Hello Arne,

Am Wed, 25 Mar 2020 12:50:34 +0100
schrieb Arne Schwabe <a...@rfc2549.org>:
> > 1) Do you run automated tests of the OpenVPN code on any build
> > server? 
> > 
> > 2) If that is the case, is there any test with a version, where 
> >    -DVERIFY_ALIGNMENT is enabled?
> > 
> I never heard of this option and Google does not want to spit
> something out for me for that.

That's a #define in the OpenVPN code, for example in
src/openvpn/buffer.h line 943 ;-)
> Compression adds a one byte header in the packet making it all
> unaligned. The newer lz4 with swap, or v2 compression methods try to
> avoid this misaligned, mainly for speed on platforms where unaligned
> access comes with a penality.

Yes, so I think, that the size of the payload of the sent ICMP-Pings
over the Tunnel changes, if the LZO compression kicks in for this
packet or not.
> I think there might still be unaligned access that are in the code
> but I am not sure how to debug them. Is there an easy way to
> reproduce them? Can a RPI configured to throw those warnings?

Yes, just compile OpenVPN with the additional 

Then increase verbositiy of the logs to 14 and grep the log for "ERROR"
Of course you have to enable --comp-lzo

RPI? You mean Raspberry PI?
Maybe on this machine the problem is not a problem. We also use OpenVPN
2.4.7 on a ARMv7, and there is no obvious problem, just on the old

Finding all problematic places in the code will still be difficult.


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