, fn->fn_bit))
                  return NULL;

            if (plen == fn->fn_bit)
                  return fn;

            /*
             *    We have more bits to go
             */
            if (addr_bit_set(addr, fn->fn_bit))
                  fn = fn->right;
            else
                  fn = fn->left;
      }
      return NULL;
}

struct fib6_node * fib6_locate(struct fib6_node *root,
                         struct in6_addr *daddr, int dst_len,
                         struct in6_addr *saddr, int src_len)
{
      struct fib6_node *fn;

      fn = fib6_locate_1(root, daddr, dst_len,
                     offsetof(struct rt6_info, rt6i_dst));

#ifdef CONFIG_IPV6_SUBTREES
      if (src_len) {
            BUG_TRAP(saddr!=NULL);
            if (fn && fn->subtree)
                  fn = fib6_locate_1(fn->subtree, saddr, src_len,
                                 offsetof(struct rt6_info, rt6i_src));
      }
#endif

      if (fn && fn->fn_flags&RTN_RTINFO)
            return fn;

      return NULL;
}


/*
 *    Deletion
 *
 */

static struct rt6_info * fib6_find_prefix(struct fib6_node *fn)
{
      if (fn->fn_flags&RTN_ROOT)
            return &ip6_null_entry;

      while(fn) {
            if(fn->left)
                  return fn->left->leaf;

            if(fn->right)
                  return fn->right->leaf;

            fn = FIB6_SUBTREE(fn);
      }
      return NULL;
}

/*
 *    Called to trim the tree of intermediate nodes when possible. "fn"
 *    is the node we want to try and remove.
 */

static struct fib6_node * fib6_repair_tree(struct fib6_node *fn)
{
      int children;
      int nstate;
      struct fib6_node *child, *pn;
      struct fib6_walker_t *w;
      int iter = 0;

      for (;;) {
            RT6_TRACE("fixing tree: plen=%d iter=%d\n", fn->fn_bit, iter);
            iter++;

            BUG_TRAP(!(fn->fn_flags&RTN_RTINFO));
            BUG_TRAP(!(fn->fn_flags&RTN_TL_ROOT));
            BUG_TRAP(fn->leaf==NULL);

            children = 0;
            child = NULL;
            if (fn->right) child = fn->right, children |= 1;
            if (fn->left) child = fn->left, children |= 2;

            if (children == 3 || FIB6_SUBTREE(fn)
#ifdef CONFIG_IPV6_SUBTREES
                /* Subtree root (i.e. fn) may have one child */
                || (children && fn->fn_flags&RTN_ROOT)
#endif
                ) {
                  fn->leaf = fib6_find_prefix(fn);
#if RT6_DEBUG >= 2
                  if (fn->leaf==NULL) {
                        BUG_TRAP(fn->leaf);
                        fn->leaf = &ip6_null_entry;
                  }
#endif
                  atomic_inc(&fn->leaf->rt6i_ref);
                  return fn->parent;
            }

            pn = fn->parent;
#ifdef CONFIG_IPV6_SUBTREES
            if (FIB6_SUBTREE(pn) == fn) {
                  BUG_TRAP(fn->fn_flags&RTN_ROOT);
                  FIB6_SUBTREE(pn) = NULL;
                  nstate = FWS_L;
            } else {
                  BUG_TRAP(!(fn->fn_flags&RTN_ROOT));
#endif
                  if (pn->right == fn) pn->right = child;
                  else if (pn->left == fn) pn->left = child;
#if RT6_DEBUG >= 2
                  else BUG_TRAP(0);
#endif
                  if (child)
                        child->parent = pn;
                  nstate = FWS_R;
#ifdef CONFIG_IPV6_SUBTREES
            }
#endif

            read_lock(&fib6_walker_lock);
            FOR_WALKERS(w) {
                  if (child == NULL) {
                        if (w->root == fn) {
                              w->root = w->node = NULL;
                              RT6_TRACE("W %p adjusted by delroot 1\n", w);
                        } else if (w->node == fn) {
                              RT6_TRACE("W %p adjusted by delnode 1, s=%d/%d\n", w, w->state, nstate);
                              w->node = pn;
                              w->state = nstate;
                        }
                  } else {
                        if (w->root == fn) {
                              w->root = child;
                              RT6_TRACE("W %p adjusted by delroot 2\n", w);
                        }
                        if (w->node == fn) {
                              w->node = child;
                              if (children&2) {
                                    RT6_TRACE("W %p adjusted by delnode 2, s=%d\n", w, w->state);
                                    w->state = w->state>=FWS_R ? FWS_U : FWS_INIT;
                              } else {
                                    RT6_TRACE("W %p adjusted by delnode 2, s=%d\n", w, w->state);
                                    w->state = w->state>=FWS_C ? FWS_U : FWS_INIT;
                              }
                        }
                  }
            }
            read_unlock(&fib6_walker_lock);

            node_free(fn);
            if (pn->fn_flags&RTN_RTINFO || FIB6_SUBTREE(pn))
                  return pn;

            rt6_release(pn->leaf);
            pn->leaf = NULL;
            fn = pn;
      }
}

static void fib6_del_route(struct fib6_node *fn, struct rt6_info **rtp,
                     struct nl_info *info)
{
      struct fib6_walker_t *w;
      struct rt6_info *rt = *rtp;

      RT6_TRACE("fib6_del_route\n");

      /* Unlink it */
      *rtp = rt->u.dst.rt6_next;
      rt->rt6i_node = NULL;
      rt6_stats.fib_rt_entries--;
      rt6_stats.fib_discarded_routes++;

      /* Reset round-robin state, if necessary */
      if (fn->rr_ptr == rt)
            fn->rr_ptr = NULL;

      /* Adjust walkers */
      read_lock(&fib6_walker_lock);
      FOR_WALKERS(w) {
            if (w->state == FWS_C && w->leaf == rt) {
                  RT6_TRACE("walker %p adjusted by delroute\n", w);
                  w->leaf = rt->u.dst.rt6_next;
                  if (w->leaf == NULL)
                        w->state = FWS_U;
            }
      }
      read_unlock(&fib6_walker_lock);

      rt->u.dst.rt6_next = NULL;

      if (fn->leaf == NULL && fn->fn_flags&RTN_TL_ROOT)
            fn->leaf = &ip6_null_entry;

      /* If it was last route, expunge its radix tree node */
      if (fn->leaf == NULL) {
            fn->fn_flags &= ~RTN_RTINFO;
            rt6_stats.fib_route_nodes--;
            fn = fib6_repair_tree(fn);
      }

      if (atomic_read(&rt->rt6i_ref) != 1) {
            /* This route is used as dummy address holder in some split
             * nodes. It is not leaked, but it still holds other resources,
             * which must be released in time. So, scan ascendant nodes
             * and replace dummy references to this route with references
             * to still alive ones.
             */
            while (fn) {
                  if (!(fn->fn_flags&RTN_RTINFO) && fn->leaf == rt) {
                        fn->leaf = fib6_find_prefix(fn);
                        atomic_inc(&fn->leaf->rt6i_ref);
                        rt6_release(rt);
                  }
                  fn = fn->parent;
            }
            /* No more references are possible at this point. */
            if (atomic_read(&rt->rt6i_ref) != 1) BUG();
      }

      inet6_rt_notify(RTM_DELROUTE, rt, info);
      rt6_release(rt);
}

int fib6_del(struct rt6_info *rt, struct nl_info *info)
{
      struct fib6_node *fn = rt->rt6i_node;
      struct rt6_info **rtp;

#if RT6_DEBUG >= 2
      if (rt->u.dst.obsolete>0) {
            BUG_TRAP(fn==NULL);
            return -ENOENT;
      }
#endif
      if (fn == NULL || rt == &ip6_null_entry)
            return -ENOENT;

      BUG_TRAP(fn->fn_flags&RTN_RTINFO);

      if (!(rt->rt6i_flags&RTF_CACHE)) {
            struct fib6_node *pn = fn;
#ifdef CONFIG_IPV6_SUBTREES
            /* clones of this route might be in another subtree */
            if (rt->rt6i_src.plen) {
                  while (!(pn->fn_flags&RTN_ROOT))
                        pn = pn->parent;
                  pn = pn->parent;
            }
#endif
            fib6_prune_clones(pn, rt);
      }

      /*
       *    Walk the leaf entries looking for ourself
       */

      for (rtp = &fn->leaf; *rtp; rtp = &(*rtp)->u.dst.rt6_next) {
            if (*rtp == rt) {
                  fib6_del_route(fn, rtp, info);
                  return 0;
            }
      }
      return -ENOENT;
}

/*
 *    Tree traversal function.
 *
 *    Certainly, it is not interrupt safe.
 *    However, it is internally reenterable wrt itself and fib6_add/fib6_del.
 *    It means, that we can modify tree during walking
 *    and use this function for garbage collection, clone pruning,
 *    cleaning tree when a device goes down etc. etc.
 *
 *    It guarantees that every node will be traversed,
 *    and that it will be traversed only once.
 *
 *    Callback function w->func may return:
 *    0 -> continue walking.
 *    positive value -> walking is suspended (used by tree dumps,
 *    and probably by gc, if it will be split to several slices)
 *    negative value -> terminate walking.
 *
 *    The function itself returns:
 *    0   -> walk is complete.
 *    >0  -> walk is incomplete (i.e. suspended)
 *    <0  -> walk is terminated by an error.
 */

static int fib6_walk_continue(struct fib6_walker_t *w)
{
      struct fib6_node *fn, *pn;

      for (;;) {
            fn = w->node;
            if (fn == NULL)
                  return 0;

            if (w->prune && fn != w->root &&
                fn->fn_flags&RTN_RTINFO && w->state < FWS_C) {
                  w->state = FWS_C;
                  w->leaf = fn->leaf;
            }
            switch (w->state) {
#ifdef CONFIG_IPV6_SUBTREES
            case FWS_S:
                  if (FIB6_SUBTREE(fn)) {
                        w->node = FIB6_SUBTREE(fn);
                        continue;
                  }
                  w->state = FWS_L;
#endif
            case FWS_L:
                  if (fn->left) {
                        w->node = fn->left;
                        w->state = FWS_INIT;
                        continue;
                  }
                  w->state = FWS_R;
            case FWS_R:
                  if (fn->right) {
                        w->node = fn->right;
                        w->state = FWS_INIT;
                        continue;
                  }
                  w->state = FWS_C;
                  w->leaf = fn->leaf;
            case FWS_C:
                  if (w->leaf && fn->fn_flags&RTN_RTINFO) {
                        int err = w->func(w);
                        if (err)
                              return err;
                        continue;
                  }
                  w->state = FWS_U;
            case FWS_U:
                  if (fn == w->root)
                        return 0;
                  pn = fn->parent;
                  w->node = pn;
#ifdef CONFIG_IPV6_SUBTREES
                  if (FIB6_SUBTREE(pn) == fn) {
                        BUG_TRAP(fn->fn_flags&RTN_ROOT);
                        w->state = FWS_L;
                        continue;
                  }
#endif
                  if (pn->left == fn) {
                        w->state = FWS_R;
                        continue;
                  }
                  if (pn->right == fn) {
                        w->state = FWS_C;
                        w->leaf = w->node->leaf;
                        continue;
                  }
#if RT6_DEBUG >= 2
                  BUG_TRAP(0);
#endif
            }
      }
}

static int fib6_walk(struct fib6_walker_t *w)
{
      int res;

      w->state = FWS_INIT;
      w->node = w->root;

      fib6_walker_link(w);
      res = fib6_walk_continue(w);
      if (res <= 0)
            fib6_walker_unlink(w);
      return res;
}

static int fib6_clean_node(struct fib6_walker_t *w)
{
      int res;
      struct rt6_info *rt;
      struct fib6_cleaner_t *c = container_of(w, struct fib6_cleaner_t, w);

      for (rt = w->leaf; rt; rt = rt->u.dst.rt6_next) {
            res = c->func(rt, c->arg);
            if (res < 0) {
                  w->leaf = rt;
                  res = fib6_del(rt, NULL);
                  if (res) {
#if RT6_DEBUG >= 2
                        printk(KERN_DEBUG "fib6_clean_node: del failed: rt=%p@%p err=%d\n", rt, rt->rt6i_node, res);
#endif
                        continue;
                  }
                  return 0;
            }
            BUG_TRAP(res==0);
      }
      w->leaf = rt;
      return 0;
}

/*
 *    Convenient frontend to tree walker.
 *
 *    func is called on each route.
 *          It may return -1 -> delete this route.
 *                        0  -> continue walking
 *
 *    prune==1 -> only immediate children of node (certainly,
 *    ignoring pure split nodes) will be scanned.
 */

static void fib6_clean_tree(struct fib6_node *root,
                      int (*func)(struct rt6_info *, void *arg),
                      int prune, void *arg)
{
      struct fib6_cleaner_t c;

      c.w.root = root;
      c.w.func = fib6_clean_node;
      c.w.prune = prune;
      c.func = func;
      c.arg = arg;

      fib6_walk(&c.w);
}

void fib6_clean_all(int (*func)(struct rt6_info *, void *arg),
                int prune, void *arg)
{
      struct fib6_table *table;
      struct hlist_node *node;
      unsigned int h;

      rcu_read_lock();
      for (h = 0; h < FIB_TABLE_HASHSZ; h++) {
            hlist_for_each_entry_rcu(table, node, &fib_table_hash[h],
                               tb6_hlist) {
                  write_lock_bh(&table->tb6_lock);
                  fib6_clean_tree(&table->tb6_root, func, prune, arg);
                  write_unlock_bh(&table->tb6_lock);
            }
      }
      rcu_read_unlock();
}

static int fib6_prune_clone(struct rt6_info *rt, void *arg)
{
      if (rt->rt6i_flags & RTF_CACHE) {
            RT6_TRACE("pruning clone %p\n", rt);
            return -1;
      }

      return 0;
}

static void fib6_prune_clones(struct fib6_node *fn, struct rt6_info *rt)
{
      fib6_clean_tree(fn, fib6_prune_clone, 1, rt);
}

/*
 *    Garbage collection
 */

static struct fib6_gc_args
{
      int               timeout;
      int               more;
} gc_args;

static int fib6_age(struct rt6_info *rt, void *arg)
{
      unsigned long now = jiffies;

      /*
       *    check addrconf expiration here.
       *    Routes are expired even if they are in use.
       *
       *    Also age clones. Note, that clones are aged out
       *    only if they are not in use now.
       */

      if (rt->rt6i_flags&RTF_EXPIRES && rt->rt6i_expires) {
            if (time_after(now, rt->rt6i_expires)) {
                  RT6_TRACE("expiring %p\n", rt);
                  return -1;
            }
            gc_args.more++;
      } else if (rt->rt6i_flags & RTF_CACHE) {
            if (atomic_read(&rt->u.dst.__refcnt) == 0 &&
                time_after_eq(now, rt->u.dst.lastuse + gc_args.timeout)) {
                  RT6_TRACE("aging clone %p\n", rt);
                  return -1;
            } else if ((rt->rt6i_flags & RTF_GATEWAY) &&
                     (!(rt->rt6i_nexthop->flags & NTF_ROUTER))) {
                  RT6_TRACE("purging route %p via non-router but gateway\n",
                          rt);
                  return -1;
            }
            gc_args.more++;
      }

      return 0;
}

static DEFINE_SPINLOCK(fib6_gc_lock);

void fib6_run_gc(unsigned long dummy)
{
      if (dummy != ~0UL) {
            spin_lock_bh(&fib6_gc_lock);
            gc_args.timeout = dummy ? (int)dummy : ip6_rt_gc_interval;
      } else {
            local_bh_disable();
            if (!spin_trylock(&fib6_gc_lock)) {
                  mod_timer(&ip6_fib_timer, jiffies + HZ);
                  local_bh_enable();
                  return;
            }
            gc_args.timeout = ip6_rt_gc_interval;
      }
      gc_args.more = 0;

      ndisc_dst_gc(&gc_args.more);
      fib6_clean_all(fib6_age, 0, NULL);

      if (gc_args.more)
            mod_timer(&ip6_fib_timer, jiffies + ip6_rt_gc_interval);
      else {
            del_timer(&ip6_fib_timer);
            ip6_fib_timer.expires = 0;
      }
      spin_unlock_bh(&fib6_gc_lock);
}

void __init fib6_init(void)
{
      fib6_node_kmem = kmem_cache_create("fib6_nodes",
                                 sizeof(struct fib6_node),
                                 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC,
                                 NULL);

      fib6_tables_init();

      __rtnl_register(PF_INET6, RTM_GETROUTE, NULL, inet6_dump_fib);
}

void fib6_gc_cleanup(void)
{
      del_timer(&ip6_fib_timer);
      kmem_cache_destroy(fib6_node_kmem);
}

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