host.Close() or cancelling context does not terminate listeners

[leoluk]

Calling Close() on a libp2p.Host does not close open listener sockets.

The Host's ctx also isn't passed to the listeners, a Background context is used instead:

https://github.com/libp2p/go-libp2p-transport-upgrader/blob/0c577bb483255c5046677a49624fb45c862d616b/upgrader.go#L39

How to properly tear down a libp2p.Host?

[Stebalien]

That context is closed when the listener is closed. The listeners are closed in https://github.com/libp2p/go-libp2p-swarm/blob/58c167a7b0c3294d416342d781465214d514e70f/swarm.go#L158-L164

Have you observed this issue in practice?

[leoluk]

Have you observed this issue in practice?

Yes, here's the code snippet that initializes libp2p:

h, err := libp2p.New(ctx,
	// Use the keypair we generated
	libp2p.Identity(priv),

	// Multiple listen addresses
	libp2p.ListenAddrStrings(
		// Listen on QUIC only.
		fmt.Sprintf("/ip4/0.0.0.0/udp/%d/quic", *p2pPort),
		fmt.Sprintf("/ip6/::/udp/%d/quic", *p2pPort),
	),

	// Enable TLS security as the only security protocol.
	libp2p.Security(libp2ptls.ID, libp2ptls.New),

	// Enable QUIC transport as the only transport.
	libp2p.Transport(libp2pquic.NewTransport),

	// Let's prevent our peer from having too many
	// connections by attaching a connection manager.
	libp2p.ConnectionManager(connmgr.NewConnManager(
		100,         // Lowwater
		400,         // HighWater,
		time.Minute, // GracePeriod
	)),

	// Let this host use the DHT to find other hosts
	libp2p.Routing(func(h host.Host) (routing.PeerRouting, error) {
		idht, err = dht.New(ctx, h, dht.Mode(dht.ModeServer),
			dht.ProtocolPrefix(protocol.ID("/"+*p2pNetworkID)),
		)
		return idht, err
	}),
)

if err != nil {
	panic(err)
}

defer func() {
	h.Close()
}()

Neither cancelling ctx, nor calling h.Close() seems to close listener sockets and we have to restart the whole process.

[Stebalien]

Ah, interesting. That's actually an issue with the QUIC transport. We reference-count and share udp sockets in the QUIC transport, closing them only after they've been idle for at least 10 seconds.

I'm not sure what the correct fix here is, unfortunately. We don't have way to "close" transports, just listeners and connections.

[Stebalien]

Closing as libp2p/go-libp2p-quic-transport#211 has been merged and this will be fixed in the next release.