openvswitch: Allow attaching helper in later commit

This patch allows to attach conntrack helper to a confirmed conntrack
entry.  Currently, we can only attach alg helper to a conntrack entry
when it is in the unconfirmed state.  This patch enables an use case
that we can firstly commit a conntrack entry after it passed some
initial conditions.  After that the processing pipeline will further
check a couple of packets to determine if the connection belongs to
a particular application, and attach alg helper to the connection
in a later stage.

Signed-off-by: Yi-Hung Wei <yihung.wei@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/openvswitch/conntrack.c b/net/openvswitch/conntrack.c
index 05249eb..df9c80b 100644 (file)
--- a/net/openvswitch/conntrack.c
+++ b/net/openvswitch/conntrack.c
@@ -971,6 +971,8 @@ static int __ovs_ct_lookup(struct net *net, struct sw_flow_key *key,
 
        ct = nf_ct_get(skb, &ctinfo);
        if (ct) {
+               bool add_helper = false;
+
                /* Packets starting a new connection must be NATted before the
                 * helper, so that the helper knows about the NAT.  We enforce
                 * this by delaying both NAT and helper calls for unconfirmed
@@ -988,16 +990,17 @@ static int __ovs_ct_lookup(struct net *net, struct sw_flow_key *key,
                }
 
                /* Userspace may decide to perform a ct lookup without a helper
-                * specified followed by a (recirculate and) commit with one.
-                * Therefore, for unconfirmed connections which we will commit,
-                * we need to attach the helper here.
+                * specified followed by a (recirculate and) commit with one,
+                * or attach a helper in a later commit.  Therefore, for
+                * connections which we will commit, we may need to attach
+                * the helper here.
                 */
-               if (!nf_ct_is_confirmed(ct) && info->commit &&
-                   info->helper && !nfct_help(ct)) {
+               if (info->commit && info->helper && !nfct_help(ct)) {
                        int err = __nf_ct_try_assign_helper(ct, info->ct,
                                                            GFP_ATOMIC);
                        if (err)
                                return err;
+                       add_helper = true;
 
                        /* helper installed, add seqadj if NAT is required */
                        if (info->nat && !nfct_seqadj(ct)) {
@@ -1007,11 +1010,13 @@ static int __ovs_ct_lookup(struct net *net, struct sw_flow_key *key,
                }
 
                /* Call the helper only if:
-                * - nf_conntrack_in() was executed above ("!cached") for a
-                *   confirmed connection, or
+                * - nf_conntrack_in() was executed above ("!cached") or a
+                *   helper was just attached ("add_helper") for a confirmed
+                *   connection, or
                 * - When committing an unconfirmed connection.
                 */
-               if ((nf_ct_is_confirmed(ct) ? !cached : info->commit) &&
+               if ((nf_ct_is_confirmed(ct) ? !cached || add_helper :
+                                             info->commit) &&
                    ovs_ct_helper(skb, info->family) != NF_ACCEPT) {
                        return -EINVAL;
                }