netdev - Re: [PATCH net-next 1/4] selftests: forwarding: Test redirecting gre or ipip packets to Ethernet

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Date:   Wed, 7 Jul 2021 09:05:24 -0600
From:   David Ahern <dsahern@...il.com>
To:     Guillaume Nault <gnault@...hat.com>
Cc:     Ido Schimmel <idosch@...sch.org>,
        David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        Shuah Khan <shuah@...nel.org>, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH net-next 1/4] selftests: forwarding: Test redirecting gre
 or ipip packets to Ethernet

On 7/6/21 1:02 PM, Guillaume Nault wrote:
> On Thu, Jul 01, 2021 at 09:38:44AM -0600, David Ahern wrote:
>> On 7/1/21 8:59 AM, Guillaume Nault wrote:
>>> I first tried to write this selftest using VRFs, but there were some
>>> problems that made me switch to namespaces (I don't remember precisely
>>> which ones, probably virtual tunnel devices in collect_md mode).
>>
>> if you hit a problem with the test not working, send me the test script
>> and I will take a look.
> 
> So I've looked again at what it'd take to make a VRF-based selftest.
> The problem is that we currently can't create collect_md tunnel
> interfaces in different VRFs, if the VRFs are part of the same netns.
> 
> Most tunnels explicitely refuse to create a collect_md device if
> another one already exists in the netns, no matter the rest of the
> tunnel parameters. This is the behaviour of ip_gre, ipip, ip6_gre and
> ip6_tunnel.
> 
> Then there's sit, which allows the creation of the second collect_md
> device in the other VRF. However, iproute2 doesn't set the
> IFLA_IPTUN_LINK attribute when it creates an external device, so it
> can't set up such a configuration.
> 
> Bareudp simply doesn't support VRF.
> 
> Finally, vxlan allows devices with different IFLA_VXLAN_LINK attributes
> to be created, but only when VXLAN_F_IPV6_LINKLOCAL is set. Removing
> the VXLAN_F_IPV6_LINKLOCAL test at the end of vxlan_config_validate()
> is enough to make two VXLAN-GPE devices work in a multi-VRF setup:

Thanks for the details. In short, some work is needed to extend VRF
support to these tunnels. That is worth doing if you have the time.