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         stoptime = Attribute("stopTime",
 112             "Time at which the simulation will stop",
 113             flags = Flags.Design)
 114
 115         cls._register_attribute(impl_type)
 116         cls._register_attribute(sched_type)
 117         cls._register_attribute(check_sum)
 118         cls._register_attribute(ns_log)
 119         cls._register_attribute(enable_dump)
 120         cls._register_attribute(verbose)
 121         cls._register_attribute(build_mode)
 122         cls._register_attribute(ns3_version)
 123         cls._register_attribute(pybindgen_version)
 124         cls._register_attribute(populate_routing_tables)
 125         cls._register_attribute(stoptime)
 126
 127     def __init__(self, ec, guid):
 128         LinuxApplication.__init__(self, ec, guid)
 129         NS3Simulation.__init__(self)
 130
 131         self._client = None
 132         self._home = "ns3-simu-%s" % self.guid
 133         self._socket_name = "ns3-%s.sock" % os.urandom(4).encode('hex')
 134         self._dce_manager_helper_uuid = None
 135         self._dce_application_helper_uuid = None
 136         self._enable_dce = None
 137
 138     @property
 139     def socket_name(self):
 140         return self._socket_name
 141
 142     @property
 143     def remote_socket(self):
 144         return os.path.join(self.run_home, self.socket_name)
 145
 146     @property
 147     def ns3_build_home(self):
 148         return os.path.join(self.node.bin_dir, "ns-3", self.get("ns3Version"),
 149                 self.get("buildMode"), "build")
 150
 151     def trace(self, name, attr = TraceAttr.ALL, block = 512, offset = 0):
 152         self._client.flush()
 153         return LinuxApplication.trace(self, name, attr, block, offset)
 154
 155     def upload_sources(self):
 156         self.node.mkdir(os.path.join(self.node.src_dir, "ns3wrapper"))
 157
 158         # upload ns3 wrapper python script
 159         ns3_wrapper = os.path.join(os.path.dirname(__file__), "..", "..", "ns3",
 160                 "ns3wrapper.py")
 161
 162         self.node.upload(ns3_wrapper,
 163                 os.path.join(self.node.src_dir, "ns3wrapper", "ns3wrapper.py"),
 164                 overwrite = False)
 165
 166         # upload ns3 wrapper debug python script
 167         ns3_wrapper_debug = os.path.join(os.path.dirname(__file__), "..", "..", "ns3",
 168                 "ns3wrapper_debug.py")
 169
 170         self.node.upload(ns3_wrapper_debug,
 171                 os.path.join(self.node.src_dir, "ns3wrapper", "ns3wrapper_debug.py"),
 172                 overwrite = False)
 173
 174         # upload ns3_server python script
 175         ns3_server = os.path.join(os.path.dirname(__file__), "..", "..", "ns3",
 176                 "ns3server.py")
 177
 178         self.node.upload(ns3_server,
 179                 os.path.join(self.node.src_dir, "ns3wrapper", "ns3server.py"),
 180                 overwrite = False)
 181
 182         if self.node.use_rpm:
 183             # upload pygccxml sources
 184             pygccxml_tar = os.path.join(os.path.dirname(__file__), "dependencies",
 185                     "%s.tar.gz" % self.pygccxml_version)
 186
 187             self.node.upload(pygccxml_tar,
 188                     os.path.join(self.node.src_dir, "%s.tar.gz" % self.pygccxml_version),
 189                     overwrite = False)
 190
 191         # Upload user defined ns-3 sources
 192         self.node.mkdir(os.path.join(self.node.src_dir, "ns-3"))
 193         src_dir = os.path.join(self.node.src_dir, "ns-3")
 194
 195         super(LinuxNS3Simulation, self).upload_sources(src_dir = src_dir)
 196
 197     def upload_extra_sources(self, sources = None, src_dir = None):
 198         return super(LinuxNS3Simulation, self).upload_sources(
 199                 sources = sources,
 200                 src_dir = src_dir)
 201
 202     def upload_start_command(self):
 203         command = self.get("command")
 204         env = self.get("env")
 205
 206         # We want to make sure the ccnd is running
 207         # before the experiment starts.
 208         # Run the command as a bash script in background,
 209         # in the host ( but wait until the command has
 210         # finished to continue )
 211         env = self.replace_paths(env)
 212         command = self.replace_paths(command)
 213
 214         shfile = os.path.join(self.app_home, "start.sh")
 215         self.node.upload_command(command,
 216                     shfile = shfile,
 217                     env = env,
 218                     overwrite = True)
 219
 220         # Run the ns3wrapper
 221         self._run_in_background()
 222
 223     def configure(self):
 224         if self.has_changed("simulatorImplementationType"):
 225             simu_type = self.get("simulatorImplementationType")
 226             stype = self.create("StringValue", simu_type)
 227             self.invoke(GLOBAL_VALUE_UUID, "Bind", "SimulatorImplementationType", stype)
 228
 229         if self.has_changed("checksumEnabled"):
 230             check_sum = self.get("checksumEnabled")
 231             btrue = self.create("BooleanValue", check_sum)
 232             self.invoke(GLOBAL_VALUE_UUID, "Bind", "ChecksumEnabled", btrue)
 233
 234         if self.has_changed("schedulerType"):
 235             sched_type = self.get("schedulerType")
 236             stype = self.create("StringValue", sched_type)
 237             self.invoke(GLOBAL_VALUE_UUID, "Bind", "SchedulerType", btrue)
 238
 239     def do_deploy(self):
 240         if not self.node or self.node.state < ResourceState.READY:
 241             self.debug("---- RESCHEDULING DEPLOY ---- node state %s " % self.node.state )
 242
 243             # ccnd needs to wait until node is deployed and running
 244             self.ec.schedule(reschedule_delay, self.deploy)
 245         else:
 246             if not self.get("command"):
 247                 self.set("command", self._start_command)
 248
 249             if not self.get("depends"):
 250                 self.set("depends", self._dependencies)
 251
 252             if self.get("sources"):
 253                 sources = self.get("sources")
 254                 source = sources.split(" ")[0]
 255                 basename = os.path.basename(source)
 256                 version = ( basename.strip().replace(".tar.gz", "")
 257                     .replace(".tar","")
 258                     .replace(".gz","")
 259                     .replace(".zip","") )
 260
 261                 self.set("ns3Version", version)
 262                 self.set("sources", source)
 263
 264             if not self.get("build"):
 265                 self.set("build", self._build)
 266
 267             if not self.get("install"):
 268                 self.set("install", self._install)
 269
 270             if not self.get("env"):
 271                 self.set("env", self._environment)
 272
 273             self.do_discover()
 274             self.do_provision()
 275
 276             # Create client
 277             self._client = LinuxNS3Client(self)
 278
 279             self.configure()
 280
 281             self.set_ready()
 282
 283     def do_start(self):
 284         """ Starts simulation execution
 285
 286         """
 287         self.info("Starting")
 288
 289         if self.state == ResourceState.READY:
 290             if self.get("populateRoutingTables") == True:
 291                 self.invoke(IPV4_GLOBAL_ROUTING_HELPER_UUID, "PopulateRoutingTables")
 292
 293             self._client.start()
 294
 295             # XXX: IS THIS REALLY NEEDED??!!!
 296             # Wait until the Simulation is actually started...
 297             is_running = False
 298             for i in xrange(1000):
 299                 is_running = self.invoke(SIMULATOR_UUID, "isRunning")
 300
 301                 if is_running:
 302                     break
 303                 else:
 304                     time.sleep(1)
 305             else:
 306                 if not is_running:
 307                     msg = " Simulation did not start"
 308                     self.error(msg)
 309                     raise RuntimeError
 310
 311             self.set_started()
 312         else:
 313             msg = " Failed to execute command '%s'" % command
 314             self.error(msg, out, err)
 315             raise RuntimeError, msg
 316
 317     def do_stop(self):
 318         """ Stops simulation execution
 319
 320         """
 321         if self.state == ResourceState.STARTED:
 322             time = None
 323             if self.get("stopTime"):
 324                 time = self.get("stopTime")
 325
 326             self._client.stop(time=time)
 327             self.set_stopped()
 328
 329     def do_release(self):
 330         self.info("Releasing resource")
 331
 332         tear_down = self.get("tearDown")
 333         if tear_down:
 334             self.node.execute(tear_down)
 335
 336         self.do_stop()
 337         self._client.shutdown()
 338         LinuxApplication.do_stop(self)
 339
 340         super(LinuxApplication, self).do_release()
 341
 342     @property
 343     def enable_dce(self):
 344         if self._enable_dce is None:
 345             from nepi.resources.ns3.ns3dceapplication import NS3BaseDceApplication
 346             rclass = ResourceFactory.get_resource_type(
 347                     NS3BaseDceApplication.get_rtype())
 348
 349             self._enable_dce = False
 350             for guid in self.ec.resources:
 351                 rm = self.ec.get_resource(guid)
 352                 if isinstance(rm, rclass):
 353                     self._enable_dce = True
 354                     break
 355
 356         return self._enable_dce
 357
 358     @property
 359     def _start_command(self):
 360         command = []
 361
 362         command.append("PYTHONPATH=$PYTHONPATH:${SRC}/ns3wrapper/")
 363
 364         command.append("python ${SRC}/ns3wrapper/ns3server.py -S %s" % \
 365                 os.path.basename(self.remote_socket) )
 366
 367         ns_log = self.get("nsLog")
 368         if ns_log:
 369             command.append("-L '%s'" % ns_log)
 370
 371         if self.get("enableDump"):
 372             command.append("-D")
 373
 374         if self.get("verbose"):
 375             command.append("-v")
 376
 377         command = " ".join(command)
 378         return command
 379
 380     @property
 381     def _dependencies(self):
 382         if self.node.use_rpm:
 383             return ( " gcc gcc-c++ python python-devel mercurial bzr tcpdump socat gccxml unzip")
 384         elif self.node.use_deb:
 385             return ( " gcc g++ python python-dev mercurial bzr tcpdump socat gccxml python-pygccxml unzip")
 386         return ""
 387
 388     @property
 389     def ns3_repo(self):
 390         return "http://code.nsnam.org"
 391
 392     @property
 393     def pygccxml_version(self):
 394         return "pygccxml-1.0.0"
 395
 396     @property
 397     def dce_repo(self):
 398         return "http://code.nsnam.org/ns-3-dce"
 399         #eturn "http://code.nsnam.org/epmancini/ns-3-dce"
 400
 401     @property
 402     def _build(self):
 403         # If the user defined local sources for ns-3, we uncompress the sources
 404         # on the remote sources directory. Else we clone ns-3 from the official repo.
 405         source = self.get("sources")
 406         if not source:
 407             clone_ns3_cmd = "hg clone %(ns3_repo)s/%(ns3_version)s ${SRC}/ns-3/%(ns3_version)s" \
 408                     % {
 409                         'ns3_version': self.get("ns3Version"),
 410                         'ns3_repo':  self.ns3_repo,
 411                       }
 412         else:
 413             if source.find(".tar.gz") > -1:
 414                 clone_ns3_cmd = (
 415                             "tar xzf ${SRC}/ns-3/%(basename)s "
 416                             " --strip-components=1 -C ${SRC}/ns-3/%(ns3_version)s "
 417                             ) % {
 418                                 'basename': os.path.basename(source),
 419                                 'ns3_version': self.get("ns3Version"),
 420                                 }
 421             elif source.find(".tar") > -1:
 422                 clone_ns3_cmd = (
 423                             "tar xf ${SRC}/ns-3/%(basename)s "
 424                             " --strip-components=1 -C ${SRC}/ns-3/%(ns3_version)s "
 425                             ) % {
 426                                 'basename': os.path.basename(source),
 427                                 'ns3_version': self.get("ns3Version"),
 428                                 }
 429             elif source.find(".zip") > -1:
 430                 basename = os.path.basename(source)
 431                 bare_basename = basename.replace(".zip", "") \
 432                         .replace(".tar", "") \
 433                         .replace(".tar.gz", "")
 434
 435                 clone_ns3_cmd = (
 436                             "unzip ${SRC}/ns-3/%(basename)s && "
 437                             "mv ${SRC}/ns-3/%(bare_basename)s ${SRC}/ns-3/%(ns3_version)s "
 438                             ) % {
 439                                 'bare_basename': basename_name,
 440                                 'basename': basename,
 441                                 'ns3_version': self.get("ns3Version"),
 442                                 }
 443
 444         clone_dce_cmd = " echo 'DCE will not be built' "
 445         if self.enable_dce:
 446             clone_dce_cmd = (
 447                         # DCE installation
 448                         # Test if dce is alredy installed
 449                         " ( "
 450                         "  ( "
 451                         "    ( test -d ${SRC}/dce/ns-3-dce ) "
 452                         "   && echo 'dce binaries found, nothing to do'"
 453                         "  ) "
 454                         " ) "
 455                         "  || "
 456                         # Get dce source code
 457                         " ( "
 458                         "   mkdir -p ${SRC}/dce && "
 459                         "   hg clone %(dce_repo)s ${SRC}/dce/ns-3-dce"
 460                         " ) "
 461                      ) % {
 462                             'dce_repo': self.dce_repo
 463                          }
 464
 465         return (
 466                 # NS3 installation
 467                 "( "
 468                 " ( "
 469                 # Test if ns-3 is alredy installed
 470                 "  ((( test -d ${SRC}/ns-3/%(ns3_version)s ) || "
 471                 "    ( test -d ${NS3BINDINGS:='None'} && test -d ${NS3LIBRARIES:='None'})) "
 472                 "  && echo 'ns-3 binaries found, nothing to do' )"
 473                 " ) "
 474                 "  || "
 475                 # If not, install ns-3 and its dependencies
 476                 " (   "
 477                 # Install pygccxml
 478                 "   (   "
 479                 "     ( "
 480                 "       python -c 'import pygccxml' && "
 481                 "       echo 'pygccxml not found' "
 482                 "     ) "
 483                 "      || "
 484                 "     ( "
 485                 "       tar xf ${SRC}/%(pygccxml_version)s.tar.gz -C ${SRC} && "
 486                 "       cd ${SRC}/%(pygccxml_version)s && "
 487                 "       python setup.py build && "
 488                 "       sudo -S python setup.py install "
 489                 "     ) "
 490                 "   ) "
 491                 # Install pybindgen
 492                 "  && "
 493                 "   (   "
 494                 "     ( "
 495                 "       test -d ${SRC}/pybindgen/%(pybindgen_version)s && "
 496                 "       echo 'binaries found, nothing to do' "
 497                 "     ) "
 498                 "      || "
 499                 # If not, clone and build
 500                 "      ( cd ${SRC} && "
 501                 "        mkdir -p ${SRC}/pybindgen && "
 502                 "        bzr checkout lp:pybindgen -r %(pybindgen_version)s ${SRC}/pybindgen/%(pybindgen_version)s && "
 503                 "        cd ${SRC}/pybindgen/%(pybindgen_version)s && "
 504                 "        ./waf configure && "
 505                 "        ./waf "
 506                 "      ) "
 507                 "   ) "
 508                 " && "
 509                 # Get ns-3 source code
 510                 "  ( "
 511                 "     mkdir -p ${SRC}/ns-3/%(ns3_version)s && "
 512                 "     %(clone_ns3_cmd)s "
 513                 "  ) "
 514                 " ) "
 515                 ") "
 516                 " && "
 517                 "( "
 518                 "   %(clone_dce_cmd)s "
 519                 ") "
 520              ) % {
 521                     'ns3_version': self.get("ns3Version"),
 522                     'pybindgen_version': self.get("pybindgenVersion"),
 523                     'pygccxml_version': self.pygccxml_version,
 524                     'clone_ns3_cmd': clone_ns3_cmd,
 525                     'clone_dce_cmd': clone_dce_cmd,
 526                  }
 527
 528     @property
 529     def _install(self):
 530         install_dce_cmd = " echo 'DCE will not be installed' "
 531         if self.enable_dce:
 532             install_dce_cmd = (
 533                         " ( "
 534                         "   ((test -d %(ns3_build_home)s/bin_dce ) && "
 535                         "    echo 'dce binaries found, nothing to do' )"
 536                         " ) "
 537                         " ||"
 538                         " (   "
 539                          # If not, copy ns-3 build to bin
 540                         "  cd ${SRC}/dce/ns-3-dce && "
 541                         "  rm -rf ${SRC}/dce/ns-3-dce/build && "
 542                         "  ./waf configure %(enable_opt)s --with-pybindgen=${SRC}/pybindgen/%(pybindgen_version)s "
 543                         "  --prefix=%(ns3_build_home)s --with-ns3=%(ns3_build_home)s && "
 544                         "  ./waf build && "
 545                         "  ./waf install && "
 546                         "  mv %(ns3_build_home)s/lib*/python*/site-packages/ns/dce.so %(ns3_build_home)s/lib/python/site-packages/ns/ "
 547                         " )"
 548                 ) % {
 549                     'ns3_version': self.get("ns3Version"),
 550                     'pybindgen_version': self.get("pybindgenVersion"),
 551                     'ns3_build_home': self.ns3_build_home,
 552                     'build_mode': self.get("buildMode"),
 553                     'enable_opt': "--enable-opt" if  self.get("buildMode") == "optimized" else ""
 554                     }
 555
 556         return (
 557                  # Test if ns-3 is alredy installed
 558                 "("
 559                 " ( "
 560                 "  ( ( (test -d %(ns3_build_home)s/lib ) || "
 561                 "    (test -d ${NS3BINDINGS:='None'} && test -d ${NS3LIBRARIES:='None'}) ) && "
 562                 "    echo 'binaries found, nothing to do' )"
 563                 " ) "
 564                 " ||"
 565                 " (   "
 566                  # If not, copy ns-3 build to bin
 567                 "  mkdir -p %(ns3_build_home)s && "
 568                 "  cd ${SRC}/ns-3/%(ns3_version)s && "
 569                 "  rm -rf ${SRC}/ns-3/%(ns3_version)s/build && "
 570                 "  ./waf configure -d %(build_mode)s --with-pybindgen=${SRC}/pybindgen/%(pybindgen_version)s "
 571                 "  --prefix=%(ns3_build_home)s && "
 572                 "  ./waf build && "
 573                 "  ./waf install && "
 574                 "  mv %(ns3_build_home)s/lib*/python* %(ns3_build_home)s/lib/python "
 575                 " )"
 576                 ") "
 577                 " && "
 578                 "( "
 579                 "   %(install_dce_cmd)s "
 580                 ") "
 581               ) % {
 582                     'ns3_version': self.get("ns3Version"),
 583                     'pybindgen_version': self.get("pybindgenVersion"),
 584                     'build_mode': self.get("buildMode"),
 585                     'ns3_build_home': self.ns3_build_home,
 586                     'install_dce_cmd': install_dce_cmd
 587                  }
 588
 589     @property
 590     def _environment(self):
 591         env = []
 592         env.append("PYTHONPATH=$PYTHONPATH:${NS3BINDINGS:=%(ns3_build_home)s/lib/python/site-packages}" % {
 593                     'ns3_build_home': self.ns3_build_home
 594                  })
 595         # If NS3LIBRARIES is defined and not empty, assign its value,
 596         # if not assign ns3_build_home/lib/ to NS3LIBRARIES and LD_LIBARY_PATH
 597         env.append("LD_LIBRARY_PATH=${NS3LIBRARIES:=%(ns3_build_home)s/lib}" % {
 598                     'ns3_build_home': self.ns3_build_home
 599                  })
 600         env.append("DCE_PATH=$NS3LIBRARIES/../bin_dce")
 601         env.append("DCE_ROOT=$NS3LIBRARIES/..")
 602
 603         return " ".join(env)
 604
 605     def replace_paths(self, command):
 606         """
 607         Replace all special path tags with shell-escaped actual paths.
 608         """
 609         return ( command
 610             .replace("${USR}", self.node.usr_dir)
 611             .replace("${LIB}", self.node.lib_dir)
 612             .replace("${BIN}", self.node.bin_dir)
 613             .replace("${SRC}", self.node.src_dir)
 614             .replace("${SHARE}", self.node.share_dir)
 615             .replace("${EXP}", self.node.exp_dir)
 616             .replace("${EXP_HOME}", self.node.exp_home)
 617             .replace("${APP_HOME}", self.app_home)
 618             .replace("${RUN_HOME}", self.run_home)
 619             .replace("${NODE_HOME}", self.node.node_home)
 620             .replace("${HOME}", self.node.home_dir)
 621             # If NS3LIBRARIES is defined and not empty, use that value,
 622             # if not use ns3_build_home/lib/
 623             .replace("${BIN_DCE}", "${NS3LIBRARIES-%s/lib}/../bin_dce" % \
 624                     self.ns3_build_home)
 625             )
 626
 627     def valid_connection(self, guid):
 628         # TODO: Validate!
 629         return True
 630