multiprocess: Add bitcoin-node process spawning support

Add bitcoin-node startup code to let it spawn and be spawned by other
processes

build_msvc/bitcoind/bitcoind.vcxproj

@@ -10,6 +10,9 @@
   </PropertyGroup>
   <ItemGroup>
     <ClCompile Include="..\..\src\bitcoind.cpp" />
+    <ClCompile Include="..\..\src\init\bitcoind.cpp">
+      <ObjectFileName>$(IntDir)init_bitcoind.obj</ObjectFileName>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\libbitcoinconsensus\libbitcoinconsensus.vcxproj">

src/Makefile.am

@@ -640,13 +640,13 @@ bitcoin_bin_ldadd = \
 
 bitcoin_bin_ldadd += $(BOOST_LIBS) $(BDB_LIBS) $(MINIUPNPC_LIBS) $(NATPMP_LIBS) $(EVENT_PTHREADS_LIBS) $(EVENT_LIBS) $(ZMQ_LIBS) $(SQLITE_LIBS)
 
-bitcoind_SOURCES = $(bitcoin_daemon_sources)
+bitcoind_SOURCES = $(bitcoin_daemon_sources) init/bitcoind.cpp
 bitcoind_CPPFLAGS = $(bitcoin_bin_cppflags)
 bitcoind_CXXFLAGS = $(bitcoin_bin_cxxflags)
 bitcoind_LDFLAGS = $(bitcoin_bin_ldflags)
 bitcoind_LDADD = $(LIBBITCOIN_SERVER) $(bitcoin_bin_ldadd)
 
-bitcoin_node_SOURCES = $(bitcoin_daemon_sources)
+bitcoin_node_SOURCES = $(bitcoin_daemon_sources) init/bitcoin-node.cpp
 bitcoin_node_CPPFLAGS = $(bitcoin_bin_cppflags)
 bitcoin_node_CXXFLAGS = $(bitcoin_bin_cxxflags)
 bitcoin_node_LDFLAGS = $(bitcoin_bin_ldflags)

src/bitcoind.cpp

@@ -12,6 +12,7 @@
 #include <compat.h>
 #include <init.h>
 #include <interfaces/chain.h>
+#include <interfaces/init.h>
 #include <node/context.h>
 #include <node/ui_interface.h>
 #include <noui.h>
@@ -104,10 +105,8 @@ int fork_daemon(bool nochdir, bool noclose, TokenPipeEnd& endpoint)
 
 #endif
 
-static bool AppInit(int argc, char* argv[])
+static bool AppInit(NodeContext& node, int argc, char* argv[])
 {
-    NodeContext node;
-
     bool fRet = false;
 
     util::ThreadSetInternalName("init");
@@ -254,10 +253,18 @@ int main(int argc, char* argv[])
     util::WinCmdLineArgs winArgs;
     std::tie(argc, argv) = winArgs.get();
 #endif
+
+    NodeContext node;
+    int exit_status;
+    std::unique_ptr<interfaces::Init> init = interfaces::MakeNodeInit(node, argc, argv, exit_status);
+    if (!init) {
+        return exit_status;
+    }
+
     SetupEnvironment();
 
     // Connect bitcoind signal handlers
     noui_connect();
 
-    return (AppInit(argc, argv) ? EXIT_SUCCESS : EXIT_FAILURE);
+    return (AppInit(node, argc, argv) ? EXIT_SUCCESS : EXIT_FAILURE);
 }

src/init/bitcoin-node.cpp

@@ -0,0 +1,43 @@
+// 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.
+
+#include <interfaces/init.h>
+#include <interfaces/ipc.h>
+#include <node/context.h>
+
+#include <memory>
+
+namespace init {
+namespace {
+const char* EXE_NAME = "bitcoin-node";
+
+class BitcoinNodeInit : public interfaces::Init
+{
+public:
+    BitcoinNodeInit(NodeContext& node, const char* arg0)
+        : m_node(node),
+          m_ipc(interfaces::MakeIpc(EXE_NAME, arg0, *this))
+    {
+        m_node.init = this;
+    }
+    interfaces::Ipc* ipc() override { return m_ipc.get(); }
+    NodeContext& m_node;
+    std::unique_ptr<interfaces::Ipc> m_ipc;
+};
+} // namespace
+} // namespace init
+
+namespace interfaces {
+std::unique_ptr<Init> MakeNodeInit(NodeContext& node, int argc, char* argv[], int& exit_status)
+{
+    auto init = std::make_unique<init::BitcoinNodeInit>(node, argc > 0 ? argv[0] : "");
+    // Check if bitcoin-node is being invoked as an IPC server. If so, then
+    // bypass normal execution and just respond to requests over the IPC
+    // channel and return null.
+    if (init->m_ipc->startSpawnedProcess(argc, argv, exit_status)) {
+        return nullptr;
+    }
+    return init;
+}
+} // namespace interfaces

src/init/bitcoind.cpp

@@ -0,0 +1,29 @@
+// 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.
+
+#include <interfaces/init.h>
+#include <node/context.h>
+
+#include <memory>
+
+namespace init {
+namespace {
+class BitcoindInit : public interfaces::Init
+{
+public:
+    BitcoindInit(NodeContext& node) : m_node(node)
+    {
+        m_node.init = this;
+    }
+    NodeContext& m_node;
+};
+} // namespace
+} // namespace init
+
+namespace interfaces {
+std::unique_ptr<Init> MakeNodeInit(NodeContext& node, int argc, char* argv[], int& exit_status)
+{
+    return std::make_unique<init::BitcoindInit>(node);
+}
+} // namespace interfaces

src/interfaces/init.h

@@ -31,6 +31,20 @@ public:
     virtual std::unique_ptr<WalletClient> makeWalletClient(Chain& chain);
     virtual Ipc* ipc();
 };
+
+//! Return implementation of Init interface for the node process. If the argv
+//! indicates that this is a child process spawned to handle requests from a
+//! parent process, this blocks and handles requests, then returns null and a
+//! status code to exit with. If this returns non-null, the caller can start up
+//! normally and use the Init object to spawn and connect to other processes
+//! while it is running.
+std::unique_ptr<Init> MakeNodeInit(NodeContext& node, int argc, char* argv[], int& exit_status);
+
+//! Return implementation of Init interface for the wallet process.
+std::unique_ptr<Init> MakeWalletInit(int argc, char* argv[], int& exit_status);
+
+//! Return implementation of Init interface for the gui process.
+std::unique_ptr<Init> MakeGuiInit(int argc, char* argv[]);
 } // namespace interfaces
 
 #endif // BITCOIN_INTERFACES_INIT_H

src/node/context.h

@@ -22,6 +22,7 @@ class PeerManager;
 namespace interfaces {
 class Chain;
 class ChainClient;
+class Init;
 class WalletClient;
 } // namespace interfaces
 
@@ -36,6 +37,8 @@ class WalletClient;
 //! any member functions. It should just be a collection of references that can
 //! be used without pulling in unwanted dependencies or functionality.
 struct NodeContext {
+    //! Init interface for initializing current process and connecting to other processes.
+    interfaces::Init* init{nullptr};
     std::unique_ptr<CAddrMan> addrman;
     std::unique_ptr<CConnman> connman;
     std::unique_ptr<CTxMemPool> mempool;