On Mon, May 27, 2024 at 07:42:03AM +0200, Leif Jakob via Bird-users wrote:

bird version: 2.0.12-7 (Debian stable)

Hi,

I use this config to install BGP routes into the linux kernel:

protocol kernel {   kernel table 300;   scan time 10;   learn on;   graceful restart;   metric 0; # needed to override in filter

  ipv6 {     import none; # kernel->bgp - nothing needed     export filter { # bgp->kernel       if ( proto = "xxx"       ) then { krt_metric = 20; accept; } # lower is choosed first by kernel       if ( proto = "yyy"       ) then { krt_metric = 30; accept; }       reject;     };   }; }

This works fine. But when the route is removed (protocol gets down) it's still in the linux kernel.

Hi Unfortunately, using krt_metric this way is rather unreliable. We set this kernel attribute for route-add operation, and do not set it for route-del operation (which should work like wildcard, assuming that there is only one route for given net with 'proto bird', but it does not work for route-replace operation where the new route has different metric than the old route. In that case the new route is added while old route is kept. We should fix this by forcing add/remove instead of replace in this case. But i would strongly suggest to set metric on per-protocol level with the option 'metric', instead of using krt_metric route attribute. Why do you need this? If you want alien/static routes to override some of BIRD routes but not others, you could import them from kernel to BIRD, make them override other BIRD routes in BIRD table so they would not be exported to kernel. -- Elen sila lumenn' omentielvo Ondrej 'Santiago' Zajicek (email: santiago@crfreenet.org) "To err is human -- to blame it on a computer is even more so."