Add support for newer RHEL-based kernels.

Fix several compilation errors being thrown in newer kernels and
remove warnings also in older ones.

Fixes #105.

This code was written by Terry Froy; I'm committing on his behalf.

mod/common/send_packet.c

@@ -72,6 +72,16 @@ verdict sendpkt_send(struct packet *in, struct packet *out)
 	}
 
 #if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 16, 0)
+# define JOOL_SKB_IGNORE_DF
+#else
+# ifdef RHEL_RELEASE_CODE
+#  if RHEL_RELEASE_CODE >= RHEL_RELEASE_VERSION(7, 2)
+#   define JOOL_SKB_IGNORE_DF
+#  endif
+# endif
+#endif
+
+#ifdef JOOL_SKB_IGNORE_DF
 	out->skb->ignore_df = true; /* FFS, kernel. */
 #else
 	out->skb->local_df = true; /* FFS, kernel. */

mod/stateful/fragment_db.c

@@ -71,6 +71,16 @@ static bool equals_function(const struct packet *key1, const struct packet *key2
 }
 
 #if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 13, 0)
+# define JOOL_INET6_HASH_FRAG
+#else
+# ifdef RHEL_RELEASE_CODE
+#  if RHEL_RELEASE_CODE >= RHEL_RELEASE_VERSION(7, 2)
+#   define JOOL_INET6_HASH_FRAG
+#  endif
+# endif
+#endif
+
+#ifdef JOOL_INET6_HASH_FRAG
 /**
  * Hash function for IPv6 keys from reassembly.c
  */

mod/stateful/nf_hook.c

@@ -59,29 +59,61 @@ static char *banner = "\n"
 
 
 #if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 13, 0)
-#define HOOK_ARG_TYPE const struct nf_hook_ops *
+# define HOOK_ARG_TYPE const struct nf_hook_ops *
 #else
-#define HOOK_ARG_TYPE unsigned int
+# ifdef RHEL_RELEASE_CODE
+#  if RHEL_RELEASE_CODE >= RHEL_RELEASE_VERSION(7, 0)
+#   define HOOK_ARG_TYPE const struct nf_hook_ops *
+#  endif
+# endif
+#endif
+
+#ifndef HOOK_ARG_TYPE
+# define HOOK_ARG_TYPE unsigned int
 #endif
 
 static unsigned int hook_ipv4(HOOK_ARG_TYPE hook, struct sk_buff *skb,
 #if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 1, 0)
 		const struct nf_hook_state *state)
-#else
+#elif !defined(RHEL_RELEASE_CODE)
 		const struct net_device *in, const struct net_device *out,
 		int (*okfn)(struct sk_buff *))
 #endif
+
+#ifdef RHEL_RELEASE_CODE
+# if RHEL_RELEASE_CODE >= RHEL_RELEASE_VERSION(7, 0)
+		const struct net_device *in,	
+		const struct net_device *out,
+# endif
+# if RHEL_RELEASE_CODE >= RHEL_RELEASE_VERSION(7, 2)
+		const struct nf_hook_state *state)
+# else
+		int (*okfn)(struct sk_buff *))
+# endif
+#endif
 {
 	return core_4to6(skb, skb->dev);
 }
 
 static unsigned int hook_ipv6(HOOK_ARG_TYPE hook, struct sk_buff *skb,
 #if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 1, 0)
 		const struct nf_hook_state *state)
-#else
+#elif !defined(RHEL_RELEASE_CODE)
 		const struct net_device *in, const struct net_device *out,
 		int (*okfn)(struct sk_buff *))
 #endif
+
+#ifdef RHEL_RELEASE_CODE
+# if RHEL_RELEASE_CODE >= RHEL_RELEASE_VERSION(7, 0)
+		const struct net_device *in,	
+		const struct net_device *out,
+# endif
+# if RHEL_RELEASE_CODE >= RHEL_RELEASE_VERSION(7, 2)
+		const struct nf_hook_state *state)
+# else
+		int (*okfn)(struct sk_buff *))
+# endif
+#endif
 {
 	return core_6to4(skb, skb->dev);
 }

mod/stateless/nf_hook.c

@@ -36,29 +36,61 @@ MODULE_PARM_DESC(disabled, "Disable the translation at the beginning of the modu
 
 
 #if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 13, 0)
-#define HOOK_ARG_TYPE const struct nf_hook_ops *
+# define HOOK_ARG_TYPE const struct nf_hook_ops *
 #else
-#define HOOK_ARG_TYPE unsigned int
+# ifdef RHEL_RELEASE_CODE
+#  if RHEL_RELEASE_CODE >= RHEL_RELEASE_VERSION(7, 0)
+#   define HOOK_ARG_TYPE const struct nf_hook_ops *
+#  endif
+# endif
+#endif
+
+#ifndef HOOK_ARG_TYPE
+# define HOOK_ARG_TYPE unsigned int
 #endif
 
 static unsigned int hook_ipv4(HOOK_ARG_TYPE hook, struct sk_buff *skb,
 #if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 1, 0)
 		const struct nf_hook_state *state)
-#else
+#elif !defined(RHEL_RELEASE_CODE)
 		const struct net_device *in, const struct net_device *out,
 		int (*okfn)(struct sk_buff *))
 #endif
+
+#ifdef RHEL_RELEASE_CODE
+# if RHEL_RELEASE_CODE >= RHEL_RELEASE_VERSION(7, 0)
+		const struct net_device *in,
+		const struct net_device *out,
+# endif
+# if RHEL_RELEASE_CODE >= RHEL_RELEASE_VERSION(7, 2)
+		const struct nf_hook_state *state)
+# else
+		int (*okfn)(struct sk_buff *))
+# endif
+#endif
 {
 	return core_4to6(skb, skb->dev);
 }
 
 static unsigned int hook_ipv6(HOOK_ARG_TYPE hook, struct sk_buff *skb,
 #if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 1, 0)
 		const struct nf_hook_state *state)
-#else
+#elif !defined(RHEL_RELEASE_CODE)
 		const struct net_device *in, const struct net_device *out,
 		int (*okfn)(struct sk_buff *))
 #endif
+
+#ifdef RHEL_RELEASE_CODE
+# if RHEL_RELEASE_CODE >= RHEL_RELEASE_VERSION(7, 0)
+		const struct net_device *in,
+		const struct net_device *out,
+# endif
+# if RHEL_RELEASE_CODE >= RHEL_RELEASE_VERSION(7, 2)
+		const struct nf_hook_state *state)
+# else
+		int (*okfn)(struct sk_buff *))
+# endif
+#endif
 {
 	return core_6to4(skb, skb->dev);
 }