[PATCH net v2] wireguard: use tunnel helpers for decapsulating ECN markings

[Toke Høiland-Jørgensen]

"Jason A. Donenfeld" <Jason at zx2c4.com> writes:

> On Mon, Apr 27, 2020 at 3:16 PM Toke Høiland-Jørgensen <toke at redhat.com> wrote:
>>
>> WireGuard currently only propagates ECN markings on tunnel decap according
>> to the old RFC3168 specification. However, the spec has since been updated
>> in RFC6040 to recommend slightly different decapsulation semantics. This
>> was implemented in the kernel as a set of common helpers for ECN
>> decapsulation, so let's just switch over WireGuard to using those, so it
>> can benefit from this enhancement and any future tweaks.
>>
>> RFC6040 also recommends dropping packets on certain combinations of
>> erroneous code points on the inner and outer packet headers which shouldn't
>> appear in normal operation. The helper signals this by a return value > 1,
>> so also add a handler for this case.
>
> Thanks for the details in your other email and for this v2. I've
> applied this to the wireguard tree and will send things up to net
> later this week with a few other things brewing there.

Thanks!

> By the way, the original code came out of a discussion I had with Dave
> Taht while I was coding this on an airplane many years ago. I read
> some old RFCs, made some changes, he tested them with cake, and told
> me that the behavior looked correct. And that's about as far as I've
> forayed into ECN land with WireGuard. It seems like it might be
> helpful (at some point) to add something to the netns.sh test to make
> sure that all this machinery is actually working and continues to work
> properly as things change in the future.

Yeah, good point. I guess I can look into that too at some point :)

-Toke