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Date: Tue, 23 Apr 2013 22:04:34 +0200
From: Antonio Quartulli <ordex@autistici.org>
Message-ID: <20130423200434.GC16603@ritirata.org>
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Subject: Re: [B.A.T.M.A.N.] [PATCH 2/7] batman-adv: use vid when computing
 local and global TT CRC
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On Wed, Apr 24, 2013 at 03:58:56AM +0800, Marek Lindner wrote:
> On Tuesday, April 23, 2013 22:34:30 Antonio Quartulli wrote:
> > @@ -1535,7 +1535,9 @@ static uint32_t batadv_tt_global_crc(struct
> > batadv_priv *bat_priv, orig_node)) continue;
> > =20
> > -                       crc ^=3D crc32c(0, tt_common->addr, ETH_ALEN);
> > +                       crc_tmp =3D crc32c(0, &tt_common->vid,
> > +                                        sizeof(tt_common->vid));
> > +                       crc ^=3D crc32c(crc_tmp, tt_common->addr, ETH_A=
LEN);
> >                 }
> >                 rcu_read_unlock();
>=20
> Is it necessary to define another variable ?=20

yes

> Why not:
>=20
> crc =3D crc32c(0, &tt_common->vid, sizeof(tt_common->vid));
> crc ^=3D crc32c(crc, tt_common->addr, ETH_ALEN);
>=20

because crc_tmp is the result of the CRC operation on the VID and the MAC
address (so one per client), while crc is the container of all the crc_tmp
xor'ed together..

>=20
> > @@ -1565,7 +1567,9 @@ static uint32_t batadv_tt_local_crc(struct batadv=
_priv=20
> *bat_priv)
> >                         if (tt_common->flags & BATADV_TT_CLIENT_NEW)
> >                                 continue;
> > =20
> > -                       crc ^=3D crc32c(0, tt_common->addr, ETH_ALEN);
> > +                       crc_tmp =3D crc32c(0, &tt_common->vid,
> > +                                        sizeof(tt_common->vid));
> > +                       crc ^=3D crc32c(crc_tmp, tt_common->addr, ETH_A=
LEN);
> >                 }
>=20
> Dito.

Idem.

Cheers,


--=20
Antonio Quartulli

=2E.each of us alone is worth nothing..
Ernesto "Che" Guevara

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