Re: [PATCH net-next] ip6_gre: Fix MTU setting

Alexander Duyck
2016-05-09T22:44:16Z

On Mon, May 9, 2016 at 3:28 PM, Tom Herbert <tom@herbertland.com> wrote:
> In ip6gre_tnl_link_config set t->tun_len and t->hlen correctly for the
> configuration. For hard_header_len and mtu calculation include
> IPv6 header and encapsulation overhead.
>
> In ip6gre_tunnel_init_common set t->tun_len and t->hlen correctly for
> the configuration. Revert to setting hard_header_len instead of
> needed_headroom.
>
> Tested:
>
> ./ip link add name tun8 type ip6gretap remote \
> 2401:db00:20:911a:face:0:27:0 local \
> 2401:db00:20:911a:face:0:25:0 ttl 225
>
> Gives MTU of 1434. That is equal to 1500 - 40 - 14 - 4 - 8.
>
> ./ip link add name tun8 type ip6gretap remote \
> 2401:db00:20:911a:face:0:27:0 local \
> 2401:db00:20:911a:face:0:25:0 ttl 225 okey 123
>
> Gives MTU of 1430. That is equal to 1500 - 40 - 14 - 4 - 8 - 4.
>
> Signed-off-by: Tom Herbert <tom@herbertland.com>

So this gives me the correct result now. However we still need patch
3 / 11 from the set you submitted next week in order to be able to
even transmit because the flags are otherwise mangled.

Tested-by: Alexander Duyck <aduyck@mirantis.com>