batman-adv: Add elp_interval hardif genl configuration

The ELP packets are transmitted every elp_interval milliseconds on an
slave/hard-interface. This value can be changed using the configuration
interface.

The BATADV_CMD_SET_HARDIF/BATADV_CMD_GET_HARDIF commands allow to set/get
the configuration of this feature using the u32 BATADV_ATTR_ELP_INTERVAL
attribute.
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>

include/uapi/linux/batman_adv.h

@@ -477,6 +477,12 @@ enum batadv_nl_attrs {
 	 */
 	BATADV_ATTR_ORIG_INTERVAL,
 
+	/**
+	 * @BATADV_ATTR_ELP_INTERVAL: defines the interval in milliseconds in
+	 *  which batman emits probing packets for neighbor sensing (ELP).
+	 */
+	BATADV_ATTR_ELP_INTERVAL,
+
 	/* add attributes above here, update the policy in netlink.c */
 
 	/**

net/batman-adv/netlink.c

@@ -159,6 +159,7 @@ static const struct nla_policy batadv_netlink_policy[NUM_BATADV_ATTR] = {
 	[BATADV_ATTR_MULTICAST_FORCEFLOOD_ENABLED]	= { .type = NLA_U8 },
 	[BATADV_ATTR_NETWORK_CODING_ENABLED]	= { .type = NLA_U8 },
 	[BATADV_ATTR_ORIG_INTERVAL]		= { .type = NLA_U32 },
+	[BATADV_ATTR_ELP_INTERVAL]		= { .type = NLA_U32 },
 };
 
 /**
@@ -825,6 +826,12 @@ static int batadv_netlink_hardif_fill(struct sk_buff *msg,
 			goto nla_put_failure;
 	}
 
+#ifdef CONFIG_BATMAN_ADV_BATMAN_V
+	if (nla_put_u32(msg, BATADV_ATTR_ELP_INTERVAL,
+			atomic_read(&hard_iface->bat_v.elp_interval)))
+		goto nla_put_failure;
+#endif /* CONFIG_BATMAN_ADV_BATMAN_V */
+
 	genlmsg_end(msg, hdr);
 	return 0;
 
@@ -910,6 +917,16 @@ static int batadv_netlink_set_hardif(struct sk_buff *skb,
 	struct batadv_hard_iface *hard_iface = info->user_ptr[1];
 	struct batadv_priv *bat_priv = info->user_ptr[0];
 
+#ifdef CONFIG_BATMAN_ADV_BATMAN_V
+	struct nlattr *attr;
+
+	if (info->attrs[BATADV_ATTR_ELP_INTERVAL]) {
+		attr = info->attrs[BATADV_ATTR_ELP_INTERVAL];
+
+		atomic_set(&hard_iface->bat_v.elp_interval, nla_get_u32(attr));
+	}
+#endif /* CONFIG_BATMAN_ADV_BATMAN_V */
+
 	batadv_netlink_notify_hardif(bat_priv, hard_iface);
 
 	return 0;