`Gossipsub`'s substreams keep all connections alive after `idle_connection_timeout`

Summary

It seems gossipsub protocol keeps active substreams for connections that exists outside the gossip-mesh. As a result, connections remain alive even after idle_connection_timeout.

This functionality appears to have changed from version v0.52.0, where gossip kept connections alive only within the mesh. Commits with relevant updates: https://github.com/libp2p/rust-libp2p/commit/fafa6bc472f6fe9501c75be6a936df2cb37e053a and https://github.com/libp2p/rust-libp2p/commit/fcd410a56c86de3b34f4896d1447ef1da959947c

Expected behavior

Gossipsub protocol should keep connections alive, but exclusively for peers within the mesh

Actual behavior

Gossipsub protocol keeps all connections alive

Relevant log output

No response

Possible Solution

Ignore gossip substreams in the connection-keep-alive algorithm. Use libp2p_swarm::stream::Stream::ignore_for_keep_alive for gossip inbound and outbound substreams.

Version

0.53.1

Would you like to work on fixing this bug ?

Maybe

Start in the gossipsub inbound and outbound substream handling and inspect libp2p_swarm::stream::Stream::ignore_for_keep_alive, along with the referenced commits. Done means gossipsub keeps connections alive only for peers in the mesh, while connections outside it can close after idle_connection_timeout; verify this against the affected behavior in version 0.53.1.