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batman-adv: fix random jitter calculation

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[ 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>
Signed-off-by: Carlos Jimenez (JavaShin-X) <javashin1986@gmail.com>
This commit is contained in:
Akinobu Mita 2020-10-25 17:17:28 -04:00 committed by Ksawlii
parent 1b01b9bda3
commit 681fcbd50c
1 changed files with 3 additions and 1 deletions
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4
net/batman-adv/bat_iv_ogm.c
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@ -283,7 +283,9 @@ batadv_iv_ogm_emit_send_time(const struct batadv_priv *bat_priv)
msecs = atomic_read(&bat_priv->orig_interval) - BATADV_JITTER; msecs = atomic_read(&bat_priv->orig_interval) - BATADV_JITTER;
msecs += prandom_u32_max(2 * BATADV_JITTER); msecs += prandom_u32_max(2 * BATADV_JITTER);
return jiffies + msecs_to_jiffies(msecs); return jiffies + msecs_to_jiffies(
atomic_read(&bat_priv->orig_interval) -
JITTER + (random32() % (2*JITTER)));
} }
/* when do we schedule a ogm packet to be sent */ /* when do we schedule a ogm packet to be sent */