[Network] az network vnet list-available-ips: support list available ips in a vnet (#12371)

Author: mmyyrroonn

src/azure-cli/azure/cli/command_modules/network/_help.py

@@ -4433,6 +4433,14 @@
     text: az network vnet show -g MyResourceGroup -n MyVNet
 """
 
+helps['network vnet list-available-ips'] = """
+type: command
+short-summary: List some available ips in the vnet.
+examples:
+  - name: List some available ips in the vnet.
+    text: az network vnet list-available-ips -g MyResourceGroup -n MyVNet
+"""
+
 helps['network vnet subnet'] = """
 type: group
 short-summary: Manage subnets in an Azure Virtual Network.

src/azure-cli/azure/cli/command_modules/network/commands.py

@@ -1028,6 +1028,7 @@ def _make_singular(value):
         g.custom_command('create', 'create_vnet', transform=transform_vnet_create_output, validator=process_vnet_create_namespace, supports_local_cache=True)
         g.generic_update_command('update', custom_func_name='update_vnet', supports_local_cache=True)
         g.command('list-endpoint-services', 'list', command_type=network_endpoint_service_sdk)
+        g.custom_command('list-available-ips', 'list_available_ips', min_api='2016-09-01', is_preview=True)
 
     with self.command_group('network vnet peering', network_vnet_peering_sdk, min_api='2016-09-01') as g:
         g.custom_command('create', 'create_vnet_peering')

src/azure-cli/azure/cli/command_modules/network/custom.py

@@ -4980,6 +4980,17 @@ def update_vnet_peering(cmd, resource_group_name, virtual_network_name, virtual_
     return ncf.virtual_network_peerings.create_or_update(
         resource_group_name, virtual_network_name, virtual_network_peering_name, peering)
 
+
+def list_available_ips(cmd, resource_group_name, virtual_network_name):
+    client = network_client_factory(cmd.cli_ctx).virtual_networks
+    vnet = client.get(resource_group_name=resource_group_name,
+                      virtual_network_name=virtual_network_name)
+    start_ip = vnet.address_space.address_prefixes[0].split('/')[0]
+    available_ips = client.check_ip_address_availability(resource_group_name=resource_group_name,
+                                                         virtual_network_name=virtual_network_name,
+                                                         ip_address=start_ip)
+    return available_ips.available_ip_addresses
+
 # endregion