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