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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 <linux/kmemcheck.h> | |
13 | #include <linux/slab.h> | |
14 | #include <linux/module.h> | |
15 | #include <net/inet_hashtables.h> | |
16 | #include <net/inet_timewait_sock.h> | |
17 | #include <net/ip.h> | |
18 | ||
19 | ||
20 | /** | |
21 | * inet_twsk_bind_unhash - unhash a timewait socket from bind hash | |
22 | * @tw: timewait socket | |
23 | * @hashinfo: hashinfo pointer | |
24 | * | |
25 | * unhash a timewait socket from bind hash, if hashed. | |
26 | * bind hash lock must be held by caller. | |
27 | * Returns 1 if caller should call inet_twsk_put() after lock release. | |
28 | */ | |
29 | void inet_twsk_bind_unhash(struct inet_timewait_sock *tw, | |
30 | struct inet_hashinfo *hashinfo) | |
31 | { | |
32 | struct inet_bind_bucket *tb = tw->tw_tb; | |
33 | ||
34 | if (!tb) | |
35 | return; | |
36 | ||
37 | __hlist_del(&tw->tw_bind_node); | |
38 | tw->tw_tb = NULL; | |
39 | inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb); | |
40 | __sock_put((struct sock *)tw); | |
41 | } | |
42 | ||
43 | /* Must be called with locally disabled BHs. */ | |
44 | static void inet_twsk_kill(struct inet_timewait_sock *tw) | |
45 | { | |
46 | struct inet_hashinfo *hashinfo = tw->tw_dr->hashinfo; | |
47 | spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash); | |
48 | struct inet_bind_hashbucket *bhead; | |
49 | ||
50 | spin_lock(lock); | |
51 | sk_nulls_del_node_init_rcu((struct sock *)tw); | |
52 | spin_unlock(lock); | |
53 | ||
54 | /* Disassociate with bind bucket. */ | |
55 | bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), tw->tw_num, | |
56 | hashinfo->bhash_size)]; | |
57 | ||
58 | spin_lock(&bhead->lock); | |
59 | inet_twsk_bind_unhash(tw, hashinfo); | |
60 | spin_unlock(&bhead->lock); | |
61 | ||
62 | atomic_dec(&tw->tw_dr->tw_count); | |
63 | inet_twsk_put(tw); | |
64 | } | |
65 | ||
66 | void inet_twsk_free(struct inet_timewait_sock *tw) | |
67 | { | |
68 | struct module *owner = tw->tw_prot->owner; | |
69 | twsk_destructor((struct sock *)tw); | |
70 | #ifdef SOCK_REFCNT_DEBUG | |
71 | pr_debug("%s timewait_sock %p released\n", tw->tw_prot->name, tw); | |
72 | #endif | |
73 | kmem_cache_free(tw->tw_prot->twsk_prot->twsk_slab, tw); | |
74 | module_put(owner); | |
75 | } | |
76 | ||
77 | void inet_twsk_put(struct inet_timewait_sock *tw) | |
78 | { | |
79 | if (atomic_dec_and_test(&tw->tw_refcnt)) | |
80 | inet_twsk_free(tw); | |
81 | } | |
82 | EXPORT_SYMBOL_GPL(inet_twsk_put); | |
83 | ||
84 | static void inet_twsk_add_node_rcu(struct inet_timewait_sock *tw, | |
85 | struct hlist_nulls_head *list) | |
86 | { | |
87 | hlist_nulls_add_head_rcu(&tw->tw_node, list); | |
88 | } | |
89 | ||
90 | static void inet_twsk_add_bind_node(struct inet_timewait_sock *tw, | |
91 | struct hlist_head *list) | |
92 | { | |
93 | hlist_add_head(&tw->tw_bind_node, list); | |
94 | } | |
95 | ||
96 | /* | |
97 | * Enter the time wait state. This is called with locally disabled BH. | |
98 | * Essentially we whip up a timewait bucket, copy the relevant info into it | |
99 | * from the SK, and mess with hash chains and list linkage. | |
100 | */ | |
101 | void __inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk, | |
102 | struct inet_hashinfo *hashinfo) | |
103 | { | |
104 | const struct inet_sock *inet = inet_sk(sk); | |
105 | const struct inet_connection_sock *icsk = inet_csk(sk); | |
106 | struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, sk->sk_hash); | |
107 | spinlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash); | |
108 | struct inet_bind_hashbucket *bhead; | |
109 | /* Step 1: Put TW into bind hash. Original socket stays there too. | |
110 | Note, that any socket with inet->num != 0 MUST be bound in | |
111 | binding cache, even if it is closed. | |
112 | */ | |
113 | bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), inet->inet_num, | |
114 | hashinfo->bhash_size)]; | |
115 | spin_lock(&bhead->lock); | |
116 | tw->tw_tb = icsk->icsk_bind_hash; | |
117 | WARN_ON(!icsk->icsk_bind_hash); | |
118 | inet_twsk_add_bind_node(tw, &tw->tw_tb->owners); | |
119 | spin_unlock(&bhead->lock); | |
120 | ||
121 | spin_lock(lock); | |
122 | ||
123 | /* | |
124 | * Step 2: Hash TW into tcp ehash chain. | |
125 | * Notes : | |
126 | * - tw_refcnt is set to 3 because : | |
127 | * - We have one reference from bhash chain. | |
128 | * - We have one reference from ehash chain. | |
129 | * We can use atomic_set() because prior spin_lock()/spin_unlock() | |
130 | * committed into memory all tw fields. | |
131 | */ | |
132 | atomic_set(&tw->tw_refcnt, 1 + 1 + 1); | |
133 | inet_twsk_add_node_rcu(tw, &ehead->chain); | |
134 | ||
135 | /* Step 3: Remove SK from hash chain */ | |
136 | if (__sk_nulls_del_node_init_rcu(sk)) | |
137 | sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1); | |
138 | ||
139 | spin_unlock(lock); | |
140 | } | |
141 | EXPORT_SYMBOL_GPL(__inet_twsk_hashdance); | |
142 | ||
143 | static void tw_timer_handler(unsigned long data) | |
144 | { | |
145 | struct inet_timewait_sock *tw = (struct inet_timewait_sock *)data; | |
146 | ||
147 | if (tw->tw_kill) | |
148 | NET_INC_STATS_BH(twsk_net(tw), LINUX_MIB_TIMEWAITKILLED); | |
149 | else | |
150 | NET_INC_STATS_BH(twsk_net(tw), LINUX_MIB_TIMEWAITED); | |
151 | inet_twsk_kill(tw); | |
152 | } | |
153 | ||
154 | struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk, | |
155 | struct inet_timewait_death_row *dr, | |
156 | const int state) | |
157 | { | |
158 | struct inet_timewait_sock *tw; | |
159 | ||
160 | if (atomic_read(&dr->tw_count) >= dr->sysctl_max_tw_buckets) | |
161 | return NULL; | |
162 | ||
163 | tw = kmem_cache_alloc(sk->sk_prot_creator->twsk_prot->twsk_slab, | |
164 | GFP_ATOMIC); | |
165 | if (tw) { | |
166 | const struct inet_sock *inet = inet_sk(sk); | |
167 | ||
168 | kmemcheck_annotate_bitfield(tw, flags); | |
169 | ||
170 | tw->tw_dr = dr; | |
171 | /* Give us an identity. */ | |
172 | tw->tw_daddr = inet->inet_daddr; | |
173 | tw->tw_rcv_saddr = inet->inet_rcv_saddr; | |
174 | tw->tw_bound_dev_if = sk->sk_bound_dev_if; | |
175 | tw->tw_tos = inet->tos; | |
176 | tw->tw_num = inet->inet_num; | |
177 | tw->tw_state = TCP_TIME_WAIT; | |
178 | tw->tw_substate = state; | |
179 | tw->tw_sport = inet->inet_sport; | |
180 | tw->tw_dport = inet->inet_dport; | |
181 | tw->tw_family = sk->sk_family; | |
182 | tw->tw_reuse = sk->sk_reuse; | |
183 | tw->tw_hash = sk->sk_hash; | |
184 | tw->tw_ipv6only = 0; | |
185 | tw->tw_transparent = inet->transparent; | |
186 | tw->tw_prot = sk->sk_prot_creator; | |
187 | atomic64_set(&tw->tw_cookie, atomic64_read(&sk->sk_cookie)); | |
188 | twsk_net_set(tw, sock_net(sk)); | |
189 | setup_timer(&tw->tw_timer, tw_timer_handler, (unsigned long)tw); | |
190 | /* | |
191 | * Because we use RCU lookups, we should not set tw_refcnt | |
192 | * to a non null value before everything is setup for this | |
193 | * timewait socket. | |
194 | */ | |
195 | atomic_set(&tw->tw_refcnt, 0); | |
196 | ||
197 | __module_get(tw->tw_prot->owner); | |
198 | } | |
199 | ||
200 | return tw; | |
201 | } | |
202 | EXPORT_SYMBOL_GPL(inet_twsk_alloc); | |
203 | ||
204 | /* These are always called from BH context. See callers in | |
205 | * tcp_input.c to verify this. | |
206 | */ | |
207 | ||
208 | /* This is for handling early-kills of TIME_WAIT sockets. | |
209 | * Warning : consume reference. | |
210 | * Caller should not access tw anymore. | |
211 | */ | |
212 | void inet_twsk_deschedule_put(struct inet_timewait_sock *tw) | |
213 | { | |
214 | if (del_timer_sync(&tw->tw_timer)) | |
215 | inet_twsk_kill(tw); | |
216 | inet_twsk_put(tw); | |
217 | } | |
218 | EXPORT_SYMBOL(inet_twsk_deschedule_put); | |
219 | ||
220 | void inet_twsk_schedule(struct inet_timewait_sock *tw, const int timeo) | |
221 | { | |
222 | /* timeout := RTO * 3.5 | |
223 | * | |
224 | * 3.5 = 1+2+0.5 to wait for two retransmits. | |
225 | * | |
226 | * RATIONALE: if FIN arrived and we entered TIME-WAIT state, | |
227 | * our ACK acking that FIN can be lost. If N subsequent retransmitted | |
228 | * FINs (or previous seqments) are lost (probability of such event | |
229 | * is p^(N+1), where p is probability to lose single packet and | |
230 | * time to detect the loss is about RTO*(2^N - 1) with exponential | |
231 | * backoff). Normal timewait length is calculated so, that we | |
232 | * waited at least for one retransmitted FIN (maximal RTO is 120sec). | |
233 | * [ BTW Linux. following BSD, violates this requirement waiting | |
234 | * only for 60sec, we should wait at least for 240 secs. | |
235 | * Well, 240 consumes too much of resources 8) | |
236 | * ] | |
237 | * This interval is not reduced to catch old duplicate and | |
238 | * responces to our wandering segments living for two MSLs. | |
239 | * However, if we use PAWS to detect | |
240 | * old duplicates, we can reduce the interval to bounds required | |
241 | * by RTO, rather than MSL. So, if peer understands PAWS, we | |
242 | * kill tw bucket after 3.5*RTO (it is important that this number | |
243 | * is greater than TS tick!) and detect old duplicates with help | |
244 | * of PAWS. | |
245 | */ | |
246 | ||
247 | tw->tw_kill = timeo <= 4*HZ; | |
248 | if (!mod_timer_pinned(&tw->tw_timer, jiffies + timeo)) { | |
249 | atomic_inc(&tw->tw_refcnt); | |
250 | atomic_inc(&tw->tw_dr->tw_count); | |
251 | } | |
252 | } | |
253 | EXPORT_SYMBOL_GPL(inet_twsk_schedule); | |
254 | ||
255 | void inet_twsk_purge(struct inet_hashinfo *hashinfo, | |
256 | struct inet_timewait_death_row *twdr, int family) | |
257 | { | |
258 | struct inet_timewait_sock *tw; | |
259 | struct sock *sk; | |
260 | struct hlist_nulls_node *node; | |
261 | unsigned int slot; | |
262 | ||
263 | for (slot = 0; slot <= hashinfo->ehash_mask; slot++) { | |
264 | struct inet_ehash_bucket *head = &hashinfo->ehash[slot]; | |
265 | restart_rcu: | |
266 | cond_resched(); | |
267 | rcu_read_lock(); | |
268 | restart: | |
269 | sk_nulls_for_each_rcu(sk, node, &head->chain) { | |
270 | if (sk->sk_state != TCP_TIME_WAIT) | |
271 | continue; | |
272 | tw = inet_twsk(sk); | |
273 | if ((tw->tw_family != family) || | |
274 | atomic_read(&twsk_net(tw)->count)) | |
275 | continue; | |
276 | ||
277 | if (unlikely(!atomic_inc_not_zero(&tw->tw_refcnt))) | |
278 | continue; | |
279 | ||
280 | if (unlikely((tw->tw_family != family) || | |
281 | atomic_read(&twsk_net(tw)->count))) { | |
282 | inet_twsk_put(tw); | |
283 | goto restart; | |
284 | } | |
285 | ||
286 | rcu_read_unlock(); | |
287 | local_bh_disable(); | |
288 | inet_twsk_deschedule_put(tw); | |
289 | local_bh_enable(); | |
290 | goto restart_rcu; | |
291 | } | |
292 | /* If the nulls value we got at the end of this lookup is | |
293 | * not the expected one, we must restart lookup. | |
294 | * We probably met an item that was moved to another chain. | |
295 | */ | |
296 | if (get_nulls_value(node) != slot) | |
297 | goto restart; | |
298 | rcu_read_unlock(); | |
299 | } | |
300 | } | |
301 | EXPORT_SYMBOL_GPL(inet_twsk_purge); |