// SPDX-License-Identifier: GPL-2.0-only
/* Event cache for netfilter. */

/*
 * (C) 2005 Harald Welte <laforge@gnumonks.org>
 * (C) 2005 Patrick McHardy <kaber@trash.net>
 * (C) 2005-2006 Netfilter Core Team <coreteam@netfilter.org>
 * (C) 2005 USAGI/WIDE Project <http://www.linux-ipv6.org>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/types.h>
#include <linux/netfilter.h>
#include <linux/skbuff.h>
#include <linux/vmalloc.h>
#include <linux/stddef.h>
#include <linux/err.h>
#include <linux/kernel.h>
#include <linux/netdevice.h>
#include <linux/slab.h>
#include <linux/export.h>

#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_core.h>
#include <net/netfilter/nf_conntrack_ecache.h>
#include <net/netfilter/nf_conntrack_extend.h>

static DEFINE_MUTEX(nf_ct_ecache_mutex);

#define DYING_NULLS_VAL                 ((1 << 30) + 1)
#define ECACHE_MAX_JIFFIES              msecs_to_jiffies(10)
#define ECACHE_RETRY_JIFFIES            msecs_to_jiffies(10)

enum retry_state {
        STATE_CONGESTED,
        STATE_RESTART,
        STATE_DONE,
};

struct nf_conntrack_net_ecache *nf_conn_pernet_ecache(const struct net *net)
{
        struct nf_conntrack_net *cnet = nf_ct_pernet(net);

        return &cnet->ecache;
}
#if IS_MODULE(CONFIG_NF_CT_NETLINK)
EXPORT_SYMBOL_GPL(nf_conn_pernet_ecache);
#endif

static enum retry_state ecache_work_evict_list(struct nf_conntrack_net *cnet)
{
        unsigned long stop = jiffies + ECACHE_MAX_JIFFIES;
        struct hlist_nulls_head evicted_list;
        enum retry_state ret = STATE_DONE;
        struct nf_conntrack_tuple_hash *h;
        struct hlist_nulls_node *n;
        unsigned int sent;

        INIT_HLIST_NULLS_HEAD(&evicted_list, DYING_NULLS_VAL);

next:
        sent = 0;
        spin_lock_bh(&cnet->ecache.dying_lock);

        hlist_nulls_for_each_entry_safe(h, n, &cnet->ecache.dying_list, hnnode) {
                struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(h);

                /* The worker owns all entries, ct remains valid until nf_ct_put
                 * in the loop below.
                 */
                if (nf_conntrack_event(IPCT_DESTROY, ct)) {
                        ret = STATE_CONGESTED;
                        break;
                }

                hlist_nulls_del_rcu(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode);
                hlist_nulls_add_head(&ct->tuplehash[IP_CT_DIR_REPLY].hnnode, &evicted_list);

                if (time_after(stop, jiffies)) {
                        ret = STATE_RESTART;
                        break;
                }

                if (sent++ > 16) {
                        spin_unlock_bh(&cnet->ecache.dying_lock);
                        cond_resched();
                        goto next;
                }
        }

        spin_unlock_bh(&cnet->ecache.dying_lock);

        hlist_nulls_for_each_entry_safe(h, n, &evicted_list, hnnode) {
                struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(h);

                hlist_nulls_del_rcu(&ct->tuplehash[IP_CT_DIR_REPLY].hnnode);
                nf_ct_put(ct);

                cond_resched();
        }

        return ret;
}

static void ecache_work(struct work_struct *work)
{
        struct nf_conntrack_net *cnet = container_of(work, struct nf_conntrack_net, ecache.dwork.work);
        int ret, delay = -1;

        ret = ecache_work_evict_list(cnet);
        switch (ret) {
        case STATE_CONGESTED:
                delay = ECACHE_RETRY_JIFFIES;
                break;
        case STATE_RESTART:
                delay = 0;
                break;
        case STATE_DONE:
                break;
        }

        if (delay >= 0)
                schedule_delayed_work(&cnet->ecache.dwork, delay);
}

static int __nf_conntrack_eventmask_report(struct nf_conntrack_ecache *e,
                                           const u32 events,
                                           const u32 missed,
                                           const struct nf_ct_event *item)
{
        struct net *net = nf_ct_net(item->ct);
        struct nf_ct_event_notifier *notify;
        u32 old, want;
        int ret;

        if (!((events | missed) & e->ctmask))
                return 0;

        rcu_read_lock();

        notify = rcu_dereference(net->ct.nf_conntrack_event_cb);
        if (!notify) {
                rcu_read_unlock();
                return 0;
        }

        ret = notify->ct_event(events | missed, item);
        rcu_read_unlock();

        if (likely(ret >= 0 && missed == 0))
                return 0;

        do {
                old = READ_ONCE(e->missed);
                if (ret < 0)
                        want = old | events;
                else
                        want = old & ~missed;
        } while (cmpxchg(&e->missed, old, want) != old);

        return ret;
}

static void nf_ct_ecache_tstamp_refresh(struct nf_conntrack_ecache *e)
{
#ifdef CONFIG_NF_CONNTRACK_TIMESTAMP
        if (local64_read(&e->timestamp))
                local64_set(&e->timestamp, ktime_get_real_ns());
#endif
}

int nf_conntrack_eventmask_report(unsigned int events, struct nf_conn *ct,
                                  u32 portid, int report)
{
        struct nf_conntrack_ecache *e;
        struct nf_ct_event item;
        unsigned int missed;
        int ret;

        if (!nf_ct_is_confirmed(ct))
                return 0;

        e = nf_ct_ecache_find(ct);
        if (!e)
                return 0;

        memset(&item, 0, sizeof(item));

        item.ct = ct;
        item.portid = e->portid ? e->portid : portid;
        item.report = report;

        /* This is a resent of a destroy event? If so, skip missed */
        missed = e->portid ? 0 : e->missed;

        nf_ct_ecache_tstamp_refresh(e);

        ret = __nf_conntrack_eventmask_report(e, events, missed, &item);
        if (unlikely(ret < 0 && (events & (1 << IPCT_DESTROY)))) {
                /* This is a destroy event that has been triggered by a process,
                 * we store the PORTID to include it in the retransmission.
                 */
                if (e->portid == 0 && portid != 0)
                        e->portid = portid;
        }

        return ret;
}
EXPORT_SYMBOL_GPL(nf_conntrack_eventmask_report);

/* deliver cached events and clear cache entry - must be called with locally
 * disabled softirqs */
void nf_ct_deliver_cached_events(struct nf_conn *ct)
{
        struct nf_conntrack_ecache *e;
        struct nf_ct_event item;
        unsigned int events;

        if (!nf_ct_is_confirmed(ct) || nf_ct_is_dying(ct))
                return;

        e = nf_ct_ecache_find(ct);
        if (e == NULL)
                return;

        events = xchg(&e->cache, 0);

        item.ct = ct;
        item.portid = 0;
        item.report = 0;

        /* We make a copy of the missed event cache without taking
         * the lock, thus we may send missed events twice. However,
         * this does not harm and it happens very rarely.
         */
        __nf_conntrack_eventmask_report(e, events, e->missed, &item);
}
EXPORT_SYMBOL_GPL(nf_ct_deliver_cached_events);

void nf_ct_expect_event_report(enum ip_conntrack_expect_events event,
                               struct nf_conntrack_expect *exp,
                               u32 portid, int report)

{
        struct net *net = nf_ct_exp_net(exp);
        struct nf_ct_event_notifier *notify;
        struct nf_conntrack_ecache *e;

        lockdep_nfct_expect_lock_held();

        rcu_read_lock();
        notify = rcu_dereference(net->ct.nf_conntrack_event_cb);
        if (!notify)
                goto out_unlock;

        e = nf_ct_ecache_find(exp->master);
        if (!e)
                goto out_unlock;

        if (e->expmask & (1 << event)) {
                struct nf_exp_event item = {
                        .exp    = exp,
                        .portid = portid,
                        .report = report
                };
                notify->exp_event(1 << event, &item);
        }
out_unlock:
        rcu_read_unlock();
}

void nf_conntrack_register_notifier(struct net *net,
                                    const struct nf_ct_event_notifier *new)
{
        struct nf_ct_event_notifier *notify;

        mutex_lock(&nf_ct_ecache_mutex);
        notify = rcu_dereference_protected(net->ct.nf_conntrack_event_cb,
                                           lockdep_is_held(&nf_ct_ecache_mutex));
        WARN_ON_ONCE(notify);
        rcu_assign_pointer(net->ct.nf_conntrack_event_cb, new);
        mutex_unlock(&nf_ct_ecache_mutex);
}
EXPORT_SYMBOL_GPL(nf_conntrack_register_notifier);

void nf_conntrack_unregister_notifier(struct net *net)
{
        mutex_lock(&nf_ct_ecache_mutex);
        RCU_INIT_POINTER(net->ct.nf_conntrack_event_cb, NULL);
        mutex_unlock(&nf_ct_ecache_mutex);
        /* synchronize_rcu() is called after netns pre_exit */
}
EXPORT_SYMBOL_GPL(nf_conntrack_unregister_notifier);

void nf_conntrack_ecache_work(struct net *net, enum nf_ct_ecache_state state)
{
        struct nf_conntrack_net *cnet = nf_ct_pernet(net);

        if (state == NFCT_ECACHE_DESTROY_FAIL &&
            !delayed_work_pending(&cnet->ecache.dwork)) {
                schedule_delayed_work(&cnet->ecache.dwork, HZ);
                net->ct.ecache_dwork_pending = true;
        } else if (state == NFCT_ECACHE_DESTROY_SENT) {
                if (!hlist_nulls_empty(&cnet->ecache.dying_list))
                        mod_delayed_work(system_percpu_wq, &cnet->ecache.dwork, 0);
                else
                        net->ct.ecache_dwork_pending = false;
        }
}

static void nf_ct_ecache_tstamp_new(const struct nf_conn *ct, struct nf_conntrack_ecache *e)
{
#ifdef CONFIG_NF_CONNTRACK_TIMESTAMP
        u64 ts = 0;

        if (nf_ct_ext_exist(ct, NF_CT_EXT_TSTAMP))
                ts = ktime_get_real_ns();

        local64_set(&e->timestamp, ts);
#endif
}

bool nf_ct_ecache_ext_add(struct nf_conn *ct, u16 ctmask, u16 expmask, gfp_t gfp)
{
        struct net *net = nf_ct_net(ct);
        struct nf_conntrack_ecache *e;

        switch (net->ct.sysctl_events) {
        case 0:
                 /* assignment via template / ruleset? ignore sysctl. */
                if (ctmask || expmask)
                        break;
                return true;
        case 2: /* autodetect: no event listener, don't allocate extension. */
                if (!READ_ONCE(nf_ctnetlink_has_listener))
                        return true;
                fallthrough;
        case 1:
                /* always allocate an extension. */
                if (!ctmask && !expmask) {
                        ctmask = ~0;
                        expmask = ~0;
                }
                break;
        default:
                WARN_ON_ONCE(1);
                return true;
        }

        e = nf_ct_ext_add(ct, NF_CT_EXT_ECACHE, gfp);
        if (e) {
                nf_ct_ecache_tstamp_new(ct, e);
                e->ctmask  = ctmask;
                e->expmask = expmask;
        }

        return e != NULL;
}
EXPORT_SYMBOL_GPL(nf_ct_ecache_ext_add);

#define NF_CT_EVENTS_DEFAULT 2
static int nf_ct_events __read_mostly = NF_CT_EVENTS_DEFAULT;

void nf_conntrack_ecache_pernet_init(struct net *net)
{
        struct nf_conntrack_net *cnet = nf_ct_pernet(net);

        net->ct.sysctl_events = nf_ct_events;

        INIT_DELAYED_WORK(&cnet->ecache.dwork, ecache_work);
        INIT_HLIST_NULLS_HEAD(&cnet->ecache.dying_list, DYING_NULLS_VAL);
        spin_lock_init(&cnet->ecache.dying_lock);

        BUILD_BUG_ON(__IPCT_MAX >= 16); /* e->ctmask is u16 */
}

void nf_conntrack_ecache_pernet_fini(struct net *net)
{
        struct nf_conntrack_net *cnet = nf_ct_pernet(net);

        cancel_delayed_work_sync(&cnet->ecache.dwork);
}