From: Nicolas Dichtel <nicolas.dichtel@6wind.com>
To: Aaron Conole <aconole@redhat.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: Thu, 28 Nov 2019 09:22:18 +0100 [thread overview]
Message-ID: <57c14a3f-25fa-76c3-d846-a616f198467e@6wind.com> (raw)
In-Reply-To: <f7tsgmkyja6.fsf@dhcp-25.97.bos.redhat.com>
Le 18/11/2019 à 22:19, Aaron Conole a écrit :
> 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.
Ok, I didn't look deeply, thank you for the explanation.
Regards,
Nicolas
prev parent reply other threads:[~2019-11-28 8:22 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
2019-11-28 8:22 ` Nicolas Dichtel [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=57c14a3f-25fa-76c3-d846-a616f198467e@6wind.com \
--to=nicolas.dichtel@6wind.com \
--cc=aconole@redhat.com \
--cc=davem@davemloft.net \
--cc=dev@openvswitch.org \
--cc=jhs@mojatatu.com \
--cc=jiri@resnulli.us \
--cc=linux-kernel@vger.kernel.org \
--cc=netdev@vger.kernel.org \
--cc=pshelar@ovn.org \
--cc=xiyou.wangcong@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).