<net/bpf.h> defines ioctl codes, so it should include <sys/ioccom.h>, so it doesn't require code that includes <net/bpf.h> to also include <sys/ioccom.h> or a header that includes it. When I originally created <sys/ioccom.h> in SunOS 4.0, I intended it to be included by header files that defined ioctls, rather than by .c files.