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fib_hash.c

/*
 * 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.
 *
 * Version: $Id: fib_hash.c,v 1.13 2001/10/31 21:55:54 davem Exp $
 *
 * Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
 *
 *          This program is free software; you can redistribute it and/or
 *          modify it under the terms of the GNU General Public License
 *          as published by the Free Software Foundation; either version
 *          2 of the License, or (at your option) any later version.
 */

#include <asm/uaccess.h>
#include <asm/system.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/skbuff.h>
#include <linux/netlink.h>
#include <linux/init.h>

#include <net/net_namespace.h>
#include <net/ip.h>
#include <net/protocol.h>
#include <net/route.h>
#include <net/tcp.h>
#include <net/sock.h>
#include <net/ip_fib.h>

#include "fib_lookup.h"

static struct kmem_cache *fn_hash_kmem __read_mostly;
static struct kmem_cache *fn_alias_kmem __read_mostly;

struct fib_node {
      struct hlist_node fn_hash;
      struct list_head  fn_alias;
      __be32                  fn_key;
};

struct fn_zone {
      struct fn_zone          *fz_next;   /* Next not empty zone  */
      struct hlist_head *fz_hash;   /* Hash table pointer   */
      int               fz_nent;    /* Number of entries    */

      int               fz_divisor; /* Hash divisor         */
      u32               fz_hashmask;      /* (fz_divisor - 1)     */
#define FZ_HASHMASK(fz)       ((fz)->fz_hashmask)

      int               fz_order;   /* Zone order           */
      __be32                  fz_mask;
#define FZ_MASK(fz)           ((fz)->fz_mask)
};

/* NOTE. On fast computers evaluation of fz_hashmask and fz_mask
 * can be cheaper than memory lookup, so that FZ_* macros are used.
 */

struct fn_hash {
      struct fn_zone    *fn_zones[33];
      struct fn_zone    *fn_zone_list;
};

static inline u32 fn_hash(__be32 key, struct fn_zone *fz)
{
      u32 h = ntohl(key)>>(32 - fz->fz_order);
      h ^= (h>>20);
      h ^= (h>>10);
      h ^= (h>>5);
      h &= FZ_HASHMASK(fz);
      return h;
}

static inline __be32 fz_key(__be32 dst, struct fn_zone *fz)
{
      return dst & FZ_MASK(fz);
}

static DEFINE_RWLOCK(fib_hash_lock);
static unsigned int fib_hash_genid;

#define FZ_MAX_DIVISOR ((PAGE_SIZE<<MAX_ORDER) / sizeof(struct hlist_head))

static struct hlist_head *fz_hash_alloc(int divisor)
{
      unsigned long size = divisor * sizeof(struct hlist_head);

      if (size <= PAGE_SIZE) {
            return kmalloc(size, GFP_KERNEL);
      } else {
            return (struct hlist_head *)
                  __get_free_pages(GFP_KERNEL, get_order(size));
      }
}

/* The fib hash lock must be held when this is called. */
static inline void fn_rebuild_zone(struct fn_zone *fz,
                           struct hlist_head *old_ht,
                           int old_divisor)
{
      int i;

      for (i = 0; i < old_divisor; i++) {
            struct hlist_node *node, *n;
            struct fib_node *f;

            hlist_for_each_entry_safe(f, node, n, &old_ht[i], fn_hash) {
                  struct hlist_head *new_head;

                  hlist_del(&f->fn_hash);

                  new_head = &fz->fz_hash[fn_hash(f->fn_key, fz)];
                  hlist_add_head(&f->fn_hash, new_head);
            }
      }
}

static void fz_hash_free(struct hlist_head *hash, int divisor)
{
      unsigned long size = divisor * sizeof(struct hlist_head);

      if (size <= PAGE_SIZE)
            kfree(hash);
      else
            free_pages((unsigned long)hash, get_order(size));
}

static void fn_rehash_zone(struct fn_zone *fz)
{
      struct hlist_head *ht, *old_ht;
      int old_divisor, new_divisor;
      u32 new_hashmask;

      old_divisor = fz->fz_divisor;

      switch (old_divisor) {
      case 16:
            new_divisor = 256;
            break;
      case 256:
            new_divisor = 1024;
            break;
      default:
            if ((old_divisor << 1) > FZ_MAX_DIVISOR) {
                  printk(KERN_CRIT "route.c: bad divisor %d!\n", old_divisor);
                  return;
            }
            new_divisor = (old_divisor << 1);
            break;
      }

      new_hashmask = (new_divisor - 1);

#if RT_CACHE_DEBUG >= 2
      printk("fn_rehash_zone: hash for zone %d grows from %d\n", fz->fz_order, old_divisor);
#endif

      ht = fz_hash_alloc(new_divisor);

      if (ht)     {
            memset(ht, 0, new_divisor * sizeof(struct hlist_head));

            write_lock_bh(&fib_hash_lock);
            old_ht = fz->fz_hash;
            fz->fz_hash = ht;
            fz->fz_hashmask = new_hashmask;
            fz->fz_divisor = new_divisor;
            fn_rebuild_zone(fz, old_ht, old_divisor);
            fib_hash_genid++;
            write_unlock_bh(&fib_hash_lock);

            fz_hash_free(old_ht, old_divisor);
      }
}

static inline void fn_free_node(struct fib_node * f)
{
      kmem_cache_free(fn_hash_kmem, f);
}

static inline void fn_free_alias(struct fib_alias *fa)
{
      fib_release_info(fa->fa_info);
      kmem_cache_free(fn_alias_kmem, fa);
}

static struct fn_zone *
fn_new_zone(struct fn_hash *table, int z)
{
      int i;
      struct fn_zone *fz = kzalloc(sizeof(struct fn_zone), GFP_KERNEL);
      if (!fz)
            return NULL;

      if (z) {
            fz->fz_divisor = 16;
      } else {
            fz->fz_divisor = 1;
      }
      fz->fz_hashmask = (fz->fz_divisor - 1);
      fz->fz_hash = fz_hash_alloc(fz->fz_divisor);
      if (!fz->fz_hash) {
            kfree(fz);
            return NULL;
      }
      memset(fz->fz_hash, 0, fz->fz_divisor * sizeof(struct hlist_head *));
      fz->fz_order = z;
      fz->fz_mask = inet_make_mask(z);

      /* Find the first not empty zone with more specific mask */
      for (i=z+1; i<=32; i++)
            if (table->fn_zones[i])
                  break;
      write_lock_bh(&fib_hash_lock);
      if (i>32) {
            /* No more specific masks, we are the first. */
            fz->fz_next = table->fn_zone_list;
            table->fn_zone_list = fz;
      } else {
            fz->fz_next = table->fn_zones[i]->fz_next;
            table->fn_zones[i]->fz_next = fz;
      }
      table->fn_zones[z] = fz;
      fib_hash_genid++;
      write_unlock_bh(&fib_hash_lock);
      return fz;
}

static int
fn_hash_lookup(struct fib_table *tb, const struct flowi *flp, struct fib_result *res)
{
      int err;
      struct fn_zone *fz;
      struct fn_hash *t = (struct fn_hash*)tb->tb_data;

      read_lock(&fib_hash_lock);
      for (fz = t->fn_zone_list; fz; fz = fz->fz_next) {
            struct hlist_head *head;
            struct hlist_node *node;
            struct fib_node *f;
            __be32 k = fz_key(flp->fl4_dst, fz);

            head = &fz->fz_hash[fn_hash(k, fz)];
            hlist_for_each_entry(f, node, head, fn_hash) {
                  if (f->fn_key != k)
                        continue;

                  err = fib_semantic_match(&f->fn_alias,
                                     flp, res,
                                     f->fn_key, fz->fz_mask,
                                     fz->fz_order);
                  if (err <= 0)
                        goto out;
            }
      }
      err = 1;
out:
      read_unlock(&fib_hash_lock);
      return err;
}

static int fn_hash_last_dflt=-1;

static void
fn_hash_select_default(struct fib_table *tb, const struct flowi *flp, struct fib_result *res)
{
      int order, last_idx;
      struct hlist_node *node;
      struct fib_node *f;
      struct fib_info *fi = NULL;
      struct fib_info *last_resort;
      struct fn_hash *t = (struct fn_hash*)tb->tb_data;
      struct fn_zone *fz = t->fn_zones[0];

      if (fz == NULL)
            return;

      last_idx = -1;
      last_resort = NULL;
      order = -1;

      read_lock(&fib_hash_lock);
      hlist_for_each_entry(f, node, &fz->fz_hash[0], fn_hash) {
            struct fib_alias *fa;

            list_for_each_entry(fa, &f->fn_alias, fa_list) {
                  struct fib_info *next_fi = fa->fa_info;

                  if (fa->fa_scope != res->scope ||
                      fa->fa_type != RTN_UNICAST)
                        continue;

                  if (next_fi->fib_priority > res->fi->fib_priority)
                        break;
                  if (!next_fi->fib_nh[0].nh_gw ||
                      next_fi->fib_nh[0].nh_scope != RT_SCOPE_LINK)
                        continue;
                  fa->fa_state |= FA_S_ACCESSED;

                  if (fi == NULL) {
                        if (next_fi != res->fi)
                              break;
                  } else if (!fib_detect_death(fi, order, &last_resort,
                                         &last_idx, &fn_hash_last_dflt)) {
                        if (res->fi)
                              fib_info_put(res->fi);
                        res->fi = fi;
                        atomic_inc(&fi->fib_clntref);
                        fn_hash_last_dflt = order;
                        goto out;
                  }
                  fi = next_fi;
                  order++;
            }
      }

      if (order <= 0 || fi == NULL) {
            fn_hash_last_dflt = -1;
            goto out;
      }

      if (!fib_detect_death(fi, order, &last_resort, &last_idx, &fn_hash_last_dflt)) {
            if (res->fi)
                  fib_info_put(res->fi);
            res->fi = fi;
            atomic_inc(&fi->fib_clntref);
            fn_hash_last_dflt = order;
            goto out;
      }

      if (last_idx >= 0) {
            if (res->fi)
                  fib_info_put(res->fi);
            res->fi = last_resort;
            if (last_resort)
                  atomic_inc(&last_resort->fib_clntref);
      }
      fn_hash_last_dflt = last_idx;
out:
      read_unlock(&fib_hash_lock);
}

/* Insert node F to FZ. */
static inline void fib_insert_node(struct fn_zone *fz, struct fib_node *f)
{
      struct hlist_head *head = &fz->fz_hash[fn_hash(f->fn_key, fz)];

      hlist_add_head(&f->fn_hash, head);
}

/* Return the node in FZ matching KEY. */
static struct fib_node *fib_find_node(struct fn_zone *fz, __be32 key)
{
      struct hlist_head *head = &fz->fz_hash[fn_hash(key, fz)];
      struct hlist_node *node;
      struct fib_node *f;

      hlist_for_each_entry(f, node, head, fn_hash) {
            if (f->fn_key == key)
                  return f;
      }

      return NULL;
}

static int fn_hash_insert(struct fib_table *tb, struct fib_config *cfg)
{
      struct fn_hash *table = (struct fn_hash *) tb->tb_data;
      struct fib_node *new_f, *f;
      struct fib_alias *fa, *new_fa;
      struct fn_zone *fz;
      struct fib_info *fi;
      u8 tos = cfg->fc_tos;
      __be32 key;
      int err;

      if (cfg->fc_dst_len > 32)
            return -EINVAL;

      fz = table->fn_zones[cfg->fc_dst_len];
      if (!fz && !(fz = fn_new_zone(table, cfg->fc_dst_len)))
            return -ENOBUFS;

      key = 0;
      if (cfg->fc_dst) {
            if (cfg->fc_dst & ~FZ_MASK(fz))
                  return -EINVAL;
            key = fz_key(cfg->fc_dst, fz);
      }

      fi = fib_create_info(cfg);
      if (IS_ERR(fi))
            return PTR_ERR(fi);

      if (fz->fz_nent > (fz->fz_divisor<<1) &&
          fz->fz_divisor < FZ_MAX_DIVISOR &&
          (cfg->fc_dst_len == 32 ||
           (1 << cfg->fc_dst_len) > fz->fz_divisor))
            fn_rehash_zone(fz);

      f = fib_find_node(fz, key);

      if (!f)
            fa = NULL;
      else
            fa = fib_find_alias(&f->fn_alias, tos, fi->fib_priority);

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

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

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

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

                  if (fi->fib_treeref > 1)
                        goto out;

                  write_lock_bh(&fib_hash_lock);
                  fi_drop = fa->fa_info;
                  fa->fa_info = fi;
                  fa->fa_type = cfg->fc_type;
                  fa->fa_scope = cfg->fc_scope;
                  state = fa->fa_state;
                  fa->fa_state &= ~FA_S_ACCESSED;
                  fib_hash_genid++;
                  write_unlock_bh(&fib_hash_lock);

                  fib_release_info(fi_drop);
                  if (state & FA_S_ACCESSED)
                        rt_cache_flush(-1);
                  rtmsg_fib(RTM_NEWROUTE, key, fa, cfg->fc_dst_len, tb->tb_id,
                          &cfg->fc_nlinfo, NLM_F_REPLACE);
                  return 0;
            }

            /* Error if we find a perfect match which
             * uses the same scope, type, and nexthop
             * information.
             */
            fa_orig = fa;
            fa = list_entry(fa->fa_list.prev, struct fib_alias, fa_list);
            list_for_each_entry_continue(fa, &f->fn_alias, fa_list) {
                  if (fa->fa_tos != tos)
                        break;
                  if (fa->fa_info->fib_priority != fi->fib_priority)
                        break;
                  if (fa->fa_type == cfg->fc_type &&
                      fa->fa_scope == cfg->fc_scope &&
                      fa->fa_info == fi)
                        goto out;
            }
            if (!(cfg->fc_nlflags & NLM_F_APPEND))
                  fa = fa_orig;
      }

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

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

      new_f = NULL;
      if (!f) {
            new_f = kmem_cache_alloc(fn_hash_kmem, GFP_KERNEL);
            if (new_f == NULL)
                  goto out_free_new_fa;

            INIT_HLIST_NODE(&new_f->fn_hash);
            INIT_LIST_HEAD(&new_f->fn_alias);
            new_f->fn_key = key;
            f = new_f;
      }

      new_fa->fa_info = fi;
      new_fa->fa_tos = tos;
      new_fa->fa_type = cfg->fc_type;
      new_fa->fa_scope = cfg->fc_scope;
      new_fa->fa_state = 0;

      /*
       * Insert new entry to the list.
       */

      write_lock_bh(&fib_hash_lock);
      if (new_f)
            fib_insert_node(fz, new_f);
      list_add_tail(&new_fa->fa_list,
             (fa ? &fa->fa_list : &f->fn_alias));
      fib_hash_genid++;
      write_unlock_bh(&fib_hash_lock);

      if (new_f)
            fz->fz_nent++;
      rt_cache_flush(-1);

      rtmsg_fib(RTM_NEWROUTE, key, new_fa, cfg->fc_dst_len, tb->tb_id,
              &cfg->fc_nlinfo, 0);
      return 0;

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


static int fn_hash_delete(struct fib_table *tb, struct fib_config *cfg)
{
      struct fn_hash *table = (struct fn_hash*)tb->tb_data;
      struct fib_node *f;
      struct fib_alias *fa, *fa_to_delete;
      struct fn_zone *fz;
      __be32 key;

      if (cfg->fc_dst_len > 32)
            return -EINVAL;

      if ((fz  = table->fn_zones[cfg->fc_dst_len]) == NULL)
            return -ESRCH;

      key = 0;
      if (cfg->fc_dst) {
            if (cfg->fc_dst & ~FZ_MASK(fz))
                  return -EINVAL;
            key = fz_key(cfg->fc_dst, fz);
      }

      f = fib_find_node(fz, key);

      if (!f)
            fa = NULL;
      else
            fa = fib_find_alias(&f->fn_alias, cfg->fc_tos, 0);
      if (!fa)
            return -ESRCH;

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

            if (fa->fa_tos != cfg->fc_tos)
                  break;

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

      if (fa_to_delete) {
            int kill_fn;

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

            kill_fn = 0;
            write_lock_bh(&fib_hash_lock);
            list_del(&fa->fa_list);
            if (list_empty(&f->fn_alias)) {
                  hlist_del(&f->fn_hash);
                  kill_fn = 1;
            }
            fib_hash_genid++;
            write_unlock_bh(&fib_hash_lock);

            if (fa->fa_state & FA_S_ACCESSED)
                  rt_cache_flush(-1);
            fn_free_alias(fa);
            if (kill_fn) {
                  fn_free_node(f);
                  fz->fz_nent--;
            }

            return 0;
      }
      return -ESRCH;
}

static int fn_flush_list(struct fn_zone *fz, int idx)
{
      struct hlist_head *head = &fz->fz_hash[idx];
      struct hlist_node *node, *n;
      struct fib_node *f;
      int found = 0;

      hlist_for_each_entry_safe(f, node, n, head, fn_hash) {
            struct fib_alias *fa, *fa_node;
            int kill_f;

            kill_f = 0;
            list_for_each_entry_safe(fa, fa_node, &f->fn_alias, fa_list) {
                  struct fib_info *fi = fa->fa_info;

                  if (fi && (fi->fib_flags&RTNH_F_DEAD)) {
                        write_lock_bh(&fib_hash_lock);
                        list_del(&fa->fa_list);
                        if (list_empty(&f->fn_alias)) {
                              hlist_del(&f->fn_hash);
                              kill_f = 1;
                        }
                        fib_hash_genid++;
                        write_unlock_bh(&fib_hash_lock);

                        fn_free_alias(fa);
                        found++;
                  }
            }
            if (kill_f) {
                  fn_free_node(f);
                  fz->fz_nent--;
            }
      }
      return found;
}

static int fn_hash_flush(struct fib_table *tb)
{
      struct fn_hash *table = (struct fn_hash *) tb->tb_data;
      struct fn_zone *fz;
      int found = 0;

      for (fz = table->fn_zone_list; fz; fz = fz->fz_next) {
            int i;

            for (i = fz->fz_divisor - 1; i >= 0; i--)
                  found += fn_flush_list(fz, i);
      }
      return found;
}


static inline int
fn_hash_dump_bucket(struct sk_buff *skb, struct netlink_callback *cb,
                 struct fib_table *tb,
                 struct fn_zone *fz,
                 struct hlist_head *head)
{
      struct hlist_node *node;
      struct fib_node *f;
      int i, s_i;

      s_i = cb->args[4];
      i = 0;
      hlist_for_each_entry(f, node, head, fn_hash) {
            struct fib_alias *fa;

            list_for_each_entry(fa, &f->fn_alias, fa_list) {
                  if (i < s_i)
                        goto next;

                  if (fib_dump_info(skb, NETLINK_CB(cb->skb).pid,
                                cb->nlh->nlmsg_seq,
                                RTM_NEWROUTE,
                                tb->tb_id,
                                fa->fa_type,
                                fa->fa_scope,
                                f->fn_key,
                                fz->fz_order,
                                fa->fa_tos,
                                fa->fa_info,
                                NLM_F_MULTI) < 0) {
                        cb->args[4] = i;
                        return -1;
                  }
            next:
                  i++;
            }
      }
      cb->args[4] = i;
      return skb->len;
}

static inline int
fn_hash_dump_zone(struct sk_buff *skb, struct netlink_callback *cb,
               struct fib_table *tb,
               struct fn_zone *fz)
{
      int h, s_h;

      if (fz->fz_hash == NULL)
            return skb->len;
      s_h = cb->args[3];
      for (h = s_h; h < fz->fz_divisor; h++) {
            if (hlist_empty(&fz->fz_hash[h]))
                  continue;
            if (fn_hash_dump_bucket(skb, cb, tb, fz, &fz->fz_hash[h]) < 0) {
                  cb->args[3] = h;
                  return -1;
            }
            memset(&cb->args[4], 0,
                   sizeof(cb->args) - 4*sizeof(cb->args[0]));
      }
      cb->args[3] = h;
      return skb->len;
}

static int fn_hash_dump(struct fib_table *tb, struct sk_buff *skb, struct netlink_callback *cb)
{
      int m, s_m;
      struct fn_zone *fz;
      struct fn_hash *table = (struct fn_hash*)tb->tb_data;

      s_m = cb->args[2];
      read_lock(&fib_hash_lock);
      for (fz = table->fn_zone_list, m=0; fz; fz = fz->fz_next, m++) {
            if (m < s_m) continue;
            if (fn_hash_dump_zone(skb, cb, tb, fz) < 0) {
                  cb->args[2] = m;
                  read_unlock(&fib_hash_lock);
                  return -1;
            }
            memset(&cb->args[3], 0,
                   sizeof(cb->args) - 3*sizeof(cb->args[0]));
      }
      read_unlock(&fib_hash_lock);
      cb->args[2] = m;
      return skb->len;
}

#ifdef CONFIG_IP_MULTIPLE_TABLES
struct fib_table * fib_hash_init(u32 id)
#else
struct fib_table * __init fib_hash_init(u32 id)
#endif
{
      struct fib_table *tb;

      if (fn_hash_kmem == NULL)
            fn_hash_kmem = kmem_cache_create("ip_fib_hash",
                                     sizeof(struct fib_node),
                                     0, SLAB_HWCACHE_ALIGN,
                                     NULL);

      if (fn_alias_kmem == NULL)
            fn_alias_kmem = kmem_cache_create("ip_fib_alias",
                                      sizeof(struct fib_alias),
                                      0, SLAB_HWCACHE_ALIGN,
                                      NULL);

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

      tb->tb_id = id;
      tb->tb_lookup = fn_hash_lookup;
      tb->tb_insert = fn_hash_insert;
      tb->tb_delete = fn_hash_delete;
      tb->tb_flush = fn_hash_flush;
      tb->tb_select_default = fn_hash_select_default;
      tb->tb_dump = fn_hash_dump;
      memset(tb->tb_data, 0, sizeof(struct fn_hash));
      return tb;
}

/* ------------------------------------------------------------------------ */
#ifdef CONFIG_PROC_FS

struct fib_iter_state {
      struct fn_zone    *zone;
      int         bucket;
      struct hlist_head *hash_head;
      struct fib_node *fn;
      struct fib_alias *fa;
      loff_t pos;
      unsigned int genid;
      int valid;
};

static struct fib_alias *fib_get_first(struct seq_file *seq)
{
      struct fib_iter_state *iter = seq->private;
      struct fn_hash *table = (struct fn_hash *) ip_fib_main_table->tb_data;

      iter->bucket    = 0;
      iter->hash_head = NULL;
      iter->fn        = NULL;
      iter->fa        = NULL;
      iter->pos   = 0;
      iter->genid = fib_hash_genid;
      iter->valid = 1;

      for (iter->zone = table->fn_zone_list; iter->zone;
           iter->zone = iter->zone->fz_next) {
            int maxslot;

            if (!iter->zone->fz_nent)
                  continue;

            iter->hash_head = iter->zone->fz_hash;
            maxslot = iter->zone->fz_divisor;

            for (iter->bucket = 0; iter->bucket < maxslot;
                 ++iter->bucket, ++iter->hash_head) {
                  struct hlist_node *node;
                  struct fib_node *fn;

                  hlist_for_each_entry(fn,node,iter->hash_head,fn_hash) {
                        struct fib_alias *fa;

                        list_for_each_entry(fa,&fn->fn_alias,fa_list) {
                              iter->fn = fn;
                              iter->fa = fa;
                              goto out;
                        }
                  }
            }
      }
out:
      return iter->fa;
}

static struct fib_alias *fib_get_next(struct seq_file *seq)
{
      struct fib_iter_state *iter = seq->private;
      struct fib_node *fn;
      struct fib_alias *fa;

      /* Advance FA, if any. */
      fn = iter->fn;
      fa = iter->fa;
      if (fa) {
            BUG_ON(!fn);
            list_for_each_entry_continue(fa, &fn->fn_alias, fa_list) {
                  iter->fa = fa;
                  goto out;
            }
      }

      fa = iter->fa = NULL;

      /* Advance FN. */
      if (fn) {
            struct hlist_node *node = &fn->fn_hash;
            hlist_for_each_entry_continue(fn, node, fn_hash) {
                  iter->fn = fn;

                  list_for_each_entry(fa, &fn->fn_alias, fa_list) {
                        iter->fa = fa;
                        goto out;
                  }
            }
      }

      fn = iter->fn = NULL;

      /* Advance hash chain. */
      if (!iter->zone)
            goto out;

      for (;;) {
            struct hlist_node *node;
            int maxslot;

            maxslot = iter->zone->fz_divisor;

            while (++iter->bucket < maxslot) {
                  iter->hash_head++;

                  hlist_for_each_entry(fn, node, iter->hash_head, fn_hash) {
                        list_for_each_entry(fa, &fn->fn_alias, fa_list) {
                              iter->fn = fn;
                              iter->fa = fa;
                              goto out;
                        }
                  }
            }

            iter->zone = iter->zone->fz_next;

            if (!iter->zone)
                  goto out;

            iter->bucket = 0;
            iter->hash_head = iter->zone->fz_hash;

            hlist_for_each_entry(fn, node, iter->hash_head, fn_hash) {
                  list_for_each_entry(fa, &fn->fn_alias, fa_list) {
                        iter->fn = fn;
                        iter->fa = fa;
                        goto out;
                  }
            }
      }
out:
      iter->pos++;
      return fa;
}

static struct fib_alias *fib_get_idx(struct seq_file *seq, loff_t pos)
{
      struct fib_iter_state *iter = seq->private;
      struct fib_alias *fa;

      if (iter->valid && pos >= iter->pos && iter->genid == fib_hash_genid) {
            fa   = iter->fa;
            pos -= iter->pos;
      } else
            fa = fib_get_first(seq);

      if (fa)
            while (pos && (fa = fib_get_next(seq)))
                  --pos;
      return pos ? NULL : fa;
}

static void *fib_seq_start(struct seq_file *seq, loff_t *pos)
{
      void *v = NULL;

      read_lock(&fib_hash_lock);
      if (ip_fib_main_table)
            v = *pos ? fib_get_idx(seq, *pos - 1) : SEQ_START_TOKEN;
      return v;
}

static void *fib_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
      ++*pos;
      return v == SEQ_START_TOKEN ? fib_get_first(seq) : fib_get_next(seq);
}

static void fib_seq_stop(struct seq_file *seq, void *v)
{
      read_unlock(&fib_hash_lock);
}

static unsigned fib_flag_trans(int type, __be32 mask, struct fib_info *fi)
{
      static const unsigned type2flags[RTN_MAX + 1] = {
            [7] = RTF_REJECT, [8] = RTF_REJECT,
      };
      unsigned flags = type2flags[type];

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

/*
 *    This outputs /proc/net/route.
 *
 *    It always works in backward compatibility mode.
 *    The format of the file is not supposed to be changed.
 */
static int fib_seq_show(struct seq_file *seq, void *v)
{
      struct fib_iter_state *iter;
      char bf[128];
      __be32 prefix, mask;
      unsigned flags;
      struct fib_node *f;
      struct fib_alias *fa;
      struct fib_info *fi;

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

      iter  = seq->private;
      f     = iter->fn;
      fa    = iter->fa;
      fi    = fa->fa_info;
      prefix      = f->fn_key;
      mask  = FZ_MASK(iter->zone);
      flags = fib_flag_trans(fa->fa_type, mask, fi);
      if (fi)
            snprintf(bf, sizeof(bf),
                   "%s\t%08X\t%08X\t%04X\t%d\t%u\t%d\t%08X\t%d\t%u\t%u",
                   fi->fib_dev ? fi->fib_dev->name : "*", prefix,
                   fi->fib_nh->nh_gw, flags, 0, 0, fi->fib_priority,
                   mask, (fi->fib_advmss ? fi->fib_advmss + 40 : 0),
                   fi->fib_window,
                   fi->fib_rtt >> 3);
      else
            snprintf(bf, sizeof(bf),
                   "*\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_printf(seq, "%-127s\n", bf);
out:
      return 0;
}

static const struct seq_operations fib_seq_ops = {
      .start  = fib_seq_start,
      .next   = fib_seq_next,
      .stop   = fib_seq_stop,
      .show   = fib_seq_show,
};

static int fib_seq_open(struct inode *inode, struct file *file)
{
      return seq_open_private(file, &fib_seq_ops,
                  sizeof(struct fib_iter_state));
}

static const struct file_operations fib_seq_fops = {
      .owner            = THIS_MODULE,
      .open           = fib_seq_open,
      .read           = seq_read,
      .llseek         = seq_lseek,
      .release    = seq_release_private,
};

int __init fib_proc_init(void)
{
      if (!proc_net_fops_create(&init_net, "route", S_IRUGO, &fib_seq_fops))
            return -ENOMEM;
      return 0;
}

void __init fib_proc_exit(void)
{
      proc_net_remove(&init_net, "route");
}
#endif /* CONFIG_PROC_FS */

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