gh-151785: Fix IPv4Interface.is_loopback to consider the network

Author: aisk

Lib/ipaddress.py

@@ -1480,6 +1480,10 @@ def with_hostmask(self):
     def is_unspecified(self):
         return self._ip == 0 and self.network.is_unspecified
 
+    @property
+    def is_loopback(self):
+        return super().is_loopback and self.network.is_loopback
+
 
 class IPv4Network(_BaseV4, _BaseNetwork):
 

Lib/test/test_ipaddress.py

@@ -2307,6 +2307,10 @@ def testReservedIpv4(self):
         self.assertFalse(ipaddress.ip_interface('0.0.0.0/31').is_unspecified)
         self.assertFalse(ipaddress.ip_interface('1.2.3.4/32').is_unspecified)
 
+        self.assertTrue(ipaddress.ip_interface('127.0.0.1/8').is_loopback)
+        self.assertFalse(ipaddress.ip_interface('127.0.0.1/4').is_loopback)
+        self.assertFalse(ipaddress.ip_interface('1.2.3.4/32').is_loopback)
+
         self.assertEqual(True, ipaddress.ip_interface(
                 '192.168.1.1/17').is_private)
         self.assertEqual(False, ipaddress.ip_network('192.169.0.0').is_private)