From 0f368f8139019d44ea69a3df5dc829afa35d42d4 Mon Sep 17 00:00:00 2001
From: Shelikhoo <xiaokangwang@outlook.com>
Date: Mon, 13 Jun 2016 15:03:58 +0800
Subject: [PATCH] KCP: comments

---
 transport/config.go          |  7 ++++++
 transport/hub/kcp.go         | 14 +++++++++++
 transport/hub/kcpv/config.go | 45 +++++++++++++++++++++++++++++++++++-
 3 files changed, 65 insertions(+), 1 deletion(-)

diff --git a/transport/config.go b/transport/config.go
index 18205c1c8..7ea9beccf 100644
--- a/transport/config.go
+++ b/transport/config.go
@@ -17,6 +17,13 @@ func (this *Config) Apply() error {
 	enableKcp = this.enableKcp
 	if enableKcp {
 		KcpConfig = this.kcpConfig
+		/*
+			KCP do not support connectionReuse,
+			it is mandatory to set connectionReuse to false
+			Since KCP have no handshake and
+			does not SlowStart, there isn't benefit to
+			use that anyway.
+		*/
 		connectionReuse = false
 	}
 	return nil
diff --git a/transport/hub/kcp.go b/transport/hub/kcp.go
index 63c67001f..d50c00c48 100644
--- a/transport/hub/kcp.go
+++ b/transport/hub/kcp.go
@@ -48,6 +48,11 @@ func (kvl *KCPVlistener) Accept() (net.Conn, error) {
 	} else {
 		kvl.previousSocketid_mapid++
 		kvl.previousSocketid[kvl.previousSocketid_mapid] = conn.GetConv()
+		/*
+			Here we assume that count(connection) < 512
+			This won't always true.
+			More work might be necessary to deal with this in a better way.
+		*/
 		if kvl.previousSocketid_mapid >= 512 {
 			delete(kvl.previousSocketid, kvl.previousSocketid_mapid-512)
 		}
@@ -93,6 +98,11 @@ func (kcpvc *KCPVconn) Write(b []byte) (int, error) {
 	kcpvc.hc.SetDeadline(kcpvc.conntokeep)
 	return kcpvc.hc.Write(b)
 }
+
+/*ApplyConf will apply kcpvc.conf to current Socket
+
+It is recommmanded to call this func once and only once
+*/
 func (kcpvc *KCPVconn) ApplyConf() error {
 	nodelay, interval, resend, nc := 0, 40, 0, 0
 	if kcpvc.conf.Mode != "manual" {
@@ -121,6 +131,10 @@ func (kcpvc *KCPVconn) ApplyConf() error {
 	return nil
 }
 
+/*Close Close the current conn
+We have to delay the close of Socket for a few second
+or the VMess EOF can be too late to send.
+*/
 func (kcpvc *KCPVconn) Close() error {
 	go func() {
 		time.Sleep(2000 * time.Millisecond)
diff --git a/transport/hub/kcpv/config.go b/transport/hub/kcpv/config.go
index 348b31de5..9b162d308 100644
--- a/transport/hub/kcpv/config.go
+++ b/transport/hub/kcpv/config.go
@@ -1,5 +1,34 @@
 package kcpv
 
+/*AdvancedConfig define behavior of KCP in detail
+
+MaximumTransmissionUnit:
+Largest protocol data unit that the layer can pass onwards
+can be discovered by running tracepath
+
+SendingWindowSize , ReceivingWindowSize:
+the size of Tx/Rx window, by packet
+
+ForwardErrorCorrectionGroupSize:
+The the size of packet to generate a Forward Error Correction
+packet, this is used to counteract packet loss.
+
+AcknowledgeNoDelay:
+Do not wait a certain of time before sending the ACK packet,
+increase bandwich cost and might increase performance
+
+Dscp:
+Differentiated services code point,
+be used to reconized to discriminate packet.
+It is recommanded to keep it 0 to avoid being detected.
+
+ReadTimeout,WriteTimeout:
+Close the Socket if it have been silent for too long,
+Small value can recycle zombie socket faster but
+can cause v2ray to kill the proxy connection it is relaying,
+Higher value can prevent server from closing zombie socket and
+waste resources.
+*/
 type AdvancedConfig struct {
 	Mtu          int  `json:"MaximumTransmissionUnit"`
 	Sndwnd       int  `json:"SendingWindowSize"`
@@ -11,6 +40,20 @@ type AdvancedConfig struct {
 	WriteTimeout int  `json:"WriteTimeout"`
 }
 
+/*Config define basic behavior of KCP
+Mode:
+can be one of these values:
+fast3,fast2,fast,normal
+<<<<<<- less delay
+->>>>>> less bandwich wasted
+
+EncryptionKey:
+a string that will be the EncryptionKey of
+All KCP connection we Listen-Accpet or
+Dial, We are not very sure about how this
+encryption hehave and DO use a unique randomly
+generated key.
+*/
 type Config struct {
 	Mode            string          `json:"Mode"`
 	Key             string          `json:"EncryptionKey"`
@@ -18,5 +61,5 @@ type Config struct {
 }
 
 var DefaultAdvancedConfigs = &AdvancedConfig{
-	Mtu: 1350, Sndwnd: 1024, Rcvwnd: 1024, Fec: 4, Dscp: 0, ReadTimeout: 18600, WriteTimeout: 18500, Acknodelay: false,
+	Mtu: 1350, Sndwnd: 1024, Rcvwnd: 1024, Fec: 4, Dscp: 0, ReadTimeout: 600, WriteTimeout: 500, Acknodelay: false,
 }