From c325faef380e8643926cae0d1c343a00f86acfc5 Mon Sep 17 00:00:00 2001
From: RPRX <63339210+rprx@users.noreply.github.com>
Date: Wed, 21 Oct 2020 09:32:16 +0000
Subject: [PATCH] Adjust Trojan over XTLS

---
 proxy/trojan/client.go   | 11 ++++++-----
 proxy/trojan/protocol.go |  8 ++++----
 proxy/trojan/server.go   |  8 +++-----
 3 files changed, 13 insertions(+), 14 deletions(-)

diff --git a/proxy/trojan/client.go b/proxy/trojan/client.go
index 74b13f91a..1586aeaf1 100644
--- a/proxy/trojan/client.go
+++ b/proxy/trojan/client.go
@@ -100,26 +100,27 @@ func (c *Client) Process(ctx context.Context, link *transport.Link, dialer inter
 		if destination.Address.Family().IsDomain() && destination.Address.Domain() == muxCoolAddress {
 			return newError(account.Flow + " doesn't support Mux").AtWarning()
 		}
-
 		if destination.Network == net.Network_UDP {
 			if !allowUDP443 && destination.Port == 443 {
 				return newError(account.Flow + " stopped UDP/443").AtInfo()
 			}
 		} else { // enable XTLS only if making TCP request
 			if xtlsConn, ok := iConn.(*xtls.Conn); ok {
-				connWriter.Flow = account.Flow
 				xtlsConn.RPRX = true
-
+				connWriter.Flow = account.Flow
 				if account.Flow == XRD {
 					xtlsConn.DirectMode = true
 				}
 			} else {
-				return newError(`failed to enable XTLS, maybe "security" is not "xtls"`).AtWarning()
+				return newError(`failed to use ` + account.Flow + `, maybe "security" is not "xtls"`).AtWarning()
 			}
 		}
 	case "":
+		if _, ok := iConn.(*xtls.Conn); ok {
+			panic(`To avoid misunderstanding, you must fill in Trojan "flow" when using XTLS.`)
+		}
 	default:
-		return newError("unsupported flow type: ", account.Flow).AtWarning()
+		return newError("unsupported flow " + account.Flow).AtWarning()
 	}
 
 	sessionPolicy := c.policyManager.ForLevel(user.Level)
diff --git a/proxy/trojan/protocol.go b/proxy/trojan/protocol.go
index 9e7553593..5c271ae80 100644
--- a/proxy/trojan/protocol.go
+++ b/proxy/trojan/protocol.go
@@ -21,17 +21,17 @@ var (
 
 const (
 	maxLength = 8192
-	// XRO is constant for XTLS origin mode
-	XRO = "xtls-rprx-origin"
 	// XRD is constant for XTLS direct mode
 	XRD = "xtls-rprx-direct"
+	// XRO is constant for XTLS origin mode
+	XRO = "xtls-rprx-origin"
 
 	commandTCP byte = 1
 	commandUDP byte = 3
 
-	// for xtls
+	// for XTLS
+	commandXRD byte = 0xf0 // XTLS direct mode
 	commandXRO byte = 0xf1 // XTLS origin mode
-	commandXRD byte = 0xf2 // XTLS direct mode
 )
 
 // ConnWriter is TCP Connection Writer Wrapper for trojan protocol
diff --git a/proxy/trojan/server.go b/proxy/trojan/server.go
index 35fadaabe..d2f9d3db5 100644
--- a/proxy/trojan/server.go
+++ b/proxy/trojan/server.go
@@ -194,24 +194,22 @@ func (s *Server) Process(ctx context.Context, network net.Network, conn internet
 	case XRO, XRD:
 		if account.Flow == clientReader.Flow {
 			if destination.Address.Family().IsDomain() && destination.Address.Domain() == muxCoolAddress {
-				return newError("XTLS doesn't support Mux").AtWarning()
+				return newError(clientReader.Flow + " doesn't support Mux").AtWarning()
 			}
-
 			if xtlsConn, ok := iConn.(*xtls.Conn); ok {
 				xtlsConn.RPRX = true
-
 				if clientReader.Flow == XRD {
 					xtlsConn.DirectMode = true
 				}
 			} else {
-				return newError(`failed to enable XTLS, maybe "security" is not "xtls"`).AtWarning()
+				return newError(`failed to use ` + clientReader.Flow + `, maybe "security" is not "xtls"`).AtWarning()
 			}
 		} else {
 			return newError("unable to use ", clientReader.Flow).AtWarning()
 		}
 	case "":
 	default:
-		return newError("unsupported flow type: ", account.Flow).AtWarning()
+		return newError("unsupported flow " + account.Flow).AtWarning()
 	}
 
 	ctx = log.ContextWithAccessMessage(ctx, &log.AccessMessage{