2010-06-16 08:51:24

by Tom Hughes

[permalink] [raw]
Subject: [PATCH] Clear IFF_XMIT_DST_RELEASE for teql interfaces

The sch_teql module, which can be used to load balance over a set of
underlying interfaces, stopped working after 2.6.30 and has been
broken in all kernels since then for any underlying interface which
requires the addition of link level headers.

The problem is that the transmit routine relies on being able to
access the destination address in the skb in order to do address
resolution once it has decided which underlying interface it is going
to transmit through.

In 2.6.31 the IFF_XMIT_DST_RELEASE flag was introduced, and set by
default for all interfaces, which causes the destination address to be
released before the transmit routine for the interface is called.

The solution is to clear that flag for teql interfaces.

Signed-off-by: Tom Hughes <[email protected]>
---
net/sched/sch_teql.c | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/net/sched/sch_teql.c b/net/sched/sch_teql.c
index 3415b6c..807643b 100644
--- a/net/sched/sch_teql.c
+++ b/net/sched/sch_teql.c
@@ -449,6 +449,7 @@ static __init void teql_master_setup(struct net_device *dev)
dev->tx_queue_len = 100;
dev->flags = IFF_NOARP;
dev->hard_header_len = LL_MAX_HEADER;
+ dev->priv_flags &= ~IFF_XMIT_DST_RELEASE;
}

static LIST_HEAD(master_dev_list);
--
1.7.0.1


2010-06-16 13:25:48

by jamal

[permalink] [raw]
Subject: Re: [PATCH] Clear IFF_XMIT_DST_RELEASE for teql interfaces

On Wed, 2010-06-16 at 09:24 +0100, Tom Hughes wrote:
> The sch_teql module, which can be used to load balance over a set of
> underlying interfaces, stopped working after 2.6.30 and has been
> broken in all kernels since then for any underlying interface which
> requires the addition of link level headers.
>
> The problem is that the transmit routine relies on being able to
> access the destination address in the skb in order to do address
> resolution once it has decided which underlying interface it is going
> to transmit through.
>
> In 2.6.31 the IFF_XMIT_DST_RELEASE flag was introduced, and set by
> default for all interfaces, which causes the destination address to be
> released before the transmit routine for the interface is called.
>
> The solution is to clear that flag for teql interfaces.
>
> Signed-off-by: Tom Hughes <[email protected]>

Sounds reasonable. Lets CC Eric and get his ACK.

cheers,
jamal

2010-06-16 14:14:27

by Eric Dumazet

[permalink] [raw]
Subject: Re: [PATCH] Clear IFF_XMIT_DST_RELEASE for teql interfaces

Le mercredi 16 juin 2010 à 09:25 -0400, jamal a écrit :
> On Wed, 2010-06-16 at 09:24 +0100, Tom Hughes wrote:
> > The sch_teql module, which can be used to load balance over a set of
> > underlying interfaces, stopped working after 2.6.30 and has been
> > broken in all kernels since then for any underlying interface which
> > requires the addition of link level headers.
> >
> > The problem is that the transmit routine relies on being able to
> > access the destination address in the skb in order to do address
> > resolution once it has decided which underlying interface it is going
> > to transmit through.
> >
> > In 2.6.31 the IFF_XMIT_DST_RELEASE flag was introduced, and set by
> > default for all interfaces, which causes the destination address to be
> > released before the transmit routine for the interface is called.
> >
> > The solution is to clear that flag for teql interfaces.
> >
> > Signed-off-by: Tom Hughes <[email protected]>
>
> Sounds reasonable. Lets CC Eric and get his ACK.
>
> cheers,
> jamal
>

Sure, I already Acked in on a previous message 5 days ago (although not
a formal patch, Stephen forwarded a bugzilla entry)

http://permalink.gmane.org/gmane.linux.network/163688

Please David, could you add bugzilla entry in commit ?

https://bugzilla.kernel.org/show_bug.cgi?id=16183

Acked-by: Eric Dumazet <[email protected]>

Thanks !

2010-06-16 21:47:38

by David Miller

[permalink] [raw]
Subject: Re: [PATCH] Clear IFF_XMIT_DST_RELEASE for teql interfaces

From: Eric Dumazet <[email protected]>
Date: Wed, 16 Jun 2010 16:14:20 +0200

> Please David, could you add bugzilla entry in commit ?
>
> https://bugzilla.kernel.org/show_bug.cgi?id=16183
>
> Acked-by: Eric Dumazet <[email protected]>

Done and applied, thanks everyone.