Merge pull request #3 from ninoseki/add-dns-server-feature

Add "act as DNS server" feature

README.md

@@ -4,7 +4,7 @@
 [![Maintainability](https://api.codeclimate.com/v1/badges/e9119ee2021f1cfb895d/maintainability)](https://codeclimate.com/github/ninoseki/doh_client/maintainability)
 [![Coverage Status](https://coveralls.io/repos/github/ninoseki/doh_client/badge.svg?branch=master)](https://coveralls.io/github/ninoseki/doh_client?branch=master)
 
-DNS over HTTPS(DoH) client for Ruby
+DNS over HTTPS (DoH) client for Ruby
 
 ## Installation
 
@@ -46,14 +46,18 @@ DoHClient::Cloudflare.resolve("example.com", { type: "A", do: true, cd: false })
 ```bash
 $ doh_client
 Commands:
-  console help [COMMAND]  # Describe available commands or one specific command
-  console resolve [NAME]  # resolve a given name
+  doh_client act_as_server   # act as a local DNS server on a given port (default: 5300)
+  doh_client help [COMMAND]  # Describe available commands or one specific command
+  doh_client resolve [NAME]  # resolve a given name
 
 Options:
   [--resolver=RESOLVER]  # a resolver to use ('google' or 'cloudflare', default: google)
 
 $ doh_client resolve example.com --type A
-# => {"Status":0,"TC":false,"RD":true,"RA":true,"AD":true,"CD":false,"Question":[{"name":"example.com.","type":1}],"Answer":[{"name":"example.com.","type":1,"TTL":5169,"data":"93.184.216.34"}]}
+# => {"Status":0,"TC":false,"RD":true,"RA":true,"AD":true,"CD":false,"Question":[{"name":"example.com.","type":1}],"Answer":[{"name":"example.com.","type":1,"TTL":5169,"data":"93.184.216.34"}]
+
+$ doh_client act_as_server
+# => Starting DNS server 0.0.0.0:5300 (tcp/udp)
 ```
 
 ## License

doh_client.gemspec

@@ -24,13 +24,15 @@ Gem::Specification.new do |spec|
   spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
   spec.require_paths = ["lib"]
 
+  spec.add_development_dependency "async-rspec", "~> 1.11"
   spec.add_development_dependency "bundler", "~> 1.16"
   spec.add_development_dependency "coveralls", "~> 0.8"
   spec.add_development_dependency "rake", "~> 12.3"
   spec.add_development_dependency "rspec", "~> 3.8"
   spec.add_development_dependency "vcr", "~> 4.0"
   spec.add_development_dependency "webmock", "~> 3.4"
 
+  spec.add_dependency "async-dns", "~> 1.2"
   spec.add_dependency "http", "~> 3.3"
   spec.add_dependency "thor", "~> 0.19"
 end

lib/doh_client.rb

@@ -8,6 +8,8 @@
 require "doh_client/client/cloudflare"
 require "doh_client/client/google"
 
+require "doh_client/server"
+
 require "doh_client/cli"
 
 module DoHClient

lib/doh_client/cli.rb

@@ -18,6 +18,22 @@ def resolve(name)
       puts hash.to_json
     end
 
+    desc "act_as_server", "act as a local DNS server on a given port (default: 5300)"
+    method_option :port, type: :numeric, default: 5300
+    def act_as_server
+      port = options[:port]
+      interfaces = [[:udp, "0.0.0.0", port], [:tcp, "0.0.0.0", port]]
+      server = DoHClient::Server.new(interfaces)
+      puts "Starting DNS server 0.0.0.0:#{port} (tcp/udp)"
+      begin
+        server.run
+      rescue Interrupt
+        puts "\nStopping DNS server..."
+      ensure
+        puts "Stopped"
+      end
+    end
+
     no_commands do
       def resolver
         case options[:resolver]

lib/doh_client/server.rb

@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+require 'async/dns'
+
+module DoHClient
+  class Server < Async::DNS::Server
+    attr_reader :client
+    def initialize(resolver)
+      super
+      @client = resolver == "cloudflare" ? DoHClient::Client::Cloudflare : DoHClient::Client::Google
+    end
+
+    def process(name, resource_class, transaction)
+      type = resource_class.to_s.split('::').last
+
+      begin
+        response = client.resolve(name, type: type)
+      rescue ResponseError => _
+        return transaction.fail!(:NXDomain) unless answers
+      end
+
+      answers = response["Answer"]
+      return transaction.fail!(:NXDomain) unless answers
+
+      transaction.append_question!
+      answers.each do |answer|
+        next unless klass = Resolv::DNS::Resource.get_class(answer["type"], resource_class::ClassValue)
+        resource = klass < Resolv::DNS::Resource::DomainName ? klass.new(Resolv::DNS::Name.create(answer["data"])) : klass.new(answer["data"])
+        transaction.response.add_answer(answer["name"], answer["TTL"], resource)
+      end
+    end
+  end
+end

spec/cli_spec.rb

@@ -1,22 +1,56 @@
+# frozen_string_literal: true
+
 require "json"
+require 'async/dns'
+require "async/rspec"
 
 RSpec.describe DoHClient::CLI, :vcr do
-  context "google" do
-    describe "#resolve" do
+  describe "#resolve" do
+    context "google" do
       it "should output a valid JSON" do
         output = capture(:stdout) { DoHClient::CLI.start %w(resolve github.com --resolver=google) }
         json = JSON.parse(output)
         expect(json).to be_a(Hash)
       end
     end
-  end
-  context "cloudflare" do
-    describe "#resolve" do
+    context "cloudflare" do
       it "should output a valid JSON" do
         output = capture(:stdout) { DoHClient::CLI.start %w(resolve github.com --resolver=cloudflare) }
         json = JSON.parse(output)
         expect(json).to be_a(Hash)
       end
     end
   end
+  describe "#act_as_server" do
+    include_context Async::RSpec::Reactor
+
+    it "should act as a server" do
+      interfaces = [[:udp, "0.0.0.0", 5300], [:tcp, "0.0.0.0", 5300]]
+      resolver = Async::DNS::Resolver.new(interfaces)
+      task = DoHClient::CLI.start %w(act_as_server)
+
+      %w(example.com github.com google.com).each do |name|
+        resolved = resolver.addresses_for(name)
+        resolved.each do |result|
+          expect(result.address).to be_a(String)
+        end
+      end
+
+      task.stop
+    end
+    it "should act as a server on a given port" do
+      interfaces = [[:udp, "0.0.0.0", 5311], [:tcp, "0.0.0.0", 5311]]
+      resolver = Async::DNS::Resolver.new(interfaces)
+      task = DoHClient::CLI.start %w(act_as_server --port 5311)
+
+      %w(example.com github.com google.com).each do |name|
+        resolved = resolver.addresses_for(name)
+        resolved.each do |result|
+          expect(result.address).to be_a(String)
+        end
+      end
+
+      task.stop
+    end
+  end
 end