class Bones::RPC::DNSResolver

Constants

DNS_PORT
RESOLV_CONF

Public Class Methods

generate_id() click to toggle source
# File lib/bones/rpc/dns_resolver.rb, line 12
def self.generate_id
  @mutex.synchronize { @identifier = (@identifier + 1) & 0xFFFF }
end
nameservers(config = RESOLV_CONF) click to toggle source
# File lib/bones/rpc/dns_resolver.rb, line 16
def self.nameservers(config = RESOLV_CONF)
  File.read(config).scan(/^\s*nameserver\s+([0-9.:]+)/).flatten
end
new() click to toggle source
# File lib/bones/rpc/dns_resolver.rb, line 20
def initialize
  @nameservers = self.class.nameservers

  # TODO: fall back on other nameservers if the first one is unavailable
  @server = @nameservers.first

  @socket = UDPSocket.new
end

Public Instance Methods

resolve(hostname) click to toggle source
# File lib/bones/rpc/dns_resolver.rb, line 29
def resolve(hostname)
  if host = resolve_hostname(hostname)
    unless ip_address = resolve_host(host)
      raise Resolv::ResolvError, "invalid entry in hosts file: #{host}"
    end
    return ip_address
  end

  query = build_query(hostname)
  @socket.send query.encode, 0, @server, DNS_PORT
  data, _ = @socket.recvfrom(512)
  response = Resolv::DNS::Message.decode(data)

  addrs = []
  # The answer might include IN::CNAME entries so filters them out
  # to include IN::A & IN::AAAA entries only.
  response.each_answer { |name, ttl, value| addrs << value.address if value.respond_to?(:address) }

  return if addrs.empty?
  return addrs.first if addrs.size == 1
  addrs
end

Private Instance Methods

build_query(hostname) click to toggle source
# File lib/bones/rpc/dns_resolver.rb, line 65
def build_query(hostname)
  Resolv::DNS::Message.new.tap do |query|
    query.id = self.class.generate_id
    query.rd = 1
    query.add_question hostname, Resolv::DNS::Resource::IN::A
  end
end
resolv() click to toggle source
# File lib/bones/rpc/dns_resolver.rb, line 61
def resolv
  @resolv ||= Resolv::Hosts.new
end
resolve_host(host) click to toggle source
# File lib/bones/rpc/dns_resolver.rb, line 73
def resolve_host(host)
  resolve_ip(Resolv::IPv4, host) || resolve_ip(Resolv::IPv6, host)
end
resolve_hostname(hostname) click to toggle source
# File lib/bones/rpc/dns_resolver.rb, line 54
def resolve_hostname(hostname)
  # Resolv::Hosts#getaddresses pushes onto a stack
  # so since we want the first occurance, simply
  # pop off the stack.
  resolv.getaddresses(hostname).pop rescue nil
end
resolve_ip(klass, host) click to toggle source
# File lib/bones/rpc/dns_resolver.rb, line 77
def resolve_ip(klass, host)
  begin
    klass.create(host)
  rescue ArgumentError
  end
end