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