ipaddress - add ability to get next closest network of any prefix size

[777GE90]

BPO	42861
Nosy	@ericvsmith, @777GE90
PRs	bpo-42861: Add next_network function to ipaddress library #24180

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2021-01-08.00:30:51.031>
labels = ['type-feature', 'library', '3.10']
title = 'ipaddress - add ability to get next closest network of any prefix size'
updated_at = <Date 2021-07-17.22:04:30.115>
user = 'https://github.com/777GE90'

bugs.python.org fields:

activity = <Date 2021-07-17.22:04:30.115>
actor = 'eric.smith'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2021-01-08.00:30:51.031>
creator = 'fasial.mahmood94'
dependencies = []
files = []
hgrepos = []
issue_num = 42861
keywords = ['patch']
message_count = 4.0
messages = ['384623', '384624', '384732', '386648']
nosy_count = 3.0
nosy_names = ['eric.smith', 'pmoody', 'fasial.mahmood94']
pr_nums = ['24180']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue42861'
versions = ['Python 3.10']

[777GE90]

The ipaddress module in Python is an excellent tool, but I noticed it is missing a feature that I needed several months ago, which is the ability to find the next closest subnet with a specific prefix length.

For example, imagine I had a IPv4Network("10.10.0.72/30"), how would I find the next possible /25 address? It is not the most straightforward thing to do, so think it would be a great enhancement to the ipaddress library.

I think this can be achieved by adding in a new method to the BaseNetwork class, the method could be defined like "next_prefix(next_prefix=None)". Calling this method would return an IPv4/v6 address that is the closest possible match with the new prefix (defined as next_prefix).

Example calls:
v4 = IPv4Network("10.10.0.72/30")
next_network = v4.next_subnet(next_prefix=25)
# Output: next_network = IPv4Network("10.10.0.128/25")

v4 = IPv4Network("10.10.0.72/30")
next_network = v4.next_subnet(next_prefix=30)
# Output: next_network = IPv4Network("10.10.0.76/30")

v4 = IPv4Network("10.10.0.72/30")
next_network = v4.next_subnet() # if next_prefix is not defined it will use the existing prefix of /30, so this call is exactly the same as the previous
# Output: next_network = IPv4Network("10.10.0.76/30")

v6 = IPv6Network("2001:db8:aaaa:aaaa:aaaa:aaaa:aaaa:0000/112")
next_network = v6.next_subnet()
# Output: next_network = IPv6Network("2001:db8:aaaa:aaaa:aaaa:aaaa:aaab:0/112")

v6 = IPv6Network("2001:db8:aaaa:aaaa:aaaa:aaaa:aaaa:0000/112")
next_network = v6.next_subnet(next_prefix=64)
# Output: next_network = IPv6Network("2001:db8:aaaa:aaab::/64")

I am going to be working on this and plan to raise a PR soon. This is my first time contributing to Python, so I appreciate your help / comments / suggestions / guidance as I go along.

[777GE90]

Not sure how to edit an issue, but I made a mistake, where I said:
"...Calling this method would return an IPv4/v6 address that is the closest possible match..."

I meant to say:
"...Calling this method would return an IPv4/v6 -NETWORK- that is the closest possible match..."

[777GE90]

Updated the title and method naming, I previously mentioned the "next subnet" and called the method "next_subnet", but technically this is wrong. What this method should be doing is finding the next closest network of prefix size n.

So I guess the method definition should be:
next_network(self, next_network=None)

[777GE90]

Bump :)

[orsenthil]

Addressed here #24180