src/nepi/resources/linux/ns3/ns3simulation.py

   1 #
   2 #    NEPI, a framework to manage network experiments
   3 #    Copyright (C) 2014 INRIA
   4 #
   5 #    This program is free software: you can redistribute it and/or modify
   6 #    it under the terms of the GNU General Public License as published by
   7 #    the Free Software Foundation, either version 3 of the License, or
   8 #    (at your option) any later version.
   9 #
  10 #    This program is distributed in the hope that it will be useful,
  11 #    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 #    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 #    GNU General Public License for more details.
  14 #
  15 #    You should have received a copy of the GNU General Public License
  16 #    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17 #
  18 # Author: Alina Quereilhac <alina.quereilhac@inria.fr>
  19
  20 from nepi.execution.attribute import Attribute, Flags, Types
  21 from nepi.execution.trace import Trace, TraceAttr
  22 from nepi.execution.resource import ResourceManager, clsinit_copy, \
  23         ResourceState, ResourceFactory, reschedule_delay
  24 from nepi.resources.linux.application import LinuxApplication
  25 from nepi.util.timefuncs import tnow, tdiffsec
  26 from nepi.resources.ns3.ns3simulation import NS3Simulation
  27 from nepi.resources.ns3.ns3wrapper import SIMULATOR_UUID, GLOBAL_VALUE_UUID, \
  28         IPV4_GLOBAL_ROUTING_HELPER_UUID
  29 from nepi.resources.linux.ns3.ns3client import LinuxNS3Client
  30
  31 import os
  32 import time
  33 import threading
  34
  35 ## TODO: Clean up DCE part. All that is DCE specific should go
  36 ##       in the linux ns3dceapplication.py
  37
  38 @clsinit_copy
  39 class LinuxNS3Simulation(LinuxApplication, NS3Simulation):
  40     _rtype = "LinuxNS3Simulation"
  41
  42     @classmethod
  43     def _register_attributes(cls):
  44         impl_type = Attribute("simulatorImplementationType",
  45                 "The object class to use as the simulator implementation",
  46             allowed = ["ns3::DefaultSimulatorImpl", "ns3::RealtimeSimulatorImpl"],
  47             default = "ns3::DefaultSimulatorImpl",
  48             type = Types.Enumerate,
  49             flags = Flags.Design)
  50
  51         sched_type = Attribute("schedulerType",
  52                 "The object class to use as the scheduler implementation",
  53                 allowed = ["ns3::MapScheduler",
  54                             "ns3::ListScheduler",
  55                             "ns3::HeapScheduler",
  56                             "ns3::MapScheduler",
  57                             "ns3::CalendarScheduler"
  58                     ],
  59             default = "ns3::MapScheduler",
  60             type = Types.Enumerate,
  61             flags = Flags.Design)
  62
  63         check_sum = Attribute("checksumEnabled",
  64                 "A global switch to enable all checksums for all protocols",
  65             default = False,
  66             type = Types.Bool,
  67             flags = Flags.Design)
  68
  69         ns_log = Attribute("nsLog",
  70             "NS_LOG environment variable. " \
  71                     " Will only generate output if ns-3 is compiled in DEBUG mode. ",
  72             flags = Flags.Design)
  73
  74         verbose = Attribute("verbose",
  75             "True to output debugging info from the ns3 client-server communication",
  76             type = Types.Bool,
  77             flags = Flags.Design)
  78
  79         enable_dump = Attribute("enableDump",
  80             "Enable dumping the remote executed ns-3 commands to a script "
  81             "in order to later reproduce and debug the experiment",
  82             type = Types.Bool,
  83             default = False,
  84             flags = Flags.Design)
  85
  86         build_mode = Attribute("buildMode",
  87             "Mode used to build ns-3 with waf. One if: debug, release, oprimized ",
  88             default = "optimized",
  89             allowed = ["debug", "release", "optimized"],
  90             type = Types.Enumerate,
  91             flags = Flags.Design)
  92
  93         ns3_version = Attribute("ns3Version",
  94             "Version of ns-3 to install from nsam repo",
  95             #default = "ns-3.19",
  96             default = "ns-3-dev",
  97             flags = Flags.Design)
  98
  99         pybindgen_version = Attribute("pybindgenVersion",
 100             "Version of pybindgen to install from bazar repo",
 101             #default = "864",
 102             default = "868",
 103             flags = Flags.Design)
 104
 105         populate_routing_tables = Attribute("populateRoutingTables",
 106             "Invokes  Ipv4GlobalRoutingHelper.PopulateRoutingTables() ",
 107             default = False,
 108             type = Types.Bool,
 109             flags = Flags.Design)
 110
 111         cls._register_attribute(impl_type)
 112         cls._register_attribute(sched_type)
 113         cls._register_attribute(check_sum)
 114         cls._register_attribute(ns_log)
 115         cls._register_attribute(enable_dump)
 116         cls._register_attribute(verbose)
 117         cls._register_attribute(build_mode)
 118         cls._register_attribute(ns3_version)
 119         cls._register_attribute(pybindgen_version)
 120         cls._register_attribute(populate_routing_tables)
 121
 122     def __init__(self, ec, guid):
 123         LinuxApplication.__init__(self, ec, guid)
 124         NS3Simulation.__init__(self)
 125
 126         self._client = None
 127         self._home = "ns3-simu-%s" % self.guid
 128         self._socket_name = "ns3-%s.sock" % os.urandom(4).encode('hex')
 129         self._dce_manager_helper_uuid = None
 130         self._dce_application_helper_uuid = None
 131         self._enable_dce = None
 132
 133     @property
 134     def socket_name(self):
 135         return self._socket_name
 136
 137     @property
 138     def remote_socket(self):
 139         return os.path.join(self.run_home, self.socket_name)
 140
 141     @property
 142     def ns3_build_home(self):
 143         return os.path.join(self.node.bin_dir, "ns-3", self.get("ns3Version"),
 144                 self.get("buildMode"), "build")
 145
 146     def trace(self, name, attr = TraceAttr.ALL, block = 512, offset = 0):
 147         self._client.flush()
 148         return LinuxApplication.trace(self, name, attr, block, offset)
 149
 150     def upload_sources(self):
 151         self.node.mkdir(os.path.join(self.node.src_dir, "ns3wrapper"))
 152
 153         # upload ns3 wrapper python script
 154         ns3_wrapper = os.path.join(os.path.dirname(__file__), "..", "..", "ns3",
 155                 "ns3wrapper.py")
 156
 157         self.node.upload(ns3_wrapper,
 158                 os.path.join(self.node.src_dir, "ns3wrapper", "ns3wrapper.py"),
 159                 overwrite = False)
 160
 161         # upload ns3 wrapper debug python script
 162         ns3_wrapper_debug = os.path.join(os.path.dirname(__file__), "..", "..", "ns3",
 163                 "ns3wrapper_debug.py")
 164
 165         self.node.upload(ns3_wrapper_debug,
 166                 os.path.join(self.node.src_dir, "ns3wrapper", "ns3wrapper_debug.py"),
 167                 overwrite = False)
 168
 169         # upload ns3_server python script
 170         ns3_server = os.path.join(os.path.dirname(__file__), "..", "..", "ns3",
 171                 "ns3server.py")
 172
 173         self.node.upload(ns3_server,
 174                 os.path.join(self.node.src_dir, "ns3wrapper", "ns3server.py"),
 175                 overwrite = False)
 176
 177         if self.node.use_rpm:
 178             # upload pygccxml sources
 179             pygccxml_tar = os.path.join(os.path.dirname(__file__), "dependencies",
 180                     "%s.tar.gz" % self.pygccxml_version)
 181
 182             self.node.upload(pygccxml_tar,
 183                     os.path.join(self.node.src_dir, "%s.tar.gz" % self.pygccxml_version),
 184                     overwrite = False)
 185
 186         # Upload user defined ns-3 sources
 187         self.node.mkdir(os.path.join(self.node.src_dir, "ns-3"))
 188         src_dir = os.path.join(self.node.src_dir, "ns-3")
 189
 190         super(LinuxNS3Simulation, self).upload_sources(src_dir = src_dir)
 191
 192     def upload_extra_sources(self, sources = None, src_dir = None):
 193         return super(LinuxNS3Simulation, self).upload_sources(
 194                 sources = sources,
 195                 src_dir = src_dir)
 196
 197     def upload_start_command(self):
 198         command = self.get("command")
 199         env = self.get("env")
 200
 201         # We want to make sure the ccnd is running
 202         # before the experiment starts.
 203         # Run the command as a bash script in background,
 204         # in the host ( but wait until the command has
 205         # finished to continue )
 206         env = self.replace_paths(env)
 207         command = self.replace_paths(command)
 208
 209         shfile = os.path.join(self.app_home, "start.sh")
 210         self.node.upload_command(command,
 211                     shfile = shfile,
 212                     env = env,
 213                     overwrite = True)
 214
 215         # Run the ns3wrapper
 216         self._run_in_background()
 217
 218     def configure(self):
 219         if self.has_changed("simulatorImplementationType"):
 220             simu_type = self.get("simulatorImplementationType")
 221             stype = self.create("StringValue", simu_type)
 222             self.invoke(GLOBAL_VALUE_UUID, "Bind", "SimulatorImplementationType", stype)
 223
 224         if self.has_changed("checksumEnabled"):
 225             check_sum = self.get("checksumEnabled")
 226             btrue = self.create("BooleanValue", check_sum)
 227             self.invoke(GLOBAL_VALUE_UUID, "Bind", "ChecksumEnabled", btrue)
 228
 229         if self.has_changed("schedulerType"):
 230             sched_type = self.get("schedulerType")
 231             stype = self.create("StringValue", sched_type)
 232             self.invoke(GLOBAL_VALUE_UUID, "Bind", "SchedulerType", btrue)
 233
 234     def do_deploy(self):
 235         if not self.node or self.node.state < ResourceState.READY:
 236             self.debug("---- RESCHEDULING DEPLOY ---- node state %s " % self.node.state )
 237
 238             # ccnd needs to wait until node is deployed and running
 239             self.ec.schedule(reschedule_delay, self.deploy)
 240         else:
 241             if not self.get("command"):
 242                 self.set("command", self._start_command)
 243
 244             if not self.get("depends"):
 245                 self.set("depends", self._dependencies)
 246
 247             if self.get("sources"):
 248                 sources = self.get("sources")
 249                 source = sources.split(" ")[0]
 250                 basename = os.path.basename(source)
 251                 version = ( basename.strip().replace(".tar.gz", "")
 252                     .replace(".tar","")
 253                     .replace(".gz","")
 254                     .replace(".zip","") )
 255
 256                 self.set("ns3Version", version)
 257                 self.set("sources", source)
 258
 259             if not self.get("build"):
 260                 self.set("build", self._build)
 261
 262             if not self.get("install"):
 263                 self.set("install", self._install)
 264
 265             if not self.get("env"):
 266                 self.set("env", self._environment)
 267
 268             self.do_discover()
 269             self.do_provision()
 270
 271             # Create client
 272             self._client = LinuxNS3Client(self)
 273
 274             self.configure()
 275
 276             self.set_ready()
 277
 278     def do_start(self):
 279         """ Starts simulation execution
 280
 281         """
 282         self.info("Starting")
 283
 284         if self.state == ResourceState.READY:
 285             if self.get("populateRoutingTables") == True:
 286                 self.invoke(IPV4_GLOBAL_ROUTING_HELPER_UUID, "PopulateRoutingTables")
 287
 288             self._client.start()
 289
 290             """
 291             # XXX: IS THIS REALLY NEEDED??
 292             # Wait until the Simulation is actually started...
 293
 294             is_running = False
 295             for i in xrange(1000):
 296                 is_running = self.invoke(SIMULATOR_UUID, "isRunning")
 297
 298                 if is_running:
 299                     break
 300                 else:
 301                     time.sleep(1)
 302             else:
 303                 if not is_running:
 304                     msg = " Simulation did not start"
 305                     self.error(msg)
 306                     raise RuntimeError
 307             """
 308
 309             self.set_started()
 310         else:
 311             msg = " Failed to execute command '%s'" % command
 312             self.error(msg, out, err)
 313             raise RuntimeError, msg
 314
 315     def do_stop(self):
 316         """ Stops simulation execution
 317
 318         """
 319         if self.state == ResourceState.STARTED:
 320             self._client.stop()
 321             self.set_stopped()
 322
 323     def do_release(self):
 324         self.info("Releasing resource")
 325
 326         tear_down = self.get("tearDown")
 327         if tear_down:
 328             self.node.execute(tear_down)
 329
 330         self.do_stop()
 331         self._client.shutdown()
 332         LinuxApplication.do_stop(self)
 333
 334         super(LinuxApplication, self).do_release()
 335
 336     @property
 337     def enable_dce(self):
 338         if self._enable_dce is None:
 339             from nepi.resources.ns3.ns3dceapplication import NS3BaseDceApplication
 340             rclass = ResourceFactory.get_resource_type(
 341                     NS3BaseDceApplication.get_rtype())
 342
 343             self._enable_dce = False
 344             for guid in self.ec.resources:
 345                 rm = self.ec.get_resource(guid)
 346                 if isinstance(rm, rclass):
 347                     self._enable_dce = True
 348                     break
 349
 350         return self._enable_dce
 351
 352     @property
 353     def _start_command(self):
 354         command = []
 355
 356         command.append("PYTHONPATH=$PYTHONPATH:${SRC}/ns3wrapper/")
 357
 358         command.append("python ${SRC}/ns3wrapper/ns3server.py -S %s" % \
 359                 os.path.basename(self.remote_socket) )
 360
 361         ns_log = self.get("nsLog")
 362         if ns_log:
 363             command.append("-L '%s'" % ns_log)
 364
 365         if self.get("enableDump"):
 366             command.append("-D")
 367
 368         if self.get("verbose"):
 369             command.append("-v")
 370
 371         command = " ".join(command)
 372         return command
 373
 374     @property
 375     def _dependencies(self):
 376         if self.node.use_rpm:
 377             return ( " gcc gcc-c++ python python-devel mercurial bzr tcpdump socat gccxml unzip")
 378         elif self.node.use_deb:
 379             return ( " gcc g++ python python-dev mercurial bzr tcpdump socat gccxml python-pygccxml unzip")
 380         return ""
 381
 382     @property
 383     def ns3_repo(self):
 384         return "http://code.nsnam.org"
 385
 386     @property
 387     def pygccxml_version(self):
 388         return "pygccxml-1.0.0"
 389
 390     @property
 391     def dce_repo(self):
 392         return "http://code.nsnam.org/ns-3-dce"
 393         #eturn "http://code.nsnam.org/epmancini/ns-3-dce"
 394
 395     @property
 396     def _build(self):
 397         # If the user defined local sources for ns-3, we uncompress the sources
 398         # on the remote sources directory. Else we clone ns-3 from the official repo.
 399         source = self.get("sources")
 400         if not source:
 401             clone_ns3_cmd = "hg clone %(ns3_repo)s/%(ns3_version)s ${SRC}/ns-3/%(ns3_version)s" \
 402                     % {
 403                         'ns3_version': self.get("ns3Version"),
 404                         'ns3_repo':  self.ns3_repo,
 405                       }
 406         else:
 407             if source.find(".tar.gz") > -1:
 408                 clone_ns3_cmd = (
 409                             "tar xzf ${SRC}/ns-3/%(basename)s "
 410                             " --strip-components=1 -C ${SRC}/ns-3/%(ns3_version)s "
 411                             ) % {
 412                                 'basename': os.path.basename(source),
 413                                 'ns3_version': self.get("ns3Version"),
 414                                 }
 415             elif source.find(".tar") > -1:
 416                 clone_ns3_cmd = (
 417                             "tar xf ${SRC}/ns-3/%(basename)s "
 418                             " --strip-components=1 -C ${SRC}/ns-3/%(ns3_version)s "
 419                             ) % {
 420                                 'basename': os.path.basename(source),
 421                                 'ns3_version': self.get("ns3Version"),
 422                                 }
 423             elif source.find(".zip") > -1:
 424                 basename = os.path.basename(source)
 425                 bare_basename = basename.replace(".zip", "") \
 426                         .replace(".tar", "") \
 427                         .replace(".tar.gz", "")
 428
 429                 clone_ns3_cmd = (
 430                             "unzip ${SRC}/ns-3/%(basename)s && "
 431                             "mv ${SRC}/ns-3/%(bare_basename)s ${SRC}/ns-3/%(ns3_version)s "
 432                             ) % {
 433                                 'bare_basename': basename_name,
 434                                 'basename': basename,
 435                                 'ns3_version': self.get("ns3Version"),
 436                                 }
 437
 438         clone_dce_cmd = " echo 'DCE will not be built' "
 439         if self.enable_dce:
 440             clone_dce_cmd = (
 441                         # DCE installation
 442                         # Test if dce is alredy installed
 443                         " ( "
 444                         "  ( "
 445                         "    ( test -d ${SRC}/dce/ns-3-dce ) "
 446                         "   && echo 'dce binaries found, nothing to do'"
 447                         "  ) "
 448                         " ) "
 449                         "  || "
 450                         # Get dce source code
 451                         " ( "
 452                         "   mkdir -p ${SRC}/dce && "
 453                         "   hg clone %(dce_repo)s ${SRC}/dce/ns-3-dce"
 454                         " ) "
 455                      ) % {
 456                             'dce_repo': self.dce_repo
 457                          }
 458
 459         return (
 460                 # NS3 installation
 461                 "( "
 462                 " ( "
 463                 # Test if ns-3 is alredy installed
 464                 "  ((( test -d ${SRC}/ns-3/%(ns3_version)s ) || "
 465                 "    ( test -d ${NS3BINDINGS:='None'} && test -d ${NS3LIBRARIES:='None'})) "
 466                 "  && echo 'ns-3 binaries found, nothing to do' )"
 467                 " ) "
 468                 "  || "
 469                 # If not, install ns-3 and its dependencies
 470                 " (   "
 471                 # Install pygccxml
 472                 "   (   "
 473                 "     ( "
 474                 "       python -c 'import pygccxml' && "
 475                 "       echo 'pygccxml not found' "
 476                 "     ) "
 477                 "      || "
 478                 "     ( "
 479                 "       tar xf ${SRC}/%(pygccxml_version)s.tar.gz -C ${SRC} && "
 480                 "       cd ${SRC}/%(pygccxml_version)s && "
 481                 "       python setup.py build && "
 482                 "       sudo -S python setup.py install "
 483                 "     ) "
 484                 "   ) "
 485                 # Install pybindgen
 486                 "  && "
 487                 "   (   "
 488                 "     ( "
 489                 "       test -d ${SRC}/pybindgen/%(pybindgen_version)s && "
 490                 "       echo 'binaries found, nothing to do' "
 491                 "     ) "
 492                 "      || "
 493                 # If not, clone and build
 494                 "      ( cd ${SRC} && "
 495                 "        mkdir -p ${SRC}/pybindgen && "
 496                 "        bzr checkout lp:pybindgen -r %(pybindgen_version)s ${SRC}/pybindgen/%(pybindgen_version)s && "
 497                 "        cd ${SRC}/pybindgen/%(pybindgen_version)s && "
 498                 "        ./waf configure && "
 499                 "        ./waf "
 500                 "      ) "
 501                 "   ) "
 502                 " && "
 503                 # Get ns-3 source code
 504                 "  ( "
 505                 "     mkdir -p ${SRC}/ns-3/%(ns3_version)s && "
 506                 "     %(clone_ns3_cmd)s "
 507                 "  ) "
 508                 " ) "
 509                 ") "
 510                 " && "
 511                 "( "
 512                 "   %(clone_dce_cmd)s "
 513                 ") "
 514              ) % {
 515                     'ns3_version': self.get("ns3Version"),
 516                     'pybindgen_version': self.get("pybindgenVersion"),
 517                     'pygccxml_version': self.pygccxml_version,
 518                     'clone_ns3_cmd': clone_ns3_cmd,
 519                     'clone_dce_cmd': clone_dce_cmd,
 520                  }
 521
 522     @property
 523     def _install(self):
 524         install_dce_cmd = " echo 'DCE will not be installed' "
 525         if self.enable_dce:
 526             install_dce_cmd = (
 527                         " ( "
 528                         "   ((test -d %(ns3_build_home)s/bin_dce ) && "
 529                         "    echo 'dce binaries found, nothing to do' )"
 530                         " ) "
 531                         " ||"
 532                         " (   "
 533                          # If not, copy ns-3 build to bin
 534                         "  cd ${SRC}/dce/ns-3-dce && "
 535                         "  rm -rf ${SRC}/dce/ns-3-dce/build && "
 536                         "  ./waf configure %(enable_opt)s --with-pybindgen=${SRC}/pybindgen/%(pybindgen_version)s "
 537                         "  --prefix=%(ns3_build_home)s --with-ns3=%(ns3_build_home)s && "
 538                         "  ./waf build && "
 539                         "  ./waf install && "
 540                         "  mv %(ns3_build_home)s/lib*/python*/site-packages/ns/dce.so %(ns3_build_home)s/lib/python/site-packages/ns/ "
 541                         " )"
 542                 ) % {
 543                     'ns3_version': self.get("ns3Version"),
 544                     'pybindgen_version': self.get("pybindgenVersion"),
 545                     'ns3_build_home': self.ns3_build_home,
 546                     'build_mode': self.get("buildMode"),
 547                     'enable_opt': "--enable-opt" if  self.get("buildMode") == "optimized" else ""
 548                     }
 549
 550         return (
 551                  # Test if ns-3 is alredy installed
 552                 "("
 553                 " ( "
 554                 "  ( ( (test -d %(ns3_build_home)s/lib ) || "
 555                 "    (test -d ${NS3BINDINGS:='None'} && test -d ${NS3LIBRARIES:='None'}) ) && "
 556                 "    echo 'binaries found, nothing to do' )"
 557                 " ) "
 558                 " ||"
 559                 " (   "
 560                  # If not, copy ns-3 build to bin
 561                 "  mkdir -p %(ns3_build_home)s && "
 562                 "  cd ${SRC}/ns-3/%(ns3_version)s && "
 563                 "  rm -rf ${SRC}/ns-3/%(ns3_version)s/build && "
 564                 "  ./waf configure -d %(build_mode)s --with-pybindgen=${SRC}/pybindgen/%(pybindgen_version)s "
 565                 "  --prefix=%(ns3_build_home)s && "
 566                 "  ./waf build && "
 567                 "  ./waf install && "
 568                 "  mv %(ns3_build_home)s/lib*/python* %(ns3_build_home)s/lib/python "
 569                 " )"
 570                 ") "
 571                 " && "
 572                 "( "
 573                 "   %(install_dce_cmd)s "
 574                 ") "
 575               ) % {
 576                     'ns3_version': self.get("ns3Version"),
 577                     'pybindgen_version': self.get("pybindgenVersion"),
 578                     'build_mode': self.get("buildMode"),
 579                     'ns3_build_home': self.ns3_build_home,
 580                     'install_dce_cmd': install_dce_cmd
 581                  }
 582
 583     @property
 584     def _environment(self):
 585         env = []
 586         env.append("PYTHONPATH=$PYTHONPATH:${NS3BINDINGS:=%(ns3_build_home)s/lib/python/site-packages}" % {
 587                     'ns3_build_home': self.ns3_build_home
 588                  })
 589         # If NS3LIBRARIES is defined and not empty, assign its value,
 590         # if not assign ns3_build_home/lib/ to NS3LIBRARIES and LD_LIBARY_PATH
 591         env.append("LD_LIBRARY_PATH=${NS3LIBRARIES:=%(ns3_build_home)s/lib}" % {
 592                     'ns3_build_home': self.ns3_build_home
 593                  })
 594         env.append("DCE_PATH=$NS3LIBRARIES/../bin_dce")
 595         env.append("DCE_ROOT=$NS3LIBRARIES/..")
 596
 597         return " ".join(env)
 598
 599     def replace_paths(self, command):
 600         """
 601         Replace all special path tags with shell-escaped actual paths.
 602         """
 603         return ( command
 604             .replace("${USR}", self.node.usr_dir)
 605             .replace("${LIB}", self.node.lib_dir)
 606             .replace("${BIN}", self.node.bin_dir)
 607             .replace("${SRC}", self.node.src_dir)
 608             .replace("${SHARE}", self.node.share_dir)
 609             .replace("${EXP}", self.node.exp_dir)
 610             .replace("${EXP_HOME}", self.node.exp_home)
 611             .replace("${APP_HOME}", self.app_home)
 612             .replace("${RUN_HOME}", self.run_home)
 613             .replace("${NODE_HOME}", self.node.node_home)
 614             .replace("${HOME}", self.node.home_dir)
 615             # If NS3LIBRARIES is defined and not empty, use that value,
 616             # if not use ns3_build_home/lib/
 617             .replace("${BIN_DCE}", "${NS3LIBRARIES-%s/lib}/../bin_dce" % \
 618                     self.ns3_build_home)
 619             )
 620
 621     def valid_connection(self, guid):
 622         # TODO: Validate!
 623         return True
 624