[PATCH net-next] netkit: Don't emit scrub attribute for single device mode

[Daniel Borkmann <daniel@iogearbox.net>]

When userspace reads a single mode netkit device via RTM_GETLINK,
it receives IFLA_NETKIT_SCRUB=NETKIT_SCRUB_DEFAULT attribute from
netkit_fill_info(). If that attribute is echoed back to recreate
the device, the seen_scrub presence check in netkit_new_link()
causes creation to fail with -EOPNOTSUPP. Since it has no meaning
for single devices at this point, just don't dump it.

Fixes: 481038960538 ("netkit: Add single device mode for netkit")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
---
 drivers/net/netkit.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/netkit.c b/drivers/net/netkit.c
index 5619209329d5..7b56a7ad7a49 100644
--- a/drivers/net/netkit.c
+++ b/drivers/net/netkit.c
@@ -1214,7 +1214,8 @@ static int netkit_fill_info(struct sk_buff *skb, const struct net_device *dev)
 		return -EMSGSIZE;
 	if (nla_put_u32(skb, IFLA_NETKIT_MODE, nk->mode))
 		return -EMSGSIZE;
-	if (nla_put_u32(skb, IFLA_NETKIT_SCRUB, nk->scrub))
+	if (nk->pair == NETKIT_DEVICE_PAIR &&
+	    nla_put_u32(skb, IFLA_NETKIT_SCRUB, nk->scrub))
 		return -EMSGSIZE;
 	if (nla_put_u16(skb, IFLA_NETKIT_HEADROOM, dev->needed_headroom))
 		return -EMSGSIZE;
-- 
2.43.0