                    Using MaraDNS as a recursive DNS server

   This document is a step-by-step guide to setting up MaraDNS as a recursive
   DNS server. It assumes that MaraDNS is already [1]compiled and installed.

Table of contents

     * [2]Basic configuration
     * [3]Using MaraDNS on a slow network
     * [4]Using other recursive DNS servers
     * [5]Using different root servers
     * [6]Having private host names
     * [7]Customizing the resolution of some names

Basic configuration

   Once MaraDNS is installed, the mararc file needs to be set up before
   MaraDNS will function as a recursive DNS server. This file only needs to
   be three lines long:

 ipv4_bind_addresses = "127.0.0.1"
 chroot_dir = "/etc/maradns"
 recursive_acl = "127.0.0.1"

   This three-line file needs to be called /etc/mararc.

   The first line is the IP address or addresses MaraDNS will use. Here, it
   has the address 127.0.0.1, which means that only the machine running
   MaraDNS will be able to access the MaraDNS server--other machines will not
   be able to see it.

   If the machine running MaraDNS will be accessed by other machines, this IP
   needs to be changed to an IP that the machine running MaraDNS has.

   It is possible to have MaraDNS run on multiple IP addresses:

 ipv4_bind_addresses = "10.1.3.2, 192.168.0.1, 127.0.0.1"

   The second line, chroot_dir is the directory MaraDNS will be run from.
   When MaraDNS is being used as a recursive DNS server, this just has to be
   an empty directory, ideally owned by the root user.

   The third line, recursive_acl, determines the range of IPs that can access
   the recursive DNS server. This is in IP/netmask format. For example, if
   one has an office which uses IPs in the form 192.168.1.1, 192.168.1.2,
   etc., and wishes to have only 192.168.1.any be allowed to make recursive
   queries:

 recursive_acl = "192.168.1.0/24"

   Here the "/24" indicates that we ignore the fourth number in an IP when
   determining who can contact MaraDNS.

   Once this is done, other machines can contact the MaraDNS server to
   perform DNS queries. For example, MaraDNS is now a DNS server which
   Windows 98 can use in "Control Panel -> Network -> TCP/IP -> DNS
   configuration", or a UNIX system can point to from /etc/resolv.conf.

Using MaraDNS on a slow network

   MaraDNS, on a slow network, may time out. MaraDNS normally only waits two
   seconds for a reply from a remote DNS server. This is not enough time to
   process queries on some slow networks. This can be changed by increasing
   the timeout_seconds value.

   Here is a mararc file which waits six seconds (instead of the default two)
   for a reply from a remote DNS server:

 ipv4_bind_addresses = "127.0.0.1"
 chroot_dir = "/etc/maradns"
 recursive_acl = "127.0.0.1"
 timeout_seconds = 6

Using other recursive DNS servers

   It is possible to have MaraDNS contact other recursive name servers,
   instead of contacting the actual root servers to process recursive queries
   by using the variable upstream_servers in the mararc file.

   In other words, one can use one's, say, ISP's DNS servers to resolve the
   names, and have MaraDNS act as a cache for the ISP's DNS servers.
   Supposing that the ISP name servers have the IPs 10.66.77.88 and
   10.99.11.22, the mararc file will look like this:

 ipv4_bind_addresses = "127.0.0.1"
 chroot_dir = "/etc/maradns"
 recursive_acl = "127.0.0.1"
 upstream_servers = {}
 upstream_servers["."] = "10.66.77.88, 10.99.11.22"

Using different root servers

   MaraDNS, by default, uses the ICANN name servers as the root name servers.
   The reason for this default is practical: In my experience, the ICANN root
   name servers are the ones which least frequently change their IP
   addresses. They are the best name servers for simple "set and forget"
   recursive environments.

   It is possible, however, to change the root DNS servers used by setting
   the root_servers variable in the mararc file. Here is what such a
   recursive configuration (this example uses the ICANN root servers; change
   this example to use another set of root servers as needed) looks like:

 ipv4_bind_addresses = "127.0.0.1"
 chroot_dir = "/etc/maradns"
 recursive_acl = "127.0.0.1"
 ipv4_alias = {}
 ipv4_alias["icann"]  = "198.41.0.4,"
 ipv4_alias["icann"] += "192.228.79.201,"
 ipv4_alias["icann"] += "192.33.4.12,"
 ipv4_alias["icann"] += "128.8.10.90,"
 ipv4_alias["icann"] += "192.203.230.10,"
 ipv4_alias["icann"] += "192.5.5.241,"
 ipv4_alias["icann"] += "192.112.36.4,"
 ipv4_alias["icann"] += "128.63.2.53,"
 ipv4_alias["icann"] += "192.36.148.17,"
 ipv4_alias["icann"] += "192.58.128.30,"
 ipv4_alias["icann"] += "193.0.14.129,"
 ipv4_alias["icann"] += "199.7.83.42,"
 ipv4_alias["icann"] += "202.12.27.33"
 root_servers["."] = "icann"

   This file will do the exact same thing as the following mararc file:

 ipv4_bind_addresses = "127.0.0.1"
 chroot_dir = "/etc/maradns"
 recursive_acl = "127.0.0.1"

   The ICANN servers listed above are the ones that MaraDNS uses when no root
   servers are specified.

   As an aside, the ipv4_alias variable is a general purpose way of giving
   names to any set of IPs in a mararc file. We can use shortcuts like this,
   in fact:

 ipv4_alias = {}
 ipv4_alias["localhost"] = "127.0.0.1"
 ipv4_bind_addresses = "localhost"
 chroot_dir = "/etc/maradns"
 recursive_acl = "localhost"
 ipv4_alias["icann-a"] = "198.41.0.4"
 ipv4_alias["icann-b"] = "192.228.79.201"
 ipv4_alias["icann-c"] = "192.33.4.12"
 ipv4_alias["icann-d"] = "128.8.10.90"
 ipv4_alias["icann-e"] = "192.203.230.10"
 ipv4_alias["icann-f"] = "192.5.5.241"
 ipv4_alias["icann-g"] = "192.112.36.4"
 ipv4_alias["icann-h"] = "128.63.2.53"
 ipv4_alias["icann-i"] = "192.36.148.17"
 ipv4_alias["icann-j"] = "192.58.128.30"
 ipv4_alias["icann-k"] = "193.0.14.129"
 ipv4_alias["icann-l"] = "199.7.83.42"
 ipv4_alias["icann-m"] = "202.12.27.33"
 ipv4_alias["icann"] = "icann-a,icann-b,icann-c,icann-d,icann-e,icann-f,"
 ipv4_alias["icann"] += "icann-g,icann-h,icann-i,icann-j,icann-k,icann-l,"
 ipv4_alias["icann"] += "icann-m"
 root_servers["."] = "icann"

   This works the same as the above two examples. The reason why we don't
   have commas in any of the aliases besides icann is because the comma
   before the quote is only needed on a line before a line that uses the +=
   operator.

   Here is what a configuration file which uses OpenNIC's glue root servers
   as the root servers. This list is current as of February 22, 2006; note
   that OpenNIC frequently changes these IPs and you need to verify that
   these IPs are current at [8]http://www.opennic.unrated.net/. A number of
   alternate root server organizations no longer exist; please make sure
   these people still exist before using this list.

 ipv4_bind_addresses = "127.0.0.1"
 chroot_dir = "/etc/maradns"
 recursive_acl = "127.0.0.1"
 ipv4_alias = {}
 # This ends with a comma because the next line is a += line
 ipv4_alias["opennic"]  = "131.161.247.232,"
 ipv4_alias["opennic"] += "208.185.249.250,"
 ipv4_alias["opennic"] += "66.227.42.140,"
 ipv4_alias["opennic"] += "66.227.42.149,"
 ipv4_alias["opennic"] += "64.81.44.251,"
 ipv4_alais["opennic"] += "216.87.84.214,"
 ipv4_alias["opennic"] += "208.185.249.251,"
 ipv4_alias["opennic"] += "131.161.247.231,"
 # This is the last line, so no comma at the end
 ipv4_alias["opennic"] += "65.243.92.254"
 # Considering how often alternate root DNS server lists change or disappear,
 # we will have the ICANN list on hand as a backup.
 ipv4_alias["icann"]  = "198.41.0.4,"
 ipv4_alias["icann"] += "192.228.79.201,"
 ipv4_alias["icann"] += "192.33.4.12,"
 ipv4_alias["icann"] += "128.8.10.90,"
 ipv4_alias["icann"] += "192.203.230.10,"
 ipv4_alias["icann"] += "192.5.5.241,"
 ipv4_alias["icann"] += "192.112.36.4,"
 ipv4_alias["icann"] += "128.63.2.53,"
 ipv4_alias["icann"] += "192.36.148.17,"
 ipv4_alias["icann"] += "192.58.128.30,"
 ipv4_alias["icann"] += "193.0.14.129,"
 ipv4_alias["icann"] += "198.32.64.12,"
 ipv4_alias["icann"] += "202.12.27.33"
 # Now, set the root servers; chance this to icann if you want to use the
 # icann servers instead.
 root_servers["."] = "opennic"

Having private host names

   One may wish to have private host names when running MaraDNS as a
   recursive name server. These are names that are not attached to the root
   servers, but will resolve on the recursive name server. For example, it
   might make sense to have "router.example.com." resolve to the IP of a
   router in an office.

   This is done by taking advantage of the fact that MaraDNS can act as both
   a recursive and authoritative name server on the same IP. MaraDNS first
   looks up authoritative names before performing recursion. For example, if
   www.google.com is defined in a MaraDNS zone file, MaraDNS will use the
   value in the zone file instead of contacting nameservers on the internet
   to get the IP for www.google.com.

   The procedure to do this is as follows:

     * Have an authoritative and recursive DNS server share the same IP. Make
       sure this DNS server is not accessible from the public internet.
     * For this authoritative server, have zone files for the zones which one
       wants to have non-public information. Recursive queries will be
       resolved as usual (since the authoritative server is also a recursive
       server); authoritative queries for the special zones will get the
       special data.
     * The [9]maradns man page has a section on firewall configuration which
       describes how to set up an IP filter to allow MaraDNS to send packets.
       Basically, don't allow outside IPs to hit this combined server on port
       53 (UDP); instead allow UDP connections to ports 15000-19095.

   Here is how the configuration may look:

 ipv4_bind_addresses = "192.168.0.1"
 chroot_dir = "/etc/maradns"
 recursive_acl = "192.168.0.0/24"
 csv2 = {}
 csv2["example.com."] = "db.example.com"

   Replace 192.168.0.1 with the IP of the machine running the recursive
   MaraDNS; replace 192.168.0.0/24 (This means "anything that begins with
   192.168.0") with the IP range allowed to access the recursive DNS server.

   The file "db.example.com." will be a csv2 zone file with records for the
   bogus example.com domain, such as router.example.com.

   If you want to have some of these private names be CNAMES for hostnames on
   the internet (e.g. "google.example.com. CNAME www.google.com."), please
   read the [10]dangling CNAME document.

   More information on having host names for an internal network is available
   in the [11]network section of the authoritative document.

Customizing the resolution of some names

   One may wish to customize the resolution of certain names when using
   MaraDNS as both an authoritative and recursive name server. For example,
   if a high-profile domain is hijacked (such as what happened with panix.com
   in January of 2005), it may be desirable to have the correct name for the
   domain be temporarily locally set. This is also useful for a list of
   blocked sites (so the user gets a friendly "this site is blocked" instead
   of just being unable to connect to the site in question), and for setups
   where some machines need special DNS resolution for names that other
   machines do not need DNS resolution for.

   The procedure for doing this is almost identical to the procedure for
   having private host names as described above. Here is an example relevant
   mararc file:

 ipv4_bind_addresses = "192.168.0.1"
 chroot_dir = "/etc/maradns"
 recursive_acl = "192.168.0.0/24"
 csv2 = {}
 csv2["example.com."] = "db.example.com"

   The only things that need to be changed in this mararc file are the
   ipv4_bind_addresses and the recursive_acl parameters. The
   csv2["example.com."] is not changed.

   Now, let us suppose we want to have the A records for "www.phishsite.foo"
   and "phishsite.foo" resolve to an IP address that we control the web site
   for. We would add the following records (lines) to the file
   /etc/maradns/db.example.com

 www.phishsite.foo. 192.168.0.2
 phishsite.foo. 192.168.0.2

   We can also add a star record:

 *.phishsite.foo. 192.168.0.2

References

   Visible links
   1. file:///home/set/tmp/compile.html
   2. file:///home/set/tmp/11544.html#basic
   3. file:///home/set/tmp/11544.html#slow
   4. file:///home/set/tmp/11544.html#upstream
   5. file:///home/set/tmp/11544.html#otherroot
   6. file:///home/set/tmp/11544.html#private
   7. file:///home/set/tmp/11544.html#custom
   8. http://www.opennic.unrated.net/
   9. file:///home/set/tmp/man.maradns.html
  10. file:///home/set/tmp/dangling.html
  11. file:///home/set/tmp/authoritative.html#network
