netfilter: connlabels: Export setting connlabel length

Add functions to change connlabel length into nf_conntrack_labels.c so
they may be reused by other modules like OVS and nftables without
needing to jump through xt_match_check() hoops.

Suggested-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Joe Stringer <joestringer@nicira.com>
Acked-by: Florian Westphal <fw@strlen.de>
Acked-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: joestringer

include/net/netfilter/nf_conntrack_labels.h

@@ -54,7 +54,11 @@ int nf_connlabels_replace(struct nf_conn *ct,
 #ifdef CONFIG_NF_CONNTRACK_LABELS
 int nf_conntrack_labels_init(void);
 void nf_conntrack_labels_fini(void);
+int nf_connlabels_get(struct net *net, unsigned int n_bits);
+void nf_connlabels_put(struct net *net);
 #else
 static inline int nf_conntrack_labels_init(void) { return 0; }
 static inline void nf_conntrack_labels_fini(void) {}
+static inline int nf_connlabels_get(struct net *net, unsigned int n_bits) { return 0; }
+static inline void nf_connlabels_put(struct net *net) {}
 #endif

net/netfilter/nf_conntrack_labels.c

@@ -14,6 +14,8 @@
 #include <net/netfilter/nf_conntrack_ecache.h>
 #include <net/netfilter/nf_conntrack_labels.h>
 
+static spinlock_t nf_connlabels_lock;
+
 static unsigned int label_bits(const struct nf_conn_labels *l)
 {
 	unsigned int longs = l->words;
@@ -89,6 +91,35 @@ int nf_connlabels_replace(struct nf_conn *ct,
 }
 EXPORT_SYMBOL_GPL(nf_connlabels_replace);
 
+int nf_connlabels_get(struct net *net, unsigned int n_bits)
+{
+	size_t words;
+
+	if (n_bits > (NF_CT_LABELS_MAX_SIZE * BITS_PER_BYTE))
+		return -ERANGE;
+
+	words = BITS_TO_LONGS(n_bits);
+
+	spin_lock(&nf_connlabels_lock);
+	net->ct.labels_used++;
+	if (words > net->ct.label_words)
+		net->ct.label_words = words;
+	spin_unlock(&nf_connlabels_lock);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(nf_connlabels_get);
+
+void nf_connlabels_put(struct net *net)
+{
+	spin_lock(&nf_connlabels_lock);
+	net->ct.labels_used--;
+	if (net->ct.labels_used == 0)
+		net->ct.label_words = 0;
+	spin_unlock(&nf_connlabels_lock);
+}
+EXPORT_SYMBOL_GPL(nf_connlabels_put);
+
 static struct nf_ct_ext_type labels_extend __read_mostly = {
 	.len    = sizeof(struct nf_conn_labels),
 	.align  = __alignof__(struct nf_conn_labels),
@@ -97,6 +128,7 @@ static struct nf_ct_ext_type labels_extend __read_mostly = {
 
 int nf_conntrack_labels_init(void)
 {
+	spin_lock_init(&nf_connlabels_lock);
 	return nf_ct_extend_register(&labels_extend);
 }
 

net/netfilter/xt_connlabel.c

@@ -42,10 +42,6 @@ static int connlabel_mt_check(const struct xt_mtchk_param *par)
 			    XT_CONNLABEL_OP_SET;
 	struct xt_connlabel_mtinfo *info = par->matchinfo;
 	int ret;
-	size_t words;
-
-	if (info->bit > XT_CONNLABEL_MAXBIT)
-		return -ERANGE;
 
 	if (info->options & ~options) {
 		pr_err("Unknown options in mask %x\n", info->options);
@@ -59,19 +55,15 @@ static int connlabel_mt_check(const struct xt_mtchk_param *par)
 		return ret;
 	}
 
-	par->net->ct.labels_used++;
-	words = BITS_TO_LONGS(info->bit+1);
-	if (words > par->net->ct.label_words)
-		par->net->ct.label_words = words;
-
+	ret = nf_connlabels_get(par->net, info->bit + 1);
+	if (ret < 0)
+		nf_ct_l3proto_module_put(par->family);
 	return ret;
 }
 
 static void connlabel_mt_destroy(const struct xt_mtdtor_param *par)
 {
-	par->net->ct.labels_used--;
-	if (par->net->ct.labels_used == 0)
-		par->net->ct.label_words = 0;
+	nf_connlabels_put(par->net);
 	nf_ct_l3proto_module_put(par->family);
 }