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From André Warnier>
Subject Re: get the incoming TCP protocol type
Date Mon, 26 Nov 2012 11:42:06 GMT
Torsten Förtsch wrote:
> On 11/26/2012 09:05 AM, André Warnier wrote:
>> there is apparently a "server variable" HTTPS which can be tested in a
>> RewriteCond, and which looks just like what I need :
>>     Will contain the text "on" if the connection is using SSL/TLS, or
>> "off" otherwise. (This variable can be safely used regardless of whether
>> or not mod_ssl is loaded).
>> Now I just have to find out how I can actually access such a "server
>> variable" inside a mod_perl handler.  But that should be a breeze,
>> considering the nice online mod_perl documentation, right ?
>> Let's see if I can beat Torsten to it..
> The problem is this "variable" is not something that is stored along
> with the other request data. It is just the temporary result of a
> function call.
> What mod_rewrite does here to provide the "variable" is 2 things:
> 1) it looks for an optional function (this is a thing APR has invented)
> named "ssl_is_https". In C it looks something like this:
>   APR_OPTIONAL_FN_TYPE(ssl_is_https) *is_https;
>   is_https=APR_RETRIEVE_OPTIONAL_FN(ssl_is_https);
> If the function cannot be found HTTPS will be off because mod_ssl is not
> loaded.
> 2) then it calls the function, which returns a boolean value.
> Apache2::ModSSL does exactly the same.
> To make this variable accessible by means of mod_rewrite to mod_perl you
> can:
> RewriteCond %{HTTPS} =on
> RewriteRule .? - E=HTTPS:42
> Later on in Perl you can ask
>   if ($r->subprocess_env->{HTTPS} eq "42") ...
> Mod_rewrite normally works in the uri translation phase, except when it
> is called in a <Directory>, <Location> or <Files> block or a .htaccess
> file. In this case it works in the fixup phase. Unfortunately,
> mod_rewrite installs its handler with APR_HOOK_FIRST priority while
> mod_perl uses APR_HOOK_REALLY_FIRST. That means a PerlFixupHandler is
> called *before* mod_rewrite in directory context.

Between the two of you, we're seeing the light at the end of the tunnel..
Many thanks.  I don't think that this is really documented anywhere, so my chances of 
finding this by myself were rather low to begin with.

I must say that I slightly prefer Torsten's solution, which looks easier (some of the URLs

to proxy already have a query string, for instance).
But I can see also that I'll have to seriously document this in the code, otherwise some 
poor maintainer is going to have a hard time in a couple of years from now, trying to 
figure out what is going on here. Specially if he has never heard of Deep Thought.

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