diff --git a/osbase/net/dns/name_test.go b/osbase/net/dns/name_test.go
new file mode 100644
index 0000000..fab7bba
--- /dev/null
+++ b/osbase/net/dns/name_test.go
@@ -0,0 +1,155 @@
+package dns
+
+import (
+	"testing"
+)
+
+func TestIsSubDomain(t *testing.T) {
+	cases := []struct {
+		parent, child string
+		expected      bool
+	}{
+		{".", ".", true},
+		{".", "test.", true},
+		{"example.com.", "example.com.", true},
+		{"example.com.", "www.example.com.", true},
+		{"example.com.", "xample.com.", false},
+		{"example.com.", "www.axample.com.", false},
+		{"example.com.", "wwwexample.com.", false},
+		{"example.com.", `www\.example.com.`, false},
+		{"example.com.", `www\\.example.com.`, true},
+	}
+	for _, c := range cases {
+		if IsSubDomain(c.parent, c.child) != c.expected {
+			t.Errorf("IsSubDomain(%q, %q): expected %v", c.parent, c.child, c.expected)
+		}
+	}
+}
+
+func TestSplitLastLabel(t *testing.T) {
+	cases := []struct {
+		name, rest, label string
+	}{
+		{"", "", ""},
+		{".", "", ""},
+		{"com.", "", "com"},
+		{"www.example.com", "www.example.", "com"},
+		{"www.example.com.", "www.example.", "com"},
+		{`www.example\.com.`, "www.", `example\.com`},
+		{`www.example\\.com.`, `www.example\\.`, "com"},
+	}
+	for _, c := range cases {
+		rest, label := SplitLastLabel(c.name)
+		if rest != c.rest || label != c.label {
+			t.Errorf("SplitLastLabel(%q) = (%q, %q), expected (%q, %q)", c.name, rest, label, c.rest, c.label)
+		}
+	}
+}
+
+func TestParseReverse(t *testing.T) {
+	cases := []struct {
+		name  string
+		ip    string
+		bits  int
+		extra bool
+	}{
+		{"example.", "invalid IP", 0, false},
+		{"0.10.200.255.in-addr.arpa.", "255.200.10.0", 32, false},
+		{"7.6.45.123.in-addr.arpa.", "123.45.6.7", 32, false},
+		{"6.45.123.in-addr.arpa.", "123.45.6.0", 24, false},
+		{"45.123.in-addr.arpa.", "123.45.0.0", 16, false},
+		{"123.in-addr.arpa.", "123.0.0.0", 8, false},
+		{"in-addr.arpa.", "0.0.0.0", 0, false},
+		{"8.7.6.45.123.in-addr.arpa.", "123.45.6.7", 32, true}, // too many fields
+		{".6.45.123.in-addr.arpa.", "123.45.6.0", 24, true},    // empty field
+		{"7.06.45.123.in-addr.arpa.", "123.45.0.0", 16, true},  // leading 0
+		{"7.256.45.123.in-addr.arpa.", "123.45.0.0", 16, true}, // number too large
+		{"a6.45.123.in-addr.arpa.", "123.45.0.0", 16, true},    // invalid character
+		{`7\.6.45.123.in-addr.arpa.`, "123.45.0.0", 16, true},  // escaped .
+		{"0.6.45.123in-addr.arpa.", "invalid IP", 0, false},    // missing .
+		{
+			"0.1.2.3.4.5.6.7.8.9.a.b.c.d.e.f.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa.",
+			"::fedc:ba98:7654:3210",
+			128,
+			false,
+		},
+		{
+			"1.2.3.4.5.6.7.8.9.a.b.c.d.e.f.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa.",
+			"::fedc:ba98:7654:3210",
+			124,
+			false,
+		},
+		{
+			"2.3.4.5.6.7.8.9.a.b.c.d.e.f.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa.",
+			"::fedc:ba98:7654:3200",
+			120,
+			false,
+		},
+		{
+			"3.4.5.6.7.8.9.a.b.c.d.e.f.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa.",
+			"::fedc:ba98:7654:3000",
+			116,
+			false,
+		},
+		{
+			"2.ip6.arpa.",
+			"2000::",
+			4,
+			false,
+		},
+		{
+			"ip6.arpa.",
+			"::",
+			0,
+			false,
+		},
+		{
+			"0.0.1.2.3.4.5.6.7.8.9.a.b.c.d.e.f.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa.", // too long
+			"::fedc:ba98:7654:3210",
+			128,
+			true,
+		},
+		{
+			"01.2.3.4.5.6.7.8.9.a.b.c.d.e.f.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa.", // missing dot
+			"::fedc:ba98:7654:3200",
+			120,
+			true,
+		},
+		{
+			"001.2.3.4.5.6.7.8.9.a.b.c.d.e.f.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa.", // missing dot
+			"::fedc:ba98:7654:3200",
+			120,
+			true,
+		},
+		{
+			`0.1\.2.3.4.5.6.7.8.9.a.b.c.d.e.f.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa.`, // escaped dot
+			"::fedc:ba98:7654:3000",
+			116,
+			true,
+		},
+		{
+			"g.1.2.3.4.5.6.7.8.9.a.b.c.d.e.f.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa.", // invalid character
+			"::fedc:ba98:7654:3210",
+			124,
+			true,
+		},
+	}
+	for _, c := range cases {
+		ip, bits, extra := ParseReverse(c.name)
+		if ip.String() != c.ip || bits != c.bits || extra != c.extra {
+			t.Errorf("ParseReverse(%q) = (%s, %v, %v), expected (%s, %v, %v)", c.name, ip, bits, extra, c.ip, c.bits, c.extra)
+		}
+	}
+}
+
+func BenchmarkParseReverseIPv4(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		ParseReverse("7.6.45.123.in-addr.arpa.")
+	}
+}
+
+func BenchmarkParseReverseIPv6(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		ParseReverse("0.1.2.3.4.5.6.7.8.9.a.b.c.d.e.f.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa.")
+	}
+}