Global RPC manager

Godot version: 3.1.dev git
OS/device including version: Gentoo Linux 4.20 kernel

When separating client & server logic codes in different projects, we have to make sure we are sending and receiving RPCs from the same path.
However, some players might want to reverse the networking protocol or send garbage data, which will result in a lot of errors serverside (no crash but still almost freezing the server).
If we have a GDScript function (or something similar) "bool accept_rpc(int from_id, string rpc_function_name, string to_path)" we could handle this ourselves by dismissing malformed RPCs without flooding the terminal.

[zEh-]

I ran into the same problem. On the server I need to detect potential attacks. On the client I want my log to not get spammed because I receive updates on objects which do not exist yet.

Both would be solved by a callback like proposed by @myrage2000. (But where to put it, as the node may not be even found).
My proposal is a signal on SceneTree like "received_invalid_rpc" when a node path is not found or the mode doesn't allow a call. (Ignoring rset here because I don't use them). That way it can either be ignored (by default) altogether(on the client) or detect potential attacks(on the server).

Otherwise I would need to implement a handshake to let my server know which nodes a client already set up which I'm currently refusing to do, as it complicates everything - Only to not get my log spammed and I still wouldn't be able to detect anything.

@Faless What do you think?

[alimalkhalifa]

My pull request at #23893 is relevant as @mhilbrunner has mentioned

[menip]

Receiving rpc calls on objects that don't exist is not engine issue, but a logic issue in code that can be fixed.

However, malicious users are still valid concern.

Edit: never mind me, forgot about obvious issues as result of async communication.

[Faless]

There is already a Global RPC manager, it's the MultiplayerAPI class, and can be accessed via the Node.multiplayer property (or the soon to be deprecated get_tree(),multiplayer).
Signals should be added to that class, see this comment .

[clayjohn]

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