Initial commit - first development version of Mininet

cleanup

@@ -0,0 +1,16 @@
+#!/bin/bash
+
+echo "Removing all links of the pattern foo-ethX"
+
+for f in `ip link show | egrep -o '(\w+-eth\w+)' ` ; do  
+  cmd="ip link del $f"
+  echo $smd
+  $cmd
+done
+
+echo "Removing excess controllers/ofprotocols/ofdatapaths/pings"
+killall -9 controller ofprotocol ofdatapath ping 2> /dev/null
+
+echo "Removing vconn junk in /tmp"
+rm -f /tmp/vconn* /tmp/vlogs* /tmp/*.out /tmp/*.log
+

mininet.py

@@ -0,0 +1,621 @@
+#!/usr/bin/python
+
+"""
+
+Mininet: A simple networking testbed for OpenFlow!
+
+Mininet creates a simple test network for OpenFlow by using
+process-based virtualization and network namespaces. 
+
+This file supports use of either the kernel or user space datapath
+from the OpenFlow reference implementation. Up to 32 switches are
+supported using the kernel datapath, and 512 (or more) switches are
+supported via the user datapath.
+
+Simulated hosts are created as processes in
+separate network namespaces. This allows a complete OpenFlow
+network to be simulated on top of a single Linux kernel.
+
+Each host has:
+   A virtual console (pipes to a shell)
+   A virtual interfaces (half of a veth pair)
+   A namespaced parent shell (and possibly some child processes)
+   
+Hosts have a network interface which is
+configured via ifconfig/ip link/etc. with data network IP
+addresses (e.g. 192.168.123.2 )
+
+In kernel datapath mode, the controller and switches are simply
+processes in the root namespace.
+
+Kernel OpenFlow datapaths are instantiated using dpctl, and are
+attached to the one side of a veth pair; the other side resides in
+the host namespace. In this mode, switch processes can simply
+connect to the controller via the loopback interface.
+
+In user datapath mode, the controller and switch are full-service
+nodes that live in their own network namespace and have management
+interfaces and IP addresses on a control network (e.g. 10.0.123.1,
+currently routed although it could be bridged.)
+
+In addition to a management interface, user mode switches also have
+several switch interfaces, halves of veth pairs whose other halves
+reside in the host nodes that the switches are connected to.
+
+Naming:
+   Host nodes are named h1-hN
+   Switch nodes are named s0-sN
+   Interfaces are named {nodename}-eth0 .. {nodename}-ethN,
+
+Thoughts/TBD:
+
+   It should be straightforward to add a function to read
+   OpenFlowVMS  spec files, but I haven't done so yet.
+   For the moment, specifying configurations and tests in Python
+   is straightforward and concise.
+   Soon, we'll want to split the various subsystems (core,
+   cli, tests, etc.) into multiple modules.
+   We may be able to get better performance by using the kernel
+   datapath (using its multiple datapath feature on multiple 
+   interfaces.) This would eliminate the ofdatapath user processes.
+   OpenVSwitch would still run at user level.
+   
+Bob Lantz
+rlantz@cs.stanford.edu
+
+History:
+11/19/09 Initial revision (user datapath only)
+12/8/08  Kernel datapath support complete
+
+"""
+
+# Note: this script must be run as root 
+# Perhaps we should do so automatically!
+
+from subprocess import call, check_call, Popen, PIPE, STDOUT
+from time import sleep
+import re, os, signal, sys, select
+flush = sys.stdout.flush
+from resource import setrlimit, RLIMIT_NPROC, RLIMIT_NOFILE
+
+# Utility routines to make it easier to run commands
+
+def run( cmd ):
+   "Simple interface to subprocess.call()"
+   return call( cmd.split( ' ' ) )
+
+def checkRun( cmd ):
+   "Simple interface to subprocess.check_call()"
+   check_call( cmd.split( ' ' ) )
+   
+def quietRun( cmd ):
+   "Run a command, routing stderr to stdout, and return the output."
+   popen = Popen( cmd.split( ' '), stdout=PIPE, stderr=STDOUT)
+   # We can't use Popen.communicate() because it uses 
+   # select(), which can't handle
+   # high file descriptor numbers! poll() can, however.
+   output = ''
+   readable = select.poll()
+   readable.register( popen.stdout )
+   while True:
+      while readable.poll(): 
+         data = popen.stdout.read( 1024 )
+         if len( data ) == 0: break
+         output += data
+      popen.poll()
+      if popen.returncode != None: break
+   return output
+   
+# Command paths
+netns = "/usr/local/bin/netns"
+bash = "/bin/bash"
+ifconfig = "/sbin/ifconfig"
+
+class Node( object ):
+   """A virtual network node is simply a shell in a network namespace.
+      We communicate with it using pipes."""
+   def __init__( self, name, inNamespace=True ):
+      self.name = name
+      closeFds = False # speed vs. memory use
+      # xpg_echo is needed so we can echo our sentinel in sendCmd
+      cmd = [ bash, '-O', 'xpg_echo' ]
+      self.inNamespace = inNamespace
+      if self.inNamespace: cmd = [ netns ] + cmd
+      self.shell = Popen( cmd, stdin=PIPE, stdout=PIPE, stderr=STDOUT,
+         close_fds=closeFds )
+      self.stdin = self.shell.stdin
+      self.stdout = self.shell.stdout
+      self.pollOut = select.poll() 
+      self.pollOut.register( self.stdout )
+      outToNode[ self.stdout ] = self
+      inToNode[ self.stdin ] = self
+      self.pid = self.shell.pid
+      self.intfCount = 0
+      self.intfs = []
+      self.ips = {}
+      self.connection = {}
+      self.waiting = False
+      # For sanity check, try bringing up loopback interface
+      # self.cmd( "ifconfig lo 127.0.0.1 up" )
+   def read( self, max ): return os.read( self.stdout.fileno(), max )
+   def write( self, data ): os.write( self.stdin.fileno(), data )
+   def terminate( self ): os.kill( self.pid, signal.SIGKILL )
+   def waitReadable( self ): self.pollOut.poll()
+   def sendCmd( self, cmd ):
+      """Send a command, followed by a command to echo a sentinel,
+         and return without waiting for the command to complete."""
+      assert not self.waiting
+      if cmd[ -1 ] == '&':
+         separator = '&'
+         cmd = cmd[ : -1 ]
+      else: separator = ';'
+      if isinstance( cmd, list): cmd = ' '.join( cmd )
+      self.write( cmd + separator + " echo -n '\\0177' \n")
+      self.waiting = True
+   def monitor( self ):
+      "Monitor a command's output, returning (done, data)."
+      assert self.waiting
+      self.waitReadable()
+      data = self.read( 1024 )
+      if len( data ) > 0 and data[ -1 ] == chr( 0177 ):
+         self.waiting = False
+         return True, data[ : -1 ]
+      else:
+         return False, data
+   def sendInt( self ):
+      "Send ^C, hopefully interrupting a running subprocess."
+      self.write( chr( 3 ) )
+   def waitOutput( self ):
+      """Wait for a command to complete (signaled by a sentinel
+      character, ASCII(127) appearing in the output stream) and return
+      the output, including trailing newline."""
+      assert self.waiting
+      output = ""
+      while True:
+         self.waitReadable()
+         data = self.read( 1024 )
+         if len(data) > 0  and data[ -1 ] == chr( 0177 ): 
+            output += data[ : -1 ]
+            break
+         else: output += data
+      self.waiting = False
+      return output
+   def cmd( self, cmd ):
+      "Send a command, wait for output, and return it."
+      self.sendCmd( cmd )
+      return self.waitOutput()
+   def cmdPrint( self, cmd ):
+      "Call cmd, printing the command and output"
+      print "***", self.name, ":", cmd
+      result = self.cmd( cmd )
+      print result,
+      return result
+   def intfName( self, n):
+      "Construct a canonical interface name node-intf for interface N."
+      return self.name + '-eth' + `n`
+   def newIntf( self ):
+      "Reserve and return a new interface name for this node."
+      intfName = self.intfName( self.intfCount)
+      self.intfCount += 1
+      self.intfs += [ intfName ]
+      return intfName
+   def setIP( self, intf, ip, bits ):
+      "Set an interface's IP address."
+      result = self.cmd( [ ifconfig, intf, ip + bits, 'up' ] )
+      self.ips[ intf ] = ip
+      return result
+   def setHostRoute( self, ip, intf ):
+      "Add a route to the given IP address via intf."
+      return self.cmd( 'route add -host ' + ip + ' dev ' + intf )
+   def setDefaultRoute( self, intf ):
+      "Set the default route to go through intf."
+      self.cmd( 'ip route flush' )
+      return self.cmd( 'route add default ' + intf )
+   def IP( self ):
+      "Return IP address of first interface"
+      return self.ips[ self.intfs[ 0 ] ]    
+   def __str__( self ): 
+      result = self.name
+      result += ": IP=" + self.IP() + " intfs=" + self.intfs
+      result += " waiting=", self.waiting
+      return result
+ 
+# Maintain mapping between i/o pipes and nodes
+# This could be useful for monitoring multiple nodes
+# using select.poll()
+
+inToNode = {}
+outToNode = {}
+def outputs(): return outToNode.keys()
+def nodes(): return outToNode.values()
+def inputs(): return [ node.stdin for node in nodes() ]
+def nodeFromFile( f ):
+   node = outToNode.get( f )
+   return node or inToNode.get( f )
+
+def createNodes( name, count ):
+   "Create and return a list of nodes."
+   nodes = [ Node( name + `i` ) for i in range( 0, count ) ]
+   # print "*** CreateNodes: created:", nodes
+   return nodes
+
+# Interface management
+# 
+# We connect nodes by creating a pair of veth interfaces,
+# and then placing them in the pair of nodes that we want
+# to communicate. Interfaces are named nodeN-ethM
+
+def makeIntfPair( intf1, intf2 ):
+   "Make a veth pair of intf1 and intf2"
+   # Delete any old interfaces with the same names
+   quietRun( 'ip link del ' + intf1 )
+   quietRun( 'ip link del ' + intf2 )
+   # Create new pair
+   cmd = 'ip link add name ' + intf1 + ' type veth peer name ' + intf2
+   return checkRun( cmd )
+   
+def moveIntf( intf, node ):
+   "Move intf to node"
+   cmd = 'ip link set ' + intf + ' netns ' + `node.pid`
+   checkRun( cmd )
+   links = node.cmd( 'ip link show' )
+   if not intf in links:
+      print "*** Error: moveIntf:", intf, "not successfully moved to",
+      print node.name,":"
+      exit( 1 )
+   return
+   
+def createLink( node1, node2 ):
+   "Create a link node1-intf1 <---> node2-intf2."
+   intf1 = node1.newIntf()
+   intf2 = node2.newIntf()
+   makeIntfPair( intf1, intf2 )
+   if node1.inNamespace: moveIntf( intf1, node1 )
+   if node2.inNamespace: moveIntf( intf2, node2 )
+   node1.connection[ intf1 ] = ( node2, intf2 )
+   node2.connection[ intf2 ] = ( node1, intf1 )
+   return intf1, intf2
+
+# Handy utilities
+
+def parsePing( pingOutput ):
+   "Parse ping output and return packets sent, received"
+   r = r'(\d+) packets transmitted, (\d+) received'
+   m = re.search( r, pingOutput )
+   if m == None:
+      print "*** Error: could not parse ping output:", pingOutput
+      exit( 1 )
+   sent, received  = int( m.group( 1 ) ), int( m.group( 2 ) )
+   return sent, received
+
+def pingTest( hosts, verbose=False ):
+   "Test that each host can reach every other host."
+   packets = 0 ; lost = 0
+   for node in hosts:
+      if verbose: 
+         print node.name, "->", ; flush()
+      for dest in hosts: 
+         if node != dest:
+            result = node.cmd( 'ping -c1 ' + dest.IP() )
+            sent, received = parsePing( result )
+            packets += sent
+            if received > sent:
+               print "*** Error: received too many packets"
+               print result
+               node.cmdPrint( 'route' )
+               exit( 1 )
+            lost += sent - received
+            if verbose: 
+               print ( dest.name if received else "X" ), ; flush()
+      if verbose: print
+   ploss = 100 * lost/packets
+   if verbose:
+      print "%d%% packet loss (%d/%d lost)" % ( ploss, lost, packets )
+      flush()
+   return ploss
+   
+def dumpNodes( nodes ):
+   "Dump ifconfig of each node."
+   for node in nodes:
+      print "*** Dumping node", node.name
+      print node.cmd( 'ip link show' )
+      print node.cmd( 'route' )
+
+def ipGen( A, B, c, d ):
+   "Generate next IP class B IP address, starting at A.B.c.d"
+   while True:
+      yield '%d.%d.%d.%d' % ( A, B, c, d )
+      d += 1
+      if d > 254:
+         d = 1
+         c += 1
+         if c > 254: break
+
+def nameGen( prefix ):
+   "Generate names starting with prefix."
+   i = 0
+   while True: 
+      yield prefix + `i`
+      i += 1
+
+# Control network support
+# Instead of routing, we could bridge or use "in-band" control
+
+def checkUp( node ):
+   "Make sure node's first interface is up."
+   return 'UP' in node.cmd( 'ifconfig ' + node.intfs[ 0 ] )
+   
+def configRoutedControlNetwork( controller, switches ):
+   "Configure a routed control network on controller and switches."
+   cip = '10.0.0.1'
+   sips = ipGen( 10, 123, 0, 1)
+   print controller.name, '<->',
+   for switch in switches:
+      print switch.name, ; flush()
+      sip = sips.next()
+      sintf = switch.intfs[ 0 ]
+      node, cintf = switch.connection[ sintf ]
+      assert node == controller
+      controller.setIP( cintf, cip,  '/24')
+      switch.setIP( sintf, sip, '/24' )
+      controller.setHostRoute( sip, cintf )
+      switch.setHostRoute( cip, sintf )
+   print
+   print "*** Testing control network"
+   while not checkUp( controller ):
+      print "*** Waiting for ", controller.intfs[ 0 ], "to come up"
+      sleep( 1 )
+   for switch in switches:
+      while not checkUp( switch ):
+         print "*** Waiting for ", controller.intfs[ 0 ], "to come up"
+         sleep( 1 )
+      if pingTest( [ switch, controller ] ) != 0:
+         print "*** Error: control network test failed"
+      else:
+         return
+      exit( 1 )
+
+def configHosts( hosts, ( a, b, c, d ) ):
+   "Configure a set of hosts, starting at IP address a.b.c.d"
+   ips = ipGen( a, b, c, d )
+   for host in hosts:
+      hintf = host.intfs[ 0 ]
+      host.setIP( hintf, ips.next(), '/24' )
+      host.setDefaultRoute( hintf )
+      # You're low priority, dude!
+      quietRun( 'renice +18 -p ' + `host.pid` )
+      print host.name, ; flush()
+   print
+
+def startController( controller, cprog='controller', cargs='ptcp:' ):
+   "Start <cprog cargs> on controller, logging to /tmp/cN.log"
+   cout = '/tmp/' + controller.name + '.log'
+   controller.cmdPrint( cprog + ' ' + cargs + 
+      ' 1> ' + cout + ' 2> ' + cout + ' &' )
+
+def stopController( controller, cprog='controller' ):
+   "Stop controller cprog on controller"
+   controller.cmd( "kill %" + cprog )
+   
+def startOpenFlowU( switch, controller ):
+   """Start OpenFlow reference user datapath on a switch, 
+      logging to /tmp/sN-{ofd,ofp}.log"""
+   ofdlog = '/tmp/' + switch.name + '-ofd.log'
+   ofplog = '/tmp/' + switch.name + '-ofp.log'
+   switch.cmd( 'ifconfig lo up' )
+   intfs = switch.intfs[ 1 : ] # 0 is mgmt interface
+   switch.cmdPrint( 'ofdatapath -i ' + ','.join( intfs ) +
+    ' ptcp: 1> ' + ofdlog + ' 2> '+ ofdlog + ' &' )
+   switch.cmdPrint( 'ofprotocol tcp:' + controller.IP() +
+      ' tcp:localhost 1> ' + ofplog + ' 2>' + ofplog + '&' )
+
+def stopOpenFlowU( switch ):
+   "Stop OpenFlow reference user datapath on a switch."
+   switch.cmd( "kill %ofdatapath" )
+   switch.cmd( "kill %ofprotocol" )   
+
+def dpgen():
+   "Generator for OpenFlow kernel datapath names."
+   dpCount = 0
+   while True:
+      yield 'nl:' + `dpCount`
+      dpCount += 1
+
+def startOpenFlowK( switch, dp, controller):
+   "Start up a switch connected to an OpenFlow reference kernel datapath."
+   ofplog = '/tmp/' + switch.name + '-ofp.log'
+   switch.cmd( 'ifconfig lo up' )
+   # Delete local datapath if it exists;
+   # then create a new one monitoring the given interfaces
+   quietRun( 'dpctl deldp ' + dp )
+   switch.cmdPrint( 'dpctl adddp ' + dp )
+   switch.cmdPrint( 'dpctl addif ' + dp + ' ' + ' '.join( switch.intfs ) )
+   switch.dp = dp
+   # Become protocol daemon
+   switch.cmdPrint( 'exec ofprotocol' +
+      ' ' + dp + ' tcp:127.0.0.1 1> ' + ofplog + ' 2>' + ofplog + '&' )
+
+def stopOpenFlowK( switch ):
+   "Terminate a switch using OpenFlow reference kernel datapath."
+   quietRun( 'dpctl deldp ' + switch.dp )
+   for intf in switch.intfs: quietRun( 'ip link del ' + intf )
+   switch.terminate()
+
+def stopOpenFlow( switch ):
+   if hasattr(switch, 'dp' ): stopOpenFlowK( switch )
+   else: stopOpenFlowU( switch )
+
+# Test scenarios and topologies
+
+def treeNet( controller, depth, fanout, snames=nameGen( 's' ), 
+   hnames=nameGen( 'h' ), kernel=True ):
+   """Return a tree network of the given depth and fanout as a triple:
+      ( root, switches, hosts ), using the given switch and host
+      name generators, with the switches connected to the given
+      controller."""
+   if ( depth == 0 ):
+      host = Node( hnames.next() )
+      print host.name, ; flush()
+      return host, [], [ host ]
+   switch = Node( snames.next(), inNamespace=(not kernel) )
+   if not kernel: createLink( switch, controller )
+   print switch.name, ; flush()
+   switches, hosts = [ switch ], []
+   for i in range( 0, fanout ):
+      child, slist, hlist = treeNet( 
+         controller, depth - 1, fanout, snames, hnames, kernel )
+      createLink( switch, child )
+      switches += slist
+      hosts += hlist
+   return switch, switches, hosts
+
+def treeNetTest( depth, fanout, test, kernel=True ):
+   """Create a tree network of the given depth and fanout, and
+      run test( controller, root, switches, hosts ) on it."""
+   if kernel: print "*** Using kernel datapath"
+   else: print "*** Using user datapath"
+   print "*** Creating controller"
+   controller = Node( 'c0', inNamespace=( not kernel ) )
+   print "*** Creating tree network depth:", depth, "fanout:", fanout
+   root, switches, hosts = treeNet( controller, depth, fanout, kernel=kernel )
+   print
+   if not kernel:
+      print "*** Configuring control network"
+      configRoutedControlNetwork( controller, switches )
+   else: dp = dpgen()
+   print "*** Configuring hosts"
+   configHosts( hosts, ( 192, 168, 123, 1 ) )
+   print "*** Starting reference controller"
+   startController( controller )
+   print "*** Starting switches"
+   for switch in switches:
+      if kernel: startOpenFlowK( switch, dp.next(), controller )
+      else: startOpenFlowU( switch, controller )
+   print "*** Running test"
+   test( controller, root, switches, hosts )
+   print "*** Stopping controller"
+   stopController( controller )
+   print "*** Stopping switches"
+   for switch in switches:
+      stopOpenFlow( switch )
+
+def treePingTest( depth, fanout, kernel=True ):
+   "Run a ping test on a tree network with the given depth and fanout."
+   test = lambda c, r, s, hosts : pingTest( hosts, verbose=True )
+   treeNetTest( depth, fanout, test, kernel)
+   
+def iperf( hosts ):
+   "Run iperf between two hosts."
+   assert len( hosts ) == 2
+   host1, host2 = hosts[ 0 ], hosts[ 1 ]
+   dumpNodes( [ host1, host2 ] )
+   host1.cmdPrint( 'killall -9 iperf')
+   host1.cmdPrint( 'iperf -s &' )
+   host2.cmdPrint( 'iperf -t 5 -c ' + host1.IP() )
+   host1.cmdPrint( 'kill -9 %iperf' )
+ 
+def iperfTest( depth=1, fanout=2, kernel=True ):
+   "Simple iperf test between two hosts."
+   def test( c, r, s, hosts ):
+      h0, hN = hosts[ 0 ], hosts[ -1 ]
+      print "*** iperfTest: Testing bandwidth between", 
+      print h0.name, "and", hN.name
+      return iperf( [ h0, hN] )
+   treeNetTest( depth, fanout, test, kernel )
+   
+def fixLimits():
+   "Fix ridiculously small resource limits."
+   setrlimit( RLIMIT_NPROC, ( 4096, 8192 ) )
+   setrlimit( RLIMIT_NOFILE, ( 16384, 32768 ) )
+
+# Simple CLI
+
+def cliHelp( nodemap, c, s, h, args  ):
+   "Semi-useful help for CLI"
+   print "available commands are:", cliCmds.keys()
+
+def cliNodes( nodemap, c, s, h, args ):
+   "List available nodes"
+   print "available nodes are:", nodemap.keys()
+      
+def cliSh( nodemap, c, s, h, args ):
+   "Run an external shell command"
+   call( [ bash, '-c', args ] )
+
+def cliPingTest( map, c, s, hosts, args ):
+   pingTest( hosts, verbose=True )
+
+def cliNet( map, c, switches, h, args ):
+   for switch in switches:
+      print switch.name, "<->",
+      for intf in switch.intfs:
+         node, rintf = switch.connection[ intf ]
+         print node.name,
+      print
+
+def cliIperf( map, c, switches, h, args ):
+   print "iperf: got args", args
+   if len( args ) != 2:
+      print "usage: iperf <h1> <h2>"
+      return
+   for host in args:
+      if host not in map:
+         print "iperf: cannot find host:", host
+         return
+   iperf( [ map[ h ] for h in args ] )
+
+cliCmds = { '?': cliHelp, 'help': cliHelp, 'net': cliNet, 'nodes': cliNodes, 
+         'pingtest': cliPingTest, 'iperf': cliIperf, 'sh': cliSh, 
+         'exit': None }
+
+def cli( controllers, switches, hosts ):
+   "Simple command-line interface to talk to nodes."
+   print "*** cli: starting"
+   nodemap = {}
+   nodes = controllers + switches + hosts
+   for node in nodes:
+      nodemap[ node.name ] = node
+   while True:
+      print "mininet> ", ; flush()
+      input = sys.stdin.readline()
+      if input == '': break
+      if input[ -1 ] == '\n': input = input[ : -1 ]
+      cmd = input.split( ' ' )
+      first = cmd[ 0 ]
+      rest = cmd[ 1: ]
+      if first in cliCmds: cliCmds[ first ]( 
+         nodemap, controllers, switches, hosts, rest )
+      elif first in nodemap and rest != []:
+         node = nodemap[ first ]
+         # Substitute IP addresses for node names in command
+         rest = [ nodemap[ arg ].IP() if arg in nodemap else arg
+            for arg in rest ]
+         rest = ' '.join( rest )
+         # Interactive commands don't work yet, and
+         # there are still issues with control-c
+         print "***", node.name, ": running", rest
+         node.sendCmd( rest )
+         while True:
+            try:
+               done, data = node.monitor()
+               print data,
+               if done: break
+            except KeyboardInterrupt: node.sendInt()
+         print
+      elif first == '': pass
+      elif first in [ 'exit', 'quit' ]: break
+      else: print "cli: unknown node or command: <", first, ">"
+   print "*** cli: exiting"
+      
+def treeInteract( depth, fanout, kernel=True ):
+   "Create a tree network and start the CLI."
+   interact = lambda c, r, s, h : cli( [ c ], s, h )
+   treeNetTest( depth, fanout, interact, kernel )
+   
+if __name__ == '__main__':
+   fixLimits()
+   # for kernel in [ False, True ]:
+   #   treePingTest( depth=3, fanout=4, kernel=kernel )
+   # treeInteract( depth=1, fanout=2, kernel=False )
+   #  iperfTest( depth=1, fanout=2, kernel=kernel )
+   treeInteract( depth=1, fanout=2, kernel=False )

netns.c

@@ -0,0 +1,24 @@
+/* netns: run a command in a network namespace.
+ * Simplified from netunshare.c on lxc.sf.net
+*/
+
+#include <stdio.h>
+#include <sched.h>
+#include <unistd.h>
+
+int main(int argc, char *argv[])
+{	
+	if (unshare(CLONE_NEWNET) == -1) {
+		perror("unshare");
+		return 1;
+	} 
+	
+	if (argc) {
+		execve(argv[1], &argv[1], __environ);
+		perror("execve");
+		return 1;
+	}
+
+	return 0;
+}
+