sctp: Change sctp to implement csum_levels

CHECKSUM_UNNECESSARY may be applied to the SCTP CRC so we need to
appropriate account for this by decrementing csum_level. This is
done by calling __skb_dec_checksum_unnecessary.

Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 2 deletions

diff --git a/net/sctp/input.c b/net/sctp/input.c
index c1b991294516..b6493b3f11a9 100644
--- a/net/sctp/input.c
+++ b/net/sctp/input.c
@@ -133,9 +133,13 @@ int sctp_rcv(struct sk_buff *skb)
         __skb_pull(skb, skb_transport_offset(skb));
         if (skb->len < sizeof(struct sctphdr))
                 goto discard_it;
-        if (!sctp_checksum_disable && !skb_csum_unnecessary(skb) &&
-                  sctp_rcv_checksum(net, skb) < 0)
+
+        skb->csum_valid = 0; /* Previous value not applicable */
+        if (skb_csum_unnecessary(skb))
+                __skb_decr_checksum_unnecessary(skb);
+        else if (!sctp_checksum_disable && sctp_rcv_checksum(net, skb) < 0)
                 goto discard_it;
+        skb->csum_valid = 1;
 
         skb_pull(skb, sizeof(struct sctphdr));