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_caching | [R] | Does this Resolver cache answers, and attempt to retrieve answer from the cache? |
do_caching | [RW] | 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) |
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 |
no_tcp | [R] | 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. |
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? If use_tcp==true, then ONLY TCP will be used as a transport. |
# File lib/Dnsruby/Resolver.rb, line 589 589: def Resolver.check_port(p, src_port=[]) 590: if (p.class != Fixnum) 591: tmp_src_ports = Array.new(src_port) 592: p.each do |x| 593: if (!Resolver.check_port(x, tmp_src_ports)) 594: return false 595: end 596: tmp_src_ports.push(x) 597: end 598: return true 599: end 600: if (Resolver.port_in_range(p)) 601: if ((p == 0) && (src_port.length > 0)) 602: return false 603: end 604: return true 605: else 606: Dnsruby.log.error("Illegal port (#{p})") 607: raise ArgumentError.new("Illegal port #{p}") 608: end 609: end
# File lib/Dnsruby/Resolver.rb, line 621 621: def Resolver.get_ports_from(p) 622: a = [] 623: if (p.class == Fixnum) 624: a = [p] 625: else 626: p.each do |x| 627: a.push(x) 628: end 629: end 630: return a 631: end
# File lib/Dnsruby/Resolver.rb, line 655 655: def Resolver.get_tsig(args) 656: tsig = nil 657: if (args.length == 1) 658: if (args[0]) 659: if (args[0].instance_of?RR::TSIG) 660: tsig = args[0] 661: elsif (args[0].instance_of?Array) 662: if (args[0].length > 2) 663: tsig = RR.new_from_hash({:type => Types.TSIG, :klass => Classes.ANY, :name => args[0][0], :key => args[0][1], :algorithm => args[0][2]}) 664: else 665: tsig = RR.new_from_hash({:type => Types.TSIG, :klass => Classes.ANY, :name => args[0][0], :key => args[0][1]}) 666: end 667: end 668: else 669: # Dnsruby.log.debug{"TSIG signing switched off"} 670: return nil 671: end 672: elsif (args.length ==2) 673: tsig = RR.new_from_hash({:type => Types.TSIG, :klass => Classes.ANY, :name => args[0], :key => args[1]}) 674: elsif (args.length ==3) 675: tsig = RR.new_from_hash({:type => Types.TSIG, :klass => Classes.ANY, :name => args[0], :key => args[1], :algorithm => args[2]}) 676: else 677: raise ArgumentError.new("Wrong number of arguments to tsig=") 678: end 679: Dnsruby.log.info{"TSIG signing now using #{tsig.name}, key=#{tsig.key}"} 680: return tsig 681: 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 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 611 611: def Resolver.port_in_range(p) 612: if ((p == 0) || ((p >= 50000) && (p <= 65535))) 613: # @TODO@ IANA port bitmap - use 50000 - 65535 for now 614: # ((Iana::IANA_PORTS.index(p)) == nil && 615: # (p > 1024) && (p < 65535))) 616: return true 617: end 618: return false 619: 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 576 576: def add_src_port(p) 577: if (Resolver.check_port(p, @src_port)) 578: a = Resolver.get_ports_from(p) 579: a.each do |x| 580: if ((@src_port.length > 0) && (x == 0)) 581: raise ArgumentError.new("src_port of 0 only allowed as only src_port value (currently #{@src_port.length} values") 582: end 583: @src_port.push(x) 584: end 585: end 586: update 587: 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 719 719: def dnssec=(d) 720: @dnssec = d 721: if (d) 722: # Set the UDP size (RFC 4035 section 4.1) 723: if (@udp_size < MinDnssecUdpSize) 724: self.udp_size = MinDnssecUdpSize 725: end 726: end 727: update 728: end
# File lib/Dnsruby/Resolver.rb, line 709 709: def do_caching=(on) 710: @do_caching=on 711: update 712: end
# File lib/Dnsruby/Resolver.rb, line 684 684: def ignore_truncation=(on) 685: @ignore_truncation = on 686: update 687: end
# File lib/Dnsruby/Resolver.rb, line 518 518: def nameserver=(n) 519: @configured = true 520: @single_res_mutex.synchronize { 521: @single_resolvers=[] 522: } 523: set_config_nameserver(n) 524: add_config_nameservers 525: end
# File lib/Dnsruby/Resolver.rb, line 515 515: def nameservers=(ns) 516: self.nameserver=(n) 517: end
# File lib/Dnsruby/Resolver.rb, line 532 532: def packet_timeout=(t) 533: @packet_timeout = t 534: update 535: end
# File lib/Dnsruby/Resolver.rb, line 699 699: def persistent_tcp=(on) 700: @persistent_tcp = on 701: update 702: end
# File lib/Dnsruby/Resolver.rb, line 704 704: def persistent_udp=(on) 705: @persistent_udp = on 706: update 707: 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 714 714: def recurse=(a) 715: @recurse = a 716: update 717: 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 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 436 436: def set_config_nameserver(n) 437: # @TODO@ Should we allow NS RRSet here? If so, then .sort_by {rand} 438: if (!@configured) 439: @config.get_ready 440: end 441: @configured = true 442: if (n).kind_of?String 443: @config.nameserver=[n] 444: else 445: @config.nameserver=n 446: end 447: add_config_nameservers 448: end
# File lib/Dnsruby/Resolver.rb, line 689 689: def src_address=(a) 690: @src_address = a 691: update 692: 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 542 542: def src_port 543: if (@src_port.length == 1) 544: return @src_port[0] 545: end 546: return @src_port 547: 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 557 557: def src_port=(p) 558: if (Resolver.check_port(p)) 559: @src_port = Resolver.get_ports_from(p) 560: update 561: end 562: 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 650 650: def tsig=(t) 651: @tsig=t 652: update 653: end
# File lib/Dnsruby/Resolver.rb, line 730 730: def udp_size=(s) 731: @udp_size = s 732: update 733: end
# File lib/Dnsruby/Resolver.rb, line 506 506: def update_internal_res(res) 507: [:port, :use_tcp, :no_tcp, :tsig, :ignore_truncation, :packet_timeout, 508: :src_address, :src_port, :recurse, 509: :udp_size, :dnssec].each do |param| 510: 511: res.send(param.to_s+"=", instance_variable_get("@"+param.to_s)) 512: end 513: end