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 #include <net/tcp.h>
19 #include <net/psp.h>
20
21 /**
22 * inet_twsk_bind_unhash - unhash a timewait socket from bind hash
23 * @tw: timewait socket
24 * @hashinfo: hashinfo pointer
25 *
26 * unhash a timewait socket from bind hash, if hashed.
27 * bind hash lock must be held by caller.
28 * Returns 1 if caller should call inet_twsk_put() after lock release.
29 */
inet_twsk_bind_unhash(struct inet_timewait_sock * tw,struct inet_hashinfo * hashinfo)30 void inet_twsk_bind_unhash(struct inet_timewait_sock *tw,
31 struct inet_hashinfo *hashinfo)
32 {
33 struct inet_bind2_bucket *tb2 = tw->tw_tb2;
34 struct inet_bind_bucket *tb = tw->tw_tb;
35
36 if (!tb)
37 return;
38
39 __sk_del_bind_node((struct sock *)tw);
40 tw->tw_tb = NULL;
41 tw->tw_tb2 = NULL;
42 inet_bind2_bucket_destroy(hashinfo->bind2_bucket_cachep, tb2);
43 inet_bind_bucket_destroy(tb);
44
45 __sock_put((struct sock *)tw);
46 }
47
48 /* Must be called with locally disabled BHs. */
inet_twsk_kill(struct inet_timewait_sock * tw)49 static void inet_twsk_kill(struct inet_timewait_sock *tw)
50 {
51 struct inet_hashinfo *hashinfo = tw->tw_dr->hashinfo;
52 spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash);
53 struct inet_bind_hashbucket *bhead, *bhead2;
54
55 spin_lock(lock);
56 sk_nulls_del_node_init_rcu((struct sock *)tw);
57 spin_unlock(lock);
58
59 /* Disassociate with bind bucket. */
60 bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), tw->tw_num,
61 hashinfo->bhash_size)];
62 bhead2 = inet_bhashfn_portaddr(hashinfo, (struct sock *)tw,
63 twsk_net(tw), tw->tw_num);
64
65 spin_lock(&bhead->lock);
66 spin_lock(&bhead2->lock);
67 inet_twsk_bind_unhash(tw, hashinfo);
68 spin_unlock(&bhead2->lock);
69 spin_unlock(&bhead->lock);
70
71 refcount_dec(&tw->tw_dr->tw_refcount);
72 inet_twsk_put(tw);
73 }
74
inet_twsk_free(struct inet_timewait_sock * tw)75 void inet_twsk_free(struct inet_timewait_sock *tw)
76 {
77 struct module *owner = tw->tw_prot->owner;
78
79 tcp_twsk_destructor((struct sock *)tw);
80 kmem_cache_free(tw->tw_prot->twsk_prot->twsk_slab, tw);
81 module_put(owner);
82 }
83
inet_twsk_put(struct inet_timewait_sock * tw)84 void inet_twsk_put(struct inet_timewait_sock *tw)
85 {
86 if (refcount_dec_and_test(&tw->tw_refcnt))
87 inet_twsk_free(tw);
88 }
89 EXPORT_SYMBOL_GPL(inet_twsk_put);
90
inet_twsk_add_node_rcu(struct inet_timewait_sock * tw,struct hlist_nulls_head * list)91 static void inet_twsk_add_node_rcu(struct inet_timewait_sock *tw,
92 struct hlist_nulls_head *list)
93 {
94 hlist_nulls_add_head_rcu(&tw->tw_node, list);
95 }
96
inet_twsk_schedule(struct inet_timewait_sock * tw,int timeo)97 static void inet_twsk_schedule(struct inet_timewait_sock *tw, int timeo)
98 {
99 __inet_twsk_schedule(tw, timeo, false);
100 }
101
102 /*
103 * Enter the time wait state.
104 * Essentially we whip up a timewait bucket, copy the relevant info into it
105 * from the SK, and mess with hash chains and list linkage.
106 *
107 * The caller must not access @tw anymore after this function returns.
108 */
inet_twsk_hashdance_schedule(struct inet_timewait_sock * tw,struct sock * sk,struct inet_hashinfo * hashinfo,int timeo)109 void inet_twsk_hashdance_schedule(struct inet_timewait_sock *tw,
110 struct sock *sk,
111 struct inet_hashinfo *hashinfo,
112 int timeo)
113 {
114 const struct inet_sock *inet = inet_sk(sk);
115 const struct inet_connection_sock *icsk = inet_csk(sk);
116 struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, sk->sk_hash);
117 spinlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
118 struct inet_bind_hashbucket *bhead, *bhead2;
119
120 /* Step 1: Put TW into bind hash. Original socket stays there too.
121 Note, that any socket with inet->num != 0 MUST be bound in
122 binding cache, even if it is closed.
123 */
124 bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), inet->inet_num,
125 hashinfo->bhash_size)];
126 bhead2 = inet_bhashfn_portaddr(hashinfo, sk, twsk_net(tw), inet->inet_num);
127
128 local_bh_disable();
129 spin_lock(&bhead->lock);
130 spin_lock(&bhead2->lock);
131
132 tw->tw_tb = icsk->icsk_bind_hash;
133 WARN_ON(!icsk->icsk_bind_hash);
134
135 tw->tw_tb2 = icsk->icsk_bind2_hash;
136 WARN_ON(!icsk->icsk_bind2_hash);
137 sk_add_bind_node((struct sock *)tw, &tw->tw_tb2->owners);
138
139 spin_unlock(&bhead2->lock);
140 spin_unlock(&bhead->lock);
141
142 spin_lock(lock);
143
144 /* Step 2: Hash TW into tcp ehash chain */
145 inet_twsk_add_node_rcu(tw, &ehead->chain);
146
147 /* Step 3: Remove SK from hash chain */
148 if (__sk_nulls_del_node_init_rcu(sk))
149 sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
150
151
152 /* Ensure above writes are committed into memory before updating the
153 * refcount.
154 * Provides ordering vs later refcount_inc().
155 */
156 smp_wmb();
157 /* tw_refcnt is set to 3 because we have :
158 * - one reference for bhash chain.
159 * - one reference for ehash chain.
160 * - one reference for timer.
161 * Also note that after this point, we lost our implicit reference
162 * so we are not allowed to use tw anymore.
163 */
164 refcount_set(&tw->tw_refcnt, 3);
165
166 inet_twsk_schedule(tw, timeo);
167
168 spin_unlock(lock);
169 local_bh_enable();
170 }
171
tw_timer_handler(struct timer_list * t)172 static void tw_timer_handler(struct timer_list *t)
173 {
174 struct inet_timewait_sock *tw = timer_container_of(tw, t, tw_timer);
175
176 inet_twsk_kill(tw);
177 }
178
inet_twsk_alloc(const struct sock * sk,struct inet_timewait_death_row * dr,const int state)179 struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk,
180 struct inet_timewait_death_row *dr,
181 const int state)
182 {
183 struct inet_timewait_sock *tw;
184
185 if (refcount_read(&dr->tw_refcount) - 1 >=
186 READ_ONCE(dr->sysctl_max_tw_buckets))
187 return NULL;
188
189 tw = kmem_cache_alloc(sk->sk_prot_creator->twsk_prot->twsk_slab,
190 GFP_ATOMIC);
191 if (tw) {
192 const struct inet_sock *inet = inet_sk(sk);
193
194 tw->tw_dr = dr;
195 /* Give us an identity. */
196 tw->tw_daddr = inet->inet_daddr;
197 tw->tw_rcv_saddr = inet->inet_rcv_saddr;
198 tw->tw_bound_dev_if = sk->sk_bound_dev_if;
199 tw->tw_tos = inet->tos;
200 tw->tw_num = inet->inet_num;
201 tw->tw_state = TCP_TIME_WAIT;
202 tw->tw_substate = state;
203 tw->tw_sport = inet->inet_sport;
204 tw->tw_dport = inet->inet_dport;
205 tw->tw_family = sk->sk_family;
206 tw->tw_reuse = sk->sk_reuse;
207 tw->tw_reuseport = sk->sk_reuseport;
208 tw->tw_hash = sk->sk_hash;
209 tw->tw_ipv6only = 0;
210 tw->tw_transparent = inet_test_bit(TRANSPARENT, sk);
211 tw->tw_connect_bind = !!(sk->sk_userlocks & SOCK_CONNECT_BIND);
212 tw->tw_prot = sk->sk_prot_creator;
213 atomic64_set(&tw->tw_cookie, atomic64_read(&sk->sk_cookie));
214 twsk_net_set(tw, sock_net(sk));
215 timer_setup(&tw->tw_timer, tw_timer_handler, 0);
216 #ifdef CONFIG_SOCK_VALIDATE_XMIT
217 tw->tw_validate_xmit_skb = NULL;
218 #endif
219 /*
220 * Because we use RCU lookups, we should not set tw_refcnt
221 * to a non null value before everything is setup for this
222 * timewait socket.
223 */
224 refcount_set(&tw->tw_refcnt, 0);
225
226 __module_get(tw->tw_prot->owner);
227 psp_twsk_init(tw, sk);
228 }
229
230 return tw;
231 }
232
233 /* These are always called from BH context. See callers in
234 * tcp_input.c to verify this.
235 */
236
237 /* This is for handling early-kills of TIME_WAIT sockets.
238 * Warning : consume reference.
239 * Caller should not access tw anymore.
240 */
inet_twsk_deschedule_put(struct inet_timewait_sock * tw)241 void inet_twsk_deschedule_put(struct inet_timewait_sock *tw)
242 {
243 struct inet_hashinfo *hashinfo = tw->tw_dr->hashinfo;
244 spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash);
245
246 /* inet_twsk_purge() walks over all sockets, including tw ones,
247 * and removes them via inet_twsk_deschedule_put() after a
248 * refcount_inc_not_zero().
249 *
250 * inet_twsk_hashdance_schedule() must (re)init the refcount before
251 * arming the timer, i.e. inet_twsk_purge can obtain a reference to
252 * a twsk that did not yet schedule the timer.
253 *
254 * The ehash lock synchronizes these two:
255 * After acquiring the lock, the timer is always scheduled (else
256 * timer_shutdown returns false), because hashdance_schedule releases
257 * the ehash lock only after completing the timer initialization.
258 *
259 * Without grabbing the ehash lock, we get:
260 * 1) cpu x sets twsk refcount to 3
261 * 2) cpu y bumps refcount to 4
262 * 3) cpu y calls inet_twsk_deschedule_put() and shuts timer down
263 * 4) cpu x tries to start timer, but mod_timer is a noop post-shutdown
264 * -> timer refcount is never decremented.
265 */
266 spin_lock(lock);
267 /* Makes sure hashdance_schedule() has completed */
268 spin_unlock(lock);
269
270 if (timer_shutdown_sync(&tw->tw_timer))
271 inet_twsk_kill(tw);
272 inet_twsk_put(tw);
273 }
274 EXPORT_SYMBOL(inet_twsk_deschedule_put);
275
__inet_twsk_schedule(struct inet_timewait_sock * tw,int timeo,bool rearm)276 void __inet_twsk_schedule(struct inet_timewait_sock *tw, int timeo, bool rearm)
277 {
278 /* timeout := RTO * 3.5
279 *
280 * 3.5 = 1+2+0.5 to wait for two retransmits.
281 *
282 * RATIONALE: if FIN arrived and we entered TIME-WAIT state,
283 * our ACK acking that FIN can be lost. If N subsequent retransmitted
284 * FINs (or previous seqments) are lost (probability of such event
285 * is p^(N+1), where p is probability to lose single packet and
286 * time to detect the loss is about RTO*(2^N - 1) with exponential
287 * backoff). Normal timewait length is calculated so, that we
288 * waited at least for one retransmitted FIN (maximal RTO is 120sec).
289 * [ BTW Linux. following BSD, violates this requirement waiting
290 * only for 60sec, we should wait at least for 240 secs.
291 * Well, 240 consumes too much of resources 8)
292 * ]
293 * This interval is not reduced to catch old duplicate and
294 * responces to our wandering segments living for two MSLs.
295 * However, if we use PAWS to detect
296 * old duplicates, we can reduce the interval to bounds required
297 * by RTO, rather than MSL. So, if peer understands PAWS, we
298 * kill tw bucket after 3.5*RTO (it is important that this number
299 * is greater than TS tick!) and detect old duplicates with help
300 * of PAWS.
301 */
302
303 if (!rearm) {
304 bool kill = timeo <= 4*HZ;
305
306 __NET_INC_STATS(twsk_net(tw), kill ? LINUX_MIB_TIMEWAITKILLED :
307 LINUX_MIB_TIMEWAITED);
308 BUG_ON(mod_timer(&tw->tw_timer, jiffies + timeo));
309 refcount_inc(&tw->tw_dr->tw_refcount);
310 } else {
311 mod_timer_pending(&tw->tw_timer, jiffies + timeo);
312 }
313 }
314
315 /* Remove all non full sockets (TIME_WAIT and NEW_SYN_RECV) for dead netns */
inet_twsk_purge(struct inet_hashinfo * hashinfo)316 void inet_twsk_purge(struct inet_hashinfo *hashinfo)
317 {
318 struct inet_ehash_bucket *head = &hashinfo->ehash[0];
319 unsigned int ehash_mask = hashinfo->ehash_mask;
320 struct hlist_nulls_node *node;
321 unsigned int slot;
322 struct sock *sk;
323
324 for (slot = 0; slot <= ehash_mask; slot++, head++) {
325 if (hlist_nulls_empty(&head->chain))
326 continue;
327
328 restart_rcu:
329 cond_resched();
330 rcu_read_lock();
331 restart:
332 sk_nulls_for_each_rcu(sk, node, &head->chain) {
333 int state = inet_sk_state_load(sk);
334
335 if ((1 << state) & ~(TCPF_TIME_WAIT |
336 TCPF_NEW_SYN_RECV))
337 continue;
338
339 if (check_net(sock_net(sk)))
340 continue;
341
342 if (unlikely(!refcount_inc_not_zero(&sk->sk_refcnt)))
343 continue;
344
345 if (check_net(sock_net(sk))) {
346 sock_gen_put(sk);
347 goto restart;
348 }
349
350 rcu_read_unlock();
351 local_bh_disable();
352 if (state == TCP_TIME_WAIT) {
353 inet_twsk_deschedule_put(inet_twsk(sk));
354 } else {
355 struct request_sock *req = inet_reqsk(sk);
356
357 inet_csk_reqsk_queue_drop_and_put(req->rsk_listener,
358 req);
359 }
360 local_bh_enable();
361 goto restart_rcu;
362 }
363 /* If the nulls value we got at the end of this lookup is
364 * not the expected one, we must restart lookup.
365 * We probably met an item that was moved to another chain.
366 */
367 if (get_nulls_value(node) != slot)
368 goto restart;
369 rcu_read_unlock();
370 }
371 }
372