esp-idf/components/lwip/port/vfs_lwip.c

// Copyright 2017 Espressif Systems (Shanghai) PTE LTD
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include <string.h>
#include <stdbool.h>
#include <stdarg.h>
#include <sys/errno.h>
#include <sys/lock.h>
#include <sys/fcntl.h>
#include "esp_vfs.h"
#include "esp_vfs_dev.h"
#include "esp_attr.h"
#include "soc/uart_struct.h"
#include "lwip/sockets.h"
#include "sdkconfig.h"

/* LWIP is a special case for VFS use.

   From the LWIP side:
   - We set LWIP_SOCKET_OFFSET dynamically at VFS registration time so that native LWIP socket functions & VFS functions
   see the same fd space. This is necessary to mix POSIX file operations defined in VFS with POSIX socket operations defined
   in LWIP, without needing to wrap all of them.

   From the VFS side:
   - ESP_VFS_FLAG_SHARED_FD_SPACE is set, so unlike other VFS implementations the FDs that the LWIP "VFS" sees and the
   FDs that the user sees are the same FDs.
*/

int lwip_socket_offset;

static int lwip_fcntl_r_wrapper(int fd, int cmd, va_list args);
static int lwip_ioctl_r_wrapper(int fd, int cmd, va_list args);

void esp_vfs_lwip_sockets_register()
{
    esp_vfs_t vfs = {
        .flags = ESP_VFS_FLAG_DEFAULT | ESP_VFS_FLAG_SHARED_FD_SPACE,
        .write = &lwip_write_r,
        .open = NULL,
        .fstat = NULL,
        .close = &lwip_close_r,
        .read = &lwip_read_r,
        .fcntl = &lwip_fcntl_r_wrapper,
        .ioctl = &lwip_ioctl_r_wrapper,
    };
    int max_fd;

    ESP_ERROR_CHECK(esp_vfs_register_socket_space(&vfs, NULL, &lwip_socket_offset, &max_fd));

    /* LWIP can't be allowed to create more sockets than fit in the per-VFS fd space. Currently this isn't configurable
     * but it's set much larger than CONFIG_LWIP_MAX_SOCKETS should ever be (max 2^12 FDs).
     */
    assert(max_fd >= lwip_socket_offset && CONFIG_LWIP_MAX_SOCKETS <= max_fd - lwip_socket_offset);
}

static int lwip_fcntl_r_wrapper(int fd, int cmd, va_list args)
{
    return lwip_fcntl_r(fd, cmd, va_arg(args, int));
}

static int lwip_ioctl_r_wrapper(int fd, int cmd, va_list args)
{
    return lwip_ioctl_r(fd, cmd, va_arg(args, void *));
}