Re: [B.A.T.M.A.N.] [RFC 14/23] batman-adv: ELP - compute the metric based on the estimated throughput

[Andrew Lunn <andrew@lunn.ch>]

On Tue, Feb 11, 2014 at 01:48:14PM +0100, Antonio Quartulli wrote:
> From: Antonio Quartulli <antonio@open-mesh.com>
> 
> Implement a stub get_throughput() function which returns the
> estimated throughput towards a given neighbour.
> Its result is then used to compute the metric value.
> 
> The metric is updated each time a new ELP packet is sent,
> this way it is possible to timely react to a metric
> variation which can imply (for example) a neighbour
> disconnection.

It is very much a style issue, but i would probably split this into
two patches. Updating the metric at send time rather than receive
should have nothing to do with estimated bandwidth.

       Andrew

> 
> Signed-off-by: Antonio Quartulli <antonio@open-mesh.com>
> ---
>  bat_v_elp.c | 49 +++++++++++++++++++++++++++++++++++++++++++------
>  types.h     |  2 ++
>  2 files changed, 45 insertions(+), 6 deletions(-)
> 
> diff --git a/bat_v_elp.c b/bat_v_elp.c
> index 4185d8c..ef4e476 100644
> --- a/bat_v_elp.c
> +++ b/bat_v_elp.c
> @@ -53,6 +53,29 @@ void batadv_elp_neigh_node_free_ref(struct batadv_elp_neigh_node *neigh)
>  }
>  
>  /**
> + * batadv_v_elp_get_throughput - get the throughput towards a neighbour
> + * @neigh: the neighbour for which the throughput has to be obtained
> + *
> + * Returns the throughput towards the given neighbour.
> + */
> +static uint32_t
> +batadv_v_elp_get_throughput(struct batadv_elp_neigh_node *neigh)
> +{
> +	struct batadv_hard_iface *hard_iface = neigh->hard_iface;
> +	struct batadv_priv *bat_priv = netdev_priv(hard_iface->soft_iface);
> +	uint32_t throughput;
> +
> +	/* get the customised user value for the throughput */
> +	throughput = atomic_read(&hard_iface->bat_v.user_throughput);
> +	/* if the user specified a value, let's return it */
> +	if (throughput != 0)
> +		return throughput;
> +
> +	/* throughput cannot be computed right now. Return base value */
> +	return atomic_read(&bat_priv->bat_v.base_throughput);
> +}
> +
> +/**
>   * batadv_v_elp_neigh_new - create a new ELP neighbour node
>   * @hard_iface: the interface the neighbour is connected to
>   * @neigh_addr: the neighbour interface address
> @@ -75,6 +98,7 @@ batadv_v_elp_neigh_new(struct batadv_hard_iface *hard_iface,
>  	memcpy(neigh->addr, neigh_addr, ETH_ALEN);
>  	neigh->last_seen = jiffies;
>  	ewma_init(&neigh->metric, 1024, 8);
> +	neigh->hard_iface = hard_iface;
>  	/* recount initialised to 2 to simplify the caller function */
>  	atomic_set(&neigh->refcount, 2);
>  
> @@ -147,19 +171,20 @@ static void batadv_v_elp_neigh_purge(struct batadv_hard_iface *hard_iface)
>  }
>  
>  /**
> - * batadv_v_elp_send_outstanding - ELP periodic broadcast sending
> + * batadv_v_elp_periodic_work - ELP periodic task per interface
>   * @work: work queue item
>   *
> - * Sends a broadcast ELP message over the interface that this work item belongs
> - * to.
> + * Sends a broadcast ELP message and reads the metric for all the neighbours
> + * connected to the interface that this work item belongs to.
>   */
> -static void batadv_v_elp_send_outstanding(struct work_struct *work)
> +static void batadv_v_elp_periodic_work(struct work_struct *work)
>  {
>  	struct batadv_hard_iface *hard_iface;
>  	struct batadv_hard_iface_bat_v *bat_v;
>  	struct batadv_priv *bat_priv;
>  	struct batadv_elp_packet *elp_packet;
>  	uint32_t elp_interval;
> +	struct batadv_elp_neigh_node *neigh;
>  	struct sk_buff *skb;
>  	uint8_t num_neighs;
>  
> @@ -181,7 +206,7 @@ static void batadv_v_elp_send_outstanding(struct work_struct *work)
>  
>  	skb = skb_copy(hard_iface->bat_v.elp_skb, GFP_ATOMIC);
>  	if (!skb)
> -		goto out;
> +		goto update_metric;
>  
>  	/* purge outdated entries first */
>  	batadv_v_elp_neigh_purge(hard_iface);
> @@ -204,6 +229,17 @@ static void batadv_v_elp_send_outstanding(struct work_struct *work)
>  
>  	atomic_inc(&hard_iface->bat_v.elp_seqno);
>  
> +update_metric:
> +	/* Instead of updating the metric each "received" ELP packet, it is
> +	 * better to do it on each ELP sending. This way, if a node is dead and
> +	 * does not send packets anymore, batman-adv is still able to timely
> +	 * react to its death.
> +	 */
> +	rcu_read_lock();
> +	hlist_for_each_entry_rcu(neigh, &hard_iface->bat_v.neigh_list, list)
> +		ewma_add(&neigh->metric, batadv_v_elp_get_throughput(neigh));
> +	rcu_read_unlock();
> +
>  restart_timer:
>  	batadv_v_elp_start_timer(hard_iface);
>  out:
> @@ -247,7 +283,7 @@ int batadv_v_elp_iface_enable(struct batadv_hard_iface *hard_iface)
>  	atomic_set(&hard_iface->bat_v.elp_interval, 500);
>  
>  	INIT_DELAYED_WORK(&hard_iface->bat_v.elp_wq,
> -			  batadv_v_elp_send_outstanding);
> +			  batadv_v_elp_periodic_work);
>  	batadv_v_elp_start_timer(hard_iface);
>  	res = 0;
>  
> @@ -332,6 +368,7 @@ static void batadv_v_elp_neigh_update(struct batadv_priv *bat_priv,
>  
>  	neigh->last_seen = jiffies;
>  	neigh->last_recv_seqno = ntohl(elp_packet->seqno);
> +	ewma_add(&neigh->metric, batadv_v_elp_get_throughput(neigh));
>  
>  out:
>  	if (neigh)
> diff --git a/types.h b/types.h
> index 54fae29..948d5dc 100644
> --- a/types.h
> +++ b/types.h
> @@ -345,6 +345,7 @@ struct batadv_gw_node {
>   * @last_unicast_tx: when the last unicast packet has been sent to this neighbor
>   * @refcount: number of contexts the object is used
>   * @rcu: struct used for freeing in an RCU-safe manner
> + * @hard_iface: the interface where this neighbor is connected to
>   */
>  struct batadv_elp_neigh_node {
>  	struct hlist_node list;
> @@ -357,6 +358,7 @@ struct batadv_elp_neigh_node {
>  	unsigned long last_unicast_tx;
>  	atomic_t refcount;
>  	struct rcu_head rcu;
> +	struct batadv_hard_iface *hard_iface;
>  };
>  
>  /**
> -- 
> 1.8.5.3
>