Inbounds & Outbounds: TCP KeepAlive better default value (#4931)

From https://github.com/XTLS/Xray-core/pull/4927

transport/internet/sockopt_linux.go

@@ -64,26 +64,6 @@ func applyOutboundSocketOptions(network string, address string, fd uintptr, conf
 			}
 		}
 
-		if config.TcpKeepAliveInterval > 0 || config.TcpKeepAliveIdle > 0 {
-			if config.TcpKeepAliveInterval > 0 {
-				if err := syscall.SetsockoptInt(int(fd), syscall.IPPROTO_TCP, syscall.TCP_KEEPINTVL, int(config.TcpKeepAliveInterval)); err != nil {
-					return errors.New("failed to set TCP_KEEPINTVL", err)
-				}
-			}
-			if config.TcpKeepAliveIdle > 0 {
-				if err := syscall.SetsockoptInt(int(fd), syscall.IPPROTO_TCP, syscall.TCP_KEEPIDLE, int(config.TcpKeepAliveIdle)); err != nil {
-					return errors.New("failed to set TCP_KEEPIDLE", err)
-				}
-			}
-			if err := syscall.SetsockoptInt(int(fd), syscall.SOL_SOCKET, syscall.SO_KEEPALIVE, 1); err != nil {
-				return errors.New("failed to set SO_KEEPALIVE", err)
-			}
-		} else if config.TcpKeepAliveInterval < 0 || config.TcpKeepAliveIdle < 0 {
-			if err := syscall.SetsockoptInt(int(fd), syscall.SOL_SOCKET, syscall.SO_KEEPALIVE, 0); err != nil {
-				return errors.New("failed to unset SO_KEEPALIVE", err)
-			}
-		}
-
 		if config.TcpCongestion != "" {
 			if err := syscall.SetsockoptString(int(fd), syscall.SOL_TCP, syscall.TCP_CONGESTION, config.TcpCongestion); err != nil {
 				return errors.New("failed to set TCP_CONGESTION", err)

transport/internet/system_dialer.go

@@ -3,6 +3,7 @@ package internet
 import (
 	"context"
 	"math/rand"
+	gonet "net"
 	"syscall"
 	"time"
 
@@ -87,14 +88,34 @@ func (d *DefaultSystemDialer) Dial(ctx context.Context, src net.Address, dest ne
 			Dest: destAddr,
 		}, nil
 	}
-	goStdKeepAlive := time.Duration(0)
-	if sockopt != nil && (sockopt.TcpKeepAliveInterval != 0 || sockopt.TcpKeepAliveIdle != 0) {
-		goStdKeepAlive = time.Duration(-1)
+	// Chrome defaults
+	keepAliveConfig := gonet.KeepAliveConfig{
+		Enable:   true,
+		Idle:     45 * time.Second,
+		Interval: 45 * time.Second,
+		Count:    -1,
+	}
+	keepAlive := time.Duration(0)
+	if sockopt != nil {
+		if sockopt.TcpKeepAliveIdle*sockopt.TcpKeepAliveInterval < 0 {
+			return nil, errors.New("invalid TcpKeepAliveIdle or TcpKeepAliveInterval value: ", sockopt.TcpKeepAliveIdle, " ", sockopt.TcpKeepAliveInterval)
+		}
+		if sockopt.TcpKeepAliveIdle < 0 || sockopt.TcpKeepAliveInterval < 0 {
+			keepAlive = -1
+			keepAliveConfig.Enable = false
+		}
+		if sockopt.TcpKeepAliveIdle > 0 {
+			keepAliveConfig.Idle = time.Duration(sockopt.TcpKeepAliveIdle) * time.Second
+		}
+		if sockopt.TcpKeepAliveInterval > 0 {
+			keepAliveConfig.Interval = time.Duration(sockopt.TcpKeepAliveInterval) * time.Second
+		}
 	}
 	dialer := &net.Dialer{
-		Timeout:   time.Second * 16,
-		LocalAddr: resolveSrcAddr(dest.Network, src),
-		KeepAlive: goStdKeepAlive,
+		Timeout:         time.Second * 16,
+		LocalAddr:       resolveSrcAddr(dest.Network, src),
+		KeepAlive:       keepAlive,
+		KeepAliveConfig: keepAliveConfig,
 	}
 
 	if sockopt != nil || len(d.controllers) > 0 {

transport/internet/system_listener.go

@@ -2,6 +2,7 @@ package internet
 
 import (
 	"context"
+	gonet "net"
 	"os"
 	"runtime"
 	"strconv"
@@ -88,9 +89,25 @@ func (dl *DefaultListener) Listen(ctx context.Context, addr net.Addr, sockopt *S
 		network = addr.Network()
 		address = addr.String()
 		lc.Control = getControlFunc(ctx, sockopt, dl.controllers)
+		// default disable keepalive
+		lc.KeepAlive = -1
 		if sockopt != nil {
-			if sockopt.TcpKeepAliveInterval != 0 || sockopt.TcpKeepAliveIdle != 0 {
-				lc.KeepAlive = time.Duration(-1)
+			if sockopt.TcpKeepAliveIdle*sockopt.TcpKeepAliveInterval < 0 {
+				return nil, errors.New("invalid TcpKeepAliveIdle or TcpKeepAliveInterval value: ", sockopt.TcpKeepAliveIdle, " ", sockopt.TcpKeepAliveInterval)
+			}
+			lc.KeepAliveConfig = gonet.KeepAliveConfig{
+				Enable:   false,
+				Idle:     -1,
+				Interval: -1,
+				Count:    -1,
+			}
+			if sockopt.TcpKeepAliveIdle > 0 {
+				lc.KeepAliveConfig.Enable = true
+				lc.KeepAliveConfig.Idle = time.Duration(sockopt.TcpKeepAliveIdle) * time.Second
+			}
+			if sockopt.TcpKeepAliveInterval > 0 {
+				lc.KeepAliveConfig.Enable = true
+				lc.KeepAliveConfig.Interval = time.Duration(sockopt.TcpKeepAliveInterval) * time.Second
 			}
 			if sockopt.TcpMptcp {
 				lc.SetMultipathTCP(true)