[NET] gso: Fix GSO feature mask in sk_setup_caps

This isn't a bug just yet as only TCP uses sk_setup_caps for GSO.
However, if and when UDP or something else starts using it this is
likely to cause a problem if we forget to add software emulation
for it at the same time.

The problem is that right now we translate GSO emulation to the
bitmask NETIF_F_GSO_MASK, which includes every protocol, even
ones that we cannot emulate.

This patch makes it provide only the ones that we can emulate.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/sock.c

@@ -998,7 +998,7 @@ void sk_setup_caps(struct sock *sk, struct dst_entry *dst)
 	__sk_dst_set(sk, dst);
 	sk->sk_route_caps = dst->dev->features;
 	if (sk->sk_route_caps & NETIF_F_GSO)
-		sk->sk_route_caps |= NETIF_F_GSO_MASK;
+		sk->sk_route_caps |= NETIF_F_GSO_SOFTWARE;
 	if (sk_can_gso(sk)) {
 		if (dst->header_len)
 			sk->sk_route_caps &= ~NETIF_F_GSO_MASK;