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