netfilter: Decrease code duplication regarding transparent socket option

There is a function in include/net/netfilter/nf_socket.h to decide if a
socket has IP(V6)_TRANSPARENT socket option set or not. However this
does the same as inet_sk_transparent() in include/net/tcp.h

include/net/tcp.h:1733
/* This helper checks if socket has IP_TRANSPARENT set */
static inline bool inet_sk_transparent(const struct sock *sk)
{
	switch (sk->sk_state) {
	case TCP_TIME_WAIT:
		return inet_twsk(sk)->tw_transparent;
	case TCP_NEW_SYN_RECV:
		return inet_rsk(inet_reqsk(sk))->no_srccheck;
	}
	return inet_sk(sk)->transparent;
}

tproxy_sk_is_transparent has also been refactored to use this function
instead of reimplementing it.
Signed-off-by: Máté Eckl <ecklm94@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/net/netfilter/nf_socket.h

@@ -3,19 +3,6 @@
 #define _NF_SOCK_H_
 
 #include <net/sock.h>
-#include <net/inet_timewait_sock.h>
-
-static inline bool nf_sk_is_transparent(struct sock *sk)
-{
-	switch (sk->sk_state) {
-	case TCP_TIME_WAIT:
-		return inet_twsk(sk)->tw_transparent;
-	case TCP_NEW_SYN_RECV:
-		return inet_rsk(inet_reqsk(sk))->no_srccheck;
-	default:
-		return inet_sk(sk)->transparent;
-	}
-}
 
 struct sock *nf_sk_lookup_slow_v4(struct net *net, const struct sk_buff *skb,
 				  const struct net_device *indev);

net/netfilter/nft_socket.c

@@ -5,6 +5,7 @@
 #include <net/netfilter/nf_tables_core.h>
 #include <net/netfilter/nf_socket.h>
 #include <net/inet_sock.h>
+#include <net/tcp.h>
 
 struct nft_socket {
 	enum nft_socket_keys		key:8;
@@ -48,7 +49,7 @@ static void nft_socket_eval(const struct nft_expr *expr,
 
 	switch(priv->key) {
 	case NFT_SOCKET_TRANSPARENT:
-		nft_reg_store8(dest, nf_sk_is_transparent(sk));
+		nft_reg_store8(dest, inet_sk_transparent(sk));
 		break;
 	default:
 		WARN_ON(1);

net/netfilter/xt_TPROXY.c

@@ -42,19 +42,8 @@ enum nf_tproxy_lookup_t {
 
 static bool tproxy_sk_is_transparent(struct sock *sk)
 {
-	switch (sk->sk_state) {
-	case TCP_TIME_WAIT:
-		if (inet_twsk(sk)->tw_transparent)
+	if (inet_sk_transparent(sk))
 		return true;
-		break;
-	case TCP_NEW_SYN_RECV:
-		if (inet_rsk(inet_reqsk(sk))->no_srccheck)
-			return true;
-		break;
-	default:
-		if (inet_sk(sk)->transparent)
-			return true;
-	}
 
 	sock_gen_put(sk);
 	return false;

net/netfilter/xt_socket.c

@@ -73,7 +73,7 @@ socket_match(const struct sk_buff *skb, struct xt_action_param *par,
 		 * if XT_SOCKET_TRANSPARENT is used
 		 */
 		if (info->flags & XT_SOCKET_TRANSPARENT)
-			transparent = nf_sk_is_transparent(sk);
+			transparent = inet_sk_transparent(sk);
 
 		if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard &&
 		    transparent && sk_fullsock(sk))
@@ -130,7 +130,7 @@ socket_mt6_v1_v2_v3(const struct sk_buff *skb, struct xt_action_param *par)
 		 * if XT_SOCKET_TRANSPARENT is used
 		 */
 		if (info->flags & XT_SOCKET_TRANSPARENT)
-			transparent = nf_sk_is_transparent(sk);
+			transparent = inet_sk_transparent(sk);
 
 		if (info->flags & XT_SOCKET_RESTORESKMARK && !wildcard &&
 		    transparent && sk_fullsock(sk))