batman-adv: Avoid u32 overflow during gateway select
authorRuben Wisniewski <ruben@freifunk-nrw.de>
Tue, 16 Jun 2015 19:06:23 +0000 (21:06 +0200)
committerAntonio Quartulli <antonio@meshcoding.com>
Tue, 11 Aug 2015 16:10:04 +0000 (18:10 +0200)
commit571a963768e7711e0bb5a30f71247b46ec9ca7b9
tree0dc9d00a5c8c27847ff5e92ad0a51ec5bbb2eb2f
parente071d93eb40c969dc8c578dde5ddd89a30fb01cb
batman-adv: Avoid u32 overflow during gateway select

The gateway selection based on fast connections is using a single value
calculated from the average tq (0-255) and the download bandwidth (in
100Kibit). The formula for the first step (tq ** 2 * 10000 * bandwidth)
tends to overflow a u32 with low bandwidth settings like 50 [100KiBit]
and a tq value of over 92.

Changing this to a 64 bit unsigned integer allows to support a
bandwidth_down with up to ~2.8e10 [100KiBit] and a perfect tq of 255. This
is ~6.6 times higher than the maximum possible value of the gateway
announcement TVLV.

This problem only affects the non-default gw_sel_class 1.

Signed-off-by: Ruben Wisniewsi <ruben@vfn-nrw.de>
[sven@narfation.org: rewritten commit message]
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Antonio Quartulli <antonio@meshcoding.com>
net/batman-adv/gateway_client.c