Compilation fix for MacOS.
Thanks to Pal Lockheart <ex@palx.org> for the original patch.
diff --git a/src/config.h b/src/config.h
index 99b22eb..f93076d 100644
--- a/src/config.h
+++ b/src/config.h
@@ -273,11 +273,16 @@
#define HAVE_BSD_NETWORK
#define HAVE_GETOPT_LONG
#define HAVE_SOCKADDR_SA_LEN
+#define NO_IPSET
/* Define before sys/socket.h is included so we get socklen_t */
#define _BSD_SOCKLEN_T_
/* Select the RFC_3542 version of the IPv6 socket API.
Define before netinet6/in6.h is included. */
-#define __APPLE_USE_RFC_3542
+#define __APPLE_USE_RFC_3542
+/* Required for Mojave. */
+#ifndef SOL_TCP
+# define SOL_TCP IPPROTO_TCP
+#endif
#define NO_IPSET
#elif defined(__NetBSD__)