Workaround for ipv4 address validation

[HJones82493]

This fixes the is_ipv4_address function. Initially intended to be a workaround for Issue #5131 it is now a removal of an external dependency. Since the check is a simple one, there is no need to rely on external sources.

[disconnect3d]

The code below uses ipaddr local variable which has been removed.

[disconnect3d]

I assume that we don't care about 3-1 octet IP addresses that the socket.inet_aton can parse e.g.:

In [11]: socket.inet_aton('0x7f000001')
Out[11]: b'\x7f\x00\x00\x01'

In [12]: socket.inet_aton('127.0.0')
Out[12]: b'\x7f\x00\x00\x00'

In [13]: socket.inet_aton('127.0')
Out[13]: b'\x7f\x00\x00\x00'

If so, we can just use the builtin ipaddress module to validate if IP is in proper format:

In [2]: ipaddress.IPv4Address('192.168.0.1')
Out[2]: IPv4Address('192.168.0.1')

In [3]: ipaddress.IPv4Address('192')
AddressValueError: Expected 4 octets in '192'

and then use the ipaddr = struct.unpack('=L', socket.inet_aton(ip))[0] line to parse it.

Note that the same problem stands for net argument - i.e. it also uses sockeet.inet_aton so we need to validate it's format first.

[HJones82493]

I didn't plan on handling 1-3 octet IPs unless we also consider those valid? I didn't think we would consider those as valid IPs.

We already have a check for valid ip that works (is_valid_ipv4) that I changed to remove the socket dependency in it. I think the best solution would be to leave the socket dependencies in the functions that use them and just put a check first, that way we don't allow it to pass IPs like '1.1.1.1 wtf' into the broken Python functions.

[disconnect3d]

Just for a reference, the socket.inet_aton issue is being discussed on Python's bug tracker: https://bugs.python.org/issue37495

[disconnect3d]

We already have a check for valid ip that works (is_valid_ipv4)
Sure, but it's better to use standard methods that work properly instead of reinventing the wheel.

The current version of is_ipv4_address still doesn't handle all the edge cases - for example, it returns True for an ip of '08.08.08.08'.

The ipaddress module has functions to check given IPs and networks. This could probably be used for both IP and CIDR checking.

[HJones82493]

The ipaddress module doesn't exist for Python 2.7

[recepsirin]

Here seems to me that it need to rewrite

[recepsirin]

between 646 and 657

[nateprewitt]

Now that we've dropped support for Python 2.7-3.6, I think we're more likely to rely on ipaddress than try to maintain this ourselves. I'm going to close this out in favor of that approach.