[3.8.y.z extended stable] Patch "sctp: Perform software checksum if packet has to be fragmented." has been added to staging queue

Kamal Mostafa kamal at canonical.com
Fri Nov 1 21:43:42 UTC 2013

This is a note to let you know that I have just added a patch titled

    sctp: Perform software checksum if packet has to be fragmented.

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:


This patch is scheduled to be released in version

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see



>From 8229ca049e4679e12d93356fa936060deaa430cb Mon Sep 17 00:00:00 2001
From: Vlad Yasevich <vyasevich at gmail.com>
Date: Tue, 15 Oct 2013 22:01:31 -0400
Subject: sctp: Perform software checksum if packet has to be fragmented.

[ Upstream commit d2dbbba77e95dff4b4f901fee236fef6d9552072 ]

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: Kamal Mostafa <kamal 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 0c04637..d111b63 100644
--- a/net/sctp/output.c
+++ b/net/sctp/output.c
@@ -551,7 +551,7 @@ 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

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