Version:            (using KDE KDE 3.5.0)
Installed from:    Compiled From Sources

Please could this be implemented at some point - presumably the next release this could happen in is KDE 4.

This is where a proxy script could return multiple values, see http://wp.netscape.com/eng/mozilla/2.0/relnotes/demo/proxy-live.html for more information.  For example (from that page):

  PROXY w3proxy.netscape.com:8080; PROXY mozilla.netscape.com:8081; DIRECT

There is code in ProxyScout::handleRequest to check each entry in this list against a record of blacklisted proxies, and return the first one that is available.  A proxy can be blacklisted by calling ProxyScout::blackListProxy via DCOP; this appears to be done in KProtocolManager::badProxy.  However, nothing ever calls KProtocolManager::badProxy!

The result of this is that only the first proxy in the list will ever be tried - if it is not responding then the request will fail.  This may not be of much interest to users with a direct Internet connection, but on a corporate intranet with multiple proxies it is very inconvenient if the one that just happens to be listed first goes down, disabling all browsing in KDE.  The only option for the user here is to manually reconfigure their proxies, so losing any advantage in having a PAC script.

I'd be happy to investigate this myself, if someone could just nudge me in the right direction of where to look.  I'd guess that the bad proxy will be detected in kio_http or something called from it, but not sure how to propagate the problem back up to KProtocolManager...