[ovs-discuss] [ovs-dev] can OVS conntrack support IP list like this: actions=ct(commit, table=0, zone=1, nat(dst=220.0.0.3, 220.0.0.7, 220.0.0.123))?

Darrell Ball dlu998 at gmail.com
Thu Nov 7 16:05:38 UTC 2019


On Wed, Nov 6, 2019 at 5:01 PM Yi Yang (杨燚)-云服务集团 <yangyi01 at inspur.com>
wrote:

> Thanks Darrell, I didn’t receive your second reply, I saw it in
> mail.openvswitch.org.
>
>
>
>>
> probably, you should give an example of what you mean by above
>
> I am not sure you are meaning to say that you want to specify an L4 port in
>
> your
>
> snat action rule or not; you will want to use ephemeral ports by not
>
> specifying a
>
> specific port in most cases
>
>>
>
>
> For SNAT, we don’t specify port, just use default port range
> “1024-65535”), but for internal source IPs, i.e. floating IPs, they are
> discrete in most cases because some floating IPs needn’t access Internet,
> for public IPs, so are they. For public IPs, maybe they are from different
> telecom carriers, we prefer egress traffic can be distributed on several
> BGP lines.
>

>
>
> table=0,ip,nw_src=172.18.0.67,…,actions=ct(commit,table=0,zone=1,nat(src=220.0.0.3,230.0.0.7,240.0.0.123))
>
>
> table=0,ip,nw_src=172.18.0.80,…,actions=ct(commit,table=0,zone=1,nat(src=220.0.0.3,230.0.0.7,240.0.0.123))
>
>
> table=0,ip,nw_src=172.19.0.23,…,actions=ct(commit,table=0,zone=1,nat(src=220.0.0.3,230.0.0.7,240.0.0.123))
>
>
>
> Ideally, we hope, for different traffic types from the same internal IP
> (say 172.18.0.67), some can SNAT to 220.0.0.3, some can SNAT to 230.0.0.7,
> some can SNAT to
>
> 240.0.0.123, that way, they can leverage total bandwidth of several BGP
> lines.
>
>
>
> I know current OVS can’t support the above IP list for snat, but it is
> indeed required in reality, I don’t understand why OVS can’t do in this
> way, is it linux conntrack limitation or what else reason? I think it is
> similar to IP range which can be supported.
>

Presently, the limitation is both at the Openflow layer and implementation
details at datapath
The layer above (a controller or even a script) can do the mapping taking
into account the desired distribution
A controller can/will often do this and similar types of configuration
specification.


>
>
>
> *发件人:* Darrell Ball [mailto:dlu998 at gmail.com]
> *发送时间:* 2019年11月6日 9:38
> *收件人:* Yi Yang (杨燚)-云服务集团 <yangyi01 at inspur.com>
> *抄送:* ovs-discuss at openvswitch.org; ovs-dev at openvswitch.org
> *主题:* Re: [ovs-dev] can OVS conntrack support IP list like this:
> actions=ct(commit, table=0, zone=1, nat(dst=220.0.0.3, 220.0.0.7,
> 220.0.0.123))?
>
>
>
>
>
>
>
> On Tue, Nov 5, 2019 at 4:32 PM Yi Yang (杨燚)-云服务集团 <yangyi01 at inspur.com>
> wrote:
>
> Hi, folks
>
>
>
> We need to do SNAT for many internal IPs by just using several public IPs,
> we also need to do DNAT by some other public IPs for exposing webservice,
> openflow rules look like the below:
>
>
>
> table=0,ip,nw_src=172.17.0.0/16,
> …,actions=ct(commit,table=0,zone=1,nat(src=
> 220.0.0.3,220.0.0.7,220.0.0.123))
>
> table=0,ip,nw_src=172.18.0.67,…,actions=ct(commit,table=0,zone=1,nat(src=22
> 0.0.0.3,220.0.0.7,220.0.0.123))
>
>
>
> for snat, you can map some subset of private IPs to a given public IP and
> so on
>
>
>
>
>
> table=0,ip,tcp,nw_dst=220.0.0.11,tp_dst=80,…,actions=ct(commit,table=0,zone
> =2,nat(dst=172.16.0.100:80))
>
> table=0,ip,tcp,nw_dst=220.0.0.11,
> tp_dst=443,…,actions=ct(commit,table=0,zone=2,nat(dst=172.16.0.100:443))
>
>
>
> you are mapping 'to' private IPs, so you have control over the range
>
>
>
>
>
>
>
>
> From ct document, it seems it can’t support IP list for nat, anybody knows
> how we can handle such cases in some kind feasible way?
>
>
>
> In addition, is it ok if multiple openflow rules use the same NAT IP:PORT
> combination? I’m not sure if it will result in some conflicts for SNAT,
> because all of them need to do dynamic source port mapping, per my test, it
> seems this isn’t a problem.
>
>
>
> IIUC, as long as tuples are unique, it should be fine
>
>
>
>
>
>
> Thank you all in advance and appreciate your help sincerely.
>
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>
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