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@xxxxxxxxxxx> 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@xxxxxxxxx>
> net: ipv4: ip_forward: fix inverted local_df test
> [ Upstream commit ca6c5d4ad216d5942ae544bbf02503041bd802aa ]
>
> Or, alternatively, also apply upstream commit 895162b1101b3ea5db08ca6822ae9672717efec0
> Author: Florian Westphal <fw@xxxxxxxxx>
> 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
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