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_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((struct sock *)tw); 39 tw->tw_tb = NULL; 40 tw->tw_tb2 = NULL; 41 inet_bind2_bucket_destroy(hashinfo->bind2_bucket_cachep, tb2); 42 inet_bind_bucket_destroy(tb); 43 44 __sock_put((struct sock *)tw); 45 } 46 47 /* Must be called with locally disabled BHs. */ 48 static 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, tw->tw_hash); 52 struct inet_bind_hashbucket *bhead, *bhead2; 53 54 spin_lock(lock); 55 sk_nulls_del_node_init_rcu((struct sock *)tw); 56 spin_unlock(lock); 57 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); 63 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); 69 70 refcount_dec(&tw->tw_dr->tw_refcount); 71 inet_twsk_put(tw); 72 } 73 74 void inet_twsk_free(struct inet_timewait_sock *tw) 75 { 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); 79 module_put(owner); 80 } 81 82 void inet_twsk_put(struct inet_timewait_sock *tw) 83 { 84 if (refcount_dec_and_test(&tw->tw_refcnt)) 85 inet_twsk_free(tw); 86 } 87 EXPORT_SYMBOL_GPL(inet_twsk_put); 88 89 static void inet_twsk_add_node_rcu(struct inet_timewait_sock *tw, 90 struct hlist_nulls_head *list) 91 { 92 hlist_nulls_add_head_rcu(&tw->tw_node, list); 93 } 94 95 static void inet_twsk_schedule(struct inet_timewait_sock *tw, int timeo) 96 { 97 __inet_twsk_schedule(tw, timeo, false); 98 } 99 100 /* 101 * Enter the time wait state. 102 * Essentially we whip up a timewait bucket, copy the relevant info into it 103 * from the SK, and mess with hash chains and list linkage. 104 * 105 * The caller must not access @tw anymore after this function returns. 106 */ 107 void inet_twsk_hashdance_schedule(struct inet_timewait_sock *tw, 108 struct sock *sk, 109 struct inet_hashinfo *hashinfo, 110 int timeo) 111 { 112 const struct inet_sock *inet = inet_sk(sk); 113 const struct inet_connection_sock *icsk = inet_csk(sk); 114 struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, sk->sk_hash); 115 spinlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash); 116 struct inet_bind_hashbucket *bhead, *bhead2; 117 118 /* Step 1: Put TW into bind hash. Original socket stays there too. 119 Note, that any socket with inet->num != 0 MUST be bound in 120 binding cache, even if it is closed. 121 */ 122 bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), inet->inet_num, 123 hashinfo->bhash_size)]; 124 bhead2 = inet_bhashfn_portaddr(hashinfo, sk, twsk_net(tw), inet->inet_num); 125 126 local_bh_disable(); 127 spin_lock(&bhead->lock); 128 spin_lock(&bhead2->lock); 129 130 tw->tw_tb = icsk->icsk_bind_hash; 131 WARN_ON(!icsk->icsk_bind_hash); 132 133 tw->tw_tb2 = icsk->icsk_bind2_hash; 134 WARN_ON(!icsk->icsk_bind2_hash); 135 sk_add_bind_node((struct sock *)tw, &tw->tw_tb2->owners); 136 137 spin_unlock(&bhead2->lock); 138 spin_unlock(&bhead->lock); 139 140 spin_lock(lock); 141 142 /* Step 2: Hash TW into tcp ehash chain */ 143 inet_twsk_add_node_rcu(tw, &ehead->chain); 144 145 /* Step 3: Remove SK from hash chain */ 146 if (__sk_nulls_del_node_init_rcu(sk)) 147 sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1); 148 149 150 /* Ensure above writes are committed into memory before updating the 151 * refcount. 152 * Provides ordering vs later refcount_inc(). 153 */ 154 smp_wmb(); 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 * Also note that after this point, we lost our implicit reference 160 * so we are not allowed to use tw anymore. 161 */ 162 refcount_set(&tw->tw_refcnt, 3); 163 164 inet_twsk_schedule(tw, timeo); 165 166 spin_unlock(lock); 167 local_bh_enable(); 168 } 169 170 static void tw_timer_handler(struct timer_list *t) 171 { 172 struct inet_timewait_sock *tw = timer_container_of(tw, t, tw_timer); 173 174 inet_twsk_kill(tw); 175 } 176 177 struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk, 178 struct inet_timewait_death_row *dr, 179 const int state) 180 { 181 struct inet_timewait_sock *tw; 182 183 if (refcount_read(&dr->tw_refcount) - 1 >= 184 READ_ONCE(dr->sysctl_max_tw_buckets)) 185 return NULL; 186 187 tw = kmem_cache_alloc(sk->sk_prot_creator->twsk_prot->twsk_slab, 188 GFP_ATOMIC); 189 if (tw) { 190 const struct inet_sock *inet = inet_sk(sk); 191 192 tw->tw_dr = dr; 193 /* Give us an identity. */ 194 tw->tw_daddr = inet->inet_daddr; 195 tw->tw_rcv_saddr = inet->inet_rcv_saddr; 196 tw->tw_bound_dev_if = sk->sk_bound_dev_if; 197 tw->tw_tos = inet->tos; 198 tw->tw_num = inet->inet_num; 199 tw->tw_state = TCP_TIME_WAIT; 200 tw->tw_substate = state; 201 tw->tw_sport = inet->inet_sport; 202 tw->tw_dport = inet->inet_dport; 203 tw->tw_family = sk->sk_family; 204 tw->tw_reuse = sk->sk_reuse; 205 tw->tw_reuseport = sk->sk_reuseport; 206 tw->tw_hash = sk->sk_hash; 207 tw->tw_ipv6only = 0; 208 tw->tw_transparent = inet_test_bit(TRANSPARENT, sk); 209 tw->tw_prot = sk->sk_prot_creator; 210 atomic64_set(&tw->tw_cookie, atomic64_read(&sk->sk_cookie)); 211 twsk_net_set(tw, sock_net(sk)); 212 timer_setup(&tw->tw_timer, tw_timer_handler, 0); 213 /* 214 * Because we use RCU lookups, we should not set tw_refcnt 215 * to a non null value before everything is setup for this 216 * timewait socket. 217 */ 218 refcount_set(&tw->tw_refcnt, 0); 219 220 __module_get(tw->tw_prot->owner); 221 } 222 223 return tw; 224 } 225 226 /* These are always called from BH context. See callers in 227 * tcp_input.c to verify this. 228 */ 229 230 /* This is for handling early-kills of TIME_WAIT sockets. 231 * Warning : consume reference. 232 * Caller should not access tw anymore. 233 */ 234 void inet_twsk_deschedule_put(struct inet_timewait_sock *tw) 235 { 236 struct inet_hashinfo *hashinfo = tw->tw_dr->hashinfo; 237 spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash); 238 239 /* inet_twsk_purge() walks over all sockets, including tw ones, 240 * and removes them via inet_twsk_deschedule_put() after a 241 * refcount_inc_not_zero(). 242 * 243 * inet_twsk_hashdance_schedule() must (re)init the refcount before 244 * arming the timer, i.e. inet_twsk_purge can obtain a reference to 245 * a twsk that did not yet schedule the timer. 246 * 247 * The ehash lock synchronizes these two: 248 * After acquiring the lock, the timer is always scheduled (else 249 * timer_shutdown returns false), because hashdance_schedule releases 250 * the ehash lock only after completing the timer initialization. 251 * 252 * Without grabbing the ehash lock, we get: 253 * 1) cpu x sets twsk refcount to 3 254 * 2) cpu y bumps refcount to 4 255 * 3) cpu y calls inet_twsk_deschedule_put() and shuts timer down 256 * 4) cpu x tries to start timer, but mod_timer is a noop post-shutdown 257 * -> timer refcount is never decremented. 258 */ 259 spin_lock(lock); 260 /* Makes sure hashdance_schedule() has completed */ 261 spin_unlock(lock); 262 263 if (timer_shutdown_sync(&tw->tw_timer)) 264 inet_twsk_kill(tw); 265 inet_twsk_put(tw); 266 } 267 EXPORT_SYMBOL(inet_twsk_deschedule_put); 268 269 void __inet_twsk_schedule(struct inet_timewait_sock *tw, int timeo, bool rearm) 270 { 271 /* timeout := RTO * 3.5 272 * 273 * 3.5 = 1+2+0.5 to wait for two retransmits. 274 * 275 * RATIONALE: if FIN arrived and we entered TIME-WAIT state, 276 * our ACK acking that FIN can be lost. If N subsequent retransmitted 277 * FINs (or previous seqments) are lost (probability of such event 278 * is p^(N+1), where p is probability to lose single packet and 279 * time to detect the loss is about RTO*(2^N - 1) with exponential 280 * backoff). Normal timewait length is calculated so, that we 281 * waited at least for one retransmitted FIN (maximal RTO is 120sec). 282 * [ BTW Linux. following BSD, violates this requirement waiting 283 * only for 60sec, we should wait at least for 240 secs. 284 * Well, 240 consumes too much of resources 8) 285 * ] 286 * This interval is not reduced to catch old duplicate and 287 * responces to our wandering segments living for two MSLs. 288 * However, if we use PAWS to detect 289 * old duplicates, we can reduce the interval to bounds required 290 * by RTO, rather than MSL. So, if peer understands PAWS, we 291 * kill tw bucket after 3.5*RTO (it is important that this number 292 * is greater than TS tick!) and detect old duplicates with help 293 * of PAWS. 294 */ 295 296 if (!rearm) { 297 bool kill = timeo <= 4*HZ; 298 299 __NET_INC_STATS(twsk_net(tw), kill ? LINUX_MIB_TIMEWAITKILLED : 300 LINUX_MIB_TIMEWAITED); 301 BUG_ON(mod_timer(&tw->tw_timer, jiffies + timeo)); 302 refcount_inc(&tw->tw_dr->tw_refcount); 303 } else { 304 mod_timer_pending(&tw->tw_timer, jiffies + timeo); 305 } 306 } 307 308 /* Remove all non full sockets (TIME_WAIT and NEW_SYN_RECV) for dead netns */ 309 void inet_twsk_purge(struct inet_hashinfo *hashinfo) 310 { 311 struct inet_ehash_bucket *head = &hashinfo->ehash[0]; 312 unsigned int ehash_mask = hashinfo->ehash_mask; 313 struct hlist_nulls_node *node; 314 unsigned int slot; 315 struct sock *sk; 316 317 for (slot = 0; slot <= ehash_mask; slot++, head++) { 318 if (hlist_nulls_empty(&head->chain)) 319 continue; 320 321 restart_rcu: 322 cond_resched(); 323 rcu_read_lock(); 324 restart: 325 sk_nulls_for_each_rcu(sk, node, &head->chain) { 326 int state = inet_sk_state_load(sk); 327 328 if ((1 << state) & ~(TCPF_TIME_WAIT | 329 TCPF_NEW_SYN_RECV)) 330 continue; 331 332 if (refcount_read(&sock_net(sk)->ns.count)) 333 continue; 334 335 if (unlikely(!refcount_inc_not_zero(&sk->sk_refcnt))) 336 continue; 337 338 if (refcount_read(&sock_net(sk)->ns.count)) { 339 sock_gen_put(sk); 340 goto restart; 341 } 342 343 rcu_read_unlock(); 344 local_bh_disable(); 345 if (state == TCP_TIME_WAIT) { 346 inet_twsk_deschedule_put(inet_twsk(sk)); 347 } else { 348 struct request_sock *req = inet_reqsk(sk); 349 350 inet_csk_reqsk_queue_drop_and_put(req->rsk_listener, 351 req); 352 } 353 local_bh_enable(); 354 goto restart_rcu; 355 } 356 /* If the nulls value we got at the end of this lookup is 357 * not the expected one, we must restart lookup. 358 * We probably met an item that was moved to another chain. 359 */ 360 if (get_nulls_value(node) != slot) 361 goto restart; 362 rcu_read_unlock(); 363 } 364 } 365