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 // 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/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) */
         struct key_vector __rcu *tnode[0];
     };
 };
 
 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 void __alias_free_mem(struct rcu_head *head)
 {
     struct fib_alias *fa = container_of(head, struct fib_alias, rcu);
     kmem_cache_free(fn_alias_kmem, fa);
 }
 
 static inline void alias_free_mem_rcu(struct fib_alias *fa)
 {
     call_rcu(&fa->rcu, __alias_free_mem);
 }
 
 #define TNODE_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_rcu();
     }
 }
 
 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 bool fib_valid_key_len(u32 key, u8 plen, struct netlink_ext_ack *extack)
 {
     if (plen > KEYLENGTH) {
         NL_SET_ERR_MSG(extack, "Invalid prefix length");
         return false;
     }
 
     if ((plen < KEYLENGTH) && (key << plen)) {
         NL_SET_ERR_MSG(extack,
                    "Invalid prefix for given prefix length");
         return false;
     }
 
     return true;
 }
 
 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);
 
     if (!fib_valid_key_len(key, plen, extack))
         return -EINVAL;
 
     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 = 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))
         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 &&
             inet_dscp_to_dsfield(fa->fa_dscp) != flp->flowi4_tos)
             continue;
         if (fi->fib_dead)
             continue;
         if (fa->fa_info->fib_scope < flp->flowi4_scope)
             continue;
         fib_alias_accessed(fa);
         err = fib_props[fa->fa_type].error;
         if (unlikely(err < 0)) {
 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->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);
 
     if (!fib_valid_key_len(key, plen, extack))
         return -EINVAL;
 
     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 (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 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;
             }
 
             /* Do not flush error routes if network namespace is
              * not being dismantled
              */
             if (!flush_all && fib_props[fa->fa_type].error) {
                 slen = fa->fa_slen;
                 continue;
             }
 
             fib_notify_alias_delete(net, n->key, &n->leaf, fa,
                         NULL);
             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 skb->len;
 
     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 skb->len;
 }
 
 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"
                    "%d\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"
                    "%d\t%08X\t%d\t%u\t%u",
                    prefix, 0, flags, 0, 0, 0,
                    mask, 0, 0, 0);
         }
         seq_pad(seq, '\n');
     }
 
     return 0;
 }
 
 static const struct seq_operations fib_route_seq_ops = {
     .start  = fib_route_seq_start,
     .next   = fib_route_seq_next,
     .stop   = fib_route_seq_stop,
     .show   = fib_route_seq_show,
 };
 
 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 */