net/ipv4/inet_timewait_sock.c

   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 /* Remove all non full sockets (TIME_WAIT and NEW_SYN_RECV) for dead netns */
 267 void inet_twsk_purge(struct inet_hashinfo *hashinfo, int family)
 268 {
 269         struct hlist_nulls_node *node;
 270         unsigned int slot;
 271         struct sock *sk;
 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                         int state = inet_sk_state_load(sk);
 281
 282                         if ((1 << state) & ~(TCPF_TIME_WAIT |
 283                                              TCPF_NEW_SYN_RECV))
 284                                 continue;
 285
 286                         if (sk->sk_family != family ||
 287                             refcount_read(&sock_net(sk)->ns.count))
 288                                 continue;
 289
 290                         if (unlikely(!refcount_inc_not_zero(&sk->sk_refcnt)))
 291                                 continue;
 292
 293                         if (unlikely(sk->sk_family != family ||
 294                                      refcount_read(&sock_net(sk)->ns.count))) {
 295                                 sock_gen_put(sk);
 296                                 goto restart;
 297                         }
 298
 299                         rcu_read_unlock();
 300                         local_bh_disable();
 301                         if (state == TCP_TIME_WAIT) {
 302                                 inet_twsk_deschedule_put(inet_twsk(sk));
 303                         } else {
 304                                 struct request_sock *req = inet_reqsk(sk);
 305
 306                                 inet_csk_reqsk_queue_drop_and_put(req->rsk_listener,
 307                                                                   req);
 308                         }
 309                         local_bh_enable();
 310                         goto restart_rcu;
 311                 }
 312                 /* If the nulls value we got at the end of this lookup is
 313                  * not the expected one, we must restart lookup.
 314                  * We probably met an item that was moved to another chain.
 315                  */
 316                 if (get_nulls_value(node) != slot)
 317                         goto restart;
 318                 rcu_read_unlock();
 319         }
 320 }
 321 EXPORT_SYMBOL_GPL(inet_twsk_purge);