IGP Metric to MED

[Corban Johnson]

Hello,
I am trying to set MED on a BGP route using the metric value from OSPF, but the attributes of the next-hop route do not seem to be available in filter evolution. Am I missing something?

Example Bird 2.0 config:

protocol bgp test_peer {                                     
 bfd on;
 med metric on;
 graceful restart on;
 ipv4 {
   table test_table;
   gateway recursive;
 };
 local as 65656;
}

protocol ospf t1_igp {
 ipv4 {
   table test_table;
 };
}


OSPF is distributing loopbacks and link nets only. BGP protocols from ‘test_peer’ will use routes learned from ‘t1_igp’ in ‘test_table’ to resolve next hop information (gateway recursive). So far, so good.

However, I also have an eBGP peer (i.e. who is not participating in my IGP above) who is multi homed with AS65656. I would like to use MED to inform the peer about my IGP distances to each exit — something like the ‘metric-out minimum-igp <offset>’ command in Junos (https://www.juniper.net/documentation/en_US/junos/topics/reference/configuration-statement/metric-out-edit-protocols-bgp.html):

> You can increase or decrease the variable metric calculated from the IGP metric (either from the igp or minimum-igp statement) by specifying a value for offset. The metric is increased by specifying a positive value for offset, and decreased by specifying a negative value for offset.

The problem seems to be that filters may only access attributes of the route currently processed, and the 'gateway recursive’ channel directive only calculates next-hop without passing any route attributes of that next-hop through.

Has anyone had any luck trying something similar?

Many thanks.