From ed4f1ad7eda52951ca2d945ae35e71f8202326b9 Mon Sep 17 00:00:00 2001
From: Mike Beaumont <mjboamail@gmail.com>
Date: Thu, 5 Jan 2023 14:30:08 +0100
Subject: [PATCH] fix: allow user rules to overwrite default passthrough rule

Signed-off-by: Mike Beaumont <mjboamail@gmail.com>
---
 .../plugin/v1alpha1/listeners.go              | 38 ++++++++++---------
 .../plugin/v1alpha1/plugin_test.go            | 38 +++++++++++++++++--
 .../testdata/basic.listeners.golden.yaml      | 10 ++---
 3 files changed, 60 insertions(+), 26 deletions(-)

diff --git a/pkg/plugins/policies/meshhttproute/plugin/v1alpha1/listeners.go b/pkg/plugins/policies/meshhttproute/plugin/v1alpha1/listeners.go
index d10eb2195105..47958bd6e6a4 100644
--- a/pkg/plugins/policies/meshhttproute/plugin/v1alpha1/listeners.go
+++ b/pkg/plugins/policies/meshhttproute/plugin/v1alpha1/listeners.go
@@ -85,6 +85,27 @@ func FindRoutes(
 ) []Route {
 	var unmergedRules []RuleAcc
 
+	// Prepend a rule to passthrough unmatched traffic
+	rules = append([]ToRouteRule{{
+		Subset: core_xds.MeshService(serviceName),
+		Rules: []api.Rule{{
+			Matches: []api.Match{{
+				Path: api.PathMatch{
+					Prefix: "/",
+				},
+			}},
+			Default: api.RuleConf{
+				BackendRefs: &[]api.BackendRef{{
+					TargetRef: common_api.TargetRef{
+						Kind: common_api.MeshService,
+						Name: serviceName,
+					},
+					Weight: 100,
+				}},
+			},
+		}},
+	}}, rules...)
+
 	for _, rule := range rules {
 		if !rule.Subset.IsSubset(core_xds.MeshService(serviceName)) {
 			continue
@@ -132,23 +153,6 @@ func FindRoutes(
 		routes = append(routes, route)
 	}
 
-	// append the default route
-	routes = append(routes, Route{
-		Matches: []api.Match{{
-			Path: api.PathMatch{
-				Prefix: "/",
-			},
-		}},
-		Filters: nil,
-		BackendRefs: []api.BackendRef{{
-			TargetRef: common_api.TargetRef{
-				Kind: common_api.MeshService,
-				Name: serviceName,
-			},
-			Weight: 100,
-		}},
-	})
-
 	return routes
 }
 
diff --git a/pkg/plugins/policies/meshhttproute/plugin/v1alpha1/plugin_test.go b/pkg/plugins/policies/meshhttproute/plugin/v1alpha1/plugin_test.go
index 7e16e0a768d6..61853b14ff5b 100644
--- a/pkg/plugins/policies/meshhttproute/plugin/v1alpha1/plugin_test.go
+++ b/pkg/plugins/policies/meshhttproute/plugin/v1alpha1/plugin_test.go
@@ -194,6 +194,18 @@ var _ = Describe("MeshHTTPRoute", func() {
 		}},
 		serviceName: "backend",
 		expectedRoutes: []plugin.Route{{
+			Matches: []api.Match{{
+				Path: api.PathMatch{
+					Prefix: "/",
+				},
+			}},
+			BackendRefs: []api.BackendRef{
+				{
+					TargetRef: builders.TargetRefService("backend"),
+					Weight:    100,
+				},
+			},
+		}, {
 			Matches: []api.Match{{
 				Path: api.PathMatch{
 					Prefix: "/v1",
@@ -217,7 +229,26 @@ var _ = Describe("MeshHTTPRoute", func() {
 					Weight:    100,
 				},
 			},
-		}, {
+		}},
+	}), Entry("overwrite-passthrough-rule", routesTestCase{
+		rules: []plugin.ToRouteRule{{
+			Subset: core_xds.MeshService("backend"),
+			Rules: []api.Rule{{
+				Matches: []api.Match{{
+					Path: api.PathMatch{
+						Prefix: "/",
+					},
+				}},
+				Default: api.RuleConf{
+					BackendRefs: &[]api.BackendRef{{
+						TargetRef: builders.TargetRefService("other-service"),
+						Weight:    100,
+					}},
+				},
+			}},
+		}},
+		serviceName: "backend",
+		expectedRoutes: []plugin.Route{{
 			Matches: []api.Match{{
 				Path: api.PathMatch{
 					Prefix: "/",
@@ -225,13 +256,12 @@ var _ = Describe("MeshHTTPRoute", func() {
 			}},
 			BackendRefs: []api.BackendRef{
 				{
-					TargetRef: builders.TargetRefService("backend"),
+					TargetRef: builders.TargetRefService("other-service"),
 					Weight:    100,
 				},
 			},
 		}},
-	}),
-	)
+	}))
 	type outboundsTestCase struct {
 		proxy      core_xds.Proxy
 		xdsContext xds_context.Context
diff --git a/pkg/plugins/policies/meshhttproute/plugin/v1alpha1/testdata/basic.listeners.golden.yaml b/pkg/plugins/policies/meshhttproute/plugin/v1alpha1/testdata/basic.listeners.golden.yaml
index b5a701bfd444..c64941995cf8 100644
--- a/pkg/plugins/policies/meshhttproute/plugin/v1alpha1/testdata/basic.listeners.golden.yaml
+++ b/pkg/plugins/policies/meshhttproute/plugin/v1alpha1/testdata/basic.listeners.golden.yaml
@@ -28,19 +28,19 @@ resources:
               name: backend
               routes:
               - match:
-                  prefix: /v1
+                  prefix: /
                 route:
                   cluster: backend
                   timeout: 0s
               - match:
-                  prefix: /v2
+                  prefix: /v1
                 route:
-                  cluster: backend-_0_
+                  cluster: backend
                   timeout: 0s
               - match:
-                  prefix: /
+                  prefix: /v2
                 route:
-                  cluster: backend
+                  cluster: backend-_0_
                   timeout: 0s
           statPrefix: backend
     metadata: