// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * 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 INET6 transport hashtables
 *
 * Authors:     Lotsa people, from code originally in tcp, generalised here
 *              by Arnaldo Carvalho de Melo <acme@mandriva.com>
 */

#include <linux/module.h>
#include <linux/random.h>

#include <net/addrconf.h>
#include <net/hotdata.h>
#include <net/inet_connection_sock.h>
#include <net/inet_hashtables.h>
#include <net/inet6_hashtables.h>
#include <net/secure_seq.h>
#include <net/ip.h>
#include <net/sock_reuseport.h>
#include <net/tcp.h>

u32 inet6_ehashfn(const struct net *net,
                  const struct in6_addr *laddr, const u16 lport,
                  const struct in6_addr *faddr, const __be16 fport)
{
        u32 lhash, fhash;

        net_get_random_once(&inet6_ehash_secret, sizeof(inet6_ehash_secret));
        net_get_random_once(&tcp_ipv6_hash_secret, sizeof(tcp_ipv6_hash_secret));

        lhash = (__force u32)laddr->s6_addr32[3];
        fhash = __ipv6_addr_jhash(faddr, tcp_ipv6_hash_secret);

        return lport + __inet6_ehashfn(lhash, 0, fhash, fport,
                                       inet6_ehash_secret + net_hash_mix(net));
}
EXPORT_SYMBOL_GPL(inet6_ehashfn);

/*
 * Sockets in TCP_CLOSE state are _always_ taken out of the hash, so
 * we need not check it for TCP lookups anymore, thanks Alexey. -DaveM
 *
 * The sockhash lock must be held as a reader here.
 */
struct sock *__inet6_lookup_established(const struct net *net,
                                        const struct in6_addr *saddr,
                                        const __be16 sport,
                                        const struct in6_addr *daddr,
                                        const u16 hnum,
                                        const int dif, const int sdif)
{
        const __portpair ports = INET_COMBINED_PORTS(sport, hnum);
        const struct hlist_nulls_node *node;
        struct inet_ehash_bucket *head;
        struct inet_hashinfo *hashinfo;
        unsigned int hash, slot;
        struct sock *sk;

        hashinfo = net->ipv4.tcp_death_row.hashinfo;
        hash = inet6_ehashfn(net, daddr, hnum, saddr, sport);
        slot = hash & hashinfo->ehash_mask;
        head = &hashinfo->ehash[slot];
begin:
        sk_nulls_for_each_rcu(sk, node, &head->chain) {
                if (sk->sk_hash != hash)
                        continue;
                if (!inet6_match(net, sk, saddr, daddr, ports, dif, sdif))
                        continue;
                if (unlikely(!refcount_inc_not_zero(&sk->sk_refcnt)))
                        goto out;

                if (unlikely(!inet6_match(net, sk, saddr, daddr, ports, dif, sdif))) {
                        sock_gen_put(sk);
                        goto begin;
                }
                goto found;
        }
        if (get_nulls_value(node) != slot)
                goto begin;
out:
        sk = NULL;
found:
        return sk;
}
EXPORT_SYMBOL(__inet6_lookup_established);

static inline int compute_score(struct sock *sk, const struct net *net,
                                const unsigned short hnum,
                                const struct in6_addr *daddr,
                                const int dif, const int sdif)
{
        int score = -1;

        if (net_eq(sock_net(sk), net) &&
            READ_ONCE(inet_sk(sk)->inet_num) == hnum &&
            sk->sk_family == PF_INET6) {
                if (!ipv6_addr_equal(&sk->sk_v6_rcv_saddr, daddr))
                        return -1;

                if (!inet_sk_bound_dev_eq(net, sk->sk_bound_dev_if, dif, sdif))
                        return -1;

                score =  sk->sk_bound_dev_if ? 2 : 1;
                if (READ_ONCE(sk->sk_incoming_cpu) == raw_smp_processor_id())
                        score++;
        }
        return score;
}

/**
 * inet6_lookup_reuseport() - execute reuseport logic on AF_INET6 socket if necessary.
 * @net: network namespace.
 * @sk: AF_INET6 socket, must be in TCP_LISTEN state for TCP or TCP_CLOSE for UDP.
 * @skb: context for a potential SK_REUSEPORT program.
 * @doff: header offset.
 * @saddr: source address.
 * @sport: source port.
 * @daddr: destination address.
 * @hnum: destination port in host byte order.
 * @ehashfn: hash function used to generate the fallback hash.
 *
 * Return: NULL if sk doesn't have SO_REUSEPORT set, otherwise a pointer to
 *         the selected sock or an error.
 */
struct sock *inet6_lookup_reuseport(const struct net *net, struct sock *sk,
                                    struct sk_buff *skb, int doff,
                                    const struct in6_addr *saddr,
                                    __be16 sport,
                                    const struct in6_addr *daddr,
                                    unsigned short hnum,
                                    inet6_ehashfn_t *ehashfn)
{
        struct sock *reuse_sk = NULL;
        u32 phash;

        if (sk->sk_reuseport) {
                phash = INDIRECT_CALL_INET(ehashfn, udp6_ehashfn, inet6_ehashfn,
                                           net, daddr, hnum, saddr, sport);
                reuse_sk = reuseport_select_sock(sk, phash, skb, doff);
        }
        return reuse_sk;
}
EXPORT_SYMBOL_GPL(inet6_lookup_reuseport);

/* called with rcu_read_lock() */
static struct sock *inet6_lhash2_lookup(const struct net *net,
                struct inet_listen_hashbucket *ilb2,
                struct sk_buff *skb, int doff,
                const struct in6_addr *saddr,
                const __be16 sport, const struct in6_addr *daddr,
                const unsigned short hnum, const int dif, const int sdif)
{
        struct sock *sk, *result = NULL;
        struct hlist_nulls_node *node;
        int score, hiscore = 0;

        sk_nulls_for_each_rcu(sk, node, &ilb2->nulls_head) {
                score = compute_score(sk, net, hnum, daddr, dif, sdif);
                if (score > hiscore) {
                        result = inet6_lookup_reuseport(net, sk, skb, doff,
                                                        saddr, sport, daddr, hnum, inet6_ehashfn);
                        if (result)
                                return result;

                        result = sk;
                        hiscore = score;
                }
        }

        return result;
}

struct sock *inet6_lookup_run_sk_lookup(const struct net *net,
                                        int protocol,
                                        struct sk_buff *skb, int doff,
                                        const struct in6_addr *saddr,
                                        const __be16 sport,
                                        const struct in6_addr *daddr,
                                        const u16 hnum, const int dif,
                                        inet6_ehashfn_t *ehashfn)
{
        struct sock *sk, *reuse_sk;
        bool no_reuseport;

        no_reuseport = bpf_sk_lookup_run_v6(net, protocol, saddr, sport,
                                            daddr, hnum, dif, &sk);
        if (no_reuseport || IS_ERR_OR_NULL(sk))
                return sk;

        reuse_sk = inet6_lookup_reuseport(net, sk, skb, doff,
                                          saddr, sport, daddr, hnum, ehashfn);
        if (reuse_sk)
                sk = reuse_sk;
        return sk;
}
EXPORT_SYMBOL_GPL(inet6_lookup_run_sk_lookup);

struct sock *inet6_lookup_listener(const struct net *net,
                                   struct sk_buff *skb, int doff,
                                   const struct in6_addr *saddr,
                                   const __be16 sport,
                                   const struct in6_addr *daddr,
                                   const unsigned short hnum,
                                   const int dif, const int sdif)
{
        struct inet_listen_hashbucket *ilb2;
        struct inet_hashinfo *hashinfo;
        struct sock *result = NULL;
        unsigned int hash2;

        /* Lookup redirect from BPF */
        if (static_branch_unlikely(&bpf_sk_lookup_enabled)) {
                result = inet6_lookup_run_sk_lookup(net, IPPROTO_TCP, skb, doff,
                                                    saddr, sport, daddr, hnum, dif,
                                                    inet6_ehashfn);
                if (result)
                        goto done;
        }

        hashinfo = net->ipv4.tcp_death_row.hashinfo;
        hash2 = ipv6_portaddr_hash(net, daddr, hnum);
        ilb2 = inet_lhash2_bucket(hashinfo, hash2);

        result = inet6_lhash2_lookup(net, ilb2, skb, doff,
                                     saddr, sport, daddr, hnum,
                                     dif, sdif);
        if (result)
                goto done;

        /* Lookup lhash2 with in6addr_any */
        hash2 = ipv6_portaddr_hash(net, &in6addr_any, hnum);
        ilb2 = inet_lhash2_bucket(hashinfo, hash2);

        result = inet6_lhash2_lookup(net, ilb2, skb, doff,
                                     saddr, sport, &in6addr_any, hnum,
                                     dif, sdif);
done:
        if (IS_ERR(result))
                return NULL;
        return result;
}
EXPORT_SYMBOL_GPL(inet6_lookup_listener);

struct sock *inet6_lookup(const struct net *net,
                          struct sk_buff *skb, int doff,
                          const struct in6_addr *saddr, const __be16 sport,
                          const struct in6_addr *daddr, const __be16 dport,
                          const int dif)
{
        struct sock *sk;
        bool refcounted;

        sk = __inet6_lookup(net, skb, doff, saddr, sport, daddr,
                            ntohs(dport), dif, 0, &refcounted);
        if (sk && !refcounted && !refcount_inc_not_zero(&sk->sk_refcnt))
                sk = NULL;
        return sk;
}
EXPORT_SYMBOL_GPL(inet6_lookup);

static int __inet6_check_established(struct inet_timewait_death_row *death_row,
                                     struct sock *sk, const __u16 lport,
                                     struct inet_timewait_sock **twp,
                                     bool rcu_lookup,
                                     u32 hash)
{
        struct inet_hashinfo *hinfo = death_row->hashinfo;
        struct inet_sock *inet = inet_sk(sk);
        const struct in6_addr *daddr = &sk->sk_v6_rcv_saddr;
        const struct in6_addr *saddr = &sk->sk_v6_daddr;
        const int dif = sk->sk_bound_dev_if;
        struct net *net = sock_net(sk);
        const int sdif = l3mdev_master_ifindex_by_index(net, dif);
        const __portpair ports = INET_COMBINED_PORTS(inet->inet_dport, lport);
        struct inet_ehash_bucket *head = inet_ehash_bucket(hinfo, hash);
        struct inet_timewait_sock *tw = NULL;
        const struct hlist_nulls_node *node;
        struct sock *sk2;
        spinlock_t *lock;

        if (rcu_lookup) {
                sk_nulls_for_each(sk2, node, &head->chain) {
                        if (sk2->sk_hash != hash ||
                            !inet6_match(net, sk2, saddr, daddr,
                                         ports, dif, sdif))
                                continue;
                        if (sk2->sk_state == TCP_TIME_WAIT)
                                break;
                        return -EADDRNOTAVAIL;
                }
                return 0;
        }

        lock = inet_ehash_lockp(hinfo, hash);
        spin_lock(lock);

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

                if (likely(inet6_match(net, sk2, saddr, daddr, ports,
                                       dif, sdif))) {
                        if (sk2->sk_state == TCP_TIME_WAIT) {
                                tw = inet_twsk(sk2);
                                if (tcp_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) {
                sk_nulls_del_node_init_rcu((struct sock *)tw);
                __NET_INC_STATS(net, LINUX_MIB_TIMEWAITRECYCLED);
        }
        spin_unlock(lock);
        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_put(tw);
        }
        return 0;

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

static u64 inet6_sk_port_offset(const struct sock *sk)
{
        const struct inet_sock *inet = inet_sk(sk);

        return secure_ipv6_port_ephemeral(sk->sk_v6_rcv_saddr.s6_addr32,
                                          sk->sk_v6_daddr.s6_addr32,
                                          inet->inet_dport);
}

int inet6_hash_connect(struct inet_timewait_death_row *death_row,
                       struct sock *sk)
{
        const struct in6_addr *daddr = &sk->sk_v6_rcv_saddr;
        const struct in6_addr *saddr = &sk->sk_v6_daddr;
        const struct inet_sock *inet = inet_sk(sk);
        const struct net *net = sock_net(sk);
        u64 port_offset = 0;
        u32 hash_port0;

        if (!inet_sk(sk)->inet_num)
                port_offset = inet6_sk_port_offset(sk);

        hash_port0 = inet6_ehashfn(net, daddr, 0, saddr, inet->inet_dport);

        return __inet_hash_connect(death_row, sk, port_offset, hash_port0,
                                   __inet6_check_established);
}
EXPORT_SYMBOL_GPL(inet6_hash_connect);