[3.5] bpo-29931 fix __lt__ check in ipaddress.ip_interface for both v4 and v6. (GH-879) (#2218)

the original logic was just comparing the network address
but this is wrong because if the network address is equal then
we need to compare the ip address for breaking the tie

add more ip_interface comparison tests.
(cherry picked from commit 7bd8d3e)

Author: serhiy-storchaka

Lib/ipaddress.py

@@ -1410,7 +1410,8 @@ def __lt__(self, other):
         if address_less is NotImplemented:
             return NotImplemented
         try:
-            return self.network < other.network
+            return (self.network < other.network or
+                    self.network == other.network and address_less)
         except AttributeError:
             # We *do* allow addresses and interfaces to be sorted. The
             # unassociated address is considered less than all interfaces.
@@ -2100,7 +2101,8 @@ def __lt__(self, other):
         if address_less is NotImplemented:
             return NotImplemented
         try:
-            return self.network < other.network
+            return (self.network < other.network or
+                    self.network == other.network and address_less)
         except AttributeError:
             # We *do* allow addresses and interfaces to be sorted. The
             # unassociated address is considered less than all interfaces.

Lib/test/test_ipaddress.py

@@ -1404,14 +1404,35 @@ def testAddressComparison(self):
                         ipaddress.ip_address('::2'))
 
     def testInterfaceComparison(self):
-        self.assertTrue(ipaddress.ip_interface('1.1.1.1') <=
-                        ipaddress.ip_interface('1.1.1.1'))
-        self.assertTrue(ipaddress.ip_interface('1.1.1.1') <=
-                        ipaddress.ip_interface('1.1.1.2'))
-        self.assertTrue(ipaddress.ip_interface('::1') <=
-                        ipaddress.ip_interface('::1'))
-        self.assertTrue(ipaddress.ip_interface('::1') <=
-                        ipaddress.ip_interface('::2'))
+        self.assertTrue(ipaddress.ip_interface('1.1.1.1/24') ==
+                        ipaddress.ip_interface('1.1.1.1/24'))
+        self.assertTrue(ipaddress.ip_interface('1.1.1.1/16') <
+                        ipaddress.ip_interface('1.1.1.1/24'))
+        self.assertTrue(ipaddress.ip_interface('1.1.1.1/24') <
+                        ipaddress.ip_interface('1.1.1.2/24'))
+        self.assertTrue(ipaddress.ip_interface('1.1.1.2/16') <
+                        ipaddress.ip_interface('1.1.1.1/24'))
+        self.assertTrue(ipaddress.ip_interface('1.1.1.1/24') >
+                        ipaddress.ip_interface('1.1.1.1/16'))
+        self.assertTrue(ipaddress.ip_interface('1.1.1.2/24') >
+                        ipaddress.ip_interface('1.1.1.1/24'))
+        self.assertTrue(ipaddress.ip_interface('1.1.1.1/24') >
+                        ipaddress.ip_interface('1.1.1.2/16'))
+
+        self.assertTrue(ipaddress.ip_interface('::1/64') ==
+                        ipaddress.ip_interface('::1/64'))
+        self.assertTrue(ipaddress.ip_interface('::1/64') <
+                        ipaddress.ip_interface('::1/80'))
+        self.assertTrue(ipaddress.ip_interface('::1/64') <
+                        ipaddress.ip_interface('::2/64'))
+        self.assertTrue(ipaddress.ip_interface('::2/48') <
+                        ipaddress.ip_interface('::1/64'))
+        self.assertTrue(ipaddress.ip_interface('::1/80') >
+                        ipaddress.ip_interface('::1/64'))
+        self.assertTrue(ipaddress.ip_interface('::2/64') >
+                        ipaddress.ip_interface('::1/64'))
+        self.assertTrue(ipaddress.ip_interface('::1/64') >
+                        ipaddress.ip_interface('::2/48'))
 
     def testNetworkComparison(self):
         # ip1 and ip2 have the same network address

Misc/NEWS

@@ -56,6 +56,9 @@ Extension Modules
 Library
 -------
 
+- bpo-29931: Fixed comparison check for ipaddress.ip_interface objects.
+  Patch by Sanjay Sundaresan.
+
 - [Security] bpo-29591: Update expat copy from 2.1.1 to 2.2.0 to get fixes
   of CVE-2016-0718 and CVE-2016-4472. See
   https://sourceforge.net/p/expat/bugs/537/ for more information.