[NETFILTER]: nf_sockopts list head cleanup

Code is using knowledge that nf_sockopt_ops::list list_head is first
field in structure by using casts. Switch to list_for_each_entry()
itetators while I am at it.
Signed-off-by: Alexey Dobriyan <adobriyan@sw.ru>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/netfilter/nf_sockopt.c

@@ -23,14 +23,13 @@ static inline int overlap(int min1, int max1, int min2, int max2)
 /* Functions to register sockopt ranges (exclusive). */
 int nf_register_sockopt(struct nf_sockopt_ops *reg)
 {
-	struct list_head *i;
+	struct nf_sockopt_ops *ops;
 	int ret = 0;
 
 	if (mutex_lock_interruptible(&nf_sockopt_mutex) != 0)
 		return -EINTR;
 
-	list_for_each(i, &nf_sockopts) {
-		struct nf_sockopt_ops *ops = (struct nf_sockopt_ops *)i;
+	list_for_each_entry(ops, &nf_sockopts, list) {
 		if (ops->pf == reg->pf
 		    && (overlap(ops->set_optmin, ops->set_optmax,
 				reg->set_optmin, reg->set_optmax)
@@ -65,7 +64,6 @@ EXPORT_SYMBOL(nf_unregister_sockopt);
 static int nf_sockopt(struct sock *sk, int pf, int val,
 		      char __user *opt, int *len, int get)
 {
-	struct list_head *i;
 	struct nf_sockopt_ops *ops;
 	int ret;
 
@@ -75,8 +73,7 @@ static int nf_sockopt(struct sock *sk, int pf, int val,
 	if (mutex_lock_interruptible(&nf_sockopt_mutex) != 0)
 		return -EINTR;
 
-	list_for_each(i, &nf_sockopts) {
-		ops = (struct nf_sockopt_ops *)i;
+	list_for_each_entry(ops, &nf_sockopts, list) {
 		if (ops->pf == pf) {
 			if (!try_module_get(ops->owner))
 				goto out_nosup;
@@ -124,7 +121,6 @@ EXPORT_SYMBOL(nf_getsockopt);
 static int compat_nf_sockopt(struct sock *sk, int pf, int val,
 			     char __user *opt, int *len, int get)
 {
-	struct list_head *i;
 	struct nf_sockopt_ops *ops;
 	int ret;
 
@@ -135,8 +131,7 @@ static int compat_nf_sockopt(struct sock *sk, int pf, int val,
 	if (mutex_lock_interruptible(&nf_sockopt_mutex) != 0)
 		return -EINTR;
 
-	list_for_each(i, &nf_sockopts) {
-		ops = (struct nf_sockopt_ops *)i;
+	list_for_each_entry(ops, &nf_sockopts, list) {
 		if (ops->pf == pf) {
 			if (!try_module_get(ops->owner))
 				goto out_nosup;