FUSE does not map functions to linux commands for network share

Using Debian 11 kernel 5.10.

I try to make fuse linux kernel library getting to work.

When I use "mkdir" in terminal for mounted path it says "function no implemented", e.g. mkdir /drv/drive1/test

Same message was for curlftpfs for "ls" command (and any command like mkdir, rm, ls returns input/ouput error) but it's problem with FTP and not fuse. On the FTP server side it logs "Command LIST -a" and 550 response code - "Couldn't open the file or directory" (FTP server runs on Windows - FileZilla FTP Server). Although connecting to FTP with FTP client for same credentials works fine (it does not use LIST command, instead - CWD). For this reason I decided to write my own network share over ftp but may there is solution to this curlftpfs issue?

Here's the C++ code (without FTP part), what am I missing?:

#define FUSE_USE_VERSION 30
#include <fuse.h>
#include <iostream>

static const char* mount_point = "/drv/drive1";
static int success = 0;

static int my_mkdir(const char* path, mode_t mode)
{
    std::cout << "called mkdir" << std::endl;

    int res = mkdir(path, mode);

    if (res == -1)
    {
        perror("mkdir err");
    }

    return res;
}

static void* my_init(fuse_conn_info*)
{
    std::cout << "init" << std::endl;

    struct fuse_context* ctx = fuse_get_context();
    ctx->private_data = &success;

    return &success;
}

static struct fuse_operations my_operations = {
    .mkdir = my_mkdir,
    .init = my_init
};

int main(int argc, char* argv[])
{
    struct fuse_args args = FUSE_ARGS_INIT(0, nullptr);
    struct fuse_chan* ch = fuse_mount(mount_point, &args);

    if (ch == nullptr)
    {
        std::cerr << "Failed to mount FUSE filesystem" << std::endl;
        return 1;
    }

    struct fuse* session = fuse_new(ch, &args, &my_operations, sizeof(my_operations), nullptr);

    int res = fuse_loop(session);

    fuse_unmount(mount_point, ch);
    fuse_destroy(session);
    fuse_opt_free_args(&args);

    return 0;
}

The 'my_init' works fine, logs in console unlike 'my_mkdir'.

Installed 'libfuse-dev' and 'libfuse3-dev' packages.

I also tried writing it in Rust and the message was "input/output error" and functions of Filesystem trait were probably not executed (fuse crate, newest version).

First using curlftpfs - got error and do not know why it is not working, may just because FTP server is running under Windows and not Linux? (so that LIST -a ftp command either does not work or is not supported?)

Then writing simplified version in Rust - again, not working but at the level of fuse crate.

Then moved to C++ as it is lower-level and closer to kernel, so may it will be fine - again, not working properly.

You can enable "debug" option in your fuse mount to see exactly which internal file operation is failing.

I would guess you need to implement some minimal set of operations such as .getattr. I recommend for you to take a fuse example program from libfuse, compile and run it, and start modifying in small steps to implement your desired fs.