/*
 * INET         An implementation of the TCP/IP protocol suite for the LINUX
 *              operating system.  INET is implemented using the BSD Socket
 *              interface as the means of communication with the user level.
 *
 *              Generic INET transport hashtables
 *
 * Authors:     Lotsa people, from code originally in tcp
 *
 *      This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 */

#include <linux/module.h>
#include <linux/random.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/wait.h>

#include <net/inet_connection_sock.h>
#include <net/inet_hashtables.h>
#include <net/secure_seq.h>
#include <net/ip.h>

static unsigned int inet_ehashfn(struct net *net, const __be32 laddr,
                                 const __u16 lport, const __be32 faddr,
                                 const __be16 fport)
{
        static u32 inet_ehash_secret __read_mostly;

        net_get_random_once(&inet_ehash_secret, sizeof(inet_ehash_secret));

        return __inet_ehashfn(laddr, lport, faddr, fport,
                              inet_ehash_secret + net_hash_mix(net));
}


static unsigned int inet_sk_ehashfn(const struct sock *sk)
{
        const struct inet_sock *inet = inet_sk(sk);
        const __be32 laddr = inet->inet_rcv_saddr;
        const __u16 lport = inet->inet_num;
        const __be32 faddr = inet->inet_daddr;
        const __be16 fport = inet->inet_dport;
        struct net *net = sock_net(sk);

        return inet_ehashfn(net, laddr, lport, faddr, fport);
}

/*
 * Allocate and initialize a new local port bind bucket.
 * The bindhash mutex for snum's hash chain must be held here.
 */
struct inet_bind_bucket *inet_bind_bucket_create(struct kmem_cache *cachep,
                                                 struct net *net,
                                                 struct inet_bind_hashbucket *head,
                                                 const unsigned short snum)
{
        struct inet_bind_bucket *tb = kmem_cache_alloc(cachep, GFP_ATOMIC);

        if (tb != NULL) {
                write_pnet(&tb->ib_net, net);
                tb->port      = snum;
                tb->fastreuse = 0;
                tb->fastreuseport = 0;
                tb->num_owners = 0;
                INIT_HLIST_HEAD(&tb->owners);
                hlist_add_head(&tb->node, &head->chain);
        }
        return tb;
}

/*
 * Caller must hold hashbucket lock for this tb with local BH disabled
 */
void inet_bind_bucket_destroy(struct kmem_cache *cachep, struct inet_bind_bucket *tb)
{
        if (hlist_empty(&tb->owners)) {
                __hlist_del(&tb->node);
                kmem_cache_free(cachep, tb);
        }
}

void inet_bind_hash(struct sock *sk, struct inet_bind_bucket *tb,
                    const unsigned short snum)
{
        struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;

        atomic_inc(&hashinfo->bsockets);

        inet_sk(sk)->inet_num = snum;
        sk_add_bind_node(sk, &tb->owners);
        tb->num_owners++;
        inet_csk(sk)->icsk_bind_hash = tb;
}

/*
 * Get rid of any references to a local port held by the given sock.
 */
static void __inet_put_port(struct sock *sk)
{
        struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
        const int bhash = inet_bhashfn(sock_net(sk), inet_sk(sk)->inet_num,
                        hashinfo->bhash_size);
        struct inet_bind_hashbucket *head = &hashinfo->bhash[bhash];
        struct inet_bind_bucket *tb;

        atomic_dec(&hashinfo->bsockets);

        spin_lock(&head->lock);
        tb = inet_csk(sk)->icsk_bind_hash;
        __sk_del_bind_node(sk);
        tb->num_owners--;
        inet_csk(sk)->icsk_bind_hash = NULL;
        inet_sk(sk)->inet_num = 0;
        inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
        spin_unlock(&head->lock);
}

void inet_put_port(struct sock *sk)
{
        local_bh_disable();
        __inet_put_port(sk);
        local_bh_enable();
}
EXPORT_SYMBOL(inet_put_port);

int __inet_inherit_port(struct sock *sk, struct sock *child)
{
        struct inet_hashinfo *table = sk->sk_prot->h.hashinfo;
        unsigned short port = inet_sk(child)->inet_num;
        const int bhash = inet_bhashfn(sock_net(sk), port,
                        table->bhash_size);
        struct inet_bind_hashbucket *head = &table->bhash[bhash];
        struct inet_bind_bucket *tb;

        spin_lock(&head->lock);
        tb = inet_csk(sk)->icsk_bind_hash;
        if (tb->port != port) {
                /* NOTE: using tproxy and redirecting skbs to a proxy
                 * on a different listener port breaks the assumption
                 * that the listener socket's icsk_bind_hash is the same
                 * as that of the child socket. We have to look up or
                 * create a new bind bucket for the child here. */
                inet_bind_bucket_for_each(tb, &head->chain) {
                        if (net_eq(ib_net(tb), sock_net(sk)) &&
                            tb->port == port)
                                break;
                }
                if (!tb) {
                        tb = inet_bind_bucket_create(table->bind_bucket_cachep,
                                                     sock_net(sk), head, port);
                        if (!tb) {
                                spin_unlock(&head->lock);
                                return -ENOMEM;
                        }
                }
        }
        inet_bind_hash(child, tb, port);
        spin_unlock(&head->lock);

        return 0;
}
EXPORT_SYMBOL_GPL(__inet_inherit_port);

static inline int compute_score(struct sock *sk, struct net *net,
                                const unsigned short hnum, const __be32 daddr,
                                const int dif)
{
        int score = -1;
        struct inet_sock *inet = inet_sk(sk);

        if (net_eq(sock_net(sk), net) && inet->inet_num == hnum &&
                        !ipv6_only_sock(sk)) {
                __be32 rcv_saddr = inet->inet_rcv_saddr;
                score = sk->sk_family == PF_INET ? 2 : 1;
                if (rcv_saddr) {
                        if (rcv_saddr != daddr)
                                return -1;
                        score += 4;
                }
                if (sk->sk_bound_dev_if) {
                        if (sk->sk_bound_dev_if != dif)
                                return -1;
                        score += 4;
                }
        }
        return score;
}

/*
 * Don't inline this cruft. Here are some nice properties to exploit here. The
 * BSD API does not allow a listening sock to specify the remote port nor the
 * remote address for the connection. So always assume those are both
 * wildcarded during the search since they can never be otherwise.
 */


struct sock *__inet_lookup_listener(struct net *net,
                                    struct inet_hashinfo *hashinfo,
                                    const __be32 saddr, __be16 sport,
                                    const __be32 daddr, const unsigned short hnum,
                                    const int dif)
{
        struct sock *sk, *result;
        struct hlist_nulls_node *node;
        unsigned int hash = inet_lhashfn(net, hnum);
        struct inet_listen_hashbucket *ilb = &hashinfo->listening_hash[hash];
        int score, hiscore, matches = 0, reuseport = 0;
        u32 phash = 0;

        rcu_read_lock();
begin:
        result = NULL;
        hiscore = 0;
        sk_nulls_for_each_rcu(sk, node, &ilb->head) {
                score = compute_score(sk, net, hnum, daddr, dif);
                if (score > hiscore) {
                        result = sk;
                        hiscore = score;
                        reuseport = sk->sk_reuseport;
                        if (reuseport) {
                                phash = inet_ehashfn(net, daddr, hnum,
                                                     saddr, sport);
                                matches = 1;
                        }
                } else if (score == hiscore && reuseport) {
                        matches++;
                        if (reciprocal_scale(phash, matches) == 0)
                                result = sk;
                        phash = next_pseudo_random32(phash);
                }
        }
        /*
         * if the nulls value we got at the end of this lookup is
         * not the expected one, we must restart lookup.
         * We probably met an item that was moved to another chain.
         */
        if (get_nulls_value(node) != hash + LISTENING_NULLS_BASE)
                goto begin;
        if (result) {
                if (unlikely(!atomic_inc_not_zero(&result->sk_refcnt)))
                        result = NULL;
                else if (unlikely(compute_score(result, net, hnum, daddr,
                                  dif) < hiscore)) {
                        sock_put(result);
                        goto begin;
                }
        }
        rcu_read_unlock();
        return result;
}
EXPORT_SYMBOL_GPL(__inet_lookup_listener);

/* All sockets share common refcount, but have different destructors */
void sock_gen_put(struct sock *sk)
{
        if (!atomic_dec_and_test(&sk->sk_refcnt))
                return;

        if (sk->sk_state == TCP_TIME_WAIT)
                inet_twsk_free(inet_twsk(sk));
        else
                sk_free(sk);
}
EXPORT_SYMBOL_GPL(sock_gen_put);

struct sock *__inet_lookup_established(struct net *net,
                                  struct inet_hashinfo *hashinfo,
                                  const __be32 saddr, const __be16 sport,
                                  const __be32 daddr, const u16 hnum,
                                  const int dif)
{
        INET_ADDR_COOKIE(acookie, saddr, daddr)
        const __portpair ports = INET_COMBINED_PORTS(sport, hnum);
        struct sock *sk;
        const struct hlist_nulls_node *node;
        /* Optimize here for direct hit, only listening connections can
         * have wildcards anyways.
         */
        unsigned int hash = inet_ehashfn(net, daddr, hnum, saddr, sport);
        unsigned int slot = hash & hashinfo->ehash_mask;
        struct inet_ehash_bucket *head = &hashinfo->ehash[slot];

        rcu_read_lock();
begin:
        sk_nulls_for_each_rcu(sk, node, &head->chain) {
                if (sk->sk_hash != hash)
                        continue;
                if (likely(INET_MATCH(sk, net, acookie,
                                      saddr, daddr, ports, dif))) {
                        if (unlikely(!atomic_inc_not_zero(&sk->sk_refcnt)))
                                goto out;
                        if (unlikely(!INET_MATCH(sk, net, acookie,
                                                 saddr, daddr, ports, dif))) {
                                sock_gen_put(sk);
                                goto begin;
                        }
                        goto found;
                }
        }
        /*
         * if the nulls value we got at the end of this lookup is
         * not the expected one, we must restart lookup.
         * We probably met an item that was moved to another chain.
         */
        if (get_nulls_value(node) != slot)
                goto begin;
out:
        sk = NULL;
found:
        rcu_read_unlock();
        return sk;
}
EXPORT_SYMBOL_GPL(__inet_lookup_established);

/* called with local bh disabled */
static int __inet_check_established(struct inet_timewait_death_row *death_row,
                                    struct sock *sk, __u16 lport,
                                    struct inet_timewait_sock **twp)
{
        struct inet_hashinfo *hinfo = death_row->hashinfo;
        struct inet_sock *inet = inet_sk(sk);
        __be32 daddr = inet->inet_rcv_saddr;
        __be32 saddr = inet->inet_daddr;
        int dif = sk->sk_bound_dev_if;
        INET_ADDR_COOKIE(acookie, saddr, daddr)
        const __portpair ports = INET_COMBINED_PORTS(inet->inet_dport, lport);
        struct net *net = sock_net(sk);
        unsigned int hash = inet_ehashfn(net, daddr, lport,
                                         saddr, inet->inet_dport);
        struct inet_ehash_bucket *head = inet_ehash_bucket(hinfo, hash);
        spinlock_t *lock = inet_ehash_lockp(hinfo, hash);
        struct sock *sk2;
        const struct hlist_nulls_node *node;
        struct inet_timewait_sock *tw = NULL;
        int twrefcnt = 0;

        spin_lock(lock);

        sk_nulls_for_each(sk2, node, &head->chain) {
                if (sk2->sk_hash != hash)
                        continue;

                if (likely(INET_MATCH(sk2, net, acookie,
                                         saddr, daddr, ports, dif))) {
                        if (sk2->sk_state == TCP_TIME_WAIT) {
                                tw = inet_twsk(sk2);
                                if (twsk_unique(sk, sk2, twp))
                                        break;
                        }
                        goto not_unique;
                }
        }

        /* Must record num and sport now. Otherwise we will see
         * in hash table socket with a funny identity.
         */
        inet->inet_num = lport;
        inet->inet_sport = htons(lport);
        sk->sk_hash = hash;
        WARN_ON(!sk_unhashed(sk));
        __sk_nulls_add_node_rcu(sk, &head->chain);
        if (tw) {
                twrefcnt = inet_twsk_unhash(tw);
                NET_INC_STATS_BH(net, LINUX_MIB_TIMEWAITRECYCLED);
        }
        spin_unlock(lock);
        if (twrefcnt)
                inet_twsk_put(tw);
        sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);

        if (twp) {
                *twp = tw;
        } else if (tw) {
                /* Silly. Should hash-dance instead... */
                inet_twsk_deschedule(tw, death_row);

                inet_twsk_put(tw);
        }
        return 0;

not_unique:
        spin_unlock(lock);
        return -EADDRNOTAVAIL;
}

static inline u32 inet_sk_port_offset(const struct sock *sk)
{
        const struct inet_sock *inet = inet_sk(sk);
        return secure_ipv4_port_ephemeral(inet->inet_rcv_saddr,
                                          inet->inet_daddr,
                                          inet->inet_dport);
}

int __inet_hash_nolisten(struct sock *sk, struct inet_timewait_sock *tw)
{
        struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
        struct hlist_nulls_head *list;
        spinlock_t *lock;
        struct inet_ehash_bucket *head;
        int twrefcnt = 0;

        WARN_ON(!sk_unhashed(sk));

        sk->sk_hash = inet_sk_ehashfn(sk);
        head = inet_ehash_bucket(hashinfo, sk->sk_hash);
        list = &head->chain;
        lock = inet_ehash_lockp(hashinfo, sk->sk_hash);

        spin_lock(lock);
        __sk_nulls_add_node_rcu(sk, list);
        if (tw) {
                WARN_ON(sk->sk_hash != tw->tw_hash);
                twrefcnt = inet_twsk_unhash(tw);
        }
        spin_unlock(lock);
        sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
        return twrefcnt;
}
EXPORT_SYMBOL_GPL(__inet_hash_nolisten);

static void __inet_hash(struct sock *sk)
{
        struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
        struct inet_listen_hashbucket *ilb;

        if (sk->sk_state != TCP_LISTEN) {
                __inet_hash_nolisten(sk, NULL);
                return;
        }

        WARN_ON(!sk_unhashed(sk));
        ilb = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)];

        spin_lock(&ilb->lock);
        __sk_nulls_add_node_rcu(sk, &ilb->head);
        sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
        spin_unlock(&ilb->lock);
}

void inet_hash(struct sock *sk)
{
        if (sk->sk_state != TCP_CLOSE) {
                local_bh_disable();
                __inet_hash(sk);
                local_bh_enable();
        }
}
EXPORT_SYMBOL_GPL(inet_hash);

void inet_unhash(struct sock *sk)
{
        struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
        spinlock_t *lock;
        int done;

        if (sk_unhashed(sk))
                return;

        if (sk->sk_state == TCP_LISTEN)
                lock = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)].lock;
        else
                lock = inet_ehash_lockp(hashinfo, sk->sk_hash);

        spin_lock_bh(lock);
        done = __sk_nulls_del_node_init_rcu(sk);
        if (done)
                sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
        spin_unlock_bh(lock);
}
EXPORT_SYMBOL_GPL(inet_unhash);

int __inet_hash_connect(struct inet_timewait_death_row *death_row,
                struct sock *sk, u32 port_offset,
                int (*check_established)(struct inet_timewait_death_row *,
                        struct sock *, __u16, struct inet_timewait_sock **),
                int (*hash)(struct sock *sk, struct inet_timewait_sock *twp))
{
        struct inet_hashinfo *hinfo = death_row->hashinfo;
        const unsigned short snum = inet_sk(sk)->inet_num;
        struct inet_bind_hashbucket *head;
        struct inet_bind_bucket *tb;
        int ret;
        struct net *net = sock_net(sk);
        int twrefcnt = 1;

        if (!snum) {
                int i, remaining, low, high, port;
                static u32 hint;
                u32 offset = hint + port_offset;
                struct inet_timewait_sock *tw = NULL;

                inet_get_local_port_range(net, &low, &high);
                remaining = (high - low) + 1;

                /* By starting with offset being an even number,
                 * we tend to leave about 50% of ports for other uses,
                 * like bind(0).
                 */
                offset &= ~1;

                for (i = 0; i < remaining; i++) {
                        port = low + (i + offset) % remaining;
                        if (inet_is_reserved_local_port(port))
                                continue;
                        head = &hinfo->bhash[inet_bhashfn(net, port,
                                        hinfo->bhash_size)];
                        spin_lock_bh(&head->lock);

                        /* Does not bother with rcv_saddr checks,
                         * because the established check is already
                         * unique enough.
                         */
                        inet_bind_bucket_for_each(tb, &head->chain) {
                                if (net_eq(ib_net(tb), net) &&
                                    tb->port == port) {
                                        if (tb->fastreuse >= 0 ||
                                            tb->fastreuseport >= 0)
                                                goto next_port;
                                        WARN_ON(hlist_empty(&tb->owners));
                                        if (!check_established(death_row, sk,
                                                                port, &tw))
                                                goto ok;
                                        goto next_port;
                                }
                        }

                        tb = inet_bind_bucket_create(hinfo->bind_bucket_cachep,
                                        net, head, port);
                        if (!tb) {
                                spin_unlock_bh(&head->lock);
                                break;
                        }
                        tb->fastreuse = -1;
                        tb->fastreuseport = -1;
                        goto ok;

                next_port:
                        spin_unlock_bh(&head->lock);
                        cond_resched();
                }

                return -EADDRNOTAVAIL;

ok:
                hint += (i + 2) & ~1;

                /* Head lock still held and bh's disabled */
                inet_bind_hash(sk, tb, port);
                if (sk_unhashed(sk)) {
                        inet_sk(sk)->inet_sport = htons(port);
                        twrefcnt += hash(sk, tw);
                }
                if (tw)
                        twrefcnt += inet_twsk_bind_unhash(tw, hinfo);
                spin_unlock(&head->lock);

                if (tw) {
                        inet_twsk_deschedule(tw, death_row);
                        while (twrefcnt) {
                                twrefcnt--;
                                inet_twsk_put(tw);
                        }
                }

                ret = 0;
                goto out;
        }

        head = &hinfo->bhash[inet_bhashfn(net, snum, hinfo->bhash_size)];
        tb  = inet_csk(sk)->icsk_bind_hash;
        spin_lock_bh(&head->lock);
        if (sk_head(&tb->owners) == sk && !sk->sk_bind_node.next) {
                hash(sk, NULL);
                spin_unlock_bh(&head->lock);
                return 0;
        } else {
                spin_unlock(&head->lock);
                /* No definite answer... Walk to established hash table */
                ret = check_established(death_row, sk, snum, NULL);
out:
                local_bh_enable();
                return ret;
        }
}

/*
 * Bind a port for a connect operation and hash it.
 */
int inet_hash_connect(struct inet_timewait_death_row *death_row,
                      struct sock *sk)
{
        return __inet_hash_connect(death_row, sk, inet_sk_port_offset(sk),
                        __inet_check_established, __inet_hash_nolisten);
}
EXPORT_SYMBOL_GPL(inet_hash_connect);

void inet_hashinfo_init(struct inet_hashinfo *h)
{
        int i;

        atomic_set(&h->bsockets, 0);
        for (i = 0; i < INET_LHTABLE_SIZE; i++) {
                spin_lock_init(&h->listening_hash[i].lock);
                INIT_HLIST_NULLS_HEAD(&h->listening_hash[i].head,
                                      i + LISTENING_NULLS_BASE);
                }
}
EXPORT_SYMBOL_GPL(inet_hashinfo_init);