Changes GBP field to set a value of NULL when set. (#145)

Signed-off-by: Jay Dunkelberger <ldunkelberger@pivotal.io>

link_linux.go

@@ -426,7 +426,7 @@ func addVxlanAttrs(vxlan *Vxlan, linkInfo *nl.RtAttr) {
 		nl.NewRtAttrChild(data, nl.IFLA_VXLAN_UDP_CSUM, boolAttr(vxlan.UDPCSum))
 	}
 	if vxlan.GBP {
-		nl.NewRtAttrChild(data, nl.IFLA_VXLAN_GBP, boolAttr(vxlan.GBP))
+		nl.NewRtAttrChild(data, nl.IFLA_VXLAN_GBP, []byte{})
 	}
 	if vxlan.NoAge {
 		nl.NewRtAttrChild(data, nl.IFLA_VXLAN_AGEING, nl.Uint32Attr(0))
@@ -1163,7 +1163,7 @@ func parseVxlanData(link Link, data []syscall.NetlinkRouteAttr) {
 		case nl.IFLA_VXLAN_UDP_CSUM:
 			vxlan.UDPCSum = int8(datum.Value[0]) != 0
 		case nl.IFLA_VXLAN_GBP:
-			vxlan.GBP = int8(datum.Value[0]) != 0
+			vxlan.GBP = true
 		case nl.IFLA_VXLAN_AGEING:
 			vxlan.Age = int(native.Uint32(datum.Value[0:4]))
 			vxlan.NoAge = vxlan.Age == 0

link_test.go

@@ -596,6 +596,39 @@ func TestLinkAddDelVxlan(t *testing.T) {
 	}
 }
 
+func TestLinkAddDelVxlanGbp(t *testing.T) {
+	if os.Getenv("TRAVIS_BUILD_DIR") != "" {
+		t.Skipf("Kernel in travis is too old for this test")
+	}
+
+	tearDown := setUpNetlinkTest(t)
+	defer tearDown()
+
+	parent := &Dummy{
+		LinkAttrs{Name: "foo"},
+	}
+	if err := LinkAdd(parent); err != nil {
+		t.Fatal(err)
+	}
+
+	vxlan := Vxlan{
+		LinkAttrs: LinkAttrs{
+			Name: "bar",
+		},
+		VxlanId:      10,
+		VtepDevIndex: parent.Index,
+		Learning:     true,
+		L2miss:       true,
+		L3miss:       true,
+		GBP:          true,
+	}
+
+	testLinkAddDel(t, &vxlan)
+	if err := LinkDel(parent); err != nil {
+		t.Fatal(err)
+	}
+}
+
 func TestLinkAddDelIPVlanL2(t *testing.T) {
 	if os.Getenv("TRAVIS_BUILD_DIR") != "" {
 		t.Skipf("Kernel in travis is too old for this test")