pkg/ip link_test: ensure SetHWAddrByIP has an effect

pkg/ip/link_test.go

@@ -28,10 +28,17 @@ import (
 	"github.com/vishvananda/netlink/nl"
 )
 
+func getHwAddr(linkname string) string {
+	veth, err := netlink.LinkByName(linkname)
+	Expect(err).NotTo(HaveOccurred())
+	return fmt.Sprintf("%s", veth.Attrs().HardwareAddr)
+}
+
 var _ = Describe("Link", func() {
 	const (
 		ifaceFormatString string = "i%d"
 		mtu               int    = 1400
+		ip4onehwaddr             = "0a:58:01:01:01:01"
 	)
 	var (
 		hostNetNS         ns.NetNS
@@ -39,6 +46,9 @@ var _ = Describe("Link", func() {
 		ifaceCounter      int = 0
 		hostVethName      string
 		containerVethName string
+
+		ip4one = net.ParseIP("1.1.1.1")
+		ip4two = net.ParseIP("1.1.1.2")
 	)
 
 	BeforeEach(func() {
@@ -129,4 +139,41 @@ var _ = Describe("Link", func() {
 			return nil
 		})
 	})
+
+	It("SetHWAddrByIP must change the interface hwaddr and be predictable", func() {
+
+		_ = containerNetNS.Do(func(ns.NetNS) error {
+			defer GinkgoRecover()
+
+			var err error
+			hwaddrBefore := getHwAddr(containerVethName)
+
+			err = ip.SetHWAddrByIP(containerVethName, ip4one, nil)
+			Expect(err).NotTo(HaveOccurred())
+			hwaddrAfter1 := getHwAddr(containerVethName)
+
+			Expect(hwaddrBefore).NotTo(Equal(hwaddrAfter1))
+			Expect(hwaddrAfter1).To(Equal(ip4onehwaddr))
+
+			return nil
+		})
+	})
+
+	It("SetHWAddrByIP must be injective", func() {
+
+		_ = containerNetNS.Do(func(ns.NetNS) error {
+			defer GinkgoRecover()
+
+			err := ip.SetHWAddrByIP(containerVethName, ip4one, nil)
+			Expect(err).NotTo(HaveOccurred())
+			hwaddrAfter1 := getHwAddr(containerVethName)
+
+			err = ip.SetHWAddrByIP(containerVethName, ip4two, nil)
+			Expect(err).NotTo(HaveOccurred())
+			hwaddrAfter2 := getHwAddr(containerVethName)
+
+			Expect(hwaddrAfter1).NotTo(Equal(hwaddrAfter2))
+			return nil
+		})
+	})
 })