Class | Dnsruby::Resolver |
In: |
lib/Dnsruby/Resolver.rb
|
Parent: | 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 :
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
These methods use a response queue to return the response and the error
Dnsruby runs a pure Ruby event loop to handle I/O in a single thread. Support for EventMachine has been deprecated.
DefaultQueryTimeout | = | 0 |
DefaultPacketTimeout | = | 10 |
DefaultRetryTimes | = | 4 |
DefaultRetryDelay | = | 5 |
DefaultPort | = | 53 |
DefaultDnssec | = | true |
AbsoluteMinDnssecUdpSize | = | 1220 |
MinDnssecUdpSize | = | 4096 |
DefaultUDPSize | = | MinDnssecUdpSize |
config | [R] | The current Config |
dnssec | [R] | Use DNSSEC for this Resolver |
do_validation | [RW] | 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. |
ignore_truncation | [R] | Should truncation be ignored? i.e. the TC bit is ignored and thus the resolver will not requery over TCP if TC is set |
packet_timeout | [R] | The timeout for any individual packet. This is the timeout used by SingleResolver |
port | [R] | The port to send queries to on the resolver |
query_timeout | [RW] | 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 |
recurse | [R] | Should the Recursion Desired bit be set? |
retry_delay | [RW] | 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. |
retry_times | [RW] | 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. |
src_address | [R] | The source address to send queries from |
tsig | [R] | |
udp_size | [R] | The maximum UDP size to be used |
use_tcp | [R] | Should TCP be used as a transport rather than UDP? |
# File lib/Dnsruby/Resolver.rb, line 559 559: def Resolver.check_port(p, src_port=[]) 560: if (p.class != Fixnum) 561: tmp_src_ports = Array.new(src_port) 562: p.each do |x| 563: if (!Resolver.check_port(x, tmp_src_ports)) 564: return false 565: end 566: tmp_src_ports.push(x) 567: end 568: return true 569: end 570: if (Resolver.port_in_range(p)) 571: if ((p == 0) && (src_port.length > 0)) 572: return false 573: end 574: return true 575: else 576: Dnsruby.log.error("Illegal port (#{p})") 577: raise ArgumentError.new("Illegal port #{p}") 578: end 579: end
# File lib/Dnsruby/Resolver.rb, line 589 589: def Resolver.get_ports_from(p) 590: a = [] 591: if (p.class == Fixnum) 592: a = [p] 593: else 594: p.each do |x| 595: a.push(x) 596: end 597: end 598: return a 599: end
# File lib/Dnsruby/Resolver.rb, line 617 617: def Resolver.get_tsig(args) 618: tsig = nil 619: if (args.length == 1) 620: if (args[0]) 621: if (args[0].instance_of?RR::TSIG) 622: tsig = args[0] 623: elsif (args[0].instance_of?Array) 624: tsig = RR.new_from_hash({:type => Types.TSIG, :klass => Classes.ANY, :name => args[0][0], :key => args[0][1]}) 625: end 626: else 627: # Dnsruby.log.debug{"TSIG signing switched off"} 628: return nil 629: end 630: elsif (args.length ==2) 631: tsig = RR.new_from_hash({:type => Types.TSIG, :klass => Classes.ANY, :name => args[0], :key => args[1]}) 632: else 633: raise ArgumentError.new("Wrong number of arguments to tsig=") 634: end 635: Dnsruby.log.info{"TSIG signing now using #{tsig.name}, key=#{tsig.key}"} 636: return tsig 637: 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 :
# File lib/Dnsruby/Resolver.rb, line 350 350: def initialize(*args) 351: # @TODO@ Should we allow :namesver to be an RRSet of NS records? Would then need to randomly order them? 352: @resolver_ruby = nil 353: @src_address = nil 354: @single_res_mutex = Mutex.new 355: @configured = false 356: @config = Config.new() 357: reset_attributes 358: 359: # Process args 360: if (args.length==1) 361: if (args[0].class == Hash) 362: args[0].keys.each do |key| 363: begin 364: if (key == :config_info) 365: @config.set_config_info(args[0][:config_info]) 366: elsif (key==:nameserver) 367: set_config_nameserver(args[0][:nameserver]) 368: elsif (key==:nameservers) 369: set_config_nameserver(args[0][:nameservers]) 370: else 371: send(key.to_s+"=", args[0][key]) 372: end 373: rescue Exception 374: Dnsruby.log.error{"Argument #{key} not valid\n"} 375: end 376: end 377: elsif (args[0].class == String) 378: set_config_nameserver(args[0]) 379: elsif (args[0].class == Config) 380: # also accepts a Config object from Dnsruby::Resolv 381: @config = args[0] 382: end 383: else 384: # Anything to do? 385: end 386: # if (@single_resolvers==[]) 387: # add_config_nameservers 388: # end 389: update 390: # ResolverRegister::register_resolver(self) 391: end
# File lib/Dnsruby/Resolver.rb, line 581 581: def Resolver.port_in_range(p) 582: if ((p == 0) || ((Iana::IANA_PORTS.index(p)) == nil && 583: (p > 1024) && (p < 65535))) 584: return true 585: end 586: return false 587: 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 546 546: def add_src_port(p) 547: if (Resolver.check_port(p, @src_port)) 548: a = Resolver.get_ports_from(p) 549: a.each do |x| 550: if ((@src_port.length > 0) && (x == 0)) 551: raise ArgumentError.new("src_port of 0 only allowed as only src_port value (currently #{@src_port.length} values") 552: end 553: @src_port.push(x) 554: end 555: end 556: update 557: end
Close the Resolver. Unfinished queries are terminated with OtherResolvError.
# File lib/Dnsruby/Resolver.rb, line 327 327: def close 328: @resolver_ruby.close if @resolver_ruby 329: end
# File lib/Dnsruby/Resolver.rb, line 670 670: def dnssec=(d) 671: @dnssec = d 672: if (d) 673: # Set the UDP size (RFC 4035 section 4.1) 674: if (@udp_size < MinDnssecUdpSize) 675: self.udp_size = MinDnssecUdpSize 676: end 677: end 678: update 679: end
# File lib/Dnsruby/Resolver.rb, line 640 640: def ignore_truncation=(on) 641: @ignore_truncation = on 642: update 643: end
# File lib/Dnsruby/Resolver.rb, line 488 488: def nameserver=(n) 489: @configured = true 490: @single_res_mutex.synchronize { 491: @single_resolvers=[] 492: } 493: set_config_nameserver(n) 494: add_config_nameservers 495: end
# File lib/Dnsruby/Resolver.rb, line 485 485: def nameservers=(ns) 486: self.nameserver=(n) 487: end
# File lib/Dnsruby/Resolver.rb, line 502 502: def packet_timeout=(t) 503: @packet_timeout = t 504: update 505: end
# File lib/Dnsruby/Resolver.rb, line 655 655: def persistent_tcp=(on) 656: @persistent_tcp = on 657: update 658: end
# File lib/Dnsruby/Resolver.rb, line 660 660: def persistent_udp=(on) 661: @persistent_udp = on 662: update 663: 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 157 157: def query(name, type=Types.A, klass=Classes.IN, set_cd=@dnssec) 158: msg = Message.new 159: msg.header.rd = 1 160: msg.add_question(name, type, klass) 161: msg.do_validation = @do_validation 162: if (@dnssec) 163: msg.header.cd = set_cd # We do our own validation by default 164: end 165: return send_message(msg) 166: end
# File lib/Dnsruby/Resolver.rb, line 665 665: def recurse=(a) 666: @recurse = a 667: update 668: 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 :
Returns :
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 314 314: def send_async(*args) # msg, client_queue, client_query_id) 315: if (!@configured) 316: add_config_nameservers 317: end 318: # @single_res_mutex.synchronize { 319: if (!@resolver_ruby) # @TODO@ Synchronize this? 320: @resolver_ruby = ResolverRuby.new(self) 321: end 322: # } 323: return @resolver_ruby.send_async(*args) 324: 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 196 196: def send_message(message) 197: Dnsruby.log.debug{"Resolver : sending message"} 198: q = Queue.new 199: send_async(message, q) 200: # # @TODO@ Add new queue tuples, e.g. : 201: # event_type = EventType::RECEIVED 202: # reply = nil 203: # while (event_type == EventType::RECEIVED) 204: # id, event_type, reply, error = q.pop 205: # Dnsruby.log.debug{"Resolver : result received"} 206: # if ((error != nil) && (event_type == EventType::ERROR)) 207: # raise error 208: # end 209: # print "Reply = #{reply}\n" 210: # end 211: # print "Reply = #{reply}\n" 212: # return reply 213: 214: id, result, error = q.pop 215: 216: if (error != nil) 217: raise error 218: else 219: return result 220: end 221: 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 249 249: def send_plain_message(message) 250: Dnsruby::TheLog.debug("Resolver : send_plain_message") 251: message.do_caching = false 252: message.do_validation = false 253: message.send_raw = true 254: q = Queue.new 255: send_async(message, q) 256: id, result, error = q.pop 257: return [result, error] 258: end
# File lib/Dnsruby/Resolver.rb, line 410 410: def set_config_nameserver(n) 411: # @TODO@ Should we allow NS RRSet here? If so, then .sort_by {rand} 412: if (!@configured) 413: @config.get_ready 414: end 415: @configured = true 416: if (n).kind_of?String 417: @config.nameserver=[n] 418: else 419: @config.nameserver=n 420: end 421: add_config_nameservers 422: end
# File lib/Dnsruby/Resolver.rb, line 645 645: def src_address=(a) 646: @src_address = a 647: update 648: 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 512 512: def src_port 513: if (@src_port.length == 1) 514: return @src_port[0] 515: end 516: return @src_port 517: 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 527 527: def src_port=(p) 528: if (Resolver.check_port(p)) 529: @src_port = Resolver.get_ports_from(p) 530: update 531: end 532: 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.
# File lib/Dnsruby/Resolver.rb, line 612 612: def tsig=(t) 613: @tsig=t 614: update 615: end
# File lib/Dnsruby/Resolver.rb, line 681 681: def udp_size=(s) 682: @udp_size = s 683: update 684: end
# File lib/Dnsruby/Resolver.rb, line 476 476: def update_internal_res(res) 477: [:port, :use_tcp, :tsig, :ignore_truncation, :packet_timeout, 478: :src_address, :src_port, :recurse, 479: :udp_size, :dnssec].each do |param| 480: 481: res.send(param.to_s+"=", instance_variable_get("@"+param.to_s)) 482: end 483: end