ConnectionEstablished is called in an already established connection

[majecty]

Recently, discovery5 tests failed occasionally.
I read the failed test log and found that a connection established event is fired in the already existing connection. It made Foundry crash.

Why this error found nowadays

Recently when we implementing a peer DB, we added an assertion that the same peer is not added twice in the DB. The assertion made Foundry panic.
It seems that the duplicated connection established event bug is aged, but recently found by the assertion.

How should we fix it

The "connection established" event should not be called in an existing connection.

ErrorLog

2020_03_18T01_56_17_226Z.1.log
2020_03_18T01_56_17_226Z.4.log

[MSNTCS]

The problem is that on_node_added is called several times with the same id. For now, in order to avoid the situation, we check whether the connection nodes contain the id inside on_node_added function which we should not.

The on_node_added function is called during the negotiation phase several times with the same id. My inspection is that the same negotiation message is sent several times by on node.

We keep PR #499 open.