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9e4abcb5 SK |
1 | .TH DNSMASQ 8 |
2 | .SH NAME | |
3 | dnsmasq \- A lightweight DHCP and caching DNS server. | |
4 | .SH SYNOPSIS | |
5 | .B dnsmasq | |
6 | .I [OPTION]... | |
7 | .SH "DESCRIPTION" | |
8 | .BR dnsmasq | |
34d0a36a | 9 | is a lightweight DNS, TFTP, PXE, router advertisement and DHCP server. It is intended to provide |
5aabfc78 | 10 | coupled DNS and DHCP service to a LAN. |
9e4abcb5 SK |
11 | .PP |
12 | Dnsmasq accepts DNS queries and either answers them from a small, local, | |
13 | cache or forwards them to a real, recursive, DNS server. It loads the | |
14 | contents of /etc/hosts so that local hostnames | |
15 | which do not appear in the global DNS can be resolved and also answers | |
ee415867 SK |
16 | DNS queries for DHCP configured hosts. It can also act as the |
17 | authoritative DNS server for one or more domains, allowing local names | |
18 | to appear in the global DNS. It can be configured to do DNSSEC | |
19 | validation. | |
9e4abcb5 | 20 | .PP |
73a08a24 SK |
21 | The dnsmasq DHCP server supports static address assignments and multiple |
22 | networks. It automatically | |
3be34541 | 23 | sends a sensible default set of DHCP options, and can be configured to |
f2621c7f | 24 | send any desired set of DHCP options, including vendor-encapsulated |
1b7ecd11 | 25 | options. It includes a secure, read-only, |
34d0a36a | 26 | TFTP server to allow net/PXE boot of DHCP hosts and also supports BOOTP. The PXE support is full featured, and includes a proxy mode which supplies PXE information to clients whilst DHCP address allocation is done by another server. |
9e4abcb5 | 27 | .PP |
81925ab7 SK |
28 | The dnsmasq DHCPv6 server provides the same set of features as the |
29 | DHCPv4 server, and in addition, it includes router advertisements and | |
30 | a neat feature which allows nameing for clients which use DHCPv4 and | |
834f36fe | 31 | stateless autoconfiguration only for IPv6 configuration. There is support for doing address allocation (both DHCPv6 and RA) from subnets which are dynamically delegated via DHCPv6 prefix delegation. |
34d0a36a SK |
32 | .PP |
33 | Dnsmasq is coded with small embedded systems in mind. It aims for the smallest possible memory footprint compatible with the supported functions, and allows uneeded functions to be omitted from the compiled binary. | |
9e4abcb5 SK |
34 | .SH OPTIONS |
35 | Note that in general missing parameters are allowed and switch off | |
832af0ba | 36 | functions, for instance "--pid-file" disables writing a PID file. On |
33820b7e SK |
37 | BSD, unless the GNU getopt library is linked, the long form of the |
38 | options does not work on the command line; it is still recognised in | |
39 | the configuration file. | |
9e4abcb5 | 40 | .TP |
7622fc06 SK |
41 | .B --test |
42 | Read and syntax check configuration file(s). Exit with code 0 if all | |
43 | is OK, or a non-zero code otherwise. Do not start up dnsmasq. | |
44 | .TP | |
9e4abcb5 SK |
45 | .B \-h, --no-hosts |
46 | Don't read the hostnames in /etc/hosts. | |
47 | .TP | |
48 | .B \-H, --addn-hosts=<file> | |
49 | Additional hosts file. Read the specified file as well as /etc/hosts. If -h is given, read | |
fd9fa481 | 50 | only the specified file. This option may be repeated for more than one |
7622fc06 | 51 | additional hosts file. If a directory is given, then read all the files contained in that directory. |
9e4abcb5 | 52 | .TP |
3d04f463 SK |
53 | .B --hostsdir=<path> |
54 | Read all the hosts files contained in the directory. New or changed files | |
55 | are read automatically. See --dhcp-hostsdir for details. | |
56 | .TP | |
832af0ba SK |
57 | .B \-E, --expand-hosts |
58 | Add the domain to simple names (without a period) in /etc/hosts | |
1f15b81d SK |
59 | in the same way as for DHCP-derived names. Note that this does not |
60 | apply to domain names in cnames, PTR records, TXT records etc. | |
832af0ba | 61 | .TP |
9e4abcb5 SK |
62 | .B \-T, --local-ttl=<time> |
63 | When replying with information from /etc/hosts or the DHCP leases | |
64 | file dnsmasq by default sets the time-to-live field to zero, meaning | |
c72daea8 | 65 | that the requester should not itself cache the information. This is |
9e4abcb5 SK |
66 | the correct thing to do in almost all situations. This option allows a |
67 | time-to-live (in seconds) to be given for these replies. This will | |
68 | reduce the load on the server at the expense of clients using stale | |
69 | data under some circumstances. | |
70 | .TP | |
824af85b SK |
71 | .B --neg-ttl=<time> |
72 | Negative replies from upstream servers normally contain time-to-live | |
73 | information in SOA records which dnsmasq uses for caching. If the | |
74 | replies from upstream servers omit this information, dnsmasq does not | |
75 | cache the reply. This option gives a default value for time-to-live | |
76 | (in seconds) which dnsmasq uses to cache negative replies even in | |
77 | the absence of an SOA record. | |
78 | .TP | |
8ef5ada2 SK |
79 | .B --max-ttl=<time> |
80 | Set a maximum TTL value that will be handed out to clients. The specified | |
81 | maximum TTL will be given to clients instead of the true TTL value if it is | |
82 | lower. The true TTL value is however kept in the cache to avoid flooding | |
83 | the upstream DNS servers. | |
84 | .TP | |
1d860415 SK |
85 | .B --max-cache-ttl=<time> |
86 | Set a maximum TTL value for entries in the cache. | |
87 | .TP | |
28de3876 R |
88 | .B --min-cache-ttl=<time> |
89 | Extend short TTL values to the time given when caching them. Note that | |
90 | artificially extending TTL values is in general a bad idea, do not do it | |
91 | unless you have a good reason, and understand what you are doing. | |
92 | Dnsmasq limits the value of this option to one hour, unless recompiled. | |
93 | .TP | |
333b2ceb SK |
94 | .B --auth-ttl=<time> |
95 | Set the TTL value returned in answers from the authoritative server. | |
96 | .TP | |
3be34541 SK |
97 | .B \-k, --keep-in-foreground |
98 | Do not go into the background at startup but otherwise run as | |
3d8df260 SK |
99 | normal. This is intended for use when dnsmasq is run under daemontools |
100 | or launchd. | |
3be34541 | 101 | .TP |
9e4abcb5 SK |
102 | .B \-d, --no-daemon |
103 | Debug mode: don't fork to the background, don't write a pid file, | |
104 | don't change user id, generate a complete cache dump on receipt on | |
3be34541 | 105 | SIGUSR1, log to stderr as well as syslog, don't fork new processes |
83b2198e SK |
106 | to handle TCP queries. Note that this option is for use in debugging |
107 | only, to stop dnsmasq daemonising in production, use | |
108 | .B -k. | |
9e4abcb5 SK |
109 | .TP |
110 | .B \-q, --log-queries | |
25cf5e37 SK |
111 | Log the results of DNS queries handled by dnsmasq. Enable a full cache dump on receipt of SIGUSR1. If the argument "extra" is supplied, ie |
112 | .B --log-queries=extra | |
113 | then the log has extra information at the start of each line. | |
114 | This consists of a serial number which ties together the log lines associated with an individual query, and the IP address of the requestor. | |
9e4abcb5 | 115 | .TP |
849a8357 SK |
116 | .B \-8, --log-facility=<facility> |
117 | Set the facility to which dnsmasq will send syslog entries, this | |
f2621c7f | 118 | defaults to DAEMON, and to LOCAL0 when debug mode is in operation. If |
9e038946 | 119 | the facility given contains at least one '/' character, it is taken to |
f2621c7f | 120 | be a filename, and dnsmasq logs to the given file, instead of |
8ef5ada2 SK |
121 | syslog. If the facility is '-' then dnsmasq logs to stderr. |
122 | (Errors whilst reading configuration will still go to syslog, | |
f2621c7f | 123 | but all output from a successful startup, and all output whilst |
5aabfc78 SK |
124 | running, will go exclusively to the file.) When logging to a file, |
125 | dnsmasq will close and reopen the file when it receives SIGUSR2. This | |
126 | allows the log file to be rotated without stopping dnsmasq. | |
f2621c7f SK |
127 | .TP |
128 | .B --log-async[=<lines>] | |
129 | Enable asynchronous logging and optionally set the limit on the | |
130 | number of lines | |
131 | which will be queued by dnsmasq when writing to the syslog is slow. | |
132 | Dnsmasq can log asynchronously: this | |
133 | allows it to continue functioning without being blocked by syslog, and | |
134 | allows syslog to use dnsmasq for DNS queries without risking deadlock. | |
135 | If the queue of log-lines becomes full, dnsmasq will log the | |
136 | overflow, and the number of messages lost. The default queue length is | |
137 | 5, a sane value would be 5-25, and a maximum limit of 100 is imposed. | |
849a8357 | 138 | .TP |
9e4abcb5 SK |
139 | .B \-x, --pid-file=<path> |
140 | Specify an alternate path for dnsmasq to record its process-id in. Normally /var/run/dnsmasq.pid. | |
141 | .TP | |
142 | .B \-u, --user=<username> | |
143 | Specify the userid to which dnsmasq will change after startup. Dnsmasq must normally be started as root, but it will drop root | |
b8187c80 | 144 | privileges after startup by changing id to another user. Normally this user is "nobody" but that |
9e4abcb5 SK |
145 | can be over-ridden with this switch. |
146 | .TP | |
147 | .B \-g, --group=<groupname> | |
148 | Specify the group which dnsmasq will run | |
149 | as. The defaults to "dip", if available, to facilitate access to | |
150 | /etc/ppp/resolv.conf which is not normally world readable. | |
151 | .TP | |
152 | .B \-v, --version | |
153 | Print the version number. | |
154 | .TP | |
155 | .B \-p, --port=<port> | |
824af85b SK |
156 | Listen on <port> instead of the standard DNS port (53). Setting this |
157 | to zero completely disables DNS function, leaving only DHCP and/or TFTP. | |
9e4abcb5 | 158 | .TP |
feba5c1d SK |
159 | .B \-P, --edns-packet-max=<size> |
160 | Specify the largest EDNS.0 UDP packet which is supported by the DNS | |
316e2730 | 161 | forwarder. Defaults to 4096, which is the RFC5625-recommended size. |
feba5c1d | 162 | .TP |
9e4abcb5 | 163 | .B \-Q, --query-port=<query_port> |
1a6bca81 SK |
164 | Send outbound DNS queries from, and listen for their replies on, the |
165 | specific UDP port <query_port> instead of using random ports. NOTE | |
166 | that using this option will make dnsmasq less secure against DNS | |
167 | spoofing attacks but it may be faster and use less resources. Setting this option | |
168 | to zero makes dnsmasq use a single port allocated to it by the | |
169 | OS: this was the default behaviour in versions prior to 2.43. | |
170 | .TP | |
171 | .B --min-port=<port> | |
172 | Do not use ports less than that given as source for outbound DNS | |
173 | queries. Dnsmasq picks random ports as source for outbound queries: | |
174 | when this option is given, the ports used will always to larger | |
175 | than that specified. Useful for systems behind firewalls. | |
9e4abcb5 SK |
176 | .TP |
177 | .B \-i, --interface=<interface name> | |
feba5c1d SK |
178 | Listen only on the specified interface(s). Dnsmasq automatically adds |
179 | the loopback (local) interface to the list of interfaces to use when | |
180 | the | |
181 | .B \--interface | |
182 | option is used. If no | |
183 | .B \--interface | |
9e4abcb5 | 184 | or |
feba5c1d SK |
185 | .B \--listen-address |
186 | options are given dnsmasq listens on all available interfaces except any | |
187 | given in | |
188 | .B \--except-interface | |
309331f5 | 189 | options. IP alias interfaces (eg "eth1:0") cannot be used with |
8a911ccc SK |
190 | .B --interface |
191 | or | |
192 | .B --except-interface | |
49333cbd SK |
193 | options, use --listen-address instead. A simple wildcard, consisting |
194 | of a trailing '*', can be used in | |
195 | .B \--interface | |
196 | and | |
197 | .B \--except-interface | |
198 | options. | |
9e4abcb5 SK |
199 | .TP |
200 | .B \-I, --except-interface=<interface name> | |
feba5c1d SK |
201 | Do not listen on the specified interface. Note that the order of |
202 | .B \--listen-address | |
203 | .B --interface | |
204 | and | |
205 | .B --except-interface | |
206 | options does not matter and that | |
207 | .B --except-interface | |
208 | options always override the others. | |
34d0a36a SK |
209 | .TP |
210 | .B --auth-server=<domain>,<interface>|<ip-address> | |
81925ab7 | 211 | Enable DNS authoritative mode for queries arriving at an interface or address. Note that the interface or address |
34d0a36a SK |
212 | need not be mentioned in |
213 | .B --interface | |
214 | or | |
215 | .B --listen-address | |
216 | configuration, indeed | |
217 | .B --auth-server | |
f25e6c6d SK |
218 | will overide these and provide a different DNS service on the |
219 | specified interface. The <domain> is the "glue record". It should | |
220 | resolve in the global DNS to a A and/or AAAA record which points to | |
221 | the address dnsmasq is listening on. When an interface is specified, | |
222 | it may be qualified with "/4" or "/6" to specify only the IPv4 or IPv6 | |
223 | addresses associated with the interface. | |
c8a80487 SK |
224 | .TP |
225 | .B --local-service | |
226 | Accept DNS queries only from hosts whose address is on a local subnet, | |
227 | ie a subnet for which an interface exists on the server. This option | |
228 | only has effect is there are no --interface --except-interface, | |
229 | --listen-address or --auth-server options. It is intended to be set as | |
230 | a default on installation, to allow unconfigured installations to be | |
231 | useful but also safe from being used for DNS amplification attacks. | |
9e4abcb5 | 232 | .TP |
3d8df260 | 233 | .B \-2, --no-dhcp-interface=<interface name> |
832af0ba | 234 | Do not provide DHCP or TFTP on the specified interface, but do provide DNS service. |
3d8df260 | 235 | .TP |
44a2a316 | 236 | .B \-a, --listen-address=<ipaddr> |
feba5c1d SK |
237 | Listen on the given IP address(es). Both |
238 | .B \--interface | |
239 | and | |
240 | .B \--listen-address | |
241 | options may be given, in which case the set of both interfaces and | |
242 | addresses is used. Note that if no | |
243 | .B \--interface | |
244 | option is given, but | |
245 | .B \--listen-address | |
246 | is, dnsmasq will not automatically listen on the loopback | |
247 | interface. To achieve this, its IP address, 127.0.0.1, must be | |
248 | explicitly given as a | |
249 | .B \--listen-address | |
250 | option. | |
9e4abcb5 | 251 | .TP |
44a2a316 SK |
252 | .B \-z, --bind-interfaces |
253 | On systems which support it, dnsmasq binds the wildcard address, | |
254 | even when it is listening on only some interfaces. It then discards | |
255 | requests that it shouldn't reply to. This has the advantage of | |
256 | working even when interfaces come and go and change address. This | |
257 | option forces dnsmasq to really bind only the interfaces it is | |
258 | listening on. About the only time when this is useful is when | |
f6b7dc47 | 259 | running another nameserver (or another instance of dnsmasq) on the |
309331f5 | 260 | same machine. Setting this option also enables multiple instances of |
f6b7dc47 SK |
261 | dnsmasq which provide DHCP service to run in the same machine. |
262 | .TP | |
54dd393f SK |
263 | .B --bind-dynamic |
264 | Enable a network mode which is a hybrid between | |
265 | .B --bind-interfaces | |
a2ce6fcc | 266 | and the default. Dnsmasq binds the address of individual interfaces, |
54dd393f SK |
267 | allowing multiple dnsmasq instances, but if new interfaces or |
268 | addresses appear, it automatically listens on those (subject to any | |
269 | access-control configuration). This makes dynamically created | |
270 | interfaces work in the same way as the default. Implementing this | |
a2ce6fcc | 271 | option requires non-standard networking APIs and it is only available |
05ff1ed7 | 272 | under Linux. On other platforms it falls-back to --bind-interfaces mode. |
54dd393f | 273 | .TP |
f6b7dc47 SK |
274 | .B \-y, --localise-queries |
275 | Return answers to DNS queries from /etc/hosts which depend on the interface over which the query was | |
b8187c80 | 276 | received. If a name in /etc/hosts has more than one address associated with |
f6b7dc47 SK |
277 | it, and at least one of those addresses is on the same subnet as the |
278 | interface to which the query was sent, then return only the | |
279 | address(es) on that subnet. This allows for a server to have multiple | |
280 | addresses in /etc/hosts corresponding to each of its interfaces, and | |
281 | hosts will get the correct address based on which network they are | |
282 | attached to. Currently this facility is limited to IPv4. | |
44a2a316 | 283 | .TP |
9e4abcb5 SK |
284 | .B \-b, --bogus-priv |
285 | Bogus private reverse lookups. All reverse lookups for private IP ranges (ie 192.168.x.x, etc) | |
feba5c1d SK |
286 | which are not found in /etc/hosts or the DHCP leases file are answered |
287 | with "no such domain" rather than being forwarded upstream. | |
9e4abcb5 | 288 | .TP |
73a08a24 | 289 | .B \-V, --alias=[<old-ip>]|[<start-ip>-<end-ip>],<new-ip>[,<mask>] |
1cff166d SK |
290 | Modify IPv4 addresses returned from upstream nameservers; old-ip is |
291 | replaced by new-ip. If the optional mask is given then any address | |
292 | which matches the masked old-ip will be re-written. So, for instance | |
293 | .B --alias=1.2.3.0,6.7.8.0,255.255.255.0 | |
294 | will map 1.2.3.56 to 6.7.8.56 and 1.2.3.67 to 6.7.8.67. This is what | |
73a08a24 SK |
295 | Cisco PIX routers call "DNS doctoring". If the old IP is given as |
296 | range, then only addresses in the range, rather than a whole subnet, | |
297 | are re-written. So | |
298 | .B --alias=192.168.0.10-192.168.0.40,10.0.0.0,255.255.255.0 | |
299 | maps 192.168.0.10->192.168.0.40 to 10.0.0.10->10.0.0.40 | |
1cff166d | 300 | .TP |
9e4abcb5 SK |
301 | .B \-B, --bogus-nxdomain=<ipaddr> |
302 | Transform replies which contain the IP address given into "No such | |
303 | domain" replies. This is intended to counteract a devious move made by | |
b8187c80 | 304 | Verisign in September 2003 when they started returning the address of |
9e4abcb5 SK |
305 | an advertising web page in response to queries for unregistered names, |
306 | instead of the correct NXDOMAIN response. This option tells dnsmasq to | |
307 | fake the correct response when it sees this behaviour. As at Sept 2003 | |
b8187c80 | 308 | the IP address being returned by Verisign is 64.94.110.11 |
32fc6dbe GH |
309 | .TP |
310 | .B \-B, --ignore-address=<ipaddr> | |
311 | Ignore replies to A-record queries which include the specified address. | |
312 | No error is generated, dnsmasq simply continues to listen for another reply. | |
313 | This is useful to defeat blocking strategies which rely on quickly supplying a | |
314 | forged answer to a DNS request for certain domain, before the correct answer can arrive. | |
9e4abcb5 SK |
315 | .TP |
316 | .B \-f, --filterwin2k | |
317 | Later versions of windows make periodic DNS requests which don't get sensible answers from | |
318 | the public DNS and can cause problems by triggering dial-on-demand links. This flag turns on an option | |
319 | to filter such requests. The requests blocked are for records of types SOA and SRV, and type ANY where the | |
320 | requested name has underscores, to catch LDAP requests. | |
321 | .TP | |
322 | .B \-r, --resolv-file=<file> | |
323 | Read the IP addresses of the upstream nameservers from <file>, instead of | |
324 | /etc/resolv.conf. For the format of this file see | |
7de060b0 SK |
325 | .BR resolv.conf (5). |
326 | The only lines relevant to dnsmasq are nameserver ones. Dnsmasq can | |
9e4abcb5 SK |
327 | be told to poll more than one resolv.conf file, the first file name specified |
328 | overrides the default, subsequent ones add to the list. This is only | |
329 | allowed when polling; the file with the currently latest modification | |
330 | time is the one used. | |
331 | .TP | |
332 | .B \-R, --no-resolv | |
333 | Don't read /etc/resolv.conf. Get upstream servers only from the command | |
b49644f3 | 334 | line or the dnsmasq configuration file. |
9e4abcb5 | 335 | .TP |
ad094275 | 336 | .B \-1, --enable-dbus[=<service-name>] |
3d8df260 SK |
337 | Allow dnsmasq configuration to be updated via DBus method calls. The |
338 | configuration which can be changed is upstream DNS servers (and | |
b8187c80 | 339 | corresponding domains) and cache clear. Requires that dnsmasq has |
ad094275 SK |
340 | been built with DBus support. If the service name is given, dnsmasq |
341 | provides service at that name, rather than the default which is | |
342 | .B uk.org.thekelleys.dnsmasq | |
3d8df260 | 343 | .TP |
9e4abcb5 SK |
344 | .B \-o, --strict-order |
345 | By default, dnsmasq will send queries to any of the upstream servers | |
824af85b | 346 | it knows about and tries to favour servers that are known to |
9e4abcb5 SK |
347 | be up. Setting this flag forces dnsmasq to try each query with each |
348 | server strictly in the order they appear in /etc/resolv.conf | |
349 | .TP | |
824af85b SK |
350 | .B --all-servers |
351 | By default, when dnsmasq has more than one upstream server available, | |
352 | it will send queries to just one server. Setting this flag forces | |
353 | dnsmasq to send all queries to all available servers. The reply from | |
c72daea8 | 354 | the server which answers first will be returned to the original requester. |
824af85b | 355 | .TP |
b5ea1cc2 SK |
356 | .B --dns-loop-detect |
357 | Enable code to detect DNS forwarding loops; ie the situation where a query sent to one | |
358 | of the upstream server eventually returns as a new query to the dnsmasq instance. The | |
359 | process works by generating TXT queries of the form <hex>.test and sending them to | |
360 | each upstream server. The hex is a UID which encodes the instance of dnsmasq sending the query | |
361 | and the upstream server to which it was sent. If the query returns to the server which sent it, then | |
362 | the upstream server through which it was sent is disabled and this event is logged. Each time the | |
363 | set of upstream servers changes, the test is re-run on all of them, including ones which | |
364 | were previously disabled. | |
365 | .TP | |
824af85b SK |
366 | .B --stop-dns-rebind |
367 | Reject (and log) addresses from upstream nameservers which are in the | |
368 | private IP ranges. This blocks an attack where a browser behind a | |
369 | firewall is used to probe machines on the local network. | |
370 | .TP | |
8ef5ada2 SK |
371 | .B --rebind-localhost-ok |
372 | Exempt 127.0.0.0/8 from rebinding checks. This address range is | |
373 | returned by realtime black hole servers, so blocking it may disable | |
374 | these services. | |
375 | .TP | |
376 | .B --rebind-domain-ok=[<domain>]|[[/<domain>/[<domain>/] | |
377 | Do not detect and block dns-rebind on queries to these domains. The | |
378 | argument may be either a single domain, or multiple domains surrounded | |
379 | by '/', like the --server syntax, eg. | |
380 | .B --rebind-domain-ok=/domain1/domain2/domain3/ | |
381 | .TP | |
9e4abcb5 SK |
382 | .B \-n, --no-poll |
383 | Don't poll /etc/resolv.conf for changes. | |
384 | .TP | |
1697269c | 385 | .B --clear-on-reload |
d9fb0be8 SK |
386 | Whenever /etc/resolv.conf is re-read or the upstream servers are set |
387 | via DBus, clear the DNS cache. | |
1697269c SK |
388 | This is useful when new nameservers may have different |
389 | data than that held in cache. | |
390 | .TP | |
9e4abcb5 | 391 | .B \-D, --domain-needed |
7de060b0 | 392 | Tells dnsmasq to never forward A or AAAA queries for plain names, without dots |
3d8df260 | 393 | or domain parts, to upstream nameservers. If the name is not known |
9e4abcb5 SK |
394 | from /etc/hosts or DHCP then a "not found" answer is returned. |
395 | .TP | |
824af85b | 396 | .B \-S, --local, --server=[/[<domain>]/[domain/]][<ipaddr>[#<port>][@<source-ip>|<interface>[#<port>]] |
5aabfc78 | 397 | Specify IP address of upstream servers directly. Setting this flag does |
9e4abcb5 SK |
398 | not suppress reading of /etc/resolv.conf, use -R to do that. If one or |
399 | more | |
400 | optional domains are given, that server is used only for those domains | |
401 | and they are queried only using the specified server. This is | |
402 | intended for private nameservers: if you have a nameserver on your | |
403 | network which deals with names of the form | |
404 | xxx.internal.thekelleys.org.uk at 192.168.1.1 then giving the flag | |
b8187c80 | 405 | .B -S /internal.thekelleys.org.uk/192.168.1.1 |
9e4abcb5 SK |
406 | will send all queries for |
407 | internal machines to that nameserver, everything else will go to the | |
408 | servers in /etc/resolv.conf. An empty domain specification, | |
409 | .B // | |
410 | has the special meaning of "unqualified names only" ie names without any | |
411 | dots in them. A non-standard port may be specified as | |
412 | part of the IP | |
413 | address using a # character. | |
414 | More than one -S flag is allowed, with | |
8ef5ada2 SK |
415 | repeated domain or ipaddr parts as required. |
416 | ||
417 | More specific domains take precendence over less specific domains, so: | |
418 | .B --server=/google.com/1.2.3.4 | |
419 | .B --server=/www.google.com/2.3.4.5 | |
420 | will send queries for *.google.com to 1.2.3.4, except *www.google.com, | |
421 | which will go to 2.3.4.5 | |
422 | ||
423 | The special server address '#' means, "use the standard servers", so | |
424 | .B --server=/google.com/1.2.3.4 | |
425 | .B --server=/www.google.com/# | |
426 | will send queries for *.google.com to 1.2.3.4, except *www.google.com which will | |
427 | be forwarded as usual. | |
9e4abcb5 SK |
428 | |
429 | Also permitted is a -S | |
430 | flag which gives a domain but no IP address; this tells dnsmasq that | |
431 | a domain is local and it may answer queries from /etc/hosts or DHCP | |
432 | but should never forward queries on that domain to any upstream | |
433 | servers. | |
434 | .B local | |
435 | is a synonym for | |
436 | .B server | |
437 | to make configuration files clearer in this case. | |
438 | ||
7de060b0 SK |
439 | IPv6 addresses may include a %interface scope-id, eg |
440 | fe80::202:a412:4512:7bbf%eth0. | |
441 | ||
824af85b SK |
442 | The optional string after the @ character tells |
443 | dnsmasq how to set the source of the queries to this | |
444 | nameserver. It should be an ip-address, which should belong to the machine on which | |
9e4abcb5 | 445 | dnsmasq is running otherwise this server line will be logged and then |
824af85b SK |
446 | ignored, or an interface name. If an interface name is given, then |
447 | queries to the server will be forced via that interface; if an | |
448 | ip-address is given then the source address of the queries will be set | |
449 | to that address. | |
450 | The query-port flag is ignored for any servers which have a | |
9e4abcb5 | 451 | source address specified but the port may be specified directly as |
824af85b SK |
452 | part of the source address. Forcing queries to an interface is not |
453 | implemented on all platforms supported by dnsmasq. | |
9e4abcb5 | 454 | .TP |
de73a497 SK |
455 | .B --rev-server=<ip-address>/<prefix-len>,<ipaddr>[#<port>][@<source-ip>|<interface>[#<port>]] |
456 | This is functionally the same as | |
457 | .B --server, | |
458 | but provides some syntactic sugar to make specifying address-to-name queries easier. For example | |
459 | .B --rev-server=1.2.3.0/24,192.168.0.1 | |
460 | is exactly equivalent to | |
461 | .B --server=/3.2.1.in-addr.arpa/192.168.0.1 | |
462 | .TP | |
979fe86b | 463 | .B \-A, --address=/<domain>/[domain/][<ipaddr>] |
9e4abcb5 SK |
464 | Specify an IP address to return for any host in the given domains. |
465 | Queries in the domains are never forwarded and always replied to | |
466 | with the specified IP address which may be IPv4 or IPv6. To give | |
467 | both IPv4 and IPv6 addresses for a domain, use repeated -A flags. | |
468 | Note that /etc/hosts and DHCP leases override this for individual | |
469 | names. A common use of this is to redirect the entire doubleclick.net | |
a222641c SK |
470 | domain to some friendly local web server to avoid banner ads. The |
471 | domain specification works in the same was as for --server, with the | |
472 | additional facility that /#/ matches any domain. Thus | |
473 | --address=/#/1.2.3.4 will always return 1.2.3.4 for any query not | |
474 | answered from /etc/hosts or DHCP and not sent to an upstream | |
979fe86b SK |
475 | nameserver by a more specific --server directive. As for --server, |
476 | one or more domains with no address returns a no-such-domain answer, so | |
477 | --address=/example.com/ is equivalent to --server=/example.com/ and returns | |
478 | NXDOMAIN for example.com and all its subdomains. | |
9e4abcb5 | 479 | .TP |
13d86c73 JD |
480 | .B --ipset=/<domain>/[domain/]<ipset>[,<ipset>] |
481 | Places the resolved IP addresses of queries for the specified domains | |
482 | in the specified netfilter ip sets. Domains and subdomains are matched | |
483 | in the same way as --address. These ip sets must already exist. See | |
484 | ipset(8) for more details. | |
485 | .TP | |
f6b7dc47 | 486 | .B \-m, --mx-host=<mx name>[[,<hostname>],<preference>] |
de37951c SK |
487 | Return an MX record named <mx name> pointing to the given hostname (if |
488 | given), or | |
489 | the host specified in the --mx-target switch | |
9e4abcb5 | 490 | or, if that switch is not given, the host on which dnsmasq |
f6b7dc47 SK |
491 | is running. The default is useful for directing mail from systems on a LAN |
492 | to a central server. The preference value is optional, and defaults to | |
493 | 1 if not given. More than one MX record may be given for a host. | |
9e4abcb5 SK |
494 | .TP |
495 | .B \-t, --mx-target=<hostname> | |
f6b7dc47 SK |
496 | Specify the default target for the MX record returned by dnsmasq. See |
497 | --mx-host. If --mx-target is given, but not --mx-host, then dnsmasq | |
498 | returns a MX record containing the MX target for MX queries on the | |
499 | hostname of the machine on which dnsmasq is running. | |
9e4abcb5 SK |
500 | .TP |
501 | .B \-e, --selfmx | |
502 | Return an MX record pointing to itself for each local | |
503 | machine. Local machines are those in /etc/hosts or with DHCP leases. | |
504 | .TP | |
505 | .B \-L, --localmx | |
506 | Return an MX record pointing to the host given by mx-target (or the | |
507 | machine on which dnsmasq is running) for each | |
508 | local machine. Local machines are those in /etc/hosts or with DHCP | |
509 | leases. | |
510 | .TP | |
f6b7dc47 SK |
511 | .B \-W, --srv-host=<_service>.<_prot>.[<domain>],[<target>[,<port>[,<priority>[,<weight>]]]] |
512 | Return a SRV DNS record. See RFC2782 for details. If not supplied, the | |
513 | domain defaults to that given by | |
514 | .B --domain. | |
515 | The default for the target domain is empty, and the default for port | |
516 | is one and the defaults for | |
517 | weight and priority are zero. Be careful if transposing data from BIND | |
518 | zone files: the port, weight and priority numbers are in a different | |
519 | order. More than one SRV record for a given service/domain is allowed, | |
3d8df260 | 520 | all that match are returned. |
f6b7dc47 | 521 | .TP |
d36b732c | 522 | .B --host-record=<name>[,<name>....],[<IPv4-address>],[<IPv6-address>] |
e759d426 SK |
523 | Add A, AAAA and PTR records to the DNS. This adds one or more names to |
524 | the DNS with associated IPv4 (A) and IPv6 (AAAA) records. A name may | |
525 | appear in more than one | |
526 | .B host-record | |
527 | and therefore be assigned more than one address. Only the first | |
528 | address creates a PTR record linking the address to the name. This is | |
529 | the same rule as is used reading hosts-files. | |
530 | .B host-record | |
531 | options are considered to be read before host-files, so a name | |
532 | appearing there inhibits PTR-record creation if it appears in | |
e46164e0 | 533 | hosts-file also. Unlike hosts-files, names are not expanded, even when |
e759d426 SK |
534 | .B expand-hosts |
535 | is in effect. Short and long names may appear in the same | |
e46164e0 SK |
536 | .B host-record, |
537 | eg. | |
538 | .B --host-record=laptop,laptop.thekelleys.org,192.168.0.1,1234::100 | |
e759d426 | 539 | .TP |
0a852541 SK |
540 | .B \-Y, --txt-record=<name>[[,<text>],<text>] |
541 | Return a TXT DNS record. The value of TXT record is a set of strings, | |
28866e95 SK |
542 | so any number may be included, delimited by commas; use quotes to put |
543 | commas into a string. Note that the maximum length of a single string | |
544 | is 255 characters, longer strings are split into 255 character chunks. | |
0a852541 | 545 | .TP |
832af0ba SK |
546 | .B --ptr-record=<name>[,<target>] |
547 | Return a PTR DNS record. | |
548 | .TP | |
1a6bca81 SK |
549 | .B --naptr-record=<name>,<order>,<preference>,<flags>,<service>,<regexp>[,<replacement>] |
550 | Return an NAPTR DNS record, as specified in RFC3403. | |
551 | .TP | |
9009d746 SK |
552 | .B --cname=<cname>,<target> |
553 | Return a CNAME record which indicates that <cname> is really | |
554 | <target>. There are significant limitations on the target; it must be a | |
555 | DNS name which is known to dnsmasq from /etc/hosts (or additional | |
d56a604a | 556 | hosts files), from DHCP, from --interface-name or from another |
611ebc5f SK |
557 | .B --cname. |
558 | If the target does not satisfy this | |
9009d746 SK |
559 | criteria, the whole cname is ignored. The cname must be unique, but it |
560 | is permissable to have more than one cname pointing to the same target. | |
561 | .TP | |
9f7f3b12 SK |
562 | .B --dns-rr=<name>,<RR-number>,[<hex data>] |
563 | Return an arbitrary DNS Resource Record. The number is the type of the | |
564 | record (which is always in the C_IN class). The value of the record is | |
a2ce6fcc | 565 | given by the hex data, which may be of the form 01:23:45 or 01 23 45 or |
9f7f3b12 SK |
566 | 012345 or any mixture of these. |
567 | .TP | |
f7029f5c | 568 | .B --interface-name=<name>,<interface>[/4|/6] |
f2621c7f | 569 | Return a DNS record associating the name with the primary address on |
f7029f5c | 570 | the given interface. This flag specifies an A or AAAA record for the given |
f2621c7f | 571 | name in the same way as an /etc/hosts line, except that the address is |
f7029f5c SK |
572 | not constant, but taken from the given interface. The interface may be |
573 | followed by "/4" or "/6" to specify that only IPv4 or IPv6 addresses | |
574 | of the interface should be used. If the interface is | |
9e038946 | 575 | down, not configured or non-existent, an empty record is returned. The |
f2621c7f SK |
576 | matching PTR record is also created, mapping the interface address to |
577 | the name. More than one name may be associated with an interface | |
578 | address by repeating the flag; in that case the first instance is used | |
579 | for the reverse address-to-name mapping. | |
580 | .TP | |
48fd1c4d | 581 | .B --synth-domain=<domain>,<address range>[,<prefix>] |
2bb73af7 SK |
582 | Create artificial A/AAAA and PTR records for an address range. The |
583 | records use the address, with periods (or colons for IPv6) replaced | |
584 | with dashes. | |
585 | ||
586 | An example should make this clearer. | |
48fd1c4d SK |
587 | .B --synth-domain=thekelleys.org.uk,192.168.0.0/24,internal- |
588 | will result in a query for internal-192-168-0-56.thekelleys.org.uk returning | |
589 | 192.168.0.56 and a reverse query vice versa. The same applies to IPv6, | |
590 | but IPv6 addresses may start with '::' | |
591 | but DNS labels may not start with '-' so in this case if no prefix is | |
592 | configured a zero is added in front of the label. ::1 becomes 0--1. | |
2bb73af7 SK |
593 | |
594 | The address range can be of the form | |
595 | <ip address>,<ip address> or <ip address>/<netmask> | |
596 | .TP | |
28866e95 SK |
597 | .B --add-mac |
598 | Add the MAC address of the requestor to DNS queries which are | |
599 | forwarded upstream. This may be used to DNS filtering by the upstream | |
600 | server. The MAC address can only be added if the requestor is on the same | |
601 | subnet as the dnsmasq server. Note that the mechanism used to achieve this (an EDNS0 option) | |
602 | is not yet standardised, so this should be considered | |
603 | experimental. Also note that exposing MAC addresses in this way may | |
ed4c0767 SK |
604 | have security and privacy implications. The warning about caching |
605 | given for --add-subnet applies to --add-mac too. | |
606 | .TP | |
607 | .B --add-subnet[[=<IPv4 prefix length>],<IPv6 prefix length>] | |
608 | Add the subnet address of the requestor to the DNS queries which are | |
609 | forwarded upstream. The amount of the address forwarded depends on the | |
610 | prefix length parameter: 32 (128 for IPv6) forwards the whole address, | |
611 | zero forwards none of it but still marks the request so that no | |
612 | upstream nameserver will add client address information either. The | |
613 | default is zero for both IPv4 and IPv6. Note that upstream nameservers | |
614 | may be configured to return different results based on this | |
615 | information, but the dnsmasq cache does not take account. If a dnsmasq | |
616 | instance is configured such that different results may be encountered, | |
617 | caching should be disabled. | |
28866e95 | 618 | .TP |
9e4abcb5 SK |
619 | .B \-c, --cache-size=<cachesize> |
620 | Set the size of dnsmasq's cache. The default is 150 names. Setting the cache size to zero disables caching. | |
621 | .TP | |
622 | .B \-N, --no-negcache | |
623 | Disable negative caching. Negative caching allows dnsmasq to remember | |
624 | "no such domain" answers from upstream nameservers and answer | |
5aabfc78 | 625 | identical queries without forwarding them again. |
9e4abcb5 | 626 | .TP |
1697269c SK |
627 | .B \-0, --dns-forward-max=<queries> |
628 | Set the maximum number of concurrent DNS queries. The default value is | |
629 | 150, which should be fine for most setups. The only known situation | |
630 | where this needs to be increased is when using web-server log file | |
631 | resolvers, which can generate large numbers of concurrent queries. | |
208b65c5 | 632 | .TP |
70b4a818 SK |
633 | .B --dnssec |
634 | Validate DNS replies and cache DNSSEC data. When forwarding DNS queries, dnsmasq requests the | |
635 | DNSSEC records needed to validate the replies. The replies are validated and the result returned as | |
636 | the Authenticated Data bit in the DNS packet. In addition the DNSSEC records are stored in the cache, making | |
637 | validation by clients more efficient. Note that validation by clients is the most secure DNSSEC mode, but for | |
638 | clients unable to do validation, use of the AD bit set by dnsmasq is useful, provided that the network between | |
639 | the dnsmasq server and the client is trusted. Dnsmasq must be compiled with HAVE_DNSSEC enabled, and DNSSEC | |
640 | trust anchors provided, see | |
ee415867 | 641 | .B --trust-anchor. |
d588ab54 SK |
642 | Because the DNSSEC validation process uses the cache, it is not |
643 | permitted to reduce the cache size below the default when DNSSEC is | |
644 | enabled. The nameservers upstream of dnsmasq must be DNSSEC-capable, | |
645 | ie capable of returning DNSSEC records with data. If they are not, | |
646 | then dnsmasq will not be able to determine the trusted status of | |
647 | answers. In the default mode, this menas that all replies will be | |
648 | marked as untrusted. If | |
649 | .B --dnssec-check-unsigned | |
650 | is set and the upstream servers don't support DNSSEC, then DNS service will be entirely broken. | |
70b4a818 | 651 | .TP |
ee415867 SK |
652 | .B --trust-anchor=[<class>],<domain>,<key-tag>,<algorithm>,<digest-type>,<digest> |
653 | Provide DS records to act a trust anchors for DNSSEC | |
654 | validation. Typically these will be the DS record(s) for Zone Signing | |
655 | key(s) of the root zone, | |
656 | but trust anchors for limited domains are also possible. The current | |
657 | root-zone trust anchors may be donwloaded from https://data.iana.org/root-anchors/root-anchors.xml | |
70b4a818 | 658 | .TP |
00a5b5d4 SK |
659 | .B --dnssec-check-unsigned |
660 | As a default, dnsmasq does not check that unsigned DNS replies are | |
661 | legitimate: they are assumed to be valid and passed on (without the | |
662 | "authentic data" bit set, of course). This does not protect against an | |
663 | attacker forging unsigned replies for signed DNS zones, but it is | |
664 | fast. If this flag is set, dnsmasq will check the zones of unsigned | |
665 | replies, to ensure that unsigned replies are allowed in those | |
d588ab54 SK |
666 | zones. The cost of this is more upstream queries and slower |
667 | performance. See also the warning about upstream servers in the | |
668 | section on | |
669 | .B --dnssec | |
00a5b5d4 | 670 | .TP |
e98bd52e SK |
671 | .B --dnssec-no-timecheck |
672 | DNSSEC signatures are only valid for specified time windows, and should be rejected outside those windows. This generates an | |
673 | interesting chicken-and-egg problem for machines which don't have a hardware real time clock. For these machines to determine the correct | |
674 | time typically requires use of NTP and therefore DNS, but validating DNS requires that the correct time is already known. Setting this flag | |
675 | removes the time-window checks (but not other DNSSEC validation.) only until the dnsmasq process receives SIGHUP. The intention is | |
676 | that dnsmasq should be started with this flag when the platform determines that reliable time is not currently available. As soon as | |
677 | reliable time is established, a SIGHUP should be sent to dnsmasq, which enables time checking, and purges the cache of DNS records | |
678 | which have not been throughly checked. | |
679 | .TP | |
f6e62e2a SK |
680 | .B --dnssec-timestamp=<path> |
681 | Enables an alternative way of checking the validity of the system time for DNSSEC (see --dnssec-no-timecheck). In this case, the | |
682 | system time is considered to be valid once it becomes later than the timestamp on the specified file. The file is created and | |
683 | its timestamp set automatically by dnsmasq. The file must be stored on a persistent filesystem, so that it and its mtime are carried | |
360f2513 SK |
684 | over system restarts. The timestamp file is created after dnsmasq has dropped root, so it must be in a location writable by the |
685 | unprivileged user that dnsmasq runs as. | |
f6e62e2a | 686 | .TP |
28866e95 | 687 | .B --proxy-dnssec |
70b4a818 SK |
688 | Copy the DNSSEC Authenticated Data bit from upstream servers to downstream clients and cache it. This is an |
689 | alternative to having dnsmasq validate DNSSEC, but it depends on the security of the network between | |
690 | dnsmasq and the upstream servers, and the trustworthiness of the upstream servers. | |
691 | .TP | |
692 | .B --dnssec-debug | |
693 | Set debugging mode for the DNSSEC validation, set the Checking Disabled bit on upstream queries, | |
ee415867 SK |
694 | and don't convert replies which do not validate to responses with |
695 | a return code of SERVFAIL. Note that | |
696 | setting this may affect DNS behaviour in bad ways, it is not an | |
697 | extra-logging flag and should not be set in production. | |
28866e95 | 698 | .TP |
baa80ae5 | 699 | .B --auth-zone=<domain>[,<subnet>[/<prefix length>][,<subnet>[/<prefix length>].....]] |
34d0a36a | 700 | Define a DNS zone for which dnsmasq acts as authoritative server. Locally defined DNS records which are in the domain |
c50f25a3 SK |
701 | will be served. If subnet(s) are given, A and AAAA records must be in one of the |
702 | specified subnets. | |
703 | ||
704 | As alternative to directly specifying the subnets, it's possible to | |
376d48c7 SK |
705 | give the name of an interface, in which case the subnets implied by |
706 | that interface's configured addresses and netmask/prefix-length are | |
707 | used; this is useful when using constructed DHCP ranges as the actual | |
708 | address is dynamic and not known when configuring dnsmasq. The | |
709 | interface addresses may be confined to only IPv6 addresses using | |
710 | <interface>/6 or to only IPv4 using <interface>/4. This is useful when | |
711 | an interface has dynamically determined global IPv6 addresses which should | |
712 | appear in the zone, but RFC1918 IPv4 addresses which should not. | |
713 | Interface-name and address-literal subnet specifications may be used | |
714 | freely in the same --auth-zone declaration. | |
715 | ||
716 | The subnet(s) are also used to define in-addr.arpa and | |
1d7e0a36 | 717 | ip6.arpa domains which are served for reverse-DNS queries. If not |
baa80ae5 SK |
718 | specified, the prefix length defaults to 24 for IPv4 and 64 for IPv6. |
719 | For IPv4 subnets, the prefix length should be have the value 8, 16 or 24 | |
720 | unless you are familiar with RFC 2317 and have arranged the | |
c50f25a3 SK |
721 | in-addr.arpa delegation accordingly. Note that if no subnets are |
722 | specified, then no reverse queries are answered. | |
333b2ceb SK |
723 | .TP |
724 | .B --auth-soa=<serial>[,<hostmaster>[,<refresh>[,<retry>[,<expiry>]]]] | |
725 | Specify fields in the SOA record associated with authoritative | |
726 | zones. Note that this is optional, all the values are set to sane defaults. | |
727 | .TP | |
728 | .B --auth-sec-servers=<domain>[,<domain>[,<domain>...]] | |
729 | Specify any secondary servers for a zone for which dnsmasq is | |
730 | authoritative. These servers must be configured to get zone data from | |
731 | dnsmasq by zone transfer, and answer queries for the same | |
6f130def | 732 | authoritative zones as dnsmasq. |
333b2ceb SK |
733 | .TP |
734 | .B --auth-peer=<ip-address>[,<ip-address>[,<ip-address>...]] | |
735 | Specify the addresses of secondary servers which are allowed to | |
736 | initiate zone transfer (AXFR) requests for zones for which dnsmasq is | |
6f130def | 737 | authoritative. If this option is not given, then AXFR requests will be |
333b2ceb SK |
738 | accepted from any secondary. |
739 | .TP | |
7de060b0 SK |
740 | .B --conntrack |
741 | Read the Linux connection track mark associated with incoming DNS | |
742 | queries and set the same mark value on upstream traffic used to answer | |
743 | those queries. This allows traffic generated by dnsmasq to be | |
744 | associated with the queries which cause it, useful for bandwidth | |
745 | accounting and firewalling. Dnsmasq must have conntrack support | |
746 | compiled in and the kernel must have conntrack support | |
747 | included and configured. This option cannot be combined with | |
748 | --query-port. | |
749 | .TP | |
49dc570a | 750 | .B \-F, --dhcp-range=[tag:<tag>[,tag:<tag>],][set:<tag>,]<start-addr>[,<end-addr>][,<mode>][,<netmask>[,<broadcast>]][,<lease time>] |
1adadf58 | 751 | .TP |
83f28bef | 752 | .B \-F, --dhcp-range=[tag:<tag>[,tag:<tag>],][set:<tag>,]<start-IPv6addr>[,<end-IPv6addr>|constructor:<interface>][,<mode>][,<prefix-len>][,<lease time>] |
1adadf58 | 753 | |
9e4abcb5 | 754 | Enable the DHCP server. Addresses will be given out from the range |
44a2a316 SK |
755 | <start-addr> to <end-addr> and from statically defined addresses given |
756 | in | |
757 | .B dhcp-host | |
758 | options. If the lease time is given, then leases | |
b8187c80 | 759 | will be given for that length of time. The lease time is in seconds, |
7622fc06 SK |
760 | or minutes (eg 45m) or hours (eg 1h) or "infinite". If not given, |
761 | the default lease time is one hour. The | |
c8257540 SK |
762 | minimum lease time is two minutes. For IPv6 ranges, the lease time |
763 | maybe "deprecated"; this sets the preferred lifetime sent in a DHCP | |
764 | lease or router advertisement to zero, which causes clients to use | |
765 | other addresses, if available, for new connections as a prelude to renumbering. | |
766 | ||
767 | This option may be repeated, with different addresses, to enable DHCP | |
44a2a316 SK |
768 | service to more than one network. For directly connected networks (ie, |
769 | networks on which the machine running dnsmasq has an interface) the | |
7de060b0 SK |
770 | netmask is optional: dnsmasq will determine it from the interface |
771 | configuration. For networks which receive DHCP service via a relay | |
772 | agent, dnsmasq cannot determine the netmask itself, so it should be | |
773 | specified, otherwise dnsmasq will have to guess, based on the class (A, B or | |
774 | C) of the network address. The broadcast address is | |
7622fc06 | 775 | always optional. It is always |
8ef5ada2 SK |
776 | allowed to have more than one dhcp-range in a single subnet. |
777 | ||
1adadf58 | 778 | For IPv6, the parameters are slightly different: instead of netmask |
4c82efc5 VG |
779 | and broadcast address, there is an optional prefix length which must |
780 | be equal to or larger then the prefix length on the local interface. If not | |
1adadf58 SK |
781 | given, this defaults to 64. Unlike the IPv4 case, the prefix length is not |
782 | automatically derived from the interface configuration. The mimimum | |
783 | size of the prefix length is 64. | |
784 | ||
34d0a36a SK |
785 | IPv6 (only) supports another type of range. In this, the start address and optional end address contain only the network part (ie ::1) and they are followed by |
786 | .B constructor:<interface>. | |
787 | This forms a template which describes how to create ranges, based on the addresses assigned to the interface. For instance | |
788 | ||
83f28bef | 789 | .B --dhcp-range=::1,::400,constructor:eth0 |
34d0a36a | 790 | |
861c8914 | 791 | will look for addresses on |
429805db SK |
792 | eth0 and then create a range from <network>::1 to <network>::400. If |
793 | the interface is assigned more than one network, then the | |
794 | corresponding ranges will be automatically created, and then | |
795 | deprecated and finally removed again as the address is deprecated and | |
796 | then deleted. The interface name may have a final "*" wildcard. Note | |
861c8914 SK |
797 | that just any address on eth0 will not do: it must not be an |
798 | autoconfigured or privacy address, or be deprecated. | |
34d0a36a | 799 | |
e4cdbbf5 VG |
800 | If a dhcp-range is only being used for stateless DHCP and/or SLAAC, |
801 | then the address can be simply :: | |
802 | ||
803 | .B --dhcp-range=::,constructor:eth0 | |
804 | ||
e4cdbbf5 | 805 | |
8ef5ada2 SK |
806 | The optional |
807 | .B set:<tag> | |
808 | sets an alphanumeric label which marks this network so that | |
0a852541 | 809 | dhcp options may be specified on a per-network basis. |
8ef5ada2 | 810 | When it is prefixed with 'tag:' instead, then its meaning changes from setting |
c5ad4e79 SK |
811 | a tag to matching it. Only one tag may be set, but more than one tag |
812 | may be matched. | |
813 | ||
e8ca69ea | 814 | The optional <mode> keyword may be |
33820b7e SK |
815 | .B static |
816 | which tells dnsmasq to enable DHCP for the network specified, but not | |
7622fc06 | 817 | to dynamically allocate IP addresses: only hosts which have static |
33820b7e SK |
818 | addresses given via |
819 | .B dhcp-host | |
52002051 SK |
820 | or from /etc/ethers will be served. A static-only subnet with address |
821 | all zeros may be used as a "catch-all" address to enable replies to all | |
822 | Information-request packets on a subnet which is provided with | |
823 | stateless DHCPv6, ie | |
e62e9b61 | 824 | .B --dhcp-range=::,static |
c5ad4e79 | 825 | |
e46164e0 | 826 | For IPv4, the <mode> may be |
7622fc06 SK |
827 | .B proxy |
828 | in which case dnsmasq will provide proxy-DHCP on the specified | |
829 | subnet. (See | |
830 | .B pxe-prompt | |
831 | and | |
832 | .B pxe-service | |
e8ca69ea SK |
833 | for details.) |
834 | ||
835 | For IPv6, the mode may be some combination of | |
7ea3d3fd | 836 | .B ra-only, slaac, ra-names, ra-stateless, ra-advrouter. |
8ef5ada2 | 837 | |
c5ad4e79 | 838 | .B ra-only |
e8ca69ea SK |
839 | tells dnsmasq to offer Router Advertisement only on this subnet, |
840 | and not DHCP. | |
841 | ||
842 | .B slaac | |
843 | tells dnsmasq to offer Router Advertisement on this subnet and to set | |
844 | the A bit in the router advertisement, so that the client will use | |
845 | SLAAC addresses. When used with a DHCP range or static DHCP address | |
846 | this results in the client having both a DHCP-assigned and a SLAAC | |
847 | address. | |
848 | ||
849 | .B ra-stateless | |
850 | sends router advertisements with the O and A bits set, and provides a | |
851 | stateless DHCP service. The client will use a SLAAC address, and use | |
852 | DHCP for other configuration information. | |
853 | ||
7023e382 | 854 | .B ra-names |
e8ca69ea | 855 | enables a mode |
7023e382 | 856 | which gives DNS names to dual-stack hosts which do SLAAC for |
884a6dfe | 857 | IPv6. Dnsmasq uses the host's IPv4 lease to derive the name, network |
7023e382 | 858 | segment and MAC address and assumes that the host will also have an |
e46164e0 | 859 | IPv6 address calculated using the SLAAC algorithm, on the same network |
884a6dfe SK |
860 | segment. The address is pinged, and if a reply is received, an AAAA |
861 | record is added to the DNS for this IPv6 | |
7023e382 | 862 | address. Note that this is only happens for directly-connected |
884a6dfe SK |
863 | networks, (not one doing DHCP via a relay) and it will not work |
864 | if a host is using privacy extensions. | |
e8ca69ea SK |
865 | .B ra-names |
866 | can be combined with | |
867 | .B ra-stateless | |
868 | and | |
869 | .B slaac. | |
c5ad4e79 | 870 | |
7ea3d3fd SK |
871 | .B ra-advrouter |
872 | enables a mode where router address(es) rather than prefix(es) are included in the advertisements. | |
873 | This is described in RFC-3775 section 7.2 and is used in mobile IPv6. In this mode the interval option | |
874 | is also included, as described in RFC-3775 section 7.3. | |
875 | ||
9e4abcb5 | 876 | .TP |
8ef5ada2 | 877 | .B \-G, --dhcp-host=[<hwaddr>][,id:<client_id>|*][,set:<tag>][,<ipaddr>][,<hostname>][,<lease_time>][,ignore] |
9e4abcb5 SK |
878 | Specify per host parameters for the DHCP server. This allows a machine |
879 | with a particular hardware address to be always allocated the same | |
880 | hostname, IP address and lease time. A hostname specified like this | |
881 | overrides any supplied by the DHCP client on the machine. It is also | |
c72daea8 | 882 | allowable to omit the hardware address and include the hostname, in |
9e4abcb5 SK |
883 | which case the IP address and lease times will apply to any machine |
884 | claiming that name. For example | |
885 | .B --dhcp-host=00:20:e0:3b:13:af,wap,infinite | |
886 | tells dnsmasq to give | |
cdeda28f | 887 | the machine with hardware address 00:20:e0:3b:13:af the name wap, and |
9e4abcb5 SK |
888 | an infinite DHCP lease. |
889 | .B --dhcp-host=lap,192.168.0.199 | |
890 | tells | |
891 | dnsmasq to always allocate the machine lap the IP address | |
8ef5ada2 SK |
892 | 192.168.0.199. |
893 | ||
894 | Addresses allocated like this are not constrained to be | |
895 | in the range given by the --dhcp-range option, but they must be in | |
896 | the same subnet as some valid dhcp-range. For | |
897 | subnets which don't need a pool of dynamically allocated addresses, | |
898 | use the "static" keyword in the dhcp-range declaration. | |
899 | ||
89500e31 SK |
900 | It is allowed to use client identifiers (called client |
901 | DUID in IPv6-land rather than | |
9e4abcb5 SK |
902 | hardware addresses to identify hosts by prefixing with 'id:'. Thus: |
903 | .B --dhcp-host=id:01:02:03:04,..... | |
904 | refers to the host with client identifier 01:02:03:04. It is also | |
905 | allowed to specify the client ID as text, like this: | |
a84fa1d0 | 906 | .B --dhcp-host=id:clientidastext,..... |
9009d746 | 907 | |
1adadf58 SK |
908 | A single |
909 | .B dhcp-host | |
910 | may contain an IPv4 address or an IPv6 address, or both. IPv6 addresses must be bracketed by square brackets thus: | |
911 | .B --dhcp-host=laptop,[1234::56] | |
30393100 SK |
912 | IPv6 addresses may contain only the host-identifier part: |
913 | .B --dhcp-host=laptop,[::56] | |
6f130def | 914 | in which case they act as wildcards in constructed dhcp ranges, with |
30393100 | 915 | the appropriate network part inserted. |
89500e31 SK |
916 | Note that in IPv6 DHCP, the hardware address may not be |
917 | available, though it normally is for direct-connected clients, or | |
918 | clients using DHCP relays which support RFC 6939. | |
1adadf58 | 919 | |
89500e31 SK |
920 | |
921 | For DHCPv4, the special option id:* means "ignore any client-id | |
a84fa1d0 SK |
922 | and use MAC addresses only." This is useful when a client presents a client-id sometimes |
923 | but not others. | |
9009d746 | 924 | |
1ab84e2f SK |
925 | If a name appears in /etc/hosts, the associated address can be |
926 | allocated to a DHCP lease, but only if a | |
927 | .B --dhcp-host | |
8ef5ada2 SK |
928 | option specifying the name also exists. Only one hostname can be |
929 | given in a | |
930 | .B dhcp-host | |
931 | option, but aliases are possible by using CNAMEs. (See | |
932 | .B --cname | |
933 | ). | |
934 | ||
935 | The special keyword "ignore" | |
33820b7e SK |
936 | tells dnsmasq to never offer a DHCP lease to a machine. The machine |
937 | can be specified by hardware address, client ID or hostname, for | |
938 | instance | |
939 | .B --dhcp-host=00:20:e0:3b:13:af,ignore | |
940 | This is | |
941 | useful when there is another DHCP server on the network which should | |
9009d746 SK |
942 | be used by some machines. |
943 | ||
a66d36ea | 944 | The set:<tag> construct sets the tag |
9009d746 | 945 | whenever this dhcp-host directive is in use. This can be used to |
8ef5ada2 SK |
946 | selectively send DHCP options just for this host. More than one tag |
947 | can be set in a dhcp-host directive (but not in other places where | |
948 | "set:<tag>" is allowed). When a host matches any | |
5aabfc78 | 949 | dhcp-host directive (or one implied by /etc/ethers) then the special |
8ef5ada2 | 950 | tag "known" is set. This allows dnsmasq to be configured to |
5aabfc78 | 951 | ignore requests from unknown machines using |
8ef5ada2 | 952 | .B --dhcp-ignore=tag:!known |
0a852541 SK |
953 | Ethernet addresses (but not client-ids) may have |
954 | wildcard bytes, so for example | |
955 | .B --dhcp-host=00:20:e0:3b:13:*,ignore | |
cdeda28f | 956 | will cause dnsmasq to ignore a range of hardware addresses. Note that |
0a852541 | 957 | the "*" will need to be escaped or quoted on a command line, but not |
9009d746 SK |
958 | in the configuration file. |
959 | ||
960 | Hardware addresses normally match any | |
cdeda28f SK |
961 | network (ARP) type, but it is possible to restrict them to a single |
962 | ARP type by preceding them with the ARP-type (in HEX) and "-". so | |
963 | .B --dhcp-host=06-00:20:e0:3b:13:af,1.2.3.4 | |
964 | will only match a | |
965 | Token-Ring hardware address, since the ARP-address type for token ring | |
9009d746 SK |
966 | is 6. |
967 | ||
1adadf58 | 968 | As a special case, in DHCPv4, it is possible to include more than one |
73a08a24 SK |
969 | hardware address. eg: |
970 | .B --dhcp-host=11:22:33:44:55:66,12:34:56:78:90:12,192.168.0.2 | |
971 | This allows an IP address to be associated with | |
9009d746 SK |
972 | multiple hardware addresses, and gives dnsmasq permission to abandon a |
973 | DHCP lease to one of the hardware addresses when another one asks for | |
974 | a lease. Beware that this is a dangerous thing to do, it will only | |
975 | work reliably if only one of the hardware addresses is active at any | |
73a08a24 SK |
976 | time and there is no way for dnsmasq to enforce this. It is, for instance, |
977 | useful to allocate a stable IP address to a laptop which | |
9009d746 | 978 | has both wired and wireless interfaces. |
5aabfc78 | 979 | .TP |
28866e95 SK |
980 | .B --dhcp-hostsfile=<path> |
981 | Read DHCP host information from the specified file. If a directory | |
982 | is given, then read all the files contained in that directory. The file contains | |
5aabfc78 SK |
983 | information about one host per line. The format of a line is the same |
984 | as text to the right of '=' in --dhcp-host. The advantage of storing DHCP host information | |
985 | in this file is that it can be changed without re-starting dnsmasq: | |
986 | the file will be re-read when dnsmasq receives SIGHUP. | |
824af85b | 987 | .TP |
28866e95 SK |
988 | .B --dhcp-optsfile=<path> |
989 | Read DHCP option information from the specified file. If a directory | |
990 | is given, then read all the files contained in that directory. The advantage of | |
824af85b | 991 | using this option is the same as for --dhcp-hostsfile: the |
1f15b81d SK |
992 | dhcp-optsfile will be re-read when dnsmasq receives SIGHUP. Note that |
993 | it is possible to encode the information in a | |
5f4dc5c6 SK |
994 | .TP |
995 | .B --dhcp-hostsdir=<path> | |
3d04f463 | 996 | This is equivalent to dhcp-hostsfile, except for the following. The path MUST be a |
5f4dc5c6 SK |
997 | directory, and not an individual file. Changed or new files within |
998 | the directory are read automatically, without the need to send SIGHUP. | |
999 | If a file is deleted for changed after it has been read by dnsmasq, then the | |
1000 | host record it contained will remain until dnsmasq recieves a SIGHUP, or | |
1001 | is restarted; ie host records are only added dynamically. | |
efb8b556 | 1002 | .TP |
3d04f463 SK |
1003 | .B --dhcp-optsdir=<path> |
1004 | This is equivalent to dhcp-optsfile, with the differences noted for --dhcp-hostsdir. | |
5f4dc5c6 | 1005 | .TP |
1f15b81d SK |
1006 | .B --dhcp-boot |
1007 | flag as DHCP options, using the options names bootfile-name, | |
1008 | server-ip-address and tftp-server. This allows these to be included | |
1009 | in a dhcp-optsfile. | |
44a2a316 SK |
1010 | .TP |
1011 | .B \-Z, --read-ethers | |
1012 | Read /etc/ethers for information about hosts for the DHCP server. The | |
1013 | format of /etc/ethers is a hardware address, followed by either a | |
1014 | hostname or dotted-quad IP address. When read by dnsmasq these lines | |
1015 | have exactly the same effect as | |
1016 | .B --dhcp-host | |
5aabfc78 | 1017 | options containing the same information. /etc/ethers is re-read when |
1adadf58 | 1018 | dnsmasq receives SIGHUP. IPv6 addresses are NOT read from /etc/ethers. |
9e4abcb5 | 1019 | .TP |
1adadf58 | 1020 | .B \-O, --dhcp-option=[tag:<tag>,[tag:<tag>,]][encap:<opt>,][vi-encap:<enterprise>,][vendor:[<vendor-class>],][<opt>|option:<opt-name>|option6:<opt>|option6:<opt-name>],[<value>[,<value>]] |
b8187c80 | 1021 | Specify different or extra options to DHCP clients. By default, |
9e4abcb5 SK |
1022 | dnsmasq sends some standard options to DHCP clients, the netmask and |
1023 | broadcast address are set to the same as the host running dnsmasq, and | |
1024 | the DNS server and default route are set to the address of the machine | |
1adadf58 | 1025 | running dnsmasq. (Equivalent rules apply for IPv6.) If the domain name option has been set, that is sent. |
f2621c7f SK |
1026 | This configuration allows these defaults to be overridden, |
1027 | or other options specified. The option, to be sent may be given as a | |
1028 | decimal number or as "option:<option-name>" The option numbers are | |
1029 | specified in RFC2132 and subsequent RFCs. The set of option-names | |
1030 | known by dnsmasq can be discovered by running "dnsmasq --help dhcp". | |
1031 | For example, to set the default route option to | |
9e4abcb5 | 1032 | 192.168.4.4, do |
f2621c7f SK |
1033 | .B --dhcp-option=3,192.168.4.4 |
1034 | or | |
1035 | .B --dhcp-option = option:router, 192.168.4.4 | |
9e4abcb5 | 1036 | and to set the time-server address to 192.168.0.4, do |
f2621c7f SK |
1037 | .B --dhcp-option = 42,192.168.0.4 |
1038 | or | |
1039 | .B --dhcp-option = option:ntp-server, 192.168.0.4 | |
c3a04081 SK |
1040 | The special address 0.0.0.0 is taken to mean "the address of the |
1041 | machine running dnsmasq". | |
1042 | ||
1043 | Data types allowed are comma separated | |
1044 | dotted-quad IPv4 addresses, []-wrapped IPv6 addresses, a decimal number, colon-separated hex digits | |
8ef5ada2 SK |
1045 | and a text string. If the optional tags are given then |
1046 | this option is only sent when all the tags are matched. | |
91dccd09 | 1047 | |
cdeda28f | 1048 | Special processing is done on a text argument for option 119, to |
832af0ba SK |
1049 | conform with RFC 3397. Text or dotted-quad IP addresses as arguments |
1050 | to option 120 are handled as per RFC 3361. Dotted-quad IP addresses | |
1051 | which are followed by a slash and then a netmask size are encoded as | |
1052 | described in RFC 3442. | |
cdeda28f | 1053 | |
1adadf58 SK |
1054 | IPv6 options are specified using the |
1055 | .B option6: | |
1056 | keyword, followed by the option number or option name. The IPv6 option | |
1057 | name space is disjoint from the IPv4 option name space. IPv6 addresses | |
1058 | in options must be bracketed with square brackets, eg. | |
1059 | .B --dhcp-option=option6:ntp-server,[1234::56] | |
c3a04081 SK |
1060 | For IPv6, [::] means "the global address of |
1061 | the machine running dnsmasq", whilst [fd00::] is replaced with the | |
1062 | ULA, if it exists, and [fe80::] with the link-local address. | |
1adadf58 | 1063 | |
9e4abcb5 | 1064 | Be careful: no checking is done that the correct type of data for the |
26128d27 | 1065 | option number is sent, it is quite possible to |
9e4abcb5 | 1066 | persuade dnsmasq to generate illegal DHCP packets with injudicious use |
91dccd09 SK |
1067 | of this flag. When the value is a decimal number, dnsmasq must determine how |
1068 | large the data item is. It does this by examining the option number and/or the | |
b8187c80 | 1069 | value, but can be overridden by appending a single letter flag as follows: |
91dccd09 | 1070 | b = one byte, s = two bytes, i = four bytes. This is mainly useful with |
3d8df260 SK |
1071 | encapsulated vendor class options (see below) where dnsmasq cannot |
1072 | determine data size from the option number. Option data which | |
1073 | consists solely of periods and digits will be interpreted by dnsmasq | |
1074 | as an IP address, and inserted into an option as such. To force a | |
1075 | literal string, use quotes. For instance when using option 66 to send | |
1076 | a literal IP address as TFTP server name, it is necessary to do | |
1077 | .B --dhcp-option=66,"1.2.3.4" | |
91dccd09 | 1078 | |
1adadf58 | 1079 | Encapsulated Vendor-class options may also be specified (IPv4 only) using |
91dccd09 | 1080 | --dhcp-option: for instance |
1b7ecd11 SK |
1081 | .B --dhcp-option=vendor:PXEClient,1,0.0.0.0 |
1082 | sends the encapsulated vendor | |
1083 | class-specific option "mftp-address=0.0.0.0" to any client whose | |
1084 | vendor-class matches "PXEClient". The vendor-class matching is | |
6b01084f SK |
1085 | substring based (see --dhcp-vendorclass for details). If a |
1086 | vendor-class option (number 60) is sent by dnsmasq, then that is used | |
1087 | for selecting encapsulated options in preference to any sent by the | |
1088 | client. It is | |
1b7ecd11 SK |
1089 | possible to omit the vendorclass completely; |
1090 | .B --dhcp-option=vendor:,1,0.0.0.0 | |
1adadf58 | 1091 | in which case the encapsulated option is always sent. |
73a08a24 | 1092 | |
1adadf58 | 1093 | Options may be encapsulated (IPv4 only) within other options: for instance |
73a08a24 SK |
1094 | .B --dhcp-option=encap:175, 190, "iscsi-client0" |
1095 | will send option 175, within which is the option 190. If multiple | |
1096 | options are given which are encapsulated with the same option number | |
1097 | then they will be correctly combined into one encapsulated option. | |
1098 | encap: and vendor: are may not both be set in the same dhcp-option. | |
1099 | ||
316e2730 SK |
1100 | The final variant on encapsulated options is "Vendor-Identifying |
1101 | Vendor Options" as specified by RFC3925. These are denoted like this: | |
1102 | .B --dhcp-option=vi-encap:2, 10, "text" | |
1103 | The number in the vi-encap: section is the IANA enterprise number | |
1adadf58 SK |
1104 | used to identify this option. This form of encapsulation is supported |
1105 | in IPv6. | |
1106 | ||
1b7ecd11 | 1107 | The address 0.0.0.0 is not treated specially in |
73a08a24 | 1108 | encapsulated options. |
9e4abcb5 | 1109 | .TP |
8ef5ada2 | 1110 | .B --dhcp-option-force=[tag:<tag>,[tag:<tag>,]][encap:<opt>,][vi-encap:<enterprise>,][vendor:[<vendor-class>],]<opt>,[<value>[,<value>]] |
6b01084f | 1111 | This works in exactly the same way as |
f2621c7f SK |
1112 | .B --dhcp-option |
1113 | except that the option will always be sent, even if the client does | |
6b01084f SK |
1114 | not ask for it in the parameter request list. This is sometimes |
1115 | needed, for example when sending options to PXELinux. | |
1116 | .TP | |
824af85b | 1117 | .B --dhcp-no-override |
1adadf58 | 1118 | (IPv4 only) Disable re-use of the DHCP servername and filename fields as extra |
824af85b SK |
1119 | option space. If it can, dnsmasq moves the boot server and filename |
1120 | information (from dhcp-boot) out of their dedicated fields into | |
1121 | DHCP options. This make extra space available in the DHCP packet for | |
1122 | options but can, rarely, confuse old or broken clients. This flag | |
1123 | forces "simple and safe" behaviour to avoid problems in such a case. | |
1124 | .TP | |
ff7eea27 SK |
1125 | .B --dhcp-relay=<local address>,<server address>[,<interface] |
1126 | Configure dnsmasq to do DHCP relay. The local address is an address | |
1127 | allocated to an interface on the host running dnsmasq. All DHCP | |
1128 | requests arriving on that interface will we relayed to a remote DHCP | |
1129 | server at the server address. It is possible to relay from a single local | |
1130 | address to multiple remote servers by using multiple dhcp-relay | |
1131 | configs with the same local address and different server | |
1132 | addresses. A server address must be an IP literal address, not a | |
1133 | domain name. In the case of DHCPv6, the server address may be the | |
1134 | ALL_SERVERS multicast address, ff05::1:3. In this case the interface | |
1135 | must be given, not be wildcard, and is used to direct the multicast to the | |
1136 | correct interface to reach the DHCP server. | |
1137 | ||
1138 | Access control for DHCP clients has the same rules as for the DHCP | |
1139 | server, see --interface, --except-interface, etc. The optional | |
1140 | interface name in the dhcp-relay config has a different function: it | |
1141 | controls on which interface DHCP replies from the server will be | |
1142 | accepted. This is intended for configurations which have three | |
1143 | interfaces: one being relayed from, a second connecting the DHCP | |
1144 | server, and a third untrusted network, typically the wider | |
1145 | internet. It avoids the possibility of spoof replies arriving via this | |
1146 | third interface. | |
1147 | ||
1148 | It is allowed to have dnsmasq act as a DHCP server on one set of | |
1149 | interfaces and relay from a disjoint set of interfaces. Note that | |
1150 | whilst it is quite possible to write configurations which appear to | |
1151 | act as a server and a relay on the same interface, this is not | |
1152 | supported: the relay function will take precedence. | |
1153 | ||
1154 | Both DHCPv4 and DHCPv6 relay is supported. It's not possible to relay | |
1155 | DHCPv4 to a DHCPv6 server or vice-versa. | |
1156 | .TP | |
1adadf58 | 1157 | .B \-U, --dhcp-vendorclass=set:<tag>,[enterprise:<IANA-enterprise number>,]<vendor-class> |
8ef5ada2 | 1158 | Map from a vendor-class string to a tag. Most DHCP clients provide a |
a222641c | 1159 | "vendor class" which represents, in some sense, the type of host. This option |
f2621c7f | 1160 | maps vendor classes to tags, so that DHCP options may be selectively delivered |
a84fa1d0 | 1161 | to different classes of hosts. For example |
8ef5ada2 | 1162 | .B dhcp-vendorclass=set:printers,Hewlett-Packard JetDirect |
a84fa1d0 | 1163 | will allow options to be set only for HP printers like so: |
8ef5ada2 | 1164 | .B --dhcp-option=tag:printers,3,192.168.4.4 |
a222641c SK |
1165 | The vendor-class string is |
1166 | substring matched against the vendor-class supplied by the client, to | |
1adadf58 SK |
1167 | allow fuzzy matching. The set: prefix is optional but allowed for |
1168 | consistency. | |
1169 | ||
1170 | Note that in IPv6 only, vendorclasses are namespaced with an | |
1171 | IANA-allocated enterprise number. This is given with enterprise: | |
1172 | keyword and specifies that only vendorclasses matching the specified | |
1173 | number should be searched. | |
a222641c | 1174 | .TP |
8ef5ada2 SK |
1175 | .B \-j, --dhcp-userclass=set:<tag>,<user-class> |
1176 | Map from a user-class string to a tag (with substring | |
a222641c SK |
1177 | matching, like vendor classes). Most DHCP clients provide a |
1178 | "user class" which is configurable. This option | |
f2621c7f | 1179 | maps user classes to tags, so that DHCP options may be selectively delivered |
a222641c SK |
1180 | to different classes of hosts. It is possible, for instance to use |
1181 | this to set a different printer server for hosts in the class | |
1182 | "accounts" than for hosts in the class "engineering". | |
a84fa1d0 | 1183 | .TP |
8ef5ada2 | 1184 | .B \-4, --dhcp-mac=set:<tag>,<MAC address> |
89500e31 | 1185 | Map from a MAC address to a tag. The MAC address may include |
cdeda28f | 1186 | wildcards. For example |
8ef5ada2 | 1187 | .B --dhcp-mac=set:3com,01:34:23:*:*:* |
cdeda28f SK |
1188 | will set the tag "3com" for any host whose MAC address matches the pattern. |
1189 | .TP | |
8ef5ada2 SK |
1190 | .B --dhcp-circuitid=set:<tag>,<circuit-id>, --dhcp-remoteid=set:<tag>,<remote-id> |
1191 | Map from RFC3046 relay agent options to tags. This data may | |
f2621c7f SK |
1192 | be provided by DHCP relay agents. The circuit-id or remote-id is |
1193 | normally given as colon-separated hex, but is also allowed to be a | |
1194 | simple string. If an exact match is achieved between the circuit or | |
1adadf58 SK |
1195 | agent ID and one provided by a relay agent, the tag is set. |
1196 | ||
1197 | .B dhcp-remoteid | |
1198 | (but not dhcp-circuitid) is supported in IPv6. | |
8ef5ada2 SK |
1199 | .TP |
1200 | .B --dhcp-subscrid=set:<tag>,<subscriber-id> | |
1adadf58 | 1201 | (IPv4 and IPv6) Map from RFC3993 subscriber-id relay agent options to tags. |
8ef5ada2 SK |
1202 | .TP |
1203 | .B --dhcp-proxy[=<ip addr>]...... | |
0793380b | 1204 | (IPv4 only) A normal DHCP relay agent is only used to forward the initial parts of |
8ef5ada2 SK |
1205 | a DHCP interaction to the DHCP server. Once a client is configured, it |
1206 | communicates directly with the server. This is undesirable if the | |
a66d36ea | 1207 | relay agent is adding extra information to the DHCP packets, such as |
8ef5ada2 SK |
1208 | that used by |
1209 | .B dhcp-circuitid | |
1210 | and | |
1211 | .B dhcp-remoteid. | |
1212 | A full relay implementation can use the RFC 5107 serverid-override | |
1213 | option to force the DHCP server to use the relay as a full proxy, with all | |
1214 | packets passing through it. This flag provides an alternative method | |
1215 | of doing the same thing, for relays which don't support RFC | |
1216 | 5107. Given alone, it manipulates the server-id for all interactions | |
1217 | via relays. If a list of IP addresses is given, only interactions via | |
1218 | relays at those addresses are affected. | |
1219 | .TP | |
1220 | .B --dhcp-match=set:<tag>,<option number>|option:<option name>|vi-encap:<enterprise>[,<value>] | |
1221 | Without a value, set the tag if the client sends a DHCP | |
73a08a24 SK |
1222 | option of the given number or name. When a value is given, set the tag only if |
1223 | the option is sent and matches the value. The value may be of the form | |
a66d36ea | 1224 | "01:ff:*:02" in which case the value must match (apart from wildcards) |
73a08a24 SK |
1225 | but the option sent may have unmatched data past the end of the |
1226 | value. The value may also be of the same form as in | |
1227 | .B dhcp-option | |
1228 | in which case the option sent is treated as an array, and one element | |
1229 | must match, so | |
1230 | ||
8ef5ada2 | 1231 | --dhcp-match=set:efi-ia32,option:client-arch,6 |
73a08a24 SK |
1232 | |
1233 | will set the tag "efi-ia32" if the the number 6 appears in the list of | |
1234 | architectures sent by the client in option 93. (See RFC 4578 for | |
316e2730 SK |
1235 | details.) If the value is a string, substring matching is used. |
1236 | ||
a66d36ea | 1237 | The special form with vi-encap:<enterprise number> matches against |
316e2730 | 1238 | vendor-identifying vendor classes for the specified enterprise. Please |
8ef5ada2 SK |
1239 | see RFC 3925 for more details of these rare and interesting beasts. |
1240 | .TP | |
1241 | .B --tag-if=set:<tag>[,set:<tag>[,tag:<tag>[,tag:<tag>]]] | |
1242 | Perform boolean operations on tags. Any tag appearing as set:<tag> is set if | |
1243 | all the tags which appear as tag:<tag> are set, (or unset when tag:!<tag> is used) | |
1244 | If no tag:<tag> appears set:<tag> tags are set unconditionally. | |
1245 | Any number of set: and tag: forms may appear, in any order. | |
1246 | Tag-if lines ares executed in order, so if the tag in tag:<tag> is a | |
1247 | tag set by another | |
1248 | .B tag-if, | |
1249 | the line which sets the tag must precede the one which tests it. | |
1250 | .TP | |
1251 | .B \-J, --dhcp-ignore=tag:<tag>[,tag:<tag>] | |
1252 | When all the given tags appear in the tag set ignore the host and do | |
26128d27 SK |
1253 | not allocate it a DHCP lease. |
1254 | .TP | |
8ef5ada2 SK |
1255 | .B --dhcp-ignore-names[=tag:<tag>[,tag:<tag>]] |
1256 | When all the given tags appear in the tag set, ignore any hostname | |
9e038946 | 1257 | provided by the host. Note that, unlike dhcp-ignore, it is permissible |
8ef5ada2 | 1258 | to supply no tags, in which case DHCP-client supplied hostnames |
832af0ba SK |
1259 | are always ignored, and DHCP hosts are added to the DNS using only |
1260 | dhcp-host configuration in dnsmasq and the contents of /etc/hosts and | |
1261 | /etc/ethers. | |
1262 | .TP | |
8ef5ada2 | 1263 | .B --dhcp-generate-names=tag:<tag>[,tag:<tag>] |
1adadf58 | 1264 | (IPv4 only) Generate a name for DHCP clients which do not otherwise have one, |
a66d36ea | 1265 | using the MAC address expressed in hex, separated by dashes. Note that |
8ef5ada2 SK |
1266 | if a host provides a name, it will be used by preference to this, |
1267 | unless | |
1268 | .B --dhcp-ignore-names | |
1269 | is set. | |
1270 | .TP | |
1271 | .B --dhcp-broadcast[=tag:<tag>[,tag:<tag>]] | |
1adadf58 | 1272 | (IPv4 only) When all the given tags appear in the tag set, always use broadcast to |
8ef5ada2 SK |
1273 | communicate with the host when it is unconfigured. It is permissible |
1274 | to supply no tags, in which case this is unconditional. Most DHCP clients which | |
824af85b SK |
1275 | need broadcast replies set a flag in their requests so that this |
1276 | happens automatically, some old BOOTP clients do not. | |
1277 | .TP | |
7de060b0 | 1278 | .B \-M, --dhcp-boot=[tag:<tag>,]<filename>,[<servername>[,<server address>|<tftp_servername>]] |
1adadf58 | 1279 | (IPv4 only) Set BOOTP options to be returned by the DHCP server. Server name and |
832af0ba SK |
1280 | address are optional: if not provided, the name is left empty, and the |
1281 | address set to the address of the machine running dnsmasq. If dnsmasq | |
1282 | is providing a TFTP service (see | |
1283 | .B --enable-tftp | |
1284 | ) then only the filename is required here to enable network booting. | |
8ef5ada2 SK |
1285 | If the optional tag(s) are given, |
1286 | they must match for this configuration to be sent. | |
7de060b0 SK |
1287 | Instead of an IP address, the TFTP server address can be given as a domain |
1288 | name which is looked up in /etc/hosts. This name can be associated in | |
1289 | /etc/hosts with multiple IP addresses, which are used round-robin. | |
1290 | This facility can be used to load balance the tftp load among a set of servers. | |
1291 | .TP | |
1292 | .B --dhcp-sequential-ip | |
1293 | Dnsmasq is designed to choose IP addresses for DHCP clients using a | |
1294 | hash of the client's MAC address. This normally allows a client's | |
1295 | address to remain stable long-term, even if the client sometimes allows its DHCP | |
1296 | lease to expire. In this default mode IP addresses are distributed | |
1297 | pseudo-randomly over the entire available address range. There are | |
1298 | sometimes circumstances (typically server deployment) where it is more | |
1299 | convenient to have IP | |
1300 | addresses allocated sequentially, starting from the lowest available | |
1301 | address, and setting this flag enables this mode. Note that in the | |
1302 | sequential mode, clients which allow a lease to expire are much more | |
1303 | likely to move IP address; for this reason it should not be generally used. | |
7622fc06 | 1304 | .TP |
751d6f4a | 1305 | .B --pxe-service=[tag:<tag>,]<CSA>,<menu text>[,<basename>|<bootservicetype>][,<server address>|<server_name>] |
7622fc06 SK |
1306 | Most uses of PXE boot-ROMS simply allow the PXE |
1307 | system to obtain an IP address and then download the file specified by | |
1308 | .B dhcp-boot | |
1309 | and execute it. However the PXE system is capable of more complex | |
1310 | functions when supported by a suitable DHCP server. | |
1311 | ||
1312 | This specifies a boot option which may appear in a PXE boot menu. <CSA> is | |
1313 | client system type, only services of the correct type will appear in a | |
1314 | menu. The known types are x86PC, PC98, IA64_EFI, Alpha, Arc_x86, | |
1315 | Intel_Lean_Client, IA32_EFI, BC_EFI, Xscale_EFI and X86-64_EFI; an | |
1316 | integer may be used for other types. The | |
1317 | parameter after the menu text may be a file name, in which case dnsmasq acts as a | |
1318 | boot server and directs the PXE client to download the file by TFTP, | |
1319 | either from itself ( | |
1320 | .B enable-tftp | |
751d6f4a SK |
1321 | must be set for this to work) or another TFTP server if the final server |
1322 | address/name is given. | |
7622fc06 SK |
1323 | Note that the "layer" |
1324 | suffix (normally ".0") is supplied by PXE, and should not be added to | |
1325 | the basename. If an integer boot service type, rather than a basename | |
1326 | is given, then the PXE client will search for a | |
1327 | suitable boot service for that type on the network. This search may be done | |
751d6f4a | 1328 | by broadcast, or direct to a server if its IP address/name is provided. |
316e2730 SK |
1329 | If no boot service type or filename is provided (or a boot service type of 0 is specified) |
1330 | then the menu entry will abort the net boot procedure and | |
751d6f4a SK |
1331 | continue booting from local media. The server address can be given as a domain |
1332 | name which is looked up in /etc/hosts. This name can be associated in | |
1333 | /etc/hosts with multiple IP addresses, which are used round-robin. | |
7622fc06 | 1334 | .TP |
8ef5ada2 | 1335 | .B --pxe-prompt=[tag:<tag>,]<prompt>[,<timeout>] |
7622fc06 SK |
1336 | Setting this provides a prompt to be displayed after PXE boot. If the |
1337 | timeout is given then after the | |
1338 | timeout has elapsed with no keyboard input, the first available menu | |
1339 | option will be automatically executed. If the timeout is zero then the first available menu | |
1340 | item will be executed immediately. If | |
1341 | .B pxe-prompt | |
a66d36ea | 1342 | is omitted the system will wait for user input if there are multiple |
7622fc06 SK |
1343 | items in the menu, but boot immediately if |
1344 | there is only one. See | |
1345 | .B pxe-service | |
1346 | for details of menu items. | |
1347 | ||
1348 | Dnsmasq supports PXE "proxy-DHCP", in this case another DHCP server on | |
1349 | the network is responsible for allocating IP addresses, and dnsmasq | |
1350 | simply provides the information given in | |
1351 | .B pxe-prompt | |
1352 | and | |
1353 | .B pxe-service | |
1354 | to allow netbooting. This mode is enabled using the | |
1355 | .B proxy | |
1356 | keyword in | |
1357 | .B dhcp-range. | |
9e4abcb5 | 1358 | .TP |
44a2a316 SK |
1359 | .B \-X, --dhcp-lease-max=<number> |
1360 | Limits dnsmasq to the specified maximum number of DHCP leases. The | |
8ef5ada2 | 1361 | default is 1000. This limit is to prevent DoS attacks from hosts which |
44a2a316 SK |
1362 | create thousands of leases and use lots of memory in the dnsmasq |
1363 | process. | |
1364 | .TP | |
fd9fa481 | 1365 | .B \-K, --dhcp-authoritative |
095f6255 SK |
1366 | Should be set when dnsmasq is definitely the only DHCP server on a network. |
1367 | For DHCPv4, it changes the behaviour from strict RFC compliance so that DHCP requests on | |
fd9fa481 | 1368 | unknown leases from unknown hosts are not ignored. This allows new hosts |
cdeda28f SK |
1369 | to get a lease without a tedious timeout under all circumstances. It also |
1370 | allows dnsmasq to rebuild its lease database without each client needing to | |
095f6255 SK |
1371 | reacquire a lease, if the database is lost. For DHCPv6 it sets the |
1372 | priority in replies to 255 (the maximum) instead of 0 (the minimum). | |
9e038946 SK |
1373 | .TP |
1374 | .B --dhcp-alternate-port[=<server port>[,<client port>]] | |
1adadf58 | 1375 | (IPv4 only) Change the ports used for DHCP from the default. If this option is |
9e038946 SK |
1376 | given alone, without arguments, it changes the ports used for DHCP |
1377 | from 67 and 68 to 1067 and 1068. If a single argument is given, that | |
1378 | port number is used for the server and the port number plus one used | |
1379 | for the client. Finally, two port numbers allows arbitrary | |
1380 | specification of both server and client ports for DHCP. | |
fd9fa481 | 1381 | .TP |
9009d746 | 1382 | .B \-3, --bootp-dynamic[=<network-id>[,<network-id>]] |
1adadf58 | 1383 | (IPv4 only) Enable dynamic allocation of IP addresses to BOOTP clients. Use this |
3d8df260 SK |
1384 | with care, since each address allocated to a BOOTP client is leased |
1385 | forever, and therefore becomes permanently unavailable for re-use by | |
9009d746 SK |
1386 | other hosts. if this is given without tags, then it unconditionally |
1387 | enables dynamic allocation. With tags, only when the tags are all | |
1388 | set. It may be repeated with different tag sets. | |
3d8df260 | 1389 | .TP |
5e9e0efb | 1390 | .B \-5, --no-ping |
23facf0d | 1391 | (IPv4 only) By default, the DHCP server will attempt to ensure that an address is |
5e9e0efb SK |
1392 | not in use before allocating it to a host. It does this by sending an |
1393 | ICMP echo request (aka "ping") to the address in question. If it gets | |
1394 | a reply, then the address must already be in use, and another is | |
1395 | tried. This flag disables this check. Use with caution. | |
1396 | .TP | |
f2621c7f SK |
1397 | .B --log-dhcp |
1398 | Extra logging for DHCP: log all the options sent to DHCP clients and | |
8ef5ada2 | 1399 | the tags used to determine them. |
f2621c7f | 1400 | .TP |
8c0b73d3 KDB |
1401 | .B --quiet-dhcp, --quiet-dhcp6, --quiet-ra |
1402 | Suppress logging of the routine operation of these protocols. Errors and | |
1403 | problems will still be logged. --quiet-dhcp and quiet-dhcp6 are | |
1404 | over-ridden by --log-dhcp. | |
1405 | .TP | |
9e4abcb5 | 1406 | .B \-l, --dhcp-leasefile=<path> |
73a08a24 | 1407 | Use the specified file to store DHCP lease information. |
208b65c5 | 1408 | .TP |
8b372704 SK |
1409 | .B --dhcp-duid=<enterprise-id>,<uid> |
1410 | (IPv6 only) Specify the server persistent UID which the DHCPv6 server | |
1411 | will use. This option is not normally required as dnsmasq creates a | |
1412 | DUID automatically when it is first needed. When given, this option | |
1413 | provides dnsmasq the data required to create a DUID-EN type DUID. Note | |
1414 | that once set, the DUID is stored in the lease database, so to change between DUID-EN and | |
1415 | automatically created DUIDs or vice-versa, the lease database must be | |
1416 | re-intialised. The enterprise-id is assigned by IANA, and the uid is a | |
1417 | string of hex octets unique to a particular device. | |
1418 | .TP | |
7cebd20f | 1419 | .B \-6 --dhcp-script=<path> |
a9530964 SK |
1420 | Whenever a new DHCP lease is created, or an old one destroyed, or a |
1421 | TFTP file transfer completes, the | |
8ef5ada2 SK |
1422 | executable specified by this option is run. <path> |
1423 | must be an absolute pathname, no PATH search occurs. | |
1424 | The arguments to the process | |
7cebd20f | 1425 | are "add", "old" or "del", the MAC |
1adadf58 | 1426 | address of the host (or DUID for IPv6) , the IP address, and the hostname, |
7cebd20f SK |
1427 | if known. "add" means a lease has been created, "del" means it has |
1428 | been destroyed, "old" is a notification of an existing lease when | |
208b65c5 SK |
1429 | dnsmasq starts or a change to MAC address or hostname of an existing |
1430 | lease (also, lease length or expiry and client-id, if leasefile-ro is set). | |
9009d746 SK |
1431 | If the MAC address is from a network type other than ethernet, |
1432 | it will have the network type prepended, eg "06-01:23:45:67:89:ab" for | |
1433 | token ring. The process is run as root (assuming that dnsmasq was originally run as | |
1697269c | 1434 | root) even if dnsmasq is configured to change UID to an unprivileged user. |
8ef5ada2 SK |
1435 | |
1436 | The environment is inherited from the invoker of dnsmasq, with some or | |
1adadf58 | 1437 | all of the following variables added |
8ef5ada2 | 1438 | |
1adadf58 | 1439 | For both IPv4 and IPv6: |
8ef5ada2 SK |
1440 | |
1441 | DNSMASQ_DOMAIN if the fully-qualified domain name of the host is | |
28866e95 SK |
1442 | known, this is set to the domain part. (Note that the hostname passed |
1443 | to the script as an argument is never fully-qualified.) | |
8ef5ada2 | 1444 | |
1adadf58 SK |
1445 | If the client provides a hostname, DNSMASQ_SUPPLIED_HOSTNAME |
1446 | ||
1447 | If the client provides user-classes, DNSMASQ_USER_CLASS0..DNSMASQ_USER_CLASSn | |
8ef5ada2 SK |
1448 | |
1449 | If dnsmasq was compiled with HAVE_BROKEN_RTC, then | |
208b65c5 | 1450 | the length of the lease (in seconds) is stored in |
1697269c | 1451 | DNSMASQ_LEASE_LENGTH, otherwise the time of lease expiry is stored in |
5aabfc78 SK |
1452 | DNSMASQ_LEASE_EXPIRES. The number of seconds until lease expiry is |
1453 | always stored in DNSMASQ_TIME_REMAINING. | |
8ef5ada2 | 1454 | |
5aabfc78 | 1455 | If a lease used to have a hostname, which is |
1697269c SK |
1456 | removed, an "old" event is generated with the new state of the lease, |
1457 | ie no name, and the former name is provided in the environment | |
8ef5ada2 SK |
1458 | variable DNSMASQ_OLD_HOSTNAME. |
1459 | ||
1460 | DNSMASQ_INTERFACE stores the name of | |
9e038946 | 1461 | the interface on which the request arrived; this is not set for "old" |
8ef5ada2 SK |
1462 | actions when dnsmasq restarts. |
1463 | ||
1464 | DNSMASQ_RELAY_ADDRESS is set if the client | |
316e2730 | 1465 | used a DHCP relay to contact dnsmasq and the IP address of the relay |
8ef5ada2 SK |
1466 | is known. |
1467 | ||
1468 | DNSMASQ_TAGS contains all the tags set during the | |
316e2730 | 1469 | DHCP transaction, separated by spaces. |
8ef5ada2 | 1470 | |
e46164e0 SK |
1471 | DNSMASQ_LOG_DHCP is set if |
1472 | .B --log-dhcp | |
1473 | is in effect. | |
a9530964 | 1474 | |
1adadf58 SK |
1475 | For IPv4 only: |
1476 | ||
1477 | DNSMASQ_CLIENT_ID if the host provided a client-id. | |
1478 | ||
dd1721c7 SK |
1479 | DNSMASQ_CIRCUIT_ID, DNSMASQ_SUBSCRIBER_ID, DNSMASQ_REMOTE_ID if a |
1480 | DHCP relay-agent added any of these options. | |
1481 | ||
1adadf58 SK |
1482 | If the client provides vendor-class, DNSMASQ_VENDOR_CLASS. |
1483 | ||
1484 | For IPv6 only: | |
1485 | ||
1486 | If the client provides vendor-class, DNSMASQ_VENDOR_CLASS_ID, | |
1487 | containing the IANA enterprise id for the class, and | |
1488 | DNSMASQ_VENDOR_CLASS0..DNSMASQ_VENDOR_CLASSn for the data. | |
1489 | ||
57f460de | 1490 | DNSMASQ_SERVER_DUID containing the DUID of the server: this is the same for |
1adadf58 SK |
1491 | every call to the script. |
1492 | ||
1493 | DNSMASQ_IAID containing the IAID for the lease. If the lease is a | |
1494 | temporary allocation, this is prefixed to 'T'. | |
1495 | ||
89500e31 | 1496 | DNSMASQ_MAC containing the MAC address of the client, if known. |
1adadf58 SK |
1497 | |
1498 | Note that the supplied hostname, vendorclass and userclass data is | |
1499 | only supplied for | |
1500 | "add" actions or "old" actions when a host resumes an existing lease, | |
1501 | since these data are not held in dnsmasq's lease | |
1502 | database. | |
1503 | ||
a9530964 SK |
1504 | |
1505 | ||
9e038946 | 1506 | All file descriptors are |
7cebd20f SK |
1507 | closed except stdin, stdout and stderr which are open to /dev/null |
1508 | (except in debug mode). | |
8ef5ada2 SK |
1509 | |
1510 | The script is not invoked concurrently: at most one instance | |
1511 | of the script is ever running (dnsmasq waits for an instance of script to exit | |
1512 | before running the next). Changes to the lease database are which | |
1513 | require the script to be invoked are queued awaiting exit of a running instance. | |
1514 | If this queueing allows multiple state changes occur to a single | |
1515 | lease before the script can be run then | |
1516 | earlier states are discarded and the current state of that lease is | |
1517 | reflected when the script finally runs. | |
1518 | ||
1519 | At dnsmasq startup, the script will be invoked for | |
7cebd20f | 1520 | all existing leases as they are read from the lease file. Expired |
8ef5ada2 | 1521 | leases will be called with "del" and others with "old". When dnsmasq |
5aabfc78 | 1522 | receives a HUP signal, the script will be invoked for existing leases |
9e038946 | 1523 | with an "old " event. |
a9530964 SK |
1524 | |
1525 | ||
1526 | There are two further actions which may appear as the first argument | |
1527 | to the script, "init" and "tftp". More may be added in the future, so | |
1528 | scripts should be written to ignore unknown actions. "init" is | |
e46164e0 | 1529 | described below in |
a9530964 SK |
1530 | .B --leasefile-ro |
1531 | The "tftp" action is invoked when a TFTP file transfer completes: the | |
1532 | arguments are the file size in bytes, the address to which the file | |
1533 | was sent, and the complete pathname of the file. | |
1534 | ||
9e038946 | 1535 | .TP |
57f460de SK |
1536 | .B --dhcp-luascript=<path> |
1537 | Specify a script written in Lua, to be run when leases are created, | |
1538 | destroyed or changed. To use this option, dnsmasq must be compiled | |
1539 | with the correct support. The Lua interpreter is intialised once, when | |
1540 | dnsmasq starts, so that global variables persist between lease | |
1541 | events. The Lua code must define a | |
1542 | .B lease | |
1543 | function, and may provide | |
1544 | .B init | |
1545 | and | |
1546 | .B shutdown | |
1547 | functions, which are called, without arguments when dnsmasq starts up | |
a9530964 SK |
1548 | and terminates. It may also provide a |
1549 | .B tftp | |
1550 | function. | |
57f460de SK |
1551 | |
1552 | The | |
1553 | .B lease | |
a9530964 | 1554 | function receives the information detailed in |
57f460de SK |
1555 | .B --dhcp-script. |
1556 | It gets two arguments, firstly the action, which is a string | |
1557 | containing, "add", "old" or "del", and secondly a table of tag value | |
1558 | pairs. The tags mostly correspond to the environment variables | |
1559 | detailed above, for instance the tag "domain" holds the same data as | |
1560 | the environment variable DNSMASQ_DOMAIN. There are a few extra tags | |
1561 | which hold the data supplied as arguments to | |
1562 | .B --dhcp-script. | |
1563 | These are | |
1564 | .B mac_address, ip_address | |
1565 | and | |
1566 | .B hostname | |
1567 | for IPv4, and | |
1568 | .B client_duid, ip_address | |
1569 | and | |
1570 | .B hostname | |
a9530964 SK |
1571 | for IPv6. |
1572 | ||
1573 | The | |
1574 | .B tftp | |
1575 | function is called in the same way as the lease function, and the | |
1576 | table holds the tags | |
1577 | .B destination_address, | |
1578 | .B file_name | |
1579 | and | |
1580 | .B file_size. | |
57f460de | 1581 | .TP |
9e038946 | 1582 | .B --dhcp-scriptuser |
57f460de | 1583 | Specify the user as which to run the lease-change script or Lua script. This defaults to root, but can be changed to another user using this flag. |
208b65c5 SK |
1584 | .TP |
1585 | .B \-9, --leasefile-ro | |
1586 | Completely suppress use of the lease database file. The file will not | |
1587 | be created, read, or written. Change the way the lease-change | |
1588 | script (if one is provided) is called, so that the lease database may | |
1589 | be maintained in external storage by the script. In addition to the | |
f2621c7f | 1590 | invocations given in |
208b65c5 SK |
1591 | .B --dhcp-script |
1592 | the lease-change script is called once, at dnsmasq startup, with the | |
1593 | single argument "init". When called like this the script should write | |
1594 | the saved state of the lease database, in dnsmasq leasefile format, to | |
1595 | stdout and exit with zero exit code. Setting this | |
1596 | option also forces the leasechange script to be called on changes | |
1597 | to the client-id and lease length and expiry time. | |
9e4abcb5 | 1598 | .TP |
832af0ba SK |
1599 | .B --bridge-interface=<interface>,<alias>[,<alias>] |
1600 | Treat DHCP request packets arriving at any of the <alias> interfaces | |
7622fc06 SK |
1601 | as if they had arrived at <interface>. This option is necessary when |
1602 | using "old style" bridging on BSD platforms, since | |
832af0ba | 1603 | packets arrive at tap interfaces which don't have an IP address. |
70772c90 | 1604 | A trailing '*' wildcard can be used in each <alias>. |
832af0ba | 1605 | .TP |
28866e95 | 1606 | .B \-s, --domain=<domain>[,<address range>[,local]] |
9009d746 SK |
1607 | Specifies DNS domains for the DHCP server. Domains may be be given |
1608 | unconditionally (without the IP range) or for limited IP ranges. This has two effects; | |
9e4abcb5 SK |
1609 | firstly it causes the DHCP server to return the domain to any hosts |
1610 | which request it, and secondly it sets the domain which it is legal | |
1b7ecd11 SK |
1611 | for DHCP-configured hosts to claim. The intention is to constrain |
1612 | hostnames so that an untrusted host on the LAN cannot advertise | |
1613 | its name via dhcp as e.g. "microsoft.com" and capture traffic not | |
1614 | meant for it. If no domain suffix is specified, then any DHCP | |
1615 | hostname with a domain part (ie with a period) will be disallowed | |
1616 | and logged. If suffix is specified, then hostnames with a domain | |
1617 | part are allowed, provided the domain part matches the suffix. In | |
1618 | addition, when a suffix is set then hostnames without a domain | |
1619 | part have the suffix added as an optional domain part. Eg on my network I can set | |
3d8df260 | 1620 | .B --domain=thekelleys.org.uk |
9e4abcb5 SK |
1621 | and have a machine whose DHCP hostname is "laptop". The IP address for that machine is available from |
1622 | .B dnsmasq | |
de37951c SK |
1623 | both as "laptop" and "laptop.thekelleys.org.uk". If the domain is |
1624 | given as "#" then the domain is read from the first "search" directive | |
28866e95 SK |
1625 | in /etc/resolv.conf (or equivalent). |
1626 | ||
1627 | The address range can be of the form | |
9009d746 SK |
1628 | <ip address>,<ip address> or <ip address>/<netmask> or just a single |
1629 | <ip address>. See | |
1630 | .B --dhcp-fqdn | |
1631 | which can change the behaviour of dnsmasq with domains. | |
28866e95 SK |
1632 | |
1633 | If the address range is given as ip-address/network-size, then a | |
1634 | additional flag "local" may be supplied which has the effect of adding | |
1635 | --local declarations for forward and reverse DNS queries. Eg. | |
1636 | .B --domain=thekelleys.org.uk,192.168.0.0/24,local | |
1637 | is identical to | |
1638 | .B --domain=thekelleys.org.uk,192.168.0.0/24 | |
1639 | --local=/thekelleys.org.uk/ --local=/0.168.192.in-addr.arpa/ | |
1640 | The network size must be 8, 16 or 24 for this to be legal. | |
9009d746 SK |
1641 | .TP |
1642 | .B --dhcp-fqdn | |
1643 | In the default mode, dnsmasq inserts the unqualified names of | |
1644 | DHCP clients into the DNS. For this reason, the names must be unique, | |
1645 | even if two clients which have the same name are in different | |
1646 | domains. If a second DHCP client appears which has the same name as an | |
a66d36ea | 1647 | existing client, the name is transferred to the new client. If |
9009d746 SK |
1648 | .B --dhcp-fqdn |
1649 | is set, this behaviour changes: the unqualified name is no longer | |
1650 | put in the DNS, only the qualified name. Two DHCP clients with the | |
1651 | same name may both keep the name, provided that the domain part is | |
1652 | different (ie the fully qualified names differ.) To ensure that all | |
1653 | names have a domain part, there must be at least | |
1654 | .B --domain | |
1655 | without an address specified when | |
1656 | .B --dhcp-fqdn | |
1657 | is set. | |
9e4abcb5 | 1658 | .TP |
c72daea8 SK |
1659 | .B --dhcp-client-update |
1660 | Normally, when giving a DHCP lease, dnsmasq sets flags in the FQDN | |
1661 | option to tell the client not to attempt a DDNS update with its name | |
1662 | and IP address. This is because the name-IP pair is automatically | |
1663 | added into dnsmasq's DNS view. This flag suppresses that behaviour, | |
1664 | this is useful, for instance, to allow Windows clients to update | |
1665 | Active Directory servers. See RFC 4702 for details. | |
1666 | .TP | |
c5ad4e79 SK |
1667 | .B --enable-ra |
1668 | Enable dnsmasq's IPv6 Router Advertisement feature. DHCPv6 doesn't | |
1669 | handle complete network configuration in the same way as DHCPv4. Router | |
1670 | discovery and (possibly) prefix discovery for autonomous address | |
1671 | creation are handled by a different protocol. When DHCP is in use, | |
1672 | only a subset of this is needed, and dnsmasq can handle it, using | |
1673 | existing DHCP configuration to provide most data. When RA is enabled, | |
1674 | dnsmasq will advertise a prefix for each dhcp-range, with default | |
1675 | router and recursive DNS server as the relevant link-local address on | |
e8ca69ea SK |
1676 | the machine running dnsmasq. By default, he "managed address" bits are set, and |
1677 | the "use SLAAC" bit is reset. This can be changed for individual | |
1678 | subnets with the mode keywords described in | |
1679 | .B --dhcp-range. | |
18f0fb05 SK |
1680 | RFC6106 DNS parameters are included in the advertisements. By default, |
1681 | the relevant link-local address of the machine running dnsmasq is sent | |
1682 | as recursive DNS server. If provided, the DHCPv6 options dns-server and | |
1683 | domain-search are used for RDNSS and DNSSL. | |
c5ad4e79 | 1684 | .TP |
c4cd95df SK |
1685 | .B --ra-param=<interface>,[high|low],[[<ra-interval>],<router lifetime>] |
1686 | Set non-default values for router advertisements sent via an | |
1687 | interface. The priority field for the router may be altered from the | |
1688 | default of medium with eg | |
1689 | .B --ra-param=eth0,high. | |
1690 | The interval between router advertisements may be set (in seconds) with | |
1691 | .B --ra-param=eth0,60. | |
1692 | The lifetime of the route may be changed or set to zero, which allows | |
1693 | a router to advertise prefixes but not a route via itself. | |
1694 | .B --ra-parm=eth0,0,0 | |
1695 | (A value of zero for the interval means the default value.) All three parameters may be set at once. | |
1696 | .B --ra-param=low,60,1200 | |
1697 | The interface field may include a wildcard. | |
8d030462 | 1698 | .TP |
2937f8a0 | 1699 | .B --enable-tftp[=<interface>[,<interface>]] |
832af0ba | 1700 | Enable the TFTP server function. This is deliberately limited to that |
9e038946 | 1701 | needed to net-boot a client. Only reading is allowed; the tsize and |
8ef5ada2 | 1702 | blksize extensions are supported (tsize is only supported in octet |
2937f8a0 SK |
1703 | mode). Without an argument, the TFTP service is provided to the same set of interfaces as DHCP service. |
1704 | If the list of interfaces is provided, that defines which interfaces recieve TFTP service. | |
832af0ba | 1705 | .TP |
8ef5ada2 | 1706 | .B --tftp-root=<directory>[,<interface>] |
832af0ba SK |
1707 | Look for files to transfer using TFTP relative to the given |
1708 | directory. When this is set, TFTP paths which include ".." are | |
1709 | rejected, to stop clients getting outside the specified root. | |
f2621c7f | 1710 | Absolute paths (starting with /) are allowed, but they must be within |
8ef5ada2 SK |
1711 | the tftp-root. If the optional interface argument is given, the |
1712 | directory is only used for TFTP requests via that interface. | |
832af0ba | 1713 | .TP |
30d0879e ST |
1714 | .B --tftp-no-fail |
1715 | Do not abort startup if specified tftp root directories are inaccessible. | |
1716 | .TP | |
5aabfc78 SK |
1717 | .B --tftp-unique-root |
1718 | Add the IP address of the TFTP client as a path component on the end | |
1719 | of the TFTP-root (in standard dotted-quad format). Only valid if a | |
1720 | tftp-root is set and the directory exists. For instance, if tftp-root is "/tftp" and client | |
1721 | 1.2.3.4 requests file "myfile" then the effective path will be | |
1722 | "/tftp/1.2.3.4/myfile" if /tftp/1.2.3.4 exists or /tftp/myfile otherwise. | |
1723 | .TP | |
832af0ba | 1724 | .B --tftp-secure |
5aabfc78 | 1725 | Enable TFTP secure mode: without this, any file which is readable by |
832af0ba SK |
1726 | the dnsmasq process under normal unix access-control rules is |
1727 | available via TFTP. When the --tftp-secure flag is given, only files | |
1728 | owned by the user running the dnsmasq process are accessible. If | |
1729 | dnsmasq is being run as root, different rules apply: --tftp-secure | |
1b7ecd11 | 1730 | has no effect, but only files which have the world-readable bit set |
832af0ba SK |
1731 | are accessible. It is not recommended to run dnsmasq as root with TFTP |
1732 | enabled, and certainly not without specifying --tftp-root. Doing so | |
1733 | can expose any world-readable file on the server to any host on the net. | |
1734 | .TP | |
61ce600b SK |
1735 | .B --tftp-lowercase |
1736 | Convert filenames in TFTP requests to all lowercase. This is useful | |
1737 | for requests from Windows machines, which have case-insensitive | |
1738 | filesystems and tend to play fast-and-loose with case in filenames. | |
1739 | Note that dnsmasq's tftp server always converts "\\" to "/" in filenames. | |
1740 | .TP | |
832af0ba SK |
1741 | .B --tftp-max=<connections> |
1742 | Set the maximum number of concurrent TFTP connections allowed. This | |
1743 | defaults to 50. When serving a large number of TFTP connections, | |
1744 | per-process file descriptor limits may be encountered. Dnsmasq needs | |
1745 | one file descriptor for each concurrent TFTP connection and one | |
1746 | file descriptor per unique file (plus a few others). So serving the | |
1747 | same file simultaneously to n clients will use require about n + 10 file | |
1748 | descriptors, serving different files simultaneously to n clients will | |
824af85b SK |
1749 | require about (2*n) + 10 descriptors. If |
1750 | .B --tftp-port-range | |
1751 | is given, that can affect the number of concurrent connections. | |
6b01084f SK |
1752 | .TP |
1753 | .B --tftp-no-blocksize | |
1754 | Stop the TFTP server from negotiating the "blocksize" option with a | |
1755 | client. Some buggy clients request this option but then behave badly | |
1756 | when it is granted. | |
824af85b SK |
1757 | .TP |
1758 | .B --tftp-port-range=<start>,<end> | |
1759 | A TFTP server listens on a well-known port (69) for connection initiation, | |
1760 | but it also uses a dynamically-allocated port for each | |
1761 | connection. Normally these are allocated by the OS, but this option | |
1762 | specifies a range of ports for use by TFTP transfers. This can be | |
1763 | useful when TFTP has to traverse a firewall. The start of the range | |
1764 | cannot be lower than 1025 unless dnsmasq is running as root. The number | |
1765 | of concurrent TFTP connections is limited by the size of the port range. | |
832af0ba | 1766 | .TP |
b8187c80 SK |
1767 | .B \-C, --conf-file=<file> |
1768 | Specify a different configuration file. The conf-file option is also allowed in | |
28866e95 SK |
1769 | configuration files, to include multiple configuration files. A |
1770 | filename of "-" causes dnsmasq to read configuration from stdin. | |
849a8357 | 1771 | .TP |
3e1551a1 | 1772 | .B \-7, --conf-dir=<directory>[,<file-extension>......], |
849a8357 | 1773 | Read all the files in the given directory as configuration |
1f15b81d SK |
1774 | files. If extension(s) are given, any files which end in those |
1775 | extensions are skipped. Any files whose names end in ~ or start with . or start and end | |
3e1551a1 SK |
1776 | with # are always skipped. If the extension starts with * then only files |
1777 | which have that extension are loaded. So | |
1778 | .B --conf-dir=/path/to/dir,*.conf | |
1779 | loads all files with the suffix .conf in /path/to/dir. This flag may be given on the command | |
1780 | line or in a configuration file. If giving it on the command line, be sure to | |
1781 | escape * characters. | |
7b1eae4f SK |
1782 | .TP |
1783 | .B --servers-file=<file> | |
1784 | A special case of | |
1785 | .B --conf-file | |
1786 | which differs in two respects. Firstly, only --server and --rev-server are allowed | |
1787 | in the configuration file included. Secondly, the file is re-read and the configuration | |
1788 | therein is updated when dnsmasq recieves SIGHUP. | |
9e4abcb5 | 1789 | .SH CONFIG FILE |
3be34541 SK |
1790 | At startup, dnsmasq reads |
1791 | .I /etc/dnsmasq.conf, | |
1792 | if it exists. (On | |
1793 | FreeBSD, the file is | |
1794 | .I /usr/local/etc/dnsmasq.conf | |
b8187c80 SK |
1795 | ) (but see the |
1796 | .B \-C | |
849a8357 SK |
1797 | and |
1798 | .B \-7 | |
1799 | options.) The format of this | |
9e4abcb5 SK |
1800 | file consists of one option per line, exactly as the long options detailed |
1801 | in the OPTIONS section but without the leading "--". Lines starting with # are comments and ignored. For | |
b49644f3 | 1802 | options which may only be specified once, the configuration file overrides |
b8187c80 | 1803 | the command line. Quoting is allowed in a config file: |
3d8df260 | 1804 | between " quotes the special meanings of ,:. and # are removed and the |
824af85b SK |
1805 | following escapes are allowed: \\\\ \\" \\t \\e \\b \\r and \\n. The later |
1806 | corresponding to tab, escape, backspace, return and newline. | |
9e4abcb5 SK |
1807 | .SH NOTES |
1808 | When it receives a SIGHUP, | |
1809 | .B dnsmasq | |
3be34541 | 1810 | clears its cache and then re-loads |
5aabfc78 SK |
1811 | .I /etc/hosts |
1812 | and | |
1813 | .I /etc/ethers | |
3d04f463 SK |
1814 | and any file given by --dhcp-hostsfile, --dhcp-hostsdir, --dhcp-optsfile, |
1815 | --dhcp-optsdir, --addn-hosts or --hostsdir. | |
5aabfc78 SK |
1816 | The dhcp lease change script is called for all |
1817 | existing DHCP leases. If | |
9e4abcb5 SK |
1818 | .B |
1819 | --no-poll | |
3be34541 SK |
1820 | is set SIGHUP also re-reads |
1821 | .I /etc/resolv.conf. | |
1822 | SIGHUP | |
b49644f3 | 1823 | does NOT re-read the configuration file. |
9e4abcb5 SK |
1824 | .PP |
1825 | When it receives a SIGUSR1, | |
1826 | .B dnsmasq | |
824af85b | 1827 | writes statistics to the system log. It writes the cache size, |
9e4abcb5 SK |
1828 | the number of names which have had to removed from the cache before |
1829 | they expired in order to make room for new names and the total number | |
fec216df SK |
1830 | of names that have been inserted into the cache. The number of cache hits and |
1831 | misses and the number of authoritative queries answered are also given. For each upstream | |
824af85b SK |
1832 | server it gives the number of queries sent, and the number which |
1833 | resulted in an error. In | |
9e4abcb5 | 1834 | .B --no-daemon |
5aabfc78 | 1835 | mode or when full logging is enabled (-q), a complete dump of the |
fec216df SK |
1836 | contents of the cache is made. |
1837 | ||
1838 | The cache statistics are also available in the DNS as answers to | |
1839 | queries of class CHAOS and type TXT in domain bind. The domain names are cachesize.bind, insertions.bind, evictions.bind, | |
1840 | misses.bind, hits.bind, auth.bind and servers.bind. An example command to query this, using the | |
1841 | .B dig | |
1842 | utility would be | |
1843 | ||
1844 | dig +short chaos txt cachesize.bind | |
1845 | ||
5aabfc78 SK |
1846 | .PP |
1847 | When it receives SIGUSR2 and it is logging direct to a file (see | |
1848 | .B --log-facility | |
1849 | ) | |
1850 | .B dnsmasq | |
1851 | will close and reopen the log file. Note that during this operation, | |
1852 | dnsmasq will not be running as root. When it first creates the logfile | |
1853 | dnsmasq changes the ownership of the file to the non-root user it will run | |
1854 | as. Logrotate should be configured to create a new log file with | |
9e038946 | 1855 | the ownership which matches the existing one before sending SIGUSR2. |
5aabfc78 SK |
1856 | If TCP DNS queries are in progress, the old logfile will remain open in |
1857 | child processes which are handling TCP queries and may continue to be | |
1858 | written. There is a limit of 150 seconds, after which all existing TCP | |
1859 | processes will have expired: for this reason, it is not wise to | |
1860 | configure logfile compression for logfiles which have just been | |
1861 | rotated. Using logrotate, the required options are | |
1862 | .B create | |
1863 | and | |
1864 | .B delaycompress. | |
1865 | ||
1866 | ||
9e4abcb5 | 1867 | .PP |
9e4abcb5 SK |
1868 | Dnsmasq is a DNS query forwarder: it it not capable of recursively |
1869 | answering arbitrary queries starting from the root servers but | |
1870 | forwards such queries to a fully recursive upstream DNS server which is | |
1871 | typically provided by an ISP. By default, dnsmasq reads | |
3be34541 SK |
1872 | .I /etc/resolv.conf |
1873 | to discover the IP | |
9e4abcb5 SK |
1874 | addresses of the upstream nameservers it should use, since the |
1875 | information is typically stored there. Unless | |
1876 | .B --no-poll | |
1877 | is used, | |
1878 | .B dnsmasq | |
3be34541 SK |
1879 | checks the modification time of |
1880 | .I /etc/resolv.conf | |
1881 | (or equivalent if | |
9e4abcb5 SK |
1882 | .B \--resolv-file |
1883 | is used) and re-reads it if it changes. This allows the DNS servers to | |
1884 | be set dynamically by PPP or DHCP since both protocols provide the | |
1885 | information. | |
3be34541 SK |
1886 | Absence of |
1887 | .I /etc/resolv.conf | |
1888 | is not an error | |
9e4abcb5 | 1889 | since it may not have been created before a PPP connection exists. Dnsmasq |
3be34541 SK |
1890 | simply keeps checking in case |
1891 | .I /etc/resolv.conf | |
1892 | is created at any | |
9e4abcb5 SK |
1893 | time. Dnsmasq can be told to parse more than one resolv.conf |
1894 | file. This is useful on a laptop, where both PPP and DHCP may be used: | |
3be34541 SK |
1895 | dnsmasq can be set to poll both |
1896 | .I /etc/ppp/resolv.conf | |
1897 | and | |
1898 | .I /etc/dhcpc/resolv.conf | |
1899 | and will use the contents of whichever changed | |
9e4abcb5 SK |
1900 | last, giving automatic switching between DNS servers. |
1901 | .PP | |
1902 | Upstream servers may also be specified on the command line or in | |
b49644f3 | 1903 | the configuration file. These server specifications optionally take a |
9e4abcb5 SK |
1904 | domain name which tells dnsmasq to use that server only to find names |
1905 | in that particular domain. | |
1906 | .PP | |
1907 | In order to configure dnsmasq to act as cache for the host on which it is running, put "nameserver 127.0.0.1" in | |
1908 | .I /etc/resolv.conf | |
1909 | to force local processes to send queries to | |
1910 | dnsmasq. Then either specify the upstream servers directly to dnsmasq | |
1911 | using | |
1912 | .B \--server | |
1913 | options or put their addresses real in another file, say | |
1914 | .I /etc/resolv.dnsmasq | |
1915 | and run dnsmasq with the | |
1916 | .B \-r /etc/resolv.dnsmasq | |
1917 | option. This second technique allows for dynamic update of the server | |
1918 | addresses by PPP or DHCP. | |
f6b7dc47 SK |
1919 | .PP |
1920 | Addresses in /etc/hosts will "shadow" different addresses for the same | |
1921 | names in the upstream DNS, so "mycompany.com 1.2.3.4" in /etc/hosts will ensure that | |
1922 | queries for "mycompany.com" always return 1.2.3.4 even if queries in | |
1923 | the upstream DNS would otherwise return a different address. There is | |
1924 | one exception to this: if the upstream DNS contains a CNAME which | |
1925 | points to a shadowed name, then looking up the CNAME through dnsmasq | |
1926 | will result in the unshadowed address associated with the target of | |
1927 | the CNAME. To work around this, add the CNAME to /etc/hosts so that | |
1928 | the CNAME is shadowed too. | |
1929 | ||
3be34541 | 1930 | .PP |
8ef5ada2 SK |
1931 | The tag system works as follows: For each DHCP request, dnsmasq |
1932 | collects a set of valid tags from active configuration lines which | |
1933 | include set:<tag>, including one from the | |
26128d27 SK |
1934 | .B dhcp-range |
1935 | used to allocate the address, one from any matching | |
1936 | .B dhcp-host | |
9009d746 | 1937 | (and "known" if a dhcp-host matches) |
8ef5ada2 SK |
1938 | The tag "bootp" is set for BOOTP requests, and a tag whose name is the |
1939 | name of the interface on which the request arrived is also set. | |
1940 | ||
a66d36ea | 1941 | Any configuration lines which include one or more tag:<tag> constructs |
8ef5ada2 SK |
1942 | will only be valid if all that tags are matched in the set derived |
1943 | above. Typically this is dhcp-option. | |
26128d27 | 1944 | .B dhcp-option |
8ef5ada2 | 1945 | which has tags will be used in preference to an untagged |
26128d27 SK |
1946 | .B dhcp-option, |
1947 | provided that _all_ the tags match somewhere in the | |
8ef5ada2 | 1948 | set collected as described above. The prefix '!' on a tag means 'not' |
e62e9b61 | 1949 | so --dhcp-option=tag:!purple,3,1.2.3.4 sends the option when the |
8ef5ada2 SK |
1950 | tag purple is not in the set of valid tags. (If using this in a |
1951 | command line rather than a configuration file, be sure to escape !, | |
1952 | which is a shell metacharacter) | |
7de060b0 SK |
1953 | |
1954 | When selecting dhcp-options, a tag from dhcp-range is second class | |
1955 | relative to other tags, to make it easy to override options for | |
1956 | individual hosts, so | |
1957 | .B dhcp-range=set:interface1,...... | |
1958 | .B dhcp-host=set:myhost,..... | |
1959 | .B dhcp-option=tag:interface1,option:nis-domain,"domain1" | |
1960 | .B dhcp-option=tag:myhost,option:nis-domain,"domain2" | |
1961 | will set the NIS-domain to domain1 for hosts in the range, but | |
1962 | override that to domain2 for a particular host. | |
1963 | ||
26128d27 | 1964 | .PP |
8ef5ada2 | 1965 | Note that for |
f6b7dc47 | 1966 | .B dhcp-range |
8ef5ada2 SK |
1967 | both tag:<tag> and set:<tag> are allowed, to both select the range in |
1968 | use based on (eg) dhcp-host, and to affect the options sent, based on | |
1969 | the range selected. | |
1970 | ||
1971 | This system evolved from an earlier, more limited one and for backward | |
1972 | compatibility "net:" may be used instead of "tag:" and "set:" may be | |
1973 | omitted. (Except in | |
1974 | .B dhcp-host, | |
1975 | where "net:" may be used instead of "set:".) For the same reason, '#' | |
1976 | may be used instead of '!' to indicate NOT. | |
f6b7dc47 | 1977 | .PP |
3be34541 SK |
1978 | The DHCP server in dnsmasq will function as a BOOTP server also, |
1979 | provided that the MAC address and IP address for clients are given, | |
1980 | either using | |
1981 | .B dhcp-host | |
1982 | configurations or in | |
1983 | .I /etc/ethers | |
1984 | , and a | |
1985 | .B dhcp-range | |
1986 | configuration option is present to activate the DHCP server | |
b8187c80 SK |
1987 | on a particular network. (Setting --bootp-dynamic removes the need for |
1988 | static address mappings.) The filename | |
8ef5ada2 SK |
1989 | parameter in a BOOTP request is used as a tag, |
1990 | as is the tag "bootp", allowing some control over the options returned to | |
3be34541 SK |
1991 | different classes of hosts. |
1992 | ||
333b2ceb SK |
1993 | .SH AUTHORITATIVE CONFIGURATION |
1994 | .PP | |
1995 | Configuring dnsmasq to act as an authoritative DNS server is | |
1996 | complicated by the fact that it involves configuration of external DNS | |
1997 | servers to provide delegation. We will walk through three scenarios of | |
1998 | increasing complexity. Prerequisites for all of these scenarios | |
81925ab7 | 1999 | are a globally accessible IP address, an A or AAAA record pointing to that address, |
333b2ceb SK |
2000 | and an external DNS server capable of doing delegation of the zone in |
2001 | question. For the first part of this explanation, we will call the A (or AAAA) record | |
2002 | for the globally accessible address server.example.com, and the zone | |
2003 | for which dnsmasq is authoritative our.zone.com. | |
2004 | ||
2005 | The simplest configuration consists of two lines of dnsmasq configuration; something like | |
2006 | ||
2007 | .nf | |
2008 | .B auth-server=server.example.com,eth0 | |
79cb46c0 | 2009 | .B auth-zone=our.zone.com,1.2.3.0/24 |
333b2ceb SK |
2010 | .fi |
2011 | ||
2012 | and two records in the external DNS | |
2013 | ||
2014 | .nf | |
2015 | server.example.com A 192.0.43.10 | |
2016 | our.zone.com NS server.example.com | |
2017 | .fi | |
2018 | ||
2019 | eth0 is the external network interface on which dnsmasq is listening, | |
2020 | and has (globally accessible) address 192.0.43.10. | |
2021 | ||
2022 | Note that the external IP address may well be dynamic (ie assigned | |
2023 | from an ISP by DHCP or PPP) If so, the A record must be linked to this | |
2024 | dynamic assignment by one of the usual dynamic-DNS systems. | |
2025 | ||
2026 | A more complex, but practically useful configuration has the address | |
2027 | record for the globally accessible IP address residing in the | |
2028 | authoritative zone which dnsmasq is serving, typically at the root. Now | |
2029 | we have | |
2030 | ||
2031 | .nf | |
2032 | .B auth-server=our.zone.com,eth0 | |
79cb46c0 | 2033 | .B auth-zone=our.zone.com,1.2.3.0/24 |
333b2ceb SK |
2034 | .fi |
2035 | ||
2036 | .nf | |
0f128eb5 | 2037 | our.zone.com A 1.2.3.4 |
333b2ceb SK |
2038 | our.zone.com NS our.zone.com |
2039 | .fi | |
2040 | ||
2041 | The A record for our.zone.com has now become a glue record, it solves | |
2042 | the chicken-and-egg problem of finding the IP address of the | |
2043 | nameserver for our.zone.com when the A record is within that | |
2044 | zone. Note that this is the only role of this record: as dnsmasq is | |
2045 | now authoritative from our.zone.com it too must provide this | |
2046 | record. If the external address is static, this can be done with an | |
2047 | .B /etc/hosts | |
2048 | entry or | |
2049 | .B --host-record. | |
333b2ceb SK |
2050 | |
2051 | .nf | |
0f128eb5 SK |
2052 | .B auth-server=our.zone.com,eth0 |
2053 | .B host-record=our.zone.com,1.2.3.4 | |
2054 | .B auth-zone=our.zone.com,1.2.3.0/24 | |
2055 | .fi | |
2056 | ||
2057 | If the external address is dynamic, the address | |
2058 | associated with our.zone.com must be derived from the address of the | |
6f130def | 2059 | relevant interface. This is done using |
0f128eb5 SK |
2060 | .B interface-name |
2061 | Something like: | |
2062 | ||
2063 | .nf | |
2064 | .B auth-server=our.zone.com,eth0 | |
2065 | .B interface-name=our.zone.com,eth0 | |
32b4e4cb | 2066 | .B auth-zone=our.zone.com,1.2.3.0/24,eth0 |
333b2ceb SK |
2067 | .fi |
2068 | ||
32b4e4cb SK |
2069 | (The "eth0" argument in auth-zone adds the subnet containing eth0's |
2070 | dynamic address to the zone, so that the interface-name returns the | |
2071 | address in outside queries.) | |
2072 | ||
333b2ceb SK |
2073 | Our final configuration builds on that above, but also adds a |
2074 | secondary DNS server. This is another DNS server which learns the DNS data | |
2075 | for the zone by doing zones transfer, and acts as a backup should | |
2076 | the primary server become inaccessible. The configuration of the | |
2077 | secondary is beyond the scope of this man-page, but the extra | |
2078 | configuration of dnsmasq is simple: | |
2079 | ||
2080 | .nf | |
2081 | .B auth-sec-servers=secondary.myisp.com | |
2082 | .fi | |
2083 | ||
2084 | and | |
2085 | ||
2086 | .nf | |
2087 | our.zone.com NS secondary.myisp.com | |
2088 | .fi | |
2089 | ||
2090 | Adding auth-sec-servers enables zone transfer in dnsmasq, to allow the | |
2091 | secondary to collect the DNS data. If you wish to restrict this data | |
2092 | to particular hosts then | |
2093 | ||
2094 | .nf | |
2095 | .B auth-peer=<IP address of secondary> | |
2096 | .fi | |
2097 | ||
2098 | will do so. | |
2099 | ||
2100 | Dnsmasq acts as an authoritative server for in-addr.arpa and | |
1d7e0a36 | 2101 | ip6.arpa domains associated with the subnets given in auth-zone |
333b2ceb SK |
2102 | declarations, so reverse (address to name) lookups can be simply |
2103 | configured with a suitable NS record, for instance in this example, | |
2104 | where we allow 1.2.3.0/24 addresses. | |
2105 | ||
2106 | .nf | |
2107 | 3.2.1.in-addr.arpa NS our.zone.com | |
2108 | .fi | |
2109 | ||
2110 | Note that at present, reverse (in-addr.arpa and ip6.arpa) zones are | |
2111 | not available in zone transfers, so there is no point arranging | |
2112 | secondary servers for reverse lookups. | |
2113 | ||
2114 | .PP | |
2115 | When dnsmasq is configured to act as an authoritative server, the | |
2116 | following data is used to populate the authoritative zone. | |
2117 | .PP | |
2118 | .B --mx-host, --srv-host, --dns-rr, --txt-record, --naptr-record | |
2119 | , as long as the record names are in the authoritative domain. | |
2120 | .PP | |
2121 | .B --cname | |
2122 | as long as the record name is in the authoritative domain. If the | |
2123 | target of the CNAME is unqualified, then it is qualified with the | |
2124 | authoritative zone name. | |
2125 | .PP | |
2126 | IPv4 and IPv6 addresses from /etc/hosts (and | |
2127 | .B --addn-hosts | |
2128 | ) and | |
2129 | .B --host-record | |
376d48c7 SK |
2130 | and |
2131 | .B --interface-name | |
333b2ceb SK |
2132 | provided the address falls into one of the subnets specified in the |
2133 | .B --auth-zone. | |
333b2ceb SK |
2134 | .PP |
2135 | Addresses of DHCP leases, provided the address falls into one of the subnets specified in the | |
376d48c7 SK |
2136 | .B --auth-zone. |
2137 | (If contructed DHCP ranges are is use, which depend on the address dynamically | |
2138 | assigned to an interface, then the form of | |
333b2ceb | 2139 | .B --auth-zone |
376d48c7 SK |
2140 | which defines subnets by the dynamic address of an interface should |
2141 | be used to ensure this condition is met.) | |
2142 | .PP | |
2143 | In the default mode, where a DHCP lease | |
333b2ceb SK |
2144 | has an unqualified name, and possibly a qualified name constructed |
2145 | using | |
2146 | .B --domain | |
2147 | then the name in the authoritative zone is constructed from the | |
2148 | unqualified name and the zone's domain. This may or may not equal | |
2149 | that specified by | |
2150 | .B --domain. | |
2151 | If | |
2152 | .B --dhcp-fqdn | |
2153 | is set, then the fully qualified names associated with DHCP leases are | |
2154 | used, and must match the zone's domain. | |
2155 | ||
2156 | ||
2157 | ||
5aabfc78 SK |
2158 | .SH EXIT CODES |
2159 | .PP | |
2160 | 0 - Dnsmasq successfully forked into the background, or terminated | |
2161 | normally if backgrounding is not enabled. | |
2162 | .PP | |
2163 | 1 - A problem with configuration was detected. | |
2164 | .PP | |
2165 | 2 - A problem with network access occurred (address in use, attempt | |
2166 | to use privileged ports without permission). | |
2167 | .PP | |
9e038946 | 2168 | 3 - A problem occurred with a filesystem operation (missing |
5aabfc78 SK |
2169 | file/directory, permissions). |
2170 | .PP | |
2171 | 4 - Memory allocation failure. | |
2172 | .PP | |
2173 | 5 - Other miscellaneous problem. | |
2174 | .PP | |
2175 | 11 or greater - a non zero return code was received from the | |
2176 | lease-script process "init" call. The exit code from dnsmasq is the | |
2177 | script's exit code with 10 added. | |
2178 | ||
1b7ecd11 SK |
2179 | .SH LIMITS |
2180 | The default values for resource limits in dnsmasq are generally | |
2181 | conservative, and appropriate for embedded router type devices with | |
2182 | slow processors and limited memory. On more capable hardware, it is | |
2183 | possible to increase the limits, and handle many more clients. The | |
2184 | following applies to dnsmasq-2.37: earlier versions did not scale as well. | |
2185 | ||
2186 | .PP | |
2187 | Dnsmasq is capable of handling DNS and DHCP for at least a thousand | |
8ef5ada2 | 2188 | clients. The DHCP lease times should not be very short (less than one hour). The |
1b7ecd11 SK |
2189 | value of |
2190 | .B --dns-forward-max | |
2191 | can be increased: start with it equal to | |
2192 | the number of clients and increase if DNS seems slow. Note that DNS | |
2193 | performance depends too on the performance of the upstream | |
2194 | nameservers. The size of the DNS cache may be increased: the hard | |
2195 | limit is 10000 names and the default (150) is very low. Sending | |
2196 | SIGUSR1 to dnsmasq makes it log information which is useful for tuning | |
2197 | the cache size. See the | |
2198 | .B NOTES | |
2199 | section for details. | |
2200 | ||
2201 | .PP | |
2202 | The built-in TFTP server is capable of many simultaneous file | |
2203 | transfers: the absolute limit is related to the number of file-handles | |
2204 | allowed to a process and the ability of the select() system call to | |
2205 | cope with large numbers of file handles. If the limit is set too high | |
2206 | using | |
2207 | .B --tftp-max | |
2208 | it will be scaled down and the actual limit logged at | |
2209 | start-up. Note that more transfers are possible when the same file is | |
2210 | being sent than when each transfer sends a different file. | |
2211 | ||
2212 | .PP | |
2213 | It is possible to use dnsmasq to block Web advertising by using a list | |
2214 | of known banner-ad servers, all resolving to 127.0.0.1 or 0.0.0.0, in | |
2215 | .B /etc/hosts | |
2216 | or an additional hosts file. The list can be very long, | |
2217 | dnsmasq has been tested successfully with one million names. That size | |
2218 | file needs a 1GHz processor and about 60Mb of RAM. | |
2219 | ||
1f15b81d SK |
2220 | .SH INTERNATIONALISATION |
2221 | Dnsmasq can be compiled to support internationalisation. To do this, | |
2222 | the make targets "all-i18n" and "install-i18n" should be used instead of | |
2223 | the standard targets "all" and "install". When internationalisation | |
2224 | is compiled in, dnsmasq will produce log messages in the local | |
2225 | language and support internationalised domain names (IDN). Domain | |
2226 | names in /etc/hosts, /etc/ethers and /etc/dnsmasq.conf which contain | |
2227 | non-ASCII characters will be translated to the DNS-internal punycode | |
2228 | representation. Note that | |
2229 | dnsmasq determines both the language for messages and the assumed | |
2230 | charset for configuration | |
2231 | files from the LANG environment variable. This should be set to the system | |
2232 | default value by the script which is responsible for starting | |
2233 | dnsmasq. When editing the configuration files, be careful to do so | |
2234 | using only the system-default locale and not user-specific one, since | |
2235 | dnsmasq has no direct way of determining the charset in use, and must | |
2236 | assume that it is the system default. | |
2237 | ||
9e4abcb5 | 2238 | .SH FILES |
b49644f3 SK |
2239 | .IR /etc/dnsmasq.conf |
2240 | ||
2241 | .IR /usr/local/etc/dnsmasq.conf | |
9e4abcb5 SK |
2242 | |
2243 | .IR /etc/resolv.conf | |
28866e95 SK |
2244 | .IR /var/run/dnsmasq/resolv.conf |
2245 | .IR /etc/ppp/resolv.conf | |
2246 | .IR /etc/dhcpc/resolv.conf | |
9e4abcb5 SK |
2247 | |
2248 | .IR /etc/hosts | |
2249 | ||
3be34541 SK |
2250 | .IR /etc/ethers |
2251 | ||
b49644f3 SK |
2252 | .IR /var/lib/misc/dnsmasq.leases |
2253 | ||
2254 | .IR /var/db/dnsmasq.leases | |
9e4abcb5 SK |
2255 | |
2256 | .IR /var/run/dnsmasq.pid | |
2257 | .SH SEE ALSO | |
9e4abcb5 SK |
2258 | .BR hosts (5), |
2259 | .BR resolver (5) | |
2260 | .SH AUTHOR | |
2261 | This manual page was written by Simon Kelley <simon@thekelleys.org.uk>. | |
2262 | ||
2263 |