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openvswitch: handle DNAT tuple collision

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With multiple DNAT rules it's possible that after destination
translation the resulting tuples collide.

For example, two openvswitch flows:
nw_dst=10.0.0.10,tp_dst=10, actions=ct(commit,table=2,nat(dst=20.0.0.1:20))
nw_dst=10.0.0.20,tp_dst=10, actions=ct(commit,table=2,nat(dst=20.0.0.1:20))

Assuming two TCP clients initiating the following connections:
10.0.0.10:5000->10.0.0.10:10
10.0.0.10:5000->10.0.0.20:10

Both tuples would translate to 10.0.0.10:5000->20.0.0.1:20 causing
nf_conntrack_confirm() to fail because of tuple collision.

Netfilter handles this case by allocating a null binding for SNAT at
egress by default.  Perform the same operation in openvswitch for DNAT
if no explicit SNAT is requested by the user and allocate a null binding
for SNAT for packets in the "original" direction.

Reported-at: https://bugzilla.redhat.com/1877128
Suggested-by: Florian Westphal <fw@strlen.de>
Fixes: 05752523e5 ("openvswitch: Interface with NAT.")
Signed-off-by: Dumitru Ceara <dceara@redhat.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Dumitru Ceara 2020-10-07 17:48:03 +02:00 committed by Jakub Kicinski
parent d42ee76ecb
commit 8aa7b526dc
1 changed files with 12 additions and 8 deletions
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20
net/openvswitch/conntrack.c
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@ -905,15 +905,19 @@ static int ovs_ct_nat(struct net *net, struct sw_flow_key *key,
}
err = ovs_ct_nat_execute(skb, ct, ctinfo, &info->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;
if (err == NF_ACCEPT && ct->status & IPS_DST_NAT) {
if (ct->status & IPS_SRC_NAT) {
if (maniptype == NF_NAT_MANIP_SRC)
maniptype = NF_NAT_MANIP_DST;
else
maniptype = NF_NAT_MANIP_SRC;
err = ovs_ct_nat_execute(skb, ct, ctinfo, &info->range,
maniptype);
err = ovs_ct_nat_execute(skb, ct, ctinfo, &info->range,
maniptype);
} else if (CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) {
err = ovs_ct_nat_execute(skb, ct, ctinfo, NULL,
NF_NAT_MANIP_SRC);
}
}
/* Mark NAT done if successful and update the flow key. */