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<title>tipidee: the tipideed program</title>
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<p>
<a href="index.html">tipidee</a><br />
<a href="//skarnet.org/software/">Software</a><br />
<a href="//skarnet.org/">skarnet.org</a>
</p>
<h1> The <tt>tipideed</tt> program </h1>
<p>
<tt>tipideed</tt> is the binary that actually does what you want from
a web server package: it serves files over HTTP.
</p>
<h2> Interface </h2>
<pre>
tipideed [ -v <em>verbosity</em> ] [ -f <em>cdbfile</em> ] [ -d <em>basedir</em> ] [ -R ] [ -U ]
</pre>
<ul>
<li> tipideed reads a stream of HTTP (1.0 or 1.1) requests on its stdin, and tries
to fulfill them, sending answers to stdout, and logs to stderr. </li>
<li> tipideed only speaks plaintext HTTP. It supports HTTPS, but the TLS layer
must be handled upstream by a program such as
<a href="//skarnet.org/software/s6-networking/s6-tlsd.html">s6-tlsd</a>. </li>
<li> tipideed stays alive until the client closes the connection or (in
HTTP 1.1) sends a request with a <tt>Connection: close</tt> header, or an error
occurs that makes it nonsensical to keep the connection open. </li>
<li> By default, the documents it serves must be in subdirectories of its
current working directory, one subdirectory for every domain it hosts. </li>
</ul>
<h2> Common usage </h2>
<p>
tipideed is intended to be run under a TCP super-server such as
<a href="//skarnet.org/software/s6-networking/s6-tcpserver.html">s6-tcpserver</a>,
for plain text HTTP, or
<a href="//skarnet.org/software/s6-networking/s6-tlsserver.html">s6-tlsserver</a>,
for HTTPS. It delegates to the super-server the job of binding and listening to
the socket, accepting connections, spawning a separate process to handle a
given connection, and potentially establishing a TLS tunnel with the client for
secure communication.
</p>
<p>
As such, a command line for tipideed, running as user <tt>www</tt>, listening
on address <tt>${ip}</tt>, would typically look like this, for HTTP:
</p>
<pre>
s6-envuidgid www s6-tcpserver -U -- ${ip} 80 s6-tcpserver-access -- tipideed
</pre>
<p>
or, for HTTPS:
</p>
<pre>
s6-envuidgid www env KEYFILE=/path/to/private/key CERTFILE=/path/to/certificate s6-tlsserver -U -- ${ip} 443 tipideed
</pre>
<p>
Most users will want to run these command lines as <em>services</em>, i.e. daemons
run in the background when the machine starts. The <tt>examples/</tt> subdirectory
of the tipidee package provides service templates to help you run tipideed under
<a href="https://wiki.gentoo.org/wiki/OpenRC">OpenRC</a>,
<a href="//skarnet.org/software/s6/">s6</a> and
<a href="//skarnet.org/software/s6-rc/">s6-rc</a>.
</p>
<h2> Exit codes </h2>
<dl>
<dt> 0 </dt> <dd> clean exit. The client closed the connection after a stream of
HTTP exchanges. </dd>
<dt> 1 </dt> <dd> Illicit client behaviour. tipideed exited because it could
not serve the client in good faith. </dd>
<dt> 2 </dt> <dd> Illicit CGI script behaviour. tipideed exited because the invoked
CGI script made it impossible to continue. Before exiting, tipideed likely has
sent a 502 (Bad Gateway) response to the client. </dd>
<dt> 100 </dt> <dd> bad usage. tipideed has been run in an incorrect way: bad command
line options, or missing environment variables, etc. </dd>
<dt> 101 </dt> <dd> cannot happen. This signals a bug in tipideed, and comes with an
error message asking you to report the bug. Please do so, on the
<a href="//skarnet.org/lists/#skaware">skaware mailing-list</a>. </dd>
<dt> 111 </dt> <dd> system call failed. If this happens while serving a request,
tipideed likely has sent a 500 (Internal Server Error) response to the
client before exiting. </dd>
</dl>
<h2> Environment variables </h2>
<h3> Reading - mandatory </h3>
<p>
tipideed expects the following variables in its environment, and will exit
with an error message if they are undefined. When tipideed is run under
<a href="//skarnet.org/s6-networking/s6-tcpserver.html">s6-tcpserver</a>
(with <a href="//skarnet.org/s6-networking/s6-tcpserver-access.html">s6-tcpserver-access</a> or
<a href="//skarnet.org/s6-networking/s6-tlsserver.html">s6-tlsserver</a>,
these variables are automatically set by the super-server. This is the way
tipidee gets its network information without having to perform network
operations itself.
</p>
<dl>
<dt> PROTO </dt>
<dd> The network protocol, normally <tt>TCP</tt>. </dd>
<dt> TCPLOCALIP </dt>
<dd> The IP address the server is bound to. It will be passed as <tt>SERVER_ADDR</tt>
to CGI scripts. </dd>
<dt> TCPLOCALPORT </dt>
<dd> The port the server is bound to. It will be passed as <tt>SERVER_PORT</tt>
to CGI scripts. </dd>
<dt> TCPLOCALHOST </dt>
<dd> The domain name associated to the local IP address. It will be
passed as <tt>SERVER_NAME</tt> to CGI scripts. </dd>
<dt> TCPREMOTEIP </dt>
<dd> The IP address of the client. It will be passed as <tt>REMOTE_ADDR</tt>
to CGI scripts. </dd>
<dt> TCPREMOTEPORT </dt>
<dd> The port of the client socket. It will be passed as <tt>REMOTE_PORT</tt>
to CGI scripts. </dd>
</dl>
<h3> Reading - optional </h3>
<p>
tipideed can function without these variables, but if they're present, it
uses them to get more information.
</p>
<dl>
<dt> TCPREMOTEHOST </dt>
<dd> The domain name associated to the IP address of the client. It will
be passed as <tt>REMOTE_HOST</tt> to CGI scripts; if absent, the value of
<tt>TCPREMOTEIP</tt> will be used instead. </dd>
<dt> TCPREMOTEINFO </dt>
<dd> The name provided by an IDENT server running on the client, if any.
This is obsolete and not expected to be present; but if present, it will
be passed as <tt>REMOTE_IDENT</tt> to CGI scripts. </dd>
<dt> SSL_PROTOCOL </dt>
<dd> The version of the TLS protocol used to cipher communications between
the client and the server. If present, tipideed will assume that the client
connection is secure, and will pass <tt>HTTPS=on</tt> to CGI scripts;
otherwise, it will assume it is running plaintext HTTP. </dd>
</dl>
<h3> Writing </h3>
<p>
When spawning a CGI or NPH script, tipideed clears all the previous variables,
so the passed environment is as close as possible to the environment of the
super-server; and it adds all the variables that are required by the
<a href="https://datatracker.ietf.org/doc/html/rfc3875#section-4.1">CGI 1.1
specification</a>. It does not add PATH_TRANSLATED, which CGI scripts should
not rely on.
</p>
<h2> Options </h2>
<dl>
<dt> -v <em>verbosity</em> </dt>
<dd> The level of log verbosity. This is the same as the <tt>global verbosity</tt>
setting in the <a href="tipidee.conf.html">configuration file</a>; an explicit
command line option overrides any setting present in the configuration file.</dd>
<dt> -f <em>file</em> </dt>
<dd> </dd>
</dl>
<h2> Detailed operation </h2>
<h2> Performance considerations </h2>
<p>
On systems that implement
<a href="https://pubs.opengroup.org/onlinepubs/9699919799/functions/posix_spawn.html">posix_spawn()</a>,
the <a href="//skarnet.org/software/s6-networking/s6-tcpserver.html">s6-tcpserver</a>
super-server (and the
<a href="//skarnet.org/software/s6-networking/s6-tlsserver.html">s6-tlsserver</a> one
as well, since both use the same underlying program) uses it instead of
<a href="https://pubs.opengroup.org/onlinepubs/9699919799/functions/fork.html">fork()</a>,
and that partly alleviates the performance penalty usually associated with servers
that spawn one process per connection.
</p>
<p>
One of tipidee's stated goals is to explore what kind of performance is achievable for
a fully compliant Web server within the limits of that model. To that effect, tipideed
is meant to be <em>fast</em>. It should serve static files as fast as any server out
there, especially on Linux (or other systems supporting
<a href="https://man7.org/linux/man-pages/man2/splice.2.html">splice())</a> where it
uses zero-copy transfer. CGI performance should be limited by the performance of the
CGI script itself, never by tipideed.
</p>
<p>
tipideed itself does not use
<a href="https://pubs.opengroup.org/onlinepubs/9699919799/functions/fork.html">fork()</a>
if the system supports
<a href="https://pubs.opengroup.org/onlinepubs/9699919799/functions/posix_spawn.html">posix_spawn()</a>
— with one exception, that you will not hit, and if you do, fork() will not
be the bottleneck. (Can you guess which case it is, without looking at the code?)
tipideed does not parse its configuration file itself, delegating the task to the
offline <a href="tipidee-config.html">tipidee-config</a> program and directly mapping
a binary file instead. To parse a client request, it uses a deterministic finite
automaton, only reading the request once, and only backtracking in pathological cases.
This should streamline request processing as much as possible.
</p>
<p>
If you have benchmarks, results of comparative testing of tipideed against
other Web servers, please share them on the
<a href="//skarnet.org/lists/#skaware">skaware mailing-list</a>.
</p>
<h2> Notes </h2>
<ul>
<li> <tt>tipideed</tt> is pronounced <em>tipi-deed</em>. You can say
<em>tipi-dee-dee</em>, but only if you're the type of person who also says
<em>PC computer</em>, <em>NIC card</em> or <em>ATM machine</em>. </li>
</ul>
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