---

yaml
---
r: 197167
b: refs/heads/master
c: ea4ceb1
h: refs/heads/master
i:
  197165: 7bb263b
  197163: edcc2f0
  197159: 9ac5451
  197151: c122162
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: f6497e38fda6970819daacb67725d67474079381
+refs/heads/master: ea4ceb18b525fd7016c10995c0f1313a729c7e2b

trunk/drivers/staging/batman-adv/vis.c

@@ -27,6 +27,22 @@
 #include "hard-interface.h"
 #include "hash.h"
 
+/* Returns the smallest signed integer in two's complement with the sizeof x */
+#define smallest_signed_int(x) (1u << (7u + 8u * (sizeof(x) - 1u)))
+
+/* Checks if a sequence number x is a predecessor/successor of y.
+   they handle overflows/underflows and can correctly check for a
+   predecessor/successor unless the variable sequence number has grown by
+   more then 2**(bitwidth(x)-1)-1.
+   This means that for a uint8_t with the maximum value 255, it would think:
+    * when adding nothing - it is neither a predecessor nor a successor
+    * before adding more than 127 to the starting value - it is a predecessor,
+    * when adding 128 - it is neither a predecessor nor a successor,
+    * after adding more than 127 to the starting value - it is a successor */
+#define seq_before(x, y) ({typeof(x) _dummy = (x - y); \
+			  _dummy > smallest_signed_int(_dummy); })
+#define seq_after(x, y) seq_before(y, x)
+
 struct hashtable_t *vis_hash;
 DEFINE_SPINLOCK(vis_hash_lock);
 static DEFINE_SPINLOCK(recv_list_lock);
@@ -212,7 +228,7 @@ 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) {
+		if (!seq_after(vis_packet->seqno, old_info->packet.seqno)) {
 			if (old_info->packet.seqno == vis_packet->seqno) {
 				recv_list_add(&old_info->recv_list,
 					      vis_packet->sender_orig);