examples/plugin: simplify Makefile

Simplify the Makefile by avoiding automake and providing our own
Makefile.in that is suitable for in-tree builds of the plugin and can
also serve as an example for standalone plugins.

But the bigger benefit of this is to allow building the example plugin
even with --disable-shared provided to configure, as this is just a
phony limitation imposed by automake/libtool.

.github/workflows/builds.yml

@@ -295,14 +295,24 @@ jobs:
         working-directory: examples/plugins/c-json-filetype
         run: make
       - name: Check C json filetype plugin
-        run: test -e examples/plugins/c-json-filetype/.libs/json-filetype.so.0.0.0
+        run: test -e examples/plugins/c-json-filetype/filetype.so
       - name: Installing headers and library
         run: |
           make install-headers
           make install-library
-      - name: Test plugin build with Makefile.example
+      - name: Cleaning source directory for standalone plugin test.
+        run: make clean
+      - name: Test plugin against installed headers
         working-directory: examples/plugins/c-json-filetype
-        run: PATH=/usr/local/bin:$PATH make -f Makefile.example
+        run: |
+          # First use sed to pretend we are q user following our
+          # directions for building a standalone plugin.
+          sed -i 's/^#LIBSURICATA_CONFIG/LIBSURICATA_CONFIG/' Makefile
+          sed -i 's/^#CPPFLAGS/CPPFLAGS/' Makefile
+          sed -i 's/^CPPFLAGS.*HAVE_CONFIG_H//' Makefile
+
+          # And build.
+          PATH=/usr/local/bin:$PATH make
 
   almalinux-9-templates:
     name: AlmaLinux 9 Test Templates

Makefile.am

@@ -7,10 +7,10 @@ EXTRA_DIST = ChangeLog COPYING LICENSE suricata.yaml.in \
              $(SURICATA_UPDATE_DIR) \
 	     lua \
 	     acsite.m4 \
-	     scripts/generate-images.sh
+	     scripts/generate-images.sh \
+	     examples
 SUBDIRS = $(HTP_DIR) rust src qa rules doc contrib etc python ebpf \
           $(SURICATA_UPDATE_DIR)
-DIST_SUBDIRS = examples/plugins/c-json-filetype $(SUBDIRS)
 
 CLEANFILES = stamp-h[0-9]*
 

examples/plugins/c-json-filetype/.gitignore

@@ -1,2 +1,3 @@
+!/Makefile.in
 *.so
 *.la

examples/plugins/c-json-filetype/Makefile.am

@@ -1,17 +0,0 @@
-plugindir = ${libdir}/suricata/plugins
-
-if BUILD_SHARED_LIBRARY
-plugin_LTLIBRARIES = json-filetype.la
-json_filetype_la_LDFLAGS = -module -shared
-json_filetype_la_SOURCES = filetype.c
-
-json_filetype_la_CPPFLAGS = -I$(abs_top_srcdir)/rust/gen -I$(abs_top_srcdir)/rust/dist
-
-else
-
-all-local:
-	@echo
-	@echo "Shared library support must be enabled to build plugins."
-	@echo
-
-endif

examples/plugins/c-json-filetype/Makefile.example

@@ -1,18 +0,0 @@
-SRCS :=		filetype.c
-
-LIBSURICATA_CONFIG ?= libsuricata-config
-
-CPPFLAGS +=	`$(LIBSURICATA_CONFIG) --cflags`
-CPPFLAGS +=	-DSURICATA_PLUGIN -I.
-CPPFLAGS +=	"-D__SCFILENAME__=\"$(*F)\""
-
-OBJS :=		$(SRCS:.c=.o)
-
-filetype.so: $(OBJS)
-	$(CC) -fPIC -shared -o $@ $(OBJS)
-
-%.o: %.c
-	$(CC) -fPIC $(CPPFLAGS) -c -o $@ $<
-
-clean:
-	rm -f *.o *.so *~

examples/plugins/c-json-filetype/Makefile.in

@@ -0,0 +1,32 @@
+# If building a plugin out of the Suricata source tree, you can use
+# libsuricata-config --cflags.
+#LIBSURICATA_CONFIG ?=	libsuricata-config
+#CPPFLAGS +=		`$(LIBSURICATA_CONFIG) --cflags`
+
+# But as this is an example in the Suricata source tree we'll look for
+# includes in the source tree.
+CPPFLAGS +=	-I@top_srcdir@/src -DHAVE_CONFIG_H
+
+# Currently the Suricata logging system requires this to be even for
+# plugins.
+CPPFLAGS +=    "-D__SCFILENAME__=\"$(*F)\""
+
+all: Makefile filetype.so
+
+filetype.so: filetype.c
+	$(CC) $(CPPFLAGS) -fPIC -shared -o $@ $^
+
+clean:
+	rm -f *.so *.o *.lo
+	rm -rf .deps
+
+distclean: clean
+	rm -f Makefile.am
+
+# Regenerate Makefile on change of Makefile.in since we're not using
+# Makefile.am.
+Makefile: Makefile.in
+	cd @top_builddir@ && ./config.status examples/plugins/c-json-filetype/Makefile
+
+# Dummy rules to satisfy make dist.
+dist distdir:

examples/plugins/c-json-filetype/README.md

@@ -3,16 +3,14 @@
 ## Building
 
 If in the Suricata source directory, this plugin can be built by
-running `make` and installed with `make install`.
-
-Note that Suricata must have been built without `--disable-shared`.
+running `make`.
 
 ## Building Standalone
 
-The file `Makefile.example` is an example of how you might build a
-plugin that is distributed separately from the Suricata source code.
+This Makefile is not generated by automake so it can serve as an
+example for plugins created outside of the Suricata source tree.
 
-It has the following dependencies:
+Building a standalone plugin has the following dependencies:
 
 - Suricata is installed
 - The Suricata library is installed: `make install-library`
@@ -20,7 +18,7 @@ It has the following dependencies:
 - The program `libsuricata-config` is in your path (installed with
   `make install-library`)
 
-The run: `make -f Makefile.example`
+Modify the Makefile to use `libsuricata-config`.
 
 Before building this plugin you will need to build and install Suricata from the
 git master branch and install the development tools and headers: