/*      $OpenBSD: if_tun.h,v 1.18 2024/11/17 00:25:07 dlg Exp $ */

/*
 * Copyright (c) 1988, Julian Onions <Julian.Onions@nexor.co.uk>
 * Nottingham University 1987.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef _NET_IF_TUN_H_
#define _NET_IF_TUN_H_

#include <sys/ioccom.h>

/*
 * tun_hdr is a multiple of 4 bytes, but is built out of uint16_t
 * fields. This allows it to sit on a 2 byte boundary in front of
 * either IP (and MPLS) or Ethernet packets for tun(4) and tap(4)
 * interfaces respectively while maintaining the alignment of their
 * payloads.
 *
 * Userland can request the use of the tun_hdr using the TUNSCAP
 * ioctl. This ioctl also allows userland to specify which "offload"
 * capabilities it is able to accept in packets it will read from the
 * kernel. It is acceptable to enable tun_hdr without enabling any
 * interface offload capabilities.
 *
 * Once the tap_hdr is enabled, userland can write packets into the
 * kernel with any of the supported features. tun(4)/tap(4) reads
 * will unconditionally handle any features specified on the packet,
 * regardless of what capabilities were specified by the TUNSCAP
 * ioctl.
 *
 * The tun_hdr can be read from one interface and written directly
 * to another without interpretation or modification.
 *
 * Use of tun_hdr and the associated capabilities are reset when a
 * tun(4)/tap(4) device is closed.
 */

struct tun_hdr {
        uint16_t        th_flags;
#define TUN_H_PRIO_MASK         0x7
#define TUN_H_VTAG              (1 << 4)  /* th_vtag is set */
#define TUN_H_TCP_MSS           (1 << 5)  /* Cut TCP frame up by th_mss */

#define TUN_H_IPV4_CSUM         (1 << 8)
#define TUN_H_TCP_CSUM          (1 << 9)
#define TUN_H_UDP_CSUM          (1 << 10)
#define TUN_H_ICMP_CSUM         (1 << 11)

        uint16_t        th_pad;

        uint16_t        th_vtag;
        uint16_t        th_mss;
};

#define TUN_OPEN        0x0001
#define TUN_INITED      0x0002
#define TUN_RCOLL       0x0004  /* unused */
#define TUN_IASET       0x0008
#define TUN_DSTADDR     0x0010
#define TUN_RWAIT       0x0040
#define TUN_ASYNC       0x0080
#define TUN_NBIO        0x0100
#define TUN_BRDADDR     0x0200
#define TUN_STAYUP      0x0400
#define TUN_LAYER2      0x0800

#define TUN_READY       (TUN_OPEN | TUN_INITED)

/* Maximum packet size */
#define TUNMTU          3000

/* Maximum receive packet size (hard limit) */
#define TUNMRU          16384

/* iface info */
struct tuninfo {
        u_int   mtu;
        u_short type;
        u_short flags;
        u_int   baudrate;
};
#define TUNSIFINFO      _IOW('t', 91, struct tuninfo)
#define TUNGIFINFO      _IOR('t', 92, struct tuninfo)

/* ioctl for changing the broadcast/point-to-point status */
#define TUNSIFMODE      _IOW('t', 93, int)

/* ioctl's for get/set debug */
#define TUNSDEBUG       _IOW('t', 94, int)
#define TUNGDEBUG       _IOR('t', 95, int)

struct tun_capabilities {
        uint32_t        tun_if_capabilities; /* IFCAP_* from net/if.h */
};

#define TUNSCAP         _IOW('t', 196, struct tun_capabilities)
#define TUNGCAP         _IOR('t', 196, struct tun_capabilities)
#define TUNDCAP         _IO('t', 196)

#endif /* _NET_IF_TUN_H_ */