1 // SPDX-License-Identifier: GPL-2.0-only
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.
7 * Generic TIME_WAIT sockets functions
9 * From code orinally in TCP
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>
21 * inet_twsk_bind_unhash - unhash a timewait socket from bind hash
22 * @tw: timewait socket
23 * @hashinfo: hashinfo pointer
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.
29 void inet_twsk_bind_unhash(struct inet_timewait_sock *tw,
30 struct inet_hashinfo *hashinfo)
32 struct inet_bind2_bucket *tb2 = tw->tw_tb2;
33 struct inet_bind_bucket *tb = tw->tw_tb;
38 __sk_del_bind_node((struct sock *)tw);
41 inet_bind2_bucket_destroy(hashinfo->bind2_bucket_cachep, tb2);
42 inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
44 __sock_put((struct sock *)tw);
47 /* Must be called with locally disabled BHs. */
48 static void inet_twsk_kill(struct inet_timewait_sock *tw)
50 struct inet_hashinfo *hashinfo = tw->tw_dr->hashinfo;
51 spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash);
52 struct inet_bind_hashbucket *bhead, *bhead2;
55 sk_nulls_del_node_init_rcu((struct sock *)tw);
58 /* Disassociate with bind bucket. */
59 bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), tw->tw_num,
60 hashinfo->bhash_size)];
61 bhead2 = inet_bhashfn_portaddr(hashinfo, (struct sock *)tw,
62 twsk_net(tw), tw->tw_num);
64 spin_lock(&bhead->lock);
65 spin_lock(&bhead2->lock);
66 inet_twsk_bind_unhash(tw, hashinfo);
67 spin_unlock(&bhead2->lock);
68 spin_unlock(&bhead->lock);
70 refcount_dec(&tw->tw_dr->tw_refcount);
74 void inet_twsk_free(struct inet_timewait_sock *tw)
76 struct module *owner = tw->tw_prot->owner;
77 twsk_destructor((struct sock *)tw);
78 kmem_cache_free(tw->tw_prot->twsk_prot->twsk_slab, tw);
82 void inet_twsk_put(struct inet_timewait_sock *tw)
84 if (refcount_dec_and_test(&tw->tw_refcnt))
87 EXPORT_SYMBOL_GPL(inet_twsk_put);
89 static void inet_twsk_add_node_rcu(struct inet_timewait_sock *tw,
90 struct hlist_nulls_head *list)
92 hlist_nulls_add_head_rcu(&tw->tw_node, list);
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.
100 void inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk,
101 struct inet_hashinfo *hashinfo)
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, *bhead2;
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.
113 bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), inet->inet_num,
114 hashinfo->bhash_size)];
115 bhead2 = inet_bhashfn_portaddr(hashinfo, sk, twsk_net(tw), inet->inet_num);
117 spin_lock(&bhead->lock);
118 spin_lock(&bhead2->lock);
120 tw->tw_tb = icsk->icsk_bind_hash;
121 WARN_ON(!icsk->icsk_bind_hash);
123 tw->tw_tb2 = icsk->icsk_bind2_hash;
124 WARN_ON(!icsk->icsk_bind2_hash);
125 sk_add_bind_node((struct sock *)tw, &tw->tw_tb2->owners);
127 spin_unlock(&bhead2->lock);
128 spin_unlock(&bhead->lock);
132 inet_twsk_add_node_rcu(tw, &ehead->chain);
134 /* Step 3: Remove SK from hash chain */
135 if (__sk_nulls_del_node_init_rcu(sk))
136 sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
140 /* tw_refcnt is set to 3 because we have :
141 * - one reference for bhash chain.
142 * - one reference for ehash chain.
143 * - one reference for timer.
144 * We can use atomic_set() because prior spin_lock()/spin_unlock()
145 * committed into memory all tw fields.
146 * Also note that after this point, we lost our implicit reference
147 * so we are not allowed to use tw anymore.
149 refcount_set(&tw->tw_refcnt, 3);
151 EXPORT_SYMBOL_GPL(inet_twsk_hashdance);
153 static void tw_timer_handler(struct timer_list *t)
155 struct inet_timewait_sock *tw = from_timer(tw, t, tw_timer);
160 struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk,
161 struct inet_timewait_death_row *dr,
164 struct inet_timewait_sock *tw;
166 if (refcount_read(&dr->tw_refcount) - 1 >=
167 READ_ONCE(dr->sysctl_max_tw_buckets))
170 tw = kmem_cache_alloc(sk->sk_prot_creator->twsk_prot->twsk_slab,
173 const struct inet_sock *inet = inet_sk(sk);
176 /* Give us an identity. */
177 tw->tw_daddr = inet->inet_daddr;
178 tw->tw_rcv_saddr = inet->inet_rcv_saddr;
179 tw->tw_bound_dev_if = sk->sk_bound_dev_if;
180 tw->tw_tos = inet->tos;
181 tw->tw_num = inet->inet_num;
182 tw->tw_state = TCP_TIME_WAIT;
183 tw->tw_substate = state;
184 tw->tw_sport = inet->inet_sport;
185 tw->tw_dport = inet->inet_dport;
186 tw->tw_family = sk->sk_family;
187 tw->tw_reuse = sk->sk_reuse;
188 tw->tw_reuseport = sk->sk_reuseport;
189 tw->tw_hash = sk->sk_hash;
191 tw->tw_transparent = inet_test_bit(TRANSPARENT, sk);
192 tw->tw_prot = sk->sk_prot_creator;
193 atomic64_set(&tw->tw_cookie, atomic64_read(&sk->sk_cookie));
194 twsk_net_set(tw, sock_net(sk));
195 timer_setup(&tw->tw_timer, tw_timer_handler, TIMER_PINNED);
197 * Because we use RCU lookups, we should not set tw_refcnt
198 * to a non null value before everything is setup for this
201 refcount_set(&tw->tw_refcnt, 0);
203 __module_get(tw->tw_prot->owner);
208 EXPORT_SYMBOL_GPL(inet_twsk_alloc);
210 /* These are always called from BH context. See callers in
211 * tcp_input.c to verify this.
214 /* This is for handling early-kills of TIME_WAIT sockets.
215 * Warning : consume reference.
216 * Caller should not access tw anymore.
218 void inet_twsk_deschedule_put(struct inet_timewait_sock *tw)
220 if (del_timer_sync(&tw->tw_timer))
224 EXPORT_SYMBOL(inet_twsk_deschedule_put);
226 void __inet_twsk_schedule(struct inet_timewait_sock *tw, int timeo, bool rearm)
228 /* timeout := RTO * 3.5
230 * 3.5 = 1+2+0.5 to wait for two retransmits.
232 * RATIONALE: if FIN arrived and we entered TIME-WAIT state,
233 * our ACK acking that FIN can be lost. If N subsequent retransmitted
234 * FINs (or previous seqments) are lost (probability of such event
235 * is p^(N+1), where p is probability to lose single packet and
236 * time to detect the loss is about RTO*(2^N - 1) with exponential
237 * backoff). Normal timewait length is calculated so, that we
238 * waited at least for one retransmitted FIN (maximal RTO is 120sec).
239 * [ BTW Linux. following BSD, violates this requirement waiting
240 * only for 60sec, we should wait at least for 240 secs.
241 * Well, 240 consumes too much of resources 8)
243 * This interval is not reduced to catch old duplicate and
244 * responces to our wandering segments living for two MSLs.
245 * However, if we use PAWS to detect
246 * old duplicates, we can reduce the interval to bounds required
247 * by RTO, rather than MSL. So, if peer understands PAWS, we
248 * kill tw bucket after 3.5*RTO (it is important that this number
249 * is greater than TS tick!) and detect old duplicates with help
254 bool kill = timeo <= 4*HZ;
256 __NET_INC_STATS(twsk_net(tw), kill ? LINUX_MIB_TIMEWAITKILLED :
257 LINUX_MIB_TIMEWAITED);
258 BUG_ON(mod_timer(&tw->tw_timer, jiffies + timeo));
259 refcount_inc(&tw->tw_dr->tw_refcount);
261 mod_timer_pending(&tw->tw_timer, jiffies + timeo);
264 EXPORT_SYMBOL_GPL(__inet_twsk_schedule);
266 /* Remove all non full sockets (TIME_WAIT and NEW_SYN_RECV) for dead netns */
267 void inet_twsk_purge(struct inet_hashinfo *hashinfo, int family)
269 struct hlist_nulls_node *node;
273 for (slot = 0; slot <= hashinfo->ehash_mask; slot++) {
274 struct inet_ehash_bucket *head = &hashinfo->ehash[slot];
279 sk_nulls_for_each_rcu(sk, node, &head->chain) {
280 int state = inet_sk_state_load(sk);
282 if ((1 << state) & ~(TCPF_TIME_WAIT |
286 if (sk->sk_family != family ||
287 refcount_read(&sock_net(sk)->ns.count))
290 if (unlikely(!refcount_inc_not_zero(&sk->sk_refcnt)))
293 if (unlikely(sk->sk_family != family ||
294 refcount_read(&sock_net(sk)->ns.count))) {
301 if (state == TCP_TIME_WAIT) {
302 inet_twsk_deschedule_put(inet_twsk(sk));
304 struct request_sock *req = inet_reqsk(sk);
306 inet_csk_reqsk_queue_drop_and_put(req->rsk_listener,
312 /* If the nulls value we got at the end of this lookup is
313 * not the expected one, we must restart lookup.
314 * We probably met an item that was moved to another chain.
316 if (get_nulls_value(node) != slot)
321 EXPORT_SYMBOL_GPL(inet_twsk_purge);