fix: wasi fd subject to garbage collection on unix

commit 81e41c5
Author: Edoardo Vacchi <[email protected]>
Date:   Thu Dec 28 11:07:28 2023 +0100

    wasi: sockets, share most logic across Windows and Unix

    Signed-off-by: Edoardo Vacchi <[email protected]>

commit 4f9f569
Author: Edoardo Vacchi <[email protected]>
Date:   Thu Dec 28 10:10:06 2023 +0100

    wasi: sockets, use the same strategy for impl as Windows

    Signed-off-by: Edoardo Vacchi <[email protected]>

internal/sysfs/file_windows.go

@@ -46,10 +46,10 @@ func writeFd(fd uintptr, buf []byte) (int, sys.Errno) {
 	return -1, sys.ENOSYS
 }
 
-func readSocket(h syscall.Handle, buf []byte) (int, sys.Errno) {
+func readSocket(h uintptr, buf []byte) (int, sys.Errno) {
 	var overlapped syscall.Overlapped
 	var done uint32
-	errno := syscall.ReadFile(h, buf, &done, &overlapped)
+	errno := syscall.ReadFile(syscall.Handle(h), buf, &done, &overlapped)
 	if errno == syscall.ERROR_IO_PENDING {
 		errno = sys.EAGAIN
 	}

internal/sysfs/sock.go

@@ -5,6 +5,7 @@ import (
 	"os"
 
 	experimentalsys "github.com/tetratelabs/wazero/experimental/sys"
+	"github.com/tetratelabs/wazero/internal/fsapi"
 	socketapi "github.com/tetratelabs/wazero/internal/sock"
 	"github.com/tetratelabs/wazero/sys"
 )
@@ -35,3 +36,197 @@ func (f *baseSockFile) Stat() (fs sys.Stat_t, errno experimentalsys.Errno) {
 	fs.Mode = os.ModeIrregular
 	return
 }
+
+var _ socketapi.TCPSock = (*tcpListenerFile)(nil)
+
+type tcpListenerFile struct {
+	baseSockFile
+
+	tl       *net.TCPListener
+	closed   bool
+	nonblock bool
+}
+
+// newTCPListenerFile is a constructor for a socketapi.TCPSock.
+//
+// The current strategy is to wrap a net.TCPListener
+// and invoking raw syscalls using syscallConnControl:
+// this internal calls RawConn.Control(func(fd)), making sure
+// that the underlying file descriptor is valid throughout
+// the duration of the syscall.
+func newDefaultTCPListenerFile(tl *net.TCPListener) socketapi.TCPSock {
+	return &tcpListenerFile{tl: tl}
+}
+
+// Accept implements the same method as documented on socketapi.TCPSock
+func (f *tcpListenerFile) Accept() (socketapi.TCPConn, experimentalsys.Errno) {
+	// Ensure we have an incoming connection, otherwise return immediately.
+	if f.nonblock {
+		if ready, errno := _pollSock(f.tl, fsapi.POLLIN, 0); !ready || errno != 0 {
+			return nil, experimentalsys.EAGAIN
+		}
+	}
+
+	// Accept normally blocks goroutines, but we
+	// made sure that we have an incoming connection,
+	// so we should be safe.
+	if conn, err := f.tl.Accept(); err != nil {
+		return nil, experimentalsys.UnwrapOSError(err)
+	} else {
+		return newTcpConn(conn.(*net.TCPConn)), 0
+	}
+}
+
+// Close implements the same method as documented on experimentalsys.File
+func (f *tcpListenerFile) Close() experimentalsys.Errno {
+	if !f.closed {
+		return experimentalsys.UnwrapOSError(f.tl.Close())
+	}
+	return 0
+}
+
+// Addr is exposed for testing.
+func (f *tcpListenerFile) Addr() *net.TCPAddr {
+	return f.tl.Addr().(*net.TCPAddr)
+}
+
+// SetNonblock implements the same method as documented on fsapi.File
+func (f *tcpListenerFile) SetNonblock(enabled bool) (errno experimentalsys.Errno) {
+	f.nonblock = enabled
+	_, errno = syscallConnControl(f.tl, func(fd uintptr) (int, experimentalsys.Errno) {
+		return 0, setNonblockSocket(fd, enabled)
+	})
+	return
+}
+
+// IsNonblock implements the same method as documented on fsapi.File
+func (f *tcpListenerFile) IsNonblock() bool {
+	return f.nonblock
+}
+
+// Poll implements the same method as documented on fsapi.File
+func (f *tcpListenerFile) Poll(flag fsapi.Pflag, timeoutMillis int32) (ready bool, errno experimentalsys.Errno) {
+	return false, experimentalsys.ENOSYS
+}
+
+var _ socketapi.TCPConn = (*tcpConnFile)(nil)
+
+type tcpConnFile struct {
+	baseSockFile
+
+	tc *net.TCPConn
+
+	// nonblock is true when the underlying connection is flagged as non-blocking.
+	// This ensures that reads and writes return experimentalsys.EAGAIN without blocking the caller.
+	nonblock bool
+	// closed is true when closed was called. This ensures proper experimentalsys.EBADF
+	closed bool
+}
+
+func newTcpConn(tc *net.TCPConn) socketapi.TCPConn {
+	return &tcpConnFile{tc: tc}
+}
+
+// Read implements the same method as documented on experimentalsys.File
+func (f *tcpConnFile) Read(buf []byte) (n int, errno experimentalsys.Errno) {
+	if len(buf) == 0 {
+		return 0, 0 // Short-circuit 0-len reads.
+	}
+	if nonBlockingFileReadSupported && f.IsNonblock() {
+		n, errno = syscallConnControl(f.tc, func(fd uintptr) (int, experimentalsys.Errno) {
+			n, err := readSocket(fd, buf)
+			errno = experimentalsys.UnwrapOSError(err)
+			errno = fileError(f, f.closed, errno)
+			return n, errno
+		})
+	} else {
+		n, errno = read(f.tc, buf)
+	}
+	if errno != 0 {
+		// Defer validation overhead until we've already had an error.
+		errno = fileError(f, f.closed, errno)
+	}
+	return
+}
+
+// Write implements the same method as documented on experimentalsys.File
+func (f *tcpConnFile) Write(buf []byte) (n int, errno experimentalsys.Errno) {
+	if nonBlockingFileWriteSupported && f.IsNonblock() {
+		return syscallConnControl(f.tc, func(fd uintptr) (int, experimentalsys.Errno) {
+			n, err := writeSocket(fd, buf)
+			errno = experimentalsys.UnwrapOSError(err)
+			errno = fileError(f, f.closed, errno)
+			return n, errno
+		})
+	} else {
+		n, errno = write(f.tc, buf)
+	}
+	if errno != 0 {
+		// Defer validation overhead until we've already had an error.
+		errno = fileError(f, f.closed, errno)
+	}
+	return
+}
+
+// Recvfrom implements the same method as documented on socketapi.TCPConn
+func (f *tcpConnFile) Recvfrom(p []byte, flags int) (n int, errno experimentalsys.Errno) {
+	if flags != MSG_PEEK {
+		errno = experimentalsys.EINVAL
+		return
+	}
+	return syscallConnControl(f.tc, func(fd uintptr) (int, experimentalsys.Errno) {
+		n, err := recvfrom(fd, p, MSG_PEEK)
+		errno = experimentalsys.UnwrapOSError(err)
+		errno = fileError(f, f.closed, errno)
+		return n, errno
+	})
+}
+
+// Shutdown implements the same method as documented on experimentalsys.Conn
+func (f *tcpConnFile) Shutdown(how int) experimentalsys.Errno {
+	// FIXME: can userland shutdown listeners?
+	var err error
+	switch how {
+	case socketapi.SHUT_RD:
+		err = f.tc.CloseRead()
+	case socketapi.SHUT_WR:
+		err = f.tc.CloseWrite()
+	case socketapi.SHUT_RDWR:
+		return f.close()
+	default:
+		return experimentalsys.EINVAL
+	}
+	return experimentalsys.UnwrapOSError(err)
+}
+
+// Close implements the same method as documented on experimentalsys.File
+func (f *tcpConnFile) Close() experimentalsys.Errno {
+	return f.close()
+}
+
+func (f *tcpConnFile) close() experimentalsys.Errno {
+	if f.closed {
+		return 0
+	}
+	f.closed = true
+	return f.Shutdown(socketapi.SHUT_RDWR)
+}
+
+// SetNonblock implements the same method as documented on fsapi.File
+func (f *tcpConnFile) SetNonblock(enabled bool) (errno experimentalsys.Errno) {
+	f.nonblock = enabled
+	_, errno = syscallConnControl(f.tc, func(fd uintptr) (int, experimentalsys.Errno) {
+		return 0, experimentalsys.UnwrapOSError(setNonblockSocket(fd, enabled))
+	})
+	return
+}
+
+// IsNonblock implements the same method as documented on fsapi.File
+func (f *tcpConnFile) IsNonblock() bool {
+	return f.nonblock
+}
+
+// Poll implements the same method as documented on fsapi.File
+func (f *tcpConnFile) Poll(flag fsapi.Pflag, timeoutMillis int32) (ready bool, errno experimentalsys.Errno) {
+	return false, experimentalsys.ENOSYS
+}

internal/sysfs/sock_supported.go

@@ -0,0 +1,29 @@
+//go:build linux || darwin || windows
+
+package sysfs
+
+import (
+	"syscall"
+
+	experimentalsys "github.com/tetratelabs/wazero/experimental/sys"
+)
+
+// syscallConnControl extracts a syscall.RawConn from the given syscall.Conn and applies
+// the given fn to a file descriptor, returning an integer or a nonzero syscall.Errno on failure.
+//
+// syscallConnControl streamlines the pattern of extracting the syscall.Rawconn,
+// invoking its syscall.RawConn.Control method, then handling properly the errors that may occur
+// within fn or returned by syscall.RawConn.Control itself.
+func syscallConnControl(conn syscall.Conn, fn func(fd uintptr) (int, experimentalsys.Errno)) (n int, errno experimentalsys.Errno) {
+	syscallConn, err := conn.SyscallConn()
+	if err != nil {
+		return 0, experimentalsys.UnwrapOSError(err)
+	}
+	// Prioritize the inner errno over Control
+	if controlErr := syscallConn.Control(func(fd uintptr) {
+		n, errno = fn(fd)
+	}); errno == 0 {
+		errno = experimentalsys.UnwrapOSError(controlErr)
+	}
+	return
+}