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_bind_bucket *tb = tw->tw_tb; 33 34 if (!tb) 35 return; 36 37 __hlist_del(&tw->tw_bind_node); 38 tw->tw_tb = NULL; 39 inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb); 40 __sock_put((struct sock *)tw); 41 } 42 43 /* Must be called with locally disabled BHs. */ 44 static void inet_twsk_kill(struct inet_timewait_sock *tw) 45 { 46 struct inet_hashinfo *hashinfo = tw->tw_dr->hashinfo; 47 spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash); 48 struct inet_bind_hashbucket *bhead; 49 50 spin_lock(lock); 51 sk_nulls_del_node_init_rcu((struct sock *)tw); 52 spin_unlock(lock); 53 54 /* Disassociate with bind bucket. */ 55 bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), tw->tw_num, 56 hashinfo->bhash_size)]; 57 58 spin_lock(&bhead->lock); 59 inet_twsk_bind_unhash(tw, hashinfo); 60 spin_unlock(&bhead->lock); 61 62 if (refcount_dec_and_test(&tw->tw_dr->tw_refcount)) 63 kfree(tw->tw_dr); 64 65 inet_twsk_put(tw); 66 } 67 68 void inet_twsk_free(struct inet_timewait_sock *tw) 69 { 70 struct module *owner = tw->tw_prot->owner; 71 twsk_destructor((struct sock *)tw); 72 #ifdef SOCK_REFCNT_DEBUG 73 pr_debug("%s timewait_sock %p released\n", tw->tw_prot->name, tw); 74 #endif 75 kmem_cache_free(tw->tw_prot->twsk_prot->twsk_slab, tw); 76 module_put(owner); 77 } 78 79 void inet_twsk_put(struct inet_timewait_sock *tw) 80 { 81 if (refcount_dec_and_test(&tw->tw_refcnt)) 82 inet_twsk_free(tw); 83 } 84 EXPORT_SYMBOL_GPL(inet_twsk_put); 85 86 static void inet_twsk_add_node_rcu(struct inet_timewait_sock *tw, 87 struct hlist_nulls_head *list) 88 { 89 hlist_nulls_add_head_rcu(&tw->tw_node, list); 90 } 91 92 static void inet_twsk_add_bind_node(struct inet_timewait_sock *tw, 93 struct hlist_head *list) 94 { 95 hlist_add_head(&tw->tw_bind_node, list); 96 } 97 98 /* 99 * Enter the time wait state. This is called with locally disabled BH. 100 * Essentially we whip up a timewait bucket, copy the relevant info into it 101 * from the SK, and mess with hash chains and list linkage. 102 */ 103 void inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk, 104 struct inet_hashinfo *hashinfo) 105 { 106 const struct inet_sock *inet = inet_sk(sk); 107 const struct inet_connection_sock *icsk = inet_csk(sk); 108 struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, sk->sk_hash); 109 spinlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash); 110 struct inet_bind_hashbucket *bhead; 111 /* Step 1: Put TW into bind hash. Original socket stays there too. 112 Note, that any socket with inet->num != 0 MUST be bound in 113 binding cache, even if it is closed. 114 */ 115 bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), inet->inet_num, 116 hashinfo->bhash_size)]; 117 spin_lock(&bhead->lock); 118 tw->tw_tb = icsk->icsk_bind_hash; 119 WARN_ON(!icsk->icsk_bind_hash); 120 inet_twsk_add_bind_node(tw, &tw->tw_tb->owners); 121 spin_unlock(&bhead->lock); 122 123 spin_lock(lock); 124 125 inet_twsk_add_node_rcu(tw, &ehead->chain); 126 127 /* Step 3: Remove SK from hash chain */ 128 if (__sk_nulls_del_node_init_rcu(sk)) 129 sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1); 130 131 spin_unlock(lock); 132 133 /* tw_refcnt is set to 3 because we have : 134 * - one reference for bhash chain. 135 * - one reference for ehash chain. 136 * - one reference for timer. 137 * We can use atomic_set() because prior spin_lock()/spin_unlock() 138 * committed into memory all tw fields. 139 * Also note that after this point, we lost our implicit reference 140 * so we are not allowed to use tw anymore. 141 */ 142 refcount_set(&tw->tw_refcnt, 3); 143 } 144 EXPORT_SYMBOL_GPL(inet_twsk_hashdance); 145 146 static void tw_timer_handler(struct timer_list *t) 147 { 148 struct inet_timewait_sock *tw = from_timer(tw, t, tw_timer); 149 150 inet_twsk_kill(tw); 151 } 152 153 struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk, 154 struct inet_timewait_death_row *dr, 155 const int state) 156 { 157 struct inet_timewait_sock *tw; 158 159 if (refcount_read(&dr->tw_refcount) - 1 >= 160 READ_ONCE(dr->sysctl_max_tw_buckets)) 161 return NULL; 162 163 tw = kmem_cache_alloc(sk->sk_prot_creator->twsk_prot->twsk_slab, 164 GFP_ATOMIC); 165 if (tw) { 166 const struct inet_sock *inet = inet_sk(sk); 167 168 tw->tw_dr = dr; 169 /* Give us an identity. */ 170 tw->tw_daddr = inet->inet_daddr; 171 tw->tw_rcv_saddr = inet->inet_rcv_saddr; 172 tw->tw_bound_dev_if = sk->sk_bound_dev_if; 173 tw->tw_tos = inet->tos; 174 tw->tw_num = inet->inet_num; 175 tw->tw_state = TCP_TIME_WAIT; 176 tw->tw_substate = state; 177 tw->tw_sport = inet->inet_sport; 178 tw->tw_dport = inet->inet_dport; 179 tw->tw_family = sk->sk_family; 180 tw->tw_reuse = sk->sk_reuse; 181 tw->tw_reuseport = sk->sk_reuseport; 182 tw->tw_hash = sk->sk_hash; 183 tw->tw_ipv6only = 0; 184 tw->tw_transparent = inet->transparent; 185 tw->tw_prot = sk->sk_prot_creator; 186 atomic64_set(&tw->tw_cookie, atomic64_read(&sk->sk_cookie)); 187 twsk_net_set(tw, sock_net(sk)); 188 timer_setup(&tw->tw_timer, tw_timer_handler, TIMER_PINNED); 189 /* 190 * Because we use RCU lookups, we should not set tw_refcnt 191 * to a non null value before everything is setup for this 192 * timewait socket. 193 */ 194 refcount_set(&tw->tw_refcnt, 0); 195 196 __module_get(tw->tw_prot->owner); 197 } 198 199 return tw; 200 } 201 EXPORT_SYMBOL_GPL(inet_twsk_alloc); 202 203 /* These are always called from BH context. See callers in 204 * tcp_input.c to verify this. 205 */ 206 207 /* This is for handling early-kills of TIME_WAIT sockets. 208 * Warning : consume reference. 209 * Caller should not access tw anymore. 210 */ 211 void inet_twsk_deschedule_put(struct inet_timewait_sock *tw) 212 { 213 if (del_timer_sync(&tw->tw_timer)) 214 inet_twsk_kill(tw); 215 inet_twsk_put(tw); 216 } 217 EXPORT_SYMBOL(inet_twsk_deschedule_put); 218 219 void __inet_twsk_schedule(struct inet_timewait_sock *tw, int timeo, bool rearm) 220 { 221 /* timeout := RTO * 3.5 222 * 223 * 3.5 = 1+2+0.5 to wait for two retransmits. 224 * 225 * RATIONALE: if FIN arrived and we entered TIME-WAIT state, 226 * our ACK acking that FIN can be lost. If N subsequent retransmitted 227 * FINs (or previous seqments) are lost (probability of such event 228 * is p^(N+1), where p is probability to lose single packet and 229 * time to detect the loss is about RTO*(2^N - 1) with exponential 230 * backoff). Normal timewait length is calculated so, that we 231 * waited at least for one retransmitted FIN (maximal RTO is 120sec). 232 * [ BTW Linux. following BSD, violates this requirement waiting 233 * only for 60sec, we should wait at least for 240 secs. 234 * Well, 240 consumes too much of resources 8) 235 * ] 236 * This interval is not reduced to catch old duplicate and 237 * responces to our wandering segments living for two MSLs. 238 * However, if we use PAWS to detect 239 * old duplicates, we can reduce the interval to bounds required 240 * by RTO, rather than MSL. So, if peer understands PAWS, we 241 * kill tw bucket after 3.5*RTO (it is important that this number 242 * is greater than TS tick!) and detect old duplicates with help 243 * of PAWS. 244 */ 245 246 if (!rearm) { 247 bool kill = timeo <= 4*HZ; 248 249 __NET_INC_STATS(twsk_net(tw), kill ? LINUX_MIB_TIMEWAITKILLED : 250 LINUX_MIB_TIMEWAITED); 251 BUG_ON(mod_timer(&tw->tw_timer, jiffies + timeo)); 252 refcount_inc(&tw->tw_dr->tw_refcount); 253 } else { 254 mod_timer_pending(&tw->tw_timer, jiffies + timeo); 255 } 256 } 257 EXPORT_SYMBOL_GPL(__inet_twsk_schedule); 258 259 void inet_twsk_purge(struct inet_hashinfo *hashinfo, int family) 260 { 261 struct inet_timewait_sock *tw; 262 struct sock *sk; 263 struct hlist_nulls_node *node; 264 unsigned int slot; 265 266 for (slot = 0; slot <= hashinfo->ehash_mask; slot++) { 267 struct inet_ehash_bucket *head = &hashinfo->ehash[slot]; 268 restart_rcu: 269 cond_resched(); 270 rcu_read_lock(); 271 restart: 272 sk_nulls_for_each_rcu(sk, node, &head->chain) { 273 if (sk->sk_state != TCP_TIME_WAIT) 274 continue; 275 tw = inet_twsk(sk); 276 if ((tw->tw_family != family) || 277 refcount_read(&twsk_net(tw)->ns.count)) 278 continue; 279 280 if (unlikely(!refcount_inc_not_zero(&tw->tw_refcnt))) 281 continue; 282 283 if (unlikely((tw->tw_family != family) || 284 refcount_read(&twsk_net(tw)->ns.count))) { 285 inet_twsk_put(tw); 286 goto restart; 287 } 288 289 rcu_read_unlock(); 290 local_bh_disable(); 291 inet_twsk_deschedule_put(tw); 292 local_bh_enable(); 293 goto restart_rcu; 294 } 295 /* If the nulls value we got at the end of this lookup is 296 * not the expected one, we must restart lookup. 297 * We probably met an item that was moved to another chain. 298 */ 299 if (get_nulls_value(node) != slot) 300 goto restart; 301 rcu_read_unlock(); 302 } 303 } 304 EXPORT_SYMBOL_GPL(inet_twsk_purge); 305