netdev - Re: VRF: ssh port forwarding between non-vrf and vrf interface.

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Message-ID: <9f442307-dd27-7493-3774-4ec72f344003@gmail.com>
Date:   Tue, 26 Jan 2021 10:28:43 -0700
From:   David Ahern <dsahern@...il.com>
To:     Ben Greear <greearb@...delatech.com>,
        netdev <netdev@...r.kernel.org>
Subject: Re: VRF: ssh port forwarding between non-vrf and vrf interface.

On 1/25/21 8:18 AM, Ben Greear wrote:
> On 1/22/21 8:02 AM, David Ahern wrote:
>> On 1/22/21 8:45 AM, Ben Greear wrote:
>>> Hello,
>>>
>>> I have a system with a management interface that is not in any VRF, and
>>> then I have
>>> a port that *is* in a VRF.  I'd like to be able to set up ssh port
>>> forwarding so that
>>> when I log into the system on the management interface it will
>>> automatically forward to
>>> an IP accessible through the VRF interface.
>>>
>>> Is there a way to do such a thing?
>>>
>>
>> For a while I had a system setup with eth0 in a management VRF and setup
>> to do NAT and port forwarding of incoming ssh connections, redirecting
>> to VMs running in a different namespace. Crossing VRFs with netfilter
>> most likely will not work without some development. You might be able to
>> do it with XDP - rewrite packet headers and redirect. That too might
>> need a bit of development depending on the netdevs involved.
>>
> 
> Maybe easier to improve ssh so that it could specify a netdev to bind to
> when
> making the call to the redirected destination?
> 

maybe. I did not realize this feature made it into ssh, but it has
supported 'rdomains' since 2017 I believe. For Linux rdomain is a VRF.