Wrong CIDR configuration in subnet will cause all IP-related functions invalid.

Here is the patch I made. Plz check it.

Thanks~

following is my experiment with the wrong CIDR in python console:
>>> net = ip.IPNetwork('10.0.0.3/24')
>>> net.cidr
IPNetwork('10.0.0.0/24')
>>> net.netmask
IPAddress('255.255.255.0')

the conclusion is we need enhance the validation:
def _validate_subnet(data, valid_values=None):
    try:
        netaddr.IPNetwork(_validate_no_whitespace(data))
        if len(data.split('/')) == 2:
            return
    except Exception:
        pass

following is my experiment with wrong cidr 10.0.4.2/24:
$ quantum net-create net3
Created a new network:
+---------------------------+--------------------------------------+
| Field | Value |
+---------------------------+--------------------------------------+
| admin_state_up | True |
| id | 3f206a91-a00b-497c-bc4d-36c8435d3293 |
| name | net3 |
| provider:network_type | gre |
| provider:physical_network | |
| provider:segmentation_id | 3 |
| router:external | False |
| shared | False |
| status | ACTIVE |
| subnets | |
| tenant_id | 51c051a17638408d8969ada0ae5b9b95 |
+---------------------------+--------------------------------------+
$ quantum subnet-create net3 10.0.4.2/24 --name subnet3
Created a new subnet:
+------------------+--------------------------------------------+
| Field | Value |
+------------------+--------------------------------------------+
| allocation_pools | {"start": "10.0.4.2", "end": "10.0.4.254"} |
| cidr | 10.0.4.2/24 |
| dns_nameservers | |
| enable_dhcp | True |
| gateway_ip | 10.0.4.1 |
| host_routes | |
| id | 95f6c03f-5881-40f8-9dcc-48c475650a35 |
| ip_version | 4 |
| name | subnet3 |
| network_id | 3f206a91-a00b-497c-bc4d-36c8435d3293 |
| tenant_id | 51c051a17638408d8969ada0ae5b9b95 |
+------------------+--------------------------------------------+
$ quantum port-create net3 --fixed-ip ip_address=10.0.4.6
Invalid input for operation: IP address 10.0.4.6 is not a valid IP for the defined networks subnets.

Fix proposed to branch: master
Review: https://review.openstack.org/35013

After this patch:
$ quantum subnet-create net4 10.0.0.4/24
Invalid input for cidr. Reason: '10.0.0.4/24' isn't a recognized IP subnet cidr, '10.0.0.0/24' is recommended.

Reviewed: https://review.openstack.org/35013
Committed: http://github.com/openstack/neutron/commit/53a66b299f18a7184972502b43441a5ad7b050fd
Submitter: Jenkins
Branch: master

commit 53a66b299f18a7184972502b43441a5ad7b050fd
Author: Yong Sheng Gong <email address hidden>
Date: Sun Jul 7 21:20:36 2013 +0800

    validate and recommend the cidr

    Bug #1195974

    It is hard to validate the CIDR typed in by user,
    the simple way is to recognize only one and recommend it
    if user's input is not the one.

    Change-Id: Ic8defe30a43a5ae69c3f737094f866b36bb68f59

Fix proposed to branch: stable/grizzly
Review: https://review.openstack.org/48405