IPv6 BGP & kernel 4.19

[Andrew Hearn]

On 20/06/2019 17:13, Benedikt Neuffer wrote:
> Hi,
> 
> On 19.06.19 20:09, Alarig Le Lay wrote:
>> Hi,
>>
>> On mer. 19 juin 09:10:53 2019, Robert Sander wrote:
>>> Hi,
>>>
>>> our routers run on Debian stretch with bird 1.6.4 from
>>> bird.network.cz/debian.
>>>
>>> Yesterday I tried kernel 4.19 from backports.debian.org and ran into a
>>> weird issue with IPv6 BGP sessions:
>>>
>>> All Peerings reported "Error: Hold timer expired" ca. every 40 minutes.
>>>
>>> IPv6 forwarding was flapping all the time.
>>>
>>> After rebooting into kernel 4.9 everything worked again.
>>>
>>> IPv4 BGP was not affected and also OSPF (v4 and v6). I could disable all
>>> IPv6 BGP peerings on this router and then it forwarded to another router
>>> learned via OSPF for IPv6 without issues.
>>>
>>> Has anyone seen such a behaviour?
>>
>> I’ve seen this with 4.19 on gentoo. For now I’m still running 4.14.
>> https://archives.gentoo.org/gentoo-user/message/fab628cc53e4a55589410f9dff6abd23
>>
> 
> Same here. Gentoo, Linux 4.19.52, Bird 2.0.4. I am running a full table
> using a separate VRF and the default table as management VRF.
> 
> Without traffic through the box (all IPv6 prefixes filtered) the bgp
> sessions is stable. With traffic the bgp session dies after some time
> and ssh connections in the default table freezes.
> 
> I did some packet captures and saw tcp retransmissions before hold timer
> expires.
> 
> Kernel 4.14.127 is here stable, too. Sadly I have no time for a kernel
> bisect until September. (And no glue where to start and how to trigger
> the bug faster.)

Sorry to bring up a fairly old thread...

We believe we are seeing this problem too, since a Stretch->Buster
upgrade - was there a solution to this?

Thanks

Andrew.