ipv6: fix a possible double free

[pohmelfs.git] / net / ipv6 / ip6_fib.c

/*
 *      Linux INET6 implementation
 *      Forwarding Information Database
 *
 *      Authors:
 *      Pedro Roque             <roque@di.fc.ul.pt>
 *
 *      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>
#include <linux/slab.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

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;
        struct net *net;
        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 net *net, struct fib6_node *fn,
                              struct rt6_info *rt);
static struct rt6_info *fib6_find_prefix(struct net *net, struct fib6_node *fn);
static struct fib6_node *fib6_repair_tree(struct net *net, 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 void fib6_gc_timer_cb(unsigned long arg);

static LIST_HEAD(fib6_walkers);
#define FOR_WALKERS(w) list_for_each_entry(w, &fib6_walkers, lh)

static inline void fib6_walker_link(struct fib6_walker_t *w)
{
        write_lock_bh(&fib6_walker_lock);
        list_add(&w->lh, &fib6_walkers);
        write_unlock_bh(&fib6_walker_lock);
}

static inline void fib6_walker_unlink(struct fib6_walker_t *w)
{
        write_lock_bh(&fib6_walker_lock);
        list_del(&w->lh);
        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
 */
#if defined(__LITTLE_ENDIAN)
# define BITOP_BE32_SWIZZLE     (0x1F & ~7)
#else
# define BITOP_BE32_SWIZZLE     0
#endif

static __inline__ __be32 addr_bit_set(const void *token, int fn_bit)
{
        const __be32 *addr = token;
        /*
         * Here,
         *      1 << ((~fn_bit ^ BITOP_BE32_SWIZZLE) & 0x1f)
         * is optimized version of
         *      htonl(1 << ((~fn_bit)&0x1F))
         * See include/asm-generic/bitops/le.h.
         */
        return (__force __be32)(1 << ((~fn_bit ^ BITOP_BE32_SWIZZLE) & 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->dst);
}

static void fib6_link_table(struct net *net, 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 & (FIB6_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, &net->ipv6.fib_table_hash[h]);
}

#ifdef CONFIG_IPV6_MULTIPLE_TABLES

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

        table = kzalloc(sizeof(*table), GFP_ATOMIC);
        if (table != NULL) {
                table->tb6_id = id;
                table->tb6_root.leaf = net->ipv6.ip6_null_entry;
                table->tb6_root.fn_flags = RTN_ROOT | RTN_TL_ROOT | RTN_RTINFO;
        }

        return table;
}

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

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

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

        return tb;
}

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

        if (id == 0)
                id = RT6_TABLE_MAIN;
        h = id & (FIB6_TABLE_HASHSZ - 1);
        rcu_read_lock();
        head = &net->ipv6.fib_table_hash[h];
        hlist_for_each_entry_rcu(tb, node, head, tb6_hlist) {
                if (tb->tb6_id == id) {
                        rcu_read_unlock();
                        return tb;
                }
        }
        rcu_read_unlock();

        return NULL;
}

static void __net_init fib6_tables_init(struct net *net)
{
        fib6_link_table(net, net->ipv6.fib6_main_tbl);
        fib6_link_table(net, net->ipv6.fib6_local_tbl);
}
#else

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

struct fib6_table *fib6_get_table(struct net *net, u32 id)
{
          return net->ipv6.fib6_main_tbl;
}

struct dst_entry *fib6_rule_lookup(struct net *net, struct flowi6 *fl6,
                                   int flags, pol_lookup_t lookup)
{
        return (struct dst_entry *) lookup(net, net->ipv6.fib6_main_tbl, fl6, flags);
}

static void __net_init fib6_tables_init(struct net *net)
{
        fib6_link_table(net, net->ipv6.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->dst.rt6_next) {
                res = rt6_dump_route(rt, w->args);
                if (res < 0) {
                        /* Frame is full, suspend walking */
                        w->leaf = rt;
                        return 1;
                }
                WARN_ON(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) {
                if (cb->args[4]) {
                        cb->args[4] = 0;
                        fib6_walker_unlink(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) {
                w->count = 0;
                w->skip = 0;

                read_lock_bh(&table->tb6_lock);
                res = fib6_walk(w);
                read_unlock_bh(&table->tb6_lock);
                if (res > 0) {
                        cb->args[4] = 1;
                        cb->args[5] = w->root->fn_sernum;
                }
        } else {
                if (cb->args[5] != w->root->fn_sernum) {
                        /* Begin at the root if the tree changed */
                        cb->args[5] = w->root->fn_sernum;
                        w->state = FWS_INIT;
                        w->node = w->root;
                        w->skip = w->count;
                } else
                        w->skip = 0;

                read_lock_bh(&table->tb6_lock);
                res = fib6_walk_continue(w);
                read_unlock_bh(&table->tb6_lock);
                if (res <= 0) {
                        fib6_walker_unlink(w);
                        cb->args[4] = 0;
                }
        }

        return res;
}

static int inet6_dump_fib(struct sk_buff *skb, struct netlink_callback *cb)
{
        struct net *net = sock_net(skb->sk);
        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;
        struct hlist_head *head;
        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;
        arg.net = net;
        w->args = &arg;

        rcu_read_lock();
        for (h = s_h; h < FIB6_TABLE_HASHSZ; h++, s_e = 0) {
                e = 0;
                head = &net->ipv6.fib_table_hash[h];
                hlist_for_each_entry_rcu(tb, node, head, tb6_hlist) {
                        if (e < s_e)
                                goto next;
                        res = fib6_dump_table(tb, skb, cb);
                        if (res != 0)
                                goto out;
next:
                        e++;
                }
        }
out:
        rcu_read_unlock();
        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->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->dst.rt6_next;
        }

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

        /*
         *      insert node
         */

        rt->dst.rt6_next = iter;
        *ins = rt;
        rt->rt6i_node = fn;
        atomic_inc(&rt->rt6i_ref);
        inet6_rt_notify(RTM_NEWROUTE, rt, info);
        info->nl_net->ipv6.rt6_stats->fib_rt_entries++;

        if ((fn->fn_flags & RTN_RTINFO) == 0) {
                info->nl_net->ipv6.rt6_stats->fib_route_nodes++;
                fn->fn_flags |= RTN_RTINFO;
        }

        return 0;
}

static __inline__ void fib6_start_gc(struct net *net, struct rt6_info *rt)
{
        if (!timer_pending(&net->ipv6.ip6_fib_timer) &&
            (rt->rt6i_flags & (RTF_EXPIRES|RTF_CACHE)))
                mod_timer(&net->ipv6.ip6_fib_timer,
                          jiffies + net->ipv6.sysctl.ip6_rt_gc_interval);
}

void fib6_force_start_gc(struct net *net)
{
        if (!timer_pending(&net->ipv6.ip6_fib_timer))
                mod_timer(&net->ipv6.ip6_fib_timer,
                          jiffies + net->ipv6.sysctl.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 = info->nl_net->ipv6.ip6_null_entry;
                        atomic_inc(&info->nl_net->ipv6.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(info->nl_net, rt);
                if (!(rt->rt6i_flags&RTF_CACHE))
                        fib6_prune_clones(info->nl_net, 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 == rt) {
                        pn->leaf = NULL;
                        atomic_dec(&rt->rt6i_ref);
                }
                if (pn != fn && !pn->leaf && !(pn->fn_flags & RTN_RTINFO)) {
                        pn->leaf = fib6_find_prefix(info->nl_net, pn);
#if RT6_DEBUG >= 2
                        if (!pn->leaf) {
                                WARN_ON(pn->leaf == NULL);
                                pn->leaf = info->nl_net->ipv6.ip6_null_entry;
                        }
#endif
                        atomic_inc(&pn->leaf->rt6i_ref);
                }
#endif
                dst_free(&rt->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(info->nl_net, fn);
        dst_free(&rt->dst);
        return err;
#endif
}

/*
 *      Routing tree lookup
 *
 */

struct lookup_args {
        int             offset;         /* key offset on rt6_info       */
        const 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, const struct in6_addr *daddr,
                               const 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,
                                        const 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,
                               const struct in6_addr *daddr, int dst_len,
                               const 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) {
                WARN_ON(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 net *net, struct fib6_node *fn)
{
        if (fn->fn_flags&RTN_ROOT)
                return net->ipv6.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 net *net,
                                           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++;

                WARN_ON(fn->fn_flags & RTN_RTINFO);
                WARN_ON(fn->fn_flags & RTN_TL_ROOT);
                WARN_ON(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(net, fn);
#if RT6_DEBUG >= 2
                        if (fn->leaf==NULL) {
                                WARN_ON(!fn->leaf);
                                fn->leaf = net->ipv6.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) {
                        WARN_ON(!(fn->fn_flags & RTN_ROOT));
                        FIB6_SUBTREE(pn) = NULL;
                        nstate = FWS_L;
                } else {
                        WARN_ON(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
                                WARN_ON(1);
#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;
        struct net *net = info->nl_net;

        RT6_TRACE("fib6_del_route\n");

        /* Unlink it */
        *rtp = rt->dst.rt6_next;
        rt->rt6i_node = NULL;
        net->ipv6.rt6_stats->fib_rt_entries--;
        net->ipv6.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->dst.rt6_next;
                        if (w->leaf == NULL)
                                w->state = FWS_U;
                }
        }
        read_unlock(&fib6_walker_lock);

        rt->dst.rt6_next = NULL;

        /* If it was last route, expunge its radix tree node */
        if (fn->leaf == NULL) {
                fn->fn_flags &= ~RTN_RTINFO;
                net->ipv6.rt6_stats->fib_route_nodes--;
                fn = fib6_repair_tree(net, 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(net, fn);
                                atomic_inc(&fn->leaf->rt6i_ref);
                                rt6_release(rt);
                        }
                        fn = fn->parent;
                }
                /* No more references are possible at this point. */
                BUG_ON(atomic_read(&rt->rt6i_ref) != 1);
        }

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

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

#if RT6_DEBUG >= 2
        if (rt->dst.obsolete>0) {
                WARN_ON(fn != NULL);
                return -ENOENT;
        }
#endif
        if (fn == NULL || rt == net->ipv6.ip6_null_entry)
                return -ENOENT;

        WARN_ON(!(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(info->nl_net, pn, rt);
        }

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

        for (rtp = &fn->leaf; *rtp; rtp = &(*rtp)->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;

                                if (w->count < w->skip) {
                                        w->count++;
                                        continue;
                                }

                                err = w->func(w);
                                if (err)
                                        return err;

                                w->count++;
                                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) {
                                WARN_ON(!(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
                        WARN_ON(1);
#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);
        struct nl_info info = {
                .nl_net = c->net,
        };

        for (rt = w->leaf; rt; rt = rt->dst.rt6_next) {
                res = c->func(rt, c->arg);
                if (res < 0) {
                        w->leaf = rt;
                        res = fib6_del(rt, &info);
                        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;
                }
                WARN_ON(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 net *net, 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.w.count = 0;
        c.w.skip = 0;
        c.func = func;
        c.arg = arg;
        c.net = net;

        fib6_walk(&c.w);
}

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

        rcu_read_lock();
        for (h = 0; h < FIB6_TABLE_HASHSZ; h++) {
                head = &net->ipv6.fib_table_hash[h];
                hlist_for_each_entry_rcu(table, node, head, tb6_hlist) {
                        write_lock_bh(&table->tb6_lock);
                        fib6_clean_tree(net, &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 net *net, struct fib6_node *fn,
                              struct rt6_info *rt)
{
        fib6_clean_tree(net, 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->dst.__refcnt) == 0 &&
                    time_after_eq(now, rt->dst.lastuse + gc_args.timeout)) {
                        RT6_TRACE("aging clone %p\n", rt);
                        return -1;
                } else if ((rt->rt6i_flags & RTF_GATEWAY) &&
                           (!(dst_get_neighbour_raw(&rt->dst)->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 expires, struct net *net)
{
        if (expires != ~0UL) {
                spin_lock_bh(&fib6_gc_lock);
                gc_args.timeout = expires ? (int)expires :
                        net->ipv6.sysctl.ip6_rt_gc_interval;
        } else {
                if (!spin_trylock_bh(&fib6_gc_lock)) {
                        mod_timer(&net->ipv6.ip6_fib_timer, jiffies + HZ);
                        return;
                }
                gc_args.timeout = net->ipv6.sysctl.ip6_rt_gc_interval;
        }

        gc_args.more = icmp6_dst_gc();

        fib6_clean_all(net, fib6_age, 0, NULL);

        if (gc_args.more)
                mod_timer(&net->ipv6.ip6_fib_timer,
                          round_jiffies(jiffies
                                        + net->ipv6.sysctl.ip6_rt_gc_interval));
        else
                del_timer(&net->ipv6.ip6_fib_timer);
        spin_unlock_bh(&fib6_gc_lock);
}

static void fib6_gc_timer_cb(unsigned long arg)
{
        fib6_run_gc(0, (struct net *)arg);
}

static int __net_init fib6_net_init(struct net *net)
{
        size_t size = sizeof(struct hlist_head) * FIB6_TABLE_HASHSZ;

        setup_timer(&net->ipv6.ip6_fib_timer, fib6_gc_timer_cb, (unsigned long)net);

        net->ipv6.rt6_stats = kzalloc(sizeof(*net->ipv6.rt6_stats), GFP_KERNEL);
        if (!net->ipv6.rt6_stats)
                goto out_timer;

        /* Avoid false sharing : Use at least a full cache line */
        size = max_t(size_t, size, L1_CACHE_BYTES);

        net->ipv6.fib_table_hash = kzalloc(size, GFP_KERNEL);
        if (!net->ipv6.fib_table_hash)
                goto out_rt6_stats;

        net->ipv6.fib6_main_tbl = kzalloc(sizeof(*net->ipv6.fib6_main_tbl),
                                          GFP_KERNEL);
        if (!net->ipv6.fib6_main_tbl)
                goto out_fib_table_hash;

        net->ipv6.fib6_main_tbl->tb6_id = RT6_TABLE_MAIN;
        net->ipv6.fib6_main_tbl->tb6_root.leaf = net->ipv6.ip6_null_entry;
        net->ipv6.fib6_main_tbl->tb6_root.fn_flags =
                RTN_ROOT | RTN_TL_ROOT | RTN_RTINFO;

#ifdef CONFIG_IPV6_MULTIPLE_TABLES
        net->ipv6.fib6_local_tbl = kzalloc(sizeof(*net->ipv6.fib6_local_tbl),
                                           GFP_KERNEL);
        if (!net->ipv6.fib6_local_tbl)
                goto out_fib6_main_tbl;
        net->ipv6.fib6_local_tbl->tb6_id = RT6_TABLE_LOCAL;
        net->ipv6.fib6_local_tbl->tb6_root.leaf = net->ipv6.ip6_null_entry;
        net->ipv6.fib6_local_tbl->tb6_root.fn_flags =
                RTN_ROOT | RTN_TL_ROOT | RTN_RTINFO;
#endif
        fib6_tables_init(net);

        return 0;

#ifdef CONFIG_IPV6_MULTIPLE_TABLES
out_fib6_main_tbl:
        kfree(net->ipv6.fib6_main_tbl);
#endif
out_fib_table_hash:
        kfree(net->ipv6.fib_table_hash);
out_rt6_stats:
        kfree(net->ipv6.rt6_stats);
out_timer:
        return -ENOMEM;
 }

static void fib6_net_exit(struct net *net)
{
        rt6_ifdown(net, NULL);
        del_timer_sync(&net->ipv6.ip6_fib_timer);

#ifdef CONFIG_IPV6_MULTIPLE_TABLES
        kfree(net->ipv6.fib6_local_tbl);
#endif
        kfree(net->ipv6.fib6_main_tbl);
        kfree(net->ipv6.fib_table_hash);
        kfree(net->ipv6.rt6_stats);
}

static struct pernet_operations fib6_net_ops = {
        .init = fib6_net_init,
        .exit = fib6_net_exit,
};

int __init fib6_init(void)
{
        int ret = -ENOMEM;

        fib6_node_kmem = kmem_cache_create("fib6_nodes",
                                           sizeof(struct fib6_node),
                                           0, SLAB_HWCACHE_ALIGN,
                                           NULL);
        if (!fib6_node_kmem)
                goto out;

        ret = register_pernet_subsys(&fib6_net_ops);
        if (ret)
                goto out_kmem_cache_create;

        ret = __rtnl_register(PF_INET6, RTM_GETROUTE, NULL, inet6_dump_fib,
                              NULL);
        if (ret)
                goto out_unregister_subsys;
out:
        return ret;

out_unregister_subsys:
        unregister_pernet_subsys(&fib6_net_ops);
out_kmem_cache_create:
        kmem_cache_destroy(fib6_node_kmem);
        goto out;
}

void fib6_gc_cleanup(void)
{
        unregister_pernet_subsys(&fib6_net_ops);
        kmem_cache_destroy(fib6_node_kmem);
}