Using bfd {} casues error messages

[David Petera]

Hello,

On 8/8/24 13:10, Nico Schottelius via Bird-users wrote:
> Salut fellow bird users,
>
> we recently tried to simplify the bfd configuration and replaced our
> existing configuration with the following:
>
> --------------------------------------------------------------------------------
> # Using BFD virtually everywhere, enable it globally
> protocol bfd { }
>
> ...
> protocol bgp incoming_r3ge {
>      local as myas;
>      direct;
>      bfd on;
> ...
> --------------------------------------------------------------------------------
>
> And now bird repots every second the following message:
>
> --------------------------------------------------------------------------------
> 2024-08-08 11:00:15.727 <ERR> bfd1: Socket error: Destination address required
> --------------------------------------------------------------------------------
>
> The router has various interfaces, some tunnel, some wireguard tunnel,
> some bridges, etc. and I have a bit trouble to spot, what is causing the
> error message.
>
> All interfaces that are used for BGP obviously have an IP address , but
> many bfd sessions are actually down that I'd expect to be up:
>
> --------------------------------------------------------------------------------
> bird> show bfd sessions
> bfd1:
> IP address                Interface  State      Since         Interval  Timeout
> 2a0a:e5c0:10:1:fa5e:3cff:fe2d:eb04 eth0       Down       2024-08-06      1.000    0.000
> 2a0a:5480:5:2::1          or3ge      Down       2024-08-06      1.000    0.000
> 2a0a:e5c0:10:1::123       eth0       Up         2024-08-06      0.100    0.500
> 2a0a:e5c0:10:1:fa5e:3cff:fe2d:eafc eth0       Down       2024-08-06      1.000    0.000
> 2a0a:e5c0:32:1::1         oserver121 Down       2024-08-06      1.000    0.000
> 2a0a:e5c0:142:2::2        iserver138 Down       2024-08-06      1.000    0.000
> 2a0a:e5c0:142:3::2        iapured2   Down       2024-08-06      1.000    0.000
> 2a0a:e5c0:43:2::1         oserver138 Down       2024-08-06      1.000    0.000
> 2a0a:e5c0:142:1::2        ir3ge      Down       2024-08-06      1.000    0.000
> 2a0a:e5c0:10:1::141       eth0       Up         2024-08-06      0.100    0.500
> 2a0a:e5c0:10:1::122       eth0       Up         2024-08-06      0.100    0.500
> bird>
> --------------------------------------------------------------------------------
>
> (excluding the two 2a0a:e5c0:10:1:.. ones, they don't have bfd enabled
> at the moment)
>
> Is using protocol bfd {} actually *not* supported?
>
> Best regards,
>
> Nico
>

have you made any revelations connected to this issue?

Do I understand it correctly that the BGP sessions are up but 
the respective BFD sessions are down?
I have encountered this kind of behavior when one side of the iBGP had 
been configured with 'direct' and the other was not, so maybe just 
double check if that is not the cause of the problem as well.

If not I would need additional information to be able to recreate it. 
What version of BIRD are you running? The previous BFD config might help 
if it was working as intended.
Also tracking down which socket is causing the errors would be very 
helpful (and if it happens to be Wireguard or such, the config and rough 
topology of it would be appreciated).

Thanks and have a nice day,
David

-- 
– David Petera (he/him) | BIRD Tech Support | CZ.NIC, z.s.p.o.