[PATCH v3] vrf: Fix conntrack-dnat conflict in vrf-device PREROUTING hook

[wenxu@ucloud.cn]

From: wenxu <wenxu@ucloud.cn>

In the ip_rcv the skb go through the PREROUTING hook first,
Then jump in vrf device go through the same hook again.
When conntrack dnat work with vrf, there will be some conflict for rules.
Because the package go through the hook twice with different nf status

ip link add user1 type vrf table 1
ip link add user2 type vrf table 2
ip l set dev tun1 master user1
ip l set dev tun2 master user2

nft add table firewall
nft add chain firewall zones { type filter hook prerouting  priority - 300 \; }
nft add rule firewall zones counter ct zone set iif map { "tun1" : 1, "tun2" : 2 }
nft add chain firewall rule-1000-ingress
nft add rule firewall rule-1000-ingress ct zone 1 tcp dport 22 ct state new counter accept
nft add rule firewall rule-1000-ingress counter drop
nft add chain firewall rule-1000-egress
nft add rule firewall rule-1000-egress tcp dport 22 ct state new counter drop
nft add rule firewall rule-1000-egress counter accept

nft add chain firewall rules-all { type filter hook prerouting priority - 150 \; }
nft add rule firewall rules-all ip daddr vmap { "2.2.2.11" : jump rule-1000-ingress }
nft add rule firewall rules-all ct zone vmap { 1 : jump rule-1000-egress }

nft add rule firewall dnat-all ct zone vmap { 1 : jump dnat-1000 }
nft add rule firewall dnat-1000 ip daddr 2.2.2.11 counter dnat to 10.0.0.7

For a package with ip daddr 2.2.2.11 and tcp dport 22, first time accept in the
rule-1000-ingress and dnat to 10.0.0.7. Then second time the packet goto the wrong
chain rule-1000-egress which leads the packet drop

So This patch avoid already dnat packet go through the prerouting hook for the
second time.

Fixes: 73e20b761acf8 ("net: vrf: Add support for PREROUTING rules on vrf
device")
Signed-off-by: wenxu <wenxu@ucloud.cn>
---
 drivers/net/vrf.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/net/vrf.c b/drivers/net/vrf.c
index 95909e2..9b01ca871 100644
--- a/drivers/net/vrf.c
+++ b/drivers/net/vrf.c
@@ -38,6 +38,10 @@
 #include <net/fib_rules.h>
 #include <net/netns/generic.h>
 
+#if IS_ENABLED(CONFIG_NF_CONNTRACK)
+#include <net/netfilter/nf_conntrack.h>
+#endif
+
 #define DRV_NAME	"vrf"
 #define DRV_VERSION	"1.0"
 
@@ -898,6 +902,14 @@ static struct sk_buff *vrf_rcv_nfhook(u8 pf, unsigned int hook,
 				      struct net_device *dev)
 {
 	struct net *net = dev_net(dev);
+#if IS_ENABLED(CONFIG_NF_CONNTRACK)
+	enum ip_conntrack_info ctinfo;
+	struct nf_conn *ct;
+
+	ct = nf_ct_get(skb, &ctinfo);
+	if (ct && (ct->status & IPS_DST_NAT))
+		return skb;
+#endif
 
 	if (nf_hook(pf, hook, net, NULL, skb, dev, NULL, vrf_rcv_finish) != 1)
 		skb = NULL;    /* kfree_skb(skb) handled by nf code */
-- 
1.8.3.1