Converted xsnet Read() ctrlStatOp logic to switch

xsnet/net.go

@@ -1195,6 +1195,7 @@ func (hc Conn) Read(b []byte) (n int, err error) {
 		var hmacIn [HMAC_CHK_SZ]uint8
 		var payloadLen uint32
 
+		//------------- Read ctrl/status opcode --------------------
 		// Read ctrl/status opcode (CSOHmacInvalid on hmac mismatch)
 		err = binary.Read(*hc.c, binary.BigEndian, &ctrlStatOp)
 		if err != nil {
@@ -1215,7 +1216,9 @@ func (hc Conn) Read(b []byte) (n int, err error) {
 			hc.Close()
 			return 0, errors.New("** ALERT - remote end detected HMAC mismatch - possible channel tampering **")
 		}
+		//----------------------------------------------------------
 
+		//------------------ Read HMAC len  ------------------------
 		// Read the hmac and payload len first
 		err = binary.Read(*hc.c, binary.BigEndian, &hmacIn)
 		if err != nil {
@@ -1230,7 +1233,9 @@ func (hc Conn) Read(b []byte) (n int, err error) {
 			logger.LogDebug(etxt)
 			return 0, errors.New(etxt)
 		}
+		//----------------------------------------------------------
 
+		//------------------ Read Payload len  ---------------------
 		err = binary.Read(*hc.c, binary.BigEndian, &payloadLen)
 		if err != nil {
 			if err.Error() == "EOF" {
@@ -1244,6 +1249,7 @@ func (hc Conn) Read(b []byte) (n int, err error) {
 			logger.LogDebug(etxt)
 			return 0, errors.New(etxt)
 		}
+		//----------------------------------------------------------
 
 		if payloadLen > MAX_PAYLOAD_LEN {
 			logger.LogDebug(fmt.Sprintf("[Insane payloadLen:%v]\n", payloadLen))
@@ -1251,6 +1257,7 @@ func (hc Conn) Read(b []byte) (n int, err error) {
 			return 1, errors.New("Insane payloadLen")
 		}
 
+		//-------------------- Read Payload ------------------------
 		var payloadBytes = make([]byte, payloadLen)
 		n, err = io.ReadFull(*hc.c, payloadBytes)
 		if err != nil {
@@ -1265,12 +1272,14 @@ func (hc Conn) Read(b []byte) (n int, err error) {
 			logger.LogDebug(etxt)
 			return 0, errors.New(etxt)
 		}
+		//----------------------------------------------------------
 
 		if hc.logCipherText {
 			log.Printf("  <:ctext:\r\n%s\r\n", hex.Dump(payloadBytes[:n]))
 		}
 		//fmt.Printf("  <:ctext:\r\n%s\r\n", hex.Dump(payloadBytes[:n]))
 
+		//---------------- Verify Payload via HMAC -----------------
 		hc.rm.Write(payloadBytes) // Calc hmac on received data
 		hTmp := hc.rm.Sum(nil)[0:HMAC_CHK_SZ]
 		//log.Printf("<%04x) HMAC:(i)%s (c)%02x\r\n", decryptN, hex.EncodeToString([]byte(hmacIn[0:])), hTmp)
@@ -1280,7 +1289,9 @@ func (hc Conn) Read(b []byte) (n int, err error) {
 			logger.LogDebug(fmt.Sprintln("** ALERT - detected HMAC mismatch, possible channel tampering **"))
 			_, _ = (*hc.c).Write([]byte{CSOHmacInvalid})
 		}
+		//----------------------------------------------------------
 
+		//------------------- Decrypt Payload ----------------------
 		db := bytes.NewBuffer(payloadBytes[:n]) //copying payloadBytes to db
 		// The StreamReader acts like a pipe, decrypting
 		// whatever is available and forwarding the result
@@ -1289,6 +1300,7 @@ func (hc Conn) Read(b []byte) (n int, err error) {
 		// The caller isn't necessarily reading the full payload so we need
 		// to decrypt to an intermediate buffer, draining it on demand of caller
 		decryptN, err := rs.Read(payloadBytes)
+		//----------------------------------------------------------
 
 		if hc.logPlainText {
 			log.Printf("  <:ptext:\r\n%s\r\n", hex.Dump(payloadBytes[:n]))
@@ -1297,6 +1309,7 @@ func (hc Conn) Read(b []byte) (n int, err error) {
 			log.Println("xsnet.Read():", err)
 			//panic(err)
 		} else {
+			//------------ Discard Padding ---------------------
 			// Padding: Read padSide, padLen, (padding | d) or (d | padding)
 			padSide := payloadBytes[0]
 			padLen := payloadBytes[1]
@@ -1307,15 +1320,17 @@ func (hc Conn) Read(b []byte) (n int, err error) {
 			} else {
 				payloadBytes = payloadBytes[0 : len(payloadBytes)-int(padLen)]
 			}
+			//--------------------------------------------------
 
+			switch ctrlStatOp {
+			case CSOChaff:
 				// Throw away pkt if it's chaff (ie., caller to Read() won't see this data)
-			if ctrlStatOp == CSOChaff {
 				log.Printf("[Chaff pkt, discarded (len %d)]\n", decryptN)
-			} else if ctrlStatOp == CSOTermSize {
+			case CSOTermSize:
 				fmt.Sscanf(string(payloadBytes), "%d %d", &hc.Rows, &hc.Cols)
 				log.Printf("[TermSize pkt: rows %v cols %v]\n", hc.Rows, hc.Cols)
 				hc.WinCh <- WinSize{hc.Rows, hc.Cols}
-			} else if ctrlStatOp == CSOExitStatus {
+			case CSOExitStatus:
 				if len(payloadBytes) > 0 {
 					hc.SetStatus(CSOType(binary.BigEndian.Uint32(payloadBytes)))
 				} else {
@@ -1323,7 +1338,7 @@ func (hc Conn) Read(b []byte) (n int, err error) {
 					hc.SetStatus(CSETruncCSO)
 				}
 				hc.Close()
-			} else if ctrlStatOp == CSOTunSetup {
+			case CSOTunSetup:
 				// server side tunnel setup in response to client
 				lport := binary.BigEndian.Uint16(payloadBytes[0:2])
 				rport := binary.BigEndian.Uint16(payloadBytes[2:4])
@@ -1335,7 +1350,7 @@ func (hc Conn) Read(b []byte) (n int, err error) {
 					logger.LogDebug(fmt.Sprintf("[Server] Got CSOTunSetup [%d:%d]", lport, rport))
 				}
 				(*hc.tuns)[rport].Ctl <- 'd' // Dial() rport
-			} else if ctrlStatOp == CSOTunSetupAck {
+			case CSOTunSetupAck:
 				lport := binary.BigEndian.Uint16(payloadBytes[0:2])
 				rport := binary.BigEndian.Uint16(payloadBytes[2:4])
 				if _, ok := (*hc.tuns)[rport]; !ok {
@@ -1346,7 +1361,7 @@ func (hc Conn) Read(b []byte) (n int, err error) {
 					logger.LogDebug(fmt.Sprintf("[Client] Got CSOTunSetupAck [%d:%d]", lport, rport))
 				}
 				(*hc.tuns)[rport].Ctl <- 'a' // Listen() for lport connection
-			} else if ctrlStatOp == CSOTunRefused {
+			case CSOTunRefused:
 				// client side receiving CSOTunRefused means the remote side
 				// could not dial() rport. So we cannot yet listen()
 				// for client-side on lport.
@@ -1358,7 +1373,7 @@ func (hc Conn) Read(b []byte) (n int, err error) {
 				} else {
 					logger.LogDebug(fmt.Sprintf("[Client] CSOTunRefused on already-closed tun [%d:%d]", lport, rport))
 				}
-			} else if ctrlStatOp == CSOTunDisconn {
+			case CSOTunDisconn:
 				// server side's rport has disconnected (server lost)
 				lport := binary.BigEndian.Uint16(payloadBytes[0:2])
 				rport := binary.BigEndian.Uint16(payloadBytes[2:4])
@@ -1368,7 +1383,7 @@ func (hc Conn) Read(b []byte) (n int, err error) {
 				} else {
 					logger.LogDebug(fmt.Sprintf("[Client] CSOTunDisconn on already-closed tun [%d:%d]", lport, rport))
 				}
-			} else if ctrlStatOp == CSOTunHangup {
+			case CSOTunHangup:
 				// client side's lport has hung up
 				lport := binary.BigEndian.Uint16(payloadBytes[0:2])
 				rport := binary.BigEndian.Uint16(payloadBytes[2:4])
@@ -1378,7 +1393,7 @@ func (hc Conn) Read(b []byte) (n int, err error) {
 				} else {
 					logger.LogDebug(fmt.Sprintf("[Server] CSOTunHangup to already-closed tun [%d:%d]", lport, rport))
 				}
-			} else if ctrlStatOp == CSOTunData {
+			case CSOTunData:
 				lport := binary.BigEndian.Uint16(payloadBytes[0:2])
 				rport := binary.BigEndian.Uint16(payloadBytes[2:4])
 				//fmt.Printf("[Got CSOTunData: [lport %d:rport %d] data:%v\n", lport, rport, payloadBytes[4:])
@@ -1391,7 +1406,7 @@ func (hc Conn) Read(b []byte) (n int, err error) {
 				} else {
 					logger.LogDebug(fmt.Sprintf("[Attempt to write data to closed tun [%d:%d]", lport, rport))
 				}
-			} else if ctrlStatOp == CSOTunKeepAlive {
+			case CSOTunKeepAlive:
 				// client side has sent keepalive for tunnels -- if client
 				// dies or exits unexpectedly the absence of this will
 				// let the server know to hang up on Dial()ed server rports.
@@ -1402,9 +1417,9 @@ func (hc Conn) Read(b []byte) (n int, err error) {
 					t.KeepAlive = 0
 					hc.Unlock()
 				}
-			} else if ctrlStatOp == CSONone {
+			case CSONone:
 				hc.dBuf.Write(payloadBytes)
-			} else {
+			default:
 				logger.LogDebug(fmt.Sprintf("[Unknown CSOType:%d]", ctrlStatOp))
 			}
 		}