net/ipv4/fib_trie.c

root/net/ipv4/fib_trie.c
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *
 *   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.
 * https://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>
 *
 * 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>
 */
#include <linux/cache.h>
#include <linux/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/rcupdate_wait.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 <linux/vmalloc.h>
#include <linux/notifier.h>
#include <net/net_namespace.h>
#include <net/inet_dscp.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 <net/fib_notifier.h>
#include <trace/events/fib.h>
#include "fib_lookup.h"

static int call_fib_entry_notifier(struct notifier_block *nb,
                                   enum fib_event_type event_type, u32 dst,
                                   int dst_len, struct fib_alias *fa,
                                   struct netlink_ext_ack *extack)
{
        struct fib_entry_notifier_info info = {
                .info.extack = extack,
                .dst = dst,
                .dst_len = dst_len,
                .fi = fa->fa_info,
                .dscp = fa->fa_dscp,
                .type = fa->fa_type,
                .tb_id = fa->tb_id,
        };
        return call_fib4_notifier(nb, event_type, &info.info);
}

static int call_fib_entry_notifiers(struct net *net,
                                    enum fib_event_type event_type, u32 dst,
                                    int dst_len, struct fib_alias *fa,
                                    struct netlink_ext_ack *extack)
{
        struct fib_entry_notifier_info info = {
                .info.extack = extack,
                .dst = dst,
                .dst_len = dst_len,
                .fi = fa->fa_info,
                .dscp = fa->fa_dscp,
                .type = fa->fa_type,
                .tb_id = fa->tb_id,
        };
        return call_fib4_notifiers(net, event_type, &info.info);
}

#define MAX_STAT_DEPTH 32

#define KEYLENGTH       (8*sizeof(t_key))
#define KEY_MAX         ((t_key)~0)

typedef unsigned int t_key;

#define IS_TRIE(n)      ((n)->pos >= KEYLENGTH)
#define IS_TNODE(n)     ((n)->bits)
#define IS_LEAF(n)      (!(n)->bits)

struct key_vector {
        t_key key;
        unsigned char pos;              /* 2log(KEYLENGTH) bits needed */
        unsigned char bits;             /* 2log(KEYLENGTH) bits needed */
        unsigned char slen;
        union {
                /* This list pointer if valid if (pos | bits) == 0 (LEAF) */
                struct hlist_head leaf;
                /* This array is valid if (pos | bits) > 0 (TNODE) */
                DECLARE_FLEX_ARRAY(struct key_vector __rcu *, tnode);
        };
};

struct tnode {
        struct rcu_head rcu;
        t_key empty_children;           /* KEYLENGTH bits needed */
        t_key full_children;            /* KEYLENGTH bits needed */
        struct key_vector __rcu *parent;
        struct key_vector kv[1];
#define tn_bits kv[0].bits
};

#define TNODE_SIZE(n)   offsetof(struct tnode, kv[0].tnode[n])
#define LEAF_SIZE       TNODE_SIZE(1)

#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 key_vector kv[1];
#ifdef CONFIG_IP_FIB_TRIE_STATS
        struct trie_use_stats __percpu *stats;
#endif
};

static struct key_vector *resize(struct trie *t, struct key_vector *tn);
static unsigned int tnode_free_size;

/*
 * synchronize_rcu after call_rcu for outstanding dirty memory; it should be
 * especially useful before resizing the root node with PREEMPT_NONE configs;
 * the value was obtained experimentally, aiming to avoid visible slowdown.
 */
unsigned int sysctl_fib_sync_mem = 512 * 1024;
unsigned int sysctl_fib_sync_mem_min = 64 * 1024;
unsigned int sysctl_fib_sync_mem_max = 64 * 1024 * 1024;

static struct kmem_cache *fn_alias_kmem __ro_after_init;
static struct kmem_cache *trie_leaf_kmem __ro_after_init;

static inline struct tnode *tn_info(struct key_vector *kv)
{
        return container_of(kv, struct tnode, kv[0]);
}

/* caller must hold RTNL */
#define node_parent(tn) rtnl_dereference(tn_info(tn)->parent)
#define get_child(tn, i) rtnl_dereference((tn)->tnode[i])

/* caller must hold RCU read lock or RTNL */
#define node_parent_rcu(tn) rcu_dereference_rtnl(tn_info(tn)->parent)
#define get_child_rcu(tn, i) rcu_dereference_rtnl((tn)->tnode[i])

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

#define NODE_INIT_PARENT(n, p) RCU_INIT_POINTER(tn_info(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 child_length(const struct key_vector *tn)
{
        return (1ul << tn->bits) & ~(1ul);
}

#define get_cindex(key, kv) (((key) ^ (kv)->key) >> (kv)->pos)

static inline unsigned long get_index(t_key key, struct key_vector *kv)
{
        unsigned long index = key ^ kv->key;

        if ((BITS_PER_LONG <= KEYLENGTH) && (KEYLENGTH == kv->pos))
                return 0;

        return index >> kv->pos;
}

/* 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 (tp->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 -1) - "u" - 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 inline void alias_free_mem_rcu(struct fib_alias *fa)
{
        kfree_rcu(fa, rcu);
}

#define TNODE_VMALLOC_MAX \
        ilog2((SIZE_MAX - TNODE_SIZE(0)) / sizeof(struct key_vector *))

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

        if (!n->tn_bits)
                kmem_cache_free(trie_leaf_kmem, n);
        else
                kvfree(n);
}

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

static struct tnode *tnode_alloc(int bits)
{
        size_t size;

        /* verify bits is within bounds */
        if (bits > TNODE_VMALLOC_MAX)
                return NULL;

        /* determine size and verify it is non-zero and didn't overflow */
        size = TNODE_SIZE(1ul << bits);

        if (size <= PAGE_SIZE)
                return kzalloc(size, GFP_KERNEL);
        else
                return vzalloc(size);
}

static inline void empty_child_inc(struct key_vector *n)
{
        tn_info(n)->empty_children++;

        if (!tn_info(n)->empty_children)
                tn_info(n)->full_children++;
}

static inline void empty_child_dec(struct key_vector *n)
{
        if (!tn_info(n)->empty_children)
                tn_info(n)->full_children--;

        tn_info(n)->empty_children--;
}

static struct key_vector *leaf_new(t_key key, struct fib_alias *fa)
{
        struct key_vector *l;
        struct tnode *kv;

        kv = kmem_cache_alloc(trie_leaf_kmem, GFP_KERNEL);
        if (!kv)
                return NULL;

        /* initialize key vector */
        l = kv->kv;
        l->key = key;
        l->pos = 0;
        l->bits = 0;
        l->slen = fa->fa_slen;

        /* link leaf to fib alias */
        INIT_HLIST_HEAD(&l->leaf);
        hlist_add_head(&fa->fa_list, &l->leaf);

        return l;
}

static struct key_vector *tnode_new(t_key key, int pos, int bits)
{
        unsigned int shift = pos + bits;
        struct key_vector *tn;
        struct tnode *tnode;

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

        tnode = tnode_alloc(bits);
        if (!tnode)
                return NULL;

        pr_debug("AT %p s=%zu %zu\n", tnode, TNODE_SIZE(0),
                 sizeof(struct key_vector *) << bits);

        if (bits == KEYLENGTH)
                tnode->full_children = 1;
        else
                tnode->empty_children = 1ul << bits;

        tn = tnode->kv;
        tn->key = (shift < KEYLENGTH) ? (key >> shift) << shift : 0;
        tn->pos = pos;
        tn->bits = bits;
        tn->slen = pos;

        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(struct key_vector *tn, struct key_vector *n)
{
        return n && ((n->pos + n->bits) == tn->pos) && IS_TNODE(n);
}

/* Add a child at position i overwriting the old value.
 * Update the value of full_children and empty_children.
 */
static void put_child(struct key_vector *tn, unsigned long i,
                      struct key_vector *n)
{
        struct key_vector *chi = get_child(tn, i);
        int isfull, wasfull;

        BUG_ON(i >= child_length(tn));

        /* update emptyChildren, overflow into fullChildren */
        if (!n && chi)
                empty_child_inc(tn);
        if (n && !chi)
                empty_child_dec(tn);

        /* update fullChildren */
        wasfull = tnode_full(tn, chi);
        isfull = tnode_full(tn, n);

        if (wasfull && !isfull)
                tn_info(tn)->full_children--;
        else if (!wasfull && isfull)
                tn_info(tn)->full_children++;

        if (n && (tn->slen < n->slen))
                tn->slen = n->slen;

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

static void update_children(struct key_vector *tn)
{
        unsigned long i;

        /* update all of the child parent pointers */
        for (i = child_length(tn); i;) {
                struct key_vector *inode = get_child(tn, --i);

                if (!inode)
                        continue;

                /* Either update the children of a tnode that
                 * already belongs to us or update the child
                 * to point to ourselves.
                 */
                if (node_parent(inode) == tn)
                        update_children(inode);
                else
                        node_set_parent(inode, tn);
        }
}

static inline void put_child_root(struct key_vector *tp, t_key key,
                                  struct key_vector *n)
{
        if (IS_TRIE(tp))
                rcu_assign_pointer(tp->tnode[0], n);
        else
                put_child(tp, get_index(key, tp), n);
}

static inline void tnode_free_init(struct key_vector *tn)
{
        tn_info(tn)->rcu.next = NULL;
}

static inline void tnode_free_append(struct key_vector *tn,
                                     struct key_vector *n)
{
        tn_info(n)->rcu.next = tn_info(tn)->rcu.next;
        tn_info(tn)->rcu.next = &tn_info(n)->rcu;
}

static void tnode_free(struct key_vector *tn)
{
        struct callback_head *head = &tn_info(tn)->rcu;

        while (head) {
                head = head->next;
                tnode_free_size += TNODE_SIZE(1ul << tn->bits);
                node_free(tn);

                tn = container_of(head, struct tnode, rcu)->kv;
        }

        if (tnode_free_size >= READ_ONCE(sysctl_fib_sync_mem)) {
                tnode_free_size = 0;
                synchronize_net();
        }
}

static struct key_vector *replace(struct trie *t,
                                  struct key_vector *oldtnode,
                                  struct key_vector *tn)
{
        struct key_vector *tp = node_parent(oldtnode);
        unsigned long i;

        /* setup the parent pointer out of and back into this node */
        NODE_INIT_PARENT(tn, tp);
        put_child_root(tp, tn->key, tn);

        /* update all of the child parent pointers */
        update_children(tn);

        /* all pointers should be clean so we are done */
        tnode_free(oldtnode);

        /* resize children now that oldtnode is freed */
        for (i = child_length(tn); i;) {
                struct key_vector *inode = get_child(tn, --i);

                /* resize child node */
                if (tnode_full(tn, inode))
                        tn = resize(t, inode);
        }

        return tp;
}

static struct key_vector *inflate(struct trie *t,
                                  struct key_vector *oldtnode)
{
        struct key_vector *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)
                goto notnode;

        /* prepare oldtnode to be freed */
        tnode_free_init(oldtnode);

        /* Assemble all of the pointers in our cluster, in this case that
         * represents all of the pointers out of our allocated nodes that
         * point to existing tnodes and the links between our allocated
         * nodes.
         */
        for (i = child_length(oldtnode), m = 1u << tn->pos; i;) {
                struct key_vector *inode = get_child(oldtnode, --i);
                struct key_vector *node0, *node1;
                unsigned long j, k;

                /* An empty child */
                if (!inode)
                        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;
                }

                /* drop the node in the old tnode free list */
                tnode_free_append(oldtnode, inode);

                /* An internal node with two children */
                if (inode->bits == 1) {
                        put_child(tn, 2 * i + 1, get_child(inode, 1));
                        put_child(tn, 2 * i, get_child(inode, 0));
                        continue;
                }

                /* We will replace this node 'inode' with two new
                 * ones, 'node0' and 'node1', 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
                 * node0's key and "1" in node1's key. Since we are
                 * moving the key position by one step, the bit that
                 * we are moving away from - the bit at position
                 * (tn->pos) - is the one that will differ between
                 * node0 and node1. So... we synthesize that bit in the
                 * two new keys.
                 */
                node1 = tnode_new(inode->key | m, inode->pos, inode->bits - 1);
                if (!node1)
                        goto nomem;
                node0 = tnode_new(inode->key, inode->pos, inode->bits - 1);

                tnode_free_append(tn, node1);
                if (!node0)
                        goto nomem;
                tnode_free_append(tn, node0);

                /* populate child pointers in new nodes */
                for (k = child_length(inode), j = k / 2; j;) {
                        put_child(node1, --j, get_child(inode, --k));
                        put_child(node0, j, get_child(inode, j));
                        put_child(node1, --j, get_child(inode, --k));
                        put_child(node0, j, get_child(inode, j));
                }

                /* link new nodes to parent */
                NODE_INIT_PARENT(node1, tn);
                NODE_INIT_PARENT(node0, tn);

                /* link parent to nodes */
                put_child(tn, 2 * i + 1, node1);
                put_child(tn, 2 * i, node0);
        }

        /* setup the parent pointers into and out of this node */
        return replace(t, oldtnode, tn);
nomem:
        /* all pointers should be clean so we are done */
        tnode_free(tn);
notnode:
        return NULL;
}

static struct key_vector *halve(struct trie *t,
                                struct key_vector *oldtnode)
{
        struct key_vector *tn;
        unsigned long i;

        pr_debug("In halve\n");

        tn = tnode_new(oldtnode->key, oldtnode->pos + 1, oldtnode->bits - 1);
        if (!tn)
                goto notnode;

        /* prepare oldtnode to be freed */
        tnode_free_init(oldtnode);

        /* Assemble all of the pointers in our cluster, in this case that
         * represents all of the pointers out of our allocated nodes that
         * point to existing tnodes and the links between our allocated
         * nodes.
         */
        for (i = child_length(oldtnode); i;) {
                struct key_vector *node1 = get_child(oldtnode, --i);
                struct key_vector *node0 = get_child(oldtnode, --i);
                struct key_vector *inode;

                /* At least one of the children is empty */
                if (!node1 || !node0) {
                        put_child(tn, i / 2, node1 ? : node0);
                        continue;
                }

                /* Two nonempty children */
                inode = tnode_new(node0->key, oldtnode->pos, 1);
                if (!inode)
                        goto nomem;
                tnode_free_append(tn, inode);

                /* initialize pointers out of node */
                put_child(inode, 1, node1);
                put_child(inode, 0, node0);
                NODE_INIT_PARENT(inode, tn);

                /* link parent to node */
                put_child(tn, i / 2, inode);
        }

        /* setup the parent pointers into and out of this node */
        return replace(t, oldtnode, tn);
nomem:
        /* all pointers should be clean so we are done */
        tnode_free(tn);
notnode:
        return NULL;
}

static struct key_vector *collapse(struct trie *t,
                                   struct key_vector *oldtnode)
{
        struct key_vector *n, *tp;
        unsigned long i;

        /* scan the tnode looking for that one child that might still exist */
        for (n = NULL, i = child_length(oldtnode); !n && i;)
                n = get_child(oldtnode, --i);

        /* compress one level */
        tp = node_parent(oldtnode);
        put_child_root(tp, oldtnode->key, n);
        node_set_parent(n, tp);

        /* drop dead node */
        node_free(oldtnode);

        return tp;
}

static unsigned char update_suffix(struct key_vector *tn)
{
        unsigned char slen = tn->pos;
        unsigned long stride, i;
        unsigned char slen_max;

        /* only vector 0 can have a suffix length greater than or equal to
         * tn->pos + tn->bits, the second highest node will have a suffix
         * length at most of tn->pos + tn->bits - 1
         */
        slen_max = min_t(unsigned char, tn->pos + tn->bits - 1, tn->slen);

        /* search though the list of children looking for nodes that might
         * have a suffix greater than the one we currently have.  This is
         * why we start with a stride of 2 since a stride of 1 would
         * represent the nodes with suffix length equal to tn->pos
         */
        for (i = 0, stride = 0x2ul ; i < child_length(tn); i += stride) {
                struct key_vector *n = get_child(tn, i);

                if (!n || (n->slen <= slen))
                        continue;

                /* update stride and slen based on new value */
                stride <<= (n->slen - slen);
                slen = n->slen;
                i &= ~(stride - 1);

                /* stop searching if we have hit the maximum possible value */
                if (slen >= slen_max)
                        break;
        }

        tn->slen = slen;

        return slen;
}

/* 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
 * 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: 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 = child_length(tn) - tn->empty_children -
 *     tn->full_children;
 *
 * new_child_length = 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 * (child_length(tn) - tn->empty_children +
 *    tn->full_children) >= inflate_threshold * new_child_length
 *
 * expand new_child_length:
 * 100 * (child_length(tn) - tn->empty_children +
 *    tn->full_children) >=
 *      inflate_threshold * child_length(tn) * 2
 *
 * shorten again:
 * 50 * (tn->full_children + child_length(tn) -
 *    tn->empty_children) >= inflate_threshold *
 *    child_length(tn)
 *
 */
static inline bool should_inflate(struct key_vector *tp, struct key_vector *tn)
{
        unsigned long used = child_length(tn);
        unsigned long threshold = used;

        /* Keep root node larger */
        threshold *= IS_TRIE(tp) ? inflate_threshold_root : inflate_threshold;
        used -= tn_info(tn)->empty_children;
        used += tn_info(tn)->full_children;

        /* if bits == KEYLENGTH then pos = 0, and will fail below */

        return (used > 1) && tn->pos && ((50 * used) >= threshold);
}

static inline bool should_halve(struct key_vector *tp, struct key_vector *tn)
{
        unsigned long used = child_length(tn);
        unsigned long threshold = used;

        /* Keep root node larger */
        threshold *= IS_TRIE(tp) ? halve_threshold_root : halve_threshold;
        used -= tn_info(tn)->empty_children;

        /* if bits == KEYLENGTH then used = 100% on wrap, and will fail below */

        return (used > 1) && (tn->bits > 1) && ((100 * used) < threshold);
}

static inline bool should_collapse(struct key_vector *tn)
{
        unsigned long used = child_length(tn);

        used -= tn_info(tn)->empty_children;

        /* account for bits == KEYLENGTH case */
        if ((tn->bits == KEYLENGTH) && tn_info(tn)->full_children)
                used -= KEY_MAX;

        /* One child or none, time to drop us from the trie */
        return used < 2;
}

#define MAX_WORK 10
static struct key_vector *resize(struct trie *t, struct key_vector *tn)
{
#ifdef CONFIG_IP_FIB_TRIE_STATS
        struct trie_use_stats __percpu *stats = t->stats;
#endif
        struct key_vector *tp = node_parent(tn);
        unsigned long cindex = get_index(tn->key, tp);
        int max_work = MAX_WORK;

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

        /* track the tnode via the pointer from the parent instead of
         * doing it ourselves.  This way we can let RCU fully do its
         * thing without us interfering
         */
        BUG_ON(tn != get_child(tp, cindex));

        /* Double as long as the resulting node has a number of
         * nonempty nodes that are above the threshold.
         */
        while (should_inflate(tp, tn) && max_work) {
                tp = inflate(t, tn);
                if (!tp) {
#ifdef CONFIG_IP_FIB_TRIE_STATS
                        this_cpu_inc(stats->resize_node_skipped);
#endif
                        break;
                }

                max_work--;
                tn = get_child(tp, cindex);
        }

        /* update parent in case inflate failed */
        tp = node_parent(tn);

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

        /* Halve as long as the number of empty children in this
         * node is above threshold.
         */
        while (should_halve(tp, tn) && max_work) {
                tp = halve(t, tn);
                if (!tp) {
#ifdef CONFIG_IP_FIB_TRIE_STATS
                        this_cpu_inc(stats->resize_node_skipped);
#endif
                        break;
                }

                max_work--;
                tn = get_child(tp, cindex);
        }

        /* Only one child remains */
        if (should_collapse(tn))
                return collapse(t, tn);

        /* update parent in case halve failed */
        return node_parent(tn);
}

static void node_pull_suffix(struct key_vector *tn, unsigned char slen)
{
        unsigned char node_slen = tn->slen;

        while ((node_slen > tn->pos) && (node_slen > slen)) {
                slen = update_suffix(tn);
                if (node_slen == slen)
                        break;

                tn = node_parent(tn);
                node_slen = tn->slen;
        }
}

static void node_push_suffix(struct key_vector *tn, unsigned char slen)
{
        while (tn->slen < slen) {
                tn->slen = slen;
                tn = node_parent(tn);
        }
}

/* rcu_read_lock needs to be hold by caller from readside */
static struct key_vector *fib_find_node(struct trie *t,
                                        struct key_vector **tp, u32 key)
{
        struct key_vector *pn, *n = t->kv;
        unsigned long index = 0;

        do {
                pn = n;
                n = get_child_rcu(n, index);

                if (!n)
                        break;

                index = get_cindex(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 >= (1ul << bits))
                 *     we have a mismatch in skip bits and failed
                 *   else
                 *     we know the value is cindex
                 *
                 * This check is safe even if bits == KEYLENGTH due to the
                 * fact that we can only allocate a node with 32 bits if a
                 * long is greater than 32 bits.
                 */
                if (index >= (1ul << n->bits)) {
                        n = NULL;
                        break;
                }

                /* keep searching until we find a perfect match leaf or NULL */
        } while (IS_TNODE(n));

        *tp = pn;

        return n;
}

/* Return the first fib alias matching DSCP with
 * priority less than or equal to PRIO.
 * If 'find_first' is set, return the first matching
 * fib alias, regardless of DSCP and priority.
 */
static struct fib_alias *fib_find_alias(struct hlist_head *fah, u8 slen,
                                        dscp_t dscp, u32 prio, u32 tb_id,
                                        bool find_first)
{
        struct fib_alias *fa;

        if (!fah)
                return NULL;

        hlist_for_each_entry(fa, fah, fa_list) {
                /* Avoid Sparse warning when using dscp_t in inequalities */
                u8 __fa_dscp = inet_dscp_to_dsfield(fa->fa_dscp);
                u8 __dscp = inet_dscp_to_dsfield(dscp);

                if (fa->fa_slen < slen)
                        continue;
                if (fa->fa_slen != slen)
                        break;
                if (fa->tb_id > tb_id)
                        continue;
                if (fa->tb_id != tb_id)
                        break;
                if (find_first)
                        return fa;
                if (__fa_dscp > __dscp)
                        continue;
                if (fa->fa_info->fib_priority >= prio || __fa_dscp < __dscp)
                        return fa;
        }

        return NULL;
}

static struct fib_alias *
fib_find_matching_alias(struct net *net, const struct fib_rt_info *fri)
{
        u8 slen = KEYLENGTH - fri->dst_len;
        struct key_vector *l, *tp;
        struct fib_table *tb;
        struct fib_alias *fa;
        struct trie *t;

        tb = fib_get_table(net, fri->tb_id);
        if (!tb)
                return NULL;

        t = (struct trie *)tb->tb_data;
        l = fib_find_node(t, &tp, be32_to_cpu(fri->dst));
        if (!l)
                return NULL;

        hlist_for_each_entry_rcu(fa, &l->leaf, fa_list) {
                if (fa->fa_slen == slen && fa->tb_id == fri->tb_id &&
                    fa->fa_dscp == fri->dscp && fa->fa_info == fri->fi &&
                    fa->fa_type == fri->type)
                        return fa;
        }

        return NULL;
}

void fib_alias_hw_flags_set(struct net *net, const struct fib_rt_info *fri)
{
        u8 fib_notify_on_flag_change;
        struct fib_alias *fa_match;
        struct sk_buff *skb;
        int err;

        rcu_read_lock();

        fa_match = fib_find_matching_alias(net, fri);
        if (!fa_match)
                goto out;

        /* These are paired with the WRITE_ONCE() happening in this function.
         * The reason is that we are only protected by RCU at this point.
         */
        if (READ_ONCE(fa_match->offload) == fri->offload &&
            READ_ONCE(fa_match->trap) == fri->trap &&
            READ_ONCE(fa_match->offload_failed) == fri->offload_failed)
                goto out;

        WRITE_ONCE(fa_match->offload, fri->offload);
        WRITE_ONCE(fa_match->trap, fri->trap);

        fib_notify_on_flag_change = READ_ONCE(net->ipv4.sysctl_fib_notify_on_flag_change);

        /* 2 means send notifications only if offload_failed was changed. */
        if (fib_notify_on_flag_change == 2 &&
            READ_ONCE(fa_match->offload_failed) == fri->offload_failed)
                goto out;

        WRITE_ONCE(fa_match->offload_failed, fri->offload_failed);

        if (!fib_notify_on_flag_change)
                goto out;

        skb = nlmsg_new(fib_nlmsg_size(fa_match->fa_info), GFP_ATOMIC);
        if (!skb) {
                err = -ENOBUFS;
                goto errout;
        }

        err = fib_dump_info(skb, 0, 0, RTM_NEWROUTE, fri, 0);
        if (err < 0) {
                /* -EMSGSIZE implies BUG in fib_nlmsg_size() */
                WARN_ON(err == -EMSGSIZE);
                kfree_skb(skb);
                goto errout;
        }

        rtnl_notify(skb, net, 0, RTNLGRP_IPV4_ROUTE, NULL, GFP_ATOMIC);
        goto out;

errout:
        rtnl_set_sk_err(net, RTNLGRP_IPV4_ROUTE, err);
out:
        rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(fib_alias_hw_flags_set);

static void trie_rebalance(struct trie *t, struct key_vector *tn)
{
        while (!IS_TRIE(tn))
                tn = resize(t, tn);
}

static int fib_insert_node(struct trie *t, struct key_vector *tp,
                           struct fib_alias *new, t_key key)
{
        struct key_vector *n, *l;

        l = leaf_new(key, new);
        if (!l)
                goto noleaf;

        /* retrieve child from parent node */
        n = get_child(tp, get_index(key, tp));

        /* 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 key_vector *tn;

                tn = tnode_new(key, __fls(key ^ n->key), 1);
                if (!tn)
                        goto notnode;

                /* 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, 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 */
        node_push_suffix(tp, new->fa_slen);
        NODE_INIT_PARENT(l, tp);
        put_child_root(tp, key, l);
        trie_rebalance(t, tp);

        return 0;
notnode:
        node_free(l);
noleaf:
        return -ENOMEM;
}

static int fib_insert_alias(struct trie *t, struct key_vector *tp,
                            struct key_vector *l, struct fib_alias *new,
                            struct fib_alias *fa, t_key key)
{
        if (!l)
                return fib_insert_node(t, tp, new, key);

        if (fa) {
                hlist_add_before_rcu(&new->fa_list, &fa->fa_list);
        } else {
                struct fib_alias *last;

                hlist_for_each_entry(last, &l->leaf, fa_list) {
                        if (new->fa_slen < last->fa_slen)
                                break;
                        if ((new->fa_slen == last->fa_slen) &&
                            (new->tb_id > last->tb_id))
                                break;
                        fa = last;
                }

                if (fa)
                        hlist_add_behind_rcu(&new->fa_list, &fa->fa_list);
                else
                        hlist_add_head_rcu(&new->fa_list, &l->leaf);
        }

        /* if we added to the tail node then we need to update slen */
        if (l->slen < new->fa_slen) {
                l->slen = new->fa_slen;
                node_push_suffix(tp, new->fa_slen);
        }

        return 0;
}

static void fib_remove_alias(struct trie *t, struct key_vector *tp,
                             struct key_vector *l, struct fib_alias *old);

/* Caller must hold RTNL. */
int fib_table_insert(struct net *net, struct fib_table *tb,
                     struct fib_config *cfg, struct netlink_ext_ack *extack)
{
        struct trie *t = (struct trie *)tb->tb_data;
        struct fib_alias *fa, *new_fa;
        struct key_vector *l, *tp;
        u16 nlflags = NLM_F_EXCL;
        struct fib_info *fi;
        u8 plen = cfg->fc_dst_len;
        u8 slen = KEYLENGTH - plen;
        dscp_t dscp;
        u32 key;
        int err;

        key = ntohl(cfg->fc_dst);

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

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

        dscp = cfg->fc_dscp;
        l = fib_find_node(t, &tp, key);
        fa = l ? fib_find_alias(&l->leaf, slen, dscp, fi->fib_priority,
                                tb->tb_id, false) : NULL;

        /* Now fa, if non-NULL, points to the first fib alias
         * with the same keys [prefix,dscp,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 tail of the section matching the suffix length
         * of the new alias.
         */

        if (fa && fa->fa_dscp == dscp &&
            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;

                nlflags &= ~NLM_F_EXCL;

                /* 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;
                hlist_for_each_entry_from(fa, fa_list) {
                        if ((fa->fa_slen != slen) ||
                            (fa->tb_id != tb->tb_id) ||
                            (fa->fa_dscp != dscp))
                                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;

                        nlflags |= NLM_F_REPLACE;
                        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)
                                goto out;

                        fi_drop = fa->fa_info;
                        new_fa->fa_dscp = fa->fa_dscp;
                        new_fa->fa_info = fi;
                        new_fa->fa_type = cfg->fc_type;
                        state = READ_ONCE(fa->fa_state);
                        new_fa->fa_state = state & ~FA_S_ACCESSED;
                        new_fa->fa_slen = fa->fa_slen;
                        new_fa->tb_id = tb->tb_id;
                        new_fa->fa_default = -1;
                        new_fa->offload = 0;
                        new_fa->trap = 0;
                        new_fa->offload_failed = 0;

                        hlist_replace_rcu(&fa->fa_list, &new_fa->fa_list);

                        if (fib_find_alias(&l->leaf, fa->fa_slen, 0, 0,
                                           tb->tb_id, true) == new_fa) {
                                enum fib_event_type fib_event;

                                fib_event = FIB_EVENT_ENTRY_REPLACE;
                                err = call_fib_entry_notifiers(net, fib_event,
                                                               key, plen,
                                                               new_fa, extack);
                                if (err) {
                                        hlist_replace_rcu(&new_fa->fa_list,
                                                          &fa->fa_list);
                                        goto out_free_new_fa;
                                }
                        }

                        rtmsg_fib(RTM_NEWROUTE, htonl(key), new_fa, plen,
                                  tb->tb_id, &cfg->fc_nlinfo, nlflags);

                        alias_free_mem_rcu(fa);

                        fib_release_info(fi_drop);
                        if (state & FA_S_ACCESSED)
                                rt_cache_flush(cfg->fc_nlinfo.nl_net);

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

        nlflags |= NLM_F_CREATE;
        err = -ENOBUFS;
        new_fa = kmem_cache_alloc(fn_alias_kmem, GFP_KERNEL);
        if (!new_fa)
                goto out;

        new_fa->fa_info = fi;
        new_fa->fa_dscp = dscp;
        new_fa->fa_type = cfg->fc_type;
        new_fa->fa_state = 0;
        new_fa->fa_slen = slen;
        new_fa->tb_id = tb->tb_id;
        new_fa->fa_default = -1;
        new_fa->offload = 0;
        new_fa->trap = 0;
        new_fa->offload_failed = 0;

        /* Insert new entry to the list. */
        err = fib_insert_alias(t, tp, l, new_fa, fa, key);
        if (err)
                goto out_free_new_fa;

        /* The alias was already inserted, so the node must exist. */
        l = l ? l : fib_find_node(t, &tp, key);
        if (WARN_ON_ONCE(!l)) {
                err = -ENOENT;
                goto out_free_new_fa;
        }

        if (fib_find_alias(&l->leaf, new_fa->fa_slen, 0, 0, tb->tb_id, true) ==
            new_fa) {
                enum fib_event_type fib_event;

                fib_event = FIB_EVENT_ENTRY_REPLACE;
                err = call_fib_entry_notifiers(net, fib_event, key, plen,
                                               new_fa, extack);
                if (err)
                        goto out_remove_new_fa;
        }

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

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

out_remove_new_fa:
        fib_remove_alias(t, tp, l, new_fa);
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 key_vector *n)
{
        t_key prefix = n->key;

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

bool fib_lookup_good_nhc(const struct fib_nh_common *nhc, int fib_flags,
                         const struct flowi4 *flp)
{
        if (nhc->nhc_flags & RTNH_F_DEAD)
                return false;

        if (ip_ignore_linkdown(nhc->nhc_dev) &&
            nhc->nhc_flags & RTNH_F_LINKDOWN &&
            !(fib_flags & FIB_LOOKUP_IGNORE_LINKSTATE))
                return false;

        if (flp->flowi4_oif && flp->flowi4_oif != nhc->nhc_oif)
                return false;

        return true;
}

/* 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 key_vector *n, *pn;
        struct fib_alias *fa;
        unsigned long index;
        t_key cindex;

        pn = t->kv;
        cindex = 0;

        n = get_child_rcu(pn, cindex);
        if (!n) {
                trace_fib_table_lookup(tb->tb_id, flp, NULL, -EAGAIN);
                return -EAGAIN;
        }

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

        /* Step 1: Travel to the longest prefix match in the trie */
        for (;;) {
                index = get_cindex(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 >= (1ul << bits))
                 *     we have a mismatch in skip bits and failed
                 *   else
                 *     we know the value is cindex
                 *
                 * This check is safe even if bits == KEYLENGTH due to the
                 * fact that we can only allocate a node with 32 bits if a
                 * long is greater than 32 bits.
                 */
                if (index >= (1ul << 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 (n->slen > n->pos) {
                        pn = n;
                        cindex = index;
                }

                n = get_child_rcu(n, 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 key_vector __rcu **cptr = n->tnode;

                /* 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)) || (n->slen == n->pos))
                        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;

                                /* If we don't have a parent then there is
                                 * nothing for us to do as we do not have any
                                 * further nodes to parse.
                                 */
                                if (IS_TRIE(pn)) {
                                        trace_fib_table_lookup(tb->tb_id, flp,
                                                               NULL, -EAGAIN);
                                        return -EAGAIN;
                                }
#ifdef CONFIG_IP_FIB_TRIE_STATS
                                this_cpu_inc(stats->backtrack);
#endif
                                /* Get Child's index */
                                pn = node_parent_rcu(pn);
                                cindex = get_index(pkey, pn);
                        }

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

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

found:
        /* this line carries forward the xor from earlier in the function */
        index = key ^ n->key;

        /* Step 3: Process the leaf, if that fails fall back to backtracing */
        hlist_for_each_entry_rcu(fa, &n->leaf, fa_list) {
                struct fib_info *fi = fa->fa_info;
                struct fib_nh_common *nhc;
                int nhsel, err;

                if ((BITS_PER_LONG > KEYLENGTH) || (fa->fa_slen < KEYLENGTH)) {
                        if (index >= (1ul << fa->fa_slen))
                                continue;
                }
                if (fa->fa_dscp && !fib_dscp_masked_match(fa->fa_dscp, flp))
                        continue;
                /* Paired with WRITE_ONCE() in fib_release_info() */
                if (READ_ONCE(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)) {
out_reject:
#ifdef CONFIG_IP_FIB_TRIE_STATS
                        this_cpu_inc(stats->semantic_match_passed);
#endif
                        trace_fib_table_lookup(tb->tb_id, flp, NULL, err);
                        return err;
                }
                if (fi->fib_flags & RTNH_F_DEAD)
                        continue;

                if (unlikely(fi->nh)) {
                        if (nexthop_is_blackhole(fi->nh)) {
                                err = fib_props[RTN_BLACKHOLE].error;
                                goto out_reject;
                        }

                        nhc = nexthop_get_nhc_lookup(fi->nh, fib_flags, flp,
                                                     &nhsel);
                        if (nhc)
                                goto set_result;
                        goto miss;
                }

                for (nhsel = 0; nhsel < fib_info_num_path(fi); nhsel++) {
                        nhc = fib_info_nhc(fi, nhsel);

                        if (!fib_lookup_good_nhc(nhc, fib_flags, flp))
                                continue;
set_result:
                        if (!(fib_flags & FIB_LOOKUP_NOREF))
                                refcount_inc(&fi->fib_clntref);

                        res->prefix = htonl(n->key);
                        res->prefixlen = KEYLENGTH - fa->fa_slen;
                        res->nh_sel = nhsel;
                        res->nhc = nhc;
                        res->type = fa->fa_type;
                        res->scope = fi->fib_scope;
                        res->dscp = fa->fa_dscp;
                        res->fi = fi;
                        res->table = tb;
                        res->fa_head = &n->leaf;
#ifdef CONFIG_IP_FIB_TRIE_STATS
                        this_cpu_inc(stats->semantic_match_passed);
#endif
                        trace_fib_table_lookup(tb->tb_id, flp, nhc, err);

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

static void fib_remove_alias(struct trie *t, struct key_vector *tp,
                             struct key_vector *l, struct fib_alias *old)
{
        /* record the location of the previous list_info entry */
        struct hlist_node **pprev = old->fa_list.pprev;
        struct fib_alias *fa = hlist_entry(pprev, typeof(*fa), fa_list.next);

        /* remove the fib_alias from the list */
        hlist_del_rcu(&old->fa_list);

        /* if we emptied the list this leaf will be freed and we can sort
         * out parent suffix lengths as a part of trie_rebalance
         */
        if (hlist_empty(&l->leaf)) {
                if (tp->slen == l->slen)
                        node_pull_suffix(tp, tp->pos);
                put_child_root(tp, l->key, NULL);
                node_free(l);
                trie_rebalance(t, tp);
                return;
        }

        /* only access fa if it is pointing at the last valid hlist_node */
        if (*pprev)
                return;

        /* update the trie with the latest suffix length */
        l->slen = fa->fa_slen;
        node_pull_suffix(tp, fa->fa_slen);
}

static void fib_notify_alias_delete(struct net *net, u32 key,
                                    struct hlist_head *fah,
                                    struct fib_alias *fa_to_delete,
                                    struct netlink_ext_ack *extack)
{
        struct fib_alias *fa_next, *fa_to_notify;
        u32 tb_id = fa_to_delete->tb_id;
        u8 slen = fa_to_delete->fa_slen;
        enum fib_event_type fib_event;

        /* Do not notify if we do not care about the route. */
        if (fib_find_alias(fah, slen, 0, 0, tb_id, true) != fa_to_delete)
                return;

        /* Determine if the route should be replaced by the next route in the
         * list.
         */
        fa_next = hlist_entry_safe(fa_to_delete->fa_list.next,
                                   struct fib_alias, fa_list);
        if (fa_next && fa_next->fa_slen == slen && fa_next->tb_id == tb_id) {
                fib_event = FIB_EVENT_ENTRY_REPLACE;
                fa_to_notify = fa_next;
        } else {
                fib_event = FIB_EVENT_ENTRY_DEL;
                fa_to_notify = fa_to_delete;
        }
        call_fib_entry_notifiers(net, fib_event, key, KEYLENGTH - slen,
                                 fa_to_notify, extack);
}

/* Caller must hold RTNL. */
int fib_table_delete(struct net *net, struct fib_table *tb,
                     struct fib_config *cfg, struct netlink_ext_ack *extack)
{
        struct trie *t = (struct trie *) tb->tb_data;
        struct fib_alias *fa, *fa_to_delete;
        struct key_vector *l, *tp;
        u8 plen = cfg->fc_dst_len;
        u8 slen = KEYLENGTH - plen;
        dscp_t dscp;
        u32 key;

        key = ntohl(cfg->fc_dst);

        l = fib_find_node(t, &tp, key);
        if (!l)
                return -ESRCH;

        dscp = cfg->fc_dscp;
        fa = fib_find_alias(&l->leaf, slen, dscp, 0, tb->tb_id, false);
        if (!fa)
                return -ESRCH;

        pr_debug("Deleting %08x/%d dsfield=0x%02x t=%p\n", key, plen,
                 inet_dscp_to_dsfield(dscp), t);

        fa_to_delete = NULL;
        hlist_for_each_entry_from(fa, fa_list) {
                struct fib_info *fi = fa->fa_info;

                if ((fa->fa_slen != slen) ||
                    (fa->tb_id != tb->tb_id) ||
                    (fa->fa_dscp != dscp))
                        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(net, cfg, fi, extack) == 0 &&
                    fib_metrics_match(cfg, fi)) {
                        fa_to_delete = fa;
                        break;
                }
        }

        if (!fa_to_delete)
                return -ESRCH;

        fib_notify_alias_delete(net, key, &l->leaf, fa_to_delete, extack);
        rtmsg_fib(RTM_DELROUTE, htonl(key), fa_to_delete, plen, tb->tb_id,
                  &cfg->fc_nlinfo, 0);

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

        fib_remove_alias(t, tp, l, fa_to_delete);

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

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

/* Scan for the next leaf starting at the provided key value */
static struct key_vector *leaf_walk_rcu(struct key_vector **tn, t_key key)
{
        struct key_vector *pn, *n = *tn;
        unsigned long cindex;

        /* this loop is meant to try and find the key in the trie */
        do {
                /* record parent and next child index */
                pn = n;
                cindex = (key > pn->key) ? get_index(key, pn) : 0;

                if (cindex >> pn->bits)
                        break;

                /* descend into the next child */
                n = get_child_rcu(pn, cindex++);
                if (!n)
                        break;

                /* guarantee forward progress on the keys */
                if (IS_LEAF(n) && (n->key >= key))
                        goto found;
        } while (IS_TNODE(n));

        /* this loop will search for the next leaf with a greater key */
        while (!IS_TRIE(pn)) {
                /* if we exhausted the parent node we will need to climb */
                if (cindex >= (1ul << pn->bits)) {
                        t_key pkey = pn->key;

                        pn = node_parent_rcu(pn);
                        cindex = get_index(pkey, pn) + 1;
                        continue;
                }

                /* grab the next available node */
                n = get_child_rcu(pn, cindex++);
                if (!n)
                        continue;

                /* no need to compare keys since we bumped the index */
                if (IS_LEAF(n))
                        goto found;

                /* Rescan start scanning in new node */
                pn = n;
                cindex = 0;
        }

        *tn = pn;
        return NULL; /* Root of trie */
found:
        /* if we are at the limit for keys just return NULL for the tnode */
        *tn = pn;
        return n;
}

static void fib_trie_free(struct fib_table *tb)
{
        struct trie *t = (struct trie *)tb->tb_data;
        struct key_vector *pn = t->kv;
        unsigned long cindex = 1;
        struct hlist_node *tmp;
        struct fib_alias *fa;

        /* walk trie in reverse order and free everything */
        for (;;) {
                struct key_vector *n;

                if (!(cindex--)) {
                        t_key pkey = pn->key;

                        if (IS_TRIE(pn))
                                break;

                        n = pn;
                        pn = node_parent(pn);

                        /* drop emptied tnode */
                        put_child_root(pn, n->key, NULL);
                        node_free(n);

                        cindex = get_index(pkey, pn);

                        continue;
                }

                /* grab the next available node */
                n = get_child(pn, cindex);
                if (!n)
                        continue;

                if (IS_TNODE(n)) {
                        /* record pn and cindex for leaf walking */
                        pn = n;
                        cindex = 1ul << n->bits;

                        continue;
                }

                hlist_for_each_entry_safe(fa, tmp, &n->leaf, fa_list) {
                        hlist_del_rcu(&fa->fa_list);
                        alias_free_mem_rcu(fa);
                }

                put_child_root(pn, n->key, NULL);
                node_free(n);
        }

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

struct fib_table *fib_trie_unmerge(struct fib_table *oldtb)
{
        struct trie *ot = (struct trie *)oldtb->tb_data;
        struct key_vector *l, *tp = ot->kv;
        struct fib_table *local_tb;
        struct fib_alias *fa;
        struct trie *lt;
        t_key key = 0;

        if (oldtb->tb_data == oldtb->__data)
                return oldtb;

        local_tb = fib_trie_table(RT_TABLE_LOCAL, NULL);
        if (!local_tb)
                return NULL;

        lt = (struct trie *)local_tb->tb_data;

        while ((l = leaf_walk_rcu(&tp, key)) != NULL) {
                struct key_vector *local_l = NULL, *local_tp;

                hlist_for_each_entry(fa, &l->leaf, fa_list) {
                        struct fib_alias *new_fa;

                        if (local_tb->tb_id != fa->tb_id)
                                continue;

                        /* clone fa for new local table */
                        new_fa = kmem_cache_alloc(fn_alias_kmem, GFP_KERNEL);
                        if (!new_fa)
                                goto out;

                        memcpy(new_fa, fa, sizeof(*fa));

                        /* insert clone into table */
                        if (!local_l)
                                local_l = fib_find_node(lt, &local_tp, l->key);

                        if (fib_insert_alias(lt, local_tp, local_l, new_fa,
                                             NULL, l->key)) {
                                kmem_cache_free(fn_alias_kmem, new_fa);
                                goto out;
                        }
                }

                /* stop loop if key wrapped back to 0 */
                key = l->key + 1;
                if (key < l->key)
                        break;
        }

        return local_tb;
out:
        fib_trie_free(local_tb);

        return NULL;
}

/* Caller must hold RTNL */
void fib_table_flush_external(struct fib_table *tb)
{
        struct trie *t = (struct trie *)tb->tb_data;
        struct key_vector *pn = t->kv;
        unsigned long cindex = 1;
        struct hlist_node *tmp;
        struct fib_alias *fa;

        /* walk trie in reverse order */
        for (;;) {
                unsigned char slen = 0;
                struct key_vector *n;

                if (!(cindex--)) {
                        t_key pkey = pn->key;

                        /* cannot resize the trie vector */
                        if (IS_TRIE(pn))
                                break;

                        /* update the suffix to address pulled leaves */
                        if (pn->slen > pn->pos)
                                update_suffix(pn);

                        /* resize completed node */
                        pn = resize(t, pn);
                        cindex = get_index(pkey, pn);

                        continue;
                }

                /* grab the next available node */
                n = get_child(pn, cindex);
                if (!n)
                        continue;

                if (IS_TNODE(n)) {
                        /* record pn and cindex for leaf walking */
                        pn = n;
                        cindex = 1ul << n->bits;

                        continue;
                }

                hlist_for_each_entry_safe(fa, tmp, &n->leaf, fa_list) {
                        /* if alias was cloned to local then we just
                         * need to remove the local copy from main
                         */
                        if (tb->tb_id != fa->tb_id) {
                                hlist_del_rcu(&fa->fa_list);
                                alias_free_mem_rcu(fa);
                                continue;
                        }

                        /* record local slen */
                        slen = fa->fa_slen;
                }

                /* update leaf slen */
                n->slen = slen;

                if (hlist_empty(&n->leaf)) {
                        put_child_root(pn, n->key, NULL);
                        node_free(n);
                }
        }
}

/* Caller must hold RTNL. */
int fib_table_flush(struct net *net, struct fib_table *tb, bool flush_all)
{
        struct trie *t = (struct trie *)tb->tb_data;
        struct nl_info info = { .nl_net = net };
        struct key_vector *pn = t->kv;
        unsigned long cindex = 1;
        struct hlist_node *tmp;
        struct fib_alias *fa;
        int found = 0;

        /* walk trie in reverse order */
        for (;;) {
                unsigned char slen = 0;
                struct key_vector *n;

                if (!(cindex--)) {
                        t_key pkey = pn->key;

                        /* cannot resize the trie vector */
                        if (IS_TRIE(pn))
                                break;

                        /* update the suffix to address pulled leaves */
                        if (pn->slen > pn->pos)
                                update_suffix(pn);

                        /* resize completed node */
                        pn = resize(t, pn);
                        cindex = get_index(pkey, pn);

                        continue;
                }

                /* grab the next available node */
                n = get_child(pn, cindex);
                if (!n)
                        continue;

                if (IS_TNODE(n)) {
                        /* record pn and cindex for leaf walking */
                        pn = n;
                        cindex = 1ul << n->bits;

                        continue;
                }

                hlist_for_each_entry_safe(fa, tmp, &n->leaf, fa_list) {
                        struct fib_info *fi = fa->fa_info;

                        if (!fi || tb->tb_id != fa->tb_id ||
                            (!(fi->fib_flags & RTNH_F_DEAD) &&
                             !fib_props[fa->fa_type].error)) {
                                slen = fa->fa_slen;
                                continue;
                        }

                        /* When not flushing the entire table, skip error
                         * routes that are not marked for deletion.
                         */
                        if (!flush_all && fib_props[fa->fa_type].error &&
                            !(fi->fib_flags & RTNH_F_DEAD)) {
                                slen = fa->fa_slen;
                                continue;
                        }

                        fib_notify_alias_delete(net, n->key, &n->leaf, fa,
                                                NULL);
                        if (fi->pfsrc_removed)
                                rtmsg_fib(RTM_DELROUTE, htonl(n->key), fa,
                                          KEYLENGTH - fa->fa_slen, tb->tb_id, &info, 0);
                        hlist_del_rcu(&fa->fa_list);
                        fib_release_info(fa->fa_info);
                        alias_free_mem_rcu(fa);
                        found++;
                }

                /* update leaf slen */
                n->slen = slen;

                if (hlist_empty(&n->leaf)) {
                        put_child_root(pn, n->key, NULL);
                        node_free(n);
                }
        }

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

/* derived from fib_trie_free */
static void __fib_info_notify_update(struct net *net, struct fib_table *tb,
                                     struct nl_info *info)
{
        struct trie *t = (struct trie *)tb->tb_data;
        struct key_vector *pn = t->kv;
        unsigned long cindex = 1;
        struct fib_alias *fa;

        for (;;) {
                struct key_vector *n;

                if (!(cindex--)) {
                        t_key pkey = pn->key;

                        if (IS_TRIE(pn))
                                break;

                        pn = node_parent(pn);
                        cindex = get_index(pkey, pn);
                        continue;
                }

                /* grab the next available node */
                n = get_child(pn, cindex);
                if (!n)
                        continue;

                if (IS_TNODE(n)) {
                        /* record pn and cindex for leaf walking */
                        pn = n;
                        cindex = 1ul << n->bits;

                        continue;
                }

                hlist_for_each_entry(fa, &n->leaf, fa_list) {
                        struct fib_info *fi = fa->fa_info;

                        if (!fi || !fi->nh_updated || fa->tb_id != tb->tb_id)
                                continue;

                        rtmsg_fib(RTM_NEWROUTE, htonl(n->key), fa,
                                  KEYLENGTH - fa->fa_slen, tb->tb_id,
                                  info, NLM_F_REPLACE);
                }
        }
}

void fib_info_notify_update(struct net *net, struct nl_info *info)
{
        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,
                                         lockdep_rtnl_is_held())
                        __fib_info_notify_update(net, tb, info);
        }
}

static int fib_leaf_notify(struct key_vector *l, struct fib_table *tb,
                           struct notifier_block *nb,
                           struct netlink_ext_ack *extack)
{
        struct fib_alias *fa;
        int last_slen = -1;
        int err;

        hlist_for_each_entry_rcu(fa, &l->leaf, fa_list) {
                struct fib_info *fi = fa->fa_info;

                if (!fi)
                        continue;

                /* local and main table can share the same trie,
                 * so don't notify twice for the same entry.
                 */
                if (tb->tb_id != fa->tb_id)
                        continue;

                if (fa->fa_slen == last_slen)
                        continue;

                last_slen = fa->fa_slen;
                err = call_fib_entry_notifier(nb, FIB_EVENT_ENTRY_REPLACE,
                                              l->key, KEYLENGTH - fa->fa_slen,
                                              fa, extack);
                if (err)
                        return err;
        }
        return 0;
}

static int fib_table_notify(struct fib_table *tb, struct notifier_block *nb,
                            struct netlink_ext_ack *extack)
{
        struct trie *t = (struct trie *)tb->tb_data;
        struct key_vector *l, *tp = t->kv;
        t_key key = 0;
        int err;

        while ((l = leaf_walk_rcu(&tp, key)) != NULL) {
                err = fib_leaf_notify(l, tb, nb, extack);
                if (err)
                        return err;

                key = l->key + 1;
                /* stop in case of wrap around */
                if (key < l->key)
                        break;
        }
        return 0;
}

int fib_notify(struct net *net, struct notifier_block *nb,
               struct netlink_ext_ack *extack)
{
        unsigned int h;
        int err;

        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) {
                        err = fib_table_notify(tb, nb, extack);
                        if (err)
                                return err;
                }
        }
        return 0;
}

static void __trie_free_rcu(struct rcu_head *head)
{
        struct fib_table *tb = container_of(head, struct fib_table, rcu);
#ifdef CONFIG_IP_FIB_TRIE_STATS
        struct trie *t = (struct trie *)tb->tb_data;

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

void fib_free_table(struct fib_table *tb)
{
        call_rcu(&tb->rcu, __trie_free_rcu);
}

static int fn_trie_dump_leaf(struct key_vector *l, struct fib_table *tb,
                             struct sk_buff *skb, struct netlink_callback *cb,
                             struct fib_dump_filter *filter)
{
        unsigned int flags = NLM_F_MULTI;
        __be32 xkey = htonl(l->key);
        int i, s_i, i_fa, s_fa, err;
        struct fib_alias *fa;

        if (filter->filter_set ||
            !filter->dump_exceptions || !filter->dump_routes)
                flags |= NLM_F_DUMP_FILTERED;

        s_i = cb->args[4];
        s_fa = cb->args[5];
        i = 0;

        /* rcu_read_lock is hold by caller */
        hlist_for_each_entry_rcu(fa, &l->leaf, fa_list) {
                struct fib_info *fi = fa->fa_info;

                if (i < s_i)
                        goto next;

                i_fa = 0;

                if (tb->tb_id != fa->tb_id)
                        goto next;

                if (filter->filter_set) {
                        if (filter->rt_type && fa->fa_type != filter->rt_type)
                                goto next;

                        if ((filter->protocol &&
                             fi->fib_protocol != filter->protocol))
                                goto next;

                        if (filter->dev &&
                            !fib_info_nh_uses_dev(fi, filter->dev))
                                goto next;
                }

                if (filter->dump_routes) {
                        if (!s_fa) {
                                struct fib_rt_info fri;

                                fri.fi = fi;
                                fri.tb_id = tb->tb_id;
                                fri.dst = xkey;
                                fri.dst_len = KEYLENGTH - fa->fa_slen;
                                fri.dscp = fa->fa_dscp;
                                fri.type = fa->fa_type;
                                fri.offload = READ_ONCE(fa->offload);
                                fri.trap = READ_ONCE(fa->trap);
                                fri.offload_failed = READ_ONCE(fa->offload_failed);
                                err = fib_dump_info(skb,
                                                    NETLINK_CB(cb->skb).portid,
                                                    cb->nlh->nlmsg_seq,
                                                    RTM_NEWROUTE, &fri, flags);
                                if (err < 0)
                                        goto stop;
                        }

                        i_fa++;
                }

                if (filter->dump_exceptions) {
                        err = fib_dump_info_fnhe(skb, cb, tb->tb_id, fi,
                                                 &i_fa, s_fa, flags);
                        if (err < 0)
                                goto stop;
                }

next:
                i++;
        }

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

stop:
        cb->args[4] = i;
        cb->args[5] = i_fa;
        return err;
}

/* rcu_read_lock needs to be hold by caller from readside */
int fib_table_dump(struct fib_table *tb, struct sk_buff *skb,
                   struct netlink_callback *cb, struct fib_dump_filter *filter)
{
        struct trie *t = (struct trie *)tb->tb_data;
        struct key_vector *l, *tp = t->kv;
        /* Dump starting at last key.
         * Note: 0.0.0.0/0 (ie default) is first key.
         */
        int count = cb->args[2];
        t_key key = cb->args[3];

        /* First time here, count and key are both always 0. Count > 0
         * and key == 0 means the dump has wrapped around and we are done.
         */
        if (count && !key)
                return 0;

        while ((l = leaf_walk_rcu(&tp, key)) != NULL) {
                int err;

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

                ++count;
                key = l->key + 1;

                memset(&cb->args[4], 0,
                       sizeof(cb->args) - 4*sizeof(cb->args[0]));

                /* stop loop if key wrapped back to 0 */
                if (key < l->key)
                        break;
        }

        cb->args[3] = key;
        cb->args[2] = count;

        return 0;
}

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

        trie_leaf_kmem = kmem_cache_create("ip_fib_trie",
                                           LEAF_SIZE,
                                           0, SLAB_PANIC | SLAB_ACCOUNT, NULL);
}

struct fib_table *fib_trie_table(u32 id, struct fib_table *alias)
{
        struct fib_table *tb;
        struct trie *t;
        size_t sz = sizeof(*tb);

        if (!alias)
                sz += sizeof(struct trie);

        tb = kzalloc(sz, GFP_KERNEL);
        if (!tb)
                return NULL;

        tb->tb_id = id;
        tb->tb_num_default = 0;
        tb->tb_data = (alias ? alias->__data : tb->__data);

        if (alias)
                return tb;

        t = (struct trie *) tb->tb_data;
        t->kv[0].pos = KEYLENGTH;
        t->kv[0].slen = KEYLENGTH;
#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 key_vector *tnode;
        unsigned int index;
        unsigned int depth;
};

static struct key_vector *fib_trie_get_next(struct fib_trie_iter *iter)
{
        unsigned long cindex = iter->index;
        struct key_vector *pn = iter->tnode;
        t_key pkey;

        pr_debug("get_next iter={node=%p index=%d depth=%d}\n",
                 iter->tnode, iter->index, iter->depth);

        while (!IS_TRIE(pn)) {
                while (cindex < child_length(pn)) {
                        struct key_vector *n = get_child_rcu(pn, cindex++);

                        if (!n)
                                continue;

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

                        return n;
                }

                /* Current node exhausted, pop back up */
                pkey = pn->key;
                pn = node_parent_rcu(pn);
                cindex = get_index(pkey, pn) + 1;
                --iter->depth;
        }

        /* record root node so further searches know we are done */
        iter->tnode = pn;
        iter->index = 0;

        return NULL;
}

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

        if (!t)
                return NULL;

        pn = t->kv;
        n = rcu_dereference(pn->tnode[0]);
        if (!n)
                return NULL;

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

        return n;
}

static void trie_collect_stats(struct trie *t, struct trie_stat *s)
{
        struct key_vector *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 fib_alias *fa;

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

                        hlist_for_each_entry_rcu(fa, &n->leaf, fa_list)
                                ++s->prefixes;
                } else {
                        s->tnodes++;
                        if (n->bits < MAX_STAT_DEPTH)
                                s->nodesizes[n->bits]++;
                        s->nullpointers += tn_info(n)->empty_children;
                }
        }
        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 = LEAF_SIZE * stat->leaves;

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

        seq_printf(seq, "\tInternal nodes: %u\n\t", stat->tnodes);
        bytes += TNODE_SIZE(0) * 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 key_vector *) * 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 = seq->private;
        unsigned int h;

        seq_printf(seq,
                   "Basic info: size of leaf:"
                   " %zd bytes, size of tnode: %zd bytes.\n",
                   LEAF_SIZE, TNODE_SIZE(0));

        rcu_read_lock();
        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
                }
                cond_resched_rcu();
        }
        rcu_read_unlock();

        return 0;
}

static struct key_vector *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 key_vector *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 key_vector *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 key_vector *n = v;

        if (IS_TRIE(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,
                           tn_info(n)->full_children,
                           tn_info(n)->empty_children);
        } else {
                __be32 val = htonl(n->key);
                struct fib_alias *fa;

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

                hlist_for_each_entry_rcu(fa, &n->leaf, fa_list) {
                        char buf1[32], buf2[32];

                        seq_indent(seq, iter->depth + 1);
                        seq_printf(seq, "  /%zu %s %s",
                                   KEYLENGTH - fa->fa_slen,
                                   rtn_scope(buf1, sizeof(buf1),
                                             fa->fa_info->fib_scope),
                                   rtn_type(buf2, sizeof(buf2),
                                            fa->fa_type));
                        if (fa->fa_dscp)
                                seq_printf(seq, " tos=%d",
                                           inet_dscp_to_dsfield(fa->fa_dscp));
                        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,
};

struct fib_route_iter {
        struct seq_net_private p;
        struct fib_table *main_tb;
        struct key_vector *tnode;
        loff_t  pos;
        t_key   key;
};

static struct key_vector *fib_route_get_idx(struct fib_route_iter *iter,
                                            loff_t pos)
{
        struct key_vector *l, **tp = &iter->tnode;
        t_key key;

        /* use cached location of previously found key */
        if (iter->pos > 0 && pos >= iter->pos) {
                key = iter->key;
        } else {
                iter->pos = 1;
                key = 0;
        }

        pos -= iter->pos;

        while ((l = leaf_walk_rcu(tp, key)) && (pos-- > 0)) {
                key = l->key + 1;
                iter->pos++;
                l = NULL;

                /* handle unlikely case of a key wrap */
                if (!key)
                        break;
        }

        if (l)
                iter->key = l->key;     /* 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;
        struct trie *t;

        rcu_read_lock();

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

        iter->main_tb = tb;
        t = (struct trie *)tb->tb_data;
        iter->tnode = t->kv;

        if (*pos != 0)
                return fib_route_get_idx(iter, *pos);

        iter->pos = 0;
        iter->key = KEY_MAX;

        return SEQ_START_TOKEN;
}

static void *fib_route_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
        struct fib_route_iter *iter = seq->private;
        struct key_vector *l = NULL;
        t_key key = iter->key + 1;

        ++*pos;

        /* only allow key of 0 for start of sequence */
        if ((v == SEQ_START_TOKEN) || key)
                l = leaf_walk_rcu(&iter->tnode, key);

        if (l) {
                iter->key = l->key;
                iter->pos++;
        } 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, struct fib_info *fi)
{
        unsigned int flags = 0;

        if (type == RTN_UNREACHABLE || type == RTN_PROHIBIT)
                flags = RTF_REJECT;
        if (fi) {
                const struct fib_nh_common *nhc = fib_info_nhc(fi, 0);

                if (nhc->nhc_gw.ipv4)
                        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 fib_route_iter *iter = seq->private;
        struct fib_table *tb = iter->main_tb;
        struct fib_alias *fa;
        struct key_vector *l = v;
        __be32 prefix;

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

        prefix = htonl(l->key);

        hlist_for_each_entry_rcu(fa, &l->leaf, fa_list) {
                struct fib_info *fi = fa->fa_info;
                __be32 mask = inet_make_mask(KEYLENGTH - fa->fa_slen);
                unsigned int flags = fib_flag_trans(fa->fa_type, mask, fi);

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

                if (fa->tb_id != tb->tb_id)
                        continue;

                seq_setwidth(seq, 127);

                if (fi) {
                        struct fib_nh_common *nhc = fib_info_nhc(fi, 0);
                        __be32 gw = 0;

                        if (nhc->nhc_gw_family == AF_INET)
                                gw = nhc->nhc_gw.ipv4;

                        seq_printf(seq,
                                   "%s\t%08X\t%08X\t%04X\t%d\t%u\t"
                                   "%u\t%08X\t%d\t%u\t%u",
                                   nhc->nhc_dev ? nhc->nhc_dev->name : "*",
                                   prefix, 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"
                                   "%u\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,
};

int __net_init fib_proc_init(struct net *net)
{
        if (!proc_create_net("fib_trie", 0444, net->proc_net, &fib_trie_seq_ops,
                        sizeof(struct fib_trie_iter)))
                goto out1;

        if (!proc_create_net_single("fib_triestat", 0444, net->proc_net,
                        fib_triestat_seq_show, NULL))
                goto out2;

        if (!proc_create_net("route", 0444, net->proc_net, &fib_route_seq_ops,
                        sizeof(struct fib_route_iter)))
                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 */
Linux
