[mirror_ubuntu-artful-kernel.git] / net / netfilter / nf_conntrack_expect.c

/* Expectation handling for nf_conntrack. */

/* (C) 1999-2001 Paul `Rusty' Russell
 * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
 * (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/types.h>
#include <linux/netfilter.h>
#include <linux/skbuff.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/stddef.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/percpu.h>
#include <linux/kernel.h>

#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_core.h>
#include <net/netfilter/nf_conntrack_expect.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_tuple.h>

LIST_HEAD(nf_conntrack_expect_list);
kmem_cache_t *nf_conntrack_expect_cachep __read_mostly;
static unsigned int nf_conntrack_expect_next_id;

/* nf_conntrack_expect helper functions */
void nf_ct_unlink_expect(struct nf_conntrack_expect *exp)
{
	struct nf_conn_help *master_help = nfct_help(exp->master);

	NF_CT_ASSERT(master_help);
	NF_CT_ASSERT(!timer_pending(&exp->timeout));

	list_del(&exp->list);
	NF_CT_STAT_INC(expect_delete);
	master_help->expecting--;
	nf_conntrack_expect_put(exp);
}

static void expectation_timed_out(unsigned long ul_expect)
{
	struct nf_conntrack_expect *exp = (void *)ul_expect;

	write_lock_bh(&nf_conntrack_lock);
	nf_ct_unlink_expect(exp);
	write_unlock_bh(&nf_conntrack_lock);
	nf_conntrack_expect_put(exp);
}

struct nf_conntrack_expect *
__nf_conntrack_expect_find(const struct nf_conntrack_tuple *tuple)
{
	struct nf_conntrack_expect *i;

	list_for_each_entry(i, &nf_conntrack_expect_list, list) {
		if (nf_ct_tuple_mask_cmp(tuple, &i->tuple, &i->mask))
			return i;
	}
	return NULL;
}

/* Just find a expectation corresponding to a tuple. */
struct nf_conntrack_expect *
nf_conntrack_expect_find_get(const struct nf_conntrack_tuple *tuple)
{
	struct nf_conntrack_expect *i;

	read_lock_bh(&nf_conntrack_lock);
	i = __nf_conntrack_expect_find(tuple);
	if (i)
		atomic_inc(&i->use);
	read_unlock_bh(&nf_conntrack_lock);

	return i;
}

/* If an expectation for this connection is found, it gets delete from
 * global list then returned. */
struct nf_conntrack_expect *
find_expectation(const struct nf_conntrack_tuple *tuple)
{
	struct nf_conntrack_expect *i;

	list_for_each_entry(i, &nf_conntrack_expect_list, list) {
	/* If master is not in hash table yet (ie. packet hasn't left
	   this machine yet), how can other end know about expected?
	   Hence these are not the droids you are looking for (if
	   master ct never got confirmed, we'd hold a reference to it
	   and weird things would happen to future packets). */
		if (nf_ct_tuple_mask_cmp(tuple, &i->tuple, &i->mask)
		    && nf_ct_is_confirmed(i->master)) {
			if (i->flags & NF_CT_EXPECT_PERMANENT) {
				atomic_inc(&i->use);
				return i;
			} else if (del_timer(&i->timeout)) {
				nf_ct_unlink_expect(i);
				return i;
			}
		}
	}
	return NULL;
}

/* delete all expectations for this conntrack */
void nf_ct_remove_expectations(struct nf_conn *ct)
{
	struct nf_conntrack_expect *i, *tmp;
	struct nf_conn_help *help = nfct_help(ct);

	/* Optimization: most connection never expect any others. */
	if (!help || help->expecting == 0)
		return;

	list_for_each_entry_safe(i, tmp, &nf_conntrack_expect_list, list) {
		if (i->master == ct && del_timer(&i->timeout)) {
			nf_ct_unlink_expect(i);
			nf_conntrack_expect_put(i);
 		}
	}
}

/* Would two expected things clash? */
static inline int expect_clash(const struct nf_conntrack_expect *a,
			       const struct nf_conntrack_expect *b)
{
	/* Part covered by intersection of masks must be unequal,
	   otherwise they clash */
	struct nf_conntrack_tuple intersect_mask;
	int count;

	intersect_mask.src.l3num = a->mask.src.l3num & b->mask.src.l3num;
	intersect_mask.src.u.all = a->mask.src.u.all & b->mask.src.u.all;
	intersect_mask.dst.u.all = a->mask.dst.u.all & b->mask.dst.u.all;
	intersect_mask.dst.protonum = a->mask.dst.protonum
					& b->mask.dst.protonum;

	for (count = 0; count < NF_CT_TUPLE_L3SIZE; count++){
		intersect_mask.src.u3.all[count] =
			a->mask.src.u3.all[count] & b->mask.src.u3.all[count];
	}

	for (count = 0; count < NF_CT_TUPLE_L3SIZE; count++){
		intersect_mask.dst.u3.all[count] =
			a->mask.dst.u3.all[count] & b->mask.dst.u3.all[count];
	}

	return nf_ct_tuple_mask_cmp(&a->tuple, &b->tuple, &intersect_mask);
}

static inline int expect_matches(const struct nf_conntrack_expect *a,
				 const struct nf_conntrack_expect *b)
{
	return a->master == b->master
		&& nf_ct_tuple_equal(&a->tuple, &b->tuple)
		&& nf_ct_tuple_equal(&a->mask, &b->mask);
}

/* Generally a bad idea to call this: could have matched already. */
void nf_conntrack_unexpect_related(struct nf_conntrack_expect *exp)
{
	struct nf_conntrack_expect *i;

	write_lock_bh(&nf_conntrack_lock);
	/* choose the the oldest expectation to evict */
	list_for_each_entry_reverse(i, &nf_conntrack_expect_list, list) {
		if (expect_matches(i, exp) && del_timer(&i->timeout)) {
			nf_ct_unlink_expect(i);
			write_unlock_bh(&nf_conntrack_lock);
			nf_conntrack_expect_put(i);
			return;
		}
	}
	write_unlock_bh(&nf_conntrack_lock);
}

/* We don't increase the master conntrack refcount for non-fulfilled
 * conntracks. During the conntrack destruction, the expectations are
 * always killed before the conntrack itself */
struct nf_conntrack_expect *nf_conntrack_expect_alloc(struct nf_conn *me)
{
	struct nf_conntrack_expect *new;

	new = kmem_cache_alloc(nf_conntrack_expect_cachep, GFP_ATOMIC);
	if (!new)
		return NULL;

	new->master = me;
	atomic_set(&new->use, 1);
	return new;
}

void nf_conntrack_expect_put(struct nf_conntrack_expect *exp)
{
	if (atomic_dec_and_test(&exp->use))
		kmem_cache_free(nf_conntrack_expect_cachep, exp);
}

static void nf_conntrack_expect_insert(struct nf_conntrack_expect *exp)
{
	struct nf_conn_help *master_help = nfct_help(exp->master);

	atomic_inc(&exp->use);
	master_help->expecting++;
	list_add(&exp->list, &nf_conntrack_expect_list);

	init_timer(&exp->timeout);
	exp->timeout.data = (unsigned long)exp;
	exp->timeout.function = expectation_timed_out;
	exp->timeout.expires = jiffies + master_help->helper->timeout * HZ;
	add_timer(&exp->timeout);

	exp->id = ++nf_conntrack_expect_next_id;
	atomic_inc(&exp->use);
	NF_CT_STAT_INC(expect_create);
}

/* Race with expectations being used means we could have none to find; OK. */
static void evict_oldest_expect(struct nf_conn *master)
{
	struct nf_conntrack_expect *i;

	list_for_each_entry_reverse(i, &nf_conntrack_expect_list, list) {
		if (i->master == master) {
			if (del_timer(&i->timeout)) {
				nf_ct_unlink_expect(i);
				nf_conntrack_expect_put(i);
			}
			break;
		}
	}
}

static inline int refresh_timer(struct nf_conntrack_expect *i)
{
	struct nf_conn_help *master_help = nfct_help(i->master);

	if (!del_timer(&i->timeout))
		return 0;

	i->timeout.expires = jiffies + master_help->helper->timeout*HZ;
	add_timer(&i->timeout);
	return 1;
}

int nf_conntrack_expect_related(struct nf_conntrack_expect *expect)
{
	struct nf_conntrack_expect *i;
	struct nf_conn *master = expect->master;
	struct nf_conn_help *master_help = nfct_help(master);
	int ret;

	NF_CT_ASSERT(master_help);

	write_lock_bh(&nf_conntrack_lock);
	list_for_each_entry(i, &nf_conntrack_expect_list, list) {
		if (expect_matches(i, expect)) {
			/* Refresh timer: if it's dying, ignore.. */
			if (refresh_timer(i)) {
				ret = 0;
				goto out;
			}
		} else if (expect_clash(i, expect)) {
			ret = -EBUSY;
			goto out;
		}
	}
	/* Will be over limit? */
	if (master_help->helper->max_expected &&
	    master_help->expecting >= master_help->helper->max_expected)
		evict_oldest_expect(master);

	nf_conntrack_expect_insert(expect);
	nf_conntrack_expect_event(IPEXP_NEW, expect);
	ret = 0;
out:
	write_unlock_bh(&nf_conntrack_lock);
	return ret;
}

#ifdef CONFIG_PROC_FS
static void *exp_seq_start(struct seq_file *s, loff_t *pos)
{
	struct list_head *e = &nf_conntrack_expect_list;
	loff_t i;

	/* strange seq_file api calls stop even if we fail,
	 * thus we need to grab lock since stop unlocks */
	read_lock_bh(&nf_conntrack_lock);

	if (list_empty(e))
		return NULL;

	for (i = 0; i <= *pos; i++) {
		e = e->next;
		if (e == &nf_conntrack_expect_list)
			return NULL;
	}
	return e;
}

static void *exp_seq_next(struct seq_file *s, void *v, loff_t *pos)
{
	struct list_head *e = v;

	++*pos;
	e = e->next;

	if (e == &nf_conntrack_expect_list)
		return NULL;

	return e;
}

static void exp_seq_stop(struct seq_file *s, void *v)
{
	read_unlock_bh(&nf_conntrack_lock);
}

static int exp_seq_show(struct seq_file *s, void *v)
{
	struct nf_conntrack_expect *expect = v;

	if (expect->timeout.function)
		seq_printf(s, "%ld ", timer_pending(&expect->timeout)
			   ? (long)(expect->timeout.expires - jiffies)/HZ : 0);
	else
		seq_printf(s, "- ");
	seq_printf(s, "l3proto = %u proto=%u ",
		   expect->tuple.src.l3num,
		   expect->tuple.dst.protonum);
	print_tuple(s, &expect->tuple,
		    __nf_ct_l3proto_find(expect->tuple.src.l3num),
		    __nf_ct_l4proto_find(expect->tuple.src.l3num,
				       expect->tuple.dst.protonum));
	return seq_putc(s, '\n');
}

static struct seq_operations exp_seq_ops = {
	.start = exp_seq_start,
	.next = exp_seq_next,
	.stop = exp_seq_stop,
	.show = exp_seq_show
};

static int exp_open(struct inode *inode, struct file *file)
{
	return seq_open(file, &exp_seq_ops);
}

struct file_operations exp_file_ops = {
	.owner   = THIS_MODULE,
	.open    = exp_open,
	.read    = seq_read,
	.llseek  = seq_lseek,
	.release = seq_release
};
#endif /* CONFIG_PROC_FS */
Commit	Line	Data
77ab9cff MJ	1	/* Expectation handling for nf_conntrack. */
	2
	3	/* (C) 1999-2001 Paul `Rusty' Russell
	4	* (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
	5	* (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>
	6	*
	7	* This program is free software; you can redistribute it and/or modify
	8	* it under the terms of the GNU General Public License version 2 as
	9	* published by the Free Software Foundation.
	10	*/
	11
	12	#include <linux/types.h>
	13	#include <linux/netfilter.h>
	14	#include <linux/skbuff.h>
	15	#include <linux/proc_fs.h>
	16	#include <linux/seq_file.h>
	17	#include <linux/stddef.h>
	18	#include <linux/slab.h>
	19	#include <linux/err.h>
	20	#include <linux/percpu.h>
	21	#include <linux/kernel.h>
	22
	23	#include <net/netfilter/nf_conntrack.h>
	24	#include <net/netfilter/nf_conntrack_core.h>
	25	#include <net/netfilter/nf_conntrack_expect.h>
	26	#include <net/netfilter/nf_conntrack_helper.h>
	27	#include <net/netfilter/nf_conntrack_tuple.h>
	28
	29	LIST_HEAD(nf_conntrack_expect_list);
	30	kmem_cache_t *nf_conntrack_expect_cachep __read_mostly;
77ab9cff MJ	31	static unsigned int nf_conntrack_expect_next_id;
	32
	33	/* nf_conntrack_expect helper functions */
	34	void nf_ct_unlink_expect(struct nf_conntrack_expect *exp)
	35	{
	36	struct nf_conn_help *master_help = nfct_help(exp->master);
	37
	38	NF_CT_ASSERT(master_help);
	39	NF_CT_ASSERT(!timer_pending(&exp->timeout));
	40
	41	list_del(&exp->list);
	42	NF_CT_STAT_INC(expect_delete);
	43	master_help->expecting--;
	44	nf_conntrack_expect_put(exp);
	45	}
	46
	47	static void expectation_timed_out(unsigned long ul_expect)
	48	{
	49	struct nf_conntrack_expect exp = (void )ul_expect;
	50
	51	write_lock_bh(&nf_conntrack_lock);
	52	nf_ct_unlink_expect(exp);
	53	write_unlock_bh(&nf_conntrack_lock);
	54	nf_conntrack_expect_put(exp);
	55	}
	56
	57	struct nf_conntrack_expect *
	58	__nf_conntrack_expect_find(const struct nf_conntrack_tuple *tuple)
	59	{
	60	struct nf_conntrack_expect *i;
	61
	62	list_for_each_entry(i, &nf_conntrack_expect_list, list) {
	63	if (nf_ct_tuple_mask_cmp(tuple, &i->tuple, &i->mask))
	64	return i;
	65	}
	66	return NULL;
	67	}
	68
	69	/* Just find a expectation corresponding to a tuple. */
	70	struct nf_conntrack_expect *
468ec44b	71	nf_conntrack_expect_find_get(const struct nf_conntrack_tuple *tuple)
77ab9cff MJ	72	{
	73	struct nf_conntrack_expect *i;
	74
	75	read_lock_bh(&nf_conntrack_lock);
	76	i = __nf_conntrack_expect_find(tuple);
	77	if (i)
	78	atomic_inc(&i->use);
	79	read_unlock_bh(&nf_conntrack_lock);
	80
	81	return i;
	82	}
	83
	84	/* If an expectation for this connection is found, it gets delete from
	85	* global list then returned. */
	86	struct nf_conntrack_expect *
	87	find_expectation(const struct nf_conntrack_tuple *tuple)
	88	{
	89	struct nf_conntrack_expect *i;
	90
	91	list_for_each_entry(i, &nf_conntrack_expect_list, list) {
	92	/* If master is not in hash table yet (ie. packet hasn't left
	93	this machine yet), how can other end know about expected?
	94	Hence these are not the droids you are looking for (if
	95	master ct never got confirmed, we'd hold a reference to it
	96	and weird things would happen to future packets). */
	97	if (nf_ct_tuple_mask_cmp(tuple, &i->tuple, &i->mask)
	98	&& nf_ct_is_confirmed(i->master)) {
	99	if (i->flags & NF_CT_EXPECT_PERMANENT) {
	100	atomic_inc(&i->use);
	101	return i;
	102	} else if (del_timer(&i->timeout)) {
	103	nf_ct_unlink_expect(i);
	104	return i;
	105	}
	106	}
	107	}
	108	return NULL;
	109	}
	110
	111	/* delete all expectations for this conntrack */
	112	void nf_ct_remove_expectations(struct nf_conn *ct)
	113	{
	114	struct nf_conntrack_expect i, tmp;
	115	struct nf_conn_help *help = nfct_help(ct);
	116
	117	/* Optimization: most connection never expect any others. */
	118	if (!help \|\| help->expecting == 0)
	119	return;
	120
	121	list_for_each_entry_safe(i, tmp, &nf_conntrack_expect_list, list) {
	122	if (i->master == ct && del_timer(&i->timeout)) {
	123	nf_ct_unlink_expect(i);
	124	nf_conntrack_expect_put(i);
	125	}
	126	}
	127	}
	128
	129	/* Would two expected things clash? */
	130	static inline int expect_clash(const struct nf_conntrack_expect *a,
	131	const struct nf_conntrack_expect *b)
	132	{
	133	/* Part covered by intersection of masks must be unequal,
	134	otherwise they clash */
	135	struct nf_conntrack_tuple intersect_mask;
136	int count;
137
138	intersect_mask.src.l3num = a->mask.src.l3num & b->mask.src.l3num;
139	intersect_mask.src.u.all = a->mask.src.u.all & b->mask.src.u.all;
140	intersect_mask.dst.u.all = a->mask.dst.u.all & b->mask.dst.u.all;
141	intersect_mask.dst.protonum = a->mask.dst.protonum
142	& b->mask.dst.protonum;
143
144	for (count = 0; count < NF_CT_TUPLE_L3SIZE; count++){
145	intersect_mask.src.u3.all[count] =
146	a->mask.src.u3.all[count] & b->mask.src.u3.all[count];
147	}
148
149	for (count = 0; count < NF_CT_TUPLE_L3SIZE; count++){
150	intersect_mask.dst.u3.all[count] =
151	a->mask.dst.u3.all[count] & b->mask.dst.u3.all[count];
152	}
153
154	return nf_ct_tuple_mask_cmp(&a->tuple, &b->tuple, &intersect_mask);
155	}
156
157	static inline int expect_matches(const struct nf_conntrack_expect *a,
158	const struct nf_conntrack_expect *b)
159	{
160	return a->master == b->master
161	&& nf_ct_tuple_equal(&a->tuple, &b->tuple)
162	&& nf_ct_tuple_equal(&a->mask, &b->mask);
163	}
164
165	/* Generally a bad idea to call this: could have matched already. */
166	void nf_conntrack_unexpect_related(struct nf_conntrack_expect *exp)
167	{
168	struct nf_conntrack_expect *i;
169
170	write_lock_bh(&nf_conntrack_lock);
171	/* choose the the oldest expectation to evict */
172	list_for_each_entry_reverse(i, &nf_conntrack_expect_list, list) {
173	if (expect_matches(i, exp) && del_timer(&i->timeout)) {
174	nf_ct_unlink_expect(i);
175	write_unlock_bh(&nf_conntrack_lock);
176	nf_conntrack_expect_put(i);
177	return;
178	}
179	}
180	write_unlock_bh(&nf_conntrack_lock);
181	}
182
183	/* We don't increase the master conntrack refcount for non-fulfilled
184	* conntracks. During the conntrack destruction, the expectations are
185	* always killed before the conntrack itself */
186	struct nf_conntrack_expect nf_conntrack_expect_alloc(struct nf_conn me)
187	{
188	struct nf_conntrack_expect *new;
189
190	new = kmem_cache_alloc(nf_conntrack_expect_cachep, GFP_ATOMIC);
191	if (!new)
192	return NULL;
193
194	new->master = me;
195	atomic_set(&new->use, 1);
196	return new;
197	}
198
199	void nf_conntrack_expect_put(struct nf_conntrack_expect *exp)
200	{
201	if (atomic_dec_and_test(&exp->use))
202	kmem_cache_free(nf_conntrack_expect_cachep, exp);
203	}
204
205	static void nf_conntrack_expect_insert(struct nf_conntrack_expect *exp)
206	{
207	struct nf_conn_help *master_help = nfct_help(exp->master);
208
209	atomic_inc(&exp->use);
210	master_help->expecting++;
211	list_add(&exp->list, &nf_conntrack_expect_list);
212
213	init_timer(&exp->timeout);
214	exp->timeout.data = (unsigned long)exp;
215	exp->timeout.function = expectation_timed_out;
216	exp->timeout.expires = jiffies + master_help->helper->timeout * HZ;
217	add_timer(&exp->timeout);
218
219	exp->id = ++nf_conntrack_expect_next_id;
220	atomic_inc(&exp->use);
221	NF_CT_STAT_INC(expect_create);
222	}
223
224	/* Race with expectations being used means we could have none to find; OK. */
225	static void evict_oldest_expect(struct nf_conn *master)
226	{
227	struct nf_conntrack_expect *i;
228
229	list_for_each_entry_reverse(i, &nf_conntrack_expect_list, list) {
230	if (i->master == master) {
231	if (del_timer(&i->timeout)) {
232	nf_ct_unlink_expect(i);
233	nf_conntrack_expect_put(i);
234	}
235	break;
236	}
237	}
238	}
239
240	static inline int refresh_timer(struct nf_conntrack_expect *i)
241	{
242	struct nf_conn_help *master_help = nfct_help(i->master);
243
244	if (!del_timer(&i->timeout))
245	return 0;
246
247	i->timeout.expires = jiffies + master_help->helper->timeout*HZ;
248	add_timer(&i->timeout);
249	return 1;
250	}
251
252	int nf_conntrack_expect_related(struct nf_conntrack_expect *expect)
253	{
254	struct nf_conntrack_expect *i;
255	struct nf_conn *master = expect->master;
256	struct nf_conn_help *master_help = nfct_help(master);
257	int ret;
258
259	NF_CT_ASSERT(master_help);
260
261	write_lock_bh(&nf_conntrack_lock);
262	list_for_each_entry(i, &nf_conntrack_expect_list, list) {
263	if (expect_matches(i, expect)) {
264	/* Refresh timer: if it's dying, ignore.. */
265	if (refresh_timer(i)) {
266	ret = 0;
267	goto out;
268	}
269	} else if (expect_clash(i, expect)) {
270	ret = -EBUSY;
271	goto out;
272	}
273	}
274	/* Will be over limit? */
275	if (master_help->helper->max_expected &&
276	master_help->expecting >= master_help->helper->max_expected)
277	evict_oldest_expect(master);
278
279	nf_conntrack_expect_insert(expect);
280	nf_conntrack_expect_event(IPEXP_NEW, expect);
281	ret = 0;
282	out:
283	write_unlock_bh(&nf_conntrack_lock);
284	return ret;
285	}
286
287	#ifdef CONFIG_PROC_FS
288	static void exp_seq_start(struct seq_file s, loff_t *pos)
289	{
290	struct list_head *e = &nf_conntrack_expect_list;
291	loff_t i;
292
293	/* strange seq_file api calls stop even if we fail,
294	* thus we need to grab lock since stop unlocks */
295	read_lock_bh(&nf_conntrack_lock);
296
297	if (list_empty(e))
298	return NULL;
299
300	for (i = 0; i <= *pos; i++) {
301	e = e->next;
302	if (e == &nf_conntrack_expect_list)
303	return NULL;
304	}
305	return e;
306	}
307
308	static void exp_seq_next(struct seq_file s, void v, loff_t pos)
309	{
310	struct list_head *e = v;
311
312	++*pos;
313	e = e->next;
314
315	if (e == &nf_conntrack_expect_list)
316	return NULL;
317
318	return e;
319	}
320
321	static void exp_seq_stop(struct seq_file s, void v)
322	{
323	read_unlock_bh(&nf_conntrack_lock);
324	}
325
326	static int exp_seq_show(struct seq_file s, void v)
327	{
328	struct nf_conntrack_expect *expect = v;
329
330	if (expect->timeout.function)
331	seq_printf(s, "%ld ", timer_pending(&expect->timeout)
332	? (long)(expect->timeout.expires - jiffies)/HZ : 0);
333	else
334	seq_printf(s, "- ");
335	seq_printf(s, "l3proto = %u proto=%u ",
336	expect->tuple.src.l3num,
337	expect->tuple.dst.protonum);
338	print_tuple(s, &expect->tuple,
339	__nf_ct_l3proto_find(expect->tuple.src.l3num),
605dcad6	340	__nf_ct_l4proto_find(expect->tuple.src.l3num,
77ab9cff MJ	341	expect->tuple.dst.protonum));
	342	return seq_putc(s, '\n');
	343	}
	344
	345	static struct seq_operations exp_seq_ops = {
	346	.start = exp_seq_start,
	347	.next = exp_seq_next,
	348	.stop = exp_seq_stop,
	349	.show = exp_seq_show
	350	};
	351
	352	static int exp_open(struct inode inode, struct file file)
	353	{
	354	return seq_open(file, &exp_seq_ops);
	355	}
	356
	357	struct file_operations exp_file_ops = {
	358	.owner = THIS_MODULE,
	359	.open = exp_open,
	360	.read = seq_read,
	361	.llseek = seq_lseek,
	362	.release = seq_release
	363	};
	364	#endif /* CONFIG_PROC_FS */