multiprocess: Add Ipc interface implementation

src/ipc/protocol.h

@@ -0,0 +1,39 @@
+// Copyright (c) 2021 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_IPC_PROTOCOL_H
+#define BITCOIN_IPC_PROTOCOL_H
+
+#include <interfaces/init.h>
+
+#include <functional>
+#include <memory>
+#include <typeindex>
+
+namespace ipc {
+//! IPC protocol interface for calling IPC methods over sockets.
+//!
+//! There may be different implementations of this interface for different IPC
+//! protocols (e.g. Cap'n Proto, gRPC, JSON-RPC, or custom protocols).
+class Protocol
+{
+public:
+    virtual ~Protocol() = default;
+
+    //! Return Init interface that forwards requests over given socket descriptor.
+    //! Socket communication is handled on a background thread.
+    virtual std::unique_ptr<interfaces::Init> connect(int fd, const char* exe_name) = 0;
+
+    //! Handle requests on provided socket descriptor, forwarding them to the
+    //! provided Init interface. Socket communication is handled on the
+    //! current thread, and this call blocks until the socket is closed.
+    virtual void serve(int fd, const char* exe_name, interfaces::Init& init) = 0;
+
+    //! Add cleanup callback to interface that will run when the interface is
+    //! deleted.
+    virtual void addCleanup(std::type_index type, void* iface, std::function<void()> cleanup) = 0;
+};
+} // namespace ipc
+
+#endif // BITCOIN_IPC_PROTOCOL_H