# Copyright 2012-2019, Damian Johnson and The Tor Project
# See LICENSE for licensing information
"""
Connection and networking based utility functions.
**Module Overview:**
::
download - download from a given url
get_connections - quieries the connections belonging to a given process
system_resolvers - provides connection resolution methods that are likely to be available
port_usage - brief description of the common usage for a port
is_valid_ipv4_address - checks if a string is a valid IPv4 address
is_valid_ipv6_address - checks if a string is a valid IPv6 address
is_valid_port - checks if something is a valid representation for a port
is_private_address - checks if an IPv4 address belongs to a private range or not
address_to_int - provides an integer representation of an IP address
expand_ipv6_address - provides an IPv6 address with its collapsed portions expanded
get_mask_ipv4 - provides the mask representation for a given number of bits
get_mask_ipv6 - provides the IPv6 mask representation for a given number of bits
.. data:: Resolver (enum)
Method for resolving a process' connections.
.. versionadded:: 1.1.0
.. versionchanged:: 1.4.0
Added **NETSTAT_WINDOWS**.
.. versionchanged:: 1.6.0
Added **BSD_FSTAT**.
.. deprecated:: 1.6.0
The SOCKSTAT connection resolver is proving to be unreliable
(:trac:`23057`), and will be dropped in the 2.0.0 release unless fixed.
==================== ===========
Resolver Description
==================== ===========
**PROC** /proc contents
**NETSTAT** netstat
**NETSTAT_WINDOWS** netstat command under Windows
**SS** ss command
**LSOF** lsof command
**SOCKSTAT** sockstat command under \\*nix
**BSD_SOCKSTAT** sockstat command under FreeBSD
**BSD_PROCSTAT** procstat command under FreeBSD
**BSD_FSTAT** fstat command under OpenBSD
==================== ===========
"""
import collections
import os
import platform
import re
import socket
import sys
import time
import stem
import stem.util
import stem.util.proc
import stem.util.system
from stem.util import conf, enum, log, str_tools
try:
# account for urllib's change between python 2.x and 3.x
import urllib.request as urllib
except ImportError:
import urllib2 as urllib
# Connection resolution is risky to log about since it's highly likely to
# contain sensitive information. That said, it's also difficult to get right in
# a platform independent fashion. To opt into the logging requried to
# troubleshoot connection resolution set the following...
LOG_CONNECTION_RESOLUTION = False
Resolver = enum.Enum(
('PROC', 'proc'),
('NETSTAT', 'netstat'),
('NETSTAT_WINDOWS', 'netstat (windows)'),
('SS', 'ss'),
('LSOF', 'lsof'),
('SOCKSTAT', 'sockstat'),
('BSD_SOCKSTAT', 'sockstat (bsd)'),
('BSD_PROCSTAT', 'procstat (bsd)'),
('BSD_FSTAT', 'fstat (bsd)')
)
FULL_IPv4_MASK = '255.255.255.255'
FULL_IPv6_MASK = 'FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF'
PORT_USES = None # port number => description
RESOLVER_COMMAND = {
Resolver.PROC: '',
# -n = prevents dns lookups, -p = include process, -W = don't crop addresses (needed for ipv6)
Resolver.NETSTAT: 'netstat -npW',
# -a = show all TCP/UDP connections, -n = numeric addresses and ports, -o = include pid
Resolver.NETSTAT_WINDOWS: 'netstat -ano',
# -n = numeric ports, -p = include process, -t = tcp sockets, -u = udp sockets
Resolver.SS: 'ss -nptu',
# -n = prevent dns lookups, -P = show port numbers (not names), -i = ip only, -w = no warnings
# (lsof provides a '-p <pid>' but oddly in practice it seems to be ~11-28% slower)
Resolver.LSOF: 'lsof -wnPi',
Resolver.SOCKSTAT: 'sockstat',
# -4 = IPv4, -c = connected sockets
Resolver.BSD_SOCKSTAT: 'sockstat -4c',
# -f <pid> = process pid
Resolver.BSD_PROCSTAT: 'procstat -f {pid}',
# -p <pid> = process pid
Resolver.BSD_FSTAT: 'fstat -p {pid}',
}
RESOLVER_FILTER = {
Resolver.PROC: '',
# tcp 0 586 192.168.0.1:44284 38.229.79.2:443 ESTABLISHED 15843/tor
Resolver.NETSTAT: '^{protocol}\\s+.*\\s+{local}\\s+{remote}\\s+ESTABLISHED\\s+{pid}/{name}\\s*$',
# tcp 586 192.168.0.1:44284 38.229.79.2:443 ESTABLISHED 15843
Resolver.NETSTAT_WINDOWS: '^\\s*{protocol}\\s+{local}\\s+{remote}\\s+ESTABLISHED\\s+{pid}\\s*$',
# tcp ESTAB 0 0 192.168.0.20:44415 38.229.79.2:443 users:(("tor",15843,9))
Resolver.SS: '^{protocol}\\s+ESTAB\\s+.*\\s+{local}\\s+{remote}\\s+users:\\(\\("{name}",(?:pid=)?{pid},(?:fd=)?[0-9]+\\)\\)$',
# tor 3873 atagar 45u IPv4 40994 0t0 TCP 10.243.55.20:45724->194.154.227.109:9001 (ESTABLISHED)
Resolver.LSOF: '^{name}\\s+{pid}\\s+.*\\s+{protocol}\\s+{local}->{remote} \\(ESTABLISHED\\)$',
# atagar tor 15843 tcp4 192.168.0.20:44092 68.169.35.102:443 ESTABLISHED
Resolver.SOCKSTAT: '^\\S+\\s+{name}\\s+{pid}\\s+{protocol}4\\s+{local}\\s+{remote}\\s+ESTABLISHED$',
# _tor tor 4397 12 tcp4 172.27.72.202:54011 127.0.0.1:9001
Resolver.BSD_SOCKSTAT: '^\\S+\\s+{name}\\s+{pid}\\s+\\S+\\s+{protocol}4\\s+{local}\\s+{remote}$',
# 3561 tor 4 s - rw---n-- 2 0 TCP 10.0.0.2:9050 10.0.0.1:22370
Resolver.BSD_PROCSTAT: '^\\s*{pid}\\s+{name}\\s+.*\\s+{protocol}\\s+{local}\\s+{remote}$',
# _tor tor 15843 20* internet stream tcp 0x0 192.168.1.100:36174 --> 4.3.2.1:443
Resolver.BSD_FSTAT: '^\\S+\\s+{name}\\s+{pid}\\s+.*\\s+{protocol}\\s+\\S+\\s+{local}\\s+[-<]-[->]\\s+{remote}$',
}
[docs]class Connection(collections.namedtuple('Connection', ['local_address', 'local_port', 'remote_address', 'remote_port', 'protocol', 'is_ipv6'])):
"""
Network connection information.
.. versionchanged:: 1.5.0
Added the **is_ipv6** attribute.
:var str local_address: ip address the connection originates from
:var int local_port: port the connection originates from
:var str remote_address: destionation ip address
:var int remote_port: destination port
:var str protocol: protocol of the connection ('tcp', 'udp', etc)
:var bool is_ipv6: addresses are ipv6 if true, and ipv4 otherwise
"""
[docs]def download(url, timeout = None, retries = None):
"""
Download from the given url.
.. versionadded:: 1.8.0
:param str url: uncompressed url to download from
:param int timeout: timeout when connection becomes idle, no timeout applied
if **None**
:param int retires: maximum attempts to impose
:returns: **bytes** content of the given url
:raises:
* :class:`~stem.DownloadTimeout` if our request timed out
* :class:`~stem.DownloadFailed` if our request fails
"""
if retries is None:
retries = 0
start_time = time.time()
try:
return urllib.urlopen(url, timeout = timeout).read()
except socket.timeout as exc:
raise stem.DownloadTimeout(url, exc, sys.exc_info()[2], timeout)
except:
exc, stacktrace = sys.exc_info()[1:3]
if timeout is not None:
timeout -= time.time() - start_time
if retries > 0 and (timeout is None or timeout > 0):
log.debug('Failed to download from %s (%i retries remaining): %s' % (url, retries, exc))
return download(url, timeout, retries - 1)
else:
log.debug('Failed to download from %s: %s' % (url, exc))
raise stem.DownloadFailed(url, exc, stacktrace)
[docs]def get_connections(resolver = None, process_pid = None, process_name = None):
"""
Retrieves a list of the current connections for a given process. This
provides a list of :class:`~stem.util.connection.Connection`. Note that
addresses may be IPv4 *or* IPv6 depending on what the platform supports.
.. versionadded:: 1.1.0
.. versionchanged:: 1.5.0
Made our resolver argument optional.
.. versionchanged:: 1.5.0
IPv6 support when resolving via proc, netstat, lsof, or ss.
:param Resolver resolver: method of connection resolution to use, if not
provided then one is picked from among those that should likely be
available for the system
:param int process_pid: pid of the process to retrieve
:param str process_name: name of the process to retrieve
:returns: **list** of :class:`~stem.util.connection.Connection` instances
:raises:
* **ValueError** if neither a process_pid nor process_name is provided
* **IOError** if no connections are available or resolution fails
(generally they're indistinguishable). The common causes are the
command being unavailable or permissions.
"""
if not resolver:
available_resolvers = system_resolvers()
if available_resolvers:
resolver = available_resolvers[0]
else:
raise IOError('Unable to determine a connection resolver')
if not process_pid and not process_name:
raise ValueError('You must provide a pid or process name to provide connections for')
def _log(msg):
if LOG_CONNECTION_RESOLUTION:
log.debug(msg)
_log('=' * 80)
_log('Querying connections for resolver: %s, pid: %s, name: %s' % (resolver, process_pid, process_name))
if isinstance(process_pid, str):
try:
process_pid = int(process_pid)
except ValueError:
raise ValueError('Process pid was non-numeric: %s' % process_pid)
if process_pid is None:
all_pids = stem.util.system.pid_by_name(process_name, True)
if len(all_pids) == 0:
if resolver in (Resolver.NETSTAT_WINDOWS, Resolver.PROC, Resolver.BSD_PROCSTAT):
raise IOError("Unable to determine the pid of '%s'. %s requires the pid to provide the connections." % (process_name, resolver))
elif len(all_pids) == 1:
process_pid = all_pids[0]
else:
if resolver in (Resolver.NETSTAT_WINDOWS, Resolver.PROC, Resolver.BSD_PROCSTAT):
raise IOError("There's multiple processes named '%s'. %s requires a single pid to provide the connections." % (process_name, resolver))
if resolver == Resolver.PROC:
return stem.util.proc.connections(pid = process_pid)
resolver_command = RESOLVER_COMMAND[resolver].format(pid = process_pid)
try:
results = stem.util.system.call(resolver_command)
except OSError as exc:
raise IOError("Unable to query '%s': %s" % (resolver_command, exc))
resolver_regex_str = RESOLVER_FILTER[resolver].format(
protocol = '(?P<protocol>\\S+)',
local = '(?P<local>[\\[\\]0-9a-f.:]+)',
remote = '(?P<remote>[\\[\\]0-9a-f.:]+)',
pid = process_pid if process_pid else '[0-9]*',
name = process_name if process_name else '\\S*',
)
_log('Resolver regex: %s' % resolver_regex_str)
_log('Resolver results:\n%s' % '\n'.join(results))
connections = []
resolver_regex = re.compile(resolver_regex_str)
def _parse_address_str(addr_type, addr_str, line):
addr, port = addr_str.rsplit(':', 1)
if not is_valid_ipv4_address(addr) and not is_valid_ipv6_address(addr, allow_brackets = True):
_log('Invalid %s address (%s): %s' % (addr_type, addr, line))
return None, None
elif not is_valid_port(port):
_log('Invalid %s port (%s): %s' % (addr_type, port, line))
return None, None
else:
_log('Valid %s:%s: %s' % (addr, port, line))
return addr.lstrip('[').rstrip(']'), int(port)
for line in results:
match = resolver_regex.match(line)
if match:
attr = match.groupdict()
local_addr, local_port = _parse_address_str('local', attr['local'], line)
remote_addr, remote_port = _parse_address_str('remote', attr['remote'], line)
if not (local_addr and local_port and remote_addr and remote_port):
continue # missing or malformed field
protocol = attr['protocol'].lower()
if protocol == 'tcp6':
protocol = 'tcp'
if protocol not in ('tcp', 'udp'):
_log('Unrecognized protocol (%s): %s' % (protocol, line))
continue
conn = Connection(local_addr, local_port, remote_addr, remote_port, protocol, is_valid_ipv6_address(local_addr))
connections.append(conn)
_log(str(conn))
_log('%i connections found' % len(connections))
if not connections:
raise IOError('No results found using: %s' % resolver_command)
return connections
[docs]def system_resolvers(system = None):
"""
Provides the types of connection resolvers likely to be available on this platform.
.. versionadded:: 1.1.0
.. versionchanged:: 1.3.0
Renamed from get_system_resolvers() to system_resolvers(). The old name
still works as an alias, but will be dropped in Stem version 2.0.0.
:param str system: system to get resolvers for, this is determined by
platform.system() if not provided
:returns: **list** of :data:`~stem.util.connection.Resolver` instances available on this platform
"""
if system is None:
if stem.util.system.is_gentoo():
system = 'Gentoo'
else:
system = platform.system()
if system == 'Windows':
resolvers = [Resolver.NETSTAT_WINDOWS]
elif system == 'Darwin':
resolvers = [Resolver.LSOF]
elif system == 'OpenBSD':
resolvers = [Resolver.BSD_FSTAT]
elif system == 'FreeBSD':
# Netstat is available, but lacks a '-p' equivalent so we can't associate
# the results to processes. The platform also has a ss command, but it
# belongs to a spreadsheet application.
resolvers = [Resolver.BSD_SOCKSTAT, Resolver.BSD_PROCSTAT, Resolver.LSOF]
else:
# Sockstat isn't available by default on ubuntu.
resolvers = [Resolver.NETSTAT, Resolver.SOCKSTAT, Resolver.LSOF, Resolver.SS]
# remove any that aren't in the user's PATH
resolvers = [r for r in resolvers if stem.util.system.is_available(RESOLVER_COMMAND[r])]
# proc resolution, by far, outperforms the others so defaults to this is able
if stem.util.proc.is_available() and os.access('/proc/net/tcp', os.R_OK) and os.access('/proc/net/udp', os.R_OK):
resolvers = [Resolver.PROC] + resolvers
return resolvers
[docs]def port_usage(port):
"""
Provides the common use of a given port. For example, 'HTTP' for port 80 or
'SSH' for 22.
.. versionadded:: 1.2.0
:param int port: port number to look up
:returns: **str** with a description for the port, **None** if none is known
"""
global PORT_USES
if PORT_USES is None:
config = conf.Config()
config_path = os.path.join(os.path.dirname(__file__), 'ports.cfg')
try:
config.load(config_path)
port_uses = {}
for key, value in config.get('port', {}).items():
if key.isdigit():
port_uses[int(key)] = value
elif '-' in key:
min_port, max_port = key.split('-', 1)
for port_entry in range(int(min_port), int(max_port) + 1):
port_uses[port_entry] = value
else:
raise ValueError("'%s' is an invalid key" % key)
PORT_USES = port_uses
except Exception as exc:
log.warn("BUG: stem failed to load its internal port descriptions from '%s': %s" % (config_path, exc))
if not PORT_USES:
return None
if isinstance(port, str) and port.isdigit():
port = int(port)
return PORT_USES.get(port)
[docs]def is_valid_ipv4_address(address):
"""
Checks if a string is a valid IPv4 address.
:param str address: string to be checked
:returns: **True** if input is a valid IPv4 address, **False** otherwise
"""
if isinstance(address, bytes):
address = str_tools._to_unicode(address)
elif not stem.util._is_str(address):
return False
# checks if theres four period separated values
if address.count('.') != 3:
return False
# checks that each value in the octet are decimal values between 0-255
for entry in address.split('.'):
if not entry.isdigit() or int(entry) < 0 or int(entry) > 255:
return False
elif entry[0] == '0' and len(entry) > 1:
return False # leading zeros, for instance in '1.2.3.001'
return True
[docs]def is_valid_ipv6_address(address, allow_brackets = False):
"""
Checks if a string is a valid IPv6 address.
:param str address: string to be checked
:param bool allow_brackets: ignore brackets which form '[address]'
:returns: **True** if input is a valid IPv6 address, **False** otherwise
"""
if isinstance(address, bytes):
address = str_tools._to_unicode(address)
elif not stem.util._is_str(address):
return False
if allow_brackets:
if address.startswith('[') and address.endswith(']'):
address = address[1:-1]
if address.count('.') == 3:
# Likely an ipv4-mapped portion. Check that its vaild, then replace with a
# filler.
ipv4_start = address.rfind(':', 0, address.find('.')) + 1
ipv4_end = address.find(':', ipv4_start + 1)
if ipv4_end == -1:
ipv4_end = None # don't crop the last character
if not is_valid_ipv4_address(address[ipv4_start:ipv4_end]):
return False
addr_comp = [address[:ipv4_start - 1] if ipv4_start != 0 else None, 'ff:ff', address[ipv4_end + 1:] if ipv4_end else None]
address = ':'.join(filter(None, addr_comp))
# addresses are made up of eight colon separated groups of four hex digits
# with leading zeros being optional
# https://en.wikipedia.org/wiki/IPv6#Address_format
colon_count = address.count(':')
if colon_count > 7:
return False # too many groups
elif colon_count != 7 and '::' not in address:
return False # not enough groups and none are collapsed
elif address.count('::') > 1 or ':::' in address:
return False # multiple groupings of zeros can't be collapsed
for entry in address.split(':'):
if not re.match('^[0-9a-fA-f]{0,4}$', entry):
return False
return True
[docs]def is_valid_port(entry, allow_zero = False):
"""
Checks if a string or int is a valid port number.
:param list,str,int entry: string, integer or list to be checked
:param bool allow_zero: accept port number of zero (reserved by definition)
:returns: **True** if input is an integer and within the valid port range, **False** otherwise
"""
try:
value = int(entry)
if str(value) != str(entry):
return False # invalid leading char, e.g. space or zero
elif allow_zero and value == 0:
return True
else:
return value > 0 and value < 65536
except TypeError:
if isinstance(entry, (tuple, list)):
for port in entry:
if not is_valid_port(port, allow_zero):
return False
return True
else:
return False
except ValueError:
return False
[docs]def is_private_address(address):
"""
Checks if the IPv4 address is in a range belonging to the local network or
loopback. These include:
* Private ranges: 10.*, 172.16.* - 172.31.*, 192.168.*
* Loopback: 127.*
.. versionadded:: 1.1.0
:param str address: string to be checked
:returns: **True** if input is in a private range, **False** otherwise
:raises: **ValueError** if the address isn't a valid IPv4 address
"""
if not is_valid_ipv4_address(address):
raise ValueError("'%s' isn't a valid IPv4 address" % address)
# checks for any of the simple wildcard ranges
if address.startswith('10.') or address.startswith('192.168.') or address.startswith('127.'):
return True
# checks for the 172.16.* - 172.31.* range
if address.startswith('172.'):
second_octet = int(address.split('.')[1])
if second_octet >= 16 and second_octet <= 31:
return True
return False
[docs]def address_to_int(address):
"""
Provides an integer representation of a IPv4 or IPv6 address that can be used
for sorting.
.. versionadded:: 1.5.0
:param str address: IPv4 or IPv6 address
:returns: **int** representation of the address
"""
# TODO: Could be neat to also use this for serialization if we also had an
# int_to_address() function.
return int(_address_to_binary(address), 2)
[docs]def expand_ipv6_address(address):
"""
Expands abbreviated IPv6 addresses to their full colon separated hex format.
For instance...
::
>>> expand_ipv6_address('2001:db8::ff00:42:8329')
'2001:0db8:0000:0000:0000:ff00:0042:8329'
>>> expand_ipv6_address('::')
'0000:0000:0000:0000:0000:0000:0000:0000'
>>> expand_ipv6_address('::ffff:5.9.158.75')
'0000:0000:0000:0000:0000:ffff:0509:9e4b'
:param str address: IPv6 address to be expanded
:raises: **ValueError** if the address can't be expanded due to being malformed
"""
if not is_valid_ipv6_address(address):
raise ValueError("'%s' isn't a valid IPv6 address" % address)
# expand ipv4-mapped portions of addresses
if address.count('.') == 3:
ipv4_start = address.rfind(':', 0, address.find('.')) + 1
ipv4_end = address.find(':', ipv4_start + 1)
if ipv4_end == -1:
ipv4_end = None # don't crop the last character
# Converts ipv4 address to its hex ipv6 representation. For instance...
#
# '5.9.158.75' => '0509:9e4b'
ipv4_bin = _address_to_binary(address[ipv4_start:ipv4_end])
groupings = [ipv4_bin[16 * i:16 * (i + 1)] for i in range(2)]
ipv6_snippet = ':'.join(['%04x' % int(group, 2) for group in groupings])
addr_comp = [address[:ipv4_start - 1] if ipv4_start != 0 else None, ipv6_snippet, address[ipv4_end + 1:] if ipv4_end else None]
address = ':'.join(filter(None, addr_comp))
# expands collapsed groupings, there can only be a single '::' in a valid
# address
if '::' in address:
missing_groups = 7 - address.count(':')
address = address.replace('::', '::' + ':' * missing_groups)
# inserts missing zeros
for index in range(8):
start = index * 5
end = address.index(':', start) if index != 7 else len(address)
missing_zeros = 4 - (end - start)
if missing_zeros > 0:
address = address[:start] + '0' * missing_zeros + address[start:]
return address
[docs]def get_mask_ipv4(bits):
"""
Provides the IPv4 mask for a given number of bits, in the dotted-quad format.
:param int bits: number of bits to be converted
:returns: **str** with the subnet mask representation for this many bits
:raises: **ValueError** if given a number of bits outside the range of 0-32
"""
if bits > 32 or bits < 0:
raise ValueError('A mask can only be 0-32 bits, got %i' % bits)
elif bits == 32:
return FULL_IPv4_MASK
# get the binary representation of the mask
mask_bin = _get_binary(2 ** bits - 1, 32)[::-1]
# breaks it into eight character groupings
octets = [mask_bin[8 * i:8 * (i + 1)] for i in range(4)]
# converts each octet into its integer value
return '.'.join([str(int(octet, 2)) for octet in octets])
[docs]def get_mask_ipv6(bits):
"""
Provides the IPv6 mask for a given number of bits, in the hex colon-delimited
format.
:param int bits: number of bits to be converted
:returns: **str** with the subnet mask representation for this many bits
:raises: **ValueError** if given a number of bits outside the range of 0-128
"""
if bits > 128 or bits < 0:
raise ValueError('A mask can only be 0-128 bits, got %i' % bits)
elif bits == 128:
return FULL_IPv6_MASK
# get the binary representation of the mask
mask_bin = _get_binary(2 ** bits - 1, 128)[::-1]
# breaks it into sixteen character groupings
groupings = [mask_bin[16 * i:16 * (i + 1)] for i in range(8)]
# converts each group into its hex value
return ':'.join(['%04x' % int(group, 2) for group in groupings]).upper()
def _get_masked_bits(mask):
"""
Provides the number of bits that an IPv4 subnet mask represents. Note that
not all masks can be represented by a bit count.
:param str mask: mask to be converted
:returns: **int** with the number of bits represented by the mask
:raises: **ValueError** if the mask is invalid or can't be converted
"""
if not is_valid_ipv4_address(mask):
raise ValueError("'%s' is an invalid subnet mask" % mask)
# converts octets to binary representation
mask_bin = _address_to_binary(mask)
mask_match = re.match('^(1*)(0*)$', mask_bin)
if mask_match:
return 32 - len(mask_match.groups()[1])
else:
raise ValueError('Unable to convert mask to a bit count: %s' % mask)
def _get_binary(value, bits):
"""
Provides the given value as a binary string, padded with zeros to the given
number of bits.
:param int value: value to be converted
:param int bits: number of bits to pad to
"""
# http://www.daniweb.com/code/snippet216539.html
return ''.join([str((value >> y) & 1) for y in range(bits - 1, -1, -1)])
# TODO: In stem 2.x we should consider unifying this with
# stem.client.datatype's _unpack_ipv4_address() and _unpack_ipv6_address().
def _address_to_binary(address):
"""
Provides the binary value for an IPv4 or IPv6 address.
:returns: **str** with the binary representation of this address
:raises: **ValueError** if address is neither an IPv4 nor IPv6 address
"""
if is_valid_ipv4_address(address):
return ''.join([_get_binary(int(octet), 8) for octet in address.split('.')])
elif is_valid_ipv6_address(address):
address = expand_ipv6_address(address)
return ''.join([_get_binary(int(grouping, 16), 16) for grouping in address.split(':')])
else:
raise ValueError("'%s' is neither an IPv4 or IPv6 address" % address)
# TODO: drop with stem 2.x
# We renamed our methods to drop a redundant 'get_*' prefix, so alias the old
# names for backward compatability.
get_system_resolvers = system_resolvers
