netfilter: conntrack: support a fixed size of 128 distinct labels

The conntrack label extension is currently variable-sized, e.g. if
only 2 labels are used by iptables rules then the labels->bits[] array
will only contain one element.

We track size of each label storage area in the 'words' member.

But in nftables and openvswitch we always have to ask for worst-case
since we don't know what bit will be used at configuration time.

As most arches are 64bit we need to allocate 24 bytes in this case:

struct nf_conn_labels {
    u8            words;   /*     0     1 */
    /* XXX 7 bytes hole, try to pack */
    long unsigned bits[2]; /*     8     24 */

Make bits a fixed size and drop the words member, it simplifies
the code and only increases memory requirements on x86 when
less than 64bit labels are required.

We still only allocate the extension if its needed.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/net/openvswitch/conntrack.c b/net/openvswitch/conntrack.c
index b4069a90e375..c644c78ed485 100644
--- a/net/openvswitch/conntrack.c
+++ b/net/openvswitch/conntrack.c
@@ -135,7 +135,7 @@ static void ovs_ct_get_labels(const struct nf_conn *ct,
         struct nf_conn_labels *cl = ct ? nf_ct_labels_find(ct) : NULL;
 
         if (cl) {
-                size_t len = cl->words * sizeof(long);
+                size_t len = sizeof(cl->bits);
 
                 if (len > OVS_CT_LABELS_LEN)
                         len = OVS_CT_LABELS_LEN;
@@ -274,7 +274,7 @@ static int ovs_ct_set_labels(struct sk_buff *skb, struct sw_flow_key *key,
                 nf_ct_labels_ext_add(ct);
                 cl = nf_ct_labels_find(ct);
         }
-        if (!cl || cl->words * sizeof(long) < OVS_CT_LABELS_LEN)
+        if (!cl || sizeof(cl->bits) < OVS_CT_LABELS_LEN)
                 return -ENOSPC;
 
         err = nf_connlabels_replace(ct, (u32 *)labels, (u32 *)mask,