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<title>s6-networking: the s6-sudoc program</title>
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<p>
<a href="index.html">s6-networking</a><br />
<a href="http://skarnet.org/software/">Software</a><br />
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<h1> The <tt>s6-sudoc</tt> program </h1>
<p>
<tt>s6-sudoc</tt> talks to a peer <a href="s6-sudod.html">s6-sudod</a>
program over a Unix socket, passing it command-line arguments, environment
variables and standard descriptors.
</p>
<h2> Interface </h2>
<pre>
s6-sudoc [ -e ] [ -t <em>timeoutconn</em> ] [ -T <em>timeoutrun</em> ] [ <em>args...</em> ]
</pre>
<ul>
<li> s6-sudoc transmits its standard input, standard output and standard error
via fd-passing over a Unix socket that must be open on its descriptors 6 and 7.
It expects a <a href="s6-sudod.html">s6-sudod</a> process to be receiving them
on the other side. </li>
<li> It also transmits its command-line arguments <em>args</em>, and also its
environment by default. Note that s6-sudod will not necessarily accept all the
environment variables that s6-sudoc tries to transmit. </li>
<li> s6-sudoc waits for the server program run by s6-sudod to finish. It exits
the same exit code as the server program. If the server program is killed by a
signal, s6-sudoc kills itself with the same signal. </li>
</ul>
<h2> Options </h2>
<ul>
<li> <tt>-e</tt> : do not attempt to transmit any environment variables
to <a href="s6-sudod.html">s6-sudod</a>. </li>
<li> <tt>-t <em>timeoutconn</em></tt> : if s6-sudod has not
managed to process the given information and start the server program after
<em>timeoutconn</em> milliseconds, give up. By default, <em>timeoutconn</em>
is 0, meaning infinite. Note that there is no reason to set up a nonzero
<em>timeoutconn</em> with a large value: s6-sudod is not supposed to block.
The option is only there to protect against ill-written services. </li>
<li> <tt>-T <em>timeoutrun</em></tt> : if the server program
has not exited after <em>timeoutrun</em> milliseconds, give up. By
default, <em>timeoutrun</em> is 0, meaning infinite. </li>
</ul>
<h2> Notes </h2>
<ul>
<li> If s6-sudoc is killed, or exits after <em>timeoutrun</em> milliseconds,
while the server program is still running, s6-sudod will send a SIGTERM and a
SIGCONT to the server program - but this does not guarantee that it will die.
If the server program keeps running, it might still read from the file that
was s6-sudoc's stdin, or write to the files that were s6-sudod's stdout or
stderr. <strong>This is a potential security risk</strong>.
Administrators should audit their server programs to make sure this does not
happen. </li>
<li> More generally, anything using signals or terminals will not be
handled transparently by the s6-sudoc + s6-sudod mechanism. The mechanism
was designed to allow programs to gain privileges in specific situations:
short-lived, simple, noninteractive processes. It was not designed to emulate
the full suid functionality and will not go out of its way to do so. </li>
</ul>
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