DNS wireformat support in Elixir?

found this in cloudflare odoh lib it says WireFormat is similar to xdr

Just a thought but try inet_dns:decode/1 in Erlang as per otp/lib/kernel/src/inet_dns.erl at master · erlang/otp · GitHub and maybe other functions in that module will help you as well.

If it works, you will have the benefit of not having to pull an extra dependency

According to the RFC RFC 8484 - DNS Queries over HTTPS (DoH) the message is formatted as per RFC 1035 which should be what inet_dns:decode/1 accepts

Thanks @evadne passed the 1st hurdle , will upate the thread with progress for others if they ever need this info. might ping here if I hit a roadblock

post "/" do
    {:ok, body, conn} = Plug.Conn.read_body(conn)

    IO.inspect(body, label: "body")
    :inet_dns.decode(body) |> IO.inspect(label: "inet_dns.decode")
    conn
    |> put_resp_content_type("application/dns-message")
    |> send_resp(
      200,
      Jason.encode!(%{
        msg: "I don't have a heart but I am alive!"
      })
    )
  end

body: <<171, 205, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 3, 119, 119, 119, 7, 101, 120, 97, 
  109, 112, 108, 101, 3, 99, 111, 109, 0, 0, 1, 0, 1>>
inet_dns.decode: {:ok,
 {:dns_rec,
  {:dns_header, 43981, false, :query, false, false, true, false, false, 0},
  [{:dns_query, 'www.example.com', :a, :in}], [], [], []}}

after lack of my erlang understanding I decided to dig into tungd/elixir-dns code out of curiosity to see how it was handling things and it is doing what @evadne suggested and has some nice wrapper around erlang code which i ended up using. https://github.com/tungd/elixir-dns/blob/master/lib/dns/record.ex

Big thanks to the elixir community for being supportive and having a solution to almost everything

Just for information, my DNS server written in Elixir uses (currently) the elixir-dns library. Because it does not seem actually maintained, I had to fork. My code may give you ideas.

Thanks @bortzmeyer , is your fork a drop-in replacement of elixir-dns ?

Yes. Currently, there is only one small (but important) patch but I will add others, while still trying to allow a merge back to the upstream.

doesn’t seem to work out of the box for me by just moving from 2.3.0 → 2.4.0 there is something different

Screenshot from 2022-10-18 14-51-221935×418 54.6 KB

Strange, I cannot reproduce the problem. IO.inspect DNS.resolve("www.bortzmeyer.org") works for me with the original elixir-dns (tested with 2.3 and 2.4) and my fork (same versions). Could you send me (stephane(at)bortzmeyer.org) the actual files (mix.exs and the program.exs)?