Implement request redirect filter in HTTPRoute rule (#218)

This commit implements the request redirect filter as part of the routing
rule in the HTTPRoute.

A common use-case for a request redirect is redirecting HTTP requests
to HTTPS. The commit updates the HTTPS termination example to include
HTTPS redirect configuration.

Notes:
- The experimental 'path' field of 'requestRedirect' is out of scope.
- The validation of the fields of `requestRedirect` is not implemented.
It is left to be done in a separate component responsible for validation
with FIXMEs added to the relevant code locations.
- If multiple redirect filters are configured, NGINX Kubernetes Gateway
will choose the first one and ignore the rest.
- NGINX will always redirect a request even if the request has already
been redirected. Thus, any backendRefs defined in the routing rule will
be ignored. However, that "always redirect" behavior is not specified
by the Gateway API. As a result, we might need to change our
implementation if different behavior becomes specified by the Gateway API
in the future.

docs/gateway-api-compatibility.md.md

@@ -87,7 +87,10 @@ Fields:
 	  * `headers` - partially supported. Only `Exact` type.
 	  * `queryParams` - partially supported. Only `Exact` type. 
 	  * `method` -  supported.
-	* `filters` - not supported.
+	* `filters`
+		* `type` - supported.
+		* `requestRedirect` - supported except for the experimental `path` field. If multiple filters with `requestRedirect` are configured, NGINX Kubernetes Gateway will choose the first one and ignore the rest. 
+		* `requestHeaderModifier`, `requestMirror`, `urlRewrite`, `extensionRef` - not supported.
 	* `backendRefs` - partially supported. Only a single backend ref without support for `weight`. Backend ref `filters` are not supported. NGINX Kubernetes Gateway will use the IP of the Service as a backend, not the IPs of the corresponding Pods. Watching for Service updates is not supported.
 * `status`
   * `parents`

examples/https-termination/README.md

@@ -1,6 +1,6 @@
 # HTTPS Termination Example
 
-In this example we expand on the simple [cafe-example](../cafe-example) by adding HTTPS termination to our routes.
+In this example, we expand on the simple [cafe-example](../cafe-example) by adding HTTPS termination to our routes and an HTTPS redirect from port 80 to 443.
 
 ## Running the Example
 
@@ -14,10 +14,11 @@ In this example we expand on the simple [cafe-example](../cafe-example) by addin
    GW_IP=XXX.YYY.ZZZ.III
    ```
 
-1. Save the HTTPS port of NGINX Kubernetes Gateway:
+1. Save the ports of NGINX Kubernetes Gateway:
 
    ```
-   GW_HTTPS_PORT=port
+   GW_HTTP_PORT=<http port number>
+   GW_HTTPS_PORT=<https port number>
    ```
 
 ## 2. Deploy the Cafe Application
@@ -52,26 +53,60 @@ In this example we expand on the simple [cafe-example](../cafe-example) by addin
    kubectl apply -f gateway.yaml
    ```
 
-   This [gateway](./gateway.yaml) configures an `https` listener is to terminate TLS connections using the `cafe-secret` we created in the step 1.
+   This [Gateway](./gateway.yaml) configures:
+   * `http` listener for HTTP traffic
+   * `https` listener for HTTPS traffic. It terminates TLS connections using the `cafe-secret` we created in step 1.
 
 1. Create the `HTTPRoute` resources:
    ```
    kubectl apply -f cafe-routes.yaml
    ```
 
-   To configure HTTPS termination for our cafe application, we will bind the `https` listener to our `HTTPRoutes` in [cafe-routes.yaml](./cafe-routes.yaml) using the [`parentReference`](https://gateway-api.sigs.k8s.io/references/spec/#gateway.networking.k8s.io/v1beta1.ParentReference) field:
+   To configure HTTPS termination for our cafe application, we will bind our `coffee` and `tea` HTTPRoutes to the `https` listener in [cafe-routes.yaml](./cafe-routes.yaml) using the [`parentReference`](https://gateway-api.sigs.k8s.io/references/spec/#gateway.networking.k8s.io/v1beta1.ParentReference) field:
 
    ```yaml
    parentRefs:
    - name: gateway
-     namespace: default
      sectionName: https
    ```
 
+   To configure an HTTPS redirect from port 80 to 443, we will bind the special `cafe-tls-redirect` HTTPRoute with a [`HTTPRequestRedirectFilter`](https://gateway-api.sigs.k8s.io/references/spec/#gateway.networking.k8s.io/v1beta1.HTTPRequestRedirectFilter) to the `http` listener:
+
+   ```yaml
+   parentRefs:
+   - name: gateway
+     sectionName: http
+   ```
+
 ## 4. Test the Application
 
-To access the application, we will use `curl` to send requests to the `coffee` and `tea` Services.
-Since our certificate is self-signed, we'll use curl's `--insecure` option to turn off certificate verification.
+To access the application, we will use `curl` to send requests to the `coffee` and `tea` Services. First, we will access the application over HTTP to test that the HTTPS redirect works. Then we will use HTTPS.
+
+### 4.1 Test HTTPS Redirect
+
+To test that NGINX sends an HTTPS redirect, we will send requests to the `coffee` and `tea` Services on HTTP port. We will use curl's `--include` option to print the response headers (we are interested in the `Location` header).
+
+To get a redirect for coffee:
+```
+curl --resolve cafe.example.com:$GW_HTTP_PORT:$GW_IP http://cafe.example.com:$GW_HTTP_PORT/coffee --include
+HTTP/1.1 302 Moved Temporarily
+...
+Location: https://cafe.example.com:443/coffee
+...
+```
+
+To get a redirect for tea:
+```
+curl --resolve cafe.example.com:$GW_HTTP_PORT:$GW_IP http://cafe.example.com:$GW_HTTP_PORT/tea --include
+HTTP/1.1 302 Moved Temporarily
+...
+Location: https://cafe.example.com:443/tea
+...
+```
+
+### 4.2 Access Coffee and Tea 
+
+Now we will access the application over HTTPS. Since our certificate is self-signed, we will use curl's `--insecure` option to turn off certificate verification.
 
 To get coffee:
 

examples/https-termination/cafe-routes.yaml

@@ -1,5 +1,22 @@
 apiVersion: gateway.networking.k8s.io/v1beta1
 kind: HTTPRoute
+metadata:
+  name: cafe-tls-redirect
+spec:
+  parentRefs:
+  - name: gateway
+    sectionName: http
+  hostnames:
+  - "cafe.example.com"
+  rules:
+  - filters:
+    - type: RequestRedirect
+      requestRedirect:
+        scheme: https
+        port: 443
+---
+apiVersion: gateway.networking.k8s.io/v1beta1
+kind: HTTPRoute
 metadata:
   name: coffee
 spec:

examples/https-termination/gateway.yaml

@@ -7,6 +7,9 @@ metadata:
 spec:
   gatewayClassName: nginx
   listeners:
+  - name: http
+    port: 80
+    protocol: HTTP
   - name: https
     port: 443
     protocol: HTTPS

internal/helpers/helpers.go

@@ -22,6 +22,11 @@ func GetStringPointer(s string) *string {
 	return &s
 }
 
+// GetIntPointer takes an int and returns a pointer to it. Useful in unit tests when initializing structs.
+func GetIntPointer(i int) *int {
+	return &i
+}
+
 // GetInt32Pointer takes an int32 and returns a pointer to it. Useful in unit tests when initializing structs.
 func GetInt32Pointer(i int32) *int32 {
 	return &i

internal/nginx/config/generator.go

@@ -82,11 +82,15 @@ func generate(virtualServer state.VirtualServer, serviceStore state.ServiceStore
 
 	s := server{ServerName: virtualServer.Hostname}
 
+	listenerPort := 80
+
 	if virtualServer.SSL != nil {
 		s.SSL = &ssl{
 			Certificate:    virtualServer.SSL.CertificatePath,
 			CertificateKey: virtualServer.SSL.CertificatePath,
 		}
+
+		listenerPort = 443
 	}
 
 	if len(virtualServer.PathRules) == 0 {
@@ -100,26 +104,41 @@ func generate(virtualServer state.VirtualServer, serviceStore state.ServiceStore
 		matches := make([]httpMatch, 0, len(rule.MatchRules))
 
 		for ruleIdx, r := range rule.MatchRules {
-
-			address, err := getBackendAddress(r.Source.Spec.Rules[r.RuleIdx].BackendRefs, r.Source.Namespace, serviceStore)
-			if err != nil {
-				warnings.AddWarning(r.Source, err.Error())
-			}
-
 			m := r.GetMatch()
 
+			var loc location
+
 			// handle case where the only route is a path-only match
 			// generate a standard location block without http_matches.
 			if len(rule.MatchRules) == 1 && isPathOnlyMatch(m) {
-				locs = append(locs, location{
-					Path:      rule.Path,
-					ProxyPass: generateProxyPass(address),
-				})
+				loc = location{
+					Path: rule.Path,
+				}
 			} else {
 				path := createPathForMatch(rule.Path, ruleIdx)
-				locs = append(locs, generateMatchLocation(path, address))
+				loc = generateMatchLocation(path)
 				matches = append(matches, createHTTPMatch(m, path))
 			}
+
+			// FIXME(pleshakov): There could be a case when the filter has the type set but not the corresponding field.
+			// For example, type is v1beta1.HTTPRouteFilterRequestRedirect, but RequestRedirect field is nil.
+			// The validation webhook catches that.
+			// If it doesn't work as expected, such situation is silently handled below in findFirstFilters.
+			// Consider reporting an error. But that should be done in a separate validation layer.
+
+			// RequestRedirect and proxying are mutually exclusive.
+			if r.Filters.RequestRedirect != nil {
+				loc.Return = generateReturnValForRedirectFilter(r.Filters.RequestRedirect, listenerPort)
+			} else {
+				address, err := getBackendAddress(r.Source.Spec.Rules[r.RuleIdx].BackendRefs, r.Source.Namespace, serviceStore)
+				if err != nil {
+					warnings.AddWarning(r.Source, err.Error())
+				}
+
+				loc.ProxyPass = generateProxyPass(address)
+			}
+
+			locs = append(locs, loc)
 		}
 
 		if len(matches) > 0 {
@@ -150,6 +169,41 @@ func generateProxyPass(address string) string {
 	return "http://" + address
 }
 
+func generateReturnValForRedirectFilter(filter *v1beta1.HTTPRequestRedirectFilter, listenerPort int) *returnVal {
+	if filter == nil {
+		return nil
+	}
+
+	hostname := "$host"
+	if filter.Hostname != nil {
+		hostname = string(*filter.Hostname)
+	}
+
+	// FIXME(pleshakov): Unknown values here must result in the implementation setting the Attached Condition for
+	// the Route to  `status: False`, with a Reason of `UnsupportedValue`. In that case, all routes of the Route will be
+	// ignored. NGINX will return 500. This should be implemented in the validation layer.
+	code := statusFound
+	if filter.StatusCode != nil {
+		code = statusCode(*filter.StatusCode)
+	}
+
+	port := listenerPort
+	if filter.Port != nil {
+		port = int(*filter.Port)
+	}
+
+	// FIXME(pleshakov): Same as the FIXME about StatusCode above.
+	scheme := "$scheme"
+	if filter.Scheme != nil {
+		scheme = *filter.Scheme
+	}
+
+	return &returnVal{
+		Code: code,
+		URL:  fmt.Sprintf("%s://%s:%d$request_uri", scheme, hostname, port),
+	}
+}
+
 func getBackendAddress(
 	refs []v1beta1.HTTPBackendRef,
 	parentNS string,
@@ -183,11 +237,10 @@ func getBackendAddress(
 	return fmt.Sprintf("%s:%d", address, *ref.Port), nil
 }
 
-func generateMatchLocation(path, address string) location {
+func generateMatchLocation(path string) location {
 	return location{
-		Path:      path,
-		ProxyPass: generateProxyPass(address),
-		Internal:  true,
+		Path:     path,
+		Internal: true,
 	}
 }