Django 1.1.1: How to save an empty IP address using PostgreSQL?

Question

I am writing a Django application that stores IP addresses with additional routing information. One of the fields for the IP model that I created is nexthop(for next hop routes), which will usually be empty. We originally intended to use MySQL, but now the project requirements have changed to use PostgreSQL.

Here is a stripped down version of my model:

class IP(models.Model):
    address = models.IPAddressField()
    netmask = models.IPAddressField(default='255.255.255.255')
    nexthop = models.IPAddressField(null=True, blank=True, default=None)
    active  = models.BooleanField('is active?', default=1)

So, with MySQL, I had no problem leaving the field nexthopempty. However, now that I have switched the development environment to Postgres, we are faced with a known problem in Django 1.1.1 in which an empty IP address causes aDataError

invalid input syntax for type inet: ""
LINE 1: ...-14 13:07:29', 1, E'1.2.3.4', E'255.255.255.255', E'', true)
                                                             ^

, , , NULL.

, IP- , .

Django , , next-hop 255.255.255.255 - (.. next-hop 255.255.255.255, ), .

, - , Django , , .

!

:

( ) :

:

IP_NEXTHOP_SENTINEL = '255.255.255.255'
class IP(models.Model):
    nexthop = models.IPAddressField(
        null=True,
        blank=True,
        default=IP_NEXTHOP_SENTINEL,
        help_text='Use %s to indicate no next-hop' % IP_NEXTHOP_SENTINEL
    )

    def save(self, *args, **kwargs):
        ## hack for Django #5622 (http://code.djangoproject.com/ticket/5622)
        if self.nexthop and self.nexthop == IP_NEXTHOP_SENTINEL:
            self.nexthop = None

:

IP , null=True nexthop. , 255.255.255.255 - , , , , save(), None, , , .

!

Answer 1

, , Django, . , , , . CharField IPAddressField, .

Answer 2

blank=True nexthop, blank=True null=True? Django docs:

null = True - , , .

Answer 3

, 255.255.255.255?

back-end ( blank=true), , ...