From c2575024a047482d8478f48255ad91e3b8e34785 Mon Sep 17 00:00:00 2001
From: Augustin Degomme <adegomme@gmail.com>
Date: Tue, 15 Dec 2020 15:50:28 +0100
Subject: [PATCH] test failure fix for #45. On NS3 < 3.30 there was a
 constraint on NSS value vs MCS value, which was lifted since. Add an explicit
 message and bail out before crashing. And use a supported value for the
 example file, in order not to fail tests. This does not seem to affect tests.

---
 examples/platforms/wifi_ns3.xml | 2 +-
 src/surf/network_ns3.cpp        | 4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/examples/platforms/wifi_ns3.xml b/examples/platforms/wifi_ns3.xml
index b737608dfd..4e633b6e42 100644
--- a/examples/platforms/wifi_ns3.xml
+++ b/examples/platforms/wifi_ns3.xml
@@ -8,7 +8,7 @@
 		<zone id="SSID_1" routing="WIFI">
 			<prop id="access_point" value="alice"/>
 			<prop id="mcs" value="2"/> <!-- Optionnal: default = 3 -->
-			<prop id="nss" value="2"/> <!-- Optionnal: default = 1 -->
+			<prop id="nss" value="1"/> <!-- Optionnal: default = 1 -->
 
 			<host id="alice" speed="1Gf"/>
 
diff --git a/src/surf/network_ns3.cpp b/src/surf/network_ns3.cpp
index 999e63e3e3..21698f75ad 100644
--- a/src/surf/network_ns3.cpp
+++ b/src/surf/network_ns3.cpp
@@ -91,6 +91,10 @@ static void zoneCreation_cb(simgrid::s4u::NetZone const& zone) {
     const char* nss = wifizone->get_property("nss");
     int mcs_value = mcs ? atoi(mcs) : 3;
     int nss_value = nss ? atoi(nss) : 1;
+#if NS3_MINOR_VERSION < 30
+    if(nss_value != 1+(mcs_value/8))
+      xbt_die("On NS3 < 3.30, NSS value has to satisfy NSS == 1+(MCS/8) constraint. Bailing out");
+#endif
     wifi.SetRemoteStationManager("ns3::ConstantRateWifiManager",
                                  "ControlMode", ns3::StringValue("HtMcs0"),
                                  "DataMode", ns3::StringValue("HtMcs" + std::to_string(mcs_value)));
-- 
2.20.1