[deliverable/linux.git] / net / ipv4 / fib_trie.c

/*
 *   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.
 *
 *   Robert Olsson <robert.olsson@its.uu.se> Uppsala Universitet
 *     & Swedish University of Agricultural Sciences.
 *
 *   Jens Laas <jens.laas@data.slu.se> Swedish University of
 *     Agricultural Sciences.
 *
 *   Hans Liss <hans.liss@its.uu.se>  Uppsala Universitet
 *
 * This work is based on the LPC-trie which is originally described in:
 *
 * An experimental study of compression methods for dynamic tries
 * Stefan Nilsson and Matti Tikkanen. Algorithmica, 33(1):19-33, 2002.
 * http://www.csc.kth.se/~snilsson/software/dyntrie2/
 *
 *
 * IP-address lookup using LC-tries. Stefan Nilsson and Gunnar Karlsson
 * IEEE Journal on Selected Areas in Communications, 17(6):1083-1092, June 1999
 *
 *
 * Code from fib_hash has been reused which includes the following header:
 *
 *
 * INET         An implementation of the TCP/IP protocol suite for the LINUX
 *              operating system.  INET is implemented using the  BSD Socket
 *              interface as the means of communication with the user level.
 *
 *              IPv4 FIB: lookup engine and maintenance routines.
 *
 *
 * Authors:     Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
 *
 *              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.
 *
 * Substantial contributions to this work comes from:
 *
 *              David S. Miller, <davem@davemloft.net>
 *              Stephen Hemminger <shemminger@osdl.org>
 *              Paul E. McKenney <paulmck@us.ibm.com>
 *              Patrick McHardy <kaber@trash.net>
 */

#define VERSION "0.409"

#include <asm/uaccess.h>
#include <linux/bitops.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/errno.h>
#include <linux/in.h>
#include <linux/inet.h>
#include <linux/inetdevice.h>
#include <linux/netdevice.h>
#include <linux/if_arp.h>
#include <linux/proc_fs.h>
#include <linux/rcupdate.h>
#include <linux/skbuff.h>
#include <linux/netlink.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/slab.h>
#include <linux/export.h>
#include <net/net_namespace.h>
#include <net/ip.h>
#include <net/protocol.h>
#include <net/route.h>
#include <net/tcp.h>
#include <net/sock.h>
#include <net/ip_fib.h>
#include "fib_lookup.h"

#define MAX_STAT_DEPTH 32

#define KEYLENGTH (8*sizeof(t_key))

typedef unsigned int t_key;

#define IS_TNODE(n) ((n)->bits)
#define IS_LEAF(n) (!(n)->bits)

#define get_index(_key, _kv) (((_key) ^ (_kv)->key) >> (_kv)->pos)

struct tnode {
        t_key key;
        unsigned char bits;             /* 2log(KEYLENGTH) bits needed */
        unsigned char pos;              /* 2log(KEYLENGTH) bits needed */
        struct tnode __rcu *parent;
        struct rcu_head rcu;
        union {
                /* The fields in this struct are valid if bits > 0 (TNODE) */
                struct {
                        unsigned int full_children;  /* KEYLENGTH bits needed */
                        unsigned int empty_children; /* KEYLENGTH bits needed */
                        struct tnode __rcu *child[0];
                };
                /* This list pointer if valid if bits == 0 (LEAF) */
                struct hlist_head list;
        };
};

struct leaf_info {
        struct hlist_node hlist;
        int plen;
        u32 mask_plen; /* ntohl(inet_make_mask(plen)) */
        struct list_head falh;
        struct rcu_head rcu;
};

#ifdef CONFIG_IP_FIB_TRIE_STATS
struct trie_use_stats {
        unsigned int gets;
        unsigned int backtrack;
        unsigned int semantic_match_passed;
        unsigned int semantic_match_miss;
        unsigned int null_node_hit;
        unsigned int resize_node_skipped;
};
#endif

struct trie_stat {
        unsigned int totdepth;
        unsigned int maxdepth;
        unsigned int tnodes;
        unsigned int leaves;
        unsigned int nullpointers;
        unsigned int prefixes;
        unsigned int nodesizes[MAX_STAT_DEPTH];
};

struct trie {
        struct tnode __rcu *trie;
#ifdef CONFIG_IP_FIB_TRIE_STATS
        struct trie_use_stats __percpu *stats;
#endif
};

static void tnode_put_child_reorg(struct tnode *tn, unsigned long i,
                                  struct tnode *n, int wasfull);
static struct tnode *resize(struct trie *t, struct tnode *tn);
/* tnodes to free after resize(); protected by RTNL */
static struct callback_head *tnode_free_head;
static size_t tnode_free_size;

/*
 * synchronize_rcu after call_rcu for that many pages; it should be especially
 * useful before resizing the root node with PREEMPT_NONE configs; the value was
 * obtained experimentally, aiming to avoid visible slowdown.
 */
static const int sync_pages = 128;

static struct kmem_cache *fn_alias_kmem __read_mostly;
static struct kmem_cache *trie_leaf_kmem __read_mostly;

/* caller must hold RTNL */
#define node_parent(n) rtnl_dereference((n)->parent)

/* caller must hold RCU read lock or RTNL */
#define node_parent_rcu(n) rcu_dereference_rtnl((n)->parent)

/* wrapper for rcu_assign_pointer */
static inline void node_set_parent(struct tnode *n, struct tnode *tp)
{
        if (n)
                rcu_assign_pointer(n->parent, tp);
}

#define NODE_INIT_PARENT(n, p) RCU_INIT_POINTER((n)->parent, p)

/* This provides us with the number of children in this node, in the case of a
 * leaf this will return 0 meaning none of the children are accessible.
 */
static inline unsigned long tnode_child_length(const struct tnode *tn)
{
        return (1ul << tn->bits) & ~(1ul);
}

/* caller must hold RTNL */
static inline struct tnode *tnode_get_child(const struct tnode *tn,
                                            unsigned long i)
{
        BUG_ON(i >= tnode_child_length(tn));

        return rtnl_dereference(tn->child[i]);
}

/* caller must hold RCU read lock or RTNL */
static inline struct tnode *tnode_get_child_rcu(const struct tnode *tn,
                                                unsigned long i)
{
        BUG_ON(i >= tnode_child_length(tn));

        return rcu_dereference_rtnl(tn->child[i]);
}

/* To understand this stuff, an understanding of keys and all their bits is
 * necessary. Every node in the trie has a key associated with it, but not
 * all of the bits in that key are significant.
 *
 * Consider a node 'n' and its parent 'tp'.
 *
 * If n is a leaf, every bit in its key is significant. Its presence is
 * necessitated by path compression, since during a tree traversal (when
 * searching for a leaf - unless we are doing an insertion) we will completely
 * ignore all skipped bits we encounter. Thus we need to verify, at the end of
 * a potentially successful search, that we have indeed been walking the
 * correct key path.
 *
 * Note that we can never "miss" the correct key in the tree if present by
 * following the wrong path. Path compression ensures that segments of the key
 * that are the same for all keys with a given prefix are skipped, but the
 * skipped part *is* identical for each node in the subtrie below the skipped
 * bit! trie_insert() in this implementation takes care of that.
 *
 * if n is an internal node - a 'tnode' here, the various parts of its key
 * have many different meanings.
 *
 * Example:
 * _________________________________________________________________
 * | i | i | i | i | i | i | i | N | N | N | S | S | S | S | S | C |
 * -----------------------------------------------------------------
 *  31  30  29  28  27  26  25  24  23  22  21  20  19  18  17  16
 *
 * _________________________________________________________________
 * | C | C | C | u | u | u | u | u | u | u | u | u | u | u | u | u |
 * -----------------------------------------------------------------
 *  15  14  13  12  11  10   9   8   7   6   5   4   3   2   1   0
 *
 * tp->pos = 22
 * tp->bits = 3
 * n->pos = 13
 * n->bits = 4
 *
 * First, let's just ignore the bits that come before the parent tp, that is
 * the bits from (tp->pos + tp->bits) to 31. They are *known* but at this
 * point we do not use them for anything.
 *
 * The bits from (tp->pos) to (tp->pos + tp->bits - 1) - "N", above - are the
 * index into the parent's child array. That is, they will be used to find
 * 'n' among tp's children.
 *
 * The bits from (n->pos + n->bits) to (tn->pos - 1) - "S" - are skipped bits
 * for the node n.
 *
 * All the bits we have seen so far are significant to the node n. The rest
 * of the bits are really not needed or indeed known in n->key.
 *
 * The bits from (n->pos) to (n->pos + n->bits - 1) - "C" - are the index into
 * n's child array, and will of course be different for each child.
 *
 * The rest of the bits, from 0 to (n->pos + n->bits), are completely unknown
 * at this point.
 */

static const int halve_threshold = 25;
static const int inflate_threshold = 50;
static const int halve_threshold_root = 15;
static const int inflate_threshold_root = 30;

static void __alias_free_mem(struct rcu_head *head)
{
        struct fib_alias *fa = container_of(head, struct fib_alias, rcu);
        kmem_cache_free(fn_alias_kmem, fa);
}

static inline void alias_free_mem_rcu(struct fib_alias *fa)
{
        call_rcu(&fa->rcu, __alias_free_mem);
}

#define TNODE_KMALLOC_MAX \
        ilog2((PAGE_SIZE - sizeof(struct tnode)) / sizeof(struct tnode *))

static void __node_free_rcu(struct rcu_head *head)
{
        struct tnode *n = container_of(head, struct tnode, rcu);

        if (IS_LEAF(n))
                kmem_cache_free(trie_leaf_kmem, n);
        else if (n->bits <= TNODE_KMALLOC_MAX)
                kfree(n);
        else
                vfree(n);
}

#define node_free(n) call_rcu(&n->rcu, __node_free_rcu)

static inline void free_leaf_info(struct leaf_info *leaf)
{
        kfree_rcu(leaf, rcu);
}

static struct tnode *tnode_alloc(size_t size)
{
        if (size <= PAGE_SIZE)
                return kzalloc(size, GFP_KERNEL);
        else
                return vzalloc(size);
}

static void tnode_free_safe(struct tnode *tn)
{
        BUG_ON(IS_LEAF(tn));
        tn->rcu.next = tnode_free_head;
        tnode_free_head = &tn->rcu;
}

static void tnode_free_flush(void)
{
        struct callback_head *head;

        while ((head = tnode_free_head)) {
                struct tnode *tn = container_of(head, struct tnode, rcu);

                tnode_free_head = head->next;
                tnode_free_size += offsetof(struct tnode, child[1 << tn->bits]);

                node_free(tn);
        }

        if (tnode_free_size >= PAGE_SIZE * sync_pages) {
                tnode_free_size = 0;
                synchronize_rcu();
        }
}

static struct tnode *leaf_new(t_key key)
{
        struct tnode *l = kmem_cache_alloc(trie_leaf_kmem, GFP_KERNEL);
        if (l) {
                l->parent = NULL;
                /* set key and pos to reflect full key value
                 * any trailing zeros in the key should be ignored
                 * as the nodes are searched
                 */
                l->key = key;
                l->pos = 0;
                /* set bits to 0 indicating we are not a tnode */
                l->bits = 0;

                INIT_HLIST_HEAD(&l->list);
        }
        return l;
}

static struct leaf_info *leaf_info_new(int plen)
{
        struct leaf_info *li = kmalloc(sizeof(struct leaf_info),  GFP_KERNEL);
        if (li) {
                li->plen = plen;
                li->mask_plen = ntohl(inet_make_mask(plen));
                INIT_LIST_HEAD(&li->falh);
        }
        return li;
}

static struct tnode *tnode_new(t_key key, int pos, int bits)
{
        size_t sz = offsetof(struct tnode, child[1 << bits]);
        struct tnode *tn = tnode_alloc(sz);
        unsigned int shift = pos + bits;

        /* verify bits and pos their msb bits clear and values are valid */
        BUG_ON(!bits || (shift > KEYLENGTH));

        if (tn) {
                tn->parent = NULL;
                tn->pos = pos;
                tn->bits = bits;
                tn->key = (shift < KEYLENGTH) ? (key >> shift) << shift : 0;
                tn->full_children = 0;
                tn->empty_children = 1<<bits;
        }

        pr_debug("AT %p s=%zu %zu\n", tn, sizeof(struct tnode),
                 sizeof(struct tnode *) << bits);
        return tn;
}

/* Check whether a tnode 'n' is "full", i.e. it is an internal node
 * and no bits are skipped. See discussion in dyntree paper p. 6
 */
static inline int tnode_full(const struct tnode *tn, const struct tnode *n)
{
        return n && ((n->pos + n->bits) == tn->pos) && IS_TNODE(n);
}

static inline void put_child(struct tnode *tn, unsigned long i,
                             struct tnode *n)
{
        tnode_put_child_reorg(tn, i, n, -1);
}

 /*
  * Add a child at position i overwriting the old value.
  * Update the value of full_children and empty_children.
  */

static void tnode_put_child_reorg(struct tnode *tn, unsigned long i,
                                  struct tnode *n, int wasfull)
{
        struct tnode *chi = rtnl_dereference(tn->child[i]);
        int isfull;

        BUG_ON(i >= tnode_child_length(tn));

        /* update emptyChildren */
        if (n == NULL && chi != NULL)
                tn->empty_children++;
        else if (n != NULL && chi == NULL)
                tn->empty_children--;

        /* update fullChildren */
        if (wasfull == -1)
                wasfull = tnode_full(tn, chi);

        isfull = tnode_full(tn, n);
        if (wasfull && !isfull)
                tn->full_children--;
        else if (!wasfull && isfull)
                tn->full_children++;

        node_set_parent(n, tn);

        rcu_assign_pointer(tn->child[i], n);
}

static void put_child_root(struct tnode *tp, struct trie *t,
                           t_key key, struct tnode *n)
{
        if (tp)
                put_child(tp, get_index(key, tp), n);
        else
                rcu_assign_pointer(t->trie, n);
}

static void tnode_clean_free(struct tnode *tn)
{
        struct tnode *tofree;
        unsigned long i;

        for (i = 0; i < tnode_child_length(tn); i++) {
                tofree = tnode_get_child(tn, i);
                if (tofree)
                        node_free(tofree);
        }
        node_free(tn);
}

static struct tnode *inflate(struct trie *t, struct tnode *oldtnode)
{
        unsigned long olen = tnode_child_length(oldtnode);
        struct tnode *tn;
        unsigned long i;
        t_key m;

        pr_debug("In inflate\n");

        tn = tnode_new(oldtnode->key, oldtnode->pos - 1, oldtnode->bits + 1);

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

        /*
         * Preallocate and store tnodes before the actual work so we
         * don't get into an inconsistent state if memory allocation
         * fails. In case of failure we return the oldnode and  inflate
         * of tnode is ignored.
         */
        for (i = 0, m = 1u << tn->pos; i < olen; i++) {
                struct tnode *inode = tnode_get_child(oldtnode, i);

                if (tnode_full(oldtnode, inode) && (inode->bits > 1)) {
                        struct tnode *left, *right;

                        left = tnode_new(inode->key & ~m, inode->pos,
                                         inode->bits - 1);
                        if (!left)
                                goto nomem;

                        right = tnode_new(inode->key | m, inode->pos,
                                          inode->bits - 1);

                        if (!right) {
                                node_free(left);
                                goto nomem;
                        }

                        put_child(tn, 2*i, left);
                        put_child(tn, 2*i+1, right);
                }
        }

        for (i = 0; i < olen; i++) {
                struct tnode *inode = tnode_get_child(oldtnode, i);
                struct tnode *left, *right;
                unsigned long size, j;

                /* An empty child */
                if (inode == NULL)
                        continue;

                /* A leaf or an internal node with skipped bits */
                if (!tnode_full(oldtnode, inode)) {
                        put_child(tn, get_index(inode->key, tn), inode);
                        continue;
                }

                /* An internal node with two children */
                if (inode->bits == 1) {
                        put_child(tn, 2*i, rtnl_dereference(inode->child[0]));
                        put_child(tn, 2*i+1, rtnl_dereference(inode->child[1]));

                        tnode_free_safe(inode);
                        continue;
                }

                /* An internal node with more than two children */

                /* We will replace this node 'inode' with two new
                 * ones, 'left' and 'right', each with half of the
                 * original children. The two new nodes will have
                 * a position one bit further down the key and this
                 * means that the "significant" part of their keys
                 * (see the discussion near the top of this file)
                 * will differ by one bit, which will be "0" in
                 * left's key and "1" in right's key. Since we are
                 * moving the key position by one step, the bit that
                 * we are moving away from - the bit at position
                 * (inode->pos) - is the one that will differ between
                 * left and right. So... we synthesize that bit in the
                 * two  new keys.
                 * The mask 'm' below will be a single "one" bit at
                 * the position (inode->pos)
                 */

                /* Use the old key, but set the new significant
                 *   bit to zero.
                 */

                left = tnode_get_child(tn, 2*i);
                put_child(tn, 2*i, NULL);

                BUG_ON(!left);

                right = tnode_get_child(tn, 2*i+1);
                put_child(tn, 2*i+1, NULL);

                BUG_ON(!right);

                size = tnode_child_length(left);
                for (j = 0; j < size; j++) {
                        put_child(left, j, rtnl_dereference(inode->child[j]));
                        put_child(right, j, rtnl_dereference(inode->child[j + size]));
                }
                put_child(tn, 2*i, resize(t, left));
                put_child(tn, 2*i+1, resize(t, right));

                tnode_free_safe(inode);
        }
        tnode_free_safe(oldtnode);
        return tn;
nomem:
        tnode_clean_free(tn);
        return ERR_PTR(-ENOMEM);
}

static struct tnode *halve(struct trie *t, struct tnode *oldtnode)
{
        unsigned long olen = tnode_child_length(oldtnode);
        struct tnode *tn, *left, *right;
        int i;

        pr_debug("In halve\n");

        tn = tnode_new(oldtnode->key, oldtnode->pos + 1, oldtnode->bits - 1);

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

        /*
         * Preallocate and store tnodes before the actual work so we
         * don't get into an inconsistent state if memory allocation
         * fails. In case of failure we return the oldnode and halve
         * of tnode is ignored.
         */

        for (i = 0; i < olen; i += 2) {
                left = tnode_get_child(oldtnode, i);
                right = tnode_get_child(oldtnode, i+1);

                /* Two nonempty children */
                if (left && right) {
                        struct tnode *newn;

                        newn = tnode_new(left->key, oldtnode->pos, 1);

                        if (!newn)
                                goto nomem;

                        put_child(tn, i/2, newn);
                }

        }

        for (i = 0; i < olen; i += 2) {
                struct tnode *newBinNode;

                left = tnode_get_child(oldtnode, i);
                right = tnode_get_child(oldtnode, i+1);

                /* At least one of the children is empty */
                if (left == NULL) {
                        if (right == NULL)    /* Both are empty */
                                continue;
                        put_child(tn, i/2, right);
                        continue;
                }

                if (right == NULL) {
                        put_child(tn, i/2, left);
                        continue;
                }

                /* Two nonempty children */
                newBinNode = tnode_get_child(tn, i/2);
                put_child(tn, i/2, NULL);
                put_child(newBinNode, 0, left);
                put_child(newBinNode, 1, right);
                put_child(tn, i/2, resize(t, newBinNode));
        }
        tnode_free_safe(oldtnode);
        return tn;
nomem:
        tnode_clean_free(tn);
        return ERR_PTR(-ENOMEM);
}

#define MAX_WORK 10
static struct tnode *resize(struct trie *t, struct tnode *tn)
{
        struct tnode *old_tn, *n = NULL;
        int inflate_threshold_use;
        int halve_threshold_use;
        int max_work;

        if (!tn)
                return NULL;

        pr_debug("In tnode_resize %p inflate_threshold=%d threshold=%d\n",
                 tn, inflate_threshold, halve_threshold);

        /* No children */
        if (tn->empty_children > (tnode_child_length(tn) - 1))
                goto no_children;

        /* One child */
        if (tn->empty_children == (tnode_child_length(tn) - 1))
                goto one_child;
        /*
         * Double as long as the resulting node has a number of
         * nonempty nodes that are above the threshold.
         */

        /*
         * From "Implementing a dynamic compressed trie" by Stefan Nilsson of
         * the Helsinki University of Technology and Matti Tikkanen of Nokia
         * Telecommunications, page 6:
         * "A node is doubled if the ratio of non-empty children to all
         * children in the *doubled* node is at least 'high'."
         *
         * 'high' in this instance is the variable 'inflate_threshold'. It
         * is expressed as a percentage, so we multiply it with
         * tnode_child_length() and instead of multiplying by 2 (since the
         * child array will be doubled by inflate()) and multiplying
         * the left-hand side by 100 (to handle the percentage thing) we
         * multiply the left-hand side by 50.
         *
         * The left-hand side may look a bit weird: tnode_child_length(tn)
         * - tn->empty_children is of course the number of non-null children
         * in the current node. tn->full_children is the number of "full"
         * children, that is non-null tnodes with a skip value of 0.
         * All of those will be doubled in the resulting inflated tnode, so
         * we just count them one extra time here.
         *
         * A clearer way to write this would be:
         *
         * to_be_doubled = tn->full_children;
         * not_to_be_doubled = tnode_child_length(tn) - tn->empty_children -
         *     tn->full_children;
         *
         * new_child_length = tnode_child_length(tn) * 2;
         *
         * new_fill_factor = 100 * (not_to_be_doubled + 2*to_be_doubled) /
         *      new_child_length;
         * if (new_fill_factor >= inflate_threshold)
         *
         * ...and so on, tho it would mess up the while () loop.
         *
         * anyway,
         * 100 * (not_to_be_doubled + 2*to_be_doubled) / new_child_length >=
         *      inflate_threshold
         *
         * avoid a division:
         * 100 * (not_to_be_doubled + 2*to_be_doubled) >=
         *      inflate_threshold * new_child_length
         *
         * expand not_to_be_doubled and to_be_doubled, and shorten:
         * 100 * (tnode_child_length(tn) - tn->empty_children +
         *    tn->full_children) >= inflate_threshold * new_child_length
         *
         * expand new_child_length:
         * 100 * (tnode_child_length(tn) - tn->empty_children +
         *    tn->full_children) >=
         *      inflate_threshold * tnode_child_length(tn) * 2
         *
         * shorten again:
         * 50 * (tn->full_children + tnode_child_length(tn) -
         *    tn->empty_children) >= inflate_threshold *
         *    tnode_child_length(tn)
         *
         */

        /* Keep root node larger  */

        if (!node_parent(tn)) {
                inflate_threshold_use = inflate_threshold_root;
                halve_threshold_use = halve_threshold_root;
        } else {
                inflate_threshold_use = inflate_threshold;
                halve_threshold_use = halve_threshold;
        }

        max_work = MAX_WORK;
        while ((tn->full_children > 0 &&  max_work-- &&
                50 * (tn->full_children + tnode_child_length(tn)
                      - tn->empty_children)
                >= inflate_threshold_use * tnode_child_length(tn))) {

                old_tn = tn;
                tn = inflate(t, tn);

                if (IS_ERR(tn)) {
                        tn = old_tn;
#ifdef CONFIG_IP_FIB_TRIE_STATS
                        this_cpu_inc(t->stats->resize_node_skipped);
#endif
                        break;
                }
        }

        /* Return if at least one inflate is run */
        if (max_work != MAX_WORK)
                return tn;

        /*
         * Halve as long as the number of empty children in this
         * node is above threshold.
         */

        max_work = MAX_WORK;
        while (tn->bits > 1 &&  max_work-- &&
               100 * (tnode_child_length(tn) - tn->empty_children) <
               halve_threshold_use * tnode_child_length(tn)) {

                old_tn = tn;
                tn = halve(t, tn);
                if (IS_ERR(tn)) {
                        tn = old_tn;
#ifdef CONFIG_IP_FIB_TRIE_STATS
                        this_cpu_inc(t->stats->resize_node_skipped);
#endif
                        break;
                }
        }


        /* Only one child remains */
        if (tn->empty_children == (tnode_child_length(tn) - 1)) {
                unsigned long i;
one_child:
                for (i = tnode_child_length(tn); !n && i;)
                        n = tnode_get_child(tn, --i);
no_children:
                /* compress one level */
                node_set_parent(n, NULL);
                tnode_free_safe(tn);
                return n;
        }
        return tn;
}

/* readside must use rcu_read_lock currently dump routines
 via get_fa_head and dump */

static struct leaf_info *find_leaf_info(struct tnode *l, int plen)
{
        struct hlist_head *head = &l->list;
        struct leaf_info *li;

        hlist_for_each_entry_rcu(li, head, hlist)
                if (li->plen == plen)
                        return li;

        return NULL;
}

static inline struct list_head *get_fa_head(struct tnode *l, int plen)
{
        struct leaf_info *li = find_leaf_info(l, plen);

        if (!li)
                return NULL;

        return &li->falh;
}

static void insert_leaf_info(struct hlist_head *head, struct leaf_info *new)
{
        struct leaf_info *li = NULL, *last = NULL;

        if (hlist_empty(head)) {
                hlist_add_head_rcu(&new->hlist, head);
        } else {
                hlist_for_each_entry(li, head, hlist) {
                        if (new->plen > li->plen)
                                break;

                        last = li;
                }
                if (last)
                        hlist_add_behind_rcu(&new->hlist, &last->hlist);
                else
                        hlist_add_before_rcu(&new->hlist, &li->hlist);
        }
}

/* rcu_read_lock needs to be hold by caller from readside */
static struct tnode *fib_find_node(struct trie *t, u32 key)
{
        struct tnode *n = rcu_dereference_rtnl(t->trie);

        while (n) {
                unsigned long index = get_index(key, n);

                /* This bit of code is a bit tricky but it combines multiple
                 * checks into a single check.  The prefix consists of the
                 * prefix plus zeros for the bits in the cindex. The index
                 * is the difference between the key and this value.  From
                 * this we can actually derive several pieces of data.
                 *   if !(index >> bits)
                 *     we know the value is cindex
                 *   else
                 *     we have a mismatch in skip bits and failed
                 */
                if (index >> n->bits)
                        return NULL;

                /* we have found a leaf. Prefixes have already been compared */
                if (IS_LEAF(n))
                        break;

                n = rcu_dereference_rtnl(n->child[index]);
        }

        return n;
}

static void trie_rebalance(struct trie *t, struct tnode *tn)
{
        int wasfull;
        t_key cindex, key;
        struct tnode *tp;

        key = tn->key;

        while (tn != NULL && (tp = node_parent(tn)) != NULL) {
                cindex = get_index(key, tp);
                wasfull = tnode_full(tp, tnode_get_child(tp, cindex));
                tn = resize(t, tn);

                tnode_put_child_reorg(tp, cindex, tn, wasfull);

                tp = node_parent(tn);
                if (!tp)
                        rcu_assign_pointer(t->trie, tn);

                tnode_free_flush();
                if (!tp)
                        break;
                tn = tp;
        }

        /* Handle last (top) tnode */
        if (IS_TNODE(tn))
                tn = resize(t, tn);

        rcu_assign_pointer(t->trie, tn);
        tnode_free_flush();
}

/* only used from updater-side */

static struct list_head *fib_insert_node(struct trie *t, u32 key, int plen)
{
        struct list_head *fa_head = NULL;
        struct tnode *l, *n, *tp = NULL;
        struct leaf_info *li;

        li = leaf_info_new(plen);
        if (!li)
                return NULL;
        fa_head = &li->falh;

        n = rtnl_dereference(t->trie);

        /* If we point to NULL, stop. Either the tree is empty and we should
         * just put a new leaf in if, or we have reached an empty child slot,
         * and we should just put our new leaf in that.
         *
         * If we hit a node with a key that does't match then we should stop
         * and create a new tnode to replace that node and insert ourselves
         * and the other node into the new tnode.
         */
        while (n) {
                unsigned long index = get_index(key, n);

                /* This bit of code is a bit tricky but it combines multiple
                 * checks into a single check.  The prefix consists of the
                 * prefix plus zeros for the "bits" in the prefix. The index
                 * is the difference between the key and this value.  From
                 * this we can actually derive several pieces of data.
                 *   if !(index >> bits)
                 *     we know the value is child index
                 *   else
                 *     we have a mismatch in skip bits and failed
                 */
                if (index >> n->bits)
                        break;

                /* we have found a leaf. Prefixes have already been compared */
                if (IS_LEAF(n)) {
                        /* Case 1: n is a leaf, and prefixes match*/
                        insert_leaf_info(&n->list, li);
                        return fa_head;
                }

                tp = n;
                n = rcu_dereference_rtnl(n->child[index]);
        }

        l = leaf_new(key);
        if (!l) {
                free_leaf_info(li);
                return NULL;
        }

        insert_leaf_info(&l->list, li);

        /* Case 2: n is a LEAF or a TNODE and the key doesn't match.
         *
         *  Add a new tnode here
         *  first tnode need some special handling
         *  leaves us in position for handling as case 3
         */
        if (n) {
                struct tnode *tn;

                tn = tnode_new(key, __fls(key ^ n->key), 1);
                if (!tn) {
                        free_leaf_info(li);
                        node_free(l);
                        return NULL;
                }

                /* initialize routes out of node */
                NODE_INIT_PARENT(tn, tp);
                put_child(tn, get_index(key, tn) ^ 1, n);

                /* start adding routes into the node */
                put_child_root(tp, t, key, tn);
                node_set_parent(n, tn);

                /* parent now has a NULL spot where the leaf can go */
                tp = tn;
        }

        /* Case 3: n is NULL, and will just insert a new leaf */
        if (tp) {
                NODE_INIT_PARENT(l, tp);
                put_child(tp, get_index(key, tp), l);
                trie_rebalance(t, tp);
        } else {
                rcu_assign_pointer(t->trie, l);
        }

        return fa_head;
}

/*
 * Caller must hold RTNL.
 */
int fib_table_insert(struct fib_table *tb, struct fib_config *cfg)
{
        struct trie *t = (struct trie *) tb->tb_data;
        struct fib_alias *fa, *new_fa;
        struct list_head *fa_head = NULL;
        struct fib_info *fi;
        int plen = cfg->fc_dst_len;
        u8 tos = cfg->fc_tos;
        u32 key, mask;
        int err;
        struct tnode *l;

        if (plen > 32)
                return -EINVAL;

        key = ntohl(cfg->fc_dst);

        pr_debug("Insert table=%u %08x/%d\n", tb->tb_id, key, plen);

        mask = ntohl(inet_make_mask(plen));

        if (key & ~mask)
                return -EINVAL;

        key = key & mask;

        fi = fib_create_info(cfg);
        if (IS_ERR(fi)) {
                err = PTR_ERR(fi);
                goto err;
        }

        l = fib_find_node(t, key);
        fa = NULL;

        if (l) {
                fa_head = get_fa_head(l, plen);
                fa = fib_find_alias(fa_head, tos, fi->fib_priority);
        }

        /* Now fa, if non-NULL, points to the first fib alias
         * with the same keys [prefix,tos,priority], if such key already
         * exists or to the node before which we will insert new one.
         *
         * If fa is NULL, we will need to allocate a new one and
         * insert to the head of f.
         *
         * If f is NULL, no fib node matched the destination key
         * and we need to allocate a new one of those as well.
         */

        if (fa && fa->fa_tos == tos &&
            fa->fa_info->fib_priority == fi->fib_priority) {
                struct fib_alias *fa_first, *fa_match;

                err = -EEXIST;
                if (cfg->fc_nlflags & NLM_F_EXCL)
                        goto out;

                /* We have 2 goals:
                 * 1. Find exact match for type, scope, fib_info to avoid
                 * duplicate routes
                 * 2. Find next 'fa' (or head), NLM_F_APPEND inserts before it
                 */
                fa_match = NULL;
                fa_first = fa;
                fa = list_entry(fa->fa_list.prev, struct fib_alias, fa_list);
                list_for_each_entry_continue(fa, fa_head, fa_list) {
                        if (fa->fa_tos != tos)
                                break;
                        if (fa->fa_info->fib_priority != fi->fib_priority)
                                break;
                        if (fa->fa_type == cfg->fc_type &&
                            fa->fa_info == fi) {
                                fa_match = fa;
                                break;
                        }
                }

                if (cfg->fc_nlflags & NLM_F_REPLACE) {
                        struct fib_info *fi_drop;
                        u8 state;

                        fa = fa_first;
                        if (fa_match) {
                                if (fa == fa_match)
                                        err = 0;
                                goto out;
                        }
                        err = -ENOBUFS;
                        new_fa = kmem_cache_alloc(fn_alias_kmem, GFP_KERNEL);
                        if (new_fa == NULL)
                                goto out;

                        fi_drop = fa->fa_info;
                        new_fa->fa_tos = fa->fa_tos;
                        new_fa->fa_info = fi;
                        new_fa->fa_type = cfg->fc_type;
                        state = fa->fa_state;
                        new_fa->fa_state = state & ~FA_S_ACCESSED;

                        list_replace_rcu(&fa->fa_list, &new_fa->fa_list);
                        alias_free_mem_rcu(fa);

                        fib_release_info(fi_drop);
                        if (state & FA_S_ACCESSED)
                                rt_cache_flush(cfg->fc_nlinfo.nl_net);
                        rtmsg_fib(RTM_NEWROUTE, htonl(key), new_fa, plen,
                                tb->tb_id, &cfg->fc_nlinfo, NLM_F_REPLACE);

                        goto succeeded;
                }
                /* Error if we find a perfect match which
                 * uses the same scope, type, and nexthop
                 * information.
                 */
                if (fa_match)
                        goto out;

                if (!(cfg->fc_nlflags & NLM_F_APPEND))
                        fa = fa_first;
        }
        err = -ENOENT;
        if (!(cfg->fc_nlflags & NLM_F_CREATE))
                goto out;

        err = -ENOBUFS;
        new_fa = kmem_cache_alloc(fn_alias_kmem, GFP_KERNEL);
        if (new_fa == NULL)
                goto out;

        new_fa->fa_info = fi;
        new_fa->fa_tos = tos;
        new_fa->fa_type = cfg->fc_type;
        new_fa->fa_state = 0;
        /*
         * Insert new entry to the list.
         */

        if (!fa_head) {
                fa_head = fib_insert_node(t, key, plen);
                if (unlikely(!fa_head)) {
                        err = -ENOMEM;
                        goto out_free_new_fa;
                }
        }

        if (!plen)
                tb->tb_num_default++;

        list_add_tail_rcu(&new_fa->fa_list,
                          (fa ? &fa->fa_list : fa_head));

        rt_cache_flush(cfg->fc_nlinfo.nl_net);
        rtmsg_fib(RTM_NEWROUTE, htonl(key), new_fa, plen, tb->tb_id,
                  &cfg->fc_nlinfo, 0);
succeeded:
        return 0;

out_free_new_fa:
        kmem_cache_free(fn_alias_kmem, new_fa);
out:
        fib_release_info(fi);
err:
        return err;
}

static inline t_key prefix_mismatch(t_key key, struct tnode *n)
{
        t_key prefix = n->key;

        return (key ^ prefix) & (prefix | -prefix);
}

/* should be called with rcu_read_lock */
int fib_table_lookup(struct fib_table *tb, const struct flowi4 *flp,
                     struct fib_result *res, int fib_flags)
{
        struct trie *t = (struct trie *)tb->tb_data;
#ifdef CONFIG_IP_FIB_TRIE_STATS
        struct trie_use_stats __percpu *stats = t->stats;
#endif
        const t_key key = ntohl(flp->daddr);
        struct tnode *n, *pn;
        struct leaf_info *li;
        t_key cindex;

        n = rcu_dereference(t->trie);
        if (!n)
                return -EAGAIN;

#ifdef CONFIG_IP_FIB_TRIE_STATS
        this_cpu_inc(stats->gets);
#endif

        pn = n;
        cindex = 0;

        /* Step 1: Travel to the longest prefix match in the trie */
        for (;;) {
                unsigned long index = get_index(key, n);

                /* This bit of code is a bit tricky but it combines multiple
                 * checks into a single check.  The prefix consists of the
                 * prefix plus zeros for the "bits" in the prefix. The index
                 * is the difference between the key and this value.  From
                 * this we can actually derive several pieces of data.
                 *   if !(index >> bits)
                 *     we know the value is child index
                 *   else
                 *     we have a mismatch in skip bits and failed
                 */
                if (index >> n->bits)
                        break;

                /* we have found a leaf. Prefixes have already been compared */
                if (IS_LEAF(n))
                        goto found;

                /* only record pn and cindex if we are going to be chopping
                 * bits later.  Otherwise we are just wasting cycles.
                 */
                if (index) {
                        pn = n;
                        cindex = index;
                }

                n = rcu_dereference(n->child[index]);
                if (unlikely(!n))
                        goto backtrace;
        }

        /* Step 2: Sort out leaves and begin backtracing for longest prefix */
        for (;;) {
                /* record the pointer where our next node pointer is stored */
                struct tnode __rcu **cptr = n->child;

                /* This test verifies that none of the bits that differ
                 * between the key and the prefix exist in the region of
                 * the lsb and higher in the prefix.
                 */
                if (unlikely(prefix_mismatch(key, n)))
                        goto backtrace;

                /* exit out and process leaf */
                if (unlikely(IS_LEAF(n)))
                        break;

                /* Don't bother recording parent info.  Since we are in
                 * prefix match mode we will have to come back to wherever
                 * we started this traversal anyway
                 */

                while ((n = rcu_dereference(*cptr)) == NULL) {
backtrace:
#ifdef CONFIG_IP_FIB_TRIE_STATS
                        if (!n)
                                this_cpu_inc(stats->null_node_hit);
#endif
                        /* If we are at cindex 0 there are no more bits for
                         * us to strip at this level so we must ascend back
                         * up one level to see if there are any more bits to
                         * be stripped there.
                         */
                        while (!cindex) {
                                t_key pkey = pn->key;

                                pn = node_parent_rcu(pn);
                                if (unlikely(!pn))
                                        return -EAGAIN;
#ifdef CONFIG_IP_FIB_TRIE_STATS
                                this_cpu_inc(stats->backtrack);
#endif
                                /* Get Child's index */
                                cindex = get_index(pkey, pn);
                        }

                        /* strip the least significant bit from the cindex */
                        cindex &= cindex - 1;

                        /* grab pointer for next child node */
                        cptr = &pn->child[cindex];
                }
        }

found:
        /* Step 3: Process the leaf, if that fails fall back to backtracing */
        hlist_for_each_entry_rcu(li, &n->list, hlist) {
                struct fib_alias *fa;

                if ((key ^ n->key) & li->mask_plen)
                        continue;

                list_for_each_entry_rcu(fa, &li->falh, fa_list) {
                        struct fib_info *fi = fa->fa_info;
                        int nhsel, err;

                        if (fa->fa_tos && fa->fa_tos != flp->flowi4_tos)
                                continue;
                        if (fi->fib_dead)
                                continue;
                        if (fa->fa_info->fib_scope < flp->flowi4_scope)
                                continue;
                        fib_alias_accessed(fa);
                        err = fib_props[fa->fa_type].error;
                        if (unlikely(err < 0)) {
#ifdef CONFIG_IP_FIB_TRIE_STATS
                                this_cpu_inc(stats->semantic_match_passed);
#endif
                                return err;
                        }
                        if (fi->fib_flags & RTNH_F_DEAD)
                                continue;
                        for (nhsel = 0; nhsel < fi->fib_nhs; nhsel++) {
                                const struct fib_nh *nh = &fi->fib_nh[nhsel];

                                if (nh->nh_flags & RTNH_F_DEAD)
                                        continue;
                                if (flp->flowi4_oif && flp->flowi4_oif != nh->nh_oif)
                                        continue;

                                if (!(fib_flags & FIB_LOOKUP_NOREF))
                                        atomic_inc(&fi->fib_clntref);

                                res->prefixlen = li->plen;
                                res->nh_sel = nhsel;
                                res->type = fa->fa_type;
                                res->scope = fi->fib_scope;
                                res->fi = fi;
                                res->table = tb;
                                res->fa_head = &li->falh;
#ifdef CONFIG_IP_FIB_TRIE_STATS
                                this_cpu_inc(stats->semantic_match_passed);
#endif
                                return err;
                        }
                }

#ifdef CONFIG_IP_FIB_TRIE_STATS
                this_cpu_inc(stats->semantic_match_miss);
#endif
        }
        goto backtrace;
}
EXPORT_SYMBOL_GPL(fib_table_lookup);

/*
 * Remove the leaf and return parent.
 */
static void trie_leaf_remove(struct trie *t, struct tnode *l)
{
        struct tnode *tp = node_parent(l);

        pr_debug("entering trie_leaf_remove(%p)\n", l);

        if (tp) {
                put_child(tp, get_index(l->key, tp), NULL);
                trie_rebalance(t, tp);
        } else {
                RCU_INIT_POINTER(t->trie, NULL);
        }

        node_free(l);
}

/*
 * Caller must hold RTNL.
 */
int fib_table_delete(struct fib_table *tb, struct fib_config *cfg)
{
        struct trie *t = (struct trie *) tb->tb_data;
        u32 key, mask;
        int plen = cfg->fc_dst_len;
        u8 tos = cfg->fc_tos;
        struct fib_alias *fa, *fa_to_delete;
        struct list_head *fa_head;
        struct tnode *l;
        struct leaf_info *li;

        if (plen > 32)
                return -EINVAL;

        key = ntohl(cfg->fc_dst);
        mask = ntohl(inet_make_mask(plen));

        if (key & ~mask)
                return -EINVAL;

        key = key & mask;
        l = fib_find_node(t, key);

        if (!l)
                return -ESRCH;

        li = find_leaf_info(l, plen);

        if (!li)
                return -ESRCH;

        fa_head = &li->falh;
        fa = fib_find_alias(fa_head, tos, 0);

        if (!fa)
                return -ESRCH;

        pr_debug("Deleting %08x/%d tos=%d t=%p\n", key, plen, tos, t);

        fa_to_delete = NULL;
        fa = list_entry(fa->fa_list.prev, struct fib_alias, fa_list);
        list_for_each_entry_continue(fa, fa_head, fa_list) {
                struct fib_info *fi = fa->fa_info;

                if (fa->fa_tos != tos)
                        break;

                if ((!cfg->fc_type || fa->fa_type == cfg->fc_type) &&
                    (cfg->fc_scope == RT_SCOPE_NOWHERE ||
                     fa->fa_info->fib_scope == cfg->fc_scope) &&
                    (!cfg->fc_prefsrc ||
                     fi->fib_prefsrc == cfg->fc_prefsrc) &&
                    (!cfg->fc_protocol ||
                     fi->fib_protocol == cfg->fc_protocol) &&
                    fib_nh_match(cfg, fi) == 0) {
                        fa_to_delete = fa;
                        break;
                }
        }

        if (!fa_to_delete)
                return -ESRCH;

        fa = fa_to_delete;
        rtmsg_fib(RTM_DELROUTE, htonl(key), fa, plen, tb->tb_id,
                  &cfg->fc_nlinfo, 0);

        list_del_rcu(&fa->fa_list);

        if (!plen)
                tb->tb_num_default--;

        if (list_empty(fa_head)) {
                hlist_del_rcu(&li->hlist);
                free_leaf_info(li);
        }

        if (hlist_empty(&l->list))
                trie_leaf_remove(t, l);

        if (fa->fa_state & FA_S_ACCESSED)
                rt_cache_flush(cfg->fc_nlinfo.nl_net);

        fib_release_info(fa->fa_info);
        alias_free_mem_rcu(fa);
        return 0;
}

static int trie_flush_list(struct list_head *head)
{
        struct fib_alias *fa, *fa_node;
        int found = 0;

        list_for_each_entry_safe(fa, fa_node, head, fa_list) {
                struct fib_info *fi = fa->fa_info;

                if (fi && (fi->fib_flags & RTNH_F_DEAD)) {
                        list_del_rcu(&fa->fa_list);
                        fib_release_info(fa->fa_info);
                        alias_free_mem_rcu(fa);
                        found++;
                }
        }
        return found;
}

static int trie_flush_leaf(struct tnode *l)
{
        int found = 0;
        struct hlist_head *lih = &l->list;
        struct hlist_node *tmp;
        struct leaf_info *li = NULL;

        hlist_for_each_entry_safe(li, tmp, lih, hlist) {
                found += trie_flush_list(&li->falh);

                if (list_empty(&li->falh)) {
                        hlist_del_rcu(&li->hlist);
                        free_leaf_info(li);
                }
        }
        return found;
}

/*
 * Scan for the next right leaf starting at node p->child[idx]
 * Since we have back pointer, no recursion necessary.
 */
static struct tnode *leaf_walk_rcu(struct tnode *p, struct tnode *c)
{
        do {
                unsigned long idx = c ? idx = get_index(c->key, p) + 1 : 0;

                while (idx < tnode_child_length(p)) {
                        c = tnode_get_child_rcu(p, idx++);
                        if (!c)
                                continue;

                        if (IS_LEAF(c))
                                return c;

                        /* Rescan start scanning in new node */
                        p = c;
                        idx = 0;
                }

                /* Node empty, walk back up to parent */
                c = p;
        } while ((p = node_parent_rcu(c)) != NULL);

        return NULL; /* Root of trie */
}

static struct tnode *trie_firstleaf(struct trie *t)
{
        struct tnode *n = rcu_dereference_rtnl(t->trie);

        if (!n)
                return NULL;

        if (IS_LEAF(n))          /* trie is just a leaf */
                return n;

        return leaf_walk_rcu(n, NULL);
}

static struct tnode *trie_nextleaf(struct tnode *l)
{
        struct tnode *p = node_parent_rcu(l);

        if (!p)
                return NULL;    /* trie with just one leaf */

        return leaf_walk_rcu(p, l);
}

static struct tnode *trie_leafindex(struct trie *t, int index)
{
        struct tnode *l = trie_firstleaf(t);

        while (l && index-- > 0)
                l = trie_nextleaf(l);

        return l;
}


/*
 * Caller must hold RTNL.
 */
int fib_table_flush(struct fib_table *tb)
{
        struct trie *t = (struct trie *) tb->tb_data;
        struct tnode *l, *ll = NULL;
        int found = 0;

        for (l = trie_firstleaf(t); l; l = trie_nextleaf(l)) {
                found += trie_flush_leaf(l);

                if (ll && hlist_empty(&ll->list))
                        trie_leaf_remove(t, ll);
                ll = l;
        }

        if (ll && hlist_empty(&ll->list))
                trie_leaf_remove(t, ll);

        pr_debug("trie_flush found=%d\n", found);
        return found;
}

void fib_free_table(struct fib_table *tb)
{
#ifdef CONFIG_IP_FIB_TRIE_STATS
        struct trie *t = (struct trie *)tb->tb_data;

        free_percpu(t->stats);
#endif /* CONFIG_IP_FIB_TRIE_STATS */
        kfree(tb);
}

static int fn_trie_dump_fa(t_key key, int plen, struct list_head *fah,
                           struct fib_table *tb,
                           struct sk_buff *skb, struct netlink_callback *cb)
{
        int i, s_i;
        struct fib_alias *fa;
        __be32 xkey = htonl(key);

        s_i = cb->args[5];
        i = 0;

        /* rcu_read_lock is hold by caller */

        list_for_each_entry_rcu(fa, fah, fa_list) {
                if (i < s_i) {
                        i++;
                        continue;
                }

                if (fib_dump_info(skb, NETLINK_CB(cb->skb).portid,
                                  cb->nlh->nlmsg_seq,
                                  RTM_NEWROUTE,
                                  tb->tb_id,
                                  fa->fa_type,
                                  xkey,
                                  plen,
                                  fa->fa_tos,
                                  fa->fa_info, NLM_F_MULTI) < 0) {
                        cb->args[5] = i;
                        return -1;
                }
                i++;
        }
        cb->args[5] = i;
        return skb->len;
}

static int fn_trie_dump_leaf(struct tnode *l, struct fib_table *tb,
                        struct sk_buff *skb, struct netlink_callback *cb)
{
        struct leaf_info *li;
        int i, s_i;

        s_i = cb->args[4];
        i = 0;

        /* rcu_read_lock is hold by caller */
        hlist_for_each_entry_rcu(li, &l->list, hlist) {
                if (i < s_i) {
                        i++;
                        continue;
                }

                if (i > s_i)
                        cb->args[5] = 0;

                if (list_empty(&li->falh))
                        continue;

                if (fn_trie_dump_fa(l->key, li->plen, &li->falh, tb, skb, cb) < 0) {
                        cb->args[4] = i;
                        return -1;
                }
                i++;
        }

        cb->args[4] = i;
        return skb->len;
}

int fib_table_dump(struct fib_table *tb, struct sk_buff *skb,
                   struct netlink_callback *cb)
{
        struct tnode *l;
        struct trie *t = (struct trie *) tb->tb_data;
        t_key key = cb->args[2];
        int count = cb->args[3];

        rcu_read_lock();
        /* Dump starting at last key.
         * Note: 0.0.0.0/0 (ie default) is first key.
         */
        if (count == 0)
                l = trie_firstleaf(t);
        else {
                /* Normally, continue from last key, but if that is missing
                 * fallback to using slow rescan
                 */
                l = fib_find_node(t, key);
                if (!l)
                        l = trie_leafindex(t, count);
        }

        while (l) {
                cb->args[2] = l->key;
                if (fn_trie_dump_leaf(l, tb, skb, cb) < 0) {
                        cb->args[3] = count;
                        rcu_read_unlock();
                        return -1;
                }

                ++count;
                l = trie_nextleaf(l);
                memset(&cb->args[4], 0,
                       sizeof(cb->args) - 4*sizeof(cb->args[0]));
        }
        cb->args[3] = count;
        rcu_read_unlock();

        return skb->len;
}

void __init fib_trie_init(void)
{
        fn_alias_kmem = kmem_cache_create("ip_fib_alias",
                                          sizeof(struct fib_alias),
                                          0, SLAB_PANIC, NULL);

        trie_leaf_kmem = kmem_cache_create("ip_fib_trie",
                                           max(sizeof(struct tnode),
                                               sizeof(struct leaf_info)),
                                           0, SLAB_PANIC, NULL);
}


struct fib_table *fib_trie_table(u32 id)
{
        struct fib_table *tb;
        struct trie *t;

        tb = kmalloc(sizeof(struct fib_table) + sizeof(struct trie),
                     GFP_KERNEL);
        if (tb == NULL)
                return NULL;

        tb->tb_id = id;
        tb->tb_default = -1;
        tb->tb_num_default = 0;

        t = (struct trie *) tb->tb_data;
        RCU_INIT_POINTER(t->trie, NULL);
#ifdef CONFIG_IP_FIB_TRIE_STATS
        t->stats = alloc_percpu(struct trie_use_stats);
        if (!t->stats) {
                kfree(tb);
                tb = NULL;
        }
#endif

        return tb;
}

#ifdef CONFIG_PROC_FS
/* Depth first Trie walk iterator */
struct fib_trie_iter {
        struct seq_net_private p;
        struct fib_table *tb;
        struct tnode *tnode;
        unsigned int index;
        unsigned int depth;
};

static struct tnode *fib_trie_get_next(struct fib_trie_iter *iter)
{
        unsigned long cindex = iter->index;
        struct tnode *tn = iter->tnode;
        struct tnode *p;

        /* A single entry routing table */
        if (!tn)
                return NULL;

        pr_debug("get_next iter={node=%p index=%d depth=%d}\n",
                 iter->tnode, iter->index, iter->depth);
rescan:
        while (cindex < tnode_child_length(tn)) {
                struct tnode *n = tnode_get_child_rcu(tn, cindex);

                if (n) {
                        if (IS_LEAF(n)) {
                                iter->tnode = tn;
                                iter->index = cindex + 1;
                        } else {
                                /* push down one level */
                                iter->tnode = n;
                                iter->index = 0;
                                ++iter->depth;
                        }
                        return n;
                }

                ++cindex;
        }

        /* Current node exhausted, pop back up */
        p = node_parent_rcu(tn);
        if (p) {
                cindex = get_index(tn->key, p) + 1;
                tn = p;
                --iter->depth;
                goto rescan;
        }

        /* got root? */
        return NULL;
}

static struct tnode *fib_trie_get_first(struct fib_trie_iter *iter,
                                       struct trie *t)
{
        struct tnode *n;

        if (!t)
                return NULL;

        n = rcu_dereference(t->trie);
        if (!n)
                return NULL;

        if (IS_TNODE(n)) {
                iter->tnode = n;
                iter->index = 0;
                iter->depth = 1;
        } else {
                iter->tnode = NULL;
                iter->index = 0;
                iter->depth = 0;
        }

        return n;
}

static void trie_collect_stats(struct trie *t, struct trie_stat *s)
{
        struct tnode *n;
        struct fib_trie_iter iter;

        memset(s, 0, sizeof(*s));

        rcu_read_lock();
        for (n = fib_trie_get_first(&iter, t); n; n = fib_trie_get_next(&iter)) {
                if (IS_LEAF(n)) {
                        struct leaf_info *li;

                        s->leaves++;
                        s->totdepth += iter.depth;
                        if (iter.depth > s->maxdepth)
                                s->maxdepth = iter.depth;

                        hlist_for_each_entry_rcu(li, &n->list, hlist)
                                ++s->prefixes;
                } else {
                        unsigned long i;

                        s->tnodes++;
                        if (n->bits < MAX_STAT_DEPTH)
                                s->nodesizes[n->bits]++;

                        for (i = 0; i < tnode_child_length(n); i++) {
                                if (!rcu_access_pointer(n->child[i]))
                                        s->nullpointers++;
                        }
                }
        }
        rcu_read_unlock();
}

/*
 *      This outputs /proc/net/fib_triestats
 */
static void trie_show_stats(struct seq_file *seq, struct trie_stat *stat)
{
        unsigned int i, max, pointers, bytes, avdepth;

        if (stat->leaves)
                avdepth = stat->totdepth*100 / stat->leaves;
        else
                avdepth = 0;

        seq_printf(seq, "\tAver depth:     %u.%02d\n",
                   avdepth / 100, avdepth % 100);
        seq_printf(seq, "\tMax depth:      %u\n", stat->maxdepth);

        seq_printf(seq, "\tLeaves:         %u\n", stat->leaves);
        bytes = sizeof(struct tnode) * stat->leaves;

        seq_printf(seq, "\tPrefixes:       %u\n", stat->prefixes);
        bytes += sizeof(struct leaf_info) * stat->prefixes;

        seq_printf(seq, "\tInternal nodes: %u\n\t", stat->tnodes);
        bytes += sizeof(struct tnode) * stat->tnodes;

        max = MAX_STAT_DEPTH;
        while (max > 0 && stat->nodesizes[max-1] == 0)
                max--;

        pointers = 0;
        for (i = 1; i < max; i++)
                if (stat->nodesizes[i] != 0) {
                        seq_printf(seq, "  %u: %u",  i, stat->nodesizes[i]);
                        pointers += (1<<i) * stat->nodesizes[i];
                }
        seq_putc(seq, '\n');
        seq_printf(seq, "\tPointers: %u\n", pointers);

        bytes += sizeof(struct tnode *) * pointers;
        seq_printf(seq, "Null ptrs: %u\n", stat->nullpointers);
        seq_printf(seq, "Total size: %u  kB\n", (bytes + 1023) / 1024);
}

#ifdef CONFIG_IP_FIB_TRIE_STATS
static void trie_show_usage(struct seq_file *seq,
                            const struct trie_use_stats __percpu *stats)
{
        struct trie_use_stats s = { 0 };
        int cpu;

        /* loop through all of the CPUs and gather up the stats */
        for_each_possible_cpu(cpu) {
                const struct trie_use_stats *pcpu = per_cpu_ptr(stats, cpu);

                s.gets += pcpu->gets;
                s.backtrack += pcpu->backtrack;
                s.semantic_match_passed += pcpu->semantic_match_passed;
                s.semantic_match_miss += pcpu->semantic_match_miss;
                s.null_node_hit += pcpu->null_node_hit;
                s.resize_node_skipped += pcpu->resize_node_skipped;
        }

        seq_printf(seq, "\nCounters:\n---------\n");
        seq_printf(seq, "gets = %u\n", s.gets);
        seq_printf(seq, "backtracks = %u\n", s.backtrack);
        seq_printf(seq, "semantic match passed = %u\n",
                   s.semantic_match_passed);
        seq_printf(seq, "semantic match miss = %u\n", s.semantic_match_miss);
        seq_printf(seq, "null node hit= %u\n", s.null_node_hit);
        seq_printf(seq, "skipped node resize = %u\n\n", s.resize_node_skipped);
}
#endif /*  CONFIG_IP_FIB_TRIE_STATS */

static void fib_table_print(struct seq_file *seq, struct fib_table *tb)
{
        if (tb->tb_id == RT_TABLE_LOCAL)
                seq_puts(seq, "Local:\n");
        else if (tb->tb_id == RT_TABLE_MAIN)
                seq_puts(seq, "Main:\n");
        else
                seq_printf(seq, "Id %d:\n", tb->tb_id);
}


static int fib_triestat_seq_show(struct seq_file *seq, void *v)
{
        struct net *net = (struct net *)seq->private;
        unsigned int h;

        seq_printf(seq,
                   "Basic info: size of leaf:"
                   " %Zd bytes, size of tnode: %Zd bytes.\n",
                   sizeof(struct tnode), sizeof(struct tnode));

        for (h = 0; h < FIB_TABLE_HASHSZ; h++) {
                struct hlist_head *head = &net->ipv4.fib_table_hash[h];
                struct fib_table *tb;

                hlist_for_each_entry_rcu(tb, head, tb_hlist) {
                        struct trie *t = (struct trie *) tb->tb_data;
                        struct trie_stat stat;

                        if (!t)
                                continue;

                        fib_table_print(seq, tb);

                        trie_collect_stats(t, &stat);
                        trie_show_stats(seq, &stat);
#ifdef CONFIG_IP_FIB_TRIE_STATS
                        trie_show_usage(seq, t->stats);
#endif
                }
        }

        return 0;
}

static int fib_triestat_seq_open(struct inode *inode, struct file *file)
{
        return single_open_net(inode, file, fib_triestat_seq_show);
}

static const struct file_operations fib_triestat_fops = {
        .owner  = THIS_MODULE,
        .open   = fib_triestat_seq_open,
        .read   = seq_read,
        .llseek = seq_lseek,
        .release = single_release_net,
};

static struct tnode *fib_trie_get_idx(struct seq_file *seq, loff_t pos)
{
        struct fib_trie_iter *iter = seq->private;
        struct net *net = seq_file_net(seq);
        loff_t idx = 0;
        unsigned int h;

        for (h = 0; h < FIB_TABLE_HASHSZ; h++) {
                struct hlist_head *head = &net->ipv4.fib_table_hash[h];
                struct fib_table *tb;

                hlist_for_each_entry_rcu(tb, head, tb_hlist) {
                        struct tnode *n;

                        for (n = fib_trie_get_first(iter,
                                                    (struct trie *) tb->tb_data);
                             n; n = fib_trie_get_next(iter))
                                if (pos == idx++) {
                                        iter->tb = tb;
                                        return n;
                                }
                }
        }

        return NULL;
}

static void *fib_trie_seq_start(struct seq_file *seq, loff_t *pos)
        __acquires(RCU)
{
        rcu_read_lock();
        return fib_trie_get_idx(seq, *pos);
}

static void *fib_trie_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
        struct fib_trie_iter *iter = seq->private;
        struct net *net = seq_file_net(seq);
        struct fib_table *tb = iter->tb;
        struct hlist_node *tb_node;
        unsigned int h;
        struct tnode *n;

        ++*pos;
        /* next node in same table */
        n = fib_trie_get_next(iter);
        if (n)
                return n;

        /* walk rest of this hash chain */
        h = tb->tb_id & (FIB_TABLE_HASHSZ - 1);
        while ((tb_node = rcu_dereference(hlist_next_rcu(&tb->tb_hlist)))) {
                tb = hlist_entry(tb_node, struct fib_table, tb_hlist);
                n = fib_trie_get_first(iter, (struct trie *) tb->tb_data);
                if (n)
                        goto found;
        }

        /* new hash chain */
        while (++h < FIB_TABLE_HASHSZ) {
                struct hlist_head *head = &net->ipv4.fib_table_hash[h];
                hlist_for_each_entry_rcu(tb, head, tb_hlist) {
                        n = fib_trie_get_first(iter, (struct trie *) tb->tb_data);
                        if (n)
                                goto found;
                }
        }
        return NULL;

found:
        iter->tb = tb;
        return n;
}

static void fib_trie_seq_stop(struct seq_file *seq, void *v)
        __releases(RCU)
{
        rcu_read_unlock();
}

static void seq_indent(struct seq_file *seq, int n)
{
        while (n-- > 0)
                seq_puts(seq, "   ");
}

static inline const char *rtn_scope(char *buf, size_t len, enum rt_scope_t s)
{
        switch (s) {
        case RT_SCOPE_UNIVERSE: return "universe";
        case RT_SCOPE_SITE:     return "site";
        case RT_SCOPE_LINK:     return "link";
        case RT_SCOPE_HOST:     return "host";
        case RT_SCOPE_NOWHERE:  return "nowhere";
        default:
                snprintf(buf, len, "scope=%d", s);
                return buf;
        }
}

static const char *const rtn_type_names[__RTN_MAX] = {
        [RTN_UNSPEC] = "UNSPEC",
        [RTN_UNICAST] = "UNICAST",
        [RTN_LOCAL] = "LOCAL",
        [RTN_BROADCAST] = "BROADCAST",
        [RTN_ANYCAST] = "ANYCAST",
        [RTN_MULTICAST] = "MULTICAST",
        [RTN_BLACKHOLE] = "BLACKHOLE",
        [RTN_UNREACHABLE] = "UNREACHABLE",
        [RTN_PROHIBIT] = "PROHIBIT",
        [RTN_THROW] = "THROW",
        [RTN_NAT] = "NAT",
        [RTN_XRESOLVE] = "XRESOLVE",
};

static inline const char *rtn_type(char *buf, size_t len, unsigned int t)
{
        if (t < __RTN_MAX && rtn_type_names[t])
                return rtn_type_names[t];
        snprintf(buf, len, "type %u", t);
        return buf;
}

/* Pretty print the trie */
static int fib_trie_seq_show(struct seq_file *seq, void *v)
{
        const struct fib_trie_iter *iter = seq->private;
        struct tnode *n = v;

        if (!node_parent_rcu(n))
                fib_table_print(seq, iter->tb);

        if (IS_TNODE(n)) {
                __be32 prf = htonl(n->key);

                seq_indent(seq, iter->depth-1);
                seq_printf(seq, "  +-- %pI4/%zu %u %u %u\n",
                           &prf, KEYLENGTH - n->pos - n->bits, n->bits,
                           n->full_children, n->empty_children);
        } else {
                struct leaf_info *li;
                __be32 val = htonl(n->key);

                seq_indent(seq, iter->depth);
                seq_printf(seq, "  |-- %pI4\n", &val);

                hlist_for_each_entry_rcu(li, &n->list, hlist) {
                        struct fib_alias *fa;

                        list_for_each_entry_rcu(fa, &li->falh, fa_list) {
                                char buf1[32], buf2[32];

                                seq_indent(seq, iter->depth+1);
                                seq_printf(seq, "  /%d %s %s", li->plen,
                                           rtn_scope(buf1, sizeof(buf1),
                                                     fa->fa_info->fib_scope),
                                           rtn_type(buf2, sizeof(buf2),
                                                    fa->fa_type));
                                if (fa->fa_tos)
                                        seq_printf(seq, " tos=%d", fa->fa_tos);
                                seq_putc(seq, '\n');
                        }
                }
        }

        return 0;
}

static const struct seq_operations fib_trie_seq_ops = {
        .start  = fib_trie_seq_start,
        .next   = fib_trie_seq_next,
        .stop   = fib_trie_seq_stop,
        .show   = fib_trie_seq_show,
};

static int fib_trie_seq_open(struct inode *inode, struct file *file)
{
        return seq_open_net(inode, file, &fib_trie_seq_ops,
                            sizeof(struct fib_trie_iter));
}

static const struct file_operations fib_trie_fops = {
        .owner  = THIS_MODULE,
        .open   = fib_trie_seq_open,
        .read   = seq_read,
        .llseek = seq_lseek,
        .release = seq_release_net,
};

struct fib_route_iter {
        struct seq_net_private p;
        struct trie *main_trie;
        loff_t  pos;
        t_key   key;
};

static struct tnode *fib_route_get_idx(struct fib_route_iter *iter, loff_t pos)
{
        struct tnode *l = NULL;
        struct trie *t = iter->main_trie;

        /* use cache location of last found key */
        if (iter->pos > 0 && pos >= iter->pos && (l = fib_find_node(t, iter->key)))
                pos -= iter->pos;
        else {
                iter->pos = 0;
                l = trie_firstleaf(t);
        }

        while (l && pos-- > 0) {
                iter->pos++;
                l = trie_nextleaf(l);
        }

        if (l)
                iter->key = pos;        /* remember it */
        else
                iter->pos = 0;          /* forget it */

        return l;
}

static void *fib_route_seq_start(struct seq_file *seq, loff_t *pos)
        __acquires(RCU)
{
        struct fib_route_iter *iter = seq->private;
        struct fib_table *tb;

        rcu_read_lock();
        tb = fib_get_table(seq_file_net(seq), RT_TABLE_MAIN);
        if (!tb)
                return NULL;

        iter->main_trie = (struct trie *) tb->tb_data;
        if (*pos == 0)
                return SEQ_START_TOKEN;
        else
                return fib_route_get_idx(iter, *pos - 1);
}

static void *fib_route_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
        struct fib_route_iter *iter = seq->private;
        struct tnode *l = v;

        ++*pos;
        if (v == SEQ_START_TOKEN) {
                iter->pos = 0;
                l = trie_firstleaf(iter->main_trie);
        } else {
                iter->pos++;
                l = trie_nextleaf(l);
        }

        if (l)
                iter->key = l->key;
        else
                iter->pos = 0;
        return l;
}

static void fib_route_seq_stop(struct seq_file *seq, void *v)
        __releases(RCU)
{
        rcu_read_unlock();
}

static unsigned int fib_flag_trans(int type, __be32 mask, const struct fib_info *fi)
{
        unsigned int flags = 0;

        if (type == RTN_UNREACHABLE || type == RTN_PROHIBIT)
                flags = RTF_REJECT;
        if (fi && fi->fib_nh->nh_gw)
                flags |= RTF_GATEWAY;
        if (mask == htonl(0xFFFFFFFF))
                flags |= RTF_HOST;
        flags |= RTF_UP;
        return flags;
}

/*
 *      This outputs /proc/net/route.
 *      The format of the file is not supposed to be changed
 *      and needs to be same as fib_hash output to avoid breaking
 *      legacy utilities
 */
static int fib_route_seq_show(struct seq_file *seq, void *v)
{
        struct tnode *l = v;
        struct leaf_info *li;

        if (v == SEQ_START_TOKEN) {
                seq_printf(seq, "%-127s\n", "Iface\tDestination\tGateway "
                           "\tFlags\tRefCnt\tUse\tMetric\tMask\t\tMTU"
                           "\tWindow\tIRTT");
                return 0;
        }

        hlist_for_each_entry_rcu(li, &l->list, hlist) {
                struct fib_alias *fa;
                __be32 mask, prefix;

                mask = inet_make_mask(li->plen);
                prefix = htonl(l->key);

                list_for_each_entry_rcu(fa, &li->falh, fa_list) {
                        const struct fib_info *fi = fa->fa_info;
                        unsigned int flags = fib_flag_trans(fa->fa_type, mask, fi);

                        if (fa->fa_type == RTN_BROADCAST
                            || fa->fa_type == RTN_MULTICAST)
                                continue;

                        seq_setwidth(seq, 127);

                        if (fi)
                                seq_printf(seq,
                                         "%s\t%08X\t%08X\t%04X\t%d\t%u\t"
                                         "%d\t%08X\t%d\t%u\t%u",
                                         fi->fib_dev ? fi->fib_dev->name : "*",
                                         prefix,
                                         fi->fib_nh->nh_gw, flags, 0, 0,
                                         fi->fib_priority,
                                         mask,
                                         (fi->fib_advmss ?
                                          fi->fib_advmss + 40 : 0),
                                         fi->fib_window,
                                         fi->fib_rtt >> 3);
                        else
                                seq_printf(seq,
                                         "*\t%08X\t%08X\t%04X\t%d\t%u\t"
                                         "%d\t%08X\t%d\t%u\t%u",
                                         prefix, 0, flags, 0, 0, 0,
                                         mask, 0, 0, 0);

                        seq_pad(seq, '\n');
                }
        }

        return 0;
}

static const struct seq_operations fib_route_seq_ops = {
        .start  = fib_route_seq_start,
        .next   = fib_route_seq_next,
        .stop   = fib_route_seq_stop,
        .show   = fib_route_seq_show,
};

static int fib_route_seq_open(struct inode *inode, struct file *file)
{
        return seq_open_net(inode, file, &fib_route_seq_ops,
                            sizeof(struct fib_route_iter));
}

static const struct file_operations fib_route_fops = {
        .owner  = THIS_MODULE,
        .open   = fib_route_seq_open,
        .read   = seq_read,
        .llseek = seq_lseek,
        .release = seq_release_net,
};

int __net_init fib_proc_init(struct net *net)
{
        if (!proc_create("fib_trie", S_IRUGO, net->proc_net, &fib_trie_fops))
                goto out1;

        if (!proc_create("fib_triestat", S_IRUGO, net->proc_net,
                         &fib_triestat_fops))
                goto out2;

        if (!proc_create("route", S_IRUGO, net->proc_net, &fib_route_fops))
                goto out3;

        return 0;

out3:
        remove_proc_entry("fib_triestat", net->proc_net);
out2:
        remove_proc_entry("fib_trie", net->proc_net);
out1:
        return -ENOMEM;
}

void __net_exit fib_proc_exit(struct net *net)
{
        remove_proc_entry("fib_trie", net->proc_net);
        remove_proc_entry("fib_triestat", net->proc_net);
        remove_proc_entry("route", net->proc_net);
}

#endif /* CONFIG_PROC_FS */