IPv6 BGP & kernel 4.19

[Daniel Suchy]

Hello,
I'm running bird 1.6.x branch (packages from Debian/Buster; currently
1.6.6) on recent 4.19 custom-build kernels without any issues (on armhf
hardware).

My BGP sessions are carrying only few routes (default + some more
specifics).

One idea that comes in my mind is default kernel limit for IPv6 routes
in memory (sysctl net.ipv6.route.max_size); and such default is quite
low for fullbgp/DFZ IPv6 deployments and it's still set to 4096 on
Debian/Buster with stock kernels. Can people having issues with 4.19
kernels check sysctl mentioned above?

- Daniel

On 11/21/19 6:12 PM, Ondrej Zajicek wrote:
> On Thu, Nov 21, 2019 at 04:09:24PM +0000, Andrew Hearn wrote:
>>> 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?
> 
> Perhaps try kernel 5.2.x or 5.3.x from buster-backports?
>