Constant delete / add route after upgrade to 1.6.3

[Xavier Trilla]

Hi Maria,

For what I'm seeing, looks like every time birds gets a route update via BGP the route is replaced, I enabled debug in kernel protocol and I'm seeing this:

2018-05-08 22:20:32 <TRACE> icewall_01_BGP > added [best] 80.84.147.0/24 via 172.17.0.1 on vlan10
2018-05-08 22:20:32 <TRACE> icewall_01_BGP < rejected by protocol 80.84.147.0/24 via 172.17.0.1 on vlan10
2018-05-08 22:20:32 <TRACE> kernel1 < replaced 80.84.147.0/24 via 172.17.0.1 on vlan10
2018-05-08 22:20:32 <TRACE> icewall_01_BGP > added [best] 78.40.178.0/24 via 172.17.0.1 on vlan10
2018-05-08 22:20:32 <TRACE> icewall_01_BGP < rejected by protocol 78.40.178.0/24 via 172.17.0.1 on vlan10
2018-05-08 22:20:32 <TRACE> kernel1 < replaced 78.40.178.0/24 via 172.17.0.1 on vlan10
2018-05-08 22:20:32 <TRACE> icewall_01_BGP > added [best] 64.17.246.0/23 via 172.17.0.1 on vlan10
2018-05-08 22:20:32 <TRACE> icewall_01_BGP < rejected by protocol 64.17.246.0/23 via 172.17.0.1 on vlan10
2018-05-08 22:20:32 <TRACE> kernel1 < replaced 64.17.246.0/23 via 172.17.0.1 on vlan10


But does it make sense? I mean, deleting and reading the route to replace it when a route update is received doesn't seem to make much sense considering the gateway does not change.

Also, I guess removing and adding the route again could lead to some packet loss.

Maybe bird needs to keep some information in the route in order to keep sync and that's why it needs to replace it? Or there is anything I'm missing...

Cheers!

Saludos Cordiales,
Xavier Trilla P.
Clouding.io

¿Un Servidor Cloud con SSDs, redundado
y disponible en menos de 30 segundos?

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-----Mensaje original-----
De: Maria Jan Matějka <jan.matejka at nic.cz> 
Enviado el: martes, 8 de mayo de 2018 16:24
Para: bird-users at network.cz; Xavier Trilla <xavier.trilla at clouding.io>; bird-users at network.cz
Asunto: RE: Constant delete / add route after upgrade to 1.6.3

On May 8, 2018 3:44:20 PM GMT+02:00, Xavier Trilla <xavier.trilla at clouding.io> wrote:
> Hi,
> 
> Some extra Info: I've changed the scan time from 20 to 60 on the 
> kernel and the CPU load on the machine has reduced, but I still see 
> too many route changes.
> 
> Thanks!
> 
> 
> Saludos Cordiales,
> Xavier Trilla P.
> Clouding.io<https://clouding.io/>
> 
> ¿Un Servidor Cloud con SSDs, redundado y disponible en menos de 30 
> segundos?
> 
> ¡Pruébalo ahora en Clouding.io<https://clouding.io/>!
> 
> De: Bird-users <bird-users-bounces at network.cz> En nombre de Xavier 
> Trilla Enviado el: martes, 8 de mayo de 2018 14:02
> Para: bird-users at network.cz
> Asunto: Constant delete / add route after upgrade to 1.6.3
> 
> Hi,
> 
> We've upgraded recently to 1.6.3 (We were using 1.2.5, which we had 
> running for like 8 years!) and after the upgraded we are seeing a 
> weird behavior.
> 
> When running ip monitor route in the machine, looks like bird is 
> constantly removing and adding routes, which could be considered 
> normal, but the thing is that it deletes a route and then adds the 
> same route again (Those routes are received via BGP):
> 
> Heres an example:
> 
> 103.72.2.0/24 via 91.126.95.153 dev vlan111  proto bird Deleted 
> 103.72.1.0/24 via 91.126.95.153 dev vlan111  proto bird
> 103.72.1.0/24 via 91.126.95.153 dev vlan111  proto bird Deleted 
> 177.75.72.0/24 via 91.126.95.153 dev vlan111  proto bird
> 177.75.72.0/24 via 91.126.95.153 dev vlan111  proto bird Deleted 
> 185.165.122.0/24 via 91.126.95.153 dev vlan111  proto bird
> 185.165.122.0/24 via 91.126.95.153 dev vlan111  proto bird Deleted 
> 196.46.242.0/24 via 91.126.95.153 dev vlan111  proto bird
> 196.46.242.0/24 via 91.126.95.153 dev vlan111  proto bird Deleted 
> 64.70.30.0/24 via 91.126.95.153 dev vlan111  proto bird
> 64.70.30.0/24 via 212.80.191.185 dev vlan2  proto bird
> 
> At the same time we are seeing the following messages on bird log:
> 
> May  8 13:56:39 icewall-01 bird: Kernel dropped some netlink messages, 
> will resync on next scan.
> May  8 13:57:02 icewall-01 bird: Kernel dropped some netlink messages, 
> will resync on next scan.
> May  8 13:57:27 icewall-01 bird: Kernel dropped some netlink messages, 
> will resync on next scan.
> May  8 13:57:32 icewall-01 bird: Kernel dropped some netlink messages, 
> will resync on next scan.
> May  8 13:57:59 icewall-01 bird: Kernel dropped some netlink messages, 
> will resync on next scan.
> 
> Any ideas why this might be happening?
> 
> Thanks!
> 
> Saludos Cordiales,
> Xavier Trilla P.
> Clouding.io<https://clouding.io/>
> 
> ¿Un Servidor Cloud con SSDs, redundado y disponible en menos de 30 
> segundos?
> 
> ¡Pruébalo ahora en Clouding.io<https://clouding.io/>!

Hello, have you tried to switch on BGP protocol tracing? Aren't the routes really sent in this way? Haven't you seen some protocol going up and down repeatedly or something like that?

This all is to find out whether the routes are flapping on the input side or in the kernel binding in BIRD.

The error message is just a warning that the buffer between kernel and BIRD has overflown which may be due to high cpu load -- but it has to be due to something.

Could you please also send your config to see whether it can be seen from it directly?

Thanks!
Maria