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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/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);
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 */
29void inet_twsk_bind_unhash(struct inet_timewait_sock *tw,
30 struct inet_hashinfo *hashinfo)
31{
32 struct inet_bind2_bucket *tb2 = tw->tw_tb2;
33 struct inet_bind_bucket *tb = tw->tw_tb;
34
35 if (!tb)
36 return;
37
38 __hlist_del(&tw->tw_bind_node);
39 tw->tw_tb = NULL;
40 inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
41
42 __hlist_del(&tw->tw_bind2_node);
43 tw->tw_tb2 = NULL;
44 inet_bind2_bucket_destroy(hashinfo->bind2_bucket_cachep, tb2);
45
46 __sock_put((struct sock *)tw);
47}
48
49/* Must be called with locally disabled BHs. */
50static void inet_twsk_kill(struct inet_timewait_sock *tw)
51{
52 struct inet_hashinfo *hashinfo = tw->tw_dr->hashinfo;
53 spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash);
54 struct inet_bind_hashbucket *bhead, *bhead2;
55
56 spin_lock(lock);
57 sk_nulls_del_node_init_rcu((struct sock *)tw);
58 spin_unlock(lock);
59
60 /* Disassociate with bind bucket. */
61 bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), tw->tw_num,
62 hashinfo->bhash_size)];
63 bhead2 = inet_bhashfn_portaddr(hashinfo, (struct sock *)tw,
64 twsk_net(tw), tw->tw_num);
65
66 spin_lock(&bhead->lock);
67 spin_lock(&bhead2->lock);
68 inet_twsk_bind_unhash(tw, hashinfo);
69 spin_unlock(&bhead2->lock);
70 spin_unlock(&bhead->lock);
71
72 refcount_dec(&tw->tw_dr->tw_refcount);
73 inet_twsk_put(tw);
74}
75
76void inet_twsk_free(struct inet_timewait_sock *tw)
77{
78 struct module *owner = tw->tw_prot->owner;
79 twsk_destructor((struct sock *)tw);
80#ifdef SOCK_REFCNT_DEBUG
81 pr_debug("%s timewait_sock %p released\n", tw->tw_prot->name, tw);
82#endif
83 kmem_cache_free(tw->tw_prot->twsk_prot->twsk_slab, tw);
84 module_put(owner);
85}
86
87void inet_twsk_put(struct inet_timewait_sock *tw)
88{
89 if (refcount_dec_and_test(&tw->tw_refcnt))
90 inet_twsk_free(tw);
91}
92EXPORT_SYMBOL_GPL(inet_twsk_put);
93
94static void inet_twsk_add_node_tail_rcu(struct inet_timewait_sock *tw,
95 struct hlist_nulls_head *list)
96{
97 hlist_nulls_add_tail_rcu(&tw->tw_node, list);
98}
99
100static void inet_twsk_add_bind_node(struct inet_timewait_sock *tw,
101 struct hlist_head *list)
102{
103 hlist_add_head(&tw->tw_bind_node, list);
104}
105
106static void inet_twsk_add_bind2_node(struct inet_timewait_sock *tw,
107 struct hlist_head *list)
108{
109 hlist_add_head(&tw->tw_bind2_node, list);
110}
111
112/*
113 * Enter the time wait state. This is called with locally disabled BH.
114 * Essentially we whip up a timewait bucket, copy the relevant info into it
115 * from the SK, and mess with hash chains and list linkage.
116 */
117void inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk,
118 struct inet_hashinfo *hashinfo)
119{
120 const struct inet_sock *inet = inet_sk(sk);
121 const struct inet_connection_sock *icsk = inet_csk(sk);
122 struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, sk->sk_hash);
123 spinlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
124 struct inet_bind_hashbucket *bhead, *bhead2;
125
126 /* Step 1: Put TW into bind hash. Original socket stays there too.
127 Note, that any socket with inet->num != 0 MUST be bound in
128 binding cache, even if it is closed.
129 */
130 bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), inet->inet_num,
131 hashinfo->bhash_size)];
132 bhead2 = inet_bhashfn_portaddr(hashinfo, sk, twsk_net(tw), inet->inet_num);
133
134 spin_lock(&bhead->lock);
135 spin_lock(&bhead2->lock);
136
137 tw->tw_tb = icsk->icsk_bind_hash;
138 WARN_ON(!icsk->icsk_bind_hash);
139 inet_twsk_add_bind_node(tw, &tw->tw_tb->owners);
140
141 tw->tw_tb2 = icsk->icsk_bind2_hash;
142 WARN_ON(!icsk->icsk_bind2_hash);
143 inet_twsk_add_bind2_node(tw, &tw->tw_tb2->deathrow);
144
145 spin_unlock(&bhead2->lock);
146 spin_unlock(&bhead->lock);
147
148 spin_lock(lock);
149
150 inet_twsk_add_node_tail_rcu(tw, &ehead->chain);
151
152 /* Step 3: Remove SK from hash chain */
153 if (__sk_nulls_del_node_init_rcu(sk))
154 sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
155
156 spin_unlock(lock);
157
158 /* tw_refcnt is set to 3 because we have :
159 * - one reference for bhash chain.
160 * - one reference for ehash chain.
161 * - one reference for timer.
162 * We can use atomic_set() because prior spin_lock()/spin_unlock()
163 * committed into memory all tw fields.
164 * Also note that after this point, we lost our implicit reference
165 * so we are not allowed to use tw anymore.
166 */
167 refcount_set(&tw->tw_refcnt, 3);
168}
169EXPORT_SYMBOL_GPL(inet_twsk_hashdance);
170
171static void tw_timer_handler(struct timer_list *t)
172{
173 struct inet_timewait_sock *tw = from_timer(tw, t, tw_timer);
174
175 inet_twsk_kill(tw);
176}
177
178struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk,
179 struct inet_timewait_death_row *dr,
180 const int state)
181{
182 struct inet_timewait_sock *tw;
183
184 if (refcount_read(&dr->tw_refcount) - 1 >=
185 READ_ONCE(dr->sysctl_max_tw_buckets))
186 return NULL;
187
188 tw = kmem_cache_alloc(sk->sk_prot_creator->twsk_prot->twsk_slab,
189 GFP_ATOMIC);
190 if (tw) {
191 const struct inet_sock *inet = inet_sk(sk);
192
193 tw->tw_dr = dr;
194 /* Give us an identity. */
195 tw->tw_daddr = inet->inet_daddr;
196 tw->tw_rcv_saddr = inet->inet_rcv_saddr;
197 tw->tw_bound_dev_if = sk->sk_bound_dev_if;
198 tw->tw_tos = inet->tos;
199 tw->tw_num = inet->inet_num;
200 tw->tw_state = TCP_TIME_WAIT;
201 tw->tw_substate = state;
202 tw->tw_sport = inet->inet_sport;
203 tw->tw_dport = inet->inet_dport;
204 tw->tw_family = sk->sk_family;
205 tw->tw_reuse = sk->sk_reuse;
206 tw->tw_reuseport = sk->sk_reuseport;
207 tw->tw_hash = sk->sk_hash;
208 tw->tw_ipv6only = 0;
209 tw->tw_transparent = inet->transparent;
210 tw->tw_prot = sk->sk_prot_creator;
211 atomic64_set(&tw->tw_cookie, atomic64_read(&sk->sk_cookie));
212 twsk_net_set(tw, sock_net(sk));
213 timer_setup(&tw->tw_timer, tw_timer_handler, TIMER_PINNED);
214 /*
215 * Because we use RCU lookups, we should not set tw_refcnt
216 * to a non null value before everything is setup for this
217 * timewait socket.
218 */
219 refcount_set(&tw->tw_refcnt, 0);
220
221 __module_get(tw->tw_prot->owner);
222 }
223
224 return tw;
225}
226EXPORT_SYMBOL_GPL(inet_twsk_alloc);
227
228/* These are always called from BH context. See callers in
229 * tcp_input.c to verify this.
230 */
231
232/* This is for handling early-kills of TIME_WAIT sockets.
233 * Warning : consume reference.
234 * Caller should not access tw anymore.
235 */
236void inet_twsk_deschedule_put(struct inet_timewait_sock *tw)
237{
238 if (del_timer_sync(&tw->tw_timer))
239 inet_twsk_kill(tw);
240 inet_twsk_put(tw);
241}
242EXPORT_SYMBOL(inet_twsk_deschedule_put);
243
244void __inet_twsk_schedule(struct inet_timewait_sock *tw, int timeo, bool rearm)
245{
246 /* timeout := RTO * 3.5
247 *
248 * 3.5 = 1+2+0.5 to wait for two retransmits.
249 *
250 * RATIONALE: if FIN arrived and we entered TIME-WAIT state,
251 * our ACK acking that FIN can be lost. If N subsequent retransmitted
252 * FINs (or previous seqments) are lost (probability of such event
253 * is p^(N+1), where p is probability to lose single packet and
254 * time to detect the loss is about RTO*(2^N - 1) with exponential
255 * backoff). Normal timewait length is calculated so, that we
256 * waited at least for one retransmitted FIN (maximal RTO is 120sec).
257 * [ BTW Linux. following BSD, violates this requirement waiting
258 * only for 60sec, we should wait at least for 240 secs.
259 * Well, 240 consumes too much of resources 8)
260 * ]
261 * This interval is not reduced to catch old duplicate and
262 * responces to our wandering segments living for two MSLs.
263 * However, if we use PAWS to detect
264 * old duplicates, we can reduce the interval to bounds required
265 * by RTO, rather than MSL. So, if peer understands PAWS, we
266 * kill tw bucket after 3.5*RTO (it is important that this number
267 * is greater than TS tick!) and detect old duplicates with help
268 * of PAWS.
269 */
270
271 if (!rearm) {
272 bool kill = timeo <= 4*HZ;
273
274 __NET_INC_STATS(twsk_net(tw), kill ? LINUX_MIB_TIMEWAITKILLED :
275 LINUX_MIB_TIMEWAITED);
276 BUG_ON(mod_timer(&tw->tw_timer, jiffies + timeo));
277 refcount_inc(&tw->tw_dr->tw_refcount);
278 } else {
279 mod_timer_pending(&tw->tw_timer, jiffies + timeo);
280 }
281}
282EXPORT_SYMBOL_GPL(__inet_twsk_schedule);
283
284void inet_twsk_purge(struct inet_hashinfo *hashinfo, int family)
285{
286 struct inet_timewait_sock *tw;
287 struct sock *sk;
288 struct hlist_nulls_node *node;
289 unsigned int slot;
290
291 for (slot = 0; slot <= hashinfo->ehash_mask; slot++) {
292 struct inet_ehash_bucket *head = &hashinfo->ehash[slot];
293restart_rcu:
294 cond_resched();
295 rcu_read_lock();
296restart:
297 sk_nulls_for_each_rcu(sk, node, &head->chain) {
298 if (sk->sk_state != TCP_TIME_WAIT) {
299 /* A kernel listener socket might not hold refcnt for net,
300 * so reqsk_timer_handler() could be fired after net is
301 * freed. Userspace listener and reqsk never exist here.
302 */
303 if (unlikely(sk->sk_state == TCP_NEW_SYN_RECV &&
304 hashinfo->pernet)) {
305 struct request_sock *req = inet_reqsk(sk);
306
307 inet_csk_reqsk_queue_drop_and_put(req->rsk_listener, req);
308 }
309
310 continue;
311 }
312
313 tw = inet_twsk(sk);
314 if ((tw->tw_family != family) ||
315 refcount_read(&twsk_net(tw)->ns.count))
316 continue;
317
318 if (unlikely(!refcount_inc_not_zero(&tw->tw_refcnt)))
319 continue;
320
321 if (unlikely((tw->tw_family != family) ||
322 refcount_read(&twsk_net(tw)->ns.count))) {
323 inet_twsk_put(tw);
324 goto restart;
325 }
326
327 rcu_read_unlock();
328 local_bh_disable();
329 inet_twsk_deschedule_put(tw);
330 local_bh_enable();
331 goto restart_rcu;
332 }
333 /* If the nulls value we got at the end of this lookup is
334 * not the expected one, we must restart lookup.
335 * We probably met an item that was moved to another chain.
336 */
337 if (get_nulls_value(node) != slot)
338 goto restart;
339 rcu_read_unlock();
340 }
341}
342EXPORT_SYMBOL_GPL(inet_twsk_purge);