added test exercising the dns error path

test/support/requests/resolvers.rb

@@ -132,6 +132,23 @@ module Requests
           end
         end
 
+        define_method :"test_resolver_#{resolver_type}_dns_error" do
+          start_test_servlet(DNSErrorServer, 0.2) do |slow_dns_server|
+            start_test_servlet(DNSErrorServer, 0.2) do |not_so_slow_dns_server|
+              nameservers = [slow_dns_server.nameserver, not_so_slow_dns_server.nameserver]
+
+              resolver_opts = options.merge(nameserver: nameservers, timeouts: [3])
+
+              HTTPX.plugin(SessionWithPool).wrap do |session|
+                uri = build_uri("/get")
+
+                response = session.get(uri, resolver_class: resolver_type, resolver_options: resolver_opts)
+                verify_error_response(response, /unknown DNS error/)
+              end
+            end
+          end
+        end
+
         # this test mocks a DNS server invalid messages back
         define_method :"test_resolver_#{resolver_type}_decoding_error" do
           session = HTTPX.plugin(SessionWithPool)

test/support/servlets/dns_error.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+require_relative "test"
+
+# from https://gist.github.com/peterc/1425383
+
+class DNSErrorServer < TestDNSResolver
+  private
+
+  def dns_response(query)
+    # Valid response header
+    response = "#{query[0, 2]}\x81\x02#{query[4, 2]}\x00\x00\x00\x00\x00\x00".b
+
+    # Append original question section
+    response << query[12..-1].b
+
+    # Use pointer to refer to domain name in question section
+    response << "\xc0\x0c".b
+
+    response
+  end
+end

test/support/servlets/slow_dns.rb

@@ -1,56 +1,13 @@
 # frozen_string_literal: true
 
 require "resolv"
-require "socket"
+require_relative "test"
 
 # from https://gist.github.com/peterc/1425383
 
-class SlowDNSServer
+class SlowDNSServer < TestDNSResolver
-  attr_reader :queries, :answers
-
-  def initialize(timeout)
-    @port = next_available_port
-    @can_log = ENV.key?("HTTPX_DEBUG")
-    @timeout = timeout
-    @queries = 0
-    @answers = 0
-  end
-
-  def nameserver
-    ["127.0.0.1", @port]
-  end
-
-  def start
-    Socket.udp_server_loop(@port) do |query, src|
-      @queries += 1
-      sleep(@timeout)
-      src.reply(dns_response(query))
-      @answers += 1
-    end
-  end
-
   private
 
-  def extract_domain(data)
-    domain = +""
-
-    # Check "Opcode" of question header for valid question
-    if (data[2].ord & 120).zero?
-      # Read QNAME section of question section
-      # DNS header section is 12 bytes long, so data starts at offset 12
-
-      idx = 12
-      len = data[idx].ord
-      # Strings are rendered as a byte containing length, then text.. repeat until length of 0
-      until len.zero?
-        domain << "#{data[idx + 1, len]}."
-        idx += len + 1
-        len = data[idx].ord
-      end
-    end
-    domain
-  end
-
   def dns_response(query)
     domain = extract_domain(query)
     ip = Resolv.getaddress(domain)
@@ -87,12 +44,4 @@ class SlowDNSServer
     response << rdata.b
     response
   end
-
-  def next_available_port
-    udp = UDPSocket.new
-    udp.bind("127.0.0.1", 0)
-    udp.addr[1]
-  ensure
-    udp.close
-  end
 end

test/support/servlets/test.rb

@@ -111,3 +111,58 @@ class TestHTTP2Server
     end
   end
 end
+
+class TestDNSResolver
+  attr_reader :queries, :answers
+
+  def initialize(timeout)
+    @port = next_available_port
+    @can_log = ENV.key?("HTTPX_DEBUG")
+    @timeout = timeout
+    @queries = 0
+    @answers = 0
+  end
+
+  def nameserver
+    ["127.0.0.1", @port]
+  end
+
+  def start
+    Socket.udp_server_loop(@port) do |query, src|
+      @queries += 1
+      sleep(@timeout)
+      src.reply(dns_response(query))
+      @answers += 1
+    end
+  end
+
+  private
+
+  def extract_domain(data)
+    domain = +""
+
+    # Check "Opcode" of question header for valid question
+    if (data[2].ord & 120).zero?
+      # Read QNAME section of question section
+      # DNS header section is 12 bytes long, so data starts at offset 12
+
+      idx = 12
+      len = data[idx].ord
+      # Strings are rendered as a byte containing length, then text.. repeat until length of 0
+      until len.zero?
+        domain << "#{data[idx + 1, len]}."
+        idx += len + 1
+        len = data[idx].ord
+      end
+    end
+    domain
+  end
+
+  def next_available_port
+    udp = UDPSocket.new
+    udp.bind("127.0.0.1", 0)
+    udp.addr[1]
+  ensure
+    udp.close
+  end
+end