Match resources of unregistered types in getresources

lib/resolv.rb

@@ -626,26 +626,28 @@ def extract_resources(msg, name, typeclass) # :nodoc:
       n0 = Name.create(name)
       msg.each_resource {|n, ttl, data|
         if n0 == n
-          case data
-          when typeclass
+          if resource_of_type?(data, typeclass)
             yield data
             yielded = true
-          when Resource::CNAME
+          elsif Resource::CNAME === data
             n0 = data.name
           end
         end
       }
       return if yielded
       msg.each_resource {|n, ttl, data|
-        if n0 == n
-          case data
-          when typeclass
-            yield data
-          end
+        if n0 == n && resource_of_type?(data, typeclass)
+          yield data
         end
       }
     end
 
+    # Decoding makes a fresh class for each resource of an unregistered type,
+    # so a class from Generic.create never matches such a resource by identity.
+    private def resource_of_type?(data, typeclass) # :nodoc:
+      typeclass === data || Resource::Generic.type_class_equal?(data.class, typeclass)
+    end
+
     def self.random(arg) # :nodoc:
       begin
         SecureRandom.random_number(arg)

test/resolv/test_resource.rb

@@ -64,6 +64,24 @@ def test_generic_question_equality
       Resolv::DNS::Message.decode(generic_question(40001))
   end
 
+  # Looking up a type that has no named class means passing a class from
+  # Generic.create, which is never the class a decoded answer carries.
+  def test_getresources_with_generic_type
+    generic = Resolv::DNS::Resource::Generic
+    message = Resolv::DNS::Message.new
+    message.add_answer("example.com.", 60, generic.create(40000, 60000).new("\x01\x02\x03"))
+    reply = Resolv::DNS::Message.decode(message.encode)
+    dns = Resolv::DNS.new
+    dns.define_singleton_method(:fetch_resource) do |_name, _typeclass, &block|
+      block.call(reply, Resolv::DNS::Name.create("example.com."))
+    end
+
+    resources = dns.getresources("example.com", generic.create(40000, 60000))
+    assert_equal ["\x01\x02\x03".b], resources.map(&:data)
+    assert_empty dns.getresources("example.com", generic.create(40001, 60000))
+    assert_empty dns.getresources("example.com", Resolv::DNS::Resource::IN::A)
+  end
+
   private def header(qdcount, ancount)
     "\x00\x00\x00\x00".b + [qdcount, ancount, 0, 0].pack('nnnn')
   end