// SPDX-License-Identifier: GPL-2.0
#include <linux/bpf.h>
#include <bpf/bpf_helpers.h>

char _license[] SEC("license") = "GPL";

#define SOL_CUSTOM                      0xdeadbeef
#define CUSTOM_INHERIT1                 0
#define CUSTOM_INHERIT2                 1
#define CUSTOM_LISTENER                 2

__s32 page_size = 0;

struct sockopt_inherit {
        __u8 val;
};

struct {
        __uint(type, BPF_MAP_TYPE_SK_STORAGE);
        __uint(map_flags, BPF_F_NO_PREALLOC | BPF_F_CLONE);
        __type(key, int);
        __type(value, struct sockopt_inherit);
} cloned1_map SEC(".maps");

struct {
        __uint(type, BPF_MAP_TYPE_SK_STORAGE);
        __uint(map_flags, BPF_F_NO_PREALLOC | BPF_F_CLONE);
        __type(key, int);
        __type(value, struct sockopt_inherit);
} cloned2_map SEC(".maps");

struct {
        __uint(type, BPF_MAP_TYPE_SK_STORAGE);
        __uint(map_flags, BPF_F_NO_PREALLOC);
        __type(key, int);
        __type(value, struct sockopt_inherit);
} listener_only_map SEC(".maps");

static __inline struct sockopt_inherit *get_storage(struct bpf_sockopt *ctx)
{
        if (ctx->optname == CUSTOM_INHERIT1)
                return bpf_sk_storage_get(&cloned1_map, ctx->sk, 0,
                                          BPF_SK_STORAGE_GET_F_CREATE);
        else if (ctx->optname == CUSTOM_INHERIT2)
                return bpf_sk_storage_get(&cloned2_map, ctx->sk, 0,
                                          BPF_SK_STORAGE_GET_F_CREATE);
        else
                return bpf_sk_storage_get(&listener_only_map, ctx->sk, 0,
                                          BPF_SK_STORAGE_GET_F_CREATE);
}

SEC("cgroup/getsockopt")
int _getsockopt(struct bpf_sockopt *ctx)
{
        __u8 *optval_end = ctx->optval_end;
        struct sockopt_inherit *storage;
        __u8 *optval = ctx->optval;

        if (ctx->level != SOL_CUSTOM)
                goto out; /* only interested in SOL_CUSTOM */

        if (optval + 1 > optval_end)
                return 0; /* EPERM, bounds check */

        storage = get_storage(ctx);
        if (!storage)
                return 0; /* EPERM, couldn't get sk storage */

        ctx->retval = 0; /* Reset system call return value to zero */

        optval[0] = storage->val;
        ctx->optlen = 1;

        return 1;

out:
        /* optval larger than PAGE_SIZE use kernel's buffer. */
        if (ctx->optlen > page_size)
                ctx->optlen = 0;
        return 1;
}

SEC("cgroup/setsockopt")
int _setsockopt(struct bpf_sockopt *ctx)
{
        __u8 *optval_end = ctx->optval_end;
        struct sockopt_inherit *storage;
        __u8 *optval = ctx->optval;

        if (ctx->level != SOL_CUSTOM)
                goto out; /* only interested in SOL_CUSTOM */

        if (optval + 1 > optval_end)
                return 0; /* EPERM, bounds check */

        storage = get_storage(ctx);
        if (!storage)
                return 0; /* EPERM, couldn't get sk storage */

        storage->val = optval[0];
        ctx->optlen = -1;

        return 1;

out:
        /* optval larger than PAGE_SIZE use kernel's buffer. */
        if (ctx->optlen > page_size)
                ctx->optlen = 0;
        return 1;
}