The patch titled
     tun: impossible to deassert IFF_ONE_QUEUE or IFF_NO_PI
has been added to the -mm tree.  Its filename is
     tun-dev-impossible-to-deassert-iff_one_queue-or-iff_no_pi.patch

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See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this

The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/

------------------------------------------------------
Subject: tun: impossible to deassert IFF_ONE_QUEUE or IFF_NO_PI
From: "Nathaniel Filardo" <[EMAIL PROTECTED]>

Taken from http://bugzilla.kernel.org/show_bug.cgi?id=9806

The TUN/TAP driver only permits one-way transitions of IFF_NO_PI or
IFF_ONE_QUEUE during the lifetime of a tap/tun interface.  Note that
tun_set_iff contains

 541         if (ifr->ifr_flags & IFF_NO_PI)
 542                 tun->flags |= TUN_NO_PI;
 543 
 544         if (ifr->ifr_flags & IFF_ONE_QUEUE)
 545                 tun->flags |= TUN_ONE_QUEUE;

This is easily fixed by adding else branches which clear these bits.

Steps to reproduce:

This is easily reproduced by setting an interface persistant using tunctl then
attempting to open it as IFF_TAP or IFF_TUN, without asserting the IFF_NO_PI
flag.  The ioctl() will succeed and the ifr.flags word is not modified, but the
interface remains in IFF_NO_PI mode (as it was set by tunctl).

Cc: "David S. Miller" <[EMAIL PROTECTED]>
Cc: Jeff Garzik <[EMAIL PROTECTED]>
Cc: Maxim Krasnyansky <[EMAIL PROTECTED]>
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
---

 drivers/net/tun.c |    4 ++++
 1 file changed, 4 insertions(+)

diff -puN 
drivers/net/tun.c~tun-dev-impossible-to-deassert-iff_one_queue-or-iff_no_pi 
drivers/net/tun.c
--- 
a/drivers/net/tun.c~tun-dev-impossible-to-deassert-iff_one_queue-or-iff_no_pi
+++ a/drivers/net/tun.c
@@ -529,9 +529,13 @@ static int tun_set_iff(struct file *file
 
        if (ifr->ifr_flags & IFF_NO_PI)
                tun->flags |= TUN_NO_PI;
+       else
+               tun->flags &= ~TUN_NO_PI;
 
        if (ifr->ifr_flags & IFF_ONE_QUEUE)
                tun->flags |= TUN_ONE_QUEUE;
+       else
+               tun->flags &= ~TUN_ONE_QUEUE;
 
        file->private_data = tun;
        tun->attached = 1;
_

Patches currently in -mm which might be from [EMAIL PROTECTED] are

tun-dev-impossible-to-deassert-iff_one_queue-or-iff_no_pi.patch

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