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 #ifdef SOCK_REFCNT_DEBUG 81 pr_debug("%s timewait_sock %p released\n", tw->tw_prot->name, tw); 82 #endif 83 kmem_cache_free(tw->tw_prot->twsk_prot->twsk_slab, tw); 84 module_put(owner); 85 } 86 87 void inet_twsk_put(struct inet_timewait_sock *tw) 88 { 89 if (refcount_dec_and_test(&tw->tw_refcnt)) 90 inet_twsk_free(tw); 91 } 92 EXPORT_SYMBOL_GPL(inet_twsk_put); 93 94 static void inet_twsk_add_node_tail_rcu(struct inet_timewait_sock *tw, 95 struct hlist_nulls_head *list) 96 { 97 hlist_nulls_add_tail_rcu(&tw->tw_node, list); 98 } 99 100 static void inet_twsk_add_bind_node(struct inet_timewait_sock *tw, 101 struct hlist_head *list) 102 { 103 hlist_add_head(&tw->tw_bind_node, list); 104 } 105 106 static void inet_twsk_add_bind2_node(struct inet_timewait_sock *tw, 107 struct hlist_head *list) 108 { 109 hlist_add_head(&tw->tw_bind2_node, list); 110 } 111 112 /* 113 * Enter the time wait state. This is called with locally disabled BH. 114 * Essentially we whip up a timewait bucket, copy the relevant info into it 115 * from the SK, and mess with hash chains and list linkage. 116 */ 117 void inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk, 118 struct inet_hashinfo *hashinfo) 119 { 120 const struct inet_sock *inet = inet_sk(sk); 121 const struct inet_connection_sock *icsk = inet_csk(sk); 122 struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, sk->sk_hash); 123 spinlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash); 124 struct inet_bind_hashbucket *bhead, *bhead2; 125 126 /* Step 1: Put TW into bind hash. Original socket stays there too. 127 Note, that any socket with inet->num != 0 MUST be bound in 128 binding cache, even if it is closed. 129 */ 130 bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), inet->inet_num, 131 hashinfo->bhash_size)]; 132 bhead2 = inet_bhashfn_portaddr(hashinfo, sk, twsk_net(tw), inet->inet_num); 133 134 spin_lock(&bhead->lock); 135 spin_lock(&bhead2->lock); 136 137 tw->tw_tb = icsk->icsk_bind_hash; 138 WARN_ON(!icsk->icsk_bind_hash); 139 inet_twsk_add_bind_node(tw, &tw->tw_tb->owners); 140 141 tw->tw_tb2 = icsk->icsk_bind2_hash; 142 WARN_ON(!icsk->icsk_bind2_hash); 143 inet_twsk_add_bind2_node(tw, &tw->tw_tb2->deathrow); 144 145 spin_unlock(&bhead2->lock); 146 spin_unlock(&bhead->lock); 147 148 spin_lock(lock); 149 150 inet_twsk_add_node_tail_rcu(tw, &ehead->chain); 151 152 /* Step 3: Remove SK from hash chain */ 153 if (__sk_nulls_del_node_init_rcu(sk)) 154 sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1); 155 156 spin_unlock(lock); 157 158 /* tw_refcnt is set to 3 because we have : 159 * - one reference for bhash chain. 160 * - one reference for ehash chain. 161 * - one reference for timer. 162 * We can use atomic_set() because prior spin_lock()/spin_unlock() 163 * committed into memory all tw fields. 164 * Also note that after this point, we lost our implicit reference 165 * so we are not allowed to use tw anymore. 166 */ 167 refcount_set(&tw->tw_refcnt, 3); 168 } 169 EXPORT_SYMBOL_GPL(inet_twsk_hashdance); 170 171 static void tw_timer_handler(struct timer_list *t) 172 { 173 struct inet_timewait_sock *tw = from_timer(tw, t, tw_timer); 174 175 inet_twsk_kill(tw); 176 } 177 178 struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk, 179 struct inet_timewait_death_row *dr, 180 const int state) 181 { 182 struct inet_timewait_sock *tw; 183 184 if (refcount_read(&dr->tw_refcount) - 1 >= 185 READ_ONCE(dr->sysctl_max_tw_buckets)) 186 return NULL; 187 188 tw = kmem_cache_alloc(sk->sk_prot_creator->twsk_prot->twsk_slab, 189 GFP_ATOMIC); 190 if (tw) { 191 const struct inet_sock *inet = inet_sk(sk); 192 193 tw->tw_dr = dr; 194 /* Give us an identity. */ 195 tw->tw_daddr = inet->inet_daddr; 196 tw->tw_rcv_saddr = inet->inet_rcv_saddr; 197 tw->tw_bound_dev_if = sk->sk_bound_dev_if; 198 tw->tw_tos = inet->tos; 199 tw->tw_num = inet->inet_num; 200 tw->tw_state = TCP_TIME_WAIT; 201 tw->tw_substate = state; 202 tw->tw_sport = inet->inet_sport; 203 tw->tw_dport = inet->inet_dport; 204 tw->tw_family = sk->sk_family; 205 tw->tw_reuse = sk->sk_reuse; 206 tw->tw_reuseport = sk->sk_reuseport; 207 tw->tw_hash = sk->sk_hash; 208 tw->tw_ipv6only = 0; 209 tw->tw_transparent = inet->transparent; 210 tw->tw_prot = sk->sk_prot_creator; 211 atomic64_set(&tw->tw_cookie, atomic64_read(&sk->sk_cookie)); 212 twsk_net_set(tw, sock_net(sk)); 213 timer_setup(&tw->tw_timer, tw_timer_handler, TIMER_PINNED); 214 /* 215 * Because we use RCU lookups, we should not set tw_refcnt 216 * to a non null value before everything is setup for this 217 * timewait socket. 218 */ 219 refcount_set(&tw->tw_refcnt, 0); 220 221 __module_get(tw->tw_prot->owner); 222 } 223 224 return tw; 225 } 226 EXPORT_SYMBOL_GPL(inet_twsk_alloc); 227 228 /* These are always called from BH context. See callers in 229 * tcp_input.c to verify this. 230 */ 231 232 /* This is for handling early-kills of TIME_WAIT sockets. 233 * Warning : consume reference. 234 * Caller should not access tw anymore. 235 */ 236 void inet_twsk_deschedule_put(struct inet_timewait_sock *tw) 237 { 238 if (del_timer_sync(&tw->tw_timer)) 239 inet_twsk_kill(tw); 240 inet_twsk_put(tw); 241 } 242 EXPORT_SYMBOL(inet_twsk_deschedule_put); 243 244 void __inet_twsk_schedule(struct inet_timewait_sock *tw, int timeo, bool rearm) 245 { 246 /* timeout := RTO * 3.5 247 * 248 * 3.5 = 1+2+0.5 to wait for two retransmits. 249 * 250 * RATIONALE: if FIN arrived and we entered TIME-WAIT state, 251 * our ACK acking that FIN can be lost. If N subsequent retransmitted 252 * FINs (or previous seqments) are lost (probability of such event 253 * is p^(N+1), where p is probability to lose single packet and 254 * time to detect the loss is about RTO*(2^N - 1) with exponential 255 * backoff). Normal timewait length is calculated so, that we 256 * waited at least for one retransmitted FIN (maximal RTO is 120sec). 257 * [ BTW Linux. following BSD, violates this requirement waiting 258 * only for 60sec, we should wait at least for 240 secs. 259 * Well, 240 consumes too much of resources 8) 260 * ] 261 * This interval is not reduced to catch old duplicate and 262 * responces to our wandering segments living for two MSLs. 263 * However, if we use PAWS to detect 264 * old duplicates, we can reduce the interval to bounds required 265 * by RTO, rather than MSL. So, if peer understands PAWS, we 266 * kill tw bucket after 3.5*RTO (it is important that this number 267 * is greater than TS tick!) and detect old duplicates with help 268 * of PAWS. 269 */ 270 271 if (!rearm) { 272 bool kill = timeo <= 4*HZ; 273 274 __NET_INC_STATS(twsk_net(tw), kill ? LINUX_MIB_TIMEWAITKILLED : 275 LINUX_MIB_TIMEWAITED); 276 BUG_ON(mod_timer(&tw->tw_timer, jiffies + timeo)); 277 refcount_inc(&tw->tw_dr->tw_refcount); 278 } else { 279 mod_timer_pending(&tw->tw_timer, jiffies + timeo); 280 } 281 } 282 EXPORT_SYMBOL_GPL(__inet_twsk_schedule); 283 284 void inet_twsk_purge(struct inet_hashinfo *hashinfo, int family) 285 { 286 struct inet_timewait_sock *tw; 287 struct sock *sk; 288 struct hlist_nulls_node *node; 289 unsigned int slot; 290 291 for (slot = 0; slot <= hashinfo->ehash_mask; slot++) { 292 struct inet_ehash_bucket *head = &hashinfo->ehash[slot]; 293 restart_rcu: 294 cond_resched(); 295 rcu_read_lock(); 296 restart: 297 sk_nulls_for_each_rcu(sk, node, &head->chain) { 298 if (sk->sk_state != TCP_TIME_WAIT) { 299 /* A kernel listener socket might not hold refcnt for net, 300 * so reqsk_timer_handler() could be fired after net is 301 * freed. Userspace listener and reqsk never exist here. 302 */ 303 if (unlikely(sk->sk_state == TCP_NEW_SYN_RECV && 304 hashinfo->pernet)) { 305 struct request_sock *req = inet_reqsk(sk); 306 307 inet_csk_reqsk_queue_drop_and_put(req->rsk_listener, req); 308 } 309 310 continue; 311 } 312 313 tw = inet_twsk(sk); 314 if ((tw->tw_family != family) || 315 refcount_read(&twsk_net(tw)->ns.count)) 316 continue; 317 318 if (unlikely(!refcount_inc_not_zero(&tw->tw_refcnt))) 319 continue; 320 321 if (unlikely((tw->tw_family != family) || 322 refcount_read(&twsk_net(tw)->ns.count))) { 323 inet_twsk_put(tw); 324 goto restart; 325 } 326 327 rcu_read_unlock(); 328 local_bh_disable(); 329 inet_twsk_deschedule_put(tw); 330 local_bh_enable(); 331 goto restart_rcu; 332 } 333 /* If the nulls value we got at the end of this lookup is 334 * not the expected one, we must restart lookup. 335 * We probably met an item that was moved to another chain. 336 */ 337 if (get_nulls_value(node) != slot) 338 goto restart; 339 rcu_read_unlock(); 340 } 341 } 342 EXPORT_SYMBOL_GPL(inet_twsk_purge); 343