class Dnsruby::Resolver
Description¶ ↑
Dnsruby::Resolver
is a DNS
stub resolver. This class performs queries with retries across multiple nameservers. The system configured resolvers are used by default.
The retry policy is a combination of the Net::DNS and dnsjava approach, and has the option of :
-
A total timeout for the query (defaults to 0, meaning “no total timeout”)
-
A retransmission system that targets the namervers concurrently once the first query round is
complete, but in which the total time per query round is split between the number of nameservers targetted for the first round. and total time for query round is doubled for each query round
Note that, if a total timeout is specified, then that will apply regardless of the retry policy (i.e. it may cut retries short).
Note also that these timeouts are distinct from the SingleResolver's packet_timeout
Timeouts apply to the initial query and response. If DNSSEC validation is to be performed, then additional queries may be required (these are performed automatically by Dnsruby
). Each additional query will be performed with its own timeouts. So, even with a query_timeout
of 5 seconds, a response which required extensive validation may take several times that long. (Future versions of Dnsruby
may expose finer-grained events for client tracking of responses and validation)
Methods¶ ↑
Synchronous¶ ↑
These methods raise an exception or return a response message with rcode==NOERROR
-
Dnsruby::Resolver#query
(name [, type [, klass]])
There are "!" versions of these two methods that return an array [response, error] instead of raising an error on failure. They can be called as follows: response, error = resolver.send_message!(...) response, error = resolver.query!(...) If the request succeeds, response will contain the Dnsruby::Message response and error will be nil. If the request fails, response will be nil and error will contain the error raised.
Asynchronous¶ ↑
These methods use a response queue to return the response and the error
-
Dnsruby::Resolver#send_async
(msg, response_queue, query_id)
Event Loop¶ ↑
Dnsruby
runs a pure Ruby event loop to handle I/O in a single thread. Support for EventMachine has been deprecated.
Constants
- AbsoluteMinDnssecUdpSize
- DefaultDnssec
- DefaultPacketTimeout
- DefaultPipeLiningMaxQueries
- DefaultPort
- DefaultQueryTimeout
- DefaultRetryDelay
- DefaultRetryTimes
- DefaultUDPSize
- MinDnssecUdpSize
Attributes
The current Config
Defines whether we will cache responses, or pass every request to the upstream resolver. This is only really useful when querying authoritative servers (as the upstream recursive resolver is likely to cache)
Defines whether validation is performed by default on this Resolver
when the query method is called. Note that send_message
and send_async
expect a Message
object to be passed in, which is already configured to the callers requirements.
Should truncation be ignored? i.e. the TC bit is ignored and thus the resolver will not requery over TCP if TC is set
If no_tcp
==true, then ONLY UDP will be used as a transport. This should not generally be used, but is provided as a debugging aid.
The timeout for any individual packet. This is the timeout used by SingleResolver
The port to send queries to on the resolver
Note that this timeout represents the total time a query may run for - multiple packets can be sent to multiple nameservers in this time. This is distinct from the SingleResolver
per-packet timeout The query_timeout
is not required - it will default to 0, which means “do not use query_timeout
”. If this is the case then the timeout will be dictated by the retry_times
and retry_delay
attributes
Should the Recursion Desired bit be set?
The query will be tried across nameservers retry_times
times, with a delay of retry_delay
seconds between each retry. The first time round, retry_delay
will be divided by the number of nameservers being targetted, and a new nameserver will be queried with the resultant delay.
The query will be tried across nameservers retry_times
times, with a delay of retry_delay
seconds between each retry. The first time round, retry_delay
will be divided by the number of nameservers being targetted, and a new nameserver will be queried with the resultant delay.
The source address to send queries from for IPv4
The source address to send queries from for IPv6
If tcp_pipelining
==true, then we reuse the TCP connection
How many times (number of messages) to reuse the pipelining connection before closing, :infinite for infinite number of requests per connection
The maximum UDP size to be used
Should TCP be used as a transport rather than UDP? If use_tcp
==true, then ONLY TCP will be used as a transport.
Public Class Methods
# File lib/dnsruby/resolver.rb, line 653 def Resolver.check_port(p, src_port=[]) unless p.is_a?(Integer) tmp_src_ports = Array.new(src_port) p.each do |x| unless Resolver.check_port(x, tmp_src_ports) return false end tmp_src_ports.push(x) end return true end if Resolver.port_in_range(p) return ! ((p == 0) && (src_port.length > 0)) else Dnsruby.log.error("Illegal port (#{p})") Dnsruby.log_and_raise("Illegal port #{p}", ArgumentError) end end
# File lib/dnsruby/resolver.rb, line 676 def Resolver.get_ports_from(p) a = [] if p.is_a?(Integer) a = [p] else p.each do |x| a.push(x) end end a end
# File lib/dnsruby/resolver.rb, line 735 def Resolver.get_tsig(args) tsig = nil if args.length == 1 if args[0] if args[0].instance_of?(RR::TSIG) tsig = args[0] elsif args[0].instance_of?(Array) tsig = RR.new_from_hash(create_tsig_options(*args[0])) end else # Dnsruby.log.debug{'TSIG signing switched off'} return nil end else tsig = RR.new_from_hash(create_tsig_options(args)) end Dnsruby.log.info{"TSIG signing now using #{tsig.name}, key=#{tsig.key}"} tsig end
Create a new Resolver
object. If no parameters are passed in, then the default system configuration will be used. Otherwise, a Hash may be passed in with the following optional elements :
-
:port
-
:use_tcp
-
:tsig
-
:ignore_truncation
-
:src_address
-
:src_address6
-
:src_port
-
:recurse
-
:udp_size
-
:config_info - see
Config
-
:nameserver - can be either a String or an array of Strings
-
:packet_timeout
-
:query_timeout
-
:retry_times
-
:retry_delay
-
:do_caching
-
:tcp_pipelining
-
:tcp_pipelining_max_queries - can be a number or :infinite symbol
# File lib/dnsruby/resolver.rb, line 436 def initialize(*args) # @TODO@ Should we allow :namesver to be an RRSet of NS records? Would then need to randomly order them? @resolver_ruby = nil @src_address = nil @src_address6 = nil @single_res_mutex = Mutex.new @configured = false @do_caching = true @config = Config.new() reset_attributes # Process args if args.length == 1 if args[0].class == Hash args[0].keys.each do |key| begin if key == :config_info @config.set_config_info(args[0][:config_info]) elsif key == :nameserver set_config_nameserver(args[0][:nameserver]) elsif key == :nameservers set_config_nameserver(args[0][:nameservers]) else send(key.to_s + '=', args[0][key]) end rescue Exception => e Dnsruby.log.error{"Argument #{key} not valid : #{e}\n"} end end elsif args[0].class == String set_config_nameserver(args[0]) elsif args[0].class == Config # also accepts a Config object from Dnsruby::Resolv @config = args[0] end else # Anything to do? end update end
# File lib/dnsruby/resolver.rb, line 672 def Resolver.port_in_range(p) (p == 0) || ((p >= 50000) && (p <= 65535)) end
Protected Class Methods
# File lib/dnsruby/resolver.rb, line 722 def Resolver.create_tsig_options(name, key, algorithm = nil) options = { type: Types.TSIG, klass: Classes.ANY, name: name, key: key } options[:algorithm] = algorithm if algorithm options end
Public Instance Methods
Can be a single Integer or a Range or an Array If an invalid port is selected (one reserved by IANA), then an ArgumentError will be raised. “0” means “any valid port” - this is only a viable option if it is the only port in the list. An ArgumentError will be raised if “0” is added to an existing set of source ports.
res.add_src_port(60000) res.add_src_port([60001,60005,60010]) res.add_src_port(60015..60115)
# File lib/dnsruby/resolver.rb, line 639 def add_src_port(p) if Resolver.check_port(p, @src_port) a = Resolver.get_ports_from(p) a.each do |x| if (@src_port.length > 0) && (x == 0) Dnsruby.log_and_raise("src_port of 0 only allowed as only src_port value (currently #{@src_port.length} values", ArgumentError) end @src_port.push(x) end end update end
Close the Resolver
. Unfinished queries are terminated with OtherResolvError
.
# File lib/dnsruby/resolver.rb, line 409 def close @resolver_ruby.close if @resolver_ruby end
# File lib/dnsruby/resolver.rb, line 798 def dnssec=(d) @dnssec = d if d # Set the UDP size (RFC 4035 section 4.1) if @udp_size < MinDnssecUdpSize self.udp_size = MinDnssecUdpSize end end update end
# File lib/dnsruby/resolver.rb, line 788 def do_caching=(on) @do_caching=on update end
# File lib/dnsruby/resolver.rb, line 758 def ignore_truncation=(on) @ignore_truncation = on update end
# File lib/dnsruby/resolver.rb, line 586 def nameserver=(n) @configured = true @single_res_mutex.synchronize { @single_resolvers=[] } set_config_nameserver(n) add_config_nameservers end
# File lib/dnsruby/resolver.rb, line 582 def nameservers=(ns) self.nameserver=(ns) end
# File lib/dnsruby/resolver.rb, line 703 def no_tcp=(on) @no_tcp=on update end
– @TODO@ Should really auto-generate these methods. Also, any way to tie them up with SingleResolver
RDoc? ++
# File lib/dnsruby/resolver.rb, line 598 def packet_timeout=(t) @packet_timeout = t update end
# File lib/dnsruby/resolver.rb, line 778 def persistent_tcp=(on) @persistent_tcp = on update end
# File lib/dnsruby/resolver.rb, line 783 def persistent_udp=(on) @persistent_udp = on update end
# File lib/dnsruby/resolver.rb, line 773 def port=(a) @port = a update end
Query for a name. If a valid Message
is received, then it is returned to the caller. Otherwise an exception (a Dnsruby::ResolvError
or Dnsruby::ResolvTimeout
) is raised.
require 'dnsruby' res = Dnsruby::Resolver.new response = res.query('example.com') # defaults to Types.A, Classes.IN response = res.query('example.com', Types.MX) response = res.query('208.77.188.166') # IPv4 address so PTR query will be made response = res.query('208.77.188.166', Types.PTR)
# File lib/dnsruby/resolver.rb, line 191 def query(name, type=Types.A, klass=Classes.IN, set_cd=@dnssec) msg = Message.new msg.do_caching = @do_caching msg.header.rd = 1 msg.add_question(name, type, klass) msg.do_validation = @do_validation if @dnssec msg.header.cd = set_cd # We do our own validation by default end send_message(msg) end
Like query, but does not raise an error when an error occurs. Instead, it returns it. @return a 2 element array: [response, error]
# File lib/dnsruby/resolver.rb, line 206 def query!(name, type=Types.A, klass=Classes.IN, set_cd=@dnssec) response = nil; error = nil begin response = query(name, type, klass, set_cd) rescue => e error = e end [response, error] end
Sends a message with send_plain_message. Effectively a wrapper around send_plain_message
, but adds the ability to configure whether an error will be raised or returned if it occurs.
@param message the message to send to the DNS
server @param error_strategy :return to return [response, error] (default),
:raise to return response only, or raise an error if one occurs
# File lib/dnsruby/resolver.rb, line 281 def query_raw(message, error_strategy = :return) unless [:return, :raise].include?(error_strategy) raise ArgumentError.new('error_strategy should be one of [:return, :raise].') end response, error = send_plain_message(message) if error_strategy == :return [response, error] else raise error if error response end end
# File lib/dnsruby/resolver.rb, line 793 def recurse=(a) @recurse = a update end
Asynchronously send a Message
to the server. The send can be done using just Dnsruby
. Support for EventMachine has been deprecated.
Dnsruby
pure Ruby event loop :¶ ↑
A client_queue is supplied by the client, along with an optional client_query_id to identify the response. The client_query_id is generated, if not supplied, and returned to the client. When the response is known, a tuple of (query_id, response_message, exception) will be added to the client_queue.
The query is sent synchronously in the caller's thread. The select thread is then used to listen for and process the response (up to pushing it to the client_queue). The client thread is then used to retrieve the response and deal with it.
Takes :
-
msg - the message to send
-
client_queue - a Queue to push the response to, when it arrives
-
client_query_id - an optional ID to identify the query to the client
-
use_tcp
- whether to use only TCP (defaults toSingleResolver.use_tcp
)
Returns :
-
client_query_id - to identify the query response to the client. This ID is
generated if it is not passed in by the client
Example invocations :¶ ↑
id = res.send_async(msg, queue) NOT SUPPORTED : id = res.send_async(msg, queue, use_tcp) id = res.send_async(msg, queue, id) id = res.send_async(msg, queue, id, use_tcp)
Example code :¶ ↑
require 'dnsruby' res = Dnsruby::Resolver.newsend query_id = 10 # can be any object you like query_queue = Queue.new res.send_async(Message.new('example.com', Types.MX), query_queue, query_id) query_id_2 = res.send_async(Message.new('example.com', Types.A), query_queue) # ...do a load of other stuff here... 2.times do response_id, response, exception = query_queue.pop # You can check the ID to see which query has been answered if exception == nil # deal with good response else # deal with problem end end
# File lib/dnsruby/resolver.rb, line 389 def send_async(msg, client_queue, client_query_id = nil) unless @configured add_config_nameservers end # @single_res_mutex.synchronize { unless @resolver_ruby # @TODO@ Synchronize this? @resolver_ruby = ResolverRuby.new(self) end # } client_query_id = @resolver_ruby.send_async(msg, client_queue, client_query_id) if @single_resolvers.length == 0 Thread.start { sleep(@query_timeout == 0 ? 1 : @query_timeout) client_queue.push([client_query_id, nil, ResolvTimeout.new('Query timed out - no nameservers configured')]) } end client_query_id end
Send a message, and wait for the response. If a valid Message
is received, then it is returned to the caller. Otherwise an exception (a Dnsruby::ResolvError
or Dnsruby::ResolvTimeout
) is raised.
send_async
is called internally.
example :
require 'dnsruby' include Dnsruby res = Dnsruby::Resolver.new begin response = res.send_message(Message.new('example.com', Types.MX)) rescue ResolvError # ... rescue ResolvTimeout # ... end
# File lib/dnsruby/resolver.rb, line 245 def send_message(message) Dnsruby.log.debug{'Resolver : sending message'} q = Queue.new send_async(message, q) _id, result, error = q.pop if error error.response = result if error.is_a?(ResolvError) raise error else result end end
Like send_message
, but does not raise an error when an error occurs. Instead, it returns it. @return a 2 element array: [response, error]
# File lib/dnsruby/resolver.rb, line 263 def send_message!(message) response = nil; error = nil begin response = send_message(message) rescue => e error = e end [response, error] end
This method takes a Message
(supplied by the client), and sends it to the configured nameservers. No changes are made to the Message
before it is sent (TSIG signatures will be applied if configured on the Resolver
). Retries are handled as the Resolver
is configured to do. Incoming responses to the query are not cached or validated (although TCP fallback will be performed if the TC bit is set and the (Single)Resolver
has ignore_truncation
set to false). Note that the Message
is left untouched - this means that no OPT records are added, even if the UDP transport for the server is specified at more than 512 bytes. If it is desired to use EDNS for this packet, then you should call the Dnsruby::PacketSender#prepare_for_dnssec(msg), or Dnsruby::PacketSender#add_opt_rr(msg) The return value from this method is the [response, error] tuple. Either of these values may be nil - it is up to the client to check.
example :
require 'dnsruby' include Dnsruby res = Dnsruby::Resolver.new response, error = res.send_plain_message(Message.new('example.com', Types.MX)) if error print "Error returned : #{error}\n" else process_response(response) end
# File lib/dnsruby/resolver.rb, line 323 def send_plain_message(message) Dnsruby::TheLog.debug('Resolver : send_plain_message') message.do_caching = false message.do_validation = false message.send_raw = true q = Queue.new send_async(message, q) _id, result, error = q.pop error.response = result if !error.nil? && error.is_a?(ResolvError) [result, error] end
# File lib/dnsruby/resolver.rb, line 506 def set_config_nameserver(n) # @TODO@ Should we allow NS RRSet here? If so, then .sort_by {rand} @config.get_ready unless @configured @configured = true @config.nameserver = n.kind_of?(String) ? [n] : n add_config_nameservers end
# File lib/dnsruby/resolver.rb, line 768 def src_address6=(a) @src_address6 = a update end
# File lib/dnsruby/resolver.rb, line 763 def src_address=(a) @src_address = a update end
The source port to send queries from Returns either a single Integer or an Array e.g. '0', or '[60001, 60002, 60007]'
Defaults to 0 - random port
# File lib/dnsruby/resolver.rb, line 608 def src_port @src_port.length == 1 ? @src_port[0] : @src_port end
Can be a single Integer or a Range or an Array If an invalid port is selected (one reserved by IANA), then an ArgumentError will be raised.
res.src_port=0 res.src_port=[60001,60005,60010] res.src_port=60015..60115
# File lib/dnsruby/resolver.rb, line 620 def src_port=(p) if Resolver.check_port(p) @src_port = Resolver.get_ports_from(p) update end end
# File lib/dnsruby/resolver.rb, line 688 def tcp_pipelining=(on) @tcp_pipelining = on update end
# File lib/dnsruby/resolver.rb, line 693 def tcp_pipelining_max_queries=(max) @tcp_pipelining_max_queries = max update end
Sets the TSIG to sign outgoing messages with. Pass in either a Dnsruby::RR::TSIG
, or a key_name and key (or just a key) Pass in nil to stop tsig signing.
-
res.tsig=(tsig_rr)
-
res.tsig=(key_name, key) # defaults to hmac-md5
-
res.tsig=(key_name, key, alg) # e.g. alg = 'hmac-sha1'
-
res.tsig=nil # Stop the resolver from signing
# File lib/dnsruby/resolver.rb, line 715 def tsig=(t) @tsig = t update end
# File lib/dnsruby/resolver.rb, line 809 def udp_size=(s) @udp_size = s update end
# File lib/dnsruby/resolver.rb, line 573 def update_internal_res(res) [:port, :use_tcp, :no_tcp, :tcp_pipelining, :tcp_pipelining_max_queries, :tsig, :ignore_truncation, :packet_timeout, :src_address, :src_address6, :src_port, :recurse, :udp_size, :dnssec].each do |param| res.send(param.to_s + '=', instance_variable_get('@' + param.to_s)) end end
# File lib/dnsruby/resolver.rb, line 698 def use_tcp=(on) @use_tcp = on update end