netfilter: kill the fake untracked conntrack objects

resurrect an old patch from Pablo Neira to remove the untracked objects.

Currently, there are four possible states of an skb wrt. conntrack.

1. No conntrack attached, ct is NULL.
2. Normal (kmem cache allocated) ct attached.
3. a template (kmalloc'd), not in any hash tables at any point in time
4. the 'untracked' conntrack, a percpu nf_conn object, tagged via
   IPS_UNTRACKED_BIT in ct->status.

Untracked is supposed to be identical to case 1.  It exists only
so users can check

-m conntrack --ctstate UNTRACKED vs.
-m conntrack --ctstate INVALID

e.g. attempts to set connmark on INVALID or UNTRACKED conntracks is
supposed to be a no-op.

Thus currently we need to check
 ct == NULL || nf_ct_is_untracked(ct)

in a lot of places in order to avoid altering untracked objects.

The other consequence of the percpu untracked object is that all
-j NOTRACK (and, later, kfree_skb of such skbs) result in an atomic op
(inc/dec the untracked conntracks refcount).

This adds a new kernel-private ctinfo state, IP_CT_UNTRACKED, to
make the distinction instead.

The (few) places that care about packet invalid (ct is NULL) vs.
packet untracked now need to test ct == NULL vs. ctinfo == IP_CT_UNTRACKED,
but all other places can omit the nf_ct_is_untracked() check.

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

1 files changed, 8 insertions, 8 deletions

diff --git a/net/netfilter/xt_CT.c b/net/netfilter/xt_CT.c
index b008db0184b8..3cbe1bcf6a74 100644
--- a/net/netfilter/xt_CT.c
+++ b/net/netfilter/xt_CT.c
@@ -26,11 +26,12 @@ static inline int xt_ct_target(struct sk_buff *skb, struct nf_conn *ct)
 	if (skb->_nfct != 0)
 		return XT_CONTINUE;
 
-	/* special case the untracked ct : we want the percpu object */
-	if (!ct)
-		ct = nf_ct_untracked_get();
-	atomic_inc(&ct->ct_general.use);
-	nf_ct_set(skb, ct, IP_CT_NEW);
+	if (ct) {
+		atomic_inc(&ct->ct_general.use);
+		nf_ct_set(skb, ct, IP_CT_NEW);
+	} else {
+		nf_ct_set(skb, ct, IP_CT_UNTRACKED);
+	}
 
 	return XT_CONTINUE;
 }
@@ -335,7 +336,7 @@ static void xt_ct_tg_destroy(const struct xt_tgdtor_param *par,
 	struct nf_conn *ct = info->ct;
 	struct nf_conn_help *help;
 
-	if (ct && !nf_ct_is_untracked(ct)) {
+	if (ct) {
 		help = nfct_help(ct);
 		if (help)
 			module_put(help->helper->me);
@@ -412,8 +413,7 @@ notrack_tg(struct sk_buff *skb, const struct xt_action_param *par)
 	if (skb->_nfct != 0)
 		return XT_CONTINUE;
 
-	nf_ct_set(skb, nf_ct_untracked_get(), IP_CT_NEW);
-	nf_conntrack_get(skb_nfct(skb));
+	nf_ct_set(skb, NULL, IP_CT_UNTRACKED);
 
 	return XT_CONTINUE;
 }