// SPDX-License-Identifier: GPL-2.0-only
/*
* INET An implementation of the TCP/IP protocol suite for the LINUX
* operating system. INET is implemented using the BSD Socket
* interface as the means of communication with the user level.
*
* Generic TIME_WAIT sockets functions
*
* From code orinally in TCP
*/
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <net/inet_hashtables.h>
#include <net/inet_timewait_sock.h>
#include <net/ip.h>
/**
* inet_twsk_bind_unhash - unhash a timewait socket from bind hash
* @tw: timewait socket
* @hashinfo: hashinfo pointer
*
* unhash a timewait socket from bind hash, if hashed.
* bind hash lock must be held by caller.
* Returns 1 if caller should call inet_twsk_put() after lock release.
*/
void inet_twsk_bind_unhash(struct inet_timewait_sock *tw,
struct inet_hashinfo *hashinfo)
{
struct inet_bind2_bucket *tb2 = tw->tw_tb2;
struct inet_bind_bucket *tb = tw->tw_tb;
if (!tb)
return;
__sk_del_bind_node((struct sock *)tw);
tw->tw_tb = NULL;
tw->tw_tb2 = NULL;
inet_bind2_bucket_destroy(hashinfo->bind2_bucket_cachep, tb2);
inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
__sock_put((struct sock *)tw);
}
/* Must be called with locally disabled BHs. */
static void inet_twsk_kill(struct inet_timewait_sock *tw)
{
struct inet_hashinfo *hashinfo = tw->tw_dr->hashinfo;
spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash);
struct inet_bind_hashbucket *bhead, *bhead2;
spin_lock(lock);
sk_nulls_del_node_init_rcu((struct sock *)tw);
spin_unlock(lock);
/* Disassociate with bind bucket. */
bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), tw->tw_num,
hashinfo->bhash_size)];
bhead2 = inet_bhashfn_portaddr(hashinfo, (struct sock *)tw,
twsk_net(tw), tw->tw_num);
spin_lock(&bhead->lock);
spin_lock(&bhead2->lock);
inet_twsk_bind_unhash(tw, hashinfo);
spin_unlock(&bhead2->lock);
spin_unlock(&bhead->lock);
refcount_dec(&tw->tw_dr->tw_refcount);
inet_twsk_put(tw);
}
void inet_twsk_free(struct inet_timewait_sock *tw)
{
struct module *owner = tw->tw_prot->owner;
twsk_destructor((struct sock *)tw);
kmem_cache_free(tw->tw_prot->twsk_prot->twsk_slab, tw);
module_put(owner);
}
void inet_twsk_put(struct inet_timewait_sock *tw)
{
if (refcount_dec_and_test(&tw->tw_refcnt))
inet_twsk_free(tw);
}
EXPORT_SYMBOL_GPL(inet_twsk_put);
static void inet_twsk_add_node_rcu(struct inet_timewait_sock *tw,
struct hlist_nulls_head *list)
{
hlist_nulls_add_head_rcu(&tw->tw_node, list);
}
static void inet_twsk_schedule(struct inet_timewait_sock *tw, int timeo)
{
__inet_twsk_schedule(tw, timeo, false);
}
/*
* Enter the time wait state.
* Essentially we whip up a timewait bucket, copy the relevant info into it
* from the SK, and mess with hash chains and list linkage.
*
* The caller must not access @tw anymore after this function returns.
*/
void inet_twsk_hashdance_schedule(struct inet_timewait_sock *tw,
struct sock *sk,
struct inet_hashinfo *hashinfo,
int timeo)
{
const struct inet_sock *inet = inet_sk(sk);
const struct inet_connection_sock *icsk = inet_csk(sk);
struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, sk->sk_hash);
spinlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
struct inet_bind_hashbucket *bhead, *bhead2;
/* Step 1: Put TW into bind hash. Original socket stays there too.
Note, that any socket with inet->num != 0 MUST be bound in
binding cache, even if it is closed.
*/
bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), inet->inet_num,
hashinfo->bhash_size)];
bhead2 = inet_bhashfn_portaddr(hashinfo, sk, twsk_net(tw), inet->inet_num);
local_bh_disable();
spin_lock(&bhead->lock);
spin_lock(&bhead2->lock);
tw->tw_tb = icsk->icsk_bind_hash;
WARN_ON(!icsk->icsk_bind_hash);
tw->tw_tb2 = icsk->icsk_bind2_hash;
WARN_ON(!icsk->icsk_bind2_hash);
sk_add_bind_node((struct sock *)tw, &tw->tw_tb2->owners);
spin_unlock(&bhead2->lock);
spin_unlock(&bhead->lock);
spin_lock(lock);
/* Step 2: Hash TW into tcp ehash chain */
inet_twsk_add_node_rcu(tw, &ehead->chain);
/* Step 3: Remove SK from hash chain */
if (__sk_nulls_del_node_init_rcu(sk))
sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
/* Ensure above writes are committed into memory before updating the
* refcount.
* Provides ordering vs later refcount_inc().
*/
smp_wmb();
/* tw_refcnt is set to 3 because we have :
* - one reference for bhash chain.
* - one reference for ehash chain.
* - one reference for timer.
* Also note that after this point, we lost our implicit reference
* so we are not allowed to use tw anymore.
*/
refcount_set(&tw->tw_refcnt, 3);
inet_twsk_schedule(tw, timeo);
spin_unlock(lock);
local_bh_enable();
}
EXPORT_SYMBOL_GPL(inet_twsk_hashdance_schedule);
static void tw_timer_handler(struct timer_list *t)
{
struct inet_timewait_sock *tw = from_timer(tw, t, tw_timer);
inet_twsk_kill(tw);
}
struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk,
struct inet_timewait_death_row *dr,
const int state)
{
struct inet_timewait_sock *tw;
if (refcount_read(&dr->tw_refcount) - 1 >=
READ_ONCE(dr->sysctl_max_tw_buckets))
return NULL;
tw = kmem_cache_alloc(sk->sk_prot_creator->twsk_prot->twsk_slab,
GFP_ATOMIC);
if (tw) {
const struct inet_sock *inet = inet_sk(sk);
tw->tw_dr = dr;
/* Give us an identity. */
tw->tw_daddr = inet->inet_daddr;
tw->tw_rcv_saddr = inet->inet_rcv_saddr;
tw->tw_bound_dev_if = sk->sk_bound_dev_if;
tw->tw_tos = inet->tos;
tw->tw_num = inet->inet_num;
tw->tw_state = TCP_TIME_WAIT;
tw->tw_substate = state;
tw->tw_sport = inet->inet_sport;
tw->tw_dport = inet->inet_dport;
tw->tw_family = sk->sk_family;
tw->tw_reuse = sk->sk_reuse;
tw->tw_reuseport = sk->sk_reuseport;
tw->tw_hash = sk->sk_hash;
tw->tw_ipv6only = 0;
tw->tw_transparent = inet_test_bit(TRANSPARENT, sk);
tw->tw_prot = sk->sk_prot_creator;
atomic64_set(&tw->tw_cookie, atomic64_read(&sk->sk_cookie));
twsk_net_set(tw, sock_net(sk));
timer_setup(&tw->tw_timer, tw_timer_handler, 0);
/*
* Because we use RCU lookups, we should not set tw_refcnt
* to a non null value before everything is setup for this
* timewait socket.
*/
refcount_set(&tw->tw_refcnt, 0);
__module_get(tw->tw_prot->owner);
}
return tw;
}
EXPORT_SYMBOL_GPL(inet_twsk_alloc);
/* These are always called from BH context. See callers in
* tcp_input.c to verify this.
*/
/* This is for handling early-kills of TIME_WAIT sockets.
* Warning : consume reference.
* Caller should not access tw anymore.
*/
void inet_twsk_deschedule_put(struct inet_timewait_sock *tw)
{
struct inet_hashinfo *hashinfo = tw->tw_dr->hashinfo;
spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash);
/* inet_twsk_purge() walks over all sockets, including tw ones,
* and removes them via inet_twsk_deschedule_put() after a
* refcount_inc_not_zero().
*
* inet_twsk_hashdance_schedule() must (re)init the refcount before
* arming the timer, i.e. inet_twsk_purge can obtain a reference to
* a twsk that did not yet schedule the timer.
*
* The ehash lock synchronizes these two:
* After acquiring the lock, the timer is always scheduled (else
* timer_shutdown returns false), because hashdance_schedule releases
* the ehash lock only after completing the timer initialization.
*
* Without grabbing the ehash lock, we get:
* 1) cpu x sets twsk refcount to 3
* 2) cpu y bumps refcount to 4
* 3) cpu y calls inet_twsk_deschedule_put() and shuts timer down
* 4) cpu x tries to start timer, but mod_timer is a noop post-shutdown
* -> timer refcount is never decremented.
*/
spin_lock(lock);
/* Makes sure hashdance_schedule() has completed */
spin_unlock(lock);
if (timer_shutdown_sync(&tw->tw_timer))
inet_twsk_kill(tw);
inet_twsk_put(tw);
}
EXPORT_SYMBOL(inet_twsk_deschedule_put);
void __inet_twsk_schedule(struct inet_timewait_sock *tw, int timeo, bool rearm)
{
/* timeout := RTO * 3.5
*
* 3.5 = 1+2+0.5 to wait for two retransmits.
*
* RATIONALE: if FIN arrived and we entered TIME-WAIT state,
* our ACK acking that FIN can be lost. If N subsequent retransmitted
* FINs (or previous seqments) are lost (probability of such event
* is p^(N+1), where p is probability to lose single packet and
* time to detect the loss is about RTO*(2^N - 1) with exponential
* backoff). Normal timewait length is calculated so, that we
* waited at least for one retransmitted FIN (maximal RTO is 120sec).
* [ BTW Linux. following BSD, violates this requirement waiting
* only for 60sec, we should wait at least for 240 secs.
* Well, 240 consumes too much of resources 8)
* ]
* This interval is not reduced to catch old duplicate and
* responces to our wandering segments living for two MSLs.
* However, if we use PAWS to detect
* old duplicates, we can reduce the interval to bounds required
* by RTO, rather than MSL. So, if peer understands PAWS, we
* kill tw bucket after 3.5*RTO (it is important that this number
* is greater than TS tick!) and detect old duplicates with help
* of PAWS.
*/
if (!rearm) {
bool kill = timeo <= 4*HZ;
__NET_INC_STATS(twsk_net(tw), kill ? LINUX_MIB_TIMEWAITKILLED :
LINUX_MIB_TIMEWAITED);
BUG_ON(mod_timer(&tw->tw_timer, jiffies + timeo));
refcount_inc(&tw->tw_dr->tw_refcount);
} else {
mod_timer_pending(&tw->tw_timer, jiffies + timeo);
}
}
EXPORT_SYMBOL_GPL(__inet_twsk_schedule);
/* Remove all non full sockets (TIME_WAIT and NEW_SYN_RECV) for dead netns */
void inet_twsk_purge(struct inet_hashinfo *hashinfo)
{
struct inet_ehash_bucket *head = &hashinfo->ehash[0];
unsigned int ehash_mask = hashinfo->ehash_mask;
struct hlist_nulls_node *node;
unsigned int slot;
struct sock *sk;
for (slot = 0; slot <= ehash_mask; slot++, head++) {
if (hlist_nulls_empty(&head->chain))
continue;
restart_rcu:
cond_resched();
rcu_read_lock();
restart:
sk_nulls_for_each_rcu(sk, node, &head->chain) {
int state = inet_sk_state_load(sk);
if ((1 << state) & ~(TCPF_TIME_WAIT |
TCPF_NEW_SYN_RECV))
continue;
if (refcount_read(&sock_net(sk)->ns.count))
continue;
if (unlikely(!refcount_inc_not_zero(&sk->sk_refcnt)))
continue;
if (refcount_read(&sock_net(sk)->ns.count)) {
sock_gen_put(sk);
goto restart;
}
rcu_read_unlock();
local_bh_disable();
if (state == TCP_TIME_WAIT) {
inet_twsk_deschedule_put(inet_twsk(sk));
} else {
struct request_sock *req = inet_reqsk(sk);
inet_csk_reqsk_queue_drop_and_put(req->rsk_listener,
req);
}
local_bh_enable();
goto restart_rcu;
}
/* If the nulls value we got at the end of this lookup is
* not the expected one, we must restart lookup.
* We probably met an item that was moved to another chain.
*/
if (get_nulls_value(node) != slot)
goto restart;
rcu_read_unlock();
}
}
EXPORT_SYMBOL_GPL(inet_twsk_purge);
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