refactor readOutsidePackets (#1642)

* refactor readOutsidePackets

They layout of this method is confusing and relys on certain parts to
return early for things to work correctly.

Change the ordering of the logic so that we do this:

- Handle unencrypted packets
- Decrypt packet
- Handle encrypted packets

This way, nothing can sneak through unencrypted to where it shouldn't
be.

* fix comment

* code review comments

* check for expected type/subtype

* check header version

* log header

* need to handle TestReply

* clean roaming / connectionManager

* dont need to roam here now, we do it earlier

* cleanup metrics and errors

* rxInvalid

* debug logger checks

* ErrOutOfWindow

message_metrics.go

@@ -13,6 +13,8 @@ type MessageMetrics struct {
 
 	rxUnknown metrics.Counter
 	txUnknown metrics.Counter
+
+	rxInvalid metrics.Counter
 }
 
 func (m *MessageMetrics) Rx(t header.MessageType, s header.MessageSubType, i int64) {
@@ -33,6 +35,11 @@ func (m *MessageMetrics) Tx(t header.MessageType, s header.MessageSubType, i int
 		}
 	}
 }
+func (m *MessageMetrics) RxInvalid(i int64) {
+	if m != nil && m.rxInvalid != nil {
+		m.rxInvalid.Inc(i)
+	}
+}
 
 func newMessageMetrics() *MessageMetrics {
 	gen := func(t string) [][]metrics.Counter {
@@ -56,6 +63,7 @@ func newMessageMetrics() *MessageMetrics {
 
 		rxUnknown: metrics.GetOrRegisterCounter("messages.rx.other", nil),
 		txUnknown: metrics.GetOrRegisterCounter("messages.tx.other", nil),
+		rxInvalid: metrics.GetOrRegisterCounter("messages.rx.invalid", nil),
 	}
 }