Gnome proxy setting "Exclusion" seems not correctly handled by Firefox

[Julien]

Binary package hint: firefox

configuration
=============
Distribution: Ubuntu Lucid Lynx Desktop 32 bits (Linux 2.6.31-20-generic #58-Ubuntu SMP Fri Mar 12 05:23:09 UTC 2010 i686 GNU/Linux)
Firefox version: 3.6.10
Gnome Version: 2.32 (Build 25/06/2010)

description
===========
When GNOME proxy server is enabled and configured with address exclusions (for local lan, local servers...), Firefox which is configured to use "proxy server settings" does not mindful of address exclusions.

reproduce the behavior
======================
You need a network with which you can acces directly - without proxy - to an HTTP server (eg. google.com: 66.249.92.104).
You need also Firefox, Gnome and Wireshark.

* In GNOME:
Menu System \ Settings \ Proxy Server
Select the radio button "Manual configuration of proxy" and check the checkbox "Use the same proxy server for all protocols"
In edit box HTTP Proxy server, enter a proxy address (does not have to be correct, eg. http://127.0.0.1/)
In Tab "Ignored Host", add the ip address of your HTTP server (here 66.249.92.104).
In first Tab, Click on button "Apply to the all system"

* In Firefox:
Edit / Settings / Advanced / Network / Connection / Parameters
Select radio button "Use proxy system parameters"

Now run wireshark with gksudo and run capture on outgoing interface.
In Firefox, try to request a random website, not specifically the HTTP server.
=> Firefox try to connect to proxy server
In Firefox, try to request the HTTP server (here http://66.249.92.104/)
=> Firefox try to connect to proxy server and not to web site directly, which is not excepted behavior.

If you perform exactly the same test with proxy configuration done in Firefox and not in gnome :
* in Firefox:
Edit / Settings / Advanced / Network / Connection / Parameters and select "Manual configuration of proxy"
In edit box HTTP Proxy server, enter a proxy address (does not have to be correct, eg. http://127.0.0.1/)
In edit box "Ignored Host", add the ip address of your HTTP server (here 66.249.92.104).

Retry tests and Firefox handles perfecly exclusion list.

[jhansonxi (jhansonxi)]

I encountered this with Ubuntu 10.04 (Lucid Lynx) x86_64. DansGuardian is installed in whitelist mode but no exclusion for loopback IP addresses. Firefox set to use system proxy settings. DansGuardian blocked a connection from Firefox to 127.0.0.1 which should have been excluded from proxy. In gnome-network-properties (Network Proxy Preferences) the exclusions are:
localhost
127.0.0.0/8
*.local

Problem was resolved when 127.0.0.1 was added to the list.

[jhansonxi (jhansonxi)]

This bug also affects Seamonkey. It does not affect Google Chrome or Ephiphany when set to use the system proxy settings.

[jhansonxi (jhansonxi)]

This is probably a duplicate of bug #226823. Bug #23369 and #353310 are possibly related.