public void TestStubResolverAcceptsSeveralAliasesForAAAARecords()
{
// Make sure that chains of aliases are supported
var relay = new IPEndPoint(IPAddress.Parse("192.168.0.1"), 53);
var expected_question = new DNSQuestion(
new Domain("example.com"),
ResourceRecordType.HOST_6ADDRESS,
AddressClass.INTERNET);
var expected_alias_answer_1 = new DNSRecord(
new Domain("example.com"), AddressClass.INTERNET, 42,
new CNAMEResource(new Domain("www.example.com")));
var expected_alias_answer_2 = new DNSRecord(
new Domain("www.example.com"), AddressClass.INTERNET, 42,
new CNAMEResource(new Domain("web1.www.example.com")));
var expected_addr_answer = new DNSRecord(
new Domain("web1.www.example.com"), AddressClass.INTERNET, 42,
new AAAAResource(IPv6Address.Parse("2001:cafe:beef::")));
var expected_packet = new DNSPacket(
42, false, QueryType.STANDARD_QUERY, false, false, true, true, ResponseType.NO_ERROR,
new DNSQuestion[] { expected_question },
new DNSRecord[] { expected_alias_answer_1, expected_alias_answer_2, expected_addr_answer },
new DNSRecord[0], new DNSRecord[0]);
Func <EndPoint, DNSQuestion, bool, DNSPacket> gives_direct_answers = (target, question, is_recursive) =>
{
Assert.That(target, Is.EqualTo(relay));
Assert.That(question, Is.EqualTo(expected_question));
return(expected_packet);
};
var resolver = new StubResolver(new NoopCache(), gives_direct_answers);
var result = resolver.Resolve(new Domain("example.com"),
ResourceRecordType.HOST_6ADDRESS,
AddressClass.INTERNET,
new EndPoint[] { relay });
var expected_result = new ResolverResult();
expected_result.answers = new DNSRecord[] { expected_addr_answer };
expected_result.aliases = new DNSRecord[] { expected_alias_answer_1, expected_alias_answer_2 };
expected_result.referrals = new DNSRecord[0];
expected_result.referral_additional = new DNSRecord[0];
Assert.That(result, Is.EqualTo(expected_result));
}
public void TestStubResolverAcceptsSOARecords()
{
// The same as the previous test, but this makes sure that less common
// record types are still recognized as answers for the appropriate queries
var relay = new IPEndPoint(IPAddress.Parse("192.168.0.1"), 53);
var expected_question = new DNSQuestion(
new Domain("example.com"),
ResourceRecordType.START_OF_AUTHORITY,
AddressClass.INTERNET);
var expected_answer = new DNSRecord(
new Domain("example.com"), AddressClass.INTERNET, 42,
new SOAResource(
new Domain("ns.example.com"),
new Domain("hostmaster.example.com"),
0,
360,
360,
360,
360));
var expected_packet = new DNSPacket(
42, false, QueryType.STANDARD_QUERY, false, false, true, true, ResponseType.NO_ERROR,
new DNSQuestion[] { expected_question }, new DNSRecord[] { expected_answer }, new DNSRecord[0], new DNSRecord[0]);
Func <EndPoint, DNSQuestion, bool, DNSPacket> gives_direct_answers = (target, question, is_recursive) =>
{
Assert.That(target, Is.EqualTo(relay));
Assert.That(question, Is.EqualTo(expected_question));
return(expected_packet);
};
var resolver = new StubResolver(new NoopCache(), gives_direct_answers);
var result = resolver.Resolve(new Domain("example.com"),
ResourceRecordType.START_OF_AUTHORITY,
AddressClass.INTERNET,
new EndPoint[] { relay });
var expected_result = new ResolverResult();
expected_result.answers = new DNSRecord[] { expected_answer };
expected_result.aliases = new DNSRecord[0];
expected_result.referrals = new DNSRecord[0];
expected_result.referral_additional = new DNSRecord[0];
Assert.That(result, Is.EqualTo(expected_result));
}
public void TestStubResolverReturnsRedirectionsWithAAAAResourceGlue()
{
// Make sure that any redirections are returned, even if there aren't any actual
// results, along with their glue if provided
var relay = new IPEndPoint(IPAddress.Parse("192.168.0.1"), 53);
var expected_question = new DNSQuestion(
new Domain("example.com"),
ResourceRecordType.HOST_ADDRESS,
AddressClass.INTERNET);
var expected_ns_answer = new DNSRecord(
new Domain("example.com"), AddressClass.INTERNET, 42,
new NSResource(new Domain("ns.example.com")));
var expected_glue_answer = new DNSRecord(
new Domain("ns.example.com"), AddressClass.INTERNET, 42,
new AAAAResource(IPv6Address.Parse("2001:cafe:beef::")));
var expected_packet = new DNSPacket(
42, false, QueryType.STANDARD_QUERY, false, false, true, true, ResponseType.NO_ERROR,
new DNSQuestion[] { expected_question }, new DNSRecord[0], new DNSRecord[] { expected_ns_answer },
new DNSRecord[] { expected_glue_answer });
Func <EndPoint, DNSQuestion, bool, DNSPacket> gives_direct_answers = (target, question, is_recursive) =>
{
Assert.That(target, Is.EqualTo(relay));
Assert.That(question, Is.EqualTo(expected_question));
return(expected_packet);
};
var resolver = new StubResolver(new NoopCache(), gives_direct_answers);
var result = resolver.Resolve(new Domain("example.com"),
ResourceRecordType.HOST_ADDRESS,
AddressClass.INTERNET,
new EndPoint[] { relay });
var expected_result = new ResolverResult();
expected_result.answers = new DNSRecord[0];
expected_result.aliases = new DNSRecord[0];
expected_result.referrals = new DNSRecord[] { expected_ns_answer };
expected_result.referral_additional = new DNSRecord[] { expected_glue_answer };
Assert.That(result, Is.EqualTo(expected_result));
}
public void TestStubResolverSequenceOfRelays()
{
// Make sure that the resolver ignores failing resolvers, as long as at least one succeeds
var good_relay = new IPEndPoint(IPAddress.Parse("192.168.0.1"), 53);
var bad_relay = new IPEndPoint(IPAddress.Parse("192.168.0.2"), 53);
var expected_question = new DNSQuestion(
new Domain("example.com"),
ResourceRecordType.HOST_ADDRESS,
AddressClass.INTERNET);
var expected_answer = new DNSRecord(
new Domain("example.com"), AddressClass.INTERNET, 42,
new AResource(IPv4Address.Parse("192.168.0.1")));
var expected_packet = new DNSPacket(
42, false, QueryType.STANDARD_QUERY, false, false, true, true, ResponseType.NO_ERROR,
new DNSQuestion[] { expected_question }, new DNSRecord[] { expected_answer }, new DNSRecord[0], new DNSRecord[0]);
Func <EndPoint, DNSQuestion, bool, DNSPacket> gives_direct_answers = (target, question, is_recursive) =>
{
if (target.Equals(bad_relay))
{
throw new SocketException();
}
Assert.That(target, Is.EqualTo(good_relay));
Assert.That(question, Is.EqualTo(expected_question));
return(expected_packet);
};
var resolver = new StubResolver(new NoopCache(), gives_direct_answers);
var result = resolver.Resolve(new Domain("example.com"),
ResourceRecordType.HOST_ADDRESS,
AddressClass.INTERNET,
new EndPoint[] { bad_relay, good_relay });
var expected_result = new ResolverResult();
expected_result.answers = new DNSRecord[] { expected_answer };
expected_result.aliases = new DNSRecord[0];
expected_result.referrals = new DNSRecord[0];
expected_result.referral_additional = new DNSRecord[0];
Assert.That(result, Is.EqualTo(expected_result));
}
public void TestStubResolverRejectsIrrelevantGlue()
{
// Make sure that any redirections are returned, but rejects any bad glue
var relay = new IPEndPoint(IPAddress.Parse("192.168.0.1"), 53);
var expected_question = new DNSQuestion(
new Domain("example.com"),
ResourceRecordType.HOST_ADDRESS,
AddressClass.INTERNET);
var expected_ns_answer = new DNSRecord(
new Domain("example.com"), AddressClass.INTERNET, 42,
new NSResource(new Domain("ns.example.com")));
var unexpected_glue_answer = new DNSRecord(
new Domain("ns2.example.com"), AddressClass.INTERNET, 42,
new AResource(IPv4Address.Parse("192.168.0.2")));
var expected_packet = new DNSPacket(
42, false, QueryType.STANDARD_QUERY, false, false, true, true, ResponseType.NO_ERROR,
new DNSQuestion[] { expected_question }, new DNSRecord[0], new DNSRecord[] { expected_ns_answer },
new DNSRecord[] { unexpected_glue_answer });
Func <EndPoint, DNSQuestion, bool, DNSPacket> gives_direct_answers = (target, question, is_recursive) =>
{
Assert.That(target, Is.EqualTo(relay));
Assert.That(question, Is.EqualTo(expected_question));
return(expected_packet);
};
var resolver = new StubResolver(new NoopCache(), gives_direct_answers);
var result = resolver.Resolve(new Domain("example.com"),
ResourceRecordType.HOST_ADDRESS,
AddressClass.INTERNET,
new EndPoint[] { relay });
var expected_result = new ResolverResult();
expected_result.answers = new DNSRecord[0];
expected_result.aliases = new DNSRecord[0];
expected_result.referrals = new DNSRecord[] { expected_ns_answer };
expected_result.referral_additional = new DNSRecord[0];
Assert.That(result, Is.EqualTo(expected_result));
}
public void TestStubResolverAcceptsARecords()
{
// The idea behind this test is to make sure that direct answers to the question are accpted
// (no CNAMEs, no referrals, etc.). A records are the most common query, so they are a good
// starting point.
var relay = new IPEndPoint(IPAddress.Parse("192.168.0.1"), 53);
var expected_question = new DNSQuestion(
new Domain("example.com"),
ResourceRecordType.HOST_ADDRESS,
AddressClass.INTERNET);
var expected_answer = new DNSRecord(
new Domain("example.com"), AddressClass.INTERNET, 42,
new AResource(IPv4Address.Parse("192.168.0.1")));
var expected_packet = new DNSPacket(
42, false, QueryType.STANDARD_QUERY, false, false, true, true, ResponseType.NO_ERROR,
new DNSQuestion[] { expected_question }, new DNSRecord[] { expected_answer }, new DNSRecord[0], new DNSRecord[0]);
Func <EndPoint, DNSQuestion, bool, DNSPacket> gives_direct_answers = (target, question, is_recursive) =>
{
Assert.That(target, Is.EqualTo(relay));
Assert.That(question, Is.EqualTo(expected_question));
return(expected_packet);
};
var resolver = new StubResolver(new NoopCache(), gives_direct_answers);
var result = resolver.Resolve(new Domain("example.com"),
ResourceRecordType.HOST_ADDRESS,
AddressClass.INTERNET,
new EndPoint[] { relay });
var expected_result = new ResolverResult();
expected_result.answers = new DNSRecord[] { expected_answer };
expected_result.aliases = new DNSRecord[0];
expected_result.referrals = new DNSRecord[0];
expected_result.referral_additional = new DNSRecord[0];
Assert.That(result, Is.EqualTo(expected_result));
}
public void TestStubResolverRecordsCNAMEAnswers()
{
// This ensures that any request for a CNAME to a paritcular domain ends up in the answers
// list (and only the answers list) if we're asking for CNAMEs
var relay = new IPEndPoint(IPAddress.Parse("192.168.0.1"), 53);
var expected_question = new DNSQuestion(
new Domain("example.com"),
ResourceRecordType.CANONICAL_NAME,
AddressClass.INTERNET);
var expected_answer = new DNSRecord(
new Domain("example.com"), AddressClass.INTERNET, 42,
new CNAMEResource(new Domain("www.example.com")));
var expected_packet = new DNSPacket(
42, false, QueryType.STANDARD_QUERY, false, false, true, true, ResponseType.NO_ERROR,
new DNSQuestion[] { expected_question }, new DNSRecord[] { expected_answer }, new DNSRecord[0], new DNSRecord[0]);
Func <EndPoint, DNSQuestion, bool, DNSPacket> gives_direct_answers = (target, question, is_recursive) =>
{
Assert.That(target, Is.EqualTo(relay));
Assert.That(question, Is.EqualTo(expected_question));
return(expected_packet);
};
var resolver = new StubResolver(new NoopCache(), gives_direct_answers);
var result = resolver.Resolve(new Domain("example.com"),
ResourceRecordType.CANONICAL_NAME,
AddressClass.INTERNET,
new EndPoint[] { relay });
var expected_result = new ResolverResult();
expected_result.answers = new DNSRecord[] { expected_answer };
expected_result.aliases = new DNSRecord[0];
expected_result.referrals = new DNSRecord[0];
expected_result.referral_additional = new DNSRecord[0];
Assert.That(result, Is.EqualTo(expected_result));
}
/**
* Does the actual work of resolution, by talking to all the servers and
* interpreting their answers.
*/
public ResolverResult Resolve(Domain domain, ResourceRecordType rtype, AddressClass addr_class, EndPoint[] servers)
{
var records = cache.Query(domain, addr_class, rtype);
if (records.Count == 0)
{
var packet = QueryServers(domain, rtype, addr_class, servers);
int found = 0;
foreach (var resource in packet.Answers)
{
if (resource.Resource != null)
{
records.Add(resource);
cache.Add(resource);
found++;
}
}
logger.Trace("Found {0} answers", found);
found = 0;
foreach (var resource in packet.AdditionalRecords)
{
if (resource.Resource != null)
{
records.Add(resource);
cache.Add(resource);
}
found++;
}
logger.Trace("Found {0} additional records", found);
found = 0;
foreach (var resource in packet.AuthoritativeAnswers)
{
if (resource.Resource != null)
{
records.Add(resource);
cache.Add(resource);
}
found++;
}
logger.Trace("Found {0} authoritative record", found);
}
else
{
logger.Trace("Cache returned {0} resources", records.Count);
}
var any_results = false;
var results = new List <DNSRecord>();
var aliases = new HashSet <Domain>();
var nameservers = new HashSet <Domain>();
var nameserver_addrs = new HashSet <IPAddress>();
var alias_rrs = new List <DNSRecord>();
var nameserver_rrs = new List <DNSRecord>();
var nameserver_addr_rrs = new List <DNSRecord>();
// We'll attack this in stages - first, record all the CNAMEs for the current domain
// (But only if we're looking specifically for A records - other records
// generally can't have aliases). Here, we're hoping that the server gives us the addresses
// in what is basically a topologically sorted order (think of chained CNAMEs as a graph).
if (rtype == ResourceRecordType.HOST_ADDRESS || rtype == ResourceRecordType.HOST_6ADDRESS)
{
foreach (var record in records)
{
var is_relevant = record.Name == domain || aliases.Contains(record.Name);
if (record.Resource != null &&
record.Resource.Type == ResourceRecordType.CANONICAL_NAME &&
is_relevant)
{
logger.Trace("Recording alias {0}", record);
aliases.Add(((CNAMEResource)record.Resource).Alias);
alias_rrs.Add(record);
any_results = true;
}
}
}
// Next, fish out any addresses that answer the query
foreach (var record in records)
{
var is_relevant = record.Name == domain || aliases.Contains(record.Name);
if (record.Resource != null && record.Resource.Type == rtype && is_relevant)
{
logger.Trace("Recording relevant answer {0}", record);
results.Add(record);
any_results = true;
}
}
// Finally, get any referrals or authority claims that we're given
foreach (var record in records)
{
if (record.Resource != null && record.Resource.Type == ResourceRecordType.NAME_SERVER)
{
logger.Trace("Recording nameserver {0}", record);
nameservers.Add(((NSResource)record.Resource).Nameserver);
nameserver_rrs.Add(record);
any_results = true;
}
}
// If the server was helpful enough to give us some glue, then make sure
// to record them as well
foreach (var record in records)
{
if (record.Resource != null &&
(record.Resource.Type == ResourceRecordType.HOST_ADDRESS ||
record.Resource.Type == ResourceRecordType.HOST_6ADDRESS) &&
nameservers.Contains(record.Name))
{
logger.Trace("Recording nameserver glue {0}", record);
switch (record.Resource.Type)
{
case ResourceRecordType.HOST_ADDRESS:
nameserver_addrs.Add(((AResource)record.Resource).Address);
break;
case ResourceRecordType.HOST_6ADDRESS:
nameserver_addrs.Add(((AAAAResource)record.Resource).Address);
break;
}
nameserver_addr_rrs.Add(record);
any_results = true;
}
}
if (!any_results)
{
throw new ResolverException(domain, "Did not get any records relevant to " + domain);
}
var result = new ResolverResult();
result.answers = results;
result.aliases = alias_rrs;
result.referrals = nameserver_rrs;
result.referral_additional = nameserver_addr_rrs;
return(result);
}