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