UDS: Make all remote addr 0.0.0.0 (#4390)

https://github.com/XTLS/Xray-core/pull/4389#issuecomment-2656360673

---------

Co-authored-by: RPRX <63339210+RPRX@users.noreply.github.com>

app/proxyman/inbound/worker.go

@@ -2,7 +2,6 @@ package inbound
 
 import (
 	"context"
-	"strings"
 	"sync"
 	"sync/atomic"
 	"time"
@@ -464,19 +463,8 @@ func (w *dsWorker) callback(conn stat.Connection) {
 			WriteCounter: w.downlinkCounter,
 		}
 	}
-	// For most of time, unix obviously have no source addr. But if we leave it empty, it will cause panic.
-	// So we use gateway as source for log.
-	// However, there are some special situations where a valid source address might be available.
-	// Such as the source address parsed from X-Forwarded-For in websocket.
-	// In that case, we keep it.
-	var source net.Destination
-	if !strings.Contains(conn.RemoteAddr().String(), "unix") {
-		source = net.DestinationFromAddr(conn.RemoteAddr())
-	} else {
-		source = net.UnixDestination(w.address)
-	}
 	ctx = session.ContextWithInbound(ctx, &session.Inbound{
-		Source:  source,
+		Source:  net.DestinationFromAddr(conn.RemoteAddr()),
 		Gateway: net.UnixDestination(w.address),
 		Tag:     w.tag,
 		Conn:    conn,

common/net/destination.go

@@ -89,12 +89,10 @@ func UnixDestination(address Address) Destination {
 // NetAddr returns the network address in this Destination in string form.
 func (d Destination) NetAddr() string {
 	addr := ""
-	if d.Address != nil {
-		if d.Network == Network_TCP || d.Network == Network_UDP {
-			addr = d.Address.String() + ":" + d.Port.String()
-		} else if d.Network == Network_UNIX {
-			addr = d.Address.String()
-		}
+	if d.Network == Network_TCP || d.Network == Network_UDP {
+		addr = d.Address.String() + ":" + d.Port.String()
+	} else if d.Network == Network_UNIX {
+		addr = d.Address.String()
 	}
 	return addr
 }

transport/internet/system_listener.go

@@ -21,19 +21,6 @@ type DefaultListener struct {
 	controllers []control.Func
 }
 
-type combinedListener struct {
-	net.Listener
-	locker *FileLocker // for unix domain socket
-}
-
-func (cl *combinedListener) Close() error {
-	if cl.locker != nil {
-		cl.locker.Release()
-		cl.locker = nil
-	}
-	return cl.Listener.Close()
-}
-
 func getControlFunc(ctx context.Context, sockopt *SocketConfig, controllers []control.Func) func(network, address string, c syscall.RawConn) error {
 	return func(network, address string, c syscall.RawConn) error {
 		return c.Control(func(fd uintptr) {
@@ -54,6 +41,40 @@ func getControlFunc(ctx context.Context, sockopt *SocketConfig, controllers []co
 	}
 }
 
+// For some reason, other component of ray will assume the listener is a TCP listener and have valid remote address.
+// But in fact it doesn't. So we need to wrap the listener to make it return 0.0.0.0(unspecified) as remote address.
+// If other issues encountered, we should able to fix it here.
+type listenUDSWrapper struct {
+	net.Listener
+	locker *FileLocker
+}
+
+func (l *listenUDSWrapper) Accept() (net.Conn, error) {
+	conn, err := l.Listener.Accept()
+	if err != nil {
+		return nil, err
+	}
+	return &listenUDSWrapperConn{Conn: conn}, nil
+}
+
+func (l *listenUDSWrapper) Close() error {
+	if l.locker != nil {
+		l.locker.Release()
+		l.locker = nil
+	}
+	return l.Listener.Close()
+}
+
+type listenUDSWrapperConn struct {
+	net.Conn
+}
+
+func (conn *listenUDSWrapperConn) RemoteAddr() net.Addr {
+	return &net.TCPAddr{
+		IP: []byte{0, 0, 0, 0},
+	}
+}
+
 func (dl *DefaultListener) Listen(ctx context.Context, addr net.Addr, sockopt *SocketConfig) (l net.Listener, err error) {
 	var lc net.ListenConfig
 	var network, address string
@@ -113,9 +134,9 @@ func (dl *DefaultListener) Listen(ctx context.Context, addr net.Addr, sockopt *S
 			callback = func(l net.Listener, err error) (net.Listener, error) {
 				if err != nil {
 					locker.Release()
-					return l, err
+					return nil, err
 				}
-				l = &combinedListener{Listener: l, locker: locker}
+				l = &listenUDSWrapper{Listener: l, locker: locker}
 				if filePerm == nil {
 					return l, nil
 				}
@@ -129,9 +150,8 @@ func (dl *DefaultListener) Listen(ctx context.Context, addr net.Addr, sockopt *S
 		}
 	}
 
-	l, err = lc.Listen(ctx, network, address)
-	l, err = callback(l, err)
-	if sockopt != nil && sockopt.AcceptProxyProtocol {
+	l, err = callback(lc.Listen(ctx, network, address))
+	if err == nil && sockopt != nil && sockopt.AcceptProxyProtocol {
 		policyFunc := func(upstream net.Addr) (proxyproto.Policy, error) { return proxyproto.REQUIRE, nil }
 		l = &proxyproto.Listener{Listener: l, Policy: policyFunc}
 	}