[ovs-dev] Odd gre_sys MTU setting (2.6.x vs 2.8.x)

[Eric Garver]

On Sat, Jan 13, 2018 at 03:57:08PM +0000, James Page wrote:
> Hi Ben s
> 
> On Sat, 13 Jan 2018 at 14:55 James Page <james.page at ubuntu.com> wrote:
> 
> > OK, I sent a patch:
> >>         https://patchwork.ozlabs.org/patch/860192/
> >
> >
> > Thanks Ben - I'll pull this patch into the Ubuntu packages and test this
> > weekend.
> >
> 
>  I pulled your patch in ontop of our current 2.8.1 packages and re-tested;
> I'm not seeing a difference in behaviour with the patch in place. I removed
> the vport_gre and ip_gre kernel modules to force a re-creation of the
> device on restart of OVS as well as trying a reboot of the test machine:
> 
> 7: 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
> 8: 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
> 9: gre_sys at NONE: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1472 qdisc
> pfifo_fast master ovs-system state UNKNOWN mode DEFAULT group default qlen
> 1000
>     link/ether 52:ad:6d:89:bb:54 brd ff:ff:ff:ff:ff:ff

Are there any errors is dmesg? It's possible setlink won't accept
UINT16_MAX. grep for "Invalid MTU".