ip_gre: clear feature flags when incompatible o_flags are set

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>
Reviewed-by: Xin Long <lucien.xin@gmail.com>
Acked-by: William Tu <u9012063@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 0 deletions

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);
         }
 }