Merge tag 'ceph-for-5.11-rc1' of git://github.com/ceph/ceph-client
[linux-2.6-microblaze.git] / net / ipv4 / inet_timewait_sock.c
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  */
29 void inet_twsk_bind_unhash(struct inet_timewait_sock *tw,
30                           struct inet_hashinfo *hashinfo)
31 {
32         struct inet_bind_bucket *tb = tw->tw_tb;
33
34         if (!tb)
35                 return;
36
37         __hlist_del(&tw->tw_bind_node);
38         tw->tw_tb = NULL;
39         inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
40         __sock_put((struct sock *)tw);
41 }
42
43 /* Must be called with locally disabled BHs. */
44 static void inet_twsk_kill(struct inet_timewait_sock *tw)
45 {
46         struct inet_hashinfo *hashinfo = tw->tw_dr->hashinfo;
47         spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash);
48         struct inet_bind_hashbucket *bhead;
49
50         spin_lock(lock);
51         sk_nulls_del_node_init_rcu((struct sock *)tw);
52         spin_unlock(lock);
53
54         /* Disassociate with bind bucket. */
55         bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), tw->tw_num,
56                         hashinfo->bhash_size)];
57
58         spin_lock(&bhead->lock);
59         inet_twsk_bind_unhash(tw, hashinfo);
60         spin_unlock(&bhead->lock);
61
62         atomic_dec(&tw->tw_dr->tw_count);
63         inet_twsk_put(tw);
64 }
65
66 void inet_twsk_free(struct inet_timewait_sock *tw)
67 {
68         struct module *owner = tw->tw_prot->owner;
69         twsk_destructor((struct sock *)tw);
70 #ifdef SOCK_REFCNT_DEBUG
71         pr_debug("%s timewait_sock %p released\n", tw->tw_prot->name, tw);
72 #endif
73         kmem_cache_free(tw->tw_prot->twsk_prot->twsk_slab, tw);
74         module_put(owner);
75 }
76
77 void inet_twsk_put(struct inet_timewait_sock *tw)
78 {
79         if (refcount_dec_and_test(&tw->tw_refcnt))
80                 inet_twsk_free(tw);
81 }
82 EXPORT_SYMBOL_GPL(inet_twsk_put);
83
84 static void inet_twsk_add_node_rcu(struct inet_timewait_sock *tw,
85                                    struct hlist_nulls_head *list)
86 {
87         hlist_nulls_add_head_rcu(&tw->tw_node, list);
88 }
89
90 static void inet_twsk_add_bind_node(struct inet_timewait_sock *tw,
91                                     struct hlist_head *list)
92 {
93         hlist_add_head(&tw->tw_bind_node, list);
94 }
95
96 /*
97  * Enter the time wait state. This is called with locally disabled BH.
98  * Essentially we whip up a timewait bucket, copy the relevant info into it
99  * from the SK, and mess with hash chains and list linkage.
100  */
101 void inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk,
102                            struct inet_hashinfo *hashinfo)
103 {
104         const struct inet_sock *inet = inet_sk(sk);
105         const struct inet_connection_sock *icsk = inet_csk(sk);
106         struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, sk->sk_hash);
107         spinlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
108         struct inet_bind_hashbucket *bhead;
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(twsk_net(tw), inet->inet_num,
114                         hashinfo->bhash_size)];
115         spin_lock(&bhead->lock);
116         tw->tw_tb = icsk->icsk_bind_hash;
117         WARN_ON(!icsk->icsk_bind_hash);
118         inet_twsk_add_bind_node(tw, &tw->tw_tb->owners);
119         spin_unlock(&bhead->lock);
120
121         spin_lock(lock);
122
123         inet_twsk_add_node_rcu(tw, &ehead->chain);
124
125         /* Step 3: Remove SK from hash chain */
126         if (__sk_nulls_del_node_init_rcu(sk))
127                 sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
128
129         spin_unlock(lock);
130
131         /* tw_refcnt is set to 3 because we have :
132          * - one reference for bhash chain.
133          * - one reference for ehash chain.
134          * - one reference for timer.
135          * We can use atomic_set() because prior spin_lock()/spin_unlock()
136          * committed into memory all tw fields.
137          * Also note that after this point, we lost our implicit reference
138          * so we are not allowed to use tw anymore.
139          */
140         refcount_set(&tw->tw_refcnt, 3);
141 }
142 EXPORT_SYMBOL_GPL(inet_twsk_hashdance);
143
144 static void tw_timer_handler(struct timer_list *t)
145 {
146         struct inet_timewait_sock *tw = from_timer(tw, t, tw_timer);
147
148         if (tw->tw_kill)
149                 __NET_INC_STATS(twsk_net(tw), LINUX_MIB_TIMEWAITKILLED);
150         else
151                 __NET_INC_STATS(twsk_net(tw), LINUX_MIB_TIMEWAITED);
152         inet_twsk_kill(tw);
153 }
154
155 struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk,
156                                            struct inet_timewait_death_row *dr,
157                                            const int state)
158 {
159         struct inet_timewait_sock *tw;
160
161         if (atomic_read(&dr->tw_count) >= dr->sysctl_max_tw_buckets)
162                 return NULL;
163
164         tw = kmem_cache_alloc(sk->sk_prot_creator->twsk_prot->twsk_slab,
165                               GFP_ATOMIC);
166         if (tw) {
167                 const struct inet_sock *inet = inet_sk(sk);
168
169                 tw->tw_dr           = dr;
170                 /* Give us an identity. */
171                 tw->tw_daddr        = inet->inet_daddr;
172                 tw->tw_rcv_saddr    = inet->inet_rcv_saddr;
173                 tw->tw_bound_dev_if = sk->sk_bound_dev_if;
174                 tw->tw_tos          = inet->tos;
175                 tw->tw_num          = inet->inet_num;
176                 tw->tw_state        = TCP_TIME_WAIT;
177                 tw->tw_substate     = state;
178                 tw->tw_sport        = inet->inet_sport;
179                 tw->tw_dport        = inet->inet_dport;
180                 tw->tw_family       = sk->sk_family;
181                 tw->tw_reuse        = sk->sk_reuse;
182                 tw->tw_reuseport    = sk->sk_reuseport;
183                 tw->tw_hash         = sk->sk_hash;
184                 tw->tw_ipv6only     = 0;
185                 tw->tw_transparent  = inet->transparent;
186                 tw->tw_prot         = sk->sk_prot_creator;
187                 atomic64_set(&tw->tw_cookie, atomic64_read(&sk->sk_cookie));
188                 twsk_net_set(tw, sock_net(sk));
189                 timer_setup(&tw->tw_timer, tw_timer_handler, TIMER_PINNED);
190                 /*
191                  * Because we use RCU lookups, we should not set tw_refcnt
192                  * to a non null value before everything is setup for this
193                  * timewait socket.
194                  */
195                 refcount_set(&tw->tw_refcnt, 0);
196
197                 __module_get(tw->tw_prot->owner);
198         }
199
200         return tw;
201 }
202 EXPORT_SYMBOL_GPL(inet_twsk_alloc);
203
204 /* These are always called from BH context.  See callers in
205  * tcp_input.c to verify this.
206  */
207
208 /* This is for handling early-kills of TIME_WAIT sockets.
209  * Warning : consume reference.
210  * Caller should not access tw anymore.
211  */
212 void inet_twsk_deschedule_put(struct inet_timewait_sock *tw)
213 {
214         if (del_timer_sync(&tw->tw_timer))
215                 inet_twsk_kill(tw);
216         inet_twsk_put(tw);
217 }
218 EXPORT_SYMBOL(inet_twsk_deschedule_put);
219
220 void __inet_twsk_schedule(struct inet_timewait_sock *tw, int timeo, bool rearm)
221 {
222         /* timeout := RTO * 3.5
223          *
224          * 3.5 = 1+2+0.5 to wait for two retransmits.
225          *
226          * RATIONALE: if FIN arrived and we entered TIME-WAIT state,
227          * our ACK acking that FIN can be lost. If N subsequent retransmitted
228          * FINs (or previous seqments) are lost (probability of such event
229          * is p^(N+1), where p is probability to lose single packet and
230          * time to detect the loss is about RTO*(2^N - 1) with exponential
231          * backoff). Normal timewait length is calculated so, that we
232          * waited at least for one retransmitted FIN (maximal RTO is 120sec).
233          * [ BTW Linux. following BSD, violates this requirement waiting
234          *   only for 60sec, we should wait at least for 240 secs.
235          *   Well, 240 consumes too much of resources 8)
236          * ]
237          * This interval is not reduced to catch old duplicate and
238          * responces to our wandering segments living for two MSLs.
239          * However, if we use PAWS to detect
240          * old duplicates, we can reduce the interval to bounds required
241          * by RTO, rather than MSL. So, if peer understands PAWS, we
242          * kill tw bucket after 3.5*RTO (it is important that this number
243          * is greater than TS tick!) and detect old duplicates with help
244          * of PAWS.
245          */
246
247         tw->tw_kill = timeo <= 4*HZ;
248         if (!rearm) {
249                 BUG_ON(mod_timer(&tw->tw_timer, jiffies + timeo));
250                 atomic_inc(&tw->tw_dr->tw_count);
251         } else {
252                 mod_timer_pending(&tw->tw_timer, jiffies + timeo);
253         }
254 }
255 EXPORT_SYMBOL_GPL(__inet_twsk_schedule);
256
257 void inet_twsk_purge(struct inet_hashinfo *hashinfo, int family)
258 {
259         struct inet_timewait_sock *tw;
260         struct sock *sk;
261         struct hlist_nulls_node *node;
262         unsigned int slot;
263
264         for (slot = 0; slot <= hashinfo->ehash_mask; slot++) {
265                 struct inet_ehash_bucket *head = &hashinfo->ehash[slot];
266 restart_rcu:
267                 cond_resched();
268                 rcu_read_lock();
269 restart:
270                 sk_nulls_for_each_rcu(sk, node, &head->chain) {
271                         if (sk->sk_state != TCP_TIME_WAIT)
272                                 continue;
273                         tw = inet_twsk(sk);
274                         if ((tw->tw_family != family) ||
275                                 refcount_read(&twsk_net(tw)->ns.count))
276                                 continue;
277
278                         if (unlikely(!refcount_inc_not_zero(&tw->tw_refcnt)))
279                                 continue;
280
281                         if (unlikely((tw->tw_family != family) ||
282                                      refcount_read(&twsk_net(tw)->ns.count))) {
283                                 inet_twsk_put(tw);
284                                 goto restart;
285                         }
286
287                         rcu_read_unlock();
288                         local_bh_disable();
289                         inet_twsk_deschedule_put(tw);
290                         local_bh_enable();
291                         goto restart_rcu;
292                 }
293                 /* If the nulls value we got at the end of this lookup is
294                  * not the expected one, we must restart lookup.
295                  * We probably met an item that was moved to another chain.
296                  */
297                 if (get_nulls_value(node) != slot)
298                         goto restart;
299                 rcu_read_unlock();
300         }
301 }
302 EXPORT_SYMBOL_GPL(inet_twsk_purge);