summaryrefslogtreecommitdiff
path: root/net/ipv4/inet_timewait_sock.c
blob: a4bab81f1462c1c61bc1185f5e10146a03a139f2 (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
/*
 * INET		An implementation of the TCP/IP protocol suite for the LINUX
 *		operating system.  INET is implemented using the  BSD Socket
 *		interface as the means of communication with the user level.
 *
 *		Generic TIME_WAIT sockets functions
 *
 *		From code orinally in TCP
 */

#include <linux/kernel.h>
#include <linux/kmemcheck.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <net/inet_hashtables.h>
#include <net/inet_timewait_sock.h>
#include <net/ip.h>


/**
 *	inet_twsk_bind_unhash - unhash a timewait socket from bind hash
 *	@tw: timewait socket
 *	@hashinfo: hashinfo pointer
 *
 *	unhash a timewait socket from bind hash, if hashed.
 *	bind hash lock must be held by caller.
 *	Returns 1 if caller should call inet_twsk_put() after lock release.
 */
void inet_twsk_bind_unhash(struct inet_timewait_sock *tw,
			  struct inet_hashinfo *hashinfo)
{
	struct inet_bind_bucket *tb = tw->tw_tb;

	if (!tb)
		return;

	__hlist_del(&tw->tw_bind_node);
	tw->tw_tb = NULL;
	inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
	__sock_put((struct sock *)tw);
}

/* Must be called with locally disabled BHs. */
static void inet_twsk_kill(struct inet_timewait_sock *tw)
{
	struct inet_hashinfo *hashinfo = tw->tw_dr->hashinfo;
	spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash);
	struct inet_bind_hashbucket *bhead;

	spin_lock(lock);
	sk_nulls_del_node_init_rcu((struct sock *)tw);
	spin_unlock(lock);

	/* Disassociate with bind bucket. */
	bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), tw->tw_num,
			hashinfo->bhash_size)];

	spin_lock(&bhead->lock);
	inet_twsk_bind_unhash(tw, hashinfo);
	spin_unlock(&bhead->lock);

	atomic_dec(&tw->tw_dr->tw_count);
	inet_twsk_put(tw);
}

void inet_twsk_free(struct inet_timewait_sock *tw)
{
	struct module *owner = tw->tw_prot->owner;
	twsk_destructor((struct sock *)tw);
#ifdef SOCK_REFCNT_DEBUG
	pr_debug("%s timewait_sock %p released\n", tw->tw_prot->name, tw);
#endif
	kmem_cache_free(tw->tw_prot->twsk_prot->twsk_slab, tw);
	module_put(owner);
}

void inet_twsk_put(struct inet_timewait_sock *tw)
{
	if (refcount_dec_and_test(&tw->tw_refcnt))
		inet_twsk_free(tw);
}
EXPORT_SYMBOL_GPL(inet_twsk_put);

static void inet_twsk_add_node_rcu(struct inet_timewait_sock *tw,
				   struct hlist_nulls_head *list)
{
	hlist_nulls_add_head_rcu(&tw->tw_node, list);
}

static void inet_twsk_add_bind_node(struct inet_timewait_sock *tw,
				    struct hlist_head *list)
{
	hlist_add_head(&tw->tw_bind_node, list);
}

/*
 * Enter the time wait state.
 * Essentially we whip up a timewait bucket, copy the relevant info into it
 * from the SK, and mess with hash chains and list linkage.
 */
void __inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk,
			   struct inet_hashinfo *hashinfo)
{
	const struct inet_sock *inet = inet_sk(sk);
	const struct inet_connection_sock *icsk = inet_csk(sk);
	struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, sk->sk_hash);
	spinlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
	struct inet_bind_hashbucket *bhead;
	/* Step 1: Put TW into bind hash. Original socket stays there too.
	   Note, that any socket with inet->num != 0 MUST be bound in
	   binding cache, even if it is closed.
	 */
	bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), inet->inet_num,
			hashinfo->bhash_size)];
	spin_lock_bh(&bhead->lock);
	tw->tw_tb = icsk->icsk_bind_hash;
	WARN_ON(!icsk->icsk_bind_hash);
	inet_twsk_add_bind_node(tw, &tw->tw_tb->owners);
	spin_unlock(&bhead->lock);

	spin_lock(lock);

	/*
	 * Step 2: Hash TW into tcp ehash chain.
	 * Notes :
	 * - tw_refcnt is set to 4 because :
	 * - We have one reference from bhash chain.
	 * - We have one reference from ehash chain.
	 * - We have one reference from timer.
	 * - One reference for ourself (our caller will release it).
	 * We can use atomic_set() because prior spin_lock()/spin_unlock()
	 * committed into memory all tw fields.
	 */
	refcount_set(&tw->tw_refcnt, 4);
	inet_twsk_add_node_rcu(tw, &ehead->chain);

	/* Step 3: Remove SK from hash chain */
	if (__sk_nulls_del_node_init_rcu(sk))
		sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);

	spin_unlock_bh(lock);
}
EXPORT_SYMBOL_GPL(__inet_twsk_hashdance);

static void tw_timer_handler(struct timer_list *t)
{
	struct inet_timewait_sock *tw = from_timer(tw, t, tw_timer);

	if (tw->tw_kill)
		__NET_INC_STATS(twsk_net(tw), LINUX_MIB_TIMEWAITKILLED);
	else
		__NET_INC_STATS(twsk_net(tw), LINUX_MIB_TIMEWAITED);
	inet_twsk_kill(tw);
}

struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk,
					   struct inet_timewait_death_row *dr,
					   const int state)
{
	struct inet_timewait_sock *tw;

	if (atomic_read(&dr->tw_count) >= dr->sysctl_max_tw_buckets)
		return NULL;

	tw = kmem_cache_alloc(sk->sk_prot_creator->twsk_prot->twsk_slab,
			      GFP_ATOMIC);
	if (tw) {
		const struct inet_sock *inet = inet_sk(sk);

		kmemcheck_annotate_bitfield(tw, flags);

		tw->tw_dr	    = dr;
		/* Give us an identity. */
		tw->tw_daddr	    = inet->inet_daddr;
		tw->tw_rcv_saddr    = inet->inet_rcv_saddr;
		tw->tw_bound_dev_if = sk->sk_bound_dev_if;
		tw->tw_tos	    = inet->tos;
		tw->tw_num	    = inet->inet_num;
		tw->tw_state	    = TCP_TIME_WAIT;
		tw->tw_substate	    = state;
		tw->tw_sport	    = inet->inet_sport;
		tw->tw_dport	    = inet->inet_dport;
		tw->tw_family	    = sk->sk_family;
		tw->tw_reuse	    = sk->sk_reuse;
		tw->tw_hash	    = sk->sk_hash;
		tw->tw_ipv6only	    = 0;
		tw->tw_transparent  = inet->transparent;
		tw->tw_prot	    = sk->sk_prot_creator;
		atomic64_set(&tw->tw_cookie, atomic64_read(&sk->sk_cookie));
		twsk_net_set(tw, sock_net(sk));
		timer_setup(&tw->tw_timer, tw_timer_handler, TIMER_PINNED);
		/*
		 * Because we use RCU lookups, we should not set tw_refcnt
		 * to a non null value before everything is setup for this
		 * timewait socket.
		 */
		refcount_set(&tw->tw_refcnt, 0);

		__module_get(tw->tw_prot->owner);
	}

	return tw;
}
EXPORT_SYMBOL_GPL(inet_twsk_alloc);

/* These are always called from BH context.  See callers in
 * tcp_input.c to verify this.
 */

/* This is for handling early-kills of TIME_WAIT sockets.
 * Warning : consume reference.
 * Caller should not access tw anymore.
 */
void inet_twsk_deschedule_put(struct inet_timewait_sock *tw)
{
	if (del_timer_sync(&tw->tw_timer))
		inet_twsk_kill(tw);
	inet_twsk_put(tw);
}
EXPORT_SYMBOL(inet_twsk_deschedule_put);

void __inet_twsk_schedule(struct inet_timewait_sock *tw, int timeo, bool rearm)
{
	/* timeout := RTO * 3.5
	 *
	 * 3.5 = 1+2+0.5 to wait for two retransmits.
	 *
	 * RATIONALE: if FIN arrived and we entered TIME-WAIT state,
	 * our ACK acking that FIN can be lost. If N subsequent retransmitted
	 * FINs (or previous seqments) are lost (probability of such event
	 * is p^(N+1), where p is probability to lose single packet and
	 * time to detect the loss is about RTO*(2^N - 1) with exponential
	 * backoff). Normal timewait length is calculated so, that we
	 * waited at least for one retransmitted FIN (maximal RTO is 120sec).
	 * [ BTW Linux. following BSD, violates this requirement waiting
	 *   only for 60sec, we should wait at least for 240 secs.
	 *   Well, 240 consumes too much of resources 8)
	 * ]
	 * This interval is not reduced to catch old duplicate and
	 * responces to our wandering segments living for two MSLs.
	 * However, if we use PAWS to detect
	 * old duplicates, we can reduce the interval to bounds required
	 * by RTO, rather than MSL. So, if peer understands PAWS, we
	 * kill tw bucket after 3.5*RTO (it is important that this number
	 * is greater than TS tick!) and detect old duplicates with help
	 * of PAWS.
	 */

	tw->tw_kill = timeo <= 4*HZ;
	if (!rearm) {
		BUG_ON(mod_timer(&tw->tw_timer, jiffies + timeo));
		atomic_inc(&tw->tw_dr->tw_count);
	} else {
		mod_timer_pending(&tw->tw_timer, jiffies + timeo);
	}
}
EXPORT_SYMBOL_GPL(__inet_twsk_schedule);

void inet_twsk_purge(struct inet_hashinfo *hashinfo, int family)
{
	struct inet_timewait_sock *tw;
	struct sock *sk;
	struct hlist_nulls_node *node;
	unsigned int slot;

	for (slot = 0; slot <= hashinfo->ehash_mask; slot++) {
		struct inet_ehash_bucket *head = &hashinfo->ehash[slot];
restart_rcu:
		cond_resched();
		rcu_read_lock();
restart:
		sk_nulls_for_each_rcu(sk, node, &head->chain) {
			if (sk->sk_state != TCP_TIME_WAIT)
				continue;
			tw = inet_twsk(sk);
			if ((tw->tw_family != family) ||
				atomic_read(&twsk_net(tw)->count))
				continue;

			if (unlikely(!refcount_inc_not_zero(&tw->tw_refcnt)))
				continue;

			if (unlikely((tw->tw_family != family) ||
				     atomic_read(&twsk_net(tw)->count))) {
				inet_twsk_put(tw);
				goto restart;
			}

			rcu_read_unlock();
			local_bh_disable();
			inet_twsk_deschedule_put(tw);
			local_bh_enable();
			goto restart_rcu;
		}
		/* If the nulls value we got at the end of this lookup is
		 * not the expected one, we must restart lookup.
		 * We probably met an item that was moved to another chain.
		 */
		if (get_nulls_value(node) != slot)
			goto restart;
		rcu_read_unlock();
	}
}
EXPORT_SYMBOL_GPL(inet_twsk_purge);