net: Discard and warn about LRO'd skbs received for forwarding

Add skb_warn_if_lro() to test whether an skb was received with LRO and
warn if so.

Change br_forward(), ip_forward() and ip6_forward() to call it) and
discard the skb if it returns true.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 14 insertions, 0 deletions

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 299ec4b31412..2220b9e2dab0 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1702,6 +1702,20 @@ static inline int skb_is_gso_v6(const struct sk_buff *skb)
         return skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6;
 }
 
+extern void __skb_warn_lro_forwarding(const struct sk_buff *skb);
+
+static inline bool skb_warn_if_lro(const struct sk_buff *skb)
+{
+        /* LRO sets gso_size but not gso_type, whereas if GSO is really
+         * wanted then gso_type will be set. */
+        struct skb_shared_info *shinfo = skb_shinfo(skb);
+        if (shinfo->gso_size != 0 && unlikely(shinfo->gso_type == 0)) {
+                __skb_warn_lro_forwarding(skb);
+                return true;
+        }
+        return false;
+}
+
 static inline void skb_forward_csum(struct sk_buff *skb)
 {
         /* Unfortunately we don't support this one.  Any brave souls? */