aboutsummaryrefslogtreecommitdiff
path: root/net/netfilter/nfnetlink.c
blob: 4bc27a6334c169690650dd900031fde729b35b73 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
/* Netfilter messages via netlink socket. Allows for user space
 * protocol helpers and general trouble making from userspace.
 *
 * (C) 2001 by Jay Schulist <jschlst@samba.org>,
 * (C) 2002-2005 by Harald Welte <laforge@gnumonks.org>
 * (C) 2005 by Pablo Neira Ayuso <pablo@eurodev.net>
 *
 * Initial netfilter messages via netlink development funded and
 * generally made possible by Network Robots, Inc. (www.networkrobots.com)
 *
 * Further development of this code funded by Astaro AG (http://www.astaro.com)
 *
 * This software may be used and distributed according to the terms
 * of the GNU General Public License, incorporated herein by reference.
 */

#include <linux/config.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/kernel.h>
#include <linux/major.h>
#include <linux/sched.h>
#include <linux/timer.h>
#include <linux/string.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/fcntl.h>
#include <linux/skbuff.h>
#include <asm/uaccess.h>
#include <asm/system.h>
#include <net/sock.h>
#include <linux/init.h>
#include <linux/spinlock.h>

#include <linux/netfilter.h>
#include <linux/netlink.h>
#include <linux/netfilter/nfnetlink.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NETFILTER);

static char __initdata nfversion[] = "0.30";

#if 0
#define DEBUGP(format, args...)	\
		printk(KERN_DEBUG "%s(%d):%s(): " format, __FILE__, \
			__LINE__, __FUNCTION__, ## args)
#else
#define DEBUGP(format, args...)
#endif

static struct sock *nfnl = NULL;
static struct nfnetlink_subsystem *subsys_table[NFNL_SUBSYS_COUNT];
DECLARE_MUTEX(nfnl_sem);

void nfnl_lock(void)
{
	nfnl_shlock();
}

void nfnl_unlock(void)
{
	nfnl_shunlock();
}

int nfnetlink_subsys_register(struct nfnetlink_subsystem *n)
{
	DEBUGP("registering subsystem ID %u\n", n->subsys_id);

	nfnl_lock();
	if (subsys_table[n->subsys_id]) {
		nfnl_unlock();
		return -EBUSY;
	}
	subsys_table[n->subsys_id] = n;
	nfnl_unlock();

	return 0;
}

int nfnetlink_subsys_unregister(struct nfnetlink_subsystem *n)
{
	DEBUGP("unregistering subsystem ID %u\n", n->subsys_id);

	nfnl_lock();
	subsys_table[n->subsys_id] = NULL;
	nfnl_unlock();

	return 0;
}

static inline struct nfnetlink_subsystem *nfnetlink_get_subsys(u_int16_t type)
{
	u_int8_t subsys_id = NFNL_SUBSYS_ID(type);

	if (subsys_id >= NFNL_SUBSYS_COUNT
	    || subsys_table[subsys_id] == NULL)
		return NULL;

	return subsys_table[subsys_id];
}

static inline struct nfnl_callback *
nfnetlink_find_client(u_int16_t type, struct nfnetlink_subsystem *ss)
{
	u_int8_t cb_id = NFNL_MSG_TYPE(type);
	
	if (cb_id >= ss->cb_count) {
		DEBUGP("msgtype %u >= %u, returning\n", type, ss->cb_count);
		return NULL;
	}

	return &ss->cb[cb_id];
}

void __nfa_fill(struct sk_buff *skb, int attrtype, int attrlen,
		const void *data)
{
	struct nfattr *nfa;
	int size = NFA_LENGTH(attrlen);

	nfa = (struct nfattr *)skb_put(skb, NFA_ALIGN(size));
	nfa->nfa_type = attrtype;
	nfa->nfa_len  = size;
	memcpy(NFA_DATA(nfa), data, attrlen);
	memset(NFA_DATA(nfa) + attrlen, 0, NFA_ALIGN(size) - size);
}

int nfattr_parse(struct nfattr *tb[], int maxattr, struct nfattr *nfa, int len)
{
	memset(tb, 0, sizeof(struct nfattr *) * maxattr);

	while (NFA_OK(nfa, len)) {
		unsigned flavor = NFA_TYPE(nfa);
		if (flavor && flavor <= maxattr)
			tb[flavor-1] = nfa;
		nfa = NFA_NEXT(nfa, len);
	}

	return 0;
}

/**
 * nfnetlink_check_attributes - check and parse nfnetlink attributes
 *
 * subsys: nfnl subsystem for which this message is to be parsed
 * nlmsghdr: netlink message to be checked/parsed
 * cda: array of pointers, needs to be at least subsys->attr_count big
 *
 */
static int
nfnetlink_check_attributes(struct nfnetlink_subsystem *subsys,
			   struct nlmsghdr *nlh, struct nfattr *cda[])
{
	int min_len;
	u_int16_t attr_count;
	u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);

	if (unlikely(cb_id >= subsys->cb_count)) {
		DEBUGP("msgtype %u >= %u, returning\n",
			cb_id, subsys->cb_count);
		return -EINVAL;
	}

	min_len = NLMSG_ALIGN(sizeof(struct nfgenmsg));
	if (unlikely(nlh->nlmsg_len < min_len))
		return -EINVAL;

	attr_count = subsys->cb[cb_id].attr_count;
	memset(cda, 0, sizeof(struct nfattr *) * attr_count);

	/* check attribute lengths. */
	if (likely(nlh->nlmsg_len > min_len)) {
		struct nfattr *attr = NFM_NFA(NLMSG_DATA(nlh));
		int attrlen = nlh->nlmsg_len - NLMSG_ALIGN(min_len);

		while (NFA_OK(attr, attrlen)) {
			unsigned flavor = NFA_TYPE(attr);
			if (flavor) {
				if (flavor > attr_count)
					return -EINVAL;
				cda[flavor - 1] = attr;
			}
			attr = NFA_NEXT(attr, attrlen);
		}
	}

	/* implicit: if nlmsg_len == min_len, we return 0, and an empty
	 * (zeroed) cda[] array. The message is valid, but empty. */

        return 0;
}

int nfnetlink_send(struct sk_buff *skb, u32 pid, unsigned group, int echo)
{
	gfp_t allocation = in_interrupt() ? GFP_ATOMIC : GFP_KERNEL;
	int err = 0;

	NETLINK_CB(skb).dst_group = group;
	if (echo)
		atomic_inc(&skb->users);
	netlink_broadcast(nfnl, skb, pid, group, allocation);
	if (echo)
		err = netlink_unicast(nfnl, skb, pid, MSG_DONTWAIT);

	return err;
}

int nfnetlink_unicast(struct sk_buff *skb, u_int32_t pid, int flags)
{
	return netlink_unicast(nfnl, skb, pid, flags);
}

/* Process one complete nfnetlink message. */
static inline int nfnetlink_rcv_msg(struct sk_buff *skb,
				    struct nlmsghdr *nlh, int *errp)
{
	struct nfnl_callback *nc;
	struct nfnetlink_subsystem *ss;
	int type, err = 0;

	DEBUGP("entered; subsys=%u, msgtype=%u\n",
		 NFNL_SUBSYS_ID(nlh->nlmsg_type),
		 NFNL_MSG_TYPE(nlh->nlmsg_type));

	/* Only requests are handled by kernel now. */
	if (!(nlh->nlmsg_flags & NLM_F_REQUEST)) {
		DEBUGP("received non-request message\n");
		return 0;
	}

	/* All the messages must at least contain nfgenmsg */
	if (nlh->nlmsg_len < 
			NLMSG_LENGTH(NLMSG_ALIGN(sizeof(struct nfgenmsg)))) {
		DEBUGP("received message was too short\n");
		return 0;
	}

	type = nlh->nlmsg_type;
	ss = nfnetlink_get_subsys(type);
	if (!ss) {
#ifdef CONFIG_KMOD
		/* don't call nfnl_shunlock, since it would reenter
		 * with further packet processing */
		up(&nfnl_sem);
		request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
		nfnl_shlock();
		ss = nfnetlink_get_subsys(type);
		if (!ss)
#endif
		goto err_inval;
	}

	nc = nfnetlink_find_client(type, ss);
	if (!nc) {
		DEBUGP("unable to find client for type %d\n", type);
		goto err_inval;
	}

	if (nc->cap_required && 
	    !cap_raised(NETLINK_CB(skb).eff_cap, nc->cap_required)) {
		DEBUGP("permission denied for type %d\n", type);
		*errp = -EPERM;
		return -1;
	}

	{
		u_int16_t attr_count = 
			ss->cb[NFNL_MSG_TYPE(nlh->nlmsg_type)].attr_count;
		struct nfattr *cda[attr_count];

		memset(cda, 0, sizeof(struct nfattr *) * attr_count);
		
		err = nfnetlink_check_attributes(ss, nlh, cda);
		if (err < 0)
			goto err_inval;

		DEBUGP("calling handler\n");
		err = nc->call(nfnl, skb, nlh, cda, errp);
		*errp = err;
		return err;
	}

err_inval:
	DEBUGP("returning -EINVAL\n");
	*errp = -EINVAL;
	return -1;
}

/* Process one packet of messages. */
static inline int nfnetlink_rcv_skb(struct sk_buff *skb)
{
	int err;
	struct nlmsghdr *nlh;

	while (skb->len >= NLMSG_SPACE(0)) {
		u32 rlen;

		nlh = (struct nlmsghdr *)skb->data;
		if (nlh->nlmsg_len < sizeof(struct nlmsghdr)
		    || skb->len < nlh->nlmsg_len)
			return 0;
		rlen = NLMSG_ALIGN(nlh->nlmsg_len);
		if (rlen > skb->len)
			rlen = skb->len;
		if (nfnetlink_rcv_msg(skb, nlh, &err)) {
			if (!err)
				return -1;
			netlink_ack(skb, nlh, err);
		} else
			if (nlh->nlmsg_flags & NLM_F_ACK)
				netlink_ack(skb, nlh, 0);
		skb_pull(skb, rlen);
	}

	return 0;
}

static void nfnetlink_rcv(struct sock *sk, int len)
{
	do {
		struct sk_buff *skb;

		if (nfnl_shlock_nowait())
			return;

		while ((skb = skb_dequeue(&sk->sk_receive_queue)) != NULL) {
			if (nfnetlink_rcv_skb(skb)) {
				if (skb->len)
					skb_queue_head(&sk->sk_receive_queue,
						       skb);
				else
					kfree_skb(skb);
				break;
			}
			kfree_skb(skb);
		}

		/* don't call nfnl_shunlock, since it would reenter
		 * with further packet processing */
		up(&nfnl_sem);
	} while(nfnl && nfnl->sk_receive_queue.qlen);
}

static void __exit nfnetlink_exit(void)
{
	printk("Removing netfilter NETLINK layer.\n");
	sock_release(nfnl->sk_socket);
	return;
}

static int __init nfnetlink_init(void)
{
	printk("Netfilter messages via NETLINK v%s.\n", nfversion);

	nfnl = netlink_kernel_create(NETLINK_NETFILTER, NFNLGRP_MAX,
	                             nfnetlink_rcv, THIS_MODULE);
	if (!nfnl) {
		printk(KERN_ERR "cannot initialize nfnetlink!\n");
		return -1;
	}

	return 0;
}

module_init(nfnetlink_init);
module_exit(nfnetlink_exit);

EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);
EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);
EXPORT_SYMBOL_GPL(nfnetlink_send);
EXPORT_SYMBOL_GPL(nfnetlink_unicast);
EXPORT_SYMBOL_GPL(nfattr_parse);
EXPORT_SYMBOL_GPL(__nfa_fill);