Make headers usable alone, include the headers they need.
There are probably much more missing.
--- sys/net/if.h.old 2009-05-15 10:51:50 +0000+++ sys/net/if.h 2009-05-15 10:52:05 +0000@@ -34,6 +34,7 @@#define _NET_IF_H_
#include <sys/cdefs.h>
+#include <sys/socket.h>#ifdef _KERNEL
#include <sys/queue.h>