Mixnet integration (#1346)

See #1345, <https://github.com/paritytech/substrate/pull/14207>.

This adds all the necessary mixnet components, and puts them together in
the "kitchen-sink" node/runtime. The components added are:

- A pallet (`frame/mixnet`). This is responsible for determining the
current mixnet session and phase, and the mixnodes to use in each
session. It provides a function that validators can call to register a
mixnode for the next session. The logic of this pallet is very similar
to that of the `im-online` pallet.
- A service (`client/mixnet`). This implements the core mixnet logic,
building on the `mixnet` crate. The service communicates with other
nodes using notifications sent over the "mixnet" protocol.
- An RPC interface. This currently only supports sending transactions
over the mixnet.

---------

Co-authored-by: David Emett <dave@sp4m.net>
Co-authored-by: Javier Viola <javier@parity.io>

substrate/client/rpc-api/src/error.rs

@@ -25,4 +25,5 @@ pub mod base {
 	pub const OFFCHAIN: i32 = 5000;
 	pub const DEV: i32 = 6000;
 	pub const STATEMENT: i32 = 7000;
+	pub const MIXNET: i32 = 8000;
 }

substrate/client/rpc-api/src/lib.rs

@@ -31,6 +31,7 @@ pub mod author;
 pub mod chain;
 pub mod child_state;
 pub mod dev;
+pub mod mixnet;
 pub mod offchain;
 pub mod state;
 pub mod statement;

substrate/client/rpc-api/src/mixnet/error.rs

@@ -0,0 +1,48 @@
+// This file is part of Substrate.
+
+// Copyright (C) Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0
+
+// This program 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.
+
+// This program 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 this program. If not, see <https://www.gnu.org/licenses/>.
+
+//! Mixnet RPC module errors.
+
+use jsonrpsee::types::error::{CallError, ErrorObject};
+use sc_mixnet::{PostErr, RemoteErr, TopologyErr};
+
+/// Mixnet RPC error type.
+pub struct Error(pub sc_mixnet::Error);
+
+/// Base code for all mixnet errors.
+const BASE_ERROR: i32 = crate::error::base::MIXNET;
+
+impl From<Error> for jsonrpsee::core::Error {
+	fn from(err: Error) -> Self {
+		let code = match err.0 {
+			sc_mixnet::Error::ServiceUnavailable => BASE_ERROR + 1,
+			sc_mixnet::Error::NoReply => BASE_ERROR + 2,
+			sc_mixnet::Error::BadReply => BASE_ERROR + 3,
+			sc_mixnet::Error::Post(PostErr::TooManyFragments) => BASE_ERROR + 101,
+			sc_mixnet::Error::Post(PostErr::SessionMixnodesNotKnown(_)) => BASE_ERROR + 102,
+			sc_mixnet::Error::Post(PostErr::SessionDisabled(_)) => BASE_ERROR + 103,
+			sc_mixnet::Error::Post(PostErr::Topology(TopologyErr::NoConnectedGatewayMixnodes)) =>
+				BASE_ERROR + 151,
+			sc_mixnet::Error::Post(PostErr::Topology(_)) => BASE_ERROR + 150,
+			sc_mixnet::Error::Post(_) => BASE_ERROR + 100,
+			sc_mixnet::Error::Remote(RemoteErr::Other(_)) => BASE_ERROR + 200,
+			sc_mixnet::Error::Remote(RemoteErr::Decode(_)) => BASE_ERROR + 201,
+		};
+		CallError::Custom(ErrorObject::owned(code, err.0.to_string(), None::<()>)).into()
+	}
+}

substrate/client/rpc-api/src/mixnet/mod.rs

@@ -0,0 +1,31 @@
+// This file is part of Substrate.
+
+// Copyright (C) Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0
+
+// This program 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.
+
+// This program 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 this program. If not, see <https://www.gnu.org/licenses/>.
+
+//! Substrate mixnet API.
+
+pub mod error;
+
+use jsonrpsee::{core::RpcResult, proc_macros::rpc};
+use sp_core::Bytes;
+
+#[rpc(client, server)]
+pub trait MixnetApi {
+	/// Submit encoded extrinsic over the mixnet for inclusion in block.
+	#[method(name = "mixnet_submitExtrinsic")]
+	async fn submit_extrinsic(&self, extrinsic: Bytes) -> RpcResult<()>;
+}