[NETFILTER]: x_tables: semi-rewrite of /proc/net/foo_tables_*

There are many small but still wrong things with /proc/net/*_tables_*
so I decided to do overhaul simultaneously making it more suitable for
per-netns /proc/net/*_tables_* implementation.

Fix
a) xt_get_idx() duplicating now standard seq_list_start/seq_list_next
   iterators
b) tables/matches/targets list was chosen again and again on every ->next
c) multiple useless "af >= NPROTO" checks -- we simple don't supply invalid
   AFs there and registration function should BUG_ON instead.

   Regardless, the one in ->next() is the most useless -- ->next doesn't
   run at all if ->start fails.
d) Don't use mutex_lock_interruptible() -- it can fail and ->stop is
   executed even if ->start failed, so unlock without lock is possible.

As side effect, streamline code by splitting xt_tgt_ops into xt_target_ops,
xt_matches_ops, xt_tables_ops.

xt_tables_ops hooks will be changed by per-netns code. Code of
xt_matches_ops, xt_target_ops is identical except the list chosen for
iterating, but I think consolidating code for two files not worth it
given "<< 16" hacks needed for it.

[Patrick: removed unused enum in x_tables.c]
Signed-off-by: NAlexey Dobriyan <adobriyan@sw.ru>
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/netfilter/x_tables.c

@@ -58,12 +58,6 @@ static struct xt_af *xt;
 #define duprintf(format, args...)
 #endif
 
-enum {
-	TABLE,
-	TARGET,
-	MATCH,
-};
-
 static const char *xt_prefix[NPROTO] = {
 	[AF_INET]	= "ip",
 	[AF_INET6]	= "ip6",
@@ -726,124 +720,190 @@ void *xt_unregister_table(struct xt_table *table)
 EXPORT_SYMBOL_GPL(xt_unregister_table);
 
 #ifdef CONFIG_PROC_FS
-static struct list_head *xt_get_idx(struct list_head *list, struct seq_file *seq, loff_t pos)
+static void *xt_table_seq_start(struct seq_file *seq, loff_t *pos)
 {
-	struct list_head *head = list->next;
+	struct proc_dir_entry *pde = (struct proc_dir_entry *)seq->private;
+	u_int16_t af = (unsigned long)pde->data;
 
-	if (!head || list_empty(list))
-		return NULL;
+	mutex_lock(&xt[af].mutex);
+	return seq_list_start(&init_net.xt.tables[af], *pos);
+}
 
-	while (pos && (head = head->next)) {
-		if (head == list)
-			return NULL;
-		pos--;
-	}
-	return pos ? NULL : head;
-}
-
-static struct list_head *type2list(u_int16_t af, u_int16_t type)
-{
-	struct list_head *list;
-
-	switch (type) {
-	case TARGET:
-		list = &xt[af].target;
-		break;
-	case MATCH:
-		list = &xt[af].match;
-		break;
-	case TABLE:
-		list = &init_net.xt.tables[af];
-		break;
-	default:
-		list = NULL;
-		break;
-	}
+static void *xt_table_seq_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+	struct proc_dir_entry *pde = (struct proc_dir_entry *)seq->private;
+	u_int16_t af = (unsigned long)pde->data;
 
-	return list;
+	return seq_list_next(v, &init_net.xt.tables[af], pos);
 }
 
-static void *xt_tgt_seq_start(struct seq_file *seq, loff_t *pos)
+static void xt_table_seq_stop(struct seq_file *seq, void *v)
 {
-	struct proc_dir_entry *pde = (struct proc_dir_entry *) seq->private;
-	u_int16_t af = (unsigned long)pde->data & 0xffff;
-	u_int16_t type = (unsigned long)pde->data >> 16;
-	struct list_head *list;
+	struct proc_dir_entry *pde = seq->private;
+	u_int16_t af = (unsigned long)pde->data;
 
-	if (af >= NPROTO)
-		return NULL;
+	mutex_unlock(&xt[af].mutex);
+}
 
-	list = type2list(af, type);
-	if (!list)
-		return NULL;
+static int xt_table_seq_show(struct seq_file *seq, void *v)
+{
+	struct xt_table *table = list_entry(v, struct xt_table, list);
 
-	if (mutex_lock_interruptible(&xt[af].mutex) != 0)
-		return NULL;
+	if (strlen(table->name))
+		return seq_printf(seq, "%s\n", table->name);
+	else
+		return 0;
+}
 
-	return xt_get_idx(list, seq, *pos);
+static const struct seq_operations xt_table_seq_ops = {
+	.start	= xt_table_seq_start,
+	.next	= xt_table_seq_next,
+	.stop	= xt_table_seq_stop,
+	.show	= xt_table_seq_show,
+};
+
+static int xt_table_open(struct inode *inode, struct file *file)
+{
+	int ret;
+
+	ret = seq_open(file, &xt_table_seq_ops);
+	if (!ret) {
+		struct seq_file *seq = file->private_data;
+
+		seq->private = PDE(inode);
+	}
+	return ret;
 }
 
-static void *xt_tgt_seq_next(struct seq_file *seq, void *v, loff_t *pos)
+static const struct file_operations xt_table_ops = {
+	.owner	 = THIS_MODULE,
+	.open	 = xt_table_open,
+	.read	 = seq_read,
+	.llseek	 = seq_lseek,
+	.release = seq_release,
+};
+
+static void *xt_match_seq_start(struct seq_file *seq, loff_t *pos)
 {
-	struct proc_dir_entry *pde = seq->private;
-	u_int16_t af = (unsigned long)pde->data & 0xffff;
-	u_int16_t type = (unsigned long)pde->data >> 16;
-	struct list_head *list;
+	struct proc_dir_entry *pde = (struct proc_dir_entry *)seq->private;
+	u_int16_t af = (unsigned long)pde->data;
 
-	if (af >= NPROTO)
-		return NULL;
+	mutex_lock(&xt[af].mutex);
+	return seq_list_start(&xt[af].match, *pos);
+}
 
-	list = type2list(af, type);
-	if (!list)
-		return NULL;
+static void *xt_match_seq_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+	struct proc_dir_entry *pde = (struct proc_dir_entry *)seq->private;
+	u_int16_t af = (unsigned long)pde->data;
 
-	(*pos)++;
-	return xt_get_idx(list, seq, *pos);
+	return seq_list_next(v, &xt[af].match, pos);
 }
 
-static void xt_tgt_seq_stop(struct seq_file *seq, void *v)
+static void xt_match_seq_stop(struct seq_file *seq, void *v)
 {
 	struct proc_dir_entry *pde = seq->private;
-	u_int16_t af = (unsigned long)pde->data & 0xffff;
+	u_int16_t af = (unsigned long)pde->data;
 
 	mutex_unlock(&xt[af].mutex);
 }
 
-static int xt_name_seq_show(struct seq_file *seq, void *v)
+static int xt_match_seq_show(struct seq_file *seq, void *v)
 {
-	char *name = (char *)v + sizeof(struct list_head);
+	struct xt_match *match = list_entry(v, struct xt_match, list);
 
-	if (strlen(name))
-		return seq_printf(seq, "%s\n", name);
+	if (strlen(match->name))
+		return seq_printf(seq, "%s\n", match->name);
 	else
 		return 0;
 }
 
-static const struct seq_operations xt_tgt_seq_ops = {
-	.start	= xt_tgt_seq_start,
-	.next	= xt_tgt_seq_next,
-	.stop	= xt_tgt_seq_stop,
-	.show	= xt_name_seq_show,
+static const struct seq_operations xt_match_seq_ops = {
+	.start	= xt_match_seq_start,
+	.next	= xt_match_seq_next,
+	.stop	= xt_match_seq_stop,
+	.show	= xt_match_seq_show,
 };
 
-static int xt_tgt_open(struct inode *inode, struct file *file)
+static int xt_match_open(struct inode *inode, struct file *file)
 {
 	int ret;
 
-	ret = seq_open(file, &xt_tgt_seq_ops);
+	ret = seq_open(file, &xt_match_seq_ops);
 	if (!ret) {
 		struct seq_file *seq = file->private_data;
-		struct proc_dir_entry *pde = PDE(inode);
 
-		seq->private = pde;
+		seq->private = PDE(inode);
 	}
+	return ret;
+}
+
+static const struct file_operations xt_match_ops = {
+	.owner	 = THIS_MODULE,
+	.open	 = xt_match_open,
+	.read	 = seq_read,
+	.llseek	 = seq_lseek,
+	.release = seq_release,
+};
 
+static void *xt_target_seq_start(struct seq_file *seq, loff_t *pos)
+{
+	struct proc_dir_entry *pde = (struct proc_dir_entry *)seq->private;
+	u_int16_t af = (unsigned long)pde->data;
+
+	mutex_lock(&xt[af].mutex);
+	return seq_list_start(&xt[af].target, *pos);
+}
+
+static void *xt_target_seq_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+	struct proc_dir_entry *pde = (struct proc_dir_entry *)seq->private;
+	u_int16_t af = (unsigned long)pde->data;
+
+	return seq_list_next(v, &xt[af].target, pos);
+}
+
+static void xt_target_seq_stop(struct seq_file *seq, void *v)
+{
+	struct proc_dir_entry *pde = seq->private;
+	u_int16_t af = (unsigned long)pde->data;
+
+	mutex_unlock(&xt[af].mutex);
+}
+
+static int xt_target_seq_show(struct seq_file *seq, void *v)
+{
+	struct xt_target *target = list_entry(v, struct xt_target, list);
+
+	if (strlen(target->name))
+		return seq_printf(seq, "%s\n", target->name);
+	else
+		return 0;
+}
+
+static const struct seq_operations xt_target_seq_ops = {
+	.start	= xt_target_seq_start,
+	.next	= xt_target_seq_next,
+	.stop	= xt_target_seq_stop,
+	.show	= xt_target_seq_show,
+};
+
+static int xt_target_open(struct inode *inode, struct file *file)
+{
+	int ret;
+
+	ret = seq_open(file, &xt_target_seq_ops);
+	if (!ret) {
+		struct seq_file *seq = file->private_data;
+
+		seq->private = PDE(inode);
+	}
 	return ret;
 }
 
-static const struct file_operations xt_file_ops = {
+static const struct file_operations xt_target_ops = {
 	.owner	 = THIS_MODULE,
-	.open	 = xt_tgt_open,
+	.open	 = xt_target_open,
 	.read	 = seq_read,
 	.llseek	 = seq_lseek,
 	.release = seq_release,
@@ -869,25 +929,25 @@ int xt_proto_init(int af)
 #ifdef CONFIG_PROC_FS
 	strlcpy(buf, xt_prefix[af], sizeof(buf));
 	strlcat(buf, FORMAT_TABLES, sizeof(buf));
-	proc = proc_net_fops_create(&init_net, buf, 0440, &xt_file_ops);
+	proc = proc_net_fops_create(&init_net, buf, 0440, &xt_table_ops);
 	if (!proc)
 		goto out;
-	proc->data = (void *) ((unsigned long) af | (TABLE << 16));
+	proc->data = (void *)(unsigned long)af;
 
 
 	strlcpy(buf, xt_prefix[af], sizeof(buf));
 	strlcat(buf, FORMAT_MATCHES, sizeof(buf));
-	proc = proc_net_fops_create(&init_net, buf, 0440, &xt_file_ops);
+	proc = proc_net_fops_create(&init_net, buf, 0440, &xt_match_ops);
 	if (!proc)
 		goto out_remove_tables;
-	proc->data = (void *) ((unsigned long) af | (MATCH << 16));
+	proc->data = (void *)(unsigned long)af;
 
 	strlcpy(buf, xt_prefix[af], sizeof(buf));
 	strlcat(buf, FORMAT_TARGETS, sizeof(buf));
-	proc = proc_net_fops_create(&init_net, buf, 0440, &xt_file_ops);
+	proc = proc_net_fops_create(&init_net, buf, 0440, &xt_target_ops);
 	if (!proc)
 		goto out_remove_matches;
-	proc->data = (void *) ((unsigned long) af | (TARGET << 16));
+	proc->data = (void *)(unsigned long)af;
 #endif
 
 	return 0;