summaryrefslogtreecommitdiff
path: root/cloudinit/net/__init__.py
blob: 91e36aca580ba03b9edf00f4d83315a9011d3fb2 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
#   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.net import network_state
from cloudinit.net.udev import generate_udev_rule
from cloudinit import util

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, 'control': 'manual'}

        # 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 = [
        'control',
        'index',
        'inet',
        'mode',
        'name',
        'subnets',
        'type',
    ]
    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 iface_start_entry(iface, index):
    fullname = iface['name']
    if index != 0:
        fullname += ":%s" % index

    control = iface['control']
    if control == "auto":
        cverb = "auto"
    elif control in ("hotplug",):
        cverb = "allow-" + control
    else:
        cverb = "# control-" + control

    subst = iface.copy()
    subst.update({'fullname': fullname, 'cverb': cverb})

    return ("{cverb} {fullname}\n"
            "iface {fullname} {inet} {mode}\n").format(**subst)


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))

    for iface in sorted(interfaces.values(),
                        key=lambda k: (order[k['type']], k['name'])):

        if content[-2:] != "\n\n":
            content += "\n"
        subnets = iface.get('subnets', {})
        if subnets:
            for index, subnet in zip(range(0, len(subnets)), subnets):
                if content[-2:] != "\n\n":
                    content += "\n"
                iface['index'] = index
                iface['mode'] = subnet['type']
                iface['control'] = subnet.get('control', 'auto')
                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'

                content += iface_start_entry(iface, index)
                content += iface_add_subnet(iface, subnet)
                content += iface_add_attrs(iface)
        else:
            # ifenslave docs say to auto the slave devices
            if 'bond-master' in iface:
                content += "auto {name}\n".format(**iface)
            content += "iface {name} {inet} {mode}\n".format(**iface)
            content += iface_add_attrs(iface)

    for route in network_state.get('routes'):
        content += render_route(route)

    # global replacements until v2 format
    content = content.replace('mac_address', 'hwaddress')
    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:
        if interface.startswith("veth"):
            continue
        if os.path.exists(sys_dev_path(interface, "bridge")):
            # skip any bridges
            continue
        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