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List:       ruby-talk
Subject:    Re: Starting XMLRPC server on virtual host returns EADDRNOTAVAIL
From:       Rene Tschirley <ruby () tschirley ! com>
Date:       2006-12-06 11:33:12
Message-ID: 4576AA67.2090203 () tschirley ! com
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Hi all!


Thanks to you all who have meditated on my problem. I was able to solve
it and for documentation purposes, I now present the solution.

Problem:
> I tried to start a Ruby XMLRPC server on a linux-based virtual host
> (using OpenVZ).
[...]
> While the code works on a non-virtual host, bind returns EADDRNOTAVAIL
> when the server is started on the virtual host:
> 
> [2006-12-05 11:35:24] INFO  WEBrick 1.3.1
> [2006-12-05 11:35:24] INFO  ruby 1.8.5 (2006-08-25) [i486-linux]
> [2006-12-05 11:35:24] WARN  TCPServer Error: Cannot assign requested
> address - bind(2)
> /usr/lib/ruby/1.8/webrick/utils.rb:73:in `initialize': Cannot assign
> requested address - bind(2) (Errno::EADDRNOTAVAIL)
>         from /usr/lib/ruby/1.8/webrick/utils.rb:73:in `new'
>         from /usr/lib/ruby/1.8/webrick/utils.rb:73:in `create_listeners'
>         from /usr/lib/ruby/1.8/webrick/utils.rb:70:in `each'
>         from /usr/lib/ruby/1.8/webrick/utils.rb:70:in `create_listeners'
>         from /usr/lib/ruby/1.8/webrick/server.rb:75:in `listen'
>         from /usr/lib/ruby/1.8/webrick/server.rb:63:in `initialize'
>         from /usr/lib/ruby/1.8/webrick/httpserver.rb:24:in `initialize'
>         from /usr/lib/ruby/1.8/xmlrpc/server.rb:635:in `new'
>         from /usr/lib/ruby/1.8/xmlrpc/server.rb:635:in `initialize'
>         from /net/usr/lib/libversand.rb:53:in `new'
> 
> I tried to define the host by giving the numeric address. I checked that
> the host can resolve the hostname. The server can ping the server
> address. The above code is started as superuser. Linux kernel version is
> 2.6.16, OpenVZ patch is version 026test015.

Solution:

The kernel routing table on a plain VE looks like this:

Destination     Gateway         Genmask         Iface
191.255.255.1   *               255.255.255.255 venet0
default         191.255.255.1   0.0.0.0         venet0

The IP address 191.255.255.1 seems to be a OpenVZ-related special IP
address which is used to route the client's IP traffic to the host.

I changed these routes to match the intranet's common values:

Destination     Gateway         Genmask         Iface
192.168.1.0     *               255.255.255.0   venet0
default         192.168.1.0     0.0.0.0         venet0

Now, the XMLRPC server is able to open the port. Somehow, the server
wasn't able to open the port with the other routing tables. Note that
the interface venet0 was correctly set to listen to IP address
192.168.1.n in both cases!


Rene


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