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/*
* OpenVPN -- An application to securely tunnel IP networks
* over a single UDP port, with support for SSL/TLS-based
* session authentication and key exchange,
* packet encryption, packet authentication, and
* packet compression.
*
* Copyright (C) 2002-2021 OpenVPN Inc <sales@openvpn.net>
* 2019 Lev Stipakov <lev@openvpn.net>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#ifdef _WIN32
#ifndef OPENVPN_RING_BUFFER_H
#define OPENVPN_RING_BUFFER_H
#include <windows.h>
#include <winioctl.h>
#include <stdint.h>
#include <stdbool.h>
/*
* Values below are taken from Wireguard Windows client
* https://github.com/WireGuard/wireguard-go/blob/master/tun/wintun/ring_windows.go#L14
*/
#define WINTUN_RING_CAPACITY 0x800000
#define WINTUN_RING_TRAILING_BYTES 0x10000
#define WINTUN_MAX_PACKET_SIZE 0xffff
#define WINTUN_PACKET_ALIGN 4
#define TUN_IOCTL_REGISTER_RINGS CTL_CODE(51820U, 0x970U, METHOD_BUFFERED, FILE_READ_DATA | FILE_WRITE_DATA)
/**
* Wintun ring buffer
* See https://github.com/WireGuard/wintun#ring-layout
*/
struct tun_ring
{
volatile ULONG head;
volatile ULONG tail;
volatile LONG alertable;
UCHAR data[WINTUN_RING_CAPACITY + WINTUN_RING_TRAILING_BYTES];
};
/**
* Struct for ring buffers registration
* See https://github.com/WireGuard/wintun#registering-rings
*/
struct tun_register_rings
{
struct
{
ULONG ring_size;
struct tun_ring *ring;
HANDLE tail_moved;
} send, receive;
};
struct TUN_PACKET_HEADER
{
uint32_t size;
};
struct TUN_PACKET
{
uint32_t size;
UCHAR data[WINTUN_MAX_PACKET_SIZE];
};
/**
* Registers ring buffers used to exchange data between
* userspace openvpn process and wintun kernel driver,
* see https://github.com/WireGuard/wintun#registering-rings
*
* @param device handle to opened wintun device
* @param send_ring pointer to send ring
* @param receive_ring pointer to receive ring
* @param send_tail_moved event set by wintun to signal openvpn
* that data is available for reading in send ring
* @param receive_tail_moved event set by openvpn to signal wintun
* that data has been written to receive ring
* @return true if registration is successful, false otherwise - use GetLastError()
*/
static bool
register_ring_buffers(HANDLE device,
struct tun_ring *send_ring,
struct tun_ring *receive_ring,
HANDLE send_tail_moved,
HANDLE receive_tail_moved)
{
struct tun_register_rings rr;
BOOL res;
DWORD bytes_returned;
ZeroMemory(&rr, sizeof(rr));
rr.send.ring = send_ring;
rr.send.ring_size = sizeof(struct tun_ring);
rr.send.tail_moved = send_tail_moved;
rr.receive.ring = receive_ring;
rr.receive.ring_size = sizeof(struct tun_ring);
rr.receive.tail_moved = receive_tail_moved;
res = DeviceIoControl(device, TUN_IOCTL_REGISTER_RINGS, &rr, sizeof(rr),
NULL, 0, &bytes_returned, NULL);
return res != FALSE;
}
#endif /* ifndef OPENVPN_RING_BUFFER_H */
#endif /* ifdef _WIN32 */
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