sctp: Allow to disable SCTP checksums via module parameter

This is a new version of my patch, now using a module parameter instead
of a sysctl, so that the option is harder to find. Please note that,
once the module is loaded, it is still possible to change the value of
the parameter in /sys/module/sctp/parameters/, which is useful if you
want to do performance comparisons without rebooting.

Computation of SCTP checksums significantly affects the performance of
SCTP. For example, using two dual-Opteron 246 connected using a Gbe
network, it was not possible to achieve more than ~730 Mbps, compared to
941 Mbps after disabling SCTP checksums.
Unfortunately, SCTP checksum offloading in NICs is not commonly
available (yet).

By default, checksums are still enabled, of course.

Signed-off-by: Lucas Nussbaum <lucas.nussbaum@ens-lyon.fr>
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 1 deletions

diff --git a/net/sctp/output.c b/net/sctp/output.c
index 47bfba6c03ec..2d65b7a7330b 100644
--- a/net/sctp/output.c
+++ b/net/sctp/output.c
@@ -531,7 +531,7 @@ int sctp_packet_transmit(struct sctp_packet *packet)
          * Note: Adler-32 is no longer applicable, as has been replaced
          * by CRC32-C as described in <draft-ietf-tsvwg-sctpcsum-02.txt>.
          */
-        if (!(dst->dev->features & NETIF_F_NO_CSUM)) {
+        if (!sctp_checksum_disable && !(dst->dev->features & NETIF_F_NO_CSUM)) {
                 crc32 = sctp_start_cksum((__u8 *)sh, cksum_buf_len);
                 crc32 = sctp_end_cksum(crc32);
         } else