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Commit 06e86806 authored by Lucas Nussbaum's avatar Lucas Nussbaum Committed by David S. Miller
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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: default avatarLucas Nussbaum <lucas.nussbaum@ens-lyon.fr>
Signed-off-by: default avatarVlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 85e8d004

include/net/sctp/structs.h

+5 −0
Original line number Diff line number Diff line
@@ -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 {

net/sctp/input.c

+2 −1
Original line number Diff line number Diff line
@@ -142,7 +142,8 @@ int sctp_rcv(struct sk_buff *skb) 
	__skb_pull(skb, skb_transport_offset(skb));

	if (skb->len < sizeof(struct sctphdr))

		goto discard_it;

	if (!skb_csum_unnecessary(skb) && sctp_rcv_checksum(skb) < 0)

	if (!sctp_checksum_disable && !skb_csum_unnecessary(skb) &&

		  sctp_rcv_checksum(skb) < 0)

		goto discard_it;



	skb_pull(skb, sizeof(struct sctphdr));

net/sctp/output.c

+1 −1
Original line number Diff line number Diff line
@@ -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

net/sctp/protocol.c

+2 −0
Original line number Diff line number Diff line
@@ -1411,4 +1411,6 @@ MODULE_ALIAS("net-pf-" __stringify(PF_INET) "-proto-132"); 
MODULE_ALIAS("net-pf-" __stringify(PF_INET6) "-proto-132");

MODULE_AUTHOR("Linux Kernel SCTP developers <lksctp-developers@lists.sourceforge.net>");

MODULE_DESCRIPTION("Support for the SCTP protocol (RFC2960)");

module_param_named(no_checksums, sctp_checksum_disable, bool, 0644);

MODULE_PARM_DESC(no_checksums, "Disable checksums computing and verification");

MODULE_LICENSE("GPL");