1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * INET An implementation of the TCP/IP protocol suite for the LINUX 4 * operating system. INET is implemented using the BSD Socket 5 * interface as the means of communication with the user level. 6 * 7 * Generic TIME_WAIT sockets functions 8 * 9 * From code orinally in TCP 10 */ 11 12 #include <linux/kernel.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_bind2_bucket *tb2 = tw->tw_tb2; 33 struct inet_bind_bucket *tb = tw->tw_tb; 34 35 if (!tb) 36 return; 37 38 __hlist_del(&tw->tw_bind_node); 39 tw->tw_tb = NULL; 40 inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb); 41 42 __hlist_del(&tw->tw_bind2_node); 43 tw->tw_tb2 = NULL; 44 inet_bind2_bucket_destroy(hashinfo->bind2_bucket_cachep, tb2); 45 46 __sock_put((struct sock *)tw); 47 } 48 49 /* Must be called with locally disabled BHs. */ 50 static void inet_twsk_kill(struct inet_timewait_sock *tw) 51 { 52 struct inet_hashinfo *hashinfo = tw->tw_dr->hashinfo; 53 spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash); 54 struct inet_bind_hashbucket *bhead, *bhead2; 55 56 spin_lock(lock); 57 sk_nulls_del_node_init_rcu((struct sock *)tw); 58 spin_unlock(lock); 59 60 /* Disassociate with bind bucket. */ 61 bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), tw->tw_num, 62 hashinfo->bhash_size)]; 63 bhead2 = inet_bhashfn_portaddr(hashinfo, (struct sock *)tw, 64 twsk_net(tw), tw->tw_num); 65 66 spin_lock(&bhead->lock); 67 spin_lock(&bhead2->lock); 68 inet_twsk_bind_unhash(tw, hashinfo); 69 spin_unlock(&bhead2->lock); 70 spin_unlock(&bhead->lock); 71 72 refcount_dec(&tw->tw_dr->tw_refcount); 73 inet_twsk_put(tw); 74 } 75 76 void inet_twsk_free(struct inet_timewait_sock *tw) 77 { 78 struct module *owner = tw->tw_prot->owner; 79 twsk_destructor((struct sock *)tw); 80 kmem_cache_free(tw->tw_prot->twsk_prot->twsk_slab, tw); 81 module_put(owner); 82 } 83 84 void inet_twsk_put(struct inet_timewait_sock *tw) 85 { 86 if (refcount_dec_and_test(&tw->tw_refcnt)) 87 inet_twsk_free(tw); 88 } 89 EXPORT_SYMBOL_GPL(inet_twsk_put); 90 91 static void inet_twsk_add_node_rcu(struct inet_timewait_sock *tw, 92 struct hlist_nulls_head *list) 93 { 94 hlist_nulls_add_head_rcu(&tw->tw_node, list); 95 } 96 97 static void inet_twsk_add_bind_node(struct inet_timewait_sock *tw, 98 struct hlist_head *list) 99 { 100 hlist_add_head(&tw->tw_bind_node, list); 101 } 102 103 static void inet_twsk_add_bind2_node(struct inet_timewait_sock *tw, 104 struct hlist_head *list) 105 { 106 hlist_add_head(&tw->tw_bind2_node, list); 107 } 108 109 /* 110 * Enter the time wait state. This is called with locally disabled BH. 111 * Essentially we whip up a timewait bucket, copy the relevant info into it 112 * from the SK, and mess with hash chains and list linkage. 113 */ 114 void inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk, 115 struct inet_hashinfo *hashinfo) 116 { 117 const struct inet_sock *inet = inet_sk(sk); 118 const struct inet_connection_sock *icsk = inet_csk(sk); 119 struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, sk->sk_hash); 120 spinlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash); 121 struct inet_bind_hashbucket *bhead, *bhead2; 122 123 /* Step 1: Put TW into bind hash. Original socket stays there too. 124 Note, that any socket with inet->num != 0 MUST be bound in 125 binding cache, even if it is closed. 126 */ 127 bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), inet->inet_num, 128 hashinfo->bhash_size)]; 129 bhead2 = inet_bhashfn_portaddr(hashinfo, sk, twsk_net(tw), inet->inet_num); 130 131 spin_lock(&bhead->lock); 132 spin_lock(&bhead2->lock); 133 134 tw->tw_tb = icsk->icsk_bind_hash; 135 WARN_ON(!icsk->icsk_bind_hash); 136 inet_twsk_add_bind_node(tw, &tw->tw_tb->owners); 137 138 tw->tw_tb2 = icsk->icsk_bind2_hash; 139 WARN_ON(!icsk->icsk_bind2_hash); 140 inet_twsk_add_bind2_node(tw, &tw->tw_tb2->deathrow); 141 142 spin_unlock(&bhead2->lock); 143 spin_unlock(&bhead->lock); 144 145 spin_lock(lock); 146 147 inet_twsk_add_node_rcu(tw, &ehead->chain); 148 149 /* Step 3: Remove SK from hash chain */ 150 if (__sk_nulls_del_node_init_rcu(sk)) 151 sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1); 152 153 spin_unlock(lock); 154 155 /* tw_refcnt is set to 3 because we have : 156 * - one reference for bhash chain. 157 * - one reference for ehash chain. 158 * - one reference for timer. 159 * We can use atomic_set() because prior spin_lock()/spin_unlock() 160 * committed into memory all tw fields. 161 * Also note that after this point, we lost our implicit reference 162 * so we are not allowed to use tw anymore. 163 */ 164 refcount_set(&tw->tw_refcnt, 3); 165 } 166 EXPORT_SYMBOL_GPL(inet_twsk_hashdance); 167 168 static void tw_timer_handler(struct timer_list *t) 169 { 170 struct inet_timewait_sock *tw = from_timer(tw, t, tw_timer); 171 172 inet_twsk_kill(tw); 173 } 174 175 struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk, 176 struct inet_timewait_death_row *dr, 177 const int state) 178 { 179 struct inet_timewait_sock *tw; 180 181 if (refcount_read(&dr->tw_refcount) - 1 >= 182 READ_ONCE(dr->sysctl_max_tw_buckets)) 183 return NULL; 184 185 tw = kmem_cache_alloc(sk->sk_prot_creator->twsk_prot->twsk_slab, 186 GFP_ATOMIC); 187 if (tw) { 188 const struct inet_sock *inet = inet_sk(sk); 189 190 tw->tw_dr = dr; 191 /* Give us an identity. */ 192 tw->tw_daddr = inet->inet_daddr; 193 tw->tw_rcv_saddr = inet->inet_rcv_saddr; 194 tw->tw_bound_dev_if = sk->sk_bound_dev_if; 195 tw->tw_tos = inet->tos; 196 tw->tw_num = inet->inet_num; 197 tw->tw_state = TCP_TIME_WAIT; 198 tw->tw_substate = state; 199 tw->tw_sport = inet->inet_sport; 200 tw->tw_dport = inet->inet_dport; 201 tw->tw_family = sk->sk_family; 202 tw->tw_reuse = sk->sk_reuse; 203 tw->tw_reuseport = sk->sk_reuseport; 204 tw->tw_hash = sk->sk_hash; 205 tw->tw_ipv6only = 0; 206 tw->tw_transparent = inet_test_bit(TRANSPARENT, sk); 207 tw->tw_prot = sk->sk_prot_creator; 208 atomic64_set(&tw->tw_cookie, atomic64_read(&sk->sk_cookie)); 209 twsk_net_set(tw, sock_net(sk)); 210 timer_setup(&tw->tw_timer, tw_timer_handler, TIMER_PINNED); 211 /* 212 * Because we use RCU lookups, we should not set tw_refcnt 213 * to a non null value before everything is setup for this 214 * timewait socket. 215 */ 216 refcount_set(&tw->tw_refcnt, 0); 217 218 __module_get(tw->tw_prot->owner); 219 } 220 221 return tw; 222 } 223 EXPORT_SYMBOL_GPL(inet_twsk_alloc); 224 225 /* These are always called from BH context. See callers in 226 * tcp_input.c to verify this. 227 */ 228 229 /* This is for handling early-kills of TIME_WAIT sockets. 230 * Warning : consume reference. 231 * Caller should not access tw anymore. 232 */ 233 void inet_twsk_deschedule_put(struct inet_timewait_sock *tw) 234 { 235 if (del_timer_sync(&tw->tw_timer)) 236 inet_twsk_kill(tw); 237 inet_twsk_put(tw); 238 } 239 EXPORT_SYMBOL(inet_twsk_deschedule_put); 240 241 void __inet_twsk_schedule(struct inet_timewait_sock *tw, int timeo, bool rearm) 242 { 243 /* timeout := RTO * 3.5 244 * 245 * 3.5 = 1+2+0.5 to wait for two retransmits. 246 * 247 * RATIONALE: if FIN arrived and we entered TIME-WAIT state, 248 * our ACK acking that FIN can be lost. If N subsequent retransmitted 249 * FINs (or previous seqments) are lost (probability of such event 250 * is p^(N+1), where p is probability to lose single packet and 251 * time to detect the loss is about RTO*(2^N - 1) with exponential 252 * backoff). Normal timewait length is calculated so, that we 253 * waited at least for one retransmitted FIN (maximal RTO is 120sec). 254 * [ BTW Linux. following BSD, violates this requirement waiting 255 * only for 60sec, we should wait at least for 240 secs. 256 * Well, 240 consumes too much of resources 8) 257 * ] 258 * This interval is not reduced to catch old duplicate and 259 * responces to our wandering segments living for two MSLs. 260 * However, if we use PAWS to detect 261 * old duplicates, we can reduce the interval to bounds required 262 * by RTO, rather than MSL. So, if peer understands PAWS, we 263 * kill tw bucket after 3.5*RTO (it is important that this number 264 * is greater than TS tick!) and detect old duplicates with help 265 * of PAWS. 266 */ 267 268 if (!rearm) { 269 bool kill = timeo <= 4*HZ; 270 271 __NET_INC_STATS(twsk_net(tw), kill ? LINUX_MIB_TIMEWAITKILLED : 272 LINUX_MIB_TIMEWAITED); 273 BUG_ON(mod_timer(&tw->tw_timer, jiffies + timeo)); 274 refcount_inc(&tw->tw_dr->tw_refcount); 275 } else { 276 mod_timer_pending(&tw->tw_timer, jiffies + timeo); 277 } 278 } 279 EXPORT_SYMBOL_GPL(__inet_twsk_schedule); 280 281 void inet_twsk_purge(struct inet_hashinfo *hashinfo, int family) 282 { 283 struct inet_timewait_sock *tw; 284 struct sock *sk; 285 struct hlist_nulls_node *node; 286 unsigned int slot; 287 288 for (slot = 0; slot <= hashinfo->ehash_mask; slot++) { 289 struct inet_ehash_bucket *head = &hashinfo->ehash[slot]; 290 restart_rcu: 291 cond_resched(); 292 rcu_read_lock(); 293 restart: 294 sk_nulls_for_each_rcu(sk, node, &head->chain) { 295 if (sk->sk_state != TCP_TIME_WAIT) { 296 /* A kernel listener socket might not hold refcnt for net, 297 * so reqsk_timer_handler() could be fired after net is 298 * freed. Userspace listener and reqsk never exist here. 299 */ 300 if (unlikely(sk->sk_state == TCP_NEW_SYN_RECV && 301 hashinfo->pernet)) { 302 struct request_sock *req = inet_reqsk(sk); 303 304 inet_csk_reqsk_queue_drop_and_put(req->rsk_listener, req); 305 } 306 307 continue; 308 } 309 310 tw = inet_twsk(sk); 311 if ((tw->tw_family != family) || 312 refcount_read(&twsk_net(tw)->ns.count)) 313 continue; 314 315 if (unlikely(!refcount_inc_not_zero(&tw->tw_refcnt))) 316 continue; 317 318 if (unlikely((tw->tw_family != family) || 319 refcount_read(&twsk_net(tw)->ns.count))) { 320 inet_twsk_put(tw); 321 goto restart; 322 } 323 324 rcu_read_unlock(); 325 local_bh_disable(); 326 inet_twsk_deschedule_put(tw); 327 local_bh_enable(); 328 goto restart_rcu; 329 } 330 /* If the nulls value we got at the end of this lookup is 331 * not the expected one, we must restart lookup. 332 * We probably met an item that was moved to another chain. 333 */ 334 if (get_nulls_value(node) != slot) 335 goto restart; 336 rcu_read_unlock(); 337 } 338 } 339 EXPORT_SYMBOL_GPL(inet_twsk_purge); 340