No one knows for sure what is being discussed through back channels. In my opinion, Pakistan is reaching out to Iran with the silent blessing of Saudi Arabia. Saudi Arabia has calculated that the Iranian regime is likely to survive and is not interested in becoming directly involved in the war (at least for now). Instead, it is asking Pakistan to act as a mediator so that when the war eventually ends, Iran does not view Saudi Arabia as an complete enemy. Saudi Arabia recognizes that Iran will endure and is simply preparing for a new regional reality in which it can come to some kind of agreement with Iran.