From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joe Perches Subject: Re: [PATCH] - trivial - Improve appletalk checksum calculation Date: Sun, 28 Oct 2007 14:01:37 -0700 Message-ID: <1193605297.26695.121.camel@localhost> References: Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: Herbert Xu , davem@davemloft.net, acme@ghostprotocols.net, netdev@vger.kernel.org To: Urs Thuermann Return-path: Received: from DSL022.labridge.com ([206.117.136.22]:1276 "EHLO perches.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751036AbXJ1V2I (ORCPT ); Sun, 28 Oct 2007 17:28:08 -0400 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Sun, 2007-10-28 at 21:18 +0100, Urs Thuermann wrote: > I have written a short test program to show this and tested it on i686 > (gcc-4.2.2) and powerpc (gcc-3.4.5) without optimization and with -O6. Thanks for that. > BTW, shouldn't unsigned long be replaced by unsigned int to avoid > 64-bit operations one some platforms? probably unsigned long should be u16. Compiled, untested. diff --git a/net/appletalk/ddp.c b/net/appletalk/ddp.c index 7c0b515..c3890cc 100644 --- a/net/appletalk/ddp.c +++ b/net/appletalk/ddp.c @@ -922,25 +922,19 @@ static int atrtr_ioctl(unsigned int cmd, void __user *arg) * Checksum: This is 'optional'. It's quite likely also a good * candidate for assembler hackery 8) */ -static unsigned long atalk_sum_partial(const unsigned char *data, - int len, unsigned long sum) +static u16 atalk_sum_partial(const unsigned char *data, + int len, u16 sum) { - /* This ought to be unwrapped neatly. I'll trust gcc for now */ while (len--) { - sum += *data; - sum <<= 1; - if (sum & 0x10000) { - sum++; - sum &= 0xffff; - } - data++; + sum += *data++; + sum = ((sum & 0x8000) >> 15) | ((sum & 0x7fff) << 1); } return sum; } /* Checksum skb data -- similar to skb_checksum */ -static unsigned long atalk_sum_skb(const struct sk_buff *skb, int offset, - int len, unsigned long sum) +static u16 atalk_sum_skb(const struct sk_buff *skb, int offset, + int len, u16 sum) { int start = skb_headlen(skb); int i, copy; @@ -1010,13 +1004,13 @@ static unsigned long atalk_sum_skb(const struct sk_buff *skb, int offset, static __be16 atalk_checksum(const struct sk_buff *skb, int len) { - unsigned long sum; + u16 sum; /* skip header 4 bytes */ sum = atalk_sum_skb(skb, 4, len-4, 0); /* Use 0xFFFF for 0. 0 itself means none */ - return sum ? htons((unsigned short)sum) : htons(0xFFFF); + return cpu_to_be16(sum ? sum : 0xFFFF); } static struct proto ddp_proto = { *