Initial version.

.gitignore

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+*.gem
+*.rbc
+.bundle
+.config
+.yardoc
+Gemfile.lock
+InstalledFiles
+_yardoc
+coverage
+doc/
+lib/bundler/man
+pkg
+rdoc
+spec/reports
+test/tmp
+test/version_tmp
+tmp
+.idea/

Gemfile

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+source 'https://rubygems.org'
+
+# Specify your gem's dependencies in mock_dns_server.gemspec
+gemspec

LICENSE.txt

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+Copyright (c) 2014, Verisign, Inc.
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+    * Redistributions in binary form must reproduce the above copyright
+      notice, this list of conditions and the following disclaimer in the
+      documentation and/or other materials provided with the distribution.
+    * Neither the name of Verisign, Inc. nor the
+      names of its contributors may be used to endorse or promote products
+      derived from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
+DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

README.md

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+# MockDnsServer
+
+A mock DNS server that can be instructed to perform actions based on
+user-provided conditions, and queried for its history of inputs and outputs.
+This server listens and responds on both UDP and TCP ports.
+
+An admin interface is provided, currently in the form of Ruby methods that
+can be called.  In the future we will probably add an HTTP interface
+to these methods. The admin methods:
+
+* instructing the server how to respond given the characteristics of the request
+* query the server for its history of inputs and outputs
+* request shutdown
+
+
+## Implementation
+
+
+### Threads
+
+```server.start``` launches its own thread in which it runs. This thread is terminated when ```server.close``` is called.
+
+Admin requests (configuration, analysis, etc.) will occur on the caller's thread.
+
+
+### Starting a Server
+
+The simplest way to run a server is to call the convenience method ```Server#with_new_server```:
+
+```ruby
+  Server.with_new_server(options) do |server|
+    # configure server with conditional actions
+    server.start
+  end
+```
+
+Options currently consist of:
+
+Option Name|Default Value|Description
+-----------|-------------|-----------|
+port       | 53          | port on which to listen (UDP and TCP)
+timeout    | 0.25 sec    | timeout for IO.select call
+verbose    | false       | Whether or not to output diagnostic messages
+
+The code above will result in the creation of a new thread in which the server will listen
+and respond indefinitely.  Terminating the server is accomplished by calling server.close
+in the caller's thread.
+
+
+### Locking
+
+A single mutex will be used to protect access to the rules and history objects.
+All mutex handling will be done by code in this gem, so the caller does not
+need to know or care that it is being done.
+
+
+### Message Read Loop
+
+The server will have the following flow of execution:
+
+```
+loop do
+  read a packet
+  attempt to parse it into a Dnsruby::Message object; if not, the message will be a string
+  mutex.synchronize do
+    action = look up rule
+    action.call # (perform appropriate action -- send or don't send response, etc.)
+    add input and output to history
+  end
+end
+```
+
+The above loop is wrapped in an IO.select timeout loop, although currently nothing
+is done at timeout time.  (Closing the server is accomplished by calling server.close
+on the caller's thread.)
+
+For TCP, since the application layer requires that the transmission begin with a 2-byte
+message length field (which is packed/unpacked with 'n'), this field is read first,
+and the server continues reading until the entire transmission is read.
+
+### Conditional Actions
+
+The server can be set up with conditional actions that will control how it responds to
+incoming requests.  Basically, a ConditionalAction consists of a proc (usually a lambda)
+that will be called to determine whether or not the action should be executed,
+and another proc (also usually a lambda) defining the action that should be performed.
+
+Only one conditional action will be performed per incoming request.
+The conditions in the conditional actions are evaluated in the order with which
+they were added to the server.  When a condition returns true, the corresponding
+action will be performed, and the message loop iteration will end.
+
+For more information about how conditional actions are created, see the ConditionalAction,
+PredicateFactory, ActionFactory, and ConditionalActionFactory classes.  For how
+the conditional actions are searched and performed, see the ConditionalActions class.
+
+
+### History
+
+To get a history of the server's events, call ```server.history_copy```.
+
+
+## Installation
+
+Add this line to your application's Gemfile:
+
+    gem 'mock_dns_server'
+
+And then execute:
+
+    $ bundle
+
+Or install it yourself as:
+
+    $ gem install mock_dns_server
+
+## Usage
+
+TODO: Write usage instructions here
+
+## Contributing
+
+1. Fork it
+2. Create your feature branch (`git checkout -b my-new-feature`)
+3. Commit your changes (`git commit -am 'Add some feature'`)
+4. Push to the branch (`git push origin my-new-feature`)
+5. Create new Pull Request

RELEASE_NOTES.md

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+## v0.1.0
+
+* First open sourced version.

Rakefile

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+# encoding: utf-8
+require 'rubygems'
+require 'bundler'
+require "bundler/gem_tasks"
+
+begin
+  Bundler.setup(:default, :development)
+rescue Bundler::BundlerError => e
+  $stderr.puts e.message
+  $stderr.puts "Run `bundle install` to install missing gems"
+  exit e.status_code
+end
+require 'rake'
+
+require 'rspec/core/rake_task'
+RSpec::Core::RakeTask.new(:spec)
+
+task :test => :spec
+task :default => :spec

bin/show_dig_request

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+#!/usr/bin/env ruby
+
+# Stands up a Mock DNS Server to receive a dig request,
+# and outputs the request to stdout using Dnsruby::Message#to_s,
+# whose output differs somewhat from dig output, but has
+# the same information..
+
+require 'mock_dns_server'
+require 'pry'
+require 'hexdump'
+
+MDS = MockDnsServer
+
+def conditional_action
+  condition = MDS::PredicateFactory.new.always_true
+  action = MDS::ActionFactory.new.puts_and_echo
+  MDS::ConditionalAction.new(condition, action, 1)
+end
+
+def run
+  MDS::Server.with_new_server(host: 'localhost', port: 9999) do |server|
+    server.add_conditional_action(conditional_action)
+    server.start
+    puts "\nReflected message as per Dnsruby:\n\n"
+    output = `dig -p 9999 @localhost #{ARGV[0]}  2>&1`
+    puts "Reflected message as per dig:\n\n#{output}\n"
+    puts "Executing pry, press [Ctrl-D] to exit.\n\n"
+    binding.pry
+    raise output if $? != 0
+  end
+end
+
+def validate_input
+  if ARGV.empty?
+    puts "Syntax is show_dig_request \"[dig arguments]\" but without specifying host or port."
+    exit -1
+  end
+end
+
+validate_input
+run

lib/mock_dns_server.rb

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+
+# This is put in a lambda so as not to pollute the namespace with variables that will be useless later
+->() {
+  file_mask = File.join(File.dirname(__FILE__), '**/*.rb')
+  files_to_require = Dir[file_mask]
+  files_to_require.each { |file| require file }
+}.call
+
+
+module MockDnsServer
+  # Your code goes here...
+end

lib/mock_dns_server/action_factory.rb

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+require 'mock_dns_server/message_builder'
+
+module MockDnsServer
+
+# Creates and returns actions that will be run upon receiving incoming messages.
+class ActionFactory
+
+  include MessageBuilder
+
+  # Echos the request back to the sender.
+  def echo
+    ->(incoming_message, sender, context, protocol) do
+      context.server.send_response(sender, incoming_message, protocol)
+    end
+  end
+
+  def puts_and_echo
+    ->(incoming_message, sender, context, protocol) do
+      puts "Received #{protocol.to_s.upcase} message from #{sender}:\n#{incoming_message}\n\n"
+      puts "Hex:\n\n"
+      puts "#{incoming_message.encode.hexdump}\n\n"
+      echo.(incoming_message, sender, context, protocol)
+    end
+  end
+
+  # Responds with the same object regardless of the request content.
+  def constant(constant_object)
+    ->(_, sender, context, protocol) do
+      context.server.send_response(sender, constant_object, protocol)
+    end
+  end
+
+
+  # Sends a SOA response.
+  def send_soa(zone, serial, expire = nil, refresh = nil)
+    send_message(soa_response(
+        name: zone, serial: serial, expire: expire, refresh: refresh))
+  end
+
+
+  # Sends a fixed DNSRuby::Message.
+  def send_message(response)
+    ->(incoming_message, sender, context, protocol) do
+
+      if [incoming_message, response].all? { |m| m.is_a?(Dnsruby::Message) }
+        response.header.id = incoming_message.header.id
+      end
+      if response.is_a?(Dnsruby::Message)
+        response.header.qr = true
+      end
+      context.server.send_response(sender, response, protocol)
+    end
+  end
+
+  # Outputs the string representation of the incoming message to stdout.
+  def puts_message
+    ->(incoming_message, sender, context, protocol) do
+      puts incoming_message
+    end
+  end
+
+
+  def zone_load(serial_history)
+    ->(incoming_message, sender, context, protocol) do
+
+      mt = MessageTransformer.new(incoming_message)
+      zone = mt.qname
+      type = mt.qtype
+
+      if serial_history.zone.downcase != zone.downcase
+        raise "Zones differ (history: #{serial_history.zone}, request: #{zone}"
+      end
+
+      if %w(AXFR IXFR).include?(type)
+        xfr_response = serial_history.xfr_response(incoming_message)
+        send_message(xfr_response).(incoming_message, sender, context, :tcp)
+      elsif type == 'SOA'
+        send_soa(zone, serial_history.high_serial).(incoming_message, sender, context, protocol)
+      end
+    end
+  end
+
+end
+end

lib/mock_dns_server/conditional_action.rb

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+module MockDnsServer
+
+class ConditionalAction
+
+  attr_accessor :condition, :action, :description, :max_uses, :use_count
+
+
+  # @param condition a proc/lambda that, when called with request as a param, returns
+  #        true or false to determine whether or not the action will be executed
+  # @param action the code (lambda or proc) to be executed; takes incoming message,
+  #        sender, server context, and (optionally) protocol as parameters
+  #        and performs an action
+  # @param max_uses maximum number of times this action should be executed
+  # @return the value returned by the action, e.g. the message, or array of messages, it sent
+  def initialize(condition, action, max_uses)
+    @condition = condition
+    @action = action
+    @max_uses = max_uses
+    @use_count = 0
+  end
+
+
+  def increment_use_count
+    @use_count += 1
+  end
+
+  def to_s
+    "#{super.to_s}; condition: #{condition.to_s}, action = #{action.to_s}, max_uses = #{max_uses}"
+  end
+
+  def eligible_to_run?
+    max_not_reached = max_uses.nil? || use_count < max_uses
+    max_not_reached && condition.call
+  end
+
+  def run(request, sender, context, protocol)
+    # TODO: Output to history?
+    action.call(request, sender, context, protocol)
+  end
+
+end
+end