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[tw->tw_bslot]; 56 57 spin_lock(&bhead->lock); 58 inet_twsk_bind_unhash(tw, hashinfo); 59 spin_unlock(&bhead->lock); 60 61 if (refcount_dec_and_test(&tw->tw_dr->tw_refcount)) 62 kfree(tw->tw_dr); 63 64 inet_twsk_put(tw); 65 } 66 67 void inet_twsk_free(struct inet_timewait_sock *tw) 68 { 69 struct module *owner = tw->tw_prot->owner; 70 twsk_destructor((struct sock *)tw); 71 #ifdef SOCK_REFCNT_DEBUG 72 pr_debug("%s timewait_sock %p released\n", tw->tw_prot->name, tw); 73 #endif 74 kmem_cache_free(tw->tw_prot->twsk_prot->twsk_slab, tw); 75 module_put(owner); 76 } 77 78 void inet_twsk_put(struct inet_timewait_sock *tw) 79 { 80 if (refcount_dec_and_test(&tw->tw_refcnt)) 81 inet_twsk_free(tw); 82 } 83 EXPORT_SYMBOL_GPL(inet_twsk_put); 84 85 static void inet_twsk_add_node_rcu(struct inet_timewait_sock *tw, 86 struct hlist_nulls_head *list) 87 { 88 hlist_nulls_add_head_rcu(&tw->tw_node, list); 89 } 90 91 static void inet_twsk_add_bind_node(struct inet_timewait_sock *tw, 92 struct hlist_head *list) 93 { 94 hlist_add_head(&tw->tw_bind_node, list); 95 } 96 97 /* 98 * Enter the time wait state. This is called with locally disabled BH. 99 * Essentially we whip up a timewait bucket, copy the relevant info into it 100 * from the SK, and mess with hash chains and list linkage. 101 */ 102 void inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk, 103 struct inet_hashinfo *hashinfo) 104 { 105 const struct inet_sock *inet = inet_sk(sk); 106 const struct inet_connection_sock *icsk = inet_csk(sk); 107 struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, sk->sk_hash); 108 spinlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash); 109 struct inet_bind_hashbucket *bhead; 110 /* Step 1: Put TW into bind hash. Original socket stays there too. 111 Note, that any socket with inet->num != 0 MUST be bound in 112 binding cache, even if it is closed. 113 */ 114 /* Cache inet_bhashfn(), because 'struct net' might be no longer 115 * available later in inet_twsk_kill(). 116 */ 117 tw->tw_bslot = inet_bhashfn(twsk_net(tw), inet->inet_num, 118 hashinfo->bhash_size); 119 bhead = &hashinfo->bhash[tw->tw_bslot]; 120 spin_lock(&bhead->lock); 121 tw->tw_tb = icsk->icsk_bind_hash; 122 WARN_ON(!icsk->icsk_bind_hash); 123 inet_twsk_add_bind_node(tw, &tw->tw_tb->owners); 124 spin_unlock(&bhead->lock); 125 126 spin_lock(lock); 127 128 inet_twsk_add_node_rcu(tw, &ehead->chain); 129 130 /* Step 3: Remove SK from hash chain */ 131 if (__sk_nulls_del_node_init_rcu(sk)) 132 sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1); 133 134 spin_unlock(lock); 135 136 /* tw_refcnt is set to 3 because we have : 137 * - one reference for bhash chain. 138 * - one reference for ehash chain. 139 * - one reference for timer. 140 * We can use atomic_set() because prior spin_lock()/spin_unlock() 141 * committed into memory all tw fields. 142 * Also note that after this point, we lost our implicit reference 143 * so we are not allowed to use tw anymore. 144 */ 145 refcount_set(&tw->tw_refcnt, 3); 146 } 147 EXPORT_SYMBOL_GPL(inet_twsk_hashdance); 148 149 static void tw_timer_handler(struct timer_list *t) 150 { 151 struct inet_timewait_sock *tw = from_timer(tw, t, tw_timer); 152 153 inet_twsk_kill(tw); 154 } 155 156 struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk, 157 struct inet_timewait_death_row *dr, 158 const int state) 159 { 160 struct inet_timewait_sock *tw; 161 162 if (refcount_read(&dr->tw_refcount) - 1 >= dr->sysctl_max_tw_buckets) 163 return NULL; 164 165 tw = kmem_cache_alloc(sk->sk_prot_creator->twsk_prot->twsk_slab, 166 GFP_ATOMIC); 167 if (tw) { 168 const struct inet_sock *inet = inet_sk(sk); 169 170 tw->tw_dr = dr; 171 /* Give us an identity. */ 172 tw->tw_daddr = inet->inet_daddr; 173 tw->tw_rcv_saddr = inet->inet_rcv_saddr; 174 tw->tw_bound_dev_if = sk->sk_bound_dev_if; 175 tw->tw_tos = inet->tos; 176 tw->tw_num = inet->inet_num; 177 tw->tw_state = TCP_TIME_WAIT; 178 tw->tw_substate = state; 179 tw->tw_sport = inet->inet_sport; 180 tw->tw_dport = inet->inet_dport; 181 tw->tw_family = sk->sk_family; 182 tw->tw_reuse = sk->sk_reuse; 183 tw->tw_reuseport = sk->sk_reuseport; 184 tw->tw_hash = sk->sk_hash; 185 tw->tw_ipv6only = 0; 186 tw->tw_transparent = inet->transparent; 187 tw->tw_prot = sk->sk_prot_creator; 188 atomic64_set(&tw->tw_cookie, atomic64_read(&sk->sk_cookie)); 189 twsk_net_set(tw, sock_net(sk)); 190 timer_setup(&tw->tw_timer, tw_timer_handler, TIMER_PINNED); 191 /* 192 * Because we use RCU lookups, we should not set tw_refcnt 193 * to a non null value before everything is setup for this 194 * timewait socket. 195 */ 196 refcount_set(&tw->tw_refcnt, 0); 197 198 __module_get(tw->tw_prot->owner); 199 } 200 201 return tw; 202 } 203 EXPORT_SYMBOL_GPL(inet_twsk_alloc); 204 205 /* These are always called from BH context. See callers in 206 * tcp_input.c to verify this. 207 */ 208 209 /* This is for handling early-kills of TIME_WAIT sockets. 210 * Warning : consume reference. 211 * Caller should not access tw anymore. 212 */ 213 void inet_twsk_deschedule_put(struct inet_timewait_sock *tw) 214 { 215 if (del_timer_sync(&tw->tw_timer)) 216 inet_twsk_kill(tw); 217 inet_twsk_put(tw); 218 } 219 EXPORT_SYMBOL(inet_twsk_deschedule_put); 220 221 void __inet_twsk_schedule(struct inet_timewait_sock *tw, int timeo, bool rearm) 222 { 223 /* timeout := RTO * 3.5 224 * 225 * 3.5 = 1+2+0.5 to wait for two retransmits. 226 * 227 * RATIONALE: if FIN arrived and we entered TIME-WAIT state, 228 * our ACK acking that FIN can be lost. If N subsequent retransmitted 229 * FINs (or previous seqments) are lost (probability of such event 230 * is p^(N+1), where p is probability to lose single packet and 231 * time to detect the loss is about RTO*(2^N - 1) with exponential 232 * backoff). Normal timewait length is calculated so, that we 233 * waited at least for one retransmitted FIN (maximal RTO is 120sec). 234 * [ BTW Linux. following BSD, violates this requirement waiting 235 * only for 60sec, we should wait at least for 240 secs. 236 * Well, 240 consumes too much of resources 8) 237 * ] 238 * This interval is not reduced to catch old duplicate and 239 * responces to our wandering segments living for two MSLs. 240 * However, if we use PAWS to detect 241 * old duplicates, we can reduce the interval to bounds required 242 * by RTO, rather than MSL. So, if peer understands PAWS, we 243 * kill tw bucket after 3.5*RTO (it is important that this number 244 * is greater than TS tick!) and detect old duplicates with help 245 * of PAWS. 246 */ 247 248 if (!rearm) { 249 bool kill = timeo <= 4*HZ; 250 251 __NET_INC_STATS(twsk_net(tw), kill ? LINUX_MIB_TIMEWAITKILLED : 252 LINUX_MIB_TIMEWAITED); 253 BUG_ON(mod_timer(&tw->tw_timer, jiffies + timeo)); 254 refcount_inc(&tw->tw_dr->tw_refcount); 255 } else { 256 mod_timer_pending(&tw->tw_timer, jiffies + timeo); 257 } 258 } 259 EXPORT_SYMBOL_GPL(__inet_twsk_schedule); 260