Looks like 4.13 introduces a new incompatibility

[Bruno Wolff III]

On Mon, Jul 10, 2017 at 04:01:04 +0200,
  "Jason A. Donenfeld" <Jason at zx2c4.com> wrote:
>Hey Bruno,
>
>Thanks for the heads up. Does this fix it?
>
>https://git.zx2c4.com/WireGuard/commit/?id=dd007ad550b3def8a858e57aa718af9b00047a28

It looks like it fixed the problem. (At least device.o gets built.) But it 
seems there is another problem.

[bruno at wolff src]$ make clean all
make -C /lib/modules/4.13.0-0.rc0.git3.1.fc27.i686+PAE/build M=/home/bruno/WireGuard/src clean
make[1]: Entering directory '/usr/src/kernels/4.13.0-0.rc0.git3.1.fc27.i686+PAE'
  CLEAN   /home/bruno/WireGuard/src/.tmp_versions
make[1]: Leaving directory '/usr/src/kernels/4.13.0-0.rc0.git3.1.fc27.i686+PAE'
make -C tools clean
make[1]: Entering directory '/home/bruno/WireGuard/src/tools'
rm -f wg *.o *.d
make[1]: Leaving directory '/home/bruno/WireGuard/src/tools'
make -C /lib/modules/4.13.0-0.rc0.git3.1.fc27.i686+PAE/build M=/home/bruno/WireGuard/src modules
make[1]: Entering directory '/usr/src/kernels/4.13.0-0.rc0.git3.1.fc27.i686+PAE'
  CC [M]  /home/bruno/WireGuard/src/main.o
  CC [M]  /home/bruno/WireGuard/src/noise.o
  CC [M]  /home/bruno/WireGuard/src/device.o
  CC [M]  /home/bruno/WireGuard/src/peer.o
  CC [M]  /home/bruno/WireGuard/src/timers.o
  CC [M]  /home/bruno/WireGuard/src/data.o
  CC [M]  /home/bruno/WireGuard/src/send.o
  CC [M]  /home/bruno/WireGuard/src/receive.o
  CC [M]  /home/bruno/WireGuard/src/socket.o
  CC [M]  /home/bruno/WireGuard/src/config.o
  CC [M]  /home/bruno/WireGuard/src/hashtables.o
  CC [M]  /home/bruno/WireGuard/src/routingtable.o
  CC [M]  /home/bruno/WireGuard/src/ratelimiter.o
  CC [M]  /home/bruno/WireGuard/src/cookie.o
/home/bruno/WireGuard/src/cookie.c: In function ‘cookie_message_create’:
/home/bruno/WireGuard/src/cookie.c:156:2: error: implicit declaration of function ‘get_random_bytes_wait’; did you mean ‘get_random_bytes_arch’? [-Werror=implicit-function-declaration]
  get_random_bytes_wait(dst->nonce, COOKIE_NONCE_LEN);
  ^~~~~~~~~~~~~~~~~~~~~
  get_random_bytes_arch
cc1: some warnings being treated as errors
make[2]: *** [scripts/Makefile.build:303: /home/bruno/WireGuard/src/cookie.o] Error 1
make[1]: *** [Makefile:1512: _module_/home/bruno/WireGuard/src] Error 2
make[1]: Leaving directory '/usr/src/kernels/4.13.0-0.rc0.git3.1.fc27.i686+PAE'
make: *** [Makefile:28: module] Error 2