diff --git a/common/buf/io.go b/common/buf/io.go
index c66a1f782..d82795cd2 100644
--- a/common/buf/io.go
+++ b/common/buf/io.go
@@ -14,6 +14,7 @@ type Reader interface {
 // ErrReadTimeout is an error that happens with IO timeout.
 var ErrReadTimeout = newError("IO timeout")
 
+// TimeoutReader is a reader that returns error if Read() operation takes longer than the given timeout.
 type TimeoutReader interface {
 	ReadTimeout(time.Duration) (MultiBuffer, error)
 }
diff --git a/common/buf/multi_buffer.go b/common/buf/multi_buffer.go
index 563e3ab3e..5a684fa4e 100644
--- a/common/buf/multi_buffer.go
+++ b/common/buf/multi_buffer.go
@@ -161,6 +161,7 @@ func (mb MultiBuffer) ToNetBuffers() net.Buffers {
 	return bs
 }
 
+// SliceBySize splits the begining of this MultiBuffer into another one, for at most size bytes.
 func (mb *MultiBuffer) SliceBySize(size int) MultiBuffer {
 	slice := NewMultiBuffer()
 	sliceSize := 0
@@ -178,6 +179,7 @@ func (mb *MultiBuffer) SliceBySize(size int) MultiBuffer {
 	return slice
 }
 
+// SplitFirst splits out the first Buffer in this MultiBuffer.
 func (mb *MultiBuffer) SplitFirst() *Buffer {
 	if len(*mb) == 0 {
 		return nil
diff --git a/common/buf/writer.go b/common/buf/writer.go
index 3944382af..6b63e6a75 100644
--- a/common/buf/writer.go
+++ b/common/buf/writer.go
@@ -137,6 +137,9 @@ func (noOpBytesWriter) ReadFrom(reader io.Reader) (int64, error) {
 }
 
 var (
-	Discard      Writer    = noOpWriter{}
+	// Discard is a Writer that swallows all contents written in.
+	Discard Writer = noOpWriter{}
+
+	// DiscardBytes is an io.Writer that swallows all contents written in.
 	DiscardBytes io.Writer = noOpBytesWriter{}
 )