[ovs-dev] Question about gretap0 and erspan0 and ip6tnl0 creation

Gregory Rose gvrose8192 at gmail.com
Thu Oct 4 20:42:12 UTC 2018


On 10/4/2018 1:13 PM, Jin, Liang wrote:
> Because we don't use that module, just curious, they were not found before, is it possible to disable gre and ipv6 module, if we don't want to use it.

The short answer is no.

The OVS 2.10 datapath incorporates gre, ip_gre and ip6_gre kernel 
modules.  Whether you use the built-in
kernel modules (4.16 or later) or the ones that come with the OVS 
datapath compatibility modules you still
get the FB devices listed.

Here on my 4.16 kernel based machine without the OVS datapath loaded you 
still get those interfaces
when you load built-in kernel gre, ip_gre and ip6_gre kernel modules:

gvrose at ubuntu-1604:~$ ip link show
...
3: ip6tnl0 at NONE: <NOARP> mtu 1452 qdisc noop state DOWN mode DEFAULT 
group default qlen 1000
     link/tunnel6 :: brd ::
4: ip6gre0 at NONE: <NOARP> mtu 1448 qdisc noop state DOWN mode DEFAULT 
group default qlen 1000
     link/gre6 00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00 brd 
00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00
5: gre0 at NONE: <NOARP> mtu 1476 qdisc noop state DOWN mode DEFAULT group 
default qlen 1000
     link/gre 0.0.0.0 brd 0.0.0.0
6: gretap0 at NONE: <BROADCAST,MULTICAST> mtu 1462 qdisc noop state DOWN 
mode DEFAULT group default qlen 1000
     link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff
7: erspan0 at NONE: <BROADCAST,MULTICAST> mtu 1446 qdisc noop state DOWN 
mode DEFAULT group default qlen 1000
     link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff

Again, these are just the FB devices required to support namespaces.

The only way I can think of to not get these devices is to revert to a 
2.9.x OVS release.

Thanks,

- Greg
>
> Thanks
> L.J.
>
> On 10/4/18, 1:09 PM, "Gregory Rose" <gvrose8192 at gmail.com> wrote:
>
>      On 10/4/2018 11:16 AM, Jin, Liang via dev wrote:
>      > Hi ovs-dev,
>      > After we upgrade ovs 2.10, we found some interface created, why they are created even in bridge scenario?   is it possible not to create them when upgrading?  Is this a bug in ovs 2.10?
>      >
>      > 24: gretap0 at NONE: <BROADCAST,MULTICAST> mtu 1462 qdisc noop state DOWN mode DEFAULT group default qlen 1000
>      >      link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff
>      > 25: erspan0 at NONE: <BROADCAST,MULTICAST> mtu 1446 qdisc noop state DOWN mode DEFAULT group default qlen 1000
>      >      link/ether 12:0e:f1:ea:1d:e0 brd ff:ff:ff:ff:ff:ff
>      > 26: gre0 at NONE: <NOARP> mtu 1476 qdisc noop state DOWN mode DEFAULT group default qlen 1
>      >      link/gre 0.0.0.0 brd 0.0.0.0
>      > 27: ip6gre0 at NONE: <NOARP> mtu 1448 qdisc noop state DOWN mode DEFAULT group default qlen 1
>      >      link/gre6 00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00 brd 00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00
>      > 28: ip6tnl0 at NONE: <NOARP> mtu 1452 qdisc noop state DOWN mode DEFAULT group default qlen 1
>      > link/tunnel6 :: brd ::
>      
>      This is not a bug - it is intended operation.   They're required as the
>      FB devices for the newly added ipv6 gre tunneling and  ipv4/ipv6 ERSPAN
>      features.
>      
>      Why do you not want them created?
>      
>      - Greg
>      
>      >
>      >
>      > Thanks
>      > L.J.
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