Example of how to interpose yourself in a message stream.

chrome/common/external_ipc_fuzzer.cc

+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/common/external_ipc_fuzzer.h"
+
+#if defined(OS_LINUX)
+#include <dlfcn.h>
+#endif
+
+typedef IPC::ChannelProxy::OutgoingMessageFilter *(*GetFuzzerFunction)();
+const char kFuzzLibraryName[] = "libipcfuzz.so";
+const char kFuzzEntryName[] = "GetFilter";
+
+IPC::ChannelProxy::OutgoingMessageFilter* LoadExternalIPCFuzzer() {
+  IPC::ChannelProxy::OutgoingMessageFilter* result = NULL;
+
+#if defined(OS_LINUX)
+
+  // Fuzz is currently linux-only feature
+  void *fuzz_library =  dlopen(kFuzzLibraryName, RTLD_NOW);
+  if (fuzz_library) {
+    GetFuzzerFunction fuzz_entry_point =
+        reinterpret_cast<GetFuzzerFunction>(
+            dlsym(fuzz_library, kFuzzEntryName));
+
+    if (fuzz_entry_point)
+      result = fuzz_entry_point();
+  }
+
+  if (!result)
+    LOG(WARNING) << dlerror() << "\n";
+
+#endif // OS_LINUX
+
+  return result;
+}
+
+
+