Cleanup / temp buffers for various things

peer/control/ping.go

@@ -33,15 +33,18 @@ type Ping struct {
 	Dst    netip.AddrPort
 }
 
-// Marshal encodes p into a fixed-size 51-byte array.
-func (p Ping) Marshal() [Size]byte {
-	var buf [Size]byte
+// Marshal encodes p into buf (which must be at least Size bytes) and returns
+// buf[:Size]. Taking the buffer lets callers reuse one across sends; every
+// field is written unconditionally so a reused buffer needs no pre-zeroing.
+func (p Ping) Marshal(buf []byte) []byte {
 	buf[0] = version
 	binary.BigEndian.PutUint64(buf[1:9], uint64(p.PingTS))
 	if p.SrcV4.IsValid() {
 		a4 := p.SrcV4.Addr().As4()
 		copy(buf[9:13], a4[:])
 		binary.BigEndian.PutUint16(buf[13:15], p.SrcV4.Port())
+	} else {
+		clear(buf[9:15])
 	}
 	a16 := p.SrcV6.Addr().As16()
 	copy(buf[15:31], a16[:])
@@ -49,7 +52,7 @@ func (p Ping) Marshal() [Size]byte {
 	a16 = p.Dst.Addr().As16()
 	copy(buf[33:49], a16[:])
 	binary.BigEndian.PutUint16(buf[49:51], p.Dst.Port())
-	return buf
+	return buf[:Size]
 }
 
 // Unmarshal decodes a Ping from a fixed-size 51-byte array.

peer/control/ping_test.go

@@ -59,7 +59,8 @@ func TestRoundTrip(t *testing.T) {
 
 	for _, tc := range cases {
 		t.Run(tc.name, func(t *testing.T) {
-			buf := tc.ping.Marshal()
+			var buf [control.Size]byte
+			tc.ping.Marshal(buf[:])
 			got, err := control.Unmarshal(buf)
 			if err != nil {
 				t.Fatalf("Unmarshal: %v", err)
@@ -80,7 +81,8 @@ func TestUnmarshalBadVersion(t *testing.T) {
 }
 
 func TestZeroEncoding(t *testing.T) {
-	buf := (control.Ping{}).Marshal()
+	var buf [control.Size]byte
+	(control.Ping{}).Marshal(buf[:])
 	for i, b := range buf {
 		if i == 0 {
 			continue // version byte