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Updated: Wednesday, February 9, 2022
 
 

dnsmasq (8)

Name

dnsmasq - A lightweight DHCP and caching DNS server.

Synopsis

dnsmasq [OPTION]...

Description

DNSMASQ(8)                  System Manager's Manual                 DNSMASQ(8)



NAME
       dnsmasq - A lightweight DHCP and caching DNS server.

SYNOPSIS
       dnsmasq [OPTION]...

DESCRIPTION
       dnsmasq  is a lightweight DNS, TFTP, PXE, router advertisement and DHCP
       server. It is intended to provide coupled DNS and  DHCP  service  to  a
       LAN.

       Dnsmasq  accepts  DNS  queries  and  either  answers them from a small,
       local, cache or forwards them to a  real,  recursive,  DNS  server.  It
       loads  the  contents of /etc/hosts so that local hostnames which do not
       appear in the global DNS can be resolved and also answers  DNS  queries
       for  DHCP  configured  hosts.  It can also act as the authoritative DNS
       server for one or more domains, allowing local names to appear  in  the
       global DNS. It can be configured to do DNSSEC validation.

       The  dnsmasq DHCP server supports static address assignments and multi-
       ple networks. It automatically sends a sensible  default  set  of  DHCP
       options, and can be configured to send any desired set of DHCP options,
       including vendor-encapsulated options. It includes a secure, read-only,
       TFTP  server  to  allow  net/PXE  boot  of DHCP hosts and also supports
       BOOTP. The PXE support is full featured,  and  includes  a  proxy  mode
       which  supplies  PXE information to clients whilst DHCP address alloca-
       tion is done by another server.

       The dnsmasq DHCPv6 server provides the same  set  of  features  as  the
       DHCPv4 server, and in addition, it includes router advertisements and a
       neat feature which allows naming  for  clients  which  use  DHCPv4  and
       stateless  autoconfiguration only for IPv6 configuration. There is sup-
       port for doing address allocation (both DHCPv6  and  RA)  from  subnets
       which are dynamically delegated via DHCPv6 prefix delegation.

       Dnsmasq  is  coded with small embedded systems in mind. It aims for the
       smallest possible memory footprint compatible with the supported  func-
       tions,   and  allows unneeded functions to be omitted from the compiled
       binary.

OPTIONS
       Note that in general missing parameters  are  allowed  and  switch  off
       functions,  for  instance  "--pid-file" disables writing a PID file. On
       BSD, unless the GNU getopt library is linked,  the  long  form  of  the
       options  does  not  work on the command line; it is still recognised in
       the configuration file.

       --test Read and syntax check configuration file(s). Exit with code 0 if
              all  is  OK,  or a non-zero code otherwise. Do not start up dns-
              masq.

       -w, --help
              Display all command-line  options.   --help  dhcp  will  display
              known  DHCPv4  configuration options, and --help dhcp6 will dis-
              play DHCPv6 options.

       -h, --no-hosts
              Don't read the hostnames in /etc/hosts.

       -H, --addn-hosts=<file>
              Additional hosts file.  Read  the  specified  file  as  well  as
              /etc/hosts.  If  --no-hosts  is  given,  read only the specified
              file. This option may be repeated for more than  one  additional
              hosts  file.  If  a  directory is given, then read all the files
              contained in that directory.

       --hostsdir=<path>
              Read all the hosts files contained  in  the  directory.  New  or
              changed  files  are  read automatically. See --dhcp-hostsdir for
              details.

       -E, --expand-hosts
              Add the domain to simple names (without a period) in  /etc/hosts
              in  the  same way as for DHCP-derived names. Note that this does
              not apply to domain names in cnames, PTR  records,  TXT  records
              etc.

       -T, --local-ttl=<time>
              When  replying with information from /etc/hosts or configuration
              or the DHCP leases file dnsmasq by default sets the time-to-live
              field  to  zero,  meaning  that  the requester should not itself
              cache the information. This is the correct thing to do in almost
              all  situations.  This option allows a time-to-live (in seconds)
              to be given for these replies. This will reduce the load on  the
              server  at  the  expense  of clients using stale data under some
              circumstances.

       --dhcp-ttl=<time>
              As 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.

       --neg-ttl=<time>
              Negative replies from upstream servers normally contain time-to-
              live information in SOA records which dnsmasq uses for  caching.
              If the replies from upstream servers omit this information, dns-
              masq does not cache the reply. This option gives a default value
              for  time-to-live (in seconds) which dnsmasq uses to cache nega-
              tive replies even in the absence of an SOA record.

       --max-ttl=<time>
              Set a maximum TTL value that will be handed out to clients.  The
              specified  maximum  TTL  will be given to clients instead of the
              true TTL value if it is lower. The true  TTL  value  is  however
              kept in the cache to avoid flooding the upstream DNS servers.

       --max-cache-ttl=<time>
              Set a maximum TTL value for entries in the cache.

       --min-cache-ttl=<time>
              Extend  short  TTL  values  to the time given when caching them.
              Note that artificially extending TTL values is in general a  bad
              idea, do not do it unless you have a good reason, and understand
              what you are doing.  Dnsmasq limits the value of this option  to
              one hour, unless recompiled.

       --auth-ttl=<time>
              Set  the  TTL  value  returned in answers from the authoritative
              server.

       -k, --keep-in-foreground
              Do not go into the background at startup but  otherwise  run  as
              normal.  This is intended for use when dnsmasq is run under dae-
              montools or launchd.

       -d, --no-daemon
              Debug mode: don't fork to the  background,  don't  write  a  pid
              file,  don't  change  user id, generate a complete cache dump on
              receipt on SIGUSR1, log to stderr as well as syslog, don't  fork
              new  processes  to  handle TCP queries. Note that this option is
              for use in debugging only, to stop dnsmasq daemonising  in  pro-
              duction, use --keep-in-foreground.

       -q, --log-queries
              Log the results of DNS queries handled by dnsmasq. Enable a full
              cache dump on receipt of SIGUSR1. If  the  argument  "extra"  is
              supplied, ie --log-queries=extra then the log has extra informa-
              tion at the start of each line.  This consists of a serial  num-
              ber  which  ties together the log lines associated with an indi-
              vidual query, and the IP address of the requestor.

       -8, --log-facility=<facility>
              Set the facility to which dnsmasq will send syslog entries, this
              defaults  to  DAEMON, and to LOCAL0 when debug mode is in opera-
              tion. If the facility given contains at least one '/' character,
              it  is  taken  to  be  a filename, and dnsmasq logs to the given
              file, instead of syslog. If the facility  is  '-'  then  dnsmasq
              logs to stderr.  (Errors whilst reading configuration will still
              go to syslog, but all output from a successful startup, and  all
              output  whilst  running,  will go exclusively to the file.) When
              logging to a file, dnsmasq will close and reopen the  file  when
              it  receives  SIGUSR2.  This  allows  the log file to be rotated
              without stopping dnsmasq.

       --log-async[=<lines>]
              Enable asynchronous logging and optionally set the limit on  the
              number  of lines which will be queued by dnsmasq when writing to
              the syslog is slow.  Dnsmasq can log asynchronously: this allows
              it  to continue functioning without being blocked by syslog, and
              allows syslog to use dnsmasq for  DNS  queries  without  risking
              deadlock.   If the queue of log-lines becomes full, dnsmasq will
              log the overflow, and the number of messages  lost. The  default
              queue  length  is  5,  a sane value would be 5-25, and a maximum
              limit of 100 is imposed.

       -x, --pid-file=<path>
              Specify an alternate path for dnsmasq to record  its  process-id
              in. Normally /var/run/dnsmasq.pid.

       -u, --user=<username>
              Specify  the  userid to which dnsmasq will change after startup.
              Dnsmasq must normally be started as root, but it will drop  root
              privileges  after  startup  by changing id to another user. Nor-
              mally this user is "nobody" but that  can  be  over-ridden  with
              this switch.

       -g, --group=<groupname>
              Specify  the  group  which  dnsmasq  will run as. The default is
              "dip",    if    available,    to    facilitate     access     to
              /etc/ppp/resolv.conf which is not normally world readable.

       -v, --version
              Print the version number.

       -p, --port=<port>
              Listen  on <port> instead of the standard DNS port (53). Setting
              this to zero completely disables DNS function, leaving only DHCP
              and/or TFTP.

       -P, --edns-packet-max=<size>
              Specify  the largest EDNS.0 UDP packet which is supported by the
              DNS forwarder. Defaults to 4096,  which  is  the  RFC5625-recom-
              mended size.

       -Q, --query-port=<query_port>
              Send outbound DNS queries from, and listen for their replies on,
              the specific UDP  port  <query_port>  instead  of  using  random
              ports. NOTE that using this option will make dnsmasq less secure
              against DNS spoofing attacks but it may be faster and  use  less
              resources.  Setting this option to zero makes dnsmasq use a sin-
              gle port allocated to it by the OS: this was the default  behav-
              iour in versions prior to 2.43.

       --min-port=<port>
              Do not use ports less than that given as source for outbound DNS
              queries. Dnsmasq picks  random  ports  as  source  for  outbound
              queries:  when  this option is given, the ports used will always
              to larger than that specified. Useful for systems  behind  fire-
              walls. If not specified, defaults to 1024.

       --max-port=<port>
              Use  ports  lower  than  that  given  as source for outbound DNS
              queries.  Dnsmasq picks random  ports  as  source  for  outbound
              queries:  when  this option is given, the ports used will always
              be lower than that specified. Useful for  systems  behind  fire-
              walls.

       -i, --interface=<interface name>
              Listen only on the specified interface(s). Dnsmasq automatically
              adds the loopback (local) interface to the list of interfaces to
              use  when  the --interface option  is used. If no --interface or
              --listen-address options are given dnsmasq listens on all avail-
              able  interfaces except any given in --except-interface options.
              On  Linux,  when  --bind-interfaces  or  --bind-dynamic  are  in
              effect,  IP  alias  interface  labels (eg "eth1:0") are checked,
              rather than interface names. In  the  degenerate  case  when  an
              interface  has  one  address, this amounts to the same thing but
              when an interface has multiple addresses it allows control  over
              which  of  those  addresses  are  accepted.   The same effect is
              achievable in default mode by using --listen-address.  A  simple
              wildcard,  consisting of a trailing '*', can be used in --inter-
              face and --except-interface options.

       -I, --except-interface=<interface name>
              Do not listen on the specified interface. Note that the order of
              --listen-address --interface and --except-interface options does
              not matter and that --except-interface options  always  override
              the  others.  The  comments about interface labels for --listen-
              address apply here.

       --auth-server=<domain>,[<interface>|<ip-address>...]
              Enable DNS authoritative mode for queries arriving at an  inter-
              face  or address. Note that the interface or address need not be
              mentioned  in  --interface  or  --listen-address  configuration,
              indeed --auth-server will override these and provide a different
              DNS service on the specified  interface.  The  <domain>  is  the
              "glue  record".  It  should  resolve  in  the global DNS to an A
              and/or AAAA record which points to the address dnsmasq  is  lis-
              tening  on.  When an interface is specified, it may be qualified
              with "/4" or "/6" to specify only the  IPv4  or  IPv6  addresses
              associated  with  the interface. Since any defined authoritative
              zones are also available as part of the normal recusive DNS ser-
              vice  supplied  by dnsmasq, it can make sense to have an --auth-
              server declaration with no interfaces  or  address,  but  simply
              specifying the primary external nameserver.

       --local-service
              Accept  DNS  queries only from hosts whose address is on a local
              subnet, ie a subnet for which an interface exists on the server.
              This  option  only  has  effect  if  there  are  no --interface,
              --except-interface, --listen-address or  --auth-server  options.
              It  is intended to be set as a default on installation, to allow
              unconfigured installations to be useful but also safe from being
              used for DNS amplification attacks.

       -2, --no-dhcp-interface=<interface name>
              Do  not  provide DHCP or TFTP on the specified interface, but do
              provide DNS service.

       -a, --listen-address=<ipaddr>
              Listen on the given IP address(es). Both --interface and  --lis-
              ten-address  options may be given, in which case the set of both
              interfaces and addresses is used. Note that  if  no  --interface
              option is given, but --listen-address is, dnsmasq will not auto-
              matically listen on the loopback interface. To achieve this, its
              IP  address,  127.0.0.1, must be explicitly given as a --listen-
              address option.

       -z, --bind-interfaces
              On systems which support it, dnsmasq binds the wildcard address,
              even  when it is listening on only some interfaces. It then dis-
              cards requests that it shouldn't reply to. This has  the  advan-
              tage  of  working  even  when  interfaces come and go and change
              address. This option forces dnsmasq  to  really  bind  only  the
              interfaces  it is listening on. About the only time when this is
              useful is when running another nameserver (or  another  instance
              of  dnsmasq)  on  the  same  machine.  Setting  this option also
              enables multiple instances of dnsmasq which provide DHCP service
              to run in the same machine.

       --bind-dynamic
              Enable  a  network  mode which is a hybrid between --bind-inter-
              faces and the default. Dnsmasq binds the address  of  individual
              interfaces,  allowing  multiple  dnsmasq  instances,  but if new
              interfaces or addresses  appear,  it  automatically  listens  on
              those  (subject to any access-control configuration). This makes
              dynamically created interfaces work  in  the  same  way  as  the
              default. Implementing this option requires non-standard network-
              ing APIs and it is only available under Linux.  On  other  plat-
              forms it falls-back to --bind-interfaces mode.

       -y, --localise-queries
              Return  answers  to DNS queries from /etc/hosts and --interface-
              name which depend on the interface  over  which  the  query  was
              received.  If  a  name has more than one address associated with
              it, and at least one of those addresses is on the same subnet as
              the  interface to which the query was sent, then return only the
              address(es) on that subnet. This allows for a  server   to  have
              multiple  addresses  in  /etc/hosts corresponding to each of its
              interfaces, and hosts will get  the  correct  address  based  on
              which  network  they are attached to. Currently this facility is
              limited to IPv4.

       -b, --bogus-priv
              Bogus private reverse lookups. All reverse lookups  for  private
              IP   ranges  (ie  192.168.x.x,  etc)  which  are  not  found  in
              /etc/hosts or the DHCP leases file are answered  with  "no  such
              domain"  rather  than  being forwarded upstream. The set of pre-
              fixes affected is the list given in RFC6303, for IPv4 and IPv6.

       -V, --alias=[<old-ip>]|[<start-ip>-<end-ip>],<new-ip>[,<mask>]
              Modify IPv4 addresses returned from upstream nameservers; old-ip
              is  replaced  by  new-ip. If the optional mask is given then any
              address which matches the masked old-ip will be re-written.  So,
              for   instance  --alias=1.2.3.0,6.7.8.0,255.255.255.0  will  map
              1.2.3.56 to 6.7.8.56 and 1.2.3.67  to  6.7.8.67.  This  is  what
              Cisco  PIX  routers call "DNS doctoring". If the old IP is given
              as range, then only addresses in the range, rather than a  whole
              subnet,              are              re-written.             So
              --alias=192.168.0.10-192.168.0.40,10.0.0.0,255.255.255.0    maps
              192.168.0.10->192.168.0.40 to 10.0.0.10->10.0.0.40

       -B, --bogus-nxdomain=<ipaddr>
              Transform  replies  which  contain the IP address given into "No
              such domain" replies. This is intended to counteract  a  devious
              move  made  by  Verisign  in  September  2003  when they started
              returning the address of an advertising web page in response  to
              queries  for unregistered names, instead of the correct NXDOMAIN
              response. This option tells dnsmasq to fake the correct response
              when  it  sees  this  behaviour.  As at Sept 2003 the IP address
              being returned by Verisign is 64.94.110.11

       --ignore-address=<ipaddr>
              Ignore replies to A-record queries which include  the  specified
              address.   No  error  is  generated, dnsmasq simply continues to
              listen for another reply.  This is  useful  to  defeat  blocking
              strategies  which rely on quickly supplying a forged answer to a
              DNS request for certain domain, before the  correct  answer  can
              arrive.

       -f, --filterwin2k
              Later versions of windows make periodic DNS requests which don't
              get sensible answers from the public DNS and can cause  problems
              by triggering dial-on-demand links. This flag turns on an option
              to filter such requests. The requests blocked are for records of
              types  SOA  and  SRV,  and type ANY where the requested name has
              underscores, to catch LDAP requests.

       -r, --resolv-file=<file>
              Read the IP addresses of the upstream nameservers  from  <file>,
              instead  of  /etc/resolv.conf.  For  the format of this file see
              resolv.conf(5).  The only lines relevant to  dnsmasq  are  name-
              server  ones.  Dnsmasq  can  be  told  to  poll  more  than  one
              resolv.conf file, the first file name  specified  overrides  the
              default,  subsequent  ones add to the list. This is only allowed
              when polling; the file with the  currently  latest  modification
              time is the one used.

       -R, --no-resolv
              Don't  read /etc/resolv.conf. Get upstream servers only from the
              command line or the dnsmasq configuration file.

       -1, --enable-dbus[=<service-name>]
              Allow dnsmasq configuration to be updated via DBus method calls.
              The  configuration  which can be changed is upstream DNS servers
              (and corresponding domains) and cache clear. Requires that  dns-
              masq  has  been  built with DBus support. If the service name is
              given, dnsmasq provides service at that name,  rather  than  the
              default which is uk.org.thekelleys.dnsmasq

       --enable-ubus[=<service-name>]
              Enable  dnsmasq  UBus interface. It sends notifications via UBus
              on DHCPACK and DHCPRELEASE events. Furthermore  it  offers  met-
              rics.   Requires  that dnsmasq has been built with UBus support.
              If the service name is given, dnsmasq provides service  at  that
              namespace, rather than the default which is dnsmasq

       -o, --strict-order
              By  default,  dnsmasq  will  send queries to any of the upstream
              servers it knows about and tries  to  favour  servers  that  are
              known  to  be  up.  Setting this flag forces dnsmasq to try each
              query with each server strictly in  the  order  they  appear  in
              /etc/resolv.conf

       --all-servers
              By  default,  when  dnsmasq  has  more  than one upstream server
              available, it will send queries to just one server. Setting this
              flag  forces  dnsmasq  to  send  all  queries  to  all available
              servers. The reply from the server which answers first  will  be
              returned to the original requester.

       --dns-loop-detect
              Enable  code  to  detect  DNS forwarding loops; ie the situation
              where a query sent to one  of  the  upstream  server  eventually
              returns  as  a  new  query  to the dnsmasq instance. The process
              works by generating TXT queries of the form <hex>.test and send-
              ing them to each upstream server. The hex is a UID which encodes
              the instance of dnsmasq  sending  the  query  and  the  upstream
              server  to which it was sent. If the query returns to the server
              which sent it, then the upstream server  through  which  it  was
              sent  is disabled and this event is logged. Each time the set of
              upstream servers changes, the test is re-run  on  all  of  them,
              including ones which were previously disabled.

       --stop-dns-rebind
              Reject  (and  log) addresses from upstream nameservers which are
              in the private ranges. This blocks an  attack  where  a  browser
              behind  a  firewall  is used to probe machines on the local net-
              work.  For  IPv6,  the  private  range  covers  the  IPv4-mapped
              addresses  in  private  space plus all link-local (LL) and site-
              local (ULA) addresses.

       --rebind-localhost-ok
              Exempt 127.0.0.0/8 and ::1 from rebinding checks.  This  address
              range is returned by realtime black hole servers, so blocking it
              may disable these services.

       --rebind-domain-ok=[<domain>]|[[/<domain>/[<domain>/]
              Do not detect and block dns-rebind on queries to these  domains.
              The  argument may be either a single domain, or multiple domains
              surrounded by '/', like  the  --server  syntax,  eg.   --rebind-
              domain-ok=/domain1/domain2/domain3/

       -n, --no-poll
              Don't poll /etc/resolv.conf for changes.

       --clear-on-reload
              Whenever /etc/resolv.conf is re-read or the upstream servers are
              set via DBus, clear the DNS cache.   This  is  useful  when  new
              nameservers may have different data than that held in cache.

       -D, --domain-needed
              Tells  dnsmasq  to  never  forward  A  or AAAA queries for plain
              names, without dots or domain parts, to upstream nameservers. If
              the name is not known from /etc/hosts or DHCP then a "not found"
              answer is returned.

       -S,                                                            --local,
       --server=[/[<domain>]/[domain/]][<ipaddr>[#<port>]][@<source-
       ip>|<interface>[#<port>]]
              Specify IP address of upstream servers  directly.  Setting  this
              flag  does  not  suppress reading of /etc/resolv.conf, use --no-
              resolv to do that. If one or more optional  domains  are  given,
              that  server is used only for those domains and they are queried
              only using the specified server. This is  intended  for  private
              nameservers:  if  you  have  a  nameserver on your network which
              deals with names of the form  xxx.internal.thekelleys.org.uk  at
              192.168.1.1  then  giving   the  flag --server=/internal.thekel-
              leys.org.uk/192.168.1.1  will  send  all  queries  for  internal
              machines  to  that  nameserver,  everything  else will go to the
              servers in /etc/resolv.conf. DNSSEC validation is turned off for
              such  private  nameservers, UNLESS a --trust-anchor is specified
              for the domain in question. An empty  domain  specification,  //
              has  the  special  meaning  of "unqualified names only" ie names
              without any dots in them. A non-standard port may  be  specified
              as  part  of  the IP address using a # character.  More than one
              --server flag is allowed, with repeated domain or  ipaddr  parts
              as required.

              More   specific  domains  take  precedence  over  less  specific
              domains,            so:             --server=/google.com/1.2.3.4
              --server=/www.google.com/2.3.4.5    will    send   queries   for
              *.google.com to 1.2.3.4, except *www.google.com, which  will  go
              to 2.3.4.5

              The   special  server  address  '#'  means,  "use  the  standard
              servers",            so             --server=/google.com/1.2.3.4
              --server=/www.google.com/# will send queries for *.google.com to
              1.2.3.4, except  *www.google.com  which  will  be  forwarded  as
              usual.

              Also  permitted  is  a  -S  flag  which gives a domain but no IP
              address; this tells dnsmasq that a domain is local  and  it  may
              answer  queries from /etc/hosts or DHCP but should never forward
              queries on that domain to any upstream servers.   --local  is  a
              synonym for --server to make configuration files clearer in this
              case.

              IPv6  addresses  may  include   an   %interface   scope-id,   eg
              fe80::202:a412:4512:7bbf%eth0.

              The  optional  string after the @ character tells dnsmasq how to
              set the source of the queries to this nameserver. It can  either
              be  an  ip-address,  an  interface  name or both. The ip-address
              should belong to the machine on which dnsmasq is running, other-
              wise  this  server  line  will be logged and then ignored. If an
              interface name is given, then queries  to  the  server  will  be
              forced  via  that  interface; if an ip-address is given then the
              source address of the queries will be set to that  address;  and
              if both are given then a combination of ip-address and interface
              name will be used to steer requests to the server.   The  query-
              port flag is ignored for any servers which have a source address
              specified but the port may be specified directly as part of  the
              source  address.  Forcing  queries to an interface is not imple-
              mented on all platforms supported by dnsmasq.

       --rev-server=<ip-address>/<prefix-len>[,<ipaddr>][#<port>][@<source-
       ip>|<interface>[#<port>]]
              This  is  functionally  the  same as --server, but provides some
              syntactic sugar to make specifying address-to-name queries  eas-
              ier.  For example --rev-server=1.2.3.0/24,192.168.0.1 is exactly
              equivalent to --server=/3.2.1.in-addr.arpa/192.168.0.1

       -A, --address=/<domain>[/<domain>...]/[<ipaddr>]
              Specify an IP address to  return  for  any  host  in  the  given
              domains.   Queries in the domains are never forwarded and always
              replied to with the specified IP address which may  be  IPv4  or
              IPv6.  To  give  both  IPv4 and IPv6 addresses for a domain, use
              repeated --address flags.  To include multiple IP addresses  for
              a  single  query,  use  --addn-hosts=<path>  instead.  Note that
              /etc/hosts and DHCP leases override this for individual names. A
              common  use  of  this  is to redirect the entire doubleclick.net
              domain to some friendly local web server to  avoid  banner  ads.
              The  domain specification works in the same was as for --server,
              with the additional facility that /#/ matches any  domain.  Thus
              --address=/#/1.2.3.4  will  always  return 1.2.3.4 for any query
              not answered from /etc/hosts or DHCP and not sent to an upstream
              nameserver  by  a  more  specific  --server  directive.  As  for
              --server, one or more domains with no address returns a no-such-
              domain  answer,  so  --address=/example.com/  is  equivalent  to
              --server=/example.com/ and returns NXDOMAIN for example.com  and
              all  its  subdomains.  An address specified as '#' translates to
              the NULL address of 0.0.0.0 and its IPv6  equivalent  of  ::  so
              --address=/example.com/#  will  return  NULL addresses for exam-
              ple.com and its subdomains. This is partly syntactic  sugar  for
              --address=/example.com/0.0.0.0 and --address=/example.com/:: but
              is also more efficient than including both as separate  configu-
              ration lines. Note that NULL addresses normally work in the same
              way as localhost, so beware that clients looking up these  names
              are likely to end up talking to themselves.

       --ipset=/<domain>[/<domain>...]/<ipset>[,<ipset>...]
              Places  the  resolved  IP  addresses  of queries for one or more
              domains in the specified Netfilter IP set. If multiple  setnames
              are  given,  then the addresses are placed in each of them, sub-
              ject to the limitations of an IP set (IPv4 addresses  cannot  be
              stored  in  an  IPv6 IP set and vice versa).  Domains and subdo-
              mains are matched in the same way as --address.  These  IP  sets
              must already exist. See ipset(8) for more details.

       -m, --mx-host=<mx name>[[,<hostname>],<preference>]
              Return  an MX record named <mx name> pointing to the given host-
              name (if given), or the host specified in the --mx-target switch
              or,  if  that  switch is not given, the host on which dnsmasq is
              running. The default is useful for directing mail  from  systems
              on  a LAN to a central server. The preference value is optional,
              and defaults to 1 if not given. More than one MX record  may  be
              given for a host.

       -t, --mx-target=<hostname>
              Specify  the  default  target for the MX record returned by dns-
              masq. See --mx-host.  If --mx-target is  given,  but  not  --mx-
              host,  then dnsmasq returns a MX record containing the MX target
              for MX queries on the hostname of the machine on  which  dnsmasq
              is running.

       -e, --selfmx
              Return  an  MX record pointing to itself for each local machine.
              Local machines are those in /etc/hosts or with DHCP leases.

       -L, --localmx
              Return an MX record pointing to the host  given  by  --mx-target
              (or  the  machine  on  which  dnsmasq is running) for each local
              machine. Local machines are those in  /etc/hosts  or  with  DHCP
              leases.

       -W, --srv-host=<_service>.<_prot>.[<domain>],[<target>[,<port>[,<prior-
       ity>[,<weight>]]]]
              Return a SRV DNS record. See RFC2782 for details.  If  not  sup-
              plied,  the  domain  defaults  to  that  given by --domain.  The
              default for the target domain is empty, and the default for port
              is  one  and  the  defaults for weight and priority are zero. Be
              careful if transposing data from  BIND  zone  files:  the  port,
              weight  and priority numbers are in a different order. More than
              one SRV record for a given service/domain is allowed,  all  that
              match are returned.

       --host-
       record=<name>[,<name>....],[<IPv4-address>],[<IPv6-address>][,<TTL>]
              Add A, AAAA and PTR records to the DNS. This adds  one  or  more
              names  to  the  DNS  with  associated  IPv4  (A) and IPv6 (AAAA)
              records. A name may appear in more than  one  --host-record  and
              therefore  be  assigned  more  than  one address. Only the first
              address creates a PTR record linking the address  to  the  name.
              This  is  the same rule as is used reading hosts-files.  --host-
              record options are considered to be read before host-files, so a
              name  appearing there inhibits PTR-record creation if it appears
              in hosts-file also. Unlike hosts-files, names are not  expanded,
              even  when --expand-hosts is in effect. Short and long names may
              appear in the same --host-record, eg.  --host-record=laptop,lap-
              top.thekelleys.org,192.168.0.1,1234::100

              If the time-to-live is given, it overrides the default, which is
              zero or the value of --local-ttl. The value is a positive  inte-
              ger and gives the time-to-live in seconds.

       -Y, --txt-record=<name>[[,<text>],<text>]
              Return  a  TXT  DNS  record. The value of TXT record is a set of
              strings, so  any number may be included,  delimited  by  commas;
              use  quotes  to  put commas into a string. Note that the maximum
              length of a single string is 255 characters, longer strings  are
              split into 255 character chunks.

       --ptr-record=<name>[,<target>]
              Return a PTR DNS record.

       --naptr-record=<name>,<order>,<preference>,<flags>,<service>,<reg-
       exp>[,<replacement>]
              Return an NAPTR DNS record, as specified in RFC3403.

       --caa-record=<name>,<flags>,<tag>,<value>
              Return a CAA DNS record, as specified in RFC6844.

       --cname=<cname>,[<cname>,]<target>[,<TTL>]
              Return a CNAME record which indicates  that  <cname>  is  really
              <target>.  There  is  a significant limitation on the target; it
              must be a DNS record which is known to dnsmasq  and  NOT  a  DNS
              record  which  comes  from an upstream server. The cname must be
              unique, but it is permissible to have more than one cname point-
              ing to the same target. Indeed it's possible to declare multiple
              cnames   to   a   target   in   a   single   line,   like    so:
              --cname=cname1,cname2,target

              If the time-to-live is given, it overrides the default, which is
              zero or the value of --local-ttl. The value is a positive  inte-
              ger and gives the time-to-live in seconds.

       --dns-rr=<name>,<RR-number>,[<hex data>]
              Return  an arbitrary DNS Resource Record. The number is the type
              of the record (which is always in the C_IN class). The value  of
              the  record  is  given by the hex data, which may be of the form
              01:23:45 or 01 23 45 or 012345 or any mixture of these.

       --interface-name=<name>,<interface>[/4|/6]
              Return DNS records associating the name with the address(es)  of
              the given interface. This flag specifies an A or AAAA record for
              the given name in the same way as  an  /etc/hosts  line,  except
              that  the  address  is  not  constant,  but taken from the given
              interface. The interface may be followed  by  "/4"  or  "/6"  to
              specify that only IPv4 or IPv6 addresses of the interface should
              be used. If the interface is down, not configured  or  non-exis-
              tent,  an  empty  record is returned. The matching PTR record is
              also created, mapping the interface address to  the  name.  More
              than  one  name  may  be associated with an interface address by
              repeating the flag; in that case the first instance is used  for
              the  reverse  address-to-name  mapping. Note that a name used in
              --interface-name may not appear in /etc/hosts.

       --synth-domain=<domain>,<address range>[,<prefix>[*]]
              Create artificial A/AAAA and PTR records for an  address  range.
              The  records either seqential numbers or the address, with peri-
              ods (or colons for IPv6) replaced with dashes.

              An examples should make this clearer. First sequential  numbers.
              --synth-domain=thekel-
              leys.org.uk,192.168.0.50,192.168.0.70,internal-* results in  the
              name   internal-0.thekelleys.org.uk.   returning   192.168.0.50,
              internal-1.thekelleys.org.uk returning 192.168.0.51 and  so  on.
              (note the *) The same principle applies to IPv6 addresses (where
              the numbers may be very large). Reverse lookups from address  to
              name behave as expected.

              Second,   --synth-domain=thekelleys.org.uk,192.168.0.0/24,inter-
              nal-   (no   *)   will   result   in   a   query   for    inter-
              nal-192-168-0-56.thekelleys.org.uk  returning 192.168.0.56 and a
              reverse query vice versa. The same applies  to  IPv6,  but  IPv6
              addresses  may start with '::' but DNS labels may not start with
              '-' so in this case if no prefix is configured a zero  is  added
              in front of the label. ::1 becomes 0--1.

              V4  mapped  IPv6  addresses,  which  have  a representation like
              ::ffff:1.2.3.4  are   handled   specially,   and   become   like
              0--ffff-1-2-3-4

              The  address  range can be of the form <ip address>,<ip address>
              or <ip address>/<netmask> in both forms of the option.

       --dumpfile=<path/to/file>
              Specify the location of a pcap-format file which dnsmasq uses to
              dump  copies  of  network packets for debugging purposes. If the
              file exists when dnsmasq starts, it is not deleted; new  packets
              are added to the end.

       --dumpmask=<mask>
              Specify  which types of packets should be added to the dumpfile.
              The argument should be the OR of the bitmasks for each  type  of
              packet to be dumped: it can be specified in hex by preceding the
              number with 0x in  the normal way. Each time a packet is written
              to  the  dumpfile, dnsmasq logs the packet sequence and the mask
              representing its type. The  current  types  are:  0x0001  -  DNS
              queries  from clients 0x0002 DNS replies to clients 0x0004 - DNS
              queries to upstream 0x0008 - DNS replies from upstream 0x0010  -
              queries  send upstream for DNSSEC validation 0x0020 - replies to
              queries for DNSSEC validation 0x0040 - replies to client queries
              which  fail  DNSSEC  validation  0x0080  replies  to queries for
              DNSSEC validation which fail validation.

       --add-mac[=base64|text]
              Add the MAC address of the requestor to DNS  queries  which  are
              forwarded  upstream.  This  may  be used to DNS filtering by the
              upstream server. The MAC  address  can  only  be  added  if  the
              requestor is on the same subnet as the dnsmasq server. Note that
              the mechanism used to achieve this (an EDNS0 option) is not  yet
              standardised,  so  this  should be considered experimental. Also
              note that exposing MAC addresses in this way may  have  security
              and  privacy  implications.  The warning about caching given for
              --add-subnet applies to --add-mac too. An  alternative  encoding
              of the MAC, as base64, is enabled by adding the "base64" parame-
              ter and a human-readable encoding of hex-and-colons  is  enabled
              by added the "text" parameter.

       --add-cpe-id=<string>
              Add  an  arbitrary  identifying  string to DNS queries which are
              forwarded upstream.

       --add-subnet[[=[<IPv4    address>/]<IPv4    prefix     length>][,[<IPv6
       address>/]<IPv6 prefix length>]]
              Add  a  subnet  address  to  the DNS queries which are forwarded
              upstream. If an address is specified in the  flag,  it  will  be
              used,  otherwise, the address of the requestor will be used. The
              amount of the address forwarded depends  on  the  prefix  length
              parameter:  32  (128  for IPv6) forwards the whole address, zero
              forwards none of it but still  marks  the  request  so  that  no
              upstream  nameserver will add client address information either.
              The default is zero for both IPv4 and IPv6. Note  that  upstream
              nameservers  may be configured to return different results based
              on this  information,  but  the  dnsmasq  cache  does  not  take
              account.  Caching is therefore disabled for such replies, unless
              the subnet address being added is constant.

              For example, --add-subnet=24,96 will add the /24 and /96 subnets
              of  the  requestor  for  IPv4 and IPv6 requestors, respectively.
              --add-subnet=1.2.3.4/24 will add 1.2.3.0/24 for IPv4  requestors
              and      ::/0      for      IPv6     requestors.      --add-sub-
              net=1.2.3.4/24,1.2.3.4/24 will add 1.2.3.0/24 for both IPv4  and
              IPv6 requestors.


       -c, --cache-size=<cachesize>
              Set  the size of dnsmasq's cache. The default is 150 names. Set-
              ting the cache size to zero disables caching. Note:  huge  cache
              size impacts performance.

       -N, --no-negcache
              Disable  negative  caching.  Negative  caching allows dnsmasq to
              remember "no such domain" answers from upstream nameservers  and
              answer identical queries without forwarding them again.

       -0, --dns-forward-max=<queries>
              Set  the  maximum  number of concurrent DNS queries. The default
              value is 150, which should be fine for  most  setups.  The  only
              known  situation  where this needs to be increased is when using
              web-server log file resolvers, which can generate large  numbers
              of concurrent queries.

       --dnssec
              Validate  DNS replies and cache DNSSEC data. When forwarding DNS
              queries, dnsmasq requests the DNSSEC records needed to  validate
              the  replies.  The replies are validated and the result returned
              as the Authenticated Data bit in the DNS packet. In addition the
              DNSSEC  records  are  stored  in the cache, making validation by
              clients more efficient. Note that validation by clients  is  the
              most  secure  DNSSEC  mode, but for clients unable to do valida-
              tion, use of the AD bit set by dnsmasq is useful, provided  that
              the  network  between  the  dnsmasq  server  and  the  client is
              trusted. Dnsmasq must be compiled with HAVE_DNSSEC enabled,  and
              DNSSEC  trust anchors provided, see --trust-anchor.  Because the
              DNSSEC validation process uses the cache, it is not permitted to
              reduce  the cache size below the default when DNSSEC is enabled.
              The nameservers upstream of dnsmasq must be  DNSSEC-capable,  ie
              capable  of returning DNSSEC records with data. If they are not,
              then dnsmasq will not be able to determine the trusted status of
              answers and this means that DNS service will be entirely broken.

       --trust-anchor=[<class>],<domain>,<key-tag>,<algorithm>,<digest-
       type>,<digest>
              Provide DS records to act a trust anchors for DNSSEC validation.
              Typically  these will be the DS record(s) for Key Signing key(s)
              (KSK) of the root zone, but trust anchors  for  limited  domains
              are  also  possible.  The current root-zone trust anchors may be
              downloaded     from     https://data.iana.org/root-anchors/root-
              anchors.xml

       --dnssec-check-unsigned[=no]
              As  a  default,  dnsmasq  checks  that  unsigned DNS replies are
              legitimate: this entails possible extra  queries  even  for  the
              majority  of  DNS zones which are not, at the moment, signed. If
              --dnssec-check-unsigned=no appears in  the  configuration,  then
              such replies they are assumed to be valid and passed on (without
              the "authentic data" bit set, of course). This does not  protect
              against  an  attacker  forging  unsigned  replies for signed DNS
              zones, but it is fast.

              Versions of dnsmasq prior to  2.80  defaulted  to  not  checking
              unsigned  replies,  and  used  --dnssec-check-unsigned to switch
              this on. Such configurations will continue to  work  as  before,
              but  those which used the default of no checking will need to be
              altered to explicitly select no checking.  The  new  default  is
              because  switching  off  checking for unsigned replies is inher-
              ently dangerous. Not only does it open the possiblity of  forged
              replies,  but  it allows everything to appear to be working even
              when the upstream namesevers do not support DNSSEC, and in  this
              case no DNSSEC validation at all is occurring.

       --dnssec-no-timecheck
              DNSSEC signatures are only valid for specified time windows, and
              should be rejected outside  those  windows.  This  generates  an
              interesting  chicken-and-egg  problem  for  machines which don't
              have a hardware real time clock. For these machines to determine
              the  correct  time  typically  requires use of NTP and therefore
              DNS, but validating  DNS  requires  that  the  correct  time  is
              already  known. Setting this flag removes the time-window checks
              (but not  other  DNSSEC  validation.)  only  until  the  dnsmasq
              process receives SIGINT. The intention is that dnsmasq should be
              started with this flag when the platform determines  that  reli-
              able  time  is not currently available. As soon as reliable time
              is established, a  SIGINT  should  be  sent  to  dnsmasq,  which
              enables time checking, and purges the cache of DNS records which
              have not been thoroughly checked.

              Earlier versions of dnsmasq overloaded  SIGHUP  (which  re-reads
              much configuration) to also enable time validation.

              If  dnsmasq  is run in debug mode (--no-daemon flag) then SIGINT
              retains its usual meaning of terminating the dnsmasq process.

       --dnssec-timestamp=<path>
              Enables an alternative way of checking the validity of the  sys-
              tem  time  for DNSSEC (see --dnssec-no-timecheck). In this case,
              the system time is considered to be valid once it becomes  later
              than  the  timestamp  on the specified file. The file is created
              and its timestamp set automatically by dnsmasq. The file must be
              stored  on a persistent filesystem, so that it and its mtime are
              carried over system restarts.  The  timestamp  file  is  created
              after  dnsmasq  has  dropped  root,  so it must be in a location
              writable by the unprivileged user that dnsmasq runs as.

       --proxy-dnssec
              Copy the DNSSEC Authenticated Data bit from upstream servers  to
              downstream  clients.   This  is an alternative to having dnsmasq
              validate DNSSEC, but it depends on the security of  the  network
              between  dnsmasq  and the upstream servers, and the trustworthi-
              ness of the upstream servers. Note that  caching  the  Authenti-
              cated  Data bit correctly in all cases is not technically possi-
              ble. If the AD bit is to be relied upon when using this  option,
              then  the cache should be disabled using --cache-size=0. In most
              cases, enabling DNSSEC validation within  dnsmasq  is  a  better
              option. See --dnssec for details.

       --dnssec-debug
              Set  debugging  mode for the DNSSEC validation, set the Checking
              Disabled bit on upstream  queries,  and  don't  convert  replies
              which  do  not validate to responses with a return code of SERV-
              FAIL. Note that setting this may affect  DNS  behaviour  in  bad
              ways,  it  is not an extra-logging flag and should not be set in
              production.

       --auth-zone=<domain>[,<subnet>[/<prefix     length>][,<subnet>[/<prefix
       length>].....][,exclude:<subnet>[/<prefix length>]].....]
              Define  a  DNS  zone  for  which  dnsmasq  acts as authoritative
              server. Locally defined DNS records which are in the domain will
              be served. If subnet(s) are given, A and AAAA records must be in
              one of the specified subnets.

              As alternative to directly specifying the subnets, it's possible
              to  give  the  name  of  an interface, in which case the subnets
              implied  by  that  interface's  configured  addresses  and  net-
              mask/prefix-length  are  used;  this  is  useful when using con-
              structed DHCP ranges as the actual address is  dynamic  and  not
              known  when  configuring dnsmasq. The interface addresses may be
              confined to only IPv6 addresses using <interface>/6 or  to  only
              IPv4  using  <interface>/4. This is useful when an interface has
              dynamically determined global IPv6 addresses which should appear
              in  the  zone,  but  RFC1918  IPv4  addresses  which should not.
              Interface-name and address-literal subnet specifications may  be
              used freely in the same --auth-zone declaration.

              It's possible to exclude certain IP addresses from responses. It
              can be used, to make  sure  that  answers  contain  only  global
              routeable  IP  addresses (by excluding loopback, RFC1918 and ULA
              addresses).

              The subnet(s) are also used to define in-addr.arpa and  ip6.arpa
              domains  which are served for reverse-DNS queries. If not speci-
              fied, the prefix length defaults to 24 for IPv4 and 64 for IPv6.
              For  IPv4 subnets, the prefix length should be have the value 8,
              16 or 24 unless you are familiar with RFC 2317 and have arranged
              the in-addr.arpa delegation accordingly. Note that if no subnets
              are specified, then no reverse queries are answered.

       --auth-soa=<serial>[,<hostmaster>[,<refresh>[,<retry>[,<expiry>]]]]
              Specify fields in the SOA record associated  with  authoritative
              zones.  Note  that  this  is optional, all the values are set to
              sane defaults.

       --auth-sec-servers=<domain>[,<domain>[,<domain>...]]
              Specify any secondary servers for a zone for  which  dnsmasq  is
              authoritative. These servers must be configured to get zone data
              from dnsmasq by zone transfer, and answer queries for  the  same
              authoritative zones as dnsmasq.

       --auth-peer=<ip-address>[,<ip-address>[,<ip-address>...]]
              Specify  the addresses of secondary servers which are allowed to
              initiate zone transfer (AXFR) requests for zones for which  dns-
              masq  is  authoritative. If this option is not given but --auth-
              sec-servers is, then AXFR requests will  be  accepted  from  any
              secondary.  Specifying  --auth-peer  without  --auth-sec-servers
              enables zone transfer but does not advertise the secondary in NS
              records returned by dnsmasq.

       --conntrack
              Read  the  Linux  connection track mark associated with incoming
              DNS queries and set the same mark value on upstream traffic used
              to  answer  those queries. This allows traffic generated by dns-
              masq to be associated with the queries which  cause  it,  useful
              for bandwidth accounting and firewalling. Dnsmasq must have con-
              ntrack support compiled in and the kernel  must  have  conntrack
              support  included and configured. This option cannot be combined
              with --query-port.

       -F,            --dhcp-range=[tag:<tag>[,tag:<tag>],][set:<tag>,]<start-
       addr>[,<end-addr>|<mode>][,<netmask>[,<broadcast>]][,<lease time>]

       -F,            --dhcp-range=[tag:<tag>[,tag:<tag>],][set:<tag>,]<start-
       IPv6addr>[,<end-IPv6addr>|constructor:<interface>][,<mode>][,<prefix-
       len>][,<lease time>]

              Enable  the  DHCP  server.  Addresses will be given out from the
              range <start-addr> to <end-addr>  and  from  statically  defined
              addresses  given  in  --dhcp-host  options. If the lease time is
              given, then leases will be given for that length  of  time.  The
              lease  time  is in seconds, or minutes (eg 45m) or hours (eg 1h)
              or "infinite". If not given, the default lease time is one  hour
              for  IPv4  and  one  day for IPv6. The minimum lease time is two
              minutes. For IPv6 ranges, the  lease  time  maybe  "deprecated";
              this  sets the preferred lifetime sent in a DHCP lease or router
              advertisement  to  zero,  which  causes  clients  to  use  other
              addresses,  if  available,  for  new connections as a prelude to
              renumbering.

              This option may be repeated, with different addresses, to enable
              DHCP  service  to  more than one network. For directly connected
              networks (ie, networks on which the machine running dnsmasq  has
              an interface) the netmask is optional: dnsmasq will determine it
              from the interface configuration.  For  networks  which  receive
              DHCP  service  via  a  relay agent, dnsmasq cannot determine the
              netmask itself, so it should  be  specified,  otherwise  dnsmasq
              will  have  to guess, based on the class (A, B or C) of the net-
              work address. The broadcast address is always  optional.  It  is
              always  allowed  to  have more than one --dhcp-range in a single
              subnet.

              For IPv6, the parameters are slightly different: instead of net-
              mask  and  broadcast address, there is an optional prefix length
              which must be equal to or larger then the prefix length  on  the
              local  interface.  If not given, this defaults to 64. Unlike the
              IPv4 case, the prefix length is not automatically  derived  from
              the  interface  configuration.  The  minimum  size of the prefix
              length is 64.

              IPv6 (only) supports another type of range. In this,  the  start
              address  and  optional end address contain only the network part
              (ie ::1) and they are followed by constructor:<interface>.  This
              forms  a template which describes how to create ranges, based on
              the addresses assigned to the interface. For instance

              --dhcp-range=::1,::400,constructor:eth0

              will look for addresses on eth0 and then  create  a  range  from
              <network>::1  to  <network>::400.  If  the interface is assigned
              more than one network, then the  corresponding  ranges  will  be
              automatically  created,  and then deprecated and finally removed
              again as the address is deprecated and then deleted. The  inter-
              face  name  may  have  a  final "*" wildcard. Note that just any
              address on eth0 will not do: it must not be an autoconfigured or
              privacy address, or be deprecated.

              If  a  --dhcp-range is only being used for stateless DHCP and/or
              SLAAC, then the address can be simply ::

              --dhcp-range=::,constructor:eth0


              The optional set:<tag> sets an alphanumeric  label  which  marks
              this network so that DHCP options may be specified on a per-net-
              work basis.  When it is prefixed with 'tag:' instead,  then  its
              meaning  changes from setting a tag to matching it. Only one tag
              may be set, but more than one tag may be matched.

              The optional <mode> keyword may be static which tells dnsmasq to
              enable  DHCP  for  the network specified, but not to dynamically
              allocate IP addresses: only hosts which  have  static  addresses
              given  via  --dhcp-host  or  from  /etc/ethers will be served. A
              static-only subnet with address all  zeros  may  be  used  as  a
              "catch-all" address to enable replies to all Information-request
              packets on a subnet which is provided with stateless DHCPv6,  ie
              --dhcp-range=::,static

              For  IPv4,  the  <mode>  may be proxy in which case dnsmasq will
              provide proxy-DHCP on the specified  subnet.  (See  --pxe-prompt
              and --pxe-service for details.)

              For  IPv6,  the  mode may be some combination of ra-only, slaac,
              ra-names, ra-stateless, ra-advrouter, off-link.

              ra-only tells dnsmasq to offer Router Advertisement only on this
              subnet, and not DHCP.

              slaac tells dnsmasq to offer Router Advertisement on this subnet
              and to set the A bit in the router advertisement,  so  that  the
              client  will use SLAAC addresses. When used with a DHCP range or
              static DHCP address this results in the  client  having  both  a
              DHCP-assigned and a SLAAC address.

              ra-stateless  sends  router advertisements with the O and A bits
              set, and provides a stateless DHCP service. The client will  use
              a  SLAAC  address, and use DHCP for other configuration informa-
              tion.

              ra-names enables a mode which  gives  DNS  names  to  dual-stack
              hosts  which  do  SLAAC  for  IPv6. Dnsmasq uses the host's IPv4
              lease to derive the name, network segment and  MAC  address  and
              assumes  that the host will also have an IPv6 address calculated
              using the SLAAC algorithm, on  the  same  network  segment.  The
              address is pinged, and if a reply is received, an AAAA record is
              added to the DNS for this IPv6 address. Note that this  is  only
              happens for directly-connected networks, (not one doing DHCP via
              a relay) and it will not work if a host is using privacy  exten-
              sions.  ra-names can be combined  with ra-stateless and slaac.

              ra-advrouter enables a mode where router address(es) rather than
              prefix(es)  are  included  in  the  advertisements.    This   is
              described in RFC-3775 section 7.2 and is used in mobile IPv6. In
              this mode the interval option is also included, as described  in
              RFC-3775 section 7.3.

              off-link  tells  dnsmasq to advertise the prefix without the on-
              link (aka L) bit set.


       -G,                                                             --dhcp-
       host=[<hwaddr>][,id:<client_id>|*][,set:<tag>][tag:<tag>][,<ipaddr>][,<host-
       name>][,<lease_time>][,ignore]
              Specify per host parameters for the DHCP server. This  allows  a
              machine  with  a  particular hardware address to be always allo-
              cated the same hostname, IP address and lease time.  A  hostname
              specified like this overrides any supplied by the DHCP client on
              the machine. It is also allowable to omit the  hardware  address
              and include the hostname, in which case the IP address and lease
              times will apply to any machine claiming that name. For  example
              --dhcp-host=00:20:e0:3b:13:af,wap,infinite tells dnsmasq to give
              the machine with hardware  address  00:20:e0:3b:13:af  the  name
              wap,  and an infinite DHCP lease.  --dhcp-host=lap,192.168.0.199
              tells dnsmasq to always allocate the machine lap the IP  address
              192.168.0.199.

              Addresses  allocated  like this are not constrained to be in the
              range given by the --dhcp-range option, but they must be in  the
              same  subnet  as some valid dhcp-range.  For subnets which don't
              need a pool of dynamically allocated addresses, use the "static"
              keyword in the --dhcp-range declaration.

              It  is  allowed to use client identifiers (called client DUID in
              IPv6-land) rather than hardware addresses to identify  hosts  by
              prefixing  with  'id:'.  Thus:  --dhcp-host=id:01:02:03:04,.....
              refers to the host with client  identifier  01:02:03:04.  It  is
              also  allowed  to  specify  the  client  ID  as text, like this:
              --dhcp-host=id:clientidastext,.....

              A single --dhcp-host may contain an IPv4 address or one or  more
              IPv6  addresses,  or  both.  IPv6 addresses must be bracketed by
              square   brackets   thus:   --dhcp-host=laptop,[1234::56]   IPv6
              addresses  may  contain  only  the host-identifier part: --dhcp-
              host=laptop,[::56] in which case they act as wildcards  in  con-
              structed   DHCP   ranges,  with  the  appropriate  network  part
              inserted. For IPv6, an address  may  include  a  prefix  length:
              --dhcp-host=laptop,[1234:50/126]  which (in this case) specifies
              four addresses, 1234::50 to 1234::53. This (an  the  ability  to
              specify  multiple  addresses)  is  useful  when  a host presents
              either a consistent name  or  hardware-ID,  but  varying  DUIDs,
              since  it allows dnsmasq to honour the static address allocation
              but assign a different adddress for each  DUID.  This  typically
              occurs when chain netbooting, as each stage of the chain gets in
              turn allocates an address.

              Note that in IPv6 DHCP, the hardware address may not  be  avail-
              able,  though  it  normally  is for direct-connected clients, or
              clients using DHCP relays which support RFC 6939.


              For DHCPv4, the  special option id:* means "ignore any client-id
              and  use  MAC  addresses  only."  This  is  useful when a client
              presents a client-id sometimes but not others.

              If a name appears in /etc/hosts, the associated address  can  be
              allocated  to  a  DHCP  lease,  but only if a --dhcp-host option
              specifying the name also exists. Only one hostname can be  given
              in  a  --dhcp-host  option,  but  aliases  are possible by using
              CNAMEs. (See --cname ).

              The special keyword "ignore" tells dnsmasq to never offer a DHCP
              lease  to  a  machine.  The machine can be specified by hardware
              address,  client  ID   or   hostname,   for   instance   --dhcp-
              host=00:20:e0:3b:13:af,ignore  This  is  useful  when  there  is
              another DHCP server on the network which should be used by  some
              machines.

              The  set:<tag>  construct sets the tag whenever this --dhcp-host
              directive is in use. This can be used to selectively  send  DHCP
              options  just  for  this host. More than one tag can be set in a
              --dhcp-host directive (but not in other places where "set:<tag>"
              is  allowed).  When a host matches any --dhcp-host directive (or
              one implied by /etc/ethers) then the special tag "known" is set.
              This  allows  dnsmasq  to  be configured to ignore requests from
              unknown machines  using  --dhcp-ignore=tag:!known  If  the  host
              matches  only  a  --dhcp-host  directive  which  cannot  be used
              because it specifies an address on  different  subnet,  the  tag
              "known-othernet" is set.

              The  tag:<tag>  construct filters which dhcp-host directives are
              used. Tagged directives are used in preference to untagged ones.

              Ethernet addresses (but not client-ids) may have wildcard bytes,
              so  for  example  --dhcp-host=00:20:e0:3b:13:*,ignore will cause
              dnsmasq to ignore a range of hardware addresses. Note  that  the
              "*" will need to be escaped or quoted on a command line, but not
              in the configuration file.

              Hardware addresses normally match any network (ARP) type, but it
              is  possible  to restrict them to a single ARP type by preceding
              them  with  the  ARP-type  (in  HEX)   and   "-".   so   --dhcp-
              host=06-00:20:e0:3b:13:af,1.2.3.4  will  only match a Token-Ring
              hardware address, since the ARP-address type for token  ring  is
              6.

              As  a  special  case,  in DHCPv4, it is possible to include more
              than      one      hardware      address.      eg:       --dhcp-
              host=11:22:33:44:55:66,12:34:56:78:90:12,192.168.0.2 This allows
              an IP address to be associated with multiple hardware addresses,
              and  gives  dnsmasq permission to abandon a DHCP lease to one of
              the hardware addresses when another one asks for a lease. Beware
              that this is a dangerous thing to do, it will only work reliably
              if only one of the hardware addresses is active at any time  and
              there  is  no  way  for  dnsmasq  to  enforce  this.  It is, for
              instance, useful to allocate a stable IP  address  to  a  laptop
              which has both wired and wireless interfaces.

       --dhcp-hostsfile=<path>
              Read  DHCP host information from the specified file. If a direc-
              tory is given, then read all the files contained in that  direc-
              tory. The file contains information about one host per line. The
              format of a line is the same as text to  the  right  of  '='  in
              --dhcp-host.  The  advantage of storing DHCP host information in
              this file is that it can be changed without re-starting dnsmasq:
              the file will be re-read when dnsmasq receives SIGHUP.

       --dhcp-optsfile=<path>
              Read  DHCP  option  information  from  the specified file.  If a
              directory is given, then read all the files  contained  in  that
              directory. The advantage of using this option is the same as for
              --dhcp-hostsfile: the --dhcp-optsfile will be re-read when  dns-
              masq  receives  SIGHUP.  Note  that it is possible to encode the
              information in a --dhcp-boot flag as  DHCP  options,  using  the
              options  names bootfile-name, server-ip-address and tftp-server.
              This allows these to be included in a --dhcp-optsfile.

       --dhcp-hostsdir=<path>
              This is equivalent to --dhcp-hostsfile, except for  the  follow-
              ing.  The  path MUST be a directory, and not an individual file.
              Changed or new files within the  directory  are  read  automati-
              cally, without the need to send SIGHUP.  If a file is deleted or
              changed after it has been read by dnsmasq, then the host  record
              it  contained will remain until dnsmasq receives a SIGHUP, or is
              restarted; ie host records are only added dynamically.

       --dhcp-optsdir=<path>
              This is equivalent  to  --dhcp-optsfile,  with  the  differences
              noted for --dhcp-hostsdir.

       -Z, --read-ethers
              Read  /etc/ethers  for  information  about  hosts  for  the DHCP
              server. The format of /etc/ethers is a  hardware  address,  fol-
              lowed  by either a hostname or dotted-quad IP address. When read
              by dnsmasq these lines have exactly the same effect  as  --dhcp-
              host options containing the same information. /etc/ethers is re-
              read when dnsmasq receives SIGHUP. IPv6 addresses are  NOT  read
              from /etc/ethers.

       -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>]]
              Specify  different or extra options to DHCP clients. By default,
              dnsmasq sends some standard options to DHCP clients, the netmask
              and  broadcast  address  are set to the same as the host running
              dnsmasq, and the DNS server and default route  are  set  to  the
              address  of the machine running dnsmasq. (Equivalent rules apply
              for IPv6.) If the domain name option has been set, that is sent.
              This  configuration  allows  these defaults to be overridden, or
              other options specified. The option, to be sent may be given  as
              a decimal number or as "option:<option-name>" The option numbers
              are specified in RFC2132 and subsequent RFCs. The set of option-
              names  known  by  dnsmasq  can be discovered by running "dnsmasq
              --help dhcp".  For example, to set the default route  option  to
              192.168.4.4,  do  --dhcp-option=3,192.168.4.4 or --dhcp-option =
              option:router, 192.168.4.4 and to set the time-server address to
              192.168.0.4,  do --dhcp-option = 42,192.168.0.4 or --dhcp-option
              = option:ntp-server, 192.168.0.4 The special address 0.0.0.0  is
              taken to mean "the address of the machine running dnsmasq".

              Data   types   allowed  are  comma  separated  dotted-quad  IPv4
              addresses, []-wrapped IPv6 addresses, a decimal  number,  colon-
              separated hex digits and a text string. If the optional tags are
              given then this option is  only  sent  when  all  the  tags  are
              matched.

              Special processing is done on a text argument for option 119, to
              conform with RFC 3397. Text or dotted-quad IP addresses as argu-
              ments  to option 120 are handled as per RFC 3361. Dotted-quad IP
              addresses which are followed by a slash and then a netmask  size
              are encoded as described in RFC 3442.

              IPv6  options are specified using the option6: keyword, followed
              by the option number or option name. The IPv6 option name  space
              is  disjoint  from the IPv4 option name space. IPv6 addresses in
              options must be bracketed with  square  brackets,  eg.   --dhcp-
              option=option6:ntp-server,[1234::56]  For  IPv6, [::] means "the
              global address of the machine running dnsmasq", whilst  [fd00::]
              is  replaced  with  the ULA, if it exists, and [fe80::] with the
              link-local address.

              Be careful: no checking is done that the correct  type  of  data
              for  the option number is sent, it is quite possible to persuade
              dnsmasq to generate illegal DHCP packets with injudicious use of
              this  flag.  When  the  value  is a decimal number, dnsmasq must
              determine how large the data item is. It does this by  examining
              the  option  number  and/or  the value, but can be overridden by
              appending a single letter flag as follows: b = one byte, s = two
              bytes,  i  = four bytes. This is mainly useful with encapsulated
              vendor class options (see below) where dnsmasq cannot  determine
              data  size  from  the  option number. Option data which consists
              solely of periods and digits will be interpreted by  dnsmasq  as
              an  IP  address, and inserted into an option as such. To force a
              literal string, use quotes. For instance when using option 66 to
              send  a  literal IP address as TFTP server name, it is necessary
              to do --dhcp-option=66,"1.2.3.4"

              Encapsulated Vendor-class options may also  be  specified  (IPv4
              only)   using  --dhcp-option:  for  instance  --dhcp-option=ven-
              dor:PXEClient,1,0.0.0.0 sends the encapsulated vendor class-spe-
              cific  option "mftp-address=0.0.0.0" to any client whose vendor-
              class matches "PXEClient". The  vendor-class  matching  is  sub-
              string  based (see --dhcp-vendorclass for details). If a vendor-
              class option (number 60) is sent by dnsmasq, then that  is  used
              for  selecting encapsulated options in preference to any sent by
              the client. It is possible to omit the  vendorclass  completely;
              --dhcp-option=vendor:,1,0.0.0.0  in  which case the encapsulated
              option is always sent.

              Options may be encapsulated (IPv4 only)  within  other  options:
              for  instance  --dhcp-option=encap:175,  190, iscsi-client0 will
              send option 175, within which is the  option  190.  If  multiple
              options  are  given  which are encapsulated with the same option
              number then they will be correctly combined  into  one  encapsu-
              lated option.  encap: and vendor: are may not both be set in the
              same --dhcp-option.

              The final variant on encapsulated options is "Vendor-Identifying
              Vendor  Options" as specified by RFC3925. These are denoted like
              this: --dhcp-option=vi-encap:2, 10, text The number in  the  vi-
              encap:  section  is  the IANA enterprise number used to identify
              this option. This form of encapsulation is supported in IPv6.

              The address 0.0.0.0 is not  treated  specially  in  encapsulated
              options.

       --dhcp-option-force=[tag:<tag>,[tag:<tag>,]][encap:<opt>,][vi-
       encap:<enterprise>,][vendor:[<vendor-class>],]<opt>,[<value>[,<value>]]
              This works in exactly the same way as --dhcp-option except  that
              the  option will always be sent, even if the client does not ask
              for it in the parameter request list. This is sometimes  needed,
              for example when sending options to PXELinux.

       --dhcp-no-override
              (IPv4  only)  Disable re-use of the DHCP servername and filename
              fields as extra option space. If it can, dnsmasq moves the  boot
              server  and filename information (from --dhcp-boot) out of their
              dedicated fields into DHCP options. This make extra space avail-
              able in the DHCP packet for options but can, rarely, confuse old
              or broken clients. This flag forces "simple and safe"  behaviour
              to avoid problems in such a case.

       --dhcp-relay=<local address>,<server address>[,<interface]
              Configure  dnsmasq  to  do  DHCP  relay. The local address is an
              address allocated to an interface on the host  running  dnsmasq.
              All  DHCP requests arriving on that interface will we relayed to
              a remote DHCP server at the server address. It  is  possible  to
              relay  from a single local address to multiple remote servers by
              using multiple --dhcp-relay configs with the same local  address
              and  different  server addresses. A server address must be an IP
              literal address, not a domain name. In the case of  DHCPv6,  the
              server   address  may  be  the  ALL_SERVERS  multicast  address,
              ff05::1:3. In this case the interface  must  be  given,  not  be
              wildcard,  and  is  used  to direct the multicast to the correct
              interface to reach the DHCP server.

              Access control for DHCP clients has the same rules  as  for  the
              DHCP  server,  see  --interface,  --except-interface,  etc.  The
              optional interface name in the --dhcp-relay config has a differ-
              ent  function:  it controls on which interface DHCP replies from
              the server will be accepted. This is intended for configurations
              which  have  three  interfaces: one being relayed from, a second
              connecting the DHCP server, and a third untrusted network, typi-
              cally  the  wider  internet.  It avoids the possibility of spoof
              replies arriving via this third interface.

              It is allowed to have dnsmasq act as a DHCP server on one set of
              interfaces  and  relay  from  a disjoint set of interfaces. Note
              that whilst it is quite possible to write  configurations  which
              appear  to  act  as  a server and a relay on the same interface,
              this is not supported: the relay function will take precedence.

              Both DHCPv4 and DHCPv6 relay is supported. It's not possible  to
              relay DHCPv4 to a DHCPv6 server or vice-versa.

       -U,    --dhcp-vendorclass=set:<tag>,[enterprise:<IANA-enterprise   num-
       ber>,]<vendor-class>
              Map from a vendor-class string to a tag. Most DHCP clients  pro-
              vide  a "vendor class" which represents, in some sense, the type
              of host. This option maps vendor classes to tags, so  that  DHCP
              options  may  be  selectively  delivered to different classes of
              hosts.  For   example   --dhcp-vendorclass=set:printers,Hewlett-
              Packard  JetDirect  will  allow  options  to  be set only for HP
              printers like so:  --dhcp-option=tag:printers,3,192.168.4.4  The
              vendor-class  string  is  substring  matched against the vendor-
              class supplied by the client, to allow fuzzy matching. The  set:
              prefix is optional but allowed for consistency.

              Note  that  in  IPv6  only, vendorclasses are namespaced with an
              IANA-allocated enterprise number. This is given with enterprise:
              keyword and specifies that only vendorclasses matching the spec-
              ified number should be searched.

       -j, --dhcp-userclass=set:<tag>,<user-class>
              Map from a user-class string to a tag (with substring  matching,
              like  vendor  classes). Most DHCP clients provide a "user class"
              which is configurable. This option maps user classes to tags, so
              that  DHCP  options  may  be  selectively delivered to different
              classes of hosts. It is possible, for instance to  use  this  to
              set a different printer server for hosts in the class "accounts"
              than for hosts in the class "engineering".

       -4, --dhcp-mac=set:<tag>,<MAC address>
              Map from a MAC address to a tag. The  MAC  address  may  include
              wildcards.  For  example --dhcp-mac=set:3com,01:34:23:*:*:* will
              set the tag "3com" for any host whose MAC  address  matches  the
              pattern.

       --dhcp-circuitid=set:<tag>,<circuit-id>,                        --dhcp-
       remoteid=set:<tag>,<remote-id>
              Map from RFC3046 relay agent options to tags. This data  may  be
              provided  by  DHCP  relay agents. The circuit-id or remote-id is
              normally given as colon-separated hex, but is also allowed to be
              a  simple string. If an exact match is achieved between the cir-
              cuit or agent ID and one provided by a relay agent, the  tag  is
              set.

              --dhcp-remoteid (but not --dhcp-circuitid) is supported in IPv6.

       --dhcp-subscrid=set:<tag>,<subscriber-id>
              (IPv4  and  IPv6)  Map  from  RFC3993  subscriber-id relay agent
              options to tags.

       --dhcp-proxy[=<ip addr>]......
              (IPv4 only) A normal DHCP relay agent is only  used  to  forward
              the initial parts of a DHCP interaction to the DHCP server. Once
              a client  is  configured,  it  communicates  directly  with  the
              server.  This  is undesirable if the relay agent is adding extra
              information to the DHCP packets, such as that  used  by  --dhcp-
              circuitid  and --dhcp-remoteid.  A full relay implementation can
              use the RFC 5107 serverid-override  option  to  force  the  DHCP
              server  to use the relay as a full proxy, with all packets pass-
              ing through it. This flag  provides  an  alternative  method  of
              doing  the  same thing, for relays which don't support RFC 5107.
              Given alone, it manipulates the server-id for  all  interactions
              via  relays.  If  a list of IP addresses is given, only interac-
              tions via relays at those addresses are affected.

       --dhcp-match=set:<tag>,<option     number>|option:<option     name>|vi-
       encap:<enterprise>[,<value>]
              Without  a  value, set the tag if the client sends a DHCP option
              of the given number or name. When a value is given, set the  tag
              only  if the option is sent and matches the value. The value may
              be of the form "01:ff:*:02" in which case the value  must  match
              (apart  from  wildcards)  but the option sent may have unmatched
              data past the end of the value. The value may  also  be  of  the
              same  form  as in --dhcp-option in which case the option sent is
              treated as an array, and one  element  must  match,  so  --dhcp-
              match=set:efi-ia32,option:client-arch,6  will  set the tag "efi-
              ia32" if the the number 6 appears in the list  of  architectures
              sent by the client in option 93. (See RFC 4578 for details.)  If
              the value is a string, substring matching is used.

              The  special  form  with  vi-encap:<enterprise  number>  matches
              against  vendor-identifying  vendor  classes  for  the specified
              enterprise. Please see RFC 3925 for more details of  these  rare
              and interesting beasts.

       --dhcp-name-match=set:<tag>,<name>[*]
              Set  the  tag  if  the  given name is supplied by a DHCP client.
              There may be a single trailing wildcard *, which has  the  usual
              meaning.  Combined  with  dhcp-ignore  or dhcp-ignore-names this
              gives the ability to ignore certain clients by name, or disallow
              certain hostnames from being claimed by a client.

       --tag-if=set:<tag>[,set:<tag>[,tag:<tag>[,tag:<tag>]]]
              Perform  boolean  operations  on  tags.  Any  tag  appearing  as
              set:<tag> is set if all the tags which appear as  tag:<tag>  are
              set,  (or unset when tag:!<tag> is used) If no tag:<tag> appears
              set:<tag> tags are set unconditionally.  Any number of set:  and
              tag:  forms  may  appear, in any order.  --tag-if lines are exe-
              cuted in order, so if the tag in  tag:<tag>  is  a  tag  set  by
              another  --tag-if,  the line which sets the tag must precede the
              one which tests it.

       -J, --dhcp-ignore=tag:<tag>[,tag:<tag>]
              When all the given tags appear in the tag set  ignore  the  host
              and do not allocate it a DHCP lease.

       --dhcp-ignore-names[=tag:<tag>[,tag:<tag>]]
              When  all the given tags appear in the tag set, ignore any host-
              name provided by the host. Note that, unlike  --dhcp-ignore,  it
              is permissible to supply no tags, in which case DHCP-client sup-
              plied hostnames are always ignored, and DHCP hosts are added  to
              the  DNS using only --dhcp-host configuration in dnsmasq and the
              contents of /etc/hosts and /etc/ethers.

       --dhcp-generate-names=tag:<tag>[,tag:<tag>]
              (IPv4 only) Generate a name for DHCP clients which do not other-
              wise have one, using the MAC address expressed in hex, separated
              by dashes. Note that if a host provides a name, it will be  used
              by preference to this, unless --dhcp-ignore-names is set.

       --dhcp-broadcast[=tag:<tag>[,tag:<tag>]]
              (IPv4  only)  When  all  the  given  tags appear in the tag set,
              always use broadcast to communicate with the  host  when  it  is
              unconfigured. It is permissible to supply no tags, in which case
              this is unconditional. Most DHCP clients  which  need  broadcast
              replies  set a flag in their requests so that this happens auto-
              matically, some old BOOTP clients do not.

       -M,           --dhcp-boot=[tag:<tag>,]<filename>,[<servername>[,<server
       address>|<tftp_servername>]]
              (IPv4 only) Set BOOTP options to be returned by the DHCP server.
              Server name and address are optional: if not provided, the  name
              is left empty, and the address set to the address of the machine
              running dnsmasq. If dnsmasq is providing  a  TFTP  service  (see
              --enable-tftp  )  then  only  the  filename  is required here to
              enable network booting.  If the optional tag(s) are given,  they
              must  match for this configuration to be sent.  Instead of an IP
              address, the TFTP server address can be given as a  domain  name
              which is looked up in /etc/hosts. This name can be associated in
              /etc/hosts with multiple IP addresses,  which  are  used  round-
              robin.   This facility can be used to load balance the tftp load
              among a set of servers.

       --dhcp-sequential-ip
              Dnsmasq is designed to choose  IP  addresses  for  DHCP  clients
              using a hash of the client's MAC address. This normally allows a
              client's address to remain stable long-term, even if the  client
              sometimes  allows its DHCP lease to expire. In this default mode
              IP addresses are distributed  pseudo-randomly  over  the  entire
              available address range. There are sometimes circumstances (typ-
              ically server deployment) where it is more convenient to have IP
              addresses  allocated  sequentially,  starting  from  the  lowest
              available address, and setting this flag enables this mode. Note
              that  in  the  sequential  mode,  clients which allow a lease to
              expire are much more likely to move IP address; for this  reason
              it should not be generally used.

       --dhcp-ignore-clid
              Dnsmasq is reading 'client identifier' (RFC 2131) option sent by
              clients (if available) to identify clients. This allow to  serve
              same  IP  address  for a host using several interfaces. Use this
              option to disable 'client identifier' reading,  i.e.  to  always
              identify a host using the MAC address.

       --pxe-service=[tag:<tag>,]<CSA>,<menu   text>[,<basename>|<bootservice-
       type>][,<server address>|<server_name>]
              Most uses of PXE boot-ROMS simply allow the PXE system to obtain
              an  IP  address  and then download the file specified by --dhcp-
              boot and execute it. However the PXE system is capable  of  more
              complex functions when supported by a suitable DHCP server.

              This  specifies  a  boot  option  which may appear in a PXE boot
              menu. <CSA> is client system type, only services of the  correct
              type  will  appear  in  a menu. The known types are x86PC, PC98,
              IA64_EFI,   Alpha,   Arc_x86,    Intel_Lean_Client,    IA32_EFI,
              X86-64_EFI,  Xscale_EFI,  BC_EFI,  ARM32_EFI  and  ARM64_EFI; an
              integer may be used for other types.  The  parameter  after  the
              menu  text  may  be a file name, in which case dnsmasq acts as a
              boot server and directs the PXE client to download the  file  by
              TFTP, either from itself ( --enable-tftp must be set for this to
              work) or another TFTP server if the final server address/name is
              given.  Note that the "layer" suffix (normally ".0") is supplied
              by PXE, and need not be added to  the  basename.  Alternatively,
              the  basename  may be a filename, complete with suffix, in which
              case no layer suffix is added. If an integer boot service  type,
              rather than a basename is given, then the PXE client will search
              for a suitable boot service for that type on the  network.  This
              search may be done by broadcast, or direct to a server if its IP
              address/name is provided.  If no boot service type  or  filename
              is  provided (or a boot service type of 0 is specified) then the
              menu entry will abort the net boot procedure and continue  boot-
              ing  from  local  media.  The  server  address can be given as a
              domain name which is looked up in /etc/hosts. This name  can  be
              associated  in  /etc/hosts with multiple IP addresses, which are
              used round-robin.

       --pxe-prompt=[tag:<tag>,]<prompt>[,<timeout>]
              Setting this provides a prompt to be displayed after  PXE  boot.
              If  the timeout is given then after the timeout has elapsed with
              no keyboard input, the first available menu option will be auto-
              matically executed. If the timeout is zero then the first avail-
              able menu item will be executed immediately. If --pxe-prompt  is
              omitted  the system will wait for user input if there are multi-
              ple items in the menu, but boot immediately  if  there  is  only
              one. See --pxe-service for details of menu items.

              Dnsmasq  supports  PXE  "proxy-DHCP",  in this case another DHCP
              server  on  the  network  is  responsible  for   allocating   IP
              addresses,  and dnsmasq simply provides the information given in
              --pxe-prompt and --pxe-service to allow netbooting. This mode is
              enabled using the proxy keyword in --dhcp-range.

       --dhcp-pxe-vendor=<vendor>[,...]
              According  to  UEFI and PXE specifications, DHCP packets between
              PXE clients and proxy PXE servers should have PXEClient in their
              vendor-class  field.  However,  the firmware of computers from a
              few vendors is customized to carry  a  different  identifier  in
              that  field.  This  option  is used to consider such identifiers
              valid for identifying PXE clients. For instance

              --dhcp-pxe-vendor=PXEClient,HW-Client

              will enable dnsmasq to also provide proxy PXE service  to  those
              PXE  clients  with  HW-Client  in  as their identifier.  >>>>>>>
              907def3... pxe: support pxe clients with custom vendor-class

       -X, --dhcp-lease-max=<number>
              Limits dnsmasq to the specified maximum number of  DHCP  leases.
              The  default  is 1000. This limit is to prevent DoS attacks from
              hosts which create thousands of leases and use lots of memory in
              the dnsmasq process.

       -K, --dhcp-authoritative
              Should be set when dnsmasq is definitely the only DHCP server on
              a network.  For DHCPv4, it changes the behaviour from strict RFC
              compliance  so that DHCP requests on unknown leases from unknown
              hosts are not ignored. This allows new  hosts  to  get  a  lease
              without  a  tedious  timeout  under  all  circumstances. It also
              allows dnsmasq to rebuild its lease database without each client
              needing  to  reacquire  a  lease,  if  the database is lost. For
              DHCPv6 it sets the priority in  replies  to  255  (the  maximum)
              instead of 0 (the minimum).

       --dhcp-rapid-commit
              Enable  DHCPv4  Rapid  Commit Option specified in RFC 4039. When
              enabled, dnsmasq will respond to a DHCPDISCOVER message  includ-
              ing  a Rapid Commit option with a DHCPACK including a Rapid Com-
              mit option and fully committed address and configuration  infor-
              mation. Should only be enabled if either the server is  the only
              server for the subnet, or multiple servers are present and  they
              each commit a binding for all clients.

       --dhcp-alternate-port[=<server port>[,<client port>]]
              (IPv4  only) Change the ports used for DHCP from the default. If
              this option is given alone, without arguments,  it  changes  the
              ports used for DHCP from 67 and 68 to 1067 and 1068. If a single
              argument is given, that port number is used for the  server  and
              the  port number plus one used for the client. Finally, two port
              numbers allows arbitrary specification of both server and client
              ports for DHCP.

       -3, --bootp-dynamic[=<network-id>[,<network-id>]]
              (IPv4  only)  Enable dynamic allocation of IP addresses to BOOTP
              clients. Use this with care, since each address allocated  to  a
              BOOTP  client  is  leased  forever, and therefore becomes perma-
              nently unavailable for re-use by other hosts. if this  is  given
              without  tags,  then  it unconditionally enables dynamic alloca-
              tion. With tags, only when the tags  are  all  set.  It  may  be
              repeated with different tag sets.

       -5, --no-ping
              (IPv4  only)  By default, the DHCP server will attempt to ensure
              that an address is not in use before allocating it to a host. It
              does  this  by  sending an ICMP echo request (aka "ping") to the
              address in question. If it gets a reply, then the  address  must
              already be in use, and another is tried. This flag disables this
              check. Use with caution.

       --log-dhcp
              Extra logging for DHCP: log all the options sent to DHCP clients
              and the tags used to determine them.

       --quiet-dhcp, --quiet-dhcp6, --quiet-ra
              Suppress  logging  of  the routine operation of these protocols.
              Errors and problems  will  still  be  logged.  --quiet-dhcp  and
              quiet-dhcp6 are over-ridden by --log-dhcp.

       -l, --dhcp-leasefile=<path>
              Use the specified file to store DHCP lease information.

       --dhcp-duid=<enterprise-id>,<uid>
              (IPv6  only)  Specify the server persistent UID which the DHCPv6
              server will use. This option is not normally required as dnsmasq
              creates  a  DUID  automatically  when  it  is first needed. When
              given, this option provides dnsmasq the data required to  create
              a  DUID-EN  type DUID. Note that once set, the DUID is stored in
              the lease database, so to change between DUID-EN  and  automati-
              cally  created  DUIDs  or vice-versa, the lease database must be
              re-initialised. The enterprise-id is assigned by IANA,  and  the
              uid is a string of hex octets unique to a particular device.

       -6 --dhcp-script=<path>
              Whenever  a  new DHCP lease is created, or an old one destroyed,
              or a TFTP file transfer completes, the executable  specified  by
              this  option  is  run.   <path> must be an absolute pathname, no
              PATH search occurs.  The arguments to  the  process  are  "add",
              "old" or "del", the MAC address of the host (or DUID for IPv6) ,
              the IP address, and the hostname, if known. "add" means a  lease
              has  been created, "del" means it has been destroyed, "old" is a
              notification of an existing  lease  when  dnsmasq  starts  or  a
              change  to  MAC  address or hostname of an existing lease (also,
              lease length or expiry and client-id, if --leasefile-ro  is  set
              and  lease  expiry  if  --script-on-renewal is set).  If the MAC
              address is from a network type other than ethernet, it will have
              the  network type prepended, eg "06-01:23:45:67:89:ab" for token
              ring. The process is run as  root  (assuming  that  dnsmasq  was
              originally  run as root) even if dnsmasq is configured to change
              UID to an unprivileged user.

              The environment is inherited from the invoker of  dnsmasq,  with
              some or all of the following variables added

              For both IPv4 and IPv6:

              DNSMASQ_DOMAIN if the fully-qualified domain name of the host is
              known, this is set to the  domain part. (Note that the  hostname
              passed to the script as an argument is never fully-qualified.)

              If the client provides a hostname, DNSMASQ_SUPPLIED_HOSTNAME

              If  the  client provides user-classes, DNSMASQ_USER_CLASS0..DNS-
              MASQ_USER_CLASSn

              If dnsmasq was compiled with HAVE_BROKEN_RTC, then the length of
              the lease (in seconds) is stored in DNSMASQ_LEASE_LENGTH, other-
              wise  the   time   of   lease   expiry   is   stored   in   DNS-
              MASQ_LEASE_EXPIRES.  The number of seconds until lease expiry is
              always stored in DNSMASQ_TIME_REMAINING.

              If a lease used to have a hostname, which is removed,  an  "old"
              event  is generated with the new state of the lease, ie no name,
              and the former name is provided in the environment variable DNS-
              MASQ_OLD_HOSTNAME.

              DNSMASQ_INTERFACE  stores the name of the interface on which the
              request arrived; this is not set for "old" actions when  dnsmasq
              restarts.

              DNSMASQ_RELAY_ADDRESS  is set if the client used a DHCP relay to
              contact dnsmasq and the IP address of the relay is known.

              DNSMASQ_TAGS contains all the tags set during the DHCP  transac-
              tion, separated by spaces.

              DNSMASQ_LOG_DHCP is set if --log-dhcp is in effect.

              For IPv4 only:

              DNSMASQ_CLIENT_ID if the host provided a client-id.

              DNSMASQ_CIRCUIT_ID,  DNSMASQ_SUBSCRIBER_ID, DNSMASQ_REMOTE_ID if
              a DHCP relay-agent added any of these options.

              If the client provides vendor-class, DNSMASQ_VENDOR_CLASS.

              DNSMASQ_REQUESTED_OPTIONS a string containing the decimal values
              in  the  Parameter  Request List option, comma separated, if the
              parameter request list option is provided by the client.

              For IPv6 only:

              If the client  provides  vendor-class,  DNSMASQ_VENDOR_CLASS_ID,
              containing  the  IANA  enterprise  id  for  the  class, and DNS-
              MASQ_VENDOR_CLASS0..DNSMASQ_VENDOR_CLASSn for the data.

              DNSMASQ_SERVER_DUID containing the DUID of the server:  this  is
              the same for every call to the script.

              DNSMASQ_IAID  containing the IAID for the lease. If the lease is
              a temporary allocation, this is prefixed to 'T'.

              DNSMASQ_MAC containing the MAC address of the client, if known.

              Note that the supplied hostname, vendorclass and userclass  data
              is only  supplied for "add" actions or "old" actions when a host
              resumes an existing lease, since these data are not held in dns-
              masq's lease database.



              All  file  descriptors are closed except stdin, which is open to
              /dev/null, and stdout and stderr which capture output  for  log-
              ging  by dnsmasq.  (In debug mode, stdio, stdout and stderr file
              are left as those inherited from the invoker of dnsmasq).

              The script is not invoked concurrently: at most one instance  of
              the  script  is  ever  running (dnsmasq waits for an instance of
              script to exit before running the next). Changes  to  the  lease
              database  are  which require the script to be invoked are queued
              awaiting exit of a running instance.  If  this  queueing  allows
              multiple state changes occur to a single lease before the script
              can be run then earlier states are  discarded  and  the  current
              state of that lease is reflected when the script finally runs.

              At  dnsmasq startup, the script will be invoked for all existing
              leases as they are read from the lease file. Expired leases will
              be  called  with  "del"  and  others  with  "old".  When dnsmasq
              receives a HUP signal, the script will be invoked  for  existing
              leases with an "old" event.


              There  are  four  further  actions which may appear as the first
              argument to the script, "init", "arp-add", "arp-del" and "tftp".
              More may be added in the future, so scripts should be written to
              ignore unknown actions. "init" is described  below  in  --lease-
              file-ro  The  "tftp" action is invoked when a TFTP file transfer
              completes: the arguments are the file size in bytes, the address
              to  which  the  file  was sent, and the complete pathname of the
              file.

              The "arp-add" and "arp-del" actions are only called  if  enabled
              with  --script-arp  They are are supplied with a MAC address and
              IP address as arguments. "arp-add" indicates the  arrival  of  a
              new entry in the ARP or neighbour table, and "arp-del" indicates
              the deletion of same.


       --dhcp-luascript=<path>
              Specify a script written in Lua, to be run when leases are  cre-
              ated,  destroyed or changed. To use this option, dnsmasq must be
              compiled with the correct support. The Lua interpreter  is  ini-
              tialised  once,  when  dnsmasq  starts, so that global variables
              persist between lease events. The Lua code must define  a  lease
              function, and may provide init and shutdown functions, which are
              called, without arguments when dnsmasq starts up and terminates.
              It may also provide a tftp function.

              The  lease function receives the information detailed in --dhcp-
              script.  It gets two arguments, firstly the action, which  is  a
              string  containing,  "add", "old" or "del", and secondly a table
              of tag value pairs. The tags mostly correspond to  the  environ-
              ment  variables  detailed  above,  for instance the tag "domain"
              holds the same data as the environment variable  DNSMASQ_DOMAIN.
              There are a few extra tags which hold the data supplied as argu-
              ments to --dhcp-script.  These are mac_address,  ip_address  and
              hostname  for IPv4, and client_duid, ip_address and hostname for
              IPv6.

              The tftp function is called in the same way as the  lease  func-
              tion,   and   the  table  holds  the  tags  destination_address,
              file_name and file_size.

              The arp and arp-old functions are called only when enabled  with
              --script-arp  and  have a table which holds the tags mac_address
              and client_address.

       --dhcp-scriptuser
              Specify the user as which to run the lease-change script or  Lua
              script.  This  defaults  to  root, but can be changed to another
              user using this flag.

       --script-arp
              Enable the "arp" and "arp-old" functions  in  the  --dhcp-script
              and --dhcp-luascript.

       -9, --leasefile-ro
              Completely  suppress  use  of  the lease database file. The file
              will not be created, read, or written. Change the way the lease-
              change  script (if one is provided) is called, so that the lease
              database may be maintained in external storage by the script. In
              addition  to  the invocations  given in --dhcp-script the lease-
              change script is called once, at dnsmasq startup, with the  sin-
              gle  argument  "init".  When  called like this the script should
              write the saved state of the lease database, in  dnsmasq  lease-
              file  format,  to  stdout  and exit with zero exit code. Setting
              this option also forces the leasechange script to be  called  on
              changes to the client-id and lease length and expiry time.

       --script-on-renewal
              Call  the  DHCP  script  when the lease expiry time changes, for
              instance when the lease is renewed.

       --bridge-interface=<interface>,<alias>[,<alias>]
              Treat DHCP (v4 and v6) requests and IPv6 Router Solicit  packets
              arriving at any of the <alias> interfaces as if they had arrived
              at <interface>.  This option allows dnsmasq to provide DHCP  and
              RA  service  over unaddressed and unbridged Ethernet interfaces,
              e.g. on an OpenStack compute host where each such interface is a
              TAP  interface  to  a  VM,  or as in "old style bridging" on BSD
              platforms.  A trailing '*' wildcard can be used in each <alias>.

              It is permissible to add more than one alias using more than one
              --bridge-interface       option       since      --bridge-inter-
              face=int1,alias1,alias2 is exactly equivalent to --bridge-inter-
              face=int1,alias1 --bridge-interface=int1,alias2

       --shared-network=<interface>,<addr>
       --shared-network=<addr>,<addr>
              The  DHCP  server  determines  which DHCP ranges are useable for
              allocating an address to a DHCP client based on the network from
              which  the DHCP request arrives, and the IP configuration of the
              server's interface on that network.  The  shared-network  option
              extends the available subnets (and therefore DHCP ranges) beyond
              the subnets configured on the arrival interface.

              The first argument is either the name of  an  interface,  or  an
              address  that is configured on a local interface, and the second
              argument is an address which defines  another  subnet  on  which
              addresses can be allocated.

              To  be  useful, there must be a suitable dhcp-range which allows
              address allocation on  this  subnet  and  this  dhcp-range  MUST
              include the netmask.

              Using  shared-network also needs extra consideration of routing.
              Dnsmasq does not have the usual  information  that  it  uses  to
              determine  the  default  route,  so the default route option (or
              other routing) MUST be configured manually. The client must have
              a route to the server: if the two-address form of shared-network
              is used, this needs to be to the first specified address. If the
              interface,address  form is used, there must be a route to all of
              the addresses configured on the interface.

              The two-address form of shared-network is  also  usable  with  a
              DHCP  relay:  the  first address is the address of the relay and
              the second, as before, specifies an extra subnet which addresses
              may be allocated from.


       -s, --domain=<domain>[,<address range>[,local]]
              Specifies  DNS  domains  for  the DHCP server. Domains may be be
              given unconditionally (without the IP range) or for  limited  IP
              ranges.  This has two effects; firstly it causes the DHCP server
              to return the domain to any hosts which request it, and secondly
              it  sets  the domain which it is legal for DHCP-configured hosts
              to claim. The intention is to constrain  hostnames  so  that  an
              untrusted  host on the LAN cannot advertise its name via DHCP as
              e.g. "microsoft.com" and capture traffic not meant for it. If no
              domain suffix is specified, then any DHCP hostname with a domain
              part (ie with a period) will be disallowed and logged. If suffix
              is  specified,  then  hostnames  with a domain part are allowed,
              provided the domain part matches the suffix. In addition, when a
              suffix is set then hostnames without a domain part have the suf-
              fix added as an optional domain part. Eg on my network I can set
              --domain=thekelleys.org.uk  and  have a machine whose DHCP host-
              name is "laptop". The IP address for that machine  is  available
              from dnsmasq both as "laptop" and "laptop.thekelleys.org.uk". If
              the domain is given as "#" then the  domain  is  read  from  the
              first "search" directive in /etc/resolv.conf (or equivalent).

              The  address  range can be of the form <ip address>,<ip address>
              or <ip address>/<netmask> or just a  single  <ip  address>.  See
              --dhcp-fqdn  which  can  change  the  behaviour  of dnsmasq with
              domains.

              If the address range is given as ip-address/network-size, then a
              additional  flag "local" may be supplied which has the effect of
              adding --local declarations for forward and reverse DNS queries.
              Eg.   --domain=thekelleys.org.uk,192.168.0.0/24,local is identi-
              cal         to         --domain=thekelleys.org.uk,192.168.0.0/24
              --local=/thekelleys.org.uk/ --local=/0.168.192.in-addr.arpa/ The
              network size must be 8, 16 or 24 for this to be legal.

       --dhcp-fqdn
              In the default mode, dnsmasq inserts the  unqualified  names  of
              DHCP  clients  into  the DNS. For this reason, the names must be
              unique, even if two clients which have the same name are in dif-
              ferent  domains.  If  a second DHCP client appears which has the
              same name as an existing client, the name is transferred to  the
              new  client.  If --dhcp-fqdn is set, this behaviour changes: the
              unqualified name is no longer put in the DNS, only the qualified
              name.  Two  DHCP  clients  with  the same name may both keep the
              name, provided that the domain part is different (ie  the  fully
              qualified  names differ.) To ensure that all names have a domain
              part, there must be at least --domain without an address  speci-
              fied when --dhcp-fqdn is set.

       --dhcp-client-update
              Normally,  when  giving  a DHCP lease, dnsmasq sets flags in the
              FQDN option to tell the client not to attempt a DDNS update with
              its  name  and  IP  address. This is because the name-IP pair is
              automatically added into dnsmasq's  DNS  view.  This  flag  sup-
              presses  that  behaviour, this is useful, for instance, to allow
              Windows clients to update Active Directory servers. See RFC 4702
              for details.

       --enable-ra
              Enable  dnsmasq's  IPv6  Router  Advertisement  feature.  DHCPv6
              doesn't handle complete network configuration in the same way as
              DHCPv4. Router discovery and (possibly) prefix discovery for au-
              tonomous address creation are handled by a  different  protocol.
              When  DHCP  is in use, only a subset of this is needed, and dns-
              masq can handle it, using existing DHCP configuration to provide
              most  data.  When RA is enabled, dnsmasq will advertise a prefix
              for each --dhcp-range, with  default  router   as  the  relevant
              link-local  address  on the machine running dnsmasq. By default,
              the "managed address" bits are set, and the "use SLAAC"  bit  is
              reset.  This can be changed for individual subnets with the mode
              keywords described in --dhcp-range.  RFC6106 DNS parameters  are
              included  in  the advertisements. By default, the relevant link-
              local address of the machine running dnsmasq is sent  as  recur-
              sive  DNS server. If provided, the DHCPv6 options dns-server and
              domain-search are used for the DNS server (RDNSS) and the domain
              search list (DNSSL).

       --ra-param=<interface>,[mtu:<integer>|<interface>|off,][high,|low,]<ra-
       interval>[,<router lifetime>]
              Set non-default values for router  advertisements  sent  via  an
              interface. The priority field for the router may be altered from
              the default of medium with eg --ra-param=eth0,high.  The  inter-
              val  between  router advertisements may be set (in seconds) with
              --ra-param=eth0,60.  The lifetime of the route may be changed or
              set to zero, which allows a router to advertise prefixes but not
              a route via itself.  --ra-param=eth0,0,0 (A value  of  zero  for
              the  interval  means the default value.) All four parameters may
              be set at once.  --ra-param=eth0,mtu:1280,low,60,1200

              The interface field may include a wildcard.

              The mtu: parameter may be an arbitrary interface name, in  which
              case  the  MTU  value for that interface is used. This is useful
              for (eg) advertising the MTU of a WAN  interface  on  the  other
              interfaces of a router.

       --dhcp-reply-delay=[tag:<tag>,]<integer>
              Delays  sending DHCPOFFER and PROXYDHCP replies for at least the
              specified number of seconds.  This can be used as workaround for
              bugs  in  PXE boot firmware that does not function properly when
              receiving an instant reply.  This option takes into account  the
              time already spent waiting (e.g. performing ping check) if any.

       --enable-tftp[=<interface>[,<interface>]]
              Enable the TFTP server function. This is deliberately limited to
              that needed to net-boot a client. Only reading is  allowed;  the
              tsize  and  blksize extensions are supported (tsize is only sup-
              ported in octet mode). Without an argument, the TFTP service  is
              provided  to the same set of interfaces as DHCP service.  If the
              list of interfaces is provided, that  defines  which  interfaces
              receive TFTP service.

       --tftp-root=<directory>[,<interface>]
              Look  for  files  to  transfer  using TFTP relative to the given
              directory. When this is set, TFTP paths which include  ".."  are
              rejected,  to  stop  clients getting outside the specified root.
              Absolute paths (starting with /) are allowed, but they  must  be
              within  the  tftp-root.  If  the  optional interface argument is
              given, the directory is only used for  TFTP  requests  via  that
              interface.

       --tftp-no-fail
              Do  not  abort  startup  if  specified tftp root directories are
              inaccessible.

       --tftp-unique-root[=ip|mac]
              Add the IP or hardware address of the TFTP client as a path com-
              ponent  on the end of the TFTP-root. Only valid if a --tftp-root
              is set and the directory exists.  Defaults to adding IP  address
              (in  standard dotted-quad format).  For instance, if --tftp-root
              is "/tftp" and client 1.2.3.4 requests file  "myfile"  then  the
              effective  path  will be "/tftp/1.2.3.4/myfile" if /tftp/1.2.3.4
              exists or /tftp/myfile otherwise.  When "=mac" is  specified  it
              will append the MAC address instead, using lowercase zero padded
              digits separated by dashes, e.g.:  01-02-03-04-aa-bb  Note  that
              resolving MAC addresses is only possible if the client is in the
              local network or obtained a DHCP lease from us.

       --tftp-secure
              Enable TFTP secure mode: without this, any file which  is  read-
              able  by  the  dnsmasq  process under normal unix access-control
              rules is available via TFTP.  When  the  --tftp-secure  flag  is
              given,  only files owned by the user running the dnsmasq process
              are accessible. If dnsmasq is being run as root, different rules
              apply:  --tftp-secure  has  no effect, but only files which have
              the world-readable bit set are accessible. It is not recommended
              to  run  dnsmasq  as  root  with TFTP enabled, and certainly not
              without specifying --tftp-root. Doing so can expose  any  world-
              readable file on the server to any host on the net.

       --tftp-lowercase
              Convert  filenames  in  TFTP  requests to all lowercase. This is
              useful for requests from  Windows  machines,  which  have  case-
              insensitive  filesystems  and  tend  to play fast-and-loose with
              case in filenames.  Note that dnsmasq's tftp server always  con-
              verts "\" to "/" in filenames.

       --tftp-max=<connections>
              Set  the  maximum number of concurrent TFTP connections allowed.
              This defaults to 50. When serving a large number of TFTP connec-
              tions,  per-process  file  descriptor limits may be encountered.
              Dnsmasq needs one file descriptor for each concurrent TFTP  con-
              nection and one file descriptor per unique file (plus a few oth-
              ers). So serving the same file simultaneously to n clients  will
              use  require  about  n  + 10 file descriptors, serving different
              files simultaneously to n clients will require about (2*n) +  10
              descriptors.  If --tftp-port-range is given, that can affect the
              number of concurrent connections.

       --tftp-mtu=<mtu size>
              Use size as the ceiling of the MTU supported by the  intervening
              network when negotiating TFTP blocksize, overriding the MTU set-
              ting of the local interface  if it is larger.

       --tftp-no-blocksize
              Stop the TFTP server from  negotiating  the  "blocksize"  option
              with  a  client. Some buggy clients request this option but then
              behave badly when it is granted.

       --tftp-port-range=<start>,<end>
              A TFTP server listens on a well-known port (69)  for  connection
              initiation,  but  it  also uses a dynamically-allocated port for
              each connection. Normally these are allocated  by  the  OS,  but
              this  option  specifies  a range of ports for use by TFTP trans-
              fers. This can be useful when TFTP has to traverse  a  firewall.
              The  start of the range cannot be lower than 1025 unless dnsmasq
              is running as root. The number of concurrent TFTP connections is
              limited by the size of the port range.

       --tftp-single-port
              Run  in  a  mode  where the TFTP server uses ONLY the well-known
              port (69) for its end of the TFTP transfer. This allows TFTP  to
              work  when  there  in NAT is the path between client and server.
              Note that this is not strictly compliant with the RFCs  specify-
              ing the TFTP protocol: use at your own risk.

       -C, --conf-file=<file>
              Specify  a configuration file. The presence of this option stops
              dnsmasq from reading the default  configuration  file  (normally
              /etc/dnsmasq.conf). Multiple files may be specified by repeating
              the option either on the command line or in configuration files.
              A  filename  of  "-"  causes  dnsmasq to read configuration from
              stdin.

       -7, --conf-dir=<directory>[,<file-extension>......],
              Read all the files  in  the  given  directory  as  configuration
              files.  If  extension(s) are given, any files which end in those
              extensions are skipped. Any files whose names end in ~ or  start
              with . or start and end with # are always skipped. If the exten-
              sion starts with * then only files which have that extension are
              loaded.  So  --conf-dir=/path/to/dir,*.conf loads all files with
              the suffix .conf in /path/to/dir. This flag may be given on  the
              command  line  or  in  a configuration file. If giving it on the
              command line, be sure to escape * characters. Files  are  loaded
              in alphabetical order of filename.

       --servers-file=<file>
              A  special  case  of  --conf-file which differs in two respects.
              Firstly, only --server and --rev-server are allowed in the  con-
              figuration  file included. Secondly, the file is re-read and the
              configuration therein is updated when dnsmasq receives SIGHUP.

CONFIG FILE
       At startup, dnsmasq reads /etc/dnsmasq.conf, if it exists. (On FreeBSD,
       the  file is /usr/local/etc/dnsmasq.conf ) (but see the --conf-file and
       --conf-dir options.) The format of this file consists of one option per
       line,  exactly  as the long options detailed in the OPTIONS section but
       without the leading "--".  Lines  starting  with  #  are  comments  and
       ignored.  For  options which may only be specified once, the configura-
       tion file overrides the command line.  Quoting is allowed in  a  config
       file:  between  "  quotes the special meanings of ,:. and # are removed
       and the following escapes are allowed: \\ \" \t \e \b \r  and  \n.  The
       later corresponding to tab, escape, backspace, return and newline.


ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:


       +---------------+-------------------------+
       |ATTRIBUTE TYPE |    ATTRIBUTE VALUE      |
       +---------------+-------------------------+
       |Availability   | service/network/dnsmasq |
       +---------------+-------------------------+
       |Stability      | Uncommitted             |
       +---------------+-------------------------+

NOTES
       When  it  receives a SIGHUP, dnsmasq clears its cache and then re-loads
       /etc/hosts and /etc/ethers and  any  file  given  by  --dhcp-hostsfile,
       --dhcp-hostsdir,   --dhcp-optsfile,   --dhcp-optsdir,  --addn-hosts  or
       --hostsdir.  The DHCP lease change script is called  for  all  existing
       DHCP leases. If --no-poll is set SIGHUP also re-reads /etc/resolv.conf.
       SIGHUP does NOT re-read the configuration file.

       When it receives a SIGUSR1, dnsmasq writes  statistics  to  the  system
       log.  It  writes  the cache size, the number of names which have had to
       removed from the cache before they expired in order to  make  room  for
       new  names  and  the total number of names that have been inserted into
       the cache. The number of cache  hits  and  misses  and  the  number  of
       authoritative queries answered are also given. For each upstream server
       it gives the number of queries sent, and the number which  resulted  in
       an  error.  In --no-daemon mode or when full logging is enabled (--log-
       queries), a complete dump of the contents of the cache is made.

       The cache statistics are also  available  in  the  DNS  as  answers  to
       queries  of  class  CHAOS and type TXT in domain bind. The domain names
       are  cachesize.bind,  insertions.bind,   evictions.bind,   misses.bind,
       hits.bind,  auth.bind  and  servers.bind.  An  example command to query
       this, using the dig utility would be

       dig +short chaos txt cachesize.bind


       When it receives SIGUSR2 and it is logging direct to a file (see --log-
       facility ) dnsmasq will close and reopen the log file. Note that during
       this operation, dnsmasq will not be running as root. When it first cre-
       ates  the logfile dnsmasq changes the ownership of the file to the non-
       root user it will run as. Logrotate should be configured  to  create  a
       new  log  file with the ownership which matches the existing one before
       sending SIGUSR2.  If TCP DNS queries are in progress, the  old  logfile
       will  remain open in child processes which are handling TCP queries and
       may continue to be written. There is a  limit  of  150  seconds,  after
       which all existing TCP processes will have expired: for this reason, it
       is not wise to configure logfile compression for  logfiles  which  have
       just been rotated. Using logrotate, the required options are create and
       delaycompress.



       Dnsmasq is a DNS query forwarder: it  is  not  capable  of  recursively
       answering arbitrary queries starting from the root servers but forwards
       such queries to a fully recursive upstream DNS server  which  is  typi-
       cally provided by an ISP. By default, dnsmasq reads /etc/resolv.conf to
       discover the IP addresses of the upstream nameservers  it  should  use,
       since  the  information  is typically stored there. Unless --no-poll is
       used, dnsmasq checks the  modification  time  of  /etc/resolv.conf  (or
       equivalent  if  --resolv-file  is  used) and re-reads it if it changes.
       This allows the DNS servers to be set dynamically by PPP or DHCP  since
       both protocols provide the information.  Absence of /etc/resolv.conf is
       not an error since it may not have been created before a PPP connection
       exists.  Dnsmasq simply keeps checking in case /etc/resolv.conf is cre-
       ated at  any  time.  Dnsmasq  can  be  told  to  parse  more  than  one
       resolv.conf  file.  This is useful on a laptop, where both PPP and DHCP
       may be used: dnsmasq can be set to poll both  /etc/ppp/resolv.conf  and
       /etc/dhcpc/resolv.conf  and  will use the contents of whichever changed
       last, giving automatic switching between DNS servers.

       Upstream servers may also be specified on the command line  or  in  the
       configuration  file.  These  server  specifications  optionally  take a
       domain name which tells dnsmasq to use that server only to  find  names
       in that particular domain.

       In  order to configure dnsmasq to act as cache for the host on which it
       is running, put "nameserver 127.0.0.1"  in  /etc/resolv.conf  to  force
       local  processes  to  send  queries to dnsmasq. Then either specify the
       upstream servers directly to dnsmasq  using  --server  options  or  put
       their  addresses  real in another file, say /etc/resolv.dnsmasq and run
       dnsmasq with the --resolv-file /etc/resolv.dnsmasq option. This  second
       technique  allows  for dynamic update of the server addresses by PPP or
       DHCP.

       Addresses in /etc/hosts will "shadow" different addresses for the  same
       names  in  the  upstream  DNS, so "mycompany.com 1.2.3.4" in /etc/hosts
       will ensure that queries for "mycompany.com" always return 1.2.3.4 even
       if  queries  in  the  upstream  DNS  would otherwise return a different
       address. There is one exception to this: if the upstream DNS contains a
       CNAME  which  points  to  a  shadowed  name,  then looking up the CNAME
       through dnsmasq will result in the unshadowed address  associated  with
       the  target  of  the  CNAME.  To  work  around  this,  add the CNAME to
       /etc/hosts so that the CNAME is shadowed too.


       The tag system works as follows: For each DHCP  request,  dnsmasq  col-
       lects a set of valid tags from active configuration lines which include
       set:<tag>, including one from the --dhcp-range  used  to  allocate  the
       address,  one from any matching --dhcp-host (and "known" or "known-oth-
       ernet" if a --dhcp-host matches) The  tag  "bootp"  is  set  for  BOOTP
       requests,  and  a  tag whose name is the name of the interface on which
       the request arrived is also set.

       Any configuration lines which include one or more tag:<tag>  constructs
       will  only  be  valid  if  all that tags are matched in the set derived
       above. Typically this is --dhcp-option.  --dhcp-option which  has  tags
       will be used in preference  to an untagged --dhcp-option, provided that
       _all_ the tags match somewhere in the set collected as described above.
       The  prefix  '!'  on  a  tag  means  'not'  so  --dhcp-option=tag:!pur-
       ple,3,1.2.3.4 sends the option when the tag purple is not in the set of
       valid  tags.  (If using this in a command line rather than a configura-
       tion file, be sure to escape !, which is a shell metacharacter)

       When selecting --dhcp-options, a tag from --dhcp-range is second  class
       relative  to  other tags, to make it easy to override options for indi-
       vidual   hosts,    so    --dhcp-range=set:interface1,......     --dhcp-
       host=set:myhost,.....          --dhcp-option=tag:interface1,option:nis-
       domain,"domain1"   --dhcp-option=tag:myhost,option:nis-domain,"domain2"
       will set the NIS-domain to domain1 for hosts in the range, but override
       that to domain2 for a particular host.


       Note that for --dhcp-range both tag:<tag> and set:<tag> are allowed, to
       both  select  the range in use based on (eg) --dhcp-host, and to affect
       the options sent, based on the range selected.

       This system evolved from an earlier, more limited one and for  backward
       compatibility  "net:"  may  be used instead of "tag:" and "set:" may be
       omitted. (Except in --dhcp-host, where "net:" may be  used  instead  of
       "set:".)  For  the same reason, '#' may be used instead of '!' to indi-
       cate NOT.

       The DHCP server in dnsmasq will function as a BOOTP server  also,  pro-
       vided that the MAC address and IP address for clients are given, either
       using --dhcp-host configurations or in /etc/ethers , and a --dhcp-range
       configuration  option  is present to activate the DHCP server on a par-
       ticular network. (Setting --bootp-dynamic removes the need  for  static
       address mappings.) The filename parameter in a BOOTP request is used as
       a tag, as is the tag "bootp", allowing some control  over  the  options
       returned to different classes of hosts.


       Source  code  for open source software components in Oracle Solaris can
       be found at https://www.oracle.com/downloads/opensource/solaris-source-
       code-downloads.html.

       This     software     was    built    from    source    available    at
       https://github.com/oracle/solaris-userland.   The  original   community
       source  was  downloaded from  http://www.thekelleys.org.uk/dnsmasq/dns-
       masq-2.84.tar.gz.

       Further information about this software can be found on the open source
       community website at http://www.thekelleys.org.uk/dnsmasq.

AUTHORITATIVE CONFIGURATION
       Configuring  dnsmasq  to  act as an authoritative DNS server is compli-
       cated by the fact  that  it  involves  configuration  of  external  DNS
       servers  to provide delegation. We will walk through three scenarios of
       increasing complexity. Prerequisites for all of these scenarios  are  a
       globally  accessible  IP  address, an A or AAAA record pointing to that
       address, and an external DNS server capable of doing delegation of  the
       zone  in question. For the first part of this explanation, we will call
       the A (or AAAA) record for the globally accessible address server.exam-
       ple.com, and the zone for which dnsmasq is authoritative our.zone.com.

       The  simplest configuration consists of two lines of dnsmasq configura-
       tion; something like

       --auth-server=server.example.com,eth0
       --auth-zone=our.zone.com,1.2.3.0/24

       and two records in the external DNS

       server.example.com       A    192.0.43.10
       our.zone.com            NS    server.example.com

       eth0 is the external network interface on which dnsmasq  is  listening,
       and has (globally accessible) address 192.0.43.10.

       Note that the external IP address may well be dynamic (ie assigned from
       an ISP by DHCP or PPP) If so, the A  record  must  be  linked  to  this
       dynamic assignment by one of the usual dynamic-DNS systems.

       A  more  complex,  but practically useful configuration has the address
       record for the globally accessible IP address residing in the  authori-
       tative  zone  which  dnsmasq  is serving, typically at the root. Now we
       have

       --auth-server=our.zone.com,eth0
       --auth-zone=our.zone.com,1.2.3.0/24

       our.zone.com             A    1.2.3.4
       our.zone.com            NS    our.zone.com

       The A record for our.zone.com has now become a glue record,  it  solves
       the chicken-and-egg problem of finding the IP address of the nameserver
       for our.zone.com when the A record is within that zone. Note that  this
       is  the  only role of this record: as dnsmasq is now authoritative from
       our.zone.com it too must provide this record. If the  external  address
       is static, this can be done with an /etc/hosts entry or --host-record.

       --auth-server=our.zone.com,eth0
       --host-record=our.zone.com,1.2.3.4
       --auth-zone=our.zone.com,1.2.3.0/24

       If  the  external  address  is  dynamic,  the  address  associated with
       our.zone.com must be derived from the address of  the  relevant  inter-
       face. This is done using --interface-name Something like:

       --auth-server=our.zone.com,eth0
       --interface-name=our.zone.com,eth0
       --auth-zone=our.zone.com,1.2.3.0/24,eth0

       (The  "eth0"  argument in --auth-zone adds the subnet containing eth0's
       dynamic address to the zone, so that the --interface-name  returns  the
       address in outside queries.)

       Our final configuration builds on that above, but also adds a secondary
       DNS server. This is another DNS server which learns the  DNS  data  for
       the  zone by doing zones transfer, and acts as a backup should the pri-
       mary server become inaccessible. The configuration of the secondary  is
       beyond  the scope of this man-page, but the extra configuration of dns-
       masq is simple:

       --auth-sec-servers=secondary.myisp.com

       and

       our.zone.com           NS    secondary.myisp.com

       Adding auth-sec-servers enables zone transfer in dnsmasq, to allow  the
       secondary to collect the DNS data. If you wish to restrict this data to
       particular hosts then

       --auth-peer=<IP address of secondary>

       will do so.

       Dnsmasq acts as an authoritative server for  in-addr.arpa and  ip6.arpa
       domains  associated with the subnets given in --auth-zone declarations,
       so reverse (address to name) lookups can be simply  configured  with  a
       suitable  NS  record,  for  instance  in  this  example, where we allow
       1.2.3.0/24 addresses.

        3.2.1.in-addr.arpa  NS    our.zone.com

       Note that at present, reverse (in-addr.arpa and ip6.arpa) zones are not
       available  in  zone transfers, so there is no point arranging secondary
       servers for reverse lookups.


       When dnsmasq is configured to act as an authoritative server, the  fol-
       lowing data is used to populate the authoritative zone.

       --mx-host,  --srv-host,  --dns-rr, --txt-record, --naptr-record, --caa-
       record, as long as the record names are in the authoritative domain.

       --cname as long as the record name is in  the authoritative domain.  If
       the  target of the CNAME is unqualified, then it  is qualified with the
       authoritative zone name. CNAME used in this way  (only)  may  be  wild-
       cards, as in

       --cname=*.example.com,default.example.com


       IPv4 and IPv6 addresses from /etc/hosts (and --addn-hosts ) and --host-
       record and --interface-name provided the address falls into one of  the
       subnets specified in the --auth-zone.

       Addresses  of  DHCP  leases, provided the address falls into one of the
       subnets specified in the --auth-zone.  (If constructed DHCP ranges  are
       is  use,  which depend on the address dynamically assigned to an inter-
       face, then the form of --auth-zone which defines subnets by the dynamic
       address  of  an  interface  should  be used to ensure this condition is
       met.)

       In the default mode, where a DHCP lease has an  unqualified  name,  and
       possibly  a  qualified name constructed using --domain then the name in
       the authoritative zone is constructed from the unqualified name and the
       zone's  domain.  This  may or may not equal that specified by --domain.
       If --dhcp-fqdn is set, then the fully qualified names  associated  with
       DHCP leases are used, and must match the zone's domain.




EXIT CODES
       0 - Dnsmasq successfully forked into the background, or terminated nor-
       mally if backgrounding is not enabled.

       1 - A problem with configuration was detected.

       2 - A problem with network access occurred (address in use, attempt  to
       use privileged ports without permission).

       3 - A problem occurred with a filesystem operation (missing file/direc-
       tory, permissions).

       4 - Memory allocation failure.

       5 - Other miscellaneous problem.

       11 or greater - a non zero return code was  received  from  the  lease-
       script  process "init" call. The exit code from dnsmasq is the script's
       exit code with 10 added.


LIMITS
       The default values for resource limits in dnsmasq are generally conser-
       vative, and appropriate for embedded router type devices with slow pro-
       cessors and limited memory. On more capable hardware, it is possible to
       increase  the  limits,  and  handle  many  more  clients. The following
       applies to dnsmasq-2.37: earlier versions did not scale as well.


       Dnsmasq is capable of handling DNS and DHCP for  at  least  a  thousand
       clients.  The  DHCP lease times should not be very short (less than one
       hour). The value of --dns-forward-max can be increased: start  with  it
       equal  to  the  number  of clients and increase if DNS seems slow. Note
       that DNS performance depends too on the  performance  of  the  upstream
       nameservers. The size of the DNS cache may be increased: the hard limit
       is 10000 names and the default (150) is very low.  Sending  SIGUSR1  to
       dnsmasq  makes  it log information which is useful for tuning the cache
       size. See the NOTES section for details.


       The built-in TFTP server is capable of many  simultaneous  file  trans-
       fers:  the  absolute  limit  is  related  to the number of file-handles
       allowed to a process and the ability of the  select()  system  call  to
       cope  with  large numbers of file handles. If the limit is set too high
       using --tftp-max it will be scaled down and the actual limit logged  at
       start-up.  Note  that more transfers are possible when the same file is
       being sent than when each transfer sends a different file.


       It is possible to use dnsmasq to block Web advertising by using a  list
       of  known  banner-ad servers, all resolving to 127.0.0.1 or 0.0.0.0, in
       /etc/hosts or an additional hosts file. The list can be very long, dns-
       masq  has  been  tested  successfully with one million names. That size
       file needs a 1GHz processor and about 60Mb of RAM.


INTERNATIONALISATION
       Dnsmasq can be compiled to support internationalisation.  To  do  this,
       the  make  targets "all-i18n" and "install-i18n" should be used instead
       of the standard targets "all" and "install". When  internationalisation
       is compiled in, dnsmasq will produce log messages in the local language
       and support internationalised  domain  names  (IDN).  Domain  names  in
       /etc/hosts,  /etc/ethers  and /etc/dnsmasq.conf which contain non-ASCII
       characters will be translated to the DNS-internal punycode  representa-
       tion.  Note  that dnsmasq determines both the language for messages and
       the assumed charset for configuration files from the  LANG  environment
       variable.  This should be set to the system default value by the script
       which is responsible for starting dnsmasq. When editing the  configura-
       tion  files,  be  careful to do so using only the system-default locale
       and not user-specific one, since dnsmasq has no direct way of determin-
       ing the charset in use, and must assume that it is the system default.


FILES
       /etc/dnsmasq.conf

       /usr/local/etc/dnsmasq.conf

       /etc/resolv.conf    /var/run/dnsmasq/resolv.conf   /etc/ppp/resolv.conf
       /etc/dhcpc/resolv.conf

       /etc/hosts

       /etc/ethers

       /var/lib/misc/dnsmasq.leases

       /var/db/dnsmasq.leases

       /var/run/dnsmasq.pid

SEE ALSO
       hosts(5), resolver(5)

AUTHOR
       This manual page was written by Simon Kelley <simon@thekelleys.org.uk>.






                                  2020-04-05                        DNSMASQ(8)