diff options
authorDavid Woodhouse <David.Woodhouse@intel.com>2009-04-27 03:23:54 -0700
committerDavid S. Miller <davem@davemloft.net>2009-04-27 03:23:54 -0700
commitf85ba78068ac137fe9c1f50d25405d2783d75c77 (patch)
parent0456b4f8b742006c2b79fcbe6b0736aa1ad39180 (diff)
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>
2 files changed, 3 insertions, 0 deletions
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 589f0ca668d..94622e5fb93 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -874,6 +874,8 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
dev = __dev_get_by_name(net, ifr->ifr_name);
if (dev) {
+ if (ifr->ifr_flags & IFF_TUN_EXCL)
+ return -EBUSY;
if ((ifr->ifr_flags & IFF_TUN) && dev->netdev_ops == &tun_netdev_ops)
tun = netdev_priv(dev);
else if ((ifr->ifr_flags & IFF_TAP) && dev->netdev_ops == &tap_netdev_ops)
diff --git a/include/linux/if_tun.h b/include/linux/if_tun.h
index 049d6c9428d..915ba5789f0 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. */