New "channels" feature in future version of Bird?

[Baptiste Jonglez]

On Fri, Jun 17, 2016 at 01:40:45PM +0200, Jan Matejka wrote:
> First of all, thank your for your question. It's good to know that the
> rework is really watched by the community.

I am interested in BGP multiprotocol support (to potentially implement a
new NLRI), and it looks like a good idea to base this work on the
integrated version.

> Import and export filters should stay as they were before. The
> "channels" feature is just an internal abstraction layer between routing
> tables and protocols. It was the best way chosen by us to allow
> protocols connect to several tables at once, like multiprotocol BGP.
> 
> In the configuration, the only change worth mentioning is that your old
> config
> 
> protocol bgp { table t1; import ...; export ...; igp table it; ... }
> 
> should change to something like
> 
> protocol bgp {
> ipv4 { table t1; import ...; export ...; };
> ipv6 { table t2; import ...; export ...; };
> vpn4 { ... };
> igp ipv4 table it4;
> igp ipv6 table it6;
> ...
> }
> 
> No replacing of filters is planned for the integrated version, at least
> in near future.

Great, thanks for the clear explanation!  I was struggling with the new
syntax, now it's clearer.

It seems that the BGP part is not yet implemented?

Also, the currently supported protocols (OSPF, radvd, RIP, static, kernel)
only support one channel per protocol instance, is that done for
simplicity?  The new syntax is a bit contrived in this case, especially
because the name of the protocol sometimes already defines the "protocol"
(ipv4/ipv6).  For instance with OSPF:

    protocol ospf { ipv6; area 0 {}; }
    → bird.conf, line 27: Different channel type

    protocol ospf3 { ipv4; area 0 {}; }
    → bird.conf, line 27: Different channel type

Multiple channels per protocol instance would only be needed for Bird
protocols that handle multiple "protocols" in the same instance (BGP, as
in your example, or Babel).

Thanks,
Baptiste
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