GNU Linux-libre 4.19.211-gnu1
[releases.git] / net / ipv4 / inet_timewait_sock.c
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  */
28 void 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. */
43 static 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
65 void 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
76 void inet_twsk_put(struct inet_timewait_sock *tw)
77 {
78         if (refcount_dec_and_test(&tw->tw_refcnt))
79                 inet_twsk_free(tw);
80 }
81 EXPORT_SYMBOL_GPL(inet_twsk_put);
82
83 static 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
89 static 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  */
100 void 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 }
141 EXPORT_SYMBOL_GPL(inet_twsk_hashdance);
142
143 static 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
154 struct 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 }
201 EXPORT_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  */
211 void 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 }
217 EXPORT_SYMBOL(inet_twsk_deschedule_put);
218
219 void __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 }
254 EXPORT_SYMBOL_GPL(__inet_twsk_schedule);
255
256 void 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];
265 restart_rcu:
266                 cond_resched();
267                 rcu_read_lock();
268 restart:
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 }
301 EXPORT_SYMBOL_GPL(inet_twsk_purge);