Add support for kTLS

Reference: https://gitlab.com/go-extension/tls

common/tls/ktls.go

@@ -0,0 +1,67 @@
+package tls
+
+import (
+	"context"
+	"net"
+
+	"github.com/sagernet/sing-box/common/ktls"
+	E "github.com/sagernet/sing/common/exceptions"
+	"github.com/sagernet/sing/common/logger"
+	aTLS "github.com/sagernet/sing/common/tls"
+)
+
+type KTLSClientConfig struct {
+	Config
+	logger             logger.ContextLogger
+	kernelTx, kernelRx bool
+}
+
+func (w *KTLSClientConfig) ClientHandshake(ctx context.Context, conn net.Conn) (aTLS.Conn, error) {
+	tlsConn, err := aTLS.ClientHandshake(ctx, conn, w.Config)
+	if err != nil {
+		return nil, err
+	}
+	kConn, err := ktls.NewConn(ctx, w.logger, tlsConn, w.kernelTx, w.kernelRx)
+	if err != nil {
+		tlsConn.Close()
+		return nil, E.Cause(err, "initialize kernel TLS")
+	}
+	return kConn, nil
+}
+
+func (w *KTLSClientConfig) Clone() Config {
+	return &KTLSClientConfig{
+		w.Config.Clone(),
+		w.logger,
+		w.kernelTx,
+		w.kernelRx,
+	}
+}
+
+type KTlSServerConfig struct {
+	ServerConfig
+	logger             logger.ContextLogger
+	kernelTx, kernelRx bool
+}
+
+func (w *KTlSServerConfig) ServerHandshake(ctx context.Context, conn net.Conn) (aTLS.Conn, error) {
+	tlsConn, err := aTLS.ServerHandshake(ctx, conn, w.ServerConfig)
+	if err != nil {
+		return nil, err
+	}
+	kConn, err := ktls.NewConn(ctx, w.logger, tlsConn, w.kernelTx, w.kernelRx)
+	if err != nil {
+		tlsConn.Close()
+		return nil, E.Cause(err, "initialize kernel TLS")
+	}
+	return kConn, nil
+}
+
+func (w *KTlSServerConfig) Clone() Config {
+	return &KTlSServerConfig{
+		w.ServerConfig.Clone().(ServerConfig),
+		w.logger,
+		w.kernelTx,
+		w.kernelRx,
+	}
+}