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, 5 insertions, 0 deletions

diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index 9661d7b765f0..9f70d54fcefc 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -218,6 +218,10 @@ extern struct sctp_globals {
 
         /* Flag to idicate if SCTP-AUTH is enabled */
         int auth_enable;
+
+        /* Flag to indicate whether computing and verifying checksum
+         * is disabled. */
+        int checksum_disable;
 } sctp_globals;
 
 #define sctp_rto_initial                (sctp_globals.rto_initial)
@@ -252,6 +256,7 @@ extern struct sctp_globals {
 #define sctp_addip_noauth               (sctp_globals.addip_noauth_enable)
 #define sctp_prsctp_enable              (sctp_globals.prsctp_enable)
 #define sctp_auth_enable                (sctp_globals.auth_enable)
+#define sctp_checksum_disable           (sctp_globals.checksum_disable)
 
 /* SCTP Socket type: UDP or TCP style. */
 typedef enum {