dns v2 - both empty string and default should be allowed for namespace and partition in CE (#21230)

* dns v2 - both empty string and default should be allowed for namespace and partition in Ce

* add changelog

* use default partition constant

* use constants in validation.

---------

Co-authored-by: Michael Zalimeni <michael.zalimeni@hashicorp.com>

.changelog/21230.txt

@@ -0,0 +1,3 @@
+```release-note:enhancement
+dns: new version was not supporting partition or namespace being set to 'default' in CE version.
+```

acl/acl_ce.go

@@ -8,12 +8,25 @@ package acl
 const (
 	WildcardPartitionName = ""
 	DefaultPartitionName  = ""
-)
+	// NonEmptyDefaultPartitionName is the name of the default partition that is
+	// not empty.  An example of this being supplied is when a partition is specified
+	// in the request for DNS by consul-dataplane.  This has been added to support
+	// DNS v1.5, which needs to be compatible with the original DNS subsystem which
+	// supports partition being "default" or empty.  Otherwise, use DefaultPartitionName.
+	NonEmptyDefaultPartitionName = "default"
+
+	// DefaultNamespaceName is used to mimic the behavior in consul/structs/intention.go,
+	// where we define IntentionDefaultNamespace as 'default' and so we use the same here.
+	// This is a little bit strange; one might want it to be "" like DefaultPartitionName.
+	DefaultNamespaceName = "default"
 
-// Reviewer Note: This is a little bit strange; one might want it to be "" like partition name
-// However in consul/structs/intention.go we define IntentionDefaultNamespace as 'default' and so
-// we use the same here
-const DefaultNamespaceName = "default"
+	// EmptyNamespaceName is the name of the default partition that is an empty string.
+	// An example of this being supplied is when a namespace is specifiedDNS v1.
+	// EmptyNamespaceName has been added to support DNS v1.5, which needs to be
+	// compatible with the original DNS subsystem which supports partition being "default" or empty.
+	// Otherwise, use DefaultNamespaceName.
+	EmptyNamespaceName = ""
+)
 
 type EnterpriseConfig struct {
 	// no fields in CE

agent/discovery/query_fetcher_v1_ce.go

@@ -14,8 +14,12 @@ func (f *V1DataFetcher) NormalizeRequest(req *QueryPayload) {
 	return
 }
 
+// validateEnterpriseTenancy validates the tenancy fields for an enterprise request to
+// make sure that they are either set to an empty string or "default" to align with the behavior
+// in CE.
 func validateEnterpriseTenancy(req QueryTenancy) error {
-	if req.Namespace != "" || req.Partition != acl.DefaultPartitionName {
+	if !(req.Namespace == acl.EmptyNamespaceName || req.Namespace == acl.DefaultNamespaceName) ||
+		!(req.Partition == acl.DefaultPartitionName || req.Partition == acl.NonEmptyDefaultPartitionName) {
 		return ErrNotSupported
 	}
 	return nil

agent/discovery/query_fetcher_v1_ce_test.go

@@ -5,7 +5,60 @@
 
 package discovery
 
+import (
+	"github.com/stretchr/testify/require"
+	"testing"
+)
+
 const (
 	defaultTestNamespace = ""
 	defaultTestPartition = ""
 )
+
+func Test_validateEnterpriseTenancy(t *testing.T) {
+	testCases := []struct {
+		name     string
+		req      QueryTenancy
+		expected error
+	}{
+		{
+			name: "empty namespace and partition returns no error",
+			req: QueryTenancy{
+				Namespace: defaultTestNamespace,
+				Partition: defaultTestPartition,
+			},
+			expected: nil,
+		},
+		{
+			name: "namespace and partition set to 'default' returns no error",
+			req: QueryTenancy{
+				Namespace: "default",
+				Partition: "default",
+			},
+			expected: nil,
+		},
+		{
+			name: "namespace set to something other than empty string or `default` returns not supported error",
+			req: QueryTenancy{
+				Namespace: "namespace-1",
+				Partition: "default",
+			},
+			expected: ErrNotSupported,
+		},
+		{
+			name: "partition set to something other than empty string or `default` returns not supported error",
+			req: QueryTenancy{
+				Namespace: "default",
+				Partition: "partition-1",
+			},
+			expected: ErrNotSupported,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			err := validateEnterpriseTenancy(tc.req)
+			require.Equal(t, tc.expected, err)
+		})
+	}
+}