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 <net/inet_hashtables.h> 13 #include <net/inet_timewait_sock.h> 14 #include <net/ip.h> 15 16 /* Must be called with locally disabled BHs. */ 17 static void __inet_twsk_kill(struct inet_timewait_sock *tw, 18 struct inet_hashinfo *hashinfo) 19 { 20 struct inet_bind_hashbucket *bhead; 21 struct inet_bind_bucket *tb; 22 /* Unlink from established hashes. */ 23 spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash); 24 25 spin_lock(lock); 26 if (hlist_nulls_unhashed(&tw->tw_node)) { 27 spin_unlock(lock); 28 return; 29 } 30 hlist_nulls_del_rcu(&tw->tw_node); 31 sk_nulls_node_init(&tw->tw_node); 32 spin_unlock(lock); 33 34 /* Disassociate with bind bucket. */ 35 bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), tw->tw_num, 36 hashinfo->bhash_size)]; 37 spin_lock(&bhead->lock); 38 tb = tw->tw_tb; 39 __hlist_del(&tw->tw_bind_node); 40 tw->tw_tb = NULL; 41 inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb); 42 spin_unlock(&bhead->lock); 43 #ifdef SOCK_REFCNT_DEBUG 44 if (atomic_read(&tw->tw_refcnt) != 1) { 45 printk(KERN_DEBUG "%s timewait_sock %p refcnt=%d\n", 46 tw->tw_prot->name, tw, atomic_read(&tw->tw_refcnt)); 47 } 48 #endif 49 inet_twsk_put(tw); 50 } 51 52 void inet_twsk_put(struct inet_timewait_sock *tw) 53 { 54 if (atomic_dec_and_test(&tw->tw_refcnt)) { 55 struct module *owner = tw->tw_prot->owner; 56 twsk_destructor((struct sock *)tw); 57 #ifdef SOCK_REFCNT_DEBUG 58 printk(KERN_DEBUG "%s timewait_sock %p released\n", 59 tw->tw_prot->name, tw); 60 #endif 61 release_net(twsk_net(tw)); 62 kmem_cache_free(tw->tw_prot->twsk_prot->twsk_slab, tw); 63 module_put(owner); 64 } 65 } 66 EXPORT_SYMBOL_GPL(inet_twsk_put); 67 68 /* 69 * Enter the time wait state. This is called with locally disabled BH. 70 * Essentially we whip up a timewait bucket, copy the relevant info into it 71 * from the SK, and mess with hash chains and list linkage. 72 */ 73 void __inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk, 74 struct inet_hashinfo *hashinfo) 75 { 76 const struct inet_sock *inet = inet_sk(sk); 77 const struct inet_connection_sock *icsk = inet_csk(sk); 78 struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, sk->sk_hash); 79 spinlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash); 80 struct inet_bind_hashbucket *bhead; 81 /* Step 1: Put TW into bind hash. Original socket stays there too. 82 Note, that any socket with inet->num != 0 MUST be bound in 83 binding cache, even if it is closed. 84 */ 85 bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), inet->num, 86 hashinfo->bhash_size)]; 87 spin_lock(&bhead->lock); 88 tw->tw_tb = icsk->icsk_bind_hash; 89 WARN_ON(!icsk->icsk_bind_hash); 90 inet_twsk_add_bind_node(tw, &tw->tw_tb->owners); 91 spin_unlock(&bhead->lock); 92 93 spin_lock(lock); 94 95 /* 96 * Step 2: Hash TW into TIMEWAIT chain. 97 * Should be done before removing sk from established chain 98 * because readers are lockless and search established first. 99 */ 100 atomic_inc(&tw->tw_refcnt); 101 inet_twsk_add_node_rcu(tw, &ehead->twchain); 102 103 /* Step 3: Remove SK from established hash. */ 104 if (__sk_nulls_del_node_init_rcu(sk)) 105 sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1); 106 107 spin_unlock(lock); 108 } 109 110 EXPORT_SYMBOL_GPL(__inet_twsk_hashdance); 111 112 struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk, const int state) 113 { 114 struct inet_timewait_sock *tw = 115 kmem_cache_alloc(sk->sk_prot_creator->twsk_prot->twsk_slab, 116 GFP_ATOMIC); 117 if (tw != NULL) { 118 const struct inet_sock *inet = inet_sk(sk); 119 120 /* Give us an identity. */ 121 tw->tw_daddr = inet->daddr; 122 tw->tw_rcv_saddr = inet->rcv_saddr; 123 tw->tw_bound_dev_if = sk->sk_bound_dev_if; 124 tw->tw_num = inet->num; 125 tw->tw_state = TCP_TIME_WAIT; 126 tw->tw_substate = state; 127 tw->tw_sport = inet->sport; 128 tw->tw_dport = inet->dport; 129 tw->tw_family = sk->sk_family; 130 tw->tw_reuse = sk->sk_reuse; 131 tw->tw_hash = sk->sk_hash; 132 tw->tw_ipv6only = 0; 133 tw->tw_transparent = inet->transparent; 134 tw->tw_prot = sk->sk_prot_creator; 135 twsk_net_set(tw, hold_net(sock_net(sk))); 136 atomic_set(&tw->tw_refcnt, 1); 137 inet_twsk_dead_node_init(tw); 138 __module_get(tw->tw_prot->owner); 139 } 140 141 return tw; 142 } 143 144 EXPORT_SYMBOL_GPL(inet_twsk_alloc); 145 146 /* Returns non-zero if quota exceeded. */ 147 static int inet_twdr_do_twkill_work(struct inet_timewait_death_row *twdr, 148 const int slot) 149 { 150 struct inet_timewait_sock *tw; 151 struct hlist_node *node; 152 unsigned int killed; 153 int ret; 154 155 /* NOTE: compare this to previous version where lock 156 * was released after detaching chain. It was racy, 157 * because tw buckets are scheduled in not serialized context 158 * in 2.3 (with netfilter), and with softnet it is common, because 159 * soft irqs are not sequenced. 160 */ 161 killed = 0; 162 ret = 0; 163 rescan: 164 inet_twsk_for_each_inmate(tw, node, &twdr->cells[slot]) { 165 __inet_twsk_del_dead_node(tw); 166 spin_unlock(&twdr->death_lock); 167 __inet_twsk_kill(tw, twdr->hashinfo); 168 #ifdef CONFIG_NET_NS 169 NET_INC_STATS_BH(twsk_net(tw), LINUX_MIB_TIMEWAITED); 170 #endif 171 inet_twsk_put(tw); 172 killed++; 173 spin_lock(&twdr->death_lock); 174 if (killed > INET_TWDR_TWKILL_QUOTA) { 175 ret = 1; 176 break; 177 } 178 179 /* While we dropped twdr->death_lock, another cpu may have 180 * killed off the next TW bucket in the list, therefore 181 * do a fresh re-read of the hlist head node with the 182 * lock reacquired. We still use the hlist traversal 183 * macro in order to get the prefetches. 184 */ 185 goto rescan; 186 } 187 188 twdr->tw_count -= killed; 189 #ifndef CONFIG_NET_NS 190 NET_ADD_STATS_BH(&init_net, LINUX_MIB_TIMEWAITED, killed); 191 #endif 192 return ret; 193 } 194 195 void inet_twdr_hangman(unsigned long data) 196 { 197 struct inet_timewait_death_row *twdr; 198 int unsigned need_timer; 199 200 twdr = (struct inet_timewait_death_row *)data; 201 spin_lock(&twdr->death_lock); 202 203 if (twdr->tw_count == 0) 204 goto out; 205 206 need_timer = 0; 207 if (inet_twdr_do_twkill_work(twdr, twdr->slot)) { 208 twdr->thread_slots |= (1 << twdr->slot); 209 schedule_work(&twdr->twkill_work); 210 need_timer = 1; 211 } else { 212 /* We purged the entire slot, anything left? */ 213 if (twdr->tw_count) 214 need_timer = 1; 215 } 216 twdr->slot = ((twdr->slot + 1) & (INET_TWDR_TWKILL_SLOTS - 1)); 217 if (need_timer) 218 mod_timer(&twdr->tw_timer, jiffies + twdr->period); 219 out: 220 spin_unlock(&twdr->death_lock); 221 } 222 223 EXPORT_SYMBOL_GPL(inet_twdr_hangman); 224 225 void inet_twdr_twkill_work(struct work_struct *work) 226 { 227 struct inet_timewait_death_row *twdr = 228 container_of(work, struct inet_timewait_death_row, twkill_work); 229 int i; 230 231 BUILD_BUG_ON((INET_TWDR_TWKILL_SLOTS - 1) > 232 (sizeof(twdr->thread_slots) * 8)); 233 234 while (twdr->thread_slots) { 235 spin_lock_bh(&twdr->death_lock); 236 for (i = 0; i < INET_TWDR_TWKILL_SLOTS; i++) { 237 if (!(twdr->thread_slots & (1 << i))) 238 continue; 239 240 while (inet_twdr_do_twkill_work(twdr, i) != 0) { 241 if (need_resched()) { 242 spin_unlock_bh(&twdr->death_lock); 243 schedule(); 244 spin_lock_bh(&twdr->death_lock); 245 } 246 } 247 248 twdr->thread_slots &= ~(1 << i); 249 } 250 spin_unlock_bh(&twdr->death_lock); 251 } 252 } 253 254 EXPORT_SYMBOL_GPL(inet_twdr_twkill_work); 255 256 /* These are always called from BH context. See callers in 257 * tcp_input.c to verify this. 258 */ 259 260 /* This is for handling early-kills of TIME_WAIT sockets. */ 261 void inet_twsk_deschedule(struct inet_timewait_sock *tw, 262 struct inet_timewait_death_row *twdr) 263 { 264 spin_lock(&twdr->death_lock); 265 if (inet_twsk_del_dead_node(tw)) { 266 inet_twsk_put(tw); 267 if (--twdr->tw_count == 0) 268 del_timer(&twdr->tw_timer); 269 } 270 spin_unlock(&twdr->death_lock); 271 __inet_twsk_kill(tw, twdr->hashinfo); 272 } 273 274 EXPORT_SYMBOL(inet_twsk_deschedule); 275 276 void inet_twsk_schedule(struct inet_timewait_sock *tw, 277 struct inet_timewait_death_row *twdr, 278 const int timeo, const int timewait_len) 279 { 280 struct hlist_head *list; 281 int slot; 282 283 /* timeout := RTO * 3.5 284 * 285 * 3.5 = 1+2+0.5 to wait for two retransmits. 286 * 287 * RATIONALE: if FIN arrived and we entered TIME-WAIT state, 288 * our ACK acking that FIN can be lost. If N subsequent retransmitted 289 * FINs (or previous seqments) are lost (probability of such event 290 * is p^(N+1), where p is probability to lose single packet and 291 * time to detect the loss is about RTO*(2^N - 1) with exponential 292 * backoff). Normal timewait length is calculated so, that we 293 * waited at least for one retransmitted FIN (maximal RTO is 120sec). 294 * [ BTW Linux. following BSD, violates this requirement waiting 295 * only for 60sec, we should wait at least for 240 secs. 296 * Well, 240 consumes too much of resources 8) 297 * ] 298 * This interval is not reduced to catch old duplicate and 299 * responces to our wandering segments living for two MSLs. 300 * However, if we use PAWS to detect 301 * old duplicates, we can reduce the interval to bounds required 302 * by RTO, rather than MSL. So, if peer understands PAWS, we 303 * kill tw bucket after 3.5*RTO (it is important that this number 304 * is greater than TS tick!) and detect old duplicates with help 305 * of PAWS. 306 */ 307 slot = (timeo + (1 << INET_TWDR_RECYCLE_TICK) - 1) >> INET_TWDR_RECYCLE_TICK; 308 309 spin_lock(&twdr->death_lock); 310 311 /* Unlink it, if it was scheduled */ 312 if (inet_twsk_del_dead_node(tw)) 313 twdr->tw_count--; 314 else 315 atomic_inc(&tw->tw_refcnt); 316 317 if (slot >= INET_TWDR_RECYCLE_SLOTS) { 318 /* Schedule to slow timer */ 319 if (timeo >= timewait_len) { 320 slot = INET_TWDR_TWKILL_SLOTS - 1; 321 } else { 322 slot = DIV_ROUND_UP(timeo, twdr->period); 323 if (slot >= INET_TWDR_TWKILL_SLOTS) 324 slot = INET_TWDR_TWKILL_SLOTS - 1; 325 } 326 tw->tw_ttd = jiffies + timeo; 327 slot = (twdr->slot + slot) & (INET_TWDR_TWKILL_SLOTS - 1); 328 list = &twdr->cells[slot]; 329 } else { 330 tw->tw_ttd = jiffies + (slot << INET_TWDR_RECYCLE_TICK); 331 332 if (twdr->twcal_hand < 0) { 333 twdr->twcal_hand = 0; 334 twdr->twcal_jiffie = jiffies; 335 twdr->twcal_timer.expires = twdr->twcal_jiffie + 336 (slot << INET_TWDR_RECYCLE_TICK); 337 add_timer(&twdr->twcal_timer); 338 } else { 339 if (time_after(twdr->twcal_timer.expires, 340 jiffies + (slot << INET_TWDR_RECYCLE_TICK))) 341 mod_timer(&twdr->twcal_timer, 342 jiffies + (slot << INET_TWDR_RECYCLE_TICK)); 343 slot = (twdr->twcal_hand + slot) & (INET_TWDR_RECYCLE_SLOTS - 1); 344 } 345 list = &twdr->twcal_row[slot]; 346 } 347 348 hlist_add_head(&tw->tw_death_node, list); 349 350 if (twdr->tw_count++ == 0) 351 mod_timer(&twdr->tw_timer, jiffies + twdr->period); 352 spin_unlock(&twdr->death_lock); 353 } 354 355 EXPORT_SYMBOL_GPL(inet_twsk_schedule); 356 357 void inet_twdr_twcal_tick(unsigned long data) 358 { 359 struct inet_timewait_death_row *twdr; 360 int n, slot; 361 unsigned long j; 362 unsigned long now = jiffies; 363 int killed = 0; 364 int adv = 0; 365 366 twdr = (struct inet_timewait_death_row *)data; 367 368 spin_lock(&twdr->death_lock); 369 if (twdr->twcal_hand < 0) 370 goto out; 371 372 slot = twdr->twcal_hand; 373 j = twdr->twcal_jiffie; 374 375 for (n = 0; n < INET_TWDR_RECYCLE_SLOTS; n++) { 376 if (time_before_eq(j, now)) { 377 struct hlist_node *node, *safe; 378 struct inet_timewait_sock *tw; 379 380 inet_twsk_for_each_inmate_safe(tw, node, safe, 381 &twdr->twcal_row[slot]) { 382 __inet_twsk_del_dead_node(tw); 383 __inet_twsk_kill(tw, twdr->hashinfo); 384 #ifdef CONFIG_NET_NS 385 NET_INC_STATS_BH(twsk_net(tw), LINUX_MIB_TIMEWAITKILLED); 386 #endif 387 inet_twsk_put(tw); 388 killed++; 389 } 390 } else { 391 if (!adv) { 392 adv = 1; 393 twdr->twcal_jiffie = j; 394 twdr->twcal_hand = slot; 395 } 396 397 if (!hlist_empty(&twdr->twcal_row[slot])) { 398 mod_timer(&twdr->twcal_timer, j); 399 goto out; 400 } 401 } 402 j += 1 << INET_TWDR_RECYCLE_TICK; 403 slot = (slot + 1) & (INET_TWDR_RECYCLE_SLOTS - 1); 404 } 405 twdr->twcal_hand = -1; 406 407 out: 408 if ((twdr->tw_count -= killed) == 0) 409 del_timer(&twdr->tw_timer); 410 #ifndef CONFIG_NET_NS 411 NET_ADD_STATS_BH(&init_net, LINUX_MIB_TIMEWAITKILLED, killed); 412 #endif 413 spin_unlock(&twdr->death_lock); 414 } 415 416 EXPORT_SYMBOL_GPL(inet_twdr_twcal_tick); 417 418 void inet_twsk_purge(struct net *net, struct inet_hashinfo *hashinfo, 419 struct inet_timewait_death_row *twdr, int family) 420 { 421 struct inet_timewait_sock *tw; 422 struct sock *sk; 423 struct hlist_nulls_node *node; 424 int h; 425 426 local_bh_disable(); 427 for (h = 0; h < (hashinfo->ehash_size); h++) { 428 struct inet_ehash_bucket *head = 429 inet_ehash_bucket(hashinfo, h); 430 spinlock_t *lock = inet_ehash_lockp(hashinfo, h); 431 restart: 432 spin_lock(lock); 433 sk_nulls_for_each(sk, node, &head->twchain) { 434 435 tw = inet_twsk(sk); 436 if (!net_eq(twsk_net(tw), net) || 437 tw->tw_family != family) 438 continue; 439 440 atomic_inc(&tw->tw_refcnt); 441 spin_unlock(lock); 442 inet_twsk_deschedule(tw, twdr); 443 inet_twsk_put(tw); 444 445 goto restart; 446 } 447 spin_unlock(lock); 448 } 449 local_bh_enable(); 450 } 451 EXPORT_SYMBOL_GPL(inet_twsk_purge); 452