1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * INET An implementation of the TCP/IP protocol suite for the LINUX
4 * operating system. INET is implemented using the BSD Socket
5 * interface as the means of communication with the user level.
6 *
7 * Generic TIME_WAIT sockets functions
8 *
9 * From code orinally in TCP
10 */
11
12 #include <linux/kernel.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 */
inet_twsk_bind_unhash(struct inet_timewait_sock * tw,struct inet_hashinfo * hashinfo)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. */
inet_twsk_kill(struct inet_timewait_sock * tw)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
inet_twsk_free(struct inet_timewait_sock * tw)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
inet_twsk_put(struct inet_timewait_sock * tw)77 void inet_twsk_put(struct inet_timewait_sock *tw)
78 {
79 if (refcount_dec_and_test(&tw->tw_refcnt))
80 inet_twsk_free(tw);
81 }
82 EXPORT_SYMBOL_GPL(inet_twsk_put);
83
inet_twsk_add_node_rcu(struct inet_timewait_sock * tw,struct hlist_nulls_head * list)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
inet_twsk_add_bind_node(struct inet_timewait_sock * tw,struct hlist_head * list)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 */
inet_twsk_hashdance(struct inet_timewait_sock * tw,struct sock * sk,struct inet_hashinfo * hashinfo)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 inet_twsk_add_node_rcu(tw, &ehead->chain);
124
125 /* Step 3: Remove SK from hash chain */
126 if (__sk_nulls_del_node_init_rcu(sk))
127 sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
128
129 spin_unlock(lock);
130
131 /* tw_refcnt is set to 3 because we have :
132 * - one reference for bhash chain.
133 * - one reference for ehash chain.
134 * - one reference for timer.
135 * We can use atomic_set() because prior spin_lock()/spin_unlock()
136 * committed into memory all tw fields.
137 * Also note that after this point, we lost our implicit reference
138 * so we are not allowed to use tw anymore.
139 */
140 refcount_set(&tw->tw_refcnt, 3);
141 }
142 EXPORT_SYMBOL_GPL(inet_twsk_hashdance);
143
tw_timer_handler(struct timer_list * t)144 static void tw_timer_handler(struct timer_list *t)
145 {
146 struct inet_timewait_sock *tw = from_timer(tw, t, tw_timer);
147
148 if (tw->tw_kill)
149 __NET_INC_STATS(twsk_net(tw), LINUX_MIB_TIMEWAITKILLED);
150 else
151 __NET_INC_STATS(twsk_net(tw), LINUX_MIB_TIMEWAITED);
152 inet_twsk_kill(tw);
153 }
154
inet_twsk_alloc(const struct sock * sk,struct inet_timewait_death_row * dr,const int state)155 struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk,
156 struct inet_timewait_death_row *dr,
157 const int state)
158 {
159 struct inet_timewait_sock *tw;
160
161 if (atomic_read(&dr->tw_count) >= dr->sysctl_max_tw_buckets)
162 return NULL;
163
164 tw = kmem_cache_alloc(sk->sk_prot_creator->twsk_prot->twsk_slab,
165 GFP_ATOMIC);
166 if (tw) {
167 const struct inet_sock *inet = inet_sk(sk);
168
169 tw->tw_dr = dr;
170 /* Give us an identity. */
171 tw->tw_daddr = inet->inet_daddr;
172 tw->tw_rcv_saddr = inet->inet_rcv_saddr;
173 tw->tw_bound_dev_if = sk->sk_bound_dev_if;
174 tw->tw_tos = inet->tos;
175 tw->tw_num = inet->inet_num;
176 tw->tw_state = TCP_TIME_WAIT;
177 tw->tw_substate = state;
178 tw->tw_sport = inet->inet_sport;
179 tw->tw_dport = inet->inet_dport;
180 tw->tw_family = sk->sk_family;
181 tw->tw_reuse = sk->sk_reuse;
182 tw->tw_reuseport = sk->sk_reuseport;
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 timer_setup(&tw->tw_timer, tw_timer_handler, TIMER_PINNED);
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 refcount_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 */
inet_twsk_deschedule_put(struct inet_timewait_sock * tw)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
__inet_twsk_schedule(struct inet_timewait_sock * tw,int timeo,bool rearm)220 void __inet_twsk_schedule(struct inet_timewait_sock *tw, int timeo, bool rearm)
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 (!rearm) {
249 BUG_ON(mod_timer(&tw->tw_timer, jiffies + timeo));
250 atomic_inc(&tw->tw_dr->tw_count);
251 } else {
252 mod_timer_pending(&tw->tw_timer, jiffies + timeo);
253 }
254 }
255 EXPORT_SYMBOL_GPL(__inet_twsk_schedule);
256
inet_twsk_purge(struct inet_hashinfo * hashinfo,int family)257 void inet_twsk_purge(struct inet_hashinfo *hashinfo, int family)
258 {
259 struct inet_timewait_sock *tw;
260 struct sock *sk;
261 struct hlist_nulls_node *node;
262 unsigned int slot;
263
264 for (slot = 0; slot <= hashinfo->ehash_mask; slot++) {
265 struct inet_ehash_bucket *head = &hashinfo->ehash[slot];
266 restart_rcu:
267 cond_resched();
268 rcu_read_lock();
269 restart:
270 sk_nulls_for_each_rcu(sk, node, &head->chain) {
271 if (sk->sk_state != TCP_TIME_WAIT)
272 continue;
273 tw = inet_twsk(sk);
274 if ((tw->tw_family != family) ||
275 refcount_read(&twsk_net(tw)->ns.count))
276 continue;
277
278 if (unlikely(!refcount_inc_not_zero(&tw->tw_refcnt)))
279 continue;
280
281 if (unlikely((tw->tw_family != family) ||
282 refcount_read(&twsk_net(tw)->ns.count))) {
283 inet_twsk_put(tw);
284 goto restart;
285 }
286
287 rcu_read_unlock();
288 local_bh_disable();
289 inet_twsk_deschedule_put(tw);
290 local_bh_enable();
291 goto restart_rcu;
292 }
293 /* If the nulls value we got at the end of this lookup is
294 * not the expected one, we must restart lookup.
295 * We probably met an item that was moved to another chain.
296 */
297 if (get_nulls_value(node) != slot)
298 goto restart;
299 rcu_read_unlock();
300 }
301 }
302 EXPORT_SYMBOL_GPL(inet_twsk_purge);
303