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| author | David Woodhouse <David.Woodhouse@intel.com> | 2009-04-27 03:23:54 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2009-04-27 03:23:54 -0700 |
| commit | f85ba78068ac137fe9c1f50d25405d2783d75c77 (patch) | |
| tree | 68325fa489b07db5cf7311b79e9e245ed02e5d9a /include/linux/if_tun.h | |
| parent | 0456b4f8b742006c2b79fcbe6b0736aa1ad39180 (diff) | |
| download | lwn-f85ba78068ac137fe9c1f50d25405d2783d75c77.tar.gz lwn-f85ba78068ac137fe9c1f50d25405d2783d75c77.zip | |
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>
Diffstat (limited to 'include/linux/if_tun.h')
| -rw-r--r-- | include/linux/if_tun.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/if_tun.h b/include/linux/if_tun.h index 049d6c9428db..915ba5789f0e 100644 --- a/include/linux/if_tun.h +++ b/include/linux/if_tun.h @@ -55,6 +55,7 @@ #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. */ |