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/slab.h>
13#include <linux/module.h>
14#include <net/inet_hashtables.h>
15#include <net/inet_timewait_sock.h>
16#include <net/ip.h>
17
18
19/**
20 * inet_twsk_bind_unhash - unhash a timewait socket from bind hash
21 * @tw: timewait socket
22 * @hashinfo: hashinfo pointer
23 *
24 * unhash a timewait socket from bind hash, if hashed.
25 * bind hash lock must be held by caller.
26 * Returns 1 if caller should call inet_twsk_put() after lock release.
27 */
28void inet_twsk_bind_unhash(struct inet_timewait_sock *tw,
29 struct inet_hashinfo *hashinfo)
30{
31 struct inet_bind_bucket *tb = tw->tw_tb;
32
33 if (!tb)
34 return;
35
36 __hlist_del(&tw->tw_bind_node);
37 tw->tw_tb = NULL;
38 inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
39 __sock_put((struct sock *)tw);
40}
41
42/* Must be called with locally disabled BHs. */
43static void inet_twsk_kill(struct inet_timewait_sock *tw)
44{
45 struct inet_hashinfo *hashinfo = tw->tw_dr->hashinfo;
46 spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash);
47 struct inet_bind_hashbucket *bhead;
48
49 spin_lock(lock);
50 sk_nulls_del_node_init_rcu((struct sock *)tw);
51 spin_unlock(lock);
52
53 /* Disassociate with bind bucket. */
54 bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), tw->tw_num,
55 hashinfo->bhash_size)];
56
57 spin_lock(&bhead->lock);
58 inet_twsk_bind_unhash(tw, hashinfo);
59 spin_unlock(&bhead->lock);
60
61 atomic_dec(&tw->tw_dr->tw_count);
62 inet_twsk_put(tw);
63}
64
65void inet_twsk_free(struct inet_timewait_sock *tw)
66{
67 struct module *owner = tw->tw_prot->owner;
68 twsk_destructor((struct sock *)tw);
69#ifdef SOCK_REFCNT_DEBUG
70 pr_debug("%s timewait_sock %p released\n", tw->tw_prot->name, tw);
71#endif
72 kmem_cache_free(tw->tw_prot->twsk_prot->twsk_slab, tw);
73 module_put(owner);
74}
75
76void inet_twsk_put(struct inet_timewait_sock *tw)
77{
78 if (refcount_dec_and_test(&tw->tw_refcnt))
79 inet_twsk_free(tw);
80}
81EXPORT_SYMBOL_GPL(inet_twsk_put);
82
83static void inet_twsk_add_node_rcu(struct inet_timewait_sock *tw,
84 struct hlist_nulls_head *list)
85{
86 hlist_nulls_add_head_rcu(&tw->tw_node, list);
87}
88
89static void inet_twsk_add_bind_node(struct inet_timewait_sock *tw,
90 struct hlist_head *list)
91{
92 hlist_add_head(&tw->tw_bind_node, list);
93}
94
95/*
96 * Enter the time wait state. This is called with locally disabled BH.
97 * Essentially we whip up a timewait bucket, copy the relevant info into it
98 * from the SK, and mess with hash chains and list linkage.
99 */
100void inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk,
101 struct inet_hashinfo *hashinfo)
102{
103 const struct inet_sock *inet = inet_sk(sk);
104 const struct inet_connection_sock *icsk = inet_csk(sk);
105 struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, sk->sk_hash);
106 spinlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
107 struct inet_bind_hashbucket *bhead;
108 /* Step 1: Put TW into bind hash. Original socket stays there too.
109 Note, that any socket with inet->num != 0 MUST be bound in
110 binding cache, even if it is closed.
111 */
112 bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), inet->inet_num,
113 hashinfo->bhash_size)];
114 spin_lock(&bhead->lock);
115 tw->tw_tb = icsk->icsk_bind_hash;
116 WARN_ON(!icsk->icsk_bind_hash);
117 inet_twsk_add_bind_node(tw, &tw->tw_tb->owners);
118 spin_unlock(&bhead->lock);
119
120 spin_lock(lock);
121
122 inet_twsk_add_node_rcu(tw, &ehead->chain);
123
124 /* Step 3: Remove SK from hash chain */
125 if (__sk_nulls_del_node_init_rcu(sk))
126 sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
127
128 spin_unlock(lock);
129
130 /* tw_refcnt is set to 3 because we have :
131 * - one reference for bhash chain.
132 * - one reference for ehash chain.
133 * - one reference for timer.
134 * We can use atomic_set() because prior spin_lock()/spin_unlock()
135 * committed into memory all tw fields.
136 * Also note that after this point, we lost our implicit reference
137 * so we are not allowed to use tw anymore.
138 */
139 refcount_set(&tw->tw_refcnt, 3);
140}
141EXPORT_SYMBOL_GPL(inet_twsk_hashdance);
142
143static void tw_timer_handler(struct timer_list *t)
144{
145 struct inet_timewait_sock *tw = from_timer(tw, t, tw_timer);
146
147 if (tw->tw_kill)
148 __NET_INC_STATS(twsk_net(tw), LINUX_MIB_TIMEWAITKILLED);
149 else
150 __NET_INC_STATS(twsk_net(tw), LINUX_MIB_TIMEWAITED);
151 inet_twsk_kill(tw);
152}
153
154struct 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 tw->tw_dr = dr;
169 /* Give us an identity. */
170 tw->tw_daddr = inet->inet_daddr;
171 tw->tw_rcv_saddr = inet->inet_rcv_saddr;
172 tw->tw_bound_dev_if = sk->sk_bound_dev_if;
173 tw->tw_tos = inet->tos;
174 tw->tw_num = inet->inet_num;
175 tw->tw_state = TCP_TIME_WAIT;
176 tw->tw_substate = state;
177 tw->tw_sport = inet->inet_sport;
178 tw->tw_dport = inet->inet_dport;
179 tw->tw_family = sk->sk_family;
180 tw->tw_reuse = sk->sk_reuse;
181 tw->tw_reuseport = sk->sk_reuseport;
182 tw->tw_hash = sk->sk_hash;
183 tw->tw_ipv6only = 0;
184 tw->tw_transparent = inet->transparent;
185 tw->tw_prot = sk->sk_prot_creator;
186 atomic64_set(&tw->tw_cookie, atomic64_read(&sk->sk_cookie));
187 twsk_net_set(tw, sock_net(sk));
188 timer_setup(&tw->tw_timer, tw_timer_handler, TIMER_PINNED);
189 /*
190 * Because we use RCU lookups, we should not set tw_refcnt
191 * to a non null value before everything is setup for this
192 * timewait socket.
193 */
194 refcount_set(&tw->tw_refcnt, 0);
195
196 __module_get(tw->tw_prot->owner);
197 }
198
199 return tw;
200}
201EXPORT_SYMBOL_GPL(inet_twsk_alloc);
202
203/* These are always called from BH context. See callers in
204 * tcp_input.c to verify this.
205 */
206
207/* This is for handling early-kills of TIME_WAIT sockets.
208 * Warning : consume reference.
209 * Caller should not access tw anymore.
210 */
211void inet_twsk_deschedule_put(struct inet_timewait_sock *tw)
212{
213 if (del_timer_sync(&tw->tw_timer))
214 inet_twsk_kill(tw);
215 inet_twsk_put(tw);
216}
217EXPORT_SYMBOL(inet_twsk_deschedule_put);
218
219void __inet_twsk_schedule(struct inet_timewait_sock *tw, int timeo, bool rearm)
220{
221 /* timeout := RTO * 3.5
222 *
223 * 3.5 = 1+2+0.5 to wait for two retransmits.
224 *
225 * RATIONALE: if FIN arrived and we entered TIME-WAIT state,
226 * our ACK acking that FIN can be lost. If N subsequent retransmitted
227 * FINs (or previous seqments) are lost (probability of such event
228 * is p^(N+1), where p is probability to lose single packet and
229 * time to detect the loss is about RTO*(2^N - 1) with exponential
230 * backoff). Normal timewait length is calculated so, that we
231 * waited at least for one retransmitted FIN (maximal RTO is 120sec).
232 * [ BTW Linux. following BSD, violates this requirement waiting
233 * only for 60sec, we should wait at least for 240 secs.
234 * Well, 240 consumes too much of resources 8)
235 * ]
236 * This interval is not reduced to catch old duplicate and
237 * responces to our wandering segments living for two MSLs.
238 * However, if we use PAWS to detect
239 * old duplicates, we can reduce the interval to bounds required
240 * by RTO, rather than MSL. So, if peer understands PAWS, we
241 * kill tw bucket after 3.5*RTO (it is important that this number
242 * is greater than TS tick!) and detect old duplicates with help
243 * of PAWS.
244 */
245
246 tw->tw_kill = timeo <= 4*HZ;
247 if (!rearm) {
248 BUG_ON(mod_timer(&tw->tw_timer, jiffies + timeo));
249 atomic_inc(&tw->tw_dr->tw_count);
250 } else {
251 mod_timer_pending(&tw->tw_timer, jiffies + timeo);
252 }
253}
254EXPORT_SYMBOL_GPL(__inet_twsk_schedule);
255
256void inet_twsk_purge(struct inet_hashinfo *hashinfo, 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];
265restart_rcu:
266 cond_resched();
267 rcu_read_lock();
268restart:
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 refcount_read(&twsk_net(tw)->count))
275 continue;
276
277 if (unlikely(!refcount_inc_not_zero(&tw->tw_refcnt)))
278 continue;
279
280 if (unlikely((tw->tw_family != family) ||
281 refcount_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}
301EXPORT_SYMBOL_GPL(inet_twsk_purge);
302