Re: Linux 3.4.92 breaks forwarding with netfilter enabled

Re: Linux 3.4.92 breaks forwarding with netfilter enabled

[Jiri Slaby]

On 06/11/2014 12:03 AM, Florian Westphal wrote:
> [ stable specific regression.  I wanted to CC stable@ on my reply below
>   but I fat-fingered the address... ]
> 
>> On Tue, Jun 10, 2014 at 12:43 PM, Egerváry Gergely <gergely@egervary.hu> wrote:
>>> Hi,
>>>
>>> we have just upgraded our systems from 3.4.91 (longterm) to 3.4.92.
>>> Since then we are experiencing dozens of MTU-related network timeout
>>> issues. Reverting back to 3.4.91 fixes all of these problems.
>>>
>>> Both kernel versions are built from vanilla sources with the same
>>> .config. These can be highly reproduced over VPN tunnels or even over
>>> simple ethernet connections when using DNAT. (TCP port forward) It
>>> looks like MTU path discovery is somehow affected.
>>>
>>> ICMP is not filtered in our network. (For testing, we flushed all
>>> iptables rules, set all policies to ACCEPT, and problem still exists.)
>>> We do not use any special sysctl settings. Was there any changes
>>> related to packet forwarding or MTU discovery?
> 
> These were in earlier releases than 3.4.92.
> 
>> some combination of old kernel and backport of ("net: ipv4:
>> ip_forward: fix inverted local_df test") ?
>> just guessing
> 
> Excellent guess.  Yes, this is the culprit.
> 
> Quoting that patch changelog:
> 
> 'This wasn't noticed earlier [..] because netfilter ip defrag did not set local_df
> until couple of days ago.'
> 
> -stable lacks commit 895162b1101b3ea5db08ca6822ae9672717efec0, so
> netfilter never sets ->local_df.  Thus all defragmented packets
> that go over the mtu are refused to be forwarded.
> 
> Gergely, please either revert
> 
> commit bd91cb56f951a7b0da8c3098ea9cd56854ece66c
> Author: Florian Westphal <fw@strlen.de>
> net: ipv4: ip_forward: fix inverted local_df test
> [ Upstream commit ca6c5d4ad216d5942ae544bbf02503041bd802aa ]
> 
> Or, alternatively, also apply upstream commit 895162b1101b3ea5db08ca6822ae9672717efec0
> Author: Florian Westphal <fw@strlen.de>
> Date:   Fri May 2 15:32:16 2014 +0200
> netfilter: ipv4: defrag: set local_df flag on defragmented skb
> 
> on top of your 3.4.92 kernel.
> 
> (The latter might be a better option since it will also fix the
>  long-standing issue where netfilter sends bogus frag-needed message
>  under very rare circumstances).

I believe, the same holds for 3.12, right? (I have just applied "defrag:
set local_df flag on defragmented skb".)

thanks,
-- 
js
suse labs

Re: Linux 3.4.92 breaks forwarding with netfilter enabled

[Florian Westphal]

Jiri Slaby <jslaby@suse.cz> wrote:
> > Gergely, please either revert
> > 
> > commit bd91cb56f951a7b0da8c3098ea9cd56854ece66c
> > Author: Florian Westphal <fw@strlen.de>
> > net: ipv4: ip_forward: fix inverted local_df test
> > [ Upstream commit ca6c5d4ad216d5942ae544bbf02503041bd802aa ]
> > 
> > Or, alternatively, also apply upstream commit 895162b1101b3ea5db08ca6822ae9672717efec0
> > Author: Florian Westphal <fw@strlen.de>
> > Date:   Fri May 2 15:32:16 2014 +0200
> > netfilter: ipv4: defrag: set local_df flag on defragmented skb
> > 
> > on top of your 3.4.92 kernel.
> > 
> > (The latter might be a better option since it will also fix the
> >  long-standing issue where netfilter sends bogus frag-needed message
> >  under very rare circumstances).
> 
> I believe, the same holds for 3.12, right? (I have just applied "defrag:
> set local_df flag on defragmented skb".)

Yes, its true for all -stable kernels (except new 3.15).

Thanks for taking care of this.

Re: Linux 3.4.92 breaks forwarding with netfilter enabled

[Guillaume Morin]

On 11 Jun 10:10, Florian Westphal wrote:
>
> Jiri Slaby <jslaby@suse.cz> wrote:
> > > Gergely, please either revert
> > > 
> > > commit bd91cb56f951a7b0da8c3098ea9cd56854ece66c
> > > Author: Florian Westphal <fw@strlen.de>
> > > net: ipv4: ip_forward: fix inverted local_df test
> > > [ Upstream commit ca6c5d4ad216d5942ae544bbf02503041bd802aa ]
> > > 
> > > Or, alternatively, also apply upstream commit 895162b1101b3ea5db08ca6822ae9672717efec0
> > > Author: Florian Westphal <fw@strlen.de>
> > > Date:   Fri May 2 15:32:16 2014 +0200
> > > netfilter: ipv4: defrag: set local_df flag on defragmented skb
> > > 
> > > on top of your 3.4.92 kernel.
> > > 
> > > (The latter might be a better option since it will also fix the
> > >  long-standing issue where netfilter sends bogus frag-needed message
> > >  under very rare circumstances).
> > 
> > I believe, the same holds for 3.12, right? (I have just applied "defrag:
> > set local_df flag on defragmented skb".)
> 
> Yes, its true for all -stable kernels (except new 3.15).
> 
> Thanks for taking care of this.

Greg, could you apply this one to 3.4,3.10,3.14 as well please?

Or do have concerns about it?

Thanks,

Guillaume.

-- 
Guillaume Morin <guillaume@morinfr.org>

Re: Linux 3.4.92 breaks forwarding with netfilter enabled

[Greg KH]

On Thu, Jun 12, 2014 at 07:25:16PM +0200, Guillaume Morin wrote:
> On 11 Jun 10:10, Florian Westphal wrote:
> >
> > Jiri Slaby <jslaby@suse.cz> wrote:
> > > > Gergely, please either revert
> > > > 
> > > > commit bd91cb56f951a7b0da8c3098ea9cd56854ece66c
> > > > Author: Florian Westphal <fw@strlen.de>
> > > > net: ipv4: ip_forward: fix inverted local_df test
> > > > [ Upstream commit ca6c5d4ad216d5942ae544bbf02503041bd802aa ]
> > > > 
> > > > Or, alternatively, also apply upstream commit 895162b1101b3ea5db08ca6822ae9672717efec0
> > > > Author: Florian Westphal <fw@strlen.de>
> > > > Date:   Fri May 2 15:32:16 2014 +0200
> > > > netfilter: ipv4: defrag: set local_df flag on defragmented skb
> > > > 
> > > > on top of your 3.4.92 kernel.
> > > > 
> > > > (The latter might be a better option since it will also fix the
> > > >  long-standing issue where netfilter sends bogus frag-needed message
> > > >  under very rare circumstances).
> > > 
> > > I believe, the same holds for 3.12, right? (I have just applied "defrag:
> > > set local_df flag on defragmented skb".)
> > 
> > Yes, its true for all -stable kernels (except new 3.15).
> > 
> > Thanks for taking care of this.
> 
> Greg, could you apply this one to 3.4,3.10,3.14 as well please?

I just did that :)

thanks,

greg k-h