Re: [B.A.T.M.A.N.] [PATCH 1/2] batman-adv: Avoid u32 overflow during gateway select

Sven Eckelmann
2015-06-21T18:27:45Z

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On Sunday 21 June 2015 09:37:13 David Miller wrote:
> From: Antonio Quartulli <antonio@meshcoding.com>
> Date: Tue, 16 Jun 2015 21:06:23 +0200
>
> > @@ -133,7 +133,7 @@ batadv_gw_get_best_gw_node(struct batadv_priv
> > *bat_priv)>
> > struct batadv_neigh_node *router;
> > struct batadv_neigh_ifinfo *router_ifinfo;
> > struct batadv_gw_node *gw_node, *curr_gw = NULL;
> >
> > - uint32_t max_gw_factor = 0, tmp_gw_factor = 0;
> > + uint64_t max_gw_factor = 0, tmp_gw_factor = 0;
> >
> > uint32_t gw_divisor;
>
> Divides are performed using these variables, so if you make
> them 64-bit the build will fail. You have to use one of the
> routines in include/linux/math64.h in this situation, but
> realize that this operation is now going to be quite expensive.

Just a minor comment: The division is currently "max_gw_factor >> 18" which
the compiler also outputs as such (shrd + shr on i586). This is the reason why
it currently also works on architectures without a native 64 bit div.

Kind regards,
Sven

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