Change Request: prevent certain files from being cached in proxies

[Sirius Rayner-Karlsson]

While working on a automated netinstall system I came across a problem that Colin Watson helped me with.

I was using a Squid proxy to cache package files, so as to lighten the need to go off-lan for each and every machine that is installed or updated. This _also_ caches files like Packages.gz. When I swapped out the loop-mounted Dapper Flight3 for Flight4, the proxy had cached Packages.gz from Flight3, causing MD5 mismatch when trying to install from out of the Flight4 ISO.

Files that are retrieved over the network, that do not have version numbers in their names, could probably be retrieved with proxies in mind and a "Cache-Control: no-cache" header passed in the request.

Thanks,

[Matt Zimmerman (mdz)]

apt already sends appropriate Cache-Control: max-age headers for these, so Squid should always re-validate Packages files against the remote web server

[Colin Watson (cjwatson)]

Matt, net-retriever does not use apt. It runs in a very early stage of the netboot installer where apt is not available.

[Colin Watson (cjwatson)]

net-retriever and preseed now use a common fetch-url command in debian-installer-utils for this.