Description

The grpc_server plugin allows you to configure parameters for the DNS-over-gRPC server to fine-tune the security posture and performance of the server.

This plugin can only be used once per gRPC listener block.

Syntax

grpc_server {
    max_streams POSITIVE_INTEGER
    max_connections POSITIVE_INTEGER
}

• max_streams limits the number of concurrent gRPC streams per connection. This helps prevent unbounded streams on a single connection, exhausting server resources. The default value is 256 if not specified. Set to 0 for unbounded.
• max_connections limits the number of concurrent TCP connections to the gRPC server. The default value is 200 if not specified. Set to 0 for unbounded.

Examples

Set custom limits for maximum streams and connections:

grpc://.:8053 {
    tls cert.pem key.pem
    grpc_server {
        max_streams 50
        max_connections 100
    }
    whoami
}

Set values to 0 for unbounded, matching CoreDNS behaviour before v1.14.0:

grpc://.:8053 {
    tls cert.pem key.pem
    grpc_server {
        max_streams 0
        max_connections 0
    }
    whoami
}