1 files changed, 36 insertions, 25 deletions

diff --git a/ringlogger/ringlogger.go b/ringlogger/ringlogger.go
index fe88fdc7..e932f88c 100644
--- a/ringlogger/ringlogger.go
+++ b/ringlogger/ringlogger.go
@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: MIT
  *
- * Copyright (C) 2019 WireGuard LLC. All Rights Reserved.
+ * Copyright (C) 2019-2022 WireGuard LLC. All Rights Reserved.
  */
 
 package ringlogger
@@ -21,6 +21,7 @@ import (
 
 const (
 	maxLogLineLength = 512
+	maxTagLength     = 5
 	maxLines         = 2048
 	magic            = 0xbadbabe
 )
@@ -44,8 +45,11 @@ type Ringlogger struct {
 	readOnly bool
 }
 
-func NewRinglogger(filename string, tag string) (*Ringlogger, error) {
-	file, err := os.OpenFile(filename, os.O_RDWR|os.O_CREATE, 0600)
+func NewRinglogger(filename, tag string) (*Ringlogger, error) {
+	if len(tag) > maxTagLength {
+		return nil, windows.ERROR_LABEL_TOO_LONG
+	}
+	file, err := os.OpenFile(filename, os.O_RDWR|os.O_CREATE, 0o600)
 	if err != nil {
 		return nil, err
 	}
@@ -54,18 +58,19 @@ func NewRinglogger(filename string, tag string) (*Ringlogger, error) {
 		return nil, err
 	}
 	mapping, err := windows.CreateFileMapping(windows.Handle(file.Fd()), nil, windows.PAGE_READWRITE, 0, 0, nil)
-	if err != nil {
+	if err != nil && err != windows.ERROR_ALREADY_EXISTS {
 		return nil, err
 	}
 	rl, err := newRingloggerFromMappingHandle(mapping, tag, windows.FILE_MAP_WRITE)
 	if err != nil {
+		windows.CloseHandle(mapping)
 		return nil, err
 	}
 	rl.file = file
 	return rl, nil
 }
 
-func NewRingloggerFromInheritedMappingHandle(handleStr string, tag string) (*Ringlogger, error) {
+func NewRingloggerFromInheritedMappingHandle(handleStr, tag string) (*Ringlogger, error) {
 	handle, err := strconv.ParseUint(handleStr, 10, 64)
 	if err != nil {
 		return nil, err
@@ -78,10 +83,6 @@ func newRingloggerFromMappingHandle(mappingHandle windows.Handle, tag string, ac
 	if err != nil {
 		return nil, err
 	}
-	if err != nil {
-		windows.CloseHandle(mappingHandle)
-		return nil, err
-	}
 	log := (*logMem)(unsafe.Pointer(view))
 	if log.magic != magic {
 		bytes := (*[unsafe.Sizeof(logMem{})]byte)(unsafe.Pointer(log))
@@ -103,12 +104,20 @@ func newRingloggerFromMappingHandle(mappingHandle windows.Handle, tag string, ac
 }
 
 func (rl *Ringlogger) Write(p []byte) (n int, err error) {
+	// Race: This isn't synchronized with the fetch_add below, so items might be slightly out of order.
+	ts := time.Now().UnixNano()
+	return rl.WriteWithTimestamp(p, ts)
+}
+
+func (rl *Ringlogger) WriteWithTimestamp(p []byte, ts int64) (n int, err error) {
 	if rl.readOnly {
 		return 0, io.ErrShortWrite
 	}
-
-	// Race: This isn't synchronized with the fetch_add below, so items might be slightly out of order.
-	ts := time.Now().UnixNano()
+	ret := len(p)
+	p = bytes.TrimSpace(p)
+	if len(p) == 0 {
+		return ret, nil
+	}
 
 	if rl.log == nil {
 		return 0, io.EOF
@@ -124,18 +133,21 @@ func (rl *Ringlogger) Write(p []byte) (n int, err error) {
 		line.line[i] = 0
 	}
 
-	text := []byte(fmt.Sprintf("[%s] %s", rl.tag, bytes.TrimSpace(p)))
-	if len(text) > maxLogLineLength-1 {
-		text = text[:maxLogLineLength-1]
+	textLen := 3 + len(p) + len(rl.tag)
+	if textLen > maxLogLineLength-1 {
+		p = p[:maxLogLineLength-1-3-len(rl.tag)]
+		textLen = maxLogLineLength - 1
 	}
-	line.line[len(text)] = 0
-	copy(line.line[:], text[:])
+	line.line[textLen] = 0
+	line.line[0] = 0 // Null out the beginning and only let it extend after the other writes have completed
+	copy(line.line[1:], rl.tag)
+	line.line[1+len(rl.tag)] = ']'
+	line.line[2+len(rl.tag)] = ' '
+	copy(line.line[3+len(rl.tag):], p[:])
+	line.line[0] = '['
 	atomic.StoreInt64(&line.timeNs, ts)
 
-	windows.FlushViewOfFile((uintptr)(unsafe.Pointer(&rl.log.nextIndex)), unsafe.Sizeof(rl.log.nextIndex))
-	windows.FlushViewOfFile((uintptr)(unsafe.Pointer(line)), unsafe.Sizeof(*line))
-
-	return len(p), nil
+	return ret, nil
 }
 
 func (rl *Ringlogger) WriteTo(out io.Writer) (n int64, err error) {
@@ -223,17 +235,16 @@ func (rl *Ringlogger) Close() error {
 	return nil
 }
 
-func (rl *Ringlogger) ExportInheritableMappingHandleStr() (str string, handleToClose windows.Handle, err error) {
+func (rl *Ringlogger) ExportInheritableMappingHandle() (handleToClose windows.Handle, err error) {
 	handleToClose, err = windows.CreateFileMapping(windows.Handle(rl.file.Fd()), nil, windows.PAGE_READONLY, 0, 0, nil)
-	if err != nil {
+	if err != nil && err != windows.ERROR_ALREADY_EXISTS {
 		return
 	}
 	err = windows.SetHandleInformation(handleToClose, windows.HANDLE_FLAG_INHERIT, windows.HANDLE_FLAG_INHERIT)
 	if err != nil {
-		windows.Close(handleToClose)
+		windows.CloseHandle(handleToClose)
 		handleToClose = 0
 		return
 	}
-	str = strconv.FormatUint(uint64(handleToClose), 10)
 	return
 }