IPv4 route via IPv6 next hop: Netlink: Network unreachable

[Nico Schottelius]

Hello,

I'm running 2.0.7 on Linux 5.4.18-0-lts (Alpine)
and I receive the route 193.228.143.0/24 from
2a0a:e5c0:1:9::2. However it is never set into the kernel, with the
error message "Netlink: Network unreachable" in syslog.

Has anyone seen this problem recently? I'm not sure if this is really a
bird2 problem or not, to be honest:

The kernel reports many messages like this in dmesg:
[4541983.369058] netlink: 'bird': attribute type 5 has an invalid length.

However, I am also puzzled that manually adding the route seems to fail:

[14:44] router1.place6:/var/log# ip route add 193.228.143.0/24 via inet6 2a0a:e5c0:1:9::2
RTNETLINK answers: Invalid argument
[14:45] router1.place6:/var/log# ip route add 193.228.143.0/24 nexthop via inet6 2a0a:e5c0:1:9::2
RTNETLINK answers: Invalid argument
[14:45] router1.place6:/var/log# ip route add 193.228.143.0/24 nexthop via inet6 2a0a:e5c0:1:9::2 dev bond0.25
RTNETLINK answers: Invalid argument
[14:45] router1.place6:/var/log#

bird status:

bird> show route all protocol bluecmd_v6
Table master4:
193.228.143.0/24     unicast [bluecmd_v6 14:31:15.880] ! (100) [AS206858i]
        via 2a0a:e5c0:1:9::2 on bond0.25
        Type: BGP univ
        BGP.origin: IGP
        BGP.as_path: 206858
        BGP.next_hop: 2a0a:e5c0:1:9::2
        BGP.local_pref: 100

Table master6:
2a10:11c0:114::/48   unicast [bluecmd_v6 14:31:15.880] * (100) [AS206858?]
        via 2a0a:e5c0:1:9::2 on bond0.25
        Type: BGP univ
        BGP.origin: Incomplete
        BGP.as_path: 206858
        BGP.next_hop: 2a0a:e5c0:1:9::2 fe80::21c:73ff:fe2c:6eca
        BGP.local_pref: 100
bird>

bird2 config:

protocol bgp bluecmd_v6 {
        local as 209898;
        neighbor 2a0a:e5c0:1:9::2 as 206858;
        direct;

        ipv4 {
            extended next hop;

            import filter from_inside_customer;
            export filter only_default_route;
        };

        ipv6 {
            import filter from_inside_customer;
            export filter only_default_route;
        };

        default bgp_local_pref pref_normal;
}

syslog:

Apr  1 14:31:15 router1 daemon.warn bird: Netlink: Network unreachable
Apr  1 14:31:22 router1 daemon.warn bird: Netlink: Network unreachable
Apr  1 14:31:42 router1 daemon.warn bird: Netlink: Network unreachable
...


Bird / Kernel / etc.:

[14:33] router1.place6:/var/log# bird --version
BIRD version 2.0.7
[14:35] router1.place6:/var/log# uname -a
Linux router1 5.4.18-0-lts #1-Alpine SMP Thu, 06 Feb 2020 09:27:36 UTC x86_64 GNU/Linux
[14:36] router1.place6:/var/log#

For reference is also attached the configuration of the opposite side
(Arista 7050):

router bgp 206858
   vrf PUBLIC
      router-id 193.228.143.0
      neighbor 2a0a:e5c0:1:9::5 remote-as 209898
      neighbor 2a0a:e5c0:1:9::5 next-hop-self
      neighbor 2a0a:e5c0:1:9::5 maximum-routes 0
      !
      address-family ipv4
         bgp next-hop address-family ipv6
         neighbor 2a0a:e5c0:1:9::5 activate
         neighbor 2a0a:e5c0:1:9::5 next-hop address-family ipv6 originate
         network 193.228.143.0/24
      !
      address-family ipv6
         neighbor 2a0a:e5c0:1:9::5 activate
         network 2a10:11c0:114::/48

linthal-core(vrf:PUBLIC)(config-router-bgp-vrf-PUBLIC)#show ipv6 bgp neighbors 2a0a:e5c0:1:9::5 advertised-routes detail

BGP routing table information for VRF PUBLIC
Router identifier 193.228.143.0, local AS number 206858
Update wait-install is disabled
BGP routing table entry for 2a10:11c0:114::/48
 Paths: 1 available
  206858
    2a0a:e5c0:1:9::2 from - (193.228.143.0)
      Origin INCOMPLETE, metric -, localpref -, weight -, valid, local, best
      Rx SAFI: Unicast
BGP routing table entry for 193.228.143.0/24
 Paths: 1 available
  206858
    - from - (193.228.143.0)
      Origin IGP, metric -, localpref -, weight -, valid, local, best
      Rx SAFI: Unicast


Any pointer in the right direction would be appreciated!

Cheers,

Nico


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