batman-adv: fix random jitter calculation
Akinobu Mita [Wed, 26 Dec 2012 02:32:10 +0000 (02:32 +0000)]
[ Upstream commit 143cdd8f33909ff5a153e3f02048738c5964ba26 ]

batadv_iv_ogm_emit_send_time() attempts to calculates a random integer
in the range of 'orig_interval +- BATADV_JITTER' by the below lines.

        msecs = atomic_read(&bat_priv->orig_interval) - BATADV_JITTER;
        msecs += (random32() % 2 * BATADV_JITTER);

But it actually gets 'orig_interval' or 'orig_interval - BATADV_JITTER'
because '%' and '*' have same precedence and associativity is
left-to-right.

This adds the parentheses at the appropriate position so that it matches
original intension.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Acked-by: Antonio Quartulli <ordex@autistici.org>
Cc: Marek Lindner <lindner_marek@yahoo.de>
Cc: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Cc: Antonio Quartulli <ordex@autistici.org>
Cc: b.a.t.m.a.n@lists.open-mesh.org
Cc: "David S. Miller" <davem@davemloft.net>
Cc: netdev@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

net/batman-adv/bat_iv_ogm.c

index a6d5d63..fa701b6 100644 (file)
@@ -72,7 +72,7 @@ static unsigned long bat_iv_ogm_emit_send_time(const struct bat_priv *bat_priv)
 {
        return jiffies + msecs_to_jiffies(
                   atomic_read(&bat_priv->orig_interval) -
-                  JITTER + (random32() % 2*JITTER));
+                  JITTER + (random32() % (2*JITTER)));
 }
 
 /* when do we schedule a ogm packet to be sent */