[zombinet] initial implementation of zombienet backchannel (#4377)

Cargo.toml

@@ -91,6 +91,7 @@ members = [
 	"node/test/polkadot-simnet/common",
 	"node/test/polkadot-simnet/node",
 	"node/test/polkadot-simnet/test",
+	"node/zombienet-backchannel",
 	"parachain/test-parachains",
 	"parachain/test-parachains/adder",
 	"parachain/test-parachains/adder/collator",

node/zombienet-backchannel/Cargo.toml

@@ -0,0 +1,22 @@
+[package]
+name = "zombienet-backchannel"
+description = "Zombienet backchannel to notify test runner and coordinate with malus actors."
+license = "GPL-3.0-only"
+version = "0.9.13"
+authors = ["Parity Technologies <admin@parity.io>"]
+edition = "2021"
+readme = "README.md"
+publish = false
+
+[dependencies]
+tokio = { version = "1.0.0", default-features = false, features = ["macros", "net", "rt-multi-thread", "sync"] }
+url = "2.0.0"
+tokio-tungstenite = "0.16"
+futures-util = "0.3.18"
+lazy_static = "1.4.0"
+parity-scale-codec = { version = "2.3.1", features = ["derive"] }
+reqwest = "0.11"
+thiserror = "1.0.30"
+tracing = "0.1.26"
+serde = { version = "1.0", features = ["derive"] }
+serde_json = "1"

node/zombienet-backchannel/src/errors.rs

@@ -0,0 +1,39 @@
+// Copyright 2021 Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Polkadot is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Polkadot Zombienet Backchannel error definitions.
+
+#[derive(Debug, thiserror::Error)]
+#[allow(missing_docs)]
+pub enum BackchannelError {
+	#[error("Error connecting websocket server")]
+	CantConnectToWS,
+
+	#[error("Backchannel not initialized yet")]
+	Uninitialized,
+
+	#[error("Backchannel already initialized")]
+	AlreadyInitialized,
+
+	#[error("Error sending new value to backchannel")]
+	SendItemFail,
+
+	#[error("Invalid host for connection backchannel")]
+	InvalidHost,
+
+	#[error("Invalid port for connection backchannel")]
+	InvalidPort,
+}