1 // SPDX-License-Identifier: GPL-2.0-only
2 /* Event cache for netfilter. */
3 
4 /*
5  * (C) 2005 Harald Welte <laforge@gnumonks.org>
6  * (C) 2005 Patrick McHardy <kaber@trash.net>
7  * (C) 2005-2006 Netfilter Core Team <coreteam@netfilter.org>
8  * (C) 2005 USAGI/WIDE Project <http://www.linux-ipv6.org>
9  */
10 
11 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
12 
13 #include <linux/types.h>
14 #include <linux/netfilter.h>
15 #include <linux/skbuff.h>
16 #include <linux/vmalloc.h>
17 #include <linux/stddef.h>
18 #include <linux/err.h>
19 #include <linux/kernel.h>
20 #include <linux/netdevice.h>
21 #include <linux/slab.h>
22 #include <linux/export.h>
23 
24 #include <net/netfilter/nf_conntrack.h>
25 #include <net/netfilter/nf_conntrack_core.h>
26 #include <net/netfilter/nf_conntrack_ecache.h>
27 #include <net/netfilter/nf_conntrack_extend.h>
28 
29 static DEFINE_MUTEX(nf_ct_ecache_mutex);
30 
31 #define DYING_NULLS_VAL			((1 << 30) + 1)
32 #define ECACHE_MAX_JIFFIES		msecs_to_jiffies(10)
33 #define ECACHE_RETRY_JIFFIES		msecs_to_jiffies(10)
34 
35 enum retry_state {
36 	STATE_CONGESTED,
37 	STATE_RESTART,
38 	STATE_DONE,
39 };
40 
41 struct nf_conntrack_net_ecache *nf_conn_pernet_ecache(const struct net *net)
42 {
43 	struct nf_conntrack_net *cnet = nf_ct_pernet(net);
44 
45 	return &cnet->ecache;
46 }
47 #if IS_MODULE(CONFIG_NF_CT_NETLINK)
48 EXPORT_SYMBOL_GPL(nf_conn_pernet_ecache);
49 #endif
50 
51 static enum retry_state ecache_work_evict_list(struct nf_conntrack_net *cnet)
52 {
53 	unsigned long stop = jiffies + ECACHE_MAX_JIFFIES;
54 	struct hlist_nulls_head evicted_list;
55 	enum retry_state ret = STATE_DONE;
56 	struct nf_conntrack_tuple_hash *h;
57 	struct hlist_nulls_node *n;
58 	unsigned int sent;
59 
60 	INIT_HLIST_NULLS_HEAD(&evicted_list, DYING_NULLS_VAL);
61 
62 next:
63 	sent = 0;
64 	spin_lock_bh(&cnet->ecache.dying_lock);
65 
66 	hlist_nulls_for_each_entry_safe(h, n, &cnet->ecache.dying_list, hnnode) {
67 		struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(h);
68 
69 		/* The worker owns all entries, ct remains valid until nf_ct_put
70 		 * in the loop below.
71 		 */
72 		if (nf_conntrack_event(IPCT_DESTROY, ct)) {
73 			ret = STATE_CONGESTED;
74 			break;
75 		}
76 
77 		hlist_nulls_del_rcu(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode);
78 		hlist_nulls_add_head(&ct->tuplehash[IP_CT_DIR_REPLY].hnnode, &evicted_list);
79 
80 		if (time_after(stop, jiffies)) {
81 			ret = STATE_RESTART;
82 			break;
83 		}
84 
85 		if (sent++ > 16) {
86 			spin_unlock_bh(&cnet->ecache.dying_lock);
87 			cond_resched();
88 			goto next;
89 		}
90 	}
91 
92 	spin_unlock_bh(&cnet->ecache.dying_lock);
93 
94 	hlist_nulls_for_each_entry_safe(h, n, &evicted_list, hnnode) {
95 		struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(h);
96 
97 		hlist_nulls_del_rcu(&ct->tuplehash[IP_CT_DIR_REPLY].hnnode);
98 		nf_ct_put(ct);
99 
100 		cond_resched();
101 	}
102 
103 	return ret;
104 }
105 
106 static void ecache_work(struct work_struct *work)
107 {
108 	struct nf_conntrack_net *cnet = container_of(work, struct nf_conntrack_net, ecache.dwork.work);
109 	int ret, delay = -1;
110 
111 	ret = ecache_work_evict_list(cnet);
112 	switch (ret) {
113 	case STATE_CONGESTED:
114 		delay = ECACHE_RETRY_JIFFIES;
115 		break;
116 	case STATE_RESTART:
117 		delay = 0;
118 		break;
119 	case STATE_DONE:
120 		break;
121 	}
122 
123 	if (delay >= 0)
124 		schedule_delayed_work(&cnet->ecache.dwork, delay);
125 }
126 
127 static int __nf_conntrack_eventmask_report(struct nf_conntrack_ecache *e,
128 					   const u32 events,
129 					   const u32 missed,
130 					   const struct nf_ct_event *item)
131 {
132 	struct net *net = nf_ct_net(item->ct);
133 	struct nf_ct_event_notifier *notify;
134 	u32 old, want;
135 	int ret;
136 
137 	if (!((events | missed) & e->ctmask))
138 		return 0;
139 
140 	rcu_read_lock();
141 
142 	notify = rcu_dereference(net->ct.nf_conntrack_event_cb);
143 	if (!notify) {
144 		rcu_read_unlock();
145 		return 0;
146 	}
147 
148 	ret = notify->ct_event(events | missed, item);
149 	rcu_read_unlock();
150 
151 	if (likely(ret >= 0 && missed == 0))
152 		return 0;
153 
154 	do {
155 		old = READ_ONCE(e->missed);
156 		if (ret < 0)
157 			want = old | events;
158 		else
159 			want = old & ~missed;
160 	} while (cmpxchg(&e->missed, old, want) != old);
161 
162 	return ret;
163 }
164 
165 static void nf_ct_ecache_tstamp_refresh(struct nf_conntrack_ecache *e)
166 {
167 #ifdef CONFIG_NF_CONNTRACK_TIMESTAMP
168 	if (local64_read(&e->timestamp))
169 		local64_set(&e->timestamp, ktime_get_real_ns());
170 #endif
171 }
172 
173 int nf_conntrack_eventmask_report(unsigned int events, struct nf_conn *ct,
174 				  u32 portid, int report)
175 {
176 	struct nf_conntrack_ecache *e;
177 	struct nf_ct_event item;
178 	unsigned int missed;
179 	int ret;
180 
181 	if (!nf_ct_is_confirmed(ct))
182 		return 0;
183 
184 	e = nf_ct_ecache_find(ct);
185 	if (!e)
186 		return 0;
187 
188 	memset(&item, 0, sizeof(item));
189 
190 	item.ct = ct;
191 	item.portid = e->portid ? e->portid : portid;
192 	item.report = report;
193 
194 	/* This is a resent of a destroy event? If so, skip missed */
195 	missed = e->portid ? 0 : e->missed;
196 
197 	nf_ct_ecache_tstamp_refresh(e);
198 
199 	ret = __nf_conntrack_eventmask_report(e, events, missed, &item);
200 	if (unlikely(ret < 0 && (events & (1 << IPCT_DESTROY)))) {
201 		/* This is a destroy event that has been triggered by a process,
202 		 * we store the PORTID to include it in the retransmission.
203 		 */
204 		if (e->portid == 0 && portid != 0)
205 			e->portid = portid;
206 	}
207 
208 	return ret;
209 }
210 EXPORT_SYMBOL_GPL(nf_conntrack_eventmask_report);
211 
212 /* deliver cached events and clear cache entry - must be called with locally
213  * disabled softirqs */
214 void nf_ct_deliver_cached_events(struct nf_conn *ct)
215 {
216 	struct nf_conntrack_ecache *e;
217 	struct nf_ct_event item;
218 	unsigned int events;
219 
220 	if (!nf_ct_is_confirmed(ct) || nf_ct_is_dying(ct))
221 		return;
222 
223 	e = nf_ct_ecache_find(ct);
224 	if (e == NULL)
225 		return;
226 
227 	events = xchg(&e->cache, 0);
228 
229 	item.ct = ct;
230 	item.portid = 0;
231 	item.report = 0;
232 
233 	/* We make a copy of the missed event cache without taking
234 	 * the lock, thus we may send missed events twice. However,
235 	 * this does not harm and it happens very rarely.
236 	 */
237 	__nf_conntrack_eventmask_report(e, events, e->missed, &item);
238 }
239 EXPORT_SYMBOL_GPL(nf_ct_deliver_cached_events);
240 
241 void nf_ct_expect_event_report(enum ip_conntrack_expect_events event,
242 			       struct nf_conntrack_expect *exp,
243 			       u32 portid, int report)
244 
245 {
246 	struct net *net = nf_ct_exp_net(exp);
247 	struct nf_ct_event_notifier *notify;
248 	struct nf_conntrack_ecache *e;
249 
250 	rcu_read_lock();
251 	notify = rcu_dereference(net->ct.nf_conntrack_event_cb);
252 	if (!notify)
253 		goto out_unlock;
254 
255 	e = nf_ct_ecache_find(exp->master);
256 	if (!e)
257 		goto out_unlock;
258 
259 	if (e->expmask & (1 << event)) {
260 		struct nf_exp_event item = {
261 			.exp	= exp,
262 			.portid	= portid,
263 			.report = report
264 		};
265 		notify->exp_event(1 << event, &item);
266 	}
267 out_unlock:
268 	rcu_read_unlock();
269 }
270 
271 void nf_conntrack_register_notifier(struct net *net,
272 				    const struct nf_ct_event_notifier *new)
273 {
274 	struct nf_ct_event_notifier *notify;
275 
276 	mutex_lock(&nf_ct_ecache_mutex);
277 	notify = rcu_dereference_protected(net->ct.nf_conntrack_event_cb,
278 					   lockdep_is_held(&nf_ct_ecache_mutex));
279 	WARN_ON_ONCE(notify);
280 	rcu_assign_pointer(net->ct.nf_conntrack_event_cb, new);
281 	mutex_unlock(&nf_ct_ecache_mutex);
282 }
283 EXPORT_SYMBOL_GPL(nf_conntrack_register_notifier);
284 
285 void nf_conntrack_unregister_notifier(struct net *net)
286 {
287 	mutex_lock(&nf_ct_ecache_mutex);
288 	RCU_INIT_POINTER(net->ct.nf_conntrack_event_cb, NULL);
289 	mutex_unlock(&nf_ct_ecache_mutex);
290 	/* synchronize_rcu() is called after netns pre_exit */
291 }
292 EXPORT_SYMBOL_GPL(nf_conntrack_unregister_notifier);
293 
294 void nf_conntrack_ecache_work(struct net *net, enum nf_ct_ecache_state state)
295 {
296 	struct nf_conntrack_net *cnet = nf_ct_pernet(net);
297 
298 	if (state == NFCT_ECACHE_DESTROY_FAIL &&
299 	    !delayed_work_pending(&cnet->ecache.dwork)) {
300 		schedule_delayed_work(&cnet->ecache.dwork, HZ);
301 		net->ct.ecache_dwork_pending = true;
302 	} else if (state == NFCT_ECACHE_DESTROY_SENT) {
303 		if (!hlist_nulls_empty(&cnet->ecache.dying_list))
304 			mod_delayed_work(system_wq, &cnet->ecache.dwork, 0);
305 		else
306 			net->ct.ecache_dwork_pending = false;
307 	}
308 }
309 
310 static void nf_ct_ecache_tstamp_new(const struct nf_conn *ct, struct nf_conntrack_ecache *e)
311 {
312 #ifdef CONFIG_NF_CONNTRACK_TIMESTAMP
313 	u64 ts = 0;
314 
315 	if (nf_ct_ext_exist(ct, NF_CT_EXT_TSTAMP))
316 		ts = ktime_get_real_ns();
317 
318 	local64_set(&e->timestamp, ts);
319 #endif
320 }
321 
322 bool nf_ct_ecache_ext_add(struct nf_conn *ct, u16 ctmask, u16 expmask, gfp_t gfp)
323 {
324 	struct net *net = nf_ct_net(ct);
325 	struct nf_conntrack_ecache *e;
326 
327 	switch (net->ct.sysctl_events) {
328 	case 0:
329 		 /* assignment via template / ruleset? ignore sysctl. */
330 		if (ctmask || expmask)
331 			break;
332 		return true;
333 	case 2: /* autodetect: no event listener, don't allocate extension. */
334 		if (!READ_ONCE(nf_ctnetlink_has_listener))
335 			return true;
336 		fallthrough;
337 	case 1:
338 		/* always allocate an extension. */
339 		if (!ctmask && !expmask) {
340 			ctmask = ~0;
341 			expmask = ~0;
342 		}
343 		break;
344 	default:
345 		WARN_ON_ONCE(1);
346 		return true;
347 	}
348 
349 	e = nf_ct_ext_add(ct, NF_CT_EXT_ECACHE, gfp);
350 	if (e) {
351 		nf_ct_ecache_tstamp_new(ct, e);
352 		e->ctmask  = ctmask;
353 		e->expmask = expmask;
354 	}
355 
356 	return e != NULL;
357 }
358 EXPORT_SYMBOL_GPL(nf_ct_ecache_ext_add);
359 
360 #define NF_CT_EVENTS_DEFAULT 2
361 static int nf_ct_events __read_mostly = NF_CT_EVENTS_DEFAULT;
362 
363 void nf_conntrack_ecache_pernet_init(struct net *net)
364 {
365 	struct nf_conntrack_net *cnet = nf_ct_pernet(net);
366 
367 	net->ct.sysctl_events = nf_ct_events;
368 
369 	INIT_DELAYED_WORK(&cnet->ecache.dwork, ecache_work);
370 	INIT_HLIST_NULLS_HEAD(&cnet->ecache.dying_list, DYING_NULLS_VAL);
371 	spin_lock_init(&cnet->ecache.dying_lock);
372 
373 	BUILD_BUG_ON(__IPCT_MAX >= 16);	/* e->ctmask is u16 */
374 }
375 
376 void nf_conntrack_ecache_pernet_fini(struct net *net)
377 {
378 	struct nf_conntrack_net *cnet = nf_ct_pernet(net);
379 
380 	cancel_delayed_work_sync(&cnet->ecache.dwork);
381 }
382