--- a/common/smtppass.c 2017-10-13 16:48:24.662028054 +0200
+++ b/common/smtppass.c 2017-10-13 17:39:57.075904361 +0200
@@ -40,11 +40,15 @@

 #define _GNU_SOURCE

+#include "config.h"
+
 #include <sys/time.h>
 #include <sys/types.h>
-#include <sys/socket.h>
 #include <sys/param.h>
 #include <sys/stat.h>
+#include <sys/socket.h>
+
+#include <netinet/in.h>

 #include <ctype.h>
 #include <stdlib.h>
@@ -61,7 +65,12 @@
 #include "usuals.h"

 #ifdef LINUX_TRANSPARENT_PROXY
+#include <linux/types.h>
 #include <linux/netfilter_ipv4.h>
+#ifdef HAVE_INET6
+#include <linux/if.h>
+#include <linux/netfilter_ipv6/ip6_tables.h>
+#endif
 #endif

 #include "compat.h"
@@ -727,7 +736,7 @@
         thread->fd = -1;
     sp_unlock();

-    return (void*)(ret == 0 ? 0 : 1);
+    return (void*)(ret == 0 ? (size_t)0 : (size_t)1);
 }

 static int make_connections(spctx_t* ctx, int client)