netdev - Re: vrf and ipsec xfrm routing problem

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Date:   Mon, 20 Jan 2020 20:21:51 -0700
From:   David Ahern <dsahern@...il.com>
To:     Ben Greear <greearb@...delatech.com>,
        netdev <netdev@...r.kernel.org>
Subject: Re: vrf and ipsec xfrm routing problem

On 1/17/20 2:52 PM, Ben Greear wrote:
>> I tried adding a route to specify the x_frm as source, but that does
>> not appear to work:
>>
>> [root@...313-63e7 lanforge]# ip route add 192.168.10.0/24 via
>> 192.168.5.1 dev x_eth4 table 4
>> [root@...313-63e7 lanforge]# ip route show vrf _vrf4
>> default via 192.168.5.1 dev eth4
>> 192.168.5.0/24 dev eth4 scope link src 192.168.5.4
>> 192.168.10.0/24 via 192.168.5.1 dev eth4
>>
>> I also tried this, but no luck:
>>
>> [root@...313-63e7 lanforge]# ip route add 192.168.10.0/24 via
>> 192.168.10.1 dev x_eth4 table 4
>> Error: Nexthop has invalid gateway.
> 
> I went looking for why this was failing.  The reason is that this code
> is hitting the error case
> in the code snippet below (from 5.2.21+ kernel).
> 
> The oif is that of _vrf4, not the x_eth4 device.
> 
> David:  Is this expected behaviour?  Do you know how to tell vrf to use
> the x_eth4

It is expected behavior for VRF. l3mdev_update_flow changes the oif to
the VRF device if the passed in oif is enslaved to a VRF.

> xfrm device as oif when routing output to certain destinations?
> 
>     rcu_read_lock();
>     {
>         struct fib_table *tbl = NULL;
>         struct flowi4 fl4 = {
>             .daddr = nh->fib_nh_gw4,
>             .flowi4_scope = scope + 1,
>             .flowi4_oif = nh->fib_nh_oif,
>             .flowi4_iif = LOOPBACK_IFINDEX,
>         };
> 
>         /* It is not necessary, but requires a bit of thinking */
>         if (fl4.flowi4_scope < RT_SCOPE_LINK)
>             fl4.flowi4_scope = RT_SCOPE_LINK;

If you put your debug here, flowi4_oif should be fib_nh_oif per the
above initialization. It gets changed by the call to fib_lookup.

--

Sabrina sent me a short script on using xfrm devices to help me get up
to speed on that config (much simpler than using any of the *SWAN
programs). I have incorporated the xfrm device setup into a script of
other vrf + ipsec tests. A couple of tests are failing the basic setup.
I have a fix for one of them (as well as the fix for the qdisc on a VRF
device). I did notice trying to add routes with the xfrm device as the
nexthop dev was failing but have not had time to dig into it. I have
busy week but will try to spend some time on this use case this week.