whenever my intarwebs fail, I debug my connection with this old, dirty hack of a python script

debug_net.py

#!/usr/bin/env python

import subprocess


def get_default_gw():
    ''' returns ip address of default gateway as a string'''
    res = subprocess.check_output(['route','-n'])
    for line in res.split('\n'):
        if line.startswith('0.0.0.0'):
            return line.split()[1]
    

def get_ip_local(with_scope=False):
    """ returns ip address as a string,
        skips adresses that starts with 127
        suffixes with /xx if with_scope=True
        """
    res = subprocess.check_output(['ip','-o','addr'])
    for line in res.split('\n'):
        if 'inet ' in line:
            addrwithscope = line.split()[3]
            if addrwithscope.startswith('127'): continue
            if with_scope:
                return addrwithscope
            else:
                return addrwithscope.split('/')[0]

def ping_ip(ip):
    try: 
        ping_res = subprocess.check_output(['ping', '-c1', '-q', get_default_gw()])
        return True
    except subprocess.CalledProcessError, e:
        return False

def host_lookup(s):
    try: 
        host_res = subprocess.check_output(['host', s])
        return True
    except subprocess.CalledProcessError, e:
        return False

def check_tcp():
    '''
    no param handling in check_output, but static address
    -> shell=True is dangerous!!
    '''
    try: 
        nc_res = subprocess.check_call('echo|nc -v example.org 80', shell=True)
        return True
    except subprocess.CalledProcessError, e:
        return False
    
    
def check_for_output(s):
    if s: return s
    else:
        return "ERROR"

if __name__ == '__main__':
    import sys
    print "** Gathering Local Information"
    print "\tLocal IP Address", check_for_output(get_ip_local())
    print "\tDefault Gateway", check_for_output(get_default_gw()),
    if ping_ip(get_default_gw()):
        print '- pings :)'
    else:
        print '- no ping response :('
        sys.exit(1)
    print "\tDNS:",
    if host_lookup('193.0.0.193'):
        print "Works :)"
    else:
        print "Failed :("
    print '** Trying to reach the net'
    print "\tPinging Nameserver (RIPE):",
    if ping_ip("193.0.0.193"):
        print 'Works! :)'
    else:
        print "Unreachable :("
    print '\tConnecting to example.org:',
    if check_tcp():
        print "Works. :)"
    else:
        print "Failed :("

requires the following executables: route, ip, ping, host, nc