Update API docs (service entry, gateway, sidecar)

networking/v1alpha3/gateway.proto

@@ -62,6 +62,15 @@ syntax = "proto3";
 //       serverCertificate: /etc/certs/servercert.pem
 //       privateKey: /etc/certs/privatekey.pem
 //   - port:
+//       number: 9443
+//       name: https
+//       protocol: HTTPS
+//     hosts:
+//     - "bookinfo-namespace/*.bookinfo.com"
+//     tls:
+//       mode: SIMPLE # enables HTTPS on this port
+//       credentialName: bookinfo-secret # fetches certs from kubernetes secret
+//   - port:
 //       number: 9080
 //       name: http-wildcard
 //       protocol: HTTP
@@ -74,6 +83,7 @@ syntax = "proto3";
 //     hosts:
 //     - "*"
 // ```
+//
 // The Gateway specification above describes the L4-L6 properties of a load
 // balancer. A `VirtualService` can then be bound to a gateway to control
 // the forwarding of traffic arriving at a particular host or gateway port.
@@ -153,6 +163,32 @@ syntax = "proto3";
 //         port:
 //           number: 5555
 // ```
+//
+// It is possible to restrict the set of virtual services that can bind to
+// a gateway server using the namespace/hostname syntax in the hosts field.
+// For example, the following Gateway allows any virtual service in the ns1
+// namespace to bind to it, while restricts only the virtual service with
+// foo.bar.com host in ns2 namespace to bind to it.
+//
+// ```yaml
+// apiVersion: networking.istio.io/v1alpha3
+// kind: Gateway
+// metadata:
+//   name: my-gateway
+//   namespace: some-config-namespace
+// spec:
+//   selector:
+//     app: my-gateway-controller
+//   servers:
+//   - port:
+//       number: 80
+//       name: http
+//       protocol: HTTP
+//     hosts:
+//     - "ns1/*"
+//     - "ns2/foo.bar.com"
+// ```
+//
 package istio.networking.v1alpha3;
 
 option go_package = "istio.io/api/networking/v1alpha3";
@@ -232,14 +268,14 @@ message Gateway {
 // ```
 message Server {
   // REQUIRED: The Port on which the proxy should listen for incoming
-  // connections. If using Unix domain socket, use 0 as the port number,
-  // with a valid protocol and port name, along with the bind parameter.
+  // connections.
   Port port = 1;
 
   // $hide_from_docs
   // The ip or the Unix domain socket to which the listener should be bound
-  // to. Format: `x.x.x.x` or `unix:///path/to/uds` or `unix://@foobar` (Linux
-  // abstract namespace).
+  // to. Format: `x.x.x.x` or `unix:///path/to/uds` or `unix://@foobar`
+  // (Linux abstract namespace). When using unix domain sockets, the port
+  // number should be 0.
   string bind = 4;
 
   // REQUIRED. One or more hosts exposed by this gateway.
@@ -319,18 +355,21 @@ message Server {
     string ca_certificates = 5;
 
     // The credentialName stands for a unique identifier that can be used
-    // to identify the serverCertificate and the privateKey. The credentialName
-    // appended with suffix "-cacert" is used to identify the CaCertificates
-    // associated with this server. Gateway workloads capable of fetching
-    // credentials from a remote credential store will be configured to retrieve
-    // the serverCertificate and the privateKey using credentialName, instead of
-    // using the file system paths specified above. If using mutual TLS,
+    // to identify the serverCertificate and the privateKey. The
+    // credentialName appended with suffix "-cacert" is used to identify
+    // the CaCertificates associated with this server. Gateway workloads
+    // capable of fetching credentials from a remote credential store such
+    // as kubernetes secrets, will be configured to retrieve the
+    // serverCertificate and the privateKey using credentialName, instead
+    // of using the file system paths specified above. If using mutual TLS,
     // gateway workloads will retrieve the CaCertificates using
-    // credentialName-cacert. The semantics of the name are platform dependent.
-    // In Kubernetes, the default Istio supplied credential server expects the
-    // credentialName to match the name of the Kubernetes secret that holds the
-    // server certificate, the private key, and the CA certificate
-    // (if using mutual TLS).
+    // credentialName-cacert. The semantics of the name are platform
+    // dependent.  In Kubernetes, the default Istio supplied credential
+    // server expects the credentialName to match the name of the
+    // Kubernetes secret that holds the server certificate, the private
+    // key, and the CA certificate (if using mutual TLS). Set the
+    // ISTIO_META_USER_SDS metadata variable in the gateway's proxy to
+    // enable the dynamic credential fetching feature.
     string credential_name = 10;
 
     // A list of alternate names to verify the subject identity in the