Add auto-redirect

redirect_server.go

@@ -0,0 +1,88 @@
+//go:build linux
+
+package tun
+
+import (
+	"context"
+	"errors"
+	"net"
+	"net/netip"
+	"time"
+
+	"github.com/sagernet/sing/common/atomic"
+	"github.com/sagernet/sing/common/control"
+	E "github.com/sagernet/sing/common/exceptions"
+	"github.com/sagernet/sing/common/logger"
+	M "github.com/sagernet/sing/common/metadata"
+)
+
+const ProtocolRedirect = "redirect"
+
+type redirectServer struct {
+	ctx        context.Context
+	handler    Handler
+	logger     logger.Logger
+	listenAddr netip.Addr
+	listener   *net.TCPListener
+	inShutdown atomic.Bool
+}
+
+func newRedirectServer(ctx context.Context, handler Handler, logger logger.Logger, listenAddr netip.Addr) *redirectServer {
+	return &redirectServer{
+		ctx:        ctx,
+		handler:    handler,
+		logger:     logger,
+		listenAddr: listenAddr,
+	}
+}
+
+func (s *redirectServer) Start() error {
+	var listenConfig net.ListenConfig
+	// listenConfig.KeepAlive = C.TCPKeepAliveInitial
+	listenConfig.KeepAlive = 10 * time.Minute
+	listener, err := listenConfig.Listen(s.ctx, M.NetworkFromNetAddr("tcp", s.listenAddr), M.SocksaddrFrom(s.listenAddr, 0).String())
+	if err != nil {
+		return err
+	}
+	s.listener = listener.(*net.TCPListener)
+	go s.loopIn()
+	return nil
+}
+
+func (s *redirectServer) Close() error {
+	s.inShutdown.Store(true)
+	return s.listener.Close()
+}
+
+func (s *redirectServer) loopIn() {
+	for {
+		conn, err := s.listener.AcceptTCP()
+		if err != nil {
+			var netError net.Error
+			//goland:noinspection GoDeprecation
+			//nolint:staticcheck
+			if errors.As(err, &netError) && netError.Temporary() {
+				s.logger.Error(err)
+				continue
+			}
+			if s.inShutdown.Load() && E.IsClosed(err) {
+				return
+			}
+			s.listener.Close()
+			s.logger.Error("serve error: ", err)
+			continue
+		}
+		var metadata M.Metadata
+		metadata.Protocol = ProtocolRedirect
+		metadata.Source = M.SocksaddrFromNet(conn.RemoteAddr())
+		destination, err := control.GetOriginalDestination(conn)
+		if err != nil {
+			_ = conn.SetLinger(0)
+			_ = conn.Close()
+			s.logger.Error("process connection from ", metadata.Source, ": invalid connection: ", err)
+			continue
+		}
+		metadata.Destination = M.SocksaddrFromNetIP(destination)
+		go s.handler.NewConnection(s.ctx, conn, metadata)
+	}
+}