[ruby/resolv] Fix TCP fallback with multiple nameservers
Under the following conditions the exception `Resolv::DNS::Requester::RequestError: host/port don't match` is raised: - Multiple nameservers are configured for Resolv::DNS - A nameserver falls back from UDP to TCP - TCP request hits Resolv::DNS timeout - Resolv::DNS retries the next nameserver More details here https://bugs.ruby-lang.org/issues/8285 https://github.com/ruby/resolv/commit/7d524df80e Co-authored-by: Julian Mehnle <julian@mehnle.net>
This commit is contained in:
Igor Pstyga
git
parent
525008cd78
commit
4be9b72fbb
@ -513,22 +513,32 @@ class Resolv
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def fetch_resource(name, typeclass)
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lazy_initialize
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begin
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requester = make_udp_requester
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rescue Errno::EACCES
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# fall back to TCP
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end
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protocols = {}
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requesters = {}
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senders = {}
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begin
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@config.resolv(name) {|candidate, tout, nameserver, port|
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requester ||= make_tcp_requester(nameserver, port)
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@config.resolv(name) do |candidate, tout, nameserver, port|
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msg = Message.new
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msg.rd = 1
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msg.add_question(candidate, typeclass)
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unless sender = senders[[candidate, nameserver, port]]
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protocol = protocols[candidate] ||= :udp
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requester = requesters[[protocol, nameserver]] ||=
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case protocol
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when :udp
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begin
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make_udp_requester
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rescue Errno::EACCES
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make_tcp_requester(nameserver, port)
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end
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when :tcp
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make_tcp_requester(nameserver, port)
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end
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unless sender = senders[[candidate, requester, nameserver, port]]
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sender = requester.sender(msg, candidate, nameserver, port)
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next if !sender
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senders[[candidate, nameserver, port]] = sender
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senders[[candidate, requester, nameserver, port]] = sender
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end
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reply, reply_name = requester.request(sender, tout)
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case reply.rcode
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@ -536,12 +546,7 @@ class Resolv
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if reply.tc == 1 and not Requester::TCP === requester
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requester.close
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# Retry via TCP:
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requester = make_tcp_requester(nameserver, port)
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senders = {}
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# This will use TCP for all remaining candidates (assuming the
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# current candidate does not already respond successfully via
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# TCP). This makes sense because we already know the full
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# response will not fit in an untruncated UDP packet.
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protocols[candidate] = :tcp
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redo
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else
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yield(reply, reply_name)
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@ -552,9 +557,9 @@ class Resolv
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else
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raise Config::OtherResolvError.new(reply_name.to_s)
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end
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}
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end
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ensure
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requester&.close
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requesters.each_value { |requester| requester&.close }
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end
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end
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@ -569,6 +574,11 @@ class Resolv
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def make_tcp_requester(host, port) # :nodoc:
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return Requester::TCP.new(host, port)
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rescue Errno::ECONNREFUSED
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# Treat a refused TCP connection attempt to a nameserver like a timeout,
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# as Resolv::DNS::Config#resolv considers ResolvTimeout exceptions as a
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# hint to try the next nameserver:
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raise ResolvTimeout
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end
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def extract_resources(msg, name, typeclass) # :nodoc:
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@ -1800,7 +1810,6 @@ class Resolv
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end
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end
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##
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# Base class for SvcParam. [RFC9460]
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@ -2499,7 +2508,6 @@ class Resolv
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attr_reader :altitude
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def encode_rdata(msg) # :nodoc:
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msg.put_bytes(@version)
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msg.put_bytes(@ssize.scalar)
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@ -3439,4 +3447,3 @@ class Resolv
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AddressRegex = /(?:#{IPv4::Regex})|(?:#{IPv6::Regex})/
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end
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@ -698,4 +698,117 @@ class TestResolvDNS < Test::Unit::TestCase
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ensure
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sock&.close
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end
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def test_multiple_servers_with_timeout_and_truncated_tcp_fallback
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begin
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OpenSSL
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rescue LoadError
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skip 'autoload problem. see [ruby-dev:45021][Bug #5786]'
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end if defined?(OpenSSL)
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num_records = 50
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with_udp_and_tcp('127.0.0.1', 0) do |u1, t1|
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with_tcp('0.0.0.0', 0) do |t2|
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_, server1_port, _, server1_address = u1.addr
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_, server2_port, _, server2_address = t2.addr
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client_thread = Thread.new do
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Resolv::DNS.open(nameserver_port: [[server1_address, server1_port], [server2_address, server2_port]]) do |dns|
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dns.timeouts = [0.1, 0.2]
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dns.getresources('foo.example.org', Resolv::DNS::Resource::IN::A)
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end
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end
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udp_server1_thread = Thread.new do
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msg, (_, client_port, _, client_address) = Timeout.timeout(5) { u1.recvfrom(4096) }
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id, word2, _qdcount, _ancount, _nscount, _arcount = msg.unpack('nnnnnn')
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opcode = (word2 & 0x7800) >> 11
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rd = (word2 & 0x0100) >> 8
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name = [3, 'foo', 7, 'example', 3, 'org', 0].pack('Ca*Ca*Ca*C')
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qr = 1
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aa = 0
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tc = 1
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ra = 1
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z = 0
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rcode = 0
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qdcount = 0
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ancount = num_records
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nscount = 0
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arcount = 0
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word2 = (qr << 15) |
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(opcode << 11) |
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(aa << 10) |
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(tc << 9) |
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(rd << 8) |
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(ra << 7) |
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(z << 4) |
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rcode
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msg = [id, word2, qdcount, ancount, nscount, arcount].pack('nnnnnn')
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type = 1
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klass = 1
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ttl = 3600
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rdlength = 4
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num_records.times do |i|
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rdata = [192, 0, 2, i].pack('CCCC') # 192.0.2.x (TEST-NET address) RFC 3330
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rr = [name, type, klass, ttl, rdlength, rdata].pack('a*nnNna*')
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msg << rr
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end
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u1.send(msg[0...512], 0, client_address, client_port)
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end
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tcp_server1_thread = Thread.new { t1.accept }
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tcp_server2_thread = Thread.new do
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ct = t2.accept
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msg = ct.recv(512)
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msg.slice!(0..1) # Size (only for TCP)
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id, word2, _qdcount, _ancount, _nscount, _arcount = msg.unpack('nnnnnn')
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rd = (word2 & 0x0100) >> 8
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opcode = (word2 & 0x7800) >> 11
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name = [3, 'foo', 7, 'example', 3, 'org', 0].pack('Ca*Ca*Ca*C')
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qr = 1
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aa = 0
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tc = 0
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ra = 1
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z = 0
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rcode = 0
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qdcount = 0
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ancount = num_records
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nscount = 0
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arcount = 0
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word2 = (qr << 15) |
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(opcode << 11) |
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(aa << 10) |
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(tc << 9) |
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(rd << 8) |
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(ra << 7) |
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(z << 4) |
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rcode
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msg = [id, word2, qdcount, ancount, nscount, arcount].pack('nnnnnn')
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type = 1
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klass = 1
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ttl = 3600
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rdlength = 4
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num_records.times do |i|
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rdata = [192, 0, 2, i].pack('CCCC') # 192.0.2.x (TEST-NET address) RFC 3330
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rr = [name, type, klass, ttl, rdlength, rdata].pack('a*nnNna*')
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msg << rr
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end
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msg = "#{[msg.bytesize].pack('n')}#{msg}" # Prefix with size
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ct.send(msg, 0)
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ct.close
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end
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result, = assert_join_threads([client_thread, udp_server1_thread, tcp_server1_thread, tcp_server2_thread])
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assert_instance_of(Array, result)
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assert_equal(50, result.length)
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result.each_with_index do |rr, i|
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assert_instance_of(Resolv::DNS::Resource::IN::A, rr)
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assert_instance_of(Resolv::IPv4, rr.address)
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assert_equal("192.0.2.#{i}", rr.address.to_s)
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assert_equal(3600, rr.ttl)
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end
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end
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end
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end
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end
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