1// SPDX-License-Identifier: GPL-2.0
2
3#include <linux/types.h>
4#include <linux/atomic.h>
5#include <linux/inetdevice.h>
6#include <linux/netfilter.h>
7#include <linux/netfilter_ipv4.h>
8#include <linux/netfilter_ipv6.h>
9
10#include <net/netfilter/nf_nat_masquerade.h>
11
12struct masq_dev_work {
13 struct work_struct work;
14 struct net *net;
15 netns_tracker ns_tracker;
16 union nf_inet_addr addr;
17 int ifindex;
18 int (*iter)(struct nf_conn *i, void *data);
19};
20
21#define MAX_MASQ_WORKER_COUNT 16
22
23static DEFINE_MUTEX(masq_mutex);
24static unsigned int masq_refcnt __read_mostly;
25static atomic_t masq_worker_count __read_mostly;
26
27unsigned int
28nf_nat_masquerade_ipv4(struct sk_buff *skb, unsigned int hooknum,
29 const struct nf_nat_range2 *range,
30 const struct net_device *out)
31{
32 struct nf_conn *ct;
33 struct nf_conn_nat *nat;
34 enum ip_conntrack_info ctinfo;
35 struct nf_nat_range2 newrange;
36 const struct rtable *rt;
37 __be32 newsrc, nh;
38
39 WARN_ON(hooknum != NF_INET_POST_ROUTING);
40
41 ct = nf_ct_get(skb, ctinfo: &ctinfo);
42
43 WARN_ON(!(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED ||
44 ctinfo == IP_CT_RELATED_REPLY)));
45
46 /* Source address is 0.0.0.0 - locally generated packet that is
47 * probably not supposed to be masqueraded.
48 */
49 if (ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip == 0)
50 return NF_ACCEPT;
51
52 rt = skb_rtable(skb);
53 nh = rt_nexthop(rt, daddr: ip_hdr(skb)->daddr);
54 newsrc = inet_select_addr(dev: out, dst: nh, scope: RT_SCOPE_UNIVERSE);
55 if (!newsrc) {
56 pr_info("%s ate my IP address\n", out->name);
57 return NF_DROP;
58 }
59
60 nat = nf_ct_nat_ext_add(ct);
61 if (nat)
62 nat->masq_index = out->ifindex;
63
64 /* Transfer from original range. */
65 memset(s: &newrange.min_addr, c: 0, n: sizeof(newrange.min_addr));
66 memset(s: &newrange.max_addr, c: 0, n: sizeof(newrange.max_addr));
67 newrange.flags = range->flags | NF_NAT_RANGE_MAP_IPS;
68 newrange.min_addr.ip = newsrc;
69 newrange.max_addr.ip = newsrc;
70 newrange.min_proto = range->min_proto;
71 newrange.max_proto = range->max_proto;
72
73 /* Hand modified range to generic setup. */
74 return nf_nat_setup_info(ct, range: &newrange, maniptype: NF_NAT_MANIP_SRC);
75}
76EXPORT_SYMBOL_GPL(nf_nat_masquerade_ipv4);
77
78static void iterate_cleanup_work(struct work_struct *work)
79{
80 struct nf_ct_iter_data iter_data = {};
81 struct masq_dev_work *w;
82
83 w = container_of(work, struct masq_dev_work, work);
84
85 iter_data.net = w->net;
86 iter_data.data = (void *)w;
87 nf_ct_iterate_cleanup_net(iter: w->iter, iter_data: &iter_data);
88
89 put_net_track(net: w->net, tracker: &w->ns_tracker);
90 kfree(objp: w);
91 atomic_dec(v: &masq_worker_count);
92 module_put(THIS_MODULE);
93}
94
95/* Iterate conntrack table in the background and remove conntrack entries
96 * that use the device/address being removed.
97 *
98 * In case too many work items have been queued already or memory allocation
99 * fails iteration is skipped, conntrack entries will time out eventually.
100 */
101static void nf_nat_masq_schedule(struct net *net, union nf_inet_addr *addr,
102 int ifindex,
103 int (*iter)(struct nf_conn *i, void *data),
104 gfp_t gfp_flags)
105{
106 struct masq_dev_work *w;
107
108 if (atomic_read(v: &masq_worker_count) > MAX_MASQ_WORKER_COUNT)
109 return;
110
111 net = maybe_get_net(net);
112 if (!net)
113 return;
114
115 if (!try_module_get(THIS_MODULE))
116 goto err_module;
117
118 w = kzalloc(sizeof(*w), gfp_flags);
119 if (w) {
120 /* We can overshoot MAX_MASQ_WORKER_COUNT, no big deal */
121 atomic_inc(v: &masq_worker_count);
122
123 INIT_WORK(&w->work, iterate_cleanup_work);
124 w->ifindex = ifindex;
125 w->net = net;
126 netns_tracker_alloc(net, tracker: &w->ns_tracker, gfp: gfp_flags);
127 w->iter = iter;
128 if (addr)
129 w->addr = *addr;
130 schedule_work(work: &w->work);
131 return;
132 }
133
134 module_put(THIS_MODULE);
135 err_module:
136 put_net(net);
137}
138
139static int device_cmp(struct nf_conn *i, void *arg)
140{
141 const struct nf_conn_nat *nat = nfct_nat(ct: i);
142 const struct masq_dev_work *w = arg;
143
144 if (!nat)
145 return 0;
146 return nat->masq_index == w->ifindex;
147}
148
149static int masq_device_event(struct notifier_block *this,
150 unsigned long event,
151 void *ptr)
152{
153 const struct net_device *dev = netdev_notifier_info_to_dev(info: ptr);
154 struct net *net = dev_net(dev);
155
156 if (event == NETDEV_DOWN) {
157 /* Device was downed. Search entire table for
158 * conntracks which were associated with that device,
159 * and forget them.
160 */
161
162 nf_nat_masq_schedule(net, NULL, ifindex: dev->ifindex,
163 iter: device_cmp, GFP_KERNEL);
164 }
165
166 return NOTIFY_DONE;
167}
168
169static int inet_cmp(struct nf_conn *ct, void *ptr)
170{
171 struct nf_conntrack_tuple *tuple;
172 struct masq_dev_work *w = ptr;
173
174 if (!device_cmp(i: ct, arg: ptr))
175 return 0;
176
177 tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
178
179 return nf_inet_addr_cmp(a1: &w->addr, a2: &tuple->dst.u3);
180}
181
182static int masq_inet_event(struct notifier_block *this,
183 unsigned long event,
184 void *ptr)
185{
186 const struct in_ifaddr *ifa = ptr;
187 const struct in_device *idev;
188 const struct net_device *dev;
189 union nf_inet_addr addr;
190
191 if (event != NETDEV_DOWN)
192 return NOTIFY_DONE;
193
194 /* The masq_dev_notifier will catch the case of the device going
195 * down. So if the inetdev is dead and being destroyed we have
196 * no work to do. Otherwise this is an individual address removal
197 * and we have to perform the flush.
198 */
199 idev = ifa->ifa_dev;
200 if (idev->dead)
201 return NOTIFY_DONE;
202
203 memset(s: &addr, c: 0, n: sizeof(addr));
204
205 addr.ip = ifa->ifa_address;
206
207 dev = idev->dev;
208 nf_nat_masq_schedule(net: dev_net(dev: idev->dev), addr: &addr, ifindex: dev->ifindex,
209 iter: inet_cmp, GFP_KERNEL);
210
211 return NOTIFY_DONE;
212}
213
214static struct notifier_block masq_dev_notifier = {
215 .notifier_call = masq_device_event,
216};
217
218static struct notifier_block masq_inet_notifier = {
219 .notifier_call = masq_inet_event,
220};
221
222#if IS_ENABLED(CONFIG_IPV6)
223static int
224nat_ipv6_dev_get_saddr(struct net *net, const struct net_device *dev,
225 const struct in6_addr *daddr, unsigned int srcprefs,
226 struct in6_addr *saddr)
227{
228#ifdef CONFIG_IPV6_MODULE
229 const struct nf_ipv6_ops *v6_ops = nf_get_ipv6_ops();
230
231 if (!v6_ops)
232 return -EHOSTUNREACH;
233
234 return v6_ops->dev_get_saddr(net, dev, daddr, srcprefs, saddr);
235#else
236 return ipv6_dev_get_saddr(net, dev, daddr, srcprefs, saddr);
237#endif
238}
239
240unsigned int
241nf_nat_masquerade_ipv6(struct sk_buff *skb, const struct nf_nat_range2 *range,
242 const struct net_device *out)
243{
244 enum ip_conntrack_info ctinfo;
245 struct nf_conn_nat *nat;
246 struct in6_addr src;
247 struct nf_conn *ct;
248 struct nf_nat_range2 newrange;
249
250 ct = nf_ct_get(skb, ctinfo: &ctinfo);
251 WARN_ON(!(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED ||
252 ctinfo == IP_CT_RELATED_REPLY)));
253
254 if (nat_ipv6_dev_get_saddr(net: nf_ct_net(ct), dev: out,
255 daddr: &ipv6_hdr(skb)->daddr, srcprefs: 0, saddr: &src) < 0)
256 return NF_DROP;
257
258 nat = nf_ct_nat_ext_add(ct);
259 if (nat)
260 nat->masq_index = out->ifindex;
261
262 newrange.flags = range->flags | NF_NAT_RANGE_MAP_IPS;
263 newrange.min_addr.in6 = src;
264 newrange.max_addr.in6 = src;
265 newrange.min_proto = range->min_proto;
266 newrange.max_proto = range->max_proto;
267
268 return nf_nat_setup_info(ct, range: &newrange, maniptype: NF_NAT_MANIP_SRC);
269}
270EXPORT_SYMBOL_GPL(nf_nat_masquerade_ipv6);
271
272/* atomic notifier; can't call nf_ct_iterate_cleanup_net (it can sleep).
273 *
274 * Defer it to the system workqueue.
275 *
276 * As we can have 'a lot' of inet_events (depending on amount of ipv6
277 * addresses being deleted), we also need to limit work item queue.
278 */
279static int masq_inet6_event(struct notifier_block *this,
280 unsigned long event, void *ptr)
281{
282 struct inet6_ifaddr *ifa = ptr;
283 const struct net_device *dev;
284 union nf_inet_addr addr;
285
286 if (event != NETDEV_DOWN)
287 return NOTIFY_DONE;
288
289 dev = ifa->idev->dev;
290
291 memset(s: &addr, c: 0, n: sizeof(addr));
292
293 addr.in6 = ifa->addr;
294
295 nf_nat_masq_schedule(net: dev_net(dev), addr: &addr, ifindex: dev->ifindex, iter: inet_cmp,
296 GFP_ATOMIC);
297 return NOTIFY_DONE;
298}
299
300static struct notifier_block masq_inet6_notifier = {
301 .notifier_call = masq_inet6_event,
302};
303
304static int nf_nat_masquerade_ipv6_register_notifier(void)
305{
306 return register_inet6addr_notifier(nb: &masq_inet6_notifier);
307}
308#else
309static inline int nf_nat_masquerade_ipv6_register_notifier(void) { return 0; }
310#endif
311
312int nf_nat_masquerade_inet_register_notifiers(void)
313{
314 int ret = 0;
315
316 mutex_lock(lock: &masq_mutex);
317 if (WARN_ON_ONCE(masq_refcnt == UINT_MAX)) {
318 ret = -EOVERFLOW;
319 goto out_unlock;
320 }
321
322 /* check if the notifier was already set */
323 if (++masq_refcnt > 1)
324 goto out_unlock;
325
326 /* Register for device down reports */
327 ret = register_netdevice_notifier(nb: &masq_dev_notifier);
328 if (ret)
329 goto err_dec;
330 /* Register IP address change reports */
331 ret = register_inetaddr_notifier(nb: &masq_inet_notifier);
332 if (ret)
333 goto err_unregister;
334
335 ret = nf_nat_masquerade_ipv6_register_notifier();
336 if (ret)
337 goto err_unreg_inet;
338
339 mutex_unlock(lock: &masq_mutex);
340 return ret;
341err_unreg_inet:
342 unregister_inetaddr_notifier(nb: &masq_inet_notifier);
343err_unregister:
344 unregister_netdevice_notifier(nb: &masq_dev_notifier);
345err_dec:
346 masq_refcnt--;
347out_unlock:
348 mutex_unlock(lock: &masq_mutex);
349 return ret;
350}
351EXPORT_SYMBOL_GPL(nf_nat_masquerade_inet_register_notifiers);
352
353void nf_nat_masquerade_inet_unregister_notifiers(void)
354{
355 mutex_lock(lock: &masq_mutex);
356 /* check if the notifiers still have clients */
357 if (--masq_refcnt > 0)
358 goto out_unlock;
359
360 unregister_netdevice_notifier(nb: &masq_dev_notifier);
361 unregister_inetaddr_notifier(nb: &masq_inet_notifier);
362#if IS_ENABLED(CONFIG_IPV6)
363 unregister_inet6addr_notifier(nb: &masq_inet6_notifier);
364#endif
365out_unlock:
366 mutex_unlock(lock: &masq_mutex);
367}
368EXPORT_SYMBOL_GPL(nf_nat_masquerade_inet_unregister_notifiers);
369