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