/* 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.
 *
 * Authors:     Lotsa people, from code originally in tcp
 */

#ifndef _INET_HASHTABLES_H
#define _INET_HASHTABLES_H


#include <linux/interrupt.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/list.h>
#include <linux/slab.h>
#include <linux/socket.h>
#include <linux/spinlock.h>
#include <linux/types.h>
#include <linux/wait.h>

#include <net/inet_connection_sock.h>
#include <net/inet_sock.h>
#include <net/ip.h>
#include <net/sock.h>
#include <net/route.h>
#include <net/tcp_states.h>
#include <net/netns/hash.h>

#include <linux/refcount.h>
#include <asm/byteorder.h>

/* This is for all connections with a full identity, no wildcards.
 * The 'e' prefix stands for Establish, but we really put all sockets
 * but LISTEN ones.
 */
struct inet_ehash_bucket {
        struct hlist_nulls_head chain;
};

/* There are a few simple rules, which allow for local port reuse by
 * an application.  In essence:
 *
 *      1) Sockets bound to different interfaces may share a local port.
 *         Failing that, goto test 2.
 *      2) If all sockets have sk->sk_reuse set, and none of them are in
 *         TCP_LISTEN state, the port may be shared.
 *         Failing that, goto test 3.
 *      3) If all sockets are bound to a specific inet_sk(sk)->rcv_saddr local
 *         address, and none of them are the same, the port may be
 *         shared.
 *         Failing this, the port cannot be shared.
 *
 * The interesting point, is test #2.  This is what an FTP server does
 * all day.  To optimize this case we use a specific flag bit defined
 * below.  As we add sockets to a bind bucket list, we perform a
 * check of: (newsk->sk_reuse && (newsk->sk_state != TCP_LISTEN))
 * As long as all sockets added to a bind bucket pass this test,
 * the flag bit will be set.
 * The resulting situation is that tcp_v[46]_verify_bind() can just check
 * for this flag bit, if it is set and the socket trying to bind has
 * sk->sk_reuse set, we don't even have to walk the owners list at all,
 * we return that it is ok to bind this socket to the requested local port.
 *
 * Sounds like a lot of work, but it is worth it.  In a more naive
 * implementation (ie. current FreeBSD etc.) the entire list of ports
 * must be walked for each data port opened by an ftp server.  Needless
 * to say, this does not scale at all.  With a couple thousand FTP
 * users logged onto your box, isn't it nice to know that new data
 * ports are created in O(1) time?  I thought so. ;-)   -DaveM
 */
#define FASTREUSEPORT_ANY       1
#define FASTREUSEPORT_STRICT    2

struct inet_bind_bucket {
        possible_net_t          ib_net;
        int                     l3mdev;
        unsigned short          port;
        signed char             fastreuse;
        signed char             fastreuseport;
        kuid_t                  fastuid;
#if IS_ENABLED(CONFIG_IPV6)
        struct in6_addr         fast_v6_rcv_saddr;
#endif
        __be32                  fast_rcv_saddr;
        unsigned short          fast_sk_family;
        bool                    fast_ipv6_only;
        struct hlist_node       node;
        struct hlist_head       bhash2;
        struct rcu_head         rcu;
};

struct inet_bind2_bucket {
        possible_net_t          ib_net;
        int                     l3mdev;
        unsigned short          port;
#if IS_ENABLED(CONFIG_IPV6)
        unsigned short          addr_type;
        struct in6_addr         v6_rcv_saddr;
#define rcv_saddr               v6_rcv_saddr.s6_addr32[3]
#else
        __be32                  rcv_saddr;
#endif
        /* Node in the bhash2 inet_bind_hashbucket chain */
        struct hlist_node       node;
        struct hlist_node       bhash_node;
        /* List of sockets hashed to this bucket */
        struct hlist_head       owners;
        signed char             fastreuse;
        signed char             fastreuseport;
};

static inline struct net *ib_net(const struct inet_bind_bucket *ib)
{
        return read_pnet(&ib->ib_net);
}

static inline struct net *ib2_net(const struct inet_bind2_bucket *ib)
{
        return read_pnet(&ib->ib_net);
}

#define inet_bind_bucket_for_each(tb, head) \
        hlist_for_each_entry(tb, head, node)

struct inet_bind_hashbucket {
        spinlock_t              lock;
        struct hlist_head       chain;
};

/* Sockets can be hashed in established or listening table.
 * We must use different 'nulls' end-of-chain value for all hash buckets :
 * A socket might transition from ESTABLISH to LISTEN state without
 * RCU grace period. A lookup in ehash table needs to handle this case.
 */
#define LISTENING_NULLS_BASE (1U << 29)
struct inet_listen_hashbucket {
        spinlock_t              lock;
        struct hlist_nulls_head nulls_head;
};

/* This is for listening sockets, thus all sockets which possess wildcards. */
#define INET_LHTABLE_SIZE       32      /* Yes, really, this is all you need. */

struct inet_hashinfo {
        /* This is for sockets with full identity only.  Sockets here will
         * always be without wildcards and will have the following invariant:
         *
         *          TCP_ESTABLISHED <= sk->sk_state < TCP_CLOSE
         *
         */
        struct inet_ehash_bucket        *ehash;
        spinlock_t                      *ehash_locks;
        unsigned int                    ehash_mask;
        unsigned int                    ehash_locks_mask;

        /* Ok, let's try this, I give up, we do need a local binding
         * TCP hash as well as the others for fast bind/connect.
         */
        struct kmem_cache               *bind_bucket_cachep;
        /* This bind table is hashed by local port */
        struct inet_bind_hashbucket     *bhash;
        struct kmem_cache               *bind2_bucket_cachep;
        /* This bind table is hashed by local port and sk->sk_rcv_saddr (ipv4)
         * or sk->sk_v6_rcv_saddr (ipv6). This 2nd bind table is used
         * primarily for expediting bind conflict resolution.
         */
        struct inet_bind_hashbucket     *bhash2;
        unsigned int                    bhash_size;

        /* The 2nd listener table hashed by local port and address */
        unsigned int                    lhash2_mask;
        struct inet_listen_hashbucket   *lhash2;

        bool                            pernet;
} ____cacheline_aligned_in_smp;

static inline struct inet_hashinfo *tcp_get_hashinfo(const struct sock *sk)
{
        return sock_net(sk)->ipv4.tcp_death_row.hashinfo;
}

static inline struct inet_listen_hashbucket *
inet_lhash2_bucket(struct inet_hashinfo *h, u32 hash)
{
        return &h->lhash2[hash & h->lhash2_mask];
}

static inline struct inet_ehash_bucket *inet_ehash_bucket(
        struct inet_hashinfo *hashinfo,
        unsigned int hash)
{
        return &hashinfo->ehash[hash & hashinfo->ehash_mask];
}

static inline spinlock_t *inet_ehash_lockp(
        struct inet_hashinfo *hashinfo,
        unsigned int hash)
{
        return &hashinfo->ehash_locks[hash & hashinfo->ehash_locks_mask];
}

int inet_ehash_locks_alloc(struct inet_hashinfo *hashinfo);

static inline void inet_ehash_locks_free(struct inet_hashinfo *hashinfo)
{
        kvfree(hashinfo->ehash_locks);
        hashinfo->ehash_locks = NULL;
}

struct inet_hashinfo *inet_pernet_hashinfo_alloc(struct inet_hashinfo *hashinfo,
                                                 unsigned int ehash_entries);
void inet_pernet_hashinfo_free(struct inet_hashinfo *hashinfo);

struct inet_bind_bucket *
inet_bind_bucket_create(struct kmem_cache *cachep, struct net *net,
                        struct inet_bind_hashbucket *head,
                        const unsigned short snum, int l3mdev);
void inet_bind_bucket_destroy(struct inet_bind_bucket *tb);

bool inet_bind_bucket_match(const struct inet_bind_bucket *tb,
                            const struct net *net, unsigned short port,
                            int l3mdev);

struct inet_bind2_bucket *
inet_bind2_bucket_create(struct kmem_cache *cachep, struct net *net,
                         struct inet_bind_hashbucket *head,
                         struct inet_bind_bucket *tb,
                         const struct sock *sk);

void inet_bind2_bucket_destroy(struct kmem_cache *cachep,
                               struct inet_bind2_bucket *tb);

struct inet_bind2_bucket *
inet_bind2_bucket_find(const struct inet_bind_hashbucket *head,
                       const struct net *net,
                       unsigned short port, int l3mdev,
                       const struct sock *sk);

bool inet_bind2_bucket_match_addr_any(const struct inet_bind2_bucket *tb,
                                      const struct net *net, unsigned short port,
                                      int l3mdev, const struct sock *sk);

static inline u32 inet_bhashfn(const struct net *net, const __u16 lport,
                               const u32 bhash_size)
{
        return (lport + net_hash_mix(net)) & (bhash_size - 1);
}

static inline struct inet_bind_hashbucket *
inet_bhashfn_portaddr(const struct inet_hashinfo *hinfo, const struct sock *sk,
                      const struct net *net, unsigned short port)
{
        u32 hash;

#if IS_ENABLED(CONFIG_IPV6)
        if (sk->sk_family == AF_INET6)
                hash = ipv6_portaddr_hash(net, &sk->sk_v6_rcv_saddr, port);
        else
#endif
                hash = ipv4_portaddr_hash(net, sk->sk_rcv_saddr, port);
        return &hinfo->bhash2[hash & (hinfo->bhash_size - 1)];
}

static inline bool inet_use_hash2_on_bind(const struct sock *sk)
{
#if IS_ENABLED(CONFIG_IPV6)
        if (sk->sk_family == AF_INET6) {
                if (ipv6_addr_any(&sk->sk_v6_rcv_saddr))
                        return false;

                if (!ipv6_addr_v4mapped(&sk->sk_v6_rcv_saddr))
                        return true;
        }
#endif
        return sk->sk_rcv_saddr != htonl(INADDR_ANY);
}

struct inet_bind_hashbucket *
inet_bhash2_addr_any_hashbucket(const struct sock *sk, const struct net *net, int port);

/* This should be called whenever a socket's sk_rcv_saddr (ipv4) or
 * sk_v6_rcv_saddr (ipv6) changes after it has been binded. The socket's
 * rcv_saddr field should already have been updated when this is called.
 */
int inet_bhash2_update_saddr(struct sock *sk, void *saddr, int family);
void inet_bhash2_reset_saddr(struct sock *sk);

void inet_bind_hash(struct sock *sk, struct inet_bind_bucket *tb,
                    struct inet_bind2_bucket *tb2, unsigned short port);

/* Caller must disable local BH processing. */
int __inet_inherit_port(const struct sock *sk, struct sock *child);

void inet_put_port(struct sock *sk);

void inet_hashinfo2_init(struct inet_hashinfo *h, const char *name,
                         unsigned long numentries, int scale,
                         unsigned long low_limit,
                         unsigned long high_limit);
int inet_hashinfo2_init_mod(struct inet_hashinfo *h);

bool inet_ehash_insert(struct sock *sk, struct sock *osk, bool *found_dup_sk);
bool inet_ehash_nolisten(struct sock *sk, struct sock *osk,
                         bool *found_dup_sk);
int inet_hash(struct sock *sk);
void inet_unhash(struct sock *sk);

struct sock *__inet_lookup_listener(const struct net *net,
                                    struct sk_buff *skb, int doff,
                                    const __be32 saddr, const __be16 sport,
                                    const __be32 daddr,
                                    const unsigned short hnum,
                                    const int dif, const int sdif);

static inline struct sock *inet_lookup_listener(struct net *net,
                                                struct sk_buff *skb, int doff,
                                                __be32 saddr, __be16 sport,
                                                __be32 daddr, __be16 dport,
                                                int dif, int sdif)
{
        return __inet_lookup_listener(net, skb, doff, saddr, sport,
                                      daddr, ntohs(dport), dif, sdif);
}

/* Socket demux engine toys. */
/* What happens here is ugly; there's a pair of adjacent fields in
   struct inet_sock; __be16 dport followed by __u16 num.  We want to
   search by pair, so we combine the keys into a single 32bit value
   and compare with 32bit value read from &...->dport.  Let's at least
   make sure that it's not mixed with anything else...
   On 64bit targets we combine comparisons with pair of adjacent __be32
   fields in the same way.
*/
#ifdef __BIG_ENDIAN
#define INET_COMBINED_PORTS(__sport, __dport) \
        ((__force __portpair)(((__force __u32)(__be16)(__sport) << 16) | (__u32)(__dport)))
#else /* __LITTLE_ENDIAN */
#define INET_COMBINED_PORTS(__sport, __dport) \
        ((__force __portpair)(((__u32)(__dport) << 16) | (__force __u32)(__be16)(__sport)))
#endif

#ifdef __BIG_ENDIAN
#define INET_ADDR_COOKIE(__name, __saddr, __daddr) \
        const __addrpair __name = (__force __addrpair) ( \
                                   (((__force __u64)(__be32)(__saddr)) << 32) | \
                                   ((__force __u64)(__be32)(__daddr)))
#else /* __LITTLE_ENDIAN */
#define INET_ADDR_COOKIE(__name, __saddr, __daddr) \
        const __addrpair __name = (__force __addrpair) ( \
                                   (((__force __u64)(__be32)(__daddr)) << 32) | \
                                   ((__force __u64)(__be32)(__saddr)))
#endif /* __BIG_ENDIAN */

static inline bool inet_match(const struct net *net, const struct sock *sk,
                              const __addrpair cookie, const __portpair ports,
                              int dif, int sdif)
{
        if (!net_eq(sock_net(sk), net) ||
            READ_ONCE(sk->sk_portpair) != ports ||
            sk->sk_addrpair != cookie)
                return false;

        /* READ_ONCE() paired with WRITE_ONCE() in sock_bindtoindex_locked() */
        return inet_sk_bound_dev_eq(net, READ_ONCE(sk->sk_bound_dev_if), dif,
                                    sdif);
}

/* Sockets in TCP_CLOSE state are _always_ taken out of the hash, so we need
 * not check it for lookups anymore, thanks Alexey. -DaveM
 */
struct sock *__inet_lookup_established(const struct net *net,
                                       const __be32 saddr, const __be16 sport,
                                       const __be32 daddr, const u16 hnum,
                                       const int dif, const int sdif);

typedef u32 (inet_ehashfn_t)(const struct net *net,
                              const __be32 laddr, const __u16 lport,
                              const __be32 faddr, const __be16 fport);

inet_ehashfn_t inet_ehashfn;

INDIRECT_CALLABLE_DECLARE(inet_ehashfn_t udp_ehashfn);

struct sock *inet_lookup_reuseport(const struct net *net, struct sock *sk,
                                   struct sk_buff *skb, int doff,
                                   __be32 saddr, __be16 sport,
                                   __be32 daddr, unsigned short hnum,
                                   inet_ehashfn_t *ehashfn);

struct sock *inet_lookup_run_sk_lookup(const struct net *net,
                                       int protocol,
                                       struct sk_buff *skb, int doff,
                                       __be32 saddr, __be16 sport,
                                       __be32 daddr, u16 hnum, const int dif,
                                       inet_ehashfn_t *ehashfn);

static inline struct sock *inet_lookup_established(struct net *net,
                                                   const __be32 saddr, const __be16 sport,
                                                   const __be32 daddr, const __be16 dport,
                                                   const int dif)
{
        return __inet_lookup_established(net, saddr, sport, daddr,
                                         ntohs(dport), dif, 0);
}

static inline struct sock *__inet_lookup(struct net *net,
                                         struct sk_buff *skb, int doff,
                                         const __be32 saddr, const __be16 sport,
                                         const __be32 daddr, const __be16 dport,
                                         const int dif, const int sdif,
                                         bool *refcounted)
{
        u16 hnum = ntohs(dport);
        struct sock *sk;

        sk = __inet_lookup_established(net, saddr, sport,
                                       daddr, hnum, dif, sdif);
        *refcounted = true;
        if (sk)
                return sk;
        *refcounted = false;
        return __inet_lookup_listener(net, skb, doff, saddr,
                                      sport, daddr, hnum, dif, sdif);
}

static inline struct sock *inet_lookup(struct net *net,
                                       struct sk_buff *skb, int doff,
                                       const __be32 saddr, const __be16 sport,
                                       const __be32 daddr, const __be16 dport,
                                       const int dif)
{
        struct sock *sk;
        bool refcounted;

        sk = __inet_lookup(net, skb, doff, saddr, sport, daddr,
                           dport, dif, 0, &refcounted);

        if (sk && !refcounted && !refcount_inc_not_zero(&sk->sk_refcnt))
                sk = NULL;
        return sk;
}

static inline
struct sock *inet_steal_sock(struct net *net, struct sk_buff *skb, int doff,
                             const __be32 saddr, const __be16 sport,
                             const __be32 daddr, const __be16 dport,
                             bool *refcounted, inet_ehashfn_t *ehashfn)
{
        struct sock *sk, *reuse_sk;
        bool prefetched;

        sk = skb_steal_sock(skb, refcounted, &prefetched);
        if (!sk)
                return NULL;

        if (!prefetched || !sk_fullsock(sk))
                return sk;

        if (sk->sk_protocol == IPPROTO_TCP) {
                if (sk->sk_state != TCP_LISTEN)
                        return sk;
        } else if (sk->sk_protocol == IPPROTO_UDP) {
                if (sk->sk_state != TCP_CLOSE)
                        return sk;
        } else {
                return sk;
        }

        reuse_sk = inet_lookup_reuseport(net, sk, skb, doff,
                                         saddr, sport, daddr, ntohs(dport),
                                         ehashfn);
        if (!reuse_sk)
                return sk;

        /* We've chosen a new reuseport sock which is never refcounted. This
         * implies that sk also isn't refcounted.
         */
        WARN_ON_ONCE(*refcounted);

        return reuse_sk;
}

static inline struct sock *__inet_lookup_skb(struct sk_buff *skb,
                                             int doff,
                                             const __be16 sport,
                                             const __be16 dport,
                                             const int sdif,
                                             bool *refcounted)
{
        struct net *net = skb_dst_dev_net_rcu(skb);
        const struct iphdr *iph = ip_hdr(skb);
        struct sock *sk;

        sk = inet_steal_sock(net, skb, doff, iph->saddr, sport, iph->daddr, dport,
                             refcounted, inet_ehashfn);
        if (IS_ERR(sk))
                return NULL;
        if (sk)
                return sk;

        return __inet_lookup(net, skb, doff, iph->saddr, sport,
                             iph->daddr, dport, inet_iif(skb), sdif,
                             refcounted);
}

static inline void sk_daddr_set(struct sock *sk, __be32 addr)
{
        sk->sk_daddr = addr; /* alias of inet_daddr */
#if IS_ENABLED(CONFIG_IPV6)
        ipv6_addr_set_v4mapped(addr, &sk->sk_v6_daddr);
#endif
}

static inline void sk_rcv_saddr_set(struct sock *sk, __be32 addr)
{
        sk->sk_rcv_saddr = addr; /* alias of inet_rcv_saddr */
#if IS_ENABLED(CONFIG_IPV6)
        ipv6_addr_set_v4mapped(addr, &sk->sk_v6_rcv_saddr);
#endif
}

int __inet_hash_connect(struct inet_timewait_death_row *death_row,
                        struct sock *sk, u64 port_offset,
                        u32 hash_port0,
                        int (*check_established)(struct inet_timewait_death_row *,
                                                 struct sock *, __u16,
                                                 struct inet_timewait_sock **,
                                                 bool rcu_lookup,
                                                 u32 hash));

int inet_hash_connect(struct inet_timewait_death_row *death_row,
                      struct sock *sk);
#endif /* _INET_HASHTABLES_H */