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

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