refactor-for-testability (#3)

Co-authored-by: jdl <jdl@desktop>
Co-authored-by: jdl <jdl@crumpington.com>
Reviewed-on: #3

peer/controlmessage.go

@@ -0,0 +1,64 @@
+package peer
+
+import (
+	"net/netip"
+	"vppn/m"
+)
+
+// ----------------------------------------------------------------------------
+
+type controlMsg[T any] struct {
+	SrcIP   byte
+	SrcAddr netip.AddrPort
+	Packet  T
+}
+
+func parseControlMsg(srcIP byte, srcAddr netip.AddrPort, buf []byte) (any, error) {
+	switch buf[0] {
+
+	case packetTypeInit:
+		packet, err := parsePacketInit(buf)
+		return controlMsg[packetInit]{
+			SrcIP:   srcIP,
+			SrcAddr: srcAddr,
+			Packet:  packet,
+		}, err
+
+	case packetTypeSyn:
+		packet, err := parsePacketSyn(buf)
+		return controlMsg[packetSyn]{
+			SrcIP:   srcIP,
+			SrcAddr: srcAddr,
+			Packet:  packet,
+		}, err
+
+	case packetTypeAck:
+		packet, err := parsePacketAck(buf)
+		return controlMsg[packetAck]{
+			SrcIP:   srcIP,
+			SrcAddr: srcAddr,
+			Packet:  packet,
+		}, err
+
+	case packetTypeProbe:
+		packet, err := parsePacketProbe(buf)
+		return controlMsg[packetProbe]{
+			SrcIP:   srcIP,
+			SrcAddr: srcAddr,
+			Packet:  packet,
+		}, err
+
+	default:
+		return nil, errUnknownPacketType
+	}
+}
+
+// ----------------------------------------------------------------------------
+
+type peerUpdateMsg struct {
+	Peer *m.Peer
+}
+
+// ----------------------------------------------------------------------------
+
+type pingTimerMsg struct{}