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. 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_bh(&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 /* 123 * Step 2: Hash TW into tcp ehash chain. 124 * Notes : 125 * - tw_refcnt is set to 4 because : 126 * - We have one reference from bhash chain. 127 * - We have one reference from ehash chain. 128 * - We have one reference from timer. 129 * - One reference for ourself (our caller will release it). 130 * We can use atomic_set() because prior spin_lock()/spin_unlock() 131 * committed into memory all tw fields. 132 */ 133 refcount_set(&tw->tw_refcnt, 4); 134 inet_twsk_add_node_rcu(tw, &ehead->chain); 135 136 /* Step 3: Remove SK from hash chain */ 137 if (__sk_nulls_del_node_init_rcu(sk)) 138 sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1); 139 140 spin_unlock_bh(lock); 141 } 142 EXPORT_SYMBOL_GPL(__inet_twsk_hashdance); 143 144 static void tw_timer_handler(struct timer_list *t) 145 { 146 struct inet_timewait_sock *tw = from_timer(tw, t, tw_timer); 147 148 if (tw->tw_kill) 149 __NET_INC_STATS(twsk_net(tw), LINUX_MIB_TIMEWAITKILLED); 150 else 151 __NET_INC_STATS(twsk_net(tw), LINUX_MIB_TIMEWAITED); 152 inet_twsk_kill(tw); 153 } 154 155 struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk, 156 struct inet_timewait_death_row *dr, 157 const int state) 158 { 159 struct inet_timewait_sock *tw; 160 161 if (atomic_read(&dr->tw_count) >= dr->sysctl_max_tw_buckets) 162 return NULL; 163 164 tw = kmem_cache_alloc(sk->sk_prot_creator->twsk_prot->twsk_slab, 165 GFP_ATOMIC); 166 if (tw) { 167 const struct inet_sock *inet = inet_sk(sk); 168 169 tw->tw_dr = dr; 170 /* Give us an identity. */ 171 tw->tw_daddr = inet->inet_daddr; 172 tw->tw_rcv_saddr = inet->inet_rcv_saddr; 173 tw->tw_bound_dev_if = sk->sk_bound_dev_if; 174 tw->tw_tos = inet->tos; 175 tw->tw_num = inet->inet_num; 176 tw->tw_state = TCP_TIME_WAIT; 177 tw->tw_substate = state; 178 tw->tw_sport = inet->inet_sport; 179 tw->tw_dport = inet->inet_dport; 180 tw->tw_family = sk->sk_family; 181 tw->tw_reuse = sk->sk_reuse; 182 tw->tw_hash = sk->sk_hash; 183 tw->tw_ipv6only = 0; 184 tw->tw_transparent = inet->transparent; 185 tw->tw_prot = sk->sk_prot_creator; 186 atomic64_set(&tw->tw_cookie, atomic64_read(&sk->sk_cookie)); 187 twsk_net_set(tw, sock_net(sk)); 188 timer_setup(&tw->tw_timer, tw_timer_handler, TIMER_PINNED); 189 /* 190 * Because we use RCU lookups, we should not set tw_refcnt 191 * to a non null value before everything is setup for this 192 * timewait socket. 193 */ 194 refcount_set(&tw->tw_refcnt, 0); 195 196 __module_get(tw->tw_prot->owner); 197 } 198 199 return tw; 200 } 201 EXPORT_SYMBOL_GPL(inet_twsk_alloc); 202 203 /* These are always called from BH context. See callers in 204 * tcp_input.c to verify this. 205 */ 206 207 /* This is for handling early-kills of TIME_WAIT sockets. 208 * Warning : consume reference. 209 * Caller should not access tw anymore. 210 */ 211 void inet_twsk_deschedule_put(struct inet_timewait_sock *tw) 212 { 213 if (del_timer_sync(&tw->tw_timer)) 214 inet_twsk_kill(tw); 215 inet_twsk_put(tw); 216 } 217 EXPORT_SYMBOL(inet_twsk_deschedule_put); 218 219 void __inet_twsk_schedule(struct inet_timewait_sock *tw, int timeo, bool rearm) 220 { 221 /* timeout := RTO * 3.5 222 * 223 * 3.5 = 1+2+0.5 to wait for two retransmits. 224 * 225 * RATIONALE: if FIN arrived and we entered TIME-WAIT state, 226 * our ACK acking that FIN can be lost. If N subsequent retransmitted 227 * FINs (or previous seqments) are lost (probability of such event 228 * is p^(N+1), where p is probability to lose single packet and 229 * time to detect the loss is about RTO*(2^N - 1) with exponential 230 * backoff). Normal timewait length is calculated so, that we 231 * waited at least for one retransmitted FIN (maximal RTO is 120sec). 232 * [ BTW Linux. following BSD, violates this requirement waiting 233 * only for 60sec, we should wait at least for 240 secs. 234 * Well, 240 consumes too much of resources 8) 235 * ] 236 * This interval is not reduced to catch old duplicate and 237 * responces to our wandering segments living for two MSLs. 238 * However, if we use PAWS to detect 239 * old duplicates, we can reduce the interval to bounds required 240 * by RTO, rather than MSL. So, if peer understands PAWS, we 241 * kill tw bucket after 3.5*RTO (it is important that this number 242 * is greater than TS tick!) and detect old duplicates with help 243 * of PAWS. 244 */ 245 246 tw->tw_kill = timeo <= 4*HZ; 247 if (!rearm) { 248 BUG_ON(mod_timer(&tw->tw_timer, jiffies + timeo)); 249 atomic_inc(&tw->tw_dr->tw_count); 250 } else { 251 mod_timer_pending(&tw->tw_timer, jiffies + timeo); 252 } 253 } 254 EXPORT_SYMBOL_GPL(__inet_twsk_schedule); 255 256 void inet_twsk_purge(struct inet_hashinfo *hashinfo, int family) 257 { 258 struct inet_timewait_sock *tw; 259 struct sock *sk; 260 struct hlist_nulls_node *node; 261 unsigned int slot; 262 263 for (slot = 0; slot <= hashinfo->ehash_mask; slot++) { 264 struct inet_ehash_bucket *head = &hashinfo->ehash[slot]; 265 restart_rcu: 266 cond_resched(); 267 rcu_read_lock(); 268 restart: 269 sk_nulls_for_each_rcu(sk, node, &head->chain) { 270 if (sk->sk_state != TCP_TIME_WAIT) 271 continue; 272 tw = inet_twsk(sk); 273 if ((tw->tw_family != family) || 274 atomic_read(&twsk_net(tw)->count)) 275 continue; 276 277 if (unlikely(!refcount_inc_not_zero(&tw->tw_refcnt))) 278 continue; 279 280 if (unlikely((tw->tw_family != family) || 281 atomic_read(&twsk_net(tw)->count))) { 282 inet_twsk_put(tw); 283 goto restart; 284 } 285 286 rcu_read_unlock(); 287 local_bh_disable(); 288 inet_twsk_deschedule_put(tw); 289 local_bh_enable(); 290 goto restart_rcu; 291 } 292 /* If the nulls value we got at the end of this lookup is 293 * not the expected one, we must restart lookup. 294 * We probably met an item that was moved to another chain. 295 */ 296 if (get_nulls_value(node) != slot) 297 goto restart; 298 rcu_read_unlock(); 299 } 300 } 301 EXPORT_SYMBOL_GPL(inet_twsk_purge); 302