dhcp6-srv.xml 91.9 KB
Newer Older
1
2
3
4
5
6
7
8
9
10
11
12
13
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
<!ENTITY mdash  "&#x2014;" >
]>

  <chapter id="dhcp6">
    <title>The DHCPv6 Server</title>

    <section id="dhcp6-start-stop">
      <title>Starting and Stopping the DHCPv6 Server</title>

      <para>
14
      It is recommended that the Kea DHCPv4 server be started and stopped
Jeremy C. Reed's avatar
Jeremy C. Reed committed
15
      using <command>keactrl</command> (described in <xref linkend="keactrl"/>).
16
17
      However, it is also possible to run the server directly: it accepts
      the following command-line switches:
18
19
      </para>

20
21
      <itemizedlist>
          <listitem>
22
23
24
25
            <simpara>
            <command>-c <replaceable>file</replaceable></command> -
            specifies the configuration file. This is the only mandatory
            switch.</simpara>
26
27
          </listitem>
          <listitem>
28
            <simpara>
29
            <command>-d</command> - specifies whether the server
30
            logging should be switched to verbose mode. In verbose mode,
31
            the logging severity and debuglevel specified in the configuration
32
33
34
35
            file are ignored and "debug" severity and the maximum debuglevel
            (99) are assumed. The flag is convenient, for temporarily
            switching the server into maximum verbosity, e.g. when
            debugging.</simpara>
36
37
          </listitem>
          <listitem>
38
39
            <simpara>
            <command>-p <replaceable>port</replaceable></command> -
40
41
            specifies UDP port on which the server will listen. This is only
            useful during testing, as a DHCPv6 server listening on
42
43
            ports other than default DHCPv6 ports will not be able to
            handle regular DHCPv6 queries.</simpara>
44
          </listitem>
Tomek Mrugalski's avatar
Tomek Mrugalski committed
45
46
          <listitem>
            <simpara>
Tomek Mrugalski's avatar
Tomek Mrugalski committed
47
              <command>-v</command> - prints out Kea version and exits.
Tomek Mrugalski's avatar
Tomek Mrugalski committed
48
49
50
51
52
            </simpara>
          </listitem>
          <listitem>
            <simpara>
              <command>-V</command> - prints out Kea extended version with
Tomek Mrugalski's avatar
Tomek Mrugalski committed
53
              additional parameters and exits.
Tomek Mrugalski's avatar
Tomek Mrugalski committed
54
55
            </simpara>
          </listitem>
56
57
      </itemizedlist>

58
      <para>
59
60
61
	    When running in a console, the server can be shut down by
	    pressing ctrl-c. It detects the key combination and shuts
	    down gracefully.
62
63
64
      </para>

      <para>
65
        On start-up, the server will detect available network interfaces
66
67
        and will attempt to open UDP sockets on all interfaces
        mentioned in the configuration file.
68
69
70
      </para>

      <para>
71
72
        Since the DHCPv6 server opens privileged ports, it requires root
        access. Make sure you run this daemon as root.
73
74
75
76
77
78
      </para>

    </section>

    <section id="dhcp6-configuration">
      <title>DHCPv6 Server Configuration</title>
79
80
81
82


<section>
  <title>Introduction</title>
83
      <para>
84
        This section explains how to configure the DHCPv6 server using the
85
86
        Kea configuration backend. (Kea configuration using any other
        backends is outside of scope of this document.) Before DHCPv6
87
88
        is started, its configuration file has to be created. The
        basic configuration looks as follows:
89
<screen>
90
{
91
# DHCPv6 configuration starts on the next line
92
93
94
95
96
97
98
99
"Dhcp6": {

# First we set up global values
    "renew-timer": 1000,
    "rebind-timer": 2000,
    "preferred-lifetime": 3000,
    "valid-lifetime": 4000,

100
101
102
103
104
105
# Next we setup the interfaces to be used by the server.
    "interfaces-config": {
        "interfaces": [ "eth0" ]
    },

# And we specify the type of a lease database
106
107
    "lease-database": {
        "type": "memfile",
108
        "persist": true,
109
110
111
112
113
114
115
116
117
118
119
120
121
122
        "name": "/var/kea/dhcp6.leases"
    },

# Finally, we list the subnets from which we will be leasing addresses.
    "subnet6": [
        {
            "subnet": "2001:db8:1::/64",
            "pools": [
                 {
                     "pool": "2001:db8:1::1-2001:db8:1::ffff"
                 }
             ]
        }
    ]
123
# DHCPv6 configuration ends with the next line
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
}

} </screen>
</para>

<para>The following paragraphs provide a brief overview of the parameters in
the above example and
their format. Subsequent sections of this chapter go into much greater detail
for these and other parameters.</para>

<para>The lines starting with a hash (#) are comments and are ignored by
the server; they do not impact its
operation in any way.</para>

<para>The configuration starts in the first line with the initial
opening curly bracket (or brace). Each configuration consists of
one or more objects. In this specific example, we have only one
object called Dhcp6. This is a simplified configuration, as usually
there will be additional objects, like <command>Logging</command> or
<command>DhcpDns</command>, but we omit them now for clarity. The Dhcp6
144
configuration starts with the <command>"Dhcp6": {</command> line
145
146
147
148
and ends with the corresponding closing brace (in the above example,
the brace after the last comment).  Everything defined between those
lines is considered to be the Dhcp6 configuration.</para>

149
<para>In the general case, the order in which those parameters appear does not
150
matter. There are two caveats here though. The first one is to remember that
151
152
153
the configuration file must be well formed JSON. That means that parameters
for any given scope must be separated by a comma and there must not be a comma
after the last parameter. When reordering a configuration file, keep in mind that
154
moving a parameter to or from the last position in a given scope may require
155
156
moving the comma as well. The second caveat is that it is uncommon &mdash; although
legal JSON &mdash; to
157
158
159
160
161
162
repeat the same parameter multiple times. If that happens, the last occurrence of a
given parameter in a given scope is used while all previous instances are
ignored. This is unlikely to cause any confusion as there are no real life
reasons to keep multiple copies of the same parameter in your configuration
file.</para>

163
164
<para>Moving onto the DHCPv6 configuration elements, the very first few elements
define some global parameters. <command>valid-lifetime</command>
165
defines for how long the addresses (leases) given out by the server are valid. If
166
nothing changes, a client that got an address is allowed to use it for 4000
167
168
169
170
171
seconds. (Note that integer numbers are specified as is, without any quotes
around them.) The address will become deprecated in 3000 seconds (clients are
allowed to keep old connections, but can't use this address for creating new
connections). <command>renew-timer</command> and <command>
rebind-timer</command> are values that define T1 and T2 timers that govern when
172
the client will begin the renewal and rebind procedures.</para>
173

174
175
176
177
178
179
180
181
182
183
184
185
186
187
<para>The <command>interfaces-config</command> map specifies the server
configuration concerning the network interfaces, on which the server should
listen to the DHCP messages. The <command>interfaces</command> parameter
specifies a list of network interfaces on which the server should listen.
Lists are opened and closed with square brackets, with elements separated
by commas. Had we wanted to listen on two interfaces, the
<command>interfaces-config</command> would look like this:
<screen>
"interfaces-config": {
    "interfaces": [ "eth0", "eth1" ]
},
</screen>
</para>

188
<para>The next couple of lines define the lease database, the place where the server
189
190
stores its lease information. This particular example tells the server to use
<command>memfile</command>, which is the simplest (and fastest) database
191
backend. It uses an in-memory database and stores leases on disk in a CSV
192
193
194
195
196
197
198
199
200
201
202
file. This is a very simple configuration. Usually, lease database configuration
is more extensive and contains additional parameters.  Note that
<command>lease-database</command>
is an object and opens up a new scope, using an opening brace.
Its parameters (just one in this example -- <command>type</command>)
follow. Had there been more than one, they would be separated by commas. This
scope is closed with a closing brace. As more parameters follow, a trailing
comma is present.</para>

<para>Finally, we need to define a list of IPv6 subnets. This is the
most important DHCPv6 configuration structure as the server uses that
203
204
information to process clients' requests. It defines all subnets from
which the server is expected to receive DHCP requests. The subnets are
205
206
specified with the <command>subnet6</command> parameter.  It is a list,
so it starts and ends with square brackets.  Each subnet definition in
207
the list has several attributes associated with it, so it is a structure
208
209
210
211
212
213
214
215
216
217
and is opened and closed with braces. At minimum, a subnet definition
has to have at least two parameters: <command>subnet</command> (that
defines the whole subnet) and <command>pool</command> (which is a list of
dynamically allocated pools that are governed by the DHCP server).</para>

<para>The example contains a single subnet. Had more than one been defined,
additional elements
in the <command>subnet6</command> parameter would be specified and
separated by commas. For example, to define two subnets, the following
syntax would be used:
218
<screen>
219
220
221
222
223
224
225
226
227
228
"subnet6": [
    {
        "pools": [
        {
            "pool": "2001:db8:1::/112"
        }
        ],
        "subnet": "2001:db8:1::/64"
    },
    {
229
230
        "pools": [ { "pool": "2001:db8:2::1-2001:db8:2::ffff" } ],
        "subnet": "2001:db8:2::/64",
231
232
233
        "interface": "eth0"
    }
]
234
</screen>
235
236
Note that indentation is optional and is used for aesthetic purposes only.
In some cases in may be preferable to use more compact notation.
237
</para>
238

239

240
241
<para>After all parameters are specified, we have two contexts open:
global and Dhcp6, hence we need two closing curly brackets to close them.
242
243
In a real life configuration file there most likely would be additional
components defined such as Logging or DhcpDdns, so the closing brace would
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
be followed by a comma and another object definition.</para>

<para>Kea 0.9 does not have configuration syntax validation
implemented yet. Such a feature is planned for the near future. For
the time being, it is convenient to use on-line JSON validators and/or
viewers to check whether the syntax is correct. One example of such a
JSON validator is available at <ulink url="http://jsonviewer.stack.hu/"/>.
</para>
</section>

<section>
  <title>Lease Storage</title>
  <para>All leases issued by the server are stored in the lease database.
  Currently there are three database backends available:
  memfile (which is the default backend), MySQL and PostgreSQL.</para>
<section>
  <title>Memfile - Basic Storage for Leases</title>

  <para>The server is able to store lease data in different repositories. Larger
  deployments may elect to store leases in a database. <xref
264
  linkend="database-configuration6"/> describes this option. In typical
265
266
267
268
269
270
  smaller deployments though, the server will use a CSV file rather than a database to
  store lease information. As well as requiring less administration, an
  advantage of using a file for storage is that it
  eliminates a dependency on third-party database software.</para>

  <para>The configuration of the file backend (Memfile) is controlled through
271
  the Dhcp6/lease-database parameters. <!-- @todo: we don't have default
272
273
274
  parameters. Let's comment this out When default parameters are used, the
  Memfile backend will write leases to a disk in the
  [kea-install-dir]/var/kea/kea-leases4.csv. -->
Jeremy C. Reed's avatar
Jeremy C. Reed committed
275
  The following configuration sets the name of the lease file to
276
  <filename>/tmp/kea-leases6.csv</filename>:
Jeremy C. Reed's avatar
Jeremy C. Reed committed
277

278
<screen>
279
"Dhcp6": {
280
281
    "lease-database": {
        <userinput>"type": "memfile"</userinput>,
282
        <userinput>"persist": true</userinput>,
283
        <userinput>"name": "/tmp/kea-leases6.csv"</userinput>
284
285
286
287
288
289
290
    }
    ...
}
</screen>
  </para>

  <para>The "persist" parameter controls whether the leases are written to disk.
291
  It is strongly recommended that this parameter is set to true at all times
292
293
294
295
  during the normal operation of the server. (Not writing leases to disk will
  mean that if a server is restarted (e.g. after a power failure), it will not
  know what addresses have been assigned.  As a result, it may hand out addresses
  to new clients that are already in use.)
296
          </para>
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
</section>

<section id="database-configuration6">
  <title>Database Configuration</title>

  <note>
    <para>Database access information must be configured for the DHCPv6 server,
    even if it has already been configured for the DHCPv4 server.  The servers
    store their information independently, so each server can use a separate
    database or both servers can use the same database.</para>
  </note>

  <para>Database configuration is controlled through the Dhcp6/lease-database
  parameters. The type of the database must be set to "mysql" or "postgresql",
  e.g.
312
<screen>
313
"Dhcp6": { "lease-database": { <userinput>"type": "mysql"</userinput>, ... }, ... }
314
</screen>
315
  Next, the name of the database is to hold the leases must be set: this is the
316
317
  name used when the lease database was created (see <xref linkend="mysql-database-create"/>
  or <xref linkend="pgsql-database-create"/>).
318
<screen>
319
"Dhcp6": { "lease-database": { <userinput>"name": "<replaceable>database-name</replaceable>" </userinput>, ... }, ... }
320
</screen>
321
322
323
  If the database is located on a different system than the DHCPv6 server, the
  database host name must also be specified (although it should be noted that this
  configuration may have a severe impact on server performance):
324
<screen>
325
"Dhcp6": { "lease-database": { <userinput>"host": <replaceable>remote-host-name</replaceable></userinput>, ... }, ... }
326
</screen>
327
328
  The usual state of affairs will be to have the database on the same machine as
  the DHCPv6 server.  In this case, set the value to the empty string:
329
<screen>
330
"Dhcp6": { "lease-database": { <userinput>"host" : ""</userinput>, ... }, ... }
331
</screen>
332
333
334
  </para>
  <para>Finally, the credentials of the account under which the server will
  access the database should be set:
335
<screen>
336
"Dhcp6": { "lease-database": { <userinput>"user": "<replaceable>user-name</replaceable>"</userinput>,
337
                               <userinput>"password": "<replaceable>password</replaceable>"</userinput>,
338
339
                              ... },
           ... }
340
</screen>
341
342
343
344
  If there is no password to the account, set the password to the empty string
  "". (This is also the default.)</para>
</section>
</section>
345

346
347
348
<section id="dhcp6-interface-selection">
  <title>Interface selection</title>
  <para>The DHCPv6 server has to be configured to listen on specific network
349
  interfaces.  The simplest network interface configuration instructs the server to
350
351
  listen on all available interfaces:
  <screen>
352
353
354
355
356
357
358
"Dhcp6": {
    "interfaces-config": {
        "interfaces": [ <userinput>"*"</userinput> ]
    }
    ...
}
</screen>
359
360
361
  The asterisk plays the role of a wildcard and means "listen on all interfaces".
  However, it is usually a good idea to explicitly specify interface names:
  <screen>
362
363
364
365
366
367
368
369
"Dhcp6": {
    "interfaces-config": {
        "interfaces": [ <userinput>"eth1", "eth3"</userinput> ]
    },
    ...
}
  </screen>
</para>
370
  <para>It is possible to use wildcard interface name (asterisk) concurrently
371
  with the actual interface names:
372
  <screen>
373
374
375
376
377
378
379
"Dhcp6": {
    "interfaces-config": {
        "interfaces": [ <userinput>"eth1", "eth3", "*"</userinput> ]
    },
    ...
}
  </screen>
380
381
382
383
It is anticipated that this will form of usage only be used where it is desired to
temporarily override a list of interface names and listen on all interfaces.
  </para>
</section>
384
385
386
387

    <section id="ipv6-subnet-id">
      <title>IPv6 Subnet Identifier</title>
      <para>
388
        The subnet identifier is a unique number associated with a particular subnet.
389
        In principle, it is used to associate clients' leases with respective subnets.
390
        When the subnet identifier is not specified for a subnet being configured, it will
391
392
393
394
395
396
397
        be automatically assigned by the configuration mechanism. The identifiers
        are assigned from 1 and are monotonically increased for each subsequent
        subnet: 1, 2, 3 ....
      </para>
      <para>
       If there are multiple subnets configured with auto-generated identifiers and
       one of them is removed, the subnet identifiers may be renumbered. For example:
398
399
400
       if there are four subnets and the third is removed the last subnet will be assigned
       the identifier that the third subnet had before removal. As a result, the leases
       stored in the lease database for subnet 3 are now associated with
401
       subnet 4, which may have unexpected consequences. In the future it is planned
402
       to implement a mechanism to preserve auto-generated subnet ids upon removal
403
       of one of the subnets. Currently, the only remedy for this issue is to
404
       manually specify a unique subnet identifier for each subnet.
405
      </para>
406

407
      <para>
408
	The following configuration will assign the specified subnet
409
410
	identifier to the newly configured subnet:

411
412
413
414
415
416
417
418
419
420
421
422
	<screen>
"Dhcp6": {
    "subnet6": [
        "subnet": "2001:db8:1::/64",
        <userinput>"id": 1024</userinput>,
        ...
    ]
}
</screen>
	This identifier will not change for this subnet unless the "id" parameter is
	removed or set to 0. The value of 0 forces auto-generation of the subnet
	identifier.
423
      </para>
424
425
      <!-- @todo: describe whether database needs to be updated after changing
      id -->
426
427
428
429
430
    </section>

    <section id="dhcp6-unicast">
      <title>Unicast traffic support</title>
      <para>
431
        When the DHCPv6 server starts, by default it listens to the DHCP traffic
432
433
434
435
436
        sent to multicast address ff02::1:2 on each interface that it is
        configured to listen on (see <xref linkend="dhcp6-interface-selection"/>).
        In some cases it is useful to configure a server to handle incoming
        traffic sent to the global unicast addresses as well. The most common
        reason for that is to have relays send their traffic to the server
437
438
439
440
        directly. To configure the server to listen on a specific unicast address, the
        notation to specify interfaces has been extended.  An interface name can be
        optionally followed by a slash, followed by the global unicast address on which
        the server should listen. This will be done in addition to normal
441
442
        link-local binding + listening on ff02::1:2 address. The sample configuration
        below shows how to listen on 2001:db8::1 (a global address)
443
444
445
        configured on the eth1 interface.
      </para>
      <para>
446
447
 <screen>
"Dhcp6": {
448
449
450
    "interfaces-config": {
        "interfaces": [ <userinput>"eth1/2001:db8::1"</userinput> ]
    },
451
    ...
452
453
}
 </screen>
454

455
        This configuration will cause the server to listen on
456
457
458
459
        eth1 on link-local address, multicast group (ff02::1:2) and 2001:db8::1.
      </para>
      <para>
        It is possible to mix interface names, wildcards and interface name/addresses
460
        on the list of interfaces. It is not possible to specify more than one
461
462
463
464
465
        unicast address on a given interface.
      </para>
      <para>
        Care should be taken to specify proper unicast addresses. The server will
        attempt to bind to those addresses specified, without any additional checks.
466
467
        This approach is selected on purpose, so the software can be used to
        communicate over uncommon addresses if the administrator so desires.
468
469
470
471
472
473
474
475
476
477
478
479
480
481
      </para>
    </section>

    <section id="dhcp6-address-config">
      <title>Subnet and Address Pool</title>
      <para>
        The essential role of a DHCPv6 server is address assignment. For this,
        the server has to be configured with at least one subnet and one pool of dynamic
        addresses to be managed. For example, assume that the server
        is connected to a network segment that uses the 2001:db8:1::/64
        prefix. The Administrator of that network has decided that addresses from range
        2001:db8:1::1 to 2001:db8:1::ffff are going to be managed by the Dhcp6
        server. Such a configuration can be achieved in the following way:
        <screen>
482
483
484
485
486
487
"Dhcp6": {
    <userinput>"subnet6": [
       {
           "subnet": "2001:db8:1::/64",
           "pools": [
               {
488
                   "pool": "2001:db8:1::1-2001:db8:1::ffff"
489
490
491
492
493
494
495
               }
           ],
           ...
       }
    ]</userinput>
}</screen>

496
497
498
499
        Note that subnet is defined as a simple string, but the pool parameter
        is actually a list of pools: for this reason, the pool definition is
        enclosed in square brackets, even though only one range of addresses
        is specified.</para>
500
501

        <para>Each <command>pool</command> is a structure that contains the
502
        parameters that describe a single pool. Currently there is only one
503
504
505
506
        parameter, <command>pool</command>, which gives the range of addresses
        in the pool. Additional parameters will be added in future releases of
        Kea.</para>

507
508
        <para>It is possible to define more than one pool in a
        subnet: continuing the previous example, further assume that
509
        2001:db8:1:0:5::/80 should also be managed by the server. It could be written as
510
511
512
513
514
        2001:db8:1:0:5:: to 2001:db8:1::5:ffff:ffff:ffff, but typing so many 'f's
        is cumbersome. It can be expressed more simply as 2001:db8:1:0:5::/80. Both
        formats are supported by Dhcp6 and can be mixed in the pool list.
        For example, one could define the following pools:
        <screen>
515
516
517
518
519
"Dhcp6": {
    <userinput>"subnet6": [
    {
        "subnet": "2001:db8:1::/64",
        "pools": [
520
521
            { "pool": "2001:db8:1::1-2001:db8:1::ffff" },
            { "pool": "2001:db8:1:05::/80" }
522
523
524
525
526
        ]</userinput>,
        ...
    }
    ]
}</screen>
527
528
529
530
531
532
533
        The number of pools is not limited, but for performance reasons it is recommended to
        use as few as possible.
      </para>
      <para>
         The server may be configured to serve more than one subnet. To add a second subnet,
         use a command similar to the following:
        <screen>
534
535
536
537
538
"Dhcp6": {
    <userinput>"subnet6": [
    {
        "subnet": "2001:db8:1::/64",
        "pools": [
539
            { "pool": "2001:db8:1::1-2001:db8:1::ffff" }
540
541
542
543
544
        ]
    },
    {
        "subnet": "2001:db8:2::/64",
        "pools": [
545
            { "pool": "2001:db8:2::/64" }
546
547
548
549
550
551
        ]
    },
</userinput>
        ...
    ]
}</screen>
552
        In this example, we allow the server to
553
        dynamically assign all addresses available in the whole subnet. Although
554
        rather wasteful, it is certainly a valid configuration to dedicate the
555
        whole /64 subnet for that purpose. Note that the Kea server does not preallocate
556
        the leases, so there is no danger in using gigantic address pools.
557
558
559
      </para>
      <para>
        When configuring a DHCPv6 server using prefix/length notation, please pay
560
561
        attention to the boundary values. When specifying that the server can use
        a given pool, it will also be able to allocate the first (typically network
562
563
564
        address) address from that pool. For example for pool 2001:db8:2::/64 the
        2001:db8:2:: address may be assigned as well. If you want to avoid this,
        use the "min-max" notation.
565
566
567
568
569
570
571
      </para>
    </section>

    <section>
<!-- @todo: add real meat to the prefix delegation config this is just place holder stuff -->
      <title>Subnet and Prefix Delegation Pools</title>
      <para>
572
        Subnets may also be configured to delegate prefixes, as defined in
573
	    <ulink url="http://tools.ietf.org/html/rfc3633">RFC 3633</ulink>.
574
575
        A subnet may have one or more prefix delegation pools.  Each pool has
        a prefixed address, which is specified as a prefix and a prefix length,
576
        as well as a delegated prefix length. <command>delegated-len</command>
577
578
579
580
	    must not be shorter (that is it must be numerically greater or equal)
	    than <command>prefix-len</command>.
	    If both <command>delegated-len</command>
	    and <command>prefix-len</command> are equal, the server will be able to
581
582
	    delegate only one prefix. The delegated <command>prefix</command> does
        not have to match the <command>subnet</command> prefix.
583
584
585
      </para>
      <para> Below is a sample subnet configuration which enables prefix
      delegation for the subnet:
586
      <screen>
587
588
589
590
591
592
"Dhcp6": {
    "subnet6": [
        {
            "subnet": "2001:d8b:1::/64",
            <userinput>"pd-pools": [
                {
593
                    "prefix": "3000:1::",
594
595
596
597
598
599
600
601
                    "prefix-len": 64,
                    "delegated-len": 96
                }
            ]</userinput>
        }
    ],
    ...
}</screen>
602
603
604
605
606
607
      </para>
    </section>

    <section id="dhcp6-std-options">
      <title>Standard DHCPv6 options</title>
      <para>
608
609
        One of the major features of a DHCPv6 server is to provide configuration
        options to clients.  Although there are several options that require
610
        special behavior, most options are sent by the server only if the client
611
        explicitly requests them.  The following example shows how to
612
        configure DNS servers, which is one of the most frequently used
613
614
        options.  Numbers in the first column are added for easier reference and
        will not appear on screen.  Options specified in this way are considered
615
616
617
        global and apply to all configured subnets.

        <screen>
618
"Dhcp6": {
619
620
621
622
623
    "option-data": [
        {
           <userinput>"name": "dns-servers",
           "code": 23,
           "space": "dhcp6",
624
           "csv-format": true,
625
626
627
628
629
           "data": "2001:db8::cafe, 2001:db8::babe"</userinput>
        },
        ...
    ]
}
630
631
</screen>
      </para>
632

633
    <para>
634
635
      The <command>option-data></command> line creates a new entry in
      the option-data table.  This table contains
636
      information on all global options that the server is supposed to configure
637
      in all subnets.  The <command>name</command> line specifies the option name.
638
      (For a complete list
639
      of currently supported names, see <xref
640
      linkend="dhcp6-std-options-list"/>.)  The next line specifies the option code,
641
642
643
      which must match one of the values from that list. The line beginning with
      <command>space</command> specifies the option space, which must always be set
      to "dhcp6" as these are standard DHCPv6 options.  For other name spaces,
644
      including custom option spaces, see <xref
645
      linkend="dhcp6-option-spaces"/>. The next line specifies the format in
646
      which the data will be entered: use of CSV (comma separated values) is
647
648
      recommended. The <command>data</command> line gives the actual value to be sent to
      clients.  Data is specified as normal text, with values separated by
649
      commas if more than one value is allowed.
650
651
652
    </para>

    <para>
653
      Options can also be configured as hexadecimal values.  If "csv-format" is
654
      set to false, the option data must be specified as a string of hexadecimal
655
      numbers.  The
656
657
658
      following commands configure the DNS-SERVERS option for all
      subnets with the following addresses: 2001:db8:1::cafe and
      2001:db8:1::babe.
659
        <screen>
660
"Dhcp6": {
661
662
663
664
665
    "option-data": [
        {
           <userinput>"name": "dns-servers",
           "code": 23,
           "space": "dhcp6",
666
           "csv-format": false,
667
668
669
670
671
672
673
674
675
676
           "data": "2001 0DB8 0001 0000 0000 0000 0000 CAFE
                    2001 0DB8 0001 0000 0000 0000 0000 BABE"</userinput>
        },
        ...
    ]
}
</screen>

       The value for the setting of the "data" element is split across two
       lines in this document for clarity: when entering the command, the
677
       whole string should be entered on the same line.  Care should be taken
678
679
       to use proper encoding when using hexadecimal format as Kea's ability
       to validate data correctness in hexadecimal is limited.
680
681
      </para>

682
683
684
685
686
687
688
      <para>
        Most of the parameters in the "option-data" structure are optional and
        can be omitted in some circumstances as discussed in the
        <xref linkend="dhcp6-option-data-defaults"/>.
      </para>


689
690
691
692
693
694
695
696
697
698
699
700
701
702
    <para>
      It is possible to override options on a per-subnet basis.  If
      clients connected to most of your subnets are expected to get the
      same values of a given option, you should use global options: you
      can then override specific values for a small number of subnets.
      On the other hand, if you use different values in each subnet,
      it does not make sense to specify global option values
      (Dhcp6/option-data), rather you should set only subnet-specific values
      (Dhcp6/subnet[X]/option-data[Y]).
     </para>
     <para>
      The following commands override the global
      DNS servers option for a particular subnet, setting a single DNS
      server with address 2001:db8:1::3.
703
704
705
706
707
708
709
710
<screen>
"Dhcp6": {
    "subnet6": [
        {
            <userinput>"option-data": [
                {
                    "name": "dns-servers",
                    "code": 23,
Jeremy C. Reed's avatar
Jeremy C. Reed committed
711
                    "space": "dhcp6",
712
                    "csv-format": true,
713
714
715
716
717
718
719
720
721
722
723
                    "data": "2001:db8:1::3"
                },
                ...
            ]</userinput>,
            ...
        },
        ...
    ],
    ...
}
</screen>
724
725
726
727
728
729
730
731
732
733
734
735
736
    </para>

    <para>
      The currently supported standard DHCPv6 options are
      listed in <xref linkend="dhcp6-std-options-list"/>.
      The "Name" and "Code"
      are the values that should be used as a name in the option-data
      structures. "Type" designates the format of the data: the meanings of
      the various types is given in <xref linkend="dhcp-types"/>.
    </para>
    <para>
      Some options are designated as arrays, which means that more than one
      value is allowed in such an option. For example the option dns-servers
737
      allows the specification of more than one IPv6 address, allowing
738
      clients to obtain the addresses of multiple DNS servers.
739
740
741
742
743
744
745
746
747
748
749
750
751
752
    </para>

<!-- @todo: describe record types -->

      <para>
        The <xref linkend="dhcp6-custom-options"/> describes the configuration
        syntax to create custom option definitions (formats). It is generally not
        allowed to create custom definitions for standard options, even if the
        definition being created matches the actual option format defined in the
        RFCs. There is an exception from this rule for standard options for which
        Kea does not provide a definition yet. In order to use such options,
        a server administrator must create a definition as described in
        <xref linkend="dhcp6-custom-options"/> in the 'dhcp6' option space. This
        definition should match the option format described in the relevant
753
754
        RFC but the configuration mechanism would allow any option format as it has
        no means to validate the format at the moment.
755
756
757
758
759
760
761
762
      </para>


    <para>
      <table frame="all" id="dhcp6-std-options-list">
        <title>List of standard DHCPv6 options</title>
        <tgroup cols='4'>
        <colspec colname='name'/>
763
764
765
        <colspec colname='code' align='center'/>
        <colspec colname='type' align='center'/>
        <colspec colname='array' align='center'/>
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
        <thead>
          <row><entry>Name</entry><entry>Code</entry><entry>Type</entry><entry>Array?</entry></row>
        </thead>
        <tbody>
<!-- Our engine uses those options on its own, admin must not configure them on his own
<row><entry>clientid</entry><entry>1</entry><entry>binary</entry><entry>false</entry></row>
<row><entry>serverid</entry><entry>2</entry><entry>binary</entry><entry>false</entry></row>
<row><entry>ia-na</entry><entry>3</entry><entry>record</entry><entry>false</entry></row>
<row><entry>ia-ta</entry><entry>4</entry><entry>uint32</entry><entry>false</entry></row>
<row><entry>iaaddr</entry><entry>5</entry><entry>record</entry><entry>false</entry></row>
<row><entry>oro</entry><entry>6</entry><entry>uint16</entry><entry>true</entry></row> -->
<row><entry>preference</entry><entry>7</entry><entry>uint8</entry><entry>false</entry></row>

<!-- Our engine uses those options on its own, admin must not configure them on his own
<row><entry>elapsed-time</entry><entry>8</entry><entry>uint16</entry><entry>false</entry></row>
<row><entry>relay-msg</entry><entry>9</entry><entry>binary</entry><entry>false</entry></row>
<row><entry>auth</entry><entry>11</entry><entry>binary</entry><entry>false</entry></row>
<row><entry>unicast</entry><entry>12</entry><entry>ipv6-address</entry><entry>false</entry></row>
<row><entry>status-code</entry><entry>13</entry><entry>record</entry><entry>false</entry></row>
<row><entry>rapid-commit</entry><entry>14</entry><entry>empty</entry><entry>false</entry></row>
<row><entry>user-class</entry><entry>15</entry><entry>binary</entry><entry>false</entry></row>
<row><entry>vendor-class</entry><entry>16</entry><entry>record</entry><entry>false</entry></row>
<row><entry>vendor-opts</entry><entry>17</entry><entry>uint32</entry><entry>false</entry></row>
<row><entry>interface-id</entry><entry>18</entry><entry>binary</entry><entry>false</entry></row>
<row><entry>reconf-msg</entry><entry>19</entry><entry>uint8</entry><entry>false</entry></row>
<row><entry>reconf-accept</entry><entry>20</entry><entry>empty</entry><entry>false</entry></row> -->
<row><entry>sip-server-dns</entry><entry>21</entry><entry>fqdn</entry><entry>true</entry></row>
<row><entry>sip-server-addr</entry><entry>22</entry><entry>ipv6-address</entry><entry>true</entry></row>
<row><entry>dns-servers</entry><entry>23</entry><entry>ipv6-address</entry><entry>true</entry></row>
<row><entry>domain-search</entry><entry>24</entry><entry>fqdn</entry><entry>true</entry></row>
<!-- <row><entry>ia-pd</entry><entry>25</entry><entry>record</entry><entry>false</entry></row> -->
<!-- <row><entry>iaprefix</entry><entry>26</entry><entry>record</entry><entry>false</entry></row> -->
<row><entry>nis-servers</entry><entry>27</entry><entry>ipv6-address</entry><entry>true</entry></row>
<row><entry>nisp-servers</entry><entry>28</entry><entry>ipv6-address</entry><entry>true</entry></row>
<row><entry>nis-domain-name</entry><entry>29</entry><entry>fqdn</entry><entry>true</entry></row>
<row><entry>nisp-domain-name</entry><entry>30</entry><entry>fqdn</entry><entry>true</entry></row>
<row><entry>sntp-servers</entry><entry>31</entry><entry>ipv6-address</entry><entry>true</entry></row>
<row><entry>information-refresh-time</entry><entry>32</entry><entry>uint32</entry><entry>false</entry></row>
<row><entry>bcmcs-server-dns</entry><entry>33</entry><entry>fqdn</entry><entry>true</entry></row>
<row><entry>bcmcs-server-addr</entry><entry>34</entry><entry>ipv6-address</entry><entry>true</entry></row>
<row><entry>geoconf-civic</entry><entry>36</entry><entry>record</entry><entry>false</entry></row>
<row><entry>remote-id</entry><entry>37</entry><entry>record</entry><entry>false</entry></row>
<row><entry>subscriber-id</entry><entry>38</entry><entry>binary</entry><entry>false</entry></row>
<row><entry>client-fqdn</entry><entry>39</entry><entry>record</entry><entry>false</entry></row>
<row><entry>pana-agent</entry><entry>40</entry><entry>ipv6-address</entry><entry>true</entry></row>
<row><entry>new-posix-timezone</entry><entry>41</entry><entry>string</entry><entry>false</entry></row>
<row><entry>new-tzdb-timezone</entry><entry>42</entry><entry>string</entry><entry>false</entry></row>
<row><entry>ero</entry><entry>43</entry><entry>uint16</entry><entry>true</entry></row>
<row><entry>lq-query</entry><entry>44</entry><entry>record</entry><entry>false</entry></row>
<row><entry>client-data</entry><entry>45</entry><entry>empty</entry><entry>false</entry></row>
<row><entry>clt-time</entry><entry>46</entry><entry>uint32</entry><entry>false</entry></row>
<row><entry>lq-relay-data</entry><entry>47</entry><entry>record</entry><entry>false</entry></row>
<row><entry>lq-client-link</entry><entry>48</entry><entry>ipv6-address</entry><entry>true</entry></row>
        </tbody>
        </tgroup>
      </table>
    </para>
    </section>

    <section id="dhcp6-custom-options">
      <title>Custom DHCPv6 options</title>
      <para>It is also possible to define options other than the standard ones.
      Assume that we want to define a new DHCPv6 option called "foo" which will have
      code 100 and will convey a single unsigned 32 bit integer value. We can define
      such an option by using the following commands:
831
832
833
834
835
836
837
<screen>
"Dhcp6": {
    "option-def": [
        {
            <userinput>"name": "foo",
            "code": 100,
            "type": "uint32",
838
            "array": false,
839
840
841
842
843
844
845
846
847
848
849
            "record-types": "",
            "space": "dhcp6",
            "encapsulate": ""</userinput>
        }, ...
    ],
    ...
}
</screen>
      The "false" value of the "array" parameter determines that the option does
      NOT comprise an array of "uint32" values but rather a single value.  Two
      other parameters have been left blank: "record-types" and "encapsulate".
850
851
852
853
854
      The former specifies the comma separated list of option data fields if the
      option comprises a record of data fields. The "record-fields" value should
      be non-empty if the "type" is set to "record". Otherwise it must be left
      blank. The latter parameter specifies the name of the option space being
      encapsulated by the particular option. If the particular option does not
855
856
857
      encapsulate any option space it should be left blank.  Note that the above
      set of comments define the format of the new option and do not set its
      values.
858
859
860
861
      </para>
      <para>Once the new option format is defined, its value is set
      in the same way as for a standard option. For example the following
      commands set a global value that applies to all subnets.
862
863
864
865
<screen>
"Dhcp6": {
    "option-data": [
        {
866
            <userinput>"name": "foo",
867
868
            "code": 100,
            "space": "dhcp6",
869
            "csv-format": true,
870
871
872
873
874
875
            "data": "12345"</userinput>
        }, ...
    ],
    ...
}
</screen>
876
877
878
879
880
881
882
883
884
885
886
887
      </para>

      <para>New options can take more complex forms than simple use of
      primitives (uint8, string, ipv6-address etc): it is possible to
      define an option comprising a number of existing primitives.
      </para>
      <para>
      Assume we want to define a new option that will consist of an IPv6
      address, followed by an unsigned 16 bit integer, followed by a
      boolean value, followed by a text string. Such an option could
      be defined in the following way:
<screen>
888
889
890
891
892
893
894
"Dhcp6": {
    "option-def": [
        {
            <userinput>"name": "bar",
            "code": 101,
            "space": "dhcp6",
            "type": "record",
895
            "array": false,
896
897
898
899
900
901
            "record-types": "ipv4-address, uint16, boolean, string",
            "encapsulate": ""</userinput>
        }, ...
    ],
    ...
}
902
903
904
905
906
907
908
909
</screen>
      The "type" is set to "record" to indicate that the option contains
      multiple values of different types.  These types are given as a comma-separated
      list in the "record-types" field and should be those listed in <xref linkend="dhcp-types"/>.
      </para>
      <para>
      The values of the option are set as follows:
<screen>
910
911
912
913
914
915
"Dhcp6": {
    "option-data": [
        {
            <userinput>"name": "bar",
            "space": "dhcp6",
            "code": 101,
916
            "csv-format": true,
917
918
919
920
921
            "data": "2001:db8:1::10, 123, false, Hello World"</userinput>
        }
    ],
    ...
}</screen>
922
923
924
925

      <command>csv-format</command> is set <command>true</command> to indicate
      that the <command>data</command> field comprises a command-separated list
      of values.  The values in the "data" must correspond to the types set in
926
927
      the "record-types" field of the option definition.
      </para>
928

929
      <note>
930
       <para>In the general case, boolean values are specified as <command>true</command> or
931
932
933
934
935
       <command>false</command>, without quotes. Some specific boolean parameters may
       accept also <command>"true"</command>, <command>"false"</command>,
       <command>0</command>, <command>1</command>, <command>"0"</command> and
       <command>"1"</command>. Future Kea versions will accept all those values
       for all boolean parameters.</para>
936
      </note>
937

938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
    </section>

    <section id="dhcp6-vendor-opts">
      <title>DHCPv6 vendor specific options</title>
      <para>
      Currently there are three option spaces defined: dhcp4 (to be used
      in DHCPv4 daemon) and dhcp6 (for the DHCPv6 daemon); there is also
      vendor-opts-space, which is empty by default, but options can be
      defined in it. Those options are called vendor-specific information
      options. The following examples show how to define an option "foo"
      with code 1 that consists of an IPv6 address, an unsigned 16 bit integer
      and a string. The "foo" option is conveyed in a vendor specific
      information option. This option comprises a single uint32 value
      that is set to "12345". The sub-option "foo" follows the data
      field holding this value.
      <screen>
954
955
956
957
958
959
960
"Dhcp6": {
    "option-def": [
        {
            <userinput>"name": "foo",
            "code": 1,
            "space": "vendor-encapsulated-options-space",
            "type": "record",
961
            "array": false,
962
963
964
965
966
967
968
            "record-types": "ipv6-address, uint16, string",
            "encapsulates": ""</userinput>
        }
    ],
    ...
}</screen>
     (Note that the option space is set to <command>vendor-opts-space</command>.)
969
970
     Once the option format is defined, the next step is to define actual values
     for that option:
971
972
973
974
975
976
977
<screen>
"Dhcp6": {
    "option-data": [
        {
            <userinput>"name": "foo"
            "space": "vendor-encapsulated-options-space",
            "code": 1,
978
            "csv-format": true,
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
            "data": "2001:db8:1::10, 123, Hello World"</userinput>
        },
        ...
    ],
    ...
}</screen>
    We should also define values for the vendor-opts, that will convey our
    option foo.
<screen>
"Dhcp6": {
    "option-data": [
        ...,
        {
            <userinput>"name": "vendor-encapsulated-options"
            "space": "dhcp6",
            "code": 17,
995
            "csv-format": true,
996
            "data": "12345"</userinput>
997
998
999
1000
        }
    ],
    ...
}</screen>
1001
1002
1003
1004
1005
1006
1007
      </para>
    </section>

    <section id="dhcp6-option-spaces">
      <title>Nested DHCPv6 options (custom option spaces)</title>
      <para>It is sometimes useful to define completely new option
      spaces.  This is useful if the user wants his new option to
1008
      convey sub-options that use a separate numbering scheme, for
1009
1010
1011
1012
      example sub-options with codes 1 and 2. Those option codes
      conflict with standard DHCPv6 options, so a separate option
      space must be defined.
      </para>
1013
1014
1015
      <para>Note that it is not required to create a new option space when
      defining sub-options for a standard option because it is
      created by default if the standard option is meant to convey
1016
1017
1018
1019
1020
1021
1022
      any sub-options (see <xref linkend="dhcp6-vendor-opts"/>).
      </para>
      <para>
      Assume that we want to have a DHCPv6 option called "container"
      with code 102 that conveys two sub-options with codes 1 and 2.
      First we need to define the new sub-options:
<screen>
1023
1024
1025
1026
1027
1028
1029
1030
"Dhcp6": {
    "option-def": [
        {
            <userinput>"name": "subopt1",
            "code": 1,
            "space": "isc",
            "type": "ipv6-address".
            "record-types": "",
1031
            "array": false,
1032
            "encapsulate": ""</userinput>
1033
1034
        },
        {
1035
            <userinput>"name": "subopt2",
1036
1037
1038
1039
            "code": 2,
            "space": "isc",
            "type": "string",
            "record-types": "",
1040
            "array": false
1041
1042
1043
1044
1045
            "encapsulate": ""</userinput>
        }
    ],
    ...
}</screen>
1046
1047
1048
1049
1050
1051
1052
    Note that we have defined the options to belong to a new option space
    (in this case, "isc").
    </para>
    <para>
The next step is to define a regular DHCPv6 option and specify that it
should include options from the isc option space:
<screen>
1053
"Dhcp6": {
1054
1055
1056
1057
1058
1059
1060
    "option-def": [
        ...,
        {
            <userinput>"name": "container",
            "code": 102,
            "space": "dhcp6",
            "type": "empty",
1061
            "array": false,
1062
1063
1064
1065
1066
1067
1068
1069
1070
            "record-types": "",
            "encapsulate": "isc"</userinput>
        }
    ],
    ...
}</screen>

    The name of the option space in which the sub-options are defined is set in
    the <command>encapsulate</command> field. The <command>type</command> field
1071
1072
    is set to <command>empty</command> which limits this option to only carrying
    data in sub-options.
1073
1074
1075
1076
    </para>
    <para>
    Finally, we can set values for the new options:
<screen>
1077
1078
1079
1080
1081
1082
"Dhcp6": {
    "option-data": [
        {
            <userinput>"name": "subopt1",
            "space": "isc",
            "code": 1,
1083
            "csv-format": true,
1084
1085
1086
1087
1088
1089
            "data": "2001:db8::abcd"</userinput>
        },
        }
            <userinput>"name": "subopt2",
            "space": "isc",
            "code": 2,
1090
            "csv-format": true,
1091
1092
1093
1094
1095
1096
            "data": "Hello world"</userinput>
        },
        {
            <userinput>"name": "container",
            "space": "dhcp6",
            "code": 102,
1097
            "csv-format": true,
1098
1099
1100
1101
1102
            "data": ""</userinput>
        }
    ],
    ...
}
1103
</screen>
1104

1105
1106
    Even though the "container" option does not carry any data except
    sub-options, the "data" field must be explicitly set to an empty value.
1107
    This is required because in the current version of Kea, the default
1108
1109
1110
    configuration values are not propagated to the configuration parsers: if the
    "data" is not set the parser will assume that this parameter is not
    specified and an error will be reported.
1111
    </para>
1112
    
1113
    <para>Note that it is possible to create an option which carries some data
1114
1115
1116
1117
1118
    in addition to the sub-options defined in the encapsulated option space.
    For example, if the "container" option from the previous example was
    required to carry an uint16 value as well as the sub-options, the "type"
    value would have to be set to "uint16" in the option definition. (Such an
    option would then have the following data structure: DHCP header, uint16
1119
1120
    value, sub-options.) The value specified with the "data" parameter &mdash; which
    should be a valid integer enclosed in quotes, e.g. "123" &mdash; would then be
1121
    assigned to the uint16 field in the "container" option.
1122
1123
1124
    </para>
    </section>

1125
    <section id="dhcp6-option-data-defaults">
1126
      <title>Unspecified parameters for DHCPv6 option configuration</title>
1127
      <para>In many cases it is not required to specify all parameters for
1128
      an option configuration and the default values can be used. However, it is
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
      important to understand the implications of not specifing some of them
      as it may result in configuration errors. The list below explains
      the behavior of the server when a particular parameter is not explicitly
      specified:

      <itemizedlist>
        <listitem>
          <simpara><command>name</command> - the server requires an option name or
          option code to identify an option. If this parameter is unspecified, the
          option code must be specified.
          </simpara>
        </listitem>

        <listitem>
          <simpara><command>code</command> - the server requires an option name or
          option code to identify an option. This parameter may be left unspecified if
          the <command>name</command> parameter is specified. However, this also
          requires that the particular option has its definition (it is either a
          standard option or an administrator created a definition for the option
          using an 'option-def' structure), as the option definition associates an
          option with a particular name. It is possible to configure an option
          for which there is no definition (unspecified option format).
          Configuration of such options requires the use of option code.
          </simpara>
        </listitem>

        <listitem>
          <simpara><command>space</command> - if the option space is unspecified it
          will default to 'dhcp6' which is an option space holding DHCPv6 standard
          options.
          </simpara>
        </listitem>

        <listitem>
          <simpara><command>data</command> - if the option data is unspecified it
          defaults to an empty value. The empty value is mostly used for the
          options which have no payload (boolean options), but it is legal to specify
          empty values for some options which carry variable length data and which
          spec allows for the length of 0. For such options, the data parameter
          may be omitted in the configuration.</simpara>
        </listitem>

        <listitem>
          <simpara><command>csv-format</command> - if this value is not specified
          and the definition for the particular option exists, the server will assume
          that the option data is specified as a list of comma separated values to be
          assigned to individual fields of the DHCP option. If the definition
          does not exist for this option, the server will assume that the data
          parameter contains the option payload in the binary format (represented
          as a string of hexadecimal digits). Note that not specifying this
          parameter doesn't imply that it defaults to a fixed value, but
          the configuration data interpretation also depends on the presence
          of the option definition. An administrator must be aware if the
          definition for the particular option exists when this parameter
          is not specified. It is generally recommended to not specify this
          parameter only for the options for which the definition exists, e.g.
          standard options. Setting <command>csv-format</command> to an explicit
          value will cause the server to strictly check the format of the option
          data specified.
          </simpara>
        </listitem>
      </itemizedlist>
      </para>

    </section>

1195
1196
1197
1198
1199
    <section id="dhcp6-config-subnets">
      <title>IPv6 Subnet Selection</title>
      <para>
        The DHCPv6 server may receive requests from local (connected to the
        same subnet as the server) and remote (connecting via relays) clients.
1200
1201
        As the server may have many subnet configurations defined, it must select
        an appropriate subnet for a given request.
1202
1203
      </para>
      <para>
1204
1205
        The server can not assume which of the configured subnets are local. In IPv4
        it is possible as there is a reasonable expectation that the
1206
1207
        server will have a (global) IPv4 address configured on the interface,
        and can use that information to detect whether a subnet is local or
1208
1209
        not. That assumption is not true in IPv6, the DHCPv6 server must be able
        to operate while only having link-local addresses. Therefore an optional
1210
1211
        &quot;interface&quot; parameter is available within a subnet definition
        to designate that a given subnet is local, i.e. reachable directly over
1212
        the specified interface. For example the server that is intended to serve
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
        a local subnet over eth0 may be configured as follows:
	<screen>
"Dhcp6": {
    "subnet6": [
        {
            "subnet": "2001:db8:beef::/48",
            "pools": [
                 {
                     "pool": "2001:db8:beef::/48"
                 }
             ],
            <userinput>"interface": "eth0"</userinput>
        }
    ],
    ...
}
1229
1230
1231
1232
1233
1234
1235
1236
</screen>
        </para>
      </section>

      <section id="dhcp6-relays">
        <title>DHCPv6 Relays</title>
        <para>
          A DHCPv6 server with multiple subnets defined must select the
1237
          appropriate subnet when it receives a request from a client.  For clients
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
          connected via relays, two mechanisms are used:
        </para>
        <para>
          The first uses the linkaddr field in the RELAY_FORW message. The name
          of this field is somewhat misleading in that it does not contain a link-layer
          address: instead, it holds an address (typically a global address) that is
          used to identify a link. The DHCPv6 server checks if the address belongs
          to a defined subnet and, if it does, that subnet is selected for the client's
          request.
        </para>
        <para>
          The second mechanism is based on interface-id options. While forwarding a client's
          message, relays may insert an interface-id option into the message that
          identifies the interface on the relay that received the message. (Some
          relays allow configuration of that parameter, but it is sometimes
          hardcoded and may range from the very simple (e.g. "vlan100") to the very cryptic:
          one example seen on real hardware was "ISAM144|299|ipv6|nt:vp:1:110"). The
          server can use this information to select the appropriate subnet.
          The information is also returned to the relay which then knows the
          interface to use to transmit the response to the client. In order for
          this to work successfully, the relay interface IDs must be unique within
          the network and the server configuration must match those values.
        </para>
        <para>
          When configuring the DHCPv6 server, it should be noted that two
          similarly-named parameters can be configured for a subnet:
          <itemizedlist>
            <listitem><simpara>
              "interface" defines which local network interface can be used
              to access a given subnet.
            </simpara></listitem>
            <listitem><simpara>
              "interface-id" specifies the content of the interface-id option
              used by relays to identify the interface on the relay to which
              the response packet is sent.
            </simpara></listitem>
          </itemizedlist>
          The two are mutually exclusive: a subnet cannot be both reachable locally
          (direct traffic) and via relays (remote traffic). Specifying both is a
          configuration error and the DHCPv6 server will refuse such a configuration.
        </para>

        <para>
          To specify interface-id with value "vlan123", the following commands can
          be used:
          <screen>
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
"Dhcp6": {
    "subnet6": [
        {
            "subnet": "2001:db8:beef::/48",
            "pools": [
                 {
                     "pool": "2001:db8:beef::/48"
                 }
             ],
            <userinput>"interface-id": "vlan123"</userinput>
        }
    ],
    ...
}
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
</screen>
        </para>
      </section>

    <section id="dhcp6-client-classifier">
      <title>Client Classification in DHCPv6</title>
      <note>
      <para>
        DHCPv6 server has been extended to support limited client classification.
        Although the current capability is modest, it is expected to be expanded
        in the future. It is envisaged that the majority of client classification
        extensions will be using hooks extensions.
      </para>
      </note>
      <para>In certain cases it is useful to differentiate between different types
      of clients and treat them differently. The process of doing classification
1314
      is conducted in two steps. The first step is to assess an incoming packet and
1315
1316
      assign it to zero or more classes. This classification is currently simple,
      but is expected to grow in capability soon. Currently the server checks whether
1317
1318
      the incoming packet includes vendor class option (16). If it has, the content
      of that option is prepended with &quot;VENDOR_CLASS_&quot; then it is interpreted as a
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
      class. For example, modern cable modems will send this option with value
      &quot;docsis3.0&quot; and as a result the packet will belong to class
      &quot;VENDOR_CLASS_docsis3.0&quot;.
      </para>

      <para>It is envisaged that the client classification will be used for changing
      behavior of almost any part of the DHCP engine processing, including assigning
      leases from different pools, assigning different option (or different values of
      the same options) etc. For now, there is only one mechanism that is taking
      advantage of client classification: subnet selection.</para>

      <para>
        Kea can be instructed to limit access to given subnets based on class information.
        This is particularly useful for cases where two types of devices share the
        same link and are expected to be served from two different subnets. The
        primary use case for such a scenario are cable networks. There are two
1335
        classes of devices: the cable modem itself, which should be handed a lease
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
        from subnet A and all other devices behind modems that should get a lease
        from subnet B. That segregation is essential to prevent overly curious
        users from playing with their cable modems. For details on how to set up
        class restrictions on subnets, see <xref linkend="dhcp6-subnet-class"/>.
      </para>

    </section>

    <section id="dhcp6-subnet-class">
      <title>Limiting access to IPv6 subnet to certain classes</title>
      <para>
1347
        In certain cases it beneficial to restrict access to certain subnets
1348
        only to clients that belong to a given class. For details on client
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
        classes, see <xref linkend="dhcp6-client-classifier"/>. This is an
        extension of a previous example from <xref linkend="dhcp6-address-config"/>.

        Let's assume that the server is connected to a network segment that uses
        the 2001:db8:1::/64 prefix. The Administrator of that network has
        decided that addresses from range 2001:db8:1::1 to 2001:db8:1::ffff are
        going to be managed by the Dhcp6 server. Only clients belonging to the
        eRouter1.0 client class are allowed to use that pool. Such a
        configuration can be achieved in the following way:

        <screen>
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
"Dhcp6": {
    "subnet6": [
        {
            "subnet": "2001:db8:1::/64",
            "pools": [
                 {
                     "pool": "2001:db8:1::-2001:db8:1::ffff"
                 }
             ],
            <userinput>"client-class": "VENDOR_CLASS_eRouter1.0"</userinput>
        }
    ],
    ...
}
</screen>
1375
1376
1377
      </para>

      <para>
1378
        Care should be taken with client classification as it is easy for
1379
1380
1381
1382
1383
1384
1385
1386
        clients that do not meet class criteria to be denied any service altogether.
      </para>
    </section>


    <section id="dhcp6-ddns-config">
      <title>Configuring DHCPv6 for DDNS</title>
      <para>
1387
      As mentioned earlier, kea-dhcp6 can be configured to generate requests to
1388
      the DHCP-DDNS server (referred to here as "D2") to update
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
      DNS entries.  These requests are known as NameChangeRequests or NCRs.
      Each NCR contains the following information:
      <orderedlist>
      <listitem><para>
      Whether it is a request to add (update) or remove DNS entries
      </para></listitem>
      <listitem><para>
      Whether the change requests forward DNS updates (AAAA records), reverse
      DNS updates (PTR records), or both.
      </para></listitem>
      <listitem><para>
      The FQDN, lease address, and DHCID
      </para></listitem>
      </orderedlist>
      The parameters controlling the generation of NCRs for submission to D2
1404
      are contained in the "dhcp-ddns" section of kea-dhcp6
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
      configuration. The mandatory parameters for the DHCP DDNS configuration
      are <command>enable-updates</command> which is unconditionally
      required, and <command>qualifying-suffix</command> which has no
      default value and is required when <command>enable-updates</command>
      is set to <command>true</command>.

      The two (disabled and enabled) minimal DHCP DDNS configurations are:
<screen>
"Dhcp6": {
    "dhcp-ddns": {
        <userinput>"enable-updates": false</userinput>
    },
    ...
}
</screen>
      and for example:
1421
<screen>
1422
1423
"Dhcp6": {
    "dhcp-ddns": {
1424
        <userinput>"enable-updates": true,
1425
        "qualifying-suffix": "example."</userinput>
1426
1427
1428
    },
    ...
}
1429
</screen>
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466

      The default values for the "dhcp-ddns" section are as follows:
      <itemizedlist>
      <listitem><simpara>
      <command>"server-ip": "127.0.0.1"</command>
      </simpara></listitem>
      <listitem><simpara>
      <command>"server-port": 53001</command>
      </simpara></listitem>
      <listitem><simpara>
      <command>"sender-ip": ""</command>
      </simpara></listitem>
      <listitem><simpara>
      <command>"sender-port": 0</command>
      </simpara></listitem>
      <listitem><simpara>
      <command>"max-queue-size": 1024</command>
      </simpara></listitem>
      <listitem><simpara>
      <command>"ncr-protocol": "UDP"</command>
      </simpara></listitem>
      <listitem><simpara>
      <command>"ncr-format": "JSON"</command>
      </simpara></listitem>
      <listitem><simpara>
      <command>"override-no-update": false</command>
      </simpara></listitem>
      <listitem><simpara>
      <command>"override-client-update": false</command>
      </simpara></listitem>
      <listitem><simpara>
      <command>"replace-client-name": false</command>
      </simpara></listitem>
      <listitem><simpara>
      <command>"generated-prefix": "myhost"</command>
      </simpara></listitem>
      </itemizedlist>
1467
      </para>
1468
1469


1470
1471
1472
      <section id="dhcpv6-d2-io-config">
      <title>DHCP-DDNS Server Connectivity</title>
      <para>
1473
1474
      In order for NCRs to reach the D2 server, kea-dhcp6 must be able
      to communicate with it.  kea-dhcp6 uses the following configuration
1475
      parameters to control how it communications with D2:
1476
1477
1478
1479
1480
1481
1482
1483
      <itemizedlist>
      <listitem><simpara>
      <command>enable-updates</command> - determines whether or not kea-dhcp6 will
      generate NCRs.  If missing, this value is assumed to be false hence DDNS updates
      are disabled.  To enable DDNS updates set this value to true:
      </simpara></listitem>
      <listitem><simpara>
      <command>server-ip</command> - IP address on which D2 listens for requests. The default is
1484
1485
      the local loopback interface at address 127.0.0.1. You may specify
      either an IPv4 or IPv6 address.
1486
1487
1488
      </simpara></listitem>
      <listitem><simpara>
      <command>server-port</command> - port on which D2 listens for requests.  The default value
1489
      is 53001.
1490
1491
1492
      </simpara></listitem>
      <listitem><simpara>
      <command>sender-ip</command> - IP address which kea-dhcp6 should use to send requests to D2.
1493
      The default value is blank which instructs kea-dhcp6 to select a suitable
1494
      address.
1495
1496
1497
      </simpara></listitem>
      <listitem><simpara>
      <command>sender-port</command> - port which kea-dhcp6 should use to send requests to D2. The
1498
      default value of 0 instructs kea-dhcp6 to select a suitable port.
1499
1500
1501
      </simpara></listitem>
      <listitem><simpara>
      <command>max-queue-size</command> - maximum number of requests allowed to queue waiting to
1502
1503
1504
1505
      be sent to D2. This value guards against requests accumulating
      uncontrollably if they are being generated faster than they can be
      delivered.  If the number of requests queued for transmission reaches
      this value, DDNS updating will be turned off until the queue backlog has
1506
      been sufficiently reduced.  The intent is to allow kea-dhcp6 to
1507
      continue lease operations.  The default value is 1024.
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
      </simpara></listitem>
      <listitem><simpara>
      <command>ncr-format</command> - Socket protocol use when sending requests to D2.  Currently
      only UDP is supported.  TCP may be available in an upcoming release.
      </simpara></listitem>
      <listitem><simpara>
      <command>ncr-protocol</command> - Packet format to use when sending requests to D2.
      Currently only JSON format is supported.  Other formats may be available
      in future releases.
      </simpara></listitem>
      </itemizedlist>
1519
      By default, kea-dhcp-ddns is assumed to running on the same machine as kea-dhcp6, and
1520
1521
1522
      all of the default values mentioned above should be sufficient.
      If, however, D2 has been configured to listen on a different address or
      port, these values must altered accordingly. For example, if D2 has been
1523
      configured to listen on 2001:db8::5 port 900, the following commands
1524
1525