Validation for CIDR is not correct

[tinyx]

I've received an error when I tried to save a CIDR like '64.34.117.2/20', and I got a database error, says the CIDR is not correct.
Then I check the source code of this plug-in, and found the piece of code here:

try:
    return IPNetwork(value)
except (AddrFormatError, TypeError), e:
    raise ValidationError(str(e))

I highly doubt that this is doing the right thing, it only check if we can convert the IP value to a valid IPNetwork object, instead of a valid CIDR.

[tinyx]

I'm gonna write my own validation for my app, so if this is a confirmed issue after you have discussed, I can try to fix it.

[rouge8]

For your example, that validation is correct. netaddr.IPNetwork is for CIDRs.

IPy also fails on your example, because the valid CIDR is actually 64.34.112.0/20:

>>> from IPy import IP
>>> IP('64.34.117.2/20')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/rouge8/.virtualenvs/c9486b2e2feb6ebe/lib/python2.7/site-packages/IPy.py", line 259, in __init__
    raise ValueError("%s has invalid prefix length (%s)" % (repr(self), self._prefixlen))
ValueError: IP('64.34.117.2/20') has invalid prefix length (20)
>>> IP('64.34.117.2/20', make_net=True)
IP('64.34.112.0/20')
>>>

[tinyx]

Sorry I may not explain the problem clearly, my original opinion was '64.34.117.2/20' is not a valid CIDR, however, the fieldform would not raise a ValidationError since that value could be converted to an IPNetwork object. So the error would not occur until it hits the database. I think more validation is necessary, ideally I think the code should look like this:

try:
    ip_network =  IPNetwork(value)
    return valid_cidr(ip_network)
except (AddrFormatError, TypeError), e:
    raise ValidationError(str(e))

And inside valid_cidr method, should raise an error on Form level if it failed.