[PATCH V2 net-next 2/6] sctp: Handle sctp packets with CHECKSUM_PARTIAL
From: Vladislav Yasevich <hidden>
Date: 2018-05-02 02:07:53
Also in:
linux-sctp
Subsystem:
networking [general], sctp protocol, the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Marcelo Ricardo Leitner, Xin Long, Linus Torvalds
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 <redacted> --- 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