batman-adv: improved roaming mechanism

With the current client announcement implementation, in case of roaming,
an update is triggered on the new AP serving the client. At that point
the new information is spread around by means of the OGM broadcasting
mechanism. Until this operations is not executed, no node is able to
correctly route traffic towards the client. This obviously causes packet
drops and introduces a delay in the time needed by the client to recover
its connections.

A new packet type called ROAMING_ADVERTISEMENT is added to account this
issue.

This message is sent in case of roaming from the new AP serving the
client to the old one and will contain the client MAC address. In this
way an out-of-OGM update is immediately committed, so that the old node
can update its global translation table. Traffic reaching this node will
then be redirected to the correct destination utilising the fresher
information. Thus reducing the packet drops and the connection recovery
delay.

Signed-off-by: Antonio Quartulli <ordex@autistici.org>
Signed-off-by: Sven Eckelmann <sven@narfation.org>

1 files changed, 5 insertions, 1 deletions

diff --git a/net/batman-adv/main.h b/net/batman-adv/main.h
index 6f53a1de778c..8eae05e4dc1b 100644
--- a/net/batman-adv/main.h
+++ b/net/batman-adv/main.h
@@ -42,7 +42,7 @@
  * -> TODO: check influence on TQ_LOCAL_WINDOW_SIZE */
 #define PURGE_TIMEOUT 200
 #define TT_LOCAL_TIMEOUT 3600 /* in seconds */
-
+#define TT_CLIENT_ROAM_TIMEOUT 600
 /* sliding packet range of received originator messages in squence numbers
  * (should be a multiple of our word size) */
 #define TQ_LOCAL_WINDOW_SIZE 64
@@ -55,6 +55,10 @@
 
 #define TT_OGM_APPEND_MAX 3 /* number of OGMs sent with the last tt diff */
 
+#define ROAMING_MAX_TIME 20 /* Time in which a client can roam at most
+			     * ROAMING_MAX_COUNT times */
+#define ROAMING_MAX_COUNT 5
+
 #define NO_FLAGS 0
 
 #define NUM_WORDS (TQ_LOCAL_WINDOW_SIZE / WORD_BIT_SIZE)