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@windriver.com>
Signed-off-by: Vlad Yasevich <vyasevich@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/net/sctp/output.c b/net/sctp/output.c
index d957fe1..cf3e22c 100644 (file)
--- a/net/sctp/output.c
+++ b/net/sctp/output.c
@@ -519,7 +519,7 @@ 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