From bba1a9227833474247b4fca08cf607d611966133 Mon Sep 17 00:00:00 2001
From: Martin Quinson <martin.quinson@ens-rennes.fr>
Date: Thu, 8 Oct 2020 22:42:47 +0200
Subject: [PATCH 1/1] new option ns3/seed to seed the ns-3 random generator

---
 docs/source/Configuring_SimGrid.rst | 10 ++++++++++
 src/surf/network_ns3.cpp            | 20 +++++++++++++++++++-
 src/surf/network_ns3.hpp            |  4 ++--
 3 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/docs/source/Configuring_SimGrid.rst b/docs/source/Configuring_SimGrid.rst
index e7a968578b..f680b51178 100644
--- a/docs/source/Configuring_SimGrid.rst
+++ b/docs/source/Configuring_SimGrid.rst
@@ -132,6 +132,7 @@ Existing Configuration Items
 - **network/weight-S:** :ref:`cfg=network/weight-S`
 
 - **ns3/TcpModel:** :ref:`options_pls`
+- **ns3/seed:** :ref:`options_pls`
 - **path:** :ref:`cfg=path`
 - **plugin:** :ref:`cfg=plugin`
 
@@ -439,6 +440,15 @@ ns-3. The only valid values (enforced on the SimGrid side) are
 'default' (no change to the ns-3 configuration), 'NewReno' or 'Reno' or
 'Tahoe'.
 
+**Option** ``ns3/seed`` **Default:** "" (don't set the seed in ns-3)
+
+This option is the random seed to provide to ns-3 with
+``ns3::RngSeedManager::SetSeed`` and ``ns3::RngSeedManager::SetRun``.
+
+If left blank, no seed is set in ns-3. If the value 'time' is
+provided, the current amount of seconds since epoch is used as a seed.
+Otherwise, the provided value must be a number to use as a seed.
+
 Configuring the Storage model
 .............................
 
diff --git a/src/surf/network_ns3.cpp b/src/surf/network_ns3.cpp
index b44c56a99e..ace2e772fc 100644
--- a/src/surf/network_ns3.cpp
+++ b/src/surf/network_ns3.cpp
@@ -7,6 +7,7 @@
 #include <unordered_set>
 
 #include "xbt/config.hpp"
+#include "xbt/str.h"
 #include "xbt/string.hpp"
 #include "xbt/utility.hpp"
 
@@ -210,7 +211,24 @@ void surf_network_model_init_NS3()
 }
 
 static simgrid::config::Flag<std::string>
-    ns3_tcp_model("ns3/TcpModel", "The ns-3 tcp model can be : NewReno or Reno or Tahoe", "default");
+    ns3_tcp_model("ns3/TcpModel", "The ns-3 tcp model can be: NewReno or Reno or Tahoe", "default");
+static simgrid::config::Flag<std::string> ns3_seed(
+    "ns3/seed",
+    "The random seed provided to ns-3. Either 'time' to seed with time(), blank to not set (default), or a number.", "",
+    [](std::string val) {
+      if (val.length() == 0)
+        return;
+      if (strcasecmp(val.c_str(), "time") == 0) {
+        std::srand(time(NULL));
+        ns3::RngSeedManager::SetSeed(std::rand());
+        ns3::RngSeedManager::SetRun(std::rand());
+      } else {
+        int v = xbt_str_parse_int(
+            val.c_str(), "Invalid value for option ns3/seed. It must be either 'time', a number, or left empty.");
+        ns3::RngSeedManager::SetSeed(v);
+        ns3::RngSeedManager::SetRun(v);
+      }
+    });
 
 namespace simgrid {
 namespace kernel {
diff --git a/src/surf/network_ns3.hpp b/src/surf/network_ns3.hpp
index 6e6359573f..70a4586c8d 100644
--- a/src/surf/network_ns3.hpp
+++ b/src/surf/network_ns3.hpp
@@ -37,8 +37,8 @@ public:
   s4u::Link::SharingPolicy sharing_policy_;
 
   void apply_event(profile::Event* event, double value) override;
-  void set_bandwidth(double value) override { THROW_UNIMPLEMENTED; }
-  void set_latency(double value) override { THROW_UNIMPLEMENTED; }
+  void set_bandwidth(double) override { THROW_UNIMPLEMENTED; }
+  void set_latency(double) override { THROW_UNIMPLEMENTED; }
   void set_bandwidth_profile(profile::Profile* profile) override;
   void set_latency_profile(profile::Profile* profile) override;
   s4u::Link::SharingPolicy get_sharing_policy() override {return sharing_policy_;}
-- 
2.20.1