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 #include <net/tcp.h> 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 78 tcp_twsk_destructor((struct sock *)tw); 79 kmem_cache_free(tw->tw_prot->twsk_prot->twsk_slab, tw); 80 module_put(owner); 81 } 82 83 void inet_twsk_put(struct inet_timewait_sock *tw) 84 { 85 if (refcount_dec_and_test(&tw->tw_refcnt)) 86 inet_twsk_free(tw); 87 } 88 EXPORT_SYMBOL_GPL(inet_twsk_put); 89 90 static void inet_twsk_add_node_rcu(struct inet_timewait_sock *tw, 91 struct hlist_nulls_head *list) 92 { 93 hlist_nulls_add_head_rcu(&tw->tw_node, list); 94 } 95 96 static void inet_twsk_schedule(struct inet_timewait_sock *tw, int timeo) 97 { 98 __inet_twsk_schedule(tw, timeo, false); 99 } 100 101 /* 102 * Enter the time wait state. 103 * Essentially we whip up a timewait bucket, copy the relevant info into it 104 * from the SK, and mess with hash chains and list linkage. 105 * 106 * The caller must not access @tw anymore after this function returns. 107 */ 108 void inet_twsk_hashdance_schedule(struct inet_timewait_sock *tw, 109 struct sock *sk, 110 struct inet_hashinfo *hashinfo, 111 int timeo) 112 { 113 const struct inet_sock *inet = inet_sk(sk); 114 const struct inet_connection_sock *icsk = inet_csk(sk); 115 struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, sk->sk_hash); 116 spinlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash); 117 struct inet_bind_hashbucket *bhead, *bhead2; 118 119 /* Step 1: Put TW into bind hash. Original socket stays there too. 120 Note, that any socket with inet->num != 0 MUST be bound in 121 binding cache, even if it is closed. 122 */ 123 bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), inet->inet_num, 124 hashinfo->bhash_size)]; 125 bhead2 = inet_bhashfn_portaddr(hashinfo, sk, twsk_net(tw), inet->inet_num); 126 127 local_bh_disable(); 128 spin_lock(&bhead->lock); 129 spin_lock(&bhead2->lock); 130 131 tw->tw_tb = icsk->icsk_bind_hash; 132 WARN_ON(!icsk->icsk_bind_hash); 133 134 tw->tw_tb2 = icsk->icsk_bind2_hash; 135 WARN_ON(!icsk->icsk_bind2_hash); 136 sk_add_bind_node((struct sock *)tw, &tw->tw_tb2->owners); 137 138 spin_unlock(&bhead2->lock); 139 spin_unlock(&bhead->lock); 140 141 spin_lock(lock); 142 143 /* Step 2: Hash TW into tcp ehash chain */ 144 inet_twsk_add_node_rcu(tw, &ehead->chain); 145 146 /* Step 3: Remove SK from hash chain */ 147 if (__sk_nulls_del_node_init_rcu(sk)) 148 sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1); 149 150 151 /* Ensure above writes are committed into memory before updating the 152 * refcount. 153 * Provides ordering vs later refcount_inc(). 154 */ 155 smp_wmb(); 156 /* tw_refcnt is set to 3 because we have : 157 * - one reference for bhash chain. 158 * - one reference for ehash chain. 159 * - one reference for timer. 160 * Also note that after this point, we lost our implicit reference 161 * so we are not allowed to use tw anymore. 162 */ 163 refcount_set(&tw->tw_refcnt, 3); 164 165 inet_twsk_schedule(tw, timeo); 166 167 spin_unlock(lock); 168 local_bh_enable(); 169 } 170 171 static void tw_timer_handler(struct timer_list *t) 172 { 173 struct inet_timewait_sock *tw = timer_container_of(tw, t, tw_timer); 174 175 inet_twsk_kill(tw); 176 } 177 178 struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk, 179 struct inet_timewait_death_row *dr, 180 const int state) 181 { 182 struct inet_timewait_sock *tw; 183 184 if (refcount_read(&dr->tw_refcount) - 1 >= 185 READ_ONCE(dr->sysctl_max_tw_buckets)) 186 return NULL; 187 188 tw = kmem_cache_alloc(sk->sk_prot_creator->twsk_prot->twsk_slab, 189 GFP_ATOMIC); 190 if (tw) { 191 const struct inet_sock *inet = inet_sk(sk); 192 193 tw->tw_dr = dr; 194 /* Give us an identity. */ 195 tw->tw_daddr = inet->inet_daddr; 196 tw->tw_rcv_saddr = inet->inet_rcv_saddr; 197 tw->tw_bound_dev_if = sk->sk_bound_dev_if; 198 tw->tw_tos = inet->tos; 199 tw->tw_num = inet->inet_num; 200 tw->tw_state = TCP_TIME_WAIT; 201 tw->tw_substate = state; 202 tw->tw_sport = inet->inet_sport; 203 tw->tw_dport = inet->inet_dport; 204 tw->tw_family = sk->sk_family; 205 tw->tw_reuse = sk->sk_reuse; 206 tw->tw_reuseport = sk->sk_reuseport; 207 tw->tw_hash = sk->sk_hash; 208 tw->tw_ipv6only = 0; 209 tw->tw_transparent = inet_test_bit(TRANSPARENT, sk); 210 tw->tw_prot = sk->sk_prot_creator; 211 atomic64_set(&tw->tw_cookie, atomic64_read(&sk->sk_cookie)); 212 twsk_net_set(tw, sock_net(sk)); 213 timer_setup(&tw->tw_timer, tw_timer_handler, 0); 214 /* 215 * Because we use RCU lookups, we should not set tw_refcnt 216 * to a non null value before everything is setup for this 217 * timewait socket. 218 */ 219 refcount_set(&tw->tw_refcnt, 0); 220 221 __module_get(tw->tw_prot->owner); 222 } 223 224 return tw; 225 } 226 227 /* These are always called from BH context. See callers in 228 * tcp_input.c to verify this. 229 */ 230 231 /* This is for handling early-kills of TIME_WAIT sockets. 232 * Warning : consume reference. 233 * Caller should not access tw anymore. 234 */ 235 void inet_twsk_deschedule_put(struct inet_timewait_sock *tw) 236 { 237 struct inet_hashinfo *hashinfo = tw->tw_dr->hashinfo; 238 spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash); 239 240 /* inet_twsk_purge() walks over all sockets, including tw ones, 241 * and removes them via inet_twsk_deschedule_put() after a 242 * refcount_inc_not_zero(). 243 * 244 * inet_twsk_hashdance_schedule() must (re)init the refcount before 245 * arming the timer, i.e. inet_twsk_purge can obtain a reference to 246 * a twsk that did not yet schedule the timer. 247 * 248 * The ehash lock synchronizes these two: 249 * After acquiring the lock, the timer is always scheduled (else 250 * timer_shutdown returns false), because hashdance_schedule releases 251 * the ehash lock only after completing the timer initialization. 252 * 253 * Without grabbing the ehash lock, we get: 254 * 1) cpu x sets twsk refcount to 3 255 * 2) cpu y bumps refcount to 4 256 * 3) cpu y calls inet_twsk_deschedule_put() and shuts timer down 257 * 4) cpu x tries to start timer, but mod_timer is a noop post-shutdown 258 * -> timer refcount is never decremented. 259 */ 260 spin_lock(lock); 261 /* Makes sure hashdance_schedule() has completed */ 262 spin_unlock(lock); 263 264 if (timer_shutdown_sync(&tw->tw_timer)) 265 inet_twsk_kill(tw); 266 inet_twsk_put(tw); 267 } 268 EXPORT_SYMBOL(inet_twsk_deschedule_put); 269 270 void __inet_twsk_schedule(struct inet_timewait_sock *tw, int timeo, bool rearm) 271 { 272 /* timeout := RTO * 3.5 273 * 274 * 3.5 = 1+2+0.5 to wait for two retransmits. 275 * 276 * RATIONALE: if FIN arrived and we entered TIME-WAIT state, 277 * our ACK acking that FIN can be lost. If N subsequent retransmitted 278 * FINs (or previous seqments) are lost (probability of such event 279 * is p^(N+1), where p is probability to lose single packet and 280 * time to detect the loss is about RTO*(2^N - 1) with exponential 281 * backoff). Normal timewait length is calculated so, that we 282 * waited at least for one retransmitted FIN (maximal RTO is 120sec). 283 * [ BTW Linux. following BSD, violates this requirement waiting 284 * only for 60sec, we should wait at least for 240 secs. 285 * Well, 240 consumes too much of resources 8) 286 * ] 287 * This interval is not reduced to catch old duplicate and 288 * responces to our wandering segments living for two MSLs. 289 * However, if we use PAWS to detect 290 * old duplicates, we can reduce the interval to bounds required 291 * by RTO, rather than MSL. So, if peer understands PAWS, we 292 * kill tw bucket after 3.5*RTO (it is important that this number 293 * is greater than TS tick!) and detect old duplicates with help 294 * of PAWS. 295 */ 296 297 if (!rearm) { 298 bool kill = timeo <= 4*HZ; 299 300 __NET_INC_STATS(twsk_net(tw), kill ? LINUX_MIB_TIMEWAITKILLED : 301 LINUX_MIB_TIMEWAITED); 302 BUG_ON(mod_timer(&tw->tw_timer, jiffies + timeo)); 303 refcount_inc(&tw->tw_dr->tw_refcount); 304 } else { 305 mod_timer_pending(&tw->tw_timer, jiffies + timeo); 306 } 307 } 308 309 /* Remove all non full sockets (TIME_WAIT and NEW_SYN_RECV) for dead netns */ 310 void inet_twsk_purge(struct inet_hashinfo *hashinfo) 311 { 312 struct inet_ehash_bucket *head = &hashinfo->ehash[0]; 313 unsigned int ehash_mask = hashinfo->ehash_mask; 314 struct hlist_nulls_node *node; 315 unsigned int slot; 316 struct sock *sk; 317 318 for (slot = 0; slot <= ehash_mask; slot++, head++) { 319 if (hlist_nulls_empty(&head->chain)) 320 continue; 321 322 restart_rcu: 323 cond_resched(); 324 rcu_read_lock(); 325 restart: 326 sk_nulls_for_each_rcu(sk, node, &head->chain) { 327 int state = inet_sk_state_load(sk); 328 329 if ((1 << state) & ~(TCPF_TIME_WAIT | 330 TCPF_NEW_SYN_RECV)) 331 continue; 332 333 if (refcount_read(&sock_net(sk)->ns.count)) 334 continue; 335 336 if (unlikely(!refcount_inc_not_zero(&sk->sk_refcnt))) 337 continue; 338 339 if (refcount_read(&sock_net(sk)->ns.count)) { 340 sock_gen_put(sk); 341 goto restart; 342 } 343 344 rcu_read_unlock(); 345 local_bh_disable(); 346 if (state == TCP_TIME_WAIT) { 347 inet_twsk_deschedule_put(inet_twsk(sk)); 348 } else { 349 struct request_sock *req = inet_reqsk(sk); 350 351 inet_csk_reqsk_queue_drop_and_put(req->rsk_listener, 352 req); 353 } 354 local_bh_enable(); 355 goto restart_rcu; 356 } 357 /* If the nulls value we got at the end of this lookup is 358 * not the expected one, we must restart lookup. 359 * We probably met an item that was moved to another chain. 360 */ 361 if (get_nulls_value(node) != slot) 362 goto restart; 363 rcu_read_unlock(); 364 } 365 } 366