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_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_schedule(struct inet_timewait_sock *tw, int timeo) 98 { 99 __inet_twsk_schedule(tw, timeo, false); 100 } 101 102 /* 103 * Enter the time wait state. 104 * Essentially we whip up a timewait bucket, copy the relevant info into it 105 * from the SK, and mess with hash chains and list linkage. 106 * 107 * The caller must not access @tw anymore after this function returns. 108 */ 109 void inet_twsk_hashdance_schedule(struct inet_timewait_sock *tw, 110 struct sock *sk, 111 struct inet_hashinfo *hashinfo, 112 int timeo) 113 { 114 const struct inet_sock *inet = inet_sk(sk); 115 const struct inet_connection_sock *icsk = inet_csk(sk); 116 struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, sk->sk_hash); 117 spinlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash); 118 struct inet_bind_hashbucket *bhead, *bhead2; 119 120 /* Step 1: Put TW into bind hash. Original socket stays there too. 121 Note, that any socket with inet->num != 0 MUST be bound in 122 binding cache, even if it is closed. 123 */ 124 bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), inet->inet_num, 125 hashinfo->bhash_size)]; 126 bhead2 = inet_bhashfn_portaddr(hashinfo, sk, twsk_net(tw), inet->inet_num); 127 128 local_bh_disable(); 129 spin_lock(&bhead->lock); 130 spin_lock(&bhead2->lock); 131 132 tw->tw_tb = icsk->icsk_bind_hash; 133 WARN_ON(!icsk->icsk_bind_hash); 134 135 tw->tw_tb2 = icsk->icsk_bind2_hash; 136 WARN_ON(!icsk->icsk_bind2_hash); 137 sk_add_bind_node((struct sock *)tw, &tw->tw_tb2->owners); 138 139 spin_unlock(&bhead2->lock); 140 spin_unlock(&bhead->lock); 141 142 spin_lock(lock); 143 144 /* Step 2: Hash TW into tcp ehash chain */ 145 inet_twsk_add_node_rcu(tw, &ehead->chain); 146 147 /* Step 3: Remove SK from hash chain */ 148 if (__sk_nulls_del_node_init_rcu(sk)) 149 sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1); 150 151 152 /* Ensure above writes are committed into memory before updating the 153 * refcount. 154 * Provides ordering vs later refcount_inc(). 155 */ 156 smp_wmb(); 157 /* tw_refcnt is set to 3 because we have : 158 * - one reference for bhash chain. 159 * - one reference for ehash chain. 160 * - one reference for timer. 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 inet_twsk_schedule(tw, timeo); 167 168 spin_unlock(lock); 169 local_bh_enable(); 170 } 171 172 static void tw_timer_handler(struct timer_list *t) 173 { 174 struct inet_timewait_sock *tw = timer_container_of(tw, t, tw_timer); 175 176 inet_twsk_kill(tw); 177 } 178 179 struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk, 180 struct inet_timewait_death_row *dr, 181 const int state) 182 { 183 struct inet_timewait_sock *tw; 184 185 if (refcount_read(&dr->tw_refcount) - 1 >= 186 READ_ONCE(dr->sysctl_max_tw_buckets)) 187 return NULL; 188 189 tw = kmem_cache_alloc(sk->sk_prot_creator->twsk_prot->twsk_slab, 190 GFP_ATOMIC); 191 if (tw) { 192 const struct inet_sock *inet = inet_sk(sk); 193 194 tw->tw_dr = dr; 195 /* Give us an identity. */ 196 tw->tw_daddr = inet->inet_daddr; 197 tw->tw_rcv_saddr = inet->inet_rcv_saddr; 198 tw->tw_bound_dev_if = sk->sk_bound_dev_if; 199 tw->tw_tos = inet->tos; 200 tw->tw_num = inet->inet_num; 201 tw->tw_state = TCP_TIME_WAIT; 202 tw->tw_substate = state; 203 tw->tw_sport = inet->inet_sport; 204 tw->tw_dport = inet->inet_dport; 205 tw->tw_family = sk->sk_family; 206 tw->tw_reuse = sk->sk_reuse; 207 tw->tw_reuseport = sk->sk_reuseport; 208 tw->tw_hash = sk->sk_hash; 209 tw->tw_ipv6only = 0; 210 tw->tw_transparent = inet_test_bit(TRANSPARENT, sk); 211 tw->tw_connect_bind = !!(sk->sk_userlocks & SOCK_CONNECT_BIND); 212 tw->tw_prot = sk->sk_prot_creator; 213 atomic64_set(&tw->tw_cookie, atomic64_read(&sk->sk_cookie)); 214 twsk_net_set(tw, sock_net(sk)); 215 timer_setup(&tw->tw_timer, tw_timer_handler, 0); 216 #ifdef CONFIG_SOCK_VALIDATE_XMIT 217 tw->tw_validate_xmit_skb = NULL; 218 #endif 219 /* 220 * Because we use RCU lookups, we should not set tw_refcnt 221 * to a non null value before everything is setup for this 222 * timewait socket. 223 */ 224 refcount_set(&tw->tw_refcnt, 0); 225 226 __module_get(tw->tw_prot->owner); 227 psp_twsk_init(tw, sk); 228 } 229 230 return tw; 231 } 232 233 /* These are always called from BH context. See callers in 234 * tcp_input.c to verify this. 235 */ 236 237 /* This is for handling early-kills of TIME_WAIT sockets. 238 * Warning : consume reference. 239 * Caller should not access tw anymore. 240 */ 241 void inet_twsk_deschedule_put(struct inet_timewait_sock *tw) 242 { 243 struct inet_hashinfo *hashinfo = tw->tw_dr->hashinfo; 244 spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash); 245 246 /* inet_twsk_purge() walks over all sockets, including tw ones, 247 * and removes them via inet_twsk_deschedule_put() after a 248 * refcount_inc_not_zero(). 249 * 250 * inet_twsk_hashdance_schedule() must (re)init the refcount before 251 * arming the timer, i.e. inet_twsk_purge can obtain a reference to 252 * a twsk that did not yet schedule the timer. 253 * 254 * The ehash lock synchronizes these two: 255 * After acquiring the lock, the timer is always scheduled (else 256 * timer_shutdown returns false), because hashdance_schedule releases 257 * the ehash lock only after completing the timer initialization. 258 * 259 * Without grabbing the ehash lock, we get: 260 * 1) cpu x sets twsk refcount to 3 261 * 2) cpu y bumps refcount to 4 262 * 3) cpu y calls inet_twsk_deschedule_put() and shuts timer down 263 * 4) cpu x tries to start timer, but mod_timer is a noop post-shutdown 264 * -> timer refcount is never decremented. 265 */ 266 spin_lock(lock); 267 /* Makes sure hashdance_schedule() has completed */ 268 spin_unlock(lock); 269 270 if (timer_shutdown_sync(&tw->tw_timer)) 271 inet_twsk_kill(tw); 272 inet_twsk_put(tw); 273 } 274 EXPORT_SYMBOL(inet_twsk_deschedule_put); 275 276 void __inet_twsk_schedule(struct inet_timewait_sock *tw, int timeo, bool rearm) 277 { 278 /* timeout := RTO * 3.5 279 * 280 * 3.5 = 1+2+0.5 to wait for two retransmits. 281 * 282 * RATIONALE: if FIN arrived and we entered TIME-WAIT state, 283 * our ACK acking that FIN can be lost. If N subsequent retransmitted 284 * FINs (or previous seqments) are lost (probability of such event 285 * is p^(N+1), where p is probability to lose single packet and 286 * time to detect the loss is about RTO*(2^N - 1) with exponential 287 * backoff). Normal timewait length is calculated so, that we 288 * waited at least for one retransmitted FIN (maximal RTO is 120sec). 289 * [ BTW Linux. following BSD, violates this requirement waiting 290 * only for 60sec, we should wait at least for 240 secs. 291 * Well, 240 consumes too much of resources 8) 292 * ] 293 * This interval is not reduced to catch old duplicate and 294 * responces to our wandering segments living for two MSLs. 295 * However, if we use PAWS to detect 296 * old duplicates, we can reduce the interval to bounds required 297 * by RTO, rather than MSL. So, if peer understands PAWS, we 298 * kill tw bucket after 3.5*RTO (it is important that this number 299 * is greater than TS tick!) and detect old duplicates with help 300 * of PAWS. 301 */ 302 303 if (!rearm) { 304 bool kill = timeo <= 4*HZ; 305 306 __NET_INC_STATS(twsk_net(tw), kill ? LINUX_MIB_TIMEWAITKILLED : 307 LINUX_MIB_TIMEWAITED); 308 BUG_ON(mod_timer(&tw->tw_timer, jiffies + timeo)); 309 refcount_inc(&tw->tw_dr->tw_refcount); 310 } else { 311 mod_timer_pending(&tw->tw_timer, jiffies + timeo); 312 } 313 } 314 315 /* Remove all non full sockets (TIME_WAIT and NEW_SYN_RECV) for dead netns */ 316 void inet_twsk_purge(struct inet_hashinfo *hashinfo) 317 { 318 struct inet_ehash_bucket *head = &hashinfo->ehash[0]; 319 unsigned int ehash_mask = hashinfo->ehash_mask; 320 struct hlist_nulls_node *node; 321 unsigned int slot; 322 struct sock *sk; 323 324 for (slot = 0; slot <= ehash_mask; slot++, head++) { 325 if (hlist_nulls_empty(&head->chain)) 326 continue; 327 328 restart_rcu: 329 cond_resched(); 330 rcu_read_lock(); 331 restart: 332 sk_nulls_for_each_rcu(sk, node, &head->chain) { 333 int state = inet_sk_state_load(sk); 334 335 if ((1 << state) & ~(TCPF_TIME_WAIT | 336 TCPF_NEW_SYN_RECV)) 337 continue; 338 339 if (check_net(sock_net(sk))) 340 continue; 341 342 if (unlikely(!refcount_inc_not_zero(&sk->sk_refcnt))) 343 continue; 344 345 if (check_net(sock_net(sk))) { 346 sock_gen_put(sk); 347 goto restart; 348 } 349 350 rcu_read_unlock(); 351 local_bh_disable(); 352 if (state == TCP_TIME_WAIT) { 353 inet_twsk_deschedule_put(inet_twsk(sk)); 354 } else { 355 struct request_sock *req = inet_reqsk(sk); 356 357 inet_csk_reqsk_queue_drop_and_put(req->rsk_listener, 358 req); 359 } 360 local_bh_enable(); 361 goto restart_rcu; 362 } 363 /* If the nulls value we got at the end of this lookup is 364 * not the expected one, we must restart lookup. 365 * We probably met an item that was moved to another chain. 366 */ 367 if (get_nulls_value(node) != slot) 368 goto restart; 369 rcu_read_unlock(); 370 } 371 } 372