batman-adv: ELP - send unicast ELP packets for throughput sampling
In case of an unused wireless link, the mac80211 throughput estimation
won't get updated further. Consequently, the reported throughput metric
will become obsolete.
With this patch unicast sampling is introduced by periodically sending
unicast ELP packets to each neighbor on idle WiFi links. These sampling
packets will fill an entire frame, so that the measurement is as
reliable as possible
Signed-off-by: Antonio Quartulli <antonio@open-mesh.com>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
diff --git a/net/batman-adv/bat_v_elp.c b/net/batman-adv/bat_v_elp.c
index 8376730..3844e7e 100644
--- a/net/batman-adv/bat_v_elp.c
+++ b/net/batman-adv/bat_v_elp.c
@@ -165,6 +165,69 @@
}
/**
+ * batadv_v_elp_wifi_neigh_probe - send link probing packets to a neighbour
+ * @neigh: the neighbour to probe
+ *
+ * Sends a predefined number of unicast wifi packets to a given neighbour in
+ * order to trigger the throughput estimation on this link by the RC algorithm.
+ * Packets are sent only if there there is not enough payload unicast traffic
+ * towards this neighbour..
+ *
+ * Return: True on success and false in case of error during skb preparation.
+ */
+static bool
+batadv_v_elp_wifi_neigh_probe(struct batadv_hardif_neigh_node *neigh)
+{
+ struct batadv_hard_iface *hard_iface = neigh->if_incoming;
+ struct batadv_priv *bat_priv = netdev_priv(hard_iface->soft_iface);
+ unsigned long last_tx_diff;
+ struct sk_buff *skb;
+ int probe_len, i;
+ int elp_skb_len;
+
+ /* this probing routine is for Wifi neighbours only */
+ if (!batadv_is_wifi_netdev(hard_iface->net_dev))
+ return true;
+
+ /* probe the neighbor only if no unicast packets have been sent
+ * to it in the last 100 milliseconds: this is the rate control
+ * algorithm sampling interval (minstrel). In this way, if not
+ * enough traffic has been sent to the neighbor, batman-adv can
+ * generate 2 probe packets and push the RC algorithm to perform
+ * the sampling
+ */
+ last_tx_diff = jiffies_to_msecs(jiffies - neigh->bat_v.last_unicast_tx);
+ if (last_tx_diff <= BATADV_ELP_PROBE_MAX_TX_DIFF)
+ return true;
+
+ probe_len = max_t(int, sizeof(struct batadv_elp_packet),
+ BATADV_ELP_MIN_PROBE_SIZE);
+
+ for (i = 0; i < BATADV_ELP_PROBES_PER_NODE; i++) {
+ elp_skb_len = hard_iface->bat_v.elp_skb->len;
+ skb = skb_copy_expand(hard_iface->bat_v.elp_skb, 0,
+ probe_len - elp_skb_len,
+ GFP_ATOMIC);
+ if (!skb)
+ return false;
+
+ /* Tell the skb to get as big as the allocated space (we want
+ * the packet to be exactly of that size to make the link
+ * throughput estimation effective.
+ */
+ skb_put(skb, probe_len - hard_iface->bat_v.elp_skb->len);
+
+ batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
+ "Sending unicast (probe) ELP packet on interface %s to %pM\n",
+ hard_iface->net_dev->name, neigh->addr);
+
+ batadv_send_skb_packet(skb, hard_iface, neigh->addr);
+ }
+
+ return true;
+}
+
+/**
* batadv_v_elp_periodic_work - ELP periodic task per interface
* @work: work queue item
*
@@ -227,6 +290,12 @@
*/
rcu_read_lock();
hlist_for_each_entry_rcu(hardif_neigh, &hard_iface->neigh_list, list) {
+ if (!batadv_v_elp_wifi_neigh_probe(hardif_neigh))
+ /* if something goes wrong while probing, better to stop
+ * sending packets immediately and reschedule the task
+ */
+ break;
+
if (!kref_get_unless_zero(&hardif_neigh->refcount))
continue;