MaaS: Add support for dynamic fabric numbering

Previously, we hardcoded the fabric name for our 3rd interface
(which serves PXE/DHCP for the target nodes) to "fabric-2",
relying on predictable index numbers to be provided by MaaS based
on the interfaces defined in /etc/network/interfaces.

However, the fabric IDs/names generated by MaaS are not predictable,
and therefore cannot be hardcoded in our reclass model / scripts.

Work around this by:
- adding support for fabric ID deduction based on CIDR matching
  during subnet create/update operation in MaaS py module;
- adding support for VLAN DHCP enablement to MaaS py module,
  which was previously handled via shell MaaS API operations
  from maas/region.sls;

While at it, revert previous commit that disabled network discovery
("MaaS: Disable network discovery"), since it turns out that network
discovery was not the culprit for subnet creation failure, but wrong
fabric numbering.

This reverts commit 8cdf22d1a1bae4694a373873cab4feb6251069b7.

Change-Id: I15fa059004356cb4aaabb38999ea378dd3c0e0bb
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>

1 files changed, 49 insertions, 0 deletions

diff --git a/mcp/patches/0005-maas-module-Obtain-fabric-ID-from-CIDR.patch b/mcp/patches/0005-maas-module-Obtain-fabric-ID-from-CIDR.patch
new file mode 100644
index 000000000..5c77a63da
--- /dev/null
+++ b/mcp/patches/0005-maas-module-Obtain-fabric-ID-from-CIDR.patch
@@ -0,0 +1,49 @@
+From: Alexandru Avadanii <Alexandru.Avadanii@enea.com>
+Date: Sat, 19 Aug 2017 02:03:01 +0200
+Subject: [PATCH] maas: module: Obtain fabric ID from CIDR
+
+MaaS subnet update requires specifying the correct fabric via reclass,
+which we used to hardcode in our OPNFV reclass model to fabric-2.
+However, fabric index numbers are not deterministic, so the old
+method is unreliable.
+
+Update MaaS custom py module to determine fabric name/ID on the
+fly, based on CIDR matching (assuming we don't have CIDR conflicts).
+
+This change maintains backwards compatibility:
+- if fabric is specified via reclass model, it will be used as-is;
+- if fabric is not specified via reclass model, we try to deduce it
+  based on CIDR; if no match is found, the old default ('') is used;
+
+Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>
+Signed-off-by: Guillermo Herrero <Guillermo.Herrero@enea.com>
+---
+
+diff --git a/_modules/maas.py b/_modules/maas.py
+index d3227ca..8a2243d 100644
+--- a/_modules/maas.py
++++ b/_modules/maas.py
+@@ -198,7 +198,8 @@
+     def fill_data(self, name, subnet, fabrics):
+         data = {
+             'name': name,
+-            'fabric': str(fabrics[subnet.get('fabric', '')]),
++            'fabric': str(fabrics[subnet.get('fabric',
++                self._get_fabric_from_cidr(subnet.get('cidr')))]),
+             'cidr': subnet.get('cidr'),
+             'gateway_ip': subnet['gateway_ip'],
+         }
+@@ -215,6 +216,13 @@
+         self._process_iprange(res_json['id'])
+         return response
+
++    def _get_fabric_from_cidr(self, cidr):
++        subnets = json.loads(self._maas.get(u'api/2.0/subnets/').read())
++        for subnet in subnets:
++            if subnet['cidr'] == cidr:
++                return subnet['vlan']['fabric']
++        return ''
++
+     def _process_iprange(self, subnet_id):
+         ipranges = json.loads(self._maas.get(u'api/2.0/ipranges/').read())
+         LOG.warn('all %s ipranges %s', subnet_id, ipranges)