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, 20 insertions, 0 deletions

diff --git a/net/batman-adv/packet.h b/net/batman-adv/packet.h
index e7f915181aba..c698b6452953 100644
--- a/net/batman-adv/packet.h
+++ b/net/batman-adv/packet.h
@@ -26,6 +26,7 @@
  * @BATADV_IV_OGM: originator messages for B.A.T.M.A.N. IV
  * @BATADV_BCAST: broadcast packets carrying broadcast payload
  * @BATADV_CODED: network coded packets
+ * @BATADV_ELP: echo location packets for B.A.T.M.A.N. V
  *
  * @BATADV_UNICAST: unicast packets carrying unicast payload traffic
  * @BATADV_UNICAST_FRAG: unicast packets carrying a fragment of the original
@@ -40,6 +41,7 @@ enum batadv_packettype {
         BATADV_IV_OGM           = 0x00,
         BATADV_BCAST            = 0x01,
         BATADV_CODED            = 0x02,
+        BATADV_ELP              = 0x03,
         /* 0x40 - 0x7f: unicast */
 #define BATADV_UNICAST_MIN     0x40
         BATADV_UNICAST          = 0x40,
@@ -235,6 +237,24 @@ struct batadv_ogm_packet {
 #define BATADV_OGM_HLEN sizeof(struct batadv_ogm_packet)
 
 /**
+ * struct batadv_elp_packet - elp (neighbor discovery) packet
+ * @packet_type: batman-adv packet type, part of the general header
+ * @version: batman-adv protocol version, part of the genereal header
+ * @orig: originator mac address
+ * @seqno: sequence number
+ * @elp_interval: currently used ELP sending interval in ms
+ */
+struct batadv_elp_packet {
+        u8     packet_type;
+        u8     version;
+        u8     orig[ETH_ALEN];
+        __be32 seqno;
+        __be32 elp_interval;
+};
+
+#define BATADV_ELP_HLEN sizeof(struct batadv_elp_packet)
+
+/**
  * struct batadv_icmp_header - common members among all the ICMP packets
  * @packet_type: batman-adv packet type, part of the general header
  * @version: batman-adv protocol version, part of the genereal header