David Laight <David.Laight@xxxxxxxxxx> wrote:
> From: Florian Westphal
> > Sent: 08 January 2016 16:24
> > To: David Laight
> > David Laight <David.Laight@xxxxxxxxxx> wrote:
> > > From: Pablo Neira Ayuso
> > > > Sent: 08 January 2016 14:02
> > > > From: Florian Westphal <fw@xxxxxxxxx>
> > > >
> > > > Needed to convert the (64bit) conntrack counters to BE ordering.
> > > >
> > > ...
> > > > switch (priv->size) {
> > > > + case 8: {
> > > > + u64 src64;
> > > > +
> > > > + switch (priv->op) {
> > > > + case NFT_BYTEORDER_NTOH:
> > > > + for (i = 0; i < priv->len / 8; i++) {
> > > > + src64 = get_unaligned_be64(&src[i]);
> > > > + src64 = be64_to_cpu((__force __be64)src64);
> > > > + put_unaligned_be64(src64, &dst[i]);
> > > > + }
> > > > + break;
> > > > + case NFT_BYTEORDER_HTON:
> > > > + for (i = 0; i < priv->len / 8; i++) {
> > > > + src64 = get_unaligned_be64(&src[i]);
> > > > + src64 = (__force u64)cpu_to_be64(src64);
> > > > + put_unaligned_be64(src64, &dst[i]);
> > > > + }
> > > > + break;
> > > > + }
> > > > + break;
> > >
> > > That is horrid.
> >
> > Yes, sorry for this, however ...
> >
> > > On a little-endian system you are byteswapping the data 3 times.
> > > Image the code on a cpu that doesn't support misaligned transfers
> > > and doesn't have a byteswap instruction.
> >
> > diff --git a/net/netfilter/nft_byteorder.c b/net/netfilter/nft_byteorder.c
> > --- a/net/netfilter/nft_byteorder.c
> > +++ b/net/netfilter/nft_byteorder.c
> > @@ -46,16 +46,16 @@ static void nft_byteorder_eval(const struct nft_expr *expr,
> > switch (priv->op) {
> > case NFT_BYTEORDER_NTOH:
> > for (i = 0; i < priv->len / 8; i++) {
> > - src64 = get_unaligned_be64(&src[i]);
> > + src64 = get_unaligned((u64 *)&src[i]);
> > src64 = be64_to_cpu((__force __be64)src64);
> > - put_unaligned_be64(src64, &dst[i]);
> > + put_unaligned(src64, (u64 *)&dst[i]);
>
> Why not just:
> src64 = get_unaligned_be64(&src[i]);
> put_unaligned(src64, (u64 *)&dst[i]);
Sure.
--
To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
