Re: [Bugme-new] [Bug 9806] New: (tun dev) Impossible to deassert IFF_ONE_QUEUE or IFF_NO_PI

Re: [Bugme-new] [Bug 9806] New: (tun dev) Impossible to deassert IFF_ONE_QUEUE or IFF_NO_PI

[Andrew Morton]

> On Wed, 23 Jan 2008 13:13:13 -0800 (PST) bugme-daemon@bugzilla.kernel.org wrote:
> http://bugzilla.kernel.org/show_bug.cgi?id=9806
> 
>            Summary: (tun dev) Impossible to deassert IFF_ONE_QUEUE or
>                     IFF_NO_PI
>            Product: Drivers
>            Version: 2.5
>      KernelVersion: 2.6.23
>           Platform: All
>         OS/Version: Linux
>               Tree: Mainline
>             Status: NEW
>           Severity: normal
>           Priority: P1
>          Component: Network
>         AssignedTo: jgarzik@pobox.com
>         ReportedBy: nwfilardo@gmail.com
> 
> 
> Problem Description:
> 
> 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).
> 

Thanks.   Could you please submit the patch via email?  Send it to
all recipients of this email.

Re: [Bugme-new] [Bug 9806] New: (tun dev) Impossible to deassert IFF_ONE_QUEUE or IFF_NO_PI

[Nathaniel Filardo]

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On Jan 24, 2008 3:33 AM, Andrew Morton <akpm@linux-foundation.org> wrote:
> > On Wed, 23 Jan 2008 13:13:13 -0800 (PST) bugme-daemon@bugzilla.kernel.org wrote:
> > http://bugzilla.kernel.org/show_bug.cgi?id=9806
> Thanks.   Could you please submit the patch via email?  Send it to
> all recipients of this email.

Attached.
--nwf;

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: tun.patch --]
[-- Type: text/x-diff; name=tun.patch, Size: 381 bytes --]

--- tun.c.orig	2008-01-23 16:09:25.000000000 -0500
+++ tun.c	2008-01-23 16:12:26.000000000 -0500
@@ -540,9 +540,13 @@
 
 	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;