#!/usr/bin/env ruby

# ----------------------------------------------------------

# dnscrypt-proxy-multi
#
# Runs multiple instances of dnscrypt-proxy.
#
# It parses a CSV file and makes use of the entries found in
# it as target remote services when creating instances of
# dnscrypt-proxy.  Remote services are checked for
# availability before an instance of dnscrypt-proxy is used
# to connect to them.  An FQDN can also be used to check if
# a remote service can resolve names.
#
# The script waits for all instances to exit before it
# exits.  It also automaticaly stops them when it receives
# SIGTERM or SIGINT.
#
# Usage: dnscrypt-proxy-multi[.rb] [options] [-- [extra_dnscrypt_proxy_opts]]
#
# Run with --help to see readable info about the options.
#
# Disclaimer: This tool comes with no warranty.
#
# Author: konsolebox
# Copyright Free / Public Domain
# July 22, 2022

# ----------------------------------------------------------

require 'csv'
require 'fileutils'
require 'optparse'
require 'resolv'
require 'socket'
require 'timeout'

module Net
  autoload :Ping, 'net/ping'
end

VERSION = '2022.07.22'
INSTANCES_LIMIT = 50
WAIT_FOR_CONNECTION_TIMEOUT = 5
WAIT_FOR_CONNECTION_PAUSE = 1
DEFAULT_PORT = 443

HEADER_MAP = {
  :name => 'Name',
  :full_name => 'Full name',
  :description => 'Description',
  :location => 'Location',
  :coordinates => 'Coordinates',
  :url => 'URL',
  :version => 'Version',
  :dnssec => 'DNSSEC validation',
  :no_logs => 'No logs',
  :namecoin => 'Namecoin',
  :resolver_addr => 'Resolver address',
  :provider_name => 'Provider name',
  :provider_key => 'Provider public key',
  :provider_key_txt => 'Provider public key TXT record'
}.freeze

@exit_status = 1
@log_buffer = []
@log_file = nil
@pids = []
@syslog_logger = nil

@params = Struct.new(
  :change_owner, :check_resolvers, :check_resolvers_timeout,
  :check_resolvers_wait, :debug, :dnscrypt_proxy, :dnscrypt_proxy_extra_args,
  :dnscrypt_proxy_syslog, :dnscrypt_proxy_syslog_prefix, :dnscrypt_proxy_user,
  :dnssec_only, :ephemeral_keys, :group, :ifilters, :ignore_ip_format,
  :instance_delay, :local_ip_range, :local_port_range, :log, :log_dir,
  :log_file, :log_level, :log_overwrite, :max_instances, :port_check_async,
  :port_check_timeout, :resolvers_list, :resolvers_list_encoding, :syslog,
  :syslog_prefix, :user, :verbose, :wait_for_connection, :write_pids,
  :write_pids_dir, :xfilters
).freeze.new

def initialize_params
  @params.change_owner = nil
  @params.check_resolvers = nil
  @params.check_resolvers_timeout = 5.0
  @params.check_resolvers_wait = 0.1
  @params.debug = false
  @params.dnscrypt_proxy = nil
  @params.dnscrypt_proxy_extra_args = nil
  @params.dnscrypt_proxy_syslog = false
  @params.dnscrypt_proxy_user = nil
  @params.ephemeral_keys = false
  @params.group = nil
  @params.ifilters = []
  @params.ignore_ip_format = false
  @params.instance_delay = 0.0
  @params.local_ip_range = '127.0.100.1-254'
  @params.local_port_range = '53'
  @params.log = false
  @params.log_dir = '/var/log/dnscrypt-proxy-multi'
  @params.log_file = nil
  @params.log_level = 6
  @params.log_overwrite = false
  @params.max_instances = 10
  @params.port_check_async = 10
  @params.port_check_timeout = 5.0
  @params.resolvers_list = '/usr/share/dnscrypt-proxy/dnscrypt-resolvers.csv'
  @params.resolvers_list_encoding = 'utf-8'
  @params.syslog = false
  @params.syslog_prefix = ''
  @params.user = nil
  @params.verbose = false
  @params.wait_for_connection = nil
  @params.write_pids = false
  @params.write_pids_dir = '/var/run/dnscrypt-proxy-multi'
  @params.xfilters = []
end

def log(msg, stderr, syslog_method, prefix = '')
  stderr ? $stderr.puts("#{prefix}#{msg}") : puts("#{prefix}#{msg}")

  if @log_buffer
    @log_buffer << "[#{Time.now.strftime('%F %T')}] #{msg}"
  elsif @log_file
    @log_file.puts "[#{Time.now.strftime('%F %T')}] #{msg}"
    @log_file.flush
  end

  @syslog_logger.method(syslog_method).call("#{@params.syslog_prefix}#{msg}") if @syslog_logger
end

def log_message(msg)
  log(msg, false, :info)
end

def log_warning(msg)
  log('[Warning] ' + msg, false, :warn)
end

def log_error(msg)
  log('[Error] ' + msg, true, :error)
end

def log_verbose(msg)
  log(msg, false, :info) if @params.verbose
end

def log_debug(msg = nil)
  if @params.debug
    msg = yield if block_given?
    log('[Debug] ' + msg.to_s, false, :debug)
  end
end

def fail(msg)
  log('[Failure] ' + msg, true, :fatal)
  exit 1
end

def which(cmd)
  raise ArgumentError.new("Argument not a string: #{cmd.inspect}") unless cmd.is_a?(String)
  return nil if cmd.empty?

  case RbConfig::CONFIG['host_os']
  when /cygwin/
    exts = nil
  when /dos|mswin|^win|mingw|msys/
    pathext = ENV['PATHEXT']
    exts = pathext ? pathext.split(';').select{ |e| e[0] == '.' } : ['.com', '.exe', '.bat']
  else
    exts = nil
  end

  if cmd[File::SEPARATOR] or (File::ALT_SEPARATOR and cmd[File::ALT_SEPARATOR])
    if exts
      ext = File.extname(cmd)

      return File.absolute_path(cmd) \
          if not ext.empty? and exts.any?{ |e| e.casecmp(ext).zero? } \
          and File.file?(cmd) and File.executable?(cmd)

      exts.each do |ext|
        exe = "#{cmd}#{ext}"
        return File.absolute_path(exe) if File.file?(exe) and File.executable?(exe)
      end
    else
      return File.absolute_path(cmd) if File.file?(cmd) and File.executable?(cmd)
    end
  else
    paths = ENV['PATH']
    paths = paths ? paths.split(File::PATH_SEPARATOR).select{ |e| File.directory?(e) } : []

    if exts
      ext = File.extname(cmd)
      has_valid_ext = !ext.empty? && exts.any?{ |e| e.casecmp(ext).zero? }

      paths.unshift('.').each do |path|
        if has_valid_ext
          exe = File.join(path, "#{cmd}")
          return File.absolute_path(exe) if File.file?(exe) and File.executable?(exe)
        end

        exts.each do |ext|
          exe = File.join(path, "#{cmd}#{ext}")
          return File.absolute_path(exe) if File.file?(exe) and File.executable?(exe)
        end
      end
    else
      paths.each do |path|
        exe = File.join(path, cmd)
        return File.absolute_path(exe) if File.file?(exe) and File.executable?(exe)
      end
    end
  end

  nil
end

def check_tcp_port(ip, port, timeout_in_seconds)
  Timeout::timeout(timeout_in_seconds) do
    start = Time.now
    TCPSocket.new(ip, port).close
    Time.now - start
  end
end

def executable_file?(path)
  File.file?(path) and File.executable_file?(path) and File.readable?(path)
end

def valid_fqdn?(name)
  return false if name =~ /\.\./ or name =~ /^\./
  labels = name.split('.')
  labels.size > 1 and labels.all? do |e|
    e =~ /^[[:alnum:]]+$/ or e =~ /^[[:alnum:]]+[[:alnum:]-]+[[:alnum:]]+$/
  end
end

def is_host_valid?(host)
  octets = host.split('.')

  if octets.last =~ /^[[:digit:]]+$/
    return false unless octets.size == 4

    octets.each_with_index do |e, i|
      n = Integer(e) rescue nil
      return false unless n and n < 255
      return false if (i == 0 or i == 3) and n == 0
    end
  else
    return false unless octets.all? do |e|
      e =~ /^[[:alnum:]]+$/ or e =~ /^[[:alnum:]]+[[:alnum:]-]+[[:alnum:]]+$/
    end
  end

  true
end

def wait_for_connection
  log_message "Waiting for connection."

  while true
    @params.wait_for_connection.each do |host, port|
      begin
        if port
          return if check_tcp_port(host, port, WAIT_FOR_CONNECTION_TIMEOUT)
        else
          return if Net::Ping::ICMP.new(host, WAIT_FOR_CONNECTION_TIMEOUT).ping
        end
      rescue SocketError => ex
        fail "Socket error exception caught while attempting to wait for connection: #{ex.message}"
      rescue SystemCallError, Timeout::Error => ex
        log_debug{ "Caught '#{ex.class}' exception while waiting for connection: #{ex.message}" }
      end

      sleep WAIT_FOR_CONNECTION_PAUSE
    end
  end
end

module RangeCommon
  def expand_simple_range(range, min, max)
    case range
    when /^[[:digit:]]+$/
      i = Integer(range)
      return nil if i < min or i > max
      [i]
    when /^[[:digit:]]+-[[:digit:]]+$/
      a, b = range.split('-').map{ |e| Integer(e) }
      return nil if a > b or a < min or b > max
      Range.new(a, b)
    else
      nil
    end
  end

  def each
    if block_given?
      enumerate do |e|
        yield e
      end
    else
      Enumerator.new do |y|
        enumerate do |e|
          y << e
        end
      end
    end
  end

  def to_s
    return @range_string || self
  end
end

class IPAddrRange
  include RangeCommon
  include Enumerable

  def initialize(range, ignore_ip_format)
    fail "Invalid IP range specificatioin: #{range}" unless range.is_a? String

    @range = range.split(',').map do |specific_range|
      sections = specific_range.split('.')
      fail "Invalid range: #{specific_range}" unless sections.size == 4

      sections.each_with_index.map do |e, i|
        min = ignore_ip_format || i == 1 || i == 2 ? 0 : 1
        max = ignore_ip_format ? 255 : 254
        expand_simple_range(e, min, max) or fail "Invalid range: #{specific_range}"
      end
    end

    @range_string = range
  end

  def enumerate_with(ports_range)
    Enumerator.new do |y|
      enumerate do |ip|
        ports_range.each do |port|
          y << [ip, port]
        end
      end
    end
  end

protected
  def enumerate
    @range.each do |a, b, c, d|
      a.each do |w|
        b.each do |x|
          c.each do |y|
            d.each do |z|
              yield "#{w}.#{x}.#{y}.#{z}"
            end
          end
        end
      end
    end
  end
end

class PortsRange
  include RangeCommon
  include Enumerable

  def initialize(range)
    fail "Invalid range: #{range}" unless range.is_a? String

    @range = range.split(',').map do |specific_range|
      expand_simple_range(specific_range, 1, 65535) or fail "Invalid range: #{specific_range}"
    end

    @range_string = range
  end

protected
  def enumerate
    @range.each do |specific_range|
      specific_range.each do |e|
        yield e
      end
    end
  end
end

Entry = Struct.new(:resolver_address, :provider_name, :provider_key, :latency, :next_) do
  def resolver_ip
    @resolver_ip ||= resolver_address.gsub(/:.*$/, '')
  end

  def resolver_port
    @resolver_port ||= Integer(resolver_address.gsub(/^.*:/, ''))
  end
end

def prepare_dir(dir)
  if not File.exist? dir
    log_message "Creating directory #{dir}."

    begin
      FileUtils.mkdir_p dir
    rescue SystemCallError => ex
      fail "Failed to create directory #{dir}: #{ex.message}"
    end
  elsif not File.directory? dir
    fail "Object exists but is not a directory: #{dir}"
  end

  if @params.change_owner
    owner = @params.change_owner
    user, group = owner.split(':')
    log_message "Changing owner of #{dir} to #{owner}."

    begin
      FileUtils.chown(user, group, [dir])
    rescue SystemCallError, ArgumentError => ex
      fail "Failed to change ownership of directory #{dir} to #{owner}: #{ex.message}"
    end
  end
end

def stop_instances
  log_message "Stopping instances."

  @pids.each do |pid|
    begin
      Process.kill('TERM', pid)
    rescue SystemCallError
    end
  end
end

def parse_check_resolvers_arg(arg)
  fqdn_list, timeout, wait = arg.split('/')
  fqdn_list = fqdn_list.split(',')

  if timeout and not timeout.empty?
    timeout = Float(timeout) rescue fail("Invalid timeout value: #{timeout}")
    @params.check_resolvers_timeout = timeout
  end

  if wait and not wait.empty?
    wait = Float(wait) rescue fail("Invalid waiting time value: #{timeout}")
    @params.check_resolvers_wait = wait
  end

  @params.check_resolvers = fqdn_list.map do |e|
    fqdn, sep, option = e.partition(":")
    validate_with_dnssec = option == 'dnssec'
    fail "Invalid FQDN option: #{option}" unless validate_with_dnssec or option.empty?
    fail "Not a valid FQDN: #{e}" unless valid_fqdn?(e)
    [fqdn, validate_with_dnssec]
  end
end

class Expression
  class Options
    attr_reader :regex
    attr_reader :multiline
    attr_reader :full_string_match
    attr_reader :ignore_case

    def initialize(opts = '')
      raise "Expecting string, not #{opts.class}." unless opts.is_a? String

      opts.split('').each do |char|
        case char
        when 'm'
          @multiline = true
        when 'i'
          @ignore_case = true
        when 'r'
          @regex = true
        when 'f'
          @full_string_match = true
        else
          fail "Invalid expression option: #{char}"
        end
      end

      fail "Option full string match ('m') can't be used along with regex ('r')." if @regex and @full_string_match
      fail "Option multiline ('m') can only be used with regex ('r')." if @multiline and not @regex

      @to_s = opts.dup.freeze
    end

    def +(opts)
      self.class.new(@to_s + opts.to_s)
    end

    def to_s
      @to_s
    end
  end

  attr_reader :expression
  attr_reader :options

  DEFAULT_OPTIONS = Options.new('')

  def initialize(expr, opts = DEFAULT_OPTIONS)
    raise "Unexpected argument type for options: #{opts.class}." unless opts.is_a? String or opts.is_a? Options
    fail "Expression can't be empty." if expr.empty?
    @options = opts.is_a?(Options) ? opts : Options.new(opts)

    if @options.regex
      i = 0
      i |= Regexp::MULTILINE if @options.multiline
      i |= Regexp::IGNORECASE if @options.ignore_case
      @expression = Regexp.new(expr, i)
    elsif @options.ignore_case
      @expression = expr.downcase
    else
      @expression = expr
    end
  end

  def validates?(str)
    raise "Expecting string to validate to be string." unless str.is_a? String

    if @options.regex
      @expression.match?(str)
    else
      str = str.downcase if @options.ignore_case

      if @options.full_string_match
        str == @expression
      else
        not str[@expression].nil?
      end
    end
  end
end

def parse_filter_arg(arg, hash = {})
  global_opts, sep, etc = arg.partition(':')

  if not sep.empty? and not global_opts['=']
    global_opts = Expression::Options.new(global_opts)
    arg = etc
  else
    global_opts = nil
  end

  arg.split(',').each do |pair|
    name_and_opts, sep, keyword = pair.partition('=')
    fail "Keyword or regex not specified." if keyword.empty?
    name, opts, etc, = name_and_opts.split('/')
    fail "Invalid extra argument: #{etc}" if etc
    sym = name.to_sym
    fail "Invalid column name: #{name}" unless HEADER_MAP.has_key? sym or sym == :*

    opts = opts ?
        (global_opts ? global_opts.to_s + opts : opts) :
        (global_opts || Expression::DEFAULT_OPTIONS)

    (hash[name.to_sym] ||= []) << Expression.new(keyword, opts)
  end

  hash
end

def all_expressions_match?(filter_pairs, row)
  raise "Expecting filter_pairs to be not empty." if filter_pairs.empty?

  filter_pairs.all? do |name, expressions|
    if name == :*
      expressions.all? do |expr|
        row.fields.any?{ |value| value and expr.validates?(value) }
      end
    else
      value = row[HEADER_MAP[name]] and expressions.all? do |expr|
        expr.validates?(value)
      end
    end
  end
end

def main
  initialize_params

  #
  # Parse options.
  #

  parser = OptionParser.new

  parser.on_tail("-h", "--help", "Show this help info and exit.") do
    $stderr.puts "dnscrypt-proxy-multi #{VERSION}"
    $stderr.puts "Runs multiple instances of dnscrypt-proxy"
    $stderr.puts
    $stderr.puts "Usage: #{$0} [options] [-- [extra_dnscrypt_proxy_opts]]"
    $stderr.puts
    $stderr.puts "Options:"
    $stderr.puts parser.summarize([], 3, 80, "").map{ |e| e.gsub(/^ {4}--/, '--') }.reject{ |e| e =~ /--resolver-check/ }
    $stderr.puts
    $stderr.puts "Notes:"
    $stderr.puts "* Directories are automatically created recursively when needed."
    $stderr.puts "* Services are checked with TCP ports since TCP is a common fallback."
    $stderr.puts "* Local ports are first used up before the next IP address in range is used."
    $stderr.puts "* Local ports are not checked if they are currently in use."
    $stderr.puts "* Names of log files are created based on the remote address, while names of"
    $stderr.puts "  PID files are based on the local address."
    $stderr.puts "* dnscrypt-proxy creates files as the calling user; not the one specified with"
    $stderr.puts "  --user, so changing ownership of directories and existing files may not be"
    $stderr.puts "  necessary."
    exit 1
  end

  parser.on("-c", "--check-resolvers=FQDN[:dnssec][,FQDN2[:dnssec],...][/TIMEOUT[/WAIT]]",
  "Check instances of dnscrypt-proxy if they can resolve all specified FQDN",
  "and replace them with another instance that targets another resolver entry",
  "if they don't.  Default timeout is #{@params.check_resolvers_timeout}.  Default amount of wait-time to",
  "allow an instance to load and initialize before checking it is #{@params.check_resolvers_wait}.") do |arg|
    parse_check_resolvers_arg arg
  end

  parser.on("--resolver-check=FQDN[:dnssec][,FQDN2[:dnssec][,...]][/TIMEOUT[/WAIT]]") do |arg|
    log_warning "Option '--resolver-check' is deprecated and will soon be removed.  Please use '--check-resolvers' instead."
    parse_check_resolvers_arg arg
  end

  parser.on("-C", "--change-owner=USER[:GROUP]",
  "Change ownership of directories to user-group before doing anything",
  "significant like opening files, instantiating dnscrypt-proxy's, or dropping",
  "privilege to a user or group if configured.") do |user_group|
    fail "User can't be an empty string." if user_group.empty?
    @params.change_owner = user_group
  end

  parser.on("-d", "--dnscrypt-proxy=PATH", "Set path to dnscrypt-proxy executable.",
  "Default is \"#{which('dnscrypt-proxy')}\".") do |path|
    fail "Not executable or file does not exist: #{path}" unless executable_file?(path)
    @params.dnscrypt_proxy = path
  end

  parser.on("-D", "--instance-delay=SECONDS",
  "Wait SECONDS seconds before creating the next instance of dnscrypt-proxy.",
  "Default is #{@params.instance_delay}.") do |secs|
    @params.instance_delay = Float(secs) rescue fail("Invalid value for instance-wait: #{secs}.")
  end

  parser.on("-E", "--ephemeral-keys",
  "Pass --ephemeral-keys option to every instance of dnscrypt-proxy.",
  "See dnscrypt-proxy(8) for more info.") do
    @params.ephemeral_keys = true
  end

  parser.on("-f", "--filter=[GLOBAL_OPTS:]NAME[/OPTS]=KEYWORD[,NAME2[/OPTS2]=KEYWORD2[,...]]",
  "This option inclusively filters resolver entries.  The NAME refers to a",
  "particular column in the CSV table, and the KEYWORD is a string that matches",
  "or submatches the entry's value in the column.  Multiple NAME=KEYWORD pairs",
  "can be specified, and a NAME can be specified more than once so that more",
  "keywords can be used to filter a column.  If NAME is '*', the KEYWORD will",
  "validate if it matches with any column.  Every instance that this options is",
  "used defines a filter group.  The entry becomes valid for inclusion once",
  "all keywords in a filter group validates with its values.  Multiple filter",
  "groups can be specified to allow different ways to validate an entry for",
  "inclusion.",
  " ",
  "Options can also be included to change how keyword-matching is performed.",
  "The usable options are 'r' (regex mode), 'm' (multi-line matching), 'i'",
  "(ignore-case)', and 'f' (full string matching).  Multi-line matching can",
  "only be used with 'r' (regex mode), while full-string matching can only be",
  "used without it.",
  " ",
  "The following table shows the usable names:",
  " --------------------------------------------------------------------------",
  "| Name             | CSV Header String   | Details                         |",
  "| ---------------- | --------------------| --------------------------------|",
  "| name             | Name                |                                 |",
  "| full_name        | Full name           |                                 |",
  "| description      | Description         |                                 |",
  "| location         | Location            |                                 |",
  "| coordinates      | Coordinates         |                                 |",
  "| url              | URL                 |                                 |",
  "| version          | Version             |                                 |",
  "| dnssec           | DNSSEC Validation   | Values are 'yes' or 'no'.       |",
  "| no_logs          | No logs             | Values are 'yes' or 'no'.       |",
  "| namecoin         | Namecoin            | Values are 'yes' or 'no'.       |",
  "| resolver_addr    | Resolver address    | IP address with port.  It's the |",
  "|                  |                     | argument to dnscrypt-proxy's    |",
  "|                  |                     | '--resolver-address' option.    |",
  "| provider_name    | Provider name       | Argument to '--provider-name'.  |",
  "| provider_key     | Provider public key | Argument to '--provider-key'.   |",
  "| provider_key_txt | Provider public key |                                 |",
  "|                  | TXT record          |                                 |",
  " --------------------------------------------------------------------------") do |arg|
    @params.ifilters << parse_filter_arg(arg)
  end

  parser.on("-g", "--group=GROUP",
  "Drop priviliges to GROUP before creating instances of dnscrypt-proxy.") do |group|
    fail "User can't be an empty string." if group.empty?
    @params.group = group
  end

  parser.on("-G", "--debug", "Show debug messages.") do
    @params.debug = true
  end

  parser.on("-i", "--local-ip=RANGE",
  "Set range of IP addresses to listen to.  Default is \"#{@params.local_ip_range}\".",
  "Example: \"127.0.1-254.1-254,10.0.0.1\"") do |range|
    @params.local_ip_range = range
  end

  parser.on("-I", "--ignore-ip-format", "Do not check if a local IP address starts or ends with 0 or 255.") do
    @params.ignore_ip_format = true
  end

  parser.on("-l", "--log [LOG_DIR]", "Enable logging files to LOG_DIR.",
  "Default directory is \"#{@params.log_dir}\".") do |dir|
    @params.log = true
    @params.log_dir = dir if dir
  end

  parser.on("-L", "--log-level=LEVEL",
  "When logging is enabled, tell dnscrypt-proxy to use log level LEVEL.",
  "Default level is #{@params.log_level}.  See dnscrypt-proxy(8) for info.") do |level|
    fail "Value for log level an unsigned integer: #{level}" unless level =~ /^[[:digit:]]+$/
    @params.log_level = Integer(level)
  end

  parser.on("-m", "--max-instances=N",
  "Set maximum number of dnscrypt-proxy instances.  Default is #{@params.max_instances}.") do |n|
    fail "Value for max instances must be an unsigned integer: #{n}" unless n =~ /^[[:digit:]]+$/
    n = Integer(n)
    fail "Value for max instances cannot be 0 or greater than #{INSTANCES_LIMIT}: #{n}" if n.zero? or n > INSTANCES_LIMIT
    @params.max_instances = n
  end

  parser.on("-o", "--log-output=FILE", "When logging is enabled, write main log output to FILE.",
  "Default is \"<LOG_DIR>/dnscrypt-proxy-multi.log\".") do |file|
    @params.log_file = file
  end

  parser.on("-O", "--log-overwrite", "When logging is enabled, do not append output to main log-file.") do
    @params.log_overwrite = true
  end

  parser.on("-p", "--local-port=RANGE", "Set range of ports to listen to.",
  "Default is \"#{@params.local_port_range}\".  Example: \"2053,5300-5399\"") do |range|
    @params.local_port_range = range
  end

  parser.on("-r", "--resolvers-list=PATH", "Set resolvers list file to use.",
  "Default is \"#{@params.resolvers_list}\".") do |path|
    fail "Not a readable file: #{path}" unless File.file?(path) and File.readable?(path)
    @params.resolvers_list = path
  end

  parser.on("-R", "--resolvers-list-encoding",
  "Set encoding of resolvers list.  Default is \"#{@params.resolvers_list_encoding}\".") do |e|
    @params.resolvers_list_encoding = e
  end

  parser.on("-s", "--port-check-async=N",
  "Set number of port-check queries to send simultaneously.  Default is #{@params.port_check_async}.") do |n|
    fail "Value for number of simultaneous checks must be an unsigned integer: #{n}" unless n =~ /^[[:digit:]]+$/
    n = Integer(n)
    fail "Value for number of simultaneous checks can't be 0." if n.zero?
    @params.port_check_async = n
  end

  parser.on("-S", "--syslog [PREFIX]",
  "Log messages to system log.  PREFIX gets inserted at the beginning of every",
  "message sent to syslog if it's specified.  See also -Z.") do |prefix|
    @params.syslog = true
    @params.syslog_prefix = prefix || ''
  end

  parser.on("-t", "--port-check-timeout=SECONDS",
  "Set timeout when waiting for a port-check reply.  Default is #{@params.port_check_timeout}.") do |secs|
    secs = Float(secs) rescue fail("Value for check timeout must be a number: #{secs}")
    fail "Value for check timeout can't be 0." if secs.zero?
    @params.port_check_timeout = secs
  end

  parser.on("-u", "--user=USER",
  "Drop priviliges to USER before creating instances of dnscrypt-proxy.",
  "Note that this might prevent dnscrypt-proxy from being able to listen to",
  "ports lower than 1024.") do |user|
    fail "User can't be an empty string." if user.empty?
    @params.user = user
  end

  parser.on("-U", "--dnscrypt-proxy-user=USER",
  "Tell dnscrypt-proxy to drop privileges as USER.",
  "Please consider that this may or may not work with --user.") do |user|
    fail "User can't be an empty string." if user.empty?
    @params.dnscrypt_proxy_user = user
  end

  parser.on("-v", "--verbose", "Show verbose messages.") do
    @params.verbose = true
  end

  parser.on("-V", "--version", "Show version and exit.") do
    $stderr.puts "dnscrypt-proxy-multi #{VERSION}"
    exit 1
  end

  parser.on("-w", "--wait-for-connection=HOST[:PORT][,HOST2[:PORT2][,...]]",
  "Wait until any of the specified hosts acknowledges connection, or responds",
  "with an ICMP Echo reply if no port is specified.  Checking with ICMP needs",
  "net-ping gem, and requires root/administrative privileges.") do |pairs|
    @params.wait_for_connection = pairs.split(',').map do |host_and_port|
      host, port = host_and_port.split(':')
      fail "Invalid host: #{host}" unless is_host_valid?(host)

      if port.nil?
        fail "Root/administrative privileges required for ICMP." unless Process.euid.zero?

        begin
          require 'net/ping'
        rescue LoadError
          fail "Gem net-ping needs to be installed to send ICMP Echo requests."
        end
      else
        port = Integer(port) rescue nil
        fail "Invalid port: #{port}" unless port and port > 0 and port < 65536
      end

      [host, port]
    end
  end

  parser.on("-W", "--write-pids [DIR]", "Enable writing PID's to DIR.",
  "Default directory is \"#{@params.write_pids_dir}\".") do |dir|
    @params.write_pids = true
    @params.write_pids_dir = dir if dir
  end

  parser.on("-x", "--exclude=[GLOBAL_OPTS:]NAME[/OPTS]=KEYWORD[,NAME2=KEYWORD2[/OPTS2][,...]]",
  "This option behaves similar to -f or --filter, but it directs entries to be",
  "excluded than included.") do |arg|
    @params.xfilters << parse_filter_arg(arg)
  end

  parser.on("-z", "--dnssec-only", "Only use resolvers that support DNSSEC validation.",
  "This gives same effect as --filter=dnssec=yes or --exclude=dnssec=no.") do
    @params.dnssec_only = true
  end

  parser.on("-Z", "--dnscrypt-proxy-syslog [PREFIX]",
  "Tell dnscrypt-proxy to log messages to system log.  It is automatically",
  "configured to have a prefix of '[REMOTE_IP:PORT]'. If PREFIX is specified,",
  "it is added to it with a space as a separator.",
  "Note that this disables file-logging in dnscrypt-proxy.") do |prefix|
    @params.dnscrypt_proxy_syslog = true
    @params.dnscrypt_proxy_syslog_prefix = prefix if prefix
  end

  parser.on("--", "All arguments after this are passed to dnscrypt-proxy.",
  "Please use this feature only if an option of dnscrypt-proxy is not yet",
  "supported by dnscrypt-proxy-multi.") do
    @params.dnscrypt_proxy_extra_args = ARGV
    parser.terminate
  end

  parser.parse!

  begin
    #
    # Enable logging to system log if wanted.
    #

    if @params.syslog
      require 'syslog/logger'

      begin
        @syslog_logger = Syslog::Logger.new('dnscrypt-proxy-multi')
      rescue SystemCallError => ex
        fail "Failed to open syslog: #{ex.message}"
      end
    end

    #
    # Show startup message.
    #

    log_message "----------------------------------------"
    log_message "Starting up."

    #
    # Setup SIGTERM trap.
    #

    Signal.trap('TERM') do
      log_message "SIGTERM caught."
      stop_instances unless @pids.empty?
      exit 1
    end

    #
    # Locate dnscrypt-proxy if it wasn't specified.
    #

    unless @params.dnscrypt_proxy
      @params.dnscrypt_proxy = which('dnscrypt-proxy')
      fail "Unable to find dnscrypt-proxy.  Please specify its location manually." unless @params.dnscrypt_proxy
    end

    #
    # Prepare stuff.
    #

    range = @params.local_ip_range
    ip_addr_range = IPAddrRange.new(range, @params.ignore_ip_format) or fail "Invalid range of IP addresses: #{range}"

    range = @params.local_port_range
    ports_range = PortsRange.new(range) or fail "Invalid range of ports: #{range}"

    log_warning "Specified local ip-port pairs are fewer than maximum number of instances." unless \
        ip_addr_range.enumerate_with(ports_range).take(@params.max_instances).to_a.size >= @params.max_instances

    prepare_dir(@params.write_pids_dir) if @params.write_pids
    prepare_dir(@params.log_dir) if @params.log
    mode = @params.log_overwrite ? 'w' : 'a'

    if @params.log
      log_file = @params.log_file || File.join(@params.log_dir, "dnscrypt-proxy-multi.log")
      fail "Log-file exists but is a directory: #{log_file}" if File.directory?(log_file)

      begin
        @log_file = File.open(log_file, mode)
      rescue Errno::EACCES, Errno::ENOENT => ex
        fail "Failed to open file #{log_file}: #{ex.message}"
      end

      @log_file.puts @log_buffer
      @log_file.flush
    end

    @log_buffer = nil

    #
    # Parse resolver list.
    #

    entries = []
    raw_count = 0

    CSV.foreach(@params.resolvers_list, encoding: @params.resolvers_list_encoding, headers: true) do |row|
      dnssec_validation, resolver_address, provider_name, provider_key = row.values_at(HEADER_MAP[:dnssec],
          HEADER_MAP[:resolver_addr], HEADER_MAP[:provider_name], HEADER_MAP[:provider_key])

      if @params.dnssec_only and dnssec_validation != 'yes'
        log_verbose "Ignoring entry that doesn't support DNSSEC validation: #{resolver_address}"
      elsif not @params.ifilters.empty? and not @params.ifilters.any?{ |set| all_expressions_match?(set, row) }
        log_verbose "Ignoring entry that doesn't match any inclusive filter set: #{resolver_address}"
      elsif not @params.xfilters.empty? and @params.xfilters.any?{ |set| all_expressions_match?(set, row) }
        log_verbose "Ignoring entry that matches an exclusive filter set: #{resolver_address}"
      elsif not resolver_address =~ /^([[:alnum:]]{1,3}.){3}[[:alnum:]]{1,3}(:[[:digit:]]+)?$/
        log_warning "Ignoring entry with invalid or unsupported resolver address: #{resolver_address}"
      elsif not provider_name =~ /^[[:alnum:]]+[[:alnum:].-]+[.][[:alpha:]]+$/
        log_warning "Ignoring entry with invalid provider name: #{resolver_address} (#{provider_name})"
      elsif not provider_key =~ /^([[:alnum:]]{4}:){15}[[:alnum:]]{4}$/
        log_warning "Ignoring entry with invalid provider key: #{resolver_address} (#{provider_key})"
      else
        unless resolver_address =~ /:[[:digit:]]+$/
          log_warning "Using default port #{DEFAULT_PORT} for #{resolver_address}."
          resolver_address = "#{resolver_address}:#{DEFAULT_PORT}"
        end

        entries << Entry.new(resolver_address, provider_name, provider_key)
      end

      raw_count += 1
    end

    fail "Resolvers list file \"#{resolvers_list}\" does not contain any entry." if raw_count == 0
    fail "All entries have been filtered out." if entries.empty?

    #
    # Drop privilege if wanted.
    #

    if @params.group
      begin
        group = Integer(@params.group) rescue @params.group
        Process::Sys.setgid(group)
      rescue SystemCallError, ArgumentError => e
        fail "Failed to change group or GID to #{@params.group}: #{e.message}"
      end
    end

    if @params.user
      begin
        user = Integer(@params.user) rescue @params.user
        Process::Sys.setuid(user)
      rescue SystemCallError, ArgumentError => e
        fail "Failed to change user or UID to #{@params.user}: #{e.message}"
      end
    end

    #
    # Wait for connection if wanted.
    #

    wait_for_connection if @params.wait_for_connection

    #
    # Check avaiability of services.
    #

    entries.each_slice(@params.port_check_async) do |r|
      threads = []

      r.each do |e|
        log_message "Checking resolver address #{e.resolver_address}."
        log_verbose "Timeout is #{@params.port_check_timeout}."

        threads << Thread.new(e) do |e|
          e.latency = check_tcp_port(e.resolver_ip, e.resolver_port, @params.port_check_timeout) rescue nil
        end
      end

      threads.each(&:join)
    end

    reachable_entries = entries.select(&:latency).sort_by(&:latency)

    if @params.verbose
      reachable_entries.each{ |e| log_verbose "Reachable entry: #{e.resolver_address} (#{e.latency})" }
      entries.reject(&:latency).each{ |e| log_verbose "Unreachable entry: #{e.resolver_address}" }
    end

    fail "No reachable entry." if reachable_entries.empty?

    #
    # Start instances.
    #

    reachable_entries_enum = reachable_entries.to_enum
    entry = nil, pid = nil
    opts = {:in => '/dev/null', :out => '/dev/null', :err => '/dev/null'}

    ip_addr_range.enumerate_with(ports_range).each do |local_ip, local_port|
      while entry = reachable_entries_enum.next rescue nil
        logfile_prefix = File.join(@params.log_dir, "dnscrypt-proxy.#{entry.resolver_ip}.#{entry.resolver_port}")

        cmd = [@params.dnscrypt_proxy,
            "--local-address=#{local_ip}:#{local_port}",
            "--resolver-address=#{entry.resolver_address}",
            "--provider-key=#{entry.provider_key}",
            "--provider-name=#{entry.provider_name}"]

        if @params.dnscrypt_proxy_syslog
          cmd << "--syslog"
          prefix = "[#{entry.resolver_ip}:#{entry.resolver_port}]"
          prefix << " #{@params.dnscrypt_proxy_syslog_prefix}" if @params.dnscrypt_proxy_syslog_prefix
          cmd << "--syslog-prefix=#{prefix}"
        elsif @params.log
          cmd += ["--logfile=#{logfile_prefix}.log", "--loglevel=#{@params.log_level}"]
        end

        cmd << "--user=#{@params.dnscrypt_proxy_user}" if @params.dnscrypt_proxy_user

        if @params.write_pids
          file = File.join(@params.write_pids_dir, "dnscrypt-proxy.#{local_ip}.#{local_port}.pid")
          cmd << "--pidfile=#{file}"
        end

        cmd << "--ephemeral-keys" if @params.ephemeral_keys
        cmd += @params.dnscrypt_proxy_extra_args if @params.dnscrypt_proxy_extra_args

        log_message "Starting dnscrypt-proxy instance for #{entry.resolver_address} (#{local_ip}:#{local_port})."

        begin
          log_verbose "Command: #{cmd.map{ |e| e.inspect }.join(' ')}" if @params.verbose

          if @params.log
            stdout, stderr = ['stdout', 'stderr'].map do |e|
              file = "#{logfile_prefix}.#{e}.log"

              begin
                File.open(file, @params.log_overwrite ? 'w' : 'a')
              rescue SystemCallError => ex
                fail "Failed to open log file #{file}: #{ex.message}"
              end
            end

            pid = Process.fork do
              opts[:out] = stdout
              opts[:err] = stderr
              Process.exec(*cmd, opts)
            end

            stdout.close
            stderr.close
          else
            pid = Process.spawn(*cmd, opts)
          end
        rescue Exception => ex
          log_error "Failed to create instance of dnscrypt-proxy: #{ex.message}"
          next
        end

        if @params.check_resolvers
          failed = false

          @params.check_resolvers.each do |fqdn, validate_with_dnssec|
            log_message "Checking if #{entry.resolver_address} (#{local_ip}:#{local_port}) can resolve #{fqdn}."
            log_verbose "Timeout is #{@params.check_resolvers_timeout}."

            sleep @params.check_resolvers_wait

            begin
              r = Resolv::DNS.new(nameserver_port: [[local_ip, local_port]])
              r.timeouts = @params.check_resolvers_timeout
              ipv4 = r.getaddress(fqdn)
              log_message "Success: #{ipv4.to_name.to_s.gsub(/\.in-addr\.arpa$/, '')}"
            rescue Resolv::ResolvError => ex
              log_error "Resolve error: #{ex.message}"
              log_verbose "Stopping instance."

              begin
                Process.kill('TERM', pid)
                Process.wait(pid)
              rescue SystemCallError
              end

              failed = true
              break
            end
          end

          next if failed
        end

        @pids << pid
        raise if @pids.size > @params.max_instances
        break
      end

      break if entry.nil? or @pids.size == @params.max_instances
      Kernel.sleep(@params.instance_delay) if @params.instance_delay > 0.0
    end

    if @pids.empty?
      log_error "No instances were started."
      log_error "Try to make sure clock is updated."
    else
      log_message "Done starting instances."

      #
      # Wait for all processes to exit.
      #

      r = Process.waitall
      @exit_status = 0 if r.is_a?(Array) and r.all?{ |a| a.last.exitstatus == 0 }
    end
  rescue SystemExit
    raise
  rescue Interrupt
    log_message "SIGINT caught."
    stop_instances unless @pids.empty?
  rescue Exception => ex
    log_error "Unknown exception with message '#{ex.message}' caught."
    log_error "Exception class: #{ex.class}"
    stop_instances unless @pids.empty?
  ensure
    log_message "Exiting."
    @log_file.close if @log_file
  end

  @exit_status
end

main