Here is what I have found:
"If a request has passed through multiple proxies then the X-Forwarded-For may contain several IPs like this:
X-Forwarded-For: client1, proxy1, proxy2"
http://www.openinfo.co.uk/apache/index.html
And this appears to be true for the one example I have seen. So fundamentally I think you simply need to look the first quad and ignore the rest. At the same time, if it is non-blank, but you can't extract the host address, you probably should treat it as if the x-forwarded-for header is simply non-existent.
Ken
On Thu, 2007-01-18 at 18:13 -0500, Jochen F. Rick wrote:
Interesting. Why would it have two x-forwarded-for addresses? In other words, what is the meaning of the other address? Which address should be used?
Peace and Luck!
Jeff
On Thu, Jan 18, 2007 at 04:16:45PM -0600, Ken Causey wrote:
I have been debugging the reported problems accessing the wiki.squeak.org wiki for those behind a proxy. I have tracked it down to the implementation of HttpRequest>>initProxyForwarding in the image. It assumes that if an x-forwarded for header exists that it is a single IP address. This appears to be a poor assumption. For example:
x-forwarded-for: 74.141.6.178, 62.90.138.162
I have not so far been able to track down documentation to confirm whether or not this is 'officially' valid. Nonetheless Swiki should probably not fail when this assumption is invalid.
Ken