-CFLAGS = $(COPTS) $(DEBUG_FLAGS) $(COMPILE_FLAGS)
-SOURCE= RELNOTES Makefile.linux $(PPPDSRCS) $(HEADERS) $(MANPAGES)
+CFLAGS= $(COPTS) $(DEBUG_FLAGS) $(COMPILE_FLAGS)
+
+ifdef USE_MS_DNS
+CFLAGS += -DUSE_MS_DNS=1
+endif
+
+ifdef IPX_CHANGE
+CFLAGS += -DIPX_CHANGE=1
+PPPDOBJS += ipxcp.o
+endif
+
+ifdef HAS_SHADOW
+CFLAGS += -DHAS_SHADOW
+LIBS += -lshadow
+endif