Ubuntu – How to make Ubuntu honor “ignore-hosts” proxy settings for IPv6

ipv6networkingPROXY

I just typed under "dconf-editor", System → Proxy → ignore-hosts, the following content:

['localhost', '127.0.0.0/8', '::1', '192.168.0.1', '2000::/3', 'fc00::/8']

But, Google Chrome (and apt-get update / upgrade) is just ignoring this settings.

EDITED: Also, Firefox doesn't honor the ingore-hosts settings, even configuring it to "Use system proxy settings".

For example, my Proxy Server (Ubuntu with Squid3) is in dual-stacked mode BUT, I do NOT want to access IPv6 web sites through the Proxy, that's why I'm trying to ignore the entire IPv6 Internet with the entry 2000::/3, but, it does not work as expected.

EDITED: Also, I don't need the proxy to access Hyperboria sites, which resides under fc00::/8 but, it doesn't work either…

Why I'm doing this?

Because my environment is already a IPv6-Only Network and, to access the old internet infrastructure (IPv4-Only), I need to go through the dual-stacked proxy. But I need the proxy only when a web site doesn't have IPv6…

How can I know that it doesn't work?!

It is simple, just access a web site that shows a IPv6 address on it, for example, http://www.sixxs.net or http://ipv6.whatismyv6.com, then, I'm still seeing the IPv6 address of the Proxy Server, so, "ignore-hosts entry '2000::/3'" doesn't seem to be working.

EDITED: Plus, when I'm trying to access a Hyperboria website, Squid returns an error that it can not reach fc00::/8 network

(Squid ERROR: (101) Network is unreachable)

(of course it can't, the cjdns router is running right on my Ubuntu Desktop, so, no need to go through proxy when browsing Hyperboria fc00::/8 but, Ubuntu isn't honoring ignore-hosts under proxy settings.

Best Answer

It looks like this won't work with Gnome proxy settings. The ignore-hosts setting works for hostnames, addresses and address ranges, but apparently does not resolve hostnames before checking against addresses.

From the ignore-hosts documentation (emphasis by me):

Also note that hostname exclusions apply only to connections made to hosts identified by name, and IP address exclusions apply only to connections made to hosts identified by address. That is, if example.com has an address of 192.168.1.1, and the :ignore-hosts list contains only "192.168.1.1", then a connection to "example.com" (eg, via a GNetworkAddress) will use the proxy, and a connection to "192.168.1.1" (eg, via a GInetSocketAddress) will not.

Related Solutions

Ubuntu – How to make the proxy settings change depending on the network I connect to

I can think of one way, but setting it up will be a bit obscure.

Basically you could use a PAC file

Install a web server on your system, any tiny web server will do, you don't need a huge system like apache.

Create a file wpad.dat with PAC directives that match based on your source address, and then configure your system to use the correct proxy.

In firefox, configure the proxy to point at your local PAC file. It would probably be something like http://localhost/wpad.dat.

Your PAC file might look somewhat like this (untested). See here for more PAC examples.

function FindProxyForURL(url, host) {   
  // If on a internal/LAN IP address, send traffic direct.
  if (isInNet(myIpAddress(), "10.10.1.0", "255.255.255.0"))
  {        
    return "PROXY 1.2.3.4:8080; PROXY 4.5.6.7:8080; DIRECT";
  }
  else
  {
    return "DIRECT";
  }
}

I have never tried it, and I am not at a system to test, but you may even be able to specify the PAC file using a file:// URL in firefox, which would mean you could skip setting up the web server.

Of course there is also the quick and easy solution, but it does require a little effort on your part as you move between locations. Install the Quick Proxy Firefox extension, and just click the button on your tool bar to toggle the proxy on or off. If you are willing to deal with this with a Firefox extension you can also try FoxyProxy, it supports setting up multiple proxy profiles, and you can easily switch between profiles.

Ubuntu – How to resolve the DNS locally when there is a proxy configured

This isn't possible when you use an HTTP proxy because:

The server you connect to is that of the proxy, not of the ultimate destination.
You send the full URL (including hostname) of your request to the proxy. The proxy then does the request on your behalf.

Therefore, it must be the proxy that does the DNS lookup.

It isn't possible to do the DNS lookup locally, and send only the IP address to the proxy server. Firstly, there is no mechanism to specify that the proxy should try a particular IP address for a particular host. You could change the URL from, say, http://example.com/mypage to http://33.33.33.33/mypage, but then the proxy server won't know which hostname to request, an importanta part of the modern web (HTTP/1.1 and later), which depends on a Host header always being present in a request, removing the restriction that all hostnames be served from different IP addresses.

Your best bet would be to configure the proxy server to use the DNS resolver of your choice. This would only be possible if you use a local proxy server that you control.

Note: When you use a SOCKS proxy or another lower-level tunnelling method, you can use a local DNS server. Just not with an HTTP proxy.