Object
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)
These methods raise an exception or return a response message with rcode==NOERROR
Dnsruby::Resolver#query(name [, type [, klass]])
These methods use a response queue to return the response and the error
Dnsruby::Resolver#send_async(msg, response_queue, query_id)
Dnsruby runs a pure Ruby event loop to handle I/O in a single thread. Support for EventMachine has been deprecated.
Should TCP be used as a transport rather than UDP? If use_tcp==true, then ONLY TCP will be used as a transport.
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.
Should truncation be ignored? i.e. the TC bit is ignored and thus the resolver will not requery over TCP if TC is set
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
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.
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.
# File lib/Dnsruby/Resolver.rb, line 593 593: def Resolver.check_port(p, src_port=[]) 594: if (p.class != Fixnum) 595: tmp_src_ports = Array.new(src_port) 596: p.each do |x| 597: if (!Resolver.check_port(x, tmp_src_ports)) 598: return false 599: end 600: tmp_src_ports.push(x) 601: end 602: return true 603: end 604: if (Resolver.port_in_range(p)) 605: if ((p == 0) && (src_port.length > 0)) 606: return false 607: end 608: return true 609: else 610: Dnsruby.log.error("Illegal port (#{p})") 611: raise ArgumentError.new("Illegal port #{p}") 612: end 613: end
# File lib/Dnsruby/Resolver.rb, line 625 625: def Resolver.get_ports_from(p) 626: a = [] 627: if (p.class == Fixnum) 628: a = [p] 629: else 630: p.each do |x| 631: a.push(x) 632: end 633: end 634: return a 635: end
# File lib/Dnsruby/Resolver.rb, line 659 659: def Resolver.get_tsig(args) 660: tsig = nil 661: if (args.length == 1) 662: if (args[0]) 663: if (args[0].instance_of?RR::TSIG) 664: tsig = args[0] 665: elsif (args[0].instance_of?Array) 666: if (args[0].length > 2) 667: tsig = RR.new_from_hash({:type => Types.TSIG, :klass => Classes.ANY, :name => args[0][0], :key => args[0][1], :algorithm => args[0][2]}) 668: else 669: tsig = RR.new_from_hash({:type => Types.TSIG, :klass => Classes.ANY, :name => args[0][0], :key => args[0][1]}) 670: end 671: end 672: else 673: # Dnsruby.log.debug{"TSIG signing switched off"} 674: return nil 675: end 676: elsif (args.length ==2) 677: tsig = RR.new_from_hash({:type => Types.TSIG, :klass => Classes.ANY, :name => args[0], :key => args[1]}) 678: elsif (args.length ==3) 679: tsig = RR.new_from_hash({:type => Types.TSIG, :klass => Classes.ANY, :name => args[0], :key => args[1], :algorithm => args[2]}) 680: else 681: raise ArgumentError.new("Wrong number of arguments to tsig=") 682: end 683: Dnsruby.log.info{"TSIG signing now using #{tsig.name}, key=#{tsig.key}"} 684: return tsig 685: 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
:tsig
:recurse
:config_info - see Config
:nameserver - can be either a String or an array of Strings
# File lib/Dnsruby/Resolver.rb, line 373 373: def initialize(*args) 374: # @TODO@ Should we allow :namesver to be an RRSet of NS records? Would then need to randomly order them? 375: @resolver_ruby = nil 376: @src_address = nil 377: @single_res_mutex = Mutex.new 378: @configured = false 379: @do_caching = true 380: @config = Config.new() 381: reset_attributes 382: 383: # Process args 384: if (args.length==1) 385: if (args[0].class == Hash) 386: args[0].keys.each do |key| 387: begin 388: if (key == :config_info) 389: @config.set_config_info(args[0][:config_info]) 390: elsif (key==:nameserver) 391: set_config_nameserver(args[0][:nameserver]) 392: elsif (key==:nameservers) 393: set_config_nameserver(args[0][:nameservers]) 394: else 395: send(key.to_s+"=", args[0][key]) 396: end 397: rescue Exception 398: Dnsruby.log.error{"Argument #{key} not valid\n"} 399: end 400: end 401: elsif (args[0].class == String) 402: set_config_nameserver(args[0]) 403: elsif (args[0].class == Config) 404: # also accepts a Config object from Dnsruby::Resolv 405: @config = args[0] 406: end 407: else 408: # Anything to do? 409: end 410: # if (@single_resolvers==[]) 411: # add_config_nameservers 412: # end 413: update 414: # ResolverRegister::register_resolver(self) 415: end
# File lib/Dnsruby/Resolver.rb, line 615 615: def Resolver.port_in_range(p) 616: if ((p == 0) || ((p >= 50000) && (p <= 65535))) 617: # @TODO@ IANA port bitmap - use 50000 - 65535 for now 618: # ((Iana::IANA_PORTS.index(p)) == nil && 619: # (p > 1024) && (p < 65535))) 620: return true 621: end 622: return false 623: end
Can be a single Fixnum 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 580 580: def add_src_port(p) 581: if (Resolver.check_port(p, @src_port)) 582: a = Resolver.get_ports_from(p) 583: a.each do |x| 584: if ((@src_port.length > 0) && (x == 0)) 585: raise ArgumentError.new("src_port of 0 only allowed as only src_port value (currently #{@src_port.length} values") 586: end 587: @src_port.push(x) 588: end 589: end 590: update 591: end
Close the Resolver. Unfinished queries are terminated with OtherResolvError.
# File lib/Dnsruby/Resolver.rb, line 349 349: def close 350: @resolver_ruby.close if @resolver_ruby 351: end
# File lib/Dnsruby/Resolver.rb, line 723 723: def dnssec=(d) 724: @dnssec = d 725: if (d) 726: # Set the UDP size (RFC 4035 section 4.1) 727: if (@udp_size < MinDnssecUdpSize) 728: self.udp_size = MinDnssecUdpSize 729: end 730: end 731: update 732: end
# File lib/Dnsruby/Resolver.rb, line 713 713: def do_caching=(on) 714: @do_caching=on 715: update 716: end
# File lib/Dnsruby/Resolver.rb, line 688 688: def ignore_truncation=(on) 689: @ignore_truncation = on 690: update 691: end
# File lib/Dnsruby/Resolver.rb, line 522 522: def nameserver=(n) 523: @configured = true 524: @single_res_mutex.synchronize { 525: @single_resolvers=[] 526: } 527: set_config_nameserver(n) 528: add_config_nameservers 529: end
# File lib/Dnsruby/Resolver.rb, line 519 519: def nameservers=(ns) 520: self.nameserver=(n) 521: end
# File lib/Dnsruby/Resolver.rb, line 642 642: def no_tcp=(on) 643: @no_tcp=on 644: update 645: end
— @TODO@ Should really auto-generate these methods. Also, any way to tie them up with SingleResolver RDoc? ++
# File lib/Dnsruby/Resolver.rb, line 536 536: def packet_timeout=(t) 537: @packet_timeout = t 538: update 539: end
# File lib/Dnsruby/Resolver.rb, line 703 703: def persistent_tcp=(on) 704: @persistent_tcp = on 705: update 706: end
# File lib/Dnsruby/Resolver.rb, line 708 708: def persistent_udp=(on) 709: @persistent_udp = on 710: update 711: end
# File lib/Dnsruby/Resolver.rb, line 698 698: def port=(a) 699: @port = a 700: update 701: 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 170 170: def query(name, type=Types.A, klass=Classes.IN, set_cd=@dnssec) 171: msg = Message.new 172: msg.do_caching = @do_caching 173: msg.header.rd = 1 174: msg.add_question(name, type, klass) 175: msg.do_validation = @do_validation 176: if (@dnssec) 177: msg.header.cd = set_cd # We do our own validation by default 178: end 179: return send_message(msg) 180: end
# File lib/Dnsruby/Resolver.rb, line 718 718: def recurse=(a) 719: @recurse = a 720: update 721: end
Asynchronously send a Message to the server. The send can be done using just Dnsruby. Support for EventMachine has been deprecated.
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 to SingleResolver.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
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)
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 329 329: def send_async(*args) # msg, client_queue, client_query_id) 330: if (!@configured) 331: add_config_nameservers 332: end 333: # @single_res_mutex.synchronize { 334: if (!@resolver_ruby) # @TODO@ Synchronize this? 335: @resolver_ruby = ResolverRuby.new(self) 336: end 337: # } 338: client_query_id = @resolver_ruby.send_async(*args) 339: if (@single_resolvers.length == 0) 340: Thread.start { 341: sleep(@query_timeout == 0 ? 1 : @query_timeout) 342: args[1].push([client_query_id, nil, ResolvTimeout.new("Query timed out - no nameservers configured")]) 343: } 344: end 345: return client_query_id 346: 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 211 211: def send_message(message) 212: Dnsruby.log.debug{"Resolver : sending message"} 213: q = Queue.new 214: send_async(message, q) 215: # # @TODO@ Add new queue tuples, e.g. : 216: # event_type = EventType::RECEIVED 217: # reply = nil 218: # while (event_type == EventType::RECEIVED) 219: # id, event_type, reply, error = q.pop 220: # Dnsruby.log.debug{"Resolver : result received"} 221: # if ((error != nil) && (event_type == EventType::ERROR)) 222: # raise error 223: # end 224: # print "Reply = #{reply}\n" 225: # end 226: # print "Reply = #{reply}\n" 227: # return reply 228: 229: id, result, error = q.pop 230: 231: if (error != nil) 232: raise error 233: else 234: return result 235: end 236: 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 264 264: def send_plain_message(message) 265: Dnsruby::TheLog.debug("Resolver : send_plain_message") 266: message.do_caching = false 267: message.do_validation = false 268: message.send_raw = true 269: q = Queue.new 270: send_async(message, q) 271: id, result, error = q.pop 272: return [result, error] 273: end
# File lib/Dnsruby/Resolver.rb, line 435 435: def set_config_nameserver(n) 436: # @TODO@ Should we allow NS RRSet here? If so, then .sort_by {rand} 437: if (!@configured) 438: @config.get_ready 439: end 440: @configured = true 441: if (n).kind_of?String 442: @config.nameserver=[n] 443: else 444: @config.nameserver=n 445: end 446: add_config_nameservers 447: end
# File lib/Dnsruby/Resolver.rb, line 693 693: def src_address=(a) 694: @src_address = a 695: update 696: end
The source port to send queries from Returns either a single Fixnum or an Array e.g. “0”, or “[60001, 60002, 60007]”
Defaults to 0 - random port
# File lib/Dnsruby/Resolver.rb, line 546 546: def src_port 547: if (@src_port.length == 1) 548: return @src_port[0] 549: end 550: return @src_port 551: end
Can be a single Fixnum 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 561 561: def src_port=(p) 562: if (Resolver.check_port(p)) 563: @src_port = Resolver.get_ports_from(p) 564: update 565: end 566: 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 654 654: def tsig=(t) 655: @tsig=t 656: update 657: end
# File lib/Dnsruby/Resolver.rb, line 734 734: def udp_size=(s) 735: @udp_size = s 736: update 737: end
# File lib/Dnsruby/Resolver.rb, line 510 510: def update_internal_res(res) 511: [:port, :use_tcp, :no_tcp, :tsig, :ignore_truncation, :packet_timeout, 512: :src_address, :src_port, :recurse, 513: :udp_size, :dnssec].each do |param| 514: 515: res.send(param.to_s+"=", instance_variable_get("@"+param.to_s)) 516: end 517: end
Disabled; run with --debug to generate this.
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