Hello, Now that the IPv6 bug is supposed to be resolved since 5.8, I tried to upgrade a router from 4.14 to 5.10 Bird starts, however while inserting routes to FIB, I have long I/O loop cycles and at some point bird is unable to keep up. I already recompiled bird in case of a header change or something like that, and to switch to a pre-compiled kernel, neither have any effect. When bird begins to loose track of itself, I have this kind of messages: Sep 24 08:44:43 edge04-hostzealot bird: Netlink: File exists Sep 24 08:44:43 edge04-hostzealot bird: Netlink: File exists Sep 24 08:44:43 edge04-hostzealot bird: Netlink: File exists Sep 24 08:44:43 edge04-hostzealot bird: Netlink: File exists Sep 24 08:44:43 edge04-hostzealot bird: Netlink: File exists Sep 24 08:44:43 edge04-hostzealot bird: ... Sep 24 08:44:43 edge04-hostzealot bird: I/O loop cycle took 28703 ms for 1 events Sep 24 08:44:43 edge04-hostzealot bird: Kernel dropped some netlink messages, will resync on next scan. Sep 24 08:45:50 edge04-hostzealot bird: Netlink: File exists Sep 24 08:45:50 edge04-hostzealot bird: Netlink: File exists Sep 24 08:45:50 edge04-hostzealot bird: Netlink: File exists Sep 24 08:45:50 edge04-hostzealot bird: Netlink: File exists Sep 24 08:45:50 edge04-hostzealot bird: Netlink: File exists Sep 24 08:45:50 edge04-hostzealot bird: ... Sep 24 08:45:51 edge04-hostzealot bird: I/O loop cycle took 36201 ms for 1 events And then ospf begins to flap and routes are re-calculated based on remaining bgp ones. Sep 24 08:46:54 edge04-hostzealot bird: Next hop address 185.107.95.180 resolvable through recursive route for 185.107.92.0/22 (I have a way more specific route in OSPF) I activated the debug, and I can see that bird is re-scanning the entire kernel table when the “I/O loop” message appears Sep 24 09:07:30 edge04-hostzealot bird: kernel_grt_ipv4: 1.0.0.0/24: seen Sep 24 09:07:30 edge04-hostzealot bird: kernel_grt_ipv4: 1.0.4.0/24: seen And it tries to insert already inserted routes Sep 24 09:08:04 edge04-hostzealot bird: kernel_grt_ipv4: 122.76.248.0/23: installing Sep 24 09:08:04 edge04-hostzealot bird: Netlink: File exists And then OSPF is clearly going down Sep 24 09:08:04 edge04-hostzealot bird: ospf_ipv4: Inactivity timer expired for nbr 45.91.126.248 on gre4 Sep 24 09:08:04 edge04-hostzealot bird: ospf_ipv4: Neighbor 45.91.126.248 on gre4 changed state from Full to Down Sep 24 09:08:04 edge04-hostzealot bird: ospf_ipv4: Neighbor 45.91.126.248 on gre4 removed Here are some more detailed logs: https://paste.swordarmor.fr/raw/HX45 https://paste.swordarmor.fr/raw/oM9s This server isn’t the fastest one on the marked, but stuffed enough to handle full views. And with an older kernel it works very well. I have RRs running on 5.10 kernels, so it’s more likely a kernel issue, but I’m not able to determine if it’s caused by the kernel itself or by the way bird is using netlink. I’m using bird 2.0.8, I didn’t try an older version. Thanks a lot, -- Alarig Le Lay