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