[PATCH 3.5 56/64] sctp: Perform software checksum if packet has to be fragmented.

[Luis Henriques]

3.5.7.24 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Vlad Yasevich <vyasevich at gmail.com>

commit d2dbbba77e95dff4b4f901fee236fef6d9552072 upstream.

IP/IPv6 fragmentation knows how to compute only TCP/UDP checksum.
This causes problems if SCTP packets has to be fragmented and
ipsummed has been set to PARTIAL due to checksum offload support.
This condition can happen when retransmitting after MTU discover,
or when INIT or other control chunks are larger then MTU.
Check for the rare fragmentation condition in SCTP and use software
checksum calculation in this case.

CC: Fan Du <fan.du at windriver.com>
Signed-off-by: Vlad Yasevich <vyasevich at gmail.com>
Acked-by: Neil Horman <nhorman at tuxdriver.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/sctp/output.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sctp/output.c b/net/sctp/output.c
index a80b310..a1e2a9b 100644
--- a/net/sctp/output.c
+++ b/net/sctp/output.c
@@ -524,7 +524,7 @@ int sctp_packet_transmit(struct sctp_packet *packet)
 	 */
 	if (!sctp_checksum_disable) {
 		if (!(dst->dev->features & NETIF_F_SCTP_CSUM) ||
-		    (dst_xfrm(dst) != NULL)) {
+		    (dst_xfrm(dst) != NULL) || packet->ipfragok) {
 			__u32 crc32 = sctp_start_cksum((__u8 *)sh, cksum_buf_len);
 
 			/* 3) Put the resultant value into the checksum field in the
-- 
1.8.3.2