pivot wolfcryptified build of wireguard.ko on make WOLFCRYPT=1 (as …

…already for wireguard-tools); tweak compat.h to allow building on kernels >= 5.6.0.

src/Kbuild

@@ -10,11 +10,15 @@ ccflags-$(if $(WIREGUARD_VERSION),y,) += -D'WIREGUARD_VERSION="$(WIREGUARD_VERSI
 
 wireguard-y := main.o noise.o device.o peer.o timers.o queueing.o send.o receive.o socket.o peerlookup.o allowedips.o ratelimiter.o cookie.o netlink.o
 
-# include $(src)/crypto/Kbuild.include
+ifndef WOLFCRYPT
+include $(src)/crypto/Kbuild.include
+endif
 include $(src)/compat/Kbuild.include
 
 obj-$(if $(KBUILD_EXTMOD),m,$(CONFIG_WIREGUARD)) := wireguard.o
 
-ccflags-y += -I$(src)/../../../../wolfssl -include $(src)/wolfcrypto_shim.h
+ifdef WOLFCRYPT
+ccflags-y += -DUSE_WOLFCRYPT -I$(src)/../../../../wolfssl -include $(src)/wolfcrypto_shim.h
 wireguard-y += wolfcrypto_shim.o
 KBUILD_EXTRA_SYMBOLS := $(src)/../../../../wolfssl/linuxkm/Module.symvers
+endif

src/compat/compat.h

@@ -42,9 +42,9 @@
 #error "WireGuard requires Linux >= 3.10"
 #endif
 
-#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 6, 0)
-#error "WireGuard has been merged into Linux >= 5.6 and therefore this compatibility module is no longer required."
-#endif
+/* #if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 6, 0) */
+/* #error "WireGuard has been merged into Linux >= 5.6 and therefore this compatibility module is no longer required." */
+/* #endif */
 
 #if defined(ISRHEL7)
 #include <linux/skbuff.h>
@@ -872,7 +872,7 @@ static inline void skb_mark_not_on_list(struct sk_buff *skb)
 #endif
 #endif
 
-#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 5, 0)
+#if !defined(USE_WOLFCRYPT) && (LINUX_VERSION_CODE >= KERNEL_VERSION(5, 5, 0))
 #define blake2s_init zinc_blake2s_init
 #define blake2s_init_key zinc_blake2s_init_key
 #define blake2s_update zinc_blake2s_update