With SCTP checksum offload available in virtio, it is now
possible for virtio to receive a sctp packet with CHECKSUM_PARTIAL
set (guest-to-guest traffic). SCTP doesn't really have a
partial checksum like TCP does, because CRC32c can't do partial
additive checksumming. It's all or nothing. So an SCTP packet
with CHECKSUM_PARTIAL will have checksum set to 0. Let SCTP
treat this as a valid checksum if CHECKSUM_PARTIAL is set.
Signed-off-by: Vladislav Yasevich <vyasevic@xxxxxxxxxx>
---
net/sctp/input.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/net/sctp/input.c b/net/sctp/input.c
index ba8a6e6..055b8ffa 100644
--- a/net/sctp/input.c
+++ b/net/sctp/input.c
@@ -80,8 +80,17 @@ static inline int sctp_rcv_checksum(struct net *net, struct sk_buff *skb)
{
struct sctphdr *sh = sctp_hdr(skb);
__le32 cmp = sh->checksum;
- __le32 val = sctp_compute_cksum(skb, 0);
+ __le32 val = 0;
+ /* In sctp PARTIAL checksum is always 0. This is a case of
+ * a packet received from guest that supports checksum offload.
+ * Assume it's correct as there is really no way to verify,
+ * and we want to avaoid computing it unnecesarily.
+ */
+ if (skb->ip_summed == CHECKSUM_PARTIAL)
+ return 0;
+
+ val = sctp_compute_cksum(skb, 0);
if (val != cmp) {
/* CRC failure, dump it. */
__SCTP_INC_STATS(net, SCTP_MIB_CHECKSUMERRORS);
--
2.9.5
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