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 <linux/kmemcheck.h> 13 #include <linux/slab.h> 14 #include <linux/module.h> 15 #include <net/inet_hashtables.h> 16 #include <net/inet_timewait_sock.h> 17 #include <net/ip.h> 18 19 20 /** 21 * inet_twsk_unhash - unhash a timewait socket from established hash 22 * @tw: timewait socket 23 * 24 * unhash a timewait socket from established hash, if hashed. 25 * ehash lock must be held by caller. 26 * Returns 1 if caller should call inet_twsk_put() after lock release. 27 */ 28 int inet_twsk_unhash(struct inet_timewait_sock *tw) 29 { 30 if (hlist_nulls_unhashed(&tw->tw_node)) 31 return 0; 32 33 hlist_nulls_del_rcu(&tw->tw_node); 34 sk_nulls_node_init(&tw->tw_node); 35 /* 36 * We cannot call inet_twsk_put() ourself under lock, 37 * caller must call it for us. 38 */ 39 return 1; 40 } 41 42 /** 43 * inet_twsk_bind_unhash - unhash a timewait socket from bind hash 44 * @tw: timewait socket 45 * @hashinfo: hashinfo pointer 46 * 47 * unhash a timewait socket from bind hash, if hashed. 48 * bind hash lock must be held by caller. 49 * Returns 1 if caller should call inet_twsk_put() after lock release. 50 */ 51 int inet_twsk_bind_unhash(struct inet_timewait_sock *tw, 52 struct inet_hashinfo *hashinfo) 53 { 54 struct inet_bind_bucket *tb = tw->tw_tb; 55 56 if (!tb) 57 return 0; 58 59 __hlist_del(&tw->tw_bind_node); 60 tw->tw_tb = NULL; 61 inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb); 62 /* 63 * We cannot call inet_twsk_put() ourself under lock, 64 * caller must call it for us. 65 */ 66 return 1; 67 } 68 69 /* Must be called with locally disabled BHs. */ 70 static void inet_twsk_kill(struct inet_timewait_sock *tw) 71 { 72 struct inet_hashinfo *hashinfo = tw->tw_dr->hashinfo; 73 struct inet_bind_hashbucket *bhead; 74 int refcnt; 75 /* Unlink from established hashes. */ 76 spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash); 77 78 spin_lock(lock); 79 refcnt = inet_twsk_unhash(tw); 80 spin_unlock(lock); 81 82 /* Disassociate with bind bucket. */ 83 bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), tw->tw_num, 84 hashinfo->bhash_size)]; 85 86 spin_lock(&bhead->lock); 87 refcnt += inet_twsk_bind_unhash(tw, hashinfo); 88 spin_unlock(&bhead->lock); 89 90 BUG_ON(refcnt >= atomic_read(&tw->tw_refcnt)); 91 atomic_sub(refcnt, &tw->tw_refcnt); 92 atomic_dec(&tw->tw_dr->tw_count); 93 inet_twsk_put(tw); 94 } 95 96 void inet_twsk_free(struct inet_timewait_sock *tw) 97 { 98 struct module *owner = tw->tw_prot->owner; 99 twsk_destructor((struct sock *)tw); 100 #ifdef SOCK_REFCNT_DEBUG 101 pr_debug("%s timewait_sock %p released\n", tw->tw_prot->name, tw); 102 #endif 103 kmem_cache_free(tw->tw_prot->twsk_prot->twsk_slab, tw); 104 module_put(owner); 105 } 106 107 void inet_twsk_put(struct inet_timewait_sock *tw) 108 { 109 if (atomic_dec_and_test(&tw->tw_refcnt)) 110 inet_twsk_free(tw); 111 } 112 EXPORT_SYMBOL_GPL(inet_twsk_put); 113 114 static void inet_twsk_add_node_rcu(struct inet_timewait_sock *tw, 115 struct hlist_nulls_head *list) 116 { 117 hlist_nulls_add_head_rcu(&tw->tw_node, list); 118 } 119 120 static void inet_twsk_add_bind_node(struct inet_timewait_sock *tw, 121 struct hlist_head *list) 122 { 123 hlist_add_head(&tw->tw_bind_node, list); 124 } 125 126 /* 127 * Enter the time wait state. This is called with locally disabled BH. 128 * Essentially we whip up a timewait bucket, copy the relevant info into it 129 * from the SK, and mess with hash chains and list linkage. 130 */ 131 void __inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk, 132 struct inet_hashinfo *hashinfo) 133 { 134 const struct inet_sock *inet = inet_sk(sk); 135 const struct inet_connection_sock *icsk = inet_csk(sk); 136 struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, sk->sk_hash); 137 spinlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash); 138 struct inet_bind_hashbucket *bhead; 139 /* Step 1: Put TW into bind hash. Original socket stays there too. 140 Note, that any socket with inet->num != 0 MUST be bound in 141 binding cache, even if it is closed. 142 */ 143 bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), inet->inet_num, 144 hashinfo->bhash_size)]; 145 spin_lock(&bhead->lock); 146 tw->tw_tb = icsk->icsk_bind_hash; 147 WARN_ON(!icsk->icsk_bind_hash); 148 inet_twsk_add_bind_node(tw, &tw->tw_tb->owners); 149 spin_unlock(&bhead->lock); 150 151 spin_lock(lock); 152 153 /* 154 * Step 2: Hash TW into tcp ehash chain. 155 * Notes : 156 * - tw_refcnt is set to 3 because : 157 * - We have one reference from bhash chain. 158 * - We have one reference from ehash chain. 159 * We can use atomic_set() because prior spin_lock()/spin_unlock() 160 * committed into memory all tw fields. 161 */ 162 atomic_set(&tw->tw_refcnt, 1 + 1 + 1); 163 inet_twsk_add_node_rcu(tw, &ehead->chain); 164 165 /* Step 3: Remove SK from hash chain */ 166 if (__sk_nulls_del_node_init_rcu(sk)) 167 sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1); 168 169 spin_unlock(lock); 170 } 171 EXPORT_SYMBOL_GPL(__inet_twsk_hashdance); 172 173 void tw_timer_handler(unsigned long data) 174 { 175 struct inet_timewait_sock *tw = (struct inet_timewait_sock *)data; 176 177 if (tw->tw_kill) 178 NET_INC_STATS_BH(twsk_net(tw), LINUX_MIB_TIMEWAITKILLED); 179 else 180 NET_INC_STATS_BH(twsk_net(tw), LINUX_MIB_TIMEWAITED); 181 inet_twsk_kill(tw); 182 } 183 184 struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk, 185 struct inet_timewait_death_row *dr, 186 const int state) 187 { 188 struct inet_timewait_sock *tw; 189 190 if (atomic_read(&dr->tw_count) >= dr->sysctl_max_tw_buckets) 191 return NULL; 192 193 tw = kmem_cache_alloc(sk->sk_prot_creator->twsk_prot->twsk_slab, 194 GFP_ATOMIC); 195 if (tw) { 196 const struct inet_sock *inet = inet_sk(sk); 197 198 kmemcheck_annotate_bitfield(tw, flags); 199 200 tw->tw_dr = dr; 201 /* Give us an identity. */ 202 tw->tw_daddr = inet->inet_daddr; 203 tw->tw_rcv_saddr = inet->inet_rcv_saddr; 204 tw->tw_bound_dev_if = sk->sk_bound_dev_if; 205 tw->tw_tos = inet->tos; 206 tw->tw_num = inet->inet_num; 207 tw->tw_state = TCP_TIME_WAIT; 208 tw->tw_substate = state; 209 tw->tw_sport = inet->inet_sport; 210 tw->tw_dport = inet->inet_dport; 211 tw->tw_family = sk->sk_family; 212 tw->tw_reuse = sk->sk_reuse; 213 tw->tw_hash = sk->sk_hash; 214 tw->tw_ipv6only = 0; 215 tw->tw_transparent = inet->transparent; 216 tw->tw_prot = sk->sk_prot_creator; 217 atomic64_set(&tw->tw_cookie, atomic64_read(&sk->sk_cookie)); 218 twsk_net_set(tw, sock_net(sk)); 219 setup_timer(&tw->tw_timer, tw_timer_handler, (unsigned long)tw); 220 /* 221 * Because we use RCU lookups, we should not set tw_refcnt 222 * to a non null value before everything is setup for this 223 * timewait socket. 224 */ 225 atomic_set(&tw->tw_refcnt, 0); 226 227 __module_get(tw->tw_prot->owner); 228 } 229 230 return tw; 231 } 232 EXPORT_SYMBOL_GPL(inet_twsk_alloc); 233 234 /* These are always called from BH context. See callers in 235 * tcp_input.c to verify this. 236 */ 237 238 /* This is for handling early-kills of TIME_WAIT sockets. */ 239 void inet_twsk_deschedule(struct inet_timewait_sock *tw) 240 { 241 if (del_timer_sync(&tw->tw_timer)) 242 inet_twsk_kill(tw); 243 } 244 EXPORT_SYMBOL(inet_twsk_deschedule); 245 246 void inet_twsk_schedule(struct inet_timewait_sock *tw, const int timeo) 247 { 248 /* timeout := RTO * 3.5 249 * 250 * 3.5 = 1+2+0.5 to wait for two retransmits. 251 * 252 * RATIONALE: if FIN arrived and we entered TIME-WAIT state, 253 * our ACK acking that FIN can be lost. If N subsequent retransmitted 254 * FINs (or previous seqments) are lost (probability of such event 255 * is p^(N+1), where p is probability to lose single packet and 256 * time to detect the loss is about RTO*(2^N - 1) with exponential 257 * backoff). Normal timewait length is calculated so, that we 258 * waited at least for one retransmitted FIN (maximal RTO is 120sec). 259 * [ BTW Linux. following BSD, violates this requirement waiting 260 * only for 60sec, we should wait at least for 240 secs. 261 * Well, 240 consumes too much of resources 8) 262 * ] 263 * This interval is not reduced to catch old duplicate and 264 * responces to our wandering segments living for two MSLs. 265 * However, if we use PAWS to detect 266 * old duplicates, we can reduce the interval to bounds required 267 * by RTO, rather than MSL. So, if peer understands PAWS, we 268 * kill tw bucket after 3.5*RTO (it is important that this number 269 * is greater than TS tick!) and detect old duplicates with help 270 * of PAWS. 271 */ 272 273 tw->tw_kill = timeo <= 4*HZ; 274 if (!mod_timer_pinned(&tw->tw_timer, jiffies + timeo)) { 275 atomic_inc(&tw->tw_refcnt); 276 atomic_inc(&tw->tw_dr->tw_count); 277 } 278 } 279 EXPORT_SYMBOL_GPL(inet_twsk_schedule); 280 281 void inet_twsk_purge(struct inet_hashinfo *hashinfo, 282 struct inet_timewait_death_row *twdr, int family) 283 { 284 struct inet_timewait_sock *tw; 285 struct sock *sk; 286 struct hlist_nulls_node *node; 287 unsigned int slot; 288 289 for (slot = 0; slot <= hashinfo->ehash_mask; slot++) { 290 struct inet_ehash_bucket *head = &hashinfo->ehash[slot]; 291 restart_rcu: 292 cond_resched(); 293 rcu_read_lock(); 294 restart: 295 sk_nulls_for_each_rcu(sk, node, &head->chain) { 296 if (sk->sk_state != TCP_TIME_WAIT) 297 continue; 298 tw = inet_twsk(sk); 299 if ((tw->tw_family != family) || 300 atomic_read(&twsk_net(tw)->count)) 301 continue; 302 303 if (unlikely(!atomic_inc_not_zero(&tw->tw_refcnt))) 304 continue; 305 306 if (unlikely((tw->tw_family != family) || 307 atomic_read(&twsk_net(tw)->count))) { 308 inet_twsk_put(tw); 309 goto restart; 310 } 311 312 rcu_read_unlock(); 313 local_bh_disable(); 314 inet_twsk_deschedule(tw); 315 local_bh_enable(); 316 inet_twsk_put(tw); 317 goto restart_rcu; 318 } 319 /* If the nulls value we got at the end of this lookup is 320 * not the expected one, we must restart lookup. 321 * We probably met an item that was moved to another chain. 322 */ 323 if (get_nulls_value(node) != slot) 324 goto restart; 325 rcu_read_unlock(); 326 } 327 } 328 EXPORT_SYMBOL_GPL(inet_twsk_purge); 329