summaryrefslogtreecommitdiff
path: root/net/netfilter/nf_nat_masquerade.c
blob: 1a506b0c6511a8481c5a1fb243b52d7776f08f7e (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
// SPDX-License-Identifier: GPL-2.0

#include <linux/types.h>
#include <linux/atomic.h>
#include <linux/inetdevice.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#include <linux/netfilter_ipv6.h>

#include <net/netfilter/nf_nat_masquerade.h>

struct masq_dev_work {
	struct work_struct work;
	struct net *net;
	netns_tracker ns_tracker;
	union nf_inet_addr addr;
	int ifindex;
	int (*iter)(struct nf_conn *i, void *data);
};

#define MAX_MASQ_WORKER_COUNT	16

static DEFINE_MUTEX(masq_mutex);
static unsigned int masq_refcnt __read_mostly;
static atomic_t masq_worker_count __read_mostly;

unsigned int
nf_nat_masquerade_ipv4(struct sk_buff *skb, unsigned int hooknum,
		       const struct nf_nat_range2 *range,
		       const struct net_device *out)
{
	struct nf_conn *ct;
	struct nf_conn_nat *nat;
	enum ip_conntrack_info ctinfo;
	struct nf_nat_range2 newrange;
	const struct rtable *rt;
	__be32 newsrc, nh;

	WARN_ON(hooknum != NF_INET_POST_ROUTING);

	ct = nf_ct_get(skb, &ctinfo);

	WARN_ON(!(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED ||
			 ctinfo == IP_CT_RELATED_REPLY)));

	/* Source address is 0.0.0.0 - locally generated packet that is
	 * probably not supposed to be masqueraded.
	 */
	if (ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip == 0)
		return NF_ACCEPT;

	rt = skb_rtable(skb);
	nh = rt_nexthop(rt, ip_hdr(skb)->daddr);
	newsrc = inet_select_addr(out, nh, RT_SCOPE_UNIVERSE);
	if (!newsrc) {
		pr_info("%s ate my IP address\n", out->name);
		return NF_DROP;
	}

	nat = nf_ct_nat_ext_add(ct);
	if (nat)
		nat->masq_index = out->ifindex;

	/* Transfer from original range. */
	memset(&newrange.min_addr, 0, sizeof(newrange.min_addr));
	memset(&newrange.max_addr, 0, sizeof(newrange.max_addr));
	newrange.flags       = range->flags | NF_NAT_RANGE_MAP_IPS;
	newrange.min_addr.ip = newsrc;
	newrange.max_addr.ip = newsrc;
	newrange.min_proto   = range->min_proto;
	newrange.max_proto   = range->max_proto;

	/* Hand modified range to generic setup. */
	return nf_nat_setup_info(ct, &newrange, NF_NAT_MANIP_SRC);
}
EXPORT_SYMBOL_GPL(nf_nat_masquerade_ipv4);

static void iterate_cleanup_work(struct work_struct *work)
{
	struct nf_ct_iter_data iter_data = {};
	struct masq_dev_work *w;

	w = container_of(work, struct masq_dev_work, work);

	iter_data.net = w->net;
	iter_data.data = (void *)w;
	nf_ct_iterate_cleanup_net(w->iter, &iter_data);

	put_net_track(w->net, &w->ns_tracker);
	kfree(w);
	atomic_dec(&masq_worker_count);
	module_put(THIS_MODULE);
}

/* Iterate conntrack table in the background and remove conntrack entries
 * that use the device/address being removed.
 *
 * In case too many work items have been queued already or memory allocation
 * fails iteration is skipped, conntrack entries will time out eventually.
 */
static void nf_nat_masq_schedule(struct net *net, union nf_inet_addr *addr,
				 int ifindex,
				 int (*iter)(struct nf_conn *i, void *data),
				 gfp_t gfp_flags)
{
	struct masq_dev_work *w;

	if (atomic_read(&masq_worker_count) > MAX_MASQ_WORKER_COUNT)
		return;

	net = maybe_get_net(net);
	if (!net)
		return;

	if (!try_module_get(THIS_MODULE))
		goto err_module;

	w = kzalloc(sizeof(*w), gfp_flags);
	if (w) {
		/* We can overshoot MAX_MASQ_WORKER_COUNT, no big deal */
		atomic_inc(&masq_worker_count);

		INIT_WORK(&w->work, iterate_cleanup_work);
		w->ifindex = ifindex;
		w->net = net;
		netns_tracker_alloc(net, &w->ns_tracker, gfp_flags);
		w->iter = iter;
		if (addr)
			w->addr = *addr;
		schedule_work(&w->work);
		return;
	}

	module_put(THIS_MODULE);
 err_module:
	put_net(net);
}

static int device_cmp(struct nf_conn *i, void *arg)
{
	const struct nf_conn_nat *nat = nfct_nat(i);
	const struct masq_dev_work *w = arg;

	if (!nat)
		return 0;
	return nat->masq_index == w->ifindex;
}

static int masq_device_event(struct notifier_block *this,
			     unsigned long event,
			     void *ptr)
{
	const struct net_device *dev = netdev_notifier_info_to_dev(ptr);
	struct net *net = dev_net(dev);

	if (event == NETDEV_DOWN) {
		/* Device was downed.  Search entire table for
		 * conntracks which were associated with that device,
		 * and forget them.
		 */

		nf_nat_masq_schedule(net, NULL, dev->ifindex,
				     device_cmp, GFP_KERNEL);
	}

	return NOTIFY_DONE;
}

static int inet_cmp(struct nf_conn *ct, void *ptr)
{
	struct nf_conntrack_tuple *tuple;
	struct masq_dev_work *w = ptr;

	if (!device_cmp(ct, ptr))
		return 0;

	tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;

	return nf_inet_addr_cmp(&w->addr, &tuple->dst.u3);
}

static int masq_inet_event(struct notifier_block *this,
			   unsigned long event,
			   void *ptr)
{
	const struct in_ifaddr *ifa = ptr;
	const struct in_device *idev;
	const struct net_device *dev;
	union nf_inet_addr addr;

	if (event != NETDEV_DOWN)
		return NOTIFY_DONE;

	/* The masq_dev_notifier will catch the case of the device going
	 * down.  So if the inetdev is dead and being destroyed we have
	 * no work to do.  Otherwise this is an individual address removal
	 * and we have to perform the flush.
	 */
	idev = ifa->ifa_dev;
	if (idev->dead)
		return NOTIFY_DONE;

	memset(&addr, 0, sizeof(addr));

	addr.ip = ifa->ifa_address;

	dev = idev->dev;
	nf_nat_masq_schedule(dev_net(idev->dev), &addr, dev->ifindex,
			     inet_cmp, GFP_KERNEL);

	return NOTIFY_DONE;
}

static struct notifier_block masq_dev_notifier = {
	.notifier_call	= masq_device_event,
};

static struct notifier_block masq_inet_notifier = {
	.notifier_call	= masq_inet_event,
};

#if IS_ENABLED(CONFIG_IPV6)
static int
nat_ipv6_dev_get_saddr(struct net *net, const struct net_device *dev,
		       const struct in6_addr *daddr, unsigned int srcprefs,
		       struct in6_addr *saddr)
{
#ifdef CONFIG_IPV6_MODULE
	const struct nf_ipv6_ops *v6_ops = nf_get_ipv6_ops();

	if (!v6_ops)
		return -EHOSTUNREACH;

	return v6_ops->dev_get_saddr(net, dev, daddr, srcprefs, saddr);
#else
	return ipv6_dev_get_saddr(net, dev, daddr, srcprefs, saddr);
#endif
}

unsigned int
nf_nat_masquerade_ipv6(struct sk_buff *skb, const struct nf_nat_range2 *range,
		       const struct net_device *out)
{
	enum ip_conntrack_info ctinfo;
	struct nf_conn_nat *nat;
	struct in6_addr src;
	struct nf_conn *ct;
	struct nf_nat_range2 newrange;

	ct = nf_ct_get(skb, &ctinfo);
	WARN_ON(!(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED ||
			 ctinfo == IP_CT_RELATED_REPLY)));

	if (nat_ipv6_dev_get_saddr(nf_ct_net(ct), out,
				   &ipv6_hdr(skb)->daddr, 0, &src) < 0)
		return NF_DROP;

	nat = nf_ct_nat_ext_add(ct);
	if (nat)
		nat->masq_index = out->ifindex;

	newrange.flags		= range->flags | NF_NAT_RANGE_MAP_IPS;
	newrange.min_addr.in6	= src;
	newrange.max_addr.in6	= src;
	newrange.min_proto	= range->min_proto;
	newrange.max_proto	= range->max_proto;

	return nf_nat_setup_info(ct, &newrange, NF_NAT_MANIP_SRC);
}
EXPORT_SYMBOL_GPL(nf_nat_masquerade_ipv6);

/* atomic notifier; can't call nf_ct_iterate_cleanup_net (it can sleep).
 *
 * Defer it to the system workqueue.
 *
 * As we can have 'a lot' of inet_events (depending on amount of ipv6
 * addresses being deleted), we also need to limit work item queue.
 */
static int masq_inet6_event(struct notifier_block *this,
			    unsigned long event, void *ptr)
{
	struct inet6_ifaddr *ifa = ptr;
	const struct net_device *dev;
	union nf_inet_addr addr;

	if (event != NETDEV_DOWN)
		return NOTIFY_DONE;

	dev = ifa->idev->dev;

	memset(&addr, 0, sizeof(addr));

	addr.in6 = ifa->addr;

	nf_nat_masq_schedule(dev_net(dev), &addr, dev->ifindex, inet_cmp,
			     GFP_ATOMIC);
	return NOTIFY_DONE;
}

static struct notifier_block masq_inet6_notifier = {
	.notifier_call	= masq_inet6_event,
};

static int nf_nat_masquerade_ipv6_register_notifier(void)
{
	return register_inet6addr_notifier(&masq_inet6_notifier);
}
#else
static inline int nf_nat_masquerade_ipv6_register_notifier(void) { return 0; }
#endif

int nf_nat_masquerade_inet_register_notifiers(void)
{
	int ret = 0;

	mutex_lock(&masq_mutex);
	if (WARN_ON_ONCE(masq_refcnt == UINT_MAX)) {
		ret = -EOVERFLOW;
		goto out_unlock;
	}

	/* check if the notifier was already set */
	if (++masq_refcnt > 1)
		goto out_unlock;

	/* Register for device down reports */
	ret = register_netdevice_notifier(&masq_dev_notifier);
	if (ret)
		goto err_dec;
	/* Register IP address change reports */
	ret = register_inetaddr_notifier(&masq_inet_notifier);
	if (ret)
		goto err_unregister;

	ret = nf_nat_masquerade_ipv6_register_notifier();
	if (ret)
		goto err_unreg_inet;

	mutex_unlock(&masq_mutex);
	return ret;
err_unreg_inet:
	unregister_inetaddr_notifier(&masq_inet_notifier);
err_unregister:
	unregister_netdevice_notifier(&masq_dev_notifier);
err_dec:
	masq_refcnt--;
out_unlock:
	mutex_unlock(&masq_mutex);
	return ret;
}
EXPORT_SYMBOL_GPL(nf_nat_masquerade_inet_register_notifiers);

void nf_nat_masquerade_inet_unregister_notifiers(void)
{
	mutex_lock(&masq_mutex);
	/* check if the notifiers still have clients */
	if (--masq_refcnt > 0)
		goto out_unlock;

	unregister_netdevice_notifier(&masq_dev_notifier);
	unregister_inetaddr_notifier(&masq_inet_notifier);
#if IS_ENABLED(CONFIG_IPV6)
	unregister_inet6addr_notifier(&masq_inet6_notifier);
#endif
out_unlock:
	mutex_unlock(&masq_mutex);
}
EXPORT_SYMBOL_GPL(nf_nat_masquerade_inet_unregister_notifiers);