Minor glitch with Ubuntu 18.04: $ gcc --version gcc (Ubuntu 7.3.0-16ubuntu3) 7.3.0
In file included from /usr/include/fcntl.h:290:0, from ../net/bpfilter/main.c:7: In function ‘open’, inlined from ‘main’ at ../net/bpfilter/main.c:58:13: /usr/include/x86_64-linux-gnu/bits/fcntl2.h:50:4: error: call to ‘__open_missing_mode’ declared with attribute error: open with O_CREAT or O_TMPFILE in second argument needs 3 arguments __open_missing_mode (); ^~~~~~~~~~~~~~~~~~~~~~ scripts/Makefile.host:107: recipe for target 'net/bpfilter/main.o' failed make[3]: *** [net/bpfilter/main.o] Error 1 I can't repro on Fedora 27 gcc (GCC) 7.3.1 20180303 (Red Hat 7.3.1-5), perhaps the GCC is broken on that Ubuntu 18.04 box of mine. The warning/ /error, however, looks potentially legit?