fix err judge

alignment_windows_test.go

@@ -0,0 +1,67 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2017-2021 WireGuard LLC. All Rights Reserved.
+ */
+
+package water
+
+import (
+	"reflect"
+	"testing"
+	"unsafe"
+)
+
+func checkAlignment(t *testing.T, name string, offset uintptr) {
+	t.Helper()
+	if offset%8 != 0 {
+		t.Errorf("offset of %q within struct is %d bytes, which does not align to 64-bit word boundaries (missing %d bytes). Atomic operations will crash on 32-bit systems.", name, offset, 8-(offset%8))
+	}
+}
+
+// TestRateJugglerAlignment checks that atomically-accessed fields are
+// aligned to 64-bit boundaries, as required by the atomic package.
+//
+// Unfortunately, violating this rule on 32-bit platforms results in a
+// hard segfault at runtime.
+func TestRateJugglerAlignment(t *testing.T) {
+	var r rateJuggler
+
+	typ := reflect.TypeOf(&r).Elem()
+	t.Logf("Peer type size: %d, with fields:", typ.Size())
+	for i := 0; i < typ.NumField(); i++ {
+		field := typ.Field(i)
+		t.Logf("\t%30s\toffset=%3v\t(type size=%3d, align=%d)",
+			field.Name,
+			field.Offset,
+			field.Type.Size(),
+			field.Type.Align(),
+		)
+	}
+
+	checkAlignment(t, "rateJuggler.current", unsafe.Offsetof(r.current))
+	checkAlignment(t, "rateJuggler.nextByteCount", unsafe.Offsetof(r.nextByteCount))
+	checkAlignment(t, "rateJuggler.nextStartTime", unsafe.Offsetof(r.nextStartTime))
+}
+
+// TestNativeTunAlignment checks that atomically-accessed fields are
+// aligned to 64-bit boundaries, as required by the atomic package.
+//
+// Unfortunately, violating this rule on 32-bit platforms results in a
+// hard segfault at runtime.
+func TestNativeTunAlignment(t *testing.T) {
+	var tun wintunRWC
+
+	typ := reflect.TypeOf(&tun).Elem()
+	t.Logf("Peer type size: %d, with fields:", typ.Size())
+	for i := 0; i < typ.NumField(); i++ {
+		field := typ.Field(i)
+		t.Logf("\t%30s\toffset=%3v\t(type size=%3d, align=%d)",
+			field.Name,
+			field.Offset,
+			field.Type.Size(),
+			field.Type.Align(),
+		)
+	}
+
+	checkAlignment(t, "NativeTun.rate", unsafe.Offsetof(tun.rate))
+}

syscalls_windows.go

@@ -326,10 +326,10 @@ func (rate *rateJuggler) update(packetLen uint64) {
 type wintunRWC struct {
 	ad       wintun.Adapter
 	s        wintun.Session
-	readwait windows.Handle
-	readbuf  []byte
 	rate     rateJuggler
+	readwait windows.Handle
 	mu       sync.Mutex
+	readbuf  []byte
 	isclosed bool
 }
 
@@ -343,6 +343,7 @@ func (w *wintunRWC) Write(b []byte) (int, error) {
 	w.rate.update(uint64(len(b)))
 	w.mu.Lock()
 	defer w.mu.Unlock()
+ALLOC:
 	packet, err := w.s.AllocateSendPacket(len(b))
 	switch err {
 	case nil:
@@ -350,6 +351,11 @@ func (w *wintunRWC) Write(b []byte) (int, error) {
 		w.s.SendPacket(packet)
 		return len(b), nil
 	case windows.ERROR_HANDLE_EOF:
+		w.s.End()
+		w.s, err = w.ad.StartSession(0x800000) // Ring capacity, 8 MiB
+		if err == nil {
+			goto ALLOC
+		}
 		return 0, os.ErrClosed
 	case windows.ERROR_BUFFER_OVERFLOW:
 		return 0, nil // Dropping when ring is full.
@@ -407,6 +413,11 @@ RETRY:
 			w.mu.Lock()
 			continue
 		}
+		w.s.End()
+		w.s, err = w.ad.StartSession(0x800000) // Ring capacity, 8 MiB
+		if err == nil {
+			continue
+		}
 		return n, err
 	}
 }