Support IPv4 mapped IPv6 addresses in IPv4 Range.

When an IPv4 scoped range is checked for the presence of an IPv6 address
and the IPv6 address falls within the IPv4 mapped address block
(::ffff:0:0/96) we will automatically convert the IPv6 address to its IPv4
equivalent before making the comparison. This can be helpful on hybrid
dual-stack machines.

Author: bd808

iptools/__init__.py

@@ -84,6 +84,10 @@ class IpRange (Sequence):
     False
     >>> 2130706433 in r
     True
+    >>> # IPv4 mapped IPv6 addresses are valid in an IPv4 block
+    >>> '::ffff:127.127.127.127' in r
+    True
+    >>> # but only if they are actually in the block :)
     >>> '::ffff:192.0.2.128' in r
     False
     >>> '::ffff:c000:0280' in r
@@ -241,6 +245,14 @@ def _cast(self, item):
         if type(item) not in [type(1), type(ipv4.MAX_IP), type(ipv6.MAX_IP)]:
             raise TypeError(
                 "expected ip address, 32-bit integer or 128-bit integer")
+
+        if ipv4 == self._ipver and item > ipv4.MAX_IP:
+            # casting an ipv6 in an ipv4 range
+            # downcast to ipv4 iff address is in the IPv4 mapped block
+            if item in IpRange(ipv6.IPV4_MAPPED):
+                item = item & ipv4.MAX_IP
+        #end if
+
         return item
     #end _cast
 

tests/iptools/iptools_test.py

@@ -45,6 +45,22 @@ def testIPv6Range(self):
         self.assertTrue('::ffff:172.16.11.12' in fixture)
         self.assertFalse('209.19.170.129' in fixture)
     #end testIPv6Range
+
+    def testV4MappedAddressInIPv6Range(self):
+        """
+        Given that the user has configured an IPv4 range
+        When the server recieves a connection from a host in that range
+         And the network stack presents that address in v4 mapped format
+        Then the address should be recognized as being in the IPv4 range.
+        """
+        fixture = iptools.IpRange('192.168.0.1/24')
+
+        self.assertTrue('192.168.0.12' in fixture)
+        self.assertFalse('192.168.1.12' in fixture)
+
+        self.assertTrue('::ffff:192.168.0.12' in fixture)
+        self.assertFalse('::ffff:192.168.1.12' in fixture)
+    #end test6to4AddressInIPv6Range
 #end class IpRangeTests
 
 # vim:se sw=4 ts=4 sts=4 et: