From: Aaron Conole <aconole@redhat.com>
To: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Cc: netdev@vger.kernel.org, Pravin B Shelar <pshelar@ovn.org>,
"David S . Miller" <davem@davemloft.net>,
Jamal Hadi Salim <jhs@mojatatu.com>,
Cong Wang <xiyou.wangcong@gmail.com>,
Jiri Pirko <jiri@resnulli.us>,
dev@openvswitch.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH net 1/2] openvswitch: support asymmetric conntrack
Date: Mon, 18 Nov 2019 16:19:29 -0500 [thread overview]
Message-ID: <f7tsgmkyja6.fsf@dhcp-25.97.bos.redhat.com> (raw)
In-Reply-To: <eb0bdc35-7f29-77c7-c013-e88f74772c24@6wind.com> (Nicolas Dichtel's message of "Tue, 12 Nov 2019 09:52:45 +0100")
Nicolas Dichtel <nicolas.dichtel@6wind.com> writes:
> Le 08/11/2019 à 22:07, Aaron Conole a écrit :
>> The openvswitch 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 openvswitch module doesn't have such capability.
>>
>> Like netfilter hook infrastructure, we should run through NAT twice to
>> keep the symmetry.
>>
>> Fixes: 05752523e565 ("openvswitch: Interface with NAT.")
>> Signed-off-by: Aaron Conole <aconole@redhat.com>
> In this case, ovs_ct_find_existing() won't be able to find the
> conntrack, right?
vswitchd normally won't allow both actions to get programmed. Even the
kernel module won't allow it, so this really will only happen when the
connection gets established via the nf_hook path, and then needs to be
processed via openvswitch. In those cases, the tuple lookup should be
correct, because the nf_nat table should contain the correct tuple data,
and the skbuff should have the correct tuples in the packet data to
begin with.
> Inverting the tuple to find the conntrack doesn't work anymore with double NAT.
> Am I wrong?
I think since the packet was double-NAT on the way out (via nf_hook
path), then the incoming reply will have the correct NAT tuples and the
lookup will happen just fine. Just that during processing, both
transformations aren't applied.
Makes sense?
> Regards,
> Nicolas
next prev parent reply other threads:[~2019-11-18 21:19 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-08 21:07 [PATCH net 1/2] openvswitch: support asymmetric conntrack Aaron Conole
2019-11-08 21:07 ` [PATCH net 2/2] act_ct: " Aaron Conole
2019-11-14 14:22 ` Roi Dayan
2019-11-14 14:24 ` Paul Blakey
2019-11-18 21:24 ` Aaron Conole
2019-11-14 16:29 ` Marcelo Ricardo Leitner
2019-11-18 21:21 ` Aaron Conole
2019-11-18 22:40 ` Marcelo Ricardo Leitner
2019-11-22 20:39 ` Aaron Conole
2019-11-22 20:43 ` Marcelo Ricardo Leitner
2019-11-09 22:15 ` [PATCH net 1/2] openvswitch: " Pravin Shelar
2019-11-18 20:39 ` Aaron Conole
2019-11-25 15:38 ` Aaron Conole
2019-11-26 4:07 ` Pravin Shelar
2019-11-12 8:52 ` Nicolas Dichtel
2019-11-18 21:19 ` Aaron Conole [this message]
2019-11-28 8:22 ` Nicolas Dichtel
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