dnsdist 2.0: experimenting the new YAML syntax

[dmachard]

Hi

I am experimenting with the new YAML syntax and trying to add the following rule for queries, but I encounter the following error on startup.

dnsdistv2-1  | dnsdist 2.0.0-alpha1 comes with ABSOLUTELY NO WARRANTY. This is free software, and you are welcome to redistribute it according to the terms of the GPL version 2
dnsdistv2-1  | terminate called after throwing an instance of 'std::runtime_error'
dnsdistv2-1  |   what():  Lua action '' could not be created: no valid function name, Lua code or Lua file

Config rule

query_rules:
  - name: "add ip in proxy protocol"
    selector:
      type: QNameSuffix
      suffixes:
        - powerdns.com
    action:
      type: Lua
      function_name: addProxyProtocolVal
      function_code: |
        function addProxyProtocolVal(dq)
          dq:addProxyProtocolValue(1, dq.localaddr:tostring())
          return DNSAction.None
        end

Am I missing something, or is it a bug?

Denis

[rgacogne]

Hi Denis! What's happening is:

• function_name has to refer to an existing Lua function, declared in a Lua file that is loaded before the YAML one. I see we have no example of that in the documentation, I'll open a PR to fix that later today, and also to output an error that is actionable
• since there is a function_name, function_code is ignored, but if it wasn't the code should be returning a Lua function, not defining it:

query_rules:
  - name: "add ip in proxy protocol"
    selector:
      type: QNameSuffix
      suffixes:
        - powerdns.com
    action:
      type: Lua
      function_code: |
        return function(dq)
          dq:addProxyProtocolValue(1, dq.localaddr:tostring())
          return DNSAction.None
        end

then again I need to make it clear in the documentation, sorry!

[rgacogne]

You will need this fix for this to work properly, though: #15351

[dmachard]

Thanks :) I'll continue running more tests.
By the way, I've shared several configuration examples here: https://github.com/dmachard/dnsdist-config-examples

[rgacogne]

Oh, that's very nice! Would you mind if I added a link to this repository in our documentation, at least until we can improve the documentation?

[dmachard]

Of course it will be great!
I will continue to convert these lua examples to Yaml

[Minxster]

Sorry to jump in on this, but I've been trying to figure out ProxyV2 in dnsdist, as I'm trying to test different backend DNS servers. But I'm running into problems with Technitium as dnsdist isn't sending proxy address over during health checks.

Can I assume that I could use similar to this to get around how dnsdist sends proxy dns calls?

[rgacogne]

I don't think your question is really relevant to this discussion, so I would suggest opening a different one for clarity's sake.
During health-check DNSdist is sending a "LOCAL" proxy payload, as defined in the proxy protocol specifications:

the connection was established on purpose by the proxy without being relayed. The connection endpoints are the sender and the receiver. Such connections exist when the proxy sends health-checks to the server. The receiver must accept this connection as valid and must use the real connection endpoints and discard the protocol block including the family which is ignored.

There is no way to change that in DNSdist right now, and if Technitium chokes on that my understanding is that this is a bug in Technitium.

[Minxster]

Thanks, I do appreciate I was being cheeky and dropping in my message 👍

It was only because I could see the code snippet from @dmachard which showed up in my GitHub searches. And it seemed to indicate I could maybe use addProxyProtocolValue to fix up the issue with the other product.