Updates docs with ingress Host header clarifications (#8062)

* Updates docs with ingress Host header changes

Clarify that a Host header is required for L7 protocols, and specify
that the default is to use the Consul DNS ingress subdomain

* Add sentence about using '*' by itself for testing

* Add optional step for using L7 routing config

* Note that port numbers may need to be added in the Hosts field

website/pages/docs/agent/config-entries/ingress-gateway.mdx

@@ -36,7 +36,8 @@ description: >-
     listener will be routable.
   - The ingress gateway will route traffic based on the host/authority header,
     expecting a value matching `<service-name>.ingress.*`, or if using namespaces,
-    `<service-name>.ingress.<namespace>.*`.
+    `<service-name>.ingress.<namespace>.*`. This matches the [Consul DNS
+    ingress subdomain](/docs/agent/dns#ingress-service-lookups).
 
   A wildcard specifier cannot be set on a listener of protocol `tcp`.
 
@@ -116,6 +117,9 @@ Listeners = [
     - `Enabled` `(bool: false)` - Set this configuration to enable TLS for
   every listener on the gateway.
 
+    If TLS is enabled, then each host defined in the `Host` field will be added
+    as a DNSSAN to the gateway's x509 certificate.
+
 - `Listeners` `(array<IngressListener>: <optional>)` - A list of listeners that
   the ingress gateway should setup, uniquely identified by their port number.
 
@@ -141,11 +145,28 @@ Listeners = [
       assumed.
 
     - `Hosts` `(array<string>: <optional>)` - A list of hosts that specify what
-      requests will match to this service. This cannot be used with a `tcp`
-      listener, and cannot be specified alongside a `*` service name.
-
-      If TLS is enabled, then each host will be added as a DNSSAN to the
-      gateway's x509 certificate.
+      requests will match this service. This cannot be used with a `tcp`
+      listener, and cannot be specified alongside a `*` service name. If not
+      specified, the default domain `<service-name>.ingress.*` will be used to
+      match services. Requests **must** send the correct host to be routed to
+      the defined service.
+
+      The wildcard specifier, `*`, can be used by itself to match all traffic
+      coming to the ingress gateway, if TLS is not enabled. This allows a user
+      to route all traffic to a single service without specifying a host,
+      allowing simpler tests and demos. Otherwise, the wildcard specifier can
+      be used as part of the host to match multiple hosts, but only in the
+      leftmost DNS label. This ensures that all defined hosts are valid DNS
+      records. For example, `*.example.com` is valid, while `example.*` and
+      `*-suffix.example.com` are not.
+
+      ~> **Note:** If a well-known port is not used, i.e. a port other than 80
+      (http) or 443 (https), then the port must be appended to the host to
+      correctly match traffic. This is defined in the [HTTP/1.1
+      RFC](https://tools.ietf.org/html/rfc2616#section-14.23). If TLS is
+      enabled, then the host **without** the port must be added to the `Hosts`
+      field as well. TLS verification only matches against the hostname of the
+      incoming connection, and thus does not take into account the port.
 
 ## ACLs
 

website/pages/docs/connect/ingress-gateway.mdx

@@ -22,16 +22,19 @@ exposed and on what port. You configure an ingress gateway by defining a set of
 to a set of backing
 [services](/docs/agent/config-entries/ingress-gateway#services).
 
-Depending on the
-[protocol](/docs/agent/config-entries/ingress-gateway#protocol) defined for a
-listener, multiple services can be specified for a single listener. In this
-case, the ingress gateway relies on host/authority headers to decide the
-service that should receive the traffic.
-
 To enable easier service discovery, a new Consul [DNS
 subdomain](/docs/agent/dns#ingress-service-lookups) is provided, on
 `<service>.ingress.<domain>`.
 
+For listeners with a
+[protocol](/docs/agent/config-entries/ingress-gateway#protocol) other than
+`tcp`, multiple services can be specified for a single listener. In this
+case, the ingress gateway relies on host/authority headers to decide the
+service that should receive the traffic. The host used to match traffic
+defaults to the [Consul DNS ingress
+subdomain](/docs/agent/dns#ingress-service-lookups), but can be changed using
+the [hosts](/docs/agent/config-entries/ingress-gateway#hosts) field.
+
 ![Ingress Gateway Architecture](/img/ingress-gateways.png)
 
 ## Prerequisites
@@ -65,6 +68,8 @@ a set of listeners that expose the desired backing services. The config entry ca
 4. **Optionally** use the `<service>.ingress.<domain>` [DNS subdomain](/docs/agent/dns#ingress-service-lookups) to discover the ingress
 gateways for a service.
 
+5. **Optionally** use the [Consul L7 traffic management](/docs/connect/l7-traffic-management) for exposed services to route traffic.
+
 ## Ingress Gateway Configuration
 
 Ingress gateways are configured in service definitions and registered with Consul like other services, with two exceptions.