middleware/kubernetes: put reverse function in own file (#863)

Move reverse function and (some) test code to reverse*.go

middleware/kubernetes/reverse_test.go

@@ -0,0 +1,33 @@
+package kubernetes
+
+import (
+	"net"
+	"testing"
+)
+
+func TestIsRequestInReverseRange(t *testing.T) {
+
+	tests := []struct {
+		cidr     string
+		name     string
+		expected bool
+	}{
+		{"1.2.3.0/24", "4.3.2.1.in-addr.arpa.", true},
+		{"1.2.3.0/24", "5.3.2.1.in-addr.arpa.", true},
+		{"1.2.3.0/24", "5.4.2.1.in-addr.arpa.", false},
+		{"5.6.0.0/16", "5.4.2.1.in-addr.arpa.", false},
+		{"5.6.0.0/16", "5.4.6.5.in-addr.arpa.", true},
+		{"5.6.0.0/16", "5.6.0.1.in-addr.arpa.", false},
+	}
+
+	k := Kubernetes{Zones: []string{"inter.webs.test"}}
+
+	for _, test := range tests {
+		_, cidr, _ := net.ParseCIDR(test.cidr)
+		k.ReverseCidrs = []net.IPNet{*cidr}
+		result := k.isRequestInReverseRange(test.name)
+		if result != test.expected {
+			t.Errorf("Expected '%v' for '%v' in %v.", test.expected, test.name, test.cidr)
+		}
+	}
+}