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 __sk_del_bind_node(sk: (struct sock *)tw);
39 tw->tw_tb = NULL;
40 tw->tw_tb2 = NULL;
41 inet_bind2_bucket_destroy(cachep: hashinfo->bind2_bucket_cachep, tb: tb2);
42 inet_bind_bucket_destroy(cachep: hashinfo->bind_bucket_cachep, tb);
43
44 __sock_put(sk: (struct sock *)tw);
45}
46
47/* Must be called with locally disabled BHs. */
48static void inet_twsk_kill(struct inet_timewait_sock *tw)
49{
50 struct inet_hashinfo *hashinfo = tw->tw_dr->hashinfo;
51 spinlock_t *lock = inet_ehash_lockp(hashinfo, hash: tw->tw_hash);
52 struct inet_bind_hashbucket *bhead, *bhead2;
53
54 spin_lock(lock);
55 sk_nulls_del_node_init_rcu(sk: (struct sock *)tw);
56 spin_unlock(lock);
57
58 /* Disassociate with bind bucket. */
59 bhead = &hashinfo->bhash[inet_bhashfn(net: twsk_net(twsk: tw), lport: tw->tw_num,
60 bhash_size: hashinfo->bhash_size)];
61 bhead2 = inet_bhashfn_portaddr(hinfo: hashinfo, sk: (struct sock *)tw,
62 net: twsk_net(twsk: tw), port: tw->tw_num);
63
64 spin_lock(lock: &bhead->lock);
65 spin_lock(lock: &bhead2->lock);
66 inet_twsk_bind_unhash(tw, hashinfo);
67 spin_unlock(lock: &bhead2->lock);
68 spin_unlock(lock: &bhead->lock);
69
70 refcount_dec(r: &tw->tw_dr->tw_refcount);
71 inet_twsk_put(tw);
72}
73
74void inet_twsk_free(struct inet_timewait_sock *tw)
75{
76 struct module *owner = tw->tw_prot->owner;
77 twsk_destructor(sk: (struct sock *)tw);
78 kmem_cache_free(s: tw->tw_prot->twsk_prot->twsk_slab, objp: tw);
79 module_put(module: owner);
80}
81
82void inet_twsk_put(struct inet_timewait_sock *tw)
83{
84 if (refcount_dec_and_test(r: &tw->tw_refcnt))
85 inet_twsk_free(tw);
86}
87EXPORT_SYMBOL_GPL(inet_twsk_put);
88
89static void inet_twsk_add_node_rcu(struct inet_timewait_sock *tw,
90 struct hlist_nulls_head *list)
91{
92 hlist_nulls_add_head_rcu(n: &tw->tw_node, h: 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, hash: sk->sk_hash);
106 spinlock_t *lock = inet_ehash_lockp(hashinfo, hash: sk->sk_hash);
107 struct inet_bind_hashbucket *bhead, *bhead2;
108
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(net: twsk_net(twsk: tw), lport: inet->inet_num,
114 bhash_size: hashinfo->bhash_size)];
115 bhead2 = inet_bhashfn_portaddr(hinfo: hashinfo, sk, net: twsk_net(twsk: tw), port: inet->inet_num);
116
117 spin_lock(lock: &bhead->lock);
118 spin_lock(lock: &bhead2->lock);
119
120 tw->tw_tb = icsk->icsk_bind_hash;
121 WARN_ON(!icsk->icsk_bind_hash);
122
123 tw->tw_tb2 = icsk->icsk_bind2_hash;
124 WARN_ON(!icsk->icsk_bind2_hash);
125 sk_add_bind_node(sk: (struct sock *)tw, list: &tw->tw_tb2->owners);
126
127 spin_unlock(lock: &bhead2->lock);
128 spin_unlock(lock: &bhead->lock);
129
130 spin_lock(lock);
131
132 inet_twsk_add_node_rcu(tw, list: &ehead->chain);
133
134 /* Step 3: Remove SK from hash chain */
135 if (__sk_nulls_del_node_init_rcu(sk))
136 sock_prot_inuse_add(net: sock_net(sk), prot: sk->sk_prot, val: -1);
137
138 spin_unlock(lock);
139
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.
148 */
149 refcount_set(r: &tw->tw_refcnt, n: 3);
150}
151EXPORT_SYMBOL_GPL(inet_twsk_hashdance);
152
153static void tw_timer_handler(struct timer_list *t)
154{
155 struct inet_timewait_sock *tw = from_timer(tw, t, tw_timer);
156
157 inet_twsk_kill(tw);
158}
159
160struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk,
161 struct inet_timewait_death_row *dr,
162 const int state)
163{
164 struct inet_timewait_sock *tw;
165
166 if (refcount_read(r: &dr->tw_refcount) - 1 >=
167 READ_ONCE(dr->sysctl_max_tw_buckets))
168 return NULL;
169
170 tw = kmem_cache_alloc(cachep: sk->sk_prot_creator->twsk_prot->twsk_slab,
171 GFP_ATOMIC);
172 if (tw) {
173 const struct inet_sock *inet = inet_sk(sk);
174
175 tw->tw_dr = dr;
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;
190 tw->tw_ipv6only = 0;
191 tw->tw_transparent = inet_test_bit(TRANSPARENT, sk);
192 tw->tw_prot = sk->sk_prot_creator;
193 atomic64_set(v: &tw->tw_cookie, i: atomic64_read(v: &sk->sk_cookie));
194 twsk_net_set(twsk: tw, net: sock_net(sk));
195 timer_setup(&tw->tw_timer, tw_timer_handler, TIMER_PINNED);
196 /*
197 * Because we use RCU lookups, we should not set tw_refcnt
198 * to a non null value before everything is setup for this
199 * timewait socket.
200 */
201 refcount_set(r: &tw->tw_refcnt, n: 0);
202
203 __module_get(module: tw->tw_prot->owner);
204 }
205
206 return tw;
207}
208EXPORT_SYMBOL_GPL(inet_twsk_alloc);
209
210/* These are always called from BH context. See callers in
211 * tcp_input.c to verify this.
212 */
213
214/* This is for handling early-kills of TIME_WAIT sockets.
215 * Warning : consume reference.
216 * Caller should not access tw anymore.
217 */
218void inet_twsk_deschedule_put(struct inet_timewait_sock *tw)
219{
220 if (del_timer_sync(timer: &tw->tw_timer))
221 inet_twsk_kill(tw);
222 inet_twsk_put(tw);
223}
224EXPORT_SYMBOL(inet_twsk_deschedule_put);
225
226void __inet_twsk_schedule(struct inet_timewait_sock *tw, int timeo, bool rearm)
227{
228 /* timeout := RTO * 3.5
229 *
230 * 3.5 = 1+2+0.5 to wait for two retransmits.
231 *
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)
242 * ]
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
250 * of PAWS.
251 */
252
253 if (!rearm) {
254 bool kill = timeo <= 4*HZ;
255
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(r: &tw->tw_dr->tw_refcount);
260 } else {
261 mod_timer_pending(timer: &tw->tw_timer, expires: jiffies + timeo);
262 }
263}
264EXPORT_SYMBOL_GPL(__inet_twsk_schedule);
265
266/* Remove all non full sockets (TIME_WAIT and NEW_SYN_RECV) for dead netns */
267void inet_twsk_purge(struct inet_hashinfo *hashinfo, int family)
268{
269 struct hlist_nulls_node *node;
270 unsigned int slot;
271 struct sock *sk;
272
273 for (slot = 0; slot <= hashinfo->ehash_mask; slot++) {
274 struct inet_ehash_bucket *head = &hashinfo->ehash[slot];
275restart_rcu:
276 cond_resched();
277 rcu_read_lock();
278restart:
279 sk_nulls_for_each_rcu(sk, node, &head->chain) {
280 int state = inet_sk_state_load(sk);
281
282 if ((1 << state) & ~(TCPF_TIME_WAIT |
283 TCPF_NEW_SYN_RECV))
284 continue;
285
286 if (sk->sk_family != family ||
287 refcount_read(r: &sock_net(sk)->ns.count))
288 continue;
289
290 if (unlikely(!refcount_inc_not_zero(&sk->sk_refcnt)))
291 continue;
292
293 if (unlikely(sk->sk_family != family ||
294 refcount_read(&sock_net(sk)->ns.count))) {
295 sock_gen_put(sk);
296 goto restart;
297 }
298
299 rcu_read_unlock();
300 local_bh_disable();
301 if (state == TCP_TIME_WAIT) {
302 inet_twsk_deschedule_put(inet_twsk(sk));
303 } else {
304 struct request_sock *req = inet_reqsk(sk);
305
306 inet_csk_reqsk_queue_drop_and_put(sk: req->rsk_listener,
307 req);
308 }
309 local_bh_enable();
310 goto restart_rcu;
311 }
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.
315 */
316 if (get_nulls_value(ptr: node) != slot)
317 goto restart;
318 rcu_read_unlock();
319 }
320}
321EXPORT_SYMBOL_GPL(inet_twsk_purge);
322

source code of linux/net/ipv4/inet_timewait_sock.c