--- a/Makefile.in	2021-05-27 12:57:29.600377496 +0300
+++ b/Makefile.in	2021-05-27 12:58:55.111381725 +0300
@@ -13,7 +13,7 @@
 SNMPTGSO = /usr/lib/snmp/dlmod/snmp_NETFLOW.so
 SNMPCONF = /etc/snmp/snmpd.conf
 SNMPLINE = dlmod netflow $(SNMPTGSO)
-CC = gcc
+CC ?= gcc
 
 # https://www.kernel.org/doc/Documentation/kbuild/modules.txt
 # https://www.kernel.org/doc/Documentation/kbuild/makefiles.txt
@@ -24,31 +24,31 @@
 
 ipt_NETFLOW.ko: version.h ipt_NETFLOW.c ipt_NETFLOW.h compat_def.h compat.h Makefile
 	@echo Compiling $(shell ./version.sh) for kernel $(KVERSION)
-	make -C $(KDIR) M=$(CURDIR) modules
+	$(MAKE) -C $(KDIR) M=$(CURDIR) modules
 	@touch $@
 compat_def.h: gen_compat_def
 	./gen_compat_def > $@
 sparse: | version.h ipt_NETFLOW.c ipt_NETFLOW.h compat.h Makefile
 	@rm -f ipt_NETFLOW.ko ipt_NETFLOW.o
 	@echo Compiling for kernel $(KVERSION)
-	make -C $(KDIR) M=$(CURDIR) modules C=1
+	$(MAKE) -C $(KDIR) M=$(CURDIR) modules C=1
 	@touch ipt_NETFLOW.ko
 coverity:
 	coverity-submit -v
 
 minstall: | ipt_NETFLOW.ko
 	@echo " *"
-	make -C $(KDIR) M=$(CURDIR) modules_install INSTALL_MOD_PATH=$(DESTDIR)
+	$(MAKE) -C $(KDIR) M=$(CURDIR) modules_install INSTALL_MOD_PATH=$(DESTDIR)
 	$(DEPMOD)
 mclean:
-	make -C $(KDIR) M=$(CURDIR) clean
+	$(MAKE) -C $(KDIR) M=$(CURDIR) clean
 lclean:
 	-rm -f *.so *_sh.o
 clean: mclean lclean
 	-rm -f *.so *.o modules.order version.h compat_def.h
 
 snmp_NETFLOW.so: snmp_NETFLOW.c
-	$(CC) -fPIC -shared -o $@ $< -lnetsnmp
+	$(CC) $(CFLAGS) $(LDFLAGS) -fPIC -shared -o $@ $< -lnetsnmp
 
 sinstall: | snmp_NETFLOW.so IPT-NETFLOW-MIB.my
 	@echo " *"
@@ -68,10 +68,10 @@
 	fi
 
 %_sh.o: libipt_NETFLOW.c
-	$(CC) $(CFLAGS) -O2 -Wall -Wunused $(IPTABLES_CFLAGS) -fPIC -o $@ -c libipt_NETFLOW.c
+	$(CC) $(CFLAGS) -Wall -Wunused $(IPTABLES_CFLAGS) -fPIC -o $@ -c libipt_NETFLOW.c
 
 %.so: %_sh.o
-	$(CC) -shared -o $@ $<
+	$(CC) $(LDFLAGS) -shared -o $@ $<
 
 version.h: ipt_NETFLOW.c ipt_NETFLOW.h compat.h Makefile
 	@./version.sh --define > version.h