From: "Michael S. Tsirkin" <mst@redhat•com>
To: Herbert Xu <herbert@gondor•hengli.com.au>
Cc: David Miller <davem@davemloft•net>,
mirqus@gmail•com, shanwei@cn•fujitsu.com,
mirq-linux@rere•qmqm.pl, netdev@vger•kernel.org,
bhutchings@solarflare•com
Subject: Re: tap/bridge: Dropping NETIF_F_GSO/NETIF_F_SG
Date: Tue, 17 May 2011 08:18:45 +0300 [thread overview]
Message-ID: <20110517051845.GA26414@redhat.com> (raw)
In-Reply-To: <20110516234538.GA11832@gondor.apana.org.au>
On Tue, May 17, 2011 at 09:45:38AM +1000, Herbert Xu wrote:
> On Mon, May 16, 2011 at 07:06:15PM -0400, David Miller wrote:
> >
> > Well the check has to exist somewhere.
> >
> > Currently userspace can configure tun/tap into whatever set
> > of offloads it likes.
> >
> > We're warning when the user asks for something that needs to be
> > corrected. So the only thing you can suggest is to duplicate these
> > changes in the tun/tap driver.
> >
> > But if we do that, and error on bad combinations instead of fixing
> > them up, we know from this discussion that existing virtualization
> > setups and tools are going to stop working.
>
> Yeah the tun driver is simply busted. We should never have allowed
> user-space to tweak the feature bits like this. Instead they should
> have gone through the ethtool interface like everyone else, or at
> least use the same underlying calls as ethtool.
>
> Actually, I think we can still do that, and apply the same rules
> as ethtool with respect to automatically turning things on/off.
>
> AFAICS the current set_offload in tun.c does not call anything
> that verifies/fixes up the settings. If you change the feature
> bits after registering the tun device it may never get fixed up
> at all.
Hmm, we get the warnings about bits dropped on each set_offload
call:
netdev_update_features is called,
that calls netdev_fix_features
No?
> Allowing an unprivileged user to tweak feature bits directly with
> no verification is just wrong.
>
> Cheers,
But we do verify bits, and only allow the user
to tweak these ones:
#define TUN_USER_FEATURES (NETIF_F_HW_CSUM|NETIF_F_TSO_ECN|NETIF_F_TSO|
\
NETIF_F_TSO6|NETIF_F_UFO)
No?
> --
> Email: Herbert Xu <herbert@gondor•apana.org.au>
> Home Page: http://gondor.apana.org.au/~herbert/
> PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
next prev parent reply other threads:[~2011-05-17 5:18 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-04 18:18 tap/bridge: Dropping NETIF_F_GSO/NETIF_F_SG Michael S. Tsirkin
2011-05-04 22:34 ` Herbert Xu
2011-05-04 23:28 ` Michał Mirosław
2011-05-05 0:19 ` Herbert Xu
2011-05-05 8:44 ` Michael S. Tsirkin
2011-05-05 9:34 ` Shan Wei
2011-05-05 10:05 ` Herbert Xu
2011-05-16 7:32 ` Michael S. Tsirkin
2011-05-16 8:07 ` Herbert Xu
2011-05-16 8:18 ` Michael S. Tsirkin
2011-05-16 9:38 ` Herbert Xu
2011-05-16 9:48 ` Michael S. Tsirkin
2011-05-16 10:43 ` Herbert Xu
2011-05-16 11:21 ` Michael S. Tsirkin
2011-05-16 12:18 ` Herbert Xu
2011-05-16 12:24 ` Michał Mirosław
2011-05-16 22:46 ` Herbert Xu
2011-05-16 23:06 ` David Miller
2011-05-16 23:45 ` Herbert Xu
2011-05-17 5:18 ` Michael S. Tsirkin [this message]
2011-05-17 5:24 ` Herbert Xu
2011-05-17 5:48 ` Michael S. Tsirkin
2011-05-17 6:25 ` Herbert Xu
2011-05-17 8:08 ` Michał Mirosław
2011-05-17 8:15 ` Michał Mirosław
2011-05-17 8:19 ` [PATCH] net: tuntap: Fix tun_net_fix_features() Michał Mirosław
2011-05-17 14:29 ` Michael S. Tsirkin
2011-05-17 14:46 ` Michał Mirosław
2011-05-17 14:54 ` Michael S. Tsirkin
2011-05-17 15:00 ` Michał Mirosław
2011-05-17 15:11 ` Michael S. Tsirkin
2011-06-01 9:25 ` Michael S. Tsirkin
2011-06-20 19:14 ` [RESENT PATCH] " Michał Mirosław
2011-06-20 19:25 ` Ben Hutchings
2011-06-20 19:44 ` Michał Mirosław
2011-05-16 10:53 ` tap/bridge: Dropping NETIF_F_GSO/NETIF_F_SG Michał Mirosław
2011-05-16 8:28 ` Michael S. Tsirkin
2011-05-05 15:26 ` Michał Mirosław
2011-05-14 6:54 ` Shan Wei
2011-05-16 7:28 ` Michael S. Tsirkin
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