xref: /linux/net/netfilter/nf_conntrack_ecache.c (revision d6fd48ef) 
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 int nf_conntrack_eventmask_report(unsigned int events, struct nf_conn *ct,
166 				  u32 portid, int report)
167 {
168 	struct nf_conntrack_ecache *e;
169 	struct nf_ct_event item;
170 	unsigned int missed;
171 	int ret;
172 
173 	if (!nf_ct_is_confirmed(ct))
174 		return 0;
175 
176 	e = nf_ct_ecache_find(ct);
177 	if (!e)
178 		return 0;
179 
180 	memset(&item, 0, sizeof(item));
181 
182 	item.ct = ct;
183 	item.portid = e->portid ? e->portid : portid;
184 	item.report = report;
185 
186 	/* This is a resent of a destroy event? If so, skip missed */
187 	missed = e->portid ? 0 : e->missed;
188 
189 	ret = __nf_conntrack_eventmask_report(e, events, missed, &item);
190 	if (unlikely(ret < 0 && (events & (1 << IPCT_DESTROY)))) {
191 		/* This is a destroy event that has been triggered by a process,
192 		 * we store the PORTID to include it in the retransmission.
193 		 */
194 		if (e->portid == 0 && portid != 0)
195 			e->portid = portid;
196 	}
197 
198 	return ret;
199 }
200 EXPORT_SYMBOL_GPL(nf_conntrack_eventmask_report);
201 
202 /* deliver cached events and clear cache entry - must be called with locally
203  * disabled softirqs */
204 void nf_ct_deliver_cached_events(struct nf_conn *ct)
205 {
206 	struct nf_conntrack_ecache *e;
207 	struct nf_ct_event item;
208 	unsigned int events;
209 
210 	if (!nf_ct_is_confirmed(ct) || nf_ct_is_dying(ct))
211 		return;
212 
213 	e = nf_ct_ecache_find(ct);
214 	if (e == NULL)
215 		return;
216 
217 	events = xchg(&e->cache, 0);
218 
219 	item.ct = ct;
220 	item.portid = 0;
221 	item.report = 0;
222 
223 	/* We make a copy of the missed event cache without taking
224 	 * the lock, thus we may send missed events twice. However,
225 	 * this does not harm and it happens very rarely.
226 	 */
227 	__nf_conntrack_eventmask_report(e, events, e->missed, &item);
228 }
229 EXPORT_SYMBOL_GPL(nf_ct_deliver_cached_events);
230 
231 void nf_ct_expect_event_report(enum ip_conntrack_expect_events event,
232 			       struct nf_conntrack_expect *exp,
233 			       u32 portid, int report)
234 
235 {
236 	struct net *net = nf_ct_exp_net(exp);
237 	struct nf_ct_event_notifier *notify;
238 	struct nf_conntrack_ecache *e;
239 
240 	rcu_read_lock();
241 	notify = rcu_dereference(net->ct.nf_conntrack_event_cb);
242 	if (!notify)
243 		goto out_unlock;
244 
245 	e = nf_ct_ecache_find(exp->master);
246 	if (!e)
247 		goto out_unlock;
248 
249 	if (e->expmask & (1 << event)) {
250 		struct nf_exp_event item = {
251 			.exp	= exp,
252 			.portid	= portid,
253 			.report = report
254 		};
255 		notify->exp_event(1 << event, &item);
256 	}
257 out_unlock:
258 	rcu_read_unlock();
259 }
260 
261 void nf_conntrack_register_notifier(struct net *net,
262 				    const struct nf_ct_event_notifier *new)
263 {
264 	struct nf_ct_event_notifier *notify;
265 
266 	mutex_lock(&nf_ct_ecache_mutex);
267 	notify = rcu_dereference_protected(net->ct.nf_conntrack_event_cb,
268 					   lockdep_is_held(&nf_ct_ecache_mutex));
269 	WARN_ON_ONCE(notify);
270 	rcu_assign_pointer(net->ct.nf_conntrack_event_cb, new);
271 	mutex_unlock(&nf_ct_ecache_mutex);
272 }
273 EXPORT_SYMBOL_GPL(nf_conntrack_register_notifier);
274 
275 void nf_conntrack_unregister_notifier(struct net *net)
276 {
277 	mutex_lock(&nf_ct_ecache_mutex);
278 	RCU_INIT_POINTER(net->ct.nf_conntrack_event_cb, NULL);
279 	mutex_unlock(&nf_ct_ecache_mutex);
280 	/* synchronize_rcu() is called after netns pre_exit */
281 }
282 EXPORT_SYMBOL_GPL(nf_conntrack_unregister_notifier);
283 
284 void nf_conntrack_ecache_work(struct net *net, enum nf_ct_ecache_state state)
285 {
286 	struct nf_conntrack_net *cnet = nf_ct_pernet(net);
287 
288 	if (state == NFCT_ECACHE_DESTROY_FAIL &&
289 	    !delayed_work_pending(&cnet->ecache.dwork)) {
290 		schedule_delayed_work(&cnet->ecache.dwork, HZ);
291 		net->ct.ecache_dwork_pending = true;
292 	} else if (state == NFCT_ECACHE_DESTROY_SENT) {
293 		if (!hlist_nulls_empty(&cnet->ecache.dying_list))
294 			mod_delayed_work(system_wq, &cnet->ecache.dwork, 0);
295 		else
296 			net->ct.ecache_dwork_pending = false;
297 	}
298 }
299 
300 bool nf_ct_ecache_ext_add(struct nf_conn *ct, u16 ctmask, u16 expmask, gfp_t gfp)
301 {
302 	struct net *net = nf_ct_net(ct);
303 	struct nf_conntrack_ecache *e;
304 
305 	switch (net->ct.sysctl_events) {
306 	case 0:
307 		 /* assignment via template / ruleset? ignore sysctl. */
308 		if (ctmask || expmask)
309 			break;
310 		return true;
311 	case 2: /* autodetect: no event listener, don't allocate extension. */
312 		if (!READ_ONCE(nf_ctnetlink_has_listener))
313 			return true;
314 		fallthrough;
315 	case 1:
316 		/* always allocate an extension. */
317 		if (!ctmask && !expmask) {
318 			ctmask = ~0;
319 			expmask = ~0;
320 		}
321 		break;
322 	default:
323 		WARN_ON_ONCE(1);
324 		return true;
325 	}
326 
327 	e = nf_ct_ext_add(ct, NF_CT_EXT_ECACHE, gfp);
328 	if (e) {
329 		e->ctmask  = ctmask;
330 		e->expmask = expmask;
331 	}
332 
333 	return e != NULL;
334 }
335 EXPORT_SYMBOL_GPL(nf_ct_ecache_ext_add);
336 
337 #define NF_CT_EVENTS_DEFAULT 2
338 static int nf_ct_events __read_mostly = NF_CT_EVENTS_DEFAULT;
339 
340 void nf_conntrack_ecache_pernet_init(struct net *net)
341 {
342 	struct nf_conntrack_net *cnet = nf_ct_pernet(net);
343 
344 	net->ct.sysctl_events = nf_ct_events;
345 
346 	INIT_DELAYED_WORK(&cnet->ecache.dwork, ecache_work);
347 	INIT_HLIST_NULLS_HEAD(&cnet->ecache.dying_list, DYING_NULLS_VAL);
348 	spin_lock_init(&cnet->ecache.dying_lock);
349 
350 	BUILD_BUG_ON(__IPCT_MAX >= 16);	/* e->ctmask is u16 */
351 }
352 
353 void nf_conntrack_ecache_pernet_fini(struct net *net)
354 {
355 	struct nf_conntrack_net *cnet = nf_ct_pernet(net);
356 
357 	cancel_delayed_work_sync(&cnet->ecache.dwork);
358 }
359