[WireGuard] fq, ecn, etc with wireguard

[Dave Taht]

I cited the wrong ecn draft:

https://tools.ietf.org/id/draft-ietf-tsvwg-ecn-tunnel-10.txt

Despite the complexity of the draft, basically copying the inner ecn
bits to the outer header on encaps, and or-ing ecn bits to inner
header (except when 00s) on decaps, seems to be the "right thing",
nowadays.


On Sat, Aug 27, 2016 at 2:03 PM, Dave Taht <dave.taht at gmail.com> wrote:
> I have been running a set of tinc based vpns for a long time now, and
> based on the complexity of the codebase, and some general flakyness
> and slowness, I am considering fiddling with wireguard for a
> replacement of it. The review of it over on
> https://plus.google.com/+gregkroahhartman/posts/NoGTVYbBtiP?hl=en was
> pretty inspiring.
>
> My principal work is on queueing algorithms (like fq_codel, and cake),
> and what I'm working on now is primarily adding these algos to wifi,
> but I do need a working vpn, and have longed to improve latency and
> loss recovery on vpns for quite some time now.
>
> A) does wireguard handle ecn encapsulation/decapsulation?
>
> https://tools.ietf.org/html/draft-ietf-tsvwg-ecn-encap-guidelines-07
>
> Doing ecn "right" through vpn with a bottleneck router with a fq_codel
> enabled qdisc allows for zero induced packet loss and good congestion
> control.
>
> B) I see that "noqueue" is the default qdisc for wireguard. What is
> the maximum outstanding queue depth held internally? How is it
> configured? I imagine it is a strict fifo queue, and that wireguard
> bottlenecks on the crypto step and drops on reads... eventually.
> Managing the queue length looks to be helpful especially in the
> openwrt/lede case.
>
> (we have managed to successfully apply something fq_codel-like within
> the mac80211 layer, see various blog entries of mine and the ongoing
> work on the make-wifi-fast mailing list)
>
> So managing the inbound queue for wireguard well, to hold induced
> latencies down to bare minimums when going from 1Gbit to XMbit, and
> it's bottlenecked on wireguard, rather than an external router, is on
> my mind. Got a pretty nice hammer in the fq_codel code, not sure why
> you have noqueue as the default.
>
> C) One flaw of fq_codel , is that multiplexing multiple outbound flows
> over a single connection endpoint degrades that aggregate flow to
> codel's behavior, and the vpn "flow" competes evenly with all other
> flows. A classic pure aqm solution would be more fair to vpn
> encapsulated flows than fq_codel is.
>
> An answer to that would be to expose "fq" properties to the underlying
> vpn protocol. For example, being able to specify an endpoint
> identifier of 2001:db8:1234::1/118:udp_port would allow for a one to
> one mapping for external fq_codel queues to internal vpn queues, and
> thus vpn traffic would compete equally with non-vpn traffic at the
> router. While this does expose more per flow information, the
> corresponding decrease for e2e latency under load, especially for
> "sparse" flows, like voip and dns, strikes me as a potential major win
> (and one way to use up a bunch of ipv6 addresses in a good cause).
> Doing that "right" however probably involves negotiating perfect
> forward secrecy for a ton of mostly idle channels (with a separate
> seqno base for each), (but I could live with merely having a /123 on
> the task)
>
> C1) (does the current codebase work with ipv6?)
>
> D) my end goal would be to somehow replicate the meshy characteristics
> of tinc, and choosing good paths through multiple potential
> connections, leveraging source specific routing and another layer 3
> routing protocol like babel, but I do grok that doing that right would
> take a ton more work...
>
> Anyway, I'll go off and read some more docs and code to see if I can
> answer a few of these questions myself. I am impressed by what little
> I understand so far.
>
> --
> Dave Täht
> Let's go make home routers and wifi faster! With better software!
> http://blog.cerowrt.org



-- 
Dave Täht
Let's go make home routers and wifi faster! With better software!
http://blog.cerowrt.org