[PATCH 4.15 09/53] ip_gre: clear feature flags when incompatible o_flags are set

[Greg Kroah-Hartman]

4.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Sabrina Dubroca <sd@xxxxxxxxxxxxxxx>


[ Upstream commit 1cc5954f44150bb70cac07c3cc5df7cf0dfb61ec ]

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@xxxxxxxxxxxxxxx>
Reviewed-by: Xin Long <lucien.xin@xxxxxxxxx>
Acked-by: William Tu <u9012063@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/ipv4/ip_gre.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -796,8 +796,14 @@ static void ipgre_link_update(struct net
 		    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);
 	}
 }