If set to "on", Squid will append your client's IP address
	in the HTTP requests it forwards. By default it looks like:

		X-Forwarded-For: 192.1.2.3

	If set to "off", it will appear as

		X-Forwarded-For: unknown

	If set to "transparent", Squid will not alter the
	X-Forwarded-For header in any way.

	If set to "delete", Squid will delete the entire
	X-Forwarded-For header.

	If set to "truncate", Squid will remove all existing
	X-Forwarded-For entries, and place the client IP as the sole entry.