plugins/ndpi: stub in dummy ndpi plugin

This plugin stub shows how a plugin like nDPI might be use the flow
init and flow update callbacks to do its work. Also shows usage of
FlowStorage to avoid modifying the Flow struct directly.

configure.ac

@@ -2293,6 +2293,19 @@ fi
     ])
     AC_SUBST(RUST_FEATURES)
 
+# nDPI support (no library checks for this stub)
+    AC_ARG_ENABLE(ndpi,
+           AS_HELP_STRING([--enable-ndpi], [Enable nDPI support]),
+           [enable_ndpi=$enableval],[enable_ndpi=no])
+    if test "x$enable_ndpi" = "xyes"; then
+        AM_CONDITIONAL([BUILD_NDPI], [true])
+        ndpi_comment=""
+    else
+        AM_CONDITIONAL([BUILD_NDPI], [false])
+        ndpi_comment="#"
+    fi
+    AC_SUBST([ndpi_comment])
+
     AC_ARG_ENABLE(warnings,
            AS_HELP_STRING([--enable-warnings], [Enable supported C compiler warnings]),[enable_warnings=$enableval],[enable_warnings=no])
     AS_IF([test "x$enable_warnings" = "xyes"], [
@@ -2513,6 +2526,7 @@ AC_CONFIG_FILES(examples/plugins/ci-capture/Makefile)
 AC_CONFIG_FILES(examples/lib/simple/Makefile examples/lib/simple/Makefile.example)
 AC_CONFIG_FILES(plugins/Makefile)
 AC_CONFIG_FILES(plugins/pfring/Makefile)
+AC_CONFIG_FILES(plugins/ndpi-dummy/Makefile)
 
 AC_OUTPUT
 

plugins/Makefile.am

@@ -3,3 +3,7 @@ SUBDIRS =
 if BUILD_PFRING
 SUBDIRS += pfring
 endif
+
+if BUILD_NDPI
+SUBDIRS += ndpi-dummy
+endif

plugins/ndpi-dummy/Makefile.am

@@ -0,0 +1,8 @@
+pkglib_LTLIBRARIES = ndpi.la
+
+ndpi_la_LDFLAGS = -module -avoid-version -shared
+
+ndpi_la_SOURCES = ndpi.c
+
+install-exec-hook:
+	cd $(DESTDIR)$(pkglibdir) && $(RM) $(pkglib_LTLIBRARIES)

plugins/ndpi-dummy/ndpi.c

@@ -0,0 +1,84 @@
+/* Copyright (C) 2024 Open Information Security Foundation
+ *
+ * You can copy, redistribute or modify this Program under the terms of
+ * the GNU General Public License version 2 as published by the Free
+ * Software Foundation.
+ *
+ * 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
+ * version 2 along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+/* License note: While this "glue" code to the nDPI library is GPLv2,
+ * nDPI is itself LGPLv3 which is known to be incompatible with the
+ * GPLv2. */
+
+#include "suricata-common.h"
+#include "suricata-plugin.h"
+#include "util-debug.h"
+
+#include "flow-callbacks.h"
+#include "flow-storage.h"
+
+static FlowStorageId flow_storage_id = { .id = -1 };
+
+static void *FlowStorageAlloc(unsigned int size)
+{
+    SCLogNotice("Allocating nDPI flow storage, size=%d", size);
+    return NULL;
+}
+
+static void FlowStorageFree(void *ptr)
+{
+    SCLogNotice("De-allocating nDPI flow storage");
+    int *dummy_storage = ptr;
+    SCLogNotice("%d", *dummy_storage);
+    SCFree(ptr);
+}
+
+static void OnFlowInit(Flow *f, const Packet *p)
+{
+    SCLogNotice("...");
+    static int counter = 0;
+    int *dummy_storage = SCCalloc(1, sizeof(int));
+    *dummy_storage = counter++;
+    FlowSetStorageById(f, flow_storage_id, dummy_storage);
+}
+
+static void OnFlowUpdate(Flow *f, Packet *p, ThreadVars *tv)
+{
+    SCLogNotice("...");
+    int *dummy_storage = FlowGetStorageById(f, flow_storage_id);
+    SCLogNotice("dummy_storage=%d", *dummy_storage);
+}
+
+static void NdpiInit(void)
+{
+    SCLogNotice("Initializing nDPI plugin");
+
+    flow_storage_id = FlowStorageRegister("ndpi", sizeof(void *), NULL, FlowStorageFree);
+    if (flow_storage_id.id < 0) {
+        FatalError("Failed to register nDPI flow storage");
+    }
+
+    SCFlowRegisterInitCallback(OnFlowInit);
+    SCFlowRegisterUpdateCallback(OnFlowUpdate);
+}
+
+const SCPlugin PluginRegistration = {
+    .name = "ndpi-dummy",
+    .author = "FirstName LastName",
+    .license = "GPLv2",
+    .Init = NdpiInit,
+};
+
+const SCPlugin *SCPluginRegister()
+{
+    return &PluginRegistration;
+}

suricata.yaml.in

@@ -81,6 +81,7 @@ stats:
 # Plugins -- Experimental -- specify the filename for each plugin shared object
 plugins:
   @pfring_comment@- @prefix@/lib/@PACKAGE_NAME@/pfring.so
+  @ndpi_comment@- @prefix@/lib/@PACKAGE_NAME@/ndpi.so
 # - /path/to/plugin.so
 
 # Configure the type of alert (and other) logging you would like.