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