Add barebones IPC framework to bitcoin-qt and bitcoind

This adds some IPC functions and classes in src/ipc/ that let bitcoin-qt fork a bitcoind process and communicate with it over a socketpair. Only a handful of IPC calls are implemented, but this demonstrates a working framework supporting bidirectional IPC calls (requests from bitcoin-qt to bitcoind and notifications from bitcoind to bitcoin-qt). The IPC protocol used in this implementation is Cap'n Proto (https://capnproto.org/), but this could be swapped out for another protocol. Can'n Proto types and libraries are only accessed in ipc/server.cpp and ipc/client.cpp, and not in any headers or other parts of bitcoin code.
bitcoin · Apr 3, 2017 · 0ca73bc · 0ca73bc
1 parent 29efc39
commit 0ca73bc
Show file tree

Hide file tree

Showing 37 changed files with 1,939 additions and 128 deletions.
diff --git a/configure.ac b/configure.ac
@@ -1111,6 +1111,7 @@ AM_CONDITIONAL([USE_LCOV],[test x$use_lcov = xyes])
 AM_CONDITIONAL([GLIBC_BACK_COMPAT],[test x$use_glibc_compat = xyes])
 AM_CONDITIONAL([HARDEN],[test x$use_hardening = xyes])
 
+AC_DEFINE_UNQUOTED(BITCOIN_DAEMON_NAME, "$BITCOIN_DAEMON_NAME", [Base name of bitcoind executable])
 AC_DEFINE(CLIENT_VERSION_MAJOR, _CLIENT_VERSION_MAJOR, [Major version])
 AC_DEFINE(CLIENT_VERSION_MINOR, _CLIENT_VERSION_MINOR, [Minor version])
 AC_DEFINE(CLIENT_VERSION_REVISION, _CLIENT_VERSION_REVISION, [Build revision])

diff --git a/src/Makefile.am b/src/Makefile.am
@@ -102,6 +102,12 @@ BITCOIN_CORE_H = \
   httpserver.h \
   indirectmap.h \
   init.h \
+  ipc/client.h \
+  ipc/interfaces.h \
+  ipc/messages.capnp.h \
+  ipc/serialize.h \
+  ipc/server.h \
+  ipc/util.h \
   key.h \
   keystore.h \
   dbwrapper.h \
@@ -173,7 +179,7 @@ obj/build.h: FORCE
 libbitcoin_util_a-clientversion.$(OBJEXT): obj/build.h
 
 # server: shared between bitcoind and bitcoin-qt
-libbitcoin_server_a_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) $(MINIUPNPC_CPPFLAGS) $(EVENT_CFLAGS) $(EVENT_PTHREADS_CFLAGS)
+libbitcoin_server_a_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) $(MINIUPNPC_CPPFLAGS) $(EVENT_CFLAGS) $(EVENT_PTHREADS_CFLAGS) $(CAPNP_RPC_CFLAGS)
 libbitcoin_server_a_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 libbitcoin_server_a_SOURCES = \
   addrman.cpp \
@@ -326,6 +332,13 @@ libbitcoin_util_a_SOURCES = \
   compat/glibc_sanity.cpp \
   compat/glibcxx_sanity.cpp \
   compat/strnlen.cpp \
+  ipc/client.cpp \
+  ipc/interfaces.cpp \
+  ipc/messages.capnp \
+  ipc/messages.capnp.c++ \
+  ipc/serialize.cpp \
+  ipc/server.cpp \
+  ipc/util.cpp \
   random.cpp \
   rpc/protocol.cpp \
   support/cleanse.cpp \
@@ -374,7 +387,7 @@ bitcoind_LDADD = \
   $(LIBMEMENV) \
   $(LIBSECP256K1)
 
-bitcoind_LDADD += $(BOOST_LIBS) $(BDB_LIBS) $(SSL_LIBS) $(CRYPTO_LIBS) $(MINIUPNPC_LIBS) $(EVENT_PTHREADS_LIBS) $(EVENT_LIBS) $(ZMQ_LIBS)
+bitcoind_LDADD += $(BOOST_LIBS) $(BDB_LIBS) $(SSL_LIBS) $(CRYPTO_LIBS) $(MINIUPNPC_LIBS) $(EVENT_PTHREADS_LIBS) $(EVENT_LIBS) $(ZMQ_LIBS) $(CAPNP_RPC_LIBS)
 
 # bitcoin-cli binary #
 bitcoin_cli_SOURCES = bitcoin-cli.cpp

diff --git a/src/Makefile.qt.include b/src/Makefile.qt.include
@@ -409,7 +409,7 @@ qt_bitcoin_qt_LDADD += $(LIBBITCOIN_ZMQ) $(ZMQ_LIBS)
 endif
 qt_bitcoin_qt_LDADD += $(LIBBITCOIN_CLI) $(LIBBITCOIN_COMMON) $(LIBBITCOIN_UTIL) $(LIBBITCOIN_CONSENSUS) $(LIBBITCOIN_CRYPTO) $(LIBUNIVALUE) $(LIBLEVELDB) $(LIBMEMENV) \
   $(BOOST_LIBS) $(QT_LIBS) $(QT_DBUS_LIBS) $(QR_LIBS) $(PROTOBUF_LIBS) $(BDB_LIBS) $(SSL_LIBS) $(CRYPTO_LIBS) $(MINIUPNPC_LIBS) $(LIBSECP256K1) \
-  $(EVENT_PTHREADS_LIBS) $(EVENT_LIBS)
+  $(EVENT_PTHREADS_LIBS) $(EVENT_LIBS) $(CAPNP_RPC_LIBS)
 qt_bitcoin_qt_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(QT_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
 qt_bitcoin_qt_LIBTOOLFLAGS = --tag CXX
 

diff --git a/src/Makefile.qttest.include b/src/Makefile.qttest.include
@@ -61,7 +61,7 @@ endif
 qt_test_test_bitcoin_qt_LDADD += $(LIBBITCOIN_CLI) $(LIBBITCOIN_COMMON) $(LIBBITCOIN_UTIL) $(LIBBITCOIN_CONSENSUS) $(LIBBITCOIN_CRYPTO) $(LIBUNIVALUE) $(LIBLEVELDB) \
   $(LIBMEMENV) $(BOOST_LIBS) $(QT_DBUS_LIBS) $(QT_TEST_LIBS) $(QT_LIBS) \
   $(QR_LIBS) $(PROTOBUF_LIBS) $(BDB_LIBS) $(SSL_LIBS) $(CRYPTO_LIBS) $(MINIUPNPC_LIBS) $(LIBSECP256K1) \
-  $(EVENT_PTHREADS_LIBS) $(EVENT_LIBS)
+  $(EVENT_PTHREADS_LIBS) $(EVENT_LIBS) $(CAPNP_RPC_LIBS)
 qt_test_test_bitcoin_qt_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(QT_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
 qt_test_test_bitcoin_qt_CXXFLAGS = $(AM_CXXFLAGS) $(QT_PIE_FLAGS)
 

diff --git a/src/bitcoind.cpp b/src/bitcoind.cpp
@@ -12,6 +12,7 @@
 #include "compat.h"
 #include "rpc/server.h"
 #include "init.h"
+#include "ipc/server.h"
 #include "noui.h"
 #include "scheduler.h"
 #include "util.h"
@@ -188,6 +189,13 @@ bool AppInit(int argc, char* argv[])
 
 int main(int argc, char* argv[])
 {
+    // Check if bitcoind is being invoked as an IPC server. If so, then bypass
+    // normal execution and just respond to requests from the IPC channel.
+    int exitStatus;
+    if (ipc::StartServer(argc, argv, exitStatus)) {
+        return exitStatus;
+    }
+
     SetupEnvironment();
 
     // Connect bitcoind signal handlers

diff --git a/src/ipc/README.md b/src/ipc/README.md
@@ -0,0 +1,52 @@
+Bitcoin Interprocess Communication
+==================================
+
+The IPC functions and classes in `src/ipc/` allow the `bitcoin-qt` process to
+fork a `bitcoind` process and communicate with it over a socketpair. This gives
+`bitcoin-qt` a code a bit of modularity, avoiding a monolithic architecture
+where UI, P2P, wallet, consensus, and database code all runs in a single
+process.
+
+In the future, the IPC mechanism could be extended to allow other subdivisions
+of functionality. For example, wallet code could run in a separate process from
+P2P code. Also in the future, IPC sockets could also be exposed more publicly.
+For example, exposed IPC server sockets could allow a `bitcoin-qt` process to
+control a `bitcoind` process other than the one it spawns internally. These
+changes would be straightforward to implement, but would create security,
+backwards-compatibility, complexity, and maintainablity concerns, so would
+require further discussion.
+
+The IPC protocol used is [Cap'n Proto](https://capnproto.org/), but the protocol
+could be swapped out for another protocol (such as JSON-RPC with long polling)
+without changing any code outside of the `src/ipc/` directory. No Cap'n Proto
+types are used or headers included in any public interface.
+
+Here are the important files in the `src/ipc/` directory:
+
+Public Interfaces
+-----------------
+
+* `interfaces.h` – `Node`, `Wallet`, `Handler` interface definitions
+
+* `client.h` – `StartClient` function to spawn a `bitcoind` process and
+                return a `Node` object controlling it through a socketpair.
+
+* `server.h` – `StartServer` function to allow a `bitcoind` process to
+                open a socket file descriptor and respond to remote commands.
+
+Other Files
+-----------
+
+* `interfaces.cpp – In-process implementations of `Node`, `Wallet`, `Handler`
+                    interfaces.
+
+* `client.cpp – IPC implementations of `Node`, `Wallet`, `Handler`
+                interfaces that forward calls to a socket.
+
+* `server.cpp – IPC implementation responding to client requests.
+
+* `messages.capnp – IPC interface definition.
+
+* `serialize.{h,cpp}` – Helper functions for translating IPC messages.
+
+* `util.{h,cpp}` – Helper functions for making and receiving IPC calls.