Netty DNS resolver ignores provided DNS server address

Expected behavior

In netty 4.1.8.Final, following code works fine. However, in 4.1.9 it does not send the request to provided address and sends it to default name server stream instead.

import java.net.{InetAddress, InetSocketAddress}

import io.netty.channel.nio.NioEventLoopGroup
import io.netty.channel.socket.nio.NioDatagramChannel
import io.netty.resolver.dns.{DnsNameResolverBuilder, DnsServerAddresses}

/** Simple dns resolver for testing stuff
  */
object Cli extends App {
  private val bossGroup = new NioEventLoopGroup()

  val res = new DnsNameResolverBuilder(bossGroup.next())
            .channelType(classOf[NioDatagramChannel])
            .nameServerAddresses(DnsServerAddresses.singleton(new InetSocketAddress("customdns.com", 33220)))
            .build()

  println(res.resolve("testaddress.com").await().get())
}

If you run this code with netty 4.1.9 in debug mode, you can see it’s sending requests to system resolvers.

I suspect the problem is the doResolveUncached in DnsNameResolver where you check whether the address stream is null. I think you should check whether the nameServerAddress is null and if it is, you should default to system resolvers. if it is defined however, you should make it into a stream and use it. But maybe im missing something.

Netty version

4.1.8.Final is fine, 4.1.9.Final is broken

JVM version (e.g. java -version)

1.8

OS version (e.g. uname -a)

mac os

[tomasherman]

i think the #2 makes sense … i think having to configure two things in order to set dns server will be confusing

[Scottmitch]

see https://github.com/netty/netty/pull/6588