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 #include <net/tcp.h> 19 #include <net/psp.h> 20 21 /** 22 * inet_twsk_bind_unhash - unhash a timewait socket from bind hash 23 * @tw: timewait socket 24 * @hashinfo: hashinfo pointer 25 * 26 * unhash a timewait socket from bind hash, if hashed. 27 * bind hash lock must be held by caller. 28 * Returns 1 if caller should call inet_twsk_put() after lock release. 29 */ 30 void inet_twsk_bind_unhash(struct inet_timewait_sock *tw, 31 struct inet_hashinfo *hashinfo) 32 { 33 struct inet_bind2_bucket *tb2 = tw->tw_tb2; 34 struct inet_bind_bucket *tb = tw->tw_tb; 35 36 if (!tb) 37 return; 38 39 __sk_del_bind_node((struct sock *)tw); 40 tw->tw_tb = NULL; 41 tw->tw_tb2 = NULL; 42 inet_bind2_bucket_destroy(hashinfo->bind2_bucket_cachep, tb2); 43 inet_bind_bucket_destroy(tb); 44 45 __sock_put((struct sock *)tw); 46 } 47 48 /* Must be called with locally disabled BHs. */ 49 static void inet_twsk_kill(struct inet_timewait_sock *tw) 50 { 51 struct inet_hashinfo *hashinfo = tw->tw_dr->hashinfo; 52 spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash); 53 struct inet_bind_hashbucket *bhead, *bhead2; 54 55 spin_lock(lock); 56 sk_nulls_del_node_init_rcu((struct sock *)tw); 57 spin_unlock(lock); 58 59 /* Disassociate with bind bucket. */ 60 bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), tw->tw_num, 61 hashinfo->bhash_size)]; 62 bhead2 = inet_bhashfn_portaddr(hashinfo, (struct sock *)tw, 63 twsk_net(tw), tw->tw_num); 64 65 spin_lock(&bhead->lock); 66 spin_lock(&bhead2->lock); 67 inet_twsk_bind_unhash(tw, hashinfo); 68 spin_unlock(&bhead2->lock); 69 spin_unlock(&bhead->lock); 70 71 refcount_dec(&tw->tw_dr->tw_refcount); 72 inet_twsk_put(tw); 73 } 74 75 void inet_twsk_free(struct inet_timewait_sock *tw) 76 { 77 struct module *owner = tw->tw_prot->owner; 78 79 tcp_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_schedule(struct inet_timewait_sock *tw, int timeo) 92 { 93 __inet_twsk_schedule(tw, timeo, false); 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 * The caller must not access @tw anymore after this function returns. 102 */ 103 void inet_twsk_hashdance_schedule(struct inet_timewait_sock *tw, 104 struct sock *sk, 105 struct inet_hashinfo *hashinfo, 106 int timeo) 107 { 108 const struct inet_sock *inet = inet_sk(sk); 109 const struct inet_connection_sock *icsk = inet_csk(sk); 110 spinlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash); 111 struct inet_bind_hashbucket *bhead, *bhead2; 112 113 /* Put TW into bind hash. Original socket stays there too. 114 * Note, that any socket with inet->num != 0 MUST be bound in 115 * binding cache, even if it is closed. 116 */ 117 bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), inet->inet_num, 118 hashinfo->bhash_size)]; 119 bhead2 = inet_bhashfn_portaddr(hashinfo, sk, twsk_net(tw), inet->inet_num); 120 121 local_bh_disable(); 122 spin_lock(&bhead->lock); 123 spin_lock(&bhead2->lock); 124 125 tw->tw_tb = icsk->icsk_bind_hash; 126 WARN_ON(!icsk->icsk_bind_hash); 127 128 tw->tw_tb2 = icsk->icsk_bind2_hash; 129 WARN_ON(!icsk->icsk_bind2_hash); 130 sk_add_bind_node((struct sock *)tw, &tw->tw_tb2->owners); 131 132 spin_unlock(&bhead2->lock); 133 spin_unlock(&bhead->lock); 134 135 spin_lock(lock); 136 137 /* tw_refcnt is set to 3 because we have : 138 * - one reference for bhash chain. 139 * - one reference for ehash chain. 140 * - one reference for timer. 141 * Also note that after this point, we lost our implicit reference 142 * so we are not allowed to use tw anymore. 143 */ 144 refcount_set(&tw->tw_refcnt, 3); 145 146 /* Ensure tw_refcnt has been set before tw is published. 147 * smp_wmb() provides the necessary memory barrier to enforce this 148 * ordering. 149 */ 150 smp_wmb(); 151 152 hlist_nulls_replace_init_rcu(&sk->sk_nulls_node, &tw->tw_node); 153 sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1); 154 155 inet_twsk_schedule(tw, timeo); 156 157 spin_unlock(lock); 158 local_bh_enable(); 159 } 160 161 static void tw_timer_handler(struct timer_list *t) 162 { 163 struct inet_timewait_sock *tw = timer_container_of(tw, t, tw_timer); 164 165 inet_twsk_kill(tw); 166 } 167 168 struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk, 169 struct inet_timewait_death_row *dr, 170 const int state) 171 { 172 struct inet_timewait_sock *tw; 173 174 if (refcount_read(&dr->tw_refcount) - 1 >= 175 READ_ONCE(dr->sysctl_max_tw_buckets)) 176 return NULL; 177 178 tw = kmem_cache_alloc(sk->sk_prot_creator->twsk_prot->twsk_slab, 179 GFP_ATOMIC); 180 if (tw) { 181 const struct inet_sock *inet = inet_sk(sk); 182 183 tw->tw_dr = dr; 184 /* Give us an identity. */ 185 tw->tw_daddr = inet->inet_daddr; 186 tw->tw_rcv_saddr = inet->inet_rcv_saddr; 187 tw->tw_bound_dev_if = sk->sk_bound_dev_if; 188 tw->tw_tos = inet->tos; 189 tw->tw_num = inet->inet_num; 190 tw->tw_state = TCP_TIME_WAIT; 191 tw->tw_substate = state; 192 tw->tw_sport = inet->inet_sport; 193 tw->tw_dport = inet->inet_dport; 194 tw->tw_family = sk->sk_family; 195 tw->tw_reuse = sk->sk_reuse; 196 tw->tw_reuseport = sk->sk_reuseport; 197 tw->tw_hash = sk->sk_hash; 198 tw->tw_ipv6only = 0; 199 tw->tw_transparent = inet_test_bit(TRANSPARENT, sk); 200 tw->tw_connect_bind = !!(sk->sk_userlocks & SOCK_CONNECT_BIND); 201 tw->tw_prot = sk->sk_prot_creator; 202 atomic64_set(&tw->tw_cookie, atomic64_read(&sk->sk_cookie)); 203 twsk_net_set(tw, sock_net(sk)); 204 timer_setup(&tw->tw_timer, tw_timer_handler, 0); 205 #ifdef CONFIG_SOCK_VALIDATE_XMIT 206 tw->tw_validate_xmit_skb = NULL; 207 #endif 208 /* 209 * Because we use RCU lookups, we should not set tw_refcnt 210 * to a non null value before everything is setup for this 211 * timewait socket. 212 */ 213 refcount_set(&tw->tw_refcnt, 0); 214 215 __module_get(tw->tw_prot->owner); 216 psp_twsk_init(tw, sk); 217 } 218 219 return tw; 220 } 221 222 /* These are always called from BH context. See callers in 223 * tcp_input.c to verify this. 224 */ 225 226 /* This is for handling early-kills of TIME_WAIT sockets. 227 * Warning : consume reference. 228 * Caller should not access tw anymore. 229 */ 230 void inet_twsk_deschedule_put(struct inet_timewait_sock *tw) 231 { 232 struct inet_hashinfo *hashinfo = tw->tw_dr->hashinfo; 233 spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash); 234 235 /* inet_twsk_purge() walks over all sockets, including tw ones, 236 * and removes them via inet_twsk_deschedule_put() after a 237 * refcount_inc_not_zero(). 238 * 239 * inet_twsk_hashdance_schedule() must (re)init the refcount before 240 * arming the timer, i.e. inet_twsk_purge can obtain a reference to 241 * a twsk that did not yet schedule the timer. 242 * 243 * The ehash lock synchronizes these two: 244 * After acquiring the lock, the timer is always scheduled (else 245 * timer_shutdown returns false), because hashdance_schedule releases 246 * the ehash lock only after completing the timer initialization. 247 * 248 * Without grabbing the ehash lock, we get: 249 * 1) cpu x sets twsk refcount to 3 250 * 2) cpu y bumps refcount to 4 251 * 3) cpu y calls inet_twsk_deschedule_put() and shuts timer down 252 * 4) cpu x tries to start timer, but mod_timer is a noop post-shutdown 253 * -> timer refcount is never decremented. 254 */ 255 spin_lock(lock); 256 /* Makes sure hashdance_schedule() has completed */ 257 spin_unlock(lock); 258 259 if (timer_shutdown_sync(&tw->tw_timer)) 260 inet_twsk_kill(tw); 261 inet_twsk_put(tw); 262 } 263 EXPORT_SYMBOL(inet_twsk_deschedule_put); 264 265 void __inet_twsk_schedule(struct inet_timewait_sock *tw, int timeo, bool rearm) 266 { 267 /* timeout := RTO * 3.5 268 * 269 * 3.5 = 1+2+0.5 to wait for two retransmits. 270 * 271 * RATIONALE: if FIN arrived and we entered TIME-WAIT state, 272 * our ACK acking that FIN can be lost. If N subsequent retransmitted 273 * FINs (or previous seqments) are lost (probability of such event 274 * is p^(N+1), where p is probability to lose single packet and 275 * time to detect the loss is about RTO*(2^N - 1) with exponential 276 * backoff). Normal timewait length is calculated so, that we 277 * waited at least for one retransmitted FIN (maximal RTO is 120sec). 278 * [ BTW Linux. following BSD, violates this requirement waiting 279 * only for 60sec, we should wait at least for 240 secs. 280 * Well, 240 consumes too much of resources 8) 281 * ] 282 * This interval is not reduced to catch old duplicate and 283 * responces to our wandering segments living for two MSLs. 284 * However, if we use PAWS to detect 285 * old duplicates, we can reduce the interval to bounds required 286 * by RTO, rather than MSL. So, if peer understands PAWS, we 287 * kill tw bucket after 3.5*RTO (it is important that this number 288 * is greater than TS tick!) and detect old duplicates with help 289 * of PAWS. 290 */ 291 292 if (!rearm) { 293 bool kill = timeo <= 4*HZ; 294 295 __NET_INC_STATS(twsk_net(tw), kill ? LINUX_MIB_TIMEWAITKILLED : 296 LINUX_MIB_TIMEWAITED); 297 BUG_ON(mod_timer(&tw->tw_timer, jiffies + timeo)); 298 refcount_inc(&tw->tw_dr->tw_refcount); 299 } else { 300 mod_timer_pending(&tw->tw_timer, jiffies + timeo); 301 } 302 } 303 304 /* Remove all non full sockets (TIME_WAIT and NEW_SYN_RECV) for dead netns */ 305 void inet_twsk_purge(struct inet_hashinfo *hashinfo) 306 { 307 struct inet_ehash_bucket *head = &hashinfo->ehash[0]; 308 unsigned int ehash_mask = hashinfo->ehash_mask; 309 struct hlist_nulls_node *node; 310 unsigned int slot; 311 struct sock *sk; 312 313 for (slot = 0; slot <= ehash_mask; slot++, head++) { 314 if (hlist_nulls_empty(&head->chain)) 315 continue; 316 317 restart_rcu: 318 cond_resched(); 319 rcu_read_lock(); 320 restart: 321 sk_nulls_for_each_rcu(sk, node, &head->chain) { 322 int state = inet_sk_state_load(sk); 323 324 if ((1 << state) & ~(TCPF_TIME_WAIT | 325 TCPF_NEW_SYN_RECV)) 326 continue; 327 328 if (check_net(sock_net(sk))) 329 continue; 330 331 if (unlikely(!refcount_inc_not_zero(&sk->sk_refcnt))) 332 continue; 333 334 if (check_net(sock_net(sk))) { 335 sock_gen_put(sk); 336 goto restart; 337 } 338 339 rcu_read_unlock(); 340 local_bh_disable(); 341 if (state == TCP_TIME_WAIT) { 342 inet_twsk_deschedule_put(inet_twsk(sk)); 343 } else { 344 struct request_sock *req = inet_reqsk(sk); 345 346 inet_csk_reqsk_queue_drop_and_put(req->rsk_listener, 347 req); 348 } 349 local_bh_enable(); 350 goto restart_rcu; 351 } 352 /* If the nulls value we got at the end of this lookup is 353 * not the expected one, we must restart lookup. 354 * We probably met an item that was moved to another chain. 355 */ 356 if (get_nulls_value(node) != slot) 357 goto restart; 358 rcu_read_unlock(); 359 } 360 } 361