netdev - [PATCH] net: optimise inet_proto_csum

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20140923085437.696B81AB26D@localhost.localdomain>
Date:	Tue, 23 Sep 2014 10:54:37 +0200 (CEST)
From:	Christophe Leroy <christophe.leroy@....fr>
To:	"David S. Miller" <davem@...emloft.net>
CC:	linux-kernel@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
	netdev@...r.kernel.org
Subject: [PATCH] net: optimise inet_proto_csum_replace4()

csum_partial() is a generic function which is not optimised for small fixed
length calculations, and its use requires to store "from" and "to" values in
memory while we already have them available in registers. This also has impact,
especially on RISC processors. In the same spirit as the change done by
Eric Dumazet on csum_replace2(), this patch rewrites inet_proto_csum_replace4()
taking into account RFC1624.

I spotted during a NATted tcp transfert that csum_partial() is one of top 5
consuming functions (around 8%), and the second user of csum_partial() is 
inet_proto_csum_replace4().

Signed-off-by: Christophe Leroy <christophe.leroy@....fr>

---
--
 net/core/utils.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/net/core/utils.c b/net/core/utils.c
index eed3433..efc76dd 100644
--- a/net/core/utils.c
+++ b/net/core/utils.c
@@ -306,16 +306,14 @@ EXPORT_SYMBOL(in6_pton);
 void inet_proto_csum_replace4(__sum16 *sum, struct sk_buff *skb,
 			      __be32 from, __be32 to, int pseudohdr)
 {
-	__be32 diff[] = { ~from, to };
 	if (skb->ip_summed != CHECKSUM_PARTIAL) {
-		*sum = csum_fold(csum_partial(diff, sizeof(diff),
-				~csum_unfold(*sum)));
+		*sum = csum_fold(csum_add(csum_sub(~csum_unfold(*sum), from),
+				 to));
 		if (skb->ip_summed == CHECKSUM_COMPLETE && pseudohdr)
-			skb->csum = ~csum_partial(diff, sizeof(diff),
-						~skb->csum);
+			skb->csum = ~csum_add(csum_sub(~(skb->csum), from), to);
 	} else if (pseudohdr)
-		*sum = ~csum_fold(csum_partial(diff, sizeof(diff),
-				csum_unfold(*sum)));
+		*sum = ~csum_fold(csum_add(csum_sub(csum_unfold(*sum), from),
+				  to));
 }
 EXPORT_SYMBOL(inet_proto_csum_replace4);
 
-- 
2.1.0

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html