Module: Async::DNS::System

Defined in:
lib/async/dns/system.rb

Overview

This module encapsulates system dependent name lookup functionality.

Defined Under Namespace

Classes: Hosts, Resource

Constant Summary collapse

RESOLV_CONF = 
"/etc/resolv.conf"
HOSTS = 
"/etc/hosts"
DEFAULT_TIMEOUT = 
5.0

Class Method Summary collapse

Class Method Details

.hosts_path ⇒ Object

Get the path to the hosts file.



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# File 'lib/async/dns/system.rb', line 21

def self.hosts_path
	if RUBY_PLATFORM =~ /mswin32|mingw|bccwin/
		Win32::Resolv.get_hosts_path
	else
		HOSTS
	end
end

.ipv6? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/async/dns/system.rb', line 30

def self.ipv6?
	begin
		list = Socket.ip_address_list
	rescue NotImplementedError
		return true
	end
	
	list.any? {|a| a.ipv6? && !a.ipv6_loopback? && !a.ipv6_linklocal? }
end

.parse_resolv_configuration(path) ⇒ Object

Parse the resolv.conf file and return a list of nameservers.



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# File 'lib/async/dns/system.rb', line 119

def self.parse_resolv_configuration(path)
	nameservers = []
	search = nil
	ndots = 1
	edns = nil
	timeout = DEFAULT_TIMEOUT
	
	File.open(path) do |file|
		file.each do |line|
			# Remove any comments:
			line.sub!(/[#;].*/, "")
			
			# Extract resolv.conf command:
			keyword, *arguments = line.split(/\s+/)
			
			case keyword
			when "nameserver"
				nameservers.concat(arguments)
			when "domain", "search"
				search = arguments
			when "options"
				arguments.each do |argument|
					key, value = argument.split(":", 2)
					
					case key
					when "ndots"
						ndots = value.to_i
					when "edns0"
						edns = 0
					when "timeout"
						timeout = value.to_f
					end
				end
			end
		end
	end
	
	return {
		nameservers: nameservers,
		search: search,
		ndots: ndots,
		edns: edns,
		timeout: timeout,
	}
end

.resolver(**options) ⇒ Object

Get a list of standard nameserver connections which can be used for querying any standard servers that the system has been configured with. There is no equivalent facility to use the hosts file at present.



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# File 'lib/async/dns/system.rb', line 166

def self.resolver(**options)
	nameservers = []
	
	if File.exist? RESOLV_CONF
		options.update(parse_resolv_configuration(RESOLV_CONF))
		nameservers = options.delete(:nameservers)
	elsif defined?(Win32::Resolv) and RUBY_PLATFORM =~ /mswin32|cygwin|mingw|bccwin/
		search, nameservers = Win32::Resolv.get_resolv_info
		options.update(search: search)
	end
	
	if search = options[:search]
		unless search.include?(".")
			search << nil
		end
	else
		options[:search] = [nil]
	end
	
	if hosts = Hosts.local
		cache = options.fetch(:cache) do
			options[:cache] = Cache.new
		end
		
		hosts.each do |name, addresses|
			addresses.each do |address|
				resource = Resource.new(address, nil)
				case address
				when Resolv::IPv4
					cache.store(name, Resolv::DNS::Resource::IN::A, resource)
				when Resolv::IPv6
					cache.store(name, Resolv::DNS::Resource::IN::AAAA, resource)
				end
			end
		end
	end
	
	timeout = options.delete(:timeout) || DEFAULT_TIMEOUT
	endpoint = Endpoint.for(nameservers, timeout: timeout)
	
	if block_given?
		yield endpoint, **options
	else
		return Resolver.new(endpoint, **options)
	end
end