act_ct: support asymmetric conntrack

The act_ct TC module shares a common conntrack and NAT infrastructure
exposed via netfilter.  It's possible that a packet needs both SNAT and
DNAT manipulation, due to e.g. tuple collision.  Netfilter can support
this because it runs through the NAT table twice - once on ingress and
again after egress.  The act_ct action doesn't have such capability.

Like netfilter hook infrastructure, we should run through NAT twice to
keep the symmetry.

Fixes: b57dc7c13ea9 ("net/sched: Introduce action ct")
Signed-off-by: Aaron Conole <aconole@redhat.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/sched/act_ct.c b/net/sched/act_ct.c
index ae0de372b1c8f003caafdf354e68a87676bd7ab7..bf2d69335d4b963e254da4c1c93b6706438eb8d4 100644 (file)
--- a/net/sched/act_ct.c
+++ b/net/sched/act_ct.c
@@ -329,6 +329,7 @@ static int tcf_ct_act_nat(struct sk_buff *skb,
                          bool commit)
 {
 #if IS_ENABLED(CONFIG_NF_NAT)
+       int err;
        enum nf_nat_manip_type maniptype;
 
        if (!(ct_action & TCA_CT_ACT_NAT))
@@ -359,7 +360,17 @@ static int tcf_ct_act_nat(struct sk_buff *skb,
                return NF_ACCEPT;
        }
 
-       return ct_nat_execute(skb, ct, ctinfo, range, maniptype);
+       err = ct_nat_execute(skb, ct, ctinfo, range, maniptype);
+       if (err == NF_ACCEPT &&
+           ct->status & IPS_SRC_NAT && ct->status & IPS_DST_NAT) {
+               if (maniptype == NF_NAT_MANIP_SRC)
+                       maniptype = NF_NAT_MANIP_DST;
+               else
+                       maniptype = NF_NAT_MANIP_SRC;
+
+               err = ct_nat_execute(skb, ct, ctinfo, range, maniptype);
+       }
+       return err;
 #else
        return NF_ACCEPT;
 #endif