netem: markov loss model transition fix
authorHagen Paul Pfeifer <hagen@jauu.net>
Tue, 22 Oct 2013 21:27:06 +0000 (23:27 +0200)
committerDavid S. Miller <davem@davemloft.net>
Fri, 25 Oct 2013 23:03:39 +0000 (19:03 -0400)
commit4a3ad7b3eade08ad1c760aaa4fe06a36f2584939
tree0006fbd7b270176d09bd80e6c7095e380c693571
parentb45bd46decd947eaa3497699d450e0851d247534
netem: markov loss model transition fix

The transition from markov state "3 => lost packets within a burst
period" to "1 => successfully transmitted packets within a gap period"
has no *additional* loss event. The loss already happen for transition
from 1 -> 3, this additional loss will make things go wild.

E.g. transition probabilities:

p13:   10%
p31:  100%

Expected:

Ploss = p13 / (p13 + p31)
Ploss = ~9.09%

... but it isn't. Even worse: we get a double loss - each time.
So simple don't return true to indicate loss, rather break and return
false.

Signed-off-by: Hagen Paul Pfeifer <hagen@jauu.net>
Cc: Stephen Hemminger <stephen@networkplumber.org>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Stefano Salsano <stefano.salsano@uniroma2.it>
Cc: Fabio Ludovici <fabio.ludovici@yahoo.it>
Signed-off-by: Hagen Paul Pfeifer <hagen@jauu.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
net/sched/sch_netem.c