batman-adv: ELP - adding basic infrastructure

The B.A.T.M.A.N. protocol originally only used a single
message type (called OGM) to determine the link qualities to
the direct neighbors and spreading these link quality
information through the whole mesh. This procedure is
summarized on the BATMAN concept page and explained in
details in the RFC draft published in 2008.

This approach was chosen for its simplicity during the
protocol design phase and the implementation. However, it
also bears some drawbacks:

 *  Wireless interfaces usually come with some packet loss,
    therefore a higher broadcast rate is desirable to allow
    a fast reaction on flaky connections.
    Other interfaces of the same host might be connected to
    Ethernet LANs / VPNs / etc which rarely exhibit packet
    loss would benefit from a lower broadcast rate to reduce
    overhead.
 *  It generally is more desirable to detect local link
    quality changes at a faster rate than propagating all
    these changes through the entire mesh (the far end of
    the mesh does not need to care about local link quality
    changes that much). Other optimizations strategies, like
    reducing overhead, might be possible if OGMs weren't
    used for all tasks in the mesh at the same time.

As a result detecting local link qualities shall be handled
by an independent message type, ELP, whereas the OGM message
type remains responsible for flooding the mesh with these
link quality information and determining the overall path
transmit qualities.

Developed by Linus during a 6 months trainee study period in
Ascom (Switzerland) AG.

Signed-off-by: Linus Luessing <linus.luessing@web.de>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Antonio Quartulli <antonio@open-mesh.com>

1 files changed, 193 insertions, 0 deletions

diff --git a/net/batman-adv/bat_v_elp.c b/net/batman-adv/bat_v_elp.c
new file mode 100644
index 000000000000..bc6e046c614c
--- /dev/null
+++ b/net/batman-adv/bat_v_elp.c
@@ -0,0 +1,193 @@
+/* Copyright (C) 2011-2016 B.A.T.M.A.N. contributors:
+ *
+ * Linus Lüssing, Marek Lindner
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "bat_v_elp.h"
+#include "main.h"
+
+#include <linux/atomic.h>
+#include <linux/byteorder/generic.h>
+#include <linux/errno.h>
+#include <linux/etherdevice.h>
+#include <linux/fs.h>
+#include <linux/if_ether.h>
+#include <linux/jiffies.h>
+#include <linux/kernel.h>
+#include <linux/netdevice.h>
+#include <linux/random.h>
+#include <linux/rculist.h>
+#include <linux/rcupdate.h>
+#include <linux/skbuff.h>
+#include <linux/stddef.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/workqueue.h>
+
+#include "bat_algo.h"
+#include "hard-interface.h"
+#include "packet.h"
+#include "send.h"
+
+/**
+ * batadv_v_elp_start_timer - restart timer for ELP periodic work
+ * @hard_iface: the interface for which the timer has to be reset
+ */
+static void batadv_v_elp_start_timer(struct batadv_hard_iface *hard_iface)
+{
+	unsigned int msecs;
+
+	msecs = atomic_read(&hard_iface->bat_v.elp_interval) - BATADV_JITTER;
+	msecs += prandom_u32() % (2 * BATADV_JITTER);
+
+	queue_delayed_work(batadv_event_workqueue, &hard_iface->bat_v.elp_wq,
+			   msecs_to_jiffies(msecs));
+}
+
+/**
+ * batadv_v_elp_periodic_work - ELP periodic task per interface
+ * @work: work queue item
+ *
+ * Emits broadcast ELP message in regular intervals.
+ */
+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_elp_packet *elp_packet;
+	struct batadv_priv *bat_priv;
+	struct sk_buff *skb;
+	u32 elp_interval;
+
+	bat_v = container_of(work, struct batadv_hard_iface_bat_v, elp_wq.work);
+	hard_iface = container_of(bat_v, struct batadv_hard_iface, bat_v);
+	bat_priv = netdev_priv(hard_iface->soft_iface);
+
+	if (atomic_read(&bat_priv->mesh_state) == BATADV_MESH_DEACTIVATING)
+		goto out;
+
+	/* we are in the process of shutting this interface down */
+	if ((hard_iface->if_status == BATADV_IF_NOT_IN_USE) ||
+	    (hard_iface->if_status == BATADV_IF_TO_BE_REMOVED))
+		goto out;
+
+	/* the interface was enabled but may not be ready yet */
+	if (hard_iface->if_status != BATADV_IF_ACTIVE)
+		goto restart_timer;
+
+	skb = skb_copy(hard_iface->bat_v.elp_skb, GFP_ATOMIC);
+	if (!skb)
+		goto restart_timer;
+
+	elp_packet = (struct batadv_elp_packet *)skb->data;
+	elp_packet->seqno = htonl(atomic_read(&hard_iface->bat_v.elp_seqno));
+	elp_interval = atomic_read(&hard_iface->bat_v.elp_interval);
+	elp_packet->elp_interval = htonl(elp_interval);
+
+	batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
+		   "Sending broadcast ELP packet on interface %s, seqno %u\n",
+		   hard_iface->net_dev->name,
+		   atomic_read(&hard_iface->bat_v.elp_seqno));
+
+	batadv_send_skb_packet(skb, hard_iface, batadv_broadcast_addr);
+
+	atomic_inc(&hard_iface->bat_v.elp_seqno);
+
+restart_timer:
+	batadv_v_elp_start_timer(hard_iface);
+out:
+	return;
+}
+
+/**
+ * batadv_v_elp_iface_enable - setup the ELP interface private resources
+ * @hard_iface: interface for which the data has to be prepared
+ *
+ * Return: 0 on success or a -ENOMEM in case of failure.
+ */
+int batadv_v_elp_iface_enable(struct batadv_hard_iface *hard_iface)
+{
+	struct batadv_elp_packet *elp_packet;
+	unsigned char *elp_buff;
+	u32 random_seqno;
+	size_t size;
+	int res = -ENOMEM;
+
+	size = ETH_HLEN + NET_IP_ALIGN + BATADV_ELP_HLEN;
+	hard_iface->bat_v.elp_skb = dev_alloc_skb(size);
+	if (!hard_iface->bat_v.elp_skb)
+		goto out;
+
+	skb_reserve(hard_iface->bat_v.elp_skb, ETH_HLEN + NET_IP_ALIGN);
+	elp_buff = skb_push(hard_iface->bat_v.elp_skb, BATADV_ELP_HLEN);
+	elp_packet = (struct batadv_elp_packet *)elp_buff;
+	memset(elp_packet, 0, BATADV_ELP_HLEN);
+
+	elp_packet->packet_type = BATADV_ELP;
+	elp_packet->version = BATADV_COMPAT_VERSION;
+
+	/* randomize initial seqno to avoid collision */
+	get_random_bytes(&random_seqno, sizeof(random_seqno));
+	atomic_set(&hard_iface->bat_v.elp_seqno, random_seqno);
+	atomic_set(&hard_iface->bat_v.elp_interval, 500);
+
+	INIT_DELAYED_WORK(&hard_iface->bat_v.elp_wq,
+			  batadv_v_elp_periodic_work);
+	batadv_v_elp_start_timer(hard_iface);
+	res = 0;
+
+out:
+	return res;
+}
+
+/**
+ * batadv_v_elp_iface_disable - release ELP interface private resources
+ * @hard_iface: interface for which the resources have to be released
+ */
+void batadv_v_elp_iface_disable(struct batadv_hard_iface *hard_iface)
+{
+	cancel_delayed_work_sync(&hard_iface->bat_v.elp_wq);
+
+	dev_kfree_skb(hard_iface->bat_v.elp_skb);
+	hard_iface->bat_v.elp_skb = NULL;
+}
+
+/**
+ * batadv_v_elp_primary_iface_set - change internal data to reflect the new
+ *  primary interface
+ * @primary_iface: the new primary interface
+ */
+void batadv_v_elp_primary_iface_set(struct batadv_hard_iface *primary_iface)
+{
+	struct batadv_hard_iface *hard_iface;
+	struct batadv_elp_packet *elp_packet;
+	struct sk_buff *skb;
+
+	/* update orig field of every elp iface belonging to this mesh */
+	rcu_read_lock();
+	list_for_each_entry_rcu(hard_iface, &batadv_hardif_list, list) {
+		if (primary_iface->soft_iface != hard_iface->soft_iface)
+			continue;
+
+		if (!hard_iface->bat_v.elp_skb)
+			continue;
+
+		skb = hard_iface->bat_v.elp_skb;
+		elp_packet = (struct batadv_elp_packet *)skb->data;
+		ether_addr_copy(elp_packet->orig,
+				primary_iface->net_dev->dev_addr);
+	}
+	rcu_read_unlock();
+}