Add appProtocol field

Since Kubernetes 1.20, the `.spec.ports[*].appProtocol` field may be set on a Service as a hint for implementations to offer richer behavior for protocols that they understand. For example, this field is used by the GKE Gateway controller to enable TLS between the load balancer and the backend.

traefik/templates/_service.tpl

@@ -46,6 +46,9 @@
     {{- if $config.nodePort }}
     nodePort: {{ $config.nodePort }}
     {{- end }}
+    {{- if $config.appProtocol }}
+    appProtocol: {{ $config.appProtocol }}
+    {{- end }}
   {{- end }}
   {{- if $config.http3 }}
   {{- if $config.http3.enabled }}
@@ -57,6 +60,9 @@
     {{- if $config.nodePort }}
     nodePort: {{ $config.nodePort }}
     {{- end }}
+    {{- if $config.appProtocol }}
+    appProtocol: {{ $config.appProtocol }}
+    {{- end }}
   {{- end }}
   {{- end }}
   {{- end }}

traefik/tests/service-config_test.yaml

@@ -177,6 +177,28 @@ tests:
           value:
             - IPv6
           documentIndex: 0
+  - it: should not have appProtocol when not specified
+    documentIndex: 0
+    asserts:
+      - isNull:
+          path: spec.ports[0].appProtocol
+      - isNull:
+          path: spec.ports[1].appProtocol
+  - it: should have custom appProtocol when specified via values
+    set:
+      ports:
+        web:
+          appProtocol: http
+        websecure:
+          appProtocol: https
+    documentIndex: 0
+    asserts:
+      - equal:
+          path: spec.ports[0].appProtocol
+          value: http
+      - equal:
+          path: spec.ports[1].appProtocol
+          value: https
   - it: should use default websecure UDP port when http3 is enabled
     set:
       ports:

traefik/values.yaml

@@ -612,6 +612,8 @@ ports:
     ## -- The port protocol (TCP/UDP)
     protocol: TCP
     # nodePort: 32443
+    ## -- Specify an application protocol. This may be used as a hint for a Layer 7 load balancer.
+    # appProtocol: https
     #
     ## -- Enable HTTP/3 on the entrypoint
     ## Enabling it will also enable http3 experimental feature