bpo-29639: change test.support.HOST to "localhost"

test.support.HOST should be "localhost" as it was in the past. See the bpo-29639.

Tests that need the IP address should use HOSTv4 (added) or the existing HOSTv6 constant.

This changes the definition and fixes tests that needed updating to deal with HOST being
the hostname rather than the hardcoded IP address.

This is only the first step in addressing https://bugs.python.org/issue29639.

4 files changed, 46 insertions, 34 deletions

diff --git a/Lib/test/support/__init__.py b/Lib/test/support/__init__.py
index bfceba1..f57b251 100644
--- a/Lib/test/support/__init__.py
+++ b/Lib/test/support/__init__.py
@@ -601,9 +601,8 @@ def requires_mac_ver(*min_version):
     return decorator
 
 
-# Don't use "localhost", since resolving it uses the DNS under recent
-# Windows versions (see issue #18792).
-HOST = "127.0.0.1"
+HOST = "localhost"
+HOSTv4 = "127.0.0.1"
 HOSTv6 = "::1"
 
 
diff --git a/Lib/test/test_smtpd.py b/Lib/test/test_smtpd.py
index 3eebe94..a9f7d5a 100644
--- a/Lib/test/test_smtpd.py
+++ b/Lib/test/test_smtpd.py
@@ -170,11 +170,11 @@ class TestFamilyDetection(unittest.TestCase):
 
     @unittest.skipUnless(support.IPV6_ENABLED, "IPv6 not enabled")
     def test_socket_uses_IPv6(self):
-        server = smtpd.SMTPServer((support.HOSTv6, 0), (support.HOST, 0))
+        server = smtpd.SMTPServer((support.HOSTv6, 0), (support.HOSTv4, 0))
         self.assertEqual(server.socket.family, socket.AF_INET6)
 
     def test_socket_uses_IPv4(self):
-        server = smtpd.SMTPServer((support.HOST, 0), (support.HOSTv6, 0))
+        server = smtpd.SMTPServer((support.HOSTv4, 0), (support.HOSTv6, 0))
         self.assertEqual(server.socket.family, socket.AF_INET)
 
 
diff --git a/Lib/test/test_smtplib.py b/Lib/test/test_smtplib.py
index 42f4266..4c9b7d3 100644
--- a/Lib/test/test_smtplib.py
+++ b/Lib/test/test_smtplib.py
@@ -19,10 +19,9 @@ import threading
 
 import unittest
 from test import support, mock_socket
+from test.support import HOST, HOSTv4, HOSTv6
 
 
-HOST = support.HOST
-
 if sys.platform == 'darwin':
     # select.poll returns a select.POLLHUP at the end of the tests
     # on darwin, so just ignore it
@@ -208,8 +207,8 @@ class DebuggingServerTests(unittest.TestCase):
         # Pick a random unused port by passing 0 for the port number
         self.serv = smtpd.DebuggingServer((HOST, 0), ('nowhere', -1),
                                           decode_data=True)
-        # Keep a note of what port was assigned
-        self.port = self.serv.socket.getsockname()[1]
+        # Keep a note of what server host and port were assigned
+        self.host, self.port = self.serv.socket.getsockname()[:2]
         serv_args = (self.serv, self.serv_evt, self.client_evt)
         self.thread = threading.Thread(target=debugging_server, args=serv_args)
         self.thread.start()
@@ -231,6 +230,11 @@ class DebuggingServerTests(unittest.TestCase):
         smtpd.DEBUGSTREAM.close()
         smtpd.DEBUGSTREAM = self.old_DEBUGSTREAM
 
+    def get_output_without_xpeer(self):
+        test_output = self.output.getvalue()
+        return re.sub(r'(.*?)^X-Peer:\s*\S+\n(.*)', r'\1\2',
+                      test_output, flags=re.MULTILINE|re.DOTALL)
+
     def testBasic(self):
         # connect
         smtp = smtplib.SMTP(HOST, self.port, local_hostname='localhost', timeout=3)
@@ -238,16 +242,16 @@ class DebuggingServerTests(unittest.TestCase):
 
     def testSourceAddress(self):
         # connect
-        port = support.find_unused_port()
+        src_port = support.find_unused_port()
         try:
-            smtp = smtplib.SMTP(HOST, self.port, local_hostname='localhost',
-                    timeout=3, source_address=('127.0.0.1', port))
-            self.assertEqual(smtp.source_address, ('127.0.0.1', port))
+            smtp = smtplib.SMTP(self.host, self.port, local_hostname='localhost',
+                                timeout=3, source_address=(self.host, src_port))
+            self.assertEqual(smtp.source_address, (self.host, src_port))
             self.assertEqual(smtp.local_hostname, 'localhost')
             smtp.quit()
         except OSError as e:
             if e.errno == errno.EADDRINUSE:
-                self.skipTest("couldn't bind to port %d" % port)
+                self.skipTest("couldn't bind to source port %d" % src_port)
             raise
 
     def testNOOP(self):
@@ -374,10 +378,14 @@ class DebuggingServerTests(unittest.TestCase):
         self.client_evt.set()
         self.serv_evt.wait()
         self.output.flush()
-        # Add the X-Peer header that DebuggingServer adds
-        m['X-Peer'] = socket.gethostbyname('localhost')
+        # Remove the X-Peer header that DebuggingServer adds as figuring out
+        # exactly what IP address format is put there is not easy (and
+        # irrelevant to our test).  Typically 127.0.0.1 or ::1, but it is
+        # not always the same as socket.gethostbyname(HOST). :(
+        test_output = self.get_output_without_xpeer()
+        del m['X-Peer']
         mexpect = '%s%s\n%s' % (MSG_BEGIN, m.as_string(), MSG_END)
-        self.assertEqual(self.output.getvalue(), mexpect)
+        self.assertEqual(test_output, mexpect)
 
     def testSendMessageWithAddresses(self):
         m = email.mime.text.MIMEText('A test message')
@@ -397,12 +405,13 @@ class DebuggingServerTests(unittest.TestCase):
         self.client_evt.set()
         self.serv_evt.wait()
         self.output.flush()
-        # Add the X-Peer header that DebuggingServer adds
-        m['X-Peer'] = socket.gethostbyname('localhost')
+        # Remove the X-Peer header that DebuggingServer adds.
+        test_output = self.get_output_without_xpeer()
+        del m['X-Peer']
         # The Bcc header should not be transmitted.
         del m['Bcc']
         mexpect = '%s%s\n%s' % (MSG_BEGIN, m.as_string(), MSG_END)
-        self.assertEqual(self.output.getvalue(), mexpect)
+        self.assertEqual(test_output, mexpect)
         debugout = smtpd.DEBUGSTREAM.getvalue()
         sender = re.compile("^sender: foo@bar.com$", re.MULTILINE)
         self.assertRegex(debugout, sender)
@@ -426,10 +435,11 @@ class DebuggingServerTests(unittest.TestCase):
         self.client_evt.set()
         self.serv_evt.wait()
         self.output.flush()
-        # Add the X-Peer header that DebuggingServer adds
-        m['X-Peer'] = socket.gethostbyname('localhost')
+        # Remove the X-Peer header that DebuggingServer adds.
+        test_output = self.get_output_without_xpeer()
+        del m['X-Peer']
         mexpect = '%s%s\n%s' % (MSG_BEGIN, m.as_string(), MSG_END)
-        self.assertEqual(self.output.getvalue(), mexpect)
+        self.assertEqual(test_output, mexpect)
         debugout = smtpd.DEBUGSTREAM.getvalue()
         sender = re.compile("^sender: foo@bar.com$", re.MULTILINE)
         self.assertRegex(debugout, sender)
@@ -452,10 +462,11 @@ class DebuggingServerTests(unittest.TestCase):
         self.client_evt.set()
         self.serv_evt.wait()
         self.output.flush()
-        # Add the X-Peer header that DebuggingServer adds
-        m['X-Peer'] = socket.gethostbyname('localhost')
+        # Remove the X-Peer header that DebuggingServer adds.
+        test_output = self.get_output_without_xpeer()
+        del m['X-Peer']
         mexpect = '%s%s\n%s' % (MSG_BEGIN, m.as_string(), MSG_END)
-        self.assertEqual(self.output.getvalue(), mexpect)
+        self.assertEqual(test_output, mexpect)
         debugout = smtpd.DEBUGSTREAM.getvalue()
         sender = re.compile("^sender: joe@example.com$", re.MULTILINE)
         self.assertRegex(debugout, sender)
@@ -481,10 +492,11 @@ class DebuggingServerTests(unittest.TestCase):
         self.client_evt.set()
         self.serv_evt.wait()
         self.output.flush()
-        # Add the X-Peer header that DebuggingServer adds
-        m['X-Peer'] = socket.gethostbyname('localhost')
+        # Remove the X-Peer header that DebuggingServer adds.
+        test_output = self.get_output_without_xpeer()
+        del m['X-Peer']
         mexpect = '%s%s\n%s' % (MSG_BEGIN, m.as_string(), MSG_END)
-        self.assertEqual(self.output.getvalue(), mexpect)
+        self.assertEqual(test_output, mexpect)
         debugout = smtpd.DEBUGSTREAM.getvalue()
         sender = re.compile("^sender: the_rescuers@Rescue-Aid-Society.com$", re.MULTILINE)
         self.assertRegex(debugout, sender)
@@ -515,10 +527,11 @@ class DebuggingServerTests(unittest.TestCase):
         # The Resent-Bcc headers are deleted before serialization.
         del m['Bcc']
         del m['Resent-Bcc']
-        # Add the X-Peer header that DebuggingServer adds
-        m['X-Peer'] = socket.gethostbyname('localhost')
+        # Remove the X-Peer header that DebuggingServer adds.
+        test_output = self.get_output_without_xpeer()
+        del m['X-Peer']
         mexpect = '%s%s\n%s' % (MSG_BEGIN, m.as_string(), MSG_END)
-        self.assertEqual(self.output.getvalue(), mexpect)
+        self.assertEqual(test_output, mexpect)
         debugout = smtpd.DEBUGSTREAM.getvalue()
         sender = re.compile("^sender: holy@grail.net$", re.MULTILINE)
         self.assertRegex(debugout, sender)
diff --git a/Lib/test/test_socket.py b/Lib/test/test_socket.py
index 27d9d49..05d8761 100644
--- a/Lib/test/test_socket.py
+++ b/Lib/test/test_socket.py
@@ -864,12 +864,12 @@ class GeneralModuleTests(unittest.TestCase):
             self.fail("Error testing host resolution mechanisms. (fqdn: %s, all: %s)" % (fqhn, repr(all_host_names)))
 
     def test_host_resolution(self):
-        for addr in [support.HOST, '10.0.0.1', '255.255.255.255']:
+        for addr in [support.HOSTv4, '10.0.0.1', '255.255.255.255']:
             self.assertEqual(socket.gethostbyname(addr), addr)
 
         # we don't test support.HOSTv6 because there's a chance it doesn't have
         # a matching name entry (e.g. 'ip6-localhost')
-        for host in [support.HOST]:
+        for host in [support.HOSTv4]:
             self.assertIn(host, socket.gethostbyaddr(host)[2])
 
     def test_host_resolution_bad_address(self):