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Simon Kelley9e4abcb2004-01-22 19:47:41 +00001.TH DNSMASQ 8
2.SH NAME
3dnsmasq \- A lightweight DHCP and caching DNS server.
4.SH SYNOPSIS
5.B dnsmasq
6.I [OPTION]...
7.SH "DESCRIPTION"
8.BR dnsmasq
Simon Kelley34d0a362013-01-02 11:40:56 +00009is a lightweight DNS, TFTP, PXE, router advertisement and DHCP server. It is intended to provide
Simon Kelley5aabfc72007-08-29 11:24:47 +010010coupled DNS and DHCP service to a LAN.
Simon Kelley9e4abcb2004-01-22 19:47:41 +000011.PP
12Dnsmasq accepts DNS queries and either answers them from a small, local,
13cache or forwards them to a real, recursive, DNS server. It loads the
14contents of /etc/hosts so that local hostnames
15which do not appear in the global DNS can be resolved and also answers
Simon Kelleyee415862014-02-11 11:07:22 +000016DNS queries for DHCP configured hosts. It can also act as the
17authoritative DNS server for one or more domains, allowing local names
18to appear in the global DNS. It can be configured to do DNSSEC
19validation.
Simon Kelley9e4abcb2004-01-22 19:47:41 +000020.PP
Simon Kelley73a08a22009-02-05 20:28:08 +000021The dnsmasq DHCP server supports static address assignments and multiple
22networks. It automatically
Simon Kelley3be34542004-09-11 19:12:13 +010023sends a sensible default set of DHCP options, and can be configured to
Simon Kelleyf2621c72007-04-29 19:47:21 +010024send any desired set of DHCP options, including vendor-encapsulated
Simon Kelley1b7ecd12007-02-05 14:57:57 +000025options. It includes a secure, read-only,
Simon Kelley34d0a362013-01-02 11:40:56 +000026TFTP 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.
Simon Kelley9e4abcb2004-01-22 19:47:41 +000027.PP
Simon Kelley81925ab2013-04-10 11:43:58 +010028The dnsmasq DHCPv6 server provides the same set of features as the
29DHCPv4 server, and in addition, it includes router advertisements and
30a neat feature which allows nameing for clients which use DHCPv4 and
Simon Kelley834f36f2013-04-17 13:52:49 +010031stateless 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.
Simon Kelley34d0a362013-01-02 11:40:56 +000032.PP
33Dnsmasq 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.
Simon Kelley9e4abcb2004-01-22 19:47:41 +000034.SH OPTIONS
35Note that in general missing parameters are allowed and switch off
Simon Kelley832af0b2007-01-21 20:01:28 +000036functions, for instance "--pid-file" disables writing a PID file. On
Simon Kelley33820b72004-04-03 21:10:00 +010037BSD, unless the GNU getopt library is linked, the long form of the
38options does not work on the command line; it is still recognised in
39the configuration file.
Simon Kelley9e4abcb2004-01-22 19:47:41 +000040.TP
Simon Kelley7622fc02009-06-04 20:32:05 +010041.B --test
42Read and syntax check configuration file(s). Exit with code 0 if all
43is OK, or a non-zero code otherwise. Do not start up dnsmasq.
44.TP
Simon Kelley9e4abcb2004-01-22 19:47:41 +000045.B \-h, --no-hosts
46Don't read the hostnames in /etc/hosts.
47.TP
48.B \-H, --addn-hosts=<file>
49Additional hosts file. Read the specified file as well as /etc/hosts. If -h is given, read
Simon Kelleyfd9fa482004-10-21 20:24:00 +010050only the specified file. This option may be repeated for more than one
Simon Kelley7622fc02009-06-04 20:32:05 +010051additional hosts file. If a directory is given, then read all the files contained in that directory.
Simon Kelley9e4abcb2004-01-22 19:47:41 +000052.TP
Simon Kelley3d04f462015-01-31 21:59:13 +000053.B --hostsdir=<path>
54Read all the hosts files contained in the directory. New or changed files
55are read automatically. See --dhcp-hostsdir for details.
56.TP
Simon Kelley832af0b2007-01-21 20:01:28 +000057.B \-E, --expand-hosts
58Add the domain to simple names (without a period) in /etc/hosts
Simon Kelley1f15b812009-10-13 17:49:32 +010059in the same way as for DHCP-derived names. Note that this does not
60apply to domain names in cnames, PTR records, TXT records etc.
Simon Kelley832af0b2007-01-21 20:01:28 +000061.TP
Simon Kelley9e4abcb2004-01-22 19:47:41 +000062.B \-T, --local-ttl=<time>
Simon Kelley832e47b2016-02-24 21:24:45 +000063When replying with information from /etc/hosts or configuration or the DHCP leases
Simon Kelley9e4abcb2004-01-22 19:47:41 +000064file dnsmasq by default sets the time-to-live field to zero, meaning
Simon Kelleyc72daea2012-01-05 21:33:27 +000065that the requester should not itself cache the information. This is
Simon Kelley9e4abcb2004-01-22 19:47:41 +000066the correct thing to do in almost all situations. This option allows a
67time-to-live (in seconds) to be given for these replies. This will
68reduce the load on the server at the expense of clients using stale
69data under some circumstances.
70.TP
Simon Kelley832e47b2016-02-24 21:24:45 +000071.B --dhcp-ttl=<time>
72As for --local-ttl, but affects only replies with information from DHCP leases. If both are given, --dhcp-ttl applies for DHCP information, and --local-ttl for others. Setting this to zero eliminates the effect of --local-ttl for DHCP.
73.TP
Simon Kelley824af852008-02-12 20:43:05 +000074.B --neg-ttl=<time>
75Negative replies from upstream servers normally contain time-to-live
76information in SOA records which dnsmasq uses for caching. If the
77replies from upstream servers omit this information, dnsmasq does not
78cache the reply. This option gives a default value for time-to-live
79(in seconds) which dnsmasq uses to cache negative replies even in
80the absence of an SOA record.
81.TP
Simon Kelley8ef5ada2010-06-03 19:42:45 +010082.B --max-ttl=<time>
83Set a maximum TTL value that will be handed out to clients. The specified
84maximum TTL will be given to clients instead of the true TTL value if it is
85lower. The true TTL value is however kept in the cache to avoid flooding
86the upstream DNS servers.
87.TP
Simon Kelley1d860412012-09-20 20:48:04 +010088.B --max-cache-ttl=<time>
89Set a maximum TTL value for entries in the cache.
90.TP
RinSatsuki28de3872015-01-10 15:22:21 +000091.B --min-cache-ttl=<time>
92Extend short TTL values to the time given when caching them. Note that
93artificially extending TTL values is in general a bad idea, do not do it
94unless you have a good reason, and understand what you are doing.
95Dnsmasq limits the value of this option to one hour, unless recompiled.
96.TP
Simon Kelley333b2ce2013-01-07 21:46:03 +000097.B --auth-ttl=<time>
98Set the TTL value returned in answers from the authoritative server.
99.TP
Simon Kelley3be34542004-09-11 19:12:13 +0100100.B \-k, --keep-in-foreground
101Do not go into the background at startup but otherwise run as
Simon Kelley3d8df262005-08-29 12:19:27 +0100102normal. This is intended for use when dnsmasq is run under daemontools
103or launchd.
Simon Kelley3be34542004-09-11 19:12:13 +0100104.TP
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000105.B \-d, --no-daemon
106Debug mode: don't fork to the background, don't write a pid file,
107don't change user id, generate a complete cache dump on receipt on
Simon Kelley3be34542004-09-11 19:12:13 +0100108SIGUSR1, log to stderr as well as syslog, don't fork new processes
Simon Kelley83b21982012-11-12 21:07:44 +0000109to handle TCP queries. Note that this option is for use in debugging
110only, to stop dnsmasq daemonising in production, use
111.B -k.
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000112.TP
113.B \-q, --log-queries
Simon Kelley25cf5e32015-01-09 15:53:03 +0000114Log the results of DNS queries handled by dnsmasq. Enable a full cache dump on receipt of SIGUSR1. If the argument "extra" is supplied, ie
115.B --log-queries=extra
116then the log has extra information at the start of each line.
117This consists of a serial number which ties together the log lines associated with an individual query, and the IP address of the requestor.
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000118.TP
Simon Kelley849a8352006-06-09 21:02:31 +0100119.B \-8, --log-facility=<facility>
120Set the facility to which dnsmasq will send syslog entries, this
Simon Kelleyf2621c72007-04-29 19:47:21 +0100121defaults to DAEMON, and to LOCAL0 when debug mode is in operation. If
Simon Kelley9e038942008-05-30 20:06:34 +0100122the facility given contains at least one '/' character, it is taken to
Simon Kelleyf2621c72007-04-29 19:47:21 +0100123be a filename, and dnsmasq logs to the given file, instead of
Simon Kelley8ef5ada2010-06-03 19:42:45 +0100124syslog. If the facility is '-' then dnsmasq logs to stderr.
125(Errors whilst reading configuration will still go to syslog,
Simon Kelleyf2621c72007-04-29 19:47:21 +0100126but all output from a successful startup, and all output whilst
Simon Kelley5aabfc72007-08-29 11:24:47 +0100127running, will go exclusively to the file.) When logging to a file,
128dnsmasq will close and reopen the file when it receives SIGUSR2. This
129allows the log file to be rotated without stopping dnsmasq.
Simon Kelleyf2621c72007-04-29 19:47:21 +0100130.TP
131.B --log-async[=<lines>]
132Enable asynchronous logging and optionally set the limit on the
133number of lines
134which will be queued by dnsmasq when writing to the syslog is slow.
135Dnsmasq can log asynchronously: this
136allows it to continue functioning without being blocked by syslog, and
137allows syslog to use dnsmasq for DNS queries without risking deadlock.
138If the queue of log-lines becomes full, dnsmasq will log the
139overflow, and the number of messages lost. The default queue length is
1405, a sane value would be 5-25, and a maximum limit of 100 is imposed.
Simon Kelley849a8352006-06-09 21:02:31 +0100141.TP
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000142.B \-x, --pid-file=<path>
143Specify an alternate path for dnsmasq to record its process-id in. Normally /var/run/dnsmasq.pid.
144.TP
145.B \-u, --user=<username>
146Specify the userid to which dnsmasq will change after startup. Dnsmasq must normally be started as root, but it will drop root
Simon Kelleyb8187c82005-11-26 21:46:27 +0000147privileges after startup by changing id to another user. Normally this user is "nobody" but that
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000148can be over-ridden with this switch.
149.TP
150.B \-g, --group=<groupname>
151Specify the group which dnsmasq will run
152as. The defaults to "dip", if available, to facilitate access to
153/etc/ppp/resolv.conf which is not normally world readable.
154.TP
155.B \-v, --version
156Print the version number.
157.TP
158.B \-p, --port=<port>
Simon Kelley824af852008-02-12 20:43:05 +0000159Listen on <port> instead of the standard DNS port (53). Setting this
160to zero completely disables DNS function, leaving only DHCP and/or TFTP.
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000161.TP
Simon Kelleyfeba5c12004-07-27 20:28:58 +0100162.B \-P, --edns-packet-max=<size>
163Specify the largest EDNS.0 UDP packet which is supported by the DNS
Simon Kelley316e2732010-01-22 20:16:09 +0000164forwarder. Defaults to 4096, which is the RFC5625-recommended size.
Simon Kelleyfeba5c12004-07-27 20:28:58 +0100165.TP
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000166.B \-Q, --query-port=<query_port>
Simon Kelley1a6bca82008-07-11 11:11:42 +0100167Send outbound DNS queries from, and listen for their replies on, the
168specific UDP port <query_port> instead of using random ports. NOTE
169that using this option will make dnsmasq less secure against DNS
170spoofing attacks but it may be faster and use less resources. Setting this option
171to zero makes dnsmasq use a single port allocated to it by the
172OS: this was the default behaviour in versions prior to 2.43.
173.TP
174.B --min-port=<port>
175Do not use ports less than that given as source for outbound DNS
176queries. Dnsmasq picks random ports as source for outbound queries:
177when this option is given, the ports used will always to larger
178than that specified. Useful for systems behind firewalls.
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000179.TP
Hans Dedecker926332a2016-01-23 10:48:12 +0000180.B --max-port=<port>
181Use ports lower than that given as source for outbound DNS queries.
182Dnsmasq picks random ports as source for outbound queries:
183when this option is given, the ports used will always be lower
184than that specified. Useful for systems behind firewalls.
185.TP
186
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000187.B \-i, --interface=<interface name>
Simon Kelleyfeba5c12004-07-27 20:28:58 +0100188Listen only on the specified interface(s). Dnsmasq automatically adds
189the loopback (local) interface to the list of interfaces to use when
190the
191.B \--interface
192option is used. If no
193.B \--interface
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000194or
Simon Kelleyfeba5c12004-07-27 20:28:58 +0100195.B \--listen-address
196options are given dnsmasq listens on all available interfaces except any
197given in
198.B \--except-interface
Simon Kelley309331f2006-04-22 15:05:01 +0100199options. IP alias interfaces (eg "eth1:0") cannot be used with
Simon Kelley8a911cc2004-03-16 18:35:52 +0000200.B --interface
201or
202.B --except-interface
Simon Kelley49333cb2013-03-15 20:30:51 +0000203options, use --listen-address instead. A simple wildcard, consisting
204of a trailing '*', can be used in
205.B \--interface
206and
207.B \--except-interface
208options.
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000209.TP
210.B \-I, --except-interface=<interface name>
Simon Kelleyfeba5c12004-07-27 20:28:58 +0100211Do not listen on the specified interface. Note that the order of
212.B \--listen-address
213.B --interface
214and
215.B --except-interface
216options does not matter and that
217.B --except-interface
218options always override the others.
Simon Kelley34d0a362013-01-02 11:40:56 +0000219.TP
220.B --auth-server=<domain>,<interface>|<ip-address>
Simon Kelley81925ab2013-04-10 11:43:58 +0100221Enable DNS authoritative mode for queries arriving at an interface or address. Note that the interface or address
Simon Kelley34d0a362013-01-02 11:40:56 +0000222need not be mentioned in
223.B --interface
224or
225.B --listen-address
226configuration, indeed
227.B --auth-server
Simon Kelleyf25e6c62013-11-17 12:23:42 +0000228will overide these and provide a different DNS service on the
229specified interface. The <domain> is the "glue record". It should
230resolve in the global DNS to a A and/or AAAA record which points to
231the address dnsmasq is listening on. When an interface is specified,
232it may be qualified with "/4" or "/6" to specify only the IPv4 or IPv6
233addresses associated with the interface.
Simon Kelleyc8a80482014-03-05 14:29:54 +0000234.TP
235.B --local-service
236Accept DNS queries only from hosts whose address is on a local subnet,
237ie a subnet for which an interface exists on the server. This option
238only has effect is there are no --interface --except-interface,
239--listen-address or --auth-server options. It is intended to be set as
240a default on installation, to allow unconfigured installations to be
241useful but also safe from being used for DNS amplification attacks.
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000242.TP
Simon Kelley3d8df262005-08-29 12:19:27 +0100243.B \-2, --no-dhcp-interface=<interface name>
Simon Kelley832af0b2007-01-21 20:01:28 +0000244Do not provide DHCP or TFTP on the specified interface, but do provide DNS service.
Simon Kelley3d8df262005-08-29 12:19:27 +0100245.TP
Simon Kelley44a2a312004-03-10 20:04:35 +0000246.B \-a, --listen-address=<ipaddr>
Simon Kelleyfeba5c12004-07-27 20:28:58 +0100247Listen on the given IP address(es). Both
248.B \--interface
249and
250.B \--listen-address
251options may be given, in which case the set of both interfaces and
252addresses is used. Note that if no
253.B \--interface
254option is given, but
255.B \--listen-address
256is, dnsmasq will not automatically listen on the loopback
257interface. To achieve this, its IP address, 127.0.0.1, must be
258explicitly given as a
259.B \--listen-address
260option.
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000261.TP
Simon Kelley44a2a312004-03-10 20:04:35 +0000262.B \-z, --bind-interfaces
263On systems which support it, dnsmasq binds the wildcard address,
264even when it is listening on only some interfaces. It then discards
265requests that it shouldn't reply to. This has the advantage of
266working even when interfaces come and go and change address. This
267option forces dnsmasq to really bind only the interfaces it is
268listening on. About the only time when this is useful is when
Simon Kelleyf6b7dc42005-01-23 12:06:08 +0000269running another nameserver (or another instance of dnsmasq) on the
Simon Kelley309331f2006-04-22 15:05:01 +0100270same machine. Setting this option also enables multiple instances of
Simon Kelleyf6b7dc42005-01-23 12:06:08 +0000271dnsmasq which provide DHCP service to run in the same machine.
272.TP
Simon Kelley54dd3932012-06-20 11:23:38 +0100273.B --bind-dynamic
274Enable a network mode which is a hybrid between
275.B --bind-interfaces
Simon Kelleya2ce6fc2012-08-06 20:05:48 +0100276and the default. Dnsmasq binds the address of individual interfaces,
Simon Kelley54dd3932012-06-20 11:23:38 +0100277allowing multiple dnsmasq instances, but if new interfaces or
278addresses appear, it automatically listens on those (subject to any
279access-control configuration). This makes dynamically created
280interfaces work in the same way as the default. Implementing this
Simon Kelleya2ce6fc2012-08-06 20:05:48 +0100281option requires non-standard networking APIs and it is only available
Simon Kelley05ff1ed2012-06-26 16:58:12 +0100282under Linux. On other platforms it falls-back to --bind-interfaces mode.
Simon Kelley54dd3932012-06-20 11:23:38 +0100283.TP
Simon Kelleyf6b7dc42005-01-23 12:06:08 +0000284.B \-y, --localise-queries
285Return answers to DNS queries from /etc/hosts which depend on the interface over which the query was
Simon Kelleyb8187c82005-11-26 21:46:27 +0000286received. If a name in /etc/hosts has more than one address associated with
Simon Kelleyf6b7dc42005-01-23 12:06:08 +0000287it, and at least one of those addresses is on the same subnet as the
288interface to which the query was sent, then return only the
289address(es) on that subnet. This allows for a server to have multiple
290addresses in /etc/hosts corresponding to each of its interfaces, and
291hosts will get the correct address based on which network they are
292attached to. Currently this facility is limited to IPv4.
Simon Kelley44a2a312004-03-10 20:04:35 +0000293.TP
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000294.B \-b, --bogus-priv
295Bogus private reverse lookups. All reverse lookups for private IP ranges (ie 192.168.x.x, etc)
Simon Kelleyfeba5c12004-07-27 20:28:58 +0100296which are not found in /etc/hosts or the DHCP leases file are answered
297with "no such domain" rather than being forwarded upstream.
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000298.TP
Simon Kelley73a08a22009-02-05 20:28:08 +0000299.B \-V, --alias=[<old-ip>]|[<start-ip>-<end-ip>],<new-ip>[,<mask>]
Simon Kelley1cff1662004-03-12 08:12:58 +0000300Modify IPv4 addresses returned from upstream nameservers; old-ip is
301replaced by new-ip. If the optional mask is given then any address
302which matches the masked old-ip will be re-written. So, for instance
303.B --alias=1.2.3.0,6.7.8.0,255.255.255.0
304will map 1.2.3.56 to 6.7.8.56 and 1.2.3.67 to 6.7.8.67. This is what
Simon Kelley73a08a22009-02-05 20:28:08 +0000305Cisco PIX routers call "DNS doctoring". If the old IP is given as
306range, then only addresses in the range, rather than a whole subnet,
307are re-written. So
308.B --alias=192.168.0.10-192.168.0.40,10.0.0.0,255.255.255.0
309maps 192.168.0.10->192.168.0.40 to 10.0.0.10->10.0.0.40
Simon Kelley1cff1662004-03-12 08:12:58 +0000310.TP
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000311.B \-B, --bogus-nxdomain=<ipaddr>
312Transform replies which contain the IP address given into "No such
313domain" replies. This is intended to counteract a devious move made by
Simon Kelleyb8187c82005-11-26 21:46:27 +0000314Verisign in September 2003 when they started returning the address of
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000315an advertising web page in response to queries for unregistered names,
316instead of the correct NXDOMAIN response. This option tells dnsmasq to
317fake the correct response when it sees this behaviour. As at Sept 2003
Simon Kelleyb8187c82005-11-26 21:46:27 +0000318the IP address being returned by Verisign is 64.94.110.11
Glen Huang32fc6db2014-12-27 15:28:12 +0000319.TP
320.B \-B, --ignore-address=<ipaddr>
321Ignore replies to A-record queries which include the specified address.
322No error is generated, dnsmasq simply continues to listen for another reply.
323This is useful to defeat blocking strategies which rely on quickly supplying a
324forged answer to a DNS request for certain domain, before the correct answer can arrive.
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000325.TP
326.B \-f, --filterwin2k
327Later versions of windows make periodic DNS requests which don't get sensible answers from
328the public DNS and can cause problems by triggering dial-on-demand links. This flag turns on an option
329to filter such requests. The requests blocked are for records of types SOA and SRV, and type ANY where the
330requested name has underscores, to catch LDAP requests.
331.TP
332.B \-r, --resolv-file=<file>
333Read the IP addresses of the upstream nameservers from <file>, instead of
334/etc/resolv.conf. For the format of this file see
Simon Kelley7de060b2011-08-26 17:24:52 +0100335.BR resolv.conf (5).
336The only lines relevant to dnsmasq are nameserver ones. Dnsmasq can
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000337be told to poll more than one resolv.conf file, the first file name specified
338overrides the default, subsequent ones add to the list. This is only
339allowed when polling; the file with the currently latest modification
340time is the one used.
341.TP
342.B \-R, --no-resolv
343Don't read /etc/resolv.conf. Get upstream servers only from the command
Simon Kelleyb49644f2004-01-30 21:36:24 +0000344line or the dnsmasq configuration file.
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000345.TP
Simon Kelleyad094272012-08-10 17:10:54 +0100346.B \-1, --enable-dbus[=<service-name>]
Simon Kelley3d8df262005-08-29 12:19:27 +0100347Allow dnsmasq configuration to be updated via DBus method calls. The
348configuration which can be changed is upstream DNS servers (and
Simon Kelleyb8187c82005-11-26 21:46:27 +0000349corresponding domains) and cache clear. Requires that dnsmasq has
Simon Kelleyad094272012-08-10 17:10:54 +0100350been built with DBus support. If the service name is given, dnsmasq
351provides service at that name, rather than the default which is
352.B uk.org.thekelleys.dnsmasq
Simon Kelley3d8df262005-08-29 12:19:27 +0100353.TP
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000354.B \-o, --strict-order
355By default, dnsmasq will send queries to any of the upstream servers
Simon Kelley824af852008-02-12 20:43:05 +0000356it knows about and tries to favour servers that are known to
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000357be up. Setting this flag forces dnsmasq to try each query with each
358server strictly in the order they appear in /etc/resolv.conf
359.TP
Simon Kelley824af852008-02-12 20:43:05 +0000360.B --all-servers
361By default, when dnsmasq has more than one upstream server available,
362it will send queries to just one server. Setting this flag forces
363dnsmasq to send all queries to all available servers. The reply from
Simon Kelleyc72daea2012-01-05 21:33:27 +0000364the server which answers first will be returned to the original requester.
Simon Kelley824af852008-02-12 20:43:05 +0000365.TP
Simon Kelleyb5ea1cc2014-07-29 16:34:14 +0100366.B --dns-loop-detect
367Enable code to detect DNS forwarding loops; ie the situation where a query sent to one
368of the upstream server eventually returns as a new query to the dnsmasq instance. The
369process works by generating TXT queries of the form <hex>.test and sending them to
370each upstream server. The hex is a UID which encodes the instance of dnsmasq sending the query
371and the upstream server to which it was sent. If the query returns to the server which sent it, then
372the upstream server through which it was sent is disabled and this event is logged. Each time the
373set of upstream servers changes, the test is re-run on all of them, including ones which
374were previously disabled.
375.TP
Simon Kelley824af852008-02-12 20:43:05 +0000376.B --stop-dns-rebind
377Reject (and log) addresses from upstream nameservers which are in the
378private IP ranges. This blocks an attack where a browser behind a
379firewall is used to probe machines on the local network.
380.TP
Simon Kelley8ef5ada2010-06-03 19:42:45 +0100381.B --rebind-localhost-ok
382Exempt 127.0.0.0/8 from rebinding checks. This address range is
383returned by realtime black hole servers, so blocking it may disable
384these services.
385.TP
386.B --rebind-domain-ok=[<domain>]|[[/<domain>/[<domain>/]
387Do not detect and block dns-rebind on queries to these domains. The
388argument may be either a single domain, or multiple domains surrounded
389by '/', like the --server syntax, eg.
390.B --rebind-domain-ok=/domain1/domain2/domain3/
391.TP
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000392.B \-n, --no-poll
393Don't poll /etc/resolv.conf for changes.
394.TP
Simon Kelley16972692006-10-16 20:04:18 +0100395.B --clear-on-reload
Simon Kelleyd9fb0be2013-07-25 21:47:17 +0100396Whenever /etc/resolv.conf is re-read or the upstream servers are set
397via DBus, clear the DNS cache.
Simon Kelley16972692006-10-16 20:04:18 +0100398This is useful when new nameservers may have different
399data than that held in cache.
400.TP
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000401.B \-D, --domain-needed
Simon Kelley7de060b2011-08-26 17:24:52 +0100402Tells dnsmasq to never forward A or AAAA queries for plain names, without dots
Simon Kelley3d8df262005-08-29 12:19:27 +0100403or domain parts, to upstream nameservers. If the name is not known
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000404from /etc/hosts or DHCP then a "not found" answer is returned.
405.TP
Simon Kelley824af852008-02-12 20:43:05 +0000406.B \-S, --local, --server=[/[<domain>]/[domain/]][<ipaddr>[#<port>][@<source-ip>|<interface>[#<port>]]
Simon Kelley5aabfc72007-08-29 11:24:47 +0100407Specify IP address of upstream servers directly. Setting this flag does
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000408not suppress reading of /etc/resolv.conf, use -R to do that. If one or
409more
410optional domains are given, that server is used only for those domains
411and they are queried only using the specified server. This is
412intended for private nameservers: if you have a nameserver on your
413network which deals with names of the form
414xxx.internal.thekelleys.org.uk at 192.168.1.1 then giving the flag
Simon Kelleyb8187c82005-11-26 21:46:27 +0000415.B -S /internal.thekelleys.org.uk/192.168.1.1
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000416will send all queries for
417internal machines to that nameserver, everything else will go to the
Simon Kelley92be34a2016-01-16 18:39:54 +0000418servers in /etc/resolv.conf. DNSSEC validation is turned off for such
419private nameservers, UNLESS a
420.B --trust-anchor
421is specified for the domain in question. An empty domain specification,
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000422.B //
423has the special meaning of "unqualified names only" ie names without any
424dots in them. A non-standard port may be specified as
425part of the IP
426address using a # character.
427More than one -S flag is allowed, with
Simon Kelley8ef5ada2010-06-03 19:42:45 +0100428repeated domain or ipaddr parts as required.
429
430More specific domains take precendence over less specific domains, so:
431.B --server=/google.com/1.2.3.4
432.B --server=/www.google.com/2.3.4.5
433will send queries for *.google.com to 1.2.3.4, except *www.google.com,
434which will go to 2.3.4.5
435
436The special server address '#' means, "use the standard servers", so
437.B --server=/google.com/1.2.3.4
438.B --server=/www.google.com/#
439will send queries for *.google.com to 1.2.3.4, except *www.google.com which will
440be forwarded as usual.
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000441
442Also permitted is a -S
443flag which gives a domain but no IP address; this tells dnsmasq that
444a domain is local and it may answer queries from /etc/hosts or DHCP
445but should never forward queries on that domain to any upstream
446servers.
447.B local
448is a synonym for
449.B server
450to make configuration files clearer in this case.
451
Simon Kelley7de060b2011-08-26 17:24:52 +0100452IPv6 addresses may include a %interface scope-id, eg
453fe80::202:a412:4512:7bbf%eth0.
454
Simon Kelley824af852008-02-12 20:43:05 +0000455The optional string after the @ character tells
456dnsmasq how to set the source of the queries to this
457nameserver. It should be an ip-address, which should belong to the machine on which
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000458dnsmasq is running otherwise this server line will be logged and then
Simon Kelley824af852008-02-12 20:43:05 +0000459ignored, or an interface name. If an interface name is given, then
460queries to the server will be forced via that interface; if an
461ip-address is given then the source address of the queries will be set
462to that address.
463The query-port flag is ignored for any servers which have a
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000464source address specified but the port may be specified directly as
Simon Kelley824af852008-02-12 20:43:05 +0000465part of the source address. Forcing queries to an interface is not
466implemented on all platforms supported by dnsmasq.
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000467.TP
Simon Kelleyde73a492014-02-17 21:43:27 +0000468.B --rev-server=<ip-address>/<prefix-len>,<ipaddr>[#<port>][@<source-ip>|<interface>[#<port>]]
469This is functionally the same as
470.B --server,
471but provides some syntactic sugar to make specifying address-to-name queries easier. For example
472.B --rev-server=1.2.3.0/24,192.168.0.1
473is exactly equivalent to
474.B --server=/3.2.1.in-addr.arpa/192.168.0.1
475.TP
Simon Kelley979fe862015-03-19 22:50:22 +0000476.B \-A, --address=/<domain>/[domain/][<ipaddr>]
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000477Specify an IP address to return for any host in the given domains.
478Queries in the domains are never forwarded and always replied to
479with the specified IP address which may be IPv4 or IPv6. To give
480both IPv4 and IPv6 addresses for a domain, use repeated -A flags.
481Note that /etc/hosts and DHCP leases override this for individual
482names. A common use of this is to redirect the entire doubleclick.net
Simon Kelleya2226412004-05-13 20:27:08 +0100483domain to some friendly local web server to avoid banner ads. The
484domain specification works in the same was as for --server, with the
485additional facility that /#/ matches any domain. Thus
486--address=/#/1.2.3.4 will always return 1.2.3.4 for any query not
487answered from /etc/hosts or DHCP and not sent to an upstream
Simon Kelley979fe862015-03-19 22:50:22 +0000488nameserver by a more specific --server directive. As for --server,
489one or more domains with no address returns a no-such-domain answer, so
490--address=/example.com/ is equivalent to --server=/example.com/ and returns
491NXDOMAIN for example.com and all its subdomains.
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000492.TP
Jason A. Donenfeld13d86c72013-02-22 18:20:53 +0000493.B --ipset=/<domain>/[domain/]<ipset>[,<ipset>]
494Places the resolved IP addresses of queries for the specified domains
495in the specified netfilter ip sets. Domains and subdomains are matched
496in the same way as --address. These ip sets must already exist. See
497ipset(8) for more details.
498.TP
Simon Kelleyf6b7dc42005-01-23 12:06:08 +0000499.B \-m, --mx-host=<mx name>[[,<hostname>],<preference>]
Simon Kelleyde379512004-06-22 20:23:33 +0100500Return an MX record named <mx name> pointing to the given hostname (if
501given), or
502the host specified in the --mx-target switch
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000503or, if that switch is not given, the host on which dnsmasq
Simon Kelleyf6b7dc42005-01-23 12:06:08 +0000504is running. The default is useful for directing mail from systems on a LAN
505to a central server. The preference value is optional, and defaults to
5061 if not given. More than one MX record may be given for a host.
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000507.TP
508.B \-t, --mx-target=<hostname>
Simon Kelleyf6b7dc42005-01-23 12:06:08 +0000509Specify the default target for the MX record returned by dnsmasq. See
510--mx-host. If --mx-target is given, but not --mx-host, then dnsmasq
511returns a MX record containing the MX target for MX queries on the
512hostname of the machine on which dnsmasq is running.
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000513.TP
514.B \-e, --selfmx
515Return an MX record pointing to itself for each local
516machine. Local machines are those in /etc/hosts or with DHCP leases.
517.TP
518.B \-L, --localmx
519Return an MX record pointing to the host given by mx-target (or the
520machine on which dnsmasq is running) for each
521local machine. Local machines are those in /etc/hosts or with DHCP
522leases.
523.TP
Simon Kelleyf6b7dc42005-01-23 12:06:08 +0000524.B \-W, --srv-host=<_service>.<_prot>.[<domain>],[<target>[,<port>[,<priority>[,<weight>]]]]
525Return a SRV DNS record. See RFC2782 for details. If not supplied, the
526domain defaults to that given by
527.B --domain.
528The default for the target domain is empty, and the default for port
529is one and the defaults for
530weight and priority are zero. Be careful if transposing data from BIND
531zone files: the port, weight and priority numbers are in a different
532order. More than one SRV record for a given service/domain is allowed,
Simon Kelley3d8df262005-08-29 12:19:27 +0100533all that match are returned.
Simon Kelleyf6b7dc42005-01-23 12:06:08 +0000534.TP
Simon Kelleydf3d54f2016-02-24 21:03:38 +0000535.B --host-record=<name>[,<name>....],[<IPv4-address>],[<IPv6-address>][,<TTL>]
Simon Kelleye759d422012-03-16 13:18:57 +0000536Add A, AAAA and PTR records to the DNS. This adds one or more names to
537the DNS with associated IPv4 (A) and IPv6 (AAAA) records. A name may
538appear in more than one
539.B host-record
540and therefore be assigned more than one address. Only the first
541address creates a PTR record linking the address to the name. This is
542the same rule as is used reading hosts-files.
543.B host-record
544options are considered to be read before host-files, so a name
545appearing there inhibits PTR-record creation if it appears in
Simon Kelleye46164e2012-04-16 16:39:38 +0100546hosts-file also. Unlike hosts-files, names are not expanded, even when
Simon Kelleye759d422012-03-16 13:18:57 +0000547.B expand-hosts
548is in effect. Short and long names may appear in the same
Simon Kelleye46164e2012-04-16 16:39:38 +0100549.B host-record,
550eg.
551.B --host-record=laptop,laptop.thekelleys.org,192.168.0.1,1234::100
Simon Kelleydf3d54f2016-02-24 21:03:38 +0000552
553If the time-to-live is given, it overrides the default, which is zero
554or the value of --local-ttl. The value is a positive integer and gives
555the time-to-live in seconds.
Simon Kelleye759d422012-03-16 13:18:57 +0000556.TP
Simon Kelley0a852542005-03-23 20:28:59 +0000557.B \-Y, --txt-record=<name>[[,<text>],<text>]
558Return a TXT DNS record. The value of TXT record is a set of strings,
Simon Kelley28866e92011-02-14 20:19:14 +0000559so any number may be included, delimited by commas; use quotes to put
560commas into a string. Note that the maximum length of a single string
561is 255 characters, longer strings are split into 255 character chunks.
Simon Kelley0a852542005-03-23 20:28:59 +0000562.TP
Simon Kelley832af0b2007-01-21 20:01:28 +0000563.B --ptr-record=<name>[,<target>]
564Return a PTR DNS record.
565.TP
Simon Kelley1a6bca82008-07-11 11:11:42 +0100566.B --naptr-record=<name>,<order>,<preference>,<flags>,<service>,<regexp>[,<replacement>]
567Return an NAPTR DNS record, as specified in RFC3403.
568.TP
Simon Kelleydf3d54f2016-02-24 21:03:38 +0000569.B --cname=<cname>,<target>[,<TTL>]
Simon Kelley9009d742008-11-14 20:04:27 +0000570Return a CNAME record which indicates that <cname> is really
571<target>. There are significant limitations on the target; it must be a
572DNS name which is known to dnsmasq from /etc/hosts (or additional
Simon Kelleyd56a6042013-10-11 14:39:03 +0100573hosts files), from DHCP, from --interface-name or from another
Simon Kelley611ebc52012-07-16 16:23:46 +0100574.B --cname.
575If the target does not satisfy this
Simon Kelley9009d742008-11-14 20:04:27 +0000576criteria, the whole cname is ignored. The cname must be unique, but it
577is permissable to have more than one cname pointing to the same target.
Simon Kelleydf3d54f2016-02-24 21:03:38 +0000578
579If the time-to-live is given, it overrides the default, which is zero
580or the value of -local-ttl. The value is a positive integer and gives
581the time-to-live in seconds.
Simon Kelley9009d742008-11-14 20:04:27 +0000582.TP
Simon Kelley9f7f3b12012-05-28 21:39:57 +0100583.B --dns-rr=<name>,<RR-number>,[<hex data>]
584Return an arbitrary DNS Resource Record. The number is the type of the
585record (which is always in the C_IN class). The value of the record is
Simon Kelleya2ce6fc2012-08-06 20:05:48 +0100586given by the hex data, which may be of the form 01:23:45 or 01 23 45 or
Simon Kelley9f7f3b12012-05-28 21:39:57 +0100587012345 or any mixture of these.
588.TP
Simon Kelleyf7029f52013-11-21 15:09:09 +0000589.B --interface-name=<name>,<interface>[/4|/6]
Simon Kelleyf2621c72007-04-29 19:47:21 +0100590Return a DNS record associating the name with the primary address on
Simon Kelleyf7029f52013-11-21 15:09:09 +0000591the given interface. This flag specifies an A or AAAA record for the given
Simon Kelleyf2621c72007-04-29 19:47:21 +0100592name in the same way as an /etc/hosts line, except that the address is
Simon Kelleyf7029f52013-11-21 15:09:09 +0000593not constant, but taken from the given interface. The interface may be
594followed by "/4" or "/6" to specify that only IPv4 or IPv6 addresses
595of the interface should be used. If the interface is
Simon Kelley9e038942008-05-30 20:06:34 +0100596down, not configured or non-existent, an empty record is returned. The
Simon Kelleyf2621c72007-04-29 19:47:21 +0100597matching PTR record is also created, mapping the interface address to
598the name. More than one name may be associated with an interface
599address by repeating the flag; in that case the first instance is used
600for the reverse address-to-name mapping.
601.TP
Simon Kelley48fd1c42013-04-25 09:49:38 +0100602.B --synth-domain=<domain>,<address range>[,<prefix>]
Simon Kelley2bb73af2013-04-24 17:38:19 +0100603Create artificial A/AAAA and PTR records for an address range. The
604records use the address, with periods (or colons for IPv6) replaced
605with dashes.
606
607An example should make this clearer.
Simon Kelley48fd1c42013-04-25 09:49:38 +0100608.B --synth-domain=thekelleys.org.uk,192.168.0.0/24,internal-
609will result in a query for internal-192-168-0-56.thekelleys.org.uk returning
610192.168.0.56 and a reverse query vice versa. The same applies to IPv6,
611but IPv6 addresses may start with '::'
612but DNS labels may not start with '-' so in this case if no prefix is
613configured a zero is added in front of the label. ::1 becomes 0--1.
Simon Kelley2bb73af2013-04-24 17:38:19 +0100614
615The address range can be of the form
616<ip address>,<ip address> or <ip address>/<netmask>
617.TP
Simon Kelley9e4cf472016-02-17 20:26:32 +0000618.B --add-mac[=base64|text]
Simon Kelley28866e92011-02-14 20:19:14 +0000619Add the MAC address of the requestor to DNS queries which are
620forwarded upstream. This may be used to DNS filtering by the upstream
621server. The MAC address can only be added if the requestor is on the same
622subnet as the dnsmasq server. Note that the mechanism used to achieve this (an EDNS0 option)
623is not yet standardised, so this should be considered
624experimental. Also note that exposing MAC addresses in this way may
Simon Kelleyed4c0762013-10-08 20:46:34 +0100625have security and privacy implications. The warning about caching
Simon Kelley1e505122016-01-25 21:29:23 +0000626given for --add-subnet applies to --add-mac too. An alternative encoding of the
Simon Kelley9e4cf472016-02-17 20:26:32 +0000627MAC, as base64, is enabled by adding the "base64" parameter and a human-readable encoding of hex-and-colons is enabled by added the "text" parameter.
Simon Kelley1e505122016-01-25 21:29:23 +0000628.TP
629.B --add-cpe-id=<string>
630Add a arbitrary identifying string to o DNS queries which are
631forwarded upstream.
Simon Kelleyed4c0762013-10-08 20:46:34 +0100632.TP
Ed Bardsleya7369be2015-08-05 21:17:18 +0100633.B --add-subnet[[=[<IPv4 address>/]<IPv4 prefix length>][,[<IPv6 address>/]<IPv6 prefix length>]]
634Add a subnet address to the DNS queries which are forwarded
635upstream. If an address is specified in the flag, it will be used,
636otherwise, the address of the requestor will be used. The amount of
637the address forwarded depends on the prefix length parameter: 32 (128
638for IPv6) forwards the whole address, zero forwards none of it but
639still marks the request so that no upstream nameserver will add client
640address information either. The default is zero for both IPv4 and
641IPv6. Note that upstream nameservers may be configured to return
642different results based on this information, but the dnsmasq cache
643does not take account. If a dnsmasq instance is configured such that
644different results may be encountered, caching should be disabled.
645
646For example,
647.B --add-subnet=24,96
648will add the /24 and /96 subnets of the requestor for IPv4 and IPv6 requestors, respectively.
649.B --add-subnet=1.2.3.4/24
650will add 1.2.3.0/24 for IPv4 requestors and ::/0 for IPv6 requestors.
651.B --add-subnet=1.2.3.4/24,1.2.3.4/24
652will add 1.2.3.0/24 for both IPv4 and IPv6 requestors.
653
Simon Kelley28866e92011-02-14 20:19:14 +0000654.TP
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000655.B \-c, --cache-size=<cachesize>
656Set the size of dnsmasq's cache. The default is 150 names. Setting the cache size to zero disables caching.
657.TP
658.B \-N, --no-negcache
659Disable negative caching. Negative caching allows dnsmasq to remember
660"no such domain" answers from upstream nameservers and answer
Simon Kelley5aabfc72007-08-29 11:24:47 +0100661identical queries without forwarding them again.
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000662.TP
Simon Kelley16972692006-10-16 20:04:18 +0100663.B \-0, --dns-forward-max=<queries>
664Set the maximum number of concurrent DNS queries. The default value is
665150, which should be fine for most setups. The only known situation
666where this needs to be increased is when using web-server log file
667resolvers, which can generate large numbers of concurrent queries.
Simon Kelley208b65c2006-08-05 21:41:37 +0100668.TP
Simon Kelley70b4a812014-01-27 22:38:48 +0000669.B --dnssec
670Validate DNS replies and cache DNSSEC data. When forwarding DNS queries, dnsmasq requests the
671DNSSEC records needed to validate the replies. The replies are validated and the result returned as
672the Authenticated Data bit in the DNS packet. In addition the DNSSEC records are stored in the cache, making
673validation by clients more efficient. Note that validation by clients is the most secure DNSSEC mode, but for
674clients unable to do validation, use of the AD bit set by dnsmasq is useful, provided that the network between
675the dnsmasq server and the client is trusted. Dnsmasq must be compiled with HAVE_DNSSEC enabled, and DNSSEC
676trust anchors provided, see
Simon Kelleyee415862014-02-11 11:07:22 +0000677.B --trust-anchor.
Simon Kelleyd588ab52014-03-02 14:30:05 +0000678Because the DNSSEC validation process uses the cache, it is not
679permitted to reduce the cache size below the default when DNSSEC is
680enabled. The nameservers upstream of dnsmasq must be DNSSEC-capable,
681ie capable of returning DNSSEC records with data. If they are not,
682then dnsmasq will not be able to determine the trusted status of
683answers. In the default mode, this menas that all replies will be
684marked as untrusted. If
685.B --dnssec-check-unsigned
686is set and the upstream servers don't support DNSSEC, then DNS service will be entirely broken.
Simon Kelley70b4a812014-01-27 22:38:48 +0000687.TP
Simon Kelleyee415862014-02-11 11:07:22 +0000688.B --trust-anchor=[<class>],<domain>,<key-tag>,<algorithm>,<digest-type>,<digest>
689Provide DS records to act a trust anchors for DNSSEC
690validation. Typically these will be the DS record(s) for Zone Signing
691key(s) of the root zone,
692but trust anchors for limited domains are also possible. The current
Ján Sáreník85016322015-07-05 21:23:27 +0100693root-zone trust anchors may be downloaded from https://data.iana.org/root-anchors/root-anchors.xml
Simon Kelley70b4a812014-01-27 22:38:48 +0000694.TP
Simon Kelley00a5b5d2014-02-28 18:10:55 +0000695.B --dnssec-check-unsigned
696As a default, dnsmasq does not check that unsigned DNS replies are
697legitimate: they are assumed to be valid and passed on (without the
698"authentic data" bit set, of course). This does not protect against an
699attacker forging unsigned replies for signed DNS zones, but it is
700fast. If this flag is set, dnsmasq will check the zones of unsigned
701replies, to ensure that unsigned replies are allowed in those
Simon Kelleyd588ab52014-03-02 14:30:05 +0000702zones. The cost of this is more upstream queries and slower
703performance. See also the warning about upstream servers in the
704section on
705.B --dnssec
Simon Kelley00a5b5d2014-02-28 18:10:55 +0000706.TP
Simon Kelleye98bd522014-03-28 20:41:23 +0000707.B --dnssec-no-timecheck
708DNSSEC signatures are only valid for specified time windows, and should be rejected outside those windows. This generates an
709interesting chicken-and-egg problem for machines which don't have a hardware real time clock. For these machines to determine the correct
710time typically requires use of NTP and therefore DNS, but validating DNS requires that the correct time is already known. Setting this flag
711removes the time-window checks (but not other DNSSEC validation.) only until the dnsmasq process receives SIGHUP. The intention is
712that dnsmasq should be started with this flag when the platform determines that reliable time is not currently available. As soon as
713reliable time is established, a SIGHUP should be sent to dnsmasq, which enables time checking, and purges the cache of DNS records
714which have not been throughly checked.
715.TP
Simon Kelleyf6e62e22015-03-01 18:17:54 +0000716.B --dnssec-timestamp=<path>
717Enables an alternative way of checking the validity of the system time for DNSSEC (see --dnssec-no-timecheck). In this case, the
718system time is considered to be valid once it becomes later than the timestamp on the specified file. The file is created and
719its timestamp set automatically by dnsmasq. The file must be stored on a persistent filesystem, so that it and its mtime are carried
Simon Kelley360f2512015-03-07 18:28:06 +0000720over system restarts. The timestamp file is created after dnsmasq has dropped root, so it must be in a location writable by the
721unprivileged user that dnsmasq runs as.
Simon Kelleyf6e62e22015-03-01 18:17:54 +0000722.TP
Simon Kelley28866e92011-02-14 20:19:14 +0000723.B --proxy-dnssec
Simon Kelley70b4a812014-01-27 22:38:48 +0000724Copy the DNSSEC Authenticated Data bit from upstream servers to downstream clients and cache it. This is an
725alternative to having dnsmasq validate DNSSEC, but it depends on the security of the network between
726dnsmasq and the upstream servers, and the trustworthiness of the upstream servers.
727.TP
728.B --dnssec-debug
729Set debugging mode for the DNSSEC validation, set the Checking Disabled bit on upstream queries,
Simon Kelleyee415862014-02-11 11:07:22 +0000730and don't convert replies which do not validate to responses with
731a return code of SERVFAIL. Note that
732setting this may affect DNS behaviour in bad ways, it is not an
733extra-logging flag and should not be set in production.
Simon Kelley28866e92011-02-14 20:19:14 +0000734.TP
Simon Kelleybaa80ae2013-05-29 16:32:07 +0100735.B --auth-zone=<domain>[,<subnet>[/<prefix length>][,<subnet>[/<prefix length>].....]]
Simon Kelley34d0a362013-01-02 11:40:56 +0000736Define a DNS zone for which dnsmasq acts as authoritative server. Locally defined DNS records which are in the domain
Simon Kelleyc50f25a2013-11-21 11:29:27 +0000737will be served. If subnet(s) are given, A and AAAA records must be in one of the
738specified subnets.
739
740As alternative to directly specifying the subnets, it's possible to
Simon Kelley376d48c2013-11-13 13:04:30 +0000741give the name of an interface, in which case the subnets implied by
742that interface's configured addresses and netmask/prefix-length are
743used; this is useful when using constructed DHCP ranges as the actual
744address is dynamic and not known when configuring dnsmasq. The
745interface addresses may be confined to only IPv6 addresses using
746<interface>/6 or to only IPv4 using <interface>/4. This is useful when
747an interface has dynamically determined global IPv6 addresses which should
748appear in the zone, but RFC1918 IPv4 addresses which should not.
749Interface-name and address-literal subnet specifications may be used
750freely in the same --auth-zone declaration.
751
752The subnet(s) are also used to define in-addr.arpa and
Lutz Preßler1d7e0a32014-04-07 22:06:23 +0100753ip6.arpa domains which are served for reverse-DNS queries. If not
Simon Kelleybaa80ae2013-05-29 16:32:07 +0100754specified, the prefix length defaults to 24 for IPv4 and 64 for IPv6.
755For IPv4 subnets, the prefix length should be have the value 8, 16 or 24
756unless you are familiar with RFC 2317 and have arranged the
Simon Kelleyc50f25a2013-11-21 11:29:27 +0000757in-addr.arpa delegation accordingly. Note that if no subnets are
758specified, then no reverse queries are answered.
Simon Kelley333b2ce2013-01-07 21:46:03 +0000759.TP
760.B --auth-soa=<serial>[,<hostmaster>[,<refresh>[,<retry>[,<expiry>]]]]
761Specify fields in the SOA record associated with authoritative
762zones. Note that this is optional, all the values are set to sane defaults.
763.TP
764.B --auth-sec-servers=<domain>[,<domain>[,<domain>...]]
765Specify any secondary servers for a zone for which dnsmasq is
766authoritative. These servers must be configured to get zone data from
767dnsmasq by zone transfer, and answer queries for the same
Simon Kelley6f130de2013-04-15 14:47:14 +0100768authoritative zones as dnsmasq.
Simon Kelley333b2ce2013-01-07 21:46:03 +0000769.TP
770.B --auth-peer=<ip-address>[,<ip-address>[,<ip-address>...]]
771Specify the addresses of secondary servers which are allowed to
772initiate zone transfer (AXFR) requests for zones for which dnsmasq is
Simon Kelley6f130de2013-04-15 14:47:14 +0100773authoritative. If this option is not given, then AXFR requests will be
Simon Kelley333b2ce2013-01-07 21:46:03 +0000774accepted from any secondary.
775.TP
Simon Kelley7de060b2011-08-26 17:24:52 +0100776.B --conntrack
777Read the Linux connection track mark associated with incoming DNS
778queries and set the same mark value on upstream traffic used to answer
779those queries. This allows traffic generated by dnsmasq to be
780associated with the queries which cause it, useful for bandwidth
781accounting and firewalling. Dnsmasq must have conntrack support
782compiled in and the kernel must have conntrack support
783included and configured. This option cannot be combined with
784--query-port.
785.TP
Simon Kelley49dc5702013-04-02 20:27:07 +0100786.B \-F, --dhcp-range=[tag:<tag>[,tag:<tag>],][set:<tag>,]<start-addr>[,<end-addr>][,<mode>][,<netmask>[,<broadcast>]][,<lease time>]
Simon Kelley1adadf52012-02-13 22:15:58 +0000787.TP
Simon Kelley83f28be2013-04-03 14:46:46 +0100788.B \-F, --dhcp-range=[tag:<tag>[,tag:<tag>],][set:<tag>,]<start-IPv6addr>[,<end-IPv6addr>|constructor:<interface>][,<mode>][,<prefix-len>][,<lease time>]
Simon Kelley1adadf52012-02-13 22:15:58 +0000789
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000790Enable the DHCP server. Addresses will be given out from the range
Simon Kelley44a2a312004-03-10 20:04:35 +0000791<start-addr> to <end-addr> and from statically defined addresses given
792in
793.B dhcp-host
794options. If the lease time is given, then leases
Simon Kelleyb8187c82005-11-26 21:46:27 +0000795will be given for that length of time. The lease time is in seconds,
Simon Kelley7622fc02009-06-04 20:32:05 +0100796or minutes (eg 45m) or hours (eg 1h) or "infinite". If not given,
797the default lease time is one hour. The
Simon Kelleyc8257542012-03-28 21:15:41 +0100798minimum lease time is two minutes. For IPv6 ranges, the lease time
799maybe "deprecated"; this sets the preferred lifetime sent in a DHCP
800lease or router advertisement to zero, which causes clients to use
801other addresses, if available, for new connections as a prelude to renumbering.
802
803This option may be repeated, with different addresses, to enable DHCP
Simon Kelley44a2a312004-03-10 20:04:35 +0000804service to more than one network. For directly connected networks (ie,
805networks on which the machine running dnsmasq has an interface) the
Simon Kelley7de060b2011-08-26 17:24:52 +0100806netmask is optional: dnsmasq will determine it from the interface
807configuration. For networks which receive DHCP service via a relay
808agent, dnsmasq cannot determine the netmask itself, so it should be
809specified, otherwise dnsmasq will have to guess, based on the class (A, B or
810C) of the network address. The broadcast address is
Simon Kelley7622fc02009-06-04 20:32:05 +0100811always optional. It is always
Simon Kelley8ef5ada2010-06-03 19:42:45 +0100812allowed to have more than one dhcp-range in a single subnet.
813
Simon Kelley1adadf52012-02-13 22:15:58 +0000814For IPv6, the parameters are slightly different: instead of netmask
Vladislav Grishenko4c82efc2013-12-03 16:05:30 +0000815and broadcast address, there is an optional prefix length which must
816be equal to or larger then the prefix length on the local interface. If not
Simon Kelley1adadf52012-02-13 22:15:58 +0000817given, this defaults to 64. Unlike the IPv4 case, the prefix length is not
818automatically derived from the interface configuration. The mimimum
819size of the prefix length is 64.
820
Simon Kelley34d0a362013-01-02 11:40:56 +0000821IPv6 (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
822.B constructor:<interface>.
823This forms a template which describes how to create ranges, based on the addresses assigned to the interface. For instance
824
Simon Kelley83f28be2013-04-03 14:46:46 +0100825.B --dhcp-range=::1,::400,constructor:eth0
Simon Kelley34d0a362013-01-02 11:40:56 +0000826
Simon Kelley861c8912013-09-25 15:30:30 +0100827will look for addresses on
Simon Kelley429805d2013-05-31 13:47:26 +0100828eth0 and then create a range from <network>::1 to <network>::400. If
829the interface is assigned more than one network, then the
830corresponding ranges will be automatically created, and then
831deprecated and finally removed again as the address is deprecated and
832then deleted. The interface name may have a final "*" wildcard. Note
Simon Kelley861c8912013-09-25 15:30:30 +0100833that just any address on eth0 will not do: it must not be an
834autoconfigured or privacy address, or be deprecated.
Simon Kelley34d0a362013-01-02 11:40:56 +0000835
Vladislav Grishenkoe4cdbbf2013-08-19 16:20:31 +0100836If a dhcp-range is only being used for stateless DHCP and/or SLAAC,
837then the address can be simply ::
838
839.B --dhcp-range=::,constructor:eth0
840
Vladislav Grishenkoe4cdbbf2013-08-19 16:20:31 +0100841
Simon Kelley8ef5ada2010-06-03 19:42:45 +0100842The optional
843.B set:<tag>
844sets an alphanumeric label which marks this network so that
Simon Kelley0a852542005-03-23 20:28:59 +0000845dhcp options may be specified on a per-network basis.
Simon Kelley8ef5ada2010-06-03 19:42:45 +0100846When it is prefixed with 'tag:' instead, then its meaning changes from setting
Simon Kelleyc5ad4e72012-02-24 16:06:20 +0000847a tag to matching it. Only one tag may be set, but more than one tag
848may be matched.
849
Simon Kelleye8ca69e2012-03-26 21:23:26 +0100850The optional <mode> keyword may be
Simon Kelley33820b72004-04-03 21:10:00 +0100851.B static
852which tells dnsmasq to enable DHCP for the network specified, but not
Simon Kelley7622fc02009-06-04 20:32:05 +0100853to dynamically allocate IP addresses: only hosts which have static
Simon Kelley33820b72004-04-03 21:10:00 +0100854addresses given via
855.B dhcp-host
Simon Kelley52002052012-10-26 11:39:02 +0100856or from /etc/ethers will be served. A static-only subnet with address
857all zeros may be used as a "catch-all" address to enable replies to all
858Information-request packets on a subnet which is provided with
859stateless DHCPv6, ie
Moritz Warninge62e9b62014-03-20 15:32:22 +0000860.B --dhcp-range=::,static
Simon Kelleyc5ad4e72012-02-24 16:06:20 +0000861
Simon Kelleye46164e2012-04-16 16:39:38 +0100862For IPv4, the <mode> may be
Simon Kelley7622fc02009-06-04 20:32:05 +0100863.B proxy
864in which case dnsmasq will provide proxy-DHCP on the specified
865subnet. (See
866.B pxe-prompt
867and
868.B pxe-service
Simon Kelleye8ca69e2012-03-26 21:23:26 +0100869for details.)
Simon Kelley8ef5ada2010-06-03 19:42:45 +0100870
Simon Kelleye8ca69e2012-03-26 21:23:26 +0100871For IPv6, the mode may be some combination of
Neil Jerram4918bd52015-06-10 22:23:20 +0100872.B ra-only, slaac, ra-names, ra-stateless, ra-advrouter, off-link.
Simon Kelleye8ca69e2012-03-26 21:23:26 +0100873
Simon Kelleyc5ad4e72012-02-24 16:06:20 +0000874.B ra-only
Simon Kelleye8ca69e2012-03-26 21:23:26 +0100875tells dnsmasq to offer Router Advertisement only on this subnet,
876and not DHCP.
877
878.B slaac
879tells dnsmasq to offer Router Advertisement on this subnet and to set
880the A bit in the router advertisement, so that the client will use
881SLAAC addresses. When used with a DHCP range or static DHCP address
882this results in the client having both a DHCP-assigned and a SLAAC
883address.
884
885.B ra-stateless
886sends router advertisements with the O and A bits set, and provides a
887stateless DHCP service. The client will use a SLAAC address, and use
888DHCP for other configuration information.
889
Simon Kelley7023e382012-03-09 12:05:49 +0000890.B ra-names
Simon Kelleye8ca69e2012-03-26 21:23:26 +0100891enables a mode
Simon Kelley7023e382012-03-09 12:05:49 +0000892which gives DNS names to dual-stack hosts which do SLAAC for
Simon Kelley884a6df2012-03-20 16:20:22 +0000893IPv6. Dnsmasq uses the host's IPv4 lease to derive the name, network
Simon Kelley7023e382012-03-09 12:05:49 +0000894segment and MAC address and assumes that the host will also have an
Simon Kelleye46164e2012-04-16 16:39:38 +0100895IPv6 address calculated using the SLAAC algorithm, on the same network
Simon Kelley884a6df2012-03-20 16:20:22 +0000896segment. The address is pinged, and if a reply is received, an AAAA
897record is added to the DNS for this IPv6
Simon Kelley7023e382012-03-09 12:05:49 +0000898address. Note that this is only happens for directly-connected
Simon Kelley884a6df2012-03-20 16:20:22 +0000899networks, (not one doing DHCP via a relay) and it will not work
900if a host is using privacy extensions.
Simon Kelleye8ca69e2012-03-26 21:23:26 +0100901.B ra-names
902can be combined with
903.B ra-stateless
904and
905.B slaac.
Simon Kelleyc5ad4e72012-02-24 16:06:20 +0000906
Simon Kelley7ea3d3f2014-04-25 22:04:05 +0100907.B ra-advrouter
908enables a mode where router address(es) rather than prefix(es) are included in the advertisements.
909This is described in RFC-3775 section 7.2 and is used in mobile IPv6. In this mode the interval option
910is also included, as described in RFC-3775 section 7.3.
911
Neil Jerram4918bd52015-06-10 22:23:20 +0100912.B off-link
913tells dnsmasq to advertise the prefix without the on-link (aka L) bit set.
914
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000915.TP
Simon Kelley8ef5ada2010-06-03 19:42:45 +0100916.B \-G, --dhcp-host=[<hwaddr>][,id:<client_id>|*][,set:<tag>][,<ipaddr>][,<hostname>][,<lease_time>][,ignore]
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000917Specify per host parameters for the DHCP server. This allows a machine
918with a particular hardware address to be always allocated the same
919hostname, IP address and lease time. A hostname specified like this
920overrides any supplied by the DHCP client on the machine. It is also
Simon Kelleyc72daea2012-01-05 21:33:27 +0000921allowable to omit the hardware address and include the hostname, in
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000922which case the IP address and lease times will apply to any machine
923claiming that name. For example
924.B --dhcp-host=00:20:e0:3b:13:af,wap,infinite
925tells dnsmasq to give
Simon Kelleycdeda282006-03-16 20:16:06 +0000926the machine with hardware address 00:20:e0:3b:13:af the name wap, and
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000927an infinite DHCP lease.
928.B --dhcp-host=lap,192.168.0.199
929tells
930dnsmasq to always allocate the machine lap the IP address
Simon Kelley8ef5ada2010-06-03 19:42:45 +0100931192.168.0.199.
932
933Addresses allocated like this are not constrained to be
934in the range given by the --dhcp-range option, but they must be in
935the same subnet as some valid dhcp-range. For
936subnets which don't need a pool of dynamically allocated addresses,
937use the "static" keyword in the dhcp-range declaration.
938
Simon Kelley89500e32013-09-20 16:29:20 +0100939It is allowed to use client identifiers (called client
940DUID in IPv6-land rather than
Simon Kelley9e4abcb2004-01-22 19:47:41 +0000941hardware addresses to identify hosts by prefixing with 'id:'. Thus:
942.B --dhcp-host=id:01:02:03:04,.....
943refers to the host with client identifier 01:02:03:04. It is also
944allowed to specify the client ID as text, like this:
Simon Kelleya84fa1d2004-04-23 22:21:21 +0100945.B --dhcp-host=id:clientidastext,.....
Simon Kelley9009d742008-11-14 20:04:27 +0000946
Simon Kelley1adadf52012-02-13 22:15:58 +0000947A single
948.B dhcp-host
949may contain an IPv4 address or an IPv6 address, or both. IPv6 addresses must be bracketed by square brackets thus:
950.B --dhcp-host=laptop,[1234::56]
Simon Kelley30393102013-01-17 16:34:16 +0000951IPv6 addresses may contain only the host-identifier part:
952.B --dhcp-host=laptop,[::56]
Simon Kelley6f130de2013-04-15 14:47:14 +0100953in which case they act as wildcards in constructed dhcp ranges, with
Simon Kelley30393102013-01-17 16:34:16 +0000954the appropriate network part inserted.
Simon Kelley89500e32013-09-20 16:29:20 +0100955Note that in IPv6 DHCP, the hardware address may not be
956available, though it normally is for direct-connected clients, or
957clients using DHCP relays which support RFC 6939.
Simon Kelley1adadf52012-02-13 22:15:58 +0000958
Simon Kelley89500e32013-09-20 16:29:20 +0100959
960For DHCPv4, the special option id:* means "ignore any client-id
Simon Kelleya84fa1d2004-04-23 22:21:21 +0100961and use MAC addresses only." This is useful when a client presents a client-id sometimes
962but not others.
Simon Kelley9009d742008-11-14 20:04:27 +0000963
Simon Kelley1ab84e22004-01-29 16:48:35 +0000964If a name appears in /etc/hosts, the associated address can be
965allocated to a DHCP lease, but only if a
966.B --dhcp-host
Simon Kelley8ef5ada2010-06-03 19:42:45 +0100967option specifying the name also exists. Only one hostname can be
968given in a
969.B dhcp-host
970option, but aliases are possible by using CNAMEs. (See
971.B --cname
972).
973
974The special keyword "ignore"
Simon Kelley33820b72004-04-03 21:10:00 +0100975tells dnsmasq to never offer a DHCP lease to a machine. The machine
976can be specified by hardware address, client ID or hostname, for
977instance
978.B --dhcp-host=00:20:e0:3b:13:af,ignore
979This is
980useful when there is another DHCP server on the network which should
Simon Kelley9009d742008-11-14 20:04:27 +0000981be used by some machines.
982
Tomas Hozzaa66d36e2013-04-22 15:08:07 +0100983The set:<tag> construct sets the tag
Simon Kelley9009d742008-11-14 20:04:27 +0000984whenever this dhcp-host directive is in use. This can be used to
Simon Kelley8ef5ada2010-06-03 19:42:45 +0100985selectively send DHCP options just for this host. More than one tag
986can be set in a dhcp-host directive (but not in other places where
987"set:<tag>" is allowed). When a host matches any
Simon Kelley5aabfc72007-08-29 11:24:47 +0100988dhcp-host directive (or one implied by /etc/ethers) then the special
Simon Kelley8ef5ada2010-06-03 19:42:45 +0100989tag "known" is set. This allows dnsmasq to be configured to
Simon Kelley5aabfc72007-08-29 11:24:47 +0100990ignore requests from unknown machines using
Simon Kelley8ef5ada2010-06-03 19:42:45 +0100991.B --dhcp-ignore=tag:!known
Simon Kelley0a852542005-03-23 20:28:59 +0000992Ethernet addresses (but not client-ids) may have
993wildcard bytes, so for example
994.B --dhcp-host=00:20:e0:3b:13:*,ignore
Simon Kelleycdeda282006-03-16 20:16:06 +0000995will cause dnsmasq to ignore a range of hardware addresses. Note that
Simon Kelley0a852542005-03-23 20:28:59 +0000996the "*" will need to be escaped or quoted on a command line, but not
Simon Kelley9009d742008-11-14 20:04:27 +0000997in the configuration file.
998
999Hardware addresses normally match any
Simon Kelleycdeda282006-03-16 20:16:06 +00001000network (ARP) type, but it is possible to restrict them to a single
1001ARP type by preceding them with the ARP-type (in HEX) and "-". so
1002.B --dhcp-host=06-00:20:e0:3b:13:af,1.2.3.4
1003will only match a
1004Token-Ring hardware address, since the ARP-address type for token ring
Simon Kelley9009d742008-11-14 20:04:27 +00001005is 6.
1006
Simon Kelley1adadf52012-02-13 22:15:58 +00001007As a special case, in DHCPv4, it is possible to include more than one
Simon Kelley73a08a22009-02-05 20:28:08 +00001008hardware address. eg:
1009.B --dhcp-host=11:22:33:44:55:66,12:34:56:78:90:12,192.168.0.2
1010This allows an IP address to be associated with
Simon Kelley9009d742008-11-14 20:04:27 +00001011multiple hardware addresses, and gives dnsmasq permission to abandon a
1012DHCP lease to one of the hardware addresses when another one asks for
1013a lease. Beware that this is a dangerous thing to do, it will only
1014work reliably if only one of the hardware addresses is active at any
Simon Kelley73a08a22009-02-05 20:28:08 +00001015time and there is no way for dnsmasq to enforce this. It is, for instance,
1016useful to allocate a stable IP address to a laptop which
Simon Kelley9009d742008-11-14 20:04:27 +00001017has both wired and wireless interfaces.
Simon Kelley5aabfc72007-08-29 11:24:47 +01001018.TP
Simon Kelley28866e92011-02-14 20:19:14 +00001019.B --dhcp-hostsfile=<path>
1020Read DHCP host information from the specified file. If a directory
1021is given, then read all the files contained in that directory. The file contains
Simon Kelley5aabfc72007-08-29 11:24:47 +01001022information about one host per line. The format of a line is the same
1023as text to the right of '=' in --dhcp-host. The advantage of storing DHCP host information
1024in this file is that it can be changed without re-starting dnsmasq:
1025the file will be re-read when dnsmasq receives SIGHUP.
Simon Kelley824af852008-02-12 20:43:05 +00001026.TP
Simon Kelley28866e92011-02-14 20:19:14 +00001027.B --dhcp-optsfile=<path>
1028Read DHCP option information from the specified file. If a directory
1029is given, then read all the files contained in that directory. The advantage of
Simon Kelley824af852008-02-12 20:43:05 +00001030using this option is the same as for --dhcp-hostsfile: the
Simon Kelley1f15b812009-10-13 17:49:32 +01001031dhcp-optsfile will be re-read when dnsmasq receives SIGHUP. Note that
1032it is possible to encode the information in a
Simon Kelley5f4dc5c2015-01-20 20:51:02 +00001033.TP
1034.B --dhcp-hostsdir=<path>
Simon Kelley3d04f462015-01-31 21:59:13 +00001035This is equivalent to dhcp-hostsfile, except for the following. The path MUST be a
Simon Kelley5f4dc5c2015-01-20 20:51:02 +00001036directory, and not an individual file. Changed or new files within
1037the directory are read automatically, without the need to send SIGHUP.
1038If a file is deleted for changed after it has been read by dnsmasq, then the
1039host record it contained will remain until dnsmasq recieves a SIGHUP, or
1040is restarted; ie host records are only added dynamically.
Simon Kelleyefb8b552015-02-07 22:36:34 +00001041.TP
Simon Kelley3d04f462015-01-31 21:59:13 +00001042.B --dhcp-optsdir=<path>
1043This is equivalent to dhcp-optsfile, with the differences noted for --dhcp-hostsdir.
Simon Kelley5f4dc5c2015-01-20 20:51:02 +00001044.TP
Simon Kelley1f15b812009-10-13 17:49:32 +01001045.B --dhcp-boot
1046flag as DHCP options, using the options names bootfile-name,
1047server-ip-address and tftp-server. This allows these to be included
1048in a dhcp-optsfile.
Simon Kelley44a2a312004-03-10 20:04:35 +00001049.TP
1050.B \-Z, --read-ethers
1051Read /etc/ethers for information about hosts for the DHCP server. The
1052format of /etc/ethers is a hardware address, followed by either a
1053hostname or dotted-quad IP address. When read by dnsmasq these lines
1054have exactly the same effect as
1055.B --dhcp-host
Simon Kelley5aabfc72007-08-29 11:24:47 +01001056options containing the same information. /etc/ethers is re-read when
Simon Kelley1adadf52012-02-13 22:15:58 +00001057dnsmasq receives SIGHUP. IPv6 addresses are NOT read from /etc/ethers.
Simon Kelley9e4abcb2004-01-22 19:47:41 +00001058.TP
Simon Kelley1adadf52012-02-13 22:15:58 +00001059.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>]]
Simon Kelleyb8187c82005-11-26 21:46:27 +00001060Specify different or extra options to DHCP clients. By default,
Simon Kelley9e4abcb2004-01-22 19:47:41 +00001061dnsmasq sends some standard options to DHCP clients, the netmask and
1062broadcast address are set to the same as the host running dnsmasq, and
1063the DNS server and default route are set to the address of the machine
Simon Kelley1adadf52012-02-13 22:15:58 +00001064running dnsmasq. (Equivalent rules apply for IPv6.) If the domain name option has been set, that is sent.
Simon Kelleyf2621c72007-04-29 19:47:21 +01001065This configuration allows these defaults to be overridden,
1066or other options specified. The option, to be sent may be given as a
1067decimal number or as "option:<option-name>" The option numbers are
1068specified in RFC2132 and subsequent RFCs. The set of option-names
1069known by dnsmasq can be discovered by running "dnsmasq --help dhcp".
1070For example, to set the default route option to
Simon Kelley9e4abcb2004-01-22 19:47:41 +00001071192.168.4.4, do
Simon Kelleyf2621c72007-04-29 19:47:21 +01001072.B --dhcp-option=3,192.168.4.4
1073or
1074.B --dhcp-option = option:router, 192.168.4.4
Simon Kelley9e4abcb2004-01-22 19:47:41 +00001075and to set the time-server address to 192.168.0.4, do
Simon Kelleyf2621c72007-04-29 19:47:21 +01001076.B --dhcp-option = 42,192.168.0.4
1077or
1078.B --dhcp-option = option:ntp-server, 192.168.0.4
Simon Kelleyc3a04082014-01-11 22:18:19 +00001079The special address 0.0.0.0 is taken to mean "the address of the
1080machine running dnsmasq".
1081
1082Data types allowed are comma separated
1083dotted-quad IPv4 addresses, []-wrapped IPv6 addresses, a decimal number, colon-separated hex digits
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001084and a text string. If the optional tags are given then
1085this option is only sent when all the tags are matched.
Simon Kelley91dccd02005-03-31 17:48:32 +01001086
Simon Kelleycdeda282006-03-16 20:16:06 +00001087Special processing is done on a text argument for option 119, to
Simon Kelley832af0b2007-01-21 20:01:28 +00001088conform with RFC 3397. Text or dotted-quad IP addresses as arguments
1089to option 120 are handled as per RFC 3361. Dotted-quad IP addresses
1090which are followed by a slash and then a netmask size are encoded as
1091described in RFC 3442.
Simon Kelleycdeda282006-03-16 20:16:06 +00001092
Simon Kelley1adadf52012-02-13 22:15:58 +00001093IPv6 options are specified using the
1094.B option6:
1095keyword, followed by the option number or option name. The IPv6 option
1096name space is disjoint from the IPv4 option name space. IPv6 addresses
1097in options must be bracketed with square brackets, eg.
1098.B --dhcp-option=option6:ntp-server,[1234::56]
Simon Kelleyc3a04082014-01-11 22:18:19 +00001099For IPv6, [::] means "the global address of
1100the machine running dnsmasq", whilst [fd00::] is replaced with the
1101ULA, if it exists, and [fe80::] with the link-local address.
Simon Kelley1adadf52012-02-13 22:15:58 +00001102
Simon Kelley9e4abcb2004-01-22 19:47:41 +00001103Be careful: no checking is done that the correct type of data for the
Simon Kelley26128d22004-11-14 16:43:54 +00001104option number is sent, it is quite possible to
Simon Kelley9e4abcb2004-01-22 19:47:41 +00001105persuade dnsmasq to generate illegal DHCP packets with injudicious use
Simon Kelley91dccd02005-03-31 17:48:32 +01001106of this flag. When the value is a decimal number, dnsmasq must determine how
1107large the data item is. It does this by examining the option number and/or the
Simon Kelleyb8187c82005-11-26 21:46:27 +00001108value, but can be overridden by appending a single letter flag as follows:
Simon Kelley91dccd02005-03-31 17:48:32 +01001109b = one byte, s = two bytes, i = four bytes. This is mainly useful with
Simon Kelley3d8df262005-08-29 12:19:27 +01001110encapsulated vendor class options (see below) where dnsmasq cannot
1111determine data size from the option number. Option data which
1112consists solely of periods and digits will be interpreted by dnsmasq
1113as an IP address, and inserted into an option as such. To force a
1114literal string, use quotes. For instance when using option 66 to send
1115a literal IP address as TFTP server name, it is necessary to do
1116.B --dhcp-option=66,"1.2.3.4"
Simon Kelley91dccd02005-03-31 17:48:32 +01001117
Simon Kelley1adadf52012-02-13 22:15:58 +00001118Encapsulated Vendor-class options may also be specified (IPv4 only) using
Simon Kelley91dccd02005-03-31 17:48:32 +01001119--dhcp-option: for instance
Simon Kelley1b7ecd12007-02-05 14:57:57 +00001120.B --dhcp-option=vendor:PXEClient,1,0.0.0.0
1121sends the encapsulated vendor
1122class-specific option "mftp-address=0.0.0.0" to any client whose
1123vendor-class matches "PXEClient". The vendor-class matching is
Simon Kelley6b010842007-02-12 20:32:07 +00001124substring based (see --dhcp-vendorclass for details). If a
1125vendor-class option (number 60) is sent by dnsmasq, then that is used
1126for selecting encapsulated options in preference to any sent by the
1127client. It is
Simon Kelley1b7ecd12007-02-05 14:57:57 +00001128possible to omit the vendorclass completely;
1129.B --dhcp-option=vendor:,1,0.0.0.0
Simon Kelley1adadf52012-02-13 22:15:58 +00001130in which case the encapsulated option is always sent.
Simon Kelley73a08a22009-02-05 20:28:08 +00001131
Simon Kelley1adadf52012-02-13 22:15:58 +00001132Options may be encapsulated (IPv4 only) within other options: for instance
Simon Kelley73a08a22009-02-05 20:28:08 +00001133.B --dhcp-option=encap:175, 190, "iscsi-client0"
1134will send option 175, within which is the option 190. If multiple
1135options are given which are encapsulated with the same option number
1136then they will be correctly combined into one encapsulated option.
1137encap: and vendor: are may not both be set in the same dhcp-option.
1138
Simon Kelley316e2732010-01-22 20:16:09 +00001139The final variant on encapsulated options is "Vendor-Identifying
1140Vendor Options" as specified by RFC3925. These are denoted like this:
1141.B --dhcp-option=vi-encap:2, 10, "text"
1142The number in the vi-encap: section is the IANA enterprise number
Simon Kelley1adadf52012-02-13 22:15:58 +00001143used to identify this option. This form of encapsulation is supported
1144in IPv6.
1145
Simon Kelley1b7ecd12007-02-05 14:57:57 +00001146The address 0.0.0.0 is not treated specially in
Simon Kelley73a08a22009-02-05 20:28:08 +00001147encapsulated options.
Simon Kelley9e4abcb2004-01-22 19:47:41 +00001148.TP
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001149.B --dhcp-option-force=[tag:<tag>,[tag:<tag>,]][encap:<opt>,][vi-encap:<enterprise>,][vendor:[<vendor-class>],]<opt>,[<value>[,<value>]]
Simon Kelley6b010842007-02-12 20:32:07 +00001150This works in exactly the same way as
Simon Kelleyf2621c72007-04-29 19:47:21 +01001151.B --dhcp-option
1152except that the option will always be sent, even if the client does
Simon Kelley6b010842007-02-12 20:32:07 +00001153not ask for it in the parameter request list. This is sometimes
1154needed, for example when sending options to PXELinux.
1155.TP
Simon Kelley824af852008-02-12 20:43:05 +00001156.B --dhcp-no-override
Simon Kelley1adadf52012-02-13 22:15:58 +00001157(IPv4 only) Disable re-use of the DHCP servername and filename fields as extra
Simon Kelley824af852008-02-12 20:43:05 +00001158option space. If it can, dnsmasq moves the boot server and filename
1159information (from dhcp-boot) out of their dedicated fields into
1160DHCP options. This make extra space available in the DHCP packet for
1161options but can, rarely, confuse old or broken clients. This flag
1162forces "simple and safe" behaviour to avoid problems in such a case.
1163.TP
Simon Kelleyff7eea22013-09-04 18:01:38 +01001164.B --dhcp-relay=<local address>,<server address>[,<interface]
1165Configure dnsmasq to do DHCP relay. The local address is an address
1166allocated to an interface on the host running dnsmasq. All DHCP
1167requests arriving on that interface will we relayed to a remote DHCP
1168server at the server address. It is possible to relay from a single local
1169address to multiple remote servers by using multiple dhcp-relay
1170configs with the same local address and different server
1171addresses. A server address must be an IP literal address, not a
1172domain name. In the case of DHCPv6, the server address may be the
1173ALL_SERVERS multicast address, ff05::1:3. In this case the interface
1174must be given, not be wildcard, and is used to direct the multicast to the
1175correct interface to reach the DHCP server.
1176
1177Access control for DHCP clients has the same rules as for the DHCP
1178server, see --interface, --except-interface, etc. The optional
1179interface name in the dhcp-relay config has a different function: it
1180controls on which interface DHCP replies from the server will be
1181accepted. This is intended for configurations which have three
1182interfaces: one being relayed from, a second connecting the DHCP
1183server, and a third untrusted network, typically the wider
1184internet. It avoids the possibility of spoof replies arriving via this
1185third interface.
1186
1187It is allowed to have dnsmasq act as a DHCP server on one set of
1188interfaces and relay from a disjoint set of interfaces. Note that
1189whilst it is quite possible to write configurations which appear to
1190act as a server and a relay on the same interface, this is not
1191supported: the relay function will take precedence.
1192
1193Both DHCPv4 and DHCPv6 relay is supported. It's not possible to relay
1194DHCPv4 to a DHCPv6 server or vice-versa.
1195.TP
Simon Kelley1adadf52012-02-13 22:15:58 +00001196.B \-U, --dhcp-vendorclass=set:<tag>,[enterprise:<IANA-enterprise number>,]<vendor-class>
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001197Map from a vendor-class string to a tag. Most DHCP clients provide a
Simon Kelleya2226412004-05-13 20:27:08 +01001198"vendor class" which represents, in some sense, the type of host. This option
Simon Kelleyf2621c72007-04-29 19:47:21 +01001199maps vendor classes to tags, so that DHCP options may be selectively delivered
Simon Kelleya84fa1d2004-04-23 22:21:21 +01001200to different classes of hosts. For example
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001201.B dhcp-vendorclass=set:printers,Hewlett-Packard JetDirect
Simon Kelleya84fa1d2004-04-23 22:21:21 +01001202will allow options to be set only for HP printers like so:
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001203.B --dhcp-option=tag:printers,3,192.168.4.4
Simon Kelleya2226412004-05-13 20:27:08 +01001204The vendor-class string is
1205substring matched against the vendor-class supplied by the client, to
Simon Kelley1adadf52012-02-13 22:15:58 +00001206allow fuzzy matching. The set: prefix is optional but allowed for
1207consistency.
1208
1209Note that in IPv6 only, vendorclasses are namespaced with an
1210IANA-allocated enterprise number. This is given with enterprise:
1211keyword and specifies that only vendorclasses matching the specified
1212number should be searched.
Simon Kelleya2226412004-05-13 20:27:08 +01001213.TP
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001214.B \-j, --dhcp-userclass=set:<tag>,<user-class>
1215Map from a user-class string to a tag (with substring
Simon Kelleya2226412004-05-13 20:27:08 +01001216matching, like vendor classes). Most DHCP clients provide a
1217"user class" which is configurable. This option
Simon Kelleyf2621c72007-04-29 19:47:21 +01001218maps user classes to tags, so that DHCP options may be selectively delivered
Simon Kelleya2226412004-05-13 20:27:08 +01001219to different classes of hosts. It is possible, for instance to use
1220this to set a different printer server for hosts in the class
1221"accounts" than for hosts in the class "engineering".
Simon Kelleya84fa1d2004-04-23 22:21:21 +01001222.TP
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001223.B \-4, --dhcp-mac=set:<tag>,<MAC address>
Simon Kelley89500e32013-09-20 16:29:20 +01001224Map from a MAC address to a tag. The MAC address may include
Simon Kelleycdeda282006-03-16 20:16:06 +00001225wildcards. For example
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001226.B --dhcp-mac=set:3com,01:34:23:*:*:*
Simon Kelleycdeda282006-03-16 20:16:06 +00001227will set the tag "3com" for any host whose MAC address matches the pattern.
1228.TP
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001229.B --dhcp-circuitid=set:<tag>,<circuit-id>, --dhcp-remoteid=set:<tag>,<remote-id>
1230Map from RFC3046 relay agent options to tags. This data may
Simon Kelleyf2621c72007-04-29 19:47:21 +01001231be provided by DHCP relay agents. The circuit-id or remote-id is
1232normally given as colon-separated hex, but is also allowed to be a
1233simple string. If an exact match is achieved between the circuit or
Simon Kelley1adadf52012-02-13 22:15:58 +00001234agent ID and one provided by a relay agent, the tag is set.
1235
1236.B dhcp-remoteid
1237(but not dhcp-circuitid) is supported in IPv6.
Simon Kelleyf2621c72007-04-29 19:47:21 +01001238.TP
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001239.B --dhcp-subscrid=set:<tag>,<subscriber-id>
Simon Kelley1adadf52012-02-13 22:15:58 +00001240(IPv4 and IPv6) Map from RFC3993 subscriber-id relay agent options to tags.
Simon Kelley824af852008-02-12 20:43:05 +00001241.TP
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001242.B --dhcp-proxy[=<ip addr>]......
Simon Kelley07933802012-02-14 20:55:25 +00001243(IPv4 only) A normal DHCP relay agent is only used to forward the initial parts of
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001244a DHCP interaction to the DHCP server. Once a client is configured, it
1245communicates directly with the server. This is undesirable if the
Tomas Hozzaa66d36e2013-04-22 15:08:07 +01001246relay agent is adding extra information to the DHCP packets, such as
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001247that used by
1248.B dhcp-circuitid
1249and
1250.B dhcp-remoteid.
1251A full relay implementation can use the RFC 5107 serverid-override
1252option to force the DHCP server to use the relay as a full proxy, with all
1253packets passing through it. This flag provides an alternative method
1254of doing the same thing, for relays which don't support RFC
12555107. Given alone, it manipulates the server-id for all interactions
1256via relays. If a list of IP addresses is given, only interactions via
1257relays at those addresses are affected.
1258.TP
1259.B --dhcp-match=set:<tag>,<option number>|option:<option name>|vi-encap:<enterprise>[,<value>]
1260Without a value, set the tag if the client sends a DHCP
Simon Kelley73a08a22009-02-05 20:28:08 +00001261option of the given number or name. When a value is given, set the tag only if
1262the option is sent and matches the value. The value may be of the form
Tomas Hozzaa66d36e2013-04-22 15:08:07 +01001263"01:ff:*:02" in which case the value must match (apart from wildcards)
Simon Kelley73a08a22009-02-05 20:28:08 +00001264but the option sent may have unmatched data past the end of the
1265value. The value may also be of the same form as in
1266.B dhcp-option
1267in which case the option sent is treated as an array, and one element
1268must match, so
1269
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001270--dhcp-match=set:efi-ia32,option:client-arch,6
Simon Kelley73a08a22009-02-05 20:28:08 +00001271
1272will set the tag "efi-ia32" if the the number 6 appears in the list of
1273architectures sent by the client in option 93. (See RFC 4578 for
Simon Kelley316e2732010-01-22 20:16:09 +00001274details.) If the value is a string, substring matching is used.
1275
Tomas Hozzaa66d36e2013-04-22 15:08:07 +01001276The special form with vi-encap:<enterprise number> matches against
Simon Kelley316e2732010-01-22 20:16:09 +00001277vendor-identifying vendor classes for the specified enterprise. Please
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001278see RFC 3925 for more details of these rare and interesting beasts.
Simon Kelleyf2621c72007-04-29 19:47:21 +01001279.TP
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001280.B --tag-if=set:<tag>[,set:<tag>[,tag:<tag>[,tag:<tag>]]]
1281Perform boolean operations on tags. Any tag appearing as set:<tag> is set if
1282all the tags which appear as tag:<tag> are set, (or unset when tag:!<tag> is used)
1283If no tag:<tag> appears set:<tag> tags are set unconditionally.
1284Any number of set: and tag: forms may appear, in any order.
1285Tag-if lines ares executed in order, so if the tag in tag:<tag> is a
1286tag set by another
1287.B tag-if,
1288the line which sets the tag must precede the one which tests it.
1289.TP
1290.B \-J, --dhcp-ignore=tag:<tag>[,tag:<tag>]
1291When all the given tags appear in the tag set ignore the host and do
Simon Kelley26128d22004-11-14 16:43:54 +00001292not allocate it a DHCP lease.
1293.TP
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001294.B --dhcp-ignore-names[=tag:<tag>[,tag:<tag>]]
1295When all the given tags appear in the tag set, ignore any hostname
Simon Kelley9e038942008-05-30 20:06:34 +01001296provided by the host. Note that, unlike dhcp-ignore, it is permissible
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001297to supply no tags, in which case DHCP-client supplied hostnames
Simon Kelley832af0b2007-01-21 20:01:28 +00001298are always ignored, and DHCP hosts are added to the DNS using only
1299dhcp-host configuration in dnsmasq and the contents of /etc/hosts and
1300/etc/ethers.
1301.TP
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001302.B --dhcp-generate-names=tag:<tag>[,tag:<tag>]
Simon Kelley1adadf52012-02-13 22:15:58 +00001303(IPv4 only) Generate a name for DHCP clients which do not otherwise have one,
Tomas Hozzaa66d36e2013-04-22 15:08:07 +01001304using the MAC address expressed in hex, separated by dashes. Note that
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001305if a host provides a name, it will be used by preference to this,
1306unless
1307.B --dhcp-ignore-names
1308is set.
1309.TP
1310.B --dhcp-broadcast[=tag:<tag>[,tag:<tag>]]
Simon Kelley1adadf52012-02-13 22:15:58 +00001311(IPv4 only) When all the given tags appear in the tag set, always use broadcast to
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001312communicate with the host when it is unconfigured. It is permissible
1313to supply no tags, in which case this is unconditional. Most DHCP clients which
Simon Kelley824af852008-02-12 20:43:05 +00001314need broadcast replies set a flag in their requests so that this
1315happens automatically, some old BOOTP clients do not.
1316.TP
Simon Kelley7de060b2011-08-26 17:24:52 +01001317.B \-M, --dhcp-boot=[tag:<tag>,]<filename>,[<servername>[,<server address>|<tftp_servername>]]
Simon Kelley1adadf52012-02-13 22:15:58 +00001318(IPv4 only) Set BOOTP options to be returned by the DHCP server. Server name and
Simon Kelley832af0b2007-01-21 20:01:28 +00001319address are optional: if not provided, the name is left empty, and the
1320address set to the address of the machine running dnsmasq. If dnsmasq
1321is providing a TFTP service (see
1322.B --enable-tftp
1323) then only the filename is required here to enable network booting.
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001324If the optional tag(s) are given,
1325they must match for this configuration to be sent.
Simon Kelley7de060b2011-08-26 17:24:52 +01001326Instead of an IP address, the TFTP server address can be given as a domain
1327name which is looked up in /etc/hosts. This name can be associated in
1328/etc/hosts with multiple IP addresses, which are used round-robin.
1329This facility can be used to load balance the tftp load among a set of servers.
1330.TP
1331.B --dhcp-sequential-ip
1332Dnsmasq is designed to choose IP addresses for DHCP clients using a
1333hash of the client's MAC address. This normally allows a client's
1334address to remain stable long-term, even if the client sometimes allows its DHCP
1335lease to expire. In this default mode IP addresses are distributed
1336pseudo-randomly over the entire available address range. There are
1337sometimes circumstances (typically server deployment) where it is more
1338convenient to have IP
1339addresses allocated sequentially, starting from the lowest available
1340address, and setting this flag enables this mode. Note that in the
1341sequential mode, clients which allow a lease to expire are much more
1342likely to move IP address; for this reason it should not be generally used.
Simon Kelley7622fc02009-06-04 20:32:05 +01001343.TP
Simon Kelley751d6f42012-02-10 15:24:51 +00001344.B --pxe-service=[tag:<tag>,]<CSA>,<menu text>[,<basename>|<bootservicetype>][,<server address>|<server_name>]
Simon Kelley7622fc02009-06-04 20:32:05 +01001345Most uses of PXE boot-ROMS simply allow the PXE
1346system to obtain an IP address and then download the file specified by
1347.B dhcp-boot
1348and execute it. However the PXE system is capable of more complex
1349functions when supported by a suitable DHCP server.
1350
1351This specifies a boot option which may appear in a PXE boot menu. <CSA> is
1352client system type, only services of the correct type will appear in a
1353menu. The known types are x86PC, PC98, IA64_EFI, Alpha, Arc_x86,
1354Intel_Lean_Client, IA32_EFI, BC_EFI, Xscale_EFI and X86-64_EFI; an
1355integer may be used for other types. The
1356parameter after the menu text may be a file name, in which case dnsmasq acts as a
1357boot server and directs the PXE client to download the file by TFTP,
1358either from itself (
1359.B enable-tftp
Simon Kelley751d6f42012-02-10 15:24:51 +00001360must be set for this to work) or another TFTP server if the final server
1361address/name is given.
Simon Kelley7622fc02009-06-04 20:32:05 +01001362Note that the "layer"
1363suffix (normally ".0") is supplied by PXE, and should not be added to
1364the basename. If an integer boot service type, rather than a basename
1365is given, then the PXE client will search for a
1366suitable boot service for that type on the network. This search may be done
Simon Kelley751d6f42012-02-10 15:24:51 +00001367by broadcast, or direct to a server if its IP address/name is provided.
Simon Kelley316e2732010-01-22 20:16:09 +00001368If no boot service type or filename is provided (or a boot service type of 0 is specified)
1369then the menu entry will abort the net boot procedure and
Simon Kelley751d6f42012-02-10 15:24:51 +00001370continue booting from local media. The server address can be given as a domain
1371name which is looked up in /etc/hosts. This name can be associated in
1372/etc/hosts with multiple IP addresses, which are used round-robin.
Simon Kelley7622fc02009-06-04 20:32:05 +01001373.TP
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001374.B --pxe-prompt=[tag:<tag>,]<prompt>[,<timeout>]
Simon Kelley7622fc02009-06-04 20:32:05 +01001375Setting this provides a prompt to be displayed after PXE boot. If the
1376timeout is given then after the
1377timeout has elapsed with no keyboard input, the first available menu
1378option will be automatically executed. If the timeout is zero then the first available menu
1379item will be executed immediately. If
1380.B pxe-prompt
Tomas Hozzaa66d36e2013-04-22 15:08:07 +01001381is omitted the system will wait for user input if there are multiple
Simon Kelley7622fc02009-06-04 20:32:05 +01001382items in the menu, but boot immediately if
1383there is only one. See
1384.B pxe-service
1385for details of menu items.
1386
1387Dnsmasq supports PXE "proxy-DHCP", in this case another DHCP server on
1388the network is responsible for allocating IP addresses, and dnsmasq
1389simply provides the information given in
1390.B pxe-prompt
1391and
1392.B pxe-service
1393to allow netbooting. This mode is enabled using the
1394.B proxy
1395keyword in
1396.B dhcp-range.
Simon Kelley9e4abcb2004-01-22 19:47:41 +00001397.TP
Simon Kelley44a2a312004-03-10 20:04:35 +00001398.B \-X, --dhcp-lease-max=<number>
1399Limits dnsmasq to the specified maximum number of DHCP leases. The
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001400default is 1000. This limit is to prevent DoS attacks from hosts which
Simon Kelley44a2a312004-03-10 20:04:35 +00001401create thousands of leases and use lots of memory in the dnsmasq
1402process.
1403.TP
Simon Kelleyfd9fa482004-10-21 20:24:00 +01001404.B \-K, --dhcp-authoritative
Simon Kelley095f6252013-01-30 11:31:02 +00001405Should be set when dnsmasq is definitely the only DHCP server on a network.
1406For DHCPv4, it changes the behaviour from strict RFC compliance so that DHCP requests on
Simon Kelleyfd9fa482004-10-21 20:24:00 +01001407unknown leases from unknown hosts are not ignored. This allows new hosts
Simon Kelleycdeda282006-03-16 20:16:06 +00001408to get a lease without a tedious timeout under all circumstances. It also
1409allows dnsmasq to rebuild its lease database without each client needing to
Simon Kelley095f6252013-01-30 11:31:02 +00001410reacquire a lease, if the database is lost. For DHCPv6 it sets the
1411priority in replies to 255 (the maximum) instead of 0 (the minimum).
Simon Kelley9e038942008-05-30 20:06:34 +01001412.TP
1413.B --dhcp-alternate-port[=<server port>[,<client port>]]
Simon Kelley1adadf52012-02-13 22:15:58 +00001414(IPv4 only) Change the ports used for DHCP from the default. If this option is
Simon Kelley9e038942008-05-30 20:06:34 +01001415given alone, without arguments, it changes the ports used for DHCP
1416from 67 and 68 to 1067 and 1068. If a single argument is given, that
1417port number is used for the server and the port number plus one used
1418for the client. Finally, two port numbers allows arbitrary
1419specification of both server and client ports for DHCP.
Simon Kelleyfd9fa482004-10-21 20:24:00 +01001420.TP
Simon Kelley9009d742008-11-14 20:04:27 +00001421.B \-3, --bootp-dynamic[=<network-id>[,<network-id>]]
Simon Kelley1adadf52012-02-13 22:15:58 +00001422(IPv4 only) Enable dynamic allocation of IP addresses to BOOTP clients. Use this
Simon Kelley3d8df262005-08-29 12:19:27 +01001423with care, since each address allocated to a BOOTP client is leased
1424forever, and therefore becomes permanently unavailable for re-use by
Simon Kelley9009d742008-11-14 20:04:27 +00001425other hosts. if this is given without tags, then it unconditionally
1426enables dynamic allocation. With tags, only when the tags are all
1427set. It may be repeated with different tag sets.
Simon Kelley3d8df262005-08-29 12:19:27 +01001428.TP
Simon Kelley5e9e0ef2006-04-17 14:24:29 +01001429.B \-5, --no-ping
Christian Demsar23facf02015-05-20 20:26:23 +01001430(IPv4 only) By default, the DHCP server will attempt to ensure that an address is
Simon Kelley5e9e0ef2006-04-17 14:24:29 +01001431not in use before allocating it to a host. It does this by sending an
1432ICMP echo request (aka "ping") to the address in question. If it gets
1433a reply, then the address must already be in use, and another is
1434tried. This flag disables this check. Use with caution.
1435.TP
Simon Kelleyf2621c72007-04-29 19:47:21 +01001436.B --log-dhcp
1437Extra logging for DHCP: log all the options sent to DHCP clients and
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001438the tags used to determine them.
Simon Kelleyf2621c72007-04-29 19:47:21 +01001439.TP
Kevin Darbyshire-Bryant8c0b73d2013-10-11 11:56:33 +01001440.B --quiet-dhcp, --quiet-dhcp6, --quiet-ra
1441Suppress logging of the routine operation of these protocols. Errors and
1442problems will still be logged. --quiet-dhcp and quiet-dhcp6 are
1443over-ridden by --log-dhcp.
1444.TP
Simon Kelley9e4abcb2004-01-22 19:47:41 +00001445.B \-l, --dhcp-leasefile=<path>
Simon Kelley73a08a22009-02-05 20:28:08 +00001446Use the specified file to store DHCP lease information.
Simon Kelley208b65c2006-08-05 21:41:37 +01001447.TP
Simon Kelley8b372702012-03-09 17:45:10 +00001448.B --dhcp-duid=<enterprise-id>,<uid>
1449(IPv6 only) Specify the server persistent UID which the DHCPv6 server
1450will use. This option is not normally required as dnsmasq creates a
1451DUID automatically when it is first needed. When given, this option
1452provides dnsmasq the data required to create a DUID-EN type DUID. Note
1453that once set, the DUID is stored in the lease database, so to change between DUID-EN and
1454automatically created DUIDs or vice-versa, the lease database must be
1455re-intialised. The enterprise-id is assigned by IANA, and the uid is a
1456string of hex octets unique to a particular device.
1457.TP
Simon Kelley7cebd202006-05-06 14:13:33 +01001458.B \-6 --dhcp-script=<path>
Simon Kelleya9530962012-03-20 22:07:35 +00001459Whenever a new DHCP lease is created, or an old one destroyed, or a
1460TFTP file transfer completes, the
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001461executable specified by this option is run. <path>
1462must be an absolute pathname, no PATH search occurs.
1463The arguments to the process
Simon Kelley7cebd202006-05-06 14:13:33 +01001464are "add", "old" or "del", the MAC
Simon Kelley1adadf52012-02-13 22:15:58 +00001465address of the host (or DUID for IPv6) , the IP address, and the hostname,
Simon Kelley7cebd202006-05-06 14:13:33 +01001466if known. "add" means a lease has been created, "del" means it has
1467been destroyed, "old" is a notification of an existing lease when
Simon Kelley208b65c2006-08-05 21:41:37 +01001468dnsmasq starts or a change to MAC address or hostname of an existing
1469lease (also, lease length or expiry and client-id, if leasefile-ro is set).
Simon Kelley9009d742008-11-14 20:04:27 +00001470If the MAC address is from a network type other than ethernet,
1471it will have the network type prepended, eg "06-01:23:45:67:89:ab" for
1472token ring. The process is run as root (assuming that dnsmasq was originally run as
Simon Kelley16972692006-10-16 20:04:18 +01001473root) even if dnsmasq is configured to change UID to an unprivileged user.
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001474
1475The environment is inherited from the invoker of dnsmasq, with some or
Simon Kelley1adadf52012-02-13 22:15:58 +00001476all of the following variables added
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001477
Simon Kelley1adadf52012-02-13 22:15:58 +00001478For both IPv4 and IPv6:
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001479
1480DNSMASQ_DOMAIN if the fully-qualified domain name of the host is
Simon Kelley28866e92011-02-14 20:19:14 +00001481known, this is set to the domain part. (Note that the hostname passed
1482to the script as an argument is never fully-qualified.)
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001483
Simon Kelley1adadf52012-02-13 22:15:58 +00001484If the client provides a hostname, DNSMASQ_SUPPLIED_HOSTNAME
1485
1486If the client provides user-classes, DNSMASQ_USER_CLASS0..DNSMASQ_USER_CLASSn
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001487
1488If dnsmasq was compiled with HAVE_BROKEN_RTC, then
Simon Kelley208b65c2006-08-05 21:41:37 +01001489the length of the lease (in seconds) is stored in
Simon Kelley16972692006-10-16 20:04:18 +01001490DNSMASQ_LEASE_LENGTH, otherwise the time of lease expiry is stored in
Simon Kelley5aabfc72007-08-29 11:24:47 +01001491DNSMASQ_LEASE_EXPIRES. The number of seconds until lease expiry is
1492always stored in DNSMASQ_TIME_REMAINING.
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001493
Simon Kelley5aabfc72007-08-29 11:24:47 +01001494If a lease used to have a hostname, which is
Simon Kelley16972692006-10-16 20:04:18 +01001495removed, an "old" event is generated with the new state of the lease,
1496ie no name, and the former name is provided in the environment
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001497variable DNSMASQ_OLD_HOSTNAME.
1498
1499DNSMASQ_INTERFACE stores the name of
Simon Kelley9e038942008-05-30 20:06:34 +01001500the interface on which the request arrived; this is not set for "old"
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001501actions when dnsmasq restarts.
1502
1503DNSMASQ_RELAY_ADDRESS is set if the client
Simon Kelley316e2732010-01-22 20:16:09 +00001504used a DHCP relay to contact dnsmasq and the IP address of the relay
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001505is known.
1506
1507DNSMASQ_TAGS contains all the tags set during the
Simon Kelley316e2732010-01-22 20:16:09 +00001508DHCP transaction, separated by spaces.
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001509
Simon Kelleye46164e2012-04-16 16:39:38 +01001510DNSMASQ_LOG_DHCP is set if
1511.B --log-dhcp
1512is in effect.
Simon Kelleya9530962012-03-20 22:07:35 +00001513
Simon Kelley1adadf52012-02-13 22:15:58 +00001514For IPv4 only:
1515
1516DNSMASQ_CLIENT_ID if the host provided a client-id.
1517
Simon Kelleydd1721c2013-02-18 21:04:04 +00001518DNSMASQ_CIRCUIT_ID, DNSMASQ_SUBSCRIBER_ID, DNSMASQ_REMOTE_ID if a
1519DHCP relay-agent added any of these options.
1520
Simon Kelley1adadf52012-02-13 22:15:58 +00001521If the client provides vendor-class, DNSMASQ_VENDOR_CLASS.
1522
1523For IPv6 only:
1524
1525If the client provides vendor-class, DNSMASQ_VENDOR_CLASS_ID,
1526containing the IANA enterprise id for the class, and
1527DNSMASQ_VENDOR_CLASS0..DNSMASQ_VENDOR_CLASSn for the data.
1528
Simon Kelley57f460d2012-02-16 20:00:32 +00001529DNSMASQ_SERVER_DUID containing the DUID of the server: this is the same for
Simon Kelley1adadf52012-02-13 22:15:58 +00001530every call to the script.
1531
1532DNSMASQ_IAID containing the IAID for the lease. If the lease is a
1533temporary allocation, this is prefixed to 'T'.
1534
Simon Kelley89500e32013-09-20 16:29:20 +01001535DNSMASQ_MAC containing the MAC address of the client, if known.
Simon Kelley1adadf52012-02-13 22:15:58 +00001536
1537Note that the supplied hostname, vendorclass and userclass data is
1538only supplied for
1539"add" actions or "old" actions when a host resumes an existing lease,
1540since these data are not held in dnsmasq's lease
1541database.
1542
Simon Kelleya9530962012-03-20 22:07:35 +00001543
1544
Simon Kelley9e038942008-05-30 20:06:34 +01001545All file descriptors are
Simon Kelley7cebd202006-05-06 14:13:33 +01001546closed except stdin, stdout and stderr which are open to /dev/null
1547(except in debug mode).
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001548
1549The script is not invoked concurrently: at most one instance
1550of the script is ever running (dnsmasq waits for an instance of script to exit
1551before running the next). Changes to the lease database are which
1552require the script to be invoked are queued awaiting exit of a running instance.
1553If this queueing allows multiple state changes occur to a single
1554lease before the script can be run then
1555earlier states are discarded and the current state of that lease is
1556reflected when the script finally runs.
1557
1558At dnsmasq startup, the script will be invoked for
Simon Kelley7cebd202006-05-06 14:13:33 +01001559all existing leases as they are read from the lease file. Expired
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001560leases will be called with "del" and others with "old". When dnsmasq
Simon Kelley5aabfc72007-08-29 11:24:47 +01001561receives a HUP signal, the script will be invoked for existing leases
Simon Kelley1e505122016-01-25 21:29:23 +00001562with an "old" event.
Simon Kelleya9530962012-03-20 22:07:35 +00001563
1564
Simon Kelley1e505122016-01-25 21:29:23 +00001565There are four further actions which may appear as the first argument
Simon Kelleye6e751b2016-02-01 17:59:07 +00001566to the script, "init", "arp-add", "arp-del" and "tftp". More may be added in the future, so
Simon Kelleya9530962012-03-20 22:07:35 +00001567scripts should be written to ignore unknown actions. "init" is
Simon Kelleye46164e2012-04-16 16:39:38 +01001568described below in
Simon Kelleya9530962012-03-20 22:07:35 +00001569.B --leasefile-ro
1570The "tftp" action is invoked when a TFTP file transfer completes: the
1571arguments are the file size in bytes, the address to which the file
1572was sent, and the complete pathname of the file.
1573
Simon Kelleye6e751b2016-02-01 17:59:07 +00001574The "arp-add" and "arp-del" actions are only called if enabled with
Simon Kelley1e505122016-01-25 21:29:23 +00001575.B --script-arp
Simon Kelleye6e751b2016-02-01 17:59:07 +00001576They are are supplied with a MAC address and IP address as arguments. "arp-add" indicates
1577the arrival of a new entry in the ARP or neighbour table, and "arp-del" indicates the deletion of same.
Simon Kelley1e505122016-01-25 21:29:23 +00001578
Simon Kelley9e038942008-05-30 20:06:34 +01001579.TP
Simon Kelley57f460d2012-02-16 20:00:32 +00001580.B --dhcp-luascript=<path>
1581Specify a script written in Lua, to be run when leases are created,
1582destroyed or changed. To use this option, dnsmasq must be compiled
1583with the correct support. The Lua interpreter is intialised once, when
1584dnsmasq starts, so that global variables persist between lease
1585events. The Lua code must define a
1586.B lease
1587function, and may provide
1588.B init
1589and
1590.B shutdown
1591functions, which are called, without arguments when dnsmasq starts up
Simon Kelleya9530962012-03-20 22:07:35 +00001592and terminates. It may also provide a
1593.B tftp
1594function.
Simon Kelley57f460d2012-02-16 20:00:32 +00001595
1596The
1597.B lease
Simon Kelleya9530962012-03-20 22:07:35 +00001598function receives the information detailed in
Simon Kelley57f460d2012-02-16 20:00:32 +00001599.B --dhcp-script.
1600It gets two arguments, firstly the action, which is a string
1601containing, "add", "old" or "del", and secondly a table of tag value
1602pairs. The tags mostly correspond to the environment variables
1603detailed above, for instance the tag "domain" holds the same data as
1604the environment variable DNSMASQ_DOMAIN. There are a few extra tags
1605which hold the data supplied as arguments to
1606.B --dhcp-script.
1607These are
1608.B mac_address, ip_address
1609and
1610.B hostname
1611for IPv4, and
1612.B client_duid, ip_address
1613and
1614.B hostname
Simon Kelleya9530962012-03-20 22:07:35 +00001615for IPv6.
1616
1617The
1618.B tftp
1619function is called in the same way as the lease function, and the
1620table holds the tags
1621.B destination_address,
1622.B file_name
1623and
1624.B file_size.
Simon Kelley1e505122016-01-25 21:29:23 +00001625
1626The
1627.B arp
1628and
1629.B arp-old
1630functions are called only when enabled with
1631.B --script-arp
1632and have a table which holds the tags
1633.B mac_addres
1634and
1635.B client_address.
Simon Kelley57f460d2012-02-16 20:00:32 +00001636.TP
Simon Kelley9e038942008-05-30 20:06:34 +01001637.B --dhcp-scriptuser
Simon Kelley57f460d2012-02-16 20:00:32 +00001638Specify 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.
Simon Kelley1e505122016-01-25 21:29:23 +00001639.TP
1640.B --script-arp
1641Enable the "arp" and "arp-old" functions in the dhcp-script and dhcp-luascript.
1642.TP
Simon Kelley208b65c2006-08-05 21:41:37 +01001643.B \-9, --leasefile-ro
1644Completely suppress use of the lease database file. The file will not
1645be created, read, or written. Change the way the lease-change
1646script (if one is provided) is called, so that the lease database may
1647be maintained in external storage by the script. In addition to the
Simon Kelleyf2621c72007-04-29 19:47:21 +01001648invocations given in
Simon Kelley208b65c2006-08-05 21:41:37 +01001649.B --dhcp-script
1650the lease-change script is called once, at dnsmasq startup, with the
1651single argument "init". When called like this the script should write
1652the saved state of the lease database, in dnsmasq leasefile format, to
1653stdout and exit with zero exit code. Setting this
1654option also forces the leasechange script to be called on changes
1655to the client-id and lease length and expiry time.
Simon Kelley9e4abcb2004-01-22 19:47:41 +00001656.TP
Simon Kelley832af0b2007-01-21 20:01:28 +00001657.B --bridge-interface=<interface>,<alias>[,<alias>]
Neil Jerram4918bd52015-06-10 22:23:20 +01001658Treat DHCP (v4 and v6) request and IPv6 Router Solicit packets
1659arriving at any of the <alias> interfaces as if they had arrived at
1660<interface>. This option allows dnsmasq to provide DHCP and RA
1661service over unaddressed and unbridged Ethernet interfaces, e.g. on an
1662OpenStack compute host where each such interface is a TAP interface to
1663a VM, or as in "old style bridging" on BSD platforms. A trailing '*'
1664wildcard can be used in each <alias>.
Simon Kelley832af0b2007-01-21 20:01:28 +00001665.TP
Simon Kelley28866e92011-02-14 20:19:14 +00001666.B \-s, --domain=<domain>[,<address range>[,local]]
Simon Kelley9009d742008-11-14 20:04:27 +00001667Specifies DNS domains for the DHCP server. Domains may be be given
1668unconditionally (without the IP range) or for limited IP ranges. This has two effects;
Simon Kelley9e4abcb2004-01-22 19:47:41 +00001669firstly it causes the DHCP server to return the domain to any hosts
1670which request it, and secondly it sets the domain which it is legal
Simon Kelley1b7ecd12007-02-05 14:57:57 +00001671for DHCP-configured hosts to claim. The intention is to constrain
1672hostnames so that an untrusted host on the LAN cannot advertise
1673its name via dhcp as e.g. "microsoft.com" and capture traffic not
1674meant for it. If no domain suffix is specified, then any DHCP
1675hostname with a domain part (ie with a period) will be disallowed
1676and logged. If suffix is specified, then hostnames with a domain
1677part are allowed, provided the domain part matches the suffix. In
1678addition, when a suffix is set then hostnames without a domain
1679part have the suffix added as an optional domain part. Eg on my network I can set
Simon Kelley3d8df262005-08-29 12:19:27 +01001680.B --domain=thekelleys.org.uk
Simon Kelley9e4abcb2004-01-22 19:47:41 +00001681and have a machine whose DHCP hostname is "laptop". The IP address for that machine is available from
1682.B dnsmasq
Simon Kelleyde379512004-06-22 20:23:33 +01001683both as "laptop" and "laptop.thekelleys.org.uk". If the domain is
1684given as "#" then the domain is read from the first "search" directive
Simon Kelley28866e92011-02-14 20:19:14 +00001685in /etc/resolv.conf (or equivalent).
1686
1687The address range can be of the form
Simon Kelley9009d742008-11-14 20:04:27 +00001688<ip address>,<ip address> or <ip address>/<netmask> or just a single
1689<ip address>. See
1690.B --dhcp-fqdn
1691which can change the behaviour of dnsmasq with domains.
Simon Kelley28866e92011-02-14 20:19:14 +00001692
1693If the address range is given as ip-address/network-size, then a
1694additional flag "local" may be supplied which has the effect of adding
1695--local declarations for forward and reverse DNS queries. Eg.
1696.B --domain=thekelleys.org.uk,192.168.0.0/24,local
1697is identical to
1698.B --domain=thekelleys.org.uk,192.168.0.0/24
1699--local=/thekelleys.org.uk/ --local=/0.168.192.in-addr.arpa/
1700The network size must be 8, 16 or 24 for this to be legal.
Simon Kelley9009d742008-11-14 20:04:27 +00001701.TP
1702.B --dhcp-fqdn
1703In the default mode, dnsmasq inserts the unqualified names of
1704DHCP clients into the DNS. For this reason, the names must be unique,
1705even if two clients which have the same name are in different
1706domains. If a second DHCP client appears which has the same name as an
Tomas Hozzaa66d36e2013-04-22 15:08:07 +01001707existing client, the name is transferred to the new client. If
Simon Kelley9009d742008-11-14 20:04:27 +00001708.B --dhcp-fqdn
1709is set, this behaviour changes: the unqualified name is no longer
1710put in the DNS, only the qualified name. Two DHCP clients with the
1711same name may both keep the name, provided that the domain part is
1712different (ie the fully qualified names differ.) To ensure that all
1713names have a domain part, there must be at least
1714.B --domain
1715without an address specified when
1716.B --dhcp-fqdn
1717is set.
Simon Kelley9e4abcb2004-01-22 19:47:41 +00001718.TP
Simon Kelleyc72daea2012-01-05 21:33:27 +00001719.B --dhcp-client-update
1720Normally, when giving a DHCP lease, dnsmasq sets flags in the FQDN
1721option to tell the client not to attempt a DDNS update with its name
1722and IP address. This is because the name-IP pair is automatically
1723added into dnsmasq's DNS view. This flag suppresses that behaviour,
1724this is useful, for instance, to allow Windows clients to update
1725Active Directory servers. See RFC 4702 for details.
1726.TP
Simon Kelleyc5ad4e72012-02-24 16:06:20 +00001727.B --enable-ra
1728Enable dnsmasq's IPv6 Router Advertisement feature. DHCPv6 doesn't
1729handle complete network configuration in the same way as DHCPv4. Router
1730discovery and (possibly) prefix discovery for autonomous address
1731creation are handled by a different protocol. When DHCP is in use,
1732only a subset of this is needed, and dnsmasq can handle it, using
1733existing DHCP configuration to provide most data. When RA is enabled,
1734dnsmasq will advertise a prefix for each dhcp-range, with default
Simon Kelley20fd11e2015-08-26 22:48:13 +01001735router as the relevant link-local address on
1736the machine running dnsmasq. By default, the "managed address" bits are set, and
Simon Kelleye8ca69e2012-03-26 21:23:26 +01001737the "use SLAAC" bit is reset. This can be changed for individual
1738subnets with the mode keywords described in
1739.B --dhcp-range.
Simon Kelley18f0fb02012-03-31 21:18:55 +01001740RFC6106 DNS parameters are included in the advertisements. By default,
1741the relevant link-local address of the machine running dnsmasq is sent
1742as recursive DNS server. If provided, the DHCPv6 options dns-server and
Simon Kelley20fd11e2015-08-26 22:48:13 +01001743domain-search are used for the DNS server (RDNSS) and the domain serach list (DNSSL).
Simon Kelleyc5ad4e72012-02-24 16:06:20 +00001744.TP
Simon Kelleyc4cd95d2013-10-10 20:58:11 +01001745.B --ra-param=<interface>,[high|low],[[<ra-interval>],<router lifetime>]
1746Set non-default values for router advertisements sent via an
1747interface. The priority field for the router may be altered from the
1748default of medium with eg
1749.B --ra-param=eth0,high.
1750The interval between router advertisements may be set (in seconds) with
1751.B --ra-param=eth0,60.
1752The lifetime of the route may be changed or set to zero, which allows
1753a router to advertise prefixes but not a route via itself.
1754.B --ra-parm=eth0,0,0
1755(A value of zero for the interval means the default value.) All three parameters may be set at once.
1756.B --ra-param=low,60,1200
1757The interface field may include a wildcard.
Simon Kelley8d030462013-07-29 15:41:26 +01001758.TP
Simon Kelley2937f8a2013-07-29 19:49:07 +01001759.B --enable-tftp[=<interface>[,<interface>]]
Simon Kelley832af0b2007-01-21 20:01:28 +00001760Enable the TFTP server function. This is deliberately limited to that
Simon Kelley9e038942008-05-30 20:06:34 +01001761needed to net-boot a client. Only reading is allowed; the tsize and
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001762blksize extensions are supported (tsize is only supported in octet
Simon Kelley2937f8a2013-07-29 19:49:07 +01001763mode). Without an argument, the TFTP service is provided to the same set of interfaces as DHCP service.
1764If the list of interfaces is provided, that defines which interfaces recieve TFTP service.
Simon Kelleyb8187c82005-11-26 21:46:27 +00001765.TP
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001766.B --tftp-root=<directory>[,<interface>]
Simon Kelley832af0b2007-01-21 20:01:28 +00001767Look for files to transfer using TFTP relative to the given
1768directory. When this is set, TFTP paths which include ".." are
1769rejected, to stop clients getting outside the specified root.
Simon Kelleyf2621c72007-04-29 19:47:21 +01001770Absolute paths (starting with /) are allowed, but they must be within
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001771the tftp-root. If the optional interface argument is given, the
1772directory is only used for TFTP requests via that interface.
Simon Kelley832af0b2007-01-21 20:01:28 +00001773.TP
Stefan Tomanek30d08792015-03-31 22:32:11 +01001774.B --tftp-no-fail
1775Do not abort startup if specified tftp root directories are inaccessible.
1776.TP
Simon Kelley5aabfc72007-08-29 11:24:47 +01001777.B --tftp-unique-root
1778Add the IP address of the TFTP client as a path component on the end
1779of the TFTP-root (in standard dotted-quad format). Only valid if a
1780tftp-root is set and the directory exists. For instance, if tftp-root is "/tftp" and client
17811.2.3.4 requests file "myfile" then the effective path will be
1782"/tftp/1.2.3.4/myfile" if /tftp/1.2.3.4 exists or /tftp/myfile otherwise.
1783.TP
Simon Kelley832af0b2007-01-21 20:01:28 +00001784.B --tftp-secure
Simon Kelley5aabfc72007-08-29 11:24:47 +01001785Enable TFTP secure mode: without this, any file which is readable by
Simon Kelley832af0b2007-01-21 20:01:28 +00001786the dnsmasq process under normal unix access-control rules is
1787available via TFTP. When the --tftp-secure flag is given, only files
1788owned by the user running the dnsmasq process are accessible. If
1789dnsmasq is being run as root, different rules apply: --tftp-secure
Simon Kelley1b7ecd12007-02-05 14:57:57 +00001790has no effect, but only files which have the world-readable bit set
Simon Kelley832af0b2007-01-21 20:01:28 +00001791are accessible. It is not recommended to run dnsmasq as root with TFTP
1792enabled, and certainly not without specifying --tftp-root. Doing so
1793can expose any world-readable file on the server to any host on the net.
1794.TP
Simon Kelley61ce6002012-04-20 21:28:49 +01001795.B --tftp-lowercase
1796Convert filenames in TFTP requests to all lowercase. This is useful
1797for requests from Windows machines, which have case-insensitive
1798filesystems and tend to play fast-and-loose with case in filenames.
1799Note that dnsmasq's tftp server always converts "\\" to "/" in filenames.
1800.TP
Simon Kelley832af0b2007-01-21 20:01:28 +00001801.B --tftp-max=<connections>
1802Set the maximum number of concurrent TFTP connections allowed. This
1803defaults to 50. When serving a large number of TFTP connections,
1804per-process file descriptor limits may be encountered. Dnsmasq needs
1805one file descriptor for each concurrent TFTP connection and one
1806file descriptor per unique file (plus a few others). So serving the
1807same file simultaneously to n clients will use require about n + 10 file
1808descriptors, serving different files simultaneously to n clients will
Simon Kelley824af852008-02-12 20:43:05 +00001809require about (2*n) + 10 descriptors. If
1810.B --tftp-port-range
1811is given, that can affect the number of concurrent connections.
Simon Kelley6b010842007-02-12 20:32:07 +00001812.TP
Simon Kelleybec366b2016-02-24 22:03:26 +00001813.B --tftp-mtu=<mtu size>
1814Use size as the ceiling of the MTU supported by the intervening network when
1815negotiating TFTP blocksize, overriding the MTU setting of the local interface if it is larger.
1816.TP
Simon Kelley6b010842007-02-12 20:32:07 +00001817.B --tftp-no-blocksize
1818Stop the TFTP server from negotiating the "blocksize" option with a
1819client. Some buggy clients request this option but then behave badly
1820when it is granted.
Simon Kelley824af852008-02-12 20:43:05 +00001821.TP
1822.B --tftp-port-range=<start>,<end>
1823A TFTP server listens on a well-known port (69) for connection initiation,
1824but it also uses a dynamically-allocated port for each
1825connection. Normally these are allocated by the OS, but this option
1826specifies a range of ports for use by TFTP transfers. This can be
1827useful when TFTP has to traverse a firewall. The start of the range
1828cannot be lower than 1025 unless dnsmasq is running as root. The number
1829of concurrent TFTP connections is limited by the size of the port range.
Simon Kelley832af0b2007-01-21 20:01:28 +00001830.TP
Simon Kelleyb8187c82005-11-26 21:46:27 +00001831.B \-C, --conf-file=<file>
1832Specify a different configuration file. The conf-file option is also allowed in
Simon Kelley28866e92011-02-14 20:19:14 +00001833configuration files, to include multiple configuration files. A
1834filename of "-" causes dnsmasq to read configuration from stdin.
Simon Kelley849a8352006-06-09 21:02:31 +01001835.TP
Simon Kelley3e1551a2014-09-09 21:46:07 +01001836.B \-7, --conf-dir=<directory>[,<file-extension>......],
Simon Kelley849a8352006-06-09 21:02:31 +01001837Read all the files in the given directory as configuration
Simon Kelley1f15b812009-10-13 17:49:32 +01001838files. If extension(s) are given, any files which end in those
1839extensions are skipped. Any files whose names end in ~ or start with . or start and end
Simon Kelley3e1551a2014-09-09 21:46:07 +01001840with # are always skipped. If the extension starts with * then only files
1841which have that extension are loaded. So
1842.B --conf-dir=/path/to/dir,*.conf
1843loads all files with the suffix .conf in /path/to/dir. This flag may be given on the command
1844line or in a configuration file. If giving it on the command line, be sure to
1845escape * characters.
Simon Kelley7b1eae42014-02-20 13:43:28 +00001846.TP
1847.B --servers-file=<file>
1848A special case of
1849.B --conf-file
1850which differs in two respects. Firstly, only --server and --rev-server are allowed
1851in the configuration file included. Secondly, the file is re-read and the configuration
1852therein is updated when dnsmasq recieves SIGHUP.
Simon Kelley9e4abcb2004-01-22 19:47:41 +00001853.SH CONFIG FILE
Simon Kelley3be34542004-09-11 19:12:13 +01001854At startup, dnsmasq reads
1855.I /etc/dnsmasq.conf,
1856if it exists. (On
1857FreeBSD, the file is
1858.I /usr/local/etc/dnsmasq.conf
Simon Kelleyb8187c82005-11-26 21:46:27 +00001859) (but see the
1860.B \-C
Simon Kelley849a8352006-06-09 21:02:31 +01001861and
1862.B \-7
1863options.) The format of this
Simon Kelley9e4abcb2004-01-22 19:47:41 +00001864file consists of one option per line, exactly as the long options detailed
1865in the OPTIONS section but without the leading "--". Lines starting with # are comments and ignored. For
Simon Kelleyb49644f2004-01-30 21:36:24 +00001866options which may only be specified once, the configuration file overrides
Simon Kelleyb8187c82005-11-26 21:46:27 +00001867the command line. Quoting is allowed in a config file:
Simon Kelley3d8df262005-08-29 12:19:27 +01001868between " quotes the special meanings of ,:. and # are removed and the
Simon Kelley824af852008-02-12 20:43:05 +00001869following escapes are allowed: \\\\ \\" \\t \\e \\b \\r and \\n. The later
1870corresponding to tab, escape, backspace, return and newline.
Simon Kelley9e4abcb2004-01-22 19:47:41 +00001871.SH NOTES
1872When it receives a SIGHUP,
1873.B dnsmasq
Simon Kelley3be34542004-09-11 19:12:13 +01001874clears its cache and then re-loads
Simon Kelley5aabfc72007-08-29 11:24:47 +01001875.I /etc/hosts
1876and
1877.I /etc/ethers
Simon Kelley3d04f462015-01-31 21:59:13 +00001878and any file given by --dhcp-hostsfile, --dhcp-hostsdir, --dhcp-optsfile,
1879--dhcp-optsdir, --addn-hosts or --hostsdir.
Simon Kelley5aabfc72007-08-29 11:24:47 +01001880The dhcp lease change script is called for all
1881existing DHCP leases. If
Simon Kelley9e4abcb2004-01-22 19:47:41 +00001882.B
1883--no-poll
Simon Kelley3be34542004-09-11 19:12:13 +01001884is set SIGHUP also re-reads
1885.I /etc/resolv.conf.
1886SIGHUP
Simon Kelleyb49644f2004-01-30 21:36:24 +00001887does NOT re-read the configuration file.
Simon Kelley9e4abcb2004-01-22 19:47:41 +00001888.PP
1889When it receives a SIGUSR1,
1890.B dnsmasq
Simon Kelley824af852008-02-12 20:43:05 +00001891writes statistics to the system log. It writes the cache size,
Simon Kelley9e4abcb2004-01-22 19:47:41 +00001892the number of names which have had to removed from the cache before
1893they expired in order to make room for new names and the total number
Simon Kelleyfec216d2014-03-27 20:54:34 +00001894of names that have been inserted into the cache. The number of cache hits and
1895misses and the number of authoritative queries answered are also given. For each upstream
Simon Kelley824af852008-02-12 20:43:05 +00001896server it gives the number of queries sent, and the number which
1897resulted in an error. In
Simon Kelley9e4abcb2004-01-22 19:47:41 +00001898.B --no-daemon
Simon Kelley5aabfc72007-08-29 11:24:47 +01001899mode or when full logging is enabled (-q), a complete dump of the
Simon Kelleyfec216d2014-03-27 20:54:34 +00001900contents of the cache is made.
1901
1902The cache statistics are also available in the DNS as answers to
1903queries of class CHAOS and type TXT in domain bind. The domain names are cachesize.bind, insertions.bind, evictions.bind,
1904misses.bind, hits.bind, auth.bind and servers.bind. An example command to query this, using the
1905.B dig
1906utility would be
1907
1908dig +short chaos txt cachesize.bind
1909
Simon Kelley5aabfc72007-08-29 11:24:47 +01001910.PP
1911When it receives SIGUSR2 and it is logging direct to a file (see
1912.B --log-facility
1913)
1914.B dnsmasq
1915will close and reopen the log file. Note that during this operation,
1916dnsmasq will not be running as root. When it first creates the logfile
1917dnsmasq changes the ownership of the file to the non-root user it will run
1918as. Logrotate should be configured to create a new log file with
Simon Kelley9e038942008-05-30 20:06:34 +01001919the ownership which matches the existing one before sending SIGUSR2.
Simon Kelley5aabfc72007-08-29 11:24:47 +01001920If TCP DNS queries are in progress, the old logfile will remain open in
1921child processes which are handling TCP queries and may continue to be
1922written. There is a limit of 150 seconds, after which all existing TCP
1923processes will have expired: for this reason, it is not wise to
1924configure logfile compression for logfiles which have just been
1925rotated. Using logrotate, the required options are
1926.B create
1927and
1928.B delaycompress.
1929
1930
Simon Kelley9e4abcb2004-01-22 19:47:41 +00001931.PP
Simon Kelley9e4abcb2004-01-22 19:47:41 +00001932Dnsmasq is a DNS query forwarder: it it not capable of recursively
1933answering arbitrary queries starting from the root servers but
1934forwards such queries to a fully recursive upstream DNS server which is
1935typically provided by an ISP. By default, dnsmasq reads
Simon Kelley3be34542004-09-11 19:12:13 +01001936.I /etc/resolv.conf
1937to discover the IP
Simon Kelley9e4abcb2004-01-22 19:47:41 +00001938addresses of the upstream nameservers it should use, since the
1939information is typically stored there. Unless
1940.B --no-poll
1941is used,
1942.B dnsmasq
Simon Kelley3be34542004-09-11 19:12:13 +01001943checks the modification time of
1944.I /etc/resolv.conf
1945(or equivalent if
Simon Kelley9e4abcb2004-01-22 19:47:41 +00001946.B \--resolv-file
1947is used) and re-reads it if it changes. This allows the DNS servers to
1948be set dynamically by PPP or DHCP since both protocols provide the
1949information.
Simon Kelley3be34542004-09-11 19:12:13 +01001950Absence of
1951.I /etc/resolv.conf
1952is not an error
Simon Kelley9e4abcb2004-01-22 19:47:41 +00001953since it may not have been created before a PPP connection exists. Dnsmasq
Simon Kelley3be34542004-09-11 19:12:13 +01001954simply keeps checking in case
1955.I /etc/resolv.conf
1956is created at any
Simon Kelley9e4abcb2004-01-22 19:47:41 +00001957time. Dnsmasq can be told to parse more than one resolv.conf
1958file. This is useful on a laptop, where both PPP and DHCP may be used:
Simon Kelley3be34542004-09-11 19:12:13 +01001959dnsmasq can be set to poll both
1960.I /etc/ppp/resolv.conf
1961and
1962.I /etc/dhcpc/resolv.conf
1963and will use the contents of whichever changed
Simon Kelley9e4abcb2004-01-22 19:47:41 +00001964last, giving automatic switching between DNS servers.
1965.PP
1966Upstream servers may also be specified on the command line or in
Simon Kelleyb49644f2004-01-30 21:36:24 +00001967the configuration file. These server specifications optionally take a
Simon Kelley9e4abcb2004-01-22 19:47:41 +00001968domain name which tells dnsmasq to use that server only to find names
1969in that particular domain.
1970.PP
1971In order to configure dnsmasq to act as cache for the host on which it is running, put "nameserver 127.0.0.1" in
1972.I /etc/resolv.conf
1973to force local processes to send queries to
1974dnsmasq. Then either specify the upstream servers directly to dnsmasq
1975using
1976.B \--server
1977options or put their addresses real in another file, say
1978.I /etc/resolv.dnsmasq
1979and run dnsmasq with the
1980.B \-r /etc/resolv.dnsmasq
1981option. This second technique allows for dynamic update of the server
1982addresses by PPP or DHCP.
Simon Kelley3be34542004-09-11 19:12:13 +01001983.PP
Simon Kelleyf6b7dc42005-01-23 12:06:08 +00001984Addresses in /etc/hosts will "shadow" different addresses for the same
1985names in the upstream DNS, so "mycompany.com 1.2.3.4" in /etc/hosts will ensure that
1986queries for "mycompany.com" always return 1.2.3.4 even if queries in
1987the upstream DNS would otherwise return a different address. There is
1988one exception to this: if the upstream DNS contains a CNAME which
1989points to a shadowed name, then looking up the CNAME through dnsmasq
1990will result in the unshadowed address associated with the target of
1991the CNAME. To work around this, add the CNAME to /etc/hosts so that
1992the CNAME is shadowed too.
1993
1994.PP
Simon Kelley8ef5ada2010-06-03 19:42:45 +01001995The tag system works as follows: For each DHCP request, dnsmasq
1996collects a set of valid tags from active configuration lines which
1997include set:<tag>, including one from the
Simon Kelley26128d22004-11-14 16:43:54 +00001998.B dhcp-range
1999used to allocate the address, one from any matching
2000.B dhcp-host
Simon Kelley9009d742008-11-14 20:04:27 +00002001(and "known" if a dhcp-host matches)
Simon Kelley8ef5ada2010-06-03 19:42:45 +01002002The tag "bootp" is set for BOOTP requests, and a tag whose name is the
2003name of the interface on which the request arrived is also set.
2004
Tomas Hozzaa66d36e2013-04-22 15:08:07 +01002005Any configuration lines which include one or more tag:<tag> constructs
Simon Kelley8ef5ada2010-06-03 19:42:45 +01002006will only be valid if all that tags are matched in the set derived
2007above. Typically this is dhcp-option.
Simon Kelley26128d22004-11-14 16:43:54 +00002008.B dhcp-option
Simon Kelley8ef5ada2010-06-03 19:42:45 +01002009which has tags will be used in preference to an untagged
Simon Kelley26128d22004-11-14 16:43:54 +00002010.B dhcp-option,
2011provided that _all_ the tags match somewhere in the
Simon Kelley8ef5ada2010-06-03 19:42:45 +01002012set collected as described above. The prefix '!' on a tag means 'not'
Moritz Warninge62e9b62014-03-20 15:32:22 +00002013so --dhcp-option=tag:!purple,3,1.2.3.4 sends the option when the
Simon Kelley8ef5ada2010-06-03 19:42:45 +01002014tag purple is not in the set of valid tags. (If using this in a
2015command line rather than a configuration file, be sure to escape !,
2016which is a shell metacharacter)
Simon Kelley7de060b2011-08-26 17:24:52 +01002017
2018When selecting dhcp-options, a tag from dhcp-range is second class
2019relative to other tags, to make it easy to override options for
2020individual hosts, so
2021.B dhcp-range=set:interface1,......
2022.B dhcp-host=set:myhost,.....
2023.B dhcp-option=tag:interface1,option:nis-domain,"domain1"
2024.B dhcp-option=tag:myhost,option:nis-domain,"domain2"
2025will set the NIS-domain to domain1 for hosts in the range, but
2026override that to domain2 for a particular host.
2027
Simon Kelley26128d22004-11-14 16:43:54 +00002028.PP
Simon Kelley8ef5ada2010-06-03 19:42:45 +01002029Note that for
Simon Kelleyf6b7dc42005-01-23 12:06:08 +00002030.B dhcp-range
Simon Kelley8ef5ada2010-06-03 19:42:45 +01002031both tag:<tag> and set:<tag> are allowed, to both select the range in
2032use based on (eg) dhcp-host, and to affect the options sent, based on
2033the range selected.
2034
2035This system evolved from an earlier, more limited one and for backward
2036compatibility "net:" may be used instead of "tag:" and "set:" may be
2037omitted. (Except in
2038.B dhcp-host,
2039where "net:" may be used instead of "set:".) For the same reason, '#'
2040may be used instead of '!' to indicate NOT.
Simon Kelleyf6b7dc42005-01-23 12:06:08 +00002041.PP
Simon Kelley3be34542004-09-11 19:12:13 +01002042The DHCP server in dnsmasq will function as a BOOTP server also,
2043provided that the MAC address and IP address for clients are given,
2044either using
2045.B dhcp-host
2046configurations or in
2047.I /etc/ethers
2048, and a
2049.B dhcp-range
2050configuration option is present to activate the DHCP server
Simon Kelleyb8187c82005-11-26 21:46:27 +00002051on a particular network. (Setting --bootp-dynamic removes the need for
2052static address mappings.) The filename
Simon Kelley8ef5ada2010-06-03 19:42:45 +01002053parameter in a BOOTP request is used as a tag,
2054as is the tag "bootp", allowing some control over the options returned to
Simon Kelley3be34542004-09-11 19:12:13 +01002055different classes of hosts.
2056
Simon Kelley333b2ce2013-01-07 21:46:03 +00002057.SH AUTHORITATIVE CONFIGURATION
2058.PP
2059Configuring dnsmasq to act as an authoritative DNS server is
2060complicated by the fact that it involves configuration of external DNS
2061servers to provide delegation. We will walk through three scenarios of
2062increasing complexity. Prerequisites for all of these scenarios
Simon Kelley81925ab2013-04-10 11:43:58 +01002063are a globally accessible IP address, an A or AAAA record pointing to that address,
Simon Kelley333b2ce2013-01-07 21:46:03 +00002064and an external DNS server capable of doing delegation of the zone in
2065question. For the first part of this explanation, we will call the A (or AAAA) record
2066for the globally accessible address server.example.com, and the zone
2067for which dnsmasq is authoritative our.zone.com.
2068
2069The simplest configuration consists of two lines of dnsmasq configuration; something like
2070
2071.nf
2072.B auth-server=server.example.com,eth0
Simon Kelley79cb46c2013-01-23 19:49:21 +00002073.B auth-zone=our.zone.com,1.2.3.0/24
Simon Kelley333b2ce2013-01-07 21:46:03 +00002074.fi
2075
2076and two records in the external DNS
2077
2078.nf
2079server.example.com A 192.0.43.10
2080our.zone.com NS server.example.com
2081.fi
2082
2083eth0 is the external network interface on which dnsmasq is listening,
2084and has (globally accessible) address 192.0.43.10.
2085
2086Note that the external IP address may well be dynamic (ie assigned
2087from an ISP by DHCP or PPP) If so, the A record must be linked to this
2088dynamic assignment by one of the usual dynamic-DNS systems.
2089
2090A more complex, but practically useful configuration has the address
2091record for the globally accessible IP address residing in the
2092authoritative zone which dnsmasq is serving, typically at the root. Now
2093we have
2094
2095.nf
2096.B auth-server=our.zone.com,eth0
Simon Kelley79cb46c2013-01-23 19:49:21 +00002097.B auth-zone=our.zone.com,1.2.3.0/24
Simon Kelley333b2ce2013-01-07 21:46:03 +00002098.fi
2099
2100.nf
Simon Kelley0f128eb2013-03-11 21:21:35 +00002101our.zone.com A 1.2.3.4
Simon Kelley333b2ce2013-01-07 21:46:03 +00002102our.zone.com NS our.zone.com
2103.fi
2104
2105The A record for our.zone.com has now become a glue record, it solves
2106the chicken-and-egg problem of finding the IP address of the
2107nameserver for our.zone.com when the A record is within that
2108zone. Note that this is the only role of this record: as dnsmasq is
2109now authoritative from our.zone.com it too must provide this
2110record. If the external address is static, this can be done with an
2111.B /etc/hosts
2112entry or
2113.B --host-record.
Simon Kelley333b2ce2013-01-07 21:46:03 +00002114
2115.nf
Simon Kelley0f128eb2013-03-11 21:21:35 +00002116.B auth-server=our.zone.com,eth0
2117.B host-record=our.zone.com,1.2.3.4
2118.B auth-zone=our.zone.com,1.2.3.0/24
2119.fi
2120
2121If the external address is dynamic, the address
2122associated with our.zone.com must be derived from the address of the
Simon Kelley6f130de2013-04-15 14:47:14 +01002123relevant interface. This is done using
Simon Kelley0f128eb2013-03-11 21:21:35 +00002124.B interface-name
2125Something like:
2126
2127.nf
2128.B auth-server=our.zone.com,eth0
2129.B interface-name=our.zone.com,eth0
Simon Kelley32b4e4c2013-11-14 10:36:55 +00002130.B auth-zone=our.zone.com,1.2.3.0/24,eth0
Simon Kelley333b2ce2013-01-07 21:46:03 +00002131.fi
2132
Simon Kelley32b4e4c2013-11-14 10:36:55 +00002133(The "eth0" argument in auth-zone adds the subnet containing eth0's
2134dynamic address to the zone, so that the interface-name returns the
2135address in outside queries.)
2136
Simon Kelley333b2ce2013-01-07 21:46:03 +00002137Our final configuration builds on that above, but also adds a
2138secondary DNS server. This is another DNS server which learns the DNS data
2139for the zone by doing zones transfer, and acts as a backup should
2140the primary server become inaccessible. The configuration of the
2141secondary is beyond the scope of this man-page, but the extra
2142configuration of dnsmasq is simple:
2143
2144.nf
2145.B auth-sec-servers=secondary.myisp.com
2146.fi
2147
2148and
2149
2150.nf
2151our.zone.com NS secondary.myisp.com
2152.fi
2153
2154Adding auth-sec-servers enables zone transfer in dnsmasq, to allow the
2155secondary to collect the DNS data. If you wish to restrict this data
2156to particular hosts then
2157
2158.nf
2159.B auth-peer=<IP address of secondary>
2160.fi
2161
2162will do so.
2163
2164Dnsmasq acts as an authoritative server for in-addr.arpa and
Lutz Preßler1d7e0a32014-04-07 22:06:23 +01002165ip6.arpa domains associated with the subnets given in auth-zone
Simon Kelley333b2ce2013-01-07 21:46:03 +00002166declarations, so reverse (address to name) lookups can be simply
2167configured with a suitable NS record, for instance in this example,
2168where we allow 1.2.3.0/24 addresses.
2169
2170.nf
2171 3.2.1.in-addr.arpa NS our.zone.com
2172.fi
2173
2174Note that at present, reverse (in-addr.arpa and ip6.arpa) zones are
2175not available in zone transfers, so there is no point arranging
2176secondary servers for reverse lookups.
2177
2178.PP
2179When dnsmasq is configured to act as an authoritative server, the
2180following data is used to populate the authoritative zone.
2181.PP
2182.B --mx-host, --srv-host, --dns-rr, --txt-record, --naptr-record
2183, as long as the record names are in the authoritative domain.
2184.PP
2185.B --cname
2186as long as the record name is in the authoritative domain. If the
2187target of the CNAME is unqualified, then it is qualified with the
2188authoritative zone name.
2189.PP
2190IPv4 and IPv6 addresses from /etc/hosts (and
2191.B --addn-hosts
2192) and
2193.B --host-record
Simon Kelley376d48c2013-11-13 13:04:30 +00002194and
2195.B --interface-name
Simon Kelley333b2ce2013-01-07 21:46:03 +00002196provided the address falls into one of the subnets specified in the
2197.B --auth-zone.
2198.PP
Simon Kelley333b2ce2013-01-07 21:46:03 +00002199Addresses of DHCP leases, provided the address falls into one of the subnets specified in the
Simon Kelley376d48c2013-11-13 13:04:30 +00002200.B --auth-zone.
2201(If contructed DHCP ranges are is use, which depend on the address dynamically
2202assigned to an interface, then the form of
Simon Kelley333b2ce2013-01-07 21:46:03 +00002203.B --auth-zone
Simon Kelley376d48c2013-11-13 13:04:30 +00002204which defines subnets by the dynamic address of an interface should
2205be used to ensure this condition is met.)
2206.PP
2207In the default mode, where a DHCP lease
Simon Kelley333b2ce2013-01-07 21:46:03 +00002208has an unqualified name, and possibly a qualified name constructed
2209using
2210.B --domain
2211then the name in the authoritative zone is constructed from the
2212unqualified name and the zone's domain. This may or may not equal
2213that specified by
2214.B --domain.
2215If
2216.B --dhcp-fqdn
2217is set, then the fully qualified names associated with DHCP leases are
2218used, and must match the zone's domain.
2219
2220
2221
Simon Kelley5aabfc72007-08-29 11:24:47 +01002222.SH EXIT CODES
2223.PP
22240 - Dnsmasq successfully forked into the background, or terminated
2225normally if backgrounding is not enabled.
2226.PP
22271 - A problem with configuration was detected.
2228.PP
22292 - A problem with network access occurred (address in use, attempt
2230to use privileged ports without permission).
2231.PP
Simon Kelley9e038942008-05-30 20:06:34 +010022323 - A problem occurred with a filesystem operation (missing
Simon Kelley5aabfc72007-08-29 11:24:47 +01002233file/directory, permissions).
2234.PP
22354 - Memory allocation failure.
2236.PP
22375 - Other miscellaneous problem.
2238.PP
223911 or greater - a non zero return code was received from the
2240lease-script process "init" call. The exit code from dnsmasq is the
2241script's exit code with 10 added.
2242
Simon Kelley1b7ecd12007-02-05 14:57:57 +00002243.SH LIMITS
2244The default values for resource limits in dnsmasq are generally
2245conservative, and appropriate for embedded router type devices with
2246slow processors and limited memory. On more capable hardware, it is
2247possible to increase the limits, and handle many more clients. The
2248following applies to dnsmasq-2.37: earlier versions did not scale as well.
2249
2250.PP
2251Dnsmasq is capable of handling DNS and DHCP for at least a thousand
Simon Kelley8ef5ada2010-06-03 19:42:45 +01002252clients. The DHCP lease times should not be very short (less than one hour). The
Simon Kelley1b7ecd12007-02-05 14:57:57 +00002253value of
2254.B --dns-forward-max
2255can be increased: start with it equal to
2256the number of clients and increase if DNS seems slow. Note that DNS
2257performance depends too on the performance of the upstream
2258nameservers. The size of the DNS cache may be increased: the hard
2259limit is 10000 names and the default (150) is very low. Sending
2260SIGUSR1 to dnsmasq makes it log information which is useful for tuning
2261the cache size. See the
2262.B NOTES
2263section for details.
2264
2265.PP
2266The built-in TFTP server is capable of many simultaneous file
2267transfers: the absolute limit is related to the number of file-handles
2268allowed to a process and the ability of the select() system call to
2269cope with large numbers of file handles. If the limit is set too high
2270using
2271.B --tftp-max
2272it will be scaled down and the actual limit logged at
2273start-up. Note that more transfers are possible when the same file is
2274being sent than when each transfer sends a different file.
2275
2276.PP
2277It is possible to use dnsmasq to block Web advertising by using a list
2278of known banner-ad servers, all resolving to 127.0.0.1 or 0.0.0.0, in
2279.B /etc/hosts
2280or an additional hosts file. The list can be very long,
2281dnsmasq has been tested successfully with one million names. That size
2282file needs a 1GHz processor and about 60Mb of RAM.
2283
Simon Kelley1f15b812009-10-13 17:49:32 +01002284.SH INTERNATIONALISATION
2285Dnsmasq can be compiled to support internationalisation. To do this,
2286the make targets "all-i18n" and "install-i18n" should be used instead of
2287the standard targets "all" and "install". When internationalisation
2288is compiled in, dnsmasq will produce log messages in the local
2289language and support internationalised domain names (IDN). Domain
2290names in /etc/hosts, /etc/ethers and /etc/dnsmasq.conf which contain
2291non-ASCII characters will be translated to the DNS-internal punycode
2292representation. Note that
2293dnsmasq determines both the language for messages and the assumed
2294charset for configuration
2295files from the LANG environment variable. This should be set to the system
2296default value by the script which is responsible for starting
2297dnsmasq. When editing the configuration files, be careful to do so
2298using only the system-default locale and not user-specific one, since
2299dnsmasq has no direct way of determining the charset in use, and must
2300assume that it is the system default.
2301
Simon Kelley9e4abcb2004-01-22 19:47:41 +00002302.SH FILES
Simon Kelleyb49644f2004-01-30 21:36:24 +00002303.IR /etc/dnsmasq.conf
2304
2305.IR /usr/local/etc/dnsmasq.conf
Simon Kelley9e4abcb2004-01-22 19:47:41 +00002306
2307.IR /etc/resolv.conf
Simon Kelley28866e92011-02-14 20:19:14 +00002308.IR /var/run/dnsmasq/resolv.conf
2309.IR /etc/ppp/resolv.conf
2310.IR /etc/dhcpc/resolv.conf
Simon Kelley9e4abcb2004-01-22 19:47:41 +00002311
2312.IR /etc/hosts
2313
Simon Kelley3be34542004-09-11 19:12:13 +01002314.IR /etc/ethers
2315
Simon Kelleyb49644f2004-01-30 21:36:24 +00002316.IR /var/lib/misc/dnsmasq.leases
2317
2318.IR /var/db/dnsmasq.leases
Simon Kelley9e4abcb2004-01-22 19:47:41 +00002319
2320.IR /var/run/dnsmasq.pid
2321.SH SEE ALSO
Simon Kelley9e4abcb2004-01-22 19:47:41 +00002322.BR hosts (5),
2323.BR resolver (5)
2324.SH AUTHOR
2325This manual page was written by Simon Kelley <simon@thekelleys.org.uk>.
2326
2327