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/config.h> 12 13 #include <net/inet_hashtables.h> 14 #include <net/inet_timewait_sock.h> 15 #include <net/ip.h> 16 17 /* Must be called with locally disabled BHs. */ 18 void __inet_twsk_kill(struct inet_timewait_sock *tw, struct inet_hashinfo *hashinfo) 19 { 20 struct inet_bind_hashbucket *bhead; 21 struct inet_bind_bucket *tb; 22 /* Unlink from established hashes. */ 23 struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, tw->tw_hash); 24 25 write_lock(&ehead->lock); 26 if (hlist_unhashed(&tw->tw_node)) { 27 write_unlock(&ehead->lock); 28 return; 29 } 30 __hlist_del(&tw->tw_node); 31 sk_node_init(&tw->tw_node); 32 write_unlock(&ehead->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 EXPORT_SYMBOL_GPL(__inet_twsk_kill); 52 53 /* 54 * Enter the time wait state. This is called with locally disabled BH. 55 * Essentially we whip up a timewait bucket, copy the relevant info into it 56 * from the SK, and mess with hash chains and list linkage. 57 */ 58 void __inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk, 59 struct inet_hashinfo *hashinfo) 60 { 61 const struct inet_sock *inet = inet_sk(sk); 62 const struct inet_connection_sock *icsk = inet_csk(sk); 63 struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, sk->sk_hash); 64 struct inet_bind_hashbucket *bhead; 65 /* Step 1: Put TW into bind hash. Original socket stays there too. 66 Note, that any socket with inet->num != 0 MUST be bound in 67 binding cache, even if it is closed. 68 */ 69 bhead = &hashinfo->bhash[inet_bhashfn(inet->num, hashinfo->bhash_size)]; 70 spin_lock(&bhead->lock); 71 tw->tw_tb = icsk->icsk_bind_hash; 72 BUG_TRAP(icsk->icsk_bind_hash); 73 inet_twsk_add_bind_node(tw, &tw->tw_tb->owners); 74 spin_unlock(&bhead->lock); 75 76 write_lock(&ehead->lock); 77 78 /* Step 2: Remove SK from established hash. */ 79 if (__sk_del_node_init(sk)) 80 sock_prot_dec_use(sk->sk_prot); 81 82 /* Step 3: Hash TW into TIMEWAIT half of established hash table. */ 83 inet_twsk_add_node(tw, &(ehead + hashinfo->ehash_size)->chain); 84 atomic_inc(&tw->tw_refcnt); 85 86 write_unlock(&ehead->lock); 87 } 88 89 EXPORT_SYMBOL_GPL(__inet_twsk_hashdance); 90 91 struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk, const int state) 92 { 93 struct inet_timewait_sock *tw = 94 kmem_cache_alloc(sk->sk_prot_creator->twsk_prot->twsk_slab, 95 SLAB_ATOMIC); 96 if (tw != NULL) { 97 const struct inet_sock *inet = inet_sk(sk); 98 99 /* Give us an identity. */ 100 tw->tw_daddr = inet->daddr; 101 tw->tw_rcv_saddr = inet->rcv_saddr; 102 tw->tw_bound_dev_if = sk->sk_bound_dev_if; 103 tw->tw_num = inet->num; 104 tw->tw_state = TCP_TIME_WAIT; 105 tw->tw_substate = state; 106 tw->tw_sport = inet->sport; 107 tw->tw_dport = inet->dport; 108 tw->tw_family = sk->sk_family; 109 tw->tw_reuse = sk->sk_reuse; 110 tw->tw_hash = sk->sk_hash; 111 tw->tw_ipv6only = 0; 112 tw->tw_prot = sk->sk_prot_creator; 113 atomic_set(&tw->tw_refcnt, 1); 114 inet_twsk_dead_node_init(tw); 115 __module_get(tw->tw_prot->owner); 116 } 117 118 return tw; 119 } 120 121 EXPORT_SYMBOL_GPL(inet_twsk_alloc); 122 123 /* Returns non-zero if quota exceeded. */ 124 static int inet_twdr_do_twkill_work(struct inet_timewait_death_row *twdr, 125 const int slot) 126 { 127 struct inet_timewait_sock *tw; 128 struct hlist_node *node; 129 unsigned int killed; 130 int ret; 131 132 /* NOTE: compare this to previous version where lock 133 * was released after detaching chain. It was racy, 134 * because tw buckets are scheduled in not serialized context 135 * in 2.3 (with netfilter), and with softnet it is common, because 136 * soft irqs are not sequenced. 137 */ 138 killed = 0; 139 ret = 0; 140 rescan: 141 inet_twsk_for_each_inmate(tw, node, &twdr->cells[slot]) { 142 __inet_twsk_del_dead_node(tw); 143 spin_unlock(&twdr->death_lock); 144 __inet_twsk_kill(tw, twdr->hashinfo); 145 inet_twsk_put(tw); 146 killed++; 147 spin_lock(&twdr->death_lock); 148 if (killed > INET_TWDR_TWKILL_QUOTA) { 149 ret = 1; 150 break; 151 } 152 153 /* While we dropped twdr->death_lock, another cpu may have 154 * killed off the next TW bucket in the list, therefore 155 * do a fresh re-read of the hlist head node with the 156 * lock reacquired. We still use the hlist traversal 157 * macro in order to get the prefetches. 158 */ 159 goto rescan; 160 } 161 162 twdr->tw_count -= killed; 163 NET_ADD_STATS_BH(LINUX_MIB_TIMEWAITED, killed); 164 165 return ret; 166 } 167 168 void inet_twdr_hangman(unsigned long data) 169 { 170 struct inet_timewait_death_row *twdr; 171 int unsigned need_timer; 172 173 twdr = (struct inet_timewait_death_row *)data; 174 spin_lock(&twdr->death_lock); 175 176 if (twdr->tw_count == 0) 177 goto out; 178 179 need_timer = 0; 180 if (inet_twdr_do_twkill_work(twdr, twdr->slot)) { 181 twdr->thread_slots |= (1 << twdr->slot); 182 mb(); 183 schedule_work(&twdr->twkill_work); 184 need_timer = 1; 185 } else { 186 /* We purged the entire slot, anything left? */ 187 if (twdr->tw_count) 188 need_timer = 1; 189 } 190 twdr->slot = ((twdr->slot + 1) & (INET_TWDR_TWKILL_SLOTS - 1)); 191 if (need_timer) 192 mod_timer(&twdr->tw_timer, jiffies + twdr->period); 193 out: 194 spin_unlock(&twdr->death_lock); 195 } 196 197 EXPORT_SYMBOL_GPL(inet_twdr_hangman); 198 199 extern void twkill_slots_invalid(void); 200 201 void inet_twdr_twkill_work(void *data) 202 { 203 struct inet_timewait_death_row *twdr = data; 204 int i; 205 206 if ((INET_TWDR_TWKILL_SLOTS - 1) > (sizeof(twdr->thread_slots) * 8)) 207 twkill_slots_invalid(); 208 209 while (twdr->thread_slots) { 210 spin_lock_bh(&twdr->death_lock); 211 for (i = 0; i < INET_TWDR_TWKILL_SLOTS; i++) { 212 if (!(twdr->thread_slots & (1 << i))) 213 continue; 214 215 while (inet_twdr_do_twkill_work(twdr, i) != 0) { 216 if (need_resched()) { 217 spin_unlock_bh(&twdr->death_lock); 218 schedule(); 219 spin_lock_bh(&twdr->death_lock); 220 } 221 } 222 223 twdr->thread_slots &= ~(1 << i); 224 } 225 spin_unlock_bh(&twdr->death_lock); 226 } 227 } 228 229 EXPORT_SYMBOL_GPL(inet_twdr_twkill_work); 230 231 /* These are always called from BH context. See callers in 232 * tcp_input.c to verify this. 233 */ 234 235 /* This is for handling early-kills of TIME_WAIT sockets. */ 236 void inet_twsk_deschedule(struct inet_timewait_sock *tw, 237 struct inet_timewait_death_row *twdr) 238 { 239 spin_lock(&twdr->death_lock); 240 if (inet_twsk_del_dead_node(tw)) { 241 inet_twsk_put(tw); 242 if (--twdr->tw_count == 0) 243 del_timer(&twdr->tw_timer); 244 } 245 spin_unlock(&twdr->death_lock); 246 __inet_twsk_kill(tw, twdr->hashinfo); 247 } 248 249 EXPORT_SYMBOL(inet_twsk_deschedule); 250 251 void inet_twsk_schedule(struct inet_timewait_sock *tw, 252 struct inet_timewait_death_row *twdr, 253 const int timeo, const int timewait_len) 254 { 255 struct hlist_head *list; 256 int slot; 257 258 /* timeout := RTO * 3.5 259 * 260 * 3.5 = 1+2+0.5 to wait for two retransmits. 261 * 262 * RATIONALE: if FIN arrived and we entered TIME-WAIT state, 263 * our ACK acking that FIN can be lost. If N subsequent retransmitted 264 * FINs (or previous seqments) are lost (probability of such event 265 * is p^(N+1), where p is probability to lose single packet and 266 * time to detect the loss is about RTO*(2^N - 1) with exponential 267 * backoff). Normal timewait length is calculated so, that we 268 * waited at least for one retransmitted FIN (maximal RTO is 120sec). 269 * [ BTW Linux. following BSD, violates this requirement waiting 270 * only for 60sec, we should wait at least for 240 secs. 271 * Well, 240 consumes too much of resources 8) 272 * ] 273 * This interval is not reduced to catch old duplicate and 274 * responces to our wandering segments living for two MSLs. 275 * However, if we use PAWS to detect 276 * old duplicates, we can reduce the interval to bounds required 277 * by RTO, rather than MSL. So, if peer understands PAWS, we 278 * kill tw bucket after 3.5*RTO (it is important that this number 279 * is greater than TS tick!) and detect old duplicates with help 280 * of PAWS. 281 */ 282 slot = (timeo + (1 << INET_TWDR_RECYCLE_TICK) - 1) >> INET_TWDR_RECYCLE_TICK; 283 284 spin_lock(&twdr->death_lock); 285 286 /* Unlink it, if it was scheduled */ 287 if (inet_twsk_del_dead_node(tw)) 288 twdr->tw_count--; 289 else 290 atomic_inc(&tw->tw_refcnt); 291 292 if (slot >= INET_TWDR_RECYCLE_SLOTS) { 293 /* Schedule to slow timer */ 294 if (timeo >= timewait_len) { 295 slot = INET_TWDR_TWKILL_SLOTS - 1; 296 } else { 297 slot = (timeo + twdr->period - 1) / twdr->period; 298 if (slot >= INET_TWDR_TWKILL_SLOTS) 299 slot = INET_TWDR_TWKILL_SLOTS - 1; 300 } 301 tw->tw_ttd = jiffies + timeo; 302 slot = (twdr->slot + slot) & (INET_TWDR_TWKILL_SLOTS - 1); 303 list = &twdr->cells[slot]; 304 } else { 305 tw->tw_ttd = jiffies + (slot << INET_TWDR_RECYCLE_TICK); 306 307 if (twdr->twcal_hand < 0) { 308 twdr->twcal_hand = 0; 309 twdr->twcal_jiffie = jiffies; 310 twdr->twcal_timer.expires = twdr->twcal_jiffie + 311 (slot << INET_TWDR_RECYCLE_TICK); 312 add_timer(&twdr->twcal_timer); 313 } else { 314 if (time_after(twdr->twcal_timer.expires, 315 jiffies + (slot << INET_TWDR_RECYCLE_TICK))) 316 mod_timer(&twdr->twcal_timer, 317 jiffies + (slot << INET_TWDR_RECYCLE_TICK)); 318 slot = (twdr->twcal_hand + slot) & (INET_TWDR_RECYCLE_SLOTS - 1); 319 } 320 list = &twdr->twcal_row[slot]; 321 } 322 323 hlist_add_head(&tw->tw_death_node, list); 324 325 if (twdr->tw_count++ == 0) 326 mod_timer(&twdr->tw_timer, jiffies + twdr->period); 327 spin_unlock(&twdr->death_lock); 328 } 329 330 EXPORT_SYMBOL_GPL(inet_twsk_schedule); 331 332 void inet_twdr_twcal_tick(unsigned long data) 333 { 334 struct inet_timewait_death_row *twdr; 335 int n, slot; 336 unsigned long j; 337 unsigned long now = jiffies; 338 int killed = 0; 339 int adv = 0; 340 341 twdr = (struct inet_timewait_death_row *)data; 342 343 spin_lock(&twdr->death_lock); 344 if (twdr->twcal_hand < 0) 345 goto out; 346 347 slot = twdr->twcal_hand; 348 j = twdr->twcal_jiffie; 349 350 for (n = 0; n < INET_TWDR_RECYCLE_SLOTS; n++) { 351 if (time_before_eq(j, now)) { 352 struct hlist_node *node, *safe; 353 struct inet_timewait_sock *tw; 354 355 inet_twsk_for_each_inmate_safe(tw, node, safe, 356 &twdr->twcal_row[slot]) { 357 __inet_twsk_del_dead_node(tw); 358 __inet_twsk_kill(tw, twdr->hashinfo); 359 inet_twsk_put(tw); 360 killed++; 361 } 362 } else { 363 if (!adv) { 364 adv = 1; 365 twdr->twcal_jiffie = j; 366 twdr->twcal_hand = slot; 367 } 368 369 if (!hlist_empty(&twdr->twcal_row[slot])) { 370 mod_timer(&twdr->twcal_timer, j); 371 goto out; 372 } 373 } 374 j += 1 << INET_TWDR_RECYCLE_TICK; 375 slot = (slot + 1) & (INET_TWDR_RECYCLE_SLOTS - 1); 376 } 377 twdr->twcal_hand = -1; 378 379 out: 380 if ((twdr->tw_count -= killed) == 0) 381 del_timer(&twdr->tw_timer); 382 NET_ADD_STATS_BH(LINUX_MIB_TIMEWAITKILLED, killed); 383 spin_unlock(&twdr->death_lock); 384 } 385 386 EXPORT_SYMBOL_GPL(inet_twdr_twcal_tick); 387