Re: [B.A.T.M.A.N.] [PATCH-maint 4/4] batman-adv: detect local excess vlans in TT request

[Simon Wunderlich <sw@simonwunderlich.de>]

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On Tuesday 25 August 2015 11:59:01 Antonio Quartulli wrote:
> On 21/08/15 17:15, Simon Wunderlich wrote:
> > If the local representation of the global TT table of one originator has
> > more VLAN entries than the respective TT update, there is some
> > inconsistency present. By detecting and reporting this inconsistency,
> > the global table gets updated and the excess VLAN will get removed in
> > the process.
> > 
> > Reported-by: Alessandro Bolletta <alessandro@mediaspot.net>
> > Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
> > ---
> > 
> >  net/batman-adv/translation-table.c | 21 +++++++++++++++++++++
> >  1 file changed, 21 insertions(+)
> > 
> > diff --git a/net/batman-adv/translation-table.c
> > b/net/batman-adv/translation-table.c index dced2da..1adb72e 100644
> > --- a/net/batman-adv/translation-table.c
> > +++ b/net/batman-adv/translation-table.c
> > @@ -2392,6 +2392,7 @@ static bool batadv_tt_global_check_crc(struct
> > batadv_orig_node *orig_node,> 
> >  	struct batadv_tvlv_tt_vlan_data *tt_vlan_tmp;
> >  	struct batadv_orig_node_vlan *vlan;
> >  	uint32_t crc;
> > 
> > +	bool found;
> > 
> >  	int i;
> >  	
> >  	/* check if each received CRC matches the locally stored one */
> > 
> > @@ -2418,6 +2419,26 @@ static bool batadv_tt_global_check_crc(struct
> > batadv_orig_node *orig_node,> 
> >  			return false;
> >  	
> >  	}
> > 
> > +	/* check if any excess VLANs exist locally for the originator
> > +	 * which are not mentioned in the TVLV from the originator.
> > +	 */
> > +	rcu_read_lock();
> > +	list_for_each_entry_rcu(vlan, &orig_node->vlan_list, list) {
> > +		found = false;
> > +
> > +		for (i = 0; i < num_vlan; i++) {
> > +			tt_vlan_tmp = tt_vlan + i;
> > +			if (ntohs(tt_vlan_tmp->vid) == vlan->vid) {
> > +				found = true;
> > +				break;
> > +			}
> > +		}
> > +
> > +		if (!found)
> > +			return false;
> > +	}
> > +	rcu_read_unlock();
> > +
> 
> NAK.
> 
> we already do this check slightly above in this function with the
> following code:
> 
> 2426                 vlan = batadv_orig_node_vlan_get(orig_node,
> 2427
> ntohs(tt_vlan_tmp->vid));
> 2428                 if (!vlan)
> 2429                         return false;
> 
> batadv_orig_node_vlan_get() returns NULL if we don't know this VLAN for
> that Originator, therefore the CRC check fails here.

That's right, however it only sweeps through the VLANs announced within the 
TT-TVLV. However, my addition tries to check if there are any excess VLAN 
locally which are NOT in that TT-TVLV. I think this patch doesn't take care of 
that, or am I missing something?

For example, think of having VLAN 6 locally with a couple of global entries at 
the originator, but the TT-TVLV only announces VLANs 3,4,5. Then the fact that 
we also have VLAN 6 is not detected, and these (probably wrong) entries are 
never cleaned up.

Thanks!
    Simon

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