support network configuration in cloud-init --local

this allows 'cloud-init --local' to fully run before networking comes up.
By doing so, we can now cleanly apply networking to the new system.

This adds support for reading ConfigDrive network configuration
and also from NoCloud.  The support is only present for ubuntu/debian
at the current time.  Other distros will follow.

Also ability to specify network configuration on kernel command line
via either ip= or network-config=<base64>.

1 files changed, 751 insertions, 0 deletions

diff --git a/cloudinit/net/__init__.py b/cloudinit/net/__init__.py
new file mode 100644
index 00000000..40929c6e
--- /dev/null
+++ b/cloudinit/net/__init__.py
@@ -0,0 +1,751 @@
+#   Copyright (C) 2013-2014 Canonical Ltd.
+#
+#   Author: Scott Moser <scott.moser@canonical.com>
+#   Author: Blake Rouse <blake.rouse@canonical.com>
+#
+#   Curtin is free software: you can redistribute it and/or modify it under
+#   the terms of the GNU Affero General Public License as published by the
+#   Free Software Foundation, either version 3 of the License, or (at your
+#   option) any later version.
+#
+#   Curtin is distributed in the hope that it will be useful, but WITHOUT ANY
+#   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+#   FOR A PARTICULAR PURPOSE.  See the GNU Affero General Public License for
+#   more details.
+#
+#   You should have received a copy of the GNU Affero General Public License
+#   along with Curtin.  If not, see <http://www.gnu.org/licenses/>.
+
+import base64
+import errno
+import glob
+import gzip
+import io
+import os
+import re
+import shlex
+
+from cloudinit import log as logging
+from cloudinit import util
+from .udev import generate_udev_rule
+from . import network_state
+
+LOG = logging.getLogger(__name__)
+
+SYS_CLASS_NET = "/sys/class/net/"
+LINKS_FNAME_PREFIX = "etc/systemd/network/50-cloud-init-"
+
+NET_CONFIG_OPTIONS = [
+    "address", "netmask", "broadcast", "network", "metric", "gateway",
+    "pointtopoint", "media", "mtu", "hostname", "leasehours", "leasetime",
+    "vendor", "client", "bootfile", "server", "hwaddr", "provider", "frame",
+    "netnum", "endpoint", "local", "ttl",
+    ]
+
+NET_CONFIG_COMMANDS = [
+    "pre-up", "up", "post-up", "down", "pre-down", "post-down",
+    ]
+
+NET_CONFIG_BRIDGE_OPTIONS = [
+    "bridge_ageing", "bridge_bridgeprio", "bridge_fd", "bridge_gcinit",
+    "bridge_hello", "bridge_maxage", "bridge_maxwait", "bridge_stp",
+    ]
+
+DEFAULT_PRIMARY_INTERFACE = 'eth0'
+
+
+def sys_dev_path(devname, path=""):
+    return SYS_CLASS_NET + devname + "/" + path
+
+
+def read_sys_net(devname, path, translate=None, enoent=None, keyerror=None):
+    try:
+        contents = ""
+        with open(sys_dev_path(devname, path), "r") as fp:
+            contents = fp.read().strip()
+        if translate is None:
+            return contents
+
+        try:
+            return translate.get(contents)
+        except KeyError:
+            LOG.debug("found unexpected value '%s' in '%s/%s'", contents,
+                      devname, path)
+            if keyerror is not None:
+                return keyerror
+            raise
+    except OSError as e:
+        if e.errno == errno.ENOENT and enoent is not None:
+            return enoent
+        raise
+
+
+def is_up(devname):
+    # The linux kernel says to consider devices in 'unknown'
+    # operstate as up for the purposes of network configuration. See
+    # Documentation/networking/operstates.txt in the kernel source.
+    translate = {'up': True, 'unknown': True, 'down': False}
+    return read_sys_net(devname, "operstate", enoent=False, keyerror=False,
+                        translate=translate)
+
+
+def is_wireless(devname):
+    return os.path.exists(sys_dev_path(devname, "wireless"))
+
+
+def is_connected(devname):
+    # is_connected isn't really as simple as that.  2 is
+    # 'physically connected'. 3 is 'not connected'. but a wlan interface will
+    # always show 3.
+    try:
+        iflink = read_sys_net(devname, "iflink", enoent=False)
+        if iflink == "2":
+            return True
+        if not is_wireless(devname):
+            return False
+        LOG.debug("'%s' is wireless, basing 'connected' on carrier", devname)
+
+        return read_sys_net(devname, "carrier", enoent=False, keyerror=False,
+                            translate={'0': False, '1': True})
+
+    except IOError as e:
+        if e.errno == errno.EINVAL:
+            return False
+        raise
+
+
+def is_physical(devname):
+    return os.path.exists(sys_dev_path(devname, "device"))
+
+
+def is_present(devname):
+    return os.path.exists(sys_dev_path(devname))
+
+
+def get_devicelist():
+    return os.listdir(SYS_CLASS_NET)
+
+
+class ParserError(Exception):
+    """Raised when parser has issue parsing the interfaces file."""
+
+
+def parse_deb_config_data(ifaces, contents, src_dir, src_path):
+    """Parses the file contents, placing result into ifaces.
+
+    '_source_path' is added to every dictionary entry to define which file
+    the configration information came from.
+
+    :param ifaces: interface dictionary
+    :param contents: contents of interfaces file
+    :param src_dir: directory interfaces file was located
+    :param src_path: file path the `contents` was read
+    """
+    currif = None
+    for line in contents.splitlines():
+        line = line.strip()
+        if line.startswith('#'):
+            continue
+        split = line.split(' ')
+        option = split[0]
+        if option == "source-directory":
+            parsed_src_dir = split[1]
+            if not parsed_src_dir.startswith("/"):
+                parsed_src_dir = os.path.join(src_dir, parsed_src_dir)
+            for expanded_path in glob.glob(parsed_src_dir):
+                dir_contents = os.listdir(expanded_path)
+                dir_contents = [
+                    os.path.join(expanded_path, path)
+                    for path in dir_contents
+                    if (os.path.isfile(os.path.join(expanded_path, path)) and
+                        re.match("^[a-zA-Z0-9_-]+$", path) is not None)
+                ]
+                for entry in dir_contents:
+                    with open(entry, "r") as fp:
+                        src_data = fp.read().strip()
+                    abs_entry = os.path.abspath(entry)
+                    parse_deb_config_data(
+                        ifaces, src_data,
+                        os.path.dirname(abs_entry), abs_entry)
+        elif option == "source":
+            new_src_path = split[1]
+            if not new_src_path.startswith("/"):
+                new_src_path = os.path.join(src_dir, new_src_path)
+            for expanded_path in glob.glob(new_src_path):
+                with open(expanded_path, "r") as fp:
+                    src_data = fp.read().strip()
+                abs_path = os.path.abspath(expanded_path)
+                parse_deb_config_data(
+                    ifaces, src_data,
+                    os.path.dirname(abs_path), abs_path)
+        elif option == "auto":
+            for iface in split[1:]:
+                if iface not in ifaces:
+                    ifaces[iface] = {
+                        # Include the source path this interface was found in.
+                        "_source_path": src_path
+                    }
+                ifaces[iface]['auto'] = True
+        elif option == "iface":
+            iface, family, method = split[1:4]
+            if iface not in ifaces:
+                ifaces[iface] = {
+                    # Include the source path this interface was found in.
+                    "_source_path": src_path
+                }
+            elif 'family' in ifaces[iface]:
+                raise ParserError(
+                    "Interface %s can only be defined once. "
+                    "Re-defined in '%s'." % (iface, src_path))
+            ifaces[iface]['family'] = family
+            ifaces[iface]['method'] = method
+            currif = iface
+        elif option == "hwaddress":
+            ifaces[currif]['hwaddress'] = split[1]
+        elif option in NET_CONFIG_OPTIONS:
+            ifaces[currif][option] = split[1]
+        elif option in NET_CONFIG_COMMANDS:
+            if option not in ifaces[currif]:
+                ifaces[currif][option] = []
+            ifaces[currif][option].append(' '.join(split[1:]))
+        elif option.startswith('dns-'):
+            if 'dns' not in ifaces[currif]:
+                ifaces[currif]['dns'] = {}
+            if option == 'dns-search':
+                ifaces[currif]['dns']['search'] = []
+                for domain in split[1:]:
+                    ifaces[currif]['dns']['search'].append(domain)
+            elif option == 'dns-nameservers':
+                ifaces[currif]['dns']['nameservers'] = []
+                for server in split[1:]:
+                    ifaces[currif]['dns']['nameservers'].append(server)
+        elif option.startswith('bridge_'):
+            if 'bridge' not in ifaces[currif]:
+                ifaces[currif]['bridge'] = {}
+            if option in NET_CONFIG_BRIDGE_OPTIONS:
+                bridge_option = option.replace('bridge_', '', 1)
+                ifaces[currif]['bridge'][bridge_option] = split[1]
+            elif option == "bridge_ports":
+                ifaces[currif]['bridge']['ports'] = []
+                for iface in split[1:]:
+                    ifaces[currif]['bridge']['ports'].append(iface)
+            elif option == "bridge_hw" and split[1].lower() == "mac":
+                ifaces[currif]['bridge']['mac'] = split[2]
+            elif option == "bridge_pathcost":
+                if 'pathcost' not in ifaces[currif]['bridge']:
+                    ifaces[currif]['bridge']['pathcost'] = {}
+                ifaces[currif]['bridge']['pathcost'][split[1]] = split[2]
+            elif option == "bridge_portprio":
+                if 'portprio' not in ifaces[currif]['bridge']:
+                    ifaces[currif]['bridge']['portprio'] = {}
+                ifaces[currif]['bridge']['portprio'][split[1]] = split[2]
+        elif option.startswith('bond-'):
+            if 'bond' not in ifaces[currif]:
+                ifaces[currif]['bond'] = {}
+            bond_option = option.replace('bond-', '', 1)
+            ifaces[currif]['bond'][bond_option] = split[1]
+    for iface in ifaces.keys():
+        if 'auto' not in ifaces[iface]:
+            ifaces[iface]['auto'] = False
+
+
+def parse_deb_config(path):
+    """Parses a debian network configuration file."""
+    ifaces = {}
+    with open(path, "r") as fp:
+        contents = fp.read().strip()
+    abs_path = os.path.abspath(path)
+    parse_deb_config_data(
+        ifaces, contents,
+        os.path.dirname(abs_path), abs_path)
+    return ifaces
+
+
+def parse_net_config_data(net_config):
+    """Parses the config, returns NetworkState dictionary
+
+    :param net_config: curtin network config dict
+    """
+    state = None
+    if 'version' in net_config and 'config' in net_config:
+        ns = network_state.NetworkState(version=net_config.get('version'),
+                                        config=net_config.get('config'))
+        ns.parse_config()
+        state = ns.network_state
+
+    return state
+
+
+def parse_net_config(path):
+    """Parses a curtin network configuration file and
+       return network state"""
+    ns = None
+    net_config = util.read_conf(path)
+    if 'network' in net_config:
+        ns = parse_net_config_data(net_config.get('network'))
+
+    return ns
+
+
+def _load_shell_content(content, add_empty=False, empty_val=None):
+    """Given shell like syntax (key=value\nkey2=value2\n) in content
+       return the data in dictionary form.  If 'add_empty' is True
+       then add entries in to the returned dictionary for 'VAR='
+       variables.  Set their value to empty_val."""
+    data = {}
+    for line in shlex.split(content):
+        key, value = line.split("=", 1)
+        if not value:
+            value = empty_val
+        if add_empty or value:
+            data[key] = value
+
+    return data
+
+
+def _klibc_to_config_entry(content, mac_addrs=None):
+    """Convert a klibc writtent shell content file to a 'config' entry
+    When ip= is seen on the kernel command line in debian initramfs
+    and networking is brought up, ipconfig will populate
+    /run/net-<name>.cfg.
+
+    The files are shell style syntax, and examples are in the tests
+    provided here.  There is no good documentation on this unfortunately.
+
+    DEVICE=<name> is expected/required and PROTO should indicate if
+    this is 'static' or 'dhcp'.
+    """
+
+    if mac_addrs is None:
+        mac_addrs = {}
+
+    data = _load_shell_content(content)
+    try:
+        name = data['DEVICE']
+    except KeyError:
+        raise ValueError("no 'DEVICE' entry in data")
+
+    # ipconfig on precise does not write PROTO
+    proto = data.get('PROTO')
+    if not proto:
+        if data.get('filename'):
+            proto = 'dhcp'
+        else:
+            proto = 'static'
+
+    if proto not in ('static', 'dhcp'):
+        raise ValueError("Unexpected value for PROTO: %s" % proto)
+
+    iface = {
+        'type': 'physical',
+        'name': name,
+        'subnets': [],
+    }
+
+    if name in mac_addrs:
+        iface['mac_address'] = mac_addrs[name]
+
+    # originally believed there might be IPV6* values
+    for v, pre in (('ipv4', 'IPV4'),):
+        # if no IPV4ADDR or IPV6ADDR, then go on.
+        if pre + "ADDR" not in data:
+            continue
+        subnet = {'type': proto}
+
+        # these fields go right on the subnet
+        for key in ('NETMASK', 'BROADCAST', 'GATEWAY'):
+            if pre + key in data:
+                subnet[key.lower()] = data[pre + key]
+
+        dns = []
+        # handle IPV4DNS0 or IPV6DNS0
+        for nskey in ('DNS0', 'DNS1'):
+            ns = data.get(pre + nskey)
+            # verify it has something other than 0.0.0.0 (or ipv6)
+            if ns and len(ns.strip(":.0")):
+                dns.append(data[pre + nskey])
+        if dns:
+            subnet['dns_nameservers'] = dns
+            # add search to both ipv4 and ipv6, as it has no namespace
+            search = data.get('DOMAINSEARCH')
+            if search:
+                if ',' in search:
+                    subnet['dns_search'] = search.split(",")
+                else:
+                    subnet['dns_search'] = search.split()
+
+        iface['subnets'].append(subnet)
+
+    return name, iface
+
+
+def config_from_klibc_net_cfg(files=None, mac_addrs=None):
+    if files is None:
+        files = glob.glob('/run/net*.conf')
+
+    entries = []
+    names = {}
+    for cfg_file in files:
+        name, entry = _klibc_to_config_entry(util.load_file(cfg_file),
+                                             mac_addrs=mac_addrs)
+        if name in names:
+            raise ValueError(
+                "device '%s' defined multiple times: %s and %s" % (
+                    name, names[name], cfg_file))
+
+        names[name] = cfg_file
+        entries.append(entry)
+    return {'config': entries, 'version': 1}
+
+
+def render_persistent_net(network_state):
+    ''' Given state, emit udev rules to map
+        mac to ifname
+    '''
+    content = ""
+    interfaces = network_state.get('interfaces')
+    for iface in interfaces.values():
+        # for physical interfaces write out a persist net udev rule
+        if iface['type'] == 'physical' and \
+           'name' in iface and iface.get('mac_address'):
+            content += generate_udev_rule(iface['name'],
+                                          iface['mac_address'])
+
+    return content
+
+
+# TODO: switch valid_map based on mode inet/inet6
+def iface_add_subnet(iface, subnet):
+    content = ""
+    valid_map = [
+        'address',
+        'netmask',
+        'broadcast',
+        'metric',
+        'gateway',
+        'pointopoint',
+        'mtu',
+        'scope',
+        'dns_search',
+        'dns_nameservers',
+    ]
+    for key, value in subnet.items():
+        if value and key in valid_map:
+            if type(value) == list:
+                value = " ".join(value)
+            if '_' in key:
+                key = key.replace('_', '-')
+            content += "    {} {}\n".format(key, value)
+
+    return content
+
+
+# TODO: switch to valid_map for attrs
+def iface_add_attrs(iface):
+    content = ""
+    ignore_map = [
+        'type',
+        'name',
+        'inet',
+        'mode',
+        'index',
+        'subnets',
+    ]
+    if iface['type'] not in ['bond', 'bridge', 'vlan']:
+        ignore_map.append('mac_address')
+
+    for key, value in iface.items():
+        if value and key not in ignore_map:
+            if type(value) == list:
+                value = " ".join(value)
+            content += "    {} {}\n".format(key, value)
+
+    return content
+
+
+def render_route(route, indent=""):
+    """ When rendering routes for an iface, in some cases applying a route
+    may result in the route command returning non-zero which produces
+    some confusing output for users manually using ifup/ifdown[1].  To
+    that end, we will optionally include an '|| true' postfix to each
+    route line allowing users to work with ifup/ifdown without using
+    --force option.
+
+    We may at somepoint not want to emit this additional postfix, and
+    add a 'strict' flag to this function.  When called with strict=True,
+    then we will not append the postfix.
+
+    1. http://askubuntu.com/questions/168033/
+             how-to-set-static-routes-in-ubuntu-server
+    """
+    content = ""
+    up = indent + "post-up route add"
+    down = indent + "pre-down route del"
+    eol = " || true\n"
+    mapping = {
+        'network': '-net',
+        'netmask': 'netmask',
+        'gateway': 'gw',
+        'metric': 'metric',
+    }
+    if route['network'] == '0.0.0.0' and route['netmask'] == '0.0.0.0':
+        default_gw = " default gw %s" % route['gateway']
+        content += up + default_gw + eol
+        content += down + default_gw + eol
+    elif route['network'] == '::' and route['netmask'] == 0:
+        # ipv6!
+        default_gw = " -A inet6 default gw %s" % route['gateway']
+        content += up + default_gw + eol
+        content += down + default_gw + eol
+    else:
+        route_line = ""
+        for k in ['network', 'netmask', 'gateway', 'metric']:
+            if k in route:
+                route_line += " %s %s" % (mapping[k], route[k])
+        content += up + route_line + eol
+        content += down + route_line + eol
+
+    return content
+
+
+def render_interfaces(network_state):
+    ''' Given state, emit etc/network/interfaces content '''
+
+    content = ""
+    interfaces = network_state.get('interfaces')
+    ''' Apply a sort order to ensure that we write out
+        the physical interfaces first; this is critical for
+        bonding
+    '''
+    order = {
+        'physical': 0,
+        'bond': 1,
+        'bridge': 2,
+        'vlan': 3,
+    }
+    content += "auto lo\niface lo inet loopback\n"
+    for dnskey, value in network_state.get('dns', {}).items():
+        if len(value):
+            content += "    dns-{} {}\n".format(dnskey, " ".join(value))
+
+    content += "\n"
+    for iface in sorted(interfaces.values(),
+                        key=lambda k: (order[k['type']], k['name'])):
+        content += "auto {name}\n".format(**iface)
+
+        subnets = iface.get('subnets', {})
+        if subnets:
+            for index, subnet in zip(range(0, len(subnets)), subnets):
+                iface['index'] = index
+                iface['mode'] = subnet['type']
+                if iface['mode'].endswith('6'):
+                    iface['inet'] += '6'
+                elif iface['mode'] == 'static' and ":" in subnet['address']:
+                    iface['inet'] += '6'
+                if iface['mode'].startswith('dhcp'):
+                    iface['mode'] = 'dhcp'
+
+                if index == 0:
+                    content += "iface {name} {inet} {mode}\n".format(**iface)
+                else:
+                    content += "auto {name}:{index}\n".format(**iface)
+                    content += \
+                        "iface {name}:{index} {inet} {mode}\n".format(**iface)
+
+                content += iface_add_subnet(iface, subnet)
+                content += iface_add_attrs(iface)
+                for route in subnet.get('routes', []):
+                    content += render_route(route, indent="    ")
+                content += "\n"
+        else:
+            content += "iface {name} {inet} {mode}\n".format(**iface)
+            content += iface_add_attrs(iface)
+            content += "\n"
+
+    for route in network_state.get('routes'):
+        content += render_route(route)
+
+    # global replacements until v2 format
+    content = content.replace('mac_address', 'hwaddress ether')
+    return content
+
+
+def render_network_state(target, network_state, eni="etc/network/interfaces",
+                         links_prefix=LINKS_FNAME_PREFIX,
+                         netrules='etc/udev/rules.d/70-persistent-net.rules'):
+
+    fpeni = os.path.sep.join((target, eni,))
+    util.ensure_dir(os.path.dirname(fpeni))
+    with open(fpeni, 'w+') as f:
+        f.write(render_interfaces(network_state))
+
+    if netrules:
+        netrules = os.path.sep.join((target, netrules,))
+        util.ensure_dir(os.path.dirname(netrules))
+        with open(netrules, 'w+') as f:
+            f.write(render_persistent_net(network_state))
+
+    if links_prefix:
+        render_systemd_links(target, network_state, links_prefix)
+
+
+def render_systemd_links(target, network_state,
+                         links_prefix=LINKS_FNAME_PREFIX):
+    fp_prefix = os.path.sep.join((target, links_prefix))
+    for f in glob.glob(fp_prefix + "*"):
+        os.unlink(f)
+
+    interfaces = network_state.get('interfaces')
+    for iface in interfaces.values():
+        if (iface['type'] == 'physical' and 'name' in iface and
+                iface.get('mac_address')):
+            fname = fp_prefix + iface['name'] + ".link"
+            with open(fname, "w") as fp:
+                fp.write("\n".join([
+                    "[Match]",
+                    "MACAddress=" + iface['mac_address'],
+                    "",
+                    "[Link]",
+                    "Name=" + iface['name'],
+                    ""
+                ]))
+
+
+def is_disabled_cfg(cfg):
+    if not cfg or not isinstance(cfg, dict):
+        return False
+    return cfg.get('config') == "disabled"
+
+
+def sys_netdev_info(name, field):
+    if not os.path.exists(os.path.join(SYS_CLASS_NET, name)):
+        raise OSError("%s: interface does not exist in %s" %
+                      (name, SYS_CLASS_NET))
+
+    fname = os.path.join(SYS_CLASS_NET, name, field)
+    if not os.path.exists(fname):
+        raise OSError("%s: could not find sysfs entry: %s" % (name, fname))
+    data = util.load_file(fname)
+    if data[-1] == '\n':
+        data = data[:-1]
+    return data
+
+
+def generate_fallback_config():
+    """Determine which attached net dev is most likely to have a connection and
+       generate network state to run dhcp on that interface"""
+    # by default use eth0 as primary interface
+    nconf = {'config': [], 'version': 1}
+
+    # get list of interfaces that could have connections
+    invalid_interfaces = set(['lo'])
+    potential_interfaces = set(get_devicelist())
+    potential_interfaces = potential_interfaces.difference(invalid_interfaces)
+    # sort into interfaces with carrier, interfaces which could have carrier,
+    # and ignore interfaces that are definitely disconnected
+    connected = []
+    possibly_connected = []
+    for interface in potential_interfaces:
+        try:
+            carrier = int(sys_netdev_info(interface, 'carrier'))
+            if carrier:
+                connected.append(interface)
+                continue
+        except OSError:
+            pass
+        # check if nic is dormant or down, as this may make a nick appear to
+        # not have a carrier even though it could acquire one when brought
+        # online by dhclient
+        try:
+            dormant = int(sys_netdev_info(interface, 'dormant'))
+            if dormant:
+                possibly_connected.append(interface)
+                continue
+        except OSError:
+            pass
+        try:
+            operstate = sys_netdev_info(interface, 'operstate')
+            if operstate in ['dormant', 'down', 'lowerlayerdown', 'unknown']:
+                possibly_connected.append(interface)
+                continue
+        except OSError:
+            pass
+
+    # don't bother with interfaces that might not be connected if there are
+    # some that definitely are
+    if connected:
+        potential_interfaces = connected
+    else:
+        potential_interfaces = possibly_connected
+    # if there are no interfaces, give up
+    if not potential_interfaces:
+        return
+    # if eth0 exists use it above anything else, otherwise get the interface
+    # that looks 'first'
+    if DEFAULT_PRIMARY_INTERFACE in potential_interfaces:
+        name = DEFAULT_PRIMARY_INTERFACE
+    else:
+        name = sorted(potential_interfaces)[0]
+
+    mac = sys_netdev_info(name, 'address')
+    target_name = name
+
+    nconf['config'].append(
+        {'type': 'physical', 'name': target_name,
+         'mac_address': mac, 'subnets': [{'type': 'dhcp'}]})
+    return nconf
+
+
+def _decomp_gzip(blob, strict=True):
+    # decompress blob. raise exception if not compressed unless strict=False.
+    with io.BytesIO(blob) as iobuf:
+        gzfp = None
+        try:
+            gzfp = gzip.GzipFile(mode="rb", fileobj=iobuf)
+            return gzfp.read()
+        except IOError:
+            if strict:
+                raise
+            return blob
+        finally:
+            if gzfp:
+                gzfp.close()
+
+
+def _b64dgz(b64str, gzipped="try"):
+    # decode a base64 string.  If gzipped is true, transparently uncompresss
+    # if gzipped is 'try', then try gunzip, returning the original on fail.
+    try:
+        blob = base64.b64decode(b64str)
+    except TypeError:
+        raise ValueError("Invalid base64 text: %s" % b64str)
+
+    if not gzipped:
+        return blob
+
+    return _decomp_gzip(blob, strict=gzipped != "try")
+
+
+def read_kernel_cmdline_config(files=None, mac_addrs=None, cmdline=None):
+    if cmdline is None:
+        cmdline = util.get_cmdline()
+
+    if 'network-config=' in cmdline:
+        data64 = None
+        for tok in cmdline.split():
+            if tok.startswith("network-config="):
+                data64 = tok.split("=", 1)[1]
+        if data64:
+            return util.load_yaml(_b64dgz(data64))
+
+    if 'ip=' not in cmdline:
+        return None
+
+    if mac_addrs is None:
+        mac_addrs = {k: sys_netdev_info(k, 'address')
+                     for k in get_devicelist()}
+
+    return config_from_klibc_net_cfg(files=files, mac_addrs=mac_addrs)
+
+
+# vi: ts=4 expandtab syntax=python