[nad] Add GetJsonPathFromConfig

modules/common/networkattachment/networkattachment.go

@@ -204,3 +204,37 @@ func EnsureNetworksAnnotation(
 
 	return annotationString, nil
 }
+
+// GetJSONPathFromConfig - returns the result of the jsonPath as string
+// from the NetworkAttachmentDefinition config.
+// if the NAD has no config, an empty string is returned.
+// The jsonPath must be in the format e.g. ".ipam"
+func GetJSONPathFromConfig(netAtt networkv1.NetworkAttachmentDefinition, path string) (string, error) {
+	var data interface{}
+	buf := new(bytes.Buffer)
+
+	if netAtt.Spec.Config == "" {
+		return buf.String(), nil
+	}
+
+	if err := json.Unmarshal([]byte(netAtt.Spec.Config), &data); err != nil {
+		return "", fmt.Errorf("failed to unmarshal JSON data: %w", err)
+	}
+
+	// use jsonpath to parse the cni config
+	jp := jsonpath.New(netAtt.Name)
+
+	// Parse the JSONPath template to get the ipam
+	err := jp.Parse(fmt.Sprintf(`{.%s}`, path))
+	if err != nil {
+		return "", fmt.Errorf("parse template error: %w", err)
+	}
+
+	// get the ipam from the config
+	err = jp.Execute(buf, data)
+	if err != nil {
+		return "", fmt.Errorf("parse execute template against nad %+v error: %w", netAtt.Spec.Config, err)
+	}
+
+	return buf.String(), nil
+}

modules/common/networkattachment/networkattachment_test.go

@@ -291,3 +291,79 @@ func TestEnsureNetworksAnnotation(t *testing.T) {
 		})
 	}
 }
+
+func TestGetJSONPathFromConfig(t *testing.T) {
+
+	tests := []struct {
+		name string
+		nad  networkv1.NetworkAttachmentDefinition
+		path string
+		want string
+	}{
+		{
+			name: "No config",
+			nad:  networkv1.NetworkAttachmentDefinition{},
+			path: ".ipam",
+			want: "",
+		},
+		{
+			name: "get .name",
+			nad: networkv1.NetworkAttachmentDefinition{
+				ObjectMeta: metav1.ObjectMeta{Name: "one", Namespace: "foo"},
+				Spec: networkv1.NetworkAttachmentDefinitionSpec{
+					Config: `
+			{
+			  "cniVersion": "0.3.1",
+			  "name": "internalapi",
+			  "type": "macvlan",
+			  "master": "internalapi",
+			  "ipam": {
+			    "type": "whereabouts",
+			    "range": "172.17.0.0/24",
+			    "range_start": "172.17.0.30",
+			    "range_end": "172.17.0.70"
+			  }
+			}
+			`,
+				},
+			},
+			path: ".name",
+			want: "internalapi",
+		},
+		{
+			name: "get .ipam.range",
+			nad: networkv1.NetworkAttachmentDefinition{
+				ObjectMeta: metav1.ObjectMeta{Name: "one", Namespace: "foo"},
+				Spec: networkv1.NetworkAttachmentDefinitionSpec{
+					Config: `
+			{
+			  "cniVersion": "0.3.1",
+			  "name": "internalapi",
+			  "type": "macvlan",
+			  "master": "internalapi",
+			  "ipam": {
+			    "type": "whereabouts",
+			    "range": "172.17.0.0/24",
+			    "range_start": "172.17.0.30",
+			    "range_end": "172.17.0.70"
+			  }
+			}
+			`,
+				},
+			},
+			path: ".ipam.range",
+			want: "172.17.0.0/24",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			g := NewWithT(t)
+
+			networkAnnotation, err := GetJSONPathFromConfig(tt.nad, tt.path)
+			g.Expect(err).NotTo(HaveOccurred())
+			g.Expect(networkAnnotation).To(HaveLen(len(tt.want)))
+			g.Expect(networkAnnotation).To(BeEquivalentTo(tt.want))
+		})
+	}
+}