ip6_fib.c

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/*
 *  Linux INET6 implementation
 *  Forwarding Information Database
 *
 *  Authors:
 *  Pedro Roque     <[email protected]>
 *
 *  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.
 */

#define pr_fmt(fmt) "IPv6: " fmt

#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>

#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...) pr_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) {
        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;
        inet_peer_base_init(&table->tb6_peers);
    }

    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)
        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) {
        /* 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)
            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, int allow_create,
                     int replace_required)
{
    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)) {
            if (!allow_create) {
                if (replace_required) {
                    pr_warn("Can't replace route, no match found\n");
                    return ERR_PTR(-ENOENT);
                }
                pr_warn("NLM_F_CREATE should be set when creating new route\n");
            }
            goto insert_above;
        }

        /*
         *  Exact match ?
         */

        if (plen == fn->fn_bit) {
            /* clean up an intermediate node */
            if (!(fn->fn_flags & RTN_RTINFO)) {
                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);

    if (!allow_create) {
        /* We should not create new node because
         * NLM_F_REPLACE was specified without NLM_F_CREATE
         * I assume it is safe to require NLM_F_CREATE when
         * REPLACE flag is used! Later we may want to remove the
         * check for replace_required, because according
         * to netlink specification, NLM_F_CREATE
         * MUST be specified if new route is created.
         * That would keep IPv6 consistent with IPv4
         */
        if (replace_required) {
            pr_warn("Can't replace route, no match found\n");
            return ERR_PTR(-ENOENT);
        }
        pr_warn("NLM_F_CREATE should be set when creating new route\n");
    }
    /*
     *  We walked to the bottom of tree.
     *  Create new leaf node without children.
     */

    ln = node_alloc();

    if (!ln)
        return ERR_PTR(-ENOMEM);
    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 || !ln) {
            if (in)
                node_free(in);
            if (ln)
                node_free(ln);
            return ERR_PTR(-ENOMEM);
        }

        /*
         * 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)
            return ERR_PTR(-ENOMEM);

        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;
    int replace = (info->nlh &&
               (info->nlh->nlmsg_flags & NLM_F_REPLACE));
    int add = (!info->nlh ||
           (info->nlh->nlmsg_flags & NLM_F_CREATE));
    int found = 0;

    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 (info->nlh &&
                (info->nlh->nlmsg_flags & NLM_F_EXCL))
                return -EEXIST;
            if (replace) {
                found++;
                break;
            }

            if (iter->dst.dev == rt->dst.dev &&
                iter->rt6i_idev == rt->rt6i_idev &&
                ipv6_addr_equal(&iter->rt6i_gateway,
                        &rt->rt6i_gateway)) {
                if (!(iter->rt6i_flags & RTF_EXPIRES))
                    return -EEXIST;
                if (!(rt->rt6i_flags & RTF_EXPIRES))
                    rt6_clean_expires(iter);
                else
                    rt6_set_expires(iter, rt->dst.expires);
                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
     */
    if (!replace) {
        if (!add)
            pr_warn("NLM_F_CREATE should be set when creating new route\n");

add:
        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)) {
            info->nl_net->ipv6.rt6_stats->fib_route_nodes++;
            fn->fn_flags |= RTN_RTINFO;
        }

    } else {
        if (!found) {
            if (add)
                goto add;
            pr_warn("NLM_F_REPLACE set, but no existing node found!\n");
            return -ENOENT;
        }
        *ins = rt;
        rt->rt6i_node = fn;
        rt->dst.rt6_next = iter->dst.rt6_next;
        atomic_inc(&rt->rt6i_ref);
        inet6_rt_notify(RTM_NEWROUTE, rt, info);
        rt6_release(iter);
        if (!(fn->fn_flags & RTN_RTINFO)) {
            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;
    int allow_create = 1;
    int replace_required = 0;

    if (info->nlh) {
        if (!(info->nlh->nlmsg_flags & NLM_F_CREATE))
            allow_create = 0;
        if (info->nlh->nlmsg_flags & NLM_F_REPLACE)
            replace_required = 1;
    }
    if (!allow_create && !replace_required)
        pr_warn("RTM_NEWROUTE with no NLM_F_CREATE or NLM_F_REPLACE\n");

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

    if (IS_ERR(fn)) {
        err = PTR_ERR(fn);
        goto out;
    }

    pn = fn;

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

        if (!fn->subtree) {
            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)
                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),
                    allow_create, replace_required);

            if (IS_ERR(sn)) {
                /* If it is failed, discard just allocated
                   root, and then (in st_failure) stale node
                   in main tree.
                 */
                node_free(sfn);
                err = PTR_ERR(sn);
                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),
                    allow_create, replace_required);

            if (IS_ERR(sn)) {
                err = PTR_ERR(sn);
                goto st_failure;
            }
        }

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

    err = fib6_add_rt2node(fn, rt, info);
    if (!err) {
        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 || 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) {
                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) {
                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)
                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) {
        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 || 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)
            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->skip) {
                    w->skip--;
                    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
                pr_debug("%s: del failed: rt=%p@%p err=%d\n",
                     __func__, 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_ro(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) {
            read_lock_bh(&table->tb6_lock);
            fib6_clean_tree(net, &table->tb6_root,
                    func, prune, arg);
            read_unlock_bh(&table->tb6_lock);
        }
    }
    rcu_read_unlock();
}
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->dst.expires) {
        if (time_after(now, rt->dst.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) {
            struct neighbour *neigh;
            __u8 neigh_flags = 0;

            neigh = dst_neigh_lookup(&rt->dst, &rt->rt6i_gateway);
            if (neigh) {
                neigh_flags = neigh->flags;
                neigh_release(neigh);
            }
            if (!(neigh_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;
    inet_peer_base_init(&net->ipv6.fib6_main_tbl->tb6_peers);

#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;
    inet_peer_base_init(&net->ipv6.fib6_local_tbl->tb6_peers);
#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
    inetpeer_invalidate_tree(&net->ipv6.fib6_local_tbl->tb6_peers);
    kfree(net->ipv6.fib6_local_tbl);
#endif
    inetpeer_invalidate_tree(&net->ipv6.fib6_main_tbl->tb6_peers);
    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);
}