ui-shared: fix the Expires header on error pages master

page.expires is an absolute time: the normal path seeds it from
page.modified and adds the relevant TTL in seconds. The error page
instead assigns cache-dynamic-ttl directly, which is a count of minutes
and carries no base, so every error page cgit has produced since
"ui-shared: cache errors for dynamic TTL" reports

  Expires: Thu, 01 Jan 1970 00:00:05 GMT

five seconds past the epoch, which is the value of the default TTL read
as seconds. The intent of that change was to stop errors being cached
forever; the effect is that they are never cached at all, since every
downstream cache is told the response was already stale.

Seed the value from page.modified and scale the TTL to seconds, matching
what calc_ttl() does for ordinary pages. prepare_context() sets
page.modified before anything can produce an error page, so the base is
always available.

Add a test. The header can be checked without any date arithmetic: a TTL
of zero has to reproduce Last-Modified exactly, and a non-zero one has
to differ from it without falling back to the epoch.

Fixes: c5975ae ("ui-shared: cache errors for "dynamic TTL"")
Signed-off-by: Konstantin Ryabitsev <konstantin@linuxfoundation.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

0 files changed, 0 insertions, 0 deletions