Re: [B.A.T.M.A.N.] [PATCH] batman-adv: Fix symmetry check / route flapping in multi interface setups

[Antonio Quartulli <ordex@autistici.org>]

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On Sat, Sep 15, 2012 at 11:51:46 +0200, Linus Lüssing wrote:
> If receiving an OGM from a neighbor other than the currently selected
> and if it has the same TQ then we are supposed to switch if this
> neighbor provides a more symmetric link than the currently selected one.
> 
> However this symmetry check currently is broken if the interface of the
> neighbor we received the OGM from and the one of the currently selected
> neighbor differ: We are currently trying to determine the symmetry of the
> link towards the selected router via the link we received the OGM from
> instead of just checking via the link towards the currently selected
> router.
> 
> This leads to way more route switches than necessary and can lead to
> permanent route flapping in many common multi interface setups.
> 
> This patch fixes this issue by using the right interface for this
> symmetry check.
> 
> Signed-off-by: Linus Lüssing <linus.luessing@web.de>
> ---
> This fixes the route flapping observed in ticket 163 (but unfortunately
> doesn't fix the main issue of this ticket, the starving routes, yet).
> 
>  bat_iv_ogm.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/bat_iv_ogm.c b/bat_iv_ogm.c
> index 7f0adad..2c6b560 100644
> --- a/bat_iv_ogm.c
> +++ b/bat_iv_ogm.c
> @@ -743,7 +743,8 @@ batadv_iv_ogm_orig_update(struct batadv_priv *bat_priv,
>  	if (router && (neigh_node->tq_avg == router->tq_avg)) {
>  		orig_node_tmp = router->orig_node;
>  		spin_lock_bh(&orig_node_tmp->ogm_cnt_lock);
> -		sum_orig = orig_node_tmp->bcast_own_sum[if_incoming->if_num];
> +		sum_orig = orig_node_tmp->
> +				bcast_own_sum[router->if_incoming->if_num];

what about:
	int if_num;
	...
		if_num = router->if_incoming->if_num;
		sum_orig = orig_node_tmp->bcast_own_sum[if_num];

?

-- 
Antonio Quartulli

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

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