Geo DNS

There are many databases and pieces of code out there that allow you to detect which country (or even city) a visitor to your website is from. Most of this code is intended to allow you to adjust the content of your website. Very useful. Really!

There are instances however where adjusting content is not enough. Sometimes you will want to redirect users to a server that is local to them. This could be because you have lag-sensitive traffic like VoIP of game servers. It could also be that you generate a lot of traffic and local traffic is simply cheaper than transit. Or maybe you have multiple entry points for VPN and email traffic into your corporate network. Whatever it is, the only way to do this transparently is to make sure your DNS hands out the right IP address to your users. Doing this based on ip-country databases is not ideal but it should get you a long way.

I looked around a bit for a way to do this. There are a few special DNS servers for this purpose. There are also some patches for Bind. I’m not a fan of either special or
patches though, they often imply maintenance.

So I wrote a little command-line script called geobind.php to convert the database provided by Webnet77 to Bind acl’s. (Requires PHP4 cli version to be installed; make sure
to edit variables at the beginning of the script.)

Once you have these acl’s you can use Binds view functionality to serve different versions of your zone file to different parts of the world. Each zone file would of course point to IP addresses that are local to that specific part of the world.

Imagine you have 3 zone files: one for europe, one for the america’s and one for the rest of the world. You simple edit named.conf.local to include the acls for europe and the america’s. E.g.:

include “/etc/bind/named.conf.options”;
include “/etc/bind/acl-europe_east.inc”;
include “/etc/bind/acl-europe_sout.inc”;
include “/etc/bind/acl-europe_west.inc”;
include “/etc/bind/acl-europe_nort.inc”;
include “/etc/bind/acl-america_cari.inc”;
include “/etc/bind/acl-america_cent.inc”;
include “/etc/bind/acl-america_nort.inc”;
include “/etc/bind/acl-america_sout.inc”;

Next you create seperate views. One for europe, one for the america’s and one for everyone else.

view “europe” {
    match-clients {
        europe_east;
        europe_nort;
        europe_sout;
        europe_west
    };
    zone “peen.net” {
        type master;
        file “/etc/bind/europe/db.peen.net”;
    };
};

view “americas” {
    match-clients {
        america_cari;
        america_nort;
        america_sout;
        america_cent
    };
    zone “peen.net” {
        type master;
        file “/etc/bind/americas/db.peen.net”;
    };
};

view “others” {
    match-clients { any; };
    zone “peen.net” {
        type master;
        file “/etc/bind/others/db.peen.net”;
    };
};

Reload Bind and see what happens! 🙂

peen:~# rndc reload