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. This is called with locally disabled BH. 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(&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 3 because : 127 * - We have one reference from bhash chain. 128 * - We have one reference from ehash chain. 129 * We can use atomic_set() because prior spin_lock()/spin_unlock() 130 * committed into memory all tw fields. 131 */ 132 atomic_set(&tw->tw_refcnt, 1 + 1 + 1); 133 inet_twsk_add_node_rcu(tw, &ehead->chain); 134 135 /* Step 3: Remove SK from hash chain */ 136 if (__sk_nulls_del_node_init_rcu(sk)) 137 sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1); 138 139 spin_unlock(lock); 140 } 141 EXPORT_SYMBOL_GPL(__inet_twsk_hashdance); 142 143 static void tw_timer_handler(unsigned long data) 144 { 145 struct inet_timewait_sock *tw = (struct inet_timewait_sock *)data; 146 147 if (tw->tw_kill) 148 NET_INC_STATS_BH(twsk_net(tw), LINUX_MIB_TIMEWAITKILLED); 149 else 150 NET_INC_STATS_BH(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 kmemcheck_annotate_bitfield(tw, flags); 169 170 tw->tw_dr = dr; 171 /* Give us an identity. */ 172 tw->tw_daddr = inet->inet_daddr; 173 tw->tw_rcv_saddr = inet->inet_rcv_saddr; 174 tw->tw_bound_dev_if = sk->sk_bound_dev_if; 175 tw->tw_tos = inet->tos; 176 tw->tw_num = inet->inet_num; 177 tw->tw_state = TCP_TIME_WAIT; 178 tw->tw_substate = state; 179 tw->tw_sport = inet->inet_sport; 180 tw->tw_dport = inet->inet_dport; 181 tw->tw_family = sk->sk_family; 182 tw->tw_reuse = sk->sk_reuse; 183 tw->tw_hash = sk->sk_hash; 184 tw->tw_ipv6only = 0; 185 tw->tw_transparent = inet->transparent; 186 tw->tw_prot = sk->sk_prot_creator; 187 atomic64_set(&tw->tw_cookie, atomic64_read(&sk->sk_cookie)); 188 twsk_net_set(tw, sock_net(sk)); 189 setup_timer(&tw->tw_timer, tw_timer_handler, (unsigned long)tw); 190 /* 191 * Because we use RCU lookups, we should not set tw_refcnt 192 * to a non null value before everything is setup for this 193 * timewait socket. 194 */ 195 atomic_set(&tw->tw_refcnt, 0); 196 197 __module_get(tw->tw_prot->owner); 198 } 199 200 return tw; 201 } 202 EXPORT_SYMBOL_GPL(inet_twsk_alloc); 203 204 /* These are always called from BH context. See callers in 205 * tcp_input.c to verify this. 206 */ 207 208 /* This is for handling early-kills of TIME_WAIT sockets. 209 * Warning : consume reference. 210 * Caller should not access tw anymore. 211 */ 212 void inet_twsk_deschedule_put(struct inet_timewait_sock *tw) 213 { 214 if (del_timer_sync(&tw->tw_timer)) 215 inet_twsk_kill(tw); 216 inet_twsk_put(tw); 217 } 218 EXPORT_SYMBOL(inet_twsk_deschedule_put); 219 220 void inet_twsk_schedule(struct inet_timewait_sock *tw, const int timeo) 221 { 222 /* timeout := RTO * 3.5 223 * 224 * 3.5 = 1+2+0.5 to wait for two retransmits. 225 * 226 * RATIONALE: if FIN arrived and we entered TIME-WAIT state, 227 * our ACK acking that FIN can be lost. If N subsequent retransmitted 228 * FINs (or previous seqments) are lost (probability of such event 229 * is p^(N+1), where p is probability to lose single packet and 230 * time to detect the loss is about RTO*(2^N - 1) with exponential 231 * backoff). Normal timewait length is calculated so, that we 232 * waited at least for one retransmitted FIN (maximal RTO is 120sec). 233 * [ BTW Linux. following BSD, violates this requirement waiting 234 * only for 60sec, we should wait at least for 240 secs. 235 * Well, 240 consumes too much of resources 8) 236 * ] 237 * This interval is not reduced to catch old duplicate and 238 * responces to our wandering segments living for two MSLs. 239 * However, if we use PAWS to detect 240 * old duplicates, we can reduce the interval to bounds required 241 * by RTO, rather than MSL. So, if peer understands PAWS, we 242 * kill tw bucket after 3.5*RTO (it is important that this number 243 * is greater than TS tick!) and detect old duplicates with help 244 * of PAWS. 245 */ 246 247 tw->tw_kill = timeo <= 4*HZ; 248 if (!mod_timer_pinned(&tw->tw_timer, jiffies + timeo)) { 249 atomic_inc(&tw->tw_refcnt); 250 atomic_inc(&tw->tw_dr->tw_count); 251 } 252 } 253 EXPORT_SYMBOL_GPL(inet_twsk_schedule); 254 255 void inet_twsk_purge(struct inet_hashinfo *hashinfo, 256 struct inet_timewait_death_row *twdr, 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(!atomic_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