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(tw->tw_num, hashinfo->bhash_size)]; 36 spin_lock(&bhead->lock); 37 tb = tw->tw_tb; 38 __hlist_del(&tw->tw_bind_node); 39 tw->tw_tb = NULL; 40 inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb); 41 spin_unlock(&bhead->lock); 42 #ifdef SOCK_REFCNT_DEBUG 43 if (atomic_read(&tw->tw_refcnt) != 1) { 44 printk(KERN_DEBUG "%s timewait_sock %p refcnt=%d\n", 45 tw->tw_prot->name, tw, atomic_read(&tw->tw_refcnt)); 46 } 47 #endif 48 inet_twsk_put(tw); 49 } 50 51 void inet_twsk_put(struct inet_timewait_sock *tw) 52 { 53 if (atomic_dec_and_test(&tw->tw_refcnt)) { 54 struct module *owner = tw->tw_prot->owner; 55 twsk_destructor((struct sock *)tw); 56 #ifdef SOCK_REFCNT_DEBUG 57 printk(KERN_DEBUG "%s timewait_sock %p released\n", 58 tw->tw_prot->name, tw); 59 #endif 60 release_net(twsk_net(tw)); 61 kmem_cache_free(tw->tw_prot->twsk_prot->twsk_slab, tw); 62 module_put(owner); 63 } 64 } 65 EXPORT_SYMBOL_GPL(inet_twsk_put); 66 67 /* 68 * Enter the time wait state. This is called with locally disabled BH. 69 * Essentially we whip up a timewait bucket, copy the relevant info into it 70 * from the SK, and mess with hash chains and list linkage. 71 */ 72 void __inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk, 73 struct inet_hashinfo *hashinfo) 74 { 75 const struct inet_sock *inet = inet_sk(sk); 76 const struct inet_connection_sock *icsk = inet_csk(sk); 77 struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, sk->sk_hash); 78 rwlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash); 79 struct inet_bind_hashbucket *bhead; 80 /* Step 1: Put TW into bind hash. Original socket stays there too. 81 Note, that any socket with inet->num != 0 MUST be bound in 82 binding cache, even if it is closed. 83 */ 84 bhead = &hashinfo->bhash[inet_bhashfn(inet->num, hashinfo->bhash_size)]; 85 spin_lock(&bhead->lock); 86 tw->tw_tb = icsk->icsk_bind_hash; 87 BUG_TRAP(icsk->icsk_bind_hash); 88 inet_twsk_add_bind_node(tw, &tw->tw_tb->owners); 89 spin_unlock(&bhead->lock); 90 91 write_lock(lock); 92 93 /* Step 2: Remove SK from established hash. */ 94 if (__sk_del_node_init(sk)) 95 sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1); 96 97 /* Step 3: Hash TW into TIMEWAIT chain. */ 98 inet_twsk_add_node(tw, &ehead->twchain); 99 atomic_inc(&tw->tw_refcnt); 100 101 write_unlock(lock); 102 } 103 104 EXPORT_SYMBOL_GPL(__inet_twsk_hashdance); 105 106 struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk, const int state) 107 { 108 struct inet_timewait_sock *tw = 109 kmem_cache_alloc(sk->sk_prot_creator->twsk_prot->twsk_slab, 110 GFP_ATOMIC); 111 if (tw != NULL) { 112 const struct inet_sock *inet = inet_sk(sk); 113 114 /* Give us an identity. */ 115 tw->tw_daddr = inet->daddr; 116 tw->tw_rcv_saddr = inet->rcv_saddr; 117 tw->tw_bound_dev_if = sk->sk_bound_dev_if; 118 tw->tw_num = inet->num; 119 tw->tw_state = TCP_TIME_WAIT; 120 tw->tw_substate = state; 121 tw->tw_sport = inet->sport; 122 tw->tw_dport = inet->dport; 123 tw->tw_family = sk->sk_family; 124 tw->tw_reuse = sk->sk_reuse; 125 tw->tw_hash = sk->sk_hash; 126 tw->tw_ipv6only = 0; 127 tw->tw_prot = sk->sk_prot_creator; 128 twsk_net_set(tw, hold_net(sock_net(sk))); 129 atomic_set(&tw->tw_refcnt, 1); 130 inet_twsk_dead_node_init(tw); 131 __module_get(tw->tw_prot->owner); 132 } 133 134 return tw; 135 } 136 137 EXPORT_SYMBOL_GPL(inet_twsk_alloc); 138 139 /* Returns non-zero if quota exceeded. */ 140 static int inet_twdr_do_twkill_work(struct inet_timewait_death_row *twdr, 141 const int slot) 142 { 143 struct inet_timewait_sock *tw; 144 struct hlist_node *node; 145 unsigned int killed; 146 int ret; 147 148 /* NOTE: compare this to previous version where lock 149 * was released after detaching chain. It was racy, 150 * because tw buckets are scheduled in not serialized context 151 * in 2.3 (with netfilter), and with softnet it is common, because 152 * soft irqs are not sequenced. 153 */ 154 killed = 0; 155 ret = 0; 156 rescan: 157 inet_twsk_for_each_inmate(tw, node, &twdr->cells[slot]) { 158 __inet_twsk_del_dead_node(tw); 159 spin_unlock(&twdr->death_lock); 160 __inet_twsk_kill(tw, twdr->hashinfo); 161 inet_twsk_put(tw); 162 killed++; 163 spin_lock(&twdr->death_lock); 164 if (killed > INET_TWDR_TWKILL_QUOTA) { 165 ret = 1; 166 break; 167 } 168 169 /* While we dropped twdr->death_lock, another cpu may have 170 * killed off the next TW bucket in the list, therefore 171 * do a fresh re-read of the hlist head node with the 172 * lock reacquired. We still use the hlist traversal 173 * macro in order to get the prefetches. 174 */ 175 goto rescan; 176 } 177 178 twdr->tw_count -= killed; 179 NET_ADD_STATS_BH(LINUX_MIB_TIMEWAITED, killed); 180 181 return ret; 182 } 183 184 void inet_twdr_hangman(unsigned long data) 185 { 186 struct inet_timewait_death_row *twdr; 187 int unsigned need_timer; 188 189 twdr = (struct inet_timewait_death_row *)data; 190 spin_lock(&twdr->death_lock); 191 192 if (twdr->tw_count == 0) 193 goto out; 194 195 need_timer = 0; 196 if (inet_twdr_do_twkill_work(twdr, twdr->slot)) { 197 twdr->thread_slots |= (1 << twdr->slot); 198 schedule_work(&twdr->twkill_work); 199 need_timer = 1; 200 } else { 201 /* We purged the entire slot, anything left? */ 202 if (twdr->tw_count) 203 need_timer = 1; 204 } 205 twdr->slot = ((twdr->slot + 1) & (INET_TWDR_TWKILL_SLOTS - 1)); 206 if (need_timer) 207 mod_timer(&twdr->tw_timer, jiffies + twdr->period); 208 out: 209 spin_unlock(&twdr->death_lock); 210 } 211 212 EXPORT_SYMBOL_GPL(inet_twdr_hangman); 213 214 void inet_twdr_twkill_work(struct work_struct *work) 215 { 216 struct inet_timewait_death_row *twdr = 217 container_of(work, struct inet_timewait_death_row, twkill_work); 218 int i; 219 220 BUILD_BUG_ON((INET_TWDR_TWKILL_SLOTS - 1) > 221 (sizeof(twdr->thread_slots) * 8)); 222 223 while (twdr->thread_slots) { 224 spin_lock_bh(&twdr->death_lock); 225 for (i = 0; i < INET_TWDR_TWKILL_SLOTS; i++) { 226 if (!(twdr->thread_slots & (1 << i))) 227 continue; 228 229 while (inet_twdr_do_twkill_work(twdr, i) != 0) { 230 if (need_resched()) { 231 spin_unlock_bh(&twdr->death_lock); 232 schedule(); 233 spin_lock_bh(&twdr->death_lock); 234 } 235 } 236 237 twdr->thread_slots &= ~(1 << i); 238 } 239 spin_unlock_bh(&twdr->death_lock); 240 } 241 } 242 243 EXPORT_SYMBOL_GPL(inet_twdr_twkill_work); 244 245 /* These are always called from BH context. See callers in 246 * tcp_input.c to verify this. 247 */ 248 249 /* This is for handling early-kills of TIME_WAIT sockets. */ 250 void inet_twsk_deschedule(struct inet_timewait_sock *tw, 251 struct inet_timewait_death_row *twdr) 252 { 253 spin_lock(&twdr->death_lock); 254 if (inet_twsk_del_dead_node(tw)) { 255 inet_twsk_put(tw); 256 if (--twdr->tw_count == 0) 257 del_timer(&twdr->tw_timer); 258 } 259 spin_unlock(&twdr->death_lock); 260 __inet_twsk_kill(tw, twdr->hashinfo); 261 } 262 263 EXPORT_SYMBOL(inet_twsk_deschedule); 264 265 void inet_twsk_schedule(struct inet_timewait_sock *tw, 266 struct inet_timewait_death_row *twdr, 267 const int timeo, const int timewait_len) 268 { 269 struct hlist_head *list; 270 int slot; 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 slot = (timeo + (1 << INET_TWDR_RECYCLE_TICK) - 1) >> INET_TWDR_RECYCLE_TICK; 297 298 spin_lock(&twdr->death_lock); 299 300 /* Unlink it, if it was scheduled */ 301 if (inet_twsk_del_dead_node(tw)) 302 twdr->tw_count--; 303 else 304 atomic_inc(&tw->tw_refcnt); 305 306 if (slot >= INET_TWDR_RECYCLE_SLOTS) { 307 /* Schedule to slow timer */ 308 if (timeo >= timewait_len) { 309 slot = INET_TWDR_TWKILL_SLOTS - 1; 310 } else { 311 slot = DIV_ROUND_UP(timeo, twdr->period); 312 if (slot >= INET_TWDR_TWKILL_SLOTS) 313 slot = INET_TWDR_TWKILL_SLOTS - 1; 314 } 315 tw->tw_ttd = jiffies + timeo; 316 slot = (twdr->slot + slot) & (INET_TWDR_TWKILL_SLOTS - 1); 317 list = &twdr->cells[slot]; 318 } else { 319 tw->tw_ttd = jiffies + (slot << INET_TWDR_RECYCLE_TICK); 320 321 if (twdr->twcal_hand < 0) { 322 twdr->twcal_hand = 0; 323 twdr->twcal_jiffie = jiffies; 324 twdr->twcal_timer.expires = twdr->twcal_jiffie + 325 (slot << INET_TWDR_RECYCLE_TICK); 326 add_timer(&twdr->twcal_timer); 327 } else { 328 if (time_after(twdr->twcal_timer.expires, 329 jiffies + (slot << INET_TWDR_RECYCLE_TICK))) 330 mod_timer(&twdr->twcal_timer, 331 jiffies + (slot << INET_TWDR_RECYCLE_TICK)); 332 slot = (twdr->twcal_hand + slot) & (INET_TWDR_RECYCLE_SLOTS - 1); 333 } 334 list = &twdr->twcal_row[slot]; 335 } 336 337 hlist_add_head(&tw->tw_death_node, list); 338 339 if (twdr->tw_count++ == 0) 340 mod_timer(&twdr->tw_timer, jiffies + twdr->period); 341 spin_unlock(&twdr->death_lock); 342 } 343 344 EXPORT_SYMBOL_GPL(inet_twsk_schedule); 345 346 void inet_twdr_twcal_tick(unsigned long data) 347 { 348 struct inet_timewait_death_row *twdr; 349 int n, slot; 350 unsigned long j; 351 unsigned long now = jiffies; 352 int killed = 0; 353 int adv = 0; 354 355 twdr = (struct inet_timewait_death_row *)data; 356 357 spin_lock(&twdr->death_lock); 358 if (twdr->twcal_hand < 0) 359 goto out; 360 361 slot = twdr->twcal_hand; 362 j = twdr->twcal_jiffie; 363 364 for (n = 0; n < INET_TWDR_RECYCLE_SLOTS; n++) { 365 if (time_before_eq(j, now)) { 366 struct hlist_node *node, *safe; 367 struct inet_timewait_sock *tw; 368 369 inet_twsk_for_each_inmate_safe(tw, node, safe, 370 &twdr->twcal_row[slot]) { 371 __inet_twsk_del_dead_node(tw); 372 __inet_twsk_kill(tw, twdr->hashinfo); 373 inet_twsk_put(tw); 374 killed++; 375 } 376 } else { 377 if (!adv) { 378 adv = 1; 379 twdr->twcal_jiffie = j; 380 twdr->twcal_hand = slot; 381 } 382 383 if (!hlist_empty(&twdr->twcal_row[slot])) { 384 mod_timer(&twdr->twcal_timer, j); 385 goto out; 386 } 387 } 388 j += 1 << INET_TWDR_RECYCLE_TICK; 389 slot = (slot + 1) & (INET_TWDR_RECYCLE_SLOTS - 1); 390 } 391 twdr->twcal_hand = -1; 392 393 out: 394 if ((twdr->tw_count -= killed) == 0) 395 del_timer(&twdr->tw_timer); 396 NET_ADD_STATS_BH(LINUX_MIB_TIMEWAITKILLED, killed); 397 spin_unlock(&twdr->death_lock); 398 } 399 400 EXPORT_SYMBOL_GPL(inet_twdr_twcal_tick); 401