[mirror_ubuntu-bionic-kernel.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.
 */

#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/lwtunnel.h>
#include <net/fib_notifier.h>

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

static struct kmem_cache *fib6_node_kmem __read_mostly;

struct fib6_cleaner {
        struct fib6_walker w;
        struct net *net;
        int (*func)(struct rt6_info *, void *arg);
        int sernum;
        void *arg;
};

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

static struct rt6_info *fib6_find_prefix(struct net *net,
                                         struct fib6_table *table,
                                         struct fib6_node *fn);
static struct fib6_node *fib6_repair_tree(struct net *net,
                                          struct fib6_table *table,
                                          struct fib6_node *fn);
static int fib6_walk(struct net *net, struct fib6_walker *w);
static int fib6_walk_continue(struct fib6_walker *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 void fib6_gc_timer_cb(unsigned long arg);

#define FOR_WALKERS(net, w) \
        list_for_each_entry(w, &(net)->ipv6.fib6_walkers, lh)

static void fib6_walker_link(struct net *net, struct fib6_walker *w)
{
        write_lock_bh(&net->ipv6.fib6_walker_lock);
        list_add(&w->lh, &net->ipv6.fib6_walkers);
        write_unlock_bh(&net->ipv6.fib6_walker_lock);
}

static void fib6_walker_unlink(struct net *net, struct fib6_walker *w)
{
        write_lock_bh(&net->ipv6.fib6_walker_lock);
        list_del(&w->lh);
        write_unlock_bh(&net->ipv6.fib6_walker_lock);
}

static int fib6_new_sernum(struct net *net)
{
        int new, old;

        do {
                old = atomic_read(&net->ipv6.fib6_sernum);
                new = old < INT_MAX ? old + 1 : 1;
        } while (atomic_cmpxchg(&net->ipv6.fib6_sernum,
                                old, new) != old);
        return new;
}

enum {
        FIB6_NO_SERNUM_CHANGE = 0,
};

void fib6_update_sernum(struct rt6_info *rt)
{
        struct fib6_table *table = rt->rt6i_table;
        struct net *net = dev_net(rt->dst.dev);
        struct fib6_node *fn;

        spin_lock_bh(&table->tb6_lock);
        fn = rcu_dereference_protected(rt->rt6i_node,
                        lockdep_is_held(&table->tb6_lock));
        if (fn)
                fn->fn_sernum = fib6_new_sernum(net);
        spin_unlock_bh(&table->tb6_lock);
}

/*
 *      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 __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 struct fib6_node *node_alloc(struct net *net)
{
        struct fib6_node *fn;

        fn = kmem_cache_zalloc(fib6_node_kmem, GFP_ATOMIC);
        if (fn)
                net->ipv6.rt6_stats->fib_nodes++;

        return fn;
}

static void node_free_immediate(struct net *net, struct fib6_node *fn)
{
        kmem_cache_free(fib6_node_kmem, fn);
        net->ipv6.rt6_stats->fib_nodes--;
}

static void node_free_rcu(struct rcu_head *head)
{
        struct fib6_node *fn = container_of(head, struct fib6_node, rcu);

        kmem_cache_free(fib6_node_kmem, fn);
}

static void node_free(struct net *net, struct fib6_node *fn)
{
        call_rcu(&fn->rcu, node_free_rcu);
        net->ipv6.rt6_stats->fib_nodes--;
}

void rt6_free_pcpu(struct rt6_info *non_pcpu_rt)
{
        int cpu;

        if (!non_pcpu_rt->rt6i_pcpu)
                return;

        for_each_possible_cpu(cpu) {
                struct rt6_info **ppcpu_rt;
                struct rt6_info *pcpu_rt;

                ppcpu_rt = per_cpu_ptr(non_pcpu_rt->rt6i_pcpu, cpu);
                pcpu_rt = *ppcpu_rt;
                if (pcpu_rt) {
                        dst_dev_put(&pcpu_rt->dst);
                        dst_release(&pcpu_rt->dst);
                        *ppcpu_rt = NULL;
                }
        }
}
EXPORT_SYMBOL_GPL(rt6_free_pcpu);

static void fib6_free_table(struct fib6_table *table)
{
        inetpeer_invalidate_tree(&table->tb6_peers);
        kfree(table);
}

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.
         */
        spin_lock_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;
                rcu_assign_pointer(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;
}
EXPORT_SYMBOL_GPL(fib6_new_table);

struct fib6_table *fib6_get_table(struct net *net, u32 id)
{
        struct fib6_table *tb;
        struct hlist_head *head;
        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, head, tb6_hlist) {
                if (tb->tb6_id == id) {
                        rcu_read_unlock();
                        return tb;
                }
        }
        rcu_read_unlock();

        return NULL;
}
EXPORT_SYMBOL_GPL(fib6_get_table);

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)
{
        struct rt6_info *rt;

        rt = lookup(net, net->ipv6.fib6_main_tbl, fl6, flags);
        if (rt->dst.error == -EAGAIN) {
                ip6_rt_put(rt);
                rt = net->ipv6.ip6_null_entry;
                dst_hold(&rt->dst);
        }

        return &rt->dst;
}

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

#endif

unsigned int fib6_tables_seq_read(struct net *net)
{
        unsigned int h, fib_seq = 0;

        rcu_read_lock();
        for (h = 0; h < FIB6_TABLE_HASHSZ; h++) {
                struct hlist_head *head = &net->ipv6.fib_table_hash[h];
                struct fib6_table *tb;

                hlist_for_each_entry_rcu(tb, head, tb6_hlist)
                        fib_seq += tb->fib_seq;
        }
        rcu_read_unlock();

        return fib_seq;
}

static int call_fib6_entry_notifier(struct notifier_block *nb, struct net *net,
                                    enum fib_event_type event_type,
                                    struct rt6_info *rt)
{
        struct fib6_entry_notifier_info info = {
                .rt = rt,
        };

        return call_fib6_notifier(nb, net, event_type, &info.info);
}

static int call_fib6_entry_notifiers(struct net *net,
                                     enum fib_event_type event_type,
                                     struct rt6_info *rt,
                                     struct netlink_ext_ack *extack)
{
        struct fib6_entry_notifier_info info = {
                .info.extack = extack,
                .rt = rt,
        };

        rt->rt6i_table->fib_seq++;
        return call_fib6_notifiers(net, event_type, &info.info);
}

struct fib6_dump_arg {
        struct net *net;
        struct notifier_block *nb;
};

static void fib6_rt_dump(struct rt6_info *rt, struct fib6_dump_arg *arg)
{
        if (rt == arg->net->ipv6.ip6_null_entry)
                return;
        call_fib6_entry_notifier(arg->nb, arg->net, FIB_EVENT_ENTRY_ADD, rt);
}

static int fib6_node_dump(struct fib6_walker *w)
{
        struct rt6_info *rt;

        for_each_fib6_walker_rt(w)
                fib6_rt_dump(rt, w->args);
        w->leaf = NULL;
        return 0;
}

static void fib6_table_dump(struct net *net, struct fib6_table *tb,
                            struct fib6_walker *w)
{
        w->root = &tb->tb6_root;
        spin_lock_bh(&tb->tb6_lock);
        fib6_walk(net, w);
        spin_unlock_bh(&tb->tb6_lock);
}

/* Called with rcu_read_lock() */
int fib6_tables_dump(struct net *net, struct notifier_block *nb)
{
        struct fib6_dump_arg arg;
        struct fib6_walker *w;
        unsigned int h;

        w = kzalloc(sizeof(*w), GFP_ATOMIC);
        if (!w)
                return -ENOMEM;

        w->func = fib6_node_dump;
        arg.net = net;
        arg.nb = nb;
        w->args = &arg;

        for (h = 0; h < FIB6_TABLE_HASHSZ; h++) {
                struct hlist_head *head = &net->ipv6.fib_table_hash[h];
                struct fib6_table *tb;

                hlist_for_each_entry_rcu(tb, head, tb6_hlist)
                        fib6_table_dump(net, tb, w);
        }

        kfree(w);

        return 0;
}

static int fib6_dump_node(struct fib6_walker *w)
{
        int res;
        struct rt6_info *rt;

        for_each_fib6_walker_rt(w) {
                res = rt6_dump_route(rt, w->args);
                if (res < 0) {
                        /* Frame is full, suspend walking */
                        w->leaf = rt;
                        return 1;
                }

                /* Multipath routes are dumped in one route with the
                 * RTA_MULTIPATH attribute. Jump 'rt' to point to the
                 * last sibling of this route (no need to dump the
                 * sibling routes again)
                 */
                if (rt->rt6i_nsiblings)
                        rt = list_last_entry(&rt->rt6i_siblings,
                                             struct rt6_info,
                                             rt6i_siblings);
        }
        w->leaf = NULL;
        return 0;
}

static void fib6_dump_end(struct netlink_callback *cb)
{
        struct net *net = sock_net(cb->skb->sk);
        struct fib6_walker *w = (void *)cb->args[2];

        if (w) {
                if (cb->args[4]) {
                        cb->args[4] = 0;
                        fib6_walker_unlink(net, 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 net *net = sock_net(skb->sk);
        struct fib6_walker *w;
        int res;

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

        if (cb->args[4] == 0) {
                w->count = 0;
                w->skip = 0;

                spin_lock_bh(&table->tb6_lock);
                res = fib6_walk(net, w);
                spin_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;

                spin_lock_bh(&table->tb6_lock);
                res = fib6_walk_continue(w);
                spin_unlock_bh(&table->tb6_lock);
                if (res <= 0) {
                        fib6_walker_unlink(net, 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 *w;
        struct fib6_table *tb;
        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, 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 net *net,
                                    struct fib6_table *table,
                                    struct fib6_node *root,
                                    struct in6_addr *addr, int plen,
                                    int offset, int allow_create,
                                    int replace_required,
                                    struct netlink_ext_ack *extack)
{
        struct fib6_node *fn, *in, *ln;
        struct fib6_node *pn = NULL;
        struct rt6key *key;
        int     bit;
        __be32  dir = 0;

        RT6_TRACE("fib6_add_1\n");

        /* insert node in tree */

        fn = root;

        do {
                struct rt6_info *leaf = rcu_dereference_protected(fn->leaf,
                                            lockdep_is_held(&table->tb6_lock));
                key = (struct rt6key *)((u8 *)leaf + offset);

                /*
                 *      Prefix match
                 */
                if (plen < fn->fn_bit ||
                    !ipv6_prefix_equal(&key->addr, addr, fn->fn_bit)) {
                        if (!allow_create) {
                                if (replace_required) {
                                        NL_SET_ERR_MSG(extack,
                                                       "Can not replace route - no match found");
                                        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)) {
                                RCU_INIT_POINTER(fn->leaf, NULL);
                                rt6_release(leaf);
                        }

                        return fn;
                }

                /*
                 *      We have more bits to go
                 */

                /* Try to walk down on tree. */
                dir = addr_bit_set(addr, fn->fn_bit);
                pn = fn;
                fn = dir ?
                     rcu_dereference_protected(fn->right,
                                        lockdep_is_held(&table->tb6_lock)) :
                     rcu_dereference_protected(fn->left,
                                        lockdep_is_held(&table->tb6_lock));
        } 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) {
                        NL_SET_ERR_MSG(extack,
                                       "Can not replace route - no match found");
                        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(net);

        if (!ln)
                return ERR_PTR(-ENOMEM);
        ln->fn_bit = plen;
        RCU_INIT_POINTER(ln->parent, pn);

        if (dir)
                rcu_assign_pointer(pn->right, ln);
        else
                rcu_assign_pointer(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 = rcu_dereference_protected(fn->parent,
                                       lockdep_is_held(&table->tb6_lock));

        /* 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, sizeof(*addr));

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

                if (!in || !ln) {
                        if (in)
                                node_free_immediate(net, in);
                        if (ln)
                                node_free_immediate(net, 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;

                RCU_INIT_POINTER(in->parent, pn);
                in->leaf = fn->leaf;
                atomic_inc(&rcu_dereference_protected(in->leaf,
                                lockdep_is_held(&table->tb6_lock))->rt6i_ref);

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

                ln->fn_bit = plen;

                RCU_INIT_POINTER(ln->parent, in);
                rcu_assign_pointer(fn->parent, in);

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

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

                ln = node_alloc(net);

                if (!ln)
                        return ERR_PTR(-ENOMEM);

                ln->fn_bit = plen;

                RCU_INIT_POINTER(ln->parent, pn);

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

                rcu_assign_pointer(fn->parent, ln);

                if (dir)
                        rcu_assign_pointer(pn->right, ln);
                else
                        rcu_assign_pointer(pn->left, ln);
        }
        return ln;
}

static bool rt6_qualify_for_ecmp(struct rt6_info *rt)
{
        return (rt->rt6i_flags & (RTF_GATEWAY|RTF_ADDRCONF|RTF_DYNAMIC)) ==
               RTF_GATEWAY;
}

static void fib6_copy_metrics(u32 *mp, const struct mx6_config *mxc)
{
        int i;

        for (i = 0; i < RTAX_MAX; i++) {
                if (test_bit(i, mxc->mx_valid))
                        mp[i] = mxc->mx[i];
        }
}

static int fib6_commit_metrics(struct dst_entry *dst, struct mx6_config *mxc)
{
        if (!mxc->mx)
                return 0;

        if (dst->flags & DST_HOST) {
                u32 *mp = dst_metrics_write_ptr(dst);

                if (unlikely(!mp))
                        return -ENOMEM;

                fib6_copy_metrics(mp, mxc);
        } else {
                dst_init_metrics(dst, mxc->mx, false);

                /* We've stolen mx now. */
                mxc->mx = NULL;
        }

        return 0;
}

static void fib6_purge_rt(struct rt6_info *rt, struct fib6_node *fn,
                          struct net *net)
{
        struct fib6_table *table = rt->rt6i_table;

        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) {
                        struct rt6_info *leaf = rcu_dereference_protected(fn->leaf,
                                            lockdep_is_held(&table->tb6_lock));
                        struct rt6_info *new_leaf;
                        if (!(fn->fn_flags & RTN_RTINFO) && leaf == rt) {
                                new_leaf = fib6_find_prefix(net, table, fn);
                                atomic_inc(&new_leaf->rt6i_ref);
                                rcu_assign_pointer(fn->leaf, new_leaf);
                                rt6_release(rt);
                        }
                        fn = rcu_dereference_protected(fn->parent,
                                    lockdep_is_held(&table->tb6_lock));
                }
        }
}

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

static int fib6_add_rt2node(struct fib6_node *fn, struct rt6_info *rt,
                            struct nl_info *info, struct mx6_config *mxc,
                            struct netlink_ext_ack *extack)
{
        struct rt6_info *leaf = rcu_dereference_protected(fn->leaf,
                                    lockdep_is_held(&rt->rt6i_table->tb6_lock));
        struct rt6_info *iter = NULL;
        struct rt6_info __rcu **ins;
        struct rt6_info __rcu **fallback_ins = NULL;
        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;
        bool rt_can_ecmp = rt6_qualify_for_ecmp(rt);
        u16 nlflags = NLM_F_EXCL;
        int err;

        if (info->nlh && (info->nlh->nlmsg_flags & NLM_F_APPEND))
                nlflags |= NLM_F_APPEND;

        ins = &fn->leaf;

        for (iter = leaf; iter;
             iter = rcu_dereference_protected(iter->dst.rt6_next,
                                lockdep_is_held(&rt->rt6i_table->tb6_lock))) {
                /*
                 *      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;

                        nlflags &= ~NLM_F_EXCL;
                        if (replace) {
                                if (rt_can_ecmp == rt6_qualify_for_ecmp(iter)) {
                                        found++;
                                        break;
                                }
                                if (rt_can_ecmp)
                                        fallback_ins = fallback_ins ?: ins;
                                goto next_iter;
                        }

                        if (rt6_duplicate_nexthop(iter, rt)) {
                                if (rt->rt6i_nsiblings)
                                        rt->rt6i_nsiblings = 0;
                                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);
                                iter->rt6i_pmtu = rt->rt6i_pmtu;
                                return -EEXIST;
                        }
                        /* If we have the same destination and the same metric,
                         * but not the same gateway, then the route we try to
                         * add is sibling to this route, increment our counter
                         * of siblings, and later we will add our route to the
                         * list.
                         * Only static routes (which don't have flag
                         * RTF_EXPIRES) are used for ECMPv6.
                         *
                         * To avoid long list, we only had siblings if the
                         * route have a gateway.
                         */
                        if (rt_can_ecmp &&
                            rt6_qualify_for_ecmp(iter))
                                rt->rt6i_nsiblings++;
                }

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

next_iter:
                ins = &iter->dst.rt6_next;
        }

        if (fallback_ins && !found) {
                /* No ECMP-able route found, replace first non-ECMP one */
                ins = fallback_ins;
                iter = rcu_dereference_protected(*ins,
                                    lockdep_is_held(&rt->rt6i_table->tb6_lock));
                found++;
        }

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

        /* Link this route to others same route. */
        if (rt->rt6i_nsiblings) {
                unsigned int rt6i_nsiblings;
                struct rt6_info *sibling, *temp_sibling;

                /* Find the first route that have the same metric */
                sibling = leaf;
                while (sibling) {
                        if (sibling->rt6i_metric == rt->rt6i_metric &&
                            rt6_qualify_for_ecmp(sibling)) {
                                list_add_tail(&rt->rt6i_siblings,
                                              &sibling->rt6i_siblings);
                                break;
                        }
                        sibling = rcu_dereference_protected(sibling->dst.rt6_next,
                                    lockdep_is_held(&rt->rt6i_table->tb6_lock));
                }
                /* For each sibling in the list, increment the counter of
                 * siblings. BUG() if counters does not match, list of siblings
                 * is broken!
                 */
                rt6i_nsiblings = 0;
                list_for_each_entry_safe(sibling, temp_sibling,
                                         &rt->rt6i_siblings, rt6i_siblings) {
                        sibling->rt6i_nsiblings++;
                        BUG_ON(sibling->rt6i_nsiblings != rt->rt6i_nsiblings);
                        rt6i_nsiblings++;
                }
                BUG_ON(rt6i_nsiblings != rt->rt6i_nsiblings);
        }

        /*
         *      insert node
         */
        if (!replace) {
                if (!add)
                        pr_warn("NLM_F_CREATE should be set when creating new route\n");

add:
                nlflags |= NLM_F_CREATE;
                err = fib6_commit_metrics(&rt->dst, mxc);
                if (err)
                        return err;

                rcu_assign_pointer(rt->dst.rt6_next, iter);
                atomic_inc(&rt->rt6i_ref);
                rcu_assign_pointer(rt->rt6i_node, fn);
                rcu_assign_pointer(*ins, rt);
                call_fib6_entry_notifiers(info->nl_net, FIB_EVENT_ENTRY_ADD,
                                          rt, extack);
                if (!info->skip_notify)
                        inet6_rt_notify(RTM_NEWROUTE, rt, info, nlflags);
                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 {
                int nsiblings;

                if (!found) {
                        if (add)
                                goto add;
                        pr_warn("NLM_F_REPLACE set, but no existing node found!\n");
                        return -ENOENT;
                }

                err = fib6_commit_metrics(&rt->dst, mxc);
                if (err)
                        return err;

                atomic_inc(&rt->rt6i_ref);
                rcu_assign_pointer(rt->rt6i_node, fn);
                rt->dst.rt6_next = iter->dst.rt6_next;
                rcu_assign_pointer(*ins, rt);
                call_fib6_entry_notifiers(info->nl_net, FIB_EVENT_ENTRY_REPLACE,
                                          rt, extack);
                if (!info->skip_notify)
                        inet6_rt_notify(RTM_NEWROUTE, rt, info, NLM_F_REPLACE);
                if (!(fn->fn_flags & RTN_RTINFO)) {
                        info->nl_net->ipv6.rt6_stats->fib_route_nodes++;
                        fn->fn_flags |= RTN_RTINFO;
                }
                nsiblings = iter->rt6i_nsiblings;
                iter->rt6i_node = NULL;
                fib6_purge_rt(iter, fn, info->nl_net);
                if (rcu_access_pointer(fn->rr_ptr) == iter)
                        fn->rr_ptr = NULL;
                rt6_release(iter);

                if (nsiblings) {
                        /* Replacing an ECMP route, remove all siblings */
                        ins = &rt->dst.rt6_next;
                        iter = rcu_dereference_protected(*ins,
                                    lockdep_is_held(&rt->rt6i_table->tb6_lock));
                        while (iter) {
                                if (iter->rt6i_metric > rt->rt6i_metric)
                                        break;
                                if (rt6_qualify_for_ecmp(iter)) {
                                        *ins = iter->dst.rt6_next;
                                        iter->rt6i_node = NULL;
                                        fib6_purge_rt(iter, fn, info->nl_net);
                                        if (rcu_access_pointer(fn->rr_ptr) == iter)
                                                fn->rr_ptr = NULL;
                                        rt6_release(iter);
                                        nsiblings--;
                                        info->nl_net->ipv6.rt6_stats->fib_rt_entries--;
                                } else {
                                        ins = &iter->dst.rt6_next;
                                }
                                iter = rcu_dereference_protected(*ins,
                                        lockdep_is_held(&rt->rt6i_table->tb6_lock));
                        }
                        WARN_ON(nsiblings != 0);
                }
        }

        return 0;
}

static 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);
}

static void fib6_update_sernum_upto_root(struct rt6_info *rt,
                                         int sernum)
{
        struct fib6_node *fn = rcu_dereference_protected(rt->rt6i_node,
                                lockdep_is_held(&rt->rt6i_table->tb6_lock));

        /* paired with smp_rmb() in rt6_get_cookie_safe() */
        smp_wmb();
        while (fn) {
                fn->fn_sernum = sernum;
                fn = rcu_dereference_protected(fn->parent,
                                lockdep_is_held(&rt->rt6i_table->tb6_lock));
        }
}

/*
 *      Add routing information to the routing tree.
 *      <destination addr>/<source addr>
 *      with source addr info in sub-trees
 *      Need to own table->tb6_lock
 */

int fib6_add(struct fib6_node *root, struct rt6_info *rt,
             struct nl_info *info, struct mx6_config *mxc,
             struct netlink_ext_ack *extack)
{
        struct fib6_table *table = rt->rt6i_table;
        struct fib6_node *fn, *pn = NULL;
        int err = -ENOMEM;
        int allow_create = 1;
        int replace_required = 0;
        int sernum = fib6_new_sernum(info->nl_net);

        if (WARN_ON_ONCE(!atomic_read(&rt->dst.__refcnt)))
                return -EINVAL;
        if (WARN_ON_ONCE(rt->rt6i_flags & RTF_CACHE))
                return -EINVAL;

        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(info->nl_net, table, root,
                        &rt->rt6i_dst.addr, rt->rt6i_dst.plen,
                        offsetof(struct rt6_info, rt6i_dst), allow_create,
                        replace_required, extack);
        if (IS_ERR(fn)) {
                err = PTR_ERR(fn);
                fn = NULL;
                goto out;
        }

        pn = fn;

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

                if (!rcu_access_pointer(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(info->nl_net);
                        if (!sfn)
                                goto failure;

                        atomic_inc(&info->nl_net->ipv6.ip6_null_entry->rt6i_ref);
                        rcu_assign_pointer(sfn->leaf,
                                           info->nl_net->ipv6.ip6_null_entry);
                        sfn->fn_flags = RTN_ROOT;

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

                        sn = fib6_add_1(info->nl_net, table, sfn,
                                        &rt->rt6i_src.addr, rt->rt6i_src.plen,
                                        offsetof(struct rt6_info, rt6i_src),
                                        allow_create, replace_required, extack);

                        if (IS_ERR(sn)) {
                                /* If it is failed, discard just allocated
                                   root, and then (in failure) stale node
                                   in main tree.
                                 */
                                node_free_immediate(info->nl_net, sfn);
                                err = PTR_ERR(sn);
                                goto failure;
                        }

                        /* Now link new subtree to main tree */
                        rcu_assign_pointer(sfn->parent, fn);
                        rcu_assign_pointer(fn->subtree, sfn);
                } else {
                        sn = fib6_add_1(info->nl_net, table, FIB6_SUBTREE(fn),
                                        &rt->rt6i_src.addr, rt->rt6i_src.plen,
                                        offsetof(struct rt6_info, rt6i_src),
                                        allow_create, replace_required, extack);

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

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

        err = fib6_add_rt2node(fn, rt, info, mxc, extack);
        if (!err) {
                fib6_update_sernum_upto_root(rt, sernum);
                fib6_start_gc(info->nl_net, 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.
                 */
                struct rt6_info *pn_leaf = rcu_dereference_protected(pn->leaf,
                                            lockdep_is_held(&table->tb6_lock));
                if (pn != fn && pn_leaf == rt) {
                        pn_leaf = NULL;
                        RCU_INIT_POINTER(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, table, pn);
#if RT6_DEBUG >= 2
                        if (!pn_leaf) {
                                WARN_ON(!pn_leaf);
                                pn_leaf = info->nl_net->ipv6.ip6_null_entry;
                        }
#endif
                        atomic_inc(&pn_leaf->rt6i_ref);
                        rcu_assign_pointer(pn->leaf, pn_leaf);
                }
#endif
                goto failure;
        }
        return err;

failure:
        /* fn->leaf could be NULL if fn is an intermediate node and we
         * failed to add the new route to it in both subtree creation
         * failure and fib6_add_rt2node() failure case.
         * In both cases, fib6_repair_tree() should be called to fix
         * fn->leaf.
         */
        if (fn && !(fn->fn_flags & (RTN_RTINFO|RTN_ROOT)))
                fib6_repair_tree(info->nl_net, table, fn);
        /* Always release dst as dst->__refcnt is guaranteed
         * to be taken before entering this function
         */
        dst_release_immediate(&rt->dst);
        return err;
}

/*
 *      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 ? rcu_dereference(fn->right) :
                             rcu_dereference(fn->left);

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

        while (fn) {
                struct fib6_node *subtree = FIB6_SUBTREE(fn);

                if (subtree || fn->fn_flags & RTN_RTINFO) {
                        struct rt6_info *leaf = rcu_dereference(fn->leaf);
                        struct rt6key *key;

                        if (!leaf)
                                goto backtrack;

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

                        if (ipv6_prefix_equal(&key->addr, args->addr, key->plen)) {
#ifdef CONFIG_IPV6_SUBTREES
                                if (subtree) {
                                        struct fib6_node *sfn;
                                        sfn = fib6_lookup_1(subtree, args + 1);
                                        if (!sfn)
                                                goto backtrack;
                                        fn = sfn;
                                }
#endif
                                if (fn->fn_flags & RTN_RTINFO)
                                        return fn;
                        }
                }
backtrack:
                if (fn->fn_flags & RTN_ROOT)
                        break;

                fn = rcu_dereference(fn->parent);
        }

        return NULL;
}

/* called with rcu_read_lock() held
 */
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)
 *      exact_match == true means we try to find fn with exact match of
 *      the passed in prefix addr
 *      exact_match == false means we try to find fn with longest prefix
 *      match of the passed in prefix addr. This is useful for finding fn
 *      for cached route as it will be stored in the exception table under
 *      the node with longest prefix length.
 */


static struct fib6_node *fib6_locate_1(struct fib6_node *root,
                                       const struct in6_addr *addr,
                                       int plen, int offset,
                                       bool exact_match)
{
        struct fib6_node *fn, *prev = NULL;

        for (fn = root; fn ; ) {
                struct rt6_info *leaf = rcu_dereference(fn->leaf);
                struct rt6key *key;

                /* This node is being deleted */
                if (!leaf) {
                        if (plen <= fn->fn_bit)
                                goto out;
                        else
                                goto next;
                }

                key = (struct rt6key *)((u8 *)leaf + offset);

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

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

                prev = fn;

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

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,
                              bool exact_match)
{
        struct fib6_node *fn;

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

#ifdef CONFIG_IPV6_SUBTREES
        if (src_len) {
                WARN_ON(saddr == NULL);
                if (fn) {
                        struct fib6_node *subtree = FIB6_SUBTREE(fn);

                        if (subtree) {
                                fn = fib6_locate_1(subtree, saddr, src_len,
                                           offsetof(struct rt6_info, rt6i_src),
                                           exact_match);
                        }
                }
        }
#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_table *table,
                                         struct fib6_node *fn)
{
        struct fib6_node *child_left, *child_right;

        if (fn->fn_flags & RTN_ROOT)
                return net->ipv6.ip6_null_entry;

        while (fn) {
                child_left = rcu_dereference_protected(fn->left,
                                    lockdep_is_held(&table->tb6_lock));
                child_right = rcu_dereference_protected(fn->right,
                                    lockdep_is_held(&table->tb6_lock));
                if (child_left)
                        return rcu_dereference_protected(child_left->leaf,
                                        lockdep_is_held(&table->tb6_lock));
                if (child_right)
                        return rcu_dereference_protected(child_right->leaf,
                                        lockdep_is_held(&table->tb6_lock));

                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.
 *      Need to own table->tb6_lock
 */

static struct fib6_node *fib6_repair_tree(struct net *net,
                                          struct fib6_table *table,
                                          struct fib6_node *fn)
{
        int children;
        int nstate;
        struct fib6_node *child;
        struct fib6_walker *w;
        int iter = 0;

        for (;;) {
                struct fib6_node *fn_r = rcu_dereference_protected(fn->right,
                                            lockdep_is_held(&table->tb6_lock));
                struct fib6_node *fn_l = rcu_dereference_protected(fn->left,
                                            lockdep_is_held(&table->tb6_lock));
                struct fib6_node *pn = rcu_dereference_protected(fn->parent,
                                            lockdep_is_held(&table->tb6_lock));
                struct fib6_node *pn_r = rcu_dereference_protected(pn->right,
                                            lockdep_is_held(&table->tb6_lock));
                struct fib6_node *pn_l = rcu_dereference_protected(pn->left,
                                            lockdep_is_held(&table->tb6_lock));
                struct rt6_info *fn_leaf = rcu_dereference_protected(fn->leaf,
                                            lockdep_is_held(&table->tb6_lock));
                struct rt6_info *pn_leaf = rcu_dereference_protected(pn->leaf,
                                            lockdep_is_held(&table->tb6_lock));
                struct rt6_info *new_fn_leaf;

                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);

                children = 0;
                child = NULL;
                if (fn_r)
                        child = fn_r, children |= 1;
                if (fn_l)
                        child = fn_l, 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
                    ) {
                        new_fn_leaf = fib6_find_prefix(net, table, fn);
#if RT6_DEBUG >= 2
                        if (!new_fn_leaf) {
                                WARN_ON(!new_fn_leaf);
                                new_fn_leaf = net->ipv6.ip6_null_entry;
                        }
#endif
                        atomic_inc(&new_fn_leaf->rt6i_ref);
                        rcu_assign_pointer(fn->leaf, new_fn_leaf);
                        return pn;
                }

#ifdef CONFIG_IPV6_SUBTREES
                if (FIB6_SUBTREE(pn) == fn) {
                        WARN_ON(!(fn->fn_flags & RTN_ROOT));
                        RCU_INIT_POINTER(pn->subtree, NULL);
                        nstate = FWS_L;
                } else {
                        WARN_ON(fn->fn_flags & RTN_ROOT);
#endif
                        if (pn_r == fn)
                                rcu_assign_pointer(pn->right, child);
                        else if (pn_l == fn)
                                rcu_assign_pointer(pn->left, child);
#if RT6_DEBUG >= 2
                        else
                                WARN_ON(1);
#endif
                        if (child)
                                rcu_assign_pointer(child->parent, pn);
                        nstate = FWS_R;
#ifdef CONFIG_IPV6_SUBTREES
                }
#endif

                read_lock(&net->ipv6.fib6_walker_lock);
                FOR_WALKERS(net, w) {
                        if (!child) {
                                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->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(&net->ipv6.fib6_walker_lock);

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

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

static void fib6_del_route(struct fib6_table *table, struct fib6_node *fn,
                           struct rt6_info __rcu **rtp, struct nl_info *info)
{
        struct fib6_walker *w;
        struct rt6_info *rt = rcu_dereference_protected(*rtp,
                                    lockdep_is_held(&table->tb6_lock));
        struct net *net = info->nl_net;

        RT6_TRACE("fib6_del_route\n");

        WARN_ON_ONCE(rt->rt6i_flags & RTF_CACHE);

        /* 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++;

        /* Flush all cached dst in exception table */
        rt6_flush_exceptions(rt);

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

        /* Remove this entry from other siblings */
        if (rt->rt6i_nsiblings) {
                struct rt6_info *sibling, *next_sibling;

                list_for_each_entry_safe(sibling, next_sibling,
                                         &rt->rt6i_siblings, rt6i_siblings)
                        sibling->rt6i_nsiblings--;
                rt->rt6i_nsiblings = 0;
                list_del_init(&rt->rt6i_siblings);
        }

        /* Adjust walkers */
        read_lock(&net->ipv6.fib6_walker_lock);
        FOR_WALKERS(net, w) {
                if (w->state == FWS_C && w->leaf == rt) {
                        RT6_TRACE("walker %p adjusted by delroute\n", w);
                        w->leaf = rcu_dereference_protected(rt->dst.rt6_next,
                                            lockdep_is_held(&table->tb6_lock));
                        if (!w->leaf)
                                w->state = FWS_U;
                }
        }
        read_unlock(&net->ipv6.fib6_walker_lock);

        /* If it was last route, expunge its radix tree node */
        if (!rcu_access_pointer(fn->leaf)) {
                fn->fn_flags &= ~RTN_RTINFO;
                net->ipv6.rt6_stats->fib_route_nodes--;
                fn = fib6_repair_tree(net, table, fn);
        }

        fib6_purge_rt(rt, fn, net);

        call_fib6_entry_notifiers(net, FIB_EVENT_ENTRY_DEL, rt, NULL);
        if (!info->skip_notify)
                inet6_rt_notify(RTM_DELROUTE, rt, info, 0);
        rt6_release(rt);
}

/* Need to own table->tb6_lock */
int fib6_del(struct rt6_info *rt, struct nl_info *info)
{
        struct fib6_node *fn = rcu_dereference_protected(rt->rt6i_node,
                                    lockdep_is_held(&rt->rt6i_table->tb6_lock));
        struct fib6_table *table = rt->rt6i_table;
        struct net *net = info->nl_net;
        struct rt6_info __rcu **rtp;
        struct rt6_info __rcu **rtp_next;

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

        WARN_ON(!(fn->fn_flags & RTN_RTINFO));

        /* remove cached dst from exception table */
        if (rt->rt6i_flags & RTF_CACHE)
                return rt6_remove_exception_rt(rt);

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

        for (rtp = &fn->leaf; *rtp; rtp = rtp_next) {
                struct rt6_info *cur = rcu_dereference_protected(*rtp,
                                        lockdep_is_held(&table->tb6_lock));
                if (rt == cur) {
                        fib6_del_route(table, fn, rtp, info);
                        return 0;
                }
                rtp_next = &cur->dst.rt6_next;
        }
        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.
 *
 *      This function is called with tb6_lock held.
 */

static int fib6_walk_continue(struct fib6_walker *w)
{
        struct fib6_node *fn, *pn, *left, *right;

        /* w->root should always be table->tb6_root */
        WARN_ON_ONCE(!(w->root->fn_flags & RTN_TL_ROOT));

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

                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
                        /* fall through */
                case FWS_L:
                        left = rcu_dereference_protected(fn->left, 1);
                        if (left) {
                                w->node = left;
                                w->state = FWS_INIT;
                                continue;
                        }
                        w->state = FWS_R;
                        /* fall through */
                case FWS_R:
                        right = rcu_dereference_protected(fn->right, 1);
                        if (right) {
                                w->node = right;
                                w->state = FWS_INIT;
                                continue;
                        }
                        w->state = FWS_C;
                        w->leaf = rcu_dereference_protected(fn->leaf, 1);
                        /* fall through */
                case FWS_C:
                        if (w->leaf && fn->fn_flags & RTN_RTINFO) {
                                int err;

                                if (w->skip) {
                                        w->skip--;
                                        goto skip;
                                }

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

                                w->count++;
                                continue;
                        }
skip:
                        w->state = FWS_U;
                        /* fall through */
                case FWS_U:
                        if (fn == w->root)
                                return 0;
                        pn = rcu_dereference_protected(fn->parent, 1);
                        left = rcu_dereference_protected(pn->left, 1);
                        right = rcu_dereference_protected(pn->right, 1);
                        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 (left == fn) {
                                w->state = FWS_R;
                                continue;
                        }
                        if (right == fn) {
                                w->state = FWS_C;
                                w->leaf = rcu_dereference_protected(w->node->leaf, 1);
                                continue;
                        }
#if RT6_DEBUG >= 2
                        WARN_ON(1);
#endif
                }
        }
}

static int fib6_walk(struct net *net, struct fib6_walker *w)
{
        int res;

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

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

static int fib6_clean_node(struct fib6_walker *w)
{
        int res;
        struct rt6_info *rt;
        struct fib6_cleaner *c = container_of(w, struct fib6_cleaner, w);
        struct nl_info info = {
                .nl_net = c->net,
        };

        if (c->sernum != FIB6_NO_SERNUM_CHANGE &&
            w->node->fn_sernum != c->sernum)
                w->node->fn_sernum = c->sernum;

        if (!c->func) {
                WARN_ON_ONCE(c->sernum == FIB6_NO_SERNUM_CHANGE);
                w->leaf = NULL;
                return 0;
        }

        for_each_fib6_walker_rt(w) {
                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,
                                         rcu_access_pointer(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
 */

static void fib6_clean_tree(struct net *net, struct fib6_node *root,
                            int (*func)(struct rt6_info *, void *arg),
                            int sernum, void *arg)
{
        struct fib6_cleaner c;

        c.w.root = root;
        c.w.func = fib6_clean_node;
        c.w.count = 0;
        c.w.skip = 0;
        c.func = func;
        c.sernum = sernum;
        c.arg = arg;
        c.net = net;

        fib6_walk(net, &c.w);
}

static void __fib6_clean_all(struct net *net,
                             int (*func)(struct rt6_info *, void *),
                             int sernum, void *arg)
{
        struct fib6_table *table;
        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, head, tb6_hlist) {
                        spin_lock_bh(&table->tb6_lock);
                        fib6_clean_tree(net, &table->tb6_root,
                                        func, sernum, arg);
                        spin_unlock_bh(&table->tb6_lock);
                }
        }
        rcu_read_unlock();
}

void fib6_clean_all(struct net *net, int (*func)(struct rt6_info *, void *),
                    void *arg)
{
        __fib6_clean_all(net, func, FIB6_NO_SERNUM_CHANGE, arg);
}

static void fib6_flush_trees(struct net *net)
{
        int new_sernum = fib6_new_sernum(net);

        __fib6_clean_all(net, NULL, new_sernum, NULL);
}

/*
 *      Garbage collection
 */

static int fib6_age(struct rt6_info *rt, void *arg)
{
        struct fib6_gc_args *gc_args = arg;
        unsigned long now = jiffies;

        /*
         *      check addrconf expiration here.
         *      Routes are expired even if they are in use.
         */

        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++;
        }

        /*      Also age clones in the exception table.
         *      Note, that clones are aged out
         *      only if they are not in use now.
         */
        rt6_age_exceptions(rt, gc_args, now);

        return 0;
}

void fib6_run_gc(unsigned long expires, struct net *net, bool force)
{
        struct fib6_gc_args gc_args;
        unsigned long now;

        if (force) {
                spin_lock_bh(&net->ipv6.fib6_gc_lock);
        } else if (!spin_trylock_bh(&net->ipv6.fib6_gc_lock)) {
                mod_timer(&net->ipv6.ip6_fib_timer, jiffies + HZ);
                return;
        }
        gc_args.timeout = expires ? (int)expires :
                          net->ipv6.sysctl.ip6_rt_gc_interval;
        gc_args.more = 0;

        fib6_clean_all(net, fib6_age, &gc_args);
        now = jiffies;
        net->ipv6.ip6_rt_last_gc = now;

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

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

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

        err = fib6_notifier_init(net);
        if (err)
                return err;

        spin_lock_init(&net->ipv6.fib6_gc_lock);
        rwlock_init(&net->ipv6.fib6_walker_lock);
        INIT_LIST_HEAD(&net->ipv6.fib6_walkers);
        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;
        rcu_assign_pointer(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;
        rcu_assign_pointer(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:
        fib6_notifier_exit(net);
        return -ENOMEM;
}

static void fib6_net_exit(struct net *net)
{
        unsigned int i;

        rt6_ifdown(net, NULL);
        del_timer_sync(&net->ipv6.ip6_fib_timer);

        for (i = 0; i < FIB6_TABLE_HASHSZ; i++) {
                struct hlist_head *head = &net->ipv6.fib_table_hash[i];
                struct hlist_node *tmp;
                struct fib6_table *tb;

                hlist_for_each_entry_safe(tb, tmp, head, tb6_hlist) {
                        hlist_del(&tb->tb6_hlist);
                        fib6_free_table(tb);
                }
        }

        kfree(net->ipv6.fib_table_hash);
        kfree(net->ipv6.rt6_stats);
        fib6_notifier_exit(net);
}

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,
                              0);
        if (ret)
                goto out_unregister_subsys;

        __fib6_flush_trees = fib6_flush_trees;
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);
}

#ifdef CONFIG_PROC_FS

struct ipv6_route_iter {
        struct seq_net_private p;
        struct fib6_walker w;
        loff_t skip;
        struct fib6_table *tbl;
        int sernum;
};

static int ipv6_route_seq_show(struct seq_file *seq, void *v)
{
        struct rt6_info *rt = v;
        struct ipv6_route_iter *iter = seq->private;

        seq_printf(seq, "%pi6 %02x ", &rt->rt6i_dst.addr, rt->rt6i_dst.plen);

#ifdef CONFIG_IPV6_SUBTREES
        seq_printf(seq, "%pi6 %02x ", &rt->rt6i_src.addr, rt->rt6i_src.plen);
#else
        seq_puts(seq, "00000000000000000000000000000000 00 ");
#endif
        if (rt->rt6i_flags & RTF_GATEWAY)
                seq_printf(seq, "%pi6", &rt->rt6i_gateway);
        else
                seq_puts(seq, "00000000000000000000000000000000");

        seq_printf(seq, " %08x %08x %08x %08x %8s\n",
                   rt->rt6i_metric, atomic_read(&rt->dst.__refcnt),
                   rt->dst.__use, rt->rt6i_flags,
                   rt->dst.dev ? rt->dst.dev->name : "");
        iter->w.leaf = NULL;
        return 0;
}

static int ipv6_route_yield(struct fib6_walker *w)
{
        struct ipv6_route_iter *iter = w->args;

        if (!iter->skip)
                return 1;

        do {
                iter->w.leaf = rcu_dereference_protected(
                                iter->w.leaf->dst.rt6_next,
                                lockdep_is_held(&iter->tbl->tb6_lock));
                iter->skip--;
                if (!iter->skip && iter->w.leaf)
                        return 1;
        } while (iter->w.leaf);

        return 0;
}

static void ipv6_route_seq_setup_walk(struct ipv6_route_iter *iter,
                                      struct net *net)
{
        memset(&iter->w, 0, sizeof(iter->w));
        iter->w.func = ipv6_route_yield;
        iter->w.root = &iter->tbl->tb6_root;
        iter->w.state = FWS_INIT;
        iter->w.node = iter->w.root;
        iter->w.args = iter;
        iter->sernum = iter->w.root->fn_sernum;
        INIT_LIST_HEAD(&iter->w.lh);
        fib6_walker_link(net, &iter->w);
}

static struct fib6_table *ipv6_route_seq_next_table(struct fib6_table *tbl,
                                                    struct net *net)
{
        unsigned int h;
        struct hlist_node *node;

        if (tbl) {
                h = (tbl->tb6_id & (FIB6_TABLE_HASHSZ - 1)) + 1;
                node = rcu_dereference_bh(hlist_next_rcu(&tbl->tb6_hlist));
        } else {
                h = 0;
                node = NULL;
        }

        while (!node && h < FIB6_TABLE_HASHSZ) {
                node = rcu_dereference_bh(
                        hlist_first_rcu(&net->ipv6.fib_table_hash[h++]));
        }
        return hlist_entry_safe(node, struct fib6_table, tb6_hlist);
}

static void ipv6_route_check_sernum(struct ipv6_route_iter *iter)
{
        if (iter->sernum != iter->w.root->fn_sernum) {
                iter->sernum = iter->w.root->fn_sernum;
                iter->w.state = FWS_INIT;
                iter->w.node = iter->w.root;
                WARN_ON(iter->w.skip);
                iter->w.skip = iter->w.count;
        }
}

static void *ipv6_route_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
        int r;
        struct rt6_info *n;
        struct net *net = seq_file_net(seq);
        struct ipv6_route_iter *iter = seq->private;

        if (!v)
                goto iter_table;

        n = rcu_dereference_bh(((struct rt6_info *)v)->dst.rt6_next);
        if (n) {
                ++*pos;
                return n;
        }

iter_table:
        ipv6_route_check_sernum(iter);
        spin_lock_bh(&iter->tbl->tb6_lock);
        r = fib6_walk_continue(&iter->w);
        spin_unlock_bh(&iter->tbl->tb6_lock);
        if (r > 0) {
                if (v)
                        ++*pos;
                return iter->w.leaf;
        } else if (r < 0) {
                fib6_walker_unlink(net, &iter->w);
                return NULL;
        }
        fib6_walker_unlink(net, &iter->w);

        iter->tbl = ipv6_route_seq_next_table(iter->tbl, net);
        if (!iter->tbl)
                return NULL;

        ipv6_route_seq_setup_walk(iter, net);
        goto iter_table;
}

static void *ipv6_route_seq_start(struct seq_file *seq, loff_t *pos)
        __acquires(RCU_BH)
{
        struct net *net = seq_file_net(seq);
        struct ipv6_route_iter *iter = seq->private;

        rcu_read_lock_bh();
        iter->tbl = ipv6_route_seq_next_table(NULL, net);
        iter->skip = *pos;

        if (iter->tbl) {
                ipv6_route_seq_setup_walk(iter, net);
                return ipv6_route_seq_next(seq, NULL, pos);
        } else {
                return NULL;
        }
}

static bool ipv6_route_iter_active(struct ipv6_route_iter *iter)
{
        struct fib6_walker *w = &iter->w;
        return w->node && !(w->state == FWS_U && w->node == w->root);
}

static void ipv6_route_seq_stop(struct seq_file *seq, void *v)
        __releases(RCU_BH)
{
        struct net *net = seq_file_net(seq);
        struct ipv6_route_iter *iter = seq->private;

        if (ipv6_route_iter_active(iter))
                fib6_walker_unlink(net, &iter->w);

        rcu_read_unlock_bh();
}

static const struct seq_operations ipv6_route_seq_ops = {
        .start  = ipv6_route_seq_start,
        .next   = ipv6_route_seq_next,
        .stop   = ipv6_route_seq_stop,
        .show   = ipv6_route_seq_show
};

int ipv6_route_open(struct inode *inode, struct file *file)
{
        return seq_open_net(inode, file, &ipv6_route_seq_ops,
                            sizeof(struct ipv6_route_iter));
}

#endif /* CONFIG_PROC_FS */