tellnes/dhr2

Domain-based HTTP Forwarding Ruleset

Domain-based HTTP Redirect Ruleset (DHR2)

Domain-based HTTP Redirect Ruleset (DHR2) is a method that is using DNS to manage the redirects of HTTP requests. This is done by inserting special TXT records in the DNS configuration and point the domain to one or more DHR2 servers.

For example if you have the following dns configuration:

example.com    IN    TXT    "v=DHR2/1; l=http://www.iana.org/domains/example/"
example.com    IN    A      192.0.43.10

then the DHR2 server responds as follows:

> curl -Is http://example.com/
HTTP/1.1 302 Moved Temporarily
Location: http://www.iana.org/domains/example/
Connection: Keep-Alive

Using CNAME

DHR2 is CNAME compatible. This is done by having several rules on the domain name that the CNAME record is pointing to.

github.example.com    IN    CNAME    server.example.com

server.example.com    IN    A        192.0.43.10
server.example.com    IN    TXT      "v=DHR2/1; l=www.example.com"
server.example.com    IN    TXT      "v=DHR2/1; l=github.com; d=github.example.com"

This will result in:

> curl -Is http://server.example.com/ | grep Location
Location: http://www.example.com/

> curl -Is http://github.example.com/ | grep Location
Location: http://github.com/

Wildcard

To match multiple domains under one when using CNAME, you can use a wildcard.

github.example.com    IN    CNAME    server.example.com
any.example.com       IN    CNAME    server.example.com

server.example.com    IN    A        192.0.43.10
server.example.com    IN    TXT      "v=DHR2/1; l=www.example.com"
server.example.com    IN    TXT      "v=DHR2/1; l=www.github.com; d=github.example.com"
server.example.com    IN    TXT      "v=DHR2/1; l=google.com; d=*.example.com"

This will result in:

> curl -Is http://server.example.com/ | grep Location
Location: http://www.example.com/

> curl -Is http://github.example.com/ | grep Location
Location: http://github.com/

> curl -Is http://any.example.com/ | grep Location
Location: http://www.google.com/

dhr2's Issues

URL rewriting using regular expressions

It would be nice to have a little more control over the destination URL. Apache already has a nice way of doing this with mod_rewrite which allows you to rewrite the URL using regular expressions.
If dhr2 would support this, it would be possible to for example send a user from www.example.com to web.myhostingprovider.ext/~example/