added sending of MP_UNREACH_NLRI

protocols/bgp/server/update_sender.go

@@ -216,12 +216,7 @@ func (u *UpdateSender) copyAttributesWithoutNextHop(pa *packet.PathAttribute) (a
 
 // RemovePath withdraws prefix `pfx` from a peer
 func (u *UpdateSender) RemovePath(pfx bnet.Prefix, p *route.Path) bool {
-	if u.fsm.options.SupportsMultiProtocol {
-		// TODO: imeplent withdraw
-		return false
-	}
-
-	err := withDrawPrefixesAddPath(u.fsm.con, u.fsm.options, pfx, p)
+	err := u.withdrawPrefix(pfx, p)
 	if err != nil {
 		log.Errorf("Unable to withdraw prefix: %v", err)
 		return false
@@ -229,6 +224,14 @@ func (u *UpdateSender) RemovePath(pfx bnet.Prefix, p *route.Path) bool {
 	return true
 }
 
+func (u *UpdateSender) withdrawPrefix(pfx bnet.Prefix, p *route.Path) error {
+	if u.fsm.options.SupportsMultiProtocol {
+		return withDrawPrefixesMultiProtocol(u.fsm.con, u.fsm.options, pfx)
+	}
+
+	return withDrawPrefixesAddPath(u.fsm.con, u.fsm.options, pfx, p)
+}
+
 // UpdateNewClient does nothing
 func (u *UpdateSender) UpdateNewClient(client routingtable.RouteTableClient) error {
 	log.Warningf("BGP Update Sender: UpdateNewClient not implemented")

protocols/bgp/server/withdraw.go

@@ -58,3 +58,17 @@ func withDrawPrefixesAddPath(out io.Writer, opt *types.Options, pfx net.Prefix,
 	}
 	return serializeAndSendUpdate(out, update, opt)
 }
+
+func withDrawPrefixesMultiProtocol(out io.Writer, opt *types.Options, pfx net.Prefix) error {
+	update := &packet.BGPUpdate{
+		PathAttributes: &packet.PathAttribute{
+			TypeCode: packet.MultiProtocolUnreachNLRICode,
+			Value: packet.MultiProtocolUnreachNLRI{
+				AFI:      packet.IPv6AFI,
+				SAFI:     packet.UnicastSAFI,
+				Prefixes: []net.Prefix{pfx},
+			},
+		},
+	}
+	return serializeAndSendUpdate(out, update, opt)
+}

protocols/bgp/server/withdraw_test.go

@@ -61,6 +61,46 @@ func TestWithDrawPrefixes(t *testing.T) {
 	}
 }
 
+func TestWithDrawPrefixesMultiProtocol(t *testing.T) {
+	tests := []struct {
+		Name     string
+		Prefix   net.Prefix
+		Expected []byte
+	}{
+		{
+			Name:   "IPv6 MP_UNREACH_NLRI",
+			Prefix: net.NewPfx(net.IPv6FromBlocks(0x2804, 0x148c, 0, 0, 0, 0, 0, 0), 32),
+			Expected: []byte{
+				0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, // BGP Marker
+				0x00, 0x22, // BGP Message Length
+				0x02,       // BGP Message Type == Update
+				0x00, 0x00, // WithDraw Octet length
+				0x00, 0x0b, // Length
+				0x80,       // Flags
+				0x0f,       // Attribute Code
+				0x08,       // Attribute length
+				0x00, 0x02, // AFI
+				0x01,                         // SAFI
+				0x20, 0x28, 0x04, 0x14, 0x8c, // Prefix
+			},
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.Name, func(t *testing.T) {
+			buf := bytes.NewBuffer([]byte{})
+			opt := &types.Options{
+				AddPathRX: false,
+			}
+			err := withDrawPrefixesMultiProtocol(buf, opt, test.Prefix)
+			if err != nil {
+				t.Fatalf("unexpected error: %v", err)
+			}
+
+			assert.Equal(t, test.Expected, buf.Bytes())
+		})
+	}
+}
+
 func TestWithDrawPrefixesAddPath(t *testing.T) {
 	testcases := []struct {
 		Name          string