types/key: export constants for key size, not a method.

Signed-off-by: David Anderson <danderson@tailscale.com>

derp/derp_client.go

@@ -210,12 +210,12 @@ func (c *Client) send(dstKey key.NodePublic, pkt []byte) (ret error) {
 	c.wmu.Lock()
 	defer c.wmu.Unlock()
 	if c.rate != nil {
-		pktLen := frameHeaderLen + dstKey.RawLen() + len(pkt)
+		pktLen := frameHeaderLen + key.NodePublicRawLen + len(pkt)
 		if !c.rate.AllowN(time.Now(), pktLen) {
 			return nil // drop
 		}
 	}
-	if err := writeFrameHeader(c.bw, frameSendPacket, uint32(dstKey.RawLen()+len(pkt))); err != nil {
+	if err := writeFrameHeader(c.bw, frameSendPacket, uint32(key.NodePublicRawLen+len(pkt))); err != nil {
 		return err
 	}
 	if _, err := c.bw.Write(dstKey.AppendTo(nil)); err != nil {

derp/derp_server.go

@@ -1017,7 +1017,7 @@ func (s *Server) verifyClient(clientKey key.NodePublic, info *clientInfo) error
 }
 
 func (s *Server) sendServerKey(lw *lazyBufioWriter) error {
-	buf := make([]byte, 0, len(magic)+s.publicKey.RawLen())
+	buf := make([]byte, 0, len(magic)+key.NodePublicRawLen)
 	buf = append(buf, magic...)
 	buf = s.publicKey.AppendTo(buf)
 	err := writeFrame(lw.bw(), frameServerKey, buf)
@@ -1469,7 +1469,7 @@ func (c *sclient) sendPacket(srcKey key.NodePublic, contents []byte) (err error)
 	withKey := !srcKey.IsZero()
 	pktLen := len(contents)
 	if withKey {
-		pktLen += srcKey.RawLen()
+		pktLen += key.NodePublicRawLen
 	}
 	if err = writeFrameHeader(c.bw.bw(), frameRecvPacket, uint32(pktLen)); err != nil {
 		return err

disco/disco.go

@@ -123,7 +123,7 @@ func (m *Ping) AppendMarshal(b []byte) []byte {
 	dataLen := 12
 	hasKey := !m.NodeKey.IsZero()
 	if hasKey {
-		dataLen += m.NodeKey.RawLen()
+		dataLen += key.NodePublicRawLen
 	}
 	ret, d := appendMsgHeader(b, TypePing, v0, dataLen)
 	n := copy(d, m.TxID[:])
@@ -141,8 +141,8 @@ func parsePing(ver uint8, p []byte) (m *Ping, err error) {
 	p = p[copy(m.TxID[:], p):]
 	// Deliberately lax on longer-than-expected messages, for future
 	// compatibility.
-	if len(p) >= m.NodeKey.RawLen() {
-		m.NodeKey = key.NodePublicFromRaw32(mem.B(p[:m.NodeKey.RawLen()]))
+	if len(p) >= key.NodePublicRawLen {
+		m.NodeKey = key.NodePublicFromRaw32(mem.B(p[:key.NodePublicRawLen]))
 	}
 	return m, nil
 }

types/key/disco.go

@@ -21,6 +21,10 @@ const (
 	// This prefix is used in the control protocol, so cannot be
 	// changed.
 	discoPublicHexPrefix = "discokey:"
+
+	// DiscoPublicRawLen is the length in bytes of a DiscoPublic, when
+	// serialized with AppendTo, Raw32 or WriteRawWithoutAllocating.
+	DiscoPublicRawLen = 32
 )
 
 // DiscoPrivate is a disco key, used for peer-to-peer path discovery.
@@ -115,12 +119,6 @@ func (k DiscoPublic) AppendTo(buf []byte) []byte {
 	return append(buf, k.k[:]...)
 }
 
-// RawLen returns the length of k when to the format handled by
-// ReadRawWithoutAllocating and WriteRawWithoutAllocating.
-func (k DiscoPublic) RawLen() int {
-	return 32
-}
-
 // String returns the output of MarshalText as a string.
 func (k DiscoPublic) String() string {
 	bs, err := k.MarshalText()

types/key/node.go

@@ -33,6 +33,10 @@ const (
 	// This prefix is used in the control protocol, so cannot be
 	// changed.
 	nodePublicHexPrefix = "nodekey:"
+
+	// NodePublicRawLen is the length in bytes of a NodePublic, when
+	// serialized with AppendTo, Raw32 or WriteRawWithoutAllocating.
+	NodePublicRawLen = 32
 )
 
 // NodePrivate is a node key, used for WireGuard tunnels and
@@ -190,12 +194,6 @@ func (k NodePublic) AppendTo(buf []byte) []byte {
 	return append(buf, k.k[:]...)
 }
 
-// RawLen returns the length of k when to the format handled by
-// ReadRawWithoutAllocating and WriteRawWithoutAllocating.
-func (k NodePublic) RawLen() int {
-	return 32
-}
-
 // ReadRawWithoutAllocating initializes k with bytes read from br.
 // The reading is done ~4x slower than io.ReadFull, but in exchange is
 // allocation-free.

wgengine/magicsock/magicsock.go

@@ -1798,7 +1798,7 @@ func (c *Conn) sendDiscoMessage(dst netaddr.IPPort, dstKey tailcfg.NodeKey, dstD
 // it was received from at the DERP layer. derpNodeSrc is zero when received
 // over UDP.
 func (c *Conn) handleDiscoMessage(msg []byte, src netaddr.IPPort, derpNodeSrc tailcfg.NodeKey) (isDiscoMsg bool) {
-	headerLen := len(disco.Magic) + key.DiscoPublic{}.RawLen()
+	const headerLen = len(disco.Magic) + key.DiscoPublicRawLen
 	if len(msg) < headerLen || string(msg[:len(disco.Magic)]) != disco.Magic {
 		return false
 	}
@@ -1809,7 +1809,7 @@ func (c *Conn) handleDiscoMessage(msg []byte, src netaddr.IPPort, derpNodeSrc ta
 	// Use naked returns for all following paths.
 	isDiscoMsg = true
 
-	sender := key.DiscoPublicFromRaw32(mem.B(msg[len(disco.Magic) : len(disco.Magic)+key.DiscoPublic{}.RawLen()]))
+	sender := key.DiscoPublicFromRaw32(mem.B(msg[len(disco.Magic):headerLen]))
 
 	c.mu.Lock()
 	defer c.mu.Unlock()