// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2017 - 2018 Covalent IO, Inc. http://covalent.io */

#include <linux/bpf.h>
#include <linux/btf_ids.h>
#include <linux/filter.h>
#include <linux/errno.h>
#include <linux/file.h>
#include <linux/net.h>
#include <linux/workqueue.h>
#include <linux/skmsg.h>
#include <linux/list.h>
#include <linux/jhash.h>
#include <linux/sock_diag.h>
#include <net/udp.h>

struct bpf_stab {
        struct bpf_map map;
        struct sock **sks;
        struct sk_psock_progs progs;
        spinlock_t lock;
};

#define SOCK_CREATE_FLAG_MASK                           \
        (BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY)

/* This mutex is used to
 *  - protect race between prog/link attach/detach and link prog update, and
 *  - protect race between releasing and accessing map in bpf_link.
 * A single global mutex lock is used since it is expected contention is low.
 */
static DEFINE_MUTEX(sockmap_mutex);

static int sock_map_prog_update(struct bpf_map *map, struct bpf_prog *prog,
                                struct bpf_prog *old, struct bpf_link *link,
                                u32 which);
static struct sk_psock_progs *sock_map_progs(struct bpf_map *map);

static struct bpf_map *sock_map_alloc(union bpf_attr *attr)
{
        struct bpf_stab *stab;

        if (attr->max_entries == 0 ||
            attr->key_size    != 4 ||
            (attr->value_size != sizeof(u32) &&
             attr->value_size != sizeof(u64)) ||
            attr->map_flags & ~SOCK_CREATE_FLAG_MASK)
                return ERR_PTR(-EINVAL);

        stab = bpf_map_area_alloc(sizeof(*stab), NUMA_NO_NODE);
        if (!stab)
                return ERR_PTR(-ENOMEM);

        bpf_map_init_from_attr(&stab->map, attr);
        spin_lock_init(&stab->lock);

        stab->sks = bpf_map_area_alloc((u64) stab->map.max_entries *
                                       sizeof(struct sock *),
                                       stab->map.numa_node);
        if (!stab->sks) {
                bpf_map_area_free(stab);
                return ERR_PTR(-ENOMEM);
        }

        return &stab->map;
}

int sock_map_get_from_fd(const union bpf_attr *attr, struct bpf_prog *prog)
{
        struct bpf_map *map;
        int ret;

        if (attr->attach_flags || attr->replace_bpf_fd)
                return -EINVAL;

        CLASS(fd, f)(attr->target_fd);
        map = __bpf_map_get(f);
        if (IS_ERR(map))
                return PTR_ERR(map);
        mutex_lock(&sockmap_mutex);
        ret = sock_map_prog_update(map, prog, NULL, NULL, attr->attach_type);
        mutex_unlock(&sockmap_mutex);
        return ret;
}

int sock_map_prog_detach(const union bpf_attr *attr, enum bpf_prog_type ptype)
{
        struct bpf_prog *prog;
        struct bpf_map *map;
        int ret;

        if (attr->attach_flags || attr->replace_bpf_fd)
                return -EINVAL;

        CLASS(fd, f)(attr->target_fd);
        map = __bpf_map_get(f);
        if (IS_ERR(map))
                return PTR_ERR(map);

        prog = bpf_prog_get(attr->attach_bpf_fd);
        if (IS_ERR(prog))
                return PTR_ERR(prog);

        if (prog->type != ptype) {
                ret = -EINVAL;
                goto put_prog;
        }

        mutex_lock(&sockmap_mutex);
        ret = sock_map_prog_update(map, NULL, prog, NULL, attr->attach_type);
        mutex_unlock(&sockmap_mutex);
put_prog:
        bpf_prog_put(prog);
        return ret;
}

static void sock_map_sk_acquire(struct sock *sk)
        __acquires(&sk->sk_lock.slock)
{
        lock_sock(sk);
        rcu_read_lock();
}

static void sock_map_sk_release(struct sock *sk)
        __releases(&sk->sk_lock.slock)
{
        rcu_read_unlock();
        release_sock(sk);
}

static void sock_map_add_link(struct sk_psock *psock,
                              struct sk_psock_link *link,
                              struct bpf_map *map, void *link_raw)
{
        link->link_raw = link_raw;
        link->map = map;
        spin_lock_bh(&psock->link_lock);
        list_add_tail(&link->list, &psock->link);
        spin_unlock_bh(&psock->link_lock);
}

static void sock_map_del_link(struct sock *sk,
                              struct sk_psock *psock, void *link_raw)
{
        bool strp_stop = false, verdict_stop = false;
        struct sk_psock_link *link, *tmp;

        spin_lock_bh(&psock->link_lock);
        list_for_each_entry_safe(link, tmp, &psock->link, list) {
                if (link->link_raw == link_raw) {
                        struct bpf_map *map = link->map;
                        struct sk_psock_progs *progs = sock_map_progs(map);

                        if (psock->saved_data_ready && progs->stream_parser)
                                strp_stop = true;
                        if (psock->saved_data_ready && progs->stream_verdict)
                                verdict_stop = true;
                        if (psock->saved_data_ready && progs->skb_verdict)
                                verdict_stop = true;
                        list_del(&link->list);
                        sk_psock_free_link(link);
                        break;
                }
        }
        spin_unlock_bh(&psock->link_lock);
        if (strp_stop || verdict_stop) {
                write_lock_bh(&sk->sk_callback_lock);
                if (strp_stop)
                        sk_psock_stop_strp(sk, psock);
                if (verdict_stop)
                        sk_psock_stop_verdict(sk, psock);

                if (psock->psock_update_sk_prot)
                        psock->psock_update_sk_prot(sk, psock, false);
                write_unlock_bh(&sk->sk_callback_lock);
        }
}

static void sock_map_unref(struct sock *sk, void *link_raw)
{
        struct sk_psock *psock = sk_psock(sk);

        if (likely(psock)) {
                sock_map_del_link(sk, psock, link_raw);
                sk_psock_put(sk, psock);
        }
}

static int sock_map_init_proto(struct sock *sk, struct sk_psock *psock)
{
        if (!sk->sk_prot->psock_update_sk_prot)
                return -EINVAL;
        psock->psock_update_sk_prot = sk->sk_prot->psock_update_sk_prot;
        return sk->sk_prot->psock_update_sk_prot(sk, psock, false);
}

static struct sk_psock *sock_map_psock_get_checked(struct sock *sk)
{
        struct sk_psock *psock;

        rcu_read_lock();
        psock = sk_psock(sk);
        if (psock) {
                if (sk->sk_prot->close != sock_map_close) {
                        psock = ERR_PTR(-EBUSY);
                        goto out;
                }

                if (!refcount_inc_not_zero(&psock->refcnt))
                        psock = ERR_PTR(-EBUSY);
        }
out:
        rcu_read_unlock();
        return psock;
}

static int sock_map_link(struct bpf_map *map, struct sock *sk)
{
        struct sk_psock_progs *progs = sock_map_progs(map);
        struct bpf_prog *stream_verdict = NULL;
        struct bpf_prog *stream_parser = NULL;
        struct bpf_prog *skb_verdict = NULL;
        struct bpf_prog *msg_parser = NULL;
        struct sk_psock *psock;
        int ret;

        stream_verdict = READ_ONCE(progs->stream_verdict);
        if (stream_verdict) {
                stream_verdict = bpf_prog_inc_not_zero(stream_verdict);
                if (IS_ERR(stream_verdict))
                        return PTR_ERR(stream_verdict);
        }

        stream_parser = READ_ONCE(progs->stream_parser);
        if (stream_parser) {
                stream_parser = bpf_prog_inc_not_zero(stream_parser);
                if (IS_ERR(stream_parser)) {
                        ret = PTR_ERR(stream_parser);
                        goto out_put_stream_verdict;
                }
        }

        msg_parser = READ_ONCE(progs->msg_parser);
        if (msg_parser) {
                msg_parser = bpf_prog_inc_not_zero(msg_parser);
                if (IS_ERR(msg_parser)) {
                        ret = PTR_ERR(msg_parser);
                        goto out_put_stream_parser;
                }
        }

        skb_verdict = READ_ONCE(progs->skb_verdict);
        if (skb_verdict) {
                skb_verdict = bpf_prog_inc_not_zero(skb_verdict);
                if (IS_ERR(skb_verdict)) {
                        ret = PTR_ERR(skb_verdict);
                        goto out_put_msg_parser;
                }
        }

        psock = sock_map_psock_get_checked(sk);
        if (IS_ERR(psock)) {
                ret = PTR_ERR(psock);
                goto out_progs;
        }

        if (psock) {
                if ((msg_parser && READ_ONCE(psock->progs.msg_parser)) ||
                    (stream_parser  && READ_ONCE(psock->progs.stream_parser)) ||
                    (skb_verdict && READ_ONCE(psock->progs.skb_verdict)) ||
                    (skb_verdict && READ_ONCE(psock->progs.stream_verdict)) ||
                    (stream_verdict && READ_ONCE(psock->progs.skb_verdict)) ||
                    (stream_verdict && READ_ONCE(psock->progs.stream_verdict))) {
                        sk_psock_put(sk, psock);
                        ret = -EBUSY;
                        goto out_progs;
                }
        } else {
                psock = sk_psock_init(sk, map->numa_node);
                if (IS_ERR(psock)) {
                        ret = PTR_ERR(psock);
                        goto out_progs;
                }
        }

        if (msg_parser)
                psock_set_prog(&psock->progs.msg_parser, msg_parser);
        if (stream_parser)
                psock_set_prog(&psock->progs.stream_parser, stream_parser);
        if (stream_verdict)
                psock_set_prog(&psock->progs.stream_verdict, stream_verdict);
        if (skb_verdict)
                psock_set_prog(&psock->progs.skb_verdict, skb_verdict);

        /* msg_* and stream_* programs references tracked in psock after this
         * point. Reference dec and cleanup will occur through psock destructor
         */
        ret = sock_map_init_proto(sk, psock);
        if (ret < 0) {
                sk_psock_put(sk, psock);
                goto out;
        }

        write_lock_bh(&sk->sk_callback_lock);
        if (stream_parser && stream_verdict && !psock->saved_data_ready) {
                if (sk_is_tcp(sk))
                        ret = sk_psock_init_strp(sk, psock);
                else
                        ret = -EOPNOTSUPP;
                if (ret) {
                        write_unlock_bh(&sk->sk_callback_lock);
                        sk_psock_put(sk, psock);
                        goto out;
                }
                sk_psock_start_strp(sk, psock);
        } else if (!stream_parser && stream_verdict && !psock->saved_data_ready) {
                sk_psock_start_verdict(sk,psock);
        } else if (!stream_verdict && skb_verdict && !psock->saved_data_ready) {
                sk_psock_start_verdict(sk, psock);
        }
        write_unlock_bh(&sk->sk_callback_lock);
        return 0;
out_progs:
        if (skb_verdict)
                bpf_prog_put(skb_verdict);
out_put_msg_parser:
        if (msg_parser)
                bpf_prog_put(msg_parser);
out_put_stream_parser:
        if (stream_parser)
                bpf_prog_put(stream_parser);
out_put_stream_verdict:
        if (stream_verdict)
                bpf_prog_put(stream_verdict);
out:
        return ret;
}

static void sock_map_free(struct bpf_map *map)
{
        struct bpf_stab *stab = container_of(map, struct bpf_stab, map);
        int i;

        /* After the sync no updates or deletes will be in-flight so it
         * is safe to walk map and remove entries without risking a race
         * in EEXIST update case.
         */
        synchronize_rcu();
        for (i = 0; i < stab->map.max_entries; i++) {
                struct sock **psk = &stab->sks[i];
                struct sock *sk;

                sk = xchg(psk, NULL);
                if (sk) {
                        sock_hold(sk);
                        lock_sock(sk);
                        rcu_read_lock();
                        sock_map_unref(sk, psk);
                        rcu_read_unlock();
                        release_sock(sk);
                        sock_put(sk);
                }
        }

        /* wait for psock readers accessing its map link */
        synchronize_rcu();

        bpf_map_area_free(stab->sks);
        bpf_map_area_free(stab);
}

static void sock_map_release_progs(struct bpf_map *map)
{
        psock_progs_drop(&container_of(map, struct bpf_stab, map)->progs);
}

static struct sock *__sock_map_lookup_elem(struct bpf_map *map, u32 key)
{
        struct bpf_stab *stab = container_of(map, struct bpf_stab, map);

        WARN_ON_ONCE(!rcu_read_lock_held());

        if (unlikely(key >= map->max_entries))
                return NULL;
        return READ_ONCE(stab->sks[key]);
}

static void *sock_map_lookup(struct bpf_map *map, void *key)
{
        struct sock *sk;

        sk = __sock_map_lookup_elem(map, *(u32 *)key);
        if (!sk)
                return NULL;
        if (sk_is_refcounted(sk) && !refcount_inc_not_zero(&sk->sk_refcnt))
                return NULL;
        return sk;
}

static void *sock_map_lookup_sys(struct bpf_map *map, void *key)
{
        struct sock *sk;

        if (map->value_size != sizeof(u64))
                return ERR_PTR(-ENOSPC);

        sk = __sock_map_lookup_elem(map, *(u32 *)key);
        if (!sk)
                return ERR_PTR(-ENOENT);

        __sock_gen_cookie(sk);
        return &sk->sk_cookie;
}

static int __sock_map_delete(struct bpf_stab *stab, struct sock *sk_test,
                             struct sock **psk)
{
        struct sock *sk = NULL;
        int err = 0;

        spin_lock_bh(&stab->lock);
        if (!sk_test || sk_test == *psk)
                sk = xchg(psk, NULL);

        if (likely(sk))
                sock_map_unref(sk, psk);
        else
                err = -EINVAL;

        spin_unlock_bh(&stab->lock);
        return err;
}

static void sock_map_delete_from_link(struct bpf_map *map, struct sock *sk,
                                      void *link_raw)
{
        struct bpf_stab *stab = container_of(map, struct bpf_stab, map);

        __sock_map_delete(stab, sk, link_raw);
}

static long sock_map_delete_elem(struct bpf_map *map, void *key)
{
        struct bpf_stab *stab = container_of(map, struct bpf_stab, map);
        u32 i = *(u32 *)key;
        struct sock **psk;

        if (unlikely(i >= map->max_entries))
                return -EINVAL;

        psk = &stab->sks[i];
        return __sock_map_delete(stab, NULL, psk);
}

static int sock_map_get_next_key(struct bpf_map *map, void *key, void *next)
{
        struct bpf_stab *stab = container_of(map, struct bpf_stab, map);
        u32 i = key ? *(u32 *)key : U32_MAX;
        u32 *key_next = next;

        if (i == stab->map.max_entries - 1)
                return -ENOENT;
        if (i >= stab->map.max_entries)
                *key_next = 0;
        else
                *key_next = i + 1;
        return 0;
}

static int sock_map_update_common(struct bpf_map *map, u32 idx,
                                  struct sock *sk, u64 flags)
{
        struct bpf_stab *stab = container_of(map, struct bpf_stab, map);
        struct sk_psock_link *link;
        struct sk_psock *psock;
        struct sock *osk;
        int ret;

        WARN_ON_ONCE(!rcu_read_lock_held());
        if (unlikely(flags > BPF_EXIST))
                return -EINVAL;
        if (unlikely(idx >= map->max_entries))
                return -E2BIG;

        link = sk_psock_init_link();
        if (!link)
                return -ENOMEM;

        ret = sock_map_link(map, sk);
        if (ret < 0)
                goto out_free;

        psock = sk_psock(sk);
        WARN_ON_ONCE(!psock);

        spin_lock_bh(&stab->lock);
        osk = stab->sks[idx];
        if (osk && flags == BPF_NOEXIST) {
                ret = -EEXIST;
                goto out_unlock;
        } else if (!osk && flags == BPF_EXIST) {
                ret = -ENOENT;
                goto out_unlock;
        }

        sock_map_add_link(psock, link, map, &stab->sks[idx]);
        stab->sks[idx] = sk;
        if (osk)
                sock_map_unref(osk, &stab->sks[idx]);
        spin_unlock_bh(&stab->lock);
        return 0;
out_unlock:
        spin_unlock_bh(&stab->lock);
        if (psock)
                sk_psock_put(sk, psock);
out_free:
        sk_psock_free_link(link);
        return ret;
}

static bool sock_map_op_okay(const struct bpf_sock_ops_kern *ops)
{
        return ops->op == BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB ||
               ops->op == BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB ||
               ops->op == BPF_SOCK_OPS_TCP_LISTEN_CB;
}

static bool sock_map_redirect_allowed(const struct sock *sk)
{
        if (sk_is_tcp(sk))
                return sk->sk_state != TCP_LISTEN;
        else
                return sk->sk_state == TCP_ESTABLISHED;
}

static bool sock_map_sk_is_suitable(const struct sock *sk)
{
        return !!sk->sk_prot->psock_update_sk_prot;
}

static bool sock_map_sk_state_allowed(const struct sock *sk)
{
        if (sk_is_tcp(sk))
                return (1 << sk->sk_state) & (TCPF_ESTABLISHED | TCPF_LISTEN);
        if (sk_is_stream_unix(sk))
                return (1 << sk->sk_state) & TCPF_ESTABLISHED;
        if (sk_is_vsock(sk) &&
            (sk->sk_type == SOCK_STREAM || sk->sk_type == SOCK_SEQPACKET))
                return (1 << sk->sk_state) & TCPF_ESTABLISHED;
        return true;
}

static int sock_hash_update_common(struct bpf_map *map, void *key,
                                   struct sock *sk, u64 flags);

int sock_map_update_elem_sys(struct bpf_map *map, void *key, void *value,
                             u64 flags)
{
        struct socket *sock;
        struct sock *sk;
        int ret;
        u64 ufd;

        if (map->value_size == sizeof(u64))
                ufd = *(u64 *)value;
        else
                ufd = *(u32 *)value;
        if (ufd > S32_MAX)
                return -EINVAL;

        sock = sockfd_lookup(ufd, &ret);
        if (!sock)
                return ret;
        sk = sock->sk;
        if (!sk) {
                ret = -EINVAL;
                goto out;
        }
        if (!sock_map_sk_is_suitable(sk)) {
                ret = -EOPNOTSUPP;
                goto out;
        }

        sock_map_sk_acquire(sk);
        if (!sock_map_sk_state_allowed(sk))
                ret = -EOPNOTSUPP;
        else if (map->map_type == BPF_MAP_TYPE_SOCKMAP)
                ret = sock_map_update_common(map, *(u32 *)key, sk, flags);
        else
                ret = sock_hash_update_common(map, key, sk, flags);
        sock_map_sk_release(sk);
out:
        sockfd_put(sock);
        return ret;
}

static long sock_map_update_elem(struct bpf_map *map, void *key,
                                 void *value, u64 flags)
{
        struct sock *sk = (struct sock *)value;
        int ret;

        if (unlikely(!sk || !sk_fullsock(sk)))
                return -EINVAL;

        if (!sock_map_sk_is_suitable(sk))
                return -EOPNOTSUPP;

        local_bh_disable();
        bh_lock_sock(sk);
        if (!sock_map_sk_state_allowed(sk))
                ret = -EOPNOTSUPP;
        else if (map->map_type == BPF_MAP_TYPE_SOCKMAP)
                ret = sock_map_update_common(map, *(u32 *)key, sk, flags);
        else
                ret = sock_hash_update_common(map, key, sk, flags);
        bh_unlock_sock(sk);
        local_bh_enable();
        return ret;
}

BPF_CALL_4(bpf_sock_map_update, struct bpf_sock_ops_kern *, sops,
           struct bpf_map *, map, void *, key, u64, flags)
{
        WARN_ON_ONCE(!rcu_read_lock_held());

        if (likely(sock_map_sk_is_suitable(sops->sk) &&
                   sock_map_op_okay(sops)))
                return sock_map_update_common(map, *(u32 *)key, sops->sk,
                                              flags);
        return -EOPNOTSUPP;
}

const struct bpf_func_proto bpf_sock_map_update_proto = {
        .func           = bpf_sock_map_update,
        .gpl_only       = false,
        .pkt_access     = true,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_CONST_MAP_PTR,
        .arg3_type      = ARG_PTR_TO_MAP_KEY,
        .arg4_type      = ARG_ANYTHING,
};

BPF_CALL_4(bpf_sk_redirect_map, struct sk_buff *, skb,
           struct bpf_map *, map, u32, key, u64, flags)
{
        struct sock *sk;

        if (unlikely(flags & ~(BPF_F_INGRESS)))
                return SK_DROP;

        sk = __sock_map_lookup_elem(map, key);
        if (unlikely(!sk || !sock_map_redirect_allowed(sk)))
                return SK_DROP;
        if ((flags & BPF_F_INGRESS) && sk_is_vsock(sk))
                return SK_DROP;

        skb_bpf_set_redir(skb, sk, flags & BPF_F_INGRESS);
        return SK_PASS;
}

const struct bpf_func_proto bpf_sk_redirect_map_proto = {
        .func           = bpf_sk_redirect_map,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_CONST_MAP_PTR,
        .arg3_type      = ARG_ANYTHING,
        .arg4_type      = ARG_ANYTHING,
};

BPF_CALL_4(bpf_msg_redirect_map, struct sk_msg *, msg,
           struct bpf_map *, map, u32, key, u64, flags)
{
        struct sock *sk;

        if (unlikely(flags & ~(BPF_F_INGRESS)))
                return SK_DROP;

        sk = __sock_map_lookup_elem(map, key);
        if (unlikely(!sk || !sock_map_redirect_allowed(sk)))
                return SK_DROP;
        if (!(flags & BPF_F_INGRESS) && !sk_is_tcp(sk))
                return SK_DROP;
        if (sk_is_vsock(sk))
                return SK_DROP;

        msg->flags = flags;
        msg->sk_redir = sk;
        return SK_PASS;
}

const struct bpf_func_proto bpf_msg_redirect_map_proto = {
        .func           = bpf_msg_redirect_map,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_CONST_MAP_PTR,
        .arg3_type      = ARG_ANYTHING,
        .arg4_type      = ARG_ANYTHING,
};

struct sock_map_seq_info {
        struct bpf_map *map;
        struct sock *sk;
        u32 index;
};

struct bpf_iter__sockmap {
        __bpf_md_ptr(struct bpf_iter_meta *, meta);
        __bpf_md_ptr(struct bpf_map *, map);
        __bpf_md_ptr(void *, key);
        __bpf_md_ptr(struct sock *, sk);
};

DEFINE_BPF_ITER_FUNC(sockmap, struct bpf_iter_meta *meta,
                     struct bpf_map *map, void *key,
                     struct sock *sk)

static void *sock_map_seq_lookup_elem(struct sock_map_seq_info *info)
{
        if (unlikely(info->index >= info->map->max_entries))
                return NULL;

        info->sk = __sock_map_lookup_elem(info->map, info->index);

        /* can't return sk directly, since that might be NULL */
        return info;
}

static void *sock_map_seq_start(struct seq_file *seq, loff_t *pos)
        __acquires(rcu)
{
        struct sock_map_seq_info *info = seq->private;

        if (*pos == 0)
                ++*pos;

        /* pairs with sock_map_seq_stop */
        rcu_read_lock();
        return sock_map_seq_lookup_elem(info);
}

static void *sock_map_seq_next(struct seq_file *seq, void *v, loff_t *pos)
        __must_hold(rcu)
{
        struct sock_map_seq_info *info = seq->private;

        ++*pos;
        ++info->index;

        return sock_map_seq_lookup_elem(info);
}

static int sock_map_seq_show(struct seq_file *seq, void *v)
        __must_hold(rcu)
{
        struct sock_map_seq_info *info = seq->private;
        struct bpf_iter__sockmap ctx = {};
        struct bpf_iter_meta meta;
        struct bpf_prog *prog;

        meta.seq = seq;
        prog = bpf_iter_get_info(&meta, !v);
        if (!prog)
                return 0;

        ctx.meta = &meta;
        ctx.map = info->map;
        if (v) {
                ctx.key = &info->index;
                ctx.sk = info->sk;
        }

        return bpf_iter_run_prog(prog, &ctx);
}

static void sock_map_seq_stop(struct seq_file *seq, void *v)
        __releases(rcu)
{
        if (!v)
                (void)sock_map_seq_show(seq, NULL);

        /* pairs with sock_map_seq_start */
        rcu_read_unlock();
}

static const struct seq_operations sock_map_seq_ops = {
        .start  = sock_map_seq_start,
        .next   = sock_map_seq_next,
        .stop   = sock_map_seq_stop,
        .show   = sock_map_seq_show,
};

static int sock_map_init_seq_private(void *priv_data,
                                     struct bpf_iter_aux_info *aux)
{
        struct sock_map_seq_info *info = priv_data;

        bpf_map_inc_with_uref(aux->map);
        info->map = aux->map;
        return 0;
}

static void sock_map_fini_seq_private(void *priv_data)
{
        struct sock_map_seq_info *info = priv_data;

        bpf_map_put_with_uref(info->map);
}

static u64 sock_map_mem_usage(const struct bpf_map *map)
{
        u64 usage = sizeof(struct bpf_stab);

        usage += (u64)map->max_entries * sizeof(struct sock *);
        return usage;
}

static const struct bpf_iter_seq_info sock_map_iter_seq_info = {
        .seq_ops                = &sock_map_seq_ops,
        .init_seq_private       = sock_map_init_seq_private,
        .fini_seq_private       = sock_map_fini_seq_private,
        .seq_priv_size          = sizeof(struct sock_map_seq_info),
};

BTF_ID_LIST_SINGLE(sock_map_btf_ids, struct, bpf_stab)
const struct bpf_map_ops sock_map_ops = {
        .map_meta_equal         = bpf_map_meta_equal,
        .map_alloc              = sock_map_alloc,
        .map_free               = sock_map_free,
        .map_get_next_key       = sock_map_get_next_key,
        .map_lookup_elem_sys_only = sock_map_lookup_sys,
        .map_update_elem        = sock_map_update_elem,
        .map_delete_elem        = sock_map_delete_elem,
        .map_lookup_elem        = sock_map_lookup,
        .map_release_uref       = sock_map_release_progs,
        .map_check_btf          = map_check_no_btf,
        .map_mem_usage          = sock_map_mem_usage,
        .map_btf_id             = &sock_map_btf_ids[0],
        .iter_seq_info          = &sock_map_iter_seq_info,
};

struct bpf_shtab_elem {
        struct rcu_head rcu;
        u32 hash;
        struct sock *sk;
        struct hlist_node node;
        u8 key[];
};

struct bpf_shtab_bucket {
        struct hlist_head head;
        spinlock_t lock;
};

struct bpf_shtab {
        struct bpf_map map;
        struct bpf_shtab_bucket *buckets;
        u32 buckets_num;
        u32 elem_size;
        struct sk_psock_progs progs;
        atomic_t count;
};

static inline u32 sock_hash_bucket_hash(const void *key, u32 len)
{
        return jhash(key, len, 0);
}

static struct bpf_shtab_bucket *sock_hash_select_bucket(struct bpf_shtab *htab,
                                                        u32 hash)
{
        return &htab->buckets[hash & (htab->buckets_num - 1)];
}

static struct bpf_shtab_elem *
sock_hash_lookup_elem_raw(struct hlist_head *head, u32 hash, void *key,
                          u32 key_size)
{
        struct bpf_shtab_elem *elem;

        hlist_for_each_entry_rcu(elem, head, node) {
                if (elem->hash == hash &&
                    !memcmp(&elem->key, key, key_size))
                        return elem;
        }

        return NULL;
}

static struct sock *__sock_hash_lookup_elem(struct bpf_map *map, void *key)
{
        struct bpf_shtab *htab = container_of(map, struct bpf_shtab, map);
        u32 key_size = map->key_size, hash;
        struct bpf_shtab_bucket *bucket;
        struct bpf_shtab_elem *elem;

        WARN_ON_ONCE(!rcu_read_lock_held());

        hash = sock_hash_bucket_hash(key, key_size);
        bucket = sock_hash_select_bucket(htab, hash);
        elem = sock_hash_lookup_elem_raw(&bucket->head, hash, key, key_size);

        return elem ? elem->sk : NULL;
}

static void sock_hash_free_elem(struct bpf_shtab *htab,
                                struct bpf_shtab_elem *elem)
{
        atomic_dec(&htab->count);
        kfree_rcu(elem, rcu);
}

static void sock_hash_delete_from_link(struct bpf_map *map, struct sock *sk,
                                       void *link_raw)
{
        struct bpf_shtab *htab = container_of(map, struct bpf_shtab, map);
        struct bpf_shtab_elem *elem_probe, *elem = link_raw;
        struct bpf_shtab_bucket *bucket;

        WARN_ON_ONCE(!rcu_read_lock_held());
        bucket = sock_hash_select_bucket(htab, elem->hash);

        /* elem may be deleted in parallel from the map, but access here
         * is okay since it's going away only after RCU grace period.
         * However, we need to check whether it's still present.
         */
        spin_lock_bh(&bucket->lock);
        elem_probe = sock_hash_lookup_elem_raw(&bucket->head, elem->hash,
                                               elem->key, map->key_size);
        if (elem_probe && elem_probe == elem) {
                hlist_del_rcu(&elem->node);
                sock_map_unref(elem->sk, elem);
                sock_hash_free_elem(htab, elem);
        }
        spin_unlock_bh(&bucket->lock);
}

static long sock_hash_delete_elem(struct bpf_map *map, void *key)
{
        struct bpf_shtab *htab = container_of(map, struct bpf_shtab, map);
        u32 hash, key_size = map->key_size;
        struct bpf_shtab_bucket *bucket;
        struct bpf_shtab_elem *elem;
        int ret = -ENOENT;

        hash = sock_hash_bucket_hash(key, key_size);
        bucket = sock_hash_select_bucket(htab, hash);

        spin_lock_bh(&bucket->lock);
        elem = sock_hash_lookup_elem_raw(&bucket->head, hash, key, key_size);
        if (elem) {
                hlist_del_rcu(&elem->node);
                sock_map_unref(elem->sk, elem);
                sock_hash_free_elem(htab, elem);
                ret = 0;
        }
        spin_unlock_bh(&bucket->lock);
        return ret;
}

static struct bpf_shtab_elem *sock_hash_alloc_elem(struct bpf_shtab *htab,
                                                   void *key, u32 key_size,
                                                   u32 hash, struct sock *sk,
                                                   struct bpf_shtab_elem *old)
{
        struct bpf_shtab_elem *new;

        if (atomic_inc_return(&htab->count) > htab->map.max_entries) {
                if (!old) {
                        atomic_dec(&htab->count);
                        return ERR_PTR(-E2BIG);
                }
        }

        new = bpf_map_kmalloc_node(&htab->map, htab->elem_size,
                                   GFP_ATOMIC | __GFP_NOWARN,
                                   htab->map.numa_node);
        if (!new) {
                atomic_dec(&htab->count);
                return ERR_PTR(-ENOMEM);
        }
        memcpy(new->key, key, key_size);
        new->sk = sk;
        new->hash = hash;
        return new;
}

static int sock_hash_update_common(struct bpf_map *map, void *key,
                                   struct sock *sk, u64 flags)
{
        struct bpf_shtab *htab = container_of(map, struct bpf_shtab, map);
        u32 key_size = map->key_size, hash;
        struct bpf_shtab_elem *elem, *elem_new;
        struct bpf_shtab_bucket *bucket;
        struct sk_psock_link *link;
        struct sk_psock *psock;
        int ret;

        WARN_ON_ONCE(!rcu_read_lock_held());
        if (unlikely(flags > BPF_EXIST))
                return -EINVAL;

        link = sk_psock_init_link();
        if (!link)
                return -ENOMEM;

        ret = sock_map_link(map, sk);
        if (ret < 0)
                goto out_free;

        psock = sk_psock(sk);
        WARN_ON_ONCE(!psock);

        hash = sock_hash_bucket_hash(key, key_size);
        bucket = sock_hash_select_bucket(htab, hash);

        spin_lock_bh(&bucket->lock);
        elem = sock_hash_lookup_elem_raw(&bucket->head, hash, key, key_size);
        if (elem && flags == BPF_NOEXIST) {
                ret = -EEXIST;
                goto out_unlock;
        } else if (!elem && flags == BPF_EXIST) {
                ret = -ENOENT;
                goto out_unlock;
        }

        elem_new = sock_hash_alloc_elem(htab, key, key_size, hash, sk, elem);
        if (IS_ERR(elem_new)) {
                ret = PTR_ERR(elem_new);
                goto out_unlock;
        }

        sock_map_add_link(psock, link, map, elem_new);
        /* Add new element to the head of the list, so that
         * concurrent search will find it before old elem.
         */
        hlist_add_head_rcu(&elem_new->node, &bucket->head);
        if (elem) {
                hlist_del_rcu(&elem->node);
                sock_map_unref(elem->sk, elem);
                sock_hash_free_elem(htab, elem);
        }
        spin_unlock_bh(&bucket->lock);
        return 0;
out_unlock:
        spin_unlock_bh(&bucket->lock);
        sk_psock_put(sk, psock);
out_free:
        sk_psock_free_link(link);
        return ret;
}

static int sock_hash_get_next_key(struct bpf_map *map, void *key,
                                  void *key_next)
{
        struct bpf_shtab *htab = container_of(map, struct bpf_shtab, map);
        struct bpf_shtab_elem *elem, *elem_next;
        u32 hash, key_size = map->key_size;
        struct hlist_head *head;
        int i = 0;

        if (!key)
                goto find_first_elem;
        hash = sock_hash_bucket_hash(key, key_size);
        head = &sock_hash_select_bucket(htab, hash)->head;
        elem = sock_hash_lookup_elem_raw(head, hash, key, key_size);
        if (!elem)
                goto find_first_elem;

        elem_next = hlist_entry_safe(rcu_dereference(hlist_next_rcu(&elem->node)),
                                     struct bpf_shtab_elem, node);
        if (elem_next) {
                memcpy(key_next, elem_next->key, key_size);
                return 0;
        }

        i = hash & (htab->buckets_num - 1);
        i++;
find_first_elem:
        for (; i < htab->buckets_num; i++) {
                head = &sock_hash_select_bucket(htab, i)->head;
                elem_next = hlist_entry_safe(rcu_dereference(hlist_first_rcu(head)),
                                             struct bpf_shtab_elem, node);
                if (elem_next) {
                        memcpy(key_next, elem_next->key, key_size);
                        return 0;
                }
        }

        return -ENOENT;
}

static struct bpf_map *sock_hash_alloc(union bpf_attr *attr)
{
        struct bpf_shtab *htab;
        int i, err;

        if (attr->max_entries == 0 ||
            attr->key_size    == 0 ||
            (attr->value_size != sizeof(u32) &&
             attr->value_size != sizeof(u64)) ||
            attr->map_flags & ~SOCK_CREATE_FLAG_MASK)
                return ERR_PTR(-EINVAL);
        if (attr->key_size > MAX_BPF_STACK)
                return ERR_PTR(-E2BIG);

        htab = bpf_map_area_alloc(sizeof(*htab), NUMA_NO_NODE);
        if (!htab)
                return ERR_PTR(-ENOMEM);

        bpf_map_init_from_attr(&htab->map, attr);

        htab->buckets_num = roundup_pow_of_two(htab->map.max_entries);
        htab->elem_size = sizeof(struct bpf_shtab_elem) +
                          round_up(htab->map.key_size, 8);
        if (htab->buckets_num == 0 ||
            htab->buckets_num > U32_MAX / sizeof(struct bpf_shtab_bucket)) {
                err = -EINVAL;
                goto free_htab;
        }

        htab->buckets = bpf_map_area_alloc(htab->buckets_num *
                                           sizeof(struct bpf_shtab_bucket),
                                           htab->map.numa_node);
        if (!htab->buckets) {
                err = -ENOMEM;
                goto free_htab;
        }

        for (i = 0; i < htab->buckets_num; i++) {
                INIT_HLIST_HEAD(&htab->buckets[i].head);
                spin_lock_init(&htab->buckets[i].lock);
        }

        return &htab->map;
free_htab:
        bpf_map_area_free(htab);
        return ERR_PTR(err);
}

static void sock_hash_free(struct bpf_map *map)
{
        struct bpf_shtab *htab = container_of(map, struct bpf_shtab, map);
        struct bpf_shtab_bucket *bucket;
        struct hlist_head unlink_list;
        struct bpf_shtab_elem *elem;
        struct hlist_node *node;
        int i;

        /* After the sync no updates or deletes will be in-flight so it
         * is safe to walk map and remove entries without risking a race
         * in EEXIST update case.
         */
        synchronize_rcu();
        for (i = 0; i < htab->buckets_num; i++) {
                bucket = sock_hash_select_bucket(htab, i);

                /* We are racing with sock_hash_delete_from_link to
                 * enter the spin-lock critical section. Every socket on
                 * the list is still linked to sockhash. Since link
                 * exists, psock exists and holds a ref to socket. That
                 * lets us to grab a socket ref too.
                 */
                spin_lock_bh(&bucket->lock);
                hlist_for_each_entry(elem, &bucket->head, node)
                        sock_hold(elem->sk);
                hlist_move_list(&bucket->head, &unlink_list);
                spin_unlock_bh(&bucket->lock);

                /* Process removed entries out of atomic context to
                 * block for socket lock before deleting the psock's
                 * link to sockhash.
                 */
                hlist_for_each_entry_safe(elem, node, &unlink_list, node) {
                        hlist_del(&elem->node);
                        lock_sock(elem->sk);
                        rcu_read_lock();
                        sock_map_unref(elem->sk, elem);
                        rcu_read_unlock();
                        release_sock(elem->sk);
                        sock_put(elem->sk);
                        sock_hash_free_elem(htab, elem);
                }
                cond_resched();
        }

        /* wait for psock readers accessing its map link */
        synchronize_rcu();

        bpf_map_area_free(htab->buckets);
        bpf_map_area_free(htab);
}

static void *sock_hash_lookup_sys(struct bpf_map *map, void *key)
{
        struct sock *sk;

        if (map->value_size != sizeof(u64))
                return ERR_PTR(-ENOSPC);

        sk = __sock_hash_lookup_elem(map, key);
        if (!sk)
                return ERR_PTR(-ENOENT);

        __sock_gen_cookie(sk);
        return &sk->sk_cookie;
}

static void *sock_hash_lookup(struct bpf_map *map, void *key)
{
        struct sock *sk;

        sk = __sock_hash_lookup_elem(map, key);
        if (!sk)
                return NULL;
        if (sk_is_refcounted(sk) && !refcount_inc_not_zero(&sk->sk_refcnt))
                return NULL;
        return sk;
}

static void sock_hash_release_progs(struct bpf_map *map)
{
        psock_progs_drop(&container_of(map, struct bpf_shtab, map)->progs);
}

BPF_CALL_4(bpf_sock_hash_update, struct bpf_sock_ops_kern *, sops,
           struct bpf_map *, map, void *, key, u64, flags)
{
        WARN_ON_ONCE(!rcu_read_lock_held());

        if (likely(sock_map_sk_is_suitable(sops->sk) &&
                   sock_map_op_okay(sops)))
                return sock_hash_update_common(map, key, sops->sk, flags);
        return -EOPNOTSUPP;
}

const struct bpf_func_proto bpf_sock_hash_update_proto = {
        .func           = bpf_sock_hash_update,
        .gpl_only       = false,
        .pkt_access     = true,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_CONST_MAP_PTR,
        .arg3_type      = ARG_PTR_TO_MAP_KEY,
        .arg4_type      = ARG_ANYTHING,
};

BPF_CALL_4(bpf_sk_redirect_hash, struct sk_buff *, skb,
           struct bpf_map *, map, void *, key, u64, flags)
{
        struct sock *sk;

        if (unlikely(flags & ~(BPF_F_INGRESS)))
                return SK_DROP;

        sk = __sock_hash_lookup_elem(map, key);
        if (unlikely(!sk || !sock_map_redirect_allowed(sk)))
                return SK_DROP;
        if ((flags & BPF_F_INGRESS) && sk_is_vsock(sk))
                return SK_DROP;

        skb_bpf_set_redir(skb, sk, flags & BPF_F_INGRESS);
        return SK_PASS;
}

const struct bpf_func_proto bpf_sk_redirect_hash_proto = {
        .func           = bpf_sk_redirect_hash,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_CONST_MAP_PTR,
        .arg3_type      = ARG_PTR_TO_MAP_KEY,
        .arg4_type      = ARG_ANYTHING,
};

BPF_CALL_4(bpf_msg_redirect_hash, struct sk_msg *, msg,
           struct bpf_map *, map, void *, key, u64, flags)
{
        struct sock *sk;

        if (unlikely(flags & ~(BPF_F_INGRESS)))
                return SK_DROP;

        sk = __sock_hash_lookup_elem(map, key);
        if (unlikely(!sk || !sock_map_redirect_allowed(sk)))
                return SK_DROP;
        if (!(flags & BPF_F_INGRESS) && !sk_is_tcp(sk))
                return SK_DROP;
        if (sk_is_vsock(sk))
                return SK_DROP;

        msg->flags = flags;
        msg->sk_redir = sk;
        return SK_PASS;
}

const struct bpf_func_proto bpf_msg_redirect_hash_proto = {
        .func           = bpf_msg_redirect_hash,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_CONST_MAP_PTR,
        .arg3_type      = ARG_PTR_TO_MAP_KEY,
        .arg4_type      = ARG_ANYTHING,
};

struct sock_hash_seq_info {
        struct bpf_map *map;
        struct bpf_shtab *htab;
        u32 bucket_id;
};

static void *sock_hash_seq_find_next(struct sock_hash_seq_info *info,
                                     struct bpf_shtab_elem *prev_elem)
{
        const struct bpf_shtab *htab = info->htab;
        struct bpf_shtab_bucket *bucket;
        struct bpf_shtab_elem *elem;
        struct hlist_node *node;

        /* try to find next elem in the same bucket */
        if (prev_elem) {
                node = rcu_dereference(hlist_next_rcu(&prev_elem->node));
                elem = hlist_entry_safe(node, struct bpf_shtab_elem, node);
                if (elem)
                        return elem;

                /* no more elements, continue in the next bucket */
                info->bucket_id++;
        }

        for (; info->bucket_id < htab->buckets_num; info->bucket_id++) {
                bucket = &htab->buckets[info->bucket_id];
                node = rcu_dereference(hlist_first_rcu(&bucket->head));
                elem = hlist_entry_safe(node, struct bpf_shtab_elem, node);
                if (elem)
                        return elem;
        }

        return NULL;
}

static void *sock_hash_seq_start(struct seq_file *seq, loff_t *pos)
        __acquires(rcu)
{
        struct sock_hash_seq_info *info = seq->private;

        if (*pos == 0)
                ++*pos;

        /* pairs with sock_hash_seq_stop */
        rcu_read_lock();
        return sock_hash_seq_find_next(info, NULL);
}

static void *sock_hash_seq_next(struct seq_file *seq, void *v, loff_t *pos)
        __must_hold(rcu)
{
        struct sock_hash_seq_info *info = seq->private;

        ++*pos;
        return sock_hash_seq_find_next(info, v);
}

static int sock_hash_seq_show(struct seq_file *seq, void *v)
        __must_hold(rcu)
{
        struct sock_hash_seq_info *info = seq->private;
        struct bpf_iter__sockmap ctx = {};
        struct bpf_shtab_elem *elem = v;
        struct bpf_iter_meta meta;
        struct bpf_prog *prog;

        meta.seq = seq;
        prog = bpf_iter_get_info(&meta, !elem);
        if (!prog)
                return 0;

        ctx.meta = &meta;
        ctx.map = info->map;
        if (elem) {
                ctx.key = elem->key;
                ctx.sk = elem->sk;
        }

        return bpf_iter_run_prog(prog, &ctx);
}

static void sock_hash_seq_stop(struct seq_file *seq, void *v)
        __releases(rcu)
{
        if (!v)
                (void)sock_hash_seq_show(seq, NULL);

        /* pairs with sock_hash_seq_start */
        rcu_read_unlock();
}

static const struct seq_operations sock_hash_seq_ops = {
        .start  = sock_hash_seq_start,
        .next   = sock_hash_seq_next,
        .stop   = sock_hash_seq_stop,
        .show   = sock_hash_seq_show,
};

static int sock_hash_init_seq_private(void *priv_data,
                                      struct bpf_iter_aux_info *aux)
{
        struct sock_hash_seq_info *info = priv_data;

        bpf_map_inc_with_uref(aux->map);
        info->map = aux->map;
        info->htab = container_of(aux->map, struct bpf_shtab, map);
        return 0;
}

static void sock_hash_fini_seq_private(void *priv_data)
{
        struct sock_hash_seq_info *info = priv_data;

        bpf_map_put_with_uref(info->map);
}

static u64 sock_hash_mem_usage(const struct bpf_map *map)
{
        struct bpf_shtab *htab = container_of(map, struct bpf_shtab, map);
        u64 usage = sizeof(*htab);

        usage += htab->buckets_num * sizeof(struct bpf_shtab_bucket);
        usage += atomic_read(&htab->count) * (u64)htab->elem_size;
        return usage;
}

static const struct bpf_iter_seq_info sock_hash_iter_seq_info = {
        .seq_ops                = &sock_hash_seq_ops,
        .init_seq_private       = sock_hash_init_seq_private,
        .fini_seq_private       = sock_hash_fini_seq_private,
        .seq_priv_size          = sizeof(struct sock_hash_seq_info),
};

BTF_ID_LIST_SINGLE(sock_hash_map_btf_ids, struct, bpf_shtab)
const struct bpf_map_ops sock_hash_ops = {
        .map_meta_equal         = bpf_map_meta_equal,
        .map_alloc              = sock_hash_alloc,
        .map_free               = sock_hash_free,
        .map_get_next_key       = sock_hash_get_next_key,
        .map_update_elem        = sock_map_update_elem,
        .map_delete_elem        = sock_hash_delete_elem,
        .map_lookup_elem        = sock_hash_lookup,
        .map_lookup_elem_sys_only = sock_hash_lookup_sys,
        .map_release_uref       = sock_hash_release_progs,
        .map_check_btf          = map_check_no_btf,
        .map_mem_usage          = sock_hash_mem_usage,
        .map_btf_id             = &sock_hash_map_btf_ids[0],
        .iter_seq_info          = &sock_hash_iter_seq_info,
};

static struct sk_psock_progs *sock_map_progs(struct bpf_map *map)
{
        switch (map->map_type) {
        case BPF_MAP_TYPE_SOCKMAP:
                return &container_of(map, struct bpf_stab, map)->progs;
        case BPF_MAP_TYPE_SOCKHASH:
                return &container_of(map, struct bpf_shtab, map)->progs;
        default:
                break;
        }

        return NULL;
}

static int sock_map_prog_link_lookup(struct bpf_map *map, struct bpf_prog ***pprog,
                                     struct bpf_link ***plink, u32 which)
{
        struct sk_psock_progs *progs = sock_map_progs(map);
        struct bpf_prog **cur_pprog;
        struct bpf_link **cur_plink;

        if (!progs)
                return -EOPNOTSUPP;

        switch (which) {
        case BPF_SK_MSG_VERDICT:
                cur_pprog = &progs->msg_parser;
                cur_plink = &progs->msg_parser_link;
                break;
#if IS_ENABLED(CONFIG_BPF_STREAM_PARSER)
        case BPF_SK_SKB_STREAM_PARSER:
                cur_pprog = &progs->stream_parser;
                cur_plink = &progs->stream_parser_link;
                break;
#endif
        case BPF_SK_SKB_STREAM_VERDICT:
                if (progs->skb_verdict)
                        return -EBUSY;
                cur_pprog = &progs->stream_verdict;
                cur_plink = &progs->stream_verdict_link;
                break;
        case BPF_SK_SKB_VERDICT:
                if (progs->stream_verdict)
                        return -EBUSY;
                cur_pprog = &progs->skb_verdict;
                cur_plink = &progs->skb_verdict_link;
                break;
        default:
                return -EOPNOTSUPP;
        }

        *pprog = cur_pprog;
        if (plink)
                *plink = cur_plink;
        return 0;
}

/* Handle the following four cases:
 * prog_attach: prog != NULL, old == NULL, link == NULL
 * prog_detach: prog == NULL, old != NULL, link == NULL
 * link_attach: prog != NULL, old == NULL, link != NULL
 * link_detach: prog == NULL, old != NULL, link != NULL
 */
static int sock_map_prog_update(struct bpf_map *map, struct bpf_prog *prog,
                                struct bpf_prog *old, struct bpf_link *link,
                                u32 which)
{
        struct bpf_prog **pprog;
        struct bpf_link **plink;
        int ret;

        ret = sock_map_prog_link_lookup(map, &pprog, &plink, which);
        if (ret)
                return ret;

        /* for prog_attach/prog_detach/link_attach, return error if a bpf_link
         * exists for that prog.
         */
        if ((!link || prog) && *plink)
                return -EBUSY;

        if (old) {
                ret = psock_replace_prog(pprog, prog, old);
                if (!ret)
                        *plink = NULL;
        } else {
                psock_set_prog(pprog, prog);
                if (link)
                        *plink = link;
        }

        return ret;
}

int sock_map_bpf_prog_query(const union bpf_attr *attr,
                            union bpf_attr __user *uattr)
{
        __u32 __user *prog_ids = u64_to_user_ptr(attr->query.prog_ids);
        u32 prog_cnt = 0, flags = 0;
        struct bpf_prog **pprog;
        struct bpf_prog *prog;
        struct bpf_map *map;
        u32 id = 0;
        int ret;

        if (attr->query.query_flags)
                return -EINVAL;

        CLASS(fd, f)(attr->target_fd);
        map = __bpf_map_get(f);
        if (IS_ERR(map))
                return PTR_ERR(map);

        rcu_read_lock();

        ret = sock_map_prog_link_lookup(map, &pprog, NULL, attr->query.attach_type);
        if (ret)
                goto end;

        prog = *pprog;
        prog_cnt = !prog ? 0 : 1;

        if (!attr->query.prog_cnt || !prog_ids || !prog_cnt)
                goto end;

        /* we do not hold the refcnt, the bpf prog may be released
         * asynchronously and the id would be set to 0.
         */
        id = data_race(prog->aux->id);
        if (id == 0)
                prog_cnt = 0;

end:
        rcu_read_unlock();

        if (copy_to_user(&uattr->query.attach_flags, &flags, sizeof(flags)) ||
            (id != 0 && copy_to_user(prog_ids, &id, sizeof(u32))) ||
            copy_to_user(&uattr->query.prog_cnt, &prog_cnt, sizeof(prog_cnt)))
                ret = -EFAULT;

        return ret;
}

static void sock_map_unlink(struct sock *sk, struct sk_psock_link *link)
{
        switch (link->map->map_type) {
        case BPF_MAP_TYPE_SOCKMAP:
                return sock_map_delete_from_link(link->map, sk,
                                                 link->link_raw);
        case BPF_MAP_TYPE_SOCKHASH:
                return sock_hash_delete_from_link(link->map, sk,
                                                  link->link_raw);
        default:
                break;
        }
}

static void sock_map_remove_links(struct sock *sk, struct sk_psock *psock)
{
        struct sk_psock_link *link;

        while ((link = sk_psock_link_pop(psock))) {
                sock_map_unlink(sk, link);
                sk_psock_free_link(link);
        }
}

void sock_map_unhash(struct sock *sk)
{
        void (*saved_unhash)(struct sock *sk);
        struct sk_psock *psock;

        rcu_read_lock();
        psock = sk_psock(sk);
        if (unlikely(!psock)) {
                rcu_read_unlock();
                saved_unhash = READ_ONCE(sk->sk_prot)->unhash;
        } else {
                saved_unhash = psock->saved_unhash;
                sock_map_remove_links(sk, psock);
                rcu_read_unlock();
        }
        if (WARN_ON_ONCE(saved_unhash == sock_map_unhash))
                return;
        if (saved_unhash)
                saved_unhash(sk);
}
EXPORT_SYMBOL_GPL(sock_map_unhash);

void sock_map_destroy(struct sock *sk)
{
        void (*saved_destroy)(struct sock *sk);
        struct sk_psock *psock;

        rcu_read_lock();
        psock = sk_psock_get(sk);
        if (unlikely(!psock)) {
                rcu_read_unlock();
                saved_destroy = READ_ONCE(sk->sk_prot)->destroy;
        } else {
                saved_destroy = psock->saved_destroy;
                sock_map_remove_links(sk, psock);
                rcu_read_unlock();
                sk_psock_stop(psock);
                sk_psock_put(sk, psock);
        }
        if (WARN_ON_ONCE(saved_destroy == sock_map_destroy))
                return;
        if (saved_destroy)
                saved_destroy(sk);
}
EXPORT_SYMBOL_GPL(sock_map_destroy);

void sock_map_close(struct sock *sk, long timeout)
{
        void (*saved_close)(struct sock *sk, long timeout);
        struct sk_psock *psock;

        lock_sock(sk);
        rcu_read_lock();
        psock = sk_psock(sk);
        if (likely(psock)) {
                saved_close = psock->saved_close;
                sock_map_remove_links(sk, psock);
                psock = sk_psock_get(sk);
                if (unlikely(!psock))
                        goto no_psock;
                rcu_read_unlock();
                sk_psock_stop(psock);
                release_sock(sk);
                cancel_delayed_work_sync(&psock->work);
                sk_psock_put(sk, psock);
        } else {
                saved_close = READ_ONCE(sk->sk_prot)->close;
no_psock:
                rcu_read_unlock();
                release_sock(sk);
        }

        /* Make sure we do not recurse. This is a bug.
         * Leak the socket instead of crashing on a stack overflow.
         */
        if (WARN_ON_ONCE(saved_close == sock_map_close))
                return;
        saved_close(sk, timeout);
}
EXPORT_SYMBOL_GPL(sock_map_close);

struct sockmap_link {
        struct bpf_link link;
        struct bpf_map *map;
};

static void sock_map_link_release(struct bpf_link *link)
{
        struct sockmap_link *sockmap_link = container_of(link, struct sockmap_link, link);

        mutex_lock(&sockmap_mutex);
        if (!sockmap_link->map)
                goto out;

        WARN_ON_ONCE(sock_map_prog_update(sockmap_link->map, NULL, link->prog, link,
                                          link->attach_type));

        bpf_map_put_with_uref(sockmap_link->map);
        sockmap_link->map = NULL;
out:
        mutex_unlock(&sockmap_mutex);
}

static int sock_map_link_detach(struct bpf_link *link)
{
        sock_map_link_release(link);
        return 0;
}

static void sock_map_link_dealloc(struct bpf_link *link)
{
        kfree(link);
}

/* Handle the following two cases:
 * case 1: link != NULL, prog != NULL, old != NULL
 * case 2: link != NULL, prog != NULL, old == NULL
 */
static int sock_map_link_update_prog(struct bpf_link *link,
                                     struct bpf_prog *prog,
                                     struct bpf_prog *old)
{
        const struct sockmap_link *sockmap_link = container_of(link, struct sockmap_link, link);
        struct bpf_prog **pprog, *old_link_prog;
        struct bpf_link **plink;
        int ret = 0;

        mutex_lock(&sockmap_mutex);

        /* If old prog is not NULL, ensure old prog is the same as link->prog. */
        if (old && link->prog != old) {
                ret = -EPERM;
                goto out;
        }
        /* Ensure link->prog has the same type/attach_type as the new prog. */
        if (link->prog->type != prog->type ||
            link->prog->expected_attach_type != prog->expected_attach_type) {
                ret = -EINVAL;
                goto out;
        }
        if (!sockmap_link->map) {
                ret = -ENOLINK;
                goto out;
        }

        ret = sock_map_prog_link_lookup(sockmap_link->map, &pprog, &plink,
                                        link->attach_type);
        if (ret)
                goto out;

        /* return error if the stored bpf_link does not match the incoming bpf_link. */
        if (link != *plink) {
                ret = -EBUSY;
                goto out;
        }

        if (old) {
                ret = psock_replace_prog(pprog, prog, old);
                if (ret)
                        goto out;
        } else {
                psock_set_prog(pprog, prog);
        }

        bpf_prog_inc(prog);
        old_link_prog = xchg(&link->prog, prog);
        bpf_prog_put(old_link_prog);

out:
        mutex_unlock(&sockmap_mutex);
        return ret;
}

static u32 sock_map_link_get_map_id(const struct sockmap_link *sockmap_link)
{
        u32 map_id = 0;

        mutex_lock(&sockmap_mutex);
        if (sockmap_link->map)
                map_id = sockmap_link->map->id;
        mutex_unlock(&sockmap_mutex);
        return map_id;
}

static int sock_map_link_fill_info(const struct bpf_link *link,
                                   struct bpf_link_info *info)
{
        const struct sockmap_link *sockmap_link = container_of(link, struct sockmap_link, link);
        u32 map_id = sock_map_link_get_map_id(sockmap_link);

        info->sockmap.map_id = map_id;
        info->sockmap.attach_type = link->attach_type;
        return 0;
}

static void sock_map_link_show_fdinfo(const struct bpf_link *link,
                                      struct seq_file *seq)
{
        const struct sockmap_link *sockmap_link = container_of(link, struct sockmap_link, link);
        u32 map_id = sock_map_link_get_map_id(sockmap_link);

        seq_printf(seq, "map_id:\t%u\n", map_id);
        seq_printf(seq, "attach_type:\t%u\n", link->attach_type);
}

static const struct bpf_link_ops sock_map_link_ops = {
        .release = sock_map_link_release,
        .dealloc = sock_map_link_dealloc,
        .detach = sock_map_link_detach,
        .update_prog = sock_map_link_update_prog,
        .fill_link_info = sock_map_link_fill_info,
        .show_fdinfo = sock_map_link_show_fdinfo,
};

int sock_map_link_create(const union bpf_attr *attr, struct bpf_prog *prog)
{
        struct bpf_link_primer link_primer;
        struct sockmap_link *sockmap_link;
        enum bpf_attach_type attach_type;
        struct bpf_map *map;
        int ret;

        if (attr->link_create.flags)
                return -EINVAL;

        map = bpf_map_get_with_uref(attr->link_create.target_fd);
        if (IS_ERR(map))
                return PTR_ERR(map);
        if (map->map_type != BPF_MAP_TYPE_SOCKMAP && map->map_type != BPF_MAP_TYPE_SOCKHASH) {
                ret = -EINVAL;
                goto out;
        }

        sockmap_link = kzalloc_obj(*sockmap_link, GFP_USER);
        if (!sockmap_link) {
                ret = -ENOMEM;
                goto out;
        }

        attach_type = attr->link_create.attach_type;
        bpf_link_init(&sockmap_link->link, BPF_LINK_TYPE_SOCKMAP, &sock_map_link_ops, prog,
                      attach_type);
        sockmap_link->map = map;

        ret = bpf_link_prime(&sockmap_link->link, &link_primer);
        if (ret) {
                kfree(sockmap_link);
                goto out;
        }

        mutex_lock(&sockmap_mutex);
        ret = sock_map_prog_update(map, prog, NULL, &sockmap_link->link, attach_type);
        mutex_unlock(&sockmap_mutex);
        if (ret) {
                bpf_link_cleanup(&link_primer);
                goto out;
        }

        /* Increase refcnt for the prog since when old prog is replaced with
         * psock_replace_prog() and psock_set_prog() its refcnt will be decreased.
         *
         * Actually, we do not need to increase refcnt for the prog since bpf_link
         * will hold a reference. But in order to have less complexity w.r.t.
         * replacing/setting prog, let us increase the refcnt to make things simpler.
         */
        bpf_prog_inc(prog);

        return bpf_link_settle(&link_primer);

out:
        bpf_map_put_with_uref(map);
        return ret;
}

static int sock_map_iter_attach_target(struct bpf_prog *prog,
                                       union bpf_iter_link_info *linfo,
                                       struct bpf_iter_aux_info *aux)
{
        struct bpf_map *map;
        int err = -EINVAL;

        if (!linfo->map.map_fd)
                return -EBADF;

        map = bpf_map_get_with_uref(linfo->map.map_fd);
        if (IS_ERR(map))
                return PTR_ERR(map);

        if (map->map_type != BPF_MAP_TYPE_SOCKMAP &&
            map->map_type != BPF_MAP_TYPE_SOCKHASH)
                goto put_map;

        if (prog->aux->max_rdonly_access > map->key_size) {
                err = -EACCES;
                goto put_map;
        }

        aux->map = map;
        return 0;

put_map:
        bpf_map_put_with_uref(map);
        return err;
}

static void sock_map_iter_detach_target(struct bpf_iter_aux_info *aux)
{
        bpf_map_put_with_uref(aux->map);
}

static struct bpf_iter_reg sock_map_iter_reg = {
        .target                 = "sockmap",
        .attach_target          = sock_map_iter_attach_target,
        .detach_target          = sock_map_iter_detach_target,
        .show_fdinfo            = bpf_iter_map_show_fdinfo,
        .fill_link_info         = bpf_iter_map_fill_link_info,
        .ctx_arg_info_size      = 2,
        .ctx_arg_info           = {
                { offsetof(struct bpf_iter__sockmap, key),
                  PTR_TO_BUF | PTR_MAYBE_NULL | MEM_RDONLY },
                { offsetof(struct bpf_iter__sockmap, sk),
                  PTR_TO_BTF_ID_OR_NULL },
        },
};

static int __init bpf_sockmap_iter_init(void)
{
        sock_map_iter_reg.ctx_arg_info[1].btf_id =
                btf_sock_ids[BTF_SOCK_TYPE_SOCK];
        return bpf_iter_reg_target(&sock_map_iter_reg);
}
late_initcall(bpf_sockmap_iter_init);