Re: [B.A.T.M.A.N.] [PATCH 2/7] batman-adv: use vid when computing local and global TT CRC

[Antonio Quartulli <ordex@autistici.org>]

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On Sat, May 04, 2013 at 08:12:22PM +0800, Marek Lindner wrote:
> On Wednesday, April 24, 2013 04:04:34 Antonio Quartulli wrote:
> > 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;
> > > > 
> > > > -                       crc ^= crc32c(0, tt_common->addr, ETH_ALEN);
> > > > +                       crc_tmp = crc32c(0, &tt_common->vid,
> > > > +                                        sizeof(tt_common->vid));
> > > > +                       crc ^= crc32c(crc_tmp, tt_common->addr,
> > > > ETH_ALEN);
> > > > 
> > > >                 }
> > > >                 rcu_read_unlock();
> > > 
> > > Is it necessary to define another variable ?
> > 
> > yes
> > 
> > > Why not:
> > > 
> > > crc = crc32c(0, &tt_common->vid, sizeof(tt_common->vid));
> > > crc ^= crc32c(crc, tt_common->addr, ETH_ALEN);
> > 
> > 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..
> 
> As we discussed on IRC please add a big comment here explaining why we do 
> things this way and not differently.

Yeah, as I told you on IRC the comment is ready :-)
Will add it in the next version

Cheers,

-- 
Antonio Quartulli

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

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