netfilter: xtables: use xt_table for hook instantiation

The respective xt_table structures already have most of the metadata
needed for hook setup. Add a 'priority' field to struct xt_table so
that xt_hook_link() can be called with a reduced number of arguments.

So should we be having more tables in the future, it comes at no
static cost (only runtime, as before) - space saved:
6807373->6806555.

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>

1 files changed, 54 insertions, 0 deletions

diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index f01955cce314..b51cb0d7234a 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -1091,6 +1091,60 @@ static const struct file_operations xt_target_ops = {
 
 #endif /* CONFIG_PROC_FS */
 
+/**
+ * xt_hook_link - set up hooks for a new table
+ * @table:      table with metadata needed to set up hooks
+ * @fn:         Hook function
+ *
+ * This function will take care of creating and registering the necessary
+ * Netfilter hooks for XT tables.
+ */
+struct nf_hook_ops *xt_hook_link(const struct xt_table *table, nf_hookfn *fn)
+{
+        unsigned int hook_mask = table->valid_hooks;
+        uint8_t i, num_hooks = hweight32(hook_mask);
+        uint8_t hooknum;
+        struct nf_hook_ops *ops;
+        int ret;
+
+        ops = kmalloc(sizeof(*ops) * num_hooks, GFP_KERNEL);
+        if (ops == NULL)
+                return ERR_PTR(-ENOMEM);
+
+        for (i = 0, hooknum = 0; i < num_hooks && hook_mask != 0;
+             hook_mask >>= 1, ++hooknum) {
+                if (!(hook_mask & 1))
+                        continue;
+                ops[i].hook     = fn;
+                ops[i].owner    = table->me;
+                ops[i].pf       = table->af;
+                ops[i].hooknum  = hooknum;
+                ops[i].priority = table->priority;
+                ++i;
+        }
+
+        ret = nf_register_hooks(ops, num_hooks);
+        if (ret < 0) {
+                kfree(ops);
+                return ERR_PTR(ret);
+        }
+
+        return ops;
+}
+EXPORT_SYMBOL_GPL(xt_hook_link);
+
+/**
+ * xt_hook_unlink - remove hooks for a table
+ * @ops:        nf_hook_ops array as returned by nf_hook_link
+ * @hook_mask:  the very same mask that was passed to nf_hook_link
+ */
+void xt_hook_unlink(const struct xt_table *table, struct nf_hook_ops *ops)
+{
+        nf_unregister_hooks(ops, hweight32(table->valid_hooks));
+        kfree(ops);
+}
+EXPORT_SYMBOL_GPL(xt_hook_unlink);
+
 int xt_proto_init(struct net *net, u_int8_t af)
 {
 #ifdef CONFIG_PROC_FS