bird 3.1.5 crashes after adding "-R" to BIRD_ARGS

[Christoph]

Some more lines from the logfile suggests an issue with netlink performance?

2026-01-05 01:16:00.367 [0001] <WARN> Netlink: File exists << many times
2026-01-05 01:16:00.367 [0001] <WARN> ...
2026-01-05 01:16:00.636 [0002] <RMT> anexia_v4: Received: Connection 
collision resolution
2026-01-05 01:16:00.687 [0001] <WARN> I/O loop cycle took 16627.101 ms 
for 6 events
2026-01-05 01:16:06.127 [0001] <WARN> Netlink: File exists
2026-01-05 01:16:06.128 [0001] <WARN> ..
2026-01-05 01:16:44.093 [0001] <WARN> kernel1: Can't scan, still pruning
2026-01-05 01:16:45.310 [0001] <WARN> Kernel dropped some netlink 
messages, will resync on next scan.
2026-01-05 01:16:45.841 [0001] <WARN> Kernel dropped some netlink 
messages, will resync on next scan.

2026-01-05 01:22:42.408 [0001] <BUG> kernel1.ipv4: Attempted to start 
channel's already started export
2026-01-05 01:24:21.910 [0001] <BUG> kernel1.ipv4: Attempted to start 
channel's already started export
2026-01-05 01:24:50.326 [0001] <WARN> I/O loop cycle took 12889.620 ms 
for 5 events


We had that "Kernel dropped some netlink..." a while ago (>5years)
and added this to our sysctl.conf back then:

# solves the "Kernel dropped some netlink messages, will resync on next 
scan." BIRD Warnings
# https://bird.network.cz/pipermail/bird-users/2017-September/011542.html
# (we did not change the wmem_default since this is apparently not needed)
net.core.rmem_max=16777216
net.core.rmem_default=4194304
net.core.wmem_max=4194304

Are these still sensible values or should they be increased further?
This is a BGP router getting 2 full tables.

best regards,
Christoph