Read more about kernel namespaces and decided to go ahead with seperate object files

src/Makefile

@@ -3,6 +3,7 @@ MODULES_DIR := /lib/modules/$(shell uname -r)
 KERNEL_DIR := ${MODULES_DIR}/build
 
 obj-m += xt_ts3init.o
+xt_ts3init-objs += ts3init_module.o ts3init_match.o ts3init_cookie.o siphash24.o
 
 all:
 	make -C ${KERNEL_DIR} M=$$PWD;

src/ts3init_cookie.c

@@ -62,7 +62,7 @@ static void check_update_seed_cache(time_t time, __u8 index,
     crypto_free_hash(desc.tfm);
 }
 
-static __u8* get_cookie_seed(time_t current_time, __u8 packet_index, 
+__u8* get_cookie_seed(time_t current_time, __u8 packet_index, 
                 struct xt_ts3init_cookie_cache* cache,
                 const __u8* cookie_seed)
 {

src/ts3init_cookie.h

@@ -12,4 +12,8 @@ struct xt_ts3init_cookie_cache
     __u8 __attribute__((aligned(8))) seed[SHA512_SIZE*2];
 };
 
+__u8* get_cookie_seed(time_t current_time, __u8 packet_index, 
+                struct xt_ts3init_cookie_cache* cache,
+                const __u8* cookie_seed);
+
 #endif /* _TS3INIT_COOKIE_H */

src/ts3init_match.c

@@ -280,3 +280,12 @@ static struct xt_match ts3init_mt_reg[] __read_mostly = {
     },
 };
 
+int __init ts3init_match_init(void)
+{
+    return xt_register_matches(ts3init_mt_reg, ARRAY_SIZE(ts3init_mt_reg));
+}
+
+void __exit ts3init_match_exit(void)
+{
+    xt_unregister_matches(ts3init_mt_reg, ARRAY_SIZE(ts3init_mt_reg));
+}

src/ts3init_module.c

@@ -2,9 +2,8 @@
  *    "ts3init" extension for Xtables
  *
  *    Description: A module to aid in ts3 spoof protection
- *                 This file just includes the actual code files so that
- *                 we do not have to export unneed symbols to the kernel
- *                 while stil organizing code into logical files.
+ *                 This file sets up the module load and remove functions
+ *                 and module meta data.
  *
  *    Authors:
  *    Niels Werensteijn <niels werensteijn [at] teampseak com>, 2016-10-03
@@ -14,9 +13,12 @@
  *    or 3 of the License, as published by the Free Software Foundation.
  */
 
-#include "siphash24.c"
-#include "ts3init_cookie.c"
-#include "ts3init_match.c"
+#include <linux/kernel.h>
+#include <linux/netfilter/x_tables.h>
+
+/* defined in ts3init_match.c */
+int __init ts3init_match_init(void);
+void __exit ts3init_match_exit(void);
 
 MODULE_AUTHOR("Niels Werensteijn <niels.werensteijn@teamspeak.com>");
 MODULE_DESCRIPTION("A module to aid in ts3 spoof protection");
@@ -24,15 +26,15 @@ MODULE_LICENSE("GPL");
 MODULE_ALIAS("ipt_ts3init");
 MODULE_ALIAS("ip6t_ts3init");
 
-static int __init ts3init_mt_init(void)
+static int __init ts3init_init(void)
 {
-    return xt_register_matches(ts3init_mt_reg, ARRAY_SIZE(ts3init_mt_reg));
+    return ts3init_match_init();
 }
 
-static void __exit ts3init_mt_exit(void)
+static void __exit ts3init_exit(void)
 {
-    xt_unregister_matches(ts3init_mt_reg, ARRAY_SIZE(ts3init_mt_reg));
+    ts3init_match_exit();
 }
 
-module_init(ts3init_mt_init);
-module_exit(ts3init_mt_exit);
+module_init(ts3init_init);
+module_exit(ts3init_exit);