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

[Christof Schulze]

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.

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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