Add deferred plugin support

Makefile

@@ -0,0 +1,24 @@
+CC		:= gcc
+CFLAGS	:=
+LDFLAGS	:= -fPIC -shared
+INSTALL	:= install
+DESTDIR	:= /
+PREFIX	:= /usr/
+
+all: plugin
+
+plugin: netfilter_openvpn.c
+	$(CC) $(CFLAGS) $(LDFLAGS) -I. -c netfilter_openvpn.c
+	$(CC) $(CFLAGS) $(LDFLAGS) -Wl,-soname,netfilter_openvpn.so -o netfilter_openvpn.so netfilter_openvpn.o
+
+install: plugin
+	mkdir -p $(DESTDIR)$(PREFIX)/lib/openvpn/plugins/
+	$(INSTALL) -m755 netfilter_openvpn.so $(DESTDIR)$(PREFIX)/lib/openvpn/plugins/
+	$(INSTALL) -m755 netfilter.py $(DESTDIR)$(PREFIX)/lib/openvpn/plugins/
+	$(INSTALL) -m600 duo_openvpn.conf.inc $(DESTDIR)/etc/duo_openvpn.conf
+
+clean:
+	rm -f *.o
+	rm -f *.so
+	rm -f *.pyc
+	rm -rf __pycache__