No buffer space available

Log entry:

ERROR defguard_gateway::gateway Failed to update network configuration: Firewall error: Netlink error: Failed while reading a message from socket: Os { code: 105, kind: Uncategorized, message: "No buffer space available" }

This error means the kernel socket receive/send buffers are too small for the volume of netlink messages the gateway is generating. This typically occurs on gateways with many peers or high peer churn.

Fix

Increase the kernel socket buffer sizes. Add the following to /etc/sysctl.conf:

net.core.rmem_max = 67108864
net.core.wmem_max = 67108864
net.ipv4.tcp_rmem = 4096 87380 67108864
net.ipv4.tcp_wmem = 4096 65536 67108864
net.core.rmem_default = 524288
net.core.wmem_default = 524288

Apply without rebooting:

sudo sysctl -p

Restart the gateway service after applying:

sudo systemctl restart defguard-gateway

More context: github.com/DefGuard/defguard/issues/1303