[network/notifications] Connection to a disabled peer with an expired back-off is backed off again

[dmitry-markin]

In peerset_report_connect() the disabled peer with a non-expired back-off is handled here:

polkadot-sdk/substrate/client/network/src/protocol/notifications/behaviour.rs

Line 592 in 76724ce

PeerState::Disabled { connections, backoff_until: Some(ref backoff) }

The next match arm therefore handles the case of the expired back-off:

polkadot-sdk/substrate/client/network/src/protocol/notifications/behaviour.rs

Line 623 in 76724ce

PeerState::Disabled { mut connections, backoff_until } => {

Nevertheless, it's assumed that backoff_untill can be Some here

polkadot-sdk/substrate/client/network/src/protocol/notifications/behaviour.rs

Lines 654 to 661 in 76724ce

	let timer_deadline = {
	let base = now + Duration::from_secs(5);
	if let Some(backoff_until) = backoff_until {
	cmp::max(base, backoff_until)
	} else {
	base
	}
	};

This is a logic error on it's own, but more importantly the base timer deadline is installed and delays the connection, even though the back-off has already expired once. (It's effectively introduced again.)

Originally discussed in #1563 (comment).