batman-adv: Introduce a configurable per interface hop penalty

In some setups multiple hard interfaces with similar link qualities
or throughput values are available. But people have expressed the desire
to consider one of them as a backup only.

Some creative solutions are currently in use: Such people are
configuring multiple batman-adv mesh/soft interfaces, wire them
together with some veth pairs and then tune the hop penalty to achieve
an effect similar to a tunable per interface hop penalty.

This patch introduces a new, configurable, per hard interface hop penalty
to simplify such setups.

Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>

1 files changed, 10 insertions, 3 deletions

diff --git a/net/batman-adv/bat_v_ogm.c b/net/batman-adv/bat_v_ogm.c
index 0d404f7bcd9f..0f8495b9eeb1 100644
--- a/net/batman-adv/bat_v_ogm.c
+++ b/net/batman-adv/bat_v_ogm.c
@@ -455,15 +455,17 @@ unlock:
  * @throughput: the current throughput
  *
  * Apply a penalty on the current throughput metric value based on the
- * characteristic of the interface where the OGM has been received. The return
- * value is computed as follows:
+ * characteristic of the interface where the OGM has been received.
+ *
+ * Initially the per hardif hop penalty is applied to the throughput. After
+ * that the return value is then computed as follows:
  * - throughput * 50%          if the incoming and outgoing interface are the
  *                             same WiFi interface and the throughput is above
  *                             1MBit/s
  * - throughput                if the outgoing interface is the default
  *                             interface (i.e. this OGM is processed for the
  *                             internal table and not forwarded)
- * - throughput * hop penalty  otherwise
+ * - throughput * node hop penalty  otherwise
  *
  * Return: the penalised throughput metric.
  */
@@ -472,9 +474,14 @@ static u32 batadv_v_forward_penalty(struct batadv_priv *bat_priv,
 				    struct batadv_hard_iface *if_outgoing,
 				    u32 throughput)
 {
+	int if_hop_penalty = atomic_read(&if_incoming->hop_penalty);
 	int hop_penalty = atomic_read(&bat_priv->hop_penalty);
 	int hop_penalty_max = BATADV_TQ_MAX_VALUE;
 
+	/* Apply per hardif hop penalty */
+	throughput = throughput * (hop_penalty_max - if_hop_penalty) /
+		     hop_penalty_max;
+
 	/* Don't apply hop penalty in default originator table. */
 	if (if_outgoing == BATADV_IF_DEFAULT)
 		return throughput;