Wireguard & hw flow offload incompatibility

[Jason A. Donenfeld]

Hi Jaap,

Thanks for the clarification. I downloaded the binary for that
hardware and triaged where the bug occurs [1]. This patch [2] should
probably fix it, but I'm rather surprised to see situations in which a
skb is missing a dst entry in ndo_start_xmit; this might point to
deeper kernel bugs in this hardware offloading feature, or some
alternative mechanism for routing being used when hardware offloading
is on. So I'm hesitant to merge this just yet, because perhaps this is
better handled in the compat layer, if it is in fact vendor silliness.
Do you have a link to the kernel source of these boxes? I'd like to
see what exactly the vendor is doing. And if you could try [2] and see
if that still crashes, this would be most appreciated.

Thanks,
Jason

[1] https://data.zx2c4.com/openwrt-mips-offloading-bug.png
[2] https://א.cc/Am4tZ0n8

On Tue, May 29, 2018 at 1:59 PM, Jaap Buurman <jaapbuurman at gmail.com> wrote:
> Dear Jason,
>
> This isn't a regression. This is simply the first time this has been
> observed. (hw) flow offload is a new feature, and hence this
> interaction with wireguard is also new.
>
> Yours sincerely,
>
> Jaap
>
> On Tue, May 29, 2018 at 1:54 PM, Jason A. Donenfeld <Jason at zx2c4.com> wrote:
>> Hi Jaap,
>>
>> Thanks for the report. Is this a _new_ bug in _new_ version of
>> WireGuard that wasn't there before. Or is this the first time you've
>> observed this?
>>
>> Thanks,
>> Jason

============ Original Mail ==============

> Dear all,
>
> When running a wireguard interface on the latest Lede master branch,
> the router will crash as soon as traffic hits the wireguard interface
> while (hw) flow offloading is enabled. I am not sure whether this is a
> bug with wireguard, hw flow offload, both or neither, so I am
> reporting the bug to both mailinglists. A more detailed description
> plus a properly formatted stack trace can be found on Lede's bug
> tracker: https://bugs.openwrt.org/index.php?do=details&task_id=1539
>
> If you require any additional information, please do not hesitate to
> contact me. Thank you very much in advance.
>
> Yours sincerely,
>
> Jaap Buurman