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I run a system that has a Pound reverse proxy in front of a squid accelerator, in turn in front of Apache2 powering a few PHP-based webapps.

The Pound daemon is configured to send X-Forwarded-For headers to Apache so the aforementioned applications can determine the true source of a message (squid is configured to transparently pass on the X-Forwarded-For headers without modification). However, Pound notates IPv4 addresses in XFF headers like ::ffff: instead of simply as, and this throws off the applications.

Aside from modifying each application to correctly handle the ::ffff: case, is there a way to either stop Pound from using the IPv6 notation or in Apache to preemptively convert the IPv6 notation back to IPv4 notation?

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up vote 2 down vote accepted

You should be able to use mod_headers to rewrite the X-Forwarded-For header prior to the php applications seeing it:

RequestHeader edit X-Forwarded-For "^::ffff:" ""
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