Add a network test that sets up 2 of 4 ehternet devices, and allows another to use dhcp

Signed-off-by: Sven Dowideit <SvenDowideit@home.org.au>

vendor/github.com/vishvananda/netlink/nl/mpls_linux.go

@@ -0,0 +1,36 @@
+package nl
+
+import "encoding/binary"
+
+const (
+	MPLS_LS_LABEL_SHIFT = 12
+	MPLS_LS_S_SHIFT     = 8
+)
+
+func EncodeMPLSStack(labels ...int) []byte {
+	b := make([]byte, 4*len(labels))
+	for idx, label := range labels {
+		l := label << MPLS_LS_LABEL_SHIFT
+		if idx == len(labels)-1 {
+			l |= 1 << MPLS_LS_S_SHIFT
+		}
+		binary.BigEndian.PutUint32(b[idx*4:], uint32(l))
+	}
+	return b
+}
+
+func DecodeMPLSStack(buf []byte) []int {
+	if len(buf)%4 != 0 {
+		return nil
+	}
+	stack := make([]int, 0, len(buf)/4)
+	for len(buf) > 0 {
+		l := binary.BigEndian.Uint32(buf[:4])
+		buf = buf[4:]
+		stack = append(stack, int(l)>>MPLS_LS_LABEL_SHIFT)
+		if (l>>MPLS_LS_S_SHIFT)&1 > 0 {
+			break
+		}
+	}
+	return stack
+}