[Babel-users] Babeld vs. BIRD [was: Please test master]

[Dave Taht]

On Tue, Sep 25, 2018 at 12:34 AM Christof Schulze
<christof.schulze at gmx.net> wrote:
>
> On Mon, Sep 24, 2018 at 06:52:21PM -0700, Dave Taht wrote:
> >Thank you very much toke!
> >
> >Thus far the bird version is interoperating with 1.8.3 and the other 6
> >babel versions I have deployed, ipv4 and ipv6 just fine. I don't get
> >source specific of course, but after I run it for a bit I'll go beat
> >it up some more with rtod in a controlled environment.
> >
> >Anyway...
> >
> >There is a longstanding kernel behavioral change that both bird and
> >FRR do, that I would like to push back into babeld itself. Here, I
> >withdraw a route:
> >
> >d at dancer:~$ ip route | grep 172.25
> >172.25.0.1 via 172.22.0.172 dev eno1 proto bird metric 32
> >d at dancer:~$ ip route | grep 172.25
> >unreachable 172.25.0.1 proto bird metric 32
> >
> >Note how the metric stays the same?
> >
> >In addition to unreachable, babeld also explicitly changing the kernel
> >metric to INFINITY also, A) makes doing atomic updates impossible.
> >(there's another bug with atomic updates than this, but...) B) It also
> >introduces a window where some other route with a lower metric can
> >still win.
> >
> >babel example:
> >
> >172.25.0.1 via 172.22.0.172 dev eno1 proto babel
> >172.25.0.1 via 172.22.0.172 dev eno1 proto static metric 1024
> >
> >vs:
> >
> >172.25.0.1 via 172.22.0.172 dev eno1 proto static metric 1024
> >unreachable 172.25.0.1  proto babel  metric 4294967295 onlink
> >
> >I don't think there's anything massively in the field that depends on
> >this behavior (? OSX? ?), and I've been bit by this multiple times.
> What exactly are you suggesting? Babeld should not set unreachable when
> removing routes? I have always wondered about that specific behavior of
> babeld.

I was suggesting it should not set the metric to infinity.
"unreachable" is a property independent of metric, at least in linux.

> >unreachable 172.25.0.1  proto babel  metric 4294967295 onlink

>
> Christof
> >
> >PS total aside: does anyone know why class E routes are not exported?
> >
> >241.0.2.0/24 dev eno1 proto kernel scope link src 241.0.2.2
> >
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-- 

Dave Täht
CEO, TekLibre, LLC
http://www.teklibre.com
Tel: 1-669-226-2619