Add AddrReplace

Add an AddrReplace call (and tests).

Equivalent to:
 $ ip addr replace $addr dev $link

addr_linux.go

@@ -27,6 +27,19 @@ func (h *Handle) AddrAdd(link Link, addr *Addr) error {
 	return h.addrHandle(link, addr, req)
 }
 
+// AddrReplace will replace (or, if not present, add) an IP address on a link device.
+// Equivalent to: `ip addr replace $addr dev $link`
+func AddrReplace(link Link, addr *Addr) error {
+	return pkgHandle.AddrReplace(link, addr)
+}
+
+// AddrReplace will replace (or, if not present, add) an IP address on a link device.
+// Equivalent to: `ip addr replace $addr dev $link`
+func (h *Handle) AddrReplace(link Link, addr *Addr) error {
+	req := h.newNetlinkRequest(syscall.RTM_NEWADDR, syscall.NLM_F_CREATE|syscall.NLM_F_REPLACE|syscall.NLM_F_ACK)
+	return h.addrHandle(link, addr, req)
+}
+
 // AddrDel will delete an IP address from a link device.
 // Equivalent to: `ip addr del $addr dev $link`
 func AddrDel(link Link, addr *Addr) error {

addr_test.go

@@ -9,7 +9,15 @@ import (
 	"testing"
 )
 
-func TestAddr(t *testing.T) {
+func TestAddrAdd(t *testing.T) {
+	DoTestAddr(t, AddrAdd)
+}
+
+func TestAddrReplace(t *testing.T) {
+	DoTestAddr(t, AddrReplace)
+}
+
+func DoTestAddr(t *testing.T, FunctionUndertest func(Link, *Addr) error) {
 	if os.Getenv("TRAVIS_BUILD_DIR") != "" {
 		t.Skipf("Fails in travis with: addr_test.go:68: Address flags not set properly, got=0, expected=128")
 	}
@@ -55,7 +63,7 @@ func TestAddr(t *testing.T) {
 	}
 
 	for _, tt := range addrTests {
-		if err = AddrAdd(link, tt.addr); err != nil {
+		if err = FunctionUndertest(link, tt.addr); err != nil {
 			t.Fatal(err)
 		}
 
@@ -122,4 +130,64 @@ func TestAddr(t *testing.T) {
 			t.Fatal("Address not removed properly")
 		}
 	}
+
+}
+
+func TestAddrAddReplace(t *testing.T) {
+	tearDown := setUpNetlinkTest(t)
+	defer tearDown()
+
+	var address = &net.IPNet{IP: net.IPv4(127, 0, 0, 2), Mask: net.CIDRMask(24, 32)}
+	var addr = &Addr{IPNet: address}
+
+	link, err := LinkByName("lo")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = AddrAdd(link, addr)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	addrs, err := AddrList(link, FAMILY_ALL)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if len(addrs) != 1 {
+		t.Fatal("Address not added properly")
+	}
+
+	err = AddrAdd(link, addr)
+	if err == nil {
+		t.Fatal("Re-adding address should fail (but succeeded unexpectedly).")
+	}
+
+	err = AddrReplace(link, addr)
+	if err != nil {
+		t.Fatal("Replacing address failed.")
+	}
+
+	addrs, err = AddrList(link, FAMILY_ALL)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if len(addrs) != 1 {
+		t.Fatal("Address not added properly")
+	}
+
+	if err = AddrDel(link, addr); err != nil {
+		t.Fatal(err)
+	}
+
+	addrs, err = AddrList(link, FAMILY_ALL)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if len(addrs) != 0 {
+		t.Fatal("Address not removed properly")
+	}
 }