Mine

diff -rN -u old-farsight-working/farsight/helpers/farsight-interfaces.c new-farsight-working/farsight/helpers/farsight-interfaces.c
--- old-farsight-working/farsight/helpers/farsight-interfaces.c 2006-08-11 16:11:25.000000000 +0200
+++ new-farsight-working/farsight/helpers/farsight-interfaces.c 2006-08-11 16:11:25.000000000 +0200
@@ -30,6 +30,9 @@
 #include <errno.h>
 #include <sys/ioctl.h>
 #include <sys/types.h>
+#if defined(__APPLE__) && defined(__MACH__)
+#include <sys/socket.h>
+#endif
 #include <net/if.h>
 #include <net/if_arp.h>
 #include <arpa/inet.h>