[B.A.T.M.A.N.] [PATCH] batman-adv: Fixing wrap-around bug in vis

["Linus Lüssing" <linus.luessing@web.de>]

When the seqno for a vis packet had a wrap around from i.e. 255 to 0,
add_packet() would falsely claim the older packet with the seqno 255 as
newer as the one with the seqno of 0 and would therefore ignore the new
packet. This happens with all following vis packets until the old vis
packet expires after 180 seconds timeout. This patch fixes this issue
and gets rid of these highly undesired 3min. breaks for the vis-server.

Signed-off-by: Linus Lüssing <linus.luessing@web.de>
---
 batman-adv-kernelland/packet.h |    3 ++-
 batman-adv-kernelland/vis.c    |    3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/batman-adv-kernelland/packet.h b/batman-adv-kernelland/packet.h
index c8b973f..df38883 100644
--- a/batman-adv-kernelland/packet.h
+++ b/batman-adv-kernelland/packet.h
@@ -106,7 +106,8 @@ struct vis_packet {
 	uint8_t  packet_type;
 	uint8_t  version;        /* batman version field */
 	uint8_t  vis_type;	 /* which type of vis-participant sent this? */
-	uint8_t  seqno;		 /* sequence number */
+	uint8_t  seqno;		 /* sequence number
+				  * (add_packet() expects uint8_t) */
 	uint8_t  entries;	 /* number of entries behind this struct */
 	uint8_t  ttl;		 /* TTL */
 	uint8_t  vis_orig[6];	 /* originator that informs about its
diff --git a/batman-adv-kernelland/vis.c b/batman-adv-kernelland/vis.c
index fa8a487..6cab4ba 100644
--- a/batman-adv-kernelland/vis.c
+++ b/batman-adv-kernelland/vis.c
@@ -213,7 +213,8 @@ static struct vis_info *add_packet(struct vis_packet *vis_packet,
 	old_info = hash_find(vis_hash, &search_elem);
 
 	if (old_info != NULL) {
-		if (vis_packet->seqno - old_info->packet.seqno <= 0) {
+		/* seqno is uint8_t, therefore checking for 127 */
+		if ((vis_packet->seqno - old_info->packet.seqno) > 127) {
 			if (old_info->packet.seqno == vis_packet->seqno) {
 				recv_list_add(&old_info->recv_list,
 					      vis_packet->sender_orig);
-- 
1.7.0