Incorrect behavior in GenericIPAddressField with protocol='both', unpack_ipv4=False

[bshen]

Basically, IPv4-mapped IPv6 addresses in the CIDR block ::ffff:0.0.0.0/104 are validated as invalid when unpack_ipv4=False, yet is valid when the first IPv4 octet is non-zero or when unpack_ipv4=True.

# my.app.models
# Django==1.8.6
from django.db import models
class TestIPNoUnpack(models.Model):
    ip = models.GenericIPAddressField(null=False, protocol='both', unpack_ipv4=False)


class TestIPUnpack(models.Model):
    ip = models.GenericIPAddressField(null=False, protocol='both', unpack_ipv4=True)



> python manage.py shell
Python 2.7.6 (default, Sep  9 2014, 15:04:36) 
Type "copyright", "credits" or "license" for more information.

IPython 4.0.1 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object', use 'object??' for extra details.

In [1]: from my.app.models import TestIPNoUnpack, TestIPUnpack

In [2]: testipunpack = TestIPUnpack(ip='::ffff:0.0.0.0')

In [3]: testipunpack.clean_fields()

In [4]: testipunpack.ip
Out[4]: '0.0.0.0'

In [5]: testipnounpack = TestIPNoUnpack(ip='::ffff:0.0.0.0')

In [6]: testipnounpack.clean_fields()
---------------------------------------------------------------------------
ValidationError                           Traceback (most recent call last)
<ipython-input-6-9a763f56e907> in <module>()
----> 1 testipnounpack.clean_fields()

.../lib/python2.7/site-packages/django/db/models/base.pyc in clean_fields(self, exclude)
   1194 
   1195         if errors:
-> 1196             raise ValidationError(errors)
   1197 
   1198     @classmethod

ValidationError: {'ip': [u'Enter a valid IPv4 or IPv6 address.']}

In [7]: testipnounpack2 = TestIPNoUnpack(ip='::ffff:0.255.255.255')

In [8]: testipnounpack2.clean_fields()
---------------------------------------------------------------------------
ValidationError                           Traceback (most recent call last)
<ipython-input-8-e228d0855286> in <module>()
----> 1 testipnounpack2.clean_fields()

.../lib/python2.7/site-packages/django/db/models/base.pyc in clean_fields(self, exclude)
   1194 
   1195         if errors:
-> 1196             raise ValidationError(errors)
   1197 
   1198     @classmethod

ValidationError: {'ip': [u'Enter a valid IPv4 or IPv6 address.']}

In [9]: testipnounpack3 = TestIPNoUnpack(ip='::ffff:1.0.0.0')

In [10]: testipnounpack3.clean_fields()

In [11]: testipnounpack3.ip
Out[11]: '::ffff:1.0.0.0'