linux-kernel - [PATCH 5.4 28/37] act_ct: support asymmetric conntrack

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Message-Id: <20191217200732.321097920@linuxfoundation.org>
Date:   Tue, 17 Dec 2019 21:09:49 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Aaron Conole <aconole@...hat.com>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 5.4 28/37] act_ct: support asymmetric conntrack

From: Aaron Conole <aconole@...hat.com>

[ Upstream commit 95219afbb980f10934de9f23a3e199be69c5ed09 ]

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@...hat.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/sched/act_ct.c |   13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

--- 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
 			  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
 		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