Currently, when resegmenting an unexpected UDP GRO packet, the full UDP
checksum will be calculated for every new SKB created by skb_segment()
because the netdev features passed in by udp_rcv_segment() lack any
information about checksum offload capabilities.
We have no need to perform this calculation again, as
1) The GRO implementation guarantees that any packets making it to the
udp_rcv_segment() function had correct checksums, and, more
importantly,
2) Upon the successful return of udp_rcv_segment(), we immediately pull
the UDP header off and either queue the segment to the socket or
hand it off to a new protocol handler. In either case, the checksum
is not needed.
Fixes: cf329aa42b66 ("udp: cope with UDP GRO packet misdirection")
Cc: Paolo Abeni <pab...@redhat.com>
Cc: Subash Abhinov Kasiviswanathan <subas...@codeaurora.org>
Signed-off-by: Sean Tranchetti <stran...@codeaurora.org>
---
include/net/udp.h | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/include/net/udp.h b/include/net/udp.h
index d8ce937..6164d5c 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -472,11 +472,15 @@ static inline struct sk_buff *udp_rcv_segment(struct sock
*sk,
struct sk_buff *skb, bool ipv4)
{
struct sk_buff *segs;
+ netdev_features_t features = NETIF_F_SG;
+
+ /* Avoid csum recalculation in skb_segment() */
+ features |= NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM;
/* the GSO CB lays after the UDP one, no need to save and restore any
* CB fragment
*/
- segs = __skb_gso_segment(skb, NETIF_F_SG, false);
+ segs = __skb_gso_segment(skb, features, false);
if (unlikely(IS_ERR_OR_NULL(segs))) {
int segs_nr = skb_shinfo(skb)->gso_segs;
--
1.9.1
