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SubjectRe: ntohs/ntohl and bitops
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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))
>
> where the byte-swap can be done at compile time. This is kind of ugly,
> I guess, so maybe a dedicate macro
>
> net_host_bit_p(ih->frag_off, IP_OFFSET)

The first suggestion isn't considered ugly, and the best form is:

if (ih->frag_off & __constant_htons(IP_OFFSET))

I'll fix that up when I get a chance, thanks for catching it Uli.
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