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Subject[PATCH net 2/2] act_ct: support asymmetric conntrack
Date
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>
---
net/sched/act_ct.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/net/sched/act_ct.c b/net/sched/act_ct.c
index fcc46025e790..f3232a00970f 100644
--- 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
--
2.21.0
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