default route via OSPF depending on the ISP

[Rohrmann Sascha]

Dear users of the Bird internet routing  daemon,

First of all I am sorry for my e-mail which I have sent some minutes before.
It was a mistake and you can ignore my last mail.

Now to my question:

I want my OSPF to distribute the default-route ONLY and ONLY if the ISP is available.
Means, if the link, or the IP isn't available, my OSPF should be quite.
Further information:

ISP                         (ISP is up)
  l                            (Link is up)
R1                          (Interface is up)

R1: everything is ok, I can reach the ISP, so I am the default-gateway for everybody below me.

ISP                         (ISP is down)
  l                            (Link is up)
R1                          (Interface is up)

R1: Oh gosh! The ISP is down! I am now no longer the default-gateway for everybody below me.

ISP                         (ISP is up)
  l                            (Link is down)
R1                          (Interface is up)

R1: Oh, I can't reach my ISP... Ok, I need to stop telling everybody below me I am the default-gateway.

I was thinking about the bfd protocol, but bfd is kinda new and you can't run more than one instance in bird.
So I need another solution...
Btw, yes I've already searched for these problem in the mailing list but I am not satisfied.
Either my keywords were wrong or there isn't any person with this kind of problem... yet.
Thank you very much for reading.

Regards.
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