netfilter: nf_conntrack: add IPS_OFFLOAD status bit

This new bit tells us that the conntrack entry is owned by the flow
table offload infrastructure.

 # cat /proc/net/nf_conntrack
 ipv4     2 tcp      6 src=10.141.10.2 dst=147.75.205.195 sport=36392 dport=443 src=147.75.205.195 dst=192.168.2.195 sport=443 dport=36392 [OFFLOAD] mark=0 zone=0 use=2

Note the [OFFLOAD] tag in the listing.

The timer of such conntrack entries look like stopped from userspace.
In practise, to make sure the conntrack entry does not go away, the
conntrack timer is periodically set to an arbitrary large value that
gets refreshed on every iteration from the garbage collector, so it
never expires- and they display no internal state in the case of TCP
flows. This allows us to save a bitcheck from the packet path via
nf_ct_is_expired().

Conntrack entries that have been offloaded to the flow table
infrastructure cannot be deleted/flushed via ctnetlink. The flow table
infrastructure is also responsible for releasing this conntrack entry.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 14 insertions, 1 deletions

diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index 316bbdc4a158..7c7921a53b13 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -1110,6 +1110,14 @@ static const struct nla_policy ct_nla_policy[CTA_MAX+1] = {
 				    .len = NF_CT_LABELS_MAX_SIZE },
 };
 
+static int ctnetlink_flush_iterate(struct nf_conn *ct, void *data)
+{
+	if (test_bit(IPS_OFFLOAD_BIT, &ct->status))
+		return 0;
+
+	return ctnetlink_filter_match(ct, data);
+}
+
 static int ctnetlink_flush_conntrack(struct net *net,
 				     const struct nlattr * const cda[],
 				     u32 portid, int report)
@@ -1122,7 +1130,7 @@ static int ctnetlink_flush_conntrack(struct net *net,
 			return PTR_ERR(filter);
 	}
 
-	nf_ct_iterate_cleanup_net(net, ctnetlink_filter_match, filter,
+	nf_ct_iterate_cleanup_net(net, ctnetlink_flush_iterate, filter,
 				  portid, report);
 	kfree(filter);
 
@@ -1168,6 +1176,11 @@ static int ctnetlink_del_conntrack(struct net *net, struct sock *ctnl,
 
 	ct = nf_ct_tuplehash_to_ctrack(h);
 
+	if (test_bit(IPS_OFFLOAD_BIT, &ct->status)) {
+		nf_ct_put(ct);
+		return -EBUSY;
+	}
+
 	if (cda[CTA_ID]) {
 		u_int32_t id = ntohl(nla_get_be32(cda[CTA_ID]));
 		if (id != (u32)(unsigned long)ct) {