add tproxy listen option

2 files changed, 63 insertions, 3 deletions

diff --git a/pkg/server/socket/listen.go b/pkg/server/socket/listen.go
index e640e16..94fb85c 100644
--- a/pkg/server/socket/listen.go
+++ b/pkg/server/socket/listen.go
@@ -14,10 +14,12 @@ type listenSocket struct {
 	proto, addr string
 	listen      net.Listener
 	redirect    bool
+	tproxy      bool
 }
 
 func newListenSocket(proto, addr string, opts opts.Opts) (S, error) {
 	redirect := opts.Bool("redirect")
+	tproxy := opts.Bool("tproxy")
 
 	if proto == "tcp" {
 		if !strings.Contains(addr, ":") {
@@ -29,16 +31,32 @@ func newListenSocket(proto, addr string, opts opts.Opts) (S, error) {
 		return nil, errors.New("redirect not supported")
 	}
 
+	if tproxy && proto != "tcp" {
+		return nil, errors.New("tproxy not supported")
+	}
+
+	if redirect && tproxy {
+		return nil, errors.New("redirect and tproxy cannot be used together")
+	}
+
 	listen, err := net.Listen(proto, addr)
 	if err != nil {
 		return nil, err
 	}
 
+	if tproxy {
+		if err := setConnTransparent(listen); err != nil {
+			listen.Close()
+			return nil, err
+		}
+	}
+
 	s := &listenSocket{
 		proto:    proto,
 		addr:     addr,
 		listen:   listen,
 		redirect: redirect,
+		tproxy:   tproxy,
 	}
 
 	return s, nil
@@ -66,6 +84,10 @@ func (s *listenSocket) Open(env env.Env) (Conn, error) {
 		}
 	}
 
+	if s.tproxy {
+		env.Set("original.addr", la.String())
+	}
+
 	if original == "" {
 		log.Println("accept", desc)
 	} else {
diff --git a/pkg/server/socket/sys.go b/pkg/server/socket/sys.go
index d09df12..70b59a6 100644
--- a/pkg/server/socket/sys.go
+++ b/pkg/server/socket/sys.go
@@ -47,16 +47,18 @@ func ioctl(fd int, req int, ptr unsafe.Pointer) error {
 	return nil
 }
 
-func getRawConn(conn net.Conn) (syscall.RawConn, error) {
+func getRawConn(conn interface{}) (syscall.RawConn, error) {
 	switch c := conn.(type) {
 	case *net.TCPConn:
 		return c.SyscallConn()
+	case *net.TCPListener:
+		return c.SyscallConn()
 	default:
 		return nil, errors.New("unknown connection type")
 	}
 }
 
-func withConnControl(conn net.Conn, f func(fd int) error) (err error) {
+func withConnControl(conn interface{}, f func(fd int) error) (err error) {
 	var c syscall.RawConn
 	var ferr error
 
@@ -75,12 +77,16 @@ func withConnControl(conn net.Conn, f func(fd int) error) (err error) {
 	return
 }
 
+func getSocketDomain(fd int) (int, error) {
+	return unix.GetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_DOMAIN)
+}
+
 func getSocketOriginalDst(fd int, sa *unix.RawSockaddrAny) error {
 	const SO_ORIGINAL_DST = 80
 
 	p, n := unsafe.Pointer(sa), int(unsafe.Sizeof(*sa))
 
-	family, err := unix.GetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_DOMAIN)
+	family, err := getSocketDomain(fd)
 	if err != nil {
 		return err
 	}
@@ -129,3 +135,35 @@ func getConnOriginalAddr(conn net.Conn, addr *string) error {
 
 	return nil
 }
+
+func setSocketTransparent(fd int) error {
+	family, err := getSocketDomain(fd)
+	if err != nil {
+		return err
+	}
+
+	var level, opt int
+
+	switch family {
+	case unix.AF_INET6:
+		level, opt = unix.SOL_IPV6, unix.IPV6_TRANSPARENT
+	case unix.AF_INET:
+		level, opt = unix.SOL_IP, unix.IP_TRANSPARENT
+	default:
+		return errors.New("unknown address family")
+	}
+
+	return unix.SetsockoptInt(fd, level, opt, 1)
+}
+
+func setConnTransparent(conn interface{}) error {
+	f := func(fd int) error {
+		   return setSocketTransparent(fd)
+	}
+
+	if err := withConnControl(conn, f); err != nil {
+		return fmt.Errorf("set-transparent: %w", err)
+	}
+
+	return nil
+}