bytepool: store *[]byte

This avoids allocations for the slice metadata.

For more details, see:
https://staticcheck.io/docs/checks#SA6002

frontend/udp/bytepool/bytepool.go

@@ -11,24 +11,27 @@ type BytePool struct {
 func New(length int) *BytePool {
 	var bp BytePool
 	bp.Pool.New = func() interface{} {
-		return make([]byte, length)
+		b := make([]byte, length)
+		return &b
 	}
 	return &bp
 }
 
 // Get returns a byte slice from the pool.
-func (bp *BytePool) Get() []byte {
-	return bp.Pool.Get().([]byte)
+func (bp *BytePool) Get() *[]byte {
+	return bp.Pool.Get().(*[]byte)
 }
 
 // Put returns a byte slice to the pool.
-func (bp *BytePool) Put(b []byte) {
-	b = b[:cap(b)]
+func (bp *BytePool) Put(b *[]byte) {
+	*b = (*b)[:cap(*b)]
+
 	// Zero out the bytes.
-	// Apparently this specific expression is optimized by the compiler, see
-	// github.com/golang/go/issues/5373.
-	for i := range b {
-		b[i] = 0
+	// This specific expression is optimized by the compiler:
+	// https://github.com/golang/go/issues/5373.
+	for i := range *b {
+		(*b)[i] = 0
 	}
+
 	bp.Pool.Put(b)
 }

frontend/udp/frontend.go

@@ -185,7 +185,7 @@ func (t *Frontend) serve() error {
 
 		// Read a UDP packet into a reusable buffer.
 		buffer := pool.Get()
-		n, addr, err := t.socket.ReadFromUDP(buffer)
+		n, addr, err := t.socket.ReadFromUDP(*buffer)
 		if err != nil {
 			pool.Put(buffer)
 			if netErr, ok := err.(net.Error); ok && netErr.Temporary() {
@@ -217,7 +217,7 @@ func (t *Frontend) serve() error {
 			}
 			action, af, err := t.handleRequest(
 				// Make sure the IP is copied, not referenced.
-				Request{buffer[:n], append([]byte{}, addr.IP...)},
+				Request{(*buffer)[:n], append([]byte{}, addr.IP...)},
 				ResponseWriter{t.socket, addr},
 			)
 			if t.EnableRequestTiming {