fib_hash.c

linux 内核源代码

/*
 * 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, <[e-mail]>
 *
 *		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;