The driver was failing to check that the SKB wasn't cloned
before adding checksum data.
Replace existing handling to extend/copy the header buffer
with skb_cow_head.
Signed-off-by: NJames Hughes <james.hughes@raspberrypi.org>
Acked-by: NEric Dumazet <edumazet@google.com>
Acked-by: NWoojung Huh <Woojung.Huh@microchip.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>