Add support for Echo requests (#25)

client.go

@@ -135,6 +135,11 @@ func (c *Session) Logoff() error {
 	return c.s.logoff(c.ctx)
 }
 
+// Echo sends an echo request to the server.
+func (c *Session) Echo() error {
+	return c.s.echo(c.ctx)
+}
+
 // Mount mounts the SMB share.
 // sharename must follow format like `<share>` or `\\<server>\<share>`.
 // Note that the mounted share doesn't inherit session's context.

internal/smb2/request.go

@@ -291,6 +291,48 @@ func (r LogoffRequestDecoder) StructureSize() uint16 {
 	return le.Uint16(r[:2])
 }
 
+// ----------------------------------------------------------------------------
+// SMB2 ECHO Request Packet
+//
+
+type EchoRequest struct {
+	PacketHeader
+}
+
+func (c *EchoRequest) Header() *PacketHeader {
+	return &c.PacketHeader
+}
+
+func (c *EchoRequest) Size() int {
+	return 64 + 4
+}
+
+func (c *EchoRequest) Encode(pkt []byte) {
+	c.Command = SMB2_ECHO
+	c.encodeHeader(pkt)
+
+	req := pkt[64:]
+	le.PutUint16(req[:2], 4) // StructureSize
+}
+
+type EchoRequestDecoder []byte
+
+func (r EchoRequestDecoder) IsInvalid() bool {
+	if len(r) < 4 {
+		return true
+	}
+
+	if r.StructureSize() != 4 {
+		return true
+	}
+
+	return false
+}
+
+func (r EchoRequestDecoder) StructureSize() uint16 {
+	return le.Uint16(r[:2])
+}
+
 // ----------------------------------------------------------------------------
 // SMB2 TREE_CONNECT Request Packet
 //

internal/smb2/response.go

@@ -631,6 +631,48 @@ func (r LogoffResponseDecoder) StructureSize() uint16 {
 	return le.Uint16(r[:2])
 }
 
+// ----------------------------------------------------------------------------
+// SMB2 ECHO Response
+//
+
+type EchoResponse struct {
+	PacketHeader
+}
+
+func (c *EchoResponse) Header() *PacketHeader {
+	return &c.PacketHeader
+}
+
+func (c *EchoResponse) Size() int {
+	return 64 + 4
+}
+
+func (c *EchoResponse) Encode(pkt []byte) {
+	c.Command = SMB2_ECHO
+	c.encodeHeader(pkt)
+
+	res := pkt[64:]
+	le.PutUint16(res[:2], 4) // StructureSize
+}
+
+type EchoResponseDecoder []byte
+
+func (r EchoResponseDecoder) IsInvalid() bool {
+	if len(r) < 4 {
+		return true
+	}
+
+	if r.StructureSize() != 4 {
+		return true
+	}
+
+	return false
+}
+
+func (r EchoResponseDecoder) StructureSize() uint16 {
+	return le.Uint16(r[:2])
+}
+
 // ----------------------------------------------------------------------------
 // SMB2 TREE_CONNECT Response
 //

session.go

@@ -291,6 +291,24 @@ func (s *session) logoff(ctx context.Context) error {
 	return nil
 }
 
+func (s *session) echo(ctx context.Context) error {
+	req := new(EchoRequest)
+
+	req.CreditCharge = 1
+
+	res, err := s.sendRecv(SMB2_ECHO, req, ctx)
+	if err != nil {
+		return err
+	}
+
+	r := EchoResponseDecoder(res)
+	if r.IsInvalid() {
+		return &InvalidResponseError{"broken echo response format"}
+	}
+
+	return nil
+}
+
 func (s *session) sendRecv(cmd uint16, req Packet, ctx context.Context) (res []byte, err error) {
 	rr, err := s.send(req, ctx)
 	if err != nil {

smb2_test.go

@@ -900,3 +900,11 @@ func TestGlob(t *testing.T) {
 		t.Errorf("unexpected matches: %v != %v", matches5, expected5)
 	}
 }
+
+func TestEcho(t *testing.T) {
+	if session == nil {
+		t.Skip()
+	}
+
+	require.NoError(t, session.Echo())
+}