net: warn if gso_type isn't set for a GSO SKB

In bug report [0] a warning in r8169 driver was reported that was
caused by an invalid GSO SKB (gso_type was 0). See [1] for a discussion
about this issue. Still the origin of the invalid GSO SKB isn't clear.

It shouldn't be a network drivers task to check for invalid GSO SKB's.
Also, even if issue [0] can be fixed, we can't be sure that a
similar issue doesn't pop up again at another place.
Therefore let gso_features_check() check for such invalid GSO SKB's.

[0] https://bugzilla.kernel.org/show_bug.cgi?id=209423
[1] https://www.spinics.net/lists/netdev/msg690794.htmlSigned-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Link: https://lore.kernel.org/r/97c78d21-7f0b-d843-df17-3589f224d2cf@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/core/dev.c

@@ -3495,6 +3495,11 @@ static netdev_features_t gso_features_check(const struct sk_buff *skb,
 	if (gso_segs > dev->gso_max_segs)
 		return features & ~NETIF_F_GSO_MASK;
 
+	if (!skb_shinfo(skb)->gso_type) {
+		skb_warn_bad_offload(skb);
+		return features & ~NETIF_F_GSO_MASK;
+	}
+
 	/* Support for GSO partial features requires software
 	 * intervention before we can actually process the packets
 	 * so we need to strip support for any partial features now