diff --git a/tun/alignment_windows_test.go b/tun/alignment_windows_test.go new file mode 100644 index 0000000..ddb3e3f --- /dev/null +++ b/tun/alignment_windows_test.go @@ -0,0 +1,67 @@ +/* SPDX-License-Identifier: MIT + * + * Copyright (C) 2017-2021 WireGuard LLC. All Rights Reserved. + */ + +package tun + +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 NativeTun + + 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)) +} \ No newline at end of file