netfilter: nf_conncount: expose connection list interface

commit 5e5cbc7b upstream.

This patch provides an interface to maintain the list of connections and
the lookup function to obtain the number of connections in the list.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

[mfo: backport: refresh context lines and use older symbol/file names:
 - nf_conntrack_count.h: new file, add include guards.
 - nf_conncount.c -> xt_connlimit.c.
   - nf_conncount_rb -> xt_connlimit_rb
   - nf_conncount_tuple -> xt_connlimit_conn
   - conncount_rb_cachep -> connlimit_rb_cachep
   - conncount_conn_cachep -> connlimit_conn_cachep]
Signed-off-by: Mauricio Faria de Oliveira <mfo@canonical.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

include/net/netfilter/nf_conntrack_count.h

+#ifndef _NF_CONNTRACK_COUNT_H
+#define _NF_CONNTRACK_COUNT_H
+
+unsigned int nf_conncount_lookup(struct net *net, struct hlist_head *head,
+				 const struct nf_conntrack_tuple *tuple,
+				 const struct nf_conntrack_zone *zone,
+				 bool *addit);
+
+bool nf_conncount_add(struct hlist_head *head,
+		      const struct nf_conntrack_tuple *tuple);
+
+void nf_conncount_cache_free(struct hlist_head *hhead);
+
+#endif

net/netfilter/xt_connlimit.c

@@ -114,7 +114,7 @@ same_source_net(const union nf_inet_addr *addr,
 	}
 }
 
-static bool add_hlist(struct hlist_head *head,
+bool nf_conncount_add(struct hlist_head *head,
 		      const struct nf_conntrack_tuple *tuple)
 {
 	struct xt_connlimit_conn *conn;
@@ -126,12 +126,12 @@ static bool add_hlist(struct hlist_head *head,
 	hlist_add_head(&conn->node, head);
 	return true;
 }
+EXPORT_SYMBOL_GPL(nf_conncount_add);
 
-static unsigned int check_hlist(struct net *net,
-				struct hlist_head *head,
-				const struct nf_conntrack_tuple *tuple,
-				const struct nf_conntrack_zone *zone,
-				bool *addit)
+unsigned int nf_conncount_lookup(struct net *net, struct hlist_head *head,
+				 const struct nf_conntrack_tuple *tuple,
+				 const struct nf_conntrack_zone *zone,
+				 bool *addit)
 {
 	const struct nf_conntrack_tuple_hash *found;
 	struct xt_connlimit_conn *conn;
@@ -176,6 +176,7 @@ static unsigned int check_hlist(struct net *net,
 
 	return length;
 }
+EXPORT_SYMBOL_GPL(nf_conncount_lookup);
 
 static void tree_nodes_free(struct rb_root *root,
 			    struct xt_connlimit_rb *gc_nodes[],
@@ -222,13 +223,15 @@ count_tree(struct net *net, struct rb_root *root,
 		} else {
 			/* same source network -> be counted! */
 			unsigned int count;
-			count = check_hlist(net, &rbconn->hhead, tuple, zone, &addit);
+
+			count = nf_conncount_lookup(net, &rbconn->hhead, tuple,
+						    zone, &addit);
 
 			tree_nodes_free(root, gc_nodes, gc_count);
 			if (!addit)
 				return count;
 
-			if (!add_hlist(&rbconn->hhead, tuple))
+			if (!nf_conncount_add(&rbconn->hhead, tuple))
 				return 0; /* hotdrop */
 
 			return count + 1;
@@ -238,7 +241,7 @@ count_tree(struct net *net, struct rb_root *root,
 			continue;
 
 		/* only used for GC on hhead, retval and 'addit' ignored */
-		check_hlist(net, &rbconn->hhead, tuple, zone, &addit);
+		nf_conncount_lookup(net, &rbconn->hhead, tuple, zone, &addit);
 		if (hlist_empty(&rbconn->hhead))
 			gc_nodes[gc_count++] = rbconn;
 	}
@@ -378,11 +381,19 @@ static int connlimit_mt_check(const struct xt_mtchk_param *par)
 	return 0;
 }
 
-static void destroy_tree(struct rb_root *r)
+void nf_conncount_cache_free(struct hlist_head *hhead)
 {
 	struct xt_connlimit_conn *conn;
-	struct xt_connlimit_rb *rbconn;
 	struct hlist_node *n;
+
+	hlist_for_each_entry_safe(conn, n, hhead, node)
+		kmem_cache_free(connlimit_conn_cachep, conn);
+}
+EXPORT_SYMBOL_GPL(nf_conncount_cache_free);
+
+static void destroy_tree(struct rb_root *r)
+{
+	struct xt_connlimit_rb *rbconn;
 	struct rb_node *node;
 
 	while ((node = rb_first(r)) != NULL) {
@@ -390,8 +401,7 @@ static void destroy_tree(struct rb_root *r)
 
 		rb_erase(node, r);
 
-		hlist_for_each_entry_safe(conn, n, &rbconn->hhead, node)
-			kmem_cache_free(connlimit_conn_cachep, conn);
+		nf_conncount_cache_free(&rbconn->hhead);
 
 		kmem_cache_free(connlimit_rb_cachep, rbconn);
 	}