From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [PATCH] net: tuntap: Fix tun_net_fix_features()
Date: Tue, 17 May 2011 17:29:43 +0300
Message-ID: <20110517142943.GA926@redhat.com>
References: <20110516081841.GA8073@redhat.com>
 <20110516093822.GA2779@gondor.apana.org.au>
 <20110516094821.GA9427@redhat.com>
 <20110516104309.GA3534@gondor.apana.org.au>
 <20110516112133.GA11274@redhat.com>
 <20110516121857.GA4495@gondor.apana.org.au>
 <BANLkTi=7i=AQfPNBEGcLFieaO9wXgBk6rg@mail.gmail.com>
 <20110516224658.GA11157@gondor.apana.org.au>
 <BANLkTimeRLQ0FLASsLE+ZxiXOk4gHt5XFQ@mail.gmail.com>
 <20110517081954.A227013A6A@rere.qmqm.pl>
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: QUOTED-PRINTABLE
Cc: netdev@vger.kernel.org, Herbert Xu <herbert@gondor.hengli.com.au>,
	Ben Hutchings <bhutchings@solarflare.com>,
	Shan Wei <shanwei@cn.fujitsu.com>
To: =?utf-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= <mirq-linux@rere.qmqm.pl>
Return-path: <netdev-owner@vger.kernel.org>
Received: from mx1.redhat.com ([209.132.183.28]:8943 "EHLO mx1.redhat.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1755238Ab1EQO3n (ORCPT <rfc822;netdev@vger.kernel.org>);
	Tue, 17 May 2011 10:29:43 -0400
Content-Disposition: inline
In-Reply-To: <20110517081954.A227013A6A@rere.qmqm.pl>
Sender: netdev-owner@vger.kernel.org
List-ID: <netdev.vger.kernel.org>

On Tue, May 17, 2011 at 10:19:54AM +0200, Micha=C5=82 Miros=C5=82aw wro=
te:
> tun->set_features are meant to limit not force the features.
>=20
> Signed-off-by: Micha=C5=82 Miros=C5=82aw <mirq-linux@rere.qmqm.pl>
> ---
>  drivers/net/tun.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>=20
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index 74e9405..f77c6d0 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -458,7 +458,7 @@ static u32 tun_net_fix_features(struct net_device=
 *dev, u32 features)
>  {
>  	struct tun_struct *tun =3D netdev_priv(dev);
> =20
> -	return (features & tun->set_features) | (features & ~TUN_USER_FEATU=
RES);
> +	return features & (tun->set_features | ~TUN_USER_FEATURES);
>  }
> =20
>  static const struct net_device_ops tun_netdev_ops =3D {
> --=20
> 1.7.2.5

One thing that this will do though: previously, if
ethtool disables offloads, then an application enables
them, the application will have the last say.
With this patch, the most conservative approach wins.
Right?
If we want to have the existing behaviour
I think the following would do this (untested). What do you think?


diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 74e9405..1d6c7bc 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1199,6 +1199,8 @@ static int set_offload(struct tun_struct *tun, un=
signed long arg)
 		return -EINVAL;
=20
 	tun->set_features =3D features;
+	tun->dev->features &=3D TUN_USER_FEATURES;
+	tun->dev->features |=3D (features & TUN_USER_FEATURES);
 	netdev_update_features(tun->dev);
=20
 	return 0;