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