[isolated-topo] make ipv4 and ipv4 BGP sessions optional, make ipv6 only topology deployable (sonic-net#106)

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### Description of PR
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Summary:
Fixes # (issue)
We have ipv6 address only topology which only establish ipv6 BGP sessions.
So we raise this PR to make ipv4 BGP sessions optional and make ipv6 only topology deployable.

### Type of change

<!--
- Fill x for your type of change.
- e.g.
- [x] Bug fix
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- [ ] Bug fix
- [x] Testbed and Framework(new/improvement)
- [ ] Test case(new/improvement)

### Back port request
- [ ] 202012
- [ ] 202205
- [ ] 202305
- [ ] 202311
- [ ] 202405

### Approach
#### What is the motivation for this PR?
We have ipv6 address only topology which only establish ipv6 BGP sessions.
#### How did you do it?
Make ipv4 BGP sessions optional and make ipv6 only topology deployable
#### How did you verify/test it?
Deploy in lab
#### Any platform specific information?

#### Supported testbed topology if it's a new test case?

### Documentation
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(If it's a new feature, new test case)
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Author: mssonicbld

ansible/library/announce_routes.py

@@ -1170,7 +1170,7 @@ def main():
         module.fail_json(msg='Unable to load topology "{}"'.format(topo_name))
     if dut_interfaces:
         topo['topology']['VMs'] = MultiServersUtils.get_vms_by_dut_interfaces(topo['topology']['VMs'], dut_interfaces)
-        for vm_name in topo['configuration'].keys():
+        for vm_name in list(topo['configuration'].keys()):
             if vm_name not in topo['topology']['VMs']:
                 topo['configuration'].pop(vm_name)
 

ansible/library/test_facts.py

@@ -180,7 +180,7 @@ def _read_testbed_topo_from_yaml():
                         {dut: i for i, dut in enumerate(tb["duts"])}
                     if 'servers' in tb:
                         tb['multi_servers_tacacs_ip'], _ = \
-                            _cidr_to_ip_mask(tb['servers'].values()[0]["ptf_ip"])
+                            _cidr_to_ip_mask(list(tb['servers'].values())[0]["ptf_ip"])
                     self.testbed_topo[tb["conf-name"]] = tb
 
         if self.testbed_filename.endswith(".csv"):

ansible/library/vlan_config.py

@@ -51,8 +51,10 @@ def main():
             vlan_configs.update({vlan: {}})
             vlan_configs[vlan]['id'] = vlan_param['id']
             vlan_configs[vlan]['tag'] = vlan_param['tag']
-            vlan_configs[vlan]['prefix'] = vlan_param['prefix']
-            vlan_configs[vlan]['prefix_v6'] = vlan_param['prefix_v6']
+            if 'prefix' in vlan_param:
+                vlan_configs[vlan]['prefix'] = vlan_param['prefix']
+            if 'prefix_v6' in vlan_param:
+                vlan_configs[vlan]['prefix_v6'] = vlan_param['prefix_v6']
             vlan_configs[vlan]['intfs'] = [port_alias[i]
                                            for i in vlan_param['intfs']]
             vlan_configs[vlan]['portchannels'] = vlan_param.get(

ansible/plugins/filter/filters.py

@@ -1,6 +1,7 @@
 import ipaddress
 import math
 import os.path
+from collections import OrderedDict
 
 from ansible import errors
 
@@ -159,7 +160,10 @@ def extract_hostname(values, topology, vm_base, inventory_hostname, dut_interfac
     if vm_base not in values:
         raise errors.AnsibleFilterError('Current vm_base: %s is not found in vm_list' % vm_base)
 
-    vms = MultiServersUtils.get_vms_by_dut_interfaces(topology, dut_interfaces) if dut_interfaces else topology
+    sorted_topo = OrderedDict()
+    for kv_tuple in sorted(topology.items(), key=lambda item: item[1]['vm_offset']):
+        sorted_topo[kv_tuple[0]] = kv_tuple[1]
+    vms = MultiServersUtils.get_vms_by_dut_interfaces(sorted_topo, dut_interfaces) if dut_interfaces else topology
     base = values.index(vm_base)
     for hostname, attr in vms.items():
         if base + attr['vm_offset'] >= len(values):

ansible/roles/eos/templates/t1-isolated-d254u2s1-spine.j2

@@ -0,0 +1 @@
+t1-spine.j2

ansible/roles/eos/templates/t1-isolated-d254u2s1-tor.j2

@@ -0,0 +1 @@
+t1-tor.j2

ansible/roles/eos/templates/t1-isolated-d254u2s2-spine.j2

@@ -0,0 +1 @@
+t1-spine.j2

ansible/roles/eos/templates/t1-isolated-d254u2s2-tor.j2

@@ -0,0 +1 @@
+t1-tor.j2

ansible/roles/vm_set/tasks/announce_routes.yml

@@ -82,7 +82,7 @@
       exabgp:
         name: "{{ vm_item.key }}-v6"
         state: "configure"
-        router_id: "{{ ptf_local_ipv4 }}"
+        router_id: "{{ configuration_properties.common.nhipv4|default('10.10.246.254') }}"
         local_ip: "{{ ptf_local_ipv6 }}"
         peer_ip: "{{ configuration[vm_item.key].bp_interface.ipv6.split('/')[0] }}"
         local_asn: "{{ configuration[vm_item.key].bgp.asn }}"
@@ -114,7 +114,7 @@
     - name: Verify that exabgp processes for IPv6 are started
       wait_for:
         host: "{{ ptf_host_ip }}"
-        port: "{{ 6000 + topology.VMs[vm_item.key].vm_offset|int }}"
+        port: "{{ 6000 + vm_item.value.vm_offset|int }}"
         state: "started"
         timeout: 180
       loop: "{{ topo_vms|dict2items }}"

ansible/templates/minigraph_dpg.j2

@@ -169,7 +169,9 @@
 {% endif %}
           <VlanID>{{ vlan_param['id'] }}</VlanID>
           <Tag>{{ vlan_param['tag'] }}</Tag>
+{% if 'prefix' in vlan_param %}
           <Subnets>{{ vlan_param['prefix'] | ipaddr('network') }}/{{ vlan_param['prefix'] | ipaddr('prefix') }}</Subnets>
+{% endif %}
 {% if 'secondary_subnet' in vlan_param %}
           <SecondarySubnets>{{ vlan_param['secondary_subnet'] | ipaddr('network') }}/{{ vlan_param['secondary_subnet'] | ipaddr('secondary_subnet') }}<SecondarySubnets>
 {% endif %}
@@ -185,6 +187,7 @@
 {% for index in range(vms_number) %}
 {% if vm_topo_config['vm'][vms[index]]['ip_intf'][dut_index|int] is not none %}
 {% for intf_index in range(vm_topo_config['vm'][vms[index]]['ip_intf'][dut_index|int]|length) %}
+{% if vm_topo_config['vm'][vms[index]]['bgp_ipv4'][dut_index|int] %}
         <IPInterface>
           <Name i:nil="true"/>
 {% if 'port-channel' in vm_topo_config['vm'][vms[index]]['ip_intf'][dut_index|int][intf_index]|lower %}
@@ -194,6 +197,8 @@
 {% endif %}
           <Prefix>{{ vm_topo_config['vm'][vms[index]]['bgp_ipv4'][dut_index|int][intf_index] }}/{{ vm_topo_config['vm'][vms[index]]['ipv4mask'][dut_index|int][intf_index] }}</Prefix>
         </IPInterface>
+{% endif %}
+{% if vm_topo_config['vm'][vms[index]]['bgp_ipv6'][dut_index|int] %}
         <IPInterface>
           <Name i:Name="true"/>
 {% if 'port-channel' in vm_topo_config['vm'][vms[index]]['ip_intf'][dut_index|int][intf_index]|lower %}
@@ -203,16 +208,19 @@
 {% endif %}
           <Prefix>{{ vm_topo_config['vm'][vms[index]]['bgp_ipv6'][dut_index|int][intf_index] }}/{{ vm_topo_config['vm'][vms[index]]['ipv6mask'][dut_index|int][intf_index] }}</Prefix>
         </IPInterface>
+{% endif %}
 {% endfor %}
 {% endif %}
 {% endfor %}
 {% if 'tor' in vm_topo_config['dut_type'] | lower %}
 {% for vlan, vlan_param in vlan_configs.items() %}
+{% if 'prefix' in vlan_param %}
         <IPInterface>
           <Name i:nil="true"/>
           <AttachTo>{{ vlan }}</AttachTo>
           <Prefix>{{ vlan_param['prefix'] }}</Prefix>
         </IPInterface>
+{% endif %}
 {%if 'secondary_subnet' in vlan_param %}
         <IPInterface>
           <Name i:nil="true"/>