Apache 2.0 Reverse Proxy for v6 access to v4 servers

[Phil Benchoff]

Old subject: A DNS question re 6to6/IPv6 host IN A records

Jeroen Massar <jeroen@unfix.org> wrote:
> http://www.ipng.nl runs IPv6 & IPv4 in one Apache 1.3
> http://games.concepts.nl runs IPv6 & IPv4 in one Apache 2.0.32 and it's
> 'abused' for a nice caching trick to allow IPv4-only webservers, like
> the current available IIS :(, to be accessed over IPv6:
>
> <VirtualHost *>
>         ServerAdmin webmaster@example.org
>         ServerName www.example.org
>         ServerAlias www.ipv6.example.org
>         ProxyRequests On
>         ProxyPass / http://www.ipv4.example.org/
>         ProxyPassReverse / http://www.ipv4.example.org/
> </VirtualHost>


I have been playing with this same thing through various betas of Apache 2.0
and the released 2.0.35.  The cool thing about this is that authentication
is passed through the reverse proxy, i.e. password-protected pages are
still password protected.  You have to be careful about things protected
by IP address or domain name since the v-4 server sees the access from
the reverse proxy. (Note: I do not have "Proxy Requests On" in my config.)

Since I started playing with this, I have had problems with partial data
being returned.  It has improved with the various releases, but I still
see it in 2.0.35.  A typical example looks like this:

   [Mon Apr 22 08:53:10 2002] [error] [client <v6 address> ] proxy: Error reading from remote server returned by /img/misc/vt-logo.gif, referer: http://<whtever>.ip6.vt.edu/public/toc.html

It appears that the Apache 2.0 server tries to fetch
htdocs/error/HTTP_BAD_GATEWAY.html.var after this happens.  I haven't looked
at it enough to figure out exactly what is going on yet.  I've only tested
under Linux, and may try a FreeBSD or Tru64 version to see if that makes
a difference.

Anybody else see this problem?

Phil