Re: ntohs/ntohl and bitops

[YOSHIFUJI Hideaki / 吉藤英明 <yoshfuji@linux-ipv6.org>]

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
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