io_uring: reset -EBUSY error when io sq thread is waken up

[thirdparty/linux.git] / net / netfilter / nf_conntrack_core.c

// SPDX-License-Identifier: GPL-2.0-only
/* Connection state tracking for netfilter.  This is separated from,
   but required by, the NAT layer; it can also be used by an iptables
   extension. */

/* (C) 1999-2001 Paul `Rusty' Russell
 * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
 * (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>
 * (C) 2005-2012 Patrick McHardy <kaber@trash.net>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/types.h>
#include <linux/netfilter.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/skbuff.h>
#include <linux/proc_fs.h>
#include <linux/vmalloc.h>
#include <linux/stddef.h>
#include <linux/slab.h>
#include <linux/random.h>
#include <linux/jhash.h>
#include <linux/siphash.h>
#include <linux/err.h>
#include <linux/percpu.h>
#include <linux/moduleparam.h>
#include <linux/notifier.h>
#include <linux/kernel.h>
#include <linux/netdevice.h>
#include <linux/socket.h>
#include <linux/mm.h>
#include <linux/nsproxy.h>
#include <linux/rculist_nulls.h>

#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_l4proto.h>
#include <net/netfilter/nf_conntrack_expect.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_seqadj.h>
#include <net/netfilter/nf_conntrack_core.h>
#include <net/netfilter/nf_conntrack_extend.h>
#include <net/netfilter/nf_conntrack_acct.h>
#include <net/netfilter/nf_conntrack_ecache.h>
#include <net/netfilter/nf_conntrack_zones.h>
#include <net/netfilter/nf_conntrack_timestamp.h>
#include <net/netfilter/nf_conntrack_timeout.h>
#include <net/netfilter/nf_conntrack_labels.h>
#include <net/netfilter/nf_conntrack_synproxy.h>
#include <net/netfilter/nf_nat.h>
#include <net/netfilter/nf_nat_helper.h>
#include <net/netns/hash.h>
#include <net/ip.h>

#include "nf_internals.h"

__cacheline_aligned_in_smp spinlock_t nf_conntrack_locks[CONNTRACK_LOCKS];
EXPORT_SYMBOL_GPL(nf_conntrack_locks);

__cacheline_aligned_in_smp DEFINE_SPINLOCK(nf_conntrack_expect_lock);
EXPORT_SYMBOL_GPL(nf_conntrack_expect_lock);

struct hlist_nulls_head *nf_conntrack_hash __read_mostly;
EXPORT_SYMBOL_GPL(nf_conntrack_hash);

struct conntrack_gc_work {
        struct delayed_work     dwork;
        u32                     last_bucket;
        bool                    exiting;
        bool                    early_drop;
        long                    next_gc_run;
};

static __read_mostly struct kmem_cache *nf_conntrack_cachep;
static DEFINE_SPINLOCK(nf_conntrack_locks_all_lock);
static __read_mostly bool nf_conntrack_locks_all;

/* every gc cycle scans at most 1/GC_MAX_BUCKETS_DIV part of table */
#define GC_MAX_BUCKETS_DIV      128u
/* upper bound of full table scan */
#define GC_MAX_SCAN_JIFFIES     (16u * HZ)
/* desired ratio of entries found to be expired */
#define GC_EVICT_RATIO  50u

static struct conntrack_gc_work conntrack_gc_work;

void nf_conntrack_lock(spinlock_t *lock) __acquires(lock)
{
        /* 1) Acquire the lock */
        spin_lock(lock);

        /* 2) read nf_conntrack_locks_all, with ACQUIRE semantics
         * It pairs with the smp_store_release() in nf_conntrack_all_unlock()
         */
        if (likely(smp_load_acquire(&nf_conntrack_locks_all) == false))
                return;

        /* fast path failed, unlock */
        spin_unlock(lock);

        /* Slow path 1) get global lock */
        spin_lock(&nf_conntrack_locks_all_lock);

        /* Slow path 2) get the lock we want */
        spin_lock(lock);

        /* Slow path 3) release the global lock */
        spin_unlock(&nf_conntrack_locks_all_lock);
}
EXPORT_SYMBOL_GPL(nf_conntrack_lock);

static void nf_conntrack_double_unlock(unsigned int h1, unsigned int h2)
{
        h1 %= CONNTRACK_LOCKS;
        h2 %= CONNTRACK_LOCKS;
        spin_unlock(&nf_conntrack_locks[h1]);
        if (h1 != h2)
                spin_unlock(&nf_conntrack_locks[h2]);
}

/* return true if we need to recompute hashes (in case hash table was resized) */
static bool nf_conntrack_double_lock(struct net *net, unsigned int h1,
                                     unsigned int h2, unsigned int sequence)
{
        h1 %= CONNTRACK_LOCKS;
        h2 %= CONNTRACK_LOCKS;
        if (h1 <= h2) {
                nf_conntrack_lock(&nf_conntrack_locks[h1]);
                if (h1 != h2)
                        spin_lock_nested(&nf_conntrack_locks[h2],
                                         SINGLE_DEPTH_NESTING);
        } else {
                nf_conntrack_lock(&nf_conntrack_locks[h2]);
                spin_lock_nested(&nf_conntrack_locks[h1],
                                 SINGLE_DEPTH_NESTING);
        }
        if (read_seqcount_retry(&nf_conntrack_generation, sequence)) {
                nf_conntrack_double_unlock(h1, h2);
                return true;
        }
        return false;
}

static void nf_conntrack_all_lock(void)
        __acquires(&nf_conntrack_locks_all_lock)
{
        int i;

        spin_lock(&nf_conntrack_locks_all_lock);

        nf_conntrack_locks_all = true;

        for (i = 0; i < CONNTRACK_LOCKS; i++) {
                spin_lock(&nf_conntrack_locks[i]);

                /* This spin_unlock provides the "release" to ensure that
                 * nf_conntrack_locks_all==true is visible to everyone that
                 * acquired spin_lock(&nf_conntrack_locks[]).
                 */
                spin_unlock(&nf_conntrack_locks[i]);
        }
}

static void nf_conntrack_all_unlock(void)
        __releases(&nf_conntrack_locks_all_lock)
{
        /* All prior stores must be complete before we clear
         * 'nf_conntrack_locks_all'. Otherwise nf_conntrack_lock()
         * might observe the false value but not the entire
         * critical section.
         * It pairs with the smp_load_acquire() in nf_conntrack_lock()
         */
        smp_store_release(&nf_conntrack_locks_all, false);
        spin_unlock(&nf_conntrack_locks_all_lock);
}

unsigned int nf_conntrack_htable_size __read_mostly;
EXPORT_SYMBOL_GPL(nf_conntrack_htable_size);

unsigned int nf_conntrack_max __read_mostly;
EXPORT_SYMBOL_GPL(nf_conntrack_max);
seqcount_t nf_conntrack_generation __read_mostly;
static unsigned int nf_conntrack_hash_rnd __read_mostly;

static u32 hash_conntrack_raw(const struct nf_conntrack_tuple *tuple,
                              const struct net *net)
{
        unsigned int n;
        u32 seed;

        get_random_once(&nf_conntrack_hash_rnd, sizeof(nf_conntrack_hash_rnd));

        /* The direction must be ignored, so we hash everything up to the
         * destination ports (which is a multiple of 4) and treat the last
         * three bytes manually.
         */
        seed = nf_conntrack_hash_rnd ^ net_hash_mix(net);
        n = (sizeof(tuple->src) + sizeof(tuple->dst.u3)) / sizeof(u32);
        return jhash2((u32 *)tuple, n, seed ^
                      (((__force __u16)tuple->dst.u.all << 16) |
                      tuple->dst.protonum));
}

static u32 scale_hash(u32 hash)
{
        return reciprocal_scale(hash, nf_conntrack_htable_size);
}

static u32 __hash_conntrack(const struct net *net,
                            const struct nf_conntrack_tuple *tuple,
                            unsigned int size)
{
        return reciprocal_scale(hash_conntrack_raw(tuple, net), size);
}

static u32 hash_conntrack(const struct net *net,
                          const struct nf_conntrack_tuple *tuple)
{
        return scale_hash(hash_conntrack_raw(tuple, net));
}

static bool nf_ct_get_tuple_ports(const struct sk_buff *skb,
                                  unsigned int dataoff,
                                  struct nf_conntrack_tuple *tuple)
{       struct {
                __be16 sport;
                __be16 dport;
        } _inet_hdr, *inet_hdr;

        /* Actually only need first 4 bytes to get ports. */
        inet_hdr = skb_header_pointer(skb, dataoff, sizeof(_inet_hdr), &_inet_hdr);
        if (!inet_hdr)
                return false;

        tuple->src.u.udp.port = inet_hdr->sport;
        tuple->dst.u.udp.port = inet_hdr->dport;
        return true;
}

static bool
nf_ct_get_tuple(const struct sk_buff *skb,
                unsigned int nhoff,
                unsigned int dataoff,
                u_int16_t l3num,
                u_int8_t protonum,
                struct net *net,
                struct nf_conntrack_tuple *tuple)
{
        unsigned int size;
        const __be32 *ap;
        __be32 _addrs[8];

        memset(tuple, 0, sizeof(*tuple));

        tuple->src.l3num = l3num;
        switch (l3num) {
        case NFPROTO_IPV4:
                nhoff += offsetof(struct iphdr, saddr);
                size = 2 * sizeof(__be32);
                break;
        case NFPROTO_IPV6:
                nhoff += offsetof(struct ipv6hdr, saddr);
                size = sizeof(_addrs);
                break;
        default:
                return true;
        }

        ap = skb_header_pointer(skb, nhoff, size, _addrs);
        if (!ap)
                return false;

        switch (l3num) {
        case NFPROTO_IPV4:
                tuple->src.u3.ip = ap[0];
                tuple->dst.u3.ip = ap[1];
                break;
        case NFPROTO_IPV6:
                memcpy(tuple->src.u3.ip6, ap, sizeof(tuple->src.u3.ip6));
                memcpy(tuple->dst.u3.ip6, ap + 4, sizeof(tuple->dst.u3.ip6));
                break;
        }

        tuple->dst.protonum = protonum;
        tuple->dst.dir = IP_CT_DIR_ORIGINAL;

        switch (protonum) {
#if IS_ENABLED(CONFIG_IPV6)
        case IPPROTO_ICMPV6:
                return icmpv6_pkt_to_tuple(skb, dataoff, net, tuple);
#endif
        case IPPROTO_ICMP:
                return icmp_pkt_to_tuple(skb, dataoff, net, tuple);
#ifdef CONFIG_NF_CT_PROTO_GRE
        case IPPROTO_GRE:
                return gre_pkt_to_tuple(skb, dataoff, net, tuple);
#endif
        case IPPROTO_TCP:
        case IPPROTO_UDP: /* fallthrough */
                return nf_ct_get_tuple_ports(skb, dataoff, tuple);
#ifdef CONFIG_NF_CT_PROTO_UDPLITE
        case IPPROTO_UDPLITE:
                return nf_ct_get_tuple_ports(skb, dataoff, tuple);
#endif
#ifdef CONFIG_NF_CT_PROTO_SCTP
        case IPPROTO_SCTP:
                return nf_ct_get_tuple_ports(skb, dataoff, tuple);
#endif
#ifdef CONFIG_NF_CT_PROTO_DCCP
        case IPPROTO_DCCP:
                return nf_ct_get_tuple_ports(skb, dataoff, tuple);
#endif
        default:
                break;
        }

        return true;
}

static int ipv4_get_l4proto(const struct sk_buff *skb, unsigned int nhoff,
                            u_int8_t *protonum)
{
        int dataoff = -1;
        const struct iphdr *iph;
        struct iphdr _iph;

        iph = skb_header_pointer(skb, nhoff, sizeof(_iph), &_iph);
        if (!iph)
                return -1;

        /* Conntrack defragments packets, we might still see fragments
         * inside ICMP packets though.
         */
        if (iph->frag_off & htons(IP_OFFSET))
                return -1;

        dataoff = nhoff + (iph->ihl << 2);
        *protonum = iph->protocol;

        /* Check bogus IP headers */
        if (dataoff > skb->len) {
                pr_debug("bogus IPv4 packet: nhoff %u, ihl %u, skblen %u\n",
                         nhoff, iph->ihl << 2, skb->len);
                return -1;
        }
        return dataoff;
}

#if IS_ENABLED(CONFIG_IPV6)
static int ipv6_get_l4proto(const struct sk_buff *skb, unsigned int nhoff,
                            u8 *protonum)
{
        int protoff = -1;
        unsigned int extoff = nhoff + sizeof(struct ipv6hdr);
        __be16 frag_off;
        u8 nexthdr;

        if (skb_copy_bits(skb, nhoff + offsetof(struct ipv6hdr, nexthdr),
                          &nexthdr, sizeof(nexthdr)) != 0) {
                pr_debug("can't get nexthdr\n");
                return -1;
        }
        protoff = ipv6_skip_exthdr(skb, extoff, &nexthdr, &frag_off);
        /*
         * (protoff == skb->len) means the packet has not data, just
         * IPv6 and possibly extensions headers, but it is tracked anyway
         */
        if (protoff < 0 || (frag_off & htons(~0x7)) != 0) {
                pr_debug("can't find proto in pkt\n");
                return -1;
        }

        *protonum = nexthdr;
        return protoff;
}
#endif

static int get_l4proto(const struct sk_buff *skb,
                       unsigned int nhoff, u8 pf, u8 *l4num)
{
        switch (pf) {
        case NFPROTO_IPV4:
                return ipv4_get_l4proto(skb, nhoff, l4num);
#if IS_ENABLED(CONFIG_IPV6)
        case NFPROTO_IPV6:
                return ipv6_get_l4proto(skb, nhoff, l4num);
#endif
        default:
                *l4num = 0;
                break;
        }
        return -1;
}

bool nf_ct_get_tuplepr(const struct sk_buff *skb, unsigned int nhoff,
                       u_int16_t l3num,
                       struct net *net, struct nf_conntrack_tuple *tuple)
{
        u8 protonum;
        int protoff;

        protoff = get_l4proto(skb, nhoff, l3num, &protonum);
        if (protoff <= 0)
                return false;

        return nf_ct_get_tuple(skb, nhoff, protoff, l3num, protonum, net, tuple);
}
EXPORT_SYMBOL_GPL(nf_ct_get_tuplepr);

bool
nf_ct_invert_tuple(struct nf_conntrack_tuple *inverse,
                   const struct nf_conntrack_tuple *orig)
{
        memset(inverse, 0, sizeof(*inverse));

        inverse->src.l3num = orig->src.l3num;

        switch (orig->src.l3num) {
        case NFPROTO_IPV4:
                inverse->src.u3.ip = orig->dst.u3.ip;
                inverse->dst.u3.ip = orig->src.u3.ip;
                break;
        case NFPROTO_IPV6:
                inverse->src.u3.in6 = orig->dst.u3.in6;
                inverse->dst.u3.in6 = orig->src.u3.in6;
                break;
        default:
                break;
        }

        inverse->dst.dir = !orig->dst.dir;

        inverse->dst.protonum = orig->dst.protonum;

        switch (orig->dst.protonum) {
        case IPPROTO_ICMP:
                return nf_conntrack_invert_icmp_tuple(inverse, orig);
#if IS_ENABLED(CONFIG_IPV6)
        case IPPROTO_ICMPV6:
                return nf_conntrack_invert_icmpv6_tuple(inverse, orig);
#endif
        }

        inverse->src.u.all = orig->dst.u.all;
        inverse->dst.u.all = orig->src.u.all;
        return true;
}
EXPORT_SYMBOL_GPL(nf_ct_invert_tuple);

/* Generate a almost-unique pseudo-id for a given conntrack.
 *
 * intentionally doesn't re-use any of the seeds used for hash
 * table location, we assume id gets exposed to userspace.
 *
 * Following nf_conn items do not change throughout lifetime
 * of the nf_conn:
 *
 * 1. nf_conn address
 * 2. nf_conn->master address (normally NULL)
 * 3. the associated net namespace
 * 4. the original direction tuple
 */
u32 nf_ct_get_id(const struct nf_conn *ct)
{
        static __read_mostly siphash_key_t ct_id_seed;
        unsigned long a, b, c, d;

        net_get_random_once(&ct_id_seed, sizeof(ct_id_seed));

        a = (unsigned long)ct;
        b = (unsigned long)ct->master;
        c = (unsigned long)nf_ct_net(ct);
        d = (unsigned long)siphash(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple,
                                   sizeof(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple),
                                   &ct_id_seed);
#ifdef CONFIG_64BIT
        return siphash_4u64((u64)a, (u64)b, (u64)c, (u64)d, &ct_id_seed);
#else
        return siphash_4u32((u32)a, (u32)b, (u32)c, (u32)d, &ct_id_seed);
#endif
}
EXPORT_SYMBOL_GPL(nf_ct_get_id);

static void
clean_from_lists(struct nf_conn *ct)
{
        pr_debug("clean_from_lists(%p)\n", ct);
        hlist_nulls_del_rcu(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode);
        hlist_nulls_del_rcu(&ct->tuplehash[IP_CT_DIR_REPLY].hnnode);

        /* Destroy all pending expectations */
        nf_ct_remove_expectations(ct);
}

/* must be called with local_bh_disable */
static void nf_ct_add_to_dying_list(struct nf_conn *ct)
{
        struct ct_pcpu *pcpu;

        /* add this conntrack to the (per cpu) dying list */
        ct->cpu = smp_processor_id();
        pcpu = per_cpu_ptr(nf_ct_net(ct)->ct.pcpu_lists, ct->cpu);

        spin_lock(&pcpu->lock);
        hlist_nulls_add_head(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode,
                             &pcpu->dying);
        spin_unlock(&pcpu->lock);
}

/* must be called with local_bh_disable */
static void nf_ct_add_to_unconfirmed_list(struct nf_conn *ct)
{
        struct ct_pcpu *pcpu;

        /* add this conntrack to the (per cpu) unconfirmed list */
        ct->cpu = smp_processor_id();
        pcpu = per_cpu_ptr(nf_ct_net(ct)->ct.pcpu_lists, ct->cpu);

        spin_lock(&pcpu->lock);
        hlist_nulls_add_head(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode,
                             &pcpu->unconfirmed);
        spin_unlock(&pcpu->lock);
}

/* must be called with local_bh_disable */
static void nf_ct_del_from_dying_or_unconfirmed_list(struct nf_conn *ct)
{
        struct ct_pcpu *pcpu;

        /* We overload first tuple to link into unconfirmed or dying list.*/
        pcpu = per_cpu_ptr(nf_ct_net(ct)->ct.pcpu_lists, ct->cpu);

        spin_lock(&pcpu->lock);
        BUG_ON(hlist_nulls_unhashed(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode));
        hlist_nulls_del_rcu(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode);
        spin_unlock(&pcpu->lock);
}

#define NFCT_ALIGN(len) (((len) + NFCT_INFOMASK) & ~NFCT_INFOMASK)

/* Released via destroy_conntrack() */
struct nf_conn *nf_ct_tmpl_alloc(struct net *net,
                                 const struct nf_conntrack_zone *zone,
                                 gfp_t flags)
{
        struct nf_conn *tmpl, *p;

        if (ARCH_KMALLOC_MINALIGN <= NFCT_INFOMASK) {
                tmpl = kzalloc(sizeof(*tmpl) + NFCT_INFOMASK, flags);
                if (!tmpl)
                        return NULL;

                p = tmpl;
                tmpl = (struct nf_conn *)NFCT_ALIGN((unsigned long)p);
                if (tmpl != p) {
                        tmpl = (struct nf_conn *)NFCT_ALIGN((unsigned long)p);
                        tmpl->proto.tmpl_padto = (char *)tmpl - (char *)p;
                }
        } else {
                tmpl = kzalloc(sizeof(*tmpl), flags);
                if (!tmpl)
                        return NULL;
        }

        tmpl->status = IPS_TEMPLATE;
        write_pnet(&tmpl->ct_net, net);
        nf_ct_zone_add(tmpl, zone);
        atomic_set(&tmpl->ct_general.use, 0);

        return tmpl;
}
EXPORT_SYMBOL_GPL(nf_ct_tmpl_alloc);

void nf_ct_tmpl_free(struct nf_conn *tmpl)
{
        nf_ct_ext_destroy(tmpl);

        if (ARCH_KMALLOC_MINALIGN <= NFCT_INFOMASK)
                kfree((char *)tmpl - tmpl->proto.tmpl_padto);
        else
                kfree(tmpl);
}
EXPORT_SYMBOL_GPL(nf_ct_tmpl_free);

static void destroy_gre_conntrack(struct nf_conn *ct)
{
#ifdef CONFIG_NF_CT_PROTO_GRE
        struct nf_conn *master = ct->master;

        if (master)
                nf_ct_gre_keymap_destroy(master);
#endif
}

static void
destroy_conntrack(struct nf_conntrack *nfct)
{
        struct nf_conn *ct = (struct nf_conn *)nfct;

        pr_debug("destroy_conntrack(%p)\n", ct);
        WARN_ON(atomic_read(&nfct->use) != 0);

        if (unlikely(nf_ct_is_template(ct))) {
                nf_ct_tmpl_free(ct);
                return;
        }

        if (unlikely(nf_ct_protonum(ct) == IPPROTO_GRE))
                destroy_gre_conntrack(ct);

        local_bh_disable();
        /* Expectations will have been removed in clean_from_lists,
         * except TFTP can create an expectation on the first packet,
         * before connection is in the list, so we need to clean here,
         * too.
         */
        nf_ct_remove_expectations(ct);

        nf_ct_del_from_dying_or_unconfirmed_list(ct);

        local_bh_enable();

        if (ct->master)
                nf_ct_put(ct->master);

        pr_debug("destroy_conntrack: returning ct=%p to slab\n", ct);
        nf_conntrack_free(ct);
}

static void nf_ct_delete_from_lists(struct nf_conn *ct)
{
        struct net *net = nf_ct_net(ct);
        unsigned int hash, reply_hash;
        unsigned int sequence;

        nf_ct_helper_destroy(ct);

        local_bh_disable();
        do {
                sequence = read_seqcount_begin(&nf_conntrack_generation);
                hash = hash_conntrack(net,
                                      &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
                reply_hash = hash_conntrack(net,
                                           &ct->tuplehash[IP_CT_DIR_REPLY].tuple);
        } while (nf_conntrack_double_lock(net, hash, reply_hash, sequence));

        clean_from_lists(ct);
        nf_conntrack_double_unlock(hash, reply_hash);

        nf_ct_add_to_dying_list(ct);

        local_bh_enable();
}

bool nf_ct_delete(struct nf_conn *ct, u32 portid, int report)
{
        struct nf_conn_tstamp *tstamp;

        if (test_and_set_bit(IPS_DYING_BIT, &ct->status))
                return false;

        tstamp = nf_conn_tstamp_find(ct);
        if (tstamp && tstamp->stop == 0)
                tstamp->stop = ktime_get_real_ns();

        if (nf_conntrack_event_report(IPCT_DESTROY, ct,
                                    portid, report) < 0) {
                /* destroy event was not delivered. nf_ct_put will
                 * be done by event cache worker on redelivery.
                 */
                nf_ct_delete_from_lists(ct);
                nf_conntrack_ecache_delayed_work(nf_ct_net(ct));
                return false;
        }

        nf_conntrack_ecache_work(nf_ct_net(ct));
        nf_ct_delete_from_lists(ct);
        nf_ct_put(ct);
        return true;
}
EXPORT_SYMBOL_GPL(nf_ct_delete);

static inline bool
nf_ct_key_equal(struct nf_conntrack_tuple_hash *h,
                const struct nf_conntrack_tuple *tuple,
                const struct nf_conntrack_zone *zone,
                const struct net *net)
{
        struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(h);

        /* A conntrack can be recreated with the equal tuple,
         * so we need to check that the conntrack is confirmed
         */
        return nf_ct_tuple_equal(tuple, &h->tuple) &&
               nf_ct_zone_equal(ct, zone, NF_CT_DIRECTION(h)) &&
               nf_ct_is_confirmed(ct) &&
               net_eq(net, nf_ct_net(ct));
}

static inline bool
nf_ct_match(const struct nf_conn *ct1, const struct nf_conn *ct2)
{
        return nf_ct_tuple_equal(&ct1->tuplehash[IP_CT_DIR_ORIGINAL].tuple,
                                 &ct2->tuplehash[IP_CT_DIR_ORIGINAL].tuple) &&
               nf_ct_tuple_equal(&ct1->tuplehash[IP_CT_DIR_REPLY].tuple,
                                 &ct2->tuplehash[IP_CT_DIR_REPLY].tuple) &&
               nf_ct_zone_equal(ct1, nf_ct_zone(ct2), IP_CT_DIR_ORIGINAL) &&
               nf_ct_zone_equal(ct1, nf_ct_zone(ct2), IP_CT_DIR_REPLY) &&
               net_eq(nf_ct_net(ct1), nf_ct_net(ct2));
}

/* caller must hold rcu readlock and none of the nf_conntrack_locks */
static void nf_ct_gc_expired(struct nf_conn *ct)
{
        if (!atomic_inc_not_zero(&ct->ct_general.use))
                return;

        if (nf_ct_should_gc(ct))
                nf_ct_kill(ct);

        nf_ct_put(ct);
}

/*
 * Warning :
 * - Caller must take a reference on returned object
 *   and recheck nf_ct_tuple_equal(tuple, &h->tuple)
 */
static struct nf_conntrack_tuple_hash *
____nf_conntrack_find(struct net *net, const struct nf_conntrack_zone *zone,
                      const struct nf_conntrack_tuple *tuple, u32 hash)
{
        struct nf_conntrack_tuple_hash *h;
        struct hlist_nulls_head *ct_hash;
        struct hlist_nulls_node *n;
        unsigned int bucket, hsize;

begin:
        nf_conntrack_get_ht(&ct_hash, &hsize);
        bucket = reciprocal_scale(hash, hsize);

        hlist_nulls_for_each_entry_rcu(h, n, &ct_hash[bucket], hnnode) {
                struct nf_conn *ct;

                ct = nf_ct_tuplehash_to_ctrack(h);
                if (nf_ct_is_expired(ct)) {
                        nf_ct_gc_expired(ct);
                        continue;
                }

                if (nf_ct_key_equal(h, tuple, zone, net))
                        return h;
        }
        /*
         * 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(n) != bucket) {
                NF_CT_STAT_INC_ATOMIC(net, search_restart);
                goto begin;
        }

        return NULL;
}

/* Find a connection corresponding to a tuple. */
static struct nf_conntrack_tuple_hash *
__nf_conntrack_find_get(struct net *net, const struct nf_conntrack_zone *zone,
                        const struct nf_conntrack_tuple *tuple, u32 hash)
{
        struct nf_conntrack_tuple_hash *h;
        struct nf_conn *ct;

        rcu_read_lock();

        h = ____nf_conntrack_find(net, zone, tuple, hash);
        if (h) {
                /* We have a candidate that matches the tuple we're interested
                 * in, try to obtain a reference and re-check tuple
                 */
                ct = nf_ct_tuplehash_to_ctrack(h);
                if (likely(atomic_inc_not_zero(&ct->ct_general.use))) {
                        if (likely(nf_ct_key_equal(h, tuple, zone, net)))
                                goto found;

                        /* TYPESAFE_BY_RCU recycled the candidate */
                        nf_ct_put(ct);
                }

                h = NULL;
        }
found:
        rcu_read_unlock();

        return h;
}

struct nf_conntrack_tuple_hash *
nf_conntrack_find_get(struct net *net, const struct nf_conntrack_zone *zone,
                      const struct nf_conntrack_tuple *tuple)
{
        return __nf_conntrack_find_get(net, zone, tuple,
                                       hash_conntrack_raw(tuple, net));
}
EXPORT_SYMBOL_GPL(nf_conntrack_find_get);

static void __nf_conntrack_hash_insert(struct nf_conn *ct,
                                       unsigned int hash,
                                       unsigned int reply_hash)
{
        hlist_nulls_add_head_rcu(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode,
                           &nf_conntrack_hash[hash]);
        hlist_nulls_add_head_rcu(&ct->tuplehash[IP_CT_DIR_REPLY].hnnode,
                           &nf_conntrack_hash[reply_hash]);
}

int
nf_conntrack_hash_check_insert(struct nf_conn *ct)
{
        const struct nf_conntrack_zone *zone;
        struct net *net = nf_ct_net(ct);
        unsigned int hash, reply_hash;
        struct nf_conntrack_tuple_hash *h;
        struct hlist_nulls_node *n;
        unsigned int sequence;

        zone = nf_ct_zone(ct);

        local_bh_disable();
        do {
                sequence = read_seqcount_begin(&nf_conntrack_generation);
                hash = hash_conntrack(net,
                                      &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
                reply_hash = hash_conntrack(net,
                                           &ct->tuplehash[IP_CT_DIR_REPLY].tuple);
        } while (nf_conntrack_double_lock(net, hash, reply_hash, sequence));

        /* See if there's one in the list already, including reverse */
        hlist_nulls_for_each_entry(h, n, &nf_conntrack_hash[hash], hnnode)
                if (nf_ct_key_equal(h, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple,
                                    zone, net))
                        goto out;

        hlist_nulls_for_each_entry(h, n, &nf_conntrack_hash[reply_hash], hnnode)
                if (nf_ct_key_equal(h, &ct->tuplehash[IP_CT_DIR_REPLY].tuple,
                                    zone, net))
                        goto out;

        smp_wmb();
        /* The caller holds a reference to this object */
        atomic_set(&ct->ct_general.use, 2);
        __nf_conntrack_hash_insert(ct, hash, reply_hash);
        nf_conntrack_double_unlock(hash, reply_hash);
        NF_CT_STAT_INC(net, insert);
        local_bh_enable();
        return 0;

out:
        nf_conntrack_double_unlock(hash, reply_hash);
        NF_CT_STAT_INC(net, insert_failed);
        local_bh_enable();
        return -EEXIST;
}
EXPORT_SYMBOL_GPL(nf_conntrack_hash_check_insert);

void nf_ct_acct_add(struct nf_conn *ct, u32 dir, unsigned int packets,
                    unsigned int bytes)
{
        struct nf_conn_acct *acct;

        acct = nf_conn_acct_find(ct);
        if (acct) {
                struct nf_conn_counter *counter = acct->counter;

                atomic64_add(packets, &counter[dir].packets);
                atomic64_add(bytes, &counter[dir].bytes);
        }
}
EXPORT_SYMBOL_GPL(nf_ct_acct_add);

static void nf_ct_acct_merge(struct nf_conn *ct, enum ip_conntrack_info ctinfo,
                             const struct nf_conn *loser_ct)
{
        struct nf_conn_acct *acct;

        acct = nf_conn_acct_find(loser_ct);
        if (acct) {
                struct nf_conn_counter *counter = acct->counter;
                unsigned int bytes;

                /* u32 should be fine since we must have seen one packet. */
                bytes = atomic64_read(&counter[CTINFO2DIR(ctinfo)].bytes);
                nf_ct_acct_update(ct, CTINFO2DIR(ctinfo), bytes);
        }
}

static void __nf_conntrack_insert_prepare(struct nf_conn *ct)
{
        struct nf_conn_tstamp *tstamp;

        atomic_inc(&ct->ct_general.use);
        ct->status |= IPS_CONFIRMED;

        /* set conntrack timestamp, if enabled. */
        tstamp = nf_conn_tstamp_find(ct);
        if (tstamp)
                tstamp->start = ktime_get_real_ns();
}

static int __nf_ct_resolve_clash(struct sk_buff *skb,
                                 struct nf_conntrack_tuple_hash *h)
{
        /* This is the conntrack entry already in hashes that won race. */
        struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(h);
        enum ip_conntrack_info ctinfo;
        struct nf_conn *loser_ct;

        loser_ct = nf_ct_get(skb, &ctinfo);

        if (nf_ct_is_dying(ct))
                return NF_DROP;

        if (!atomic_inc_not_zero(&ct->ct_general.use))
                return NF_DROP;

        if (((ct->status & IPS_NAT_DONE_MASK) == 0) ||
            nf_ct_match(ct, loser_ct)) {
                struct net *net = nf_ct_net(ct);

                nf_ct_acct_merge(ct, ctinfo, loser_ct);
                nf_ct_add_to_dying_list(loser_ct);
                nf_conntrack_put(&loser_ct->ct_general);
                nf_ct_set(skb, ct, ctinfo);

                NF_CT_STAT_INC(net, insert_failed);
                return NF_ACCEPT;
        }

        nf_ct_put(ct);
        return NF_DROP;
}

/**
 * nf_ct_resolve_clash_harder - attempt to insert clashing conntrack entry
 *
 * @skb: skb that causes the collision
 * @repl_idx: hash slot for reply direction
 *
 * Called when origin or reply direction had a clash.
 * The skb can be handled without packet drop provided the reply direction
 * is unique or there the existing entry has the identical tuple in both
 * directions.
 *
 * Caller must hold conntrack table locks to prevent concurrent updates.
 *
 * Returns NF_DROP if the clash could not be handled.
 */
static int nf_ct_resolve_clash_harder(struct sk_buff *skb, u32 repl_idx)
{
        struct nf_conn *loser_ct = (struct nf_conn *)skb_nfct(skb);
        const struct nf_conntrack_zone *zone;
        struct nf_conntrack_tuple_hash *h;
        struct hlist_nulls_node *n;
        struct net *net;

        zone = nf_ct_zone(loser_ct);
        net = nf_ct_net(loser_ct);

        /* Reply direction must never result in a clash, unless both origin
         * and reply tuples are identical.
         */
        hlist_nulls_for_each_entry(h, n, &nf_conntrack_hash[repl_idx], hnnode) {
                if (nf_ct_key_equal(h,
                                    &loser_ct->tuplehash[IP_CT_DIR_REPLY].tuple,
                                    zone, net))
                        return __nf_ct_resolve_clash(skb, h);
        }

        /* We want the clashing entry to go away real soon: 1 second timeout. */
        loser_ct->timeout = nfct_time_stamp + HZ;

        /* IPS_NAT_CLASH removes the entry automatically on the first
         * reply.  Also prevents UDP tracker from moving the entry to
         * ASSURED state, i.e. the entry can always be evicted under
         * pressure.
         */
        loser_ct->status |= IPS_FIXED_TIMEOUT | IPS_NAT_CLASH;

        __nf_conntrack_insert_prepare(loser_ct);

        /* fake add for ORIGINAL dir: we want lookups to only find the entry
         * already in the table.  This also hides the clashing entry from
         * ctnetlink iteration, i.e. conntrack -L won't show them.
         */
        hlist_nulls_add_fake(&loser_ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode);

        hlist_nulls_add_head_rcu(&loser_ct->tuplehash[IP_CT_DIR_REPLY].hnnode,
                                 &nf_conntrack_hash[repl_idx]);
        return NF_ACCEPT;
}

/**
 * nf_ct_resolve_clash - attempt to handle clash without packet drop
 *
 * @skb: skb that causes the clash
 * @h: tuplehash of the clashing entry already in table
 * @hash_reply: hash slot for reply direction
 *
 * A conntrack entry can be inserted to the connection tracking table
 * if there is no existing entry with an identical tuple.
 *
 * If there is one, @skb (and the assocated, unconfirmed conntrack) has
 * to be dropped.  In case @skb is retransmitted, next conntrack lookup
 * will find the already-existing entry.
 *
 * The major problem with such packet drop is the extra delay added by
 * the packet loss -- it will take some time for a retransmit to occur
 * (or the sender to time out when waiting for a reply).
 *
 * This function attempts to handle the situation without packet drop.
 *
 * If @skb has no NAT transformation or if the colliding entries are
 * exactly the same, only the to-be-confirmed conntrack entry is discarded
 * and @skb is associated with the conntrack entry already in the table.
 *
 * Failing that, the new, unconfirmed conntrack is still added to the table
 * provided that the collision only occurs in the ORIGINAL direction.
 * The new entry will be added after the existing one in the hash list,
 * so packets in the ORIGINAL direction will continue to match the existing
 * entry.  The new entry will also have a fixed timeout so it expires --
 * due to the collision, it will not see bidirectional traffic.
 *
 * Returns NF_DROP if the clash could not be resolved.
 */
static __cold noinline int
nf_ct_resolve_clash(struct sk_buff *skb, struct nf_conntrack_tuple_hash *h,
                    u32 reply_hash)
{
        /* This is the conntrack entry already in hashes that won race. */
        struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(h);
        const struct nf_conntrack_l4proto *l4proto;
        enum ip_conntrack_info ctinfo;
        struct nf_conn *loser_ct;
        struct net *net;
        int ret;

        loser_ct = nf_ct_get(skb, &ctinfo);
        net = nf_ct_net(loser_ct);

        l4proto = nf_ct_l4proto_find(nf_ct_protonum(ct));
        if (!l4proto->allow_clash)
                goto drop;

        ret = __nf_ct_resolve_clash(skb, h);
        if (ret == NF_ACCEPT)
                return ret;

        ret = nf_ct_resolve_clash_harder(skb, reply_hash);
        if (ret == NF_ACCEPT)
                return ret;

drop:
        nf_ct_add_to_dying_list(loser_ct);
        NF_CT_STAT_INC(net, drop);
        NF_CT_STAT_INC(net, insert_failed);
        return NF_DROP;
}

/* Confirm a connection given skb; places it in hash table */
int
__nf_conntrack_confirm(struct sk_buff *skb)
{
        const struct nf_conntrack_zone *zone;
        unsigned int hash, reply_hash;
        struct nf_conntrack_tuple_hash *h;
        struct nf_conn *ct;
        struct nf_conn_help *help;
        struct hlist_nulls_node *n;
        enum ip_conntrack_info ctinfo;
        struct net *net;
        unsigned int sequence;
        int ret = NF_DROP;

        ct = nf_ct_get(skb, &ctinfo);
        net = nf_ct_net(ct);

        /* ipt_REJECT uses nf_conntrack_attach to attach related
           ICMP/TCP RST packets in other direction.  Actual packet
           which created connection will be IP_CT_NEW or for an
           expected connection, IP_CT_RELATED. */
        if (CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
                return NF_ACCEPT;

        zone = nf_ct_zone(ct);
        local_bh_disable();

        do {
                sequence = read_seqcount_begin(&nf_conntrack_generation);
                /* reuse the hash saved before */
                hash = *(unsigned long *)&ct->tuplehash[IP_CT_DIR_REPLY].hnnode.pprev;
                hash = scale_hash(hash);
                reply_hash = hash_conntrack(net,
                                           &ct->tuplehash[IP_CT_DIR_REPLY].tuple);

        } while (nf_conntrack_double_lock(net, hash, reply_hash, sequence));

        /* We're not in hash table, and we refuse to set up related
         * connections for unconfirmed conns.  But packet copies and
         * REJECT will give spurious warnings here.
         */

        /* Another skb with the same unconfirmed conntrack may
         * win the race. This may happen for bridge(br_flood)
         * or broadcast/multicast packets do skb_clone with
         * unconfirmed conntrack.
         */
        if (unlikely(nf_ct_is_confirmed(ct))) {
                WARN_ON_ONCE(1);
                nf_conntrack_double_unlock(hash, reply_hash);
                local_bh_enable();
                return NF_DROP;
        }

        pr_debug("Confirming conntrack %p\n", ct);
        /* We have to check the DYING flag after unlink to prevent
         * a race against nf_ct_get_next_corpse() possibly called from
         * user context, else we insert an already 'dead' hash, blocking
         * further use of that particular connection -JM.
         */
        nf_ct_del_from_dying_or_unconfirmed_list(ct);

        if (unlikely(nf_ct_is_dying(ct))) {
                nf_ct_add_to_dying_list(ct);
                NF_CT_STAT_INC(net, insert_failed);
                goto dying;
        }

        /* See if there's one in the list already, including reverse:
           NAT could have grabbed it without realizing, since we're
           not in the hash.  If there is, we lost race. */
        hlist_nulls_for_each_entry(h, n, &nf_conntrack_hash[hash], hnnode)
                if (nf_ct_key_equal(h, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple,
                                    zone, net))
                        goto out;

        hlist_nulls_for_each_entry(h, n, &nf_conntrack_hash[reply_hash], hnnode)
                if (nf_ct_key_equal(h, &ct->tuplehash[IP_CT_DIR_REPLY].tuple,
                                    zone, net))
                        goto out;

        /* Timer relative to confirmation time, not original
           setting time, otherwise we'd get timer wrap in
           weird delay cases. */
        ct->timeout += nfct_time_stamp;

        __nf_conntrack_insert_prepare(ct);

        /* Since the lookup is lockless, hash insertion must be done after
         * starting the timer and setting the CONFIRMED bit. The RCU barriers
         * guarantee that no other CPU can find the conntrack before the above
         * stores are visible.
         */
        __nf_conntrack_hash_insert(ct, hash, reply_hash);
        nf_conntrack_double_unlock(hash, reply_hash);
        local_bh_enable();

        help = nfct_help(ct);
        if (help && help->helper)
                nf_conntrack_event_cache(IPCT_HELPER, ct);

        nf_conntrack_event_cache(master_ct(ct) ?
                                 IPCT_RELATED : IPCT_NEW, ct);
        return NF_ACCEPT;

out:
        ret = nf_ct_resolve_clash(skb, h, reply_hash);
dying:
        nf_conntrack_double_unlock(hash, reply_hash);
        local_bh_enable();
        return ret;
}
EXPORT_SYMBOL_GPL(__nf_conntrack_confirm);

/* Returns true if a connection correspondings to the tuple (required
   for NAT). */
int
nf_conntrack_tuple_taken(const struct nf_conntrack_tuple *tuple,
                         const struct nf_conn *ignored_conntrack)
{
        struct net *net = nf_ct_net(ignored_conntrack);
        const struct nf_conntrack_zone *zone;
        struct nf_conntrack_tuple_hash *h;
        struct hlist_nulls_head *ct_hash;
        unsigned int hash, hsize;
        struct hlist_nulls_node *n;
        struct nf_conn *ct;

        zone = nf_ct_zone(ignored_conntrack);

        rcu_read_lock();
 begin:
        nf_conntrack_get_ht(&ct_hash, &hsize);
        hash = __hash_conntrack(net, tuple, hsize);

        hlist_nulls_for_each_entry_rcu(h, n, &ct_hash[hash], hnnode) {
                ct = nf_ct_tuplehash_to_ctrack(h);

                if (ct == ignored_conntrack)
                        continue;

                if (nf_ct_is_expired(ct)) {
                        nf_ct_gc_expired(ct);
                        continue;
                }

                if (nf_ct_key_equal(h, tuple, zone, net)) {
                        /* Tuple is taken already, so caller will need to find
                         * a new source port to use.
                         *
                         * Only exception:
                         * If the *original tuples* are identical, then both
                         * conntracks refer to the same flow.
                         * This is a rare situation, it can occur e.g. when
                         * more than one UDP packet is sent from same socket
                         * in different threads.
                         *
                         * Let nf_ct_resolve_clash() deal with this later.
                         */
                        if (nf_ct_tuple_equal(&ignored_conntrack->tuplehash[IP_CT_DIR_ORIGINAL].tuple,
                                              &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple))
                                continue;

                        NF_CT_STAT_INC_ATOMIC(net, found);
                        rcu_read_unlock();
                        return 1;
                }
        }

        if (get_nulls_value(n) != hash) {
                NF_CT_STAT_INC_ATOMIC(net, search_restart);
                goto begin;
        }

        rcu_read_unlock();

        return 0;
}
EXPORT_SYMBOL_GPL(nf_conntrack_tuple_taken);

#define NF_CT_EVICTION_RANGE    8

/* There's a small race here where we may free a just-assured
   connection.  Too bad: we're in trouble anyway. */
static unsigned int early_drop_list(struct net *net,
                                    struct hlist_nulls_head *head)
{
        struct nf_conntrack_tuple_hash *h;
        struct hlist_nulls_node *n;
        unsigned int drops = 0;
        struct nf_conn *tmp;

        hlist_nulls_for_each_entry_rcu(h, n, head, hnnode) {
                tmp = nf_ct_tuplehash_to_ctrack(h);

                if (test_bit(IPS_OFFLOAD_BIT, &tmp->status))
                        continue;

                if (nf_ct_is_expired(tmp)) {
                        nf_ct_gc_expired(tmp);
                        continue;
                }

                if (test_bit(IPS_ASSURED_BIT, &tmp->status) ||
                    !net_eq(nf_ct_net(tmp), net) ||
                    nf_ct_is_dying(tmp))
                        continue;

                if (!atomic_inc_not_zero(&tmp->ct_general.use))
                        continue;

                /* kill only if still in same netns -- might have moved due to
                 * SLAB_TYPESAFE_BY_RCU rules.
                 *
                 * We steal the timer reference.  If that fails timer has
                 * already fired or someone else deleted it. Just drop ref
                 * and move to next entry.
                 */
                if (net_eq(nf_ct_net(tmp), net) &&
                    nf_ct_is_confirmed(tmp) &&
                    nf_ct_delete(tmp, 0, 0))
                        drops++;

                nf_ct_put(tmp);
        }

        return drops;
}

static noinline int early_drop(struct net *net, unsigned int hash)
{
        unsigned int i, bucket;

        for (i = 0; i < NF_CT_EVICTION_RANGE; i++) {
                struct hlist_nulls_head *ct_hash;
                unsigned int hsize, drops;

                rcu_read_lock();
                nf_conntrack_get_ht(&ct_hash, &hsize);
                if (!i)
                        bucket = reciprocal_scale(hash, hsize);
                else
                        bucket = (bucket + 1) % hsize;

                drops = early_drop_list(net, &ct_hash[bucket]);
                rcu_read_unlock();

                if (drops) {
                        NF_CT_STAT_ADD_ATOMIC(net, early_drop, drops);
                        return true;
                }
        }

        return false;
}

static bool gc_worker_skip_ct(const struct nf_conn *ct)
{
        return !nf_ct_is_confirmed(ct) || nf_ct_is_dying(ct);
}

static bool gc_worker_can_early_drop(const struct nf_conn *ct)
{
        const struct nf_conntrack_l4proto *l4proto;

        if (!test_bit(IPS_ASSURED_BIT, &ct->status))
                return true;

        l4proto = nf_ct_l4proto_find(nf_ct_protonum(ct));
        if (l4proto->can_early_drop && l4proto->can_early_drop(ct))
                return true;

        return false;
}

#define DAY     (86400 * HZ)

/* Set an arbitrary timeout large enough not to ever expire, this save
 * us a check for the IPS_OFFLOAD_BIT from the packet path via
 * nf_ct_is_expired().
 */
static void nf_ct_offload_timeout(struct nf_conn *ct)
{
        if (nf_ct_expires(ct) < DAY / 2)
                ct->timeout = nfct_time_stamp + DAY;
}

static void gc_worker(struct work_struct *work)
{
        unsigned int min_interval = max(HZ / GC_MAX_BUCKETS_DIV, 1u);
        unsigned int i, goal, buckets = 0, expired_count = 0;
        unsigned int nf_conntrack_max95 = 0;
        struct conntrack_gc_work *gc_work;
        unsigned int ratio, scanned = 0;
        unsigned long next_run;

        gc_work = container_of(work, struct conntrack_gc_work, dwork.work);

        goal = nf_conntrack_htable_size / GC_MAX_BUCKETS_DIV;
        i = gc_work->last_bucket;
        if (gc_work->early_drop)
                nf_conntrack_max95 = nf_conntrack_max / 100u * 95u;

        do {
                struct nf_conntrack_tuple_hash *h;
                struct hlist_nulls_head *ct_hash;
                struct hlist_nulls_node *n;
                unsigned int hashsz;
                struct nf_conn *tmp;

                i++;
                rcu_read_lock();

                nf_conntrack_get_ht(&ct_hash, &hashsz);
                if (i >= hashsz)
                        i = 0;

                hlist_nulls_for_each_entry_rcu(h, n, &ct_hash[i], hnnode) {
                        struct net *net;

                        tmp = nf_ct_tuplehash_to_ctrack(h);

                        scanned++;
                        if (test_bit(IPS_OFFLOAD_BIT, &tmp->status)) {
                                nf_ct_offload_timeout(tmp);
                                continue;
                        }

                        if (nf_ct_is_expired(tmp)) {
                                nf_ct_gc_expired(tmp);
                                expired_count++;
                                continue;
                        }

                        if (nf_conntrack_max95 == 0 || gc_worker_skip_ct(tmp))
                                continue;

                        net = nf_ct_net(tmp);
                        if (atomic_read(&net->ct.count) < nf_conntrack_max95)
                                continue;

                        /* need to take reference to avoid possible races */
                        if (!atomic_inc_not_zero(&tmp->ct_general.use))
                                continue;

                        if (gc_worker_skip_ct(tmp)) {
                                nf_ct_put(tmp);
                                continue;
                        }

                        if (gc_worker_can_early_drop(tmp))
                                nf_ct_kill(tmp);

                        nf_ct_put(tmp);
                }

                /* could check get_nulls_value() here and restart if ct
                 * was moved to another chain.  But given gc is best-effort
                 * we will just continue with next hash slot.
                 */
                rcu_read_unlock();
                cond_resched();
        } while (++buckets < goal);

        if (gc_work->exiting)
                return;

        /*
         * Eviction will normally happen from the packet path, and not
         * from this gc worker.
         *
         * This worker is only here to reap expired entries when system went
         * idle after a busy period.
         *
         * The heuristics below are supposed to balance conflicting goals:
         *
         * 1. Minimize time until we notice a stale entry
         * 2. Maximize scan intervals to not waste cycles
         *
         * Normally, expire ratio will be close to 0.
         *
         * As soon as a sizeable fraction of the entries have expired
         * increase scan frequency.
         */
        ratio = scanned ? expired_count * 100 / scanned : 0;
        if (ratio > GC_EVICT_RATIO) {
                gc_work->next_gc_run = min_interval;
        } else {
                unsigned int max = GC_MAX_SCAN_JIFFIES / GC_MAX_BUCKETS_DIV;

                BUILD_BUG_ON((GC_MAX_SCAN_JIFFIES / GC_MAX_BUCKETS_DIV) == 0);

                gc_work->next_gc_run += min_interval;
                if (gc_work->next_gc_run > max)
                        gc_work->next_gc_run = max;
        }

        next_run = gc_work->next_gc_run;
        gc_work->last_bucket = i;
        gc_work->early_drop = false;
        queue_delayed_work(system_power_efficient_wq, &gc_work->dwork, next_run);
}

static void conntrack_gc_work_init(struct conntrack_gc_work *gc_work)
{
        INIT_DEFERRABLE_WORK(&gc_work->dwork, gc_worker);
        gc_work->next_gc_run = HZ;
        gc_work->exiting = false;
}

static struct nf_conn *
__nf_conntrack_alloc(struct net *net,
                     const struct nf_conntrack_zone *zone,
                     const struct nf_conntrack_tuple *orig,
                     const struct nf_conntrack_tuple *repl,
                     gfp_t gfp, u32 hash)
{
        struct nf_conn *ct;

        /* We don't want any race condition at early drop stage */
        atomic_inc(&net->ct.count);

        if (nf_conntrack_max &&
            unlikely(atomic_read(&net->ct.count) > nf_conntrack_max)) {
                if (!early_drop(net, hash)) {
                        if (!conntrack_gc_work.early_drop)
                                conntrack_gc_work.early_drop = true;
                        atomic_dec(&net->ct.count);
                        net_warn_ratelimited("nf_conntrack: table full, dropping packet\n");
                        return ERR_PTR(-ENOMEM);
                }
        }

        /*
         * Do not use kmem_cache_zalloc(), as this cache uses
         * SLAB_TYPESAFE_BY_RCU.
         */
        ct = kmem_cache_alloc(nf_conntrack_cachep, gfp);
        if (ct == NULL)
                goto out;

        spin_lock_init(&ct->lock);
        ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple = *orig;
        ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode.pprev = NULL;
        ct->tuplehash[IP_CT_DIR_REPLY].tuple = *repl;
        /* save hash for reusing when confirming */
        *(unsigned long *)(&ct->tuplehash[IP_CT_DIR_REPLY].hnnode.pprev) = hash;
        ct->status = 0;
        ct->timeout = 0;
        write_pnet(&ct->ct_net, net);
        memset(&ct->__nfct_init_offset[0], 0,
               offsetof(struct nf_conn, proto) -
               offsetof(struct nf_conn, __nfct_init_offset[0]));

        nf_ct_zone_add(ct, zone);

        /* Because we use RCU lookups, we set ct_general.use to zero before
         * this is inserted in any list.
         */
        atomic_set(&ct->ct_general.use, 0);
        return ct;
out:
        atomic_dec(&net->ct.count);
        return ERR_PTR(-ENOMEM);
}

struct nf_conn *nf_conntrack_alloc(struct net *net,
                                   const struct nf_conntrack_zone *zone,
                                   const struct nf_conntrack_tuple *orig,
                                   const struct nf_conntrack_tuple *repl,
                                   gfp_t gfp)
{
        return __nf_conntrack_alloc(net, zone, orig, repl, gfp, 0);
}
EXPORT_SYMBOL_GPL(nf_conntrack_alloc);

void nf_conntrack_free(struct nf_conn *ct)
{
        struct net *net = nf_ct_net(ct);

        /* A freed object has refcnt == 0, that's
         * the golden rule for SLAB_TYPESAFE_BY_RCU
         */
        WARN_ON(atomic_read(&ct->ct_general.use) != 0);

        nf_ct_ext_destroy(ct);
        kmem_cache_free(nf_conntrack_cachep, ct);
        smp_mb__before_atomic();
        atomic_dec(&net->ct.count);
}
EXPORT_SYMBOL_GPL(nf_conntrack_free);


/* Allocate a new conntrack: we return -ENOMEM if classification
   failed due to stress.  Otherwise it really is unclassifiable. */
static noinline struct nf_conntrack_tuple_hash *
init_conntrack(struct net *net, struct nf_conn *tmpl,
               const struct nf_conntrack_tuple *tuple,
               struct sk_buff *skb,
               unsigned int dataoff, u32 hash)
{
        struct nf_conn *ct;
        struct nf_conn_help *help;
        struct nf_conntrack_tuple repl_tuple;
        struct nf_conntrack_ecache *ecache;
        struct nf_conntrack_expect *exp = NULL;
        const struct nf_conntrack_zone *zone;
        struct nf_conn_timeout *timeout_ext;
        struct nf_conntrack_zone tmp;

        if (!nf_ct_invert_tuple(&repl_tuple, tuple)) {
                pr_debug("Can't invert tuple.\n");
                return NULL;
        }

        zone = nf_ct_zone_tmpl(tmpl, skb, &tmp);
        ct = __nf_conntrack_alloc(net, zone, tuple, &repl_tuple, GFP_ATOMIC,
                                  hash);
        if (IS_ERR(ct))
                return (struct nf_conntrack_tuple_hash *)ct;

        if (!nf_ct_add_synproxy(ct, tmpl)) {
                nf_conntrack_free(ct);
                return ERR_PTR(-ENOMEM);
        }

        timeout_ext = tmpl ? nf_ct_timeout_find(tmpl) : NULL;

        if (timeout_ext)
                nf_ct_timeout_ext_add(ct, rcu_dereference(timeout_ext->timeout),
                                      GFP_ATOMIC);

        nf_ct_acct_ext_add(ct, GFP_ATOMIC);
        nf_ct_tstamp_ext_add(ct, GFP_ATOMIC);
        nf_ct_labels_ext_add(ct);

        ecache = tmpl ? nf_ct_ecache_find(tmpl) : NULL;
        nf_ct_ecache_ext_add(ct, ecache ? ecache->ctmask : 0,
                                 ecache ? ecache->expmask : 0,
                             GFP_ATOMIC);

        local_bh_disable();
        if (net->ct.expect_count) {
                spin_lock(&nf_conntrack_expect_lock);
                exp = nf_ct_find_expectation(net, zone, tuple);
                if (exp) {
                        pr_debug("expectation arrives ct=%p exp=%p\n",
                                 ct, exp);
                        /* Welcome, Mr. Bond.  We've been expecting you... */
                        __set_bit(IPS_EXPECTED_BIT, &ct->status);
                        /* exp->master safe, refcnt bumped in nf_ct_find_expectation */
                        ct->master = exp->master;
                        if (exp->helper) {
                                help = nf_ct_helper_ext_add(ct, GFP_ATOMIC);
                                if (help)
                                        rcu_assign_pointer(help->helper, exp->helper);
                        }

#ifdef CONFIG_NF_CONNTRACK_MARK
                        ct->mark = exp->master->mark;
#endif
#ifdef CONFIG_NF_CONNTRACK_SECMARK
                        ct->secmark = exp->master->secmark;
#endif
                        NF_CT_STAT_INC(net, expect_new);
                }
                spin_unlock(&nf_conntrack_expect_lock);
        }
        if (!exp)
                __nf_ct_try_assign_helper(ct, tmpl, GFP_ATOMIC);

        /* Now it is inserted into the unconfirmed list, bump refcount */
        nf_conntrack_get(&ct->ct_general);
        nf_ct_add_to_unconfirmed_list(ct);

        local_bh_enable();

        if (exp) {
                if (exp->expectfn)
                        exp->expectfn(ct, exp);
                nf_ct_expect_put(exp);
        }

        return &ct->tuplehash[IP_CT_DIR_ORIGINAL];
}

/* On success, returns 0, sets skb->_nfct | ctinfo */
static int
resolve_normal_ct(struct nf_conn *tmpl,
                  struct sk_buff *skb,
                  unsigned int dataoff,
                  u_int8_t protonum,
                  const struct nf_hook_state *state)
{
        const struct nf_conntrack_zone *zone;
        struct nf_conntrack_tuple tuple;
        struct nf_conntrack_tuple_hash *h;
        enum ip_conntrack_info ctinfo;
        struct nf_conntrack_zone tmp;
        struct nf_conn *ct;
        u32 hash;

        if (!nf_ct_get_tuple(skb, skb_network_offset(skb),
                             dataoff, state->pf, protonum, state->net,
                             &tuple)) {
                pr_debug("Can't get tuple\n");
                return 0;
        }

        /* look for tuple match */
        zone = nf_ct_zone_tmpl(tmpl, skb, &tmp);
        hash = hash_conntrack_raw(&tuple, state->net);
        h = __nf_conntrack_find_get(state->net, zone, &tuple, hash);
        if (!h) {
                h = init_conntrack(state->net, tmpl, &tuple,
                                   skb, dataoff, hash);
                if (!h)
                        return 0;
                if (IS_ERR(h))
                        return PTR_ERR(h);
        }
        ct = nf_ct_tuplehash_to_ctrack(h);

        /* It exists; we have (non-exclusive) reference. */
        if (NF_CT_DIRECTION(h) == IP_CT_DIR_REPLY) {
                ctinfo = IP_CT_ESTABLISHED_REPLY;
        } else {
                /* Once we've had two way comms, always ESTABLISHED. */
                if (test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {
                        pr_debug("normal packet for %p\n", ct);
                        ctinfo = IP_CT_ESTABLISHED;
                } else if (test_bit(IPS_EXPECTED_BIT, &ct->status)) {
                        pr_debug("related packet for %p\n", ct);
                        ctinfo = IP_CT_RELATED;
                } else {
                        pr_debug("new packet for %p\n", ct);
                        ctinfo = IP_CT_NEW;
                }
        }
        nf_ct_set(skb, ct, ctinfo);
        return 0;
}

/*
 * icmp packets need special treatment to handle error messages that are
 * related to a connection.
 *
 * Callers need to check if skb has a conntrack assigned when this
 * helper returns; in such case skb belongs to an already known connection.
 */
static unsigned int __cold
nf_conntrack_handle_icmp(struct nf_conn *tmpl,
                         struct sk_buff *skb,
                         unsigned int dataoff,
                         u8 protonum,
                         const struct nf_hook_state *state)
{
        int ret;

        if (state->pf == NFPROTO_IPV4 && protonum == IPPROTO_ICMP)
                ret = nf_conntrack_icmpv4_error(tmpl, skb, dataoff, state);
#if IS_ENABLED(CONFIG_IPV6)
        else if (state->pf == NFPROTO_IPV6 && protonum == IPPROTO_ICMPV6)
                ret = nf_conntrack_icmpv6_error(tmpl, skb, dataoff, state);
#endif
        else
                return NF_ACCEPT;

        if (ret <= 0) {
                NF_CT_STAT_INC_ATOMIC(state->net, error);
                NF_CT_STAT_INC_ATOMIC(state->net, invalid);
        }

        return ret;
}

static int generic_packet(struct nf_conn *ct, struct sk_buff *skb,
                          enum ip_conntrack_info ctinfo)
{
        const unsigned int *timeout = nf_ct_timeout_lookup(ct);

        if (!timeout)
                timeout = &nf_generic_pernet(nf_ct_net(ct))->timeout;

        nf_ct_refresh_acct(ct, ctinfo, skb, *timeout);
        return NF_ACCEPT;
}

/* Returns verdict for packet, or -1 for invalid. */
static int nf_conntrack_handle_packet(struct nf_conn *ct,
                                      struct sk_buff *skb,
                                      unsigned int dataoff,
                                      enum ip_conntrack_info ctinfo,
                                      const struct nf_hook_state *state)
{
        switch (nf_ct_protonum(ct)) {
        case IPPROTO_TCP:
                return nf_conntrack_tcp_packet(ct, skb, dataoff,
                                               ctinfo, state);
        case IPPROTO_UDP:
                return nf_conntrack_udp_packet(ct, skb, dataoff,
                                               ctinfo, state);
        case IPPROTO_ICMP:
                return nf_conntrack_icmp_packet(ct, skb, ctinfo, state);
#if IS_ENABLED(CONFIG_IPV6)
        case IPPROTO_ICMPV6:
                return nf_conntrack_icmpv6_packet(ct, skb, ctinfo, state);
#endif
#ifdef CONFIG_NF_CT_PROTO_UDPLITE
        case IPPROTO_UDPLITE:
                return nf_conntrack_udplite_packet(ct, skb, dataoff,
                                                   ctinfo, state);
#endif
#ifdef CONFIG_NF_CT_PROTO_SCTP
        case IPPROTO_SCTP:
                return nf_conntrack_sctp_packet(ct, skb, dataoff,
                                                ctinfo, state);
#endif
#ifdef CONFIG_NF_CT_PROTO_DCCP
        case IPPROTO_DCCP:
                return nf_conntrack_dccp_packet(ct, skb, dataoff,
                                                ctinfo, state);
#endif
#ifdef CONFIG_NF_CT_PROTO_GRE
        case IPPROTO_GRE:
                return nf_conntrack_gre_packet(ct, skb, dataoff,
                                               ctinfo, state);
#endif
        }

        return generic_packet(ct, skb, ctinfo);
}

unsigned int
nf_conntrack_in(struct sk_buff *skb, const struct nf_hook_state *state)
{
        enum ip_conntrack_info ctinfo;
        struct nf_conn *ct, *tmpl;
        u_int8_t protonum;
        int dataoff, ret;

        tmpl = nf_ct_get(skb, &ctinfo);
        if (tmpl || ctinfo == IP_CT_UNTRACKED) {
                /* Previously seen (loopback or untracked)?  Ignore. */
                if ((tmpl && !nf_ct_is_template(tmpl)) ||
                     ctinfo == IP_CT_UNTRACKED) {
                        NF_CT_STAT_INC_ATOMIC(state->net, ignore);
                        return NF_ACCEPT;
                }
                skb->_nfct = 0;
        }

        /* rcu_read_lock()ed by nf_hook_thresh */
        dataoff = get_l4proto(skb, skb_network_offset(skb), state->pf, &protonum);
        if (dataoff <= 0) {
                pr_debug("not prepared to track yet or error occurred\n");
                NF_CT_STAT_INC_ATOMIC(state->net, error);
                NF_CT_STAT_INC_ATOMIC(state->net, invalid);
                ret = NF_ACCEPT;
                goto out;
        }

        if (protonum == IPPROTO_ICMP || protonum == IPPROTO_ICMPV6) {
                ret = nf_conntrack_handle_icmp(tmpl, skb, dataoff,
                                               protonum, state);
                if (ret <= 0) {
                        ret = -ret;
                        goto out;
                }
                /* ICMP[v6] protocol trackers may assign one conntrack. */
                if (skb->_nfct)
                        goto out;
        }
repeat:
        ret = resolve_normal_ct(tmpl, skb, dataoff,
                                protonum, state);
        if (ret < 0) {
                /* Too stressed to deal. */
                NF_CT_STAT_INC_ATOMIC(state->net, drop);
                ret = NF_DROP;
                goto out;
        }

        ct = nf_ct_get(skb, &ctinfo);
        if (!ct) {
                /* Not valid part of a connection */
                NF_CT_STAT_INC_ATOMIC(state->net, invalid);
                ret = NF_ACCEPT;
                goto out;
        }

        ret = nf_conntrack_handle_packet(ct, skb, dataoff, ctinfo, state);
        if (ret <= 0) {
                /* Invalid: inverse of the return code tells
                 * the netfilter core what to do */
                pr_debug("nf_conntrack_in: Can't track with proto module\n");
                nf_conntrack_put(&ct->ct_general);
                skb->_nfct = 0;
                NF_CT_STAT_INC_ATOMIC(state->net, invalid);
                if (ret == -NF_DROP)
                        NF_CT_STAT_INC_ATOMIC(state->net, drop);
                /* Special case: TCP tracker reports an attempt to reopen a
                 * closed/aborted connection. We have to go back and create a
                 * fresh conntrack.
                 */
                if (ret == -NF_REPEAT)
                        goto repeat;
                ret = -ret;
                goto out;
        }

        if (ctinfo == IP_CT_ESTABLISHED_REPLY &&
            !test_and_set_bit(IPS_SEEN_REPLY_BIT, &ct->status))
                nf_conntrack_event_cache(IPCT_REPLY, ct);
out:
        if (tmpl)
                nf_ct_put(tmpl);

        return ret;
}
EXPORT_SYMBOL_GPL(nf_conntrack_in);

/* Alter reply tuple (maybe alter helper).  This is for NAT, and is
   implicitly racy: see __nf_conntrack_confirm */
void nf_conntrack_alter_reply(struct nf_conn *ct,
                              const struct nf_conntrack_tuple *newreply)
{
        struct nf_conn_help *help = nfct_help(ct);

        /* Should be unconfirmed, so not in hash table yet */
        WARN_ON(nf_ct_is_confirmed(ct));

        pr_debug("Altering reply tuple of %p to ", ct);
        nf_ct_dump_tuple(newreply);

        ct->tuplehash[IP_CT_DIR_REPLY].tuple = *newreply;
        if (ct->master || (help && !hlist_empty(&help->expectations)))
                return;

        rcu_read_lock();
        __nf_ct_try_assign_helper(ct, NULL, GFP_ATOMIC);
        rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(nf_conntrack_alter_reply);

/* Refresh conntrack for this many jiffies and do accounting if do_acct is 1 */
void __nf_ct_refresh_acct(struct nf_conn *ct,
                          enum ip_conntrack_info ctinfo,
                          const struct sk_buff *skb,
                          u32 extra_jiffies,
                          bool do_acct)
{
        /* Only update if this is not a fixed timeout */
        if (test_bit(IPS_FIXED_TIMEOUT_BIT, &ct->status))
                goto acct;

        /* If not in hash table, timer will not be active yet */
        if (nf_ct_is_confirmed(ct))
                extra_jiffies += nfct_time_stamp;

        if (READ_ONCE(ct->timeout) != extra_jiffies)
                WRITE_ONCE(ct->timeout, extra_jiffies);
acct:
        if (do_acct)
                nf_ct_acct_update(ct, CTINFO2DIR(ctinfo), skb->len);
}
EXPORT_SYMBOL_GPL(__nf_ct_refresh_acct);

bool nf_ct_kill_acct(struct nf_conn *ct,
                     enum ip_conntrack_info ctinfo,
                     const struct sk_buff *skb)
{
        nf_ct_acct_update(ct, CTINFO2DIR(ctinfo), skb->len);

        return nf_ct_delete(ct, 0, 0);
}
EXPORT_SYMBOL_GPL(nf_ct_kill_acct);

#if IS_ENABLED(CONFIG_NF_CT_NETLINK)

#include <linux/netfilter/nfnetlink.h>
#include <linux/netfilter/nfnetlink_conntrack.h>
#include <linux/mutex.h>

/* Generic function for tcp/udp/sctp/dccp and alike. */
int nf_ct_port_tuple_to_nlattr(struct sk_buff *skb,
                               const struct nf_conntrack_tuple *tuple)
{
        if (nla_put_be16(skb, CTA_PROTO_SRC_PORT, tuple->src.u.tcp.port) ||
            nla_put_be16(skb, CTA_PROTO_DST_PORT, tuple->dst.u.tcp.port))
                goto nla_put_failure;
        return 0;

nla_put_failure:
        return -1;
}
EXPORT_SYMBOL_GPL(nf_ct_port_tuple_to_nlattr);

const struct nla_policy nf_ct_port_nla_policy[CTA_PROTO_MAX+1] = {
        [CTA_PROTO_SRC_PORT]  = { .type = NLA_U16 },
        [CTA_PROTO_DST_PORT]  = { .type = NLA_U16 },
};
EXPORT_SYMBOL_GPL(nf_ct_port_nla_policy);

int nf_ct_port_nlattr_to_tuple(struct nlattr *tb[],
                               struct nf_conntrack_tuple *t)
{
        if (!tb[CTA_PROTO_SRC_PORT] || !tb[CTA_PROTO_DST_PORT])
                return -EINVAL;

        t->src.u.tcp.port = nla_get_be16(tb[CTA_PROTO_SRC_PORT]);
        t->dst.u.tcp.port = nla_get_be16(tb[CTA_PROTO_DST_PORT]);

        return 0;
}
EXPORT_SYMBOL_GPL(nf_ct_port_nlattr_to_tuple);

unsigned int nf_ct_port_nlattr_tuple_size(void)
{
        static unsigned int size __read_mostly;

        if (!size)
                size = nla_policy_len(nf_ct_port_nla_policy, CTA_PROTO_MAX + 1);

        return size;
}
EXPORT_SYMBOL_GPL(nf_ct_port_nlattr_tuple_size);
#endif

/* Used by ipt_REJECT and ip6t_REJECT. */
static void nf_conntrack_attach(struct sk_buff *nskb, const struct sk_buff *skb)
{
        struct nf_conn *ct;
        enum ip_conntrack_info ctinfo;

        /* This ICMP is in reverse direction to the packet which caused it */
        ct = nf_ct_get(skb, &ctinfo);
        if (CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL)
                ctinfo = IP_CT_RELATED_REPLY;
        else
                ctinfo = IP_CT_RELATED;

        /* Attach to new skbuff, and increment count */
        nf_ct_set(nskb, ct, ctinfo);
        nf_conntrack_get(skb_nfct(nskb));
}

static int nf_conntrack_update(struct net *net, struct sk_buff *skb)
{
        struct nf_conntrack_tuple_hash *h;
        struct nf_conntrack_tuple tuple;
        enum ip_conntrack_info ctinfo;
        struct nf_nat_hook *nat_hook;
        unsigned int status;
        struct nf_conn *ct;
        int dataoff;
        u16 l3num;
        u8 l4num;

        ct = nf_ct_get(skb, &ctinfo);
        if (!ct || nf_ct_is_confirmed(ct))
                return 0;

        l3num = nf_ct_l3num(ct);

        dataoff = get_l4proto(skb, skb_network_offset(skb), l3num, &l4num);
        if (dataoff <= 0)
                return -1;

        if (!nf_ct_get_tuple(skb, skb_network_offset(skb), dataoff, l3num,
                             l4num, net, &tuple))
                return -1;

        if (ct->status & IPS_SRC_NAT) {
                memcpy(tuple.src.u3.all,
                       ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.all,
                       sizeof(tuple.src.u3.all));
                tuple.src.u.all =
                        ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.all;
        }

        if (ct->status & IPS_DST_NAT) {
                memcpy(tuple.dst.u3.all,
                       ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u3.all,
                       sizeof(tuple.dst.u3.all));
                tuple.dst.u.all =
                        ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u.all;
        }

        h = nf_conntrack_find_get(net, nf_ct_zone(ct), &tuple);
        if (!h)
                return 0;

        /* Store status bits of the conntrack that is clashing to re-do NAT
         * mangling according to what it has been done already to this packet.
         */
        status = ct->status;

        nf_ct_put(ct);
        ct = nf_ct_tuplehash_to_ctrack(h);
        nf_ct_set(skb, ct, ctinfo);

        nat_hook = rcu_dereference(nf_nat_hook);
        if (!nat_hook)
                return 0;

        if (status & IPS_SRC_NAT &&
            nat_hook->manip_pkt(skb, ct, NF_NAT_MANIP_SRC,
                                IP_CT_DIR_ORIGINAL) == NF_DROP)
                return -1;

        if (status & IPS_DST_NAT &&
            nat_hook->manip_pkt(skb, ct, NF_NAT_MANIP_DST,
                                IP_CT_DIR_ORIGINAL) == NF_DROP)
                return -1;

        return 0;
}

static bool nf_conntrack_get_tuple_skb(struct nf_conntrack_tuple *dst_tuple,
                                       const struct sk_buff *skb)
{
        const struct nf_conntrack_tuple *src_tuple;
        const struct nf_conntrack_tuple_hash *hash;
        struct nf_conntrack_tuple srctuple;
        enum ip_conntrack_info ctinfo;
        struct nf_conn *ct;

        ct = nf_ct_get(skb, &ctinfo);
        if (ct) {
                src_tuple = nf_ct_tuple(ct, CTINFO2DIR(ctinfo));
                memcpy(dst_tuple, src_tuple, sizeof(*dst_tuple));
                return true;
        }

        if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb),
                               NFPROTO_IPV4, dev_net(skb->dev),
                               &srctuple))
                return false;

        hash = nf_conntrack_find_get(dev_net(skb->dev),
                                     &nf_ct_zone_dflt,
                                     &srctuple);
        if (!hash)
                return false;

        ct = nf_ct_tuplehash_to_ctrack(hash);
        src_tuple = nf_ct_tuple(ct, !hash->tuple.dst.dir);
        memcpy(dst_tuple, src_tuple, sizeof(*dst_tuple));
        nf_ct_put(ct);

        return true;
}

/* Bring out ya dead! */
static struct nf_conn *
get_next_corpse(int (*iter)(struct nf_conn *i, void *data),
                void *data, unsigned int *bucket)
{
        struct nf_conntrack_tuple_hash *h;
        struct nf_conn *ct;
        struct hlist_nulls_node *n;
        spinlock_t *lockp;

        for (; *bucket < nf_conntrack_htable_size; (*bucket)++) {
                lockp = &nf_conntrack_locks[*bucket % CONNTRACK_LOCKS];
                local_bh_disable();
                nf_conntrack_lock(lockp);
                if (*bucket < nf_conntrack_htable_size) {
                        hlist_nulls_for_each_entry(h, n, &nf_conntrack_hash[*bucket], hnnode) {
                                if (NF_CT_DIRECTION(h) != IP_CT_DIR_ORIGINAL)
                                        continue;
                                ct = nf_ct_tuplehash_to_ctrack(h);
                                if (iter(ct, data))
                                        goto found;
                        }
                }
                spin_unlock(lockp);
                local_bh_enable();
                cond_resched();
        }

        return NULL;
found:
        atomic_inc(&ct->ct_general.use);
        spin_unlock(lockp);
        local_bh_enable();
        return ct;
}

static void nf_ct_iterate_cleanup(int (*iter)(struct nf_conn *i, void *data),
                                  void *data, u32 portid, int report)
{
        unsigned int bucket = 0, sequence;
        struct nf_conn *ct;

        might_sleep();

        for (;;) {
                sequence = read_seqcount_begin(&nf_conntrack_generation);

                while ((ct = get_next_corpse(iter, data, &bucket)) != NULL) {
                        /* Time to push up daises... */

                        nf_ct_delete(ct, portid, report);
                        nf_ct_put(ct);
                        cond_resched();
                }

                if (!read_seqcount_retry(&nf_conntrack_generation, sequence))
                        break;
                bucket = 0;
        }
}

struct iter_data {
        int (*iter)(struct nf_conn *i, void *data);
        void *data;
        struct net *net;
};

static int iter_net_only(struct nf_conn *i, void *data)
{
        struct iter_data *d = data;

        if (!net_eq(d->net, nf_ct_net(i)))
                return 0;

        return d->iter(i, d->data);
}

static void
__nf_ct_unconfirmed_destroy(struct net *net)
{
        int cpu;

        for_each_possible_cpu(cpu) {
                struct nf_conntrack_tuple_hash *h;
                struct hlist_nulls_node *n;
                struct ct_pcpu *pcpu;

                pcpu = per_cpu_ptr(net->ct.pcpu_lists, cpu);

                spin_lock_bh(&pcpu->lock);
                hlist_nulls_for_each_entry(h, n, &pcpu->unconfirmed, hnnode) {
                        struct nf_conn *ct;

                        ct = nf_ct_tuplehash_to_ctrack(h);

                        /* we cannot call iter() on unconfirmed list, the
                         * owning cpu can reallocate ct->ext at any time.
                         */
                        set_bit(IPS_DYING_BIT, &ct->status);
                }
                spin_unlock_bh(&pcpu->lock);
                cond_resched();
        }
}

void nf_ct_unconfirmed_destroy(struct net *net)
{
        might_sleep();

        if (atomic_read(&net->ct.count) > 0) {
                __nf_ct_unconfirmed_destroy(net);
                nf_queue_nf_hook_drop(net);
                synchronize_net();
        }
}
EXPORT_SYMBOL_GPL(nf_ct_unconfirmed_destroy);

void nf_ct_iterate_cleanup_net(struct net *net,
                               int (*iter)(struct nf_conn *i, void *data),
                               void *data, u32 portid, int report)
{
        struct iter_data d;

        might_sleep();

        if (atomic_read(&net->ct.count) == 0)
                return;

        d.iter = iter;
        d.data = data;
        d.net = net;

        nf_ct_iterate_cleanup(iter_net_only, &d, portid, report);
}
EXPORT_SYMBOL_GPL(nf_ct_iterate_cleanup_net);

/**
 * nf_ct_iterate_destroy - destroy unconfirmed conntracks and iterate table
 * @iter: callback to invoke for each conntrack
 * @data: data to pass to @iter
 *
 * Like nf_ct_iterate_cleanup, but first marks conntracks on the
 * unconfirmed list as dying (so they will not be inserted into
 * main table).
 *
 * Can only be called in module exit path.
 */
void
nf_ct_iterate_destroy(int (*iter)(struct nf_conn *i, void *data), void *data)
{
        struct net *net;

        down_read(&net_rwsem);
        for_each_net(net) {
                if (atomic_read(&net->ct.count) == 0)
                        continue;
                __nf_ct_unconfirmed_destroy(net);
                nf_queue_nf_hook_drop(net);
        }
        up_read(&net_rwsem);

        /* Need to wait for netns cleanup worker to finish, if its
         * running -- it might have deleted a net namespace from
         * the global list, so our __nf_ct_unconfirmed_destroy() might
         * not have affected all namespaces.
         */
        net_ns_barrier();

        /* a conntrack could have been unlinked from unconfirmed list
         * before we grabbed pcpu lock in __nf_ct_unconfirmed_destroy().
         * This makes sure its inserted into conntrack table.
         */
        synchronize_net();

        nf_ct_iterate_cleanup(iter, data, 0, 0);
}
EXPORT_SYMBOL_GPL(nf_ct_iterate_destroy);

static int kill_all(struct nf_conn *i, void *data)
{
        return net_eq(nf_ct_net(i), data);
}

void nf_conntrack_cleanup_start(void)
{
        conntrack_gc_work.exiting = true;
        RCU_INIT_POINTER(ip_ct_attach, NULL);
}

void nf_conntrack_cleanup_end(void)
{
        RCU_INIT_POINTER(nf_ct_hook, NULL);
        cancel_delayed_work_sync(&conntrack_gc_work.dwork);
        kvfree(nf_conntrack_hash);

        nf_conntrack_proto_fini();
        nf_conntrack_seqadj_fini();
        nf_conntrack_labels_fini();
        nf_conntrack_helper_fini();
        nf_conntrack_timeout_fini();
        nf_conntrack_ecache_fini();
        nf_conntrack_tstamp_fini();
        nf_conntrack_acct_fini();
        nf_conntrack_expect_fini();

        kmem_cache_destroy(nf_conntrack_cachep);
}

/*
 * Mishearing the voices in his head, our hero wonders how he's
 * supposed to kill the mall.
 */
void nf_conntrack_cleanup_net(struct net *net)
{
        LIST_HEAD(single);

        list_add(&net->exit_list, &single);
        nf_conntrack_cleanup_net_list(&single);
}

void nf_conntrack_cleanup_net_list(struct list_head *net_exit_list)
{
        int busy;
        struct net *net;

        /*
         * This makes sure all current packets have passed through
         *  netfilter framework.  Roll on, two-stage module
         *  delete...
         */
        synchronize_net();
i_see_dead_people:
        busy = 0;
        list_for_each_entry(net, net_exit_list, exit_list) {
                nf_ct_iterate_cleanup(kill_all, net, 0, 0);
                if (atomic_read(&net->ct.count) != 0)
                        busy = 1;
        }
        if (busy) {
                schedule();
                goto i_see_dead_people;
        }

        list_for_each_entry(net, net_exit_list, exit_list) {
                nf_conntrack_proto_pernet_fini(net);
                nf_conntrack_ecache_pernet_fini(net);
                nf_conntrack_expect_pernet_fini(net);
                free_percpu(net->ct.stat);
                free_percpu(net->ct.pcpu_lists);
        }
}

void *nf_ct_alloc_hashtable(unsigned int *sizep, int nulls)
{
        struct hlist_nulls_head *hash;
        unsigned int nr_slots, i;

        if (*sizep > (UINT_MAX / sizeof(struct hlist_nulls_head)))
                return NULL;

        BUILD_BUG_ON(sizeof(struct hlist_nulls_head) != sizeof(struct hlist_head));
        nr_slots = *sizep = roundup(*sizep, PAGE_SIZE / sizeof(struct hlist_nulls_head));

        hash = kvcalloc(nr_slots, sizeof(struct hlist_nulls_head), GFP_KERNEL);

        if (hash && nulls)
                for (i = 0; i < nr_slots; i++)
                        INIT_HLIST_NULLS_HEAD(&hash[i], i);

        return hash;
}
EXPORT_SYMBOL_GPL(nf_ct_alloc_hashtable);

int nf_conntrack_hash_resize(unsigned int hashsize)
{
        int i, bucket;
        unsigned int old_size;
        struct hlist_nulls_head *hash, *old_hash;
        struct nf_conntrack_tuple_hash *h;
        struct nf_conn *ct;

        if (!hashsize)
                return -EINVAL;

        hash = nf_ct_alloc_hashtable(&hashsize, 1);
        if (!hash)
                return -ENOMEM;

        old_size = nf_conntrack_htable_size;
        if (old_size == hashsize) {
                kvfree(hash);
                return 0;
        }

        local_bh_disable();
        nf_conntrack_all_lock();
        write_seqcount_begin(&nf_conntrack_generation);

        /* Lookups in the old hash might happen in parallel, which means we
         * might get false negatives during connection lookup. New connections
         * created because of a false negative won't make it into the hash
         * though since that required taking the locks.
         */

        for (i = 0; i < nf_conntrack_htable_size; i++) {
                while (!hlist_nulls_empty(&nf_conntrack_hash[i])) {
                        h = hlist_nulls_entry(nf_conntrack_hash[i].first,
                                              struct nf_conntrack_tuple_hash, hnnode);
                        ct = nf_ct_tuplehash_to_ctrack(h);
                        hlist_nulls_del_rcu(&h->hnnode);
                        bucket = __hash_conntrack(nf_ct_net(ct),
                                                  &h->tuple, hashsize);
                        hlist_nulls_add_head_rcu(&h->hnnode, &hash[bucket]);
                }
        }
        old_size = nf_conntrack_htable_size;
        old_hash = nf_conntrack_hash;

        nf_conntrack_hash = hash;
        nf_conntrack_htable_size = hashsize;

        write_seqcount_end(&nf_conntrack_generation);
        nf_conntrack_all_unlock();
        local_bh_enable();

        synchronize_net();
        kvfree(old_hash);
        return 0;
}

int nf_conntrack_set_hashsize(const char *val, const struct kernel_param *kp)
{
        unsigned int hashsize;
        int rc;

        if (current->nsproxy->net_ns != &init_net)
                return -EOPNOTSUPP;

        /* On boot, we can set this without any fancy locking. */
        if (!nf_conntrack_hash)
                return param_set_uint(val, kp);

        rc = kstrtouint(val, 0, &hashsize);
        if (rc)
                return rc;

        return nf_conntrack_hash_resize(hashsize);
}

static __always_inline unsigned int total_extension_size(void)
{
        /* remember to add new extensions below */
        BUILD_BUG_ON(NF_CT_EXT_NUM > 9);

        return sizeof(struct nf_ct_ext) +
               sizeof(struct nf_conn_help)
#if IS_ENABLED(CONFIG_NF_NAT)
                + sizeof(struct nf_conn_nat)
#endif
                + sizeof(struct nf_conn_seqadj)
                + sizeof(struct nf_conn_acct)
#ifdef CONFIG_NF_CONNTRACK_EVENTS
                + sizeof(struct nf_conntrack_ecache)
#endif
#ifdef CONFIG_NF_CONNTRACK_TIMESTAMP
                + sizeof(struct nf_conn_tstamp)
#endif
#ifdef CONFIG_NF_CONNTRACK_TIMEOUT
                + sizeof(struct nf_conn_timeout)
#endif
#ifdef CONFIG_NF_CONNTRACK_LABELS
                + sizeof(struct nf_conn_labels)
#endif
#if IS_ENABLED(CONFIG_NETFILTER_SYNPROXY)
                + sizeof(struct nf_conn_synproxy)
#endif
        ;
};

int nf_conntrack_init_start(void)
{
        unsigned long nr_pages = totalram_pages();
        int max_factor = 8;
        int ret = -ENOMEM;
        int i;

        /* struct nf_ct_ext uses u8 to store offsets/size */
        BUILD_BUG_ON(total_extension_size() > 255u);

        seqcount_init(&nf_conntrack_generation);

        for (i = 0; i < CONNTRACK_LOCKS; i++)
                spin_lock_init(&nf_conntrack_locks[i]);

        if (!nf_conntrack_htable_size) {
                /* Idea from tcp.c: use 1/16384 of memory.
                 * On i386: 32MB machine has 512 buckets.
                 * >= 1GB machines have 16384 buckets.
                 * >= 4GB machines have 65536 buckets.
                 */
                nf_conntrack_htable_size
                        = (((nr_pages << PAGE_SHIFT) / 16384)
                           / sizeof(struct hlist_head));
                if (nr_pages > (4 * (1024 * 1024 * 1024 / PAGE_SIZE)))
                        nf_conntrack_htable_size = 65536;
                else if (nr_pages > (1024 * 1024 * 1024 / PAGE_SIZE))
                        nf_conntrack_htable_size = 16384;
                if (nf_conntrack_htable_size < 32)
                        nf_conntrack_htable_size = 32;

                /* Use a max. factor of four by default to get the same max as
                 * with the old struct list_heads. When a table size is given
                 * we use the old value of 8 to avoid reducing the max.
                 * entries. */
                max_factor = 4;
        }

        nf_conntrack_hash = nf_ct_alloc_hashtable(&nf_conntrack_htable_size, 1);
        if (!nf_conntrack_hash)
                return -ENOMEM;

        nf_conntrack_max = max_factor * nf_conntrack_htable_size;

        nf_conntrack_cachep = kmem_cache_create("nf_conntrack",
                                                sizeof(struct nf_conn),
                                                NFCT_INFOMASK + 1,
                                                SLAB_TYPESAFE_BY_RCU | SLAB_HWCACHE_ALIGN, NULL);
        if (!nf_conntrack_cachep)
                goto err_cachep;

        ret = nf_conntrack_expect_init();
        if (ret < 0)
                goto err_expect;

        ret = nf_conntrack_acct_init();
        if (ret < 0)
                goto err_acct;

        ret = nf_conntrack_tstamp_init();
        if (ret < 0)
                goto err_tstamp;

        ret = nf_conntrack_ecache_init();
        if (ret < 0)
                goto err_ecache;

        ret = nf_conntrack_timeout_init();
        if (ret < 0)
                goto err_timeout;

        ret = nf_conntrack_helper_init();
        if (ret < 0)
                goto err_helper;

        ret = nf_conntrack_labels_init();
        if (ret < 0)
                goto err_labels;

        ret = nf_conntrack_seqadj_init();
        if (ret < 0)
                goto err_seqadj;

        ret = nf_conntrack_proto_init();
        if (ret < 0)
                goto err_proto;

        conntrack_gc_work_init(&conntrack_gc_work);
        queue_delayed_work(system_power_efficient_wq, &conntrack_gc_work.dwork, HZ);

        return 0;

err_proto:
        nf_conntrack_seqadj_fini();
err_seqadj:
        nf_conntrack_labels_fini();
err_labels:
        nf_conntrack_helper_fini();
err_helper:
        nf_conntrack_timeout_fini();
err_timeout:
        nf_conntrack_ecache_fini();
err_ecache:
        nf_conntrack_tstamp_fini();
err_tstamp:
        nf_conntrack_acct_fini();
err_acct:
        nf_conntrack_expect_fini();
err_expect:
        kmem_cache_destroy(nf_conntrack_cachep);
err_cachep:
        kvfree(nf_conntrack_hash);
        return ret;
}

static struct nf_ct_hook nf_conntrack_hook = {
        .update         = nf_conntrack_update,
        .destroy        = destroy_conntrack,
        .get_tuple_skb  = nf_conntrack_get_tuple_skb,
};

void nf_conntrack_init_end(void)
{
        /* For use by REJECT target */
        RCU_INIT_POINTER(ip_ct_attach, nf_conntrack_attach);
        RCU_INIT_POINTER(nf_ct_hook, &nf_conntrack_hook);
}

/*
 * We need to use special "null" values, not used in hash table
 */
#define UNCONFIRMED_NULLS_VAL   ((1<<30)+0)
#define DYING_NULLS_VAL         ((1<<30)+1)

int nf_conntrack_init_net(struct net *net)
{
        int ret = -ENOMEM;
        int cpu;

        BUILD_BUG_ON(IP_CT_UNTRACKED == IP_CT_NUMBER);
        BUILD_BUG_ON_NOT_POWER_OF_2(CONNTRACK_LOCKS);
        atomic_set(&net->ct.count, 0);

        net->ct.pcpu_lists = alloc_percpu(struct ct_pcpu);
        if (!net->ct.pcpu_lists)
                goto err_stat;

        for_each_possible_cpu(cpu) {
                struct ct_pcpu *pcpu = per_cpu_ptr(net->ct.pcpu_lists, cpu);

                spin_lock_init(&pcpu->lock);
                INIT_HLIST_NULLS_HEAD(&pcpu->unconfirmed, UNCONFIRMED_NULLS_VAL);
                INIT_HLIST_NULLS_HEAD(&pcpu->dying, DYING_NULLS_VAL);
        }

        net->ct.stat = alloc_percpu(struct ip_conntrack_stat);
        if (!net->ct.stat)
                goto err_pcpu_lists;

        ret = nf_conntrack_expect_pernet_init(net);
        if (ret < 0)
                goto err_expect;

        nf_conntrack_acct_pernet_init(net);
        nf_conntrack_tstamp_pernet_init(net);
        nf_conntrack_ecache_pernet_init(net);
        nf_conntrack_helper_pernet_init(net);
        nf_conntrack_proto_pernet_init(net);

        return 0;

err_expect:
        free_percpu(net->ct.stat);
err_pcpu_lists:
        free_percpu(net->ct.pcpu_lists);
err_stat:
        return ret;
}