Re: [PATCH net] ip_gre: clear feature flags when incompatible o_flags are set

[Xin Long <lucien.xin@gmail.com>]

On Tue, Apr 10, 2018 at 6:57 PM, Sabrina Dubroca <sd@queasysnail.net> wrote:
> Commit dd9d598c6657 ("ip_gre: add the support for i/o_flags update via
> netlink") added the ability to change o_flags, but missed that the
> GSO/LLTX features are disabled by default, and only enabled some gre
> features are unused. Thus we also need to disable the GSO/LLTX features
> on the device when the TUNNEL_SEQ or TUNNEL_CSUM flags are set.
>
> These two examples should result in the same features being set:
>
>     ip link add gre_none type gre local 192.168.0.10 remote 192.168.0.20 ttl 255 key 0
>
>     ip link set gre_none type gre seq
>     ip link add gre_seq type gre local 192.168.0.10 remote 192.168.0.20 ttl 255 key 1 seq
>
> Fixes: dd9d598c6657 ("ip_gre: add the support for i/o_flags update via netlink")
> Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
> ---
>  net/ipv4/ip_gre.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
> index a8772a978224..9c169bb2444d 100644
> --- a/net/ipv4/ip_gre.c
> +++ b/net/ipv4/ip_gre.c
> @@ -781,8 +781,14 @@ static void ipgre_link_update(struct net_device *dev, bool set_mtu)
>                     tunnel->encap.type == TUNNEL_ENCAP_NONE) {
>                         dev->features |= NETIF_F_GSO_SOFTWARE;
>                         dev->hw_features |= NETIF_F_GSO_SOFTWARE;
> +               } else {
> +                       dev->features &= ~NETIF_F_GSO_SOFTWARE;
> +                       dev->hw_features &= ~NETIF_F_GSO_SOFTWARE;
>                 }
>                 dev->features |= NETIF_F_LLTX;
> +       } else {
> +               dev->hw_features &= ~NETIF_F_GSO_SOFTWARE;
> +               dev->features &= ~(NETIF_F_LLTX | NETIF_F_GSO_SOFTWARE);
>         }
>  }
>
> --
> 2.16.2
>
Reviewed-by: Xin Long <lucien.xin@gmail.com>