netdev - [PATCH iproute2] tc/netem: loss gemodel options fixes

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Date:	Sat, 10 May 2014 13:34:58 -0700
From:	Jay Vosburgh <jay.vosburgh@...onical.com>
To:	Stephen Hemminger <stephen@...workplumber.org>
cc:	netdev@...r.kernel.org, netem@...ts.linux-foundation.org
Subject: [PATCH iproute2] tc/netem: loss gemodel options fixes


	First, the default value for 1-k is documented as being 0, but is
currently being set to 1. (100%).  This causes all packets to be dropped
in the good state if 1-k is not explicitly specified.  Fix this by setting
the default to 0.

	Second, the 1-h option is parsed correctly, however, the kernel is
expecting "h", not 1-h.  Fix this by inverting the "1-h" percentage before
sending to and after receiving from the kernel.  This does change the
behavior, but makes it consistent with the netem documentation and the
literature on the Gilbert-Elliot model, which refer to "1-h" and "1-k,"
not "h" or "k" directly.

	Last, fix a minor formatting issue for the options reporting.

Signed-off-by: Jay Vosburgh <jay.vosburgh@...onical.com>
---
 tc/q_netem.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/tc/q_netem.c b/tc/q_netem.c
index c83e301..8abe07f 100644
--- a/tc/q_netem.c
+++ b/tc/q_netem.c
@@ -307,7 +307,7 @@ static int netem_parse_opt(struct qdisc_util *qu, int argc, char **argv,
 				/* set defaults */
 				set_percent(&gemodel.r, 1.);
 				set_percent(&gemodel.h, 0);
-				set_percent(&gemodel.k1, 1.);
+				set_percent(&gemodel.k1, 0);
 				loss_type = NETEM_LOSS_GE;
 
 				if (!NEXT_IS_NUMBER())
@@ -325,6 +325,10 @@ static int netem_parse_opt(struct qdisc_util *qu, int argc, char **argv,
 					explain1("loss gemodel h");
 					return -1;
 				}
+				/* netem option is "1-h" but kernel
+				 * expects "h".
+				 */
+				gemodel.h = max_percent_value - gemodel.h;
 
 				if (!NEXT_IS_NUMBER())
 					continue;
@@ -625,10 +629,11 @@ static int netem_print_opt(struct qdisc_util *qu, FILE *f, struct rtattr *opt)
 	}
 
 	if (gemodel) {
-		fprintf(f, "loss gemodel p %s",
+		fprintf(f, " loss gemodel p %s",
 			sprint_percent(gemodel->p, b1));
 		fprintf(f, " r %s", sprint_percent(gemodel->r, b1));
-		fprintf(f, " 1-h %s", sprint_percent(gemodel->h, b1));
+		fprintf(f, " 1-h %s", sprint_percent(max_percent_value -
+						     gemodel->h, b1));
 		fprintf(f, " 1-k %s", sprint_percent(gemodel->k1, b1));
 	}
 
-- 
1.8.3.2

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