make: Detect kernel version in Makefile

Makefile

@@ -10,6 +10,9 @@ else
   DEBFLAGS = -Ofast
 endif
 
+KERNEL_VERSION_MAJOR := $(shell uname -r | awk -F '.' '{print $$1}')
+KERNEL_VERSION_MINOR := $(shell uname -r | awk -F '.' '{print $$2}')
+EXTRA_CFLAGS += -D__KERNEL_VERSION_MINOR__=$(KERNEL_VERSION_MINOR)
 EXTRA_CFLAGS += -D__IPC__=$(IPC)
 
 ifeq ($(ONE_PIPE),y)
@@ -19,13 +22,15 @@ endif
 EXTRA_CFLAGS += $(DEBFLAGS)
 EXTRA_CFLAGS += -std=gnu99 -Wno-declaration-after-statement -fgnu89-inline -D__KERNEL__
 
-
 TARGET = ccp
 ccp-objs := libccp/serialize.o libccp/ccp_priv.o libccp/machine.o libccp/ccp.o ccpkp/ccpkp.o ccpkp/lfq/lfq.o tcp_ccp.o ccp_nl.o
 
 obj-m := $(TARGET).o
 
 all:
+ifneq ($(KERNEL_VERSION_MAJOR),4)
+	$(error "Only kernel version 4 is supported: $(KERNEL_VERSION_MAJOR) $(KERNEL_VERSION_MINOR)")
+endif 
 	$(MAKE) -C /lib/modules/$(shell uname -r)/build M=$(CURDIR) modules
 
 clean: