Add --iface-regex options to flannel

Flannel use interface for inter-host communication setted on --iface options
Defaults to the interface for the default route on the machine.

flannel config set via daemonset, and flannel config on all nodes is the same.
But different nodes can have different interface names for the inter-host communication network

The option --iface-regex allows the flannel to find the interface on which the address is set from the inter-host communication network

roles/network_plugin/flannel/defaults/main.yml

@@ -5,9 +5,15 @@
 # flannel_public_ip: "{{ access_ip|default(ip|default(ansible_default_ipv4.address)) }}"
 
 ## interface that should be used for flannel operations
-## This is actually an inventory node-level item
+## This is actually an inventory cluster-level item
 # flannel_interface:
 
+## Select interface that should be used for flannel operations by regexp on Name or IP
+## This is actually an inventory cluster-level item
+## example: select interface with ip from net 10.0.0.0/23
+## single quote and escape backslashes
+# flannel_interface_regexp: '10\\.0\\.[0-2]\\.\\d{1,3}'
+
 # You can choose what type of flannel backend to use
 # please refer to flannel's docs : https://github.com/coreos/flannel/blob/master/README.md
 flannel_backend_type: "vxlan"

roles/network_plugin/flannel/templates/cni-flannel.yml.j2

@@ -66,7 +66,7 @@ spec:
           requests:
             cpu: {{ flannel_cpu_requests }}
             memory: {{ flannel_memory_requests }}
-        command: [ "/opt/bin/flanneld", "--ip-masq", "--kube-subnet-mgr"{% if flannel_interface is defined %}, "--iface={{ flannel_interface }}"{% endif %} ]
+        command: [ "/opt/bin/flanneld", "--ip-masq", "--kube-subnet-mgr"{% if flannel_interface is defined %}, "--iface={{ flannel_interface }}"{% endif %}{% if flannel_interface_regexp is defined %}, "--iface-regex={{ flannel_interface_regexp }}"{% endif %} ]
         securityContext:
           privileged: true
         env: