linux-stable/include/linux/if_tun.h
David Woodhouse f85ba78068 tun: add IFF_TUN_EXCL flag to avoid opening a persistent device.
When creating a certain types of VPN, NetworkManager will first attempt
to find an available tun device by iterating through 'vpn%d' until it
finds one that isn't already busy. Then it'll set that to be persistent
and owned by the otherwise unprivileged user that the VPN dæmon itself
runs as.

There's a race condition here -- during the period where the vpn%d
device is created and we're waiting for the VPN dæmon to actually
connect and use it, if we try to create _another_ device we could end up
re-using the same one -- because trying to open it again doesn't get
-EBUSY as it would while it's _actually_ busy.

So solve this, we add an IFF_TUN_EXCL flag which causes tun_set_iff() to
fail if it would be opening an existing persistent tundevice -- so that
we can make sure we're getting an entirely _new_ device.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-04-27 03:23:54 -07:00

88 lines
2.8 KiB
C

/*
* Universal TUN/TAP device driver.
* Copyright (C) 1999-2000 Maxim Krasnyansky <max_mk@yahoo.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* 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.
*/
#ifndef __IF_TUN_H
#define __IF_TUN_H
#include <linux/types.h>
#include <linux/if_ether.h>
/* Read queue size */
#define TUN_READQ_SIZE 500
/* TUN device flags */
#define TUN_TUN_DEV 0x0001
#define TUN_TAP_DEV 0x0002
#define TUN_TYPE_MASK 0x000f
#define TUN_FASYNC 0x0010
#define TUN_NOCHECKSUM 0x0020
#define TUN_NO_PI 0x0040
#define TUN_ONE_QUEUE 0x0080
#define TUN_PERSIST 0x0100
#define TUN_VNET_HDR 0x0200
/* Ioctl defines */
#define TUNSETNOCSUM _IOW('T', 200, int)
#define TUNSETDEBUG _IOW('T', 201, int)
#define TUNSETIFF _IOW('T', 202, int)
#define TUNSETPERSIST _IOW('T', 203, int)
#define TUNSETOWNER _IOW('T', 204, int)
#define TUNSETLINK _IOW('T', 205, int)
#define TUNSETGROUP _IOW('T', 206, int)
#define TUNGETFEATURES _IOR('T', 207, unsigned int)
#define TUNSETOFFLOAD _IOW('T', 208, unsigned int)
#define TUNSETTXFILTER _IOW('T', 209, unsigned int)
#define TUNGETIFF _IOR('T', 210, unsigned int)
#define TUNGETSNDBUF _IOR('T', 211, int)
#define TUNSETSNDBUF _IOW('T', 212, int)
/* TUNSETIFF ifr flags */
#define IFF_TUN 0x0001
#define IFF_TAP 0x0002
#define IFF_NO_PI 0x1000
#define IFF_ONE_QUEUE 0x2000
#define IFF_VNET_HDR 0x4000
#define IFF_TUN_EXCL 0x8000
/* Features for GSO (TUNSETOFFLOAD). */
#define TUN_F_CSUM 0x01 /* You can hand me unchecksummed packets. */
#define TUN_F_TSO4 0x02 /* I can handle TSO for IPv4 packets */
#define TUN_F_TSO6 0x04 /* I can handle TSO for IPv6 packets */
#define TUN_F_TSO_ECN 0x08 /* I can handle TSO with ECN bits. */
/* Protocol info prepended to the packets (when IFF_NO_PI is not set) */
#define TUN_PKT_STRIP 0x0001
struct tun_pi {
__u16 flags;
__be16 proto;
};
/*
* Filter spec (used for SETXXFILTER ioctls)
* This stuff is applicable only to the TAP (Ethernet) devices.
* If the count is zero the filter is disabled and the driver accepts
* all packets (promisc mode).
* If the filter is enabled in order to accept broadcast packets
* broadcast addr must be explicitly included in the addr list.
*/
#define TUN_FLT_ALLMULTI 0x0001 /* Accept all multicast packets */
struct tun_filter {
__u16 flags; /* TUN_FLT_ flags see above */
__u16 count; /* Number of addresses */
__u8 addr[0][ETH_ALEN];
};
#endif /* __IF_TUN_H */