chore: add loopback detect for direct outbound

adapter/outbound/direct.go

@@ -3,6 +3,7 @@ package outbound
 import (
 	"context"
 	"errors"
+	"fmt"
 	"net/netip"
 
 	N "github.com/metacubex/mihomo/common/net"
@@ -13,6 +14,7 @@ import (
 
 type Direct struct {
 	*Base
+	loopBack *loopBackDetector
 }
 
 type DirectOption struct {
@@ -22,17 +24,23 @@ type DirectOption struct {
 
 // DialContext implements C.ProxyAdapter
 func (d *Direct) DialContext(ctx context.Context, metadata *C.Metadata, opts ...dialer.Option) (C.Conn, error) {
+	if d.loopBack.CheckConn(metadata.SourceAddrPort()) {
+		return nil, fmt.Errorf("reject loopback connection to: %s", metadata.RemoteAddress())
+	}
 	opts = append(opts, dialer.WithResolver(resolver.DefaultResolver))
 	c, err := dialer.DialContext(ctx, "tcp", metadata.RemoteAddress(), d.Base.DialOptions(opts...)...)
 	if err != nil {
 		return nil, err
 	}
 	N.TCPKeepAlive(c)
-	return NewConn(c, d), nil
+	return d.loopBack.NewConn(NewConn(c, d)), nil
 }
 
 // ListenPacketContext implements C.ProxyAdapter
 func (d *Direct) ListenPacketContext(ctx context.Context, metadata *C.Metadata, opts ...dialer.Option) (C.PacketConn, error) {
+	if d.loopBack.CheckPacketConn(metadata.SourceAddrPort()) {
+		return nil, fmt.Errorf("reject loopback connection to: %s", metadata.RemoteAddress())
+	}
 	// net.UDPConn.WriteTo only working with *net.UDPAddr, so we need a net.UDPAddr
 	if !metadata.Resolved() {
 		ip, err := resolver.ResolveIPWithResolver(ctx, metadata.Host, resolver.DefaultResolver)
@@ -45,7 +53,7 @@ func (d *Direct) ListenPacketContext(ctx context.Context, metadata *C.Metadata,
 	if err != nil {
 		return nil, err
 	}
-	return newPacketConn(pc, d), nil
+	return d.loopBack.NewPacketConn(newPacketConn(pc, d)), nil
 }
 
 func NewDirectWithOption(option DirectOption) *Direct {
@@ -60,6 +68,7 @@ func NewDirectWithOption(option DirectOption) *Direct {
 			rmark:  option.RoutingMark,
 			prefer: C.NewDNSPrefer(option.IPVersion),
 		},
+		loopBack: newLoopBackDetector(),
 	}
 }
 
@@ -71,6 +80,7 @@ func NewDirect() *Direct {
 			udp:    true,
 			prefer: C.DualStack,
 		},
+		loopBack: newLoopBackDetector(),
 	}
 }
 
@@ -82,5 +92,6 @@ func NewCompatible() *Direct {
 			udp:    true,
 			prefer: C.DualStack,
 		},
+		loopBack: newLoopBackDetector(),
 	}
 }

adapter/outbound/direct_loopback_detect.go

@@ -0,0 +1,68 @@
+package outbound
+
+import (
+	"net/netip"
+
+	"github.com/metacubex/mihomo/common/callback"
+	C "github.com/metacubex/mihomo/constant"
+
+	"github.com/puzpuzpuz/xsync/v3"
+)
+
+type loopBackDetector struct {
+	connMap       *xsync.MapOf[netip.AddrPort, struct{}]
+	packetConnMap *xsync.MapOf[netip.AddrPort, struct{}]
+}
+
+func newLoopBackDetector() *loopBackDetector {
+	return &loopBackDetector{
+		connMap:       xsync.NewMapOf[netip.AddrPort, struct{}](),
+		packetConnMap: xsync.NewMapOf[netip.AddrPort, struct{}](),
+	}
+}
+
+func (l *loopBackDetector) NewConn(conn C.Conn) C.Conn {
+	metadata := C.Metadata{}
+	if metadata.SetRemoteAddr(conn.LocalAddr()) != nil {
+		return conn
+	}
+	connAddr := metadata.AddrPort()
+	if !connAddr.IsValid() {
+		return conn
+	}
+	l.connMap.Store(connAddr, struct{}{})
+	return callback.NewCloseCallbackConn(conn, func() {
+		l.connMap.Delete(connAddr)
+	})
+}
+
+func (l *loopBackDetector) NewPacketConn(conn C.PacketConn) C.PacketConn {
+	metadata := C.Metadata{}
+	if metadata.SetRemoteAddr(conn.LocalAddr()) != nil {
+		return conn
+	}
+	connAddr := metadata.AddrPort()
+	if !connAddr.IsValid() {
+		return conn
+	}
+	l.packetConnMap.Store(connAddr, struct{}{})
+	return callback.NewCloseCallbackPacketConn(conn, func() {
+		l.packetConnMap.Delete(connAddr)
+	})
+}
+
+func (l *loopBackDetector) CheckConn(connAddr netip.AddrPort) bool {
+	if !connAddr.IsValid() {
+		return false
+	}
+	_, ok := l.connMap.Load(connAddr)
+	return ok
+}
+
+func (l *loopBackDetector) CheckPacketConn(connAddr netip.AddrPort) bool {
+	if !connAddr.IsValid() {
+		return false
+	}
+	_, ok := l.packetConnMap.Load(connAddr)
+	return ok
+}