xref: /openbmc/linux/net/ipv4/inet_timewait_sock.c (revision 22246614)
1 /*
2  * INET		An implementation of the TCP/IP protocol suite for the LINUX
3  *		operating system.  INET is implemented using the  BSD Socket
4  *		interface as the means of communication with the user level.
5  *
6  *		Generic TIME_WAIT sockets functions
7  *
8  *		From code orinally in TCP
9  */
10 
11 #include <linux/kernel.h>
12 #include <net/inet_hashtables.h>
13 #include <net/inet_timewait_sock.h>
14 #include <net/ip.h>
15 
16 /* Must be called with locally disabled BHs. */
17 static void __inet_twsk_kill(struct inet_timewait_sock *tw,
18 			     struct inet_hashinfo *hashinfo)
19 {
20 	struct inet_bind_hashbucket *bhead;
21 	struct inet_bind_bucket *tb;
22 	/* Unlink from established hashes. */
23 	rwlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash);
24 
25 	write_lock(lock);
26 	if (hlist_unhashed(&tw->tw_node)) {
27 		write_unlock(lock);
28 		return;
29 	}
30 	__hlist_del(&tw->tw_node);
31 	sk_node_init(&tw->tw_node);
32 	write_unlock(lock);
33 
34 	/* Disassociate with bind bucket. */
35 	bhead = &hashinfo->bhash[inet_bhashfn(tw->tw_num, hashinfo->bhash_size)];
36 	spin_lock(&bhead->lock);
37 	tb = tw->tw_tb;
38 	__hlist_del(&tw->tw_bind_node);
39 	tw->tw_tb = NULL;
40 	inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
41 	spin_unlock(&bhead->lock);
42 #ifdef SOCK_REFCNT_DEBUG
43 	if (atomic_read(&tw->tw_refcnt) != 1) {
44 		printk(KERN_DEBUG "%s timewait_sock %p refcnt=%d\n",
45 		       tw->tw_prot->name, tw, atomic_read(&tw->tw_refcnt));
46 	}
47 #endif
48 	inet_twsk_put(tw);
49 }
50 
51 void inet_twsk_put(struct inet_timewait_sock *tw)
52 {
53 	if (atomic_dec_and_test(&tw->tw_refcnt)) {
54 		struct module *owner = tw->tw_prot->owner;
55 		twsk_destructor((struct sock *)tw);
56 #ifdef SOCK_REFCNT_DEBUG
57 		printk(KERN_DEBUG "%s timewait_sock %p released\n",
58 		       tw->tw_prot->name, tw);
59 #endif
60 		release_net(twsk_net(tw));
61 		kmem_cache_free(tw->tw_prot->twsk_prot->twsk_slab, tw);
62 		module_put(owner);
63 	}
64 }
65 EXPORT_SYMBOL_GPL(inet_twsk_put);
66 
67 /*
68  * Enter the time wait state. This is called with locally disabled BH.
69  * Essentially we whip up a timewait bucket, copy the relevant info into it
70  * from the SK, and mess with hash chains and list linkage.
71  */
72 void __inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk,
73 			   struct inet_hashinfo *hashinfo)
74 {
75 	const struct inet_sock *inet = inet_sk(sk);
76 	const struct inet_connection_sock *icsk = inet_csk(sk);
77 	struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, sk->sk_hash);
78 	rwlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
79 	struct inet_bind_hashbucket *bhead;
80 	/* Step 1: Put TW into bind hash. Original socket stays there too.
81 	   Note, that any socket with inet->num != 0 MUST be bound in
82 	   binding cache, even if it is closed.
83 	 */
84 	bhead = &hashinfo->bhash[inet_bhashfn(inet->num, hashinfo->bhash_size)];
85 	spin_lock(&bhead->lock);
86 	tw->tw_tb = icsk->icsk_bind_hash;
87 	BUG_TRAP(icsk->icsk_bind_hash);
88 	inet_twsk_add_bind_node(tw, &tw->tw_tb->owners);
89 	spin_unlock(&bhead->lock);
90 
91 	write_lock(lock);
92 
93 	/* Step 2: Remove SK from established hash. */
94 	if (__sk_del_node_init(sk))
95 		sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
96 
97 	/* Step 3: Hash TW into TIMEWAIT chain. */
98 	inet_twsk_add_node(tw, &ehead->twchain);
99 	atomic_inc(&tw->tw_refcnt);
100 
101 	write_unlock(lock);
102 }
103 
104 EXPORT_SYMBOL_GPL(__inet_twsk_hashdance);
105 
106 struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk, const int state)
107 {
108 	struct inet_timewait_sock *tw =
109 		kmem_cache_alloc(sk->sk_prot_creator->twsk_prot->twsk_slab,
110 				 GFP_ATOMIC);
111 	if (tw != NULL) {
112 		const struct inet_sock *inet = inet_sk(sk);
113 
114 		/* Give us an identity. */
115 		tw->tw_daddr	    = inet->daddr;
116 		tw->tw_rcv_saddr    = inet->rcv_saddr;
117 		tw->tw_bound_dev_if = sk->sk_bound_dev_if;
118 		tw->tw_num	    = inet->num;
119 		tw->tw_state	    = TCP_TIME_WAIT;
120 		tw->tw_substate	    = state;
121 		tw->tw_sport	    = inet->sport;
122 		tw->tw_dport	    = inet->dport;
123 		tw->tw_family	    = sk->sk_family;
124 		tw->tw_reuse	    = sk->sk_reuse;
125 		tw->tw_hash	    = sk->sk_hash;
126 		tw->tw_ipv6only	    = 0;
127 		tw->tw_prot	    = sk->sk_prot_creator;
128 		twsk_net_set(tw, hold_net(sock_net(sk)));
129 		atomic_set(&tw->tw_refcnt, 1);
130 		inet_twsk_dead_node_init(tw);
131 		__module_get(tw->tw_prot->owner);
132 	}
133 
134 	return tw;
135 }
136 
137 EXPORT_SYMBOL_GPL(inet_twsk_alloc);
138 
139 /* Returns non-zero if quota exceeded.  */
140 static int inet_twdr_do_twkill_work(struct inet_timewait_death_row *twdr,
141 				    const int slot)
142 {
143 	struct inet_timewait_sock *tw;
144 	struct hlist_node *node;
145 	unsigned int killed;
146 	int ret;
147 
148 	/* NOTE: compare this to previous version where lock
149 	 * was released after detaching chain. It was racy,
150 	 * because tw buckets are scheduled in not serialized context
151 	 * in 2.3 (with netfilter), and with softnet it is common, because
152 	 * soft irqs are not sequenced.
153 	 */
154 	killed = 0;
155 	ret = 0;
156 rescan:
157 	inet_twsk_for_each_inmate(tw, node, &twdr->cells[slot]) {
158 		__inet_twsk_del_dead_node(tw);
159 		spin_unlock(&twdr->death_lock);
160 		__inet_twsk_kill(tw, twdr->hashinfo);
161 		inet_twsk_put(tw);
162 		killed++;
163 		spin_lock(&twdr->death_lock);
164 		if (killed > INET_TWDR_TWKILL_QUOTA) {
165 			ret = 1;
166 			break;
167 		}
168 
169 		/* While we dropped twdr->death_lock, another cpu may have
170 		 * killed off the next TW bucket in the list, therefore
171 		 * do a fresh re-read of the hlist head node with the
172 		 * lock reacquired.  We still use the hlist traversal
173 		 * macro in order to get the prefetches.
174 		 */
175 		goto rescan;
176 	}
177 
178 	twdr->tw_count -= killed;
179 	NET_ADD_STATS_BH(LINUX_MIB_TIMEWAITED, killed);
180 
181 	return ret;
182 }
183 
184 void inet_twdr_hangman(unsigned long data)
185 {
186 	struct inet_timewait_death_row *twdr;
187 	int unsigned need_timer;
188 
189 	twdr = (struct inet_timewait_death_row *)data;
190 	spin_lock(&twdr->death_lock);
191 
192 	if (twdr->tw_count == 0)
193 		goto out;
194 
195 	need_timer = 0;
196 	if (inet_twdr_do_twkill_work(twdr, twdr->slot)) {
197 		twdr->thread_slots |= (1 << twdr->slot);
198 		schedule_work(&twdr->twkill_work);
199 		need_timer = 1;
200 	} else {
201 		/* We purged the entire slot, anything left?  */
202 		if (twdr->tw_count)
203 			need_timer = 1;
204 	}
205 	twdr->slot = ((twdr->slot + 1) & (INET_TWDR_TWKILL_SLOTS - 1));
206 	if (need_timer)
207 		mod_timer(&twdr->tw_timer, jiffies + twdr->period);
208 out:
209 	spin_unlock(&twdr->death_lock);
210 }
211 
212 EXPORT_SYMBOL_GPL(inet_twdr_hangman);
213 
214 void inet_twdr_twkill_work(struct work_struct *work)
215 {
216 	struct inet_timewait_death_row *twdr =
217 		container_of(work, struct inet_timewait_death_row, twkill_work);
218 	int i;
219 
220 	BUILD_BUG_ON((INET_TWDR_TWKILL_SLOTS - 1) >
221 			(sizeof(twdr->thread_slots) * 8));
222 
223 	while (twdr->thread_slots) {
224 		spin_lock_bh(&twdr->death_lock);
225 		for (i = 0; i < INET_TWDR_TWKILL_SLOTS; i++) {
226 			if (!(twdr->thread_slots & (1 << i)))
227 				continue;
228 
229 			while (inet_twdr_do_twkill_work(twdr, i) != 0) {
230 				if (need_resched()) {
231 					spin_unlock_bh(&twdr->death_lock);
232 					schedule();
233 					spin_lock_bh(&twdr->death_lock);
234 				}
235 			}
236 
237 			twdr->thread_slots &= ~(1 << i);
238 		}
239 		spin_unlock_bh(&twdr->death_lock);
240 	}
241 }
242 
243 EXPORT_SYMBOL_GPL(inet_twdr_twkill_work);
244 
245 /* These are always called from BH context.  See callers in
246  * tcp_input.c to verify this.
247  */
248 
249 /* This is for handling early-kills of TIME_WAIT sockets. */
250 void inet_twsk_deschedule(struct inet_timewait_sock *tw,
251 			  struct inet_timewait_death_row *twdr)
252 {
253 	spin_lock(&twdr->death_lock);
254 	if (inet_twsk_del_dead_node(tw)) {
255 		inet_twsk_put(tw);
256 		if (--twdr->tw_count == 0)
257 			del_timer(&twdr->tw_timer);
258 	}
259 	spin_unlock(&twdr->death_lock);
260 	__inet_twsk_kill(tw, twdr->hashinfo);
261 }
262 
263 EXPORT_SYMBOL(inet_twsk_deschedule);
264 
265 void inet_twsk_schedule(struct inet_timewait_sock *tw,
266 		       struct inet_timewait_death_row *twdr,
267 		       const int timeo, const int timewait_len)
268 {
269 	struct hlist_head *list;
270 	int slot;
271 
272 	/* timeout := RTO * 3.5
273 	 *
274 	 * 3.5 = 1+2+0.5 to wait for two retransmits.
275 	 *
276 	 * RATIONALE: if FIN arrived and we entered TIME-WAIT state,
277 	 * our ACK acking that FIN can be lost. If N subsequent retransmitted
278 	 * FINs (or previous seqments) are lost (probability of such event
279 	 * is p^(N+1), where p is probability to lose single packet and
280 	 * time to detect the loss is about RTO*(2^N - 1) with exponential
281 	 * backoff). Normal timewait length is calculated so, that we
282 	 * waited at least for one retransmitted FIN (maximal RTO is 120sec).
283 	 * [ BTW Linux. following BSD, violates this requirement waiting
284 	 *   only for 60sec, we should wait at least for 240 secs.
285 	 *   Well, 240 consumes too much of resources 8)
286 	 * ]
287 	 * This interval is not reduced to catch old duplicate and
288 	 * responces to our wandering segments living for two MSLs.
289 	 * However, if we use PAWS to detect
290 	 * old duplicates, we can reduce the interval to bounds required
291 	 * by RTO, rather than MSL. So, if peer understands PAWS, we
292 	 * kill tw bucket after 3.5*RTO (it is important that this number
293 	 * is greater than TS tick!) and detect old duplicates with help
294 	 * of PAWS.
295 	 */
296 	slot = (timeo + (1 << INET_TWDR_RECYCLE_TICK) - 1) >> INET_TWDR_RECYCLE_TICK;
297 
298 	spin_lock(&twdr->death_lock);
299 
300 	/* Unlink it, if it was scheduled */
301 	if (inet_twsk_del_dead_node(tw))
302 		twdr->tw_count--;
303 	else
304 		atomic_inc(&tw->tw_refcnt);
305 
306 	if (slot >= INET_TWDR_RECYCLE_SLOTS) {
307 		/* Schedule to slow timer */
308 		if (timeo >= timewait_len) {
309 			slot = INET_TWDR_TWKILL_SLOTS - 1;
310 		} else {
311 			slot = DIV_ROUND_UP(timeo, twdr->period);
312 			if (slot >= INET_TWDR_TWKILL_SLOTS)
313 				slot = INET_TWDR_TWKILL_SLOTS - 1;
314 		}
315 		tw->tw_ttd = jiffies + timeo;
316 		slot = (twdr->slot + slot) & (INET_TWDR_TWKILL_SLOTS - 1);
317 		list = &twdr->cells[slot];
318 	} else {
319 		tw->tw_ttd = jiffies + (slot << INET_TWDR_RECYCLE_TICK);
320 
321 		if (twdr->twcal_hand < 0) {
322 			twdr->twcal_hand = 0;
323 			twdr->twcal_jiffie = jiffies;
324 			twdr->twcal_timer.expires = twdr->twcal_jiffie +
325 					      (slot << INET_TWDR_RECYCLE_TICK);
326 			add_timer(&twdr->twcal_timer);
327 		} else {
328 			if (time_after(twdr->twcal_timer.expires,
329 				       jiffies + (slot << INET_TWDR_RECYCLE_TICK)))
330 				mod_timer(&twdr->twcal_timer,
331 					  jiffies + (slot << INET_TWDR_RECYCLE_TICK));
332 			slot = (twdr->twcal_hand + slot) & (INET_TWDR_RECYCLE_SLOTS - 1);
333 		}
334 		list = &twdr->twcal_row[slot];
335 	}
336 
337 	hlist_add_head(&tw->tw_death_node, list);
338 
339 	if (twdr->tw_count++ == 0)
340 		mod_timer(&twdr->tw_timer, jiffies + twdr->period);
341 	spin_unlock(&twdr->death_lock);
342 }
343 
344 EXPORT_SYMBOL_GPL(inet_twsk_schedule);
345 
346 void inet_twdr_twcal_tick(unsigned long data)
347 {
348 	struct inet_timewait_death_row *twdr;
349 	int n, slot;
350 	unsigned long j;
351 	unsigned long now = jiffies;
352 	int killed = 0;
353 	int adv = 0;
354 
355 	twdr = (struct inet_timewait_death_row *)data;
356 
357 	spin_lock(&twdr->death_lock);
358 	if (twdr->twcal_hand < 0)
359 		goto out;
360 
361 	slot = twdr->twcal_hand;
362 	j = twdr->twcal_jiffie;
363 
364 	for (n = 0; n < INET_TWDR_RECYCLE_SLOTS; n++) {
365 		if (time_before_eq(j, now)) {
366 			struct hlist_node *node, *safe;
367 			struct inet_timewait_sock *tw;
368 
369 			inet_twsk_for_each_inmate_safe(tw, node, safe,
370 						       &twdr->twcal_row[slot]) {
371 				__inet_twsk_del_dead_node(tw);
372 				__inet_twsk_kill(tw, twdr->hashinfo);
373 				inet_twsk_put(tw);
374 				killed++;
375 			}
376 		} else {
377 			if (!adv) {
378 				adv = 1;
379 				twdr->twcal_jiffie = j;
380 				twdr->twcal_hand = slot;
381 			}
382 
383 			if (!hlist_empty(&twdr->twcal_row[slot])) {
384 				mod_timer(&twdr->twcal_timer, j);
385 				goto out;
386 			}
387 		}
388 		j += 1 << INET_TWDR_RECYCLE_TICK;
389 		slot = (slot + 1) & (INET_TWDR_RECYCLE_SLOTS - 1);
390 	}
391 	twdr->twcal_hand = -1;
392 
393 out:
394 	if ((twdr->tw_count -= killed) == 0)
395 		del_timer(&twdr->tw_timer);
396 	NET_ADD_STATS_BH(LINUX_MIB_TIMEWAITKILLED, killed);
397 	spin_unlock(&twdr->death_lock);
398 }
399 
400 EXPORT_SYMBOL_GPL(inet_twdr_twcal_tick);
401