Bug#625914: [Bridge] Bug#625914: linux-image-2.6.38-2-amd64: bridging is not interacting well with multicast in 2.6.38-4
On Tue, 10 May 2011 11:05:40 -0700
Noah Meyerhans <noahm@debian.org> wrote:
> On Tue, May 10, 2011 at 01:42:49PM +0100, Ben Hutchings wrote:
> > > > This is pretty weird. Debian version 2.6.38-3 has a few bridging
> > > > changes from stable 2.6.38.3 and 2.6.38.4, but they don't look like they
> > > > would cause this.
> > >
> > > I have apparently filed the bug against the wrong version of Debian's
> > > kernel. 2.6.38-3 is not affected, and works as expected. The change
> > > was introduced in -4. That may have been clear from the report itself,
> > > but the report was filed against -3. I've fixed that in the BTS.
> >
> > I gathered that, and then made the same mistake in writing the above!
> > The version with the regression, 2.6.38-4, includes the changes from
> > stable 2.6.38.3 and 2.6.38.4
>
> With a little help from git bisect, I've tracked this regression down to
> the following commit to the stable-2.6.38.y tree:
>
> commit 5f1c356a3fadc0c19922d660da723b79bcc9aad7
> Author: Herbert Xu <herbert@gondor.apana.org.au>
> Date: Fri Mar 18 05:27:28 2011 +0000
>
> bridge: Reset IPCB when entering IP stack on NF_FORWARD
>
> [ Upstream commit 6b1e960fdbd75dcd9bcc3ba5ff8898ff1ad30b6e ]
>
> Whenever we enter the IP stack proper from bridge netfilter we
> need to ensure that the skb is in a form the IP stack expects
> it to be in.
>
> The entry point on NF_FORWARD did not meet the requirements of
> the IP stack, therefore leading to potential crashes/panics.
>
> This patch fixes the problem.
>
> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
> Acked-by: Stephen Hemminger <shemminger@vyatta.com>
> Signed-off-by: David S. Miller <davem@davemloft.net>
> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
>
> The diff is
> diff --git a/net/bridge/br_netfilter.c b/net/bridge/br_netfilter.c
> index 4b5b66d..49d50ea 100644
> --- a/net/bridge/br_netfilter.c
> +++ b/net/bridge/br_netfilter.c
> @@ -741,6 +741,9 @@ static unsigned int br_nf_forward_ip(unsigned int
> hook, struct sk_buff *skb,
> nf_bridge->mask |= BRNF_PKT_TYPE;
> }
>
> + if (br_parse_ip_options(skb))
> + return NF_DROP;
> +
> /* The physdev module checks on this */
> nf_bridge->mask |= BRNF_BRIDGED;
> nf_bridge->physoutdev = skb->dev;
>
> If I revert this change, network connectivity functions as expected for
> the VMs on this host.
>
> I don't know enough about this change or the problem it was supposed to
> solve to be able to guess about what's going wrong.
>
> noah
>
There were two more follow on commits in stable related to this.
I recommend merging 2.6.38.6 which includes these.
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