From 29407c90b66605360df8698979eb90640671bf23 Mon Sep 17 00:00:00 2001
From: sagitchu <sagitchu@gmail.com>
Date: Tue, 21 Apr 2026 11:33:41 +0800
Subject: [PATCH] perf(kcp): optimize tunnel transport defaults for high
 throughput

- Set KCP mode to fast3 (NoDelay:1, Interval:10ms) for lower latency
- Double SndWnd/RcvWnd from 1024 to 2048 for higher BDP
- Disable FEC (datashard:0, parityshard:0) to eliminate 30% overhead
- Disable compression for tunnel transport
- Increase relay mux MaxStreamBuffer to 2MB for better UDP throughput
- Add kcp.datashard/kcp.parityshard metadata keys support

Before: 210Mbps TCP / 35Mbps UDP (93% loss)
After:  should approach direct-connection speed (~400Mbps+)
---
 go-backend/internal/http/handler/mutations.go | 34 ++++++++++++++++---
 go-gost/x/dialer/kcp/metadata.go              |  6 ++++
 go-gost/x/listener/kcp/metadata.go            |  6 ++++
 3 files changed, 42 insertions(+), 4 deletions(-)

diff --git a/go-backend/internal/http/handler/mutations.go b/go-backend/internal/http/handler/mutations.go
index 42fb10c..fc98f98 100644
--- a/go-backend/internal/http/handler/mutations.go
+++ b/go-backend/internal/http/handler/mutations.go
@@ -3457,9 +3457,15 @@ func buildTunnelChainConfig(tunnelID int64, fromNodeID int64, targets []tunnelRu
 			connectorMetadata["nodelay"] = true
 			connectorMetadata["mux.keepaliveInterval"] = "15s"
 			connectorMetadata["mux.keepaliveTimeout"] = "45s"
+			connectorMetadata["mux.maxFrameSize"] = 32768
+			connectorMetadata["mux.maxStreamBuffer"] = 2097152
 		}
 		if isKCPTunnelProtocol(protocol) {
 			connectorMetadata["connectTimeout"] = "30s"
+			connectorMetadata["mux.keepaliveInterval"] = "15s"
+			connectorMetadata["mux.keepaliveTimeout"] = "45s"
+			connectorMetadata["mux.maxFrameSize"] = 32768
+			connectorMetadata["mux.maxStreamBuffer"] = 2097152
 		}
 		if len(connectorMetadata) > 0 {
 			connector["metadata"] = connectorMetadata
@@ -3505,9 +3511,15 @@ func buildTunnelChainServiceConfig(tunnelID int64, chainNode tunnelRuntimeNode,
 		handlerMetadata["nodelay"] = true
 		handlerMetadata["mux.keepaliveInterval"] = "15s"
 		handlerMetadata["mux.keepaliveTimeout"] = "45s"
+		handlerMetadata["mux.maxFrameSize"] = 32768
+		handlerMetadata["mux.maxStreamBuffer"] = 2097152
 	}
 	if isKCPTunnelProtocol(protocol) {
 		handlerMetadata["connectTimeout"] = "30s"
+		handlerMetadata["mux.keepaliveInterval"] = "15s"
+		handlerMetadata["mux.keepaliveTimeout"] = "45s"
+		handlerMetadata["mux.maxFrameSize"] = 32768
+		handlerMetadata["mux.maxStreamBuffer"] = 2097152
 	}
 	if len(handlerMetadata) > 0 {
 		handlerCfg["metadata"] = handlerMetadata
@@ -3621,8 +3633,15 @@ func buildTunnelDialerConfig(protocol string) map[string]interface{} {
 	}
 	if isKCPTunnelProtocol(protocol) {
 		dialer["metadata"] = map[string]interface{}{
-			"kcp.keepalive": 10,
-			"kcp.tcp":       false,
+			"kcp.keepalive":   10,
+			"kcp.tcp":         false,
+			"kcp.mode":        "fast3",
+			"kcp.sndwnd":      2048,
+			"kcp.rcvwnd":      2048,
+			"kcp.mtu":         1400,
+			"kcp.datashard":   0,
+			"kcp.parityshard": 0,
+			"kcp.nocomp":      true,
 		}
 	}
 	return dialer
@@ -3634,8 +3653,15 @@ func buildTunnelListenerConfig(protocol string) map[string]interface{} {
 	}
 	if isKCPTunnelProtocol(protocol) {
 		listener["metadata"] = map[string]interface{}{
-			"kcp.keepalive": 10,
-			"kcp.tcp":       false,
+			"kcp.keepalive":   10,
+			"kcp.tcp":         false,
+			"kcp.mode":        "fast3",
+			"kcp.sndwnd":      2048,
+			"kcp.rcvwnd":      2048,
+			"kcp.mtu":         1400,
+			"kcp.datashard":   0,
+			"kcp.parityshard": 0,
+			"kcp.nocomp":      true,
 		}
 	}
 	return listener
diff --git a/go-gost/x/dialer/kcp/metadata.go b/go-gost/x/dialer/kcp/metadata.go
index c544eda..b587727 100644
--- a/go-gost/x/dialer/kcp/metadata.go
+++ b/go-gost/x/dialer/kcp/metadata.go
@@ -85,6 +85,12 @@ func (d *kcpDialer) parseMetadata(md mdata.Metadata) (err error) {
 		if md.IsExists("kcp.nocomp") {
 			d.md.config.NoComp = mdutil.GetBool(md, "kcp.nocomp")
 		}
+		if md.IsExists("kcp.datashard") {
+			d.md.config.DataShard = mdutil.GetInt(md, "kcp.datashard")
+		}
+		if md.IsExists("kcp.parityshard") {
+			d.md.config.ParityShard = mdutil.GetInt(md, "kcp.parityshard")
+		}
 	}
 
 	d.md.handshakeTimeout = mdutil.GetDuration(md, handshakeTimeout)
diff --git a/go-gost/x/listener/kcp/metadata.go b/go-gost/x/listener/kcp/metadata.go
index 5b7ce9b..7c091e5 100644
--- a/go-gost/x/listener/kcp/metadata.go
+++ b/go-gost/x/listener/kcp/metadata.go
@@ -88,6 +88,12 @@ func (l *kcpListener) parseMetadata(md mdata.Metadata) (err error) {
 		if md.IsExists("kcp.nocomp") {
 			l.md.config.NoComp = mdutil.GetBool(md, "kcp.nocomp")
 		}
+		if md.IsExists("kcp.datashard") {
+			l.md.config.DataShard = mdutil.GetInt(md, "kcp.datashard")
+		}
+		if md.IsExists("kcp.parityshard") {
+			l.md.config.ParityShard = mdutil.GetInt(md, "kcp.parityshard")
+		}
 	}
 
 	l.md.backlog = mdutil.GetInt(md, backlog)