How to pipe ipv6 channel into ipv6 channel or possible alternatives

[Nick Cao]

I'm trying to use babel (namely, with the ipv6 sadr channel) together with bgp, and thus I got route from both channels to be installed into kernel.
But the limitation of kernel protocol dictates that I seem to have no choice other than separate the routes into different kernel routing tables, then use ip rules to take them into effect.
However I found some interesting discussion in the mailing list (https://bird.network.cz/pipermail/bird-users/2017-May/011277.html),
indicating that we can convert (or pipe) ipv6 channel into ipv6 sadr channel, which, sadly still has't made it's way into bird as far as I know.
I'd like to ask whether there's some way to mimic that sort of behavior, or is there any alternative to that so that ipv6 sadr channel can play nicely with the ipv6 channel.

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Nick Cao <nickcao at nichi.co>