[v3] batman-adv: Fix symmetry check / route flapping in multi interface setups

  From: Linus Lüssing <linus.luessing@web.de>

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>
---
 bat_iv_ogm.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)
  

Yes, looks good. Makes the symmetry patch look more, ehm, "symmetric".

> Gesendet: Sonntag, 23. September 2012 um 11:16 Uhr
> Von: "Marek Lindner" <lindner_marek@yahoo.de>
> An: b.a.t.m.a.n@lists.open-mesh.org
> Cc: "Linus Lüssing" <linus.luessing@web.de>
> Betreff: [PATCHv3] batman-adv: Fix symmetry check / route flapping in multi interface setups
>
> From: Linus Lüssing <linus.luessing@web.de>
> 
> 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>
> ---
>  bat_iv_ogm.c |    7 +++++--
>  1 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/bat_iv_ogm.c b/bat_iv_ogm.c
> index 7f0adad..75403a4 100644
> --- a/bat_iv_ogm.c
> +++ b/bat_iv_ogm.c
> @@ -657,6 +657,7 @@ batadv_iv_ogm_orig_update(struct batadv_priv *bat_priv,
>  	struct batadv_neigh_node *router = NULL;
>  	struct batadv_orig_node *orig_node_tmp;
>  	struct hlist_node *node;
> +	int if_num;
>  	uint8_t sum_orig, sum_neigh;
>  	uint8_t *neigh_addr;
>  	uint8_t tq_avg;
> @@ -743,12 +744,14 @@ 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];
> +		if_num = router->if_incoming->if_num;
> +		sum_orig = orig_node_tmp->bcast_own_sum[if_num];
>  		spin_unlock_bh(&orig_node_tmp->ogm_cnt_lock);
>  
>  		orig_node_tmp = neigh_node->orig_node;
>  		spin_lock_bh(&orig_node_tmp->ogm_cnt_lock);
> -		sum_neigh = orig_node_tmp->bcast_own_sum[if_incoming->if_num];
> +		if_num = neigh_node->if_incoming->if_num;
> +		sum_neigh = orig_node_tmp->bcast_own_sum[if_num];
>  		spin_unlock_bh(&orig_node_tmp->ogm_cnt_lock);
>  
>  		if (sum_orig >= sum_neigh)
> -- 
> 1.7.9.1
> 
>
  

On Sunday, September 23, 2012 18:44:54 Linus Lüssing wrote:
> Yes, looks good. Makes the symmetry patch look more, ehm, "symmetric".

Ok, merged the patch in revision 6c9d9ee.

Thanks,
Marek