veth pair ping fail if one of them enslaved into a VRF

veth pair ping fail if one of them enslaved into a VRF

[Zoltán Elek]

Hi!

I have a simple scenario, with a veth pair, IP addresses assigned from
the same subnet. They can ping eachother. But when I put one of them
into a VRF (in the example below, I put veth in-vrf into the test-vrf
VRF) the ping fails. My first question: that is the expected behavior?
And my second question: is there any way to overcome this?

Here are my test commands:
ip link add out-of-vrf type veth peer name in-vrf
ip link set dev out-of-vrf up
ip link set dev in-vrf up
ip link add test-vrf type vrf table 10
ip link set dev test-vrf up
ip -4 addr add 100.127.253.2/24 dev in-vrf
ip -4 addr add 100.127.253.1/24 dev out-of-vrf

Then ping works as expected:
ping -c1 -I 100.127.253.1 100.127.253.2

After I put the in-vrf into test-vrf, ping fails:
ip link set in-vrf vrf test-vrf up

Thanks,
Zoltan Elek,
VI1

Re: veth pair ping fail if one of them enslaved into a VRF

[Ido Schimmel]

On Tue, Jul 02, 2019 at 08:42:15PM +0200, Zoltán Elek wrote:
> Hi!
> 
> I have a simple scenario, with a veth pair, IP addresses assigned from
> the same subnet. They can ping eachother. But when I put one of them
> into a VRF (in the example below, I put veth in-vrf into the test-vrf
> VRF) the ping fails. My first question: that is the expected behavior?
> And my second question: is there any way to overcome this?
> 
> Here are my test commands:
> ip link add out-of-vrf type veth peer name in-vrf
> ip link set dev out-of-vrf up
> ip link set dev in-vrf up
> ip link add test-vrf type vrf table 10
> ip link set dev test-vrf up
> ip -4 addr add 100.127.253.2/24 dev in-vrf
> ip -4 addr add 100.127.253.1/24 dev out-of-vrf
> 
> Then ping works as expected:
> ping -c1 -I 100.127.253.1 100.127.253.2
> 
> After I put the in-vrf into test-vrf, ping fails:
> ip link set in-vrf vrf test-vrf up

You need to re-order the FIB rules so that lookup for 100.127.253.1
happens in table 10 and not in the local table:

# ip -4 rule add pref 32765 table local
# ip -4 rule del pref 0
# ip -4 rule show 
1000:   from all lookup [l3mdev-table] 
32765:  from all lookup local 
32766:  from all lookup main 
32767:  from all lookup default 

Bad:

ping 16735 [001] 13726.398115: fib:fib_table_lookup: table 255 oif 0 iif
9 proto 0 100.127.253.2/0 -> 100.127.253.1/0 tos 0 scope 0 flags 4 ==>
dev out-of-vrf gw 0.0.0.0 src 100.127.253.1 err 0

Good:

ping 16665 [001] 13500.937145: fib:fib_table_lookup: table 10 oif 0 iif
9 proto 0 100.127.253.2/0 -> 100.127.253.1/0 tos 0 scope 0 flags 4 ==>
dev in-vrf gw 0.0.0.0 src 100.127.253.2 err 0

> 
> Thanks,
> Zoltan Elek,
> VI1

Re: veth pair ping fail if one of them enslaved into a VRF

[Zoltán Elek]

Thank you for the detailed answer, I tried your solution and it works
as expected.

Ido Schimmel <idosch@idosch.org> ezt írta (időpont: 2019. júl. 2., K, 21:21):
>
> On Tue, Jul 02, 2019 at 08:42:15PM +0200, Zoltán Elek wrote:
> > Hi!
> >
> > I have a simple scenario, with a veth pair, IP addresses assigned from
> > the same subnet. They can ping eachother. But when I put one of them
> > into a VRF (in the example below, I put veth in-vrf into the test-vrf
> > VRF) the ping fails. My first question: that is the expected behavior?
> > And my second question: is there any way to overcome this?
> >
> > Here are my test commands:
> > ip link add out-of-vrf type veth peer name in-vrf
> > ip link set dev out-of-vrf up
> > ip link set dev in-vrf up
> > ip link add test-vrf type vrf table 10
> > ip link set dev test-vrf up
> > ip -4 addr add 100.127.253.2/24 dev in-vrf
> > ip -4 addr add 100.127.253.1/24 dev out-of-vrf
> >
> > Then ping works as expected:
> > ping -c1 -I 100.127.253.1 100.127.253.2
> >
> > After I put the in-vrf into test-vrf, ping fails:
> > ip link set in-vrf vrf test-vrf up
>
> You need to re-order the FIB rules so that lookup for 100.127.253.1
> happens in table 10 and not in the local table:
>
> # ip -4 rule add pref 32765 table local
> # ip -4 rule del pref 0
> # ip -4 rule show
> 1000:   from all lookup [l3mdev-table]
> 32765:  from all lookup local
> 32766:  from all lookup main
> 32767:  from all lookup default
>
> Bad:
>
> ping 16735 [001] 13726.398115: fib:fib_table_lookup: table 255 oif 0 iif
> 9 proto 0 100.127.253.2/0 -> 100.127.253.1/0 tos 0 scope 0 flags 4 ==>
> dev out-of-vrf gw 0.0.0.0 src 100.127.253.1 err 0
>
> Good:
>
> ping 16665 [001] 13500.937145: fib:fib_table_lookup: table 10 oif 0 iif
> 9 proto 0 100.127.253.2/0 -> 100.127.253.1/0 tos 0 scope 0 flags 4 ==>
> dev in-vrf gw 0.0.0.0 src 100.127.253.2 err 0
>
> >
> > Thanks,
> > Zoltan Elek,
> > VI1