Give network interface to namespace, run shell, cleanup after exit

pppns.py

#! /usr/bin/python3

''' pppns - set ip netns for ppp0 '''
import os
import pwd
import sys
import optparse

r={
    'ip': 'sudo ip',
    'device': 'ppp0',
    'namespace': 'nsppp0',
    'username': pwd.getpwuid(os.getuid()).pw_name,
    'getpid': os.getpid(),
}

def docmd(cmd):
    sys.stderr.write('# '+cmd+'\n')
    sys.stderr.flush()
    return os.system(cmd)

def netns_setup(r):
    inet=[]
    docmd('sudo echo "device %(device)s netns %(namespace)s"' %r)
    cmd='%(ip)s addr ls dev %(device)s' % r
    fd=os.popen(cmd,'r')
    for line in fd:
        bits=line.strip().split()
        if len(bits)<2: continue
        if bits[0]=='inet' or bits[0]=='inet6':
            inet.append(bits[1])

    routes=[]
    for cmd in ( '%(ip)s route ls' % r , '%(ip)s -6 route ls' % r ):
        fd=os.popen(cmd,'r')
        for line in fd:
            if line.find('dev %(device)s' % r)>=0:
                i=line.find(' expires ')
                if i>0: line=line[:i]
                routes.append(line)

    # Make namespace
    docmd ( '%(ip)s netns add %(namespace)s' % r )

    # Add the link to the namespace
    docmd( '%(ip)s link set %(device)s netns %(namespace)s' % r )

    # Bring it up 
    docmd( '%(ip)s netns exec %(namespace)s ip link set dev %(device)s up' % r  )

    # Configure the link
    for ipaddress in inet:
        r['ipaddress']=ipaddress
        docmd( '%(ip)s netns exec %(namespace)s ip addr add dev %(device)s %(ipaddress)s' % r )

    # Add the routes
    for route in routes:
        r['route']=route
        docmd ( '%(ip)s netns exec %(namespace)s ip route add %(route)s' % r )
    docmd ( '%(ip)s netns exec %(namespace)s ip route add default dev %(device)s' % r )
    docmd ( '%(ip)s netns exec %(namespace)s ip -6 route add default dev %(device)s' % r )

    docmd ('%(ip)s netns exec %(namespace)s sudo -u %(username)s -s' % r)

    # CLEANUP
    docmd ( '%(ip)s netns exec %(namespace)s ip link set %(device)s netns %(getpid)s' % r )
    docmd( '%(ip)s link set dev %(device)s up' % r  )
    for ipaddress in inet:
        r['ipaddress']=ipaddress
        docmd( '%(ip)s addr add dev %(device)s %(ipaddress)s' % r )
    for route in routes:
        r['route']=route
        docmd ( '%(ip)s route add %(route)s' % r )
    docmd( '%(ip)s netns del %(namespace)s' % r )
    docmd('echo Done')

if __name__=="__main__":
    import optparse
    usage="Usage: %prog [interface] [cmd]\n"+__doc__+"\n"
    parser=optparse.OptionParser(usage)
    parser.add_option("-d","--debug",dest="debug", action="count", default=0, help="DEBUG level")
    parser.add_option("-n","--netns",dest="netns", action="store", default='', help="net namespace")
    (options,args) = parser.parse_args()
    cmd=[]
    device='ppp0'
    if len(args)>0: device=args[0]
    if len(args)>1: cmd=args[1:]
    r['device']=device
    namespace=options.netns
    if namespace=='': namespace='ns_'+device
    r['namespace']=namespace
    r['device']=device
    netns_setup(r)