#!/usr/bin/python

"""
Create a network and start sshd(8) on each host.

While something like rshd(8) would be lighter and faster,
(and perfectly adequate on an in-machine network)
the advantage of running sshd is that scripts can work
unchanged on mininet and hardware.

In addition to providing ssh access to hosts, this example
demonstrates:

- creating a convenience function to construct networks
- connecting the host network to the root namespace
- running server processes (sshd in this case) on hosts
"""

from __future__ import print_function
import sys

from mininet.net import Mininet
from mininet.cli import CLI
from mininet.log import lg
from mininet.node import Node
from mininet.topolib import TreeTopo
from mininet.util import waitListening


def TreeNet( depth=1, fanout=2, **kwargs ):
    "Convenience function for creating tree networks."
    topo = TreeTopo( depth, fanout )
    return Mininet( topo, **kwargs )

def connectToRootNS( network, switch, ip, routes ):
    """Connect hosts to root namespace via switch. Starts network.
      network: Mininet() network object
      switch: switch to connect to root namespace
      ip: IP address for root namespace node
      routes: host networks to route to"""
    # Create a node in root namespace and link to switch 0
    root = Node( 'root', inNamespace=False )
    intf = network.addLink( root, switch ).intf1
    root.setIP( ip, intf=intf )
    # Start network that now includes link to root namespace
    network.start()
    # Add routes from root ns to hosts
    for route in routes:
        root.cmd( 'route add -net ' + route + ' dev ' + str( intf ) )

def sshd( network, cmd='/usr/sbin/sshd', opts='-D',
          ip='10.123.123.1/32', routes=None, switch=None ):
    """Start a network, connect it to root ns, and run sshd on all hosts.
       ip: root-eth0 IP address in root namespace (10.123.123.1/32)
       routes: Mininet host networks to route to (10.0/24)
       switch: Mininet switch to connect to root namespace (s1)"""
    if not switch:
        switch = network[ 's1' ]  # switch to use
    if not routes:
        routes = [ '10.0.0.0/24' ]
    connectToRootNS( network, switch, ip, routes )
    for host in network.hosts:
        host.cmd( cmd + ' ' + opts + '&' )
    print( "*** Waiting for ssh daemons to start" )
    for server in network.hosts:
        waitListening( server=server, port=22, timeout=5 )

    print()
    print( "*** Hosts are running sshd at the following addresses:" )
    print()
    for host in network.hosts:
        print( host.name, host.IP() )
    print()
    print( "*** Type 'exit' or control-D to shut down network" )
    CLI( network )
    for host in network.hosts:
        host.cmd( 'kill %' + cmd )
    network.stop()

if __name__ == '__main__':
    lg.setLogLevel( 'info')
    net = TreeNet( depth=1, fanout=4 )
    # get sshd args from the command line or use default args
    # useDNS=no -u0 to avoid reverse DNS lookup timeout
    argvopts = ' '.join( sys.argv[ 1: ] ) if len( sys.argv ) > 1 else (
        '-D -o UseDNS=no -u0' )
    sshd( net, opts=argvopts )