manager: warn about dnscache and old virtio driver

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

2 files changed, 138 insertions, 0 deletions

diff --git a/manager/pitfalls.go b/manager/pitfalls.go
new file mode 100644
index 00000000..b178b615
--- /dev/null
+++ b/manager/pitfalls.go
@@ -0,0 +1,136 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2019-2021 WireGuard LLC. All Rights Reserved.
+ */
+
+package manager
+
+import (
+	"log"
+	"strings"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+	"golang.org/x/sys/windows/svc/mgr"
+)
+
+func checkForPitfalls() {
+	go func() {
+		pitfallDnsCacheDisabled()
+		pitfallVirtioNetworkDriver()
+	}()
+}
+
+func pitfallDnsCacheDisabled() {
+	scm, err := mgr.Connect()
+	if err != nil {
+		return
+	}
+	defer scm.Disconnect()
+	svc := mgr.Service{Name: "dnscache"}
+	svc.Handle, err = windows.OpenService(scm.Handle, windows.StringToUTF16Ptr(svc.Name), windows.SERVICE_QUERY_CONFIG)
+	if err != nil {
+		return
+	}
+	defer svc.Close()
+	cfg, err := svc.Config()
+	if err != nil {
+		return
+	}
+	if cfg.StartType != mgr.StartDisabled {
+		return
+	}
+
+	log.Printf("Warning: the %q (dnscache) service is disabled; please re-enable it", cfg.DisplayName)
+}
+
+/* TODO: put this into x/sys/windows */
+
+var versionDll = windows.NewLazySystemDLL("version.dll")
+var getFileVersionInfo = versionDll.NewProc("GetFileVersionInfoW")
+var getFileVersionInfoSize = versionDll.NewProc("GetFileVersionInfoSizeW")
+var verQueryValue = versionDll.NewProc("VerQueryValueW")
+
+type VS_FIXEDFILEINFO struct {
+	Signature        uint32
+	StrucVersion     uint32
+	FileVersionMS    uint32
+	FileVersionLS    uint32
+	ProductVersionMS uint32
+	ProductVersionLS uint32
+	FileFlagsMask    uint32
+	FileFlags        uint32
+	FileOS           uint32
+	FileType         uint32
+	FileSubtype      uint32
+	FileDateMS       uint32
+	FileDateLS       uint32
+}
+
+var ntQuerySystemInformation = windows.NewLazySystemDLL("ntdll.dll").NewProc("NtQuerySystemInformation")
+
+const systemModuleInformation = 11
+
+type RTL_PROCESS_MODULE_INFORMATION struct {
+	Section          windows.Handle
+	MappedBase       uintptr
+	ImageBase        uintptr
+	ImageSize        uint32
+	Flags            uint32
+	LoadOrderIndex   uint16
+	InitOrderIndex   uint16
+	LoadCount        uint16
+	OffsetToFileName uint16
+	FullPathName     [256]byte
+}
+
+type RTL_PROCESS_MODULES struct {
+	NumberOfModules uint32
+	FirstModule     RTL_PROCESS_MODULE_INFORMATION
+}
+
+func pitfallVirtioNetworkDriver() {
+	var modules []RTL_PROCESS_MODULE_INFORMATION
+	for bufferSize := uint32(128 * 1024); ; {
+		moduleBuffer := make([]byte, bufferSize)
+		ret, _, _ := ntQuerySystemInformation.Call(systemModuleInformation, uintptr(unsafe.Pointer(&moduleBuffer[0])), uintptr(bufferSize), uintptr(unsafe.Pointer(&bufferSize)))
+		switch windows.NTStatus(ret) {
+		case windows.STATUS_INFO_LENGTH_MISMATCH:
+			continue
+		case windows.STATUS_SUCCESS:
+			break
+		default:
+			return
+		}
+		mods := (*RTL_PROCESS_MODULES)(unsafe.Pointer(&moduleBuffer[0]))
+		modules = unsafe.Slice(&mods.FirstModule, mods.NumberOfModules)
+		break
+	}
+	for i := range modules {
+		if !strings.EqualFold(windows.ByteSliceToString(modules[i].FullPathName[modules[i].OffsetToFileName:]), "netkvm.sys") {
+			continue
+		}
+		driverPath := `\\?\GLOBALROOT` + windows.ByteSliceToString(modules[i].FullPathName[:])
+		zero := uint32(0)
+		ret, _, _ := getFileVersionInfoSize.Call(uintptr(unsafe.Pointer(windows.StringToUTF16Ptr(driverPath))), uintptr(unsafe.Pointer(&zero)))
+		if ret == 0 {
+			return
+		}
+		infoSize := uint32(ret)
+		versionInfo := make([]byte, infoSize)
+		ret, _, _ = getFileVersionInfo.Call(uintptr(unsafe.Pointer(windows.StringToUTF16Ptr(driverPath))), 0, uintptr(infoSize), uintptr(unsafe.Pointer(&versionInfo[0])))
+		var fixedInfo *VS_FIXEDFILEINFO
+		fixedInfoLen := uint32(unsafe.Sizeof(*fixedInfo))
+		ret, _, _ = verQueryValue.Call(uintptr(unsafe.Pointer(&versionInfo[0])), uintptr(unsafe.Pointer(windows.StringToUTF16Ptr(`\`))), uintptr(unsafe.Pointer(&fixedInfo)), uintptr(unsafe.Pointer(&fixedInfoLen)))
+		if ret == 0 {
+			return
+		}
+		const minimumGoodVersion = (100 << 48) | (85 << 32) | (104 << 16) | (20800 << 0)
+		version := (uint64(fixedInfo.FileVersionMS) << 32) | uint64(fixedInfo.FileVersionLS)
+		if version >= minimumGoodVersion {
+			return
+		}
+		log.Println("Warning: the VirtIO network driver (NetKVM) is out of date and may cause known problems; please update to v100.85.104.20800 or later")
+		return
+	}
+}
diff --git a/manager/service.go b/manager/service.go
index af9004de..15ea88f0 100644
--- a/manager/service.go
+++ b/manager/service.go
@@ -56,6 +56,8 @@ func (service *managerService) Execute(args []string, r <-chan svc.ChangeRequest
 
 	log.Println("Starting", version.UserAgent())
 
+	checkForPitfalls()
+
 	path, err := os.Executable()
 	if err != nil {
 		serviceError = services.ErrorDetermineExecutablePath