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| author | Laurent Bercot <ska-skaware@skarnet.org> | 2014-12-15 23:08:59 +0000 |
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| committer | Laurent Bercot <ska-skaware@skarnet.org> | 2014-12-15 23:08:59 +0000 |
| commit | e0fc82203d677a6f1e808e9a1a46176c109d89be (patch) | |
| tree | e9609209b755e3f7a8480aea86601ffe9d4ca540 /doc/s6-tcpserver4.html | |
| download | s6-networking-e0fc82203d677a6f1e808e9a1a46176c109d89be.tar.xz | |
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| -rw-r--r-- | doc/s6-tcpserver4.html | 123 |
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diff --git a/doc/s6-tcpserver4.html b/doc/s6-tcpserver4.html new file mode 100644 index 0000000..e0270e0 --- /dev/null +++ b/doc/s6-tcpserver4.html @@ -0,0 +1,123 @@ +<html> + <head> + <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> + <meta http-equiv="Content-Language" content="en" /> + <title>s6-networking: the s6-tcpserver4 program</title> + <meta name="Description" content="s6-networking: the s6-tcpserver4 program" /> + <meta name="Keywords" content="s6-networking s6-tcpserver4 tcpserver ucspi tcp server super-server ipv4" /> + <!-- <link rel="stylesheet" type="text/css" href="http://skarnet.org/default.css" /> --> + </head> +<body> + +<p> +<a href="index.html">s6-networking</a><br /> +<a href="http://skarnet.org/software/">Software</a><br /> +<a href="http://skarnet.org/">skarnet.org</a> +</p> + +<h1> The <tt>s6-tcpserver4</tt> program </h1> + +<p> +<tt>s6-tcpserver4</tt> is a super-server for IPv4 TCP +connections. It accepts connections from clients, and forks a +program to handle each connection. +</p> + +<h2> Interface </h2> + +<pre> + s6-tcpserver4 [ -1 ] [ -v <em>verbosity</em> ] [ -c <em>maxconn</em> ] [ -C <em>localmaxconn</em> ] [ -b <em>backlog</em> ] [ -G <em>gidlist</em> ] [ -g <em>gid</em> ] [ -u <em>uid</em> ] [ -U ] <em>ip</em> <em>port</em> <em>prog...</em> +</pre> + +<ul> + <li> s6-tcpserver4 binds to local IPv4 address <em>ip</em>, +port <em>port</em>. </li> + <li> It closes its stdin and stdout. </li> + <li> For every TCP connection to this address and port, it +forks. The child sets some environment variables, then +executes <em>prog...</em> with stdin reading from the network +socket and stdout writing to it. </li> + <li> Depending on the verbosity level, it logs what it does to stderr. </li> + <li> It runs until killed by a signal. Depending on the received +signal, it may kill its children before exiting. </li> +</ul> + +<h2> Environment variables </h2> + +<p> + For each connection, an instance of <em>prog...</em> is spawned with +the following variables set: +</p> + +<ul> + <li> PROTO: always set to TCP </li> + <li> TCPREMOTEIP: set to the originating address </li> + <li> TCPREMOTEPORT: set to the originating port </li> + <li> TCPCONNNUM: set to the number of connections originating from +the same IP address </li> +</ul> + +<h2> Options </h2> + +<ul> + <li> <tt>-1</tt> : write <em>port</em> to stdout, before +closing it, right after binding and listening to the network socket. +If stdout is suitably redirected, this can be used by monitoring +programs to check when the server is ready to accept connections. </li> + <li> <tt>-v <em>verbosity</em></tt> : be more or less verbose. +By default, <em>verbosity</em> is 1: print warning messages to stderr. +0 means only print fatal error messages ; 2 means print status and +connection information for every client. </li> + <li> <tt>-c <em>maxconn</em></tt> : accept at most +<em>maxconn</em> concurrent connections. Default is 40. It is +impossible to set it higher than 1000. </li> + <li> <tt>-C <em>localmaxconn</em></tt> : accept at most +<em>localmaxconn</em> connections from the same IP address. +Default is 40. It is impossible to set it higher than <em>maxconn</em>. </li> + <li> <tt>-b <em>backlog</em></tt> : set a maximum of +<em>backlog</em> backlog connections on the socket. Extra +connection attempts will rejected by the kernel. </li> + <li> <tt>-G <em>gidlist</em></tt> : change s6-tcpserver4's +supplementary group list to <em>gidlist</em> after binding the socket. +This is only valid when run as root. <em>gidlist</em> must be a +comma-separated list of numerical group IDs. </li> + <li> <tt>-g <em>gid</em></tt> : change s6-tcpserver4's groupid +to <em>gid</em> after binding the socket. This is only valid when run +as root. </li> + <li> <tt>-u <em>uid</em></tt> : change s6-tcpserver4's userid +to <em>uid</em> after binding the socket. This is only valid when run +as root. </li> + <li> <tt>-U</tt> : change s6-tcpserver4's user id, group id and +supplementary group list +according to the values of the UID, GID and GIDLIST environment variables +after binding the socket. This is only valid when run as root. +This can be used with the +<a href="http://skarnet.org/software/s6/s6-envuidgid.html">s6-envuidgid</a> +program to easily script a service that binds to a privileged socket +then drops its privileges to those of a named non-root account. </li> +</ul> + +<h2> Signals </h2> + +<ul> + <li> SIGTERM: exit. </li> + <li> SIGHUP: send a SIGTERM and a SIGCONT to all children. </li> + <li> SIGQUIT: send a SIGTERM and a SIGCONT to all children, then exit. </li> + <li> SIGABRT: send a SIGKILL to all children, then exit. </li> +</ul> + +<h2> Notes </h2> + +<ul> + <li> Unlike its ancestor +<a href="http://cr.yp.to/ucspi-tcp/tcpserver.html">tcpserver</a>, +s6-tcpserver4 performs just the bare minimum: the point is to have a +very small and very fast process to serve connections with the least +possible overhead. Features such as additional environment variables, +access control and DNS resolution are provided +via the <a href="s6-tcpserver-access.html">s6-tcpserver-access</a> +program. </li> +</ul> + +</body> +</html> |