From: Maximilian Bosch <maximilian@mbosch.me>
To: Mike Manning <mmanning@vyatta.att-mail.com>, netdev@vger.kernel.org
Subject: Re: VRF Issue Since kernel 5
Date: Sun, 19 Apr 2020 22:35:16 +0200 [thread overview]
Message-ID: <20200419203516.jrpm5jzokmswkpue@topsnens> (raw)
In-Reply-To: <d81f97fe-be4b-041d-1233-7e69758d96ef@vyatta.att-mail.com>
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Hi!
> Can you please clarify what the issue is with using 'ip vrf exec <vrf>
> ssh' for running the ssh client in the vrf?
well, SSH was just an example to demonstrate the issue. As mentioned in
my previous emails, the `ip vrf exec`-wrapper is only needed for
processes that do TCP, UDP-traffic is still leaked through the VRF.
Thanks
Maximilian
On Wed, Apr 08, 2020 at 11:07:31AM +0100, Mike Manning wrote:
> Hi Maximilian,
> Can you please clarify what the issue is with using 'ip vrf exec <vrf>
> ssh' for running the ssh client in the vrf? This is the recommended
> method for running an application in a VRF. As part of our VRF
> development on this a couple of years ago, we provided a changeset for
> openssh so that the vrf could be specified as an option, cf
> https://bugzilla.mindrot.org/show_bug.cgi?id=2784. That was not applied
> due to the ease of using 'ip vrf exec'.
>
> Alternatively, to run the ssh client in the default VRF, you can bind it
> to an address on an interface (or specify the interface) in the default
> VRF using ssh -b (or -B) option, or similarly add an entry in
> /etc/ssh/ssh_config for BindAddress (or BindInterface).
>
> Then for egress, leak a route in the default table to get to the gateway
> via the VRF (as you must already be doing), and for ingress, leak a
> route in the VRF's table for the return path to the ssh client. For
> this, get the table id for the vrf from 'ip vrf', add the route for the
> client prefix with the additional 'table <tbl-id>' option, and confirm
> the route with 'ip route show vrf <vrf-name>'.
>
> I have started looking at the issue you have reported, but as you may
> appreciate, it is not trivial. This client-side use-case is not typical,
> as VRF config is generally applied to routers or switches, not hosts.
>
> Thanks
> Mike
>
>
> On 05/04/2020 17:52, David Ahern wrote:
> > On 4/2/20 5:02 PM, Maximilian Bosch wrote:
> >> Hi!
> >>
> >>> I do not see how this worked on 4.19. My comment above is a fundamental
> >>> property of VRF and has been needed since day 1. That's why 'ip vrf
> >>> exec' exists.
> >> I'm afraid I have to disagree here: first of all, I created a
> >> regression-test in NixOS for this purpose a while ago[1]. The third test-case
> >> (lines 197-208) does basically what I demonstrated in my previous emails
> >> (opening SSH connetions through a local VRF). This worked fine until we
> >> bumped our default kernel to 5.4.x which is the reason why this testcase
> >> is temporarily commented out.
> > I do not have access to a NixOS install, nor the time to create one.
> > Please provide a set of ip commands to re-create the test that work with
> > Ubuntu, debian or fedora.
> >
> >
> >> After skimming through the VRF-related changes in 4.20 and 5.0 (which
> >> might've had some relevant changes as you suggested previously), I
> >> rebuilt the kernels 5.4.29 and 5.5.13 with
> >> 3c82a21f4320c8d54cf6456b27c8d49e5ffb722e[2] reverted on top and the
> >> commented-out testcase works fine again. In other words, my usecase
> >> seems to have worked before and the mentioned commit appears to cause
> >> the "regression".
> > The vyatta folks who made the changes will take a look.
>
>
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next prev parent reply other threads:[~2020-04-19 20:35 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-09 7:46 VRF Issue Since kernel 5 Gowen
2019-09-09 9:28 ` Alexis Bauvin
[not found] ` <CWLP265MB1554B902B7F3B43E6E75FD0DFDB70@CWLP265MB1554.GBRP265.PROD.OUTLOOK.COM>
2019-09-09 12:01 ` Alexis Bauvin
2019-09-09 19:43 ` Gowen
2019-09-10 14:22 ` Gowen
2019-09-10 16:36 ` David Ahern
2019-09-11 5:09 ` Gowen
2019-09-11 11:19 ` Gowen
2019-09-11 11:49 ` Gowen
2019-09-11 12:15 ` Mike Manning
[not found] ` <CWLP265MB155485682829AD9B66AB66FCFDB10@CWLP265MB1554.GBRP265.PROD.OUTLOOK.COM>
[not found] ` <CWLP265MB155424EF95E39E98C4502F86FDB10@CWLP265MB1554.GBRP265.PROD.OUTLOOK.COM>
2019-09-11 16:09 ` David Ahern
2019-09-12 6:54 ` Gowen
2020-03-10 20:47 ` Maximilian Bosch
2020-03-12 1:06 ` David Ahern
2020-04-01 18:16 ` Maximilian Bosch
2020-04-01 19:18 ` David Ahern
2020-04-01 20:35 ` Maximilian Bosch
2020-04-01 20:41 ` David Ahern
2020-04-02 23:02 ` Maximilian Bosch
2020-04-05 16:52 ` David Ahern
2020-04-08 10:07 ` Mike Manning
2020-04-08 15:36 ` David Ahern
2020-04-19 20:35 ` Maximilian Bosch [this message]
2019-09-11 16:53 ` David Ahern
2019-09-10 16:39 ` David Ahern
2019-09-11 17:02 ` David Ahern
2019-09-12 6:50 ` Gowen
2019-09-13 17:41 ` David Ahern
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