cache the serialized OOB in the conn, not in the packet info

We're allocating a lot of packetInfo structs during the lifetime of a
connection. It's better to keep that struct as small as possible.

conn.go

@@ -12,7 +12,7 @@ import (
 
 type connection interface {
 	ReadPacket() (*receivedPacket, error)
-	WritePacket(b []byte, addr net.Addr, info *packetInfo) (int, error)
+	WritePacket(b []byte, addr net.Addr, oob []byte) (int, error)
 	LocalAddr() net.Addr
 	io.Closer
 }
@@ -60,6 +60,6 @@ func (c *basicConn) ReadPacket() (*receivedPacket, error) {
 	}, nil
 }
 
-func (c *basicConn) WritePacket(b []byte, addr net.Addr, info *packetInfo) (n int, err error) {
+func (c *basicConn) WritePacket(b []byte, addr net.Addr, _ []byte) (n int, err error) {
 	return c.PacketConn.WriteTo(b, addr)
 }

conn_generic.go

@@ -11,3 +11,5 @@ func newConn(c net.PacketConn) (connection, error) {
 func inspectReadBuffer(interface{}) (int, error) {
 	return 0, nil
 }
+
+func (i *packetInfo) OOB() []byte { return nil }

conn_oob.go

@@ -171,8 +171,8 @@ func (c *oobConn) ReadPacket() (*receivedPacket, error) {
 	}, nil
 }
 
-func (c *oobConn) WritePacket(b []byte, addr net.Addr, info *packetInfo) (n int, err error) {
+func (c *oobConn) WritePacket(b []byte, addr net.Addr, oob []byte) (n int, err error) {
-	n, _, err = c.OOBCapablePacketConn.WriteMsgUDP(b, info.OOB(), addr.(*net.UDPAddr))
+	n, _, err = c.OOBCapablePacketConn.WriteMsgUDP(b, oob, addr.(*net.UDPAddr))
 	return n, err
 }
 
@@ -180,11 +180,6 @@ func (info *packetInfo) OOB() []byte {
 	if info == nil {
 		return nil
 	}
-	info.once.Do(info.computeOOB)
-	return info.oob
-}
-
-func (info *packetInfo) computeOOB() {
 	if ip4 := info.addr.To4(); ip4 != nil {
 		// struct in_pktinfo {
 		// 	unsigned int   ipi_ifindex;  /* Interface index */
@@ -208,7 +203,7 @@ func (info *packetInfo) computeOOB() {
 			off += 4
 		}
 		copy(oob[off:], ip4)
-		info.oob = oob
+		return oob
 	} else if len(info.addr) == 16 {
 		// struct in6_pktinfo {
 		// 	struct in6_addr ipi6_addr;    /* src/dst IPv6 address */
@@ -224,8 +219,9 @@ func (info *packetInfo) computeOOB() {
 		off := cmsgLen(0)
 		off += copy(oob[off:], info.addr)
 		binary.LittleEndian.PutUint32(oob[off:], info.ifIndex)
-		info.oob = oob
+		return oob
 	}
+	return nil
 }
 
 func cmsgLen(datalen int) int {

conn_windows.go

@@ -35,3 +35,5 @@ func inspectReadBuffer(c net.PacketConn) (int, error) {
 	}
 	return size, serr
 }
+
+func (i *packetInfo) OOB() []byte { return nil }

packet_handler_map.go

@@ -469,7 +469,7 @@ func (h *packetHandlerMap) maybeSendStatelessReset(p *receivedPacket, connID pro
 	rand.Read(data)
 	data[0] = (data[0] & 0x7f) | 0x40
 	data = append(data, token[:]...)
-	if _, err := h.conn.WritePacket(data, p.remoteAddr, p.info); err != nil {
+	if _, err := h.conn.WritePacket(data, p.remoteAddr, p.info.OOB()); err != nil {
 		h.logger.Debugf("Error sending Stateless Reset: %s", err)
 	}
 }

send_conn.go

@@ -17,16 +17,22 @@ type sconn struct {
 
 	remoteAddr net.Addr
 	info       *packetInfo
+	oob        []byte
 }
 
 var _ sendConn = &sconn{}
 
 func newSendConn(c connection, remote net.Addr, info *packetInfo) sendConn {
-	return &sconn{connection: c, remoteAddr: remote, info: info}
+	return &sconn{
+		connection: c,
+		remoteAddr: remote,
+		info:       info,
+		oob:        info.OOB(),
+	}
 }
 
 func (c *sconn) Write(p []byte) error {
-	_, err := c.WritePacket(p, c.remoteAddr, c.info)
+	_, err := c.WritePacket(p, c.remoteAddr, c.oob)
 	return err
 }
 

server.go

@@ -556,7 +556,7 @@ func (s *baseServer) sendRetry(remoteAddr net.Addr, hdr *wire.Header, info *pack
 	if s.config.Tracer != nil {
 		s.config.Tracer.SentPacket(remoteAddr, &replyHdr.Header, protocol.ByteCount(buf.Len()), nil)
 	}
-	_, err = s.conn.WritePacket(buf.Bytes(), remoteAddr, info)
+	_, err = s.conn.WritePacket(buf.Bytes(), remoteAddr, info.OOB())
 	return err
 }
 
@@ -633,7 +633,7 @@ func (s *baseServer) sendError(remoteAddr net.Addr, hdr *wire.Header, sealer han
 	if s.config.Tracer != nil {
 		s.config.Tracer.SentPacket(remoteAddr, &replyHdr.Header, protocol.ByteCount(len(raw)), []logging.Frame{ccf})
 	}
-	_, err := s.conn.WritePacket(raw, remoteAddr, info)
+	_, err := s.conn.WritePacket(raw, remoteAddr, info.OOB())
 	return err
 }
 
@@ -656,7 +656,7 @@ func (s *baseServer) sendVersionNegotiationPacket(p *receivedPacket, hdr *wire.H
 			nil,
 		)
 	}
-	if _, err := s.conn.WritePacket(data, p.remoteAddr, p.info); err != nil {
+	if _, err := s.conn.WritePacket(data, p.remoteAddr, p.info.OOB()); err != nil {
 		s.logger.Debugf("Error sending Version Negotiation: %s", err)
 	}
 }

session.go

@@ -62,8 +62,6 @@ type cryptoStreamHandler interface {
 type packetInfo struct {
 	addr    net.IP
 	ifIndex uint32
-	once    sync.Once
-	oob     []byte
 }
 
 type receivedPacket struct {