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Date: Sat, 14 Jan 2006 18:52:13 +0900 (JST)
Message-Id: <20060114.185213.131923397.yoshfuji@linux-ipv6.org>
To: pavel@ucw.cz
Cc: davem@davemloft.net, drepper@redhat.com, linux-kernel@vger.kernel.org,
       yoshfuji@linux-ipv6.org
Subject: Re: ntohs/ntohl and bitops
From: YOSHIFUJI Hideaki / =?iso-2022-jp?B?GyRCNUhGIzFRTEAbKEI=?= 
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In article <20060112010406.GA2367@ucw.cz> (at Thu, 12 Jan 2006 01:04:06 +0000), Pavel Machek <pavel@ucw.cz> says:

> 
> On Wed 11-01-06 00:00:20, David S. Miller wrote:
> > From: Ulrich Drepper <drepper@redhat.com>
> > Date: Tue, 10 Jan 2006 14:02:52 -0800
> > 
> > > I just saw this in a patch:
> > > 
> > > +               if (ntohs(ih->frag_off) & IP_OFFSET)
> > > +                       return EBT_NOMATCH;
> > > 
> > > This isn't optimal, it requires a byte switch little endian machines.
> > > The compiler isn't smart enough.  It would be better to use
> > > 
> > >      if (ih->frag_off & ntohs(IP_OFFSET))
:
> Could you possibly 
> #define IP_OFFSET htons(1234)
> ?

In this case, you should use __constant_htons().
I still prefer:
   if (ih->frag_off & htons(IP_OFFSET))
though.

--yoshfuji