-CFLAGS = $(COPTS) $(DEBUG_FLAGS) $(COMPILE_FLAGS)
-SOURCE= RELNOTES Makefile.linux $(PPPDSRCS) $(HEADERS) $(MANPAGES)
+COMPILE_FLAGS= -D_linux_=1 -DHAVE_PATHS_H -DIPX_CHANGE
+
+CFLAGS= $(COPTS) $(COMPILE_FLAGS) $(INCLUDE_DIRS)
+
+ifdef CHAPMS
+CFLAGS += -DCHAPMS=1
+LIBS := -ldes $(LIBS)
+PPPDOBJS += md4.o chap_ms.o
+endif
+
+ifdef HAS_SHADOW
+CFLAGS += -DHAS_SHADOW
+LIBS := -lshadow -lcrypt $(LIBS)
+endif
+
+# For "Pluggable Authentication Modules", see ftp.redhat.com:/pub/pam/.
+ifdef USE_PAM
+CFLAGS += -DUSE_PAM
+LIBS := -lpam -ldl $(LIBS)
+endif
+
+# Lock library binary for Linux is included in 'linux' subdirectory.
+ifdef LOCKLIB
+LIBS := -llock $(LIBS)
+CFLAGS += -DLOCKLIB=1
+endif